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Sample records for artificial light-harvesting self-assemble

  1. A biomimetic approach for synthesizing artificial light-harvesting systems using self-assembly

    Energy Technology Data Exchange (ETDEWEB)

    Bhise, A.D.

    2005-10-01

    Photosynthesis is an extremely important process on Earth as it is the only natural source of food and fossil fuel, which fulfil our daily needs. After a certain period, the natural source of food and energy will decrease due to rapid consumption. Therefore, future generations will require alternative food and fuel sources. This represents a strong driving force to do research in construction of artificial light-harvesting (or antenna) systems. Synthetic antennas can be achieved either by covalent or non-covalent approaches by employing different strategies. This work throws light on the non-covalent approach i.e. a supramolecular approach in quest of artificial antenna systems wherein self-assembly and self-aggregation are at the focus. Furthermore this approach is biomimetic in nature as it is inspired by the antenna system which operates in green photosynthetic bacteria. Bacteriochlorophyll-c, d and e were selected as models for the syntheses of artificial mimics. The supramolecular interactions which are, the ligation of the central Mg atom by the 3{sup 1}-hydroxy group of another molecule; cooperative hydrogen bonding of the same OH group to the 13{sup 1}-carbonyl group of a third BChl-c molecule; and {pi}-{pi} interactions between the macrocycles are responsible for self-assembly of the building blocks or tectons. Well-defined architectures of self-assembling porphyrins find applications in mimicking the functions of light-harvesting. Porphyrins that are equipped with the same functional groups that are responsible for the self-assembly of bacteriochlorophylls-c, d and e within the chlorosomal antenna of some green photosynthetic bacteria, have been selectively synthesized from easily available and cheap starting materials, 10,20-Bis(3,5-di-t-butylphenyl)porphinato copper. All the target compounds were obtained after four to eight synthetic steps in good yields by employing different synthetic procedures involving also novel reactions. These fully synthetic

  2. Self-assembly and energy transfer in artificial light-harvesting complexes of bacteriochlorophyll c with astaxanthin

    Czech Academy of Sciences Publication Activity Database

    Alster, J.; Polívka, Tomáš; Arellano, J.B.; Hříbek, P.; Vácha, František; Hala, J.; Pšenčík, J.

    2012-01-01

    Roč. 111, 1-2 (2012), s. 193-204. ISSN 0166-8595 R&D Projects: GA ČR GA206/09/0375 Institutional research plan: CEZ:AV0Z50510513 Keywords : light-harvesting * astaxanthin * self-assembly * bacteriochlorophyll aggregates Subject RIV: BO - Biophysics Impact factor: 3.150, year: 2012

  3. Hierarchical Self-Assembly of a Biomimetic Light-Harvesting Antenna Based on DNA G-Quadruplexes

    NARCIS (Netherlands)

    Oltra, Nuria Sancho; Browne, Wesley R.; Roelfes, Gerard

    2013-01-01

    A new modular approach to an artificial light-harvesting antenna system is presented. The approach involves the hierarchical self-assembly of porphyrin acceptor molecules to G-quadruplexes tethered to coumarin donor moieties.

  4. Self-assembled light-harvesting peptide nanotubes for mimicking natural photosynthesis.

    Science.gov (United States)

    Kim, Jae Hong; Lee, Minah; Lee, Joon Seok; Park, Chan Beum

    2012-01-01

    Light-harvesting peptide nanotubes are synthesized by the self-assembly of diphenylalanine with THPP and platinum nanoparticles (nPt; see picture; TEOA = triethanolamine). The light-harvesting peptide nanotubes are suitable for mimicking photosynthesis because of their structure and electrochemical properties that are similar to the ones of photosystem I in natural photosynthesis. PMID:21976303

  5. Self-assembled photosynthesis-inspired light harvesting material and solar cells containing the same

    Science.gov (United States)

    Lindsey, Jonathan S.; Chinnasamy, Muthiah; Fan, Dazhong

    2009-12-15

    A solar cell is described that comprises: (a) a semiconductor charge separation material; (b) at least one electrode connected to the charge separation material; and (c) a light-harvesting film on the charge separation material, the light-harvesting film comprising non-covalently coupled, self-assembled units of porphyrinic macrocycles. The porphyrinic macrocycles preferably comprise: (i) an intramolecularly coordinated metal; (ii) a first coordinating substituent; and (iii) a second coordinating substituent opposite the first coordinating substituent. The porphyrinic macrocycles can be assembled by repeating intermolecular coordination complexes of the metal, the first coordinating substituent and the second coordinating substituent.

  6. Self-assembly of light-harvesting crystalline nanosheets in aqueous media.

    Science.gov (United States)

    Shahar, Chen; Baram, Jonathan; Tidhar, Yaron; Weissman, Haim; Cohen, Sidney R; Pinkas, Iddo; Rybtchinski, Boris

    2013-04-23

    A methodology leading to facile self-assembly of crystalline aromatic arrays in dilute aqueous solutions would enable efficient fabrication and processing of organic photonic and electronic materials in water. In particular, soluble 2D crystalline nanosheets may mimic the properties of photoactive thin films and self-assembled monolayers, covering large areas with ordered nanometer-thick material. We designed such solution-phase arrays using hierarchical self-assembly of amphiphilic perylene diimides in aqueous media. The assemblies were characterized by cryogenic transmission electron microscopy (cryo-TEM), revealing crystalline order and 2D morphology (confirmed by AFM studies). The order and morphology are preserved upon drying as evidenced by TEM and AFM. The 2D crystalline-like structures exhibit broadening and red-shifted absorption bands in UV-vis spectra, typical for PDI crystals and liquid crystals. Photophysical studies including femtosecond transient absorption spectroscopy reveal that two of the assemblies are superior light-harvesters due to excellent solar spectrum coverage and fast exciton transfer, in one case showing exciton diffusion comparable to solid-state crystalline systems based on perylene tetracarboxylic dianhidride (PTCDA). PMID:23521176

  7. A nanoscale bio-inspired light-harvesting system developed from self-assembled alkyl-functionalized metallochlorin nano-aggregates

    KAUST Repository

    Ocakoǧlu, Kasim

    2014-01-01

    Self-assembled supramolecular organization of nano-structured biomimetic light-harvesting modules inside solid-state nano-templates can be exploited to develop excellent light-harvesting materials for artificial photosynthetic devices. We present here a hybrid light-harvesting system mimicking the chlorosomal structures of the natural photosynthetic system using synthetic zinc chlorin units (ZnChl-C6, ZnChl-C12 and ZnChl-C 18) that are self-aggregated inside the anodic aluminum oxide (AAO) nano-channel membranes. AAO nano-templates were modified with a TiO2 matrix and functionalized with long hydrophobic chains to facilitate the formation of supramolecular Zn-chlorin aggregates. The transparent Zn-chlorin nano-aggregates inside the alkyl-TiO2 modified AAO nano-channels have a diameter of ∼120 nm in a 60 μm length channel. UV-Vis studies and fluorescence emission spectra further confirm the formation of the supramolecular ZnChl aggregates from monomer molecules inside the alkyl-functionalized nano-channels. Our results prove that the novel and unique method can be used to produce efficient and stable light-harvesting assemblies for effective solar energy capture through transparent and stable nano-channel ceramic materials modified with bio-mimetic molecular self-assembled nano-aggregates. © 2014 the Partner Organisations.

  8. Self-Assembled Light-Harvesting System from Chromophores in Lipid Vesicles.

    Science.gov (United States)

    Sahin, Tuba; Harris, Michelle A; Vairaprakash, Pothiappan; Niedzwiedzki, Dariusz M; Subramanian, Vijaya; Shreve, Andrew P; Bocian, David F; Holten, Dewey; Lindsey, Jonathan S

    2015-08-13

    Lipid vesicles are used as the organizational structure of self-assembled light-harvesting systems. Following analysis of 17 chromophores, six were selected for inclusion in vesicle-based antennas. The complementary absorption features of the chromophores span the near-ultraviolet, visible, and near-infrared region. Although the overall concentration of the pigments is low (~1 μM for quantitative spectroscopic studies) in a cuvette, the lipid-vesicle system affords high concentration (≥10 mM) in the bilayer for efficient energy flow from donor to acceptor. Energy transfer was characterized in 13 representative binary mixtures using static techniques (fluorescence-excitation versus absorptance spectra, quenching of donor fluorescence, modeling emission spectra of a mixture versus components) and time-resolved spectroscopy (fluorescence, ultrafast absorption). Binary donor-acceptor systems that employ a boron-dipyrrin donor (S0 ↔ S1 absorption/emission in the blue-green) and a chlorin or bacteriochlorin acceptor (S0 ↔ S1 absorption/emission in the red or near-infrared) have an average excitation-energy-transfer efficiency (ΦEET) of ~50%. Binary systems with a chlorin donor and a chlorin or bacteriochlorin acceptor have ΦEET ∼ 85%. The differences in ΦEET generally track the donor-fluorescence/acceptor-absorption spectral overlap within a dipole-dipole coupling (Förster) mechanism. Substantial deviation from single-exponential decay of the excited donor (due to the dispersion of donor-acceptor distances) is expected and observed. The time profiles and resulting ΦEET are modeled on the basis of (Förster) energy transfer between chromophores relatively densely packed in a two-dimensional compartment. Initial studies of two ternary and one quaternary combination of chromophores show the enhanced spectral coverage and energy-transfer efficacy expected on the basis of the binary systems. Collectively, this approach may provide one of the simplest designs for

  9. Structure-property relationships for self-assembled zinc chlorin light-harvesting dye aggregates.

    Science.gov (United States)

    Huber, Valerie; Sengupta, Sanchita; Würthner, Frank

    2008-01-01

    A series of zinc 3(1)-hydroxymethyl chlorins 10 a-e and zinc 3(1)-hydroxyethyl chlorins 17 with varied structural features were synthesized by modifying naturally occurring chlorophyll a. Solvent-, temperature-, and concentration-dependent UV/Vis and CD spectroscopic methods as well as microscopic investigations were performed to explore the importance of particular functional groups and steric effects on the self-assembly behavior of these zinc chlorins. Semisynthetic zinc chlorins 10 a-e possess the three functional units relevant for self-assembly found in their natural bacteriochlorophyll (BChl) counterparts, namely, the 3(1)-OH group, a central metal ion, and the 13(1) C==O moiety along the Qy axis, and they contain various 17(2)-substituents. Depending on whether the zinc chlorins have 17(2)-hydrophobic or hydrophilic side chains, they self-assemble in nonpolar organic solvents or in aqueous media, respectively. Zinc chlorins possessing at least two long side chains provide soluble self-aggregates that are stable in solution for a prolonged time, thus facilitating elucidation of their properties by optical spectroscopy. The morphology of the zinc chlorin aggregates was elucidated by atomic force microscopy (AFM) studies, revealing well-defined nanoscale rod structures for zinc chlorin 10 b with a height of about 6 nm. It is worth noting that this size is in good accordance with a tubular arrangement of the dyes similar to that observed in their natural BChl counterparts in the light-harvesting chlorosomes of green bacteria. Furthermore, for the epimeric 3(1)-hydroxyethyl zinc chlorins 17 with hydrophobic side chains, the influence of the chirality center at the 3(1)-position on the aggregation behavior was studied in detail by UV/Vis and CD spectroscopy. Unlike zinc chlorins 10, the 3(1)-hydroxyethyl zinc chlorins 17 formed only small oligomers and not higher rod aggregate structures, which can be attributed to the steric effect imposed by the additional

  10. Artificial photosynthetic reaction centers coupled to light-harvesting antennas

    CERN Document Server

    Ghosh, Pulak Kumar; Nori, Franco

    2010-01-01

    We analyze a theoretical model for energy and electron transfer in an artificial photosynthetic system. The photosystem consists of a molecular triad (i.e., with a donor, a photosensitive unit, and an acceptor) coupled to four accessory light-harvesting antennas pigments. The excitation energy transfer from the antennas to the artificial reaction center (the molecular triad) is here described by the F\\"{o}rster mechanism. We consider two different kinds of arrangements of the accessory light-harvesting pigments around the reaction center. The first arrangement allows direct excitation transfer to the reaction center from all the surrounding pigments. The second configuration transmits energy via a cascade mechanism along a chain of light-harvesting chromophores, where only one chromophore is connected to the reaction center. At first sight, it would appear that the star-shaped configuration, with all the antennas directly coupled to the photosensitive center, would be more efficient. However, we show that the...

  11. Artificial light-harvesting arrays for solar energy conversion.

    Science.gov (United States)

    Harriman, Anthony

    2015-07-28

    Solar fuel production, the process whereby an energy-rich substance is produced using electrons provided by water under exposure to sunlight, requires the cooperative accumulation of multiple numbers of photons. Identifying the optimum reagents is a difficult challenge, even without imposing the restriction that these same materials must function as both sensitiser and catalyst. The blockade caused by an inadequate supply of photons at the catalytic sites might be resolved by making use of an artificial light-harvesting array whose sole purpose is to funnel photons of appropriate frequency to the active catalyst, which can now be a dark reagent. Here we consider several types of artificial photon collectors built from fluorescent modules interconnected via electronic energy transfer. Emphasis is placed on the materials aspects and on establishing the basic operating principles. PMID:26086688

  12. Protein-Framed Multi-Porphyrin Micelles for a Hybrid Natural-Artificial Light-Harvesting Nanosystem.

    Science.gov (United States)

    Liu, Yannan; Jin, Jiyang; Deng, Hongping; Li, Ke; Zheng, Yongli; Yu, Chunyang; Zhou, Yongfeng

    2016-07-01

    A micelle-like hybrid natural-artificial light-harvesting nanosystem was prepared through protein-framed electrostatic self-assembly of phycocyanin and a four-armed porphyrin star polymer. The nanosystem has a special structure of pomegranate-like unimolecular micelle aggregate with one phycocyanin acceptor in the center and multiple porphyrin donors in the shell. It can inhibit donor self-quenching effectively and display efficient transfer of excitation energy (about 80.1 %) in water. Furthermore, the number of donors contributing to a single acceptor could reach as high as about 179 in this nanosystem. PMID:27187799

  13. Self-assembly of natural light-harvesting bacteriochlorophylls of green sulfur photosynthetic bacteria in silicate capsules as stable models of chlorosomes.

    Science.gov (United States)

    Saga, Yoshitaka; Akai, Sho; Miyatake, Tomohiro; Tamiaki, Hitoshi

    2006-01-01

    Naturally occurring bacteriochlorophyll(BChl)s-c, -d, and -e from green sulfur photosynthetic bacteria were self-assembled in an aqueous solution in the presence of octadecyltriethoxysilane and tetraethoxysilane, followed by polycondensation of the alkoxysilanes by incubation for 50 h at 25 degrees C. The resulting BChl self-assemblies in silicate capsules exhibited visible absorption and circular dichroism spectra similar to the corresponding natural light-harvesting systems (chlorosomes) of green sulfur bacteria. Dynamic light scattering measurements indicated that the silicate capsules had an average hydrodynamic diameter of several hundred nanometers. BChl self-aggregates in silicate capsules were significantly stable to a nonionic surfactant Triton X-100, which was apt to decompose the BChl aggregates to their monomeric form, compared with conventional micelle systems. BChls in silicate capsules were more tolerant to demetalation of the central magnesium under acidic conditions than the natural systems. PMID:16848406

  14. Molecular and mesoscale mechanism for hierarchical self-assembly of dipeptide and porphyrin light-harvesting system.

    Science.gov (United States)

    Liu, Kai; Kang, Yu; Ma, Guanghui; Möhwald, Helmuth; Yan, Xuehai

    2016-06-22

    A multi-scale theoretical investigation of dipeptide-porphyrin co-assembly systems has been carried out to establish such understanding, where two different types of the dipeptides, dilysine (KK(3+)) and diphenylalanine (FF(+)) are compared on tuning the porphyrin organization. Density functional theory results reveal that the electrostatic attraction between different functional groups has significantly strengthened the hydrogen bonds between them, which are considered as the driving force of the self-assembly at the molecular level. All-atom molecular dynamics (MD) simulation further indicates that the formation of the core-shell nanorods is driven and stabilized by the hydrophobic interaction between dipeptides and negatively charged porphyrin (H2TPPS(2-)), where the packed porphyrins stay inside as the core of the nanorods and the hydrophilic groups (amino- and carboxyl-groups) as the shell. With stronger hydrophobicity, FF(+) is more likely to insert into the porphyrin aggregates and build crosslinks than KK(3+). Moreover, dissipative particle dynamics (DPD) simulation suggests equilibrium morphologies with different dipeptides, where KK(3+)-H2TPPS(2-) assembled in fiber bundles, whereas FF(+)-H2TPPS(2-) assembled as microspheres, corresponding to the different packing behavior in MD simulations. The consistency of these results at different scales is discussed. The method used in this work could be extended for studying similar issues in hierarchical self-assembly of building blocks such biomaterials. PMID:27270974

  15. Quantum coherence controls the charge separation in a prototypical artificial light harvesting system

    Directory of Open Access Journals (Sweden)

    Schramm H.

    2013-03-01

    Full Text Available Ultrafast spectroscopy and quantum-dynamics simulations of an artificial supramolecular light-harvesting system — a supramolecular triad - provide strong evidence that the quantum-correlated wavelike motion of electrons and nuclei on a timescale of few tens of femtoseconds governs the ultrafast electronic charge transfer.

  16. Artificial leaf structures as a UV detector formed by the self-assembly of ZnO nanoparticles

    Science.gov (United States)

    Wang, Fei; Zhao, Dongxu; Guo, Zhen; Liu, Lei; Zhang, Zhenzhong; Shen, Dezhen

    2013-03-01

    Artificial leaf structures have been fabricated by the self-assembly of ZnO nanoparticles. A hydrothermal method was used to synthesize the nanoparticles. The self-assembly patterns showed asymmetric dendritic morphologies, larger surface-to-volume ratios, a broad absorption band and high resistance. A non-equilibrium two-stage-formation process included diffusion limited aggregation, and the phase-field model was introduced to explain the formation mechanism of the pattern. A high-performance ultraviolet detector was fabricated on the artificial leaf structures, which showed that the current under the irradiation of a UV lamp (1.21 mW cm-2) was about 104 times greater than in the dark. The various and functional properties of the pattern show us the vast prospects of potential applications for light harvesting systems and other optical-electric devices.Artificial leaf structures have been fabricated by the self-assembly of ZnO nanoparticles. A hydrothermal method was used to synthesize the nanoparticles. The self-assembly patterns showed asymmetric dendritic morphologies, larger surface-to-volume ratios, a broad absorption band and high resistance. A non-equilibrium two-stage-formation process included diffusion limited aggregation, and the phase-field model was introduced to explain the formation mechanism of the pattern. A high-performance ultraviolet detector was fabricated on the artificial leaf structures, which showed that the current under the irradiation of a UV lamp (1.21 mW cm-2) was about 104 times greater than in the dark. The various and functional properties of the pattern show us the vast prospects of potential applications for light harvesting systems and other optical-electric devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr33748k

  17. Design of a minimal polypeptide unit for bacteriochlorophyll binding and self-assembly based on photosynthetic bacterial light-harvesting proteins.

    Science.gov (United States)

    Noy, Dror; Dutton, P Leslie

    2006-02-21

    We introduce LH1beta24, a minimal 24 amino acid polypeptide that binds and assembles bacteriochlorophylls (BChls) in micelles of octyl beta-glucoside (OG) into complexes with spectral properties that resemble those of B820, a universal intermediate in the assembly of native purple bacterial light-harvesting complexes (LHs). LH1beta24 was designed by a survey of sequences and crystal structures of bacterial LH proteins from different organisms combined with currently available information from in vitro reconstitution studies and genetically modified LHs in vivo. We took as a template for the design sphbeta31, a truncated 31 amino acid analogue of the native beta-apoprotein from the core LH complex of Rhodobacter sphaeroides. This peptide self-assembles with BChls to form B820 and, upon cooling and lowering OG concentration, forms red-shifted B850 spectral species that are considered analogous to native LH complexes. We find that LH1beta24 self-assembles with BChl in OG to form homodimeric B820-type subunits comprising two LH1beta24 and two BChl molecules per subunit. We demonstrate, by modeling the structure using the highly homologous structure of LH2 from Rhodospirillum molischianum, that it has the minimal size for BChl binding. Additionally, we have compared the self-assembly of sphbeta31 and LH1beta24 with BChls and discovered that the association enthalpies and entropies of both species are similar to those measured for native LH1 from Rhodospirillum rubrum. However, sphbeta31 readily aggregates into intermediate higher oligomeric species and further to form B850 species; moreover, the assembly process of these oligomers is not reversible, and they are apparently large nonspecific BChl-peptide coaggregates rather than well-defined nativelike LH complexes. Similar aggregates were observed during LH1beta24 assembly, but these were formed less readily and required lower temperatures than sphbeta31. In view of these results, we reevaluate previous in vitro

  18. Extension of Light-Harvesting Ability of Photosynthetic Light-Harvesting Complex 2 (LH2) through Ultrafast Energy Transfer from Covalently Attached Artificial Chromophores.

    Science.gov (United States)

    Yoneda, Yusuke; Noji, Tomoyasu; Katayama, Tetsuro; Mizutani, Naoto; Komori, Daisuke; Nango, Mamoru; Miyasaka, Hiroshi; Itoh, Shigeru; Nagasawa, Yutaka; Dewa, Takehisa

    2015-10-14

    Introducing appropriate artificial components into natural biological systems could enrich the original functionality. To expand the available wavelength range of photosynthetic bacterial light-harvesting complex 2 (LH2 from Rhodopseudomonas acidophila 10050), artificial fluorescent dye (Alexa Fluor 647: A647) was covalently attached to N- and C-terminal Lys residues in LH2 α-polypeptides with a molar ratio of A647/LH2 ≃ 9/1. Fluorescence and transient absorption spectroscopies revealed that intracomplex energy transfer from A647 to intrinsic chromophores of LH2 (B850) occurs in a multiexponential manner, with time constants varying from 440 fs to 23 ps through direct and B800-mediated indirect pathways. Kinetic analyses suggested that B800 chromophores mediate faster energy transfer, and the mechanism was interpretable in terms of Förster theory. This study demonstrates that a simple attachment of external chromophores with a flexible linkage can enhance the light harvesting activity of LH2 without affecting inherent functions of energy transfer, and can achieve energy transfer in the subpicosecond range. Addition of external chromophores, thus, represents a useful methodology for construction of advanced hybrid light-harvesting systems that afford solar energy in the broad spectrum. PMID:26403467

  19. Vibronic coupling explains the ultrafast carotenoid-to-bacteriochlorophyll energy transfer in natural and artificial light harvesters

    OpenAIRE

    Perlík, Václav; Seibt, Joachim; Cranston, Laura J.; Cogdell, Richard J.; Lincoln, Craig N.; Savolainen, Janne; Šanda, František; Mančal, Tomáš; Hauer, Jürgen

    2015-01-01

    The initial energy transfer in photosynthesis occurs between the light-harvesting pigments and on ultrafast timescales. We analyze the carotenoid to bacteriochlorophyll energy transfer in LH2 Marichromatium purpuratum as well as in an artificial light-harvesting dyad system by using transient grating and two-dimensional electronic spectroscopy with 10 fs time resolution. We find that F\\"orster-type models reproduce the experimentally observed 60 fs transfer times, but overestimate coupling co...

  20. Time dependent DFT investigation of the optical properties of artificial light harvesting special pairs.

    Science.gov (United States)

    Agnihotri, Neha; Steer, Ronald P

    2016-06-01

    Computational modeling of selected artificial special pairs has been carried out. The structures chosen are bio-inspired molecular models of the light harvesting system II that have been previously investigated experimentally. Time-dependent density functional theory calculations have been employed to characterize the inter-macrocycle interactions resulting from two zinc porphyrins that are covalently linked with rigid linkers that vary the inter-porphyrin distance and the inter-planar angle in a C2v framework. The effects of varying the linker structure have been explored for electronic states with energies up to and including the Soret-correlated states in the dimer. An expansion of the Gouterman four orbital model for the monomers to an eight orbital model in the dimers provides a reasonable explanation of the inter-macrocycle interactions and provides insight into their experimental properties. PMID:27212274

  1. Artificial light-harvesting antennae: electronic energy transfer by way of molecular funnels.

    Science.gov (United States)

    Ziessel, Raymond; Harriman, Anthony

    2011-01-14

    Electronic energy transfer (EET) plays a critical role in many biological processes and is used by nature to direct energy to a site where chemical reactions need to be initiated. Such EET can occur over large distances and can involve many individual molecules of identical, similar or disparate chemical identity. Advances in spectroscopy and data processing have allowed the rates of EET to be measured on extremely fast timescales such that improved mechanistic insight becomes feasible. At the same time, highly sophisticated synthetic operations have been devised that facilitate the isolation and purification of elaborate multi-component molecular arrays. A key feature of these arrays concerns the logical positioning of individual units in a way that favours directed EET along the molecular axis or along some other preferred pathway. The availability of these novel molecular materials allows close examination of popular theoretical models and paves the way for the development of advanced molecular sensors, artificial light harvesters, fluorescent labels and sensitizers. Of particular interest is the spectacular growth in the application of boron dipyrromethene dyes as basic reagents in such artificial photon collectors and these compounds have dominated the market in recent years because of their synthetic versatility and valuable photophysical properties. In this article, recent developments in the field are highlighted in terms of synthesis and subsequent spectroscopic exploration. PMID:20957235

  2. Stepwise photoconversion of an artificial light-harvesting array built from extended BODIPY units.

    Science.gov (United States)

    Harriman, Anthony; Stachelek, Patrycja; Sutter, Alexandra; Ziessel, Raymond

    2015-06-01

    A molecular dyad, comprising two disparate extended boron dipyrromethene (BODIPY) units, has been identified as a potential component of artificial light-harvesting arrays. Highly efficient, intramolecular electronic energy transfer takes place under illumination but there is some competition from light-induced electron transfer along the molecular axis. The primary energy acceptor has a somewhat shortened excited-state lifetime and reduced emission quantum yield due to charge transfer from a terminal amine residue, the latter being required for the molecular system to operate in organic solar cells. Under continuous illumination with simulated solar light, the dyad undergoes very slow decomposition. In a protic solvent, both BODIPY units degrade at the same rate via an autocatalytic process. The products, one of which is a protonated analogue of the donor, degrade further by independent routes. In aprotic solvents or thin plastic films, the acceptor BODIPY dye absorbing at lowest energy undergoes photochemical degradation as above but the donor is much more stable under these conditions. At each stage of degradation, the molecule retains the ability to sensitize an amorphous silicon solar cell and the overall turnover number with respect to absorbed photons exceeds 10 million. The optical properties of the target compound nicely complement those of the solar cell and sensitization helps to avoid Staebler-Wronski photo-degradation. PMID:25898915

  3. J-aggregates of amphiphilic cyanine dyes: Self-organization of artificial light harvesting complexes

    Directory of Open Access Journals (Sweden)

    Stefan Kirstein

    2006-01-01

    Full Text Available The simultaneous chemical linkage of cyanine dye chromophores with both hydrophobic and hydrophilic substituents leads to a new type of amphiphilic molecules with the ability of spontaneous self-organization into highly ordered aggregates of various structures and morphologies. These aggregates carry the outstanding optical properties of J-aggregates, namely, efficient exciton coupling and fast exciton energy migration, which are essential for the build up of artificial light harvesting systems. The morphology of the aggregates depends sensitively on the molecular structure of the chemical substituents of the dye chromophore. Accordingly, lamellar ribbon-like structures, vesicles , tubes, and bundles of tubes are found depending on the dyes and the structure can further be altered by addition of surfactants, alcohols, or other additives. Altogether the tubular structure is the most noticeable structural motif of these types of J-aggregates. The optical spectra are characterized in general by a complex exciton spectrum which is composed of several electronic transitions. The spectrum is red-shifted as a total with respect to the monomer absorption and exhibits resonance fluorescence from the lowest energy transition. For the tubular structures, the optical spectra can be related to a structural model. Although the molecules itself are strictly achiral, a pronounced circular dichroism (CD is observed for the tubular aggregates and explained by unequal distribution of left- and right-handed helicity of the tubes. Photo-induced electron transfer (PET reactions from the dye aggregates to electron acceptor molecules lead to superquenching which proves the delocalization of the excitation. This property is used to synthesize metal nanoparticles on the aggregate surface by photo-induced reduction of metal ions.

  4. Vibronic coupling explains the ultrafast carotenoid-to-bacteriochlorophyll energy transfer in natural and artificial light harvesters

    CERN Document Server

    Perlík, Václav; Cranston, Laura J; Cogdell, Richard J; Lincoln, Craig N; Savolainen, Janne; Šanda, František; Mančal, Tomáš; Hauer, Jürgen

    2015-01-01

    The initial energy transfer in photosynthesis occurs between the light-harvesting pigments and on ultrafast timescales. We analyze the carotenoid to bacteriochlorophyll energy transfer in LH2 Marichromatium purpuratum as well as in an artificial light-harvesting dyad system by using transient grating and two-dimensional electronic spectroscopy with 10 fs time resolution. We find that F\\"orster-type models reproduce the experimentally observed 60 fs transfer times, but overestimate coupling constants, which leads to a disagreement with both linear absorption and electronic 2D-spectra. We show that a vibronic model, which treats carotenoid vibrations on both electronic ground and excited state as part of the system's Hamiltonian, reproduces all measured quantities. Importantly, the vibronic model presented here can explain the fast energy transfer rates with only moderate coupling constants, which are in agreement with structure based calculations. Counterintuitively, the vibrational levels on the carotenoid el...

  5. DNA-mediated self-assembly of artificial vesicles.

    Directory of Open Access Journals (Sweden)

    Maik Hadorn

    Full Text Available BACKGROUND: Although multicompartment systems made of single unilamellar vesicles offer the potential to outperform single compartment systems widely used in analytic, synthetic, and medical applications, their use has remained marginal to date. On the one hand, this can be attributed to the binary character of the majority of the current tethering protocols that impedes the implementation of real multicomponent or multifunctional systems. On the other hand, the few tethering protocols theoretically providing multicompartment systems composed of several distinct vesicle populations suffer from the readjustment of the vesicle formation procedure as well as from the loss of specificity of the linking mechanism over time. METHODOLOGY/PRINCIPAL FINDINGS: In previous studies, we presented implementations of multicompartment systems and resolved the readjustment of the vesicle formation procedure as well as the loss of specificity by using linkers consisting of biotinylated DNA single strands that were anchored to phospholipid-grafted biotinylated PEG tethers via streptavidin as a connector. The systematic analysis presented herein provides evidences for the incorporation of phospholipid-grafted biotinylated PEG tethers to the vesicle membrane during vesicle formation, providing specific anchoring sites for the streptavidin loading of the vesicle membrane. Furthermore, DNA-mediated vesicle-vesicle self-assembly was found to be sequence-dependent and to depend on the presence of monovalent salts. CONCLUSIONS/SIGNIFICANCE: This study provides a solid basis for the implementation of multi-vesicle assemblies that may affect at least three distinct domains. (i Analysis. Starting with a minimal system, the complexity of a bottom-up system is increased gradually facilitating the understanding of the components and their interaction. (ii Synthesis. Consecutive reactions may be implemented in networks of vesicles that outperform current single compartment

  6. Towards building artificial light harvesting complexes: enhanced singlet-singlet energy transfer between donor and acceptor pairs bound to albumins.

    Science.gov (United States)

    Kumar, Challa V; Duff, Michael R

    2008-12-01

    singlet-singlet energy transfer. Such systems may form a basis for the design and construction of protein-based multi-chromophore self-assemblies for solar light harvesting, conversion and storage. PMID:19037505

  7. Vibronic coupling explains the ultrafast carotenoid-to-bacteriochlorophyll energy transfer in natural and artificial light harvesters.

    Science.gov (United States)

    Perlík, Václav; Seibt, Joachim; Cranston, Laura J; Cogdell, Richard J; Lincoln, Craig N; Savolainen, Janne; Šanda, František; Mančal, Tomáš; Hauer, Jürgen

    2015-06-01

    The initial energy transfer steps in photosynthesis occur on ultrafast timescales. We analyze the carotenoid to bacteriochlorophyll energy transfer in LH2 Marichromatium purpuratum as well as in an artificial light-harvesting dyad system by using transient grating and two-dimensional electronic spectroscopy with 10 fs time resolution. We find that Förster-type models reproduce the experimentally observed 60 fs transfer times, but overestimate coupling constants, which lead to a disagreement with both linear absorption and electronic 2D-spectra. We show that a vibronic model, which treats carotenoid vibrations on both electronic ground and excited states as part of the system's Hamiltonian, reproduces all measured quantities. Importantly, the vibronic model presented here can explain the fast energy transfer rates with only moderate coupling constants, which are in agreement with structure based calculations. Counterintuitively, the vibrational levels on the carotenoid electronic ground state play the central role in the excited state population transfer to bacteriochlorophyll; resonance between the donor-acceptor energy gap and the vibrational ground state energies is the physical basis of the ultrafast energy transfer rates in these systems. PMID:26049454

  8. Vibronic coupling explains the ultrafast carotenoid-to-bacteriochlorophyll energy transfer in natural and artificial light harvesters

    Science.gov (United States)

    Perlík, Václav; Seibt, Joachim; Cranston, Laura J.; Cogdell, Richard J.; Lincoln, Craig N.; Savolainen, Janne; Šanda, František; Mančal, Tomáš; Hauer, Jürgen

    2015-06-01

    The initial energy transfer steps in photosynthesis occur on ultrafast timescales. We analyze the carotenoid to bacteriochlorophyll energy transfer in LH2 Marichromatium purpuratum as well as in an artificial light-harvesting dyad system by using transient grating and two-dimensional electronic spectroscopy with 10 fs time resolution. We find that Förster-type models reproduce the experimentally observed 60 fs transfer times, but overestimate coupling constants, which lead to a disagreement with both linear absorption and electronic 2D-spectra. We show that a vibronic model, which treats carotenoid vibrations on both electronic ground and excited states as part of the system's Hamiltonian, reproduces all measured quantities. Importantly, the vibronic model presented here can explain the fast energy transfer rates with only moderate coupling constants, which are in agreement with structure based calculations. Counterintuitively, the vibrational levels on the carotenoid electronic ground state play the central role in the excited state population transfer to bacteriochlorophyll; resonance between the donor-acceptor energy gap and the vibrational ground state energies is the physical basis of the ultrafast energy transfer rates in these systems.

  9. Vibronic coupling explains the ultrafast carotenoid-to-bacteriochlorophyll energy transfer in natural and artificial light harvesters

    Energy Technology Data Exchange (ETDEWEB)

    Perlík, Václav; Seibt, Joachim; Šanda, František; Mančal, Tomáš [Institute of Physics, Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 5, Prague 121 16 (Czech Republic); Cranston, Laura J.; Cogdell, Richard J. [Institute of Molecular Cell and System Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow Biomedical Research Centre, 120 University Place, Glasgow G12 8TA, Scotland (United Kingdom); Lincoln, Craig N.; Hauer, Jürgen, E-mail: juergen.hauer@tuwien.ac.at [Photonics Institute, Vienna University of Technology, Gusshausstrasse 27, 1040 Vienna (Austria); Savolainen, Janne [Department of Physical Chemistry II, Ruhr-University Bochum, 44780 Bochum (Germany)

    2015-06-07

    The initial energy transfer steps in photosynthesis occur on ultrafast timescales. We analyze the carotenoid to bacteriochlorophyll energy transfer in LH2 Marichromatium purpuratum as well as in an artificial light-harvesting dyad system by using transient grating and two-dimensional electronic spectroscopy with 10 fs time resolution. We find that Förster-type models reproduce the experimentally observed 60 fs transfer times, but overestimate coupling constants, which lead to a disagreement with both linear absorption and electronic 2D-spectra. We show that a vibronic model, which treats carotenoid vibrations on both electronic ground and excited states as part of the system’s Hamiltonian, reproduces all measured quantities. Importantly, the vibronic model presented here can explain the fast energy transfer rates with only moderate coupling constants, which are in agreement with structure based calculations. Counterintuitively, the vibrational levels on the carotenoid electronic ground state play the central role in the excited state population transfer to bacteriochlorophyll; resonance between the donor-acceptor energy gap and the vibrational ground state energies is the physical basis of the ultrafast energy transfer rates in these systems.

  10. Vibronic coupling explains the ultrafast carotenoid-to-bacteriochlorophyll energy transfer in natural and artificial light harvesters

    International Nuclear Information System (INIS)

    The initial energy transfer steps in photosynthesis occur on ultrafast timescales. We analyze the carotenoid to bacteriochlorophyll energy transfer in LH2 Marichromatium purpuratum as well as in an artificial light-harvesting dyad system by using transient grating and two-dimensional electronic spectroscopy with 10 fs time resolution. We find that Förster-type models reproduce the experimentally observed 60 fs transfer times, but overestimate coupling constants, which lead to a disagreement with both linear absorption and electronic 2D-spectra. We show that a vibronic model, which treats carotenoid vibrations on both electronic ground and excited states as part of the system’s Hamiltonian, reproduces all measured quantities. Importantly, the vibronic model presented here can explain the fast energy transfer rates with only moderate coupling constants, which are in agreement with structure based calculations. Counterintuitively, the vibrational levels on the carotenoid electronic ground state play the central role in the excited state population transfer to bacteriochlorophyll; resonance between the donor-acceptor energy gap and the vibrational ground state energies is the physical basis of the ultrafast energy transfer rates in these systems

  11. Self-Assembled Local Artificial Substrates of GaAs on Si Substrate

    Directory of Open Access Journals (Sweden)

    Frigeri C

    2010-01-01

    Full Text Available Abstract We propose a self-assembling procedure for the fabrication of GaAs islands by Droplet Epitaxy on silicon substrate. Controlling substrate temperature and amount of supplied gallium is possible to tune the base size of the islands from 70 up to 250 nm and the density from 107 to 109 cm−2. The islands show a standard deviation of base size distribution below 10% and their shape evolves changing the aspect ratio from 0.3 to 0.5 as size increases. Due to their characteristics, these islands are suitable to be used as local artificial substrates for the integration of III–V quantum nanostructures directly on silicon substrate.

  12. Highly permeable artificial water channels that can self-assemble into two-dimensional arrays.

    Science.gov (United States)

    Shen, Yue-Xiao; Si, Wen; Erbakan, Mustafa; Decker, Karl; De Zorzi, Rita; Saboe, Patrick O; Kang, You Jung; Majd, Sheereen; Butler, Peter J; Walz, Thomas; Aksimentiev, Aleksei; Hou, Jun-li; Kumar, Manish

    2015-08-11

    Bioinspired artificial water channels aim to combine the high permeability and selectivity of biological aquaporin (AQP) water channels with chemical stability. Here, we carefully characterized a class of artificial water channels, peptide-appended pillar[5]arenes (PAPs). The average single-channel osmotic water permeability for PAPs is 1.0(± 0.3) × 10(-14) cm(3)/s or 3.5(± 1.0) × 10(8) water molecules per s, which is in the range of AQPs (3.4 ∼ 40.3 × 10(8) water molecules per s) and their current synthetic analogs, carbon nanotubes (CNTs, 9.0 × 10(8) water molecules per s). This permeability is an order of magnitude higher than first-generation artificial water channels (20 to ∼ 10(7) water molecules per s). Furthermore, within lipid bilayers, PAP channels can self-assemble into 2D arrays. Relevant to permeable membrane design, the pore density of PAP channel arrays (∼ 2.6 × 10(5) pores per μm(2)) is two orders of magnitude higher than that of CNT membranes (0.1 ∼ 2.5 × 10(3) pores per μm(2)). PAP channels thus combine the advantages of biological channels and CNTs and improve upon them through their relatively simple synthesis, chemical stability, and propensity to form arrays. PMID:26216964

  13. Energy transfer in aggregates of bacteriochlorophyll c self-assembled with azulene derivatives.

    Science.gov (United States)

    Matěnová, Martina; Lorelei Horhoiu, Viviana; Dang, Florian-Xuan; Pospíšil, Petr; Alster, Jan; Burda, Jaroslav V; Balaban, Teodor Silviu; Pšenčík, Jakub

    2014-08-21

    Bacteriochlorophyll (BChl) c is the main light-harvesting pigment of certain photosynthetic bacteria. It is found in the form of self-assembled aggregates in the so-called chlorosomes. Here we report the results of co-aggregation experiments of BChl c with azulene and its tailored derivatives. We have performed spectroscopic and quantum chemical characterization of the azulenes, followed by self-assembly experiments. The results show that only azulenes with sufficient hydrophobicity are able to induce aggregation of BChl c. Interestingly, only azulene derivatives possessing a conjugated phenyl ring were capable of efficient (∼50%) excitation energy transfer to BChl molecules. These aggregates represent an artificial light-harvesting complex with enhanced absorption between 220 and 350 nm compared to aggregates of pure BChl c. The results provide insight into the principles of self-assembly of BChl aggregates and suggest an important role of the π-π interactions in efficient energy transfer. PMID:24999619

  14. Genetic exchange leading to self-assembling RNA species upon encapsulation in artificial protocells.

    Science.gov (United States)

    Zenisek, Sergio-Francis M; Hayden, Eric J; Lehman, Niles

    2007-01-01

    The encapsulation of information-bearing macromolecules inside protocells is a critical step in scenarios for the origins of life on the Earth as well as for the construction of artificial living systems. For these protocells to emulate life, they must be able to transmit genetic information to other cells. We have used a water-in-oil emulsion system to simulate the compartmentalization of catalytic RNA molecules. By exploiting RNA-directed recombination reactions previously developed in our laboratory, including a ribozyme self-assembly pathway, we demonstrate that it is possible for information to be exchanged among protocells. This can happen either indirectly by the passage of divalent cations through the inter-protocellular medium (oil), or by the direct interaction of two or more protocells that allows RNA molecules to be exchanged. The degree of agitation affects the ability of such exchange. The consequences of these results include the implications that prototypical living systems can transmit information among compartments, and that the environment can regulate the extent of this crosstalk. PMID:17567246

  15. Selective internalization of self-assembled artificial oil bodies by HER2/neu-positive cells

    International Nuclear Information System (INIS)

    A novel delivery carrier was developed using artificial oil bodies (AOBs). Plant seed oil bodies (OBs) consist of a triacylglycerol matrix surrounded by a monolayer of phospholipids embedded with the storage protein oleosin (Ole). Ole consists of a central hydrophobic domain with two amphiphatic arms that extrude from the surface of OBs. In this study, a bivalent anti-HER2/neu affibody domain (ZH2) was fused with Ole at the C terminus. After overproduction in Escherichia coli, the fusion protein (Ole-ZH2) was recovered to assemble AOBs. The size of self-assembled AOBs was tailored by varying the oil/Ole-ZH2 ratio and pH to reach a nanoscale. Upon co-incubation with tumor cells, the nanoscale AOBs encapsulated with a hydrophobic fluorescence dye were selectively internalized by HER2/neu-overexpressing cells and displayed biocompatibility with the cells. In addition, the ZH2-mediated endosomal entry of AOBs occurred in a time- and AOB dose-dependent manner. The internalization efficiency was as high as 90%. The internalized AOBs disintegrated at the non-permissive pH (e.g. in acidic endosomes) and the cargo dye was released. Results of in vitro study revealed a sustained and prolonged release profile. Taken together, our findings indicate the potential of AOBs as a delivery carrier.

  16. Selective internalization of self-assembled artificial oil bodies by HER2/neu-positive cells

    Science.gov (United States)

    Chiang, Chung-Jen; Lin, Li-Jen; Lin, Che-Chin; Chang, Chih-Hsiang; Chao, Yun-Peng

    2011-01-01

    A novel delivery carrier was developed using artificial oil bodies (AOBs). Plant seed oil bodies (OBs) consist of a triacylglycerol matrix surrounded by a monolayer of phospholipids embedded with the storage protein oleosin (Ole). Ole consists of a central hydrophobic domain with two amphiphatic arms that extrude from the surface of OBs. In this study, a bivalent anti-HER2/neu affibody domain (ZH2) was fused with Ole at the C terminus. After overproduction in Escherichia coli, the fusion protein (Ole-ZH2) was recovered to assemble AOBs. The size of self-assembled AOBs was tailored by varying the oil/Ole-ZH2 ratio and pH to reach a nanoscale. Upon co-incubation with tumor cells, the nanoscale AOBs encapsulated with a hydrophobic fluorescence dye were selectively internalized by HER2/neu-overexpressing cells and displayed biocompatibility with the cells. In addition, the ZH2-mediated endosomal entry of AOBs occurred in a time- and AOB dose-dependent manner. The internalization efficiency was as high as 90%. The internalized AOBs disintegrated at the non-permissive pH (e.g. in acidic endosomes) and the cargo dye was released. Results of in vitro study revealed a sustained and prolonged release profile. Taken together, our findings indicate the potential of AOBs as a delivery carrier.

  17. Selective internalization of self-assembled artificial oil bodies by HER2/neu-positive cells

    Energy Technology Data Exchange (ETDEWEB)

    Chiang, Chung-Jen; Lin, Che-Chin [Department of Medical Laboratory Science and Biotechnology, China Medical University, Taichung, Taiwan (China); Lin, Li-Jen [School of Chinese Medicine, China Medical University, Taichung, Taiwan (China); Chang, Chih-Hsiang; Chao, Yun-Peng, E-mail: cjchiang@mail.cmu.edu.tw, E-mail: ypchao@fcu.edu.tw [Department of Chemical Engineering, Feng Chia University, Taichung, Taiwan (China)

    2011-01-07

    A novel delivery carrier was developed using artificial oil bodies (AOBs). Plant seed oil bodies (OBs) consist of a triacylglycerol matrix surrounded by a monolayer of phospholipids embedded with the storage protein oleosin (Ole). Ole consists of a central hydrophobic domain with two amphiphatic arms that extrude from the surface of OBs. In this study, a bivalent anti-HER2/neu affibody domain (ZH2) was fused with Ole at the C terminus. After overproduction in Escherichia coli, the fusion protein (Ole-ZH2) was recovered to assemble AOBs. The size of self-assembled AOBs was tailored by varying the oil/Ole-ZH2 ratio and pH to reach a nanoscale. Upon co-incubation with tumor cells, the nanoscale AOBs encapsulated with a hydrophobic fluorescence dye were selectively internalized by HER2/neu-overexpressing cells and displayed biocompatibility with the cells. In addition, the ZH2-mediated endosomal entry of AOBs occurred in a time- and AOB dose-dependent manner. The internalization efficiency was as high as 90%. The internalized AOBs disintegrated at the non-permissive pH (e.g. in acidic endosomes) and the cargo dye was released. Results of in vitro study revealed a sustained and prolonged release profile. Taken together, our findings indicate the potential of AOBs as a delivery carrier.

  18. An enzyme-coupled artificial photosynthesis system prepared from antenna protein-mimetic tyrosyl bolaamphiphile self-assembly.

    Science.gov (United States)

    Kwak, Jinyoung; Kim, Min-Chul; Lee, Sang-Yup

    2016-08-11

    An artificial photosynthesis system coupled with an enzyme was constructed using the nanospherical self-assembly of tyrosyl bolaamphiphiles, which worked as a host matrix exhibiting an antenna effect that allowed enhanced energy transfer to the ZnDPEG photosensitizer. The excited electrons from the photosensitizer were transferred to NAD+ to produce NADH, which subsequently initiated the conversion of an aldehyde to ethanol by alcohol dehydrogenase. Production of NADH and ethanol was enhanced by increasing the concentration of tyrosyl bolaamphiphiles. Spectroscopic investigations proved that the photosensitizer closely associated with the surface of the bolaamphiphile assembly through hydrogen bonds that allowed energy transfer between the host matrix and the photosensitizer. This study demonstrates that the self-assembly of bolaamphiphiles could be applicable to the construction of biomimetic energy systems exploiting biochemical activity. PMID:27480074

  19. Carrier relaxation dynamics in self-assembled quantum dots studied by artificial control of nonradiative losses

    Energy Technology Data Exchange (ETDEWEB)

    Davydov, V.; Nair, S.V.; Lee, J.-S.; Ren, H.-W. [JST, Tsukuba (Japan). ERATO Single Quantum Dot Project; Ignatiev, I.V.; Kozin, I.E. [JST, Tsukuba (Japan). ERATO Single Quantum Dot Project; Sankt-Peterburgskij Univ. (Russian Federation). Research Inst. of Physics; Sugou, S. [JST, Tsukuba (Japan). ERATO Single Quantum Dot Project; NEC Corp., Tsukuba (Japan). Opto-Electronics Research Lab.; Masumoto, Y. [JST, Tsukuba (Japan). ERATO Single Quantum Dot Project; Tsukuba Univ., Sakura, Ibaraki (Japan). Inst. of Physics

    2001-03-08

    Efficient single-step relaxation processes with emission of acoustic phonons are observed by a technique based on an artificial control of nonradiative losses by an external electric field. This observation is supported by the PL kinetics measurements. The findings give new and important insights into the interaction of the confined electron-hole pairs with the phonon subsystem. (orig.)

  20. The supramolecular organization of self-assembling chlorosomal bacteriochlorophyll c, d, or e mimics.

    Science.gov (United States)

    Jochum, Tobias; Reddy, Chilla Malla; Eichhöfer, Andreas; Buth, Gernot; Szmytkowski, Jedrzej; Kalt, Heinz; Moss, David; Balaban, Teodor Silviu

    2008-09-01

    Bacteriochlorophylls (BChls) c, d, and e are the main light-harvesting pigments of green photosynthetic bacteria that self-assemble into nanostructures within the chlorosomes forming the most efficient antennas of photosynthetic organisms. All previous models of the chlorosomal antennae, which are quite controversially discussed because no single crystals could be grown so far from these organelles, involve a strong hydrogen-bonding interaction between the 3(1) hydroxyl group and the 13(1) carbonyl group. We have synthesized different self-assemblies of BChl c mimics having the same functional groups as the natural counterparts, that is, a hydroxyethyl substituent, a carbonyl group and a divalent metal atom ligated by a tetrapyrrole. These artificial BChl mimics have been shown by single crystal x-ray diffraction to form extended stacks that are packed by hydrophobic interactions and in the absence of hydrogen bonding. Time-resolved photoluminescence proves the ordered nature of the self-assembled stacks. FT-IR spectra show that on self-assembly the carbonyl frequency is shifted by approximately 30 cm(-1) to lower wavenumbers. From the FT-IR data we can infer the proximal interactions between the BChls in the chlorosomes consistent with a single crystal x-ray structure that shows a weak electrostatic interaction between carbonyl groups and the central zinc atom. PMID:18755898

  1. Biohybrid photosynthetic antenna complexes for enhanced light-harvesting.

    Science.gov (United States)

    Springer, Joseph W; Parkes-Loach, Pamela S; Reddy, Kanumuri Ramesh; Krayer, Michael; Jiao, Jieying; Lee, Gregory M; Niedzwiedzki, Dariusz M; Harris, Michelle A; Kirmaier, Christine; Bocian, David F; Lindsey, Jonathan S; Holten, Dewey; Loach, Paul A

    2012-03-14

    Biohybrid antenna systems have been constructed that contain synthetic chromophores attached to 31mer analogues of the bacterial photosynthetic core light-harvesting (LH1) β-polypeptide. The peptides are engineered with a Cys site for bioconjugation with maleimide-terminated chromophores, which include synthetic bacteriochlorins (BC1, BC2) with strong near-infrared absorption and commercial dyes Oregon green (OGR) and rhodamine red (RR) with strong absorption in the blue-green to yellow-orange regions. The peptides place the Cys 14 (or 6) residues before a native His site that binds bacteriochlorophyll a (BChl-a) and, like the native LH proteins, have high helical content as probed by single-reflection IR spectroscopy. The His residue associates with BChl-a as in the native LH1 β-polypeptide to form dimeric ββ-subunit complexes [31mer(-14Cys)X/BChl](2), where X is one of the synthetic chromophores. The native-like BChl-a dimer has Q(y) absorption at 820 nm and serves as the acceptor for energy from light absorbed by the appended synthetic chromophore. The energy-transfer characteristics of biohybrid complexes have been characterized by steady-state and time-resolved fluorescence and absorption measurements. The quantum yields of energy transfer from a synthetic chromophore located 14 residues from the BChl-coordinating His site are as follows: OGR (0.30) BChl](n) are accompanied by a bathochromic shift of the Q(y) absorption of the BChl-a oligomer as far as the 850-nm position found in cyclic native photosynthetic LH2 complexes. Room-temperature stabilized oligomeric biohybrids have energy-transfer quantum yields comparable to those of the dimeric subunit complexes as follows: OGR (0.20) self-assembly characteristics of the native antenna complexes, offer enhanced coverage of the solar spectrum, and illustrate a versatile paradigm for the construction of artificial LH systems. PMID:22375881

  2. The chlorosome: a prototype for efficient light harvesting in photosynthesis.

    Science.gov (United States)

    Oostergetel, Gert T; van Amerongen, Herbert; Boekema, Egbert J

    2010-06-01

    Three phyla of bacteria include phototrophs that contain unique antenna systems, chlorosomes, as the principal light-harvesting apparatus. Chlorosomes are the largest known supramolecular antenna systems and contain hundreds of thousands of BChl c/d/e molecules enclosed by a single membrane leaflet and a baseplate. The BChl pigments are organized via self-assembly and do not require proteins to provide a scaffold for efficient light harvesting. Their excitation energy flows via a small protein, CsmA embedded in the baseplate to the photosynthetic reaction centres. Chlorosomes allow for photosynthesis at very low light intensities by ultra-rapid transfer of excitations to reaction centres and enable organisms with chlorosomes to live at extraordinarily low light intensities under which no other phototrophic organisms can grow. This article reviews several aspects of chlorosomes: the supramolecular and molecular organizations and the light-harvesting and spectroscopic properties. In addition, it provides some novel information about the organization of the baseplate. PMID:20130996

  3. A novel artificial nerve graft for repairing long-distance sciatic nerve defects: a self-assembling peptide nanofiber scaffold-containing poly(lactic-co-glycolic acid) conduit

    OpenAIRE

    Wang, Xianghai; Pan, Mengjie; Wen, Jinkun; Tang, Yinjuan; Hamilton, Audra D.; Li, Yuanyuan; Qian, Changhui; Liu, Zhongying; Wu, Wutian; Guo, Jiasong

    2014-01-01

    In this study, we developed a novel artificial nerve graft termed self-assembling peptide nanofiber scaffold (SAPNS)-containing poly(lactic-co-glycolic acid) (PLGA) conduit (SPC) and used it to bridge a 10-mm-long sciatic nerve defect in the rat. Retrograde tracing, behavioral testing and histomorphometric analyses showed that compared with the empty PLGA conduit implantation group, the SPC implantation group had a larger number of growing and extending axons, a markedly increased diameter of...

  4. OligArch: A software tool to allow artificially expanded genetic information systems (AEGIS to guide the autonomous self-assembly of long DNA constructs from multiple DNA single strands

    Directory of Open Access Journals (Sweden)

    Kevin M. Bradley

    2014-08-01

    Full Text Available Synthetic biologists wishing to self-assemble large DNA (L-DNA constructs from small DNA fragments made by automated synthesis need fragments that hybridize predictably. Such predictability is difficult to obtain with nucleotides built from just the four standard nucleotides. Natural DNA's peculiar combination of strong and weak G:C and A:T pairs, the context-dependence of the strengths of those pairs, unimolecular strand folding that competes with desired interstrand hybridization, and non-Watson–Crick interactions available to standard DNA, all contribute to this unpredictability. In principle, adding extra nucleotides to the genetic alphabet can improve the predictability and reliability of autonomous DNA self-assembly, simply by increasing the information density of oligonucleotide sequences. These extra nucleotides are now available as parts of artificially expanded genetic information systems (AEGIS, and tools are now available to generate entirely standard DNA from AEGIS DNA during PCR amplification. Here, we describe the OligArch (for "oligonucleotide architecting" software, an application that permits synthetic biologists to engineer optimally self-assembling DNA constructs from both six- and eight-letter AEGIS alphabets. This software has been used to design oligonucleotides that self-assemble to form complete genes from 20 or more single-stranded synthetic oligonucleotides. OligArch is therefore a key element of a scalable and integrated infrastructure for the rapid and designed engineering of biology.

  5. Principles of light harvesting from single photosynthetic complexes.

    Science.gov (United States)

    Schlau-Cohen, G S

    2015-06-01

    Photosynthetic systems harness sunlight to power most life on Earth. In the initial steps of photosynthetic light harvesting, absorbed energy is converted to chemical energy with near-unity quantum efficiency. This is achieved by an efficient, directional and regulated flow of energy through a network of proteins. Here, we discuss the following three key principles of this flow and of photosynthetic light harvesting: thermal fluctuations of the protein structure; intrinsic conformational switches with defined functional consequences; and environmentally triggered conformational switches. Through these principles, photosynthetic systems balance two types of operational costs: metabolic costs, or the cost of maintaining and running the molecular machinery, and opportunity costs, or the cost of losing any operational time. Understanding how the molecular machinery and dynamics are designed to balance these costs may provide a blueprint for improved artificial light-harvesting devices. With a multi-disciplinary approach combining knowledge of biology, this blueprint could lead to low-cost and more effective solar energy conversion. Photosynthetic systems achieve widespread light harvesting across the Earth's surface; in the face of our growing energy needs, this is functionality we need to replicate, and perhaps emulate. PMID:26052423

  6. Natural Light Harvesting Systems: Unraveling the quantum puzzles

    CERN Document Server

    Thilagam, A

    2013-01-01

    In natural light harvesting systems, the sequential quantum events of photon absorption by specialized biological antenna complexes, charge separation, exciton formation and energy transfer to localized reaction centers culminates in the conversion of solar to chemical energy. A notable feature in these processes is the exceptionally high efficiencies (> 95 %) at which excitation is transferred from the illuminated protein complex site to the reaction centers. Such high exciton propagation rates within a system of interwoven biomolecular network structures, is yet to be replicated in artificial light harvesting complexes. A clue to unraveling the quantum puzzles of nature may lie in the observation of long lived coherences lasting several picoseconds in the electronic spectra of photosynthetic complexes, even in noisy environmental baths. A number of experimental and theoretical studies have been devoted to unlocking the links between quantum processes and information protocols, in the hope of finding answers...

  7. Self-assembled nanostructures

    CERN Document Server

    Zhang, Jin Z; Liu, Jun; Chen, Shaowei; Liu, Gang-yu

    2003-01-01

    Nanostructures refer to materials that have relevant dimensions on the nanometer length scales and reside in the mesoscopic regime between isolated atoms and molecules in bulk matter. These materials have unique physical properties that are distinctly different from bulk materials. Self-Assembled Nanostructures provides systematic coverage of basic nanomaterials science including materials assembly and synthesis, characterization, and application. Suitable for both beginners and experts, it balances the chemistry aspects of nanomaterials with physical principles. It also highlights nanomaterial-based architectures including assembled or self-assembled systems. Filled with in-depth discussion of important applications of nano-architectures as well as potential applications ranging from physical to chemical and biological systems, Self-Assembled Nanostructures is the essential reference or text for scientists involved with nanostructures.

  8. Efficient exciton transport in layers of self-assembled porphyrin derivatives

    NARCIS (Netherlands)

    Huijser, A.; Suijkerbuijk, B.M.J.M.; Klein Gebbink, R.J.M.; Savenije, T.J.; Siebbeles, D.A.

    2008-01-01

    The photosynthetic apparatus of green sulfur bacteria, the chlorosome, is generally considered as a highly efficient natural light-harvesting system. The efficient exciton transport through chlorosomes toward the reaction centers originates from self-assembly of the bacteriochlorophyll molecules. Th

  9. Photovoltaic self-assembly.

    Energy Technology Data Exchange (ETDEWEB)

    Lavin, Judith; Kemp, Richard Alan; Stewart, Constantine A.

    2010-10-01

    This late-start LDRD was focused on the application of chemical principles of self-assembly on the ordering and placement of photovoltaic cells in a module. The drive for this chemical-based self-assembly stems from the escalating prices in the 'pick-and-place' technology currently used in the MEMS industries as the size of chips decreases. The chemical self-assembly principles are well-known on a molecular scale in other material science systems but to date had not been applied to the assembly of cells in a photovoltaic array or module. We explored several types of chemical-based self-assembly techniques, including gold-thiol interactions, liquid polymer binding, and hydrophobic-hydrophilic interactions designed to array both Si and GaAs PV chips onto a substrate. Additional research was focused on the modification of PV cells in an effort to gain control over the facial directionality of the cells in a solvent-based environment. Despite being a small footprint research project worked on for only a short time, the technical results and scientific accomplishments were significant and could prove to be enabling technology in the disruptive advancement of the microelectronic photovoltaics industry.

  10. PS2013 Satellite Workshop on Photosynthetic Light-Harvesting Systems

    Energy Technology Data Exchange (ETDEWEB)

    Niederman, Robert A. [Rutgers Univ., New Brunswick, NJ (United States); Blankenship, Robert E. [Washington Univ., St. Louis, MO (United States); Frank, Harry A. [Univ. of Connecticut, Storrs, CT (United States)

    2015-02-07

    These funds were used for partial support of the PS2013 Satellite Workshop on Photosynthetic Light-Harvesting Systems, that was held on 8-11 August, 2013, at Washington University, St. Louis, MO. This conference, held in conjunction with the 16th International Congress on Photosynthesis/St. Louis, continued a long tradition of light-harvesting satellite conferences that have been held prior to the previous six international photosynthesis congresses. In this Workshop, the basis was explored for the current interest in replacing fossil fuels with energy sources derived form direct solar radiation, coupled with light-driven electron transport in natural photosynthetic systems and how they offer a valuable blueprint for conversion of sunlight to useful energy forms. This was accomplished through sessions on the initial light-harvesting events in the biological conversion of solar energy to chemically stored energy forms, and how these natural photosynthetic processes serve as a guide to the development of robust bio-hybrid and artificial systems for solar energy conversion into both electricity or chemical fuels. Organized similar to a Gordon Research Conference, a lively, informal and collegial setting was established, highlighting the exchange of exciting new data and unpublished results from ongoing studies. A significant amount of time was set aside for open discussion and interactive poster sessions, with a special session devoted to oral presentations by talented students and postdoctoral fellows judged to have the best posters. This area of research has seen exceptionally rapid progress in recent years, with the availability of a number of antenna protein structures at atomic resolution, elucidation of the molecular surface architecture of native photosynthetic membranes by atomic force microscopy and the maturing of ultrafast spectroscopic and molecular biological techniques for the investigation and manipulation of photosynthetic systems. The conferees

  11. Programming Light-Harvesting Efficiency Using DNA Origami.

    Science.gov (United States)

    Hemmig, Elisa A; Creatore, Celestino; Wünsch, Bettina; Hecker, Lisa; Mair, Philip; Parker, M Andy; Emmott, Stephen; Tinnefeld, Philip; Keyser, Ulrich F; Chin, Alex W

    2016-04-13

    The remarkable performance and quantum efficiency of biological light-harvesting complexes has prompted a multidisciplinary interest in engineering biologically inspired antenna systems as a possible route to novel solar cell technologies. Key to the effectiveness of biological "nanomachines" in light capture and energy transport is their highly ordered nanoscale architecture of photoactive molecules. Recently, DNA origami has emerged as a powerful tool for organizing multiple chromophores with base-pair accuracy and full geometric freedom. Here, we present a programmable antenna array on a DNA origami platform that enables the implementation of rationally designed antenna structures. We systematically analyze the light-harvesting efficiency with respect to number of donors and interdye distances of a ring-like antenna using ensemble and single-molecule fluorescence spectroscopy and detailed Förster modeling. This comprehensive study demonstrates exquisite and reliable structural control over multichromophoric geometries and points to DNA origami as highly versatile platform for testing design concepts in artificial light-harvesting networks. PMID:26906456

  12. A srikaya-like light-harvesting antenna based on graphene quantum dots and porphyrin unimolecular micelles.

    Science.gov (United States)

    Liu, Yannan; Li, Shanlong; Li, Ke; Zheng, Yongli; Zhang, Meng; Cai, Caiyun; Yu, Chunyang; Zhou, Yongfeng; Yan, Deyue

    2016-07-19

    A novel hybrid light-harvesting antenna with a srikaya-like structure of multi-graphene quantum dots (GQDs) as donors and one porphyrin unimolecular micelle as the acceptor was constructed through electrostatic self-assembly. The constructed antenna showed a high energy transfer efficiency of up to 93.6% and an antenna effect of 7.3 in an aqueous solution. PMID:27374891

  13. A novel artificial nerve graft for repairing long-distance sciatic nerve defects: a self-assembling peptide nanofiber scaffold-containing poly(lactic-co-glycolic acid) conduit.

