Increase of (CdSe/ZnS)Cys quantum dot luminescence intensity in the presence of TPPS{sub 4} porphyrin

Energy Technology Data Exchange (ETDEWEB)

Parra, Gustavo G.; Borissevitch, Iouri E. [Universidade de Sao Paulo (FFCLRP/USP), Ribeirao Preto, SP (Brazil). Fac. de Filosofia, Ciencias e Letras de Ribeirao Preto. Dept. de Fisica; Kuzmin, Vladimir A. [Emanuel Institute of Biophysical Chemistry, RAS-RU, Moscow (Russian Federation); Oleinikov, Vladimir A. [Shemyakin and Ovchinnikov Institute of Biooganic Cemistry, RAS-RU, Moscow (Russian Federation)

2012-07-01

Full text: Nanocrystal semiconductor particles or Quantum Dots (QD) possess extraordinary photophysical characteristics, such as extreme high fluorescence quantum yield and optical absorption and very narrow fluorescence band, which can be easily shifted by changing of QD particle size. Due to these characteristics, QD is promising for fluorescence cancer diagnostics and photodynamic treatment. The efficiency of these processes can be in- creased by energy transfer between QD and classic fluorescence probes and photosensitizers (PS). In this work we present on the study of the increase of (CdSe/ZnS)Cys quantum dot luminescence intensity, stimulated by interaction with TPPS{sub 4} porphyrin. The optical absorption and steady-state and time-resolved fluorescence techniques were employed. Water soluble QD (CdSe/ZnS) with emission at 580 nm, functionalized with cysteine (Cys), were studied. TPPS{sub 4} porphyrin was used as a stimulator of QD luminescence. All experiments were realized in PBS buffer (pH 7.3; 7.5 mM) in Milli-Q quality water. The TPPS{sub 4} adding into the QD solutions until the 5{mu}M concentration produced an increase in QD luminescence intensity and lifetime, while for TPPS{sub 4} concentrations higher than 20{mu}M the reduction of the fluorescence intensity was observed, the emission spectra and fluorescence decays profile being unchanged. This effect can not be due to the electrostatic interaction between (CdSe/ZnS)Cys and TPPS{sub 4} because both, (CdSe/ZnS)Cys and TPPS{sub 4}, are negatively charged. We suppose that TPPS{sub 4} porphyrin interacts directly with QD (ZnS) shell, reducing the dangling bound number. This reduction decreases, in turn, the probability of nonradiative ways of the excitation energy dissipation. When the majority of dangling bound is occupied by the TPPS{sub 4} molecules, the effect of QD luminescence reduction (quenching) by porphyrin predominates, probably, via the energy transfer from QD to TPPS{sub 4}. However

Response of optically stimulated luminescence dosimeters subjected to X-rays in diagnostic energy range

International Nuclear Information System (INIS)

Musa, Y; Hashim, S; Karim, M K A; Ang, W C; Salehhon, N; Bakar, K A

2017-01-01

The use of optically stimulated luminescence (OSL) for dosimetry applications has recently increased considerably due to availability of commercial OSL dosimeters (nanoDots) for clinical use. The OSL dosimeter has a great potential to be used in clinical dosimetry because of its prevailing advantages in both handling and application. However, utilising nanoDot OSLDs for dose measurement in diagnostic radiology can only be guaranteed when the performance and characteristics of the dosimeters are apposite. In the present work, we examined the response of commercially available nanoDot OSLD (Al 2 O 3 :C) subjected to X-rays in general radiography. The nanoDots response with respect to reproducibility, dose linearity and signal depletion were analysed using microStar reader (Landauer, Inc., Glenwood, IL). Irradiations were performed free-in-air using 70, 80 and 120 kV tube voltages and tube currents ranging from 10 – 100 mAs. The results showed that the nanoDots exhibit good linearity and reproducibility when subjected to diagnostic X-rays, with coefficient of variations (CV) ranging between 2.3% to 3.5% representing a good reproducibility. The results also indicated average of 1% signal reduction per readout. Hence, the nanoDots showed a promising potential for dose measurement in general X-ray procedure. (paper)

Optical stimulated luminescence (OSL) dating

International Nuclear Information System (INIS)

Banerjee, D.

1999-01-01

Since the pioneering work by Huntley et al. (1985), optical dating is being increasingly recognised as an important technique for establishing a time frame of deposition of sediments (Aitken, 1998). Optical dating differs from thermoluminescence (TL) dating in that visible/infrared light from lasers or LEDs (light-emitting-diodes) is used as a means of stimulation, in contrast to thermal stimulation. It has several advantages over TL dating: (i) the resetting of the OSL (optically stimulated luminescence) clock is more effective than that of TL clock; for sediments transported under water or in other situations where the sediment grains have undergone inhomogeneous bleaching, this property ensures that ages based on optical dating are generally more reliable than TL ages, (ii) the optical dating technique is non-destructive, and multiple readouts of the optical signal is possible; this feature has resulted in the development of single-aliquot and single-grain protocols (Murray and Wintle, 1999; Banerjee et al. 1999), (iii) the sample is not heated as in TL; thus, spurious luminescence is avoided and there is a significant reduction in blackbody radiation. Dating of materials which change phase on heating is also practical, and finally, (iv) thermal quenching of luminescence is negligible, allowing accurate estimation of kinetic parameters using standard techniques and providing access to deep OSL traps. This characteristic may be helpful in extending the limits of optical dating beyond the last 150 ka from a global point of view

Non-Enzymatic-Browning-Reaction: A Versatile Route for Production of Nitrogen-Doped Carbon Dots with Tunable Multicolor Luminescent Display

Science.gov (United States)

Wei, Weili; Xu, Can; Wu, Li; Wang, Jiasi; Ren, Jinsong; Qu, Xiaogang

2014-01-01

The non-enzymatic browning, namely Maillard reaction is commonly invoked to account for abiotic chemical transformations of organic matter. Here we report a new reaction pathway via the Maillard reaction to systematically synthesize a series of nitrogen-doped carbon dots (C-dots) with superhigh quantum yield (QY) and tunable multicolor luminescent displayment. The starting materials are glucose and the serial amino acid analogues which allow systemically controlling luminescent and physicochemical properties of C-dots at will. Unexpectedly, the as-prepared C-dots possess bright photoluminescence with QY up to 69.1% which is almost the highest ever reported, favorable biocompatibility, excellent aqueous and nonaqueous dispersibility, ultrahigh photostability, and readily functionalization. We have demonstrated that they are particularly suitable for multicolor luminescent display and long-term and real-time cellular imaging. Furthermore, the methodology is readily scalable to large yield, and can provide sufficient amount of C-dots for practical demands.

Scintillation and optical stimulated luminescence of Ce-doped CaF2

International Nuclear Information System (INIS)

Yanagida, Takayuki; Fujimoto, Yutaka; Watanabe, Kenichi; Fukuda, Kentaro; Kawaguchi, Noriaki; Miyamoto, Yuka; Nanto, Hidehito

2014-01-01

Scintillation and optical stimulated luminescence of Ce 0.1–20% doped CaF 2 crystals prepared by Tokuyama Corp. were investigated. In X-ray induced scintillation spectra, luminescence due to Ce 3+ 5d–4f transition appeared around 320 nm with typically 40 ns decay time. By 241 Am 5.5 MeV α-ray irradiation, 0.1% doped one showed the highest scintillation light yield and the light yield monotonically decreased with Ce concentrations. Optically stimulated luminescence after X-ray irradiation was observed around 320 nm under 550 or 830 nm stimulation in all samples. As a result, intensities of optically stimulated luminescence were proportional to Ce concentrations. Consequently, scintillation and optically stimulated luminescence resulted to have a complementary relation in Ce-doped CaF 2 system. - Highlights: • Optical, scintillation, and OSL properties of Ce 0.1–20% doped CaF 2 were studied. • Scintillation light yield exhibited inverse proportionality to Ce concentrations. • OSL intensities showed proportionality to Ce concentrations. • Complementary relation of scintillation and OSL was experimentally confirmed

Optically stimulated luminescence dosimetry with gypsum wallboard (drywall)

International Nuclear Information System (INIS)

Thompson, J. W.; Burdette, K. E.; Inrig, E. L.; Dewitt, R.; Mistry, R.; Rink, W. J.; Boreham, D. R.

2010-01-01

Gypsum wallboard (drywall) represents an attractive target for retrospective dosimetry by optically stimulated luminescence (OSL) in the event of a radiological accident or malicious use of nuclear material. In this study, wallboard is shown to display a radiation-induced luminescence signal (RIS) as well as a natural background signal (NS), which is comparable in intensity to the RIS. Excitation and emission spectra show that maximum luminescence intensity is obtained for stimulation with blue light-emitting diodes (470 nm) and for detection in the ultraviolet region (290-370 nm). It is necessary to decrease the optical stimulation power dramatically in order to adequately separate the RIS from the interfering background signal. The necessary protocols are developed for accurately measuring the absorbed dose as low as 500 mGy and demonstrate that the RIS decays logarithmically with storage time, with complete erasure expected within 1-4 d. (authors)

Plasmon-enhanced optically stimulated luminescence

International Nuclear Information System (INIS)

Guidelli, E. J.; Baffa, O.; Ramos, A. P.

2015-10-01

Full text: Optically Stimulated Luminescence dosimeters (OSLD) have been largely used for personal, medical, and industrial radiation dosimetry. Developing highly sensitive and small-sized radiation detectors and dosimeters is essential for improving spatial resolution and consequently diagnosis quality and treatment efficacy in the case of applications in radiodiagnosis and radiation therapy, for instance. Conventional methods to improve the OSLD sensitivity consist of doping and co-doping the host materials with atoms of other elements, thereby increasing the amount of trapping and/or luminescent centers. Our group is researching on the use of the plasmon properties of noble metal nanoparticles to increase OSL intensity. Upon incidence of a light beam with appropriate resonant wavelengths, the oscillation of the free electrons at the nanoparticle surface originates the Localized Surface Plasmons (LSP) and the consequent plasmon resonance band. The interaction between the LSP and the surrounding luminescent material leads to new optical properties largely employed for enhancing several luminescent processes. Here we will show our results regarding the use of LSP to increase OSLD sensitivity. The interaction between the traps/luminescent centers and the plasmons depends on the distance between them, on the plasmon resonance band intensity and position, as well as on the surrounding medium. Therefore, the plasmon-enhanced luminescence is a promising tool to develop more sensitive and miniaturized OSLD. (Author)

Plasmon-enhanced optically stimulated luminescence

Energy Technology Data Exchange (ETDEWEB)

Guidelli, E. J.; Baffa, O. [Universidade de Sao Paulo, Faculdade de Filosofia, Ciencias e Letras de Ribeirao Preto, Departamento de Fisica, Av. Bandeirantes 3900, 14040-901 Ribeirao Preto, Sao Paulo (Brazil); Ramos, A. P., E-mail: ederguidelli@gmail.com [Universidade de Sao Paulo, Faculdade de Filosofia, Ciencias e Letras de Ribeirao Preto, Departamento de Quimica, Av. Bandeirantes 3900, 14040-901 Ribeirao Preto, Sao Paulo (Brazil)

2015-10-15

Full text: Optically Stimulated Luminescence dosimeters (OSLD) have been largely used for personal, medical, and industrial radiation dosimetry. Developing highly sensitive and small-sized radiation detectors and dosimeters is essential for improving spatial resolution and consequently diagnosis quality and treatment efficacy in the case of applications in radiodiagnosis and radiation therapy, for instance. Conventional methods to improve the OSLD sensitivity consist of doping and co-doping the host materials with atoms of other elements, thereby increasing the amount of trapping and/or luminescent centers. Our group is researching on the use of the plasmon properties of noble metal nanoparticles to increase OSL intensity. Upon incidence of a light beam with appropriate resonant wavelengths, the oscillation of the free electrons at the nanoparticle surface originates the Localized Surface Plasmons (LSP) and the consequent plasmon resonance band. The interaction between the LSP and the surrounding luminescent material leads to new optical properties largely employed for enhancing several luminescent processes. Here we will show our results regarding the use of LSP to increase OSLD sensitivity. The interaction between the traps/luminescent centers and the plasmons depends on the distance between them, on the plasmon resonance band intensity and position, as well as on the surrounding medium. Therefore, the plasmon-enhanced luminescence is a promising tool to develop more sensitive and miniaturized OSLD. (Author)

Luminescence optically stimulated: theory and applications

International Nuclear Information System (INIS)

Rivera M, T.; Azorin N, J.

2002-01-01

The thermally stimulated luminescence (Tl) has occupied an important place in the Solid state physics (FES) by the flexibility of the phenomena, mainly for its applications in the fields of Radiation Physics (FR) and Medical Physics (MF). The reason of this phenomena lies in the fact of the electrons release by the action of heat. Under that same reason, it can be used the action of another stimulant agent for releasing the trapped electrons in the metastable states (EM), this agent is the light which has the same effect that the heat, giving as result the production of light photons at using light in the visible spectra, of different wavelength that the excitation light. This phenomena is called Luminescence optically stimulated (LOE). The LOE has a great impact in the Solid State Physics (FES), dating and now in the use of the phenomena as a dosimetric method, alternate to the Tl, for its use in the ionizing and non-ionizing radiations fields. (Author)

SU-F-P-50: Performance Evaluation of Optically Stimulated Luminescence (OSL) NanoDots in Therapy and Imaging In-Vivo Dose Measurement During Patient Treatment

Energy Technology Data Exchange (ETDEWEB)

Kumar, S; Sarkar, B; Kaur, H; Rathinamuthu, S; Giri, U; Jassal, K; Ganesh, T; Munshi, A; Mohanti, B; Krishnankutty, S; Sathiya, J [Fortis Memorial Research Institute, Gurgaon, Haryana (India)

2016-06-15

Purpose: This study was designed to evaluate the performance of optically stimulated Luminescence (OSL) nanoDots as in-vivo dosimeter. For the measurements of surface doses as well as scattered plus leakage doses, nanoDots were used during the setup verification as well as during the treatment delivery. Methods: For a total seven patients undergoing radiotherapy by volumetric modulated arc therapy, surface doses from image guidance and scattered plus leakage doses from treatment delivery were measured. Two sets of calibration curves were generated – one for therapy and another for imaging. Two different nanoDots were used for imaging and therapy doses. Imaging nanoDots were placed at the isocenter only at the time of CBCT and therapy nanoDots were placed at 25 cm away from the isocenter (either in cranial or in caudal direction) only at the time of treatment delivery. During the entire course, nanoDots were placed at the same measurement points. NanoDots were read after 15 minutes of their exposure. For the next fraction, nanoDots were corrected for the residual doses from the previous fractions. Results: Measured surface doses during imaging were 0.14±0.32 cGy, 0.11±0.04 cGy, 0.12±0.53 cGy, 0.04±0.02 cGy, 0.13±0.23 cGy, 0.11±0.43 cGy, 0.10±0.04 cGy with overall mean dose of 0.08±0.1 cGy. Measured doses during treatment delivery, indicative of scattered and leakage dose, were 0.84±0.43 cGy, 1.3±0.4 cGy, 1.4±0.4 cGy, 0.18±0.48 cGy, 0.78±0.29 cGy, 0.27±0.08 cGy, 0.78±0.07 cGy with overall mean dose of 0.61±1.3 cGy. Conclusion: This dosimeter can be used as supplementary unit to verify the doses. No change in the prescription is recommended based on nanoDots measurement. This study is on-going therefore we are presenting only mere number of patients. A large volume data will be presented after completion of the study with proper statistical analysis.

Neutron dosimetry using optically stimulated luminescence

International Nuclear Information System (INIS)

Miller, S.D.; Eschbach, P.A.

1991-06-01

The addition of thermoluminescent (TL) materials within hydrogenous matrices to detect neutron-induced proton recoils for radiation dosimetry is a well-known concept. Previous attempts to implement this technique have met with limited success, primarily due to the high temperatures required for TL readout and the low melting temperatures of hydrogen-rich plastics. Research in recent years at Pacific Northwest laboratories (PNL) has produced a new Optically Stimulated Luminescence (OSL) technique known as the Cooled Optically Stimulated Luminescence (COSL) that offers, for the first time, the capability of performing extremely sensitive radiation dosimetry at low temperatures. In addition to its extreme sensitivity, the COSL technique offers multiple readout capability, limited fading in a one-year period, and the capability of analyzing single grains within a hydrogenous matrix. 4 refs., 10 figs

Dosimetry based on thermally and optically stimulated luminescence

International Nuclear Information System (INIS)

Agersnap Larsen, Niels

1999-01-01

Thermally Stimulated Luminescence (TL) and Optically Stimulated Luminescence (OSL) properties of quartz and α-Al 2 O 3 have been investigated. Anneling-induced OSL and TL sensitivity changes in quartz has been investigated by experiments and modelling. This study does not support a pre-dose effect to account for the observed annealing-induced sensitivity change. The experimental data indicates a more simple mechanism that involves alteration of the concentration of the defect centers. Results from modelling of removal or creation of defect centers comparing well with experimentally obtained data. Thermal quenching of luminescence for the main emission center, the F-center, in α-Al 2 O 3 :C has been investigated by analysing TL curves obtained at different heating rates. The thermal quenching dependence of luminescence is found to follow the classical Mott-Seitz expression. Basic investigations of OSL properties of αAl 2 O 3 :C, including: the thermal depth of the OSL traps, the temperature dependence of OSL, and the OSL stimulation spectra. Simultaneous measurements of TL and thermally stimulated conductivity (TSC) are presented for γ-irradiated αAl 2 O 3 :C. Activation energy analysis of the data reveals a superposition of several first-order TL and TSC peaks caused by release of charge carriers from a distribution of trapping states. Furthermore a description of an experimental method developed to determine the sign of the thermally released charge carriers has been presented. (au)

Preparation of carbon quantum dots based high photostability luminescent membranes.

Science.gov (United States)

Zhao, Jinxing; Liu, Cui; Li, Yunchuan; Liang, Jiyuan; Liu, Jiyan; Qian, Tonghui; Ding, Jianjun; Cao, Yuan-Cheng

2017-06-01

Urethane acrylate (UA) was used to prepare carbon quantum dots (C-dots) luminescent membranes and the resultants were examined with FT-IR, mechanical strength, scanning electron microscope (SEM) and quantum yields (QYs). FT-IR results showed the polyurethane acrylate (PUA) prepolymer -C = C-vibration at 1101 cm -1 disappeared but there was strong vibration at1687cm -1 which was contributed from the-C = O groups in cross-linking PUA. Mechanical strength results showed that the different quantity of C-dots loadings and UV-curing time affect the strength. SEM observations on the cross-sections of the membranes are uniform and have no structural defects, which prove that the C-dots are compatible with the water-soluble PUA resin. The C-dot loading was increased from 0 to 1 g, the maximum tensile stress was nearly 2.67 MPa, but the tensile strain was decreased from 23.4% to 15.1% and 7.2% respectively. QYs results showed that the C-dots in the membrane were stable after 120 h continuous irradiation. Therefore, the C-dots photoluminescent film is the promising material for the flexible devices in the future applications. Copyright © 2016 John Wiley & Sons, Ltd.

Quantitative analysis of time-resolved infrared stimulated luminescence in feldspars

DEFF Research Database (Denmark)

Pagonis, Vasilis; Ankjærgaard, Christina; Jain, Mayank

2016-01-01

Time-resolved infrared-stimulated luminescence (TR-IRSL) from feldspar samples is of importance in the field of luminescence dating, since it provides information on the luminescence mechanism in these materials. In this paper we present new analytical equations which can be used to analyze TR-IR...

Conversion of the luminescence of laser dyes in opal matrices to stimulated emission

International Nuclear Information System (INIS)

Alimov, O K; Basiev, T T; Orlovskii, Yu V; Osiko, V V; Samoilovich, M I

2008-01-01

The luminescence and laser characteristics of a synthetic opal matrix filled with organic dyes are studied upon excitation by nanosecond laser pulses. The appearance of stimulated emission in a partially ordered scattering medium is investigated. It is shown that if the luminescence spectrum of a dye (oxazine-17) is located far outside the photonic bandgap of the opal matrix, stimulated emission along a preferential direction in the (111) plane is observed when pumping exceeds a threshold even without an external optical cavity. The stimulated emission spectrum is considerably narrower than the luminescence spectrum and consists of several narrow lines located within the dye luminescence band. If the luminescence spectrum of a dye (rhodamine 6G) overlaps with the photonic bandgap of the opal matrix, a different picture is observed. The loss of radiation in the matrix leads to the red shift of the luminescence spectrum, while the stimulated emission as in the case of oxazine-17 lies is observed within the luminescence band. (active media, lasers, and amplifiers)

Dosimetry based on thermally and optically stimulated luminescence

Energy Technology Data Exchange (ETDEWEB)

Agersnap Larsen, Niels

1999-01-01

Thermally Stimulated Luminescence (TL) and Optically Stimulated Luminescence (OSL) properties of quartz and {alpha}-Al{sub 2}O{sub 3} have been investigated. Anneling-induced OSL and TL sensitivity changes in quartz has been investigated by experiments and modelling. This study does not support a pre-dose effect to account for the observed annealing-induced sensitivity change. The experimental data indicates a more simple mechanism that involves alteration of the concentration of the defect centers. Results from modelling of removal or creation of defect centers comparing well with experimentally obtained data. Thermal quenching of luminescence for the main emission center, the F-center, in {alpha}-Al{sub 2}O{sub 3}:C has been investigated by analysing TL curves obtained at different heating rates. The thermal quenching dependence of luminescence is found to follow the classical Mott-Seitz expression. Basic investigations of OSL properties of {alpha}Al{sub 2}O{sub 3}:C, including: the thermal depth of the OSL traps, the temperature dependence of OSL, and the OSL stimulation spectra. Simultaneous measurements of TL and thermally stimulated conductivity (TSC) are presented for {gamma}-irradiated {alpha}Al{sub 2}O{sub 3}:C. Activation energy analysis of the data reveals a superposition of several first-order TL and TSC peaks caused by release of charge carriers from a distribution of trapping states. Furthermore a description of an experimental method developed to determine the sign of the thermally released charge carriers has been presented. (au) 8 tabs., 59 ills., 90 refs.

Zinc and nitrogen ornamented bluish white luminescent carbon dots for engrossing bacteriostatic activity and Fenton based bio-sensor.

Science.gov (United States)

Das, Poushali; Ganguly, Sayan; Bose, Madhuparna; Mondal, Subhadip; Choudhary, Sumita; Gangopadhyay, Subhashis; Das, Amit Kumar; Banerjee, Susanta; Das, Narayan Chandra

2018-07-01

Carbon dots with heteroatom co-doping associated with consummate luminescence features are of acute interest in diverse applications such as biomolecule markers, chemical sensing, photovoltaic, and trace element detection. Herein, we demonstrate a straightforward, highly efficient hydrothermal dehydration technique to synthesize zinc and nitrogen co-doped multifunctional carbon dots (N, Zn-CDs) with superior quantum yield (50.8%). The luminescence property of the carbon dots can be tuned by regulating precursor ratio and surface oxidation states in the carbon dots. A unique attribution of the as-prepared carbon dots is the high monodispersity and robust excitation-independent emission behavior that is stable in enormously reactive environment and over a wide range of pH. These N, Zn-CDs unveils captivating bacteriostatic activity against gram-negative bacteria Escherichia coli. Furthermore, the excellent luminescence properties of these carbon dots were applied as a platform of sensitive biosensor for the detection of hydrogen peroxide. Under optimized conditions, these N, Zn-CDs reveals high sensitivity over a broad range of concentrations with an ultra-low limit of detection (LOD) indicating their pronounced prospective as a fluorescent probe for chemical sensing. Overall, the experimental outcomes propose that these zero-dimensional nano-dots could be developed as bacteriostatic agents to control and prevent the persistence and spreading of bacterial infections and as a fluorescent probe for hydrogen peroxide detection. Copyright © 2018 Elsevier B.V. All rights reserved.

Quantitative analysis of time-resolved infrared stimulated luminescence in feldspars

Energy Technology Data Exchange (ETDEWEB)

Pagonis, Vasilis, E-mail: vpagonis@mcdaniel.edu [McDaniel College, Physics Department, Westminster, MD 21157 (United States); Ankjærgaard, Christina [Soil Geography and Landscape Group & Netherlands Centre for Luminescence dating, Wageningen University, PO Box 47, 6700 AA Wageningen (Netherlands); Jain, Mayank [Center for Nuclear Technologies, Technical University of Denmark, DTU Risø Campus, Roskilde (Denmark); Chithambo, Makaiko L. [Department of Physics and Electronics, Rhodes University, PO BOX 94, Grahamstown 6140 (South Africa)

2016-09-15

Time-resolved infrared-stimulated luminescence (TR-IRSL) from feldspar samples is of importance in the field of luminescence dating, since it provides information on the luminescence mechanism in these materials. In this paper we present new analytical equations which can be used to analyze TR-IRSL signals, both during and after short infrared stimulation pulses. The equations are developed using a recently proposed kinetic model, which describes localized electronic recombination via tunneling between trapped electrons and recombination centers in luminescent materials. Recombination is assumed to take place from the excited state of the trapped electron to the nearest-neighbor center within a random distribution of luminescence recombination centers. Different possibilities are examined within the model, depending on the relative importance of electron de-excitation and recombination. The equations are applied to experimental TR-IRSL data of natural feldspars, and good agreement is found between experimental and modeling results.

Freestanding silicon quantum dots: origin of red and blue luminescence.

Science.gov (United States)

Gupta, Anoop; Wiggers, Hartmut

2011-02-04

In this paper, we studied the behavior of silicon quantum dots (Si-QDs) after etching and surface oxidation by means of photoluminescence (PL) measurements, Fourier transform infrared spectroscopy (FTIR) and electron paramagnetic resonance spectroscopy (EPR). We observed that etching of red luminescing Si-QDs with HF acid drastically reduces the concentration of defects and significantly enhances their PL intensity together with a small shift in the emission spectrum. Additionally, we observed the emergence of blue luminescence from Si-QDs during the re-oxidation of freshly etched particles. Our results indicate that the red emission is related to the quantum confinement effect, while the blue emission from Si-QDs is related to defect states at the newly formed silicon oxide surface.

Application of Quantum Dot nanocrystal in Luminescent solar concentrators

Science.gov (United States)

Bakhoda, Shokoufeh; Khalaji Assadi, Morteza; Ahmadi Kandjani, Sohrab; Kayiem, Hussain H. Al; Hussain Bhat, Aamir

2018-03-01

The basic design of luminescent solar concentrator is a transparent plate doped with an appropriate luminescent material (organic dyes, quantum dots), which is able to absorb sunlight (direct and diffuse), and then guides photons produced by photoluminescence to its narrow edges where they are converted by photovoltaic cells. Unfortunately, LSCs have suffered from numerous efficiency losses. Therefore, new luminescent species and novel approaches are needed for its practical application. This paper deals with investigation of nonhazardous, environmental friendly luminescent species include CuInS2/ZnS core/shell QDs. The CuInS2/ZnS QDs possess advantages of Stocks shift as large as more than 130 nm and high photoluminescence quantum yield of 80%. The paper presents the effect of large stock shift CuInS2/ZnS QDs on reducing the reabsorption losses in LSC by using experimental investigation. The LSC sheets were fabricated by dispersing CuInS2/ZnS QDs particles in a polymethylmethacrylate waveguide. A series of LSCs (dimension 4.0 cm × 3.0 cm × 0.3cm) with different CuInS2/ZnS QDs particles concentration (0.015 and 0.03 wt.%) were fabricated and their optical properties (absorptions/emissions) were characterized. The results show that the CuInS2/ZnS QDs-LSC provides a promising way for the reduction of reabsorption losses in LSCs.

General radiographic attributes of optically stimulated luminescence dosimeters: A basic insight

Science.gov (United States)

Musa, Y.; Hashim, S.; Ghoshal, S. K.; Bradley, D. A.; Ahmad, N. E.; Karim, M. K. A.; Hashim, A.; Kadir, A. B. A.

2018-06-01

We report the ubiquitous radiographic characteristics of optically stimulated luminescence dosimeters (OSLD) so called nanoDot OSLDs (Landauer Inc., Glendwood, IL). The X-ray irradiations were performed in free air ambiance to inspect the repeatability, the reproducibility, the signal depletion, the element correction factors (ECFs), the dose response and the energy dependence. Repeatability of multiple readouts after single irradiation to 10 mGy revealed a coefficient of variation below 3%, while the reproducibility in repeated irradiation-readout-annealing cycles was above 2%. The OSL signal depletion for three nanoDots with simultaneous irradiation to 20 mGy and sequential readouts of 25 times displayed a consistent signal reduction ≈0.5% per readout with R2 values over 0.98. ECFs for individual OSLDs were varied from 0.97 to 1.03. In the entire dose range under 80 kV, a good linearity with an R2 exceeding 0.99 was achieved. Besides, the percentage difference between OSLD and ion-chamber dose was less than 5%, which was superior to TLD. The X-ray photon irradiated energy response factors (between 0.76 and 1.12) in the range of 40-150 kV (26.1-61.2 keV) exhibited significant energy dependence. Indeed, the nanoDot OSLDs disclosed good repeatability, reproducibility and linearity. The OSLDs measured doses were closer to ion-chamber doses than that of TLD. It can be further improved up to ≈3% by applying the individual dosimeter ECF. On top, the energy dependent uncertainties can be minimized using the energy correction factors. It is established that the studied nanoDot OSLDs are prospective for measuring entrance dose in general radiographic practices.

Spatially-resolved measurement of optically stimulated luminescence and time-resolved luminescence

International Nuclear Information System (INIS)

Bailiff, I.K.; Mikhailik, V.B.

2003-01-01

Spatially-resolved measurements of optically stimulated luminescence (OSL) were performed using a two-dimensional scanning system designed for use with planar samples. The scanning system employs a focused laser beam to stimulate a selected area of the sample, which is moved under the beam by a motorised stage. Exposure of the sample is controlled by an electronic shutter. Mapping of the distribution of OSL using a continuous wave laser source was obtained with sub-millimeter resolution for samples of sliced brick, synthetic single crystal quartz, concrete and dental ceramic. These revealed sporadic emission in the case of brick or concrete and significant spatial variation of emission for quartz and dental ceramic slices. Determinations of absorbed dose were performed for quartz grains within a slice of modern brick. Reconfiguration of the scanner with a pulsed laser source enabled quartz and feldspathic minerals within a ceramic sample to be thinner region. about 6 nm from the extrapolation of themeasuring the time-resolved luminescence spectrum

Quantitative analysis of time-resolved infrared stimulated luminescence in feldspars

DEFF Research Database (Denmark)

Pagonis, Vasilis; Ankjærgaard, Christina; Jain, Mayank

2016-01-01

Time-resolved infrared-stimulated luminescence (TR-IRSL) from feldspar samples is of importance in the field of luminescence dating, since it provides information on the luminescence mechanism in these materials. In this paper we present new analytical equations which can be used to analyze TR-IR....... The equations are applied to experimental TR-IRSL data of natural feldspars, and good agreement is found between experimental and modeling results....

Dependence of the thermal influence on luminescence lifetimes from quartz on the duration of optical stimulation

International Nuclear Information System (INIS)

Chithambo, M.L.

2003-01-01

Time-resolved luminescence spectra may be measured from quartz at various stages of continuous optical stimulation in order to investigate properties of the spectra associated with the 'fast', 'medium', and 'slow' components of continuous optically stimulated luminescence (OSL). In this work, temperature related changes of luminescence lifetimes and luminescence intensity, both evaluated from time-resolved luminescence spectra recorded in the 'fast' 'medium' and 'slow' component regions of quartz OSL, have been investigated. The luminescence, stimulated at 525 nm, and measured at intervals between 20 deg. C and 200 deg. C reaches maximum intensity at 100 deg. C and decreases thereafter up to 200 deg. C, the maximum temperature of the investigations. Luminescence lifetimes, on the other hand, remain constant within 40±3 μs between 20 deg. C and 100 deg. C and then decrease down to about μs at 200 deg. C. The initial increase of luminescence intensity with temperature between 20 deg. C and 100 deg. C is discussed in terms of thermal assistance to luminescence stimulation. Beyond 100 deg. C, radiative recombination is affected by quenching of luminescence and reduction in luminescence lifetimes. The activation energy for thermal quenching was evaluated to be in the range 0.63±0.07 eV at all stimulation times and that of thermal assistance was evaluated to be about 0.06 eV for the 'fast' and 'medium' component regions and about 0.1 eV for the 'slow' component region of the OSL

Experimental and modelling study of pulsed optically stimulated luminescence in quartz, marble and beta irradiated salt

International Nuclear Information System (INIS)

Pagonis, V; Mian, S M; Barnold, C; Chithambo, M L; Christensen, E

2009-01-01

Optical stimulation luminescence (OSL) signals can be obtained using continuous-wave optical stimulation (CW-OSL), the linear modulation optical stimulation method (LM-OSL) and the time-resolved optical stimulation (TR-OSL) method. During TR-OSL measurements, the stimulation and emission of luminescence are experimentally separated in time by using short light pulses. This paper presents new TR-OSL data for annealed high purity synthetic quartz, for marble and for commercially available iodized salt. A new type of behaviour for TR-OSL signals for quartz and iodized salt is presented, in which the OSL signal exhibits a nonmonotonic behaviour during optical stimulation; this type of behaviour has not been reported previously in the literature for quartz. Furthermore, a luminescence component with very long luminescence lifetime is reported for some quartz aliquots, which may be due to the presence of a delayed-OSL (DOSL) mechanism in quartz. A new kinetic model for TR-OSL in quartz is presented, which is based on a main electron trap and on several luminescence centres. The model is used to quantitatively fit several sets of experimental data of pulsed optically stimulated luminescence from quartz.

Effect of ion-implantation enhanced intermixing on luminescence of InAs/InP quantum dots

Energy Technology Data Exchange (ETDEWEB)

Li, Q; Barik, S; Tan, H H; Jagadish, C [Department of Electronic Materials Engineering, Research School of Physical Sciences and Engineering, Australian National University, Canberra 0200 (Australia)

2008-10-21

Temperature dependent photoluminescence spectra of ion implanted InAs/InP quantum dots (QDs) followed by rapid thermal annealing were studied. By employing a recently developed luminescence model for localized states ensemble, the broadening of the distribution of the localized QD states was determined from the fitting to the luminescence peak energy positions. The broadening of the distribution of the localized QD states reduces due to ion-implantation enhanced intermixing. The contribution of carrier distribution within the localized QD states to the luminescence linewidth decreases after ion-implantation enhanced intermixing. The effect of doses and types of ions used for implantation were also investigated.

Design of Interrogation Protocols for Radiation Dose Measurements Using Optically-Stimulated Luminescent Dosimeters.

Science.gov (United States)

Abraham, Sara A; Kearfott, Kimberlee J; Jawad, Ali H; Boria, Andrew J; Buth, Tobias J; Dawson, Alexander S; Eng, Sheldon C; Frank, Samuel J; Green, Crystal A; Jacobs, Mitchell L; Liu, Kevin; Miklos, Joseph A; Nguyen, Hien; Rafique, Muhammad; Rucinski, Blake D; Smith, Travis; Tan, Yanliang

2017-03-01

Optically-stimulated luminescent dosimeters are capable of being interrogated multiple times post-irradiation. Each interrogation removes a fraction of the signal stored within the optically-stimulated luminescent dosimeter. This signal loss must be corrected to avoid systematic errors in estimating the average signal of a series of optically-stimulated luminescent dosimeter interrogations and requires a minimum number of consecutive readings to determine an average signal that is within a desired accuracy of the true signal with a desired statistical confidence. This paper establishes a technical basis for determining the required number of readings for a particular application of these dosimeters when using certain OSL dosimetry systems.

Semiconductor Quantum Dots with Photoresponsive Ligands.

Science.gov (United States)

Sansalone, Lorenzo; Tang, Sicheng; Zhang, Yang; Thapaliya, Ek Raj; Raymo, Françisco M; Garcia-Amorós, Jaume

2016-10-01

Photochromic or photocaged ligands can be anchored to the outer shell of semiconductor quantum dots in order to control the photophysical properties of these inorganic nanocrystals with optical stimulations. One of the two interconvertible states of the photoresponsive ligands can be designed to accept either an electron or energy from the excited quantum dots and quench their luminescence. Under these conditions, the reversible transformations of photochromic ligands or the irreversible cleavage of photocaged counterparts translates into the possibility to switch luminescence with external control. As an alternative to regulating the photophysics of a quantum dot via the photochemistry of its ligands, the photochemistry of the latter can be controlled by relying on the photophysics of the former. The transfer of excitation energy from a quantum dot to a photocaged ligand populates the excited state of the species adsorbed on the nanocrystal to induce a photochemical reaction. This mechanism, in conjunction with the large two-photon absorption cross section of quantum dots, can be exploited to release nitric oxide or to generate singlet oxygen under near-infrared irradiation. Thus, the combination of semiconductor quantum dots and photoresponsive ligands offers the opportunity to assemble nanostructured constructs with specific functions on the basis of electron or energy transfer processes. The photoswitchable luminescence and ability to photoinduce the release of reactive chemicals, associated with the resulting systems, can be particularly valuable in biomedical research and can, ultimately, lead to the realization of imaging probes for diagnostic applications as well as to therapeutic agents for the treatment of cancer.

Infrared stimulated luminescence dating of an Eemian (MIS 5e) site in Denmark using K-feldspar

DEFF Research Database (Denmark)

Buylaert, Jan-Pieter; Huot, Sebastian; Murray, Andrew S.

2011-01-01

Infrared stimulated luminescence (IRSL) dating of K-feldspars may be an alternative to quartz optically stimulated luminescence (OSL) dating when the quartz OSL signal is too close to saturation or when the quartz luminescence characteristics are unsuitable. In this paper, Eemian (MIS 5e) coastal...

Optically stimulated luminescence from quartz measured using the linear modulation technique

DEFF Research Database (Denmark)

Bulur, E.; Bøtter-Jensen, L.; Murray, A.S.

2000-01-01

The optically stimulated luminescence (OSL) from heated natural quartz has been investigated using the linear modulation technique (LMT), in which the excitation light intensity is increased linearly during stimulation. In contrast to conventional stimulation, which usually produces a monotonical...

Cooperative effects in CdSe/ZnS-PEGOH quantum dot luminescence quenching by a water soluble porphyrin

Energy Technology Data Exchange (ETDEWEB)

Borissevitch, I.E., E-mail: iourib@ffclrp.usp.br [Departamento de Fisica, Faculdade de Filosofia Ciencia e Letras de Ribeirao Preto, Universidade de Sao Paulo, Av. Bandeirantes 3900, Ribeirao Preto, SP (Brazil); Parra, G.G. [Departamento de Fisica, Faculdade de Filosofia Ciencia e Letras de Ribeirao Preto, Universidade de Sao Paulo, Av. Bandeirantes 3900, Ribeirao Preto, SP (Brazil); Zagidullin, V.E.; Lukashev, E.P.; Knox, P.P.; Paschenko, V.Z.; Rubin, A.B. [Department of Biophysics, Faculty of Biology, M.V. Lomonosov Moscow State University, Vorobyovy Gory, 119991 Moscow (Russian Federation)

2013-02-15

In this work we report on the study of the interaction of CdSe/ZnS-PEGOH 570 Quantum Dot (QD) with negatively charged meso-tetrakis(p-sulfonato-phenyl)porphyrin (TPPS{sub 4}) using optical absorption and fluorescence spectroscopies accompanied with time resolved 'single photon counting' and dynamic and resonance light scattering techniques. In the steady-state experiments the QD luminescence quenching by TPPS{sub 4} was well approximated by a square law. In the time-resolved experiments we observed a typical multi-exponential luminescence decay curve, successfully fitted by a bi-exponential approximation. At QD interaction with porphyrin the time quenching of both components was described by a linear Stern-Volmer dependence. The discrepancy between Stern-Volmer dependences in the steady-state and time resolved experiments may be due to formation of mixed m(TPPS{sub 4})+n(QD) complexes, in which one TPPS{sub 4} molecule can quench several excited QDs. This idea is in accordance with the dynamic and resonance light scattering data, which demonstrate an increase of the scattering particle size at the TPPS{sub 4} addition to QD solutions. - Highlights: Black-Right-Pointing-Pointer Quantum Dot luminescence quenching by TPPS porphyrin was studied in water solutions. Black-Right-Pointing-Pointer The size of particles in QD solutions possessed increase at the TPPS4 addition. Black-Right-Pointing-Pointer Quenching of the QD luminescence by TPPS4 is realized in contact QD-porphyrin complexes. Black-Right-Pointing-Pointer The formation of mixed quantum dot-porphyrin aggregates takes place.

Search for the dose-sensitive optically stimulated luminescence response in natural carbonates

International Nuclear Information System (INIS)

Jaek, Ivar; Huett, Galina; Rammo, Ilmar; Vasilchenko, Valeri

2001-01-01

Carbonates of different origin, such as Iceland spar, calcites, and mollusc shells, used as electron spin resonance and thermoluminescence paleodosimeters, were studied in order to determine their suitability for optically stimulated luminescence dating. The stimulation/excitation spectra of the afterglow of the samples were recorded in the wavelength range of 250-1100 nm. The results of the study show that these spectra present either excitation spectra of Mn 2+ ion fluorescence (samples of calcites and Iceland spar, red emission recorded) or the excitation spectra of primary phosphorescence (samples of carbonates, including molluscs shells; short-wave emission bands recorded). The recorded stimulation spectra revealed no spectral bands sensitive to stimulation by ionizing radiation, which would disappear as a result of heating and could thus be related to deep traps in carbonates, needed dating. The cause of this situation which is unusual in luminescent crystals, including luminescence (paleo)dosimeters, and the ways of overcoming the difficulties in optical dating of natural carbonates are discussed. (author)

Thermally and optically stimulated luminescence of early medieval blue-green glass mosaics

Energy Technology Data Exchange (ETDEWEB)

Galli, A. E-mail: anna.galli@mater.unimib.it; Martini, M.; Montanari, C.; Sibilia, E

2004-12-01

The preliminary results of a study related to luminescent mechanisms in glass mosaic tesserae are presented. The samples came from a medieval glass deposit found during archaeological excavations in the S. Lorenzo Church in Milan. Energy Dispersive X-rays Fluorescence (EDXRF) measurements were performed to obtain information on the elemental composition of the materials. Thermally Stimulated Luminescence (TSL, both conventional and wavelength resolved) and Optically Stimulated Luminescence (OSL) analyses allowed to get information about traps and luminescence centres. The observed luminescence characteristics were close to that of quartz, showing the presence of an easy to bleach trap (300 deg. C, 1.95 eV) and of a hard to bleach trap (350 deg. C, 2.20 eV); charge transfer phenomena, involving the low-temperature peaks have been observed. There is a strong indication that the easy to bleach traps are responsible for both OSL and TSL emission at 300 deg. C.

Thermally and optically stimulated luminescence of early medieval blue-green glass mosaics

International Nuclear Information System (INIS)

Galli, A.; Martini, M.; Montanari, C.; Sibilia, E.

2004-01-01

The preliminary results of a study related to luminescent mechanisms in glass mosaic tesserae are presented. The samples came from a medieval glass deposit found during archaeological excavations in the S. Lorenzo Church in Milan. Energy Dispersive X-rays Fluorescence (EDXRF) measurements were performed to obtain information on the elemental composition of the materials. Thermally Stimulated Luminescence (TSL, both conventional and wavelength resolved) and Optically Stimulated Luminescence (OSL) analyses allowed to get information about traps and luminescence centres. The observed luminescence characteristics were close to that of quartz, showing the presence of an easy to bleach trap (300 deg. C, 1.95 eV) and of a hard to bleach trap (350 deg. C, 2.20 eV); charge transfer phenomena, involving the low-temperature peaks have been observed. There is a strong indication that the easy to bleach traps are responsible for both OSL and TSL emission at 300 deg. C

Optical annealing of CaF2:Mn for cooled optically stimulated luminescence

International Nuclear Information System (INIS)

Miller, S.D.; Stahl, K.A.; Endres, G.W.R.; McDonald, J.C.

1989-01-01

Optical annealing of the cooled optically stimulated luminescence in CaF 2 :Mn at room temperature has been demonstrated. The laser of choice for optical annealing of CaF 2 : Mn is a 326 nm helium-cadmium ultraviolet laser. A complete cycle of readout and annealing of the CaF 2 :Mn cooled optically stimulated dosemeters can now be accomplished without heating the dosemeters above room temperature. This annealing work represents the next step toward creating a proton-recoil-based fast neutron dosimetry system based on the cooled optically stimulated luminescence technique. (author)

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.

Down- and up-conversion luminescent carbon dot fluid: inkjet printing and gel glass fabrication

Science.gov (United States)

Wang, Fu; Xie, Zheng; Zhang, Bing; Liu, Yun; Yang, Wendong; Liu, Chun-Yan

2014-03-01

Room temperature liquid-like nanoparticles have emerged as an exciting new research and development area, because their properties could be tailored over a broad range by manipulating geometric and chemical characteristics of the inorganic core and organic canopy. However, related applications are rarely reported due to the multi-step synthesis process and potential toxicity of cadmium based nanomaterials. In this study, we prepared inexpensive and eco-friendly carbon dot fluid by the direct thermal decomposition method. The carbon dot fluid can be excited from UV to near infrared light, and can be prepared as highly concentrated luminescent ink or incorporated into sol-gel derived organically modified silicate glass, suggesting that it has great application potential in the field of printable electronics, solid state lighting and so on.Room temperature liquid-like nanoparticles have emerged as an exciting new research and development area, because their properties could be tailored over a broad range by manipulating geometric and chemical characteristics of the inorganic core and organic canopy. However, related applications are rarely reported due to the multi-step synthesis process and potential toxicity of cadmium based nanomaterials. In this study, we prepared inexpensive and eco-friendly carbon dot fluid by the direct thermal decomposition method. The carbon dot fluid can be excited from UV to near infrared light, and can be prepared as highly concentrated luminescent ink or incorporated into sol-gel derived organically modified silicate glass, suggesting that it has great application potential in the field of printable electronics, solid state lighting and so on. Electronic supplementary information (ESI) available: Details of FTIR, XRD and DLS of CDF, optical properties of CDF, TEM images of other obtained products, luminescent spectra of CDF at different temperatures, and the optical photographs of CDF inks and silica glasses with different concentrations

Cooled optically stimulated luminescence in CaF2:Mn

International Nuclear Information System (INIS)

Miller, S.D.; Endres, G.W.R.; McDonald, J.C.; Swinth, K.L.

1988-01-01

A new optically stimulated luminescence technique has been developed for the readout of CaF 2 :Mn thermoluminescent material. Minimum detectable gamma exposures may potentially be measured at 10 nC.kg -1 using the 254 nm line of a mercury lamp. Additional studies were done on CaF 2 :Mn using 351 nm excimer laser stimulation. (author)

Optical parameters of ITO/TPD/Alq3/Al luminescent structures, containing arrays of CdSe/ZnS colloidal quantum dots

Science.gov (United States)

Mikhailov, I. I.; Tarasov, S. A.; Lamkin, I. A.; Tadtaev, P. O.; Kozlovich, L. I.; Solomonov, A. V.; Stepanov, E. M.

2016-08-01

The luminescent organic ITO/TPD/Alq3/Al structures and CdSe/ZnS quantum dots (QD) arrays were created. Electrical and optical properties of the samples were examined. The luminescence of the layers and QD arrays was shown in the range of wavelengths from 400 to 680 nm. Luminescent structures with phosphors corresponding to the emission standards with CRI>98 and with color temperature of 5500 K and 6504 K were created.

Luminescence properties of In(Zn)P alloy core/ZnS shell quantum dots

Science.gov (United States)

Thuy, Ung Thi Dieu; Reiss, Peter; Liem, Nguyen Quang

2010-11-01

Chemically synthesized InP/ZnS core/shell quantum dots (QDs) are studied using time-resolved photoluminescence spectroscopy and x-ray diffraction. Zinc stearate, which is added during the synthesis of the InP core, significantly improves the optical characteristics of the QDs. The luminescence quantum yield (QY) reaches 60%-70% and the emission is tunable from 485 to 586 nm by varying the Zn2+:In3+ molar ratio and growth temperature. The observed increased Stokes shift, luminescence decay time, and QY in the presence of Zn are rationalized by the formation of an In(Zn)P alloy structure that causes band-edge fluctuation to enhance the confinement of the excited carriers.

Aqueous synthesis of highly luminescent glutathione-capped Mn{sup 2+}-doped ZnS quantum dots

Energy Technology Data Exchange (ETDEWEB)

Kolmykov, Oleksii [Université de Lorraine, Laboratoire Réactions et Génie des Procédés (LRGP), UMR 7274, CNRS, 1 rue Grandville, BP 20451, 54001 Nancy Cedex (France); Coulon, Joël [Université de Lorraine, Laboratoire de Chimie Physique et Microbiologie pour l' Environnement (LCPME), UMR 7564, CNRS, Faculté de Pharmacie, 5 rue Albert Lebrun, 54000 Nancy (France); Lalevée, Jacques [Institut de Science des Matériaux de Mulhouse (IS2M), UMR 7361, CNRS, 15 rue Jean Starcky, 68093 Mulhouse (France); Alem, Halima; Medjahdi, Ghouti [Université de Lorraine, Institut Jean Lamour (IJL), UMR 7198, CNRS, BP 70239, 54506 Vandoeuvre-lès-Nancy Cedex (France); Schneider, Raphaël, E-mail: raphael.schneider@univ-lorraine.fr [Université de Lorraine, Laboratoire Réactions et Génie des Procédés (LRGP), UMR 7274, CNRS, 1 rue Grandville, BP 20451, 54001 Nancy Cedex (France)

2014-11-01

In this paper, an aqueous-based route has been developed to prepare highly luminescent glutathione (GSH)-capped Mn-doped ZnS quantum dots (QDs). The dots obtained have an average diameter of 4.3 nm and exhibit the Mn{sup 2+}-related orange luminescence with very low surface defect density. The highest photoluminescence was observed for a Mn{sup 2+} to Zn{sup 2+} molar ratio of 3%. Consecutive overcoating of the Mn:ZnS@GSH QDs by a ZnS shell was done, and the core/shell structured QDs exhibit a PL quantum yield of 23%. Transmission electron microscopy, X-ray powder diffraction, electron spin resonance, X-ray photoelectron spectroscopy, UV–visible spectroscopy and spectrofluorometry have been used to characterize the crystal structure, the doping status, and the optical properties of the doped-QDs. Our systematic investigation shows that Mn:ZnS/ZnS@GSH QDs are highly promising fluorescent labels in biological applications.

Radiation-induced growth and isothermal decay of infrared-stimulated luminescence from feldspar

DEFF Research Database (Denmark)

Guralnik, Benny; Li, Bo; Jain, Mayank

2015-01-01

the growth and decay of laboratory-regenerated luminescence signals. Here we review a selection of common models describing the response of infrared stimulated luminescence (IRSL) of feldspar to constant radiation and temperature as administered in the laboratory. We use this opportunity to introduce...

Optically stimulated luminescence (OSL) and some other luminescence images from granite slices exposed with radiations

International Nuclear Information System (INIS)

Hashimoto, T.; Notoya, S.; Ojima, T.; Hoteida, M.

1995-01-01

Optically stimulated luminescence (OSL) images of some X- and γ-irradiated granite slices were obtained using photon detection through a 570 nm bandpass filter with diode-laser excitation of 910 nm. Alternative photo-induced phosphorescence (PIP) images, which were colour photographed immediately after the sunlight exposure of slice samples, were also found to be helpful in the observation of the luminescence properties and to filter selection for OSL measurements. These OSL and PIP images were compared with some other colour luminescence images, including thermoluminescence images (TLCI) and after-glow images (AGCI). It was obvious that there exists a variety of coloured emissions derived mainly from feldspar constituents and these were found to be dependent on the geological history or metamorphism of the granites. (Author)

An optically stimulated luminescence study of porcelain related to radiation dosimetry

DEFF Research Database (Denmark)

Poolton, N.R.J.; Bøtter-Jensen, L.; Jungner, H.

1995-01-01

Stokes and anti-Stokes shifted in energy. Glazing is shown in some cases to be considerably more sensitive as a radiation dosemeter than the main porcelain ceramic. By comparison with the properties of artifical phosphors, the principal luminescent matrix is identified as being Al2O3......This article describes the essential features regarding the photo-stimulated luminescence of porcelain: both the main ceramic and glazing materials are studied. In each case, radiation dose dependent signals are observed, superimposed on dose independent luminescence transitions that are both...

SU-F-T-327: Total Body Irradiation In-Vivo Dose Measurements Using Optically Stimulated Luminescence (OSL) NanoDots and Farmer Type Ion Chamber

International Nuclear Information System (INIS)

Kaur, H; Kumar, S; Sarkar, B; Ganesh, T; Giri, U; Jassal, K; Rathinamuthu, S; Gulia, G; Gopal, V; Mohanti, B; Munshi, A

2016-01-01

Purpose: This study was performed to analyze the agreement between optically stimulated luminescence (OSL) nanoDots measured doses and 0.6 cc Farmer type ionization chamber measured doses during total body irradiation (TBI). Methods: In-vivo dose measurements using OSL nanoDots and Farmer chamber were done in a total of twelve patients who received TBI at our center by bilateral parallel-opposed beams technique. In this technique, the patient is kept inside the TBI box which is filled with rice bags and irradiated using two bilateral parallel opposed beams of 40×40 cm"2 size with 45° collimator rotation at an SSD of 333.5 cm in an Elekta Synergy linear accelerator. All patients received a dose of 2 Gy in single fraction as conditioning regimen. The beams were equally weighted at the midplane of the box. The nanoDots were placed over forehead, right and left neck, right and left lung, umbilicus, right and left abdomen, medial part of thigh, knee and toe. A 0.6 cc Farmer chamber was placed in between the thighs of the patient. Measured doses are reported along with the statistical comparisons using paired sample t-test. Results: For the above sites the mean doses were 212.2±21.1, 218.2±7.6, 218.7±9.3, 215.6±9.5, 217.5±11.5, 214.5±7.7, 218.3±6.8, 221.5±15, 229.1±11.0, 220.5±7.7 and 223.3±5.1 cGy respectively. For all OSL measurements the mean dose was 218.6±11.8 cGy. Farmer chamber measurements yielded a mean dose of 208.8±15.6 cGy. Statistical analysis revealed that there was no significant difference between OSL measured doses in forehead, right and left neck, right and left lung, umbilicus, right and left abdomen and toe and Farmer chamber measured doses (0.72≤p≤0.06). However the mean OSL doses at thigh and knee were statistically different (p<0.05) from the Farmer chamber measurements. Conclusion: OSL measurements were found to be in agreement with Farmer type ionization chamber measurements in in-vivo dosimetry of TBI.

Thermo-optical properties of optically stimulated luminescence in feldspars

DEFF Research Database (Denmark)

Poolton, N.R.J.; Bøtter-Jensen, L.; Johnsen, O.

1995-01-01

Optically stimulated luminescence processes in feldspars are subject to competing thermal enhancement and quenching processes: this article describes the thermal enhancement effects for orthoclase, albite and plagioclase feldspars. It is demonstrated that certain lattice vibrational modes can be ...

C8-structured carbon quantum dots: Synthesis, blue and green double luminescence, and origins of surface defects

Science.gov (United States)

Xifang, Chen; Wenxia, Zhang; Qianjin, Wang; Jiyang, Fan

Carbon quantum dots (CQDs) have attracted great attention in the past few years due to their low cytotoxicity, exploited various synthesis methods, unexampled abundance of raw materials on earth, and robust near-infrared to near-UV luminescence. Carbon nanoparticles have applications in biological labeling, delivery of drugs and biological molecules into cells, and light emitting diodes and lasing. CQDs generally exist as nanodiamonds or graphite quantum dots according to previous research reports. In this study, we report the first synthesis of the third-allotrope CQDs through carbonization of sucrose and study their luminescence properties. These CQDs have a body-centered cubic structure and each lattice point is composed of eight atoms which form a sub-cube (so called C8 crystal structure). High-resolution transmission electron microscopy and X-ray diffraction confirm the C8 structure of the synthesized carbon nanocrystallites with an average size of 2 nm. The C8 CQDs exhibit double-band luminescence with two peaks centered at around 432 and 520 nm. The study based on the photoluminescence, UV-Vis absorption, Fourier-transform infrared, and X-ray photoelectron spectroscopies reveals that the green emission originates from the C=O related surface defect.

Infrared (IR) stimulated luminescence from modern bricks in retrospective dosimetry applications

International Nuclear Information System (INIS)

Niedermayer, M.; Goeksu, H.Y.; Dalheimer, A.; Bayer, A.

2000-01-01

It has frequently been observed that certain roof tiles and bricks, especially from relatively modern European buildings, do not contain enough quartz grains in a suitable grain size range to permit dose reconstruction using thermoluminescence (TL) or optically stimulated luminescence (OSL) methods. In this paper the feasibility of using infrared-stimulated luminescence (IRSL) on the feldspar fraction of such bricks and tiles has been investigated. Appropriate preheating treatments were employed in order to select the most stable signals, and procedures were developed to enhance the signal to noise ratio. The possible effect of anomalous fading under application of these procedures was tested. In the dose range above 100 mGy, it has been demonstrated that using IRSL on the feldspar fraction of such material provides a feasible alternative to the use of green-light-stimulated luminescence (GLSL) on the quartz fraction, for the purposes of retrospective dosimetry. Furthermore, since the use of IRSL as described in this paper involves the measurement of polymineral fine grain fractions of bricks, a technique for the calibration of the built-in β source against the γ source in Secondary Standard Dosimetry facilities for routine use of the technique is described

Analytical expressions for time-resolved optically stimulated luminescence experiments in quartz

International Nuclear Information System (INIS)

Pagonis, V.; Lawless, J.; Chen, R.; Chithambo, M.L.

2011-01-01

Optically stimulated luminescence (OSL) signals can be obtained using a time-resolved optical stimulation (TR-OSL) method, also known as pulsed OSL. During TR-OSL measurements, the stimulation and emission of luminescence are experimentally separated in time using short light pulses. This paper presents analytical expressions for the TR-OSL intensity observed during and after such a pulse in quartz experiments. The analytical expressions are derived using a recently published kinetic model which describes thermal quenching phenomena in quartz samples. In addition, analytical expressions are derived for the concentration of electrons in the conduction band during and after the TR-OSL pulse, and for the maximum signals attained during optical stimulation of the samples. The relevance of the model for dosimetric applications is examined, by studying the dependence of the maximum TR-OSL signals on the degree of initial trap filling, and also on the probability of electron retrapping into the dosimetric trap. Analytical expressions are derived for two characteristic times of the TR-OSL mechanism; these times are the relaxation time for electrons in the conduction band, and the corresponding relaxation time for the radiative transition within the luminescence center. The former relaxation time is found to depend on several experimental parameters, while the latter relaxation time depends only on internal parameters characteristic of the recombination center. These differences between the two relaxation times can be explained by the presence of localized and delocalized transitions in the quartz sample. The analytical expressions in this paper are shown to be equivalent to previous analytical expressions derived using a different mathematical approach. A description of thermal quenching processes in quartz based on AlO 4 - /AlO 4 defects is presented, which illustrates the connection between the different descriptions of the luminescence process found in the literature

Direct determination of graphene quantum dots based on terbium-sensitized luminescence

Science.gov (United States)

Llorent-Martínez, Eulogio J.; Molina-García, Lucía; Durán, Gema M.; Ruiz-Medina, Antonio; Ríos, Ángel

2018-06-01

Graphene quantum dots (GQD) were determined in water samples using terbium-sensitized luminescence (TSL). Terbium ions complex with GQD due to the carboxylic groups that are usually present in these nanomaterials, increasing the luminescence signal of terbium. In Tb(III)-GQD complexes, GQD absorb energy at their characteristic excitation wavelength and transfer it to terbium ion, which emits at its particular emission wavelength. The analytical signal, measured at λexc = 257 nm and λem = 545 nm, increases proportionally to GQD concentration between 50 and 500 μg L-1. Under optimum conditions, the proposed method presents a detection limit of 15 μg L-1 and is selective to GQD in the presence of other nanomaterials of similar size. As GQD are highly water-soluble, they are potential contaminants in environmental or drinking waters water samples, and hence the method was applied to the analysis of different drinking waters which were the target samples for the application of the developed method.

Optically stimulated luminescence dosimetry using natural and synthetic materials

DEFF Research Database (Denmark)

Bøtter-Jensen, L.; McKeever, S.W.S.

1996-01-01

The application of optically stimulated luminescence (OSL) for use in radiation dosimetry is reviewed. A broad description is given of OSL techniques developed at Riso National Laboratory and at Oklahoma State University, and recent collaborative investigations on the properties of a variety...

Design of Biotin-Functionalized Luminescent Quantum Dots

Directory of Open Access Journals (Sweden)

Kimihiro Susumu

2007-01-01

Full Text Available We report the design and synthesis of a tetraethylene glycol- (TEG- based bidentate ligand functionalized with dihydrolipoic acid (DHLA and biotin (DHLA—TEG—biotin to promote biocompatibility of luminescent quantum dots (QD's. This new ligand readily binds to CdSe—ZnS core-shell QDs via surface ligand exchange. QDs capped with a mixture of DHLA and DHLA—TEG—biotin or polyethylene glycol- (PEG- (molecular weight average ∼600 modified DHLA (DHLA—PEG600 and DHLA—TEG—biotin are easily dispersed in aqueous buffer solutions. In particular, homogeneous buffer solutions of QDs capped with a mixture of DHLA—PEG600 and DHLA—TEG—biotin that are stable over broad pH range have been prepared. QDs coated with mixtures of DHLA/DHLA—TEG—biotin and with DHLA—PEG600/DHLA—TEG—biotin were tested in surface binding assays and the results indicate that biotin groups on the QD surface interact specifically with NeutrAvidin-functionalized microtiter well plates.

Quantum Dots and Their Multimodal Applications: A Review

Directory of Open Access Journals (Sweden)

Paul H. Holloway

2010-03-01

Full Text Available Semiconducting quantum dots, whose particle sizes are in the nanometer range, have very unusual properties. The quantum dots have band gaps that depend in a complicated fashion upon a number of factors, described in the article. Processing-structure-properties-performance relationships are reviewed for compound semiconducting quantum dots. Various methods for synthesizing these quantum dots are discussed, as well as their resulting properties. Quantum states and confinement of their excitons may shift their optical absorption and emission energies. Such effects are important for tuning their luminescence stimulated by photons (photoluminescence or electric field (electroluminescence. In this article, decoupling of quantum effects on excitation and emission are described, along with the use of quantum dots as sensitizers in phosphors. In addition, we reviewed the multimodal applications of quantum dots, including in electroluminescence device, solar cell and biological imaging.

Creating high yield water soluble luminescent graphene quantum dots via exfoliating and disintegrating carbon nanotubes and graphite flakes.

Science.gov (United States)

Lin, Liangxu; Zhang, Shaowei

2012-10-21

We have developed an effective method to exfoliate and disintegrate multi-walled carbon nanotubes and graphite flakes. With this technique, high yield production of luminescent graphene quantum dots with high quantum yield and low oxidization can be achieved.

Stimulation of mineral-specific luminescence from multi-mineral samples

DEFF Research Database (Denmark)

Duller, G.A.T.; Bøtter-Jensen, L.; Poolton, N.R.J.

1995-01-01

Grains of quartz and potassium-rich feldspar have been mixed in known ratios to produce samples of known mineralogical composition, analogous to those found in natural sedimentary deposits. The variation of the green light stimulated luminescence (GLSL), as a function of sample temperature......, was measured for each of these mixtures in order to attempt to isolate a luminescence signal that originates specifically from just one of the components. As the sample is heated from room temperature to 450 degrees C, thermal quenching reduces the signal from the quartz component to near zero, while that from...... geological samples....

Cooperative effects in CdSe/ZnS-PEGOH quantum dot luminescence quenching by a water soluble porphyrin

International Nuclear Information System (INIS)

Borissevitch, I.E.; Parra, G.G.; Zagidullin, V.E.; Lukashev, E.P.; Knox, P.P.; Paschenko, V.Z.; Rubin, A.B.

2013-01-01

In this work we report on the study of the interaction of CdSe/ZnS-PEGOH 570 Quantum Dot (QD) with negatively charged meso-tetrakis(p-sulfonato-phenyl)porphyrin (TPPS 4 ) using optical absorption and fluorescence spectroscopies accompanied with time resolved “single photon counting” and dynamic and resonance light scattering techniques. In the steady-state experiments the QD luminescence quenching by TPPS 4 was well approximated by a square law. In the time-resolved experiments we observed a typical multi-exponential luminescence decay curve, successfully fitted by a bi-exponential approximation. At QD interaction with porphyrin the time quenching of both components was described by a linear Stern–Volmer dependence. The discrepancy between Stern–Volmer dependences in the steady-state and time resolved experiments may be due to formation of mixed m(TPPS 4 )+n(QD) complexes, in which one TPPS 4 molecule can quench several excited QDs. This idea is in accordance with the dynamic and resonance light scattering data, which demonstrate an increase of the scattering particle size at the TPPS 4 addition to QD solutions. - Highlights: ► Quantum Dot luminescence quenching by TPPS porphyrin was studied in water solutions. ► The size of particles in QD solutions possessed increase at the TPPS4 addition. ► Quenching of the QD luminescence by TPPS4 is realized in contact QD–porphyrin complexes. ► The formation of mixed quantum dot–porphyrin aggregates takes place.

