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Sample records for two-photon excited fluorescent

  1. Two-photon excited fluorescence emission from hemoglobin

    Science.gov (United States)

    Sun, Qiqi; Zeng, Yan; Zhang, Wei; Zheng, Wei; Luo, Yi; Qu, Jianan Y.

    2015-03-01

    Hemoglobin, one of the most important proteins in blood, is responsible for oxygen transportation in almost all vertebrates. Recently, we discovered two-photon excited hemoglobin fluorescence and achieved label-free microvascular imaging based on the hemoglobin fluorescence. However, the mechanism of its fluorescence emission still remains unknown. In this work, we studied the two-photon excited fluorescence properties of the hemoglobin subunits, heme/hemin (iron (II)/(III) protoporphyrin IX) and globin. We first studied the properties of heme and the similar spectral and temporal characteristics of heme and hemoglobin fluorescence provide strong evidence that heme is the fluorophore in hemoglobin. Then we studied the fluorescence properties of hemin, globin and methemoglobin, and found that the hemin may have the main effect on the methemoglobin fluorescence and that globin has tryptophan fluorescence like other proteins. Finally, since heme is a centrosymmetric molecule, that the Soret band fluorescence of heme and hemoglobin was not observed in the single photon process in the previous study may be due to the parity selection rule. The discovery of heme two-photon excited fluorescence may open a new window for heme biology research, since heme as a cofactor of hemoprotein has many functions, including chemical catalysis, electron transfer and diatomic gases transportation.

  2. Two-photon excited UV fluorescence for protein crystal detection

    International Nuclear Information System (INIS)

    Madden, Jeremy T.; DeWalt, Emma L.; Simpson, Garth J.

    2011-01-01

    Complementary measurements using SONICC and TPE-UVF allow the sensitive and selective detection of protein crystals. Two-photon excited ultraviolet fluorescence (TPE-UVF) microscopy is explored for sensitive protein-crystal detection as a complement to second-order nonlinear optical imaging of chiral crystals (SONICC). Like conventional ultraviolet fluorescence (UVF), TPE-UVF generates image contrast based on the intrinsic fluorescence of aromatic residues, generally producing higher fluorescence emission within crystals than the mother liquor by nature of the higher local protein concentration. However, TPE-UVF has several advantages over conventional UVF, including (i) insensitivity to optical scattering, allowing imaging in turbid matrices, (ii) direct compatibility with conventional optical plates and windows by using visible light for excitation, (iii) elimination of potentially damaging out-of-plane UV excitation, (iv) improved signal to noise through background reduction from out-of-plane excitation and (v) relatively simple integration into instrumentation developed for SONICC

  3. Time gated fluorescence lifetime imaging and micro-volume spectroscopy using two-photon excitation

    NARCIS (Netherlands)

    Sytsma, J.; Vroom, J.M.; de Grauw, C.J.; Gerritsen, H.C.

    A scanning microscope utilizing two-photon excitation in combination with fluorescence lifetime contrast is presented. The microscope makes use of a tunable femtosecond titanium:sapphire laser enabling the two-photon excitation of a broad range of fluorescent molecules, including UV probes.

  4. Two-photon-excited fluorescence spectroscopy of atomic fluorine at 170 nm

    Science.gov (United States)

    Herring, G. C.; Dyer, Mark J.; Jusinski, Leonard E.; Bischel, William K.

    1988-01-01

    Two-photon-excited fluorescence spectroscopy of atomic fluorine is reported. A doubled dye laser at 286-nm is Raman shifted in H2 to 170 nm (sixth anti-Stokes order) to excite ground-state 2P(0)J fluorine atoms to the 2D(0)J level. The fluorine atoms are detected by one of two methods: observing the fluorescence decay to the 2PJ level or observing F(+) production through the absorption of an additional photon by the excited atoms. Relative two-photon absorption cross sections to and the radiative lifetimes of the 2D(0)J states are measured.

  5. Combined Raman and continuous-wave-excited two-photon fluorescence cell imaging

    NARCIS (Netherlands)

    Uzunbajakava, N.; Otto, Cornelis

    2003-01-01

    We demonstrate a confocal optical microscope that combines cw two-photon-excited fluorescence microscopy with confocal Raman microscopy. With this microscope fast image acquisition with fluorescence imaging can be used to select areas of interest for subsequent chemical analysis with spontaneous

  6. Diagnostics of MCF plasmas using Lyman-α fluorescence excited by one or two photons

    International Nuclear Information System (INIS)

    Voslamber, D.

    1998-11-01

    Laser-induced Lyman-α fluorescence of the hydrogen isotopes is investigated with regard to diagnostic applications in magnetically confined fusion plasmas. A formal analysis is presented for two excitation schemes: one-photon and Doppler-free two-photon excitation. The analysis includes estimates of the expected experimental errors arising from the photon noise and from the sensitivity of the observed fluorescence signals to variations of the plasma and laser parameters. Both excitation schemes are suitable primarily for application in the plasma edge, but even in the plasma bulk of large machines they can still be applied in combination with a diagnostic neutral beam. The two-photon excitation scheme is particularly attractive because it involves absorption spectra that are resolved within the Doppler width. This implies a large diagnostic potential and in particular offers a way to measure the deuterium-tritium fuel mix in fusion reactors. (author)

  7. Two-photon excited fluorescence microscopy application for ex vivo investigation of ocular fundus samples

    Science.gov (United States)

    Peters, Sven; Hammer, Martin; Schweitzer, Dietrich

    2011-07-01

    Two-photon excited fluorescence (TPEF) imaging of ocular tissue has recently become a promising tool in ophthalmology for diagnostic and research purposes. The feasibility and the advantages of TPEF imaging, namely deeper tissue penetration and improved high-resolution imaging of microstructures, have been demonstrated lately using human ocular samples. The autofluorescence properties of endogenous fluorophores in ocular fundus tissue are well known from spectrophotometric analysis. But fluorophores, especially when it comes to fluorescence lifetime, typically display a dependence of their fluorescence properties on local environmental parameters. Hence, a more detailed investigation of ocular fundus autofluorescence ideally in vivo is of utmost interest. The aim of this study is to determine space-resolved the stationary and time-resolved fluorescence properties of endogenous fluorophores in ex vivo porcine ocular fundus samples by means of two-photon excited fluorescence spectrum and lifetime imaging microscopy (FSIM/FLIM). By our first results, we characterized the autofluorescence of individual anatomical structures of porcine retina samples excited at 760 nm. The fluorescence properties of almost all investigated retinal layers are relatively homogenous. But as previously unknown, ganglion cell bodies show a significantly shorter fluorescence lifetime compared to the adjacent mueller cells. Since all retinal layers exhibit bi-exponential autofluorescence decays, we were able to achieve a more precise characterization of fluorescence properties of endogenous fluorophores compared to a present in vivo FLIM approach by confocal scanning laser ophthalmoscope (cSLO).

  8. Bulky Counterions: Enhancing the Two-Photon Excited Fluorescence of Gold Nanoclusters.

    Science.gov (United States)

    Bertorelle, Franck; Moulin, Christophe; Soleilhac, Antonin; Comby-Zerbino, Clothilde; Dugourd, Philippe; Russier-Antoine, Isabelle; Brevet, Pierre-François; Antoine, Rodolphe

    2018-01-19

    Increasing fluorescence quantum yields of ligand-protected gold nanoclusters has attracted wide research interest. The strategy consisting in using bulky counterions has been found to dramatically enhance the fluorescence. In this Communication, we push forward this concept to the nonlinear optical regime. We show that by an appropriate choice of bulky counterions and of solvent, a 30-fold increase in two-photon excited fluorescence (TPEF) signal at ≈600 nm for gold nanoclusters can be obtained. This would correspond to a TPEF cross-section in the range of 0.1 to 1 GM. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Diagnosis of basal cell carcinoma by two photon excited fluorescence combined with lifetime imaging

    Science.gov (United States)

    Fan, Shunping; Peng, Xiao; Liu, Lixin; Liu, Shaoxiong; Lu, Yuan; Qu, Junle

    2014-02-01

    Basal cell carcinoma (BCC) is the most common type of human skin cancer. The traditional diagnostic procedure of BCC is histological examination with haematoxylin and eosin staining of the tissue biopsy. In order to reduce complexity of the diagnosis procedure, a number of noninvasive optical methods have been applied in skin examination, for example, multiphoton tomography (MPT) and fluorescence lifetime imaging microscopy (FLIM). In this study, we explored two-photon optical tomography of human skin specimens using two-photon excited autofluorescence imaging and FLIM. There are a number of naturally endogenous fluorophores in skin sample, such as keratin, melanin, collagen, elastin, flavin and porphyrin. Confocal microscopy was used to obtain structures of the sample. Properties of epidermic and cancer cells were characterized by fluorescence emission spectra, as well as fluorescence lifetime imaging. Our results show that two-photon autofluorescence lifetime imaging can provide accurate optical biopsies with subcellular resolution and is potentially a quantitative optical diagnostic method in skin cancer diagnosis.

  10. Two photon versus one photon fluorescence excitation in whispering gallery mode microresonators

    International Nuclear Information System (INIS)

    Pastells, Carme; Marco, M.-Pilar; Merino, David; Loza-Alvarez, Pablo; Pasquardini, Laura; Lunelli, Lorenzo; Pederzolli, Cecilia; Daldosso, Nicola; Farnesi, Daniele; Berneschi, Simone; Righini, Giancarlo C.; Quercioli, Franco; Nunzi Conti, Gualtiero; Soria, Silvia

    2016-01-01

    We investigate the feasibility of both one photon and two photon fluorescence excitation using whispering gallery mode microresonators. We report the linear and non linear fluorescence real-time detection of labeled IgG covalently bonded to the surface of a silica whispering gallery mode resonator (WGMR). The immunoreagents have been immobilized onto the surface of the WGMR sensor after being activated with an epoxy silane and an orienting layer. The developed immunosensor presents great potential as a robust sensing device for fast and early detection of immunoreactions. We also investigate the potential of microbubbles as nonlinear enhancement platform. The dyes used in these studies are dylight800, tetramethyl rhodamine isothiocyanate, rhodamine 6G and fluorescein. All measurements were performed in a modified confocal microscope. - Highlights: • One photon fluorescence overlaps with the semiconductor pump laser gain bandwidth. • We report on the feasibility to excite two photon fluorescence in microbubble resonators. • Our functionalization process maintains a good quality factor of the microresonator.

  11. Two photon versus one photon fluorescence excitation in whispering gallery mode microresonators

    Energy Technology Data Exchange (ETDEWEB)

    Pastells, Carme; Marco, M.-Pilar [Nanobiotechnology for Diagnostics Group (Nb4Dg), IQAC-CSIC, 08034 Barcelona (Spain); CIBER de Bioingeniería, Biomateriales y Nanomedicina, 08034 Barcelona (Spain); Merino, David; Loza-Alvarez, Pablo [ICFO-Institut de Ciències Fotòniques, Castelldefels, 08860 Barcelona (Spain); Pasquardini, Laura [Fondazione Bruno Kessler, 38123 Povo, TN (Italy); Lunelli, Lorenzo [Fondazione Bruno Kessler, 38123 Povo, TN (Italy); IBF-CNR, 38123 Povo, TN (Italy); Pederzolli, Cecilia [Fondazione Bruno Kessler, 38123 Povo, TN (Italy); Daldosso, Nicola [Department of Computer Science, University of Verona, Strada le Grazie 15, 37134 Verona (Italy); Farnesi, Daniele [CNR-IFAC “Nello Carrara” Institute of Applied Physics, 50019 Sesto Fiorentino, FI (Italy); Museo Storico della Fisica e Centro Studi e Ricerche “E. Fermi”, 00184 Roma (Italy); Berneschi, Simone [CNR-IFAC “Nello Carrara” Institute of Applied Physics, 50019 Sesto Fiorentino, FI (Italy); Righini, Giancarlo C. [CNR-IFAC “Nello Carrara” Institute of Applied Physics, 50019 Sesto Fiorentino, FI (Italy); Museo Storico della Fisica e Centro Studi e Ricerche “E. Fermi”, 00184 Roma (Italy); Quercioli, Franco [CNR-INO National Institute of Optics, Sesto Fiorentino, FI (Italy); Nunzi Conti, Gualtiero [CNR-IFAC “Nello Carrara” Institute of Applied Physics, 50019 Sesto Fiorentino, FI (Italy); Soria, Silvia, E-mail: s.soria@ifac.cnr.it [CNR-IFAC “Nello Carrara” Institute of Applied Physics, 50019 Sesto Fiorentino, FI (Italy)

    2016-02-15

    We investigate the feasibility of both one photon and two photon fluorescence excitation using whispering gallery mode microresonators. We report the linear and non linear fluorescence real-time detection of labeled IgG covalently bonded to the surface of a silica whispering gallery mode resonator (WGMR). The immunoreagents have been immobilized onto the surface of the WGMR sensor after being activated with an epoxy silane and an orienting layer. The developed immunosensor presents great potential as a robust sensing device for fast and early detection of immunoreactions. We also investigate the potential of microbubbles as nonlinear enhancement platform. The dyes used in these studies are dylight800, tetramethyl rhodamine isothiocyanate, rhodamine 6G and fluorescein. All measurements were performed in a modified confocal microscope. - Highlights: • One photon fluorescence overlaps with the semiconductor pump laser gain bandwidth. • We report on the feasibility to excite two photon fluorescence in microbubble resonators. • Our functionalization process maintains a good quality factor of the microresonator.

  12. Simple fibre based dispersion management for two-photon excited fluorescence imaging through an endoscope

    DEFF Research Database (Denmark)

    Dimopoulos, Konstantinos; Marti, Dominik; Andersen, Peter E.

    2018-01-01

    We want to implement two-photon excitation fluorescence microscopy (TPEFM) into endoscopes, since TPEFM can provide relevant biomarkers for cancer staging and grading in hollow organs, endoscopically accessible through natural orifices. However, many obstacles must be overcome, among others...... the delivery of short laser pulses to the distal end of the endoscope. To this avail, we present imaging results using an all-fibre dispersion management scheme in a TPEFM setup. The scheme has been conceived by Jespersen et al. in 20101 and relies on the combination of a single mode fibre with normal...

  13. Adapting a compact confocal microscope system to a two-photon excitation fluorescence imaging architecture.

    Science.gov (United States)

    Diaspro, A; Corosu, M; Ramoino, P; Robello, M

    1999-11-01

    Within the framework of a national National Institute of Physics of Matter (INFM) project, we have realised a two-photon excitation (TPE) fluorescence microscope based on a new generation commercial confocal scanning head. The core of the architecture is a mode-locked Ti:Sapphire laser (Tsunami 3960, Spectra Physics Inc., Mountain View, CA) pumped by a high-power (5 W, 532 nm) laser (Millennia V, Spectra Physics Inc.) and an ultracompact confocal scanning head, Nikon PCM2000 (Nikon Instruments, Florence, Italy) using a single-pinhole design. Three-dimensional point-spread function has been measured to define spatial resolution performances. The TPE microscope has been used with a wide range of excitable fluorescent molecules (DAPI, Fura-2, Indo-1, DiOC(6)(3), fluoresceine, Texas red) covering a single photon spectral range from UV to green. An example is reported on 3D imaging of the helical structure of the sperm head of the Octopus Eledone cirrhosa labelled with an UV excitable dye, i.e., DAPI. The system can be easily switched for operating both in conventional and two-photon mode. Copyright 1999 Wiley-Liss, Inc.

  14. Stimulated emission depletion following two photon excitation

    OpenAIRE

    Marsh, R. J.; Armoogum, D. A.; Bain, A. J.

    2002-01-01

    The technique of stimulated emission depletion of fluorescence (STED) from a two photon excited molecular population is demonstrated in the S, excited state of fluorescein in ethylene glycol and methanol. Two photon excitation (pump) is achieved using the partial output of a regeneratively amplified Ti:Sapphire laser in conjunction with an optical parametric amplifier whose tuneable output provides a synchronous depletion (dump) pulse. Time resolved fluorescence intensity and anisotropy measu...

  15. Stratum corneum lipid organization as observed by atomic force, confocal and two-photon excitation fluorescence microscopy

    DEFF Research Database (Denmark)

    Norlén, Lars; Plasencia Gil, Maria Inés; Bagatolli, Luis

    2008-01-01

    -related biophysical techniques (e.g. atomic force microscopy and confocal/two-photon excitation fluorescence microscopy), it was recently shown that reconstituted membranes composed of extracted decontaminated human stratum corneum lipids do not form a fluid phase, but exclusively a single-gel phase that segregates...

  16. Two-photon excited fluorescence spectroscopy and imaging of melanin in vitro and in vivo

    Science.gov (United States)

    Krasieva, Tatiana B.; Liu, Feng; Sun, Chung-Ho; Kong, Yu; Balu, Mihaela; Meyskens, Frank L.; Tromberg, Bruce J.

    2012-03-01

    The ability to detect early melanoma non-invasively would improve clinical outcome and reduce mortality. Recent advances in two-photon excited fluorescence (TPEF) in vivo microscopy offer a powerful tool in early malignant melanoma diagnostics. The goal of this work was to develop a TPEF optical index for measuring relative concentrations of eumelanin and pheomelanin since ex vivo studies show that changes in this ratio have been associated with malignant transformation. We acquired TPEF emission spectra (λex=1000 nm) of melanin from several specimens, including human hair, malignant melanoma cell lines, and normal melanocytes and keratinocytes in different skin layers (epidermis, papillary dermis) in five healthy volunteers in vivo. We found that the pheomelanin emission peaks at around 620 nm and is blue-shifted from the eumelanin with broad maximum at 640-680nm. We defined "optical melanin index" (OMI) as a ratio of fluorescence signal intensities measured at 645 nm and 615nm. The measured OMI for a melanoma cell line MNT-1 was 1.6+/-0.2. The MNT-46 and MNT-62 lines (Mc1R gene knockdown) showed an anticipated change in melanins production ratio and had OMI of 0.55+/-0.05 and 0.17+/-0.02, respectively, which strongly correlated with HPLC data obtained for these lines. Average OMI measured for basal cells layers (melanocytes and keratinocytes) in normal human skin type I, II-III (not tanned and tanned) in vivo was 0.5, 1.05 and 1.16 respectively. We could not dependably detect the presence of pheomelanin in highly pigmented skin type V-VI. These data suggest that a non-invasive TPEF index could potentially be used for rapid melanin ratio characterization both in vitro and in vivo, including pigmented lesions.

  17. Water-Soluble Triarylborane Chromophores for One- and Two-Photon Excited Fluorescence Imaging of Mitochondria in Cells.

    Science.gov (United States)

    Griesbeck, Stefanie; Zhang, Zuolun; Gutmann, Marcus; Lühmann, Tessa; Edkins, Robert M; Clermont, Guillaume; Lazar, Adina N; Haehnel, Martin; Edkins, Katharina; Eichhorn, Antonius; Blanchard-Desce, Mireille; Meinel, Lorenz; Marder, Todd B

    2016-10-04

    Three water-soluble tetracationic quadrupolar chromophores comprising two three-coordinate boron π-acceptor groups bridged by thiophene-containing moieties were synthesised for biological imaging applications. Compound 3 containing the bulkier 5-(3,5-Me2 C6 H2 )-2,2'-(C4 H2 S)2 -5'-(3,5-Me2 C6 H2 ) bridge is stable over a long period of time, exhibits a high fluorescence quantum yield and strong one- and two-photon absorption (TPA), and has a TPA cross section of 268 GM at 800 nm in water. Confocal laser scanning fluorescence microscopy studies in live cells indicated localisation of the chromophore at the mitochondria; moreover, cytotoxicity measurements proved biocompatibility. Thus, chromophore 3 has excellent potential for one- and two-photon-excited fluorescence imaging of mitochondrial function in cells. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Two-photon excitation with pico-second fluorescence lifetime imaging to detect nuclear association of flavanols

    Energy Technology Data Exchange (ETDEWEB)

    Mueller-Harvey, Irene, E-mail: i.mueller-harvey@reading.ac.uk [Chemistry and Biochemistry Laboratory, Food Production and Quality Research Division, School of Agriculture, Policy and Development, University of Reading, P O Box 236, Reading RG6 6AT (United Kingdom); Feucht, Walter, E-mail: walter.feucht@gmail.com [Department of Plant Sciences, Technical University of Munich (TUM), Wissenschaftszentrum Weihenstephan (WZW), D-85354 Freising (Germany); Polster, Juergen, E-mail: j.polster@wzw.tum.de [Department of Physical Biochemistry, Technical University of Munich (TUM), Wissenschaftszentrum Weihenstephan (WZW), D-85354 Freising (Germany); Trnkova, Lucie, E-mail: lucie.trnkova@uhk.cz [University of Hradec Kralove, Faculty of Science, Department of Chemistry, Rokitanskeho 62, 50003 Hradec Kralove (Czech Republic); Burgos, Pierre, E-mail: pierre.burgos@stfc.ac.uk [Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell-Oxford, Didcot, Oxfordshire, OX11 0QX (United Kingdom); Parker, Anthony W., E-mail: tony.parker@stfc.ac.uk [Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell-Oxford, Didcot, Oxfordshire, OX11 0QX (United Kingdom); Botchway, Stanley W., E-mail: stan.botchway@stfc.ac.uk [Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell-Oxford, Didcot, Oxfordshire, OX11 0QX (United Kingdom)

    2012-03-16

    Highlights: Black-Right-Pointing-Pointer This fluorescence lifetime imaging microscopy (FLIM) technique for flavanols overcomes autofluorescence interference in cells. Black-Right-Pointing-Pointer Plant flavanols differed in their lifetimes. Black-Right-Pointing-Pointer Dissolved and bound flavanols revealed contrasting lifetime changes. Black-Right-Pointing-Pointer This technique will allow studying of flavanol trafficking in live cells. - Abstract: Two-photon excitation enabled for the first time the observation and measurement of excited state fluorescence lifetimes from three flavanols in solution, which were {approx}1.0 ns for catechin and epicatechin, but <45 ps for epigallocatechin gallate (EGCG). The shorter lifetime for EGCG is in line with a lower fluorescence quantum yield of 0.003 compared to catechin (0.015) and epicatechin (0.018). In vivo experiments with onion cells demonstrated that tryptophan and quercetin, which tend to be major contributors of background fluorescence in plant cells, have sufficiently low cross sections for two-photon excitation at 630 nm and therefore do not interfere with detection of externally added or endogenous flavanols in Allium cepa or Taxus baccata cells. Applying two-photon excitation to flavanols enabled 3-D fluorescence lifetime imaging microscopy and showed that added EGCG penetrated the whole nucleus of onion cells. Interestingly, EGCG and catechin showed different lifetime behaviour when bound to the nucleus: EGCG lifetime increased from <45 to 200 ps, whilst catechin lifetime decreased from 1.0 ns to 500 ps. Semi-quantitative measurements revealed that the relative ratios of EGCG concentrations in nucleoli associated vesicles: nucleus: cytoplasm were ca. 100:10:1. Solution experiments with catechin, epicatechin and histone proteins provided preliminary evidence, via the appearance of a second lifetime ({tau}{sub 2} = 1.9-3.1 ns), that both flavanols may be interacting with histone proteins. We conclude that there

  19. Application of laser fluorescence spectroscopy by two-photon excitation into atomic hydrogen density measurement in reactive plasmas

    International Nuclear Information System (INIS)

    Kajiwara, Toshinori; Takeda, Kazuyuki; Kim, Hee Je; Park, Won Zoo; Muraoka, Katsunori; Akazaki, Masanori; Okada, Tatsuo; Maeda, Mitsuo.

    1990-01-01

    Density profiles of hydrogen atoms in reactive plasmas of hydrogen and methane gases were measured, for the first time, using the laser fluorescence spectroscopy by two-photon excitation of Lyman beta transition and observation at the Balmer alpha radiation. Absolute density determinations showed atomic densities of around 3 x 10 17 m -3 , or the degree of dissociation to be 10 -4 . Densities along the axis perpendicular to the RF electrode showed peaked profiles, which were due to the balance of atomic hydrogen production by electron impact on molecules against diffusion loss to the walls. (author)

  20. Mercury effects on Thalassiosira weissflogii: Applications of two-photon excitation chlorophyll fluorescence lifetime imaging and flow cytometry

    International Nuclear Information System (INIS)

    Wu Yun; Zeng Yan; Qu, Jianan Y.; Wang Wenxiong

    2012-01-01

    The toxic effects of inorganic mercury [Hg(II)] and methylmercury (MeHg) on the photosynthesis and population growth in a marine diatom Thalassiosira weissflogii were investigated using two methods: two-photon excitation fluorescence lifetime imaging (FLIM) and flow cytometry (FCM). For photosynthesis, Hg(II) exposure increased the average chlorophyll fluorescence lifetime, whereas such increment was not found under MeHg stress. This may be caused by the inhibitory effect of Hg(II) instead of MeHg on the electron transport chain. For population growth, modeled specific growth rate data showed that the reduction in population growth by Hg(II) mainly resulted from an increased number of injured cells, while the live cells divided at the normal rates. However, MeHg inhibitory effects on population growth were contributed by the reduced division rates of all cells. Furthermore, the cell images and the FCM data reflected the morphological changes of diatom cells under Hg(II)/MeHg exposure vividly and quantitatively. Our results demonstrated that the toxigenicity mechanisms between Hg(II) and MeHg were different in the algal cells.

  1. Volumetric label-free imaging and 3D reconstruction of mammalian cochlea based on two-photon excitation fluorescence microscopy

    International Nuclear Information System (INIS)

    Zhang, Xianzeng; Zhan, Zhenlin; Xie, Shusen; Geng, Yang; Ye, Qing

    2013-01-01

    The visualization of the delicate structure and spatial relationship of intracochlear sensory cells has relied on the laborious procedures of tissue excision, fixation, sectioning and staining for light and electron microscopy. Confocal microscopy is advantageous for its high resolution and deep penetration depth, yet disadvantageous due to the necessity of exogenous labeling. In this study, we present the volumetric imaging of rat cochlea without exogenous dyes using a near-infrared femtosecond laser as the excitation mechanism and endogenous two-photon excitation fluorescence (TPEF) as the contrast mechanism. We find that TPEF exhibits strong contrast, allowing cellular and even subcellular resolution imaging of the cochlea, differentiating cell types, visualizing delicate structures and the radial nerve fiber. Our results further demonstrate that 3D reconstruction rendered with z-stacks of optical sections enables better revealment of fine structures and spatial relationships, and easily performed morphometric analysis. The TPEF-based optical biopsy technique provides great potential for new and sensitive diagnostic tools for hearing loss or hearing disorders, especially when combined with fiber-based microendoscopy. (paper)

  2. Endogenous Two-Photon Excited Fluorescence Provides Label-Free Visualization of the Inflammatory Response in the Rodent Spinal Cord

    Directory of Open Access Journals (Sweden)

    Ortrud Uckermann

    2015-01-01

    Full Text Available Activation of CNS resident microglia and invasion of external macrophages plays a central role in spinal cord injuries and diseases. Multiphoton microscopy based on intrinsic tissue properties offers the possibility of label-free imaging and has the potential to be applied in vivo. In this work, we analyzed cellular structures displaying endogenous two-photon excited fluorescence (TPEF in the pathologic spinal cord. It was compared qualitatively and quantitatively to Iba1 and CD68 immunohistochemical staining in two models: rat spinal cord injury and mouse encephalomyelitis. The extent of tissue damage was retrieved by coherent anti-Stokes Raman scattering (CARS and second harmonic generation imaging. The pattern of CD68-positive cells representing postinjury activated microglia/macrophages was colocalized to the TPEF signal. Iba1-positive microglia were found in areas lacking any TPEF signal. In peripheral areas of inflammation, we found similar numbers of CD68-positive microglia/macrophages and TPEF-positive structures while the number of Iba1-positive cells was significantly higher. Therefore, we conclude that multiphoton imaging of unstained spinal cord tissue enables retrieving the extent of microglia activation by acquisition of endogenous TPEF. Future application of this technique in vivo will enable monitoring inflammatory responses of the nervous system allowing new insights into degenerative and regenerative processes.

  3. Endogenous Two-Photon Excited Fluorescence Provides Label-Free Visualization of the Inflammatory Response in the Rodent Spinal Cord

    Science.gov (United States)

    Uckermann, Ortrud; Galli, Roberta; Beiermeister, Rudolf; Sitoci-Ficici, Kerim-Hakan; Later, Robert; Leipnitz, Elke; Chavakis, Triantafyllos; Koch, Edmund; Schackert, Gabriele; Steiner, Gerald; Kirsch, Matthias

    2015-01-01

    Activation of CNS resident microglia and invasion of external macrophages plays a central role in spinal cord injuries and diseases. Multiphoton microscopy based on intrinsic tissue properties offers the possibility of label-free imaging and has the potential to be applied in vivo. In this work, we analyzed cellular structures displaying endogenous two-photon excited fluorescence (TPEF) in the pathologic spinal cord. It was compared qualitatively and quantitatively to Iba1 and CD68 immunohistochemical staining in two models: rat spinal cord injury and mouse encephalomyelitis. The extent of tissue damage was retrieved by coherent anti-Stokes Raman scattering (CARS) and second harmonic generation imaging. The pattern of CD68-positive cells representing postinjury activated microglia/macrophages was colocalized to the TPEF signal. Iba1-positive microglia were found in areas lacking any TPEF signal. In peripheral areas of inflammation, we found similar numbers of CD68-positive microglia/macrophages and TPEF-positive structures while the number of Iba1-positive cells was significantly higher. Therefore, we conclude that multiphoton imaging of unstained spinal cord tissue enables retrieving the extent of microglia activation by acquisition of endogenous TPEF. Future application of this technique in vivo will enable monitoring inflammatory responses of the nervous system allowing new insights into degenerative and regenerative processes. PMID:26355949

  4. Fluorescence excitation analysis by two-photon confocal laser scanning microscopy: a new method to identify fluorescent nanoparticles on histological tissue sections

    Directory of Open Access Journals (Sweden)

    Kahn E

    2012-10-01

    Full Text Available Edmond Kahn,1 Nicolas Tissot,3 Perrine Frere,3 Aurélien Dauphin,3 Mohamed Boumhras,2,4 Claude-Marie Bachelet,3 Frédérique Frouin,1 Gérard Lizard21Institut National de la Santé et de la Recherche Médicale (INSERM U678/UMR-S UPMC, CHU Pitié-Salpêtrière, Paris, France; 2Equipe Biochimie du Peroxysome, Inflammation et Métabolisme Lipidique EA7270, Faculté des Sciences Gabriel, Université de Bourgogne-INSERM Dijon, France; 3Plateforme d'Imagerie cellulaire, UPMC, Paris, France; 4Laboratory of Biochemistry and Neuroscience, Applied Toxicology Group, Faculty of Science and Technology, Settat, MoroccoAbstract: In the present study, we make use of the ability of two-photon confocal laser scanning microscopes (CLSMs equipped with tunable lasers to produce spectral excitation image sequences. Furthermore, unmixing, which is usually performed on emission image sequences, is performed on these excitation image sequences. We use factor analysis of medical image sequences (FAMIS, which produces factor images, to unmix spectral image sequences of stained structures in tissue sections to provide images of characterized stained cellular structures. This new approach is applied to histological tissue sections of mouse aorta containing labeled iron nanoparticles stained with Texas Red and counterstained with SYTO13, to obtain visual information about the accumulation of these nanoparticles in the arterial wall. The possible presence of Texas Red is determined using a two-photon CLSM associated with FAMIS via the excitation spectra. Texas Red and SYTO13 are thus differentiated, and corresponding factor images specify their possible presence and cellular localization. In conclusion, the designed protocol shows that sequences of images obtained by excitation in a two-photon CLSM enables characterization of Texas Red-stained nanoparticles and other markers. This methodology offers an alternative and complementary solution to the conventional use of emission

  5. Two-photon excitation of argon

    International Nuclear Information System (INIS)

    Pindzola, P.S.; Payne, M.C.

    1982-01-01

    The authors calculate two photon excitation parameters for various excited states of argon assuming the absorption of near resonance broad-bandwidth laser radiation. Results are given for the case of two photons absorbed for the same laser beam as well as the case of absorbing photons of different frequency from each of two laser beams. The authors use multiconfiguration Hartree-Fock wave functions to evaluate the second-order sums over matrix elements. Various experimental laser schemes are suggested for the efficient excitation and subsequent ionization of argon

  6. Details of the Collagen and Elastin Architecture in the Human Limbal Conjunctiva, Tenon's Capsule and Sclera Revealed by Two-Photon Excited Fluorescence Microscopy.

    Science.gov (United States)

    Park, Choul Yong; Marando, Catherine M; Liao, Jason A; Lee, Jimmy K; Kwon, Jiwon; Chuck, Roy S

    2016-10-01

    To investigate the architecture and distribution of collagen and elastin in human limbal conjunctiva, Tenon's capsule, and sclera. The limbal conjunctiva, Tenon's capsule, and sclera of human donor corneal buttons were imaged with an inverted two-photon excited fluorescence microscope. No fixation process was necessary. The laser (Ti:sapphire) was tuned at 850 nm for two-photon excitation. Backscatter signals of second harmonic generation (SHG) and autofluorescence (AF) were collected through a 425/30-nm and a 525/45-nm emission filter, respectively. Multiple, consecutive, and overlapping (z-stack) images were acquired. Collagen signals were collected with SHG, whereas elastin signals were collected with AF. The size and density of collagen bundles varied widely depending on depth: increasing from conjunctiva to sclera. In superficial image planes, collagen bundles were image planes (episclera and superficial sclera), collagen bundles were thicker (near 100 μm in width) and densely packed. Comparatively, elastin fibers were thinner and sparse. The orientation of elastin fibers was independent of collagen fibers in superficial layers; but in deep sclera, elastin fibers wove through collagen interbundle gaps. At the limbus, both collagen and elastin fibers were relatively compact and were distributed perpendicular to the limbal annulus. Two-photon excited fluorescence microscopy has enabled us to understand in greater detail the collagen and elastin architecture of the human limbal conjunctiva, Tenon's capsule, and sclera.

  7. Scanless two-photon excitation of channelrhodopsin-2

    DEFF Research Database (Denmark)

    Papagiakoumou, E.; Anselmi, F.; Bègue, A.

    2010-01-01

    developed a method that combines generalized phase contrast with temporal focusing (TF-GPC) to shape two-photon excitation for this purpose. The illumination patterns are generated automatically from fluorescence images of neurons and shaped to cover the cell body or dendrites, or distributed groups...... of cells. The TF-GPC two-photon excitation patterns generated large photocurrents in Channelrhodopsin-2–expressing cultured cells and neurons and in mouse acute cortical slices. The amplitudes of the photocurrents can be precisely modulated by controlling the size and shape of the excitation volume and...

  8. Fs-transient absorption and fluorescence upconversion after two- photon excitation of carotenoids in solution and in LHC II

    CERN Document Server

    Wall, P J; Fleming, G R

    2000-01-01

    With time resolved two-photon techniques we determined the lifetime and two-photon spectrum of the forbidden S/sub 1/ state of beta - carotene (9+or-0.2 ps), lutein (15+or-0.5 ps) and the energy transferring carotenoids in LHC II (250+or-50 fs). (7 refs).

  9. Uniform silica nanoparticles encapsulating two-photon absorbing fluorescent dye

    International Nuclear Information System (INIS)

    Wu Weibing; Liu Chang; Wang Mingliang; Huang Wei; Zhou Shengrui; Jiang Wei; Sun Yueming; Cui Yiping; Xu Chunxinag

    2009-01-01

    We have prepared uniform silica nanoparticles (NPs) doped with a two-photon absorbing zwitterionic hemicyanine dye by reverse microemulsion method. Obvious solvatochromism on the absorption spectra of dye-doped NPs indicates that solvents can partly penetrate into the silica matrix and then affect the ground and excited state of dye molecules. For dye-doped NP suspensions, both one-photon and two-photon excited fluorescence are much stronger and recorded at shorter wavelength compared to those of free dye solutions with comparative overall dye concentration. This behavior is possibly attributed to the restricted twisted intramolecular charge transfer (TICT), which reduces fluorescence quenching when dye molecules are trapped in the silica matrix. Images from two-photon laser scanning fluorescence microscopy demonstrate that the dye-doped silica NPs can be actively uptaken by Hela cells with low cytotoxicity. - Graphical abstract: Water-soluble silica NPs doped with a two-photon absorbing zwitterionic hemicyanine dye were prepared. They were found of enhanced one-photon and two-photon excited fluorescence compared to free dye solutions. Images from two-photon laser scanning fluorescence microscopy demonstrate that the dye-doped silica NPs can be actively uptaken by Hela cells.

  10. Two-photon excited fluorescence from higher electronic states of chlorophylls in photosynthetic antenna complexes a new approach to detect strong excitonic chlorophyll a/b coupling

    CERN Document Server

    Leupold, D; Ehlert, J; Irrgang, K D; Renger, G; Lokstein, H

    2002-01-01

    Stepwise two-photon excitation of chlorophyll a and b in the higher plant main light-harvesting complex (LHC II) and the minor complex CP29 (as well as in organic solution) with 100-fs pulses in the Q/sub y/ region results in a weak blue fluorescence. The dependence of the spectral shape of the blue fluorescence on excitation wavelength offers a new approach to elucidate the long-standing problem of the origin of spectral "chlorophyll forms" in pigment-protein complexes, in particular the characterization of chlorophyll a/b-heterodimers. As a first result we present evidence for the existence of strong chlorophyll a/b-interactions (excitonically coupled transitions at 650 and 680 nm) in LHC II at ambient temperature. In comparison with LHC II, the experiments with CP29 provide further evidence that the lowest energy chlorophyll a transition (at ~680 nm) is not excitonically coupled to chlorophyll b. (22 refs).

  11. Effect of detergents on the physico-chemical properties of skin stratum corneum: A two-photon excitation fluorescence microscopy study

    DEFF Research Database (Denmark)

    Bloksgaard, Maria; Brewer, Jonathan R.; Pashkovski, Eugene

    2014-01-01

    OBJECTIVE: Understanding the structural and dynamical features of skin is critical for advancing innovation in personal care and drug discovery. Synthetic detergent mixtures used in commercially available body wash products are thought to be less aggressive towards the skin barrier when compared...... to conventional detergents. The aim of this work is to comparatively characterize the effect of a mild synthetic cleanser mixture (SCM) and sodium dodecyl sulphate (SDS) on the hydration state of the intercellular lipid matrix and on proton activity of excised skin stratum corneum (SC). METHOD: Experiments were...... performed using two-photon excitation fluorescence microscopy. Fluorescent images of fluorescence reporters sensitive to proton activity and hydration of SC were obtained in excised skin and examined in presence and absence of SCM and SDS detergents. RESULTS: Hydration of the intercellular lipid matrix...

  12. Doppler-free two-photon excitation of 238U

    International Nuclear Information System (INIS)

    Hodgkinson, D.P.; Wort, D.J.H.

    1981-04-01

    A theory of resonantly enhanced two-photon absorption is presented and tested in a number of experiments in which 238 U vapour is excited by two continuous wave dye lasers. Good quantitative agreement between theory and experiment is found. In particular the central prediction of the theory, that antiparallel laser beams of modest intensity can pump an appreciable fraction of the Maxwell velocity distribution, has been checked directly by measuring the spectral width of the fluorescence from the two-photon excited level. (author)

  13. The translated conceptual survey of physics / stablization of the focal plane in two photon excitation fluorescence microscopy

    Science.gov (United States)

    Wada, Asma

    As a reflection of my career to be an effective college physics teacher, my thesis is in two parts. The first is in education research, the focus of this part is to have a tool to evaluate pedagogies I have learned at the school and plan to apply in my classrooms back home. Consequently, this resulted in the development of the translated conceptual survey of physics ( TCSP). (TCSP) was designed by combining some questions from the Force Conceptual Inventory (FCI), and the Conceptual Survey of Electricity and Magnetism (CSEM) to assess student's understanding of basic concepts of Newtonian mechanics and electricity and magnetism in introductory physics. The idea of developing this questionnaire is to use it in classrooms back home as a part of a long term objective to implement what has been realized in the area of education research to improve the quality of teaching physics there. The survey was initially written in English, validated with interviews with native English speakers, translated into Arabic, and then validated via an interview with a native Arabic speaker. We then administered the survey to two different English-speaking intro physics courses and analyzed the results for consistency. The objective of the second part in my thesis is to expand my knowledge in an area of physics that I have interest in, and getting involved in a scientific research to develop skills I need as a teacher. My research is in optical physics, in particular, I am working on one of the challenges in implementing two photon excitation luorescence (TPEF) microscopy in imaging living systems. (TPEF) microscopy has been shown to be an invaluable tool for investigating biological structure and function in living organisms. The utility of (TPEF) imaging for this application arises from several important factors including it's ability to image deep within tissue, and to do so without harming the organism. Both of these advantages arise from the fact that (TPEF) imaging is done with

  14. Nonlinear spectral imaging of human normal skin, basal cell carcinoma and squamous cell carcinoma based on two-photon excited fluorescence and second-harmonic generation

    Science.gov (United States)

    Xiong, S. Y.; Yang, J. G.; Zhuang, J.

    2011-10-01

    In this work, we use nonlinear spectral imaging based on two-photon excited fluorescence (TPEF) and second harmonic generation (SHG) for analyzing the morphology of collagen and elastin and their biochemical variations in basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and normal skin tissue. It was found in this work that there existed apparent differences among BCC, SCC and normal skin in terms of their thickness of the keratin and epithelial layers, their size of elastic fibers, as well as their distribution and spectral characteristics of collagen. These differences can potentially be used to distinguish BCC and SCC from normal skin, and to discriminate between BCC and SCC, as well as to evaluate treatment responses.

  15. Laser fluorescence spectroscopy by two-photon excitation for detection of hydrogen atoms in a periphery region of high temperature plasmas

    International Nuclear Information System (INIS)

    Kim, Hee-Je; Kajiwara, Toshinori; Motoyama, Sumio; Muraoka, Katsunori; Akazaki, Masanori; Okada, Tatsuo; Maeda, Mitsuo

    1989-01-01

    For measurements of atomic hydrogen density in the periphery region of high temperature plasmas, laser fluorescence spectroscopy (LFS) by two-photon excitation (1s-3s, 3d) was developed. Based upon the theoretical estimates for laser source requirements, which indicated the laser energy and spectral width to be more than 10 mJ (assuming the pulse duration of 10 ns) and several tens of picometers around the wavelength of 205.1 nm, respectively, the first Stokes generation in deuterium gas of ArF laser output was adopted and shown to have the necessary performance. Through the LFS experiment employing the laser source, the minimum detectable limit of atomic hydrogen, normalized by a laser power and an observing solid angle, was demonstrated to be 1 x 10 14 [m -3 · MW · sr], which is usually sufficient for the above purpose, and the accuracy of the density determination was shown to be within a factor 2. (author)

  16. Correlating two-photon excited fluorescence imaging of breast cancer cellular redox state with seahorse flux analysis of normalized cellular oxygen consumption

    Science.gov (United States)

    Hou, Jue; Wright, Heather J.; Chan, Nicole; Tran, Richard; Razorenova, Olga V.; Potma, Eric O.; Tromberg, Bruce J.

    2016-06-01

    Two-photon excited fluorescence (TPEF) imaging of the cellular cofactors nicotinamide adenine dinucleotide and oxidized flavin adenine dinucleotide is widely used to measure cellular metabolism, both in normal and pathological cells and tissues. When dual-wavelength excitation is used, ratiometric TPEF imaging of the intrinsic cofactor fluorescence provides a metabolic index of cells-the "optical redox ratio" (ORR). With increased interest in understanding and controlling cellular metabolism in cancer, there is a need to evaluate the performance of ORR in malignant cells. We compare TPEF metabolic imaging with seahorse flux analysis of cellular oxygen consumption in two different breast cancer cell lines (MCF-7 and MDA-MB-231). We monitor metabolic index in living cells under both normal culture conditions and, for MCF-7, in response to cell respiration inhibitors and uncouplers. We observe a significant correlation between the TPEF-derived ORR and the flux analyzer measurements (R=0.7901, p<0.001). Our results confirm that the ORR is a valid dynamic index of cell metabolism under a range of oxygen consumption conditions relevant for cancer imaging.

  17. Label-free imaging of brain and brain tumor specimens with combined two-photon excited fluorescence and second harmonic generation microscopy

    Science.gov (United States)

    Jiang, Liwei; Wang, Xingfu; Wu, Zanyi; Du, Huiping; Wang, Shu; Li, Lianhuang; Fang, Na; Lin, Peihua; Chen, Jianxin; Kang, Dezhi; Zhuo, Shuangmu

    2017-10-01

    Label-free imaging techniques are gaining acceptance within the medical imaging field, including brain imaging, because they have the potential to be applied to intraoperative in situ identifications of pathological conditions. In this paper, we describe the use of two-photon excited fluorescence (TPEF) and second harmonic generation (SHG) microscopy in combination for the label-free detection of brain and brain tumor specimens; gliomas. Two independently detecting channels were chosen to subsequently collect TPEF/SHG signals from the specimen to increase TPEF/SHG image contrasts. Our results indicate that the combined TPEF/SHG microscopic techniques can provide similar rat brain structural information and produce a similar resolution like conventional H&E staining in neuropathology; including meninges, cerebral cortex, white-matter structure corpus callosum, choroid plexus, hippocampus, striatum, and cerebellar cortex. It can simultaneously detect infiltrating human brain tumor cells, the extracellular matrix collagen fiber of connective stroma within brain vessels and collagen depostion in tumor microenvironments. The nuclear-to-cytoplasmic ratio and collagen content can be extracted as quantitative indicators for differentiating brain gliomas from healthy brain tissues. With the development of two-photon fiberscopes and microendoscope probes and their clinical applications, the combined TPEF and SHG microcopy may become an important multimodal, nonlinear optical imaging approach for real-time intraoperative histological diagnostics of residual brain tumors. These occur in various brain regions during ongoing surgeries through the method of simultaneously identifying tumor cells, and the change of tumor microenvironments, without the need for the removal biopsies and without the need for tissue labelling or fluorescent markers.

  18. Enhanced Emission from Single Isolated Gold Quantum Dots Investigated Using Two-Photon-Excited Fluorescence Near-Field Scanning Optical Microscopy.

    Science.gov (United States)

    Abeyasinghe, Neranga; Kumar, Santosh; Sun, Kai; Mansfield, John F; Jin, Rongchao; Goodson, Theodore

    2016-12-21

    New approaches in molecular nanoscopy are greatly desired for interrogation of biological, organic, and inorganic objects with sizes below the diffraction limit. Our current work investigates emergent monolayer-protected gold quantum dots (nanoclusters, NCs) composed of 25 Au atoms by utilizing two-photon-excited fluorescence (TPEF) near-field scanning optical microscopy (NSOM) at single NC concentrations. Here, we demonstrate an approach to synthesize and isolate single NCs on solid glass substrates. Subsequent investigation of the NCs using TPEF NSOM reveals that, even when they are separated by distances of several tens of nanometers, we can excite and interrogate single NCs individually. Interestingly, we observe an enhanced two-photon absorption (TPA) cross section for single Au 25 NCs that can be attributed to few-atom local field effects and to local field-induced microscopic cascading, indicating their potential for use in ultrasensitive sensing, disease diagnostics, cancer cell therapy, and molecular computers. Finally, we report room-temperature aperture-based TPEF NSOM imaging of these NCs for the first time at 30 nm point resolution, which is a ∼5-fold improvement compared to the previous best result for the same technique. This report unveils the unique combination of an unusually large TPA cross section and the high photostability of Au NCs to (non-destructively) investigate stable isolated single NCs using TPEF NSOM. This is the first reported optical study of monolayer-protected single quantum clusters, opening some very promising opportunities in spectroscopy of nanosized objects, bioimaging, ultrasensitive sensing, molecular computers, and high-density data storage.

  19. Broadband Doppler-limited two-photon and stepwise excitation spectroscopy with laser frequency combs

    Science.gov (United States)

    Hipke, Arthur; Meek, Samuel A.; Ideguchi, Takuro; Hänsch, Theodor W.; Picqué, Nathalie

    2014-07-01

    Multiplex two-photon excitation spectroscopy is demonstrated at Doppler-limited resolution. We describe first Fourier-transform two-photon spectroscopy of an atomic sample with two mode-locked laser oscillators in a dual-comb technique. Each transition is uniquely identified by the modulation imparted by the interfering comb excitations. The temporal modulation of the spontaneous two-photon fluorescence is monitored with a single photodetector, and the spectrum of all excited transitions is revealed by a Fourier transform.

  20. Two-Photon Fluorescence Microscope for Microgravity Research

    Science.gov (United States)

    Fischer, David G.; Zimmerli, Gregory A.; Asipauskas, Marius

    2005-01-01

    A two-photon fluorescence microscope has been developed for the study of biophysical phenomena. Two-photon microscopy is a novel form of laser-based scanning microscopy that enables three-dimensional imaging without many of the problems inherent in confocal microscopy. Unlike one-photon optical microscopy, two-photon microscopy utilizes the simultaneous nonlinear absorption of two near-infrared photons. However, the efficiency of two-photon absorption is much lower than that of one-photon absorption, so an ultra-fast pulsed laser source is typically employed. On the other hand, the critical energy threshold for two-photon absorption leads to fluorophore excitation that is intrinsically localized to the focal volume. Consequently, two-photon microscopy enables optical sectioning and confocal performance without the need for a signal-limiting pinhole. In addition, there is a reduction (relative to one-photon optical microscopy) in photon-induced damage because of the longer excitation wavelength. This reduction is especially advantageous for in vivo studies. Relative to confocal microscopy, there is also a reduction in background fluorescence, and, because of a reduction in Rayleigh scattering, there is a 4 increase of penetration depth. The prohibitive cost of a commercial two-photon fluorescence-microscope system, as well as a need for modularity, has led to the construction of a custom-built system (see Figure 1). This system includes a coherent mode-locked titanium: sapphire laser emitting 120-fs-duration pulses at a repetition rate of 80 MHz. The pulsed laser has an average output power of 800 mW and a wavelength tuning range of 700 to 980 nm, enabling the excitation of a variety of targeted fluorophores. The output from the laser is attenuated, spatially filtered, and then directed into a confocal scanning head that has been modified to provide for side entry of the laser beam. The laser output coupler has been replaced with a dichroic filter that reflects the

  1. Automated evaluation of liver fibrosis in thioacetamide, carbon tetrachloride, and bile duct ligation rodent models using second-harmonic generation/two-photon excited fluorescence microscopy.

    Science.gov (United States)

    Liu, Feng; Chen, Long; Rao, Hui-Ying; Teng, Xiao; Ren, Ya-Yun; Lu, Yan-Qiang; Zhang, Wei; Wu, Nan; Liu, Fang-Fang; Wei, Lai

    2017-01-01

    Animal models provide a useful platform for developing and testing new drugs to treat liver fibrosis. Accordingly, we developed a novel automated system to evaluate liver fibrosis in rodent models. This system uses second-harmonic generation (SHG)/two-photon excited fluorescence (TPEF) microscopy to assess a total of four mouse and rat models, using chemical treatment with either thioacetamide (TAA) or carbon tetrachloride (CCl 4 ), and a surgical method, bile duct ligation (BDL). The results obtained by the new technique were compared with that using Ishak fibrosis scores and two currently used quantitative methods for determining liver fibrosis: the collagen proportionate area (CPA) and measurement of hydroxyproline (HYP) content. We show that 11 shared morphological parameters faithfully recapitulate Ishak fibrosis scores in the models, with high area under the receiver operating characteristic (ROC) curve (AUC) performance. The AUC values of 11 shared parameters were greater than that of the CPA (TAA: 0.758-0.922 vs 0.752-0.908; BDL: 0.874-0.989 vs 0.678-0.966) in the TAA mice and BDL rat models and similar to that of the CPA in the TAA rat and CCl 4 mouse models. Similarly, based on the trends in these parameters at different time points, 9, 10, 7, and 2 model-specific parameters were selected for the TAA rats, TAA mice, CCl 4 mice, and BDL rats, respectively. These parameters identified differences among the time points in the four models, with high AUC accuracy, and the corresponding AUC values of these parameters were greater compared with those of the CPA in the TAA rat and mouse models (rats: 0.769-0.894 vs 0.64-0.799; mice: 0.87-0.93 vs 0.739-0.836) and similar to those of the CPA in the CCl 4 mouse and BDL rat models. Similarly, the AUC values of 11 shared parameters and model-specific parameters were greater than those of HYP in the TAA rats, TAA mice, and CCl 4 mouse models and were similar to those of HYP in the BDL rat models. The automated

  2. A new approach to dual-color two-photon microscopy with fluorescent proteins

    Directory of Open Access Journals (Sweden)

    Rebane Aleks

    2010-02-01

    Full Text Available Abstract Background Two-photon dual-color imaging of tissues and cells labeled with fluorescent proteins (FPs is challenging because most two-photon microscopes only provide one laser excitation wavelength at a time. At present, methods for two-photon dual-color imaging are limited due to the requirement of large differences in Stokes shifts between the FPs used and their low two-photon absorption (2PA efficiency. Results Here we present a new method of dual-color two-photon microscopy that uses the simultaneous excitation of the lowest-energy electronic transition of a blue fluorescent protein and a higher-energy electronic transition of a red fluorescent protein. Conclusion Our method does not require large differences in Stokes shifts and can be extended to a variety of FP pairs with larger 2PA efficiency and more optimal imaging properties.

  3. Two-Photon Fluorescence Microscopy Developed for Microgravity Fluid Physics

    Science.gov (United States)

    Fischer, David G.; Zimmerli, Gregory A.; Asipauskas, Marius

    2004-01-01

    Recent research efforts within the Microgravity Fluid Physics Branch of the NASA Glenn Research Center have necessitated the development of a microscope capable of high-resolution, three-dimensional imaging of intracellular structure and tissue morphology. Standard optical microscopy works well for thin samples, but it does not allow the imaging of thick samples because of severe degradation caused by out-of-focus object structure. Confocal microscopy, which is a laser-based scanning microscopy, provides improved three-dimensional imaging and true optical sectioning by excluding the out-of-focus light. However, in confocal microscopy, out-of-focus object structure is still illuminated by the incoming beam, which can lead to substantial photo-bleaching. In addition, confocal microscopy is plagued by limited penetration depth, signal loss due to the presence of a confocal pinhole, and the possibility of live-cell damage. Two-photon microscopy is a novel form of laser-based scanning microscopy that allows three-dimensional imaging without many of the problems inherent in confocal microscopy. Unlike one-photon microscopy, it utilizes the nonlinear absorption of two near-infrared photons. However, the efficiency of two-photon absorption is much lower than that of one-photon absorption because of the nonlinear (i.e., quadratic) electric field dependence, so an ultrafast pulsed laser source must typically be employed. On the other hand, this stringent energy density requirement effectively localizes fluorophore excitation to the focal volume. Consequently, two-photon microscopy provides optical sectioning and confocal performance without the need for a signal-limiting pinhole. In addition, there is a reduction in photo-damage because of the longer excitation wavelength, a reduction in background fluorescence, and a 4 increase in penetration depth over confocal methods because of the reduction in Rayleigh scattering.

  4. Arduino Due based tool to facilitate in vivo two-photon excitation microscopy.

    Science.gov (United States)

    Artoni, Pietro; Landi, Silvia; Sato, Sebastian Sulis; Luin, Stefano; Ratto, Gian Michele

    2016-04-01

    Two-photon excitation spectroscopy is a powerful technique for the characterization of the optical properties of genetically encoded and synthetic fluorescent molecules. Excitation spectroscopy requires tuning the wavelength of the Ti:sapphire laser while carefully monitoring the delivered power. To assist laser tuning and the control of delivered power, we developed an Arduino Due based tool for the automatic acquisition of high quality spectra. This tool is portable, fast, affordable and precise. It allowed studying the impact of scattering and of blood absorption on two-photon excitation light. In this way, we determined the wavelength-dependent deformation of excitation spectra occurring in deep tissues in vivo.

  5. Two-photon laser-induced fluorescence studies of HS radicals, DS radicals, and I atoms

    Energy Technology Data Exchange (ETDEWEB)

    Tiee, J J; Ferris, M J; Loge, G W; Wampler, F B

    1983-04-15

    A two-photon laser-induced excitation and fluorescence technique has been used to study the A /sup 2/..sigma../sup +/ - X/sup 2/PI transition of HS and DS radicals and various high-lying /sup 4/P/sup 0/, /sup 2/D/sup 0/, and /sup 4/D/sup 0/ states of the I atom. The two-photon excitation cross sections and detection sensitivity are discussed. 13 references, 5 figures.

  6. Two-photon excitation spectroscopy of carotenoid-containing and carotenoid-depleted LH2 complexes from purple bacteria.

    Science.gov (United States)

    Stepanenko, Ilya; Kompanetz, Viktor; Makhneva, Zoya; Chekalin, Sergey; Moskalenko, Andrei; Razjivin, Andrei

    2009-08-27

    We applied two-photon fluorescence excitation spectroscopy to LH2 complex from purple bacteria Allochromatium minutissimum and Rhodobacter sphaeroides . Bacteriochlorophyll fluorescence was measured under two-photon excitation of the samples within the 1200-1500 nm region. Spectra were obtained for both carotenoid-containing and -depleted complexes of each bacterium to allow their direct comparison. The depletion of carotenoids did not alter the two-photon excitation spectra of either bacteria. The spectra featured a wide excitation band around 1350 nm (2x675 nm, 14,800 cm(-1)) which strongly resembled two-photon fluorescence excitation spectra of similar complexes published by other authors. We consider obtained experimental data to be evidence of direct two-photon excitation of bacteriochlorophyll excitonic states in this spectral region.

  7. Two-photon excitation in chip electrophoresis enabling label-free fluorescence detection in non-UV transparent full-body polymer chips.

    Science.gov (United States)

    Geissler, David; Belder, Detlev

    2015-12-01

    One of the most commonly employed detection methods in microfluidic research is fluorescence detection, due to its ease of integration and excellent sensitivity. Many analytes though do not show luminescence when excited in the visible light spectrum, require suitable dyes. Deep-ultraviolet (UV) excitation (electrophoresis of small aromatic compounds. Various polymers, such as poly(methyl methacrylate), cyclic olefin polymer, and copolymer as well as poly(dimethylsiloxane) were investigated and compared with respect to achievable LOD and ruggedness against photodamage. To demonstrate the applicability of the technique, the method was also applied to the determination of serotonin and tryptamine in fruit samples. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Two-photon fluorescence and fluorescence imaging of two styryl heterocyclic dyes combined with DNA.

    Science.gov (United States)

    Gao, Chao; Liu, Shu-yao; Zhang, Xian; Liu, Ying-kai; Qiao, Cong-de; Liu, Zhao-e

    2016-03-05

    Two new styryl heterocyclic two-photon (TP) materials, 4-[4-(N-methyl)styrene]-imidazo [4,5-f][1,10] phenanthroline-benzene iodated salt (probe-1) and 4,4-[4-(N-methyl)styrene]-benzene iodated salt (probe-2) were successfully synthesized and studied as potential fluorescent probes of DNA detection. The linear and nonlinear photophysical properties of two compounds in different solvents were investigated. The absorption, one- and two-photon fluorescent spectra of the free dye and dye-DNA complex were also examined to evaluate their photophysical properties. The binding constants of dye-DNA were obtained according to Scatchard equation with good values. The results showed that two probes could be used as fluorescent DNA probes by two-photon excitation, and TP fluorescent properties of probe-1 are superior to that of probe-2. The fluorescent method date indicated that the mechanisms of dye-DNA complex interaction may be groove binding for probe-1 and electrostatic interaction for probe-2, respectively. The MTT assay experiments showed two probes are low toxicity. Moreover, the TP fluorescence imaging of DNA detection in living cells at 800 nm indicated that the ability to locate in cell nuclei of probe-1 is better than that of probe-2. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. Near-IR Two-Photon Fluorescent Sensor for K(+) Imaging in Live Cells.

    Science.gov (United States)

    Sui, Binglin; Yue, Xiling; Kim, Bosung; Belfield, Kevin D

    2015-08-19

    A new two-photon excited fluorescent K(+) sensor is reported. The sensor comprises three moieties, a highly selective K(+) chelator as the K(+) recognition unit, a boron-dipyrromethene (BODIPY) derivative modified with phenylethynyl groups as the fluorophore, and two polyethylene glycol chains to afford water solubility. The sensor displays very high selectivity (>52-fold) in detecting K(+) over other physiological metal cations. Upon binding K(+), the sensor switches from nonfluorescent to highly fluorescent, emitting red to near-IR (NIR) fluorescence. The sensor exhibited a good two-photon absorption cross section, 500 GM at 940 nm. Moreover, it is not sensitive to pH in the physiological pH range. Time-dependent cell imaging studies via both one- and two-photon fluorescence microscopy demonstrate that the sensor is suitable for dynamic K(+) sensing in living cells.

  10. Enhanced-locality fiber-optic two-photon-fluorescence live-brain interrogation

    Energy Technology Data Exchange (ETDEWEB)

    Fedotov, I. V.; Doronina-Amitonova, L. V. [International Laser Center, Physics Department, M.V. Lomonosov Moscow State University, Moscow 119992 (Russian Federation); Russian Quantum Center, ul. Novaya 100, Skolkovo, Moscow Region 1430125 (Russian Federation); Kurchatov Institute National Research Center, Moscow (Russian Federation); Sidorov-Biryukov, D. A.; Fedotov, A. B. [International Laser Center, Physics Department, M.V. Lomonosov Moscow State University, Moscow 119992 (Russian Federation); Russian Quantum Center, ul. Novaya 100, Skolkovo, Moscow Region 1430125 (Russian Federation); Anokhin, K. V. [Kurchatov Institute National Research Center, Moscow (Russian Federation); P.K. Anokhin Institute of Normal Physiology, Russian Academy of Medical Sciences, Moscow (Russian Federation); Kilin, S. Ya. [B.I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, Minsk (Belarus); Sakoda, K. [National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044 (Japan); Zheltikov, A. M. [International Laser Center, Physics Department, M.V. Lomonosov Moscow State University, Moscow 119992 (Russian Federation); Russian Quantum Center, ul. Novaya 100, Skolkovo, Moscow Region 1430125 (Russian Federation); Department of Physics and Astronomy, Texas A and M University, College Station, Texas 77843 (United States); Center of Photochemistry, Russian Academy of Sciences, ul. Novatorov 7a, Moscow 117421 (Russian Federation)

    2014-02-24

    Two-photon excitation is shown to substantially enhance the locality of fiber-based optical interrogation of strongly scattering biotissues. In our experiments, a high-numerical-aperture, large-core-are fiber probe is used to deliver the 200-fs output of a 100-MHz mode-locked ytterbium fiber laser to samples of live mouse brain, induce two-photon fluorescence of nitrogen–vacancy centers in diamond markers in brain sample. Fiber probes with a high numerical aperture and a large core area are shown to enable locality enhancement in fiber-laser–fiber-probe two-photon brain excitation and interrogation without sacrificing the efficiency of fluorescence response collection.

  11. Nonlinear behavior of photoluminescence from silicon particles under two-photon excitation

    International Nuclear Information System (INIS)

    Xu Xingsheng; Yokoyama, Shiyoshi

    2011-01-01

    Two-photon excited fluorescence (TPEF) under continuous-wave excitation from silicon particles produced by a pulsed laser is investigated. Spectra and images of TPEF from silicon particles are studied under different excitation intensities and operation modes (continuous wave or pulse). It is found that the photoluminescence depends superlinearly on the excitation intensity and that the spectral shape and peaks vary with different silicon particles. The above phenomena show the nonlinear behavior of TPEF from silicon particles, and stimulated emission is a possible process.

  12. Molecular engineering of two-photon fluorescent probes for bioimaging applications

    Science.gov (United States)

    Liu, Hong-Wen; Liu, Yongchao; Wang, Peng; Zhang, Xiao-Bing

    2017-03-01

    During the past two decades, two-photon microscopy (TPM), which utilizes two near-infrared photons as the excitation source, has emerged as a novel, attractive imaging tool for biological research. Compared with one-photon microscopy, TPM offers several advantages, such as lowering background fluorescence in living cells and tissues, reducing photodamage to biosamples, and a photobleaching phenomenon, offering better 3D spatial localization, and increasing penetration depth. Small-molecule-based two-photon fluorescent probes have been well developed for the detection and imaging of various analytes in biological systems. In this review, we will give a general introduction of molecular engineering of two-photon fluorescent probes based on different fluorescence response mechanisms for bioimaging applications during the past decade. Inspired by the desired advantages of small-molecule two-photon fluorescent probes in biological imaging applications, we expect that more attention will be devoted to the development of new two-photon fluorophores and applications of TPM in areas of bioanalysis and disease diagnosis.

  13. Spectral, energy, and time parameters of two-photon fluorescence of 2,5-diphenyloxazole polycrystals

    International Nuclear Information System (INIS)

    Agal'tsov, A.M.; Gorelik, V.S.; Rakhmatullaev, I.A.

    1995-01-01

    Two-photon fluorescence (TPF) spectra of 2,5-diphenyloxazole polycrystals (known in the literature as PPO) were obtained and studied as a function of the pump power and time delay. The fluorescence spectrum shape observed upon two-photon excitation is shown to be distinctly different from that observed upon electron-beam excitation. It is shown that high pump powers result in stimulated fluorescence. PPO exhibits a high TPF quantum yield, the integrated conversion efficiency of exciting radiation to TPF being 40%. The TPF decay time is measured to be 20 ns. The spectral data obtained for PPO polycrystals can be used in the development of new TPF light sources tunable in the UV region. 10 refs., 4 figs., 1 tab

  14. Applications of two-photon fluorescence microscopy in deep-tissue imaging

    Science.gov (United States)

    Dong, Chen-Yuan; Yu, Betty; Hsu, Lily L.; Kaplan, Peter D.; Blankschstein, D.; Langer, Robert; So, Peter T. C.

    2000-07-01

    Based on the non-linear excitation of fluorescence molecules, two-photon fluorescence microscopy has become a significant new tool for biological imaging. The point-like excitation characteristic of this technique enhances image quality by the virtual elimination of off-focal fluorescence. Furthermore, sample photodamage is greatly reduced because fluorescence excitation is limited to the focal region. For deep tissue imaging, two-photon microscopy has the additional benefit in the greatly improved imaging depth penetration. Since the near- infrared laser sources used in two-photon microscopy scatter less than their UV/glue-green counterparts, in-depth imaging of highly scattering specimen can be greatly improved. In this work, we will present data characterizing both the imaging characteristics (point-spread-functions) and tissue samples (skin) images using this novel technology. In particular, we will demonstrate how blind deconvolution can be used further improve two-photon image quality and how this technique can be used to study mechanisms of chemically-enhanced, transdermal drug delivery.

  15. Fluorenyl benzothiadiazole and benzoselenadiazole near-IR fluorescent probes for two-photon fluorescence imaging (Conference Presentation)

    Science.gov (United States)

    Belfield, Kevin D.; Yao, Sheng; Kim, Bosung; Yue, Xiling

    2016-03-01

    Imaging biological samples with two-photon fluorescence (2PF) microscopy has the unique advantage of resulting high contrast 3D resolution subcellular image that can reach up to several millimeters depth. 2PF probes that absorb and emit at near IR region need to be developed. Two-photon excitation (2PE) wavelengths are less concerned as 2PE uses wavelengths doubles the absorption wavelength of the probe, which means 2PE wavelengths for probes even with absorption at visible wavelength will fall into NIR region. Therefore, probes that fluoresce at near IR region with high quantum yields are needed. A series of dyes based on 5-thienyl-2, 1, 3-benzothiadiazole and 5-thienyl-2, 1, 3-benzoselenadiazole core were synthesized as near infrared two-photon fluorophores. Fluorescence maxima wavelengths as long as 714 nm and fluorescence quantum yields as high as 0.67 were achieved. The fluorescence quantum yields of the dyes were nearly constant, regardless of solvents polarity. These diazoles exhibited large Stokes shift (GM), and high two-photon fluorescence figure of merit (FM , 1.04×10-2 GM). Cells incubated on a 3D scaffold with one of the new probes (encapsulated in Pluronic micelles) exhibited bright fluorescence, enabling 3D two-photon fluorescence imaging to a depth of 100 µm.

  16. Selective labeling of a single organelle by using two-photon conversion of a photoconvertible fluorescent protein

    Science.gov (United States)

    Watanabe, Wataru; Shimada, Tomoko; Matsunaga, Sachihiro; Kurihara, Daisuke; Arimura, Shin-ichi; Tsutsumi, Nobuhiro; Fukui, Kiichi; Itoh, Kazuyoshi

    2008-02-01

    We present space-selective labeling of organelles by using two-photon conversion of a photoconvertible fluorescent protein with near-infrared femtosecond laser pulses. Two-photon excitation of photoconvertible fluorescent-protein, Kaede, enables space-selective labeling of organelles. We alter the fluorescence of target mitochondria in a tobacco BY-2 cell from green to red by focusing femtosecond laser pulses with a wavelength of 750 nm.