    Science.gov (United States)

    Wang, Xianghai; Pan, Mengjie; Wen, Jinkun; Tang, Yinjuan; Hamilton, Audra D; Li, Yuanyuan; Qian, Changhui; Liu, Zhongying; Wu, Wutian; Guo, Jiasong

    2014-12-15

    In this study, we developed a novel artificial nerve graft termed self-assembling peptide nanofiber scaffold (SAPNS)-containing poly(lactic-co-glycolic acid) (PLGA) conduit (SPC) and used it to bridge a 10-mm-long sciatic nerve defect in the rat. Retrograde tracing, behavioral testing and histomorphometric analyses showed that compared with the empty PLGA conduit implantation group, the SPC implantation group had a larger number of growing and extending axons, a markedly increased diameter of regenerated axons and a greater thickness of the myelin sheath in the conduit. Furthermore, there was an increase in the size of the neuromuscular junction and myofiber diameter in the target muscle. These findings suggest that the novel artificial SPC nerve graft can promote axonal regeneration and remyelination in the transected peripheral nerve and can be used for repairing peripheral nerve injury. PMID:25657734

  14. Ion sensing, light harvesting, energy conversion & self-assembly in rationally designed molecular constructs

    OpenAIRE

    Büyükçakır, Onur

    2013-01-01

    Ankara : Materials Science and Nanotechnology Program of the Graduate School of Engineering and Science of Bilkent Univ., 2013. Thesis (Ph. D.) -- Bilkent University, 2013 Includes bibliographical references leaves 144-163. Büyükçakır, Onur Ph. D.

  15. Functionalized Nanoparticles and Surfaces for Controlled Chemical Catalysis and Effective Light Harvesting

    Energy Technology Data Exchange (ETDEWEB)

    Marye Anne Fox, James K. Whitesell

    2012-11-02

    We have prepared a range of such arrays as key components for biotechnology and photonic applications. These involve self-assembled arrays of increasing complexity with three-dimensionally disposed multilayer interactions. These arrays also include dendrimers as the distinguishing structural building blocks. These photoactive integrated systems have a regular, highly-branched, three-dimensional architecture. Structural modifications of these units include variation of the core, bridging layers, and terminal groups. These modifications result in a large array of dendritic molecules with potential applications for light harvesting.

  16. [INVITED] Self-assembled optical metamaterials

    Science.gov (United States)

    Baron, Alexandre; Aradian, Ashod; Ponsinet, Virginie; Barois, Philippe

    2016-08-01

    Self-assembled metamaterials constitute a promising platform to achieving bulk and homogenous optical materials that exhibit unusual effective medium properties. For many years now, the research community has contemplated lithographically fabricated metasurfaces, with extraordinary optical features. However, achieving large volumes at low cost is still a challenge by top-down fabrication. Bottom-up fabrication, that relies both on nanochemistry and self-assembly, is capable of building such materials while greatly reducing the energy footprint in the formulation of the metamaterial. Self-assembled metamaterials have shown that they are capable of reaching unprecedented values of bulkiness and homogeneity figures of merit. This feat is achieved by synthesizing plasmonic nanoresonators (meta-atoms in the sense of artificial polarizable units) and assembling them into a fully three-dimensional matrix through a variety of methods. Furthermore it has been shown that a wide range of material parameters can be tailored by controlling the geometry and composition of the meta-atoms as well as the volume fraction of the nano-objects in the metamaterial. Here we conduct a non-comprehensive review of some of the recent trends in self-assembled optical metamaterials and illustrate these trends with our recent work.

  17. Self-assembly via microfluidics

    OpenAIRE

    Wang, Lei; Sánchez, Samuel

    2015-01-01

    The self-assembly of amphiphilic building blocks has attracted extensive interest in myriad fields in recent years, due to their great potential in the nanoscale design of functional hybrid materials. Microfluidic techniques provide an intriguing method to control kinetic aspects of the self-assembly of molecular amphiphiles by the facile adjustment of the hydrodynamics of the fluids. Up to now, there have been several reports about one-step direct self-assembly of different building blocks w...

  18. Artificial and self-assembled vortex-pinning centers in superconducting Ba(Fe1-xCox)2As2 thin films as a route to obtaining very high critical-current densities

    Science.gov (United States)

    Tarantini, C.; Lee, S.; Kametani, F.; Jiang, J.; Weiss, J. D.; Jaroszynski, J.; Folkman, C. M.; Hellstrom, E. E.; Eom, C. B.; Larbalestier, D. C.

    2012-12-01

    We report on the superior vortex pinning of single- and multilayer Ba(Fe1-xCox)2As2 thin films with self-assembled c-axis and artificially introduced ab-plane pins. Ba(Fe1-xCox)2As2 can accept a very high density of pins (15-20 vol %) without Tc suppression. The matching field is greater than 12 T, producing a significant enhancement of the critical current density Jc, an almost isotropic Jc(θ, 20 T) > 105 A/cm2, and global pinning force density Fp of ˜50 GN/m3. This scenario strongly differs from the high-temperature superconducting cuprates where the addition of pins without Tc suppression is limited to 2-4 vol %, leading to small HIrr enhancements and improved Jc only below 3-5 T.

  19. Solid-state NMR applied to photosynthetic light-harvesting complexes.

    Science.gov (United States)

    Pandit, Anjali; de Groot, Huub J M

    2012-03-01

    This short review describes how solid-state NMR has provided a mechanistic and electronic picture of pigment-protein and pigment-pigment interactions in photosynthetic antenna complexes. NMR results on purple bacterial antenna complexes show how the packing of the protein and the pigments inside the light-harvesting oligomers induces mutual conformational stress. The protein scaffold produces deformation and electrostatic polarization of the BChl macrocycles and leads to a partial electronic charge transfer between the BChls and their coordinating histidines, which can tune the light-harvesting function. In chlorosome antennae assemblies, the NMR template structure reveals how the chromophores can direct their self-assembly into higher macrostructures which, in turn, tune the light-harvesting properties of the individual molecules by controlling their disorder, structural deformation, and electronic polarization without the need for a protein scaffold. These results pave the way for addressing the next challenge, which is to resolve the functional conformational dynamics of the lhc antennae of oxygenic species that allows them to switch between light-emitting and light-energy dissipating states. PMID:21842288

  20. Coded nanoscale self-assembly

    Indian Academy of Sciences (India)

    Prathyush Samineni; Debabrata Goswami

    2008-12-01

    We demonstrate coded self-assembly in nanostructures using the code seeded at the component level through computer simulations. Defects or cavities occur in all natural assembly processes including crystallization and our simulations capture this essential aspect under surface minimization constraints for self-assembly. Our bottom-up approach to nanostructures would provide a new dimension towards nanofabrication and better understanding of defects and crystallization process.

  1. Design strategies for self-assembly of discrete targets

    International Nuclear Information System (INIS)

    Both biological and artificial self-assembly processes can take place by a range of different schemes, from the successive addition of identical building blocks to hierarchical sequences of intermediates, all the way to the fully addressable limit in which each component is unique. In this paper, we introduce an idealized model of cubic particles with patterned faces that allows self-assembly strategies to be compared and tested. We consider a simple octameric target, starting with the minimal requirements for successful self-assembly and comparing the benefits and limitations of more sophisticated hierarchical and addressable schemes. Simulations are performed using a hybrid dynamical Monte Carlo protocol that allows self-assembling clusters to rearrange internally while still providing Stokes-Einstein-like diffusion of aggregates of different sizes. Our simulations explicitly capture the thermodynamic, dynamic, and steric challenges typically faced by self-assembly processes, including competition between multiple partially completed structures. Self-assembly pathways are extracted from the simulation trajectories by a fully extendable scheme for identifying structural fragments, which are then assembled into history diagrams for successfully completed target structures. For the simple target, a one-component assembly scheme is most efficient and robust overall, but hierarchical and addressable strategies can have an advantage under some conditions if high yield is a priority

  2. Design strategies for self-assembly of discrete targets

    Science.gov (United States)

    Madge, Jim; Miller, Mark A.

    2015-07-01

    Both biological and artificial self-assembly processes can take place by a range of different schemes, from the successive addition of identical building blocks to hierarchical sequences of intermediates, all the way to the fully addressable limit in which each component is unique. In this paper, we introduce an idealized model of cubic particles with patterned faces that allows self-assembly strategies to be compared and tested. We consider a simple octameric target, starting with the minimal requirements for successful self-assembly and comparing the benefits and limitations of more sophisticated hierarchical and addressable schemes. Simulations are performed using a hybrid dynamical Monte Carlo protocol that allows self-assembling clusters to rearrange internally while still providing Stokes-Einstein-like diffusion of aggregates of different sizes. Our simulations explicitly capture the thermodynamic, dynamic, and steric challenges typically faced by self-assembly processes, including competition between multiple partially completed structures. Self-assembly pathways are extracted from the simulation trajectories by a fully extendable scheme for identifying structural fragments, which are then assembled into history diagrams for successfully completed target structures. For the simple target, a one-component assembly scheme is most efficient and robust overall, but hierarchical and addressable strategies can have an advantage under some conditions if high yield is a priority.

  3. Exciton dynamics in light harvesting systems

    International Nuclear Information System (INIS)

    The optical line shape of molecular ring aggregates with 18 molecular units, modeling bacteria photo-synthetic light harvesting systems, is investigated theoretically. The molecular units are described by two-level systems with an average excitation energy ε and interacting with each other through nearest-neighbor interaction. Furthermore, quasi-static and dynamic fluctuations of the local excitation energies are taken into account simulating slow motions of the protein backbone and fast molecular vibrations, respectively. The fluctuations are described by colored dichotomic Markov processes with exponentially decaying correlation functions with small (λs) and large (λ) decay constants, respectively. The optical line shape is discussed in dependence of the model parameters including a possible elliptical deformation. Furthermore we investigate the coupled coherent and incoherent energy transport in chlorosomes

  4. Light-Harvesting Nanoparticle Core-Shell Clusters with Controllable Optical Output.

    Science.gov (United States)

    Sun, Dazhi; Tian, Ye; Zhang, Yugang; Xu, Zhihua; Sfeir, Matthew Y; Cotlet, Mircea; Gang, Oleg

    2015-06-23

    We used DNA self-assembly methods to fabricate a series of core-shell gold nanoparticle-DNA-colloidal quantum dot (AuNP-DNA-Qdot) nanoclusters with satellite-like architecture to modulate optical (photoluminescence) response. By varying the intercomponent distance through the DNA linker length designs, we demonstrate precise tuning of the plasmon-exciton interaction and the optical behavior of the nanoclusters from regimes characterized by photoluminescence quenching to photoluminescence enhancement. The combination of detailed X-ray scattering probing with photoluminescence intensity and lifetime studies revealed the relation between the cluster structure and its optical output. Compared to conventional light-harvesting systems like conjugated polymers and multichromophoric dendrimers, the proposed nanoclusters bring enhanced flexibility in controlling the optical behavior toward a desired application, and they can be regarded as controllable optical switches via the optically pumped color. PMID:25933097

  5. Self-assembly of cyclodextrins

    DEFF Research Database (Denmark)

    Fülöp, Z.; Kurkov, S.V.; Nielsen, T.T.;

    2012-01-01

    The design of functional cyclodextrin (CD) nanoparticles is a developing area in the field of nanomedicine. CDs can not only help in the formation of drug carriers but also increase the local concentration of drugs at the site of action. CD monomers form aggregates by self-assembly, a tendency that...... increases upon formation of inclusion complexes with lipophilic drugs. However, the stability of such aggregates is not sufficient for parenteral administration. In this review CD polymers and CD containing nanoparticles are categorized, with focus on self-assembled CD nanoparticles. It is described how the...

  6. Binary ionic porphyrin nanosheets: electronic and light-harvesting properties regulated by crystal structure

    Science.gov (United States)

    Tian, Yongming; M. Beavers, Christine; Busani, Tito; Martin, Kathleen E.; Jacobsen, John L.; Mercado, Brandon Q.; Swartzentruber, Brian S.; van Swol, Frank; Medforth, Craig J.; Shelnutt, John A.

    2012-02-01

    Crystalline solids self-assembled from anionic and cationic porphyrins provide a new class of multifunctional optoelectronic micro- and nanomaterials. A 1 : 1 combination of zinc(ii) tetra(4-sulfonatophenyl)porphyrin (ZnTPPS) and tin(iv) tetra(N-methyl-4-pyridiniumyl)porphyrin (SnTNMePyP) gives porphyrin nanosheets with high aspect ratios and varying thickness. The room temperature preparation of the nanosheets has provided the first X-ray crystal structure of a cooperative binary ionic (CBI) solid. The unit cell contains one and one-half molecules of aquo-ZnTPPS4- (an electron donor) and three half molecules of dihydroxy-SnTNMePyP4+ (an electron acceptor). Charge balance in the solid is reached without any non-porphyrinic ions, as previously determined for other CBI nanomaterials by non-crystallographic means. The crystal structure reveals a complicated molecular arrangement with slipped π-π stacking only occurring in isolated dimers of one of the symmetrically unique zinc porphyrins. Consistent with the crystal structure, UV-visible J-aggregate bands indicative of exciton delocalization and extended π-π stacking are not observed. XRD measurements show that the structure of the Zn/Sn nanosheets is distinct from that of Zn/Sn four-leaf clover-like CBI solids reported previously. In contrast with the Zn/Sn clovers that do exhibit J-aggregate bands and are photoconductive, the nanosheets are not photoconductive. Even so, the nanosheets act as light-harvesting structures in an artificial photosynthesis system capable of reducing water to hydrogen but not as efficiently as the Zn/Sn clovers.Crystalline solids self-assembled from anionic and cationic porphyrins provide a new class of multifunctional optoelectronic micro- and nanomaterials. A 1 : 1 combination of zinc(ii) tetra(4-sulfonatophenyl)porphyrin (ZnTPPS) and tin(iv) tetra(N-methyl-4-pyridiniumyl)porphyrin (SnTNMePyP) gives porphyrin nanosheets with high aspect ratios and varying thickness. The room

  7. Mechanisms of light harvesting by photosystem II in plants

    CERN Document Server

    Amarnath, Kapil; Schneider, Anna R; Fleming, Graham R

    2015-01-01

    Light harvesting by photosystem II (PSII) in plants is highly efficient and acclimates to rapid changes in the intensity of sunlight. However, the mechanisms of PSII light harvesting have remained experimentally inaccessible. Using a structure-based model of excitation energy flow in 200 nanometer (nm) x 200 nm patches of the grana membrane, where PSII is located, we accurately simulated chlorophyll fluorescence decay data with no free parameters. Excitation movement through the light harvesting antenna is diffusive, but becomes subdiffusive in the presence of charge separation at reaction centers. The influence of membrane morphology on light harvesting efficiency is determined by the excitation diffusion length of 50 nm in the antenna. Our model provides the basis for understanding how nonphotochemical quenching mechanisms affect PSII light harvesting in grana membranes.

  8. Development of Scaffolds for Light Harvesting and Photocatalysis from the Coat Protein of Tobacco Mosaic Virus

    Science.gov (United States)

    Dedeo, Michel Toussaint

    The utility of a previously developed TMV-based light harvesting system has been dramatically expanded through the introduction of reactive handles for the site-specific modification of the interior and exterior surfaces. Further experiments to reengineer the coat protein have produced structures with unique, unexpected, and useful assembly properties that complement the newly available surface modifications. Energy transfer from chromophores in the RNA channel of self-assembled TMV structures to the exterior was made possible by conjugation of acceptor dyes and porphyrins to the N-terminus. By repositioning the N-terminus to the pore through circular permutation, this process was repeated to create structures that mimic the light harvesting 1 complex of photosynthetic bacteria. To study and improve upon natural photosynthesis, closely packed chromophore arrays and gold nanoparticles were tethered to the pore of stabilized TMV disks through introduction of a uniquely reactive lysine. Finally, a dimeric TMV coat protein was produced to control the distribution and arrangement of synthetic groups with synergistic activity.

  9. Self-assembly of self-assembled molecular triangles

    Indian Academy of Sciences (India)

    Mili C Naranthatta; V Ramkumar; Dillip Kumar Chand

    2014-09-01

    A rare variety of self-assembledmolecular triangle [Pd3(bpy)3(imidazolate)3](NO3)3, 1 is prepared by the combination of Pd(bpy)(NO3)2 with imidazole, at 1:1 ratio, in acetonitrile-water. Deprotonation of imidazole happened during the course of the complexation reaction where upon the metallomacrocycle is formed. The bowl-shaped trinuclear architecture of 1 is crafted with three peripheral bpy units capable of - stacking interactions. While the solution state structure of 1 can be best described as a trinuclear complex, in the solidstate well-fashioned intermolecular - and CH- interactions are observed. Thus, in the solid-state further self-assembly of already self-assembled molecular triangle is witnessed. The triangular panels are arranged in a linear manner utilizing intermolecular - interactions where upon two out of three bpy units of each molecule participated in the chain formation.

  10. Multifunctional self-assembled monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Zawodzinski, T.; Bar, G.; Rubin, S.; Uribe, F. [Los Alamos National Lab., NM (United States); Ferrais, J. [Texas Univ., Dallas, TX (United States)

    1996-06-01

    This is the final report of at three year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The specific goals of this research project were threefold: to develop multifunctional self-assembled monolayers, to understand the role of monolayer structure on the functioning of such systems, and to apply this knowledge to the development of electrochemical enzyme sensors. An array of molecules that can be used to attach electrochemically active biomolecules to gold surfaces has been synthesized. Several members of a class of electroactive compounds have been characterized and the factors controlling surface modification are beginning to be characterized. Enzymes have been attached to self-assembled molecules arranged on the gold surface, a critical step toward the ultimate goal of this project. Several alternative enzyme attachment strategies to achieve robust enzyme- modified surfaces have been explored. Several means of juxtaposing enzymes and mediators, electroactive compounds through which the enzyme can exchange electrons with the electrode surface, have also been investigated. Finally, the development of sensitive biosensors based on films loaded with nanoscale-supported gold particles that have surface modified with the self-assembled enzyme and mediator have been explored.

  11. Exciton coupling induces vibronic hyperchromism in light-harvesting complexes

    International Nuclear Information System (INIS)

    The recently suggested possibility that weak vibronic transitions can be excitonically enhanced in light-harvesting complexes is studied in detail. A vibronic exciton dimer model that includes ground-state vibrations is investigated using the multi-configuration time-dependent Hartree method with a parameter set typical to photosynthetic light-harvesting complexes. The absorption spectra are discussed based on the Coulomb coupling, the detuning of the site energies, and the number of vibrational modes. Fluorescence spectra calculations show that the spectral densities obtained from the low-temperature fluorescence line-narrowing measurements of light-harvesting systems need to be corrected for the effects of excitons. For the J-aggregate configuration, as in most light-harvesting complexes, the true spectral density has a larger amplitude than that obtained from the measurement

  12. Spectroscopic Investigations of the Photophysics of Cryptophyte Light-Harvesting

    Science.gov (United States)

    Dinshaw, Rayomond

    The biological significance of photosynthesis is indisputable as it is necessary for nearly all life on earth. Photosynthesis provides chemical energy for plants, algae, and bacteria, while heterotrophic organisms rely on these species as their ultimate food source. The initial step in photosynthesis requires the absorption of sunlight to create electronic excitations. Light-harvesting proteins play the functional role of capturing solar radiation and transferring the resulting excitation to the reaction centers where it is used to carry out the chemical reactions of photosynthesis. Despite the wide variety of light-harvesting protein structures and arrangements, most light-harvesting proteins are able to utilize the captured solar energy for charge separation with near perfect quantum efficiency.1 This thesis will focus on understanding the energy transfer dynamics and photophysics of a specific subset of light-harvesting antennae known as phycobiliproteins. These proteins are extracted from cryptophyte algae and are investigated using steady-state and ultrafast spectroscopic techniques.

  13. Dissecting the photosystem II light-harvesting antenna

    OpenAIRE

    Andersson, Jenny

    2003-01-01

    In photosynthesis, sunlight is converted into chemical energy that is stored mainly as carbohydrates and supplies basically all life on Earth with energy. In order to efficiently absorb the light energy, plants have developed the outer light harvesting antenna, which is composed of ten different protein subunits (LHC) that bind chlorophyll a and b as well as different carotenoids. In addition to the light harvesting function, the antenna has the capacity to dissipate excess energy as heat (fe...

  14. Synergistic Two-Photon Absorption Enhancement in Photosynthetic Light Harvesting

    Science.gov (United States)

    Chen, Kuo-Mei; Chen, Yu-Wei; Gao, Ting-Fong

    2012-06-01

    The grand scale fixation of solar energies into chemical substances by photosynthetic reactions of light-harvesting organisms provides Earth's other life forms a thriving environment. Scientific explorations in the past decades have unraveled the fundamental photophysical and photochemical processes in photosynthesis. Higher plants, green algae, and light-harvesting bacteria utilize organized pigment-protein complexes to harvest solar power efficiently and the resultant electronic excitations are funneled into a reaction center, where the first charge separation process takes place. Here we show experimental evidences that green algae (Chlorella vulgaris) in vivo display a synergistic two-photon absorption enhancement in their photosynthetic light harvesting. Their absorption coefficients at various wavelengths display dramatic dependence on the photon flux. This newly found phenomenon is attributed to a coherence-electronic-energy-transfer-mediated (CEETRAM) photon absorption process of light-harvesting pigment-protein complexes of green algae. Under the ambient light level, algae and higher plants can utilize this quantum mechanical mechanism to create two entangled electronic excitations adjacently in their light-harvesting networks. Concerted multiple electron transfer reactions in the reaction centers and oxygen evolving complexes can be implemented efficiently by the coherent motion of two entangled excitons from antennae to the charge separation reaction sites. To fabricate nanostructured, synthetic light-harvesting apparatus, the paramount role of the CEETRAM photon absorption mechanism should be seriously considered in the strategic guidelines.

  15. Supramolecular coordination polymer formed from artificial light-harvesting dendrimer.

    Science.gov (United States)

    Lee, Hosoowi; Jeong, Young-Hwan; Kim, Joo-Ho; Kim, Inhye; Lee, Eunji; Jang, Woo-Dong

    2015-09-30

    We report the formation of supramolecular coordination polymers formed from multiporphyrin dendrimers (PZnPM; M = FB or Cu), composed of the focal freebase porphyrin (PFB) or cupper porphyrin (PCu) with eight zinc porphyrin (PZn) wings, and multipyridyl porphyrins (PyPM; M = FB or Cu), PFB or PCu with eight pyridyl groups, through multiple axial coordination interactions of pyridyl groups to PZns. UV-vis absorption spectra were recorded upon titration of PyPFB to PZnPFB. Differential spectra, obtained by subtracting the absorption of PZnPFB without guest addition as well as the absorption of PyPFB, exhibited clear isosbestic points with saturation binding at 1 equiv addition of PyPFB to PZnPFB. Job's plot analysis also indicated 1:1 stoichiometry for the saturation binding. The apparent association constant between PZnPFB and PyPFB (2.91 × 10(6) M(-1)), estimated by isothermal titration calorimetry, was high enough for fibrous assemblies to form at micromolar concentrations. The formation of a fibrous assembly from PZnPFB and PyPFB was visualized by atomic force microscopy and transmission electron microscopy (TEM). When a 1:1 mixture solution of PZnPFB and PyPFB (20 μM) in toluene was cast onto mica, fibrous assemblies with regular height (ca. 2 nm) were observed. TEM images obtained from 1:1 mixture solution of PZnPFB and PyPFB (0.1 wt %) in toluene clearly showed the formation of nanofibers with a regular diameter of ca. 6 nm. Fluorescence emission measurement of PZnPM indicated efficient intramolecular energy transfer from PZn to the focal PFB or PCu. By the formation of supramolecular coordination polymers, the intramolecular energy transfer changed to intermolecular energy transfer from PZnPM to PyPM. When the nonfluorescent PyPCu was titrated to fluorescent PZnPFB, fluorescence emission from the focal PFB was gradually decreased. By the titration of fluorescent PyPFB to nonfluorescent PZnPCu, fluorescence emission from PFB in PyPFB was gradually increased due to the efficient energy transfer from PZn wings in PZnPCu to PyPFB. PMID:26349620

  16. Light harvesting by dye linked conducting polymers

    Energy Technology Data Exchange (ETDEWEB)

    Troensegaard Nielsen, K.

    2006-06-15

    The fact that the fossil fuel is finite and that the detrimental long-term effects of letting CO2 into our atmosphere exist, have created an enormous interest in developing new, cheap, renewable and less polluting energy resources. One of the most obvious abundant sources of energy in the solar system is the sun. Unfortunately the well developed silicon solar cells are very costly to produce. In an attempt to produce cheap and flexible solar cells, plastic solar cells have received a lot of attention in the last decades. There are still a lot of parameters to optimize if the plastic solar cell shall be able to compete with the silicon solar cells. One of the parameters is to ensure a high degree of charge carrier separation. Charge carrier separation can only happen at heterojunctions, which cover for example the interfaces between the polymers and the electrodes or the interface between an n-conductor and a p-conductor. The facts that the charge carrier separation only happens at the heterojunctions limits the thickness of the active layer in solar cells and thereby the effectiveness of the solar cells. In this project the charge carrier separation is attempted optimized by making plastic solar cells with a molecular heterojunction. The molecular heterojunction has been obtained by synthesizing a three domain super molecular assembly termed NPN. NPN consists of two poly[1-(2,5-dioctyltolanyl)ethynylene] chains (N-domains) coupled to the [10,20-bis(3,5-bistert-butylphenyl]-5,15-dibromoporphinato]zinc(II) (P-domain). It is shown that the N domains in NPN work as effective light harvesting antennas for the P domain and effectively transfer electrically generated excitons in the N domain to the P domain. Unfortunately the P domain does not separate the charge carriers but instead works as a charge carrier trap. This results in a performance of solar cells made of NPN that is much lower than the performance of solar cells made of pure poly[1-(2,5-dioctyltolanyl

  17. A self-assembled ionophore

    Science.gov (United States)

    Tirumala, Sampath K.

    1997-11-01

    Ionophores are compounds that bind and transport ions. Ion binding and transport are fundamental to many biological and chemical processes. In this thesis we detail the structural characterization and cation binding properties of a self-assembled ionophore built from an isoguanosine (isoG) derivative, 5sp'-t-butyldimethylsilyl-2sp',3sp'-isopropylidene isoG 30. We begin with a summary of the themes that facilitate ionophore design and the definitions of "self-assembly" and "self-assembled ionophore" in Chapter 1. In Chapter 2, we describe the structural characterization of the isoG 30 self-assembly. IsoG possesses complementary hydrogen bond donor and acceptor sites suitable to form a Csb4-symmetric tetramer, (isoG)sb4 51, that is stable even in high dielectric organic solvents such as CDsb3CN and dsb6-acetone. The isoG tetramer 51 has been characterized by vapor phase osmometry, UV spectroscopy, and by 1D and 2D NMR spectroscopy. The isoG tetramer 51 organizes by hydrogen bonding between the Watson-Crick face of one isoG base and the complementary bottom edge of another purine. The tetramer 51 is stabilized by an inner and outer ring of hydrogen bonds. The inner ring forms between the imino NH1 proton of one monomer and the C2 carbonyl oxygen of an adjacent monomer, while the outer ring is made up of four NH6-N3 hydrogen bonds. The isoG tetramer 51 is thermodynamically stable, with an equilibrium constant (Ksba) of ca. 10sp9-10sp{10} Msp{-3} at room temperature, and a DeltaGsp° of tetramer formation of -12.5 kcal molsp{-1} in dsb6-acetone at 25sp°C. The van't Hoff plots indicated that the thermodynamic parameters for tetramer formation were DeltaHsp° = -18.2 ± 0.87 kcal molsp{-1} and DeltaSsp°sb{298} = -19.1 ± 5.45 eu. In Chapter 3, we describe the cation binding properties of isoG tetramer 51. The isoG tetramer 51 has a central cavity, containing four oxygen atoms, that is suitable for cation coordination. Depending on the cation, the resulting iso

  18. Anisotropic Organization and Microscopic Manipulation of Self-Assembling Synthetic Porphyrin Microrods That Mimic Chlorosomes: Bacterial Light-Harvesting Systems

    Czech Academy of Sciences Publication Activity Database

    Chappaz-Gillot, C.; Marek, P.L.; Blaive, B.J.; Canard, G.; Burck, J.; Hahn, H.; Jávor fi, T.; Kelemen, L.; Krupke, R.; Mossinger, D.; Ormos, P.; Reddy, C.M.; Roussel, C.; Steinbach, G.; Szabo, M.; Ulrich, A.S.; Vanthuyne, V.N.; Vijayaraghavan, A.; Župčanová, Anita; Balaban, T.S.

    2012-01-01

    Roč. 134, č. 2 (2012), s. 944-954. ISSN 0002-7863 Institutional support: RVO:60077344 Keywords : Green photosynthetic bacteria * Bacteriochlorophyll-C * Chlorobium-Tepidum Subject RIV: CE - Biochemistry Impact factor: 10.677, year: 2012

  19. Self-assembled controllable microswimmers

    Science.gov (United States)

    Grosjean, Galien; Lagubeau, Guillaume; Darras, Alexis; Lumay, Geoffroy; Hubert, Maxime; Vandewalle, Nicolas

    2015-11-01

    Because they cause a deformation of the interface, floating particles interact. In particular, identical particles attract each other. To counter this attraction, particles possessing a large magnetic moment m-> are used. When m-> is perpendicular to the surface, dipole-dipole interaction is repulsive. This competition of forces can lead to the spontaneous formation of organized structures. By using submillimetric steel spheres for which m-> ~ B-> , interdistances in the system can be precisely tuned. Here, we deform these self-assemblies by adding a horizontal contribution m-> to the magnetic moment. Time reversal symmetry is broken in the system, leading to locomotion at low Reynolds number. Moreover, swimming direction depends on the orientation of field, meaning that swimming trajectories can be finely controlled. A model allows to understand the breaking of symmetry, while a study of the vibration modes gives further informations on the dynamics of this sytem. Because this system forms by self-assembly, it allows miniaturization with applications such as cargo transport or solvent flows. It is highly versatile, being composed of simple passive particles and controlled by magnetic fields.

  20. Quantum entanglement in photosynthetic light-harvesting complexes

    Science.gov (United States)

    Sarovar, Mohan; Ishizaki, Akihito; Fleming, Graham R.; Whaley, K. Birgitta

    2010-06-01

    Light-harvesting components of photosynthetic organisms are complex, coupled, many-body quantum systems, in which electronic coherence has recently been shown to survive for relatively long timescales, despite the decohering effects of their environments. Here, we analyse entanglement in multichromophoric light-harvesting complexes, and establish methods for quantification of entanglement by describing necessary and sufficient conditions for entanglement and by deriving a measure of global entanglement. These methods are then applied to the Fenna-Matthews-Olson protein to extract the initial state and temperature dependencies of entanglement. We show that, although the Fenna-Matthews-Olson protein in natural conditions largely contains bipartite entanglement between dimerized chromophores, a small amount of long-range and multipartite entanglement should exist even at physiological temperatures. This constitutes the first rigorous quantification of entanglement in a biological system. Finally, we discuss the practical use of entanglement in densely packed molecular aggregates such as light-harvesting complexes.

  1. Quantum entanglement phenomena in photosynthetic light harvesting complexes

    CERN Document Server

    Whaley, K Birgitta; Ishizaki, Akihito

    2010-01-01

    We review recent theoretical calculations of quantum entanglement in photosynthetic light harvesting complexes. These works establish, for the first time, a manifestation of this characteristically quantum mechanical phenomenon in biologically functional structures. We begin by summarizing calculations on model biomolecular systems that aim to reveal non-trivial characteristics of quantum entanglement in non-equilibrium biological environments. We then discuss and compare several calculations performed recently of excitonic dynamics in the Fenna-Matthews-Olson light harvesting complex and of the entanglement present in this widely studied pigment-protein structure. We point out the commonalities between the derived results and also identify and explain the differences. We also discuss recent work that examines entanglement in the structurally more intricate light harvesting complex II (LHCII). During this overview, we take the opportunity to clarify several subtle issues relating to entanglement in such biomo...

  2. Biomimetic Branched Hollow Fibers Templated by Self-assembled Fibrous Polyvinylpyrrolidone (PVP) Structures in Aqueous Solution

    OpenAIRE

    Qiu, Penghe; Mao, Chuanbin

    2010-01-01

    Branched hollow fibers are common in nature, but to form artificial fibers with a similar branched hollow structure is still a challenge. We discovered that polyvinylpyrrolidone (PVP) could self-assemble into branched hollow fibers in an aqueous solution after aging the PVP solution for about two weeks. Based on this finding, we demonstrated two approaches by which the self-assembly of PVP into branched hollow fibers could be exploited to template the formation of branched hollow inorganic fi...

  3. Molecular self-assembly advances and applications

    CERN Document Server

    Dequan, Alex Li

    2012-01-01

    In the past several decades, molecular self-assembly has emerged as one of the main themes in chemistry, biology, and materials science. This book compiles and details cutting-edge research in molecular assemblies ranging from self-organized peptide nanostructures and DNA-chromophore foldamers to supramolecular systems and metal-directed assemblies, even to nanocrystal superparticles and self-assembled microdevices

  4. Self-assembled nanomaterials for photoacoustic imaging.

    Science.gov (United States)

    Wang, Lei; Yang, Pei-Pei; Zhao, Xiao-Xiao; Wang, Hao

    2016-02-01

    In recent years, extensive endeavors have been paid to construct functional self-assembled nanomaterials for various applications such as catalysis, separation, energy and biomedicines. To date, different strategies have been developed for preparing nanomaterials with diversified structures and functionalities via fine tuning of self-assembled building blocks. In terms of biomedical applications, bioimaging technologies are urgently calling for high-efficient probes/contrast agents for high-performance bioimaging. Photoacoustic (PA) imaging is an emerging whole-body imaging modality offering high spatial resolution, deep penetration and high contrast in vivo. The self-assembled nanomaterials show high stability in vivo, specific tolerance to sterilization and prolonged half-life stability and desirable targeting properties, which is a kind of promising PA contrast agents for biomedical imaging. Herein, we focus on summarizing recent advances in smart self-assembled nanomaterials with NIR absorption as PA contrast agents for biomedical imaging. According to the preparation strategy of the contrast agents, the self-assembled nanomaterials are categorized into two groups, i.e., the ex situ and in situ self-assembled nanomaterials. The driving forces, assembly modes and regulation of PA properties of self-assembled nanomaterials and their applications for long-term imaging, enzyme activity detection and aggregation-induced retention (AIR) effect for diagnosis and therapy are emphasized. Finally, we conclude with an outlook towards future developments of self-assembled nanomaterials for PA imaging. PMID:26757620

  5. Self-assembled nanomaterials for photoacoustic imaging

    Science.gov (United States)

    Wang, Lei; Yang, Pei-Pei; Zhao, Xiao-Xiao; Wang, Hao

    2016-01-01

    In recent years, extensive endeavors have been paid to construct functional self-assembled nanomaterials for various applications such as catalysis, separation, energy and biomedicines. To date, different strategies have been developed for preparing nanomaterials with diversified structures and functionalities via fine tuning of self-assembled building blocks. In terms of biomedical applications, bioimaging technologies are urgently calling for high-efficient probes/contrast agents for high-performance bioimaging. Photoacoustic (PA) imaging is an emerging whole-body imaging modality offering high spatial resolution, deep penetration and high contrast in vivo. The self-assembled nanomaterials show high stability in vivo, specific tolerance to sterilization and prolonged half-life stability and desirable targeting properties, which is a kind of promising PA contrast agents for biomedical imaging. Herein, we focus on summarizing recent advances in smart self-assembled nanomaterials with NIR absorption as PA contrast agents for biomedical imaging. According to the preparation strategy of the contrast agents, the self-assembled nanomaterials are categorized into two groups, i.e., the ex situ and in situ self-assembled nanomaterials. The driving forces, assembly modes and regulation of PA properties of self-assembled nanomaterials and their applications for long-term imaging, enzyme activity detection and aggregation-induced retention (AIR) effect for diagnosis and therapy are emphasized. Finally, we conclude with an outlook towards future developments of self-assembled nanomaterials for PA imaging.

  6. Dynamic self-assembly of microscale rotors and swimmers.

    Science.gov (United States)

    Davies Wykes, Megan S; Palacci, Jérémie; Adachi, Takuji; Ristroph, Leif; Zhong, Xiao; Ward, Michael D; Zhang, Jun; Shelley, Michael J

    2016-05-18

    Biological systems often involve the self-assembly of basic components into complex and functioning structures. Artificial systems that mimic such processes can provide a well-controlled setting to explore the principles involved and also synthesize useful micromachines. Our experiments show that immotile, but active, components self-assemble into two types of structure that exhibit the fundamental forms of motility: translation and rotation. Specifically, micron-scale metallic rods are designed to induce extensile surface flows in the presence of a chemical fuel; these rods interact with each other and pair up to form either a swimmer or a rotor. Such pairs can transition reversibly between these two configurations, leading to kinetics reminiscent of bacterial run-and-tumble motion. PMID:27121100

  7. Molecular Factors Controlling Photosynthetic Light Harvesting by Carotenoids

    Czech Academy of Sciences Publication Activity Database

    Polívka, Tomáš; Frank, H.A.

    2010-01-01

    Roč. 43, č. 8 (2010), s. 1125-1134. ISSN 0001-4842 Institutional research plan: CEZ:AV0Z50510513 Keywords : carotenoids * energy transfer * photosynthesis * light-harvesting Subject RIV: BO - Biophysics Impact factor: 21.840, year: 2010

  8. The chlorosome: a prototype for efficient light harvesting in photosynthesis

    NARCIS (Netherlands)

    Oostergetel, G.; Amerongen, van H.; Boekema, E.J.

    2010-01-01

    Three phyla of bacteria include phototrophs that contain unique antenna systems, chlorosomes, as the principal light-harvesting apparatus. Chlorosomes are the largest known supramolecular antenna systems and contain hundreds of thousands of BChl c/d/e molecules enclosed by a single membrane leaflet

  9. The chlorosome : a prototype for efficient light harvesting in photosynthesis

    NARCIS (Netherlands)

    Oostergetel, Gert T.; van Amerongen, Herbert; Boekema, Egbert J.

    2010-01-01

    Three phyla of bacteria include phototrophs that contain unique antenna systems, chlorosomes, as the principal light-harvesting apparatus. Chlorosomes are the largest known supramolecular antenna systems and contain hundreds of thousands of BChl c/d/e molecules enclosed by a single membrane leaflet

  10. Lamellar organization of pigments in chlorosomes, the light harvesting complexes of green photosynthetic bacteria.

    Science.gov (United States)

    Psencík, J; Ikonen, T P; Laurinmäki, P; Merckel, M C; Butcher, S J; Serimaa, R E; Tuma, R

    2004-08-01

    Chlorosomes of green photosynthetic bacteria constitute the most efficient light harvesting complexes found in nature. In addition, the chlorosome is the only known photosynthetic system where the majority of pigments (BChl) is not organized in pigment-protein complexes but instead is assembled into aggregates. Because of the unusual organization, the chlorosome structure has not been resolved and only models, in which BChl pigments were organized into large rods, were proposed on the basis of freeze-fracture electron microscopy and spectroscopic constraints. We have obtained the first high-resolution images of chlorosomes from the green sulfur bacterium Chlorobium tepidum by cryoelectron microscopy. Cryoelectron microscopy images revealed dense striations approximately 20 A apart. X-ray scattering from chlorosomes exhibited a feature with the same approximately 20 A spacing. No evidence for the rod models was obtained. The observed spacing and tilt-series cryoelectron microscopy projections are compatible with a lamellar model, in which BChl molecules aggregate into semicrystalline lateral arrays. The diffraction data further indicate that arrays are built from BChl dimers. The arrays form undulating lamellae, which, in turn, are held together by interdigitated esterifying alcohol tails, carotenoids, and lipids. The lamellar model is consistent with earlier spectroscopic data and provides insight into chlorosome self-assembly. PMID:15298919

  11. Design directed self-assembly of donor-acceptor polymers.

    Science.gov (United States)

    Marszalek, Tomasz; Li, Mengmeng; Pisula, Wojciech

    2016-09-21

    Donor-acceptor polymers with an alternating array of donor and acceptor moieties have gained particular attention during recent years as active components of organic electronics. By implementation of suitable subunits within the conjugated backbone, these polymers can be made either electron-deficient or -rich. Additionally, their band gap and light absorption can be precisely tuned for improved light-harvesting in solar cells. On the other hand, the polymer design can also be modified to encode the desired supramolecular self-assembly in the solid-state that is essential for an unhindered transport of charge carriers. This review focuses on three major factors playing a role in the assembly of donor-acceptor polymers on surfaces which are (1) nature, geometry and substitution position of solubilizing alkyl side chains, (2) shape of the conjugated polymer defined by the backbone curvature, and (3) molecular weight which determines the conjugation length of the polymer. These factors adjust the fine balance between attractive and repulsive forces and ensure a close polymer packing important for an efficient charge hopping between neighboring chains. On the microscopic scale, an appropriate domain formation with a low density of structural defects in the solution deposited thin film is crucial for the charge transport. The charge carrier transport through such thin films is characterized by field-effect transistors as basic electronic elements. PMID:27440174

  12. Recent development of peptide self-assembly

    Institute of Scientific and Technical Information of China (English)

    Xiubo Zhao; Fang Pan; Jian R. Lu

    2008-01-01

    Amino acids are the building blocks to build peptides and proteins. Recent development in peptide synthesis has however enabled us to mimic this natural process by preparing various long and short peptides possessing different conformations and biological functions. The self-assembly of short designed peptides into molecular nanostructures is becoming a growing interest in nanobiotechnology. Self-assembled peptides exhibit several attractive features for applications in tissue regeneration, drug delivery, biological surface engineering as well as in food science, cosmetic industry and antibiotics. The aim of this review is to introduce the readers to a number of representative studies on peptide self-assembly.

  13. Limits of quantum speedup in photosynthetic light harvesting

    CERN Document Server

    Hoyer, Stephan; Whaley, K Birgitta

    2009-01-01

    In the initial stages of photosynthesis, energy collected from light is transferred across a network of chlorophyll molecules to a reaction center. Recent experimental evidence showing long lived quantum coherences in this energy transport in several photosynthetic light-harvesting complexes has suggested that coherence may play an important role in the function of these systems. In particular, it has been hypothesized that excitation transport in such systems may feature speedups analogous to those found in quantum algorithms. The most direct analogy to such transport is found in quantum walks, which form the basis of a powerful class of quantum algorithms including quantum search. Unlike idealized quantum walks, however, real light harvesting complexes are characterized by disorder, energy funnels and decoherence. Whether any quantum speedup can be found in this situation is unclear. Here we characterize quantum speedup for excitation energy transfer in the Fenna-Matthews-Olson (FMO) complex of green sulfur...

  14. Light-harvesting materials: Soft support for energy conversion

    Energy Technology Data Exchange (ETDEWEB)

    Stolley, Ryan M.; Helm, Monte L.

    2014-11-10

    To convert solar energy into viable fuel sources, coupling light-harvesting materials to catalysts is a critical challenge. Now, coupling between an organic supramolecular hydrogel and a non precious metal catalyst has been demonstrated to be effective for photocatalytic H2 production. Ryan M. Stolley and Monte L. Helm are at Pacific Northwest National Laboratory (PNNL), Richland, WA, USA 99352. PNNL is operated by Battelle for the US Department of Energy. e-mail: Monte.Helm@pnnl.gov

  15. Semiconductor Nanocrystals as Light Harvesters in Solar Cells

    OpenAIRE

    Lioz Etgar

    2013-01-01

    Photovoltaic cells use semiconductors to convert sunlight into electrical current and are regarded as a key technology for a sustainable energy supply. Quantum dot-based solar cells have shown great potential as next generation, high performance, low-cost photovoltaics due to the outstanding optoelectronic properties of quantum dots and their multiple exciton generation (MEG) capability. This review focuses on QDs as light harvesters in solar cells, including different structures of QD-based ...

  16. Directed Self-Assembly of Nanodispersions

    Energy Technology Data Exchange (ETDEWEB)

    Furst, Eric M [University of Delaware

    2013-11-15

    Directed self-assembly promises to be the technologically and economically optimal approach to industrial-scale nanotechnology, and will enable the realization of inexpensive, reproducible and active nanostructured materials with tailored photonic, transport and mechanical properties. These new nanomaterials will play a critical role in meeting the 21st century grand challenges of the US, including energy diversity and sustainability, national security and economic competitiveness. The goal of this work was to develop and fundamentally validate methods of directed selfassembly of nanomaterials and nanodispersion processing. The specific aims were: 1. Nanocolloid self-assembly and interactions in AC electric fields. In an effort to reduce the particle sizes used in AC electric field self-assembly to lengthscales, we propose detailed characterizations of field-driven structures and studies of the fundamental underlying particle interactions. We will utilize microscopy and light scattering to assess order-disorder transitions and self-assembled structures under a variety of field and physicochemical conditions. Optical trapping will be used to measure particle interactions. These experiments will be synergetic with calculations of the particle polarizability, enabling us to both validate interactions and predict the order-disorder transition for nanocolloids. 2. Assembly of anisotropic nanocolloids. Particle shape has profound effects on structure and flow behavior of dispersions, and greatly complicates their processing and self-assembly. The methods developed to study the self-assembled structures and underlying particle interactions for dispersions of isotropic nanocolloids will be extended to systems composed of anisotropic particles. This report reviews several key advances that have been made during this project, including, (1) advances in the measurement of particle polarization mechanisms underlying field-directed self-assembly, and (2) progress in the

  17. From Self-Assembled Vesicles to Protocells

    OpenAIRE

    Chen, Irene A.; Walde, Peter

    2010-01-01

    Self-assembled vesicles are essential components of primitive cells. We review the importance of vesicles during the origins of life, fundamental thermodynamics and kinetics of self-assembly, and experimental models of simple vesicles, focusing on prebiotically plausible fatty acids and their derivatives. We review recent work on interactions of simple vesicles with RNA and other studies of the transition from vesicles to protocells. Finally we discuss current challenges in understanding the ...

  18. Mechanical Self-Assembly Science and Applications

    CERN Document Server

    2013-01-01

    Mechanical Self-Assembly: Science and Applications introduces a novel category of self-assembly driven by mechanical forces. This book discusses self-assembly in various types of small material structures including thin films, surfaces, and micro- and nano-wires, as well as the practice's potential application in micro and nanoelectronics, MEMS/NEMS, and biomedical engineering. The mechanical self-assembly process is inherently quick, simple, and cost-effective, as well as accessible to a large number of materials, such as curved surfaces for forming three-dimensional small structures. Mechanical self-assembly is complementary to, and sometimes offer advantages over, the traditional micro- and nano-fabrication. This book also: Presents a highly original aspect of the science of self-assembly Describes the novel methods of mechanical assembly used to fabricate a variety of new three-dimensional material structures in simple and cost-effective ways Provides simple insights to a number of biological systems and ...

  19. Early events in the biosynthesis and assembly of the cyanobacterial light-harvesting system

    Science.gov (United States)

    Anderson, Lamont

    1996-02-01

    The cyanobacteria are photosynthetic procaryotes that employ a mechanism of photosynthesis which is essentially identical to the systems found in plant chloroplasts and the eukaryotic green algae. Cyanobacteria can drive photosynthesis with light energy from a broad region of the visible spectrum (500 - 650 nm wavelength) that is not available to plants and green algae, which are limited to the narrow band of light energy that is absorbed by chlorophyll (660-680 nm). The light-harvesting capacity of the cyanobacteria is a function of a complex protein structure that resides on the surface of the photosynthetic membrane in contact with the PSII chlorophyll reaction centers. This light-harvesting complex is called a phycobilisome and functions as a protein scaffold for a rigid array of chromophores that absorbs light energy and transfers it to chlorophyll. The chromophores are linear tetrapyrroles (the bilins) that are covalently attached to the biliproteins, which comprise 80 - 85% of the total phycobilisome mass. There are three major classes of spectrally distinct biliproteins [phycoerythrin (PE), (lambda) max equals 565 nm; phycocyanin (PC), (lambda) max equals 617 nm; and allophycocyanin (AP), (lambda) max equals 650 nm] and their spatial organization within the phycobilisome creates an array of donor and acceptor chromophores that is optimized for resonance energy transfer to chlorophyll on a picosecond timescale and at close to 100% efficiency. The cyanobacteria can exert control over the biliprotein composition of the phycobilisomes in response to both light quality and light quantity, and they do so primarily by light-responsive transcription control mechanisms. The biosynthesis and assembly of a phycobilisome is an interesting example of self-assembly in a complex protein system. A phycobilisome from Synechocystis sp. strain 6701 can contain 400 proteins derived from a repertoire of 16 different polypeptides that includes the (alpha) and (beta) subunits for

  20. Molecular self-assembly approaches for supramolecular electronic and organic electronic devices

    Science.gov (United States)

    Yip, Hin-Lap

    Molecular self-assembly represents an efficient bottom-up strategy to generate structurally well-defined aggregates of semiconducting pi-conjugated materials. The capability of tuning the chemical structures, intermolecular interactions and nanostructures through molecular engineering and novel materials processing renders it possible to tailor a large number of unprecedented properties such as charge transport, energy transfer and light harvesting. This approach does not only benefit traditional electronic devices based on bulk materials, but also generate a new research area so called "supramolecular electronics" in which electronic devices are built up with individual supramolecular nanostructures with size in the sub-hundred nanometers range. My work combined molecular self-assembly together with several novel materials processing techniques to control the nucleation and growth of organic semiconducting nanostructures from different type of pi-conjugated materials. By tailoring the interactions between the molecules using hydrogen bonds and pi-pi stacking, semiconducting nanoplatelets and nanowires with tunable sizes can be fabricated in solution. These supramolecular nanostructures were further patterned and aligned on solid substrates through printing and chemical templating methods. The capability to control the different hierarchies of organization on surface provides an important platform to study their structural-induced electronic properties. In addition to using molecular self-assembly to create different organic nanostructures, functional self-assembled monolayer (SAM) formed by spontaneous chemisorption on surfaces was used to tune the interfacial property in organic solar cells. Devices showed dramatically improved performance when appropriate SAMs were applied to optimize the contact property for efficiency charge collection.

  1. Formation of the light-harvesting complex I (B870) of anoxygenic phototrophic purple bacteria.

    Science.gov (United States)

    Drews, G

    1996-09-01

    adjust to changes in oxygen tension, light intensity, temperature, and substrates to grow under chemotrophic or phototrophic conditions. The photosynthetic apparatus (PSA), localized mainly on intracytoplasmic membranes (ICM), is usually synthesized only under low oxygen partial pressure. The cellular amount and composition of the PSA are modified upon changing light intensity in relation to cell growth (Drews and Golecki 1995). The morphogenesis of cellular structures like ICM is quite different from self-assembly. Self-assembly is a reversible process of aggregation of the constituents of a complex structure without protein synthesis and is driven by weak or strong forces in the interactions of the constituents. Morphogenesis results from the interplay of numerous gene products and the cellular organization and is always dependent upon pre-existent structures (Harold 1995). The morphogenesis of the photosynthetic membrane in purple bacteria has been studied in its different steps. The regulation at the transcriptional and post-transcriptional levels in purple bacteria, and the structure and morphogenesis of the ICM have been described recently (Armstrong 1995; Bauer 1995; Biel 1995; Drews and Golecki 1995; Klug 1995). In this mini-review, I will focus on the minimal requirements for the in vitro assembly of light-harvesting (LH) complex I (B870) from its constituents in detergent micelles and compare the results with observations on the complex process of targeting and import of LHI polypeptides into the membrane and assembly of B870. PMID:8703191

  2. Origin of Long Lived Coherences in Light-Harvesting Complexes

    CERN Document Server

    Christensson, Niklas; Pullerits, Tonu; Mancal, Tomas

    2012-01-01

    A vibronic exciton model is developed to investigate the origin of long lived coherences in light-harvesting complexes. Using experimentally determined parameters and uncorrelated site energy fluctuations, the model predicts oscillations in the nonlinear spectra of the Fenna-Matthews-Olson (FMO) complex with a dephasing time of 1.3 ps at 77 K. These oscillations correspond to the coherent superposition of vibronic exciton states with dominant contributions from vibrational excitations on the same pigment. Purely electronic coherences are found to decay on a 200 fs timescale.

  3. Beta-Sheet-Forming, Self-Assembled Peptide Nanomaterials towards Optical, Energy, and Healthcare Applications.

    Science.gov (United States)

    Kim, Sungjin; Kim, Jae Hong; Lee, Joon Seok; Park, Chan Beum

    2015-08-12

    Peptide self-assembly is an attractive route for the synthesis of intricate organic nanostructures that possess remarkable structural variety and biocompatibility. Recent studies on peptide-based, self-assembled materials have expanded beyond the construction of high-order architectures; they are now reporting new functional materials that have application in the emerging fields such as artificial photosynthesis and rechargeable batteries. Nevertheless, there have been few reviews particularly concentrating on such versatile, emerging applications. Herein, recent advances in the synthesis of self-assembled peptide nanomaterials (e.g., cross β-sheet-based amyloid nanostructures, peptide amphiphiles) are selectively reviewed and their new applications in diverse, interdisciplinary fields are described, ranging from optics and energy storage/conversion to healthcare. The applications of peptide-based self-assembled materials in unconventional fields are also highlighted, such as photoluminescent peptide nanostructures, artificial photosynthetic peptide nanomaterials, and lithium-ion battery components. The relation of such functional materials to the rapidly progressing biomedical applications of peptide self-assembly, which include biosensors/chips and regenerative medicine, are discussed. The combination of strategies shown in these applications would further promote the discovery of novel, functional, small materials. PMID:25929870

  4. Patterned self-assembled film guided electrodeposition

    Institute of Scientific and Technical Information of China (English)

    ZHOU; Feng; LI; Bin; XU; Tao; CHEN; Miao; HAO; Jingcheng; LI

    2004-01-01

    The paper describes the fabrication of polypyrrole (PPy) microstructures through patterned self-assembled film guided electrodeposition. Thus the patterned self-assembled monolayer is prepared by microcontact printing (μCP) and used as the template in the electrodeposition of PPy. It has been found that the self-assembled monolayer plays completely different roles on different substrates in directing the deposition of the PPy. Namely, the electrodeposition mainly occurs on the exposed area of the gold substrates patterned with dodecanethiol (DDT) and octadecanelthiol (ODT) and on the indium tin oxide (ITO) substrate patterned with octadecyltrichlorosilane (OTS), while PPy nucleates on the OTS covered area and no deposition is found on the exposed area of a semiconductor substrate (silicon). This is attributed to the cooperative effect between the substrate conductivity and the compatibility of the PPy oligomer with the covered or exposed area of the substrate surface.

  5. Manipulating Excited-State Dynamics of Individual Light-Harvesting Chromophores through Restricted Motions in a Hydrated Nanoscale Protein Cavity.

    Science.gov (United States)

    Noriega, Rodrigo; Finley, Daniel T; Haberstroh, John; Geissler, Phillip L; Francis, Matthew B; Ginsberg, Naomi S

    2015-06-11

    Manipulating the photophysical properties of light-absorbing units is a crucial element in the design of biomimetic light-harvesting systems. Using a highly tunable synthetic platform combined with transient absorption and time-resolved fluorescence measurements and molecular dynamics simulations, we interrogate isolated chromophores covalently linked to different positions in the interior of the hydrated nanoscale cavity of a supramolecular protein assembly. We find that, following photoexcitation, the time scales over which these chromophores are solvated, undergo conformational rearrangements, and return to the ground state are highly sensitive to their position within this cavity and are significantly slower than in a bulk aqueous solution. Molecular dynamics simulations reveal the hindered translations and rotations of water molecules within the protein cavity with spatial specificity. The results presented herein show that fully hydrated nanoscale protein cavities are a promising way to mimic the tight protein pockets found in natural light-harvesting complexes. We also show that the interplay between protein, solvent, and chromophores can be used to substantially tune the relaxation processes within artificial light-harvesting assemblies in order to significantly improve the yield of interchromophore energy transfer and extend the range of excitation transport. Our observations have implications for other important, similarly sized bioinspired materials, such as nanoreactors and biocompatible targeted delivery agents. PMID:26035585

  6. Self-assembly of chlorophenols in water

    Science.gov (United States)

    Rogalska, Ewa; Rogalski, Marek; Gulik-Krzywicki, Tadeusz; Gulik, Annette; Chipot, Christophe

    1999-01-01

    In saturated solutions of some di- and trichlorophenols, structures with complex morphologies, consisting of thin, transparent sheets often coiling into helices and ultimately twisting into filaments, were observed under the optical microscope. Freeze-fracture electron microscopy, x-ray diffraction, phase diagrams, and molecular modeling were performed to elucidate the observed phenomena. Here, we present evidence that the chlorophenols studied, when interacting with water, self-assemble into bilayers. The fact that some chlorophenols form the same supramolecular structures as those described previously for structurally nonrelated surfactants sheds light on the mechanisms of self-assembly. PMID:10359753

  7. From self-assembled vesicles to protocells.

    Science.gov (United States)

    Chen, Irene A; Walde, Peter

    2010-07-01

    Self-assembled vesicles are essential components of primitive cells. We review the importance of vesicles during the origins of life, fundamental thermodynamics and kinetics of self-assembly, and experimental models of simple vesicles, focusing on prebiotically plausible fatty acids and their derivatives. We review recent work on interactions of simple vesicles with RNA and other studies of the transition from vesicles to protocells. Finally we discuss current challenges in understanding the biophysics of protocells, as well as conceptual questions in information transmission and self-replication. PMID:20519344

  8. Remote control of self-assembled microswimmers

    CERN Document Server

    Grosjean, Galien; Darras, Alexis; Hubert, Maxime; Lumay, Geoffroy; Vandewalle, Nicolas

    2015-01-01

    Physics governing the locomotion of microorganisms and other microsystems is dominated by viscous damping. An effective swimming strategy involves the non-reciprocal and periodic deformations of the considered body. Here, we show that a magnetocapillary-driven self-assembly, composed of three soft ferromagnetic beads, is able to swim along a liquid-air interface when powered by an external magnetic field. More importantly, we demonstrate that trajectories can be fully controlled, opening ways to explore low Reynolds number swimming. This magnetocapillary system spontaneously forms by self-assembly, allowing miniaturization and other possible applications such as cargo transport or solvent flows.

  9. Ultrafast Energy Relaxation in Single Light-Harvesting Complexes

    CERN Document Server

    Malý, Pavel; Cogdell, Richard J; Mančal, Tomáš; van Grondelle, Rienk

    2015-01-01

    Energy relaxation in light-harvesting complexes has been extensively studied by various ultrafast spectroscopic techniques, the fastest processes being in the sub-100 fs range. At the same time much slower dynamics have been observed in individual complexes by single-molecule fluorescence spectroscopy (SMS). In this work we employ a pump-probe type SMS technique to observe the ultrafast energy relaxation in single light-harvesting complexes LH2 of purple bacteria. After excitation at 800 nm, the measured relaxation time distribution of multiple complexes has a peak at 95 fs and is asymmetric, with a tail at slower relaxation times. When tuning the excitation wavelength, the distribution changes in both its shape and position. The observed behaviour agrees with what is to be expected from the LH2 excited states structure. As we show by a Redfield theory calculation of the relaxation times, the distribution shape corresponds to the expected effect of Gaussian disorder of the pigment transition energies. By repe...

  10. Green grasses as light harvesters in dye sensitized solar cells

    Science.gov (United States)

    Shanmugam, Vinoth; Manoharan, Subbaiah; Sharafali, A.; Anandan, Sambandam; Murugan, Ramaswamy

    2015-01-01

    Chlorophylls, the major pigments presented in plants are responsible for the process of photosynthesis. The working principle of dye sensitized solar cell (DSSC) is analogous to natural photosynthesis in light-harvesting and charge separation. In a similar way, natural dyes extracted from three types of grasses viz. Hierochloe Odorata (HO), Torulinium Odoratum (TO) and Dactyloctenium Aegyptium (DA) were used as light harvesters in dye sensitized solar cells (DSSCs). The UV-Vis absorption spectroscopy, Fourier transform infrared (FT-IR), and liquid chromatography-mass spectrometry (LC-MS) were used to characterize the dyes. The electron transport mechanism and internal resistance of the DSSCs were investigated by the electrochemical impedance spectroscopy (EIS). The performance of the cells fabricated with the grass extract shows comparable efficiencies with the reported natural dyes. Among the three types of grasses, the DSSC fabricated with the dye extracted from Hierochloe Odorata (HO) exhibited the maximum efficiency. LC-MS investigations indicated that the dominant pigment present in HO dye was pheophytin a (Pheo a).

  11. Broadband enhancement of light harvesting in luminescent solar concentrator

    CERN Document Server

    Xiao, Yun-Feng; Xiao, Lixin; Sun, Fang-Wen; Gong, Qihuang

    2010-01-01

    Luminescent solar concentrator (LSC) can absorb large-area incident sunlight, then emit luminescence with high quantum efficiency, which finally be collected by a small photovoltaic (PV) system. The light-harvesting area of the PV system is much smaller than that of the LSC system, potentially improving the efficiency and reducing the cost of solar cells. Here, based on Fermi-golden rule, we present a theoretical description of the luminescent process in nanoscale LSCs where the conventional ray-optics model is no longer applicable. As an example calculated with this new model, we demonstrate that a slot waveguide consisting of a nanometer-sized low-index slot region sandwiched by two high-index regions provides a broadband enhancement of light harvesting by the luminescent centers in the slot region. This is because the slot waveguide can (1) greatly enhance the spontaneous emission due to the Purcell effect, (2) dramatically increase the effective absorption cross-section of luminescent centers, and (3) str...

  12. Ultrafast energy relaxation in single light-harvesting complexes.

    Science.gov (United States)

    Malý, Pavel; Gruber, J Michael; Cogdell, Richard J; Mančal, Tomáš; van Grondelle, Rienk

    2016-03-15

    Energy relaxation in light-harvesting complexes has been extensively studied by various ultrafast spectroscopic techniques, the fastest processes being in the sub-100-fs range. At the same time, much slower dynamics have been observed in individual complexes by single-molecule fluorescence spectroscopy (SMS). In this work, we use a pump-probe-type SMS technique to observe the ultrafast energy relaxation in single light-harvesting complexes LH2 of purple bacteria. After excitation at 800 nm, the measured relaxation time distribution of multiple complexes has a peak at 95 fs and is asymmetric, with a tail at slower relaxation times. When tuning the excitation wavelength, the distribution changes in both its shape and position. The observed behavior agrees with what is to be expected from the LH2 excited states structure. As we show by a Redfield theory calculation of the relaxation times, the distribution shape corresponds to the expected effect of Gaussian disorder of the pigment transition energies. By repeatedly measuring few individual complexes for minutes, we find that complexes sample the relaxation time distribution on a timescale of seconds. Furthermore, by comparing the distribution from a single long-lived complex with the whole ensemble, we demonstrate that, regarding the relaxation times, the ensemble can be considered ergodic. Our findings thus agree with the commonly used notion of an ensemble of identical LH2 complexes experiencing slow random fluctuations. PMID:26903650

  13. Bola-amphiphile self-assembly

    DEFF Research Database (Denmark)

    Svaneborg, Carsten

    2012-01-01

    Bola-amphiphiles are rod-like molecules where both ends of the molecule likes contact with water, while the central part of the molecule dislikes contact with water. What do such molecules do when they are dissolved in water? They self-assemble into micelles. This is a Dissipartive particle dynam...