Influence of pH on luminescence from water-soluble colloidal Mn-doped ZnSe quantum dots capped with different mercaptoacids

International Nuclear Information System (INIS)

Hardzei, Maryia; Artemyev, Mikhail

2012-01-01

Water-soluble ZnSe/ZnS core–shell quantum dots with ZnSe core doped by manganese ions show different luminescence response to pH changes in aqueous solutions depending on the type of solubilizing agents (thioglycolic acid, mercaptoundecanoic acid, sodium mercaptopropylsulfonate). In the case of long-chain mercaptoundecanoic acid only excitonic emission is affected by pH changes. Short-chain thioglycolic acid brings about equal excitonic/Mn emission variations with pH, while mercaptopropylsulfonate-stabilized quantum dots are insensitive to pH. The mechanism discussed here is based on the competition between different relaxation channels for excited excitons in ZnSe: excitonic radiative recombination, energy transfer to Mn ion and the photogenerated electron trapping due to the presence of protonated carboxyl group. ZnSe:Mn/ZnS quantum dots stabilized with long-chain mercaptoacids may be used as a new type of fluorescence ratiometric pH-sensor or indicator. - Highlights: ► Prepared ZnSe:Mn/ZnS quantum dots capped with different mercaptoacids in water. ► Photoluminescence intensity of ZnSe:Mn/ZnS quantum dots varied with pH. ► Character of luminescence variations depends on the sort of mercaptoacid capping. ► Competition between different excitonic relaxation channels for different caps.

Towards dating Quaternary sediments using the quartz Violet Stimulated Luminescence (VSL) signal

DEFF Research Database (Denmark)

Ankjærgaard, C.; Jain, Mayank; Wallinga, J.

2013-01-01

Quaternary sediments using the violet (402 nm) stimulated luminescence (VSL) signal of quartz.We develop and test a new post-blue VSL single aliquot regenerative dose dating protocol, and demonstrate that the VSL signal originates from a deep trap at about 1.9 eV with a thermal lifetime of 1011 years at 10......Quartz optically stimulated luminescence (OSL) dating is widely used to determine the time of deposition and burial of Late Quaternary sediments. Application of the method is usually limited to the past 150,000 years due to early saturation of the OSL signal. Here we explore the potential to date...

Determination of U, Th and K for optically stimulated luminescence dating by NAA

International Nuclear Information System (INIS)

Qin Yali; Chen Zhe; Wu Weiming

2010-01-01

Optically stimulated luminescence dating techniques have been widely used in northern Loess ancient soil series and recorded climate environment change, ancient earthquake, the ancients site and archaeology research. The determination of U, Th and K using neutron activation analysis (NAA) has been optimized for the samples related to OSL dating research. The procedure for determination of U, Th, K in loess have been fixed by using Miniature neutron source reactor. This procedure of NAA will provide a reliable data base for optically stimulated luminescence dating research. (authors)

Container Verification Using Optically Stimulated Luminescence

International Nuclear Information System (INIS)

Tanner, Jennifer E.; Miller, Steven D.; Conrady, Matthew M.; Simmons, Kevin L.; Tinker, Michael R.

2008-01-01

Containment verification is a high priority for safeguards containment and surveillance. Nuclear material containers, safeguards equipment cabinets, camera housings, and detector cable conduit are all vulnerable to tampering. Even with a high security seal on a lid or door, custom-built hinges and interfaces, and special colors and types of finishes, the surfaces of enclosures can be tampered with and any penetrations repaired and covered over. With today's technology, these repairs would not be detected during a simple visual inspection. Several suggested solutions have been to develop complicated networks of wires, fiber-optic cables, lasers or other sensors that line the inside of a container and alarm when the network is disturbed. This results in an active system with real time evidence of tampering but is probably not practical for most safeguards applications. A more practical solution would be to use a passive approach where an additional security feature was added to surfaces which would consist of a special coating or paint applied to the container or enclosure. One type of coating would incorporate optically stimulated luminescent (OSL) material. OSL materials are phosphors that luminesce in proportion to the ionizing radiation dose when stimulated with the appropriate optical wavelengths. The OSL fluoresces at a very specific wavelength when illuminated at another, very specific wavelength. The presence of the pre-irradiated OSL material in the coating is confirmed using a device that interrogates the surface of the enclosure using the appropriate optical wavelength and then reads the resulting luminescence. The presence of the OSL indicates that the integrity of the surface is intact. The coating itself could be transparent which would allow the appearance of the container to remain unchanged or the OSL material could be incorporated into certain paints or epoxies used on various types of containers. The coating could be applied during manufacturing

SU-F-T-327: Total Body Irradiation In-Vivo Dose Measurements Using Optically Stimulated Luminescence (OSL) NanoDots and Farmer Type Ion Chamber

Energy Technology Data Exchange (ETDEWEB)

Kaur, H; Kumar, S; Sarkar, B; Ganesh, T; Giri, U; Jassal, K; Rathinamuthu, S; Gulia, G; Gopal, V; Mohanti, B; Munshi, A [Fortis Memorial Research Institute, Gurgaon, Haryana (India)

2016-06-15

Purpose: This study was performed to analyze the agreement between optically stimulated luminescence (OSL) nanoDots measured doses and 0.6 cc Farmer type ionization chamber measured doses during total body irradiation (TBI). Methods: In-vivo dose measurements using OSL nanoDots and Farmer chamber were done in a total of twelve patients who received TBI at our center by bilateral parallel-opposed beams technique. In this technique, the patient is kept inside the TBI box which is filled with rice bags and irradiated using two bilateral parallel opposed beams of 40×40 cm{sup 2} size with 45° collimator rotation at an SSD of 333.5 cm in an Elekta Synergy linear accelerator. All patients received a dose of 2 Gy in single fraction as conditioning regimen. The beams were equally weighted at the midplane of the box. The nanoDots were placed over forehead, right and left neck, right and left lung, umbilicus, right and left abdomen, medial part of thigh, knee and toe. A 0.6 cc Farmer chamber was placed in between the thighs of the patient. Measured doses are reported along with the statistical comparisons using paired sample t-test. Results: For the above sites the mean doses were 212.2±21.1, 218.2±7.6, 218.7±9.3, 215.6±9.5, 217.5±11.5, 214.5±7.7, 218.3±6.8, 221.5±15, 229.1±11.0, 220.5±7.7 and 223.3±5.1 cGy respectively. For all OSL measurements the mean dose was 218.6±11.8 cGy. Farmer chamber measurements yielded a mean dose of 208.8±15.6 cGy. Statistical analysis revealed that there was no significant difference between OSL measured doses in forehead, right and left neck, right and left lung, umbilicus, right and left abdomen and toe and Farmer chamber measured doses (0.72≤p≤0.06). However the mean OSL doses at thigh and knee were statistically different (p<0.05) from the Farmer chamber measurements. Conclusion: OSL measurements were found to be in agreement with Farmer type ionization chamber measurements in in-vivo dosimetry of TBI.

Improvement of the luminescent properties of cadmium sulfide quantum dots by a post-synthesis modification

Energy Technology Data Exchange (ETDEWEB)

López, Israel; Gómez, Idalia, E-mail: maria.gomezd@uanl.edu.mx

2014-11-15

Here the improvement of the luminescent properties of CdS quantum dots by a post-synthesis modification with aqueous solutions of NaOH at different concentrations is presented. The CdS quantum dots were synthesized by a microwave-assisted method using citrate ions as stabilizer. The addition of the hydroxide ions increased the intensity of the orange-red emission by about 80%. Besides, a violet-blue emission was achieved by means of this post-synthesis modification. The hydroxide ions control the precipitation equilibria of the CdS and Cd(OH){sub 2}, dissolving and precipitating the surface of the quantum dots. The NaOH treatment increases the number of traps, which produces less band-edge and more deep-trap emission, which explains the decrease and increase in the intensity of the violet-blue and orange-red emissions, respectively.

Improvement of the luminescent properties of cadmium sulfide quantum dots by a post-synthesis modification

International Nuclear Information System (INIS)

López, Israel; Gómez, Idalia

2014-01-01

Here the improvement of the luminescent properties of CdS quantum dots by a post-synthesis modification with aqueous solutions of NaOH at different concentrations is presented. The CdS quantum dots were synthesized by a microwave-assisted method using citrate ions as stabilizer. The addition of the hydroxide ions increased the intensity of the orange-red emission by about 80%. Besides, a violet-blue emission was achieved by means of this post-synthesis modification. The hydroxide ions control the precipitation equilibria of the CdS and Cd(OH) 2 , dissolving and precipitating the surface of the quantum dots. The NaOH treatment increases the number of traps, which produces less band-edge and more deep-trap emission, which explains the decrease and increase in the intensity of the violet-blue and orange-red emissions, respectively

Interaction of porphyrins with CdTe quantum dots

International Nuclear Information System (INIS)

Zhang Xing; Liu Zhongxin; Ma Lun; Hossu, Marius; Chen Wei

2011-01-01

Porphyrins may be used as photosensitizers for photodynamic therapy, photocatalysts for organic pollutant dissociation, agents for medical imaging and diagnostics, applications in luminescence and electronics. The detection of porphyrins is significantly important and here the interaction of protoporphyrin-IX (PPIX) with CdTe quantum dots was studied. It was observed that the luminescence of CdTe quantum dots was quenched dramatically in the presence of PPIX. When CdTe quantum dots were embedded into silica layers, almost no quenching by PPIX was observed. This indicates that PPIX may interact and alter CdTe quantum dots and thus quench their luminescence. The oxidation of the stabilizers such as thioglycolic acid (TGA) as well as the nanoparticles by the singlet oxygen generated from PPIX is most likely responsible for the luminescence quenching. The quenching of quantum dot luminescence by porphyrins may provide a new method for photosensitizer detection.

Influence of electric field on the properties of the polymer stabilized luminescent quantum dots in aqueous solutions

Energy Technology Data Exchange (ETDEWEB)

Zharkova, Irina S.; Markina, Natalia E. [Saratov State University, Astrakhanskaya 83, 410012 Saratov (Russian Federation); Markin, Alexey V., E-mail: av_markin@mail.ru [Saratov State University, Astrakhanskaya 83, 410012 Saratov (Russian Federation); Drozd, Daniil D.; Speranskaya, Elena S. [Saratov State University, Astrakhanskaya 83, 410012 Saratov (Russian Federation); Goryacheva, Irina Yu. [Saratov State University, Astrakhanskaya 83, 410012 Saratov (Russian Federation); Saint-Petersburg State University, Universitetskii pr. 26, 198504 Petrodvorets, Saint-Petersburg (Russian Federation)

2016-08-15

The application of external electric field for verification of quantum dots (QDs) stability in aqueous medium was proposed. Hydrophilic CdSe core-shell nanocrystals were synthesized and used with three polymer-based organic stabilizers, two of which contain PEG chains. An increasing of the stability under applied electric field (EF) was shown for stabilizer containing higher amount of PEG chains and terminal amino-groups: introduction of additional PEG chains allowed reducing degradation of luminescence intensity for about 60%. The changes of QDs solutions after EF treatment were examined by dynamic light scattering measurements, luminescence and absorbance spectroscopy, and conductivity measurements and explained by decreasing of quantum yield of the samples due to degradation of stabilizer coating. - Highlights: • Hydrophilic QDs with three types of stabilizer coatings were prepared and treated by electric field in water environment. • Permanent QDs luminescence quenching in aqueous medium under low electric field strength was observed. • Luminescence stability to EF treatment increases by stabilizer with higher PEG content. • Redox mechanism of luminescence quenching was proved via conductivity, DLS, and UV-visible absorbance measurements.

Modelling the thermal quenching mechanism in quartz based on time-resolved optically stimulated luminescence

International Nuclear Information System (INIS)

Pagonis, V.; Ankjaergaard, C.; Murray, A.S.; Jain, M.; Chen, R.; Lawless, J.; Greilich, S.

2010-01-01

This paper presents a new numerical model for thermal quenching in quartz, based on the previously suggested Mott-Seitz mechanism. In the model electrons from a dosimetric trap are raised by optical or thermal stimulation into the conduction band, followed by an electronic transition from the conduction band into an excited state of the recombination center. Subsequently electrons in this excited state undergo either a direct radiative transition into a recombination center, or a competing thermally assisted non-radiative process into the ground state of the recombination center. As the temperature of the sample is increased, more electrons are removed from the excited state via the non-radiative pathway. This reduction in the number of available electrons leads to both a decrease of the intensity of the luminescence signal and to a simultaneous decrease of the luminescence lifetime. Several simulations are carried out of time-resolved optically stimulated luminescence (TR-OSL) experiments, in which the temperature dependence of luminescence lifetimes in quartz is studied as a function of the stimulation temperature. Good quantitative agreement is found between the simulation results and new experimental data obtained using a single-aliquot procedure on a sedimentary quartz sample.

The potential of optically stimulated luminescence for medieval building; A case study at Termez, Uzbekistan

International Nuclear Information System (INIS)

Vieillevigne, Emmanuelle; Guibert, Pierre; Rita Zuccarello, Agnese; Bechtel, Francoise

2006-01-01

Luminescence techniques thermoluminescence (TL) and optically stimulated luminescence (OSL) are generally used to assess the chronology of the last firing of ceramics. In the field of building archaeology, fired bricks can be dated by these techniques. Nevertheless, these luminescence ages are not exactly related to the construction of the building itself, but to the production of the building materials. In some cases, re-use is possible and this raises problems with the interpretation of the dating results. This led us to employ optically stimulated luminescence in a less conventional way. Before bricks were sealed in masonry by mortar, they would have been exposed to day light, and, as a result, the optical traps of the crystals on the material surface should have been bleached (zeroed by light). Dating the end of the bleaching period is possible by OSL using blue light for stimulation and by IRSL (infrared stimulated luminescence) using IR stimulation. Thus the OSL or IRSL age for these crystals is directly related to the construction of the architectural structure. Experiments were carried out to determine the suitability of this approach and to solve practical problems of sampling. The results show that the bleaching light penetrates between 0.5 to 1 mm into the bricks, according to their transparency. This depth is sufficient to collect enough quartz and feldspar inclusions that have been affected by light in the past, and thus date the construction of the masonry directly. Attempts at surface dating of bricks collected at the medieval citadel of Termez, Uzbekistan, already dated by TL, were the starting point of this research

Optically stimulated luminescence of ZnO obtained by thermal treatment of ZnS chemically synthesized

International Nuclear Information System (INIS)

Cruz V, C.; Burruel I, S.E.; Orante B, V.R.; Grijalva M, H.; Perez S, R.; Bernal, R.

2005-01-01

In this work, we report the optically stimulated luminescence (OSL) dosimetry of new nano phosphors of ZnO obtained by thermal annealing of chemically synthesized ZnS powder. The synthesized ZnS nano powder was compressed in order to form pellet shaped pellets, which were afterwards subjected to a thermal annealing at 700 C during 24 h under air atmosphere. X-ray diffraction (XRD) patterns and energy-disperse X-ray Spectrometry (EDS) analyses confirmed the transformation of ZnS to ZnO. Samples were exposed to several doses of beta radiation up to 600 Gy, and the optically stimulated luminescence with 470 nm wavelength light was recorded as a function of dose. The intensity of the OSL signal increases by increasing dose, for what it is concluded that these new phosphor materials are suitable to be used in optically stimulated luminescence dosimetry. (Author)

Comparative dose evaluations between XVI and OBI cone beam CT systems using Gafchromic XRQA2 film and nanoDot optical stimulated luminescence dosimeters

International Nuclear Information System (INIS)

Giaddui, Tawfik; Cui Yunfeng; Galvin, James; Yu Yan; Xiao Ying

2013-01-01

Purpose: To investigate the effect of energy (kVp) and filters (no filter, half Bowtie, and full Bowtie) on the dose response curves of the Gafchromic XRQA2 film and nanoDot optical stimulated luminescence dosimeters (OSLDs) in CBCT dose fields. To measure surface and internal doses received during x-ray volume imager (XVI) (Version R4.5) and on board imager (OBI) (Version 1.5) CBCT imaging protocols using these two types of dosimeters. Methods: Gafchromic XRQA2 film and nanoDot OSLD dose response curves were generated at different kV imaging settings used by XVI (software version R4.5) and OBI (software version 1.5) CBCT systems. The settings for the XVI system were: 100 kVp/F0 (no filter), 120 kVp/F0, and 120 kVp/F1 (Bowtie filter), and for the OBI system were: 100 kVp/full fan, 125 kVp/full fan, and 125 kVp/half fan. XRQA2 film was calibrated in air to air kerma levels between 0 and 11 cGy and scanned using reflection scanning mode with the Epson Expression 10000 XL flat-bed document scanner. NanoDot OSLDs were calibrated on phantom to surface dose levels between 0 and 14 cGy and read using the inLight TM MicroStar reader. Both dosimeters were used to measure in field surface and internal doses in a male Alderson Rando Phantom. Results: Dose response curves of XRQA2 film and nanoDot OSLDs at different XVI and OBI CBCT settings were reported. For XVI system, the surface dose ranged between 0.02 cGy in head region during fast head and neck scan and 4.99 cGy in the chest region during symmetry scan. On the other hand, the internal dose ranged between 0.02 cGy in the head region during fast head and neck scan and 3.17 cGy in the chest region during chest M20 scan. The average (internal and external) dose ranged between 0.05 cGy in the head region during fast head and neck scan and 2.41 cGy in the chest region during chest M20 scan. For OBI system, the surface dose ranged between 0.19 cGy in head region during head scan and 4.55 cGy in the pelvis region during spot

Pottery versus sediment: Optically stimulated luminescence dating of the Neolithic Vinča culture, Serbia

DEFF Research Database (Denmark)

Bate, Stephen; Stevens, Thomas; Buylaert, Jan-Pieter

2017-01-01

Optically stimulated luminescence (OSL) dating was applied to the Neolithic Vinča culture's type-site, Vinča Belo-Brdo, to establish best protocols for routine luminescence dating of similar Holocene sites, critical in understanding Neolithic to Chalcolithic cultural development. Equivalent dose ...

Radiation ray discrimination method using photo-stimulated luminescence fluorescent material

International Nuclear Information System (INIS)

Atsumi, Yoshihiro; Takebe, Masahiro; Abe, Ken.

1996-01-01

An IP (imaging plate) using PSL (photo-stimulated luminescence fluorescent material) is formed by coating a photo-stimulated luminescence fluorescent material on a thin plastic plate. A predetermined colorants is added to the PSL material. A colorant which absorbs a light having a wavelength of about 600nm is preferred. After irradiating various kinds of radiation rays to the IP, and then irradiating a white light thereto for a predetermined period of time, lights at several kinds of wavelength specific to several kinds of radiation rays to be measured are successively irradiated to the IP. The ratios between the luminance intensity of the fluorescent light emitted from the IP in this case and that emitted when a light of one specific wavelength is irradiated are successively calculated. The light of the specific wavelength preferably has a wavelength of 600nm. With such procedures, the kinds of the several radiation rays which are irradiated to the IP can be discriminated. (I.N.)

InP/ZnSe/ZnS core-multishell quantum dots for improved luminescence efficiency

Science.gov (United States)

Greco, Tonino; Ippen, Christian; Wedel, Armin

2012-04-01

Semiconductor quantum dots (QDs) exhibit unique optical properties like size-tunable emission color, narrow emission peak, and high luminescence efficiency. QDs are therefore investigated towards their application in light-emitting devices (QLEDs), solar cells, and for bio-imaging purposes. In most cases QDs made from cadmium compounds like CdS, CdSe or CdTe are studied because of their facile and reliable synthesis. However, due to the toxicity of Cd compounds and the corresponding regulation (e.g. RoHS directive in Europe) these materials are not feasible for customer applications. Indium phosphide is considered to be the most promising alternative because of the similar band gap (InP 1.35 eV, CdSe 1.73 eV). InP QDs do not yet reach the quality of CdSe QDs, especially in terms of photoluminescence quantum yield and peak width. Typically, QDs are coated with another semiconductor material of wider band gap, often ZnS, to passivate surface defects and thus improve luminescence efficiency. Concerning CdSe QDs, multishell coatings like CdSe/CdS/ZnS or CdSe/ZnSe/ZnS have been shown to be advantageous due to the improved compatibility of lattice constants. Here we present a method to improve the luminescence efficiency of InP QDs by coating a ZnSe/ZnS multishell instead of a ZnS single shell. ZnSe exhibits an intermediate lattice constant of 5.67 Å between those of InP (5.87 Å) and ZnS (5.41 Å) and thus acts as a wetting layer. As a result, InP/ZnSe/ZnS is introduced as a new core-shell quantum dot material which shows improved photoluminescence quantum yield (up to 75 %) compared to the conventional InP/ZnS system.

Further investigations into pulsed optically stimulated luminescence from feldspars using blue and green light

International Nuclear Information System (INIS)

Ankjaergaard, C.; Jain, M.; Kalchgruber, R.; Lapp, T.; Klein, D.; McKeever, S.W.S.; Murray, A.S.; Morthekai, P.

2009-01-01

The purpose of this paper is to investigate characteristics of luminescence signals resulting from pulsed optical stimulation of feldspars and thereby to understand the underlying processes giving rise to the signal. Fourteen different feldspar specimens were investigated using time-resolved optically stimulated luminescence (TR-OSL), and these signals can be mathematically described as a sum of 4 exponential components (a, b, c, d). The slowest component, d, increases with the duration of the light pulse as expected from the exponential model. The stimulation temperature dependence experiment suggests that the TR-OSL signal decay is governed by the recombination process and not by the excited state lifetime. Furthermore data from the TR-OSL signal dependence on stimulation time and preheat temperature suggest that the recombination process may not be a sum of exponentials, although the model cannot be rejected definitively.

Luminescence optically stimulated: theory and applications; Luminiscencia opticamente estimulada: teoria y aplicaciones

Energy Technology Data Exchange (ETDEWEB)

Rivera M, T.; Azorin N, J. [Departamento de Fisica, Universidad Autonoma Metropolitana-Iztapalapa, 09340 Mexico D.F. (Mexico)

2002-07-01

The thermally stimulated luminescence (Tl) has occupied an important place in the Solid state physics (FES) by the flexibility of the phenomena, mainly for its applications in the fields of Radiation Physics (FR) and Medical Physics (MF). The reason of this phenomena lies in the fact of the electrons release by the action of heat. Under that same reason, it can be used the action of another stimulant agent for releasing the trapped electrons in the metastable states (EM), this agent is the light which has the same effect that the heat, giving as result the production of light photons at using light in the visible spectra, of different wavelength that the excitation light. This phenomena is called Luminescence optically stimulated (LOE). The LOE has a great impact in the Solid State Physics (FES), dating and now in the use of the phenomena as a dosimetric method, alternate to the Tl, for its use in the ionizing and non-ionizing radiations fields. (Author)

Optically stimulated luminescence dating of rock surfaces

DEFF Research Database (Denmark)

Sohbati, Reza

There are many examples of rock surfaces, rock art and stone structures whose ages are of great importance to the understanding of various phenomena in geology, climatology and archaeology. Optically stimulated luminescence (OSL) dating is a well-established chronological tool that has successfully...... to include the effects of the environmental dose rate. By fitting the model to the dose-depth variation from a single clast, four events (two light exposures of different durations each followed by a burial period) in the history of a single cobble are identified and quantified. However, the use of model...

Optimising the separation of quartz and feldspar optically stimulated luminescence using pulsed excitation

International Nuclear Information System (INIS)

Ankjaergaard, C.; Jain, M.; Thomsen, K.J.; Murray, A.S.

2010-01-01

In luminescence dating, the two most commonly used natural minerals, quartz and feldspar, are exposed to different dose rates in the natural environment, and so record different doses. The luminescence signals also have different stabilities. For accurate dosimetry, the signals from these two minerals must be separated, either by physical separation of the mineral grains, or by instrumental separation of the luminescence signals. The luminescence signals from quartz and feldspar have different luminescence lifetimes under pulsed optical stimulation. This difference in lifetime can be used to discriminate between the two signals from a mixed quartz-feldspar sample. The purpose of this study is to identify optimum measurement conditions for the best separation of quartz OSL from that of feldspar in a mixed sample using pulsed stimulation and time-resolved OSL. We integrate the signal from 5 μs after the LEDs are switched off until just before the LEDs are switched on again, with the pulse on-time equal to the pulse off-time of 50 μs. By using only the initial interval of the pulsed OSL decay curve (equivalent to 0.2 s of CW-OSL using blue light at 50 mW cm -2 ) we find that the quartz to feldspar pulsed OSL intensity ratio is at a maximum. By using these parameters with an additional infrared (IR) stimulation at 175 o C before measurement (to further reduce the feldspar signal intensity), we obtain a factor of 25 enhancement in signal separation compared to that from a conventional prior-IR CW measurement. This ratio can be further improved if the counting window in the pulse off-time is restricted to detect between 20 and 50 μs instead of the entire off-period.

Magnetic enhancement of photoluminescence from blue-luminescent graphene quantum dots

Science.gov (United States)

Chen, Qi; Shi, Chentian; Zhang, Chunfeng; Pu, Songyang; Wang, Rui; Wu, Xuewei; Wang, Xiaoyong; Xue, Fei; Pan, Dengyu; Xiao, Min

2016-02-01

Graphene quantum-dots (GQDs) have been predicted and demonstrated with fascinating optical and magnetic properties. However, the magnetic effect on the optical properties remains experimentally unexplored. Here, we conduct a magneto-photoluminescence study on the blue-luminescence GQDs at cryogenic temperatures with magnetic field up to 10 T. When the magnetic field is applied, a remarkable enhancement of photoluminescence emission has been observed together with an insignificant change in circular polarization. The results have been well explained by the scenario of magnetic-field-controlled singlet-triplet mixing in GQDs owing to the Zeeman splitting of triplet states, which is further verified by temperature-dependent experiments. This work uncovers the pivotal role of intersystem crossing in GQDs, which is instrumental for their potential applications such as light-emitting diodes, photodynamic therapy, and spintronic devices.

Identifying irradiated flour by photo-stimulated luminescence technique

International Nuclear Information System (INIS)

Ros Anita Ahmad Ramli; Muhammad Samudi Yasir; Zainon Othman; Wan Saffiey Wan Abdullah

2013-01-01

Full-text: The photo-stimulated luminescence technique is recommended by European Committee for standardization for the detection food irradiation (EN 13751:2009). This study shows on luminescence technique to identify gamma irradiated five types of flour (corn flour, tapioca flour, wheat flour, glutinos rice flour and rice flour) at three difference dose levels in the range 0.2 - 1 kGy. The signal level is compare with two thresholds (700 and 5000). The majority of irradiated samples produce a strong signal above the upper threshold (5000 counts/ 60 s). All the control samples gave negative screening result while the signals below the lower threshold (700 counts/ 60s) suggest that the sample has not been irradiated. A few samples show the signal levels between the two thresholds (intermediate signals) suggest that further investigation. Reported procedure was also tested over 60 days, confirming the applicability and feasibility of proposed methods. (author)

Modeling of the shape of infrared stimulated luminescence signals in feldspars

DEFF Research Database (Denmark)

Pagonis, Vasilis; Jain, Mayank; Murray, Andrew S.

2012-01-01

This paper presents a new empirical model describing infrared (IR) stimulation phenomena in feldspars. In the model electrons from the ground state of an electron trap are raised by infrared optical stimulation to the excited state, and subsequently recombine with a nearest-neighbor hole via...... corresponds to a fast rate of recombination processes taking place along the infrared stimulated luminescence (IRSL) curves. The subsequent decay of the simulated IRSL signal is characterized by a much slower recombination rate, which can be described by a power-law type of equation.Several simulations...

Limits to depletion of blue-green light stimulated luminescence in feldspars: Implications for quartz dating

DEFF Research Database (Denmark)

Jain, M.; Singhvi, A.K.

2001-01-01

stimulation curve of otherwise pure quartz. In this study, the functional relationship between the infra-red stimulated luminescence (IRSL) and BGSL of feldspars, (1) at different preheats, and (2) with IR bleaching at different stimulation temperatures and durations, is examined. The results suggest two trap...

Pure zinc sulfide quantum dot as highly selective luminescent probe for determination of hazardous cyanide ion

International Nuclear Information System (INIS)

Shamsipur, Mojtaba; Rajabi, Hamid Reza

2014-01-01

A rapid and simple fluorescence method is presented for selective and sensitive determination of hazardous cyanide ion in aqueous solution based on functionalized zinc sulfide (ZnS) quantum dot (QD) as luminescent prob. The ultra-small ZnS QDs were synthesized using a chemical co-precipitation method in the presence of 2-mercaptoethanol (ME) as an efficient capping agent. The prepared pure ZnS QDs was applied as an optical sensor for determination of cyanide ions in aqueous solutions. ZnS nanoparticles have exhibited a strong fluorescent emission at about 424 nm. The fluorescence intensity of QDs is linearly proportional to the cyanide ion concentration in the range 2.44 × 10 −6 to 2.59 × 10 −5 M with a detection limit of 1.70 × 10 −7 M at pH 11. The designed fluorescent sensor possesses remarkable selectivity for cyanide ion over other anions such as Cl − , Br − , F − , I − , IO 3 − , ClO 4 − , BrO 3 − , CO 3 2− , NO 2 − , NO 3 − , SO 4 2− , S 2 O 4 2− , C 2 O 4 2− , SCN − , N 3 − , citrate and tartarate with negligible influences on the cyanide detection by fluorescence spectroscopy. - Highlights: • Preparation of functionalized ZnS quantum dots in aqueous media • Highly selective quantum dot based luminescent probe for determination of cyanide • Fast and sensitive determination of hazardous CN − by fluorescence quenching

Luminescence dating

International Nuclear Information System (INIS)

Rieser, U.

2013-01-01

The luminescence techniques have evolved over the last 40 years to a powerful dating instrument in archaeology and geoscience. Depending on how the luminescence is stimulated, one distinguishes the phenomena of thermoluminescence (TL), optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL). Each of these phenomena has its specific potential for dating various archaeological materials in the time range from medieval back to palaeolithic periods, or, speaking in geological terms, for dating of Holocene and late Pleistocene objects. The OSL and IRSL techniques are sometimes treated together as 'optical dating'. The luminescence techniques differ from other major dating techniques, such as 14 C, essentially by their applicability to inorganic materials, their wide age-range from about 100 years to more than 100,000 years and the kind of datable events which are the last exposure to heat or to light. (author). 10 refs., 3 figs.

Luminescence dating

International Nuclear Information System (INIS)

Rieser, U.

2009-01-01

The luminescence techniques have evolved over the last 40 years to a powerful dating instrument in archaeology and geoscience. Depending on how the luminescence is stimulated, one distinguishes the phenomena of thermoluminescence (TL), optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL). Each of these phenomena has its specific potential for dating various archaeological materals in the time range from medieval back to palaeolithic periods, or, speaking in geological terms, for dating of Holocene and late Pleistocene objects. The OSL and IRSL techniques are sometimes treated together as 'optical dating'. The luminescence techniques differ from other major dating techniques, such as 14 C, essentially by their applicability to inorganic materials, their wide age-range from about 100 years to more than 100,000 years and the kind of datable events which are the last exposure to heat or to light. (author). 10 refs., 3 figs.

Luminescence dating

International Nuclear Information System (INIS)

Rieser, U.

2008-01-01

The luminescence techniques have evolved over the last 40 years to a powerful dating instrument in archaeology and geoscience. Depending on how the luminescence is stimulated, one distinguishes the phenomena of thermoluminescence (TL), optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL). Each of these phenomena has its specific potential for dating various archaeological materals in the time range from medieval back to palaeolithic periods, or, speaking in geological terms, for dating of Holocene and late Pleistocene objects. The OSL and IRSL techniques are sometimes treated together as 'optical dating'. The luminescence techniques differ from other major dating techniques, such as 14 C, essentially by their applicability to inorganic materials, their wide age-range from about 100 years to more than 100,000 years and the kind of datable events which are the last exposure to heat or to light. (author). 10 refs., 3 figs

Luminescence dating

International Nuclear Information System (INIS)

Rieser, U.

2012-01-01

The luminescence techniques have evolved over the last 40 years to a powerful dating instrument in archaeology and geoscience. Depending on how the luminescence is stimulated, one distinguishes the phenomena of thermoluminescence (TL), optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL). Each of these phenomena has its specific potential for dating various archaeological materials in the time range from medieval back to palaeolithic periods, or, speaking in geological terms, for dating of Holocene and late Pleistocene objects. The OSL and IRSL techniques are sometimes treated together as 'optical dating'. The luminescence techniques differ from other major dating techniques, such as 14 C, essentially by their applicability to inorganic materials, their wide age-range from about 100 years to more than 100,000 years and the kind of datable events which are the last exposure to heat or to light. (author). 10 refs., 3 figs.

Luminescence dating

International Nuclear Information System (INIS)

Rieser, U.

2009-01-01

The luminescence techniques have evolved over the last 40 years to a powerful dating instrument in archaeology and geoscience. Depending on how the luminescence is stimulated, one distinguishes the phenomena of thermoluminescence (TL), optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL). Each of these phenomena has its specific potential for dating various archaeological materals in the time range from medieval back to palaeolithic periods, or, speaking in geological terms, for dating of Holocene and late Pleistocene objects. The OSL and IRSL techniques are sometimes treated together as 'optical dating'. The luminescence techniques differ from other major dating techniques, such as 14 C, essentially by their applicability to inorganic materials, their wide age-range from about 100 years to more than 100,000 years and the kind of datable events which are the last exposure to heat or to light. (author). 10 refs., 3 figs

Optically stimulated luminescence (OSL) of dental enamel for retrospective assessment of radiation exposure

International Nuclear Information System (INIS)

Yukihara, E.G.; Mittani, J.; McKeever, S.W.S.; Simon, S.L.

2007-01-01

This paper briefly reviews the optically stimulated luminescence (OSL) properties of dental enamel and discusses the potential and challenges of OSL for filling the technology gap in biodosimetry required for medical triage following a radiological/nuclear accident or terrorist event. The OSL technique uses light to stimulate a radiation-induced luminescence signal from materials previously exposed to ionizing radiation. This luminescence originates from radiation-induced defects in insulating crystals and is proportional to the absorbed dose of ionizing radiation. In our research conducted to date, we focused on fundamental investigations of the OSL properties of dental enamel using extracted teeth and tabletop OSL readers. The objective was to obtain information to support the development of the necessary instrumentation for retrospective dosimetry using dental enamel in laboratory, or for in situ and non-invasive accident dosimetry using dental enamel in emergency triage. An OSL signal from human dental enamel was detected using blue, green, or IR stimulation. Blue/green stimulation associated with UV emission detection seems to be the most appropriate combination in the sense that there is no signal from un-irradiated samples and the shape of the OSL decay is clear. Improvements in the minimum detection level were achieved by incorporating an ellipsoidal mirror in the OSL system to maximize light collection. Other possibilities to improve the sensitivity and research steps necessary to establish the feasibility of the technique for retrospective assessment of radiation exposure are also discussed

Further investigations into pulsed optically stimulated luminescence from feldspars using blue and green light

DEFF Research Database (Denmark)

Ankjærgaard, Christina; Jain, Mayank; Kalchgruber, R.

2009-01-01

The purpose of this paper is to investigate characteristics of luminescence signals resulting from pulsed optical stimulation of feldspars and thereby to understand the underlying processes giving rise to the signal. Fourteen different feldspar specimens were investigated using time-resolved opti......The purpose of this paper is to investigate characteristics of luminescence signals resulting from pulsed optical stimulation of feldspars and thereby to understand the underlying processes giving rise to the signal. Fourteen different feldspar specimens were investigated using time...... suggests that the TR-OSL signal decay is governed by the recombination process and not by the excited state lifetime. Furthermore data from the TR-OSL signal dependence on stimulation time and preheat temperature suggest that the recombination process may not be a sum of exponentials, although the model...... cannot be rejected definitively....

Highly efficient luminescent solar concentrators based on earth-abundant indirect-bandgap silicon quantum dots

Science.gov (United States)

Meinardi, Francesco; Ehrenberg, Samantha; Dhamo, Lorena; Carulli, Francesco; Mauri, Michele; Bruni, Francesco; Simonutti, Roberto; Kortshagen, Uwe; Brovelli, Sergio

2017-02-01

Building-integrated photovoltaics is gaining consensus as a renewable energy technology for producing electricity at the point of use. Luminescent solar concentrators (LSCs) could extend architectural integration to the urban environment by realizing electrode-less photovoltaic windows. Crucial for large-area LSCs is the suppression of reabsorption losses, which requires emitters with negligible overlap between their absorption and emission spectra. Here, we demonstrate the use of indirect-bandgap semiconductor nanostructures such as highly emissive silicon quantum dots. Silicon is non-toxic, low-cost and ultra-earth-abundant, which avoids the limitations to the industrial scaling of quantum dots composed of low-abundance elements. Suppressed reabsorption and scattering losses lead to nearly ideal LSCs with an optical efficiency of η = 2.85%, matching state-of-the-art semi-transparent LSCs. Monte Carlo simulations indicate that optimized silicon quantum dot LSCs have a clear path to η > 5% for 1 m2 devices. We are finally able to realize flexible LSCs with performances comparable to those of flat concentrators, which opens the way to a new design freedom for building-integrated photovoltaics elements.

Highly luminescent and photostable quantum dot-silica monolith and its application to light-emitting diodes.

Science.gov (United States)

Jun, Shinae; Lee, Junho; Jang, Eunjoo

2013-02-26

A highly luminescent and photostable quantum dot-silica monolith (QD-SM) substance was prepared by preliminary surface exchange of the QDs and base-catalyzed sol-gel condensation of silica. The SM was heavily doped with 6-mercaptohexanol exchanged QDs up to 12 vol % (26 wt %) without particle aggregation. Propylamine catalyst was important in maintaining the original luminescence of the QDs in the SM during sol-gel condensation. The silica layer was a good barrier against oxygen and moisture, so that the QD-SM maintained its initial luminescence after high-power UV radiation (∼1 W) for 200 h and through the 150 °C LED encapsulant curing process. Green and red light-emitting QD-SMs were applied as color-converting layers on blue LEDs, and the external quantum efficiency reached up to 89% for the green QD-SM and 63% for the red one. A white LED made with a mixture of green and red QDs in the SM, in which the color coordinate was adjusted at (0.23, 0.21) in CIE1931 color space for a backlight application, showed an efficacy of 47 lm/W, the highest value yet reported.

Low-Energy Electron-Stimulated Luminescence of Thin H20 and D20 Layers on Pt(111)

International Nuclear Information System (INIS)

Petrik, Nikolay G.; Kimmel, Greg A.

2005-01-01

The electron-stimulated luminescence (ESL) from amorphous solid water and crystalline ice films deposited on Pt(111) at 100 K is investigated as a function of the film thickness, incident electron energy (5 ? 1000 eV), isotopic composition, and film structure. The ESL emission spectrum has a characteristic double-peaked shape that has been attributed to a transition between a superexcited state ( ) and the dissociative, first excited state ( ) in water: Comparing the electron-stimulated luminescence and O2 electron-stimulated desorption (ESD) yields versus incident electron energy, we find the ESL threshold blue-shifted from the O2 ESD threshold by ∼3 eV, which is close to the center of the emission spectrum near 400 nm and supports the assignment for the ESL. For thin films, radiative and non-radiative interactions with the substrate tend to quench the luminescence. The luminescence yield increases with coverage since the interactions with the substrate become less important. The ESL yield from D2O is ∼ 4 times higher than from H2O. Using layered films of H2O and D2O, this sizable isotopic effect on the ESL is exploited to spatially profile the luminescence emission within the ASW films. These experiments show that most of the luminescence is emitted from within the penetration depth of the incident electron. However, the results depend on the order of the isotopes in the film, and this asymmetry can be modeled by assuming some migration of the excited states within the film. The ESL is very sensitive to defects and structural changes in solid water, and the emission yield is significantly higher from amorphous films than from crystalline ice

Yellow stimulated luminescence from potassium feldspar: Observations on its suitability for dating

International Nuclear Information System (INIS)

Lauer, T.; Krbetschek, M.; Mauz, B.; Frechen, M.

2012-01-01

Yellow stimulated luminescence (Y-OSL) is the light detected from potassium-rich feldspars at 410 nm under stimulation by a yellow light source emitting 590 nm. The investigation of this study aimed at understanding basic luminescence physics of Y-OSL in order to assess the suitability of the technique for dating. The Y-OSL signal properties tested were signal intensity, thermal assistance, thermal stability, sensitivity to daylight and the suitability of a single aliquot regenerative (SAR) protocol to be employed for equivalent dose (D e ) estimation. D e measurements were conducted on samples of Holocene, last glacial and Tertiary age. The tests were undertaken on sedimentary feldspar separates extracted from aeolian, fluvial and coastal deposits. Results from experiments show that the signal intensity increases by measuring Y-OSL at elevated temperature suggesting thermal assistance characteristics similar to infrared stimulated luminescence (IRSL). The yellow stimulated signal remains unaffected by preheat temperatures up to ∼200 °C suggesting higher thermal stability than the IRSL signal. The Y-OSL signal is less light sensitive than the IRSL signal and D e residuals obtained from modern samples are up to 7 Gy indicating suitability of the technique for ‘older’ and well-bleached sediments. The dose recovery tests successfully recovered the given dose if the specific light sensitivity of Y-OSL is taken into account. For every sample Y-OSL D e values obtained by a single aliquot regenerative dose protocol (SAR) are higher than those obtained by an IRSL SAR approach. From these results we infer high thermal stability and a minimal anomalous fading of the Y-OSL signal. We conclude that Y-OSL has a high potential to date Quaternary sediments that were sufficiently bleached in nature.

Optically stimulated luminescence of natural NaCl mineral from Dead Sea exposed to gamma radiation

International Nuclear Information System (INIS)

Roman L, J.; Cruz Z, E.; Pina L, Y. I.; Marcazzo, J.

2016-10-01

Luminescence properties such as radioluminescence, thermoluminescence and optically stimulated luminescence have been studied on natural sodium chloride (NaCl) for dosimetric purposes in retrospective dosimetry (Timar-Gabor et al., 2013; Druzhyna et al., 2016). In this work, the optically stimulated luminescence (Cw-OSL) emissions of natural salt minerals, collected from Dead Sea in summer of 2015, were studied. The Cw-OSL dose response of natural salt was analyzed in the range between 0.2 and 10 Gy gamma dose of "6"0Co. Samples exposed at 3 Gy exhibited good repeatability with a variation coefficient of 4.6%. The thermal stability of the Cw-OSL response was analyzed to different temperatures from 50 up to 250 degrees Celsius using a heating rate of 5 degrees Celsius. The results showed that the natural Dead Sea salt minerals could be applied as natural dosimeter of gamma radiation. (Author)

Optically stimulated luminescence of natural NaCl mineral from Dead Sea exposed to gamma radiation

Energy Technology Data Exchange (ETDEWEB)

Roman L, J.; Cruz Z, E. [UNAM, Instituto de Ciencias Nucleares, Ciudad Universitaria, 04510 Ciudad de Mexico (Mexico); Pina L, Y. I. [UNAM, Facultad de Ciencias, Ciudad Universitaria, 04510 Ciudad de Mexico (Mexico); Marcazzo, J., E-mail: jesus.roman@nucleares.unam.mx [Instituto de Fisica Arroyo Seco - UNICEN, Pinto 399, 7000 Tandil (Argentina)

2016-10-15

Luminescence properties such as radioluminescence, thermoluminescence and optically stimulated luminescence have been studied on natural sodium chloride (NaCl) for dosimetric purposes in retrospective dosimetry (Timar-Gabor et al., 2013; Druzhyna et al., 2016). In this work, the optically stimulated luminescence (Cw-OSL) emissions of natural salt minerals, collected from Dead Sea in summer of 2015, were studied. The Cw-OSL dose response of natural salt was analyzed in the range between 0.2 and 10 Gy gamma dose of {sup 60}Co. Samples exposed at 3 Gy exhibited good repeatability with a variation coefficient of 4.6%. The thermal stability of the Cw-OSL response was analyzed to different temperatures from 50 up to 250 degrees Celsius using a heating rate of 5 degrees Celsius. The results showed that the natural Dead Sea salt minerals could be applied as natural dosimeter of gamma radiation. (Author)

Luminescent, water-soluble silicon quantum dots via micro-plasma surface treatment

International Nuclear Information System (INIS)

Wu, Jeslin J; Siva Santosh Kumar Kondeti, Vighneswara; Bruggeman, Peter J; Kortshagen, Uwe R

2016-01-01

Silicon quantum dots (SiQDs), with their broad absorption, narrow and size-tunable emission, and potential biocompatibility are highly attractive materials in biological imaging applications. The inherent hydrophobicity and instability of hydrogen-terminated SiQDs are obstacles to their widespread implementation. In this work, we successfully produced highly luminescent, hydrophilic SiQDs with long-term stability in water using non-thermal plasma techniques. Hydrogen-terminated SiQDs were produced in a low-pressure plasma and subsequently treated in water using an atmospheric-pressure plasma jet for surface modification. Preliminary assessments of the chemical mechanism(s) involved in the creation of water-soluble SiQDs were performed using Fenton’s reaction and various plasma chemistries, suggesting both OH and O species play a key role in the oxidation of the SiQDs. (letter)

Na-rich feldspar as a luminescence dosimeter in infrared stimulated luminescence (IRSL) dating

DEFF Research Database (Denmark)

Sohbati, Reza; Murray, Andrew; Jain, Mayank

2013-01-01

on geological origin and erosion history, but the dosimetry of K-rich feldspar grains extracted from rocks is complicated because the internal dose rate is very dependent on the original feldspar grain size. The in situ grain size information is lost during the crushing process used to separate the grains...... settings for which independent age control is available. The blue and yellow luminescence emissions are measured for IR stimulation at 50 °C (IR50), and post-IR IR stimulation at 290 °C (pIRIR290). Thermal stability experiments imply that the corresponding signals in both emissions have comparable thermal...... stabilities and that all signals have similar recombination kinetics and are thermally stable over geological timescales. The IR50 doses measured using blue and yellow emissions are similar to or lower than quartz doses while pIRIR290 blue doses are higher than those from yellow emission and quartz doses...

Mathematical characterization of continuous wave infrared stimulated luminescence signals (CW-IRSL) from feldspars

International Nuclear Information System (INIS)

Pagonis, V.; Phan, Huy; Goodnow, Rebecca; Rosenfeld, Sara; Morthekai, P.

2014-01-01

Continuous-wave infrared stimulated luminescence signals (CW-IRSL) from feldspars have been the subject of many experimental studies, due to their importance in luminescence dating and dosimetry. Accurate mathematical characterization of the shape of these CW-IRSL signals in feldspars is of practical and theoretical importance, especially in connection with “anomalous fading” of luminescence signals in dating studies. These signals are known to decay in a non-exponential manner and their exact mathematical shape as a function of stimulation time is an open research question. At long stimulation times the IRSL decay has been shown experimentally to follow a power law of decay, and previous researchers have attempted to fit the overall shape of these signals empirically using the well known Becquerel function (or compressed hyperbola decay law). This paper investigates the possibility of fitting CW-IRSL curves using either the Becquerel decay law, or a recently developed analytical equation based on localized electronic recombination of donor–acceptor pairs in luminescent materials. It is shown that both mathematical approaches can give excellent fits to experimental CW-IRSL curves, and the precision of the fitting process is studied by analyzing a series of curves measured using a single aliquot of a feldspar sample. Both fitting equations are solutions of differential equations involving numerically similar time dependent recombination probabilities k(t). It is concluded that both fitting equations provide approximately equivalent mathematical descriptions of the CW-IRSL curves in feldspars, and can be used as mathematical representations of the shape of CW-IRSL signals. - Highlights: • Feldspar CW-IRSL curves fitted using Becquerel decay law and new analytical equation. • Both mathematical approaches give excellent fits to experimental CW-IRSL curves. • Series of experimental CW-IRSL curves analyzed using both fitting expressions. • The time

Studies on highly luminescent AgInS{sub 2} and Ag–Zn–In–S quantum dots

Energy Technology Data Exchange (ETDEWEB)

Xiang, Weidong, E-mail: xiangweidong001@126.com [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035 (China); College of Materials Science and Engineering, Tongji University, Shanghai 201804 (China); Xie, Cuiping; Wang, Jing; Zhong, Jiasong; Liang, Xiaojuan; Yang, Hailong; Luo, Le [College of Materials Science and Engineering, Tongji University, Shanghai 201804 (China); Chen, Zhaoping [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035 (China)

2014-03-05

Highlights: • The quantum yield of the obtained ternary AgInS{sub 2} QDs was up to 62% with the emission peak of 642 nm under the excitation of 460 nm. • Colorful luminescent Ag–Zn–In–S QDs were obtained by adding Zn salts directly as well as Ag and In precursors. • The obtained highly luminescent quantum dots showed promising applications in the white light emitting diodes (W-LED). • The electroluminescence (EL) of AgInS{sub 2} QDs was observed in QD-LED device. -- Abstract: Silver indium sulfide (AIS) quantum dots (QDs) with different Ag/In molar ratios were synthesized via a hot-injection method. Intense photoluminescence (PL) originating from the donor–acceptor pair recombination were observed for all the samples and the emission peak blue-shifted from 739 to 632 nm, being similar to the behavior of the absorption onset as the Ag/In ratios decreased. The highest PL quantum yield (QY) of the obtained ternary AIS QDs was ca. 62% with an optimum ratio of Ag/In = 1/4. Compared with AIS QDs, when Zn ions were introduced, the absorption spectra of the obtained quaternary Ag–Zn–In–S QDs were blue-shifted, and their emission peaks moved to higher energies accordingly, showing a tunable emission from red to green by altering the band gap energy. In order to further study the electroluminescence (EL) as well as looking forward to the applications in the optoelectronic devices of the obtained highly luminescent nanoparticles, the colloidal AIS QDs were deposited as thin films to the sandwich-like structured QD-LED. The experimental results showed that the obtained EL device exhibited EL emission originated from QDs thin films by adjusting the turn on voltage, which is for the first time to realize EL of AIS QDs in such QD-LED.

Super-Resolution Definition of Coordinates of Single Semiconductor Nanocrystal (Quantum Dot: Luminescence Intensity Dependence

Directory of Open Access Journals (Sweden)

Eremchev M. Yu.

2015-01-01

Full Text Available In this research a relation between the accuracy of restoration of the single quantum dots (QD CdSe/CdS/ZnS cross-cut coordinates and luminescence intensity was investigated. It was shown that the limit of the accuracy of determining the coordinates of a single QD for a considerable total amount of registered photons approaches its limiting value that is comparable to the size of the QD. It also means that the installation used in the research is mechanically stable enough to reach the limiting values of determination accuracy of point emitters coordinates.

Low-cost photovoltaics: Luminescent solar concentrators and colloidal quantum dot solar cells

Science.gov (United States)

Leow, Shin Woei

Solar energy has long been lauded as an inexhaustible fuel source with more energy reaching the earth's surface in one hour than the global consumption for a year. Although capable of satisfying the world's energy requirements, solar energy remains an expensive technology that has yet to attain grid parity. Another drawback is that existing solar farms require large quantities of land in order to generate power at useful rates. In this work, we look to luminescent solar concentrator systems and quantum dot technology as viable solutions to lowering the cost of solar electricity production with the flexibility to integrate such technologies into buildings to achieve dual land use. Luminescent solar concentrator (LSC) windows with front-facing photovoltaic (PV) cells were built and their gain and power efficiency were investigated. Conventional LSCs employ a photovoltaic (PV) cell that is placed on the edge of the LSC, facing inward. This work describes a new design with the PV cells on the front-face allowing them to receive both direct solar irradiation and wave-guided photons emitted from a dye embedded in an acrylic sheet, which is optically coupled to the PV cells. Parameters investigated include the thickness of the waveguide, edge treatment of the window, cell width, and cell placement. The data allowed us to make projections that aided in designing windows for maximized overall efficiency. A gain in power of 2.2x over the PV cells alone was obtained with PV cell coverage of 5%, and a power conversion efficiency as high as 6.8% was obtained with a PV cell coverage of 31%. Balancing the trade-offs between gain and efficiency, the design with the lowest cost per watt attained a power efficiency of 3.8% and a gain of 1.6x. With the viability of the LSC demonstrated, a weighted Monte-Carlo Ray Tracing program was developed to study the transport of photons and loss mechanisms in the LSC to aid in design optimization. The program imports measured absorption

Basic study on electrically stimulated luminescence (ESL) as a dosimetry and dating method

International Nuclear Information System (INIS)

Sato, H.; Yamanaka, C.; Ikeya, M.

2003-01-01

Electrically stimulated luminescence (ESL) of calcium carbonate has been studied for application as dosimetry and dating. A powdered calcium carbonate was sandwiched by electrodes, which supplied electric field. Luminescence and surface current through a powdered sample were measured using a photomultiplier and a digital multimeter, respectively. A linear dependence of ESL on the absorbed dose by γ-rays was found when the applied voltage was below the breakdown threshold. Reciprocal electric charges through the sample had also linear relation with the absorbed dose. We propose that the luminescence and electric charge under intense electric field in calcium carbonate become new methods for dosimetry and dating on the basis of the surface defects of the calcium carbonate grains produced by the irradiation of γ-rays

Nanodiamonds and silicon quantum dots: ultrastable and biocompatible luminescent nanoprobes for long-term bioimaging.

Science.gov (United States)

Montalti, M; Cantelli, A; Battistelli, G

2015-07-21

Fluorescence bioimaging is a powerful, versatile, method for investigating, both in vivo and in vitro, the complex structures and functions of living organisms in real time and space, also using super-resolution techniques. Being poorly invasive, fluorescence bioimaging is suitable for long-term observation of biological processes. Long-term detection is partially prevented by photobleaching of organic fluorescent probes. Semiconductor quantum dots, in contrast, are ultrastable, fluorescent contrast agents detectable even at the single nanoparticle level. Emission color of quantum dots is size dependent and nanoprobes emitting in the near infrared (NIR) region are ideal for low back-ground in vivo imaging. Biocompatibility of nanoparticles, containing toxic elements, is debated. Recent safety concerns enforced the search for alternative ultrastable luminescent nanoprobes. Most recent results demonstrated that optimized silicon quantum dots (Si QDs) and fluorescent nanodiamonds (FNDs) show almost no photobleaching in a physiological environment. Moreover in vitro and in vivo toxicity studies demonstrated their unique biocompatibility. Si QDs and FNDs are hence ideal diagnostic tools and promising non-toxic vectors for the delivery of therapeutic cargos. Most relevant examples of applications of Si QDs and FNDs to long-term bioimaging are discussed in this review comparing the toxicity and the stability of different nanoprobes.

Hydrothermal synthesis of highly luminescent blue-emitting ZnSe(S) quantum dots exhibiting low toxicity

Energy Technology Data Exchange (ETDEWEB)

Mirnajafizadeh, Fatemeh; Ramsey, Deborah; McAlpine, Shelli [School of Chemistry, University of New South Wales, Sydney, NSW 2052 (Australia); Wang, Fan; Reece, Peter [School of Physics, University of New South Wales, Sydney, NSW 2052 (Australia); Stride, John Arron, E-mail: j.stride@unsw.edu.au [School of Chemistry, University of New South Wales, Sydney, NSW 2052 (Australia); Bragg Institute, Australian Nuclear Science and Technology Organisation, PMB 1, Menai, NSW 2234 (Australia)

2016-07-01

Highly luminescent quantum dots (QDs) that emit in the visible spectrum are of interest to a number of imaging technologies, not least that of biological samples. One issue that hinders the application of luminescent markers in biology is the potential toxicity of the fluorophore. Here we show that hydrothermally synthesized ZnSe(S) QDs have low cytotoxicity to both human colorectal carcinoma cells (HCT-116) and human skin fibroblast cells (WS1). The QDs exhibited a high degree of crystallinity, with a strong blue photoluminescence at up to 29% quantum yield relative to 4′,6-diamidino-2-phenylindole (DAPI) without post-synthetic UV-irradiation. Confocal microscopy images obtained of HCT-116 cells after incubation with the QDs highlighted the stability of the particles in cell media. Cytotoxicity studies showed that both HCT-116 and WS1 cells retain 100% viability after treatment with the QDs at concentrations up to 0.5 g/L, which makes them of potential use in biological imaging applications. - Highlights: • Highly luminescent ZnSe(S) QDs were synthesized using a simple, one-step hydrothermal method. • The as-synthesized QDs were found to be nontoxic in the presence of biological cells. • The QDs were stable in biological media with identical emission profile to that in water.

Pure zinc sulfide quantum dot as highly selective luminescent probe for determination of hazardous cyanide ion

Energy Technology Data Exchange (ETDEWEB)

Shamsipur, Mojtaba, E-mail: mshamsipur@yahoo.com [Department of Chemistry, Razi University, Kermanshah (Iran, Islamic Republic of); Rajabi, Hamid Reza, E-mail: h.rajabi@mail.yu.ac.ir [Chemistry Department, Yasouj University, Yasouj 75918-74831 (Iran, Islamic Republic of)

2014-03-01

A rapid and simple fluorescence method is presented for selective and sensitive determination of hazardous cyanide ion in aqueous solution based on functionalized zinc sulfide (ZnS) quantum dot (QD) as luminescent prob. The ultra-small ZnS QDs were synthesized using a chemical co-precipitation method in the presence of 2-mercaptoethanol (ME) as an efficient capping agent. The prepared pure ZnS QDs was applied as an optical sensor for determination of cyanide ions in aqueous solutions. ZnS nanoparticles have exhibited a strong fluorescent emission at about 424 nm. The fluorescence intensity of QDs is linearly proportional to the cyanide ion concentration in the range 2.44 × 10{sup −6} to 2.59 × 10{sup −5} M with a detection limit of 1.70 × 10{sup −7} M at pH 11. The designed fluorescent sensor possesses remarkable selectivity for cyanide ion over other anions such as Cl{sup −}, Br{sup −}, F{sup −}, I{sup −}, IO{sub 3}{sup −}, ClO{sub 4}{sup −}, BrO{sub 3}{sup −}, CO{sub 3}{sup 2−}, NO{sub 2}{sup −}, NO{sub 3}{sup −}, SO{sub 4}{sup 2−}, S{sub 2}O{sub 4}{sup 2−}, C{sub 2}O{sub 4}{sup 2−}, SCN{sup −}, N{sub 3}{sup −}, citrate and tartarate with negligible influences on the cyanide detection by fluorescence spectroscopy. - Highlights: • Preparation of functionalized ZnS quantum dots in aqueous media • Highly selective quantum dot based luminescent probe for determination of cyanide • Fast and sensitive determination of hazardous CN{sup −} by fluorescence quenching.

Red-IR stimulated luminescence in K-feldspar: Single or multiple trap origin?

DEFF Research Database (Denmark)

Andersen, Martin Thalbitzer; Jain, Mayank; Tidemand-Lichtenberg, Peter

2012-01-01

We investigate on the origins of the infra-red stimulated luminescence (IRSL) signals in 3 potassium feldspars based on IR-red spectroscopy (700–1050 nm) using a fiber-coupled tunable Ti:Sapphire laser, in combination with different thermal and optical (pre)treatments of the samples. We also...

Systematic development of new thermoluminescence and optically stimulated luminescence materials

Energy Technology Data Exchange (ETDEWEB)

Yukihara, E.G., E-mail: eduardo.yukihara@okstate.edu [Physics Department, 145 Physical Sciences II, Oklahoma State University, Stillwater, OK 74078 (United States); Milliken, E.D.; Oliveira, L.C. [Physics Department, 145 Physical Sciences II, Oklahoma State University, Stillwater, OK 74078 (United States); Orante-Barron, V.R. [Departamento de Investigacion en Polimeros y Materiales, Universidad de Sonora, Hermosillo, Sonora 83000, Mexico (Mexico); Jacobsohn, L.G. [Center for Optical Materials Science and Engineering Technologies (COMSET), and School of Materials Science and Engineering, Clemson University, Clemson, SC (United States); Blair, M.W. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

2013-01-15

This paper presents an overview of a systematic study to develop new thermoluminescence (TL) and optically stimulated luminescence (OSL) materials using solution combustion synthesis (SCS) for applications such as personal OSL dosimetry, 2D dose mapping, and temperature sensing. A discussion on the material requirements for these applications is included. We present X-ray diffraction (XRD) data on single phase materials obtained with SCS, as well as radioluminescence (RL), TL and OSL data of lanthanide-doped materials. The results demonstrate the possibility of producing TL and OSL materials with sensitivity similar to or approaching those of commercial TL and OSL materials used in dosimetry (e.g., LiF:Mg,Ti and Al{sub 2}O{sub 3}:C) using SCS. The results also show that the luminescence properties can be improved by Li co-doping and annealing. The presence of an atypical TL background and anomalous fading are discussed and deserve attention in future investigations. We hope that these preliminary results on the use of SCS for production of TL and OSL materials are helpful to guide future efforts towards the development of new luminescence materials for different applications. - Highlights: Black-Right-Pointing-Pointer TL and OSL material produced with sensitivity similar to commercial materials. Black-Right-Pointing-Pointer Luminescence properties improved by Li co-doping and annealing. Black-Right-Pointing-Pointer The presence of atypical TL background and anomalous fading observed.

Luminescent solar concentrators utilizing stimulated emission.

Science.gov (United States)

Kaysir, Md Rejvi; Fleming, Simon; MacQueen, Rowan W; Schmidt, Timothy W; Argyros, Alexander

2016-03-21

Luminescent solar concentrators (LSCs) are an emerging technology that aims primarily to reduce the cost of solar energy, with great potential for building integrated photovoltaic (PV) structures. However, realizing LSCs with commercially viable efficiency is currently hindered by reabsorption losses. Here, we introduce an approach to reducing reabsorption as well as improving directional emission in LSCs by using stimulated emission. Light from a seed laser (potentially an inexpensive laser diode) passes through the entire area of the LSC panel, modifying the emission spectrum of excited dye molecules such that it is spectrally narrower, at wavelengths that minimize reabsorption to allow net gain in the system, and directed towards a small PV cell. A mathematical model, taking into account thermodynamic considerations, of such a system is presented which identifies key parameters and allows evaluation in terms of net effective output power.

Stimulated emission and lasing from all-inorganic perovskite quantum dots

Science.gov (United States)

Sun, Handong; Wang, Yue; Li, Xiaoming; Haibo, Zeng

We present superior optical gain and lasing properties in a new class of emerging quantum materials, the colloidal all-inorganic cesium lead halide perovskite quantum dots (IPQDs) (CsPbX3, X = Cl, Br, I). Our result has indicated that such material system show combined merits of both colloidal quantum dots and halide perovskites. Low-threshold and ultrastable stimulated emission was demonstrated under atmospheric condition. The flexibility and advantageous optical gain properties of these CsPbX3 IPQDs were manifested by demonstration of an optically pumped micro-laser. The nonlinear optical properties including the multi-photon absorption and resultant photoluminescence of the CsPbX3 nanocrystals were investigated. A large two-photon absorption cross-section of up to ~1.2×105 GM is determined from 9 nm-sized CsPbBr3 nanocrystals. Moreover, low-threshold frequency-upconverted stimulated emission by two-photon absorption was observed from the thin films of close-packed CsPbBr3 nanocrystals. We further realize the three-photon pumped stimulated emission in green spectra range from colloidal IPQD.

Scintillation properties of quantum-dot doped styrene based plastic scintillators

International Nuclear Information System (INIS)

Park, J.M.; Kim, H.J.; Hwang, Y.S.; Kim, D.H.; Park, H.W.

2014-01-01

We fabricated quantum-dot doped plastic scintillators in order to control the emission wavelength. We studied the characterization of the quantum-dots (CdSe/ZnS) and PPO (2, 5-diphenyloxazole) doped styrene based plastic scintillators. PPO is usually used as a dopant to enhance the scintillation properties of organic scintillators with a maximum emission wavelength of 380 nm. In order to study the scintillation properties of the quantum-dots doped plastic scintillators, the samples were irradiated with X-ray, photon, and 45 MeV proton beams. We observed that only PPO doped plastic scintillators shows a luminescence peak around 380 nm. However, both the quantum-dots and PPO doped plastic scintillators shows luminescence peaks around 380 nm and 520 nm. Addition of quantum-dots had shifted the luminescence spectrum from 380 nm (PPO) toward the region of 520 nm (Quantum-dots). Emissions with wavelength controllable plastic scintillators can be matched to various kinds of photosensors such as photomultiplier tubes, photo-diodes, avalanche photo-diodes, and CCDs, etc. Also quantum-dots doped plastic scintillator, which is irradiated 45 MeV proton beams, shows that the light yield of quantum-dots doped plastic scintillator is increases as quantum-dots doping concentration increases at 520 nm. And also the plastic scintillators were irradiated with Cs-137 γ-ray for measuring fluorescence decay time. -- Highlights: • Quantum-dot doped plastic scintillator is grown by the thermal polymerization method. • Quantum-dot doped plastic scintillators can control the emission wavelength to match with photo-sensor. • Quantum-dots and PPO doped plastic scintillators emitted luminescence peaks around 380 nm and 520 nm. • We observed the energy transfer from PPO to quantum-dot in the quantum-dot doped plastic scintillator

Scintillation properties of quantum-dot doped styrene based plastic scintillators

Energy Technology Data Exchange (ETDEWEB)

Park, J.M.; Kim, H.J., E-mail: hongjooknu@gmail.com; Hwang, Y.S.; Kim, D.H.; Park, H.W.

