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Visible Light (visible + light)
Terms modified by Visible Light Selected AbstractsProduction of Conjugated Linoleic Acid-Rich Potato ChipsJOURNAL OF FOOD SCIENCE, Issue 1 2007Vishal P. Jain ABSTRACT:, Conjugated linoleic acid (CLA) is found primarily in diary and beef products, but the health benefits of CLA can only be realized if they are consumed at much greater levels than a normal healthy dietary intake. We have recently shown that a CLA-rich soy oil can be produced by simple isomerization of linoleic acid in soy oil by photoirradiation. This oil may allow greatly increased dietary CLA without significantly elevating fat intake. The objective of this study was to prepare CLA-rich potato chips by frying in CLA-rich soy oil. Soy oil was photoisomerized in the presence of iodine catalyst with UV/visible light. The irradiated oil was clay processed to remove the residual iodine and this oil was then used to fry potato chips. Oil was extracted from fried chips and analyzed for its CLA content with gas chromatography. A 1-oz serving of CLA-rich potato chips contained approximately 2.4 g CLA as compared to 0.1 g CLA in 3-oz serving of steak fillet and 0.06 g CLA in 8-oz serving of whole milk. The peroxide value of the oil extracted from potato chips was found to be 1 meq/1000 g sample, which was within the acceptable commercial standards. This study may lead to the commercialization of CLA-rich food products. [source] Oxygen-Generating Gel Systems Induced by Visible LightADVANCED FUNCTIONAL MATERIALS, Issue 5 2010Kosuke Okeyoshi Abstract Toward complete artificial photosynthesis systems to generate hydrogen and oxygen using visible light and water, oxygen-generating gel systems are designed and fabricated using the electrostatic interactions of ionic functional groups and steric effects of a polymer network. By using a graft polymer chain with Ru(bpy)32+ units as sensitizers to closely arrange RuO2 nanoparticles as catalyst, the functional groups transmit multiple electrons cooperatively to generate oxygen. In this paper, a novel strategy is shown to design a hierarchical network structure using colloidal nanoparticles and macromonomers. Such a soft material to oxidize water inside a hydrogel is useful as a solar-energy converting system. [source] Densification of Oxide Nanoparticle Thin Films by Irradiation with Visible LightADVANCED FUNCTIONAL MATERIALS, Issue 8 2009Massimo F. Bertino Abstract A technique is presented that allows for altering of the physical characteristics of films of TiO2 nanoparticles by exposure to visible light. In this technique, dye-sensitized oxide nanoparticles are deposited on a substrate by dip-coating. Photodissociation of the organic ligand layer leads to cross-linking of the nanoparticles. Consequently, irradiated films have a decreased porosity, an increased index of refraction and an increased hydrophobicity. Films irradiated with green light are compared to films irradiated with UV light. Within experimental error, visible- and UV-illumination induces the same changes in the films. The mechanism of surfactant elimination in dye-sensitized oxide particles is discussed, patterning is demonstrated, and prospective applications of the technique are considered. [source] Illumination of Cellulose with Linearly Polarized Visible LightMACROMOLECULAR SYMPOSIA, Issue 1 2008A. Konieczna - Molenda Abstract Summary: Aqueous suspensions of cellulose of long polysaccharide chains, were illuminated with visible polarized light (VPL) for 20 and 50 hrs. Crystal structure, thermal properties with Differential Scanning Calorimetry (DSC) and degree of polymerization (DP) of the samples were determined. Additionally, kinetic of enzymatic as well as acid-catalyzed hydrolysis of cellulose was estimated. Illumination of cellulose with VPL for 50 hrs increased its DP by 15%. X-ray diffraction patterns revealed that the illumination resulted in an increase in the amount of cellulose crystalline phase. The DSC measurements indicated differences in the water molecules distribution depending on the sample treatment confirming an increase in the crystallinity of the illuminated cellulose. After prolonged illumination, cellulose was resistant to oxidation and had lower susceptibility to enzymatic and acid-catalyzed