  14. DNA addition using linear self-assembly

    Institute of Scientific and Technical Information of China (English)

    ZHAO Jian; QIAN LuLu; LIU Qiang; ZHANG ZhiZhou; HE Lin

    2007-01-01

    This paper presents a DNA algorithm which adds two nonnegative binary integers using self-assembly in constant steps. The approach has the benefit of greater experimental simplicity when compared with previous DNA addition algorithms. For the addition of two binary n-bit integers, O(n) is different from DNA strands and only O(1) biochemical experimental procedures are required.

  15. Functional materials of self-assembled compounds

    NARCIS (Netherlands)

    Hameren, R. van

    2010-01-01

    The research described in the thesis entitled “Functional materials of self-assembled compounds” has been carried out at the interface of physics and chemistry, with the aim to explore new scientific opportunities and develop new applications. The research mainly focuses on porphyrins, chromophoric

  16. Self-assembled nanogaps for molecular electronics

    DEFF Research Database (Denmark)

    Tang, Qingxin; Tong, Yanhong; Jain, Titoo;

    2009-01-01

    A nanogap for molecular devices was realized using solution-based self-assembly. Gold nanorods were assembled to gold nanoparticle-coated conducting SnO2:Sb nanowires via thiol end-capped oligo(phenylenevinylene)s (OPVs). The molecular gap was easily created by the rigid molecule itself during se...

  17. Self-assembled nanolaminate coatings (SV)

    Energy Technology Data Exchange (ETDEWEB)

    Fan, H.

    2012-03-01

    Sandia National Laboratories (Sandia) and Lockheed Martin Aeronautics (LM Aero) are collaborating to develop affordable, self-assembled, nanocomposite coatings and associated fabrication processes that will be tailored to Lockheed Martin product requirements. The purpose of this project is to develop a family of self-assembled coatings with properties tailored to specific performance requirements, such as antireflective (AR) optics, using Sandia-developed self-assembled techniques. The project met its objectives by development of a simple and economic self-assembly processes to fabricate multifunctional coatings. Specifically, materials, functionalization methods, and associated coating processes for single layer and multiple layers coatings have been developed to accomplish high reflective coatings, hydrophobic coatings, and anti-reflective coatings. Associated modeling and simulations have been developed to guide the coating designs for optimum optical performance. The accomplishments result in significant advantages of reduced costs, increased manufacturing freedom/producibility, improved logistics, and the incorporation of new technology solutions not possible with conventional technologies. These self-assembled coatings with tailored properties will significantly address LMC's needs and give LMC a significant competitive lead in new engineered materials. This work complements SNL's LDRD and BES programs aimed at developing multifunctional nanomaterials for microelectronics and optics as well as structure/property investigations of self-assembled nanomaterials. In addition, this project will provide SNL with new opportunities to develop and apply self-assembled nanocomposite optical coatings for use in the wavelength ranges of 3-5 and 8-12 micrometers, ranges of vital importance to military-based sensors and weapons. The SANC technologies will be applied to multiple programs within the LM Company including the F-35, F-22, ADP (Future Strike Bomber

  18. Self-assembly of azide containing dipeptides.

    Science.gov (United States)

    Yuran, Sivan; Razvag, Yair; Das, Priyadip; Reches, Meital

    2014-07-01

    Functional structures and materials are formed spontaneously in nature through the process of self-assembly. Mimicking this process in vitro will lead to the formation of new substances that would impact many areas including energy production and storage, biomaterials and implants, and drug delivery. The considerable structural diversity of peptides makes them appealing building blocks for self-assembly in vitro. This paper describes the self-assembly of three aromatic dipeptides containing an azide moiety: H-Phe(4-azido)-Phe(4-azido)-OH, H-Phe(4-azido)-Phe-OH, and H-Phe-Phe(4-azido)-OH. The peptide H-Phe(4-azido)-Phe(4-azido)-OH self-assembled into porous spherical structures, whereas the peptides H-Phe(4-azido)-Phe-OH and H-Phe-Phe(4-azido)-OH did not form any ordered structures under the examined experimental conditions. The azido group of the peptide can serve as a photo cross-linking agent upon irradiation with UV light. To examine the effect of this group and its activity on the self-assembled structures, we irradiated the assemblies in solution for different time periods. Using electron microscopy, we determined that the porous spherical assemblies formed by the peptide H-Phe(4-azido)-Phe(4-azido)-OH underwent a structural change upon irradiation. In addition, using FT-IR, we detected the chemical change of the peptide azido group. Moreover, using indentation experiments with atomic force microscopy, we showed that the Young's modulus of the spherical assemblies increased after 20 min of irradiation with UV light. Overall, irradiating the solution of the peptide assemblies containing the azido group resulted in a change both in the morphology and mechanical properties of the peptide-based structures. These ordered assemblies or their peptide monomer building blocks can potentially be incorporated into other peptide assemblies to generate stiffer and more stable materials. PMID:24889029

  19. Modeling coherent excitation energy transfer in photosynthetic light harvesting systems

    Science.gov (United States)

    Huo, Pengfei

    2011-12-01

    Recent non-linear spectroscopy experiments suggest the excitation energy transfer in some biological light harvesting systems initially occurs coherently. Treating such processes brings significant challenge for conventional theoretical tools that usually involve different approximations. In this dissertation, the recently developed Iterative Linearized Density Matrix (ILDM) propagation scheme, which is non-perturbative and non-Markovian is extended to study coherent excitation energy transfer in various light harvesting complexes. It is demonstrated that the ILDM approach can successfully describe the coherent beating of the site populations on model systems and gives quantitative agreement with both experimental results and the results of other theoretical methods have been developed recently to going beyond the usual approximations, thus providing a new reliable theoretical tool to study this phenomenon. This approach is used to investigate the excited energy transfer dynamics in various experimentally studied bacteria light harvesting complexes, such as Fenna-Matthews-Olsen (FMO) complex, Phycocyanin 645 (PC645). In these model calculations, quantitative agreement is found between computed de-coherence times and quantum beating pattens observed in the non-linear spectroscopy. As a result of these studies, it is concluded that the stochastic resonance behavior is important in determining the optimal throughput. To begin addressing possible mechanics for observed long de-coherence time, various models which include correlation between site energy fluctuations as well as correlation between site energy and inter-site coupling are developed. The influence of both types of correlation on the coherence and transfer rate is explored using with a two state system-bath hamiltonian parametrized to model the reaction center of Rhodobacter sphaeroides bacteria. To overcome the disadvantages of a fully reduced approach or a full propagation method, a brownian dynamics

  20. Robustness and Optimality of Light Harvesting in Cyanobacterial Photosystem I

    CERN Document Server

    Sener, M K; Ritz, T; Park, S; Fromme, P; Schulten, K; Sener, Melih K.; Lu, Deyu; Ritz, Thorsten; Park, Sanghyun; Fromme, Petra; Schulten, Klaus

    2002-01-01

    As most biological species, photosynthetic lifeforms have evolved to function optimally, despite thermal disorder and with fault tolerance. It remains a challenge to understand how this is achieved. To address this challenge the function of the protein-pigment complex photosystem I (PSI) of the cyanobacterium Synechococcus elongatus is investigated theoretically. The recently obtained high resolution structure of this complex exhibits an aggregate of 96 chlorophylls that are electronically coupled to function as a light-harvesting antenna complex. This paper constructs an effective Hamiltonian for the chlorophyll aggregate to describe excitation transfer dynamics and spectral properties of PSI. For this purpose, a new kinetic expansion method, the sojourn expansion, is introduced. Our study shows that at room temperature fluctuations of site energies have little effect on the calculated excitation lifetime and quantum yield, which compare favorably with experimental results. The efficiency of the system is fo...

  1. Semiconductor Nanocrystals as Light Harvesters in Solar Cells

    Directory of Open Access Journals (Sweden)

    Lioz Etgar

    2013-02-01

    Full Text Available Photovoltaic cells use semiconductors to convert sunlight into electrical current and are regarded as a key technology for a sustainable energy supply. Quantum dot-based solar cells have shown great potential as next generation, high performance, low-cost photovoltaics due to the outstanding optoelectronic properties of quantum dots and their multiple exciton generation (MEG capability. This review focuses on QDs as light harvesters in solar cells, including different structures of QD-based solar cells, such as QD heterojunction solar cells, QD-Schottky solar cells, QD-sensitized solar cells and the recent development in organic-inorganic perovskite heterojunction solar cells. Mechanisms, procedures, advantages, disadvantages and the latest results obtained in the field are described. To summarize, a future perspective is offered.

  2. Quantum superpositions in photosynthetic light harvesting: delocalization and entanglement

    Energy Technology Data Exchange (ETDEWEB)

    Ishizaki, Akihito; Fleming, Graham R, E-mail: GRFleming@lbl.go [Department of Chemistry, University of California, Berkeley, CA 94720 (United States); Physical Bioscience Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

    2010-05-15

    We explore quantum entanglement among the chlorophyll molecules in light-harvesting complex II, which is the most abundant photosynthetic antenna complex in plants containing over 50% of the world's chlorophyll molecules. Our results demonstrate that there exists robust quantum entanglement under physiological conditions for the case of a single elementary excitation. However, this nonvanishing entanglement is not unexpected because entanglement in the single-excitation manifold is conceptually the same as quantum delocalized states, which are the spectroscopically detectable energy eigenstates of the system. We discuss the impact of the surrounding environments and correlated fluctuations in electronic energies of different pigments upon quantum delocalization and quantum entanglement. It is demonstrated that investigations with tools quantifying the entanglement can provide us with more detailed information on the nature of quantum delocalization, in particular the so-called dynamic localization, which is difficult for a traditional treatment to capture.

  3. Self-assembling membranes and related methods thereof

    Science.gov (United States)

    Capito, Ramille M; Azevedo, Helena S; Stupp, Samuel L

    2013-08-20

    The present invention relates to self-assembling membranes. In particular, the present invention provides self-assembling membranes configured for securing and/or delivering bioactive agents. In some embodiments, the self-assembling membranes are used in the treatment of diseases, and related methods (e.g., diagnostic methods, research methods, drug screening).

  4. Controlling and imaging biomimetic self-assembly

    Science.gov (United States)

    Aliprandi, Alessandro; Mauro, Matteo; de Cola, Luisa

    2016-01-01

    The self-assembly of chemical entities represents a very attractive way to create a large variety of ordered functional structures and complex matter. Although much effort has been devoted to the preparation of supramolecular nanostructures based on different chemical building blocks, an understanding of the mechanisms at play and the ability to monitor assembly processes and, in turn, control them are often elusive, which precludes a deep and comprehensive control of the final structures. Here the complex supramolecular landscape of a platinum(II) compound is characterized fully and controlled successfully through a combination of supramolecular and photochemical approaches. The supramolecular assemblies comprise two kinetic assemblies and their thermodynamic counterpart. The monitoring of the different emission properties of the aggregates, used as a fingerprint for each species, allows the real-time visualization of the evolving self-assemblies. The control of multiple supramolecular pathways will help the design of complex systems in and out of their thermodynamic equilibrium.

  5. Ternary self-assemblies in water

    DEFF Research Database (Denmark)

    Hill, Leila R.; Blackburn, Octavia A.; Jones, Michael W.;

    2013-01-01

    The self-assembly of higher order structures in water is realised by using the association of 1,3-biscarboxylates to binuclear meta-xylyl bridged DO3A complexes. Two dinicotinate binding sites are placed at a right-angle in a rhenium complex, which is shown to form a 1 : 2 complex with α,α'-bis(E......The self-assembly of higher order structures in water is realised by using the association of 1,3-biscarboxylates to binuclear meta-xylyl bridged DO3A complexes. Two dinicotinate binding sites are placed at a right-angle in a rhenium complex, which is shown to form a 1 : 2 complex with α...

  6. Towards negative index self-assembled metamaterials

    CERN Document Server

    Fruhnert, Martin; Lederer, Falk; Rockstuhl, Carsten

    2016-01-01

    We investigate the magnetic response of meta-atoms that can be fabricated by a bottom-up technique. Usually such meta-atoms consist of a dielectric core surrounded by a large number of solid metallic nanoparticles. In contrast to those meta-atoms considered thus far, we study here for the first time hollow metallic nanoparticles (shells). In doing so we solve one of the most pertinent problems of current self-assembled metamaterials, namely implementing meta-atoms with sufficiently large resonance strength and small absorption. Both conditions have to be met for deep sub-wavelength meta-atoms to obtain effectively homogeneous metamaterials which may be meaningfully described by negative material parameters. Eventually we show that by using these findings self-assembled negative index materials come in reach.

  7. Dissipative self-assembly of vesicular nanoreactors.

    Science.gov (United States)

    Maiti, Subhabrata; Fortunati, Ilaria; Ferrante, Camilla; Scrimin, Paolo; Prins, Leonard J

    2016-07-01

    Dissipative self-assembly is exploited by nature to control important biological functions, such as cell division, motility and signal transduction. The ability to construct synthetic supramolecular assemblies that require the continuous consumption of energy to remain in the functional state is an essential premise for the design of synthetic systems with lifelike properties. Here, we show a new strategy for the dissipative self-assembly of functional supramolecular structures with high structural complexity. It relies on the transient stabilization of vesicles through noncovalent interactions between the surfactants and adenosine triphosphate (ATP), which acts as the chemical fuel. It is shown that the lifetime of the vesicles can be regulated by controlling the hydrolysis rate of ATP. The vesicles sustain a chemical reaction but only as long as chemical fuel is present to keep the system in the out-of-equilibrium state. The lifetime of the vesicles determines the amount of reaction product produced by the system. PMID:27325101

  8. Self-assembly of chlorophenols in water

    OpenAIRE

    Rogalska, Ewa; Rogalski, Marek; Gulik-Krzywicki, Tadeusz; Gulik, Annette; Chipot, Christophe

    1999-01-01

    In saturated solutions of some di- and trichlorophenols, structures with complex morphologies, consisting of thin, transparent sheets often coiling into helices and ultimately twisting into filaments, were observed under the optical microscope. Freeze-fracture electron microscopy, x-ray diffraction, phase diagrams, and molecular modeling were performed to elucidate the observed phenomena. Here, we present evidence that the chlorophenols studied, when interacting with water, self-assemble into...

  9. Magnetic Films on Self-assembled Nanospheres

    Institute of Scientific and Technical Information of China (English)

    T.Ulbrich; I.Guhr; T.Schrefl; O.Hellwig; S.van; Dijken; M.Albrecht

    2007-01-01

    1 Results Nanoparticle media using arrays of monodisperse nanoparticles with high magneticanisotropy are assumed to be the ideal future magnetic recording media. However,key requirements like control of the magnetic anisotropy orientation along with magnetic domain isolation have not been achieved so far. Here, we report on a combination of a two-dimensional topographic pattern formed of self-assembled nanoparticles with sizes as small as 20 nm and magnetic multilayer film deposition[1]. The so formed n...

  10. Self-Assembly of Information in Networks

    OpenAIRE

    Rosvall, M.; K. Sneppen

    2006-01-01

    We model self-assembly of information in networks to investigate necessary conditions for building a global perception of a system by local communication. Our approach is to let agents chat in a model system to self-organize distant communication-pathways. We demonstrate that simple local rules allow agents to build a perception of the system, that is robust to dynamical changes and mistakes. We find that messages are most effectively forwarded in the presence of hubs, while transmission in h...

  11. Single photon ionisation of self assembled monolayers

    Science.gov (United States)

    King, B. V.; Savina, M. R.; Tripa, C. E.; Calaway, W. F.; Veryovkin, I. V.; Moore, J. F.; Pellin, M. J.

    2002-05-01

    Self assembled monolayers formed from benzenethiol, diphenylsulphide and diphenyldisulphide have been analysed using secondary ion mass spectrometry (SIMS), sputter neutral mass spectrometry (SNMS) and laser desorption photoionisation mass spectrometry (LDPI). The peak corresponding to the parent ion was much stronger in LDPI than with SIMS or SNMS analysis and fragmentation was lower. A useful yield of order 0.5% was obtained for LDPI from diphenyldisulphide.

  12. Parallel Computation Using Active Self-assembly

    OpenAIRE

    Chen, Moya; Xin, Doris; Woods, Damien

    2013-01-01

    We study the computational complexity of the recently proposed nubot model of molecular-scale self-assembly. The model generalises asynchronous cellular automata to have non-local movement where large assemblies of molecules can be pushed and pulled around, analogous to millions of molecular motors in animal muscle effecting the rapid movement of macroscale arms and legs. We show that the nubot model is capable of simulating Boolean circuits of polylogarithmic depth and polynomial size, in on...

  13. Templated Self Assemble of Nano-Structures

    Energy Technology Data Exchange (ETDEWEB)

    Suo, Zhigang [Harvard University

    2013-04-29

    This project will identify and model mechanisms that template the self-assembly of nanostructures. We focus on a class of systems involving a two-phase monolayer of molecules adsorbed on a solid surface. At a suitably elevated temperature, the molecules diffuse on the surface to reduce the combined free energy of mixing, phase boundary, elastic field, and electrostatic field. With no template, the phases may form a pattern of stripes or disks. The feature size is on the order of 1-100 nm, selected to compromise the phase boundary energy and the long-range elastic or electrostatic interaction. Both experimental observations and our theoretical simulations have shown that the pattern resembles a periodic lattice, but has abundant imperfections. To form a perfect periodic pattern, or a designed aperiodic pattern, one must introduce a template to guide the assembly. For example, a coarse-scale pattern, lithographically defined on the substrate, will guide the assembly of the nanoscale pattern. As another example, if the molecules on the substrate surface carry strong electric dipoles, a charged object, placed in the space above the monolayer, will guide the assembly of the molecular dipoles. In particular, the charged object can be a mask with a designed nanoscale topographic pattern. A serial process (e.g., e-beam lithography) is necessary to make the mask, but the pattern transfer to the molecules on the substrate is a parallel process. The technique is potentially a high throughput, low cost process to pattern a monolayer. The monolayer pattern itself may serve as a template to fabricate a functional structure. This project will model fundamental aspects of these processes, including thermodynamics and kinetics of self-assembly, templated self-assembly, and self-assembly on unconventional substrates. It is envisioned that the theory will not only explain the available experimental observations, but also motivate new experiments.

  14. Self Assembly of Complex Building Blocks

    Science.gov (United States)

    Stucke, David; Crespi, Vincent

    2004-03-01

    A genetic search algorithm for optimizing the packing density of self-assembled multicomponent crystals of nanoparticles applied to complex colloidal building blocks will be presented. The algorithm searches the complex multi-dimensional space to find preferred crystal structures where standard methods fail. Mixtures of colloidal molecules and the structures found to be preferred to phase separation for different species of coloidal molecule mixtures will be shown.

  15. Single photon ionisation of self assembled monolayers

    International Nuclear Information System (INIS)

    Self assembled monolayers formed from benzenethiol, diphenylsulphide and diphenyldisulphide have been analysed using secondary ion mass spectrometry (SIMS), sputter neutral mass spectrometry (SNMS) and laser desorption photoionisation mass spectrometry (LDPI). The peak corresponding to the parent ion was much stronger in LDPI than with SIMS or SNMS analysis and fragmentation was lower. A useful yield of order 0.5% was obtained for LDPI from diphenyldisulphide

  16. Self-assembly of Fmoc-diphenylalanine inside liquid marbles.

    Science.gov (United States)

    Braun, Hans-Georg; Cardoso, André Zamith

    2012-09-01

    Liquid marbles made from Lycopodium clavatum spores are used to encapsulate aqueous solutions of 9-fluorenylmethoxycarbonyl-diphenylalanine (Fmoc-FF). Acidification of the Fmoc-FF solution at the liquid/air interface of the liquid marble triggers the self-assembly of ribbon-like peptide fibrils into an ultrathin peptide membrane (50-500 nm). The membrane incorporates the lycopodium microparticles and as a result stabilizes the liquid marble against collapse, that could otherwise occur through particle disintegration at the floating interphase. Ultrathin nanostructured peptide membrane formation at the liquid/air interface is also observed within artificial microstructured floating objects. Thus, peptide membranes formed were inspected by SEM and TEM. Electron diffraction data reveal information about the molecular organization inside the oligopeptide membranes. PMID:22584262

  17. Self-assembled tunable photonic hyper-crystals

    CERN Document Server

    Smolyaninova, Vera N; Lahneman, David; Narimanov, Evgenii E; Smolyaninov, Igor I

    2013-01-01

    We demonstrate a novel artificial optical material, a photonic hyper-crystal, which combines the most interesting features of hyperbolic metamaterials and photonic crystals. Similar to hyperbolic metamaterials, photonic hyper-crystals exhibit broadband divergence in their photonic density of states due to the lack of usual diffraction limit on the photon wave vector. On the other hand, similar to photonic crystals, hyperbolic dispersion law of extraordinary photons is modulated by forbidden gaps near the boundaries of photonic Brillouin zones. Three dimensional self-assembly of photonic hyper-crystals has been achieved by application of external magnetic field to a cobalt nanoparticle-based ferrofluid. Unique spectral properties of photonic hyper-crystals lead to extreme sensitivity of the material to monolayer coatings of cobalt nanoparticles, which should find numerous applications in biological and chemical sensing.

  18. Formal Verification of Self-Assembling Systems

    CERN Document Server

    Sterling, Aaron

    2010-01-01

    This paper introduces the theory and practice of formal verification of self-assembling systems. We interpret a well-studied abstraction of nanomolecular self assembly, the Abstract Tile Assembly Model (aTAM), into Computation Tree Logic (CTL), a temporal logic often used in model checking. We then consider the class of "rectilinear" tile assembly systems. This class includes most aTAM systems studied in the theoretical literature, and all (algorithmic) DNA tile self-assembling systems that have been realized in laboratories to date. We present a polynomial-time algorithm that, given a tile assembly system T as input, either provides a counterexample to T's rectilinearity or verifies whether T has a unique terminal assembly. Using partial order reductions, the verification search space for this algorithm is reduced from exponential size to O(n^2), where n x n is the size of the assembly surface. That reduction is asymptotically the best possible. We report on experimental results obtained by translating tile ...

  19. Self-assembled plasmonic nanohole arrays.

    Science.gov (United States)

    Lee, Si Hoon; Bantz, Kyle C; Lindquist, Nathan C; Oh, Sang-Hyun; Haynes, Christy L

    2009-12-01

    We present a simple and massively parallel nanofabrication technique to produce self-assembled periodic nanohole arrays over a millimeter-sized area of metallic film, with a tunable hole shape, diameter, and periodicity. Using this method, 30 x 30 microm(2) defect-free areas of 300 nm diameter or smaller holes were obtained in silver; this area threshold is critical because it is larger than the visible wavelength propagation length of surface plasmon waves ( approximately 27 microm) in the silver film. Measured optical transmission spectra show highly homogeneous characteristics across the millimeter-size patterned area, and they are in good agreement with FDTD simulations. The simulations also reveal intense electric fields concentrated near the air/silver interface, which was used for surface-enhanced Raman spectroscopy (SERS). Enhancement factors (EFs) measured with different hole shape and excitation wavelengths on the self-assembled nanohole arrays were 10(4)-10(6). With an additional Ag electroless plating step, the EF was further increased up to 3 x 10(6). The periodic nanohole arrays produced using this tunable self-assembly method show great promise as inexpensive SERS substrates as well as surface plasmon resonance biosensing platforms. PMID:19831350

  20. Enhanced Conversion Efficiencies in Dye-Sensitized Solar Cells Achieved through Self-Assembled Platinum(II) Metallacages

    Science.gov (United States)

    He, Zuoli; Hou, Zhiqiang; Xing, Yonglei; Liu, Xiaobin; Yin, Xingtian; Que, Meidan; Shao, Jinyou; Que, Wenxiu; Stang, Peter J.

    2016-01-01

    Two-component self-assembly supramolecular coordination complexes with particular photo-physical property, wherein unique donors are combined with a single metal acceptor, can be utilized for many applications including in photo-devices. In this communication, we described the synthesis and characterization of two-component self-assembly supramolecular coordination complexes (SCCs) bearing triazine and porphyrin faces with promising light-harvesting properties. These complexes were obtained from the self-assembly of a 90° Pt(II) acceptor with 2,4,6-tris(4-pyridyl)-1,3,5-triazine (TPyT) or 5,10,15,20-Tetra(4-pyridyl)-21H,23H-porphine (TPyP). The greatly improved conversion efficiencies of the dye-sensitized TiO2 solar cells were 6.79 and 6.08 respectively, while these SCCs were introduced into the TiO2 nanoparticle film photoanodes. In addition, the open circuit voltage (Voc) of dye-sensitized solar cells was also increased to 0.769 and 0.768 V, which could be ascribed to the inhibited interfacial charge recombination due to the addition of SCCs. PMID:27404912

  1. Enhanced Conversion Efficiencies in Dye-Sensitized Solar Cells Achieved through Self-Assembled Platinum(II) Metallacages.

    Science.gov (United States)

    He, Zuoli; Hou, Zhiqiang; Xing, Yonglei; Liu, Xiaobin; Yin, Xingtian; Que, Meidan; Shao, Jinyou; Que, Wenxiu; Stang, Peter J

    2016-01-01

    Two-component self-assembly supramolecular coordination complexes with particular photo-physical property, wherein unique donors are combined with a single metal acceptor, can be utilized for many applications including in photo-devices. In this communication, we described the synthesis and characterization of two-component self-assembly supramolecular coordination complexes (SCCs) bearing triazine and porphyrin faces with promising light-harvesting properties. These complexes were obtained from the self-assembly of a 90° Pt(II) acceptor with 2,4,6-tris(4-pyridyl)-1,3,5-triazine (TPyT) or 5,10,15,20-Tetra(4-pyridyl)-21H,23H-porphine (TPyP). The greatly improved conversion efficiencies of the dye-sensitized TiO2 solar cells were 6.79 and 6.08 respectively, while these SCCs were introduced into the TiO2 nanoparticle film photoanodes. In addition, the open circuit voltage (Voc) of dye-sensitized solar cells was also increased to 0.769 and 0.768 V, which could be ascribed to the inhibited interfacial charge recombination due to the addition of SCCs. PMID:27404912

  2. Self-assembled biomimetic nanoreactors I: Polymeric template

    Science.gov (United States)

    McTaggart, Matt; Malardier-Jugroot, Cecile; Jugroot, Manish

    2015-09-01

    The variety of nanoarchitectures made feasible by the self-assembly of alternating copolymers opens new avenues for biomimicry. Indeed, self-assembled structures allow the development of nanoreactors which combine the efficiency of high surface area metal active centres to the effect of confinement due to the very small cavities generated by the self-assembly process. A novel self-assembly of high molecular weight alternating copolymers is characterized in the present study. The self-assembly is shown to organize into nanosheets, providing a 2 nm hydrophobic cavity with a 1D confinement.

  3. Potential control of DNA self-assembly on gold electrode

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The self-assembly monolayer (SAM) was prepared with 2-aminoethanethiol (AET) on the gold electrode.A new approach based on potential was first used to control DNA self-assembly covalently onto the SAM with the activation of 1-ethyl-3(3-dimethylaminopropyl)-carbodiimide (EDC) and N-hydroxysulfosuccinimide (NHS). The influence of potential on DNA self-assembly was investigated by means of cyclic voltammetry (CV), AC impedance, Auger electron spectrometry (AES) and atomic force microscopy (AFM). The result proves that controlled potential can affect the course of DNA self-assembly. More negative potential can restrain the DNA self-assembly, while more positive potential can accelerate the DNA self-assembly, which is of great significance for the control of DNA self-assembly and will find wide application in the field of DNA-based devices.

  4. Amphiphilic, hydrophilic, or hydrophobic synthetic bacteriochlorins in biohybrid light-harvesting architectures: consideration of molecular designs.

    Science.gov (United States)

    Jiang, Jianbing; Reddy, Kanumuri Ramesh; Pavan, M Phani; Lubian, Elisa; Harris, Michelle A; Jiao, Jieying; Niedzwiedzki, Dariusz M; Kirmaier, Christine; Parkes-Loach, Pamela S; Loach, Paul A; Bocian, David F; Holten, Dewey; Lindsey, Jonathan S

    2014-11-01

    Biohybrid light-harvesting architectures can be constructed that employ native-like bacterial photosynthetic antenna peptides as a scaffold to which synthetic chromophores are attached to augment overall spectral coverage. Synthetic bacteriochlorins are attractive to enhance capture of solar radiation in the photon-rich near-infrared spectral region. The effect of the polarity of the bacteriochlorin substituents on the antenna self-assembly process was explored by the preparation of a bacteriochlorin-peptide conjugate using a synthetic amphiphilic bacteriochlorin (B1) to complement prior studies using hydrophilic (B2, four carboxylic acids) or hydrophobic (B3) bacteriochlorins. The amphiphilic bioconjugatable bacteriochlorin B1 with a polar ammonium-terminated tail was synthesized by sequential Pd-mediated reactions of a 3,13-dibromo-5-methoxybacteriochlorin. Each bacteriochlorin bears a maleimido-terminated tether for attachment to a cysteine-containing analog of the Rhodobacter sphaeroides antenna β-peptide to give conjugates β-B1, β-B2, and β-B3. Given the hydrophobic nature of the β-peptide, the polarity of B1 and B2 facilitated purification of the respective conjugate compared to the hydrophobic B3. Bacteriochlorophyll a (BChl a) associates with each conjugate in aqueous micellar media to form a dyad containing two β-peptides, two covalently attached synthetic bacteriochlorins, and a datively bonded BChl-a pair, albeit to a limited extent for β-B2. The reversible assembly/disassembly of dyad (β-B2/BChl)2 was examined in aqueous detergent (octyl glucoside) solution by temperature variation (15-35 °C). The energy-transfer efficiency from the synthetic bacteriochlorin to the BChl-a dimer was found to be 0.85 for (β-B1/BChl)2, 0.40 for (β-B2/BChl)2, and 0.85 for (β-B3/BChl)2. Thus, in terms of handling, assembly and energy-transfer efficiency taken together, the amphiphilic design examined herein is more attractive than the prior hydrophilic or

  5. Electronic Energy transfer in light-harvesting antenna complexes

    Science.gov (United States)

    Hossein-Nejad, Hoda

    The studies presented in this thesis explore electronic energy transfer (EET) in light-harvesting antenna complexes and investigate the role of quantum coherence in EET. The dynamics of energy transfer are investigated in three distinct length scales and a different formulation of the exciton transport problem is applied at each scale. These scales include: the scale of a molecular dimer, the scale of a single protein and the scale of a molecular aggregate. The antenna protein phycoerythrin 545 (PE545) isolated from the photosynthetic cryptophyte algae Rhodomonas CS4 is specifically studied in two chapters of this thesis. It is found that formation of small aggregates delocalizes the excitation across chromophores of adjacent proteins, and that this delocalization has a dramatic effect in enhancing the rate of energy transfer between pigments. Furthermore, we investigate EET from a donor to an acceptor via an intermediate site and observe that interference of coherent pathways gives a finite correction to the transfer rate that is sensitively dependent on the nature of the vibrational interactions in the system. The statistical fluctuations of a system exhibiting EET are investigated in the final chapter. The techniques of non-equilibrium statistical mechanics are applied to investigate the steady-state of a typical system exhibiting EET that is perturbed out of equilibrium due to its interaction with a fluctuating bath.

  6. Energy transfer between two aggregates in light-harvesting complexes

    International Nuclear Information System (INIS)

    Energy transfer processes between two aggregates in a coupled chromophoric-pigment (protein) system are studied via the standard master equation approach. Each pigment of the two aggregates is modeled as a two-level system. The excitation energy is assumed to be transferred from the donor aggregate to the acceptor aggregate. The model can be used to theoretically simulate many aspects of light-harvesting complexes (LHCs). By applying the real bio-parameters of photosynthesis, we numerically investigate the efficiency of energy transfer (EET) between the two aggregates in terms of some factors, e.g., the initial coherence of the donor aggregate, the coupling strengthes between the two aggregates and between different pigments, and the effects of noise from the environment. Our results provide evidence for that the actual numbers of pigments in the chromophoric rings of LHCs should be the optimum parameters for a high EET. We also give a detailed analysis of the effects of noise on the EET

  7. Excitation migration in fluctuating light-harvesting antenna systems.

    Science.gov (United States)

    Chmeliov, Jevgenij; Trinkunas, Gediminas; van Amerongen, Herbert; Valkunas, Leonas

    2016-01-01

    Complex multi-exponential fluorescence decay kinetics observed in various photosynthetic systems like photosystem II (PSII) have often been explained by the reversible quenching mechanism of the charge separation taking place in the reaction center (RC) of PSII. However, this description does not account for the intrinsic dynamic disorder of the light-harvesting proteins as well as their fluctuating dislocations within the antenna, which also facilitate the repair of RCs, state transitions, and the process of non-photochemical quenching. Since dynamic fluctuations result in varying connectivity between pigment-protein complexes, they can also lead to non-exponential excitation decay kinetics. Based on this presumption, we have recently proposed a simple conceptual model describing excitation diffusion in a continuous medium and accounting for possible variations of the excitation transfer pathways. In the current work, this model is further developed and then applied to describe fluorescence kinetics originating from very diverse antenna systems, ranging from PSII of various sizes to LHCII aggregates and even the entire thylakoid membrane. In all cases, complex multi-exponential fluorescence kinetics are perfectly reproduced on the entire relevant time scale without assuming any radical pair equilibration at the side of the excitation quencher, but using just a few parameters reflecting the mean excitation energy transfer rate as well as the overall average organization of the photosynthetic antenna. PMID:25605669

  8. Electron properties in directed self-assembly Ge/SiC/Si quantum dots

    Science.gov (United States)

    Yang, Dongyue

    Artificially ordered semiconductor quantum dot (QD) patterns may be used to implement functionalities such as spintronic bandgap systems, quantum simulation and quantum computing, by manipulating the interaction between confined carriers via direct exchange coupling. In this dissertation, magnetotransport measurements have been conducted to investigate the electronic orbital and spin states of directed self-assembly single- and few-Ge/SiC/Si QD devices, fabricated by a directed self-assembly QD growth technique developed by our group. Diamagnetic and Zeeman energy shifts of electrons confined around the QD have been observed from the magnetotransport experiments. A triple-barrier resonant tunneling model has been proposed to describe the electron and spin transport. The strength of the Coulomb interaction between electrons confined at neighboring QDs has been observed dependent on the dot separation, and represents an important parameter for fabricating QD-based molecules and artificial arrays, which may be implemented as building blocks for future quantum simulation and quantum computing architectures.

  9. Self-assembly of colloidal surfactants

    Science.gov (United States)

    Kegel, Willem

    2012-02-01

    We developed colloidal dumbbells with a rough and a smooth part, based on a method reported in Ref. [1]. Specific attraction between the smooth parts occurs upon addition of non-adsorbing polymers of appropriate size. We present the first results in terms of the assemblies that emerge in these systems. [4pt] [1] D.J. Kraft, W.S. Vlug, C.M. van Kats, A. van Blaaderen, A. Imhof and W.K. Kegel, Self-assembly of colloids with liquid protrusions, J. Am. Chem. Soc. 131, 1182, (2009)

  10. Fabrication of self-assembled microsphere monolayers

    Czech Academy of Sciences Publication Activity Database

    Domonkos, Mária; Ižák, Tibor; Kromka, Alexander

    Bratislava: Slovenská vákuová spoločnosť, 2014 - (Michalka, M.; Vincze, A.; Veselý, M.), s. 125-128 ISBN 978-80-971179-4-8. [School of Vacuum Technology /17./. Štrbské Pleso (SK), 02.10.2014-05.10.2014] R&D Projects: GA ČR(CZ) GBP108/12/G108 Institutional support: RVO:68378271 Keywords : self-assembly * monolayer * microspheres * spin-coating Subject RIV: BM - Solid Matter Physics ; Magnetism

  11. Ionically self-assembled monolayers (ISAMs)

    Science.gov (United States)

    Janik, John

    2001-04-01

    Ionically self-assembled monolayers (ISAMs), fabricated by alternate adsorption of cationic and anionic components, yield exceptionally homogeneous thin films with sub-nanometer control of the thickness and relative special location of the component materials. Using organic electrochromic materials such as polyaniline, we report studies of electrochromic responses in ISAM films. Reversible changes in the absorption spectrum are observed with the application of voltages on the order of 1.0 V. Measurements are made using both liquid electrolytes and in all-solid state devices incorporating solid polyelectrolytes such as poly(2-acylamido 2-methyl propane sulfonic acid) (PAMPS).

  12. Self-assembly of information in networks

    Science.gov (United States)

    Rosvall, M.; Sneppen, K.

    2006-06-01

    We model self-assembly of information in networks to investigate necessary conditions for building a global perception of a system by local communication. Our approach is to let agents chat in a model system to self-organize distant communication pathways. We demonstrate that simple local rules allow agents to build a perception of the system, that is robust to dynamical changes and mistakes. We find that messages are most effectively forwarded in the presence of hubs, while transmission in hub-free networks is more robust against misinformation and failures.

  13. Self-Assembly of Information in Networks

    CERN Document Server

    Rosvall, M

    2006-01-01

    We model self-assembly of information in networks to investigate necessary conditions for building a global perception of a system by local communication. Our approach is to let agents chat in a model system to self-organize distant communication-pathways. We demonstrate that simple local rules allow agents to build a perception of the system, that is robust to dynamical changes and mistakes. We find that messages are most effectively forwarded in the presence of hubs, while transmission in hub-free networks is more robust against misinformation and failures.

  14. Self-assembly of magnetic biofunctional nanoparticles

    International Nuclear Information System (INIS)

    Spherical, ferromagnetic FePt nanoparticles with a particle size of 3 nm were prepared by the simultaneous polyol reduction of Fe(acac)3 and Pt(acac)2 in phenyl ether in the presence of oleic acid and oleylamine. The oleic acid ligands can be replaced with 11-mercaptoundecanoic acid, giving particles that can be dispersed in water. Both x-ray diffraction and transmission electron microscopy indicated that FePt particles were not affected by ligands replacement. Dispersions of the FePt particles with 11-mercaptoundecanoic acid ligands and ammonium counter ions gave self-assembled films consisting of highly ordered hexagonal arrays of particles

  15. Reversible self-assembly of gels through metal-ligand interactions

    OpenAIRE

    Yuichiro Kobayashi; Yoshinori Takashima; Akihito Hashidzume; Hiroyasu Yamaguchi; Akira Harada

    2013-01-01

    Metal-ligand interactions with various proteins form in vivo metal assemblies. In recent years, metallosupramolecular approaches have been utilized to forge an assortment of fascinating two- and three-dimensional nano-architectures, and macroscopic materials, such as metal-ligand coordination polymeric materials, have promise in artificial systems. However to the best of our knowledge, the self-assembly of macroscopic materials through metal-ligand interactions has yet to be reported. Herein ...

  16. Surface-Cross-Linked Micelles as Multifunctionalized Organic Nanoparticles for Controlled Release, Light Harvesting, and Catalysis.

    Science.gov (United States)

    Zhao, Yan

    2016-06-14

    Surfactant micelles are dynamic entities with a rapid exchange of monomers. By "clicking" tripropargylammonium-containing surfactants with diazide cross-linkers, we obtained surface-cross-linked micelles (SCMs) that could be multifunctionalized for different applications. They triggered membrane fusion through tunable electrostatic interactions with lipid bilayers. Antenna chromophores could be installed on them to create artificial light-harvesting complexes with efficient energy migration among tens to hundreds of chromophores. When cleavable cross-linkers were used, the SCMs could break apart in response to redox or pH signals, ejecting entrapped contents quickly as a result of built-in electrostatic stress. They served as caged surfactants whose surface activity was turned on by environmental stimuli. They crossed cell membranes readily. Encapsulated fluorophores showed enhanced photophysical properties including improved quantum yields and greatly expanded Stokes shifts. Catalytic groups could be installed on the surface or in the interior, covalently attached or physically entrapped. As enzyme mimics, the SCMs enabled rational engineering of the microenvironment around the catalysts to afford activity and selectivity not possible with conventional catalysts. PMID:27181610

  17. Triggered self-assembly of magnetic nanoparticles

    Science.gov (United States)

    Ye, L.; Pearson, T.; Cordeau, Y.; Mefford, O. T.; Crawford, T. M.

    2016-01-01

    Colloidal magnetic nanoparticles are candidates for application in biology, medicine and nanomanufac-turing. Understanding how these particles interact collectively in fluids, especially how they assemble and aggregate under external magnetic fields, is critical for high quality, safe, and reliable deployment of these particles. Here, by applying magnetic forces that vary strongly over the same length scale as the colloidal stabilizing force and then varying this colloidal repulsion, we can trigger self-assembly of these nanoparticles into parallel line patterns on the surface of a disk drive medium. Localized within nanometers of the medium surface, this effect is strongly dependent on the ionic properties of the colloidal fluid but at a level too small to cause bulk colloidal aggregation. We use real-time optical diffraction to monitor the dynamics of self-assembly, detecting local colloidal changes with greatly enhanced sensitivity compared with conventional light scattering. Simulations predict the triggering but not the dynamics, especially at short measurement times. Beyond using spatially-varying magnetic forces to balance interactions and drive assembly in magnetic nanoparticles, future measurements leveraging the sensitivity of this approach could identify novel colloidal effects that impact real-world applications of these nanoparticles. PMID:26975332

  18. Triggered self-assembly of magnetic nanoparticles

    Science.gov (United States)

    Ye, L.; Pearson, T.; Cordeau, Y.; Mefford, O. T.; Crawford, T. M.

    2016-03-01

    Colloidal magnetic nanoparticles are candidates for application in biology, medicine and nanomanufac-turing. Understanding how these particles interact collectively in fluids, especially how they assemble and aggregate under external magnetic fields, is critical for high quality, safe, and reliable deployment of these particles. Here, by applying magnetic forces that vary strongly over the same length scale as the colloidal stabilizing force and then varying this colloidal repulsion, we can trigger self-assembly of these nanoparticles into parallel line patterns on the surface of a disk drive medium. Localized within nanometers of the medium surface, this effect is strongly dependent on the ionic properties of the colloidal fluid but at a level too small to cause bulk colloidal aggregation. We use real-time optical diffraction to monitor the dynamics of self-assembly, detecting local colloidal changes with greatly enhanced sensitivity compared with conventional light scattering. Simulations predict the triggering but not the dynamics, especially at short measurement times. Beyond using spatially-varying magnetic forces to balance interactions and drive assembly in magnetic nanoparticles, future measurements leveraging the sensitivity of this approach could identify novel colloidal effects that impact real-world applications of these nanoparticles.

  19. Self-Assemblies of novel molecules, VECAR

    Science.gov (United States)

    Shrestha, Bijay; Kim, Hye-Young; Lee, Soojin; Novak, Brian; Moldovan, Dorel

    2015-03-01

    VECAR is a newly synthesized molecule, which is an amphiphilic antioxidant molecule that consists of two molecular groups, vitamin-E and Carnosine, linked by a hydrocarbon chain. The hydrocarbon chain is hydrophobic and both vitamin-E and Carnosine ends are hydrophilic. In the synthesis process, the length of the hydrophobic chain of VECAR molecules can vary from the shortest (n =0) to the longest (n =18), where n indicates the number of carbon atoms in the chain. We conducted MD simulation studies of self-assembly of VECAR molecules in water using GROMACS on LONI HPC resources. Our study shows that there is a strong correlation between the shape and atomistic structure of the self-assembled nano-structures (SANs) and the chain-length (n) of VECAR molecules. We will report the results of data analyses including the atomistic structure of each SANs and the dynamic and energetic mechanisms of their formation as function of time. In summary, both VECAR molecules of chain-length n =18 and 9 form worm-like micelles, which may be used as a drug delivery system. This research is supported by the Louisiana Board of Regents-RCS Grant (LEQSF(2012-15)-RD-A-19).

  20. Quantum transport through complex networks - from light-harvesting proteins to semiconductor devices

    Energy Technology Data Exchange (ETDEWEB)

    Kreisbeck, Christoph

    2012-06-18

    Electron transport through small systems in semiconductor devices plays an essential role for many applications in micro-electronics. One focus of current research lies on establishing conceptually new devices based on ballistic transport in high mobility AlGaAs/AlGa samples. In the ballistic regime, the transport characteristics are determined by coherent interference effects. In order to guide experimentalists to an improved device design, the characterization and understanding of intrinsic device properties is crucial. We develop a time-dependent approach that allows us to simulate experimentally fabricated, complex devicegeometries with an extension of up to a few micrometers. Particularly, we explore the physical origin of unexpected effects that have been detected in recent experiments on transport through Aharonov-Bohm waveguide-interferometers. Such interferometers can be configured as detectors for transfer properties of embedded quantum systems. We demonstrate that a four-terminal waveguide-ring is a suitable setup for measuring the transmission phase of a harmonic quantum dot. Quantum effects are not restricted exclusively to artificial devices but have been found in biological systems as well. Pioneering experiments reveal quantum effects in light-harvesting complexes, the building blocks of photosynthesis. We discuss the Fenna-Matthews-Olson complex, which is a network of coupled bacteriochlorophylls. It acts as an energy wire in the photosynthetic apparatus of green sulfur bacteria. Recent experimental findings suggest that energy transfer takes place in the form of coherent wave-like motion, rather than through classical hopping from one bacteriochlorophyll to the next. However, the question of why and how coherent transfer emerges in light-harvesting complexes is still open. The challenge is to merge seemingly contradictory features that are observed in experiments on two-dimensional spectroscopy into a consistent theory. Here, we provide such a

  1. Self-assembly, self-organization and division of labour

    OpenAIRE

    Sendova-Franks, A. B.

    1999-01-01

    The prospect of generic principles of biological organization being uncovered through the increasingly broad use of the concepts of 'self-assembly' and 'self-organization' in biology will only be fulfilled if students of different levels of biological organization use the same terms with the same meanings. We consider the different ways the terms 'self-assembly' and 'self-organization' have been used, from studies of molecules to studies of animal societies. By linking 'self-assembly' and 'se...

  2. Molecular Component Structures Mediated Formation of Self-assemblies

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Molecular recognition directed self-assemblies from complementary molecular components, melamine and barbituric acid derivatives were studied by means of NMR, fluorescence, and TEM. It was found that both the process of the self-assembly and the morphologies of the result ed self-assemblies could be mediated by modifying the structures of the molecular components used. The effect of the structures of the molecular components on the formation of the self-as semblies was discussed in terms of intermolecular interactions.

  3. Self-assembled software and method of overriding software execution

    Science.gov (United States)

    Bouchard, Ann M.; Osbourn, Gordon C.

    2013-01-08

    A computer-implemented software self-assembled system and method for providing an external override and monitoring capability to dynamically self-assembling software containing machines that self-assemble execution sequences and data structures. The method provides an external override machine that can be introduced into a system of self-assembling machines while the machines are executing such that the functionality of the executing software can be changed or paused without stopping the code execution and modifying the existing code. Additionally, a monitoring machine can be introduced without stopping code execution that can monitor specified code execution functions by designated machines and communicate the status to an output device.

  4. Enhancing light-harvesting power with coherent vibrational interactions: A quantum heat engine picture

    International Nuclear Information System (INIS)

    Recent evidence suggests that quantum effects may have functional importance in biological light-harvesting systems. Along with delocalized electronic excitations, it is now suspected that quantum coherent interactions with certain near-resonant vibrations may contribute to light-harvesting performance. However, the actual quantum advantage offered by such coherent vibrational interactions has not yet been established. We investigate a quantum design principle, whereby coherent exchange of single energy quanta between electronic and vibrational degrees of freedom can enhance a light-harvesting system’s power above what is possible by thermal mechanisms alone. We present a prototype quantum heat engine which cleanly illustrates this quantum design principle and quantifies its quantum advantage using thermodynamic measures of performance. We also demonstrate the principle’s relevance in parameter regimes connected to natural light-harvesting structures

  5. Enhancing light-harvesting power with coherent vibrational interactions: A quantum heat engine picture

    Energy Technology Data Exchange (ETDEWEB)

    Killoran, N.; Huelga, S. F.; Plenio, M. B. [Institut für Theoretische Physik, Universität Ulm, Albert-Einstein-Allee 11, D-89069 Ulm (Germany)

    2015-10-21

    Recent evidence suggests that quantum effects may have functional importance in biological light-harvesting systems. Along with delocalized electronic excitations, it is now suspected that quantum coherent interactions with certain near-resonant vibrations may contribute to light-harvesting performance. However, the actual quantum advantage offered by such coherent vibrational interactions has not yet been established. We investigate a quantum design principle, whereby coherent exchange of single energy quanta between electronic and vibrational degrees of freedom can enhance a light-harvesting system’s power above what is possible by thermal mechanisms alone. We present a prototype quantum heat engine which cleanly illustrates this quantum design principle and quantifies its quantum advantage using thermodynamic measures of performance. We also demonstrate the principle’s relevance in parameter regimes connected to natural light-harvesting structures.

  6. Light harvesting complexes of Chromera velia, photosynthetic relative of apicomplexan parasites

    KAUST Repository

    Tichý, Josef

    2013-06-01

    The structure and composition of the light harvesting complexes from the unicellular alga Chromera velia were studied by means of optical spectroscopy, biochemical and electron microscopy methods. Two different types of antennae systems were identified. One exhibited a molecular weight (18-19 kDa) similar to FCP (fucoxanthin chlorophyll protein) complexes from diatoms, however, single particle analysis and circular dichroism spectroscopy indicated similarity of this structure to the recently characterized XLH antenna of xanthophytes. In light of these data we denote this antenna complex CLH, for "Chromera Light Harvesting" complex. The other system was identified as the photosystem I with bound Light Harvesting Complexes (PSI-LHCr) related to the red algae LHCI antennae. The result of this study is the finding that C. velia, when grown in natural light conditions, possesses light harvesting antennae typically found in two different, evolutionary distant, groups of photosynthetic organisms. © 2013 Elsevier B.V. All rights reserved.

  7. Atomistic study of energy funneling in the light-harvesting complex of green sulfur bacteria

    CERN Document Server

    Huh, Joonsuk; Brookes, Jennifer C; Valleau, Stéphanie; Fujita, Takatoshi; Aspuru-Guzik, Alán

    2013-01-01

    Phototrophic organisms such as plants, photosynthetic bacteria and algae use microscopic complexes of pigment molecules to absorb sunlight. Within the light-harvesting complexes, which frequently have multiple functional and structural subunits, the energy is transferred in the form of molecular excitations with very high efficiency. Green sulfur bacteria are considered to be amongst the most efficient light-harvesting organisms. Despite multiple experimental and theoretical studies of these bacteria the physical origin of the efficient and robust energy transfer in their light-harvesting complexes is not well understood. To study excitation dynamics at the systems level we introduce an atomistic model that mimic a complete light-harvesting apparatus of green sulfur bacteria. The model contains about 4000 pigment molecules and comprises a double wall roll for the chlorosome, a baseplate and six Fenna-Matthews-Olson trimer complexes. We show that the fast relaxation within functional subunits combined with the...

  8. Three-Dimensionally Isotropic Negative Refractive Index Materials from Block Copolymer Self-Assembled Chiral Gyroid Networks

    KAUST Repository

    Hur, Kahyun

    2011-10-17

    Metamaterials are engineered artificial materials that offer new functionalities such as super-resolution imaging and cloaking. Calculations of the photonic properties of three-dimensionally isotropic metamaterials with cubic double gyroid and alternating gyroid morphologies from block copolymer self-assembly are presented.

  9. Fabrication of bioinspired nanostructured materials via colloidal self-assembly

    Science.gov (United States)

    Huang, Wei-Han

    ultimate strains than nacre and pure GO paper (also synthesized by filtration). Specifically, it exhibits ˜30 times higher fracture energy than filtrated graphene paper and nacre, ˜100 times tougher than filtrated GO paper. Besides reinforced nanocomposites, we further explored the self-assembly of spherical colloids and the templating nanofabrication of moth-eye-inspired broadband antireflection coatings. Binary crystalline structures can be easily accomplished by spin-coating double-layer nonclose-packed colloidal crystals as templates, followed by colloidal templating. The polymer matrix between self-assembled colloidal crystal has been used as a sacrificial template to define the resulting periodic binary nanostructures, including intercalated arrays of silica spheres and polymer posts, gold nanohole arrays with binary sizes, and dimple-nipple antireflection coatings. The binary-structured antireflection coatings exhibit better antireflective properties than unitary coatings. Natural optical structures and nanocomposites teach us a great deal on how to create high performance artificial materials. The bottom-up technologies developed in this thesis are scalable and compatible with standard industrial processes, promising for manufacturing high-performance materials for the benefits of human beings.

  10. Self-assembled ultra small ZnO nanocrystals for dye-sensitized solar cell application

    International Nuclear Information System (INIS)

    We demonstrate a facile chemical approach to produce self-assembled ultra-small mesoporous zinc oxide nanocrystals using sodium salicylate (SS) as a template under hydrothermal conditions. These ZnO nanomaterials have been successfully fabricated as a photoanode for the dye-sensitized solar cell (DSSC) in the presence of N719 dye and iodine–triiodide electrolyte. The structural features, crystallinity, purity, mesophase and morphology of the nanostructure ZnO are investigated by several characterization tools. N2 sorption analysis revealed high surface areas (203 m2 g−1) and narrow pore size distributions (5.1–5.4 nm) for different samples. The mesoporous structure and strong photoluminescence facilitates the high dye loading at the mesoscopic void spaces and light harvesting in DSSC. By utilizing this ultra-small ZnO photoelectrode with film thickness of about 7 μm in the DSSC with an open-circuit voltage (VOC) of 0.74 V, short-circuit current density (JSC) of 3.83 mA cm−2 and an overall power conversion efficiency of 1.12% has been achieved. - Graphical abstract: Ultra-small ZnO nanocrystals have been synthesized with sodium salicylate as a template and using it as a photoanode in a dye-sensitized solar cell 1.12% power conversion efficiency has been observed. - Highlights: • Synthesis of self-assembled ultra-small mesoporous ZnO nanocrystals by using sodium salicylate as a template. • Mesoporous ZnO materials have high BET surface areas and void space. • ZnO nanoparticles serve as a photoanode for the dye-sensitized solar cell (DSSC). • Using ZnO nanocrystals as photoelectrode power conversion efficiency of 1.12% has been achieved

  11. Supramolecular self-assemblies as functional nanomaterials

    Science.gov (United States)

    Busseron, Eric; Ruff, Yves; Moulin, Emilie; Giuseppone, Nicolas

    2013-07-01

    In this review, we survey the diversity of structures and functions which are encountered in advanced self-assembled nanomaterials. We highlight their flourishing implementations in three active domains of applications: biomedical sciences, information technologies, and environmental sciences. Our main objective is to provide the reader with a concise and straightforward entry to this broad field by selecting the most recent and important research articles, supported by some more comprehensive reviews to introduce each topic. Overall, this compilation illustrates how, based on the rules of supramolecular chemistry, the bottom-up approach to design functional objects at the nanoscale is currently producing highly sophisticated materials oriented towards a growing number of applications with high societal impact.

  12. Self-assembly of block copolymers

    Directory of Open Access Journals (Sweden)

    Hidenori Otsuka

    2001-05-01

    Full Text Available Block copolymers in a selective solvent have a tendency to self-assemble at surfaces and into micelles1–4. At an aqueous interface, the amphiphilic property of block copolymers composed of hydrophilic and hydrophobic segments can cause the distal end of the hydrophilic chain to extend into the bulk aqueous solution, anchoring the hydrophilic block to the substrate surface through hydrophobic segments1, 2. In an aqueous solution, micelles with core-shell structure are formed by the segregation of insoluble blocks into the core, which is surrounded by a hydrophilic shell composed of hydrophilic blocks3, 4. This interfacial activity of amphiphilic block copolymers provides their utility in the biomedical field as colloidal dispersants, surface modifiers and drug carriers, prompting many studies of block copolymer adsorption on solid surfaces5, 6, 7, 8, force measurements between tethered layers9, 10, 11 and the characterization of micelle properties12, 13, 14.

  13. Pseudotannins self-assembled into antioxidant complexes.

    Science.gov (United States)

    Cheng, H A; Drinnan, C T; Pleshko, N; Fisher, O Z

    2015-10-21

    Natural tannins are attractive as building blocks for biomaterials due to their antioxidant properties and ability to form interpolymer complexes (IPCs) with other macromolecules. One of the major challenges to tannin usage in biomedical applications is their instability at physiological conditions and a lack of control over the purity and reactivity. Herein, we report the synthesis and characterization of tannin-like polymers with controlled architecture, reactivity, and size. These pseudotannins were synthesized by substituting linear dextran chains with gallic, resorcylic, and protocatechuic pendant groups to mimic the structure of natural hydrolysable tannins. We demonstrate that these novel materials can self-assemble to form reductive and colloidally stable nanoscale and microscale particles. Specifically, the synthesis, turbidity, particle size, antioxidant power, and cell uptake of IPCs derived from pseudotannins and poly(ethylene glycol) was evaluated. PMID:26313262

  14. Shape Restoration by Active Self-Assembly

    Directory of Open Access Journals (Sweden)

    D. Arbuckle

    2005-01-01

    Full Text Available Shape restoration is defined as the problem of constructing a desired, or goal, solid shape Sg by growing an initial solid Si, which is a subset of the goal but is otherwise unknown. This definition attempts to capture abstractly a situation that often arises in the physical world when a solid object loses its desired shape due to wear and tear, corrosion or other phenomena. For example, if the top of the femur becomes distorted, the hip joint no longer functions properly and may have to be replaced surgically. Growing it in place back to its original shape would be an attractive alternative to replacement. This paper presents a solution to the shape restoration problem by using autonomous assembly agents (robots that self-assemble to fill the volume between Sg and Si. If the robots have very small dimension (micro or nano, the desired shape is approximated with high accuracy. The assembly agents initially execute a random walk. When two robots meet, they may exchange a small number of messages. The robot behavior is controlled by a finite state machine with a small number of states. Communication contact models chemical communication, which is likely to be the medium of choice for robots at the nanoscale, while small state and small messages are limitations that also are expected of nanorobots. Simulations presented here show that swarms of such robots organize themselves to achieve shape restoration by using distributed algorithms. This is one more example of an interesting geometric problem that can be solved by the Active Self-Assembly paradigm introduced in previous papers by the authors.

  15. Self-assembled levan nanoparticles for targeted breast cancer imaging.

    Science.gov (United States)

    Kim, Sun-Jung; Bae, Pan Kee; Chung, Bong Hyun

    2015-01-01

    We report on the targeted imaging of breast cancer using self-assembled levan nanoparticles. Indocyanine green (ICG) was encapsulated in levan nanoparticles via self-assembly. Levan-ICG nanoparticles were found to be successfully accumulated in breast cancer via specific interaction between fructose moieties in levan and overexpressed glucose transporter 5 in breast cancer cells. PMID:25383444

  16. Self-assembly behaviour of conjugated terthiophene surfactants in water

    NARCIS (Netherlands)

    van Rijn, Patrick; Janeliunas, Dainius; Brizard, Aurelie M.; Stuart, Marc C. A.; Koper, Ger J. M.; Eelkema, Rienk; van Esch, Jan H.

    2011-01-01

    Conjugated self-assembled systems in water are of great interest because of their potential application in biocompatible supramolecular electronics, but so far their supramolecular chemistry remains almost unexplored. Here we present amphiphilic terthiophenes as a general self-assembling platform fo

  17. Self-Assembly of Micromachining Systems Powered by Janus Micromotors.

    Science.gov (United States)

    Maggi, Claudio; Simmchen, Juliane; Saglimbeni, Filippo; Katuri, Jaideep; Dipalo, Michele; De Angelis, Francesco; Sanchez, Samuel; Di Leonardo, Roberto

    2016-01-27

    Janus particles can self-assemble around microfabricated gears in reproducible configurations with a high degree of spatial and orientational order. The final configuration maximizes the torque applied on the rotor leading to a unidirectional and steady rotating motion. The interplay between geometry and dynamical behavior leads to the self-assembly of Janus micromotors starting from randomly distributed particles. PMID:26649462

  18. Efficient energy transfer in light-harvesting systems, I: optimal temperature, reorganization energy, and spatial-temporal correlations

    CERN Document Server

    Wu, Jianlan; Shen, Young; Cao, Jianshu; Silbey, Robert J

    2010-01-01

    Understanding the mechanisms of efficient and robust energy transfer in light-harvesting systems provides new insights for the optimal design of artificial systems. In this paper, we use the Fenna-Matthews-Olson (FMO) protein complex and phycocyanin 645 (PC 645) to explore the general dependence on physical parameters that help maximize the efficiency and maintain its stability. With the Haken-Strobl model, the maximal energy transfer efficiency (ETE) is achieved under an intermediate optimal value of dephasing rate. Guided by the insight, we use the generalized Bloch-Redfield (GBR) equation approach to correctly describe dissipative exciton dynamics and find that maximal ETE can be achieved under various physical conditions, including temperature, reorganization energy, and spatial-temporal correlations in noise. We also identify regimes of reorganization energy where the ETE changes monotonically with temperature or spatial correlation and therefore cannot be optimized with respect to these two variables.

  19. Role of peripheral phenanthroline groups in the self-assembly of self-assembled molecular triangles

    Indian Academy of Sciences (India)

    Mili C Naranthatta; V Ramkumar; Dillip Kumar Chand

    2015-02-01

    Self-assembled molecular triangles [Pd3(phen)3(imidazolate)3](NO3)3, 1a and [Pd3(phen)3 (imidazolate)3](PF6)3, 1b are prepared by the combination of imidazole with Pd(phen)(NO3)2 and Pd(phen) (PF6)2, respectively. Imidazole was deprotonated during the complexation reactions and the imidazolate so formed acted as a bis-monodentate bridging ligand to form the bowl-shaped trinuclear architectures of 1a/b. Relative orientation of the imidazolate moieties can be best described as syn,anti,anti as observed in the crystal structure of 1b. However, in solution state, slow conformational changes are assumed on the basis of 1HNMR spectral data. The molecular triangles are crafted with three peripheral phen units capable of − stacking interactions. Well-fashioned intermolecular − interactions are observed in the solid-state, wherein further self-assembly of already self-assembled triangle is observed.

  20. Small-angle neutron scattering studies of chemical reaction and reaction-induced self-assembly

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, H. [Advanced Science Research Center(ASRC), Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195 (Japan); Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8501 (Japan); Koizumi, S. [Advanced Science Research Center(ASRC), Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195 (Japan); Hashimoto, T. [Advanced Science Research Center(ASRC), Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195 (Japan) and Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8501 (Japan)]. E-mail: hashimoto.takeji@jaea.go.jp; Kurosaki, K. [Department of Materials Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8501 (Japan); Ohmae, M. [Department of Materials Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8501 (Japan); Kobayashi, S. [Department of Materials Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8501 (Japan)

    2006-11-15

    We have investigated a self-assembling process of cellulose artificially synthesized via enzymatic polymerization by means of in-situ and time-resolved small-angle neutron scattering (SANS). The results elucidated the following: (i) cellulose molecules were synthesized at a special reaction site of the enzyme (cellulase) located on or near the smooth surface of the self-assembled enzymes formed in the reaction medium; (ii) the synthesized molecules associated themselves via diffusion-limited aggregation (DLA) and crystallized into fibrils and (iii) the fibrils formed the aggregates, which had the surface fractal dimension D {sub s} increasing from 2 to 2.3 with the reaction time, on the smooth surface of the enzyme aggregates.

