Evaluation of 405nm CW visible blue light as a means of inactivating Tulane Virus on Blueberries

USDA-ARS?s Scientific Manuscript database

Introduction: Visible blue light (405nm) is effective against bacteria but its potential as a nonthermal intervention for viruses on foods, such as berries that are prone to norovirus contamination has not been evaluated. Tulane virus (TV) is now a common human norovirus surrogate that can be propa...

Nano-lithographically fabricated titanium dioxide based visible frequency three dimensional gap photonic crystal.

PubMed

Subramania, Ganapathi; Lee, Yun-Ju; Brener, Igal; Luk, Ting-Shan; Clem, Paul G

2007-10-01

Photonic crystals (PC) have emerged as important types of structures for light manipulation. Ultimate control of light is possible by creating PCs with a complete three dimensional (3D) gap [1, 2]. This has proven to be a considerable challenge in the visible and ultraviolet frequencies mainly due to complications in integrating transparent, high refractive index (n) materials with fabrication techniques to create ~ 100nm features with long range translational order. In this letter, we demonstrate a nano-lithography approach based on a multilevel electron beam direct write and physical vapor deposition, to fabricate four-layer titania woodpile PCs that potentially exhibit complete 3D gap at visible wavelengths. We achieved a short wavelength bandedge of 525nm with a 300nm lattice constant PC. Due to the nanoscale precision and capability for defect control, the nanolithography approach represents an important step toward novel visible photonic devices for lighting, lasers, sensing and biophotonics.

Differences in visible and near-infrared light reflectance between orange fruit and leaves

NASA Technical Reports Server (NTRS)

Gausman, H. W.; Escobar, D. E.; Berumen, A.

1975-01-01

The objective was to find the best time during the season (April 26, 1972 to January 8, 1973) to distinguish orange fruit from leaves by spectrophotometrically determining at 10-day intervals when the difference in visible (550- and 650-nm wavelengths) and near-infrared (850-nm wavelength) light reflectance between fruit and nearby leaves was largest. December 5 to January 8 was the best time to distinguish fruit from leaves. During this period the fruit's color was rapidly changing from green to yellow, and the difference in visible light reflectance between fruit and leaves was largest. The difference in near-infrared reflectance between leaves and fruit remained essentially constant during ripening when the difference in visible light reflectance between leaves and fruit was largest.

4 Gbps direct modulation of 450 nm GaN laser for high-speed visible light communication.

PubMed

Lee, Changmin; Zhang, Chong; Cantore, Michael; Farrell, Robert M; Oh, Sang Ho; Margalith, Tal; Speck, James S; Nakamura, Shuji; Bowers, John E; DenBaars, Steven P

2015-06-15

We demonstrate high-speed data transmission with a commercial high power GaN laser diode at 450 nm. 2.6 GHz bandwidth was achieved at an injection current of 500 mA using a high-speed visible light communication setup. Record high 4 Gbps free-space data transmission rate was achieved at room temperature.

Inactivation of bacterial biofilms using visible-light-activated unmodified ZnO nanorods

NASA Astrophysics Data System (ADS)

Aponiene, Kristina; Serevičius, Tomas; Luksiene, Zivile; Juršėnas, Saulius

2017-09-01

Various zinc oxide (ZnO) nanostructures are widely used for photocatalytic antibacterial applications. Since ZnO possesses a wide bandgap, it is believed that only UV light may efficiently assist bacterial inactivation, and diverse crystal lattice modifications should be applied in order to narrow the bandgap for efficient visible-light absorption. In this work we show that even unmodified ZnO nanorods grown by an aqueous chemical growth technique are found to possess intrinsic defects that can be activated by visible light (λ = 405 nm) and successfully applied for total inactivation of various highly resistant bacterial biofilms rather than more sensitive planktonic bacteria. Time-resolved fluorescence analysis has revealed that visible-light excitation creates long-lived charge carriers (τ > 1 μs), which might be crucial for destructive biochemical reactions achieving significant bacterial biofilm inactivation. ZnO nanorods covered with bacterial biofilms of Enterococcus faecalis MSCL 302 after illumination by visible light (λ = 405 nm) were inactivated by 2 log, and Listeria monocytogenes ATCL3C 7644 and Escherichia coli O157:H7 biofilms by 4 log. Heterogenic waste-water microbial biofilms, consisting of a mixed population of mesophilic bacteria after illumination with visible light were also completely destroyed.

Fabrication of PAN@TiO2/Ag nanofibrous membrane with high visible light response and satisfactory recyclability for dye photocatalytic degradation

NASA Astrophysics Data System (ADS)

Shi, Yongzheng; Yang, Dongzhi; Li, Yuan; Qu, Jin; Yu, Zhong-Zhen

2017-12-01

Although TiO2-based photocatalysts have exhibited a great potential for degradation of organic pollutants, it is still necessary to simultaneously enhance their visible-light-driven photocatalytic efficiency and physical recyclability. Herein, highly efficient, visible-light-driven photocatalytically active, and recyclable nanofibrous membranes with thin TiO2/Ag heterojunction layer are prepared using electrospun polyacrylonitrile (PAN) nanofibrous membrane as the substrate. By regulating the concentration and hydrolysis process of Ti precursors, TiO2 nanoparticles steadily grow on the PAN nanofibers with high-specific surface area to form a continuous mesoporous shell with the thickness of 20 nm for efficient degradation of organic pollutants. Furthermore, to form a stable heterojunction structure, Ag nanoparticles are deposited on the TiO2 surface by using dopamine as a binder and reductant. The presence of Ag nanoparticles leads to an obvious red-shift from 380 nm to 490 nm, which improves the utilization efficiency of visible light, and reduces the electron/hole recombination rate simultaneously. The resulting PAN@TiO2/Ag membranes hold enhanced photocatalytic activity for methylene blue degradation within 1 h under visible light irradiation, and satisfactory recyclability, which endow them with a great potential for adsorption and photocatalytic applications.

Impact of long-wavelength UVA and visible light on melanocompetent skin.

PubMed

Mahmoud, Bassel H; Ruvolo, Eduardo; Hexsel, Camile L; Liu, Yang; Owen, Michael R; Kollias, Nikiforos; Lim, Henry W; Hamzavi, Iltefat H

2010-08-01

The purpose of this study was to determine the effect of visible light on the immediate pigmentation and delayed tanning of melanocompetent skin; the results were compared with those induced by long-wavelength UVA (UVA1). Two electromagnetic radiation sources were used to irradiate the lower back of 20 volunteers with skin types IV-VI: UVA1 (340-400 nm) and visible light (400-700 nm). Pigmentation was assessed by visual examination, digital photography with a cross-polarized filter, and diffused reflectance spectroscopy at 7 time points over a 2-week period. Confocal microscopy and skin biopsies for histopathological examination using different stains were carried out. Irradiation was also carried out on skin type II. Results showed that although both UVA1 and visible light can induce pigmentation in skin types IV-VI, pigmentation induced by visible light was darker and more sustained. No pigmentation was observed in skin type II. The quality and quantity of pigment induced by visible light and UVA1 were different. These findings have potential implications on the management of photoaggravated pigmentary disorders, the proper use of sunscreens, and the treatment of depigmented lesions.

Green-Light-Sensitive BODIPY Photoprotecting Groups for Amines

PubMed Central

2018-01-01

We describe a series of easily accessible, visible-light-sensitive (λ > 500 nm) BODIPY (boron-dipyrromethene)-based photoprotecting groups (PPGs) for primary and secondary amines, based on a carbamate linker. The caged compounds are stable under aqueous conditions for 24 h and can be efficiently uncaged in vitro with visible light (λ = 530 nm). These properties allow efficient photodeprotection of amines, rendering these novel PPGs potentially suitable for various applications, including the delivery of caged drugs and their remote activation. PMID:29369628

Photoacoustic and filter measurements related to aerosol light absorption during the Northern Front Range Air Quality Study (Colorado 1996/1997)

NASA Astrophysics Data System (ADS)

Moosmüller, H.; Arnott, W. P.; Rogers, C. F.; Chow, J. C.; Frazier, C. A.; Sherman, L. E.; Dietrich, D. L.

1998-11-01

A new photoacoustic instrument for the measurement of aerosol light absorption was collocated with conventional aerosol instrumentation during the 1996-1997 winter intensive monitoring period of the Northern Front Range Air Quality Study. Measurements of the light absorption efficiency for black carbon were 5 m2/g at 685 nm and 10 m2/g at 532 nm, and for elemental carbon, they were 3.6 m2/g at 685 nm. We show that these values together with previous photoacoustic measurements of aerosol light absorption shed some light on the wavelength dependence of absorption efficiency for carbonaceous aerosol in the visible and near-visible region. Integrating plate type filter measurements of aerosol light absorption result in far larger values than those measured with the photoacoustic instrument. We demonstrate that a recently published correction technique [Horvath, 1997] can yield improved agreement.

Mitochondrial damage and cytoskeleton reorganization in human dermal fibroblasts exposed to artificial visible light similar to screen-emitted light.

PubMed

Rascalou, Adeline; Lamartine, Jérôme; Poydenot, Pauline; Demarne, Frédéric; Bechetoille, Nicolas

2018-05-05

Artificial visible light is everywhere in modern life. Social communication confronts us with screens of all kinds, and their use is on the rise. We are therefore increasingly exposed to artificial visible light, the effects of which on skin are poorly known. The purpose of this study was to model the artificial visible light emitted by electronic devices and assess its effect on normal human fibroblasts. The spectral irradiance emitted by electronic devices was optically measured and equipment was developed to accurately reproduce such artificial visible light. Effects on normal human fibroblasts were analyzed on human genome microarray-based gene expression analysis. At cellular level, visualization and image analysis were performed on the mitochondrial network and F-actin cytoskeleton. Cell proliferation, ATP release and type I procollagen secretion were also measured. We developed a device consisting of 36 LEDs simultaneously emitting blue, green and red light at distinct wavelengths (450 nm, 525 nm and 625 nm) with narrow spectra and equivalent radiant power for the three colors. A dose of 99 J/cm 2 artificial visible light was selected so as not to induce cell mortality following exposure. Microarray analysis revealed 2984 light-modulated transcripts. Functional annotation of light-responsive genes revealed several enriched functions including, amongst others, the "mitochondria" and "integrin signaling" categories. Selected results were confirmed by real-time quantitative PCR, analyzing 24 genes representing these two categories. Analysis of micro-patterned culture plates showed marked fragmentation of the mitochondrial network and disorganization of the F-actin cytoskeleton following exposure. Functionally, there was considerable impairment of cell growth and spread, ATP release and type I procollagen secretion in exposed fibroblasts. Artificial visible light induces drastic molecular and cellular changes in normal human fibroblasts. This may impede normal cellular functions and contribute to premature skin aging. The present results extend our knowledge of the effects of the low-energy wavelengths that are increasingly used to treat skin disorders. Copyright © 2018 Japanese Society for Investigative Dermatology. Published by Elsevier B.V. All rights reserved.

Photo-oxidation of polymer-like amorphous hydrogenated carbon under visible light illumination

DOE PAGES

Baxamusa, Salmaan; Laurence, Ted; Worthington, Matthew; ...

2015-11-10

Amorphous hydrogenated carbon (a-C:H), a polymer-like network typically synthesized by plasma chemical vapor deposition, has long been understood to exhibit optical absorption of visible light (λ > 400 nm). In this report we explain that this absorption is accompanied by rapid photo-oxidation (within minutes) that behaves in most respects like classic polymer photo-oxidation with the exception that it occurs under visible light illumination rather than ultraviolet illumination.

CMOS-compatible plenoptic detector for LED lighting applications.

PubMed

Neumann, Alexander; Ghasemi, Javad; Nezhadbadeh, Shima; Nie, Xiangyu; Zarkesh-Ha, Payman; Brueck, S R J

2015-09-07

LED lighting systems with large color gamuts, with multiple LEDs spanning the visible spectrum, offer the potential of increased lighting efficiency, improved human health and productivity, and visible light communications addressing the explosive growth in wireless communications. The control of this "smart lighting system" requires a silicon-integrated-circuit-compatible, visible, plenoptic (angle and wavelength) detector. A detector element, based on an offset-grating-coupled dielectric waveguide structure and a silicon photodetector, is demonstrated with an angular resolution of less than 1° and a wavelength resolution of less than 5 nm.

Development of a visible light transmission (VLT) measurement system using an open-path optical method

NASA Astrophysics Data System (ADS)

Nurulain, S.; Manap, H.

2017-09-01

This paper describes about a visible light transmission (VLT) measurement system using an optical method. VLT rate plays an important role in order to determine the visibility of a medium. Current instrument to measure visibility has a gigantic set up, costly and mostly fails to function at low light condition environment. This research focuses on the development of a VLT measurement system using a simple experimental set-up and at a low cost. An open path optical technique is used to measure a few series of known-VLT thin film that act as sample of different visibilities. This measurement system is able to measure the light intensity of these thin films within the visible light region (535-540 nm) and the response time is less than 1s.

Visible Light Induces Melanogenesis in Human Skin through a Photoadaptive Response.

PubMed

Randhawa, Manpreet; Seo, InSeok; Liebel, Frank; Southall, Michael D; Kollias, Nikiforos; Ruvolo, Eduardo

2015-01-01

Visible light (400-700 nm) lies outside of the spectral range of what photobiologists define as deleterious radiation and as a result few studies have studied the effects of visible light range of wavelengths on skin. This oversight is important considering that during outdoors activities skin is exposed to the full solar spectrum, including visible light, and to multiple exposures at different times and doses. Although the contribution of the UV component of sunlight to skin damage has been established, few studies have examined the effects of non-UV solar radiation on skin physiology in terms of inflammation, and limited information is available regarding the role of visible light on pigmentation. The purpose of this study was to determine the effect of visible light on the pro-pigmentation pathways and melanin formation in skin. Exposure to visible light in ex-vivo and clinical studies demonstrated an induction of pigmentation in skin by visible light. Results showed that a single exposure to visible light induced very little pigmentation whereas multiple exposures with visible light resulted in darker and sustained pigmentation. These findings have potential implications on the management of photo-aggravated pigmentary disorders, the proper use of sunscreens, and the treatment of depigmented lesions.

Ultrathin ZnSe nanowires: one-pot synthesis via a heat-triggered precursor slow releasing route, controllable Mn doping and application in UV and near-visible light detection.

PubMed

Li, Dong; Xing, Guanjie; Tang, Shilin; Li, Xiaohong; Fan, Louzhen; Li, Yunchao

2017-10-12

We report herein a heat-triggered precursor slow releasing route for the one-pot synthesis of ultrathin ZnSe nanowires (NWs), which relies on the gradual dissolving of Se powder into oleylamine containing a soluble Zn precursor under heating. This route allows the reaction system to maintain a high monomer concentration throughout the entire reaction process, thus enabling the generation of ZnSe NWs with diameter down to 2.1 nm and length approaching 400 nm. The size-dependent optical properties and band-edge energy levels of the ZnSe NWs were then explored in depth by UV-visible spectroscopy and cyclic voltammetry, respectively. Considering their unique absorption properties, these NWs were specially utilized for fabricating photoelectrochemical-type photodetectors (PDs). Impressively, the PDs based on the ZnSe NWs with diameters of 2.1 and 4.5 nm exhibited excellent responses to UVA and near-visible light, respectively: both possessed ultrahigh on/off ratios (5150 for UVA and 4213 for near-visible light) and ultrawide linear response ranges (from 2.0 to 9000 μW cm -2 for UVA and 5.0 to 8000 μW cm -2 for near-visible light). Furthermore, these ZnSe NWs were selectively doped with various amounts of Mn 2+ to tune their emission properties. As a result, ZnSe NW film-based photochromic cards were creatively developed for visually detecting UVA and near-visible radiation.

Visible-light vertical-cavity surface-emitting lasers grown by solid-source molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Saarinen, Mika J.; Xiang, Ning; Dumitrescu, Mihail M.; Vilokkinen, Ville; Melanen, Petri; Orsila, Seppo; Uusimaa, Petteri; Savolainen, Pekka; Pessa, Markus

2001-05-01

Visible vertical-cavity surface-emitting lasers (VCSELs) are potential light sources for polymer optical fibre (POF) data transmission systems. Minimum attenuation of light in standard PMMA-POFs occurs at about 650 nm. For POFs of a few tens of meters in length VCSELs at slightly longer wavelengths (670 - 690 nm) are also acceptable. So far, the visible VCSELs have been grown by metal organic chemical vapour deposition (MOCVD). They may also be grown by a novel variant of molecular beam epitaxy (MBE), a so-called all-solid-source MBE or SSMBE. In this paper, we describe growth of the first visible-light VCSELs by SSMBE and present the main results obtained. In particular, we have achieved lasing action at a sub-milliamp cw drive current for a VCSEL having the emission window of 8um in diameter, while a 10um device exhibited an external quantum efficiency of 6.65% in CW operation at room temperature. The lasing action up to temperature of 45°C has been demonstrated.

A broadband LED source in visible to short-wave-infrared wavelengths for spectral tumor diagnostics

NASA Astrophysics Data System (ADS)

Hayashi, Daiyu; van Dongen, Anne Marie; Boerekamp, Jack; Spoor, Sandra; Lucassen, Gerald; Schleipen, Jean

2017-06-01

Various tumor types exhibit the spectral fingerprints in the absorption and reflection spectra in visible and especially in near- to short-wave-infrared wavelength ranges. For the purpose of spectral tumor diagnostics by means of diffuse reflectance spectroscopy, we developed a broadband light emitting diode (LED) source consisting of a blue LED for optical excitation, Lu3Al5O12:Ce3+,Cr3+ luminescent garnet for visible to near infrared emissions, and Bismuth doped GeO2 luminescent glass for near-infrared to short-wave infrared emissions. It emits broad-band light emissions continuously in 470-1600 nm with a spectral gap at 900-1000 nm. In comparison to the currently available broadband light sources like halogen lamps, high-pressure discharge lamps and super continuum lasers, the light sources of this paper has significant advantages for spectral tissue diagnostics in high-spectral stability, improved light coupling to optical fibers, potential in low light source cost and enabling battery-drive.

Visible light neutralizes the effect produced by ultraviolet radiation in proteins.

PubMed

Espinoza, J Horacio; Mercado-Uribe, Hilda

2017-02-01

The damage produced by UV-C radiation (100-280nm) in organisms and cells is a well known fact. The main reactions of proteins to UV-C radiation consist in the alteration of their secondary structures, exposure of hydrophobic residues, unfolding and aggregation. Furthermore, it has been found that electromagnetic radiation of lower energy (visible light, where wavelengths are between 400 and 750nm) also induces different disturbances in biomolecules. For instance, it has been observed that blue visible light from emitting diodes (LEDs) produces severe damage in murine cone photoreceptor-derived cells, and it can be even more harmful for some organisms than UV radiation. Recently, it has been found that the exposure of proteins to green and red light produces conformational changes, considerably increasing their cohesion enthalpies. This is presumably due to the strengthening of the hydrogen bonds and the formation of new ones. Therefore, it seems that visible light acts contrary to what it is observed for UV-C: instead of unfolding the proteins it folds them further, halting the damage produced by UV-C. This can be understood if we consider the modification of the folding energy-landscape; visible light induces the descent of the proteins into deeper states impeding the unfolding produced by UV-C. Copyright © 2016 Elsevier B.V. All rights reserved.

Visible optical radiation generates bactericidal effect applicable for inactivation of health care associated germs demonstrated by inactivation of E. coli and B. subtilis using 405-nm and 460-nm light emitting diodes

NASA Astrophysics Data System (ADS)

Hönes, Katharina; Stangl, Felix; Sift, Michael; Hessling, Martin

2015-07-01

The Ulm University of Applied Sciences is investigating a technique using visible optical radiation (405 nm and 460 nm) to inactivate health-hazardous bacteria in water. A conceivable application could be point-of-use disinfection implementations in developing countries for safe drinking water supply. Another possible application field could be to provide sterile water in medical institutions like hospitals or dental surgeries where contaminated pipework or long-term disuse often results in higher germ concentrations. Optical radiation for disinfection is presently mostly used in UV wavelength ranges but the possibility of bacterial inactivation with visible light was so far generally disregarded. One of the advantages of visible light is, that instead of mercury arc lamps, light emitting diodes could be used, which are commercially available and therefore cost-efficient concerning the visible light spectrum. Furthermore they inherit a considerable longer life span than UV-C LEDs and are non-hazardous in contrast to mercury arc lamps. Above all there are specific germs, like Bacillus subtilis, which show an inactivation resistance to UV-C wavelengths. Due to the totally different deactivation mechanism even higher disinfection rates are reached, compared to Escherichia coli as a standard laboratory germ. By 460 nm a reduction of three log-levels appeared with Bacillus subtilis and a half log-level with Escherichia coli both at a dose of about 300 J/cm². By the more efficient wavelength of 405 nm four and a half log-levels are reached with Bacillus subtilis and one and a half log-level with Escherichia coli also both at a dose of about 300 J/cm². In addition the employed optical setup, which delivered a homogeneous illumination and skirts the need of a stirring technique to compensate irregularities, was an important improvement compared to previous published setups. Evaluated by optical simulation in ZEMAX® the designed optical element provided proven homogeneity distributions with maximum variation of ± 10 %.

A UV-Vis photoacoustic spectrophotometer.

PubMed

Wiegand, Joseph R; Mathews, L Dalila; Smith, Geoffrey D

2014-06-17

A novel photoacoustic spectrophotometer (PAS) for the measurement of gas-phase and aerosol absorption over the UV-visible region of the spectrum is described. Light from a broadband Hg arc lamp is filtered in eight separate bands from 300 to 700 nm using bandpass interference filters (centered at 301 nm, 314 nm, 364 nm, 405 nm, 436 nm, 546 nm, 578 and 687 nm) and modulated with an optical chopper before entering the photoacoustic cell. All wavelength bands feature a 20-s detection limit of better than 3.0 Mm(-1) with the exception of the lower-intensity 687 nm band for which it is 10.2 Mm(-1). Validation measurements of gas-phase acetone and nigrosin aerosol absorption cross sections at several wavelengths demonstrate agreement to within 10% with those measured previously (for acetone) and those predicted by Mie theory (for nigrosin). The PAS instrument is used to measure the UV-visible absorption spectrum of ambient aerosol demonstrating a dramatic increase in the UV region with absorption increasing by 300% from 405 to 301 nm. This type of measurement throughout the UV-visible region and free from artifacts associated with filter-based methods has not been possible previously, and we demonstrate its promise for classifying and quantifying different types of light-absorbing ambient particles.

Highly Transparent, Visible-Light Photodetector Based on Oxide Semiconductors and Quantum Dots.

PubMed

Shin, Seung Won; Lee, Kwang-Ho; Park, Jin-Seong; Kang, Seong Jun

2015-09-09

Highly transparent phototransistors that can detect visible light have been fabricated by combining indium-gallium-zinc oxide (IGZO) and quantum dots (QDs). A wide-band-gap IGZO film was used as a transparent semiconducting channel, while small-band-gap QDs were adopted to absorb and convert visible light to an electrical signal. Typical IGZO thin-film transistors (TFTs) did not show a photocurrent with illumination of visible light. However, IGZO TFTs decorated with QDs showed enhanced photocurrent upon exposure to visible light. The device showed a responsivity of 1.35×10(4) A/W and an external quantum efficiency of 2.59×10(4) under illumination by a 635 nm laser. The origin of the increased photocurrent in the visible light was the small band gap of the QDs combined with the transparent IGZO films. Therefore, transparent phototransistors based on IGZO and QDs were fabricated and characterized in detail. The result is relevant for the development of highly transparent photodetectors that can detect visible light.

Photocatalytic antibacterial effects on TiO2-anatase upon UV-A and UV-A/VIS threshold irradiation.

PubMed

Wu, Yanyun; Geis-Gerstorfer, Jürgen; Scheideler, Lutz; Rupp, Frank

2016-01-01

Photocatalysis mediated by the anatase modification of titanium dioxide (TiO2) has shown antibacterial effects in medical applications. The aim of this study was to investigate the possibility of expanding the excitation wavelengths for photocatalytic antibacterial effects from ultraviolet (UV) into the visible light range. After deposition of salivary pellicle and adhesion of Streptococcus gordonii on anatase, different irradiation protocols were applied to induce photocatalysis: ultraviolet A (UV-A) > 320 nm; ultraviolet/visible (UV-A/VIS) light > 380 nm and > 390 nm; and VIS light 400-410 nm. A quartz crystal microbalance with dissipation (QCM-D) tests and microscopic examination were used to observe the photoinduced antibacterial effects. Salivary pellicle could be photocatalytically decomposed under all irradiation protocols. In contrast, effective photocatalytic attack of bacteria could be observed by UV-A as well as by UV-A/VIS at 380 nm < λ < 390 nm only. Wavelengths above 380 nm show promise for in situ therapeutic antifouling applications.

Phototoxicity in Human Retinal Pigment Epithelial Cells Promoted by Hypericin, a Component of St. John’s Wort†

PubMed Central

Wielgus, Albert R.; Chignell, Colin F.; Miller, David S.; Van Houten, Ben; Meyer, Joel; Hu, Dan-Ning; Roberts, Joan E.

2007-01-01

St. John’s Wort (SJW), an over-the-counter antidepressant, contains hypericin, which absorbs light in the UV and visible ranges. In vivo studies have determined that hypericin is phototoxic to skin and our previous in vitro studies with lens tissues have determined that it is potentially phototoxic to the human lens. To determine if hypericin might also be phototoxic to the human retina, we exposed human retinal pigment epithelial cells to 10−7 to 10−5 M hypericin. Fluorescence emission detected from the cells (λexc = 488 nm; λem = 505 nm) confirmed hypericin uptake by human RPE. Neither hypericin exposure alone nor visible light exposure alone reduced cell viability. However when irradiated with 0.7 J/cm2 of visible light (λ> 400 nm) there was loss of cell viability as measured by MTS and LDH assays. The presence of hypericin in irradiated hRPE cells significantly changed the redox equilibrium of glutathione and a decrease in the activity of glutathione reductase. Increased lipid peroxidation as measured by the TBARS assay correlated to hypericin concentration in hRPE cells and visible light radiation. Thus, ingested SJW is potentially phototoxic to retina and could contribute to retinal or early macular degeneration. PMID:17576381

A multispectral sorting device for wheat kernels

USDA-ARS?s Scientific Manuscript database

A low-cost multispectral sorting device was constructed using three visible and three near-infrared light-emitting diodes (LED) with peak emission wavelengths of 470 nm (blue), 527 nm (green), 624 nm (red), 850 nm, 940 nm, and 1070 nm. The multispectral data were collected by rapidly (~12 kHz) blin...

Control of the orientation and photoinduced phase transitions of macrocyclic azobenzene.

PubMed

Uchida, Emi; Sakaki, Kouji; Nakamura, Yumiko; Azumi, Reiko; Hirai, Yuki; Akiyama, Haruhisa; Yoshida, Masaru; Norikane, Yasuo

2013-12-16

Photoinduced phase transitions caused by photochromic reactions bring about a change in the state of matter at constant temperature. Herein, we report the photoinduced phase transitions of crystals of a photoresponsive macrocyclic compound bearing two azobenzene groups (1) at room temperature on irradiation with UV (365 nm) and visible (436 nm) light. The trans/trans isomer undergoes photoinduced phase transitions (crystal-isotropic phase-crystal) on UV light irradiation. The photochemically generated crystal exhibited reversible phase transitions between the crystal and the mesophase on UV and visible light irradiation. The molecular order of the randomly oriented crystals could be increased by irradiating with linearly polarized visible light, and the value of the order parameter was determined to be -0.84. Heating enhances the thermal cis-to-trans isomerization and subsequent cooling returned crystals of the trans/trans isomer. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A polymeric-semiconductor-metal-complex hybrid photocatalyst for visible-light CO(2) reduction.

PubMed

Maeda, Kazuhiko; Sekizawa, Keita; Ishitani, Osamu

2013-10-03

A polymeric carbon nitride semiconductor is demonstrated to photocatalyse CO2 reduction to formic acid under visible light (λ > 400 nm) with a high turnover number (>200 for 20 hours) and selectivity (>80%), when coupled with a molecular ruthenium complex as a catalyst.

Visible Light Induces Melanogenesis in Human Skin through a Photoadaptive Response

PubMed Central

Randhawa, Manpreet; Seo, InSeok; Liebel, Frank; Southall, Michael D.; Kollias, Nikiforos; Ruvolo, Eduardo

2015-01-01

Visible light (400–700 nm) lies outside of the spectral range of what photobiologists define as deleterious radiation and as a result few studies have studied the effects of visible light range of wavelengths on skin. This oversight is important considering that during outdoors activities skin is exposed to the full solar spectrum, including visible light, and to multiple exposures at different times and doses. Although the contribution of the UV component of sunlight to skin damage has been established, few studies have examined the effects of non-UV solar radiation on skin physiology in terms of inflammation, and limited information is available regarding the role of visible light on pigmentation. The purpose of this study was to determine the effect of visible light on the pro-pigmentation pathways and melanin formation in skin. Exposure to visible light in ex-vivo and clinical studies demonstrated an induction of pigmentation in skin by visible light. Results showed that a single exposure to visible light induced very little pigmentation whereas multiple exposures with visible light resulted in darker and sustained pigmentation. These findings have potential implications on the management of photo-aggravated pigmentary disorders, the proper use of sunscreens, and the treatment of depigmented lesions. PMID:26121474

Far-ultraviolet spectral changes of titanium dioxide with gold nanoparticles by ultraviolet and visible light

NASA Astrophysics Data System (ADS)

Tanabe, Ichiro; Kurawaki, Yuji

2018-05-01

Attenuated total reflectance spectra including the far-ultraviolet (FUV, ≤ 200 nm) region of titanium dioxide (TiO2) with and without gold (Au) nanoparticles were measured. A newly developed external light-irradiation system enabled to observe spectral changes of TiO2 with Au nanoparticles upon light irradiations. Absorption in the FUV region decreased and increased by the irradiation with ultraviolet and visible light, respectively. These spectral changes may reflect photo-induced electron transfer from TiO2 to Au nanoparticles under ultraviolet light and from Au nanoparticles to TiO2 under visible light, respectively.

Design and development of a new generation of UV-visible-light-driven nanosized codoped titanium dioxide photocatalysts and biocides/sporocides, and environmental applications

NASA Astrophysics Data System (ADS)

Hamal, Dambar B.

For solar environmental remediation, a new generation of nanosized (< 10 nm) titanium dioxide photocatalysts codoped with metals and nonmetals, or metals only were prepared by the xero-gel and aero-gel methods. For silver or cobalt-based xero-gel titanium dioxide photocatalysts, photoactivities tests revealed that codoping of titanium dioxide with a metal (1% Ag or 2% Co) and nonmetals (carbon and sulfur) is necessary to achieve high-activities for acetaldehyde degradation under visible light (wavelength > 420 nm). It was concluded that high visible-light-activities for acetaldehyde degradation over codoped titanium dioxide were attributed to an interplay of anatase crystallinity, high-surface area, reduced band-gap (< 3.0 eV), uniform dispersion of doped metal ions, and suppressed recombination rate of photogenerated electronhole pairs. Moreover, the nature and amount of codoped metals play a significant role in visible-light-induced photocatalysis. Metals (Al, Ga, and In) doped/codoped titanium dioxide photocatalysts were prepared by the aero-gel method. The photocatalytic studies showed that activities of metal doped/codoped photocatalysts under UV light (wavelength < 400 nm) were found to be dependent on pollutants. Indium demonstrated beneficial effects in both textural and photocatalytic properties. Gallium and indium codoped titanium dioxide photocatalysts displayed even better performance in the CO oxidation reaction under UV light. Notably, titanium dioxide codoped with Ga, In, and Pt, exhibited unique photoactivities for the CO oxidation under both UV and visible light irradiation, indicating that this system could have promise for the water-gas shift reaction for hydrogen production. Silver-based nanostructured titanium dioxide samples were developed for killing human pathogens (Escherichia coli cells and Bacillus subtilis spores). Biocidal tests revealed that silver, carbon, and sulfur codoped titanium dioxide nanoparticles (< 10 nm) possess very strong antimicrobial actions on both E. coli (logarithmic kill > 8) and B. subtilis spores (logarithmic kill > 5) for 30 minute exposures in dark conditions compared with Degussa P25. It was believed that the carbon and sulfur codoped titanium dioxide support and Ag species acted synergistically during deactivation of both E. coli and B. subtilis spores. Thus, titanium dioxide codoped with silver, carbon, sulfur can serve as a multifunctional generic biocide and a visible-light-active photocatalyst.