  17. Fluorescent Pluronic nanodots for in vivo two-photon imaging

    International Nuclear Information System (INIS)

    Maurin, Mathieu; Vurth, Laeticia; Vial, Jean-Claude; Baldeck, Patrice; Stephan, Olivier; Marder, Seth R; Sanden, Boudewijn Van der

    2009-01-01

    We report the synthesis of new nanosized fluorescent probes based on bio-compatible polyethylene-polypropylene glycol (Pluronic) materials. In aqueous solution, mini-emulsification of Pluronic with a high fluorescent di-stryl benzene-modified derivative, exhibiting a two-photon absorption cross section as high as 2500 Goeppert-Mayer units at 800 nm, leads to nanoparticles exhibiting a hydrodynamic radius below 100 nm. We have demonstrated that these new probes with luminescence located in the spectral region of interest for bio-imaging (the yellow part of the visible spectrum) allow deep (500 μm) bio-imaging of the mice brain vasculature. The dose injected during our experiments is ten times lower when compared to the classical commercial rhodamine-B isothicyanate-Dextran system but gives similar results to homogeneous blood plasma staining. The mean fluorescent signal intensity stayed constant during more than 1 h.

  18. Imaging Live Drosophila Brain with Two-Photon Fluorescence Microscopy

    Science.gov (United States)

    Ahmed, Syeed Ehsan

    Two-photon fluorescence microscopy is an imaging technique which delivers distinct benefits for in vivo cellular and molecular imaging. Cyclic adenosine monophosphate (cAMP), a second messenger molecule, is responsible for triggering many physiological changes in neural system. However, the mechanism by which this molecule regulates responses in neuron cells is not yet clearly understood. When cAMP binds to a target protein, it changes the structure of that protein. Therefore, studying this molecular structure change with fluorescence resonance energy transfer (FRET) imaging can shed light on the cAMP functioning mechanism. FRET is a non-radiative dipole-dipole coupling which is sensitive to small distance change in nanometer scale. In this study we have investigated the effect of dopamine in cAMP dynamics in vivo. In our study two-photon fluorescence microscope was used for imaging mushroom bodies inside live Drosophila melanogaster brain and we developed a method for studying the change in cyclic AMP level.

  19. A spirobifluorene-based two-photon fluorescence probe for mercury ions and its applications in living cells

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Haibo, E-mail: xiaohb@shnu.edu.cn; Zhang, Yanzhen; Zhang, Wu; Li, Shaozhi; Tan, Jingjing; Han, Zhongying

    2017-05-01

    A novel spirobifluorene derivative SPF-TMS, which containing dithioacetal groups and triphenylamine units, was synthesized. The probing behaviors toward various metal ions were investigated via UV/Vis absorption spectra as well as one-photon fluorescence changes. The results indicated that SPF-TMS exhibits high sensitivity and selectivity for mercury ions. The detection limit was at least 8.6 × 10{sup −8}M, which is excellent comparing with other optical sensors for Hg{sup 2+}. When measured by two-photon excited fluorescence technique in THF at 800 nm, the two-photon cross-section of SPF-TMS is 272 GM. Especially, upon reaction with mercury species, SPF-TMS yielded another two-photon dye SPF-DA. Both SPF-TMS and SPF-DA emit strong two-photon induced fluorescence and can be applied in cell imaging by two-photon microscopy. - Highlights: • We report a spirobifluorene-based molecule as two-photon fluorescent probe with large two-photon cross-section. • The molecule has exclusive selectivity and sensitivity for mercury species. • The molecule has large two-photon emission changes before and after addition of Hg{sup 2+}. • Both the probe and the mercury ion-promoted reaction product can be applied in cell imaging by two-photon microscopy.

  20. Supramolecular assembly affording a ratiometric two-photon fluorescent nanoprobe for quantitative detection and bioimaging.

    Science.gov (United States)

    Wang, Peng; Zhang, Cheng; Liu, Hong-Wen; Xiong, Mengyi; Yin, Sheng-Yan; Yang, Yue; Hu, Xiao-Xiao; Yin, Xia; Zhang, Xiao-Bing; Tan, Weihong

    2017-12-01

    Fluorescence quantitative analyses for vital biomolecules are in great demand in biomedical science owing to their unique detection advantages with rapid, sensitive, non-damaging and specific identification. However, available fluorescence strategies for quantitative detection are usually hard to design and achieve. Inspired by supramolecular chemistry, a two-photon-excited fluorescent supramolecular nanoplatform ( TPSNP ) was designed for quantitative analysis with three parts: host molecules (β-CD polymers), a guest fluorophore of sensing probes (Np-Ad) and a guest internal reference (NpRh-Ad). In this strategy, the TPSNP possesses the merits of (i) improved water-solubility and biocompatibility; (ii) increased tissue penetration depth for bioimaging by two-photon excitation; (iii) quantitative and tunable assembly of functional guest molecules to obtain optimized detection conditions; (iv) a common approach to avoid the limitation of complicated design by adjustment of sensing probes; and (v) accurate quantitative analysis by virtue of reference molecules. As a proof-of-concept, we utilized the two-photon fluorescent probe NHS-Ad-based TPSNP-1 to realize accurate quantitative analysis of hydrogen sulfide (H 2 S), with high sensitivity and good selectivity in live cells, deep tissues and ex vivo -dissected organs, suggesting that the TPSNP is an ideal quantitative indicator for clinical samples. What's more, TPSNP will pave the way for designing and preparing advanced supramolecular sensors for biosensing and biomedicine.

  1. Sensing for intracellular thiols by water-insoluble two-photon fluorescent probe incorporating nanogel

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Xudong; Zhang, Xin; Wang, Shuangqing; Li, Shayu [Beijing National Laboratory for Molecular Sciences, Key laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Hu, Rui, E-mail: hurui@iccas.ac.cn [Beijing National Laboratory for Molecular Sciences, Key laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Li, Yi, E-mail: yili@mail.ipc.ac.cn [Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Yang, Guoqiang, E-mail: gqyang@iccas.ac.cn [Beijing National Laboratory for Molecular Sciences, Key laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China)

    2015-04-15

    Highlights: • A novel “turn-on” two-photon fluorescent probe based on a π-conjugated triarylboron luminogen was designed and synthesized. • Fast, selective and sensitive detection of biothiols in 100% aqueous solution by simply loaded on a nanogel. • Single-photon and two-photon fluorescent bioimaging of biothiols in NIH/3T3 fibroblasts. - Abstract: A novel “turn-on” two-photon fluorescent probe containing a π-conjugated triarylboron luminogen and a maleimide moiety DMDP-M based on the photo-induced electron transfer (PET) mechanism for biothiol detection was designed and synthesized. By simply loading the hydrophobic DMDP-M on a cross-linked Pluronic{sup ®} F127 nanogel (CL-F127), a probing system DMDP-M/CL-F127 was established, which shows quick response, high selectivity and sensitivity to cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) in aqueous phase. The DMDP-M/CL-F127 system presented the fastest response to Cys with a rate constant of 0.56 min{sup −1}, and the detection limit to Cys was calculated to be as low as 0.18 μM. The DMDP-M/CL-F127 system has been successfully applied to the fluorescence imaging of biothiols in NIH/3T3 fibroblasts either with single-photon or two-photon excitation because of its high biocompatibility and cell-membrane permeability. The present work provides a general, simple and efficient strategy for the application of hydrophobic molecules to sensing biothiols in aqueous phase, and a novel sensing system for intracellular biothiols fitted for both single-photon and two-photon fluorescence imaging.

  2. Time-resolved stimulated emission depletion and energy transfer dynamics in two-photon excited EGFP

    Science.gov (United States)

    Masters, T. A.; Robinson, N. A.; Marsh, R. J.; Blacker, T. S.; Armoogum, D. A.; Larijani, B.; Bain, A. J.

    2018-04-01

    Time and polarization-resolved stimulated emission depletion (STED) measurements are used to investigate excited state evolution following the two-photon excitation of enhanced green fluorescent protein (EGFP). We employ a new approach for the accurate STED measurement of the hitherto unmeasured degree of hexadecapolar transition dipole moment alignment ⟨α40 ⟩ present at a given excitation-depletion (pump-dump) pulse separation. Time-resolved polarized fluorescence measurements as a function of pump-dump delay reveal the time evolution of ⟨α40 ⟩ to be considerably more rapid than predicted for isotropic rotational diffusion in EGFP. Additional depolarization by homo-Förster resonance energy transfer is investigated for both ⟨α20 ⟩ (quadrupolar) and ⟨α40 ⟩ transition dipole alignments. These results point to the utility of higher order dipole correlation measurements in the investigation of resonance energy transfer processes.

  3. CdSe/AsS core-shell quantum dots: preparation and two-photon fluorescence.

    Science.gov (United States)

    Wang, Junzhong; Lin, Ming; Yan, Yongli; Wang, Zhe; Ho, Paul C; Loh, Kian Ping

    2009-08-19

    Arsenic(II) sulfide (AsS)-coated CdSe core-shell nanocrystals can be prepared by a cluster-complex deposition approach under mild conditions. At 60 degrees C, growth of an AsS shell onto a CdSe nanocrystal can be realized through the crystallization of a cluster complex of AsS/butylamine in a mixed solvent of isopropanol/chloroform. The new, type I core-shell nanocrystal exhibits markedly enhanced one-photon fluorescence as well two-photon upconversion fluorescence. The nanocrystals can be used for infrared-excited upconversion cellular labeling.

  4. Whispering gallery modes in two-photon fluorescence from spherical DCM dye microresonators

    Science.gov (United States)

    Mamonov, Evgeniy A.; Maydykovskiy, Anton I.; Mitetelo, Nikolai V.; Venkatakrishnarao, Dasari; Chandrasekar, Rajadurai; Murzina, Tatyana V.

    2018-03-01

    Organic microstructures are well known for their resonator properties, which bring about whispering gallery mode (WGM) excitation. Here we report on experimental evidence of the WGM in the two-photon fluorescence (TPF) of DCM dye microspheres made using the self-assembly method. The WGM excitation accompanying the overall TPF in the spectral range from 530\\div640 nm demonstrated a quality factor of approximately 102 for spheres that were several microns in diameter. The power dependence of the TPF intensity proved the second order nature of the interaction process involved.

  5. Single pulse two photon fluorescence lifetime imaging (SP-FLIM) with MHz pixel rate.

    Science.gov (United States)

    Eibl, Matthias; Karpf, Sebastian; Weng, Daniel; Hakert, Hubertus; Pfeiffer, Tom; Kolb, Jan Philip; Huber, Robert

    2017-07-01

    Two-photon-excited fluorescence lifetime imaging microscopy (FLIM) is a chemically specific 3-D sensing modality providing valuable information about the microstructure, composition and function of a sample. However, a more widespread application of this technique is hindered by the need for a sophisticated ultra-short pulse laser source and by speed limitations of current FLIM detection systems. To overcome these limitations, we combined a robust sub-nanosecond fiber laser as the excitation source with high analog bandwidth detection. Due to the long pulse length in our configuration, more fluorescence photons are generated per pulse, which allows us to derive the lifetime with a single excitation pulse only. In this paper, we show high quality FLIM images acquired at a pixel rate of 1 MHz. This approach is a promising candidate for an easy-to-use and benchtop FLIM system to make this technique available to a wider research community.

  6. Tuning Ag29 nanocluster light emission from red to blue with one and two-photon excitation.

    Science.gov (United States)

    Russier-Antoine, Isabelle; Bertorelle, Franck; Hamouda, Ramzi; Rayane, Driss; Dugourd, Philippe; Sanader, Željka; Bonačić-Koutecký, Vlasta; Brevet, Pierre-François; Antoine, Rodolphe

    2016-02-07

    We demonstrate that the tuning of the light emission from red to blue in dihydrolipoic acid (DHLA) capped Ag29 nanoclusters can be trigged with one and two photon excitations. The cluster stoichiometry was determined with mass spectrometry and found to be Ag29(DHLA)12. In a detailed optical investigation, we show that these silver nanoclusters exhibit a strong red photoluminescence visible to the naked eye and characterized by a quantum yield of nearly ∼2% upon one-photon excitation. In the nonlinear optical (NLO) study of the properties of the clusters, the two-photon excited fluorescence spectra were recorded and their first hyperpolarizability obtained. The two-photon absorption cross-section at ∼800 nm for Ag29(DHLA)12 is higher than 10(4) GM and the hyperpolarizability is 106 × 10(-30) esu at the same excitation wavelength. The two-photon excited fluorescence spectrum appears strongly blue-shifted as compared to the one-photon excited spectrum, displaying a broad band between 400 and 700 nm. The density functional theory (DFT) provides insight into the structural and electronic properties of Ag29(DHLA)12 as well as into interplay between metallic subunit or core and ligands which is responsible for unique optical properties.

  7. Deep brain two-photon NIR fluorescence imaging for study of Alzheimer's disease

    Science.gov (United States)

    Chen, Congping; Liang, Zhuoyi; Zhou, Biao; Ip, Nancy Y.; Qu, Jianan Y.

    2018-02-01

    Amyloid depositions in the brain represent the characteristic hallmarks of Alzheimer's disease (AD) pathology. The abnormal accumulation of extracellular amyloid-beta (Aβ) and resulting toxic amyloid plaques are considered to be responsible for the clinical deficits including cognitive decline and memory loss. In vivo two-photon fluorescence imaging of amyloid plaques in live AD mouse model through a chronic imaging window (thinned skull or craniotomy) provides a mean to greatly facilitate the study of the pathological mechanism of AD owing to its high spatial resolution and long-term continuous monitoring. However, the imaging depth for amyloid plaques is largely limited to upper cortical layers due to the short-wavelength fluorescence emission of commonly used amyloid probes. In this work, we reported that CRANAD-3, a near-infrared (NIR) probe for amyloid species with excitation wavelength at 900 nm and emission wavelength around 650 nm, has great advantages over conventionally used probes and is well suited for twophoton deep imaging of amyloid plaques in AD mouse brain. Compared with a commonly used MeO-X04 probe, the imaging depth of CRANAD-3 is largely extended for open skull cranial window. Furthermore, by using two-photon excited fluorescence spectroscopic imaging, we characterized the intrinsic fluorescence of the "aging pigment" lipofuscin in vivo, which has distinct spectra from CRANAD-3 labeled plaques. This study reveals the unique potential of NIR probes for in vivo, high-resolution and deep imaging of brain amyloid in Alzheimer's disease.

  8. Two-photon induced fluorescence of Cy5-DNA in buffer solution and on silver island films

    International Nuclear Information System (INIS)

    Lukomska, Joanna; Gryczynski, Ignacy; Malicka, Joanna; Makowiec, Slawomir; Lakowicz, Joseph R.; Gryczynski, Zygmunt

    2005-01-01

    We report the observation of a strong two-photon induced fluorescence emission of Cy5-DNA within the tunable range of a Ti:Sapphire laser. The estimated two-photon cross-section for Cy5-DNA of 400 GM is about 3.5-fold higher than it was reported for rhodamine B. The fundamental anisotropies of Cy5-DNA are close to the theoretical limits of 2/5 and 4/7 for one- and two-photon excitation, respectively. We also observed an enhanced two-photon induced fluorescence (TPIF) of Cy5-DNA deposited on silver island films (SIFs). In the presence of SIFs, the TPIF is about 100-fold brighter. The brightness increase of Cy5-DNA TPIF near SIFs is mostly due to enhanced local field

  9. Direct measurements of neutral density depletion by two-photon absorption laser-induced fluorescence spectroscopy

    International Nuclear Information System (INIS)

    Aanesland, A.; Liard, L.; Leray, G.; Jolly, J.; Chabert, P.

    2007-01-01

    The ground state density of xenon atoms has been measured by spatially resolved laser-induced fluorescence spectroscopy with two-photon excitation in the diffusion chamber of a magnetized Helicon plasma. This technique allows the authors to directly measure the relative variations of the xenon atom density without any assumptions. A significant neutral gas density depletion was measured in the core of the magnetized plasma, in agreement with previous theoretical and experimental works. It was also found that the neutral gas density was depleted near the radial walls

  10. Femtosecond two-photon laser-induced fluorescence of krypton for high-speed flow imaging.

    Science.gov (United States)

    Wang, Yejun; Capps, Cade; Kulatilaka, Waruna D

    2017-02-15

    Ultrashort-pulse (femtosecond-duration) two-photon laser-induced fluorescence (fs-TPLIF) of an inert gas tracer krypton (Kr) is investigated. A detailed spectroscopic study of fluorescence channels followed by the 5p'←←4p excitation of Kr at 204.1 nm is reported. The experimental line positions in the 750-840 nm emission region agree well with the NIST Atomic Spectra Database. The present work provides an accurate listing of relative line strengths in this spectral region. In the range of laser pulse energies investigated, a quadratic dependence was observed between the Kr-TPLIF signal and the laser pulse energy. The single-laser-shot 2D TPLIF images recorded in an unsteady jet demonstrate the potential of using fs excitation at 204.1 nm for mixing and flow diagnostic studies using Kr as an inert gas tracer.

  11. Non-invasive imaging of skin cancer with fluorescence lifetime imaging using two photon tomography

    Science.gov (United States)

    Patalay, Rakesh; Talbot, Clifford; Alexandrov, Yuriy; Munro, Ian; Breunig, Hans Georg; König, Karsten; Warren, Sean; Neil, Mark A. A.; French, Paul M. W.; Chu, Anthony; Stamp, Gordon W.; Dunsby, Christopher

    2011-07-01

    Multispectral fluorescence lifetime imaging (FLIM) using two photon microscopy as a non-invasive technique for the diagnosis of skin lesions is described. Skin contains fluorophores including elastin, keratin, collagen, FAD and NADH. This endogenous contrast allows tissue to be imaged without the addition of exogenous agents and allows the in vivo state of cells and tissues to be studied. A modified DermaInspect® multiphoton tomography system was used to excite autofluorescence at 760 nm in vivo and on freshly excised ex vivo tissue. This instrument simultaneously acquires fluorescence lifetime images in four spectral channels between 360-655 nm using time-correlated single photon counting and can also provide hyperspectral images. The multispectral fluorescence lifetime images were spatially segmented and binned to determine lifetimes for each cell by fitting to a double exponential lifetime model. A comparative analysis between the cellular lifetimes from different diagnoses demonstrates significant diagnostic potential.

  12. Crossed-coil detection of two-photon excited nuclear quadrupole resonance

    Science.gov (United States)

    Eles, Philip T.; Michal, Carl A.

    2005-08-01

    Applying a recently developed theoretical framework for determining two-photon excitation Hamiltonians using average Hamiltonian theory, we calculate the excitation produced by half-resonant irradiation of the pure quadrupole resonance of a spin-3/2 system. This formalism provides expressions for the single-quantum and double-quantum nutation frequencies as well as the Bloch-Siegert shift. The dependence of the excitation strength on RF field orientation and the appearance of the free-induction signal along an axis perpendicular to the excitation field provide an unmistakable signature of two-photon excitation. We demonstrate single- and double-quantum excitation in an axially symmetric system using 35Cl in a single crystal of potassium chlorate ( ωQ = 28 MHz) with crossed-coil detection. A rotation plot verifies the orientation dependence of the two-photon excitation, and double-quantum coherences are observed directly with the application of a static external magnetic field.

  13. Two-Photon Excitation Microscopy for the Study of Living Cells and Tissues

    Science.gov (United States)

    Benninger, Richard K.P.; Piston, David W.

    2013-01-01

    Two-photon excitation microscopy is an alternative to confocal microscopy that provides advantages for three-dimensional and deep tissue imaging. This unit will describe the basic physical principles behind two-photon excitation and discuss the advantages and limitations of its use in laser-scanning microscopy. The principal advantages of two-photon microscopy are reduced phototoxicity, increased imaging depth, and the ability to initiate highly localized photochemistry in thick samples. Practical considerations for the application of two-photon microscopy will then be discussed, including recent technological advances. This unit will conclude with some recent applications of two-photon microscopy that highlight the key advantages over confocal microscopy and the types of experiments which would benefit most from its application. PMID:23728746

  14. Reactive quenching of two-photon excited xenon atoms by Cl2

    International Nuclear Information System (INIS)

    Bruce, M.R.; Layne, W.B.; Meyer, E.; Keto, J.W.

    1987-01-01

    Total binary and tertiary quench rates have been measured for the reaction Xe (5p 5 6p) + Cl 2 at thermal temperatures. Xenon atoms are excited by state-selective, two-photon absorption with a uv laser. The time dependent fluorescence from the excited atom in the IR and from XeCl* (B) product near 308 nm have been measured with subnanosecond time resolution. The decay rates are measured as a function of Cl 2 pressure to 20 Torr and Xe pressure to 400 Torr. The measured reaction rates (k 2 ∼ 10 -9 cm 3 sec -1 ) are consistent with a harpoon model described in a separate paper. We also measure large termolecular reaction rates for collisions with xenon atoms (k 3 ∼ 10 -28 cm 6 sec -1 ). Total product fluorescence has been examined using a gated optical multichannel analyzer. We measure unit branching fractions for high vibrational levels of XeCl* (B) with very little C state fluorescence observed. The measured termolecular rates suggest similar processes will dominate at the high buffer-gas pressures used in XeCl lasers. The effect of these large reactive cross sections for neutral xenon atoms on models of the XeCl laser will be discussed

  15. Two-photon excited autofluorescence imaging of freshly isolated frog retinas.

    Science.gov (United States)

    Lu, Rong-Wen; Li, Yi-Chao; Ye, Tong; Strang, Christianne; Keyser, Kent; Curcio, Christine A; Yao, Xin-Cheng

    2011-06-01

    The purpose of this study was to investigate cellular sources of autofluorescence signals in freshly isolated frog (Rana pipiens) retinas. Equipped with an ultrafast laser, a laser scanning two-photon excitation fluorescence microscope was employed for sub-cellular resolution examination of both sliced and flat-mounted retinas. Two-photon imaging of retinal slices revealed autofluorescence signals over multiple functional layers, including the photoreceptor layer (PRL), outer nuclear layer (ONL), outer plexiform layer (OPL), inner nuclear layer (INL), inner plexiform layer (IPL), and ganglion cell layer (GCL). Using flat-mounted retinas, depth-resolved imaging of individual retinal layers further confirmed multiple sources of autofluorescence signals. Cellular structures were clearly observed at the PRL, ONL, INL, and GCL. At the PRL, the autofluorescence was dominantly recorded from the intracellular compartment of the photoreceptors; while mixed intracellular and extracellular autofluorescence signals were observed at the ONL, INL, and GCL. High resolution autofluorescence imaging clearly revealed mosaic organization of rod and cone photoreceptors; and sub-cellular bright autofluorescence spots, which might relate to connecting cilium, was observed in the cone photoreceptors only. Moreover, single-cone and double-cone outer segments could be directly differentiated.

  16. Folate receptor targeting silica nanoparticle probe for two-photon fluorescence bioimaging

    Science.gov (United States)

    Wang, Xuhua; Yao, Sheng; Ahn, Hyo-Yang; Zhang, Yuanwei; Bondar, Mykhailo V.; Torres, Joseph A.; Belfield, Kevin D.

    2010-01-01

    Narrow dispersity organically modified silica nanoparticles (SiNPs), diameter ~30 nm, entrapping a hydrophobic two-photon absorbing fluorenyl dye, were synthesized by hydrolysis of triethoxyvinylsilane and (3-aminopropyl)triethoxysilane in the nonpolar core of Aerosol-OT micelles. The surface of the SiNPs were functionalized with folic acid, to specifically deliver the probe to folate receptor (FR) over-expressing Hela cells, making these folate two-photon dye-doped SiNPs potential candidates as probes for two-photon fluorescence microscopy (2PFM) bioimaging. In vitro studies using FR over-expressing Hela cells and low FR expressing MG63 cells demonstrated specific cellular uptake of the functionalized nanoparticles. One-photon fluorescence microscopy (1PFM) imaging, 2PFM imaging, and two-photon fluorescence lifetime microscopy (2P-FLIM) imaging of Hela cells incubated with folate-modified two-photon dye-doped SiNPs were demonstrated. PMID:21258480

  17. Pressure broadening of atomic oxygen two-photon absorption laser induced fluorescence

    NARCIS (Netherlands)

    Marinov, D.; Drag, C.; Blondel, C.; Guaitella, O.; Golda, J.; Klarenaar, B.L.M.; Engeln, R.A.H.; Schulz-von der Gathen, V.; Booth, J.-P.

    2016-01-01

    Atomic oxygen, considered to be a determining reactant in plasma applications at ambient pressure, is routinely detected by two-photon absorption laser induced fluorescence (TALIF). Here, pressure broadening of the (2p 4 3 P 2  →  3p 3 P J=0,1,2) two-photon transition in oxygen atoms was

  18. Enhanced Size Selection in Two-Photon Excitation for CsPbBr3 Perovskite Nanocrystals.

    Science.gov (United States)

    Chen, Junsheng; Chábera, Pavel; Pascher, Torbjörn; Messing, Maria E; Schaller, Richard; Canton, Sophie; Zheng, Kaibo; Pullerits, Tõnu

    2017-10-19

    Cesium lead bromide (CsPbBr 3 ) perovskite nanocrystals (NCs), with large two-photon absorption (TPA) cross-section and bright photoluminescence (PL), have been demonstrated as stable two-photon-pumped lasing medium. With two-photon excitation, red-shifted PL spectrum and increased PL lifetime is observed compared with one-photon excitation. We have investigated the origin of such difference using time-resolved laser spectroscopies. We ascribe the difference to the enhanced size selection of NCs by two-photon excitation. Because of inherent nonlinearity, the size dependence of absorption cross-section under TPA is stronger. Consequently, larger size NCs are preferably excited, leading to longer excited-state lifetime and red-shifted PL emission. In a broad view, the enhanced size selection in two-photon excitation of CsPbBr 3 NCs is likely a general feature of the perovskite NCs and can be tuned via NC size distribution to influence their performance within NC-based nonlinear optical materials and devices.

  19. Imaging-guided two-photon excitation-emission-matrix measurements of human skin tissues

    Science.gov (United States)

    Yu, Yingqiu; Lee, Anthony M. D.; Wang, Hequn; Tang, Shuo; Zhao, Jianhua; Lui, Harvey; Zeng, Haishan

    2012-07-01

    There are increased interests on using multiphoton imaging and spectroscopy for skin tissue characterization and diagnosis. However, most studies have been done with just a few excitation wavelengths. Our objective is to perform a systematic study of the two-photon fluorescence (TPF) properties of skin fluorophores, normal skin, and diseased skin tissues. A nonlinear excitation-emission-matrix (EEM) spectroscopy system with multiphoton imaging guidance was constructed. A tunable femtosecond laser was used to vary excitation wavelengths from 730 to 920 nm for EEM data acquisition. EEM measurements were performed on excised fresh normal skin tissues, seborrheic keratosis tissue samples, and skin fluorophores including: NADH, FAD, keratin, melanin, collagen, and elastin. We found that in the stratum corneum and upper epidermis of normal skin, the cells have large sizes and the TPF originates from keratin. In the lower epidermis, cells are smaller and TPF is dominated by NADH contributions. In the dermis, TPF is dominated by elastin components. The depth resolved EEM measurements also demonstrated that keratin structure has intruded into the middle sublayers of the epidermal part of the seborrheic keratosis lesion. These results suggest that the imaging guided TPF EEM spectroscopy provides useful information for the development of multiphoton clinical devices for skin disease diagnosis.

  20. Silole-Based Red Fluorescent Organic Dots for Bright Two-Photon Fluorescence In vitro Cell and In vivo Blood Vessel Imaging.

    Science.gov (United States)

    Chen, Bin; Feng, Guangxue; He, Bairong; Goh, Chiching; Xu, Shidang; Ramos-Ortiz, Gabriel; Aparicio-Ixta, Laura; Zhou, Jian; Ng, Laiguan; Zhao, Zujin; Liu, Bin; Tang, Ben Zhong

    2016-02-10

    Robust luminescent dyes with efficient two-photon fluorescence are highly desirable for biological imaging applications, but those suitable for organic dots fabrication are still rare because of aggregation-caused quenching. In this work, a red fluorescent silole, 2,5-bis[5-(dimesitylboranyl)thiophen-2-yl]-1-methyl-1,3,4-triphenylsilole ((MesB)2 DTTPS), is synthesized and characterized. (MesB)2 DTTPS exhibits enhanced fluorescence efficiency in nanoaggregates, indicative of aggregation-enhanced emission (AEE). The organic dots fabricated by encapsulating (MesB)2 DTTPS within lipid-PEG show red fluorescence peaking at 598 nm and a high fluorescence quantum yield of 32%. Upon excitation at 820 nm, the dots show a large two-photon absorption cross section of 3.43 × 10(5) GM, which yields a two-photon action cross section of 1.09 × 10(5) GM. These (MesB)2 DTTPS dots show good biocompatibility and are successfully applied to one-photon and two-photon fluorescence imaging of MCF-7 cells and two-photon in vivo visualization of the blood vascular of mouse muscle in a high-contrast and noninvasive manner. Moreover, the 3D blood vasculature located at the mouse ear skin with a depth of over 100 μm can also be visualized clearly, providing the spatiotemporal information about the whole blood vascular network. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Thermally activated delayed fluorescence organic dots for two-photon fluorescence lifetime imaging

    Science.gov (United States)

    He, Tingchao; Ren, Can; Li, Zhuohua; Xiao, Shuyu; Li, Junzi; Lin, Xiaodong; Ye, Chuanxiang; Zhang, Junmin; Guo, Lihong; Hu, Wenbo; Chen, Rui

    2018-05-01

    Autofluorescence is a major challenge in complex tissue imaging when molecules present in the biological tissue compete with the fluorophore. This issue may be resolved by designing organic molecules with long fluorescence lifetimes. The present work reports the two-photon absorption (TPA) properties of a thermally activated delayed fluorescence (TADF) molecule with carbazole as the electron donor and dicyanobenzene as the electron acceptor (i.e., 4CzIPN). The results indicate that 4CzIPN exhibits a moderate TPA cross-section (˜9 × 10-50 cm4 s photon-1), high fluorescence quantum yield, and a long fluorescence lifetime (˜1.47 μs). 4CzIPN was compactly encapsulated into an amphiphilic copolymer via nanoprecipitation to achieve water-soluble organic dots. Interestingly, 4CzIPN organic dots have been utilized in applications involving two-photon fluorescence lifetime imaging (FLIM). Our work aptly demonstrates that TADF molecules are promising candidates of nonlinear optical probes for developing next-generation multiphoton FLIM applications.

  2. Selective two-photon excitation of a vibronic state by correlated photons.

    Science.gov (United States)

    Oka, Hisaki

    2011-03-28

    We theoretically investigate the two-photon excitation of a molecular vibronic state by correlated photons with energy anticorrelation. A Morse oscillator having three sets of vibronic states is used, as an example, to evaluate the selectivity and efficiency of two-photon excitation. We show that a vibrational mode can be selectively excited with high efficiency by the correlated photons, without phase manipulation or pulse-shaping techniques. This can be achieved by controlling the quantum correlation so that the photon pair concurrently has two pulse widths, namely, a temporally narrow width and a spectrally narrow width. Though this concurrence is seemingly contradictory, we can create such a photon pair by tailoring the quantum correlation between two photons.

  3. Highly selective population of two excited states in nonresonant two-photon absorption

    International Nuclear Information System (INIS)

    Zhang Hui; Zhang Shi-An; Sun Zhen-Rong

    2011-01-01

    A nonresonant two-photon absorption process can be manipulated by tailoring the ultra-short laser pulse. In this paper, we theoretically demonstrate a highly selective population of two excited states in the nonresonant two-photon absorption process by rationally designing a spectral phase distribution. Our results show that one excited state is maximally populated while the other state population is widely tunable from zero to the maximum value. We believe that the theoretical results may play an important role in the selective population of a more complex nonlinear process comprising nonresonant two-photon absorption, such as resonance-mediated (2+1)-three-photon absorption and (2+1)-resonant multiphoton ionization. (atomic and molecular physics)

  4. Sub-diffraction positioning of a two-photon excited and optically trapped quantum dot

    DEFF Research Database (Denmark)

    Pedersen, Liselotte Jauffred; Kyrsting, Anders Højbo; Christensen, Eva Arnspang

    2014-01-01

    Colloidal quantum dots are luminescent long-lived probes that can be two-photon excited and manipulated by a single laser beam. Therefore, quantum dots can be used for simultaneous single molecule visualization and force manipulation using an infra-red laser. Here, we show that even a single opti...

  5. Phosphorus ligand imaging with two-photon fluorescence spectroscopy: towards rational catalyst immobilization

    NARCIS (Netherlands)

    Marras, F.; Kluwer, A.M.; Siekierzycka, J.R.; Vozza, A.; Brouwer, A.M.; Reek, J.N.H.

    2010-01-01

    Spotless catalysts: Ligand immobilization was studied by two-photon fluorescence microscopy with a fluorescent nixantphos ligand as probe (see picture). In the immobilization process ligand aggregates form in solution and are deposited on the support, where they appear as bright spots in

  6. Attosecond Two-Photon Interferometry for Doubly Excited States of Helium

    International Nuclear Information System (INIS)

    Feist, J.; Nagele, S.; Burgdoerfer, J.; Ticknor, C.; Collins, L. A.; Schneider, B. I.

    2011-01-01

    We show that the correlation dynamics in coherently excited doubly excited resonances of helium can be followed in real time by two-photon interferometry. This approach promises to map the evolution of the two-electron wave packet onto experimentally easily accessible noncoincident single-electron spectra. We analyze the interferometric signal in terms of a semianalytical model which is validated by a numerical solution of the time-dependent two-electron Schroedinger equation in its full dimensionality.

  7. Vibrational excitation of hydrogen molecules by two-photon absorption and third-harmonic generation

    Science.gov (United States)

    Miyamoto, Yuki; Hara, Hideaki; Hiraki, Takahiro; Masuda, Takahiko; Sasao, Noboru; Uetake, Satoshi; Yoshimi, Akihiro; Yoshimura, Koji; Yoshimura, Motohiko

    2018-01-01

    We report the coherent excitation of the vibrational state of hydrogen molecules by two-photon absorption and the resultant third-harmonic generation (THG). Parahydrogen molecules cooled by liquid nitrogen are irradiated by mid-infrared nanosecond pulses at 4.8 μm with a nearly Fourier-transform-limited linewidth. The first excited vibrational state of parahydrogen is populated by two-photon absorption of the mid-infrared photons. Because of the narrow linewidth of the mid-infrared pulses, coherence between the ground and excited states is sufficient to induce higher-order processes. Near-infrared photons from the THG are observed at 1.6 μm. The dependence of the intensity of the near-infrared radiation on mid-infrared pulse energy, target pressure, and cell length is determined. We used a simple formula for THG with consideration of realistic experimental conditions to explain the observed results.

  8. Rotational temperature measurement of NO gas using two-photon excitation spectrum

    Science.gov (United States)

    Ozaki, Tadao; Matsui, Yoshihiko; Ohsawa, Toshihiko

    1981-04-01

    The rotational temperature of nitric oxide gas has been measured by means of a single-beam two-photon excitation spectrum method using a pulsed continuously tunable dye laser. The nitric oxide gas was enclosed at about 40 Torr in a quartz cell which was put in an electric oven. The NO γ (0-0) band and R11+Q21 branches were used to obtain the two-photon excitation spectrum. The rotational temperatures were determined using the fact that molecules are distributed in the rotational levels according to the Boltzmann law. The temperature range was from room temperature to about 470 K. Observed temperatures were in good agreement with cell temperatures which were obtained by using a thermocouple.

  9. Circular dichroism probed by two-photon fluorescence microscopy in enantiopure chiral polyfluorene thin films

    NARCIS (Netherlands)

    Savoini, M.; Wu, Xiaofei; Celebrano, M.; Ziegler, J.; Biagioni, P.; Meskers, S.C.J.; Duo, L.; Hecht, B.; Finazzi, M.

    2012-01-01

    Two-photon fluorescence scanning confocal microscopy sensitive to circular dichroism with a diffraction-limited resolution well below 500 nm is demonstrated. With this method, the spatial variation of the circular dichroism of thermally annealed chiral polyfluorene thin films has been imaged. We

  10. Concentration of atomic hydrogen in a dielectric barrier discharge measured by two-photon absorption fluorescence

    Science.gov (United States)

    Dvořák, P.; Talába, M.; Obrusník, A.; Kratzer, J.; Dědina, J.

    2017-08-01

    Two-photon absorption laser-induced fluorescence (TALIF) was utilized for measuring the concentration of atomic hydrogen in a volume dielectric barrier discharge (DBD) ignited in mixtures of Ar, H2 and O2 at atmospheric pressure. The method was calibrated by TALIF of krypton diluted in argon at atmospheric pressure, proving that three-body collisions had a negligible effect on quenching of excited krypton atoms. The diagnostic study was complemented with a 3D numerical model of the gas flow and a zero-dimensional model of the chemistry in order to better understand the reaction kinetics and identify the key pathways leading to the production and destruction of atomic hydrogen. It was determined that the density of atomic hydrogen in Ar-H2 mixtures was in the order of 1021 m-3 and decreased when oxygen was added into the gas mixture. Spatially resolved measurements and simulations revealed a sharply bordered region with low atomic hydrogen concentration when oxygen was added to the gas mixture. At substoichiometric oxygen/hydrogen ratios, this H-poor region is confined to an area close to the gas inlet and it is shown that the size of this region is not only influenced by the chemistry but also by the gas flow patterns. Experimentally, it was observed that a decrease in H2 concentration in the feeding Ar-H2 mixture led to an increase in H production in the DBD.

  11. Polarised two-photon excitation of quantum well excitons for manipulation of optically pumped terahertz lasers

    Energy Technology Data Exchange (ETDEWEB)

    Slavcheva, G., E-mail: gsk23@bath.ac.uk [Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ (United Kingdom); Kavokin, A.V., E-mail: A.Kavokin@soton.ac.uk [School of Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); Spin Optics Laboratory, St. Petersburg State University, 1, Ulyanovskaya 198504 (Russian Federation)

    2014-11-15

    Optical pumping of excited exciton states in a semiconductor quantum well embedded in a microcavity is a tool for realisation of ultra-compact terahertz (THz) lasers based on stimulated optical transition between excited (2p) and ground (1s) exciton state. We show that the probability of two-photon absorption by a 2p-exciton is strongly dependent on the polarisation of both pumping photons. Five-fold variation of the threshold power for terahertz lasing by switching from circular to co-linear pumping is predicted. We identify photon polarisation configurations for achieving maximum THz photon generation quantum efficiency.

  12. Two-photon excited autofluorescence imaging of human retinal pigment epithelial cells

    Science.gov (United States)

    Han, Meng; Blindewald-Wittich, Almut; Holz, Frank G.; Giese, Günter; Niemz, Markolf H.; Snyder, Sarah; Sun, Hui; Yu, Jiayi; Agopov, Michael; La Schiazza, Olivier; Bille, Josef F.

    2006-01-01

    Degeneration of retinal pigment epithelial (RPE) cells severely impairs the visual function of retina photoreceptors. However, little is known about the events that trigger the death of RPE cells at the subcellular level. Two-photon excited autofluorescence (TPEF) imaging of RPE cells proves to be well suited to investigate both the morphological and the spectral characteristics of the human RPE cells. The dominant fluorophores of autofluorescence derive from lipofuscin (LF) granules that accumulate in the cytoplasm of the RPE cells with increasing age. Spectral TPEF imaging reveals the existence of abnormal LF granules with blue shifted autofluorescence in RPE cells of aging patients and brings new insights into the complicated composition of the LF granules. Based on a proposed two-photon laser scanning ophthalmoscope, TPEF imaging of the living retina may be valuable for diagnostic and pathological studies of age related eye diseases.

  13. Calculation of the 1s-2s two-photon excitation cross-section in atomic hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Celik, G.; Celik, E.; Kilic, H.S. [Selcuk Univ., Dept. of Physics, Faculty of Arts and Science (Turkey)

    2008-12-15

    The two-photon excitation cross-section of atomic hydrogen is calculated using explicit summation over intermediate states within the framework of dipole approximation. The matrix element for two-photon excitation is transformed into finite sums, consisting of the product of a radial and angular part. Nine intermediate states are employed in the calculation of the transition matrix element. The two-photon excitation cross-section obtained for the transition 1s{sup 2}S{sub 1/2}-2s{sup 2}S{sub 1/2} in atomic hydrogen is in good agreement with the literature. (authors)

  14. Calculation of the 1s-2s two-photon excitation cross-section in atomic hydrogen

    International Nuclear Information System (INIS)

    Celik, G.; Celik, E.; Kilic, H.S.

    2008-01-01

    The two-photon excitation cross-section of atomic hydrogen is calculated using explicit summation over intermediate states within the framework of dipole approximation. The matrix element for two-photon excitation is transformed into finite sums, consisting of the product of a radial and angular part. Nine intermediate states are employed in the calculation of the transition matrix element. The two-photon excitation cross-section obtained for the transition 1s 2 S 1/2 -2s 2 S 1/2 in atomic hydrogen is in good agreement with the literature. (authors)

  15. Measurement of wavefront aberrations in cortex and peripheral nerve using a two-photon excitation guidestar

    Science.gov (United States)

    Futia, Gregory L.; Fontaine, Arjun; McCullough, Connor; Ozbay, Baris N.; George, Nickolas M.; Caldwell, John; Restrepo, Diego; Weir, Richard; Gibson, Emily A.

    2018-02-01

    Neural-machine interfaces using optogenetics are of interest due to their minimal invasiveness and potential for parallel read in and read out of activity. One possible biological target for such an interface is the peripheral nerve, where axonlevel imaging or stimulation could greatly improve interfacing with artificial limbs or enable neuron/fascicle level neuromodulation in the vagus nerve. Two-photon imaging has been successful in imaging brain activity using genetically encoded calcium or voltage indicators, but in the peripheral nerve, this is severely limited by scattering and aberrations from myelin. We employ a Shack-Hartman wavefront sensor and two-photon excitation guidestar to quantify optical scattering and aberrations in peripheral nerves and cortex. The sciatic and vagus nerves, and cortex from a ChAT-Cre ChR-eYFP transgenic mouse were excised and imaged directly. In peripheral nerves, defocus was the strongest aberration followed by astigmatism and coma. Peripheral nerve had orders of magnitude higher aberration compared with cortex. These results point to the potential of adaptive optics for increasing the depth of two-photon access into peripheral nerves.

  16. Two-Photon-Excited Silica and Organosilica Nanoparticles for Spatiotemporal Cancer Treatment.

    Science.gov (United States)

    Croissant, Jonas G; Zink, Jeffrey I; Raehm, Laurence; Durand, Jean-Olivier

    2018-04-01

    Coherent two-photon-excited (TPE) therapy in the near-infrared (NIR) provides safer cancer treatments than current therapies lacking spatial and temporal selectivities because it is characterized by a 3D spatial resolution of 1 µm 3 and very low scattering. In this review, the principle of TPE and its significance in combination with organosilica nanoparticles (NPs) are introduced and then studies involving the design of pioneering TPE-NIR organosilica nanomaterials are discussed for bioimaging, drug delivery, and photodynamic therapy. Organosilica nanoparticles and their rich and well-established chemistry, tunable composition, porosity, size, and morphology provide ideal platforms for minimal side-effect therapies via TPE-NIR. Mesoporous silica and organosilica nanoparticles endowed with high surface areas can be functionalized to carry hydrophobic and biologically unstable two-photon absorbers for drug delivery and diagnosis. Currently, most light-actuated clinical therapeutic applications with NPs involve photodynamic therapy by singlet oxygen generation, but low photosensitizing efficiencies, tumor resistance, and lack of spatial resolution limit their applicability. On the contrary, higher photosensitizing yields, versatile therapies, and a unique spatial resolution are available with engineered two-photon-sensitive organosilica particles that selectively impact tumors while healthy tissues remain untouched. Patients suffering pathologies such as retinoblastoma, breast, and skin cancers will greatly benefit from TPE-NIR ultrasensitive diagnosis and therapy. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Nanoshells for in vivo imaging using two-photon excitation microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gao Liang; Nammalvar, Vengadesan [Department of Bioengineering, Rice University, Houston, TX 77005 (United States); Vadakkan, Tegy J, E-mail: lg3@rice.edu, E-mail: venkyn@rice.edu [Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX 77030 (United States)

    2011-09-07

    Gold nanoshells have been intensively investigated and applied to various biomedical fields because of their flexible optical tunability and biological compatibility. They hold great potential to serve as luminescent contrast agents excitable with near-infrared (NIR) lasers. In this paper, we describe the development of nanoshells with a peak of plasmon resonance at 800 nm and their subsequent use for in vivo blood vessel imaging using two-photon excitation microscopy at an excitation wavelength of 750 nm. We were able to image single nanoshell particles in blood vessels and generate optical contrast for blood vessel structure using luminescent signals. These results confirm the feasibility of engineering nanoshells with controlled optical properties for single-particle-based in vivo imaging.

  18. Sensitive and rapid detection of endogenous hydrogen sulfide distributing in different mouse viscera via a two-photon fluorescent probe

    International Nuclear Information System (INIS)

    Chen, Qian; Yang, Jinfeng; Li, Yinhui; Zheng, Jing; Yang, Ronghua

    2015-01-01

    Development of efficient methods for detection of endogenous H 2 S in living cells and tissues is of considerable significance for better understanding the biological and pathological functions of H 2 S. Two-photon (TP) fluorescent probes are favorable as powerful molecular tools for studying physiological process due to its non-invasiveness, high spatiotemporal resolution and deep-tissues imaging. Up to date, several TP probes for intracellular H 2 S imaging have been designed, but real-time imaging of endogenous H 2 S-related biological processes in tissues is hampered due to low sensitivity, long response time and interference from other biothiols. To address this issue, we herein report a novel two-photon fluorescent probe (TPP-H 2 S) for highly sensitive and fast monitoring and imaging H 2 S levels in living cells and tissues. In the presence of H 2 S, it exhibits obviously improved sensitivity (LOD: 0.12 μM) and fast response time (about 2 min) compared with the reported two-photon H 2 S probes. With two-photon excitation, TPP-H 2 S displays high signal-to-noise ratio and sensitivity even no interference in cell growth media. As further application, TPP-H 2 S is applied for fast imaging of H 2 S in living cells and different fresh tissues by two-photon confocal microscope. Most importantly we first measured the endogenous H 2 S level in different viscera by vivisection and found that the distribution of endogenous H 2 S mostly in brain, liver and lung. The excellent sensing properties of TPP-H 2 S make it a practically useful tool for further studying biological roles of H 2 S. - Highlights: • This two-photon probe exhibits an improved sensitivity and response time to H 2 S. • This probe shows excellent membrane permeability and fast visualization of H 2 S in living cells and tissues. • This probe is successfully applied to measure the endogenously produced H 2 S levels in different viscera of mouse.

  19. Two Photon Absorption Laser Induced Fluorescence for Neutral Hydrogen Profile Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Scime, Earl E. [West Virginia Univ., Morgantown, WV (United States)

    2016-09-23

    The magnitude and spatial dependence of neutral density in magnetic confinement fusion experiments is a key physical parameter, particularly in the plasma edge. Modeling codes require precise measurements of the neutral density to calculate charge-exchange power losses and drag forces on rotating plasmas. However, direct measurements of the neutral density are problematic. In this work, we proposed to construct a laser-based diagnostic capable of providing spatially resolved measurements of the neutral density in the edge of plasma in the DIII-D tokamak. The diagnostic concept is based on two-photon absorption laser induced fluorescence (TALIF). By injecting two beams of 205 nm light (co or counter propagating), ground state hydrogen (or deuterium or tritium) can be excited from the n = 1 level to the n = 3 level at the location where the two beams intersect. Individually, the beams experience no absorption, and therefore have no difficulty penetrating even dense plasmas. After excitation, a fraction of the hydrogen atoms decay from the n = 3 level to the n = 2 level and emit photons at 656 nm (the Hα line). Calculations based on the results of previous TALIF experiments in magnetic fusion devices indicated that a laser pulse energy of approximately 3 mJ delivered in 5 ns would provide sufficient signal-to-noise for detection of the fluorescence. In collaboration with the DIII-D engineering staff and experts in plasma edge diagnostics for DIII-D from Oak Ridge National Laboratory (ORNL), WVU researchers designed a TALIF system capable of providing spatially resolved measurements of neutral deuterium densities in the DIII-D edge plasma. The laser systems were specified, purchased, and assembled at WVU. The TALIF system was tested on a low-power hydrogen discharge at WVU and the plan was to move the instrument to DIII-D for installation in collaboration with ORNL researchers. After budget cuts at DIII-D, the DIII-D facility declined to support

  20. Two Photon Absorption Laser Induced Fluorescence for Neutral Hydrogen Profile Measurements

    International Nuclear Information System (INIS)

    Scime, Earl E.

    2016-01-01

    The magnitude and spatial dependence of neutral density in magnetic confinement fusion experiments is a key physical parameter, particularly in the plasma edge. Modeling codes require precise measurements of the neutral density to calculate charge-exchange power losses and drag forces on rotating plasmas. However, direct measurements of the neutral density are problematic. In this work, we proposed to construct a laser-based diagnostic capable of providing spatially resolved measurements of the neutral density in the edge of plasma in the DIII-D tokamak. The diagnostic concept is based on two-photon absorption laser induced fluorescence (TALIF). By injecting two beams of 205 nm light (co or counter propagating), ground state hydrogen (or deuterium or tritium) can be excited from the n = 1 level to the n = 3 level at the location where the two beams intersect. Individually, the beams experience no absorption, and therefore have no difficulty penetrating even dense plasmas. After excitation, a fraction of the hydrogen atoms decay from the n = 3 level to the n = 2 level and emit photons at 656 nm (the H α line). Calculations based on the results of previous TALIF experiments in magnetic fusion devices indicated that a laser pulse energy of approximately 3 mJ delivered in 5 ns would provide sufficient signal-to-noise for detection of the fluorescence. In collaboration with the DIII-D engineering staff and experts in plasma edge diagnostics for DIII-D from Oak Ridge National Laboratory (ORNL), WVU researchers designed a TALIF system capable of providing spatially resolved measurements of neutral deuterium densities in the DIII-D edge plasma. The laser systems were specified, purchased, and assembled at WVU. The TALIF system was tested on a low-power hydrogen discharge at WVU and the plan was to move the instrument to DIII-D for installation in collaboration with ORNL researchers. After budget cuts at DIII-D, the DIII-D facility declined to support installation on their

  1. Construction of an efficient two-photon fluorescent probe for imaging nitroreductase in live cells and tissues

    Science.gov (United States)

    Zhou, Liyi; Gong, Liang; Hu, Shunqin

    2018-06-01

    Compared with traditional confocal microscopy, two-photon fluorescence microscopy (TPFM), which excites a two-photon (TP) fluorophore by near-infrared light, provides improved three-dimensional image resolution with increased tissue-image depth (>500 μm) and an extended observation time. Therefore, the development of novel functional TP fluorophores has attracted great attention in recent years. Herein, a novel TP fluorophore CM-NH2, which have the donor-π-acceptor (D-π-A)-structure, was designed and synthesized. We further used this dye developed a new type of TP fluorescent probe CM-NO2 for detecting nitroreductase (NTR). Upon incubated with NTR for 15 min, CM-NO2 displayed a 90-fold fluorescence enhancement at 505 nm and the maximal TP action cross-section value after reaction was detected and calculated to be 200 GM at 760 nm. The probe exhibited excellent properties such as high sensitivity, high selectivity, low cytotoxicity, and high photostability. Moreover, the probe was utilized to image the tumor hypoxia in live HeLa cells. Finally, using the CM-NO2 to image NTR in tissues was demonstrated.

  2. In vivo imaging of cerebral energy metabolism with two-photon fluorescence lifetime microscopy of NADH.

    Science.gov (United States)

    Yaseen, Mohammad A; Sakadžić, Sava; Wu, Weicheng; Becker, Wolfgang; Kasischke, Karl A; Boas, David A

    2013-02-01

    Minimally invasive, specific measurement of cellular energy metabolism is crucial for understanding cerebral pathophysiology. Here, we present high-resolution, in vivo observations of autofluorescence lifetime as a biomarker of cerebral energy metabolism in exposed rat cortices. We describe a customized two-photon imaging system with time correlated single photon counting detection and specialized software for modeling multiple-component fits of fluorescence decay and monitoring their transient behaviors. In vivo cerebral NADH fluorescence suggests the presence of four distinct components, which respond differently to brief periods of anoxia and likely indicate different enzymatic formulations. Individual components show potential as indicators of specific molecular pathways involved in oxidative metabolism.

  3. Novel xenon calibration scheme for two-photon absorption laser induced fluorescence of hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Elliott, Drew; Scime, Earl; Short, Zachary, E-mail: zdshort@mix.wvu.edu [Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26056 (United States)

    2016-11-15

    Two photon absorption laser induced fluorescence (TALIF) measurements of neutral hydrogen and its isotopes are typically calibrated by performing TALIF measurements on krypton with the same diagnostic system and using the known ratio of the absorption cross sections [K. Niemi et al., J. Phys. D 34, 2330 (2001)]. Here we present the measurements of a new calibration method based on a ground state xenon scheme for which the fluorescent emission wavelength is nearly identical to that of hydrogen, thereby eliminating chromatic effects in the collection optics and simplifying detector calibration. We determine that the ratio of the TALIF cross sections of xenon and hydrogen is 0.024 ± 0.001.

  4. GPC light shaper for speckle-free one- and two-photon contiguous pattern excitation

    DEFF Research Database (Denmark)

    Bañas, Andrew Rafael; Palima, Darwin; Villangca, Mark Jayson

    2014-01-01

    Generalized Phase Contrast (GPC) is an efficient method for generating speckle-free contiguous optical distributions useful in diverse applications such as static beam shaping, optical manipulation and recently, for excitation in two-photon optogenetics. To fully utilize typical Gaussian lasers...... in such applications, we analytically derive conditions for photon efficient light shaping with GPC. When combined with the conditions for optimal contrast developed in previous works, our analysis further simplifies GPCx2019;s implementation. The results of our analysis are applied to practical illumination shapes......, such as a circle and different rectangles commonly used in industrial or commercial applications. We also show simple and efficient beam shaping of arbitrary shapes geared towards biophotonics research and other contemporary applications. Optimized GPC configurations consistently give ~84% efficiency and ~3x...

  5. Photonic crystal fibre enables short-wavelength two-photon laser scanning fluorescence microscopy with fura-2

    International Nuclear Information System (INIS)

    McConnell, Gail; Riis, Erling

    2004-01-01

    We report on a novel and compact reliable laser source capable of short-wavelength two-photon laser scanning fluorescence microscopy based on soliton self-frequency shift effects in photonic crystal fibre. We demonstrate the function of the system by performing two-photon microscopy of smooth muscle cells and cardiac myocytes from the rat pulmonary vein and Chinese hamster ovary cells loaded with the fluorescent calcium indicator fura-2/AM

  6. Quantitative determination of localized tissue oxygen concentration in vivo by two-photon excitation phosphorescence lifetime measurements

    NARCIS (Netherlands)

    Mik, Egbert G.; van Leeuwen, Ton G.; Raat, Nicolaas J.; Ince, Can

    2004-01-01

    This study describes the use of two-photon excitation phosphorescence lifetime measurements for quantitative oxygen determination in vivo. Doubling the excitation wavelength of Pd-porphyrin from visible light to the infrared allows for deeper tissue penetration and a more precise and confined

  7. Two-Photon Absorption Properties of Gold Fluorescent Protein: A Combined Molecular Dynamics and Quantum Chemistry Study.

    Science.gov (United States)

    Simsek, Yusuf; Brown, Alex

    2018-05-09

    Molecular dynamic (MD) simulations were carried out to obtain the conformational changes of the chromophore in the gold fluorescent protein (PDB ID: 1OXF). To obtain two-photon absorption (TPA) cross-sections, time dependent density functional theory (TD-DFT) computations were performed for chromophore geometries sampled along the trajectory. The TD-DFT computations used the CAM-B3LYP functional and 6-31+G(d) basis set with the conductor-like polarizable continuum model (PCM) with parameters for water. Results showed that two dihedral angles change remarkably over the simulation time. TPA cross-sections were found to average 20 GM for the excitation to S1 between 430 and 460 nm; however, the maximal and minimal values were 35GM and 5GM, respectively. Besides the effects of the dihedrals on the spectroscopic properties, some bond lengths affected the excitation energies and the TPA cross-sections significantly (up to ±25-30%) while the effects of bond angles were smaller (±5%). Overall the present results provide insight in the effects of conformational exibility on TPA (with gold fluorescent protein as a specific example) and suggest that further experimental measurements of TPA for gold fluorescent protein should be undertaken.

  8. N-doped carbon dots derived from bovine serum albumin and formic acid with one- and two-photon fluorescence for live cell nuclear imaging.

    Science.gov (United States)

    Tan, Mingqian; Li, Xintong; Wu, Hao; Wang, Beibei; Wu, Jing

    2015-12-01

    Carbon dots with both one- and two-photon fluorescence have drawn great attention for biomedical imaging. Herein, nitrogen-doped carbon dots were facilely developed by one-pot hydrothermal method using bovine serum albumin and formic acid as carbon sources. They are highly water-soluble with strong fluorescence when excited with ultraviolet or near infrared light. The carbon dots have a diameter of ~8.32 nm and can emit strong two-photon induced fluorescence upon excitation at 750 nm with a femtosecond laser. X-ray photoelectron spectrometer analysis revealed that the carbon dots contained three components, C, N and O, corresponding to the peak at 285, 398 and 532 eV, respectively. The Fourier-transform infrared spectroscopy analysis revealed that there are carboxyl and carboxylic groups on the surface, which allowed further linking of functional molecules. pH stability study demonstrated that the carbon dots are able to be used in a wide range of pH values. The fluorescence mechanism is also discussed in this study. Importantly, these carbon dots are biocompatible and highly photostable, which can be directly applied for both one- and two-photon living cell imaging. After proper surface functionalization with TAT peptide, they can be used as fluorescent probes for live cell nuclear-targeted imaging. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. Two-photon induced fluorescence and other optical effects in irradiated and doped fused silica

    International Nuclear Information System (INIS)

    Kramer, S.D.

    1986-07-01

    The objective of this program was to assess and identify irradiation techniques which could be used to modify the optical charactistics of doped fused silica. Primary emphasis was placed on determining if gamma ray or neutron bombardment of the glass would enhance certain Raman and nonlinear optical effects. In particular, the effect of irradiation on optical two photon induced fluorescence was studied in detail. The maximum radiation exposures used were 10 6 rads (Si) of gamma rays and neutron fluences of 1 x 10 14 neutrons/cm 2 . The optical measurements were made at room temperature between one and four months after irradiation. The maximum input light intensity was 10 9 watts/cm 2 at a near infrared (1.06 μ) input wavelength which was chosen to lie in a transparent spectral region of the glass. Under these experimental conditions a careful search revealed no detectable two-photon induced fluorescence in the region from 550 to 900 nm. The upper limit for the photon efficiency of this process was determined to be less than 1 x 10 -10 %. 89 refs., 12 figs

  10. 3D imaging of intrinsic crystalline defects in zinc oxide by spectrally resolved two-photon fluorescence microscopy

    Science.gov (United States)

    Al-Tabich, A.; Inami, W.; Kawata, Y.; Jablonski, R.; Worasawat, S.; Mimura, H.

    2017-05-01

    We present a method for three-dimensional intrinsic defect imaging in zinc oxide (ZnO) by spectrally resolved two-photon fluorescence microscopy, based on the previously presented method of observing a photoluminescence distribution in wide-gap semiconductor crystals [Noor et al., Appl. Phys. Lett. 92(16), 161106 (2008)]. A tightly focused light beam radiated by a titanium-sapphire laser is used to obtain a two-photon excitation of selected area of the ZnO sample. Photoluminescence intensity of a specific spectral range is then selected by optical band pass filters and measured by a photomultiplier tube. Reconstruction of the specimen image is done by scanning the volume of interest by a piezoelectric positioning stage and measuring the spectrally resolved photoluminescence intensity at each point. The method has been proved to be effective at locating intrinsic defects of the ZnO crystalline structure in the volume of the crystal. The method was compared with other defect imaging and 3D imaging techniques like scanning tunneling microscopy and confocal microscopy. In both cases, our method shows superior penetration abilities and, as the only method, allows location of the defects of the chosen type in 3D. In this paper, we present the results of oxygen vacancies and zinc antisites imaging in ZnO nanorods.

  11. Integrated femtosecond stimulated Raman scattering and two-photon fluorescence imaging of subcellular lipid and vesicular structures

    Science.gov (United States)

    Li, Xuesong; Lam, Wen Jiun; Cao, Zhe; Hao, Yan; Sun, Qiqi; He, Sicong; Mak, Ho Yi; Qu, Jianan Y.

    2015-11-01

    The primary goal of this study is to demonstrate that stimulated Raman scattering (SRS) as a new imaging modality can be integrated into a femtosecond (fs) nonlinear optical (NLO) microscope system. The fs sources of high pulse peak power are routinely used in multimodal nonlinear microscopy to enable efficient excitation of multiple NLO signals. However, with fs excitations, the SRS imaging of subcellular lipid and vesicular structures encounters significant interference from proteins due to poor spectral resolution and a lack of chemical specificity, respectively. We developed a unique NLO microscope of fs excitation that enables rapid acquisition of SRS and multiple two-photon excited fluorescence (TPEF) signals. In the in vivo imaging of transgenic C. elegans animals, we discovered that by cross-filtering false positive lipid signals based on the TPEF signals from tryptophan-bearing endogenous proteins and lysosome-related organelles, the imaging system produced highly accurate assignment of SRS signals to lipid. Furthermore, we demonstrated that the multimodal NLO microscope system could sequentially image lipid structure/content and organelles, such as mitochondria, lysosomes, and the endoplasmic reticulum, which are intricately linked to lipid metabolism.

  12. Optical nonlinearities of colloidal InP@ZnS core-shell quantum dots probed by Z-scan and two-photon excited emission

    International Nuclear Information System (INIS)

    Wawrzynczyk, Dominika; Szeremeta, Janusz; Samoc, Marek; Nyk, Marcin

    2015-01-01

    Spectrally resolved nonlinear optical properties of colloidal InP@ZnS core-shell quantum dots of various sizes were investigated with the Z-scan technique and two-photon fluorescence excitation method using a femtosecond laser system tunable in the range from 750 nm to 1600 nm. In principle, both techniques should provide comparable results and can be interchangeably used for determination of the nonlinear optical absorption parameters, finding maximal values of the cross sections and optimizing them. We have observed slight differences between the two-photon absorption cross sections measured by the two techniques and attributed them to the presence of non-radiative paths of absorption or relaxation. The most significant value of two-photon absorption cross section σ 2 for 4.3 nm size InP@ZnS quantum dot was equal to 2200 GM, while the two-photon excitation action cross section σ 2 Φ was found to be 682 GM at 880 nm. The properties of these cadmium-free colloidal quantum dots can be potentially useful for nonlinear bioimaging

  13. Surface plasmon-enhanced two-photon excited whispering-gallery modes ultraviolet laser from Zno microwire

    Directory of Open Access Journals (Sweden)

    Yunpeng Wang

    2017-11-01

    Full Text Available The two-photon excited UV laser with narrow line width and high Q value was obtained. The total internal reflection from the four side surfaces of the quadrilateral-ZnO microwire offered the whispering gallery mode (WGM resonant cavity. The UV emission, resonant mechanism, and laser mode characteristics were discussed in detail for this special type of micro-cavity. In addition, in order to enhance the power of the two-photon excited UV laser, the surface plasmon enhancement by the Au nanoparticles was also performed and explained well by the theory of the localized surface plasmon.

  14. Measurement of drug-target engagement in live cells by two-photon fluorescence anisotropy imaging.

    Science.gov (United States)

    Vinegoni, Claudio; Fumene Feruglio, Paolo; Brand, Christian; Lee, Sungon; Nibbs, Antoinette E; Stapleton, Shawn; Shah, Sunil; Gryczynski, Ignacy; Reiner, Thomas; Mazitschek, Ralph; Weissleder, Ralph

    2017-07-01

    The ability to directly image and quantify drug-target engagement and drug distribution with subcellular resolution in live cells and whole organisms is a prerequisite to establishing accurate models of the kinetics and dynamics of drug action. Such methods would thus have far-reaching applications in drug development and molecular pharmacology. We recently presented one such technique based on fluorescence anisotropy, a spectroscopic method based on polarization light analysis and capable of measuring the binding interaction between molecules. Our technique allows the direct characterization of target engagement of fluorescently labeled drugs, using fluorophores with a fluorescence lifetime larger than the rotational correlation of the bound complex. Here we describe an optimized protocol for simultaneous dual-channel two-photon fluorescence anisotropy microscopy acquisition to perform drug-target measurements. We also provide the necessary software to implement stream processing to visualize images and to calculate quantitative parameters. The assembly and characterization part of the protocol can be implemented in 1 d. Sample preparation, characterization and imaging of drug binding can be completed in 2 d. Although currently adapted to an Olympus FV1000MPE microscope, the protocol can be extended to other commercial or custom-built microscopes.

  15. Transient absorption study of two-photon excitation mechanism in the LH2 complex from purple bacterium Rhodobacter sphaeroides.

    Science.gov (United States)

    Stepanenko, Ilya; Kompanetz, Viktor; Makhneva, Zoya; Chekalin, Sergey; Moskalenko, Andrei; Razjivin, Andrei

    2012-03-08

    The mechanism of two-photon excitation of a peripheral light-harvesting complex LH2 (B800-850) from purple bacterium Rhodobacter sphaeroides was explained on the basis of femtosecond transient absorption data. Fast bleaching of the B850 absorption band was measured under two-photon excitation by 1350 nm femtosecond pulses, showing fast subpicosecond arrival of excitation energy to B850 circular aggregates. Any spectral changes connected with the B800 absorption band of B800-BChl molecules were absent. A similar picture was observed under one-photon excitation of the LH2 complex by 675 nm femtosecond pulses. We believe these effects may be attributed to direct excitation of high-energy excitonic states of a B850 circular aggregate or its vibrational manifold in accordance with the model of Abe [Chem. Phys. 2001, 264, 355-363].

  16. Comparing temporally-focused GPC and CGH for two-photon excitation and optogenetics in turbid media

    DEFF Research Database (Denmark)

    Villangca, Mark Jayson; Bañas, Andrew Rafael; Aabo, Thomas

    2013-01-01

    a 4f setup that directly converts phase information to intensity. The GPC method has been used with temporal focusing for excitation in two-photon optogenetics [1-3]. The computer generated hologram (CGH) is also used to generate arbitrary light patterns and has been used for optical manipulation...

  17. Deep two-photon microscopic imaging through brain tissue using the second singlet state from fluorescent agent chlorophyll α in spinach leaf.

    Science.gov (United States)

    Shi, Lingyan; Rodríguez-Contreras, Adrián; Budansky, Yury; Pu, Yang; Nguyen, Thien An; Alfano, Robert R

    2014-06-01

    Two-photon (2P) excitation of the second singlet (S₂) state was studied to achieve deep optical microscopic imaging in brain tissue when both the excitation (800 nm) and emission (685 nm) wavelengths lie in the "tissue optical window" (650 to 950 nm). S₂ state technique was used to investigate chlorophyll α (Chl α) fluorescence inside a spinach leaf under a thick layer of freshly sliced rat brain tissue in combination with 2P microscopic imaging. Strong emission at the peak wavelength of 685 nm under the 2P S₂ state of Chl α enabled the imaging depth up to 450 μm through rat brain tissue.

  18. Direct two-photon excitation of Sm3+, Eu3+, Tb3+, Tb.DOTA-, and Tb.propargylDO3A in solution

    Science.gov (United States)

    Sørensen, Thomas Just; Blackburn, Octavia A.; Tropiano, Manuel; Faulkner, Stephen

    2012-07-01

    We have observed direct two-photon excitation of samarium, europium and terbium ions in solution upon near IR excitation using a tuneable pulsed light source, and have also studied two-photon processes in a pair of related terbium complexes, namely [Tb.DOTA]- and Tb.propargylDO3A. Direct two-photon excitation of lanthanides is observed in simple systems in the absence of sensitizing chromophores. Where even simple chromophores such as a triple bond are present in the complex, then single and two-photon excitation of chromophore excited states competes with direct two-photon excitation of the ions and is the dominant pathway for sensitizing formation of the lanthanide excited state.