  1. Bio-Photoelectrochemical Solar Cells Incorporating Reaction Center and Reaction Center Plus Light Harvesting Complexes

    Science.gov (United States)

    Yaghoubi, Houman

    onto Au electrodes via surface exposed cysteine residues. This resulted in photocurrent densities as large as ~600 nA cm-2 while still the incident photon to generated electron quantum efficiency was as low as %3 x 10-4. 2- The second approach is to immobilize wild type RCs of Rhodobacter sphaeroides on the surface of a Au underlying electrode using self-assembled monolayers of carboxylic acid terminated oligomers and cytochrome c charge mediating layers, with a preferential orientation from the primary electron donor site. This approach resulted in EQE of up to 0.06%, which showed 200 times efficiency improvement comparing to the first approach. In the third approach, instead of isolated protein complexes, RCs plus light harvesting (LH) complexes were employed for a better photon absorption. Direct attachment of RC-LH1 complexes on Au working electrodes, resulted in 0.21% EQE which showed 3.5 times efficiency improvement over the second approach (700 times higher than the first approach). The main impact of this work is the harnessing of biological RCs for efficient energy harvesting in man-made structures. Specifically, the results in this work will advance the application of RCs in devices for energy harvesting and will enable a better understanding of bio and nanomaterial interfaces, thereby advancing the application of biological materials in electronic devices. At the end, this work offers general guidelines that can serve to improve the performance of bio-hybrid solar cells.

  2. Surface modification by using of immobilized electrostatic self-assembly of bacteriorhodopsin as protein memory

    Directory of Open Access Journals (Sweden)

    Ashkan Zare Karizak

    2014-11-01

    Full Text Available Bacteriorhodopsin (BR is the light harvesting and photoactive proton pump found in the membrane of a salt marsh bacteria. This protein has significant potential to use in optical computing and memory devices due to unique intrinsic physical properties of photo and bioelectric. All these features make BR one of the most promising protein candidates in protein memories. Protein memory is a kind of optical memory with a large storage capacity and high speed processing features. BR protein was used with the polymer film in order to create better stability. In order to investigate immobilization of electrostatic self-assembly of BR on glass and polycarbonate as protein memories was used. Polycarbonate is a layer of compact disc (CD structure which considered dye immobilized on its surface and have reading and writing abilities of information via 0,1 bites. In this study, surfaces of polycarbonate modified by the mixture of 5% sulfuric acid and 20% acetic acid; furthermore, by using of PEI as cationic resin the surface of polycarbonate was charged and BR immobilized on it electrostatically. The modified surfaces were characterized by AFM technique. Also, light activity for reading data is retained. This is an appropriate method for optimal stability and activity assay of the protein and also is suitable for preparation of protein memories.

  3. {beta}-Carotene to bacteriochlorophyll c energy transfer in self-assembled aggregates mimicking chlorosomes

    Energy Technology Data Exchange (ETDEWEB)

    Alster, J. [Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 121 16 Praha (Czech Republic); Polivka, T. [Institute of Physical Biology, University of South Bohemia, Zamek 136, 373 33 Nove Hrady (Czech Republic); Biology Centre, Academy of Sciences of the Czech Republic, Branisovska 31, 370 05 Ceske Budejovice (Czech Republic); Arellano, J.B. [Instituto de Recursos Naturales y Agrobiologia de Salamanca (IRNASA-CSIC), Apdo. 257, 37071 Salamanca (Spain); Chabera, P. [Institute of Physical Biology, University of South Bohemia, Zamek 136, 373 33 Nove Hrady (Czech Republic); Vacha, F. [Institute of Physical Biology, University of South Bohemia, Zamek 136, 373 33 Nove Hrady (Czech Republic); Biology Centre, Academy of Sciences of the Czech Republic, Branisovska 31, 370 05 Ceske Budejovice (Czech Republic); Psencik, J., E-mail: psencik@karlov.mff.cuni.cz [Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 121 16 Praha (Czech Republic); Institute of Physical Biology, University of South Bohemia, Zamek 136, 373 33 Nove Hrady (Czech Republic)

    2010-07-19

    Carotenoids are together with bacteriochlorophylls important constituents of chlorosomes, the light-harvesting antennae of green photosynthetic bacteria. Majority of bacteriochlorophyll molecules form self-assembling aggregates inside the chlorosomes. Aggregates of bacteriochlorophylls with optical properties similar to those of chlorosomes can also be prepared in non-polar organic solvents or in aqueous environments when a suitable non-polar molecule is added. In this work, the ability of {beta}-carotene to induce aggregation of bacteriochlorophyll c in aqueous buffer was studied. Excitation relaxation and energy transfer in the carotenoid-bacteriochlorophyll assemblies were measured using femtosecond and nanosecond transient absorption spectroscopy. A fast, {approx}100-fs energy transfer from the S{sub 2} state of {beta}-carotene to bacteriochlorophyll c was revealed, while no evidence for significant energy transfer from the S{sub 1} state was found. Picosecond formation of the carotenoid triplet state (T{sub 1}) was observed, which was likely generated by singlet homo-fission from the S{sub 1} state of {beta}-carotene.

  4. Controlling decay dynamics of quantum emitters with Plsmonic self assembly templates

    Science.gov (United States)

    Indukuri, S. R. K. Chaitanya; Basu, J. K.

    2015-03-01

    Controlling the emission of quantum dots by tailoring local density of states(LDOS) in self assembled plasmonic template. Using very small diameter gold (Au) spherical nanoantenna within a polymer tem plate randomly dispersed with quantum dots, we show how the photoluminescence intensity and lifetime anisotropy of these dots can be significantly enhanced through LDOS tuning. We also studied the effect of dispersion, wider range of geometric and spectral parameters bringing out the versatility of these functional plasmonic templates. We studied the effect of nano antenna distribution on radiative and non radiative decay rates in the templates. We demonstrated that the decay dynamics in the plasmonic templates can be controlled in a facile manner by changing the filling fraction of the Au nanoparticles. This polarization dependent anisotropic decay dynamics for the quantum emitters is determined by polarization dependent LDOS of the plasmonic templates as demonstrated by FDTD simulations. Our work provides a new method to achieve spontaneous emission intensity and anisotropy enhancement with nanoscale plasmon resonators for applications from controlled photon emitters to light harvesting. DST, India Nanomission.

  5. The Power of Nondeterminism in Self-Assembly

    CERN Document Server

    Bryans, Nathaniel; Doty, David; Kari, Lila; Seki, Shinnosuke

    2010-01-01

    We investigate the role of nondeterminism in Winfree's abstract Tile Assembly Model (aTAM), which was conceived to model artificial molecular self-assembling systems constructed from DNA. Of particular practical importance is to find tile systems that minimize resources such as the number of distinct tile types, each of which corresponds to a set of DNA strands that must be custom-synthesized in actual molecular implementations of the aTAM. We seek to identify to what extent the use of nondeterminism in tile systems affects the resources required by such molecular shape-building algorithms. We first show a "molecular computability theoretic" result: there is an infinite shape S that is uniquely assembled by a tile system but not by any deterministic tile system. We then show an analogous phenomenon in the finitary "molecular complexity theoretic" case: there is a finite shape S that is uniquely assembled by a tile system with c tile types, but every deterministic tile system that uniquely assembles S has mor...

  6. Solvent mediated self-assembly of solids

    Energy Technology Data Exchange (ETDEWEB)

    De Yoreo, J.; Wilson, W.D.; Palmore, T.

    1997-12-12

    Solvent-mediated crystallization represents a robust approach to self-assembly of nanostructures and microstructures. In organic systems, the relative ease with which the structure of hydrogen- bonded molecules can be manipulated allows for generation of a wide variety of nanoscale crystal structures. In living organisms, control over the micron-to-millimeter form of inorganic crystals is achieved through introduction of bio-organic molecules. The purpose of this proposal is to understand the interplay between solution chemistry, molecular structure, surface chemistry, and the processes of nucleation and crystal growth in solvent-mediated systems, with the goal of developing the atomic and molecular basis of a solvent-mediated self-assembly technology. We will achieve this purpose by: (1) utilizing an atomic force microscopy (AFM) approach that provides in situ, real time imaging during growth from solutions, (2) by modifying kinetic Monte Carlo (KMC) models to include solution-surface kinetics, (3) by introducing quantum chemistry (QC) calculations of the potentials of the relevant chemical species and the near-surface structure of the solution, and (4) by utilizing molecular dynamics (MD) simulations to identify the minimum energy pathways to the solid state. Our work will focus on two systems chosen to address both the manometer and micron-to-millimeter length scales of assembly, the family of 2,5- diketopiperazines (X-DKPs) and the system of CaCO{sub 3} with amino acids. Using AFM, we will record the evolution of surface morphology, critical lengths, step speeds, and step-step interactions as a function of supersaturation and temperature. In the case of the X-DKPs, these measurements will be repeated as the molecular structure of the growth unit is varied. In the case of CaCO{sub 3}, they will be performed as a function of solution chemistry including pH, ionic strength, and amino acid content. In addition, we will measure nucleation rates and orientations of

  7. Designed self-assembly of molecular necklaces.

    Science.gov (United States)

    Park, Ki-Min; Kim, Soo-Young; Heo, Jungseok; Whang, Dongmok; Sakamoto, Shigeru; Yamaguchi, Kentaro; Kim, Kimoon

    2002-03-13

    This paper reports an efficient strategy to synthesize molecular necklaces, in which a number of small rings are threaded onto a large ring, utilizing the principles of self-assembly and coordination chemistry. Our strategy involves (1) threading a molecular "bead" with a short "string" to make a pseudorotaxane and then (2) linking the pseudorotaxanes with a metal complex with two cis labile ligands acting as an "angle connector" to form a cyclic product (molecular necklace). A 4- or 3-pyridylmethyl group is attached to each end of 1,4-diaminobutane or 1,5-diaminopentane to produce the short "strings" (C4N4(2+), C4N3(2+), C5N4(2+), and C5N3(2+)), which then react with a cucurbituril (CB) "bead" to form stable pseudorotaxanes (PR44(2+), PR43(2+), PR54(2+), and PR53(2+), respectively). The reaction of the pseudorotaxanes with Pt(en)(NO(3))(2) (en = ethylenediamine) produces a molecular necklace [4]MN, in which three molecular "beads" are threaded on a triangular framework, and/or a molecular necklace [5]MN, in which four molecular "beads" are threaded on a square framework. Under refluxing conditions, the reaction with PR44(2+) or PR54(2+) yields exclusively [4]MN (MN44T or MN54T, respectively), whereas that with PR43(2+) or PR53(2+) produces exclusively [5]MN (MN43S or MN53S, respectively). The products have been characterized by various methods including X-ray crystallography. At lower temperatures, on the other hand, the reaction with PR44(2+) or PR54(2+) affords both [4]MN and [5]MN. The supermolecules reported here are the first series of molecular necklaces obtained as thermodynamic products. The overall structures of the molecular necklaces are strongly influenced by the structures of pseudorotaxane building blocks, which is discussed in detail on the basis of the X-ray crystal structures. The temperature dependence of the product distribution observed in this self-assembly process is also discussed. PMID:11878967

  8. Light harvesting via energy transfer in the dye solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Siegers, Conrad

    2007-11-09

    The PhD-thesis ''Light Harvesting via Energy Transfer in the Dye Solar Cell'' (University of Freiburg, July 2007) describes the conceptual design, synthesis and testing of energy donor acceptor sensitizers for the dye solar cell (DSC). Under monochromatic illumination solar cells sensitized with the novel donor acceptor systems revealed a higher power conversion efficiency than cells containing exclusively the acceptor component. The following approach led to this conclusion: (i) the choice of suitable chromophores as energy donor and acceptor moieties according to the Foerster-theory, (ii) the synthesis of different donor acceptor systems, (iii) the development of a methodology allowing the quantification of energy transfer within dye solar cells, and (iv) the evaluation of characteristics of DSCs that were sensitized with the different donor acceptor systems. The acceptor chromophores used in this work were derived from [Ru(dcbpy)2acac]Cl (dcbpy = 4,4'-dicarboxy-2,2'-bipyridin, acac = acetylacetonato). This complex offered the opportunity to introduce substituents at the acac-ligand's terminal CH3 groups without significantly affecting its excellent photoelectrochemical properties. Alkylated 4-amino-1,8-naphthalimides (termed Fluorols in the following) were used as energy donor chromophores. This class of compounds fulfils the requirements for efficient energy transfer to [Ru(dcbpy)2acac]Cl. Covalently linking donor and acceptor chromophores to one another was achieved by two different concepts. A dyad comprising one donor and one acceptor chromophore was synthesized by subsequent hydrosilylation steps of an olefin-bearing donor and an acceptor precursor to the dihydrosilane HSiMe2-CH2CH2-SiMe2H. A series of polymers comprising multiple donor and acceptor units was made by the addition of alkyne-bearing chromophores to hyperbranched polyglycerol azide (''Click-chemistry''). In this series the donor acceptor

  9. Initial condition of stochastic self-assembly

    Science.gov (United States)

    Davis, Jason K.; Sindi, Suzanne S.

    2016-02-01

    The formation of a stable protein aggregate is regarded as the rate limiting step in the establishment of prion diseases. In these systems, once aggregates reach a critical size the growth process accelerates and thus the waiting time until the appearance of the first critically sized aggregate is a key determinant of disease onset. In addition to prion diseases, aggregation and nucleation is a central step of many physical, chemical, and biological process. Previous studies have examined the first-arrival time at a critical nucleus size during homogeneous self-assembly under the assumption that at time t =0 the system was in the all-monomer state. However, in order to compare to in vivo biological experiments where protein constituents inherited by a newly born cell likely contain intermediate aggregates, other possibilities must be considered. We consider one such possibility by conditioning the unique ergodic size distribution on subcritical aggregate sizes; this least-informed distribution is then used as an initial condition. We make the claim that this initial condition carries fewer assumptions than an all-monomer one and verify that it can yield significantly different averaged waiting times relative to the all-monomer condition under various models of assembly.

  10. Self-Assembly of Tetraphenylalanine Peptides.

    Science.gov (United States)

    Mayans, Enric; Ballano, Gema; Casanovas, Jordi; Díaz, Angélica; Pérez-Madrigal, Maria M; Estrany, Francesc; Puiggalí, Jordi; Cativiela, Carlos; Alemán, Carlos

    2015-11-16

    Three different tetraphenylalanine (FFFF) based peptides that differ at the N- and C-termini have been synthesized by using standard procedures to study their ability to form different nanoassemblies under a variety of conditions. The FFFF peptide assembles into nanotubes that show more structural imperfections at the surface than those formed by the diphenylalanine (FF) peptide under the same conditions. Periodic DFT calculations (M06L functional) were used to propose a model that consists of three FFFF molecules defining a ring through head-to-tail NH3(+)⋅⋅⋅(-)OOC interactions, which in turn stack to produce deformed channels with internal diameters between 12 and 16 Å. Depending on the experimental conditions used for the peptide incubation, N-fluorenylmethoxycarbonyl (Fmoc) protected FFFF self-assembles into a variety of polymorphs: ultra-thin nanoplates, fibrils, and star-like submicrometric aggregates. DFT calculations indicate that Fmoc-FFFF prefers a parallel rather than an antiparallel β-sheet assembly. Finally, coexisting multiple assemblies (up to three) were observed for Fmoc-FFFF-OBzl (OBzl = benzyl ester), which incorporates aromatic protecting groups at the two peptide terminals. This unusual and noticeable feature is attributed to the fact that the assemblies obtained by combining the Fmoc and OBzl groups contained in the peptide are isoenergetic. PMID:26419936

  11. Self-assembling holographic biosensors and biocomputers.

    Energy Technology Data Exchange (ETDEWEB)

    Light, Yooli Kim; Bachand, George David (Sandia National Laboratories, Albuquerque, NM); Schoeniger, Joseph S.; Trent, Amanda M. (Sandia National Laboratories, Albuquerque, NM)

    2006-05-01

    We present concepts for self-assembly of diffractive optics with potential uses in biosensors and biocomputers. The simplest such optics, diffraction gratings, can potentially be made from chemically-stabilized microtubules migrating on nanopatterned tracks of the motor protein kinesin. We discuss the fabrication challenges involved in patterning sub-micron-scale structures with proteins that must be maintained in aqueous buffers to preserve their activity. A novel strategy is presented that employs dry contact printing onto glass-supported amino-silane monolayers of heterobifunctional crosslinkers, followed by solid-state reactions of these cross-linkers, to graft patterns of reactive groups onto the surface. Successive solution-phase addition of cysteine-mutant proteins and amine-reactive polyethylene glycol allows assembly of features onto the printed patterns. We present data from initial experiments showing successful micro- and nanopatterning of lines of single-cysteine mutants of kinesin interleaved with lines of polyethylene, indicating that this strategy can be employed to arrays of features with resolutions suitable for gratings.

  12. Restricted meniscus convective self-assembly.

    Science.gov (United States)

    Chen, Kai; Stoianov, Stefan V; Bangerter, Justin; Robinson, Hans D

    2010-04-15

    Convective (or evaporation-induced) self-assembly is a standard technique for depositing uniform, poly-crystalline coatings of nanospheres across multiple square centimeters on the timescale of minutes. In this paper, we present a variation of this technique, where the drying meniscus is restricted by a straight-edge located approximately 100 microm above the substrate adjacent to the drying zone. Surprisingly, we find this technique to yield films at roughly twice the growth rate compared to the standard technique. We attribute this to differing rates of diffusion of vapor from the drying crystal in the two cases. We also investigate the crystal growth rate dependence on ambient relative humidity and find, contrary to some previous reports, that the growth rate depends strongly on the humidity. We introduce a model which indicates that while the length of the drying zone may increase with humidity, this alone cannot compensate for the simultaneous reduction in evaporation rate, so a lower humidity must always lead to a higher growth speed. Comparing the model to our experimental results, we find that the length of the drying zone is constant and mostly independent of parameters such as humidity and surface tension. PMID:20132947

  13. Functional Self-Assembled Nanofibers by Electrospinning

    Science.gov (United States)

    Greiner, A.; Wendorff, J. H.

    Electrospinning constitutes a unique technique for the production of nanofibers with diameters down to the range of a few nanometers. In strong contrast to conventional fiber producing techniques, it relies on self-assembly processes driven by the Coulomb interactions between charged elements of the fluids to be spun to nanofibers. The transition from a macroscopic fluid object such as a droplet emerging from a die to solid nanofibers is controlled by a set of complex physical instability processes. They give rise to extremely high extensional deformations and strain rates during fiber formation causing among others a high orientational order in the nanofibers as well as enhanced mechanical properties. Electrospinning is predominantly applied to polymer based materials including natural and synthetic polymers, but, more recently, its use has been extended towards the production of metal, ceramic and glass nanofibers exploiting precursor routes. The nanofibers can be functionalized during electrospinning by introducing pores, fractal surfaces, by incorporating functional elements such as catalysts, quantum dots, drugs, enzymes or even bacteria. The production of individual fibers, random nonwovens, or orientationally highly ordered nonwovens is achieved by an appropriate selection of electrode configurations. Broad areas of application exist in Material and Life Sciences for such nanofibers, including not only optoelectronics, sensorics, catalysis, textiles, high efficiency filters, fiber reinforcement but also tissue engineering, drug delivery, and wound healing. The basic electrospinning process has more recently been extended towards compound co-electrospinning and precision deposition electrospinning to further broaden accessible fiber architectures and potential areas of application.

  14. Equation of State for Phospholipid Self-Assembly

    DEFF Research Database (Denmark)

    Marsh, Derek

    2016-01-01

    Phospholipid self-assembly is the basis of biomembrane stability. The entropy of transfer from water to self-assembled micelles of lysophosphatidylcholines and diacyl phosphatidylcholines with different chain lengths converges to a common value at a temperature of 44°C. The corresponding enthalpies...... of transfer converge at ∼-18°C. An equation of state for the free energy of self-assembly formulated from this thermodynamic data depends on the heat capacity of transfer as the sole parameter needed to specify a particular lipid. For lipids lacking calorimetric data, measurement of the critical...

  15. Atomic structures of peptide self-assembly mimics

    OpenAIRE

    Makabe, Koki; McElheny, Dan; Tereshko, Valentia; Hilyard, Aaron; Gawlak, Grzegorz; Yan, Shude; Koide, Akiko; Koide, Shohei

    2006-01-01

    Although the β-rich self-assemblies are a major structural class for polypeptides and the focus of intense research, little is known about their atomic structures and dynamics due to their insoluble and noncrystalline nature. We developed a protein engineering strategy that captures a self-assembly segment in a water-soluble molecule. A predefined number of self-assembling peptide units are linked, and the β-sheet ends are capped to prevent aggregation, which yields a mono-dispersed soluble p...

  16. Self-assembly of latex particles for colloidal crystals

    Institute of Scientific and Technical Information of China (English)

    Zhirong Li; Jingxia wang; Yanlin Song

    2011-01-01

    Self-assembly of latex particles is of great importance for fabricating various functional colloidal crystals.In this paper,we review recent research on the self-assembly of latex particles for colloidal crystals,covering the assembly forces and various assembly approaches of latex particles,including self-assembly by gravity sedimentation,vertical deposition,physical confinement,electric field,and magnetic field.Furthermore,some simple methods for assembling latex particles such as spin coating,spray coating,and printing are also summarized.

  17. Enhancing light-harvesting power with coherent vibrational interactions: a quantum heat engine picture

    CERN Document Server

    Killoran, Nathan; Plenio, Martin B

    2014-01-01

    Recent evidence suggests that quantum effects may have functional importance in biological light-harvesting systems. Along with delocalized electronic excitations, it is now suspected that quantum coherent interactions with certain near-resonant vibrations contribute to light-harvesting performance. However, the actual quantum advantage offered by such coherent vibrational interactions has not yet been established. We investigate a quantum design principle, whereby coherent exchange of single energy quanta between electronic and vibrational degrees of freedom can enhance a light-harvesting system's power above what is possible by thermal mechanisms alone. We present a prototype quantum heat engine which cleanly illustrates this quantum design principle, and quantify its quantum advantage using thermodynamic measures of performance. We also demonstrate the principle's applicability for realistic biological structures.

  18. A novel type of light-harvesting antenna protein of red algal origin in algae with secondary plastids

    OpenAIRE

    Sturm, Sabine; Engelken, Johannes; Gruber, Ansgar; Vugrinec, Sascha; G. Kroth, Peter; Adamska, Iwona; Lavaud, Johann

    2013-01-01

    Background: Light, the driving force of photosynthesis, can be harmful when present in excess; therefore, any light harvesting system requires photoprotection. Members of the extended light-harvesting complex (LHC) protein superfamily are involved in light harvesting as well as in photoprotection and are found in the red and green plant lineages, with a complex distribution pattern of subfamilies in the different algal lineages.Results: Here, we demonstrate that the recently discovered "red l...

  19. Nanoparticles Self-Assembly Driven by High Affinity Repeat Protein Pairing.

    Science.gov (United States)

    Gurunatha, Kargal L; Fournier, Agathe C; Urvoas, Agathe; Valerio-Lepiniec, Marie; Marchi, Valérie; Minard, Philippe; Dujardin, Erik

    2016-03-22

    Proteins are the most specific yet versatile biological self-assembling agents with a rich chemistry. Nevertheless, the design of new proteins with recognition capacities is still in its infancy and has seldom been exploited for the self-assembly of functional inorganic nanoparticles. Here, we report on the protein-directed assembly of gold nanoparticles using purpose-designed artificial repeat proteins having a rigid but modular 3D architecture. αRep protein pairs are selected for their high mutual affinity from a library of 10(9) variants. Their conjugation onto gold nanoparticles drives the massive colloidal assembly of free-standing, one-particle thick films. When the average number of proteins per nanoparticle is lowered, the extent of self-assembly is limited to oligomeric particle clusters. Finally, we demonstrate that the aggregates are reversibly disassembled by an excess of one free protein. Our approach could be optimized for applications in biosensing, cell targeting, or functional nanomaterials engineering. PMID:26863288

  20. Optical orientation in self assembled quantum dots

    International Nuclear Information System (INIS)

    We examined Zeeman splitting in a series of lnxGa(1-x)As/GaAs self assembled quantum dots (SAQD's) with different pump polarisations. All these measurements were made in very low external magnetic fields where direct determination of the Zeeman splitting energy is impossible due to its small value in comparison to the photoluminescence linewidths. The use of a technique developed by M. J. Snelling allowed us to obtain the Zeeman splitting and hence the excitonic g-factors indirectly. We observed a linear low field splitting, becoming increasingly non-linear at higher fields. We attribute this non-linearity to field induced level mixing. It is believed these are the first low field measurements in these structures. A number of apparent nuclear effects in the Zeeman splitting measurements led us onto the examination of nuclear effects in these structures. The transverse and oblique Hanie effects then allowed us to obtain the sign of the electronic g-factors in two of our samples, for one sample, a (311) grown In0.5Ga0.5As/GaAs SAQD sample, we were able to ascertain the spin relaxation time, the maximum value of the nuclear field, and provide evidence of the existence of nuclear spin freezing in at least one of our samples. We have then used a novel technique investigated by D. J. Guerrier, to examine optically detected nuclear magnetic resonance in our samples. We believe this is the first such study on these structures. We could not ascertain the dipolar indium resonance signal, even though all other isotopes were seen. We have therefore suggested a number of possible mechanisms that may be responsible for the lack of an indium resonance signal. (author)

  1. Biohydrogen production with the light-harvesting function of grana from spirulina and colloidal platinum

    Energy Technology Data Exchange (ETDEWEB)

    Amao, Yutaka; Nakamura, Naoki [Department of Applied Chemistry, Oita University Dannoharu 700, Oita 870-1192 (Japan)

    2006-01-15

    Biohydrogen production with the light-harvesting function of grana from spirulina by use of three-component system consisting of NADH, methylviologen (MV{sup 2+}) and colloidal platinum was investigated. The decay rate of chlorophyll included in grana was suppressed by addition of NADH and little degradation was observed in 120min irradiation. The biohydrogen production system was developed using the light-harvesting function of grana and platinum colloid in the presence of NADH and MV{sup 2+} and the amount of hydrogen produced was estimated to be 0.14{mu}mol after 4h irradiation. (author)

  2. Self-Assembled Nanostructured Health Monitoring Sensors Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The objective of the proposed NASA SBIR program is to design, fabricate and evaluate the performance of self-assembled nanostructured sensors for the health...

  3. Self-assembled microsphere gratings on rib waveguides

    OpenAIRE

    Tai, Chao-Yi; Unal, Bayram; Wilkinson, James S.; Mohamed A. Ghanem; Bartlett, Philip N.

    2003-01-01

    We report the spectral transmission of a rib waveguide side-coupled to a self-assembled polystyrene microsphere array. A transmission stopband was observed at ? ~ 1590nm, showing the potential for realising wavelength-selective devices

  4. Self-Assembling Wireless Autonomous Reconfigurable Modules (SWARM) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Payload Systems Inc. and the MIT Space Systems Laboratory propose Self-assembling, Wireless, Autonomous, Reconfigurable Modules (SWARM) as an innovative approach to...

  5. Urethane tetrathiafulvalene derivatives: synthesis, self-assembly and electrochemical properties

    Directory of Open Access Journals (Sweden)

    Xiang Sun

    2015-11-01

    Full Text Available This paper reports the self-assembly of two new tetrathiafulvalene (TTF derivatives that contain one or two urethane groups. The formation of nanoribbons was evidenced by scanning electron microscopy (SEM and X-ray diffraction (XRD, which showed that the self-assembly ability of T1 was better than that of T2. The results revealed that more urethane groups in a molecule did not necessarily instigate self-assembly. UV–vis and FTIR spectra were measured to explore noncovalent interactions. The driving forces for self-assembly of TTF derivatives were mainly hydrogen bond interactions and π–π stacking interactions. The electronic conductivity of the T1 and T2 films was tested by a four-probe method.

  6. Scaling up self-assembly: bottom-up approaches to macroscopic particle organization.

    Science.gov (United States)

    Lash, M H; Fedorchak, M V; McCarthy, J J; Little, S R

    2015-07-28

    This review presents an overview of recent work in the field of non-Brownian particle self-assembly. Compared to nanoparticles that naturally self-assemble due to Brownian motion, larger, non-Brownian particles (d > 6 μm) are less prone to autonomously organize into crystalline arrays. The tendency for particle systems to experience immobilization and kinetic arrest grows with particle radius. In order to overcome this kinetic limitation, some type of external driver must be applied to act as an artificial "thermalizing force" upon non-Brownian particles, inducing particle motion and subsequent crystallization. Many groups have explored the use of various agitation methods to overcome the natural barriers preventing self-assembly to which non-Brownian particles are susceptible. The ability to create materials from a bottom-up approach with these characteristics would allow for precise control over their pore structure (size and distribution) and surface properties (topography, functionalization and area), resulting in improved regulation of key characteristics such as mechanical strength, diffusive properties, and possibly even photonic properties. This review will highlight these approaches, as well as discuss the potential impact of bottom-up macroscale particle assembly. The applications of such technology range from customizable and autonomously self-assembled niche microenvironments for drug delivery and tissue engineering to new acoustic dampening, battery, and filtration materials, among others. Additionally, crystals made from non-Brownian particles resemble naturally derived materials such as opals, zeolites, and biological tissue (i.e. bone, cartilage and lung), due to their high surface area, pore distribution, and tunable (multilevel) hierarchy. PMID:25947543

  7. Self-assembled helical nanostructures from an asymmetrical perylene diimide

    Institute of Scientific and Technical Information of China (English)

    Lan Ying Yang; Min Min Shi; Mang Wang; Hong Zheng Chen

    2008-01-01

    An asymmetrical perylene diimide 3,N-(4-methoxyphenyl)-N'-(4-nitrophenyl)-perylene-3,4,9,10-tetracarboxylic diimide,was synthesized,and its self-assembly and dissociation behaviors in chloroform was studied in detail bv UV-vis and fluorescence spectroscopies.The resulting unique helical nanostructures from 3 were proposed to be self-assembled via the cooperative actions of π-π stacking,steric hindrance and electrophile-nucleophile type pairing.

  8. Self-assembled functional molecular materials for optoelectronic applications

    OpenAIRE

    Kwok, CC; W. Lu; Che, CM

    2008-01-01

    There has been a growing interest to develop functional organic and organometallic materials in nano-scale by self assembly reactions as these materials could have unique electronic properties and applications. We have found that functionalized organometallic nano-wires which the formations are directed by weak Pt⋯Pt interactions along the dimension of the aggregates can be readily obtained by self-assembly reactions. These platinum(II) nano-wires exhibit interesting photophysical properties,...

  9. Using lateral capillary forces to compute by self-assembly

    OpenAIRE

    Rothemund, Paul W. K.

    2000-01-01

    Investigations of DNA computing have highlighted a fundamental connection between self-assembly (SA) and computation: in principle, any computation can be performed by a suitable self-assembling system. In practice, exploration of this connection is limited by our ability to control the geometry and specificity of binding interactions. Recently, a system has been developed that uses surface tension to assemble plastic tiles according to shape complementarity and likeness of wetting [Bowden, N...

  10. Construction of Supramolecular Architectures via Self-assembly

    Institute of Scientific and Technical Information of China (English)

    Takeharu; Haino

    2007-01-01

    1 Results In this paper we report supramolecular polymeric nano networks formed by the molecular-recognition-directed self-assembly between a calix[5]arene and C60[1]. Covalently-linked double-calix[5]arenes take up C60 into their cavities[2]. This complementary interaction creates a strong non-covalent bonding; thus,the iterative self-assembly between dumbbell fullerene 1 and ditopic host 2 can produce the supramolecular polymer networks (See Fig.1).

  11. Atomic force microscopy investigations of peptide self-assembly

    OpenAIRE

    Sedman, Victoria L.

    2006-01-01

    The ability of short peptide fragments to self-assemble in isolation as amyloid and amyloid-like structures has prompted their use as model systems for the study of amyloid formation and recently also for their utilisation as novel nanofibrillar material. The atomic force microscope (AFM) is used here to investigate the self-assembly of two peptide systems and the development of strategies to directly manipulate and control the structures they form. The studies presented in Chapter 2 addr...

  12. Characterization and utilization of self-assembled diphenylalanine nanotubes

    OpenAIRE

    Xu, Kairuo

    2011-01-01

    Diphenylalanine (FF) peptide is the core-recognition motif of β-amyloid polypeptide, a peptide associated with diseases such as Alzheimer’s and which is known to be capable of self-assembly. FF has attracted interest in nanotechnology due to the physical and chemical stability and mechanical rigidity of the self-assembled nanotube form of the peptide. A number of promising applications of FF nanotubes have previously been explored. To extend this work to biomedical and pharmaceutical areas, a...

  13. RT Self-assembly of Silica Nanoparticles on Optical Fibres

    DEFF Research Database (Denmark)

    Canning, John; Lindoy, Lachlan; Huyang, George;

    2013-01-01

    The room temperature deposition of self-assembling silica nanoparticles onto D-shaped optical fibres x201c;D-fibrex201d;), drawn from milled preforms fabricated by modified chemical vapor deposition, is studied and preliminary results reported here.......The room temperature deposition of self-assembling silica nanoparticles onto D-shaped optical fibres x201c;D-fibrex201d;), drawn from milled preforms fabricated by modified chemical vapor deposition, is studied and preliminary results reported here....

  14. Effect of polymerization on hierarchical self-assembly into nanosheets.

    Science.gov (United States)

    Ikeda, Taichi

    2015-01-20

    The oligomers consisting of phenyl-capped bithiophene and tetra(ethylene glycol)s linked by azide-alkyne Huisgen cycloaddition were synthesized. The relationship between the degree of polymerization and self-assembling ability was investigated in o-dichlorobenzene and dimethyl sulfoxide. From the absorption spectrum, it was confirmed that the critical degree of polymerization (CDP) for thiophene unit aggregation was 4. The morphology of the aggregated product was observed by atomic force microscopy. The oligomers 4mer and 5mer could not self-assemble into well-defined structures due to the weak driving force for the self-assembly. In the cases of 6mer and 7mer, aggregates with nonwell-defined and nanosheet structures coexisted. In the cases of 8mer and 9mer, the nanosheet was the main product. The critical point between 7mer and 8mer could be confirmed by different aggregation behaviors in the cooling process of the solution (nonsigmoidal and sigmoidal). In the cases of 8mer and 9mer, polymer folding prior to intermolecular self-assembly, which was supported by sigmoidal aggregation behavior, leads to the nanosheet formation. On the contrary, shorter oligomers than 8mer experience intermolecular aggregation prior to intramolecular polymer folding, which was supported by the nonsigmoidal aggregation behavior. This is the first report to prove the existence of CDP for folded polymer nanosheet formation which requires hierarchical self-assembly, i.e., polymer folding followed by intermolecular self-assembly. PMID:25526560

  15. Synthetic Self-Assembled Materials in Biological Environments.

    Science.gov (United States)

    Versluis, Frank; van Esch, Jan H; Eelkema, Rienk

    2016-06-01

    Synthetic self-assembly has long been recognized as an excellent approach for the formation of ordered structures on the nanoscale. Although the development of synthetic self-assembling materials has often been inspired by principles observed in nature (e.g., the assembly of lipids, DNA, proteins), until recently the self-assembly of synthetic molecules has mainly been investigated ex vivo. The past few years however, have witnessed the emergence of a research field in which synthetic, self-assembling systems are used that are capable of operating as bioactive materials in biological environments. Here, this up-and-coming field, which has the potential of becoming a key area in chemical biology and medicine, is reviewed. Two main categories of applications of self-assembly in biological environments are identified and discussed, namely therapeutic and imaging agents. Within these categories key concepts, such as triggers and molecular constraints for in vitro/in vivo self-assembly and the mode of interaction between the assemblies and the biological materials will be discussed. PMID:27042774

  16. Photoelectron transport tuning of self-assembled subbands

    Science.gov (United States)

    Xiong, Zhengwei; Wang, Xinmin; Wu, Weidong; Wang, Xuemin; Peng, Liping; Zhao, Yan; Yan, Dawei; Jiang, Tao; Shen, Changle; Zhan, Zhiqiang; Cao, Linhong; Li, Weihua

    2016-02-01

    Conventionally, electrical transport of quantum subbands occurs at very high electric fields, indicating that the medium is easy to break down. In the experiments and practical applications, the extreme condition is difficult to satisfy. For quantum information transmission, low power consumption and convenient implementation are what we expect. In this paper, we engineered a special quantum dot array (QDA) embedded in a single crystal matrix. By external optical field excitation, we found a series of subbands made of the self-assembled QDA discretely located in the matrix. Changing the spacing between the quantum dots leads to the variation of subband spacing. Artificially manipulating the microcosmic QDA system can bring interesting macroscopic effects, such as an enhanced absorption intensity in the ultraviolet range, a blue-shift of the surface plasmon resonance peak and nonlinear absorption changed from two-photon absorption to saturated absorption. The intrinsic mechanism of the subband optical response was revealed due to the strong quantum confinement effect and dominant intraband transitions. The weak surface plasmon resonance absorption of Ni QDA gave an excellent figure of merit of the order of 10-10. The composite films are expectation enough to become a prime candidate for nonlinear applications near 532 nm. Therefore with interplay of the weak optical field and subbands, we achieved a tunable photoelectron transport process.Conventionally, electrical transport of quantum subbands occurs at very high electric fields, indicating that the medium is easy to break down. In the experiments and practical applications, the extreme condition is difficult to satisfy. For quantum information transmission, low power consumption and convenient implementation are what we expect. In this paper, we engineered a special quantum dot array (QDA) embedded in a single crystal matrix. By external optical field excitation, we found a series of subbands made of the self-assembled

  17. Specific RNA self-assembly with minimal paranemic motifs

    Science.gov (United States)

    Afonin, Kirill A.; Cieply, Dennis J.; Leontis, Neocles B.

    2016-01-01

    The paranemic crossover (PX) is a motif for assembling two nucleic acid molecules using Watson-Crick (WC) basepairing without unfolding pre-formed secondary structure in the individual molecules. Once formed, the paranemic assembly motif comprises adjacent parallel double helices that cross over at every possible point over the length of the motif. The interaction is reversible as it does not require denaturation of basepairs internal to each interacting molecular unit. Paranemic assembly has been demonstrated for DNA but not for RNA, and only for motifs with four or more cross-over points and lengths of five or more helical half-turns. Here we report the design of RNA molecules that paranemically assemble with the minimum number of two cross-overs spanning the major groove to form paranemic motifs with a length of three half-turns (3HT). Dissociation constants (Kds) were measured for series of molecules in which the number of basepairs between the cross-over points was varied from five to eight basepairs. The paranemic 3HT complex with six basepairs (3HT_6M) was found to be the most stable with Kd = 1×10−8 M. The half-time for kinetic exchange of the 3HT_6M complex was determined to be ~100 minutes, from which we calculated association and dissociation rate constants ka = 5.11×103 M−1sec−1 and kd = 5.11×10−5 sec−1. RNA paranemic assembly of 3HT and 5HT complexes is blocked by single-base substitutions that disrupt individual inter-molecular Watson-Crick basepairs and is restored by compensatory substitutions that restore those basepairs. The 3HT motif appears suitable for specific, programmable, and reversible tecto-RNA self-assembly for constructing artificial RNA molecular machines. PMID:18072767

  18. Multireference excitation energies for bacteriochlorophylls A within light harvesting system 2

    DEFF Research Database (Denmark)

    Anda, Andre; Hansen, Thorsten; De Vico, Luca

    2016-01-01

    Light-harvesting system 2 (LH2) of purple bacteria is one of the most popular antenna complexes used to study Nature's way of collecting and channeling solar energy. The dynamics of the absorbed energy is probed by ultrafast spectroscopy. Simulation of these experiments relies on fitting a range of...

  19. Supermolecular organization of photosystem II and its associated light-harvesting antenna in Arabidopsis thaliana

    NARCIS (Netherlands)

    Yakushevska, AE; Jensen, PE; Keegstra, W; van Roon, H; Scheller, HV; Boekema, EJ; Dekker, JP; Yakushevska, Alevtyna E.; Jensen, Poul E.; Scheller, Henrik V.; Dekker, Jan P.

    2001-01-01

    The organization of Arabidopsis thaliana photosystem II (PSII) and its associated light-harvesting antenna (LHCII) was studied in isolated PSII-LHCII supercomplexes and native membrane-bound crystals by transmission electron microscopy and image analysis. Over 4000 single-particle projections of PSI

  20. Organization of the Bacterial Light-Harvesting Apparatus Rationalized by Exciton Transport Optimization

    CERN Document Server

    Harel, Elad

    2011-01-01

    Photosynthesis, the process by which energy from sunlight drives cellular metabolism, relies on a unique organization of light-harvesting and reaction center complexes. Recently, the organization of light-harvesting LH2 complexes and dimeric reaction center-light harvesting I-PufX (RC-LH1-PufX) core complexes in membranes of purple non-sulfur bacteria was revealed by atomic force microscopy (AFM)1. Here, we report that the structure of LH2 and its organization within the membrane can be largely rationalized by a simple physical model that relies primarily on exciton transfer optimization. The process through which the light-harvesting complexes transfer excitation energy has been recognized to incorporate both coherent and incoherent processes mediated by the surrounding protein environment. Using the Haken-Strobl model, we show that the organization of the complexes in the membrane can be almost entirely explained by simple electrostatic considerations and that quantum effects act primarily to enforce robust...

  1. Studying the Effect of Light Quality on the Size of the Photosystem II Light Harvesting Complex

    Science.gov (United States)

    Muhoz, Romualdo; Quiles, Maria J.

    2003-01-01

    In this article the effect of light quality on the size of the photosystem II (PSII) light harvesting complex (LHCII) is studied by measuring the chlorophyll fluorescence emitted by leaf sections of oat ("Avena sativa," var. Prevision) plants previously treated with either white light or with light filtered through blue, green, red or farred…

  2. Light harvesting complexes and chromatic adaptation of Eustigmatophyte alga \\kur{Trachydiscus minutus}

    OpenAIRE

    PAZDERNÍK, Marek

    2015-01-01

    The chromatic adaptation of Trachydiscus minutus was investigated by separation of light harvesting complexes (antennae and photosystems) on a sucrose gradient using variety of detergents and their concentrations, further complex purification and characterization was done using biochemical separation and spectroscopic techniques.

  3. Vibrational Beatings Conceal Evidence of Electronic Coherence in the FMO Light-Harvesting Complex

    NARCIS (Netherlands)

    Tempelaar, Roel; Jansen, Thomas L. C.; Knoester, Jasper

    2014-01-01

    In biological light harvesting, solar energy is captured by photosynthetic antennae for subsequent storage into chemical bonds. The remarkable efficiency reached in transferring the energy between the collection and storage events recently has been attributed to long-lived electronic coherence prese

  4. Assembly of the Major Light-Harvesting Complex II in Lipid Nanodiscs.

    NARCIS (Netherlands)

    Pandit, A.; Shirzad-Wasei, N.; Wlodarczyk, L.M.; Roon, H. van; Boekema, E.J.; Dekker, J.P.; Grip, W.J. de

    2011-01-01

    Self-aggregation of isolated plant light-harvesting complexes (LHCs) upon detergent extraction is associated with fluorescence quenching and is used as an in vitro model to study the photophysical processes of nonphotochemical quenching (NPQ). In the NPQ state, in vivo induced under excess solar lig

  5. Assembly of the Major Light-Harvesting Complex II in Lipid Nanodiscs

    NARCIS (Netherlands)

    Pandit, Anjali; Shirzad-Wasei, Nazhat; Wlodarczyk, Lucyna M.; van Roon, Henny; Boekema, Egbert J.; Dekker, Jan P.; de Grip, Willem J.; Brown, Leonid S.

    2011-01-01

    Self-aggregation of isolated plant light-harvesting complexes (LHCs) upon detergent extraction is associated with fluorescence quenching and is used as an in vitro model to study the photophysical processes of nonphotochemical quenching (NPQ). In the NPQ state, in vivo induced under excess solar lig

  6. Efficient Light Harvesting in a Dark, Hot, Acidic Environment : The Structure and Function of PSI-LHCI from Galdieria sulphuraria

    NARCIS (Netherlands)

    Thangaraj, Balakumar; Jolley, Craig C.; Sarrou, Iosifina; Bultema, Jelle B.; Greyslak, Jason; Whitelegge, Julian P.; Lin, Su; Kouril, Roman; Subramanyam, Rajagopal; Boekema, Egbert J.; Fromme, Petra; Kouřil, Roman; Brown, Leonid S.

    2011-01-01

    Photosystem l-light harvesting complex I (PSI-LHCI) was isolated from the thermoacidophilic red alga Galdieria sulphuraria, and its structure, composition, and light-harvesting function were characterized by electron microscopy, mass spectrometry, and ultrafast optical spectroscopy. The results show

  7. Energy transfer and clustering of photosynthetic light-harvesting complexes in reconstituted lipid membranes

    Energy Technology Data Exchange (ETDEWEB)

    Dewa, Takehisa, E-mail: takedewa@nitech.ac.jp [Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Japan Science and Technology, PRESTO, 4-1-8 Honcho Kawaguchi, Saitama 332-0012 (Japan); Sumino, Ayumi; Watanabe, Natsuko; Noji, Tomoyasu [Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Nango, Mamoru, E-mail: nango@nitech.ac.jp [Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan)

    2013-06-20

    Highlights: ► Photosynthetic light-harvesting complexes were reconstituted into lipid membranes. ► Energy transfers between light-harvesting complexes were examined. ► Atomic force microscopy indicated cluster formation of light-harvesting complexes. ► Efficient energy transfer was observed for the clustered complexes in the membranes. - Abstract: In purple photosynthetic bacteria, light-harvesting complex 2 (LH2) and light harvesting/reaction centre core complex (LH1-RC) play the key roles of capturing and transferring light energy and subsequent charge separation. These photosynthetic apparatuses form a supramolecular assembly; however, how the assembly influences the efficiency of energy conversion is not yet clear. We addressed this issue by evaluating the energy transfer in reconstituted photosynthetic protein complexes LH2 and LH1-RC and studying the structures and the membrane environment of the LH2/LH1-RC assemblies, which had been embedded into various lipid bilayers. Thus, LH2 and LH1-RC from Rhodopseudomonas palustris 2.1.6 were reconstituted in phosphatidylglycerol (PG), phosphatidylcholine (PC), and phosphatidylethanolamine (PE)/PG/cardiolipin (CL). Efficient energy transfer from LH2 to LH1-RC was observed in the PC and PE/PG/CL membranes. Atomic force microscopy revealed that LH2 and LH1-RC were heterogeneously distributed to form clusters in the PC and PE/PG/CL membranes. The results indicated that the phospholipid species influenced the cluster formation of LH2 and LH1-RC as well as the energy transfer efficiency.

  8. Functional architectures based on self-assembly of bio-inspired dipeptides: Structure modulation and its photoelectronic applications.

    Science.gov (United States)

    Chen, Chengjun; Liu, Kai; Li, Junbai; Yan, Xuehai

    2015-11-01

    Getting inspiration from nature and further developing functional architectures provides an effective way to design innovative materials and systems. Among bio-inspired materials, dipeptides and its self-assembled architectures with functionalities have recently been the subject of intensive studies. However, there is still a great challenge to explore its applications likely due to the lack of effective adaptation of their self-assembled structures as well as a lack of understanding of the self-assembly mechanisms. In this context, taking diphenylalanine (FF, a core recognition motif for molecular self-assembly of the Alzheimer's β-amyloid polypeptides) as a model of bio-inspired dipeptides, recent strategies on modulation of dipeptide-based architectures were introduced with regard to both covalent (architectures modulation by coupling functional groups) and non-covalent ways (controlled architectures by different assembly pathways). Then, applications are highlighted in some newly emerging fields of innovative photoelectronic devices and materials, such as artificial photosynthetic systems for renewable solar energy storage and renewable optical waveguiding materials for optoelectronic devices. At last, the challenges and future perspectives of these bio-inspired dipeptides are also addressed. PMID:26365127

  9. Sequential programmable self-assembly: Role of cooperative interactions

    Science.gov (United States)

    Halverson, Jonathan D.; Tkachenko, Alexei V.

    2016-03-01

    We propose a general strategy of "sequential programmable self-assembly" that enables a bottom-up design of arbitrary multi-particle architectures on nano- and microscales. We show that a naive realization of this scheme, based on the pairwise additive interactions between particles, has fundamental limitations that lead to a relatively high error rate. This can be overcome by using cooperative interparticle binding. The cooperativity is a well known feature of many biochemical processes, responsible, e.g., for signaling and regulations in living systems. Here we propose to utilize a similar strategy for high precision self-assembly, and show that DNA-mediated interactions provide a convenient platform for its implementation. In particular, we outline a specific design of a DNA-based complex which we call "DNA spider," that acts as a smart interparticle linker and provides a built-in cooperativity of binding. We demonstrate versatility of the sequential self-assembly based on spider-functionalized particles by designing several mesostructures of increasing complexity and simulating their assembly process. This includes a number of finite and repeating structures, in particular, the so-called tetrahelix and its several derivatives. Due to its generality, this approach allows one to design and successfully self-assemble virtually any structure made of a "GEOMAG" magnetic construction toy, out of nanoparticles. According to our results, once the binding cooperativity is strong enough, the sequential self-assembly becomes essentially error-free.

  10. Self-assembly of size-controlled liposomes on DNA nanotemplates.

    Science.gov (United States)

    Yang, Yang; Wang, Jing; Shigematsu, Hideki; Xu, Weiming; Shih, William M; Rothman, James E; Lin, Chenxiang

    2016-05-01

    Artificial lipid-bilayer membranes are valuable tools for the study of membrane structure and dynamics. For applications such as the study of vesicular transport and drug delivery, there is a pressing need for artificial vesicles with controlled size. However, controlling vesicle size and shape with nanometre precision is challenging, and approaches to achieve this can be heavily affected by lipid composition. Here, we present a bio-inspired templating method to generate highly monodispersed sub-100-nm unilamellar vesicles, where liposome self-assembly was nucleated and confined inside rigid DNA nanotemplates. Using this method, we produce homogeneous liposomes with four distinct predefined sizes. We also show that the method can be used with a variety of lipid compositions and probe the mechanism of templated liposome formation by capturing key intermediates during membrane self-assembly. The DNA nanotemplating strategy represents a conceptually novel way to guide lipid bilayer formation and could be generalized to engineer complex membrane/protein structures with nanoscale precision. PMID:27102682

  11. Self-assembly of size-controlled liposomes on DNA nanotemplates

    Science.gov (United States)

    Yang, Yang; Wang, Jing; Shigematsu, Hideki; Xu, Weiming; Shih, William M.; Rothman, James E.; Lin, Chenxiang

    2016-05-01

    Artificial lipid-bilayer membranes are valuable tools for the study of membrane structure and dynamics. For applications such as the study of vesicular transport and drug delivery, there is a pressing need for artificial vesicles with controlled size. However, controlling vesicle size and shape with nanometre precision is challenging, and approaches to achieve this can be heavily affected by lipid composition. Here, we present a bio-inspired templating method to generate highly monodispersed sub-100-nm unilamellar vesicles, where liposome self-assembly was nucleated and confined inside rigid DNA nanotemplates. Using this method, we produce homogeneous liposomes with four distinct predefined sizes. We also show that the method can be used with a variety of lipid compositions and probe the mechanism of templated liposome formation by capturing key intermediates during membrane self-assembly. The DNA nanotemplating strategy represents a conceptually novel way to guide lipid bilayer formation and could be generalized to engineer complex membrane/protein structures with nanoscale precision.

  12. Self-assembly and structural-functional flexibility of oxygenic photosynthetic machineries: personal perspectives.

    Science.gov (United States)

    Garab, Győző

    2016-01-01

    This short review, with a bit of historical aspect and a strong personal bias and emphases on open questions, is focusing on the (macro-)organization and structural-functional flexibilities of the photosynthetic apparatus of oxygenic photosynthetic organisms at different levels of the structural complexity-selected problems that have attracted most my attention in the past years and decades. These include (i) the anisotropic organization of the pigment-protein complexes and photosynthetic membranes-a basic organizing principle of living matter, which can, and probably should be adopted to intelligent materials; (ii) the organization of protein complexes into chiral macrodomains, large self-assembling highly organized but structurally flexible entities with unique spectroscopic fingerprints-structures, where, important, high-level regulatory functions appear to 'reside'; (iii) a novel, dissipation-assisted mechanism of structural changes, based on a thermo-optic effect: ultrafast thermal transients in the close vicinity of dissipation of unused excitation energy, which is capable of inducing elementary structural changes; it makes plants capable of responding to excess excitation with reaction rates proportional to the overexcitation above the light-saturation of photosynthesis; (iv) the 3D ultrastructure of the granum-stroma thylakoid membrane assembly and other multilamellar membrane systems, and their remodelings-associated with regulatory mechanisms; (v) the molecular organization and structural-functional plasticity of the main light-harvesting complex of plants, in relation to their crystal structure and different in vivo and in vitro states; and (vi) the enigmatic role of non-bilayer lipids and lipid phases in the bilayer thylakoid membrane-warranting its high protein content and contributing to its structural flexibility. PMID:26494196

  13. Bioprinting synthetic self-assembling peptide hydrogels for biomedical applications.

    Science.gov (United States)

    Loo, Yihua; Hauser, Charlotte A E

    2016-02-01

    Three-dimensional (3D) bioprinting is a disruptive technology for creating organotypic constructs for high-throughput screening and regenerative medicine. One major challenge is the lack of suitable bioinks. Short synthetic self-assembling peptides are ideal candidates. Several classes of peptides self-assemble into nanofibrous hydrogels resembling the native extracellular matrix. This is a conducive microenvironment for maintaining cell survival and physiological function. Many peptides also demonstrate stimuli-responsive gelation and tuneable mechanical properties, which facilitates extrusion before dispensing and maintains the shape fidelity of the printed construct in aqueous media. The inherent biocompatibility and biodegradability bodes well for in vivo applications as implantable tissues and drug delivery matrices, while their short length and ease of functionalization facilitates synthesis and customization. By applying self-assembling peptide inks to bioprinting, the dynamic complexity of biological tissue can be recreated, thereby advancing current biomedical applications of peptide hydrogel scaffolds. PMID:26694103

  14. Self-Assembly in Biosilicification and Biotemplated Silica Materials

    Directory of Open Access Journals (Sweden)

    Francisco M. Fernandes

    2014-09-01

    Full Text Available During evolution, living organisms have learned to design biomolecules exhibiting self-assembly properties to build-up materials with complex organizations. This is particularly evidenced by the delicate siliceous structures of diatoms and sponges. These structures have been considered as inspiration sources for the preparation of nanoscale and nanostructured silica-based materials templated by the self-assembled natural or biomimetic molecules. These templates range from short peptides to large viruses, leading to biohybrid objects with a wide variety of dimensions, shapes and organization. A more recent strategy based on the integration of biological self-assembly as the driving force of silica nanoparticles organization offers new perspectives to elaborate highly-tunable, biofunctional nanocomposites.

  15. A novel autonomous self-assembly distributed swarm flying robot

    Institute of Scientific and Technical Information of China (English)

    Wei Hongxing; Li Ning; Liu Miao; Tan Jindong

    2013-01-01

    Swarm intelligence embodied by many species such as ants and bees has inspired scholars in swarm robotic researches.This paper presents a novel autonomous self-assembly distributed swarm flying robot-DSFR,which can drive on the ground,autonomously accomplish self-assembly and then fly in the air coordinately.Mechanical and electrical designs ofa DSFR module,as well as the kinematics and dynamics analysis,are specifically investigated.Meanwhile,this paper brings forward a generalized adjacency matrix to describe configurations of DSFR structures.Also,the distributed flight control model is established for vertical taking-off and horizontal hovering,which can be applied to control of DSFR systems with arbitrary configurations.Finally,some experiments are carried out to testify and validate the DSFR design,the autonomous self-assembly strategy and the distributed flight control laws.

  16. Comparing open and closed molecular self-assembly

    CERN Document Server

    Castelnovo, Martin; Foret, Lionel

    2014-01-01

    We study theoretically in the present work the self-assembly of molecules in an open system, which is fed by monomers and depleted in partial or complete clusters. Such a scenario is likely to occur for example in the context of viral self-assembly. We provide a general formula for the mean-field size distribution which is valid both at equilibrium in a closed system, and in the stationary state in an open system. This allows us to explore in a simple way out-of-equilibrium features for self-assembly and compare them to equilibrium properties. In particular, we identify a region of parameter space for which the out-of-equilibrium size distribution in the presence of external fluxes is equal to the equilibrium size distribution in the absence of external fluxes, up to a constant renormalization factor. The range of validity of this result and its consequences are discussed.

  17. Biomedical exploitation of self assembled peptide based nanostructures.

    Science.gov (United States)

    Roy, Anupam; Franco, Octavio L; Mandal, Santi M

    2013-11-01

    Nowadays, peptide based disease prevention is an important topic in biomedical science, which may radically change the traditional use of biomaterials and improve the life quality. Self-assembled nanostructured peptides have been receiving extreme attention in the drug delivery field due their high biocompatibility levels, better loading capacity, extended circulation and localization in required target site. This article focuses on the composition and synthesis of different forms of self-assembled peptide nanostructures as nanotubes, nanofibers, nanoparticles, nanotapes and nanogels. The most important properties for their self assembled mechanism and their biomedical applications are also discussed. Various potential applications of nanostructures peptide could be developed designed for therapeutic agent's delivery, biosensors, anticancerous and antimicrobial activities. PMID:23968344

  18. Self-assembling peptides and their potential applications in biomedicine.

    Science.gov (United States)

    Rymer, Sarah-Jane; Tendler, Saul J B; Bosquillon, Cynthia; Washington, Clive; Roberts, Clive J

    2011-08-01

    For many years, peptides have been known to self-assemble to form nano- and micro-scale structures. Their nature of assembly and assembled morphology has since been investigated as this area of research has important implications for the development of both drug delivery and tissue regeneration. In this article, we explore the process of peptide self-assembly in vivo, and experiments that exploit the structures formed. Particular focus is directed towards diphenylalanine, the simplest self-assembling peptide, which generally forms tube-like structures on assembly. In addition, different peptides that may assemble into a range of other morphologies are highlighted and potential applications in regenerative medicine and drug delivery discussed. PMID:22826867

  19. Self-assembly and application of diphenylalanine-based nanostructures.

    Science.gov (United States)

    Yan, Xuehai; Zhu, Pengli; Li, Junbai

    2010-06-01

    Micro- and nanostructures fabricated from biological building blocks have attracted tremendous attention owing to their potential for application in biology and in nanotechnology. Many biomolecules, including peptides and proteins, can interact and self-assemble into highly ordered supramolecular architectures with functionality. By imitating the processes where biological peptides or proteins are assembled in nature, one can delicately design and synthesize various peptide building blocks composed of several to dozens of amino acids for the creation of biomimetic or bioinspired nanostructured materials. This tutorial review aims to introduce a new kind of peptide building block, the diphenylalanine motif, extracted with inspiration of a pathogenic process towards molecular self-assembly. We highlight recent and current advances in fabrication and application of diphenylalanine-based peptide nanomaterials. We also highlight the preparation of such peptide-based nanostructures as nanotubes, spherical vesicles, nanofibrils, nanowires and hybrids through self-assembly, the improvement of their properties and the extension of their applications. PMID:20502791

  20. Functional self-assembled lipidic systems derived from renewable resources

    Science.gov (United States)

    Silverman, Julian R.; Samateh, Malick; John, George

    2015-01-01

    Self-assembled lipidic amphiphile systems can create a variety of multi-functional soft materials with value-added properties. When employing natural reagents and following biocatalytic syntheses, self-assembling monomers may be inherently designed for degradation, making them potential alternatives to conventional and persistent polymers. By using non-covalent forces, self-assembled amphiphiles can form nanotubes, fibers, and other stimuli responsive architectures prime for further applied research and incorporation into commercial products. By viewing these lipid derivatives under a lens of green principles, there is the hope that in developing a structure–function relationship and functional smart materials that research may remain safe, economic, and efficient. PMID:26766923

  1. Multivalent Protein Assembly Using Monovalent Self-Assembling Building Blocks

    Directory of Open Access Journals (Sweden)

    Katja Petkau-Milroy

    2013-10-01

    Full Text Available Discotic molecules, which self-assemble in water into columnar supramolecular polymers, emerged as an alternative platform for the organization of proteins. Here, a monovalent discotic decorated with one single biotin was synthesized to study the self-assembling multivalency of this system in regard to streptavidin. Next to tetravalent streptavidin, monovalent streptavidin was used to study the protein assembly along the supramolecular polymer in detail without the interference of cross-linking. Upon self-assembly of the monovalent biotinylated discotics, multivalent proteins can be assembled along the supramolecular polymer. The concentration of discotics, which influences the length of the final polymers at the same time dictates the amount of assembled proteins.

  2. Hydrodynamic Self-Assembly of Topographical Patterns on Soft Materials

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Satish [Univ. of Minnesota, Minneapolis, MN (United States)

    2016-01-06

    The objective of this project is to use theoretical tools to explore fundamentally new ways of creating and controlling surface topography on soft materials (e.g., polymeric liquids, gels, colloidal suspensions) that make use of principles from hydrodynamics and self-assembly. Surface topography is known to have a significant impact on the optical, adhesive, and wetting properties of materials, so improved fundamental understanding of how to create and control it will help enable the tailoring of these properties to desired specifications. Self-assembly is the spontaneous organization of an ordered structure, and hydrodynamics often plays an important role in the self-assembly of soft materials. This research supported through this project has led to the discovery of a number of novel phenomena that are described in published journal articles. In this way, the research significantly adds to the fundamental understanding of the topics investigated.

  3. Actinide sequestration using self-assembled monolayers on mesoporous supports.

    Science.gov (United States)

    Fryxell, Glen E; Lin, Yuehe; Fiskum, Sandy; Birnbaum, Jerome C; Wu, Hong; Kemner, Ken; Kelly, Shelley

    2005-03-01

    Surfactant templated synthesis of mesoporous ceramics provides a versatile foundation upon which to create high efficiency environmental sorbents. These nanoporous ceramic oxides condense a huge amount of surface area into a very small volume. The ceramic oxide interface is receptive to surface functionalization through molecular self-assembly. The marriage of mesoporous ceramics with self-assembled monolayer chemistry creates a powerful new class of environmental sorbent materials called self-assembled monolayers on mesoporous supports (SAMMS). These SAMMS materials are highly efficient sorbents whose interfacial chemistry can be fine-tuned to selectively sequester a specific target species, such as heavy metals, tetrahedral oxometalate anions, and radionuclides. Details addressing the design, synthesis, and characterization of SAMMS materials specifically designed to sequester actinides, of central importance to the environmental cleanup necessary after 40 years of weapons-grade plutonium production, as well as evaluation of their binding affinities and kinetics are presented. PMID:15787373

  4. Self-Assemblies of Acicular Hollow Fe/C Nanostructures.

    Science.gov (United States)

    Li, Wangchang; Qiao, Xiaojing; Li, Mingyu; Zheng, Qiuyu; Ren, Qingguo; Zhu, Y Q; Peng, H X

    2015-08-01

    Self-assemblies of acicular hollow Fe/C structures were synthesized using D-glucose monohydrate and ferric chloride as precursors by a simple hydrothermal process followed by carbonization at 800 °C. The self-assembled structures with an overall diameter of 15~20 µm composed of radially formed hollow needles from a central core with an average diameter of ca. 1 µm and a length up to 10 µm. The end of the needles was revealed to be a awl shape with a hollow structure formed during the self-assembly process and the subsequent heat treatment. The hollow structure was probably caused by the Kirkendall effect at 800 °C. The materials exhibit ferromagnetic characteristic with saturation magnetization (Ms), remanent magnetization (Mr), and coercivity (Hc) of 22.2 emu/g, 3 emu/g, and 151.22 Oe, respectively, with Ms much lower than that of Fe3O4. PMID:26369160

  5. Nano-engineering by optically directed self-assembly.

    Energy Technology Data Exchange (ETDEWEB)

    Furst, Eric (University of Delaware, Newark, DE); Dunn, Elissa (Yale University, New Haven, CT); Park, Jin-Gyu (Yale University, New Haven, CT); Brinker, C. Jeffrey; Sainis, Sunil (Yale University, New Haven, CT); Merrill, Jason (Yale University, New Haven, CT); Dufresne, Eric (Yale University, New Haven, CT); Reichert, Matthew D.; Brotherton, Christopher M.; Bogart, Katherine Huderle Andersen; Molecke, Ryan A.; Koehler, Timothy P.; Bell, Nelson Simmons; Grillet, Anne Mary; Gorby, Allen D.; Singh, John (University of Delaware, Newark, DE); Lele, Pushkar (University of Delaware, Newark, DE); Mittal, Manish (University of Delaware, Newark, DE)

    2009-09-01

    Lack of robust manufacturing capabilities have limited our ability to make tailored materials with useful optical and thermal properties. For example, traditional methods such as spontaneous self-assembly of spheres cannot generate the complex structures required to produce a full bandgap photonic crystals. The goal of this work was to develop and demonstrate novel methods of directed self-assembly of nanomaterials using optical and electric fields. To achieve this aim, our work employed laser tweezers, a technology that enables non-invasive optical manipulation of particles, from glass microspheres to gold nanoparticles. Laser tweezers were used to create ordered materials with either complex crystal structures or using aspherical building blocks.