Pseudo and true visible light photocatalytic activity of nanotube titanic acid/graphene composites

NASA Astrophysics Data System (ADS)

Wang, Xiaodong; Liu, Xiaogang; Xue, Xiaoxiao; Pan, Hui; Zhang, Min; Li, Qiuye; Yu, Laigui; Yang, Jianjun; Zhang, Zhijun

2013-09-01

Nanotube titanic acid/graphene (NTA/Gr) composites were prepared by an easy hydrothermal treatment of graphene oxide (GO) and NTA in a mixed solvent of ethanol-water. As-prepared NTA/Gr composites and GO were characterized by means of Fourier transform infrared spectrometry, X-ray diffraction, diffuse-reflection spectrometry, thermal analysis, and transmission electron microscopy. Besides, the photocatalytic activities of as-prepared NTA/Gr composites were evaluated by monitoring the degradation of methyl orange (MO) under visible light irradiation. It has been found that extending hydrothermal reaction time (24 h instead of 3 h) leads to great changes in the morphology and crystal structure of as-prepared composites. Namely, the orthorhombic NTA (ca. 10 nm in diameter) in the composite transformed to anatase TiO2 particle (ca. 20-30 nm in diameter) while the Gr sheets (with micrometers-long wrinkles) in it transformed to a few Gr fragments (ca. 50 nm in diameter). Correspondingly, the NTA/Gr composite transformed to titanium dioxide/graphene (TiO2/Gr) composite. In the meantime, pure GO only has adsorption effect but it has no photocatalytic activity in the visible light region. Nevertheless, increasing Gr ratio results in enhanced visible light absorption capability and photocatalytic activity of NTA/Gr composites as well as the TiO2/Gr composites. This demonstrates that the true visible light photocatalytic activity of NTA/Gr composites as well as the TiO2/Gr composites for the degradation of MO is not as excellent as expected, and their high apparent activity is attributed to the strong adsorption of MO on the composites.

MoS2 quantum dots@TiO2 nanotube composites with enhanced photoexcited charge separation and high-efficiency visible-light driven photocatalysis

NASA Astrophysics Data System (ADS)

Zhao, Fenfen; Rong, Yuefei; Wan, Junmin; Hu, Zhiwen; Peng, Zhiqin; Wang, Bing

2018-03-01

MoS2 quantum dots (QDs) that are 5 nm in size were deposited on the surface of ultrathin TiO2 nanotubes (TNTs) with 5 nm wall thickness by using an improved hydrothermal method to form a MoS2 QDs@TNT visible-light photocatalyst. The ultrathin TNTs with high percentage of photocatalytic reactive facets were fabricated by the commercially available TiO2 nanoparticles (P25) through an improved hydrothermal method, and the MoS2 QDs were acquired by using a surfactant-assisted technique. The novel MoS2 QDs@TNT photocatalysts showed excellent photocatalytic activity with a decolorization rate of 92% or approximately 3.5 times more than that of pure TNTs for the high initial concentration of methylene blue solution (20 mg l-1) within 40 min under visible-light irradiation. MoS2 as the co-catalysts favored the broadening of TNTs into the visible-light absorption scope. The quantum confinement and edge effects of the MoS2 QDs and the heterojunction formed between the MoS2 QDs and TNTs efficiently extended the lifetime of photoinduced charges, impeded the recombination of photoexcited electron-hole pairs, and improved the visible-light-driven high-efficiency photocatalysis.

Temperature and salinity correction coefficients for light absorption by water in the visible to infrared spectral region.

PubMed

Röttgers, Rüdiger; McKee, David; Utschig, Christian

2014-10-20

The light absorption coefficient of water is dependent on temperature and concentration of ions, i.e. the salinity in seawater. Accurate knowledge of the water absorption coefficient, a, and/or its temperature and salinity correction coefficients, Ψ(T) and Ψ(S), respectively, is essential for a wide range of optical applications. Values are available from published data only at specific narrow wavelength ranges or at single wavelengths in the visible and infrared regions. Ψ(T) and Ψ(S) were therefore spectrophotometrically measured throughout the visible, near, and short wavelength infrared spectral region (400 to ~2700 nm). Additionally, they were derived from more precise measurements with a point-source integrating-cavity absorption meter (PSICAM) for 400 to 700 nm. When combined with earlier measurements from the literature in the range of 2600 - 14000 nm (wavenumber: 3800 - 700 cm(-1)), the coefficients are provided for 400 to 14000 nm (wavenumber: 25000 to 700 cm(-1)).

Complete erasing of ghost images caused by deeply trapped electrons on computed radiography plates

NASA Astrophysics Data System (ADS)

Ohuchi, H.; Kondo, Y.

2011-03-01

The ghost images, i.e., latent image that is unerasable with visible light (LIunVL) and reappearing image appeared on computed radiography (CR) plates were completely erased by simultaneous exposing them to filtered ultraviolet light and visible light. Three different types of CR plates (Agfa, Kodak, and Fuji) were irradiated with 50 kV X-ray beams in the dose range 8.1 mGy to 8.0 Gy, and then conventionally erased for 2 h with visible light. The remaining LIunVL could be erased by repeating 6 h simultaneous exposures to filtered ultraviolet light and visible light. After the sixth round of exposure, all the LIunVL in the three types of CR plates were erased to the same level as in an unirradiated plate and no latent images reappeared after storage at 0°C for 14 days. The absorption spectra of deep centers were specified using polychromatic ultraviolet light from a deep-ultraviolet lamp. It was found that deep centers showed a dominant peak in the absorption spectra at around 324 nm for the Agfa and Kodak plates, and at around 320 nm for the Fuji plate, in each case followed by a few small peaks. After completely erasing CR plates, these peaks were no longer observed.

Cube-like Cu{sub 2}MoS{sub 4} photocatalysts for visible light-driven degradation of methyl orange

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Ke; Chen, Wenxing; Chen, Haiping

2015-07-15

Cube-like Cu{sub 2}MoS{sub 4} nanoparticles with low-index facets and high crystallinity were fabricated via a hydrothermal method. The as-obtained nanocubes with an average size of 40-60 nm are composed of stacking-Cu{sub 2}MoS{sub 4} layers separated by a weak Van der Waals gap of 0.5 nm. A strong absorption at visible light region is observed in the nanocube aqueous solution, indicating its optical-band gap of 1.78 eV. The photocatalytic measurements reveal that the nanocubes can thoroughly induce the degradation of methyl orange under visible light irradiation with good structural stability. Our finding may provide a way in design and fabrication ofmore » transition metal dichalcogenide nanostructures for practical applications.« less

Development of a visible-light-sensitized europium complex for time-resolved fluorometric application.

PubMed

Jiang, Lina; Wu, Jing; Wang, Guilan; Ye, Zhiqiang; Zhang, Wenzhu; Jin, Dayong; Yuan, Jingli; Piper, James

2010-03-15

The time-resolved luminescence bioassay technique using luminescent lanthanide complexes as labels is a highly sensitive and widely used bioassay method for clinical diagnostics and biotechnology. A major drawback of the current technique is that the luminescent lanthanide labels require UV excitation (typically less than 360 nm), which can damage living biological systems and is holding back further development of time-resolved luminescence instruments. Herein we describe two approaches for preparing a visible-light-sensitized Eu(3+) complex in aqueous media for time-resolved fluorometric applications: a dissociation enhancement aqueous solution that can be excited by visible light for ethylenediaminetetraacetate (EDTA)-Eu(3+) detection and a visible-light-sensitized water-soluble Eu(3+) complex conjugated bovine serum albumin (BSA) for biolabeling and time-resolved luminescence bioimaging. In the first approach, a weakly acidic aqueous solution consisting of 4,4'-bis(1'',1'',1'',2'',2'',3'',3''-heptafluoro-4'',6''-hexanedion-6''-yl)-o-terphenyl (BHHT), 2-(N,N-diethylanilin-4-yl)-4,6-bis(3,5-dimethylpyrazol-1-yl)-1,3,5-triazine (DPBT), and Triton X-100 was prepared. This solution shows a strong luminescence enhancement effect for EDTA-Eu(3+) with a wide excitation wavelength range from UV to visible light (a maximum at 387 nm) and a long luminescence lifetime (520 micros), to provide a novel dissociation enhancement solution for time-resolved luminescence detection of EDTA-Eu(3+). In the second approach, a ternary Eu(3+) complex, 4,4'-bis(1'',1'',1'',2'',2'',3'',3''-heptafluoro-4'',6''-hexanedion-6''-yl)-chlorosulfo-o-terphenyl (BHHCT)-Eu(3+)-DPBT, was covalently bound to BSA to form a water-soluble BSA-BHHCT-Eu(3+)-DPBT conjugate. This biocompatible conjugate is of the visible-light excitable feature in aqueous media with a wide excitation wavelength range from UV to visible light (a maximum at 387 nm), a long luminescence lifetime (460 micros), and a higher quantum yield (27%). The conjugate was successfully used for streptavidin (SA) labeling and time-resolved luminescence imaging detection of three environmental pathogens, Giardia lamblia , Cryptosporidium muris , and Cryptosporidium parvum , in water samples. Our strategy gives a general idea for designing a visible-light-sensitized Eu(3+) complex for time-resolved luminescence bioassay applications.

AgBr/diatomite for the efficient visible-light-driven photocatalytic degradation of Rhodamine B

NASA Astrophysics Data System (ADS)

Fang, Jing; Zhao, Huamei; Liu, Qinglei; Zhang, Wang; Gu, Jiajun; Su, Yishi; Abbas, Waseem; Su, Huilan; You, Zhengwei; Zhang, Di

2018-03-01

The treatment of organic pollution via photocatalysis has been investigated for a few decades. However, earth-abundant, cheap, stable, and efficient substrates are still to be developed. Here, we prepare an efficient visible-light-driven photocatalyst via the deposition of Ag nanoparticles (< 60 nm) on diatomite and the conversion of Ag to AgBr nanoparticles (< 600 nm). Experimental results show that 95% of Rhodamine B could be removed within 20 min, and the degradation rate constant ( κ) is 0.11 min-1 under 100 mW/cm2 light intensity. For comparison, AgBr/SiO2 ( κ = 0.04 min-1) and commercial AgBr nanoparticles ( κ = 0.05 min-1) were measured as well. The experimental results reveal that diatomite acted more than a substrate benefiting the dispersion of AgBr nanoparticles, as well as a cooperator to help harvest visible light and adsorb dye molecules, leading to the efficient visible-light-driven photocatalytic performance of AgBr/diatomite. Considering the low cost (10 per ton) and large-scale availability of diatomite, our study provides the possibility to prepare other types of diatomite-based efficient photocatalytic composites with low-cost but excellent photocatalytic performance.

Visible light-induced photocatalytic degradation of Reactive Blue-19 over highly efficient polyaniline-TiO2 nanocomposite: a comparative study with solar and UV photocatalysis.

PubMed

Kalikeri, Shankramma; Kamath, Nidhi; Gadgil, Dhanashri Jayant; Shetty Kodialbail, Vidya

2018-02-01

Polyaniline-TiO 2 (PANI-TiO 2 ) nanocomposite was prepared by in situ polymerisation method. X-ray diffractogram (XRD) showed the formation of PANI-TiO 2 nanocomposite with the average crystallite size of 46 nm containing anatase TiO 2 . The PANI-TiO 2 nanocomposite consisted of short-chained fibrous structure of PANI with spherical TiO 2 nanoparticles dispersed at the tips and edge of the fibres. The average hydrodynamic diameter of the nanocomposite was 99.5 nm. The band gap energy was 2.1 eV which showed its ability to absorb light in the visible range. The nanocomposite exhibited better visible light-mediated photocatalytic activity than TiO 2 (Degussa P25) in terms of degradation of Reactive Blue (RB-19) dye. The photocatalysis was favoured under initial acidic pH, and complete degradation of 50 mg/L dye could be achieved at optimum catalyst loading of 1 g/L. The kinetics of degradation followed the Langmuir-Hinshelhood model. PANI-TiO 2 nanocomposite showed almost similar photocatalytic activity under UV and visible light as well as in the solar light which comprises of radiation in both UV and visible light range. Chemical oxygen demand removal of 86% could also be achieved under visible light, confirming that simultaneous mineralization of the dye occurred during photocatalysis. PANI-TiO 2 nanocomposites are promising photocatalysts for the treatment of industrial wastewater containing RB-19 dye.

Plate-Focusing Based on a Meta-Molecule of Dendritic Structure in the Visible Frequency.

PubMed

Cheng, Suna; An, Di; Chen, Huan; Zhao, Xiaopeng

2018-05-31

To study the potential application of metasurfaces in lens technology, we propose a dendritic meta-molecule surface (also referred to as a dendritic metasurface) and realize the focusing effect in the visible spectrum through simulations and experiments. Using asymmetric dendritic structures, this metasurface can achieve distinct broadband anomalous reflection and refraction. When the metasurface is rotated by 180° around the z axis, anomalous reflection and refraction in vertically incident optical waves are in opposite directions. Considering this feature, a metasurface is designed to achieve a prominent plate-focusing effect. Samples with a transmission peak of green light at 555 nm, yellow light at 580 nm, and red light at 650 nm were prepared using bottom-up electrochemical deposition, and the focus intensity of approximately 10% and focal length of almost 600 µm were experimentally demonstrated.

Far-ultraviolet spectral changes of titanium dioxide with gold nanoparticles by ultraviolet and visible light.

PubMed

Tanabe, Ichiro; Kurawaki, Yuji

2018-05-15

Attenuated total reflectance spectra including the far-ultraviolet (FUV, ≤200nm) region of titanium dioxide (TiO 2 ) with and without gold (Au) nanoparticles were measured. A newly developed external light-irradiation system enabled to observe spectral changes of TiO 2 with Au nanoparticles upon light irradiations. Absorption in the FUV region decreased and increased by the irradiation with ultraviolet and visible light, respectively. These spectral changes may reflect photo-induced electron transfer from TiO 2 to Au nanoparticles under ultraviolet light and from Au nanoparticles to TiO 2 under visible light, respectively. Copyright © 2017 Elsevier B.V. All rights reserved.

Photochemical Construction of Carbonitride Structures for Red-Light Redox Catalysis.

PubMed

Yang, Pengju; Wang, Ruirui; Zhou, Min; Wang, Xinchen

2018-05-22

Metal-free carbonitride(CN) semiconductors are appealing light-transducers for photocatalytic redox reactions owing to the unique band gap and stability. To harness solar energy efficiently, CN catalysts that are active over a wider range of the visible spectrum are desired. Now a photochemical approach has been used to prepare a new-type triazine-based CN structure. The obtained CN shows extraordinary light-harvesting characteristics, with suitable semiconductor-redox potentials. The light absorption edge of the CN reaches up to 735 nm, which is significantly longer than that of the conventional CN semiconductor at about 460 nm. As expected, the CN can efficiently catalyze oxidation of alcohols and reduction of CO 2 with visible light, even under red-light irradiation. The results represent an important step toward the development of red-light-responsive triazine-based structures for solar applications. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

In-line monitoring technique with visible light from 1.3 microm-band SHG module for optical access systems.

PubMed

Kubo, Takahiro; Taniguchi, Tomohiro; Tadanaga, Osamu; Sakurai, Naoya; Kimura, Hideaki; Hadama, Hisaya; Asobe, Masaki

2010-02-01

We propose an in-line monitoring technique that uses 650 nm visible light for performing maintenance work on Fiber-to-the-home (FTTH) network quickly without the need for measuring skills or external devices. This technique is characterized by visible light (650 nm) generated by an SHG module from the 1.3 microm-band line signal. We fabricate a 1.3 microm-band quasi phase matched LiNbO(3) (QPM-LN) module, and the measure the 650 nm second harmonic (SH) power to test the proposed short-pulse modulation method. The results confirm the feasibility of the short-pulse modulation method with different peak factors (PFs) (1.0-7.3). We also examine the effect of short-pulse modulation on system performance at the optical receiver by measuring the bit error rate (BER) of received data (1.25 Gb/s). The BER is basically unaffected by the PF (1.0-5.5). This means that the proposed technique has little influence on data reception as regards PF (1.0-5.5).

The modification of spectral characteristics of cytostatics by optical beams

NASA Astrophysics Data System (ADS)

Pascu, Mihail Lucian; Brezeanu, Mihail; Carstocea, Benone D.; Voicu, Letitia; Gazdaru, Doina M.; Smarandache, Adriana A.

2004-10-01

Besides the biochemical action of methotrexate (MTX) and 5-fluorouracil (FU) their effect in destroying cancer tumours could be enhanced by exposure to light at different doses. Absorption, excitation and emission spectra of 10-4M - 10-5M MTX solutions in natural saline and sodium hydroxide at pH = 8.4 were measured, while their exposure to coherent and uncoherent light in the visible and near ultraviolet (UV) spectral ranges was made (Hg lamps and Nitrogen pulsed laser radiation were used). Absorption spectra exhibit spectral bands in the range 200 nm - 450 nm. The 200 - 450 nm excitation spectra were measured with emission centered on 470 nm; MTX fluorescence excitation was measured at 390 nm and the emission was detected between 400 nm and 600 nm showing a maximum at 470 nm. Spectra modifications, nonlinearly depending on exposure time (varying from 1 min to 20 min), evidenced MTX photo-dissociation to the fluorescent compound 2,4 diamino-formylpteridine. In the 5-FU case the absorption spectra exhibit bands between 200 nm and 450 nm. The emission fluorescence spectra were measured between 400 nm and 600 nm, with λex = 350 nm for UV Hg lamp and with λex = 360 nm for laser irradiated samples; at irradiation with N2 laser emitted radiation the excitation spectra were measured in the range of 200 nm - 400 nm, with λem = 440 nm. New vascularity rapid destruction was observed for conjunctive impregnated with 5-FU solution whilst exposed to incoherent UV and visible light.

Spectral fluorescent properties of tissues in vivo with excitation in the red wavelength range

NASA Astrophysics Data System (ADS)

Stratonnikov, Alexander A.; Loschenov, Victor B.; Klimov, D. V.; Edinac, N. E.; Wolnukhin, V. A.; Strashkevich, I. A.

1997-12-01

The spectral fluorescence analysis is a promising method for differential tissue diagnostic. Usually the UV and visible light is used for fluorescence excitation with emission registration in the visible wavelength range. The light penetration length in this wavelength range is very small allowing one to analyze only the surface region of the tissue. Here we present the tissue fluorescent spectra in vivo excited in the red wavelength region. As excitation light source we used compact He-Ne laser (632.8 nm) and observed the fluorescence in 650 - 800 nm spectral range. The various tissues including normal skin, psoriasis, tumors, necrosis as well as photosensitized tissues have been measured.

In vivo ratiometric Zn2+ imaging in zebrafish larvae using a new visible light excitable fluorescent sensor.

PubMed

Liu, Zhipeng; Zhang, Changli; Chen, Yuncong; Qian, Fang; Bai, Yang; He, Weijiang; Guo, Zijian

2014-02-07

A visible light excitable ratiometric Zn(2+) sensor was developed by integrating a Zn(2+) chelator as the ICT donor of the fluorophore sulfamoylbenzoxadiazole, which displays the Zn(2+)-induced hypsochromic emission shift (40 nm) and favors the in vivo ratiometric Zn(2+) imaging in zebrafish larvae.

SU-F-T-166: On the Nature of the Background Visible Light Observed in Fiber Optic Dosimetry of Proton Beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Darafsheh, A; Kassaee, A; Finlay, J

Purpose: The nature of the background visible light observed during fiber optic dosimetry of proton beams, whether it is due to Cherenkov radiation or not, has been debated in the literature recently. In this work, experimentally and by means of Monte Carlo simulations, we shed light on this problem and investigated the nature of the background visible light observed in fiber optics irradiated with proton beams. Methods: A bare silica fiber optics was embedded in tissue-mimicking phantoms and irradiated with clinical proton beams with energies of 100–225 MeV at Roberts Proton Therapy Center. Luminescence spectroscopy was performed by a CCD-coupledmore » spectrograph to analyze in detail the emission spectrum of the fiber tip across the visible range of 400–700 nm. Monte Carlo simulation was performed by using FLUKA Monte Carlo code to simulate Cherenkov light and ionizing radiation dose deposition in the fiber. Results: The experimental spectra of the irradiated silica fiber shows two distinct peaks at 450 and 650 nm, whose spectral shape is different from that of Cherenkov radiation. We believe that the nature of these peaks are connected to the point defects of silica including oxygen-deficiency center (ODC) and non-bridging oxygen hole center (NBOHC). Monte Carlo simulations confirmed the experimental observations that Cherenkov radiation cannot be solely responsible for such a signal. Conclusion: We showed that Cherenkov radiation is not the dominant visible signal observed in bare fiber optics irradiated with proton beams. We observed two distinct peaks at 450 and 650 nm whose nature is connected with the point defects of silica fiber including oxygen-deficiency center and non-bridging oxygen hole center.« less

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

PubMed

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

2016-03-31

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

Simple Hydrogen Plasma Doping Process of Amorphous Indium Gallium Zinc Oxide-Based Phototransistors for Visible Light Detection.

PubMed

Kang, Byung Ha; Kim, Won-Gi; Chung, Jusung; Lee, Jin Hyeok; Kim, Hyun Jae

2018-02-28

A homojunction-structured amorphous indium gallium zinc oxide (a-IGZO) phototransistor that can detect visible light is reported. The key element of this technology is an absorption layer composed of hydrogen-doped a-IGZO. This absorption layer is fabricated by simple hydrogen plasma doping, and subgap states are induced by increasing the amount of hydrogen impurities. These subgap states, which lead to a higher number of photoexcited carriers and aggravate the instability under negative bias illumination stress, enabled the detection of a wide range of visible light (400-700 nm). The optimal condition of the hydrogen-doped absorption layer (HAL) is fabricated at a hydrogen partial pressure ratio of 2%. As a result, the optimized a-IGZO phototransistor with the HAL exhibits a high photoresponsivity of 1932.6 A/W, a photosensitivity of 3.85 × 10 6 , and a detectivity of 6.93 × 10 11 Jones under 635 nm light illumination.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mokhtari, Narges; Daneshpajouh, Shahram; Seyedbagheri, Seyedali

This study has investigated different visible-light irradiation's effect on the formation of silver nanoparticles from silver nitrate using the culture supernatant of Klebsiella pneumonia. Our study shows that visible-light emission can significantly prompt the synthesis of silver nanoparticles. Also, the study experimentally investigated the liquid mixing process effect on silver nanoparticle synthesis by visible-light irradiation. This study successfully synthesized uniformly dispersed silver nanoparticles with a uniform size and shape in the range of 1-6 nm with an average size of 3 nm. Furthermore, the study investigated the mechanism of the reduction of silver ions by culture supernatant of K. pneumonia,more » and used X-ray diffraction to characterize silver chloride as an intermediate compound. Silver chloride was prepared synthetically and used as a substrate for the synthesis of silver nanoparticles by culture supernatant of K. pneumonia. The silver nanoparticles have been prepared from silver chloride during this investigation for the first time.« less

Luminescence spectroscopic observation of singlet oxygen formation in extra virgin olive oil as affected by irradiation light wavelengths, 1,4-diazabicyclo[2.2.2]octane, irradiation time, and oxygen bubbling.

PubMed

Jung, Mun Y; Choi, Dong S; Park, Ki H; Lee, Bosoon; Min, David B

2011-01-01

A spectrofluorometer equipped with a highly sensitive near-IR InGaAs detector was used for the direct visualization of singlet oxygen emission at 1268 nm in olive oil during light irradiation with various different wavelengths. The virgin olive oil in methylene chloride (20% w/v, oxygen saturated) was irradiated at the 301, 417, 454, 483, and 668 nm, then the emission at 1268 nm, singlet oxygen dimole decaying was observed. The result showed the highest production of (1)O(2) with light irradiation at 417 nm, and followed by at 668 nm in virgin olive oil, indicating that pheophytin a and chlorophyll a were the most responsible components for the production of singlet oxygen. The UV light irradiations at the wavelength of 200, 250, and 300 nm did not induce any detectable luminescence emission at 1268 nm, but 350 nm produced weak emission at 1269 nm. The quantity of (1)O(2) produced with excitation at 350 nm was about 1/6 of that of irradiation at 417 nm. Addition of an efficient (1)O(2) quencher, 1,4-diazabicyclo[2.2.2]octane, in virgin olive oil in methylene chloride greatly decreased the luminescence emission at 1268 nm, confirming the singlet oxygen production in olive oil. Singlet oxygen production was more efficient in oxygen-purged virgin olive oil than in oxygen non-purged olive oil. This represents first report on the direct observation of singlet oxygen formation in olive oil as well as in real-food system after visible light illumination. Practical Application: The present results show the positive evidence of the singlet oxygen involvement in rapid oxidative deterioration of virgin olive oil under visible light. This paper also shows the effects of different wavelength of light irradiation on the formation of singlet oxygen in olive oil. The present results would provide important information for the understanding of the mechanism involved in rapid oxidative quality deterioration of virgin olive oil under light illumination and for searching the preventive methods of deterioration of olive oil quality under light.

Two dimensional visible-light-active Pt-BiOI photoelectrocatalyst for efficient ethanol oxidation reaction in alkaline media

NASA Astrophysics Data System (ADS)

Zhai, Chunyang; Hu, Jiayue; Sun, Mingjuan; Zhu, Mingshan

2018-02-01

Two dimensional (2D) BiOI nanoplates were synthesized and used as support for the deposition of Pt nanoparticles. Owing to broad visible light absorption (up to 660 nm), the as-obtained Pt-BiOI electrode was used as effective photoelectrocatalyst in the application of catalytic ethanol oxidation in alkaline media under visible light irradiation. Compared to dark condition, the Pt-BiOI modified electrode displayed 3 times improved catalytic activity towards ethanol oxidation under visible light irradiation. The synergistic effect of electrocatalytic and photocatalytic, and the unique of 2D structures contribute to the improvement of catalytic activity. The mechanism of enhanced photoelectrocatalytic process is proposed. The present results suggest that 2D visible-light-activated BiOI can be served as promising support for the decoration of Pt and applied in the fields of photoelectrochemical and photo-assisted fuel cell applications

Donor-acceptor-pair emission in fluorescent 4H-SiC grown by PVT method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Xi, E-mail: liuxi@mail.sic.ac.cn; Zhuo, Shi-Yi; Gao, Pan

Fluorescent SiC, which contains donor and acceptor impurities with optimum concentrations, can work as a phosphor for visible light emission by donor-acceptor-pair (DAP) recombination. In this work, 3 inch N-B-Al co-doped fluorescent 4H-SiC crystals are prepared by PVT method. The p-type fluorescent 4H-SiC with low aluminum doping concentration can show intensive yellow-green fluorescence at room temperature. N-B DAP peak wavelength shifts from 578nm to 525nm and weak N-Al DAP emission occurred 403/420 nm quenches, when the temperature increases from 4K to 298K. The aluminum doping induces higher defect concentration in the fluorescent crystal and decreases optical transmissivity of the crystalmore » in the visible light range. It triggers more non-radiative recombination and light absorption losses in the crystal.« less

Spectrally-resolved measurements of aerosol extinction at ultraviolet and visible wavelengths

NASA Astrophysics Data System (ADS)

Flores, M.; Washenfelder, R. A.; Brock, C. A.; Brown, S. S.; Rudich, Y.

2012-12-01

Aerosols play an important role in the Earth's radiative budget. Aerosol extinction includes both the scattering and absorption of light, and these vary with wavelength, aerosol diameter, and aerosol composition. Historically, aerosol absorption has been measured using filter-based or extraction methods that are prone to artifacts. There have been few investigations of ambient aerosol optical properties at the blue end of the visible spectrum and into the ultraviolet. Brown carbon is particularly important in this spectral region, because it both absorbs and scatters light, and encompasses a large and variable group of organic compounds from biomass burning and secondary organic aerosol. We have developed a laboratory instrument that combines new, high-power LED light sources with high-finesse optical cavities to achieve sensitive measurements of aerosol optical extinction. This instrument contains two broadband channels, with spectral coverage from 360 - 390 nm and 385 - 420 nm. Using this instrument, we report aerosol extinction in the ultraviolet and near-visible spectral region as a function of chemical composition and structure. We have measured the extinction cross-sections between 360 - 420 nm with 0.5 nm resolution using different sizes and concentrations of polystyrene latex spheres, ammonium sulfate, and Suwannee River fulvic acid. Fitting the real and imaginary part of the refractive index allows the absorption and scattering to be determined.

On the evaluation of air mass factors for atmospheric near-ultraviolet and visible absorption spectroscopy

NASA Technical Reports Server (NTRS)

Perliski, Lori M.; Solomon, Susan

1993-01-01

The interpretation of UV-visible twilight absorption measurements of atmospheric chemical constituents is dependent on how well the optical path, or air mass factor, of light collected by the spectrometer is understood. A simple single scattering model and a Monte Carlo radiative transfer scheme have been developed to study the effects of multiple scattering, aerosol scattering, surface albedo and refraction on air mass factors for scattered light observations. At fairly short visible wavelengths (less than about 450 nm), stratospheric air mass factors are found to be relatively insensitive to multiple scattering, surface albedo and refraction, as well as aerosol scattering by background aerosols. Longer wavelengths display greater sensitivity to refraction and aerosol scattering. Tropospheric air mass factors are found to be highly dependent on aerosol scattering, surface albedo and, at long visible wavelengths (about 650 nm), refraction. Absorption measurements of NO2 and O4 are shown to support these conclusions.

Effect of light quality on development of fruiting bodies of Panus fragilis

Treesearch

Orson K. Miller; John G. Palmer

1977-01-01

Under a system that permits mass screening of mycelia within bands of the visible spectrum, fruit bodies initiated and developed in two light bands (387-400nm and 425-430nm) in axenic culture. Either or both of these light bands will trigger fruitbody initiation at as low an energy level as 0.2 K (1 K = 1,000 microwatts/cm2). Maturation of sporocarp and hymenium...

Which way is up? Asymmetric spectral input along the dorsal-ventral axis influences postural responses in an amphibious annelid.

PubMed

Jellies, John

2014-11-01

Medicinal leeches are predatory annelids that exhibit countershading and reside in aquatic environments where light levels might be variable. They also leave the water and must contend with terrestrial environments. Yet, leeches generally maintain a dorsal upward position despite lacking statocysts. Leeches respond visually to both green and near-ultraviolet (UV) light. I used LEDs to test the hypothesis that ventral, but not dorsal UV would evoke compensatory movements to orient the body. Untethered leeches were tested using LEDs emitting at red (632 nm), green (513 nm), blue (455 nm) and UV (372 nm). UV light evoked responses in 100 % of trials and the leeches often rotated the ventral surface away from it. Visible light evoked no or modest responses (12-15 % of trials) and no body rotation. Electrophysiological recordings showed that ventral sensilla responded best to UV, dorsal sensilla to green. Additionally, a higher order interneuron that is engaged in a variety of parallel networks responded vigorously to UV presented ventrally, and both the visible and UV responses exhibited pronounced light adaptation. These results strongly support the suggestion that a dorsal light reflex in the leech uses spectral comparisons across the dorsal-ventral axis rather than, or in addition to, luminance.

A filterless, visible-blind, narrow-band, and near-infrared photodetector with a gain

NASA Astrophysics Data System (ADS)

Shen, Liang; Zhang, Yang; Bai, Yang; Zheng, Xiaopeng; Wang, Qi; Huang, Jinsong

2016-06-01

In many applications of near-infrared (NIR) light detection, a band-pass filter is needed to exclude the noise caused by visible light. Here, we demonstrate a filterless, visible-blind, narrow-band NIR photodetector with a full-width at half-maximum of <50 nm for the response spectrum. These devices have a thick (>4 μm) nanocomposite absorbing layers made of polymer-fullerene:lead sulfide (PbS) quantum dots (QDs). The PbS QDs yield a photoconductive gain due to their hole-trapping effect, which effectively enhances both the responsivity and the visible rejection ratio of the external quantum efficiency by >10 fold compared to those without PbS QDs. Encouragingly, the inclusion of the PbS QDs does not increase the device noise. We directly measured a noise equivalent power (NEP) of 6.1 pW cm-2 at 890 nm, and a large linear dynamic range (LDR) over 11 orders of magnitude. The highly sensitive visible-blind NIR narrow-band photodetectors may find applications in biomedical engineering.

Irradiation of skin with visible light induces reactive oxygen species and matrix-degrading enzymes.