  19. A Reversible DNA Logic Gate Platform Operated by One- and Two-Photon Excitations.

    Science.gov (United States)

    Tam, Dick Yan; Dai, Ziwen; Chan, Miu Shan; Liu, Ling Sum; Cheung, Man Ching; Bolze, Frederic; Tin, Chung; Lo, Pik Kwan

    2016-01-04

    We demonstrate the use of two different wavelength ranges of excitation light as inputs to remotely trigger the responses of the self-assembled DNA devices (D-OR). As an important feature of this device, the dependence of the readout fluorescent signals on the two external inputs, UV excitation for 1 min and/or near infrared irradiation (NIR) at 800 nm fs laser pulses, can mimic function of signal communication in OR logic gates. Their operations could be reset easily to its initial state. Furthermore, these DNA devices exhibit efficient cellular uptake, low cytotoxicity, and high bio-stability in different cell lines. They are considered as the first example of a photo-responsive DNA logic gate system, as well as a biocompatible, multi-wavelength excited system in response to UV and NIR. This is an important step to explore the concept of photo-responsive DNA-based systems as versatile tools in DNA computing, display devices, optical communication, and biology. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Photo-redox activated drug delivery systems operating under two photon excitation in the near-IR.

    Science.gov (United States)

    Guardado-Alvarez, Tania M; Devi, Lekshmi Sudha; Vabre, Jean-Marie; Pecorelli, Travis A; Schwartz, Benjamin J; Durand, Jean-Olivier; Mongin, Olivier; Blanchard-Desce, Mireille; Zink, Jeffrey I

    2014-05-07

    We report the design and synthesis of a nano-container consisting of mesoporous silica nanoparticles with the pore openings covered by "snap-top" caps that are opened by near-IR light. A photo transducer molecule that is a reducing agent in an excited electronic state is covalently attached to the system. Near IR two-photon excitation causes inter-molecular electron transfer that reduces a disulfide bond holding the cap in place, thus allowing the cargo molecules to escape. We describe the operation of the "snap-top" release mechanism by both one- and two-photon activation. This system presents a proof of concept of a near-IR photoredox-induced nanoparticle delivery system that may lead to a new type of photodynamic drug release therapy.

  1. Search for the two-photon decay of the 2+ first excited states in 18O and 28Si

    International Nuclear Information System (INIS)

    Music, M.

    1986-01-01

    The present work describes an attempt to measure the probability for the two-photon transition between two adjacent nuclear states in the presence of an allowed, strongly predominant one-photon decay, using the Heidelberg-Darmstadt Crystal Ball Spectrometer. The branching ratios of the two-photon decay of the first excited, 2 + levels of 18 O and 28 Si relative to the one-photon, E2 transitions to the 0 + ground states were determined to be: Wγγ/Wγ = (0.7±2.4) x 10 -6 for the 2 + >0 + transition in 18 O and Wγγ/Wγ = (1.6±1.8) x 10 -6 for the 2 + >0 + transition in 28 Si. Since both results are consistent with zero, it is possible to express them as the upper limits for the two-photon decay (3 δ) of 7.9 x 10 -6 of 18 O and 6.9 x 10 -6 of 28 Si 2 + levels. These values are by far the smallest ones reported to be observed in a two-photon decay of a nuclear state. For 18 O, the result disproves theoretical estimates of the corresponding two-photon E1F1 matrix element was well as experimental values deduced from multiple-Coulomb-excitation measurements. The main experimental difficulties were caused by the gamma rays from one-photon transitions and were found to be connected with cross-talk events due to Bremsstrahlung of Compton electrons and not - as generally believed - positron annihilation in flight. (orig.)

  2. Spatially and Temporally Resolved Atomic Oxygen Measurements in Short Pulse Discharges by Two Photon Laser Induced Fluorescence

    Science.gov (United States)

    Lempert, Walter; Uddi, Mruthunjaya; Mintusov, Eugene; Jiang, Naibo; Adamovich, Igor

    2007-10-01

    Two Photon Laser Induced Fluorescence (TALIF) is used to measure time-dependent absolute oxygen atom concentrations in O2/He, O2/N2, and CH4/air plasmas produced with a 20 nanosecond duration, 20 kV pulsed discharge at 10 Hz repetition rate. Xenon calibrated spectra show that a single discharge pulse creates initial oxygen dissociation fraction of ˜0.0005 for air like mixtures at 40-60 torr total pressure. Peak O atom concentration is a factor of approximately two lower in fuel lean (φ=0.5) methane/air mixtures. In helium buffer, the initially formed atomic oxygen decays monotonically, with decay time consistent with formation of ozone. In all nitrogen containing mixtures, atomic oxygen concentrations are found to initially increase, for time scales on the order of 10-100 microseconds, due presumably to additional O2 dissociation caused by collisions with electronically excited nitrogen. Further evidence of the role of metastable N2 is demonstrated from time-dependent N2 2^nd Positive and NO Gamma band emission spectroscopy. Comparisons with modeling predictions show qualitative, but not quantitative, agreement with the experimental data.

  3. Imaging of Fluoride Ion in Living Cells and Tissues with a Two-Photon Ratiometric Fluorescence Probe

    Directory of Open Access Journals (Sweden)

    Xinyue Zhu

    2015-01-01

    Full Text Available A reaction-based two-photon (TP ratiometric fluorescence probe Z2 has been developed and successfully applied to detect and image fluoride ion in living cells and tissues. The Z2 probe was designed designed to utilize an ICT mechanism between n-butylnaphthalimide as a fluorophore and tert-butyldiphenylsilane (TBDPS as a response group. Upon addition of fluoride ion, the Si-O bond in the Z2 would be cleaved, and then a stronger electron-donating group was released. The fluorescent changes at 450 and 540 nm, respectively, made it possible to achieve ratiometric fluorescence detection. The results indicated that the Z2 could ratiometrically detect and image fluoride ion in living cells and tissues in a depth of 250 μm by two-photon microscopy (TPM.

  4. An ESIPT-based two-photon fluorescent probe detection of hydrogen peroxide in live cells and tissues.

    Science.gov (United States)

    Zhou, Liyi; Peng, Yongbo; Wang, Qianqian; Lin, Qinlu

    2017-02-01

    A variety of diseases associated with human aging, which have a strong oxidative stress, but connecting age-related diseases and oxidative stress of the basic molecular mechanisms still insufficiently understood. Oxidative stress origins from the unregulated production of reactive oxygen species (ROS), and oxidative damaging to tissues and organs from subsequent oxidation-reduction chemistry by cellular mismanagement. In particular, H 2 O 2 is a major by-product of ROS in live organisms and a common marker for oxidative stress, and its dynamic equilibrium can have various physiological and pathological consequences. H 2 O 2 is a small molecule, but it is an essential oxygen metabolite in living systems and acts as an important compound in cellular signal transduction by reversible oxidation of proteins. To quantitatively detect of H 2 O 2 in biosystems, herein, we adopted a 2-(2'-hydroxyphenyl)-4(3H)-quinazolinone (HPQ), a small organic fluorophore known for its luminescence mechanism through excited-state intramolecular proton transfer (ESIPT). HPQ was employed as a precursor to develop a turn-on probe (HPQ-H) for bioimaging applications. After cleavaging the boronic ester moiety by H 2 O 2 , HPQ-H releases a HPQ fluorophore which shows a 45-fold fluorescence intensity enhancement with high sensitivity and selectivity over other reactive oxygen species (ROS), and a high resolution imaging and large tissue-imaging depth (70-170μm) in living cells and tissues images under two-photon excitation (720nm). Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Selective Two-Photon Absorptive Resonance Femtosecond-Laser Electronic-Excitation Tagging (STARFLEET) Velocimetry in Flow and Combustion Diagnostics

    Science.gov (United States)

    Jiang, Naibo; Halls, Benjamin R.; Stauffer, Hans U.; Roy, Sukesh; Danehy, Paul M.; Gord, James R.

    2016-01-01

    Selective Two-Photon Absorptive Resonance Femtosecond-Laser Electronic-Excitation Tagging (STARFLEET), a non-seeded ultrafast-laser-based velocimetry technique, is demonstrated in reactive and non-reactive flows. STARFLEET is pumped via a two-photon resonance in N2 using 202.25-nm 100-fs light. STARFLEET greatly reduces the per-pulse energy required (30 µJ/pulse) to generate the signature FLEET emission compared to the conventional FLEET technique (1.1 mJ/pulse). This reduction in laser energy results in less energy deposited in the flow, which allows for reduced flow perturbations (reactive and non-reactive), increased thermometric accuracy, and less severe damage to materials. Velocity measurements conducted in a free jet of N2 and in a premixed flame show good agreement with theoretical velocities and further demonstrate the significantly less-intrusive nature of STARFLEET.

  6. Determination of the 1s-2s two-photon excitation cross-section in atomic hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Bickel, G.A.; McRae, G.A

    2000-07-01

    Hydrogen atoms are ablated from zirconium alloys into the gas phase by a pulsed Nd:YAG laser and photo-ionized with three photons at 243 nm via the two-photon 1s {sup 2}S{sub 1/2}-2s {sup 2}S{sub 1/2} resonant transition. A determination of the effective 1s-2s two-photon excitation cross-section is necessary to quantify the hydrogen atom density in the ablation plume. A measurement of the ion signal vs photo-ionization beam energy is fitted to an expression derived from the rate equations. The temporal and spatial properties of the photo-ionization laser beam, transit of the H atoms through the beam, and detector geometry are taken into account. The effective two-photon cross-section for this experimental configuration, derived with the rate equation formalism, is 3.3 {+-} 0.8 X 10{sup -28} cm{sup 4} W{sup -1}. This compares well with the ab initio prediction of 5 {+-} 1 X 10{sup -28} cm{sup 4} W{sup -1} under these experimental conditions. (author)

  7. Determination of the 1s-2s two-photon excitation cross-section in atomic hydrogen

    International Nuclear Information System (INIS)

    Bickel, G.A.; McRae, G.A.

    2000-01-01

    Hydrogen atoms are ablated from zirconium alloys into the gas phase by a pulsed Nd:YAG laser and photo-ionized with three photons at 243 nm via the two-photon 1s 2 S 1/2 -2s 2 S 1/2 resonant transition. A determination of the effective 1s-2s two-photon excitation cross-section is necessary to quantify the hydrogen atom density in the ablation plume. A measurement of the ion signal vs photo-ionization beam energy is fitted to an expression derived from the rate equations. The temporal and spatial properties of the photo-ionization laser beam, transit of the H atoms through the beam, and detector geometry are taken into account. The effective two-photon cross-section for this experimental configuration, derived with the rate equation formalism, is 3.3 ± 0.8 X 10 -28 cm 4 W -1 . This compares well with the ab initio prediction of 5 ± 1 X 10 -28 cm 4 W -1 under these experimental conditions. (author)

  8. Two-photon excited whispering-gallery mode ultraviolet laser from an individual ZnO microneedle

    Science.gov (United States)

    Zhu, G. P.; Xu, C. X.; Zhu, J.; Lv, C. G.; Cui, Y. P.

    2009-02-01

    Wurtzite structural ZnO microneedles with hexagonal cross section were fabricated by vapor-phase transport method and an individual microneedle was employed as a lasing microcavity. Under excitation of a femtosecond pulse laser with 800 nm wavelength, the ultraviolet (UV) laser emission was obtained, which presented narrow linewidth and high Q value. The UV emission, resonant mechanism, and laser mode characteristics were discussed in detail. The results demonstrated that the UV laser originated from the whispering-gallery mode induced by two-photon absorption assisted by Rabi oscillation.

  9. Dynamic characterization of hydrophobic and hydrophilic solutes in oleic-acid enhanced transdermal delivery using two-photon fluorescence microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Tseng, Te-Yu; Yang, Chiu-Sheng; Chen, Yang-Fang [Department of Physics, National Taiwan University, Taipei, Taiwan (China); Tsai, Tsung-Hua [Department of Dermatology, Far Eastern Memorial Hospital, New Taipei City, Taiwan (China); Dong, Chen-Yuan, E-mail: cydong@phys.ntu.edu.tw [Department of Physics, National Taiwan University, Taipei, Taiwan (China); Center for Quantum Science and Engineering, National Taiwan University, Taipei, Taiwan (China); Center for Optoelectronic Biomedicine, National Taiwan University, Taipei, Taiwan (China)

    2014-10-20

    In this letter, we propose an efficient methodology of investigating dynamic properties of sulforhodamine B and rhodamine B hexyl ester molecules transporting across ex-vivo human stratum corneum with and without oleic acid enhancement. Three-dimensional, time-lapse fluorescence images of the stratum corneum can be obtained using two-photon fluorescence microscopy. Furthermore, temporal quantifications of transport enhancements in diffusion parameters can be achieved with the use of Fick's second law. Dynamic characterization of solutes transporting across the stratum corneum is an effective method for understanding transient phenomena in transdermal delivery of probe molecules, leading to improved delivery strategies of molecular species for therapeutic purposes.

  10. Direct Vpr-Vpr Interaction in Cells monitored by two Photon Fluorescence Correlation Spectroscopy and Fluorescence Lifetime Imaging

    Directory of Open Access Journals (Sweden)

    Mély Yves

    2008-09-01

    Full Text Available Abstract Background The human immunodeficiency virus type 1 (HIV-1 encodes several regulatory proteins, notably Vpr which influences the survival of the infected cells by causing a G2/M arrest and apoptosis. Such an important role of Vpr in HIV-1 disease progression has fuelled a large number of studies, from its 3D structure to the characterization of specific cellular partners. However, no direct imaging and quantification of Vpr-Vpr interaction in living cells has yet been reported. To address this issue, eGFP- and mCherry proteins were tagged by Vpr, expressed in HeLa cells and their interaction was studied by two photon fluorescence lifetime imaging microscopy and fluorescence correlation spectroscopy. Results Results show that Vpr forms homo-oligomers at or close to the nuclear envelope. Moreover, Vpr dimers and trimers were found in the cytoplasm and in the nucleus. Point mutations in the three α helices of Vpr drastically impaired Vpr oligomerization and localization at the nuclear envelope while point mutations outside the helical regions had no effect. Theoretical structures of Vpr mutants reveal that mutations within the α-helices could perturb the leucine zipper like motifs. The ΔQ44 mutation has the most drastic effect since it likely disrupts the second helix. Finally, all Vpr point mutants caused cell apoptosis suggesting that Vpr-mediated apoptosis functions independently from Vpr oligomerization. Conclusion We report that Vpr oligomerization in HeLa cells relies on the hydrophobic core formed by the three α helices. This oligomerization is required for Vpr localization at the nuclear envelope but not for Vpr-mediated apoptosis.

  11. Characterization of scintillating CaWO{sub 4} crystals for the CRESST experiment using two-photon excitation

    Energy Technology Data Exchange (ETDEWEB)

    Hampf, Raphael; Dandl, Thomas; Muenster, Andrea; Oberauer, Lothar; Roth, Sabine; Schoenert, Stefan; Ulrich, Andreas [Physik-Department and Excellence Cluster Universe, Technische Universitaet Muenchen, D-85747 Garching (Germany)

    2016-07-01

    In the CRESST experiment for direct dark matter search, phonon and photon signals from cryogenic CaWO{sub 4} crystals are used to search for WIMP-induced nuclear recoil events. We present a novel table-top setup in which the scintillation of CaWO{sub 4} is induced by 0.7 ns laser pulses of 355 nm wavelength. The excitation occurs via two-photon absorption in the bulk material. The scintillation light is observed by time resolved optical spectroscopy. By varying the focusing of the laser-beam the excitation density can be made high enough to study quenching effects due to exciton-exciton annihilation. This allows to perform experiments to test models for the quenching factors of different ionizing projectiles in CaWO{sub 4} which are used to identify these projectiles on an event by event basis.

  12. Two-photon excitation of higher sodium levels and population transfer in a flame

    International Nuclear Information System (INIS)

    Dijk, C.A. van.

    1978-01-01

    Studies of the higher excited states of alkali atoms in the inelastic collisional interaction between excited alkali atoms and flame particles have been made. The emphasis is on an exploration of the possibilities that a flame, in combination with a laser, offers for such studies, rather than on obtaining detailed information concerning collisional transitions. Sodium atoms in a H 2 -O 2 -Ar flame at atmospheric pressure and a temperature of 1800 K were chosen as the system to be investigated. (C.F.)

  13. Ratiometric two-photon excited photoluminescence of quantum dots triggered by near-infrared-light for real-time detection of nitric oxide release in situ

    International Nuclear Information System (INIS)

    Jin, Hui; Gui, Rijun; Sun, Jie; Wang, Yanfeng

    2016-01-01

    Probe-donor integrated nanocomposites were developed from conjugating silica-coated Mn"2"+:ZnS quantum dots (QDs) with MoS_2 QDs and photosensitive nitric oxide (NO) donors (Fe_4S_3(NO)_7"−, RBS). Under excitation with near-infrared (NIR) light at 808 nm, the Mn"2"+:ZnS@SiO_2/MoS_2-RBS nanocomposites showed the dual-emissive two-photon excited photoluminescence (TPEPL) that induced RBS photolysis to release NO in situ. NO caused TPEPL quenching of Mn"2"+:ZnS QDs, but it produced almost no impact on the TPEPL of MoS_2 QDs. Hence, the nanocomposites were developed as a novel QDs-based ratiometric TPEPL probe for real-time detection of NO release in situ. The ratiometric TPEPL intensity is nearly linear (R"2 = 0.9901) with NO concentration in the range of 0.01∼0.8 μM, which corresponds to the range of NO release time (0∼15 min). The detection limit was calculated to be approximately 4 nM of NO. Experimental results confirmed that this novel ratiometric TPEPL probe possessed high selectivity and sensitivity for the detection of NO against potential competitors, and especially showed high detection performance for NIR-light triggered NO release in tumor intracellular microenvironments. These results would promote the development of versatile probe-donor integrated systems, also providing a facile and efficient strategy to real-time detect the highly controllable drug release in situ, especially in physiological microenvironments. - Highlights: • Mn"2"+:ZnS@SiO_2/MoS_2-RBS nanocomposites were developed as a novel ratiometric two-photon excited fluorescence probe. • This probe could conduct real-time detection of nitric oxide release in situ. • High feasibility of this probe was confirmed in tumor intracellular microenvironments.

  14. Two-photon excitation of porphyrin-functionalized porous silicon nanoparticles for photodynamic therapy.

    Science.gov (United States)

    Secret, Emilie; Maynadier, Marie; Gallud, Audrey; Chaix, Arnaud; Bouffard, Elise; Gary-Bobo, Magali; Marcotte, Nathalie; Mongin, Olivier; El Cheikh, Khaled; Hugues, Vincent; Auffan, Mélanie; Frochot, Céline; Morère, Alain; Maillard, Philippe; Blanchard-Desce, Mireille; Sailor, Michael J; Garcia, Marcel; Durand, Jean-Olivier; Cunin, Frédérique

    2014-12-03

    Porous silicon nanoparticles (pSiNPs) act as a sensitizer for the 2-photon excitation of a pendant porphyrin using NIR laser light, for imaging and photodynamic therapy. Mannose-functionalized pSiNPs can be vectorized to MCF-7 human breast cancer cells through a mannose receptor-mediated endocytosis mechanism to provide a 3-fold enhancement of the 2-photon PDT effect. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. LETTER TO THE EDITOR: Green emission and bandgap narrowing due to two-photon excitation in thin film CdS formed by spray pyrolysis

    Science.gov (United States)

    Ullrich, B.; Schroeder, R.

    2001-08-01

    Thin (10 µm) film CdS on Pyrex® formed by spray pyrolysis is excited below the gap at 804 nm with 200 fs laser pulses at room temperature. Excitation intensities up to 250 GW cm-2 evoke green bandgap emission due to two-photon transitions. This two-photon photoluminescence does not show a red emission contribution in contrast to the single-photon excited emission, which is dominated by broad emission in the red spectral range. It is demonstrated that two-photon excitation causes photo-induced bandgap narrowing due to Debye screening. At 250 GW cm-2 bandgap narrowing of 47 meV is observed, which corresponds to an excited electron density of 1.6×1018 cm-3.

  16. Detection of carbon monoxide (CO) in sooting hydrocarbon flames using femtosecond two-photon laser-induced fluorescence (fs-TPLIF)

    Science.gov (United States)

    Wang, Yejun; Kulatilaka, Waruna D.

    2018-01-01

    Ultrashort-pulse, femtosecond (fs)-duration, two-photon laser-induced fluorescence (fs-TPLIF) measurements of carbon monoxide (CO) are reported in rich, sooting hydrocarbon flames. CO-TPLIF detection using conventional nanosecond or picosecond lasers are often plagued by photochemical interferences, specifically under fuel-rich flames conditions. In the current study, we investigate the commonly used CO two-photon excitation scheme of the B1Σ+ ← X1Σ+ electronic transition, using approximately 100-fs-duration excitation pulses. Fluorescence emission was observed in the Ångström band originating from directly populated B1Σ+ upper state, as well as, in the third positive band from collisionally populated b3Σ+ upper state. The current work was focused on the Ångström band emission. Interference from nascent C2 emissions originating from hot soot particles in the flame could be reduced to a negligible level using a narrower detection gate width. In contrast, avoiding interferences from laser-generated C2 Swan-band emissions required specific narrowband spectral filtering in sooting flame conditions. The observed less than quadratic laser pulse energy dependence of the TPLIF signal suggests the presence of strong three-photon ionization and stimulated emission processes. In a range of CH4/air and C2H4/air premixed flames investigated, the measured CO fluorescence signals agree well with the calculated equilibrium CO number densities. Reduced-interference CO-TPLIF imaging in premixed C2H4/O2/N2 jet flames is also reported.

  17. Emissions in potassium vapour under 4S1/2-7S1/2 two-photon nsec excitation

    International Nuclear Information System (INIS)

    Pentaris, D.; Chatzikyriakos, G.; Armyras, A.; Efthimiopoulos, T.

    2010-01-01

    The two-photon excitation of 4S 1/2 -7S 1/2 transition of potassium atoms is studied. Several coherent emissions and processes are possible, such as parametric four-wave (PFWM), parametric six-wave (PSWM) mixing and competition with the stimulated hyper Raman (SHRS) and the amplified spontaneous emission (ASE). The radiations at the transitions 6P 3/2,1/2 -4S 1/2 , 6S 1/2 -4P 3/2,1/2 and 5P 3/2,1/2 -4S 1/2 are emitted only in the forward direction (indicating a parametric process), while the radiation at the transition 4P 3/2,1/2 -4S 1/2 is emitted in the forward and in the backward direction, indicating an ASE process.

  18. Imaging hydrogen flames by two-photon, laser-induced fluorescence

    Science.gov (United States)

    Miles, R.; Lempert, W.; Kumar, V.; Diskin, G.

    1991-01-01

    A nonintrusive multicomponent imaging system is developed which can image hydrogen, hot oxygen, and air simultaneously. An Ar-F excimer laser is injection-locked to cover the Q1 two-photon transition in molecular hydrogen which allows the observation of both hot oxygen and cold hydrogen. Rayleigh scattering from the water molecules occurs at the same frequency as the illuminating laser allowing analysis of the air density. Images of ignited and nonignited hydrogen jets are recorded with a high-sensitivity gated video camera. The images permit the analysis of turbulent hydrogen-core jet, the combustion zone, and the surrounding air, and two-dimensional spatial correlations can be made to study the turbulent structure and couplings between different regions of the flow field. The method is of interest to the study of practical combustion systems which employ hydrogen-air diffusion flames.

  19. Three-dimensional cell organization leads to almost immediate HRE activity as demonstrated by molecular imaging of MG-63 spheroids using two-photon excitation microscopy.

    Science.gov (United States)

    Indovina, Paola; Collini, Maddalena; Chirico, Giuseppe; Santini, Maria Teresa

    2007-02-20

    Hypoxia through HRE (hypoxia-responsive element) activity in MG-63 human osteosarcoma cells grown in monolayer and as very small, three-dimensional tumor spheroids was investigated using molecular imaging techniques. MG-63 cells were stably transfected with a vector constructed with multiple copies of the HRE sequence of the human vascular endothelial growth factor (VEGF) gene and with the enhanced green fluorescent protein (EGFP) coding sequence. During hypoxia when HIF-1alpha (hypoxia-inducible factor-1alpha) is stabilized, the binding of HIF-1 to the HRE sequences of the vector allows the transcription of EGFP and the appearance of fluorescence. Transfected monolayer cells were characterized by flow cytometric analysis in response to various hypoxic conditions and HIF-1alpha expression in these cells was assessed by Western blotting. Two-photon excitation (TPE) microscopy was then used to examine both MG-63-transfected monolayer cells and spheroids at 2 and 5 days of growth in normoxic conditions. Monolayer cells reveal almost no fluorescence, whereas even very small spheroids (HRE activation. This activation of the HRE sequences, which control a wide variety of genes, suggests that monolayer cells and spheroids of the MG-63 cell line have different genes activated and thus diverse functional activities.

  20. Two-photon excitation laser scanning microscopy of rabbit nasal septal cartilage following Nd:YAG-laser-mediated stress relaxation

    Science.gov (United States)

    Kim, Charlton C.; Wallace, Vincent P.; Coleno, Mariah L.; Dao, Xavier; Tromberg, Bruce J.; Wong, Brian J.

    2000-04-01

    Laser irradiation of hyaline cartilage result in stable shape changes due to temperature dependent stress relaxation. In this study, we determined the structural changes in chondrocytes within rabbit nasal septal cartilage tissue over a 12-day period using a two-photon laser scanning microscope (TPM) following Nd:YAG laser irradiation. During laser irradiation surface temperature, stress relaxation, and diffuse reflectance, were measured dynamically. Each specimen received one or two sequential laser exposures. The cartilage reached a peak surface temperature of about 61 degrees C during irradiation. Cartilage denatured in 50 percent EtOH was used as a positive control. TPM was performed to detect the fluorescence emission from the chondrocytes. Images of chondrocytes were obtained at depths up to 150 microns, immediately following laser exposure, and also following 12 days in culture. Few differences in the pattern or intensity of fluorescence was observed between controls and irradiated specimens imaged immediately following exposure, regardless of the number of laser pulses. However, following twelve days in tissue culture, the irradiated specimens increase, whereas the native tissue diminishes, in intensity and distribution of fluorescence in the cytoplasm. In contrast, the positive control shows only extracellular matrices and empty lacuna, feature consistent with cell membrane lysis.

  1. Two-photon excitation laser scanning microscopy of porcine nasal septal cartilage following Nd:YAG laser-mediated stress relaxation

    Science.gov (United States)

    Kim, Charlton C.; Wallace, Vincent P.; Rasouli, Alexandre; Coleno, Mariah L.; Dao, Xavier; Tromberg, Bruce J.; Wong, Brian J.

    2000-05-01

    Laser irradiation of hyaline cartilage result in stable shape changes due to temperature dependent stress relaxation. In this study, we determined the structural changes in chondrocytes within porcine nasal septal cartilage tissue over a 4-day period using a two-photon laser scanning microscope (TPM) following Nd:YAG laser irradiation (lambda equals 1.32 micrometer) using parameters that result in mechanical stress relaxation (6.0 W, 5.4 mm spot diameter). TPM excitation (780 nm) result in induction of fluorescence from endogenous agents such as NADH, NADPH, and flavoproteins in the 400 - 500 nm spectral region. During laser irradiation diffuse reflectance (from a probe HeNe laser, (lambda) equals 632.8 nm), surface temperature, and stress relaxation were measured dynamically. Each specimen received one, two, or three sequential laser exposures (average irradiation times of 5, 6, and 8 seconds). The cartilage reached a peak surface temperature of about 70 degrees Celsius during irradiation. Cartilage denatured in 50% EtOH (20 minutes) was used as a positive control. TPM was performed using a mode-locked 780 nm Titanium:Sapphire (Ti:Al203) beam with a, 63X, 1.2 N.A. water immersion objective (working distance of 200 mm) to detect the fluorescence emission from the chondrocytes. Images of chondrocytes were obtained at depths up to 150 microns (lateral resolution equals 35 micrometer X 35 micrometer). Images were obtained immediately following laser exposure, and also after 4 days in culture. In both cases, the irradiated and non-irradiated specimens do not show any discernible difference in general shape or auto fluorescence. In contrast, positive controls (immersed in 50% ethanol), show markedly increased fluorescence relative to both the native and irradiated specimens, in the cytoplasmic region.

  2. Preparation of a Two-Photon Fluorescent Probe for Imaging H2O2 in Lysosomes in Living Cells and Tissues.

    Science.gov (United States)

    Ren, Mingguang; Deng, Beibei; Kong, Xiuqi; Tang, Yonghe; Lin, Weiying

    2017-01-01

    Hydrogen peroxide (H 2 O 2 ) plays important roles in many physiological and pathological processes. At the cellular organelle level, the abnormal concentrations of H 2 O 2 in the lysosomes may cause redox imbalance and the loss of the critical functions of the lysosomes. Herein, we describe the preparation of a potent lysosome-targeted two-photon fluorescent probe (Lyso-HP) for the detection of H 2 O 2 in the lysosomes in the living cells. This unique fluorescent probe can also be employed to effectively detect H 2 O 2 in the living tissues using two-photon fluorescence microscopy.

  3. A two photon absorption laser induced fluorescence diagnostic for fusion plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Magee, R. M.; Galante, M. E.; McCarren, D.; Scime, E. E. [Physics Department, West Virginia University, Morgantown, West Virginia 26506 (United States); Boivin, R. L.; Brooks, N. H.; Groebner, R. J.; Hill, D. N. [General Atomics, San Diego, California 92121 (United States); Porter, G. D. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

    2012-10-15

    The quality of plasma produced in a magnetic confinement fusion device is influenced to a large extent by the neutral gas surrounding the plasma. The plasma is fueled by the ionization of neutrals, and charge exchange interactions between edge neutrals and plasma ions are a sink of energy and momentum. Here we describe a diagnostic capable of measuring the spatial distribution of neutral gas in a magnetically confined fusion plasma. A high intensity (5 MW/cm{sup 2}), narrow bandwidth (0.1 cm{sup -1}) laser is injected into a hydrogen plasma to excite the Lyman {beta} transition via the simultaneous absorption of two 205 nm photons. The absorption rate, determined by measurement of subsequent Balmer {alpha} emission, is proportional to the number of particles with a given velocity. Calibration is performed in situ by filling the chamber to a known pressure of neutral krypton and exciting a transition close in wavelength to that used in hydrogen. We present details of the calibration procedure, including a technique for identifying saturation broadening, measurements of the neutral density profile in a hydrogen helicon plasma, and discuss the application of the diagnostic to plasmas in the DIII-D tokamak.

  4. A two photon absorption laser induced fluorescence diagnostic for fusion plasmas.

    Science.gov (United States)

    Magee, R M; Galante, M E; McCarren, D; Scime, E E; Boivin, R L; Brooks, N H; Groebner, R J; Hill, D N; Porter, G D

    2012-10-01

    The quality of plasma produced in a magnetic confinement fusion device is influenced to a large extent by the neutral gas surrounding the plasma. The plasma is fueled by the ionization of neutrals, and charge exchange interactions between edge neutrals and plasma ions are a sink of energy and momentum. Here we describe a diagnostic capable of measuring the spatial distribution of neutral gas in a magnetically confined fusion plasma. A high intensity (5 MW/cm(2)), narrow bandwidth (0.1 cm(-1)) laser is injected into a hydrogen plasma to excite the Lyman β transition via the simultaneous absorption of two 205 nm photons. The absorption rate, determined by measurement of subsequent Balmer α emission, is proportional to the number of particles with a given velocity. Calibration is performed in situ by filling the chamber to a known pressure of neutral krypton and exciting a transition close in wavelength to that used in hydrogen. We present details of the calibration procedure, including a technique for identifying saturation broadening, measurements of the neutral density profile in a hydrogen helicon plasma, and discuss the application of the diagnostic to plasmas in the DIII-D tokamak.

  5. Ratiometric two-photon excited photoluminescence of quantum dots triggered by near-infrared-light for real-time detection of nitric oxide release in situ

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Hui [Shandong Sino-Japanese Center for Collaborative Research of Carbon Nanomaterials, Collaborative Innovation Center for Marine Biomass Fiber Materials and Textiles, College of Chemistry and Chemical Engineering, Laboratory of Fiber Materials and Modern Textile, The Growing Base for State Key Laboratory, Qingdao University, Shandong 266071 (China); Gui, Rijun, E-mail: guirijun@qdu.edu.cn [Shandong Sino-Japanese Center for Collaborative Research of Carbon Nanomaterials, Collaborative Innovation Center for Marine Biomass Fiber Materials and Textiles, College of Chemistry and Chemical Engineering, Laboratory of Fiber Materials and Modern Textile, The Growing Base for State Key Laboratory, Qingdao University, Shandong 266071 (China); Sun, Jie; Wang, Yanfeng [Institute of Materia Medica, Shandong Academy of Medical Sciences, Jinan 250062 (China)

    2016-05-30

    Probe-donor integrated nanocomposites were developed from conjugating silica-coated Mn{sup 2+}:ZnS quantum dots (QDs) with MoS{sub 2} QDs and photosensitive nitric oxide (NO) donors (Fe{sub 4}S{sub 3}(NO){sub 7}{sup −}, RBS). Under excitation with near-infrared (NIR) light at 808 nm, the Mn{sup 2+}:ZnS@SiO{sub 2}/MoS{sub 2}-RBS nanocomposites showed the dual-emissive two-photon excited photoluminescence (TPEPL) that induced RBS photolysis to release NO in situ. NO caused TPEPL quenching of Mn{sup 2+}:ZnS QDs, but it produced almost no impact on the TPEPL of MoS{sub 2} QDs. Hence, the nanocomposites were developed as a novel QDs-based ratiometric TPEPL probe for real-time detection of NO release in situ. The ratiometric TPEPL intensity is nearly linear (R{sup 2} = 0.9901) with NO concentration in the range of 0.01∼0.8 μM, which corresponds to the range of NO release time (0∼15 min). The detection limit was calculated to be approximately 4 nM of NO. Experimental results confirmed that this novel ratiometric TPEPL probe possessed high selectivity and sensitivity for the detection of NO against potential competitors, and especially showed high detection performance for NIR-light triggered NO release in tumor intracellular microenvironments. These results would promote the development of versatile probe-donor integrated systems, also providing a facile and efficient strategy to real-time detect the highly controllable drug release in situ, especially in physiological microenvironments. - Highlights: • Mn{sup 2+}:ZnS@SiO{sub 2}/MoS{sub 2}-RBS nanocomposites were developed as a novel ratiometric two-photon excited fluorescence probe. • This probe could conduct real-time detection of nitric oxide release in situ. • High feasibility of this probe was confirmed in tumor intracellular microenvironments.

  6. Upconversion luminescent logic gates and turn-on sensing of glutathione based on two-photon excited quantum dots conjugated with dopamine.

    Science.gov (United States)

    Gui, Rijun; Jin, Hui; Liu, Xifeng; Wang, Zonghua; Zhang, Feifei; Xia, Jianfei; Yang, Min; Bi, Sai

    2014-12-07

    Under the two-photon excitation, upconversion luminescent "INHIBIT" and "OR" logic gates of water-dispersed CdTe quantum dots (QDs) were constituted by conjugating the QDs with dopamine. This facilitated the development of a novel QDs-based upconversion luminescent probe for efficient turn-on sensing of glutathione.

  7. Theoretical investigation of the hyper-Raman scattering in hexagonal semiconductors under two-photon excitation near resonance with the An=2 exciton level

    Science.gov (United States)

    Semenova, L. E.

    2018-04-01

    The hyper-Raman scattering of light by LO-phonons under two-photon excitation near resonance with the An=2 exciton level in the wurtzite semiconductors A2B6 was theoretically investigated, taking into account the influence of the complex structure of the top valence band.

  8. Femtosecond, two-photon laser-induced-fluorescence imaging of atomic oxygen in an atmospheric-pressure plasma jet

    Science.gov (United States)

    Schmidt, Jacob B.; Sands, Brian L.; Kulatilaka, Waruna D.; Roy, Sukesh; Scofield, James; Gord, James R.

    2015-06-01

    Femtosecond, two-photon-absorption laser-induced-fluorescence (fs-TALIF) spectroscopy is employed to measure space- and time-resolved atomic-oxygen distributions in a nanosecond, repetitively pulsed, externally grounded, atmospheric-pressure plasma jet flowing helium with a variable oxygen admixture. The high-peak-intensity, low-average-energy femtosecond pulses result in increased TALIF signal with reduced photolytic inferences. This allows 2D imaging of absolute atomic-oxygen number densities ranging from 5.8   ×   1015 to 2.0   ×   1012cm-3 using a cooled CCD with an external intensifier. Xenon is used for signal and imaging-system calibrations to quantify the atomic-oxygen fluorescence signal. Initial results highlight a transition in discharge morphology from annular to filamentary, corresponding with a change in plasma chemistry from ozone to atomic oxygen production, as the concentration of oxygen in the feed gas is changed at a fixed voltage-pulse-repetition rate. In this configuration, significant concentrations of reactive oxygen species may be remotely generated by sustaining an active discharge beyond the confines of the dielectric capillary, which may benefit applications that require large concentrations of reactive oxygen species such as material processing or biomedical devices.

  9. Broadband high-resolution two-photon spectroscopy with laser frequency combs

    OpenAIRE

    Hipke, Arthur; Meek, Samuel A.; Ideguchi, Takuro; Hänsch, Theodor W.; Picqué, Nathalie

    2013-01-01

    Two-photon excitation spectroscopy with broad spectral span is demonstrated at Doppler-limited resolution. We describe first Fourier transform two-photon spectroscopy of an atomic sample with two mode-locked laser oscillators in a dual-comb technique. Each transition is uniquely identified by the modulation imparted by the interfering comb excitations. The temporal modulation of the spontaneous two-photon fluorescence is monitored with a single photodetector, and the spectrum is revealed by a...

  10. Two-photon absorption laser-induced fluorescence of atomic oxygen in the afterglow of pulsed positive corona discharge

    Science.gov (United States)

    Ono, Ryo; Takezawa, Kei; Oda, Tetsuji

    2009-08-01

    Atomic oxygen is measured in the afterglow of pulsed positive corona discharge using time-resolved two-photon absorption laser-induced fluorescence. The discharge occurs in a 14 mm point-to-plane gap in dry air. After the discharge pulse, the atomic oxygen density decreases at a rate of 5×104 s-1. Simultaneously, ozone density increases at almost the same rate, where the ozone density is measured using laser absorption method. This agreement between the increasing rate of atomic oxygen and decreasing rate of ozone proves that ozone is mainly produced by the well-known three-body reaction, O+O2+M→O3+M. No other process for ozone production such as O2(v)+O2→O3+O is observed. The spatial distribution of atomic oxygen density is in agreement with that of the secondary streamer luminous intensity. This agreement indicates that atomic oxygen is mainly produced in the secondary streamer channels, not in the primary streamer channels.

  11. Two-photon imaging of formaldehyde in live cells and animals utilizing a lysosome-targetable and acidic pH-activatable fluorescent probe.

    Science.gov (United States)

    Xie, Xilei; Tang, Fuyan; Shangguan, Xiaoyan; Che, Shiyi; Niu, Jinye; Xiao, Yongsheng; Wang, Xu; Tang, Bo

    2017-06-13

    Lyso-TPFP presents lysosomal targetability and an acidic pH-activatable response toward formaldehyde. Thus, it exclusively visualizes lysosomal formaldehyde and is immune against it in neutral cytosol and other organelles. In addition, two-photon fluorescence imaging endows Lyso-TPFP with the capability of in situ tracking formaldehyde in live cells and animals.

  12. High-density optical data storage based on grey level recording in photobleaching polymers using two-photon excitation under ultrashort pulse and continuous wave illumination

    International Nuclear Information System (INIS)

    Ganic, D.; Day, D.; Gu, M.

    1999-01-01

    Full text: Two-photon excitation has been employed in three-dimensional optical data storage by many researchers in an attempt to increase the storage density of a given material. The probability of two-photon excitation is proportional to the squared intensity of the incident light; this effect produces excitation only within a small region of the focus spot. Another advantage of two-photon excitation is the use of infrared illumination, which results in the reduction of scattering and enables the recording of layers at a deep depth in a thick material. The storage density thus obtained using multi-layered bit optical recording can be as high as Tbit/cm 3 . To increase this storage density even further, grey level recording can be employed. This method utilises variable exposure times of a laser beam focused into a photobleaching sample. As a result, the bleached area possesses a certain pixel value which depends upon the exposure time; this can increase the storage density many times depending upon the number of grey levels used. Our experiment shows that it is possible to attain grey level recording using both ultrashort pulsed and continuous-wave illumination. Although continuous wave illumination requires an average power of approximately 2 orders of magnitude higher than that for ultrashort pulsed illumination, it is a preferred method of recording due to its relatively low system cost and compactness. Copyright (1999) Australian Optical Society

  13. A bistriphenylamine-substituted spirobifluorene derivative exhibiting excellent nonlinearity/transparency/thermal stability trade-off and strong two-photon induced blue fluorescence

    Energy Technology Data Exchange (ETDEWEB)

    Yin, Hongyao [Department of Chemistry, Shanghai Normal University, Shanghai 200234 (China); Xiao, Haibo, E-mail: xiaohb@shnu.edu.cn [Department of Chemistry, Shanghai Normal University, Shanghai 200234 (China); Ding, Lei [Department of Chemistry, Shanghai Normal University, Shanghai 200234 (China); Zhang, Chun; Ren, Aiming [State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023 (China); Li, Bo [Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, Shanghai 200241 (China)

    2015-02-01

    A spirobifluorene-bridged donor/donor chromophore, 2,7-bis-(4-(N,N-diphenylamino)phen-1-yl)-9,9′-spirobifluorene (SPF-TP), was found to combine excellent transparency in the near UV–visible region (λ{sub cut-off} ≤ 420 nm), large two-photon absorption cross-section (4.5 × 10{sup 3}GM) and high thermal stability (T{sub d} = 501 °C). In comparison to the reported two-photon absorption molecules, SPF-TP represents the best thermal stability so far described in the literature. The main electronic factors explaining the high two-photon absorption activities of SPF-TP were analyzed by theoretical calculations. Cyclic voltammograms were employed to explore the causes of the excellent transparency of SPF-TP. It was found that the spiroconjugation effect is responsible for the excellent nonlinearity/transparency/thermal stability trade-off in SPF-TP. In addition, SPF-TP is also a good two-photon induced blue fluorescent material with high fluorescence quantum yield (Φ = 0.90, in THF). - Highlights: • We report a molecule exhibiting excellent transparency. • The two-photon absorption cross-section is as large as 4.5 × 10{sup 3}GM. • The molecule exhibits excellent thermal stability. • The molecule is a good two-photon induced blue fluorescent material. • The spiroconjugation effect explains the excellent properties.

  14. A bistriphenylamine-substituted spirobifluorene derivative exhibiting excellent nonlinearity/transparency/thermal stability trade-off and strong two-photon induced blue fluorescence

    International Nuclear Information System (INIS)

    Yin, Hongyao; Xiao, Haibo; Ding, Lei; Zhang, Chun; Ren, Aiming; Li, Bo

    2015-01-01

    A spirobifluorene-bridged donor/donor chromophore, 2,7-bis-(4-(N,N-diphenylamino)phen-1-yl)-9,9′-spirobifluorene (SPF-TP), was found to combine excellent transparency in the near UV–visible region (λ cut-off  ≤ 420 nm), large two-photon absorption cross-section (4.5 × 10 3 GM) and high thermal stability (T d  = 501 °C). In comparison to the reported two-photon absorption molecules, SPF-TP represents the best thermal stability so far described in the literature. The main electronic factors explaining the high two-photon absorption activities of SPF-TP were analyzed by theoretical calculations. Cyclic voltammograms were employed to explore the causes of the excellent transparency of SPF-TP. It was found that the spiroconjugation effect is responsible for the excellent nonlinearity/transparency/thermal stability trade-off in SPF-TP. In addition, SPF-TP is also a good two-photon induced blue fluorescent material with high fluorescence quantum yield (Φ = 0.90, in THF). - Highlights: • We report a molecule exhibiting excellent transparency. • The two-photon absorption cross-section is as large as 4.5 × 10 3 GM. • The molecule exhibits excellent thermal stability. • The molecule is a good two-photon induced blue fluorescent material. • The spiroconjugation effect explains the excellent properties

  15. Fluorescence anisotropy of tyrosinate anion using one-, two- and three-photon excitation: tyrosinate anion fluorescence.

    Science.gov (United States)

    Kierdaszuk, Borys

    2013-03-01

    We examined the emission spectra and steady-state anisotropy of tyrosinate anion fluorescence with one-photon (250-310 nm), two-photon (570-620 nm) and three-photon (750-930 nm) excitation. Similar emission spectra of the neutral (pH 7.2) and anionic (pH 13) forms of N-acetyl-L-tyrosinamide (NATyrA) (pKa 10.6) were observed for all modes of excitation, with the maxima at 302 and 352 nm, respectively. Two-photon excitation (2PE) and three-photon excitation (3PE) spectra of the anionic form were the same as that for one-photon excitation (1PE). In contrast, 2PE spectrum from the neutral form showed ~30-nm shift to shorter wavelengths relative to 1PE spectrum (λmax 275 nm) at two-photon energy (550 nm), the latter being overlapped with 3PE spectrum, both at two-photon energy (550 nm). Two-photon cross-sections for NATyrA anion at 565-580 nm were 10 % of that for N-acetyl-L-tryptophanamide (NATrpA), and increased to 90 % at 610 nm, while for the neutral form of NATyrA decreased from 2 % of that for NATrpA at 570 nm to near zero at 585 nm. Surprisingly, the fundamental anisotropy of NATyrA anion in vitrified solution at -60 °C was ~0.05 for 2PE at 610 nm as compared to near 0.3 for 1PE at 305 nm, and wavelength-dependence appears to be a basic feature of its anisotropy. In contrast, the 3PE anisotropy at 900 nm was about 0.5, and 3PE and 1PE anisotropy values appear to be related by the cos(6) θ to cos(2) θ photoselection factor (approx. 10/6) independently of excitation wavelength. Attention is drawn to the possible effect of tyrosinate anions in proteins on their multi-photon induced fluorescence emission and excitation spectra as well as excitation anisotropy spectra.

  16. A fast-response two-photon fluorescent probe for imaging endogenous H2O2 in living cells and tissues

    Science.gov (United States)

    Lu, Yanan; Shi, Xiaomin; Fan, Wenlong; Black, Cory A.; Lu, Zhengliang; Fan, Chunhua

    2018-02-01

    As a second messenger, hydrogen peroxide plays significant roles in numerous physiological and pathological processes and is related to various diseases including inflammatory disease, diabetes, neurodegenerative disorders, cardiovascular disease and Alzheimer's disease. Two-photon (TP) fluorescent probes reported for the detection of endogenous H2O2 are rare and most have drawbacks such as slow response and low sensitivity. In this report, we demonstrate a simple H2O2-specific TP fluorescent probe (TX-HP) containing a two-photon dye 6-hydroxy-2,3,4,4a-tetrahydro-1H-xanthen-1-one (TX) on the modulation of the ICT process. The probe exhibits a rapid fluorescent response to H2O2 in 9 min with both high sensitivity and selectivity. The probe can detect exogenous H2O2 in living cells. Furthermore, the probe is successfully utilized for imaging H2O2 in liver tissues.

  17. Control of excitation in the fluorescence microscope.

    Science.gov (United States)

    Lea, D J; Ward, D J

    1979-01-01

    In fluorescence microscopy image brightness and contrast and the rate of fading depend upon the intensity of illumination of the specimen. An iris diaphragm or neutral density filters may be used to reduce fluorescence excitation. Also the excitation bandwidth may be varied by using a broad band exciter filter with a set of interchangeable yellow glass filters at the lamphouse.

  18. Two-photon fluorescent polysiloxane-based films with thermally responsive self switching properties achieved by a unique reversible spirocyclization mechanism.

    Science.gov (United States)

    Zuo, Yujing; Yang, Tingxin; Zhang, Yu; Gou, Zhiming; Tian, Minggang; Kong, Xiuqi; Lin, Weiying

    2018-03-14

    Responsiveness and reversibility are present in nature, and are ubiquitous in biological systems. The realization of reversibility and responsiveness is of great importance in the development of properties and the design of new materials. However, two-photon fluorescent thermal-responsive materials have not been reported to date. Herein, we engineered thermally responsive polysiloxane materials ( Dns-non ) that exhibited unique two-photon luminescence, and this is the first report about thermally responsive luminescent materials with two-photon fluorescence. The fluorescence of Dns-non could switch from the "on" to "off" state through a facile heating and cooling process, which could be observed by the naked eye. Monitoring the temperature of the CPU in situ was achieved by easily coating D1-non onto the CPU surface, which verified the potential application in devices of Dns-non . A unique alkaline tuned reversible transition mechanism of rhodamine-B from its spirocyclic to its ring-open state was proposed. Furthermore, Dns-non appeared to be a useful cell adhesive for the culture of cells on the surface. We believe that the constructed thermally responsive silicon films which have promising utilization as a new type of functional fluorescent material, may show broad applications in materials chemistry or bioscience.

  19. Multiphoton-Excited Fluorescence of Silicon-Vacancy Color Centers in Diamond

    Science.gov (United States)

    Higbie, J. M.; Perreault, J. D.; Acosta, V. M.; Belthangady, C.; Lebel, P.; Kim, M. H.; Nguyen, K.; Demas, V.; Bajaj, V.; Santori, C.

    2017-05-01

    Silicon-vacancy color centers in nanodiamonds are promising as fluorescent labels for biological applications, with a narrow, nonbleaching emission line at 738 nm. Two-photon excitation of this fluorescence offers the possibility of low-background detection at significant tissue depth with high three-dimensional spatial resolution. We measure the two-photon fluorescence cross section of a negatively charged silicon vacancy (Si -V- ) in ion-implanted bulk diamond to be 0.74 (19 )×10-50 cm4 s /photon at an excitation wavelength of 1040 nm. Compared to the diamond nitrogen-vacancy center, the expected detection threshold of a two-photon excited Si -V center is more than an order of magnitude lower, largely due to its much narrower linewidth. We also present measurements of two- and three-photon excitation spectra, finding an increase in the two-photon cross section with decreasing wavelength, and we discuss the physical interpretation of the spectra in the context of existing models of the Si -V energy-level structure.

  20. Two-photon excitation processes to near-ultraviolet states in Ce3+:CaF2

    International Nuclear Information System (INIS)

    Hamilton, D.S.

    1982-11-01

    The two-photon transition to the lowest Ce 3+ 5d state in Ce 3+ :CaF 2 has been investigated. At liquid helium temperatures, a no-phonon resonance line is observed and is accompanied by a vibrational sideband. The peak cross section for this transition is of order 1 x 10 -53 cm 4 s indicating strong parity mixing for the 5d levels. The no-phonon line shows a polarization anisotropy consistent with a tetragonal Ce 3+ site of C 4 /sub V/ symmetry. The phonon side band shows a different anisotropy than the no-phonon line and its polarization characteristics are a function of phonon frequency and temperature

  1. Electron Energy Loss and One- and Two-Photon Excited SERS Probing of “Hot” Plasmonic Silver Nanoaggregates

    DEFF Research Database (Denmark)

    Kadkhodazadeh, Shima; Wagner, Jakob Birkedal; Joseph, Virginia

    2013-01-01

    in an optical experiment and electron energy loss intensity at energies corresponding to excitation wavelengths used for optical probing. This inverse relation exists independent on specific nanoaggregate geometries and is mainly controlled by the gap size between the particles forming the aggregate. The ratio...... between two- and one-photon excited SERS measured at different excitation wavelengths provides information about local fields in the hottest spots and their dependence on the photon energy. Our data verify experimentally the predicted increase of local optical fields in the hot spots with increasing wave...

  2. Polarized two-photon photoselection in EGFP: Theory and experiment.

    Science.gov (United States)

    Masters, T A; Marsh, R J; Blacker, T S; Armoogum, D A; Larijani, B; Bain, A J

    2018-04-07

    In this work, we present a complete theoretical description of the excited state order created by two-photon photoselection from an isotropic ground state; this encompasses both the conventionally measured quadrupolar (K = 2) and the "hidden" degree of hexadecapolar (K = 4) transition dipole alignment, their dependence on the two-photon transition tensor and emission transition dipole moment orientation. Linearly and circularly polarized two-photon absorption (TPA) and time-resolved single- and two-photon fluorescence anisotropy measurements are used to determine the structure of the transition tensor in the deprotonated form of enhanced green fluorescent protein. For excitation wavelengths between 800 nm and 900 nm, TPA is best described by a single element, almost completely diagonal, two-dimensional (planar) transition tensor whose principal axis is collinear to that of the single-photon S 0 → S 1 transition moment. These observations are in accordance with assignments of the near-infrared two-photon absorption band in fluorescent proteins to a vibronically enhanced S 0 → S 1 transition.

  3. Polarized two-photon photoselection in EGFP: Theory and experiment

    Science.gov (United States)

    Masters, T. A.; Marsh, R. J.; Blacker, T. S.; Armoogum, D. A.; Larijani, B.; Bain, A. J.

    2018-04-01

    In this work, we present a complete theoretical description of the excited state order created by two-photon photoselection from an isotropic ground state; this encompasses both the conventionally measured quadrupolar (K = 2) and the "hidden" degree of hexadecapolar (K = 4) transition dipole alignment, their dependence on the two-photon transition tensor and emission transition dipole moment orientation. Linearly and circularly polarized two-photon absorption (TPA) and time-resolved single- and two-photon fluorescence anisotropy measurements are used to determine the structure of the transition tensor in the deprotonated form of enhanced green fluorescent protein. For excitation wavelengths between 800 nm and 900 nm, TPA is best described by a single element, almost completely diagonal, two-dimensional (planar) transition tensor whose principal axis is collinear to that of the single-photon S0 → S1 transition moment. These observations are in accordance with assignments of the near-infrared two-photon absorption band in fluorescent proteins to a vibronically enhanced S0 → S1 transition.

  4. A multifunctional magnetic nanocarrier bearing fluorescent dye for targeted drug delivery by enhanced two-photon triggered release

    International Nuclear Information System (INIS)

    Banerjee, Shashwat S; Chen, D-H

    2009-01-01

    We report a novel nanoformulation for targeted drug delivery which utilizes nanophotonics through the fusion of nanotechnology with biomedical application. The approach involves an energy-transferring magnetic nanoscopic co-assembly fabricated of rhodamine B (RDB) fluorescent dye grafted gum arabic modified Fe 3 O 4 magnetic nanoparticle and photosensitive linker by which dexamethasone drug is conjugated to the magnetic nano-assembly. The advantage offered by this nanoformulation is the indirect photo-triggered-on-demand drug release by efficient up-converting energy of the near-IR (NIR) light to higher energy and intraparticle energy transfer from the dye grafted magnetic nanoparticle to the linker for drug release by cleavage. The synthesized nanoparticles were found to be of ultra-small size (13.33 nm) and are monodispersed in an aqueous suspension. Dexamethasone (Dexa) drug conjugated to RDB-GAMNP by photosensitive linker showed appreciable release of Dexa by photo-triggered response on exposure to radiation having a wavelength in the NIR region whereas no detectable release was observed in the dark. Photo-triggered response for the nanoformulation not bearing the rhodamine B dye was drastically less as less Dexa was released on exposure to NIR radiation which suggest that the photo-cleavage of linker and release of Dexa mainly originated from the indirect excitation through the uphill energy conversions based on donor-acceptor model FRET. The promising pathway of nanophotonics for the on-demand release of the drug makes this nanocarrier very promising for applications in nanomedicine.

  5. Water soluble two-photon fluorescent organic probes for long-term imaging of lysosomes in live cells and tumor spheroids.

    Science.gov (United States)

    Kumari, Pratibha; Verma, Sanjay K; Mobin, Shaikh M

    2018-01-11

    The morphological alteration of lysosomes is a powerful indicator of various pathological disorders. In this regard, we have designed and synthesized a new water soluble fluorescent Schiff-base ligand (L-lyso) containing two hydroxyl groups. L-lyso exhibits excellent two-photon properties with tracking of lysosomes in live cells as well as in 3D tumor spheroids. Furthermore, it can label lysosomes for more than 3 days. Thus, L-lyso has an edge over the commercially available expensive LysoTracker probes and also over other reported probes in terms of its long-term imaging, water solubility and facile synthesis.

  6. Dipolar versus octupolar triphenylamine-based fluorescent organic nanoparticles as brilliant one- and two-photon emitters for (bio)imaging.

    Science.gov (United States)

    Parthasarathy, Venkatakrishnan; Fery-Forgues, Suzanne; Campioli, Elisa; Recher, Gaëlle; Terenziani, Francesca; Blanchard-Desce, Mireille

    2011-11-18

    Two related triphenylamine-based dipolar and octupolar fluorophores are used to prepare aqueous suspensions of fluorescent organic nanoparticles (FONs) via the reprecipitation method. The obtained spherical nanoparticles (30-40 nm in diameter) are fluorescent in aqueous solution (up to 15% fluorescence quantum yield) and exhibit extremely high one- and two-photon brightness, superior to those obtained for quantum dots. Despite the two chromophores showing similar fluorescence in solution, the fluorescence of FONs made from the octupolar derivative is significantly red-shifted compared to that generated by the dipolar FONs. In addition, the maximum two-photon absorption cross section of the FONs made from the octupolar derivative is 55% larger than that of the dipolar derivative FONs. The experimental observations provide evidence that the different molecular shape (rodlike versus three-branched) and charge distribution (dipolar versus octupolar) of the two chromophores strongly affect the packing inside the nanoparticles as well as their spectroscopic properties and colloidal stability in pure water. The use of these FONs as probes for biphotonic in-vivo imaging is investigated on Xenopus laevis tadpoles to test their utilization for angiography. When using FONs made from the octupolar dye, the formation of microagglomerates (2-5 μm scale) is observed in vivo, with subsequent lethal occlusion of the blood vessels. Conversely, the nanoparticles of the dipolar dye allow acute imaging of blood vessels thanks to their suitable size and brightness, while no toxic effect is observed. Such a goal cannot be achieved with the dissolved dye, which permeates the vessel walls. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Excited-state kinetics of the carotenoid S//1 state in LHC II and two-photon excitation spectra of lutein and beta-carotene in solution Efficient Car S//1 yields Chl electronic energy transfer via hot S//1 states?

    CERN Document Server

    Walla, P J; Linden, Patricia A; Ohta, Kaoru

    2002-01-01

    The excited-state dynamics of the carotenoids (Car) in light- harvesting complex II (LHC II) of Chlamydomonas reinhardtii were studied by transient absorption measurements. The decay of the Car S //1 population ranges from similar to 200 fs to over 7 ps, depending on the excitation and detection wavelengths. In contrast, a 200 fs Car S//1 yields Chlorophyll (Chl) energy transfer component was the dominant time constant for our earlier two-photon fluorescence up- conversion measurements (Walla, P.J. ; et al. J. Phys. Chem. B 2000, 104, 4799-4806). We also present the two-photon excitation (TPE) spectra of lutein and beta-carotene in solution and compare them with the TPE spectrum of LHC II. The TPE-spectrum of LHC II has an onset much further to the blue and a width that is narrower than expected from comparison to the S//1 fluorescence of lutein and beta-carotene in solution. Different environments may affect the shape of the S//1 spectrum significantly. To explain the blue shift of the TPE spectrum and the d...

  8. Two-Photon Fluorescence Microscopy for Determination of the Riboflavin Concentration in the Anterior Corneal Stroma When Using the Dresden Protocol.

    Science.gov (United States)

    Seiler, Theo G; Ehmke, Tobias; Fischinger, Isaak; Zapp, Daniel; Stachs, Oliver; Seiler, Theo; Heisterkamp, Alexander

    2015-10-01

    To determine the riboflavin concentration gradient in the anterior corneal stroma when using the Dresden protocol with different dextran solutions. Three different groups of porcine corneas, five each, were compared regarding the riboflavin concentration in the anterior stroma. Before all experiments, stable hydration conditions were established for the corresponding solution. All groups were treated with 0.1% riboflavin in different dextran solutions (15%, 16%, 20%). After imbibition, two-photon microscopy was used to determine fluorescence intensity. For signal attenuation and concentration determination corneas were saturated and measured a second time by two-photon microscopy. Additionally, the distribution was calculated mathematically and compared to the empiric results. Riboflavin concentration is decreasing with depth for all dextran solutions. A nearly constant concentration could be determined over the first 75 μm. Analysis of the fit functions leads to diffusion coefficients of D = 2.97 × 10-7 cm2/s for the 15% dextran solution, D = 2.34 × 10-7 cm2/s for the 16% dextran solution, and D = 1.28 × 10-7 cm2/s for the 20% dextran solution. The riboflavin gradients of the 20% dextran group were statistically significantly different from 15% dextran starting at a depth of 220 μm and deeper (P = 0.047). The 16% dextran group differed statistically at a depth of 250 μm and deeper (P = 0.047). These results show a significant difference to those published previously. With correct settings two-photon microscopy is a precise way to determine the concentration of riboflavin in cornea. The measured gradient is excellently fit by a Gaussian distribution, which comes out as a solution of Fick's second law.

  9. Images of photoreceptors in living primate eyes using adaptive optics two-photon ophthalmoscopy

    Science.gov (United States)

    Hunter, Jennifer J.; Masella, Benjamin; Dubra, Alfredo; Sharma, Robin; Yin, Lu; Merigan, William H.; Palczewska, Grazyna; Palczewski, Krzysztof; Williams, David R.

    2011-01-01

    In vivo two-photon imaging through the pupil of the primate eye has the potential to become a useful tool for functional imaging of the retina. Two-photon excited fluorescence images of the macaque cone mosaic were obtained using a fluorescence adaptive optics scanning laser ophthalmoscope, overcoming the challenges of a low numerical aperture, imperfect optics of the eye, high required light levels, and eye motion. Although the specific fluorophores are as yet unknown, strong in vivo intrinsic fluorescence allowed images of the cone mosaic. Imaging intact ex vivo retina revealed that the strongest two-photon excited fluorescence signal comes from the cone inner segments. The fluorescence response increased following light stimulation, which could provide a functional measure of the effects of light on photoreceptors. PMID:21326644

  10. An organic dye with very large Stokes-shift and broad tunability of fluorescence: Potential two-photon probe for bioimaging and ultra-sensitive solid-state gas sensor

    Energy Technology Data Exchange (ETDEWEB)

    He, Tingchao; Tian, Xiaoqing; Lin, Xiaodong, E-mail: linxd@szu.edu.cn, E-mail: hdsun@ntu.edu.sg [College of Physics Science and Technology, Shenzhen University, Shenzhen 518060 (China); Wang, Yue; Zhao, Xin; Sun, Handong, E-mail: linxd@szu.edu.cn, E-mail: hdsun@ntu.edu.sg [Division of Physics and Applied Physics, and Centre for Disruptive Photonic Technologies (CDPT), School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371 (Singapore); Gao, Yang; Grimsdale, Andrew C. [School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798 (Singapore)

    2016-01-04

    Light-emitting nonlinear optical molecules, especially those with large Stokes shifts and broad tunability of their emission wavelength, have attracted considerable attention for various applications including biomedical imaging and fluorescent sensors. However, most fluorescent chromophores have only limited potential for such applications due to small Stokes shifts, narrow tunability of fluorescence emissions, and small optical nonlinearity in highly polar solvents. In this work, we demonstrate that a two-photon absorbing stilbene chromophore exhibits a large two-photon absorption action cross-section (ηδ = 320 GM) in dimethylsulfoxide (DMSO) and shows broad fluorescence tunability (125 nm) by manipulating the polarity of the surrounding medium. Importantly, a very large Stokes shift of up to 227 nm is achieved in DMSO. Thanks to these features, this chromophore can be utilized as a two-photon probe for bioimaging applications and in an ultrasensitive solid-state gas detector.

  11. A novel mitochondria-targeted two-photon fluorescent probe for dynamic and reversible detection of the redox cycles between peroxynitrite and glutathione.

    Science.gov (United States)

    Sun, Chunlong; Du, Wen; Wang, Peng; Wu, Yang; Wang, Baoqin; Wang, Jun; Xie, Wenjun

    2017-12-16

    Redox homeostasis is important for maintenance of normal physiological functions within cells. Redox state of cells is primarily a consequence of precise balance between levels of reducing equivalents and reactive oxygen species. Redox homeostasis between peroxynitrite (ONOO - ) and glutathione (GSH) is closely associated with physiological and pathological processes, such as prolonged relaxation in vascular tissues and smooth muscle preparations, attenuation of hepatic necrosis, and activation of matrix metalloproteinase-2. We report a two-photon fluorescent probe (TP-Se) based on water-soluble carbazole-based compound, which integrates with organic selenium, to monitor changes in ONOO - /GSH levels in cells. This probe can reversibly respond to ONOO - and GSH and exhibits high selectivity, sensitivity, and mitochondrial targeting. The probe was successfully applied to visualize changes in redox cycles during ONOO - outbreak and antioxidant GSH repair in cells. The probe will lead to significant development on redox events involved in cellular redox regulation. Copyright © 2017 Elsevier Inc. All rights reserved.

  12. Determination of the D/T fuel mixture using two-photon laser induced fluorescence in combination with neutral beam injection

    International Nuclear Information System (INIS)

    Voslamber, D.; Mandl, W.

    1997-08-01

    Doppler-free two-photon induced fluorescence in the Lyman-α lines of H, D and T has been suggested previously as a local and isotope-selective diagnostic of the intrinsic neutral hydrogen densities in magnetically confined fusion plasmas. In the present paper it is shown that the diagnostic potential of this method is significantly increased if it is combined with neutral atom beams whose characteristics are such that efficient production of thermal ground state atoms via charge exchange reactions is achieved. Considerably deeper plasma regions than just the plasma edge can thus be probed and local, isotope-selective information is obtained on the more relevant ions rather than on the neutrals. Additional diagnostic possibilities, e.g. those arising from the spectroscopic investigation of the beam particles themselves, are also discussed. (author)

  13. Fluorescent excitation of interstellar H2

    NARCIS (Netherlands)

    Black, J.H.; Dishoeck, van E.F.

    1987-01-01

    The infrared emission spectrum of H2 excited by ultraviolet absorption, followed by fluorescence, was investigated using comprehensive models of interstellar clouds for computing the spectrum and to assess the effects on the intensity to various cloud properties, such as density, size, temperature,

  14. Identification of CW two-photon transitions in Na2 and NaK

    International Nuclear Information System (INIS)

    Morgan, G.P.

    1983-01-01

    This thesis reports on the two-photon visible excitation spectra of sodium and potassium vapors. In the past, similar work has been performed on sodium and many atomic two-photon transitions have been characterized. However, many extra signals exist which do not possess the ground, 3S, state hyperfine splitting. These extra transitions are due to the sodium dimer Na 2 . 79 such transitions, from 5800A - 6500A, which lie within the resolution of the apparatus have been studied. The molecules are excited with a lowpower narrow band counterpropagating cw dye laser beam and two-photon fluorescence. The fluorescence intensities of many of these transitions are greater than the 3S to 5S and 3S to 4D atomic signals, where the 3P enhancing state lies 300 cm -1 from resonance. By comparing the number density of the atomic with any molecular ground state and also the two-photon transition rates to excited states, the intermediate enhancing state for a two-photon transition in Na 2 can be predicted to be less than 1 cm -1 from resonance with the two-photon transition. This observation, along with published Dunham coefficients, is used to identify the states involved in the two-photon transitions

  15. Two-photon physics

    International Nuclear Information System (INIS)

    Bardeen, W.A.

    1981-10-01

    A new experimental frontier has recently been opened to the study of two photon processes. The first results of many aspects of these reactions are being presented at this conference. In contrast, the theoretical development of research ito two photon processes has a much longer history. This talk reviews the many different theoretical ideas which provide a detailed framework for our understanding of two photon processes

  16. Cardiac muscle organization revealed in 3-D by imaging whole-mount mouse hearts using two-photon fluorescence and confocal microscopy.

    Science.gov (United States)

    Sivaguru, Mayandi; Fried, Glenn; Sivaguru, Barghav S; Sivaguru, Vignesh A; Lu, Xiaochen; Choi, Kyung Hwa; Saif, M Taher A; Lin, Brian; Sadayappan, Sakthivel

    2015-11-01

    The ability to image the entire adult mouse heart at high resolution in 3-D would provide enormous advantages in the study of heart disease. However, a technique for imaging nuclear/cellular detail as well as the overall structure of the entire heart in 3-D with minimal effort is lacking. To solve this problem, we modified the benzyl alcohol:benzyl benzoate (BABB) clearing technique by labeling mouse hearts with periodic acid Schiff (PAS) stain. We then imaged the hearts with a combination of two-photon fluorescence microscopy and automated tile-scan imaging/stitching. Utilizing the differential spectral properties of PAS, we could identify muscle and nuclear compartments in the heart. We were also able to visualize the differences between a 3-month-old normal mouse heart and a mouse heart that had undergone heart failure due to the expression of cardiac myosin binding protein-C (cMyBP-C) gene mutation (t/t). Using 2-D and 3-D morphometric analysis, we found that the t/t heart had anomalous ventricular shape, volume, and wall thickness, as well as a disrupted sarcomere pattern. We further validated our approach using decellularized hearts that had been cultured with 3T3 fibroblasts, which were tracked using a nuclear label. We were able to detect the 3T3 cells inside the decellularized intact heart tissue, achieving nuclear/cellular resolution in 3-D. The combination of labeling, clearing, and two-photon microscopy together with tiling eliminates laborious and time-consuming physical sectioning, alignment, and 3-D reconstruction.