2014-02-15

We fabricated quantum-dot doped plastic scintillators in order to control the emission wavelength. We studied the characterization of the quantum-dots (CdSe/ZnS) and PPO (2, 5-diphenyloxazole) doped styrene based plastic scintillators. PPO is usually used as a dopant to enhance the scintillation properties of organic scintillators with a maximum emission wavelength of 380 nm. In order to study the scintillation properties of the quantum-dots doped plastic scintillators, the samples were irradiated with X-ray, photon, and 45 MeV proton beams. We observed that only PPO doped plastic scintillators shows a luminescence peak around 380 nm. However, both the quantum-dots and PPO doped plastic scintillators shows luminescence peaks around 380 nm and 520 nm. Addition of quantum-dots had shifted the luminescence spectrum from 380 nm (PPO) toward the region of 520 nm (Quantum-dots). Emissions with wavelength controllable plastic scintillators can be matched to various kinds of photosensors such as photomultiplier tubes, photo-diodes, avalanche photo-diodes, and CCDs, etc. Also quantum-dots doped plastic scintillator, which is irradiated 45 MeV proton beams, shows that the light yield of quantum-dots doped plastic scintillator is increases as quantum-dots doping concentration increases at 520 nm. And also the plastic scintillators were irradiated with Cs-137 γ-ray for measuring fluorescence decay time. -- Highlights: • Quantum-dot doped plastic scintillator is grown by the thermal polymerization method. • Quantum-dot doped plastic scintillators can control the emission wavelength to match with photo-sensor. • Quantum-dots and PPO doped plastic scintillators emitted luminescence peaks around 380 nm and 520 nm. • We observed the energy transfer from PPO to quantum-dot in the quantum-dot doped plastic scintillator.

Irradiation route to aqueous synthesis of highly luminescent ZnSe quantum dots and its function as a copper ion fluorescence sensor

Energy Technology Data Exchange (ETDEWEB)

Rao, Yeluri Narayana; Datta, Aparna [UGC-DAE Consortium for Scientific Research, Kolkata Centre, III/LB-8 Bidhannagar, Kolkata 700 098 (India); Das, Satyendra K. [Radiochemistry Division, Variable Energy Cyclotron Centre, 1/AF Bidhannagar, Kolkata 700 064 (India); Saha, Abhijit, E-mail: abhijit@alpha.iuc.res.in [UGC-DAE Consortium for Scientific Research, Kolkata Centre, III/LB-8 Bidhannagar, Kolkata 700 098 (India)

2016-08-15

Highlights: • Radiation chemical technique can provide a useful route for synthesis of ZnSe QDs. • Chelating nature of ethylene diamine is exploited for capping nanoparticles. • ZnSe QDs can be a suitable sensitive alternative to toxic cadmium-based system. • Cu(II) ion is probed by QDs in the presence of other physiologically relevant ions. - Abstract: Size-controlled synthesis of stable ZnSe QDs with narrow distribution in aqueous environment through conventional soft chemical method still poses a challenge. The proposed radiation assisted strategy demonstrates aqueous synthesis of stable, monodisperse and luminescent ZnSe QDs capped with chelating ethylene diamine under ambient conditions and at room temperature. Radiation chemical method facilitates in slow and in-situ release of selenium ion from sodium selenosulfate. The concentrations of precursors, such as zinc salt, selenium source, ethylene diamine and absorbed radiation (7–90 kGy) dose were optimized for obtaining good quality particles. Selective quenching of luminescence of as-synthesized quantum dots (QDs) by Cu{sup 2+} ions vis-à-vis other physiologically important cations provide evidence for use of ZnSe quantum dots as alternative to toxic Cd-based quantum dots to probe Cu{sup 2+} ions. The linear relation of ratio of loss in emission intensity as a function of concentration of Cu(II) indicates detection limit in nano-molar range.

Changes in optically stimulated luminescent dosimeter (OSLD) dosimetric characteristics with accumulated dose

International Nuclear Information System (INIS)

Jursinic, Paul A.

2010-01-01

Purpose: A new type of in vivo dosimeter, an optically stimulated luminescent dosimeter (OSLD), has now become commercially available for clinical use. The OSLD is a plastic disk infused with aluminum oxide doped with carbon (Al 2 O 3 :C). Crystals of Al 2 O 3 :C, when exposed to ionizing radiation, store energy that is released as luminescence (420 nm) when the OSLD is illuminated with stimulation light (540 nm). The intensity of the luminescence depends on the dose absorbed by the OSLD and the intensity of the stimulation light. The effects of accumulated dose on OSLD response were investigated. Methods: The OSLDs used in this work were nanodot dosimeters, which were read with a MicroStar reader (Landauer, Inc., Glenwood, IL). Dose to the OSLDs was delivered by 6 MV x rays and gamma rays from Co-60 and Ir-192. The signal on the OSLDs after irradiation is removed by optical annealing with a 150 W tungsten-halogen lamp or a 14 W compact fluorescent lamp was investigated. Results: It was found that OSLD response to dose was supralinear and this response was altered with the amount of accumulated dose to the OSLD. The OSLD response can be modeled by a quadratic and an exponential equation. For accumulated doses up to 60 Gy, the OSLD sensitivity (counts/dose) decreases and the extent of supralinear increases. Above 60 Gy of accumulated dose the sensitivity increases and the extent of supralinearity decreases or reaches a plateau, depending on how the OSLDs were optically annealed. With preirradiation of OSLDs with greater than 1 kGy, it is found that the sensitivity reaches a plateau 2.5 folds greater than that of an OSLD with no accumulated dose and the supralinearity disappears. A regeneration of the luminescence signal in the dark after full optical annealing occurs with a half time of about two days. The extent of this regeneration signal depends on the amount of accumulated dose. Conclusions: For in vivo dosimetric measurements, a precision of ±0.5% can be

Thermoluminescence, luminescence optically stimulated and creation of defects in alkaline halogenides contaminated with Europium

International Nuclear Information System (INIS)

Barboza F, M.

1999-01-01

The alkaline halogenides have been subject matter of investigations related with the search of sensor materials for X-ray bidimensional images or optical memories. The understanding of the damage formation processes generated by ionizing and non-ionizing radiations is important for the correct design of devices that working as detectors and dosemeters of both type of radiations. In this work we present the investigation results related with the defects produced by the ionizing radiation type X and ultraviolet light in the range of 200-360 nm in crystals of KCl: Eu 2+ and KBr:Eu 2+ . It is examined the thermoluminescence and luminescence spectra with the purpose of identifying the exciton processes, owing to the excitation of the halogenide ions in which the primary defects correspond to the F and H centers. It has been found that the 400-600 nm emission is associated with the luminescence type that in his turn can be associated with autotrapped excitons perturbed by the impurity. On the other hand, it is examined the emission spectra of the luminescence optically stimulated in crystals of KBr: Eu 2+ and KCl: Eu 2+ finding too that such materials would be used as optical memories susceptible of to store information, and through of photostimulation to read this. It was determined that the F centers participate in the luminescence optically stimulated in these crystals, as well as too in the recombination processes responsible by the thermoluminescent emission. (Author)

Violet stimulated luminescence dating of quartz from Luochuan (Chinese loess plateau): Agreement with independent chronology up to ∼600 ka

DEFF Research Database (Denmark)

Ankjærgaard, C.; Guralnik, B.; Buylaert, Jan-Pieter

2016-01-01

Luminescence dating at the Luochuan loess type (China) section is at present limited to ∼0.1 Ma using quartz blue light stimulated luminescence (BLSL), but can be extended back in time to ∼0.5 Ma by resorting to the more developmental post-infrared infrared stimulated luminescence (post-IR IRSL...... demonstrate that the Multi-Aliquot Additive-Dose (MAAD) protocol produces a VSL chronology at Luochuan which is in agreement with independent ages up to ∼0.6 Ma. For a more representative environmental dose rate of ∼2 Gy/ka (∼35% lower than at Luochuan), the documented range of MAAD-VSL sensitivity (200...

Luminescence detection of shellfish

International Nuclear Information System (INIS)

Sanderson, D.C.W.; Carmichael, L.A.; Spencer, J.Q.; Naylor, J.D.

1996-01-01

The Scottish Universities Research and Reactor Centre (SURRC) has been active in the development and application of luminescence techniques in the detection of irradiated foods, in support of UK legislation. Thermoluminescence (TL), photostimulated luminescence (PSL) and photo-transfer luminescence (PTTL) are radiation-specific phenomena which arise due to energy stored by trapped charge carriers following irradiation. The energy released following stimulation is accompanied by detectable luminescence. The TL method involves preparation of pure silicate extracts from the sample and subsequent TL analysis, whereas PSL uses stimulation by electromagnetic radiation (visible, or near visible wavelengths) thus avoiding heating the sample. (author)

Characterization of optically stimulated luminescence for assessment of breast doses in mammography screening

International Nuclear Information System (INIS)

Alothmany, N.; Jiman, A.; Molla, N.I.; Natto, H.; Tayeb, M.; Nadwi, F.; Yusuf, M.; Alothmany, D.; Kinsara, A.A.; Saoudi, A.; Mail, N.; Khafaji, M.A.

2016-01-01

Landauer optically stimulated luminescence (OSL) technology nanoDot dosimeters (OSLDs) are characterized for use in mammography screening at various tube voltages, mAs values and target/filter combinations. The average glandular dose (AGD) for a 50-mm breast, based on the representative compressed breast thickness of a 45-mm polymethyl methacrylate (PMMA) phantom, is assessed using OSLDs with different beam conditions. Further, the linearity of the OSLD response is measured and angular dependence tests are performed for various tube potentials, mAs and target/filter combinations. The breast-absorbed doses are measured at various depths for a 32-kVp X-ray beam at 100 mAs, with a Mo/Rh target/filter combination. The measured incident air kerma values at different lateral positions exhibit a maximum deviation of 6%, and the average relative response of the OSLDs at the reference point (center) with respect to various lateral positions is found to be 1.001 ± 0.09%. The calculated AGD values are in the 1.3 ± 0.1-3.5 ± 0.2 mGy range, depending on the tube potential, tube loading and target/filter combinations. An exposure setup featuring the auto-exposure control (AEC) mode, 28 kVp, 73.8 mAs, and a Mo/Rh target/filter combination may be preferred for mammography screening for a compressed breast thickness of 45 mm. (authors)

Fabrication of blue luminescent MoS{sub 2} quantum dots by wet grinding assisted co-solvent sonication

Energy Technology Data Exchange (ETDEWEB)

Ali, Junaid; Siddiqui, Ghayas Uddin [Department of Mechatronics Engineering, Jeju National University, Jeju (Korea, Republic of); Choi, Kyung Hyun, E-mail: amm@jejunu.ac.kr [Department of Mechatronics Engineering, Jeju National University, Jeju (Korea, Republic of); Jang, Yunseok [Department of Printed Electronics, Korea Institute of Machinery & Materials, Daejeon, Republic of Korea (Korea, Republic of); Lee, Kangtaek [Department of Chemical and Biomolecular Engineering, Yonsei University (Korea, Republic of)

2016-01-15

Molybdenum disulfide (MoS{sub 2}) belongs to transition-metal dichalcogenides (TMDs) family and has vital position among 2D materials. Here, an efficient strategy for the synthesis of zero-dimensional MoS{sub 2} quantum dots (QDs) has been represented. This strategy consists of wet grinding of pristine MoS{sub 2} in N-methyl-2-pyrrolidone (NMP) followed by sonication in NMP and 1,2-dichlorobenzene (o-DCB). The efficacy of this approach to synthesize MoS{sub 2} QDs has been reported by analyzing the as synthesized MoS{sub 2} QDs by different characterization techniques such as high resolution transmission electron microscopy, energy dispersive x-ray spectroscopy, Raman spectroscopy, photoluminescence spectroscopy, Fourier transform infrared spectroscopy and UV–vis spectroscopy. The concentration (yield) of as synthesized MoS{sub 2} QDs was found to be 7 mg mL{sup −1}. Most of the MoS{sub 2} QDs were measured around 2–5 nm in size. The as synthesized MoS{sub 2} QDs showed distinct blue luminescence upon UV excitation. - Highlights: • Synthesis of MoS{sub 2} quantum dots. • Wet grinding of MoS{sub 2} flakes for 6 h in NMP. • Ultrasonication of MoS{sub 2} in NMP and DCB. • Particle size 2–5 nm and concentration 7 mg/ml. • MoS{sub 2} QDs showed blue luminescence.

The thermoluminescence and optically stimulated luminescence properties of Cr-doped alpha alumina transparent ceramics

International Nuclear Information System (INIS)

Liu, Qiang; Yang, Qiu Hong; Zhao, Guang Gen; Lu, Shen Zhou; Zhang, Hao Jia

2013-01-01

Highlights: •Polycrystalline Cr:α-Al 2 O 3 transparent ceramics were obtained with vacuum sintering method. •The influence of different concentration of Cr 2 O 3 on the thermoluminescence and optical stimulated luminescence properties of Cr:α-Al 2 O 3 transparent ceramics was studied. •It had a main peak at 503 K of very high intensity and linear concentration dependence up to high concentration. •It showed so interesting results with high TL sensitivity and high stability of OSL signal that Cr:α-Al 2 O 3 transparent ceramics might be a promising material in TL dosimetry and replace Cr:α-Al 2 O 3 crystals. -- Abstract: Polycrystalline Cr:α-Al 2 O 3 transparent ceramics were fabricated by conventional solid-state processing under vacuum condition. The SEM microstructure photographs of Cr:α-Al 2 O 3 transparent ceramics doped with different content of Cr 2 O 3 were investigated. The absorption, emission spectra, thermoluminescence and optical stimulated luminescence of Cr:α-Al 2 O 3 transparent ceramics were comparable to those of Cr:α-Al 2 O 3 crystals. The influence of different concentration of Cr 2 O 3 on the thermoluminescence and optical stimulated luminescence properties of Cr:α-Al 2 O 3 transparent ceramics was discussed. It showed so interesting results with high TL sensitivity and high stability of OSL signal that Cr:α-Al 2 O 3 transparent ceramics might be a promising material in TL dosimetry and replace Cr:α-Al 2 O 3 crystals

Quantum dot-polymer conjugates for stable luminescent displays.

Science.gov (United States)

Ghimire, Sushant; Sivadas, Anjaly; Yuyama, Ken-Ichi; Takano, Yuta; Francis, Raju; Biju, Vasudevanpillai

2018-05-23

The broad absorption of light in the UV-Vis-NIR region and the size-based tunable photoluminescence color of semiconductor quantum dots make these tiny crystals one of the most attractive antennae in solar cells and phosphors in electrooptical devices. One of the primary requirements for such real-world applications of quantum dots is their stable and uniform distribution in optically transparent matrices. In this work, we prepare transparent thin films of polymer-quantum dot conjugates, where CdSe/ZnS quantum dots are uniformly distributed at high densities in a chitosan-polystyrene copolymer (CS-g-PS) matrix. Here, quantum dots in an aqueous solution are conjugated to the copolymer by a phase transfer reaction. With the stable conjugation of quantum dots to the copolymer, we prevent undesired phase separation between the two and aggregation of quantum dots. Furthermore, the conjugate allows us to prepare transparent thin films in which quantum dots are uniformly distributed at high densities. The CS-g-PS copolymer helps us in not only preserving the photoluminescence properties of quantum dots in the film but also rendering excellent photostability to quantum dots at the ensemble and single particle levels, making the conjugate a promising material for photoluminescence-based devices.

Dependence of (anomalous) fading of infra-red stimulated luminescence on trap occupancy in feldspars

DEFF Research Database (Denmark)

Morthekai, P.; Jain, Mayank; Gach, Grzegorz

2013-01-01

Dose dependency of anomalous fading of infra-red stimulated luminescence (IRSL) from feldspars has been investigated using radiations of different ionisation qualities. The rate of fading of the IRSL signal after proton irradiation (9.4–30%/decade) is on an average almost twice compared...

Hydrothermal synthesis of two photoluminescent nitrogen-doped graphene quantum dots emitted green and khaki luminescence

International Nuclear Information System (INIS)

Zhu, Xiaohua; Zuo, Xiaoxi; Hu, Ruiping; Xiao, Xin; Liang, Yong; Nan, Junmin

2014-01-01

A simple and effective chemical synthesis of the photoluminescent nitrogen-doped graphene quantum dots (N-GQDs) biomaterial is reported. Using the hydrothermal treatment of graphene oxide (GO) in the presence of hydrogen peroxide (H 2 O 2 ) and ammonia, the N-GQDs are synthesized through H 2 O 2 exfoliating the GO into nanocrystals with lateral dimensions and ammonia passivating the generated active surface. Then, after a dialytic separation, two water-soluble N-GQDs with average size of about 2.1 nm/6.2 nm, which emit green/khaki luminescence and exhibit excitation dependent/independent photoluminescence (PL) behaviors, are obtained. In addition, it is also demonstrated that these two N-GQDs are stable over a broad pH range and have the upconversion PL property, showing this approach provides a simple and effective method to synthesize the functional N-GQDs. - Highlights: • Nitrogen-doped graphene quantum dots (N-GQDs) are prepared by hydrothermal routine. • Two N-GQDs with different size distribution emit green/khaki photoluminescence. • Two N-GQDs exhibit excitation-dependent/independent photoluminescence behaviors

Intense Visible Luminescence in CdSe Quantum Dots by Efficiency Surface Passivation with H2O Molecules

Directory of Open Access Journals (Sweden)

Hyeoung Woo Park

2012-01-01

Full Text Available We have investigated the effect of water (H2O cooling and heat treatment on the luminescence efficiency of core CdSe quantum dots (QDs. The photoluminescence (PL quantum yield of the CdSe QDs was enhanced up to ~85%, and some periodic bright points were observed in wide color ranges during the heat treatment of QDs mixed with H2O. The PL enhancement of QDs could be attributed to the recovery of QDs surface traps by unreacted ligands confined within the hydrophilic H2O molecule containers.

Effect of antimony incorporation on the density, shape, and luminescence of InAs quantum dots

Science.gov (United States)

Chen, J. F.; Chiang, C. H.; Wu, Y. H.; Chang, L.; Chi, J. Y.

2008-07-01

This work investigates the surfactant effect on exposed and buried InAs quantum dots (QDs) by incorporating Sb into the QD layers with various Sb beam equivalent pressures (BEPs). Secondary ion mass spectroscopy shows the presence of Sb in the exposed and buried QD layers with the Sb intensity in the exposed layer substantially exceeding that in the buried layer. Incorporating Sb can reduce the density of the exposed QDs by more than two orders of magnitude. However, a high Sb BEP yields a surface morphology with a regular periodic structure of ellipsoid terraces. A good room-temperature photoluminescence (PL) at ˜1600 nm from the exposed QDs is observed, suggesting that the Sb incorporation probably improves the emission efficiency by reducing the surface recombination velocity at the surface of the exposed QDs. Increasing Sb BEP causes a blueshift of the emission from the exposed QDs due to a reduction in the dot height as suggested by atomic force microscopy. Increasing Sb BEP can also blueshift the ˜1300 nm emission from the buried QDs by decreasing the dot height. However, a high Sb BEP yields a quantum well-like PL feature formed by the clustering of the buried QDs into an undulated planar layer. These results indicate a marked Sb surfactant effect that can be used to control the density, shape, and luminescence of the exposed and buried QDs.

Optically stimulated luminescence from quartz measured using the linear modulation technique

International Nuclear Information System (INIS)

Bulur, E.; Boetter-Jensen, L.; Murray, A.S.

2000-01-01

The optically stimulated luminescence (OSL) from heated natural quartz has been investigated using the linear modulation technique (LMT), in which the excitation light intensity is increased linearly during stimulation. In contrast to conventional stimulation, which usually produces a monotonically decreasing signal, linearly increasing the stimulation power gives peaks in the signal as a function of time. In cases where the OSL signal contains more than one component, the linear increase in power of the stimulation light may result in a curve containing overlapping peaks, where the most easily stimulated component occurs at a shorter time. This allows the separation of the overlapping OSL components, which are assumed to originate from different traps. The LM-OSL curve from quartz shows an initial peak followed by a broad one. Deconvolution using curve fitting has shown that the composite OSL curve from quartz can be approximated well by using a linear combination of first-order peaks. In addition to the three known components, i.e. fast, medium and slow components from continuous-wave-OSL studies, an additional slow component is also identified for the first time. The dose responses and thermal stabilities of the various components are also studied

Quantum-dot nano-cavity lasers with Purcell-enhanced stimulated emission

DEFF Research Database (Denmark)

Gregersen, Niels; Skovgård, Troels Suhr; Lorke, Michael

2012-01-01

We present a rate equation model for quantum-dot light-emitting devices that take into account Purcell enhancement of both spontaneous emission and stimulated emission as well as the spectral profile of the optical and electronic density-of-states. We find that below threshold the b-factor in a q...

Thermally stimulated luminescence and electron paramagnetic resonance studies on uranium doped calcium phosphate

CERN Document Server

Natarajan, V; Veeraraghavan, R; Sastry, M D

2003-01-01

Thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) studies on uranium doped calcium phosphate yielded mechanistic information on the observed glow peaks at 365, 410 and 450 K. TSL spectral studies of the glow peaks showed that UO sub 2 sup 2 sup + acts as the luminescent center. Electron paramagnetic resonance studies on gamma-irradiated samples revealed that the predominant radiation induced centers are H sup 0 , PO sub 4 sup 2 sup - , PO sub 3 sup 2 sup - and O sup - ion. Studies on the temperature dependence studies of the EPR spectra of samples annealed to different temperatures indicate the role of H sup 0 and PO sub 4 sup 2 sup - ions in the main glow peak at 410 K.

Optically stimulated luminescence dating of the Huanghe river terrace in Lanzhou basin

International Nuclear Information System (INIS)

Wang Ping; Yuan Daoyang; Liu Xinwang; Jiang Hanchao

2007-01-01

In this paper, profile observation and geologic strata structure analysis on the third level terrace at Fanjiaping on the south bank of the Huanghe River in the Lanzhou basin were reported, and systemically collected samples of fluvial sediments and the overlying diluvium and aeolian loess were analyzed by optically stimulated luminescence (OSL). The granulometric and magnetic susceptibility samples from the fine grain sedimentary layer at the middle of the profile were collected at a 2.5 cm interval. According to simplified multiple aliquot dating on fine grain quartz of 16 optically stimulated luminescence samples and electron spin resonance (ESR) dating of the underlying early fluvial layer, the following chronology results of the strata profile of the third terrace were obtained. The under- lying early fluvial layer is of gravels that belong to Fanjiaping formation in early and middle Pleistogene. The river-bed sedimentation of the Huanghe River started about 80,000 years ago. The accumulation of mainly proluvial sediments started about 70,000 years ago. And the continuous loess accumulation began about 55,000 years ago. The age of formation of the third terrace of Huanghe River was estimated at about 70,000 years, corresponding to the time between the last interglacial period and the last glacial period in the late Pleistocene. (authors)

Optically stimulated luminescence in retrospective dosimetry

International Nuclear Information System (INIS)

Boetter-Jensen, L.; Murray, A.S.

2002-01-01

Since the beginning of the 1990s the exploration of optically stimulated luminescence in retrospective accident dosimetry has driven an intensive investigation and development programme at Ris deg. into measurement facilities and techniques. This paper reviews some of the outcomes of this programme, including the evaluation of the single-aliquot regenerative-dose measurement protocol with brick quartz and the determination of dose-depth profiles in building materials as a guide to determining the mean energy of the incident radiation. Investigations into heated materials are most advanced, and a lower detection limit for quartz extracted from Chernobyl bricks was determined to be <10 mGy. The first results from the measurement of doses in unheated building materials such as mortar and concrete are also discussed. Both small-aliquot and single-grain techniques have been used to assess accident doses in these cement based building materials more commonly found in workplaces. Finally some results of a preliminary investigation of the OSL properties of household chemicals are discussed with reference to their potential as accident dosemeters. (author)

Doping the dots: doped quantum dots for luminescent solar concentrators

NARCIS (Netherlands)

Eilers, J.J.

2015-01-01

In this thesis, synthesis methods for luminescent organically capped colloidal ZnSe QDs of different sizes, ranging from 4.0 to 7.5 nm are reported. These QDs are analyzed using TEM, absorption spectroscopy, photoluminescence measurements and temperature dependent photoluminescence decay

Charge recombination processes in minerals studied using optically stimulated luminescence and time-resolved exo-electrons

DEFF Research Database (Denmark)

Tsukamoto, Sumiko; Murray, Andrew; Ankjærgaard, Christina

2010-01-01

electron concentration in the conduction band. In this study, TR-OSE and time-resolved optically stimulated luminescence (TR-OSL) were measured for the first time using quartz, K-feldspar and NaCl by stimulating the samples using pulsed blue LEDs at different temperatures between 50 and 250 °C after beta...... irradiation and preheating to 280 °C. The majority of TR-OSE signals from all the samples decayed much faster than TR-OSL signals irrespective of the stimulation temperatures. This suggests that the lifetime of OSL in these dosimeters arises mainly from the relaxation of an excited state of the recombination...

Imaging and Manipulating Energy Transfer Among Quantum Dots at Individual Dot Resolution.

Science.gov (United States)

Nguyen, Duc; Nguyen, Huy A; Lyding, Joseph W; Gruebele, Martin

2017-06-27

Many processes of interest in quantum dots involve charge or energy transfer from one dot to another. Energy transfer in films of quantum dots as well as between linked quantum dots has been demonstrated by luminescence shift, and the ultrafast time-dependence of energy transfer processes has been resolved. Bandgap variation among dots (energy disorder) and dot separation are known to play an important role in how energy diffuses. Thus, it would be very useful if energy transfer could be visualized directly on a dot-by-dot basis among small clusters or within films of quantum dots. To that effect, we report single molecule optical absorption detected by scanning tunneling microscopy (SMA-STM) to image energy pooling from donor into acceptor dots on a dot-by-dot basis. We show that we can manipulate groups of quantum dots by pruning away the dominant acceptor dot, and switching the energy transfer path to a different acceptor dot. Our experimental data agrees well with a simple Monte Carlo lattice model of energy transfer, similar to models in the literature, in which excitation energy is transferred preferentially from dots with a larger bandgap to dots with a smaller bandgap.

SELF-ORGANIZATION OF LEAD SULFIDE QUANTUM DOTS INTO SUPERSTRUCTURES

Directory of Open Access Journals (Sweden)

Elena V. Ushakova

2014-11-01

Full Text Available The method of X-ray structural analysis (X-ray scattering at small angles is used to show that the structures obtained by self-organization on a substrate of lead sulfide (PbS quantum dots are ordered arrays. Self-organization of quantum dots occurs at slow evaporation of solvent from a cuvette. The cuvette is a thin layer of mica with teflon ring on it. The positions of peaks in SAXS pattern are used to calculate crystal lattice of obtained ordered structures. Such structures have a primitive orthorhombic crystal lattice. Calculated lattice parameters are: a = 21,1 (nm; b = 36,2 (nm; c = 62,5 (nm. Dimensions of structures are tens of micrometers. The spectral properties of PbS QDs superstructures and kinetic parameters of their luminescence are investigated. Absorption band of superstructures is broadened as compared to the absorption band of the quantum dots in solution; the luminescence band is slightly shifted to the red region of the spectrum, while its bandwidth is not changed much. Luminescence lifetime of obtained structures has been significantly decreased in comparison with the isolated quantum dots in solution, but remained the same for the lead sulfide quantum dots close-packed ensembles. Such superstructures can be used to produce solar cells with improved characteristics.

Time-resolved infrared stimulated luminescence signals in feldspars: Analysis based on exponential and stretched exponential functions

International Nuclear Information System (INIS)

Pagonis, V.; Morthekai, P.; Singhvi, A.K.; Thomas, J.; Balaram, V.; Kitis, G.; Chen, R.

2012-01-01

Time-resolved infrared-stimulated luminescence (TR-IRSL) signals from feldspar samples have been the subject of several recent experimental studies. These signals are of importance in the field of luminescence dating, since they exhibit smaller fading effects than the commonly employed continuous-wave infrared signals (CW-IRSL). This paper presents a semi-empirical analysis of TR-IRSL data from feldspar samples, by using a linear combination of exponential and stretched exponential (SE) functions. The best possible estimates of the five parameters in this semi-empirical approach are obtained using five popular commercially available software packages, and by employing a variety of global optimization techniques. The results from all types of software and from the different fitting algorithms were found to be in close agreement with each other, indicating that a global optimum solution has likely been reached during the fitting process. Four complete sets of TR-IRSL data on well-characterized natural feldspars were fitted by using such a linear combination of exponential and SE functions. The dependence of the extracted fitting parameters on the stimulation temperature is discussed within the context of a recently proposed model of luminescence processes in feldspar. Three of the four feldspar samples studied in this paper are K-rich, and these exhibited different behavior at higher stimulation temperatures, than the fourth sample which was a Na-rich feldspar. The new method of analysis proposed in this paper can help isolate mathematically the more thermally stable components, and hence could lead to better dating applications in these materials. - Highlights: ► TR-IRSL from four feldspars were analyzed using exponential and stretched exponential functions. ► A variety of global optimization techniques give good agreement. ► Na-rich sample behavior is different from the three K-rich samples. ► Experimental data are fitted for stimulation temperatures

Development of optically stimulated luminescence reader systems in BARC

International Nuclear Information System (INIS)

Kulkarni, M.S.

2008-01-01

BARC has very vast experience in the development of thermoluminescence (TL) reader systems both for routine personnel monitoring and research application. However, optically stimulated luminescence (OSL) related instrumentation is a recent development in BARC. The increasing popularity of OSL technique in the radiation dosimetry applications in the recent past has driven investigation and developmental programme in the OSL measurement facilities at BARC. As the consequence of the efforts directed towards the indigenous development of OSL reader system, OSL readers with various readout modes like continuous wave (CW) OSL mode, linear intensity modulated OSL (LM-OSL), pulsed OSL (POSL) have been developed. In addition to these conventional modes of operation a novel non-linear OSL mode (NL-OSL) has also been developed for the OSL measurements. This paper reviews the details of the development of OSL reader system including experience with high intensity blue/green LED stimulation light source and detection system. Also discussed are recently developed versatile integrated TL/OSL reader systems for TL and OSL measurements. (author)

Single photon detection and signal analysis for high sensitivity dosimetry based on optically stimulated luminescence with beryllium oxide

Science.gov (United States)

Radtke, J.; Sponner, J.; Jakobi, C.; Schneider, J.; Sommer, M.; Teichmann, T.; Ullrich, W.; Henniger, J.; Kormoll, T.

2018-01-01

Single photon detection applied to optically stimulated luminescence (OSL) dosimetry is a promising approach due to the low level of luminescence light and the known statistical behavior of single photon events. Time resolved detection allows to apply a variety of different and independent data analysis methods. Furthermore, using amplitude modulated stimulation impresses time- and frequency information into the OSL light and therefore allows for additional means of analysis. Considering the impressed frequency information, data analysis by using Fourier transform algorithms or other digital filters can be used for separating the OSL signal from unwanted light or events generated by other phenomena. This potentially lowers the detection limits of low dose measurements and might improve the reproducibility and stability of obtained data. In this work, an OSL system based on a single photon detector, a fast and accurate stimulation unit and an FPGA is presented. Different analysis algorithms which are applied to the single photon data are discussed.

Identifying irradiated flours by photo-stimulated luminescence technique

Energy Technology Data Exchange (ETDEWEB)

Ramli, Ros Anita Ahmad; Yasir, Muhamad Samudi [Faculty of Science and Technology, National University of Malaysia, Bangi, 43000 Kajang, Selangor (Malaysia); Othman, Zainon; Abdullah, Wan Saffiey Wan [Malaysian Nuclear Agency, Bangi 43000 Kajang, Selangor (Malaysia)

2014-02-12

Photo-stimulated luminescence (PSL) technique was used in this study to detect gamma irradiation treatment of five types of flours (corn, rice, tapioca, wheat and glutinous rice) at four different doses 0, 0.2, .05 and 1kGy. The signal level was compared with two threshold values (700 and 5000). With the exception of glutinous rice, all irradiated samples produced a strong signal above the upper threshold (5000 counts/60s). All control samples produced negative result with the signals below the lower threshold (700 counts/60s) suggesting that the samples have not been irradiated. Irradiated glutinous rice samples produced intermediate signals (700 - 5000 counts/60s) which were subsequently confirmed using calibrated PSL. The PSL signals remained stable after 90 days of storage. The findings of this study will be useful to facilitate control of food irradiation application in Malaysia.

Identifying irradiated flours by photo-stimulated luminescence technique

International Nuclear Information System (INIS)

Ramli, Ros Anita Ahmad; Yasir, Muhamad Samudi; Othman, Zainon; Abdullah, Wan Saffiey Wan

2014-01-01

Photo-stimulated luminescence (PSL) technique was used in this study to detect gamma irradiation treatment of five types of flours (corn, rice, tapioca, wheat and glutinous rice) at four different doses 0, 0.2, .05 and 1kGy. The signal level was compared with two threshold values (700 and 5000). With the exception of glutinous rice, all irradiated samples produced a strong signal above the upper threshold (5000 counts/60s). All control samples produced negative result with the signals below the lower threshold (700 counts/60s) suggesting that the samples have not been irradiated. Irradiated glutinous rice samples produced intermediate signals (700 - 5000 counts/60s) which were subsequently confirmed using calibrated PSL. The PSL signals remained stable after 90 days of storage. The findings of this study will be useful to facilitate control of food irradiation application in Malaysia

UV induced photoluminescence and thermally stimulated luminescence of ThO2:Tb3+ phosphor

International Nuclear Information System (INIS)

Godbole, S.V.; Nagpal, J.S.; Page, A.G.

2000-01-01

Thorium oxide doped with trivalent terbium ions offers itself as a novel phosphor with its photo- and thermally-stimulated luminescence (PL and TSL) characteristics showing a marked change on sustained exposure to 254 and 365 nm ultraviolet (UV) radiation. The reduction in luminescence intensity of Tb 3+ ions, on irradiation with 254 nm photons and subsequent restoration on exposure to 365 nm, has been correlated with the complimentary behaviour in UV-induced TSL. These changes are, in turn, ascribed to inter-configurational (f-d) transitions and e-h formation and recombination processes. UV radiation induced TSL output increases linearly with incident UV radiant energy at a constant radiation flux; however, for a fixed exposure, TSL output increases with increase in radiant flux

On luminescence lifetimes in quartz

International Nuclear Information System (INIS)

Chithambo, M.L.; Galloway, R.B.

2000-01-01

In this paper we present results of investigations concerning the time dependence of luminescence emission relative to the time of stimulation in quartz. Measurements of time-resolved spectra were performed on a new versatile pulsed light emitting diode system using 525 nm stimulation, an 11 μs duration pulse, a repetition rate of 11 kHz and a 64 μs dynamic range. Effects on luminescence lifetime resulting from sample treatments such as optical stimulation, irradiation, and preheating, are reported

A gamma/neutron-discriminating, Cooled, Optically Stimulated Luminescence (COSL) dosemeter

International Nuclear Information System (INIS)

Eschbach, P.A.; Miller, S.D.

1992-07-01

The Cooled Optically Stimulated Luminescence (COSL) of CaF 2 :Mn (grain sizes from 0.1 to 100 microns) powder embedded in a hydrogenous matrix is reported as a function of fast-neutron dose. When all the CaF 2 :Mn grains are interrogated at once, the COSL plastic dosemeters have a minimum detectable limit of 1 cSv fast neutrons; the gamma component from the bare 252 cf exposure was determined with a separate dosemeter. We report here on a proton-recoil-based dosemeter that generates pulse height spectra, much like the scintillator of Hornyak, (2) to provide information on both the neutron and gamma dose

Optically stimulated luminescence in electronic components for emergency dosimetry

International Nuclear Information System (INIS)

Geber-Bergstrand, T.; Bernhardsson, C.; Mattsson, S.; Raeaef, C.L.

2015-01-01

Document available in abstract form only. Full text of publication follows: Accidents and, luckily more rarely, attacks involving nuclear or radiological material do occur from time to time. A very possible consequence of an accident or attack of this kind is that nearby people might be exposed to ionising radiation. Since these types of exposure situations, unlike the ones occurring in medicine, are unplanned, there are no radiation-monitoring data available. For several reasons, it is nevertheless of value to find out the dose that these people have received. The first and most urgent reason is after-the-event triage, to be able to carry out proper medical treatments and also to focus the available medical assets to the persons needing it the most. This is where different retrospective dosimetry techniques, such as luminescence, can be employed. Various electronic components from mobile phones and other portable devices have been studied using optically stimulated luminescence for their potential use in retrospective dosimetry. Previous investigations have been performed in laboratory conditions and have showed very promising properties for emergency dosimetry. In this study, the more practical parts of using electronic components in retrospective dosimetry have been considered. In a triage situation, one of the key parameters to consider is time; thus, effort has been made to speed up the readout procedure, yet without the loss of too much accuracy. (authors)

Protease-activated quantum dot probes

International Nuclear Information System (INIS)

Chang, Emmanuel; Miller, Jordan S.; Sun, Jiantang; Yu, William W.; Colvin, Vicki L.; Drezek, Rebekah; West, Jennifer L.

2005-01-01

We have developed a novel nanoparticulate luminescent probe with inherent signal amplification upon interaction with a targeted proteolytic enzyme. This construct may be useful for imaging in cancer detection and diagnosis. In this system, quantum dots (QDs) are bound to gold nanoparticles (AuNPs) via a proteolytically degradable peptide sequence to non-radiatively suppress luminescence. A 71% reduction in luminescence was achieved with conjugation of AuNPs to QDs. Release of AuNPs by peptide cleavage restores radiative QD photoluminescence. Initial studies observed a 52% rise in luminescence over 47 h of exposure to 0.2 mg/mL collagenase. These probes can be customized for targeted degradation simply by changing the sequence of the peptide linker

Combining infrared- and green-laser stimulation sources in single-grain luminescence measurements of feldspar and quartz

DEFF Research Database (Denmark)

Duller, G.A.T.; Bøtter-Jensen, L.; Murray, A.S.

2003-01-01

A system designed for measurement of the optically stimulated luminescence (OSL) from individual sand-sized mineral grains has been constructed. Previously, this system was equipped only with a green laser emitting at 532 run, but now an infrared (IR) laser at 830 run has been added. It is now...... possible to interchangeably use the two laser sources for optical stimulation. This is especially valuable for the measurement of feldspars. The power density using the IR laser at the grain is similar to500 W cm(-2), and stimulation for 1 s reduces the OSL signal to near background level. Initial results...

Thermally and optically stimulated luminescence of new ZnO nano phosphors exposed to beta radiation

International Nuclear Information System (INIS)

Cruz V, C.; Burruel I, S.E.; Grijalva M, H.; Chernov, V.; Bernal, R.

2006-01-01

In this work, we report the thermoluminescence (TL) and the optically stimulated luminescence (OSL) of ZnO nano phosphors obtained by thermal annealing of ZnS powders synthesized by precipitation in a chemical bath deposition reaction. To obtain nanocrystalline ZnO, ZnS pellet-shaped samples were subjected to a sintering process at 700 C during 24 under air atmosphere. Some samples were exposed to beta particles in the 0.15-10.15 kGy dose range and the integrated thermoluminescence as a function of dose increased as dose increased, with no saturation clue for the tested doses. Computerized glow-curve deconvolution of the experimental TL curves in individual peaks revealed a second order kinetics. In order to test the BOSL (Blue Optically Stimulated Luminescence) response, samples were beta irradiated with doses up to 600 Gy, showing an increasing OSL intensity as dose increases. From the experimental results that we have obtained, we conclude that the new ZnO phosphors under investigation are good candidates to be used as dosimetric materials. (Author)

On optically stimulated luminescence properties of household salt as a retrospective dosemeter

International Nuclear Information System (INIS)

Timar-Gabor, A.; Trandafir, O.

2013-01-01

Thermoluminescence (TL) and optically stimulated luminescence (OSL) in the UV (270-370 nm) spectral region have been investigated for five types of table salt (NaCl) available in Romanian supermarkets with a view to applying them in retrospective dosimetry. The salt samples gave bright TL signals with two main peaks at ∼ 100 deg. C and at 300 or 260 deg. C, depending on the origin of the salt and bright OSL signals under continuous stimulation with blue light. The OSL signal (stimulated at 100 deg. C after a pre-heat of 10 s at 150 deg. C) was used for investigations in a standard multiple aliquot procedure. The dose- response was found to be linear in the dose range investigated (up to ∼ 100 mGy) and the lower limit of detection for the samples varied from ∼ 0.01 to 14 mGy. These characteristics, along with the widespread abundance and low cost of household salt, confirm its potential as a retrospective dosemeter. (authors)

Time-resolved luminescence from quartz: An overview of contemporary developments and applications

Energy Technology Data Exchange (ETDEWEB)

Chithambo, M.L., E-mail: m.chithambo@ru.ac.za [Department of Physics and Electronics, Rhodes University, PO BOX 94, Grahamstown 6140 (South Africa); Ankjærgaard, C. [Soil Geography and Landscape Group, Wageningen University Netherlands Centre for Luminescence Dating, Droevendaalsesteeg 3, 6708 PB Wageningen, The Netherlands (Netherlands); Pagonis, V. [McDaniel College, Physics Department, Westminster, MD 21157 (United States)

2016-01-15

Time-resolved optical stimulation of luminescence has become established as a key method for measurement of optically stimulated luminescence from quartz, feldspar and α-Al{sub 2}O{sub 3}:C, all materials of interest in dosimetry. The aim of time-resolved optical stimulation is to separate in time the stimulation and emission of luminescence. The luminescence is stimulated from a sample using a brief light pulse and the emission monitored during stimulation in the presence of scattered stimulating light or after pulsing, over photomultiplier noise only. Although the use of the method in retrospective dosimetry has been somewhat limited, the technique has been successfully applied to study mechanisms in the processes leading up to luminescence emission. The main means for this has been the temperature dependence of the luminescence intensity as well as the luminescence lifetimes determined from time-resolved luminescence spectra. In this paper we review some key developments in theory and applications to quartz including methods of evaluating lifetimes, techniques of evaluating kinetic parameters using both the dependence of luminescence intensity and lifetime on measurement temperature, and of lifetimes on annealing temperature. We then provide an overview of some notable applications such as separation of quartz signals from a quartz–feldspar admixture and the utility of the dynamic throughput, a measure of luminescence measured as a function of the pulse width. The paper concludes with some suggestions of areas where further exploration would advance understanding of dynamics of luminescence in quartz and help address some outstanding problems in its application.

Luminescent Surface Quaternized Carbon Dots

KAUST Repository

Bourlinos, Athanasios B.

2012-01-10

Thermal oxidation of a salt precursor made from the acid base combination of tris(hydroxymethyl)aminomethane and betaine hydrochloride results in light-emitting surface quaternized carbon dots that are water-dispersible, display anion exchange properties, and exhibit uniform size/surface charge. © 2011 American Chemical Society.

Luminescent Surface Quaternized Carbon Dots

KAUST Repository

Bourlinos, Athanasios B.; Zbořil, Radek; Petr, Jan; Bakandritsos, Aristides; Krysmann, Marta; Giannelis, Emmanuel P.

2012-01-01

Thermal oxidation of a salt precursor made from the acid base combination of tris(hydroxymethyl)aminomethane and betaine hydrochloride results in light-emitting surface quaternized carbon dots that are water-dispersible, display anion exchange properties, and exhibit uniform size/surface charge. © 2011 American Chemical Society.

Surface chemistry and density distribution influence on visible luminescence of silicon quantum dots: an experimental and theoretical approach.

Science.gov (United States)

Dutt, Ateet; Matsumoto, Yasuhiro; Santana-Rodríguez, G; Ramos, Estrella; Monroy, B Marel; Santoyo Salazar, J

2017-01-04

The impact of the surface reconstruction of the density distribution and photoluminescence of silicon quantum dots (QDs) embedded in a silicon oxide matrix (SiO x ) has been studied. Annealing treatments carried out on the as-deposited samples provoked the effusion of hydrogen species. Moreover, depending on the surrounding density and coalescence of QDs, they resulted in a change in the average size of the particles depending on the initial local environment. The shift in the luminescence spectra all over the visible region (blue, green and red) shows a strong dependence on the resultant change in the size and/or the passivation environment of QDs. Density functional theoretical (DFT) calculations support this fact and explain the possible electronic transitions (HOMO-LUMO gap) involved. Passivation in the presence of oxygen species lowers the band gap of Si 29 and Si 35 nanoclusters up to 1.7 eV, whereas, surface passivation in the environment of hydrogen species increases the band gap up to 4.4 eV. These results show a good agreement with the quantum confinement model described in this work and explain the shift in the luminescence all over the visible region. The results reported here offer vital insight into the mechanism of emission from silicon quantum dots which has been one of the most debated topics in the last two decades. QDs with multiple size distribution in different local environments (band gap) observed in this work could be used for the fabrication of light emission diodes (LEDs) or shift-conversion thin films in third generation efficient tandem solar cells for the maximum absorption of the solar spectrum in different wavelength regions.

Protocols for Thermoluminescence and Optically Stimulated Luminescence Research at DOSAR

International Nuclear Information System (INIS)

Bernal, SM

2004-01-01

The Life Sciences Division (LSD) of Oak Ridge National Laboratory (ORNL) has a long record of radiation dosimetry research at the Dosimetry Applications Research (DOSAR) facility complex. These facilities have been used by a broad segment of the research community to perform a variety of experiments in areas including, but not limited to, radiobiology, radiation dosimeter and instrumentation development and calibration, and materials testing in a variety of radiation environments. Collaborations with the University of Tennessee-Knoxville (UTK) have also led to important contributions in the area of archaeometry, particularly as it relates to the use of radiation dosimetry to date archaeological artifacts. This manual is to serve as the primary instruction and operation manual for dosimetric and archaeometric research at DOSAR involving thermoluminescence (TL) and optically stimulated luminescence (OSL). Its purpose is to (1) provide protocols for common practices associated with the research, (2) outline the relevant organizational structure, (3) identify the Quality Assurance plan, and (4) describe all the procedures, operations, and responsibilities for safe and proper operation of associated equipment. Each person who performs research at DOSAR using TL/OSL equipment is required to read the latest revision of this manual and be familiar with its contents, and to sign and date the manual's master copy indicating that the manual has been read and understood. The TL/OSL Experimenter is also required to sign the manual after each revision to signify that the changes are understood. Each individual is responsible for completely understanding the proper operation of the TL/OSL equipment used and for following the guidance contained within this manual. The instructions, protocols, and operating procedures in this manual do not replace, supersede, or alter the hazard mitigation controls identified in the Research Safety Summary (''Thermoluminescence/Optically Stimulated

A new luminescence detection and stimulation head for the Risø TL/OSL reader

International Nuclear Information System (INIS)

Lapp, T.; Kook, M.; Murray, A.S.; Thomsen, K.J.; Buylaert, J.-P.; Jain, M.

2015-01-01

A new automated Detection And Stimulation Head (DASH) has been developed for the Risø TL/OSL luminescence reader to provide easy access to new technologies, new signals and new measurement methods. The automated DASH includes a filter changer and a detector changer that makes it possible to change stimulation filters (4 × 4 filter combinations possible) and detectors (3 detectors possible) as part of a measurements sequence. The new automated DASH with dedicated driver electronics does not affect the use of other attachments, and can be retrospectively fitted to existing Risø TL/OSL readers. - Highlights: • A new detection and stimulation head for the Risø TL/OSL reader is described. • An example of the use of the filter changer is presented. • The power and spatial uniformity of blue, green and IR stimulation are characterised. • The potential of an EMCCD camera detector is described.

Application of quantum dots CdZnSeS / ZnS luminescence, enhanced by plasmons of silver rough surface for detection of albumin in blood facies of infected person

Science.gov (United States)

Konstantinova, E.; Zyubin, A.; Moiseeva, E.; Matveeva, K.; Slezhkin, V.; Samusev, I.; Bryukhanov, V.

2017-12-01

The study of the luminescence of CdZnSeS / ZnS quantum dots (QDs) absorbed on the rough surface of a silver film, including the energy transfer between human serum albumin molecules, isolated from the blood plasma of healthy and infected with sepsis patients, was performed by spectral-kinetic methods.

Aluminum Nitride Ceramic as an Optically Stimulable Luminescence Dosimeter Plate

Directory of Open Access Journals (Sweden)

Go Okada

2016-04-01

Full Text Available Photostimulable storage phosphors have been used in a wide range of applications including radiation measurements in one- and two-dimensional spaces, called point dosimetry and radiography. In this work, we report that an aluminum nitride (AlN ceramic plate, which is practically used as a heat sink (SHAPAL®, Tokuyama Corp., Yamaguchi, Japan, shows good optically-stimulated luminescence (OSL properties with sufficiently large signal and capability for imaging applications, and we have characterized the AlN plate for OSL applications. Upon interaction with X-rays, the sample color turns yellowish, due to a radiation-induced photoabsorption band in the UV-blue range below ~500 nm. After irradiating the sample with X-rays, an intense OSL emission can be observed in the UV (360 nm spectral region during stimulation by red light. Although our measurement setup is not optimized, dose detection was confirmed as low as ~3 mGy to over 20 Gy. Furthermore, we have successfully demonstrated that the SHAPAL® AlN ceramic plate has great potential to be used as an imaging plate in radiography.

Biocompatible Quantum Dots for Biological Applications

Science.gov (United States)

Rosenthal, Sandra J.; Chang, Jerry C.; Kovtun, Oleg; McBride, James R.; Tomlinson, Ian D.

2011-01-01

Semiconductor quantum dots are quickly becoming a critical diagnostic tool for discerning cellular function at the molecular level. Their high brightness, long-lasting, sizetunable, and narrow luminescence set them apart from conventional fluorescence dyes. Quantum dots are being developed for a variety of biologically oriented applications, including fluorescent assays for drug discovery, disease detection, single protein tracking, and intracellular reporting. This review introduces the science behind quantum dots and describes how they are made biologically compatible. Several applications are also included, illustrating strategies toward target specificity, and are followed by a discussion on the limitations of quantum dot approaches. The article is concluded with a look at the future direction of quantum dots. PMID:21276935

Layer-by-layer assembly of multicolored semiconductor quantum dots towards efficient blue, green, red and full color optical films

International Nuclear Information System (INIS)

Zhang Jun; Li Qian; Di Xiaowei; Liu Zhiliang; Xu Gang

2008-01-01

Multicolored semiconductor quantum dots have shown great promise for construction of miniaturized light-emitting diodes with compact size, low weight and cost, and high luminescent efficiency. The unique size-dependent luminescent property of quantum dots offers the feasibility of constructing single-color or full-color output light-emitting diodes with one type of material. In this paper, we have demonstrated the facile fabrication of blue-, green-, red- and full-color-emitting semiconductor quantum dot optical films via a layer-by-layer assembly technique. The optical films were constructed by alternative deposition of different colored quantum dots with a series of oppositely charged species, in particular, the new use of cationic starch on glass substrates. Semiconductor ZnSe quantum dots exhibiting blue emission were deposited for fabrication of blue-emitting optical films, while semiconductor CdTe quantum dots with green and red emission were utilized for construction of green- and red-emitting optical films. The assembly of integrated blue, green and red semiconductor quantum dots resulted in full-color-emitting optical films. The luminescent optical films showed very bright emitting colors under UV irradiation, and displayed dense, smooth and efficient luminous features, showing brighter luminescence in comparison with their corresponding quantum dot aqueous colloid solutions. The assembled optical films provide the prospect of miniaturized light-emitting-diode applications.

Gamma response characterizations of optically stimulated luminescence (OSL) affects personal dosimetry

Science.gov (United States)

Monthonwattana, S.; Esor, J.; Rungseesumran, T.; Intang, A.

2017-06-01

Optically Stimulated Luminescence (OSL) is the current technique of personal dosimetry changed by Nuclear Technology Service Center instead of Thermoluminescence dosimetry (TLD) because OSL has more advantages, such as repeat reading and elimination of heating process. In this study, OSL was used to test the gamma response characterizations. Detailed OSL investigation on personal dosimetry was carried out in the dose range of 0.2 - 3.0 mSv. The batch homogeneity was 7.66%. R2 value of the linear regression was 0.9997. The difference ratio of angular dependence at ± 60° was 8.7%. Fading of the reading was about 3%.

Cultivating Fluorescent Flowers with Highly Luminescent Carbon Dots Fabricated by a Double Passivation Method.

Science.gov (United States)

Han, Shuai; Chang, Tao; Zhao, Haiping; Du, Huanhuan; Liu, Shan; Wu, Baoshuang; Qin, Shenjun

2017-07-07

In this work, we present the fabrication of highly luminescent carbon dots (CDs) by a double passivation method with the assistance of Ca(OH)₂. In the reaction process, Ca 2+ protects the active functional groups from overconsumption during dehydration and carbonization, and the electron-withdrawing groups on the CD surface are converted to electron-donating groups by the hydroxyl ions. As a result, the fluorescence quantum yield of the CDs was found to increase with increasing Ca(OH)₂ content in the reaction process. A blue-shift optical spectrum of the CDs was also found with increasing Ca(OH)₂ content, which could be attributed to the increasing of the energy gaps for the CDs. The highly photoluminescent CDs obtained (quantum yield: 86%) were used to cultivate fluorescent carnations by a water culture method, while the results of fluorescence microscopy analysis indicated that the CDs had entered the plant tissue structure.

Optically stimulated luminescence (OSL) dating of quartzite cobbles from the Tapada do Montinho archaeological site (east-central Portugal)

DEFF Research Database (Denmark)

Sohbati, Reza; Murray, Andrew S.; Buylaert, Jan-Pieter

2012-01-01

The burial age of an alluvially deposited cobble pavement at the Tapada do Montinho archaeological site (east-central Portugal) is investigated using optically stimulated luminescence (OSL) dating. Measurements on the cobbles (quartzite clasts) were carried out on intact slices and large aliquots...

Luminescence sensitivity changes in quartz

CERN Document Server

Wintle, A G

1999-01-01

In the luminescence dating of sedimentary or heated quartz, some heat treatment is usually applied to the sample immediately prior to the measurement of the optically stimulated luminescence. In this paper we report experiments on a 30,000-year-old sedimentary quartz, in which we use the luminescence response to a test dose to monitor the changes in sensitivity that are caused by holding the quartz at temperatures from 160 to 280 deg. C for times from 10 s to 22 h. For an optically bleached sample, the monitoring is by both optically stimulated luminescence and the 110 deg. C TL peak; both luminescence signals are shown to have the same sensitisation (i.e. activation energy) characteristics. For natural or laboratory irradiated samples only the 110 deg. C TL peak can be used; sensitivity increases of up to a factor of 1.3 and 3 are observed for the natural and laboratory irradiated aliquots, respectively. Up to four exponential components are used to deconvolve the sensitivity change data; the dominant compon...

Soft X-ray imaging by optically stimulated luminescence from color centers in lithium fluoride

Energy Technology Data Exchange (ETDEWEB)

Bonfigli, F. [ENEA, C.R. Frascati, Via E. Fermi, 45, 00044 Frascati (Rome) (Italy)], E-mail: bonfigli@frascati.enea.it; Almaviva, S.; Baldacchini, G.; Bollanti, S.; Flora, F.; Lai, A.; Montereali, R.M. [ENEA, C.R. Frascati, Via E. Fermi, 45, 00044 Frascati (Rome) (Italy); Nichelatti, E. [ENEA, C.R. Casaccia, Via Anguillarese 301, 00060 S.Maria di Galeria (Rome) (Italy); Tomassetti, G.; Ritucci, A.; Reale, L. [Universita de L' Aquila e INFN, Dip. di Fisica, Coppito, L' Aquila (Italy); Faenov, A. Ya.; Pikuz, T.A. [MISDC of VNIIFTRI Mendeleevo, Moscow region, 141570 (Russian Federation); Larciprete, R. [ISC-CNR, Sezione Montelibretti, Via Salaria, Km. 29.3, 00016 Monterotondo Scalo (Rome) (Italy); Gregoratti, L.; Kiskinova, M. [Sincrotrone Trieste, S. S. 14, Km. 163.5, 34012 Basovizza (TS) (Italy)

2007-07-15

An innovative X-ray imaging detector based on Optically Stimulated Luminescence from color centers in lithium fluoride is presented. Regular photoluminescent patterns produced on LiF samples by different intense X-ray sources, like synchrotrons, laser plasma sources and a capillary discharge laser have been investigated by a Confocal Laser Scanning Microscope. The use of a LiF-based imaging plate for X-ray microscopy is also discussed showing microradiographies of small animals.

Luminescence characteristics of dental ceramics for retrospective dosimetry: a preliminary study

International Nuclear Information System (INIS)

Bailiff, I.K.; Correcher, V.; Delgado, A.; Goksu, Y.; Huebner, S.

2002-01-01

Ceramic materials that are widely employed in dental prosthetics and repairs exhibit luminescent properties. Because of their use in the body, these materials are potentially of interest in situations where retrospective dosimetry for individuals is required but where monitoring was not planned. The luminescent properties of dental ceramics obtained in Germany, Spain and the UK were examined. Linear dose-response characteristics were obtained in the range <100 mGy to 10 Gy using thermoluminescence (TL), optically stimulated luminescence and infrared-stimulated luminescence measurement techniques. Measurements of time-resolved luminescence were also performed to examine the nature of the luminescence recombination under visible (470 nm) and IR (855 nm) stimulation. The results obtained by TL and optically stimulated techniques suggest that there may be deeper traps than previously observed in certain types of dental ceramic. Such traps may be less susceptible to optical and athermal fading than was reported in earlier studies. (author)

Development of photo stimulated luminescence technique for detecting irradiated food

International Nuclear Information System (INIS)

Ros Anita Ahmad Ramli; Ahmad Zainuri Mohd Dzomir; Zainon Othman; Wan Saffiey Wan Abdullah

2012-01-01

The exposure of food to ionizing radiation is being progressively used in many countries to inactivate food pathogens, to eradicate pests and to extend shelf-life of food. To ensure free consumer choice, irradiated food will be labeled. The availability of a reliable method to detect irradiated food is important to enforce legal controls on labeling requirements, ensure proper distribution and increase consumer confidence. This paper reports on the preliminary application of photo stimulated luminescence technique (PSL) as a potential method to detect irradiated food and perhaps be used for monitoring irradiated food on sale locally in the near future. Thus this study will be beneficial and relevant for application of food irradiation towards improving food safety and security in Malaysia. (author)

Artful and multifaceted applications of carbon dot in biomedicine.

Science.gov (United States)

Jaleel, Jumana Abdul; Pramod, K

2018-01-10

Carbon dots (C-dots) are luminescent carbon nanomaterial having good biocompatibility and low toxicity. The characteristic fluorescence emission property of C-dots establishes their role in optical imaging. C-dots which are superior to fluorescent dyes and semiconductor quantum dots act as a safer in vivo imaging probe. Apart from their bioimaging application, other applications in biomedicine such as drug delivery, cancer therapy, and gene delivery were studied. In this review, we present multifaceted applications of C-dots along with their synthesis, surface passivation, doping, and toxicity profile. Copyright © 2017 Elsevier B.V. All rights reserved.

Synthesis of quantum dots

Science.gov (United States)

McDaniel, Hunter

2017-10-17

Common approaches to synthesizing alloyed quantum dots employ high-cost, air-sensitive phosphine complexes as the selenium precursor. Disclosed quantum dot synthesis embodiments avoid these hazardous and air-sensitive selenium precursors. Certain embodiments utilize a combination comprising a thiol and an amine that together reduce and complex the elemental selenium to form a highly reactive selenium precursor at room temperature. The same combination of thiol and amine acts as the reaction solvent, stabilizing ligand, and sulfur source in the synthesis of quantum dot cores. A non-injection approach may also be used. The optical properties of the quantum dots synthesized by this new approach can be finely tuned for a variety of applications by controlling size and/or composition of size and composition. Further, using the same approach, a shell can be grown around a quantum dot core that improves stability, luminescence efficiency, and may reduce toxicity.

Luminescence properties of Si-containing porous matrix–PbS nanoparticle systems

International Nuclear Information System (INIS)

Tarasov, S. A.; Aleksandrova, O. A.; Lamkin, I. A.; Maksimov, A. I.; Maraeva, E. V.; Mikhailov, I. I.; Moshnikov, V. A.; Musikhin, S. F.; Nalimova, S. S.; Permyakov, N. V.; Spivak, Yu. M.; Travkin, P. G.

2015-01-01

The luminescence properties of systems that contain lead-sulfide nanoparticles deposited onto substrates fabricated from porous silicon, oxidized porous silicon, and porous (tin-oxide)–(silicon-oxide) layers are studied. It is shown that the structure and composition of the matrix induce a strong effect on the luminescence spectra of colloidal quantum dots, defining their emission wavelength

Bioconjugates of luminescent CdSe-ZnS quantum dots with an engineered two-domain protein G for use in fluoroimmunoassays

Science.gov (United States)

Tran, Phan T.; Goldman, Ellen R.; Mattoussi, Hedi M.; Anderson, George P.; Mauro, J. Matthew

2001-06-01

Colloidal semiconductor quantum dots (QDs) seem suitable for labeling certain biomolecules for use in fluorescent tagging applications, such as fluoro-immunoassays. Compared to organic dye labels, Qds are resistant to photo-degradation, and these luminescent nanoparticles have size-dependent emission spectra spanning a wide range of wavelengths in the visible and near IR. We previously described an electrostatic self-assembly approach for conjugating highly luminescent colloidal CdSe-ZnS core-shell Qds with engineered two-domain recombinant proteins. Here we describe the application of this approach to prepare QD conjugates with the (Beta) 2 immunoglobin G (IgG) binding domain of streptococcal protein G (PG) appended with a basic lucine zipper attachment domain (PG-zb). We also demonstrate that the QD/PG conjugates retain their ability to bind IgG antibodies, and that a specific antibody coupled to QD via the PG functional domain efficiently binds its antigen. These preliminary results indicate that electrostatically self-assembled QD/PG-zb/IgG bioconjugates can be used in fluoro-immunoassays.

UV induced photoluminescence and thermally stimulated luminescence of ThO{sub 2}:Tb{sup 3+} phosphor

Energy Technology Data Exchange (ETDEWEB)

Godbole, S.V.; Nagpal, J.S.; Page, A.G. E-mail: agpage@magnum.barc.ernet.in

2000-08-15

Thorium oxide doped with trivalent terbium ions offers itself as a novel phosphor with its photo- and thermally-stimulated luminescence (PL and TSL) characteristics showing a marked change on sustained exposure to 254 and 365 nm ultraviolet (UV) radiation. The reduction in luminescence intensity of Tb{sup 3+} ions, on irradiation with 254 nm photons and subsequent restoration on exposure to 365 nm, has been correlated with the complimentary behaviour in UV-induced TSL. These changes are, in turn, ascribed to inter-configurational (f-d) transitions and e-h formation and recombination processes. UV radiation induced TSL output increases linearly with incident UV radiant energy at a constant radiation flux; however, for a fixed exposure, TSL output increases with increase in radiant flux.

Spectroscopic characteristics of carbon dots (C-dots) derived from carbon fibers and conversion to sulfur-bridged C-dots nanosheets.

Science.gov (United States)

Vinci, John C; Ferrer, Ivonne M; Guterry, Nathan W; Colón, Verónica M; Destino, Joel F; Bright, Frank V; Colón, Luis A

2015-09-01

We synthesized sub-10 nm carbon nanoparticles (CNPs) consistent with photoluminescent carbon dots (C-dots) from carbon fiber starting material. The production of different C-dots fractions was monitored over seven days. During the course of the reaction, one fraction of C-dots species with relatively high photoluminescence was short-lived, emerging during the first hour of reaction but disappearing after one day of reaction. Isolation of this species during the first hour of the reaction was crucial to obtaining higher-luminescent C-dots species. When the reaction proceeded for one week, the appearance of larger nanostructures was observed over time, with lateral dimensions approaching 200 nm. The experimental evidence suggests that these larger species are formed from small C-dot nanoparticles bridged together by sulfur-based moieties between the C-dot edge groups, as if the C-dots polymerized by cross-linking the edge groups through sulfur bridges. Their size can be tailored by controlling the reaction time. Our results highlight the variety of CNP products, from sub-10 nm C-dots to ~200 nm sulfur-containing carbon nanostructures, that can be produced over time during the oxidation reaction of the graphenic starting material. Our work provides a clear understanding of when to stop the oxidation reaction during the top-down production of C-dots to obtain highly photoluminescent species or a target average particle size.

A high sensitivity optically stimulated luminescence scanning system for measurement of single sand-sized grains

DEFF Research Database (Denmark)

Duller, G.A.T.; Bøtter-Jensen, L.; Kohsiek, P.

1999-01-01

An instrument has been designed for the routine analysis of the optically stimulated luminescence signal from single grains of sand. The system is capable of analysing over 3000 individual grains in a single measurement sequence, and the OSL signal from each grain can be read in less than 3 s....... The design principles are described, along with preliminary measurements that illustrate the operation of the system and its capabilities....

Development of optically stimulated luminescence techniques using natural minerals and ceramics, and their application to retrospective dosimetry

International Nuclear Information System (INIS)

Boetter-Jensen, L.