PubMed

Liebel, Frank; Kaur, Simarna; Ruvolo, Eduardo; Kollias, Nikiforos; Southall, Michael D

2012-07-01

Daily skin exposure to solar radiation causes cells to produce reactive oxygen species (ROS), which are a primary factor in skin damage. Although the contribution of the UV component to skin damage has been established, few studies have examined the effects of non-UV solar radiation on skin physiology. Solar radiation comprises <10% of UV, and thus the purpose of this study was to examine the physiological response of skin to visible light (400-700 nm). Irradiation of human skin equivalents with visible light induced production of ROS, proinflammatory cytokines, and matrix metalloproteinase (MMP)-1 expression. Commercially available sunscreens were found to have minimal effects on reducing visible light-induced ROS, suggesting that UVA/UVB sunscreens do not protect the skin from visible light-induced responses. Using clinical models to assess the generation of free radicals from oxidative stress, higher levels of free radical activity were found after visible light exposure. Pretreatment with a photostable UVA/UVB sunscreen containing an antioxidant combination significantly reduced the production of ROS, cytokines, and MMP expression in vitro, and decreased oxidative stress in human subjects after visible light irradiation. Taken together, these findings suggest that other portions of the solar spectrum aside from UV, particularly visible light, may also contribute to signs of premature photoaging in skin.

Visible camera cryostat design and performance for the SuMIRe Prime Focus Spectrograph (PFS)

NASA Astrophysics Data System (ADS)

Smee, Stephen A.; Gunn, James E.; Golebiowski, Mirek; Hope, Stephen C.; Madec, Fabrice; Gabriel, Jean-Francois; Loomis, Craig; Le fur, Arnaud; Dohlen, Kjetil; Le Mignant, David; Barkhouser, Robert; Carr, Michael; Hart, Murdock; Tamura, Naoyuki; Shimono, Atsushi; Takato, Naruhisa

2016-08-01

We describe the design and performance of the SuMIRe Prime Focus Spectrograph (PFS) visible camera cryostats. SuMIRe PFS is a massively multi-plexed ground-based spectrograph consisting of four identical spectrograph modules, each receiving roughly 600 fibers from a 2394 fiber robotic positioner at the prime focus. Each spectrograph module has three channels covering wavelength ranges 380 nm - 640 nm, 640 nm - 955 nm, and 955 nm - 1.26 um, with the dispersed light being imaged in each channel by a f/1.07 vacuum Schmidt camera. The cameras are very large, having a clear aperture of 300 mm at the entrance window, and a mass of 280 kg. In this paper we describe the design of the visible camera cryostats and discuss various aspects of cryostat performance.

Spectral transmission of the human crystalline lens in adult and elderly persons: color and total transmission of visible light.

PubMed

Artigas, Jose M; Felipe, Adelina; Navea, Amparo; Fandiño, Adriana; Artigas, Cristina

2012-06-26

To experimentally measure the spectral transmission of human crystalline lenses belonging to adult and elderly persons, and to determine the color and total transmission of visible light of such crystalline lenses. The spectral transmission curve of 32 human crystalline lenses was measured using a PerkinElmer 800UV/VIS spectrometer. Total transmission of visible light and the chromatic coordinates of these crystalline lenses were determined from these curves for solar illumination. The crystalline lens that filters UV and its transmission in the visible spectrum decreases with age; such a decrease is greater for short wavelengths. The total transmission of visible light decreases, especially after the age of 70 years, and the crystalline color becomes yellower and saturated. The great variability existing in the spectral transmission of the human crystalline lens is lesser between the ages of 40 and 59 years, but greater from the age of 60 and older. The decrement in transmittance between these two age groups varies from 40% for 420 nm to 18% for 580 nm. Nevertheless, it is proven that age is not the only parameter affecting crystalline transmission. In the range of 40 to 59 years, age does not bear an influence on total transmission of light, but from 60 years and older it does. Moreover, the light transmitted decreases with age. This total transmission of light is similar to or lower than the amount that the different intraocular lenses transmit, even with a yellow or orange filter. The color of the human lens becomes yellowish and saturated with age.

Visible light detoxification by 2,9,16,23-tetracarboxyl phthalocyanine copper modified amorphous titania

NASA Astrophysics Data System (ADS)

Chen, Feng; Deng, Zhigang; Li, Xiaopei; Zhang, Jinlong; Zhao, Jincai

2005-10-01

Visible light detoxification of methyl orange (MO) was achieved with a photo-stable 2,9,16,23-tetracarboxyl phthalocyanine (TcPc)/amorphous TiO 2 hybrid photocatalyst. TcPc/amorphous TiO 2 exhibits an excellent photocatalytic activity under visible irradiation ( λ > 550 nm). Besides the active oxygen species, sensitizer radical cation, TcPc + rad , was also found to react with MO directly and induce the photodegradation of MO significantly for the first time in dye sensitized photocatalytic system.

The photochemistry in Photosystem II at 5 K is different in visible and far-red light.

PubMed

Mokvist, Fredrik; Sjöholm, Johannes; Mamedov, Fikret; Styring, Stenbjörn

2014-07-08

We have earlier shown that all electron transfer reactions in Photosystem II are operational up to 800 nm at room temperature [Thapper, A., et al. (2009) Plant Cell 21, 2391-2401]. This led us to suggest an alternative charge separation pathway for far-red excitation. Here we extend these studies to a very low temperature (5 K). Illumination of Photosystem II (PS II) with visible light at 5 K is known to result in oxidation of almost similar amounts of YZ and the Cyt b559/ChlZ/CarD2 pathway. This is reproduced here using laser flashes at 532 nm, and we find the partition ratio between the two pathways to be 1:0.8 at 5 K [the partition ratio is here defined as (yield of YZ/CaMn4 oxidation):(yield of Cyt b559/ChlZ/CarD2 oxidation)]. The result using far-red laser flashes is very different. We find partition ratios of 1.8 at 730 nm, 2.7 at 740 nm, and >2.7 at 750 nm. No photochemistry involving these pathways is observed above 750 nm at this temperature. Thus, far-red illumination preferentially oxidizes YZ, while the Cyt b559/ChlZ/CarD2 pathway is hardly touched. We propose that the difference in the partition ratio between visible and far-red light at 5 K reflects the formation of a different first stable charge pair. In visible light, the first stable charge pair is considered to be PD1+QA-. In contrast, we propose that the electron hole is residing on the ChlD1 molecule after illumination by far-red light at 5 K, resulting in the first stable charge pair being ChlD1+QA-. ChlD1 is much closer to YZ (11.3 Å) than to any component in the Cyt b559/ChlZ/CarD2 pathway (shortest ChlD1-CarD2 distance of 28.8 Å). This would then explain that far-red illumination preferentially drives efficient electron transfer from YZ. We also discuss mechanisms for accounting for the absorption of the far-red light and the existence of hitherto unobserved charge transfer states. The involvement of two or more of the porphyrin molecules in the core of the Photosystem II reaction center is proposed.

Solution-processed PCDTBT capped low-voltage InGaZnO{sub x} thin film phototransistors for visible-light detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Han; Xiao, Yubin; Chen, Zefeng

The effects of visible-light detection based on solution processed poly[N-9′′-hepta-decanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′, 3′benzothiadiazole) (PCDTBT) capped InGaZnOx (IGZO) phototransistors with Al{sub 2}O{sub x} serving as gate dielectric are investigated in this paper. The high-k dielectric is used to lower the device operating voltage down to 2 V. Photons emitted from laser sources with the wavelengths (λ) of 532 nm and 635 nm are absorbed through the layer of PCDTBT to generate electron-hole-pairs (EHPs). After the separation of EHPs, electrons are injected into IGZO layer through the p-n junction formed between the IGZO (n-type semiconductor) and the PCDTBT (p-type semiconductor). The photo-generated carriers boost the drain currentmore » of the transistors as well as bring about the negative threshold voltage shift. Significant enhanced detection performance is achieved under the laser wavelength of 532 nm. The highest photoresponsivity reaches up to 20 A/W, while the photoresponse rise time comes to 10 ms and the fall time comes to approximate 76 ms, which is much faster than trap assisted IGZO visible light detection. The fabricated phototransistors favor the application of visible-light detectors and/or optical switches.« less

Photocatalytic hydrogen generation from water under visible light using core/shell nano-catalysts.

PubMed

Wang, X; Shih, K; Li, X Y

2010-01-01

A microemulsion technique was employed to synthesize nano-sized photocatalysts with a core (CdS)/shell (ZnS) structure. The primary particles of the photocatalysts were around 10 nm, and the mean size of the catalyst clusters in water was about 100 nm. The band gaps of the catalysts ranged from 2.25 to 2.46 eV. The experiments of photocatalytic H(2) generation showed that the catalysts (CdS)(x)/(ZnS)(1-x) with x ranging from 0.1 to 1 were able to produce hydrogen from water photolysis under visible light. The catalyst with x=0.9 had the highest rate of hydrogen production. The catalyst loading density also influenced the photo-hydrogen production rate, and the best catalyst concentration in water was 1 g L(-1). The stability of the nano-catalysts in terms of size, morphology and activity was satisfactory during an extended test period for a specific hydrogen production rate of 2.38 mmol g(-1) L(-1) h(-1) and a quantum yield of 16.1% under visible light (165 W Xe lamp, lambda>420 nm). The results demonstrate that the (CdS)/(ZnS) core/shell nano-particles are a novel photo-catalyst for renewable hydrogen generation from water under visible light. This is attributable to the large band-gap ZnS shell that separates the electron/hole pairs generated by the CdS core and hence reduces their recombinations.

Study of cylindrical optical micro-structure technology used in infrared laser protection

NASA Astrophysics Data System (ADS)

Sun, Yanjun; Liu, Shunrui; Wang, Zhining; Zhao, Yixuan; Wu, Boqi; Leng, Yanbing; Wang, Li

2016-10-01

The paper aimed at the problem that strong absorption in visible wavelengths and equipment or operator injury caused by specular reflection exist in infrared laser protection technology to propose an infrared laser non-specular reflection optical micro-structure formed from optical window surface. It has the function of little effect on visible light transmission and large-angle scattering to 1064nm infrared laser in order to enable laser protection. The paper uses light track method to design double-side micro-cylindrical lens arrays with dislocation construction. Array period T and curvature radius of lens units R should meet the condition:0

Dynamic Features for Iris Recognition.

PubMed

da Costa, R M; Gonzaga, A

2012-08-01

The human eye is sensitive to visible light. Increasing illumination on the eye causes the pupil of the eye to contract, while decreasing illumination causes the pupil to dilate. Visible light causes specular reflections inside the iris ring. On the other hand, the human retina is less sensitive to near infra-red (NIR) radiation in the wavelength range from 800 nm to 1400 nm, but iris detail can still be imaged with NIR illumination. In order to measure the dynamic movement of the human pupil and iris while keeping the light-induced reflexes from affecting the quality of the digitalized image, this paper describes a device based on the consensual reflex. This biological phenomenon contracts and dilates the two pupils synchronously when illuminating one of the eyes by visible light. In this paper, we propose to capture images of the pupil of one eye using NIR illumination while illuminating the other eye using a visible-light pulse. This new approach extracts iris features called "dynamic features (DFs)." This innovative methodology proposes the extraction of information about the way the human eye reacts to light, and to use such information for biometric recognition purposes. The results demonstrate that these features are discriminating features, and, even using the Euclidean distance measure, an average accuracy of recognition of 99.1% was obtained. The proposed methodology has the potential to be "fraud-proof," because these DFs can only be extracted from living irises.

Light-induced inhibition of laccase in Pycnoporus sanguineus.

PubMed

Hernández, Christian A; Perroni, Yareni; Pérez, José Antonio García; Rivera, Beatriz Gutiérrez; Alarcón, Enrique

2016-03-01

The aim was to determine which specific regions of the visible light spectrum were responsible for the induction or inhibition of laccase in Pycnoporus sanguineus. Cultures were exposed to various bandwidth lights: blue (460 nm), green (525 nm), white (a combination of 460 and 560 nm), red (660 nm), and darkness. The results indicate that short wavelengths strongly inhibit the production of laccase: green (3.76 ± 1.12 U/L), blue (1.94 ± 0.36 U/L), and white (1.05 ± 0.21 U/L) in proportions of 85.8, 92.6, and 96.0%, respectively; whereas long wavelengths inhibit laccase production only partially i.e., red light (14.05 ± 4.79 U/L) in a proportion of 46.8%. Maximum activity was induced in absence of visible light (30 °C, darkness), i.e., 30.76 ± 4.0 U/L. It is concluded that the production of laccase in P. sanguineus responds to light stimuli [measured as wavelengths and lx] and that it does so inversely. This can be explained as an ecological mechanism of environmental recognition, given that P. sanguineus develops inside lignocellulose structures in conditions of darkness. The presence of short wavelength light (460-510 nm) would indicate that the organism finds itself in an external environment, unprovided of lignin, and that it is therefore unnecessary to secrete laccase. This possible new regulation in the laccase production in P. sanguineus has important biotechnological implications, for it would be possible to control the production of laccase using light stimuli.

Visible red light enhances physiological anagen entry in vivo and has direct and indirect stimulative effects in vitro.

PubMed

Sheen, Yi-Shuan; Fan, Sabrina Mai-Yi; Chan, Chih-Chieh; Wu, Yueh-Feng; Jee, Shiou-Hwa; Lin, Sung-Jan

2015-01-01

Hair follicles are located at the interface of the external and internal environments and their cycling has been shown to be regulated by intra- and extra-follicular factors. The aim of this study is to examine whether or how hair follicles respond to visible light. We examined the effect of 3 mW red (630 nm, 1 J/cm(2)), 2 mW green (522 nm, 1 J/cm(2)), and 2 mW blue light (463 nm, 1 J/cm(2)) on telogen in mice for 3 weeks. The photobiologic effects of red light on cell proliferation of outer root sheath keratinocytes and dermal papilla cells were studied in vitro. We found that red light accelerated anagen entry faster than green and blue light in mice. Red light irradiation stimulated the proliferation of both outer root sheath keratinocytes and dermal papilla cells in a dose-dependent manner by promoting cell cycle progression. This stimulative effect was mediated via extracellular signal-regulated kinase phosphorylation in both cells. In a co-culture condition, dermal papilla cells irradiated by red light further enhanced keratinocyte proliferation, suggesting enhanced epithelial-mesenchymal interaction. In search for factors that mediated this paracrine effect, we found fibroblast growth factor 7 was upregulated in both mRNA and protein levels. The stimulative paracrine effect on keratinocytes was significantly inhibited by neutralizing antibody against fibroblast growth factor 7. These results suggest that hair follicles respond to visible light in vivo. Red light may promote physiological telogen to anagen transition by directly stimulating outer root sheath keratinocytes and indirectly by enhancing epithelial-mesenchymal interaction in vitro. © 2014 Wiley Periodicals, Inc.

Disparity in Cutaneous Pigmentary Response to LED vs Halogen Incandescent Visible Light: Results from a Single Center, Investigational Clinical Trial Determining a Minimal Pigmentary Visible Light Dose.

PubMed

Soleymani, Teo; Cohen, David E; Folan, Lorcan M; Okereke, Uchenna R; Elbuluk, Nada; Soter, Nicholas A

2017-11-01

Background: While most of the attention regarding skin pigmentation has focused on the effects of ultraviolet radiation, the cutaneous effects of visible light (400 to 700nm) are rarely reported. The purpose of this study was to investigate the cutaneous pigmentary response to pure visible light irradiation, examine the difference in response to different sources of visible light irradiation, and determine a minimal pigmentary dose of visible light irradiation in melanocompetent subjects with Fitzpatrick skin type III - VI. The study was designed as a single arm, non-blinded, split-side dual intervention study in which subjects underwent visible light irradiation using LED and halogen incandescent light sources delivered at a fluence of 0.14 Watts/cm2 with incremental dose progression from 20 J/cm2 to 320 J/cm2. Pigmentation was assessed by clinical examination, cross-polarized digital photography, and analytic colorimetry. Immediate, dose-responsive pigment darkening was seen with LED light exposure in 80% of subjects, beginning at 60 Joules. No pigmentary changes were seen with halogen incandescent light exposure at any dose in any subject. This study is the first to report a distinct difference in cutaneous pigmentary response to different sources of visible light, and the first to demonstrate cutaneous pigment darkening from visible LED light exposure. Our findings raise the concern that our increasing daily artificial light surroundings may have clandestine effects on skin biology.

J Drugs Dermatol. 2017;16(11):1105-1110.

Coumarin-Based Oxime Esters: Photobleachable and Versatile Unimolecular Initiators for Acrylate and Thiol-Based Click Photopolymerization under Visible Light-Emitting Diode Light Irradiation.

PubMed

Li, Zhiquan; Zou, Xiucheng; Zhu, Guigang; Liu, Xiaoya; Liu, Ren

2018-05-09

Developing efficient unimolecular visible light-emitting diode (LED) light photoinitiators (PIs) with photobleaching capability, which are essential for various biomedical applications and photopolymerization of thick materials, remains a great challenge. Herein, we demonstrate the synthesis of a series of novel PIs, containing coumarin moieties as chromophores and oxime ester groups as initiation functionalities and explore their structure-activity relationship. The investigated oxime esters can effectively induce acrylates and thiol-based click photopolymerization under 450 nm visible LED light irradiation. The initiator O-3 exhibited excellent photobleaching capability and enabled photopolymerization of thick materials (∼4.8 mm). The efficient unimolecular photobleachable initiators show great potential in dental materials and 3D printings.

300 mW of coherent light at 488 nm using a generic approach

NASA Astrophysics Data System (ADS)

Karamehmedović, Emir; Pedersen, Christian; Andersen, Martin T.; Tidemand-Lichtenberg, Peter

2008-02-01

We present a generic approach for efficient generation of CW light with a predetermined wavelength within the visible or UV spectrum. Based on sum-frequency generation (SFG), the circulating intra-cavity field of a high-finesse diode pumped CW solid-state laser (DPSSL) and the output from a tapered, single-frequency external cavity diode laser (ECDL) are mixed inside a 10 mm periodically poled KTP crstal (pp-KTP). The pp-KTP is situated inside the DPSSL cavity to enhance conversion efficiency of the nonlinear mixing process. This approach combines different solid state technologies; the tuneability of ECDLs, the high intra-cavity filed of DPSSLs and flexible quasi phase matching in pp-tapered ECDL with a center wavelength of 766 nm in combination with a high finesse Nd:YVo4 laser at 1342 nm. Up to 308 mW of light at 488nm was measured in our experiments. The conversion of te ECDL beam was up to 47% after it was transmitted through a PM fiber, and up to 32% without fiber coupling. Replacing the seed laser and the nonlinear crystal makes it possible to generate light at virtually any desired wavelength withing the visible spectrum.

Broadband Optical Active Waveguides Written by Femtosecond Laser Pulses in Lithium Fluoride

NASA Astrophysics Data System (ADS)

Ismael, Chiamenti; Francesca, Bonfigli; Anderson, S. L. Gomes; Rosa, Maria Montereali; Larissa, N. da Costa; Hypolito, J. Kalinowski

2014-01-01

Broadband waveguiding through light-emitting strips directly written in a blank lithium fluoride crystal with a femtosecond laser is reported. Light guiding was observed at several optical wavelengths, from blue, 458 nm, to near-infrared, at 1550 nm. Visible photoluminescence spectra of the optically active F2 and F3+ color centers produced by the fs laser writing process were measured. The wavelength-dependent refractive index increase was estimated to be in the order of 10-3-10-4 in the visible and near-infrared spectral intervals, which is consistent with the stable formation of point defects in LiF.

Visible-light-responsive photocatalysts toward water oxidation based on NiTi-layered double hydroxide/reduced graphene oxide composite materials.

PubMed

Li, Bei; Zhao, Yufei; Zhang, Shitong; Gao, Wa; Wei, Min

2013-10-23

A visible-light responsive photocatalyst was fabricated by anchoring NiTi-layered double hydroxide (NiTi-LDH) nanosheets to the surface of reduced graphene oxide sheets (RGO) via an in situ growth method; the resulting NiTi-LDH/RGO composite displays excellent photocatalytic activity toward water splitting into oxygen with a rate of 1.968 mmol g(-1) h(-1) and a quantum efficiency as high as 61.2% at 500 nm, which is among the most effective visible-light photocatalysts. XRD patterns and SEM images indicate that the NiTi-LDH nanosheets (diameter: 100-200 nm) are highly dispersed on the surface of RGO. UV-vis absorption spectroscopy exhibits that the introduction of RGO enhances the visible-light absorption range of photocatalysts, which is further verified by the largely decreased band gap (∼1.78 eV) studied by cyclic voltammetry measurements. Moreover, photoluminescence (PL) measurements indicate a more efficient separation of electron-hole pairs; electron spin resonance (ESR) and Raman scattering spectroscopy confirm the electrons transfer from NiTi-LDH nanosheets to RGO, accounting for the largely enhanced carrier mobility and the resulting photocatalytic activity in comparison with pristine NiTi-LDH material. Therefore, this work demonstrates a facile approach for the fabrication of visible-light responsive NiTi-LDH/RGO composite photocatalysts, which can be used as a promising candidate in solar energy conversion and environmental science.

Heterojunctions of mixed phase TiO2 nanotubes with Cu, CuPt, and Pt nanoparticles: interfacial band alignment and visible light photoelectrochemical activity

NASA Astrophysics Data System (ADS)

Kar, Piyush; Zhang, Yun; Mahdi, Najia; Thakur, Ujwal K.; Wiltshire, Benjamin D.; Kisslinger, Ryan; Shankar, Karthik

2018-01-01

Anodically formed, vertically oriented, self-organized cylindrical TiO2 nanotube arrays composed of the anatase phase undergo an interesting morphological and phase transition upon flame annealing to square-shaped nanotubes composed of both anatase and rutile phases. This is the first report on heterojunctions consisting of metal nanoparticles (NPs) deposited on square-shaped TiO2 nanotube arrays (STNAs) with mixed rutile and anatase phase content. A simple photochemical deposition process was used to form Cu, CuPt, and Pt NPs on the STNAs, and an enhancement in the visible light photoelectrochemical water splitting performance for the NP-decorated STNAs was observed over the bare STNAs. Under narrow band illumination by visible photons at 410 nm and 505 nm, Cu NP-decorated STNAs performed the best, producing photocurrents 80% higher and 50 times higher than bare STNAs, respectively. Probing the energy level structure at the NP-STNA interface using ultraviolet photoelectron spectroscopy revealed Schottky barrier formation in the NP-decorated STNAs, which assists in separating the photogenerated charge carriers, as also confirmed by longer charge carrier lifetimes in NP-decorated STNAs. While all the NP-decorated STNAs showed enhanced visible light absorption compared to the bare STNAs, only the Cu NPs exhibited a clear plasmonic behavior with an extinction cross section that peaked at 550 nm.

Heterojunctions of mixed phase TiO2 nanotubes with Cu, CuPt, and Pt nanoparticles: interfacial band alignment and visible light photoelectrochemical activity.

PubMed

Kar, Piyush; Zhang, Yun; Mahdi, Najia; Thakur, Ujwal K; Wiltshire, Benjamin D; Kisslinger, Ryan; Shankar, Karthik

2018-01-05

Anodically formed, vertically oriented, self-organized cylindrical TiO 2 nanotube arrays composed of the anatase phase undergo an interesting morphological and phase transition upon flame annealing to square-shaped nanotubes composed of both anatase and rutile phases. This is the first report on heterojunctions consisting of metal nanoparticles (NPs) deposited on square-shaped TiO 2 nanotube arrays (STNAs) with mixed rutile and anatase phase content. A simple photochemical deposition process was used to form Cu, CuPt, and Pt NPs on the STNAs, and an enhancement in the visible light photoelectrochemical water splitting performance for the NP-decorated STNAs was observed over the bare STNAs. Under narrow band illumination by visible photons at 410 nm and 505 nm, Cu NP-decorated STNAs performed the best, producing photocurrents 80% higher and 50 times higher than bare STNAs, respectively. Probing the energy level structure at the NP-STNA interface using ultraviolet photoelectron spectroscopy revealed Schottky barrier formation in the NP-decorated STNAs, which assists in separating the photogenerated charge carriers, as also confirmed by longer charge carrier lifetimes in NP-decorated STNAs. While all the NP-decorated STNAs showed enhanced visible light absorption compared to the bare STNAs, only the Cu NPs exhibited a clear plasmonic behavior with an extinction cross section that peaked at 550 nm.

Rise and Fall: Poly(phenyl vinyl ketone) Photopolymerization and Photodegradation under Visible and UV Radiation.

PubMed

Reeves, Jennifer A; Allegrezza, Michael L; Konkolewicz, Dominik

2017-07-01

Vinyl ketone polymers, including phenyl vinyl ketone (PVK), are an important class of polymers due to their ability to degrade upon irradiation with ultraviolet light which makes them useful for a variety of applications. However, traditional radical methods for synthesizing PVK polymers give rise to poor control or are unable to produce block copolymers. This work uses reversible addition-fragmentation chain transfer polymerization (RAFT) and photochemistry to polymerize PVK. When visible blue radiation of 440 ± 10 nm is used as the light source for the photopolymerization, rapid polymerization and well-defined polymers are created. This RAFT method uses PVK as both monomer and radical initiator, exciting the PVK mono-mer by 440 ± 10 nm irradiation to avoid the use of an additional radical initiator. Once the poly-mer is synthesized, it is stable against degradation by blue light (440 ± 10 nm), but upon exposure to ultraviolet (UV) radiation (310 ± 20 nm) significant decrease in molecular weight is observed. The degradation is observed for all poly(PVK) materials synthesized. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Impact of natural photosensitizer extraction solvent upon light absorbance in dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Suhaimi, Suriati; Mohamed Siddick, Siti Zubaidah; Ahmad Hambali, Nor Azura Malini; Retnasamy, Vithyacharan; Abdul Wahid, Mohamad Halim; Mohamad Shahimin, Mukhzeer

2017-02-01

Natural pigmentations of Ardisia, Bawang Sabrang, Harum Manis mango, Oxalis Triangularis and Rosella were used to study the general trend in performance of dyes as a photosensitizer in the application of dye-sensitized solar cells (DSSCs) based on optical light absorbance and photoelectrochemical characteristics. From the Ultraviolet-Visible Spectrophotometer with the recorded absorption measurements in the range between 400 nm to 800 nm, the dyes extracted from Rosella and Oxalis Triangularis in water solvent exhibited the conversion efficiency up to 0.68% and 0.67%, respectively. The light absorbance peak for dye extracted from Ardisia, Bawang Sabrang, Oxalis Triangularis and Rosella in water and ethanol solvent resulted in the range between 500 nm to 650 nm, while the Harum Manis mango resulted in the broader spectra in both water and ethanol solvent. The light absorbance spectra of each the dyes shows shifted wavelength spectrum when the extracted dye is adsorbed onto TiO2 film surface that might influenced the absorption of light by TiO2 particle in the visible region. The capabilities of the dyes to absorb light when bonded onto the TiO2 photoanode was found to be significant with the current-voltage conversion of the cell. The results demonstrates just the tip of the vastness of natural dyes' (native to tropical region) feasibility and applicability as a photosensitizer.

Development of optical components for METIS instrument

NASA Astrophysics Data System (ADS)

Nardello, M.; Zuccon, S.; Corso, A. J.; Zuppella, P.; Naletto, G.; Fineschi, S.; Antonucci, E.; Pelizzo, M. G.

2014-09-01

The ESA mission Solar Orbiter (SOLO) is dedicated to the study of Solar Atmosphere and Heliosphere. As a part of the payload, the instrument METIS (Multi Element Telescope for Imaging and Spectroscopy) will provide images of the corona, both in the visible range and at the hydrogen Lyman-α emission line (121.6 nm). The realization of optical coatings, based on Al and MgF2, able to reflect/transmit such spectral component is therefore necessary. Since optical characteristics of materials in the VUV range are not well studied and greatly varying with realization process, we implemented a study of their properties in different deposition conditions. This is aimed to the realization of a custom designed filter, able to transmit the 121.6 nm while reflecting the visible light, and thus separate visible from UV light paths in the METIS instrument.

Bactericidal effect of visible light in the presence of erythrosine on Porphyromonas gingivalis and Fusobacterium nucleatum compared with diode laser, an in vitro study.

PubMed

Habiboallah, Ghanbari; Mahdi, Zakeri; Mahbobeh, Naderi Nasab; Mina, Zareian Jahromi; Sina, Faghihi; Majid, Zakeri

2014-12-27

Recently, photodynamic therapy (PDT) has been introduced as a new modality in oral bacterial decontamination. Besides, the ability of laser irradiation in the presence of photosensitizing agent to lethal effect on oral bacteria is well documented. Current research aims to evaluate the effect of photodynamic killing of visible blue light in the presence of plaque disclosing agent erythrosine as photosensitizer on Porphyromonas gingivalis associated with periodontal bone loss and Fusobacterium nucleatum associated with soft tissue inflammation, comparing with the near-infrared diode laser. Standard suspension of P. gingivalis and F. nucleatum were exposed to Light Emitting Diode (LED) (440-480 nm) used to photopolymerize composite resine dental restoration in combination with erythrosine (22 µm) up to 5 minutes. Bacterial sample were also exposed to a near-infrared diode laser (wavelength, 830 nm), using identical irradiation parameters for comparison. Bacterial samples from each treatment groups (radiation-only group, erythrosine-only group and light or laser with erythrosine group) were subcultured onto the surface of agar plates. Survival of these bacteria was determined by counting the number of colony forming units (CFU) after incubation. Exposure to visible blue light and diode laser in conjugation with erythrosine significantly reduced both species examined viability, whereas erythrosine-treated samples exposed to visible light suggested a statically meaningful differences comparing to diode laser. In addition, bactericidal effect of visible light or diode laser alone on P. gingivalis as black-pigmented bacteria possess endogenous porphyrins was noticeably. Our result suggested that visible blue light source in the presence of plaque disclosing agent erythrosine could can be consider as potential approach of PDT to kill the main gram-negative periodontal pathogens. From a clinical standpoint, this regimen could be established as an additional minimally invasive antibacterial treatment of plaque induced periodontal pathologies.

Relative Water Content, Bidirectional Reflectance and Bidirectional Transmittance of the Interior of Detached Leaves During Dry Down.

NASA Technical Reports Server (NTRS)

Vanderbilt, Vern; Daughtry, Craig; Dahlgren, Robert

2015-01-01

Remotely sensing the water status of plants and the water content of canopies remain long-term goals of remote sensing research [1]. Estimates of canopy water content commonly involve measurements in the 900nm to 2000nm portion of the optical spectrum [1]. We have used optical polarization techniques to remove leaf surface reflection and to demonstrate that the visible light reflected by the interior of green healthy corn leaves measured in situ inversely depends upon the leaf relative water content (RWC) [2]. In the research reported here, we again used optical polarization techniques in order to remove the leaf surface reflection from our measurements. This allowed us to monitor the interiors of detached corn leaf samples during leaf dry down measuring for each sample the RWC, bidirectional spectral reflectance and bidirectional spectral transmittance over the wavelength range 450nm to 2,500nm. Our new results like our earlier results show light scattered by the leaf interior measured in the visible wavelength region generally increased as leaf RWC decreased. However, the spectral character and the much improved signal noise of our new results shows the RWC-linked visible light scattering changes are due to leaf structural changes. Our new results show that scattering changes that occur with changing leaf RWC are not attributable to molecular configuration changes in cellular pigments.

Role of cloned carotenoid genes expressed in Escherichia coli in protecting against inactivation by near-UV light and specific phototoxic molecules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tuveson, R.W.; Larson, R.A.; Kagan, J.

1988-10-01

Genes controlling carotenoid synthesis were cloned from Erwinia herbicola and expressed in an Escherichia coli strain. Carotenoids protect against high fluences of near-UV (NUV; 320 to 400 nm) but not against far-UV (200-300 nm). Protection of E. coli cells was not observed following treatment with either psoralen or 8-methoxypsoralen plus NUV. However, significant protection of cells producing carotenoids was observed with three photosensitizing molecules activated by NUV (alpha-terthienyl, harmine, and phenylheptatriyne) which are thought to have the membrane as an important lethal target. Protection of carotenoid-producing cells against inactivation was not observed with acridine orange plus visible light but wasmore » seen with toluidine blue O plus visible light.« less

Role of cloned carotenoid genes expressed in Escherichia coli in protecting against inactivation by near-UV light and specific phototoxic molecules.