hydrolysis. [source] Effect of Visible Light on Normal and P23H-3 Transgenic Rat Retinas: Characterization of a Novel Retinoic Acid Derivative Present in the P23H-3 RetinaPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2006Todd Duncan ABSTRACT Transgenic rats with the P23H mutation in rhodopsin exhibit increased susceptibility to light damage, compared with normal animals. It is known that light-induced retinal damage requires repetitive bleaching of rhodopsin and that photoreceptor cell loss is by apoptosis; however, the underlying molecular mechanism(s) leading to photoreceptor cell death are still unknown. Photoproducts, such as all- trans retinal or other retinoid metabolites, released by the extensive bleaching of rhodopsin could lead to activation of degenerative processes, especially in animals genetically predisposed to retinal degenerations. Using wild-type and transgenic rats carrying the P23H opsin mutation, we evaluated the effects of acute intense visible light on retinoid content, type and distribution in ocular tissues. Rats were exposed to green light (480,590 nm) for 0, 5, 10, 30 and 120 min. Following light treatment, rats were sacrificed and neural retinas were dissected free of the retinal pigment epithelium. Retinoids were extracted from retinal tissues and then subjected to HPLC and mass spectral analysis. We found that the light exposure affected relative levels of retinoids in the neural retina and retinal pigment epithelium of wild-type and P23H rat eyes similarly. In the P23H rat retina but not the wild-type rat retina, we found a retinoic acid-like compound with an absorbance maximum of 357 nm and a mass of 304 daltons. Production of this retinoic acid-like compound in transgenic rats is influenced by the age of the animals and the duration of light exposure. It is possible that this unique retinoid may be involved in the process of light-induced retinal degeneration. [source] The Hierarchical Self-Assembly of Charge Nanocarriers: A Highly Cooperative Process Promoted by Visible Light,ANGEWANDTE CHEMIE, Issue 39 2010Dr. Emilie Moulin Es werde Licht: Auf Triarylaminen basierende Bausteine reagieren auf sichtbares Licht unter Bildung von kationischen Radikalen, die sich hierarchisch zu molekularen Drähten selbstorganisieren, die wiederum größere Fasern bilden (siehe Bild). Das auf Stimuli reagierende supramolekulare Gerüst, das durch Ladungstransfer gebildet und durch Erhitzen reversibel abgebaut wird, verhindert das Quenchen von Löchern im Inneren der Drähte. [source] Photocatalytic Overall Water Splitting Promoted by Two Different Cocatalysts for Hydrogen and Oxygen Evolution under Visible Light,ANGEWANDTE CHEMIE, Issue 24 2010Kazuhiko Maeda Dr. Harmonische Zusammenarbeit: Nanopartikel aus Mn3O4 und aus Kern/Schale-strukturiertem Rh/Cr2O3 als Cokatalysatoren auf der Oberfläche eines GaN-ZnO-Mischkristalls als Katalysator beschleunigen die O2 - bzw. H2 -Entwicklung unter sichtbarem Licht (,>420,nm) und verbessern so die Wasserspaltungsaktivität gegenüber analogen Systemen, die nur mit Mn3O4 oder Rh/Cr2O3 modifiziert wurden. [source] ChemInform Abstract: Efficient Nonsacrifical Water Splitting Through Two-Step Photoexcitation by Visible Light Using a Modified Oxynitride as a Hydrogen Evolution Photocatalyst.CHEMINFORM, Issue 27 2010Kazuhiko Maeda Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Water Splitting by Visible Light: A Nanophotocathode for Hydrogen ProductionCHEMINFORM, Issue 19 2010Thomas Nann Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Self-Templated Synthesis of Nanoporous CdS Nanostructures for Highly Efficient Photocatalytic Hydrogen Production under Visible Light.CHEMINFORM, Issue 13 2008Ningzhong Bao Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Nitrogen Extrusion from Pyrazoline-Substituted Porphyrins and Chlorins Using Long Wavelength Visible Light.CHEMINFORM, Issue 18 2003Angela Desjardins Abstract For Abstract see ChemInform Abstract in Full Text. [source] Preparation of Core,Shell-Structured Nanoparticles (with a Noble-Metal or Metal Oxide Core and a Chromia Shell) and Their Application in Water Splitting by Means of Visible LightCHEMISTRY - A EUROPEAN JOURNAL, Issue 26 2010Kazuhiko Maeda Dr. Abstract Core,shell-structured nanoparticles, consisting of a noble metal or metal oxide core and a chromia (Cr2O3) shell, were studied as promoters for photocatalytic water splitting under visible light. Core nanoparticles were loaded by impregnation, adsorption or photodeposition onto a solid solution of gallium nitride and zinc oxide (abbreviated GaN:ZnO), which is a particulate semiconductor photocatalyst with a band gap of approximately 2.7,eV, and a Cr2O3 shell was formed by photodeposition using a K2CrO4 precursor. Photodeposition of Cr2O3 on GaN:ZnO modified with a noble metal (Rh, Pd and Pt) or metal oxide (NiOx, RuO2 and Rh2O3) co-catalyst resulted in enhanced photocatalytic activity for overall water splitting under visible light (,>400,nm). This enhancement in activity was primarily due to the suppression of undesirable reverse reactions (H2,O2 recombination and/or O2 photoreduction) and/or protection of the core component from chemical corrosion, depending on the core type. Among the core materials examined, Rh species exhibited relatively high performance for this application. The activity for visible-light water splitting on GaN:ZnO modified with an Rh/Cr2O3 core,shell configuration was dependent on both the dispersion of Rh nanoparticles and the valence state. In addition, the morphology of the Cr2O3 photodeposits was significantly affected by the valence state of Rh and the pH at which the photoreduction of K2CrO4 was conducted. When a sufficient amount of K2CrO4 was used as the precursor and the solution pH ranged from 3 to 7.5, Cr2O3 was successfully formed with a constant shell thickness (,2,nm) on metallic Rh nanoparticles, which resulted in an effective promoter for overall water splitting. [source] Visible light initiated polymerization of styrenic monolithic stationary phases using 470,nm light emitting diode arraysJOURNAL OF SEPARATION SCIENCE, JSS, Issue 1 2010Zarah Walsh Abstract Poly(styrene- co -divinylbenzene) monolithic stationary phases have been synthesized for the first time by photoinitiated polymerization. An initiator composed of (+)-(S)-camphorquinone/ethyl-4-dimethylaminobenzoate/N- methoxy-4-phenylpyridinium tetrafluoroborate was activated using a 470,nm light emitting diode array as the light source. Spatially controlled polymerization of styrenic monoliths has been achieved within specific sections of a 100,,m id polytetrafluoroethylene-coated fused-silica capillary using simple photo masking. The sharpness of the edges was confirmed by optical microscopy, while SEM was used to verify a typical porous, globular morphology. Flow resistance data were used to assess the permeability of the monoliths and they were found to have good flow through properties with a flow resistance of 0.725,MPa/cm at 1,,L/min (water, 20°C). Conductivity profiling along the length of the capillary was used to assess their lateral homogeneity. Monoliths which were axially rotated during polymerization were found to be homogeneous along the whole length of the capillary. The monolithic stationary phases were applied to the RP gradient separation of a mixture of proteins. Column fabrication showed excellent reproducibility with the retention factor (k) having a RSD value of 2.6% for the batch and less than 1.73% on individual columns. [source] Visible light-induced killing of bacteria as a function of wavelength: Implication for wound healingLASERS IN SURGERY AND MEDICINE, Issue 6 2010Anat Lipovsky MSc Abstract Background and objective Visible light (400,800,nm) at high intensity was previously found to kill bacteria that are frequently found in infected wounds, while low-power white light enhances bacterial proliferation. The phototoxic effect was found to involve induction of reactive oxygen species (ROS) production by the bacteria. The aim of the present study was to identify the most effective wavelengths in the visible range for inducing a bactericidal effect. Experimental ROS production in Staphylococcus aureus and Escherichia coli as a function of wavelengths in the visible range (400,500, 500,800, 415, and 455,nm) was studied using the electron paramagnetic resonance (EPR) spin trapping technique. The phototoxicity of 415 and 455,nm light at different fluencies on the survival of S. aureus and E. coli was assessed by colony count of the bacteria following irradiation. Results ROS production following blue (400,500,nm) light illumination was found to be