2000-09-01

This thesis summarises research and development of optically stimulated luminescence (OSL) and its applications by the author at Risoe National Laboratory, up to 1999. These developments have been directed primarily at retrospective accident dosimetry and luminescence dating. Experimental investigations include the studies of OSL properties of the natural minerals quartz and feldspars and the artificial materials porcelain and aluminium oxide (Al 2 O 3 ). Blue light emitting diodes and infrared laser diodes are shown to provide simple and practical alternatives to broad-band light and visible laser stimulation. The development of OSL apparatus designed for the rapid measurement of single grains of phosphors also opens up a new area of luminescence measurement, allowing the detailed examination of dose distributions within a multiple-grain sample. This is of particular importance to the studies of incompletely reset geological sediments, and to accident dosimetry measurements using unheated materials. Al 2 O 3 :C single crystals are tested as environmental OSL dosemeters for assessing both the natural background photon radiation dose rates in the field and the natural dose rates inside bricks collected for accident dose evaluation. Environmental doses of the order of few μGy are measured with high precision. UV photo-stimulated luminescence spectra obtained from porcelain samples are used to confirm that the main component responsible for the OSL signal from porcelain is Al 2 O 3 . OSL single-aliquot regenerative-dose (SAR) techniques are used with quartz extracted from Chernobyl bricks to determine the accrued dose after the accident. This has improved the measurement precision significantly, from about 5-6 % using traditional methods to now less than 2 %. Depth-dose profiles measured in Chernobyl bricks are compared with those obtained in the laboratory using different gamma sources and these comparisons show that the average energy of the accident radiation was

Development of optically stimulated luminescence techniques using natural minerals and ceramics, and their application to retrospective dosimetry

Energy Technology Data Exchange (ETDEWEB)

Boetter-Jensen, L

2000-09-01

This thesis summarises research and development of optically stimulated luminescence (OSL) and its applications by the author at Risoe National Laboratory, up to 1999. These developments have been directed primarily at retrospective accident dosimetry and luminescence dating. Experimental investigations include the studies of OSL properties of the natural minerals quartz and feldspars and the artificial materials porcelain and aluminium oxide (Al{sub 2}O{sub 3}). Blue light emitting diodes and infrared laser diodes are shown to provide simple and practical alternatives to broad-band light and visible laser stimulation. The development of OSL apparatus designed for the rapid measurement of single grains of phosphors also opens up a new area of luminescence measurement, allowing the detailed examination of dose distributions within a multiple-grain sample. This is of particular importance to the studies of incompletely reset geological sediments, and to accident dosimetry measurements using unheated materials. Al{sub 2}O{sub 3}:C single crystals are tested as environmental OSL dosemeters for assessing both the natural background photon radiation dose rates in the field and the natural dose rates inside bricks collected for accident dose evaluation. Environmental doses of the order of few {mu}Gy are measured with high precision. UV photo-stimulated luminescence spectra obtained from porcelain samples are used to confirm that the main component responsible for the OSL signal from porcelain is Al{sub 2}O{sub 3}. OSL single-aliquot regenerative-dose (SAR) techniques are used with quartz extracted from Chernobyl bricks to determine the accrued dose after the accident. This has improved the measurement precision significantly, from about 5-6 % using traditional methods to now less than 2 %. Depth-dose profiles measured in Chernobyl bricks are compared with those obtained in the laboratory using different gamma sources and these comparisons show that the average energy of

Study of optically stimulated luminescence (OSL) for radiation detection. Application to an optical fibre γ-radiation sensor

International Nuclear Information System (INIS)

Roy, O.

1998-01-01

This work shows up the usefulness of the Optically Stimulated Luminescence (OSL) to resolve radioprotection problems. We study the use of OSL as a gamma dosimetric technique with respect to the ALARA's concept (As Low As Reasonably Achievable). A new approach based on optical fibers and luminescent materials showing OSL properties (closely related to Thermoluminescence phenomena) is presented in order to improve the remote real time dosimetry monitoring. Like thermoluminescent materials (TLD), OSL materials can trap charges under an irradiation (UV, X, γ,...). Instead of heating, the charges trapped are released by light stimulation and produce a visible luminescence which amount is proportional to trap the 'data stored' left by irradiation, enabling the dose measurement. The OSL phenomenon offers the same advantages as TLD plus the interesting possibility of a remote optical stimulation. The end-user objective deals with the development of a γ-radiation Optical FIber Sensor (OFS) for dose measurement which can offer new functionalities based on OSL materials coupled with an optical fiber. Rare earth doped Alkaline Earth Sulphides (AES), BAFX:EU 2+ (X = Cl, Br, I) and halogen alkaline have been studied (crystalline form, synthesis techniques, influence of dopants and color centers). Their characteristics are presented and extensively discussed. A specific experimental set-up to characterise various OSL phosphors has been developed. It allows the study of sensitivity, linearity, time decay behaviour of OSL signal and zeroing time. A joint study of OSL and TL has shown the technical limitations as well as the thermal fading and the origin of the long zeroing time. An Optical Fiber Sensor (OFS) based on OSL and using MgS:Sm has been developed for practical applications on nuclear fields. Its specifications are presented and discussed, moreover improvements are proposed. (author)

NaCl samples for optical luminescence dosimetry

International Nuclear Information System (INIS)

Catli, S.

2005-01-01

Optically stimulated luminescence (OSL) have been used broadly for luminescence dosimetry and dating. In many cases, it has been pointed out that the decay of the OSL do not generally behave according to a simple exponential function. In this study the Infra-red stimulated luminescence (IRSL) intensity from NaCl samples were experimentally measured. The decay curves for this sample were fitted to some functions and it is in good agreement with the function y = α + b exp(-cx). The IRSL decay curves from NaCl using different β-doses have been obtained and investigated their dose response

Delivery and reveal of localization of upconversion luminescent microparticles and quantum dots in the skin in vivo by fractional laser microablation, multimodal imaging, and optical clearing

Science.gov (United States)

Volkova, Elena K.; Yanina, Irina Yu; Genina, Elina A.; Bashkatov, Alexey N.; Konyukhova, Julia G.; Popov, Alexey P.; Speranskaya, Elena S.; Bucharskaya, Alla B.; Navolokin, Nikita A.; Goryacheva, Irina Yu.; Kochubey, Vyacheslav I.; Sukhorukov, Gleb B.; Meglinski, Igor V.; Tuchin, Valery V.

2018-02-01

Delivery and spatial localization of upconversion luminescent microparticles [Y2O3:Yb, Er] (mean size ˜1.6 μm) and quantum dots (QDs) (CuInS2/ZnS nanoparticles coated with polyethylene glycol-based amphiphilic polymer, mean size ˜20 nm) inside rat skin was studied in vivo using a multimodal optical imaging approach. The particles were embedded into the skin dermis to the depth from 300 to 500 μm through microchannels performed by fractional laser microablation. Low-frequency ultrasound was applied to enhance penetration of the particles into the skin. Visualization of the particles was revealed using a combination of luminescent spectroscopy, optical coherence tomography, confocal microscopy, and histochemical analysis. Optical clearing was used to enhance the image contrast of the luminescent signal from the particles. It was demonstrated that the penetration depth of particles depends on their size, resulting in a different detection time interval (days) of the luminescent signal from microparticles and QDs inside the rat skin in vivo. We show that luminescent signal from the upconversion microparticles and QDs was detected after the particle delivery into the rat skin in vivo during eighth and fourth days, respectively. We hypothesize that the upconversion microparticles have created a long-time depot localized in the laser-created channels, as the QDs spread over the surrounding tissues.

Advantages and disadvantages of luminescence dosimetry

Energy Technology Data Exchange (ETDEWEB)

Olko, Pawel, E-mail: Pawel.Olko@ifj.edu.p [Institute of Nuclear Physics Polish Academy of Science (IFJ PAN), Krakow (Poland)

2010-03-15

Owing to their excellent dosimetric properties, luminescence detectors of ionizing radiation are now extensively applied in individual dosimetry services. The most frequently used personal dosemeters are based on Optically Stimulated Luminescence (OSL), radiophotoluminescence (RPL) or thermoluminescence (TL). Luminescence detectors have also found several applications in clinical dosimetry, especially around new radiation modalities in radiotherapy, such as Intensity Modulated Radiotherapy (IMRT) or ion beam radiotherapy. Requirements of luminescence detectors applied in individual and clinical dosimetry and some recent developments in luminescence of detectors and techniques leading to significant improvements of the functionality and accuracy of dosimetry systems are reviewed and discussed.

Decay kinetics and thermally stimulated luminescence of Mn.sup.4 +./sup. in SrTiO.sub.3./sub

Czech Academy of Sciences Publication Activity Database

Bryknar, Z.; Potůček, Zdeněk; Trepakov, Vladimír; Shen, M. Y.; Goto, T.

2001-01-01

Roč. 154, - (2001), s. 341-345 ISSN 1042-0150 R&D Projects: GA ČR GA202/00/1425 Institutional research plan: CEZ:AV0Z1010914 Keywords : thermally stimulated luminescence * decay kinetics * strontium titanate * manganese Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.380, year: 2001

Thermally stimulated luminescence and persistent luminescence of β-irradiated YAG:Pr"3"+ nanophosphors produced by combustion synthesis

International Nuclear Information System (INIS)

Santacruz-Gomez, K.; Meléndrez, R.; Gil-Tolano, M.I.; Jimenez, J.A.; Makale, M.T.; Barboza-Flores, M.; Castaneda, B.; Soto-Puebla, D.; Pedroza-Montero, M.; McKittrick, J.; Hirata, G.A.

2016-01-01

In this work, the thermally stimulated luminescence (TSL) and persistent luminescence (PLUM) properties of praseodymium doped yttrium aluminum garnet (YAG:Pr"3"+) exposed to β-irradiation are reported. X-ray diffraction (XRD) confirms a single phase of YAG obtained by the combustion method. Transmission electron microscopy (TEM) shows that powder particles appear to be irregular crystals with an average size of 67 nm. TSL glow-curve deconvolution of YAG:Pr"3"+ after β-irradiation consist in six peaks centered at 394, 450, 467, 543, 637 and 705 K. The TSL fading and PLUM signals were found to be associated with at least with two different kinds of traps, corresponding to the peaks located at 394, 450 and 467 K. YAG:Pr"3"+ nanophosphors analyzed in this work showed interesting features about the dosimetric sensitivity as well as the reproducibility for both TSL/PLUM techniques, with good linearity dose response. These results indicate that nanocrystalline YAG:Pr3"+ is a good candidate for dosimetric applications in the range of 80 mGy-20 Gy. - Highlights: • β-irradiated YAG:Pr"3"+ TSL consist in 394, 450, 467, 543, 637 and 705 K peaks. • YAG:Pr"3"+ is a good candidate for dosimetry in the range of 80 mGy-20 Gy. • PLUM can be potentially used for in vivo, in situ and quasi in real time dosimetry.

Luminescent properties of fluorophosphate glasses with lead chalcogenides molecular clusters

International Nuclear Information System (INIS)

Kolobkova, E.V.; Kukushkin, D.S.; Nikonorov, N.V.; Shakhverdov, T.A.; Sidorov, A.I.; Vasiliev, V.N.

2015-01-01

Fluorophosphate glasses containing lead, selenium, and sulfur exhibit an intense luminescence in the 400–620 nm spectral region when excited by the 240–420 nm radiation. This luminescence is due to the presence of (PbSe) n and/or (PbS) n molecular clusters in the glasses, which appear in the as-prepared glasses before quantum dots formation. The thermal treatment at temperatures less than the glass transition temperature results in the red-shift of the luminescence bands and in an increase in the luminescence intensity. Heating the thermally treated glass samples leads to the reversible thermal quenching of the luminescence. - Highlights: • Fluorophosphate glasses with Pb, Se, and S ions contain (PbSe) n or (PbS) n molecular clusters. • (PbSe) n and (PbS) n molecular clusters possess luminescence in the visible with UV excitation. • Heating the glass leads to the reversible thermal quenching of the luminescence

Optically stimulated luminescence properties of Tm3+ doped KMgF3 fluoro perovskite

International Nuclear Information System (INIS)

Camargo, L.; Marcazzo, J.; Perez C, L.; Cruz Zaragoza, E.; Martinez O, S. A.

2017-10-01

In this work the optically stimulated luminescence (OSL) properties of undoped and Tm 3+ doped KMgF 3 fluoro perovskite have been investigated for the first time. OSL efficiency for stimulation with different wavelengths has been analyzed for each compound. The maximum OSL emission was found with blue light stimulation. The radioluminescence (Rl) spectra have shown two emission peaks at 455 and 360 nm, which can be ascribed to the 1 D 2 - 3 F 4 and 1 D 2 - 3 H 6 transitions of the Tm 3+ cations. It has been found that doping with Thulium 0.5 mol % renders the most intense OSL emission. Furthermore, several dosimetric properties such as OSL response as a function of dose, reproducibility of the OSL signal after several cycles of irradiation readout and the minimum detectable dose have been investigated. Finally, the OSL response of KMgF 3 : Tm 3+ has been compared to that of commercial Al 2 O 3 :C and the possible application of this fluoro perovskite to OSL dosimetry has been evaluated. (Author)

Efficient Luminescence from Perovskite Quantum Dot Solids

KAUST Repository

Kim, Younghoon; Yassitepe, Emre; Voznyy, Oleksandr; Comin, Riccardo; Walters, Grant; Gong, Xiwen; Kanjanaboos, Pongsakorn; Nogueira, Ana F.; Sargent, Edward H.

2015-01-01

© 2015 American Chemical Society. Nanocrystals of CsPbX3 perovskites are promising materials for light-emitting optoelectronics because of their colloidal stability, optically tunable bandgap, bright photoluminescence, and excellent photoluminescence quantum yield. Despite their promise, nanocrystal-only films of CsPbX3 perovskites have not yet been fabricated; instead, highly insulating polymers have been relied upon to compensate for nanocrystals' unstable surfaces. We develop solution chemistry that enables single-step casting of perovskite nanocrystal films and overcomes problems in both perovskite quantum dot purification and film fabrication. Centrifugally cast films retain bright photoluminescence and achieve dense and homogeneous morphologies. The new materials offer a platform for optoelectronic applications of perovskite quantum dot solids.

Efficient Luminescence from Perovskite Quantum Dot Solids

KAUST Repository

Kim, Younghoon

2015-11-18

© 2015 American Chemical Society. Nanocrystals of CsPbX3 perovskites are promising materials for light-emitting optoelectronics because of their colloidal stability, optically tunable bandgap, bright photoluminescence, and excellent photoluminescence quantum yield. Despite their promise, nanocrystal-only films of CsPbX3 perovskites have not yet been fabricated; instead, highly insulating polymers have been relied upon to compensate for nanocrystals\\' unstable surfaces. We develop solution chemistry that enables single-step casting of perovskite nanocrystal films and overcomes problems in both perovskite quantum dot purification and film fabrication. Centrifugally cast films retain bright photoluminescence and achieve dense and homogeneous morphologies. The new materials offer a platform for optoelectronic applications of perovskite quantum dot solids.

Surface exposure dating of non-terrestrial bodies using optically stimulated luminescence: A new method

DEFF Research Database (Denmark)

Sohbati, Reza; Jain, Mayank; Murray, Andrew

2012-01-01

We propose a new method for in situ surface exposure dating of non-terrestrial geomorphological features using optically stimulated luminescence (OSL); our approach is based on the progressive emptying of trapped charge with exposure to light at depth into a mineral surface. A complete model of t...... charge population. The potential dating applications for (a) include dust accumulation, volcanic rocks and impact-related sediments, and for (b) fault scarps, rock-falls, landslides and ice-scoured bedrock. Using assumptions based on terrestrial observations we expect that this approach...

Europium enabled luminescent nanoparticles for biomedical applications

Energy Technology Data Exchange (ETDEWEB)

Syamchand, S.S., E-mail: syamchand.ss@gmail.com; Sony, G., E-mail: emailtosony@gmail.com

2015-09-15

Lanthanide based nanoparticles are receiving great attention ought to their excellent luminescent and magnetic properties and find challenging biomedical applications. Among the luminescent lanthanide NPs, europium based NPs (Eu-NPs) are better candidates for immunoassay and imaging applications. The Eu-NPs have an edge over quantum dots (QDs) by means of their stable luminescence, long fluorescence lifetime, sharp emission peaks with narrow band width, lack of blinking and biocompatibility. This review surveys the synthesis and properties of a variety of Eu-NPs consolidated from different research articles, for their applications in medicine and biology. The exquisite luminescent properties of Eu-NPs are explored for developing biomedical applications such as immunoassay and bioimaging including multimodal imaging. The biomedical applications of Eu-NPs are mostly diagnostic in nature and mainly focus on various key analytes present in biological systems. The luminescent properties of europium enabled NPs are influenced by a number of factors such as the site symmetry, the metal nanoparticles, metal ions, quantum dots, surfactants, morphology of Eu-NPs, crystal defect, phenomena like antenna effect and physical parameters like temperature. Through this review we explore and assimilate all the factors which affect the luminescence in Eu-NPs and coil a new thread of parameters that control the luminescence in Eu-NPs, which would provide further insight in developing Eu-based nanoprobes for future biomedical prospects. - Highlights: • The review describes 14 major factors that influence the luminescence properties of europium enabled luminescent nanoparticles (Eu-NPs). • Surveys different types of europium containing nanoparticles that have been reported for their biomedical applications. • Eu-NPs are conveniently divided into four different categories, based on the type of the substrates involved. The four categories are (1) virgin Eu-substrate based NPs; (2

Europium enabled luminescent nanoparticles for biomedical applications

International Nuclear Information System (INIS)

Syamchand, S.S.; Sony, G.

2015-01-01

Lanthanide based nanoparticles are receiving great attention ought to their excellent luminescent and magnetic properties and find challenging biomedical applications. Among the luminescent lanthanide NPs, europium based NPs (Eu-NPs) are better candidates for immunoassay and imaging applications. The Eu-NPs have an edge over quantum dots (QDs) by means of their stable luminescence, long fluorescence lifetime, sharp emission peaks with narrow band width, lack of blinking and biocompatibility. This review surveys the synthesis and properties of a variety of Eu-NPs consolidated from different research articles, for their applications in medicine and biology. The exquisite luminescent properties of Eu-NPs are explored for developing biomedical applications such as immunoassay and bioimaging including multimodal imaging. The biomedical applications of Eu-NPs are mostly diagnostic in nature and mainly focus on various key analytes present in biological systems. The luminescent properties of europium enabled NPs are influenced by a number of factors such as the site symmetry, the metal nanoparticles, metal ions, quantum dots, surfactants, morphology of Eu-NPs, crystal defect, phenomena like antenna effect and physical parameters like temperature. Through this review we explore and assimilate all the factors which affect the luminescence in Eu-NPs and coil a new thread of parameters that control the luminescence in Eu-NPs, which would provide further insight in developing Eu-based nanoprobes for future biomedical prospects. - Highlights: • The review describes 14 major factors that influence the luminescence properties of europium enabled luminescent nanoparticles (Eu-NPs). • Surveys different types of europium containing nanoparticles that have been reported for their biomedical applications. • Eu-NPs are conveniently divided into four different categories, based on the type of the substrates involved. The four categories are (1) virgin Eu-substrate based NPs; (2

Detection of irradiated spices using photo-stimulated luminescence technique (PSL)

Energy Technology Data Exchange (ETDEWEB)

Ramli, Ros Anita Ahmad; Yasir, Muhamad Samudi [Faculty of Science and Technology, National University of Malaysia, Bangi, 43000 Kajang, Selangor (Malaysia); Othman, Zainon; Abdullah, Wan Saffiey Wan [Malaysian Nuclear Agency, Bangi 43000 Kajang, Selangor (Malaysia)

2014-09-03

Photo-stimulated luminescence (PSL) technique was applied to detect irradiated black pepper (Piper nigrum), cinnamon (Cinnamomum verum) and turmeric (Curcuma longa) after dark storage for 1 day, 3 and 6 months. Using screening and calibrated PSL, all samples were correctly discriminated between non-irradiated and spices irradiated with doses 1, 5 and 10 kGy. The PSL photon counts (PCs) of irradiated spices increased with increasing dose, with turmeric showing highest sensitivity index to irradiation compared to black pepper and cinnamon. The differences in response are possibly attributed to the varying quantity and quality of silicate minerals present in each spice sample. PSL signals of all irradiated samples reduced after 3 and 6 months storage. The results of this study provide a useful database on the applicability of PSL technique for the detection of Malaysian irradiated spices.

Detection of irradiated spices using photo-stimulated luminescence technique (PSL)

International Nuclear Information System (INIS)

Ramli, Ros Anita Ahmad; Yasir, Muhamad Samudi; Othman, Zainon; Abdullah, Wan Saffiey Wan

2014-01-01

Photo-stimulated luminescence (PSL) technique was applied to detect irradiated black pepper (Piper nigrum), cinnamon (Cinnamomum verum) and turmeric (Curcuma longa) after dark storage for 1 day, 3 and 6 months. Using screening and calibrated PSL, all samples were correctly discriminated between non-irradiated and spices irradiated with doses 1, 5 and 10 kGy. The PSL photon counts (PCs) of irradiated spices increased with increasing dose, with turmeric showing highest sensitivity index to irradiation compared to black pepper and cinnamon. The differences in response are possibly attributed to the varying quantity and quality of silicate minerals present in each spice sample. PSL signals of all irradiated samples reduced after 3 and 6 months storage. The results of this study provide a useful database on the applicability of PSL technique for the detection of Malaysian irradiated spices

Detection of irradiated spices using photo-stimulated luminescence technique (PSL)

Science.gov (United States)

Ramli, Ros Anita Ahmad; Yasir, Muhamad Samudi; Othman, Zainon; Abdullah, Wan Saffiey Wan

2014-09-01

Photo-stimulated luminescence (PSL) technique was applied to detect irradiated black pepper (Piper nigrum), cinnamon (Cinnamomum verum) and turmeric (Curcuma longa) after dark storage for 1 day, 3 and 6 months. Using screening and calibrated PSL, all samples were correctly discriminated between non-irradiated and spices irradiated with doses 1, 5 and 10 kGy. The PSL photon counts (PCs) of irradiated spices increased with increasing dose, with turmeric showing highest sensitivity index to irradiation compared to black pepper and cinnamon. The differences in response are possibly attributed to the varying quantity and quality of silicate minerals present in each spice sample. PSL signals of all irradiated samples reduced after 3 and 6 months storage. The results of this study provide a useful database on the applicability of PSL technique for the detection of Malaysian irradiated spices.

Theranostic carbon dots derived from garlic with efficient anti-oxidative effects towards macrophages

DEFF Research Database (Denmark)

Yang, Chuanxu; Ogaki, Ryosuke; Hansen, Line

2015-01-01

Luminescent garlic carbon dots with superior photostability are synthesized via microwave assisted heating. The garlic dots are biocompatible, have low toxicity and can be used as benign theranostic nanoparticles for bioimaging with efficient anti-oxidative effects towards macrophages....

A luminescence imaging system based on a CCD camera

DEFF Research Database (Denmark)

Duller, G.A.T.; Bøtter-Jensen, L.; Markey, B.G.

1997-01-01

Stimulated luminescence arising from naturally occurring minerals is likely to be spatially heterogeneous. Standard luminescence detection systems are unable to resolve this variability. Several research groups have attempted to use imaging photon detectors, or image intensifiers linked...... to photographic systems, in order to obtain spatially resolved data. However, the former option is extremely expensive and it is difficult to obtain quantitative data from the latter. This paper describes the use of a CCD camera for imaging both thermoluminescence and optically stimulated luminescence. The system...

Photoluminescence studies of single InGaAs quantum dots

DEFF Research Database (Denmark)

Leosson, Kristjan; Jensen, Jacob Riis; Hvam, Jørn Märcher

1999-01-01

Semiconductor quantum dots are considered a promising material system for future optical devices and quantum computers. We have studied the low-temperature photoluminescence properties of single InGaAs quantum dots embedded in GaAs. The high spatial resolution required for resolving single dots...... to resolve luminescence lines from individual quantum dots, revealing an atomic-like spectrum of sharp transition lines. A parameter of fundamental importance is the intrinsic linewidth of these transitions. Using high-resolution spectroscopy we have determined the linewidth and investigated its dependence...... on temperature, which gives information about how the exciton confined to the quantum dot interacts with the surrounding lattice....

Brightly Luminescent and Color-Tunable Colloidal CH3NH3PbX3 (X = Br, I, Cl) Quantum Dots: Potential Alternatives for Display Technology.

Science.gov (United States)

Zhang, Feng; Zhong, Haizheng; Chen, Cheng; Wu, Xian-gang; Hu, Xiangmin; Huang, Hailong; Han, Junbo; Zou, Bingsuo; Dong, Yuping

2015-04-28

Organometal halide perovskites are inexpensive materials with desirable characteristics of color-tunable and narrow-band emissions for lighting and display technology, but they suffer from low photoluminescence quantum yields at low excitation fluencies. Here we developed a ligand-assisted reprecipitation strategy to fabricate brightly luminescent and color-tunable colloidal CH3NH3PbX3 (X = Br, I, Cl) quantum dots with absolute quantum yield up to 70% at room temperature and low excitation fluencies. To illustrate the photoluminescence enhancements in these quantum dots, we conducted comprehensive composition and surface characterizations and determined the time- and temperature-dependent photoluminescence spectra. Comparisons between small-sized CH3NH3PbBr3 quantum dots (average diameter 3.3 nm) and corresponding micrometer-sized bulk particles (2-8 μm) suggest that the intense increased photoluminescence quantum yield originates from the increase of exciton binding energy due to size reduction as well as proper chemical passivations of the Br-rich surface. We further demonstrated wide-color gamut white-light-emitting diodes using green emissive CH3NH3PbBr3 quantum dots and red emissive K2SiF6:Mn(4+) as color converters, providing enhanced color quality for display technology. Moreover, colloidal CH3NH3PbX3 quantum dots are expected to exhibit interesting nanoscale excitonic properties and also have other potential applications in lasers, electroluminescence devices, and optical sensors.

High-resolution light microscopy using luminescent nanoparticles.

Science.gov (United States)

Ohulchanskyy, Tymish Y; Roy, Indrajit; Yong, Ken-Tye; Pudavar, Haridas E; Prasad, Paras N

2010-01-01

This review presents recent progress in the development of the luminescent nanoparticles for confocal and multiphoton microscopy. Four classes of nanomaterials are discussed: (1) silica-based nanoparticles doped with fluorescent molecules, (2) gold nanoparticles, (3) semiconductor nanocrystals (quantum dots/rods), and (4) nanophosphors. Special considerations are given to recently developed imaging nanoprobes, such as (1) organically modified silica (ORMOSIL) nanoparticles doped with two-photon absorbing fluorophores, which exhibit aggregation-enhanced fluorescence (AEF), and (2) nanophosphors (ceramic nanoparticles containing luminescent lanthanoid ions). Advantages and disadvantages of every class of nanomaterials and their specific applications are briefly discussed.

Hyperbolic metamaterials based on quantum-dot plasmon-resonator nanocomposites

DEFF Research Database (Denmark)

Zhukovsky, Sergei; Ozel, T.; Mutlugun, E.

2014-01-01

We theoretically demonstrate that nanocomposites made of colloidal semiconductor quantum dot monolayers placed between metal nanoparticle monolayers can function as multilayer hyperbolic metamaterials. Depending on the thickness of the spacer between the quantum dot and nanoparticle layers......, the effective permittivity tensor of the nanocomposite is shown to become indefinite, resulting in increased photonic density of states and strong enhancement of quantum dot luminescence. This explains the results of recent experiments [T. Ozel et al., ACS Nano 5, 1328 (2011)] and confirms that hyperbolic...

Enhancing and quenching luminescence with gold nanoparticle films: the influence of substrate on the luminescent properties

International Nuclear Information System (INIS)

Guidelli, Eder José; Baffa, Oswaldo; Ramos, Ana Paula

2016-01-01

Gold nanoparticle (AuNP) films were sputtered over glass and aluminum substrates to enhance optically stimulated luminescence (OSL), a luminescent technique employed for radiation detection, from x-ray irradiated NaCl nanocrystals. The AuNP films deposited over glass led to enhanced-OSL emission, whereas the AuNP films deposited on aluminum substrates quenched the OSL emission. The enhanced-OSL intensity is proportional to the optical density of the film's plasmon resonance band at the stimulation wavelength. For the case of the AuNP/aluminum films, the luminescence quenching diminishes, and OSL intensity partially recovers upon increasing the distance between the AuNPs and the aluminum substrates, and between the luminescent nanocrystals and the AuNP films. These results suggest that plasmonic interactions between the emitter nanocrystals, the localized surface plasmons (LSP) of the AuNPs, and the substrate are responsible for the OSL enhancement and quenching. In this sense, the substrate dictates whether LSP relaxation occurs by radiative or non-radiative transisitions, leading to enhanced or quenched OSL, respectively. Therefore, besides showing that AuNP films can enhance and/or tune the sensitivity of luminescent radiation detectors, and demonstrating OSL as a new technique to investigate mechanisms of plasmon-enhanced luminescence, these results bring insights on how substrates strongly modify the optical properties of AuNP films. (paper)

Device and method for luminescence enhancement by resonant energy transfer from an absorptive thin film

Science.gov (United States)

Akselrod, Gleb M.; Bawendi, Moungi G.; Bulovic, Vladimir; Tischler, Jonathan R.; Tisdale, William A.; Walker, Brian J.

2017-12-12

Disclosed are a device and a method for the design and fabrication of the device for enhancing the brightness of luminescent molecules, nanostructures, and thin films. The device includes a mirror, a dielectric medium or spacer, an absorptive layer, and a luminescent layer. The absorptive layer is a continuous thin film of a strongly absorbing organic or inorganic material. The luminescent layer may be a continuous luminescent thin film or an arrangement of isolated luminescent species, e.g., organic or metal-organic dye molecules, semiconductor quantum dots, or other semiconductor nanostructures, supported on top of the absorptive layer.

Specific features of electroluminescence in heterostructures with InSb quantum dots in an InAs matrix

Energy Technology Data Exchange (ETDEWEB)

Parkhomenko, Ya. A.; Ivanov, E. V.; Moiseev, K. D., E-mail: mkd@iropt2.ioffe.rssi.ru [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)

2013-11-15

The electrical and electroluminescence properties of a single narrow-gap heterostructure based on a p-n junction in indium arsenide, containing a single layer of InSb quantum dots in the InAs matrix, are studied. The presence of quantum dots has a significant effect on the shape of the reverse branch of the current-voltage characteristic of the heterostructure. Under reverse bias, the room-temperature electroluminescence spectra of the heterostructure with quantum dots, in addition to a negative-luminescence band with a maximum at the wavelength {lambda} = 3.5 {mu}m, contained a positive-luminescence emission band at 3.8 {mu}m, caused by radiative transitions involving localized states of quantum dots at the type-II InSb/InAs heterointerface.

SU-F-T-654: Pacemaker Dose Estimate Using Optically Stimulated Luminescent Dosimeter for Left Breast Intraoperative Radiation Therapy

Energy Technology Data Exchange (ETDEWEB)

Chen, Y; Goenka, A; Sharma, A; Wang, L; Cao, Y; Jamshidi, A [Northwell Health, Lake Success, NY (United States)

2016-06-15

Purpose: To assess and report the in vivo dose for a patient with a pacemaker being treated in left breast intraoperative radiation therapy (IORT). The ZEISS Intrabeam 50 kVp X-ray beam with a spherical applicator was used. Methods: The optically stimulated luminescent dosimeters (OSLDs) (Landauer nanoDots) were employed and calibrated under the conditions of the Intrabeam 50 kVp X-rays. The nanoDots were placed on the patient at approximately 15 cm away from the lumpectomy cavity both under and above a shield of lead equivalence 0.25 mm (RayShield X-Drape D-110) covering the pacemaker area during IORT with a 5 cm spherical applicator. Results: The skin surface dose near the pacemaker during the IORT with a prescription of 20 Gy was measured as 4.0±0.8 cGy. The dose behind the shield was 0.06±0.01 Gy, demonstrating more than 98% dose reduction. The in vivo skin surface doses during a typical breast IORT at a 4.5 cm spherical applicator surface were further measured at 5, 10, 15, and 20 cm away to be 159±11 cGy, 15±1 cGy, 6.6±0.5 cGy, and 1.8±0.1 cGy, respectively. A power law fit to the dose versus the distance z from the applicator surface yields the dose fall off at the skin surface following z^-2.5, which can be used to estimate skin doses in future cases. The comparison to an extrapolation of depth dose in water reveals an underestimate of far field dose using the manufactory provided data. Conclusion: The study suggests the appropriateness of OSLD as an in vivo skin dosimeter in IORT using the Intrabeam system in a wide dose range. The pacemaker dose measured during the left breast IORT was within a safe limit.

Direct Observation of Electron-to-Hole Energy Transfer in CdSe Quantum Dots

NARCIS (Netherlands)

Hendry, E.; Koeberg, M.; Wang, F.; Zhang, H.; de Mello Donega, C.; Vanmaekelbergh, D.; Bonn, M.

2006-01-01

We independently determine the subpicosecond cooling rates for holes and electrons in CdSe quantum dots. Time-resolved luminescence and terahertz spectroscopy reveal that the rate of hole cooling, following photoexcitation of the quantum dots, depends critically on the electron excess energy. This

Optically stimulated luminescence of ZnO obtained by thermal treatment of ZnS chemically synthesized; Luminiscencia opticamente estimulada de ZnO obtenido por tratamiento termico de ZnS sintetizado quimicamente

Energy Technology Data Exchange (ETDEWEB)

Cruz V, C.; Burruel I, S.E.; Orante B, V.R.; Grijalva M, H.; Perez S, R.; Bernal, R. [Universidad de Sonora, A.P. 130, Hermosillo (Mexico)

2005-07-01

In this work, we report the optically stimulated luminescence (OSL) dosimetry of new nano phosphors of ZnO obtained by thermal annealing of chemically synthesized ZnS powder. The synthesized ZnS nano powder was compressed in order to form pellet shaped pellets, which were afterwards subjected to a thermal annealing at 700 C during 24 h under air atmosphere. X-ray diffraction (XRD) patterns and energy-disperse X-ray Spectrometry (EDS) analyses confirmed the transformation of ZnS to ZnO. Samples were exposed to several doses of beta radiation up to 600 Gy, and the optically stimulated luminescence with 470 nm wavelength light was recorded as a function of dose. The intensity of the OSL signal increases by increasing dose, for what it is concluded that these new phosphor materials are suitable to be used in optically stimulated luminescence dosimetry. (Author)

Real-time luminescence from Al2O3 fiber dosimeters

International Nuclear Information System (INIS)

Polf, J.C.; Yukihara, E.G.; Akselrod, M.S.; McKeever, S.W.S.

2004-01-01

The real-time luminescence signal from Al 2 O 3 single crystal fibers, monitored during simultaneous irradiation and optical stimulation, was investigated using computer simulations and experimental measurements. Both radioluminescence (RL) and optically stimulated luminescence (OSL) signals were studied. The simulations were performed initially using a simple one-trap/one-recombination-center energy band model, and then extended to include shallow and deep electron traps as well. Real-time luminescence experiments were performed for different radiation dose rates and optical stimulation powers using periodic laser stimulation of the samples through a fiber optic cable, and the experimental results were compared with the predictions from the computer simulations. The luminescence signal was observed, both theoretically and experimentally, to increase from its initial value to a steady-state level. The steady-state RL and OSL levels were found to be dependent on dose rate, the steady-state level of the real-time OSL being independent of laser power. It was also shown that the total integrated absorbed dose throughout the irradiation period can be determined by correcting the real-time OSL signal for depletion caused by each laser stimulation pulse. The effects of the shallow and deep traps on the time-dependence of the real-time luminescence signal were studied comparing the experimental data from several Al 2 O 3 fibers known to have different trapping state concentrations. The additional traps were found to slow the response of the real-time luminescence such that the time to reach steady state was increased as the additional traps were added

Testing optically stimulated luminescence dating on sand-sized quartz of deltaic deposits from the Sperchios delta plain, central Greece

Directory of Open Access Journals (Sweden)

Evangelos Tsakalos

2018-04-01

Full Text Available This study reports on the first investigation into the potential of luminescence dating to establish a chronological framework for the depositional sequences of the Sperchios delta plain, central Greece. A series of three borehole cores (20 m deep and two shallow cores (4 m deep, from across the delta plain, were extracted, and samples were collected for luminescence dating. The luminescence ages of sand-sized quartz grains were obtained from small aliquots of quartz, using the Single-Aliquot Regenerative-dose (SAR protocol. The equivalent dose determination included a series of tests and the selection of the Minimum Age Model (MAM as the most appropriate statistical model. This made it possible to confirm the applicability of quartz Optically Stimulated Luminescence (OSL dating to establish absolute chronology for deltaic sediments from the Sperchios delta plain.Testing age results of the five cores showed that the deltaic sediments were deposited during the Holocene. A relatively rapid deposition is implied for the top ∼14 m possibly as a result of the deceleration in the rate of the sea-level rise and the transition to terrestrial conditions, while on the deeper parts, the reduced sedimentation rate may indicate a lagoonal or coastal environment. Keywords: Luminescence dating, Holocene, Sedimentation rates, Deltaic deposits, Sperchios delta plain, Central Greece

Commissioning optically stimulated luminescence in vivo dosimeters for fast neutron therapy

Energy Technology Data Exchange (ETDEWEB)

Young, Lori A., E-mail: layoung@uw.edu; Sandison, George [Department of Radiation Oncology, University of Washington, Seattle, Washington 98115 (United States); Yang, Fei [Sylvester comprehensive Cancer Center, University of Miami, Miami, Florida 33124 (United States); Woodworth, Davis [Department of Physics, University of Reno, Reno, Nevada 89557 (United States); McCormick, Zephyr [Department of Physics, University of California, Santa Barbara, California 93106 (United States)

2016-01-15

Purpose: Clinical in vivo dosimeters intended for use with photon and electron therapies have not been utilized for fast neutron therapy because they are highly susceptible to neutron damage. The objective of this work was to determine if a commercial optically stimulated luminescence (OSL) in vivo dosimetry system could be adapted for use in fast neutron therapy. Methods: A 50.5 MeV fast neutron beam generated by a clinical neutron therapy cyclotron was used to irradiate carbon doped aluminum oxide (Al{sub 2}O{sub 3}:C) optically simulated luminescence dosimeters (OSLDs) in a solid water phantom under standard calibration conditions, 150 cm SAD, 1.7 cm depth, and 10.3 × 10.0 cm field size. OSLD fading and electron trap depletion studies were performed with the OSLDs irradiated with 20 and 50 cGy and monitored over a 24-h period to determine the optimal time for reading the dosimeters during calibration. Four OSLDs per group were calibrated over a clinical dose range of 0–150 cGy. Results: OSLD measurement uncertainties were lowered to within ±2%–3% of the expected dose by minimizing the effect of transient fading that occurs with neutron irradiation and maintaining individual calibration factors for each dosimeter. Dose dependent luminescence fading extended beyond the manufacturer’s recommended 10 min period for irradiation with photon or electron beams. To minimize OSL variances caused by inconsistent fading among dosimeters, the observed optimal time for reading the OSLDs postirradiation was between 30 and 90 min. No field size, wedge factor, or gantry angle dependencies were observed in the OSLDs irradiated by the studied fast neutron beam. Conclusions: Measurements demonstrated that uncertainties less than ±3% were attainable in OSLDs irradiated with fast neutrons under clinical conditions. Accuracy and precision comparable to clinical OSL measurements observed with photons can be achieved by maintaining individual OSLD calibration factors and

STUDIES ON BIOLUMINESCENCE : XVII. FLUORESCENCE AND INHIBITION OF LUMINESCENCE IN CTENOPHORES BY ULTRA-VIOLET LIGHT.

Science.gov (United States)

Harvey, E N

1925-01-20

1. Small dumps of the luminous cells of Mnemiopsis cannot readily be stimulated mechanically but will luminesce on treatment with saponin solution. Larger groups of luminous cells (such as are connected with two paddle plates) luminesce on mechanical stimulation. This suggests that mechanical stimulation to luminesce occurs chiefly through a nerve mechanism which has been broken up in the small dumps of luminous tissue. 2. The smallest bits of luminous tissue, even cells freed from the animal by agitation, that will pass through filter paper, lose their power to luminesce in daylight and regain it (at least partially) in the dark. 3. Luminescence of the whole animal and of individual cells is suppressed by near ultra-violet light (without visible light). 4. Inhibition in ultra-violet light is not due to stimulation (by the ultra-violet light) of the animal to luminesce, thereby using up the store of photogenic material. 5. Animals stimulated mechanically several times and placed in ultra-violet light show a luminescence along the meridians in the same positions as the luminescence that appears on stimulation. This luminescence in the ultra-violet or "tonic luminescence," is not obtained with light adapted ctenophores and is interpreted to be a fluorescence of the product of oxidation of the photogenic material. 6. Marked fluorescence of the luminous organ of the glowworm (Photuris) and of the luminous slime of Chatopterus may be observed in ultra-violet but no marked fluorescence of the luminous substances of Cypridina is apparent. 7. Evidence is accumulating to show a close relation between fluorescent and chemiluminescent substances in animals, similar to that described for unsaturated silicon compounds and the Grignard reagents.

Exciton dephasing in single InGaAs quantum dots

DEFF Research Database (Denmark)

Leosson, Kristjan; Østergaard, John Erland; Jensen, Jacob Riis

2000-01-01

The homogeneous linewidth of excitonic transitions is a parameter of fundamental physical importance. In self-assembled quantum dot systems, a strong inhomogeneous broadening due to dot size fluctuations masks the homogeneous linewidth associated with transitions between individual states....... The homogeneous and inhomogeneous broadening of InGaAs quantum dot luminescence is of central importance for the potential application of this material system in optoelectronic devices. Recent measurements of MOCVD-grown InAs/InGaAs quantum dots indicate a large homogeneous broadening at room temperature due...... to fast dephasing. We present an investigation of the low-temperature homogeneous linewidth of individual PL lines from MBE-grown In0.5Ga0.5As/GaAs quantum dots....

Silica coating of luminescent quantum dots prepared in aqueous media for cellular labeling

Energy Technology Data Exchange (ETDEWEB)

Ma, Yunfei; Li, Yan, E-mail: yli@ecust.edu.cn; Zhong, Xinhua, E-mail: zhongxh@ecust.edu.cn

2014-12-15

Graphical abstract: A facile route based on modified Stöber method was used for the synthesis of silica coated QDs (QD@SiO{sub 2}) starting from aqueously prepared CdTe/CdS QDs. The resultant QD@SiO{sub 2} exhibited a significant increase in emission efficiency compared with that of the initial QDs, along with a small size (∼5 nm in diameter), great stability and low cytotoxicity, which makes it a good candidate as robust biomarker. - Highlights: • We present a facile modified Stöber method to prepare highly luminescent QD@SiO{sub 2}. • The PL efficiency of QDs increases significantly after silica coating. • QD@SiO{sub 2} exhibits small size (∼5 nm) and great dispersibility in aqueous solution. • QD@SiO{sub 2} presents extraordinary photo and colloidal stability. • The silica shell eliminates QD cytotoxicity, providing the access of bioconjugation. - Abstract: Silica coating is an effective approach for rendering luminescent quantum dots (QDs) with water dispersibility and biocompatibility. However, it is still challenging to prepare silica-coated QDs (QD@SiO{sub 2}) with high emission efficiency, small size and great stability in favor for bioapplication. Herein, we reported a modified Stöber method for silica coating of aqueously-prepared CdTe/CdS QDs. With the coexistence of Cd{sup 2+} and thioglycolic acid (TGA), a thin silica shell was formed around QDs by the hydrolysis of tetraethyl orthosilicate (TEOS). The resultant QD@SiO{sub 2} with a small size (∼5 nm in diameter) exhibits significantly higher emission efficiencies than that of the initial QDs. Also, QD@SiO{sub 2} has extraordinary photo and colloidal stability (pH range of 5–13, 4.0 M NaCl solution). Protected by the silica shell, the cytotoxicity of QDs could be reduced. Moreover, the QD@SiO{sub 2} conjugated with folic acid (FA) presents high specific binding toward receptor-positive HeLa cells over receptor-negative A549 cells.

Chemical role of amines in the colloidal synthesis of CdSe quantum dots and their luminescence properties

International Nuclear Information System (INIS)

Nose, Katsuhiro; Fujita, Hiroshi; Omata, Takahisa; Otsuka-Yao-Matsuo, Shinya; Nakamura, Hiroyuki; Maeda, Hideaki

2007-01-01

The role of organic amines in the colloidal synthesis of CdSe quantum dots (QDs) has been studied. CdSe QDs were synthesized from the source solutions containing 5 vol% of amines having various alkyl chain lengths, stereochemical sizes and electron donation abilities. The role of the additional amines was evaluated on the basis of the photoluminescence (PL) properties such as PL wavelength and intensity of the obtained CdSe QDs. The observed PL spectra were explained by the fact that the amines behaved as capping ligands on the surface of the QDs in the product colloidal solution and complex ligands for cadmium in the source solutions. It was shown that the particle size was controlled by the diffusion process depending on the mass and stereochemical shape of the amines, and the luminescence intensity increased with the increasing electron donation ability and capping density of the amines

Luminescent ZnO quantum dots as an efficient sensor for free chlorine detection in water.

Science.gov (United States)

Singh, Kulvinder; Mehta, S K

2016-04-21

Highly luminescent ZnO quantum dots (QDs) synthesized via a simple and facile route are used for the preparation of an optical sensor for the detection of free chlorine. The concentration of free chlorine greatly affects the PL emission of the ZnO QDs at 525 nm. Since hypochlorite gains electrons with high efficiency, it takes electrons from the oxygen vacancies of ZnO QDs, which gives rise to defect emission in ZnO QDs. UV-vis data analysis shows that free chlorine does not affect the optical absorption spectra of ZnO QDs. The optical sensing of free chlorine using ZnO QDs has several advantages, like quick response time, good selectivity and of course high sensitivity. The pH has very little effect on the PL emission of ZnO QDs. It does not interfere in the sensing mechanism for free chlorine. After 60 s, the response of the ZnO QDs remains stable. The present sensor shows high selectivity with respect to various common cations, as well as anions.

PREFACE: Quantum dots as probes in biology

Science.gov (United States)

Cieplak, Marek

2013-05-01

The recent availability of nanostructured materials has resulted in an explosion of research focused on their unique optical, thermal, mechanical and magnetic properties. Optical imagining, magnetic enhancement of contrast and drug delivery capabilities make the nanoparticles of special interest in biomedical applications. These materials have been involved in the development of theranostics—a new field of medicine that is focused on personalized tests and treatment. It is likely that multimodal nanomaterials will be responsible for future diagnostic advances in medicine. Quantum dots (QD) are nanoparticles which exhibit luminescence either through the formation of three-dimensional excitons or excitations of the impurities. The excitonic luminescence can be tuned by changing the size (the smaller the size, the higher the frequency). QDs are usually made of semiconducting materials. Unlike fluorescent proteins and organic dyes, QDs resist photobleaching, allow for multi-wavelength excitations and have narrow emission spectra. The techniques to make QDs are cheap and surface modifications and functionalizations can be implemented. Importantly, QDs could be synthesized to exhibit useful optomagnetic properties and, upon functionalization with an appropriate biomolecule, directed towards a pre-selected target for diagnostic imaging and photodynamic therapy. This special issue on Quantum dots in Biology is focused on recent research in this area. It starts with a topical review by Sreenivasan et al on various physical mechanisms that lead to the QD luminescence and on using wavelength shifts for an improvement in imaging. The next paper by Szczepaniak et al discusses nanohybrids involving QDs made of CdSe coated by ZnS and combined covalently with a photosynthetic enzyme. These nanohybrids are shown to maintain the enzymatic activity, however the enzyme properties depend on the size of a QD. They are proposed as tools to study photosynthesis in isolated

Exploiting the optical and luminescence characteristic of quantum dots for optical device fabrication

Science.gov (United States)

Suriyaprakash, Jagadeesh; Qiao, Ting Ting

2018-02-01

One can design a robust optical device by engineering the optical band gap of the quantum dots (QDs) owing to their size-tunable quantum confinement effect. To do this, understanding the optical effects of QDs and composite materials is crucial. In this context, various sizes (2.8-4.2 nm) of CdSe QDs-PMMA nanocomposite are fabricated in a two-step process and their absorbance, luminescence and optical constants studied systematically. The ellipsometry spectroscopic analysis exhibits the heterogeneous medium feature of Ψ value and also the measured refractive index (1.51-1.59) values are increased with decreased band gap (2.24-2.10 eV). The observed red shift in the UV-Vis and photoluminescence spectra is indicative of early stage CdSe QD followed by a nucleation process of bigger size QD. In addition, the growth kinetics of the reaction and the band gap of the QDs are evaluated with respect to the time to testify the colloidal QDs formation. The thickness and QD composition of the nanocomposite thin films calculated by effective medium approximation are 100 nm and 8-12%, respectively. Morphology and structural feature transmission electron microscopy study of the fabricated nanocomposite demonstrated that spherical CdSe QDs are well dispersed in PMMA.

Onion like growth and inverted many-particle energies in quantum dots

International Nuclear Information System (INIS)

Bimberg, D.

2008-01-01

Use of surfactants like antimony in MOCVD growth enables novel growth regimes for quantum dots (QDs). The quantum dot ensemble luminescence no longer appears as a single inhomogeneously broadened peak but shows a multi-modal structure. Quantum dot subensembles are forming which differ in height by exactly one monolayer. For the first time the systematic dependence of excitonic properties on quantum dot size and shape can be investigated in detail. Both biexcitonic binding energy and excitonic fine-structure splitting vary from large positive through zero to negative values. Correlation and piezoelectric effects explain the observations

Thermally and optically stimulated luminescence of AlN-Y2O3 ceramics after ionising irradiation

DEFF Research Database (Denmark)

Trinkler, L.; Bos, A.J.J.; Winkelman, A.J.M.

1999-01-01

, an essential drawback of AlN-Y2O3 is its high fading rate. Special attention has been focused on understanding and improving the fading properties. In particular, the influence of the ceramics production conditions and the additive concentration on the fading rate have been studied. Experimental results......Thermally (TL) and optically stimulated luminescence (OSL) were studied in AlN-Y2O3 ceramics after irradiation with ionising radiation. The extremely high TL sensitivity (approximately 60 times the sensitivity of LiF:Mg,Tl (TLD-100)) makes AlN-Y2O3 ceramics attractive as a TLD material. However...... on spectral properties and thermal evolution of OSL are also presented. The stimulation spectrum covers the spectral range from green to infrared light. A combination of thermal and optical stimulation allowed a correlation to be found between parameters of OSL and TL after the same irradiation dose...

Highly luminescent N, S- Co-doped carbon dots and their direct use as mercury(II) sensor

Energy Technology Data Exchange (ETDEWEB)

Wang, Yu [Key Lab of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Department of Advanced Organic Materials Science and Engineering, Kyungpook National University, Daegu, 702-701 (Korea, Republic of); Kim, Sung-Hoon, E-mail: shokim@knu.ac.kr [Department of Advanced Organic Materials Science and Engineering, Kyungpook National University, Daegu, 702-701 (Korea, Republic of); Feng, Liang, E-mail: fengl@dicp.ac.cn [Key Lab of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China)

2015-08-26

Heteroatom doping has been proven as an efficient way to improve the fluorescent efficiency of carbon dots. Co-doping with heteroatoms may introduce more active sites to carbon dots, which would broaden applications of CDs in sensing. In this work, highly luminescent nitrogen and sulfur co-doped carbon dots (NSCDs) were synthesized through a facile one-step microwave assisted method by using citric acid and rubeanic acid as carbon, nitrogen, and sulfur sources. The well-isolated NSCDs not only exhibit an enhanced fluorescent efficiency with a relatively high quantum yield up to 17.6%, but also show potential use as a multi-sensing platform based on their fluorescence “on-off-on” and color changing behaviors. The NSCDs can be directly used for the selective determination of mercury cations without any functionalization. The detection limit is approximately calculated as 0.18 μM and linear range is 0–20 μM. The sensing mechanism is proposed as coordination reaction induced by oligomers upon the carbon core. Furthermore, in the presence of cyanide anions, the fluorescence shows linear recovery associated with the concentration of cyanide, indicating its potential usage for the detection of cyanide ion. The optimized pH range for such fluorescence “on-off-on” sensing system is investigated as pH 6–8, suggesting potential applications in bio-sensing and imaging area. In addition, by adding hydrosulfide anion to NSCDs@Hg{sup 2+} complex, a notable color change could be clearly observed due to the formation of fuscous HgS. In application, a handy test paper for direct and rapid detection of Hg{sup 2+} is manufactured for the evaluation of usage of NSCDs in the real circumstance. - Highlights: • NSCDs were synthesized by using citric acid and rubeanic acid. • NSCDs exhibited an enhanced fluorescent efficiency with high QY up to 17.6%. • NSCDs presented good sensing performance to mercury ions. • NSCDs showed potential use as a multi-sensing platform.

Highly luminescent N, S- Co-doped carbon dots and their direct use as mercury(II) sensor

International Nuclear Information System (INIS)

Wang, Yu; Kim, Sung-Hoon; Feng, Liang

2015-01-01

Heteroatom doping has been proven as an efficient way to improve the fluorescent efficiency of carbon dots. Co-doping with heteroatoms may introduce more active sites to carbon dots, which would broaden applications of CDs in sensing. In this work, highly luminescent nitrogen and sulfur co-doped carbon dots (NSCDs) were synthesized through a facile one-step microwave assisted method by using citric acid and rubeanic acid as carbon, nitrogen, and sulfur sources. The well-isolated NSCDs not only exhibit an enhanced fluorescent efficiency with a relatively high quantum yield up to 17.6%, but also show potential use as a multi-sensing platform based on their fluorescence “on-off-on” and color changing behaviors. The NSCDs can be directly used for the selective determination of mercury cations without any functionalization. The detection limit is approximately calculated as 0.18 μM and linear range is 0–20 μM. The sensing mechanism is proposed as coordination reaction induced by oligomers upon the carbon core. Furthermore, in the presence of cyanide anions, the fluorescence shows linear recovery associated with the concentration of cyanide, indicating its potential usage for the detection of cyanide ion. The optimized pH range for such fluorescence “on-off-on” sensing system is investigated as pH 6–8, suggesting potential applications in bio-sensing and imaging area. In addition, by adding hydrosulfide anion to NSCDs@Hg 2+ complex, a notable color change could be clearly observed due to the formation of fuscous HgS. In application, a handy test paper for direct and rapid detection of Hg 2+ is manufactured for the evaluation of usage of NSCDs in the real circumstance. - Highlights: • NSCDs were synthesized by using citric acid and rubeanic acid. • NSCDs exhibited an enhanced fluorescent efficiency with high QY up to 17.6%. • NSCDs presented good sensing performance to mercury ions. • NSCDs showed potential use as a multi-sensing platform

Luminescence dating at Rose cottage cave: a progress report

CSIR Research Space (South Africa)

Woodborne, S

1997-10-01

Full Text Available Deal with infrared-stimulated luminescence and thermoluminescence dates from Rose Cottage Cave in South Africa. Discrepancy between luminescence and radiocarbon dates; Concentration of radioactive elements in sediments before and after leaching...

Conjugation of E. coli O157:H7 Antibody to CdSe/ZnS Quantum Dots

Directory of Open Access Journals (Sweden)

N. T. Vo

2015-01-01

Full Text Available The conjugation of antibody to semiconductor quantum dots plays a very important role in many applications such as bioimaging, biomarking, and biosensing. In this research, we present some results of highly luminescent core/shell structure CdSe/ZnS on which the E. coli antibody was conjugated. The CdSe core was synthesized successfully with chemical “green” method. For biological applications, the capping surfactant, trioctylphosphine oxide, was substituted by a new one, mercaptopropionic acid (MPA, before the antibody attachment step. Finally, the E. coli antibody was attached to quantum dots CdSe/ZnS. Morphology, structure, and optical properties were investigated with PL, UV-Vis, TEM, and XRD methods. The successful ligand substitution and antibody attachment were confirmed by zeta potential measurement, FTIR spectroscopy, and TEM. The results showed quantum dots size of 2.3 nm, uniform distribution, and high luminescence. CdSe/ZnS core/shell structure had better stability and enhanced the luminescence efficiency up to threefold compared with the core CdSe. MPA ligand shifted the initial hydrophobic quantum dots to hydrophilic ones, which helped to dissolve them in organic solvents and attach the antibody.

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...

Characterization of nanoDot optically stimulated luminescence detectors and high-sensitivity MCP-N thermoluminescent detectors in the 40-300 kVp energy range.

Science.gov (United States)

Poirier, Yannick; Kuznetsova, Svetlana; Villarreal-Barajas, Jose Eduardo

2018-01-01

To investigate empirically the energy dependence of the detector response of two in vivo luminescence detectors, LiF:Mg,Cu,P (MCP-N) high-sensitivity TLDs and Al 2 O 3 :C OSLDs, in the 40-300-kVp energy range in the context of in vivo surface dose measurement. As these detectors become more prevalent in clinical and preclinical in vivo measurements, knowledge of the variation in the empirical dependence of the measured response of these detectors across a wide spectrum of beam qualities is important. We characterized a large range of beam qualities of three different kilovoltage x-ray units: an Xstrahl 300 Orthovoltage unit, a Precision x-Ray X-RAD 320ix biological irradiator, and a Varian On-Board Imaging x-ray unit. The dose to water was measured in air according to the AAPM's Task Group 61 protocol. The OSLDs and TLDs were irradiated under reference conditions on the surface of a water phantom to provide full backscatter conditions. To assess the change in sensitivity in the long term, we separated the in vivo dosimeters of each type into an experimental and a reference group. The experimental dosimeters were irradiated using the kilovoltage x-ray units at each beam quality used in this investigation, while the reference group received a constant 10 cGy irradiation at 6 MV from a Varian clinical linear accelerator. The individual calibration of each detector was verified in cycles where both groups received a 10 cGy irradiation at 6 MV. The nanoDot OSLDs were highly reproducible, with ±1.5% variation in response following >40 measurement cycles. The TLDs lost ~20% of their signal sensitivity over the course of the study. The relative light output per unit dose to water of the MCP-N TLDs did not vary with beam quality for beam qualities with effective energies <50 keV (~150 kVp/6 mm Al). At higher energies, they showed a reduced (~75-85%) light output per unit dose relative to 6 MV x rays. The nanoDot OSLDs exhibited a very strong (120

Charge recombination processes in minerals studied using optically stimulated luminescence and time-resolved exo-electrons

International Nuclear Information System (INIS)

Tsukamoto, Sumiko; Murray, Andrew; Ankjaergaard, Christina; Jain, Mayank; Lapp, Torben

2010-01-01

A time-resolved optically stimulated exo-electron (TR-OSE) measurement system has been developed using a Photon Timer attached to a gas-flow semi-proportional pancake electron detector within a Risoe TL/OSL reader. The decay rate of the exo-electron emission after the stimulation pulse depends on the probability of (1) escape of electrons into the detector gas from the conduction band by overcoming the work function of the material and (2) thermalization of electrons in the conduction band, and subsequent re-trapping/recombination. Thus, we expect the exo-electron signal to reflect the instantaneous electron concentration in the conduction band. In this study, TR-OSE and time-resolved optically stimulated luminescence (TR-OSL) were measured for the first time using quartz, K-feldspar and NaCl by stimulating the samples using pulsed blue LEDs at different temperatures between 50 and 250 0 C after beta irradiation and preheating to 280 0 C. The majority of TR-OSE signals from all the samples decayed much faster than TR-OSL signals irrespective of the stimulation temperatures. This suggests that the lifetime of OSL in these dosimeters arises mainly from the relaxation of an excited state of the recombination centre, rather than from residence time of an electron in the conduction band.

Luminescent behavior of cadmium sulfide quantum dots for gallic acid estimation

Science.gov (United States)

Singh, Suman; Garg, Sourav; Chahal, Jitender; Raheja, Khushboo; Singh, Deepak; Singla, M. L.

2013-03-01

Thioglycolic acid capped cadmium sulfide (CdS/T) quantum dots have been synthesized using wet chemistry and their optical behavior has been investigated using UV-visible absorption and fluorescence spectroscopy. The role of the capping agent, sulfide source concentration, pH and temperature has been studied and discussed. Studies showed that alkaline pH leads to a decrease in the size of quantum dots and reflux temperature above 70 °C resulted in red-shift of emission spectra which is due to narrowing of the bandgap. Further, to reduce the toxicity and photochemical instability of quantum dots, the quantum dots have been functionalized with polyethylene glycol (PEG), which resulted in a 20% enhancement of the fluorescence intensity. The application potential of CdS/T-PEG quantum dots was further studied using gallic acid as a model compound. The sensing is based on fluorescence quenching of quantum dots in the presence of gallic acid, and this study showed linearity in the range from 1.3 × 10-8 to 46.5 × 10-8 mM, with a detection limit of 3.6 × 10-8 mM.

Luminescent behavior of cadmium sulfide quantum dots for gallic acid estimation

International Nuclear Information System (INIS)

Singh, Suman; Garg, Sourav; Chahal, Jitender; Raheja, Khushboo; Singla, M L; Singh, Deepak

2013-01-01

Thioglycolic acid capped cadmium sulfide (CdS/T) quantum dots have been synthesized using wet chemistry and their optical behavior has been investigated using UV–visible absorption and fluorescence spectroscopy. The role of the capping agent, sulfide source concentration, pH and temperature has been studied and discussed. Studies showed that alkaline pH leads to a decrease in the size of quantum dots and reflux temperature above 70 °C resulted in red-shift of emission spectra which is due to narrowing of the bandgap. Further, to reduce the toxicity and photochemical instability of quantum dots, the quantum dots have been functionalized with polyethylene glycol (PEG), which resulted in a 20% enhancement of the fluorescence intensity. The application potential of CdS/T-PEG quantum dots was further studied using gallic acid as a model compound. The sensing is based on fluorescence quenching of quantum dots in the presence of gallic acid, and this study showed linearity in the range from 1.3 × 10 −8 to 46.5 × 10 −8 mM, with a detection limit of 3.6 × 10 −8 mM. (paper)

Luminescent monolayer MoS{sub 2} quantum dots produced by multi-exfoliation based on lithium intercalation

Energy Technology Data Exchange (ETDEWEB)

Qiao, Wen [Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructures and Jiangsu Provincial Laboratory for NanoTechnology, Nanjing University, Nanjing 210093 (China); Yan, Shiming [Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructures and Jiangsu Provincial Laboratory for NanoTechnology, Nanjing University, Nanjing 210093 (China); College of Science, Henan University of Technology, Zhengzhou 450001 (China); Song, Xueyin; Zhang, Xing; He, Xueming [Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructures and Jiangsu Provincial Laboratory for NanoTechnology, Nanjing University, Nanjing 210093 (China); Zhong, Wei, E-mail: wzhong@nju.edu.cn [Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructures and Jiangsu Provincial Laboratory for NanoTechnology, Nanjing University, Nanjing 210093 (China); Du, Youwei [Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructures and Jiangsu Provincial Laboratory for NanoTechnology, Nanjing University, Nanjing 210093 (China)

2015-12-30

Graphical abstract: - Highlights: • A new preparation, multi-exfoliation method based on lithium (Li) intercalation, has been demonstrated for preparing monolayer molybdenum disulfide (MoS{sub 2}) quantum dots (QDs). • The advantage of this approach is that it is capable of producing monolayer MoS{sub 2} QDs in a large number, regardless of whether the raw material is bulk or nanoparticles. • The PL intensity excited at 300 nm can be enhanced by five times after ultrasonicated heating treatment. - Abstract: An effective multi-exfoliation method based on lithium (Li) intercalation has been demonstrated for preparing monolayer molybdenum disulfide (MoS{sub 2}) quantum dots (QDs). The cutting mechanism of MoS{sub 2} QDs may involve the complete breakup around the defects and edges during the reaction of Li{sub x}MoS{sub 2} with water and its following ultrasonication process. The multiply exfoliation make the MoS{sub 2} fragile and easier to break up. After the third exfoliation, a large number of monolayer MoS{sub 2} QDs is formed. The as-prepared MoS{sub 2} QDs show photoluminescence (PL) inactive due to the existence of 1T phase. After heating treatment, the PL intensity excited at 300 nm is enhanced by five times. The MoS{sub 2} QDs solution has an excitation-dependent luminescence emission which shifts to longer wavelengths when the excitation wavelength changes from 280 nm to 370 nm. The optical properties are explored based on the quantum confinement and edge effect.

The research of characteristic difference of selected frequency luminescence for desert sand

International Nuclear Information System (INIS)

Liu Chao; Wei Mingjian; Li Huhou

2011-01-01

The characters of selected frequency luminescence of four groups of samples from Badain Jaran desert are measured by BG2003 luminescence spectrograph. The measurement subjects include selected frequency optical stimulate luminescence spectrum, selected frequency thermoluminescence spectrum and the dose response curve. A double-peak map is obtained by the result from all groups of data and spectrum. The difference is emerged between each group. The optical stimulate luminescence and thermoluminescence is applied in the measurement process. The dispersion of photon count on every response wavelength is analyzed. Based on the analysis, a better result can be gained by selected frequency thermoluminescence. (authors)

Luminescence lifetimes in quartz: dependence on annealing temperature prior to beta irradiation

International Nuclear Information System (INIS)

Galloway, R.B.