  6. Parallelism and Time in Hierarchical Self-Assembly

    OpenAIRE

    Chen, Ho-Lin; Doty, David

    2011-01-01

    We study the role that parallelism plays in time complexity of Winfree's abstract Tile Assembly Model (aTAM), a model of molecular algorithmic self-assembly. In the "hierarchical" aTAM, two assemblies, both consisting of multiple tiles, are allowed to aggregate together, whereas in the "seeded" aTAM, tiles attach one at a time to a growing assembly. Adleman, Cheng, Goel, and Huang ("Running Time and Program Size for Self-Assembled Squares", STOC 2001) showed how to assemble an n x n square in...

  7. DNA Self-Assembly For Constructing 3D Boxes

    OpenAIRE

    Kao, Ming-Yang; Ramachandran, Vijay

    2001-01-01

    We propose a mathematical model of DNA self-assembly using 2D tiles to form 3D nanostructures. This is the first work to combine studies in self-assembly and nanotechnology in 3D, just as Rothemund and Winfree did in the 2D case. Our model is a more precise superset of their Tile Assembly Model that facilitates building scalable 3D molecules. Under our model, we present algorithms to build a hollow cube, which is intuitively one of the simplest 3D structures to construct. We also introduce fi...

  8. Large-Scale Self-Assembled Ag Nanotubes

    Institute of Scientific and Technical Information of China (English)

    WEI Guodan; NAN Cewen; YU Dapeng

    2005-01-01

    A high yield of silver nanotubes with large aspect ratio were conveniently synthesized via an organic-assist solvothermal preparation technique using polyvinyl pyrrolidone (PVP) as a capping reagent and architecture soft-template. The molecular ratio between the repeating unit of PVP and AgNO3 plays a crucial role in determining the geometric shape of the product. Such novel-type Ag nanotubes were self-assembled by Ag nanoparticles, which had largely similar crystallographic orientation, forming a texture. The fact that nanoparticles without anisotropic crystal structures can form such superstructures by self-assembly may open a window for understanding a range of nanotube formation processes.

  9. Self-Assembled Peptide Gels for 3D Cell Culture

    OpenAIRE

    Tang, Claire

    2010-01-01

    Under specific conditions short peptides modified with an N-terminal fluorenyl-9-methoxycarbonyl (Fmoc) group can self-assemble into hydrogel scaffolds similar in properties to the natural extracellular matrix. Fmoc-diphenylalanine (Fmoc-FF) for instance, has been shown to form hydrogels at physiological pH that have the ability to support 2D and 3D cell culture. The aim of this investigation is to provide further understanding of the self-assembly mechanism of such systems in order to progre...

  10. Probing the lateral composition profile of self-assembled islands

    International Nuclear Information System (INIS)

    We apply a selective etching procedure to probe the lateral composition profile of self-assembled SiGe pyramids on a Si(001) substrate surface. We find that the pyramids consist of highly Si intermixed corners, whereas the edges, the apex, and the center of the pyramids remain Ge rich. Our results cannot be explained by existing growth models that minimize strain energy. We use a model that includes surface interdiffusion during island growth, underlining the paramount importance of surface processes during the formation of self-assembled quantum dot heterostructures in many different material systems

  11. Structural simulations of nanomaterials self-assembled from ionic macrocycles.

    Energy Technology Data Exchange (ETDEWEB)

    van Swol, Frank B.; Medforth, Craig John (University of New Mexico, Albuquerque, NM)

    2010-10-01

    Recent research at Sandia has discovered a new class of organic binary ionic solids with tunable optical, electronic, and photochemical properties. These nanomaterials, consisting of a novel class of organic binary ionic solids, are currently being developed at Sandia for applications in batteries, supercapacitors, and solar energy technologies. They are composed of self-assembled oligomeric arrays of very large anions and large cations, but their crucial internal arrangement is thus far unknown. This report describes (a) the development of a relevant model of nonconvex particles decorated with ions interacting through short-ranged Yukawa potentials, and (b) the results of initial Monte Carlo simulations of the self-assembly binary ionic solids.

  12. Energy transfer in an LH4-like light harvesting complex from the aerobic purple photosynthetic bacterium Roseobacter denitrificans

    Energy Technology Data Exchange (ETDEWEB)

    Niedzwiedzki, Dariusz; Fuciman, Marcel; Frank, Harry A; Blankenship, R. E.

    A peripheral light-harvesting complex from the aerobic purple bacterium Roseobacter (R.) denitrificans was purified and its photophysical properties characterized. The complex contains two types of pigments, bacteriochlorophyll (BChl) a and the carotenoid (Car) spheroidenone and possesses unique spectroscopic properties. It appears to lack the B850 bacteriochlorophyll a Q{sub y} band that is typical for similar light-harvesting complex 2 antennas. Circular dichroism and low temperature steady-state absorption spectroscopy revealed that the B850 band is present but is shifted significantly to shorter wavelengths and overlaps with the B800 band at room temperature. Such a spectral signature classifies this protein as a member of the light-harvesting complex 4 class of peripheral light-harvesting complexes, along with the previously known light-harvesting complex 4 from Rhodopseudomonas palustris. The influence of the spectral change on the light-harvesting ability was studied using steady-state absorption, fluorescence, circular dichroism, femtosecond and microsecond time-resolved absorption and time-resolved fluorescence spectroscopies. The results were compared to the properties of the similar (in pigment composition) light-harvesting complex 2 from aerobically grown Rhodobacter sphaeroides and are understood within the context of shared similarities and differences and the putative influence of the pigments on the protein structure and its properties.

  13. A light-harvesting siphonaxanthin-chlorophyll a/b-protein complex of marine green alga,Bryopsis corticulans

    Institute of Scientific and Technical Information of China (English)

    CHEN Hui; SHEN Shihua; HE Junfang; LENG Jing; LI Liangbi; KUANG Tingyun

    2004-01-01

    A light-harvesting chlorophyll a/b-protein complex (LHCP) was isolated directly from thylakoid membranes of marine green alga, Bryopsis corticulans, by two consecutive runs of liquid chromatography. The trimeric form of the light-harvesting complex has been obtained by sucrose gradient ultracentrifugation. The result of SDSPAGE shows that the light-harvesting complex is composed of at least five apoproteins in which a protein with apparent molecular weight of about 31 kD was never found in the major light-harvesting complex (LHC Ⅱ) from higher plants.The isolated Bryopsis corticulans light-harvesting complex contains a specific carotenoid, siphonaxanthin, as well as chlorophyll (Chl) a, Chl b, neoxanthin and violaxanthin. Siphonaxanthin which is present in the light-harvesting siphonaxanthin-chlorophyll a/b-protein complex of Bryopsis corticulans is responsible for enhanced absorption in the blue-green region (530 nm). Efficient energy transfer from both siphonaxanthin and Chl b to Chl a in Bryopsis corticulans LHCP, which has similar absorption and fluorescence emission spectra to those of the lutein-chlorophyll a/b-protein of higher plants, proved that molecular arrangement of the light-harvesting pigments was highly ordered in the Bryopsis corticulans LHCP. The siphonaxanthin-chlorophyll a/b-proteins allow enhanced absorption of blue-green light, the predominant light available in deep ocean waters or shaded subtidal marine habitats.

  14. Purple-bacterial light harvesting benefits more from energy funnelling than from delocalisation

    CERN Document Server

    Baghbanzadeh, Sima

    2015-01-01

    Light-harvesting complexes of purple bacteria have two properties that are thought to contribute to the efficiency of their exciton transport: an energy funnel that directs excitons towards the reaction centre as well as substantial excitonic delocalisation, which can enhance transport through supertransfer. To determine the relative importance of these two features, we compared models of the light-harvesting apparatus with thousands of counterfactual situations in which the extent of delocalisation and the energy landscape were altered. We find that the influence of delocalisation is usually minor and sometimes deleterious, especially when compared to the decisive importance of a funnel in the energy landscape. Consequently, delocalisation is most likely a side-effect of the dense chlorophyll packing that evolved to increase light absorption per reaction centre.

  15. Clustered Geometries Exploiting Quantum Coherence Effects for Efficient Energy Transfer in Light Harvesting

    CERN Document Server

    Ai, Qing; Jin, Bih-Yaw; Cheng, Yuan-Chung

    2013-01-01

    Elucidating quantum coherence effects and geometrical factors for efficient energy transfer in photosynthesis has the potential to uncover non-classical design principles for advanced organic materials. We study energy transfer in a linear light-harvesting model to reveal that dimerized geometries with strong electronic coherences within donor and acceptor pairs exhibit significantly improved efficiency, which is in marked contrast to predictions of the classical F\\"orster theory. We reveal that energy tuning due to coherent delocalization of photoexcitations is mainly responsible for the efficiency optimization. This coherence-assisted energy-tuning mechanism also explains the energetics and chlorophyll arrangements in the widely-studied Fenna-Matthews-Olson complex. We argue that a clustered network with rapid energy relaxation among donors and resonant energy transfer from donor to acceptor states provides a basic formula for constructing efficient light-harvesting systems, and the general principles revea...

  16. Synthesis and Functional Reconstitution of Light-Harvesting Complex II into Polymeric Membrane Architectures.

    Science.gov (United States)

    Zapf, Thomas; Tan, Cherng-Wen Darren; Reinelt, Tobias; Huber, Christoph; Shaohua, Ding; Geifman-Shochat, Susana; Paulsen, Harald; Sinner, Eva-Kathrin

    2015-12-01

    One of most important processes in nature is the harvesting and dissipation of solar energy with the help of light-harvesting complex II (LHCII). This protein, along with its associated pigments, is the main solar-energy collector in higher plants. We aimed to generate stable, highly controllable, and sustainable polymer-based membrane systems containing LHCII-pigment complexes ready for light harvesting. LHCII was produced by cell-free protein synthesis based on wheat-germ extract, and the successful integration of LHCII and its pigments into different membrane architectures was monitored. The unidirectionality of LHCII insertion was investigated by protease digestion assays. Fluorescence measurements indicated chlorophyll integration in the presence of LHCII in spherical as well as planar bilayer architectures. Surface plasmon enhanced fluorescence spectroscopy (SPFS) was used to reveal energy transfer from chlorophyll b to chlorophyll a, which indicates native folding of the LHCII proteins. PMID:26473750

  17. Progress in the Structure-based Simulation of Plant Light-Harvesting Complexes

    International Nuclear Information System (INIS)

    Full text: Water-oxidisation in plants occurs in super complexes that contain a catalytic core and various light-harvesting complexes (LHCII, CP24, CP26 and CP29). We applied our combined quantum chemical / electrostatic approach to calculate the exciton Hamiltonian of LHCII and CP29 on the basis of the known crystal structures in order to gain a molecular understanding of light-harvesting. Simulations of linear optical spectra allow us to assess the validity of the computed quantities. The two homologous complexes LHCII and CP29 are compared with respect to the location of the terminal emitter domain and the pigment-protein interactions that lead to specific transition energy shifts. (author)

  18. Excited state coherent dynamics in light-harvesting complexes from photosynthetic marine algae

    Science.gov (United States)

    Richards, G. H.; Wilk, K. E.; Curmi, P. M. G.; Quiney, H. M.; Davis, J. A.

    2012-08-01

    We explore coherence dynamics in light-harvesting complexes and their interactions with other electronic states and vibrational modes. This is achieved by utilizing a two-colour four-wave mixing spectroscopy to excite and analyse a specific coherence pathway in the phycocyanin-645 (PC645) light-harvesting complex. We observe the dephasing rate increase as a function of temperature and oscillations in the signal intensity as a function of waiting time which reveals coherent excitation of pathways not directly resonant with the laser pulses. This coherent excitation of non-resonant electronic states implies strong coupling to phonon modes, which is necessary if coherent energy transfer between non-resonant states is to play any role in photosynthetic energy transfer.

  19. Excited state coherent dynamics in light-harvesting complexes from photosynthetic marine algae

    International Nuclear Information System (INIS)

    We explore coherence dynamics in light-harvesting complexes and their interactions with other electronic states and vibrational modes. This is achieved by utilizing a two-colour four-wave mixing spectroscopy to excite and analyse a specific coherence pathway in the phycocyanin-645 (PC645) light-harvesting complex. We observe the dephasing rate increase as a function of temperature and oscillations in the signal intensity as a function of waiting time which reveals coherent excitation of pathways not directly resonant with the laser pulses. This coherent excitation of non-resonant electronic states implies strong coupling to phonon modes, which is necessary if coherent energy transfer between non-resonant states is to play any role in photosynthetic energy transfer. (paper)

  20. Computational Methodologies and Physical Insights into Electronic Energy Transfer in Photosynthetic Light-Harvesting Complexes

    CERN Document Server

    Pachon, Leonardo A

    2012-01-01

    We examine computational techniques and methodologies currently in use to explore electronic excitation energy transfer in the context of light-harvesting complexes in photosynthetic antenna systems, and comment on some new insights into the underlying physics. Advantages and pitfalls of these methodologies are discussed, as are some physical insights into the photosynthetic dynamics. By combining results from molecular modelling of the complexes (structural description) with an effective non-equilibrium statistical description (time evolution), we identify some general features, regardless of the particular distribution in the protein scaffold, that are central to light-harvesting dynamics and, that could ultimately be related to the high efficiency of the overall process. Based on these general common features, some possible new directions in the field are discussed.

  1. ARCHITECTURE OF A CHARGE-TRANSFER STATE REGULATING LIGHT HARVESTING IN A PLANT ANTENNA PROTEIN

    Energy Technology Data Exchange (ETDEWEB)

    Fleming, Graham; Ahn, Tae Kyu; Avenson, Thomas J.; Ballottari, Matteo; Cheng, Yuan-Chung; Niyogi, Krishna K.; Bassi, Roberto; Fleming, Graham R.

    2008-04-02

    Energy-dependent quenching of excess absorbed light energy (qE) is a vital mechanism for regulating photosynthetic light harvesting in higher plants. All of the physiological characteristics of qE have been positively correlated with charge-transfer between coupled chlorophyll and zeaxanthin molecules in the light-harvesting antenna of photosystem II (PSII). In this work, we present evidence for charge-transfer quenching in all three of the individual minor antenna complexes of PSII (CP29, CP26, and CP24), and we conclude that charge-transfer quenching in CP29 involves a de-localized state of an excitonically coupled chlorophyll dimer. We propose that reversible conformational changes in CP29 can `tune? the electronic coupling between the chlorophylls in this dimer, thereby modulating the energy of the chlorophylls-zeaxanthin charge-transfer state and switching on and off the charge-transfer quenching during qE.

  2. Quantitative investigations of quantum coherence for a light-harvesting protein at conditions simulating photosynthesis.

    Science.gov (United States)

    Turner, Daniel B; Dinshaw, Rayomond; Lee, Kyung-Koo; Belsley, Michael S; Wilk, Krystyna E; Curmi, Paul M G; Scholes, Gregory D

    2012-04-14

    Recent measurements using two-dimensional electronic spectroscopy (2D ES) have shown that the initial dynamic response of photosynthetic proteins can involve quantum coherence. We show how electronic coherence can be differentiated from vibrational coherence in 2D ES. On that basis we conclude that both electronic and vibrational coherences are observed in the phycobiliprotein light-harvesting complex PC645 from Chroomonas sp. CCMP270 at ambient temperature. These light-harvesting antenna proteins of the cryptophyte algae are suspended in the lumen, where the pH drops significantly under sustained illumination by sunlight. Here we measured 2D ES of PC645 at increasing levels of acidity to determine if the change in pH affects the quantum coherence; quantitative analysis reveals that the dynamics are insensitive to the pH change. PMID:22374579

  3. Anti-Correlated Pigment Fluctuations of Allophycocyanin for Highly Efficient Photosynthetic Light Harvesting in Cyanobacteria

    Science.gov (United States)

    Moran, Andrew; Nome, Rene; Scherer, Norbert

    2008-03-01

    The phycobiliprotein, allophycocyanin (APC), is an excellent model system for the study of light harvesting pigment interactions with a protein bath. This work investigates the relaxation of electronic excitations in APC with electric field-resolved transient grating and photon echo spectroscopies. Transient grating experiments observe a 35 fs internal conversion process between single exciton levels. Most importantly, our analysis shows that anti-correlated phycocyanobilin pigment energy level fluctuations cause the anti-diagonal orientation of the node in the measured dispersive photon echo spectrum. We believe this novel observation to reflect concerted protein bath fluctuations over the 2 nm length scale that separates the pigments. Consideration of the Forster energy transfer rate theory suggests that APC has evolved with this property to enhance its photosynthetic light harvesting efficiency.

  4. Structure and Order of Phosphonic Acid-Based Self-Assembled Based Self-Assembled

    Energy Technology Data Exchange (ETDEWEB)

    Dubey, M.; Weidner, T; Gamble, L; Castner, D

    2010-01-01

    Organophosphonic acid self-assembled monolayers (SAMs) on oxide surfaces have recently seen increased use in electrical and biological sensor applications. The reliability and reproducibility of these sensors require good molecular organization in these SAMs. In this regard, packing, order, and alignment in the SAMs is important, as it influences the electron transport measurements. In this study, we examine the order of hydroxyl- and methyl-terminated phosphonate films deposited onto silicon oxide surfaces by the tethering by aggregation and growth method using complementary, state-of-art surface characterization tools. Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and in situ sum frequency generation (SFG) spectroscopy are used to study the order of the phosphonate SAMs in vacuum and under aqueous conditions, respectively. X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry results show that these samples form chemically intact monolayer phosphonate films. NEXAFS and SFG spectroscopy showed that molecular order exists in the octadecylphosphonic acid and 11-hydroxyundecylphosphonic acid SAMs. The chain tilt angles in these SAMs were approximately 37{sup o} and 45{sup o}, respectively.

  5. On Improving the Performance of Nonphotochemical Quenching in CP29 Light-Harvesting Antenna Complex

    OpenAIRE

    Berman, Gennady P.; Nesterov, Alexander I; Sayre, Richard T.; Still, Susanne

    2015-01-01

    We model and simulate the performance of charge-transfer in nonphotochemical quenching (NPQ) in the CP29 light-harvesting antenna-complex associated with photosystem II (PSII). The model consists of five discrete excitonic energy states and two sinks, responsible for the potentially damaging processes and charge-transfer channels, respectively. We demonstrate that by varying (i) the parameters of the chlorophyll-based dimer, (ii) the resonant properties of the protein-solvent environment inte...

  6. Flow of excitation energy in the cryptophyte light-harvesting antenna phycocyanin 645.

    OpenAIRE

    Marin, A.; Doust, A.B.; Scholes, G. D.; Wilk, K.E.; P. M. G. Curmi; Stokkum, van, I.H.M.; Grondelle, van, J Joop

    2011-01-01

    We report a detailed description of the energy migration dynamics in the phycocyanin 645 (PC645) antenna complex from the photosynthetic alga Chroomonas CCMP270. Many of the cryptophyceae are known to populate greater depths than most other algal families, having developed a 99.5% efficient light-harvesting system. In this study, we used femtosecond time-resolved spectroscopy and global analysis to characterize the excited-state dynamics of PC645. Several different pump colors were selected t...

  7. Subunit interactions and protein stability in the cyanobacterial light-harvesting proteins.

    OpenAIRE

    Plank, T; Toole, C; Anderson, L K

    1995-01-01

    Strain 4R is a phycocyanin-minus mutant of the unicellular cyanobacterium Synechocystis sp. strain 6803. Although it lacks the light-harvesting protein phycocyanin, 4R has normal levels of phycocyanin (cpc) transcripts. Sequence analysis of the cpcB gene encoding the phycocyanin beta subunit shows an insertion mutation in 4R that causes early termination of translation. Other work has shown that the phycocyanin alpha subunit and the linker proteins encoded on the cpc transcripts are all funct...

  8. Cyanobacterial Light-Harvesting Phycobilisomes Uncouple From Photosystem I During Dark-To-Light Transitions

    OpenAIRE

    Volha Chukhutsina; Luca Bersanini; Eva-Mari Aro; Herbert van Amerongen

    2015-01-01

    Photosynthetic organisms cope with changes in light quality by balancing the excitation energy flow between photosystems I (PSI) and II (PSII) through a process called state transitions. Energy redistribution has been suggested to be achieved by movement of the light-harvesting phycobilisome between PSI and PSII, or by nanometre scale rearrangements of the recently discovered PBSPSII- PSI megacomplexes. The alternative ‘spillover’ model, on the other hand, states that energy redistribution is...

  9. Dark excited states of carotenoid in light harvesting complex probing with femtosecond stimulated Raman spectroscopy

    Directory of Open Access Journals (Sweden)

    Sakai S.

    2013-03-01

    Full Text Available Vibrational dynamics of dark excited states in carotenoids have been investigated using tunable Raman pump pulses. The S1 state has same vibrational dynamics in light-harvesting complex (LH1 and solution. The S* state in LH1 has similar vibrational modes with the triplet state of carotenoid. However, the so-called S* state in solution does not have the modes and is concluded to be different from the S* state in LH1.

  10. Single-molecule exploration of photoprotective mechanisms in light-harvesting complexes

    Science.gov (United States)

    Yang, Hsiang-Yu; Schlau-Cohen, Gabriela S.; Gwizdala, Michal; Krüger, Tjaart; Xu, Pengqi; Croce, Roberta; van Grondelle, Rienk; Moerner, W. E.

    2015-03-01

    Plants harvest sunlight by converting light energy to electron flow through the primary events in photosynthesis. One important question is how the light harvesting machinery adapts to fluctuating sunlight intensity. As a result of various regulatory processes, efficient light harvesting and photoprotection are balanced. Some of the biological steps in the photoprotective processes have been extensively studied and physiological regulatory factors have been identified. For example, the effect of lumen pH in changing carotenoid composition has been explored. However, the importance of photophysical dynamics in the initial light-harvesting steps and its relation to photoprotection remain poorly understood. Conformational and excited-state dynamics of multi-chromophore pigment-protein complexes are often difficult to study and limited information can be extracted from ensemble-averaged measurements. To address the problem, we use the Anti-Brownian ELectrokinetic (ABEL) trap to investigate the fluorescence from individual copies of light-harvesting complex II (LHCII), the primary antenna protein in higher plants, in a solution-phase environment. Perturbative surface immobilization or encapsulation schemes are avoided, and therefore the intrinsic dynamics and heterogeneity in the fluorescence of individual proteins are revealed. We perform simultaneous measurements of fluorescence intensity (brightness), excited-state lifetime, and emission spectrum of single trapped proteins. By analyzing the correlated changes between these observables, we identify forms of LHCII with different fluorescence intensities and excited-state lifetimes. The distinct forms may be associated with different energy dissipation mechanisms in the energy transfer chain. Changes of relative populations in response to pH and carotenoid composition are observed, which may extend our understanding of the molecular mechanisms of photoprotection.

  11. A thioredoxin-like/β-propeller protein maintains the efficiency of light harvesting in Arabidopsis

    Science.gov (United States)

    Brooks, Matthew D.; Sylak-Glassman, Emily J.; Fleming, Graham R.; Niyogi, Krishna K.

    2013-01-01

    The light-harvesting complexes of plants have evolved the ability to switch between efficient light harvesting and quenching forms to optimize photosynthesis in response to the environment. Several distinct mechanisms, collectively termed “nonphotochemical quenching” (NPQ), provide flexibility in this response. Here we report the isolation and characterization of a mutant, suppressor of quenching 1 (soq1), that has high NPQ even in the absence of photosystem II subunit S (PsbS), a protein that is necessary for the rapidly reversible component of NPQ. The formation of NPQ in soq1 was light intensity-dependent, and it exhibited slow relaxation kinetics and other characteristics that distinguish it from known NPQ components. Treatment with chemical inhibitors or an uncoupler, as well as crosses to mutants known to affect other NPQ components, showed that the NPQ in soq1 does not require a transthylakoid pH gradient, zeaxanthin formation, or the phosphorylation of light-harvesting complexes, and it appears to be unrelated to the photosystem II damage-and-repair cycle. Measurements of pigments and chlorophyll fluorescence lifetimes indicated that the additional NPQ in soq1 is the result of a decrease in chlorophyll excited-state lifetime and not pigment bleaching. The SOQ1 gene was isolated by map-based cloning, and it encodes a previously uncharacterized thylakoid membrane protein with thioredoxin-like and β-propeller domains located in the lumen and a haloacid-dehalogenase domain exposed to the chloroplast stroma. We propose that the role of SOQ1 is to prevent formation of a slowly reversible form of antenna quenching, thereby maintaining the efficiency of light harvesting. PMID:23818601

  12. Discrete redox signaling pathways regulate photosynthetic light-harvesting and chloroplast gene transcription.

    Directory of Open Access Journals (Sweden)

    John F Allen

    Full Text Available In photosynthesis in chloroplasts, two related regulatory processes balance the actions of photosystems I and II. These processes are short-term, post-translational redistribution of light-harvesting capacity, and long-term adjustment of photosystem stoichiometry initiated by control of chloroplast DNA transcription. Both responses are initiated by changes in the redox state of the electron carrier, plastoquinone, which connects the two photosystems. Chloroplast Sensor Kinase (CSK is a regulator of transcription of chloroplast genes for reaction centres of the two photosystems, and a sensor of plastoquinone redox state. We asked whether CSK is also involved in regulation of absorbed light energy distribution by phosphorylation of light-harvesting complex II (LHC II. Chloroplast thylakoid membranes isolated from a CSK T-DNA insertion mutant and from wild-type Arabidopsis thaliana exhibit similar light- and redox-induced (32P-labelling of LHC II and changes in 77 K chlorophyll fluorescence emission spectra, while room-temperature chlorophyll fluorescence emission transients from Arabidopsis leaves are perturbed by inactivation of CSK. The results indicate indirect, pleiotropic effects of reaction centre gene transcription on regulation of photosynthetic light-harvesting in vivo. A single, direct redox signal is transmitted separately to discrete transcriptional and post-translational branches of an integrated cytoplasmic regulatory system.

  13. Design principles and fundamental trade-offs in biomimetic light harvesting

    International Nuclear Information System (INIS)

    Recent developments in synthetic and supramolecular chemistry have created opportunities to design organic systems with tailored nanoscale structure for various technological applications. A key application area is the capture of light energy and its conversion into electrochemical or chemical forms for photovoltaic or sensing applications. In this work we consider cylindrical assemblies of chromophores that model structures produced by several supramolecular techniques. Our study is especially guided by the versatile structures produced by virus-templated assembly. We use a multi-objective optimization framework to determine design principles and limitations in light harvesting performance for such assemblies, both in the presence and absence of disorder. We identify a fundamental trade-off in cylindrical assemblies that is encountered when attempting to maximize both efficiency of energy transfer and absorption bandwidth. We also rationalize the optimal design strategies and provide explanations for why various structures provide optimal performance. Most importantly, we find that the optimal design strategies depend on the amount of energetic and structural disorder in the system. The aim of these studies is to develop a program of quantum-informed rational design for construction of organic assemblies that have the same degree of tailored nanoscale structure as biological photosynthetic light harvesting complexes, and consequently have the potential to reproduce their remarkable light harvesting performance. (paper)

  14. On the theory of frequency-shifted secondary emission of light-harvesting molecular systems

    International Nuclear Information System (INIS)

    The expressions are obtained for the intensity of the frequency-shifted secondary emission of a chromophore playing the role of a reaction center in the simplest model three-chromophore molecular 'light-harvesting' antenna, which is constructed and oriented in space so that the incident photons coherently excite two of its chromophore pigments. The quantum-field formalism was used, which takes into account the generalized (quantum-electrodynamic) dipole-dipole, as well as radiative and nonradiative dissipative interactions between pigments and the reaction center of the antenna. The special features of the excitation spectrum of the Raman scattering line and the frequency-shifted fluorescence spectrum of the reaction center of the molecular antenna under study are discussed. A comparison of the expressions obtained for the excitation and fluorescence spectra and with the corresponding expressions obtained for a bichromophore molecular system, which differs from a three-chromophore antenna by the absence of one of the pigments, revealed the properties of the mechanism of action of light-harvesting molecular antennas that have not been found earlier. In particular, it is shown that 'the light-harvesting' caused by the collective dissipative interactions of pigments with the reaction center of the antenna can substantially exceed a sum of contributions from separate pigments

  15. Efficient energy transfer in light-harvesting systems, I: optimal temperature, reorganization energy and spatial-temporal correlations

    Energy Technology Data Exchange (ETDEWEB)

    Wu Jianlan; Liu Fan; Shen Young; Cao Jianshu; Silbey, Robert J, E-mail: jianshu@mit.ed, E-mail: silbey@mit.ed [Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States)

    2010-10-15

    Understanding the mechanisms of efficient and robust energy transfer in light-harvesting systems provides new insights for the optimal design of artificial systems. In this paper, we use the Fenna-Matthews-Olson (FMO) protein complex and phycocyanin 645 (PC 645) to explore the general dependence on physical parameters that help maximize the efficiency and maintain its stability. With the Haken-Strobl model, the maximal energy transfer efficiency (ETE) is achieved under an intermediate optimal value of dephasing rate. To avoid the infinite temperature assumption in the Haken-Strobl model and the failure of the Redfield equation in predicting the Forster rate behavior, we use the generalized Bloch-Redfield (GBR) equation approach to correctly describe dissipative exciton dynamics, and we find that maximal ETE can be achieved under various physical conditions, including temperature, reorganization energy and spatial-temporal correlations in noise. We also identify regimes of reorganization energy where the ETE changes monotonically with temperature or spatial correlation and therefore cannot be optimized with respect to these two variables.

  16. Efficient energy transfer in light-harvesting systems, I: optimal temperature, reorganization energy and spatial-temporal correlations

    International Nuclear Information System (INIS)

    Understanding the mechanisms of efficient and robust energy transfer in light-harvesting systems provides new insights for the optimal design of artificial systems. In this paper, we use the Fenna-Matthews-Olson (FMO) protein complex and phycocyanin 645 (PC 645) to explore the general dependence on physical parameters that help maximize the efficiency and maintain its stability. With the Haken-Strobl model, the maximal energy transfer efficiency (ETE) is achieved under an intermediate optimal value of dephasing rate. To avoid the infinite temperature assumption in the Haken-Strobl model and the failure of the Redfield equation in predicting the Forster rate behavior, we use the generalized Bloch-Redfield (GBR) equation approach to correctly describe dissipative exciton dynamics, and we find that maximal ETE can be achieved under various physical conditions, including temperature, reorganization energy and spatial-temporal correlations in noise. We also identify regimes of reorganization energy where the ETE changes monotonically with temperature or spatial correlation and therefore cannot be optimized with respect to these two variables.

  17. Efficient energy transfer in light-harvesting systems, I: optimal temperature, reorganization energy and spatial-temporal correlations

    Science.gov (United States)

    Wu, Jianlan; Liu, Fan; Shen, Young; Cao, Jianshu; Silbey, Robert J.

    2010-10-01

    Understanding the mechanisms of efficient and robust energy transfer in light-harvesting systems provides new insights for the optimal design of artificial systems. In this paper, we use the Fenna-Matthews-Olson (FMO) protein complex and phycocyanin 645 (PC 645) to explore the general dependence on physical parameters that help maximize the efficiency and maintain its stability. With the Haken-Strobl model, the maximal energy transfer efficiency (ETE) is achieved under an intermediate optimal value of dephasing rate. To avoid the infinite temperature assumption in the Haken-Strobl model and the failure of the Redfield equation in predicting the Forster rate behavior, we use the generalized Bloch-Redfield (GBR) equation approach to correctly describe dissipative exciton dynamics, and we find that maximal ETE can be achieved under various physical conditions, including temperature, reorganization energy and spatial-temporal correlations in noise. We also identify regimes of reorganization energy where the ETE changes monotonically with temperature or spatial correlation and therefore cannot be optimized with respect to these two variables.

  18. Synthesis of perylene-porphyrin building blocks and polymers thereof for the production of light-harvesting arrays

    Science.gov (United States)

    Loewe, Robert S.; Tomizaki, Kin-ya; Lindsey, Jonathan S.

    2005-07-12

    The present invention provides methods, compounds, and compositions for the synthesis of light harvesting arrays, such arrays comprising: (a) a first substrate comprising a first electrode; and (b) a layer of light harvesting rods electrically coupled to said first electrode, each of said light harvesting rods comprising a polymer of Formula I: wherein m is at least 1; X.sup.1 is a charge separation group, and X.sup.2 through X.sup.m+1 are chromophores. At least one of X.sup.2 through X.sup.m+1 has at least one perylene group coupled thereto.

  19. Differential Self-Assembly of Novel Redox Crown Ethers

    Science.gov (United States)

    Merithew, Andrew William

    Retinal prosthesis relies on the stimulation of living nerve tissue behind the rods and cones of the eye. The current state of the art relies on electrodes controlled by cameras which directly stimulate the nerve tissue to elicit a response to an image. These types of retinal implants have allowed for short-term crude vision in patients but have had limited long term success due to external battery packs and electroplating of the implanted electrodes. Ionic stimulation is one of the principle mechanisms that sensory neurons utilize in the generation of an action potential. In a complex transduction pathway, ionic gradients are constantly altered inside the neuron by voltage sensors or mechanically controlled gates embedded in the neuronal cell membrane; responsible for the open and close state of these ion channels. It has been demonstrated that local concentration increases of K + by direct injection proximal to the nerve can elicit nerve firing at a concentration of 15-20 mM (3-4X normal concentration) increase in K + concentration. As part of a larger concept of integrating biotechnology with nanofabrication, the materials for the development of potassium selective sequestration/storage and delivery were developed in the form of a redox-gated K+ selective crown ether. The structure of the anthraquinone-based crown was deduced by computational simulation and stoichiometry of the complex confirmed by mass spec. along with 2D diffusion NMR techniques. In this instance, the stoichiometry could be controlled by the addition of different salts to give a 1:1 complex with large, aromatic anions and a 2:1 complex with smaller anions such as triflate. The synthesis of the molecule was optimized by computational modeling and simulations of transport through an artificial membrane. The selectivity of the architecture developed was specific for K+ over Na+, the other major ionic species present in the blood. The mechanism influencing the self-assembly of this class of

  20. Cell differentiation on disk- and string-shaped hydrogels fabricated from Ca(2+) -responsive self-assembling peptides.

    Science.gov (United States)

    Fukunaga, Kazuto; Tsutsumi, Hiroshi; Mihara, Hisakazu

    2016-11-01

    We recently developed a self-assembling peptide, E1Y9, that self-assembles into nanofibers and forms a hydrogel in the presence of Ca(2+) . E1Y9 derivatives conjugated with functional peptide sequences derived from extracellular matrices (ECMs) reportedly self-assemble into peptide nanofibers that enhance cell adhesion and differentiation. In this study, E1Y9/E1Y9-IKVAV-mixed hydrogels were constructed to serve as artificial ECMs that promote cell differentiation. E1Y9 and E1Y9-IKVAV co-assembled into networked nanofibers, and hydrogels with disk and string shapes were formed in response to Ca(2+) treatment. The neuronal differentiation of PC12 cells was facilitated on hydrogels of both shapes that contained the IKVAV motifs. Moreover, long neurites extended along the long axis of the string-shaped gel, suggesting that the structure of hydrogels of this shape can affect cellular orientation. Thus, E1Y9 hydrogels can potentially be used as artificial ECMs with desirable bioactivities and shapes that could be useful in tissue engineering applications. © 2015 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 476-483, 2016. PMID:26501895

  1. Self-assembling biomolecular catalysts for hydrogen production

    Science.gov (United States)

    Jordan, Paul C.; Patterson, Dustin P.; Saboda, Kendall N.; Edwards, Ethan J.; Miettinen, Heini M.; Basu, Gautam; Thielges, Megan C.; Douglas, Trevor

    2016-02-01

    The chemistry of highly evolved protein-based compartments has inspired the design of new catalytically active materials that self-assemble from biological components. A frontier of this biodesign is the potential to contribute new catalytic systems for the production of sustainable fuels, such as hydrogen. Here, we show the encapsulation and protection of an active hydrogen-producing and oxygen-tolerant [NiFe]-hydrogenase, sequestered within the capsid of the bacteriophage P22 through directed self-assembly. We co-opted Escherichia coli for biomolecular synthesis and assembly of this nanomaterial by expressing and maturing the EcHyd-1 hydrogenase prior to expression of the P22 coat protein, which subsequently self assembles. By probing the infrared spectroscopic signatures and catalytic activity of the engineered material, we demonstrate that the capsid provides stability and protection to the hydrogenase cargo. These results illustrate how combining biological function with directed supramolecular self-assembly can be used to create new materials for sustainable catalysis.

  2. Real-time tracking of superparamagnetic nanoparticle self-assembly.

    Science.gov (United States)

    Siffalovic, P; Majkova, E; Chitu, L; Jergel, M; Luby, S; Capek, I; Satka, A; Timmann, A; Roth, S V

    2008-12-01

    The spontaneous self-assembly process of superparamagnetic nanoparticles in a fast-drying colloidal drop is observed in real time. The grazing-incidence small-angle X-ray scattering (GISAXS) technique is employed for an in situ tracking of the reciprocal space, with a 3 ms delay time between subsequent frames delivered by a new generation of X-ray cameras. A focused synchrotron beam and sophisticated sample oscillations make it possible to relate the dynamic reciprocal to direct space features and to localize the self-assembly. In particular, no nanoparticle ordering is found inside the evaporating drop and near-surface region down to a drop thickness of 90 microm. Scanning through the shrinking drop-contact line indicates the start of self-assembly near the drop three-phase interface, in accord with theoretical predictions. The results obtained have direct implications for establishing the self-assembly process as a routine technological step in the preparation of new nanostructures. PMID:19003821

  3. Chemical reaction mediated self-assembly of PTCDA into nanofibers.

    Science.gov (United States)

    Sayyad, Arshad S; Balakrishnan, Kaushik; Ajayan, Pulickel M

    2011-09-01

    Uniform and crystalline nanofibers of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA), an insoluble organic semiconducting molecule, have been achieved by self-assembling the molecules using chemical reaction mediated conversion of an appropriately designed soluble precursor, perylene tetracarboxylic acid (PTCA) using carbodiimide chemistry. PMID:21814688

  4. Long coherence times in self-assembled semiconductor quantum dots

    DEFF Research Database (Denmark)

    Birkedal, Dan; Leosson, K.; Hvam, Jørn Märcher

    We report measurements of ultra-long coherence in self-assembled quantum dots. Transient four-wave mixing experiments at 5 K show an average dephasing time of 372 ps, corresponding to a homogeneous linewidth of 3.5 mueV, which is significantly smaller than the linewidth observed in single...

  5. Surface dispersion and hardening of self-assembled diacetylene nanotubes.

    Science.gov (United States)

    Lee, Sang Beom; Koepsel, Richard R; Russell, Alan J

    2005-11-01

    We describe here the first method for dispersion of individual self-assembled diacetylene nanotubes on surfaces. Complete polymerization by UV exposure was achieved as demonstrated by nanotubes that were resistant to aggressive organic solvents and temperatures well above the melting point of the monomer. The polymerized tubes displayed reversible thermochromic and mechanochromic properties. PMID:16277453

  6. Amphiphilic self-assembly of alkanols in protic ionic liquids.

    Science.gov (United States)

    Jiang, Haihui Joy; FitzGerald, Paul A; Dolan, Andrew; Atkin, Rob; Warr, Gregory G

    2014-08-21

    Strong cohesive forces in protic ionic liquids (PILs) can induce a liquid nanostructure consisting of segregated polar and apolar domains. Small-angle X-ray scattering has shown that these forces can also induce medium chain length n-alkanols to self-assemble into micelle- and microemulsion-like structures in ethylammonium (EA(+)) and propylammonium (PA(+)) PILs, in contrast to their immiscibility with both water and ethanolammonium (EtA(+)) PILs. These binary mixtures are structured on two distinct length scales: one associated with the self-assembled n-alkanol aggregates and the other with the underlying liquid nanostructure. This suggests that EA(+) and PA(+) enable n-alkanol aggregation by acting as cosurfactants, which EtA(+) cannot do because its terminating hydroxyl renders the cation nonamphiphilic. The primary determining factor for miscibility and self-assembly is the ratio of alkyl chain lengths of the alkanol and PIL cation, modulated by the anion type. These results show how ILs can support the self-assembly of nontraditional amphiphiles and enable the creation of new forms of soft matter. PMID:25068766

  7. Microcolumns with self-assembled particle frits for proteomics

    DEFF Research Database (Denmark)

    Ishihama, Yasushi; Rappsilber, Juri; Andersen, Jens S;

    2002-01-01

    LC-MS-MS experiments in proteomics are usually performed with packed microcolumns employing frits or outlets smaller than the particle diameter to retain the packing material. We have developed packed microcolumns using self-assembled particles (SAPs) as frits that are smaller than the size of the...

  8. From coordination polymers to hierarchical self-assembled structures

    NARCIS (Netherlands)

    Yan, Y.; Keizer, de A.; Cohen Stuart, M.A.; Besseling, N.A.M.

    2011-01-01

    In this review, novel hierarchical self-assembled structures based on reversible organo-metallic supramolecular polymers are discussed. Firstly, we discuss recent advances in the field of coordination polymers, considering cases in which transition metal ions and bis- or multiligands are used to bui

  9. Self-Assembled Monolayers deposition in Supercritical Carbon Dioxide

    OpenAIRE

    Rabbia, Laurent; Perrut, Vincent; Pons, Patrick; Lellouchi, Djemel

    2009-01-01

    Self-Assembled Monolayers of organic molecules have been successfully deposited onto wafer surface in supercritical carbon dioxide. Deposition method and apparatus are described. The layers are characterized by AFM and water droplet contact angle. Interest of this technique compared to liquid and vapor phase is discussed and studied for surface conversion from hydrophilic to hydrophobic for different materials.

  10. Hierarchical self-assembly of complex polyhedral microcontainers

    Science.gov (United States)

    Filipiak, David J.; Azam, Anum; Leong, Timothy G.; Gracias, David H.

    2009-07-01

    The concept of self-assembly of a two-dimensional (2D) template to a three-dimensional (3D) structure has been suggested as a strategy to enable highly parallel fabrication of complex, patterned microstructures. We have previously studied the surface-tension-based self-assembly of patterned, microscale polyhedral containers (cubes, square pyramids and tetrahedral frusta). In this paper, we describe the observed hierarchical self-assembly of more complex, patterned polyhedral containers in the form of regular dodecahedra and octahedra. The hierarchical design methodology, combined with the use of self-correction mechanisms, was found to greatly reduce the propagation of self-assembly error that occurs in these more complex systems. It is a highly effective way to mass-produce patterned, complex 3D structures on the microscale and could also facilitate encapsulation of cargo in a parallel and cost-effective manner. Furthermore, the behavior that we have observed may be useful in the assembly of complex systems with large numbers of components.

  11. Multiphonon capture processes in self-assembled quantum dots

    DEFF Research Database (Denmark)

    Magnúsdóttir, Ingibjörg; Uskov, A.; Bischoff, Svend;

    2001-01-01

    We investigate capture of carriers from states in the continuous part of the energy spectrum into the discrete states of self-assembled InAs/GaAs QDs via emission of one or two phonons. We are not aware of any other investigations of two-phonon mediated capture processes in QDs, but we show that...

  12. Understanding the self-assembly of TCNQ on Cu(111)

    DEFF Research Database (Denmark)

    Stradi, Daniele; Borca, Bogdana; Barja, Sara;

    2016-01-01

    The structure of self-assembled monolayers of 7,7',8,8'-tetracyano-p-quinodimethane (TCNQ) adsorbed on Cu(111) has been studied using a combination of scanning tunnelling microscopy (STM) experiments and density functional theory (DFT) calculations. We show that the polymorphism of the self-assem...

  13. Self-assembled materials from thermosensitive and biohybrid block copolymers

    NARCIS (Netherlands)

    de Graaf, A.J.

    2012-01-01

    In this research, several block copolymers were synthesized and characterized with regard to possible pharmaceutical applications. All block copolymers were thermosensitive and self-assembled at 37 °C into structures like micelles and hydrogels, which can be used for innovative drug delivery purpose

  14. Long lived coherence in self-assembled quantum dots

    DEFF Research Database (Denmark)

    Birkedal, Dan; Leosson, Kristjan; Hvam, Jørn Märcher

    2001-01-01

    We report measurements of ultralong coherence in self-assembled quantum dots. Transient four-wave mixing experiments at 5 K show an average dephasing time of 372 ps, corresponding to a homogeneous linewidth of 3.5 mu eV, which is significantly smaller than the linewidth observed in single...

  15. Photoinduced self-assembly of nanostructure in glass

    OpenAIRE

    Shimotsuma Y.; Asai T; Sakakura M.; Hirao K.; Miura K; Kazansky P. G.

    2013-01-01

    Ultrashort-pulsed laser direct writing can be useful for a 3D material processing. Especially the localized form-birefringence originated from self-assembled nanostructure in isotropic material (i.e. SiO2 and GeO2 glass) was demonstrated.

  16. Encapsulation of gold nanoparticles into self-assembling protein nanoparticles

    OpenAIRE

    Yang Yongkun; Burkhard Peter

    2012-01-01

    Abstract Background Gold nanoparticles are useful tools for biological applications due to their attractive physical and chemical properties. Their applications can be further expanded when they are functionalized with biological molecules. The biological molecules not only provide the interfaces for interactions between nanoparticles and biological environment, but also contribute their biological functions to the nanoparticles. Therefore, we used self-assembling protein nanoparticles (SAPNs...

  17. Soft self-assembled nanoparticles with temperature-dependent properties

    Science.gov (United States)

    Rovigatti, Lorenzo; Capone, Barbara; Likos, Christos N.

    2016-02-01

    The fabrication of versatile building blocks that reliably self-assemble into desired ordered and disordered phases is amongst the hottest topics in contemporary materials science. To this end, microscopic units of varying complexity, aimed at assembling the target phases, have been thought, designed, investigated and built. Such a path usually requires laborious fabrication techniques, especially when specific functionalisation of the building blocks is required. Telechelic star polymers, i.e., star polymers made of a number of f di-block copolymers consisting of solvophobic and solvophilic monomers grafted on a central anchoring point, spontaneously self-assemble into soft patchy particles featuring attractive spots (patches) on the surface. Here we show that the tunability of such a system can be widely extended by controlling the physical and chemical parameters of the solution. Indeed, under fixed external conditions the self-assembly behaviour depends only on the number of arms and on the ratio of solvophobic to solvophilic monomers. However, changes in temperature and/or solvent quality make it possible to reliably change the number and size of the attractive patches. This allows the steering of the mesoscopic self-assembly behaviour without modifying the microscopic constituents. Interestingly, we also demonstrate that diverse combinations of the parameters can generate stars with the same number of patches but different radial and angular stiffness. This mechanism could provide a neat way of further fine-tuning the elastic properties of the supramolecular network without changing its topology.

  18. Photoinduced self-assembly of nanostructure in glass

    Directory of Open Access Journals (Sweden)

    Shimotsuma Y.

    2013-11-01

    Full Text Available Ultrashort-pulsed laser direct writing can be useful for a 3D material processing. Especially the localized form-birefringence originated from self-assembled nanostructure in isotropic material (i.e. SiO2 and GeO2 glass was demonstrated.

  19. Self-assembling electroactive hydrogels for flexible display technology

    International Nuclear Information System (INIS)

    We have assessed the potential of self-assembling hydrogels for use in conformal displays. The self-assembling process can be used to alter the transparency of the material to all visible light due to scattering by fibres. The reversible transition is shown to be of low energy by differential scanning calorimetry. For use in technology it is imperative that this transition is controlled electrically. We have thus synthesized novel self-assembling hydrogelator molecules which contain an electroactive group. The well-known redox couple of anthraquinone/anthrahydroquinone has been used as the hydrophobic component for a series of small molecule gelators. They are further functionalized with peptide combinations of L-phenylalanine and glycine to provide the hydrophilic group to complete 'head-tail' models of self-assembling gels. The gelation and electroactive characteristics of the series were assessed. Cyclic voltammetry shows the reversible redox cycle to be only superficially altered by functionalization. Additionally, spectroelectrochemical measurements show a reversible transparency and colour change induced by the redox process.

  20. Electrostatic Force Microscopy of Self Assembled Peptide Structures

    DEFF Research Database (Denmark)

    Clausen, Casper Hyttel; Dimaki, Maria; Pantagos, Spyros P.;

    2011-01-01

    In this report electrostatic force microscopy (EFM) is used to study different peptide self-assembled structures, such as tubes and particles. It is shown that not only geometrical information can be obtained using EFM, but also information about the composition of different structures. In...

  1. Probabilistic Analysis of Pattern Formation in Monotonic Self-Assembly.

    Science.gov (United States)

    Moore, Tyler G; Garzon, Max H; Deaton, Russell J

    2015-01-01

    Inspired by biological systems, self-assembly aims to construct complex structures. It functions through piece-wise, local interactions among component parts and has the potential to produce novel materials and devices at the nanoscale. Algorithmic self-assembly models the product of self-assembly as the output of some computational process, and attempts to control the process of assembly algorithmically. Though providing fundamental insights, these computational models have yet to fully account for the randomness that is inherent in experimental realizations, which tend to be based on trial and error methods. In order to develop a method of analysis that addresses experimental parameters, such as error and yield, this work focuses on the capability of assembly systems to produce a pre-determined set of target patterns, either accurately or perhaps only approximately. Self-assembly systems that assemble patterns that are similar to the targets in a significant percentage are "strong" assemblers. In addition, assemblers should predominantly produce target patterns, with a small percentage of errors or junk. These definitions approximate notions of yield and purity in chemistry and manufacturing. By combining these definitions, a criterion for efficient assembly is developed that can be used to compare the ability of different assembly systems to produce a given target set. Efficiency is a composite measure of the accuracy and purity of an assembler. Typical examples in algorithmic assembly are assessed in the context of these metrics. In addition to validating the method, they also provide some insight that might be used to guide experimentation. Finally, some general results are established that, for efficient assembly, imply that every target pattern is guaranteed to be assembled with a minimum common positive probability, regardless of its size, and that a trichotomy exists to characterize the global behavior of typical efficient, monotonic self-assembly systems

  2. A Two-Piece Derivative of a Group I Intron RNA as a Platform for Designing Self-Assembling RNA Templates to Promote Peptide Ligation

    Directory of Open Access Journals (Sweden)

    Takahiro Tanaka

    2012-01-01

    Full Text Available Multicomponent RNA-peptide complexes are attractive from the viewpoint of artificial design of functional biomacromolecular systems. We have developed self-folding and self-assembling RNAs that serve as templates to assist chemical ligation between two reactive peptides with RNA-binding capabilities. The design principle of previous templates, however, can be applied only to limited classes of RNA-binding peptides. In this study, we employed a two-piece derivative of a group I intron RNA from the Tetrahymena large subunit ribosomal RNA (LSU rRNA as a platform for new template RNAs. In this group I intron-based self-assembling platform, modules for the recognition of substrate peptides can be installed independently from modules holding the platform structure. The new self-assembling platform allows us to expand the repertoire of substrate peptides in template RNA design.

  3. Self-assembly of [Et,Et]-bacteriochlorophyll cF on highly oriented pyrolytic graphite revealed by scanning tunneling microscopy.

    Science.gov (United States)

    Möltgen, H; Kleinermanns, K; Jesorka, A; Schaffner, K; Holzwarth, A R

    2002-06-01

    The chlorosomal light-harvesting antennae of green phototrophic bacteria consist of large supramolecular aggregates of bacteriochlorophyll c (BChl c). The supramolecular structure of (3(1)-R/S)-BChl c on highly oriented pyrolytic graphite (HOPG) and molybdenum disulfide (MoS2) has been investigated by scanning tunneling microscopy (STM). On MoS2, we observed single BChl c molecules, dimers or tetramers, depending on the polarity of the solvent. On HOPG, we observed extensive self-assembly of the dimers and tetramers. We propose C=O...H-O...Mg bonding networks for the observed dimer chains, in agreement with former ultraviolet-visible and infrared spectroscopic work. The BChl c moieties in the tetramers are probably linked by four C=O...H-O hydrogen bonds to form a circle and further stabilized by Mg...O-H bondings to underlying BChl c layers. The tetramers form highly ordered, distinct chains and extended two-dimensional networks. We investigated semisynthetic chlorins for comparison by STM but observed that only BChl c self-assembles to well-structured large aggregates on HOPG. The results on the synthetic chlorins support our structure proposition. PMID:12081324

  4. Self-assembled photosystem-I biophotovoltaics on nanostructured TiO(2 )and ZnO.

    Science.gov (United States)

    Mershin, Andreas; Matsumoto, Kazuya; Kaiser, Liselotte; Yu, Daoyong; Vaughn, Michael; Nazeeruddin, Md K; Bruce, Barry D; Graetzel, Michael; Zhang, Shuguang

    2012-01-01

    The abundant pigment-protein membrane complex photosystem-I (PS-I) is at the heart of the Earth's energy cycle. It is the central molecule in the "Z-scheme" of photosynthesis, converting sunlight into the chemical energy of life. Commandeering this intricately organized photosynthetic nanocircuitry and re-wiring it to produce electricity carries the promise of inexpensive and environmentally friendly solar power. We here report that dry PS-I stabilized by surfactant peptides functioned as both the light-harvester and charge separator in solar cells self-assembled on nanostructured semiconductors. Contrary to previous attempts at biophotovoltaics requiring elaborate surface chemistries, thin film deposition, and illumination concentrated into narrow wavelength ranges the devices described here are straightforward and inexpensive to fabricate and perform well under standard sunlight yielding open circuit photovoltage of 0.5 V, fill factor of 71%, electrical power density of 81 µW/cm(2) and photocurrent density of 362 µA/cm(2), over four orders of magnitude higher than any photosystem-based biophotovoltaic to date. PMID:22355747

  5. Tissue engineering by self-assembly and bio-printing of living cells

    Energy Technology Data Exchange (ETDEWEB)

    Jakab, Karoly; Marga, Francoise; Forgacs, Gabor [Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211 (United States); Norotte, Cyrille [Department of Biology, University of Missouri, Columbia, MO 65211 (United States); Murphy, Keith [Organovo, Inc., 5871 Oberlin Drive, San Diego, CA 92121 (United States); Vunjak-Novakovic, Gordana, E-mail: forgacsg@missouri.ed [Department of Biomedical Engineering, Columbia University, New York, NY 10032 (United States)

    2010-06-15

    Biofabrication of living structures with desired topology and functionality requires the interdisciplinary effort of practitioners of the physical, life and engineering sciences. Such efforts are being undertaken in many laboratories around the world. Numerous approaches are pursued, such as those based on the use of natural or artificial scaffolds, decellularized cadaveric extracellular matrices and, most lately, bioprinting. To be successful in this endeavor, it is crucial to provide in vitro micro-environmental clues for the cells resembling those in the organism. Therefore, scaffolds, populated with differentiated cells or stem cells, of increasing complexity and sophistication are being fabricated. However, no matter how sophisticated scaffolds are, they can cause problems stemming from their degradation, eliciting immunogenic reactions and other a priori unforeseen complications. It is also being realized that ultimately the best approach might be to rely on the self-assembly and self-organizing properties of cells and tissues and the innate regenerative capability of the organism itself, not just simply prepare tissue and organ structures in vitro followed by their implantation. Here we briefly review the different strategies for the fabrication of three-dimensional biological structures, in particular bioprinting. We detail a fully biological, scaffoldless, print-based engineering approach that uses self-assembling multicellular units as bio-ink particles and employs early developmental morphogenetic principles, such as cell sorting and tissue fusion. (topical review)

  6. Tissue engineering by self-assembly and bio-printing of living cells

    International Nuclear Information System (INIS)

    Biofabrication of living structures with desired topology and functionality requires the interdisciplinary effort of practitioners of the physical, life and engineering sciences. Such efforts are being undertaken in many laboratories around the world. Numerous approaches are pursued, such as those based on the use of natural or artificial scaffolds, decellularized cadaveric extracellular matrices and, most lately, bioprinting. To be successful in this endeavor, it is crucial to provide in vitro micro-environmental clues for the cells resembling those in the organism. Therefore, scaffolds, populated with differentiated cells or stem cells, of increasing complexity and sophistication are being fabricated. However, no matter how sophisticated scaffolds are, they can cause problems stemming from their degradation, eliciting immunogenic reactions and other a priori unforeseen complications. It is also being realized that ultimately the best approach might be to rely on the self-assembly and self-organizing properties of cells and tissues and the innate regenerative capability of the organism itself, not just simply prepare tissue and organ structures in vitro followed by their implantation. Here we briefly review the different strategies for the fabrication of three-dimensional biological structures, in particular bioprinting. We detail a fully biological, scaffoldless, print-based engineering approach that uses self-assembling multicellular units as bio-ink particles and employs early developmental morphogenetic principles, such as cell sorting and tissue fusion. (topical review)

  7. Stimuli-Responsive Codelivery of Oligonucleotides and Drugs by Self-Assembled Peptide Nanoparticles.

    Science.gov (United States)

    Sigg, Severin J; Postupalenko, Viktoriia; Duskey, Jason T; Palivan, Cornelia G; Meier, Wolfgang

    2016-03-14

    Ever more emerging combined treatments exploiting synergistic effects of drug combinations demand smart, responsive codelivery carriers to reveal their full potential. In this study, a multifunctional stimuli-responsive amphiphilic peptide was designed and synthesized to self-assemble into nanoparticles capable of co-bearing and -releasing hydrophobic drugs and antisense oligonucleotides for combined therapies. The rational design was based on a hydrophobic l-tryptophan-d-leucine repeating unit derived from a truncated sequence of gramicidin A (gT), to entrap hydrophobic cargo, which is combined with a hydrophilic moiety of histidines to provide electrostatic affinity to nucleotides. Stimuli-responsiveness was implemented by linking the hydrophobic and hydrophilic sequence through an artificial amino acid bearing a disulfide functional group (H3SSgT). Stimuli-responsive peptides self-assembled in spherical nanoparticles in sizes (100-200 nm) generally considered as preferable for drug delivery applications. Responsive peptide nanoparticles revealed notable nucleotide condensing abilities while maintaining the ability to load hydrophobic cargo. The disulfide cleavage site introduced in the peptide sequence induced responsiveness to physiological concentrations of reducing agent, serving to release the incorporated molecules. Furthermore, the peptide nanoparticles, singly loaded or coloaded with boron-dipyrromethene (BODIPY) and/or antisense oligonucleotides, were efficiently taken up by cells. Such amphiphilic peptides that led to noncytotoxic, reduction-responsive nanoparticles capable of codelivering hydrophobic and nucleic acid payloads simultaneously provide potential toward combined treatment strategies to exploit synergistic effects. PMID:26871486

  8. Self Assembly of Nano Metric Metallic Particles for Realization of Photonic and Electronic Nano Transistors

    OpenAIRE

    Asaf Shahmoon; Ofer Limon; Olga Girshevitz; Zeev Zalevsky

    2010-01-01

    In this paper, we present the self assembly procedure as well as experimental results of a novel method for constructing well defined arrangements of self assembly metallic nano particles into sophisticated nano structures. The self assembly concept is based on focused ion beam (FIB) technology, where metallic nano particles are self assembled due to implantation of positive gallium ions into the insulating material (e.g., silica as in silicon on insulator wafers) that acts as intermediary la...

  9. Anion-dipole interactions make the homopolymers self-assemble into multiple nanostructures.

    Science.gov (United States)

    Wang, Long-Hai; Zhang, Zi-Dan; Hong, Chun-Yan; He, Xue-Hao; You, Wei; You, Ye-Zi

    2015-05-27

    Anion-dipole interactions can make homopolymers self-assemble like an amphiphilic block copolymer. Generally, common homopolymers cannot self-assemble into multiple nanostructures. Here, it is reported that anion-dipole interactions can enable a number of homopolymers to achieve a variety of self-assembly behaviors in aqueous solution. Such interactions and self-assembly features have been exclusively reserved for amphiphilic (block) polymers until now. PMID:25873566

  10. Colloidal Self-Assembly Driven by Deformability & Near-Critical Phenomena

    NARCIS (Netherlands)

    Evers, C.H.J.

    2016-01-01

    Self-assembly is the spontaneous formation of patterns or structures without human intervention. This thesis aims to increase our understanding of self-assembly. In self-assembly of proteins, the building blocks are very small and complex. Consequently, grasping the basic principles that drive the f

  11. Toward three-dimensional microelectronic systems: directed self-assembly of silicon microcubes via DNA surface functionalization.