higher than that of red (500,800,nm). Within the blue range, light of 415,nm induced more ROS than 455,nm, which correlated with results obtained for the reduction in colony count of S. aureus and E. coli following illumination using equal intensities of these two wavelengths. At low fluencies, both 415 and 455,nm enhanced proliferation of S. aureus but reduced viability of E. coli. Conclusion Intense blue light, preferably at 415,nm, could be used for bacterial eradication. However, it should be noted that low intensity of visible light can be dangerous since it may promote proliferation of the microorganisms. Lasers Surg. Med. 42:467,472, 2010. © 2010 Wiley,Liss, Inc. [source] Encapsulation of adult human mesenchymal stem cells within collagen-agarose microenvironments,BIOTECHNOLOGY & BIOENGINEERING, Issue 4 2005Anna Batorsky Abstract Reliable control over the process of cell differentiation is a major challenge in moving stem cell-based therapies forward. The composition of the extracellular matrix (ECM) is known to play an important role in modulating differentiation. We have developed a system to encapsulate adult human mesenchymal stem cells (hMSC) within spherical three-dimensional (3D) microenvironments consisting of a defined mixture of collagen Type I and agarose polymers. These protein-based beads were produced by emulsification of liquid hMSC-matrix suspensions in a silicone fluid phase and subsequent gelation to form hydrogel beads, which were collected by centrifugation and placed in culture. Bead size and size distribution could be varied by changing the encapsulation parameters (impeller speed and blade separation), and beads in the range of 30,150 microns in diameter were reliably produced. Collagen concentrations up to 40% (wt/wt) could be incorporated into the bead matrix. Visible light and fluorescence microscopy confirmed that the collagen matrix was uniformly distributed throughout the beads. Cell viability post-encapsulation was in the range of 75,90% for all bead formulations (similar to control slab gels) and remained at this level for 8 days in culture. Fluorescent staining of the actin cytoskeleton revealed that hMSC spreading increased with increasing collagen concentration. This system of producing 3D microenvironments of defined matrix composition therefore offers a way to control cell-matrix interactions and thereby guide hMSC differentiation. The bead format allows the use of small amounts of matrix proteins, and such beads can potentially be used as a cell delivery vehicle in tissue repair applications. © 2005 Wiley Periodicals, Inc. [source] Gross and Microscopic Findings in Patients Submitted to Nonablative Full-Face Resurfacing Using Intense Pulsed Light: A Preliminary StudyDERMATOLOGIC SURGERY, Issue 8 2002Enrique Hernández-Pérez MD background. Intense pulsed light (IPL) is a noncoherent, nonlaser, filtered flashlamp emitting a broadband visible light that has been shown to be effective in photoepilation, as well as in a number of vascular and pigmented lesions of the skin. Their efficacy has also been reported recently in the treatment of photodamaged facial skin. In the last condition, however, there are few studies showing the clinical and microscopic changes produced by IPL. objective. To assess the gross and microscopic changes that occur in photodamaged skin submitted to nonablative full-face resurfacing (NAFFR) using IPL. methods. Five women were submitted to five NAFFR sessions using IPL, one every 2 weeks. Skin biopsies and photographs were taken on all of the patients before the first procedure and after the last one, as well as weekly clinical assessment. Data concerning skin features (wrinkles, oiliness, thickness, dilated pores, and general appearance) were all assessed. Microscopic improvement of the aging features in the epidermis and dermis were all assessed. For the statistical analysis a t test for small samples was used. results. All the patients showed clinical and microscopic improvement in every one of the parameters assessed. The t test for small samples showed a statistically significant difference (P < 0.01) in epidermal thickness. conclusion. Facial photodamage was clinically and microscopically improved using IPL. Use of IPL as a rejuvenating method seems to be promising, with minimal side effects, a wide