  17. Quantitative 3-dimensional imaging of auxin and cytokinin levels in transgenic soybean and medicago truncatula roots via two-photon induced fluorescence imaging

    Science.gov (United States)

    Fisher, Jon; Gaillard, Paul; Nurmalasari, Ni Putu Dewi; Fellbaum, Carl; Subramaniam, Sen; Smith, Steve

    2018-02-01

    Industrial nitrogen fertilizers account for nearly 50% of the fossil fuel costs in modern agriculture and contribute to soil and water pollution. Therefore, significant interest exists in understanding and characterizing the efficiency of nitrogen fixation, and the biochemical signaling pathways which orchestrate the plant-microbial symbiosis through which plants fix nitrogen. Legume plant species exhibit a particularly efficient nitrogen uptake mechanism, using root nodules which house nitrogen-fixing rhizobial bacteria. While nodule development has been widely studied, there remain significant gaps in understanding the regulatory hormones' role in plant development. In this work, we produce 3-dimensional maps of auxin (AX) and cytokinin (CK) hormone concentrations within model plant root tips and nodules with respect to root architecture and cell type. Soybean and Medicago plants were transfected with a two-color fluorescent vector with AXsensitive green fluorescent protein (GFP) and CK-sensitive TdTomato (TdT). 3D images of soybean root nodules were captured using two-photon induced fluorescence microscopy. The resulting images were computationally analyzed using the localization code first developed by Weeks and later adapted by Kilfoil, and analyzed in the context of the root architecture. Statistical analysis of the resulting 3D hormone level maps reproduce-well the known roles of AX and CK in developing plant roots, and are the first quantitative description of these regulatory hormones tied to specific plant architecture. The analytical methods used, and the spatial distribution of these key regulatory hormones in plant roots, nodule primordia and root nodules, and their statistical interpretation are presented.

  18. Interface-Targeting Strategy Enables Two-Photon Fluorescent Lipid Droplet Probes for High-Fidelity Imaging of Turbid Tissues and Detecting Fatty Liver.

    Science.gov (United States)

    Guo, Lifang; Tian, Minggang; Feng, Ruiqing; Zhang, Ge; Zhang, Ruoyao; Li, Xuechen; Liu, Zhiqiang; He, Xiuquan; Sun, Jing Zhi; Yu, Xiaoqiang

    2018-04-04

    Lipid droplets (LDs) with unique interfacial architecture not only play crucial roles in protecting a cell from lipotoxicity and lipoapoptosis but also closely relate with many diseases such as fatty liver and diabetes. Thus, as one of the important applied biomaterials, fluorescent probes with ultrahigh selectivity for in situ and high-fidelity imaging of LDs in living cells and tissues are critical to elucidate relevant physiological and pathological events as well as detect related diseases. However, available probes only utilizing LDs' waterless neutral cores but ignoring the unique phospholipid monolayer interfaces exhibit low selectivity. They cannot differentiate neutral cores of LDs from intracellular other lipophilic microenvironments, which results in extensively cloud-like background noise and severely limited their bioapplications. Herein, to design LD probes with ultrahigh selectivity, the exceptional interfacial architecture of LDs is considered adequately and thus an interface-targeting strategy is proposed for the first time. According to the novel strategy, we have developed two amphipathic fluorescent probes (N-Cy and N-Py) by introducing different cations into a lipophilic fluorophore (nitrobenzoxadiazole (NBD)). Consequently, their cationic moiety precisely locates the interfaces through electrostatic interaction and simultaneously NBD entirely embeds into the waterless core via hydrophobic interaction. Thus, high-fidelity and background-free fluorescence imaging of LDs are expectably realized in living cells in situ. Moreover, LDs in turbid tissues like skeletal muscle slices have been clearly imaged (up to 82 μm depth) by a two-photon microscope. Importantly, using N-Cy, we not only intuitively monitored the variations of LDs in number, size, and morphology but also clearly revealed their abnormity in hepatic tissues resulting from fatty liver. Therefore, these unique probes provide excellent imaging tools for elucidating LD

  19. Production mechanism of atomic nitrogen in atmospheric pressure pulsed corona discharge measured using two-photon absorption laser-induced fluorescence

    International Nuclear Information System (INIS)

    Teramoto, Yoshiyuki; Ono, Ryo; Oda, Tetsuji

    2012-01-01

    To study the production mechanism of atomic nitrogen, the temporal profile and spatial distribution of atomic nitrogen are measured in atmospheric pressure pulsed positive corona discharge using two-photon absorption laser-induced fluorescence. The absolute atomic nitrogen density in the streamer filaments is estimated from decay rate of atomic nitrogen in N 2 discharge. The results indicate that the absolute atomic nitrogen density is approximately constant against discharge energy. When the discharge voltage is 21.5 kV, production yield of atomic nitrogen produced by an N 2 discharge pulse is estimated to be 2.9 - 9.8 × 10 13 atoms and the energy efficiency of atomic nitrogen production is estimated to be about 1.8 - 6.1 × 10 16 atoms/J. The energy efficiency of atomic nitrogen production in N 2 discharge is constant against the discharge energy, while that in N 2 /O 2 discharge increases with discharge energy. In the N 2 /O 2 discharge, two-step process of N 2 dissociation plays significant role for atomic nitrogen production.

  20. Nonlinear excitation fluorescence microscopy: source considerations for biological applications

    Science.gov (United States)

    Wokosin, David L.

    2008-02-01

    Ultra-short-pulse solid-state laser sources have improved contrast within fluorescence imaging and also opened new windows of investigation in biological imaging applications. Additionally, the pulsed illumination enables harmonic scattering microscopy which yields intrinsic structure, symmetry and contrast from viable embryos, cells and tissues. Numerous human diseases are being investigated by the combination of (more) intact dynamic tissue imaging of cellular function with gene-targeted specificity and electrophysiology context. The major limitation to more widespread use of multi-photon microscopy has been the complete system cost and added complexity above and beyond commercial camera and confocal systems. The current status of all-solid-state ultrafast lasers as excitation sources will be reviewed since these lasers offer tremendous potential for affordable, reliable, "turnkey" multiphoton imaging systems. This effort highlights the single box laser systems currently commercially available, with defined suggestions for the ranges for individual laser parameters as derived from a biological and fluorophore limited perspective. The standard two-photon dose is defined by 800nm, 10mW, 200fs, and 80Mhz - at the sample plane for tissue culture cells, i.e. after the full scanning microscope system. Selected application-derived excitation wavelengths are well represented by 700nm, 780nm, ~830nm, ~960nm, 1050nm, and 1250nm. Many of the one-box lasers have fixed or very limited excitation wavelengths available, so the lasers will be lumped near 780nm, 800nm, 900nm, 1050nm, and 1250nm. The following laser parameter ranges are discussed: average power from 200mW to 2W, pulse duration from 70fs to 700fs, pulse repetition rate from 20MHz to 200MHz, with the laser output linearly polarized with an extinction ratio at least 100:1.

  1. Combined two-photon excitation and d → f energy-transfer in Ir/lanthanide dyads with time-gated selection from a two-component emission spectrum.

    Science.gov (United States)

    Edkins, Robert M; Sykes, Daniel; Beeby, Andrew; Ward, Michael D

    2012-10-14

    In a pair of Ir/Eu and Ir/Tb dyads, two-photon excitation of the Ir-phenylpyridine chromophore at 780 nm is followed by partial d → f energy-transfer to give a combination of short-lived Ir-based (blue) and long-lived lanthanide-based (red or green) emission; these components can be selected separately by time-gated detection.

  2. Tale of two photons

    International Nuclear Information System (INIS)

    Anon.

    1994-01-01

    A very profitable spinoff from electron- positron collisions is two-photon physics. Rather than the electron and positron interacting directly via an exchanged photon, two virtual (transient) photons, one from each particle, get tangled up. With new electron-positron colliders appearing on the scene, a topical meeting on two-photon physics - 'From DAPHNE to LEP 200 and beyond' - held from 2-4 February in Paris, in the premises of the Ministry of Higher Education and Research, was particularly timely. Some 60 physicists, both experimentalists and theorists, participated, with some thirty speakers

  3. Two Photon Distribution Amplitudes

    International Nuclear Information System (INIS)

    El Beiyad, M.; Pire, B.; Szymanowski, L.; Wallon, S.

    2008-01-01

    The factorization of the amplitude of the process γ*γ→γγ in the low energy and high photon virtuality region is demonstrated at the Born order and in the leading logarithmic approximation. The leading order two photon (generalized) distribution amplitudes exhibit a characteristic ln Q 2 behaviour and obey new inhomogeneous evolution equations

  4. Ion and electron spectroscopy of strontium in the vicinity of the two-photon-excited 5p2 1S0 state

    Science.gov (United States)

    Dimitriou, A.; Cohen, S.

    2014-07-01

    Two-photon ionization of ground-state strontium is investigated experimentally in the 360-370-nm spectral range with dye laser pulses of long (˜ns) duration and low (˜1010W cm-2) intensity. The Sr+ spectra recorded with linear laser polarization are dominated by the presence of the highly correlated 5p21S0 state and by the even parity [4d6d

  5. Two-Photon Probes for Lysosomes and Mitochondria: Simultaneous Detection of Lysosomes and Mitochondria in Live Tissues by Dual-Color Two-Photon Microscopy Imaging.

    Science.gov (United States)

    Lim, Chang Su; Hong, Seung Taek; Ryu, Seong Shick; Kang, Dong Eun; Cho, Bong Rae

    2015-10-01

    Novel two-photon (TP) probes were developed for lysosomes (PLT-yellow) and mitochondria (BMT-blue and PMT-yellow). These probes emitted strong TP-excited fluorescence in cells at widely separated wavelength regions and displayed high organelle selectivity, good cell permeability, low cytotoxicity, and pH insensitivity. The BMT-blue and PLT-yellow probes could be utilized to detect lysosomes and mitochondria simultaneously in live tissues by using dual-color two-photon microscopy, with minimum interference from each other. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Two-photon excited fluorescence imaging of the pancreatic solid pseudopapillary tumor without hematoxylin and eosin stains.

    Science.gov (United States)

    Xu, Yahao; Liao, Chenxi; Chen, Jing; Chen, Youting; Zhu, Xiaoqin; Chen, Jianxin

    2016-05-01

    Solid pseudopapillary tumor (SPT) of the pancreas is an epithelial tumor with low-grade malignant potential and present more common in females. At present, the gold standard for accurate diagnosis of pancreatic tumor was mostly depending on the pathological and/or cytological evaluation. In this work, TPEF microscopy was applied to obtain the images of human normal pancreas and SPT of the pancreas without hematoxylin and eosin (H&E) staining, for the purpose of identifying the organization structural, cell morphological, and cytoplasm changing, which were then compared to their corresponding H&E stained histopathological results. Our results showed that high-resolution TPEF imaging of the pancreatic SPT can clearly distinguish the pathological features from normal pancreas in unstained histological sections, and the results are consistent with the histological results. Moreover, we measured the nuclear-cytoplasmic ratios of the pancreatic SPT and normal pancreas to characterize their difference in the cytomorphological feature. It indicated that this technique can achieve the consistent information of pathological diagnosis, and has the potential to substantially improve the optical diagnosis and treatment of the pancreatic SPT without H&E staining in the future. SCANNING 38:245-250, 2016. © 2015 Wiley Periodicals, Inc. © Wiley Periodicals, Inc.

  7. Preparation, one- and two-photon properties of carbazole derivatives containing nitrogen heterocyclic ring

    Science.gov (United States)

    Zhang, Yichi; Wang, Ping; Li, Liang; Chen, Zhimin; He, Chunying; Wu, Yiqun

    Preparation of recording materials with high two-photon absorption activities is one of the important issues to superhigh- density two-photon absorption (TPA) three-dimensional (3D) optical data storage. In this paper, three new carbazole derivatives containing nitrogen heterocyclic ring with symmetric and asymmetric structures are prepared using ethylene as the π bridge between the carbazole unit and nitrogen heterocyclic ring, namely, 9-butyl-3-(2-(1,8- naphthyridin)vinyl)-carbazole (material 1), 9-butyl-3,6-bis(2-(1,8-naphthyl)vinyl)-carbazole (material 2) and 9-butyl-3,6- bis(2-(quinolin)vinyl)-carbazole (material 3). Their one photon properties including linear absorption spectra, fluorescence emission spectra, and fluorescence quantum yields are studied. The fluorescence excited by 120 fs pulse at 800 nm Ti: sapphire laser operating at 1 kHz repetition rate with different incident powers of 9-butyl-3-(2-(quinolin) vinyl)-carbazole (material 3) was investigated, and two-photon absorption cross-sections has been obtained. It is shown that material 3 containing quinoline rings as electron acceptor with symmetric structure exhibit high two-photon absorption activity. The result implies that material 3 (9-butyl-3-(2-(quinolin) vinyl)-carbazole) is a good candidate as a promising recording material for super-high-density two-photon absorption (TPA) three-dimensional (3D) optical data storage. The influence of chemical structure of the materials on the optical properties is discussed.

  8. Two-Photon Autofluorescence Imaging Reveals Cellular Structures Throughout the Retina of the Living Primate Eye.

    Science.gov (United States)

    Sharma, Robin; Williams, David R; Palczewska, Grazyna; Palczewski, Krzysztof; Hunter, Jennifer J

    2016-02-01

    Although extrinsic fluorophores can be introduced to label specific cell types in the retina, endogenous fluorophores, such as NAD(P)H, FAD, collagen, and others, are present in all retinal layers. These molecules are a potential source of optical contrast and can enable noninvasive visualization of all cellular layers. We used a two-photon fluorescence adaptive optics scanning light ophthalmoscope (TPF-AOSLO) to explore the native autofluorescence of various cell classes spanning several layers in the unlabeled retina of a living primate eye. Three macaques were imaged on separate occasions using a custom TPF-AOSLO. Two-photon fluorescence was evoked by pulsed light at 730 and 920 nm excitation wavelengths, while fluorescence emission was collected in the visible range from several retinal layers and different locations. Backscattered light was recorded simultaneously in confocal modality and images were postprocessed to remove eye motion. All retinal layers yielded two-photon signals and the heterogeneous distribution of fluorophores provided optical contrast. Several structural features were observed, such as autofluorescence from vessel walls, Müller cell processes in the nerve fibers, mosaics of cells in the ganglion cell and other nuclear layers of the inner retina, as well as photoreceptor and RPE layers in the outer retina. This in vivo survey of two-photon autofluorescence throughout the primate retina demonstrates a wider variety of structural detail in the living eye than is available through conventional imaging methods, and broadens the use of two-photon imaging of normal and diseased eyes.

  9. Insights into esophagus tissue architecture using two-photon confocal microscopy

    Science.gov (United States)

    Liu, Nenrong; Wang, Yue; Feng, Shangyuan; Chen, Rong

    2013-08-01

    In this paper, microstructures of human esophageal mucosa were evaluated using the two-photon laser scanning confocal microscopy (TPLSCM), based on two-photon excited fluorescence (TPEF) and second harmonic generation (SHG). The distribution of epithelial cells, muscle fibers of muscularis mucosae has been distinctly obtained. Furthermore, esophageal submucosa characteristics with cancer cells invading into were detected. The variation of collagen, elastin and cancer cells is very relevant to the pathology in esophagus, especially early esophageal cancer. Our experimental results indicate that the MPM technique has the much more advantages for label-free imaging, and has the potential application in vivo in the clinical diagnosis and monitoring of early esophageal cancer.

  10. In vivo two-photon imaging of retina in rabbits and rats.

    Science.gov (United States)

    Jayabalan, Gopal Swamy; Wu, Yi-Kai; Bille, Josef F; Kim, Samuel; Mao, Xiao Wen; Gimbel, Howard V; Rauser, Michael E; Fan, Joseph T

    2018-01-01

    The purpose of this study was to evaluate the retina using near-infrared (NIR) two-photon scanning laser ophthalmoscopy. New Zealand white rabbits, albino rats, and brown Norway rats were used in this study. An autofluorescence image of the retina, including the retinal cells and its associated vasculatures was obtained by a real-time scan using the ophthalmoscope. Furthermore, the retinal vessels, nerve fiber layers and the non-pigmented retina were recorded with two-photon fluorescein angiography (FA); and the choroidal vasculatures were recorded using two-photon indocyanine green angiography (ICGA). Two-photon ICGA was achieved by exciting a second singlet state at ∼398 nm. Simultaneous two-photon FA and two-photon ICGA were performed to characterize the retinal and choroidal vessels with a single injection. The minimum laser power threshold required to elicit two-photon fluorescence was determined. The two-photon ophthalmoscope could serve as a promising tool to detect and monitor the disease progression in animal models. Moreover, these high-resolution images of retinal and choroidal vessels can be acquired in a real-time scan with a single light source, requiring no additional filters for FA or ICGA. The combination of FA and ICGA using the two-photon ophthalmoscope will help researchers to characterize the retinal diseases in animal models, and also to classify the types (classic, occult or mixed) of choroidal neovascularization (CNV) in macular degeneration. Furthermore, the prototype can be adapted to image the retina of rodents and rabbits. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. A vacuum-UV laser-induced fluorescence experiment for measurement of rotationally and vibrationally excited H2

    International Nuclear Information System (INIS)

    Vankan, P.; Heil, S.B.S.; Mazouffre, S.; Engeln, R.; Schram, D.C.; Doebele, H.F.

    2004-01-01

    An experimental setup is built to detect spatially resolved rovibrationally excited hydrogen molecules via laser-induced fluorescence. To excite the hydrogen molecules, laser radiation is produced in the vacuum UV part of the spectrum. The laser radiation is tunable between 120 nm and 230 nm and has a bandwith of 0.15 cm -1 . The wavelength of the laser radiation is calibrated by simultaneous recording of the two-photon laser induced fluorescence spectrum of nitric oxide. The excited hydrogen populations are calibrated on the basis of coherent anti-Stokes Raman scattering measurements. A population distribution is measured in the shock region of a pure hydrogen plasma expansion. The higher rotational levels (J>5) show overpopulation compared to a Boltzmann distribution determined from the lower rotational levels (J≤5)

  12. Saturated excitation of Fluorescence to quantify excitation enhancement in aperture antennas

    KAUST Repository

    Aouani, Heykel

    2012-07-23

    Fluorescence spectroscopy is widely used to probe the electromagnetic intensity amplification on optical antennas, yet measuring the excitation intensity amplification is a challenge, as the detected fluorescence signal is an intricate combination of excitation and emission. Here, we describe a novel approach to quantify the electromagnetic amplification in aperture antennas by taking advantage of the intrinsic non linear properties of the fluorescence process. Experimental measurements of the fundamental f and second harmonic 2f amplitudes of the fluorescence signal upon excitation modulation are used to quantify the electromagnetic intensity amplification with plasmonic aperture antennas. © 2012 Optical Society of America.

  13. Saturated excitation of Fluorescence to quantify excitation enhancement in aperture antennas

    KAUST Repository

    Aouani, Heykel; Hostein, Richard; Mahboub, Oussama; Devaux, Eloï se; Rigneault, Hervé ; Ebbesen, Thomas W.; Wenger, Jé rô me

    2012-01-01

    Fluorescence spectroscopy is widely used to probe the electromagnetic intensity amplification on optical antennas, yet measuring the excitation intensity amplification is a challenge, as the detected fluorescence signal is an intricate combination of excitation and emission. Here, we describe a novel approach to quantify the electromagnetic amplification in aperture antennas by taking advantage of the intrinsic non linear properties of the fluorescence process. Experimental measurements of the fundamental f and second harmonic 2f amplitudes of the fluorescence signal upon excitation modulation are used to quantify the electromagnetic intensity amplification with plasmonic aperture antennas. © 2012 Optical Society of America.

  14. Highly sensitive measurement in two-photon absorption cross section and investigation of the mechanism of two-photon-induced polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Lu Youmei E-mail: luym19@cc.tuat.ac.jp; Hasegawa, Fuyuki; Goto, Takamichi; Ohkuma, Satoshi; Fukuhara, Setsuko; Kawazu, Yukie; Totani, Kenro; Yamashita, Takashi; Watanabe, Toshiyuki E-mail: toshi@cc.tuat.ac.jp

    2004-10-01

    A novel two-photon initiator, 4,4'-bis[4-(di-n-butylamino)styryl]-benzene with the side-group methyl (Me) (abbreviated as Chromophore 1), was synthesized in comparison with the chromophore with the side group methoxy (MeO) (abbreviated as Chromophore 2). Femtosecond laser-induced fluorescence intensity was used to evaluate two-photon absorption (TPA) cross section, {delta}, by means of a charge-coupled device, USB-2000 (abbreviated as CCD). Results showed that changing the side group from Me to MeO led to a significant red-shift of the two-photon absorption ({sup 2}{lambda}{sub max}). However, the microstructures obtained by two-photon-induced polymerization (TPIP) demonstrated that the sensitivities of Chromophore 1 increased despite a two-fold decrease in the two-photon cross section {delta}{sub max,} relative to Chromophore 2. Correlated with the appearance that the long-lived charge transfer emission of the chromophore in the monomer bulk, we suggest that the intramolecular charge transfer (intra-CT) takes place within the excited dye. Then intermolecular charge transfer was successive as a result of the formation of an exciplex between the dye and the monomer. The Me group was favorable for the intra-CT, relative to MeO, which contributed to the enhancement of the sensitivity of TPIP.

  15. A portable tube exciting X-ray fluorescence analysis system

    International Nuclear Information System (INIS)

    Yang Qiang; Lai Wanchang; Ge Liangquan

    2009-01-01

    Article introduced a portable tube exciting X-ray fluorescence analysis system which is based on arm architecture. Also, we designed Tube control circuit and finished preliminary application. The energy and the intensity of the photon can be adjusted continuously by using the tube. Experiments show that high excitation efficiency obtained by setting the appropriate parameters of the tube for the various elements. (authors)

  16. Optimal Fluorescence Waveband Determination for Detecting Defective Cherry Tomatoes Using a Fluorescence Excitation-Emission Matrix

    Directory of Open Access Journals (Sweden)

    In-Suck Baek

    2014-11-01

    Full Text Available A multi-spectral fluorescence imaging technique was used to detect defective cherry tomatoes. The fluorescence excitation and emission matrix was used to measure for defects, sound surface and stem areas to determine the optimal fluorescence excitation and emission wavelengths for discrimination. Two-way ANOVA revealed the optimal excitation wavelength for detecting defect areas was 410 nm. Principal component analysis (PCA was applied to the fluorescence emission spectra of all regions at 410 nm excitation to determine the emission wavelengths for defect detection. The major emission wavelengths were 688 nm and 506 nm for the detection. Fluorescence images combined with the determined emission wavebands demonstrated the feasibility of detecting defective cherry tomatoes with >98% accuracy. Multi-spectral fluorescence imaging has potential utility in non-destructive quality sorting of cherry tomatoes.

  17. Novel triphenylamine-cored two-photon absorbing dyes for labeling of biomolecules

    International Nuclear Information System (INIS)

    Xiao Haibo; Mei Chong; Wang Yaochuan; Li, Hui; Qian Shixiong; Yin Hongyao; Xu Zhisong

    2011-01-01

    Highlights: → Two novel triphenylamine-cored chromophores were synthesized. → These two dyes have sizable two-photon absorption cross-section at 800 nm. → They possess reasonable water solubility and are suitable as labels in aqueous biological environments. → These dyes have strong chelating ability. → They display a large set of reactivity for coupling to biomolecules. - Abstract: Two novel, V-shaped and Y-shaped dipicolinate derivatives branched from triphenylamine, {4-[(E)-2-(2,6-dimethoxycarbonylpyridin-4-yl)vinyl]}-N-phenyl-N-{4- [(E)-2-(2,6-dimethoxycarbonylpyridin-4-yl)vinylphenyl]}aniline (1) and {4-[(E)-2-(2,6-dimethoxycarbonylpyridin-4-yl) vinyl]}-N,N-bis {4-[(E)-2-(2,6-dimethoxycarbonyl pyridin-4-yl)vinylphenyl]}aniline (2) were synthesized. These compounds were designed for large two-photon absorption and in particular for labeling of biomolecules. Their linear absorption, fluorescence properties and their two-photon absorption properties as well as two-photon fluorescence cell imaging were examined. When excited at 800 nm, the two-photon absorption cross-section values of chromophores 1 and 2 in THF were 208 GM, 376 GM, respectively. These two-photon absorbing dyes possess reasonable water solubility, strong chelating ability and display a large set of reactivity for coupling to biomolecules, which are apparently due to the two methoxycarbonyl groups in pyridine ring. This work suggests that chromophores 1 and 2 are promising labels potentially applicable for the tracking of biomolecules using two-photon scanning microscopy.

  18. Melanin fluorescence spectra by step-wise three photon excitation

    Science.gov (United States)

    Lai, Zhenhua; Kerimo, Josef; DiMarzio, Charles A.

    2012-03-01

    Melanin is the characteristic chromophore of human skin with various potential biological functions. Kerimo discovered enhanced melanin fluorescence by stepwise three-photon excitation in 2011. In this article, step-wise three-photon excited fluorescence (STPEF) spectrum between 450 nm -700 nm of melanin is reported. The melanin STPEF spectrum exhibited an exponential increase with wavelength. However, there was a probability of about 33% that another kind of step-wise multi-photon excited fluorescence (SMPEF) that peaks at 525 nm, shown by previous research, could also be generated using the same process. Using an excitation source at 920 nm as opposed to 830 nm increased the potential for generating SMPEF peaks at 525 nm. The SMPEF spectrum peaks at 525 nm photo-bleached faster than STPEF spectrum.

  19. Molecular photosensitisers for two-photon photodynamic therapy.

    Science.gov (United States)

    Bolze, F; Jenni, S; Sour, A; Heitz, V

    2017-11-30

    Two-photon excitation has attracted the attention of biologists, especially after the development of two-photon excited microscopy in the nineties. Since then, new applications have rapidly emerged such as the release of biologically active molecules and photodynamic therapy (PDT) using two-photon excitation. PDT, which requires a light-activated drug (photosensitiser), is a clinically approved and minimally invasive treatment for cancer and for non-malignant diseases. This feature article focuses on the engineering of molecular two-photon photosensitisers for PDT, which should bring important benefits to the treatment, increase the treatment penetration depth with near-infrared light excitation, improve the spatial selectivity and reduce the photodamage to healthy tissues. After an overview of the two-photon absorption phenomenon and the methods to evaluate two-photon induced phototoxicity on cell cultures, the different classes of photosensitisers described in the literature are discussed. The two-photon PDT performed with historical one-photon sensitisers are briefly presented, followed by specifically engineered cyclic tetrapyrrole photosensitisers, purely organic photosensitisers and transition metal complexes. Finally, targeted two-photon photosensitisers and theranostic agents that should enhance the selectivity and efficiency of the treatment are discussed.

  20. Linear photophysics, two-photon absorption and femtosecond transient absorption spectroscopy of styryl dye bases

    Energy Technology Data Exchange (ETDEWEB)

    Shaydyuk, Ye.O. [Institute of Physics, Prospect Nauki, 46, Kyiv-28 03028 Ukraine (Ukraine); Levchenko, S.M. [Institute of Molecular Biology and Genetics, 150, Akademika Zabolotnoho Str., Kyiv 036803 (Ukraine); Kurhuzenkau, S.A. [Department of Chemistry, University of Parma, Parco Area delle Scienze 17/A, Parma 43124 (Italy); Anderson, D. [NanoScienece Technology Center, University of Central Florida, 12424 Research Parkway, PAV400, Orlando, FL 32826 (United States); Department of Chemistry, University of Central Florida, 4111 Libra Drive, PSB225, Orlando, FL 32816 (United States); Masunov, A.E. [NanoScienece Technology Center, University of Central Florida, 12424 Research Parkway, PAV400, Orlando, FL 32826 (United States); Department of Chemistry, University of Central Florida, 4111 Libra Drive, PSB225, Orlando, FL 32816 (United States); South Ural State University, Lenin pr. 76, Chelyabinsk 454080 (Russian Federation); Department of Condensed Matter Physics, National Research Nuclear University MEPhI, Kashirskoye shosse 31, Moscow 115409 (Russian Federation); Photochemistry Center RAS, ul. Novatorov 7a, Moscow 119421 (Russian Federation); Kachkovsky, O.D.; Slominsky, Yu.L.; Bricks, J.L. [Insitute of Organic Chemistry, Murmanskaya Street, 5, Kyiv 03094 (Ukraine); Belfield, K.D. [College of Science and Liberal Arts, New Jersey Institute of Technology, University Heights, Newark, NJ 07102 (United States); School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an, 710062 (China); Bondar, M.V., E-mail: mbondar@mail.ucf.edu [Institute of Physics, Prospect Nauki, 46, Kyiv-28 03028 Ukraine (Ukraine)

    2017-03-15

    The steady-state and time-resolved linear spectral properties, two-photon absorption spectra and fast relaxation processes in the excited states of styryl base-type derivatives were investigated. The nature of linear absorption, fluorescence and excitation anisotropy spectra were analyzed in solvents of different polarity at room temperature and specific dependence of the solvatochromic behavior on the donor-acceptor strength of the terminal substituents was shown. Two-photon absorption (2PA) efficiency of styryl dye bases was determined in a broad spectral range using two-photon induced fluorescence technique, and cross-sections maxima of ~ 100 GM were found. The excited state absorption (ESA) and fast relaxation processes in the molecular structures were investigated by transient absorption femtosecond pump-probe methodology. The role of twisted intramolecular charge transfer (TICT) effect in the excited state of styryl dye base with dimethylamino substituent was shown. The experimental spectroscopic data were also verified by quantum chemical calculations at the Time Dependent Density Functional Theory level, combined with a polarizable continuum model.

  1. Intravital Fluorescence Excitation in Whole-Animal Optical Imaging.

    Science.gov (United States)

    Nooshabadi, Fatemeh; Yang, Hee-Jeong; Bixler, Joel N; Kong, Ying; Cirillo, Jeffrey D; Maitland, Kristen C

    2016-01-01

    Whole-animal fluorescence imaging with recombinant or fluorescently-tagged pathogens or cells enables real-time analysis of disease progression and treatment response in live animals. Tissue absorption limits penetration of fluorescence excitation light, particularly in the visible wavelength range, resulting in reduced sensitivity to deep targets. Here, we demonstrate the use of an optical fiber bundle to deliver light into the mouse lung to excite fluorescent bacteria, circumventing tissue absorption of excitation light in whole-animal imaging. We present the use of this technology to improve detection of recombinant reporter strains of tdTomato-expressing Mycobacterium bovis BCG (Bacillus Calmette Guerin) bacteria in the mouse lung. A microendoscope was integrated into a whole-animal fluorescence imager to enable intravital excitation in the mouse lung with whole-animal detection. Using this technique, the threshold of detection was measured as 103 colony forming units (CFU) during pulmonary infection. In comparison, the threshold of detection for whole-animal fluorescence imaging using standard epi-illumination was greater than 106 CFU.

  2. Enhanced two-photon emission from a dressed biexciton

    International Nuclear Information System (INIS)

    Sánchez Muñoz, Carlos; Laussy, Fabrice P; Tejedor, Carlos; Valle, Elena del

    2015-01-01

    Radiative two-photon cascades from biexcitons in semiconductor quantum dots under resonant two-photon excitation are promising candidates for the generation of photon pairs. In this work, we propose a scheme to obtain two-photon emission that allows us to operate under very intense driving fields. This approach relies on the Purcell enhancement of two-photon virtual transitions between states of the biexciton dressed by the laser. The richness provided by the biexcitonic level structure allows to reach a variety of regimes, from antibunched and bunched photon pairs with polarization orthogonal to the driving field, to polarization entangled two-photon emission. This provides evidence that the general paradigm of two-photon emission from a ladder of dressed states can find interesting, particular implementations in a variety of systems. (paper)

  3. An integrated single- and two-photon non-diffracting light-sheet microscope

    Science.gov (United States)

    Lau, Sze Cheung; Chiu, Hoi Chun; Zhao, Luwei; Zhao, Teng; Loy, M. M. T.; Du, Shengwang

    2018-04-01

    We describe a fluorescence optical microscope with both single-photon and two-photon non-diffracting light-sheet excitations for large volume imaging. With a special design to accommodate two different wavelength ranges (visible: 400-700 nm and near infrared: 800-1200 nm), we combine the line-Bessel sheet (LBS, for single-photon excitation) and the scanning Bessel beam (SBB, for two-photon excitation) light sheet together in a single microscope setup. For a transparent thin sample where the scattering can be ignored, the LBS single-photon excitation is the optimal imaging solution. When the light scattering becomes significant for a deep-cell or deep-tissue imaging, we use SBB light-sheet two-photon excitation with a longer wavelength. We achieved nearly identical lateral/axial resolution of about 350/270 nm for both imagings. This integrated light-sheet microscope may have a wide application for live-cell and live-tissue three-dimensional high-speed imaging.

  4. Light emitting diode excitation emission matrix fluorescence spectroscopy.

    Science.gov (United States)

    Hart, Sean J; JiJi, Renée D

    2002-12-01

    An excitation emission matrix (EEM) fluorescence instrument has been developed using a linear array of light emitting diodes (LED). The wavelengths covered extend from the upper UV through the visible spectrum: 370-640 nm. Using an LED array to excite fluorescence emission at multiple excitation wavelengths is a low-cost alternative to an expensive high power lamp and imaging spectrograph. The LED-EEM system is a departure from other EEM spectroscopy systems in that LEDs often have broad excitation ranges which may overlap with neighboring channels. The LED array can be considered a hybrid between a spectroscopic and sensor system, as the broad LED excitation range produces a partially selective optical measurement. The instrument has been tested and characterized using fluorescent dyes: limits of detection (LOD) for 9,10-bis(phenylethynyl)-anthracene and rhodamine B were in the mid parts-per-trillion range; detection limits for the other compounds were in the low parts-per-billion range (LED-EEMs were analyzed using parallel factor analysis (PARAFAC), which allowed the mathematical resolution of the individual contributions of the mono- and dianion fluorescein tautomers a priori. Correct identification and quantitation of six fluorescent dyes in two to six component mixtures (concentrations between 12.5 and 500 ppb) has been achieved with root mean squared errors of prediction (RMSEP) of less than 4.0 ppb for all components.

  5. Development of laser excited atomic fluorescence and ionization methods

    International Nuclear Information System (INIS)

    Winefordner, J.D.

    1991-01-01

    Progress report: May 1, 1988 to December 31, 1991. The research supported by DE-FG05-88ER13881 during the past (nearly) 3 years can be divided into the following four categories: (1) theoretical considerations of the ultimate detection powers of laser fluorescence and laser ionization methods; (2) experimental evaluation of laser excited atomic fluorescence; (3) fundamental studies of atomic and molecular parameters in flames and plasmas; (4) other studies

  6. Fluorescence study of some xanthine dyes under stepped laser excitation

    International Nuclear Information System (INIS)

    Chirkova, L.V.; Ketsle, G.A.; Ermagambetov, K.T.

    1996-01-01

    Paper is devoted to definition of triplet state in molecules of xanthine dyes and study of intramolecular energy circulation. Stepped two-quanta excitation of dyes has been carried out with help of experimental unit. Intensive luminescence activated by excitation of triplet molecules of dyes within triplet-triplet band with wave length of 1060 nm was registered for eosin. Given luminescence spectrally coincides with fast fluorescence. 5 refs., 6 figs

  7. Integrated ultrasonic particle positioning and low excitation light fluorescence imaging

    International Nuclear Information System (INIS)

    Bernassau, A. L.; Al-Rawhani, M.; Beeley, J.; Cumming, D. R. S.

    2013-01-01

    A compact hybrid system has been developed to position and detect fluorescent micro-particles by combining a Single Photon Avalanche Diode (SPAD) imager with an acoustic manipulator. The detector comprises a SPAD array, light-emitting diode (LED), lenses, and optical filters. The acoustic device is formed of multiple transducers surrounding an octagonal cavity. By stimulating pairs of transducers simultaneously, an acoustic landscape is created causing fluorescent micro-particles to agglomerate into lines. The fluorescent pattern is excited by a low power LED and detected by the SPAD imager. Our technique combines particle manipulation and visualization in a compact, low power, portable setup

  8. Continuous excitation chlorophyll fluorescence parameters: a review for practitioners.

    Science.gov (United States)

    Banks, Jonathan M

    2017-08-01

    This review introduces, defines and critically reviews a number of chlorophyll fluorescence parameters with specific reference to those derived from continuous excitation chlorophyll fluorescence. A number of common issues and criticisms are addressed. The parameters fluorescence origin (F0) and the performance indices (PI) are discussed as examples. This review attempts to unify definitions for the wide range of parameters available for measuring plant vitality, facilitating their calculation and use. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  9. Single molecule photodynamics by means of one- and two-photon approach

    International Nuclear Information System (INIS)

    Chirico, Giuseppe; Cannone, Fabio; Diaspro, Alberto

    2003-01-01

    Single molecule spectroscopy allows to investigate heterogeneous behaviours on photochemical and structural grounds. We report on studies of the effect of the excitation intensity on the internal photodynamics of simple dyes immobilized on chemically etched glass slides. The use of the excitation intensity needed for two-photon excitation induces local heating, structural changes and transitions to dark states. Similar behaviour is found on single green fluorescent proteins immobilized on glass slides or embedded in silica gels upon single-photon excitation. However, by sampling the images with sufficiently low frequency, we are able to follow relevant biological events, such as the unfolding kinetics. We find that the glass slides are preferable in terms of the signal-to-noise ratio but the protein is not preserved in its native state, while evidence for the native conformation of the single proteins in the silica gels is found in the uniformity of the fluorescence emission

  10. Fluorescent vibration-rotation excitation of cometary C2

    NARCIS (Netherlands)

    Gredel, R.; Dishoeck, van E.F.; Black, J.H.

    1989-01-01

    The statistical equilibrium equations that determine the population densities of the energy levels in cometary C2 molecules due to fluorescent excitation are examined in detail. The adopted model and molecular parameters are discussed, and a theoretical estimate is made of the two intercombination

  11. Choice of excitation source for determination of rare earth elements with radioisotope excited X ray fluorescence

    International Nuclear Information System (INIS)

    Zhang Quanshi; Chang Yongfu

    2000-01-01

    The comparisons of two radioisotope source ( 241 Am and 238 Pu) which are the most available in the radioisotope excited X Ray Fluorescence (XRF) analysis technique and two characteristic X ray series (KX and LX) analyzed for the determination of the rare-earth (RE) elements were investigated in detail. According to the principle of emission and detection of X ray , the relative excitation efficiencies were calculated by the some fundamental physical parameters including the photoelectric mass attenuation coefficient, the fluorescent yield, the absorption jump factor, the emission probability of the detected fluorescent line with reference to other liens of the same series etc., The advantages and disadvantages of the two conditions are discussed. These results may determine the optimal excitation and detection conditions for different rare-earth elements. The experimental results with nine rare-earth elements (Ce, Nd, Sm, Tb, Tm, Ho, Er, Yb and Lu) are in agreement with the results of theoretical calculations

  12. The development of efficient two-photon singlet oxygen sensitizers

    DEFF Research Database (Denmark)

    Nielsen, Christian Benedikt

    The development of efficient two-photon singlet oxygen sensitizers is addressed focusing on organic synthesis. Photophysical measurements were carried out on new lipophilic molecules, where two-photon absorption cross sections and singlet oxygen quantumyields were measured. Design principles...... for making efficient two-photon singlet oxygen sensitizers were then constructed from these results. Charge-transfer in the excited state of the prepared molecules was shown to play a pivotal role in the generationof singlet oxygen. This was established through studies of substituent effects on both...... the singlet oxygen yield and the two-photon absorption cross section, where it was revealed that a careful balancing of the amount of charge transfer present in theexcited state of the sensitizer is necessary to obtain both a high singlet oxygen quantum yield and a high two-photon cross section. An increasing...

  13. Two-photon spin generation and detection

    Energy Technology Data Exchange (ETDEWEB)

    Miah, M Idrish, E-mail: m.miah@griffith.edu.a [Nanoscale Science and Technology Centre, Griffith University, Nathan, Brisbane, QLD 4111 (Australia)

    2009-02-21

    A time- and polarization-resolved two-photon pump-probe investigation is performed in lightly doped GaAs. We generate spin-polarized electrons in bulk GaAs at various temperatures using right-circularly polarized two-photon excitation and detect them by probing the spin-dependent transmission of the sample. The spin polarization (P) of conduction band electrons, as measured using probe pulses with the same (right) and opposite (left) circular polarization, is measured in dependences of pump-probe delay ({Delta}t), lattice temperature (T{sub L}), doping density (n) as well as of the excess photon energy {Delta}E{sub 2{omega}}= {h_bar}2{omega} - E{sub g}, where E{sub g} is the band gap energy. P is found to be decayed with {Delta}t and enhanced with the decrease in T{sub L} or the increase in n. It is also found that P decreases with the increase in {Delta}E{sub 2{omega}}and depolarizes rapidly for {Delta}E{sub 2{omega}}> {Delta}E{sub SO}, where {Delta}E{sub SO} is the spin-orbit splitting energy. The results demonstrate that due to a much longer absorption depth highly polarized spins can be generated optically by two-photon pumping of bulk semiconductors.

  14. Two-photon spin generation and detection

    International Nuclear Information System (INIS)

    Miah, M Idrish

    2009-01-01

    A time- and polarization-resolved two-photon pump-probe investigation is performed in lightly doped GaAs. We generate spin-polarized electrons in bulk GaAs at various temperatures using right-circularly polarized two-photon excitation and detect them by probing the spin-dependent transmission of the sample. The spin polarization (P) of conduction band electrons, as measured using probe pulses with the same (right) and opposite (left) circular polarization, is measured in dependences of pump-probe delay (Δt), lattice temperature (T L ), doping density (n) as well as of the excess photon energy ΔE 2ω = ℎ2ω - E g , where E g is the band gap energy. P is found to be decayed with Δt and enhanced with the decrease in T L or the increase in n. It is also found that P decreases with the increase in ΔE 2ω and depolarizes rapidly for ΔE 2ω > ΔE SO , where ΔE SO is the spin-orbit splitting energy. The results demonstrate that due to a much longer absorption depth highly polarized spins can be generated optically by two-photon pumping of bulk semiconductors.

  15. Scanless multitarget-matching multiphoton excitation fluorescence microscopy

    Directory of Open Access Journals (Sweden)

    Junpeng Qiu

    2018-03-01

    Full Text Available Using the combination of a reflective blazed grating and a reflective phase-only diffractive spatial light modulator (SLM, scanless multitarget-matching multiphoton excitation fluorescence microscopy (SMTM-MPM was achieved. The SLM shaped an incoming mode-locked, near-infrared Ti:sapphire laser beam into an excitation pattern with addressable shapes and sizes that matched the samples of interest in the field of view. Temporal and spatial focusing were simultaneously realized by combining an objective lens and a blazed grating. The fluorescence signal from illuminated areas was recorded by a two-dimensional sCMOS camera. Compared with a conventional temporal focusing multiphoton microscope, our microscope achieved effective use of the laser power and decreased photodamage with higher axial resolution.

  16. Fluorescence excitation studies of molecular photoionization in external electric fields

    International Nuclear Information System (INIS)

    Poliakoff, E.D.; Dehmer, J.L.; Parr, A.C.; Leroi, G.E.

    1985-01-01

    Using molecular nitrogen as an example, we show that fluorescence excitation spectroscopy can be used to measure partial photoionization cross sections of free molecules in external electric fields. The production of the N 2 + (B 2 Σ/sub u/ + ) state was studied and the threshold for this process was found to shift linearly with the square root of the applied field. This behavior is compared with the hydrogenic case and with previously studied systems

  17. Lettuce flavonoids screening and phenotyping by chlorophyll fluorescence excitation ratio.

    Science.gov (United States)

    Zivcak, Marek; Brückova, Klaudia; Sytar, Oksana; Brestic, Marian; Olsovska, Katarina; Allakhverdiev, Suleyman I

    2017-06-01

    Environmentally induced variation and the genotypic differences in flavonoid and phenolic content in lettuce can be reliably detected using the appropriate parameters derived from the records of rapid non-invasive fluorescence technique. The chlorophyll fluorescence excitation ratio method was designed as a rapid and non-invasive tool to estimate the content of UV-absorbing phenolic compounds in plants. Using this technique, we have assessed the dynamics of accumulation of flavonoids related to developmental changes and environmental effects. Moreover, we have tested appropriateness of the method to identify the genotypic differences and fluctuations in total phenolics and flavonoid content in lettuce. Six green and two red genotypes of lettuce (Lactuca sativa L.) grown in pots were exposed to two different environments for 50 days: direct sunlight (UV-exposed) and greenhouse conditions (low UV). The indices based on the measurements of chlorophyll fluorescence after red, green and UV excitation indicated increase of the content of UV-absorbing compounds and anthocyanins in the epidermis of lettuce leaves. In similar, the biochemical analyses performed at the end of the experiment confirmed significantly higher total phenolic and flavonoid content in lettuce plants exposed to direct sun compared to greenhouse conditions and in red compared to green genotypes. As the correlation between the standard fluorescence indices and the biochemical records was negatively influenced by the presence of red genotypes, we proposed the use of a new parameter named Modified Flavonoid Index (MFI) taking into an account both absorbance changes due to flavonol and anthocyanin content, for which the correlation with flavonoid and phenolic content was relatively good. Thus, our results confirmed that the fluorescence excitation ratio method is useful for identifying the major differences in phenolic and flavonoid content in lettuce plants and it can be used for high-throughput pre

  18. NIR-emitting molecular-based nanoparticles as new two-photon absorbing nanotools for single particle tracking

    Science.gov (United States)

    Daniel, J.; Godin, A. G.; Clermont, G.; Lounis, B.; Cognet, L.; Blanchard-Desce, M.

    2015-07-01

    In order to provide a green alternative to QDs for bioimaging purposes and aiming at designing bright nanoparticles combining both large one- and two-photon brightness, a bottom-up route based on the molecular engineering of dedicated red to NIR emitting dyes that spontaneously form fluorescent organic nanoparticles (FONs) has been implemented. These fully organic nanoparticles built from original quadrupolar dyes are prepared using a simple, expeditious and green protocol that yield very small molecular-based nanoparticles (radius ~ 7 nm) suspension in water showing a nice NIR emission (λem=710 nm). These FONs typically have absorption coefficient more than two orders larger than popular NIR-emitting dyes (such as Alexa Fluor 700, Cy5.5 ….) and much larger Stokes shift values (i.e. up to over 5500 cm-1). They also show very large two-photon absorption response in the 800-1050 nm region (up to about 106 GM) of major promise for two-photon excited fluorescence microscopy. Thanks to their brightness and enhanced photostability, these FONs could be imaged as isolated nanoparticles and tracked using wide-field imaging. As such, thanks to their size and composition (absence of heavy metals), they represent highly promising alternatives to NIR-emitting QDs for use in bioimaging and single particle tracking applications. Moreover, efficient FONs coating was achieved by using a polymeric additive built from a long hydrophobic (PPO) and a short hydrophilic (PEO) segment and having a cationic head group able to interact with the highly negative surface of FONs. This electrostatically-driven interaction promotes both photoluminescence and two-photon absorption enhancement leading to an increase of two-photon brightness of about one order of magnitude. This opens the way to wide-field single particle tracking under two-photon excitation

  19. Electromagnetically induced two-photon transparency in rubidium atoms

    International Nuclear Information System (INIS)

    Wang, D.; Gao, J.Y.; Xu, J.H.; Bassani, F.; La Rocca, G.C.; Salerno Univ.

    2001-01-01

    We present an experimental demonstration of electromagnetically induced two-photon transparency (EITT) in room temperature rubidium vapor. The 8S 1/2 to 5P 1/2 fluorescence is used to monitor the 5S 1/2 (F = 3) to 8S 1/2 (F = 3) two-photon absorption near resonance with the intermediate state 5P 3/2 . A controlling pump laser beam is employed to coherently couple the 5P 3/2 and 5D 5/2 states, thus producing two dressed intermediate states which give rise to destructive interference in the two-photon transition. An induced two-photon transparency of about 80% has been obtained at resonance; our experimental findings are in good agreement with the general theory of Agarwal et al. (1996), when the appropriate spectroscopic parameters are used. (orig.)

  20. Calculation of the spatial resolution in two-photon absorption spectroscopy applied to plasma diagnosis

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Lechuga, M. [Departamento de Física Teórica, Atómica y Óptica, Universidad de Valladolid, 47011-Valladolid (Spain); Laser Processing Group, Instituto de Óptica “Daza de Valdés,” CSIC, 28006-Madrid (Spain); Fuentes, L. M. [Departamento de Física Aplicada, Universidad de Valladolid, 47011-Valladolid (Spain); Grützmacher, K.; Pérez, C., E-mail: concha@opt.uva.es; Rosa, M. I. de la [Departamento de Física Teórica, Atómica y Óptica, Universidad de Valladolid, 47011-Valladolid (Spain)

    2014-10-07

    We report a detailed characterization of the spatial resolution provided by two-photon absorption spectroscopy suited for plasma diagnosis via the 1S-2S transition of atomic hydrogen for optogalvanic detection and laser induced fluorescence (LIF). A precise knowledge of the spatial resolution is crucial for a correct interpretation of measurements, if the plasma parameters to be analysed undergo strong spatial variations. The present study is based on a novel approach which provides a reliable and realistic determination of the spatial resolution. Measured irradiance distribution of laser beam waists in the overlap volume, provided by a high resolution UV camera, are employed to resolve coupled rate equations accounting for two-photon excitation, fluorescence decay and ionization. The resulting three-dimensional yield distributions reveal in detail the spatial resolution for optogalvanic and LIF detection and related saturation due to depletion. Two-photon absorption profiles broader than the Fourier transform-limited laser bandwidth are also incorporated in the calculations. The approach allows an accurate analysis of the spatial resolution present in recent and future measurements.

  1. Calculation of the spatial resolution in two-photon absorption spectroscopy applied to plasma diagnosis

    International Nuclear Information System (INIS)

    Garcia-Lechuga, M.; Fuentes, L. M.; Grützmacher, K.; Pérez, C.; Rosa, M. I. de la

    2014-01-01

    We report a detailed characterization of the spatial resolution provided by two-photon absorption spectroscopy suited for plasma diagnosis via the 1S-2S transition of atomic hydrogen for optogalvanic detection and laser induced fluorescence (LIF). A precise knowledge of the spatial resolution is crucial for a correct interpretation of measurements, if the plasma parameters to be analysed undergo strong spatial variations. The present study is based on a novel approach which provides a reliable and realistic determination of the spatial resolution. Measured irradiance distribution of laser beam waists in the overlap volume, provided by a high resolution UV camera, are employed to resolve coupled rate equations accounting for two-photon excitation, fluorescence decay and ionization. The resulting three-dimensional yield distributions reveal in detail the spatial resolution for optogalvanic and LIF detection and related saturation due to depletion. Two-photon absorption profiles broader than the Fourier transform-limited laser bandwidth are also incorporated in the calculations. The approach allows an accurate analysis of the spatial resolution present in recent and future measurements.

  2. Laser-excited fluorescence spectroscopy of oxide glasses

    International Nuclear Information System (INIS)

    Weber, M.J.

    1977-01-01

    Laser-induced fluorescence line narrowing was applied to investigate the local fields and interactions of paramagnetic ions in oxide glasses. Studies included the site dependence of energy levels, radiative and nonradiative transition probabilities, homogeneous line broadening, and ion--ion energy transfer of rare earth ions. These results and the experimental techniques are reviewed briefly; the use of paramagnetic ions other than the rare earths is also considered. Recently, laser-excited fluorescence spectroscopy was used to investigate modifications in the local structure of lithium borate glass caused by compositional changes and phase separation and the site dependence of nonradiative relaxation of paramagnetic ions by multiphonon processes. These results and their implications are discussed. 6 figures

  3. Polymer filters for ultraviolet-excited integrated fluorescence sensing

    International Nuclear Information System (INIS)

    Dandin, Marc; Abshire, Pamela; Smela, Elisabeth

    2012-01-01

    Optical filters for blocking ultraviolet (UV) light were fabricated by doping various polymer hosts with a UV absorbing chromophore. The polymers were polydimethylsiloxane (PDMS), a silicone elastomer frequently used in microfluidics, SU-8, a photopatternable epoxy, and Humiseal 1B66, an acrylic coating used for moisture protection of integrated circuits. The chromophore was 2-(2′-hydroxy-5′-methylphenyl) benzotriazole (BTA), which has a high extinction coefficient between 300 nm and 400 nm. We demonstrate filters 5 µm thick that exhibit high ultraviolet rejection (nearly −40 dB at 342 nm) yet pass visible light (near 0 dB above 400 nm), making them ideal for ultraviolet-excited fluorescence sensing within microsystems. The absorbance of the BTA depended on the host polymer. These filters are promising for integrated fluorescence spectroscopy in bioanalytical platforms because they can be patterned by dry etching, molding or exposure to ultraviolet light. (paper)

  4. Fluorescent vibration-rotation excitation of cometary C2

    International Nuclear Information System (INIS)

    Gredel, R.; Van Dishoeck, E.F.; Black, J.H.

    1989-01-01

    The statistical equilibrium equations that determine the population densities of the energy levels in cometary C2 molecules due to fluorescent excitation are examined in detail. The adopted model and molecular parameters are discussed, and a theoretical estimate is made of the two intercombination transition moments. From the theoretical population densities in the various rotational levels, flux ratios and synthetic emission profiles are calculated as functions of the a 3Pi(u) - X 1Sigma(g)+ and the c 3Sigma(u)+ - X 3Sigma(g)+ intercombination transition moments. The influence of each of these two transitions separately on the vibrational and rotational excitation temperatures is investigated. The observed emission spectra of the (0,0) Swan band in Comet Halley are presented and compared to the synthetic profiles. 70 references

  5. Fluorescent vibration-rotation excitation of cometary C2

    Science.gov (United States)

    Gredel, Roland; Van Dishoeck, Ewine F.; Black, John H.

    1989-01-01

    The statistical equilibrium equations that determine the population densities of the energy levels in cometary C2 molecules due to fluorescent excitation are examined in detail. The adopted model and molecular parameters are discussed, and a theoretical estimate is made of the two intercombination transition moments. From the theoretical population densities in the various rotational levels, flux ratios and synthetic emission profiles are calculated as functions of the a 3Pi(u) - X 1Sigma(g)+ and the c 3Sigma(u)+ - X 3Sigma(g)+ intercombination transition moments. The influence of each of these two transitions separately on the vibrational and rotational excitation temperatures is investigated. The observed emission spectra of the (0,0) Swan band in Comet Halley are presented and compared to the synthetic profiles.

  6. Colorectal cancer detection by hyperspectral imaging using fluorescence excitation scanning

    Science.gov (United States)

    Leavesley, Silas J.; Deal, Joshua; Hill, Shante; Martin, Will A.; Lall, Malvika; Lopez, Carmen; Rider, Paul F.; Rich, Thomas C.; Boudreaux, Carole W.

    2018-02-01

    Hyperspectral imaging technologies have shown great promise for biomedical applications. These techniques have been especially useful for detection of molecular events and characterization of cell, tissue, and biomaterial composition. Unfortunately, hyperspectral imaging technologies have been slow to translate to clinical devices - likely due to increased cost and complexity of the technology as well as long acquisition times often required to sample a spectral image. We have demonstrated that hyperspectral imaging approaches which scan the fluorescence excitation spectrum can provide increased signal strength and faster imaging, compared to traditional emission-scanning approaches. We have also demonstrated that excitation-scanning approaches may be able to detect spectral differences between colonic adenomas and adenocarcinomas and normal mucosa in flash-frozen tissues. Here, we report feasibility results from using excitation-scanning hyperspectral imaging to screen pairs of fresh tumoral and nontumoral colorectal tissues. Tissues were imaged using a novel hyperspectral imaging fluorescence excitation scanning microscope, sampling a wavelength range of 360-550 nm, at 5 nm increments. Image data were corrected to achieve a NIST-traceable flat spectral response. Image data were then analyzed using a range of supervised and unsupervised classification approaches within ENVI software (Harris Geospatial Solutions). Supervised classification resulted in >99% accuracy for single-patient image data, but only 64% accuracy for multi-patient classification (n=9 to date), with the drop in accuracy due to increased false-positive detection rates. Hence, initial data indicate that this approach may be a viable detection approach, but that larger patient sample sizes need to be evaluated and the effects of inter-patient variability studied.

  7. Synthesis, structure and two-photon absorption properties of a new multi-branched compound, 1,2,4,5-tetrakis(4-pyridylvinyl)benzene

    International Nuclear Information System (INIS)

    Wang Lei; Tao Xutang; Yang Jiaxiang; Yu Wentao; Ren Yan; Xin Qian; Liu Zhi; Jiang Minhua

    2004-01-01

    A conjugated and symmetric multi-branched compound, 1,2,4,5-tetrakis(4-pyridylvinyl)benzene (TKPVB), has been synthesized and the crystal structures of TKPVB and its intermediate, 1,2,4,5-tetrakis(dimethoxyphosphorylmethyl)benzene, were determined by diffraction method. TKPVB with four units of 4-vinylpyridine moieties attached to the central benzene core presents an A-π-A general framework, where A is a π-deficient pyridine ring. The single-photon and two-photon absorption and fluorescence properties in different solvents of varying polarity have been investigated. It is also found that the one- and two-photon-induced fluorescence spectra are quite similar, which indicate that the one- and two-photon allowed-excited states are the same

  8. Porous Porphyrin-Based Organosilica Nanoparticles for NIR Two-Photon Photodynamic Therapy and Gene Delivery in Zebrafish

    KAUST Repository

    Mauriello Jimenez, Chiara; Aggad, Dina; Croissant, Jonas G.; Tresfield, Karen; Laurencin, Danielle; Berthomieu, Dorothé e; Cubedo, Nicolas; Rossel, Mireille; Alsaiari, Shahad K.; Anjum, Dalaver H.; Sougrat, Rachid; Roldan-Gutierrez, Manuel A.; Richeter, Sé bastien; Oliviero, Erwan; Raehm, Laurence; Charnay, Clarence; Cattoë n, Xavier; Clé ment, Sé bastien; Wong Chi Man, Michel; Maynadier, Marie; Chaleix, Vincent; Sol, Vincent; Garcia, Marcel; Gary-Bobo, Magali; Khashab, Niveen M.; Bettache, Nadir; Durand, Jean-Olivier

    2018-01-01

    functionalization of the nanoparticles with aminopropyltriethoxysilane, two-photon-excited photodynamic therapy in zebrafish is successfully achieved. Two-photon photochemical internalization in cancer cells of the nanoparticles loaded with siRNA is also performed

  9. A series of fluorene-based two-photon absorbing molecules: synthesis, linear and nonlinear characterization, and bioimaging

    Science.gov (United States)

    Andrade, Carolina D.; Yanez, Ciceron O.; Rodriguez, Luis; Belfield, Kevin D.

    2010-01-01

    The synthesis, structural, and photophysical characterization of a series of new fluorescent donor–acceptor and acceptor-acceptor molecules, based on the fluorenyl ring system, with two-photon absorbing properties is described. These new compounds exhibited large Stokes shifts, high fluorescent quantum yields, and, significantly, high two-photon absorption cross sections, making them well suited for two-photon fluorescence microscopy (2PFM) imaging. Confocal and two-photon fluorescence microscopy imaging of COS-7 and HCT 116 cells incubated with probe I showed endosomal selectivity, demonstrating the potential of this class of fluorescent probes in multiphoton fluorescence microscopy. PMID:20481596

  10. Precision two-photon spectroscopy of alkali elements

    Indian Academy of Sciences (India)

    effect is eliminated if the wave vector of the photons is ka = −kb, i.e., the two beams .... atomic cesium, and the metre is (indirectly) defined from the wavelength of .... plasma absorb radiation, the electrical circuit parameters may vary and this .... two-photon excitation followed by an ionization step in Ca [71], Sr [72] and Gd [73] ...

  11. Versatile single-molecule multi-color excitation and detection fluorescence setup for studying biomolecular dynamics

    KAUST Repository

    Sobhy, M. A.; Elshenawy, M. M.; Takahashi, Masateru; Whitman, B. H.; Walter, N. G.; Hamdan, S. M.

    2011-01-01

    Single-molecule fluorescence imaging is at the forefront of tools applied to study biomolecular dynamics both in vitro and in vivo. The ability of the single-molecule fluorescence microscope to conduct simultaneous multi-color excitation

  12. Fluorescence of Bacteria, Pollens, and Naturally Occurring Airborne Particles: Excitation/Emission Spectra

    National Research Council Canada - National Science Library

    Hill, Steven C; Mayo, Michael W; Chang, Richard K

    2009-01-01

    The fluorescence intensity as a function of excitation and emission wavelengths (EEM spectra) was measured for different species of bacteria, biochemical constituents of cells, pollens, and vegetation...

  13. A Compact Fluorescence Lifetime Excitation-Emission Spectrometer (FLEXEMS) for Detecting Trace Organics, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — In this Small Business Innovative Research (SBIR) effort, Leiden Measurement Technology (LMT) proposes to design and build the Fluorescence Lifetime Excitation...

  14. A Compact Fluorescence Lifetime Excitation-Emission Spectrometer (FLEXEMS) for Detecting Trace Organics, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — In this Small Business Innovative Research (SBIR) effort, Leiden Measurement Technology (LMT) proposes to design and build the Fluorescence Lifetime Excitation...

  15. Two-photon couplings of quarkonia with arbitrary JPC

    International Nuclear Information System (INIS)

    Barnes, T.; Tennessee Univ., Knoxville, TN

    1992-01-01

    We present theoretical results for the two-photon widths of relativistic quarkonium states with arbitrary angular momenta. These relativistic formulas are required to obtain reasonable agreement with the absolute scale of quarkonium decay rates to two photons, and have previously only been derived for spin-singlet q bar q states. We also evaluate these formulas numerically for ell ≤3 q = u, d states in a Coulomb-plus-linear q bar q potential model. Light-quark higher-ell and radially-excited q bar q states should be observable experimentally, as their two-photon widths are typically found to be ∼1 KeV. The radially-excited 1 S 0 higher-mass quarkonium states such as c bar c and b bar b should also be observable in γγ, but orbitally-excited c bar c states with ell>1 and b bar b states with ell>0 are expected to have very small two-photon widths. The helicity structure of the higher-ell q bar q couplings is predicted to be nontrivial, with both λ=0 and λ=2γγ final states contributing significantly; these results may be useful as signatures for q bar q states

  16. Advances and challenges in label-free nonlinear optical imaging using two-photon excitation fluorescence and second harmonic generation for cancer research

    NARCIS (Netherlands)

    Thomas, Giju; van Voskuilen, Johan; Gerritsen, Hans C.; Sterenborg, H. J. C. M.

    2014-01-01

    Nonlinear optical imaging (NLOI) has emerged to be a promising tool for bio-medical imaging in recent times. Among the various applications of NLOI, its utility is the most significant in the field of pre-clinical and clinical cancer research. This review begins by briefly covering the core

  17. Porous Porphyrin-Based Organosilica Nanoparticles for NIR Two-Photon Photodynamic Therapy and Gene Delivery in Zebrafish

    KAUST Repository

    Mauriello Jimenez, Chiara

    2018-03-30

    Periodic mesoporous organosilica nanoparticles emerge as promising vectors for nanomedicine applications. Their properties are very different from those of well-known mesoporous silica nanoparticles as there is no silica source for their synthesis. So far, they have only been synthesized from small bis-silylated organic precursors. However, no studies employing large stimuli-responsive precursors have been reported on such hybrid systems yet. Here, the synthesis of porphyrin-based organosilica nanoparticles from a large octasilylated metalated porphyrin precursor is described for applications in near-infrared two-photon-triggered spatiotemporal theranostics. The nanoparticles display unique interconnected large cavities of 10-80 nm. The framework of the nanoparticles is constituted with J-aggregates of porphyrins, which endows them with two-photon sensitivity. The nanoparticle efficiency for intracellular tracking is first demonstrated by the in vitro near-infrared imaging of breast cancer cells. After functionalization of the nanoparticles with aminopropyltriethoxysilane, two-photon-excited photodynamic therapy in zebrafish is successfully achieved. Two-photon photochemical internalization in cancer cells of the nanoparticles loaded with siRNA is also performed for the first time. Furthermore, siRNA targeting green fluorescent protein complexed with the nanoparticles is delivered in vivo in zebrafish embryos, which demonstrates the versatility of the nanovectors for biomedical applications.

  18. Holographic Two-Photon Induced Photopolymerization

    Data.gov (United States)

    Federal Laboratory Consortium — Holographic two-photon-induced photopolymerization (HTPIP) offers distinct advantages over conventional one-photon-induced photopolymerization and current techniques...

  19. Atomic frequency reference at 1033 nm for ytterbium (Yb)-doped fiber lasers and applications exploiting a rubidium (Rb) 5S_1/2 to 4D_5/2 one-colour two-photon transition

    Science.gov (United States)

    Roy, Ritayan; Condylis, Paul C.; Johnathan, Yik Jinen; Hessmo, Björn

    2017-04-01

    We demonstrate a two-photon transition of rubidium (Rb) atoms from the ground state (5$S_{1/2}$) to the excited state (4$D_{5/2}$), using a home-built ytterbium (Yb)-doped fiber amplifier at 1033 nm. This is the first demonstration of an atomic frequency reference at 1033 nm as well as of a one-colour two-photon transition for the above energy levels. A simple optical setup is presented for the two-photon transition fluorescence spectroscopy, which is useful for frequency stabilization for a broad class of lasers. This spectroscopy has potential applications in the fiber laser industry as a frequency reference, particularly for the Yb-doped fiber lasers. This two-photon transition also has applications in atomic physics as a background- free high- resolution atom detection and for quantum communication, which is outlined in this article.

  20. Quarkonium two-photon decays in QCD

    International Nuclear Information System (INIS)

    Dulyan, L.S.; Khodjamirian, A.Yu.; Magakian, A.D.

    1989-01-01

    The two-photon decay of tensor charmonium χ c2 → 2 γ is calculated with account of gluon condensate effects. The result is in good agreement with experiment. The two-photon width of pseudoscalar b-quarkonium η b → 2 γ is estimated. 19 refs.; 1 fig.; 1 tab

  1. Two-Photon Vibrational Spectroscopy using local optical fields of gold and silver nanostructures

    Science.gov (United States)

    Kneipp, Katrin; Kneipp, Janina; Kneipp, Harald

    2007-03-01

    Spectroscopic effects can be strongly affected when they take place in the immediate vicinity of metal nanostructures due to coupling to surface plasmons. We introduce a new approach that suggests highly efficient two-photon labels as well as two-photon vibrational spectroscopy for non-destructive chemical probing. The underlying spectroscopic effect is the incoherent inelastic scattering of two photons on the vibrational quantum states performed in the enhanced local optical fields of gold nanoparticles, surface enhanced hyper Raman scattering (SEHRS). We infer effective two-photon cross sections for SEHRS on the order of 10^5 GM, similar or higher than the best known cross sections for two-photon fluorescence. SEHRS combines the advantages of two-photon spectroscopy with the structural information of vibrational spectroscopy, and the high sensitivity and nanometer-scale local confinement of plasmonics-based spectroscopy.

  2. Laser-excited fluorescence for measuring atmospheric pollution

    Science.gov (United States)

    Menzies, R. T.

    1975-01-01

    System measures amount of given pollutant at specific location. Infrared laser aimed at location has wavelength that will cause molecules of pollutant to fluoresce. Detector separates fluorescence from other radiation and measures its intensity to indicate concentration of pollutant.

  3. Optimization of tube parameters in a tube excited X-ray fluorescence (TEXRF) system using secondary fluorescers

    International Nuclear Information System (INIS)

    Islam, A.; Biswas, S.K.

    1995-12-01

    A study of the optimization of excitation parameters in a tube excited X-ray fluorescence system (TEXRF) having Mo as the primary target has been carried out for biological matrix. Fe, Zn and Mo were used as the secondary fluorecers. For the present investigation a cellulose based synthetic standard containing K, Cr, Ni, Zn, Se and Y was excited with the TEXRF system. All experiments were carried out under the same experimental conditions except the tube potential. For each fluorescer the minimum detection limits (MDL) of excited elements were calculated for the corresponding tube voltage. The MDLs were found to be increasing with decreasing atomic number and it was also observed that the maximum sensitivity with Fe and Zn secondary fluorescers for elements analyzed occurred around 35 kV of the excitation potential. For Mo secondary fluorescer maximum sensitivity was found at higher excitation potential. In most cases MDLs were minimum at 40-45 kV of the excitation potential. 5 refs., 12 figs

  4. Excitation-emission spectra and fluorescence quantum yields for fresh and aged biogenic secondary organic aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyun Ji; Laskin, Alexander; Laskin, Julia; Nizkorodov, Sergey A.