    Science.gov (United States)

    Lämmerhardt, Nico; Merzsch, Stephan; Ledig, Johannes; Bora, Achyut; Waag, Andreas; Tornow, Marc; Mischnick, Petra

    2013-07-01

    The huge and intelligent processing power of three-dimensional (3D) biological "processors" like the human brain with clock speeds of only 0.1 kHz is an extremely fascinating property, which is based on a massively parallel interconnect strategy. Artificial silicon microprocessors are 7 orders of magnitude faster. Nevertheless, they do not show any indication of intelligent processing power, mostly due to their very limited interconnectivity. Massively parallel interconnectivity can only be realized in three dimensions. Three-dimensional artificial processors would therefore be at the root of fabricating artificially intelligent systems. A first step in this direction would be the self-assembly of silicon based building blocks into 3D structures. We report on the self-assembly of such building blocks by molecular recognition, and on the electrical characterization of the formed assemblies. First, planar silicon substrates were functionalized with self-assembling monolayers of 3-aminopropyltrimethoxysilane for coupling of oligonucleotides (single stranded DNA) with glutaric aldehyde. The oligonucleotide immobilization was confirmed and quantified by hybridization with fluorescence-labeled complementary oligonucleotides. After the individual processing steps, the samples were analyzed by contact angle measurements, ellipsometry, atomic force microscopy, and fluorescence microscopy. Patterned DNA-functionalized layers were fabricated by microcontact printing (μCP) and photolithography. Silicon microcubes of 3 μm edge length as model objects for first 3D self-assembly experiments were fabricated out of silicon-on-insulator (SOI) wafers by a combination of reactive ion etching (RIE) and selective wet etching. The microcubes were then surface-functionalized using the same protocol as on planar substrates, and their self-assembly was demonstrated both on patterned silicon surfaces (88% correctly placed cubes), and to cube aggregates by complementary DNA

  12. Ultrathin efficient perovskite solar cells employing a periodic structure of a composite hole conductor for elevated plasmonic light harvesting and hole collection

    Science.gov (United States)

    Long, Mingzhu; Chen, Zefeng; Zhang, Tiankai; Xiao, Yubin; Zeng, Xiaoliang; Chen, Jian; Yan, Keyou; Xu, Jianbin

    2016-03-01

    We developed a molecule/polymer composite hole transporting material (HTM) with a periodic microstructure for morphology replication of a corrugated Au electrode, which in combination plays a dual role in the optical and electronic enhancement of high performance perovskite solar cells (PSCs). The electro-optics revealed that perovskite couldn't readily extinct the red light even though the thickness increased to 370 nm, but we found that the quasi periodic microstructure composite (PMC) HTM in combination with the conformal Au electrode could promote the absorption through the enhanced cavity effects, leading to comparable absorption even using much thinner perovskite (240 nm). We identified that the cavity was the combination of Fabry-Pérot interferometer and surface plasmonic resonance, with light harvesting enhancement through surface plasmon polariton or waveguide modes that propagate in the plane of the perovskite layer. On the other hand, the PMC HTM increased hole conductivity by one order of magnitude with respect to standard spiro-OMeTAD HTM due to molecular packing and self-assembly, embodying traceable hole mobility and density elevation up to 3 times, and thus the hysteresis was greatly avoided. Owing to dual optical and electronic enhancement, the PMC PSC afforded high efficiency PSC using as thin as 240 nm perovskite layer, delivering a Voc of 1.05 V, Jsc of 22.9 mA cm-2, FF of 0.736, and efficiency amounting to 17.7% PCE, the highest efficiency with ultrathin perovskite layer.We developed a molecule/polymer composite hole transporting material (HTM) with a periodic microstructure for morphology replication of a corrugated Au electrode, which in combination plays a dual role in the optical and electronic enhancement of high performance perovskite solar cells (PSCs). The electro-optics revealed that perovskite couldn't readily extinct the red light even though the thickness increased to 370 nm, but we found that the quasi periodic microstructure

  13. Theory of femtosecond coherent double-pump single-molecule spectroscopy: Application to light harvesting complexes

    International Nuclear Information System (INIS)

    We develop a first principles theoretical description of femtosecond double-pump single-molecule signals of molecular aggregates. We incorporate all singly excited electronic states and vibrational modes with significant exciton-phonon coupling into a system Hamiltonian and treat the ensuing system dynamics within the Davydov D1 Ansatz. The remaining intra- and inter-molecular vibrational modes are treated as a heat bath and their effect is accounted for through lineshape functions. We apply our theory to simulate single-molecule signals of the light harvesting complex II. The calculated signals exhibit pronounced oscillations of mixed electron-vibrational (vibronic) origin. Their periods decrease with decreasing exciton-phonon coupling

  14. Geometry, supertransfer, and optimality in the light harvesting of purple bacteria

    CERN Document Server

    Baghbanzadeh, Sima

    2016-01-01

    The remarkable rotational symmetry of the photosynthetic antenna complexes of purple bacteria has long been thought to enhance their light harvesting and excitation energy transport. We study the role of symmetry by modeling hypothetical antennas whose symmetry is broken by altering the orientations of the bacteriochlorophyll pigments. We find that in both LH2 and LH1 complexes, symmetry increases energy transfer rates by enabling the cooperative, coherent process of supertransfer. The enhancement is particularly pronounced in the LH1 complex, whose natural geometry outperforms the average randomized geometry by 5.5 standard deviations, one of the most significant increase due to coherent effects in any photosynthetic complex studied to date.

  15. Recent trends in mesoscopic solar cells based on molecular and nanopigment light harvesters

    KAUST Repository

    Grätzel, Carole

    2013-01-01

    Mesoscopic solar cells are one of the most promising photovoltaic technologies among third generation photovoltaics due to their low cost and high efficiency. The morphology of wide-band semiconductors, sensitized with molecular or nanosized light harvesters, used as electron collectors contribute substantially to the device performance. Recent developments in the use of organic-inorganic layer structured perovskites as light absorbers and as electron or hole transport materials allows reduction in the thickness of photoanodes to the submicron level and have raised the power conversion efficiency of solid state mesoscopic solar cells above the 10% level.

  16. Coherence dynamics in light-harvesting complexes with two-colour spectroscopy

    Science.gov (United States)

    Richards, Gethin H.; Curmi, Paul M. G.; Wilk, Krystyna E.; Quiney, Harry M.; Davis, Jeffrey A.

    2013-03-01

    We investigate coherent dynamics in the cryptophyte light-harvesting complex Phycocyanin-645 (PC-645). A two-colour four-wave mixing experiment allows us to isolate a coherence pathway and observe its evolution in the absence of other signals. We measured a decoherence time of 540fs for the coherence [1]. Additionally oscillations in the signal pathway give evidence for the coherent excitation of states outside the bandwidth of the laser pulse. This suggests strong coupling between the excited states and phonon modes [1].

  17. Coherence dynamics in light-harvesting complexes with two-colour spectroscopy

    Directory of Open Access Journals (Sweden)

    Quiney Harry M.

    2013-03-01

    Full Text Available We investigate coherent dynamics in the cryptophyte light-harvesting complex Phycocyanin-645 (PC-645. A two-colour four-wave mixing experiment allows us to isolate a coherence pathway and observe its evolution in the absence of other signals. We measured a decoherence time of 540fs for the coherence [1]. Additionally oscillations in the signal pathway give evidence for the coherent excitation of states outside the bandwidth of the laser pulse. This suggests strong coupling between the excited states and phonon modes [1].

  18. Neutron and light scattering studies of light-harvesting photosynthetic antenna complexes

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Kuo-Hsiang; Blankenship, R. E.

    2011-06-28

    Small-angle neutron scattering (SANS) and dynamic light scattering (DLS) have been employed in studying the structural information of various biological systems, particularly in systems without high-resolution structural information available. In this report, we briefly present some principles and biological applications of neutron scattering and DLS, compare the differences in information that can be obtained with small-angle X-ray scattering (SAXS), and then report recent studies of SANS and DLS, together with other biophysical approaches, for light-harvesting antenna complexes and reaction centers of purple and green phototrophic bacteria.

  19. Facile Synthesis of Colloidal CuO Nanocrystals for Light-Harvesting Applications

    Directory of Open Access Journals (Sweden)

    Yee-Fun Lim

    2012-01-01

    Full Text Available CuO is an earth-abundant, nontoxic, and low band-gap material; hence it is an attractive candidate for application in solar cells. In this paper, a synthesis of CuO nanocrystals by a facile alcohothermal route is reported. The nanocrystals are dispersible in a solvent mixture of methanol and chloroform, thus enabling the processing of CuO by solution. A bilayer solar cell comprising of CuO nanocrystals and phenyl-C61-butyric acid methyl ester (PCBM achieved a power conversion efficiency of 0.04%, indicating the potential of this material for light-harvesting applications.

  20. Energy transfer from conjugated polymer to bacterial light-harvesting complex

    Science.gov (United States)

    Buczynska, D.; Bujak, Ł.; Loi, M. A.; Brotosudarmo, T. H. P.; Cogdell, R.; Mackowski, S.

    2012-10-01

    Energy transfer from a conjugated polymer blend (poly(9,9-dioctylfluorenyl-2,7-diyl):poly (2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene) to a light-harvesting complex 2 from purple bacteria has been demonstrated using time-resolved fluorescence spectroscopy. For our hybrid nanostructure, we observe a 30% reduction of the fluorescence lifetime of the polymer emission as compared to the pure polymer layer. This result is an important step towards integrating naturally evolved biomolecules with synthetic materials into biohybrid organic electronic systems.

  1. Toward understanding as photosynthetic biosignatures: light harvesting and energy transfer calculation

    Science.gov (United States)

    Komatsu, Y.; Umemura, M.; Shoji, M.; Shiraishi, K.; Kayanuma, M.; Yabana, K.

    2014-03-01

    Among several proposed biosignatures, red edge is a direct evidence of photosynthetic life if it is detected (Kiang et al 2007). Red edge is a sharp change in reflectance spectra of vegetation in NIR region (about 700-750 nm). The sign of red edge is observed by Earthshine or remote sensing (Wolstencroft & Raven 2002, Woolf et al 2002). But, why around 700-750 nm? The photosynthetic organisms on Earth have evolved to optimize the sunlight condition. However, if we consider about photosynthetic organism on extrasolar planets, they should have developed to utilize the spectra of its principal star. Thus, it is not strange even if it shows different vegetation spectra. In this study, we focused on the light absorption mechanism of photosynthetic organisms on Earth and investigated the fundamental properties of the light harvesting mechanisms, which is the first stage for the light absorption. Light harvesting complexes contain photosynthetic pigments like chlorophylls. Effective light absorption and the energy transfer are accomplished by the electronic excitations of collective photosynthetic pigments. In order to investigate this mechanism, we constructed an energy transfer model by using a dipole-dipole approximation for the interactions between electronic excitations. Transition moments and transition energies of each pigment are calculated at the time-dependent density functional theory (TDDFT) level (Marques & Gross 2004). Quantum dynamics simulation for the excitation energy transfer was calculated by the Liouvelle's equation. We adopted the model to purple bacteria, which has been studied experimentally and known to absorb lower energy. It is meaningful to focus on the mechanism of this bacteria, since in the future mission, M planets will become a important target. We calculated the oscillator strengths in one light harvesting complex and confirmed the validity by comparing to the experimental data. This complex is made of an inner and an outer ring. The

  2. Mechanisms of energy transfer and conversion in plant light-harvesting complex II

    OpenAIRE

    Ferreira de Barros, Tiago

    2009-01-01

    The light-harvesting complex of photosystem II (LHC-II) is the major antenna complex in plant photosynthesis. It accounts for roughly 30% of the total protein in plant chloroplasts, which makes it arguably the most abundant membrane protein on Earth, and binds about half of plant chlorophyll (Chl). The complex assembles as a trimer in the thylakoid membrane and binds a total of 54 pigment molecules, including 24 Chl a, 18 Chl b, 6 lutein (Lut), 3 neoxanthin (Neo) and 3 violaxanthin (Vio). LHC...

  3. Facile Synthesis of Colloidal CuO Nanocrystals for Light-Harvesting Applications

    KAUST Repository

    Lim, Yee-Fun

    2012-01-01

    CuO is an earth-abundant, nontoxic, and low band-gap material; hence it is an attractive candidate for application in solar cells. In this paper, a synthesis of CuO nanocrystals by a facile alcohothermal route is reported. The nanocrystals are dispersible in a solvent mixture of methanol and chloroform, thus enabling the processing of CuO by solution. A bilayer solar cell comprising of CuO nanocrystals and phenyl-C61-butyric acid methyl ester (PCBM) achieved a power conversion efficiency of 0.04%, indicating the potential of this material for light-harvesting applications.

  4. Self-Assembly of Graphene on Carbon Nanotube Surfaces

    Science.gov (United States)

    Li, Kaiyuan; Eres, Gyula; Howe, Jane; Chuang, Yen-Jun; Li, Xufan; Gu, Zhanjun; Zhang, Litong; Xie, Sishen; Pan, Zhengwei

    2013-08-01

    The rolling up of a graphene sheet into a tube is a standard visualization tool for illustrating carbon nanotube (CNT) formation. However, the actual processes of rolling up graphene sheets into CNTs in laboratory syntheses have never been demonstrated. Here we report conformal growth of graphene by carbon self-assembly on single-wall and multi-wall CNTs using chemical vapor deposition (CVD) of methane without the presence of metal catalysts. The new graphene layers roll up into seamless coaxial cylinders encapsulating the existing CNTs, but their adhesion to the primary CNTs is weak due to the existence of lattice misorientation. Our study shows that graphene nucleation and growth by self-assembly of carbon on the inactive carbon basal plane of CNTs occurs by a new mechanism that is markedly different from epitaxial growth on metal surfaces, opening up the possibility of graphene growth on many other non-metal substrates by simple methane CVD.

  5. Stable doping of carbon nanotubes via molecular self assembly

    Energy Technology Data Exchange (ETDEWEB)

    Lee, B.; Chen, Y.; Podzorov, V., E-mail: podzorov@physics.rutgers.edu [Department of Physics and Institute for Advanced Materials and Devices for Nanotechnology, Rutgers University, New Jersey 08854 (United States); Cook, A.; Zakhidov, A. [Department of Physics and NanoTech Institute, University of Texas at Dallas, Richardson, Texas 75083 (United States)

    2014-10-14

    We report a novel method for stable doping of carbon nanotubes (CNT) based on methods of molecular self assembly. A conformal growth of a self-assembled monolayer of fluoroalkyl trichloro-silane (FTS) at CNT surfaces results in a strong increase of the sheet conductivity of CNT electrodes by 60–300%, depending on the CNT chirality and composition. The charge carrier mobility of undoped partially aligned CNT films was independently estimated in a field-effect transistor geometry (~100 cm²V⁻¹s⁻¹). The hole density induced by the FTS monolayer in CNT sheets is estimated to be ~1.8 ×10¹⁴cm⁻². We also show that FTS doping of CNT anodes greatly improves the performance of organic solar cells. This large and stable doping effect, easily achieved in large-area samples, makes this approach very attractive for applications of CNTs in transparent and flexible electronics.

  6. Coherence and dephasing in self-assembled quantum dots

    DEFF Research Database (Denmark)

    Hvam, Jørn Märcher; Leosson, K.; Birkedal, Dan

    We measured dephasing times in InGaAl/As self-assembled quantum dots at low temperature using degenerate four-wave mixing. At 0K, the coherence time of the quantum dots is lifetime limited, whereas at finite temperatures pure dephasing by exciton-phonon interactions governs the quantum dot cohere...... coherence. The inferred homogeneous line widths are significantly smaller than the line widths usually observed in the photoluminescence from single quantum dots indicating an additional inhomogeneours broadening mechanism in the latter.......We measured dephasing times in InGaAl/As self-assembled quantum dots at low temperature using degenerate four-wave mixing. At 0K, the coherence time of the quantum dots is lifetime limited, whereas at finite temperatures pure dephasing by exciton-phonon interactions governs the quantum dot...

  7. Directed self-assembly of microscale hydrogels by electrostatic interaction

    International Nuclear Information System (INIS)

    The unique benefit of electrostatic self-assembly of microscale components in solution is demonstrated for the first time. In particular, positive and negative treatment of poly(ethylene glycol) (PEG) facilitates a novel bottom-up assembly approach using electrostatic interaction from microgels with opposite charges. Fundamental investigations of electrostatic interaction of microgels reveal that the contact area of microgels determines the total energy of construct and thus the final patterns. The electrostatic self-assembly approach enables the fabrication of large and complex biological related structures (e.g., multi-layer spheroid) with accurate control. By the design of the microgels, the thickness and number of microgels in each layer can be controlled. Biological investigations of positive and negative treatments of PEG further prove the possibility of using this approach in tissue engineering, regenerative medicine and drug delivery. (paper)

  8. Multidimensional hierarchical self-assembly of amphiphilic cylindrical block comicelles

    Science.gov (United States)

    Qiu, Huibin; Hudson, Zachary M.; Winnik, Mitchell A.; Manners, Ian

    2015-03-01

    Self-assembly of molecular and block copolymer amphiphiles represents a well-established route to micelles with a wide variety of shapes and gel-like phases. We demonstrate an analogous process, but on a longer length scale, in which amphiphilic P-H-P and H-P-H cylindrical triblock comicelles with hydrophobic (H) or polar (P) segments that are monodisperse in length are able to self-assemble side by side or end to end in nonsolvents for the central or terminal segments, respectively. This allows the formation of cylindrical supermicelles and one-dimensional (1D) or 3D superstructures that persist in both solution and the solid state. These assemblies possess multiple levels of structural hierarchy in combination with existence on a multimicrometer-length scale, features that are generally only found in natural materials.

  9. Self-assembly does not account for the hydrophobic effect.

    Science.gov (United States)

    Abraham, Michael H; Blandamer, Michael J

    2002-07-01

    Marmur has claimed that large values of activity coefficients for nonelectrolytes, particularly in the context of hydrophobic interactions between solutes in aqueous solution at ambient temperature and pressure, cannot be accounted for by thermodynamics, and has suggested that association (self-assembly) of solute molecules in solution solves this dilemma. We show that the analysis of Marmur is incorrect, specifically because the equilibrium in solution between monomeric solute molecules and associated solute molecules is entirely ignored. We show further that activity coefficients such as that for nitromethane solute in hexane solvent, 39.7, and that for solute hexane in solvent water, 4.48 x 10(5), can be calculated as 31.9 and 4.71 x 10(5), respectively, by methods based on well-known molecule-molecule interactions. No assumption of self-assembly is required. PMID:12083940

  10. Molecular Gels Materials with Self-Assembled Fibrillar Networks

    CERN Document Server

    Weiss, Richard G

    2006-01-01

    Molecular gels and fibrillar networks – a comprehensive guide to experiment and theory Molecular Gels: Materials with Self-Assembled Fibrillar Networks provides a comprehensive treatise on gelators, especially low molecular-mass gelators (LMOGs), and the properties of their gels. The structures and modes of formation of the self-assembled fibrillar networks (SAFINs) that immobilize the liquid components of the gels are discussed experimentally and theoretically. The spectroscopic, rheological, and structural features of the different classes of LMOGs are also presented. Many examples of the application of the principal analytical techniques for investigation of molecular gels (including SANS, SAXS, WAXS, UV-vis absorption, fluorescence and CD spectroscopies, scanning electron, transmission electron and optical microscopies, and molecular modeling) are presented didactically and in-depth, as are several of the theories of the stages of aggregation of individual LMOG molecules leading to SAFINs. Several actua...

  11. Charged diphenylalanine nanotubes and controlled hierarchical self-assembly.

    Science.gov (United States)

    Wang, Minjie; Du, Lingjie; Wu, Xinglong; Xiong, Shijie; Chu, Paul K

    2011-06-28

    Hexagonal hierarchical microtubular structures are produced by diphenylalanine self-assembly and the ratio of the relative humidity in the growth chamber to the diphenylalanine concentration (defined as the RH-FF ratio) determines the microtubular morphology. The hexagonal arrangement of the diphenylalanine molecules first induces the hexagonal nanotubes with opposite charges on the two ends, and the dipolar electric field on the nanotubes serves as the driving force. Side-by-side hexagonal aggregation and end-to-end arrangement ensue finally producing a hexagonal hierarchical microtubular structure. Staining experiments and the external electric field-induced parallel arrangement provide evidence of the existence of opposite charges and dipolar electric field. In this self-assembly, the different RH-FF ratios induce different contents of crystalline phases. This leads to different initial nanotube numbers finally yielding different microtubular morphologies. Our calculation based on the dipole model supports the dipole-field mechanism that leads to the different microtubular morphologies. PMID:21591732

  12. Self-assembled arrays of peptide nanotubes by vapour deposition.

    Science.gov (United States)

    Adler-Abramovich, Lihi; Aronov, Daniel; Beker, Peter; Yevnin, Maya; Stempler, Shiri; Buzhansky, Ludmila; Rosenman, Gil; Gazit, Ehud

    2009-12-01

    The use of bionanostructures in real-world applications will require precise control over biomolecular self-assembly and the ability to scale up production of these materials. A significant challenge is to control the formation of large, homogeneous arrays of bionanostructures on macroscopic surfaces. Previously, bionanostructure formation has been based on the spontaneous growth of heterogenic populations in bulk solution. Here, we demonstrate the self-assembly of large arrays of aromatic peptide nanotubes using vapour deposition methods. This approach allows the length and density of the nanotubes to be fine-tuned by carefully controlling the supply of the building blocks from the gas phase. Furthermore, we show that the nanotube arrays can be used to develop high-surface-area electrodes for energy storage applications, highly hydrophobic self-cleaning surfaces and microfluidic chips. PMID:19893524

  13. Synthesis and Self-Assembly of Triangulenium Salts

    DEFF Research Database (Denmark)

    Shi, Dong

    -processed self-assembling method was developed to make aggregates with uniform morphologies and excellent stabilities in an equilibrium state either with pure ATOTA+ salts or with mixed systems of ATOTA+ salts and lipid molecules in aqueous media. Special emphasis was given to effects of the counterions in......-assembly and triangulenium salts. Chapters 3 to 6 are mainly focused on the synthesis and self-assembly of trioxatriangulenium salts in aqueous media. In particular, chapter 3 reports a direct selfassembly of a synthetic triangulenium salt mixed with DMPC lipid (5/95 by molar ratio) to make mono disperse......This thesis describes the design and synthesis of asymmetrically substituted amphiphilic tis(dialkylamino)trioxiatriangulenium (ATOTA+) salts with different counter ions. Attention was focused on exploring the assembling properties of the ATOTA+ salts in aqueous media. A direct vortexing...

  14. Protein-directed self-assembly of a fullerene crystal

    Science.gov (United States)

    Kim, Kook-Han; Ko, Dong-Kyun; Kim, Yong-Tae; Kim, Nam Hyeong; Paul, Jaydeep; Zhang, Shao-Qing; Murray, Christopher B.; Acharya, Rudresh; Degrado, William F.; Kim, Yong Ho; Grigoryan, Gevorg

    2016-04-01

    Learning to engineer self-assembly would enable the precise organization of molecules by design to create matter with tailored properties. Here we demonstrate that proteins can direct the self-assembly of buckminsterfullerene (C60) into ordered superstructures. A previously engineered tetrameric helical bundle binds C60 in solution, rendering it water soluble. Two tetramers associate with one C60, promoting further organization revealed in a 1.67-Å crystal structure. Fullerene groups occupy periodic lattice sites, sandwiched between two Tyr residues from adjacent tetramers. Strikingly, the assembly exhibits high charge conductance, whereas both the protein-alone crystal and amorphous C60 are electrically insulating. The affinity of C60 for its crystal-binding site is estimated to be in the nanomolar range, with lattices of known protein crystals geometrically compatible with incorporating the motif. Taken together, these findings suggest a new means of organizing fullerene molecules into a rich variety of lattices to generate new properties by design.

  15. Symmetric organization of self-assembled carbon nitride

    International Nuclear Information System (INIS)

    A scheme for creating 'flower-like' nanostructures of carbon nitride is described that involves the self-assembly of nanocrystals following laser ablation of a solid graphite target immersed in aqueous ammonia solution. The primary nanocrystals possess rod-like symmetry, and then self-assemble upon drying to form nanoleaf or nanopetal shaped structures. Samples were characterized using x-ray diffraction (XRD), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), x-ray photoelectron microscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The analyses confirmed their composition to be consistent with that of crystalline β-phase carbon nitride. The morphologies of the carbon nitride nanostructures depended strongly on the synthesis conditions and upon the conditions under which the aqueous suspension of ablated particles were dried

  16. Prospects for using self-assembled nucleic acid structures.

    Science.gov (United States)

    Rudchenko, M N; Zamyatnin, A A

    2015-04-01

    According to the central dogma in molecular biology, nucleic acids are assigned with key functions on storing and executing genetic information in any living cell. However, features of nucleic acids are not limited only with properties providing template-dependent biosynthetic processes. Studies of DNA and RNA unveiled unique features of these polymers able to make various self-assembled three-dimensional structures that, among other things, use the complementarity principle. Here, we review various self-assembled nucleic acid structures as well as application of DNA and RNA to develop nanomaterials, molecular automata, and nanodevices. It can be expected that in the near future results of these developments will allow designing novel next-generation diagnostic systems and medicinal drugs. PMID:25869355

  17. Self-assembly of nanomaterials at fluid interfaces.

    Science.gov (United States)

    Toor, Anju; Feng, Tao; Russell, Thomas P

    2016-05-01

    Recent developments in the field of the self-assembly of nanoscale materials such as nanoparticles, nanorods and nanosheets at liquid/liquid interfaces are reviewed. Self-assembly behavior of both biological and synthetic particles is discussed. For biological nanoparticles, the nanoparticle assembly at fluid interfaces provides a simple route for directing nanoparticles into 2D or 3D constructs with hierarchical ordering. The interfacial assembly of single-walled carbon nanotubes (SWCNTs) at liquid interfaces would play a key role in applications such as nanotube fractionation, flexible electronic thin-film fabrication and synthesis of porous SWCNT/polymer composites foams. Liquids can be structured by the jamming of nanoparticle surfactants at fluid interfaces. By controlling the interfacial packing of nanoparticle surfactants using external triggers, a new class of materials can be generated that combines the desirable characteristics of fluids such as rapid transport of energy carriers with the structural stability of a solid. PMID:27233643

  18. Self-Reproducing by Self-Assembly and Fission

    Czech Academy of Sciences Publication Activity Database

    Wiedermann, Jiří

    Auckland : CDMTCS, 2004 - (Calude, C.; Calude, E.; Dinneen, M.), s. 1-10 - (CDMTCS Research Report Series. 252). [DLT'04. International Conference on Developments in Language Theory /8./. Auckland (NZ), 13.12.2004-17.12.2004] R&D Projects: GA AV ČR 1ET100300419 Institutional research plan: CEZ:AV0Z1030915 Keywords : cellular automata * self-assembly * self-reproducing automata Subject RIV: BA - General Mathematics http://hdl.handle.net/2292/3759

  19. Electrostatically Directed Self-Assembly of Ultrathin Supramolecular Polymer Microcapsules

    OpenAIRE

    Parker, Richard M.; Zhang, Jing; Zheng, Yu; Coulston, Roger J.; Smith, Clive A; Salmon, Andrew R; Yu, Ziyi; Oren A. Scherman; Abell, Chris

    2015-01-01

    Supramolecular self-assembly offers routes to challenging architectures on the molecular and macroscopic scale. Coupled with microfluidics it has been used to make microcapsules—where a 2D sheet is shaped in 3D, encapsulating the volume within. In this paper, a versatile methodology to direct the accumulation of capsule-forming components to the droplet interface using electrostatic interactions is described. In this approach, charged copolymers are selectively partitioned to the microdroplet...

  20. Intrinsic universality and the computational power of self-assembly.

    Science.gov (United States)

    Woods, Damien

    2015-07-28

    Molecular self-assembly, the formation of large structures by small pieces of matter sticking together according to simple local interactions, is a ubiquitous phenomenon. A challenging engineering goal is to design a few molecules so that large numbers of them can self-assemble into desired complicated target objects. Indeed, we would like to understand the ultimate capabilities and limitations of this bottom-up fabrication process. We look to theoretical models of algorithmic self-assembly, where small square tiles stick together according to simple local rules in order to carry out a crystal growth process. In this survey, we focus on the use of simulation between such models to classify and separate their computational and expressive powers. Roughly speaking, one model simulates another if they grow the same structures, via the same dynamical growth processes. Our journey begins with the result that there is a single intrinsically universal tile set that, with appropriate initialization and spatial scaling, simulates any instance of Winfree's abstract Tile Assembly Model. This universal tile set exhibits something stronger than Turing universality: it captures the geometry and dynamics of any simulated system in a very direct way. From there we find that there is no such tile set in the more restrictive non-cooperative model, proving it weaker than the full Tile Assembly Model. In the two-handed model, where large structures can bind together in one step, we encounter an infinite set of infinite hierarchies of strictly increasing simulation power. Towards the end of our trip, we find one tile to rule them all: a single rotatable flipable polygonal tile that simulates any tile assembly system. We find another tile that aperiodically tiles the plane (but with small gaps). These and other recent results show that simulation is giving rise to a kind of computational complexity theory for self-assembly. It seems this could be the beginning of a much longer journey

  1. Tailoring self-assembled monolayers at the electrochemical interface

    Indian Academy of Sciences (India)

    S Varatharajan; Sheela Berchmans; V Yegnaraman

    2009-09-01

    The main focus of this review is to illustrate the amenability of self-assembled monolayers (SAMs) for functionalisation with different receptors, catalytic materials, biomolecules, enzymes, antigen-antibody, etc for various applications. The review discusses initially about the preparation and characterization of SAMs and tailoring of SAMs by incorporation of suitable recognition elements. A description of how the molecular recognition is achieved through forces like electrostatic, covalent and host-guest interactions is included in the review.

  2. Stability of Self-Assembled Polymeric Micelles in Serum

    OpenAIRE

    Lu, Jiao; Owen, Shawn C.; Shoichet, Molly S.

    2011-01-01

    The stability of polymeric nanoparticles in serum is critical to their use in drug delivery where dilution after intravenous injection often results in nanoparticle disassembly and drug unloading; however, few investigate this in biologically relevant media. To gain greater insight into nanoparticle stability in blood, the stability of self-assembled polymeric micelles of poly(d,l-lactide-co-2-methyl-2-carboxytrimethylene carbonate)-g-poly(ethylene glycol), P(LA-co-TMCC)-g-PEG, were tested in...

  3. The effects of self-assembly in solutions of polyelectrolytes

    OpenAIRE

    Limberger, Roman E.

    2004-01-01

    The PhD thesis "The Effects of Self-Assembly in Solutions of Polyelectrolytes" written by Roman E. Limberger contains the introduction, the literature review, two original parts, the consequences, the acknowledgements, the list of references and four appendices. In the introduction the relevance of the present thesis is explained. The literature review is divided into two parts. The first part is dedicated to the consideration of the main theoretical models and the results in the study of...

  4. Self-Assembly of Graphene on Carbon Nanotube Surfaces

    OpenAIRE

    Li, Kaiyuan; Eres, Gyula; Howe, Jane; Chuang, Yen-Jun; Li, Xufan; Gu, Zhanjun; Zhang, Litong; Xie, Sishen; Pan, Zhengwei

    2013-01-01

    The rolling up of a graphene sheet into a tube is a standard visualization tool for illustrating carbon nanotube (CNT) formation. However, the actual processes of rolling up graphene sheets into CNTs in laboratory syntheses have never been demonstrated. Here we report conformal growth of graphene by carbon self-assembly on single-wall and multi-wall CNTs using chemical vapor deposition (CVD) of methane without the presence of metal catalysts. The new graphene layers roll up into seamless coax...

  5. Purification of ethanol for highly sensitive self-assembly experiments

    OpenAIRE

    Kathrin Barbe; Martin Kind; Christian Pfeiffer; Andreas Terfort

    2014-01-01

    Ethanol is the preferred solvent for the formation of self-assembled monolayers (SAMs) of thiolates on gold. By applying a thin film sensor system, we could demonstrate that even the best commercial qualities of ethanol contain surface-active contaminants, which can compete with the desired thiolates for surface sites. Here we present that gold nanoparticles deposited onto zeolite X can be used to remove these contaminants by chemisorption. This nanoparticle-impregnated zeolite does not only ...

  6. Self-assembly of phenylalanine-based molecules.

    Science.gov (United States)

    German, Helen W; Uyaver, Sahin; Hansmann, Ulrich H E

    2015-03-01

    Using molecular dynamics, we study the self-assembly of phenylalanine with charged end-groups at various temperatures and concentrations. As in the case of diphenylalanine, we observe the formation of nanotubes; however, phenylalanine aggregates in layers of four, not six, molecules. The observed aggregates are consistent with recent experimental measurements of fibrils obtained from mice with phenylketonuria. We investigate the stability and the mechanism by which these tubular structures form and discuss potential toxicity mechanisms. PMID:25347763

  7. Hydrophobic Interactions Modulate Self-Assembly of Nanoparticles

    OpenAIRE

    Sánchez-Iglesias, Ana; Grzelczak, Marek; Altantzis, Thomas; Goris, Bart; Perez-Juste, Jorge; Bals, Sara; Van Tendeloo, Gustaaf; Donaldson, Jr., Stephen H.; Chmelka, Bradley F.; Israelachvili, Jacob N.; Liz-Marzán, Luis M.

    2012-01-01

    Abstract: Hydrophobic interactions constitute one of the most important types of nonspecific interactions in biological systems, which emerge when water molecules rearrange as two hydrophobic species come close to each other. The prediction of hydrophobic interactions at the level of nanoparticles (Brownian objects) remains challenging because of uncontrolled diffusive motion of the particles. We describe here a general methodology for solvent-induced, reversible self-assembly of gold nanopar...

  8. Self-assembled containers based on extended tetrathiafulvalene.

    Science.gov (United States)

    Bivaud, Sébastien; Goeb, Sébastien; Croué, Vincent; Dron, Paul I; Allain, Magali; Sallé, Marc

    2013-07-10

    Two original self-assembled containers constituted each by six electroactive subunits are described. They are synthesized from a concave tetratopic π-extended tetrathiafulvalene ligand bearing four pyridyl units and cis-M(dppf)(OTf)2 (M = Pd or Pt; dppf = 1,1'-bis(diphenylphosphino)ferrocene; OTf = trifluoromethane-sulfonate) complexes. Both fully characterized assemblies present an oblate spheroidal cavity that can incorporate one perylene molecule. PMID:23795694

  9. Self-assembled materials from thermosensitive and biohybrid block copolymers

    OpenAIRE

    De Graaf, A.J.

    2012-01-01

    In this research, several block copolymers were synthesized and characterized with regard to possible pharmaceutical applications. All block copolymers were thermosensitive and self-assembled at 37 °C into structures like micelles and hydrogels, which can be used for innovative drug delivery purposes. Some of the synthesized polymers were biohybrid, in the sense that they contained peptide segments which enabled their cleavage by enzymes that are upregulated in diseased tissues. First, method...

  10. Self Assembled Monolayers for Quartz Crystal Microbalance based Biosensing

    OpenAIRE

    Myrskog, Annica

    2009-01-01

    The work in this thesis has been focused on developing surfaces for use in biosensor systems, especially for quartz crystal microbalances. The surfaces were prepared by adsorption of organosulfur molecules onto gold substrates, so called self assembled monolayers (SAMs). By chemical synthesis these thiols can be specifically tailored to provide surfaces with desired properties. The investigated surfaces were all based on thiols terminated with carboxylic acid groups to render hydrophilic surf...

  11. Self-assembled mannan nanogel : cytocompatibility and cell localization

    OpenAIRE

    Ferreira, Sílvia A.; Carvalho, Vera; Vilanova, Manuel; Costa, Carla Isabel; Teixeira, João P.; Gama, F. M.

    2012-01-01

    Amphiphilic mannan, produced by the Michael addition of hydrophobic 1-hexadecanethiol to vinyl methacrylated mannan, self-assembles in aqueous medium through hydrophobic interactions among alkyl chains. Resultant nanogel is stable, spherical, polydisperse, with 50–140 nm mean hydrodynamic diameter depending on the polymer degree of substitution, and nearly neutral negative surface charge. No cytotoxicity of mannan nanogel is detected up to about 0.4 mg/mL in mouse embryo fibroblast cell line ...

  12. Self-assembled hexagonal double fishnets as negative index materials

    CERN Document Server

    Lodewijks, Kristof; Van Roy, Willem; Borghs, Gustaaf; Van Dorpe, Pol

    2010-01-01

    We show experimentally the successful use of colloidal lithography for the fabrication of negative index metamaterials in the near-infrared wavelength range. In particular, we investigated a specific implementation of the widely studied double fishnet metamaterials, consisting of a gold-silica-gold layer stack perforated by a hexagonal array of round holes. Tuning of the hole diameter allows us to tailor these self-assembled metamaterials both as single- ({\\epsilon} < 0) and double ({\\epsilon} < 0 and {\\mu} < 0) negative metamaterials.

  13. Host-Guest Self-assembly in Block Copolymer Blends

    OpenAIRE

    Woon Ik Park; YongJoo Kim; Jae Won Jeong; Kyungho Kim; Jung-Keun Yoo; Yoon Hyung Hur; Jong Min Kim; Thomas, Edwin L.; Alfredo Alexander-Katz; Yeon Sik Jung

    2013-01-01

    Ultrafine, uniform nanostructures with excellent functionalities can be formed by self-assembly of block copolymer (BCP) thin films. However, extension of their geometric variability is not straightforward due to their limited thin film morphologies. Here, we report that unusual and spontaneous positioning between host and guest BCP microdomains, even in the absence of H-bond linkages, can create hybridized morphologies that cannot be formed from a neat BCP. Our self-consistent field theory (...

  14. Antifouling Self-assembled Monolayers on Microelectrodes for Patterning Biomolecules

    OpenAIRE

    Noel, John; Teizer, Winfried; Hwang, Wonmuk

    2009-01-01

    We present a procedure for forming a poly(ethylene glycol) (PEG) trimethoxysilane self-assembled monolayer (SAM) on a silicon substrate with gold microelectrodes. The PEG-SAM is formed in a single assembly step and prevents biofouling on silicon and gold surfaces. The SAM is used to coat microelectrodes patterned with standard, positive-tone lithography. Using the microtubule as an example, we apply a DC voltage to induce electrophoretic migration to the SAM-coated electrode in a reversible m...

  15. Self-assembled monolayers formed on AZ31 Mg alloy

    Science.gov (United States)

    Salman, S. A.; Okido, M.

    2012-07-01

    Self-assembled monolayer (SAM) was successfully adsorbed on the AZ31 Mg alloy surface using oleic acid and stearic acid with various organic solvents, such as acetone, ethanol, and hexane. The surface monolayers were characterized using contact angle measurements, X-ray photoelectron spectroscopy (XPS) and anodic polarization test. It was shown that the higher contact angle and the best anti-corrosion property were obtained with treatment in oleic acid with ethanol solution.

  16. Investigating self-assembled protein nanotubes using atomic force microscopy

    OpenAIRE

    Niu, Lijiang

    2009-01-01

    Self-assembled protein nanotubular materials are attractive as putative building blocks for a variety of applications. Knowledge of the three-dimensional structures and the physical properties of these protein nanotubes then becomes a prerequisite for their use in rational materials design. The main purpose of the work presented in this thesis is to investigate both the structural and mechanical properties of protein nanotubes utilizing atomic force microscopy (AFM). Several different protein...

  17. The self-assembly of a camptothecin-lysine nanotube.

    Science.gov (United States)

    Sun, Yuan; Shieh, Aileen; Kim, Se Hye; King, Samantha; Kim, Anne; Sun, Hui-Lung; Croce, Carlo M; Parquette, Jon R

    2016-06-15

    A simple, low molecular weight camptothecin-lysine conjugate is reported to self-assemble into nanotubes with diameters of 70-100nm and a drug loading level of 60.5%. The nanotubes exhibited promising in vitro cytotoxicity against cancer cell lines A549, NCI-H460 and NCI-H23. The release of active camptothecin was highly dependent on conjugate concentration, temperature and pH of the solution. PMID:27156772

  18. Mechanical Self-Assembly of a Strain-Engineered Flexible Layer: Wrinkling, Rolling, and Twisting

    Science.gov (United States)

    Chen, Zi; Huang, Gaoshan; Trase, Ian; Han, Xiaomin; Mei, Yongfeng

    2016-01-01

    Self-shaping of curved structures, especially those involving flexible thin layers, is attracting increasing attention because of their broad potential applications in, e.g., nanoelectromechanical andmicroelectromechanical systems, sensors, artificial skins, stretchable electronics, robotics, and drug delivery. Here, we provide an overview of recent experimental, theoretical, and computational studies on the mechanical self-assembly of strain-engineered thin layers, with an emphasis on systems in which the competition between bending and stretching energy gives rise to a variety of deformations, such as wrinkling, rolling, and twisting. We address the principle of mechanical instabilities, which is often manifested in wrinkling or multistability of strain-engineered thin layers. The principles of shape selection and transition in helical ribbons are also systematically examined. We hope that a more comprehensive understanding of the mechanical principles underlying these rich phenomena can foster the development of techniques for manufacturing functional three-dimensional structures on demand for a broad spectrum of engineering applications.

  19. Evolutionary dynamics in a simple model of self-assembly

    Science.gov (United States)

    Johnston, Iain G.; Ahnert, Sebastian E.; Doye, Jonathan P. K.; Louis, Ard A.

    2011-06-01

    We investigate the evolutionary dynamics of an idealized model for the robust self-assembly of two-dimensional structures called polyominoes. The model includes rules that encode interactions between sets of square tiles that drive the self-assembly process. The relationship between the model’s rule set and its resulting self-assembled structure can be viewed as a genotype-phenotype map and incorporated into a genetic algorithm. The rule sets evolve under selection for specified target structures. The corresponding complex fitness landscape generates rich evolutionary dynamics as a function of parameters such as the population size, search space size, mutation rate, and method of recombination. Furthermore, these systems are simple enough that in some cases the associated model genome space can be completely characterized, shedding light on how the evolutionary dynamics depends on the detailed structure of the fitness landscape. Finally, we apply the model to study the emergence of the preference for dihedral over cyclic symmetry observed for homomeric protein tetramers.

  20. Molecular Motions in Functional Self-Assembled Nanostructures

    Directory of Open Access Journals (Sweden)

    Jean-Marc Saiter

    2013-01-01

    Full Text Available The construction of “smart” materials able to perform specific functions at the molecular scale through the application of various stimuli is highly attractive but still challenging. The most recent applications indicate that the outstanding flexibility of self-assembled architectures can be employed as a powerful tool for the development of innovative molecular devices, functional surfaces and smart nanomaterials. Structural flexibility of these materials is known to be conferred by weak intermolecular forces involved in self-assembly strategies. However, some fundamental mechanisms responsible for conformational lability remain unexplored. Furthermore, the role played by stronger bonds, such as coordination, ionic and covalent bonding, is sometimes neglected while they can be employed readily to produce mechanically robust but also chemically reversible structures. In this review, recent applications of structural flexibility and molecular motions in self-assembled nanostructures are discussed. Special focus is given to advanced materials exhibiting significant performance changes after an external stimulus is applied, such as light exposure, pH variation, heat treatment or electromagnetic field. The crucial role played by strong intra- and weak intermolecular interactions on structural lability and responsiveness is highlighted.

  1. SELF-ASSEMBLING AMPHIPHILIC POLYELECTROLYTES AND THEIR NANOSTRUCTURES

    Institute of Scientific and Technical Information of China (English)

    Yotaro Morishima

    2000-01-01

    The self-assembling behavior of random copolymers of sodium 2-(acrylamido)-2-methylpropanesulfonate (AMPS)and hydrophobic comonomers possessing dodecyl groups linked by various spacer bonds was discussed with a focus on the effect of the spacer. The characterization of association behavior of such polymers in water using quasielastic light scattering,capillary electrophoresis, NMR relaxation, various fluorescence, and viscoelastic methods was described. These copolymers form a variety of self-assembled nanostructures depending on the type of the spacer. Random copolymers of AMPS and Ndodecylmethacrylamide show a strong preference for intrapolymer self-association even in concentrated aqueous solutions forming single-macromolecular self-assemblies (unimolecular micelles). In contrast, random copolymers of AMPS and dodecyl methacrylate are prone to undergo interpolymer associations yielding multipolymer micelles. In random copolymers of AMPS and a methacrylate substituted a nonionic surfactant (HO(CH2CH2O)25C12H25) (C12E25), dodecyl groups are much less restricted by the polymer backbone because they are linked via a long, flexible hydrophilic spacer. Thus, the polymerbound C12E25 surfactant moieties form micelles similar to those formed by discrete surfactants, but they are bridged by polymer chains forming a network structure.

  2. Equilibrium self-assembly of small RNA viruses

    Science.gov (United States)

    Bruinsma, R. F.; Comas-Garcia, M.; Garmann, R. F.; Grosberg, A. Y.

    2016-03-01

    We propose a description for the quasiequilibrium self-assembly of small, single-stranded (ss) RNA viruses whose capsid proteins (CPs) have flexible, positively charged, disordered tails that associate with the negatively charged RNA genome molecules. We describe the assembly of such viruses as the interplay between two coupled phase-transition-like events: the formation of the protein shell (the capsid) by CPs and the condensation of a large ss viral RNA molecule. Electrostatic repulsion between the CPs competes with attractive hydrophobic interactions and attractive interaction between neutralized RNA segments mediated by the tail groups. An assembly diagram is derived in terms of the strength of attractive interactions between CPs and between CPs and the RNA molecules. It is compared with the results of recent studies of viral assembly. We demonstrate that the conventional theory of self-assembly, which does describe the assembly of empty capsids, is in general not applicable to the self-assembly of RNA-encapsidating virions.

  3. Molecular pathways for defect annihilation in directed self-assembly.

    Energy Technology Data Exchange (ETDEWEB)

    Hur, Su-Mi; Thapar, Vikram; Ramirez-Hernandez, Abelardo; Khaira, Gurdaman S.; Segal-Peretz, Tamar; Rincon-Delgadillo, Paulina A.; Li, Weihua; Muller, Marcus; Nealey, Paul F.; de Pablo, Juan J.

    2015-11-17

    Over the last few years, the directed self-assembly of block copolymers by surface patterns has transitioned from academic curiosity to viable contender for commercial fabrication of next-generation nanocircuits by lithography. Recently, it has become apparent that kinetics, and not only thermodynamics, plays a key role for the ability of a polymeric material to self-assemble into a perfect, defect-free ordered state. Perfection, in this context, implies not more than one defect, with characteristic dimensions on the order of 5 nm, over a sample area as large as 100 cm2. In this work, we identify the key pathways and the corresponding free-energy barriers for eliminating defects, and we demonstrate that an extraordinarily large thermodynamic driving force is not necessarily sufficient for their removal. By adopting a concerted computational and experimental approach, we explain the molecular origins of these barriers, how they depend on material characteristics, and we propose strategies designed to over-come them. The validity of our conclusions for industrially-relevant patterning processes is established by relying on instruments and assembly lines that are only available at state-of-the-art fabrication facilities and, through this confluence of fundamental and applied research, we are able to discern the evolution of morphology at the smallest relevant length scales - a handful of nanometers -, and present a view of defect annihilation in directed self-assembly at an unprecedented level of detail.

  4. Self-assembled elastin-like polypeptide particles.

    Science.gov (United States)

    Osborne, Jill L; Farmer, Robin; Woodhouse, Kimberly A

    2008-01-01

    In this work, the self-assembly of a recombinant elastin-based block copolymer containing both hydrophobic and cross-linking domains from the human elastin protein was investigated. The particle formation and dynamic behavior were characterized using inverted microscopy and dynamic light scattering. The morphology and stability were evaluated using scanning and transmission electron microscopy. Above a critical temperature the molecules self-assembled into a bimodal distribution of nano- and micron-sized particles. The larger particles increased in size through coalescence. Micron-sized particle formation appeared largely reversible, although a self-assembly/disassembly hysteresis was observed. At high polyethylene glycol (PEG) concentrations particle coalescence and settling were reduced, particle stability seemed enhanced and PEG coated the particles. Particle stabilization was also achieved through covalent cross-linking using glutaraldehyde. This study laid the foundation for optimization of particle size and stability through modification of the solvent system and has shown that this family of elastin-based polypeptides holds potential for use as particulate drug carriers. PMID:17881311

  5. Three dimensional self-assembly at the nanoscale

    Science.gov (United States)

    Gracias, D. H.

    2013-05-01

    At the nanoscale, three dimensional manipulation and assembly becomes extremely challenging and also cost prohibitive. Self-assembly provides an attractive and possibly the only highly parallel methodology to structure truly three dimensional patterned materials and devices at this size scale for applications in electronics, optics, robotics and medicine. This is a concise review along with a perspective of an important and exciting field in nanotechnology and is related to a Nanoengineering Pioneer Award that I received at this SPIE symposium for my contributions to the 3D selfassembly of nanostructures. I detail a historical account of 3D self-assembly and outline important developments in this area which is put into context with the larger research areas of 3D nanofabrication, assembly and nanomanufacturing. A focus in this review is on our work as it relates to the self-assembly with lithographically patterned units; this approach provides a means for heterogeneous integration of periodic, curved and angled nanostructures with precisely defined three dimensional patterns.

  6. Modeling the self-assembly of nanoparticle and nanorod superlattices

    Science.gov (United States)

    Titov, Alexey; Kral, Petr

    2008-03-01

    Coloidal semiconductor PbSe/CdSE nanoparticles (NP) of the sizes of 3-10 nm can self-assemble in fcc, hcp and single-hexagonal (sh) superlattices [1]. We model the Coulombic, van der Waals and steric interactions between these NPs to understand the exact conditions under which they can self-assemble in these lattice structures. Our simulations show that non-local dipoles of the NPs and their screening by the conducting substrate are both crucial for the sh lattice formation. We model analogously the self-assembly of semiconducting CdSe nanorods (NRs), realized also in the presence of electric fields [2], and the binary semiconducting-metallic nanoparticle superlattices [3]. [1] D. Talapin, E. Shevchenko, C. B. Murray, A. Titov and P. Kr'al, Nano Letters 7, 1213 (2007). [2] A. Titov and P. Kr'al, submitted. [3] E. V. Shevchenko, D. V. Talapin, N. A. Kotov, S. O'Brien, C. B. Murray, Nature 439, 55-59 (2006).

  7. Large-scale dissipative particle dynamics simulations of self-assembly amphiphilic systems†

    Science.gov (United States)

    Li, Xuejin; Tang, Yu-Hang

    2014-01-01

    We present large-scale simulation results on the self-assembly of amphiphilic systems in bulk solution and under soft confinement. Self-assembled unilamellar and multilamellar vesicles are formed from amphiphilic molecules in bulk solution. The system is simulated by placing amphiphilic molecules inside large unilamellar vesicles (LUVs) and the dynamic soft confinement-induced self-assembled vesicles are investigated. Moreover, the self-assembly of sickle hemoglobin (HbS) is simulated in a crowded and fluctuating intracellular space and our results demonstrate that the HbS self-assemble into polymer fibers causing the LUV shape to be distorted. PMID:24938634

  8. Templated self-assembly of SiGe quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Dais, Christian

    2009-08-19

    This PhD thesis reports on the fabrication and characterization of exact aligned SiGe quantum dot structures. In general, SiGe quantum dots which nucleate via the Stranski-Krastanov growth mode exhibit broad size dispersion and nucleate randomly on the surface. However, to tap the full potential of SiGe quantum dots it is necessary to control the positioning and size of the dots on a nanometer length, e.g. for electronically addressing of individual dots. This can be realized by so-called templated self-assembly, which combines top-down lithography with bottom-up selfassembly. In this process the lithographically defined pits serve as pre-defined nucleation points for the epitaxially grown quantum dots. In this thesis, extreme ultraviolet interference lithography at a wavelength of e=13.4 nm is employed for prepatterning of the Si substrates. This technique allows the precise and fast fabrication of high-resolution templates with a high degree of reproducibility. The subsequent epitaxial deposition is either performed by molecular beam epitaxy or low-pressure chemical vapour deposition. It is shown that the dot nucleation on pre-patterned substrates depends strongly on the lithography parameters, e.g. size and periodicity of the pits, as well as on the epitaxy parameters, e.g. growth temperature or material coverage. The interrelations are carefully analyzed by means of scanning force microscopy, transmission electron microscopy and X-ray diffraction measurements. Provided that correct template and overgrowth parameters are chosen, perfectly aligned and uniform SiGe quantum dot arrays of different period, size as well as symmetry are created. In particular, the quantum dot arrays with the so far smallest period (35 nm) and smallest size dispersion are fabricated in this thesis. Furthermore, the strain fields of the underlying quantum dots allow the fabrication of vertically aligned quantum dot stacks. Combining lateral and vertical dot alignment results in three

  9. A Bloch equation approach to intensity dependent optical spectra of light harvesting complex II: excitation dependence of light harvesting complex II pump-probe spectra.

    Science.gov (United States)

    Richter, Marten; Renger, Thomas; Knorr, Andreas

    2008-01-01

    On the basis of the recent progress in the resolution of the structure of the antenna light harvesting complex II (LHC II) of the photosystem II, we propose a microscopically motivated theory to predict excitation intensity-dependent spectra. We show that optical Bloch equations provide the means to include all 2( N ) excited states of an oligomer complex of N coupled two-level systems and analyze the effects of Pauli Blocking and exciton-exciton annihilation on pump-probe spectra. We use LHC Bloch equations for 14 Coulomb coupled two-level systems, which describe the S (0) and S (1) level of every chlorophyll molecule. All parameter introduced into the Hamiltonian are based on microscopic structure and a quantum chemical model. The derived Bloch equations describe not only linear absorption but also the intensity dependence of optical spectra in a regime where the interplay of Pauli Blocking effects as well as exciton-exciton annihilation effects are important. As an example, pump-probe spectra are discussed. The observed saturation of the spectra for high intensities can be viewed as a relaxation channel blockade on short time scales due to Pauli blocking. The theoretical investigation is useful for the interpretation of the experimental data, if the experimental conditions exceed the low intensity pump limit and effects like strong Pauli Blocking and exciton-exciton annihilation need to be considered. These effects become important when multiple excitations are generated by the pump pulse in the complex. PMID:17924202

  10. Self-Assembly of Plasmonic Nanoclusters for Optical Metauids

    Science.gov (United States)

    Schade, Nicholas Benjamin

    I discuss experimental progress towards developing a material with an isotropic, negative index of refraction at optical frequencies. The simplest way to make such a material is to create a metafluid, or a disordered collection of subwavelength, isotropic electromagnetic resonators. Small clusters of metal particles, such as tetrahedra, serve as these constituents. What is needed are methods for manufacturing these structures with high precision and in sufficient yield that their resonances are identical. Jonathan Fan et al. [Science, 328 (5982), 1135-1138, 2010] demonstrated that colloidal self-assembly is a means of preparing electromagnetic resonators from metal nanoparticles. However, the resonances are sensitive to the separation gaps between particles. Standard synthesis routes for metal nanoparticles yield crystals or nanoshells that are inadequate for metafluids due to polydispersity, faceting, and thermal instabilities. To ensure that the separation gaps and resonances are uniform, more monodisperse spherical particles are needed. An additional challenge is the self-assembly of tetrahedral clusters in high yield from these particles. In self-assembly approaches that others have examined previously, the yield of any particular type of cluster is low. In this dissertation I present solutions to several of these problems, developed in collaboration with my research group and others. We demonstrate that slow chemical etching can transform octahedral gold crystals into ultrasmooth, monodisperse nanospheres. The particles can serve as seeds for the growth of larger octahedra which can in turn be etched. The size of the gold nanospheres can therefore be adjusted as desired. We further show that in colloidal mixtures of two sphere species that strongly bind to one another, the sphere size ratio determines the size distribution of self-assembled clusters. At a critical size ratio, tetrahedral clusters assemble in high yield. We explain the experimentally observed

  11. Two-dimensional electronic spectroscopy and photosynthesis: Fundamentals and applications to photosynthetic light-harvesting

    International Nuclear Information System (INIS)

    Graphical abstract: 2D electronic spectroscopy, when combined with theoretical approaches, can investigate structure-function relationships in photosynthetic complexes by probing electronic energy transfer and excited state orientations. Display Omitted Highlights: → We review theoretical principles and experimental implementation of 2D spectroscopy. → 2DES monitors energy transfer, observes coherence, determines excited state geometry, and compares to homology models. → 2DES reveals structure-function relationships in the Photosystem II supercomplex. - Abstract: In natural light harvesting systems, pigment-protein complexes are able to harvest sunlight with near unity quantum efficiency. These complexes exhibit emergent properties that cannot be simply extrapolated from knowledge of their component parts. In this perspective, we focus on how two-dimensional electronic spectroscopy (2DES) can provide an incisive tool to probe the electronic, energetic, and spatial landscapes that must be understood to describe photosynthetic light-harvesting. We review the theoretical and experimental principles of 2DES, and demonstrate its application to the study of the Photosystem II supercomplex of green plants. We illustrate several capabilities of 2DES, including monitoring energy transfer pathways, observing excitonic coherence, determining excitonic geometry, and informing on the atomic structure.

  12. Protein kinase that phosphorylates light-harvesting complex is autophosphorylated and is associated with photosystem II

    International Nuclear Information System (INIS)

    Thylakoid membranes were phosphorylated with [γ-32P]ATP and extracted with octyl glucoside and cholate. Among the radiolabeled phosphoproteins in the extract was a previously characterized protein kinase of 64-kDa apparent mass. The ability of this enzyme to undergo autophosphorylation in situ was used to monitor its distribution in the membrane. Fractionation studies showed that the kinase is confined to granal regions of the thylakoid, where it appears to be associated with the light-harvesting chlorophyll-protein complex of photosystem II. The kinetics of kinase autophosphorylation were investigated both in situ and in extracted, purified enzyme. In the membrane, autophosphorylation saturated within 20-30 min and was reversed with a half-time of 7-8 min upon removal of ATP or oxidative inactivation of the kinase; the accompanying dephosphorylation of light-harvesting complex was slower and kinetically complex. Fluoride (10 mM) inhibited these dephosphorylations. Autophosphorylation of the isolated kinase was independent of enzyme concentration, indicative of an intramolecular mechanism. A maximum of one serine residue per mole of kinase was esterified. Autophosphorylation was more rapid in the presence of histone IIIs, an exogenous substrate. Dephosphorylation of the isolated enzyme was not observed

  13. Light-Harvesting Antenna System from the Phototrophic Bacterium Roseiflexus castenholzii

    Energy Technology Data Exchange (ETDEWEB)

    Collins, Aaron M. [Washington Univ., St. Louis, MO (United States); Qian, Pu [Univ. of Sheffield (United Kingdom); Tang, Qun [Univ. of California, Riverside, CA (United States); Bocian, David F [Univ. of California, Riverside, CA (United States); Hunter, C. Neil [Univ. of Sheffield (United Kingdom); Blankenship, Robert E. [Washington Univ., St. Louis, MO (United States)

    2010-08-12

    Photosynthetic organisms have evolved diverse light-harvesting complexes to harness light of various qualities and intensities. Photosynthetic bacteria can have (bacterio)chlorophyll Qy antenna absorption bands ranging from ~650 to ~1100 nm. This broad range of wavelengths has allowed many organisms to thrive in unique light environments. Roseiflexus castenholzii is a niche-adapted, filamentous anoxygenic phototroph (FAP) that lacks chlorosomes, the dominant antenna found in most green bacteria, and here we describe the purification of a full complement of photosynthetic complexes: the light-harvesting (LH) antenna, reaction center (RC), and core complex (RC-LH). By high-performance liquid chromatography separation of bacteriochlorophyll and bacteriopheophytin pigments extracted from the core complex and the RC, the number of subunits that comprise the antenna was determined to be 15 ± 1. Resonance Raman spectroscopy of the carbonyl stretching region displayed modes indicating that 3C-acetyl groups of BChl a are all involved in molecular interactions probably similar to those found in LH1 complexes from purple photosynthetic bacteria. Finally, two-dimensional projections of negatively stained core complexes and the LH antenna revealed a closed, slightly elliptical LH ring with an average diameter of 130 ± 10 Å surrounding a single RC that lacks an H-subunit but is associated with a tetraheme c-type cytochrome.

  14. Integral Light-Harvesting Complex Expression In Symbiodinium Within The Coral Acropora aspera Under Thermal Stress.

    Science.gov (United States)

    Gierz, Sarah L; Gordon, Benjamin R; Leggat, William

    2016-01-01

    Coral reef success is largely dependent on the symbiosis between coral hosts and dinoflagellate symbionts belonging to the genus Symbiodinium. Elevated temperatures can result in the expulsion of Symbiodinium or loss of their photosynthetic pigments and is known as coral bleaching. It has been postulated that the expression of light-harvesting protein complexes (LHCs), which bind chlorophylls (chl) and carotenoids, are important in photobleaching. This study explored the effect a sixteen-day thermal stress (increasing daily from 25-34 °C) on integral LHC (chlorophyll a-chlorophyll c2-peridinin protein complex (acpPC)) gene expression in Symbiodinium within the coral Acropora aspera. Thermal stress leads to a decrease in Symbiodinium photosynthetic efficiency by day eight, while symbiont density was significantly lower on day sixteen. Over this time period, the gene expression of five Symbiodinium acpPC genes was quantified. Three acpPC genes exhibited up-regulated expression when corals were exposed to temperatures above 31.5 °C (acpPCSym_1:1, day sixteen; acpPCSym_15, day twelve; and (acpPCSym_18), day ten and day sixteen). In contrast, the expression of acpPCSym_5:1 and acpPCSym_10:1 was unchanged throughout the experiment. Interestingly, the three acpPC genes with increased expression cluster together in a phylogenetic analysis of light-harvesting complexes. PMID:27117333

  15. The terminal phycobilisome emitter, LCM: A light-harvesting pigment with a phytochrome chromophore.

    Science.gov (United States)

    Tang, Kun; Ding, Wen-Long; Höppner, Astrid; Zhao, Cheng; Zhang, Lun; Hontani, Yusaku; Kennis, John T M; Gärtner, Wolfgang; Scheer, Hugo; Zhou, Ming; Zhao, Kai-Hong

    2015-12-29

    Photosynthesis relies on energy transfer from light-harvesting complexes to reaction centers. Phycobilisomes, the light-harvesting antennas in cyanobacteria and red algae, attach to the membrane via the multidomain core-membrane linker, LCM. The chromophore domain of LCM forms a bottleneck for funneling the harvested energy either productively to reaction centers or, in case of light overload, to quenchers like orange carotenoid protein (OCP) that prevent photodamage. The crystal structure of the solubly modified chromophore domain from Nostoc sp. PCC7120 was resolved at 2.2 Å. Although its protein fold is similar to the protein folds of phycobiliproteins, the phycocyanobilin (PCB) chromophore adopts ZZZssa geometry, which is unknown among phycobiliproteins but characteristic for sensory photoreceptors (phytochromes and cyanobacteriochromes). However, chromophore photoisomerization is inhibited in LCM by tight packing. The ZZZssa geometry of the chromophore and π-π stacking with a neighboring Trp account for the functionally relevant extreme spectral red shift of LCM. Exciton coupling is excluded by the large distance between two PCBs in a homodimer and by preservation of the spectral features in monomers. The structure also indicates a distinct flexibility that could be involved in quenching. The conclusions from the crystal structure are supported by femtosecond transient absorption spectra in solution. PMID:26669441

  16. Zeaxanthin Radical Cation Formation in Minor Light-Harvesting Complexes of Higher Plant Antenna

    Energy Technology Data Exchange (ETDEWEB)

    Avenson, Thomas H.; Ahn, Tae Kyu; Zigmantas, Donatas; Niyogi, Krishna K.; Li, Zhirong; Ballottari, Matteo; Bassi, Roberto; Fleming, Graham R.

    2008-01-31

    Previous work on intact thylakoid membranes showed that transient formation of a zeaxanthin radical cation was correlated with regulation of photosynthetic light-harvesting via energy-dependent quenching. A molecular mechanism for such quenching was proposed to involve charge transfer within a chlorophyll-zeaxanthin heterodimer. Using near infrared (880-1100 nm) transient absorption spectroscopy, we demonstrate that carotenoid (mainly zeaxanthin) radical cation generation occurs solely in isolated minor light-harvesting complexes that bind zeaxanthin, consistent with the engagement of charge transfer quenching therein. We estimated that less than 0.5percent of the isolated minor complexes undergo charge transfer quenching in vitro, whereas the fraction of minor complexes estimated to be engaged in charge transfer quenching in isolated thylakoids was more than 80 times higher. We conclude that minor complexes which bind zeaxanthin are sites of charge transfer quenching in vivo and that they can assume Non-quenching and Quenching conformations, the equilibrium LHC(N)<--> LHC(Q) of which is modulated by the transthylakoid pH gradient, the PsbS protein, and protein-protein interactions.