safety margin, and minimal downtime. [source] Highly Efficient Visible-Light-Induced Photocleavage of DNA by a Ruthenium-Substituted Fluorinated PorphyrinEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2009Michelle Cunningham Abstract A new porphyrin, meso -5-(pentafluorophenyl)-10,15,20-tris(4-pyridyl)porphyrin, has been synthesized. Coordination of two [Ru(bipy)2Cl]+ moieties (where bipy = 2,2,-bipyridine) to the pyridyl nitrogen atoms in the 10,15-positions gives the target complex. Electronic transitions associated with the ruthenium,porphyrin include an intense Soret band and four less intense Q-bands in the visible region of the spectrum. An intense ,,,* transition in the UV region associated with the bipyridyl groups and a metal-to-ligand charge-transfer (MLCT) band appearing as a shoulder to the Soret band are also observed. Electrochemical properties associated with the complex include a redox couple in the cathodic region with E1/2 = ,0.84 V vs. Ag/AgCl attributed to the porphyrin and a redox couple in the anodic region at E1/2 = 0.79 V vs. Ag/AgCl due to the RuIII/II couple. DNA titrations and ethidium bromide displacement experiments indicate the ruthenium porphyrin interacts with DNA potentially through a partial intercalation mechanism. Irradiation of aqueous solutions of the ruthenated complex and supercoiled DNA at a 100:1 base pair/complex ratio with visible light above 400 nm indicates that the complex causes double-strand breaks of the DNA.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Switchable Fluorescent and Solvatochromic Molecular Probes Based on 4-Amino- N -methylphthalimide and a Photochromic DiaryletheneEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 15 2008Sergey F. Yan Abstract New fluorescent photochromic compounds (1 -H and 1 -Boc) have been synthesized and characterized in different solvents. The fluorescence emission can be switched "on" and "off" with visible light and UV, respectively, by means of the photochromic reaction. The emission wavelength and efficiency strongly depend on the polarity of the solvent. The compounds show a positive solvatochromic effect in the emission maxima, and their fluorescence quantum yield decreases as the solvent's polarity increases (from cyclohexane to dioxane). In solvents more polar than dioxane the emission is too weak and therefore undetectable, and thus 1 -H and 1 -Boc behave as "normal" photochromic compounds. The photochromic reaction is also sensitive to the environment. A decrease of more than an order of magnitude was found for the quantum yield of the colouring reaction (,OF,CF) for 1 -H in ethanol compared with cyclohexane, and an about threefold decrease in ,OF,CF was observed for the compound 1 -Boc in polar solvents (compared with apolar solvents). For both compounds the ring-opening reaction was found not to dependent on the solvent. The novel fluorescent molecular switches 1 -H and 1 -Boc are able to probe the polarity of their microenvironment. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Graphite Oxide as a Photocatalyst for Hydrogen Production from WaterADVANCED FUNCTIONAL MATERIALS, Issue 14 2010Te-Fu Yeh Abstract A graphite oxide (GO) semiconductor photocatalyst with an apparent bandgap of 2.4,4.3,eV is synthesized by a modified Hummers' procedure. The as-synthesized GO photocatalyst has an interlayer spacing of 0.42,nm because of its moderate oxidation level. Under irradiation with UV or visible light, this GO photocatalyst steadily catalyzes H2 generation from a 20,vol % aqueous methanol solution and pure water. As the GO sheets extensively disperse in water, a cocatalyst is not required for H2 generation over the GO photocatalyst. During photocatalytic reaction, the GO loses some oxygen functional groups, leading to bandgap reduction and increased conductivity. This structural variation does not affect the stable H2 generation over the GO. The encouraging results presented in this study demonstrate the potential of graphitic materials as a medium for water splitting under solar illumination. [source] Diversity and distribution of pigmented heterotrophic bacteria in marine environmentsFEMS MICROBIOLOGY ECOLOGY, Issue 1 2006Hailian Du Abstract A systematic investigation of marine pigmented heterotrophic bacteria (PHB) based on the cultivation method and