    2013-05-10

    Certain biogenic secondary organic aerosols (SOA) become absorbent and fluorescent when exposed to reduced nitrogen compounds such as ammonia, amines and their salts. Fluorescent SOA may potentially be mistaken for biological particles by detection methods relying on fluorescence. This work quantifies the spectral distribution and effective quantum yields of fluorescence of SOA generated from two monoterpenes, limonene and a-pinene, and two different oxidants, ozone (O3) and hydroxyl radical (OH). The SOA was generated in a smog chamber, collected on substrates, and aged by exposure to ~100 ppb ammonia vapor in air saturated with water vapor. Absorption and excitation-emission matrix (EEM) spectra of aqueous extracts of aged and control SOA samples were measured, and the effective absorption coefficients and fluorescence quantum yields (~0.005 for 349 nm excitation) were determined from the data. The strongest fluorescence for the limonene-derived SOA was observed for excitation = 420+- 50 nm and emission = 475 +- 38 nm. The window of the strongest fluorescence shifted to excitation = 320 +- 25 nm and emission = 425 +- 38 nm for the a-pinene-derived SOA. Both regions overlap with the excitation-emission matrix (EEM) spectra of some of the fluorophores found in primary biological aerosols. Our study suggests that, despite the low quantum yield, the aged SOA particles should have sufficient fluorescence intensities to interfere with the fluorescence detection of common bioaerosols.

  5. vuv fluorescence from selective high-order multiphoton excitation of N2

    International Nuclear Information System (INIS)

    Coffee, Ryan N.; Gibson, George N.

    2004-01-01

    Recent fluorescence studies suggest that ultrashort pulse laser excitation may be highly selective. Selective high-intensity laser excitation holds important consequences for the physics of multiphoton processes. To establish the extent of this selectivity, we performed a detailed comparative study of the vacuum ultraviolet fluorescence resulting from the interaction of N 2 and Ar with high-intensity infrared ultrashort laser pulses. Both N 2 and Ar reveal two classes of transitions, inner-valence ns ' l ' . From their pressure dependence, we associate each transition with either plasma or direct laser excitation. Furthermore, we qualitatively confirm such associations with the time dependence of the fluorescence signal. Remarkably, only N 2 presents evidence of direct laser excitation. This direct excitation produces ionic nitrogen fragments with inner-valence (2s) holes, two unidentified transitions, and one molecular transition, the N 2 + :X 2 Σ g + 2 Σ u + . We discuss these results in the light of a recently proposed model for multiphoton excitation

  6. Study on excitation and fluorescence spectrums of Japanese citruses to construct machine vision systems for acquiring fluorescent images

    Science.gov (United States)

    Momin, Md. Abdul; Kondo, Naoshi; Kuramoto, Makoto; Ogawa, Yuichi; Shigi, Tomoo

    2011-06-01

    Research was conducted to acquire knowledge of the ultraviolet and visible spectrums from 300 -800 nm of some common varieties of Japanese citrus, to investigate the best wave-lengths for fluorescence excitation and the resulting fluorescence wave-lengths and to provide a scientific background for the best quality fluorescent imaging technique for detecting surface defects of citrus. A Hitachi U-4000 PC-based microprocessor controlled spectrophotometer was used to measure the absorption spectrum and a Hitachi F-4500 spectrophotometer was used for the fluorescence and excitation spectrums. We analyzed the spectrums and the selected varieties of citrus were categorized into four groups of known fluorescence level, namely strong, medium, weak and no fluorescence.The level of fluorescence of each variety was also examined by using machine vision system. We found that around 340-380 nm LEDs or UV lamps are appropriate as lighting devices for acquiring the best quality fluorescent image of the citrus varieties to examine their fluorescence intensity. Therefore an image acquisition device was constructed with three different lighting panels with UV LED at peak 365 nm, Blacklight blue lamps (BLB) peak at 350 nm and UV-B lamps at peak 306 nm. The results from fluorescent images also revealed that the findings of the measured spectrums worked properly and can be used for practical applications such as for detecting rotten, injured or damaged parts of a wide variety of citrus.

  7. Effects of autoionizing states on two-photon double ionization of the H2 molecule

    International Nuclear Information System (INIS)

    Guan, Xiaoxu; Bartschat, Klaus; Koesterke, Lars; Schneider, Barry I

    2014-01-01

    We report angle-resolved and angle-integrated cross sections for two-photon double-ionization of H by a strong laser pulse. The effect of doubly excited states on the predicted cross sections is addressed.

  8. Broadband two-photon absorption cross sections of benzothiazole derivatives and benzobisthiazolium salts

    Science.gov (United States)

    Noskovičova, Eva; Lorenc, Dušan; Magdolen, Peter; Sigmundová, Ivica; Zahradník, Pavol; Velič, Dušan

    2018-05-01

    Two-photon absorption (TPA) cross sections of conjugated donor-π-acceptor dipolar structures containing benzothiazole or benzobisthiazolium moieties are determined in a broad spectral range from 700 nm to 1000 nm using two-photon induced fluorescence technique. The TPA cross section values range from 150 GM to 4600 GM. The largest values are observed in near-infrared region. The dipolar derivative of benzothiazole has the largest TPA cross section of 4600 GM at wavelength of 890 nm. A combination of the large TPA in the near-infrared region and the high emission quantum yield makes these compounds excellent candidates for two-photon fluorescence microscopy.

  9. Optical chromatography using a photonic crystal fiber with on-chip fluorescence excitation

    CSIR Research Space (South Africa)

    Ashok, AC

    2010-03-01

    Full Text Available The authors describe the realization of integrated optical chromatography, in conjunction with on-chip fluorescence excitation, in a monolithically fabricated poly-dimethylsiloxane (PDMS) microfluidic chip. The unique endlessly-single-mode guiding...

  10. Intravital Confocal and Two-photon Imaging of Dual-color Cells and Extracellular Matrix Mimics

    Science.gov (United States)

    Bal, Ufuk; Andresen, Volker; Baggett, Brenda; Utzinger, Urs

    2013-01-01

    To optimize imaging of cells in three dimensional culture we studied confocal backscattering, Second Harmonic Generation (SHG) and autofluorescence as source of contrast in extracellular matrix (ECM) mimics and evaluated the attenuation as well as bleaching of endogenous cellular fluorescence signals. All common ECM mimics exhibit contrast observable with confocal reflectance microscopy. SHG imaging on collagen I based hydrogels provides high contrast and good optical penetration depth. Agarose is a useful embedding medium because it allows for large optical penetration and exhibits minimal autofluorescence while still providing good reflectance to detect voids in the embedding medium. We labeled breast cancer cells’ outline with DsRed2 and nucleus with eGFP. DsRed2 can be excited with confocal imaging at 568nm, and with two photon excitation (TPE) in the red and longer NIR. eGFP was excited at 488nm for confocal and in the NIR for TPE. While there is small difference in the bleaching rate for eGFP between confocal and TPE we observed significant difference for DsRed2 where bleaching is strongest during TPE in the red wavelengths and smallest during confocal imaging. After a few hundred microns depth in a collagen I hydrogel, TPE fluorescence becomes twice as strong compared to confocal imaging. PMID:23380006

  11. Fluorescence image excited by a scanning UV-LED light

    Science.gov (United States)

    Tsai, Hsin-Yi; Chen, Yi-Ju; Huang, Kuo-Cheng

    2013-03-01

    An optical scanning system using UV-LED light to induced fluorescence technology can enhance a fluorescence image significantly in a short period. It has several advantages such as lower power consumption, no scattering effect in skins, and multilayer images can be obtained to analyze skin disease. From the experiment results, the light intensity increases with increase spot size and decrease scanning speed, but the image resolution is oppositely. Moreover, the system could be widely used in clinical diagnosis and photodynamic therapy for skin disease because even the irradiated time of fluorescence substance is short but it will provide accurately positioning of fluorescence object.

  12. Optimizing pulse compressibility in completely all-fibered Ytterbium chirped pulse amplifiers for in vivo two photon laser scanning microscopy.

    Science.gov (United States)

    Fernández, A; Grüner-Nielsen, L; Andreana, M; Stadler, M; Kirchberger, S; Sturtzel, C; Distel, M; Zhu, L; Kautek, W; Leitgeb, R; Baltuska, A; Jespersen, K; Verhoef, A

    2017-08-01

    A simple and completely all-fiber Yb chirped pulse amplifier that uses a dispersion matched fiber stretcher and a spliced-on hollow core photonic bandgap fiber compressor is applied in nonlinear optical microscopy. This stretching-compression approach improves compressibility and helps to maximize the fluorescence signal in two-photon laser scanning microscopy as compared with approaches that use standard single mode fibers as stretcher. We also show that in femtosecond all-fiber systems, compensation of higher order dispersion terms is relevant even for pulses with relatively narrow bandwidths for applications relying on nonlinear optical effects. The completely all-fiber system was applied to image green fluorescent beads, a stained lily-of-the-valley root and rat-tail tendon. We also demonstrated in vivo imaging in zebrafish larvae, where we simultaneously measure second harmonic and fluorescence from two-photon excited red-fluorescent protein. Since the pulses are compressed in a fiber, this source is especially suited for upgrading existing laser scanning (confocal) microscopes with multiphoton imaging capabilities in space restricted settings or for incorporation in endoscope-based microscopy.

  13. Charm production in two-photon collisions

    International Nuclear Information System (INIS)

    Linde, F.L.

    1988-01-01

    The analysis focuses on the production of charmonium resonances η c , χ 0 and χ 2 in two-photon interactions. The measurement of the inclusive production of charged D* mesons is described. 97 refs.; 54 figs.; 15 tabs

  14. Exclusive hadron production in two photon reactions

    International Nuclear Information System (INIS)

    Poppe, M.

    1986-02-01

    This paper summarises experimental results on exclusive hadron production in two photon collisions at electron positron storage rings and attempts some interpretation. Experimental know how is described and new suggestions are made for future analyses. New model calculations on resonance form factors and pair production amplitudes are presented. The two photon vertex is decomposed such that experiments can be parameterised with the minimal number of free parameters. Selection rules for off shell photon collisions are given in addition to Yang's theorems. (orig.)

  15. Induction of the 'in vivo' chlorophyll fluorescence excited by CW and pulse-periodical laser radiation

    International Nuclear Information System (INIS)

    Zakhidov, Eh.A.; Zakhidov, M.A.; Kasymdzhanov, M.A.; Khabibullaev, P.K.

    1996-01-01

    Inductional changes of fluorescence of the native chlorophyll molecules in plant leaves excited by CW and pulse-periodical laser radiation are studied. The opportunity of controlling of the photosynthesis efficiency through fluorescence response at different rates of the electron flow in charge transfer chain of the photosynthetic apparatus of plant is shown. (author). 13 refs.; 4 refs

  16. Calcium rubies: a family of red-emitting functionalizable indicators suitable for two-photon Ca2+ imaging.

    Science.gov (United States)

    Collot, Mayeul; Loukou, Christina; Yakovlev, Aleksey V; Wilms, Christian D; Li, Dongdong; Evrard, Alexis; Zamaleeva, Alsu; Bourdieu, Laurent; Léger, Jean-François; Ropert, Nicole; Eilers, Jens; Oheim, Martin; Feltz, Anne; Mallet, Jean-Maurice

    2012-09-12

    We designed Calcium Rubies, a family of functionalizable BAPTA-based red-fluorescent calcium (Ca(2+)) indicators as new tools for biological Ca(2+) imaging. The specificity of this Ca(2+)-indicator family is its side arm, attached on the ethylene glycol bridge that allows coupling the indicator to various groups while leaving open the possibility of aromatic substitutions on the BAPTA core for tuning the Ca(2+)-binding affinity. Using this possibility we now synthesize and characterize three different CaRubies with affinities between 3 and 22 μM. Their long excitation and emission wavelengths (peaks at 586/604 nm) allow their use in otherwise challenging multicolor experiments, e.g., when combining Ca(2+) uncaging or optogenetic stimulation with Ca(2+) imaging in cells expressing fluorescent proteins. We illustrate this capacity by the detection of Ca(2+) transients evoked by blue light in cultured astrocytes expressing CatCh, a light-sensitive Ca(2+)-translocating channelrhodopsin linked to yellow fluorescent protein. Using time-correlated single-photon counting, we measured fluorescence lifetimes for all CaRubies and demonstrate a 10-fold increase in the average lifetime upon Ca(2+) chelation. Since only the fluorescence quantum yield but not the absorbance of the CaRubies is Ca(2+)-dependent, calibrated two-photon fluorescence excitation measurements of absolute Ca(2+) concentrations are feasible.

  17. Simultaneous morphological and functional imaging of the honeybee's brain by two-photon microscopy

    International Nuclear Information System (INIS)

    Haase, A.

    2011-01-01

    Thanks to its rather simply structured but highly performing brain, the honeybee (Apis mellifera) is an important model for neurobiological studies. Therefore there is a great need for new functional imaging modalities adapted to this species. Herein we give a detailed report on the development and performance of a platform for in vivo functional and morphological imaging of the honeybee's brain, focusing on its primary olfactory centres, the antennal lobes (ALs). The experimental setup consists of a two-photon microscope combined with a synchronized odour stimulus generator. Our imaging platform allows to simultaneously obtain both morphological measurements of the ALs functional units, the glomeruli, and in vivo calcium recording of their neural activity. We were able to record the characteristic glomerular response maps to odour stimuli applied to the bee's antennae. Our approach offers several advantages over the commonly used conventional fluorescence microscopy. Two-photon microscopy provides substantial enhancement in both spatial and temporal resolutions, while minimizing photo damage. Calcium recordings show a more than fourfold improvement in the functional signal with respect to the techniques available up to now. Finally, the extended penetration depth, thanks to the infrared excitation, allows the functional imaging of profound glomeruli which have not been optically accessible up to now.

  18. Intravital two-photon microscopy of immune cell dynamics in corneal lymphatic vessels.

    Directory of Open Access Journals (Sweden)

    Philipp Steven

    Full Text Available BACKGROUND: The role of lymphatic vessels in tissue and organ transplantation as well as in tumor growth and metastasis has drawn great attention in recent years. METHODOLOGY/PRINCIPAL FINDINGS: We now developed a novel method using non-invasive two-photon microscopy to simultaneously visualize and track specifically stained lymphatic vessels and autofluorescent adjacent tissues such as collagen fibrils, blood vessels and immune cells in the mouse model of corneal neovascularization in vivo. The mouse cornea serves as an ideal tissue for this technique due to its easy accessibility and its inducible and modifiable state of pathological hem- and lymphvascularization. Neovascularization was induced by suture placement in corneas of Balb/C mice. Two weeks after treatment, lymphatic vessels were stained intravital by intrastromal injection of a fluorescently labeled LYVE-1 antibody and the corneas were evaluated in vivo by two-photon microscopy (TPM. Intravital TPM was performed at 710 nm and 826 nm excitation wavelengths to detect immunofluorescence and tissue autofluorescence using a custom made animal holder. Corneas were then harvested, fixed and analyzed by histology. Time lapse imaging demonstrated the first in vivo evidence of immune cell migration into lymphatic vessels and luminal transport of individual cells. Cells immigrated within 1-5.5 min into the vessel lumen. Mean velocities of intrastromal corneal immune cells were around 9 µm/min and therefore comparable to those of T-cells and macrophages in other mucosal surfaces. CONCLUSIONS: To our knowledge we here demonstrate for the first time the intravital real-time transmigration of immune cells into lymphatic vessels. Overall this study demonstrates the valuable use of intravital autofluorescence two-photon microscopy in the model of suture-induced corneal vascularizations to study interactions of immune and subsequently tumor cells with lymphatic vessels under close as possible

  19. Laser excited fluorescence spectrum of Ho3+:SrF2 single crystal

    International Nuclear Information System (INIS)

    Lal, Bansi; Ramachandra Rao, D.

    1980-01-01

    The fluorescence spectrum of Ho 3+ : SrF 2 single crystal excited by the various lines of an Ar + laser, is reported. The three fluorescence groups recorded in the region 5300-7700 A, correspond to the transitions from ( 5 F 4 , 5 S 2 ) to 5 I 8 , 5 F 5 to 5 I 8 , 5 F 3 to 5 I 7 and ( 5 F 4 , 5 S 2 ) to 5 I 7 . Marked changes in the total integrated intensity of the various fluorescence groups with the change in the exciting wavelength are observed. (author)

  20. Electrically Induced Two-Photon Transparency in Semiconductor Quantum Wells

    International Nuclear Information System (INIS)

    Hayat, Alex; Nevet, Amir; Orenstein, Meir

    2009-01-01

    We demonstrate experimentally two-photon transparency, achieved by current injection into a semiconductor quantum-well structure which exhibits two-photon emission. The two-photon induced luminescence is progressively reduced by the injected current, reaching the point of two-photon transparency - a necessary condition for semiconductor two-photon gain and lasing. These results agree with our calculations.

  1. Plant Cell Imaging Based on Nanodiamonds with Excitation-Dependent Fluorescence

    Science.gov (United States)

    Su, Li-Xia; Lou, Qing; Jiao, Zhen; Shan, Chong-Xin

    2016-09-01

    Despite extensive work on fluorescence behavior stemming from color centers of diamond, reports on the excitation-dependent fluorescence of nanodiamonds (NDs) with a large-scale redshift from 400 to 620 nm under different excitation wavelengths are so far much fewer, especially in biological applications. The fluorescence can be attributed to the combined effects of the fraction of sp2-hybridized carbon atoms among the surface of the fine diamond nanoparticles and the defect energy trapping states on the surface of the diamond. The excitation-dependent fluorescent NDs have been applied in plant cell imaging for the first time. The results reported in this paper may provide a promising route to multiple-color bioimaging using NDs.

  2. Plant Cell Imaging Based on Nanodiamonds with Excitation-Dependent Fluorescence.

    Science.gov (United States)

    Su, Li-Xia; Lou, Qing; Jiao, Zhen; Shan, Chong-Xin

    2016-12-01

    Despite extensive work on fluorescence behavior stemming from color centers of diamond, reports on the excitation-dependent fluorescence of nanodiamonds (NDs) with a large-scale redshift from 400 to 620 nm under different excitation wavelengths are so far much fewer, especially in biological applications. The fluorescence can be attributed to the combined effects of the fraction of sp(2)-hybridized carbon atoms among the surface of the fine diamond nanoparticles and the defect energy trapping states on the surface of the diamond. The excitation-dependent fluorescent NDs have been applied in plant cell imaging for the first time. The results reported in this paper may provide a promising route to multiple-color bioimaging using NDs.

  3. Two-photon superradiance in extended medium

    International Nuclear Information System (INIS)

    Branzan, V.; Enache, N.

    1993-01-01

    The possibility of collectivization of an ensemble of atoms of an extended system (the distance between atoms is larger or equal to the wave-length of a spontaneous emitted radiation) during two-photon spontaneous decay is theoretically investigated. It is demonstrated that such systems of inverted atoms should emit phase-correlated pairs of photons. The time-space correlation among atoms is realized due to the two-photon exchanging through the electromagnetic field's vacuum. An increase of the spontaneous decay rate of the two-atom inverted ensemble is demonstrated. The dependence of two-photon superradiance on the sample geometry is investigated. A non-equilibrium method of the elimination of the atoms level Fermi-operators is proposed. (Author)

  4. High contrast two-photon imaging of fingermarks

    Science.gov (United States)

    Stoltzfus, Caleb R.; Rebane, Aleksander

    2016-04-01

    Optically-acquired fingermarks are widely used as evidence across law enforcement agencies as well as in the courts of law. A common technique for visualizing latent fingermarks on nonporous surfaces consists of cyanoacrylate fuming of the fingerprint material, followed by impregnation with a fluorescent dye, which under ultra violet (UV) illumination makes the fingermarks visible and thus accessible for digital recording. However, there exist critical circumstances, when the image quality is compromised due to high background scattering, high auto-fluorescence of the substrate material, or other detrimental photo-physical and photo-chemical effects such as light-induced damage to the sample. Here we present a novel near-infrared (NIR), two-photon induced fluorescence imaging modality, which significantly enhances the quality of the fingermark images, especially when obtained from highly reflective and/or scattering surfaces, while at the same time reducing photo-damage to sensitive forensic samples.

  5. Squeezing via two-photon transitions

    Science.gov (United States)

    Savage, C. M.; Walls, D. F.

    1986-05-01

    The squeezing spectrum for a cavity field mode interacting with an ensemble of three-level 'Lambda-configuration' atoms by an effective two-photon transition is calculated. The advantage of the three-level Lambda system as a squeezing medium, that is, optical nonlinearity without atomic saturation, has recently been pointed out by Reid, Walls, and Dalton. Perfect squeezing is predicted at the turning points for dispersive optical bistability and good squeezing for a range of other cases. Three-level ladder atoms interacting by an effective two-photon transition are also shown to give perfect squeezing in the dispersive limit.

  6. A review of two photon physics

    International Nuclear Information System (INIS)

    Cooper, S.

    1982-08-01

    This talk is intended as an introduction for those not yet expert in two-photon physics, especially those e + e - one-photon physicists who still think of two-photon events as background. I concentrate on the physics questions involved, especially emphasizing the areas where I feel progress can be made in the near future, and of necessity leaving most experimental details to be found in the references. After a quick survey of the field and a few words about kinematics, I discuss in detail two major fields: the photon structure function and resonance production. (orig.)

  7. Two-photon Doppler cooling of alkaline-earth-metal and ytterbium atoms

    International Nuclear Information System (INIS)

    Magno, Wictor C.; Cavasso Filho, Reinaldo L.; Cruz, Flavio C.

    2003-01-01

    The possibility of laser cooling of alkaline-earth-metal atoms and ytterbium atoms using a two-photon transition is analyzed. We consider a 1 S 0 - 1 S 0 transition with excitation in near resonance with the 1 P 1 level. This greatly increases the two-photon transition rate, allowing an effective transfer of momentum. The experimental implementation of this technique is discussed and we show that for calcium, for example, two-photon cooling can be used to achieve a Doppler limit of 123 μK. The efficiency of this cooling scheme and the main loss mechanisms are analyzed

  8. Two-photon absorption of a supramolecular pseudoisocyanine J-aggregate assembly

    International Nuclear Information System (INIS)

    Belfield, Kevin D.; Bondar, Mykhailo V.; Hernandez, Florencio E.; Przhonska, Olga V.; Yao, Sheng

    2006-01-01

    Linear spectral properties, including excitation anisotropy, of pseudoisocyanine or 1,1'-diethyl-2,2'-cyanine iodide (PIC) J-aggregates in aqueous solutions with J-band position at 573 nm were investigated. Two-photon absorption of PIC J-aggregates and monomer molecules was studied using an open aperture Z-scan technique. A strong enhancement of the two-photon absorption cross-section of PIC in the supramolecular J-aggregate assembly was observed in aqueous solution. This enhancement is attributed to a strong coupling of the molecular transition dipoles. No two-photon absorption at the peak of the J-band was detected

  9. Electron Correlations and Two-Photon States in Polycyclic Aromatic Hydrocarbon Molecules: A Peculiar Role of Geometry

    OpenAIRE

    Aryanpour, K.; Shukla, A.; Mazumdar, S.

    2013-01-01

    We present numerical studies of one- and two-photon excited states ordering in a number of polycyclic aromatic hydrocarbon molecules: coronene, hexa-peri-hexabenzocoronene and circumcoronene, all possessing $D_{6h}$ point group symmetry versus ovalene with $D_{2h}$ symmetry, within the Pariser-Parr-Pople model of interacting $\\pi$-electrons. The calculated energies of the two-photon states as well as their relative two-photon absorption cross-sections within the interacting model are qualitat...

  10. Saturated two-photon absorption by atoms in a perturber gas

    International Nuclear Information System (INIS)

    Nienhuis, G.

    1980-01-01

    We derive a general expression for the two-photon absorption spectrum of a three-state atom excited by two mono-chromatic radiation fields. Collisional line-broadening effects are incorporated, and the result allows inclusion of profiles with a validity outside the impact limit. Results of previous work are recovered in the appropriate limits. Saturation affects the different lines in the two-photon absorption spectrum in a different fashion. (orig.)

  11. Suppression of two-photon resonantly enhanced nonlinear processes in extended media

    International Nuclear Information System (INIS)

    Garrett, W.R.; Moore, M.A.; Payne, M.G.; Wunderlich, R.K.

    1988-11-01

    On the basis of combined experimental and theoretical studies of nonlinear processes associated with two-photon excitations near 3d and 4d states in Na, we show how resonantly enhanced stimulated hyper-Raman emission, parametric four-wave mixing processes and total resonant two-photon absorption can become severely suppressed through the actions of internally generated fields on the total atomic response in extended media. 7 refs., 3 figs

  12. Review of Two-Photon Interactions

    International Nuclear Information System (INIS)

    Urner, David

    2004-01-01

    Presented are recent results of two-photon interactions. Topics include photon structure functions, inclusive hadron production, differential cross sections derived from tagged γγ fusion events and results in exclusive hadron production, particularly the observations of the η'c

  13. Two-photon transitions to exciton polaritons

    International Nuclear Information System (INIS)

    Hassan, A.R.

    1979-08-01

    A semiclassical theory for the creation of excitonic polariton states by two-photon absorption, via an intermediate exciton state, is given. A band model has been introduced which gives the dominant contribution to this process. A numerical calculation is found to be in good agreement with a recent observation in CuCl. (author)

  14. Pion-pair production by two photons

    International Nuclear Information System (INIS)

    Terazawa, Hidezumi.

    1994-07-01

    The cross section for pion-pair production by two photons is calculated approximately by using the low energy theorem previously derived from partially-conserved-axial-vector-current hypothesis and current algebra, and found to agree very well with the experimental data recently obtained by the Mark II, TPC/Two-Gamma and CLEO Collaborations. (author)

  15. Cine: Line excitation by infrared fluorescence in cometary atmospheres

    Science.gov (United States)

    de Val-Borro, Miguel; Cordiner, Martin A.; Milam, Stefanie N.; Charnley, Steven B.

    2017-03-01

    CINE is a Python module for calculating infrared pumping efficiencies that can be applied to the most common molecules found in cometary comae such as water, hydrogen cyanide or methanol. Excitation by solar radiation of vibrational bands followed by radiative decay to the ground vibrational state is one of the main mechanisms for molecular excitation in comets. This code calculates the effective pumping rates for rotational levels in the ground vibrational state scaled by the heliocentric distance of the comet. Line transitions are queried from the latest version of the HITRAN spectroscopic repository using the astroquery affiliated package of astropy. Molecular data are obtained from the LAMDA database. These coefficients are useful for modeling rotational emission lines observed in cometary spectra at sub-millimeter wavelengths. Combined with computational methods to solve the radiative transfer equations based, e.g., on the Monte Carlo algorithm, this model can retrieve production rates and rotational temperatures from the observed emission spectrum.

  16. Spectrum of acetylene fluorescence excited by single XUV photons

    International Nuclear Information System (INIS)

    Schmieder, R.W.

    1982-01-01

    The spectrum of visible emission from photofragments of acetylene excited by single 16.85 eV photons has been recorded for the first time. The spectrum is dominated by the Swan and Deslandres-d'Azambuja bands of C 2 and the 431.5 nm band of CH. The yields of these emissions are of the order 10 -3 photons per absorbed incident photon. The experimental conditions suggest that the emission results from primary C* 2 and CH* photofragments

  17. Fluorescence enhancing under UV-NIR simultaneous-excitation in ZnS:Cu,Mn phosphors

    Directory of Open Access Journals (Sweden)

    L. J. Xie

    2012-12-01

    Full Text Available The fluorescence properties of a long-lasting phosphor, ZnS:Cu,Mn was studied for the first time under simultaneously excitation of both UV and NIR light. Up to 20% fluorescence enhancement of the phosphor was observed. In the present simultaneously-excitation process, broad-band NIR light was absorbed and converted to visible photons via a single-photon upconversion path. We propose that a novel kind of spectral-conversion material with the unique ability to simultaneously convert both UV and NIR photons can be developed and is promising in the application of enhancing the EQE of solar cells.

  18. Differentiation of ocular fundus fluorophores by fluorescence lifetime imaging using multiple excitation and emission wavelengths

    Science.gov (United States)

    Hammer, M.; Schweitzer, D.; Schenke, S.; Becker, W.; Bergmann, A.

    2006-10-01

    Ocular fundus autofluorescence imaging has been introduced into clinical diagnostics recently. It is in use for the observation of the age pigment lipofuscin, a precursor of age - related macular degeneration (AMD). But other fluorophores may be of interest too: The redox pair FAD - FADH II provides information on the retinal energy metabolism, advanced glycation end products (AGE) indicate protein glycation associated with pathologic processes in diabetes as well as AMD, and alterations in the fluorescence of collagen and elastin in connective tissue give us the opportunity to observe fibrosis by fluorescence imaging. This, however, needs techniques able to differentiate particular fluorophores despite limited permissible ocular exposure as well as excitation wavelength (limited by the transmission of the human ocular lens to >400 nm). We present an ophthalmic laser scanning system (SLO), equipped with picosecond laser diodes (FWHM 100 ps, 446 nm or 468 nm respectively) and time correlated single photon counting (TCSPC) in two emission bands (500 - 560 nm and 560 - 700 nm). The decays were fitted by a bi-exponential model. Fluorescence spectra were measured by a fluorescence spectrometer fluorolog. Upon excitation at 446 nm, the fluorescence of AGE, FAD, and lipofuscin were found to peak at 503 nm, 525 nm, and 600 nm respectively. Accordingly, the statistical distribution of the fluorescence decay times was found to depend on the different excitation wavelengths and emission bands used. The use of multiple excitation and emission wavelengths in conjunction with fluorescence lifetime imaging allows us to discriminate between intrinsic fluorophores of the ocular fundus. Taken together with our knowledge on the anatomical structure of the fundus, these findings suggest an association of the short, middle and long fluorescence decay time to the retinal pigment epithelium, the retina, and connective tissue respectively.

  19. Two-photon imaging and analysis of neural network dynamics

    International Nuclear Information System (INIS)

    Luetcke, Henry; Helmchen, Fritjof

    2011-01-01

    The glow of a starry night sky, the smell of a freshly brewed cup of coffee or the sound of ocean waves breaking on the beach are representations of the physical world that have been created by the dynamic interactions of thousands of neurons in our brains. How the brain mediates perceptions, creates thoughts, stores memories and initiates actions remains one of the most profound puzzles in biology, if not all of science. A key to a mechanistic understanding of how the nervous system works is the ability to measure and analyze the dynamics of neuronal networks in the living organism in the context of sensory stimulation and behavior. Dynamic brain properties have been fairly well characterized on the microscopic level of individual neurons and on the macroscopic level of whole brain areas largely with the help of various electrophysiological techniques. However, our understanding of the mesoscopic level comprising local populations of hundreds to thousands of neurons (so-called 'microcircuits') remains comparably poor. Predominantly, this has been due to the technical difficulties involved in recording from large networks of neurons with single-cell spatial resolution and near-millisecond temporal resolution in the brain of living animals. In recent years, two-photon microscopy has emerged as a technique which meets many of these requirements and thus has become the method of choice for the interrogation of local neural circuits. Here, we review the state-of-research in the field of two-photon imaging of neuronal populations, covering the topics of microscope technology, suitable fluorescent indicator dyes, staining techniques, and in particular analysis techniques for extracting relevant information from the fluorescence data. We expect that functional analysis of neural networks using two-photon imaging will help to decipher fundamental operational principles of neural microcircuits.

  20. Two-photon imaging and analysis of neural network dynamics

    Science.gov (United States)

    Lütcke, Henry; Helmchen, Fritjof

    2011-08-01

    The glow of a starry night sky, the smell of a freshly brewed cup of coffee or the sound of ocean waves breaking on the beach are representations of the physical world that have been created by the dynamic interactions of thousands of neurons in our brains. How the brain mediates perceptions, creates thoughts, stores memories and initiates actions remains one of the most profound puzzles in biology, if not all of science. A key to a mechanistic understanding of how the nervous system works is the ability to measure and analyze the dynamics of neuronal networks in the living organism in the context of sensory stimulation and behavior. Dynamic brain properties have been fairly well characterized on the microscopic level of individual neurons and on the macroscopic level of whole brain areas largely with the help of various electrophysiological techniques. However, our understanding of the mesoscopic level comprising local populations of hundreds to thousands of neurons (so-called 'microcircuits') remains comparably poor. Predominantly, this has been due to the technical difficulties involved in recording from large networks of neurons with single-cell spatial resolution and near-millisecond temporal resolution in the brain of living animals. In recent years, two-photon microscopy has emerged as a technique which meets many of these requirements and thus has become the method of choice for the interrogation of local neural circuits. Here, we review the state-of-research in the field of two-photon imaging of neuronal populations, covering the topics of microscope technology, suitable fluorescent indicator dyes, staining techniques, and in particular analysis techniques for extracting relevant information from the fluorescence data. We expect that functional analysis of neural networks using two-photon imaging will help to decipher fundamental operational principles of neural microcircuits.

  1. Two-photon imaging and analysis of neural network dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Luetcke, Henry; Helmchen, Fritjof [Brain Research Institute, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich (Switzerland)

    2011-08-15

    The glow of a starry night sky, the smell of a freshly brewed cup of coffee or the sound of ocean waves breaking on the beach are representations of the physical world that have been created by the dynamic interactions of thousands of neurons in our brains. How the brain mediates perceptions, creates thoughts, stores memories and initiates actions remains one of the most profound puzzles in biology, if not all of science. A key to a mechanistic understanding of how the nervous system works is the ability to measure and analyze the dynamics of neuronal networks in the living organism in the context of sensory stimulation and behavior. Dynamic brain properties have been fairly well characterized on the microscopic level of individual neurons and on the macroscopic level of whole brain areas largely with the help of various electrophysiological techniques. However, our understanding of the mesoscopic level comprising local populations of hundreds to thousands of neurons (so-called 'microcircuits') remains comparably poor. Predominantly, this has been due to the technical difficulties involved in recording from large networks of neurons with single-cell spatial resolution and near-millisecond temporal resolution in the brain of living animals. In recent years, two-photon microscopy has emerged as a technique which meets many of these requirements and thus has become the method of choice for the interrogation of local neural circuits. Here, we review the state-of-research in the field of two-photon imaging of neuronal populations, covering the topics of microscope technology, suitable fluorescent indicator dyes, staining techniques, and in particular analysis techniques for extracting relevant information from the fluorescence data. We expect that functional analysis of neural networks using two-photon imaging will help to decipher fundamental operational principles of neural microcircuits.

  2. Fluorescence excitation-emission matrix spectroscopy of vitiligo skin in vivo (Conference Presentation)

    Science.gov (United States)

    Zhao, Jianhua; Richer, Vincent; Al Jasser, Mohammed; Zandi, Soodabeh; Kollias, Nikiforos; Kalia, Sunil; Zeng, Haishan; Lui, Harvey

    2016-02-01

    Fluorescence signals depend on the intensity of the exciting light, the absorption properties of the constituent molecules, and the efficiency with which the absorbed photons are converted to fluorescence emission. The optical features and appearance of vitiligo have been explained primarily on the basis of reduced epidermal pigmentation, which results in abnormal white patches on the skin. The objective of this study is to explore the fluorescence properties of vitiligo and its adjacent normal skin using fluorescence excitation-emission matrix (EEM) spectroscopy. Thirty five (35) volunteers with vitiligo were acquired using a double-grating spectrofluorometer with excitation and emission wavelengths of 260-450 nm and 300-700 nm respectively. As expected, the most pronounced difference between the spectra obtained from vitiligo lesions compared to normally pigmented skin was that the overall fluorescence was much higher in vitiligo; these differences increased at shorter wavelengths, thus matching the characteristic spectral absorption of epidermal melanin. When comparing the fluorescence spectra from vitiligo to normal skin we detected three distinct spectral bands centered at 280nm, 310nm, and 335nm. The 280nm band may possibly be related to inflammation, whereas the 335 nm band may arise from collagen or keratin cross links. The source of the 310 nm band is uncertain; it is interesting to note its proximity to the 311 nm UV lamps used for vitiligo phototherapy. These differences are accounted for not only by changes in epidermal pigment content, but also by other optically active cutaneous biomolecules.

  3. Can Two-Photon Interference be Considered the Interference of Two Photons?

    International Nuclear Information System (INIS)

    Pittman, T.B.; Strekalov, D.V.; Migdall, A.; Rubin, M.H.; Sergienko, A.V.; Shih, Y.H.

    1996-01-01

    We report on a open-quote open-quote postponed compensation close-quote close-quote experiment in which the observed two-photon entangled state interference cannot be pictured in terms of the overlap of the two individual photon wave packets of a parametric down-conversion pair on a beam splitter. In the sense of a quantum eraser, the distinguishability of the different two-photon Feynman amplitudes leading to a coincidence detection is removed by delaying the compensation until after the output of an unbalanced two-photon interferometer. copyright 1996 The American Physical Society

  4. Two photon absorption energy transfer in the light-harvesting complex of photosystem II (LHC-II) modified with organic boron dye

    Science.gov (United States)

    Chen, Li; Liu, Cheng; Hu, Rui; Feng, Jiao; Wang, Shuangqing; Li, Shayu; Yang, Chunhong; Yang, Guoqiang

    2014-07-01

    The plant light-harvesting complexes of photosystem II (LHC-II) play important roles in collecting solar energy and transferring the energy to the reaction centers of photosystems I and II. A two photon absorption compound, 4-(bromomethyl)-N-(4-(dimesitylboryl)phenyl)-N-phenylaniline (DMDP-CH2Br), was synthesized and covalently linked to the LHC-II in formation of a LHC-II-dye complex, which still maintained the biological activity of LHC-II system. Under irradiation with femtosecond laser pulses at 754 nm, the LHC-II-dye complex can absorb two photons of the laser light effectively compared with the wild type LHC-II. The absorbed excitation energy is then transferred to chlorophyll a with an obvious fluorescence enhancement. The results may be interesting and give potentials for developing hybrid photosystems.

  5. Single-organelle tracking by two-photon conversion

    Science.gov (United States)

    Watanabe, Wataru; Shimada, Tomoko; Matsunaga, Sachihiro; Kurihara, Daisuke; Fukui, Kiichi; Shin-Ichi Arimura, Shin-Ichi; Tsutsumi, Nobuhiro; Isobe, Keisuke; Itoh, Kazuyoshi

    2007-03-01

    Spatial and temporal information about intracellular objects and their dynamics within a living cell are essential for dynamic analysis of such objects in cell biology. A specific intracellular object can be discriminated by photoactivatable fluorescent proteins that exhibit pronounced light-induced spectral changes. Here, we report on selective labeling and tracking of a single organelle by using two-photon conversion of a photoconvertible fluorescent protein with near-infrared femtosecond laser pulses. We performed selective labeling of a single mitochondrion in a living tobacco BY-2 cell using two-photon photoconversion of Kaede. Using this technique, we demonstrated that, in plants, the directed movement of individual mitochondria along the cytoskeletons was mediated by actin filaments, whereas microtubules were not required for the movement of mitochondria. This single-organelle labeling technique enabled us to track the dynamics of a single organelle, revealing the mechanisms involved in organelle dynamics. The technique has potential application in direct tracking of selective cellular and intracellular structures.

  6. Two-Photon Activation of p-Hydroxyphenacyl Phototriggers: Toward Spatially Controlled Release of Diethyl Phosphate and ATP.

    Science.gov (United States)

    Houk, Amanda L; Givens, Richard S; Elles, Christopher G

    2016-03-31

    Two-photon activation of the p-hydroxyphenacyl (pHP) photoactivated protecting group is demonstrated for the first time using visible light at 550 nm from a pulsed laser. Broadband two-photon absorption measurements reveal a strong two-photon transition (>10 GM) near 4.5 eV that closely resembles the lowest-energy band at the same total excitation energy in the one-photon absorption spectrum of the pHP chromophore. The polarization dependence of the two-photon absorption band is consistent with excitation to the same S3 ((1)ππ*) excited state for both one- and two-photon activation. Monitoring the progress of the uncaging reaction under nonresonant excitation at 550 nm confirms a quadratic intensity dependence and that two-photon activation of the uncaging reaction is possible using visible light in the range 500-620 nm. Deprotonation of the pHP chromophore under mildly basic conditions shifts the absorption band to lower energy (3.8 eV) in both the one- and two-photon absorption spectra, suggesting that two-photon activation of the pHP chromophore may be possible using light in the range 550-720 nm. The results of these measurements open the possibility of spatially and temporally selective release of biologically active compounds from the pHP protecting group using visible light from a pulsed laser.

  7. Fluorescence spectra of Rhodamine 6G for high fluence excitation laser radiation

    CERN Document Server

    Hung, J; Olaizola, A M

    2003-01-01

    Fluorescence spectral changes of Rhodamine 6G in ethanol and glycerol solutions and deposited as a film on a silica surface have been studied using a wide range of pumping field fluence at 532 nm at room temperature. Blue shift of the fluorescence spectra and fluorescence quenching of the dye molecule in solution are observed at high excitation fluence values. Such effects are not reported for the film sample. The effects are interpreted as the result of population redistribution in the solute-solvent molecular system induced by the high fluence field and the fluence dependence of the radiationless decay mechanism.

  8. Dual fluorescence excitation spectra of methyl salicylate in a free jet

    Science.gov (United States)

    Heimbrook, Lou Ann; Kenny, Jonathan E.; Kohler, Bryan E.; Scott, Gary W.

    1981-11-01

    Separate fluorescence excitation spectra of the blue- and UV-emitting forms of methyl salicylate cooled in a free-jet expansion are reported. This study represents the first observation of the detailed vibrational structure of these transitions. The two excitation spectra have no features in common, and their intensity patterns are very different. Many individual lines are ˜2 cm-1 wide (nearly laser limited), although in the excitation spectrum of the UV emission, spectral congestion persists at high energies despite the high degree of cooling. (AIP)

  9. Oral cancer detection based on fluorescence polarization of blood plasma at excitation wavelength 405 nm

    Science.gov (United States)

    Pachaiappan, Rekha; Prakasarao, Aruna; Manoharan, Yuvaraj; Dornadula, Koteeswaran; Singaravelu, Ganesan

    2017-02-01

    During metabolism the metabolites such as hormones, proteins and enzymes were released in to the blood stream by the cells. These metabolites reflect any change that occurs due to any disturbances in normal metabolic function of the human system. This was well observed with the altered spectral signatures observed with fluorescence spectroscopic technique. Previously many have reported on the significance of native fluorescence spectroscopic method in the diagnosis of cancer. As fluorescence spectroscopy is sensitive and simple, it has complementary techniques such as excitation-emission matrix, synchronous and polarization. The fluorescence polarization measurement provides details about any association or binding reactions and denaturing effects that occurs due to change in the micro environment of cells and tissues. In this study, we have made an attempt in the diagnosis of oral cancer at 405 nm excitation using fluorescence polarization measurement. The fluorescence anisotropic values calculated from polarized fluorescence spectral data of normal and oral cancer subjects yielded a good accuracy when analyzed with linear discriminant analysis based artificial neural network. The results will be discussed in detail.

  10. Probing two-photon exchange with OLYMPUS

    International Nuclear Information System (INIS)

    Kohl, M.

    2014-01-01

    Two-photon exchange is believed to be responsible for the discrepancies in the proton electric to magnetic form factor ratio found with the Rosenbluth and polarization transfer methods. If this explanation is correct, one expects significant differences in the lepton-proton cross sections between positrons and electrons. The OLYMPUS experiment at DESY in Hamburg, Germany was designed to measure the ratio of unpolarized positron-proton and electron-proton elastic scattering cross sections over a wide kinematic range with high precision, in order to quantify the effect of two-photon exchange. The experiment used intense beams of electrons and positrons stored in the DORIS ring at 2.0 GeV interacting with an internal windowless hydrogen gas target. The current status of OLYMPUS will be discussed. (authors)

  11. Symmetry adaptation in two-photon spectroscopy

    International Nuclear Information System (INIS)

    Kibler, M.

    1991-11-01

    Symmetry adaptation techniques are applied to the determination of the intensity of two-photon transitions for transition ions in finite symmetry environments. The case of intra-configurational transitions are discussed with some details and some results on inter-configurational transitions are briefly reported. In particular, for intra-configurational transitions, a model is described which takes into account the following ingredients: (symmetry, second- plus third-order mechanisms, S-, L- and J-mixings). (author) 20 refs

  12. Analysis of River sediments from the Tigre river (Venezuela) by radioisotope excited x-ray fluorescence

    International Nuclear Information System (INIS)

    LaBrecque, J.J.; Rosales, P.A.; Schorin, H.

    1985-01-01

    This paper describes qualitative elemental scans by both energy dispersive (radioisotope excited) and conventional wavelength dispersive x-ray fluorescence of different grain size fractions of river sediments. An internal standard thin-film technique was used. The precision of Rb, Sr, Y and Zr determination for SY-3 standard reference rock and one real sample for five independently prepared samples is demonstrated

  13. Determination of uranium in geologic materials by laser-excited fluorescence

    International Nuclear Information System (INIS)

    McHugh, J.B.

    1982-01-01

    A laser-excited fluorescence method is described for the determination of trace amounts of uranium in rocks and soils. The limit of detection is less than 1 ppm, and the relative standard deviation ranges from 2.6 to 12.5%. The method was evaluated by using known geological reference samples

  14. Fluorescence, Absorption, and Excitation Spectra of Polycyclic Aromatic Hydrocarbons as a Tool for Quantitative Analysis

    Science.gov (United States)

    Rivera-Figueroa, A. M.; Ramazan, K. A.; Finlayson-Pitts, B. J.

    2004-01-01

    A quantitative and qualitative study of the interplay between absorption, fluorescence, and excitation spectra of pollutants called polycyclic aromatic hydrocarbons (PAHs) is conducted. The study of five PAH displays the correlation of the above-mentioned properties along with the associated molecular changes.

  15. Determination of heavy metals in polar snow and ice by laser-excited atomic fluorescence spectrometry

    International Nuclear Information System (INIS)

    Bolshov, M.A.; Boutron, C.F.

    1994-01-01

    The new laser-excited atomic fluorescence spectrometry technique offers unrivalled sensitivity for the determination of trace metals in a wide variety of samples. This has allowed the direct determination of Pb, Cd and Bi in Antarctic and Greenland snow and ice down to the sub pg/g level. (authors). 11 refs., 2 figs

  16. Excitation of fluorescent nanoparticles by channel plasmon polaritons propagating in V-grooves

    DEFF Research Database (Denmark)

    Cuesta, Irene Fernandez; Nielsen, Rasmus Bundgaard; Boltasseva, Alexandra

    2009-01-01

    Recently, it has been proven that light can be squeezed into metallic channels with subwavelength lateral dimensions. Here, we present the study of the propagation of channel plasmon polaritons confined in gold V-grooves, filled with fluorescent particles. In this way, channel plasmon polaritons......-diameter beads, we show the possibility of individual excitation, what may have applications to develop very sensitive biosensors....

  17. Contribution to the analysis of light elements using x fluorescence excited by radio-elements

    International Nuclear Information System (INIS)

    Robert, A.

    1964-01-01

    In order to study the possibilities of using radioactive sources for the X-fluorescence analysis of light elements, the principle is given, after a brief description of X-fluorescence, of the excitation of this phenomenon by X, β and α emission from radio-elements. The operation and use of the proportional gas counter for X-ray detection is described. A device has been studied for analysing the elements of the 2. and 3. periods of the Mendeleev table. It makes it possible to excite the fluorescence with a radioactive source emitting X-rays or a particles; the X-ray fluorescence penetrates into a window-less proportional counter, this being made possible by the use of an auxiliary electric field in the neighbourhood of the sample. The gas detection pressure leading to the maximum detection yield is given. The spectra are given for the K α lines of 3. period elements excited by 55 Fe, 3 H/Zr and 210 Po sources; for the 2. period the K α spectra of carbon and of fluorine excited by the α particles of 210 Po. (author) [fr

  18. Ultratrace determination of lead in whole blood using electrothermal atomization laser-excited atomic fluorescence spectrometry.

    Science.gov (United States)

    Wagner, E P; Smith, B W; Winefordner, J D

    1996-09-15

    Laser-excited atomic fluorescence has been used to detect lead that was electrothermally atomized from whole blood in a graphite furnace. A 9 kHz repetition rate copper vapor laser pumped dye laser was used to excite the lead at 283.3 nm, and the resulting atomic fluorescence was detected at 405.8 nm. No matrix modification was used other than a 1:21 dilution of the whole blood with high-purity water. Using the atomic fluorescence peak area as the analytical measure and a background correction technique based upon a simultaneous measurement of the transmitted laser intensity, excellent agreement for NIST and CDC certified whole blood reference samples was obtained with aqueous standards. A limit of detection in blood of 10 fg/mL (100 ag absolute) was achieved.

  19. Two-photon Microscopy and Polarimetry for Assessment of Myocardial Tissue Organization

    Science.gov (United States)

    Archambault-Wallenburg, Marika

    Optical methods can provide useful tissue characterization tools. For this project, two-photon microscopy and polarized light examinations (polarimetry) were used to assess the organizational state of myocardium in healthy, infarcted, and stem-cell regenerated states. Two-photon microscopy visualizes collagen through second-harmonic generation and myocytes through two-photon excitation autofluorescence, providing information on the composition and structure/organization of the tissue. Polarimetry measurements yield a value of linear retardance that can serve as an indicator of tissue anisotropy, and with a dual-projection method, information about the anisotropy axis orientation can also be extracted. Two-photon microscopy results reveal that stem-cell treated tissue retains more myocytes and structure than infarcted myocardium, while polarimetry findings suggest that the injury caused by temporary ligation of a coronary artery is less severe and more diffuse that than caused by a permanent ligation. Both these methods show potential for tissue characterization.

  20. Versatile single-molecule multi-color excitation and detection fluorescence setup for studying biomolecular dynamics

    KAUST Repository

    Sobhy, M. A.

    2011-11-07

    Single-molecule fluorescence imaging is at the forefront of tools applied to study biomolecular dynamics both in vitro and in vivo. The ability of the single-molecule fluorescence microscope to conduct simultaneous multi-color excitation and detection is a key experimental feature that is under continuous development. In this paper, we describe in detail the design and the construction of a sophisticated and versatile multi-color excitation and emission fluorescence instrument for studying biomolecular dynamics at the single-molecule level. The setup is novel, economical and compact, where two inverted microscopes share a laser combiner module with six individual laser sources that extend from 400 to 640 nm. Nonetheless, each microscope can independently and in a flexible manner select the combinations, sequences, and intensities of the excitation wavelengths. This high flexibility is achieved by the replacement of conventional mechanical shutters with acousto-optic tunable filter (AOTF). The use of AOTF provides major advancement by controlling the intensities, duration, and selection of up to eight different wavelengths with microsecond alternation time in a transparent and easy manner for the end user. To our knowledge this is the first time AOTF is applied to wide-field total internal reflection fluorescence (TIRF) microscopy even though it has been commonly used in multi-wavelength confocal microscopy. The laser outputs from the combiner module are coupled to the microscopes by two sets of four single-mode optic fibers in order to allow for the optimization of the TIRF angle for each wavelength independently. The emission is split into two or four spectral channels to allow for the simultaneous detection of up to four different fluorophores of wide selection and using many possible excitation and photoactivation schemes. We demonstrate the performance of this new setup by conducting two-color alternating excitation single-molecule fluorescence resonance energy

  1. Structural and dynamical aspects of skin studied by multiphoton excitation fluorescence microscopy-based methods

    DEFF Research Database (Denmark)

    Bloksgaard, Maria; Brewer, Jonathan R.; Bagatolli, Luis

    2013-01-01

    ' parameters. Specifically, by applying these methods, spatially resolved maps of water dipolar relaxation (generalized polarization function using the 6-lauroyl-2-(N,N-dimethylamino)naphthale probe), activity of protons (fluorescence lifetime imaging using a proton sensitive fluorescence probe--2,7-bis-(2......-carboxyethyl)-5-(and-6)-carboxyfluorescein) and diffusion coefficients of distinct fluorescence probes (raster imaging correlation spectroscopy) can be obtained from different regions of the tissue. Comparative studies of different tissue strata, but also between equivalent regions of normal and abnormal......This mini-review reports on applications of particular multiphoton excitation microscopy-based methodologies employed in our laboratory to study skin. These approaches allow in-depth optical sectioning of the tissue, providing spatially resolved information on specific fluorescence probes...

  2. Test and Control System for Chlorophyll Fluorescence Parameters Using LED as Excitation Source

    Directory of Open Access Journals (Sweden)

    Zou Qiuying

    2014-05-01

    Full Text Available A new scheme on test and control system for chlorophyll fluorescence is presented in this work, which uses light-emitting diode (LED excitation by means of measuring the fluorescence parameter fpsII. The system takes programmable power supply as LEDs illumination drive power with high sensitivity and signal-to-noise ratio. MINIPAM is used to measure fluorescence parameter fpsII and keeps communication with upper PC by serial port. The upper PC can control the power supply and process the data received from MINIPAM by software which is programmed in VB6. The results show that the system has a lot of advantages such as high accuracy and convenience. The effect of environmental factors on fluorescence parameters is analyzed comprehensively. It will be a practical measurement and control system for photosynthetic ability and have wide application foreground.

  3. Uncovering of melanin fluorescence in human skin tissue

    Science.gov (United States)

    Scholz, Matthias; Stankovic, Goran; Seewald, Gunter; Leupold, Dieter

    2007-07-01

    Due to its extremely low fluorescence quantum yield, in the conventionally (one-photon) excited autofluorescence of skin tissue, melanin fluorescence is masked by several other endogenous and possibly also exogenous fluorophores (e.g. NADH, FAD, Porphyrins). A first step to enhance the melanin contribution had been realized by two-photon fs-pulse excitation in the red/near IR, based on the fact that melanin can be excited by stepwise two-photon absorption, whereas all other fluorophores in this spectral region allow only simultaneous two-photon excitation. Now, the next and decisive step has been realized: Using an extremely sensitive detection system, for the first time twophoton fluorescence of skin tissue excited with pulses in the ns-range could be measured. The motivation for this step was based on the fact that the population density of the fluorescent level resulting from a stepwise excitation has a different dependence of the pulse duration than that from a simultaneous excitation (Δt2 vs. Δt). Due to this strong discrimination between the fluorophores, practically pure melanin fluorescence can be obtained. Examples for in-vivo, ex-vivo as well as paraffin embedded skin tissue will be shown. The content of information with respect to early diagnosis of skin deseases will be discussed.

  4. Simultaneous control of emission localization and two-photon absorption efficiency in dissymmetrical chromophores

    International Nuclear Information System (INIS)

    Tretiak, Sergei

    2009-01-01

    The aim of the present work is to demonstrate that combined spectral tuning of fluorescence and two-photon absorption (TPA) properties of multipolar chromophores can be achieved by introduction of slight electronic chemical dissymmetry. In that perspective, two novel series of structurally related chromophores have been designed and studied: a first series based on rod-like quadrupolar chromophores bearing different electron-donating (D) end groups and a second series based on three-branched octupolar chromophores built from a trigonal donating moiety and bearing various acceptor (A) peripheral groups. The influence of the electronic dissymmetry is investigated by combined experimental and theoretical studies of the linear and nonlinear optical properties of dissymmetric chromophores compared to their symmetrical counterparts. In both types of systems (i.e. quadrupoles and octupoles) experiments and theory reveal that excitation is essentially delocalized and that excitation involves synchronized charge redistribution between the different D and A moieties within the multipolar structure (i.e. concerted intramolecular charge transfer). In contrast, the emission stems only from a particular dipolar subunit bearing the strongest D or A moieties due to fast excitation localization after excitation prior to emission. Hence control of emission characteristics (polarization and emission spectrum) in addition to localization can be achieved by controlled introduction of electronic dissymmetry (i.e. replacement of one of the D or A end-groups by a slightly stronger D(prime) or A(prime) units). Interestingly dissymmetrical functionalization of both quadrupolar and octupolar compounds does not lead to significant loss in TPA responses and can even be beneficial due to the spectral broadening and peak position tuning that it allows. This study thus reveals an original molecular engineering route strategy allowing major TPA enhancement in multipolar structures due to concerted

  5. Radiative corrections to two photon physics

    International Nuclear Information System (INIS)

    Neervan, W.L. van; Vermaseren, J.A.M.

    1983-06-01

    The authors develop a method to calculate radiative corrections to two photon reactions of the type e + e - →e + e - X where X is an arbitrary final state. To illustrate this they take the example where X stands for a point-like pseudoscalar. It will be shown that the method is an improvement on the standard way in adding real and virtual photon contributions to the (differential) cross-sections. This makes it possible to compute differential and total cross-sections to a very high precision and with a minimum of computer time which is not possible by using more conventional methods. (Auth.)

  6. Inclusive two-photon reactions at TRISTAN

    International Nuclear Information System (INIS)

    Drees, M.

    1995-01-01

    After briefly reviewing past accomplishments of TRISTAN experiments in the field of inclusive two-photon reactions, I discuss open problems in the Monte Carlo simulation of such reactions. The main emphasis is on multiple scattering, i.e. events where at least two pairs of partons scatter within the same γγ collision to form at least four (mini)jets. The cross section for such events might just be observable at TRISTAN. While theoretical arguments for the existence of such events are strong, they have not yet been directly observed experimentally, thereby potentially opening a new opportunity for TRISTAN experiments. (author)

  7. Two-photon physics at LEP

    International Nuclear Information System (INIS)

    Ginzburg, I.F.

    1988-01-01

    The two-photon production of hadrons in e + e - collisions e + e - →e + e - h from which the γγ→h cross sections are extracted is discussed. The common features of these processes are: hadrons move, as a rule, along e + e - beam axis, their total transverse momentum K perpendicular or perpendicular to is small; the total hadron energy is usually less than √S/2. Physical problems of soft processes, exotics, hard processes, semihard processes are considered. New possibilities of LEP, the most interesting and real are presented

  8. Two-photon cooling of magnesium atoms

    DEFF Research Database (Denmark)

    Malossi, N.; Damkjær, S.; Hansen, P. L.

    2005-01-01

    A two-photon mechanism for cooling atoms below the Doppler temperature is analyzed. We consider the magnesium ladder system (3s2)S01¿(3s3p)P11 at 285.2nm followed by the (3s3p)P11¿(3s3d)D21 transition at 880.7nm . For the ladder system quantum coherence effects may become important. Combined with...... and experiment is excellent. In addition, by properly choosing the Rabi frequencies of the two optical transitions a velocity independent atomic dark state is observed....

  9. Non-typical fluorescence studies of excited and ground state proton and hydrogen transfer

    KAUST Repository

    Gil, Michał; Kijak, Michał; Piwonski, Hubert Marek; Herbich, Jerzy; Waluk, Jacek

    2017-01-01

    Fluorescence studies of tautomerization have been carried out for various systems that exhibit single and double proton or hydrogen translocation in various environments, such as liquid and solid condensed phases, ultracold supersonic jets, and finally, polymer matrices with single emitters.We focus on less explored areas of application of fluorescence for tautomerization studies, using porphycene, a porphyrin isomer, as an example. Fluorescence anisotropy techniques allow investigations of self-exchange reactions, where the reactant and product are formally identical. Excitation with polarized light makes it possible to monitor tautomerization in single molecules and to detect their three-dimensional orientation. Analysis of fluorescence from single vibronic levels of jet-isolated porphycene not only demonstrates coherent tunneling of two internal protons, but also indicates that the process is vibrational mode-specific. Next, we present bifunctional proton donoracceptor systems, molecules that are able, depending on the environment, to undergo excited state single intramolecular or double intermolecular proton transfer. For molecules that have donor and acceptor groups located in separate moieties linked by a single bond, excited state tautomerization can be coupled to mutual twisting of the two subunits.

  10. Non-typical fluorescence studies of excited and ground state proton and hydrogen transfer

    KAUST Repository

    Gil, Michał

    2017-02-03

    Fluorescence studies of tautomerization have been carried out for various systems that exhibit single and double proton or hydrogen translocation in various environments, such as liquid and solid condensed phases, ultracold supersonic jets, and finally, polymer matrices with single emitters.We focus on less explored areas of application of fluorescence for tautomerization studies, using porphycene, a porphyrin isomer, as an example. Fluorescence anisotropy techniques allow investigations of self-exchange reactions, where the reactant and product are formally identical. Excitation with polarized light makes it possible to monitor tautomerization in single molecules and to detect their three-dimensional orientation. Analysis of fluorescence from single vibronic levels of jet-isolated porphycene not only demonstrates coherent tunneling of two internal protons, but also indicates that the process is vibrational mode-specific. Next, we present bifunctional proton donoracceptor systems, molecules that are able, depending on the environment, to undergo excited state single intramolecular or double intermolecular proton transfer. For molecules that have donor and acceptor groups located in separate moieties linked by a single bond, excited state tautomerization can be coupled to mutual twisting of the two subunits.

  11. Effects of fluorescence excitation geometry on the accuracy of DNA fragment sizing by flow cytometry

    Energy Technology Data Exchange (ETDEWEB)

    Werner, James H. [Division of Bioscience, Los Alamos National Laboratory, Mail Stop M888, Los Alamos, New Mexico 87545-0001 (United States); Larson, Erica J. [Division of Bioscience, Los Alamos National Laboratory, Mail Stop M888, Los Alamos, New Mexico 87545-0001 (United States); Goodwin, Peter M. [Division of Bioscience, Los Alamos National Laboratory, Mail Stop M888, Los Alamos, New Mexico 87545-0001 (United States); Ambrose, W. Patrick [Division of Bioscience, Los Alamos National Laboratory, Mail Stop M888, Los Alamos, New Mexico 87545-0001 (United States); Keller, Richard A. [Division of Bioscience, Los Alamos National Laboratory, Mail Stop M888, Los Alamos, New Mexico 87545-0001 (United States)

    2000-06-01

    We report on various excitation geometries used in ultrasensitive flow cytometry that yield a linear relation between the fluorescence intensity measured from individual strained DNA fragments and the lengths of the fragments (in base pairs). This linearity holds for DNA samples that exhibit a wide range of conformations. The variety of DNA conformations leads to a distribution of dipole moment orientations for the dye molecules intercalated into the DNA. It is consequently important to use an excitation geometry such that all dye molecules are detected with similar efficiency. To estimate the conformation and the extent of elongation of the strained fragments in the flow, fluorescence polarization anisotropy and autocorrelation measurements were performed. Significant extension was observed for DNA fragments under the flow conditions frequently used for DNA fragment sizing. Classical calculations of the fluorescence emission collected over a finite solid angle are in agreement with the experimental measurements and have confirmed the relative insensitivity to DNA conformation of an orthogonal excitation geometry. Furthermore, the calculations suggested a modified excitation geometry that has increased our sizing resolution. (c) 2000 Optical Society of America.

  12. Effects of fluorescence excitation geometry on the accuracy of DNA fragment sizing by flow cytometry

    International Nuclear Information System (INIS)

    Werner, James H.; Larson, Erica J.; Goodwin, Peter M.; Ambrose, W. Patrick; Keller, Richard A.

    2000-01-01

    We report on various excitation geometries used in ultrasensitive flow cytometry that yield a linear relation between the fluorescence intensity measured from individual strained DNA fragments and the lengths of the fragments (in base pairs). This linearity holds for DNA samples that exhibit a wide range of conformations. The variety of DNA conformations leads to a distribution of dipole moment orientations for the dye molecules intercalated into the DNA. It is consequently important to use an excitation geometry such that all dye molecules are detected with similar efficiency. To estimate the conformation and the extent of elongation of the strained fragments in the flow, fluorescence polarization anisotropy and autocorrelation measurements were performed. Significant extension was observed for DNA fragments under the flow conditions frequently used for DNA fragment sizing. Classical calculations of the fluorescence emission collected over a finite solid angle are in agreement with the experimental measurements and have confirmed the relative insensitivity to DNA conformation of an orthogonal excitation geometry. Furthermore, the calculations suggested a modified excitation geometry that has increased our sizing resolution. (c) 2000 Optical Society of America

  13. Excited-state absorption and fluorescence dynamics of Er3+:KY3F10

    Science.gov (United States)

    Labbé, C.; Doualan, J. L.; Moncorgé, R.; Braud, A.; Camy, P.

    2018-05-01

    We report here on a complete investigation of the excited-state absorption and fluorescence dynamics of Er3+ doped KY3F10 single crystals versus dopant concentrations and optical excitation conditions. Radiative and effective (including non-radiative relaxations) emission lifetimes and branching ratios are determined from a Judd-Ofelt analysis of the absorption spectra and via specific fluorescence experiments using wavelength selective laser excitations. Excited-state absorption and emission spectra are registered within seven spectral domains, i.e. 560 nm, 650 nm, 710 nm, 810 nm, 970 nm, 1550 nm and 2750 nm. A maximum gain cross-section of 0.93 × 10-21 cm2 is determined at the potential laser wavelength of 2.801 μm for a population ratio of 0.48. Saturation of fluorescence intensities and variations of population ratios versus pumping rates are registered and confronted with a rate equation model to derive the rates of the most important up-conversion and cross-relaxation energy transfers occurring at high dopant concentrations.

  14. Role of excited state solvent fluctuations on time-dependent fluorescence Stokes shift

    Energy Technology Data Exchange (ETDEWEB)

    Li, Tanping, E-mail: tanping@lsu.edu, E-mail: revatik@lsu.edu; Kumar, Revati, E-mail: tanping@lsu.edu, E-mail: revatik@lsu.edu [Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803 (United States)

    2015-11-07

    We explore the connection between the solvation dynamics of a chromophore upon photon excitation and equilibrium fluctuations of the solvent. Using molecular dynamics simulations, fluorescence Stokes shift for the tryptophan in Staphylococcus nuclease was examined using both nonequilibrium calculations and linear response theory. When the perturbed and unperturbed surfaces exhibit different solvent equilibrium fluctuations, the linear response approach on the former surface shows agreement with the nonequilibrium process. This agreement is excellent when the perturbed surface exhibits Gaussian statistics and qualitative in the case of an isomerization induced non-Gaussian statistics. However, the linear response theory on the unperturbed surface breaks down even in the presence of Gaussian fluctuations. Experiments also provide evidence of the connection between the excited state solvent fluctuations and the total fluorescence shift. These observations indicate that the equilibrium statistics on the excited state surface characterize the relaxation dynamics of the fluorescence Stokes shift. Our studies specifically analyze the Gaussian fluctuations of the solvent in the complex protein environment and further confirm the role of solvent fluctuations on the excited state surface. The results are consistent with previous investigations, found in the literature, of solutes dissolved in liquids.

  15. Comparison of conventional and total reflection excitation geometry for fluorescence X-ray absorption spectroscopy on droplet samples

    International Nuclear Information System (INIS)

    Falkenberg, G.; Pepponi, G.; Streli, C.; Wobrauschek, P.

    2003-01-01

    X-ray absorption fine structure (XAFS) experiments in fluorescence mode have been performed in total reflection excitation geometry and conventional 45 deg. /45 deg. excitation/detection geometry for comparison. The experimental results have shown that XAFS measurements are feasible under normal total reflection X-ray fluorescence (TXRF) conditions, i.e. on droplet samples, with excitation in grazing incidence and using a TXRF experimental chamber. The application of the total reflection excitation geometry for XAFS measurements increases the sensitivity compared to the conventional geometry leading to lower accessible concentration ranges. However, XAFS under total reflection excitation condition fails for highly concentrated samples because of the self-absorption effect

  16. Characterization of excited-state reactions with instant spectra of fluorescence kinetics

    International Nuclear Information System (INIS)

    Tomin, Vladimir I.; Ushakou, Dzmitryi V.

    2015-01-01

    Comprehensible knowledge of the excited-state proton transfer processes in organic compounds is overwhelmingly important not only for physics, but also chemistry and Life Sciences, since they play a key role in main processes of photosynthesis and functioning of biological organisms. Moreover compounds with Excited-State Intramolecular Proton Transfer (ESIPT) are in the focus of the interest of scientists throughout the world, because dual fluorescence spectra of such objects corresponding to two forms of molecular structure (normal and photoproduct) are very sensitive to characteristics of molecular microenvironment. This property allows to use such substances as fluorescent probes for diverse applications in chemistry and Life Sciences. But at the same time studying of proton transfer processes is not simple, because this process is characterized by extremely fast times (on picoseconds time scale and less order) and very often contribution of reverse reactions is essentially complicates an interpretation of observed properties of dual fluorescence. Hence, understanding of a role of reversible reactions is crucial for a comprehensive description of all processes accompanying excited state reactions. We discuss new approach for treatment ESIPT reaction on the basis of experimentally measured instant spectra of dual fluorescence and temporal behavior of ratiometric signal of normal to tautomer form intensities. Simple analytical expressions show in transparent way how to distinguish a degree of reverse reaction contribution to ratiometric signal. A validation of the approach under consideration is fulfilled with two different flavonols – 3-hydroxyflavone and 4′-(Dimethylamino)-3-hydroxyflavone – representing two extreme cases in affecting reversible reaction on dual emission. A comparing of new approach and traditional method when we analyze kinetics of separate the N* and T* fluorescence bands decays, has been carried out. - Highlights: • The excited

  17. Characterization of excited-state reactions with instant spectra of fluorescence kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Tomin, Vladimir I., E-mail: tomin@apsl.edu.pl; Ushakou, Dzmitryi V.