2002-01-01

It is well known that the thermal history of a quartz sample influences the optically stimulated luminescence sensitivity of the quartz. It is found that the optically stimulated luminescence lifetime, determined from time resolved spectra obtained with pulsed stimulation, also depends on past thermal treatment. For samples at 20 deg. C during stimulation, the lifetime depends on beta dose and on duration of preheating at 220 deg. C prior to stimulation for quartz annealed at 600 deg. C and above, but is independent of these factors for quartz annealed at 500 deg. C and below. For stimulation at higher temperatures, the lifetime becomes shorter if the sample is held at temperatures above 125 deg. C during stimulation, in a manner consistent with thermal quenching. A single exponential decay is all that is required to fit the time resolved spectra for un-annealed quartz regardless of the temperature during stimulation (20-175 deg. C), or to fit the time resolved spectra from all samples held at 20 deg. C during stimulation, regardless of annealing temperature (20-1000 deg. C). An additional shorter lifetime is found for some combinations of annealing temperature and temperature during stimulation. The results are discussed in terms of a model previously used to explain thermal sensitisation. The luminescence lifetime data are best explained by the presence of two principal luminescence centres, their relative importance depending on the annealing temperature, with a third centre involved for limited combinations of annealing temperature and temperature during stimulation

High-Performance CuInS ₂ Quantum Dot Laminated Glass Luminescent Solar Concentrators for Windows

Energy Technology Data Exchange (ETDEWEB)

Bergren, Matthew R. [UbiQD, Inc., Los Alamos, New Mexico 87544, United States; Makarov, Nikolay S. [UbiQD, Inc., Los Alamos, New Mexico 87544, United States; Ramasamy, Karthik [UbiQD, Inc., Los Alamos, New Mexico 87544, United States; Jackson, Aaron [UbiQD, Inc., Los Alamos, New Mexico 87544, United States; Guglielmetti, Rob [National Renewable Energy Laboratory, Golden, Colorado 80401, United States; McDaniel, Hunter [UbiQD, Inc., Los Alamos, New Mexico 87544, United States

2018-01-30

Building-integrated sunlight harvesting utilizing laminated glass luminescent solar concentrators (LSCs) is proposed. By incorporating high quantum yield (>90%), NIR-emitting CuInS2/ZnS quantum dots into the polymer interlayer between two sheets of low-iron float glass, a record optical efficiency of 8.1% is demonstrated for a 10 cm x 10 cm device that transmits ~44% visible light. After completing prototypes by attaching silicon solar cells along the perimeter of the device, the electrical power conversion efficiency was certified at 2.2% with a black background and at 2.9% using a reflective substrate. This 'drop-in' LSC solution is particularly attractive because it fits within the existing glazing industry value chain with only modest changes to typical glazing products. Performance modeling predicts >1 GWh annual electricity production for a typical urban skyscraper in most major U.S. cities, enabling significant energy cost savings and potentially 'net-zero' buildings.

Dose-dependent optically stimulated luminescence of synthetic quartz at room temperature

International Nuclear Information System (INIS)

Kale, Y.D.; Gandhi, Y.H.; Gartia, R.K.

2008-01-01

Physical conditions such as annealing temperature, duration of annealing, ionizing radiation, etc., play a significant role in the applications of optically stimulated luminescence (OSL) dating as well as OSL dosimetry. Many efforts are made to understand the effect of these physical parameters on quartz specimens owing to its use in such applications. Such factors induce changes in OSL decay pattern. The definite correlation between color centers and luminescence sensitivity can be established on account of such pre-treatments to the specimen. The purpose of present investigations is to study the effect of ionizing radiation under identical physical conditions on OSL properties measured at room temperature. The shapes of decay curve and dose-response data are considered for this purpose. This study can reveal the changes in color centers in response to the pre-conditions to the specimen. It was found that the OSL decay remains slow and OSL properties change systematically with the rise in beta dose up to a critical dose; however, it changes the pattern when the beta exposure to the specimen was increased higher than the critical dose. This critical dose was found to be different for different temperature of annealing. The shape of decay curve up to the critical dose was also studied by considering the difference of OSL intensities between two successive durations from the observed OSL decay data. The results are explained based on the changes in available shallow traps during OSL measurement at room temperature with changes in pre-conditions to the specimens. The results also have been confirmed with the corresponding changes in ESR signals

Uncertainties associated with the use of optically stimulated luminescence in personal dosimetry

International Nuclear Information System (INIS)

Benevides, L.; Romanyukha, A.; Hull, F.; Duffy, M.; Voss, S.; Moscovitch, M.

2011-01-01

This study investigates several sources of uncertainty associated with the application of optically stimulated luminescence (OSL) to personal dosimetry. A commercial OSL system based on Al 2 O 3 :C was used for this study. First, it is demonstrated that the concept of repeated evaluation (readout) of the same dosemeter, often referred to as 're-analysis', can introduce uncertainty in the re-estimated dose. This uncertainty is associated with the fact that the re-analysis process depletes some of the populated traps, resulting in a continuous decrease of the OSL signal with each repeated reading. Furthermore, the rate of depletion may be dose-dependent. Second, it is shown that the previously reported light-induced fading in this system is the result of light leaks through miniature openings in the dosemeter badge. (authors)

Direct and indirect dating of gypsum occurrences in deserts using luminescence methods

International Nuclear Information System (INIS)

Nagar, Y.C.; Juyal, N.; Singhyi, A.K.; Kocurek, G.; Wadhawan, S.K.

2005-01-01

In the present study we have made an attempt to directly date gypsum or provide indirect age estimate for gypsum formation through dating the associated sediments (quartz) using the luminescence dating technique. In the direct dating of gypsum, we explored the Optically Stimulated Luminescence (OSL) and Thermally Stimulated Luminescence (TL) behaviour of gypsum. The associated sediments (indirect dating) were dated using the traces of quartz extract from gypsum (concentration 0.1% ) and the underlying and overlying quartz sand in playa

Photoluminescence study of carbon dots from ginger and galangal herbs using microwave technique

Science.gov (United States)

Isnaeni; Rahmawati, I.; Intan, R.; Zakaria, M.

2018-03-01

Carbon dots are new type of fluorescent nanoparticle that can be synthesis easily from natural sources. We have synthesized carbon dots from ginger and galangal herbs using microwave technique and studied their optical properties. We synthesized colloidal carbon dots in water solvent by varying microwave processing time. UV-Vis absorbance, photoluminescence, time-resolved photoluminescence, and transmission electron microscope were utilized to study properties of carbon dots. We found that microwave processing time significantly affect optical properties of synthesized carbon dots. UV-Vis absorbance spectra and time-resolved photoluminescence results show that luminescent of carbon dots is dominated by recombination process from n-π* surface energy level. With further development, these carbon dots are potential for several applications.

Dating by Infrared Stimulated Luminescence of a prehistoric campfire from Serido region in northeastern Brazil

International Nuclear Information System (INIS)

Santana, Sergio T.; Khoury, Helen J.; Borges, Fabio M.; Sullasi, Henry L.; Avila, Gabriela M.; Pessis, Anne-Marie; Guzzo, Pedro L.

2011-01-01

This study aimed to determine the age of a prehistoric campfire from Serido region in northeastern Brazil. The dating was performed by Infrared Stimulated Luminescence (IRSL) by the method of multiple aliquot regenerative doses. Samples were collected from five different parts of the campfire in order to determine the accumulated dose, and samples of two parts of the campfire for determine the annual dose rate. After a statistical analysis of these values, we calculated an average age of 3640 +- 710 years. This age allowed to define a time frame for archaeological studies in this region. (author)

The influence of bio-conjugation on photoluminescence of CdSe/ZnS quantum dots

Energy Technology Data Exchange (ETDEWEB)

Torchynska, Tetyana V. [ESFM Instituto Politécnico Nacional, Av. Instituto Politécnico Nacional, México, D.F. 07738 (Mexico); Vorobiev, Yuri V. [Centro de Investigación y de Estudios Avanzados del IPN (CINVESTAV) Querétaro, Libramiento Norponiente 2000, Fracc. Real de Juriquilla, 76230 Querétaro (Mexico); Makhniy, Victor P. [Yuri Fedkovych Chernivtsi National University, 2 Kotsyubynsky Str., 58012 Chernivtsi (Ukraine); Horley, Paul P., E-mail: paul.horley@cimav.edu.mx [Centro de Investigación en Materiales Avanzados, S.C. (CIMAV), Chihuahua/Monterrey, 120 Avenida Miguel de Cervantes, 31109 Chihuahua (Mexico)

2014-11-15

We report a considerable blue shift in the luminescence spectra of CdSe/ZnS quantum dots conjugated to anti-interleukin-10 antibodies. This phenomenon can be explained theoretically by accounting for bio-conjugation as a process causing electrostatic interaction between a quantum dot and an antibody, which reduces effective volume of the dot core. To solve the Schrödinger equation for an exciton confined in the quantum dot, we use mirror boundary conditions that were successfully tested for different geometries of quantum wells.

Optically stimulated luminescence (OSL) as a chronometer for surface exposure dating

DEFF Research Database (Denmark)

Sohbati, Reza; Murray, Andrew S.; Chapot, Melissa S.

2012-01-01

We pioneer a technique of surface-exposure dating based upon the characteristic form of an optically stimulated luminescence (OSL) bleaching profile beneath a rock surface; this evolves as a function of depth and time. As a field illustration of this new method, the maximum age of a premier example...... exposure histories; one of these samples was exposed at the time of sampling and one was buried and no longer light exposed. A third sample is known to have been first exposed 80 years ago and was still exposed at the time of sampling. First, the OSL-depth profile of the known-age sample is modeled...... to estimate material-dependent and environmental parameters. These parameters are then used to fit the model to the corresponding data for the samples of unknown exposure history. From these fits we calculate that the buried sample was light exposed for similar to 700 years before burial and that the unburied...

Identifying well-bleached quartz using the different bleaching rates of quartz and feldspar luminescence signals

DEFF Research Database (Denmark)

Murray, A.S.; Thomsen, Kristina Jørkov; Masuda, N.

2012-01-01

When dating older sedimentary deposits using quartz, there are no unambiguous methods for identifying the presence of incomplete bleaching. Current statistical analysis of dose distributions depends entirely on the assumption that incomplete bleaching and mixing are the main causes of any excess...... dispersion in the distribution; the only existing way to test this assumption is using independent age control. Here we suggest a new approach to this question, based on the differential bleaching rates of quartz and feldspar luminescence signals. We first present data that confirm the differences...... in relative bleaching rates of quartz optically stimulated luminescence (OSL) and feldspar luminescence stimulated at 50 °C by infrared light (IR50) and feldspar luminescence stimulated at 290 °C by infrared light after a stimulation at 50 °C (pIRIR290), and use recently deposited samples to determine...

Fiber-optic, real-time dosimeter based on optically stimulated luminescence of Al2O3:C and KBr:Eu for potential use in the radiotherapy of cancer

International Nuclear Information System (INIS)

Gaza, Razvan

2004-01-01

This thesis describes a single-fiber dosimetry system based on optically stimulated luminescence (OSL) of artificially grown single crystals of Al 2 O 3 :C and KBr:Eu, with potential application in the medical field, especially in radio oncology. Small fiber-shaped dosimeters with dimensions (diameter/length) on the order of 500 μm/5 mm are attached to one end of an optical fiber, resulting in fiber probes with diameters of less than 1 mm and lengths of up to 15 m. The opposite end of the fiber is connected to an OSL reader that contains a stimulation light source (laser) and a photomultiplier tube that is used for luminescence detection. During irradiation, an optomechanical shutter periodically allows laser light to be transmitted down the optical fiber, to stimulate the luminescence response from the dosimeter being irradiated at a remote location. The luminescence measured during each interval of laser stimulation is indicative of the radiation dose absorbed in the dosimeter since the previous stimulation. The integral absorbed dose is obtained via a summation procedure from the measured dose fractions. Several operating procedures and data processing algorithms were developed in order to increase the speed and accuracy of the measurements, and integrated into the software that controls automated operation of the OSL readers. Periodic modulation of the stimulation also allows the OSL signal to be discriminated from background fluorescence, and thus yields measurements that are unaffected by Cerenkov light (the so-called 'stem effect'). Depending on the type of material used, the speed of the measurements, expressed as the time required to estimate an individual dose fraction, can be as short as 67 ms. Integral dose estimates from real-time OSL of Al 2 O 3 :C and KBr:Eu were obtained for water-phantom irradiations performed with medical teletherapy sources, and were found to agree within 3.7% and 2.8%, respectively, with reference measurements from ionization

Synthesis of strongly fluorescent graphene quantum dots by cage-opening buckminsterfullerene

Czech Academy of Sciences Publication Activity Database

Chua, C. K.; Sofer, Z.; Šimek, P.; Jankovský, O.; Klímová, K.; Bakardjieva, Snejana; Hrdličková-Kučková, Š.; Pumera, M.

2015-01-01

Roč. 9, č. 3 (2015), s. 2548-2555 ISSN 1936-0851 Institutional support: RVO:61388980 Keywords : fullerenes * graphene * luminescence * oxidation * quantum dots Subject RIV: CA - Inorganic Chemistry Impact factor: 13.334, year: 2015

Optically stimulated luminescence of Tb{sup 3+}/Sm{sup 3+} doubly doped K{sub 2}YF{sub 5} single crystals

Energy Technology Data Exchange (ETDEWEB)

Camargo, L.; Marcazzo, J.; Santiago, M.; Caselli, E. [Universidad Nacional del Centro de la Provincia de Buenos Aires, Instituto de Fisica Arroyo Seco, Gral. Pinto 399, B7000GHG, Tandil (Argentina); Khaidukov, N. M., E-mail: jmarcass@exa.unicen.edu.ar [Kurnakov Institute of General and Inorganic Chemistry, RAS, Leninskii Prospekt 31, 119991 Moscow (Russian Federation)

2014-08-15

In this work optically stimulated luminescence (OSL) properties of K{sub 2}YF{sub 5} crystals doubly doped with Tb{sup 3+} and Sm{sup 3+} ions have been investigated for the first time. OSL responses for different dopant concentration and for optical stimulation with different wavelengths have been analyzed for each compound. Dosimetric properties of the most efficient composition, namely, K{sub 2}YF{sub 5}:1.0 at.% Tb{sup 3+}; 1.0 at.% Sm{sup 3+}, have been studied. Finally, the possible application of this single crystal as OSL dosimeter has been evaluated. (Author)

Dual-excitation upconverting nanoparticle and quantum dot aptasensor for multiplexed food pathogen detection.

Science.gov (United States)

Kurt, Hasan; Yüce, Meral; Hussain, Babar; Budak, Hikmet

2016-07-15

In this report, a dual-excitation sensing method was developed using aptamer-functionalized quantum dots and upconverting nanoparticles, exhibiting Stokes and anti-Stokes type excitation profiles, respectively. Conjugation of the aptamer-functionalized luminescent nanoparticles with the magnetic beads, comprising short DNA sequences that were partially complementary to the aptamer sequences, enabled facile separation of the analyte-free conjugates for fluorescent measurement. UV-Visible spectroscopy, Circular Dichroism spectroscopy, Dynamic Light Scattering and Polyacrylamide Gel Electrophoresis techniques were used to characterize the aptamer probes developed. The target-specific luminescent conjugates were applied for multiplex detection of model food pathogens, Salmonella typhimurium, and Staphylococcus aureus, in which the fluorescent emission spectra were obtained under UV excitation at 325nm for quantum dots and NIR excitation at 980nm for upconverting nanoparticles, respectively. The dual-excitation strategy was aimed to minimize cross-talk between the luminescent signals for multiplexed detection, and yielded limit of detection values of 16 and 28cfumL(-1) for Staphylococcus aureus, and Salmonella typhimurium, respectively. By employing a greater number of quantum dots and upconverting nanoparticles with non-overlapping fluorescent emissions, the proposed methodology might be exploited further to detect several analytes, simultaneously. Copyright © 2016 Elsevier B.V. All rights reserved.

Ligand removal and photo-activation of CsPbBr3 quantum dots for enhanced optoelectronic devices.

Science.gov (United States)

Moyen, Eric; Kanwat, Anil; Cho, Sinyoung; Jun, Haeyeon; Aad, Roy; Jang, Jin

2018-05-10

Perovskite quantum dots have recently emerged as a promising light source for optoelectronic applications. However, integrating them into devices while preserving their outstanding optical properties remains challenging. Due to their ionic nature, perovskite quantum dots are extremely sensitive and degrade on applying the simplest processes. To maintain their colloidal stability, they are surrounded by organic ligands; these prevent efficient charge carrier injection in devices and have to be removed. Here we report on a simple method, where a moderate thermal process followed by exposure to UV in air can efficiently remove ligands and increase the photo-luminescence of the room temperature synthesized perovskite quantum dot thin films. Annealing is accompanied by a red shift of the emission wavelength, usually attributed to the coalescence and irreversible degradation of the quantum dots. We show that it is actually related to the relaxation of the quantum dots upon the ligand removal, without the creation of non-radiative recombining defects. The quantum dot surface, as devoid of ligands, is subsequently photo-oxidized and smoothened upon exposure to UV in air, which drastically enhances their photo-luminescence. This adequate combination of treatments improves by more than an order of magnitude the performances of perovskite quantum dot light emitting diodes.

Towards Luminescence Dating Of Mosaic Glass

Science.gov (United States)

Galli, A.; Martini, M.; Sibila, E.; Villa, I.

The possibility of dating archaeological glass by means of luminescent techniques has been investigated in recent years, despite the difficulties of this application, mainly linked to the amorphous structure of the material. We focused in particular on mosaic glass, after the encouraging results obtained on byzantine and medieval samples. Further studies were devoted to the comprehension of the luminescent mechanisms in silica glasses, and to the investigation of the relationships between luminescence, colouring or opacifier ions and crystalline phase of the vitreous matrix. The results of a study on the dosimetric characteristics of thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) of a few medieval blue-green mosaic glasses from the San Lorenzo church (Milan) are presented, and the experimental protocols established to identify their suitability for dating are discussed.

State of art: Optically stimulated luminescence dosimetry – Frontiers of future research

International Nuclear Information System (INIS)

Yukihara, Eduardo G.; McKeever, Stephen W.S.; Akselrod, Mark S.

2014-01-01

Since the commercial adoption of the optically stimulated luminescence (OSL) technique in dosimetry, almost 20 years ago, we have seen major advances in the deployment of OSL dosimeters in different areas, including personal, medical, and space dosimetry. The objective of this paper is to provide a critical overlook at the OSL technique from three different points of view: strengths, challenges and opportunities. We discuss factors that made the OSL technique successful: its simplicity, accuracy, wide dynamic range of measured dose, ease for automation, re-read capability, ability to perform imaging, and the availability of diverse instruments and materials. We look into problems that were overcome and others that remain in several areas of new applications into which OSL has expanded in the past 10 years, such as medical, space, neutron and accident dosimetry. Finally, we discuss unexplored possibilities, new driving forces, and open questions. We hope the broad overview presented here will encourage more discussion and stimulate the research that will advance our fundamental understanding of the OSL process. - Highlights: • Critical overlook of the OSL technique is presented. • Factors that made the OSL technique successful are discussed. • New applications in medical, space and accident dosimetry are discussed. • Unexplored possibilities, new driving forces, and open questions are presented

On the correlation between annealing and variabilities in pulsed-luminescence from quartz

International Nuclear Information System (INIS)

Chithambo, M.L.

2006-01-01

Properties of luminescence lifetimes in quartz related to annealing between 500 and 900 deg. C have been investigated. The luminescence was pulse-stimulated at 470nm from sets of granular quartz annealed at 500, 600, 700, 800, and 900 deg. C. The lifetimes decrease with annealing temperature from about 42 to 33μs when the annealing temperature is increased from 500 to 900 deg. C. Luminescence lifetimes are most sensitive to duration of annealing at 600 deg. C, decreasing from 40.2+/-0.7μs by as much as 7μs when the duration of annealing is changed from 10 to 60min. However, at 800-900 deg. C lifetimes are essentially independent of annealing temperature at about 33μs. Increasing the exciting beta dose causes an increase in the lifetimes of the stimulated luminescence in the sample annealed at 800 deg. C but not in those annealed at either 500 or 600 deg. C. The temperature-resolved distribution of luminescence lifetimes is affected by thermal quenching of luminescence. These features may be accounted for with reference to two principal luminescence centres involved in the luminescence emission process

Optically stimulated luminescence properties of Tm{sup 3+} doped KMgF{sub 3} fluoro perovskite

Energy Technology Data Exchange (ETDEWEB)

Camargo, L.; Marcazzo, J. [UNCPBA, Facultad de Ciencias Exactas, Instituto de Fisica Arroyo Seco, Gral. Pinto 399, B7000GHG Tandil, Buenos Aires (Argentina); Perez C, L.; Cruz Zaragoza, E. [UNAM, Instituto de Ciencias Nucleares, Apdo. Postal 70543, 04510 Ciudad de Mexico (Mexico); Martinez O, S. A., E-mail: jmarcass@exa.unicen.edu.ar [Universidad Pedagogica y Tecnologica de Colombia, Grupo de Fisica Nuclear Aplicada y Simulacion, Av. Central del Norte 39-115, 150003 Tunja, Bocaya (Colombia)

2017-10-15

In this work the optically stimulated luminescence (OSL) properties of undoped and Tm{sup 3+} doped KMgF{sub 3} fluoro perovskite have been investigated for the first time. OSL efficiency for stimulation with different wavelengths has been analyzed for each compound. The maximum OSL emission was found with blue light stimulation. The radioluminescence (Rl) spectra have shown two emission peaks at 455 and 360 nm, which can be ascribed to the {sup 1}D{sub 2}-{sup 3}F{sub 4} and {sup 1}D{sub 2}-{sup 3}H{sub 6} transitions of the Tm{sup 3+} cations. It has been found that doping with Thulium 0.5 mol % renders the most intense OSL emission. Furthermore, several dosimetric properties such as OSL response as a function of dose, reproducibility of the OSL signal after several cycles of irradiation readout and the minimum detectable dose have been investigated. Finally, the OSL response of KMgF{sub 3}: Tm{sup 3+} has been compared to that of commercial Al{sub 2}O{sub 3}:C and the possible application of this fluoro perovskite to OSL dosimetry has been evaluated. (Author)

Homogeneous Synthesis and Electroluminescence Device of Highly Luminescent CsPbBr3 Perovskite Nanocrystals.

Science.gov (United States)

Wei, Song; Yang, Yanchun; Kang, Xiaojiao; Wang, Lan; Huang, Lijian; Pan, Daocheng

2017-03-06

Highly luminescent CsPbBr 3 perovskite nanocrystals (PNCs) are homogeneously synthesized by mixing toluene solutions of PbBr 2 and cesium oleate at room temperature in open air. We found that PbBr 2 can be easily dissolved in nonpolar toluene in the presence of tetraoctylammonium bromide, which allows us to homogeneously prepare CsPbBr 3 perovskite quantum dots and prevents the use of harmful polar organic solvents, such as N,N-dimethylformamide, dimethyl sulfoxide, and N-methyl-2-pyrrolidone. Additionally, this method can be extended to synthesize highly luminescent CH 3 NH 3 PbBr 3 perovskite quantum dots. An electroluminescence device with a maximal luminance of 110 cd/m 2 has been fabricated by using high-quality CsPbBr 3 PNCs as the emitting layer.

Optically stimulated luminescence dosimetry performance of natural Brazilian topaz exposed to beta radiation

International Nuclear Information System (INIS)

Bernal, R.; Souza, D. N.; Valerio, M. E. G.; Cruz-Vazquez, C.; Barboza-Flores, M.

2006-01-01

Optically stimulated luminescence (OSL) has become the technique of choice in many areas of dosimetry. Natural materials like topaz are available in large quantities in Brazil and other countries. They have been studied to investigate the possibility of use its thermoluminescence (TL) properties for dosimetric applications. In this work, we investigate the possibility of utilising the OSL properties of natural Brazilian topaz in dosimetry. Bulk topaz samples were exposed to doses up to 100 Gy of beta radiation and the integrated OSL as a function of the dose showed linear behaviour. The fading occurs in the first 20 min after irradiation but it is <6% of the integrated OSL measured shortly after exposure. We conclude that natural colourless topaz is a very suitable phosphor for OSL dosimetry. (authors)

Thermo-stimulated luminescence of ion-irradiated yttria-stabilized zirconia

Energy Technology Data Exchange (ETDEWEB)

Costantini, Jean-Marc [CEA, DMN, SRMA, 91191 Gif-sur Yvette Cedex (France); Beuneu, Francois [LSI, CEA-CNRS-Ecole Polytechnique, 91128 Palaiseau Cedex (France); Fasoli, Mauro; Galli, Anna; Vedda, Anna; Martini, Marco, E-mail: jean-marc.costantini@cea.fr [CNR-IFN (Italy)

2011-03-23

Yttria-stabilized zirconia (ZrO{sub 2}:Y{sup 3+}) single crystals (with 9.5 mol% Y{sub 2}O{sub 3}) were irradiated with ions (from 1 MeV He to 2.6 GeV U). Electron paramagnetic resonance (EPR) data show that two kinds of colour centres (F{sup +}-type and T centres) are produced. Thermo-stimulated luminescence (TSL) data exhibit a quite strong peak at {approx} 500-550 K in the glow curves of all irradiated samples regardless of the ion species and energy. Moreover, the 3D-TSL measurements reveal that this peak is correlated with a light emission at a wavelength of {approx} 620 nm (i.e. photon energy {approx} 2 eV). The TSL peak maximum temperatures are consistent with characteristic temperatures of about 500 K of annealing stages of colour centres. However, the trap-depth energies (ranging between 0.7 and 1.4 eV) deduced from the initial rise of partially cleaned TSL peaks, or from a rough approximation using Urbach's formula, are rather larger than the activation energies for defect recovery, ranging between 0.3 and 0.7 eV, as deduced from the EPR data. The processes involved in TSL are discussed in relation to available photoluminescence and defect energy-level data.

Photo-, thermo- and optically stimulated luminescence of monoclinic zirconia

Energy Technology Data Exchange (ETDEWEB)

Kiisk, Valter, E-mail: valter.kiisk@ut.ee [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); Puust, Laurits; Utt, Kathriin; Maaroos, Aarne; Mändar, Hugo [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); Viviani, Erica; Piccinelli, Fabio [Department of Biotechnology, University of Verona, Strada Le Grazie 15, 37134 Verona (Italy); Saar, Rando; Joost, Urmas; Sildos, Ilmo [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia)

2016-06-15

We carried out a careful photoluminescence (PL) and thermoluminescence (TL) characterization of nominally pure monoclinic ZrO{sub 2} nanopowders subject to oxidative vs reductive annealing (up to 1450 °C). The two kinds of studied zirconia (sol-gel-prepared vs commercial powder) exhibited virtually identical 490 nm PL emission band and 280 nm PL excitation band with slight, but clearly detectable variations in the spectral shape. The TL glow peaks, recorded over the temperature range −100 to 300 °C, showed an interplay depending on the type and treatment of sample. There is a strong evidence that the −35 and 205 °C glow peaks are due to oxygen vacancies whereas the 5 °C glow peak may relate to oxygen interstitials and the 110 °C glow peak to surface defects. Although a number of distinct glow peaks emerge, the material still seems to contain a quasi-continuous distribution of trap depths. In comparison to TL, we also demonstrate effective optically stimulated luminescence (OSL) from this polymorph of ZrO{sub 2} under red and NIR illumination at ~1 W/cm{sup 2}. All traps responsible for the principal TL peaks were also found to be OSL-active, which widens the applied importance of the material.

Blue and green luminescence of reduced graphene oxide quantum dots

Czech Academy of Sciences Publication Activity Database

Štengl, Václav; Bakardjieva, Snejana; Henych, Jiří; Lang, Kamil; Kormunda, M.

2013-01-01

Roč. 63, november (2013), s. 537-546 ISSN 0008-6223 Institutional support: RVO:61388980 Keywords : different solvents * graphene oxides * green luminescence * intensive cavitations * N-methyl-2-pyrrolidone Subject RIV: CA - Inorganic Chemistry Impact factor: 6.160, year: 2013

Quantum dots as a probe to detect uranium

International Nuclear Information System (INIS)

Singhal, Pallavi; Jha, S.K.; Tripathi, R.M.

2016-01-01

Uranium is one of the most toxic heavy metals. A number of methods have been developed to detect uranium at lower concentrations. Here in we proposed a method which can sense the presence of uranium in nm-μM concentration range. We have synthesized CdSe and CdSe/CdS core shell quantum dots with different thickness of CdS shell and monitor their luminescence property in presence of uranium. Interestingly a quenching in QDs luminescence was observed on addition of uranium in uM concentrations. We have also carried out time resolved studies which suggests faster luminescence decay on addition of uranium. Both time resolved studies and energetic suggest that electron transfer from QDs to uranium is favourable and quenching in luminescence is due to electron transfer from QD to uranium and is found to be different with different thickness of CdS shell. The results presented reveal the promising potential of QDs for their use as chemical sensors to detect uranium. (author)

The interpretation of quartz optically stimulated luminescence equivalent dose versus time plots

International Nuclear Information System (INIS)

Bailey, R.M.

2000-01-01

Numerical modelling has shown that the form of the quartz OSL shine plateau (hereafter 'D e (t)-plot') is influenced by the effects of phototransferred TL in the ∼110 deg. C region. It is suggested also that the presence of multiple OSL components (as described by Partial bleaching and the decay form characteristics of quartz OSL. Radiat. Meas., 27, 123-136. The form of the optically stimulated luminescence signal of quartz: implications of dating. Unpublished PhD thesis, University of London) affects the form of the D e (t)-plot. Laboratory measurements of a fully reset and artificially dosed sample yielded non-flat D e (t)-plots, the deviation being greater for the larger of the two simulated palaeodoses, in accordance with theoretical predictions. It is suggested that the so-called 'shine plateau' test is of limited use in assessing the bleaching history of quartz sediments

Optically Active CdSe-Dot/CdS-Rod Nanocrystals with Induced Chirality and Circularly Polarized Luminescence.

Science.gov (United States)

Cheng, Jiaji; Hao, Junjie; Liu, Haochen; Li, Jiagen; Li, Junzi; Zhu, Xi; Lin, Xiaodong; Wang, Kai; He, Tingchao

2018-05-30

Ligand-induced chirality in semiconductor nanocrystals (NCs) has attracted attention because of the tunable optical properties of the NCs. Induced circular dichroism (CD) has been observed in CdX (X = S, Se, Te) NCs and their hybrids, but circularly polarized luminescence (CPL) in these fluorescent nanomaterials has been seldom reported. Herein, we describe the successful preparation of l- and d-cysteine-capped CdSe-dot/CdS-rods (DRs) with tunable CD and CPL behaviors and a maximum anisotropic factor ( g lum ) of 4.66 × 10 -4 . The observed CD and CPL activities are sensitive to the relative absorption ratio of the CdS shell to the CdSe core, suggesting that the anisotropic g-factors in both CD and CPL increase to some extent for a smaller shell-to-core absorption ratio. In addition, the molar ratio of chiral cysteine to the DRs is investigated. Instead of enhancing the chiral interactions between the chiral molecules and DRs, an excess of cysteine molecules in aqueous solution inhibits both the CD and CPL activities. Such chiral and emissive NCs provide an ideal platform for the rational design of semiconductor nanomaterials with chiroptical properties.

Colloidal quantum dot light-emitting devices

Directory of Open Access Journals (Sweden)

Vanessa Wood

2010-07-01

Full Text Available Colloidal quantum dot light-emitting devices (QD-LEDs have generated considerable interest for applications such as thin film displays with improved color saturation and white lighting with a high color rendering index (CRI. We review the key advantages of using quantum dots (QDs in display and lighting applications, including their color purity, solution processability, and stability. After highlighting the main developments in QD-LED technology in the past 15 years, we describe the three mechanisms for exciting QDs – optical excitation, Förster energy transfer, and direct charge injection – that have been leveraged to create QD-LEDs. We outline the challenges facing QD-LED development, such as QD charging and QD luminescence quenching in QD thin films. We describe how optical downconversion schemes have enabled researchers to overcome these challenges and develop commercial lighting products that incorporate QDs to achieve desirable color temperature and a high CRI while maintaining efficiencies comparable to inorganic white LEDs (>65 lumens per Watt. We conclude by discussing some current directions in QD research that focus on achieving higher efficiency and air-stable QD-LEDs using electrical excitation of the luminescent QDs.

High resolution optically stimulated luminescence dating of a sediment core from the southwestern Sea of Okhotsk

DEFF Research Database (Denmark)

Sugisaki, S.; Buylaert, J. P.; Murray, A. S.

2012-01-01

(D-e), with stimulation by both infrared and blue light. The suitability of the measurement procedure was confirmed using dose recovery tests. A high resolution record (similar to 2 OSL ages/m) identified clear sedimentation rate changes down the core. The OSL ages are significantly dependent......Optically stimulated luminescence (OSL) dating is now widely accepted as a chronometer for terrestrial sediment. More recently, it has been suggested that OSL may also be useful in the dating of deep-sea marine sediments. In this paper, we test the usefulness of high resolution quartz OSL dating...... in application to a 19 m marine sediment core (MR0604-PC04A) taken from the southwestern Sea of Okhotsk, immediately to the north of Hokkaido, Japan. Fine-grained quartz (4 to 11 mu m) was chosen as the dosimeter, and a single-aliquot regenerative-dose protocol was used for the determination of equivalent dose...

Fast and Straightforward Synthesis of Luminescent Titanium(IV Dioxide Quantum Dots

Directory of Open Access Journals (Sweden)

Václav Štengl

2017-01-01

Full Text Available The nucleus of titania was prepared by reaction of solution titanium oxosulphate with hydrazine hydrate. These titania nuclei were used for titania quantum dots synthesis by a simple and fast method. The prepared titanium(IV dioxide quantum dots were characterized by measurement of X-ray powder diffraction (XRD, X-ray photoelectron spectroscopy (XPS, atomic force microscopy (AFM, high-resolution electron microscopy (HRTEM, and selected area electron diffraction (SAED. The optical properties were determined by photoluminescence (PL spectra. The prepared titanium(IV dioxide quantum dots have the narrow range of UV excitation (365–400 nm and also a close range of emission maxima (450–500 nm.

Linewidth statistics of single InGaAs quantum dot photolumincescence lines

DEFF Research Database (Denmark)

Leosson, Kristjan; Jensen, Jacob Riis; Hvam, Jørn Märcher

2000-01-01

We have used photoluminescence spectroscopy with high spatial and spectral resolution to measure the linewidths of single emission lines from In0.5Ga0.5As/GaAs self-assembled quantum dots. At 10 K, we find a broad, asymmetric distribution of linewidths with a maximum at 50 mu eV. The distribution......-dot luminescence lines depends only weakly on temperature up to 50 K, showing a broadening of 0.4 mu eV/K. Above 50 K, a thermally activated behavior of the linewidth is observed. This temperature dependence is consistent with the discrete energy level structure of the dots....

Thermal dependence of luminescence lifetimes and radioluminescence in quartz

Energy Technology Data Exchange (ETDEWEB)

Pagonis, V., E-mail: vpagonis@mcdaniel.edu [McDaniel College, Physics Department, Westminster, MD 21157 (United States); Chithambo, M.L. [Department of Physics and Electronics, Rhodes University, PO BOX 94, Grahamstown 6140 (South Africa); Chen, R. [Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, Tel-Aviv 69978 (Israel); Chruścińska, A. [Institute of Physics, Nicholas Copernicus University, 87-100 Toruń (Poland); Fasoli, M. [Department of Materials Science, University of Milano-Bicocca, Via Cozzi 53, 20125 Milano (Italy); Li, S.H. [Department of Earth Sciences, The University of Hong Kong (Hong Kong); Martini, M. [Department of Materials Science, University of Milano-Bicocca, Via Cozzi 53, 20125 Milano (Italy); Ramseyer, K. [Institut für Geologie, Baltzerstrasse 1-3, 3012 Bern (Switzerland)

2014-01-15

During time-resolved optical stimulation experiments (TR-OSL), one uses short light pulses to separate the stimulation and emission of luminescence in time. Experimental TR-OSL results show that the luminescence lifetime in quartz of sedimentary origin is independent of annealing temperature below 500 °C, but decreases monotonically thereafter. These results have been interpreted previously empirically on the basis of the existence of two separate luminescence centers L{sub H} and L{sub L} in quartz, each with its own distinct luminescence lifetime. Additional experimental evidence also supports the presence of a non-luminescent hole reservoir R, which plays a critical role in the predose effect in this material. This paper extends a recently published analytical model for thermal quenching in quartz, to include the two luminescence centers L{sub H} and L{sub L}, as well as the hole reservoir R. The new extended model involves localized electronic transitions between energy states within the two luminescence centers, and is described by a system of differential equations based on the Mott–Seitz mechanism of thermal quenching. It is shown that by using simplifying physical assumptions, one can obtain analytical solutions for the intensity of the light during a TR-OSL experiment carried out with previously annealed samples. These analytical expressions are found to be in good agreement with the numerical solutions of the equations. The results from the model are shown to be in quantitative agreement with published experimental data for commercially available quartz samples. Specifically the model describes the variation of the luminescence lifetimes with (a) annealing temperatures between room temperature and 900 °C, and (b) with stimulation temperatures between 20 and 200 °C. This paper also reports new radioluminescence (RL) measurements carried out using the same commercially available quartz samples. Gaussian deconvolution of the RL emission spectra was

Highly luminescent core-shell InP/ZnX (X = S, Se) quantum dots prepared via a phosphine synthetic route.

Science.gov (United States)

Mordvinova, Natalia; Vinokurov, Alexander; Kuznetsova, Tatiana; Lebedev, Oleg I; Dorofeev, Sergey

2017-01-24

Here we report a simple method for the creation of highly luminescent core-shell InP/ZnX (X = S, Se) quantum dots (QDs) on the basis of a phosphine synthetic route. In this method a Zn precursor was added to the reaction mixture at the beginning of the synthesis to form an In(Zn)P alloy structure, which promoted the formation of a ZnX shell. Core-shell InP/ZnX QDs exhibit highly intensive emission with a quantum yield over 50%. The proposed method is primarily important for practical applications. Advantages of this method compared to the widely used SILAR technique are discussed. We further demonstrate that the SILAR approach consisting of consequent addition of Zn and chalcogen precursors to pre-prepared non-doped InP colloidal nanoparticles is not quite suitable for shell growth without the addition of special activator agents or the use of very reactive precursors.

SU-F-BRE-14: Uncertainty Analysis for Dose Measurements Using OSLD NanoDots

Energy Technology Data Exchange (ETDEWEB)

Kry, S; Alvarez, P; Stingo, F; Followill, D [UT MD Anderson Cancer Center, Houston, TX (United States)

2014-06-15

Purpose: Optically stimulated luminescent dosimeters (OSLD) are an increasingly popular dosimeter for research and clinical applications. It is also used by the Radiological Physics Center for remote auditing of machine output. In this work we robustly calculated the reproducibility and uncertainty of the OSLD nanoDot. Methods: For the RPC dose calculation, raw readings are corrected for depletion, element sensitivity, fading, linearity, and energy. System calibration is determined for the experimental OSLD irradiated at different institutions by using OSLD irradiated by the RPC under reference conditions (i.e., standards): 1 Gy in a Cobalt beam. The intra-dot and inter-dot reproducibilities (coefficient of variation) were determined from the history of RPC readings of these standards. The standard deviation of the corrected OSLD signal was then calculated analytically using a recursive formalism that did not rely on the normality assumption of the underlying uncertainties, or on any type of mathematical approximation. This analytical uncertainty was compared to that empirically estimated from >45,000 RPC beam audits. Results: The intra-dot variability was found to be 0.59%, with only a small variation between readers. Inter-dot variability was found to be 0.85%. The uncertainty in each of the individual correction factors was empirically determined. When the raw counts from each OSLD were adjusted for the appropriate correction factors, the analytically determined coefficient of variation was 1.8% over a range of institutional irradiation conditions that are seen at the RPC. This is reasonably consistent with the empirical observations of the RPC, where the coefficient of variation of the measured beam outputs is 1.6% (photons) and 1.9% (electrons). Conclusion: OSLD nanoDots provide sufficiently good precision for a wide range of applications, including the RPC remote monitoring program for megavoltage beams. This work was supported by PHS grant CA10953 awarded by

Gemini surfactant for fluorescent and stable quantum dots in aqueous solution

Energy Technology Data Exchange (ETDEWEB)

Li Haibing [Key Laboratory of Pesticide and Chemical Biology (CCNU), Ministry of Education, College of Chemistry, Central China Normal University, Wuhan 430079 (China); Wang Xiaoqiong [Key Laboratory of Pesticide and Chemical Biology (CCNU), Ministry of Education, College of Chemistry, Central China Normal University, Wuhan 430079 (China); Gao Zhinong [Department of Chemistry, Wuhan University, Wuhan 430072 (China); He Zhike [Department of Chemistry, Wuhan University, Wuhan 430072 (China)

2007-05-23

Highly fluorescent and stable CdSe/ZnS core/shell quantum dots (QDs) coated with gemini surfactant are successfully synthesized in aqueous media. Analyses of luminescence spectrometry, ultraviolet-visible (UV-vis) spectrophotometry, and transmission electron micrographs (TEMs) indicate that the water-soluble QDs are monodisperse and have a luminescence enhancement compared with the original hydrophobic QDs. The water-soluble QDs coated with gemini surfactant are shown to be biocompatible, photostable, and have been proven to be suitable for live cell imaging.

Gemini surfactant for fluorescent and stable quantum dots in aqueous solution

International Nuclear Information System (INIS)

Li Haibing; Wang Xiaoqiong; Gao Zhinong; He Zhike

2007-01-01

Highly fluorescent and stable CdSe/ZnS core/shell quantum dots (QDs) coated with gemini surfactant are successfully synthesized in aqueous media. Analyses of luminescence spectrometry, ultraviolet-visible (UV-vis) spectrophotometry, and transmission electron micrographs (TEMs) indicate that the water-soluble QDs are monodisperse and have a luminescence enhancement compared with the original hydrophobic QDs. The water-soluble QDs coated with gemini surfactant are shown to be biocompatible, photostable, and have been proven to be suitable for live cell imaging

Controllable synthesis, growth mechanism and optical properties of the ZnSe quantum dots and nanoparticles with different crystalline phases

Energy Technology Data Exchange (ETDEWEB)

Feng, Bo [Key Laboratory of Excited State Physics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 3888 Eastern Nan-Hu Road, Changchun 130033 (China); Graduate School of the Chinese Academy of Sciences, Beijing 100049 (China); Institute of Condensed State Physics, Jilin Normal University, Siping 136000 (China); Yang, Jinghai, E-mail: jhyang1@jlnu.edu.cn [Institute of Condensed State Physics, Jilin Normal University, Siping 136000 (China); Cao, Jian; Yang, Lili; Gao, Ming; Wei, Maobin; Liu, Yang [Institute of Condensed State Physics, Jilin Normal University, Siping 136000 (China); Song, Hang [Key Laboratory of Excited State Physics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 3888 Eastern Nan-Hu Road, Changchun 130033 (China)

2013-03-15

Graphical abstract: The ZnSe quantum dots (3.5 nm) with the wurtzite structure exhibited a strong near band-edge emission (NBE) peak centered at 422 nm. The zinc blende ZnSe nanoparticles (21 nm) exhibited near-band-edge luminescence peak centered at 472 nm. Highlights: ► The results of TEM showed that the ZnSe quantum dots were about 3.5 nm. ► The ZnSe quantum dots exhibited a near band-edge emission peak centered at 422 nm. ► The ZnSe nanoparticles exhibited near-band-edge luminescence peak centered at 472 nm. - Abstract: ZnSe precursors were prepared by a solvothermal method at 180 °C without any surface-active agents. ZnSe quantum dots and nanoparticles were obtained by annealing the precursors at 300 °C for 2 h in argon atmosphere. The ZnSe quantum dots were about 3.5 nm, while the ZnSe nanoparticles were about 21 nm, as observed using TEM. The growth mechanisms for the two samples were discussed; this proved that the high coordination ability of ethylenediamine to zinc played an important role in the final phase of the products. The ZnSe quantum dots with the wurtzite structure exhibited a strong near band-edge emission (NBE) peak centered at 422 nm, which was blue-shifted in comparison to that of the bulk ZnSe, which was mainly caused by the quantum confinement effect. However, the zinc blende ZnSe nanoparticles exhibited a near-band-edge luminescence peak centered at 472 nm.

Gain investigation of Perylene-Red-doped PMMA for stimulated luminescent solar concentrators.

Science.gov (United States)

Kaysir, Md Rejvi; Fleming, Simon; Argyros, Alexander

2018-04-01

Luminescent solar concentrators (LSCs) utilizing stimulated emission by a seed laser are a promising approach to overcome the limitations of conventional LSCs, with a significant reduction of the photovoltaic material. In our previous work, we demonstrated the principle of a stimulated LSC (s-LSC) and correspondingly developed a model for quantifying the output power of such a system, taking into account different important physical parameters. The model suggested Perylene Red (PR) dye as a potential candidate for s-LSCs. Here, we experimentally investigate the gain of PR-doped polymethyl methacrylate (PMMA) required for s-LSCs using a single pump wavelength (instead of the solar spectrum) as a proof of principle. The results found from the experiment are well matched with the previously developed numerical model except for gain saturation, which occurs at a comparatively small seed laser signal power. To investigate the gain saturation, two approaches were taken: investigating (i) spectral hole burning and (ii) triplet state absorption. Experimental investigation of spectral hole burning with PR dyes showed a small effect on the gain saturation. We developed a general state model considering triplet state absorption of the PR dyes for the second approach. The state model suggests that the PR dyes suffer from significant triplet state absorption loss, which obstructs the normal operation of the PR-based s-LSC system.

Overview of Stabilizing Ligands for Biocompatible Quantum Dot Nanocrystals

Directory of Open Access Journals (Sweden)

Aaron Clapp

2011-11-01

Full Text Available Luminescent colloidal quantum dots (QDs possess numerous advantages as fluorophores in biological applications. However, a principal challenge is how to retain the desirable optical properties of quantum dots in aqueous media while maintaining biocompatibility. Because QD photophysical properties are directly related to surface states, it is critical to control the surface chemistry that renders QDs biocompatible while maintaining electronic passivation. For more than a decade, investigators have used diverse strategies for altering the QD surface. This review summarizes the most successful approaches for preparing biocompatible QDs using various chemical ligands.

Contribution to numerical radiology. Study of a bidimensional imaging device that use Electrically Stimulated Luminescence. The case of mammography

International Nuclear Information System (INIS)

Ayral, Jean-Luc

1990-01-01

Projection radiography is in a fast change period. This work describes the study and demonstration of a new type of 2D flat X-Ray sensor for mammography and delivering a digital signal. X-ray transmission study of breast tissues leads to: a- definition of X-Ray photons properties for optimized signal-to-noise ratio, and b-specifications of a 2D X-Ray sensor such as mean exposure, dynamic range and pixel size. Then the X-Ray detection processes using a direct or a delayed luminescence mechanism are reviewed. The detailed analysis of the different ways for detecting visible photons is combined with the System specifications (pixel size, image reading time) in order to characterize (from a signal-to-noise ratio aspect) an X-Ray imaging system integrating a delayed luminescence property. The imaging plate and associated luminescent material are specified by their minimum X-Ray absorption and conversion gain. The Gudden- Pohl effect, or Electrically Stimulated Luminescence (ESL) is experimentally studied and quantified under X-Ray excitation in ZnCdS: Cu, Al materials. An original UV sensitization technique opens us the way to highly reproducible results and large sensitivity. The obtained information storage time in the material is compatible with a delayed image reading. These results allow the achievement of an X-Ray imaging demonstrator integrating the ESL imaging plate, an intensified CCD sensor and the sensitization technique. First images are obtained. Further conception of real dimension X-Ray imaging System for mammography is described. (author) [fr

Thermally stimulated luminescence of KDP activated crystals

International Nuclear Information System (INIS)

Tagaeva, B.S.

2005-01-01

The aim of this work is the study of recombination luminescence pure and doped by the ions Tl, Se, Pb and Cu of crystals double potassium phosphates (KDP) at irradiation by X-rays. It is established that in the given crystals mechanisms for under-threshold defect formation are realize. The impurity ions results the basic crystal light sum redistribution in the TL peaks. Explanations for some phenomena are given. (author)

Optically stimulated luminescence (OSL) from Ag-doped Li2B4O7 crystals

International Nuclear Information System (INIS)

Kananen, B.E.; Maniego, E.S.; Golden, E.M.; Giles, N.C.; McClory, J.W.; Adamiv, V.T.; Burak, Ya.V.; Halliburton, L.E.

2016-01-01

Optically stimulated luminescence (CW-OSL) is observed from Ag-doped lithium tetraborate (Li 2 B 4 O 7 ) crystals. Photoluminescence, optical absorption, and electron paramagnetic resonance (EPR) are used to identify the defects participating in the OSL process. As-grown crystals have Ag + ions substituting for Li + ions. They also have Ag + ions occupying interstitial sites. During a room-temperature exposure to ionizing radiation, holes are trapped at the Ag + ions that replace Li + ions and electrons are trapped at the interstitial Ag + ions, i.e., the radiation forms Ag 2+ (4d 9 ) ions and Ag 0 (4d 10 5s 1 ) atoms. These Ag 2+ and Ag 0 centers have characteristic EPR spectra. The Ag 0 centers also have a broad optical absorption band peaking near 370 nm. An OSL response is observed when the stimulation wavelength overlaps this absorption band. Specifically, stimulation with 400 nm light produces an intense OSL response when emission is monitored near 270 nm. Electrons optically released from the Ag 0 centers recombine with holes trapped at Ag 2+ ions to produce the ultraviolet emission. The OSL response is progressively smaller as the stimulation light is moved to longer wavelengths (i.e., away from the 370 nm peak of the absorption band of the Ag 0 electron traps). Oxygen vacancies are also present in the Ag-doped Li 2 B 4 O 7 crystals, and their role in the OSL process as a secondary relatively short-lived electron trap is described.

Optically stimulated luminescence of electronic components for forensic, retrospective, and accident dosimetry

International Nuclear Information System (INIS)

Inrig, E.L.; Godfrey-Smith, D.I.; Khanna, S.

2008-01-01

This study investigated the optically stimulated luminescence (OSL) response of electronic components found within portable electronic devices such as cell phones and pagers, portable computers, music and video players, global positioning system receivers, cameras, and digital watches. The analysis of components extracted from these ubiquitous devices was proposed for applications ranging from rapid accident dose reconstruction to the tracking and attribution of gamma-emitting radiological materials. Surface-mount resistors with alumina porcelain substrates consistently produced OSL following irradiation, with minimum detectable doses on the order of 10 mGy for a typical sample. Since the resistor ceramics were found to exhibit anomalous fading, dose reconstruction procedures were developed to correct for this using laboratory measurements of fading rates carried out over approximately 3 months. Two trials were conducted in which cellular phones were affixed to an anthropomorphic phantom and irradiated using gamma-ray sources; ultimately, analysis of the devices used in these trials succeeded in reconstructing doses in the range of 0.1-0.6Gy

Spatially Controlled Fabrication of Brightly Fluorescent Nanodiamond-Array with Enhanced Far-Red Si-V Luminescence

Science.gov (United States)

Singh, Sonal; Thomas, Vinoy; Martyshkin, Dmitry; Kozlovskaya, Veronika; Kharlampieva, Eugenia

2014-01-01

We demonstrate a novel approach to precise pattern fluorescent nanodiamond-arrays with enhanced far-red intense photostable luminescence from silicon-vacancy (Si-V) defect centers. The precision-patterned pre-growth seeding of nanodiamonds is achieved by scanning probe “Dip-Pen” nanolithography technique using electrostatically-driven transfer of nanodiamonds from “inked” cantilevers to a UV-treated hydrophilic SiO2 substrate. The enhanced emission from nanodiamond-dots in the far-red is achieved by incorporating Si-V defect centers in subsequent chemical vapor deposition treatment. The development of a suitable nanodiamond ink, mechanism of ink transport, and effect of humidity, dwell time on nanodiamond patterning are investigated. The precision-patterning of as-printed (pre-CVD) arrays with dot diameter and dot height as small as 735 nm ± 27 nm, 61 nm ± 3 nm, respectively and CVD-treated fluorescent ND-arrays with consistently patterned dots having diameter and height as small as 820 nm ± 20 nm, 245 nm ± 23 nm, respectively using 1 s dwell time and 30% RH is successfully achieved. We anticipate that the far-red intense photostable luminescence (~738 nm) observed from Si-V defect centers integrated in spatially arranged nanodiamonds could be beneficial for the development of the next generation fluorescent based devices and applications. PMID:24394286

Size quantization patterns in self-assembled InAs/GaAs quantum dots

Science.gov (United States)

Colocci, M.; Bogani, F.; Carraresi, L.; Mattolini, R.; Bosacchi, A.; Franchi, S.; Frigeri, P.; Taddei, S.; Rosa-Clot, M.

1997-07-01

Molecular beam epitaxy has been used for growing self-assembled InAs quantum dots. A continuous variation of the InAs average coverage across the sample has been obtained by properly aligning the (001) GaAs substrate with respect to the molecular beam. Excitation of a large number of dots (laser spot diameter ≈ 100 μm) results in structured photoluminescence spectra; a clear quantization of the dot sizes is deduced from the distinct luminescence bands separated in energy by an average spacing of 20-30 meV. We ascribe the individual bands of the photoluminescence spectrum after low excitation to families of dots with roughly the same diameter and heights differing by one monolayer.

Microwave-assisted synthesis of highly luminescent N- and S-co-doped carbon dots as a ratiometric fluorescent probe for levofloxacin.

Science.gov (United States)

Li, Huiyu; Xu, Yuan; Ding, Jie; Zhao, Li; Zhou, Tianyu; Ding, Hong; Chen, Yanhua; Ding, Lan

2018-01-10

Uniform N- and S-co-doped carbon dots (NSCDs) with fluorescence quantum yields of up to 64% were synthesized via a one-step microwave-assisted method. Ammonium citrate and L-cysteine act as precursors, and synthesis is completed in 2.5 min using a 750 W microwave oven to give a 62% yield. The NSCDs show bright blue fluorescence (with excitation/emission peaks at 353/426 nm) and have narrow size distribution. On exposure to levofloxacin (LEV), the emission maximum shifts to 499 nm. This effect was used to design ratiometric (2-wavelength) assays for LEV. The fluorometric method (based on measurement of the fluorescence intensity ratio at 499 and 426 nm) has a detection limit of 5.1 μg·L -1 (3σ/k) and a linear range that extends from 0.01 to 70 mg·L -1 . The method was applied to the determination of LEV in three kinds of spiked water samples and has recoveries in the range from 98.6 to 106.8%. The fluorescent probe described here is highly selective and sensitive. Graphical Abstract Highly luminescent N- and S-co-doped carbon dots were synthesized using AC (ammonium citrate) and Cys (L-cysteine) by microwave-assisted method, and were applied to the visual and ratiometric fluorescence determination of LEV (levofloxacin).

Interplay of coupling and superradiant emission in the optical response of a double quantum dot

Science.gov (United States)

Sitek, Anna; Machnikowski, Paweł

2009-09-01

We study theoretically the optical response of a double quantum dot structure to an ultrafast optical excitation. We show that the interplay of a specific type of coupling between the dots and their collective interaction with the radiative environment leads to very characteristic features in the time-resolved luminescence as well as in the absorption spectrum of the system. For a sufficiently strong coupling, these effects survive even if the transition energy mismatch between the two dots exceeds by far the emission linewidth.

The behavior of thermally and optically stimulated luminescence of SrAl2O4:Eu2+,Dy3+ long persistent phosphor after blue light illumination

International Nuclear Information System (INIS)

Chernov, V.; Melendrez, R.; Pedroza-Montero, M.; Yen, W.M.; Barboza-Flores, M.

2008-01-01

The behavior of afterglow (AG), thermoluminescence (TL), infrared stimulated luminescence (IRSL) and phototransferred TL (PTTL) under thermal and/or infrared (IR) stimulation in blue (470 nm) light illuminated at room temperature (RT) SrAl 2 O 4 :Eu 2+ , Dy 3+ is presented. The TL glow curve consists of four peaks with maxima at about 340, 430, 560 and 680 K. The 340 and 440 K peaks are described well by second order kinetics with activation energies of 0.83 and 1.05 eV, respectively. The AG decay is fitted by the Becquerel's law with exponent 1.5 and correlates well with the thermal emptying of the traps responsible for the 340 K peak. The 340 and 430 K TL peak traps are destroyed under IR (830 nm) stimulation creating IRSL. IR stimulation after illumination with blue light and preliminary heating restore partially the 340 and 430 K TL peaks by phototransfer from deeper traps. The shape of the IRSL decay curves depends strongly on the preheating temperature and is determined by simultaneous refilling of the 340 and 430 K TL traps and their reverse filling due to phototransfer from the deeper traps under IR stimulation. The obtained data are interpreted by the transformation of Eu 2+ and Dy 3+ to Eu 3+ and Dy 2+ under blue light illumination and their reverse transformation under thermal or IR stimulation. The Eu 2+ ions are the luminescent centers and the Dy 2+ centers are the IR sensitive traps responsible for the TL peaks, AG and IRSL

Intrinsic luminescence of un-doped borate glasses

International Nuclear Information System (INIS)

Kindrat, I.I.; Padlyak, B.V.; Drzewiecki, A.

2017-01-01

The nature of intrinsic luminescence in the un-doped borate glasses of different compositions has been investigated using spectroscopic methods including photoluminescence, optical absorption, electron paramagnetic resonance (EPR), and thermally stimulated luminescence (TSL). The un-doped borate glasses with Li 2 B 4 O 7 , LiKB 4 O 7 , CaB 4 O 7 , and LiCaBO 3 basic compositions were obtained from corresponding polycrystalline compounds in the air with usage the standard technology of glasses. Three different broad emission bands in the UV–Visible spectral range have been observed under different wavelength of photoexcitation. The luminescence kinetics of the observed emission bands have been registered and analysed. The nature and possible mechanisms of the intrinsic luminescence in the investigated borate glasses are considered and discussed based on the obtained results and referenced data.

Limestone: some observations on luminescence in the region of 360 nm

International Nuclear Information System (INIS)

Galloway, R.B.

2003-01-01

An empirical study of luminescence around 360 nm from limestone is presented. Thermoluminescence glow curves from natural limestone show broad peaks at 440 deg. C, 350 deg. C, 530 deg. C and 286 deg. C in order of decreasing amplitude in contrast to the usual observation, for luminescence around 535 nm, of a sharp peak at 286 deg. C with a broader less intense peak at 350 deg. C. Recuperation occurs around 350 deg. C and 525 deg. C, which has a time dependence consistent with quantum tunnelling. Dependent on the history of heating and light exposure of the sample, sharp peaks at about 325 deg. C and 425 deg. C can be observed. Laboratory irradiated limestone shows a peak at 140 deg. C. The stimulation of luminescence by light of 470 nm with preheating at 145 deg. C for 300 s, shows an increasing signal for successive cycles of measurement associated with the heating, light exposure having little influence. Beta irradiation of a sample, with the same measurement conditions, gives a signal which increases in proportion to radiation dose but which does not survive storage for 17 h. Time resolved luminescence spectra, with no preheating, show a luminescence lifetime between stimulation and emission of less than a few μs for natural limestone, and an exponential increase in signal with increase in temperature (over the rang 20-167 deg. C) during stimulation. A signal proportional to laboratory applied beta dose is measurable at room temperature, with lifetime between stimulation and emission of this signal of 35 μs, but it does not survive heating to 100 deg. C

Thermal and electron stimulated luminescence of natural bones, commercial hydroxyapatite and collagen.

Science.gov (United States)

Roman-Lopez, J; Correcher, V; Garcia-Guinea, J; Rivera, T; Lozano, I B

2014-01-01

The luminescence (cathodoluminescence and thermoluminescence) properties of natural bones (Siberian mammoth and adult elephant), commercial hydroxyapatite and collagen were analyzed. Chemical analyses of the natural bones were determined using by Electron Probe Micro-Analysis (EMPA). Structural, molecular and thermal characteristics were determined by X-ray Diffraction (XRD), Raman spectroscopy and Differential Thermal and Thermogravimetric analysis (DTA-TG). Cathodoluminescence (CL) spectra of natural bones and collagen showed similar intense broad bands at 440 and 490 nm related to luminescence of the tetrahedral anion [Formula: see text] or structural defects. A weaker luminescence exhibited at 310 nm could be attributed to small amount of rare earth elements (REEs). Four luminescent bands at 378, 424, 468 and 576 nm were observed in the commercial hydroxyapatite (HAP). Both natural bones and collagen samples exhibited natural thermoluminescence (NTL) with well-defined glow curves whereas that the induced thermoluminescence (ITL) only appears in the samples of commercial hydroxyapatite and collagen. Additional explanations for the TL anomalous fading of apatite, as a crucial difficulty performing dosimetry and dating, are also considered. Copyright © 2013 Elsevier B.V. All rights reserved.

Luminescence spectroscopy with synchrotron radiation: History, highlights, future

International Nuclear Information System (INIS)

Zimmerer, Georg

2006-01-01

Luminescence spectroscopy and the investigation of dynamical processes with synchrotron radiation (SR) started about 35 years ago in nearly all SR laboratories existing at that time. In the present paper, the pioneering experiments are particularly emphasized. The exciting development is illustrated presenting highlights for the whole period from the beginning to the present day. The highlights are taken from fields like exciton self-trapping, inelastic electron-electron scattering, optically stimulated desorption, cross luminescence, or probing of cluster properties with luminescence spectroscopic methods. More technological aspects play a role in present day's experiments, like quantum cutting in rare-earth-doped insulators. Promising two-photon excitation and light amplification experiments with SR will be included, as well as the first results obtained in a luminescence experiment with selective Vaccum ultraviolet-free electron laser excitation. Finally, a few ideas concerning the future development of luminescence spectroscopy with SR will be sketched

Exploring procedures for the rapid assessment of optically stimulated luminescence range-finder ages

International Nuclear Information System (INIS)

Roberts, Helen M.; Durcan, Julie A.; Duller, Geoff A.T.

2009-01-01

Optically stimulated luminescence (OSL) dating of sediments is a lengthy, labour-intensive, and time-consuming procedure. However, in some situations a rough approximation of the OSL age is all that is necessary e.g. for a pilot field campaign, to plan a sampling strategy, or to determine the resolution required for a dating campaign. Thus, it would be useful to establish an approximate OSL age without the lengthy and involved processes normally used. This paper explores how the standard procedures involved in OSL age determinations can be simplified to yield range-finder ages. Three areas are examined, namely, laboratory preparation, D e estimation, and dose-rate determination. The consequences of circumventing some of the preparation and measurement steps of conventional OSL dating are examined for a variety of sediments, by comparing the OSL range-finder ages to those obtained using full quartz OSL preparation and measurement procedures.

Evaluation of trapping parameters of thermally stimulated luminescence glow curves in Cu-doped Li2B4O7 phosphor

International Nuclear Information System (INIS)

Manam, J.; Sharma, S.K.

2005-01-01

Evaluation of trapping parameters, including order of kinetics, activation energy and frequency factor, is one of the most important aspect of studies in the field of thermally stimulated luminescence (TSL). A polycrystalline sample of Cu-doped Li 2 B 4 O 7 was prepared by the melting method. Formation of the doped compound was checked by use of Fourier-transform infrared (FTIR) spectroscopy. TSL studies of the Cu-doped lithium tetraborate sample shows three glow peaks, the maximum emission occurring, respectively, at a temperature of 175 deg. C, 290 deg. C and 350 deg. C, the intensity of the 175 deg. C-glow peak being the maximum. The trapping parameters associated with this prominent glow peak of Cu-doped lithium tetraborate are reported herein, using the isothermal luminescence decay and glow curve shape (Chen's) methods. Our results show very good agreement between the trapping parameters calculated by the two methods

Comparative photoluminescence study of close-packed and colloidal InP/ZnS quantum dots

Science.gov (United States)

Thuy, Ung Thi Dieu; Thuy, Pham Thi; Liem, Nguyen Quang; Li, Liang; Reiss, Peter

2010-02-01

This letter reports on the comparative photoluminescence study of InP/ZnS quantum dots in the close-packed solid state and in colloidal solution. The steady-state photoluminescence spectrum of the close-packed InP/ZnS quantum dots peaks at a longer wavelength than that of the colloidal ones. Time-resolved photoluminescence shows that the close-packed quantum dots possess a shorter luminescence decay time and strongly increased spectral shift with the time delayed from the excitation moment in comparison with the colloidal ones. The observed behavior is discussed on the basis of energy transfer enabled by the short interparticle distance between the close-packed quantum dots.