  17. A protochlorophyllide light-harvesting complex involved in de-etiolation of higher plants

    International Nuclear Information System (INIS)

    When etiolated angiosperm seedlings break through the soil after germination, they are immediately exposed to sunlight, but at this stage they are unable to perform photosynthesis1. In the absence of chlorophyll a and chlorophyll b, two other porphyrin species cooperate as the basic light-harvesting structure of etiolated plants. Protochlorophyllide a and protochlorophyllide b (ref. 2) form supramolecular complexes with NADPH and two closely related NADPH:protochlorophyllide oxidoreductase (POR) proteins—PORA and PORB (ref. 3)—in the prolamellar body of etioplasts. Here we report that these light-harvesting POR–protochlorophyllide complexes, named LHPP, are essential for the establishment of the photosynthetic apparatus and also confer photoprotection on the plant. They collect sunlight for rapid chlorophyll a biosynthesis and, simultaneously, dissipate excess light energy in the bulk of non-photoreducible protochlorophyllide b. Based on this dual function, it seems that LHPP provides the link between skotomorphogenesis and photosynthesis that is required for efficient de-etiolation

  18. Realizing omnidirectional light harvesting by employing hierarchical architecture for dye sensitized solar cells

    Science.gov (United States)

    Hsieh, Ming-Yang; Lai, Fang-I.; Chen, Wei-Chun; Hsieh, Min-Chi; Hu, Hsiang-Yi; Yu, Peichen; Kuo, Hao-Chung; Kuo, Shou-Yi

    2016-03-01

    To improve the omnidirectional light-harvesting in dye-sensitized solar cells (DSSCs), here we present a dandelion-like structure composed of ZnO hemispherical shells and nanorods. Uniformly distributed hemispherical shells effectively suppress the reflection over the broadband region at incident angles up to 60°, greatly improving the optical absorption of the DSSCs. In addition, modulating the length of the ZnO nanorods controls the omnidirectional characteristics of DSSCs. This phenomenon is attributed to the degree of periodicity of the ZnO dandelion-like structures. Cells with shorter rods exhibit a high degree of periodicity, thus the conversion efficiencies of the cells show specific angle-independent features. On the other hand, the cells with longer lengths reveal angle-dependent photovoltaic performance. Along with the simulation, the cells with dandelion-like ZnO structures can couple incident photons efficiently to achieve excellent broadband and omnidirectional light-harvesting performances experimentally, and the DSSCs enhanced the conversion efficiency by 48% at large incident angles. All these findings not only provide further insight into the light-trapping mechanism in these complex three-dimensional nanostructures but also offer efficient omnidirectional and broadband nanostructured photovoltaics for advanced applications.

  19. Integral Light-Harvesting Complex Expression In Symbiodinium Within The Coral Acropora aspera Under Thermal Stress

    Science.gov (United States)

    Gierz, Sarah L.; Gordon, Benjamin R.; Leggat, William

    2016-04-01

    Coral reef success is largely dependent on the symbiosis between coral hosts and dinoflagellate symbionts belonging to the genus Symbiodinium. Elevated temperatures can result in the expulsion of Symbiodinium or loss of their photosynthetic pigments and is known as coral bleaching. It has been postulated that the expression of light-harvesting protein complexes (LHCs), which bind chlorophylls (chl) and carotenoids, are important in photobleaching. This study explored the effect a sixteen-day thermal stress (increasing daily from 25–34 °C) on integral LHC (chlorophyll a-chlorophyll c2-peridinin protein complex (acpPC)) gene expression in Symbiodinium within the coral Acropora aspera. Thermal stress leads to a decrease in Symbiodinium photosynthetic efficiency by day eight, while symbiont density was significantly lower on day sixteen. Over this time period, the gene expression of five Symbiodinium acpPC genes was quantified. Three acpPC genes exhibited up-regulated expression when corals were exposed to temperatures above 31.5 °C (acpPCSym_1:1, day sixteen; acpPCSym_15, day twelve; and acpPCSym_18, day ten and day sixteen). In contrast, the expression of acpPCSym_5:1 and acpPCSym_10:1 was unchanged throughout the experiment. Interestingly, the three acpPC genes with increased expression cluster together in a phylogenetic analysis of light-harvesting complexes.

  20. Polaron effects on the performance of light-harvesting systems: a quantum heat engine perspective

    Science.gov (United States)

    Xu, Dazhi; Wang, Chen; Zhao, Yang; Cao, Jianshu

    2016-02-01

    We explore energy transfer in a generic three-level system, which is coupled to three non-equilibrium baths. Built on the concept of quantum heat engine, our three-level model describes non-equilibrium quantum processes including light-harvesting energy transfer, nano-scale heat transfer, photo-induced isomerization, and photovoltaics in double quantum-dots. In the context of light-harvesting, the excitation energy is first pumped up by sunlight, then is transferred via two excited states which are coupled to a phonon bath, and finally decays to the reaction center. The efficiency of this process is evaluated by steady state analysis via a polaron-transformed master equation; thus the entire range of the system-phonon coupling strength can be covered. We show that the coupling with the phonon bath not only modifies the steady state, resulting in population inversion, but also introduces a finite steady state coherence which optimizes the energy transfer flux and efficiency. In the strong coupling limit, the steady state coherence disappears and the efficiency recovers the heat engine limit given by Scovil and Schultz-Dubois (1959 Phys. Rev. Lett. 2 262).

  1. Colloidal self-assembly concepts for light management in photovoltaics

    Directory of Open Access Journals (Sweden)

    Matthias Karg

    2015-05-01

    Full Text Available Colloidal particles show interaction with electromagnetic radiation at optical frequencies. At the same time clever colloid design and functionalization concepts allow for versatile particle assembly providing monolayers of macroscopic dimensions. This has led to a significant interest in assembled colloidal structures for light harvesting in photovoltaic devices. In particular thin-film solar cells suffer from weak absorption of incoming photons. Consequently light management using assembled colloidal structures becomes vital for enhancing the efficiency of a given device. This review aims at giving an overview of recent developments in colloid synthesis, functionalization and assembly with a focus on light management structures in photovoltaics. We distinguish between optical effects related to the single particle properties as well as collective optical effects, which originate from the assembled structures. Colloidal templating approaches open yet another dimension for controlling the interaction with light. We focus in this respect on structured electrodes that have received much attention due to their dual functionality as light harvesting systems and conductive electrodes and highlight the impact of inter-particle spacing for templating.

  2. Directed self-assembly of block copolymers for next generation nanolithography

    Directory of Open Access Journals (Sweden)

    Seong-Jun Jeong

    2013-12-01

    Full Text Available Directed self-assembly of block copolymers has received a great deal of research attention as a promising nanolithography to complement the intrinsic limitations of conventional photolithography. In this review, we highlight the recent progress in the development of the directed self-assembly process for practical utilization in semiconductor applications. Various advanced directed self-assembly approaches are examined, in which block copolymer self-assembly is synergistically integrated with conventional photolithography, such as ArF lithography or I-line lithography, via either epitaxial self-assembly or the graphoepitaxy principle. We focus on the practical advantages anticipated from directed self-assembly integration, such as pattern density multiplication, feature size uniformity improvement, line edge roughness reduction, as well as cost reduction. Additionally, a direction for future research on directed self-assembly is suggested with diverse potential applications.

  3. A Theoretical and Experimental Study of DNA Self-assembly

    Science.gov (United States)

    Chandran, Harish

    The control of matter and phenomena at the nanoscale is fast becoming one of the most important challenges of the 21st century with wide-ranging applications from energy and health care to computing and material science. Conventional top-down approaches to nanotechnology, having served us well for long, are reaching their inherent limitations. Meanwhile, bottom-up methods such as self-assembly are emerging as viable alternatives for nanoscale fabrication and manipulation. A particularly successful bottom up technique is DNA self-assembly where a set of carefully designed DNA strands form a nanoscale object as a consequence of specific, local interactions among the different components, without external direction. The final product of the self-assembly process might be a static nanostructure or a dynamic nanodevice that performs a specific function. Over the past two decades, DNA self-assembly has produced stunning nanoscale objects such as 2D and 3D lattices, polyhedra and addressable arbitrary shaped substrates, and a myriad of nanoscale devices such as molecular tweezers, computational circuits, biosensors and molecular assembly lines. In this dissertation we study multiple problems in the theory, simulations and experiments of DNA self-assembly. We extend the Turing-universal mathematical framework of self-assembly known as the Tile Assembly Model by incorporating randomization during the assembly process. This allows us to reduce the tile complexity of linear assemblies. We develop multiple techniques to build linear assemblies of expected length N using far fewer tile types than previously possible. We abstract the fundamental properties of DNA and develop a biochemical system, which we call meta-DNA, based entirely on strands of DNA as the only component molecule. We further develop various enzyme-free protocols to manipulate meta-DNA systems and provide strand level details along with abstract notations for these mechanisms. We simulate DNA circuits by

  4. A Light Switch Based on Protein S-Nitrosylation Fine-Tunes Photosynthetic Light Harvesting in Chlamydomonas.

    Science.gov (United States)

    Berger, Hanna; De Mia, Marcello; Morisse, Samuel; Marchand, Christophe H; Lemaire, Stéphane D; Wobbe, Lutz; Kruse, Olaf

    2016-06-01

    Photosynthetic eukaryotes are challenged by a fluctuating light supply, demanding for a modulated expression of nucleus-encoded light-harvesting proteins associated with photosystem II (LHCII) to adjust light-harvesting capacity to the prevailing light conditions. Here, we provide clear evidence for a regulatory circuit that controls cytosolic LHCII translation in response to light quantity changes. In the green unicellular alga Chlamydomonas reinhardtii, the cytosolic RNA-binding protein NAB1 represses translation of certain LHCII isoform mRNAs. Specific nitrosylation of Cys-226 decreases NAB1 activity and could be demonstrated in vitro and in vivo. The less active, nitrosylated form of NAB1 is found in cells acclimated to limiting light supply, which permits accumulation of light-harvesting proteins and efficient light capture. In contrast, elevated light supply causes its denitrosylation, thereby activating the repression of light-harvesting protein synthesis, which is needed to control excitation pressure at photosystem II. Denitrosylation of recombinant NAB1 is efficiently performed by the cytosolic thioredoxin system in vitro. To our knowledge, NAB1 is the first example of stimulus-induced denitrosylation in the context of photosynthetic acclimation. By identifying this novel redox cross-talk pathway between chloroplast and cytosol, we add a new key element required for drawing a precise blue print of the regulatory network of light harvesting. PMID:27208221

  5. Light-harvesting regulation from leaf to molecule with the emphasis on rapid changes in antenna size.

    Science.gov (United States)

    Xu, Da-Quan; Chen, Yue; Chen, Gen-Yun

    2015-05-01

    In the sunlight-fluctuating environment, plants often encounter both light-deficiency and light-excess cases. Therefore, regulation of light harvesting is absolutely essential for photosynthesis in order to maximize light utilization at low light and avoid photodamage of the photosynthetic apparatus at high light. Plants have developed a series of strategies of light-harvesting regulation during evolution. These strategies include rapid responses such as leaf movement and chloroplast movement, state transitions, and reversible dissociation of some light-harvesting complex of the photosystem II (LHCIIs) from PSII core complexes, and slow acclimation strategies such as changes in the protein abundance of light-harvesting antenna and modifications of leaf morphology, structure, and compositions. This review discusses successively these strategies and focuses on the rapid change in antenna size, namely reversible dissociation of some peripheral light-harvesting antennas (LHCIIs) from PSII core complex. It is involved in protective role and species dependence of the dissociation, differences between the dissociation and state transitions, relationship between the dissociation and thylakoid protein phosphorylation, and possible mechanism for thermal dissipation by the dissociated LHCIIs. PMID:25773873

  6. Combustion and self-assembly of nanoenergetic materials

    Science.gov (United States)

    Malchi, Jonathan Yaniv

    The recent worldwide interest in nanotechnology spans a wide variety of scientific fields such as electronics, biology, materials science and medicine. Because of their extremely small dimensions, nanoparticles demonstrate properties different from matter at larger scales. Understanding these unusual properties and utilizing them for macroscale devices is an overall goal for nanotechnology. Moreover, manipulating these small particles into organized structures is crucial for taking full advantage of what nanotechnology has to offer, however it has proven to be a difficult task. Recent work utilizing electrostatic forces shows great potential for the self-assembly of nanoparticles into organized two-dimensional and three-dimensional structures. Overall, this work examines how nanotechnology and self-assembly can benefit the field of energetic materials. Because of aluminum's high energy density and low cost, it has been used in the field of energetic materials for several decades. In order to achieve sufficient energy release rates, aluminum is typically manufactured as a powder having spherical particles with diameters on the micron scale. It is well-known that decreasing the original particle diameter of a fuel particle will increase the burning time and, thus, energy release rate. Therefore, aluminum particles have recently been made to have diameters on the nanoscale, and shown to be advantageous for several applications. The combustion of nanoaluminum (nAl) in various systems is the primary focus of this study. A progression of experiments is used to analyze the combustion of nAl: (1) a fully heterogeneous flame spread system, (2) a semi-homogeneous sonicated thermite system and (3) a quasi-homogeneous self-assembled thermite system. The flame spread experiment physically separates the nAl from the gaseous oxidizer allowing for a well-understood convective, diffusive, reactive system to be analyzed. Because of the simplicity of the experimental setup, variables

  7. Self-Assembled Conjugated Polymer Nanometer Scale Devices

    Institute of Scientific and Technical Information of China (English)

    Wenping Hu; Hiroshi Nakashima; Keiichi Torimitsu; Yunqi Liu; Daoben Zhu

    2005-01-01

    @@ 1Introduction Nanometer scale devices, as the next generation devices of electronics, have got a worldwide attention and rapid development recently. Simultaneously, conjugated polymers have been applied in organic electronics successfully because of their outstanding electronic-photonic properties. However, as far as we know few reports have dealt with the fabrication of nanometer scale devices by using conjugated polymers, although the combination of nanometer scale devices and polymers will not only extend conjugated polymers to Nanoelectronics, but also excavate the behaviors of polymer molecules at nano-molecular level, such as the electron transport through polymer molecules. One reason for this case is due to the lack of rigidity for most polymers.It results in the failure to bridge them between electrodes or to stand on substrates, therefore, fails to be characterized by scanning probe microscopy. Another reason is that the non-functionalized end-group of most polymers is impossible to graft on substrates through chemical bonds. Here, we introduce a self-assembled conjugated polymer can be used to fabricate nanodevices by self-assembly. The conjugated polymer is a derivative of poly(p-phenyleneethynylene)s (PPE) with thioacetyl end groups (Fig. 1). In general, it is known that for self-assembling ideal nanojunctions the materials should possess: a) conductivity, b) rigidity (for wiring and bridging between electrodes), and c) connectivity (for covalent attachment to metallic or semiconductor solid surfaces). PPE provides good conductivity owing to its special π-conjugated configuration. It is also believed that in principle PPE molecules possess rigidity because of the presence of the triple bond in their molecules,which prevents the rotation of adjacent phenyl rings with respect to each other.

  8. Self-assembly of cyclo-diphenylalanine peptides in vacuum.

    Science.gov (United States)

    Jeon, Joohyun; Shell, M Scott

    2014-06-19

    The diphenylalanine (FF) peptide self-assembles into a variety of nanostructures, including hollow nanotubes that form in aqueous solution with an unusually high degree of hydrophilic surface area. In contrast, diphenylalanine can also be vapor-deposited in vacuum to produce rodlike assemblies that are extremely hydrophobic; in this process FF has been found to dehydrate and cyclize to cyclo-diphenylalanine (cyclo-FF). An earlier study used all-atom molecular dynamics (MD) simulations to understand the early stages of the self-assembly of linear-FF peptides in solution. Here, we examine the self-assembly of cyclo-FF peptides in vacuum and compare it to these previous results to understand the differences underlying the two cases. Using all-atom replica exchange MD simulations, we consider systems of 50 cyclo-FF peptides and examine free energies along various structural association coordinates. We find that cyclo-FF peptides form ladder-like structures connected by double hydrogen bonds, and that multiple such ladders linearly align in a cooperative manner to form larger-scale, elongated assemblies. Unlike linear-FFs which mainly assemble through the interplay between hydrophobic and hydrophilic interactions, the assembly of cyclo-FFs in vacuum is primarily driven by electrostatic interactions along the backbone that induce alignment at long-range, followed by van der Waals interactions between side chains that become important for close-range packing. While both solution and vacuum phase driving forces result in ladder-like structures, the clustering of ladders is opposite: linear-FF peptide ladders form assemblies with side-chains buried inward, while cyclo-FF ladders point outward. PMID:24877752

  9. Self-assembly of 33-mer gliadin peptide oligomers.

    Science.gov (United States)

    Herrera, M G; Benedini, L A; Lonez, C; Schilardi, P L; Hellweg, T; Ruysschaert, J-M; Dodero, V I

    2015-11-28

    The 33-mer gliadin peptide, LQLQPF(PQPQLPY)3PQPQPF, is a highly immunogenic peptide involved in celiac disease and probably in other immunopathologies associated with gliadin. Herein, dynamic light scattering measurements showed that 33-mer, in the micromolar concentration range, forms polydisperse nano- and micrometer range particles in aqueous media. This behaviour is reminiscent of classical association of colloids and we hypothesized that the 33-mer peptide self-assembles into micelles that could be the precursors of 33-mer oligomers in water. Deposition of 33-mer peptide aqueous solution on bare mica generated nano- and microstructures with different morphologies as revealed by atomic force microscopy. At 6 μM, the 33-mer is organised in isolated and clusters of spherical nanostructures. In the 60 to 250 μM concentration range, the spherical oligomers associated mainly in linear and annular arrangements and structures adopting a "sheet" type morphology appeared. At higher concentrations (610 μM), mainly filaments and plaques immersed in a background of nanospherical structures were detected. The occurrence of different morphologies of oligomers and finally the filaments suggests that the unique specific geometry of the 33-mer oligomers has a crucial role in the subsequent condensation and organization of their fractal structures into the final filaments. The self-assembly process on mica is described qualitatively and quantitatively by a fractal diffusion limited aggregation (DLA) behaviour with the fractal dimension in the range of 1.62 ± 0.02 to 1.73 ± 0.03. Secondary structure evaluation of the oligomers by Attenuated Total Reflection FTIR spectroscopy (ATR-FTIR) revealed the existence of a conformational equilibrium of self-assembled structures, from an extended conformation to a more folded parallel beta elongated structures. Altogether, these findings provide structural and morphological information about supramolecular organization of the 33-mer

  10. Rapid self-assembly of block copolymers to photonic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Yan; Sveinbjornsson, Benjamin R; Grubbs, Robert H; Weitekamp, Raymond; Miyake, Garret M; Atwater, Harry A; Piunova, Victoria; Daeffler, Christopher Scot; Hong, Sung Woo; Gu, Weiyin; Russell, Thomas P.

    2016-07-05

    The invention provides a class of copolymers having useful properties, including brush block copolymers, wedge-type block copolymers and hybrid wedge and polymer block copolymers. In an embodiment, for example, block copolymers of the invention incorporate chemically different blocks comprising polymer size chain groups and/or wedge groups that significantly inhibit chain entanglement, thereby enhancing molecular self-assembly processes for generating a range of supramolecular structures, such as periodic nanostructures and microstructures. The present invention also provides useful methods of making and using copolymers, including block copolymers.

  11. Self-Assembled Supramolecular Architectures Lyotropic Liquid Crystals

    CERN Document Server

    Garti, Nissim

    2012-01-01

    This book will describe fundamentals and recent developments in the area of Self-Assembled Supramolecular Architecture and their relevance to the  understanding of the functionality of  membranes  as delivery systems for active ingredients. As the heirarchial architectures determine their performance capabilities, attention will be paid to theoretical and design aspects related to the construction of lyotropic liquid crystals: mesophases such as lamellar, hexagonal, cubic, sponge phase micellosomes. The book will bring to the reader mechanistic aspects, compositional c

  12. Buckling Instability of Self-Assembled Colloidal Columns

    Science.gov (United States)

    Swan, James W.; Vasquez, Paula A.; Furst, Eric M.

    2014-09-01

    Suspended, slender self-assembled domains of magnetically responsive colloids are observed to buckle in microgravity. Upon cessation of the magnetic field that drives their assembly, these columns expand axially and buckle laterally. This phenomenon resembles the buckling of long beams due to thermal expansion; however, linear stability analysis predicts that the colloidal columns are inherently susceptible to buckling because they are freely suspended in a Newtonian fluid. The dominant buckling wavelength increases linearly with column thickness and is quantitatively described using an elastohydrodynamic model and the suspension thermodynamic equation of state.

  13. Crossbar nanoarchitectonics of the crosslinked self-assembled monolayer

    OpenAIRE

    Hamoudi, Hicham

    2014-01-01

    A bottom-up approach was devised to build a crossbar device using the crosslinked SAM of the 5,5′-bis (mercaptomethyl)-2,2′-bipyridine-Ni2+ (BPD- Ni2+) on a gold surface. To avoid metal diffusion through the organic film, the author used (i) nanoscale bottom electrodes to reduce the probability of defects on the bottom electrodes and (ii) molecular crosslinked technology to avoid metal diffusion through the SAMs. The properties of the crosslinked self-assembled monolayer were determined by XP...

  14. Self-assembly of silk fibroin under osmotic stress

    Science.gov (United States)

    Sohn, Sungkyun

    The supramolecular self-assembly behavior of silk fibroin was investigated using osmotic stress technique. In Chapter 2, a ternary phase diagram of water-silk-LiBr was constructed based on X-ray results on the osmotically stressed regenerated silk fibroin of Bombyx mori silkworm. Microscopic data indicated that silk I is a hydrated structure and a rough estimate of the number of water molecules lost by the structure upon converting from silk I to silk II has been made, and found to be about 2.2 per [GAGAGS] hexapeptide. In Chapter 3, wet-spinning of osmotically stressed, regenerated silk fibroin was performed, based on the prediction that the enhanced control over structure and phase behavior using osmotic stress method helps improve the physical properties of wet-spun regenerated silk fibroin fibers. The osmotic stress was applied in order to pre-structure the regenerated silk fibroin molecule from its original random coil state to more oriented state, manipulating the phase of the silk solution in the phase diagram before the start of spinning. Monofilament fiber with a diameter of 20 microm was produced. In Chapter 4, we investigated if there is a noticeable synergistic osmotic pressure increase between co-existing polymeric osmolyte and salt when extremely highly concentrated salt molecules are present both at sample subphase and stressing subphase, as is the case of silk fibroin self-assembly. The equilibration method that measures osmotic pressure relative to a reference with known osmotic pressure was introduced. Osmotic pressure of aqueous LiBr solution up to 2.75M was measured and it was found that the synergistic effect was insignificant up to this salt concentration. Solution parameters of stressing solutions and Arrhenius kinetics based on time-temperature relationship for the equilibration process were derived as well. In Chapter 5, self-assembly behavior of natural silk fibroin within the gland of Bombyx mori silkworm was investigated using osmotic

  15. Development of self-assembling nanowires containing electronically active oligothiophenes

    Science.gov (United States)

    Tsai, Wei-Wen

    This dissertation discusses the development of conductive one-dimensional nanowires from self-assembling oligothiophene molecules. Self-assembly has been demonstrated to be a promising alternative approach towards high performance, solution processable, and low-cost organic electronics. One of the many challenges in this field is the control of supramolecular morphologies of ordered structures containing pi-conjugated moieties. This research demonstrated several successful strategies to achieve self assembly of conductive nanowires using synergistic interactions combining pi stacking and hydrogen bonding. The first approach used was to develop a hairpin-shaped sexithiophene molecule, which features two arms of the conjugated structure. The diamidocyclohexyl headgroup of this molecule successfully directs the self-assembly from hydrogen bonding among the amides, forming high-aspect-ratio one-dimensional nanowires with well-defined diameters of 3.0 +/- 0.3 nm. The molecular orientation in the nanostructures promotes formation of sexithiophene H and J aggregates that facilitate efficient charge transport. Organic field-effect transistors were fabricated to reveal improved intrinsic hole mobility from films of the nanostructures, 3.46 x 10-6 cm2V-1s-1, which is one order of magnitude higher than films cast from unassembled molecules. Bulk heterojunction solar cells were developed from this molecule and fullerenes utilizing solution-phase fabrication methods. Intimate mix of the molecule and phenyl-C61-butyric acid methyl ester creates structured interfaces for efficient exciton splitting. The charge carrier mobilities of each material are improved by self-assembly in solution and thermal-energy assisted phase separation.The photovoltaic devices achieved the highest open-circuit voltage of 0.62 V, short-circuit current of 1.79 mA/cm2, fill factor of 35%, and power conversion efficiency of 0.48%. Another strategy to one-dimensional nanowires studied here involved the

  16. Purification of ethanol for highly sensitive self-assembly experiments

    Directory of Open Access Journals (Sweden)

    Kathrin Barbe

    2014-08-01

    Full Text Available Ethanol is the preferred solvent for the formation of self-assembled monolayers (SAMs of thiolates on gold. By applying a thin film sensor system, we could demonstrate that even the best commercial qualities of ethanol contain surface-active contaminants, which can compete with the desired thiolates for surface sites. Here we present that gold nanoparticles deposited onto zeolite X can be used to remove these contaminants by chemisorption. This nanoparticle-impregnated zeolite does not only show high capacities for surface-active contaminants, such as thiols, but can be fully regenerated via a simple pyrolysis protocol.

  17. The self assembly of thymine at Au(110)/liquid interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Molina Contreras, J.R. [Departamento de Ingenieria Electrica y Electronica, Instituto Tecnologico de Aguascalientes, Mexico (Mexico); Smith, C.I.; Bowfield, A.; Weightman, P. [Physics Department, University of Liverpool (United Kingdom); Tillner, F. [Fachbereich Physik, Universitaet Konstanz (Germany)

    2012-06-15

    We show that thymine self-assembles into an ordered structure when adsorbed at a Au(110)/liquid interface. Reflection anisotropy spectroscopy (RAS) shows that as found for cytosine and adenine the adsorbed thymine molecules are oriented essentially vertically on the Au(110) surface with the molecule aligned along one of the principal axes of the Au(110) surface. Simulations of the RA spectra to an empirical model indicates that as found for adsorbed cytosine and adenine, thymine is aligned along the [1 anti 10] direction on the Au(110) surface. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. Shape Changes of Self-Assembled Actin Bilayer Composite Membranes

    CERN Document Server

    Hackl, W; Sackmann, E

    1997-01-01

    We report the self-assembly of thin actin shells beneath the membranes of giant vesicles. Ion-carrier mediated influx of Mg2+ induces actin polymerization in the initially spherical vesicles. Buckling of the vesicles and the formation of blisters after thermally induced bilayer expansion is demonstrated. Bilayer flickering is dominated by tension generated by its coupling to the actin cortex. Quantitative flicker analysis suggests the bilayer and the actin cortex are separated by 0.4 \\mum to 0.5 \\mum due to undulation forces.

  19. Electrically addressing a single self-assembled quantum dot

    CERN Document Server

    Ellis, D J P; Atkinson, P; Ritchie, D A; Shields, A J

    2006-01-01

    We report on the use of an aperture in an aluminum oxide layer to restrict current injection into a single self-assembled InAs quantum dot, from an ensemble of such dots within a large mesa. The insulating aperture is formed through the wet-oxidation of a layer of AlAs. Under photoluminescence we observe that only one quantum dot in the ensemble exhibits a Stark shift, and that the same single dot is visible under electroluminescence. Autocorrelation measurements performed on the electroluminescence confirm that we are observing emission from a single quantum dot.

  20. Preface: Special Topic on Supramolecular Self-Assembly at Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Bartels, Ludwig [Department of Chemistry and the Materials Science and Engineering Program, University of California - Riverside, Riverside, California 92521 (United States); Ernst, Karl-Heinz [EMPA, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dubendorf (Switzerland); Gao, Hong-Jun [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics,Chinese Academy of Sciences, Beijing 100190 (China); Thiel, Patricia A. [Department of Chemistry, Department of Materials Science and Engineering, Ames Laboratory,Iowa State University, Ames, Iowa 50011 (United States)

    2015-03-14

    Supramolecular self-assembly at surfaces is one of the most exciting and active fields in Surface Science today. Applications can take advantage of two key properties: (i) versatile pattern formation over a broad length scale and (ii) tunability of electronic structure and transport properties, as well as frontier orbital alignment. It provides a new frontier for Chemical Physics as it uniquely combines the versatility of Organic Synthesis and the Physics of Interfaces. The Journal of Chemical Physics is pleased to publish this Special Topic Issue, showcasing recent advances and new directions.

  1. Self-assembled switches based on electroactuated multiwalled nanotubes

    Science.gov (United States)

    Dujardin, E.; Derycke, V.; Goffman, M. F.; Lefèvre, R.; Bourgoin, J. P.

    2005-11-01

    A fabrication process for nanoelectromechanical systems (NEMS) based on multiwalled carbon nanotubes (CNTs) suspended across metallic trenches is described. The process is versatile and allows the production of CNT-NEMS with singly or doubly clamped nanotubes at an adjustable height above a bottom electrode. When a voltage bias is applied between the nanotube and the bottom electrode, the devices act as very efficient electrical switches. Surface functionalization of the bottom electrode with a self-assembled monolayer is implemented to improve the switching reversibility. Moreover, it opens opportunities to use these CNT-NEMS as a vertical cross-bar junction for molecular electronics studies.

  2. Surfactant self-assembly in alcohol-rich solutions

    International Nuclear Information System (INIS)

    Ionic conductivity and viscosity measurements are achieved along alcohol dilution lines of a single-isotropic phase domain, which extends from the alcohol corner to sponge phase domain to brine corner, of an alcohol-surfactant-brine phase diagram. The results are discussed in terms of amphiphilic self-assembly which leads to stable mixtures of the slightly miscible alcohol and brine used. We show the formation of reverse micelles, whose cores are either dry or charged of brine according to the samples composition, and whose sizes remain small near the sponge phase structure

  3. Fabrication of Nanostructures Using Self-Assembled Peptides as Templates

    DEFF Research Database (Denmark)

    Castillo, Jaime

    2015-01-01

    advantages of diphenylalanine are explained step by step offering new alternatives to fabricate nanostructures in a simple and rapid way. The chapter is complemented with techniques to manipulate the self-assembled diphenylalanine nanostructures without changing its properties during the manipulation process.......This chapter evaluates the use of a short-aromatic dipeptide, diphenylalanine, as a template in the fabrication of new nanostructures (nanowires, coaxial nanocables, nanochannels) using materials such as silicon, conducting and non-conducting polymers. Diphenylalanine self-organize into...

  4. Casting Metal Nanowires Within Discrete Self-Assembled Peptide Nanotubes

    Science.gov (United States)

    Reches, Meital; Gazit, Ehud

    2003-04-01

    Tubular nanostructures are suggested to have a wide range of applications in nanotechnology. We report our observation of the self-assembly of a very short peptide, the Alzheimer's β-amyloid diphenylalanine structural motif, into discrete and stiff nanotubes. Reduction of ionic silver within the nanotubes, followed by enzymatic degradation of the peptide backbone, resulted in the production of discrete nanowires with a long persistence length. The same dipeptide building block, made of D-phenylalanine, resulted in the production of enzymatically stable nanotubes.

  5. Metal nanowires from self-assembled protein fibers

    Science.gov (United States)

    Parthasarathy, Raghuveer; Lin, Xiao-Min; Jaeger, Heinrich M.; Sawicki, George; Scheibel, Thomas; Lindquist, Susan L.

    2002-03-01

    We present gold and silver nanowires formed by metallization of self-assembled yeast prion proteins. The proteins form 10nm wide, microns long fibers, which we metallize by growth of gold or silver crystals from specific nucleation sites on the genetically engineered fiber surface. This site-specific metal decoration is the first step toward more elaborate functionalization of these biological nanostructures. Deposition of fibers onto substrates with in-plane electrodes will allow electronic transport measurements, correlated with images (TEM and AFM) of the nanowire structure.

  6. A 3D Optical Metamaterial Made by Self-Assembly

    KAUST Repository

    Vignolini, Silvia

    2011-10-24

    Optical metamaterials have unusual optical characteristics that arise from their periodic nanostructure. Their manufacture requires the assembly of 3D architectures with structure control on the 10-nm length scale. Such a 3D optical metamaterial, based on the replication of a self-assembled block copolymer into gold, is demonstrated. The resulting gold replica has a feature size that is two orders of magnitude smaller than the wavelength of visible light. Its optical signature reveals an archetypal Pendry wire metamaterial with linear and circular dichroism. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Nanostructured Columns from Self-assembly of Complementary Molecular Components

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Nanostructured columns with a length about several tens of micrometer and a diameter of about 80 nm were obtained by molecular recognition directed self-assembly of a pair of comple mentary molecular components, 4-amino-2,6-didodecylamino-1,3,5-triazine (M) and 5- (4-dode cyloxybenzylidene)-(1H, 3H)-2,4,6-pyrimidinetrione (B) in chloroform. In this system, with positive cooperativity, r-aromatic stacking and van der Waals interactions as well as hydrogen bonds cause the formation of the nanocolumns.

  8. Electrostatic self-assembly of microsphere lens arrays

    OpenAIRE

    Matteo Cornaglia; Hui Yang; Thomas Lehnert; Gijs, Martin A.M.

    2014-01-01

    We propose a novel versatile method for the rapid and low-cost fabrication of microsphere arrays to be used as lenses of desired geometry and optical properties. Our method is based on the electrostatic self-assembly of dielectric microspheres in Parylene-C/glass well templates, with the array geometry patterned in the Parylene-C layer via standard clean room techniques. While different particle sizes and materials can be used to tune the light focusing properties of the microlenses, we demon...

  9. Fractal Self-Assembled Nanostructures on Monocrystalline Silicon Surface

    OpenAIRE

    Bagraev, N. T.; Bouravleuv, A.D.; Gehlhoff, W.; Klyachkin, L. E.; Malyarenko, A. M.; Romanov, V. V.; Rykov, S. A.

    2004-01-01

    We present ultra-shallow diffusion profiles performed by short-time diffusion of boron from the gas phase using controlled surface injection of self-interstitials and vacancies into the n-type Si(100) wafers. The diffusion profiles of this art are found to consist of both longitudinal and lateral silicon quantum wells of the p-type that are self-assembled between the alloys of microdefects, which are produced by previous oxidation. These alloys appear to be passivated during short-time diffus...

  10. Manipulation of self-assembly amyloid peptide nanotubes by dielectrophoresis.

    Science.gov (United States)

    Castillo, Jaime; Tanzi, Simone; Dimaki, Maria; Svendsen, Winnie

    2008-12-01

    Self-assembled amyloid peptide nanotubes (SAPNT) were manipulated and immobilized using dielectrophoresis. Micro-patterned electrodes of Au were fabricated by photolithography and lifted off on a silicon dioxide layer. SAPNT were manipulated by adjusting the amplitude and frequency of the applied voltage. The immobilized SAPNT were evaluated by SEM and atomic force microscopy. The conductivity of the immobilized SAPNT was studied by I-V characterization, for both single SAPNT and bundles. This work illustrates a way to manipulate and integrate biological nanostructures into novel bio-nanoassemblies with concrete applications, such as field-effect transistors, microprobes, microarrays, and biosensing devices. PMID:19130587

  11. Selective electroless copper deposition on self-assembled dithiol monolayers.

    Science.gov (United States)

    Aldakov, Dmitry; Bonnassieux, Yvan; Geffroy, Bernard; Palacin, Serge

    2009-03-01

    The paper reports the use of self-assembled monolayers (SAMs) of dithiols to induce electroless copper deposition on a gold substrate. The metallization catalyst, palladium nanoparticles, is bound on the dithiol SAM. The assembly process is followed by IR and X-ray photoelectron spectroscopies to confirm the formation of a monolayer with bound catalyst. Electroless metallization is then carried out with a steady deposition rate of 130 nm/min. Additionally, microcontact printing of the catalyst on the SAM by poly(dimethylsiloxane) stamps is used to localize copper deposits. Resulting metallization is selective and allows for a high resolution. PMID:20355979

  12. Directed Formation of DNA Nanoarrays through Orthogonal Self-Assembly

    Directory of Open Access Journals (Sweden)

    Eugen Stulz

    2011-06-01

    Full Text Available We describe the synthesis of terpyridine modified DNA strands which selectively form DNA nanotubes through orthogonal hydrogen bonding and metal complexation interactions. The short DNA strands are designed to self-assemble into long duplexes through a sticky-end approach. Addition of weakly binding metals such as Zn(II and Ni(II induces the formation of tubular arrays consisting of DNA bundles which are 50-200 nm wide and 2-50 nm high. TEM shows additional long distance ordering of the terpy-DNA complexes into fibers.

  13. Self-assembled manganese oxide structures through direct oxidation

    KAUST Repository

    Zhao, Chao

    2012-12-01

    The morphology and phase of self-assembled manganese oxides during different stages of thermal oxidation were studied. Very interesting morphological patterns of Mn oxide films were observed. At the initial oxidation stage, the surface was characterized by the formation of ring-shaped patterns. As the oxidation proceeded to the intermediate stage, concentric plates formed to relax the compressive stress. Our experimental results gave a clear picture of the evolution of the structures. We also examined the properties of the structures. © 2012 Elsevier B.V.

  14. Preface: Special Topic on Supramolecular Self-Assembly at Surfaces

    International Nuclear Information System (INIS)

    Supramolecular self-assembly at surfaces is one of the most exciting and active fields in Surface Science today. Applications can take advantage of two key properties: (i) versatile pattern formation over a broad length scale and (ii) tunability of electronic structure and transport properties, as well as frontier orbital alignment. It provides a new frontier for Chemical Physics as it uniquely combines the versatility of Organic Synthesis and the Physics of Interfaces. The Journal of Chemical Physics is pleased to publish this Special Topic Issue, showcasing recent advances and new directions

  15. Biomimetic engineering: towards a self-assembled nanotechnology

    International Nuclear Information System (INIS)

    Full text: The Nanoscience and Systems program was set up within CSIRO Telecommunications and Industrial Physics three years ago with an emphasis on biomimetic engineering, with the aim of developing new cross-disciplinary research in traditional physics areas. By combining expertise in experimental and theoretical physics with biology and chemistry, new approaches towards understanding and using nanoscale systems and devices are being explored. Research in the program ranges from using self-assembled lipid membranes for surface passivation of GaAs transistors to the electrical properties of nanoparticle films and devices. An overview of the research will be given, highlighting the diversity of nanotechnology applications

  16. Self-Assembling DNA Quadruplex Conjugated to MRI Contrast Agents

    OpenAIRE

    Cai, Jianfeng; Shapiro, Erik M.; Hamilton, Andrew D.

    2009-01-01

    We report the preparation and magnetic resonance (MR) characterization of new MRI contrast agents based on gadolinium complexes conjugated to a self-assembling DNA quadruplex scaffold. As a single gadolinium-DOTA chelated DNA strand, the r1 molar relaxivity is 6.4 mM-1 s-1 per Gd and increases to 11.7 mM-1 s-1 per Gd upon formation of a DNA quadruplex. Similar results were obtained when a gadolinium-DOTA dendrimer was conjugated to DNA, the r1 molar relaxivity increasing to 12.9 mM-1 s-1 per ...

  17. S-layer architectures : extending the morphogenetic potential of S-layer protein self-assembly

    International Nuclear Information System (INIS)

    supporting substances for the fabrication of pure S-layer cages is very difficult. Providing a sufficient volume within lipid vesicles, giant unilamellar vesicles (GUVs) specifically coated with S-layer protein on the inside and/or on the outside could be fabricated. The use of carbon nanotubes as templates for S-layer recrystallization paved the way for the design of novel S-layer decorated tubular morphologies. The results of this project constitute a key enabling technology for the fabrication of nanoporous protein cages and fibers by exerting self-assembly strategies common in nature. Such nano containers can be used for the construction of artificial viruses, for controlled drug targeting and delivery, affinity matrices, and for the synthesis of spatially constrained nanoparticles (author)

  18. Efficiency Enhancement of InGaN-Based Solar Cells via Stacking Layers of Light-Harvesting Nanospheres.

    Science.gov (United States)

    Al-Amri, Amal M; Fu, Po-Han; Lai, Kun-Yu; Wang, Hsin-Ping; Li, Lain-Jong; He, Jr-Hau

    2016-01-01

    An effective light-harvesting scheme for InGaN-based multiple quantum well solar cells is demonstrated using stacking layers of polystyrene nanospheres. Light-harvesting efficiencies on the solar cells covered with varied stacks of nanospheres are evaluated through numerical and experimental methods. The numerical simulation reveals that nanospheres with 3 stacking layers exhibit the most improved optical absorption and haze ratio as compared to those obtained by monolayer nanospheres. The experimental demonstration, agreeing with the theoretical analyses, shows that the application of 3-layer nanospheres improves the conversion efficiency of the solar cell by ~31%. PMID:27339612

  19. Efficiency Enhancement of InGaN-Based Solar Cells via Stacking Layers of Light-Harvesting Nanospheres

    Science.gov (United States)

    Al-Amri, Amal M.; Fu, Po-Han; Lai, Kun-Yu; Wang, Hsin-Ping; Li, Lain-Jong; He, Jr-Hau

    2016-01-01

    An effective light-harvesting scheme for InGaN-based multiple quantum well solar cells is demonstrated using stacking layers of polystyrene nanospheres. Light-harvesting efficiencies on the solar cells covered with varied stacks of nanospheres are evaluated through numerical and experimental methods. The numerical simulation reveals that nanospheres with 3 stacking layers exhibit the most improved optical absorption and haze ratio as compared to those obtained by monolayer nanospheres. The experimental demonstration, agreeing with the theoretical analyses, shows that the application of 3-layer nanospheres improves the conversion efficiency of the solar cell by ~31%. PMID:27339612

  20. Efficiency Enhancement of InGaN-Based Solar Cells via Stacking Layers of Light-Harvesting Nanospheres

    KAUST Repository

    Al-Amri, Amal M.

    2016-06-24

    An effective light-harvesting scheme for InGaN-based multiple quantum well solar cells is demonstrated using stacking layers of polystyrene nanospheres. Light-harvesting efficiencies on the solar cells covered with varied stacks of nanospheres are evaluated through numerical and experimental methods. The numerical simulation reveals that nanospheres with 3 stacking layers exhibit the most improved optical absorption and haze ratio as compared to those obtained by monolayer nanospheres. The experimental demonstration, agreeing with the theoretical analyses, shows that the application of 3-layer nanospheres improves the conversion efficiency of the solar cell by ~31%.

  1. On Improving the Performance of Nonphotochemical Quenching in CP29 Light-Harvesting Antenna Complex

    CERN Document Server

    Berman, Gennady P; Sayre, Richard T; Still, Susanne

    2015-01-01

    We model and simulate the performance of charge-transfer in nonphotochemical quenching (NPQ) in the CP29 light-harvesting antenna-complex associated with photosystem II (PSII). The model consists of five discrete excitonic energy states and two sinks, responsible for the potentially damaging processes and charge-transfer channels, respectively. We demonstrate that by varying (i) the parameters of the chlorophyll-based dimer, (ii) the resonant properties of the protein-solvent environment interaction, and (iii) the energy transfer rates to the sinks, one can significantly improve the performance of the NPQ. Our analysis suggests strategies for improving the performance of the NPQ in response to environmental changes, and may stimulate experimental verification.

  2. Modeling Electronic-Nuclear Interactions for Excitation Energy Transfer Processes in Light-Harvesting Complexes.

    Science.gov (United States)

    Lee, Mi Kyung; Coker, David F

    2016-08-18

    An accurate approach for computing intermolecular and intrachromophore contributions to spectral densities to describe the electronic-nuclear interactions relevant for modeling excitation energy transfer processes in light harvesting systems is presented. The approach is based on molecular dynamics (MD) calculations of classical correlation functions of long-range contributions to excitation energy fluctuations and a separate harmonic analysis and single-point gradient quantum calculations for electron-intrachromophore vibrational couplings. A simple model is also presented that enables detailed analysis of the shortcomings of standard MD-based excitation energy fluctuation correlation function approaches. The method introduced here avoids these problems, and its reliability is demonstrated in accurate predictions for bacteriochlorophyll molecules in the Fenna-Matthews-Olson pigment-protein complex, where excellent agreement with experimental spectral densities is found. This efficient approach can provide instantaneous spectral densities for treating the influence of fluctuations in environmental dissipation on fast electronic relaxation. PMID:27472379

  3. On improving the performance of nonphotochemical quenching in CP29 light-harvesting antenna complex

    Science.gov (United States)

    Berman, Gennady P.; Nesterov, Alexander I.; Sayre, Richard T.; Still, Susanne

    2016-03-01

    We model and simulate the performance of charge-transfer in nonphotochemical quenching (NPQ) in the CP29 light-harvesting antenna-complex associated with photosystem II (PSII). The model consists of five discrete excitonic energy states and two sinks, responsible for the potentially damaging processes and charge-transfer channels, respectively. We demonstrate that by varying (i) the parameters of the chlorophyll-based dimer, (ii) the resonant properties of the protein-solvent environment interaction, and (iii) the energy transfer rates to the sinks, one can significantly improve the performance of the NPQ. Our analysis suggests strategies for improving the performance of the NPQ in response to environmental changes, and may stimulate experimental verification.

  4. Multireference excitation energies for Bacteriochlorophylls A within light harvesting system 2

    DEFF Research Database (Denmark)

    Anda, Andre; Hansen, Thorsten; De Vico, Luca

    2016-01-01

    Light-harvesting system 2 (LH2) of purple bacteria is one of the most popular antenna complexes used to study Nature's way of collecting and channeling solar energy. The dynamics of the absorbed energy is probed by ultrafast spectroscopy. Simulation of these experiments relies on fitting a range of...... parameters to reproduce the spectra. Here, we present a method that can determine key parameters to chemical accuracy. These will eliminate free variables in the modeling, thus reducing the problem. Using MS-RASPT2/RASSCF calculations, we compute excitation energies and transition dipole moments of all...... bacteriochlorophylls in LH2. We find that the excitation energies vary among the bacteriochlorophyll monomers and that they are regulated by the curvature of the macrocycle ring and the dihedral angle of an acetyl moiety. Increasing the curvature lifts the ground state energy, which causes a red shift of the...

  5. Investigation of detergent effects on the solution structure of spinach Light Harvesting Complex II

    Energy Technology Data Exchange (ETDEWEB)

    Cardoso, Mateus B; Smolensky, Dmitriy; Heller, William T; O' Neill, Hugh, E-mail: hellerwt@ornl.gov, E-mail: oneillhm@ornl.gov [Center for Structural Molecular Biology, Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

    2010-11-01

    The properties of spinach light harvesting complex II (LHC II), stabilized in the detergents Triton X-100 (TX100) and n-Octyl-{beta}-D-Glucoside (BOG), were investigated by small-angle neutron scattering (SANS). The LHC II-BOG scattering curve overlaid well with the theoretical scattering curve generated from the crystal structure of LHC II indicating that the protein preparation was in its native functional state. On the other hand, the simulated LHC II curve deviated significantly from the LHC II-TX100 experimental data. Analysis by circular dichroism spectroscopy supported the SANS analysis and showed that LHC II-TX100 is inactivated. This investigation has implications for extracting and stabilizing photosynthetic membrane proteins for the development of biohybrid photoconversion devices.

  6. Population and Entanglement Dynamics in Light Harvesting Complex II (LH2)

    CERN Document Server

    Yeh, Shu-Hao; Kais, Sabre

    2012-01-01

    The electronic excitation population and entanglement dynamics in the chromophores of photosynthetic light harvesting complex 2 (LH2) B850 ring from purple bacteria (Rhodopseudomonas acidophila) have been studied and analyzed theoretically at both physiological and cryogenic temperature. Similar to the well-studied Fenna-Matthews-Olson (FMO) protein, oscillations of excitation population and pairwise entanglement are observed in LH2 by using a scaled hierarchical equation of motion (HEOM) approach. However, this oscillation time (300 fs) is much shorter compared to the FMO protein (650 fs) at cryogenic temperature. The environment and high temperature are found to enhance the propagation speed of exciton wave packet but shorten the coherence time and suppress both oscillation amplitude of concurrence and population. The calculation of bipartite entanglement between chromophore electronic excitation shows the existence of a long-lived entanglement in this system, illustrates that such quantum effect could surv...

  7. Design principles and fundamental trade-offs in biomimetic light harvesting

    CERN Document Server

    Sarovar, Mohan

    2012-01-01

    Recent developments in synthetic and supramolecular chemistry have created opportunities to design organic systems with tailored nanoscale structure for various technological applications. A key application area is the capture of light energy and its conversion into electrochemical or chemical forms for photovoltaic or sensing applications. In this work we consider cylindrical assemblies of chromophores that model structures produced by several supramolecular techniques. Our study is especially guided by the versatile structures produced by virus-templated assembly. We use a multi-objective optimization framework to determine design principles and limitations in light harvesting performance for such assemblies, both in the presence and absence of disorder. We identify a fundamental trade-off in cylindrical assemblies that is encountered when attempting to maximize both efficiency of energy transfer and absorption bandwidth. We also rationalize the optimal design strategies and provide explanations for why var...

  8. Memory-assisted exciton diffusion in the chlorosome light-harvesting antenna of green sulfur bacteria

    CERN Document Server

    Fujita, Takatoshi; Saikin, Semion K; Aspuru-Guzik, Alan

    2012-01-01

    Chlorosomes are likely the largest and most efficient natural light-harvesting photosynthetic antenna systems. They are composed of large numbers of bacteriochlorophylls organized into supramolecular aggregates. We explore the microscopic origin of the fast excitation energy transfer in the chlorosome using the recently-resolved structure and atomistic-detail simulations. Despite the dynamical disorder effects on the electronic transitions of the bacteriochlorophylls, our simulations show that the exciton delocalizes over the entire aggregate in about 200 fs. The memory effects associated to the dynamical disorder assist the exciton diffusion through the aggregates and enhance the diffusion coefficients as a factor of two as compared to the model without memory. Furthermore, exciton diffusion in the chlorosome is found to be highly anisotropic with the preferential transfer towards the baseplate, which is the next functional element in the photosynthetic system.

  9. New Light-Harvesting Materials Using Accurate and Efficient Bandgap Calculations

    DEFF Research Database (Denmark)

    Castelli, Ivano Eligio; Hüser, Falco; Pandey, Mohnish;

    2014-01-01

    materials for different applications where the bandgaps are used as descriptors for the efficiency of a photoelectrochemical device. Here, new light harvesting materials are proposed to be used in a one-photon photoelectrochemical device for water splitting by combining the estimation of the bandgaps with......Electronic bandgap calculations are presented for 2400 experimentally known materials from the Materials Project database and the bandgaps, obtained with different types of functionals within density functional theory and (partial) self-consistent GW approximation, are compared for 20 randomly...... chosen compounds forming an unconventional set of ternary and quaternary materials. It is shown that the computationally cheap GLLB-SC potential gives results in good agreement (around 15%) with the more advanced and demanding eigenvalue-self-consistent GW. This allows for a high-throughput screening of...

  10. Investigation of detergent effects on the solution structure of spinach Light Harvesting Complex II

    Science.gov (United States)

    Cardoso, Mateus B.; Smolensky, Dmitriy; Heller, William T.; O'Neill, Hugh

    2010-11-01

    The properties of spinach light harvesting complex II (LHC II), stabilized in the detergents Triton X-100 (TX100) and n-Octyl-β-D-Glucoside (BOG), were investigated by small-angle neutron scattering (SANS). The LHC II-BOG scattering curve overlaid well with the theoretical scattering curve generated from the crystal structure of LHC II indicating that the protein preparation was in its native functional state. On the other hand, the simulated LHC II curve deviated significantly from the LHC II-TX100 experimental data. Analysis by circular dichroism spectroscopy supported the SANS analysis and showed that LHC II-TX100 is inactivated. This investigation has implications for extracting and stabilizing photosynthetic membrane proteins for the development of biohybrid photoconversion devices.

  11. The fundamental role of localised vibrations in excitation dynamics in photosynthetic light-harvesting systems

    CERN Document Server

    Kolli, Avinash; Scholes, Gregory D; Olaya-Castro, Alexandra

    2012-01-01

    The importance of fast vibrations in enhancing and controlling energy transfer and conversion in biomolecules is an issue of current debate. In this article we show that coupling between localised high-frequency vibrations and electronic degrees of freedom is fundamental for efficient excitation transport in photosynthetic light-harvesting systems with high degree of disorder. We consider the cryptophyte antennae protein phycoerythrin 545 and discuss how the balance between electronic interactions and coupling to fast vibronic modes supports the biological function of these antennae by generating a non-cascaded transport that leads to a rapid, directed and wider spatial distribution of excitation energy across the complex. Furthermore, we illustrate signatures of vibronic influence in the beating of excitonic coherences and show that mechanisms supporting coherent evolution of excitons also assist coupling to selected modes that enhance energy transfer to preferential sites in the complex. We therefore argue ...

  12. Excited-state dynamics in light-harvesting complex of Rhodobacter sphaeroides

    Institute of Scientific and Technical Information of China (English)

    LIU KangJun; LIU WeiMin; YAN YongLi; DONG ZhiWei; XU ChunHe; QIAN ShiXiong

    2008-01-01

    Photodynamics of peripheral antenna complexes, light-harvesting complex (LH2) of Rhodobacter (Rb) Sphaeroides 601, was studied using femtosecond pump-probe technique at different laser wavelengths. The obtained results reveal dramatic dynamical evolutions within B800 and B850 absorption bands of antenna complexes LH2. At excitation wavelength around 835 nm, a sharp photobleaching signal was observed which was assigned to the contribution of the two-exciton state, which was further confirmed by the power dependence measurement. Rate equations with eight-level scheme were used to calculate the population evolution in LH2 and the transient dynamics under femtosecond pulse excitation. The research results prove that not only the transition from ground state to one-exciton state but also that from one-exciton state to two-exciton state contribute to the photodynamics of B850.

  13. Theoretical characterization of excitation energy transfer in chlorosome light-harvesting antennae from green sulfur bacteria

    CERN Document Server

    Fujita, Takatoshi; Saikin, Semion K; Brookes, Jennifer C; Aspuru-Guzik, Alan

    2013-01-01

    Chlorosomes are the largest and most efficient natural light-harvesting antenna systems. They contain thousands of pigment molecules - bacteriochlorophylls (BChls)- that are organized into supramolecular aggregates and form a very efficient network for excitonic energy migration. Here, we present a theoretical study of excitation energy transfer (EET) in the chlorosome based on experimental evidence of the molecular assembly. Our model for the exciton dynamics throughout the antenna combines a stochastic time propagation of the excitonic wave function with molecular dynamics simulations of supramolecular structure, and electronic structure calculations of the excited states. The simulation results reveal a detailed picture of the EET in the chlorosome. Coherent energy transfer is significant only for the first 50 fs after the initial excitation, and the wavelike motion of the exciton is completely damped at 100 fs. Characteristic time constants of incoherent energy transfer, subsequently, vary from 1 ps to se...

  14. Vibrational beatings conceal evidence of electronic coherence in the FMO light-harvesting complex.

    Science.gov (United States)

    Tempelaar, Roel; Jansen, Thomas L C; Knoester, Jasper

    2014-11-13

    In biological light harvesting, solar energy is captured by photosynthetic antennae for subsequent storage into chemical bonds. The remarkable efficiency reached in transferring the energy between the collection and storage events recently has been attributed to long-lived electronic coherence present in such antennae systems. We present numerical simulations indicating that the spectroscopic transients that supported this hypothesis are not induced by electronic coherence but instead are caused by vibrational (nuclear) motion in the electronic ground state potential. Besides emphasizing the significance of such nuclear modes, our findings stimulate a reconsideration of the role of electronic coherence in promoting energy transfer in natural photosynthesis. Furthermore, they require us to rethink how energy transfer efficiency is reflected in spectral signals. PMID:25321492

  15. Theory of femtosecond coherent double-pump single-molecule spectroscopy: Application to light harvesting complexes

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Lipeng; Zhao, Yang, E-mail: YZhao@ntu.edu.sg [Division of Materials Science, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Gelin, Maxim F.; Domcke, Wolfgang [Department of Chemistry, Technische Universität München, Garching D-85747 (Germany)

    2015-04-28

    We develop a first principles theoretical description of femtosecond double-pump single-molecule signals of molecular aggregates. We incorporate all singly excited electronic states and vibrational modes with significant exciton-phonon coupling into a system Hamiltonian and treat the ensuing system dynamics within the Davydov D{sub 1} Ansatz. The remaining intra- and inter-molecular vibrational modes are treated as a heat bath and their effect is accounted for through lineshape functions. We apply our theory to simulate single-molecule signals of the light harvesting complex II. The calculated signals exhibit pronounced oscillations of mixed electron-vibrational (vibronic) origin. Their periods decrease with decreasing exciton-phonon coupling.

  16. Disentangling electronic and vibrational coherence in the Phycocyanin-645 light-harvesting complex

    CERN Document Server

    Richards, Gethin H; Curmi, Paul M G; Davis, Jeffrey A

    2013-01-01

    Energy transfer between chromophores in photosynthesis proceeds with near unity quantum efficiency. Understanding the precise mechanisms of these processes is made difficult by the complexity of the electronic structure and interactions with different vibrational modes. Two-dimensional spectroscopy has helped resolve some of the ambiguities and identified quantum effects that may be important for highly efficient energy transfer. Many questions remain, however, including whether the coherences observed are electronic and/or vibrational in nature and what role they play. We utilise a two-colour four-wave mixing experiment with control of the wavelength and polarization to selectively excite specific coherence pathways. For the light-harvesting complex PC645, from cryptophyte algae, we reveal and identify specific contributions from both electronic and vibrational coherences and determine an excited state structure based on two strongly-coupled electronic states and two vibrational modes. Separation of the cohe...

  17. Consequences of Decreased Light Harvesting Capability on Photosystem II Function in Synechocystis sp. PCC 6803

    Directory of Open Access Journals (Sweden)

    Aparna Nagarajan

    2014-12-01

    Full Text Available Cyanobacteria use large pigment-protein complexes called phycobilisomes to harvest light energy primarily for photosystem II (PSII. We used a series of mutants with partial to complete reduction of phycobilisomes to examine the effects of antenna truncation on photosystem function in Synechocystis sp. PCC 6803. The antenna mutants CB, CK, and PAL expressed increasing levels of functional PSII centers to compensate for the loss of phycobilisomes, with a concomitant decrease in photosystem I (PSI. This increased PSII titer led to progressively higher oxygen evolution rates on a per chlorophyll basis. The mutants also exhibited impaired S-state transition profiles for oxygen evolution. Additionally, P700+ re-reduction rates were impacted by antenna reduction. Thus, a decrease in antenna size resulted in overall physiological changes in light harvesting and delivery to PSII as well as changes in downstream electron transfer to PSI.

  18. Si nanowire metal-insulator-semiconductor photodetectors as efficient light harvesters

    International Nuclear Information System (INIS)

    Novel ITO-Si nanowire (NW) metal-insulator-semiconductor (MIS) photodetectors were fabricated by using n-type Si NWs as detection units and ITO films as top gate electrodes. Measurements on the Si NW based device reveal a significant photoresponse, including photocurrent generation with an external quantum efficiency (EQE) of ∼ 35% at a peak wavelength of 600 nm at zero external bias, and with an EQE of 70% at a peak wavelength of 800 nm at - 0.5 V bias. The NW device shows a flat and low reflectance and almost constant EQE up to a 60 deg. incident angle of illumination, demonstrating efficient visible-light harvesting by the Si NW antenna.

  19. Investigation of detergent effects on the solution structure of spinach Light Harvesting Complex II

    International Nuclear Information System (INIS)

    The properties of spinach light harvesting complex II (LHC II), stabilized in the detergents Triton X-100 (TX100) and n-Octyl-β-D-Glucoside (BOG), were investigated by small-angle neutron scattering (SANS). The LHC II-BOG scattering curve overlaid well with the theoretical scattering curve generated from the crystal structure of LHC II indicating that the protein preparation was in its native functional state. On the other hand, the simulated LHC II curve deviated significantly from the LHC II-TX100 experimental data. Analysis by circular dichroism spectroscopy supported the SANS analysis and showed that LHC II-TX100 is inactivated. This investigation has implications for extracting and stabilizing photosynthetic membrane proteins for the development of biohybrid photoconversion devices.

  20. Electronic coherence and the kinetics of inter-complex energy transfer in light-harvesting systems.

    Science.gov (United States)

    Huo, Pengfei; Miller, Thomas F

    2015-12-14

    We apply real-time path-integral dynamics simulations to characterize the role of electronic coherence in inter-complex excitation energy transfer (EET) processes. The analysis is performed using a system-bath model that exhibits the essential features of light-harvesting networks, including strong intra-complex electronic coupling and weak inter-complex coupling. Strong intra-complex coupling is known to generate both static and dynamic electron coherences, which delocalize the exciton over multiple chromophores and potentially influence the inter-complex EET dynamics. With numerical results from partial linearized density matrix (PLDM) real-time path-integral calculations, it is found that both static and dynamic coherence are correlated with the rate of inter-complex EET. To distinguish the impact of these two types of intra-complex coherence on the rate of inter-complex EET, we use Multi-Chromophore Förster Resonance Energy Transfer (MC-FRET) theory to map the original parameterization of the system-bath model to an alternative parameterization for which the effects of static coherence are preserved while the effects of dynamic coherence are largely eliminated. It is then shown that both parameterizations of the model (i.e., the original that supports dynamic coherence and the alternative that eliminates it), exhibit nearly identical EET kinetics and population dynamics over a wide range of parameters. These observations are found to hold for cases in which either the EET donor or acceptor is a dimeric complex and for cases in which the dimeric complex is either symmetric or asymmetric. The results from this study suggest that dynamic coherence plays only a minor role in the actual kinetics of inter-complex EET, whereas static coherence largely governs the kinetics of incoherent inter-complex EET in light-harvesting networks. PMID:26073739

  1. Selective Surface Acoustic Wave-Based Organophosphorus Sensor Employing a Host-Guest Self-Assembly Monolayer of β-Cyclodextrin Derivative.

    Science.gov (United States)

    Pan, Yong; Mu, Ning; Shao, Shengyu; Yang, Liu; Wang, Wen; Xie, Xiao; He, Shitang

    2015-01-01

    Self-assembly and molecular imprinting technologies are very attractive technologies for the development of artificial recognition systems and provide chemical recognition based on need and not happenstance. In this paper, we employed a b-cyclodextrin derivative surface acoustic wave (SAW) chemical sensor for detecting the chemical warfare agents (CWAs) sarin (O-Isoprophyl methylphosphonofluoridate, GB). Using sarin acid (isoprophyl hydrogen methylphosphonate) as an imprinting template, mono[6-deoxy-6-[(mercaptodecamethylene)thio

  2. Selective Surface Acoustic Wave-Based Organophosphorus Sensor Employing a Host-Guest Self-Assembly Monolayer of β-Cyclodextrin Derivative

    Directory of Open Access Journals (Sweden)

    Yong Pan

    2015-07-01

    Full Text Available Self-assembly and molecular imprinting technologies are very attractive technologies for the development of artificial recognition systems and provide chemical recognition based on need and not happenstance. In this paper, we employed a b-cyclodextrin derivative surface acoustic wave (SAW chemical sensor for detecting the chemical warfare agents (CWAs sarin (O-Isoprophyl methylphosphonofluoridate, GB. Using sarin acid (isoprophyl hydrogen methylphosphonate as an imprinting template, mono[6-deoxy-6-[(mercaptodecamethylenethio

  3. Live visualizations of single isolated tubulin protein self-assembly via tunneling current: effect of electromagnetic pumping during spontaneous growth of microtubule

    Science.gov (United States)

    Sahu, Satyajit; Ghosh, Subrata; Fujita, Daisuke; Bandyopadhyay, Anirban

    2014-12-01

    As we bring tubulin protein molecules one by one into the vicinity, they self-assemble and entire event we capture live via quantum tunneling. We observe how these molecules form a linear chain and then chains self-assemble into 2D sheet, an essential for microtubule, --fundamental nano-tube in a cellular life form. Even without using GTP, or any chemical reaction, but applying particular ac signal using specially designed antenna around atomic sharp tip we could carry out the self-assembly, however, if there is no electromagnetic pumping, no self-assembly is observed. In order to verify this atomic scale observation, we have built an artificial cell-like environment with nano-scale engineering and repeated spontaneous growth of tubulin protein to its complex with and without electromagnetic signal. We used 64 combinations of plant, animal and fungi tubulins and several doping molecules used as drug, and repeatedly observed that the long reported common frequency region where protein folds mechanically and its structures vibrate electromagnetically. Under pumping, the growth process exhibits a unique organized behavior unprecedented otherwise. Thus, ``common frequency point'' is proposed as a tool to regulate protein complex related diseases in the future.