    2015-10-15

    Comprehensible knowledge of the excited-state proton transfer processes in organic compounds is overwhelmingly important not only for physics, but also chemistry and Life Sciences, since they play a key role in main processes of photosynthesis and functioning of biological organisms. Moreover compounds with Excited-State Intramolecular Proton Transfer (ESIPT) are in the focus of the interest of scientists throughout the world, because dual fluorescence spectra of such objects corresponding to two forms of molecular structure (normal and photoproduct) are very sensitive to characteristics of molecular microenvironment. This property allows to use such substances as fluorescent probes for diverse applications in chemistry and Life Sciences. But at the same time studying of proton transfer processes is not simple, because this process is characterized by extremely fast times (on picoseconds time scale and less order) and very often contribution of reverse reactions is essentially complicates an interpretation of observed properties of dual fluorescence. Hence, understanding of a role of reversible reactions is crucial for a comprehensive description of all processes accompanying excited state reactions. We discuss new approach for treatment ESIPT reaction on the basis of experimentally measured instant spectra of dual fluorescence and temporal behavior of ratiometric signal of normal to tautomer form intensities. Simple analytical expressions show in transparent way how to distinguish a degree of reverse reaction contribution to ratiometric signal. A validation of the approach under consideration is fulfilled with two different flavonols – 3-hydroxyflavone and 4′-(Dimethylamino)-3-hydroxyflavone – representing two extreme cases in affecting reversible reaction on dual emission. A comparing of new approach and traditional method when we analyze kinetics of separate the N* and T* fluorescence bands decays, has been carried out. - Highlights: • The excited

  18. Fluorescence fluctuation of Rhodamine 6G dye for high repetition rate laser excitation

    International Nuclear Information System (INIS)

    Singh, Nageshwar; Patel, Hemant K.; Dixit, S.K.; Vora, H.S.

    2013-01-01

    In this paper, fluorescence from Rhodamine 6G dye for stationary and flowing liquid medium, excited by copper vapor laser, operating at 6 kHz pulse repetition frequency, was investigated. Large fluctuations in spectral width (about 5 nm) and spectral intensity in the fluorescence from stationary dye solution were observed, while fluctuations in the spectral width diminish in a flowing dye medium. However, this increases spectral intensity and slightly red shifts the fluorescence peak emission wavelength. Theoretical analysis was carried out to explain the observed results by incorporating the temperature induced refractive index, beam deflection and spectral variation in stationary dye solution. Numerical analysis of thermal load and contour of temperature in the optical pumped region inside the dye cell in stationary, 0.2 and 1.5 m/s flow velocity was also investigated to support our analysis. - Highlights: ► High repetition rate excitation generates inhomogeneity in the gain medium. ► Fluorescence of Rhodamine 6G in stationary and flowing medium was carried out. ► Fluorescence fluctuations lessen in flowing medium in contrast to stationary medium. ► Our theoretical and numerical analysis enlightens the experimented outcome trend.

  19. Multimodal optical coherence tomography and fluorescence lifetime imaging with interleaved excitation sources for simultaneous endogenous and exogenous fluorescence.

    Science.gov (United States)

    Shrestha, Sebina; Serafino, Michael J; Rico-Jimenez, Jesus; Park, Jesung; Chen, Xi; Zhaorigetu, Siqin; Walton, Brian L; Jo, Javier A; Applegate, Brian E

    2016-09-01

    Multimodal imaging probes a variety of tissue properties in a single image acquisition by merging complimentary imaging technologies. Exploiting synergies amongst the data, algorithms can be developed that lead to better tissue characterization than could be accomplished by the constituent imaging modalities taken alone. The combination of optical coherence tomography (OCT) with fluorescence lifetime imaging microscopy (FLIM) provides access to detailed tissue morphology and local biochemistry. The optical system described here merges 1310 nm swept-source OCT with time-domain FLIM having excitation at 355 and 532 nm. The pulses from 355 and 532 nm lasers have been interleaved to enable simultaneous acquisition of endogenous and exogenous fluorescence signals, respectively. The multimodal imaging system was validated using tissue phantoms. Nonspecific tagging with Alexa Flour 532 in a Watanbe rabbit aorta and active tagging of the LOX-1 receptor in human coronary artery, demonstrate the capacity of the system for simultaneous acquisition of OCT, endogenous FLIM, and exogenous FLIM in tissues.

  20. Resonant production in two photon collisions

    International Nuclear Information System (INIS)

    Butler, F.

    1988-12-01

    Using 220 picobarn/sup /minus/1/ of data collected by the Mark II detector at PEP, we have measured the width of the /eta/' for quasi real photons. The width is separately measured in the three reactions e + e/sup /minus// → e + e/sup /minus///eta/ 0 π + π/sup /minus//; /eta/ 0 → γγ, e + e/sup /minus// → e + e/sup /minus///eta/ 0 π + π/sup /minus//; /eta/ 0 → π + π/sup /minus//(π 0 ,γ) and e + e/sup /minus// → e + e/sup /minus///rho/ 0 γ, giving a statistically weighted average two-photon width of Γ/sub /eta/'→γγ/ = 5. 21+-0.28 keV. As a by-product of the measurement of Γ/sub /eta/'→γγ/ using the decay mode /eta/' → /rho/γ, we also measured a two-photon decay width for the a 2 (1320) of Γ/sub a 2(1320)→γγ/ = 1.17+-0. 15+-0.25 keV. 47 refs., 50 figs., 8 tabs

  1. Comparison of sensitivities and detection limits between direct excitation and secondary excitation modes in energy dispersive x-ray fluorescence analysis

    International Nuclear Information System (INIS)

    Artz, B.E.; Short, M.A.

    1976-01-01

    A comparison was made between the direct tube excitation mode and the secondary target excitation mode using a Kevex 0810 energy dispersive x-ray fluorescence system. Relative sensitivities and detection limits were determined with two system configurations. The first configuration used a standard, high power, x-ray fluorescence tube to directly excite the specimen. Several x-ray tubes, including chromium, molybdenum, and tungsten, both filtered and not filtered, were employed. The second configuration consisted of using the x-ray tube to excite a secondary target which in turn excited the specimen. Appropriate targets were compared to the direct excitation results. Relative sensitivities and detection limits were determined for K-series lines for elements from magnesium to barium contained in a low atomic number matrix and in a high atomic number matrix

  2. Spatial distribution of fluorescent light emitted from neon and nitrogen excited by low energy electron beams

    International Nuclear Information System (INIS)

    Morozov, A.; Kruecken, R.; Ulrich, A.; Wieser, J.

    2006-01-01

    Side-view intensity profiles of fluorescent light were measured for neon and nitrogen excited with 12 keV electron beams at gas pressures from 250 to 1400 hPa. The intensity profiles were compared with theoretical profiles calculated using the CASINO program which performs Monte Carlo simulations of electron scattering. It was assumed that the spatial distribution of fluorescent intensity is directly proportional to the spatial distribution of energy loss by primary electrons. The comparison shows good correlation of experimental data and the results of numeric simulations

  3. Theoretical study on X-Ray Fluorescence Analysis: Contribution of the self-excitation phenomenon

    International Nuclear Information System (INIS)

    RAKOTONDRAJAONA, H.N.J.L.

    1999-01-01

    This work consist in setting up, firstly, fluorescence intensities due to the contribution of secondary and tertiary excitation phenomena which settle among the elements of the same sample during the analysis through X fluorescence, inspired by Sherman calculations. Secondly, we have experimentally checked these expression from the analysis of twelve samples; containing all the following elements: Iron, Copper and Zinc. The difference between the theoretical results and the experimental results has been valued from the formula of the test of χ 2 . We consider that this difference is noticeable compared to other errors due to analysis method. [fr

  4. Fluorescence excited in a thunderstorm atmosphere by relativistic runaway electron avalanches

    Science.gov (United States)

    Babich, L. P.; Bochkov, E. I.

    2017-05-01

    The spectrum and spatiotemporal evolution of the fluorescence of an atmospheric discharge developing in the regime of relativistic runaway electron avalanche (RREA) generation have been calculated without involving the relativistic feedback. The discharges generating narrow bipolar pulses, along with the discharges responsible for terrestrial gamma-ray flashes, are shown to be relatively dark. Nevertheless, the fluorescence excited by a discharge involving RREAs can be recorded with cameras used to record high-altitude optical phenomena. A possible connection between a certain class of optical phenomena observed at the tops of thunderclouds and RREA emission is pointed out.

  5. Synthesis of novel fluorene-based two-photon absorbing molecules and their applications in optical data storage, microfabrication, and stimulated emission depletion

    Science.gov (United States)

    Yanez, Ciceron

    2009-12-01

    polymer matrix, generating a data storage capacity of up to 1.8 x 1013 bits/cm3. The possibility of using these PAGs in microfabrication is described in Chapter III, where two-photon induced cationic ring-opening polymerization (CROP) crosslinking of an SU8 resin is employed to produce free-standing microstructures. Chapter IV describes the investigation of one- and two-photon stimulated emission transitions by the fluorescence quenching of a sulfonyl-containing fluorene compound in solution at room temperate using a picosecond pump-probe technique. The nature of stimulated transitions under various fluorescence excitation and quenching conditions were analyzed theoretically, and good agreement with experimental data was demonstrated. Two-photon stimulated transitions S1 → S0 were shown at lambdaq = 1064 nm. The two-photon stimulated emission cross section of the sulfonyl fluorophore was estimated as delta2PE (lambda q) ≈ 240--280 GM, making this compound a good candidate for use in two-photon stimulated emission depletion (STED) microscopy.

  6. Studies of the fluorescent excited state of impurities in ionic crystals

    International Nuclear Information System (INIS)

    Romestain, Robert

    1972-01-01

    The author of this research thesis first presents experimental methods used in this research: principles (recall on the optical spectrum of an impurity in a solid, use of fluorescence polarization) and techniques (sample preparation, liquid helium cryostat, application of a disturbance, optical detection). Then, he reports the study of the Mn ++ ion in a tetrahedron crystalline field, the study of the Jahn Teller effect on the excited state of the F + centre in CaO, and the study by double resonance of a specific excited state of this same centre in CaO

  7. Two-photon resonant, stimulated processes in krypton and xenon

    International Nuclear Information System (INIS)

    Miller, J.C.

    1988-11-01

    Both on-axis and conical emissions have been observed following two-photon pumping of the 5p states of krypton and the 6p', 7p, 8p, and 4f states of xenon. In the former case, coherent emissions from the 5p states to the 5s are observed, and in the latter case, many p→s, d→p, and f→d cascade emissions are observed. By analogy to the well-studied alkali and alkaline earth examples, the emissions are discussed in terms of amplified spontaneous emission (ASE), stimulated hyper-Raman scattering, and parametric four-wave mixing. The physical processes responsible for the conical emission and for intensity anomalies in the xenon p→s emissions are not understood at present. Interference effects due to coherent cancellation between competing excitation pathways may be occurring. 4 refs., 3 figs

  8. Review: two-photon scanning systems for clinical high resolution in vivo tissue imaging

    Science.gov (United States)

    König, K.; Müller, J.; Höfer, M.; Müller, C.; Weinigel, M.; Bückle, R.; Elsner, P.; Kaatz, M.; Messerschmidt, B.

    2008-02-01

    The femtosecond laser multiphoton tomograph DermaInspect as well as high NA two-photon GRIN microendoscopes for in vivo tomography of human skin have been used to detect malignant melanoma as well as to study the diffusion and intradermal accumulation of topically applied cosmetical and pharmaceutical components. So far, more than 500 patients and volunteers in Europe, Australia, and Asia have been investigated with this unique tomograph. Near infrared 80 MHz picojoule femtosecond laser pulses were employed to excite endogenous fluorophores such as NAD(P)H, flavoproteins, melanin, and elastin as well as fluorescent components of a variety of ointments via a twophoton excitation process. In addition, collagen has been imaged by second harmonic generation. Using a two-PMT detection system, the ratio of elastin to collagen was determined during optical sectioning. A high submicron spatial resolution and 50 picosecond temporal resolution was achieved using galvoscan mirrors and piezodriven focusing optics as well as a time-correlated single photon counting module with a fast microchannel plate detector and fast photomultipliers. Individual intratissue cells, mitochondria, melanosomes, and the morphology of the nuclei as well as extracellular matrix elements could be clearly visualized due to molecular imaging and the calculation of fluorescence lifetime images. Nanoparticles and intratissue drugs have been detected non-invasively, in situ and over a period of up to 3 months. In addition, hydration effects and UV effects were studied by monitoring modifications of cellular morphology and autofluorescence. The system was used to observe the diffusion through the stratum corneum and the accumulation and release of functionalized nanoparticles along hair shafts and epidermal ridges. The DermaInspect been also employed to gain information on skin age and wound healing in patients with ulcers. Novel developments include a galvo/piezo-scan driven flexible articulated arm as

  9. Plastic lab-on-a-chip for fluorescence excitation with integrated organic semiconductor lasers.

    Science.gov (United States)

    Vannahme, Christoph; Klinkhammer, Sönke; Lemmer, Uli; Mappes, Timo

    2011-04-25

    Laser light excitation of fluorescent markers offers highly sensitive and specific analysis for bio-medical or chemical analysis. To profit from these advantages for applications in the field or at the point-of-care, a plastic lab-on-a-chip with integrated organic semiconductor lasers is presented here. First order distributed feedback lasers based on the organic semiconductor tris(8-hydroxyquinoline) aluminum (Alq3) doped with the laser dye 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyril)-4H-pyrane (DCM), deep ultraviolet induced waveguides, and a nanostructured microfluidic channel are integrated into a poly(methyl methacrylate) (PMMA) substrate. A simple and parallel fabrication process is used comprising thermal imprint, DUV exposure, evaporation of the laser material, and sealing by thermal bonding. The excitation of two fluorescent marker model systems including labeled antibodies with light emitted by integrated lasers is demonstrated.

  10. Increased fluorescence of PbS quantum dots in photonic crystals by excitation enhancement

    Science.gov (United States)

    Barth, Carlo; Roder, Sebastian; Brodoceanu, Daniel; Kraus, Tobias; Hammerschmidt, Martin; Burger, Sven; Becker, Christiane

    2017-07-01

    We report on the enhanced fluorescence of lead sulfide quantum dots interacting with leaky modes of slab-type silicon photonic crystals. The photonic crystal slabs were fabricated, supporting leaky modes in the near infrared wavelength range. Lead sulfite quantum dots which are resonant in the same spectral range were prepared in a thin layer above the slab. We selectively excited the leaky modes by tuning the wavelength and angle of incidence of the laser source and measured distinct resonances of enhanced fluorescence. By an appropriate experiment design, we ruled out directional light extraction effects and determined the impact of enhanced excitation. Three-dimensional numerical simulations consistently explain the experimental findings by strong near-field enhancements in the vicinity of the photonic crystal surface. Our study provides a basis for systematic tailoring of photonic crystals used in biological applications such as biosensing and single molecule detection, as well as quantum dot solar cells and spectral conversion applications.

  11. Parallel excitation-emission multiplexed fluorescence lifetime confocal microscopy for live cell imaging.

    Science.gov (United States)

    Zhao, Ming; Li, Yu; Peng, Leilei

    2014-05-05

    We present a novel excitation-emission multiplexed fluorescence lifetime microscopy (FLIM) method that surpasses current FLIM techniques in multiplexing capability. The method employs Fourier multiplexing to simultaneously acquire confocal fluorescence lifetime images of multiple excitation wavelength and emission color combinations at 44,000 pixels/sec. The system is built with low-cost CW laser sources and standard PMTs with versatile spectral configuration, which can be implemented as an add-on to commercial confocal microscopes. The Fourier lifetime confocal method allows fast multiplexed FLIM imaging, which makes it possible to monitor multiple biological processes in live cells. The low cost and compatibility with commercial systems could also make multiplexed FLIM more accessible to biological research community.

  12. Microsphere imaging with confocal microscopy and two photon microscopy

    International Nuclear Information System (INIS)

    Chun, Hyung Su; An, Kyung Won; Lee, Jai Hyung

    2002-01-01

    We have acquired images of polystyrene and fused-silica microsphere by using conventional optical microscopy, confocal microscopy and two-photon microscopy, and performed comparative analysis of these images. Different from conventional optical microscopy, confocal and two-photon microscopy had good optical sectioning capability. In addition, confocal microscopy and two-photon microscopy had better lateral resolution than conventional optical microscopy. These results are attributed to confocality and nonlinearity of confocal microscopy and two photon microscopy, respectively.

  13. On the kinematics of the two-photon Cherenkov effect

    International Nuclear Information System (INIS)

    Afanas'ev, G.N.; Stepanovskij, Yu.P.

    2003-01-01

    We study the kinematics of the two-photon Cherenkov effect. In the general case, the emission angles of two photons satisfy certain inequalities and the corresponding radiation intensities are rather diffused. In special cases, when the above inequalities reduce to equalities, the emission angles of two photons are fixed and the corresponding radiation intensities should have sharp maxima at these angles. This makes easier the experimental study of the two-photon Cherenkov effect

  14. Analysis of Spectral Features of Seawaterbiooptical Components Fluorescence from the Excitation-emission Matrix

    Science.gov (United States)

    Salyuk, P. A.; Nagorny, I. G.

    The paper presents the method for processing of excitation-emission matrix of sea water and the allocation of the spectral characteristics of different types of colored dissolved organic matter (CDOM) and phytoplankton cells in seawater. The method consists of identification of regularly observed fluorescence peaks of CDOM in marine waters of different type and definition of the spectral ranges, where the predominant influence of these peaks are observed.

  15. Influence of different environments on the excited-state proton transfer and dual fluorescence of fisetin

    Science.gov (United States)

    Guharay, Jayanti; Dennison, S. Moses; Sengupta, Pradeep K.

    1999-05-01

    The influence of different protic and aprotic solvent environments on the excited-state intramolecular proton transfer (ESIPT) leading to a dual fluorescence behaviour of a biologically important, naturally occurring, polyhydroxyflavone, fisetin (3,3',4',7-tetrahydroxyflavone), has been investigated. The normal fluorescence band, in particular, is extremely sensitive to solvent polarity with νmax shifting from 24 510 cm -1 in dioxane ( ET(30)=36.0) to 20 790 cm -1 in methanol ( ET(30)=55.5). This is rationalized in terms of solvent dipolar relaxation process, which also accounts for the red edge excitation shifts (REES) observed in viscous environments such as glycerol at low temperatures. Significant solvent dependence of the tautomer fluorescence properties ( νmax, yield and decay kinetics) reveals the influence of external hydrogen bonding perturbation on the internal hydrogen bond of the molecule. These excited-state relaxation phenomena and their relevant parameters have been used to probe the microenvironment of fisetin in a membrane mimetic system, namely AOT reverse micelles in n-heptane at different water/surfactant molar ratio ( w0).

  16. Fluorescent molecular probes based on excited state prototropism in lipid bilayer membrane

    Science.gov (United States)

    Mohapatra, Monalisa; Mishra, Ashok K.

    2012-03-01

    Excited state prototropism (ESPT) is observed in molecules having one or more ionizable protons, whose proton transfer efficiency is different in ground and excited states. The interaction of various ESPT molecules like naphthols and intramolecular ESPT (ESIPT) molecules like hydroxyflavones etc. with different microheterogeneous media have been studied in detail and excited state prototropism as a probe concept has been gaining ground. The fluorescence of different prototropic forms of such molecules, on partitioning to an organized medium like lipid bilayer membrane, often show sensitive response to the local environment with respect to the local structure, physical properties and dynamics. Our recent work using 1-naphthol as an ESPT fluorescent molecular probe has shown that the incorporation of monomeric bile salt molecules into lipid bilayer membranes composed from dipalmitoylphosphatidylcholine (DPPC, a lung surfactant) and dimyristoylphosphatidylcholine (DMPC), in solid gel and liquid crystalline phases, induce appreciable wetting of the bilayer up to the hydrocarbon core region, even at very low (fisetin, an ESIPT molecule having antioxidant properties, in lipid bilayer membrane has been sensitively monitored from its intrinsic fluorescence behaviour.

  17. Fluorescence detection of glutathione and oxidized glutathione in blood with a NIR-excitable cyanine probe

    Science.gov (United States)

    Liu, Chang-hui; Qi, Feng-pei; Wen, Fu-bin; Long, Li-ping; Liu, Ai-juan; Yang, Rong-hua

    2018-04-01

    Cyanine has been widely utilized as a near infrared (NIR) fluorophore for detection of glutathione (GSH). However, the excitation of most of the reported cyanine-based probes was less than 800 nm, which inevitably induce biological background absorption and lower the sensitivity, limiting their use for detection of GSH in blood samples. To address this issue, here, a heptamethine cyanine probe (DNIR), with a NIR excitation wavelength at 804 nm and a NIR emission wavelength at 832 nm, is employed for the detection of GSH and its oxidized form (GSSG) in blood. The probe displays excellent selectivity for GSH over GSSG and other amino acids, and rapid response to GSH, in particular a good property for indirect detection of GSSG in the presence of enzyme glutathione reductase and the reducing agent nicotinamideadenine dinucleotide phosphate, without further separation prior to fluorescent measurement. To the best of our knowledge, this is the first attempt to explore NIR fluorescent approach for the simultaneous assay of GSH and GSSG in blood. As such, we expect that our fluorescence sensors with both NIR excitation and NIR emission make this strategy suitable for the application in complex physiological systems.

  18. Simulation of Far-Field Superresolution Fluorescence Imaging with Two-Color One-Photon Excitation of Reversible Photoactivatable Protein

    International Nuclear Information System (INIS)

    Wang Chen; Qiao Ling-Ling; Mao Zheng-Le

    2011-01-01

    We propose to achieve far-field super-resolution imaging by using offset two-color one-photon (2C1P) excitation of reversible photoactivatable fluorescence proteins. Due to the distinctive photoswitching performance of the proteins, such as dronpa, the fluorescence emission will only come from the overlapped region of activation beam and excitation beam. The analysis solution of rate equation shows that the resolution of offset 2C1P microscope is 'engineered' by laser power of excitation and activation beams and the power ratio between them. Superior lateral and transverse resolution is theoretically demonstrated compared with conventional fluorescence scanning microscopy. (fundamental areas of phenomenology(including applications))

  19. Two Photon Induced Lasing in 1550 nm Quantum Dash Optical Gain Media

    DEFF Research Database (Denmark)

    Capua, Amir; Saal, Abigael; Reithmaier, Johann Peter

    2011-01-01

    We report on a unique lasing mechanism observed in quantum dash Gain media. While the gain media is electrically pumped below lasing threshold, a strong optical pulse excites carriers by two photon absorption into high energy states of the quantum dashes and wetting layer. Fast inter band carrier...

  20. Novel nanocarriers for topical drug delivery: investigating delivery efficiency and distribution in skin using two-photon microscopy

    Science.gov (United States)

    Kirejev, Vladimir; Guldbrand, Stina; Bauer, Brigitte; Smedh, Maria; Ericson, Marica B.

    2011-03-01

    The complex structure of skin represents an effective barrier against external environmental factors, as for example, different chemical and biochemical compounds, yeast, bacterial and viral infections. However, this impermeability prevents efficient transdermal drug delivery which limits the number of drugs that are able to penetrate the skin efficiently. Current trends in drug application through skin focus on the design and use of nanocarriers for transport of active compounds. The transport systems applied so far have several drawbacks, as they often have low payload, high toxicity, a limited variability of inclusion molecules, or long degradation times. The aim of these current studies is to investigate novel topical drug delivery systems, e.g. nanocarriers based on cyclic oligosaccharides - cyclodextrins (CD) or iron (III)-based metal-organic frameworks (MOF). Earlier studies on cell cultures imply that these drug nanocarriers show promising characteristics compared to other drug delivery systems. In our studies, we use two-photon microscopy to investigate the ability of the nanocarriers to deliver compounds through ex-vivo skin samples. Using near infrared light for excitation in the so called optical window of skin allows deep-tissue visualization of drug distribution and localization. In addition, it is possible to employ two-photon based fluorescence correlation spectroscopy for quantitative analysis of drug distribution and concentrations in different cell layers.

  1. Two-photon interference : spatial aspects of two-photon entanglement, diffraction, and scattering

    NARCIS (Netherlands)

    Peeters, Wouter Herman

    2010-01-01

    This dissertation contains scientific research within the realm of quantum optics, which is a branch of physics. An experimental and theoretical study is made of two-photon interference phenomena in various optical systems. Spatially entangled photon pairs are produced via the nonlinear optical

  2. Excited state fluorescence quenching of the U O2++ ion by monovalent anions

    International Nuclear Information System (INIS)

    Santarine, G.A.

    1987-01-01

    The reactions of the Uranyl ion U O 2 ++ in the excited state with the monovalent inorganic ions N O 3 - and I O 3 - in aqueous solutions at normal temperature were studied, using three techniques: Fluorescence in the steady state - Flash photolysis - Fluorescence decay after excitation. With increasing concentration of these ions it was observed a decrease in the normalized intensity and a decrease in the decay time of the fluorescence of the Uranyl ion in the solution and a corresponding appearance of the radicals N O 3 . or I O 3 . . In each case the radical was identified by its optical absorption spectrum. These results suggest that the quenching of fluorescence of the Uranyl ion in each case is owing to an electron transfer reaction. In the case of the Nitrate ion the transfer may occur after the formation of an ionic par (U O 2 + ...N O 3 ) in the ground state. Evidence for static quenching in the system Uranyl iodate was not forthcoming. A mechanism for the determination of the velocity constant (probability per ion pair per unit time) is proposed for each of the systems. (author)

  3. Excited state hydrogen bonding fluorescent probe: Role of structure and environment

    Energy Technology Data Exchange (ETDEWEB)

    Dey, Debarati, E-mail: debaratidey07@gmail.com [Department of Chemistry, Vidyasagar College, 39 Sankar Ghosh Lane, Kolkata 700006 (India); Sarangi, Manas Kumar [Chemical Sciences Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064 (India); Ray, Angana; Bhattacharyya, Dhananjay [Computational Science Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064 (India); Maity, Dilip Kumar [Department of Chemistry, University College of Science and Technology, 92 A.P.C. Road, Kolkata 700009 (India)

    2016-05-15

    An environment sensitive fluorescent probe, 11-benzoyl-dibenzo[a,c]phenazine (BDBPZ), has been synthesized and characterized that acts via excited state hydrogen bonding (ESHB). On interaction with hydrogen bond donating solvents the fluorescence intensity of BDBPZ increases abruptly with a concomitant bathochromic shift. The extent of fluorescence increment and the red-shift of λ{sub max} depend on hydrogen bond donating ability of the solvent associated. ESHB restricts the free rotation of the benzoyl group and hence blocks the non-radiative deactivation pathway. BDBPZ forms an exciplex with organic amine in nonpolar medium that readily disappears on increasing the polarity of the solvent. In polar environment the fluorescence of both the free molecule and excited state hydrogen bonded species are quenched on addition of amine unlike its parent dibenzo[a,c]phenazine (DBPZ), that remains very much inaccessible towards the solvent as well as quencher molecules due to its structure. This newly synthesized derivative BDBPZ is much more interactive due to the benzoyl group that is flanked outside the skeletal aromatic rings of DBPZ, which helps to sense the environment properly and thus shows better ESHB capacity than DBPZ.

  4. Сomparative Analysis of 0.266 and 0.355 µm Fluorescence Excitation Wavelengths for Laser Fluores-Cence Monitoring of Oil Pollution Detection

    Directory of Open Access Journals (Sweden)

    M. L. Belov

    2017-01-01

    Full Text Available The on-line detection of pipeline spillage is really essential for the fast oil spill response to the ecological and economical consequences. However existing on-line pipelines spillage detection systems have a sensibility of 0.2 – 1 % of pipe flow and do not detect the smaller-sized spillages.For unpeopled or sparsely populated regions an advanced technique for detection of pipeline spillages (including low-intensity ones is to monitor oil pollution (petroleum spills on the earth surface along the pipeline using, for example, an air drone.The laser remote sensing method is an effective method to detect the pipelines spillage.The paper is dedicated to development of laser fluorescence detection method of oil pollution. The remote sensing laser method to monitor oil pollution is based on the fluorescence excitation of oil in UV spectral band and on the data record of the earth surface laser-induced fluorescence radiation.For laser fluorescence method of monitoring oil pollution the paper presents a comparative analysis  of 0.266 and 0.355 µm wavelengths of the fluorescence excitation in terms of earth atmosphere propagation, eye-safety, laser characteristics, and petroleum fluorescence excitation efficiency.It is shown that in terms of eye-safety, laser characteristics, and propagation in the earth atmosphere a 0.355 µm laser wavelength of the fluorescence excitation has a sure advantage.In the context of petroleum fluorescence excitation efficiency a 0.266 µm laser wavelength of the fluorescence excitation has the advantage, but this advantage depends heavily on the petroleum base. For low-sulfur (sweet oil for instance,  it is not that big.At large, in solving the task of oil pollution detection because of the oil pipeline spillages the 0.355 µm wavelength of fluorescence excitation ought to be preferable. However, when creating a monitoring system for the pipeline with a specific petroleum base the irreversible decision depends on the

  5. Two-photon NADH imaging exposes boundaries of oxygen diffusion in cortical vascular supply regions

    OpenAIRE

    Kasischke, Karl A; Lambert, Elton M; Panepento, Ben; Sun, Anita; Gelbard, Harris A; Burgess, Robert W; Foster, Thomas H; Nedergaard, Maiken

    2010-01-01

    Oxygen transport imposes a possible constraint on the brain's ability to sustain variable metabolic demands, but oxygen diffusion in the cerebral cortex has not yet been observed directly. We show that concurrent two-photon fluorescence imaging of endogenous nicotinamide adenine dinucleotide (NADH) and the cortical microcirculation exposes well-defined boundaries of tissue oxygen diffusion in the mouse cortex. The NADH fluorescence increases rapidly over a narrow, very low pO2 range with a p ...

  6. Two-photon transitions in hydrogen atoms embedded in weakly coupled plasmas

    International Nuclear Information System (INIS)

    Paul, S.; Ho, Y. K.

    2008-01-01

    The pseudostate method has been applied to calculate energy eigenvalues and corresponding eigenfunctions of the hydrogen atom in Debye plasma environments. Resonant two-photon transition rates from the ground state of atomic hydrogen to 2s and 3s excited states have been computed as a function of photon frequency in the length and velocity gauges for different Debye lengths. A two-photon transparency is found in correspondence to each resonance for 1s-3s. The transparency frequency and resonance enhancement frequency vary significantly with the Debye length.

  7. Fluorescence Intrinsic Characterization of Excitation-Emission Matrix Using Multi-Dimensional Ensemble Empirical Mode Decomposition

    Directory of Open Access Journals (Sweden)

    Tzu-Chien Hsiao

    2013-11-01

    Full Text Available Excitation-emission matrix (EEM fluorescence spectroscopy is a noninvasive method for tissue diagnosis and has become important in clinical use. However, the intrinsic characterization of EEM fluorescence remains unclear. Photobleaching and the complexity of the chemical compounds make it difficult to distinguish individual compounds due to overlapping features. Conventional studies use principal component analysis (PCA for EEM fluorescence analysis, and the relationship between the EEM features extracted by PCA and diseases has been examined. The spectral features of different tissue constituents are not fully separable or clearly defined. Recently, a non-stationary method called multi-dimensional ensemble empirical mode decomposition (MEEMD was introduced; this method can extract the intrinsic oscillations on multiple spatial scales without loss of information. The aim of this study was to propose a fluorescence spectroscopy system for EEM measurements and to describe a method for extracting the intrinsic characteristics of EEM by MEEMD. The results indicate that, although PCA provides the principal factor for the spectral features associated with chemical compounds, MEEMD can provide additional intrinsic features with more reliable mapping of the chemical compounds. MEEMD has the potential to extract intrinsic fluorescence features and improve the detection of biochemical changes.

  8. Comparison of fluorescence rejection methods of baseline correction and shifted excitation Raman difference spectroscopy

    Science.gov (United States)

    Cai, Zhijian; Zou, Wenlong; Wu, Jianhong

    2017-10-01

    Raman spectroscopy has been extensively used in biochemical tests, explosive detection, food additive and environmental pollutants. However, fluorescence disturbance brings a big trouble to the applications of portable Raman spectrometer. Currently, baseline correction and shifted-excitation Raman difference spectroscopy (SERDS) methods are the most prevailing fluorescence suppressing methods. In this paper, we compared the performances of baseline correction and SERDS methods, experimentally and simulatively. Through the comparison, it demonstrates that the baseline correction can get acceptable fluorescence-removed Raman spectrum if the original Raman signal has good signal-to-noise ratio, but it cannot recover the small Raman signals out of large noise background. By using SERDS method, the Raman signals, even very weak compared to fluorescence intensity and noise level, can be clearly extracted, and the fluorescence background can be completely rejected. The Raman spectrum recovered by SERDS has good signal to noise ratio. It's proved that baseline correction is more suitable for large bench-top Raman system with better quality or signal-to-noise ratio, while the SERDS method is more suitable for noisy devices, especially the portable Raman spectrometers.

  9. [Atomic/ionic fluorescence in microwave plasma torch discharge with excitation of high current and microsecond pulsed hollow cathode lamp: Ca atomic/ionic fluorescence spectrometry].

    Science.gov (United States)

    Gong, Zhen-bin; Liang, Feng; Yang, Peng-yuan; Jin, Qin-han; Huang, Ben-li

    2002-02-01

    A system of atomic and ionic fluorescence spectrometry in microwave plasma torch (MPT) discharge excited by high current microsecond pulsed hollow cathode lamp (HCMP HCL) has been developed. The operation conditions for Ca atomic and ionic fluorescence spectrometry have been optimized. Compared with atomic fluorescence spectrometry (AFS) in argon microwave induced plasma (MIP) and MPT with the excitation of direct current and conventional pulsed HCL, the system with HCMP HCL excitation can improve AFS and ionic fluorescence spectrometry (IFS) detection limits in MPT atomizer and ionizer. Detection limits (3 sigma) with HCMP HCL-MPT-AFS/IFS are 10.1 ng.mL-1 for Ca I 422.7 nm, 14.6 ng.mL-1 for Ca II 393.4 nm, and 37.4 ng.mL-1 for Ca II 396.8 nm, respectively.

  10. Comment on ’Single Pentacene Molecules Detected by Fluorescence Excitation in a P-Terphenyl Crystal’

    Science.gov (United States)

    1990-12-10

    8217 NO 11 TITLE (include Security Classification) Comment on "Single Pentacene Molecules Detected by Fluorescence Excitation in a p-Terphenyl Crystal" 12...8217 {Continue on reverse it necessary and identify by block numboer) Using h--,Ihly efficient Fluorescence excitation spectroscov of individual pentacene ...molecular impurities in p-terphenvl crystals, we have observed that some pentacene defects exhibit spcntaneous spectral jumps in their resonance frequency at

  11. Characterization of dissolved organic matter in fogwater by excitation-emission matrix fluorescence spectroscopy

    Science.gov (United States)

    Birdwell, J.E.; Valsaraj, K.T.

    2010-01-01

    Dissolved organic matter (DOM) present in fogwater samples collected in southeastern Louisiana and central-eastern China has been characterized using excitation-emission matrix fluorescence spectroscopy. The goal of the study was to illustrate the utility of fluorescence for obtaining information on the large fraction of organic carbon in fogwaters (typically >40% by weight) that defies characterization in terms of specific chemical compounds without the difficulty inherent in obtaining sufficient fogwater volume to isolate DOM for assessment using other spectroscopic and chemical analyses. Based on the findings of previous studies using other characterization methods, it was anticipated that the unidentified organic carbon fraction would have characteristic peaks associated with humic substances and fluorescent amino acids. Both humic- and protein-like fluorophores were observed in the fogwater spectra and fluorescence-derived indices for the fogwater had similar values to those of soil and sediment porewater. Greater biological character was observed in samples with higher organic carbon concentrations. Fogwaters are shown to contain a mixture of terrestrially- and microbially-derived fluorescent organic material, which is expected to be derived from an array of different sources, such as suspended soil and dust particles, biogenic emissions and organic substances generated by atmospheric processes. The fluorescence results indicate that much of the unidentified organic carbon present in fogwater can be represented by humic-like and biologically-derived substances similar to those present in other aquatic systems, though it should be noted that fluorescent signatures representative of DOM produced by atmospheric processing of organic aerosols may be contributing to or masked by humic-like fluorophores. ?? 2010.

  12. Comparison of Cherenkov excited fluorescence and phosphorescence molecular sensing from tissue with external beam irradiation.

    Science.gov (United States)

    Lin, Huiyun; Zhang, Rongxiao; Gunn, Jason R; Esipova, Tatiana V; Vinogradov, Sergei; Gladstone, David J; Jarvis, Lesley A; Pogue, Brian W

    2016-05-21

    Ionizing radiation delivered by a medical linear accelerator (LINAC) generates Cherenkov emission within the treated tissue. A fraction of this light, in the 600-900 nm wavelength region, propagates through centimeters of tissue and can be used to excite optical probes in vivo, enabling molecular sensing of tissue analytes. The success of isolating the emission signal from this Cherenkov excitation background is dependent on key factors such as: (i) the Stokes shift of the probe spectra; (ii) the excited state lifetime; (iii) the probe concentration; (iv) the depth below the tissue surface; and (v) the radiation dose used. Previous studies have exclusively focused on imaging phosphorescent dyes, rather than fluorescent dyes. However there are only a few biologically important phosphorescent dyes and yet in comparison there are thousands of biologically relevant fluorescent dyes. So in this study the focus was a study of efficacy of Cherenkov-excited luminescence using fluorescent commercial near-infrared probes, IRDye 680RD, IRDye 700DX, and IRDye 800CW, and comparing them to the well characterized phosphorescent probe Oxyphor PtG4, an oxygen sensitive dye. Each probe was excited by Cherenkov light from a 6 MV external radiation beam, and measured in continuous wave or time-gated modes. The detection was performed by spectrally resolving the luminescence signals, and measuring them with spectrometer-based separation on an ICCD detector. The results demonstrate that IRDye 700DX and PtG4 allowed for the maximal signal to noise ratio. In the case of the phosphorescent probe, PtG4, with emission decays on the microsecond (μs) time scale, time-gated acquisition was possible, and it allowed for higher efficacy in terms of the probe concentration and detection depth. Phantoms containing the probe at 5 mm depth could be detected at concentrations down to the nanoMolar range, and at depths into the tissue simulating phantom near 3 cm. In vivo studies showed that 5

  13. Two photon processes in surface photovoltage spectroscopy

    International Nuclear Information System (INIS)

    Craig, R.P.; Thurgate, S.M.

    1996-01-01

    Full text: A significant mid-gap effect has been found in Surface Photovoltage Spectroscopy measurements of cleaved GaAs, InP and Si wafer which is normally interpreted as arising from transitions between surface states and band edges. This large mid-gap effect common to various materials is puzzling as such a high proportion of mid-gap states seems unlikely. Most theories of surface states predict states that tail from the band edges into the gap or states that have a well defined energy in the gap. None propose a large state exactly at E G /2. We recently investigated the variation in SPS spectra with flux density. We find a non-linear correlation in the magnitude of Band-Bending arising from mid-gap and band-gap photon energies. We suggest that the mid-gap feature is due to a two photon absorption process leading to carrier pair generation mediated by mid-gap states in the continuum of band-gap surface states

  14. Scanless functional imaging of hippocampal networks using patterned two-photon illumination through GRIN lenses

    KAUST Repository

    Moretti, Claudio

    2016-09-12

    Patterned illumination through the phase modulation of light is increasingly recognized as a powerful tool to investigate biological tissues in combination with two-photon excitation and light-sensitive molecules. However, to date two-photon patterned illumination has only been coupled to traditional microscope objectives, thus limiting the applicability of these methods to superficial biological structures. Here, we show that phase modulation can be used to efficiently project complex two-photon light patterns, including arrays of points and large shapes, in the focal plane of graded index (GRIN) lenses. Moreover, using this approach in combination with the genetically encoded calcium indicator GCaMP6, we validate our system performing scanless functional imaging in rodent hippocampal networks in vivo ~1.2 mm below the brain surface. Our results open the way to the application of patterned illumination approaches to deep regions of highly scattering biological tissues, such as the mammalian brain.

  15. Quantum-correlated two-photon transitions to excitons in semiconductor quantum wells.

    Science.gov (United States)

    Salazar, L J; Guzmán, D A; Rodríguez, F J; Quiroga, L

    2012-02-13

    The dependence of the excitonic two-photon absorption on the quantum correlations (entanglement) of exciting biphotons by a semiconductor quantum well is studied. We show that entangled photon absorption can display very unusual features depending on space-time-polarization biphoton parameters and absorber density of states for both bound exciton states as well as for unbound electron-hole pairs. We report on the connection between biphoton entanglement, as quantified by the Schmidt number, and absorption by a semiconductor quantum well. Comparison between frequency-anti-correlated, unentangled and frequency-correlated biphoton absorption is addressed. We found that exciton oscillator strengths are highly increased when photons arrive almost simultaneously in an entangled state. Two-photon-absorption becomes a highly sensitive probe of photon quantum correlations when narrow semiconductor quantum wells are used as two-photon absorbers.

  16. A vacuum-UV laser-induced fluorescence experiment for measurement of rotationally and vibrationally excited H2

    NARCIS (Netherlands)

    Vankan, P.J.W.; Heil, S.B.S.; Mazouffre, S.; Engeln, R.A.H.; Schram, D.C.; Döbele, H.F.

    2004-01-01

    An experimental setup is built to detect spatially resolved rovibrationally excited hydrogen molecules via laser-induced fluorescence. To excite the hydrogen molecules, laser radiation is produced in the vacuum UV part of the spectrum. The laser radiation is tunable between 120 nm and 230 nm and has

  17. Superior optical nonlinearity of an exceptional fluorescent stilbene dye

    Energy Technology Data Exchange (ETDEWEB)

    He, Tingchao [College of Physics Science and Technology, Shenzhen University, Shenzhen 518060 (China); Division of Physics and Applied Physics, Centre for Disruptive Photonic Technologies (CDPT), School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371 (Singapore); Sreejith, Sivaramapanicker; Zhao, Yanli [Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371 (Singapore); Gao, Yang; Grimsdale, Andrew C. [School of Materials Science and Engineering, Nanyang Technological University, Singapore, Singapore 639798 (Singapore); Lin, Xiaodong, E-mail: linxd@szu.edu.cn, E-mail: hdsun@ntu.edu.sg [College of Physics Science and Technology, Shenzhen University, Shenzhen 518060 (China); Sun, Handong, E-mail: linxd@szu.edu.cn, E-mail: hdsun@ntu.edu.sg [Division of Physics and Applied Physics, Centre for Disruptive Photonic Technologies (CDPT), School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371 (Singapore)

    2015-03-16

    Strong multiphoton absorption and harmonic generation in organic fluorescent chromophores are, respectively, significant in many fields of research. However, most of fluorescent chromophores fall short of the full potential due to the absence of the combination of such different nonlinear upconversion behaviors. Here, we demonstrate that an exceptional fluorescent stilbene dye could exhibit efficient two- and three-photon absorption under the excitation of femtosecond pulses in solution phase. Benefiting from its biocompatibility and strong excited state absorption behavior, in vitro two-photon bioimaging and superior optical limiting have been exploited, respectively. Simultaneously, the chromophore could generate efficient three-photon excited fluorescence and third-harmonic generation (THG) when dispersed into PMMA film, circumventing the limitations of classical fluorescent chromophores. Such chromophore may find application in the production of coherent light sources of higher photon energy. Moreover, the combination of three-photon excited fluorescence and THG can be used in tandem to provide complementary information in biomedical studies.

  18. High-resolution two-photon spectroscopy of a 5 p56 p ←5 p6 transition of xenon

    Science.gov (United States)

    Altiere, Emily; Miller, Eric R.; Hayamizu, Tomohiro; Jones, David J.; Madison, Kirk W.; Momose, Takamasa

    2018-01-01

    We report high-resolution Doppler-free two-photon excitation spectroscopy of Xe from the ground state to the 5 p5(P 3 /2 2 ) 6 p [3 /2 ] 2 2 electronic excited state. This is a first step to developing a comagnetometer using polarized 129Xe atoms for planned neutron electric dipole moment measurements at TRIUMF. Narrow linewidth radiation at 252.5 nm produced by a continuous wave laser was built up in an optical cavity to excite the two-photon transition, and the near-infrared emission from the 5 p56 p excited state to the 5 p56 s intermediate electronic state was used to detect the two-photon transition. Hyperfine constants and isotope shift parameters were evaluated and compared with previously reported values. In addition, the detected photon count rate was estimated from the observed intensities.

  19. Single excitation-emission fluorescence spectrum (EEF) for determination of cetane improver in diesel fuel.

    Science.gov (United States)

    Insausti, Matías; Fernández Band, Beatriz S

    2015-04-05

    A highly sensitive spectrofluorimetric method has been developed for the determination of 2-ethylhexyl nitrate in diesel fuel. Usually, this compound is used as an additive in order to improve cetane number. The analytical method consists in building the chemometric model as a first step. Then, it is possible to quantify the analyte with only recording a single excitation-emission fluorescence spectrum (EEF), whose data are introduced in the chemometric model above mentioned. Another important characteristic of this method is that the fuel sample was used without any pre-treatment for EEF. This work provides an interest improvement to fluorescence techniques using the rapid and easily applicable EEF approach to analyze such complex matrices. Exploding EEF was the key to a successful determination, obtaining a detection limit of 0.00434% (v/v) and a limit of quantification of 0.01446% (v/v). Copyright © 2015 Elsevier B.V. All rights reserved.

  20. Thin coating thickness determination using radioisotope-excited x-ray fluorescence spectrometry

    International Nuclear Information System (INIS)

    Del Castillo, Lorena A.; Calix, Virginia S.

    2001-01-01

    Three different approaches on thin coating thickness determination using a radioisotope-excited x-ray fluorescence spectrometry were demonstrated and results were compared. A standard of thin layer of gold (Au) on a nickel (Ni) substrate from the US National Bureau of Standards (with a nominal thickness of 0.300505 microns of at least 99.9% Au electrodeposited over 2 nils of Ni) on low carbon steel (1010) was analyzed using a Cd 109-excited XRF system. Au thickness computations were done using the (a) thin standard approach, (b) thick standard approach, and (c) x-ray absorption method (ASTM A754-79 1982). These three methods yielded results within the limit set by the American Society for Testing Materials (ASTM), which is +/-3%. Of the three methods, the thick standard yielded the best result with 0.124% error. (Author)

  1. Portable X-ray fluorescence analyzer of high sensitivity using X-ray tube excitation

    International Nuclear Information System (INIS)

    Vatai, E.; Ando, L.

    1982-01-01

    A review of the three main methods of X-ray fluorescence analysis and their problems is given. The attainable accuracy and effectiveness of each method are discussed. The main properties of portable X-ray analyzers required by the industry are described. The results and experiences of R and D activities in ATOMKI (Debrecen, Hungary) for developing portable X-ray analyzers are presented. The only way for increasing the accuracy and decreasing the measuring time is the application of X-ray tube excitation instead of radioactive sources. The new ATOMKI equipment presently under construction and patenting uses X-ray tube excitation; it will increase the accuracy of concentration determination by one order of magnitude. (D.Gy.)

  2. Laser-excited atomic-fluorescence spectrometry with electrothermal tube atomization.

    Science.gov (United States)

    Vera, J A; Leong, M B; Stevenson, C L; Petrucci, G; Winefordner, J D

    1989-12-01

    The performance of graphite-tube electrothermal atomizers is evaluated for laser-excited atomic-fluorescence spectrometry for several elements. Three pulsed laser systems are used to pump tunable dye lasers which subsequently are used to excite Pb, Ga, In, Fe, Ir, and Tl atoms in the hot graphite tube. The dye laser systems used are pumped by nitrogen, copper vapour and Nd:YAG lasers. Detection limits in the femtogram and subfemtogram range are typically obtained for all elements. A commercial graphite-tube furnace is important for the successful utilization of the laser-based method when the determination of trace elements is intended, especially when complicated matrices may be present.

  3. Fluorescence-based calculus detection using a 405-nm excitation wavelength

    Science.gov (United States)

    Brede, O.; Schelle, F.; Krueger, S.; Oehme, B.; Dehn, C.; Frentzen, M.; Braun, A.

    2011-03-01

    The aim of this study was to assess the difference of fluorescence signals of cement and calculus using a 405 nm excitation wavelength. A total number of 20 freshly extracted teeth was used. The light source used for this study was a blue LED with a wavelength of 405nm. For each tooth the spectra of calculus and cementum were measured separately. Fluorescence light was collimated into an optical fibre and spectrally analyzed using an echelle spectrometer (aryelle 200, Lasertechnik Berlin, Germany) with an additionally bandpass (fgb 67, Edmund Industrial Optics, Karlsruhe, Germany). From these 40 measurements the median values were calculated over the whole spectrum, leading to two different median spectra, one for calculus and one for cementum. For further statistical analysis we defined 8 areas of interest (AOI) in wavelength regions, showing remarkable differences in signal strength. In 7 AOIs the intensity of the calculus spectrum differed statistically significant from the intensity of the cementum spectrum (p calculus and cement between 600nm and 700nm. Thus, we can conclude that fluorescence of calculus shows a significant difference to the fluorescence of cement. A differentiation over the intensity is possible as well as over the spectrum. Using a wavelength of 405nm, it is possible to distinguish between calculus and cement. These results could be used for further devices to develop a method for feedback controlled calculus removal.

  4. Mapping the local organization of cell membranes using excitation-polarization-resolved confocal fluorescence microscopy.

    Science.gov (United States)

    Kress, Alla; Wang, Xiao; Ranchon, Hubert; Savatier, Julien; Rigneault, Hervé; Ferrand, Patrick; Brasselet, Sophie

    2013-07-02

    Fluorescence anisotropy and linear dichroism imaging have been widely used for imaging biomolecular orientational distributions in protein aggregates, fibrillar structures of cells, and cell membranes. However, these techniques do not give access to complete orientational order information in a whole image, because their use is limited to parts of the sample where the average orientation of molecules is known a priori. Fluorescence anisotropy is also highly sensitive to depolarization mechanisms such as those induced by fluorescence energy transfer. A fully excitation-polarization-resolved fluorescence microscopy imaging that relies on the use of a tunable incident polarization and a nonpolarized detection is able to circumvent these limitations. We have developed such a technique in confocal epifluorescence microscopy, giving access to new regions of study in the complex and heterogeneous molecular organization of cell membranes. Using this technique, we demonstrate morphological changes at the subdiffraction scale in labeled COS-7 cell membranes whose cytoskeleton is perturbed. Molecular orientational order is also seen to be affected by cholesterol depletion, reflecting the strong interplay between lipid-packing regions and their nearby cytoskeleton. This noninvasive optical technique can reveal local organization in cell membranes when used as a complement to existing methods such as generalized polarization. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  5. Laser-excited Fluorescence And Electron-spin Resonance Of Er3+ In Polycrystalline Alcl3

    OpenAIRE

    Ceotto G.; Pires M.A.; Sanjurjo J.A.; Rettori C.; Barberis G.E.

    1990-01-01

    The green fluorescence transitions among the levels corresponding to the 4S3/2 and 4I15/2 configurations of Er3+ diluted in AlCl3 have been measured using laser excitation. The data allow us to determine the crystalline-field splittings of these levels and, in turn, the spin-Hamiltonian parameters. The electron-paramagnetic-resonance spectrum observed at low temperatures is in good agreement with that expected from these parameters. © 1990 The American Physical Society.

  6. Fluorescence excitation-emission matrix spectroscopy for degradation monitoring of machinery lubricants

    Science.gov (United States)

    Sosnovski, Oleg; Suresh, Pooja; Dudelzak, Alexander E.; Green, Benjamin

    2018-02-01

    Lubrication oil is a vital component of heavy rotating machinery defining the machine's health, operational safety and effectiveness. Recently, the focus has been on developing sensors that provide real-time/online monitoring of oil condition/lubricity. Industrial practices and standards for assessing oil condition involve various analytical methods. Most these techniques are unsuitable for online applications. The paper presents the results of studying degradation of antioxidant additives in machinery lubricants using Fluorescence Excitation-Emission Matrix (EEM) Spectroscopy and Machine Learning techniques. EEM Spectroscopy is capable of rapid and even standoff sensing; it is potentially applicable to real-time online monitoring.

  7. Two-photon microscopy for non-invasive, quantitative monitoring of stem cell differentiation.

    Directory of Open Access Journals (Sweden)

    William L Rice

    Full Text Available BACKGROUND: The engineering of functional tissues is a complex multi-stage process, the success of which depends on the careful control of culture conditions and ultimately tissue maturation. To enable the efficient optimization of tissue development protocols, techniques suitable for monitoring the effects of added stimuli and induced tissue changes are needed. METHODOLOGY/PRINCIPAL FINDINGS: Here, we present the quantitative use of two-photon excited fluorescence (TPEF and second harmonic generation (SHG as a noninvasive means to monitor the differentiation of human mesenchymal stem cells (hMSCs using entirely endogenous sources of contrast. We demonstrate that the individual fluorescence contribution from the intrinsic cellular fluorophores NAD(PH, flavoproteins and lipofuscin can be extracted from TPEF images and monitored dynamically from the same cell population over time. Using the redox ratio, calculated from the contributions of NAD(PH and flavoproteins, we identify distinct patterns in the evolution of the metabolic activity of hMSCs maintained in either propagation, osteogenic or adipogenic differentiation media. The differentiation of these cells is mirrored by changes in cell morphology apparent in high resolution TPEF images and by the detection of collagen production via SHG imaging. Finally, we find dramatic increases in lipofuscin levels in hMSCs maintained at 20% oxygen vs. those in 5% oxygen, establishing the use of this chromophore as a potential biomarker for oxidative stress. CONCLUSIONS/SIGNIFICANCE: In this study we demonstrate that it is possible to monitor the metabolic activity, morphology, ECM production and oxidative stress of hMSCs in a non-invasive manner. This is accomplished using generally available multiphoton microscopy equipment and simple data analysis techniques, such that the method can widely adopted by laboratories with a diversity of comparable equipment. This method therefore represents a powerful tool

  8. Fluorescence detection of single molecules using pulsed near-field optical excitation and time correlated photon counting

    International Nuclear Information System (INIS)

    Ambrose, W.P.; Goodwin, P.M.; Martin, J.C.; Keller, R.A.

    1994-01-01

    Pulsed excitation, time correlated single photon counting and time gated detection are used in near-field optical microscopy to enhance fluorescence images and measure the fluorescence lifetimes of single molecules of Rhodamine 6G on silica surfaces. Time gated detection is used to reject prompt scattered background and to improve the image signal to noise ratio. The excited state lifetime of a single Rhodamine 6G molecule is found to depend on the position of the near-field probe. We attribute the lifetime variations to spontaneous emission rate alterations by the fluorescence reflected from and quenching by the aluminum coated probe

  9. Multi-color imaging of fluorescent nanodiamonds in living HeLa cells using direct electron-beam excitation.

    Science.gov (United States)

    Nawa, Yasunori; Inami, Wataru; Lin, Sheng; Kawata, Yoshimasa; Terakawa, Susumu; Fang, Chia-Yi; Chang, Huan-Cheng

    2014-03-17

    Multi-color, high spatial resolution imaging of fluorescent nanodiamonds (FNDs) in living HeLa cells has been performed with a direct electron-beam excitation-assisted fluorescence (D-EXA) microscope. In this technique, fluorescent materials are directly excited with a focused electron beam and the resulting cathodoluminescence (CL) is detected with nanoscale resolution. Green- and red-light-emitting FNDs were employed for two-color imaging, which were observed simultaneously in the cells with high spatial resolution. This technique could be applied generally for multi-color immunostaining to reveal various cell functions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Two-photon decay in heavy atoms and ions

    International Nuclear Information System (INIS)

    Mokler, P.H.; Dunford, R.W

    2003-08-01

    We review the status of and comment on current developments in the field of two-photon decay in atomic physics research. Recent work has focused on two-photon decays in highly-charged ions and two-photon decay of inner-shell vacancies in heavy neutral atoms. We emphasize the importance of measuring the shape of the continuum emission in two-photon decay as a probe of relativistic effects in the strong central fields found in heavy atomic systems. New experimental approaches and their consequences will be discussed. (orig.)

  11. Resonance production in two-photon interactions

    International Nuclear Information System (INIS)

    Roe, N.A.

    1989-02-01

    Resonance production in two-photon interactions is studied using data collected with the ASP detector at the PEP e + e/sup /minus// storage ring located at the Stanford Linear Accelerator Center. The ASP detector is a non-magnetic lead-glass calorimeter constructed from 632 lead-glass bars. It covers 94% of 4π in solid angle, extending to within 20/degree/ of the beamline. Lead-scintillator calorimeters extend the coverage to within 21 mr of the beamline on both sides. Energy resolution of √E/10%, where E is the energy is GeV, is achieved for electrons and photons in the lead-glass calorimeter, and particle trajectories are reconstructed with high efficiency. A total luminosity of 108 pb/sup /minus/1/ was collected with the ASP detector at a center-of-mass energy of 29 GeV. The observed process is e + e/sup /minus// → e + e/sup /minus//γ*γ* → e + e/sup /minus//X, is a pseudoscalar resonance (J/sup PC/ = 0/sup /minus/+/) and γ* is a virtual (mass /ne/ 0) photon. The outgoing electrons scatter down the beampipe and are not detected. The observed resonances are the /eta/ and /eta/' mesons, with masses of 549 and 958 MeV, respectively. They are detected in the γγ decay mode; a total of 2380 +- 49 /eta/ → γγ and 568 +- 26 /eta/' → γγ events are observed. From the number of events, the detection efficiency, and the calculated production cross sections the radiative widths, Γ/sub γγ/, of the /eta/ and /eta/' were measured and found to be: Γ/sub γγ/(/eta/) = .481 +- .010 +- .047keV and Γ/sub γγ/(/eta/') = 4.71 +- .22 +- .70keV. These results are in good agreement with the world average values. 67 refs., 42 figs., 20 tabs

  12. Resonance production in two-photon interactions

    Energy Technology Data Exchange (ETDEWEB)

    Roe, N.A.

    1989-02-01

    Resonance production in two-photon interactions is studied using data collected with the ASP detector at the PEP e/sup +/e/sup /minus// storage ring located at the Stanford Linear Accelerator Center. The ASP detector is a non-magnetic lead-glass calorimeter constructed from 632 lead-glass bars. It covers 94% of 4..pi.. in solid angle, extending to within 20/degree/ of the beamline. Lead-scintillator calorimeters extend the coverage to within 21 mr of the beamline on both sides. Energy resolution of ..sqrt..E/10%, where E is the energy is GeV, is achieved for electrons and photons in the lead-glass calorimeter, and particle trajectories are reconstructed with high efficiency. A total luminosity of 108 pb/sup /minus/1/ was collected with the ASP detector at a center-of-mass energy of 29 GeV. The observed process is e/sup +/e/sup /minus// ..-->.. e/sup +/e/sup /minus//..gamma..*..gamma..* ..-->.. e/sup +/e/sup /minus//X, is a pseudoscalar resonance (J/sup PC/ = 0/sup /minus/+/) and ..gamma..* is a virtual (mass /ne/ 0) photon. The outgoing electrons scatter down the beampipe and are not detected. The observed resonances are the /eta/ and /eta/' mesons, with masses of 549 and 958 MeV, respectively. They are detected in the ..gamma gamma.. decay mode; a total of 2380 +- 49 /eta/ ..-->.. ..gamma gamma.. and 568 +- 26 /eta/' ..-->.. ..gamma gamma.. events are observed. From the number of events, the detection efficiency, and the calculated production cross sections the radiative widths, GAMMA/sub ..gamma gamma../, of the /eta/ and /eta/' were measured and found to be: GAMMA/sub ..gamma gamma../(/eta/) = .481 +- .010 +- .047keV and GAMMA/sub ..gamma gamma../(/eta/') = 4.71 +- .22 +- .70keV. These results are in good agreement with the world average values. 67 refs., 42 figs., 20 tabs.

  13. A small molecular pH-dependent fluorescent probe for cancer cell imaging in living cell.

    Science.gov (United States)

    Ma, Junbao; Li, Wenqi; Li, Juanjuan; Shi, Rongguang; Yin, Gui; Wang, Ruiyong

    2018-05-15

    A novel pH-dependent two-photon fluorescent molecular probe ABMP has been prepared based on the fluorophore of 2, 4, 6-trisubstituted pyridine. The probe has an absorption wavelength at 354 nm and corresponding emission wavelength at 475 nm with the working pH range from 2.20 to 7.00, especially owning a good liner response from pH = 2.40 to pH = 4.00. ABMP also has excellent reversibility, photostability and selectivity which promotes its ability in analytical application. The probe can be excited with a two-photon fluorescence microscopy and the fluorescence cell imaging indicated that the probe can distinguish Hela cancer cells out of normal cells with a two-photon fluorescence microscopy which suggested its potential application in tumor cell detection. Copyright © 2018 Elsevier B.V. All rights reserved.

  14. Impact of laser excitation intensity on deep UV fluorescence detection in microchip electrophoresis.

    Science.gov (United States)

    Schulze, Philipp; Ludwig, Martin; Belder, Detlev

    2008-12-01

    A high intensity 266 nm continuous wave (cw-) laser developed for material processing was utilised as an excitation source for sensitive native fluorescence detection of unlabelled compounds in MCE. This 120 mW laser was attached via an optical fibre into a commercial epifluorescence microscope. With this MCE set-up we evaluated the impact of laser power on the S/N of aromatic compounds as well as of proteins. Compared with a previous work which used a 4 mW pulsed laser for excitation, improved S/N for small aromatics and to a lesser extent for proteins could be attained. The LOD of the system was determined down to 24 ng/mL for serotonin (113 nM), 24 ng/mL for propranolol (81 nM), 80 ng/mL for tryptophan (392 nM) and 80 ng/mL for an aromatic diol (475 nM). Sensitive protein detection was obtained at concentrations of 5 microg/mL for lysocyme, trypsinogen and chymotrypsinogen (340, 208 and 195 nM, respectively). Finally, a comparison of the cw- with a pulsed 266 nm laser, operating at the same average power, showed a higher attainable sensitivity of the cw-laser. This can be attributed to fluorescence saturation and photobleaching effects of the pulsed laser at high pulse energies.

  15. Polarized X-ray excitation for scatter reduction in X-ray fluorescence computed tomography.

    Science.gov (United States)

    Vernekohl, Don; Tzoumas, Stratis; Zhao, Wei; Xing, Lei

    2018-05-25

    X-ray fluorescence computer tomography (XFCT) is a new molecular imaging modality which uses X-ray excitation to stimulate the emission of fluorescent photons in high atomic number contrast agents. Scatter contamination is one of the main challenges in XFCT imaging which limits the molecular sensitivity. When polarized X-rays are used, it is possible to reduce the scatter contamination significantly by placing detectors perpendicular to the polarization direction. This study quantifies scatter contamination for polarized and unpolarized X-ray excitation and determines the advantages of scatter reduction. The amount of scatter in preclinical XFCT is quantified in Monte Carlo simulations. The fluorescent X-rays are emitted isotropically, while scattered X-rays propagate in polarization direction. The magnitude of scatter contamination is studied in XFCT simulations of a mouse phantom. In this study, the contrast agent gold is examined as an example but a scatter reduction from polarized excitation is also expected for other elements. The scatter reduction capability is examined for different polarization intensities with a monoenergetic X-ray excitation energy of 82 keV. The study evaluates two different geometrical shapes of CZT detectors which are modeled with an energy resolution of 1 keV FWHM at an X-ray energy of 80 keV. Benefits of a detector placement perpendicular to the polarization direction are shown in iterative and analytic image reconstruction including scatter correction. The contrast to noise ratio (CNR) and the normalized mean square error (NMSE) are analyzed and compared for the reconstructed images. A substantial scatter reduction for common detector sizes was achieved for 100% and 80% linear polarization while lower polarization intensities provide a decreased scatter reduction. By placing the detector perpendicular to the polarization direction, a scatter reduction by factor up to 5.5 can be achieved for common detector sizes. The image

  16. Compact 3D printed module for fluorescence and label-free imaging using evanescent excitation

    Science.gov (United States)

    Pandey, Vikas; Gupta, Shalini; Elangovan, Ravikrishnan

    2018-01-01

    Total internal reflection fluorescence (TIRF) microscopy is widely used for selective excitation and high-resolution imaging of fluorophores, and more recently label-free nanosized objects, with high vertical confinement near a liquid-solid interface. Traditionally, high numerical aperture objectives (>1.4) are used to simultaneously generate evanescent waves and collect fluorescence emission signals which limits their use to small area imaging (filters to prevent specular reflection within the objective lenses. We have developed a compact 3D module called cTIRF that can generate evanescent waves in microscope glass slides via a planar waveguide illumination. The module can be attached as a fixture to any existing optical microscope, converting it into a TIRF and enabling high signal-to-noise ratio (SNR) fluorescence imaging using any magnification objective. As the incidence optics is perpendicular to the detector, label-free evanescent scattering-based imaging of submicron objects can also be performed without using emission filters. SNR is significantly enhanced in this case as compared to cTIRF alone, as seen through our model experiments performed on latex beads and mammalian cells. Extreme flexibility and the low cost of our approach makes it scalable for limited resource settings.

  17. An excited-state intramolecular photon transfer fluorescence probe for localizable live cell imaging of cysteine

    Science.gov (United States)

    Liu, Wei; Chen, Wen; Liu, Si-Jia; Jiang, Jian-Hui

    2017-03-01

    Small molecule probes suitable for selective and specific fluorescence imaging of some important but low-concentration intracellular reactive sulfur species such as cysteine (Cys) pose a challenge in chemical biology. We present a readily available, fast-response fluorescence probe CHCQ-Ac, with 2-(5‧-chloro-2-hydroxyl-phenyl)-6-chloro-4(3 H)-quinazolinone (CHCQ) as the fluorophore and acrylate group as the functional moiety, that enables high-selectivity and high-sensitivity for detecting Cys in both solution and biological system. After specifically reacted with Cys, the probe undergoes a seven-membered intramolecular cyclization and released the fluorophore CHCQ with excited-state intramolecular photon transfer effect. A highly fluorescent, insoluble aggregate was then formed to facilitate high-sensitivity and high-resolution imaging. The results showed that probe CHCQ-Ac affords a remarkably large Stokes shift and can detect Cys under physiological pH condition with no interference from other analytes. Moreover, this probe was proved to have excellent chemical stability, low cytotoxicity and good cell permeability. Our design of this probe provides a novel potential tool to visualize and localize cysteine in bioimaging of live cells that would greatly help to explore various Cys-related physiological and pathological cellular processes in cell biology and diagnostics.

  18. Application of radionuclide sources for excitation in energy-dispersive X-ray fluorescence analysis

    International Nuclear Information System (INIS)

    Hoffmann, P.

    1986-01-01

    X-ray fluorescence (XRF) analysis is in broad application in many fields of science where elemental determinations are necessary. Solid and liquid samples are analyzed by this method. Solids are introduced in thin or thick samples as melted glass, pellets, powders or as original specimen. The excitation of X-ray spectra can be performed by specific and polychromic radiation of X-ray tubes, by protons, deuterons, α-particles, heavy ions and synchrotron radiation from accelerators and by α-particles, X- and γ-rays and by bremsstrahlung generated by β - -particles from radionuclide sources. The radionuclides are devided into groups with respect to their decay mode and the energy of the emitted radiation. The broad application of radionuclides in XRF excitation is shown in examples as semi-quantitative analysis of glasses, as quantitative analysis of coarse ceramics and as quantitative determination of heavy elements (mainly actinides) in solutions. The advantages and disadvantages of radionuclide excitation in XRF analysis are discussed. (orig.) [de

  19. Two-photon stimulated emission and pulse amplification

    International Nuclear Information System (INIS)

    Yuen, H.P.

    1975-01-01

    Threshold conditions are given for the sustained operation of standing-wave and long-pulse traveling-wave two-photon lasers. Pulse shortening in long-pulse two-photon amplification, a behavior absent in the one-photon case, is also demonstrated analytically. (U.S.)