Tuneable light-emitting carbon-dot/polymer flexible films prepared through one-pot synthesis

Science.gov (United States)

Bhunia, Susanta Kumar; Nandi, Sukhendu; Shikler, Rafi; Jelinek, Raz

2016-02-01

Development of efficient, inexpensive, and environmentally-friendly light emitters, particularly devices that produce white light, have drawn intense interest due to diverse applications in the lighting industry, photonics, solar energy, and others. We present a simple strategy for the fabrication of flexible transparent films exhibiting tuneable light emission through one-pot synthesis of polymer matrixes with embedded carbon dots assembled in situ. Importantly, different luminescence colours were produced simply by preparing C-dot/polymer films using carbon precursors that yielded C-dots exhibiting distinct fluorescence emission profiles. Furthermore, mixtures of C-dot precursors could be also employed for fabricating films exhibiting different colours. In particular, we successfully produced films emitting white light with attractive properties (i.e. ``warm'' white light with a high colour rendering index) - a highly sought after goal in optical technologies.Development of efficient, inexpensive, and environmentally-friendly light emitters, particularly devices that produce white light, have drawn intense interest due to diverse applications in the lighting industry, photonics, solar energy, and others. We present a simple strategy for the fabrication of flexible transparent films exhibiting tuneable light emission through one-pot synthesis of polymer matrixes with embedded carbon dots assembled in situ. Importantly, different luminescence colours were produced simply by preparing C-dot/polymer films using carbon precursors that yielded C-dots exhibiting distinct fluorescence emission profiles. Furthermore, mixtures of C-dot precursors could be also employed for fabricating films exhibiting different colours. In particular, we successfully produced films emitting white light with attractive properties (i.e. ``warm'' white light with a high colour rendering index) - a highly sought after goal in optical technologies. Electronic supplementary information (ESI

Luminescent GdVO_4:Sm"3"+ quantum dots enhance power conversion efficiency of bulk heterojunction polymer solar cells by Förster resonance energy transfer

International Nuclear Information System (INIS)

Bishnoi, Swati; Gupta, Vinay; Sharma, Gauri D.; Chand, Suresh; Sharma, Chhavi; Kumar, Mahesh; Haranath, D.; Naqvi, Sheerin

2016-01-01

In this work, we report enhanced power conversion efficiency (PCE) of bulk heterojunction polymer solar cells by Förster resonance energy transfer (FRET) from samarium-doped luminescent gadolinium orthovanadate (GdVO_4:Sm"3"+) quantum dots (QDs) to polythieno[3,4-b]-thiophene-co-benzodithiophene (PTB7) polymer. The photoluminescence emission spectrum of GdVO_4:Sm"3"+ QDs overlaps with the absorption spectrum of PTB7, leading to FRET from GdVO_4:Sm"3"+ to PTB7, and significant enhancements in the charge-carrier density of excited and polaronic states of PTB7 are observed. This was confirmed by means of femtosecond transient absorption spectroscopy. The FRET from GdVO_4:Sm"3"+ QDs to PTB7 led to a remarkable increase in the power conversion efficiency (PCE) of PTB7:GdVO_4:Sm"3"+:PC_7_1BM ([6,6]-phenyl-C_7_1-butyric acid methyl ester) polymer solar cells. The PCE in optimized ternary blend PTB7:GdVO_4:Sm"3"+:PC_7_1BM (1:0.1:1.5) is increased to 8.8% from 7.2% in PTB7:PC_7_1BM. This work demonstrates the potential of rare-earth based luminescent QDs in enhancing the PCE of polymer solar cells.

Photoluminescence under high-electric field of PbS quantum dots

Directory of Open Access Journals (Sweden)

B. Ullrich

2012-12-01

Full Text Available The effect of a laterally applied electric field (≤10 kV/cm on the photoluminescence of colloidal PbS quantum dots (diameter of 2.7 nm on glass was studied. The field provoked a blueshift of the emission peak, a reduction of the luminescent intensity, and caused an increase in the full width at half maximum of the emission spectrum. Upon comparison with the photoluminescence of p-type GaAs exhibits the uniqueness of quantum dot based electric emission control with respect to bulk materials.

Detection of herbs and spices irradiated through optically stimulated luminescence

International Nuclear Information System (INIS)

Preciado, S.; Agundez A, Z.; Barboza F, M.; Cruz Z, E.

2003-01-01

The irradiation of foods is one of the common practices in several countries of the American and European continents. In spite of the widespread use of irradiation methods and technics of nutritious products, it doesn't exist a method of general use at the present time for the detection of previously submitted foods to irradiation with pasteurization ends or sterilization. In the present work the results are presented obtained in the detection of herbs and spices exposed to radiation in the range of 0.1 - 3 KGy, by means of the photostimulation with light of 470 nm. It was used for it a RIS0 model team TL/OSL-GIVE-15 conditioned with a β ray source, 90 Sr/ 90 Y and a source of light of 50 mW/cm2. samples of chili guajillo were studied, pepper, cumin, mint and camomile; achieving you to detect exhibitions of the order of 8.33x10 -4 KGy that which is indicative of the high sensitivity of the luminescence technique optically stimulated. The answer of the samples with regard to the radiation dose presents a range of lineality for low dose of the order of 0.5 KGy; and supralineal for further dose without to arrive to a saturation stage. (Author)

Preheat-induced signal enhancement in the infrared stimulated luminescence of young and bleached sediment samples

International Nuclear Information System (INIS)

Richardson, C.A.

2000-01-01

Natural and laboratory bleached surface and young samples of potassium feldspar sand separates and polymineral silt had their infrared stimulated luminescence (IRSL) signal measured before and after preheating at 220 deg. C for 10 min or 160 deg. C for 16 h. For both preheats, the laboratory bleached sand samples underwent a signal enhancement which was stable with laboratory storage. The youngest samples also showed natural signal enhancement. The silt sample showed no recuperation of bleached signal on preheating, but some in the natural signal. A range of filtered bleaches was applied to one surface sand sample. Signal levels before and after preheating were reduced by filtering out the UV from the bleaching spectrum. The unfiltered bleach, however, most closely reproduced the behaviour of the natural sample

Time-resolved luminescence from feldspars: New insight into fading

DEFF Research Database (Denmark)

Tsukamoto, S.; Denby, P.M.; Murray, A.S.

2006-01-01

Time-resolved infrared optically stimulated luminescence (IR-OSL) signals of K- and Na-feldspar samples extracted from sediments were measured in UV, blue and red detection windows, using a fast photon counter and pulsed IR stimulation (lambda = 875 nm). We observe that the relative contribution ...

Radiation dose response correlation between thermoluminescence and optically stimulated luminescence in quartz

International Nuclear Information System (INIS)

Oniya, E.O.; Polymeris, G.S.; Tsirliganis, N.C.; Kitis, G.

2012-01-01

The fast, linearly modulated optically stimulated luminescence (LM-OSL) component in quartz is the main dosimetric signal used for the dating applications of this material. Since the blue light stimulation (470 nm, 40 mW cm −2 ) time needed to obtain the fast LM-OSL component is less than 50 s the electron trapping levels responsible for it are still highly populated. In this way an active radiation history is created which could play an important role in the dosimetric characteristics of the fast OSL signal. In the present work the dose response behavior of the fast OSL signal is investigated in quartz samples with an annealed radiation history and quartz samples possessing an artificial radiation history. A computerized curve de-convolution analysis of the LM-OSL curves for 50 s stimulation time showed that it consists of three individual OSL components. The faster component C 1 with peak maximum time around 5 s has a linear dose response in virgin samples, which turns to a slight superlinearity as a function of the artificial radiation history. On the other hand the component C 2 with peak maximum time at 12 s is slightly superlinear which turns into strong superlinearity as a function of artificial radiation history. Finally, component C 3 with peak maximum time at about 45 s is strongly superlinear for both virgin samples and as a function of artificial radiation history. The implications to practical application are discussed. - Highlights: ► The fast OSL component consists of three components. ► The linearity of first fast component does not depend on radiation history. ► The linearity of second and third components depend on radiation history. ► The TL between 180 and 300 °C is the major source of OSL.

Contribution to digital radiography. Study of a 2D X-ray sensor for mammography using the electrically-stimulated-luminescence effect

International Nuclear Information System (INIS)

Ayral, Jean-Luc

1990-01-01

Radiography is in a fast change period. This work describes the study and demonstration of a new type of 2D flat X-Ray sensor for mammography and delivering a digital signal. X-ray transmission study of breast tissues leads to: a-definition of X-Ray photons properties for optimized signal-to-noise ratio, and b-specifications of a 2D X-Ray sensor such as mean exposure, dynamic range and pixel size. Then the X-Ray detection processes using a direct or a delayed luminescence mechanism are reviewed. The detailed analysis of the different ways for detecting visible photons is combined with the system specifications (pixel size, image reading time) in order to characterize (from a signal-to-noise ratio aspect) an X-Ray imaging system integrating a delayed luminescence property. The imaging plate and associated luminescent material are specified by their minimum X-Ray absorption and conversion gain. The Gudden-Pohl effect, or Electrically Stimulated Luminescence (ESL) is experimentally studied and quantified under X-Ray excitation in ZnCdS: Cu, Al materials. An original UV sensitization technique opens us the way to highly reproducible results and large sensitivity. The obtained information storage time in the material is compatible with a delayed image reading. These results allow the achievement of an X-Ray imaging demonstrator integrating the ESL imaging plate, an intensified CCD sensor and the sensitization technique. First images are obtained. Further conception of real dimension X-Ray imaging system for mammography is described. (author) [fr

Characterization of an optically stimulated luminescence (OSL) material for thermal neutron detection: SrS:Ce,Sm,B

International Nuclear Information System (INIS)

Ravotti, Federico; Garcia, Pierre; Prevost, Hildegarde; Dusseau, Laurent; Lapraz, Dominique; Vaille, Jean-Roch; Benoit, David

2008-01-01

SrS:Ce,Sm exhibits some interesting phosphorescent and charge storage properties that are used in OSL (optically stimulated luminescence) radiation dosimetry. To enhance the thermal neutron sensitivity of this phosphor, a new material obtained by boron doping has been developed. This OSL, B material was analysed with respect to its optical and structural characteristics in order to study possible modifications induced by doping procedure. Optical study highlights a decrease in the material luminescence of about 40% with TL and OSL experiments. The emission spectrum remains the same after boron addition. This result is in agreement with the structural characterization analysis since the lattice parameters were not modified. 11B MAS NMR results indicate that boron atoms are present in the host lattice in form of BO4 groups. Consequences on dosimetry applications are discussed. The neutron response of the OSL, B irradiated in a nuclear reactor is linear up to a fluence of 5 x 1011 cm -2 and it is possible to separate the thermal neutron and gamma components. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Advances in luminescence instrument systems

DEFF Research Database (Denmark)

Bøtter-Jensen, L.; Bulur, E.; Duller, G.A.T.

2000-01-01

We report on recent advances in the development of luminescence measurement systems and techniques at Riso. These include: (1) optical stimulation units based on new-generation powerful blue light (470 nm) emitting diodes providing up to 28 mW/cm(2) for OSL measurements; (2) an infrared (830 nm...

Thermoluminescence, luminescence optically stimulated and creation of defects in alkaline halogenides contaminated with Europium; Termoluminiscencia, luminiscencia opticamente estimulada y creacion de defectos en halogenuros alcalinos contaminados con Europio

Energy Technology Data Exchange (ETDEWEB)

Barboza F, M. [Centro de Investigacion en Fisica, Universidad de Sonora, Apartado Postal 5-088, 83190 Hermosillo, Sonora (Mexico)

1999-07-01

The alkaline halogenides have been subject matter of investigations related with the search of sensor materials for X-ray bidimensional images or optical memories. The understanding of the damage formation processes generated by ionizing and non-ionizing radiations is important for the correct design of devices that working as detectors and dosemeters of both type of radiations. In this work we present the investigation results related with the defects produced by the ionizing radiation type X and ultraviolet light in the range of 200-360 nm in crystals of KCl: Eu{sup 2+} and KBr:Eu{sup 2+}. It is examined the thermoluminescence and luminescence spectra with the purpose of identifying the exciton processes, owing to the excitation of the halogenide ions in which the primary defects correspond to the F and H centers. It has been found that the 400-600 nm emission is associated with the luminescence type that in his turn can be associated with autotrapped excitons perturbed by the impurity. On the other hand, it is examined the emission spectra of the luminescence optically stimulated in crystals of KBr: Eu{sup 2+} and KCl: Eu{sup 2+} finding too that such materials would be used as optical memories susceptible of to store information, and through of photostimulation to read this. It was determined that the F centers participate in the luminescence optically stimulated in these crystals, as well as too in the recombination processes responsible by the thermoluminescent emission. (Author)

Integrated photonics using colloidal quantum dots

Science.gov (United States)

Menon, Vinod M.; Husaini, Saima; Okoye, Nicky; Valappil, Nikesh V.

2009-11-01

Integrated photonic devices were realized using colloidal quantum dot composites such as flexible microcavity laser, microdisk emitters and integrated active-passive waveguides. The microcavity laser structure was realized using spin coating and consisted of an all-polymer distributed Bragg reflector with a poly-vinyl carbazole cavity layer embedded with InGaP/ZnS colloidal quantum dots. These microcavities can be peeled off the substrate yielding a flexible structure that can conform to any shape and whose emission spectra can be mechanically tuned. Planar photonic devices consisting of vertically coupled microring resonators, microdisk emitters, active-passive integrated waveguide structures and coupled active microdisk resonators were realized using soft lithography, photo-lithography, and electron beam lithography, respectively. The gain medium in all these devices was a composite consisting of quantum dots embedded in SU8 matrix. Finally, the effect of the host matrix on the optical properties of the quantum dots using results of steady-state and time-resolved luminescence measurements was determined. In addition to their specific functionalities, these novel device demonstrations and their development present a low-cost alternative to the traditional photonic device fabrication techniques.

Optically stimulated luminescence in x-ray irradiated xSnO-(25-x)SrO-75B2O3 glass

Science.gov (United States)

Nanto, H.; Nakagawa, R.; Takei, Y.; Hirasawa, K.; Miyamoto, Y.; Masai, H.; Kurobori, T.; Yanagida, T.; Fujimoto, Y.

2015-06-01

An intense optically stimulated luminescence (OSL) was observed, for the first time, in x-ray irradiated xSnO-(25-x)SrO-75B2O3 glass. It was found that the peak wavelength of OSL emission spectrum and its stimulation spectrum is about 400 nm and 600 nm, respectively. The OSL intensity is depended on the SnO contents (x=0.05-1.5) and the most intense OSL was observed in 1.0 mol% SnO doped glass. It was found that the OSL intensity is increased with increasing x-ray absorbed dose. Fairly good fading characteristics were observed in the x-ray irradiated glass, showing that this glass is useful as a candidate for OSL sensor materials for ionizing radiation monitoring.

Desiccants for retrospective dosimetry using optically stimulated luminescence (OSL)

International Nuclear Information System (INIS)

Geber-Bergstrand, Therése; Bernhardsson, Christian; Christiansson, Maria; Mattsson, Sören; Rääf, Christopher L.

2015-01-01

Optically stimulated luminescence (OSL) was used to test different kinds of desiccants for their potential use in retrospective dosimetry. Desiccants are used for the purpose of absorbing liquids and can be found in a number of items which may be found in the immediate environment of a person, including hand bags, drug packages, and the vehicles of rescue service teams. Any material exhibiting OSL properties suitable for retrospective dosimetry is a useful addition to the existing dosimetry system available in emergency preparedness. Eleven kinds of desiccants were investigated in order to obtain an overview of the fundamental OSL properties necessary for retrospective dosimetry. Measurements were made using a Risø TL/OSL reader and irradiations were achieved with the 90 Sr/ 90 Y source incorporated in the reader. Several of the desiccants exhibited promising properties as retrospective dosemeters. Some of the materials exhibited a strong as-received signal, i.e. without any laboratory irradiation, but the origin of this signal has not yet been established. The minimum detectable dose ranged from 8 to 450 mGy for ten of the materials and for one material (consisting of natural clay) the minimum detectable dose was 1.8 Gy. - Highlights: • Desiccants can be used as fortuitous dosemeters using OSL. • The minimum detectable dose for processed desiccants range from 8 to 450 mGy. • The minimum detectable dose for natural clay was 1.8 Gy

Study of optically stimulated luminescence (OSL) for radiation detection. Application to an optical fibre {gamma}-radiation sensor; Etude de la luminescence stimulee optiquement (OSL) pour la detection de rayonnements: application a un capteur a fibre optique de rayonnement {gamma}

Energy Technology Data Exchange (ETDEWEB)

Roy, O. [CEA Saclay, 91 - Gif-sur-Yvette (France). Dept. d`Electronique et d`Instrumentation Nucleaire]|[Paris-7 Univ., 75 (France)

1998-12-31

This work shows up the usefulness of the Optically Stimulated Luminescence (OSL) to resolve radioprotection problems. We study the use of OSL as a gamma dosimetric technique with respect to the ALARA`s concept (As Low As Reasonably Achievable). A new approach based on optical fibers and luminescent materials showing OSL properties (closely related to Thermoluminescence phenomena) is presented in order to improve the remote real time dosimetry monitoring. Like thermoluminescent materials (TLD), OSL materials can trap charges under an irradiation (UV, X, {gamma},...). Instead of heating, the charges trapped are released by light stimulation and produce a visible luminescence which amount is proportional to trap the `data stored` left by irradiation, enabling the dose measurement. The OSL phenomenon offers the same advantages as TLD plus the interesting possibility of a remote optical stimulation. The end-user objective deals with the development of a {gamma}-radiation Optical FIber Sensor (OFS) for dose measurement which can offer new functionalities based on OSL materials coupled with an optical fiber. Rare earth doped Alkaline Earth Sulphides (AES), BAFX:EU{sup 2+} (X = Cl, Br, I) and halogen alkaline have been studied (crystalline form, synthesis techniques, influence of dopants and color centers). Their characteristics are presented and extensively discussed. A specific experimental set-up to characterise various OSL phosphors has been developed. It allows the study of sensitivity, linearity, time decay behaviour of OSL signal and zeroing time. A joint study of OSL and TL has shown the technical limitations as well as the thermal fading and the origin of the long zeroing time. An Optical Fiber Sensor (OFS) based on OSL and using MgS:Sm has been developed for practical applications on nuclear fields. Its specifications are presented and discussed, moreover improvements are proposed. (author) 320 refs.

Novel cookie-with-chocolate carbon dots displaying extremely acidophilic high luminescence

Science.gov (United States)

Lu, Siyu; Zhao, Xiaohuan; Zhu, Shoujun; Song, Yubin; Yang, Bai

2014-10-01

A fluorescent carbon dot with a cookie-with-chocolate film structure (about 5 × 5 μm2) showed a high fluorescence quantum yield (61.12%) at low pH. It was hydrothermally synthesized from l-serine and l-tryptophan. The formation mechanism of the film with carbon dots (CDs) was investigated. The film structure was formed by hydrogen bonding and π-π stacking interactions between aromatic rings. The strong blue fluorescence of the CDs increased under strong acidic conditions owing to the changes in the N-groups. These cookie-like CDs are attractive for their potential use as effective fluorescent probes for the sensitive detection of aqueous H+ and Fe3+.A fluorescent carbon dot with a cookie-with-chocolate film structure (about 5 × 5 μm2) showed a high fluorescence quantum yield (61.12%) at low pH. It was hydrothermally synthesized from l-serine and l-tryptophan. The formation mechanism of the film with carbon dots (CDs) was investigated. The film structure was formed by hydrogen bonding and π-π stacking interactions between aromatic rings. The strong blue fluorescence of the CDs increased under strong acidic conditions owing to the changes in the N-groups. These cookie-like CDs are attractive for their potential use as effective fluorescent probes for the sensitive detection of aqueous H+ and Fe3+. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03965c

Room-temperature light-emission from Ge quantum dots in photonic crystals

Energy Technology Data Exchange (ETDEWEB)

Xia Jinsong [Advanced Research Laboratories, Musashi Institute of Technolgy, 8-15-1 Todoroki, Setagaya-ku, Tokyo 158-0082 (Japan)], E-mail: jxia@sc.musashi-tech.ac.jp; Nemoto, Koudai; Ikegami, Yuta [Advanced Research Laboratories, Musashi Institute of Technolgy, 8-15-1 Todoroki, Setagaya-ku, Tokyo 158-0082 (Japan); Usami, Noritaka [Institute of Materials Research, Tohoku University, 2-2-1 Katahira, Aoba-ku, Sendai Japan (Japan)], E-mail: usa@imr.tohoku.ac.jp; Nakata, Yasushi [Horiba, Ltd., 1-7-8 Higashi-Kanda, Chiyoda-ku, Tokyo 101-0031 (Japan)], E-mail: yasushi.nakata@horiba.com; Shiraki, Yasuhiro [Advanced Research Laboratories, Musashi Institute of Technolgy, 8-15-1 Todoroki, Setagaya-ku, Tokyo 158-0082 (Japan)

2008-11-03

Multiple layers of Ge self-assembled quantum dots were embedded into two-dimensional silicon photonic crystal microcavities fabricated on silicon-on-insulator substrates. Microphotoluminescence was used to study the light-emission characteristic of the Ge quantum dots in the microcavities. Strong resonant room-temperature light-emission was observed in the telecommunication wavelength region. Significant enhancement of the luminescence from Ge dots was obtained due to the resonance in the cavities. Multiple sharp resonant peaks dominated the spectrum, showing strong optical resonance inside the cavity. By changing the lattice constant of photonic crystal structure, the wavelengths of the resonant peaks are tuned in the wide wavelength range from 1.2 to 1.6 {mu}m.

Tailoring surface groups of carbon quantum dots to improve photoluminescence behaviors

International Nuclear Information System (INIS)

Tian, Ruixue; Hu, Shengliang; Wu, Lingling; Chang, Qing; Yang, Jinlong; Liu, Jun

2014-01-01

Highlights: • We develop a facile and green method to tailor surface groups. • Photoluminescence behaviors of carbon quantum dots are improved by tailoring their surface groups. • Highly luminescent efficiency is produced by amino-hydrothermal treatment of reduced carbon quantum dots. - Abstract: A facile and green method to tailor surface groups of carbon quantum dots (CQDs) is developed by hydrothermal treatment in an autoclave. The photoluminescence (PL) behaviors of CQDs depend on the types of surface groups. Highly efficient photoluminescence is obtained through amino-hydrothermal treatment of the CQDs reduced by NaBH 4 . The effects of surface groups on PL behavior are attributed to the degrees of energy band bending induced by surface groups

Luminescence dating in archaeology

International Nuclear Information System (INIS)

Wintle, A.G.

2001-01-01

Thermoluminescence (TL) dating is routinely applied to burnt lithic material. Simple fires are capable of enabling stones weighing a few hundred grams to reach 450 o C, thus zeroing the TL signal. TL dates have been obtained for Upper and Lower Paleolithic sites in Europe and the Near East. TL dating continues to be used for dating pottery and for authentification of ceramic works of art. Some recent studies report the use of optically stimulated luminescence (OSL) (also know as photoluminescence) for dating very small samples of quartz, e.g. from small pieces of pottery or frm metallurgical slag The major recent advance has been in the development of a reliable laboratory procedure for using the OSL signal from quartz to obtain the past radiation exposure. The quartz OSL signal is extremely sensitive to light and is reduced to a negligible level on exposure to direct sunlight for radionuclides during burial, signal to date san.sized quartz grains extracted from sediments, The OSL signal is stimulated by 470 nm light from emitting diodes and the detected using flirters centred on 340 nm A similar signal can be obtained from feldspar grain when are exposed to infrared wavelengths around 880 nm. The infrared stimulated luminescence (IRSL) signals is also rapidly depleted by exposure to sunlight, and dating of colluvial deposits from archaeological sites has been reported

Dosimetry in the multi kilo-Gray range using optically-stimulated luminescence (OSL) and thermally-transferred OSL from quartz

International Nuclear Information System (INIS)

Burbidge, C.I.; Cabo Verde, S.I.; Fernandes, A.C.; Prudencio, M.I.; Botelho, M.L.; Dias, M.I.; Cardoso, G.

2011-01-01

This study explores the potential for using photon-stimulated luminescence of quartz grains to retrospectively evaluate multi-kGy gamma radiation doses. Subsamples from two ceramic tiles were given 60 Co gamma doses of 1, 3, 5, 15 and 30 kGy (nominal), accompanied by PMMA dosimeters and quartz grains from a geological sample known to exhibit thermally-transferred optically-stimulated luminescence (TTOSL). Following gamma irradiation, quartz grains were prepared from each subsample. OSL and TTOSL signals were measured for different preheat temperatures, and following re-irradiation with beta doses designed to equal the nominal gamma doses. OSL responses to 10 Gy beta test doses were measured following each cycle of high dose irradiation. Gamma doses were predicted from the beta responses, to evaluate the effectiveness of retrospective dose evaluation for different signal integrals, preheat combinations, and dose intervals. The use of linear modulation limited maximum OSL signal levels to 1.5 x 10 6 cps without reducing detector sensitivity, for the measurement of smaller TTOSL signals. The dosimetric behaviour of the three samples differed significantly: the best results were obtained from the pre-prepared geological quartz. OSL signals evident at short stimulation times, which are conventionally used for dosimetry and dating, did not in general appear appropriate for dosimetry in the range of doses examined. They exhibited dose response characteristics that were highly preheat dependant and variable in form between samples, which contained rapidly saturating and/or non-monotonic components. Higher preheats, up to 300 o C, preferentially removed OSL and TTOSL signals evident at longer stimulation times: those that remained yielded growth in signal with dose to approximately 10 kGy, but the accuracy of retrospective dose determinations was variable. TTOSL signals evident at short stimulation times increased proportionally with dose when 300 o C preheats were used, up

Performance of CVD diamond as an optically and thermally stimulated luminescence dosemeter

International Nuclear Information System (INIS)

Preciado-Flores, S.; Schreck, M.; Melendrez, R.; Chernov, V.; Bernal, R.; Cruz-Vazquez, C.; Cruz-Zaragoza, E.; Barboza-Flores, M.

2006-01-01

Diamond is a material with extreme physical properties. Its radiation hardness, chemical inertness and tissue equivalence qualify it as an ideal material for radiation dosimetry. In the present work, the optically stimulated luminescence (OSL) and thermoluminescence (TL) characteristics of a 10 μm thick CVD diamond (polycrystalline diamond films prepared by chemical vapor deposition) film were studied in order to test its performance as a beta radiation dosemeter. The TL response is composed of four main TL glow peaks; two of these are in the range of 150-200 deg. C and two additional peaks in the 250-400 deg. C temperature range. The integrated TL as a function of radiation dose is linear up to 100 Gy and increases with increasing dose exposure. The dose dependence of the integrated OSL exhibits a similar behavior. The observed OSL/TL behavior for the CVD diamond film clearly demonstrate its capability for applications in radiation dosimetry with special relevance in medical dosimetry owing to the diamond's intrinsic material properties. (authors)

Luminescence in Sulfides: A Rich History and a Bright Future

Directory of Open Access Journals (Sweden)

Philippe F. Smet

2010-04-01

Full Text Available Sulfide-based luminescent materials have attracted a lot of attention for a wide range of photo-, cathodo- and electroluminescent applications. Upon doping with Ce3+ and Eu2+, the luminescence can be varied over the entire visible region by appropriately choosing the composition of the sulfide host. Main application areas are flat panel displays based on thin film electroluminescence, field emission displays and ZnS-based powder electroluminescence for backlights. For these applications, special attention is given to BaAl2S4:Eu, ZnS:Mn and ZnS:Cu. Recently, sulfide materials have regained interest due to their ability (in contrast to oxide materials to provide a broad band, Eu2+-based red emission for use as a color conversion material in white-light emitting diodes (LEDs. The potential application of rare-earth doped binary alkaline-earth sulfides, like CaS and SrS, thiogallates, thioaluminates and thiosilicates as conversion phosphors is discussed. Finally, this review concludes with the size-dependent luminescence in intrinsic colloidal quantum dots like PbS and CdS, and with the luminescence in doped nanoparticles.

Thermal quenching of luminescence processes in feldspars

DEFF Research Database (Denmark)

Poolton, N.R.J.; Bøtter-Jensen, L.; Duller, G.A.T.

1995-01-01

, which display very different behaviour. The first involves the internal transitions of common transition metal ions. The second is typical of centres not displaying excited states within the band gap that are likely to arise from direct recombination between the conduction band and the ground state......The technique of optically stimulated luminescence has important uses in the dose evaluation of irradiated feldspars. The luminescence process involves the eviction of electrons from donor traps, charge transfer through the conduction band, and recombination at acceptor sites; each...

Paper-based biodetection using luminescent nanoparticles.

Science.gov (United States)

Ju, Qiang; Noor, M Omair; Krull, Ulrich J

2016-05-10

Point-of-care and in-field technologies for rapid, sensitive and selective detection of molecular biomarkers have attracted much interest. Rugged bioassay technology capable of fast detection of markers for pathogens and genetic diseases would in particular impact the quality of health care in the developing world, but would also make possible more extensive screening in developed countries to tackle problems such as those associated with water and food quality, and tracking of infectious organisms in hospitals and clinics. Literature trends indicate an increasing interest in the use of nanomaterials, and in particular luminescent nanoparticles, for assay development. These materials may offer attributes for development of assays and sensors that could achieve improvements in analytical figures of merit, and provide practical advantages in sensitivity and stability. There is opportunity for cost-efficiency and technical simplicity by implementation of luminescent nanomaterials as the basis for transduction technology, when combined with the use of paper substrates, and the ubiquitous availability of cell phone cameras and associated infrastructure for optical detection and transmission of results. Luminescent nanoparticles have been described for a broad range of bioanalytical targets including small molecules, oligonucleotides, peptides, proteins, saccharides and whole cells (e.g., cancer diagnostics). The luminescent nanomaterials that are described herein for paper-based bioassays include metal nanoparticles, quantum dots and lanthanide-doped nanocrystals. These nanomaterials often have broad and strong absorption and narrow emission bands that improve opportunity for multiplexed analysis, and can be designed to provide emission at wavelengths that are efficiently processed by conventional digital cameras. Luminescent nanoparticles can be embedded in paper substrates that are designed to direct fluid flow, and the resulting combination of technologies can offer

A study on the real-time radiation dosimetry measurement system based on optically stimulated luminescence

International Nuclear Information System (INIS)

Liu Yanping; Du Yanzhao; Chen Zhaoyang; Ba Weizhen; Fan Yanwei; Pan Shilie; Guo Qi

2008-01-01

The optically stimulated luminescent (OSL) radiation dosimeter technically surveys a wide dynamic measurement range and a high sensitivity. Optical fiber dosimeters provide capability for remote monitoring of the radiation in the locations which are difficult-to-access and hazardous. In addition, optical fiber dosimeters are immune to electrical and radio-frequency interference. In this paper, a novel remote optical fiber radiation dosimeter is described. The optical fiber dosimeter takes advantage of the charge trapping materials CaS:Ce, Sm that exhibit OSL. The measuring range of the dosimeter is from 0.1 to 100 Gy. The equipment is relatively simple and small in size, and has low power consumption. This device is suitable for measuring the space radiation dose and also can be used in high radiation dose condition and other dangerous radiation occasions. (authors)

A portable luminescence dating instrument

DEFF Research Database (Denmark)

Kook, M.H.; Murray, A.S.; Lapp, Torben

2011-01-01

We describe a portable luminescence reader suitable for use in remote localities in the field. The instrument weighs about 8kg and is based around a 30mm bialkali photomultiplier detecting signals through a glass filter centered on 340nm. Stimulation is by 470nm blue LEDs (24W in total) operating...

Fabrication of CdSe quantum dots/permutite luminescent materials

Indian Academy of Sciences (India)

Administrator

tosuccinic acid-capped CdSe quantum dots (QDs) were prepared in aqueous solution by using SeO2 as selenium source and NaBH4 as reductant. Secondly, the commercial permutite was treated with acetic acid to induce a partial dealumnization, which can introduce a large number of intracrystal mesopores, and the.

Photoluminescence, reddish orange long persistent luminescence and photostimulated luminescence properties of praseodymium doped CdGeO3 phosphor

International Nuclear Information System (INIS)

Jin, Yahong; Hu, Yihua; Chen, Li; Fu, Yinrong; Mu, Zhongfei; Wang, Tao; Lin, Jun

2014-01-01

Highlights: • A novel phosphor CdGeO 3 :Pr 3+ was synthesized successfully. • The persistent luminescence properties of CdGeO 3 :Pr 3+ were studied. • The photostimulated luminescence properties of CdGeO 3 :Pr 3+ were investigated. • The persistent and photostimulated luminescence mechanisms were discussed in detail. - Abstract: Praseodymium doped CdGeO 3 phosphors were prepared successfully by a conventional high temperature solid-state reaction method. It showed reddish orange long persistent luminescence (LPL) after the short UV-irradiation. The reddish orange photostimulated luminescence (PSL) was also observed upon near infrared stimulation at 980 nm after per-exposure into UV light. The origin of LPL and PSL was identified with the emission from Pr 3+ ions with the aid of traps in host lattice. The optimal concentration of Pr 3+ ions for the brightest photoluminescence (PL) emission and the best LPL characteristic were experimentally to be about 3% and 0.5 mol%, respectively. The trapping and de-trapping processes of charge carriers between shallower and deep traps were illustrated. A model was proposed on the basis of experimental results to study the mechanisms of LPL and PSL

Remote auditing of radiotherapy facilities using optically stimulated luminescence dosimeters

Energy Technology Data Exchange (ETDEWEB)

Lye, Jessica, E-mail: jessica.lye@arpansa.gov.au; Dunn, Leon; Kenny, John; Alves, Andrew [Australian Clinical Dosimetry Service, Yallambie, Victoria 3085 (Australia); Lehmann, Joerg; Williams, Ivan [Australian Clinical Dosimetry Service, Yallambie, Victoria 3085, Australia and School of Applied Science, RMIT University, Melbourne 3000 (Australia); Kron, Tomas [School of Applied Science, RMIT University, Melbourne 3000, Australia and Peter MacCallum Cancer Centre, Melbourne 3008 (Australia); Oliver, Chris; Butler, Duncan; Johnston, Peter [Australian Radiation Protection and Nuclear Safety Agency, Yallambie, Victoria 3085 (Australia); Franich, Rick [School of Applied Science, RMIT University, Melbourne 3000 (Australia)

2014-03-15

Purpose: On 1 July 2012, the Australian Clinical Dosimetry Service (ACDS) released its Optically Stimulated Luminescent Dosimeter (OSLD) Level I audit, replacing the previous TLD based audit. The aim of this work is to present the results from this new service and the complete uncertainty analysis on which the audit tolerances are based. Methods: The audit release was preceded by a rigorous evaluation of the InLight® nanoDot OSLD system from Landauer (Landauer, Inc., Glenwood, IL). Energy dependence, signal fading from multiple irradiations, batch variation, reader variation, and dose response factors were identified and quantified for each individual OSLD. The detectors are mailed to the facility in small PMMA blocks, based on the design of the existing Radiological Physics Centre audit. Modeling and measurement were used to determine a factor that could convert the dose measured in the PMMA block, to dose in water for the facility's reference conditions. This factor is dependent on the beam spectrum. The TPR{sub 20,10} was used as the beam quality index to determine the specific block factor for a beam being audited. The audit tolerance was defined using a rigorous uncertainty calculation. The audit outcome is then determined using a scientifically based two tiered action level approach. Audit outcomes within two standard deviations were defined as Pass (Optimal Level), within three standard deviations as Pass (Action Level), and outside of three standard deviations the outcome is Fail (Out of Tolerance). Results: To-date the ACDS has audited 108 photon beams with TLD and 162 photon beams with OSLD. The TLD audit results had an average deviation from ACDS of 0.0% and a standard deviation of 1.8%. The OSLD audit results had an average deviation of −0.2% and a standard deviation of 1.4%. The relative combined standard uncertainty was calculated to be 1.3% (1σ). Pass (Optimal Level) was reduced to ≤2.6% (2σ), and Fail (Out of Tolerance) was reduced to >3

Spatially controlled fabrication of a bright fluorescent nanodiamond-array with enhanced far-red Si-V luminescence.

Science.gov (United States)

Singh, Sonal; Thomas, Vinoy; Martyshkin, Dmitry; Kozlovskaya, Veronika; Kharlampieva, Eugenia; Catledge, Shane A

2014-01-31

We demonstrate a novel approach to precisely pattern fluorescent nanodiamond-arrays with enhanced far-red intense photostable luminescence from silicon-vacancy (Si-V) defect centers. The precision-patterned pre-growth seeding of nanodiamonds is achieved by a scanning probe 'dip-pen' nanolithography technique using electrostatically driven transfer of nanodiamonds from 'inked' cantilevers to a UV-treated hydrophilic SiO2 substrate. The enhanced emission from nanodiamond dots in the far-red is achieved by incorporating Si-V defect centers in a subsequent chemical vapor deposition treatment. The development of a suitable nanodiamond ink and mechanism of ink transport, and the effect of humidity and dwell time on nanodiamond patterning are investigated. The precision patterning of as-printed (pre-CVD) arrays with dot diameter and dot height as small as 735 nm ± 27 nm and 61 nm ± 3 nm, respectively, and CVD-treated fluorescent ND-arrays with consistently patterned dots having diameter and height as small as 820 nm ± 20 nm and, 245 nm ± 23 nm, respectively, using 1 s dwell time and 30% RH is successfully achieved. We anticipate that the far-red intense photostable luminescence (~738 nm) observed from Si-V defect centers integrated in spatially arranged nanodiamonds could be beneficial for the development of next generation fluorescence-based devices and applications.

High luminescent L-cysteine capped CdTe quantum dots prepared at different reaction times

Science.gov (United States)

Kiprotich, Sharon; Onani, Martin O.; Dejene, Francis B.

2018-04-01

This paper reports a facile synthesis route of high luminescent L-cysteine capped CdTe quantum dots (QDs). The effect of reaction time on the growth mechanism, optical and physical properties of the CdTe QDs was investigated in order to find the suitability of them towards optical and medical applications. The representative high-resolution transmission microscopy (HRTEM) analysis showed that the as-obtained CdTe QDs appeared as spherical particles with excellent monodispersity. The images exhibited clear lattice fringes which are indicative of good crystallinity. The X-ray diffraction (XRD) pattern displayed polycrystalline nature of the QDs which correspond well to zinc blende phase of bulk CdTe. The crystallite sizes calculated from the Scherrer equation were less than 10 nm for different reaction times which were in close agreement with the values estimated from HRTEM. An increase in reaction time improved crystallinity of the sample as explained by highest peak intensity of the XRD supported by the photoluminescence emission spectra which showed high intensity at a longer growth time. It was observed that for prolonged growth time the emission bands were red shifted from about 517-557 nm for 5-180 min of reaction time due to increase in particle sizes. Ultraviolet and visible analysis displayed well-resolved absorption bands which were red shifted upon an increase in reaction time. There was an inverse relation between the band gap and reaction time. Optical band gap decreases from 3.98 to 2.59 eV with the increase in reaction time from 15 to 180 min.

Crystal structure, intensity luminescence characteristics and stimulated radiation of disordered gallate LaSr2Ga11O20-Nd3+

International Nuclear Information System (INIS)

Kaminskij, A.A.; Mill', B.V.; Belokoneva, E.L.; Butashin, A.V.; Sarkisov, S.Eh.; Kurbanov, K.; Khodzhabagyan, G.G.

1986-01-01

LnA 2 2+ Ga 11 O 20 and A 3 2+ M 0.5 5+ Ga 10.5 O 20 compounds are synthesized, LaSr 2 Ga 11 O 20 and LaSr 2 Ga 11 O 20 -Nd 3+ monocrystals are grown by Czochralski method. Their X-ray diffraction analysis is conducted, absorption - luminescence characteristics are obtained, stimulated Nd 3+ ion radiation is excited and investigated in two generating channel waves 4 F 3/2 → 4 I 11/2,13/2 at 300 K

High-temperature peaks of thermostimulated luminescence in the ammonium halogens

International Nuclear Information System (INIS)

Kim, L.M.; Musenova, Eh.K.; Mukhamedrakhimov, K.U.

2003-01-01

The ammonium halogen crystals (AHC) are the close analogs of the alkali halogen crystals by the type of chemical bonds and crystal lattice structure. The ammonium halogen after irradiation by X-rays within 80-300 K range have two peaks of thermo-stimulation luminescence. Its maximums in dependence of anions type are in the 110-120 K and 170-180 K ranges. The first range is related with activation of auto-localized holes migration, and the second one - with the NH 3 + defects decay. Experimentally is established, that the pure ammonium halogens have memory about the previous irradiation at heating up to 300 K. After repeat irradiation the recombination luminescence high-temperature peak's shoulder is appearing. The second luminescence peak's shoulder revealing does not depend on the impurity center nature. It is known, that in the AHC there is the next thermo-stimulation luminescence peak within 340-360 K. The thermal annealing of this peak leads to the memory effect disappearance. So, the observing phenomenon is related with own defect of the matrix in the cation sublattice. Experimentally is established, that at a room temperature the AHC memorizing about previous irradiation during 20 h

Low temperature synthesis of silicon quantum dots with plasma chemistry control in dual frequency non-thermal plasmas.

Science.gov (United States)

Sahu, Bibhuti Bhusan; Yin, Yongyi; Han, Jeon Geon; Shiratani, Masaharu

2016-06-21

The advanced materials process by non-thermal plasmas with a high plasma density allows the synthesis of small-to-big sized Si quantum dots by combining low-temperature deposition with superior crystalline quality in the background of an amorphous hydrogenated silicon nitride matrix. Here, we make quantum dot thin films in a reactive mixture of ammonia/silane/hydrogen utilizing dual-frequency capacitively coupled plasmas with high atomic hydrogen and nitrogen radical densities. Systematic data analysis using different film and plasma characterization tools reveals that the quantum dots with different sizes exhibit size dependent film properties, which are sensitively dependent on plasma characteristics. These films exhibit intense photoluminescence in the visible range with violet to orange colors and with narrow to broad widths (∼0.3-0.9 eV). The observed luminescence behavior can come from the quantum confinement effect, quasi-direct band-to-band recombination, and variation of atomic hydrogen and nitrogen radicals in the film growth network. The high luminescence yields in the visible range of the spectrum and size-tunable low-temperature synthesis with plasma and radical control make these quantum dot films good candidates for light emitting applications.

Luminescence of two-dimensional ordered array of the ZnO quantum nanodots, obtained by means of the synthetic opal

International Nuclear Information System (INIS)

Gruzintsev, A.N.; Volkov, V.T.; Emelchenko, G.A.; Karpov, I.A.; Maslov, W.M.; Michailov, G.M.; Yakimov, E.E.

2004-01-01

The luminescence properties of ZnO films of different thickness obtained on a synthetic opal were investigated. Several narrow peaks in the exciton emission region related to the size quantum effect of the electron wave functions were detected. Two-dimensional ordered array of ZnO quantum dots formed inside the opal pores on the second sphere layer were found by the atomic force microscopy (AFM) and angle dependence of the luminescence spectra

Facile synthetic method for pristine graphene quantum dots and graphene oxide quantum dots: origin of blue and green luminescence.

Science.gov (United States)

Liu, Fei; Jang, Min-Ho; Ha, Hyun Dong; Kim, Je-Hyung; Cho, Yong-Hoon; Seo, Tae Seok

2013-07-19

Pristine graphene quantum dots and graphene oxide quantum dots are synthesized by chemical exfoliation from the graphite nanoparticles with high uniformity in terms of shape (circle), size (less than 4 nm), and thickness (monolayer). The origin of the blue and green photoluminescence of GQDs and GOQDs is attributed to intrinsic and extrinsic energy states, respectively. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Solvothermal synthesis of InP quantum dots and their enhanced luminescent efficiency by post-synthetic treatments.

Science.gov (United States)

Byun, Ho-June; Lee, Ju Chul; Yang, Heesun

2011-03-01

InP quantum dots (QDs) were solvothermally synthesized by using a greener phosphorus source of P(N(CH(3))(2))(3) instead of highly toxic P(TMS)(3) widely used, and subsequently subjected to a size-sorting processing. While as-grown QDs showed an undetectably low emission intensity, post-synthetic treatments such as photo-etching, photo-radiation, and photo-assisted ZnS shell coating gave rise to a substantial increase in emission efficiency due to the effective removal and passivation of surface states. The emission efficiency of the photo-etched QDs was further enhanced by a consecutive UV photo-radiation, attributable to the photo-oxidation at QD surface. Furthermore, a relatively thick ZnS shell on the surface of InP QDs that were surface-modified with hydrophilic ligands beforehand was photochemically generated in an aqueous solution at room temperature. The resulting InP/ZnS core/shell QDs, emitting from blue to red wavelengths, were more efficient than the above photo-treated InP QDs, and their luminescent properties (emission bandwidth and quantum yield) were comparable to those of InP QDs synthesized with P(TMS)(3). Structural, size, and compositional analyses on InP/ZnS QDs were also conducted to elucidate their core/shell structure. Copyright © 2010 Elsevier Inc. All rights reserved.

Establishing personal dosimetry procedure using optically stimulated luminescence dosimeters in photon and mixed photon-neutron radiation fields

International Nuclear Information System (INIS)

Le Ngoc Thiem; Bui Duc Ky; Trinh Van Giap; Nguyen Huu Quyet; Ho Quang Tuan; Vu Manh Khoi; Chu Vu Long

2017-01-01

According to Vietnamese Law on Atomic Energy, personal dosimetry (PD) for radiation workers is required periodically in order to fulfil the national legal requirements on occupational radiation dose management. Since the radiation applications have become popular in Vietnamese society, the thermal luminescence dosimeters (TLDs) have been used as passive dosimeters for occupational monitoring in the nation. Together with the quick increase in radiation applications and the number of personnel working in radiation fields, the Optically Stimulated Luminescence Dosimeters (OSLDs) have been first introduced since 2015. This work presents the establishment of PD measuring procedure using OSLDs which are used for measuring photons and betas known as Inlight model 2 OSL (OSLDs-p,e) and for measuring mixed radiations of neutrons, photons and betas known as Inlight LDR model 2 (OSLDs-n,p,e). Such following features of OSLDs are investigated: detection limit, energy response, linearity, reproducibility, angular dependency and fading with both types of OSLDs-p,e and OSLDs-n,p,e. The result of an intercomparison in PD using OSLDs is also presented in the work. The research work also indicates that OSL dosimetry can be an alternative method applied in PD and possibly become one of the most popular personal dosimetry method in the future. (author)

Two optically active molybdenum disulfide quantum dots as tetracycline sensors

Energy Technology Data Exchange (ETDEWEB)

Wang, Zhuosen; Lin, Jintai [School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China); Gao, Jinwei [Institute for Advanced Materials, Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006 (China); Wang, Qianming, E-mail: qmwang@scnu.edu.cn [Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education, School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China); School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China); Guangzhou Key Laboratory of Materials for Energy Conversion and Storage, 510006 (China)

2016-08-01

In this work, we use the hydrothermal method to develop two luminescent MoS{sub 2} quantum dots (QDs) from L-cysteine and glutathione as sulfur precursors. The special blue emissions give rise to an instantaneous determination of tetracycline (TC) through the quenching of its luminescence. The accessibility of the optical materials and recognition mechanism have been extensively studied. This strategy demonstrated that MoS{sub 2} could act as a new platform for anchoring bioactive species or particular functional moieties. - Highlights: • MoS{sub 2} nanostructures with water solubility have been fabricated. • Blue emission has been achieved. • It displays selective detection to tetracyclines in water.

Dipole-Dipole Electron Excitation Energy Transfer in the System CdSe/ZnS Quantum Dot - Eosin in Butyral Resin Matrix

Science.gov (United States)

Myslitskaya, N. A.; Samusev, I. G.; Bryukhanov, V. V.

2014-11-01

The electron excitation energy transfer from CdSe/ZnS quantum dots to eosin molecules in the polymer matrix of butyral resin is investigated. The main characteristics of energy transfer are determined. By means of luminescence microscopy and correlation spectroscopy methods we found that quantum dots in the polymer are in an aggregate state.

A polymeric dosimeter film based on optically-stimulated luminescence for dose measurements below 1 kGy

International Nuclear Information System (INIS)

Kovacs, A.; Baranyai, M.; Wojnarovits, L.; Slezsak, I.; McLaughlin, W.L.; Miller, S.D.; Miller, A.; Fuochi, P.G.; Lavalle, M.

1999-01-01

A new potential dosimetry system 'Sunna' containing a microcrystalline dispersion of an optically-stimulated fluor in a plastic matrix has been recently developed to measure and image high doses. Our previous investigations have revealed that the new dosimeter system is capable of measuring absorbed doses in the dose range of 1-100 kGy. The optically-stimulated luminescence (OSL) analysis is based on the blue light stimulation of the colour center states produced upon irradiation, and the intensity of the resulting red-light emission is used to measure absorbed dose. This analysis is carried out with a simple table-top fluorimeter developed for this purpose having also the ability to calculate the mathematical formula of the calibration function. The Sunna dosimeter was recently investigated for potential use in lower dose range below 1 kGy. These investigations have shown that the film is suitable for measuring doses in the range of 1-1000 Gy for both electron and gamma radiation. To test the applicability of the film, its reproducibility, stability, sensitivity to ambient and UV light and irradiation temperature were measured. The stability of the dosimeter was investigated by monitoring the change of the OSL signal with storage time after irradiation. Further experiments proved the homogeneity of the film with respect to thickness variation, and limited differences in its response were found between batches. (author)

EXPERIMENTAL STUDY OF 3D SELF-ASSEMBLED PHOTONIC CRYSTALS AND COLLOIDAL CORE-SHELL SEMICONDUCTOR QUANTUM DOTS

Directory of Open Access Journals (Sweden)

Pham Thu Nga

2017-11-01

Full Text Available In this contribution we present an experimental study of 3D opal photonic crystals. The samples are opals constituted by colloidal silica spheres, realized with self-assembly technique. The sphere diameter is selected in order to obtain coupling of the photonic band gap with the emission from CdSe/ZnS colloidal quantum dots. The quantum dots infiltrated in the opals is expected to be enhanced or suppressed depending on the detection angle from the photonic crystal. The structural and optical characterization of the SiO2 opal photonic crystals are performed by field-emission scanning electron microscopy and reflectivity spectroscopy. Measurements performed on samples permits to put into evidence the influence of the different preparation methods on the optical properties. Study of self-activated luminescence of the pure opals is also presented. It is shown that the luminescence of the sample with QDs have original QD emission and not due to the photonic crystal structure. The optical properties of colloidal core-shell semiconductor quantum dots of CdSe/ZnS which are prepared in our lab will be mention.

Emergency dose estimation using optically stimulated luminescence from human tooth enamel

International Nuclear Information System (INIS)

Sholom, S.; DeWitt, R.; Simon, S.L.; Bouville, A.; McKeever, S.W.S.

2011-01-01

Human teeth were studied for potential use as emergency Optically Stimulated Luminescence (OSL) dosimeters. By using multiple-teeth samples in combination with a custom-built sensitive OSL reader, 60 Co-equivalent doses below 0.64 Gy were measured immediately after exposure with the lowest value being 27 mGy for the most sensitive sample. The variability of OSL sensitivity, from individual to individual using multiple-teeth samples, was determined to be 53%. X-ray and beta exposure were found to produce OSL curves with the same shape that differed from those due to ultraviolet (UV) exposure; as a result, correlation was observed between OSL signals after X-ray and beta exposure and was absent if compared to OSL signals after UV exposure. Fading of the OSL signal was 'typical' for most teeth with just a few of incisors showing atypical behavior. Typical fading dependences were described by a bi-exponential decay function with 'fast' (decay time around of 12 min) and 'slow' (decay time about 14 h) components. OSL detection limits, based on the techniques developed to-date, were found to be satisfactory from the point of view of medical triage requirements if conducted within 24 h of the exposure.

Emergency dose estimation using optically stimulated luminescence from human tooth enamel

Energy Technology Data Exchange (ETDEWEB)

Sholom, S., E-mail: sergey.sholom@okstate.edu [Oklahoma State University, Stillwater, OK (United States); DeWitt, R. [Oklahoma State University, Stillwater, OK (United States); Simon, S.L.; Bouville, A. [National Cancer Institute, National Institutes of Health, Bethesda, MD (United States); McKeever, S.W.S. [Oklahoma State University, Stillwater, OK (United States)

2011-09-15

Human teeth were studied for potential use as emergency Optically Stimulated Luminescence (OSL) dosimeters. By using multiple-teeth samples in combination with a custom-built sensitive OSL reader, {sup 60}Co-equivalent doses below 0.64 Gy were measured immediately after exposure with the lowest value being 27 mGy for the most sensitive sample. The variability of OSL sensitivity, from individual to individual using multiple-teeth samples, was determined to be 53%. X-ray and beta exposure were found to produce OSL curves with the same shape that differed from those due to ultraviolet (UV) exposure; as a result, correlation was observed between OSL signals after X-ray and beta exposure and was absent if compared to OSL signals after UV exposure. Fading of the OSL signal was 'typical' for most teeth with just a few of incisors showing atypical behavior. Typical fading dependences were described by a bi-exponential decay function with 'fast' (decay time around of 12 min) and 'slow' (decay time about 14 h) components. OSL detection limits, based on the techniques developed to-date, were found to be satisfactory from the point of view of medical triage requirements if conducted within 24 h of the exposure.

Dating Last Interglacial Coastal Systems Using New Feldspar Luminescence Technologies

Science.gov (United States)

Lamothe, M.

2017-12-01

The recent explosion in new luminescence dating technologies offers new opportunities to explore Quaternary marine coastal facies and landforms. However, tectonic and climatic processes controlling the development of Pleistocene coastal lithosomes are commonly obscured by their poorly constrained geological age. Luminescence dating of feldspar probes one order of magnitude deeper into geological time than radiocarbon and more than 5 times the current age range of quartz optically-stimulated luminescence, routinely used in luminescence dating. However, feldspar luminescence stimulated by infrared photons (eg IRSL) is hampered by anomalous fading. Successful correction methods developed by us over the last 15 years did produce sound chronologies but the fading-corrected ages carried large uncertainties. New approaches initiated by other laboratories, mainly in Europe, have isolated high temperature post-IRSL luminescence as this signal seems to be only slightly affected by fading. However, the gain in stability seems to be lessened due to bleachibility issues, generating age overestimations. We developed a novel protocol known as post-isothermal IRSL dating (Pit-IR) that focuses on a dual system of luminescence signals, probing low (50C) and medium (225C) temperature IRSL signals following isothermal treatments of various intensities. These protocols have been tested on Last interglacial coastal sediments in strikingly different GIA contexts along the Atlantic coastal areas of SE USA as well as from Morocco, Brazil and LIG sites in the Mediterranean basin. A systematic analysis of these results would suggest that a) falling-stages sequences are more commonly preserved as the OSL/IRSL ages are preferentially dating from the end of the MIS5e high stand and b) MIS5a marine sediments may be detectable away from areas generally thought to be affected by peripheral bulge collapse.

Nonradiative recombination in GaN quantum dots formed in the AlN matrix

International Nuclear Information System (INIS)

Aleksandrov, I. A.; Zhuravlev, K. S.; Mansurov, V. G.

2009-01-01

The mechanisms of temperature quenching of steady-state photoluminescence are studied for structures with hexagonal GaN quantum dots embedded in the AlN matrix. The structures are grown by molecular beam epitaxy. The study is conducted for structures with differently sized quantum dots, for which the peak of the photoluminescence band is in the range from 2.5 to 4.0 eV. It is found that the activation energy of thermal quenching of photoluminescence varies from 27 to 110 meV, as the quantum-dot height is decreased from 5 to 2 nm. A model is suggested to interpret the results. According to the model, the photo-luminescence signal is quenched because of the transfer of charge carriers from energy levels in the quantum dots to defect levels in the matrix.

Poly(ethylene glycol)/carbon quantum dot composite solid films exhibiting intense and tunable blue–red emission

International Nuclear Information System (INIS)

Hao, Yanling; Gan, Zhixing; Xu, Jiaqing; Wu, Xinglong; Chu, Paul K.

2014-01-01

Highlights: • Poly(ethylene glycol)/carbon quantum dots (PEG/CQDs) composite solid films exhibiting strong and tunable blue–red emission were prepared. Successful preparation of tunable emitting CQDs solid films can extend the application of carbon quantum dots in photoelectric devices. • The mechanism of the tunable emission from the PEG/CQDs composite solid films was discussed. • On the basis of the characteristics of the PL from solid films in this work, the complex PL origins of CQDs were further defined. The PL mechanism provides insights into the fluorescence mechanism of CQDs and may promotes their applications. • Poly(ethylene glycol); carbon quantum dots; Strong and tunable blue-red emission; The fluorescent quantum yield of 12.6%. - Abstract: Although carbon quantum dots (CQDs) possess excellent luminescence properties, it is a challenge to apply water-soluble CQDs to tunable luminescent devices. Herein, quaternary CQDs are incorporated into poly(ethylene glycol) to produce poly(ethylene glycol)/CQD composite solid films which exhibit strong and tunable blue–red emission. The fluorescent quantum yield reaches 12.6% which is comparable to that of many liquid CQDs and the photoluminescence characteristics are determined to elucidate the fluorescence mechanism. The CQD solid films with tunable optical properties bode well for photoelectric devices especially displays

Green synthesis of biocompatible carbon dots using aqueous extract of Trapa bispinosa peel

Energy Technology Data Exchange (ETDEWEB)

Mewada, Ashmi; Pandey, Sunil, E-mail: gurus.spandey@gmail.com; Shinde, Sachin; Mishra, Neeraj; Oza, Goldie; Thakur, Mukeshchand; Sharon, Maheshwar; Sharon, Madhuri, E-mail: sharonmadhuri@gmail.com

2013-07-01

We are reporting highly economical plant based method for the production of luminescent water soluble carbon dots (C-dot) using Indian water plant Trapa bispinosa peel extract without adding any external oxidizing agent at 90 °C. C-dots ranging from 5 to 10 nm were found in the solution with a prominent green fluorescence under UV-light (λ{sub ex} = 365 nm). UV–vis spectra recorded at different time intervals (30–120 min) displayed signature absorption of C-dots between 400 and 600 nm. Fluorescence spectra of the dispersion after 120 min of synthesis exhibited characteristic emission peaks of C-dots when excited at 350, 400, 450 and 500 nm. C-dots were further analyzed using X-ray diffraction (XRD), Raman Spectroscopy and Thermo-Gravimetric Analysis (TGA). Structure of the C-dots was found to be turbostratic when studied using XRD. C-dots synthesized by our method were found to be exceptionally biocompatible against MDCK cells. Highlights: • Novel report on biosynthesis of water soluble carbon dots using plant source • Prominent green fluorescence under UV light • Highly biocompatible nanoparticles against MDCK cells • Excellent imaging properties under fluorescent light.

AgesGalore-A software program for evaluating spatially resolved luminescence data

International Nuclear Information System (INIS)

Greilich, S.; Harney, H.-L.; Woda, C.; Wagner, G.A.

2006-01-01

Low-light luminescence is usually recorded by photomultiplier tubes (PMTs) yielding integrated photon-number data. Highly sensitive CCD (charged coupled device) detectors allow for the spatially resolved recording of luminescence. The resulting two-dimensional images require suitable software for data processing. We present a recently developed software program specially designed for equivalent-dose evaluation in the framework of optically stimulated luminescence (OSL) dating. The software is capable of appropriate CCD data handling, parameter estimation using a Bayesian approach, and the pixel-wise fitting of functions for time and dose dependencies to the luminescence signal. The results of the fitting procedure and the equivalent-dose evaluation can be presented and analyzed both as spatial and as frequency distributions

Detection irradiated shallot (Allium Cepa) and spices using technique of Photo Stimulated Luminescence (PSL)

International Nuclear Information System (INIS)

Noor Azianti Abd Rashid

2012-01-01

This study was carried out to investigate the effectiveness of Photo Stimulated Luminescence (PSL) in detecting the food that has been irradiated qualitatively and quantitatively. The samples used were onions (Allium Cepa) and spices. The shallots which are from India and Thailand was irradiated using Gamma Cell at dose of 0 kGy, 0.2 kGy, 0.4 kGy and 1.0. While for the spices, there were 10 types of spices used such as powder of paprika, parsley, turmeric, tarragon, coriander, mint leaves, basil, rosemary flower, chives and herbs mixture which was irradiated at the dose of 0 kGy and 8.7 kGy respectively. The result shows that the PSL method could differentiate samples which are irradiated and not irradiated. Even though the PSL value increases proportionally to the radiation dose, the relationship between these two means are not that clearly clarified and needed to be studied furthermore.(author)

Recombination luminescence from H centers and conversion of H centers into I centers in alkali iodides

International Nuclear Information System (INIS)

Berzina, B.J.

1981-01-01

The study is aimed at the search for H-plus-electron centers of luminescence and the investigation of the conversion of H- into I centers by the luminescence of H-plus-electron centers in alkali iodide crystals. KI, RbI and NaI crystals were studied at 12 K. H and F centers were created by irradiation with ultraviolet light corresponding to the absorption band of anion excitons. Then the excitation of electron centers by red light irradiation was followed. The spectra of stimulated recombination luminescence were studied. The luminescence of H-plus- electron centers had been observed and the conclusion was made that this center was formed on immobile H centers. In case of stable H centers the optically stimulated conversion of H centers into I centers occurs. The assumption is advanced on the spontaneous annihilation of near placed unstable F, H centers which leads to the creation of H-plus-electron luminescence centers and to the spontaneous H-I-centers conversion [ru

Quantum Dot/Liquid Crystal Nanocomposites in Photonic Devices

Directory of Open Access Journals (Sweden)

Andrea L. Rodarte

2015-07-01

Full Text Available Quantum dot/liquid crystal nano-composites are promising new materials for a variety of applications in energy harvesting, displays and photonics including the liquid crystal laser. To realize many applications, however, we need to control and stabilize nano-particle dispersion in different liquid crystal host phases and understand how the particles behave in an anisotropic fluid. An ideal system will allow for the controlled assembly of either well-defined nano-particle clusters or a uniform particle distribution. In this paper, we investigate mesogen-functionalized quantum dots for dispersion in cholesteric liquid crystal. These nanoparticles are known to assemble into dense stable packings in the nematic phase, and such structures, when localized in the liquid crystal defects, can potentially enhance the coupling between particles and a cholesteric cavity. Controlling the dispersion and assembly of quantum dots using mesogenic surface ligands, we demonstrate how resonant fluid photonic cavities can result from the co-assembly of luminescent nanoparticles in the presence of cholesteric liquid crystalline ordering.

Application of quantum dots as analytical tools in automated chemical analysis: A review

International Nuclear Information System (INIS)

Frigerio, Christian; Ribeiro, David S.M.; Rodrigues, S. Sofia M.; Abreu, Vera L.R.G.; Barbosa, João A.C.; Prior, João A.V.; Marques, Karine L.; Santos, João L.M.

2012-01-01

Highlights: ► Review on quantum dots application in automated chemical analysis. ► Automation by using flow-based techniques. ► Quantum dots in liquid chromatography and capillary electrophoresis. ► Detection by fluorescence and chemiluminescence. ► Electrochemiluminescence and radical generation. - Abstract: Colloidal semiconductor nanocrystals or quantum dots (QDs) are one of the most relevant developments in the fast-growing world of nanotechnology. Initially proposed as luminescent biological labels, they are finding new important fields of application in analytical chemistry, where their photoluminescent properties have been exploited in environmental monitoring, pharmaceutical and clinical analysis and food quality control. Despite the enormous variety of applications that have been developed, the automation of QDs-based analytical methodologies by resorting to automation tools such as continuous flow analysis and related techniques, which would allow to take advantage of particular features of the nanocrystals such as the versatile surface chemistry and ligand binding ability, the aptitude to generate reactive species, the possibility of encapsulation in different materials while retaining native luminescence providing the means for the implementation of renewable chemosensors or even the utilisation of more drastic and even stability impairing reaction conditions, is hitherto very limited. In this review, we provide insights into the analytical potential of quantum dots focusing on prospects of their utilisation in automated flow-based and flow-related approaches and the future outlook of QDs applications in chemical analysis.

Angular dependence of the nanoDot OSL dosimeter

International Nuclear Information System (INIS)

Kerns, James R.; Kry, Stephen F.; Sahoo, Narayan; Followill, David S.; Ibbott, Geoffrey S.

2011-01-01

Purpose: Optically stimulated luminescent detectors (OSLDs) are quickly gaining popularity as passive dosimeters, with applications in medicine for linac output calibration verification, brachytherapy source verification, treatment plan quality assurance, and clinical dose measurements. With such wide applications, these dosimeters must be characterized for numerous factors affecting their response. The most abundant commercial OSLD is the InLight/OSL system from Landauer, Inc. The purpose of this study was to examine the angular dependence of the nanoDot dosimeter, which is part of the InLight system. Methods: Relative dosimeter response data were taken at several angles in 6 and 18 MV photon beams, as well as a clinical proton beam. These measurements were done within a phantom at a depth beyond the build-up region. To verify the observed angular dependence, additional measurements were conducted as well as Monte Carlo simulations in MCNPX. Results: When irradiated with the incident photon beams parallel to the plane of the dosimeter, the nanoDot response was 4% lower at 6 MV and 3% lower at 18 MV than the response when irradiated with the incident beam normal to the plane of the dosimeter. Monte Carlo simulations at 6 MV showed similar results to the experimental values. Examination of the results in Monte Carlo suggests the cause as partial volume irradiation. In a clinical proton beam, no angular dependence was found. Conclusions: A nontrivial angular response of this OSLD was observed in photon beams. This factor may need to be accounted for when evaluating doses from photon beams incident from a variety of directions.