sequencing analysis of 16S rRNA genes was conducted in Chinese coastal and shelf waters and the Pacific Ocean. Both the abundance of PHB and the ratio of PHB to CFU decreased along trophic gradients from coastal to oceanic waters, with the highest values of 9.9 × 103 cell mL,1 and 39.6%, respectively, in the Yangtze River Estuary. In contrast to the total heterotrophic bacteria (TB) and CFU, which were present in the whole water column, PHB were primarily confined to the euphotic zone, with the highest abundance of PHB and ratio of PHB to CFU occurring in surface water. In total, 247 pigmented isolates were obtained during this study, and the phylogenetic analysis showed a wide genetic diversity covering 25 genera of six phylogenetic classes: Alphaproteobacteria, Gammaproteobacteria, Actinobacteria, Bacilli, Flavobacteria and Sphingobacteria. PHB belonging to Alphaproteobacteria, Flavobacteria and Sphingobacteria were obtained mainly from the South China Sea and East China Sea; PHB from the Pacific Ocean water were predominantly affiliated with Gammaproteobacteria, and most isolates from the Yangtze River Estuary fell into the classes Actinobacteria and Bacilli. The isolates exhibited various colours (e.g. golden, yellow, red, pink and orange), with genus or species specificity. Furthermore, the pigment of PHB cells absorbed light mainly in the wavelength range between 450 and 550 nm. In conclusion, our work has revealed that PHB with broad genetic diversity are widely distributed in the marine environment, and may account for up to 39.6% of culturable bacteria, equivalent to 1.4% of the total microbial community. This value might even be underestimated because it is probable that not all pigmented bacteria were isolated. Their abundance and genetic distribution are heavily influenced by environmental properties, such as light and nutrition, suggesting that they have important roles in the marine ecosystem, especially in the absorption of visible light. [source] Helically ,-Stacked Conjugated Polymers Bearing Photoresponsive and Chiral Moieties in Side Chains: Reversible Photoisomerization-Enforced Switching Between Emission and Quenching of Circularly Polarized FluorescenceADVANCED FUNCTIONAL MATERIALS, Issue 8 2010Hiroyuki Hayasaka Abstract Novel multifunctional conjugated polymers, [poly(p -phenylene)s and poly(bithienylene-phenylene)s with (R)- and (S)-configurations], which have fluorescence, chirality, and photoresponsive properties, have been designed and synthesized. The polymers are composed of ,-conjugated main chains, where poly(p -phenylene) and poly(bithienylene-phenylene) are fluorescence moieties, and the side chains of the photochromic dithienylethene moiety are linked with chiral alkyl groups. The polymer films exhibit right- or left-handed circularly polarized fluorescence (CPF) and also show reversible quenching and emitting behaviors as a result of photochemical isomerization of the dithienylethene moiety upon irradiation with ultraviolet and visible light. This is the first report realizing the reversible switching of CPF using chirality and photoresponsive properties. [source] Oxygen-Generating Gel Systems Induced by Visible LightADVANCED FUNCTIONAL MATERIALS, Issue 5 2010Kosuke Okeyoshi Abstract Toward complete artificial photosynthesis systems to generate hydrogen and oxygen using visible light and water, oxygen-generating gel systems are designed and fabricated using the electrostatic interactions of ionic functional groups and steric effects of a polymer network. By using a graft polymer chain with Ru(bpy)32+ units as sensitizers to closely arrange RuO2 nanoparticles as catalyst, the functional groups transmit multiple electrons cooperatively to generate oxygen. In this paper, a novel strategy is shown to design a hierarchical network structure using colloidal nanoparticles and macromonomers. Such a soft material to oxidize water inside a hydrogel is useful as a solar-energy converting system. [source] High-Performance Photoresponsive Organic Nanotransistors with Single-Layer Graphenes as Two-Dimensional ElectrodesADVANCED FUNCTIONAL MATERIALS, Issue 17 2009Yang Cao Abstract Graphene behaves as a robust semimetal with the high electrical conductivity stemming from its high-quality tight two-dimensional crystallographic lattice. It is therefore a