PubMed Central

Tuveson, R W; Larson, R A; Kagan, J

1988-01-01

Genes controlling carotenoid synthesis were cloned from Erwinia herbicola and expressed in an Escherichia coli strain. Carotenoids protect against high fluences of near-UV (NUV; 320 to 400 nm) but not against far-UV (200-300 nm). Protection of E. coli cells was not observed following treatment with either psoralen or 8-methoxypsoralen plus NUV. However, significant protection of cells producing carotenoids was observed with three photosensitizing molecules activated by NUV (alpha-terthienyl, harmine, and phenylheptatriyne) which are thought to have the membrane as an important lethal target. Protection of carotenoid-producing cells against inactivation was not observed with acridine orange plus visible light but was seen with toluidine blue O plus visible light. PMID:3049544

Microwave-assisted polyol synthesis and characterization of pvp-capped cds nanoparticles for the photocatalytic degradation of tartrazine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Darwish, Maher, E-mail: m-darwish@razi.tums.ac.ir; Mohammadi, Ali, E-mail: alimohammadi@tums.ac.ir; Nanotechnology Research Centre, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran

2016-02-15

Highlights: • PVP-stabilized CdS nanoparticles have been fabricated by a polyol-microwave method. • CdS nanoparticles were characterized and the size was approximately 48 ± 10 nm. • Catalytic activity of our nanoparticles was examined for tartrazine degradation. • Remarkable results were obtained under both UV and visible light irradiations. - Abstract: Polyvinylpyrrolidone capped cadmium sulfide nanoparticles have been successfully synthesized by a facile polyol method with ethylene glycol. Microwave irradiation and calcination were used to control the size and shape of nanoparticles. Characterization with scanning electron microscopy revealed a restricted nanoparticles growth comparing with the uncapped product, hexagonal phase andmore » 48 nm average particle size were confirmed by X-ray diffraction, and finally mechanism of passivation was suggested depending on Fourier transform infrared spectra. The efficiency of nanoparticles was evaluated by the photocatalytic degradation of tartrazine in aqueous solution under UVC and visible light irradiation. Complete degradation of the dye was observed after 90 min of UVC irradiation under optimized conditions. Kinetic of reaction fitted well to the pseudo-first-order kinetic and Langmuir–Hinshelwood models. Furthermore, 85% degradation of the dye in 9 h under visible light suggests that cadmium sulfide is a promising tool to work under visible light for environmental remediation.« less

An accessible visible-light actinometer for the determination of photon flux and optical pathlength in flow photo microreactors.

PubMed

Roibu, Anca; Fransen, Senne; Leblebici, M Enis; Meir, Glen; Van Gerven, Tom; Kuhn, Simon

2018-04-03

Coupling photochemistry with flow microreactors enables novel synthesis strategies with higher efficiencies compared to batch systems. Improving the reproducibility and understanding of the photochemical reaction mechanisms requires quantitative tools such as chemical actinometry. However, the choice of actinometric systems which can be applied in microreactors is limited, due to their short optical pathlength in combination with a large received photon flux. Furthermore, actinometers for the characterization of reactions driven by visible light between 500 and 600 nm (e.g. photosensitized oxidations) are largely missing. In this paper, we propose a new visible-light actinometer which can be applied in flow microreactors between 480 and 620 nm. This actinometric system is based on the photoisomerization reaction of a diarylethene derivative from its closed to the open form. The experimental protocol for actinometric measurements is facile and characterized by excellent reproducibility and we also present an analytical estimation to calculate the photon flux. Furthermore, we propose an experimental methodology to determine the average pathlength in microreactors using actinometric measurements. In the context of a growing research interest on using flow microreactors for photochemical reactions, the proposed visible-light actinometer facilitates the determination of the received photon flux and average pathlength in confined geometries.

Two-dimensional TiO2-based nanosheets co-modified by surface-enriched carbon dots and Gd2O3 nanoparticles for efficient visible-light-driven photocatalysis

NASA Astrophysics Data System (ADS)

Lu, Dingze; Fang, Pengfei; Ding, Junqian; Yang, Minchen; Cao, Yufei; Zhou, Yawei; Peng, Kui; Kondamareddy, Kiran Kumar; Liu, Min

2017-02-01

Two-dimensional TiO2-based nanosheets (TNSs) co-modified by surface-enriched carbon dots (CDs) and Gd2O3 nanoparticles: (Gd-C-TNSs), capable of exhibiting visible-light-driven photo catalysis were synthesized using a two-pot hydrothermal route. The samples had a sheet-like structure, thickness of approximately 3.6 nm, large specific surface area of 240-350 cm2/g. The CDs (2-3 nm) and Gd2O3 nanoparticles (1-2 nm) were highly dispersed over the surface of the nanosheets. The co-modification by Gd2O3 nanoparticles and CDs influenced the crystallinity, crystal structure, and surface area of the TNSs, and improved the visible-light absorption. Surface photocurrent and fluorescence spectral studies revealed that the photo-generated charge carrier separation efficiency could be improved by an appropriate amount of modification. A very high efficiency was obtained using 0.5 at% Gd/Ti and 3.0 g/L of CDs. The visible-light-induced photocatalytic activity is enhanced under the isolated Cr(VI) system, isolated Rhodamin B (RhB) system, and the synergism between RhB degradation and Cr(VI) reduction for the Gd-C-TNSs photocatalysts. Initially, the photocatalytic activity gradually increased with an increase in the amount of CDs, and then decreased after attaining a maximum, in the case where 0.5 at% Gd/Ti and 3.0 g/L of CDs were used. The enhancement in the photocatalytic activity was attributed to the synergetic effect of the Gd2O3 nanoparticles, TNSs, and CDs in the Gd-C-TNSs composites. The effect led to a fast separation and slow recombination of photo-induced electron-hole pairs. An alternate mechanism for enhanced visible-light photocatalytic activity was also considered.

Visible-light-driven dynamic cancer therapy and imaging using graphitic carbon nitride nanoparticles.

PubMed

Heo, Nam Su; Lee, Sun Uk; Rethinasabapathy, Muruganantham; Lee, Eun Zoo; Cho, Hye-Jin; Oh, Seo Yeong; Choe, Sang Rak; Kim, Yeonho; Hong, Won G; Krishnan, Giribabu; Hong, Won Hi; Jeon, Tae-Joon; Jun, Young-Si; Kim, Hae Jin; Huh, Yun Suk

2018-09-01

Organic graphitic carbon nitride nanoparticles (NP-g-CN), less than 30 nm in size, were synthesized and evaluated for photodynamic therapy (PDT) and cell imaging applications. NP-g-CN particles were prepared through an intercalation process using a rod-like melamine-cyanuric acid adduct (MCA) as the molecular precursor and a eutectic mixture of LiCl-KCl (45:55 wt%) as the reaction medium for polycondensation. The nano-dimensional NP-g-CN penetrated the malignant tumor cells with minimal hindrance and effectively generated reactive oxygen species (ROS) under visible light irradiation, which could ablate cancer cells. When excited by visible light irradiation (λ > 420 nm), NP-g-CN introduced to HeLa and cos-7 cells generated a significant amount of ROS and killed the cancerous cells selectively. The cytotoxicity of NP-g-CN was manipulated by altering the light irradiation and the BP-g-CN caused more damage to the cancer cells than normal cells at low concentrations. As a potential non-toxic organic nanomaterial, the synthesized NP-g-CN are biocompatible with less cytotoxicity than toxic inorganic materials. The combined effects of the high efficacy of ROS generation under visible light irradiation, low toxicity, and bio-compatibility highlight the potential of NP-g-CN for PDT and imaging without further modification. Copyright © 2018 Elsevier B.V. All rights reserved.

ZnCr2S4: Highly effective photocatalyst converting nitrate into N2 without over-reduction under both UV and pure visible light

NASA Astrophysics Data System (ADS)

Yue, Mufei; Wang, Rong; Cheng, Nana; Cong, Rihong; Gao, Wenliang; Yang, Tao

2016-08-01

We propose several superiorities of applying some particular metal sulfides to the photocatalytic nitrate reduction in aqueous solution, including the high density of photogenerated excitons, high N2 selectivity (without over-reduction to ammonia). Indeed, ZnCr2S4 behaved as a highly efficient photocatalyst, and with the assistance of 1 wt% cocatalysts (RuOx, Ag, Au, Pd, or Pt), the efficiency was greatly improved. The simultaneous loading of Pt and Pd led to a synergistic effect. It offered the highest nitrate conversion rate of ~45 mg N/h together with the N2 selectivity of ~89%. Such a high activity remained steady after 5 cycles. The optimal apparent quantum yield at 380 nm was 15.46%. More importantly, with the assistance of the surface plasma resonance effect of Au, the visible light activity achieved 1.352 mg N/h under full arc Xe-lamp, and 0.452 mg N/h under pure visible light (λ > 400 nm). Comparing to the previous achievements in photocatalytic nitrate removal, our work on ZnCr2S4 eliminates the over-reduction problem, and possesses an extremely high and steady activity under UV-light, as well as a decent conversion rate under pure visible light.

ZnCr2S4: Highly effective photocatalyst converting nitrate into N2 without over-reduction under both UV and pure visible light.

PubMed

Yue, Mufei; Wang, Rong; Cheng, Nana; Cong, Rihong; Gao, Wenliang; Yang, Tao

2016-08-03

We propose several superiorities of applying some particular metal sulfides to the photocatalytic nitrate reduction in aqueous solution, including the high density of photogenerated excitons, high N2 selectivity (without over-reduction to ammonia). Indeed, ZnCr2S4 behaved as a highly efficient photocatalyst, and with the assistance of 1 wt% cocatalysts (RuOx, Ag, Au, Pd, or Pt), the efficiency was greatly improved. The simultaneous loading of Pt and Pd led to a synergistic effect. It offered the highest nitrate conversion rate of ~45 mg N/h together with the N2 selectivity of ~89%. Such a high activity remained steady after 5 cycles. The optimal apparent quantum yield at 380 nm was 15.46%. More importantly, with the assistance of the surface plasma resonance effect of Au, the visible light activity achieved 1.352 mg N/h under full arc Xe-lamp, and 0.452 mg N/h under pure visible light (λ > 400 nm). Comparing to the previous achievements in photocatalytic nitrate removal, our work on ZnCr2S4 eliminates the over-reduction problem, and possesses an extremely high and steady activity under UV-light, as well as a decent conversion rate under pure visible light.

Capturing latent fingerprints from metallic painted surfaces using UV-VIS spectroscope

NASA Astrophysics Data System (ADS)

Makrushin, Andrey; Scheidat, Tobias; Vielhauer, Claus

2015-03-01

In digital crime scene forensics, contactless non-destructive detection and acquisition of latent fingerprints by means of optical devices such as a high-resolution digital camera, confocal microscope, or chromatic white-light sensor is the initial step prior to destructive chemical development. The applicability of an optical sensor to digitalize latent fingerprints primarily depends on reflection properties of a substrate. Metallic painted surfaces, for instance, pose a problem for conventional sensors which make use of visible light. Since metallic paint is a semi-transparent layer on top of the surface, visible light penetrates it and is reflected off of the metallic flakes randomly disposed in the paint. Fingerprint residues do not impede light beams making ridges invisible. Latent fingerprints can be revealed, however, using ultraviolet light which does not penetrate the paint. We apply a UV-VIS spectroscope that is capable of capturing images within the range from 163 to 844 nm using 2048 discrete levels. We empirically show that latent fingerprints left behind on metallic painted surfaces become clearly visible within the range from 205 to 385 nm. Our proposed streakiness score feature determining the proportion of a ridge-valley pattern in an image is applied for automatic assessment of a fingerprint's visibility and distinguishing between fingerprint and empty regions. The experiments are carried out with 100 fingerprint and 100 non-fingerprint samples.

Effect of core quantum-dot size on power-conversion-efficiency for silicon solar-cells implementing energy-down-shift using CdSe/ZnS core/shell quantum dots.

PubMed

Baek, Seung-Wook; Shim, Jae-Hyoung; Seung, Hyun-Min; Lee, Gon-Sub; Hong, Jin-Pyo; Lee, Kwang-Sup; Park, Jea-Gun

2014-11-07

Silicon solar cells mainly absorb visible light, although the sun emits ultraviolet (UV), visible, and infrared light. Because the surface reflectance of a textured surface with SiNX film on a silicon solar cell in the UV wavelength region (250-450 nm) is higher than ∼27%, silicon solar-cells cannot effectively convert UV light into photo-voltaic power. We implemented the concept of energy-down-shift using CdSe/ZnS core/shell quantum-dots (QDs) on p-type silicon solar-cells to absorb more UV light. CdSe/ZnS core/shell QDs demonstrated clear evidence of energy-down-shift, which absorbed UV light and emitted green-light photoluminescence signals at a wavelength of 542 nm. The implementation of 0.2 wt% (8.8 nm QDs layer) green-light emitting CdSe/ZnS core/shell QDs reduced the surface reflectance of the textured surface with SiNX film on a silicon solar-cell from 27% to 15% and enhanced the external quantum efficiency (EQE) of silicon solar-cells to around 30% in the UV wavelength region, thereby enhancing the power conversion efficiency (PCE) for p-type silicon solar-cells by 5.5%.

A Difference in Cutaneous Pigmentary Response to LED Versus Halogen Incandescent Visible Light: A Case Report from a Single Center, Investigational Clinical Trial Determining a Minimal Pigmentary Visible Light Dose.

PubMed

Soleymani, Teo; Soter, Nicholas A; Folan, Lorcan M; Elbuluk, Nada; Okereke, Uchenna R; Cohen, David E

2017-04-01

BACKGROUND: While most of the attention regarding skin pigmentation has focused on the effects on ultraviolet radiation, the cutaneous effects of visible light (400 to 700nm) are rarely reported. In this report, we describe a case of painful erythema and induration that resulted from direct irradiation of UV-naïve skin with visible LED light in a patient with Fitzpatrick type II skin.

METHODS AND RESULTS: A 24-year-old healthy woman with Fitzpatrick type II skin presented to our department to participate in a clinical study. As part of the study, the subject underwent visible light irradiation with an LED and halogen incandescent visible light source. After 5 minutes of exposure, the patient complained of appreciable pain at the LED exposed site. Evaluation demonstrated erythema and mild induration. There were no subjective or objective findings at the halogen incandescent irradiated site, which received equivalent fluence (0.55 Watts / cm2). The study was halted as the subject was unable to tolerate the full duration of visible light irradiation.

CONCLUSION: This case illustrates the importance of recognizing the effects of visible light on skin. While the vast majority of investigational research has focused on ultraviolet light, the effects of visible light have been largely overlooked and must be taken into consideration, in all Fitzpatrick skin types.

J Drugs Dermatol. 2017;16(4):388-392.

Tannic Acid/Fe3+/Ag Nanofilm Exhibiting Superior Photodynamic and Physical Antibacterial Activity.

PubMed

Xu, Ziqiang; Wang, Xiuhua; Liu, Xiangmei; Cui, Zhenduo; Yang, Xianjin; Yeung, Kelvin Wai Kwok; Chung, Jonathan Chiyuen; Chu, Paul K; Wu, Shuilin

2017-11-15

Silver nanoparticles (AgNPs) enwrapped in the biologically safe tannic acid (TA)/Fe 3+ nanofilm are synthesized by an ultrafast, green, simple, and universal method. The physical antibacterial activity and photodynamic antibacterial therapy (PAT) efficacy of the TA/Fe 3+ /AgNPs nanofilm were investigated for the first time, which exhibited a strong physical antibacterial activity as well as great biocompatibility, through in vitro and in vivo studies. The results disclosed that this hybrid coating could possess high PAT capabilities upon irradiation under a visible light of 660 nm, which is longer than those of previously reported green and blue sensitization light, thus allowing deeper light penetration into biological tissues. Electron spin resonance (ESR) spectra proved that the PAT efficacy of the TA/Fe 3+ /AgNPs nanofilm was associated with the yields of singlet oxygen ( 1 O 2 ) under the irradiation of visible light (660 nm). A higher PAT efficiency of 100 and 94% against Escherichia coli and Staphylococcus aureus could be achieved within 20 min of illumination under 660 nm visible light, whereas the innate physical antibacterial activity of AgNPs could endow the implants with long-term prevention of bacterial infection. The mechanism of PAT may be associated with the formation of oxidative stress and oxidative damage to key biomolecules (proteins and lipids) in bacteria. Our results reveal that the synergistic action of both PAT and physical action of AgNPs in this hybrid nanofilm is an effective way to inactivate bacteria, with minimal side effects.

Laser Deposition of Polymer Nanocomposite Thin Films and Hard Materials and Their Optical Characterization

DTIC Science & Technology

2013-12-05

visible light on instruments such as microscope tips and micro- surgical tools. Hard carbon known as diamond-like carbon films produced by pulsed laser ...visible (610 nm) LED source and a supplemental infra-red 980-nm laser diode (for the studies of the upconversion fluorescence). The basic package...5/2013 Final Performance Report 15 Sep 2012- 14 Sep 2013 LASER DEPOSITION OF POLYMER NANOCOMPOSITE THIN FILMS AND HARD MATERIALS AND THEIR OPTICAL

Significantly enhanced visible light response in single TiO2 nanowire by nitrogen ion implantation

NASA Astrophysics Data System (ADS)

Wu, Pengcheng; Song, Xianyin; Si, Shuyao; Ke, Zunjian; Cheng, Li; Li, Wenqing; Xiao, Xiangheng; Jiang, Changzhong

2018-05-01

The metal-oxide semiconductor TiO2 shows enormous potential in the field of photoelectric detection; however, UV-light absorption only restricts its widespread application. It is considered that nitrogen doping can improve the visible light absorption of TiO2, but the effect of traditional chemical doping is far from being used for visible light detection. Herein, we dramatically broadened the absorption spectrum of the TiO2 nanowire (NW) by nitrogen ion implantation and apply the N-doped single TiO2 NW to visible light detection for the first time. Moreover, this novel strategy effectively modifies the surface states and thus regulates the height of Schottky barriers at the metal/semiconductor interface, which is crucial to realizing high responsivity and a fast response rate. Under the illumination of a laser with a wavelength of 457 nm, our fabricated photodetector exhibits favorable responsivity (8 A W-1) and a short response time (0.5 s). These results indicate that ion implantation is a promising method in exploring the visible light detection of TiO2.

Significantly enhanced visible light response in single TiO2 nanowire by nitrogen ion implantation.

PubMed

Wu, Pengcheng; Song, Xianyin; Si, Shuyao; Ke, Zunjian; Cheng, Li; Li, Wenqing; Xiao, Xiangheng; Jiang, Changzhong

2018-05-04

The metal-oxide semiconductor TiO 2 shows enormous potential in the field of photoelectric detection; however, UV-light absorption only restricts its widespread application. It is considered that nitrogen doping can improve the visible light absorption of TiO 2 , but the effect of traditional chemical doping is far from being used for visible light detection. Herein, we dramatically broadened the absorption spectrum of the TiO 2 nanowire (NW) by nitrogen ion implantation and apply the N-doped single TiO 2 NW to visible light detection for the first time. Moreover, this novel strategy effectively modifies the surface states and thus regulates the height of Schottky barriers at the metal/semiconductor interface, which is crucial to realizing high responsivity and a fast response rate. Under the illumination of a laser with a wavelength of 457 nm, our fabricated photodetector exhibits favorable responsivity (8 A W -1 ) and a short response time (0.5 s). These results indicate that ion implantation is a promising method in exploring the visible light detection of TiO 2 .

Photocatalytic water oxidation by a pyrochlore oxide upon irradiation with visible light: rhodium substitution into yttrium titanate.

PubMed

Kiss, Borbala; Didier, Christophe; Johnson, Timothy; Manning, Troy D; Dyer, Matthew S; Cowan, Alexander J; Claridge, John B; Darwent, James R; Rosseinsky, Matthew J

2014-12-22

A stable visible-light-driven photocatalyst (λ≥450 nm) for water oxidation is reported. Rhodium substitution into the pyrochlore Y2 Ti2 O7 is demonstrated by monitoring Vegard's law evolution of the unit-cell parameters with changing rhodium content, to a maximum content of 3 % dopant. Substitution renders the solid solutions visible-light active. The overall rate of oxygen evolution is comparable to WO3 but with superior light-harvesting and surface-area-normalized turnover rates, making Y2 Ti1.94 Rh0.06 O7 an excellent candidate for use in a Z-scheme water-splitting system. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Solar light-driven photocatalysis using mixed-phase bismuth ferrite (BiFeO3/Bi25FeO40) nanoparticles for remediation of dye-contaminated water: kinetics and comparison with artificial UV and visible light-mediated photocatalysis.

PubMed

Kalikeri, Shankramma; Shetty Kodialbail, Vidya

2018-05-01

Mixed-phase bismuth ferrite (BFO) nanoparticles were prepared by co-precipitation method using potassium hydroxide as the precipitant. X-ray diffractogram (XRD) of the particles showed the formation of mixed-phase BFO nanoparticles containing BiFeO 3 /Bi 25 FeO 40 phases with the crystallite size of 70 nm. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed the formation of quasi-spherical particles. The BFO nanoparticles were uniform sized with narrow size range and with the average hydrodynamic diameter of 76 nm. The band gap energy of 2.2 eV showed its ability to absorb light even in the visible range. Water contaminated with Acid Yellow (AY-17) and Reactive Blue (RB-19) dye was treated by photocatalysis under UV, visible, and solar light irradiation using the BFO nanoparticles. The BFO nanoparticles showed maximum photocatalytical activity under solar light as compared to UV and visible irradiations, and photocatalysis was favored under acidic pH. Complete degradation of AY-17 dyes and around 95% degradation of RB-19 could be achieved under solar light at pH 5. The kinetics of degradation followed the Langmuir-Hinshelhood kinetic model showing that the heterogeneous photocatalysis is adsorption controlled. The findings of this work prove the synthesized BFO nanoparticles as promising photocatalysts for the treatment of dye-contaminated industrial wastewater.

Analysis of optical transmission by 400-500 nm visible light into aesthetic dental biomaterials.

PubMed

Watts, D C; Cash, A J

1994-04-01

The penetration of visible light into dental biomaterials is an essential factor in photoinitiation of setting reactions and in the optical aspects of dental aesthetics. Light of visible blue wavelengths, 400-500 nm, has been applied at normal angles to 0.2-5.0 mm sections of human dentine and representative ceramic, polymerceramic composites and hybrid glass-polyalkenoate materials. The integrated optical transmission has been determined for each material section. The data have been converted to absorbance values and analysed to check for mathematical conformity to the Beer-Lambert Law. It is found that conformity (typically, P < 0.01) to the linear Beer-Lambert Law is only attained by making a substantial correction for the intensity of light reflected from the surface of aesthetic biomaterials. This is otherwise expressed by distinguishing between true and apparent absorbance. From linear regression of apparent absorbance with section thickness, the intercept depends upon the logarithm of the surface-reflection ratio. This factor ranges from 30% to 90% in the materials investigated. It follows that there is a high degree of inefficiency in the transmission of visible light into and through aesthetic biomaterials for the purposes of photoactivation using existing technology. Means by which this limitation and inefficiency may be reduced are discussed. While the reflectivity of aesthetic biomaterials has been perceived by dental practitioners, the magnitude of this effect and its implications in connection with light-cured materials have not been analysed and emphasized hitherto.

Yttrium oxide based three dimensional metamaterials for visible light cloaking

NASA Astrophysics Data System (ADS)

Rai, Pratyush; Kumar, Prashanth S.; Varadan, Vijay K.; Ruffin, Paul; Brantley, Christina; Edwards, Eugene

2014-04-01

Metamaterial with negative refractive index is the key phenomenon behind the concept of a cloaking device to hide an object from light in visible spectrum. Metamaterials made of two and three dimensional lattices of periodically placed electromagnetic resonant cells can achieve absorption and propagation of incident electromagnetic radiation as confined electromagnetic fields confined to a waveguide as surface plasmon polaritons, which can be used for shielding an object from in-tune electromagnetic radiation. The periodicity and dimensions of resonant cavity determine the frequency, which are very small as compared to the wavelength of incident light. Till now the phenomena have been demonstrated only for lights in near infrared spectrum. Recent advancements in fabrication techniques have made it possible to fabricate array of three dimensional nanostructures with cross-sections as small as 25 nm that are required for negative refractive index for wavelengths in visible light spectrum of 400-700 nm and for wider view angle. Two types of metamaterial designs, three dimensional concentric split ring and fishnet, are considered. Three dimensional structures consisted of metal-dielectric-metal stacks. The metal is silver and dielectric is yttrium oxide, other than conventional materials such as FR4 and Duroid. High κ dielectric and high refractive index as well as large crystal symmetry of Yttrium oxide has been investigated as encapsulating medium. Dependence of refractive index on wavelength and bandwidth of negative refractive index region are analyzed for application towards cloaking from light in visible spectrum.

Nanoparticle optical notch filters

NASA Astrophysics Data System (ADS)

Kasinadhuni, Pradeep Kumar

Developing novel light blocking products involves the design of a nanoparticle optical notch filter, working on the principle of localized surface plasmon resonance (LSPR). These light blocking products can be used in many applications. One such application is to naturally reduce migraine headaches and light sensitivity. Melanopsin ganglion cells present in the retina of the human eye, connect to the suprachiasmatic nucleus (SCN-the body's clock) in the brain, where they participate in the entrainment of the circadian rhythms. As the Melanopsin ganglion cells are involved in triggering the migraine headaches in photophobic patients, it is necessary to block the part of visible spectrum that activates these cells. It is observed from the action potential spectrum of the ganglion cells that they absorb light ranging from 450-500nm (blue-green part) of the visible spectrum with a λmax (peak sensitivity) of around 480nm (blue line). Currently prescribed for migraine patients is the FL-41 coating, which blocks a broad range of wavelengths, including wavelengths associated with melanopsin absorption. The nanoparticle optical notch filter is designed to block light only at 480nm, hence offering an effective prescription for the treatment of migraine headaches.

Wavelength, beam size and type dependences of cerebral low-level light therapy: A Monte Carlo study on visible Chinese human

NASA Astrophysics Data System (ADS)

Li, Ting; Zhao, Yue; Duan, Meixue; Sun, Yunlong; Li, Kai

2014-02-01

Low level light therapy (LLLT) has been clinically utilized for many indications in medicine requiring protection from cell/tissue death, stimulation of healing and repair of injuries, pain reduction, swelling and inflammation. Presently, use of LLLT to treat stroke, traumatic brain injury, and cognitive dysfunction is attracting growing interest. Near-infrared light can penetrate into the brain tissue, allowing noninvasive treatment to be carried out with few treatment-related adverse events. Optimization of LLLT treatment effect is one key issue of the field; however, only a few experimental tests on mice for wavelength selection have been reported. We addressed this issue by low-cost, straightforward and quantitative comparisons on light dosage distribution in Visible Chinese human head with Monte Carlo modeling of light propagation. Optimized selection in wavelength, beam type and size were given based on comparisons among frequently-used setups (i.e., wavelengths: 660 nm, 810 nm, 980 nm; beam type: Gaussian and flat beam; beam diameter: 2 cm, 4 cm, 6cm).This study provided an efficient way to guide optimization of LLLT setup and selection on wavelength, beam type and size for clinical brain LLLT.

Synthesis and Visible-Light Photocatalytic Activity of CeO₂ Nanoboxes Based on Pearson’s Principle.

PubMed

Ge, Shengsong; Bao, Liwei; Shao, Qian; Zhang, Qiaoxia; Liu, Zingyun

2017-01-01

The CeO₂ nanoboxes with well-defined hollow structure were fabricated by template-engaged coordinating etching of Cu₂O cubes based on Pearson’s hard and soft acid-base principle. The morphologically uniform CeO₂ nanoboxes have an average edge length of 400 nm and shell thickness of around 60 nm. The strong chemical affinity between Cu+ and S₂O(2− 3) was the driving force for the etching of Cu₂O templates and the formation of shells. A possible formation mechanism of CeO₂ nanoboxes was proposed. The synthesized CeO₂ nanoboxes exhibit good photocatalytic activity for photodegradation of acid orange 7 (AO 7) under visible light irradiation.

A novel fabrication methodology for sulfur-doped ZnO nanorods as an active photoanode for improved water oxidation in visible-light regime

NASA Astrophysics Data System (ADS)

Khan, A.; Ahmed, M. I.; Adam, A.; Azad, A.-M.; Qamar, M.

2017-02-01

Incorporation of foreign moiety in the lattice of semiconductors significantly alters their optoelectronic behavior and opens a plethora of new applications. In this paper, we report the synthesis of sulfur-doped zinc oxide (S-doped ZnO) nanorods by reacting ZnO nanorods with diammonium sulfide in vapor phase. Microscopic investigation revealed that the morphological features, such as, the length (2-4 μm) and width (100-250 nm) of the original hexagonal ZnO nanorods remained intact post-sulfidation. X-ray photoelectron spectroscopy analysis of the sulfide sample confirmed the incorporation of sulfur into ZnO lattice. The optical measurements suggested the extension of absorption threshold into visible region upon sulfidation. Photoelectrochemical (PEC) activities of pure and S-doped ZnO nanorods were compared for water oxidation in visible light (λ > 420 nm), which showed several-fold increment in the performance of S-doped ZnO sample; the observed amelioration in the PEC activity was rationalized in terms of preferred visible light absorption and low resistance of sulfide sample, as evidenced by optical and electrochemical impedance spectroscopy.

Plant Habitat (PH)

NASA Technical Reports Server (NTRS)

Onate, Bryan

2016-01-01

The International Space Station (ISS) will soon have a platform for conducting fundamental research of Large Plants. Plant Habitat (PH) is designed to be a fully controllable environment for high-quality plant physiological research. PH will control light quality, level, and timing, temperature, CO2, relative humidity, and irrigation, while scrubbing ethylene. Additional capabilities include leaf temperature and root zone moisture and oxygen sensing. The light cap will have red (630 nm), blue (450 nm), green (525 nm), far red (730 nm) and broad spectrum white LEDs. There will be several internal cameras (visible and IR) to monitor and record plant growth and operations.

Toxic wavelength of blue light changes as insects grow.

PubMed

Shibuya, Kazuki; Onodera, Shun; Hori, Masatoshi

2018-01-01

Short-wavelength visible light (blue light: 400-500 nm) has lethal effects on various insects, such as fruit flies, mosquitoes, and flour beetles. However, the most toxic wavelengths of blue light might differ across developmental stages. Here, we investigate how the toxicity of blue light changes with the developmental stages of an insect by irradiating Drosophila melanogaster with different wavelengths of blue light. Specifically, the lethal effect on eggs increased at shorter light wavelengths (i.e., toward 405 nm). In contrast, wavelengths from 405 to 466 nm had similar lethal effects on larvae. A wavelength of 466 nm had the strongest lethal effect on pupae; however, mortality declined as pupae grew. A wavelength of 417 nm was the most harmful to adults at low photon flux density, while 466 nm was the most harmful to adults at high photon flux density. These findings suggest that, as the morphology of D. melanogaster changes with growth, the most harmful wavelength also changes. In addition, our results indicated that reactive oxygen species influence the lethal effect of blue light. Our findings show that blue light irradiation could be used as an effective pest control method by adjusting the wavelength to target specific developmental stages.

Polymer-cholesteric liquid-crystalline composites with a broad light reflection band

NASA Astrophysics Data System (ADS)

Mitov, Michel

2016-05-01

Cholesteric liquid crystals selectively reflect the light. The reflection bandgap is typically limited to 100 nm in the visible spectrum and, at the best, 50% of the unpolarized incident light is reflected. Solutions are found in biopolymers and polymer-liquid crystal composite materials to go beyond these limits.

Fully Integrated Optical Spectrometer in Visible and Near-IR in CMOS.

PubMed

Hong, Lingyu; Sengupta, Kaushik

2017-12-01

Optical spectrometry in the visible and near-infrared range has a wide range of applications in healthcare, sensing, imaging, and diagnostics. This paper presents the first fully integrated optical spectrometer in standard bulk CMOS process without custom fabrication, postprocessing, or any external optical passive structure such as lenses, gratings, collimators, or mirrors. The architecture exploits metal interconnect layers available in CMOS processes with subwavelength feature sizes to guide, manipulate, control, diffract light, integrated photodetector, and read-out circuitry to detect dispersed light, and then back-end signal processing for robust spectral estimation. The chip, realized in bulk 65-nm low power-CMOS process, measures 0.64 mm 0.56 mm in active area, and achieves 1.4 nm in peak detection accuracy for continuous wave excitations between 500 and 830 nm. This paper demonstrates the ability to use these metal-optic nanostructures to miniaturize complex optical instrumentation into a new class of optics-free CMOS-based systems-on-chip in the visible and near-IR for various sensing and imaging applications.