Spatially controlled fabrication of a bright fluorescent nanodiamond-array with enhanced far-red Si-V luminescence

International Nuclear Information System (INIS)

Singh, Sonal; Thomas, Vinoy; Kharlampieva, Eugenia; Catledge, Shane A; Martyshkin, Dmitry; Kozlovskaya, Veronika

2014-01-01

We demonstrate a novel approach to precisely pattern fluorescent nanodiamond-arrays with enhanced far-red intense photostable luminescence from silicon-vacancy (Si-V) defect centers. The precision-patterned pre-growth seeding of nanodiamonds is achieved by a scanning probe ‘dip-pen’ nanolithography technique using electrostatically driven transfer of nanodiamonds from ‘inked’ cantilevers to a UV-treated hydrophilic SiO 2 substrate. The enhanced emission from nanodiamond dots in the far-red is achieved by incorporating Si-V defect centers in a subsequent chemical vapor deposition treatment. The development of a suitable nanodiamond ink and mechanism of ink transport, and the effect of humidity and dwell time on nanodiamond patterning are investigated. The precision patterning of as-printed (pre-CVD) arrays with dot diameter and dot height as small as 735 nm ± 27 nm and 61 nm ± 3 nm, respectively, and CVD-treated fluorescent ND-arrays with consistently patterned dots having diameter and height as small as 820 nm ± 20 nm and, 245 nm ± 23 nm, respectively, using 1 s dwell time and 30% RH is successfully achieved. We anticipate that the far-red intense photostable luminescence (∼738 nm) observed from Si-V defect centers integrated in spatially arranged nanodiamonds could be beneficial for the development of next generation fluorescence-based devices and applications. (paper)

Synthesis and characterization of the europium (III) complex as an organic luminescent material

Energy Technology Data Exchange (ETDEWEB)

Zhuo Zuliang; Zhang Fujun; Xu Zheng; Lu Lifang; Li Junming; Wang Yongsheng [Key Laboratory of Luminescence and Optical Information (Beijing Jiaotong University), Ministry of Education, Beijing 100044 (China); Lv Yuguang, E-mail: fjzhang@bjtu.edu.c [The Provincial Key Laboratory of Biomaterials, College of Chemistry and Pharmacy, Jiamusi University, Jiamusi 154007 (China)

2010-11-15

The red emission organic material Eu(coumarin){sub 3{center_dot}}2H{sub 2}O complex was synthesized and its morphology, energy level alignment and luminescence characteristics were studied by using scanning electron microscopy, Fourier transform infrared spectra, cyclic voltammetry and ultraviolet-visible absorption spectra and fluorescence spectra. Eu(coumarin){sub 3{center_dot}}2H{sub 2}O shows bright red emission originating from Eu{sup 3+} ions under 345 nm light excitation. The luminescence lifetime of Eu{sup 3+} in this complex is about 580 {mu}s. To improve the quality of Eu(coumarin){sub 3{center_dot}}2H{sub 2}O thin films, Eu(coumarin){sub 3{center_dot}}2H{sub 2}O was doped with a poly(N-vinylcarbazole) (PVK) solution. The organic materials 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) and aluminum quinoline (Alq{sub 3}) were used as hole-blocking and electron-transporting layers in our fabricated electroluminescence (EL) devices on indium tin oxide (ITO) substrates, respectively. The EL devices ITO/poly-(3,4-ethylenedioxythiophene):poly-(styrenesulphonic acid) (PEDOT:PSS)/emitting layer (PVK:Eu)/BCP/Alq{sub 3}/Al were fabricated, and EL spectra were measured under different driving voltages. There is one emission peaking at 490 nm in addition to the characteristic emission peaks of Eu{sup 3+}, which should be attributed to the spectral overlap between the PVK emission and electroplex emission originating from PVK and BCP interfaces. This explanation can be positively supported by the dependence of the EL spectral variation of ITO/ PVK/BCP/Alq{sub 3}/Al devices on the driving voltage.

Manifested luminescence and magnetic responses of stoichiometry dependent Cd{sub 1− x}Mn{sub x}Se quantum dots

Energy Technology Data Exchange (ETDEWEB)

Sarma, Runjun; Deka, Geetamoni; Mohanta, Dambarudhar, E-mail: best@tezu.ernet.in

2015-02-15

Highlights: • Thio-glycolic acid (TGA) coated Cd{sub 1−x}Mn{sub x}Se quantum dots have been prepared with varying x • Formation of QD heterostructure can be expected at a nonzero, but higher value of x. • The deep defect related emission can be attributed to V{sub Cd}–V{sub Se} di-vacancies, which is dominant for smaller values of x. • An appreciable charge transfer between Mn{sup 2+} ions and capping agent TGA is anticipated. - Abstract: We report on stoichiometry dependent manifested physical properties of thioglycolic acid (TGA) coated Cd{sub 1− x}Mn{sub x}Se QDs. While possessing a wurtzite phase, with increasing x, the QDs exhibited a notable blue-shifting of the onset of absorption. Attributed to V{sub Cd}–V{sub Se} di-vacancies, the QDs describe an intense deep-defect related emission response at smaller values of x (=0 to 0.3). Due to the facilitation of magnetic Mn{sup 2+} ion migration from the core to the QD surfaces, {sup 4}T{sub 1}–{sup 6}A{sub 1} transition based Mn{sup 2+} orange emission get suppressed at a higher x (=0.6 to 1). While the FT-IR spectra of the alloyed QDs display characteristic Mn–OH stretching mode at ∼644 cm{sup −1}, the peak located at ∼703 cm{sup −1} is assigned to Cd-Se bending. Furthermore, the QDs with a low x (=0.3), exhibit paramagnetic characteristics owing to the presence of uncorrelated, isolated Mn{sup 2+} spins. The collective luminescence and magnetic features would find immense scope in bio-labeling and imaging applications, apart from solid state luminescent components.

Electroluminescence of colloidal ZnSe quantum dots

International Nuclear Information System (INIS)

Dey, S.C.; Nath, S.S.

2011-01-01

The article reports a green chemical synthesis of colloidal ZnSe quantum dots at a moderate temperature. The prepared colloid sample is characterised by UV-vis absorption spectroscopy and transmission electron microscopy. UV-vis spectroscopy reveals as-expected blue-shift with strong absorption edge at 400 nm and micrographs show a non-uniform size distribution of ZnSe quantum dots in the range 1-4 nm. Further, photoluminescence and electroluminescence spectroscopies are carried out to study optical emission. Each of the spectroscopies reveals two emission peaks, indicating band-to-band transition and defect related transition. From the luminescence studies, it can be inferred that the recombination of electrons and holes resulting from interband transition causes violet emission and the recombination of a photon generated hole with a charged state of Zn-vacancy gives blue emission. Meanwhile electroluminescence study suggests the application of ZnSe quantum dots as an efficient light emitting device with the advantage of colour tuning (violet-blue-violet). - Highlights: → Synthesis of ZnSe quantum dots by a green chemical route. → Characterisation: UV-vis absorption spectroscopy and transmission electron microscopy. → Analysis of UV-vis absorption spectrum and transmission electron micrographs. → Study of electro-optical properties by photoluminescence and electroluminescence. → Conclusion: ZnSe quantum dots can be used as LED with dual colour emission.

Photoluminescence of carbon dots from mesoporous silica

Science.gov (United States)

Nelson, D. K.; Razbirin, B. S.; Starukhin, A. N.; Eurov, D. A.; Kurdyukov, D. A.; Stovpiaga, E. Yu; Golubev, V. G.

2016-09-01

Photophysical properties of carbon dots were investigated under various excitation conditions and over a wide temperature region - from room to liquid helium temperatures. The carbon dots (CDs) were synthesized using mesoporous silica particles as a reactor and (3-aminopropyl)triethoxysilane (APTES) as a precursor. The photoluminescence spectra of CDs exhibit a strong dependence on the excitation wavelength and demonstrate a significant inhomogeneous broadening. Lowering sample temperature reveals the doublet structure of the spectra, which is associated with the vibronic structure of radiative transitions. The vibration energy ∼1200 cm-1 is close to the energy of Csbnd O stretching vibration. Long-lived phosphorescence of carbon dots with its decay time ∼0.2 s at T = 80 K was observed. The fluorescence and phosphorescence spectra are shown to be spectrally separated. The long-lived component of the emission was ascribed to optically forbidden triplet-singlet transitions. The value of the singlet-triplet splitting was found to be about 0.3 eV. Photo-induced polarization of the luminescence of carbon dots was revealed. The degree of the linear polarization is dependent on the wavelengths of both excitation and emitted light. The effect indicates a hidden anisotropy of optical dipole transitions in the dots and demonstrates the loss of the dipole orientation during the electron energy relaxation.

Testing the application of quartz and feldspar luminescence dating to MIS 5 Japanese marine deposits

DEFF Research Database (Denmark)

Thiel, Christine; Tsukamoto, Sumiko; Tokuyasu, Kayoko

2015-01-01

The applicability of both quartz and feldspar luminescence dating was tested on twenty-five samples from a marine succession now forming a coastal cliff at Oga Peninsula, Honshu Island, Japan. The quartz optically stimulated luminescence (OSL) signal shows thermal instability and linear modulated...

Strongly luminescent monolayered MoS2 prepared by effective ultrasound exfoliation.

Science.gov (United States)

Štengl, Václav; Henych, Jiří

2013-04-21

Intense ultrasound in a pressurized batch reactor was used for preparation of monolayered MoS2 nanosheets from natural mineral molybdenite. Exfoliation of bulk MoS2 using ultrasound is an attractive route to large-scale preparation of monolayered crystals. To evaluate the quality of delamination, methods like X-ray diffraction, Raman spectroscopy and microscopic techniques (TEM and AFM) were employed. From single- or few-layered products obtained from intense sonication, MoS2 quantum dots (MoSQDs) were prepared by a one-pot reaction by refluxing exfoliated nanosheets of MoS2 in ethylene glycol under atmospheric pressure. The synthesised MoSQDs were characterised by photoluminescence spectroscopy and laser-scattering particle size analysis. Our easy preparation leads to very strongly green luminescing quantum dots.

Dynamics of Charged Excitons and Biexcitons in CsPbBr3 Perovskite Nanocrystals Revealed by Femtosecond Transient-Absorption and Single-Dot Luminescence Spectroscopy.

Science.gov (United States)

Yarita, Naoki; Tahara, Hirokazu; Ihara, Toshiyuki; Kawawaki, Tokuhisa; Sato, Ryota; Saruyama, Masaki; Teranishi, Toshiharu; Kanemitsu, Yoshihiko

2017-04-06

Metal-halide perovskite nanocrystals (NCs) are promising photonic materials for use in solar cells, light-emitting diodes, and lasers. The optoelectronic properties of these devices are determined by the excitons and exciton complexes confined in their NCs. In this study, we determined the relaxation dynamics of charged excitons and biexcitons in CsPbBr 3 NCs using femtosecond transient-absorption (TA), time-resolved photoluminescence (PL), and single-dot second-order photon correlation spectroscopy. Decay times of ∼40 and ∼200 ps were obtained from the TA and PL decay curves for biexcitons and charged excitons, respectively, in NCs with an average edge length of 7.7 nm. The existence of charged excitons even under weak photoexcitation was confirmed by the second-order photon correlation measurements. We found that charged excitons play a dominant role in luminescence processes of CsPbBr 3 NCs. Combining different spectroscopic techniques enabled us to clarify the dynamical behaviors of excitons, charged excitons, and biexcitons.

Reduced graphene oxide-germanium quantum dot nanocomposite: electronic, optical and magnetic properties

Science.gov (United States)

Amollo, Tabitha A.; Mola, Genene T.; Nyamori, Vincent O.

2017-12-01

Graphene provides numerous possibilities for structural modification and functionalization of its carbon backbone. Localized magnetic moments can, as well, be induced in graphene by the formation of structural defects which include vacancies, edges, and adatoms. In this work, graphene was functionalized using germanium atoms, we report the effect of the Ge ad atoms on the structural, electrical, optical and magnetic properties of graphene. Reduced graphene oxide (rGO)-germanium quantum dot nanocomposites of high crystalline quality were synthesized by the microwave-assisted solvothermal reaction. Highly crystalline spherical shaped germanium quantum dots, of diameter ranging between 1.6-9.0 nm, are anchored on the basal planes of rGO. The nanocomposites exhibit high electrical conductivity with a sheet resistance of up to 16 Ω sq-1. The electrical conductivity is observed to increase with the increase in Ge content in the nanocomposites. High defect-induced magnetization is attained in the composites via germanium adatoms. The evolution of the magnetic moments in the nanocomposites and the coercivity showed marked dependence on the Ge quantum dots size and concentration. Quantum confinement effects is evidenced in the UV-vis absorbance spectra and photoluminescence emission spectra of the nanocomposites which show marked size-dependence. The composites manifest strong absorption in the UV region, strong luminescence in the near UV region, and a moderate luminescence in the visible region.

Photon and energy propagation in Cd Se quantum dot systems

International Nuclear Information System (INIS)

Alves, Guilherme A.; Santos, Erasto J.; Monte, Adamo F.G.

2011-01-01

Full text. Photon propagation is a crucial process in a wide type of optical materials being responsible for the dynamics and excitation spreading. The addition of Cd Se quantum dots (QDs) into a polystyrene (PS) matrix introduces new properties in the polymeric matrix making this new system a good candidate for improvement in light- emitting devices. A confocal microscope was adapted to scan the spatial distribution of emitted luminescence from the sample surface. Energy transfer processes could be associated with the photon propagation provided by the measured luminescence spatial distribution. We proposed that this energy propagation is caused by the photons capture and emission between the dots and besides other mechanics such as electronic transfer, hopping and resonance. This dynamic process can be understood by the spatial migration of excited states. These facts demonstrate the great importance of the energy transfer, absorption and capture processes in a QD system for the improvement of optical electronic devices. It has been found that re-absorption by ground and excited states plays an important role for the energy propagation. The investigation have been done for a wide range of inter-dot distance in such a way that we could observe how the energy transfer behaves according to this distance. We observed that the photon migration length (PML) increases by increasing the QD concentration and reaches the highest value for a given QD concentration, i.e., for a specific inter-dot distance. However, above this concentration the PML starts to decrease. This behavior indicates that the inter-dots distance is crucial in order to get the highest energy flux inside the sample. Thus, by measuring the PML and its wavelength dependence it is possible to understand the whole dynamics in the QD/PS system. All the processes verified so far give us the possibility to classify the QD/PS system as a good candidate to be employed in an optical QD-based device

Optically stimulated luminescence of MgB{sub 4}O{sub 7}:Ce,Li for gamma and neutron dosimetry

Energy Technology Data Exchange (ETDEWEB)

Yukihara, E.G.; Doull, B.A.; Gustafson, T. [Physics Department, Oklahoma State University, Stillwater, OK 74078 (United States); Oliveira, L.C. [Physics Department, Oklahoma State University, Stillwater, OK 74078 (United States); Departamento de Física, FFCLRP-Universidade de São Paulo, 14040-901 Ribeirão Preto-SP (Brazil); Kurt, K. [Physics Department, Oklahoma State University, Stillwater, OK 74078 (United States); Mersin University Science and Letter Faculty Physics Department 33343 Mersin (Turkey); Milliken, E.D. [Physics Department, Oklahoma State University, Stillwater, OK 74078 (United States); R& D Pigments, Ferro Corporation, 251 W. Wylie Ave, Washington, PA 15301 (United States)

2017-03-15

The objective of this work was to develop a new optically stimulated luminescence (OSL) material for dosimetry applications that is tissue equivalent and has high sensitivity to ionizing radiation, fast luminescence lifetime, and intrinsic neutron sensitivity. To achieve this combination of properties, we started with a host material with low effective atomic number, MgB{sub 4}O{sub 7} (Z{sub eff}=8.2){sub ,} with an appropriate dopant characterized by short luminescence lifetime (Ce{sup 3+}). The samples were synthesized using Solution Combustion Synthesis with excess boric acid to achieve the correct crystallographic phase and Li co-doping to enhance its sensitivity. We investigated the thermoluminescence (TL) and OSL properties as a function of annealing temperature, radiation dose, dopant concentration, and time elapsed after irradiation (i.e., signal fading). We also applied a step-annealing procedure to investigate the depth of the trapping centers associated with the OSL signal. The samples obtained are characterized by a dominant TL peak at ~210 °C with intensity comparable to LiF:Mg,Ti. The OSL intensity is ~50% of that from Al{sub 2}O{sub 3}:C when using Hoya U-340 filters and shows no saturation up to almost 1 kGy. The OSL signal seems to originate from trapping center with stability > 150 °C, which means that the OSL fading is expected to be small. After the first day, in which fading associated with shallow traps is observed, fading of the total OSL signal was <4% within 6 days. The possibility of enhancing the neutron sensitivity was also demonstrated by synthesizing the material with enriched {sup 10}B. Although further development and characterization of the material may be needed, this work demonstrates that this host/dopant combination can be a viable alternative in OSL dosimetry, particularly for 2D dose mapping and neutron dosimetry applications.

Radioluminescence properties of the CdSe/ZnS Quantum Dot nanocrystals with analysis of long-memory trends

International Nuclear Information System (INIS)

Nikolopoulos, D.; Valais, I.; Michail, C.; Bakas, A.; Fountzoula, C.; Cantzos, D.; Bhattacharyya, D.; Sianoudis, I.; Fountos, G.; Yannakopoulos, P.; Panayiotakis, G.; Kandarakis, I.

2016-01-01

This paper reports radioluminescence properties of the CdSe/ZnS quantum dots. Three quantum dot samples were prepared with concentrations 14.2 × 10"−"5 mg/mL, 21.3 × 10"−"5 mg/mL and 28.5 × 10"−"5 mg/mL, respectively. The ultraviolet induced emission spectra of CdSe/ZnS dots exhibited a peak at 550 nm ranging between 450 nm and 650 nm. Discrepancies observed between 250 nm and 450 nm were attributed to the solvent and cuvette. The absolute efficiency calculated from random fractional-Gaussian luminescence segments varied. Long-memory fractional-Brownian segments were also found. The quantum dot solution with concentration of 21.3 × 10"−"5 mg/mL exhibited the maximum absolute efficiency value at 90 kVp. The CdSe/ZnS dots have demonstrated potential for detection of X-rays in the medical imaging energy range. - Highlights: • Luminescence properties of CdSe/ZnS QDs under UV and X-ray irradiation. • Detrended fluctuation analysis used to identify long-memory trends in the signal. • QDs of high concentrations exhibited high absolute efficiency up to 80 kVp. • CdSe/ZnS showed potential for detection of X-rays in the medical imaging energies.

The Large-Scale Synthesis of Vinyl-Functionalized Silicon Quantum Dot and Its Application in Miniemulsion Polymerization

Directory of Open Access Journals (Sweden)

Xuan-Dung Mai

2016-01-01

Full Text Available Stable luminescence, size-tunability, and biocompatibility encourage the deployment of Cd-free NPs into diverse biological applications. Here we report one-pot synthesis of blue-emitting and polymerizable silicon quantum dots (Si QDs from which water-soluble Si QDs embedded polystyrene nanoparticles (SiQD@PS NPs were prepared using a miniemulsion polymerization approach. The hydrodynamic size of NPs was controlled by KOH to oleic acid molar ratio. Studies on the photoluminescence properties of SiQD@PS NPs in different conditions reveal that they exhibit two-photon luminescence property and high stability against pH and UV exposure. These NPs add new size regime to the Si QDs based luminescent makers for bioimaging and therapy applications.

Luminescent GdVO{sub 4}:Sm{sup 3+} quantum dots enhance power conversion efficiency of bulk heterojunction polymer solar cells by Förster resonance energy transfer

Energy Technology Data Exchange (ETDEWEB)

Bishnoi, Swati [CSIR-Network of Institutes for Solar Energy, New Delhi 110001 (India); Luminescent Materials and Devices Group, CSIR-National Physical Laboratory, New Delhi 110012 (India); Academy of Scientific and Innovative Research (AcSIR), CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Gupta, Vinay, E-mail: drvinaygupta@netscape.net; Sharma, Gauri D.; Chand, Suresh [CSIR-Network of Institutes for Solar Energy, New Delhi 110001 (India); Organic and Hybrid Solar Cells Group, Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, New Delhi 110012 (India); Sharma, Chhavi; Kumar, Mahesh [Ultrafast Optoelectronics and Terahertz Photonics Lab, Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, New Delhi 110012 (India); Haranath, D. [CSIR-Network of Institutes for Solar Energy, New Delhi 110001 (India); Luminescent Materials and Devices Group, CSIR-National Physical Laboratory, New Delhi 110012 (India); Naqvi, Sheerin [Luminescent Materials and Devices Group, CSIR-National Physical Laboratory, New Delhi 110012 (India)

2016-07-11

In this work, we report enhanced power conversion efficiency (PCE) of bulk heterojunction polymer solar cells by Förster resonance energy transfer (FRET) from samarium-doped luminescent gadolinium orthovanadate (GdVO{sub 4}:Sm{sup 3+}) quantum dots (QDs) to polythieno[3,4-b]-thiophene-co-benzodithiophene (PTB7) polymer. The photoluminescence emission spectrum of GdVO{sub 4}:Sm{sup 3+} QDs overlaps with the absorption spectrum of PTB7, leading to FRET from GdVO{sub 4}:Sm{sup 3+} to PTB7, and significant enhancements in the charge-carrier density of excited and polaronic states of PTB7 are observed. This was confirmed by means of femtosecond transient absorption spectroscopy. The FRET from GdVO{sub 4}:Sm{sup 3+} QDs to PTB7 led to a remarkable increase in the power conversion efficiency (PCE) of PTB7:GdVO{sub 4}:Sm{sup 3+}:PC{sub 71}BM ([6,6]-phenyl-C{sub 71}-butyric acid methyl ester) polymer solar cells. The PCE in optimized ternary blend PTB7:GdVO{sub 4}:Sm{sup 3+}:PC{sub 71}BM (1:0.1:1.5) is increased to 8.8% from 7.2% in PTB7:PC{sub 71}BM. This work demonstrates the potential of rare-earth based luminescent QDs in enhancing the PCE of polymer solar cells.

Fiber optical dose rate measurement based on the luminescence of beryllium oxide

Directory of Open Access Journals (Sweden)

Teichmann Tobias

2018-01-01

Full Text Available This work presents a fiber optical dose rate measurement system based on the radioluminescence and optically stimulated luminescence of beryllium oxide. The system consists of a small, radiation sensitive probe which is coupled to a light detection unit with a long and flexible light guide. Exposing the beryllium oxide probe to ionizing radiation results in the emission of light with an intensity which is proportional to the dose rate. Additionally, optically stimulated luminescence can be used to obtain dose and dose rate information during irradiation or retrospectively. The system is capable of real time dose rate measurements in fields of high dose rates and dose rate gradients and in complex, narrow geometries. This enables the application for radiation protection measurements as well as for quality control in radiotherapy. One inherent drawback of fiber optical dosimetry systems is the generation of Cherenkov radiation and luminescence in the light guide itself when it is exposed to ionizing radiation. This so called “stem” effect leads to an additional signal which introduces a deviation in the dose rate measurement and reduces the spatial resolution of the system, hence it has to be removed. The current system uses temporal discrimination of the effect for radioluminescence measurements in pulsed radiation fields and modulated optically stimulated luminescence for continuous irradiation conditions. This work gives an overview of the major results and discusses new-found obstacles of the applied methods of stem discrimination.

Colloidal quantum dot photovoltaics: The effect of polydispersity

KAUST Repository

Zhitomirsky, David

2012-02-08

The size-effect tunability of colloidal quantum dots enables facile engineering of the bandgap at the time of nanoparticle synthesis. The dependence of effective bandgap on nanoparticle size also presents a challenge if the size dispersion, hence bandgap variability, is not well-controlled within a given quantum dot solid. The impact of this polydispersity is well-studied in luminescent devices as well as in unipolar electronic transport; however, the requirements on monodispersity have yet to be quantified in photovoltaics. Here we carry out a series of combined experimental and model-based studies aimed at clarifying, and quantifying, the importance of quantum dot monodispersity in photovoltaics. We successfully predict, using a simple model, the dependence of both open-circuit voltage and photoluminescence behavior on the density of small-bandgap (large-diameter) quantum dot inclusions. The model requires inclusion of trap states to explain the experimental data quantitatively. We then explore using this same experimentally tested model the implications of a broadened quantum dot population on device performance. We report that present-day colloidal quantum dot photovoltaic devices with typical inhomogeneous linewidths of 100-150 meV are dominated by surface traps, and it is for this reason that they see marginal benefit from reduction in polydispersity. Upon eliminating surface traps, achieving inhomogeneous broadening of 50 meV or less will lead to device performance that sees very little deleterious impact from polydispersity. © 2012 American Chemical Society.

MO-A-BRB-00: TG191: Clinical Use of Luminescent Dosimeters

Energy Technology Data Exchange (ETDEWEB)

NONE

2016-06-15

This presentation will highlight the upcoming TG-191 report: Clinical Use of Luminescent Dosimeters. Luminescent dosimetry based on TLD and OSLD is a practical, accurate, and precise technique for point dosimetry in medical physics applications. The charges of Task Group 191 were to detail the methodologies for practical and optimal luminescent dosimetry in a clinical setting. This includes (1) To review the variety of TLD/OSL materials available, including features and limitations of each. (2) To outline the optimal steps to achieve accurate and precise dosimetry with luminescent detectors and to evaluate the uncertainty induced when less rigorous procedures are used. (3) To develop consensus guidelines on the optimal use of luminescent dosimeters for clinical practice. (4) To develop guidelines for special medically relevant uses of TLDs/OSLs (e.g., mixed field i.e. photon/neutron dosimetry, particle beam dosimetry, skin dosimetry). While this report provides general guidelines for arbitrary TLD and OSLD processes, the report, and therefore this presentation, provide specific guidance for TLD-100 (LiF:Ti,Mg) and nanoDot (Al2O3:C) dosimeters because of their prevalence in clinical practice. Learning Objectives: Understand the available dosimetry systems, and basic theory of their operation Understand the range of dose determination methodologies and the uncertainties associated with them Become familiar with special considerations for TLD/OSLD relevant for special clinical situations Learn recommended commissioning and QA procedures for these dosimetry systems.

MO-A-BRB-01: TG191: Clinical Use of Luminescent Dosimeters

Energy Technology Data Exchange (ETDEWEB)

Kry, S. [UT MD Anderson Cancer Center (United States)

2016-06-15

This presentation will highlight the upcoming TG-191 report: Clinical Use of Luminescent Dosimeters. Luminescent dosimetry based on TLD and OSLD is a practical, accurate, and precise technique for point dosimetry in medical physics applications. The charges of Task Group 191 were to detail the methodologies for practical and optimal luminescent dosimetry in a clinical setting. This includes (1) To review the variety of TLD/OSL materials available, including features and limitations of each. (2) To outline the optimal steps to achieve accurate and precise dosimetry with luminescent detectors and to evaluate the uncertainty induced when less rigorous procedures are used. (3) To develop consensus guidelines on the optimal use of luminescent dosimeters for clinical practice. (4) To develop guidelines for special medically relevant uses of TLDs/OSLs (e.g., mixed field i.e. photon/neutron dosimetry, particle beam dosimetry, skin dosimetry). While this report provides general guidelines for arbitrary TLD and OSLD processes, the report, and therefore this presentation, provide specific guidance for TLD-100 (LiF:Ti,Mg) and nanoDot (Al2O3:C) dosimeters because of their prevalence in clinical practice. Learning Objectives: Understand the available dosimetry systems, and basic theory of their operation Understand the range of dose determination methodologies and the uncertainties associated with them Become familiar with special considerations for TLD/OSLD relevant for special clinical situations Learn recommended commissioning and QA procedures for these dosimetry systems.

MO-A-BRB-01: TG191: Clinical Use of Luminescent Dosimeters

International Nuclear Information System (INIS)

Kry, S.

2016-01-01

This presentation will highlight the upcoming TG-191 report: Clinical Use of Luminescent Dosimeters. Luminescent dosimetry based on TLD and OSLD is a practical, accurate, and precise technique for point dosimetry in medical physics applications. The charges of Task Group 191 were to detail the methodologies for practical and optimal luminescent dosimetry in a clinical setting. This includes (1) To review the variety of TLD/OSL materials available, including features and limitations of each. (2) To outline the optimal steps to achieve accurate and precise dosimetry with luminescent detectors and to evaluate the uncertainty induced when less rigorous procedures are used. (3) To develop consensus guidelines on the optimal use of luminescent dosimeters for clinical practice. (4) To develop guidelines for special medically relevant uses of TLDs/OSLs (e.g., mixed field i.e. photon/neutron dosimetry, particle beam dosimetry, skin dosimetry). While this report provides general guidelines for arbitrary TLD and OSLD processes, the report, and therefore this presentation, provide specific guidance for TLD-100 (LiF:Ti,Mg) and nanoDot (Al2O3:C) dosimeters because of their prevalence in clinical practice. Learning Objectives: Understand the available dosimetry systems, and basic theory of their operation Understand the range of dose determination methodologies and the uncertainties associated with them Become familiar with special considerations for TLD/OSLD relevant for special clinical situations Learn recommended commissioning and QA procedures for these dosimetry systems.

MO-A-BRB-00: TG191: Clinical Use of Luminescent Dosimeters

International Nuclear Information System (INIS)

2016-01-01

This presentation will highlight the upcoming TG-191 report: Clinical Use of Luminescent Dosimeters. Luminescent dosimetry based on TLD and OSLD is a practical, accurate, and precise technique for point dosimetry in medical physics applications. The charges of Task Group 191 were to detail the methodologies for practical and optimal luminescent dosimetry in a clinical setting. This includes (1) To review the variety of TLD/OSL materials available, including features and limitations of each. (2) To outline the optimal steps to achieve accurate and precise dosimetry with luminescent detectors and to evaluate the uncertainty induced when less rigorous procedures are used. (3) To develop consensus guidelines on the optimal use of luminescent dosimeters for clinical practice. (4) To develop guidelines for special medically relevant uses of TLDs/OSLs (e.g., mixed field i.e. photon/neutron dosimetry, particle beam dosimetry, skin dosimetry). While this report provides general guidelines for arbitrary TLD and OSLD processes, the report, and therefore this presentation, provide specific guidance for TLD-100 (LiF:Ti,Mg) and nanoDot (Al2O3:C) dosimeters because of their prevalence in clinical practice. Learning Objectives: Understand the available dosimetry systems, and basic theory of their operation Understand the range of dose determination methodologies and the uncertainties associated with them Become familiar with special considerations for TLD/OSLD relevant for special clinical situations Learn recommended commissioning and QA procedures for these dosimetry systems.

Plasmon resonance-induced photoluminescence enhancement of CdTe/Cds quantum dots thin films

Energy Technology Data Exchange (ETDEWEB)

Wang, Hongyu [Nanjing University of Posts and Telecommunications, Nanjing 210003 (China); National Laboratory of Solid State Microstructure and School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Xu, Ling, E-mail: xuling@nju.edu.cn [National Laboratory of Solid State Microstructure and School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Wu, Yangqing; Xu, Jun; Ma, Zhongyuan; Chen, Kunji [National Laboratory of Solid State Microstructure and School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China)

2016-11-30

Highlights: • CdTe/CdS quantum dots/Au nano-rods nano-composite films were fabricated. • PL intensity of the quantum dots films was enhanced due to Au nanorods. • Internal quantum efficiency increased due to localized surface plasmon resonance. • The lifetimes of quantum dots films decreased after interaction with Au nano-rods. - Abstract: CdTe/CdS quantum dots/Au nano-rods nano-composite films were fabricated on planar Si substrates. The optical properties of all samples were investigated and the corresponding simulations were studied. It was found that the photoluminescence intensity of the CdTe/CdS quantum dots films was enhanced about 9-fold after the incorporation of Au nano-rods, the internal quantum efficiency increased from 24.3% to 35.2% due to the localized surface plasmon resonance. The time-resolved luminescence decay curves showed that the lifetimes of CdTe/CdS quantum dots films decreased to 2.8 ns after interaction with Au nano-rods. The results of finite-difference time-domain simulation indicated that Au nano-rods induced the localization of electric field, which enhanced the PL intensity of quantum dots films in the vicinity of Au nano-rods.

Photonic emitters and circuits based on colloidal quantum dot composites

Science.gov (United States)

Menon, Vinod M.; Husaini, Saima; Valappil, Nikesh; Luberto, Matthew

2009-02-01

We discuss our work on light emitters and photonic circuits realized using colloidal quantum dot composites. Specifically we will report our recent work on flexible microcavity laser, microdisk emitters and integrated active - passive waveguides. The entire microcavity laser structure was realized using spin coating and consisted of an all-polymer distributed Bragg reflector with a poly-vinyl carbazole cavity layer embedded with InGaP/ZnS colloidal quantum dots. These microcavities can be peeled off the substrate yielding a flexible structure that can conform to any shape and whose emission spectra can be mechanically tuned. The microdisk emitters and the integrated waveguide structures were realized using soft lithography and photo-lithography, respectively and were fabricated using a composite consisting of quantum dots embedded in SU8 matrix. Finally, we will discuss the effect of the host matrix on the optical properties of the quantum dots using results of steady-state and time-resolved luminescence measurements. In addition to their specific functionalities, these novel device demonstrations and their development present a low cost alternative to the traditional photonic device fabrication techniques.

Conjugation of biotin-coated luminescent quantum dots with single domain antibody-rhizavidin fusions

Directory of Open Access Journals (Sweden)

Jinny L. Liu

2016-06-01

Full Text Available Straightforward and effective methods are required for the bioconjugation of proteins to surfaces and particles. Previously we demonstrated that the fusion of a single domain antibody with the biotin binding molecule rhizavidin provided a facile method to coat biotin-modified surfaces with a highly active and oriented antibody. Here, we constructed similar single domain antibody—rhizavidin fusions as well as unfused rhizavidin with a His-tag. The unfused rhizavidin produced efficiently and its utility for assay development was demonstrated in surface plasmon resonance experiments. The single domain antibody-rhizavidin fusions were utilized to coat quantum dots that had been prepared with surface biotins. Preparation of antibody coated quantum dots by this means was found to be both easy and effective. The prepared single domain antibody-quantum dot reagent was characterized by surface plasmon resonance and applied to toxin detection in a fluoroimmunoassay sensing format.

Optical properties of pH-sensitive carbon-dots with different modifications

Energy Technology Data Exchange (ETDEWEB)

Kong, Weiguang, E-mail: 11236095@zju.edu.cn [Department of Physics and State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou, Zhejiang 310027 (China); Wu, Huizhen, E-mail: hzwu@zju.edu.cn [Department of Physics and State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou, Zhejiang 310027 (China); Ye, Zhenyu, E-mail: yzheny@zju.edu.cn [Department of Physics and State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou, Zhejiang 310027 (China); Li, Ruifeng, E-mail: hbrook@zju.edu.cn [Department of Physics and State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou, Zhejiang 310027 (China); Xu, Tianning, E-mail: xtn9886@zju.edu.cn [Department of Physics and State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou, Zhejiang 310027 (China); Department of Science, Zhijiang College of Zhejiang University of Technology, Hangzhou, Zhejiang 310024 (China); Zhang, Bingpo, E-mail: 11006080@zju.edu.cn [Department of Physics and State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou, Zhejiang 310027 (China)

2014-04-15

Carbon dots with unique characters of chemical inertness, low cytotoxicity and good biocompatibility, demonstrate important applications in biology and optoelectronics. In this paper we report the optical properties of pH-sensitive carbon dots with different surface modifications. The as-prepared carbon dots can be well dispersed in water by modifying with acid, alkali or metal ions though they tend to form a suspension when being directly dispersed in water. We find that the carbon dots dispersed in water show a new emission and absorption character which is tunable due to the pH-sensitive nature. It is firstly proved that the addition of bivalent copper ions offers a high color contrast for visual colorimetric assays for pH measurement. The effect of surface defects with different modification on the performances of the carbon dots is also explored with a core–shell model. The hydro-dispersed carbon dots can be potentially utilized for cellular imaging or metal ion probes in biochemistry. -- Highlights: • The dispersibility in water of as-prepared carbon dots is effectively improved by the addition of acid, alkali or metal ions. • The effect of hydrolysis on the optical properties of the carbon dots is studied. • The luminescent carbon dots show a pH-sensitive fluorescence and absorption property. • The addition of bivalent copper ions in the post-treated carbon dots offers a high color contrast for visual colorimetric assays for pH measurement. • The effect of surface defects and ligands on the performances of the carbon dots is also explored.

Photoluminescence Enhancement of Silole-Capped Silicon Quantum Dots Based on Förster Resonance Energy Transfer.

Science.gov (United States)

Kim, Seongwoong; Kim, Sungsoo; Ko, Young Chun; Sohn, Honglae

2015-07-01

Photoluminescent porous silicon were prepared by an electrochemical etch of n-type silicon under the illumination with a 300 W tungsten filament bulb for the duration of etch. The red photoluminescence emitting at 650 nm with an excitation wavelength of 450 nm is due to the quantum confinement of silicon quantum dots in porous silicon. HO-terminated red luminescent PS was obtained by an electrochemical treatment of fresh PS with the current of 150 mA for 60 seconds in water and sodium chloride. As-prepared PS was sonicated, fractured, and centrifuged in toluene solution to obtain photoluminescence silicon quantum dots. Dichlorotetraphenylsilole exhibiting an emission band at 520 nm was reacted with HO-terminated silicon quantum dots to give a silole-capped silicon quantum dots. The optical characterization of silole-derivatized silicon quantum dots was investigated by UV-vis and fluorescence spectrometer. The fluorescence emission efficiency of silole-capped silicon quantum dots was increased by about 2.5 times due to F6rster resonance energy transfer from silole moiety to silicon quantum dots.

Phosphine synthetic route features and postsynthetic treatment of InP quantum dots

International Nuclear Information System (INIS)

Mordvinova, Natalia; Vinokurov, Alexander; Dorofeev, Sergey; Kuznetsova, Tatiana; Znamenkov, Konstantin

2014-01-01

Highlights: • Quantum dots with average diameter of 3–5 nm were synthesized. • PH 3 was used as novel phosphorous precursor. • Electrophoresis was demonstrated to be an effective method of purification of QDs. • Photoeching leads to quantum yields about 20%. • The concentration and time dependencies for photoetching of QDs were obtained. -- Abstract: In this paper we report on the development of synthesis of InP quantum dots with a gaseous phosphine PH 3 as a source of phosphorus and myristic acid and TOP/TOPO as stabilizers. Samples synthesized using myristic acid as stabilizer at relatively low temperatures were found to contain admixture of In(OH) 3 . We studied the influence of HF concentration and duration of illumination on luminescence properties of InP quantum dots during photoetching process. Quantum yields of photoetched samples reached about 20%. Additionally, electrophoresis as a new technique of purification and size-depended separation of synthesized quantum dots was developed

Thermally and optically stimulated luminescence correlated processes in X-ray irradiated KCl:Eu2+

International Nuclear Information System (INIS)

Chernov, V.; Melendrez Ao, R.; Piters, T.M.; Barboza-Flores, M.

2001-01-01

The effect of optical bleaching on thermoluminescence (TL) and thermal bleaching on optically stimulated luminescence (OSL) outputs in X-ray irradiated KCl : Eu 2+ have been investigated. The X-ray induced glow curves reveal three main peaks located at 370, 410 and 470 K. Illumination with 560 nm light leads to a drastic change of the TL glow curve. The 470 K peak is destroyed during bleaching. The other peaks initially increase in intensity and only after sufficiently long bleaching begin to decrease. After long-time bleaching, the TL peaks in X-ray irradiated crystals look like the TL peaks found in UV irradiated crystals. The effect of thermal bleaching on OSL is also very pronounced. The temperature dependencies show a step-by-step decrease of the OSL intensity correlated with the positions of the TL peaks. The result obtained shows that centers responsible for the TL peaks participate in OSL, but this participation seems not to be direct and is complicated by processes accompanying the F center bleaching

X-ray micro-modulated luminescence tomography (XMLT)

Science.gov (United States)

Cong, Wenxiang; Liu, Fenglin; Wang, Chao; Wang, Ge

2014-01-01

Imaging depth of optical microscopy has been fundamentally limited to millimeter or sub-millimeter due to strong scattering of light in a biological sample. X-ray microscopy can resolve spatial details of few microns deep inside a sample but contrast resolution is inadequate to depict heterogeneous features at cellular or sub-cellular levels. To enhance and enrich biological contrast at large imaging depth, various nanoparticles are introduced and become essential to basic research and molecular medicine. Nanoparticles can be functionalized as imaging probes, similar to fluorescent and bioluminescent proteins. LiGa5O8:Cr3+ nanoparticles were recently synthesized to facilitate luminescence energy storage with x-ray pre-excitation and subsequently stimulated luminescence emission by visible/near-infrared (NIR) light. In this paper, we propose an x-ray micro-modulated luminescence tomography (XMLT, or MLT to be more general) approach to quantify a nanophosphor distribution in a thick biological sample with high resolution. Our numerical simulation studies demonstrate the feasibility of the proposed approach. PMID:24663898

Luminescence lifetimes in natural quartz annealed beyond its second phase inversion temperature

International Nuclear Information System (INIS)

Chithambo, M.L.

2015-01-01

The influence of annealing, irradiation dose, preheating and measurement temperature on luminescence lifetimes has been studied in quartz annealed at 1000 °C. The measurements were supplemented by studies on quartz annealed at 900 and 800 °C. Lifetimes increase with dose as well as with temperature and duration of annealing between 800 and 1000 °C. Preheating produces the same effect. The changes are accounted for in terms of hole-transfer from the non-radiative luminescence centre to and between radiative centres. The influence of measurement temperature on lifetimes depends on whether the stimulation is carried out from ambient to 200 °C or otherwise. This result is unlike that in quartz annealed at or below 500 °C where lifetimes are independent of the direction of heating. In particular, lifetimes decrease monotonically when measurements are made from 20 to 200 °C but not when recorded from 200 to 20 °C. The latter produces a pattern resembling that in quartz annealed up to 500 °C. The results are concluded as evidence of thermal effects on separate luminescence centres. In support of this, different values of the activation energy for thermal quenching were found for each supposed luminescence centre. The change of the corresponding luminescence intensity with temperature is also qualitatively consistent with this notion. - Highlights: • Luminescence lifetimes in natural quartz annealed beyond its second phase inversion temperature is reported. • Lifetimes increase with dose, annealing between 800 and 1000 °C, and preheating. • Lifetimes under stimulation temperature are affected by direction of heating. • Changes are accounted for in terms of hole-transfer luminescence centres.

Surface processes during purification of InP quantum dots

Directory of Open Access Journals (Sweden)

Natalia Mordvinova

2014-08-01

Full Text Available Recently, a new simple and fast method for the synthesis of InP quantum dots by using phosphine as phosphorous precursor and myristic acid as surface stabilizer was reported. Purification after synthesis is necessary to obtain samples with good optical properties. Two methods of purification were compared and the surface processes which occur during purification were studied. Traditional precipitation with acetone is accompanied by a small increase in photoluminescence. It occurs that during the purification the hydrolysis of the indium precursor takes place, which leads to a better surface passivation. The electrophoretic purification technique does not increase luminescence efficiency but yields very pure quantum dots in only a few minutes. Additionally, the formation of In(OH3 during the low temperature synthesis was explained. Purification of quantum dots is a very significant part of postsynthetical treatment that determines the properties of the material. But this subject is not sufficiently discussed in the literature. The paper is devoted to the processes that occur at the surface of quantum dots during purification. A new method of purification, electrophoresis, is investigated and described in particular.

Optical pumping and negative luminescence polarization in charged GaAs quantum dots

Science.gov (United States)

Shabaev, Andrew; Stinaff, Eric A.; Bracker, Allan S.; Gammon, Daniel; Efros, Alexander L.; Korenev, Vladimir L.; Merkulov, Igor

2009-01-01

Optical pumping of electron spins and negative photoluminescence polarization are observed when interface quantum dots in a GaAs quantum well are excited nonresonantly by circularly polarized light. Both observations can be explained by the formation of long-lived dark excitons through hole spin relaxation in the GaAs quantum well prior to exciton capture. In this model, optical pumping of resident electron spins is caused by capture of dark excitons and recombination in charged quantum dots. Negative polarization results from accumulation of dark excitons in the quantum well and is enhanced by optical pumping. The dark exciton model describes the experimental results very well, including intensity and bias dependence of the photoluminescence polarization and the Hanle effect.

Self-assembly and photoluminescence evolution of hydrophilic and hydrophobic quantum dots in sol–gel processes

Energy Technology Data Exchange (ETDEWEB)

Yang, Ping, E-mail: mse_yangp@ujn.edu.cn [School of Material Science and Engineering, University of Jinan, Jinan 250022 (China); Matras-Postolek, Katarzyna [Faculty of Chemical Engineering and Technology, Cracow University of Technology, Krakow 31-155 (Poland); Song, Xueling; Zheng, Yan; Liu, Yumeng; Ding, Kun; Nie, Shijie [School of Material Science and Engineering, University of Jinan, Jinan 250022 (China)

2015-10-15

Graphical abstract: Highly luminescent quantum dots (QDs) with tunable photoluminescence (PL) wavelength were assembled into various morphologies including chain, hollow spheres, fibers, and ring structures through sol–gel processes. The PL properties during assembly as investigated. - Highlights: • Highly luminescent quantum dots (QDs) were synthesized from several ligands. • The evolution of PL in self-assembly via sol–gel processes was investigated. • CdTe QDs were assembled into a chain by controlling hydrolysis and condensation reactions. • Hollow spheres, fibers, and ring structures were created via CdSe/ZnS QDs in sol–gel processes. - Abstract: Highly luminescent quantum dots (QDs) with tunable photoluminescence (PL) wavelength were synthesized from several ligands to investigate the PL evolution in QD self-assembly via sol–gel processes. After ligand exchange, CdTe QDs were assembled into a chain by controlling the hydrolysis and condensation reaction of 3-mercaptopropyl-trimethoxysilane. The chain was then coated with a SiO{sub 2} shell from tetraethyl orthosilicate (TEOS). Hollow spheres, fibers, and ring structures were created from CdSe/ZnS QDs via various sol–gel processes. CdTe QDs revealed red-shifted and narrowed PL spectrum after assembly compared with their initial one. In contrast, the red-shift of PL spectra of CdSe/ZnS QDs is small. By optimizing experimental conditions, SiO{sub 2} spheres with multiple CdSe/ZnS QDs were fabricated using TEOS and MPS. The QDs in these SiO{sub 2} spheres retained their initial PL properties. This result is useful for application because of their high stability and high PL efficiency of 33%.

Fourier transform spectra of quantum dots

Science.gov (United States)

Damian, V.; Ardelean, I.; Armăşelu, Anca; Apostol, D.

2010-05-01

Semiconductor quantum dots are nanometer-sized crystals with unique photochemical and photophysical properties that are not available from either isolated molecules or bulk solids. These nanocrystals absorb light over a very broad spectral range as compared to molecular fluorophores which have very narrow excitation spectra. High-quality QDs are proper to be use in different biological and medical applications (as fluorescent labels, the cancer treatment and the drug delivery). In this article, we discuss Fourier transform visible spectroscopy of commercial quantum dots. We reveal that QDs produced by Evident Technologies when are enlightened by laser or luminescent diode light provides a spectral shift of their fluorescence spectra correlated to exciting emission wavelengths, as shown by the ARCspectroNIR Fourier Transform Spectrometer. In the final part of this paper we show an important biological application of CdSe/ZnS core-shell ODs as microbial labeling both for pure cultures of cyanobacteria (Synechocystis PCC 6803) and for mixed cultures of phototrophic and heterotrophic microorganisms.

Optically stimulated luminescence (OSL) from Ag-doped Li{sub 2}B{sub 4}O{sub 7} crystals

Energy Technology Data Exchange (ETDEWEB)

Kananen, B.E.; Maniego, E.S.; Golden, E.M.; Giles, N.C.; McClory, J.W. [Department of Engineering Physics, Air Force Institute of Technology, Wright-Patterson Air Force Base, OH 45433 (United States); Adamiv, V.T.; Burak, Ya.V. [Vlokh Institute of Physical Optics, Dragomanov 23, L’viv 79005 (Ukraine); Halliburton, L.E., E-mail: Larry.Halliburton@mail.wvu.edu [Department of Physics and Astronomy, West Virginia University, Morgantown, WV 26506 (United States)

2016-09-15

Optically stimulated luminescence (CW-OSL) is observed from Ag-doped lithium tetraborate (Li{sub 2}B{sub 4}O{sub 7}) crystals. Photoluminescence, optical absorption, and electron paramagnetic resonance (EPR) are used to identify the defects participating in the OSL process. As-grown crystals have Ag{sup +} ions substituting for Li{sup +} ions. They also have Ag{sup +} ions occupying interstitial sites. During a room-temperature exposure to ionizing radiation, holes are trapped at the Ag{sup +} ions that replace Li{sup +} ions and electrons are trapped at the interstitial Ag{sup +} ions, i.e., the radiation forms Ag{sup 2+} (4d{sup 9}) ions and Ag{sup 0} (4d{sup 10}5s{sup 1}) atoms. These Ag{sup 2+} and Ag{sup 0} centers have characteristic EPR spectra. The Ag{sup 0} centers also have a broad optical absorption band peaking near 370 nm. An OSL response is observed when the stimulation wavelength overlaps this absorption band. Specifically, stimulation with 400 nm light produces an intense OSL response when emission is monitored near 270 nm. Electrons optically released from the Ag{sup 0} centers recombine with holes trapped at Ag{sup 2+} ions to produce the ultraviolet emission. The OSL response is progressively smaller as the stimulation light is moved to longer wavelengths (i.e., away from the 370 nm peak of the absorption band of the Ag{sup 0} electron traps). Oxygen vacancies are also present in the Ag-doped Li{sub 2}B{sub 4}O{sub 7} crystals, and their role in the OSL process as a secondary relatively short-lived electron trap is described.

Highly Luminescent Phase-Stable CsPbI3 Perovskite Quantum Dots Achieving Near 100% Absolute Photoluminescence Quantum Yield.

Science.gov (United States)

Liu, Feng; Zhang, Yaohong; Ding, Chao; Kobayashi, Syuusuke; Izuishi, Takuya; Nakazawa, Naoki; Toyoda, Taro; Ohta, Tsuyoshi; Hayase, Shuzi; Minemoto, Takashi; Yoshino, Kenji; Dai, Songyuan; Shen, Qing

2017-10-24

Perovskite quantum dots (QDs) as a new type of colloidal nanocrystals have gained significant attention for both fundamental research and commercial applications owing to their appealing optoelectronic properties and excellent chemical processability. For their wide range of potential applications, synthesizing colloidal QDs with high crystal quality is of crucial importance. However, like most common QD systems such as CdSe and PbS, those reported perovskite QDs still suffer from a certain density of trapping defects, giving rise to detrimental nonradiative recombination centers and thus quenching luminescence. In this paper, we show that a high room-temperature photoluminescence quantum yield of up to 100% can be obtained in CsPbI 3 perovskite QDs, signifying the achievement of almost complete elimination of the trapping defects. This is realized with our improved synthetic protocol that involves introducing organolead compound trioctylphosphine-PbI 2 (TOP-PbI 2 ) as the reactive precursor, which also leads to a significantly improved stability for the resulting CsPbI 3 QD solutions. Ultrafast kinetic analysis with time-resolved transient absorption spectroscopy evidence the negligible electron or hole-trapping pathways in our QDs, which explains such a high quantum efficiency. We expect the successful synthesis of the "ideal" perovskite QDs will exert profound influence on their applications to both QD-based light-harvesting and -emitting devices.

Temperature dependence of the fundamental excitonic resonance in lead-salt quantum dots

International Nuclear Information System (INIS)

Yue, Fangyu; Tomm, Jens W.; Kruschke, Detlef; Ullrich, Bruno; Chu, Junhao

2015-01-01

The temperature dependences of the fundamental excitonic resonance in PbS and PbSe quantum dots fabricated by various technologies are experimentally determined. Above ∼150 K, sub-linearities of the temperature shifts and halfwidths are observed. This behavior is analyzed within the existing standard models. Concordant modeling, however, becomes possible only within the frame of a three-level system that takes into account both bright and dark excitonic states as well as phonon-assisted carrier redistribution between these states. Our results show that luminescence characterization of lead-salt quantum dots necessarily requires both low temperatures and excitation densities in order to provide reliable ensemble parameters

Optically stimulated luminescence of common plastic materials for accident dose reconstruction

Energy Technology Data Exchange (ETDEWEB)

Chang, I.; Lee, J. I.; Kim, J. L. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Chung, K. S. [Gyeongsang National Univ., Jinju (Korea, Republic of)

2014-05-15

Optically stimulate luminescence(OSL) has many applications in a variety of radiation dosimetry fields, including personal dosimetry, environmental radiation level monitor, retrospective dosimetry for dating, and reconstruction of radiation doses from radiation accident. In the reconstruction of radiation doses from radiation accident, OSL technique has been used to estimate the doses exposed to public area through analysis of housewares or house construing materials. Recently, many efforts have been carried out for dose reconstruction using personal electronic devices such as mobile phones and USB memory chips. Some of natural minerals such as quartz and feldspar have OSL properties. Quartz is the second most abundant mineral in continental crust of the Earth. In some of common plastics, inorganic fillers (quartz, alumina etc.) are added to make strengthen of their properties depends on applications areas. The aim of this research is to explore a possibility of use of the common plastic materials for dose reconstruction in radiation accident case. In this research the OSL dose response-curve and fading characteristics of the common plastics were tested and evaluated. Finally, we expect this work contribute to elevate the possibility of the dose reconstruction. The general conclusion of this work is that the possibility of dose reconstruction using common plastic materials is showed using the OSL characteristics of the materials. However, the tested common plastic materials have relatively low sensitivities. Further work is required to establish a database of OSL properties of common plastic materials for emergency dose reconstruction by using housewares.

Two-step excitation structure changes of luminescence centers and strong tunable blue emission on surface of silica nanospheres

Energy Technology Data Exchange (ETDEWEB)

Yang, Lei, E-mail: nanoyang@qq.com; Jiang, Zhongcheng; Dong, Jiazhang; Zhang, Liuqian [Hunan University, College of Materials Science and Engineering (China); Pan, Anlian, E-mail: anlian.pan@gmail.com; Zhuang, Xiujuan [Hunan University, Key Laboratory for Micro-Nano Physics and Technology of Hunan Province (China)

2015-10-15

We report a scheme for investigating two-step stimulated structure change of luminescence centers. Amorphous silica nanospheres with uniform diameter of 9–15 nm have been synthesized by Stöber method. Strong hydroxyl-related infrared-absorption band is observed in infrared spectrum. The surface hydroxyl groups exert great influence on the luminescent behavior of silica. They provide stable and intermediate energy states to accommodate excitation electrons. The existence of these surface states reduces the energy barrier of photochemical reactions, creating conditions for two-step excitation process. By carefully examining excitation and emission process, the nearest excitation band is absent in both optical absorption spectrum and excitation spectrum. This later generated state confirms the generation of new luminescence centers as well as the existence of photochemical reactions. Stimulated by different energies, two-step excitation process impels different photochemical reactions, prompting generation of different lattice defects on surface area of silica. Thereby, tunable luminescence is achieved. After thermal treatment, strong gap excitation band appears with the disappearance of strong surface excitation band. Strong blue luminescence also disappears. The research is significance to precise introducing structural defects and controlling position of luminescence peaks.

Optically stimulated luminescence study on gamma-irradiated ice frozen from H sub 2 O and D sub 2 O

CERN Document Server

Yada, T; Hirai, M; Yamanaka, C; Ikeya, M

2002-01-01

Optically stimulated luminescence (OSL) and thermoluminescence (TL) for gamma-irradiated ice samples have been investigated as future dating techniques for icy bodies in the solar system. The OSL around 400nm lasted more than 600s for gamma-irradiated H sub 2 O ice and D sub 2 O ice under 623-nm-light stimulation at 90 K; the latter was used to study the migration of hydrogen atoms. A defect containing trapped electrons is the most suitable explanation of the OSL emissions. The intensity of the TL peak at 120 K increased linearly with gamma-dosage increasing up to 15 kGy for both D sub 2 O ice and H sub 2 O ice. Intensities of both OSL and TL for D sub 2 O ice were larger than those for H sub 2 O ice. The TL peak related to H sub 2 O was observed but its thermal characteristics did not agree with those of OH and HO sub 2 radicals measured by ESR. The OSL method should be employed in future surveys in the solar system.

Structural and optical changes induced by incorporation of antimony into InAs/GaAs(001) quantum dots

International Nuclear Information System (INIS)

Taboada, A. G.; Alonso-Alvarez, D.; Alen, B.; Rivera, A.; Ripalda, J. M.; Llorens, J. M.; Martin-Sanchez, J.; Gonzalez, Y.; Sanchez, A. M.; Beltran, A. M.; Molina, S. I.; Bozkurt, M.; Ulloa, J. M.; Koenraad, P. M.; Garcia, J. M.

2010-01-01

We present experimental evidence of Sb incorporation inside InAs/GaAs(001) quantum dots exposed to an antimony flux immediately before capping with GaAs. The Sb composition profile inside the nanostructures as measured by cross-sectional scanning tunneling and electron transmission microscopies show two differentiated regions within the quantum dots, with an Sb rich alloy at the tip of the quantum dots. Atomic force microscopy and transmission electron microscopy micrographs show increased quantum-dot height with Sb flux exposure. The evolution of the reflection high-energy electron-diffraction pattern suggests that the increased height is due to changes in the quantum-dot capping process related to the presence of segregated Sb atoms. These structural and compositional changes result in a shift of the room-temperature photoluminescence emission from 1.26 to 1.36 μm accompanied by an order of magnitude increase in the room-temperature quantum-dot luminescence intensity.

Luminescence spectra of CdSe/ZnSe double layers of quantum dots

Energy Technology Data Exchange (ETDEWEB)

Reznitsky, Alexander; Permogorov, Sergei; Korenev, Vladimir V.; Sedova, Irina; Sorokin, Sergey; Sitnikova, Alla; Ivanov, Sergei [A.F. Ioffe Physico-Technical Institute, Polytekhnicheskaya 26, 194021 St. Petersburg (Russian Federation); Klochikhin, Albert [B.P. Konstantinov Nuclear Physics Institute, St. Petersburg (Russian Federation)

2009-12-15

We have studied the emission spectra and structural properties of double CdSe/ZnSe quantum dot (QD) sheet structures grown by molecular beam epitaxy in order to elucidate the mechanisms of the electronic and strain field interaction between the QD planes. The thickness of the ZnSe barrier separating the CdSe sheets was in the range of 10-60 monolayers (ML) in the set of samples studied. We have found that coupling between dots in adjacent layers becomes relatively strong in CdSe/ZnSe double layers structures with 25-27 ML barrier, while it is rather weak when the barrier thickness exceeds 30 ML. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Sizes of water-soluble luminescent quantum dots measured by fluorescence correlation spectroscopy

International Nuclear Information System (INIS)

Zhang Pudun; Li Liang; Dong Chaoqing; Qian Huifeng; Ren Jicun

2005-01-01

In this paper, fluorescence correlation spectroscopy (FCS) was applied to measure the size of water-soluble quantum dots (QDs). The measurements were performed on a home-built FCS system based on the Stokes-Einstein equation. The obtained results showed that for bare CdTe QDs the sizes from FCS were larger than the ones from transmission electron microscopy (TEM). The brightness of QDs was also evaluated using FCS technique. It was found that the stability of the surface chemistry of QDs would be significantly improved by capping it with hard-core shell. Our data demonstrated that FCS is a simple, fast, and effective method for characterizing the fluorescent quantum dots, and is especially suitable for determining the fluorescent nanoparticles less than 10 nm in water solution

Luminescence nanothermometry

Science.gov (United States)

Jaque, Daniel; Vetrone, Fiorenzo

2012-07-01

The current status of luminescence nanothermometry is reviewed in detail. Based on the main parameters of luminescence including intensity, bandwidth, bandshape, polarization, spectral shift and lifetime, we initially describe and compare the different classes of luminescence nanothermometry. Subsequently, the various luminescent materials used in each case are discussed and the mechanisms at the root of the luminescence thermal sensitivity are described. The most important results obtained in each case are summarized and the advantages and disadvantages of these approaches are discussed.The current status of luminescence nanothermometry is reviewed in detail. Based on the main parameters of luminescence including intensity, bandwidth, bandshape, polarization, spectral shift and lifetime, we initially describe and compare the different classes of luminescence nanothermometry. Subsequently, the various luminescent materials used in each case are discussed and the mechanisms at the root of the luminescence thermal sensitivity are described. The most important results obtained in each case are summarized and the advantages and disadvantages of these approaches are discussed. This work was supported by the Universidad Autónoma de Madrid and Comunidad Autónoma de Madrid (Project S2009/MAT-1756), by the Spanish Ministerio de Educacion y Ciencia (MAT2010-16161) and by Caja Madrid Foundation.

Quantum dot based probing of mannitol: An implication in clinical diagnostics

Energy Technology Data Exchange (ETDEWEB)

Ghosh, Debasmita; Ghosh, Srabanti [UGC-DAE Consortium for Scientific Research, Kolkata Centre, III/LB-8 Bidhannagar, Kolkata 700098 (India); Saha, Abhijit, E-mail: abhijit@alpha.iuc.res.in [UGC-DAE Consortium for Scientific Research, Kolkata Centre, III/LB-8 Bidhannagar, Kolkata 700098 (India)

2010-08-24

We demonstrate that mannitol, an important diuretic, can be determined with cysteine-capped CdS quantum dots (QDs) using optical spectroscopy. Unique luminescence enhancement of QDs was observed on interaction with mannitol. The binding between QDs and mannitol was monitored by UV-vis, Fourier transform infra-red and Raman spectroscopy. The binding constant was determined following the Langmuir binding isotherm. A quantitative correlation between mannitol concentration and PL enhancement of CdS QDs has been established. We also observed that possible interfering agents, such as, urea, uric acid, creatinine, some metal ions, glucose, sorbitol or sucrose had no significant effect on luminescence of CdS QDs. The proposed strategy can be a very fast, simple and potential tool for the monitoring of diuretics and assaying intestinal permeability.

Ultrastable green fluorescence carbon dots with a high quantum yield for bioimaging and use as theranostic carriers

DEFF Research Database (Denmark)

Yang, Chuanxu; Thomsen, Rasmus Peter; Ogaki, Ryosuke

2015-01-01

to widely used semiconductor quantum dots. However, it remains a great challenge to prepare highly stable, water-soluble green luminescent Cdots with a high quantum yield. Herein we report a new synthesis route for green luminescent Cdots imbuing these desirable properties and demonstrate their potential...... in biomedical applications. Oligoethylenimine (OEI)–β-cyclodextrin (βCD) Cdots were synthesised using a simple and fast heating method in phosphoric acid. The synthesised Cdots showed strong green fluorescence under UV excitation with a 30% quantum yield and exhibited superior stability over a wide pH range. We...

Multiplexed measurements by time resolved spectroscopy using colloidal CdSe/ZnS quantum dots

Energy Technology Data Exchange (ETDEWEB)

Kaiser, U.; Jimenez de Aberasturi, D.; Malinowski, R.; Amin, F.; Parak, W. J.; Heimbrodt, W., E-mail: Wolfram.Heimbrodt@physik.uni-marburg.de [Department of Physics and Materials Sciences Center, Philipps-University of Marburg, Renthof 5, D-35032 Marburg (Germany)

2014-01-27

Multiplexed measurements of analytes in parallel is a topical demand in bioanalysis and bioimaging. An interesting alternative to commonly performed spectral multiplexing is lifetime multiplexing. In this Letter, we present a proof of principle of single-color lifetime multiplexing by coupling the same fluorophore to different nanoparticles. The effective lifetime of the fluorophores can be tuned by more than one order of magnitude due to resonance energy transfer from donor states. Measurements have been done on a model systems consisting of ATTO-590 dye molecules linked to either gold particles or to CdSe/ZnS core shell quantum dots. Both systems show the same luminescence spectrum of ATTO-590 dye emission in continuous wave excitation, but can be distinguished by means of time resolved measurements. The dye molecules bound to gold particles exhibit a mono-exponential decay with a lifetime of 4.5 ns, whereas the dye molecules bound to CdSe/ZnS dots show a nonexponential decay with a slow component of about 135 ns due to the energy transfer from the quantum dots. We demonstrate the fundamental possibility to determine the mixing ratio for dyes with equal luminescence spectra but very different transients. This opens up a pathway independent of the standard optical multiplexing with many different fluorophores emitting from the near ultraviolet to the near infrared spectral region.

Redox reactions and mechanism of luminescence in BaFCl:Eu

CERN Document Server

Upadeo, S V; Gundurao, T K

1998-01-01

The phenomenon of stimulable luminescence of phosphors pre-irradiated with high-energy radiation is widely used in the field of imaging. Phosphors such as BaFX:Eu (X = Cl, Br) are extensively used in x-ray screens for digital image processing. There is, however, divided opinion regarding the mechanism responsible for the luminescence process in these materials. In this paper we have discussed the role of Eu sup 3 sup +reversible Eu sup 2 sup + conversion in BaFCl:Eu phosphor using PL, TL, TL emission and ESR techniques. (author)

Imaging surface plasmon polaritons using proximal self-assembled InGaAs quantum dots

Energy Technology Data Exchange (ETDEWEB)

Bracher, Gregor; Schraml, Konrad; Blauth, Mäx; Wierzbowski, Jakob; López, Nicolás Coca; Bichler, Max; Müller, Kai; Finley, Jonathan J.; Kaniber, Michael, E-mail: Michael.Kaniber@wsi.tum.de [Walter Schottky Institut and Physik Department, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany and Nanosystems Initiative Munich, Schellingstraße 4, 80799 München (Germany)

2014-07-21

We present optical investigations of hybrid plasmonic nanosystems consisting of lithographically defined plasmonic Au-waveguides or beamsplitters on GaAs substrates coupled to proximal self-assembled InGaAs quantum dots. We designed a sample structure that enabled us to precisely tune the distance between quantum dots and the sample surface during nano-fabrication and demonstrated that non-radiative processes do not play a major role for separations down to ∼10 nm. A polarized laser beam focused on one end of the plasmonic nanostructure generates propagating surface plasmon polaritons that, in turn, create electron-hole pairs in the GaAs substrate during propagation. These free carriers are subsequently captured by the quantum dots ∼25 nm below the surface, giving rise to luminescence. The intensity of the spectrally integrated quantum dot luminescence is used to image the propagating plasmon modes. As the waveguide width reduces from 5 μm to 1 μm, we clearly observe different plasmonic modes at the remote waveguide end, enabling their direct imaging in real space. This imaging technique is applied to a plasmonic beamsplitter facilitating the determination of the splitting ratio between the two beamsplitter output ports as the interaction length L{sub i} is varied. A splitting ratio of 50:50 is observed for L{sub i}∼9±1 μm and 1 μm wide waveguides for excitation energies close to the GaAs band edge. Our experimental findings are in good agreement with mode profile and finite difference time domain simulations for both waveguides and beamsplitters.