  20. Quantum efficiency and two-photon absorption cross-section of conjugated polyelectrolytes used for protein conformation measurements with applications on amyloid structures

    Energy Technology Data Exchange (ETDEWEB)

    Stabo-Eeg, Frantz [Norwegian University of Science and Technology, N-7491 Trondheim (Norway)], E-mail: Frantz.Stabo-Eeg@phys.ntnu.no; Lindgren, Mikael [Norwegian University of Science and Technology, N-7491 Trondheim (Norway); Nilsson, K. Peter R.; Inganaes, Olle; Hammarstroem, Per [IFM Department of Physics, Chemistry and Biology Linkoeping University, S-581 83 Linkoeping (Sweden)

    2007-07-27

    Amyloid diseases such as Alzheimer's and spongiform encephalopathies evolve from aggregation of proteins due to misfolding of the protein structure. Early disease handling require sophisticated but yet simple techniques to follow the complex properties of the aggregation process. Conjugated polyelectrolytes (CPEs) have shown promising capabilities acting as optical biological sensors, since they can specifically bind to polypeptides both in solution and in solid phase. The structural changes in biomolecules can be monitored by changes of the optical spectra of the CPEs, both in absorption and emission modes. Notably, the studied CPEs possess multi-photon excitation capability, making them potential for in vivo imaging using laser scanning microscopy. Aggregation of proteins depends on concentration, temperature and pH. The optical effect on the molecular probe in various environments must also be investigated if applied in these environments. Here we present the results of quantum efficiency and two-photon absorption cross-section of three CPEs: POMT, POWT and PTAA in three different pH buffer systems. The extinction coefficient and quantum efficiency were measured. POMT was found to have the highest quantum efficiency being approximately 0.10 at pH 2.0. The two-photon absorption cross-section was measured for POMT and POWT and was found to be more than 18-25 times and 7-11 times that of Fluorescein, respectively. We also show how POMT fluorescence can be used to distinguish conformational differences between amyloid fibrils formed from reduced and non-reduced insulin in spectrally resolved images recorded with a laser scanning microscope using both one- and two-photon excitation.

  1. Dynamical modeling of pulsed two-photon interference

    International Nuclear Information System (INIS)

    Fischer, Kevin A; Lagoudakis, Konstantinos G; Vučković, Jelena; Müller, Kai

    2016-01-01

    Single-photon sources are at the heart of quantum-optical networks, with their uniquely quantum emission and phenomenon of two-photon interference allowing for the generation and transfer of nonclassical states. Although a few analytical methods have been briefly investigated for describing pulsed single-photon sources, these methods apply only to either perfectly ideal or at least extremely idealized sources. Here, we present the first complete picture of pulsed single-photon sources by elaborating how to numerically and fully characterize non-ideal single-photon sources operating in a pulsed regime. In order to achieve this result, we make the connection between quantum Monte-Carlo simulations, experimental characterizations, and an extended form of the quantum regression theorem. We elaborate on how an ideal pulsed single-photon source is connected to its photocount distribution and its measured degree of second- and first-order optical coherence. By doing so, we provide a description of the relationship between instantaneous source correlations and the typical experimental interferometers (Hanbury-Brown and Twiss, Hong–Ou–Mandel, and Mach–Zehnder) used to characterize such sources. Then, we use these techniques to explore several prototypical quantum systems and their non-ideal behaviors. As an example numerical result, we show that for the most popular single-photon source—a resonantly excited two-level system—its error probability is directly related to its excitation pulse length. We believe that the intuition gained from these representative systems and characters can be used to interpret future results with more complicated source Hamiltonians and behaviors. Finally, we have thoroughly documented our simulation methods with contributions to the Quantum Optics Toolbox in Python in order to make our work easily accessible to other scientists and engineers. (paper)

  2. Mid-infrared two-photon absorption in an extended-wavelength InGaAs photodetector

    Science.gov (United States)

    Piccardo, Marco; Rubin, Noah A.; Meadowcroft, Lauren; Chevalier, Paul; Yuan, Henry; Kimchi, Joseph; Capasso, Federico

    2018-01-01

    We investigate the nonlinear optical response of a commercial extended-wavelength In0.81Ga0.19As uncooled photodetector. Degenerate two-photon absorption in the mid-infrared range is observed using a quantum cascade laser emitting at λ = 4.5 μm as the excitation source. From the measured two-photon photocurrent signal, we extract a two-photon absorption coefficient β(2) = 0.6 ± 0.2 cm/MW, in agreement with the theoretical value obtained from the Eg-3 scaling law. Considering the wide spectral range covered by extended-wavelength InxGa1-xAs alloys, this result holds promise for applications based on two-photon absorption for this family of materials at wavelengths between 1.8 and 5.6 μm.

  3. Visible to near-IR fluorescence from single-digit detonation nanodiamonds: excitation wavelength and pH dependence.

    Science.gov (United States)

    Reineck, Philipp; Lau, Desmond W M; Wilson, Emma R; Nunn, Nicholas; Shenderova, Olga A; Gibson, Brant C

    2018-02-06

    Detonation nanodiamonds are of vital significance to many areas of science and technology. However, their fluorescence properties have rarely been explored for applications and remain poorly understood. We demonstrate significant fluorescence from the visible to near-infrared spectral regions from deaggregated, single-digit detonation nanodiamonds dispersed in water produced via post-synthesis oxidation. The excitation wavelength dependence of this fluorescence is analyzed in the spectral region from 400 nm to 700 nm as well as the particles' absorption characteristics. We report a strong pH dependence of the fluorescence and compare our results to the pH dependent fluorescence of aromatic hydrocarbons. Our results significantly contribute to the current understanding of the fluorescence of carbon-based nanomaterials in general and detonation nanodiamonds in particular.

  4. Study on discrimination of oral cancer from normal using blood plasma based on fluorescence steady and excited state at excitation wavelength 280 nm

    Science.gov (United States)

    Rekha, Pachaiappan; Aruna, Prakasa Rao; Ganesan, Singaravelu

    2016-03-01

    Many research works based on fluorescence spectroscopy have proven its potential in the diagnosis of various diseases using the spectral signatures of the native key fluorophores such as tryptophan, tyrosine, collagen, NADH, FAD and porphyrin. These fluorophores distribution, concentration and their conformation may be changed depending upon the pathological and metabolic conditions of cells and tissues. In this study, we have made an attempt to characterize the blood plasma of normal subject and oral cancer patients by native fluorescence spectroscopy at 280 nm excitation. Further, the fluorescence data were analyzed by employing the multivariate statistical method - linear discriminant analyses (LDA) using leaves one out cross validation method. The results illustrate the potential of fluorescence spectroscopy technique in the diagnosis of oral cancer using blood plasma.

  5. Determination of rare-earth elements in rocks by isotope-excited X-ray fluorescence spectrometry

    DEFF Research Database (Denmark)

    Kunzendorf, Helmar; Wollenberg, H.A.

    1970-01-01

    Isotope-excited X-ray fluorescence spectrometry furnishes a rapid determination of rare-earth elements in unprepared rock samples. The samples are excited by 241Am γ-rays, generating X-ray spectra on a multichannel pulse-height analyser. Gaussian peaks of the Kα and Kβ X-ray energies are treated ......-ray spectrometric scan of a longitudinally sliced drill core showed a close correlation between rare-earth abundances and appropriate minerals.......Isotope-excited X-ray fluorescence spectrometry furnishes a rapid determination of rare-earth elements in unprepared rock samples. The samples are excited by 241Am γ-rays, generating X-ray spectra on a multichannel pulse-height analyser. Gaussian peaks of the Kα and Kβ X-ray energies are treated...

  6. Study on germ toxicity of exciting energy resource 147Pm of fluorescent paint

    International Nuclear Information System (INIS)

    Zhu Shoupeng; Lun Minyue; Tao Feng

    1993-02-01

    The germ toxicity of exciting energy resource 147 Pm of fluorescent paint was studied. It was shown that the placenta was a barrier for 147 Pm entering into the fetus. The retention T 1/2 was 105 days in testes. The retention value of 147 Pm in testis was high and hardly to excrete. The results showed that 147 Pm can induce abnormal sperms, most of them were non-hock sperms. The chromosome aberrations in germ cells also can be induced. Among the type of chromosome aberrations of spermatogonia, chromatid breakage was predominant. The 147 Pm can cause the chromosome fragment and translocations of primary spermatocytes, and increasing of lethality. The dominant skeletal aberrations in offspring is proportional to the accumulated radioactivity of 147 Pm in tests

  7. Selective two-photon collagen crosslinking in situ measured by Brillouin microscopy (Conference Presentation)

    Science.gov (United States)

    Kwok, Sheldon J. J.; Kuznetsov, Ivan A.; Kim, Moonseok; Choi, Myunghwan; Scarcelli, Giuliano; Yun, Seok-Hyun

    2017-02-01

    Two-photon polymerization and crosslinking are commonly used methods for microfabrication of three-dimensional structures with applications spanning from photonic microdevices, drug delivery systems, to cellular scaffolds. However, the use of two-photon processes for precise, internal modification of biological tissues has not yet been reported. One of the major challenges has been a lack of appropriate tools to monitor and characterize crosslinked regions nondestructively. Here, we demonstrate spatially selective two-photon collagen crosslinking (2P-CXL) in intact tissue for the first time. Using riboflavin photosensitizer and femtosecond laser irradiation, we crosslinked a small volume of tissue within animal corneas. Collagen fiber orientations and photobleaching were characterized by second harmonic generation and two-photon fluorescence imaging, respectively. Using confocal Brillouin microscopy, we measured local changes in longitudinal mechanical moduli and visualized the cross-linked pattern without perturbing surrounding non-irradiated regions. 2P-CXL-induced tissue stiffening was comparable to that achieved with conventional one-photon CXL. Our results demonstrate the ability to selectively stiffen biological tissue in situ at high spatial resolution, with broad implications in ophthalmology, laser surgery, and tissue engineering.

  8. Two-photon processes in highly charged ions

    International Nuclear Information System (INIS)

    Jahrsetz, Thorsten

    2015-01-01

    Two-photon processes are atomic processes in which an atom interacts simultaneously with two photons. Such processes describe a wide range of phenomena, such as two-photon decay and elastic or inelastic scattering of photons. In recent years two-photon processes involving highly charged heavy ions have become an active area of research. Such studies do not only consider the total transition or scattering rates but also their angular and polarization dependence. To support such examinations in this thesis I present a theoretical framework to describe these properties in all two-photon processes with bound initial and final states and involving heavy H-like or He-like ions. I demonstrate how this framework can be used in some detailed studies of different two-photon processes. Specifically a detailed analysis of two-photon decay of H-like and He-like ions in strong external electromagnetic fields shows the importance of considering the effect of such fields for the physics of such systems. Furthermore I studied the elastic Rayleigh as well as inelastic Raman scattering by heavy H-like ions. I found a number of previously unobserved phenomena in the angular and polarization dependence of the scattering cross-sections that do not only allow to study interesting details of the electronic structure of the ion but might also be useful for the measurement of weak physical effects in such systems.

  9. Two-photon processes in highly charged ions

    Energy Technology Data Exchange (ETDEWEB)

    Jahrsetz, Thorsten

    2015-03-05

    Two-photon processes are atomic processes in which an atom interacts simultaneously with two photons. Such processes describe a wide range of phenomena, such as two-photon decay and elastic or inelastic scattering of photons. In recent years two-photon processes involving highly charged heavy ions have become an active area of research. Such studies do not only consider the total transition or scattering rates but also their angular and polarization dependence. To support such examinations in this thesis I present a theoretical framework to describe these properties in all two-photon processes with bound initial and final states and involving heavy H-like or He-like ions. I demonstrate how this framework can be used in some detailed studies of different two-photon processes. Specifically a detailed analysis of two-photon decay of H-like and He-like ions in strong external electromagnetic fields shows the importance of considering the effect of such fields for the physics of such systems. Furthermore I studied the elastic Rayleigh as well as inelastic Raman scattering by heavy H-like ions. I found a number of previously unobserved phenomena in the angular and polarization dependence of the scattering cross-sections that do not only allow to study interesting details of the electronic structure of the ion but might also be useful for the measurement of weak physical effects in such systems.

  10. Determination of rare-earth elements in rocks by isotope-excited X-ray fluorescence spectrometry

    DEFF Research Database (Denmark)

    Kunzendorf, Helmar; Wollenberg, H.A.

    1970-01-01

    Isotope-excited X-ray fluorescence spectrometry furnishes a rapid determination of rare-earth elements in unprepared rock samples. The samples are excited by 241Am γ-rays, generating X-ray spectra on a multichannel pulse-height analyser. Gaussian peaks of the Kα and Kβ X-ray energies are treated......-ray spectrometric scan of a longitudinally sliced drill core showed a close correlation between rare-earth abundances and appropriate minerals....

  11. 8 nm nanodiamonds as markers for 2 photon excited luminescent microscopy

    International Nuclear Information System (INIS)

    Kharin, A; Rogov, A; Bonacina, L; Geloen, A; Lysenko, V

    2016-01-01

    Structural and luminescent properties of stable suspensions of fluorescent nanodiamonds were investigated. Measurement of the effective hydrodynamic radius yields particles less than 30 nm diameter, while the TEM measurements made on the same particles shows average diameter about 8 nm. It was found that NDs have relatively low toxicity. Upon incubation, 3T3-L1 cells spontaneously take up nanodiamonds that uniformly distribute in cells cytoplasm. The possibility of fluorescent imaging using both single ore two-photon excitation was shown. (paper)

  12. The general expression for the transition amplitude of two-photon ionization of atomic hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Karule, E [Institute of Atomic Physics and Spectroscopy, University of Latvia, Raina Boulevard 19, Riga, LV-1586 (Latvia); Moine, B [Universite Paris Sud, 91405 Orsay Cedex (France)

    2003-05-28

    Two-photon ionization of atomic hydrogen with an excess photon is revisited. The non-relativistic dipole approximation and Coulomb Green function (CGF) formalism are applied. Using the CGF Sturmian expansion straightforwardly, one gets the radial transition amplitude in the form of an infinite sum over Gauss hypergeometric functions which are polynomials. It is convergent if all intermediate states are in the discrete spectrum. In the case of two-photon ionization with an excess photon, when photoionization is also possible, intermediate states are in the continuum. We performed the explicit summation over intermediate states and got a simple general expression for the radial transition amplitude in the form of a finite sum over Appell hypergeometric functions, which are not polynomials. An Appell function may be expressed as an infinite sum over Gauss functions. In the case of ionization by an excess photon, Gauss functions are transformed to give a convergent radial transition amplitude for the whole region. The generalized cross sections for two-photon above-threshold ionization of atomic hydrogen in the ground state and excited states calculated by us agree very well with results of previous calculations. Generalized cross sections for two-photon ionization of positronium in the ground state are obtained by scaling those for atomic hydrogen.

  13. Picosecond phase conjugation in two-photon absorption in poly-di-acetylenes

    International Nuclear Information System (INIS)

    Nunzi, Dominique Jean-Michel

    1990-01-01

    Poly-di-acetylenes exhibit a large two-photon absorption at 1064 nm wavelength. Its different effects on phase-conjugate nonlinearity are described in the framework of picosecond experiments. In solutions, gels, and films (optically thin media), third-order susceptibility appears as an increasing intensity dependent function. Phase measurements by nonlinear interferometry with the substrate or with the solvent are compared with predictions of a resonantly driven three level system. Phase-conjugate response exhibits a multi-exponential decay. Polarization symmetries analysis shows a one-dimensional effect. Study under strong static electric field action reveals that we face charged species bound to photoconductive polymer chains. In PTS single crystals (optically thick media), response saturates and cancels at high light intensity. This is well accounted for by propagation equations solved in large two-photon absorption conditions. The effect is exploited in a phase conjugation experiment under external optical pump excitation. We thus demonstrate that enhanced nonlinearity is a two-photon absorption relayed and amplified by mid-gap absorbing species which have been created by this two-photon absorption. We formally face a four-photon absorption described by a positive imaginary seventh-order non-linearity. (author) [fr

  14. Investigation of the vacuum ultraviolet fluorescence of gaseous xenon under optical excitation in an extended wavelength region

    International Nuclear Information System (INIS)

    Brodmann, R.; Zimmerer, G.; Hamburg Univ.; Hahn, U.

    1976-02-01

    The fluorescence of Xe at a pressure of 10 Torr has been excited by monochromatic light in the wavelength region from 1,040 A to 1,500 A. Besides the well known first and second continuum additional emission bands appear at 1,192 A and 1,300 A. They are ascribed to an atomic transition 5d(3/2) 1 → 1 S 0 and a molecular transition O + sub(u)(6s'(1/2) + 1 S 0 ) → O + sub(g)( 1 S 0 + 1 S 0 ). The excitation spectra of the first and second continuum yield high fluorescence efficiency if higher Rydberg states are excited. Excitation of the first resonance line of Xe results in a low fluorescence intensity. Obviously the formation of highly excited molecules Xe** and intramolecular relaxation play an important role for the population of the vibrationally relaxed excited states (O + sub(u), 1sub(u)) of the Xe* 2 molecule. (orig.) [de

  15. CERN: A tale of two photons

    International Nuclear Information System (INIS)

    Anon.

    1993-01-01

    When precision data from the several million Zs carefully collected over several years by the four big experiments - Aleph, Delphi, L3 and Opal - at CERN's LEP electron-positron collider have otherwise consistently underlined conventional physics, a hint of something unexplained quickly packs the seminar rooms. In 1991, the L3 experiment turned up two examples of Z decays producing a muon pair accompanied by a widely separated pair of high energy photons, with the photon pair in each case taking some 60 GeV of energy (actually 58.8 and 59.0 GeV). Nothing to get excited about at the time, but ongoing data analysis tuned into this channel. This year two more events turned up, one again with a muon pair accompanied by a 60 GeV photon pair, the other with an electron (electron-positron) pair and a 62 GeV photon pair. At first L3 preferred to keep this quiet, and the news was not announced at the major international meeting in Dallas last August. The first public announcement of the four unexplained events (out of a total of 1.6 million Z decays) came in a LEP Experiments Committee session at CERN in October

  16. Exciton molecule in semiconductors by two-photon absorption

    International Nuclear Information System (INIS)

    Arya, K.; Hassan, A.R.

    1976-07-01

    Direct creation of bi-exciton states by two-photon absorption in direct gap semiconductors is investigated theoretically. A numerical application to the case of CuCl shows that the two-photon absorption coefficient for bi-excitonic transitions is larger than that for two-photon interband transitions by three orders of magnitude. It becomes comparable to that for one-photon excitonic transitions for available laser intensities. The main contribution to this enhancement of the absorption coefficient for the transitions to the bi-exciton states is found to be from the resonance effect

  17. Effect of Solvation on Electron Detachment and Excitation Energies of a Green Fluorescent Protein Chromophore Variant.

    Science.gov (United States)

    Bose, Samik; Chakrabarty, Suman; Ghosh, Debashree

    2016-05-19

    Hybrid quantum mechanics/molecular mechanics (QM/MM) is applied to the fluorinated green fluorescent protein (GFP) chromophore (DFHBDI) in its deprotonated form to understand the solvatochromic shifts in its vertical detachment energy (VDE) and vertical excitation energy (VEE). This variant of the GFP chromophore becomes fluorescent in an RNA environment and has a wide range of applications in biomedical and biochemical fields. From microsolvation studies, we benchmark (with respect to full QM) the accuracy of our QM/MM calculations with effective fragment potential (EFP) as the MM method of choice. We show that while the solvatochromic shift in the VEE is minimal (0.1 eV blue shift) and its polarization component is only 0.03 eV, the effect of the solvent on the VDE is quite large (3.85 eV). We also show by accurate calculations on the solvatochromic shift of the VDE that polarization accounts for ∼0.23 eV and therefore cannot be neglected. The effect of the counterions on the VDE of the deprotonated chromophore in solvation is studied in detail, and a charge-smearing scheme is suggested for charged chromophores.

  18. Electrothermal atomization laser-excited atomic fluorescence spectroscopy for the determination of indium

    International Nuclear Information System (INIS)

    Aucelio, R.Q.; Smith, B.W.; Winefordner, J.D.

    1998-01-01

    A dye laser pumped by a high-repetition-rate copper vapor laser was used as the excitation source to determine indium at parts-per-trillion level by electrothermal atomization laser-excited atomic fluorescence spectrometry (ETA-LEAFS). A comparison was made between wall atomization, in pyrolytic and nonpyrolytic graphite tubes, and platform atomization. The influence of several chemical modifiers either in solution or precoated in the graphite tube was evaluated. The influence of several acids and NaOH in the analyte solution was also studied. Optimization of the analytical conditions was carried out to achieve the best signal-to-background ratio and consequently an absolute limit of detection of 1 fg. Some possible interferents of the method were evaluated. The method was evaluated by determining indium in blood, urine, soil, and urban dust samples. Recoveries between 99.17 and 109.17% are reported. A precision of 4.1% at the 10 ng g -1 level in water standards was achieved. copyright 1998 Society for Applied Spectroscopy

  19. X-ray fluorescence in some medium-Z elements excited by 59.5 keV photons

    International Nuclear Information System (INIS)

    Han, I.; Shahin, M.; Demir, L.; Narmanli, E.

    2010-01-01

    K X-ray fluorescence parameters cross sections and average shell fluorescence yields) for selected ten elements in the atomic range 42 ≤ Z ≤ 66 have been experimentally determined at photon excitation energy of 59.5 keV. K X-rays emitted from the samples have been counted by a Si (Li) detector. The K spectra for investigated elements have been derived from the measured K shell X-ray spectra by peak fitting process. Experimental results of K X-ray fluorescence parameters have been compared with theory. In general there is an agreement within the standard uncertainties of the experimental and theoretical values

  20. Two-photon mapping of localized field enhancements in thin nanostrip antennas

    DEFF Research Database (Denmark)

    Beermann, I.; Novikov, S.M.; Søndergaard, Thomas

    2008-01-01

    scanning optical microscopy, in which two-photon-excited photoluminescence (TPL) excited with a strongly focused laser beam at the wavelength 745 nm is detected. We use TPL images to map the local field enhancements from individual nanostrips at a resolution of 0.35µm and compare results with theoretical......Resonant scattering and local field enhancements by 11-nm-thin gold nanostrip antennas due to constructive interference of counter propagating slow surface plasmon polaritons is investigated. We characterize nanostrips of widths between 50-530 nm using both reflection spectroscopy and nonlinear...

  1. Standard Model Higgs decay for two Photons in CMS

    CERN Multimedia

    Daniel Denegri

    2000-01-01

    Simulated two-photon mass distribution for SM Higgs and expected background in the CMS PbW04 crystal calorimeter for an integrated luminosity of 10 . 5 pb-1, with detailed simulation of calorimeter response.

  2. All-optical femtosecond switch using two-photon absorption

    International Nuclear Information System (INIS)

    Yavuz, D. D.

    2006-01-01

    Utilizing a two-photon absorption scheme in an alkali-metal vapor cell, we suggest a technique where a strong laser beam switches off another laser beam of different wavelength in femtosecond time scales

  3. Mass distribution for the two-photon channel

    CERN Multimedia

    ATLAS, collaboration

    2012-01-01

    Mass distribution for the two-photon channel. The strongest evidence for this new particle comes from analysis of events containing two photons. The smooth dotted line traces the measured background from known processes. The solid line traces a statistical fit to the signal plus background. The new particle appears as the excess around 126.5 GeV. The full analysis concludes that the probability of such a peak is three chances in a million.

  4. Two-photon quantum interference in a Michelson interferometer

    International Nuclear Information System (INIS)

    Odate, Satoru; Wang Haibo; Kobayashi, Takayoshi

    2005-01-01

    We have observed two-photon quantum interference in a Michelson interferometer. For the first time, we experimentally demonstrated two-photon quantum interference patterns, which show the transition from nonsubwavelength interference fringes to the general subwavelength interference. At the same time, a photon bunching effect was also shown by a postselection. The |1, 1> state with a single photon in a mode corresponding to each arm of the interferometer was exclusively postselected by using path difference between two arms

  5. Coherence revivals in two-photon frequency combs

    International Nuclear Information System (INIS)

    Torres-Company, Victor; Lancis, Jesus; Lajunen, Hanna; Friberg, Ari T.

    2011-01-01

    We describe and theoretically analyze the self-imaging Talbot effect of entangled photon pairs in the time domain. Rich phenomena are observed in coherence propagation along dispersive media of mode-locked two-photon states with frequency entanglement exhibiting a comblike correlation function. Our results can be used to remotely transfer frequency standards through optical fiber networks with two-photon light, avoiding the requirement of dispersion compensation.

  6. Silver content determination in mining and ore dressing using radionuclide-excited X-ray fluorescence analysis

    International Nuclear Information System (INIS)

    Koerner, B.; George, R.; Ratnikow, W.

    1989-01-01

    A laborsaving method based on radionuclide-excited X-ray fluorescence is described for the determination of silver in mining and ore dressing. Detection limits reached under operation conditions and measuring errors are discussed and compared with results from chemical analyses

  7. Environment-sensitive quinolone demonstrating long-lived fluorescence and unusually slow excited-state intramolecular proton transfer kinetics

    Czech Academy of Sciences Publication Activity Database

    Zamotaiev, O. M.; Shvadchak, Volodymyr; Sych, T. P.; Melnychuk, N. A.; Yushchenko, Dmytro A.; Mely, Y.; Pivovarenko, V. G.

    2016-01-01

    Roč. 4, č. 3 (2016), č. článku 034004. ISSN 2050-6120 Institutional support: RVO:61388963 Keywords : quinolone * fluorescent probes * local polarity * hydration * excited-state intramolecular proton transfer * kinetics Subject RIV: CC - Organic Chemistry Impact factor: 2.656, year: 2016

  8. Volumetric Two-photon Imaging of Neurons Using Stereoscopy (vTwINS)

    Science.gov (United States)

    Song, Alexander; Charles, Adam S.; Koay, Sue Ann; Gauthier, Jeff L.; Thiberge, Stephan Y.; Pillow, Jonathan W.; Tank, David W.

    2017-01-01

    Two-photon laser scanning microscopy of calcium dynamics using fluorescent indicators is a widely used imaging method for large scale recording of neural activity in vivo. Here we introduce volumetric Two-photon Imaging of Neurons using Stereoscopy (vTwINS), a volumetric calcium imaging method that employs an elongated, V-shaped point spread function to image a 3D brain volume. Single neurons project to spatially displaced “image pairs” in the resulting 2D image, and the separation distance between images is proportional to depth in the volume. To demix the fluorescence time series of individual neurons, we introduce a novel orthogonal matching pursuit algorithm that also infers source locations within the 3D volume. We illustrate vTwINS by imaging neural population activity in mouse primary visual cortex and hippocampus. Our results demonstrate that vTwINS provides an effective method for volumetric two-photon calcium imaging that increases the number of neurons recorded while maintaining a high frame-rate. PMID:28319111

  9. Phonon-Assisted Two-Photon Interference from Remote Quantum Emitters.

    Science.gov (United States)

    Reindl, Marcus; Jöns, Klaus D; Huber, Daniel; Schimpf, Christian; Huo, Yongheng; Zwiller, Val; Rastelli, Armando; Trotta, Rinaldo

    2017-07-12

    Photonic quantum technologies are on the verge of finding applications in everyday life with quantum cryptography and quantum simulators on the horizon. Extensive research has been carried out to identify suitable quantum emitters and single epitaxial quantum dots have emerged as near-optimal sources of bright, on-demand, highly indistinguishable single photons and entangled photon-pairs. In order to build up quantum networks, it is essential to interface remote quantum emitters. However, this is still an outstanding challenge, as the quantum states of dissimilar "artificial atoms" have to be prepared on-demand with high fidelity and the generated photons have to be made indistinguishable in all possible degrees of freedom. Here, we overcome this major obstacle and show an unprecedented two-photon interference (visibility of 51 ± 5%) from remote strain-tunable GaAs quantum dots emitting on-demand photon-pairs. We achieve this result by exploiting for the first time the full potential of a novel phonon-assisted two-photon excitation scheme, which allows for the generation of highly indistinguishable (visibility of 71 ± 9%) entangled photon-pairs (fidelity of 90 ± 2%), enables push-button biexciton state preparation (fidelity of 80 ± 2%) and outperforms conventional resonant two-photon excitation schemes in terms of robustness against environmental decoherence. Our results mark an important milestone for the practical realization of quantum repeaters and complex multiphoton entanglement experiments involving dissimilar artificial atoms.

  10. A bioaccumulative cyclometalated platinum(II) complex with two-photon-induced emission for live cell imaging.

    Science.gov (United States)

    Koo, Chi-Kin; Wong, Ka-Leung; Man, Cornelia Wing-Yin; Lam, Yun-Wah; So, Leo King-Yan; Tam, Hoi-Lam; Tsao, Sai-Wah; Cheah, Kok-Wai; Lau, Kai-Chung; Yang, Yang-Yi; Chen, Jin-Can; Lam, Michael Hon-Wah

    2009-02-02

    The cyclometalated platinum(II) complex [Pt(L)Cl], where HL is a new cyclometalating ligand 2-phenyl-6-(1H-pyrazol-3-yl)pyridine containing C(phenyl), N(pyridyl), and N(pyrazolyl) donor moieties, was found to possess two-photon-induced luminescent properties. The two-photon-absorption cross section of the complex in N,N-dimethylformamide at room temperature was measured to be 20.8 GM. Upon two-photon excitation at 730 nm from a Ti:sapphire laser, bright-green emission was observed. Besides its two-photon-induced luminescent properties, [Pt(L)Cl] was able to be rapidly accumulated in live HeLa and NIH3T3 cells. The two-photon-induced luminescence of the complex was retained after live cell internalization and can be observed by two-photon confocal microscopy. Its bioaccumulation properties enabled time-lapse imaging of the internalization process of the dye into living cells. Cytotoxicity of [Pt(L)Cl] to both tested cell lines was low, according to MTT assays, even at loadings as high as 20 times the dose concentration for imaging for 6 h.

  11. Intramolecular evolution from a locally excited state to an excimer-like state in a multichromophoric dendrimer evidenced by a femtosecond fluorescence upconversion study

    NARCIS (Netherlands)

    Karni, Y.; Jordens, S.; Belder, G. De; Schweitzer, G.; Hofkens, J.; Gensch, T.; Maus, M.; Schryver, F.C. De; Herrmann, A.; Müllen, K.

    1999-01-01

    A time-resolved fluorescence upconversion study on a polyphenylene dendrimer with eight peryleneimide chromophores on the surface and on a monochromophoric model compound is reported. The time-dependent fluorescence spectra of the dendrimer show that the initial excitation is into a locally excited

  12. Efficient multi-site two-photon functional imaging of neuronal circuits.

    Science.gov (United States)

    Castanares, Michael Lawrence; Gautam, Vini; Drury, Jack; Bachor, Hans; Daria, Vincent R

    2016-12-01

    Two-photon imaging using high-speed multi-channel detectors is a promising approach for optical recording of cellular membrane dynamics at multiple sites. A main bottleneck of this technique is the limited number of photons captured within a short exposure time (~1ms). Here, we implement temporal gating to improve the two-photon fluorescence yield from holographically projected multiple foci whilst maintaining a biologically safe incident average power. We observed up to 6x improvement in the signal-to-noise ratio (SNR) in Fluorescein and cultured hippocampal neurons showing evoked calcium transients. With improved SNR, we could pave the way to achieving multi-site optical recording of fluorogenic probes with response times in the order of ~1ms.

  13. Laser-induced fluorescence with an OPO system. Part II: direct determination of lead content in seawater by electrothermal atomization-laser-excited atomic fluorescence (ETA-LEAF).

    Science.gov (United States)

    Le Bihan, A; Lijour, Y; Giamarchi, P; Burel-Deschamps, L; Stephan, L

    2003-03-01

    Fluorescence was induced by coupling a laser with an optical parametric oscillator (OPO) to develop an analytical method for the direct determination of lead content, at ultra-trace level, in seawater by electrothermal atomization-laser-excited atomic fluorescence (ETA-LEAF). The optimization of atomization conditions, laser pulse energy, and mainly temporal parameters allowed us to reach a 3 fg detection limit (0.3 ng L(-1)) despite the low repetition rate of the device. The expected error on predicted concentrations of lead, at trace levels, in seawater was below 15%.

  14. Additive controlled synthesis of gold nanorods (GNRs) for two-photon luminescence imaging of cancer cells

    International Nuclear Information System (INIS)

    Zhu Jing; Roy, Indrajit; Hu Rui; Ding Hong; Zhao Lingling; He, Guang S; Prasad, Paras N; Yong, Ken-Tye; Swihart, Mark T; Cui Yiping

    2010-01-01

    Gold nanorods (GNRs) with a longitudinal surface plasmon resonance peak that is tunable from 600 to 1100 nm have been fabricated in a cetyl trimethylammoniumbromide (CTAB) micellar medium using hydrochloric acid and silver nitrate as additives to control their shape and size. By manipulating the concentrations of silver nitrate and hydrochloric acid, the aspect ratio of the GNRs was reliably and reproducibly tuned from 2.5 to 8. The GNRs were first coated with polyelectrolyte multilayers and then bioconjugated to transferrin (Tf) to target pancreatic cancer cells. Two-photon imaging excited from the bioconjugated GNRs demonstrated receptor-mediated uptake of the bioconjugates into Panc-1 cells, overexpressing the transferrin receptor (TfR). The bioconjugated GNR formulation exhibited very low toxicity, suggesting that it is biocompatible and potentially suitable for targeted two-photon bioimaging.

  15. Two-Photon Pumped Synchronously Mode-Locked Bulk GaAs Laser

    Science.gov (United States)

    Cao, W. L.; Vaucher, A. M.; Ling, J. D.; Lee, C. H.

    1982-04-01

    Pulses 7 picoseconds or less in duration have been generated from a bulk GaAs crystal by a synchronous mode-locking technique. The GaAs crystal was optically pumped by two-photon absorption of the emission from a mode-locked Nd:glass laser. Two-photon absorption as the means of excitation increases the volume of the gain medium by increasing the pene-tration depth of the pump intensity, enabling generation of intra-cavity pulses with peak power in the megawatt range. Tuning of the wavelength of the GaAs emission is achieved by varying the temperature. A tuning range covering 840 nm to 885 nm has been observed over a temperature range from 97°K to 260°K. The intensity of the GaAs emission has also been observed to decrease as the temperature of the crystal is increased.

  16. Two-Photon or Higher-Order Absorbing Optical Materials for Generation of Reactive Species

    Science.gov (United States)

    Cumpston, Brian (Inventor); Lipson, Matthew (Inventor); Marder, Seth R. (Inventor); Perry, Joseph W. (Inventor)

    2013-01-01

    Disclosed are highly efficient multiphoton absorbing compounds and methods of their use. The compounds generally include a bridge of pi-conjugated bonds connecting electron donating groups or electron accepting groups. The bridge may be substituted with a variety of substituents as well. Solubility, lipophilicity, absorption maxima and other characteristics of the compounds may be tailored by changing the electron donating groups or electron accepting groups, the substituents attached to or the length of the pi-conjugated bridge. Numerous photophysical and photochemical methods are enabled by converting these compounds to electronically excited states upon simultaneous absorption of at least two photons of radiation. The compounds have large two-photon or higher-order absorptivities such that upon absorption, one or more Lewis acidic species, Lewis basic species, radical species or ionic species are formed.

  17. Additive controlled synthesis of gold nanorods (GNRs) for two-photon luminescence imaging of cancer cells

    Energy Technology Data Exchange (ETDEWEB)

    Zhu Jing; Roy, Indrajit; Hu Rui; Ding Hong; Zhao Lingling; He, Guang S; Prasad, Paras N [Institute for Lasers, Photonics and Biophotonics, University at Buffalo, State University of New York, Buffalo, NY 14260-4200 (United States); Yong, Ken-Tye [School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Swihart, Mark T [Department of Chemical and Biological Engineering, University at Buffalo, State University of New York, Buffalo, NY 14260-4200 (United States); Cui Yiping, E-mail: ktyong@ntu.edu.sg, E-mail: cyp@seu.edu.cn, E-mail: pnprasad@buffalo.edu [Advanced Photonics Center, School of Electronic Science and Engineering, Southeast University, Nanjing 210096 (China)

    2010-07-16

    Gold nanorods (GNRs) with a longitudinal surface plasmon resonance peak that is tunable from 600 to 1100 nm have been fabricated in a cetyl trimethylammoniumbromide (CTAB) micellar medium using hydrochloric acid and silver nitrate as additives to control their shape and size. By manipulating the concentrations of silver nitrate and hydrochloric acid, the aspect ratio of the GNRs was reliably and reproducibly tuned from 2.5 to 8. The GNRs were first coated with polyelectrolyte multilayers and then bioconjugated to transferrin (Tf) to target pancreatic cancer cells. Two-photon imaging excited from the bioconjugated GNRs demonstrated receptor-mediated uptake of the bioconjugates into Panc-1 cells, overexpressing the transferrin receptor (TfR). The bioconjugated GNR formulation exhibited very low toxicity, suggesting that it is biocompatible and potentially suitable for targeted two-photon bioimaging.

  18. Additive controlled synthesis of gold nanorods (GNRs) for two-photon luminescence imaging of cancer cells

    Science.gov (United States)

    Zhu, Jing; Yong, Ken-Tye; Roy, Indrajit; Hu, Rui; Ding, Hong; Zhao, Lingling; Swihart, Mark T.; He, Guang S.; Cui, Yiping; Prasad, Paras N.

    2010-07-01

    Gold nanorods (GNRs) with a longitudinal surface plasmon resonance peak that is tunable from 600 to 1100 nm have been fabricated in a cetyl trimethylammoniumbromide (CTAB) micellar medium using hydrochloric acid and silver nitrate as additives to control their shape and size. By manipulating the concentrations of silver nitrate and hydrochloric acid, the aspect ratio of the GNRs was reliably and reproducibly tuned from 2.5 to 8. The GNRs were first coated with polyelectrolyte multilayers and then bioconjugated to transferrin (Tf) to target pancreatic cancer cells. Two-photon imaging excited from the bioconjugated GNRs demonstrated receptor-mediated uptake of the bioconjugates into Panc-1 cells, overexpressing the transferrin receptor (TfR). The bioconjugated GNR formulation exhibited very low toxicity, suggesting that it is biocompatible and potentially suitable for targeted two-photon bioimaging.

  19. Two-Photon Luminescence and Second Harmonic Generation from Gold Micro-Plates

    Directory of Open Access Journals (Sweden)

    Xu Wang

    2014-09-01

    Full Text Available Micron-sized gold plates were prepared by reducing chloroauric acid with lemongrass extract. Their two-photon luminescence (TPL and second harmonic generation (SHG were investigated. The results show that the TPL and SHG intensity of gold plates is dependent on the wavelength and polarization of excitation laser. The TPL intensity of gold plates decreases with the increase of the excitation wavelength except for a small peak around 820–840 nm, while SHG intensity increases with the excitation wavelength redshift. In addition, it is found that the TPL intensity of the gold plate’s edge is related with the angle between the edge orientation and the polarization direction of the excitation light. The TPL intensity increases with the angle increase from 0° to 90°.

  20. Extreme nonlinearities in InAs/InP nanowire gain media: the two-photon induced laser

    DEFF Research Database (Denmark)

    Capua, Amir; Kami, Ouri; Eisenstein, Gadi

    2012-01-01

    We demonstrate a novel laser oscillation scheme in an InAs / InP wire-like quantum dash gain medium. A short optical pulse excites carriers by two photon absorption which relax to the energy levels providing gain thereby enabling laser oscillations. The nonlinear dynamic interaction is analyzed a...

  1. Some secrets of fluorescent proteins: distinct bleaching in various mounting fluids and photoactivation of cyan fluorescent proteins at YFP-excitation.

    Science.gov (United States)

    Malkani, Naila; Schmid, Johannes A

    2011-04-07

    The use of spectrally distinct variants of green fluorescent protein (GFP) such as cyan or yellow mutants (CFP and YFP, respectively) is very common in all different fields of life sciences, e.g. for marking specific proteins or cells or to determine protein interactions. In the latter case, the quantum physical phenomenon of fluorescence resonance energy transfer (FRET) is exploited by specific microscopy techniques to visualize proximity of proteins. When we applied a commonly used FRET microscopy technique--the increase in donor (CFP)-fluorescence after bleaching of acceptor fluorophores (YFP), we obtained good signals in live cells, but very weak signals for the same samples after fixation and mounting in commercial microscopy mounting fluids. This observation could be traced back to much faster bleaching of CFP in these mounting media. Strikingly, the opposite effect of the mounting fluid was observed for YFP and also for other proteins such as Cerulean, TFP or Venus. The changes in photostability of CFP and YFP were not caused by the fixation but directly dependent on the mounting fluid. Furthermore we made the interesting observation that the CFP-fluorescence intensity increases by about 10-15% after illumination at the YFP-excitation wavelength--a phenomenon, which was also observed for Cerulean. This photoactivation of cyan fluorescent proteins at the YFP-excitation can cause false-positive signals in the FRET-microscopy technique that is based on bleaching of a yellow FRET acceptor. Our results show that photostability of fluorescent proteins differs significantly for various media and that CFP bleaches significantly faster in commercial mounting fluids, while the opposite is observed for YFP and some other proteins. Moreover, we show that the FRET microscopy technique that is based on bleaching of the YFP is prone to artifacts due to photoactivation of cyan fluorescent proteins under these conditions.

  2. System and method for controlling depth of imaging in tissues using fluorescence microscopy under ultraviolet excitation following staining with fluorescing agents

    Science.gov (United States)

    Levenson, Richard; Demos, Stavros

    2018-05-08

    A method is disclosed for analyzing a thin tissue sample and adapted to be supported on a slide. The tissue sample may be placed on a slide and exposed to one or more different exogenous fluorophores excitable in a range of about 300 nm-200 nm, and having a useful emission band from about 350 nm-900 nm, and including one or more fluorescent dyes or fluorescently labeled molecular probes that accumulate in tissue or cellular components. The fluorophores may be excited with a first wavelength of UV light between about 200 nm-290 nm. An optical system collects emissions from the fluorophores at a second wavelength, different from the first wavelength, which are generated in response to the first wavelength of UV light, to produce an image for analysis.

  3. Focused fluorescence excitation with time-reversed ultrasonically encoded light and imaging in thick scattering media

    International Nuclear Information System (INIS)

    Lai, Puxiang; Suzuki, Yuta; Xu, Xiao; Wang, Lihong V

    2013-01-01

    Scattering dominates light propagation in biological tissue, and therefore restricts both resolution and penetration depth in optical imaging within thick tissue. As photons travel into the diffusive regime, typically 1 mm beneath human skin, their trajectories transition from ballistic to diffusive due to the increased number of scattering events, which makes it impossible to focus, much less track, photon paths. Consequently, imaging methods that rely on controlled light illumination are ineffective in deep tissue. This problem has recently been addressed by a novel method capable of dynamically focusing light in thick scattering media via time reversal of ultrasonically encoded (TRUE) diffused light. Here, using photorefractive materials as phase conjugate mirrors, we show a direct visualization and dynamic control of optical focusing with this light delivery method, and demonstrate its application for focused fluorescence excitation and imaging in thick turbid media. These abilities are increasingly critical for understanding the dynamic interactions of light with biological matter and processes at different system levels, as well as their applications for biomedical diagnosis and therapy. (letter)

  4. High sensitivity detection of selenium by laser excited atomic fluorescence spectrometry using electrothermal atomization

    International Nuclear Information System (INIS)

    Heitmann, U.; Hese, A.; Schoknecht, G.; Gries, W.

    1995-01-01

    The high sensitivity detection of the trace element selenium is reported. The analytical method applied is Laser Excited Atomic Fluorescence Spectrometry using Electrothermal Atomization within a graphite furnace atomizer. For the production of tunable laser radiation in the VUV spectral region a laser system was developed which consists of two dye lasers pumped by a Nd:YAG laser. The laser radiations are subsequently frequency doubled and sum frequency mixed by nonlinear optical KDP or BBO crystals, respectively. The system works with a repetition rate of 20 Hz and provides output energies of up to 100 μJ in the VUV at a pulse duration of 5 ns. The analytical investigations were focused on the detection of selenium in aqueous solutions and samples of human whole blood. From measurements on aqueous standards detection limits of 1.5 ng/l for selenium were obtained, with corresponding absolute detected masses of only 15 fg. The linear dynamic range spanned six orders of magnitude and good precision was achieved. In case of human whole blood samples the recovery was found to be within the range of 96% to 104%. The determination of the selenium content yielded medians of [119.5 ± 17.3] μg/l for 200 frozen blood samples taken in 1988 and [109.1 ± 15.6] μg/l for 103 fresh blood samples. (author)

  5. Excitation and deexcitation of N2 molecular levels. Induced fluorescence by electrons and laser

    International Nuclear Information System (INIS)

    Perez Fernandez-Mayoralas, A.

    1989-01-01

    The electron impact excitation followed by fluorescence induced by N 2 -laser absorption was used to study the lifetime of the lowest vibrational level of the B 3 π g electronic state of N 2 . The experimental result of this work is 13 + 1 μs. To measure the lifetime of B 3 π g (v=2,3,5,6,7,8) levels the delayed coincidence method by electron impact was use. The lifetime values were compared with recent experimental and theoretical results. The relative intensi-ties of 3 π g --- A 3 Σ Ω + system bands, in the range (6540-10500 A o ) was measured using a hollow cathode lamp as spectral source. The relative transition moments and its dependence versus the r-centroid was obtained. Total cross sections for electron scattering by N molecules in the range 600 - 5000 eV have been obtained from measurements of the attenuation of a linear electron beam. The results have been compared with available experimental cross sections and with theoretical calculations based on the first Born approximation. (Author)

  6. New all-optical method for measuring molecular permanent dipole moment difference using two-photon absorption spectroscopy

    International Nuclear Information System (INIS)

    Rebane, A.; Drobizhev, M.; Makarov, N.S.; Beuerman, E.; Tillo, S.; Hughes, T.

    2010-01-01

    Stark effect, in combination with spectral hole burning and single-molecule spectroscopy, has been a fruitful technique to study permanent electric dipole moment of molecules in condensed phase. However, because measuring Stark shifts relies on external fields and narrow line- or hole-widths, the applicability of this method at ambient conditions required by most biological systems has remained limited. Here we demonstrate a new all-optical method for measuring the molecular dipole moment difference between ground and excited states using two-photon absorption (2PA) spectroscopy. We show that the value and orientation of the static dipole moment difference can be determined from the corresponding absolute 2PA cross-section. We use this new method to determine for the first time the strength of local electric field E loc =0.1-1.0x10 8 V/cm inside beta-barrel of Fruit series of red fluorescent proteins. Because our method does not rely on external field and is applicable in liquid solutions, it is well suited for the study of biological systems.

  7. NEAR-IR TWO PHOTON MICROSCOPY IMAGING OF SILICA NANOPARTICLES FUNCTIONALIZED WITH ISOLATED SENSITIZED Yb(III) CENTERS

    Energy Technology Data Exchange (ETDEWEB)

    Lapadula, Giuseppe; Bourdolle, Adrien; Allouche, Florian; Conley, Matthew P.; Maron, Laurent; Lukens, Wayne W.; Guyot, Yannick; Andraud, Chantal; Brasselet, Sophie; Copé; ret, Christophe; Maury, Olivier; Andersen, Richard A.

    2013-01-12

    Bright nano objects emitting in the near infrared with a maximal cross section of 41.4 x 103 GM (Goppert Mayer), were prepared by implanting ca. 180 4,4 diethylaminostyryl 2,2 bipyridine (DEAS) Yb(III) complexes on the surface of 12 nm silica nanoparticles. The surface complexes ([DEAS Ln SiO2], Ln =Y,Yb) were characterized using IR, solid state NMR, UV Vis, EXAFS spectroscopies in combination with the preparation and characterization of similar molecular analogues by analytical techniques (IR, solution NMR, UV Vis, X ray crystallography) as well as DFT calculations. Starting from the partial dehydroxylation of the silica at 700 C on high vacuum having 0.8 OH.nm 2, the grafting of Ln(N(SiMe3)2)3 generate ≤SiO Ln(N(SiMe3)2)2, which upon thermal step and coordination of the DEAS chromophore yields (≤SiO)3Ln(DEAS). Surface and molecular analogues display similar properties, in terms of DEAS binding constants absorption maxima and luminescence properties (intense emission band assigned to a ligand centered CT fluorescence and life time) in the solid state, consistent with the molecular nature of the surface species. The densely functionalized nanoparticles can be dispersed via ultra-sonication in small ca. 15-20 nm aggregates (1 to 6 elementary particles) that were detected using two photon microscopy imaging at 720 nm excitation, making them promising nano objects for bio imaging.

  8. Interference of two photons in parametric down conversion

    International Nuclear Information System (INIS)

    Ghosh, R.; Hong, C.K.; Ou, Z.Y.; Mandel, L.

    1986-01-01

    A theoretical treatment is given of the process in which the two photons produced simultaneously in the parametric frequency splitting of light are allowed to interfere. It is shown that, while there is no interference in the usual sense involving quantities that are of the second order in the field, fourth-order interference effects are present. These may be revealed by measuring the joint probability of detecting two photons at two points x,x' in the interference plane with photoelectric detectors as a function of the separation x-x'. The probability exhibits a cosine modulation with x-x', with visibility that can approach 100%, even though the integration time in the experiment may greatly exceed the reciprocal bandwidth of the photons. The interference effect has a nonclassical origin and implies a violation of local realism in the highly correlated two-photon state

  9. Sub-threshold excited Cl Kβ (K-V) x-ray fluorescence from CF3Cl molecule

    International Nuclear Information System (INIS)

    Perera, R.C.C.; Cowan, P.L.; Lindle, D.W.; LaVilla, R.E.

    1987-10-01

    With the availability of tunable synchrotron radiation sources, unoccupied molecular orbits (below vacuum level) can be selectively populated producing highly excited neutral molecules. X-ray fluorescence spectra from molecules were obtained with excitation below the ionization threshold and were observed to have significant intensity changes, absolute and relative energy position shifts and line width changes as compared to fluorescence spectra excited above the threshold. As an example, the Cl Kβ (K-V) emission spectra from CF 3 Cl vapor are presented. The energy shifts and intensity changes are explained in terms of perturbation effects due to the presence of an electron in an unoccupied molecular orbital. The narrow line widths obtained in the spectra excited below threshold are explained in terms of the ''effective'' hole production region in a core state limited by the broadening of the unoccupied level. The change in line widths as a function of below-threshold excitation energy is proposed as a novel technique to study the localized properties and reorganization effects of a hole in a core level. 10 refs., 4 figs., 1 tab

  10. Two-photon time-lapse microscopy of BODIPY-cholesterol reveals anomalous sterol diffusion in chinese hamster ovary cells

    Directory of Open Access Journals (Sweden)

    Lund Frederik W

    2012-10-01

    Full Text Available Abstract Background Cholesterol is an important membrane component, but our knowledge about its transport in cells is sparse. Previous imaging studies using dehydroergosterol (DHE, an intrinsically fluorescent sterol from yeast, have established that vesicular and non-vesicular transport modes contribute to sterol trafficking from the plasma membrane. Significant photobleaching, however, limits the possibilities for in-depth analysis of sterol dynamics using DHE. Co-trafficking studies with DHE and the recently introduced fluorescent cholesterol analog BODIPY-cholesterol (BChol suggested that the latter probe has utility for prolonged live-cell imaging of sterol transport. Results We found that BChol is very photostable under two-photon (2P-excitation allowing the acquisition of several hundred frames without significant photobleaching. Therefore, long-term tracking and diffusion measurements are possible. Two-photon temporal image correlation spectroscopy (2P-TICS provided evidence for spatially heterogeneous diffusion constants of BChol varying over two orders of magnitude from the cell interior towards the plasma membrane, where D ~ 1.3 μm2/s. Number and brightness (N&B analysis together with stochastic simulations suggest that transient partitioning of BChol into convoluted membranes slows local sterol diffusion. We observed sterol endocytosis as well as fusion and fission of sterol-containing endocytic vesicles. The mobility of endocytic vesicles, as studied by particle tracking, is well described by a model for anomalous subdiffusion on short time scales with an anomalous exponent α ~ 0.63 and an anomalous diffusion constant of Dα = 1.95 x 10-3 μm2/sα. On a longer time scale (t > ~5 s, a transition to superdiffusion consistent with slow directed transport with an average velocity of v ~ 6 x 10-3 μm/s was observed. We present an analytical model that bridges the two regimes and fit this model to vesicle

  11. Two-photon NADH imaging exposes boundaries of oxygen diffusion in cortical vascular supply regions.

    Science.gov (United States)

    Kasischke, Karl A; Lambert, Elton M; Panepento, Ben; Sun, Anita; Gelbard, Harris A; Burgess, Robert W; Foster, Thomas H; Nedergaard, Maiken

    2011-01-01

    Oxygen transport imposes a possible constraint on the brain's ability to sustain variable metabolic demands, but oxygen diffusion in the cerebral cortex has not yet been observed directly. We show that concurrent two-photon fluorescence imaging of endogenous nicotinamide adenine dinucleotide (NADH) and the cortical microcirculation exposes well-defined boundaries of tissue oxygen diffusion in the mouse cortex. The NADH fluorescence increases rapidly over a narrow, very low pO(2) range with a p(50) of 3.4 ± 0.6 mm Hg, thereby establishing a nearly binary reporter of significant, metabolically limiting hypoxia. The transient cortical tissue boundaries of NADH fluorescence exhibit remarkably delineated geometrical patterns, which define the limits of tissue oxygen diffusion from the cortical microcirculation and bear a striking resemblance to the ideal Krogh tissue cylinder. The visualization of microvessels and their regional contribution to oxygen delivery establishes penetrating arterioles as major oxygen sources in addition to the capillary network and confirms the existence of cortical oxygen fields with steep microregional oxygen gradients. Thus, two-photon NADH imaging can be applied to expose vascular supply regions and to localize functionally relevant microregional cortical hypoxia with micrometer spatial resolution.

  12. Doppler-free two-photon spectroscopy of Yb atoms and efficient generation of a cascade of two photons at 611.3 nm and 555.8 nm

    International Nuclear Information System (INIS)

    Song, Minsoo; Yoon, Duseong; Yoon, Taihyun

    2011-01-01

    We performed high-resolution Doppler-free two-photon spectroscopy of Yb atoms in an effusive atomic beam and generated a cascade of two photons at 611.3 nm (idler) and 555.8 nm (signal) with a narrow bandwidth of 37 MHz. Efficient population transfer from the ground state (6s 2 1 S 0 ) to the upper state (6s7s 1 S 0 ), where direct transition at 291.1 nm is dipole forbidden, was achieved through a resonant two-photon excitation enhanced by the electromagnetically-induced transparency mediated by the intermediate state (6s6p 1 P 1 ). From the upper state, a cascade of two photons in sequence was emitted via the spin triplet state (6s 2 3 P 1 ). Numerical calculations of the density matrix equations taking into account the residual Doppler effect and strong driving fields explain quantitatively the experimental results for the dependences of the idler and the signal beam intensities on the various parameters of the driving fields. We report on the generation of a cascade of two photons with fluxes at the level of a few times 10 6 photons/s detected at a solid angle of 0.01 sr.

  13. Doppler-free two-photon spectroscopy of Yb atoms and efficient generation of a cascade of two photons at 611.3 nm and 555.8 nm

    Energy Technology Data Exchange (ETDEWEB)

    Song, Minsoo; Yoon, Duseong; Yoon, Taihyun [Korea University, Seoul (Korea, Republic of)

    2011-10-15

    We performed high-resolution Doppler-free two-photon spectroscopy of Yb atoms in an effusive atomic beam and generated a cascade of two photons at 611.3 nm (idler) and 555.8 nm (signal) with a narrow bandwidth of 37 MHz. Efficient population transfer from the ground state (6s{sup 2} {sup 1}S{sub 0}) to the upper state (6s7s {sup 1}S{sub 0}), where direct transition at 291.1 nm is dipole forbidden, was achieved through a resonant two-photon excitation enhanced by the electromagnetically-induced transparency mediated by the intermediate state (6s6p {sup 1}P{sub 1}). From the upper state, a cascade of two photons in sequence was emitted via the spin triplet state (6s{sup 2} {sup 3}P{sub 1}). Numerical calculations of the density matrix equations taking into account the residual Doppler effect and strong driving fields explain quantitatively the experimental results for the dependences of the idler and the signal beam intensities on the various parameters of the driving fields. We report on the generation of a cascade of two photons with fluxes at the level of a few times 10{sup 6} photons/s detected at a solid angle of 0.01 sr.

  14. Fluorescence and Auger Decay Properties of the Core-Excited F-Like Ions from Ne to Kr

    International Nuclear Information System (INIS)

    Wang Xiang-Li; Dong Chen-Zhong; Su Mao-Gen; Koike Fumihiro

    2012-01-01

    We systematically study the decay properties of the K-shell excited F-like ions with 10≤Z≤36 based on the multiconfiguration Dirac—Fock method. The Breit interaction, the QED corrections and the nuclear finite mass effects are also considered as perturbation. Auger transition rates, radiative, Auger and natural widths, as well as fluorescence and Auger yields for K-shell excited F-like ions are presented. It is shown by means of concrete figures that the decay properties change significantly with the increase of the atomic number Z; the Auger rate is overtaken at Z = 30 by the radiative decay rate. Several fitting formulae for the radiative and Auger widths and the fluorescence yields have been evaluated which is expected to be useful in plasma analysis and plasma modeling. (atomic and molecular physics)

  15. Mannose-functionalized porous silica-coated magnetic nanoparticles for two-photon imaging or PDT of cancer cells

    International Nuclear Information System (INIS)

    Perrier, Marine; Gary-Bobo, Magali; Lartigue, Lenaïc; Brevet, David; Morère, Alain; Garcia, Marcel; Maillard, Philippe; Raehm, Laurence; Guari, Yannick; Larionova, Joulia; Durand, Jean-Olivier; Mongin, Olivier; Blanchard-Desce, Mireille

    2013-01-01

    An original fluorophore engineered for two-photon excitation or a porphyrin derivative were entrapped in the silica shell of magnetic porous silica nanoparticles during the synthesis of the silica moiety without damaging the structure of the organic part. The mild conditions involved allowed obtaining microporous or mesoporous silica magnetic nanoparticles, respectively. Mannose was grafted on the surface of the nanoparticles to target MCF-7 breast cancer cells. The studies of magnetic properties of these hybrid nanoparticles show that they present a blocking temperature at 190 K. The nano-objects designed with the two-photon fluorophore were efficient for two-photon imaging of MCF-7 cancer cells, whereas the nano-objects with the photosensitizer efficiently killed cancer cells. The presence of the mannose moiety was demonstrated to improve both imaging and therapy properties.

  16. Mannose-functionalized porous silica-coated magnetic nanoparticles for two-photon imaging or PDT of cancer cells

    Energy Technology Data Exchange (ETDEWEB)

    Perrier, Marine [UMR 5253 CNRS-UM2-ENSCM-UM1, Institut Charles Gerhardt Montpellier (France); Gary-Bobo, Magali [Faculte de Pharmacie, Universite Montpellier 1, Universite Montpellier 2, Institut des Biomolecules Max Mousseron UMR 5247 CNRS (France); Lartigue, Lenaiec; Brevet, David [UMR 5253 CNRS-UM2-ENSCM-UM1, Institut Charles Gerhardt Montpellier (France); Morere, Alain; Garcia, Marcel [Faculte de Pharmacie, Universite Montpellier 1, Universite Montpellier 2, Institut des Biomolecules Max Mousseron UMR 5247 CNRS (France); Maillard, Philippe [Universite Paris-Sud, UMR 176 CNRS, Institut Curie (France); Raehm, Laurence; Guari, Yannick, E-mail: yannick.guari@um2.fr; Larionova, Joulia; Durand, Jean-Olivier, E-mail: durand@univ-montp2.fr [UMR 5253 CNRS-UM2-ENSCM-UM1, Institut Charles Gerhardt Montpellier (France); Mongin, Olivier [Universite de Rennes 1, Institut des Sciences Chimiques de Rennes, CNRS UMR 6226 (France); Blanchard-Desce, Mireille [Universite Bordeaux, Institut des Sciences Moleculaires, UMR CNRS 5255 (France)

    2013-05-15

    An original fluorophore engineered for two-photon excitation or a porphyrin derivative were entrapped in the silica shell of magnetic porous silica nanoparticles during the synthesis of the silica moiety without damaging the structure of the organic part. The mild conditions involved allowed obtaining microporous or mesoporous silica magnetic nanoparticles, respectively. Mannose was grafted on the surface of the nanoparticles to target MCF-7 breast cancer cells. The studies of magnetic properties of these hybrid nanoparticles show that they present a blocking temperature at 190 K. The nano-objects designed with the two-photon fluorophore were efficient for two-photon imaging of MCF-7 cancer cells, whereas the nano-objects with the photosensitizer efficiently killed cancer cells. The presence of the mannose moiety was demonstrated to improve both imaging and therapy properties.

  17. 340nm UV LED excitation in time-resolved fluorescence system for europium-based immunoassays detection

    OpenAIRE

    Rodenko, Olga; Fodgaard, Henrik; Tidemand-Lichtenberg, Peter; Pedersen, Christian

    2017-01-01

    In immunoassay analyzers for in-vitro diagnostics, Xenon flash lamps have been widely used as excitation light sources. Recent advancements in UV LED technology and its advantages over the flash lamps such as smaller footprint, better wall-plug efficiency, narrow emission spectrum, and no significant afterglow, have made them attractive light sources for gated detection systems. In this paper, we report on the implementation of a 340 nm UV LED based time-resolved fluorescence system based on ...

  18. A new two-photon mechanism of the formation of a continuous spectrum of photons emitted by secondary emission products of atomic particles

    International Nuclear Information System (INIS)

    Veksler, V.I.

    1986-01-01

    A two-photon mechanism of the formation of a continuous spectrum of photons emitted by products of metal sputtering is considered. The following process of the two-photon mechanism is considered: the continuous spectrum is formed under quadrupole two-photon transitions in sputtered excited atoms having vacancies at the d level in atoms of transition metals or at the of level in lanthanides found against the filled conduction band. It is shown that the suggested mechanism should play an essential role in the formation of the continuous spectrum of optical radiation

  19. Effects of autoionizing states on two-photon double ionization of the H2 molecule

    International Nuclear Information System (INIS)

    Guan, Xiaoxu; Bartschat, Klaus; Schneider, Barry I; Koesterke, Lars

    2014-01-01

    Treating the effects of autoionizing intermediate states on two-photon double ionization (DI) of the H 2 molecule using time-dependent laser pulses is a significant computational challenge. Relatively long exposure times are critical to understanding the dynamics. Using the fixed-nuclei approximation, we demonstrate how the doubly excited states enhance the angle-integrated generalized cross sections in H 2 , and how they affect the angular distribution pattern of the ejected electrons. As the energy approaches the threshold for sequential DI, there is a sharp rise in the cross section due to virtual sequential ionization

  20. Rate amplification of the two photon emission from para-hydrogen toward the neutrino mass measurement

    International Nuclear Information System (INIS)

    Masuda, Takahiko; Hara, Hideaki; Miyamoto, Yuki; Kuma, Susumu; Nakano, Itsuo; Ohae, Chiaki; Sasao, Noboru; Tanaka, Minoru; Uetake, Satoshi; Yoshimi, Akihiro; Yoshimura, Koji; Yoshimura, Motohiko

    2015-01-01

    We recently reported an experiment which focused on demonstrating the macro-coherent amplification mechanism. This mechanism, which was proposed for neutrino mass measurements, indicates that a multi-particle emission rate should be amplified by coherence in a suitable medium. Using a para-hydrogen molecule gas target and the adiabatic Raman excitation method, we observed that the two photon emission rate was amplified by a factor of more than 10 15 from the spontaneous emission rate. This paper briefly summarizes the previous experimental result and presents the current status and the future prospect

  1. Two photon laser spectroscopy of antiprotonic helium atoms at CERN’s AD

    CERN Document Server

    Hori, M

    2014-01-01

    The ASACUSA collaboration of CERN has carried out two-photon laser spectroscopy of antiprotonic helium atoms using counter-propagating ultraviolet laser beams. This excited some non-linear transitions of the antiproton at the wavelengths λ = 139.8–197.0 nm, in a way that reduced the thermal Doppler broadening of the observed resonances. The resulting narrow spectral lines allowed the measurement of three transition frequencies with fractional precisions of 2.3–5 parts in 109. By comparing these values with three-body QED calculations, the antiproton-to-electron mass ratio was derived as 1836.1526736(23). We briefly review these results.

  2. Rate amplification of the two photon emission from para-hydrogen toward the neutrino mass measurement

    Energy Technology Data Exchange (ETDEWEB)

    Masuda, Takahiko, E-mail: masuda@okayama-u.ac.jp; Hara, Hideaki; Miyamoto, Yuki [Okayama University, Research Core for Extreme Quantum World (Japan); Kuma, Susumu [Atomic, Molecular and Optical Physics Laboratory, RIKEN (Japan); Nakano, Itsuo [Okayama University, Research Core for Extreme Quantum World (Japan); Ohae, Chiaki [University of Electro-Communications, Department of Engineering Science (Japan); Sasao, Noboru [Okayama University, Research Core for Extreme Quantum World (Japan); Tanaka, Minoru [Osaka University, Department of Physics (Japan); Uetake, Satoshi [Okayama University, Research Center of Quantum Universe (Japan); Yoshimi, Akihiro; Yoshimura, Koji [Okayama University, Research Core for Extreme Quantum World (Japan); Yoshimura, Motohiko [Okayama University, Research Center of Quantum Universe (Japan)

    2015-11-15

    We recently reported an experiment which focused on demonstrating the macro-coherent amplification mechanism. This mechanism, which was proposed for neutrino mass measurements, indicates that a multi-particle emission rate should be amplified by coherence in a suitable medium. Using a para-hydrogen molecule gas target and the adiabatic Raman excitation method, we observed that the two photon emission rate was amplified by a factor of more than 10{sup 15} from the spontaneous emission rate. This paper briefly summarizes the previous experimental result and presents the current status and the future prospect.

  3. Fluorescence from colours used for japanese painting under N_2 laser excitation

    OpenAIRE

    Miyoshi, Tadaki

    1988-01-01

    The fluorescence spectra have been measured for various colours used for Japanese painting in order to identify the pigments in paintings. Fluorescence was observed in various natural and synthetic colours. The fluorescence intensities of these colours are generally weaker than those of oil colours.

  4. On the theory of the two-photon linear photovoltaic effect in n-GaP

    Energy Technology Data Exchange (ETDEWEB)

    Rasulov, V. R.; Rasulov, R. Ya., E-mail: r-rasulov51@mail.ru [Fergana State University (Uzbekistan)

    2016-02-15

    A quantitative theory of the diagonal (ballistic) and nondiagonal (shift) band index contributions to the two-photon current of the linear photovoltaic effect in a semiconductor with a complex band due to the asymmetry of events of electron scattering at phonons and photons is developed. It is shown that processes caused by the simultaneous absorption of two photons do not contribute to the ballistic photocurrent in n-GaP. This is due to the fact that, in this case, there is no asymmetric distribution of the momentum of electrons excited with photons; this distribution arises upon the sequential absorption of two photons with the involvement of LO phonons. It is demonstrated that the temperature dependence of the shift contribution to the two-photon photocurrent in n-GaP is determined by the temperature dependence of the light-absorption coefficient caused by direct optical transitions of electrons between subbands X{sub 1} and X{sub 3}. It is shown that the spectral dependence of the photocurrent has a feature in the light frequency range ω → Δ/2ℏ, which is related to the hump-like shape of subband X{sub 1} in n-GaP{sup 1} and the root-type singularity of the state density determined as k{sub ω}{sup -1}= (2ℏω–Δ){sup –1/2}, where Δ is the energy gap between subbands X{sub 1} and X{sub 3}. The spectral and temperature dependences of the coefficient of absorption of linearly polarized light in n-GaP are obtained with regard to the cone-shaped lower subband of the conduction band.

  5. Fluorescence and picosecond induced absorption from the lowest singlet excited states of quercetin in solutions and polymer films

    Science.gov (United States)

    Bondarev, S. L.; Tikhomirov, S. A.; Buganov, O. V.; Knyukshto, V. N.; Raichenok, T. F.