Human infrared vision is triggered by two-photon chromophore isomerization

PubMed Central

Palczewska, Grazyna; Vinberg, Frans; Stremplewski, Patrycjusz; Bircher, Martin P.; Salom, David; Komar, Katarzyna; Zhang, Jianye; Cascella, Michele; Wojtkowski, Maciej; Kefalov, Vladimir J.; Palczewski, Krzysztof

2014-01-01

Vision relies on photoactivation of visual pigments in rod and cone photoreceptor cells of the retina. The human eye structure and the absorption spectra of pigments limit our visual perception of light. Our visual perception is most responsive to stimulating light in the 400- to 720-nm (visible) range. First, we demonstrate by psychophysical experiments that humans can perceive infrared laser emission as visible light. Moreover, we show that mammalian photoreceptors can be directly activated by near infrared light with a sensitivity that paradoxically increases at wavelengths above 900 nm, and display quadratic dependence on laser power, indicating a nonlinear optical process. Biochemical experiments with rhodopsin, cone visual pigments, and a chromophore model compound 11-cis-retinyl-propylamine Schiff base demonstrate the direct isomerization of visual chromophore by a two-photon chromophore isomerization. Indeed, quantum mechanics modeling indicates the feasibility of this mechanism. Together, these findings clearly show that human visual perception of near infrared light occurs by two-photon isomerization of visual pigments. PMID:25453064

Comparison of a chimeric anti-carcinoembryonic antigen antibody conjugated with visible or near-infrared fluorescent dyes for imaging pancreatic cancer in orthotopic nude mouse models

NASA Astrophysics Data System (ADS)

Maawy, Ali A.; Hiroshima, Yukihiko; Kaushal, Sharmeela; Luiken, George A.; Hoffman, Robert M.; Bouvet, Michael

2013-12-01

The aim of this study was to evaluate a set of visible and near-infrared dyes conjugated to a tumor-specific chimeric antibody for high-resolution tumor imaging in orthotopic models of pancreatic cancer. BxPC-3 human pancreatic cancer was orthotopically implanted into pancreata of nude mice. Mice received a single intravenous injection of a chimeric anti-carcinoembryonic antigen antibody conjugated to one of the following fluorophores: 488-nm group (Alexa Fluor 488 or DyLight 488); 550-nm group (Alexa Fluor 555 or DyLight 550); 650-nm group (Alexa Fluor 660 or DyLight 650), or the 750-nm group (Alexa Fluor 750 or DyLight 755). After 24 h, the Olympus OV100 small-animal imaging system was used for noninvasive and intravital fluorescence imaging of mice. Dyes were compared with respect to depth of imaging, resolution, tumor-to-background ratio (TBR), photobleaching, and hemoglobin quenching. The longer wavelength dyes had increased depth of penetration and ability to detect the smallest tumor deposits and provided the highest TBRs, resistance to hemoglobin quenching, and specificity. The shorter wavelength dyes were more photostable. This study showed unique advantages of each dye for specific cancer imaging in a clinically relevant orthotopic model.

Visible-light-assisted SLCs template synthesis of sea anemone-like Pd/PANI nanocomposites with high electrocatalytic activity for methane oxidation in acidic medium

NASA Astrophysics Data System (ADS)

Tan, De-Xin; Wang, Yan-Li

2018-03-01

Sea anemone-like palladium (Pd)/polyaniline (PANI) nanocomposites were synthesized via visible-light-assisted swollen liquid crystals (SLCs) template method. The resulting samples were characterized by transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy dispersive spectrometer (EDS), x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), ultraviolet-visible (UV–vis) absorption spectroscopy and Fourier transform infrared (FT-IR) spectroscopy, respectively. The electrocatalytic properties of Pd/PANI nanocomposites modified glass carbon electrode (GCE) for methane oxidation were investigated by cycle voltammetry (CV) and chronoamperometry. Those dispersed sea anemone-like Pd/PANI nanocomposites had an average diameter of 320 nm. The obtained Pd nanoparticles with an average diameter of about 45 nm were uniformly distributed in PANI matrix. Sea anemone-like Pd/PANI nanocomposites exhibited excellent electrocatalytic activity and stability for oxidation of methane (CH4).

Study of optical materials to be used on Multi Element Telescope for Imaging and Spectroscopy instrument

NASA Astrophysics Data System (ADS)

Nardello, Marco; Zuccon, Sara; Corso, Alain Jodi; Zuppella, Paola; Gerlin, Francesca; Tessarolo, Enrico; Pelizzo, Maria Guglielmina

2015-04-01

The European Space Agency mission Solar Orbiter (SOLO) is dedicated to the study of the solar atmosphere and heliosphere. As a part of the payload, the instrument METIS (Multi Element Telescope for Imaging and Spectroscopy) will provide images of the corona, both in the visible range and at the hydrogen Lyman-α emission line (121.6 nm). The realization of optical coatings, based on Al and MgF2, able to reflect/transmit such spectral components is, therefore, necessary. Since optical characteristics of materials in the vacuum ultraviolet range are not well studied and vary greatly with the realization process, we implemented a study of their properties in different deposition conditions. This is aimed to the realization of a custom designed filter able to transmit the 121.6 nm wavelength while reflecting visible light, and thus separating visible from ultraviolet light paths in the METIS instrument.

Complete erasing of ghost images on computed radiography plates and role of deeply trapped electrons

NASA Astrophysics Data System (ADS)

Ohuchi-Yoshida, Hiroko; Kondo, Yasuhiro

2011-12-01

Computed radiography (CR) plates made of europium-doped Ba(Sr)FBr(I) were simultaneously exposed to filtered ultraviolet light and visible light in order to erase ghost images, i.e., latent image that is unerasable with visible light (LIunVL) and reappearing one, which are particularly observed in plates irradiated with a high dose and/or cumulatively over-irradiated. CR samples showing LIunVLs were prepared by irradiating three different types of CR plates (Agfa ADC MD10, Kodak Directview Mammo EHRM2, and Fuji ST-VI) with 50 kV X-ray beams in the dose range 8.1 mGy-8.0 Gy. After the sixth round of simultaneous 6 h exposures to filtered ultraviolet light and visible light, all the LIunVLs in the three types of CR plates were erased to the same level as in an unirradiated plate and no latent images reappeared after storage at 0 °C for 14 days. With conventional exposure to visible light, LIunVLs consistently remained in all types of CR plates irradiated with higher doses of X-rays and latent images reappeared in the Agfa M10 plates after storage at 0 °C. Electrons trapped in deep centers cause LIunVLs and they can be erased by simultaneous exposures to filtered ultraviolet light and visible light. To study electrons in deep centers, the absorption spectra were examined in all types of irradiated CR plates by using polychromatic ultraviolet light from a deep-ultraviolet lamp. It was found that deep centers showed a dominant peak in the absorption spectra at around 324 nm for the Agfa M10 and Kodak EHRM2 plates, and at around 320 nm for the Fuji ST-VI plate, in each case followed by a few small peaks. The peak heights were dose-dependent for all types of CR samples, suggesting that the number of electrons trapped in deep centers increases with the irradiation dose.

Architecture, development and implementation of a SWIR to visible integrated up-conversion imaging device

NASA Astrophysics Data System (ADS)

Sarusi, Gabby; Templeman, Tzvi; Hechster, Elad; Nissim, Nimrod; Vitenberg, Vladimir; Maman, Nitzan; Tal, Amir; Solodar, Assi; Makov, Guy; Abdulhalim, Ibrahim; Visoly-Fisher, Iris; Golan, Yuval

2016-04-01

A new concept of short wavelength infrared (SWIR) to visible upconversion integrated imaging device is proposed, modeled and some initial measured results are presented. The device is a hybrid inorganic-organic device that comprises six nano-metric scale sub-layers grown on n-type GaAs substrates. The first layer is a ~300nm thick PbSe nano-columnar absorber layer grown in (111) orientation to the substrate plan (100), with a diameter of 8- 10nm and therefore exhibit quantum confinement effects parallel to the substrate and bulk properties perpendicular to it. The advantage of this structure is the high oscillator strength and hence absorption to incoming SWIR photons while maintaining the high bulk mobility of photo-excited charges along the columns. The top of the PbSe absorber layer is coated with 20nm thick metal layer that serves as a dual sided mirror, as well as a potentially surface plasmon enhanced absorption in the PbSe nano-columns layer. The photo-excited charges (holes and electrons in opposite directions) are drifted under an external applied field to the OLED section (that is composed of a hole transport layer, an emission layer and an electron transport layer) where they recombine with injected electron from the transparent cathode and emit visible light through this cathode. Due to the high absorption and enhanced transport properties this architecture has the potential of high quantum efficiency, low cost and easy implementation in any optical system. As a bench-mark, alternative concept where InGaAs/InP heterojunction couple to liquid crystal optical spatial light modulator (OSLM) structure was built that shows a full upconversion to visible of 1550nm laser light.

Postmodification of MOF-5 using secondary complex formation using 8- hydroxyquinoline (HOQ) for the development of visible light active photocatalysts

NASA Astrophysics Data System (ADS)

Thakare, Sanjay R.; Ramteke, Shruti M.

2018-05-01

A novel HOQ@MOF-5 compound photocatalyst was successfully constructed by interacting 8- Hydroxyquinoline with MOF-5 synthesized through a room temperature method. The secondary complex formation between the Zn cluster with 8-Hydroxyquinoline harnessed visible light and acted as a mediator to transfer photoinduced electrons to MOF-5 for enhancing the photocatalytic reaction rate with visible light. HOQ@MOF-5 was characterized by various spectroscopic techniques, such as XRD showing the crystalline nature of compound, UV-Visible spectroscopy showing the 2.54 eV band gap of HOQ@MOF-5 and morphological analysis tools, such as the nanoparticle nature of the compound with 9.561 nm particle size. The photocatalytic effect was estimated using the photocatalytic degradation of phenol as a representative organic pollutant under visible light irradiation. This work provides a new compound acting as source of electrons transfer for the development of efficient photocatalysts for remediation of environmental pollution.

Use of a Reflective Ultraviolet Imaging System (RUVIS) on Two-Dimensional Dust Impressions Created with Footwear on Multiple Substrates

NASA Astrophysics Data System (ADS)

Engelson, Brian Aaron

Footwear impression evidence in dust is often difficult to locate in ambient light and is a fragile medium that both collection and enhancement techniques can destroy or distort. The collection of footwear impression evidence always begins with non-destructive photographic techniques; however, current methods are limited to oblique lighting of the impression followed by an attempt to photograph in situ. For the vast majority of footwear impressions, an interactive collection method, and thus a potentially destructive procedure, is subsequently carried out to gather the evidence. Therefore, alternative non-destructive means for the preservation and enhancement of footwear impressions in dust merits further attention. Previous research performed with reflected ultraviolet (UV) photography and reflected ultraviolet imaging systems (RUVIS) has shown that there are additional non-destructive methodologies that can be applied to the search for and documentation of footwear impressions in dust. Unfortunately, these prior studies did not include robust comparisons to traditional oblique white light, instead choosing to focus on different UV wavelengths. This study, however, seeks to evaluate the use of a RUVIS device paired with a 254 nanometer (nm) UV light source to locate 2-D footwear impressions in dust on multiple substrates against standard oblique white light techniques and assess the visibility of the impression and amount of background interference present. The optimal angle of incident UV light for each substrate was also investigated. Finally, this study applied an image enhancement technique in order to evaluate its usefulness when looking at the visibility of a footwear impression and the amount of background interference present for enhanced white light and RUVIS pictures of footwear impressions in dust. A collection of eight different substrate types was gathered for investigation, including vinyl composition tile (VCT), ceramic tile, marble tile, magazine paper, steel sheet metal, vinyl flooring, wood flooring, and carpet. Heel impressions were applied to the various substrates utilizing vacuum collected dust and normal walking pressure. Each substrate was then explored and photographed in ambient fluorescent light, oblique white light at 0°, 15°, 30°, and 0° with the light source below the surface plane of the substrate, and 254 nm UV light at 0°, 15°, 30°, 45°, 60°, 75°, 90° and 0° with the light source below the surface plane of the substrate. All pictures were evaluated for clarity and visible detail of the footwear impression and the amount of background interference present, selecting for the best images within a lighting condition group. Additional intra- and intergroup comparisons were carried out to explore differences created by the various lighting conditions. Enhanced images were then created with the best scored pictures and evaluated for additional modifications in impression visibility and background interference. Photographs of footwear impressions in dust illuminated with ambient fluorescent light proved to be the most difficult conditions under which a footwear impression could be visualized. However, both oblique white light and 254 nm UV light lighting conditions showed improvements in either visualization or background dropout, or both, over ambient light conditions. An assessment of the white light and 254 nm UV light RUVIS images also demonstrated that the best angles for the light source for all substrates were oblique 0 and oblique 0° below the surface plane of the substrate lighting. It was found that white light photographs generally provided higher visibility ratings, while RUVIS 254 nm UV light photographs provided better grades for reducing background interference. Enhanced images of white light conditions provided generally poorer quality and quantity of details, while enhanced RUVIS images seemed to improve upon these areas. The use of a RUVIS to capture photographs of footwear impression evidence in dust was found to be a successful secondary non-destructive technique that can be paired with traditional oblique white light procedures. Additionally, the use of below the surface plane of the substrate lighting techniques were found to improve either visibility or background dropout, or both, over standard 0 oblique lighting, depending on the light source, and should be employed, when applicable. Finally, further investigation into digital photo-editing enhancement techniques for footwear impression evidence in dust is needed.

Topological insulator infrared pseudo-bolometer with polarization sensitivity

DOEpatents

Sharma, Peter Anand

2017-10-25

Topological insulators can be utilized in a new type of infrared photodetector that is intrinsically sensitive to the polarization of incident light and static magnetic fields. The detector isolates single topological insulator surfaces and allows light collection and exposure to static magnetic fields. The wavelength range of interest is between 750 nm and about 100 microns. This detector eliminates the need for external polarization selective optics. Polarization sensitive infrared photodetectors are useful for optoelectronics applications, such as light detection in environments with low visibility in the visible wavelength regime.

Visible light emission induced by Krq+ (4 ≤ q ≤ 9) ions colliding with the Cu surface

NASA Astrophysics Data System (ADS)

Guo, Yipan; Yang, Zhihu; Xu, Qiumei; Ren, Jieru; Zhao, Hongyun; Zhao, Yongtao

2017-09-01

In this paper, we report visible light emission from 320 keV Krq+ (4 ≤ q ≤ 9) ions on the Cu target. The wavelength range measured is from 300 nm to 656 nm. Two Cu I spectra deriving from different initial states and one Kr I line are detected. Specifically, the two Cu I lines belong to transitions 3d104p(2P03/2) - 3d104s (2S1/2) at 324.78 nm (A) and 3d104p(2P01/2) - 3d104s(2S1/2) at 327.42 nm (B), respectively, and the photon yield ratio of spectra lines (A) and (B) are about 2:1. The Kr I line belongs to transition 4s24p5(2P03/2)11d 2[3/2]0 - 4s24p5(2P03/2)5p 2[1/2] at 486.12 nm (C). In addition, the experimental results show that the photon yields of all lines are increasing with the charge state increase.

A Comparison between Two Heterodyne Light Sources Using Different Electro-Optic Modulators for Optical Temperature Measurements at Visible Wavelengths

PubMed Central

Twu, Ruey-Ching; Lee, Yi-Huan; Hou, Hong-Yao

2010-01-01

In this paper we have successfully demonstrated a z-propagating Zn-indiffused lithium niobate electro-optic modulator used for optical heterodyne interferometry. Compared to a commercial buck-type electro-optic modulator, the proposed waveguide-type modulator has a lower driving voltage and smaller phase variation while measuring visible wavelengths of 532 nm and 632.8 nm. We also demonstrate an optical temperature measurement system using a homemade modulator. The results show that the measurement sensitivities are almost the same values of 25 deg/°C for both the homemade and the buck-type modulators for a sensing light with a wavelength of 632.8 nm. Because photorefractive impacts are essential in the buck-type modulator at a wavelength of 532 nm, it is difficult to obtain reliable phase measurements, whereas the stable phase operation of the homemade one allows the measurement sensitivity to be improved up to 30 deg/°C with the best measurement resolution at about 0.07 °C for 532 nm. PMID:22163429

Aluminum nitride integrated photonics platform for the ultraviolet to visible spectrum.

PubMed

Lu, Tsung-Ju; Fanto, Michael; Choi, Hyeongrak; Thomas, Paul; Steidle, Jeffrey; Mouradian, Sara; Kong, Wei; Zhu, Di; Moon, Hyowon; Berggren, Karl; Kim, Jeehwan; Soltani, Mohammad; Preble, Stefan; Englund, Dirk

2018-04-30

We demonstrate a wide-bandgap semiconductor photonics platform based on nanocrystalline aluminum nitride (AlN) on sapphire. This photonics platform guides light at low loss from the ultraviolet (UV) to the visible spectrum. We measure ring resonators with intrinsic quality factor (Q) exceeding 170,000 at 638 nm and Q >20,000 down to 369.5 nm, which shows a promising path for low-loss integrated photonics in UV and visible spectrum. This platform opens up new possibilities in integrated quantum optics with trapped ions or atom-like color centers in solids, as well as classical applications including nonlinear optics and on-chip UV-spectroscopy.

Spectroscopy of Tb3+ ions in monoclinic KLu(WO4)2 crystal application of an intermediate configuration interaction theory

NASA Astrophysics Data System (ADS)

Loiko, Pavel; Volokitina, Anna; Mateos, Xavier; Dunina, Elena; Kornienko, Alexey; Vilejshikova, Elena; Aguiló, Magdalena; Díaz, Francesc

2018-04-01

The spectroscopic properties of Tb3+ ions in monoclinic KLu(WO4)2 double tungstate crystal are studied with polarized light. The absorption spectra in the visible, near- and mid-IR including the transitions to all lower-lying 7FJ (J = 0 … 5) excited states are measured. The maximum absorption cross-section for the 7F6 → 5D4 transition is 3.42 × 10-21 cm2 at 486.7 nm for light polarization E || Nm. The transition probabilities for Tb3+ ions are calculated within the Judd-Ofelt theory modified for the case of an intermediate configuration interaction (ICI). The radiative lifetime of the 5D4 state is 450 μs and the luminescence quantum yield is >90%. The polarized stimulated-emission cross-section spectra for all 5D4 → 7FJ (J = 0 … 6) emission channels are evaluated. The maximum σSE is 11.4 × 10-21 cm2 at 549.4 nm (for E || Nm). Tb3+:KLu(WO4)2 features high transition cross-sections for polarized light being promising for color-tunable visible lasers and imaging.

One-step formation of TiO2 hollow spheres via a facile microwave-assisted process for photocatalytic activity

NASA Astrophysics Data System (ADS)

Mohamad Alosfur, Firas K.; Ridha, Noor J.; Hafizuddin Haji Jumali, Mohammad; Radiman, S.

2018-04-01

Mesoporous TiO2 hollow spherical nanostructures with high surface areas were successfully prepared using a microwave method. The prepared hollow spheres had a size range between 200 and 500 nm. The spheres consisted of numerous smaller TiO2 nanoparticles with an average diameter of 8 nm. The particles had an essentially mesoporous structure, with a pore size in the range of 2-50 nm. The results confirmed that the synthesised of anatase TiO2 nanoparticles with specific surface area approximately 172.3 m2 g-1. The effect of ultraviolet and visible light irradiation and catalyst dosage on the TiO2 photocatalytic activity was studied by measuring the degradation rate of methylene blue. The maximum dye degradation performances with low catalyst loading (30 mg) were 99% and 63.4% using the same duration of ultraviolet and visible light irradiation, respectively (120 min).

Visible-light system for detecting doxorubicin contamination on skin and surfaces.

PubMed

Van Raalte, J; Rice, C; Moss, C E

1990-05-01

A portable system that uses fluorescence stimulated by visible light to identify doxorubicin contamination on skin and surfaces was studied. When activated by violet-blue light in the 465-nm range, doxorubicin fluoresces, emitting orange-red light in the 580-nm range. The light source to stimulate fluorescence was a slide projector with a filter to selectively pass short-wave (blue) visible light. Fluorescence was both observed visually with viewing spectacles and photographed. Solutions of doxorubicin in sterile 0.9% sodium chloride injection were prepared in nine standard concentrations ranging from 2 to 0.001 mg/mL. Droplets of each admixture were placed on stainless steel, laboratory coat cloth, pieces of latex examination glove, bench-top absorbent padding, and other materials on which antineoplastics might spill or leak. These materials then were stored for up to eight weeks and photographed weekly. The relative ability of water, household bleach, hydrogen peroxide solution, and soap solution to deactivate doxorubicin was also measured. Finally, this system was used to inspect the antineoplastic-drug preparation and administration areas of three outpatient cancer clinics for doxorubicin contamination. Doxorubicin fluorescence was easily detectable with viewing spectacles when a slide projector was used as the light source. The photographic method was sensitive for doxorubicin concentrations from 2.0 to 0.001 mg/mL. Immersion of study materials in bleach for one minute eliminated detectable fluorescence. Doxorubicin contamination is detectable for at least eight weeks in the ambient environment. Probable doxorubicin contamination was detected in two of the three clinics surveyed. A safe, portable system that uses fluorescence stimulated by visible light is a sensitive method for detecting doxorubicin on skin and surfaces.

Light-Irradiation Wavelength and Intensity Changes Influence Aflatoxin Synthesis in Fungi

PubMed Central

Suzuki, Tadahiro

2018-01-01

Fungi respond to light irradiation by forming conidia and occasionally synthesizing mycotoxins. Several light wavelengths, such as blue and red, affect the latter. However, the relationship between light irradiation and mycotoxin synthesis varies depending on the fungal species or strain. This study focused on aflatoxin (AF), which is a mycotoxin, and the types of light irradiation that increase AF synthesis. Light-irradiation tests using the visible region indicated that blue wavelengths in the lower 500 nm region promoted AF synthesis. In contrast, red wavelengths of 660 nm resulted in limited significant changes compared with dark conditions. Irradiation tests with different intensity levels indicated that a low light intensity increased AF synthesis. For one fungal strain, light irradiation decreased the AF synthesis under all wavelength conditions. However, the decrease was mitigated by 525 nm low intensity irradiation. Thus, blue-green low intensity irradiation may increase AF synthesis in fungi. PMID:29304012

Preparation and enhanced visible-light photocatalytic H2-production activity of CdS-sensitized Pt/TiO2 nanosheets with exposed (001) facets.

PubMed

Qi, Lifang; Yu, Jiaguo; Jaroniec, Mietek

2011-05-21

CdS-sensitized Pt/TiO(2) nanosheets with exposed (001) facets were prepared by hydrothermal treatment of a Ti(OC(4)H(9))(4)-HF-H(2)O mixed solution followed by photochemical reduction deposition of Pt nanoparticles (NPs) on TiO(2) nanosheets (TiO(2) NSs) and chemical bath deposition of CdS NPs on Pt/TiO(2) NSs, successively. The UV and visible-light driven photocatalytic activity of the as-prepared samples was evaluated by photocatalytic H(2) production from lactic acid aqueous solution under UV and visible-light (λ ≥ 420 nm) irradiation. It was shown that no photocatalytic H(2)-production activity was observed on the pure TiO(2) NSs under UV and/or visible-light irradiation. Deposition of CdS NPs on Pt/TiO(2) NSs caused significant enhancement of the UV and visible-light photocatalytic H(2)-production rates. The morphology of TiO(2) particles had also significant influence on the visible-light H(2)-production activity. Among TiO(2) NSs, P25 and the NPs studied, the CdS-sensitized Pt/TiO(2) NSs show the highest photocatalytic activity (13.9% apparent quantum efficiency obtained at 420 nm), exceeding that of CdS-sensitized Pt/P25 by 10.3% and that of Pt/NPs by 1.21%, which can be attributed to the combined effect of several factors including the presence of exposed (001) facets, surface fluorination and high specific surface area. After many replication experiments of the photocatalytic hydrogen production in the presence of lactic acid, the CdS-sensitized Pt/TiO(2) NSs did not show great loss in the photocatalytic activity, confirming that the CdS/Pt/TiO(2) NSs system is stable and not photocorroded. © The Owner Societies 2011

Preparation of plasmonic porous Au@AgVO3 belt-like nanocomposites with enhanced visible light photocatalytic activity.

PubMed

Fu, Haitao; Yang, Xiaohong; Zhang, Zhikui; Wang, Wenwen; An, Xizhong; Dong, Yu; Li, Xue

2018-07-20

This study reports a visible light-driven plasmonic photocatalyst of Au deposited AgVO 3 nanocomposites prepared by a hydrothermal method, and further in situ modification of Au nanoparticles by a reducing agent of NaHSO 3 in an aqueous solution at room temperature. Various characterization techniques, such as SEM, TEM, XRD, EDS, XPS, and Brunauer-Emmett-Teller, were used to reveal the morphology, composition, and related properties. The results show that belt-like AgVO 3 nanoparticles with a width of ∼100 nm were successfully synthesized, and Au nanoparticles with controlled sizes (5-20 nm) were well distributed on the surface of the nanobelts. The UV-vis absorption spectra indicate that the decoration of Au nanoparticles can modulate the optical properties of the nanocomposites, namely, red shift occurs with the increase of Au content. The photocatalytic activities were measured by monitoring the degradation of Rhodamine B (RhB) with the presence of photocatalysts under visible light irradiation. The photodegradation results show that AgVO 3 nanobelts exhibit good visible light photocatalytic activities with a degradation efficiency of 98% in 50 min and a reaction rate constant of 0.025 min -1 towards 30 ppm RhB. With the modification of Au nanoparticles, photocatalytic activity basically increases with the molar ratio of Au to V. Among the Au@AgVO 3 nanocomposites, the 3% (molar ratio) Au decorated AgVO 3 nanobelts showed the highest photocatalytic activity, and the k (0.064 min -1 ) was almost two times higher than that of the pure AgVO 3 nanobelts. This can be attributed to several factors including specific surface areas, optical properties, and the energy band structure of the composites under visible light illumination. These findings may be useful for the practical use of visible light-driven photocatalysts with enhanced photocatalytic efficiencies for environmental remediation.

Preparation of plasmonic porous Au@AgVO3 belt-like nanocomposites with enhanced visible light photocatalytic activity

NASA Astrophysics Data System (ADS)

Fu, Haitao; Yang, Xiaohong; Zhang, Zhikui; Wang, Wenwen; An, Xizhong; Dong, Yu; Li, Xue

2018-07-01

This study reports a visible light-driven plasmonic photocatalyst of Au deposited AgVO3 nanocomposites prepared by a hydrothermal method, and further in situ modification of Au nanoparticles by a reducing agent of NaHSO3 in an aqueous solution at room temperature. Various characterization techniques, such as SEM, TEM, XRD, EDS, XPS, and Brunauer–Emmett–Teller, were used to reveal the morphology, composition, and related properties. The results show that belt-like AgVO3 nanoparticles with a width of ∼100 nm were successfully synthesized, and Au nanoparticles with controlled sizes (5–20 nm) were well distributed on the surface of the nanobelts. The UV–vis absorption spectra indicate that the decoration of Au nanoparticles can modulate the optical properties of the nanocomposites, namely, red shift occurs with the increase of Au content. The photocatalytic activities were measured by monitoring the degradation of Rhodamine B (RhB) with the presence of photocatalysts under visible light irradiation. The photodegradation results show that AgVO3 nanobelts exhibit good visible light photocatalytic activities with a degradation efficiency of 98% in 50 min and a reaction rate constant of 0.025 min‑1 towards 30 ppm RhB. With the modification of Au nanoparticles, photocatalytic activity basically increases with the molar ratio of Au to V. Among the Au@AgVO3 nanocomposites, the 3% (molar ratio) Au decorated AgVO3 nanobelts showed the highest photocatalytic activity, and the k (0.064 min‑1) was almost two times higher than that of the pure AgVO3 nanobelts. This can be attributed to several factors including specific surface areas, optical properties, and the energy band structure of the composites under visible light illumination. These findings may be useful for the practical use of visible light-driven photocatalysts with enhanced photocatalytic efficiencies for environmental remediation.

Multifunction interferometry using the electron mobility visibility and mean free path relationship.

PubMed

Pornsuwancharoen, N; Youplao, P; Amiri, I S; Aziz, M S; Tran, Q L; Ali, J; Yupapin, P; Grattan, K T V

2018-05-08

A conventional Michelson interferometer is modified and used to form the various types of interferometers. The basic system consists of a conventional Michelson interferometer with silicon-graphene-gold embedded between layers on the ports. When light from the monochromatic source is input into the system via the input port (silicon waveguide), the change in optical path difference (OPD) of light traveling in the stacked layers introduces the change in the optical phase, which affects to the electron mean free path within the gold layer, induces the change in the overall electron mobility can be seen by the interferometer output visibility. Further plasmonic waves are introduced on the graphene thin film and the electron mobility occurred within the gold layer, in which the light-electron energy conversion in terms of the electron mobility can be observed, the gold layer length is 100 nm. The measurement resolution in terms of the OPD of ∼50 nm is achieved. In applications, the outputs of the drop port device of the modified Michelson interferometer can be arranged by the different detectors, where the polarized light outputs, the photon outputs, the electron spin outputs can be obtained by the interference fringe visibility, mobility visibility and the spin up-down splitting output energies. The modified Michelson interferometer theory and the detection schemes are given in details. © 2018 Wiley Periodicals, Inc.

Efficient telecom to visible wavelength conversion in doubly resonant gallium phosphide microdisks

NASA Astrophysics Data System (ADS)

Lake, David P.; Mitchell, Matthew; Jayakumar, Harishankar; dos Santos, Laís Fujii; Curic, Davor; Barclay, Paul E.

2016-01-01

Resonant second harmonic generation between 1550 nm and 775 nm with normalized outside efficiency > 3.8 × 10 - 4 mW - 1 is demonstrated in a gallium phosphide microdisk supporting high-Q modes at visible ( Q ˜ 10 4 ) and infrared ( Q ˜ 10 5 ) wavelengths. The double resonance condition is satisfied for a specific pump power through intracavity photothermal temperature tuning using ˜ 360 μ W of 1550 nm light input to a fiber taper and coupled to a microdisk resonance. Power dependent efficiency consistent with a simple model for thermal tuning of the double resonance condition is observed.

Medium resolution spectra of the shuttle glow in the visible region of the spectrum

NASA Technical Reports Server (NTRS)

Viereck, R. A.; Murad, E.; Pike, C. P.; Mende, S. B.; Swenson, G. R.; Culbertson, F. L.; Springer, B. C.

1992-01-01

Recent spectral measurements of the visible shuttle glow (lambda = 400 - 800 nm) at medium resolution (1 nm) reveal the same featureless continuum with a maximum near 680 nm that was reported previously. This is also in good agreement with recent laboratory experiments that attribute the glow to the emissions of NO2 formed by the recombination of O + NO. The data that are presented were taken from the aft flight deck with a hand-held spectrograph and from the shuttle bay with a low-light-level television camera. Shuttle glow images and spectra are presented and compared with laboratory data and theory.

Method for transmittance measurements in sunglasses for a kiosk

NASA Astrophysics Data System (ADS)

Mello, Marcio M.; Figueiredo, M.; Konda, R. A.; Ventura, Liliane

2013-03-01

Light transmittance measurements through sunglasses lenses is one of the required tests of the Brazilian Standard NBR15111(2004). Its measurement establishes the category of the sample and determines the required ultraviolet, visible and infrared protection, as well as the attenuation coefficient for signal light recognition. However, these measurements are usually performed by spectrophotometers and educated users, who are acknowledged to manage the equipment, use the weighting functions (WF) and interpret the data. We propose an alternative method, which consists in having matching optics and electronics to obtain a close WF to be used in transmittance measurements, and create an accessible device, for public self-use, providing a simple way for measuring and educating the public about sunglasses protection. Measurements were made in 30 samples for UV test, performed for the 280 - 400nm range, where UVA and UVB light sources and two photodiode sensors with Erythema action response are assembled, and for traffic signal a visible light sensor was used with spectral human eye response and different LEDs. As for the visible test, the visible light sensor was used for different light sources: incandescent, fluorescent, and a set of LEDs, while the infrared test is performed by several LEDs that provide the 780 - 2000nm range, and an infrared sensor. For these tests, only the samples spectrum were used. The transmittances were within the deviation limit required by NBR15111. The results have led us to build a self service kiosk for public use providing the category, UV protection and IR protection of the sunglasses as well as the information regarding its use for driving.

Visible and UV photo-detection in ZnO nanostructured thin films via simple tuning of solution method.