promising electrode material. Here, a general methodology for making stable photoresponsive field effect transistors, whose device geometries are comparable to traditional macroscopic semiconducting devices at the nanometer scale, using cut graphene sheets as 2D contacts is detailed. These contacts are produced through oxidative cutting of individual 2D planar graphene by electron beam lithography and oxygen plasma etching. Nanoscale organic transistors based on graphene contacts show high-performance FET behavior with bulk-like carrier mobility, high on/off current ratio, and high reproducibility. Due to the presence of photoactive molecules, the devices display reversible changes in current when they are exposed to visible light. The calculated responsivity of the devices is found to be as high as ,8.3,A,W,1. This study forms the basis for making new types of ultrasensitive molecular devices, thus initiating broad research interest in the field of nanoscale/molecular electronics. [source] Densification of Oxide Nanoparticle Thin Films by Irradiation with Visible LightADVANCED FUNCTIONAL MATERIALS, Issue 8 2009Massimo F. Bertino Abstract A technique is presented that allows for altering of the physical characteristics of films of TiO2 nanoparticles by exposure to visible light. In this technique, dye-sensitized oxide nanoparticles are deposited on a substrate by dip-coating. Photodissociation of the organic ligand layer leads to cross-linking of the nanoparticles. Consequently, irradiated films have a decreased porosity, an increased index of refraction and an increased hydrophobicity. Films irradiated with green light are compared to films irradiated with UV light. Within experimental error, visible- and UV-illumination induces the same changes in the films. The mechanism of surfactant elimination in dye-sensitized oxide particles is discussed, patterning is demonstrated, and prospective applications of the technique are considered. [source] Photosensitization of TiO2 Nanostructures with CdS Quantum Dots: Particulate versus Tubular Support ArchitecturesADVANCED FUNCTIONAL MATERIALS, Issue 5 2009David R. Baker Abstract TiO2 nanotube arrays and particulate films are modified with CdS quantum dots with an aim to tune the response of the photoelectrochemical cell in the visible region. The method of successive ionic layer adsorption and reaction facilitates size control of CdS quantum dots. These CdS nanocrystals, upon excitation with visible light, inject electrons into the TiO2 nanotubes and particles and thus enable their use as photosensitive electrodes. Maximum incident photon to charge carrier efficiency (IPCE) values of 55% and 26% are observed for CdS sensitized TiO2 nanotube and nanoparticulate architectures respectively. The nearly doubling of IPCE observed with the TiO2 nanotube architecture is attributed to the increased efficiency of charge separation and transport of electrons. [source] Enhanced Light-Harvesting and Photocatalytic Properties in Morph -TiO2 from Green-Leaf BiotemplatesADVANCED FUNCTIONAL MATERIALS, Issue 1 2009Xufan Li Abstract The unique structure of green leaves endows them with an extremely high light-harvesting efficiency. In this work, green leaves are applied as biotemplates to synthesize morph -TiO2. The structural features favorable for light harvesting from the macro- to the nanoscale are replicated in morph -TiO2 through a two-step infiltration process and the N contained in the original leaves is self-doped into the resulting samples. The absorbance intensities within the visible-light range of morph -TiO2 derived from different leaves increase by 103,258% and the band-gap-absorption onsets at the edge of the UV and visible-light range show a red-shift of 25,100,nm compared to those in TiO2 without the template. The photocatalytic activity of morph -TiO2 is also improved, as proven by an electron paramagnetic resonance (EPR) study and degradation of rhodamine dye under irradiation with UV and visible light. The present work, as a new strategy, is of far-reaching significance in learning from nature, driving us to make full use of the most-abundant resources and structure-introduced functions endowed by nature, opening up possibilities for extensive study of the physical and chemical properties of morph -structured oxides and extending