  4. Self-assembly of channel type β-CD dimers induced by dodecane.

    Science.gov (United States)

    Zhou, Chengcheng; Cheng, Xinhao; Zhao, Qiang; Yan, Yun; Wang, Jide; Huang, Jianbin

    2014-01-01

    Cyclodextrins (CDs) can hardly self-assemble into well-defined structures. Here we report if they preassemble into channel type dimers assisted by dodecane, well-defined vesicles and bricks can be formed. Unlike the traditional self-assembly of amphiphilic molecules driven by hydrophobic effect, the self-assembly of the channel type dodecane@2β-CD supramolecular building block is predoninantly driven by hydrogen-bonds. More water molecules are found in the lyophilized vesicles than in the bricks, suggesting water molecules play an important role in the self-assembly of the channel-type dimers of β-CD. The amount of structural water in the self-assembly is closely related to the curvature of the final self-assembled structures. Our work reveals that the channel-type dimer of β-CD may represent a new sort of building block for advanced structures. PMID:25532046

  5. Morphology and Pattern Control of Diphenylalanine Self-Assembly via Evaporative Dewetting.

    Science.gov (United States)

    Chen, Jiarui; Qin, Shuyu; Wu, Xinglong; Chu, And Paul K

    2016-01-26

    Self-assembled peptide nanostructures have unique physical and biological properties and promising applications in electrical devices and functional molecular recognition. Although solution-based peptide molecules can self-assemble into different morphologies, it is challenging to control the self-assembly process. Herein, controllable self-assembly of diphenylalanine (FF) in an evaporative dewetting solution is reported. The fluid mechanical dimensionless numbers, namely Rayleigh, Marangoni, and capillary numbers, are introduced to control the interaction between the solution and FF molecules in the self-assembly process. The difference in the film thickness reflects the effects of Rayleigh and Marangoni convection, and the water vapor flow rate reveals the role of viscous fingering in the emergence of aligned FF flakes. By employing dewetting, various FF self-assembled patterns, like concentric and spokelike, and morphologies, like strips and hexagonal tubes/rods, can be produced, and there are no significant lattice structural changes in the FF nanostructures. PMID:26654935

  6. Parallelism and Time in Hierarchical Self-Assembly

    CERN Document Server

    Chen, Ho-Lin

    2011-01-01

    We study the role that parallelism plays in time complexity of Winfree's abstract Tile Assembly Model (aTAM), a model of molecular algorithmic self-assembly. In the "hierarchical" aTAM, two assemblies, both consisting of multiple tiles, are allowed to aggregate together, whereas in the "seeded" aTAM, tiles attach one at a time to a growing assembly. Adleman, Cheng, Goel, and Huang ("Running Time and Program Size for Self-Assembled Squares", STOC 2001) showed how to assemble an n x n square in O(n) time in the seeded aTAM using O(log n / log log n) unique tile types, where both of these parameters are optimal. They asked whether the hierarchical aTAM could allow a tile system to use the ability to form large assemblies in parallel before they attach to break the Omega(n) lower bound for assembly time. We show that there is a tile system with the optimal O(log n / log log n) tile types that assembles an n x n square using O(log^2 n) parallel "stages", which is close to the optimal Omega(log n) stages, forming t...

  7. Synthesis and self-assembly of complex hollow materials

    KAUST Repository

    Zeng, Hua Chun

    2011-01-01

    Hollow materials with interiors or voids and pores are a class of lightweight nanostructured matters that promise many future technological applications, and they have received significant research attention in recent years. On the basis of well-known physicochemical phenomena and principles, for example, several solution-based protocols have been developed for the general preparation of these complex materials under mild reaction conditions. This article is thus a short introductory review on the synthetic aspects of this field of development. The synthetic methodologies can be broadly divided into three major categories: (i) template-assisted synthesis, (ii) self-assembly with primary building blocks, and (iii) induced matter relocations. In most cases, both synthesis and self-assembly are involved in the above processes. Further combinations of these methodologies appear to be very important, as they will allow one to prepare functional materials at a higher level of complexity and precision. The synthetic strategies are introduced through some simple case studies with schematic illustrations. Salient features of the methods developed have been summarized, and some urgent issues of this field have also been indicated. © 2011 The Royal Society of Chemistry.

  8. Wafer-scale self-assembled plasmonic thin films

    International Nuclear Information System (INIS)

    Plasmonic films have become important for many applications including photonics, energy conversion, and chemical sensing, but the fabrication of these films often requires special equipment, great care, and skill. Colloidal metal nanoparticles offer an alternative as they have been shown to self-assemble into highly-ordered monolayer films by the simple and inexpensive technique of drop casting. Using this technique, we fabricated wafer-scale films of highly-ordered 6 nm Au nanoparticles and evaluated them as candidates for plasmonic applications. These colloidal films were found to support uniform and high-quality plasmon modes over the entire area of the wafer. A combination of microscopy and spectroscopy was used to evaluate and correlate the structural and optical qualities of the films. Electron and atomic force microscopy showed that the nanoscale structure of the films was compact and highly ordered, with few defects or bilayers. Spectroscopic ellipsometry showed that the majority of the film was optically quite uniform with some bilayer patches and voids. These were subsequently confirmed by microscopy. Optical analysis of the thin film showed a prominent plasmon resonance band across the entire wafer. The plasmon frequency was quite insensitive to the presence of voids or bilayers. The width of the plasmon band was more sensitive to bilayers, however, and was found to be as much as 15% wider than in monolayer regions. These results indicate that self-assembled colloidal thin films should be suitable for large-scale plasmonic applications.

  9. Liposomes self-assembled from electrosprayed composite microparticles

    International Nuclear Information System (INIS)

    Composite microparticles, consisting of polyvinylpyrrolidone (PVP), naproxen (NAP) and lecithin (PC), have been successfully prepared using an electrospraying process and exploited as templates to manipulate molecular self-assembly for the synthesis of liposomes in situ. Field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM) observations demonstrate that the microparticles have an average diameter of 960 ± 140 nm and a homogeneous structure. X-ray diffraction (XRD) patterns, differential scanning calorimetry (DSC) and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) results verify that the building blocks NAP and PC are scattered in the polymer matrix in a molecular way owing to the very fast drying of the electrospraying process and the favorable secondary interactions among the components. FESEM, scanning probe microscope (SPM) and TEM observations demonstrate that the liposomes can be achieved through molecular self-assembly in situ when the microparticles contact water thanks to ‘like prefers like’ and by means of the confinement effect of the microparticles. The liposomes have an encapsulation rate of 91.3%, and 80.7% of the drug in the liposomes can be freed into the dissolution medium in a sustained way and by a diffusion mechanism over a period of 24 h. The developed strategy not only provides a new, facile, and effective method to assemble and organize molecules of multiple components into liposomes with electrosprayed microparticles as templates, but also opens a new avenue for nanofabrication in a step-by-step and controllable way. (paper)

  10. Protein-directed self-assembly of a fullerene crystal

    Science.gov (United States)

    Kim, Kook-Han; Ko, Dong-Kyun; Kim, Yong-Tae; Kim, Nam Hyeong; Paul, Jaydeep; Zhang, Shao-Qing; Murray, Christopher B.; Acharya, Rudresh; DeGrado, William F.; Kim, Yong Ho; Grigoryan, Gevorg

    2016-01-01

    Learning to engineer self-assembly would enable the precise organization of molecules by design to create matter with tailored properties. Here we demonstrate that proteins can direct the self-assembly of buckminsterfullerene (C60) into ordered superstructures. A previously engineered tetrameric helical bundle binds C60 in solution, rendering it water soluble. Two tetramers associate with one C60, promoting further organization revealed in a 1.67-Å crystal structure. Fullerene groups occupy periodic lattice sites, sandwiched between two Tyr residues from adjacent tetramers. Strikingly, the assembly exhibits high charge conductance, whereas both the protein-alone crystal and amorphous C60 are electrically insulating. The affinity of C60 for its crystal-binding site is estimated to be in the nanomolar range, with lattices of known protein crystals geometrically compatible with incorporating the motif. Taken together, these findings suggest a new means of organizing fullerene molecules into a rich variety of lattices to generate new properties by design. PMID:27113637

  11. Aqueous Two Phase System Assisted Self-Assembled PLGA Microparticles

    Science.gov (United States)

    Yeredla, Nitish; Kojima, Taisuke; Yang, Yi; Takayama, Shuichi; Kanapathipillai, Mathumai

    2016-06-01

    Here, we produce poly(lactide-co-glycolide) (PLGA) based microparticles with varying morphologies, and temperature responsive properties utilizing a Pluronic F127/dextran aqueous two-phase system (ATPS) assisted self-assembly. The PLGA polymer, when emulsified in Pluronic F127/dextran ATPS, forms unique microparticle structures due to ATPS guided-self assembly. Depending on the PLGA concentration, the particles either formed a core-shell or a composite microparticle structure. The microparticles facilitate the simultaneous incorporation of both hydrophobic and hydrophilic molecules, due to their amphiphilic macromolecule composition. Further, due to the lower critical solution temperature (LCST) properties of Pluronic F127, the particles exhibit temperature responsiveness. The ATPS based microparticle formation demonstrated in this study, serves as a novel platform for PLGA/polymer based tunable micro/nano particle and polymersome development. The unique properties may be useful in applications such as theranostics, synthesis of complex structure particles, bioreaction/mineralization at the two-phase interface, and bioseparations.

  12. Development of self-assembled bacterial cellulose-starch nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Grande, Cristian J. [Faculty of Mechanical Engineering, Catholic University of Peru (PUCP), Lima 32 (Peru); Torres, Fernando G., E-mail: fgtorres@pucp.edu.pe [Faculty of Mechanical Engineering, Catholic University of Peru (PUCP), Lima 32 (Peru); Gomez, Clara M., E-mail: Clara.Gomez@uv.es [Departament de Quimica Fisica and Institut de Ciencia dels Materials, Dr Moliner 50, Universitat de Valencia, E-46100 Burjassot, Valencia (Spain); Troncoso, Omar P. [Faculty of Mechanical Engineering, Catholic University of Peru (PUCP), Lima 32 (Peru); Canet-Ferrer, Josep; Martinez-Pastor, Juan [Unit of Optoelectronic Materials and Devices of the University of Valencia, P.O. Box 22085, 46071 Valencia (Spain)

    2009-05-05

    A bioinspired bottom-up process was developed to produce self-assembled nanocomposites of cellulose synthesized by Acetobacter bacteria and native starch. This process takes advantage of the way some bacteria extrude cellulose nanofibres and of the transport process that occurs during the gelatinization of starch. Potato and corn starch were added into the culture medium and partially gelatinized in order to allow the cellulose nanofibrils to grow in the presence of a starch phase. The bacterial cellulose (BC)-starch gels were hot pressed into sheets that had a BC volume fraction higher than 90%. During this step starch was forced to further penetrate the BC network. The self-assembled BC-starch nanocomposites showed a coherent morphology that was assessed by Atomic Force Microscopy (AFM) and Environmental Scanning Electron Microscopy (ESEM). The nanocomposites structure was studied using X-ray diffraction and ATR-FTIR spectroscopy. The degree of crystallinity of the final nanocomposites was used to estimate the volume fraction of BC. The aim of this paper is to explore a new methodology that could be used to produce nanomaterials by introducing a different phase into a cellulose nanofibre network during its assembly.

  13. Wafer-scale self-assembled plasmonic thin films

    Energy Technology Data Exchange (ETDEWEB)

    Desireddy, Anil; Joshi, Chakra P. [Department of Chemistry, University of Toledo, Toledo, OH 43606 (United States); Sestak, Michelle; Little, Scott [Department of Physics and Astronomy, University of Toledo, Toledo, OH 43606 (United States); Wright Center for Photovoltaics Innovation and Commercialization, University of Toledo, Toledo, OH 43606 (United States); Kumar, Santosh [Department of Chemistry, University of Toledo, Toledo, OH 43606 (United States); Podraza, Nikolas J.; Marsillac, Sylvain; Collins, Robert W. [Department of Physics and Astronomy, The University of Toledo, Toledo, OH 43606 (United States); Wright Center for Photovoltaics Innovation and Commercialization, University of Toledo, Toledo, OH 43606 (United States); Bigioni, Terry P., E-mail: Terry.Bigioni@utoledo.edu [Department of Chemistry, University of Toledo, Toledo, OH 43606 (United States); Wright Center for Photovoltaics Innovation and Commercialization, University of Toledo, Toledo, OH 43606 (United States)

    2011-07-01

    Plasmonic films have become important for many applications including photonics, energy conversion, and chemical sensing, but the fabrication of these films often requires special equipment, great care, and skill. Colloidal metal nanoparticles offer an alternative as they have been shown to self-assemble into highly-ordered monolayer films by the simple and inexpensive technique of drop casting. Using this technique, we fabricated wafer-scale films of highly-ordered 6 nm Au nanoparticles and evaluated them as candidates for plasmonic applications. These colloidal films were found to support uniform and high-quality plasmon modes over the entire area of the wafer. A combination of microscopy and spectroscopy was used to evaluate and correlate the structural and optical qualities of the films. Electron and atomic force microscopy showed that the nanoscale structure of the films was compact and highly ordered, with few defects or bilayers. Spectroscopic ellipsometry showed that the majority of the film was optically quite uniform with some bilayer patches and voids. These were subsequently confirmed by microscopy. Optical analysis of the thin film showed a prominent plasmon resonance band across the entire wafer. The plasmon frequency was quite insensitive to the presence of voids or bilayers. The width of the plasmon band was more sensitive to bilayers, however, and was found to be as much as 15% wider than in monolayer regions. These results indicate that self-assembled colloidal thin films should be suitable for large-scale plasmonic applications.

  14. Self-Assembling Multifunctional Peptide Dimers for Gene Delivery Systems

    Directory of Open Access Journals (Sweden)

    Kitae Ryu

    2015-01-01

    Full Text Available Self-assembling multifunctional peptide was designed for gene delivery systems. The multifunctional peptide (MP consists of cellular penetrating peptide moiety (R8, matrix metalloproteinase-2 (MMP-2 specific sequence (GPLGV, pH-responsive moiety (H5, and hydrophobic moiety (palmitic acid (CR8GPLGVH5-Pal. MP was oxidized to form multifunctional peptide dimer (MPD by DMSO oxidation of thiols in terminal cysteine residues. MPD could condense pDNA successfully at a weight ratio of 5. MPD itself could self-assemble into submicron micelle particles via hydrophobic interaction, of which critical micelle concentration is about 0.01 mM. MPD showed concentration-dependent but low cytotoxicity in comparison with PEI25k. MPD polyplexes showed low transfection efficiency in HEK293 cells expressing low level of MMP-2 but high transfection efficiency in A549 and C2C12 cells expressing high level of MMP-2, meaning the enhanced transfection efficiency probably due to MMP-induced structural change of polyplexes. Bafilomycin A1-treated transfection results suggest that the transfection of MPD is mediated via endosomal escape by endosome buffering ability. These results show the potential of MPD for MMP-2 targeted gene delivery systems due to its multifunctionality.

  15. Free surface BCP self-assembly process characterization with CDSEM

    Science.gov (United States)

    Levi, Shimon; Weinberg, Yakov; Adan, Ofer; Klinov, Michael; Argoud, Maxime; Claveau, Guillaume; Tiron, Raluca

    2016-03-01

    A simple and common practice to evaluate Block copolymers (BCP) self-assembly performances, is on a free surface wafer. With no guiding pattern the BCP designed to form line space pattern for example, spontaneously rearranges to form a random fingerprint type of a pattern. The nature of the rearrangement is dictated by the physical properties of the BCP moieties, wafer surface treatment and the self-assembly process parameters. Traditional CDSEM metrology algorithms are designed to measure pattern with predefined structure, like linespace or oval via holes. Measurement of pattern with expected geometry can reduce measurement uncertainty. Fingerprint type of structure explored in this dissertation, poses a challenge for CD-SEM measurement uncertainty and offers an opportunity to explore 2D metrology capabilities. To measure this fingerprints we developed a new metrology approach that combines image segmentation and edge detection to measure 2D pattern with arbitrary rearrangement. The segmentation approach enabled to quantify the quality of the BCP material and process, detecting 2D attributes such as: CD and CDU at one axis, and number of intersections, length and number of PS fragments, etched PMMA spaces and donut shapes numbers on the second axis. In this paper we propose a 2D metrology to measure arbitrary BCP pattern on a free surface wafer. We demonstrate experimental results demonstrating precision data, and characterization of PS-b-PMMA BCP, intrinsic period L0 = 38nm (Arkema), processed at different bake time and temperatures.

  16. Development of self-assembled bacterial cellulose-starch nanocomposites

    International Nuclear Information System (INIS)

    A bioinspired bottom-up process was developed to produce self-assembled nanocomposites of cellulose synthesized by Acetobacter bacteria and native starch. This process takes advantage of the way some bacteria extrude cellulose nanofibres and of the transport process that occurs during the gelatinization of starch. Potato and corn starch were added into the culture medium and partially gelatinized in order to allow the cellulose nanofibrils to grow in the presence of a starch phase. The bacterial cellulose (BC)-starch gels were hot pressed into sheets that had a BC volume fraction higher than 90%. During this step starch was forced to further penetrate the BC network. The self-assembled BC-starch nanocomposites showed a coherent morphology that was assessed by Atomic Force Microscopy (AFM) and Environmental Scanning Electron Microscopy (ESEM). The nanocomposites structure was studied using X-ray diffraction and ATR-FTIR spectroscopy. The degree of crystallinity of the final nanocomposites was used to estimate the volume fraction of BC. The aim of this paper is to explore a new methodology that could be used to produce nanomaterials by introducing a different phase into a cellulose nanofibre network during its assembly.

  17. Self-assembly mechanism in colloids: perspectives from statistical physics

    Science.gov (United States)

    Giacometti, Achille

    2012-06-01

    Motivated by recent experimental findings in chemical synthesis of colloidal particles, we draw an analogy between self-assembly processes occurring in biological systems (e.g. protein folding) and a new exciting possibility in the field of material science. We consider a self-assembly process whose elementary building blocks are decorated patchy colloids of various types, that spontaneously drive the system toward a unique and predetermined targeted macroscopic structure. To this aim, we discuss a simple theoretical model — the Kern-Frenkel model — describing a fluid of colloidal spherical particles with a pre-defined number and distribution of solvophobic and solvophilic regions on their surface. The solvophobic and solvophilic regions are described via a short-range square-well and a hard-sphere potentials, respectively. Integral equation and perturbation theories are presented to discuss structural and thermodynamical properties, with particular emphasis on the computation of the fluid-fluid (or gas-liquid) transition in the temperaturedensity plane. The model allows the description of both one and two attractive caps, as a function of the fraction of covered attractive surface, thus interpolating between a square-well and a hard-sphere fluid, upon changing the coverage. By comparison with Monte Carlo simulations, we assess the pros and the cons of both integral equation and perturbation theories in the present context of patchy colloids, where the computational effort for numerical simulations is rather demanding.

  18. A coarse-grained model of microtubule self-assembly

    Science.gov (United States)

    Regmi, Chola; Cheng, Shengfeng

    Microtubules play critical roles in cell structures and functions. They also serve as a model system to stimulate the next-generation smart, dynamic materials. A deep understanding of their self-assembly process and biomechanical properties will not only help elucidate how microtubules perform biological functions, but also lead to exciting insight on how microtubule dynamics can be altered or even controlled for specific purposes such as suppressing the division of cancer cells. Combining all-atom molecular dynamics (MD) simulations and the essential dynamics coarse-graining method, we construct a coarse-grained (CG) model of the tubulin protein, which is the building block of microtubules. In the CG model a tubulin dimer is represented as an elastic network of CG sites, the locations of which are determined by examining the protein dynamics of the tubulin and identifying the essential dynamic domains. Atomistic MD modeling is employed to directly compute the tubulin bond energies in the surface lattice of a microtubule, which are used to parameterize the interactions between CG building blocks. The CG model is then used to study the self-assembly pathways, kinetics, dynamics, and nanomechanics of microtubules.

  19. Structure of self - assembled two-dimensional spherical crystals

    Science.gov (United States)

    Bausch, Andreas R.

    2004-03-01

    Dense spherical particles on a flat surface usually pack into a simple triangular lattice, similar to billiard balls at the start of a game. The minimum energy configuration for interacting particles on the curved surface of a sphere, however, presents special difficulties, as recognized already by J.J. Thomson. We describe experimental investigations of the structure of two-dimensional spherical crystals. The crystals, formed by beads self-assembled on water droplets in oil, serve as model systems for exploring very general theories about the minimum energy configurations of particles with arbitrary repulsive interactions on curved surfaces. Above a critical system size we find that crystals develop distinctive high-angle grain boundaries or "scars" not found in planar crystals. The number of excess defects in a scar is shown to grow linearly with the dimensionless system size. First experiments where the melting of the crystal structure was observable will be discussed. Dynamic triangulation methods allow the analysis of the dynamics of the defects. Possible modifications towards mechanically stabilized self assembly structures result in so called Colloidosomes, which are promising for many different encapsulation purposes.

  20. Structural Diversity of Self-Assembled Iridescent Arthropod Biophotonic Nanostructures

    Science.gov (United States)

    Saranathan, Vinod Kumar; Prum, Richard O.

    2015-03-01

    Many organisms, especially arthropods, produce vivid interference colors using diverse mesoscopic (100-350 nm) integumentary biophotonic nanostructures that are increasingly being investigated for technological applications. Despite a century of interest, we lack precise structural knowledge of many biophotonic nanostructures and mechanisms controlling their development, when such knowledge can open novel biomimetic routes to facilely self-assemble tunable, multi-functional materials. Here, we use synchrotron small angle X-ray scattering and electron microscopy to characterize the photonic nanostructure of 140 iridescent integumentary scales and setae from 127 species of terrestrial arthropods in 85 genera from 5 orders. We report a rich nanostructural diversity, including triply-periodic bicontinuous networks, close-packed spheres, inverse columnar, perforated lamellar, and disordered sponge-like morphologies, commonly observed as stable phases of amphiphilic surfactants, block copolymer, and lyotropic lipid-water systems. Diverse arthropod lineages appear to have independently evolved to utilize the self-assembly of infolding bilayer membranes to develop biophotonic nanostructures that span the phase-space of amphiphilic morphologies, but at optical length scales.

  1. Self-assembled rosette nanotubes encapsulate and slowly release dexamethasone

    Directory of Open Access Journals (Sweden)

    Chen Y

    2011-05-01

    Full Text Available Yupeng Chen1,2, Shang Song2, Zhimin Yan3, Hicham Fenniri3, Thomas J Webster2,41Department of Chemistry, Brown University, Providence, RI, USA; 2School of Engineering, Brown University, Providence, RI, USA; 3National Institute for Nanotechnology and Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada; 4Department of Orthopedics, Brown University, Providence, RI, USAAbstract: Rosette nanotubes (RNTs are novel, self-assembled, biomimetic, synthetic drug delivery materials suitable for numerous medical applications. Because of their amphiphilic character and hollow architecture, RNTs can be used to encapsulate and deliver hydrophobic drugs otherwise difficult to deliver in biological systems. Another advantage of using RNTs for drug delivery is their biocompatibility, low cytotoxicity, and their ability to engender a favorable, biologically-inspired environment for cell adhesion and growth. In this study, a method to incorporate dexamethasone (DEX, an inflammatory and a bone growth promoting steroid into RNTs was developed. The drug-loaded RNTs were characterized using diffusion ordered nuclear magnetic resonance spectroscopy (DOSY NMR and UV-Vis spectroscopy. Results showed for the first time that DEX can be easily and quickly encapsulated into RNTs and released to promote osteoblast (bone-forming cell functions over long periods of time. As a result, RNTs are presented as a novel material for the targeted delivery of hydrophobic drugs otherwise difficult to deliver.Keywords: nanotubes, drug delivery, self-assembly, physiological conditions

  2. Self-Assembly of Porphyrin J-Aggregates

    Science.gov (United States)

    Snitka, Valentinas; Rackaitis, Mindaugas; Navickaite, Gintare

    2006-03-01

    The porphyrin nanotubes were built by ionic self-assembly of two oppositely charged porphyrins in aqueous solution. The porphyrins in the acid aqueous solution self-assemble into J-aggregates, wheels or other structures. The electrostatic forces between these porphyrin blocks contribute to the formation of porphyrin aggregates in the form of nanotubes, enhance the structural stability of these nanostructures. The nanotubes were composed mixing aqueous solutions of the two porphyrins - anionic Meso-tetra(4- sulfonatophrnyl)porhine dihydrochloride (TPPS4) and cationic Meso-tetra(4-pyridyl)porphine (T4MPyP). The porphyrin nanotubes obtained are hollow structures with the length of 300 nm and diameter 50 nm. Photocatalytic porphyrins are used to reduce metal complexes from aqueous solution and to control the deposition of Au from AuHCl4 and Au nanoparticles colloid solutions onto porphyrin nanotubes. Porphyrin nanotubes are shown to reduce metal complexes and deposit the metal selectively onto the inner or outer surface of the tubes, leading to nanotube-metal composite structures.

  3. 2D-self-assembly of chiral buckybowls

    International Nuclear Information System (INIS)

    Full text: So-called buckybowls, quasi-fragments of buckminster fullerene, are promising candidates for surface modifications for organic photovoltaics and controlled carbon nanotube growth. Corannulene (COR, C20H10) is the simplest curved fragment with a central C5 ring, surrounded by five aromatic C6 rings. We investigated the self-assembly of the C5-symmetric pentaphenyl-corannulene (Ph5Cor), a chiral derivative with five phenyl groups at the rim, on Cu(111). Fivefold symmetry is incompatible with the translational order in all 17 2D plane groups, and this system is therefore of fundamental interest for 2D self-assembly. STM shows packing motifs in which the five substituents are interdigitated and are compatible with LEED results. Workfuntion change measurements via UPS reveal an unusual large interface dipole. We compare our findings with those obtained for other penta-substituted COR derivatives on Cu(111) and present preliminary results for thermally- induced dehydrogenation into polymeric structures. (author)

  4. Probabilistic Performance Guarantees for Distributed Self-Assembly

    KAUST Repository

    Fox, Michael J.

    2015-04-01

    In distributed self-assembly, a multitude of agents seek to form copies of a particular structure, modeled here as a labeled graph. In the model, agents encounter each other in spontaneous pairwise interactions and decide whether or not to form or sever edges based on their two labels and a fixed set of local interaction rules described by a graph grammar. The objective is to converge on a graph with a maximum number of copies of a given target graph. Our main result is the introduction of a simple algorithm that achieves an asymptotically maximum yield in a probabilistic sense. Notably, agents do not need to update their labels except when forming or severing edges. This contrasts with certain existing approaches that exploit information propagating rules, effectively addressing the decision problem at the level of subgraphs as opposed to individual vertices. We are able to obey more stringent locality requirements while also providing smaller rule sets. The results can be improved upon if certain requirements on the labels are relaxed. We discuss limits of performance in self-assembly in terms of rule set characteristics and achievable maximum yield.

  5. Stochastic lag time in nucleated linear self-assembly

    Science.gov (United States)

    Tiwari, Nitin S.; van der Schoot, Paul

    2016-06-01

    Protein aggregation is of great importance in biology, e.g., in amyloid fibrillation. The aggregation processes that occur at the cellular scale must be highly stochastic in nature because of the statistical number fluctuations that arise on account of the small system size at the cellular scale. We study the nucleated reversible self-assembly of monomeric building blocks into polymer-like aggregates using the method of kinetic Monte Carlo. Kinetic Monte Carlo, being inherently stochastic, allows us to study the impact of fluctuations on the polymerization reactions. One of the most important characteristic features in this kind of problem is the existence of a lag phase before self-assembly takes off, which is what we focus attention on. We study the associated lag time as a function of system size and kinetic pathway. We find that the leading order stochastic contribution to the lag time before polymerization commences is inversely proportional to the system volume for large-enough system size for all nine reaction pathways tested. Finite-size corrections to this do depend on the kinetic pathway.

  6. Self-assembly of protein aggregates in ageing disorders: the lens and cataract model

    OpenAIRE

    Clark, John I.

    2013-01-01

    Cataract, neurodegenerative disease, macular degeneration and pathologies of ageing are often characterized by the slow progressive destabilization of proteins and their self-assembly to amyloid-like fibrils and aggregates. During normal cell differentiation, protein self-assembly is well established as a dynamic mechanism for cytoskeletal organization. With the increased emphasis on ageing disorders, there is renewed interest in small-molecule regulators of protein self-assembly. Synthetic p...

  7. A new building block for DNA network formation by self-assembly and polymerase chain reaction

    OpenAIRE

    Holger Bußkamp; Sascha Keller; Marta Robotta; Malte Drescher; Andreas Marx

    2014-01-01

    The predictability of DNA self-assembly is exploited in many nanotechnological approaches. Inspired by naturally existing self-assembled DNA architectures, branched DNA has been developed that allows self-assembly to predesigned architectures with dimensions on the nanometer scale. DNA is an attractive material for generation of nanostructures due to a plethora of enzymes which modify DNA with high accuracy, providing a toolbox for many different manipulations to construct nanometer scaled ob...

  8. Real time monitoring of superparamagnetic nanoparticle self-assembly on surfaces of magnetic recording media

    International Nuclear Information System (INIS)

    Nanoparticle self-assembly dynamics are monitored in real-time by detecting optical diffraction from an all-nanoparticle grating as it self-assembles on a grating pattern recorded on a magnetic medium. The diffraction efficiency strongly depends on concentration, pH, and colloidal stability of nanoparticle suspensions, demonstrating the nanoparticle self-assembly process is highly tunable. This metrology could provide an alternative for detecting nanoparticle properties such as colloidal stability

  9. Self-assembly of PEGylated gold nanoparticles with satellite structures as seeds.

    Science.gov (United States)

    Bachelet, Marie; Chen, Rongjun

    2016-07-21

    We report a very simple method for the self-assembly of spherical gold nanoparticles (AuNPs), coated with poly(ethylene glycol) (PEG), through a slow evaporation process at room temperature. Clusters of particles forming satellite structures may act as seeds for the self-assembly in a crystallization-like process. Based on the transmission electron microscopy (TEM) images obtained a mechanism for the self-assembly was suggested. PMID:27384086

  10. Engineering protocells: prospects for self-assembly and nanoscale production-lines.

    Science.gov (United States)

    Miller, David M; Gulbis, Jacqueline M

    2015-01-01

    The increasing ease of producing nucleic acids and proteins to specification offers potential for design and fabrication of artificial synthetic "organisms" with a myriad of possible capabilities. The prospects for these synthetic organisms are significant, with potential applications in diverse fields including synthesis of pharmaceuticals, sources of renewable fuel and environmental cleanup. Until now, artificial cell technology has been largely restricted to the modification and metabolic engineering of living unicellular organisms. This review discusses emerging possibilities for developing synthetic protocell "machines" assembled entirely from individual biological components. We describe a host of recent technological advances that could potentially be harnessed in design and construction of synthetic protocells, some of which have already been utilized toward these ends. More elaborate designs include options for building self-assembling machines by incorporating cellular transport and assembly machinery. We also discuss production in miniature, using microfluidic production lines. While there are still many unknowns in the design, engineering and optimization of protocells, current technologies are now tantalizingly close to the capabilities required to build the first prototype protocells with potential real-world applications. PMID:25815781

  11. Engineering Protocells: Prospects for Self-Assembly and Nanoscale Production-Lines

    Directory of Open Access Journals (Sweden)

    David M. Miller

    2015-03-01

    Full Text Available The increasing ease of producing nucleic acids and proteins to specification offers potential for design and fabrication of artificial synthetic “organisms” with a myriad of possible capabilities. The prospects for these synthetic organisms are significant, with potential applications in diverse fields including synthesis of pharmaceuticals, sources of renewable fuel and environmental cleanup. Until now, artificial cell technology has been largely restricted to the modification and metabolic engineering of living unicellular organisms. This review discusses emerging possibilities for developing synthetic protocell “machines” assembled entirely from individual biological components. We describe a host of recent technological advances that could potentially be harnessed in design and construction of synthetic protocells, some of which have already been utilized toward these ends. More elaborate designs include options for building self-assembling machines by incorporating cellular transport and assembly machinery. We also discuss production in miniature, using microfluidic production lines. While there are still many unknowns in the design, engineering and optimization of protocells, current technologies are now tantalizingly close to the capabilities required to build the first prototype protocells with potential real-world applications.

  12. Charge Effects on the Self-Assembly of Protein Block Copolymer Nanostructures

    Science.gov (United States)

    Olsen, Bradley

    Self-assembly of globular protein-polymer block copolymers into nanostructured phases provides a simple method for structural control in biomaterials. Electrostatics play a major role in the self-assembly of these structures from aqueous solutions. While the specific distribution of charge on the protein plays a relatively minor role in self-assembly, large changes in the total charge have a large impact on the concentration at which the proteins self-assemble. While for near-neutral proteins salt screening promotes disassembly and suggests that electrostatic interactions are attractive, proteins with a highly asymmetric charge have repulsive interactions that suppress self-assembly. Using a zwitterionic block in the bioconjugate was also explored as a means to promote self-assembly; however, zwitterionic fusions self-assemble over a narrower range of composition than fusions of any of the nonionic polymers explored. This suggests that dipolar attractions in charge-asymmetric protein-polymer materials play a significant role in the driving force for self-assembly. However, the sensitivity of zwitterionic materials to salt conditions in the buffer also provides a powerful handle for tuning polymer solubility, enabling salt to be used as a method to induce self-assembly.

  13. Combing and self-assembly phenomena in dry films of Taxol-stabilized microtubules

    Directory of Open Access Journals (Sweden)

    Rose Franck

    2007-01-01

    Full Text Available AbstractMicrotubules are filamentous proteins that act as a substrate for the translocation of motor proteins. As such, they may be envisioned as a scaffold for the self-assembly of functional materials and devices. Physisorption, self-assembly and combing are here investigated as a potential prelude to microtubule-templated self-assembly. Dense films of self-assembled microtubules were successfully produced, as well as patterns of both dendritic and non-dendritic bundles of microtubules. They are presented in the present paper and the mechanism of their formation is discussed.

  14. Hexanol-induced order-disorder transitions in lamellar self-assembling aggregates of bacteriochlorophyll c in Chlorobium tepidum chlorosomes.

    Science.gov (United States)

    Arellano, Juan B; Torkkeli, Mika; Tuma, Roman; Laurinmäki, Pasi; Melø, Thor B; Ikonen, Teemu P; Butcher, Sarah J; Serimaa, Ritva E; Psencík, Jakub

    2008-03-01

    Chlorosomes are light-harvesting complexes of green photosynthetic bacteria. Chlorosomes contain bacteriochlorophyll (BChl) c, d, or e aggregates that exhibit strong excitonic coupling. The short-range order, which is responsible for the coupling, has been proposed to be augmented by pigment arrangement into undulated lamellar structures with spacing between 2 and 3 nm. Treatment of chlorosomes with hexanol reversibly converts the aggregated chlorosome chlorophylls into a form with spectral properties very similar to that of the monomer. Although this transition has been extensively studied, the structural basis remains unclear due to variability in the obtained morphologies. Here we investigated hexanol-induced structural changes in the lamellar organization of BChl c in chlorosomes from Chlorobium tepidum by a combination of X-ray scattering, electron cryomicroscopy, and optical spectroscopy. At a low hexanol/pigment ratio, the lamellae persisted in the presence of hexanol while the short-range order and exciton interactions between chlorin rings were effectively eliminated, producing a monomer-like absorption. The result suggested that hexanol hydroxyls solvated the chlorin rings while the aliphatic tail partitioned into the hydrophobic part of the lamellar structure. This partitioning extended the chlorosome along its long axis. Further increase of the hexanol/pigment ratio produced round pigment-hexanol droplets, which lost all lamellar order. After hexanol removal the spectral properties were restored. In the samples treated under the high hexanol/pigment ratio, lamellae reassembled in small domains after hexanol removal while the shape and long-range order were irreversibly lost. Thus, all the interactions required for establishing the short-range order by self-assembly are provided by BChl c molecules alone. However, the long-range order and overall shape are imposed by an external structure, e.g., the proteinaceous chlorosome baseplate. PMID:18197717

  15. Diamond functionalization with light-harvesting molecular wires: improved surface coverage by optimized Suzuki cross-coupling conditions

    Czech Academy of Sciences Publication Activity Database

    Yeap, W. S.; Bevk, D.; Liu, X.; Krýsová, Hana; Pasquarelli, A.; Vanderzande, D.; Lutsen, L.; Kavan, Ladislav; Fahlman, M.; Maes, W.; Haenen, K.

    2014-01-01

    Roč. 4, AUG 2014 (2014), s. 42044-42053. ISSN 2046-2069 R&D Projects: GA ČR GA13-31783S Institutional support: RVO:61388955 Keywords : Functionalizations * Light-harvesting * Molecular wires Subject RIV: CG - Electrochemistry Impact factor: 3.840, year: 2014

  16. Role of Carotenoids in Light-Harvesting Processes in an Antenna Protein from the Chromophyte Xanthonema debile

    Czech Academy of Sciences Publication Activity Database

    Durchan, Milan; Tichý, Josef; Litvín, Radek; Šlouf, V.; Gardian, Zdenko; Hříbek, P.; Vácha, František; Polívka, Tomáš

    2012-01-01

    Roč. 116, č. 30 (2012), s. 8880-8889. ISSN 1520-6106 Institutional research plan: CEZ:AV0Z50510513 Institutional support: RVO:60077344 Keywords : xanthophytes * carotenoids * light harvesting * energy transfer Subject RIV: BO - Biophysics Impact factor: 3.607, year: 2012

  17. Low-temperature time-resolved spectroscopic study of the major light-harvesting complex of Amphidinium carterae

    Czech Academy of Sciences Publication Activity Database

    Šlouf, V.; Fuciman, M.; Johanning, S.; Hofmann, E.; Frank, H.A.; Polívka, Tomáš

    2013-01-01

    Roč. 117, 1-3 (2013), s. 257-265. ISSN 0166-8595 R&D Projects: GA ČR(CZ) GAP205/11/1164 Institutional support: RVO:60077344 Keywords : Dinoflagellates * Energy transfer * Light-harvesting * Carotenoid Subject RIV: BO - Biophysics Impact factor: 3.185, year: 2013

  18. Site-specific incorporation of perylene into an N-terminally modified light-harvesting complex II

    OpenAIRE

    Peneva, Kalina; Gundlach, Kristina; Herrmann, Andreas; Paulsen, Harald; Muellen, Klaus; Müllen, Klaus

    2010-01-01

    Employing the utility of the native chemical ligation, site-specific attachment of an ultrastable perylene dye to a derivative of the major light-harvesting complex (LHCII) was demonstrated. Biochemical analysis of the conjugate indicated that the structure and function of LHCII remain largely unaffected by the N-terminal modification.

  19. Economic photoprotection in photosystem II that retains a complete light-harvesting system with slow energy traps

    Science.gov (United States)

    Belgio, Erica; Kapitonova, Ekaterina; Chmeliov, Jevgenij; Duffy, Christopher D. P.; Ungerer, Petra; Valkunas, Leonas; Ruban, Alexander V.

    2014-07-01

    The light-harvesting antenna of higher plant photosystem II has an intrinsic capability for self-defence against intense sunlight. The thermal dissipation of excess energy can be measured as the non-photochemical quenching of chlorophyll fluorescence. It has recently been proposed that the transition between the light-harvesting and self-defensive modes is associated with a reorganization of light-harvesting complexes. Here we show that despite structural changes, the photosystem II cross-section does not decrease. Our study reveals that the efficiency of energy trapping by the non-photochemical quencher(s) is lower than the efficiency of energy capture by the reaction centres. Consequently, the photoprotective mechanism works effectively for closed rather than open centres. This type of defence preserves the exceptional efficiency of electron transport in a broad range of light intensities, simultaneously ensuring high photosynthetic productivity and, under hazardous light conditions, sufficient photoprotection for both the reaction centre and the light-harvesting pigments of the antenna.

  20. Moth-Eye TiO2 Layer for Improving Light Harvesting Efficiency in Perovskite Solar Cells.

    Science.gov (United States)

    Kang, Seong Min; Jang, Segeun; Lee, Jong-Kwon; Yoon, Jungjin; Yoo, Dong-Eun; Lee, Jin-Wook; Choi, Mansoo; Park, Nam-Gyu

    2016-05-01

    A moth-eye nanostructured mp-TiO2 film using conventional lithography, nano-imprinting and polydimethyl-siloxane (PDMS) stamping methods is demonstrated for the first time. Power conversion efficiency of the moth-eye patterned perovskite solar cell is improved by ≈11%, which mainly results from increasing light harvesting efficiency by structural optical property. PMID:26990492

  1. Genes encoding major light-harvesting polypeptides are clustered on the genome of the cyanobacterium Fremyella diplosiphon.

    OpenAIRE

    Conley, P. B.; Lemaux, P G; Lomax, T L; Grossman, A R

    1986-01-01

    The polypeptide composition of the phycobilisome, the major light-harvesting complex of prokaryotic cyanobacteria and certain eukaryotic algae, can be modulated by different light qualities in cyanobacteria exhibiting chromatic adaptation. We have identified genomic fragments encoding a cluster of phycobilisome polypeptides (phycobiliproteins) from the chromatically adapting cyanobacterium Fremyella diplosiphon using previously characterized DNA fragments of phycobiliprotein genes from the eu...

  2. Studies of Structure and Dynamics of Light Harvesting Complex 1 of R. Sphaeroides by Solid State NMR

    Energy Technology Data Exchange (ETDEWEB)

    McDermott, Ann E [Columbia University

    2014-11-14

    Studies of the structure and dynamics of a light harvesting complex from photosynthetic bacteria are described. Using Nuclear Magnetic Resonance methods, we explored the idea that optical properties are modulated via a conformational switch in the BChl chromophores, in a way that provides benefits for the efficiency of energy conversion.

  3. Single-residue insertion switches the quaternary structure and exciton states of cryptophyte light-harvesting proteins.

    Science.gov (United States)

    Harrop, Stephen J; Wilk, Krystyna E; Dinshaw, Rayomond; Collini, Elisabetta; Mirkovic, Tihana; Teng, Chang Ying; Oblinsky, Daniel G; Green, Beverley R; Hoef-Emden, Kerstin; Hiller, Roger G; Scholes, Gregory D; Curmi, Paul M G

    2014-07-01

    Observation of coherent oscillations in the 2D electronic spectra (2D ES) of photosynthetic proteins has led researchers to ask whether nontrivial quantum phenomena are biologically significant. Coherent oscillations have been reported for the soluble light-harvesting phycobiliprotein (PBP) antenna isolated from cryptophyte algae. To probe the link between spectral properties and protein structure, we determined crystal structures of three PBP light-harvesting complexes isolated from different species. Each PBP is a dimer of αβ subunits in which the structure of the αβ monomer is conserved. However, we discovered two dramatically distinct quaternary conformations, one of which is specific to the genus Hemiselmis. Because of steric effects emerging from the insertion of a single amino acid, the two αβ monomers are rotated by ∼73° to an "open" configuration in contrast to the "closed" configuration of other cryptophyte PBPs. This structural change is significant for the light-harvesting function because it disrupts the strong excitonic coupling between two central chromophores in the closed form. The 2D ES show marked cross-peak oscillations assigned to electronic and vibrational coherences in the closed-form PC645. However, such features appear to be reduced, or perhaps absent, in the open structures. Thus cryptophytes have evolved a structural switch controlled by an amino acid insertion to modulate excitonic interactions and therefore the mechanisms used for light harvesting. PMID:24979784

  4. Highly efficient energy transfer from a carbonyl carotenoid to chlorophyll a in the main light harvesting complex of Chromera velia

    Czech Academy of Sciences Publication Activity Database

    Durchan, Milan; Kesan, G.; Šlouf, M.; Fuciman, M.; Staleva, H.; Tichý, Josef; Litvín, Radek; Bína, David; Vácha, František; Polívka, Tomáš

    2014-01-01

    Roč. 1837, č. 10 (2014), s. 1748-1755. ISSN 0005-2728 R&D Projects: GA ČR(CZ) GAP205/11/1164; GA ČR GBP501/12/G055 Institutional support: RVO:60077344 Keywords : Energy transfer * Light-harvesting * Carbonyl carotenoids Subject RIV: BO - Biophysics Impact factor: 5.353, year: 2014

  5. Molecular engineering and characterization of self-assembled biorecognition surfaces

    Science.gov (United States)

    Pan, Sheng

    The development of molecular engineering techniques for the fabrication of biomaterial surfaces is of importance in the field of biomaterials. It offers opportunities for better understanding of biological processes on material surfaces and rational design of contemporary biomaterials. Our work in this area aims to develop novel engineering strategies to design biorecognition surfaces via self-assembly and surface derivatization. Fundamental issues regarding self-assembled monolayer (SAM) structure, formation kinetics, and chemical derivatization were investigated systematically using electron spectroscopy for chemical analysis (ESCA), time-of-flight secondary ion mass spectrometry (TOF-SIMS), infrared reflection absorption spectroscopy (IRAS), atomic force microscopy (AFM), and contact angle measurements. Novel engineering concepts based on multifunctionality and statistical pattern matching were introduced and applied to develop biomimetic surfaces. Our study illustrated that molecules underwent structural transition and orientation development during self-assembly formation, from a disordered, low-density, more liquid-like structure to a highly ordered, closed-packed crystalline-like structure. Surface properties, such as wettability and the reactivity of outermost functional groups can be related to film structure, packing density, as well as molecular orientation. Given the order and organization of SAMs, the accessibility and reactivity of the outermost functional groups, reaction kinetics, stoichiometry, and SAMs stability were studied systematically by surface derivatization of trifluoroacetic anhydride (TFAA). The TFAA derivatization reactions exhibited rapid kinetics on the hydroxyl-terminated SAMs. The data from complementary surface analytical techniques consistently indicated a nearly complete surface reaction. Biomimetic surfaces were made by random immobilization of amino acid of arginine (R), glycine (G), and aspartic acid (D) on well-defined SAMs

  6. Principles Governing the Self Assembly of Polypeptide Nanoparticles

    Science.gov (United States)

    Wahome, Newton

    Self assembling systems on the nanometer scale afford the advantage of being able to control submicron level events. In this study, we focus on the self-assembling polypeptide nanoparticles (SAPN). The SAPN scaffold is made up of oligomerizing domains that align along the principle rotational axes of icosahedral symmetry. By aligning them along these axes, a particle with spherical geometry can be achieved. This particle can be utilized as a vaccine, as a drug delivery vehicle, or as a biomedical imaging device. This research will try to answer why the SAPN self-assembles into distinct molecular weight ranges while mostly maintaining a spherical morphology. The first means will be theoretical and computational, where we will utilize a mathematical formalism to find out how the packing of SAPN's monomeric units can occur within symmetric space. Then molecular dynamics will be run within this symmetric space to test the per amino acid residue susceptibility of SAPN towards becoming polymorphic in nature. Means for examining the aggregation propensity of SAPN will be also be tested. Specifically, the relationship of different sequences of SAPN with pH will be elucidated. Co-assembly of SAPN to reduce the surface density of an aggregation prone epitope will be tested. Also, aggregation reduction consisting of the exchange of an anionic denaturant with a positively charged suppressor in order to mitigate a priori peptide association and misfolding, will also be attempted. SAPN has been shown to be an immunogenic platform for the presentation of pathogen derived antigens. We will attempt to show the efficacy of presenting an antigen from HIV-1 which is structurally restrained to best match the native conformation on the virus. Immunological studies will be performed to test the effect of this approach, as well testing the antigenicity of the nanoparticle in the absence of adjuvant. Finally, the antigen presenting nanoparticles will undergo formulation testing, to measure

  7. Applications of molecular self-assembly in tissue engineering

    Science.gov (United States)

    Harrington, Daniel Anton

    This thesis studied the application of three self-assembling molecular systems, as potential biomaterials for tissue engineering applications. Cholesteryl-(L-lactic acid)n molecules form thermotropic liquid crystals, which could be coated onto the inner and outer pores of biodegradable PLLA scaffolds, while retaining the lamellar order of the neat material. Primary bovine chondrocytes were cultured on these structures, demonstrating improved attachment and extended retention of phenotype on the C-LA-coated scaffolds. No difference in fibronectin adsorption to C-LA and PLLA surfaces was observed, suggesting a strong role for cholesterol in influencing cell phenotype. A family of peptide-amphiphiles, bearing the "RGD" adhesion sequence from fibronectin, was also assessed in the contexts of cartilage and bladder repair. These molecules self-assemble into one-dimensional fibers, with diameters of 6--8 nm, and lengths of 500 nm or greater. Chondrocytes were seeded and cultured on covalently-crosslinked PA gels and embedded within calcium-triggered PA gels. Cells became dormant over time, but remained viable, suggesting an inappropriate display of the adhesion sequence to cells. A family of "branched" PA molecules with lysine dendron headgroups was designed, in an effort to increase the spatial separation between molecules in the assembled state, and to theoretically improve epitope accessibility. These molecules coated reliably onto PGA fiber scaffolds, and dramatically increased the attachment of human bladder smooth muscle cells, possibly through better epitope display or electrostatic attraction. They also formed strong gels with several negatively-charged biologically-relevant macromolecules. In a third system, amphiphilic segmented dendrimers based on phenylene vinylene and L-lysine entered cells through an endocytic pathway with no discernible toxic effect on cell proliferation or morphology. These amphiphiles formed complex aggregates in aqueous solution, likely

  8. From self-assembly fundamental knowledge to nanomedicine developments.

    Science.gov (United States)

    Monduzzi, Maura; Lampis, Sandrina; Murgia, Sergio; Salis, Andrea

    2014-03-01

    This review highlights the key role of NMR techniques in demonstrating the molecular aspects of the self-assembly of surfactant molecules that nowadays constitute the basic knowledge which modern nanoscience relies on. The aim is to provide a tutorial overview. The story of a rigorous scientific approach to understand self-assembly in surfactant systems and biological membranes starts in the early seventies when the progresses of SAXRD and NMR technological facilities allowed to demonstrate the existence of ordered soft matter, and the validity of Tanford approach concerning self-assembly at a molecular level. Particularly, NMR quadrupolar splittings, NMR chemical shift anisotropy, and NMR relaxation of dipolar and quadrupolar nuclei in micellar solutions, microemulsions, and liquid crystals proved the existence of an ordered polar-apolar interface, on the NMR time scale. NMR data, rationalized in terms of the two-step model of relaxation, allowed to quantify the dynamic aspects of the supramolecular aggregates in different soft matter systems. In addition, NMR techniques allowed to obtain important information on counterion binding as well as on size of the aggregate through molecular self-diffusion. Indeed NMR self-diffusion proved without any doubt the existence of bicontinuous microemulsions and bicontinuous cubic liquid crystals, suggested by pioneering and brilliant interpretation of SAXRD investigations. Moreover, NMR self-diffusion played a fundamental role in the understanding of microemulsion and emulsion nanostructures, phase transitions in phase diagrams, and particularly percolation phenomena in microemulsions. Since the nineties, globalization of the knowledge along with many other technical facilities such as electron microscopy, particularly cryo-EM, produced huge progresses in surfactant and colloid science. Actually we refer to nanoscience: bottom up/top down strategies allow to build nanodevices with applications spanning from ICT to food

  9. The light-harvesting complexes of higher-plant Photosystem I : Lhca1/4 and Lhca2/3 form two red-emitting heterodimers

    NARCIS (Netherlands)

    Wientjes, Emilie; Croce, Roberta

    2011-01-01

    The outer antenna of higher-plant PSI (Photosystem I) is composed of four complexes [Lhc (light-harvesting complex) al-Lhca4] belonging to the light-harvesting protein family. Difficulties in their purification have so far prevented the determination of their properties and most of the knowledge abo

  10. Initiation of Chondrocyte Self-Assembly Requires an Intact Cytoskeletal Network.

    Science.gov (United States)

    Lee, Jennifer K; Hu, Jerry C Y; Yamada, Soichiro; Athanasiou, Kyriacos A

    2016-02-01

    Self-assembly and self-organization have recently emerged as robust scaffold-free tissue engineering methodologies that can be used to generate various tissues, including cartilage, vessel, and liver. Self-assembly, in particular, is a scaffold-free platform for tissue engineering that does not require the input of exogenous energy to the system. Although self-assembly can generate functional tissues, most notably neocartilage, the mechanisms of self-assembly remain unclear. To study the self-assembling process, we used articular chondrocytes as a model to identify parameters that can affect this process. Specifically, the roles of cell-cell and cell-matrix adhesion molecules, surface-bound collagen, and the actin cytoskeletal network were investigated. Using time-lapse imaging, we analyzed the early stages of chondrocyte self-assembly. Within hours, chondrocytes rapidly coalesced into cell clusters before compacting to form tight cellular structures. Chondrocyte self-assembly was found to depend primarily on integrin function and secondarily on cadherin function. In addition, actin or myosin II inhibitors prevented chondrocyte self-assembly, suggesting that cell adhesion alone is not sufficient, but rather the active contractile actin cytoskeleton is essential for proper chondrocyte self-assembly and the formation of neocartilage. Better understanding of the self-assembly mechanisms allows for the rational modulation of this process toward generating neocartilages with improved properties. These findings are germane to understanding self-assembly, an emerging platform for tissue engineering of a plethora of tissues, especially as these neotissues are poised for translation. PMID:26729374

  11. Dephasing and dissipation in a source-drain model of light-harvesting systems.

    Science.gov (United States)

    Xiong, Shi-Jie; Chen, Lipeng; Zhao, Yang

    2014-09-15

    The energy transport process in natural-light-harvesting systems is investigated by solving the time-dependent Schrödinger equation for a source-network-drain model incorporating the effects of dephasing and dissipation, owing to coupling with the environment. In this model, the network consists of electronically coupled chromophores, which can host energy excitations (excitons) and are connected to source channels, from which the excitons are generated, thereby simulating exciton creation from sunlight. After passing through the network, excitons are captured by the reaction centers and converted into chemical energy. In addition, excitons can reradiate in green plants as photoluminescent light or be destroyed by nonphotochemical quenching (NPQ). These annihilation processes are described in the model by outgoing channels, which allow the excitons to spread to infinity. Besides the photoluminescent reflection, the NPQ processes are the main outgoing channels accompanied by energy dissipation and dephasing. From the simulation of wave-packet dynamics in a one-dimensional chain, it is found that, without dephasing, the motion remains superdiffusive or ballistic, despite the strong energy dissipation. At an increased dephasing rate, the wave-packet motion is found to switch from superdiffusive to diffusive in nature. When a steady energy flow is injected into a site of a linear chain, exciton dissipation along the chain, owing to photoluminescence and NPQ processes, is examined by using a model with coherent and incoherent outgoing channels. It is found that channel coherence leads to suppression of dissipation and multiexciton super-radiance. With this method, the effects of NPQ and dephasing on energy transfer in the Fenna-Matthews-Olson complex are investigated. The NPQ process and the photochemical reflection are found to significantly reduce the energy-transfer efficiency in the complex, whereas the dephasing process slightly enhances the efficiency. The

  12. Self-Assembled PbSe Nanowire:Perovskite Hybrids

    KAUST Repository

    Yang, Zhenyu

    2015-12-02

    © 2015 American Chemical Society. Inorganic semiconductor nanowires are of interest in nano- and microscale photonic and electronic applications. Here we report the formation of PbSe nanowires based on directional quantum dot alignment and fusion regulated by hybrid organic-inorganic perovskite surface ligands. All material synthesis is carried out at mild temperatures. Passivation of PbSe quantum dots was achieved via a new perovskite ligand exchange. Subsequent in situ ammonium/amine substitution by butylamine enables quantum dots to be capped by butylammonium lead iodide, and this further drives the formation of a PbSe nanowire superlattice in a two-dimensional (2D) perovskite matrix. The average spacing between two adjacent nanowires agrees well with the thickness of single atomic layer of 2D perovskite, consistent with the formation of a new self-assembled semiconductor nanowire:perovskite heterocrystal hybrid.

  13. Novel biosensing platform based on self-assembled supramolecular hydrogel.

    Science.gov (United States)

    Ma, Dong; Zhang, Li-Ming

    2013-07-01

    The supramolecular hydrogel self-assembled from α-cyclodextrin (α-CD) and an amphiphilic triblock copolymer was used for the first time as a biosensing platform by the in-situ incorporation of horseradish peroxidase and polyaniline (PANI) nanoparticles. It was found that the used triblock copolymer could disperse well PANI nanoparticles in aqueous system and then interact with α-CD in the presence of horseradish peroxidase for the formation of supramolecular hydrogel composite. The content of PANI nanoparticles was found to affect the gelation time and gel strength. The circular dichroism analyses showed that the entrapped horseradish peroxidase could retain its native conformation. By electrochemical experiments, the incorporated PANI nanoparticles were confirmed to improve the current response and enzymatic activity, and the fabricated biosensor was found to provide a fast amperometric response to hydrogen peroxide. PMID:23623078

  14. Self assembled monolayers of octadecyltrichlorosilane for dielectric materials

    Science.gov (United States)

    Kumar, Vijay; Puri, Paridhi; Nain, Shivani; Bhat, K. N.; Sharma, N. N.

    2016-04-01

    Treatment of surfaces to change the interaction of fluids with them is a critical step in constructing useful microfluidics devices, especially those used in biological applications. Selective modification of inorganic materials such as Si, SiO2 and Si3N4 is of great interest in research and technology. We evaluated the chemical formation of OTS self-assembled monolayers on silicon substrates with different dielectric materials. Our investigations were focused on surface modification of formerly used common dielectric materials SiO2, Si3N4 and a-poly. The improvement of wetting behaviour and quality of monolayer films were characterized using Atomic force microscope, Scanning electron microscope, Contact angle goniometer, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) monolayer deposited oxide surface.

  15. IONIC SELF-ASSEMBLY AND HUMIDITY SENSITIVITY OF POLYELECTROLYTE MULTILAYERS

    Institute of Scientific and Technical Information of China (English)

    Hai-hu Yu; De-sheng Jiang

    2002-01-01

    Multilayer thin films of alternately adsorbed layers of polyelectrolytes PDDA and PS-119 were formed on both planar silica substrates and optical fibers through the ionic self-assembly technique. Intrinsic Fabry-Perot cavities were fabricated by stepwise assembling the polyelectrolytes onto the ends of optical fibers for the purposes of fiber optical device and sensor development. Ionically assembled polyelectrolyte multilayer thin films, in whichthere are hydrophilic side groups with strong affinity towards water molecules, are a category of humidity-sensitive functional materials. The polyelectrolyte multilayer thin film Fabry-Perot cavity-type fiber optical humidity sensor can work over a wide range from about 0% RH to about 100% RH with a response time less than 1 s.

  16. Tribological properties of OTS self-assembled monolayers

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Octadecyltrichlorosilane (OTS) self-assembled monolayers (SAMs)were prepared on the substrates of silicon and glass. The tribological properties were tested with a self-made point-contact pure sliding micro tribometer. The effect of humidity on the tribological properties of both OTS SAMs and the naked substrates were studied. When the substrate is covered by OTS monolayer, the friction coefficient is reduced from 0.5 to 0.1 and the stick-slip phenomenon is weakened. OTS monolayer can keep its friction coefficient steady in a wide range of humidity, because it is highly hydrophobic and thus not sensitive to humidity. In addition, the OTS monolayer has a considerable anti-wear ability.

  17. Random lasing actions in self-assembled perovskite nanoparticles

    CERN Document Server

    Liu, Shuai; Li, Jiankai; Gu, Zhiyuan; Wang, Kaiyang; Xiao, Shumin; Song, Qinghai

    2015-01-01

    Solution-based perovskite nanoparticles have been intensively studied in past few years due to their applications in both photovoltaic and optoelectronic devices. Here, based on the common ground between the solution-based perovskite and random lasers, we have studied the mirrorless lasing actions in self-assembled perovskite nanoparticles. After the synthesis from solution, discrete lasing peaks have been observed from the optically pumped perovskites without any well-defined cavity boundaries. The obtained quality (Q) factors and thresholds of random lasers are around 500 and 60 uJ/cm2, respectively. Both values are comparable to the conventional perovskite microdisk lasers with polygon shaped cavity boundaries. From the corresponding studies on laser spectra and fluorescence microscope images, the lasing actions are considered as random lasers that are generated by strong multiple scattering in random gain media. In additional to conventional single-photon excitation, due to the strong nonlinear effects of...

  18. Sequence dependent proton conduction in self-assembled peptide nanostructures

    Science.gov (United States)

    Lerner Yardeni, Jenny; Amit, Moran; Ashkenasy, Gonen; Ashkenasy, Nurit

    2016-01-01

    The advancement of diverse electrochemistry technologies depends on the development of novel proton conducting polymers. Inspired by the efficacy of proton transport through proteins, we show in this work that self-assembling peptide nanostructures may be a promising alternative for such organic proton conducting materials. We demonstrate that aromatic amino acids, which participate in charge transport in nature, unprecedentedly promote proton conduction under both high and low relative humidity conditions for d,l α-cyclic peptide nanotubes. For dehydrated networks long-range order of the assemblies, induced by the aromatic side chains, is shown to be a dominating factor for promoting conductivity. However, for hydrated networks this order of effect is less significant and conductivity can be improved by the introduction of proton donating carboxylic acid peptide side chains in addition to the aromatic side chains despite the lower order of the assemblies. Based on these observations, a novel cyclic peptide that incorporates non-natural naphthyl side chains was designed. Self-assembled nanotubes of this peptide show greatly improved dehydrated conductivity, while maintaining high conductivity under hydrated conditions. We envision that the demonstrated modularity and versatility of these bio inspired nanostructures will make them extremely attractive building blocks for the fabrication of devices for energy conversion and storage applications, as well as other applications that involve proton transport, whether dry or wet conductivity is desired.The advancement of diverse electrochemistry technologies depends on the development of novel proton conducting polymers. Inspired by the efficacy of proton transport through proteins, we show in this work that self-assembling peptide nanostructures may be a promising alternative for such organic proton conducting materials. We demonstrate that aromatic amino acids, which participate in charge transport in nature

  19. Control of Nanomaterial Self-Assembly in Ultrasonically Levitated Droplets.

    Science.gov (United States)

    Seddon, Annela M; Richardson, Sam J; Rastogi, Kunal; Plivelic, Tomás S; Squires, Adam M; Pfrang, Christian

    2016-04-01

    We demonstrate that acoustic trapping can be used to levitate and manipulate droplets of soft matter, in particular, lyotropic mesophases formed from self-assembly of different surfactants and lipids, which can be analyzed in a contact-less manner by X-ray scattering in a controlled gas-phase environment. On the macroscopic length scale, the dimensions and the orientation of the particle are shaped by the ultrasonic field, while on the microscopic length scale the nanostructure can be controlled by varying the humidity of the atmosphere around the droplet. We demonstrate levitation and in situ phase transitions of micellar, hexagonal, bicontinuous cubic, and lamellar phases. The technique opens up a wide range of new experimental approaches of fundamental importance for environmental, biological, and chemical research. PMID:26979408

  20. Self-assembling peptides form nanodiscs that stabilize membrane proteins

    DEFF Research Database (Denmark)

    Midtgaard, Søren Roi; Pedersen, Martin Cramer; Kirkensgaard, Jacob Judas Kain; Sørensen, Kasper Kildegaard; Mortensen, Kell; Jensen, Knud Jørgen; Arleth, Lise

    2014-01-01

    New methods to handle membrane bound proteins, e.g. G-protein coupled receptors (GPCRs), are highly desirable. Recently, apoliprotein A1 (ApoA1) based lipoprotein particles have emerged as a new platform for studying membrane proteins, and it has been shown that they can self-assemble in...... combination with phospholipids to form discoidal shaped particles that can stabilize membrane proteins. In the present study, we have investigated an ApoA1 mimetic peptide with respect to its solution structure when in complex with phospholipids. This was achieved using a powerful combination of small-angle X...... show that, like the ApoA1 and derived nanodiscs, these peptide discs can accommodate and stabilize a membrane protein. Finally, we exploit their dynamic properties and show that the 18A discs may be used for transferring membrane proteins and associated phospholipids directly and gently into...