PubMed

Khokhra, Richa; Bharti, Bandna; Lee, Heung-No; Kumar, Rajesh

2017-11-08

This study demonstrates significant visible light photo-detection capability of pristine ZnO nanostructure thin films possessing substantially high percentage of oxygen vacancies [Formula: see text] and zinc interstitials [Formula: see text], introduced by simple tuning of economical solution method. The demonstrated visible light photo-detection capability, in addition to the inherent UV light detection ability of ZnO, shows great dependency of [Formula: see text] and [Formula: see text] with the nanostructure morphology. The dependency was evaluated by analyzing the presence/percentage of [Formula: see text] and [Formula: see text] using photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS) measurements. Morphologies of ZnO viz. nanoparticles (NPs), nanosheets (NSs) and nanoflowers (NFs), as a result of tuning of synthesis method contended different concentrations of defects, demonstrated different photo-detection capabilities in the form of a thin film photodetector. The photo-detection capability was investigated under different light excitations (UV; 380~420 nm, white ; λ > 420 nm and green; 490~570 nm). The as fabricated NSs photodetector possessing comparatively intermediate percentage of [Formula: see text] ~ 47.7% and [Formula: see text] ~ 13.8% exhibited superior performance than that of NPs and NFs photodetectors, and ever reported photodetectors fabricated by using pristine ZnO nanostructures in thin film architecture. The adopted low cost and simplest approach makes the pristine ZnO-NSs applicable for wide-wavelength applications in optoelectronic devices.

UV/vis and NIR light-responsive spiropyran self-assembled monolayers.

PubMed

Ivashenko, Oleksii; van Herpt, Jochem T; Feringa, Ben L; Rudolf, Petra; Browne, Wesley R

2013-04-02

Self-assembled monolayers of a 6-nitro BIPS spiropyran (SP) modified with a disulfide-terminated aliphatic chain were prepared on polycrystalline gold surfaces and characterized by UV/vis absorption, surface-enhanced Raman scattering (SERS), and X-ray photoelectron spectroscopies (XPS). The SAMs obtained are composed of the ring-closed form (i.e., spiropyran) only. Irradiation with UV light results in conversion of the monolayer to the merocyanine form (MC), manifested in the appearance of an N(+) contribution in the N 1s region of the XPS spectrum of the SAMs, the characteristic absorption band of the MC form in the visible region at 555 nm, and the C-O stretching band in the SERS spectrum. Recovery of the initial state of the monolayer was observed both thermally and after irradiation with visible light. Several switching cycles were performed and monitored by SERS spectroscopy, demonstrating the stability of the SAMs during repeated switching between SP and MC states. A key finding in the present study is that ring-opening of the surface-immobilized spiropyrans can be induced by irradiation with continuous wave NIR (785 nm) light as well as by irradiation with UV light. We demonstrate that ring-opening by irradiation at 785 nm proceeds by a two-photon absorption pathway both in the SAMs and in the solid state. Hence, spiropyran SAMs on gold can undergo reversible photochemical switching from the SP to the MC form with both UV and NIR and the reverse reaction induced by irradiation with visible light or heating. Furthermore, the observation of NIR-induced switching with a continuous wave source holds important consequences in the study of photochromic switches on surfaces using SERS and emphasizes the importance of the use of multiple complementary techniques in characterizing photoresponsive SAMs.

TiO{sub 2}/N-graphene nanocomposite via a facile in-situ hydrothermal sol–gel strategy for visible light photodegradation of eosin Y

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yingliang; Pei, Fuyun, E-mail: xusg@zzu.edu.cn; Lu, Ruijuan

2014-12-15

Highlights: • TiO{sub 2}/N-graphene is synthesized via in-situ hydrothermal sol–gel strategy. • TiO{sub 2} nanoparticles are chemically anchored on N-graphene nanosheets. • The band gap of TiO{sub 2}/N-graphene is red-shifted from neat TiO{sub 2} nanoparticles. • 5-NGT nanocomposite has the best visible light photodegradation performance. - Abstract: TiO{sub 2}/N-graphene nanocomposites are synthesized via a facile in-situ hydrothermal sol–gel strategy in order to improve the photocatalytic efficiency for pollutant photodegradation under visible light irradiation. The as-prepared nanocomposites are respectively characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and UV–vis diffuse reflectance spectroscopy. Results indicated that neatmore » TiO{sub 2} nanoparticles have an average diameter about 6.70 nm while TiO{sub 2} nanoparticles in TiO{sub 2}/N-graphene nanocomposites synthesized through in-situ hydrothermal sol–gel strategy bear an average diameter of ∼1 nm and are anchored on N-graphene nanosheets via chemical bonding. Both neat TiO{sub 2} nanoparticles and chemically anchored TiO{sub 2} nanoparticles in TiO{sub 2}/N-graphene nanocomposites take on the crystal type of anatase. The band gap of TiO{sub 2}/N-graphene nanocomposites is red-shifted compared with neat TiO{sub 2} nanoparticles. The evaluation of photodegradation performance under visible light irradiation suggested that the nanocomposite with 5 wt% N-graphene content has the best visible light photodegradation performance.« less

Absorption and electrochromic modulation of near-infrared light: realized by tungsten suboxide

NASA Astrophysics Data System (ADS)

Li, Guilian; Zhang, Shouhao; Guo, Chongshen; Liu, Shaoqin

2016-05-01

In the present study, needle-like tungsten suboxide W18O49 nanocrystals were fabricated as the optical active substance to realize the aim of optical control of near-infrared light. The W18O49 nanocrystals were selected in this regard due to their unique optical performance. As revealed by the powder absorption result, the needle-like W18O49 nanocrystals show strong and wide photoabsorption in the entire near infrared region of 780-2500 nm, from which thin films with the W18O49 nanocrystal coating thus benefits and can strongly shield off almost all near infrared irradiation, whereas transmitting the majority of visible light. To make it more tunable, the W18O49 nanocrystals were finally assembled onto an ITO glass via the layer-by-layer strategy for later electrochromic investigation. The nanostructured architectures of the W18O49 nanocrystal electrochromic films exhibit high contrast, faster switching response, higher coloration efficiencies (150 cm2 C-1 at 650 nm and 255 cm2 C-1 at 1300 nm), better long-term redox switching stability (reversibility of 98% after 500 cycles) and wide electrochromic spectrum coverage of both the visible and infrared regions.In the present study, needle-like tungsten suboxide W18O49 nanocrystals were fabricated as the optical active substance to realize the aim of optical control of near-infrared light. The W18O49 nanocrystals were selected in this regard due to their unique optical performance. As revealed by the powder absorption result, the needle-like W18O49 nanocrystals show strong and wide photoabsorption in the entire near infrared region of 780-2500 nm, from which thin films with the W18O49 nanocrystal coating thus benefits and can strongly shield off almost all near infrared irradiation, whereas transmitting the majority of visible light. To make it more tunable, the W18O49 nanocrystals were finally assembled onto an ITO glass via the layer-by-layer strategy for later electrochromic investigation. The nanostructured architectures of the W18O49 nanocrystal electrochromic films exhibit high contrast, faster switching response, higher coloration efficiencies (150 cm2 C-1 at 650 nm and 255 cm2 C-1 at 1300 nm), better long-term redox switching stability (reversibility of 98% after 500 cycles) and wide electrochromic spectrum coverage of both the visible and infrared regions. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr09147k

Predicting color traits of intact broiler breast fillets using visible and infrared-light

USDA-ARS?s Scientific Manuscript database

The ability of using visible and near-infrared (Vis/NIR) spectroscopy with wavelengths ranging from 400 to 2500nm to predict broiler breast fillets color traits was assessed in this study. Deboning fillets from 214 carcasses slaughtered in a commercial processing plant were included in this work, sp...

Up-conversion luminescence coupled to plasmonic gold nanorods for light harvesting and hydrogen production.

PubMed

AlGhamdi, H; Katsiev, K; Wahab, A K; Llorca, J; Idriss, H

2017-12-05

The conversion of infrared light to visible-light which allows a larger fraction of sun-light to be used is needed to improve light-harvesting. In this work a tri-functional material composed of an up-converter (NaYF 4 -Yb-Tm), plasmonic gold nanorods and CdS was made photocatalytically active using 980 nm wavelength light for the reduction of H + to H 2 .

Photodegradation of methyl red under visible light by mesoporous carbon nitride

NASA Astrophysics Data System (ADS)

Hu, Yueyue; Zhang, Min; Xiao, Zaozao; Jiang, Tao; Yan, Bing; Li, Jian

2018-02-01

Mesoporous carbon nitride (mpg-C3N4) with tunable microstructure has been successfully prepared through a simple polymerization reaction of cyanamide by a nano hard-templating approach. The obtained materials have been characterized using X-ray diffraction (XRD), N2 adsorption, and Fourier transform infrared (FT-IR) spectroscopy. The results show that the pore diameter of the mpg-C3N4 materials can be easily tuned from 3.8 to 10.5 nm. The mpg-C3N4 materials are demonstrated to exhibit much higher visible light photocatalytic activity than that of g-C3N4 for the degradation of aqueous methyl red (MR). The high surface areas and large pore volume contributed to the efficient visible light photocatalytic activity.

Light absorption of organic aerosol from pyrolysis of corn stalk

NASA Astrophysics Data System (ADS)

Li, Xinghua; Chen, Yanju; Bond, Tami C.

2016-11-01

Organic aerosol (OA) can absorb solar radiation in the low-visible and ultra-violet wavelengths thereby modifying radiative forcing. Agricultural waste burning emits a large quantity of organic carbon in many developing countries. In this work, we improved the extraction and analysis method developed by Chen and Bond, and extended the spectral range of OC absorption. We examined light absorbing properties of primary OA from pyrolysis of corn stalk, which is a major type of agricultural wastes. Light absorption of bulk liquid extracts of OA was measured using a UV-vis recording spectrophotometer. OA can be extracted by methanol at 95%, close to full extent, and shows polar character. Light absorption of organic aerosol has strong spectral dependence (Absorption Ångström exponent = 7.7) and is not negligible at ultra-violet and low-visible regions. Higher pyrolysis temperature produced OA with higher absorption. Imaginary refractive index of organic aerosol (kOA) is 0.041 at 400 nm wavelength and 0.005 at 550 nm wavelength, respectively.

Three-dimensional all-dielectric metamaterial solid immersion lens for subwavelength imaging at visible frequencies

PubMed Central

Fan, Wen; Yan, Bing; Wang, Zengbo; Wu, Limin

2016-01-01

Although all-dielectric metamaterials offer a low-loss alternative to current metal-based metamaterials to manipulate light at the nanoscale and may have important applications, very few have been reported to date owing to the current nanofabrication technologies. We develop a new “nano–solid-fluid assembly” method using 15-nm TiO2 nanoparticles as building blocks to fabricate the first three-dimensional (3D) all-dielectric metamaterial at visible frequencies. Because of its optical transparency, high refractive index, and deep-subwavelength structures, this 3D all-dielectric metamaterial-based solid immersion lens (mSIL) can produce a sharp image with a super-resolution of at least 45 nm under a white-light optical microscope, significantly exceeding the classical diffraction limit and previous near-field imaging techniques. Theoretical analysis reveals that electric field enhancement can be formed between contacting TiO2 nanoparticles, which causes effective confinement and propagation of visible light at the deep-subwavelength scale. This endows the mSIL with unusual abilities to illuminate object surfaces with large-area nanoscale near-field evanescent spots and to collect and convert the evanescent information into propagating waves. Our all-dielectric metamaterial design strategy demonstrates the potential to develop low-loss nanophotonic devices at visible frequencies. PMID:27536727

False color viewing device

DOEpatents

Kronberg, J.W.

1992-10-20

A viewing device for observing objects in near-infrared false-color comprising a pair of goggles with one or more filters in the apertures, and pads that engage the face for blocking stray light from the sides so that all light reaching the user's eyes come through the filters. The filters attenuate most visible light and pass near-infrared (having wavelengths longer than approximately 700 nm) and a small amount of blue-green and blue-violet (having wavelengths in the 500 to 520 nm and shorter than 435 nm, respectively). The goggles are useful for looking at vegetation to identify different species and for determining the health of the vegetation, and to detect some forms of camouflage. 7 figs.

False color viewing device

DOEpatents

Kronberg, James W.

1992-01-01

A viewing device for observing objects in near-infrared false-color comprising a pair of goggles with one or more filters in the apertures, and pads that engage the face for blocking stray light from the sides so that all light reaching the user's eyes come through the filters. The filters attenuate most visible light and pass near-infrared (having wavelengths longer than approximately 700 nm) and a small amount of blue-green and blue-violet (having wavelengths in the 500 to 520 nm and shorter than 435 nm, respectively). The goggles are useful for looking at vegetation to identify different species and for determining the health of the vegetation, and to detect some forms of camouflage.

False color viewing device

DOEpatents

Kronberg, J.W.

1991-05-08

This invention consists of a viewing device for observing objects in near-infrared false-color comprising a pair of goggles with one or more filters in the apertures, and pads that engage the face for blocking stray light from the sides so that all light reaching, the user`s eyes come through the filters. The filters attenuate most visible light and pass near-infrared (having wavelengths longer than approximately 700 nm) and a small amount of blue-green and blue-violet (having wavelengths in the 500 to 520 nm and shorter than 435 nm, respectively). The goggles are useful for looking at vegetation to identify different species and for determining the health of the vegetation, and to detect some forms of camouflage.

Near-infrared (NIR) optogenetics using up-conversion system

NASA Astrophysics Data System (ADS)

Hososhima, Shoko; Yuasa, Hideya; Ishizuka, Toru; Yawo, Hiromu

2015-03-01

Non-invasive remote control technologies designed to manipulate neural functions for a comprehensive and quantitative understanding of the neuronal network in the brain as well as for the therapy of neurological disorders have long been awaited. Recently, it has become possible to optically manipulate the neuronal activity using biological photo-reactive molecules such as channelrhodopsin-2 (ChR2). However, ChR2 and its relatives are mostly reactive to visible light which does not effectively penetrate through biological tissues. In contrast, near-infrared (NIR) light penetrates deep into the tissues because biological systems are almost transparent to light within this so-called `imaging window'. Here we used lanthanide nanoparticles (LNPs), which are composed of rare-earth elements, as luminous bodies to activate channelrhodopsins (ChRs) since they absorb low-energy NIR light to emit high-energy visible light (up-conversion). Neuron-glioma-hybrid ND-7/23 cells were cultured with LNP(NaYF4:Sc/Yb/Er) particles (peak emission, 543 nm) and transfected to express C1V1 (peak absorbance, 539 nm), a chimera of ChR1 and VChR1. The photocurrents were generated in response to NIR laser light (976 nm) to a level comparable to that evoked by a filtered Hg lamp (530-550 nm). NIR light pulses also evoked action potentials in the cultured neurons that expressed C1V1. It is suggested that the green luminescent light emitted from LNPs effectively activated C1V1 to generate the photocurrent. With the optimization of LNPs, acceptor photo-reactive biomolecules and optics, this system could be applied to non-invasively actuate neurons deep in the brain.

Is "good enough" good enough for portable visible and near-visible spectrometry?

NASA Astrophysics Data System (ADS)

Scheeline, Alexander

2015-06-01

Some uses of portable spectrometers require the same quality as laboratory instruments. Such quality is challenging because of temperature and humidity variation, dust, and vibration. Typically, one chooses materials and mechanical layout to minimize the influence of these noise and background sources. Mechanical stability is constrained by limits on instrument mass and ergonomics. An alternative approach is to make minimally adequate hardware, compensating for variability in software. We describe an instrument developed specifically to use software to compensate for marginal hardware. An initial instantiation of the instrument is limited to 430 - 700 nm. Simple changes will allow expansion to cover 315 - 1000 nm. Outside this range, costs are likely to increase significantly. Inherent wavelength calibration comes from knowing the peak emission wavelength of an LED light source, and fitting of instrument dispersion to a model of order placement with each measurement. Dynamic range is determined by the product of camera response and intentionally wide throughput variation among hundreds of diffraction orders. Resolution degrades gracefully at low light levels, but is limited to ~ 2 nm at high light levels as initially fabricated and ~ 1 nm in principle. Stray light may be measured in real-time. Diffuse stray light can be employed for turbidimetry fluorimetry, and to aid compensation of working curve nonlinearity. While unsuitable for, Raman spectroscopy, the instrument shows promise for absorption, fluorescence, reflectance, and surface plasmon resonance spectrometries. To aid non-expert users, real-time training, measurement sequencing, and outcome interpretation are programmed with QR codes or web-linked instructions.

Reductive and oxidative degradation of iopamidol, iodinated X-ray contrast media, by Fe(III)-oxalate under UV and visible light treatment.

PubMed

Zhao, Cen; Arroyo-Mora, Luis E; DeCaprio, Anthony P; Sharma, Virender K; Dionysiou, Dionysios D; O'Shea, Kevin E

2014-12-15

Iopamidol, widely employed as iodinated X-ray contrast media (ICM), is readily degraded in a Fe(III)-oxalate photochemical system under UV (350 nm) and visible light (450 nm) irradiation. The degradation is nicely modeled by pseudo first order kinetics. The rates of hydroxyl radical (OH) production for Fe(III)-oxalate/H2O2/UV (350 nm) and Fe(III)-oxalate/H2O2/visible (450 nm) systems were 1.19 ± 0.12 and 0.30 ± 0.01 μM/min, respectively. The steady-state concentration of hydroxyl radical (OH) for the Fe(III)-oxalate/H2O2/UV (350 nm) conditions was 10.88 ± 1.13 × 10(-14) M and 2.7 ± 0.1 × 10(-14) M for the Fe(III)-oxalate/H2O2/visible (450 nm). The rate of superoxide anion radical (O2(-)) production under Fe(III)-oxalate/H2O2/UV (350 nm) was 0.19 ± 0.02 μM/min with a steady-state concentration of 5.43 ± 0.473 × 10(-10) M. Detailed product studies using liquid chromatography coupled to Q-TOF/MS demonstrate both reduction (multiple dehalogenations) and oxidation (aromatic ring and side chains) contribute to the degradation pathways. The reduction processes appear to be initiated by the carbon dioxide anion radical (CO2(-)) while oxidation processes are consistent with OH initiated reaction pathways. Unlike most advanced oxidation processes the Fe(III)-oxalate/H2O2/photochemical system can initiate to both reductive and oxidative degradation processes. The observed reductive dehalogenation is an attractive remediation strategy for halogenated organic compounds as the process can dramatically reduce the formation of the problematic disinfection by-products often associated with oxidative treatment processes. Copyright © 2014 Elsevier Ltd. All rights reserved.

Covering the optical spectrum through collective rare-earth doping of NaGdF4 nanoparticles: 806 and 980 nm excitation routes.

PubMed

Skripka, A; Marin, R; Benayas, A; Canton, P; Hemmer, E; Vetrone, F

2017-05-17

Today, at the frontier of biomedical research, the need has been clearly established for integrating disease detection and therapeutic function in one single theranostic system. Light-emitting nanoparticles are being intensively investigated to fulfil this demand, by continuously developing nanoparticle systems simultaneously emitting in both the UV/visible (light-triggered release and activation of drugs) and the near-infrared (imaging and tracking) spectral regions. In this work, rare-earth (RE) doped nanoparticles (RENPs) were synthesized via a thermal decomposition process and spectroscopically investigated as potential candidates as all-in-one optical imaging, diagnostic and therapeutic agents. These core/shell/shell nanoparticles (NaGdF 4 :Er 3+ ,Ho 3+ ,Yb 3+ /NaGdF 4 :Nd 3+ ,Yb 3+ /NaGdF 4 ) are optically excited by heating-free 806 nm light that, aside from minimizing the local thermal load, also allows to obtain a deeper sub-tissue penetration with respect to the still widely used 980 nm light. Moreover, these water-dispersed nanoplatforms offer interesting assets as triggers/probes for biomedical applications, by virtue of a plethora of emission bands (spanning the 380-1600 nm range). Our results pave the way to use these RENPs for UV/visible-triggered photodynamic therapy/drug release, while simultaneously tracking the nanoparticle biodistribution and monitoring their therapeutic action through the near-infrared signal that overlaps with biological transparency windows.

Enhanced Deformation of Azobenzene-Modified Liquid Crystal Polymers under Dual Wavelength Exposure: A Photophysical Model

NASA Astrophysics Data System (ADS)

Liu, Ling; Onck, Patrick R.

2017-08-01

Azobenzene-embedded liquid crystal polymers can undergo mechanical deformation in response to ultraviolet (UV) light. The natural rodlike trans state azobenzene absorbs UV light and isomerizes to a bentlike cis state, which disturbs the order of the polymer network, leading to an anisotropic deformation. The current consensus is that the magnitude of the photoinduced deformation is related to the statistical building up of molecules in the cis state. However, a recent experimental study [Liu and Broer, Nat. Commun. 6 8334 (2015)., 10.1038/ncomms9334] shows that a drastic (fourfold) increase of the photoinduced deformation can be generated by exposing the samples simultaneously to 365 nm (UV) and 455 nm (visible) light. To elucidate the physical mechanism that drives this increase, we develop a two-light attenuation model and an optomechanical constitutive relation that not only accounts for the statistical accumulation of cis azobenzenes, but also for the dynamic trans-cis-trans oscillatory isomerization process. Our experimentally calibrated model predicts that the optimal single-wavelength exposure is 395 nm light, a pronounced shift towards the visible spectrum. In addition, we identify a range of optimal combinations of two-wavelength lights that generate a favorable response for a given amount of injected energy. Our model provides mechanistic insight into the different (multi)wavelength exposures used in experiments and, at the same time, opens new avenues towards enhanced, multiwavelength optomechanical behavior.

The effect of nanoparticles size on photocatalytic and antimicrobial properties of Ag-Pt/TiO2 photocatalysts

NASA Astrophysics Data System (ADS)

Zielińska-Jurek, Anna; Wei, Zhishun; Wysocka, Izabela; Szweda, Piotr; Kowalska, Ewa

2015-10-01

Ag-Pt-modified TiO2 nanocomposites were synthesized using the sol-gel method. Bimetallic modified TiO2 nanoparticles exhibited improved photocatalytic activity under visible-light irradiation, better than monometallic Ag/TiO2 and Pt/TiO2 nanoparticles (NPs). All modified powders showed localized surface plasmon resonance (LSPR) in visible region. The photocatalysts' characteristics by X-ray diffractometry (XRD), scanning transmission electron microscopy (STEM), diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption (BET method for specific surface area) showed that sample with the highest photocatalytic activity had anatase structure, about 93 m2/g specific surface area, maximum plasmon absorption at ca. 420 nm and contained small NPs of silver of 6 nm and very fine platinum NPs of 3 nm. The photocatalytic activity was estimated by measuring the decomposition rate of phenol in 0.2 mM aqueous solution under Vis and UV/vis light irradiation. It was found that size of platinum was decisive for the photocatalytic activity under visible light irradiation, i.e., the smaller Pt NPs were, the higher was photocatalytic activity. While, antimicrobial activities, estimated for bacteria Escherichia coli and Staphylococcus aureus, and pathogenic fungi belonging to Candida family, were only observed for photocatalysts containing silver, i.e., Ag/TiO2 and Ag-Pt/TiO2 nanocomposites.

Novel UV-Visible Photodetector in Photovoltaic Mode with Fast Response and Ultrahigh Photosensitivity Employing Se/TiO2 Nanotubes Heterojunction.

PubMed

Zheng, Lingxia; Hu, Kai; Teng, Feng; Fang, Xiaosheng

2017-02-01

A feasible strategy for hybrid photodetector by integrating an array of self-ordered TiO 2 nanotubes (NTs) and selenium is demonstrated to break the compromise between the responsivity and response speed. Novel heterojunction between the TiO 2 NTs and Se in combination with the surface trap states at TiO 2 help regulate the electron transport and facilitate the separation of photogenerated electron-hole pairs under photovoltaic mode (at zero bias), leading to a high responsivity of ≈100 mA W -1 at 620 nm light illumination and the ultrashort rise/decay time (1.4/7.8 ms). The implanting of intrinsic p-type Se into TiO 2 NTs broadens the detection range to UV-visible (280-700 nm) with a large detectivity of over 10 12 Jones and a high linear dynamic range of over 80 dB. In addition, a maximum photocurrent of ≈10 7 A is achieved at 450 nm light illumination and an ultrahigh photosensitivity (on/off ratio up to 10 4 ) under zero bias upon UV and visible light illumination is readily achieved. The concept of employing novel heterojunction geometry holds great potential to pave a new way to realize high performance and energy-efficient optoelectronic devices for practical applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photofragmentation of colloidal solutions of gold nanoparticles under femtosecond laser pulses in IR and visible ranges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Danilov, P A; Zayarnyi, D A; Ionin, A A

The specific features of photofragmentation of sols of gold nanoparticles under focused femtosecond laser pulses in IR (1030 nm) and visible (515 nm) ranges is experimentally investigated. A high photofragmentation efficiency of nanoparticles in the waist of a pulsed laser beam in the visible range (at moderate radiation scattering) is demonstrated; this efficiency is related to the excitation of plasmon resonance in nanoparticles on the blue shoulder of its spectrum, in contrast to the regime of very weak photofragmentation in an IR-laser field of comparable intensity. Possible mechanisms of femtosecond laser photofragmentation of gold nanoparticles are discussed. (extreme light fieldsmore » and their applications)« less

Influence of daylight on the fate of silver and zinc oxide nanoparticles in natural aquatic environments.

PubMed

Odzak, Niksa; Kistler, David; Sigg, Laura

2017-07-01

Nanoparticles, such as silver (Ag-NP) and zinc oxide (ZnO-NP), are increasingly used in many consumer products. These nanoparticles (NPs) will likely be exposed to the aquatic environment (rain, river, lake water) and to light (visible and UV) in the products where they are applied, or after those products are discharged. Dissolution of Ag-NP and ZnO-NP is an important process because the dissolved Ag + and Zn 2+ are readily available and toxic for aquatic organisms. The objective of this study was to investigate the role of daylight (UV and visible) for the fate of engineered Ag-NP and ZnO-NPs in different types of natural waters. Ag-NP and ZnO-NP were exposed to rainwater, river Rhine, and lake waters (Greifen, Lucerne, Cristallina, Gruère) under different light conditions (no light, UV 300-400 nm and visible light 400-700 nm) for up to 8 days. Stronger agglomeration of Ag-NP was observed in the waters with higher ionic strength in comparison to those with lower ionic strength. Visible light tended to increase the dissolution of Ag-NP under most natural water conditions in comparison to dark conditions, whereas UV-light led to decreased dissolved Ag + after longer exposure time. These effects illustrate the dynamic interactions of Ag-NP with light, which may lead both to increased oxidation and to increased reduction of Ag + by organic compounds under UV-light. In the case of ZnO-NP, agglomeration occurred at higher ionic strength, but the effects of pH were predominant for dissolution, which occurred up to concentrations close to the solubility limit of ZnO(s) at pH around 8.2 and to nearly complete dissolution of ZnO-NP at lower pH (pH 4.8-6.5), with both visible and UV-light facilitating dissolution. This study thus shows that light conditions play an important role in the dissolution processes of nanoparticles. Copyright © 2017 Elsevier Ltd. All rights reserved.

Organization of the Topical Meeting on Tunable Solid State Lasers Held in North Falmouth, Massachusetts on 1-3 May 1989

DTIC Science & Technology

1989-08-30

nm to produce blue light at 455 nm (Figure 1). A 20 Hz doubled Nd:YAG pump laser emitting up to 150 mJ at 532 nm 147 WA4-2 was used to resonantly...pumped by a diode laser, then in addition to the processes of Fig. 1, excited state absorption of the pump light from both 4I13,/z and 4I3112 may be...are visible and UV systems pumped at wavelengths that are available from semiconductor diode lasers and infrared emitting systems having high slope

Tunable UV- and Visible-Light Photoresponse Based on p-ZnO Nanostructures/n-ZnO/Glass Peppered with Au Nanoparticles.

PubMed

Hsu, Cheng-Liang; Lin, Yu-Hong; Wang, Liang-Kai; Hsueh, Ting-Jen; Chang, Sheng-Po; Chang, Shoou-Jinn

2017-05-03

UV- and visible-light photoresponse was achieved via p-type K-doped ZnO nanowires and nanosheets that were hydrothermally synthesized on an n-ZnO/glass substrate and peppered with Au nanoparticles. The K content of the p-ZnO nanostructures was 0.36 atom %. The UV- and visible-light photoresponse of the p-ZnO nanostructures/n-ZnO sample was roughly 2 times higher than that of the ZnO nanowires. The Au nanoparticles of various densities and diameter sizes were deposited on the p-ZnO nanostructures/n-ZnO samples by a simple UV photochemical reaction method yielding a tunable and enhanced UV- and visible-light photoresponse. The maximum UV and visible photoresponse of the Au nanoparticle sample was obtained when the diameter size of the Au nanoparticle was approximately 5-35 nm. On the basis of the localized surface plasmon resonance effect, the UV, blue, and green photocurrent/dark current ratios of Au nanoparticle/p-ZnO nanostructures/n-ZnO are ∼1165, ∼94.6, and ∼9.7, respectively.

Rational Design of Zirconium-doped Titania Photocatalysts with Synergistic Brønsted Acidity and Photoactivity.

PubMed

Ma, Runyuan; Wang, Liang; Zhang, Bingsen; Yi, Xianfeng; Zheng, Anmin; Deng, Feng; Yan, Xuhua; Pan, Shuxiang; Wei, Xiao; Wang, Kai-Xue; Su, Dang Sheng; Xiao, Feng-Shou

2016-10-06

The preparation of photocatalysts with high activities under visible-light illumination is challenging. We report the rational design and construction of a zirconium-doped anatase catalyst (S-Zr-TiO 2 ) with Brønsted acidity and photoactivity as an efficient catalyst for the degradation of phenol under visible light. Electron microscopy images demonstrate that the zirconium sites are uniformly distributed on the sub-10 nm anatase crystals. UV-visible spectrometry indicates that the S-Zr-TiO 2 is a visible-light-responsive catalyst with narrower band gap than conventional anatase. Pyridine-adsorption infrared and acetone-adsorption 13 C NMR spectra confirm the presence of Brønsted acidic sites on the S-Zr-TiO 2 sample. Interestingly, the S-Zr-TiO 2 catalyst exhibits high catalytic activity in the degradation of phenol under visible-light illumination, owing to a synergistic effect of the Brønsted acidity and photoactivity. Importantly, the S-Zr-TiO 2 shows good recyclability. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

NASA Astrophysics Data System (ADS)

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

2018-04-01

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

CdS nanoparticles/CeO2 nanorods composite with high-efficiency visible-light-driven photocatalytic activity

NASA Astrophysics Data System (ADS)

You, Daotong; Pan, Bao; Jiang, Fan; Zhou, Yangen; Su, Wenyue

2016-02-01

Different mole ratios of CdS nanoparticles (NPs)/CeO2 nanorods (NRs) composites with effective contacts were synthesized through a two-step hydrothermal method. The crystal phase, microstructure, optical absorption properties, electrochemical properties and photocatalytic H2 production activity of these composites were investigated. It was concluded that the photogenerated charge carriers in the CdS NPs/CeO2 NRs composite with a proper mole ratio (1:1) exhibited the longest lifetime and highest separation efficiency, which was responsible for the highest H2-production rate of 8.4 mmol h-1 g-1 under visible-light irradiation (λ > 420 nm). The superior photocatalytic H2 evolution properties are attributed to the transfer of visible-excited electrons of CdS NPs to CeO2 NRs, which can effectively extend the light absorption range of wide-band gap CeO2 NRs. This work provides feasible routes to develop visible-light responsive CeO2-based nanomaterial for efficient solar utilization.

Enhancing visible light photo-oxidation of water with TiO2 nanowire arrays via cotreatment with H2 and NH3: synergistic effects between Ti3+ and N.

PubMed

Hoang, Son; Berglund, Sean P; Hahn, Nathan T; Bard, Allen J; Mullins, C Buddie

2012-02-29

We report a synergistic effect involving hydrogenation and nitridation cotreatment of TiO(2) nanowire (NW) arrays that improves the water photo-oxidation performance under visible light illumination. The visible light (>420 nm) photocurrent of the cotreated TiO(2) is 0.16 mA/cm(2) and accounts for 41% of the total photocurrent under simulated AM 1.5 G illumination. Electron paramagnetic resonance (EPR) spectroscopy reveals that the concentration of Ti(3+) species in the bulk of the TiO(2) following hydrogenation and nitridation cotreatment is significantly higher than that of the sample treated solely with ammonia. It is believed that the interaction between the N-dopant and Ti(3+) is the key to the extension of the active spectrum and the superior visible light water photo-oxidation activity of the hydrogenation and nitridation cotreated TiO(2) NW arrays. © 2012 American Chemical Society

ZrO2-modified mesoporous nanocrystalline TiO2-xNx as efficient visible light photocatalysts.