their potential for use in applications such as solar cells, photocatalysts, photoelectrical devices, and photoinduced sensors. [source] Cover Picture: Spectroscopic and Photophysical Properties of a Highly Derivatized C60 Fullerol (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 1 2006Mater. Abstract The photo-oxidative stress in aqueous milieus can readily be generated in the presence of newly synthesized highly derivatized fullerenes (fullerols) reported in the Full Paper by Vileno and co-workers on p.,120. Their basic structural and photophysical properties were characterized using a range of methods, including X-ray photoelectron and IR spectroscopies, and electron spin resonance. Moreover, a significant drop of the local stiffness of a living cell was monitored using atomic force microscopy. This cell softening was attributed to the early effects of the photo-oxidative stress. Hydroxylated C60 molecules, also called fullerols, are a class of water-soluble fullerenes. Here we report the synthesis in acidic conditions of a highly derivatized fullerol (up to 36 carbons per C60 are oxidized). Spectroscopic investigations (X-ray photoelectron spectroscopy and infrared absorption) highlight the coexistence of both acidic and basic forms for the hydroxyl addends of derivatized C60. pH titrimetry reveals that, at millimolar concentrations, only ten protons per fullerol molecule are labile. Such a low value, as compared to 36 hydroxyl groups, is explained by the formation of clusters. A UV-vis absorption study performed over a large range of concentrations also points to the aggregation phenomenon. Moreover, this study shows that the clusters of fullerols appear at relatively low (micromolar) concentrations. An electron spin resonance (ESR) study, based on the attack of singlet oxygen (1,g) on 2,2,6,6-tetramethyl-4-piperidinol (TMP-OH), has proved the potential of hydroxylated C60 for performing efficient generation of singlet oxygen in aqueous solution. ESR measurements, which allow detection and quantification of 1,g, have also revealed the generation of reactive oxygen species (ROS). The yield of generation of 1,g and ROS is strongly correlated to the concentration of fullerol, thus also pointing to the aggregation of fullerol molecules. Exposing glioblastoma cells to oxidative stress in the presence of hydroxylated C60 and visible light has also been performed. Atomic force microscopy is used to monitor the relevant diminishment of the Young's modulus values for cells exposed to the oxidative stress. These results point to a possible application field of fullerols for performing bio-oxidations. [source] Bulk Photovoltaic Effect at Visible Wavelength in Epitaxial Ferroelectric BiFeO3 Thin FilmsADVANCED MATERIALS, Issue 15 2010Wei Ji Appreciable photovoltaic responses to visible light are observed in epitaxial ferroelectric BiFeO3 thin films by sputtering deposition. The photocurrent direction is opposite to the BiFeO3 polarization vector and can be switched by poling the films in different directions (see figure). The as-deposited films are strongly self-polarized, exhibiting significant photovoltaic response before any electrical poling process. [source] Scintillating Metal-Organic Frameworks: A New Class of Radiation Detection Materials,ADVANCED MATERIALS, Issue 1 2009F. P. Doty Metal-organic frameworks containing an organic fluorophore such as stilbene dicarboxylate emit prompt visible light when they interact with ionizing radiation (e.g., high-energy protons or alpha particles). A completely new class of scintillation materials is created by this development, with the potential to rationally tailor properties for specific radiation detection applications. [source] Cu-Doped ZnO Nanowires for Efficient and Multispectral Photodetection Applications,ADVANCED MATERIALS, Issue 11 2008Nikolai Kouklin Cu-doped ZnO nanowires exhibiting high sensitivity to both UV and visible light are prepared by a vapor,liquid,solid method. The nanowires are highly resistive in the dark but exhibit several orders of magnitude enhancement in photoconductivity under UV and white-light irradiation because of an avalanche-type photocarrier multiplication effect, paving the way for their use in nanoscale photodetection applications. [source] | ||||||||||||||||||||||||||||||||||||||||