    2017-03-01

    The spectroscopic and photophysical properties of the biologically important plant antioxidant quercetin in organic solvents, polymer films of polyvinyl alcohol, and a buffer solution at pH 7.0 are studied by stationary luminescence and femtosecond laser spectroscopy at room temperature and 77 K. The large magnitude of the dipole moment of the quercetin molecule in the excited Franck-Condon state μ e FC = 52.8 C m indicates the dipolar nature of quercetin in this excited state. The transient induced absorption spectra S 1→ S n in all solvents are characterized by a short-wave band at λ abs max = 460 nm with exponential decay times in the range of 10.0-20.0 ps. In the entire spectral range at times of >100 ps, no residual induced absorption was observed that could be attributed to the triplet-triplet transitions T 1 → T k in quercetin. In polar solvents, two-band fluorescence was also recorded at room temperature, which is due to the luminescence of the initial enol form of quercetin ( 415 nm) and its keto form with a transferred proton (550 nm). The short-wave band is absent in nonpolar 2-methyltetrahydrofuran (2-MTHF). The spectra of fluorescence and fluorescence excitation exhibit a low dependence on the wavelength of excitation and detection, which may be related to the solvation and conformational changes in the quercetin molecule. Decreasing the temperature of a glassy-like freezing quercetin solution in ethanol and 2-MTHF to 77 K leads to a strong increase in the intensity (by a factor of 100) of both bands. The energy circuits for the proton transfer process are proposed depending on the polarity of the medium. The main channel for the exchange of electronic excitation energy in the quercetin molecule at room temperature is the internal conversion S 1 ⇝ S 0, induced by the state with a proton transfer.

  6. Electron correlations and two-photon states in polycyclic aromatic hydrocarbon molecules: A peculiar role of geometry

    Energy Technology Data Exchange (ETDEWEB)

    Aryanpour, Karan [Department of Physics, University of Arizona, Tucson, Arizona 85721 (United States); Shukla, Alok [Department of Physics, Indian Institute of Technology, Powai, Mumbai 400076 (India); Mazumdar, Sumit [Department of Physics, University of Arizona, Tucson, Arizona 85721 (United States); College of Optical Sciences, University of Arizona, Tucson, Arizona 85721 (United States)

    2014-03-14

    We present numerical studies of one- and two-photon excited states ordering in a number of polycyclic aromatic hydrocarbon molecules: coronene, hexa-peri-hexabenzocoronene, and circumcoronene, all possessing D{sub 6h} point group symmetry versus ovalene with D{sub 2h} symmetry, within the Pariser-Parr-Pople model of interacting π-electrons. The calculated energies of the two-photon states as well as their relative two-photon absorption cross-sections within the interacting model are qualitatively different from single-particle descriptions. More remarkably, a peculiar role of molecular geometry is found. The consequence of electron correlations is far stronger for ovalene, where the lowest spin-singlet two-photon state is a quantum superposition of pairs of lowest spin triplet states, as in the linear polyenes. The same is not true for D{sub 6h} group hydrocarbons. Our work indicates significant covalent character, in valence bond language, of the ground state, the lowest spin triplet state and a few of the lowest two-photon states in D{sub 2h} ovalene but not in those with D{sub 6h} symmetry.

  7. Electron correlations and two-photon states in polycyclic aromatic hydrocarbon molecules: A peculiar role of geometry

    International Nuclear Information System (INIS)

    Aryanpour, Karan; Shukla, Alok; Mazumdar, Sumit

    2014-01-01

    We present numerical studies of one- and two-photon excited states ordering in a number of polycyclic aromatic hydrocarbon molecules: coronene, hexa-peri-hexabenzocoronene, and circumcoronene, all possessing D 6h point group symmetry versus ovalene with D 2h symmetry, within the Pariser-Parr-Pople model of interacting π-electrons. The calculated energies of the two-photon states as well as their relative two-photon absorption cross-sections within the interacting model are qualitatively different from single-particle descriptions. More remarkably, a peculiar role of molecular geometry is found. The consequence of electron correlations is far stronger for ovalene, where the lowest spin-singlet two-photon state is a quantum superposition of pairs of lowest spin triplet states, as in the linear polyenes. The same is not true for D 6h group hydrocarbons. Our work indicates significant covalent character, in valence bond language, of the ground state, the lowest spin triplet state and a few of the lowest two-photon states in D 2h ovalene but not in those with D 6h symmetry

  8. Electron correlations and two-photon states in polycyclic aromatic hydrocarbon molecules: a peculiar role of geometry.

    Science.gov (United States)

    Aryanpour, Karan; Shukla, Alok; Mazumdar, Sumit

    2014-03-14

    We present numerical studies of one- and two-photon excited states ordering in a number of polycyclic aromatic hydrocarbon molecules: coronene, hexa-peri-hexabenzocoronene, and circumcoronene, all possessing D(6h) point group symmetry versus ovalene with D(2h) symmetry, within the Pariser-Parr-Pople model of interacting π-electrons. The calculated energies of the two-photon states as well as their relative two-photon absorption cross-sections within the interacting model are qualitatively different from single-particle descriptions. More remarkably, a peculiar role of molecular geometry is found. The consequence of electron correlations is far stronger for ovalene, where the lowest spin-singlet two-photon state is a quantum superposition of pairs of lowest spin triplet states, as in the linear polyenes. The same is not true for D(6h) group hydrocarbons. Our work indicates significant covalent character, in valence bond language, of the ground state, the lowest spin triplet state and a few of the lowest two-photon states in D(2h) ovalene but not in those with D(6h) symmetry.

  9. Two-photon direct frequency comb spectroscopy of alkali atoms

    Science.gov (United States)

    Palm, Christopher; Pradhananga, Trinity; Nguyen, Khoa; Montcrieffe, Caitlin; Kimball, Derek

    2012-11-01

    We have studied transition frequencies and excited state hyperfine structure in rubidium using 2-photon transitions excited directly with the frequency-doubled output of a erbium fiber optical frequency comb. The frequency comb output is directed in two counterpropagating directions through a vapor cell containing the rubidium vapor. A pair of optical filters is used to select teeth of the comb in order to identify the transition wavelengths. A photomultiplier tube (PMT) measures fluorescence from a decay channel wavelength selected with another optical filter. Using different combinations of filters enables a wide range of transitions to be investigated. By scanning the repetition rate, a Doppler-free spectrum can be obtained enabling kHz-resolution spectral measurements. An interesting dependence of the 2-photon spectrum on the energy of the intermediate state of the 2-photon transition is discussed. Our investigations are laying the groundwork for a long-term research program to use direct frequency comb spectroscopy to understand the complex spectra of rare-earth atoms.

  10. Two-photon optics of Bessel-Gaussian modes

    CSIR Research Space (South Africa)

    McLaren, M

    2013-09-01

    Full Text Available In this paper we consider geometrical two-photon optics of Bessel-Gaussian modes generated in spontaneous parametric down-conversion of a Gaussian pump beam. We provide a general theoretical expression for the orbital angular momentum (OAM) spectrum...

  11. Space-time description of the two-photon decay

    International Nuclear Information System (INIS)

    Hrasko, P.

    1981-09-01

    The time correlation of photons in a two-photon decay is shown to depend on the instantaneous nature of the wave-function collapse in an essential way so the latter hypothesis can be verified by the experimental study of these correlations. (author)

  12. Positron two-photon annihilation coincidence technique: difference mode

    Energy Technology Data Exchange (ETDEWEB)

    Karol, P J; Klobuchar, R L [Carnegie-Mellon Univ., Pittsburgh, Pa. (USA). Dept. of Chemistry

    1978-05-01

    A difference (or comparative) mode in the measurement of two-photon coincidences from positron or positronium annihilation has been developed. The method can be used to advantage, particularly in gases, in determining annihilation parameters such as quenching cross sections for low concentration strongly quenching chemical species in a reference medium which is relatively non-quenching.

  13. Excited-state intramolecular proton transfer of 2-acetylindan-1,3-dione studied by ultrafast absorption and fluorescence spectroscopy

    Directory of Open Access Journals (Sweden)

    Pramod Kumar Verma

    2016-03-01

    Full Text Available We employ transient absorption from the deep-UV to the visible region and fluorescence upconversion to investigate the photoinduced excited-state intramolecular proton-transfer dynamics in a biologically relevant drug molecule, 2-acetylindan-1,3-dione. The molecule is a ß-diketone which in the electronic ground state exists as exocyclic enol with an intramolecular H-bond. Upon electronic excitation at 300 nm, the first excited state of the exocyclic enol is initially populated, followed by ultrafast proton transfer (≈160 fs to form the vibrationally hot endocyclic enol. Subsequently, solvent-induced vibrational relaxation takes place (≈10 ps followed by decay (≈390 ps to the corresponding ground state.

  14. Two-photon absorption and two-photon circular dichroism of hexahelicene derivatives: a study of the effect of the nature of intramolecular charge transfer

    Czech Academy of Sciences Publication Activity Database

    Díaz, C.; Vesga, Y.; Echevarria, L.; Stará, Irena G.; Starý, Ivo; Anger, E.; Shen, C.; Moussa, M. E. S.; Vanthuyne, N.; Crassous, J.; Rizzo, A.; Hernández, F. E.

    2015-01-01

    Roč. 5, č. 23 (2015), s. 17429-17437 ISSN 2046-2069 Institutional support: RVO:61388963 Keywords : [6]helicene * two photon absorption * two photon CD Subject RIV: CC - Organic Chemistry Impact factor: 3.289, year: 2015

  15. CW 3μm lasing via two-photon pumping in cesium vapor with a 1W source

    Science.gov (United States)

    Haluska, Nathan D.; Rice, Christopher A.; Perram, Glen P.

    2018-02-01

    We report the first CW lasing from two-photon pumping via a virtual state. Pulsed and the CW lasing of the 3096 nm 72 P1/2 to 72 S1/2 line are observed from degenerate two-photon pumping of the cesium 72 S1/2 to 62 D3/2 transition. High intensity pulses excite over 17 lasing wavelengths. Under lower intensity CW excitation, 3 μm lasing is still observed with efficiencies of 0.7%. CW experiments utilized a Cs heat pipe at 150 °C to 270 °C, and a highly-focused, single pass, Ti-Sapphire pump with no aid of a cavity. Unlike normal DPALS, this architecture does not require buffer gas, and heat is released optically so a flowing system is not required. Both suggest a very simple device with excellent beam quality is possible. This proof of concept can be greatly enhanced with more optimal conditions such as non-degenerate pumping to further increase the two-photon pump cross section and the addition of a cavity to improve mode volume overlap. These improvements may lead to an increase in efficiencies to a theoretical maximum of 14%. Results suggest two-photon pumping with diodes is feasible.

  16. Comparison of confocal microscopy and two-photon microscopy in mouse cornea in vivo.

    Science.gov (United States)

    Lee, Jun Ho; Lee, Seunghun; Gho, Yong Song; Song, In Seok; Tchah, Hungwon; Kim, Myoung Joon; Kim, Ki Hean

    2015-03-01

    High-resolution imaging of the cornea is important for studying corneal diseases at cellular levels. Confocal microscopy (CM) has been widely used in the clinic, and two-photon microscopy (TPM) has recently been introduced in various pre-clinical studies. We compared the performance of CM and TPM in normal mouse corneas and neovascularized mouse corneas induced by suturing. Balb/C mice and C57BL/6 mice expressing green fluorescent protein (GFP) were used to compare modalities based on intrinsic contrast and extrinsic fluorescence contrast. CM based on reflection (CMR), CM based on fluorescence (CMF), and TPM based on intrinsic/extrinsic fluorescence and second harmonic generation (SHG) were compared by imaging the same sections of mouse corneas sequentially in vivo. In normal mouse corneas, CMR visualized corneal cell morphologies with some background noise, and CMF visualized GFP expressing corneal cells clearly. TPM visualized corneal cells and collagen in the stroma based on fluorescence and SHG, respectively. However, in neovascularized mouse corneas, CMR could not resolve cells deep inside the cornea due to high background noise from the effects of increased structural irregularity induced by suturing. CMF and TPM visualized cells and induced vasculature better than CMR because both collect signals from fluorescent cells only. Both CMF and TPM had signal decays with depth due to the structural irregularity, with CMF having faster signal decay than TPM. CMR, CMF, and TPM showed different degrees of image degradation in neovascularized mouse corneas. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. The fluorescence action spectra of some saturated hydrocarbon liquids for excitation energies above and below their ionization thresholds

    International Nuclear Information System (INIS)

    Ostafin, A.E.; Lipsky, S.

    1993-01-01

    Fluorescence action spectra have been obtained for the neat liquids, cis-decalin, trans-decalin, bicyclohexyl, cyclohexane, methylcyclohexane, isobutylcyclohexane, 2,3,4-trimethylpentane, 2,3-dimethylbutane, 3-methylhexane, 3-methylpentane, n-decane, n-dodecane, and n-pentadecane at excitation energies, ε, ranging from their absorption onsets (at ca. 7 eV) to 10.3 eV. For all compounds, with the exception of cis-decalin, the fluorescence quantum yield is observed to monotonically decline with increasing ε, reaching a minimum value at an energy, ε m (a few tenths of an eV above the liquid phase ionization threshold, ε l ) followed by a slow increase. In the case of cis-decalin, the fluorescence quantum yield remains constant over the entire range of excitation energies studied, permitting its use as a quantum counter replacing the standard sodium salicylate, at least over a spectral range from 185 to 120 nm. The recovery of the fluorescence quantum yield for ε>ε m is attributed to an increasing probability for electron ejection followed by e - +RH + geminate recombination, to produce an excited state of RH with energy less than ε l . From a simple analysis of the action spectrum, a lower bound estimate of the electron ejection probability, φ ± , is obtained as a function of ε. In the case of cyclohexane, where φ ± has been obtained by other techniques at ε congruent 10 eV, the lower bound estimate agrees with the experimental value. From this agreement, arguments are presented to make plausible the conjecture that in all these liquids, the initially produced e - +RH + geminate ion pair first rapidly internally converts to an ion-pair state ca

  18. [Vermicomposting of different organic materials and three-dimensional excitation emission matrix fluorescence spectroscopic characterization of their dissolved organic matter].

    Science.gov (United States)

    Yang, Wei; Wang, Dong-sheng; Liu, Man-qiang; Hu, Feng; Li, Hui-xin; Huang, Zhong-yang; Chang, Yi-jun; Jiao, Jia-guo

    2015-10-01

    In this experiment, different proportions of the cattle manure, tea-leaf, herb and mushroom residues, were used as food for earthworm (Eisenia fetida) to study the growth of the earth-worm. Then the characteristics and transformation of nutrient content and three-dimensional excitation emission matrix fluorescence (3DEEM) of dissolved organic matter (DOM) during vermistabilization were investigated by means of chemical and spectroscopic methods. The result showed that the mixture of different ratios of cattle manure with herb residue, and cattle manure with tea-leaf were conducive to the growth of earthworm, while the materials compounded with mushroom residue inhibited the growth of earthworm. With the increasing time of verimcomposting, the pH in vermicompost tended to be circumneutral and weakly acidic, and there were increases in electrical conductivity, and the contents of total nitrogen, total phosphorus, available nitrogen, and available phosphorus, while the total potassium and available potassium increased first and then decreased, and the organic matter content decreased. 3DEEM and fluorescence regional integration results indicated that, the fluorescence of protein-like fluorescence peaks declined significantly, while the intensity of humic-like fluorescence peak increased significantly in DOM. Vermicomposting process might change the compositions of DOM with elevated concentrations of humic acid and fulvic acid in the organics. In all, this study suggested the suitability of 3DEEM for monitoring the organics transformation and assessing the maturity in the vermicomposting.

  19. Neural plasticity explored by correlative two-photon and electron/SPIM microscopy

    Science.gov (United States)

    Allegra Mascaro, A. L.; Silvestri, L.; Costantini, I.; Sacconi, L.; Maco, B.; Knott, G. W.; Pavone, F. S.

    2013-06-01

    Plasticity of the central nervous system is a complex process which involves the remodeling of neuronal processes and synaptic contacts. However, a single imaging technique can reveal only a small part of this complex machinery. To obtain a more complete view, complementary approaches should be combined. Two-photon fluorescence microscopy, combined with multi-photon laser nanosurgery, allow following the real-time dynamics of single neuronal processes in the cerebral cortex of living mice. The structural rearrangement elicited by this highly confined paradigm of injury can be imaged in vivo first, and then the same neuron could be retrieved ex-vivo and characterized in terms of ultrastructural features of the damaged neuronal branch by means of electron microscopy. Afterwards, we describe a method to integrate data from in vivo two-photon fluorescence imaging and ex vivo light sheet microscopy, based on the use of major blood vessels as reference chart. We show how the apical dendritic arbor of a single cortical pyramidal neuron imaged in living mice can be found in the large-scale brain reconstruction obtained with light sheet microscopy. Starting from its apical portion, the whole pyramidal neuron can then be segmented and located in the correct cortical layer. With the correlative approach presented here, researchers will be able to place in a three-dimensional anatomic context the neurons whose dynamics have been observed with high detail in vivo.

  20. Deformed two-photon squeezed states in noncommutative space

    International Nuclear Information System (INIS)

    Zhang Jianzu

    2004-01-01

    Recent studies on nonperturbation aspects of noncommutative quantum mechanics explored a new type of boson commutation relations at the deformed level, described by deformed annihilation-creation operators in noncommutative space. This correlated boson commutator correlates different degrees of freedom, and shows an essential influence on dynamics. This Letter devotes to the development of formalism of deformed two-photon squeezed states in noncommutative space. General representations of deformed annihilation-creation operators and the consistency condition for the electromagnetic wave with a single mode of frequency in noncommunicative space are obtained. Two-photon squeezed states are studied. One finds that variances of the dimensionless Hermitian quadratures of the annihilation operator in one degree of freedom include variances in the other degree of freedom. Such correlations show the new feature of spatial noncommutativity and allow a deeper understanding of the correlated boson commutator

  1. Meson production in two-photon interactions at LHC energies

    Energy Technology Data Exchange (ETDEWEB)

    Da Silva, D. T.; Goncalves, V. P.; Sauter, W. K. [Instituto de Fisica e Matematica, Universidade Federal de Pelotas, Campus Universitario UFPel, CP 354, 96010-900, Capao do Leao-RS (Brazil)

    2013-03-25

    The LHC opens a new kinematical regime at high energy, where several questions related to the description of the high-energy regime of the Quantum Chromodynamics (QCD) remain without satisfactory answers. Some open questions are the search for non-q-bar q resonances, the determination of the spectrum of q-bar q states and the identification of states with anomalous {gamma}{gamma} couplings. A possible way to study these problems is the study of meson production in two-photon interactions. In this contribution we calculate the meson production in two-photon interactions at LHC energies considering proton - proton collisions and estimate the total cross section for the production of the mesons {pi}, a, f, {eta} and {chi}.

  2. Multichannel modeling and two-photon coherent transfer paths in NaK

    Science.gov (United States)

    Schulze, T. A.; Temelkov, I. I.; Gempel, M. W.; Hartmann, T.; Knöckel, H.; Ospelkaus, S.; Tiemann, E.

    2013-08-01

    We explore possible pathways for the creation of ultracold polar NaK molecules in their absolute electronic and rovibrational ground state starting from ultracold Feshbach molecules. In particular, we present a multichannel analysis of the electronic ground and K(4p)+Na(3s) excited-state manifold of NaK, analyze the spin character of both the Feshbach molecular state and the electronically excited intermediate states and discuss possible coherent two-photon transfer paths from Feshbach molecules to rovibronic ground-state molecules. The theoretical study is complemented by the demonstration of stimulated Raman adiabatic passage from the X1Σ+(v=0) state to the a3Σ+ manifold on a molecular beam experiment.

  3. Two-photon or higher-order absorbing optical materials and methods of use

    Science.gov (United States)

    Marder, Seth (Inventor); Perry, Joseph (Inventor)

    2012-01-01

    Compositions capable of simultaneous two-photon absorption and higher order absorptivities are provided. Compounds having a donor-pi-donor or acceptor-pi-acceptor structure are of particular interest, where the donor is an electron donating group, acceptor is an electron accepting group, and pi is a pi bridge linking the donor and/or acceptor groups. The pi bridge may additionally be substituted with electron donating or withdrawing groups to alter the absorptive wavelength of the structure. Also disclosed are methods of generating an excited state of such compounds through optical stimulation with light using simultaneous absorption of photons of energies individually insufficient to achieve an excited state of the compound, but capable of doing so upon simultaneous absorption of two or more such photons. Applications employing such methods are also provided, including controlled polymerization achieved through focusing of the light source(s) used.

  4. A reagentless enzymatic fluorescent biosensor for glucose based on upconverting glasses, as excitation source, and chemically modified glucose oxidase.

    Science.gov (United States)

    Del Barrio, Melisa; Cases, Rafael; Cebolla, Vicente; Hirsch, Thomas; de Marcos, Susana; Wilhelm, Stefan; Galbán, Javier

    2016-11-01

    Upon near-infrared excitation Tm(3+)+Yb(3+) doped fluorohafnate glasses present upconversion properties and emit visible light. This property permits to use these glasses (UCG) as excitation sources for fluorescent optical biosensors. Taking this into account, in this work a fluorescent biosensor for glucose determination is designed and evaluated. The biosensor combines the UCG and the fluorescence of the enzyme glucose oxidase chemically modified with a fluorescein derivative (GOx-FS), whose intensity is modified during the enzymatic reaction with glucose. Optical parameters have been optimized and a mathematical model describing the behavior of the analytical signal is suggested. Working in FIA mode, the biosensor responds to glucose concentrations up to, at least, 15mM with a limit of detection of 1.9mM. The biosensor has a minimum lifetime of 9 days and has been applied to glucose determination in drinks. The applicability of the sensor was tested by glucose determination in two fruit juices. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. In situ detection of atomic and molecular iodine using Resonance and Off-Resonance Fluorescence by Lamp Excitation: ROFLEX

    Directory of Open Access Journals (Sweden)

    J. C. Gómez Martín

    2011-01-01

    Full Text Available We demonstrate a new instrument for in situ detection of atmospheric iodine atoms and molecules based on atomic and molecular resonance and off-resonance ultraviolet fluorescence excited by lamp emission. The instrument combines the robustness, light weight, low power consumption and efficient excitation of radio-frequency discharge light sources with the high sensitivity of the photon counting technique. Calibration of I2 fluorescence is achieved via quantitative detection of the molecule by Incoherent Broad Band Cavity-enhanced Absorption Spectroscopy. Atomic iodine fluorescence signal is calibrated by controlled broad band photolysis of known I2 concentrations in the visible spectral range at atmospheric pressure. The instrument has been optimised in laboratory experiments to reach detection limits of 1.2 pptv for I atoms and 13 pptv for I2, for S/N = 1 and 10 min of integration time. The ROFLEX system has been deployed in a field campaign in northern Spain, representing the first concurrent observation of ambient mixing ratios of iodine atoms and molecules in the 1–350 pptv range.

  6. Analysis of Indium Tin Oxide Film Using Argon Fluroide (ArF) Laser-Excited Atomic Fluorescence of Ablated Plumes.

    Science.gov (United States)

    Ho, Sut Kam; Garcia, Dario Machado

    2017-04-01

    A two-pulse laser-excited atomic fluorescence (LEAF) technique at 193 nm wavelength was applied to the analysis of indium tin oxide (ITO) layer on polyethylene terephthalate (PET) film. Fluorescence emissions from analytes were induced from plumes generated by first laser pulse. Using this approach, non-selective LEAF can be accomplished for simultaneous multi-element analysis and it overcomes the handicap of strict requirement for laser excitation wavelength. In this study, experimental conditions including laser fluences, times for gating and time delay between pulses were optimized to reveal high sensitivity with minimal sample destruction and penetration. With weak laser fluences of 100 and 125 mJ/cm 2 for 355 and 193 nm pulses, detection limits were estimated to be 0.10% and 0.43% for Sn and In, respectively. In addition, the relation between fluorescence emissions and number of laser shots was investigated; reproducible results were obtained for Sn and In. It shows the feasibility of depth profiling by this technique. Morphologies of samples were characterized at various laser fluences and number of shots to examine the accurate penetration. Images of craters were also investigated using scanning electron microscopy (SEM). The results demonstrate the imperceptible destructiveness of film after laser shot. With such weak laser fluences and minimal destructiveness, this LEAF technique is suitable for thin-film analysis.

  7. Two-photon polarization Fourier spectroscopy of metastable atomic hydrogen

    International Nuclear Information System (INIS)

    Duncan, A.J.; Beyer, H.-J.; Kleinpoppen, H.; Sheikh, Z.A,; B-Z Univ., Multan

    1997-01-01

    A novel Fourier-transform spectroscopic method using two-photon polarization to determine the spectral distribution of the two photons emitted in the spontaneous decay of metastable atomic hydrogen is described. The method uses birefringent retardation plates and takes advantage of the subtle interplay between the spectral properties and the entangled polarization properties of the radiation emitted in the decay. Assuming the validity of the theoretical spectral distribution, it is shown that the experimental results agree well with theory. On the other hand, success in solving the inverse problem of determining the spectral distribution from the experimental results is limited by the small number of experimental points. However, making reasonable assumptions it is deduced that the observed spectrum is characterized by a broadband signal of width (0.43 ± 0.06) x 10 16 rad s -1 and centre angular frequency (0.77 ± 0.03) x 10 16 rad s -1 in good agreement with the predictions of 0.489 x 10 16 rad s -1 and 0.775 x 10 16 rad s -1 , respectively, obtained from the theoretical spectral distribution modified to take account of the absorption of the two-photon radiation in air. The values of 1.5 fs for the coherence time and 440 nm for the coherence length for single photons of the two-photon pair which are obtained from the measured bandwidth imply that, in the ideal case, these values are determined by the essentially zero lifetime of the virtual intermediate state of the decay process rather than the long lifetime of the metastable state which, it is suggested, determines the coherence time and coherence length appropriate to certain types of fourth-order interference experiments. (Author)

  8. Two-Photon Absorption in Organometallic Bromide Perovskites

    KAUST Repository

    Walters, Grant

    2015-07-21

    Organometallic trihalide perovskites are solution processed semiconductors that have made great strides in third generation thin film light harvesting and light emitting optoelectronic devices. Recently it has been demonstrated that large, high purity single crystals of these perovskites can be synthesized from the solution phase. These crystals’ large dimensions, clean bandgap, and solid-state order, have provided us with a suitable medium to observe and quantify two-photon absorption in perovskites. When CH3NH3PbBr3 single crystals are pumped with intense 800 nm light, we observe band-to-band photoluminescence at 572 nm, indicative of two-photon absorption. We report the nonlinear absorption coefficient of CH3NH3PbBr3 perovskites to be 8.6 cm GW-1 at 800 nm, comparable to epitaxial single crystal semiconductors of similar bandgap. We have leveraged this nonlinear process to electrically autocorrelate a 100 fs pulsed laser using a two-photon perovskite photodetector. This work demonstrates the viability of organometallic trihalide perovskites as a convenient and low-cost nonlinear absorber for applications in ultrafast photonics.

  9. Particle Production in Two-Photon Collisions at Belle

    International Nuclear Information System (INIS)

    Nakazawa, Hideyuki

    2010-01-01

    Experimental study of η η production in two-photon collisions: The differential cross section for the process γ γ → η η has been measured in the kinematic range above the η η threshold, 1.096 GeV -1 data sample collected with the Belle detector at the KEKB e + e - collider. In the W range 1.1-2.0 GeV/c 2 we perform an analysis of resonance amplitudes for various partial waves; at higher energy we extract the contributions of χ cJ charmonia and compare the energy and angular dependence of the cross section with the predictions of theoretical models. Observation of η c (2S) in six-prong final states produced in two-photon collisions: We report the observation of η c (2S), produced in two-photon collisions, and decaying to the six-prong final states 3(π + π - ), K + K - 2(π + π - ), and K 0 S K + ππ + π - (including the charge-conjugate state). This analysis is based on a large data sample accumulated by the Belle experiment at the KEKB asymmetric-energy electron-positron collider. This is the first observation of decay modes of the η c (2S) other than K 0 S K + π - . (author)

  10. Two-photon exchange in elastic electron-nucleon scattering

    International Nuclear Information System (INIS)

    Blunden, P.G.; Melnitchouk, W.; Tjon, J.A.

    2005-01-01

    A detailed study of two-photon exchange in unpolarized and polarized elastic electron-nucleon scattering is presented, taking particular account of nucleon finite size effects. Contributions from nucleon elastic intermediate states are found to have a strong angular dependence, which leads to a partial resolution of the discrepancy between the Rosenbluth and polarization transfer measurements of the proton electric to magnetic form factor ratio, G E /G M . The two-photon exchange contribution to the longitudinal polarization transfer P L is small, whereas the contribution to the transverse polarization transfer P T is enhanced at backward angles by several percent, increasing with Q 2 . This gives rise to a small, E /G M obtained from the polarization transfer ratio P T /P L at large Q 2 . We also compare the two-photon exchange effects with data on the ratio of e + p to e - p cross sections, which is predicted to be enhanced at backward angles. Finally, we evaluate the corrections to the form factors of the neutron and estimate the elastic intermediate state contribution to the 3 He form factors

  11. Two-Photon Absorption in Organometallic Bromide Perovskites

    KAUST Repository

    Walters, Grant; Sutherland, Brandon R; Hoogland, Sjoerd; Shi, Dong; Comin, Riccardo; Sellan, Daniel P.; Bakr, Osman; Sargent, Edward H.

    2015-01-01

    Organometallic trihalide perovskites are solution processed semiconductors that have made great strides in third generation thin film light harvesting and light emitting optoelectronic devices. Recently it has been demonstrated that large, high purity single crystals of these perovskites can be synthesized from the solution phase. These crystals’ large dimensions, clean bandgap, and solid-state order, have provided us with a suitable medium to observe and quantify two-photon absorption in perovskites. When CH3NH3PbBr3 single crystals are pumped with intense 800 nm light, we observe band-to-band photoluminescence at 572 nm, indicative of two-photon absorption. We report the nonlinear absorption coefficient of CH3NH3PbBr3 perovskites to be 8.6 cm GW-1 at 800 nm, comparable to epitaxial single crystal semiconductors of similar bandgap. We have leveraged this nonlinear process to electrically autocorrelate a 100 fs pulsed laser using a two-photon perovskite photodetector. This work demonstrates the viability of organometallic trihalide perovskites as a convenient and low-cost nonlinear absorber for applications in ultrafast photonics.

  12. One- and two-photon spectra of Nd3+ clusters in CaF2 and SrF2 crystals

    International Nuclear Information System (INIS)

    Basiev, Tasoltan T; Voronov, Valerii V; Glotova, M Yu; Papashvili, A G; Karasik, Aleksandr Ya

    2003-01-01

    The polarised two-photon (IR) and one-photon (visible) luminescence excitation spectra of Nd 3+ nanoclusters in CaF 2 and SrF 2 crystals are measured at 10 K using a F - 2 :LiF colour centre laser tunable in spectral ranges 1090 - 1230 nm and 545 - 615 nm with an emission linewidth of ∼0.02 - 0.03 cm -1 , an average output power of ∼55 mW, and a pulse repetition rate of 10 Hz. The two-photon excitation spectra at the 4 I 9/2 → 4 G 5/2 transition reveal the structure, which is absent upon one-photon excitation, which can be explained by different selection rules for some Stark - Stark transitions upon one- and two-photon absorption. (special issue devoted to the memory of academician a m prokhorov)

  13. Evaluation of an inductively-coupled plasma with an extended-sleeve torch as an atomization cell for laser-excited fluorescence spectrometry.

    Science.gov (United States)

    Kosinski, M A; Uchida, H; Winefordner, J D

    1983-05-01

    An inductively-coupled plasma (ICP) with an extended-sleeve torch has been evaluated as an atomization cell for laser-excited fluorescence spectrometry. Limits of detection for 20 lines are given. The detection power is almost equivalent to that obtained by excitation with a hollow-cathode lamp. Interelement effects and spectral interferences are discussed.

  14. 340nm UV LED excitation in time-resolved fluorescence system for europium-based immunoassays detection

    DEFF Research Database (Denmark)

    Rodenko, Olga; Fodgaard, Henrik; Tidemand-Lichtenberg, Peter

    2017-01-01

    In immunoassay analyzers for in-vitro diagnostics, Xenon flash lamps have been widely used as excitation light sources. Recent advancements in UV LED technology and its advantages over the flash lamps such as smaller footprint, better wall-plug efficiency, narrow emission spectrum......, and no significant afterglow, have made them attractive light sources for gated detection systems. In this paper, we report on the implementation of a 340 nm UV LED based time-resolved fluorescence system based on europium chelate as a fluorescent marker. The system performance was tested with the immunoassay based...... on the cardiac marker, TnI. The same signal-to-noise ratio as for the flash lamp based system was obtained, operating the LED below specified maximum current. The background counts of the system and its main contributors were measured and analyzed. The background of the system of the LED based unit was improved...

  15. Long-lived visible luminescence of UV LEDs and impact on LED excited time-resolved fluorescence applications

    International Nuclear Information System (INIS)

    Jin, D; Connally, R; Piper, J

    2006-01-01

    We report the results of a detailed study of the spectral and temporal properties of visible emission from three different GaN-based ultraviolet (UV) light emitting diodes (UV LEDs). The primary UV emission in the 360-380 nm band decays rapidly (less than 1 μs) following switch-off; however, visible luminescence (470-750 nm) with a decay lifetime of tens of microseconds was observed at approximately 10 -4 of the UV intensity. For applications of UV LEDs in time-resolved fluorescence (TRF) employing lanthanide chelates, the visible luminescence from the LEDs competes with the target Eu 3+ or Tb 3+ fluorescence in both spectral and temporal domains. A UV band-pass filter (Schott UG11 glass) was therefore used to reduce the visible luminescence of the UV LEDs by three orders of magnitude relative to UV output to yield a practical excitation source for TRF

  16. N-Annulated perylene-substituted and fused porphyrin dimers with intense near-infrared one-photon and two-photon absorption

    KAUST Repository

    Luo, Jie

    2015-01-21

    Fusion of two N-annulated perylene (NP) units with a fused porphyrin dimer along the S0-S1 electronic transition moment axis has resulted in new near-infrared (NIR) dyes 1a/1b with very intense absorption (ε>1.3×105M-1cm-1) beyond 1250nm. Both compounds displayed moderate NIR fluorescence with fluorescence quantum yields of 4.4×10-6 and 6.0×10-6 for 1a and 1b, respectively. The NP-substituted porphyrin dimers 2a/2b have also been obtained by controlled oxidative coupling and cyclodehydrogenation, and they showed superimposed absorptions of the fused porphyrin dimer and the NP chromophore. The excited-state dynamics of all of these compounds have been studied by femtosecond transient absorption measurements, which revealed porphyrin dimer-like behaviour. These new chromophores also exhibited good nonlinear optical susceptibility with large two-photon absorption cross-sections in the NIR region due to extended π-conjugation. Time-dependent density functional theory calculations have been performed to aid our understanding of their electronic structures and absorption spectra.

  17. Fluorescence lifetime selectivity in excitation-emission matrices for qualitative analysis of a two-component system

    International Nuclear Information System (INIS)

    Millican, D.W.; McGown, L.B.

    1989-01-01

    Steady-state fluorescence excitation-emission matrices (EEMs), and phase-resolved EEMs (PREEMs) collected at modulation frequencies of 6, 18, and 30 MHz, were used for qualitative analysis of mixtures of benzo[k]fluoranthene (τ = 8 ns) and benzo[b]fluoranthene (τ = 29 ns) in ethanol. The EEMs of the individual components were extracted from mixture EEMs by means of wavelength component vector-gram (WCV) analysis. Phase resolution was found to be superior to steady-state measurements for extraction of the component spectra, for mixtures in which the intensity contributions from the two components are unequal

  18. Mapping the Local Organization of Cell Membranes Using Excitation-Polarization-Resolved Confocal Fluorescence Microscopy

    OpenAIRE

    Kress, Alla; Wang, Xiao; Ranchon, Hubert; Savatier, Julien; Rigneault, Hervé; Ferrand, Patrick; Brasselet, Sophie

    2013-01-01

    International audience; Fluorescence anisotropy and linear dichroism imaging have been widely used for imaging biomolecular orientational distributions in protein aggregates, fibrillar structures of cells, and cell membranes. However, these techniques do not give access to complete orientational order information in a whole image, because their use is limited to parts of the sample where the average orientation of molecules is known a priori. Fluorescence anisotropy is also highly sensitive t...

  19. Magnetic-Field Induced Enhancement in the Fluorescence Yield Spectrum of Doubly Excited States in Helium

    International Nuclear Information System (INIS)

    Stroem, Magnus; Saathe, Conny; Agaaker, Marcus; Soederstroem, Johan; Rubensson, Jan-Erik; Stranges, Stefano; Richter, Robert; Alagia, Michele; Gorczyca, T. W.; Robicheaux, F.

    2006-01-01

    An influence of static magnetic fields on the fluorescence yield spectrum of He in the vicinity of the N=2 thresholds has been observed. The experimental results are in excellent agreement with predictions based on multichannel quantum defect theory, and it is demonstrated that the Rydberg electron l mixing due to the diamagnetic interaction is essential for the description of the observed fluorescence yield intensity enhancement

  20. Excitation of Surface Plasmon Polaritons by Fluorescent Light from Organic Nanofibers

    DEFF Research Database (Denmark)

    Sobolewska, Elżbieta Karolina; Jozefowski, Leszek; Kawalec, Tomasz

    2017-01-01

    -coherent excitation indicates its prospect for future integrated systems. To support our experimental results, we investigate the proposed geometries by analytical calculations and finite-difference-time-domain (FDTD) modelling. The experimentally obtained angular leakage radiation peak positions can readily...... be predicted by our analytical calculations. Nevertheless, the experimental results exhibit a distinct asymmetry in the peak intensities. In agreement with our FDTD calculations, we address this asymmetrical SPP excitation to the nanofiber molecular orientation. The proposed structure’s high flexibility...

  1. Fluorescence enhancement and quenching of Eu(TTFA)3 by Ag nanoparticles at different excitations

    International Nuclear Information System (INIS)

    Wang, Qingru; Shi, Qiang; Li, Shuhong; Wang, Wenjun; Zheng, Shiling

    2015-01-01

    The luminescence properties of Eu(TTFA) 3 complex in presence of silver nanoparticles were investigated at three excitation wavelengths of 350 nm, 383 nm and 463 nm, respectively. Luminescence quenching and enhancement were both observed at three different excitation and emission wavelengths. Luminescence at 612 nm, 578 nm, 590 nm and 650 nm were enhanced at excitation wavelength of 350 nm, and quenched at excitation wavelength of 383 nm. The enhancement factor reached to 1.6 and the quench factor was about 0.65. For 463 nm excitation, the luminescence at 612 nm was quenched, and the quench factor reached to 0.85. Luminescence at other three emission wavelengths (578 nm, 590 nm, and 650 nm) was enhanced, with the greatest enhancement factor of ∼5. - Highlights: • The luminescence enhancement and quenching were both obtained by using the Ag nanoparticles. • The luminescence enhancement and quenching highly depends on the excitation and emission wavelengths. • The enhancement factor of luminescence also has a great relationship with the intrinsic quantum yield

  2. Spatial discrimination against background with different optical systems for collection of fluorescence in laser-excited atomic fluorescence spectrometry with a graphite tube electrothermal atomizer.

    Science.gov (United States)

    Yuzefovsky, A I; Lonardo, R F; Michel, R G

    1995-07-01

    A single 90 degrees off-axis ellipsoidal mirror fragment was used in a dispersive detection system for electrothermal atomization laser-excited atomic fluorescence spectrometry. The performance of the new optical arrangement was compared with those of optical arrangements that employed a plane mirror in combination with biconvex or plano-convex lenses. All the optical arrangements collected fluorescence in a scheme called front surface illustration. BEAM-4, an optical ray tracing program, was used for calculations of spatial ray distributions and optical collection efficiency for the various optical configurations. Experimentally, the best collection efficiency was obtained by use of the ellipsoidal mirror, in qualitative agreement with simulations done by use of the BEAM-4 software. The best detection limit for cobalt with the new optical arrangement was 20 fg, which was a factor of 5 better than that obtained with conventional optical arrangements with otherwise the same instrumentation. The signal-to-background ratio and the fluorescence collection efficiency were also studied as a function of position of the optical components for the various optical arrangements. For both cobalt and phosphorus, the signal-to-background ratio with the new optical arrangement remained stable within 10-20% during +/- 8 mm shifts in the position of the detection system from the focal plane of the optics. Overall, the new optical arrangement offered high collection efficiency, excellent sensitivity, and facile optical alignment due to efficient spatial separation between the fluorescence signal and the background radiation. The advantages of the new optical arrangement were particularly important during measurements in the presence of high levels of blackbody radiation.

  3. Towards Precision Measurement of the 21S0-31D2 Two-Photon Transition in Atomic Helium

    Science.gov (United States)

    Huang, Yi-Jan; Guan, Yu-Chan; Suen, Te-Hwei; Wang, Li-Bang; Shy, Jow-Tsong

    2017-04-01

    We intend to accurately measure the frequency for 2S-3D two-photon transition and to deduce the 2S ionization energy to an accuracy below 100 kHz from the theoretical calculation of the 3D state. In this talk, we present a precision measurement of the 21S0 -31D2 two-photon transition in atomic helium at 1009 nm. A master oscillator power amplifier (MOPA) is seeded by an external cavity diode laser (ECDL) is constructed to generate more than 700 mW laser power with TEM00 beam profile at 1009 nm. To observe the two-photon transition, a helium cell is placed inside a power enhancement optical cavity and the helium atoms at 21S metastable level are prepared by a pulsed RF discharge and monitor the 668 nm 31D2 to 21P1 fluorescence after RF discharge is turned off . The absolute frequency metrology of the ECDL is carried out by an Er-fiber optical frequency comb (OFC). The two-photon spectrum is obtained by tuning the repetition frequency of the OFC. The 21S0-31D2 frequency is determined to be 594414291.967 (80) MHz in He-4. More results will be presented at the annual meeting.

  4. Characterization of CDOM of river waters in China using fluorescence excitation-emission matrix and regional integration techniques

    Science.gov (United States)

    Zhao, Ying; Song, Kaishan; Shang, Yingxin; Shao, Tiantian; Wen, Zhidan; Lv, Lili

    2017-08-01

    The spatial characteristics of fluorescent dissolved organic matter (FDOM) components in river waters in China were first examined by excitation-emission matrix spectra and fluorescence regional integration (FRI) with the data collected during September to November between 2013 and 2015. One tyrosine-like (R1), one tryptophan-like (R2), one fulvic-like (R3), one microbial protein-like (R4), and one humic-like (R5) components have been identified by FRI method. Principal component analysis (PCA) was conducted to assess variations in the five FDOM components (FRί (ί = 1, 2, 3, 4, and 5)) and the humification index for all 194 river water samples. The average fluorescence intensities of the five fluorescent components and the total fluorescence intensities FSUM differed under spatial variation among the seven major river basins (Songhua, Liao, Hai, Yellow and Huai, Yangtze, Pearl, and Inflow Rivers) in China. When all the river water samples were pooled together, the fulvic-like FR3 and the humic-like FR5 showed a strong positive linear relationship (R2 = 0.90, n = 194), indicating that the two allochthonous FDOM components R3 and R5 may originate from similar sources. There is a moderate strong positive correlation between the tryptophan-like FR2 and the microbial protein-like FR4 (R2 = 0.71, n = 194), suggesting that parts of two autochthonous FDOM components R2 and R4 are likely from some common sources. However, the total allochthonous substance FR(3+5) and the total autochthonous substances FR(1+2+4) exhibited a weak correlation (R2 = 0.40, n = 194). Significant positive linear relationships between FR3 (R2 = 0.69, n = 194), FR5 (R2 = 0.79, n = 194), and chromophoric DOM (CDOM) absorption coefficient a(254) were observed, which demonstrated that the CDOM absorption was dominated by the allochthonous FDOM components R3 and R5.

  5. Inclusive $D*^{+-}$ Production in Two-Photon Collisions at LEP

    CERN Document Server

    Achard, P.; Aguilar-Benitez, M.; Alcaraz, J.; Alemanni, G.; Allaby, J.; Aloisio, A.; Alviggi, M.G.; Anderhub, H.; Andreev, Valery P.; Anselmo, F.; Arefev, A.; Azemoon, T.; Aziz, T.; Bagnaia, P.; Bajo, A.; Baksay, G.; Baksay, L.; Baldew, S.V.; Banerjee, S.; Banerjee, Sw.; Barczyk, A.; Barillere, R.; Bartalini, P.; Basile, M.; Batalova, N.; Battiston, R.; Bay, A.; Becattini, F.; Becker, U.; Behner, F.; Bellucci, L.; Berbeco, R.; Berdugo, J.; Berges, P.; Bertucci, B.; Betev, B.L.; Biasini, M.; Biglietti, M.; Biland, A.; Blaising, J.J.; Blyth, S.C.; Bobbink, G.J.; Bohm, A.; Boldizsar, L.; Borgia, B.; Bottai, S.; Bourilkov, D.; Bourquin, M.; Braccini, S.; Branson, J.G.; Brochu, F.; Burger, J.D.; Burger, W.J.; Cai, X.D.; Capell, M.; Cara Romeo, G.; Carlino, G.; Cartacci, A.; Casaus, J.; Cavallari, F.; Cavallo, N.; Cecchi, C.; Cerrada, M.; Chamizo, M.; Chang, Y.H.; Chemarin, M.; Chen, A.; Chen, G.; Chen, G.M.; Chen, H.F.; Chen, H.S.; Chiefari, G.; Cifarelli, L.; Cindolo, F.; Clare, I.; Clare, R.; Coignet, G.; Colino, N.; Costantini, S.; de la Cruz, B.; Cucciarelli, S.; van Dalen, J.A.; de Asmundis, R.; Deglon, P.; Debreczeni, J.; Degre, A.; Deiters, K.; della Volpe, D.; Delmeire, E.; Denes, P.; DeNotaristefani, F.; De Salvo, A.; Diemoz, M.; Dierckxsens, M.; Dionisi, C.; Dittmar, M.; Doria, A.; Dova, M.T.; Duchesneau, D.; Echenard, B.; Eline, A.; El Mamouni, H.; Engler, A.; Eppling, F.J.; Ewers, A.; Extermann, P.; Falagan, M.A.; Falciano, S.; Favara, A.; Fay, J.; Fedin, O.; Felcini, M.; Ferguson, T.; Fesefeldt, H.; Fiandrini, E.; Field, J.H.; Filthaut, F.; Fisher, P.H.; Fisher, W.; Fisk, I.; Forconi, G.; Freudenreich, K.; Furetta, C.; Galaktionov, Iouri; Ganguli, S.N.; Garcia-Abia, Pablo; Gataullin, M.; Gentile, S.; Giagu, S.; Gong, Z.F.; Grenier, Gerald Jean; Grimm, O.; Gruenewald, M.W.; Guida, M.; van Gulik, R.; Gupta, V.K.; Gurtu, A.; Gutay, L.J.; Haas, D.; Hakobyan, R.S.; Hatzifotiadou, D.; Hebbeker, T.; Herve, Alain; Hirschfelder, J.; Hofer, H.; Hohlmann, M.; Holzner, G.; Hou, S.R.; Hu, Y.; Jin, B.N.; Jones, Lawrence W.; de Jong, P.; Josa-Mutuberria, I.; Kafer, D.; Kaur, M.; Kienzle-Focacci, M.N.; Kim, J.K.; Kirkby, Jasper; Kittel, W.; Klimentov, A.; Konig, A.C.; Kopal, M.; Koutsenko, V.; Kraber, M.; Kraemer, R.W.; Krenz, W.; Kruger, A.; Kunin, A.; Ladron de Guevara, P.; Laktineh, I.; Landi, G.; Lebeau, M.; Lebedev, A.; Lebrun, P.; Lecomte, P.; Lecoq, P.; Le Coultre, P.; Le Goff, J.M.; Leiste, R.; Levtchenko, M.; Levtchenko, P.; Li, C.; Likhoded, S.; Lin, C.H.; Lin, W.T.; Linde, F.L.; Lista, L.; Liu, Z.A.; Lohmann, W.; Longo, E.; Lu, Y.S.; Lubelsmeyer, K.; Luci, C.; Luminari, L.; Lustermann, W.; Ma, W.G.; Malgeri, L.; Malinin, A.; Mana, C.; Mangeol, D.; Mans, J.; Martin, J.P.; Marzano, F.; Mazumdar, K.; McNeil, R.R.; Mele, S.; Merola, L.; Meschini, M.; Metzger, W.J.; Mihul, A.; Milcent, H.; Mirabelli, G.; Mnich, J.; Mohanty, G.B.; Muanza, G.S.; Muijs, A.J.M.; Musicar, B.; Musy, M.; Nagy, S.; Natale, S.; Napolitano, M.; Nessi-Tedaldi, F.; Newman, H.; Niessen, T.; Nisati, A.; Kluge, Hannelies; Ofierzynski, R.; Organtini, G.; Palomares, C.; Pandoulas, D.; Paolucci, P.; Paramatti, R.; Passaleva, G.; Patricelli, S.; Paul, Thomas Cantzon; Pauluzzi, M.; Paus, C.; Pauss, F.; Pedace, M.; Pensotti, S.; Perret-Gallix, D.; Petersen, B.; Piccolo, D.; Pierella, F.; Pioppi, M.; Piroue, P.A.; Pistolesi, E.; Plyaskin, V.; Pohl, M.; Pojidaev, V.; Pothier, J.; Prokofev, D.O.; Prokofiev, D.; Quartieri, J.; Rahal-Callot, G.; Rahaman, M.A.; Raics, P.; Raja, N.; Ramelli, R.; Rancoita, P.G.; Ranieri, R.; Raspereza, A.; Razis, P.; Ren, D.; Rescigno, M.; Reucroft, S.; Riemann, S.; Riles, Keith; Roe, B.P.; Romero, L.; Rosca, A.; Rosier-Lees, S.; Roth, Stefan; Rosenbleck, C.; Roux, B.; Rubio, J.A.; Ruggiero, G.; Rykaczewski, H.; Sakharov, A.; Saremi, S.; Sarkar, S.; Salicio, J.; Sanchez, E.; Sanders, M.P.; Schafer, C.; Schegelsky, V.; Schmidt-Kaerst, S.; Schmitz, D.; Schopper, H.; Schotanus, D.J.; Schwering, G.; Sciacca, C.; Servoli, L.; Shevchenko, S.; Shivarov, N.; Shoutko, V.; Shumilov, E.; Shvorob, A.; Siedenburg, T.; Son, D.; Spillantini, P.; Steuer, M.; Stickland, D.P.; Stoyanov, B.; Straessner, A.; Sudhakar, K.; Sultanov, G.; Sun, L.Z.; Sushkov, S.; Suter, H.; Swain, J.D.; Szillasi, Z.; Tang, X.W.; Tarjan, P.; Tauscher, L.; Taylor, L.; Tellili, B.; Teyssier, D.; Timmermans, Charles; Ting, Samuel C.C.; Ting, S.M.; Tonwar, S.C.; Toth, J.; Tully, C.; Tung, K.L.; Ulbricht, J.; Valente, E.; Van de Walle, R.T.; Veszpremi, V.; Vesztergombi, G.; Vetlitsky, I.; Vicinanza, D.; Viertel, G.; Villa, S.; Vivargent, M.; Vlachos, S.; Vodopianov, I.; Vogel, H.; Vogt, H.; Vorobev, I.; Vorobyov, A.A.; Wadhwa, M.; Wallraff, W.; Wang, X.L.; Wang, Z.M.; Weber, M.; Wienemann, P.; Wilkens, H.; Wynhoff, S.; Xia, L.; Xu, Z.Z.; Yamamoto, J.; Yang, B.Z.; Yang, C.G.; Yang, H.J.; Yang, M.; Yeh, S.C.; Zalite, A.; Zalite, Yu.; Zhang, Z.P.; Zhao, J.; Zhu, G.Y.; Zhu, R.Y.; Zhuang, H.L.; Zichichi, A.; Zilizi, G.; Zimmermann, B.; Zoller, M.

    2002-01-01

    Inclusive D^{*+-} production in two-photon collisions is studied with the L3 detector at LEP, using 683 pb^{-1} of data collected at centre-of-mass energies from 183 to 208 GeV. Differential cross sections are determined as functions of the transverse momentum and pseudorapidity of the D^{*+-} mesons in the kinematic region 1 GeV e^+e^-D^{*+-}X)$ in this kinematical region is measured and the sigma(e^+e^- ---> e^+e^- cc{bar}X) cross section is derived. The measurements are compared with next-to-leading order perturbative QCD calculations.

  6. New two-photon based nanoscopic modalities and optogenetics

    DEFF Research Database (Denmark)

    Glückstad, Jesper

    that can be equipped with optical trapping handles for convenient mechanical control using only optical forces [6]. These microstructures illustrated above can be effectively handled with simultaneous top- and side-view on our BioPhotonics Workstation to undertake six-degree-of-freedom optical actuation...... of two-photon polymerised microstructures equipped with features easily entering the submicron-regime. Aided by European collaborators who fabricated test structures with built-in waveguides for us, we were able to put the idea of optically steerable freestanding waveguides – coined: wave-guided optical...

  7. Two photon production of charm states - a charmonium calculation

    International Nuclear Information System (INIS)

    Suaya, R.

    1980-03-01

    The comparison of the nonrelativistic multichannel calculation with the double Rutherford process shows that duality is satisfied, in the sense that if one averages the actual cross sections for a wide enough range of W one gets the same result as for nonstrongly interacting point like quarks. It has been shown for the case of e + e - annihilation that duality in this sense follows from nonrelativistic potential models; and it has been verified that this proof can be extended to two-photon processes

  8. Two-photon exclusive processes in quantum chromodynamics

    International Nuclear Information System (INIS)

    Brodsky, S.J.

    1986-07-01

    QCD predictions for γγ annihilation into single mesons, meson pairs, and baryon pairs are reviewed. Two-photon exclusive processes provide the most sensitive and practical measure of the distribution amplitudes, and thus a critical confrontation between QCD and experiment. Both the angular distribution and virtual photon mass dependence of these amplitudes are sensitive to the shapes of the phi (chi, Q). Novel effects involving the production of qq anti q anti q states at threshold are also discussed, and a new method is presented for systematically incorporating higher-order QCD corrections in γγ reactions

  9. Two-photon exclusive processes in quantum chromodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Brodsky, S.J.

    1986-07-01

    QCD predictions for ..gamma gamma.. annihilation into single mesons, meson pairs, and baryon pairs are reviewed. Two-photon exclusive processes provide the most sensitive and practical measure of the distribution amplitudes, and thus a critical confrontation between QCD and experiment. Both the angular distribution and virtual photon mass dependence of these amplitudes are sensitive to the shapes of the phi (chi, Q). Novel effects involving the production of qq anti q anti q states at threshold are also discussed, and a new method is presented for systematically incorporating higher-order QCD corrections in ..gamma gamma.. reactions.

  10. Direct and indirect two-photon processes in semiconductors

    International Nuclear Information System (INIS)

    Hassan, A.R.

    1986-07-01

    The expressions describing direct and indirect two-photon absorption in crystals are given. They are valid both near and far from the energy gap. A perturbative approach through two different band models is adopted. The effects of the non-parabolicity and the degeneracy of the energy bands are considered. The numerical results are compared with the other theories and with a recent experimental data in Zn and AgCl. It is shown that the dominant transition mechanisms are of the allowed-allowed type near and far from the gap for both direct and indirect processes. (author)

  11. {Lambda}{bar {Lambda}} production in two-photon interactions

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, S.; Kubota, Y.; Lattery, M.; ONeill, J.J.; Patton, S.; Poling, R.; Riehle, T.; Savinov, V.; Smith, A. [University of Minnesota, Minneapolis, Minnesota 55455 (United States); Alam, M.S.; Athar, S.B.; Ling, Z.; Mahmood, A.H.; Severini, H.; Timm, S.; Wappler, F. [State University of New York at Albany, Albany, New York 12222 (United States); Anastassov, A.; Blinov, S.; Duboscq, J.E.; Fujino, D.; Fulton, R.; Gan, K.K.; Hart, T.; Honscheid, K.; Kagan, H.; Kass, R.; Lee, J.; Spencer, M.B.; Sung, M.; Undrus, A.; Wanke, R.; Wolf, A.; Zoeller, M.M. [Ohio State University, Columbus, Ohio 43210 (United States); Nemati, B.; Richichi, S.J.; Ross, W.R.; Skubic, P.; Wood, M. [University of Oklahoma, Norman, Oklahoma 73019 (United States); Bishai, M.; Fast, J.; Gerndt, E.; Hinson, J.W.; Menon, N.; Miller, D.H.; Shibata, E.I.; Shipsey, I.P.; Yurko, M. [Purdue University, West Lafayette, Indiana 47907 (United States); Gibbons, L.; Johnson, S.D.; Kwon, Y.; Roberts, S.; Thorndike, E.H. [University of Rochester, Rochester, New York 14627 (United States); Jessop, C.P.; Lingel, K.; Marsiske, H.; Perl, M.L.; Schaffner, S.F.; Ugolini, D.; Wang, R.; Zhou, X. [Stanford Linear Accelerator Center, Stanford University, Stanford, California 94309 (United States); Coan, T.E.; Fadeyev, V.; Korolkov, I.; Maravin, Y.; Narsky, I.; Shelkov, V.; Staeck, J.; Stroynowski, R.; Volobouev, I.; Ye, J. [Southern Methodist University, Dallas, Texas 75275 (United States); Artuso, M.; Efimov, A.; Frasconi, F.; Gao, M.; Goldberg, M.; He, D.; Kopp, S.; Moneti, G.C.; Mountain, R.; Mukhin, Y.; Schuh, S.; Skwarnicki, T.; Stone, S.; Viehhauser, G.; Xing, X. [Syracuse University, Syracuse, New York 13244 (United States); Bartelt, J.; Csorna, S.E.; Jain, V.; Marka, S. [Vanderbilt University, Nashville, Tennessee 37235 (United States); Freyberger, A.; Gibaut, D.; Godang, R.; Kinoshita, K.; Lai, I.C.; Pomianowski, P.; Schrenk, S.; and others

    1997-09-01

    Using the CLEO detector at the Cornell e{sup +}e{sup {minus}} storage ring CESR we study the two-photon production of {Lambda}{bar {Lambda}}, making the first observation of {gamma}{gamma}{r_arrow}{Lambda}{bar {Lambda}}. We present the cross section for {gamma}{gamma}{r_arrow}{Lambda}{bar {Lambda}} as a function of the {gamma}{gamma} center of mass energy and compare it to that predicted by the quark-diquark model. {copyright} {ital 1997} {ital The American Physical Society}

  12. Time-resolved UV-excited microarray reader for fluorescence energy transfer (FRET) measurements

    Science.gov (United States)

    Orellana, Adelina; Hokkanen, Ari P.; Pastinen, Tomi; Takkinen, Kristina; Soderlund, Hans

    2001-05-01

    Analytical systems based on immunochemistry are largely used in medical diagnostics and in biotechnology. There is a significant pressure to develop the present assay formats to become easier to use, faster, and less reagent consuming. Further developments towards high density array--like multianalyte measurement systems would be valuable. To this aim we have studied the applicability of fluorescence resonance energy transfer and time-resolved fluorescence resonance energy transfer in immunoassays on microspots and in microwells. We have used engineered recombinant antibodies detecting the pentameric protein CRP as a model analyte system, and tested different assay formats. We describe also the construction of a time-resolved scanning epifluorometer with which we could measure the FRET interaction between the slow fluorescence decay from europium chelates and its energy transfer to the rapidly decaying fluorophore Cy5.

  13. Determination of mercury in microwave-digested soil by laser-excited atomic fluorescence spectrometry with electrothermal atomization.

    Science.gov (United States)

    Pagano, S T; Smith, B W; Winefordner, J D

    1994-12-01

    A sample digestion procedure was developed which employs microwave heating of soil and sediment in concentrated nitric acid in a high-pressure closed vessel. Complete dissolution of mercury into the sample solution occurs within 5 min at 59 W/vessel without loss of analyte through overpressurization. Laser-excited atomic fluorescence spectrometry with electrothermal atomization (LEAFS-ETA) was used as the detection method. The scheme uses a two-step excitation, with lambda(1) = 253.7 nm and lambda(2) = 435.8 nm. Direct line fluorescence was measured at 546.2 nm. The absolute instrumental limit of detection was 14 fg; 1.4 pg/ml with a 10 mul sample injection. The recoveries of mercury in two spiked samples were 94 and 98%. The SRM 8406 (Mercury in River Sediment) was digested and analyzed for mercury, and the results (58.4 +/- 1.8 ng/g) agreed well with the reference value of 60 ng/g. The results obtained by LEAFS-ETA with microwave sample digestion are in good agreement with those found by cold vapor atomic absorption spectrometry with EPA Series Method 245.5 sample digestion, which is one of the most commonly used methods for the determination of mercury in soil.

  14. Imaging time-resolved electrothermal atomization laser-excited atomic fluorescence spectrometry for determination of mercury in seawater.

    Science.gov (United States)

    Le Bihan, Alain; Cabon, Jean-Yves; Deschamps, Laure; Giamarchi, Philippe

    2011-06-15

    In this study, direct determination of mercury at the nanogram per liter level in the complex seawater matrix by imaging time-resolved electrothermal atomization laser-excited atomic fluorescence spectrometry (ITR-ETA-LEAFS) is described. In the case of mercury, the use of a nonresonant line for fluorescence detection with only one laser excitation is not possible. For measurements at the 253.652 nm resonant line, scattering phenomena have been minimized by eliminating the simultaneous vaporization of salts and by using temporal resolution and the imaging mode of the camera. Electrothermal conditions (0.1 M oxalic acid as matrix modifier, low atomization temperature) have been optimized in order to suppress chemical interferences and to obtain a good separation of specific signal and seawater background signal. For ETA-LEAFS, a specific response has been obtained for Hg with the use of time resolution. Moreover, an important improvement of the detection limit has been obtained by selecting, from the furnace image, pixels collecting the lowest number of scattered photons. Using optimal experimental conditions, a detection limit of 10 ng L(-1) for 10 μL of sample, close to the lowest concentration level of total Hg in the open ocean, has been obtained.

  15. Development of an electrothermal atomization laser-excited atomic fluorescence spectrometry procedure for direct measurements of arsenic in diluted serum.

    Science.gov (United States)

    Swart, D J; Simeonsson, J B

    1999-11-01

    A procedure for the direct determination of arsenic in diluted serum by electrothermal atomization laser-excited atomic fluorescence spectrometry (ETA-LEAFS) is reported. Laser radiation needed to excite As at 193.696 and 197.197 nm is generated as the second anti-Stokes stimulated Raman scattering output of a frequency-doubled dye laser operating near 230.5 and 235.5 nm, respectively. Two different LEAFS schemes have been utilized and provide limits of detection of 200-300 fg for As in aqueous standards. When measurements of serum samples diluted 1:10 with deionized water are performed, a stable background signal is observed that can be accounted for by taking measurements with the laser tuned off-wavelength. No As is detected in any of the bovine or human serum samples analyzed. Measurements of 100 pg/mL standard additions of As to a diluted bovine serum sample utilizing either inorganic or organic As species demonstrate a linear relationship of the fluorescence signal to As spike concentration, but exhibit a sensitivity of approximately half that observed in pure aqueous standards. The limit of detection for As in 1:10 diluted serum samples is 65 pg/mL or 650 fg absolute mass, which corresponds to 0.65 ng/mL As in undiluted serum. To our knowledge, the ETA-LEAFS procedure is currently the only one capable of directly measuring As in diluted serum at these levels.

  16. Two-photon induced collagen cross-linking in bioartificial cardiac tissue

    Science.gov (United States)

    Kuetemeyer, Kai; Kensah, George; Heidrich, Marko; Meyer, Heiko; Martin, Ulrich; Gruh, Ina; Heisterkamp, Alexander

    2011-08-01

    Cardiac tissue engineering is a promising strategy for regenerative therapies to overcome the shortage of donor organs for transplantation. Besides contractile function, the stiffness of tissue engineered constructs is crucial to generate transplantable tissue surrogates with sufficient mechanical stability to withstand the high pressure present in the heart. Although several collagen cross-linking techniques have proven to be efficient in stabilizing biomaterials, they cannot be applied to cardiac tissue engineering, as cell death occurs in the treated area. Here, we present a novel method using femtosecond (fs) laser pulses to increase the stiffness of collagen-based tissue constructs without impairing cell viability. Raster scanning of the fs laser beam over riboflavin-treated tissue induced collagen cross-linking by two-photon photosensitized singlet oxygen production. One day post-irradiation, stress-strain measurements revealed increased tissue stiffness by around 40% being dependent on the fibroblast content in the tissue. At the same time, cells remained viable and fully functional as demonstrated by fluorescence imaging of cardiomyocyte mitochondrial activity and preservation of active contraction force. Our results indicate that two-photon induced collagen cross-linking has great potential for studying and improving artificially engineered tissue for regenerative therapies.

  17. Theory of even-parity states and two-photon spectra of conjugated polymers

    Science.gov (United States)

    McWilliams, P. C. M.; Hayden, G. W.; Soos, Z. G.

    1991-04-01

    The two-photon absorption (TPA) spectrum of interacting π electrons in conjugated polymers is shown to be qualitatively different from any single-particle description, including the Hartree-Fock limit. Alternating transfer integrals t(1+/-δ) along the backbone lead to a weak TPA below the one-photon gap Eg for arbitrarily weak correlations at δ=0, for intermediate correlations at δ=0.07 in polyenes, and for strong correlations at any δtheory to Eg in the limit of strong correlations in Hubbard models and is around 1.5Eg for Pariser-Parr-Pople (PPP) parameters. The PPP model, which accounts for one- and two-photon excitations of finite polyenes, is extended to even-parity states in polydiacetylenes (PDA's), polyacetylene (PA), and polysilanes (PS's). Previous experimental data for PDA and PS support both the strong TPA above Eg and weak TPA slightly below Eg for δ=0.15 in PDA and above Eg for δ~0.3 in PS. The strong TPA expected around 1.5Eg in isolated PA strands shifts to ~Eg due to interchain π-electron dispersion forces. TPA intensities in correlated states are shown to reflect both ionicity and mean-square charge separation. The even-parity states of conjugated polymers, like those of polyenes, show qualitatively different features associated with electron-electron correlations.

  18. Facile and Scalable Preparation of Fluorescent Carbon Dots for Multifunctional Applications

    Directory of Open Access Journals (Sweden)

    Dan Wang

    2017-06-01

    Full Text Available The synthesis of fluorescent nanomaterials has received considerable attention due to the great potential of these materials for a wide range of applications, from chemical sensing through bioimaging to optoelectronics. Herein, we report a facile and scalable approach to prepare fluorescent carbon dots (FCDs via a one-pot reaction of citric acid with ethylenediamine at 150 °C under ambient air pressure. The resultant FCDs possess an optical bandgap of 3.4 eV and exhibit strong excitation-wavelength-independent blue emission (λEm = 450 nm under either one- or two-photon excitation. Owing to their low cytotoxicity and long fluorescence lifetime, these FCDs were successfully used as internalized fluorescent probes in human cancer cell lines (HeLa cells for two-photon excited imaging of cells by fluorescence lifetime imaging microscopy with a high-contrast resolution. They were also homogenously mixed with commercial inks and used to draw fluorescent patterns on normal papers and on many other substrates (e.g., certain flexible plastic films, textiles, and clothes. Thus, these nanomaterials are promising for use in solid-state fluorescent sensing, security labeling, and wearable optoelectronics.

  19. [Atomic/ionic fluorescence in microwave plasma torch discharge excited by high current microsecond pulsed hollow cathode lamp-europium atomic/ionic fluorescence spectrometry].

    Science.gov (United States)

    Gong, Z; Liang, F; Yang, P; Jin, Q; Huang, B

    1999-06-01

    Eu atomic and ionic fluorescence spectrometry in microwave plasma torch discharge excited by high current microsecond pulsed hollow cathode lamp (HCMP HCL-MPT AFS/IFS) was studied. Operating conditions were optimized. The best detection limits for AFS and IFS obtained with a desolvated ultrasonic nebulization system were 42.0 ng/mL for Eu I 462.7 nm and 21.8 ng/mL for Eu II 381.97 nm, respectively, both were better than those given by the instruction manual of a Baird ICP AFS-2000 spectrometer using pneumatic concentric nebulizer with desolvation for AFS, but were significantly higher than those obtained by using the Baird spectrometer with a mini-monochromator and a ultrasonic nebulzer system.

  20. Ultrafast excited and ground-state dynamics of the green fluorescent protein chromophore in solution

    NARCIS (Netherlands)

    Vengris, M.; van Stokkum, I.H.M.; He, X.; Bell, A.F.; Tonge, P.J.; van Grondelle, R.; Larsen, D.S.

    2004-01-01

    Ultrafast dispersed pump-dump-probe spectroscopy was applied to HBDI (4′-hydroxybenzylidene-2,3-dimethylimidazolinone), a model green fluorescent protein (GFP) chromophore in solution with different protonation states. The measured three-dimensional data was analyzed using a global analysis method