PubMed

Wang, Xinchen; Yu, Jimmy C; Chen, Yilin; Wu, Ling; Fu, Xianzhi

2006-04-01

Mesoporous nanocrystalline TiO2-xNx and TiO2-xNx/ZrO2 visible-light photocatalysts have been prepared by a sol-gel method. The photocatalysts were characterized by XRD, N2 adsorption-desorption, TEM, XPS, UV/Vis, and IR spectroscopy. The photocatalytic activity of the samples was evaluated by the decomposition of ethylene in air under visible light (lambda > 450 nm) illumination. Results revealed that nitrogen was doped into the lattice of TiO2 by the thermal treatment of NH3-adsorbed TiO2 hydrous gels, converting the TiO2 into a visible-light responsive catalyst. The introduction of ZrO2 into TiO2-xNx considerably inhibits the undesirable crystal growth during calcination. Consequently, the ZrO2-modified TiO2-xNx displays higher porosity, higher specific surface area, and an improved thermal stability over the corresponding unmodified TiO2-xNx samples.

Protection of therapeutic antibodies from visible light induced degradation: Use safe light in manufacturing and storage.

PubMed

Du, Cheng; Barnett, Gregory; Borwankar, Ameya; Lewandowski, Angela; Singh, Nripen; Ghose, Sanchayita; Borys, Michael; Li, Zheng Jian

2018-06-01

As macromolecules, biologics are susceptible to light exposure, which induces oxidation of multiple amino acid residues including tryptophan, tyrosine, phenylalanine, cysteine and methionine. Pertaining to safety, efficacy and potency, light-induced oxidation of biologics has been widely studied and necessary precautions need to be taken during biologics manufacturing process, drug substance and products handling and storage. Proteins will degrade to varying extents depending on the protein properties, degradation pathways, formulation compositions and type of light source. In addition to UV light, which has been widely known to degrade proteins, visible light from indoor fluorescent lighting also can mediate protein degradation. In this report, we examine and identify wavelengths in the visual spectrum (400-700 nm) that can cause monoclonal antibody and histidine buffer degradation. Installation of safe lights which exclude the identified damaging wavelengths from visible spectra in manufacturing and storage areas can provide a balance between lighting requirement for human operators and their safety and conservation of product quality. Copyright © 2018 Elsevier B.V. All rights reserved.

Vertically oriented TiO(x)N(y) nanopillar arrays with embedded Ag nanoparticles for visible-light photocatalysis.

PubMed

Jiang, Weitao; Ullah, Najeeb; Divitini, Giorgio; Ducati, Caterina; Kumar, R Vasant; Ding, Yucheng; Barber, Zoe H

2012-03-27

We present a straightforward method to produce highly crystalline, vertically oriented TiO(x)N(y) nanopillars (up to 1 μm in length) with a band gap in the visible-light region. This process starts with reactive dc sputtering to produce a TiN porous film, followed by a simple oxidation process at elevated temperatures in oxygen or air. By controlling the oxidation conditions, the band gap of the prepared TiO(x)N(y) can be tuned to different wavelength within the range of visible light. Furthermore, in order to inhibit carrier recombination to enhance the photocatalytic activity, Ag nanoparticles have been embedded into the nanogaps between the TiO(x)N(y) pillars by photoinduced reduction of Ag(+) (aq) irradiated with visible light. Transmission electron microscopy reveals that the Ag nanoparticles with a diameter of about 10 nm are uniformly dispersed along the pillars. The prepared TiO(x)N(y) nanopillar matrix and Ag:TiO(x)N(y) network show strong photocatalytic activity under visible-light irradiation, evaluated via degradation of Rhodamine B. © 2012 American Chemical Society

UV/visible albedos from airborne measurements

NASA Astrophysics Data System (ADS)

Webb, A.; Kylling, A.; Stromberg, I.

2003-04-01

During the INSPECTRO campaign effective surface albedo was measured at UV and visible wavelengths from two airborne platforms, a Cessna light aircraft and a hot air balloon. On board the Cessna was a scanning spectroradiometer measuring from 300 - 500nm at 10nm intervals. The NILU cube, with 6 faces and two UV channels at 312 and 340nm, was suspended beneath the hot air balloon. Flights took place over East Anglia during September, 2002. Balloon flights were made below cloud layers, while the Cessna flew both above and below cloud. The Cessna also flew over Barton Bendish, where surface albedos have been measured for ground truthing of satellite data, and measured the effective albedo at four visible wave- lengths in the centres of the satellite bandpass functions. Results of measurements from the different platforms are compared, and model simulations used to deduce the surface albedo from the effective albedo at altitude, giving, for example, an albedo of 0.02 ± 0.01 at 340nm.

Synthesis and photoluminescence study in Eu3+:Y2WO6 phosphors

NASA Astrophysics Data System (ADS)

Sonali, Mondal, Manisha; Rai, Vineet Kumar

2018-05-01

Eu3+ doped Y2WO6 phosphors were synthesized by solid state reaction method. The photoluminescence properties of the Eu3+:Y2WO6 phosphors were studied for different concentration of Eu3+ ions. The luminescence intensity is found maximum at 0.3 mol% of Eu3+ ions. The excitation spectra monitored at ˜617 nm lies in the 220 - 350 nm region occurs due to charge transfer state (CTS) band of the europium-oxygen interactions, which is caused by an electron transfer from oxygen 2p orbital to an empty 4f shell of europium ions. The phosphors effectively excited by ˜393 nm near-ultraviolet (NUV) light gives efficient red emission band (˜ 617 nm) corresponding to 5D0 → 7F2 transition. The concentration dependence photoluminescence study and the mechanisms behind the photoluminescence properties have been explored with the help of suitable energy level diagram. Moreover, the CIE colour coordinate lie in the near white region so the prepared phosphors can be suitably use in making visible downconverter and in making visible light display devices.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dunach, M.; Marti, T.; Khorana, H.G.

The light-dark adaptation reactions of a set of bacteriorhodopsin (bR) mutants that affect function and color of the chromophore were examined by using visible absorption spectroscopy. The absorbance spectra of the mutants Arg-82 in equilibrium Ala (Gln), Asp-85 in equilibrium Ala (Asn, Glu), Tyr-185 in equilibrium Phe, and Asp-212 in equilibrium Ala (Asn, Glu) were measured at different pH values during and after illumination. None of these mutants exhibited a normal dark-light adaptation, which in wild-type bR causes a red shift of the visible absorption maximum from 558 nm (dark-adapted bR) to 568 nm (light-adapted bR). Instead a reversible lightmore » reaction occurs in the Asp-85 and Asp-212 mutants from a blue form with lambda max near 600 nm to a pink form with lambda max near 480 nm. This light-induced shift explains the appearance of a reversed light adaptation previously observed for the Asp-212 mutants. In the case of the Tyr-185 and Arg-82 mutants, light causes a purple-to-blue transformation similar to the effect of lowering the pH. However, the blue forms observed in these mutants are not identical to those formed by acid titration or deionization of wild-type bR. It is suggested that in all of these mutants, the chromophore has lost the ability to undergo the normal 13-cis, 15-syn to all-trans, 15-anti light-driven isomerization, which occurs in native bR. Instead these mutants may have as stable forms all-trans,syn and 13-cis,anti chromophores, which are not allowed in native bR, except transiently.« less

ZnSe quantum dots modified with a Ni(cyclam) catalyst for efficient visible-light driven CO2 reduction in water.

PubMed

Kuehnel, Moritz F; Sahm, Constantin D; Neri, Gaia; Lee, Jonathan R; Orchard, Katherine L; Cowan, Alexander J; Reisner, Erwin

2018-03-07

A precious metal and Cd-free photocatalyst system for efficient CO 2 reduction in water is reported. The hybrid assembly consists of ligand-free ZnSe quantum dots (QDs) as a visible-light photosensitiser combined with a phosphonic acid-functionalised Ni(cyclam) catalyst, NiCycP. This precious metal-free photocatalyst system shows a high activity for aqueous CO 2 reduction to CO (Ni-based TON CO > 120), whereas an anchor-free catalyst, Ni(cyclam)Cl 2 , produced three times less CO. Additional ZnSe surface modification with 2-(dimethylamino)ethanethiol (MEDA) partially suppresses H 2 generation and enhances the CO production allowing for a Ni-based TON CO of > 280 and more than 33% selectivity for CO 2 reduction over H 2 evolution, after 20 h visible light irradiation ( λ > 400 nm, AM 1.5G, 1 sun). The external quantum efficiency of 3.4 ± 0.3% at 400 nm is comparable to state-of-the-art precious metal photocatalysts. Transient absorption spectroscopy showed that band-gap excitation of ZnSe QDs is followed by rapid hole scavenging and very fast electron trapping in ZnSe. The trapped electrons transfer to NiCycP on the ps timescale, explaining the high performance for photocatalytic CO 2 reduction. With this work we introduce ZnSe QDs as an inexpensive and efficient visible light-absorber for solar fuel generation.

High light harvesting efficiency CuInS2 quantum dots/TiO2/MoS2 photocatalysts for enhanced visible light photocatalytic H2 production.

PubMed

Yuan, Yong-Jun; Fang, Gaoliang; Chen, Daqin; Huang, Yanwei; Yang, Ling-Xia; Cao, Da-Peng; Wang, Jingjing; Yu, Zhen-Tao; Zou, Zhi-Gang

2018-04-24

Expanding the photoresponse range of TiO2-based photocatalysts is of great interest for photocatalytic H2 production. Herein, noble-metal-free CuInS2 quantum dots were employed as a novel inorganic dye to expand the visible light absorption of TiO2/MoS2 for solar H2 generation. The as-prepared CuInS2/TiO2/MoS2 photocatalysts exhibit broad absorption from the ultraviolet to near-infrared region. Under visible light irradiation (λ > 420 nm), the CuInS2/TiO2/MoS2 photocatalyst with 0.6 mmol g-1 CuInS2 and 0.5 wt% MoS2 showed the highest H2 evolution rate with a value of 1034 μmol h-1 g-1. Moreover, a considerable H2 evolution rate of 141 μmol h-1 g-1 was obtained under the irradiation of the optimized CuInS2/TiO2/MoS2 photocatalyst with >500 nm light. The reaction mechanism of the CuInS2/TiO2/MoS2 photocatalyst for photocatalytic H2 evolution was investigated in detail by photoluminescence decay study, and the results showed that the photoexcited electrons of CuInS2 can be transferred efficiently through TiO2 to MoS2 and then react with the absorbed protons to generate H2. The reported sensitization strategy tremendously improves the visible light absorption capacity and the photocatalytic performance of TiO2-based photocatalysts.

Penning plasma based simultaneous light emission source of visible and VUV lights

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vyas, G. L., E-mail: glvyas27@gmail.com; Prakash, R.; Pal, U. N.

In this paper, a laboratory-based penning plasma discharge source is reported which has been developed in two anode configurations and is able to produce visible and VUV lights simultaneously. The developed source has simultaneous diagnostics facility using Langmuir probe and optical emission spectroscopy. The two anode configurations, namely, double ring and rectangular configurations, have been studied and compared for optimum use of the geometry for efficient light emissions and recording. The plasma is produced using helium gas and admixture of three noble gases including helium, neon, and argon. The source is capable to produce eight spectral lines for pure heliummore » in the VUV range from 20 to 60 nm and total 24 spectral lines covering the wavelength range 20–106 nm for the admixture of gases. The large range of VUV lines is generated from gaseous admixture rather from the sputtered materials. The recorded spectrum shows that the plasma light radiations in both visible and VUV range are larger in double ring configuration than that of the rectangular configurations at the same discharge operating conditions. To clearly understand the difference, the imaging of the discharge using ICCD camera and particle-in-cell simulation using VORPAL have also been carried out. The effect of ion diffusion, metastable collision with the anode wall and the nonlinear effects are correlated to explain the results.« less

Raman spectroscopy of white wines.

PubMed

Martin, Coralie; Bruneel, Jean-Luc; Guyon, François; Médina, Bernard; Jourdes, Michael; Teissedre, Pierre-Louis; Guillaume, François

2015-08-15

The feasibility of exploiting Raman scattering to analyze white wines has been investigated using 3 different wavelengths of the incoming laser radiation in the near-UV (325 nm), visible (532 nm) and near infrared (785 nm). To help in the interpretation of the Raman spectra, the absorption properties in the UV-visible range of two wine samples as well as their laser induced fluorescence have also been investigated. Thanks to the strong intensity enhancement of the Raman scattered light due to electronic resonance with 325 nm laser excitation, hydroxycinnamic acids may be detected and analyzed selectively. Fructose and glucose may also be easily detected below ca. 1000 cm(-1). This feasibility study demonstrates the potential of the Raman spectroscopic technique for the analysis of white wines. Copyright © 2015 Elsevier Ltd. All rights reserved.

Photo- and thermal degradation of olive oil measured using an optical fibre smartphone spectrofluorimeter

NASA Astrophysics Data System (ADS)

Hossain, Md Arafat; Canning, John; Cook, Kevin; Ast, Sandra; Jamalipour, Abbas

2017-04-01

Degradation of olive oil under light and heat are analysed using an optical fibre based low-cost portable smartphone spectrofluorimeter. Visible fluorescence bands associated with phenolic acids, vitamins and chlorophyll centred at λ 452, 525 and 670 nm respectively are generated using near-UV excitation (LED λex 370 nm), of extra virgin olive oil are degraded more likely than refined olive oil under light and heat exposure. Packaging is shown to be critical when assessing the origin of degradation.

Soft-templating synthesis of mesoporous graphitic carbon nitride with enhanced photocatalytic H2 evolution under visible light.

PubMed

Yan, Hongjian

2012-04-07

g-C(3)N(4) with worm-like pore and narrow pore size distribution was synthesized by using Pluronic P123 as soft-template. The worm-like porous g-C(3)N(4) not only possesses high BET surface area but also redshifts its absorbance edge up to 800 nm, and shows photocatalytic activity even when the irradiation light λ > 700 nm. This journal is © The Royal Society of Chemistry 2012

Template synthesis of Ag/AgCl microrods and their efficient visible light-driven photocatalytic performance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Hua; Xiao, Liang; Huang, Jianhua, E-mail: jhhuang@zstu.edu.cn

2014-09-15

Highlights: • Preparation ofAg/AgCl microrods by reaction of Ag{sub 2}WO{sub 4} microrods with NaCl solution. • Generation of metallic Ag is induced by the ambient light in the synthesis process. • Ag/AgCl shows excellent visible light-driven photodegradation of organic dyes. - Abstract: Ag/AgCl microrods, aggregated by nanoparticles with a diameter ranging from 100 nm to 2 μm, were prepared by an ion-exchange reaction at 80 °C between Ag{sub 2}WO{sub 4} template and NaCl solution. The existence of metallic Ag species was confirmed by XRD, DRS and XPS measurements. Ag/AgCl microrods showed excellent photocatalytic activity for the degradation of rhodamine Bmore » and methylene blue under visible light irradiation. The degradation rate constants of rhodamine B and methylene blue are 0.176 and 0.114 min{sup −1}, respectively. The cycling photodegradation experiments suggest that Ag/AgCl microds could be employed as stable plasmonic photocatalysts for the degradation of organic dyes under visible light irradiation.« less

Wide-band tunable photonic bandgap device and laser in dye-doped liquid crystal refilled cholesteric liquid crystal polymer template system

NASA Astrophysics Data System (ADS)

Lin, Jia-De; Lin, Hong-Lin; Lin, Hsin-Yu; Wei, Guan-Jhong; Lee, Chia-Rong

2017-02-01

The scientists in the field of liquid crystal (LC) have paid significant attention in the exploration of novel cholesteric LC (CLC) polymer template (simply called template) in recent years. The self-assembling nanostructural template with chirality can effectively overcome the limitation in the optical features of traditional CLCs, such as enhancement of reflectivity over 50%, multiple photonic bandgaps (PBGs), and changeable optical characteristics by flexibly replacing the refilling LC materials, and so on. This work fabricates two gradient-pitched CLC templates with two opposite handednesses, which are then merged as a spatially tunable and highly reflective CLC template sample. This sample can simultaneously reflect right- and left-circularly polarized lights and the tunable spectral range includes the entire visible region. By increasing the temperature of the template sample exceeding the clearing point of the refilling LC, the light scattering significantly decreases and the reflectance effectively increase to exceed 50% in the entire visible region. This device has a maximum reflectance over 85% and a wide-band spatial tunability in PBG between 400 nm and 800 nm which covers the entire visible region. Not only the sample can be employed as a wide-band spatially tunable filter, but also the system doping with two suitable laser dyes which emitted fluorescence can cover entire visible region can develop a low-threshold, mirror-less laser with a spatial tunability at spectral regions including blue to red region (from 484 nm to 634 nm) and simultaneous lasing emission of left- and right-circular polarizations.

Polydopamine-Coated TiO2 Nanotubes for Selective Photocatalytic Oxidation of Benzyl Alcohol to Benzaldehyde Under Visible Light.

PubMed

Tripathy, Jyotsna; Loget, Gabriel; Altomare, Marco; Schmuki, Patrik

2016-05-01

TiO2 nanotube arrays grown by anodization were coated with thin layers of polydopamine as visible light sensitizer. The PDA-coated TiO2 scaffolds were used as photocatalyst for selective oxidation of benzyl alcohol under monochromatic irradiation at 473 nm. Benzaldehyde was selectively formed and no by-products could be detected. A maximized reaction yield was obtained in O2-saturated acetonitrile. A mechanism is proposed that implies firstly the charge carrier generation in polydopamine as a consequence of visible light absorption. Secondly, photo-promoted electrons are injected in TiO2 conduction band, and subsequently transferred to dissolved O2 to form O*2- radicals. These radicals react with benzyl alcohol and lead to its selective dehydrogenation oxidation towards benzaldehyde.

Cytotoxicity of All-Trans-Retinal Increases Upon Photodegradation†

PubMed Central

Różanowska, Małgorzata; Handzel, Kinga; Boulton, Michael E.; Różanowski, Bartosz

2013-01-01

All-trans-retinal (AtRal) can accumulate in the retina as a result of excessive exposure to light. The purpose of this study was to compare cytotoxicity of AtRal and photodegraded AtRal (dAtRal) on cultured human retinal pigment epithelial cells in dark and upon exposure to visible light. AtRal was degraded by exposure to visible light. Cytotoxicity was monitored by imaging of cell morphology, propidium iodide staining of cells with permeable plasma membrane and measurements of reductive activity of cells. Generation of singlet oxygen photosensitized by AtRal and dAtRal was monitored by time-resolved measurements of characteristic singlet oxygen phosphorescence. Photodegradation of AtRal resulted in a decrease in absorption of visible light and accumulation of the degradation products with absorption maximum at ~330 nm. Toxicity of dAtRal was concentration-dependent and was greater during irradiation with visible light than in dark. DAtRal was more cytotoxic than AtRal both in dark and during exposure to visible light. Photochemical properties of dAtRal indicate that it may be responsible for the maximum in the action spectra of retinal photodamage recorded in animals. In conclusion, photodegradation products of AtRal may impose a significant threat to the retina and therefore their roles in retinal pathology need to be explored. PMID:22515697

Synthesis of mesoporous TiO(2-x)N(x) spheres by template free homogeneous co-precipitation method and their photo-catalytic activity under visible light illumination.

PubMed

Parida, K M; Naik, Brundabana

2009-05-01

The article presents preparation, characterization and catalytic activity evaluation of an efficient nitrogen doped mesoporous titania sphere photo-catalyst for degradation of methylene blue (MB) and methyl orange (MO) under visible light illumination. Nitrogen doped titania was prepared by soft chemical route i.e. template free, slow and controlled homogeneous co-precipitation from titanium oxysulfate sulfuric acid complex hydrate, urea, ethanol and water. The molar composition of TiOSO(4) to urea was varied to prepare different atomic % nitrogen doped titania. Mesoporous anatase TiO(2-x)N(x) spheres with average crystallite size of 10 nm and formation of titanium oxynitride center were confirmed from HRTEM, XRD and XPS study. UV-vis DRS showed a strong absorption in the range of 400-500 nm which supports its use in visible spectrum of light. Nitrogen adsorption-desorption study supports the porous nature of the doped material. All the TiO(2-x)N(x) samples showed higher photo-catalytic activity than Degussa P(25) and undoped mesoporous titania. Sample containing around one atomic % nitrogen showed highest activity among the TiO(2-x)N(x) samples.

ZnO-nanorods: A possible white LED phosphor

NASA Astrophysics Data System (ADS)

Sarangi, Sachindra Nath; T., Arun; Ray, Dinseh K.; Sahoo, Pratap Kumar; Nozaki, Shinji; Sugiyama, Noriyuki; Uchida, Kazuo

2017-05-01

The white light-emitting diodes (LEDs) have drawn much attention to replace conventional lighting sources because of low energy consumption, high light efficiency and long lifetime. Although the most common approach to produce white light is to combine a blue LED chip and a yellow phosphor, such a white LED cannot be used for a general lighting application, which requires a broad luminescence spectrum in the visible wavelength range. We have successfully chemically synthesized the ZnO nanorods showing intense broad luminescence in the visible wavelength range and made a white LED using the ZnO nanorods as phosphor excited with a blue LED. Their lengths and diameters were 2 - 10 μm and 200 - 800 nm, respectively. The wurtzite structure was confirmed by the x-ray diffraction measurement. The PL spectrum obtained by exciting the ZnO nanorods with the He-Cd laser has two peaks, one associated with the near band-edge recombination and the other with recombination via defects. The peak intensity of the near band-edge luminescence at 388 nm is much weaker than that of the defect-related luminescence. The latter luminescence peak ranges from 450 to 850 nm and broad enough to be used as a phosphor for a white LED. A white LED has been fabricated using a blue LED with 450 nm emission and ZnO nanorod powders. The LED performances show a white light emission and the electroluminescence measurement shows a stiff increase in white light intensity with increasing blue LED current. The Commission International de1'Eclairage (CIE) chromaticity colour coordinates of 450 nm LED pumped white emission shows a coordinate of (0.31, 0.32) for white LED at 350 mA. These results indicate that ZnO nanorods provides an alternate and effective approach to achieve high-performance white LEDs and also other optoelectronic devices.

Hypericin and pulsed laser therapy of squamous cell cancer in vitro.

PubMed

Bublik, Michael; Head, Christian; Benharash, Peyman; Paiva, Marcos; Eshraghi, Adrian; Kim, Taiho; Saxton, Romaine

2006-06-01

This in vitro study compares continuous wave and pulsed laser light at longer wavelengths for activation of the phototoxic drug hypericin in human cancer cells. Two-photon pulsed laser light now allows high-resolution fluorescent imaging of cancer cells and should provide deeper tissue penetration with near infrared light for improved detection as well as phototoxicity in human tumors. Cultured Seoul National University (SNU)-1 tumor cells from a squamous cell carcinoma (SCC) were incubated with hypericin before photoirradiation at four laser wavelengths. Phototoxicity of hypericin sensitized SCC cells was measured by dimethyl thiazoldiphenyl (MTT) tetrazolium bromide cell viability assays and by confocal fluorescence microscopy via 532-nm and infrared two-photon pulsed laser light. Phototoxic response increased linearly with hypericin dose of 0.1-2 microM, light exposure time of 5-120 sec, and pulsed dye laser wavelengths of 514-593 nm. Light energy delivery for 50% cell phototoxicity (LD50) response was 9 joules at 514 nm, 3 joules at 550 nm, and less than 1 joule at the 593 nm hypericin light absorption maxima. Fluorescence confocal microscopy revealed membrane and perinuclear localization of hypericin in the SNU cells with membrane damage seen after excitation with visible 532 nm continuous wave light or two-photon 700-950 nm picosecond pulsed laser irradiation. Hypericin may be a powerful tumor targetting drug when combined with pulsed laser light in patients with recurrent head and neck SCC.

Emergence of two near-infrared windows for in vivo and intraoperative SERS.

PubMed

Lane, Lucas A; Xue, Ruiyang; Nie, Shuming

2018-04-06

Two clear windows in the near-infrared (NIR) spectrum are of considerable current interest for in vivo molecular imaging and spectroscopic detection. The main rationale is that near-infrared light can penetrate biological tissues such as skin and blood more efficiently than visible light because these tissues scatter and absorb less light at longer wavelengths. The first clear window, defined as light wavelengths between 650nm and 950nm, has been shown to be far superior for in vivo and intraoperative optical imaging than visible light. The second clear window, operating in the wavelength range of 1000-1700nm, has been reported to further improve detection sensitivity, spatial resolution, and tissue penetration because tissue photon scattering and background interference are further reduced at longer wavelengths. Here we discuss recent advances in developing biocompatible plasmonic nanoparticles for in vivo and intraoperative surface-enhanced Raman scattering (SERS) in both the first and second NIR windows. In particular, a new class of 'broad-band' plasmonic nanostructures is well suited for surface Raman enhancement across a broad range of wavelengths allowing a direct comparison of detection sensitivity and tissue penetration between the two NIR window. Also, optimized and encoded SERS nanoparticles are generally nontoxic and are much brighter than near-infrared quantum dots (QDs), raising new possibilities for ultrasensitive detection of microscopic tumors and image-guided precision surgery. Copyright © 2018 Elsevier Ltd. All rights reserved.

Compact laser transmitter delivering a long-range infrared beam aligned with a monitoring visible beam.

PubMed

Lee, Hong-Shik; Kim, Haeng-In; Lee, Sang-Shin

2012-06-10

A compact laser transmitter, which takes advantage of an optical subassembly module, was proposed and demonstrated, providing precisely aligned collinear IR and visible beams. The collimated IR beam acts as a long-range projectile for simulated combat, carrying an optical pulsed signal, whereas the visible beam plays the role of tracking the IR beam. The proposed laser transmitter utilizes IR (λ(1)=905 nm) and visible (λ(2)=660 nm) light sources, a fiber-optic collimator, and a beam combiner, which includes a wavelength division multiplexing (WDM) filter in conjunction with optical fiber. The device was built via the laser welding technique and then evaluated by investigating the characteristics of the generated light beams. The IR collimated beam produced had a Gaussian profile and a divergence angle of ~1.3 mrad, and the visible monitoring beam was appropriately collimated to be readily discernible in the vicinity of the transmitter. The two beams were highly aligned within an angle of 0.004 deg as anticipated. Finally, we performed a practical outdoor field test to assess the IR beam with the help of a receiver. An effective trajectory was observed ranging up to 660 m with an overall detectable beam width of ~60 cm.

Correlations between Colonization of Onion Thrips and Leaf Reflectance Measures across Six Cabbage Varieties

PubMed Central

Bálint, János; Nagy, Balázs Vince; Fail, József

2013-01-01

The main purpose of this study was to reveal if the UV-A, and visible light reflection of leaves of white cabbage varieties is correlated to resistance against onion thrips. The antixenotic resistance (AR) against onion thrips and thrips damage differed between varieties Balashi, Bloktor, Riana – considered resistant – and Green Gem, Hurricane, Quisor – considered susceptible. The solar UV-A (340–400 nm) and visible (401–650 nm) light reflection of white cabbage leaves were recorded. Correlation between AR against onion thrips and reflection of leaves in UV-A and visible range of the studied white cabbage varieties were computed. According to the AR evaluation onion thrips density was always higher on susceptible than on resistant varieties. The UV-A light reflection of head forming leaves and the contrast between head and exterior leaves (H/E) was negatively correlated with onion thrips host preference at an early stage of cabbage head formation. The visible light reflection of both head forming and exterior leaves was also negatively correlated with onion thrips host preference. Susceptible varieties had greater damage ratings at harvest than resistant ones and positive correlations were observed between AR and damage. AR against onion thrips may be affected by differences in reflection of cabbage leaves at an early growth stage. It is suggested that more intensive reflection of leaves and/or higher contrast values between the reflectance intensity of head versus outer leaves made the resistant varieties less attractive to onion thrips. Our results reported here provide the first evidence of negative correlation between UV-A and visible reflection of leaves and AR of white cabbage against a dangerous insect pest, opening new perspectives for understanding the role of reflection by plant leaves in pest management. PMID:24040093

Imaging System Performance and Visibility as Affected by the Physical Environment

DTIC Science & Technology

2013-09-30

devoted to the topic of light propagation and imaging across the air-sea interface and within the surface boundary layer of natural water bodies...Zaneveld and Pegau (2003) was used to estimate the horizontal visibility of a black target, y: y = 4.8 / α, (2) where α is the...attenuation coefficient at 532 nm, was necessary for predictions of horizontal visibility of a black target. Equations (2) and (3) were applied to IOP data

Light spectrum modifies the utilization pattern of energy sources in Pseudomonas sp. DR 5-09

PubMed Central

Rosberg, Anna Karin; Windstam, Sofia T.; Karlsson, Maria E.; Bergstrand, Karl-Johan; Khalil, Sammar; Wohanka, Walter

2017-01-01

Despite the overruling impact of light in the phyllosphere, little is known regarding the influence of light spectra on non-phototrophic bacteria colonizing the leaf surface. We developed an in vitro method to study phenotypic profile responses of bacterial pure cultures to different bands of the visible light spectrum using monochromatic (blue: 460 nm; red: 660 nm) and polychromatic (white: 350–990 nm) LEDs, by modification and optimization of a protocol for the Phenotype MicroArray™ technique (Biolog Inc., CA, USA). The new protocol revealed high reproducibility of substrate utilization under all conditions tested. Challenging the non-phototrophic bacterium Pseudomonas sp. DR 5–09 with white, blue, and red light demonstrated that all light treatments affected the respiratory profile differently, with blue LED having the most decisive impact on substrate utilization by impairing respiration of 140 substrates. The respiratory activity was decreased on 23 and 42 substrates under red and white LEDs, respectively, while utilization of one, 16, and 20 substrates increased in the presence of red, blue, and white LEDs, respectively. Interestingly, on four substrates contrasting utilization patterns were found when the bacterium was exposed to different light spectra. Although non-phototrophic bacteria do not rely directly on light as an energy source, Pseudomonas sp. DR 5–09 changed its respiratory activity on various substrates differently when exposed to different lights. Thus, ability to sense and distinguish between different wavelengths even within the visible light spectrum must exist, and leads to differential regulation of substrate usage. With these results, we hypothesize that different light spectra might be a hitherto neglected key stimulus for changes in microbial lifestyle and habits of substrate usage by non-phototrophic phyllospheric microbiota, and thus might essentially stratify leaf microbiota composition and diversity. PMID:29267321

Light spectrum modifies the utilization pattern of energy sources in Pseudomonas sp. DR 5-09.

PubMed

Gharaie, Samareh; Vaas, Lea A I; Rosberg, Anna Karin; Windstam, Sofia T; Karlsson, Maria E; Bergstrand, Karl-Johan; Khalil, Sammar; Wohanka, Walter; Alsanius, Beatrix W

2017-01-01

Despite the overruling impact of light in the phyllosphere, little is known regarding the influence of light spectra on non-phototrophic bacteria colonizing the leaf surface. We developed an in vitro method to study phenotypic profile responses of bacterial pure cultures to different bands of the visible light spectrum using monochromatic (blue: 460 nm; red: 660 nm) and polychromatic (white: 350-990 nm) LEDs, by modification and optimization of a protocol for the Phenotype MicroArray™ technique (Biolog Inc., CA, USA). The new protocol revealed high reproducibility of substrate utilization under all conditions tested. Challenging the non-phototrophic bacterium Pseudomonas sp. DR 5-09 with white, blue, and red light demonstrated that all light treatments affected the respiratory profile differently, with blue LED having the most decisive impact on substrate utilization by impairing respiration of 140 substrates. The respiratory activity was decreased on 23 and 42 substrates under red and white LEDs, respectively, while utilization of one, 16, and 20 substrates increased in the presence of red, blue, and white LEDs, respectively. Interestingly, on four substrates contrasting utilization patterns were found when the bacterium was exposed to different light spectra. Although non-phototrophic bacteria do not rely directly on light as an energy source, Pseudomonas sp. DR 5-09 changed its respiratory activity on various substrates differently when exposed to different lights. Thus, ability to sense and distinguish between different wavelengths even within the visible light spectrum must exist, and leads to differential regulation of substrate usage. With these results, we hypothesize that different light spectra might be a hitherto neglected key stimulus for changes in microbial lifestyle and habits of substrate usage by non-phototrophic phyllospheric microbiota, and thus might essentially stratify leaf microbiota composition and diversity.

Mild Deoxygenation of Sulfoxides over Plasmonic Molybdenum Oxide Hybrid with Dramatic Activity Enhancement under Visible Light.