Porous silicon: silicon quantum dots for photonic applications

International Nuclear Information System (INIS)

Pavesi, L.; Guardini, R.

1996-01-01

Porous silicon formation and structure characterization are briefly illustrated. Its luminescence properties rae presented and interpreted on the basis of exciton recombination in quantum dot structures: the trap-controlled hopping mechanism is used to describe the recombination dynamics. Porous silicon application to photonic devices is considered: porous silicon multilayer in general, and micro cavities in particular are described. The present situation in the realization of porous silicon LEDs is considered, and future developments in this field of research are suggested. (author). 30 refs., 30 figs., 13 tabs

Luminescence dating of the Zeketai loess section in the Ili Basin, northwestern China: Methodological considerations

Science.gov (United States)

Qin, Jintang; Zhou, Liping

2018-04-01

Loess deposits in Xinjiang, northwestern China are ideal archives for past environmental changes in the Westerlies-dominated central Asia. Among previous luminescence dating studies of loess in Xinjiang, few have attempted to systematically investigate the methodological aspects. In this study, we report results of a multiple-procedure luminescence dating of the Zeketai loess section in the Ili Basin, central Xinjiang. Optically stimulated luminescence (OSL) and post-infrared infrared stimulated luminescence (pIRIR) signals were used for quartz and polymineral grains of different sizes. The pIRIR ages obtained with two protocols agree well with each other and constrain the loess deposition between 50 ka and 88 ka. The OSL ages of fine-grained quartz are in stratigraphic order and range from 37 ka to 61 ka, but are ∼30% younger than the pIRIR295 ages of both fine and medium grained polyminerals. Although the causes of the discrepancy between the ages derived from different luminescence dating protocols are still to be understood, we stress that the quartz OSL ages of loess in this region are likely to be underestimated, especially for samples older than 40 ka. The polymineral or potassium feldspar pIRIR signal is recommended for dating loess in the Ili Basin, at least as an internal check.

Fiber-coupled Luminescence Dosimetry in Therapeutic and Diagnostic Radiology

DEFF Research Database (Denmark)

Andersen, Claus Erik

2011-01-01

. Some crystalline phosphors, such as carbon-doped aluminium oxide (Al2O3:C) have the ability to store charge produced in the crystal during irradiation. The stored charge may later be released by fiber-guided laser light under emission of so-called optically stimulated luminescence (OSL). The OSL signal......Fiber-coupled luminescence dosimetry is an emerging technology with several potentially attractive features of relevance for uses in therapeutic and diagnostic radiology: direct water equivalence (i.e. no significant perturbation of the radiation field in a water phantom or a patient), sub......-mm detector size, high dynamic range (below a mGy to several Gy), microsecond time resolution, and absence of electrical wires or other electronics in the dosimeter probe head. Fiber-coupled luminescence dosimetry systems typically consist of one or more small samples of phosphor, e.g. a mg of plastic...

Studies on α-Al2O3: C based optically stimulated luminescence badge for eye lens monitoring applications

International Nuclear Information System (INIS)

Kumar, Munish; Kulkarni, M.S.; Ratna, P.; Gaikwad, N.; Tripathi, S.M.; Sharma, S.D.; Babu, D.A.R.; Bhatnagar, Amit; Muthe, K.P.; Sharma, D.N.

2014-01-01

The prototype two element eye-lens dosimeter badge based on indigenously developed α-Al 2 O 3 : C optically stimulated luminescence dosimeter was investigated comprehensively for its suitability for eye-lens monitoring applications. The badge is calibrated to measure the eye-lens dose in terms of H p (3). The minimum measurable dose using the eye-lens dosimeter badge is observed to be ∼ 35 μSv. This prototype eye-lens dosimeter badge was found to be suitable for measuring doses from X-rays, beta and gamma radiations to the eye-lens. The satisfactory performance of the prototype two element eye-lens dosimeter badge along with its attractive features such as multiple readout, less processing time, very good beta response uniquely position it for monitoring the eye-lens dose are presented. (author)

Optically stimulated luminescence techniques in retrospective dosimetry using single grains of quartz extracted from unheated materials

Energy Technology Data Exchange (ETDEWEB)

Joerkov Thomsen, Kristina

2004-02-01

This work investigates the possibility of applying optically stimulated luminescence (OSL) in retrospective dose determinations using unheated materials. It focuses on identifying materials suitable for use in assessment of doses absorbed as a consequence of radiation accidents (i.e. accident dosimetry). Special attention has been paid to quartz extracted from unheated building materials such as concrete and mortar. The single-aliquot regeneration-dose (SAR) protocol has been used to determine absorbed doses in small aliquots as well as single grains of quartz. It is shown that OSL measurements of single grains of quartz extracted from poorly-bleached building materials can provide useful information on radiation accident doses, even when the luminescence sensitivity is low. Sources of variance in well-bleached single grain dose distributions have been investigated in detail and it is concluded that the observed variability in the data is consistent with the sum (in quadrature) of a component, which depends on the number of photons detected from each grain, and a fixed component independent of light level. Dose depth profiles through laboratory irradiated concrete bricks have successfully been measured and minimum detection limits of less than 100 mGy are derived. Measurements of thermal transfer in single grains of poorly-bleached quartz show that thermal transfer is variable on a grain-to-grain basis and that it can be a source of variance in single-grain dose distributions. Furthermore, the potential of using common household and workplace chemicals, such as table salt, washing powder and water softener, in retrospective dosimetry has been investigated. It is concluded that such materials should be considered as retrospective dosimeters in the event of a radiation accident. (au)

Study of quantum dot based on tin/yttrium mixed oxide doped with terbium to be used as biomarker

International Nuclear Information System (INIS)

Paganini, Paula P.; Felinto, Maria Claudia F.C.; Kodaira, Claudia A.; Brito, Hermi F.; Nunes, Luiz Antonio O.

2009-01-01

Quantum dots (semiconductors nanocrystals) have brought a promising field to develop a new generation of luminescent biomarkers. The use of lanthanides ions as luminescent markers has many advantages, for example a security method, low cost, high specificity and also the luminescence can be promptly measured with high sensibility and accuracy. These luminescent dots are functionalized with biomolecules. For the luminophore particle to be connect with biologicals molecules (for example covalent antibody) is necessary a previous chemical treatment to modify luminophore particle surface and this process is called functionalization. A prior chemical treatment with changes on the surface luminophore particle is necessary to couple the luminophore to biological molecules. This process can be used as coating which can protect these particles from being dissolved by acid as well as provide functional groups for biological conjugation. This work presents a photoluminescence study of nanoparticles based on tin/yttrium mixed oxides doped with terbium (SnO 2 /Y 2 O 3 :Tb 3+ ), synthesized by coprecipitation method. The nanoparticles were submitted to thermal treatment and characterized by X-Ray Powder Diffraction (XRD) that showed cassiterite phase formation and the influence of thermal treatment on nanoparticles structures. These nanoparticles going to be functionalized with a natural polysaccharide (chitosan) in order to form microspheres. These microspheres going to be irradiated with gamma radiation to sterilization and it can be evaluated if the nanoparticles are resistant to irradiation and they do not lose functionality with this process. (author)

Analysis of luminescence from common salt (NaCl) for application to retrospective dosimetry

International Nuclear Information System (INIS)

Spooner, N.A.; Smith, B.W.; Williams, O.M.; Creighton, D.F.; McCulloch, I.; Hunter, P.G.; Questiaux, D.G.; Prescott, J.R.

2011-01-01

Thermoluminescence (TL), Optically-Stimulated Luminescence (OSL) and Infrared-Stimulated Luminescence (IRSL) emitted from a set of 19 salt (NaCl) samples were studied for potential application to retrospective dosimetry. TL emission spectra revealed intense TL emissions from most samples, centred on 590 nm; UV and blue emissions were also found. Significant thermally-induced sensitivity changes were observed and TL, OSL and IRSL growth curves were measured. Pulse anneal analysis was performed, as was quantitative imaging of the TL, OSL and IRSL to assess sample heterogeneity. Kinetic analysis found lifetimes at 20 °C of the 200 °C and 240 °C TL peaks to be 0.6 ka and 4 ka respectively; sufficient for application to retrospective dosimetry.

Homeotropic alignment and Förster resonance energy transfer: The way to a brighter luminescent solar concentrator

Energy Technology Data Exchange (ETDEWEB)

Tummeltshammer, Clemens; Taylor, Alaric; Kenyon, Anthony J.; Papakonstantinou, Ioannis, E-mail: i.papakonstantinou@ucl.ac.uk [Department of Electronic and Electrical Engineering, University College London, London WC1E 7JE (United Kingdom)

2014-11-07

We investigate homeotropically aligned fluorophores and Förster resonance energy transfer (FRET) for luminescent solar concentrators using Monte-Carlo ray tracing. The homeotropic alignment strongly improves the trapping efficiency, while FRET circumvents the low absorption at homeotropic alignment by separating the absorption and emission processes. We predict that this design doped with two organic dye molecules can yield a 82.9% optical efficiency improvement compared to a single, arbitrarily oriented dye molecule. We also show that quantum dots are prime candidates for absorption/donor fluorophores due to their wide absorption band. The potentially strong re-absorption and low quantum yield of quantum dots is not a hindrance for this design.

Electrochemical tuning of optical properties of graphitic quantum dots

International Nuclear Information System (INIS)

Ge, Juan; Li, Yan; Zhang, Bo-Ping; Ma, Ning; Wang, Jun; Pu, Chang; Xiang, Ying-Chang

2015-01-01

Graphitic quantum dots (GQDs), as a new class of quantum dots, possess unique properties. Among the various reported approaches for their fabrication, electrochemical method possesses numerous advantages compared with others. In particular, the formation process of the GQDs could be precisely controlled by this method through adjusting the electrochemical parameters and environment. In this study, GQDs with multi-color fluorescence (FL) were obtained by this method through tuning only the applied potential window of cycling voltammetry. The luminescence mechanism of those GQDs was discussed and explained by the ultraviolet (UV)–visible, photoluminescence (PL), and photoluminescence excitation (PLE) spectra. The influence of the applied potential window on the PL properties of GQDs and the relationship between the degree of surface oxidation and PL properties were also investigated. - Highlights: • We produced the graphite quantum dots (GQDs) by an electrochemical method. • We changed the applied potentials of cycling voltammetry (CV). • Varying of applied potentials changed surface oxygen-containing groups of GQDs. • Higher surface oxidation degree resulted in the red-shift of PL spectra

Single-grain and multigrain luminescence dating of on-ice and lake-bottom deposits at Lake Hoare, Taylor Valley, Antarctica

DEFF Research Database (Denmark)

Berger, G.W.; Doran, P.T.; Thomsen, Kristina Jørkov

2010-01-01

The large radiocarbon (14C) reservoir effect in Antarctica varies regionally and with settings. Luminescence sediment dating has potential as an alternate geochronometer. Extending our earlier tests of the effectiveness of resetting of photon-stimulated-luminescence (PSL) that employed only multi...

Study of Optically Stimulated Luminescence of LiF:Mg,Ti for beta and gamma dosimetry

International Nuclear Information System (INIS)

Matsushima, Luciana C.; Veneziani, Glauco R.; Campos, Letícia L.

2013-01-01

Modern advances in radiation medicine – radiodiagnosis, radiotherapy and interventional radiography – each present dosimetry challenges for the medical physicist that did not exist previously. In all of these areas a constant balance has to be made between the treatment necessary to destroy the tumor and the unnecessary exposure of healthy tissue. Innovative applications of OSL dosimetry are now appearing in each of these areas to help the medical physicist and oncologist design the most effective, and least deleterious, treatment for their patients. High sensitivity, precise delivery of light, fast readout times, simpler readers and easier automation are the main advantages of OSL in comparison with TLD. This work aimed to study the application of OSL technique using lithium fluoride dosimeters doped with magnesium and titanium (LiF:Mg,Ti) for application in beta and gamma dosimetry. -- Highlights: •Study of Optically Stimulated Luminescence of LiF:Mg,Ti and microLiF:Mg,Ti. •OSL response of TLD-100 dosimeters to beta and gamma radiation. •Analysis of repeatability and lowest levels of detection of detectors LiF:Mg,Ti

Hydrothermal green synthesis of magnetic Fe3O4-carbon dots by lemon and grape fruit extracts and as a photoluminescence sensor for detecting of E. coli bacteria.

Science.gov (United States)

Ahmadian-Fard-Fini, Shahla; Salavati-Niasari, Masoud; Ghanbari, Davood

2018-10-05

The aim of this work is preparing of a photoluminescence nanostructures for rapid detection of bacterial pathogens. Firstly, carbon dots (CDs) were synthesized by grape fruit, lemon, turmeric extracts and hydrothermal method. Then Fe 3 O 4 (magnetite) nanoparticles was achieved using these bio-compatible capping agents. Finally, magnetite-carbon dots were synthesized as a novel magnetic and photoluminescence nanocomposite. X-ray diffraction (XRD) confirms the crystallinity and phase of the products, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) investigate the morphology, shape and size of the magnetite, carbon dot and nanocomposites. Fourier transform infrared (FT-IR) spectroscopy shows the purity of the nanostructures. Ultraviolet-visible (UV-Vis) absorption and photo-luminescence (PL) spectroscopy show suitable photo-luminescence under ultraviolet irradiation. Vibrating sample magnetometer (VSM) shows super paramagnetic property of the product. Interestingly carbon dots were used as a non-toxic photoluminescence sensor for detecting of Escherichia coli (E. coli) bacteria. Results show quenching of photoluminescence of the CDs nanocomposite by increasing amount of E. coli bacteria. Copyright © 2018 Elsevier B.V. All rights reserved.

A new mathematical approximation of sunlight attenuation in rocks for surface luminescence dating

Energy Technology Data Exchange (ETDEWEB)

Laskaris, Nikolaos, E-mail: nick.laskaris@gmail.com [University of the Aegean, Department of Mediterranean Studies, Laboratory of Archaeometry, 1 Demokratias Avenue, Rhodes 85100 (Greece); Liritzis, Ioannis, E-mail: liritzis@rhodes.aegean.gr [University of the Aegean, Department of Mediterranean Studies, Laboratory of Archaeometry, 1 Demokratias Avenue, Rhodes 85100 (Greece)

2011-09-15

The attenuation of sunlight through different rock surfaces and the thermoluminescence (TL) or Optical stimulated luminescence (OSL) residuals clock resetting derived from sunlight induced eviction of electrons from electron traps, is a prerequisite criterion for potential dating. The modeling of change of residual luminescence as a function of two variables, the solar radiation path length (or depth) and exposure time offers further insight into the dating concept. The double exponential function modeling based on the Lambert-Beer law, valid under certain assumptions, constructed by a quasi-manual equation fails to offer a general and statistically sound expression of the best fit for most rock types. A cumulative log-normal distribution fitting provides a most satisfactory mathematical approximation for marbles, marble schists and granites, where absorption coefficient and residual luminescence parameters are defined per each type of rock or marble quarry. The new model is applied on available data and age determination tests. - Highlights: > Study of aattenuation of sunlight through different rock surfaces. > Study of the thermoluminescence (TL) or Optical stimulated luminescence (OSL) residuals as a function of depth. > A Cumulative Log-Normal Distribution fitting provides the most satisfactory modeling for marbles, marble schists and granites. > The new model (Cummulative Log-Norm Fitting) is applied on available data and age determination tests.

A new mathematical approximation of sunlight attenuation in rocks for surface luminescence dating

International Nuclear Information System (INIS)

Laskaris, Nikolaos; Liritzis, Ioannis

2011-01-01

The attenuation of sunlight through different rock surfaces and the thermoluminescence (TL) or Optical stimulated luminescence (OSL) residuals clock resetting derived from sunlight induced eviction of electrons from electron traps, is a prerequisite criterion for potential dating. The modeling of change of residual luminescence as a function of two variables, the solar radiation path length (or depth) and exposure time offers further insight into the dating concept. The double exponential function modeling based on the Lambert-Beer law, valid under certain assumptions, constructed by a quasi-manual equation fails to offer a general and statistically sound expression of the best fit for most rock types. A cumulative log-normal distribution fitting provides a most satisfactory mathematical approximation for marbles, marble schists and granites, where absorption coefficient and residual luminescence parameters are defined per each type of rock or marble quarry. The new model is applied on available data and age determination tests. - Highlights: → Study of aattenuation of sunlight through different rock surfaces. → Study of the thermoluminescence (TL) or Optical stimulated luminescence (OSL) residuals as a function of depth. → A Cumulative Log-Normal Distribution fitting provides the most satisfactory modeling for marbles, marble schists and granites. → The new model (Cummulative Log-Norm Fitting) is applied on available data and age determination tests.

Principal and secondary luminescence lifetime components in annealed natural quartz

International Nuclear Information System (INIS)

Chithambo, M.L.; Ogundare, F.O.; Feathers, J.

2008-01-01

Time-resolved luminescence spectra from quartz can be separated into components with distinct principal and secondary lifetimes depending on certain combinations of annealing and measurement temperature. The influence of annealing on properties of the lifetimes related to irradiation dose and temperature of measurement has been investigated in sedimentary quartz annealed at various temperatures up to 900 deg. C. Time-resolved luminescence for use in the analysis was pulse stimulated from samples at 470 nm between 20 and 200 deg. C. Luminescence lifetimes decrease with measurement temperature due to increasing thermal effect on the associated luminescence with an activation energy of thermal quenching equal to 0.68±0.01eV for the secondary lifetime but only qualitatively so for the principal lifetime component. Concerning the influence of annealing temperature, luminescence lifetimes measured at 20 deg. C are constant at about 33μs for annealing temperatures up to 600 0 C but decrease to about 29μs when the annealing temperature is increased to 900 deg. C. In addition, it was found that lifetime components in samples annealed at 800 deg. C are independent of radiation dose in the range 85-1340 Gy investigated. The dependence of lifetimes on both the annealing temperature and magnitude of radiation dose is described as being due to the increasing importance of a particular recombination centre in the luminescence emission process as a result of dynamic hole transfer between non-radiative and radiative luminescence centres

Assessment of diagnostic multileaf collimator for cephalometric exposure reduction using optically stimulated luminescent dosemeters

International Nuclear Information System (INIS)

Han, Su Chul; Kim, Kum Bae; Jung, Haijo; Ji, YoungHoon; Park, Seungwoo

2017-01-01

A diagnostic multileaf collimator (MLC) was developed for diagnostic radiography dose reduction. Optically stimulated luminescent dosemeters (OSLDs) were used to evaluate the efficacy of this device for dental radiography cephalometric exposure reduction. The OSLD dosimetric characteristics for 80 kVp cephalometric exposure were first obtained. The batch homogeneity and reproducibility were 1.67 % and 0.18-1.58, respectively. Good linearity was obtained between the OSLD dose and response, and the angular dependence was within ±4 %. The equivalent organ doses for the left eye, right eye and thyroid were 41.20±6.58, 178.86±1.71 and 171.12±8.78 mSv and 36.80±0.33, 156.63±0.22 and 22.04±0.13 mSv for the open and MLC fields, respectively. The MLC-induced dose reductions for the left and right eyes of in field were 10.67±16.78 and 12.42±8.84 %, respectively, and that of the thyroid gland of out of field was 87±8.82 %, considering combined uncertainty. Therefore, use of diagnostic MLC for dose reduction during dental radiography cephalometric exposure is both feasible and effective. (authors)

Insect wings as retrospective/accidental/forensic dosimeters: An optically stimulated luminescence investigation

International Nuclear Information System (INIS)

Kazakis, Nikolaos A.; Tsetine, Anastasia Th.; Kitis, George; Tsirliganis, Nestor C.

2016-01-01

Estimation of the radiation released during nuclear accidents or radiological terrorist events is imperative for the prediction of health effects following such an exposure. In addition, in several cases there is a need to identify the prior presence of radioactive materials at buildings or sites (nuclear forensics). To this direction, several materials have been the research object of numerous studies the last decade in an attempt to identify potentially new retrospective/accidental/forensic dosimeters. However, the studies targeting biological materials are limited and their majority is mainly focused on the luminescence behavior of human biological material. Consequently, the use of such materials in retrospective dosimetry presumes the exposure of humans in the radiation field. The present work constitutes the first attempt to seek non-human biological materials, which can be found in nature in abundance or in/on other living organisms. To this end, the present work investigates the basic optically stimulated luminescence behavior of insect wings, which exhibit several advantages compared to other materials. Insects are ubiquitous, have a short life expectancy and exhibit a low decomposition rate after their death. Findings of the present study are encouraging towards the potential use of insects' wings at retrospective/accidental/forensic dosimetry, since they exhibit linear OSL response over a wide dose range and imperceptible loss of signal several days after their irradiation when they are kept in dark. On the other hand, the calculated lower detection limit is not low enough to allow their use as emergency dosimeters when individuals are exposed to non-lethal doses. In addition, wings exhibit strong optical fading when they are exposed to daylight and thus special care should be taken during the sampling procedure in order to use the wings as accidental/forensic dosimeters, by seeking (dead) insects in dark places, such as behind furniture, equipment or in

New ages for Middle and Later Stone Age deposits at Mumba rockshelter, Tanzania: optically stimulated luminescence dating of quartz and feldspar grains.

Science.gov (United States)

Gliganic, Luke A; Jacobs, Zenobia; Roberts, Richard G; Domínguez-Rodrigo, Manuel; Mabulla, Audax Z P

2012-04-01

The archaeological deposits at Mumba rockshelter, northern Tanzania, have been excavated for more than 70 years, starting with Margit and Ludwig Köhl-Larsen in the 1930s. The assemblages of Middle Stone Age (MSA) and Later Stone Age (LSA) artefacts collected from this site constitute the type sequences for these cultural phases in East Africa. Despite its archaeological importance, however, the chronology of the site is poorly constrained, despite the application since the 1980s of several dating methods (radiocarbon, uranium-series and amino acid racemisation) to a variety of materials recovered from the deposits. Here, we review these previous chronologies for Mumba and report new ages obtained from optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL) measurements on single grains of quartz and multi-grain aliquots of potassium (K) feldspar from the MSA and LSA deposits. Measurements of single grains of quartz allowed the rejection of unrepresentative grains and the application of appropriate statistical models to obtain the most reliable age estimates, while measurements of K-feldspars allowed the chronology to be extended to older deposits. The seven quartz ages and four K-feldspar ages provide improved temporal constraints on the archaeological sequence at Mumba. The deposits associated with the latest Kisele Industry (Bed VI-A) and the earliest Mumba Industry (Bed V) are dated to 63.4 ± 5.7 and 56.9 ± 4.8 ka (thousands of years ago), respectively, thus constraining the time of transition between these two archaeological phases to ~60 ka. An age of 49.1 ± 4.3 ka has been obtained for the latest deposits associated with the Mumba Industry, which show no evidence for post-depositional mixing and contain ostrich eggshell (OES) beads and abundant microlithics. The Nasera Industry deposits (Bed III) contain large quantities of OES beads and date to 36.8 ± 3.4 ka. We compare the luminescence ages with the previous chronologies for

Dosimetric methodology for extremities of individuals occupationally exposed to beta radiation using the optically stimulated luminescence technique

International Nuclear Information System (INIS)

Pinto, Teresa Cristina Nathan Outeiro

2010-01-01

A dosimetric methodology was established for the determination of extremity doses of individuals occupationally exposed to beta radiation, using Al 2 O 3 :C detectors and the optically stimulated luminescence (OSL) reader system microStar, Landauer. The main parts of the work were: characterization of the dosimetric material Al 2 O 3 :C using the OSL technique; establishment of the dose evaluation methodology; dose rate determination of beta radiation sources; application of the established method in a practical test with individuals occupationally exposed to beta radiation during a calibration simulation of clinical applicators; validation of the methodology by the comparison between the dose results of the practical test using the OSL and the thermoluminescence (TL) techniques. The results show that both the OSL Al-2O 3 :C detectors and the technique may be utilized for individual monitoring of extremities and beta radiation. (author)

Fabrication of carbon quantum dots with nano-defined position and pattern in one step via sugar-electron-beam writing.

Science.gov (United States)

Weng, Yuyan; Li, Zhiyun; Peng, Lun; Zhang, Weidong; Chen, Gaojian

2017-12-14

Quantum dots (QDs) are promising materials in nanophotonics, biological imaging, and even quantum computing. Precise positioning and patterning of QDs is a prerequisite for realizing their actual applications. Contrary to the traditional two discrete steps of fabricating and positioning QDs, herein, a novel sugar-electron-beam writing (SEW) method is reported for producing QDs via electron-beam lithography (EBL) that uses a carefully chosen synthetic resist, poly(2-(methacrylamido)glucopyranose) (PMAG). Carbon QDs (CQDs) could be fabricated in situ through electron beam exposure, and the nanoscale position and luminescence intensity of the produced CQDs could be precisely controlled without the assistance of any other fluorescent matter. We have demonstrated that upon combining an electron beam with a glycopolymer, in situ production of CQDs occurs at the electron beam spot center with nanoscale precision at any place and with any patterns, an advancement that we believe will stimulate innovations in future applications.

New Nanomaterials and Luminescent Optical Sensors for Detection of Hydrogen Peroxide

Directory of Open Access Journals (Sweden)

Natalia A. Burmistrova

2015-10-01

Full Text Available Accurate methods that can continuously detect low concentrations of hydrogen peroxide (H2O2 have a huge application potential in biological, pharmaceutical, clinical and environmental analysis. Luminescent probes and nanomaterials are used for fabrication of sensors for H2O2 that can be applied for these purposes. In contrast to previous reviews focusing on the chemical design of molecular probes for H2O2, this mini-review highlights the latest luminescent nanoparticular materials and new luminescent optical sensors for H2O2 in terms of the nanomaterial composition and luminescent receptor used in the sensors. The nanomaterial section is subdivided into schemes based on gold nanoparticles, polymeric nanoparticles with embedded enzymes, probes showing aggregation-induced emission enhancement, quantum dots, lanthanide-based nanoparticles and carbon based nanomaterials, respectively. Moreover, the sensors are ordered according to the type of luminescent receptor used within the sensor membranes. Among them are lanthanide complexes, metal-ligand complexes, oxidic nanoparticles and organic dyes. Further, the optical sensors are confined to those that are capable to monitor the concentration of H2O2 in a sample over time or are reusable. Optical sensors responding to gaseous H2O2 are not covered. All nanomaterials and sensors are characterized with respect to the analytical reaction towards H2O2, limit of detection (LOD, analytical range, electrolyte, pH and response time/incubation time. Applications to real samples are given. Finally, we assess the suitability of the nanomaterials to be used in membrane-based sensors and discuss future trends and perspectives of these sensors in biomedical research.

Optical fibre dosemeter systems for clinical applications based on radioluminescence and optically stimulated luminescence from Al₂O₃:C

DEFF Research Database (Denmark)

Marckmann, C.J.; Andersen, C.E.; Aznar, M.C.

2006-01-01

Optical fibre dosemeter systems based on radioluminescence and optically stimulated luminescence (OSL) from carbon-doped aluminium oxide (Al2O3:C) crystals were developed for in vivo real-time dose rate and absorbed dose measurements in radiotherapy and mammography. A technique was also developed...... for making ultra-small dosemeter probes that can easily be placed inside patients in radiation treatment. These probes have shown excellent properties in both head and neck intensity-modulated radiation therapy treatment and in mammography. The dose-response of the OSL signal for the new optical fibre...

Formation of carbon quantum dots and nanodiamonds in laser ablation of a carbon film

Science.gov (United States)

Sidorov, A. I.; Lebedev, V. F.; Kobranova, A. A.; Nashchekin, A. V.

2018-01-01

We have experimentally shown that nanosecond near-IR pulsed laser ablation of a thin amorphous carbon film produces carbon quantum dots with a graphite structure and nanodiamonds with a characteristic size of 20 - 500 nm on the substrate surface. The formation of these nanostructures is confirmed by electron microscopic images, luminescence spectra and Raman spectra. The mechanisms explaining the observed effects are proposed.

Dual-excitation upconverting nanoparticle and quantum dot aptasensor for multiplexed food pathogen detection

OpenAIRE

Kurt, Hasan; Yüce, Meral; Yuce, Meral; Hussain, Babar; Budak, Hikmet

2016-01-01

In this report, a dual-excitation sensing method was developed using aptamer-functionalized quantum dots and upconverting nanoparticles, exhibiting Stokes and anti-Stokes type excitation profiles, respectively. Conjugation of the aptamer-functionalized luminescent nanoparticles with the magnetic beads, comprising short DNA sequences that were partially complementary to the aptamer sequences, enabled facile separation of the analyte-free conjugates for fluorescent measurement. UV–Visible spect...

Templated self-assembly of SiGe quantum dots

Energy Technology Data Exchange (ETDEWEB)

Dais, Christian

2009-08-19

-dimensional quantum dot crystals. The analyzed SiGe quantum dots have a type II band alignment, with holes confined in the dots and electrons confined in the strained Si in the surrounding of the dots. The recombination energy of these indirect excitons depends on size, Ge content and strain distribution of the quantum dots. It is shown that the structural uniformity of the created quantum dot structures is reflected in their optical properties, resulting in a narrow and stable photoluminescence emission with well separated no-phonon and transversal optical phonon lines. The narrow dot luminescence can be shifted by varying Ge coverage, dot size or dot period. Furthermore excitation-power dependent and temperature dependent photoluminescence measurements are discussed. Band structure calculations indicate that the electronic states of the quantum dot crystals are electronically coupled at least in vertical direction. For the quantum dot crystal with a lateral period of 35 nm even a coupling in all three dimensions is calculated. Thus, the three-dimensional dot arrangement represents not only from the structural but also from the electronic point of view an artificial crystal. (orig.)

Comparison of the Optical Properties of Graphene and Alkyl-terminated Si and Ge Quantum Dots.

Science.gov (United States)

de Weerd, Chris; Shin, Yonghun; Marino, Emanuele; Kim, Joosung; Lee, Hyoyoung; Saeed, Saba; Gregorkiewicz, Tom

2017-10-31

Semiconductor quantum dots are widely investigated due to their size dependent energy structure. In particular, colloidal quantum dots represent a promising nanomaterial for optoelectronic devices, such as photodetectors and solar cells, but also luminescent markers for biotechnology, among other applications. Ideal materials for these applications should feature efficient radiative recombination and absorption transitions, altogether with spectral tunability over a wide range. Group IV semiconductor quantum dots can fulfill these requirements and serve as an alternative to the commonly used direct bandgap materials containing toxic and/or rare elements. Here, we present optical properties of butyl-terminated Si and Ge quantum dots and compare them to those of graphene quantum dots, finding them remarkably similar. We investigate their time-resolved photoluminescence emission as well as the photoluminescence excitation and linear absorption spectra. We contemplate that their emission characteristics indicate a (semi-) resonant activation of the emitting channel; the photoluminescence excitation shows characteristics similar to those of a molecule. The optical density is consistent with band-to-band absorption processes originating from core-related states. Hence, these observations strongly indicate a different microscopic origin for absorption and radiative recombination in the three investigated quantum dot systems.

A New Generation of Luminescent Materials Based on Low-Dimensional Perovskites

KAUST Repository

Pan, Jun

2017-06-02

Low-dimensional perovskites with high luminescence properties are promising materials for optoelectronic applications. In this article, properties of two emerging types of low-dimensional perovskites are discussed, including perovskite quantum dots CsPbX3 (X = Cl, Br or I) and zero-dimensional perovskite Cs4PbBr6. Moreover, their application for light down conversion in LCD backlighting systems and in visible light communication are also presented. With their superior optical properties, we believe that further development of these materials will potentially open more prospective applications, especially for optoelectronics devices.

Optically stimulated luminescence dating as a tool for calculating sedimentation rates in Chinese loess: comparisons with grain-size records

DEFF Research Database (Denmark)

Stevens, Thomas; Lu, HY

2009-01-01

Understanding loess sedimentation rates is crucial for constraining past atmospheric dust dynamics, regional climatic change and local depositional environments. However, the derivation of loess sedimentation rates is complicated by the lack of available methods for independent calculation......) the influences on sediment grain-size and accumulation; and (ii) their relationship through time and across the depositional region. This uncertainty has led to the widespread use of assumptions concerning the relationship between sedimentation rate and grain-size in order to derive age models and climate...... reconstructions. To address this uncertainty, detailed independent age models, based on optically stimulated luminescence dating, undertaken at 10 to 40 cm intervals at five sections across the Loess Plateau in China, have been used to calculate sedimentation rates and make comparisons with grain-size changes...

Spectrally resolved thermally stimulated luminescence of irradiated anion-defective alumina single crystals

Energy Technology Data Exchange (ETDEWEB)

Kortov, V., E-mail: vskortov@mail.ru [Ural Federal University, Mira Str. 19, 620002 Ekaterinburg (Russian Federation); Lushchik, A.; Nagirnyi, V. [Institute of Physics, University of Tartu, W. Ostwald Str. 1, 50411 Tartu (Estonia); Ananchenko, D. [Ural Federal University, Mira Str. 19, 620002 Ekaterinburg (Russian Federation); Romet, I. [Institute of Physics, University of Tartu, W. Ostwald Str. 1, 50411 Tartu (Estonia)

2017-06-15

Thermally stimulated luminescence (TSL) spectra in the 313–580 K temperature range have been studied in anion-defective alumina crystals (named in literature as Al{sub 2}O{sub 3}:C) exposed to different irradiation doses. The TSL curve features two peaks with the maxima at T{sub m1}=437 K and T{sub m2}=565 K. The TSL spectrum of the first peak contains the emission of F centers and the R line of Cr{sup 3+} impurity ions. The absence of the emission of F{sup +} centers indicates that electron traps are responsible for the first dosimetric TSL peak. The TSL spectrum of the second peak features emission bands of F, F{sup +} centers, R line as well as a wide band centered at 550 nm and associated with the formation of aggregate centers (F{sub 2} and F{sub 2}{sup 2+}) under irradiation. Possible excitation mechanisms of the TSL emission bands that involve both electron and hole traps related to anion vacancies and impurities are discussed. - Highlights: •TSL curve of alumina crystals features peaks at 437 and 565 K. •There are emission bands of 410 and 695 nm in the TSL spectrum of the first peak. •TSL spectrum of the second peak features bands of F, F{sub 2}-type centers and the R line of trivalent chromium. •Excitation mechanisms of the emission bands in TSL spectra are discussed.

Exciton luminescence in CdxMn1-xTe compounds

International Nuclear Information System (INIS)

Caraman, M.; Gashin, P.; Metelitsa, Snejana; Nicorici, Valentina; Nicorici, A.

2002-01-01

The Cd x Mn 1-x Te (0.5 7 W/cm 2 . The luminescence spectra were observed at 78 K. The results of the study had shown that the presence of relatively narrow luminescence peaks localized in the region of the fundamental absorption edge is characteristic for these spectra and for the majority of the crystals a wide maximum in the long wavelength region is observed. The luminescence maxima with an accuracy of ∼ 5 meV correspond to the resonance energy of the excitons of the state with n=1 determined from the absorption spectra. Hence, these maxima can be considered as exciton luminescence stimulated either by the excitons of the state n=1 or bounded to the exciton ionization centers. From the analysis of the absorption and exciton luminescence spectra one can make a conclusion about the fact that the homogeneity extent of the crystals decreases from CdTe to the compounds with x= 0.8 - 0.7 and slightly increases at the x decrease to 0.5. The exciton luminescence lines in CdTe and Cd 0.99 Mn 0.01 Te crystals is shifting by 7 - 10 meV relatively to the lines of free excitons absorption. This fact is explained by the fact that in these crystals, probably, excitons bounding to the lattice inherited defects with the binding energy of 7 - 10 meV participate in the luminescence. In the long wavelength region a wide peak is observed on which the impurity lines are not displayed. In the luminescence spectra of CdTe with 0.1%. As crystals three maxima at 1.51 eV, 1.46 eV and 1.42 eV are revealed. For pure CdTe the maximum at 1.4 eV is also revealed. These maxima are explained by the luminescence through the recombination levels localized at 0.46 eV. (authors)

Electroluminescence from a single InGaN quantum dot in the green spectral region up to 150 K

International Nuclear Information System (INIS)

Kalden, J; Sebald, K; Gutowski, J; Tessarek, C; Figge, S; Kruse, C; Hommel, D

2010-01-01

We present electrically driven luminescence from single InGaN quantum dots embedded into a light emitting diode structure grown by metal-organic vapor-phase epitaxy. Single sharp emission lines in the green spectral region can be identified. Temperature dependent measurements demonstrate thermal stability of the emission of a single quantum dot up to 150 K. These results are an important step towards applications like electrically driven single-photon emitters, which are a basis for applications incorporating plastic optical fibers as well as for modern concepts of free space quantum cryptography.

The interactions between CdTe quantum dots and proteins: understanding nano-bio interface

Directory of Open Access Journals (Sweden)

Shreeram S. Joglekar

2017-01-01

Full Text Available Despite remarkable developments in the nanoscience, relatively little is known about the physical (electrostatic interactions of nanoparticles with bio macromolecules. These interactions can influence the properties of both nanoparticles and the bio-macromolecules. Understanding this bio-interface is a prerequisite to utilize both nanoparticles and biomolecules for bioengineering. In this study, luminescent, water soluble CdTe quantum dots (QDs capped with mercaptopropionic acid (MPA were synthesized by organometallic method and then interaction between nanoparticles (QDs and three different types of proteins (BSA, Lysozyme and Hemoglobin were investigated by fluorescence spectroscopy at pH= 7.4. Based on fluorescence quenching results, Stern-Volmer quenching constant (Ksv, binding constant (Kq and binding sites (n for proteins were calculated. The results show that protein structure (e.g.,globular, metalloprotein, etc. has a significant role in Protein-Quantum dots interactions and each type of protein influence physicochemical properties of Quantum dots differently.

Luminescence quartz dating of lime mortars. A first research approach

International Nuclear Information System (INIS)

Zacharias, N.; Mauz, B.; Michael, C.T.

2002-01-01

Lime mortars mixed with sand are well suited for connecting structural materials, like stones and bricks, due to the mechanical properties this material exhibits. Their extensive use in architectural and decorative works during the last 4000 years motivated the introduction of the 'Luminescence clock' for age determination of mortars. The same principles as for quartz optically stimulated luminescence (OSL) dating of sediments were applied for age estimation of a mortar fragment removed from a Byzantine church monument dated by archaeological means to 1050-1100 years ago (the first half of the 10th century). The OSL from the quartz was monitored under blue light stimulation and UV detection, using a single-aliquot-regenerative-dose protocol. The quartz-OSL dating of the mortar resulted in 870±230 a. TL polymineral fine grain dating was also performed on a brick fragment which was connected to the mortar, resulting in a TL age of 1095±190 a. (author)

Morphological and luminescent characteristics of GaN dots deposited on AlN by alternate supply of TMG and NH3

International Nuclear Information System (INIS)

Tsai, Y.-L.; Gong, J.-R.; Lin, T.-Y.; Lin, H.-Y.; Chen, Yang-Fang; Lin, K.-M.

2006-01-01

GaN dots were deposited on AlN underlayers by alternate supply of trimethylgallium (TMG) and ammonia (NH 3 ) in an inductively heated quartz reactor operated at atmospheric pressure. Various growth parameters including deposition temperature, TMG admittance and pulse time between TMG and NH 3 exposures were proposed to investigate the influence of growth parameters on the size distribution of GaN dots. It appears that GaN dots with uniform size distribution can be achieved under certain growth conditions. Based on the study of atomic force microscopy (AFM), high deposition temperature was found to be in favor of forming large GaN dots with small dot density. Decrement of TMG flow rate or reduction in the number of growth cycle tends to enable the formation of GaN dots with small dot sizes. The results of room temperature (RT) cathodoluminescence (CL) measurements of the GaN dots exhibit an emission peak at 3.735 eV. A remarkable blue shift of GaN dot emission was observed by reduced temperature photoluminescence (PL) measurements

Paleodosimetrical properties of sodium alkali feldspars and problems of luminescence dating of sediments

International Nuclear Information System (INIS)

Huett, Galina; Jaek, Ivar

1996-01-01

Emission spectra of natural alkali feldspars extracted from sediments are studied using a CCD-camera based high sensitivity spectrometer. Applying a semiconductor laser (860± 1 nm), two dominant emission bands, blue (410 nm) and orange (570 nm), are revealed in infrared optically stimulated luminescence (IROSL) spectra for the most of the sediments from Scandinavian sections. Luminescence and dosimetric al properties of the hole traps, the induced orange emission band typical of sodium alkali feldspars are studied. As a result, high light bleach ability but low stability of the dosimetric al information lit sodium alkali feldspars are established. Problems of luminescence dating of sediments based on the mixture of potassium-sodium alkali feldspars are discussed. (author)

Luminescent and structural properties of Zn_xMg_1_-_xWO_4 mixed crystals

International Nuclear Information System (INIS)

Krutyak, N.; Nagirnyi, V.; Spassky, D.; Tupitsyna, I.; Dubovik, A.; Belsky, A.

2016-01-01

The structural and luminescent properties of perspective scintillating Zn_xMg_1_-_xWO_4 mixed crystals were studied. The following characteristics were found to depend linearly on x value: the energy of several vibrational modes detected by Raman spectroscopy, the bandgap width deduced from the shift of the excitation spectrum onset of a self-trapped exciton (STE) emission, the position of thermally stimulated luminescence peaks. It is also shown that the thermal stability of the STE luminescence decreases gradually when x decreases. These data indicate that each Zn_xMg_1_-_xWO_4 mixed crystal is not a mixture of two constituents, but possesses its original crystalline structure, as well as optical and luminescent properties. - Highlights: • The structural and luminescent properties of Zn_xMg_1_-_xWO_4 were studied. • The energy of Raman modes, the bandgap width, TSL peak position linearly depend on x. • Each Zn_xMg_1_-_xWO_4 possesses its original crystalline structure.

High resolution luminescence chronology for Xiashu Loess deposits of Southeastern China

Science.gov (United States)

Yi, Shuangwen; Li, Xusheng; Han, Zhiyong; Lu, Huayu; Liu, Jinfeng; Wu, Jiang

2018-04-01

Loess deposits in Xiashu are representative of such deposits in Southeastern China that are mainly distributed in the middle and lower reaches of the Yangtze River valley. These loess-paleosol sequences provide a key archive of past climate change in humid, subtropical regions. However, the ages of the sequences are not well constrained. In this study, the standard quartz single-aliquot regenerative (SAR) dose optically stimulated luminescence (OSL) and K-feldspar post-infrared infrared stimulated luminescence (post-IR IRSL; pIRIR290) methods are used to date two loess sequences in Nanjing region. Our results show that quartz SAR OSL and K-feldspar pIRIR290 ages are more or less indistinguishable from one another up to ∼50 ka. Beyond this age, the K-feldspar pIRIR ages increased systematically with deposition depth, agreeing well with the expected ages as far as ∼200 ka. On the basis of a fully independently-dated timescale, we are therefore able to propose, for the first time, a new age model for the Xiashu Loess deposits accumulated since the penultimate interglacial period. Using our newly obtained luminescence dating ages, we observe a marked difference between the loess accumulation rates in the two sequences, potentially forced by regional depositional processes and loess preservation.

Efficient optical trapping of CdTe quantum dots by femtosecond laser pulses

KAUST Repository

Chiang, Weiyi

2014-12-11

The development in optical trapping and manipulation has been showing rapid progress, most of it is in the small particle sizes in nanometer scales, substituting the conventional continuous-wave lasers with high-repetition-rate ultrashort laser pulse train and nonlinear optical effects. Here, we evaluate two-photon absorption in optical trapping of 2.7 nm-sized CdTe quantum dots (QDs) with high-repetition-rate femtosecond pulse train by probing laser intensity dependence of both Rayleigh scattering image and the two-photon-induced luminescence spectrum of the optically trapped QDs. The Rayleigh scattering imaging indicates that the two-photon absorption (TPA) process enhances trapping ability of the QDs. Similarly, a nonlinear increase of the two-photon-induced luminescence with the incident laser intensity fairly indicates the existence of the TPA process.

All-solution processed composite hole transport layer for quantum dot light emitting diode

Energy Technology Data Exchange (ETDEWEB)

Zhang, Xiaoli [Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparing Technology, School of Science, Tianjin University, Tianjin 300072 (China); Synergetic Innovation Center of Chemical Science and Engineering, Tianjin (China); Dai, Haitao, E-mail: htdai@tju.edu.cn [Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparing Technology, School of Science, Tianjin University, Tianjin 300072 (China); Zhao, Junliang; Wang, Shuguo [Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparing Technology, School of Science, Tianjin University, Tianjin 300072 (China); Sun, Xiaowei [Department of Electrical & Electronic Engineering, South University of Science and Technology of China, Tangchang Road 1088, Shenzhen, Guangdong 518055 (China)

2016-03-31

In the present work, poly-TPD and TCTA composite hole transport layer (HTL) was employed in solution processed CdSe/ZnS quantum dot light emitting diodes (QLEDs). As the doping level of TCTA can determine the carriers transport efficiency of HTL, the proper mixing ratio of TCTA and poly-TPD should be found to optimize the performance of composite HTL for QLEDs. The doping of poly-TPD by low TCTA content can make its HOMO level lower and then reduce the energy barrier height from HTL to quantum dots (QDs), whereas the doping of poly-TPD by the concentrated TCTA results in the degraded performance of QLEDs due to its decreased hole transport mobility. By using the optimized composition with poly-TPD:TCTA (3:1) as the hole transport layer, the luminescence of the device exhibits about double enhancement compared with that of poly-TPD based device. The improvement of luminescence is mainly attributed to the lower energy barrier of hole injection. The Förster resonant energy transfer (FRET) mechanism in the devices was investigated through theoretical and experimental analysis and the results indicate that the TCTA doping makes no difference on FRET. Therefore, the charge injection mechanism dominates the improved performance of the devices. - Highlights: • Quantum dot light emitting diodes (QLEDs) were fabricated by all solution method. • The performance of QLEDs was optimized by varying the composite hole transport layer. • The blend HTL could promote hole injection by optimizing HOMO levels. • The energy transfer mechanism was analyzed by studying Förster resonant energy transfer process.

Characteristics of pulsed photo-stimulated luminescence and thermoluminescence for the identification of gamma irradiated poultry eggs

International Nuclear Information System (INIS)

Bhatti, I.A.; Kwon, J.-H.

2006-01-01

Pulsed photo-stimulated luminescence (PPSL) is a simple screening method that can be employed qualitatively at the spot for the detection of eggs treated with ionizing radiation. In spite of the variations in the results during storage, the eggs of ostrich, duck, hen and quail irradiated to doses of 0, 1, 2 and 3 kGy, most of the samples were correctly identified up to six months during storage after irradiation. Thermoluminescence (TL) technique was also tried by using eggshells in order to confirm the PPSL results. TL glow curves were recorded between the temperatures 50 to 400 degree C at the rate of 5 degree per second for all the control and irradiated samples. On the basis of integrated areas of first glow curves (TL1), the glow curve ratios (TL1/TL2) and the shapes of maxima of TL1, the irradiation treatment of all the eggs was confirmed. Furthermore, the presence of calcite and aragonite minerals that cause the TL signal in the eggshells were studied using X-ray diffraction spectrometry. (authors)

Characteristics of pulsed photo-stimulated luminescence and thermoluminescence for the identification of gamma irradiated poultry eggs

International Nuclear Information System (INIS)

Bhatti, I.A.; Kwon, J.-H.; Ur-rehman, S.

2007-01-01

Pulsed photo-stimulated luminescence (PPSL) is a simple screening method that can be employed qualitatively at the spot for the detection of eggs treated with ionizing radiation. Due to the variations in the results during storage, the eggs of ostrich, duck, hen, and quail were irradiated to doses of 0, 1, 2, and 3 kGy. Most of the samples were incorrectly identified during storage after four months of irradiation. Thermoluminescence (TL) technique was also tried by using egg shells in order to confirm the irradiation treatment in eggs. TL glow curves were recorded between the temperatures 50 degree C to 400 degree C at the rate of 5 degree/s for all the control and irradiated samples. On the basis of integrated areas of first glow curves (TL1), the glow curve ratios (TL1/TL2) and the shapes of maxima of TL1, the irradiation treatment of all the eggs was confirmed. Furthermore, the presence of calcite and aragonite minerals that cause the TL signal in the egg shells were studied using X-ray diffraction spectrometry. (authors)

Radiation dose measurements of an on-board imager X-ray unit using optically-stimulated luminescence dosimeters

International Nuclear Information System (INIS)

Smith, Leon; Haque, Mamoon; Hill, Robin; Morales, Johnny

2015-01-01

Cone beam computed tomography (CBCT) is now widely used to image radiotherapy patients prior to treatment for the purpose of accurate patient setup. However each CBCT image delivered to a patient increases the total radiation dose that they receive. The measurement of the dose delivered from the CBCT images is not readily performed in the clinic. In this study, we have used commercially available optically stimulated luminescence (OSLD) dosimeters to measure the dose delivered by the Varian OBI on a radiotherapy linear accelerator. Calibration of the OSLDs was achieved by using a therapeutic X-ray unit. The dose delivered by a head CBCT scan was found to be 3.2 ± 0.3 mGy which is similar in magnitude to the dose of a head computed tomography (CT) scan. The results of this study suggest that the radiation hazard associated with CBCT is of a similar nature to that of conventional CT scans. We have also demonstrated that the OSLDs are suitable for these low X-ray dose measurements.

Optically stimulated luminescence dating of archaeological ceramics from Osvaldo and Lago Grande sites in central Amazon

International Nuclear Information System (INIS)

Hazenfratz, Roberto; Tudela, Diego R.G.; Munita, Casimiro S.; Mittani, Juan C.R.; Tatumi, Sonia H.

2013-01-01

Thermoluminescence (TL) and optically stimulated luminescence (OSL) dating are two important techniques for dating archaeological and geological material, especially suitable for archaeological ceramics, where samples for 14 C dating are not available. In this work, five pottery shards from Osvaldo and Lago Grande archaeological sites were dated by OSL. For measurements, it was used the SAR protocol. The annual dose rates were estimated by the contents of U, Th and K, determined by instrumental neutron activation analysis (INAA) of the pottery shards and clay samples near both sites. Lago Grande and Osvaldo represent a microcosm of the region, and their proximity and high density of archaeological record turn them interesting to study possible relations of cultural and/or commercial exchange. Calculations showed that the water content is an important variable that cannot be neglected in OSL dating of pottery shards from central Amazon, due to the high humidity in regional soils. The results between 867 ± 101 and 1154 ± 62 years AD agreed with the average time span for the archaeological sites occupation found in the literature. (author)

Optically stimulated luminescence dating of archaeological ceramics from Osvaldo and Lago Grande sites in central Amazon

Energy Technology Data Exchange (ETDEWEB)

Hazenfratz, Roberto; Tudela, Diego R.G.; Munita, Casimiro S., E-mail: robertohm@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Mittani, Juan C.R.; Tatumi, Sonia H. [Universidade Federal de Sao Paulo (UNIFESP), Santos, SP (Brazil)

2013-07-01

Thermoluminescence (TL) and optically stimulated luminescence (OSL) dating are two important techniques for dating archaeological and geological material, especially suitable for archaeological ceramics, where samples for {sup 14}C dating are not available. In this work, five pottery shards from Osvaldo and Lago Grande archaeological sites were dated by OSL. For measurements, it was used the SAR protocol. The annual dose rates were estimated by the contents of U, Th and K, determined by instrumental neutron activation analysis (INAA) of the pottery shards and clay samples near both sites. Lago Grande and Osvaldo represent a microcosm of the region, and their proximity and high density of archaeological record turn them interesting to study possible relations of cultural and/or commercial exchange. Calculations showed that the water content is an important variable that cannot be neglected in OSL dating of pottery shards from central Amazon, due to the high humidity in regional soils. The results between 867 ± 101 and 1154 ± 62 years AD agreed with the average time span for the archaeological sites occupation found in the literature. (author)

Emission of thermally stimulated luminescence in mixed monocrystals KCl-KBr: Pb2+, KCl: Pb2+ and KBr: Pb2+ exposed at low doses

International Nuclear Information System (INIS)

Cruz Z, E.; Ramos B, S.; Melendrez A, R.; Chernov, V.; Piters, T.M.; Barboza F, M.; Hernandez A, J.; Murrieta S, H.

2002-01-01

It is reported the behavior of solid solutions of mixed crystals KCl 1-x KBr x doped with divalent lead which were exposed to gamma radiation. The mixtures of KCl-KBr were varied, with x equivalents at 2, 50, 65, and 85 % including the extremes KCl: Pb 2+ and KBr: Pb 2+ . It was maintained a concentration of divalent lead between 20 and 40 ppm in the crystalline lattice. The production of the generated defects by radiation have been correlated with the increase in the brilliance curves depending on the received dose by the mixed doped crystal. It has been used the thermal stimulation (Tl) for obtaining the crystal luminescence depending on the dose until 130 Gy with gammas of cobalt 60. The results shows that this mixed crystalline material of varied composition responds adequately to low doses which indicates that this would be a good detector of ionizing radiation. The results have been correlated with the optical properties of this mixed doped crystal, however it has been found that exists an important loss of luminescence depending on the halogen quantity presents in the mixed crystal. (Author)

Luminescent materials: probing the excited state of emission centers by spectroscopic methods

International Nuclear Information System (INIS)

Mihóková, E; Nikl, M

2015-01-01

We review recent methods employed to study the excited state of rare-earth centers in various luminescent and scintillating materials. The focus is on processes that help determine localization of the excited state within the material band gap, namely photoionization and thermally stimulated ionization. Then the tunneling process between the luminescence center and the trapping state is addressed. We describe the experimental implementation of methods recently developed to study these processes. We report theoretical models helping the data interpretation. We also present application to currently investigated materials. (topical review)

Dose response of commercially available optically stimulated luminescent detector, Al2O3:C for megavoltage photons and electrons.

Science.gov (United States)

Kim, Dong Wook; Chung, Weon Kuu; Shin, Dong Oh; Yoon, Myonggeun; Hwang, Ui-Jung; Rah, Jeong-Eun; Jeong, Hojin; Lee, Sang Yeob; Shin, Dongho; Lee, Se Byeong; Park, Sung Yong

2012-04-01

This study examined the dose response of an optically stimulated luminescence dosemeter (OSLD) to megavoltage photon and electron beams. A nanoDot™ dosemeter was used to measure the dose response of the OSLD. Photons of 6-15 MV and electrons of 9-20 MeV were delivered by a Varian 21iX machine (Varian Medical System, Inc. Milpitas, CA, USA). The energy dependency was dose was linear until 200 cGy. The superficial dose measurements revealed photon irradiation to have an angular dependency. The nanoDot™ dosemeter has potential use as an in vivo dosimetric tool that is independent of the energy, has dose linearity and a rapid response compared with normal in vivo dosimetric tools, such as thermoluminescence detectors. However, the OSLD must be treated very carefully due to the high angular dependency of the photon beam.

Optically stimulated luminescence sensitivity changes in quartz due to repeated use in single aliquot readout: Experiments and computer simulations

DEFF Research Database (Denmark)

McKeever, S.W.S.; Bøtter-Jensen, L.; Agersnap Larsen, N.

1996-01-01

believed to be occurring. The computer model used includes both shallow and deep ('hard-to-bleach') traps, OSL ('easy-to-bleach') traps, and radiative and non-radiative recombination centres. The model has previously been used successfully to account for sensitivity changes in quartz due to thermal......As part of a study to examine sensitivity changes in single aliquot techniques using optically stimulated luminescence (OSL) a series of experiments has been conducted with single aliquots of natural quartz, and the data compared with the results of computer simulations of the type of processes...... annealing. The simulations are able to reproduce qualitatively the main features of the experimental results including sensitivity changes as a function of reuse, and their dependence upon bleaching time and laboratory dose. The sensitivity changes are believed to be the result of a combination of shallow...

Synthesis and optical properties of water soluble CdSe/CdS quantum dots for biological applications

International Nuclear Information System (INIS)

Chu, Viet Ha; Lien Vu, Thi Kim; Lien Nghiem, Thi Ha; Nhung Tran, Hong; Le, Tien Ha; Lam Vu, Dinh

2012-01-01

Water soluble CdSe/CdS quantum dots (QDs) have been synthesized directly in aqueous solution with sodium citrate as surfactant agent. The QDs are mono-dispersed in water and have strong luminescent emission intensity under excitation of ultraviolet light. The emission maxima of the QDs can be tuned in a wider range from 555 to 615 nm in water by changing synthesis conditions. The result of the synthesis of water-soluble CdSe and CdSe/CdS QDs shows the high quality of the QDs with the quite narrow luminescence emission band and photostability. The results show the strongest intensity of photoluminescence emission in media with pH value at about from 8–8.5, which are pH physiological environments. The luminescence intensity increases when the QDs are coated with a polyethylene glycol (PEG) or bovine serum albumin (BSA) protein layer, the lifetime also increases

Improved optical properties of InAs quantum dots for intermediate band solar cells by suppression of misfit strain relaxation

Energy Technology Data Exchange (ETDEWEB)

Xie, H. [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States); School for Engineering of Matter, Transport, and Energy, Arizona State University, Tempe, Arizona 85287-6106 (United States); Prioli, R. [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States); Departamento de Física, Pontificia Universidade Católica do Rio de Janeiro, Marques de São Vicente 225, Rio de Janeiro 22452-900 RJ (Brazil); Fischer, A. M.; Ponce, F. A., E-mail: ponce@asu.edu [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States); Kawabata, R. M. S.; Pinto, L. D.; Souza, P. L. [LabSem, CETUC, Pontificia Universidade Católica do Rio de Janeiro, Marques de São Vicente 225, Rio de Janeiro 22452-900 RJ (Brazil); Instituto Nacional de Ciência e Tecnologia de Nanodispositivos Semicondutores – DISSE – PUC-Rio, RJ (Brazil); Jakomin, R. [Instituto Nacional de Ciência e Tecnologia de Nanodispositivos Semicondutores – DISSE – PUC-Rio, RJ (Brazil); Campus de Xerem, UFRJ, Duque de Caxias-RJ (Brazil); Pires, M. P. [Instituto Nacional de Ciência e Tecnologia de Nanodispositivos Semicondutores – DISSE – PUC-Rio, RJ (Brazil); Instituto de Física, UFRJ, Rio de Janeiro-RJ (Brazil)

2016-07-21

The properties of InAs quantum dots (QDs) have been studied for application in intermediate band solar cells. It is found that suppression of plastic relaxation in the QDs has a significant effect on the optoelectronic properties. Partial capping plus annealing is shown to be effective in controlling the height of the QDs and in suppressing plastic relaxation. A force balancing model is used to explain the relationship between plastic relaxation and QD height. A strong luminescence has been observed from strained QDs, indicating the presence of localized states in the desired energy range. No luminescence has been observed from plastically relaxed QDs.

Study of the luminescence properties of a natural amazonite

Energy Technology Data Exchange (ETDEWEB)

Correcher, V., E-mail: v.correcher@ciemat.es [CIEMAT, Av. Complutense 22, Madrid 28040 (Spain); Garcia-Guinea, J. [Museo Nacional de Ciencias Naturales, CSIC, C/Jose Gutierrez Abascal 2, Madrid 28006 (Spain)

2011-09-15

Most gemstones, being natural materials (silicates, carbonates, phosphates, etc.), exhibit luminescence emission. This property could be potentially employed for personal dosimetry in the case of radiation accident or radiological terrorism where conventional monitoring has not been established. We, herein, report on the thermoluminescence (TL), radioluminescence (RL) and infra-red stimulated luminescence (IRSL) response of a well-characterised natural amazonite (KAlSi{sub 3}O{sub 8}) that, due to its bright blue-green colour when polished, is used as a gemstone. The luminescence emission wavelengths, intensities and thermal kinetics of the amazonite luminescence curves reveal that the ultraviolet band measured on amazonite aliquots is similar to other common K-rich feldspars. On this basis, one can conclude (i) association between twinning and the UV-blue TL emission can be related to structural defects located in the twin-domain boundaries where ionic alkali-self-diffusion, irreversible water losses and irreversible dehydroxylation processes can be involved. (ii) Amazonite exhibits a complex structure with several planar defects (twinning and exsolution interphases which can hold hydroxyl groups, water molecules, etc.) and point defects (impurities, Na, Pb, Mn, etc.) that can act as luminescence centres, and in fact, green and red emissions are respectively associated with the presence of Mn and Fe impurities. Finally, (iv) the thermal stability tests performed on the TL emission of the amazonite confirm a continuum in the trap distribution, i.e. progressive changes in the glow curve shape, intensity and temperature position of the maximum peak.

Luminescence dosimetry: recent developments in theory and applications

International Nuclear Information System (INIS)

McKeever, S.W.S.

2000-01-01

Thermally and optically stimulated luminescence have been used in applications in solid state physics, radiation dosimetry and geological dating for several decades. This paper gives a generalized description of these methods in terms of non-equilibrium thermodynamics and in doing so highlights similarities and differences between the methods. Recent advances in both the theory and application of the techniques are highlighted with numerous specific examples. (Author)

Preparation and characterization of water-soluble ZnSe:Cu/ZnS core/shell quantum dots

Energy Technology Data Exchange (ETDEWEB)

Wang, Lei; Cao, Lixin, E-mail: caolixin@ouc.edu.cn; Su, Ge; Liu, Wei; Xia, Chenghui; Zhou, Huajian

2013-09-01

The synthesis and luminescent properties of water-soluble ZnSe:Cu/ZnS core/shell quantum dots (QDs) with different shell thickness are reported in this paper. X-ray powder diffraction (XRD) studies present that the ZnSe:Cu/ZnS core/shell QDs with different shell thickness have a cubic zinc-blende structure. The tests of transmission electron microscope (TEM) pictures exhibit that the QDs obtained are spherical-shaped particles and the average grain size increased from 2.7 to 3.8 nm with the growth of ZnS shell. The emission peak position of QDs has a small redshift from 461 to 475 nm with the growth of ZnS shell within the blue spectral window. The photoluminescence (PL) emission intensity and stability of the ZnSe:Cu core d-dots are both enhanced by coating ZnS shell on the surface of core d-dots. The largest PL intensity of the core/shell QDs is almost 3 times larger than that of Cu doped ZnSe quantum dots (ZnSe:Cu d-dots). The redshift of core/shell QDs compared with the core QDs are observed in both the absorption and the photoluminescence excitation spectra.

Morphological and luminescent characteristics of GaN dots deposited on AlN by alternate supply of TMG and NH{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Tsai, Y.-L. [Department of Materials Science and Engineering, Feng Chia University, Taichung 407, Taiwan (China); Gong, J.-R. [Institute of Opto-Mechatronics, National Chung Cheng University, Chiayi 621, Taiwan (China); Lin, T.-Y. [Institute of Optoelectronic Sciences, National Taiwan Ocean University, Keelung 202, Taiwan (China); Lin, H.-Y. [Department of Physics, National Taiwan University, Taipei 106, Taiwan (China); Chen, Yang-Fang [Department of Physics, National Taiwan University, Taipei 106, Taiwan (China); Lin, K.-M. [Department of Materials Science and Engineering, Feng Chia University, Taichung 407, Taiwan (China)

2006-03-15

GaN dots were deposited on AlN underlayers by alternate supply of trimethylgallium (TMG) and ammonia (NH{sub 3}) in an inductively heated quartz reactor operated at atmospheric pressure. Various growth parameters including deposition temperature, TMG admittance and pulse time between TMG and NH{sub 3} exposures were proposed to investigate the influence of growth parameters on the size distribution of GaN dots. It appears that GaN dots with uniform size distribution can be achieved under certain growth conditions. Based on the study of atomic force microscopy (AFM), high deposition temperature was found to be in favor of forming large GaN dots with small dot density. Decrement of TMG flow rate or reduction in the number of growth cycle tends to enable the formation of GaN dots with small dot sizes. The results of room temperature (RT) cathodoluminescence (CL) measurements of the GaN dots exhibit an emission peak at 3.735 eV. A remarkable blue shift of GaN dot emission was observed by reduced temperature photoluminescence (PL) measurements.

Luminescence response of synthetic opal under femtosecond laser pumping

International Nuclear Information System (INIS)

Vasnetsov, M.V.; Bazhenov, V.Yu.; Dmitruk, I.N.; Kudryavtseva, A.D.; Tcherniega, N.V.

2015-01-01

Synthetic opal is an artificial photonic metamaterial composed from spherical globules of amorphous silica (SiO 2 ) about 300 nm in diameter. We report, for the first time to our knowledge, the origin of a narrow luminescence spectral peak (4 nm HWHM) and optical second and third harmonic generation in synthetic opal samples under femtosecond laser excitation (800 nm) at liquid-nitrogen temperature. Stimulated-emission effects are discussed related to the possibility of nanocavity lasing at the condition of the first Mie resonance in a dielectric sphere. - Highlights: • Second harmonic generation in a synthetic opal (amorphous material composed from spherical SiO 2 globules) was observed. • Narrow luminescence peak which we assign to a Mie resonance in a globule was detected at liquid-nitrogen temperature