PubMed

Kuwahara, Yasutaka; Yoshimura, Yukihiro; Haematsu, Kohei; Yamashita, Hiromi

2018-06-17

Harvesting solar light to boost commercially important organic synthesis still remains a challenge. Coupling of conventional noble metal catalysts with plasmonic oxide materials which exhibit intense plasmon absorption in the visible light region is a promising option for efficient solar energy utilization in catalysis. Herein we for the first time demonstrate that plasmonic hydrogen molybdenum bronze coupled with Pt nanoparticles (Pt/H x MoO 3-y ) shows a high catalytic performance in the deoxygenation of sulfoxides with 1 atm H 2 at room temperature, with dramatic activity enhancement under visible light irradiation relative to dark condition. The plasmonic molybdenum oxide hybrids with strong plasmon resonance peaks pinning at around 556 nm are obtained via a facile H-spillover process. Pt/H x MoO 3-y hybrid provides excellent selectivity for the deoxygenation of various sulfoxides as well as pyridine N-oxides, in which drastically improved catalytic efficiencies are obtained under the irradiation of visible light. Comprehensive analyses reveal that oxygen vacancies massively introduced via a H-spillover process are the main active sites, and reversible redox property of Mo atoms and strong plasmonic absorption play key roles in this reaction. The catalytic system works under extremely mild conditions and can boost the reaction by the assist of visible light, offering an ultimately greener protocol to produce sulfides from sulfoxides. Our findings may open up a new strategy for designing plasmon-based catalytic systems that can harness visible light efficiently.

Analysis of Biomolecules by Atmospheric Pressure Visible-Wavelength MALDI-Ion Trap-MS in Transmission Geometry

NASA Astrophysics Data System (ADS)

West, Raymond E.; Findsen, Eric W.; Isailovic, Dragan

2013-10-01

We report the development of a new AP visible-wavelength MALDI-ion trap-MS instrument with significantly improved performance over our previously reported system ( Int. J. Mass Spectrom. 315, 66-73 (2012)). A Nd:YAG pulsed laser emitting light at 532 nm was used to desorb and ionize oligosaccharides and peptides in transmission geometry through a glass slide. Limits of detection (LODs) achieved in MS mode correspond to picomole quantities of oligosaccharides and femtomole quantities of peptides. Tandem MS (MS/MS) experiments enabled identification of enzymatically digested proteins and oligosaccharides by comparison of MS/MS spectra with data found in protein and glycan databases. Moreover, the softness of ionization, LODs, and fragmentation spectra of biomolecules by AP visible-wavelength MALDI-MS were compared to those obtained by AP UV MALDI-MS using a Nd:YAG laser emitting light at 355 nm. AP visible-wavelength MALDI appears to be a softer ionization technique then AP UV MALDI for the analysis of sulfated peptides, while visible-wavelength MALDI-MS, MS/MS, and MS/MS/MS spectra of other biomolecules analyzed were mostly similar to those obtained by AP UV MALDI-MS. Therefore, the methodology presented will be useful for MS and MSn analyses of biomolecules at atmospheric pressure. Additionally, the AP visible-wavelength MALDI developed can be readily used for soft ionization of analytes on various mass spectrometers.

Hydrothermal synthesis infrared to visible upconversion luminescence of SrMoO4: Er3+/Yb3+ phosphor

NASA Astrophysics Data System (ADS)

Sinha, Shriya; Kumar, Kaushal

2018-04-01

The upconversion emission properties in Er3+/Yb3+ doped SrMoO4 phosphor synthesized via hydrothermal method is investigated upon 980 nm laser light excitation. The crystal structure and morphology of the synthesized phosphor are characterized by X-ray diffraction and field emission scanning electron microscopy. The X-ray diffraction pattern suggests that SrMoO4 phosphor has tetragonal phase structure. The phosphor emits strong green (525 and 552 nm) and red (665 nm) UC emissions along with weak blue (410 and 488 nm) and near infrared (798 nm) emission bands. The color emitted from the phosphor is shifted from yellow to green region with increasing the power density from 15 to 65 W/cm2. The result indicates that the present material is suitable for making infrared to visible up-converts and display devices.

Final Technical Report - Polymeric Multilayer Infrared Reflecting Mirrors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reed, John

2016-09-16

The goal of this project was to develop a clear, polymeric, multilayer film with an expanded infrared (IR) reflection band which would allow improved rejection of incident IR energy. The IR reflection band is covering the region from about 850 nm to 1830 nm. This film is essentially clear and colorless in the visible portion of the electromagnetic spectra (visible light transmission of about 89%) while reflecting 90-95% of the IR energy over the portion of the spectra indicated above. This film has a nominal thickness of 3 mils, is polymeric in nature (contains no metals, metal oxides, or othermore » material types) and is essentially clear in appearance This film can then be used as a component of other products such as a solar window film, an IR reflecting interlayer for laminated glass, a heat rejecting skylight film, a base film for daylight redirecting products, a greenhouse film, and many more applications. One of the main strengths of this product is that because it is a standalone IR rejecting film, it can be incorporated and retrofitted into many applications that desire or require the transmission of visible light, but want to block other portions of the solar spectra, especially the IR portion. Many of the applications exist in the window glazing product area where this film can provide for substantial energy improvements in applications where visible light is desired.« less

Hydrogen incorporation by plasma treatment gives mesoporous black TiO 2 thin films with visible photoelectrochemical water oxidation activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Islam, Syed Z.; Reed, Allen; Nagpure, Suraj

In this work, we use neutron reflectometry (NR) to investigate the roles of hydrogen in plasma treated hydrogen doped mesoporous black titania thin films in their visible light absorption and enhanced photoactivity for water oxidation. The cubic ordered mesoporous TiO 2 thin films are prepared by a surfactant-templated sol-gel method and are treated with hydrogen plasma, an approach hypothesized to capitalize on the high degree of disorder in the material and the high energy of the plasma species to achieve efficient hydrogen doping. UV-vis absorbance spectra indicate that H 2 plasma treatment makes TiO 2 films black, with broad-spectrum enhancementmore » of visible light absorption, and XPS analysis shows peak for Ti 3+ state in treated films. The presence of hydrogen in black mesoporous titania (H-TiO 2) films is confirmed by the scattering length density (SLD) profiles obtained from neutron reflectometry measurements. The H-TiO 2 shows ca. 28 times and 8 times higher photocurrent for photoelectrochemical water oxidation compared to undoped TiO 2 films under UV (365 nm) and blue (455 nm) LED irradiation, respectively. These findings provide the first direct evidence that the dramatic change in visible light absorbance of H-treated black TiO 2 is accompanied by significant hydrogen uptake and not just Ti 3+ generation or surface disordering.« less

Hydrogen incorporation by plasma treatment gives mesoporous black TiO 2 thin films with visible photoelectrochemical water oxidation activity

DOE PAGES

Islam, Syed Z.; Reed, Allen; Nagpure, Suraj; ...

2017-10-26

In this work, we use neutron reflectometry (NR) to investigate the roles of hydrogen in plasma treated hydrogen doped mesoporous black titania thin films in their visible light absorption and enhanced photoactivity for water oxidation. The cubic ordered mesoporous TiO 2 thin films are prepared by a surfactant-templated sol-gel method and are treated with hydrogen plasma, an approach hypothesized to capitalize on the high degree of disorder in the material and the high energy of the plasma species to achieve efficient hydrogen doping. UV-vis absorbance spectra indicate that H 2 plasma treatment makes TiO 2 films black, with broad-spectrum enhancementmore » of visible light absorption, and XPS analysis shows peak for Ti 3+ state in treated films. The presence of hydrogen in black mesoporous titania (H-TiO 2) films is confirmed by the scattering length density (SLD) profiles obtained from neutron reflectometry measurements. The H-TiO 2 shows ca. 28 times and 8 times higher photocurrent for photoelectrochemical water oxidation compared to undoped TiO 2 films under UV (365 nm) and blue (455 nm) LED irradiation, respectively. These findings provide the first direct evidence that the dramatic change in visible light absorbance of H-treated black TiO 2 is accompanied by significant hydrogen uptake and not just Ti 3+ generation or surface disordering.« less

Highly Efficient Low-Temperature N-Doped TiO2 Catalysts for Visible Light Photocatalytic Applications

PubMed Central

Mahy, Julien G.; Cerfontaine, Vincent; Devred, François; Gaigneaux, Eric M.; Heinrichs, Benoît; Lambert, Stéphanie D.

2018-01-01

In this paper, TiO2 prepared with an aqueous sol-gel synthesis by peptization process is doped with nitrogen precursor to extend its activity towards the visible region. Three N-precursors are used: urea, ethylenediamine and triethylamine. Different molar N/Ti ratios are tested and the synthesis is adapted for each dopant. For urea- and trimethylamine-doped samples, anatase-brookite TiO2 nanoparticles of 6–8 nm are formed, with a specific surface area between 200 and 275 m2·g−1. In ethylenediamine-doped samples, the formation of rutile phase is observed, and TiO2 nanoparticles of 6–8 nm with a specific surface area between 185 and 240 m2·g−1 are obtained. X-ray photoelectron spectroscopy (XPS) and diffuse reflectance measurements show the incorporation of nitrogen in TiO2 materials through Ti–O–N bonds allowing light absorption in the visible region. Photocatalytic tests on the remediation of water polluted with p-nitrophenol show a marked improvement for all doped catalysts under visible light. The optimum doping, taking into account cost, activity and ease of synthesis, is up-scaled to a volume of 5 L and compared to commercial Degussa P25 material. This up-scaled sample shows similar properties compared to the lab-scale sample, i.e., a photoactivity 4 times higher than commercial P25. PMID:29642626

Visible-to-telecom quantum frequency conversion of light from a single quantum emitter.

PubMed

Zaske, Sebastian; Lenhard, Andreas; Keßler, Christian A; Kettler, Jan; Hepp, Christian; Arend, Carsten; Albrecht, Roland; Schulz, Wolfgang-Michael; Jetter, Michael; Michler, Peter; Becher, Christoph

2012-10-05

We demonstrate efficient (>30%) quantum frequency conversion of visible single photons (711 nm) emitted by a quantum dot to a telecom wavelength (1313 nm). Analysis of the first- and second-order coherence before and after wavelength conversion clearly proves that pivotal properties, such as the coherence time and photon antibunching, are fully conserved during the frequency translation process. Our findings underline the great potential of single photon sources on demand in combination with quantum frequency conversion as a promising technique that may pave the way for a number of new applications in quantum technology.

Visible light spectral domain optical coherence microscopy system for ex vivo imaging

NASA Astrophysics Data System (ADS)

Lichtenegger, Antonia; Harper, Danielle J.; Augustin, Marco; Eugui, Pablo; Fialová, Stanislava; Woehrer, Adelheid; Hitzenberger, Christoph K.; Baumann, Bernhard

2017-02-01

A visible light spectral domain optical coherence microscopy system operating in the wavelength range of 450-680 nm was developed. The resulting large wavelength range of 230 nm enabled an ultrahigh axial resolution of 0.88μm in tissue. The setup consisted of a Michelson interferometer combined with a homemade spectrometer with a spectral resolution of 0.03 nm. Scanning of 1 x 1 mm2 and 0.5 x 0.5 mm2 areas was performed by an integrated microelectromechanical mirror. After scanning the light beam is focused onto the tissue by a commercial objective with a 10 x magnification, resulting in a transverse resolution of 2 μm . Specification measurements showed that a -89 dB sensitivity with a 24 dB/mm roll-off could be achieved with the system. First of all the capabilities of the system were tested by investigating millimeter paper, tape and the USAF (US Air Force) 1951 resolution test target. Finally cerebral tissues from non-pathological and Alzheimer's disease affected brains were investigated. The results showed that structures, such as white and gray matter, could be distinguished. Furthermore a first effort was made to differentiate Alzheimer's disease from healthy brain tissue.

Photocurrent enhancement of SiNW-FETs by integrating protein-shelled CdSe quantum dots

NASA Astrophysics Data System (ADS)

Moh, Sang Hyun; Kulkarni, Atul; San, Boi Hoa; Lee, Jeong Hun; Kim, Doyoun; Park, Kwang Su; Lee, Min Ho; Kim, Taesung; Kim, Kyeong Kyu

2016-01-01

We proposed a new strategy to increase the photoresponsivity of silicon NW field-effect transistors (FETs) by integrating CdSe quantum dots (QDs) using protein shells (PSs). CdSe QDs were synthesized using ClpP, a bacterial protease, as protein shells to control the size and stability of QD and to facilitate the mounting of QDs on SiNWs. The photocurrent of SiNW-FETs in response to light at a wavelength of 480 nm was enhanced by a factor of 6.5 after integrating CdSe QDs because of the coupling of the optical properties of SiNWs and QDs. As a result, the photoresponsivity to 480 nm light reached up to 3.1 × 106, the highest value compared to other SiNW-based devices in the visible light range.We proposed a new strategy to increase the photoresponsivity of silicon NW field-effect transistors (FETs) by integrating CdSe quantum dots (QDs) using protein shells (PSs). CdSe QDs were synthesized using ClpP, a bacterial protease, as protein shells to control the size and stability of QD and to facilitate the mounting of QDs on SiNWs. The photocurrent of SiNW-FETs in response to light at a wavelength of 480 nm was enhanced by a factor of 6.5 after integrating CdSe QDs because of the coupling of the optical properties of SiNWs and QDs. As a result, the photoresponsivity to 480 nm light reached up to 3.1 × 106, the highest value compared to other SiNW-based devices in the visible light range. Electronic supplementary information (ESI) available: Materials and methods. See DOI: 10.1039/c5nr07901b

Two dimensional imaging of photoluminescence from rice for quick and non-destructive evaluation

NASA Astrophysics Data System (ADS)

Katsumata, T.; Suzuki, T.; Aizawa, H.; Matashige, E.

2005-05-01

The visible PL with broad peak at wavelength of λ=462 nm are observed from polished rice, flour and corn starch under illumination of ultra-violet (UV) light. PL peaking at λ=462 nm is excited effectively with UV light at λ=365 nm. Peak intensity is found to vary with the source and the breed of the rice specimens. PL images from rice also reveal the uniformity of the rice products. Two-dimensional images of PL, which reavealed the uniformity of rice under UV irradiation, are potentially useful for the evaluation and the quality control of the rice products.

Enhanced Deformation of Azobenzene-Modified Liquid Crystal Polymers under Dual Wavelength Exposure: A Photophysical Model.

PubMed

Liu, Ling; Onck, Patrick R

2017-08-04

Azobenzene-embedded liquid crystal polymers can undergo mechanical deformation in response to ultraviolet (UV) light. The natural rodlike trans state azobenzene absorbs UV light and isomerizes to a bentlike cis state, which disturbs the order of the polymer network, leading to an anisotropic deformation. The current consensus is that the magnitude of the photoinduced deformation is related to the statistical building up of molecules in the cis state. However, a recent experimental study [Liu and Broer, Nat. Commun. 6 8334 (2015).NCAOBW2041-172310.1038/ncomms9334] shows that a drastic (fourfold) increase of the photoinduced deformation can be generated by exposing the samples simultaneously to 365 nm (UV) and 455 nm (visible) light. To elucidate the physical mechanism that drives this increase, we develop a two-light attenuation model and an optomechanical constitutive relation that not only accounts for the statistical accumulation of cis azobenzenes, but also for the dynamic trans-cis-trans oscillatory isomerization process. Our experimentally calibrated model predicts that the optimal single-wavelength exposure is 395 nm light, a pronounced shift towards the visible spectrum. In addition, we identify a range of optimal combinations of two-wavelength lights that generate a favorable response for a given amount of injected energy. Our model provides mechanistic insight into the different (multi)wavelength exposures used in experiments and, at the same time, opens new avenues towards enhanced, multiwavelength optomechanical behavior.

Self-Organized TiO₂-MnO₂ Nanotube Arrays for Efficient Photocatalytic Degradation of Toluene.

PubMed

Nevárez-Martínez, María C; Kobylański, Marek P; Mazierski, Paweł; Wółkiewicz, Jolanta; Trykowski, Grzegorz; Malankowska, Anna; Kozak, Magda; Espinoza-Montero, Patricio J; Zaleska-Medynska, Adriana

2017-03-31

Vertically oriented, self-organized TiO₂-MnO₂ nanotube arrays were successfully obtained by one-step anodic oxidation of Ti-Mn alloys in an ethylene glycol-based electrolyte. The as-prepared samples were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), UV-Vis absorption, photoluminescence spectroscopy, X-ray diffraction (XRD), and micro-Raman spectroscopy. The effect of the applied potential (30-50 V), manganese content in the alloy (5-15 wt. %) and water content in the electrolyte (2-10 vol. %) on the morphology and photocatalytic properties was investigated for the first time. The photoactivity was assessed in the toluene removal reaction under visible light, using low-powered LEDs as an irradiation source (λ max = 465 nm). Morphology analysis showed that samples consisted of auto-aligned nanotubes over the surface of the alloy, their dimensions were: diameter = 76-118 nm, length = 1.0-3.4 μm and wall thickness = 8-11 nm. It was found that the increase in the applied potential led to increase the dimensions while the increase in the content of manganese in the alloy brought to shorter nanotubes. Notably, all samples were photoactive under the influence of visible light and the highest degradation achieved after 60 min of irradiation was 43%. The excitation mechanism of TiO₂-MnO₂ NTs under visible light was presented, pointing out the importance of MnO₂ species for the generation of e - and h⁺.

Er{sup 3+}/Yb{sup 3+}co-doped bismuth molybdate nanosheets upconversion photocatalyst with enhanced photocatalytic activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adhikari, Rajesh; Gyawali, Gobinda; Cho, Sung Hun

2014-01-15

In this paper, we report the microwave hydrothermal synthesis of Er{sup 3+}/Yb{sup 3+} co-doped Bi{sub 2}MoO{sub 6} upconversion photocatalyst. Crystal structure, morphology, elemental composition, optical properties and BET surface area were analyzed in detail. Infrared to visible upconversion luminescence at 532 nm and 546 nm of the co-doped samples was investigated under excitation at 980 nm. The results revealed that the co-doping of Er{sup 3+}/Yb{sup 3+} into Bi{sub 2}MoO{sub 6} exhibited enhanced photocatalytic activity for the decomposition of rhodamine B under simulated solar light irradiation. Enhanced photocatalytic activity can be attributed to the energy transfer between Er{sup 3+}/Yb{sup 3+} andmore » Bi{sub 2}MoO{sub 6} via infrared to visible upconversion from Er{sup 3+}/Yb{sup 3+} ion and higher surface area of the Bi{sub 2}MoO{sub 6} nanosheets. Therefore, this synthetic approach may exhibit a better alternative to fabricate upconversion photocatalyst for integral solar light absorption. - Graphical abstract: Schematic illustration of the upconversion photocatalysis. Display Omitted - Highlights: • Er{sup 3+}/Yb{sup 3+} co-doped Bi{sub 2}MoO{sub 6} upconversion photocatalyst is successfully synthesized. • We obtained the nanosheets having high surface area. • Upconversion of IR to visible light was confirmed. • Upconversion phenomena can be utilized for effective photocatalysis.« less

Replacing effective spectral radiance by temperature in occupational exposure limits to protect against retinal thermal injury from light and near IR radiation.

PubMed

Madjidi, Faramarz; Behroozy, Ali

2014-01-01

Exposure to visible light and near infrared (NIR) radiation in the wavelength region of 380 to 1400 nm may cause thermal retinal injury. In this analysis, the effective spectral radiance of a hot source is replaced by its temperature in the exposure limit values in the region of 380-1400 nm. This article describes the development and implementation of a computer code to predict those temperatures, corresponding to the exposure limits proposed by the American Conference of Governmental Industrial Hygienists (ACGIH). Viewing duration and apparent diameter of the source were inputs for the computer code. At the first stage, an infinite series was created for calculation of spectral radiance by integration with Planck's law. At the second stage for calculation of effective spectral radiance, the initial terms of this infinite series were selected and integration was performed by multiplying these terms by a weighting factor R(λ) in the wavelength region 380-1400 nm. At the third stage, using a computer code, the source temperature that can emit the same effective spectral radiance was found. As a result, based only on measuring the source temperature and accounting for the exposure time and the apparent diameter of the source, it is possible to decide whether the exposure to visible and NIR in any 8-hr workday is permissible. The substitution of source temperature for effective spectral radiance provides a convenient way to evaluate exposure to visible light and NIR.

Light-triggered self-assembly of triarylamine-based nanospheres

NASA Astrophysics Data System (ADS)

Moulin, Emilie; Niess, Frédéric; Fuks, Gad; Jouault, Nicolas; Buhler, Eric; Giuseppone, Nicolas

2012-10-01

Tailored triarylamine units modified with terpyridine ligands were coordinated to Zn2+ ions and characterized as discrete dimeric entities. Interestingly, when these complexes were subsequently irradiated with simple visible light in chloroform, they readily self-assembled into monodisperse spheres with a mean diameter of 160 nm.Tailored triarylamine units modified with terpyridine ligands were coordinated to Zn2+ ions and characterized as discrete dimeric entities. Interestingly, when these complexes were subsequently irradiated with simple visible light in chloroform, they readily self-assembled into monodisperse spheres with a mean diameter of 160 nm. Electronic supplementary information (ESI) available: Synthetic procedures and products' characterization (2-4 and 6-9). 1H NMR titration of compound 6 by Zn(OTf)2 to form complex 7. Kinetic measurements by UV-Vis-NIR spectroscopy. Transmission electron microscopy imaging for complexes 8 and 9. UV-Vis-NIR for an Fe2+ analogue of complex 7. Dynamic light scattering and time autocorrelation function for self-assembly of complexes 7-9. Copies of 1H and 13C NMR spectra for compounds 2-4 and 6. See DOI: 10.1039/c2nr32168h

Photostimulated near-infrared persistent luminescence as a new optical read-out from Cr3+-doped LiGa5O8

PubMed Central

Liu, Feng; Yan, Wuzhao; Chuang, Yen-Jun; Zhen, Zipeng; Xie, Jin; Pan, Zhengwei

2013-01-01

In conventional photostimulable storage phosphors, the optical information written by x-ray or ultraviolet irradiation is usually read out as a visible photostimulated luminescence (PSL) signal under the stimulation of a low-energy light with appropriate wavelength. Unlike the transient PSL, here we report a new optical read-out form, photostimulated persistent luminescence (PSPL) in the near-infrared (NIR), from a Cr3+-doped LiGa5O8 NIR persistent phosphor exhibiting a super-long NIR persistent luminescence of more than 1,000 h. An intense PSPL signal peaking at 716 nm can be repeatedly obtained in a period of more than 1,000 h when an ultraviolet-light (250–360 nm) pre-irradiated LiGa5O8:Cr3+ phosphor is repeatedly stimulated with a visible light or a NIR light. The LiGa5O8:Cr3+ phosphor has promising applications in optical information storage, night-vision surveillance, and in vivo bio-imaging. PMID:23532003

Atomic-level molybdenum oxide nanorings with full-spectrum absorption and photoresponsive properties.

PubMed

Yang, Yong; Yang, Yang; Chen, Shuangming; Lu, Qichen; Song, Li; Wei, Yen; Wang, Xun

2017-11-16

Superthin nanostructures, particularly with atomic-level thicknesses, typically display unique optical properties because of their exceptional light-matter interactions. Here, we report a facile strategy for the synthesis of sulfur-doped molybdenum oxide nanorings with an atomic-level size (thickness of 0.5 nm) and a tunable ring-in-ring architecture. These atomic-level nanorings displayed strong photo-absorption in both the visible and infrared-light ranges and acted as a photothermal agent. Under irradiation with an 808 nm laser with an intensity of 1 W/cm 2 , a composite of the nanorings embedded in polydimethylsiloxane showed an ultrafast photothermal effect, delivering a local temperature of up to 400 °C within 20 s, which to the best of our knowledge is the highest temperature by light irradiation reported to date. Meanwhile, the resulting nanorings were also employed as a photoinitiator to remotely induce a visible-light shape memory response, self-healing, reshaping performance and reversible actuation of dynamic three-dimensional structures. This study demonstrates an advancement towards controlling atomic-level-sized nanostructures and achieving greatly enhanced optical performances for optoelectronics.

Silicon coupled with plasmon nanocavities generates bright visible hot luminescence

NASA Astrophysics Data System (ADS)

Cho, Chang-Hee; Aspetti, Carlos O.; Park, Joohee; Agarwal, Ritesh

2013-04-01

To address the limitations in device speed and performance in silicon-based electronics, there have been extensive studies on silicon optoelectronics with a view to achieving ultrafast optical data processing. The biggest challenge has been to develop an efficient silicon-based light source, because the indirect bandgap of silicon gives rise to extremely low emission efficiencies. Although light emission in quantum-confined silicon at sub-10 nm length scales has been demonstrated, there are difficulties in integrating quantum structures with conventional electronics. It is desirable to develop new concepts to obtain emission from silicon at length scales compatible with current electronic devices (20-100 nm), which therefore do not utilize quantum-confinement effects. Here, we demonstrate an entirely new method to achieve bright visible light emission in `bulk-sized' silicon coupled with plasmon nanocavities at room temperature, from non-thermalized carrier recombination. The highly enhanced emission (internal quantum efficiency of >1%) in plasmonic silicon, together with its size compatibility with current silicon electronics, provides new avenues for developing monolithically integrated light sources on conventional microchips.

Titanium dioxide encapsulation of supported Ag nanoparticles on the porous silica bead for increased photocatalytic activity

NASA Astrophysics Data System (ADS)

Liu, Hui; Deng, Lu; Sun, Chaochao; Li, Junqi; Zhu, Zhenfeng

2015-01-01

A new synthetic strategy has been developed to encapsulate Ag nanoparticles in heterogeneous catalysts to prevent their dropping and sintering. Ag nanoparticles with diameters about 5-10 nm were first supported on the porous silica bead. These were then covered with a fresh layer of titanium dioxide with the thickness about 5 nm. SEM and TEM images were used to confirm the success of each synthesis step, and the photocatalytic activity of the as-synthesized samples was evaluated by photocatalytic decolorization of Rhodamine B (Rh B) aqueous solution at ambient temperature under both UV and visible light irradiation. The resulting titanium dioxide encapsulated Ag nanoparticles exhibited an enhanced photocatalytic activity under both UV and visible light irradiation, this can be attributed to effective charge separation and light harvesting of the plasmonic silver nanoparticles decoration, even the reducing of the exciton recombination rate caused by the small grain size of anatase TiO2 nanocrystals.

Highly sensitive visible to infrared MoTe2 photodetectors enhanced by the photogating effect

NASA Astrophysics Data System (ADS)

Huang, Hai; Wang, Jianlu; Hu, Weida; Liao, Lei; Wang, Peng; Wang, Xudong; Gong, Fan; Chen, Yan; Wu, Guangjian; Luo, Wenjin; Shen, Hong; Lin, Tie; Sun, Jinglan; Meng, Xiangjian; Chen, Xiaoshuang; Chu, Junhao

2016-11-01

Two-dimensional materials are promising candidates for electronic and optoelectronic applications. MoTe2 has an appropriate bandgap for both visible and infrared light photodetection. Here we fabricate a high-performance photodetector based on few-layer MoTe2. Raman spectral properties have been studied for different thicknesses of MoTe2. The photodetector based on few-layer MoTe2 exhibits broad spectral range photodetection (0.6-1.55 μm) and a stable and fast photoresponse. The detectivity is calculated to be 3.1 × 109 cm Hz1/2 W-1 for 637 nm light and 1.3 × 109 cm Hz1/2 W-1 for 1060 nm light at a backgate voltage of 10 V. The mechanisms of photocurrent generation have been analyzed in detail, and it is considered that a photogating effect plays an important role in photodetection. The appreciable performance and detection over a broad spectral range make it a promising material for high-performance photodetectors.

Space- and Ground-based Coronal Spectro-Polarimetry

NASA Astrophysics Data System (ADS)

Fineschi, Silvano; Bemporad, Alessandro; Rybak, Jan; Capobianco, Gerardo

This presentation gives an overview of the near-future perspectives of ultraviolet and visible-light spectro-polarimetric instrumentation for probing coronal magnetism from space-based and ground-based observatories. Spectro-polarimetric imaging of coronal emission-lines in the visible-light wavelength-band provides an important diagnostics tool of the coronal magnetism. The interpretation in terms of Hanle and Zeeman effect of the line-polarization in forbidden emission-lines yields information on the direction and strength of the coronal magnetic field. As study case, this presentation will describe the Torino Coronal Magnetograph (CorMag) for the spectro-polarimetric observation of the FeXIV, 530.3 nm, forbidden emission-line. CorMag - consisting of a Liquid Crystal (LC) Lyot filter and a LC linear polarimeter - has been recently installed on the Lomnicky Peak Observatory 20cm Zeiss coronagraph. The preliminary results from CorMag will be presented. The linear polarization by resonance scattering of coronal permitted line-emission in the ultraviolet (UV)can be modified by magnetic fields through the Hanle effect. Space-based UV spectro-polarimeters would provide an additional tool for the disgnostics of coronal magnetism. As a case study of space-borne UV spectro-polarimeters, this presentation will describe the future upgrade of the Sounding-rocket Coronagraphic Experiment (SCORE) to include the capability of imaging polarimetry of the HI Lyman-alpha, 121.6 nm. SCORE is a multi-wavelength imager for the emission-lines, HeII 30.4 nm and HI 121.6 nm, and visible-light broad-band emission of the polarized K-corona. SCORE has flown successfully in 2009. This presentation will describe how in future re-flights SCORE could observe the expected Hanle effect in corona with a HI Lyman-alpha polarimeter.

Cu-TiO2 nanorods with enhanced ultraviolet- and visible-light photoactivity for bisphenol A degradation.

PubMed

Chiang, Li-Fen; Doong, Ruey-An

2014-07-30

In this study, the microwave-assisted sol-gel method and chemical reduction were used to synthesize Cu-TiO2 nanorod composites for enhanced photocatalytic degradation of bisphenol A (BPA) in the presence of UV and visible lights. The electron microscopic images showed that the Cu nanoparticles at 4.5±0.1nm were well-deposited onto the surface of TiO2 nanorods after chemical reduction of Cu ions by NaBH4. The X-ray diffractometry patterns and X-ray photoelectron spectroscopic results indicated that Cu species on the Cu-TiO2 nanorods were mainly the mixture of Cu2O and Cu(0). The Cu-TiO2 nanorods showed excellent photocatalytic activity toward BPA photodegradation under the irradiation of UV and visible lights. The pseudo-first-order rate constant (kobs) for BPA photodegradation by 7wt% Cu-TiO2 nanorods were 18.4 and 3.8 times higher than those of as-synthesized TiO2 nanorods and Degussa P25 TiO2, respectively, under the UV light irradiation. In addition, the kobs for BPA photodegradation by 7wt% Cu-TiO2 nanorods increased by a factor of 5.8 when compared with that of Degussa P25 TiO2 under the irradiation of 460±40nm visible light. Results obtained in this study clearly demonstrate the feasibility of using one-dimensional Cu-TiO2 nanorods for photocatalytic degradation of BPA and other pharmaceutical and personal care products in water and wastewater treatment plants. Copyright © 2014 Elsevier B.V. All rights reserved.

Room-Temperature and Aqueous-Phase Synthesis of Plasmonic Molybdenum Oxide Nanoparticles for Visible-Light-Enhanced Hydrogen Generation.

PubMed

Shi, Jiayuan; Kuwahara, Yasutaka; Wen, Meicheng; Navlani-García, Miriam; Mori, Kohsuke; An, Taicheng; Yamashita, Hiromi

2016-09-06

A straightforward aqueous synthesis of MoO3-x nanoparticles at room temperature was developed by using (NH4 )6 Mo7 O24 ⋅4 H2 O and MoCl5 as precursors in the absence of reductants, inert gas, and organic solvents. SEM and TEM images indicate the as-prepared products are nanoparticles with diameters of 90-180 nm. The diffuse reflectance UV-visible-near-IR spectra of the samples indicate localized surface plasmon resonance (LSPR) properties generated by the introduction of oxygen vacancies. Owing to its strong plasmonic absorption in the visible-light and near-infrared region, such nanostructures exhibit an enhancement of activity toward visible-light catalytic hydrogen generation. MoO3-x nanoparticles synthesized with a molar ratio of Mo(VI) /Mo(V) 1:1 show the highest yield of H2 evolution. The cycling catalytic performance has been investigated to indicate the structural and chemical stability of the as-prepared plasmonic MoO3-x nanoparticles, which reveals its potential application in visible-light catalytic hydrogen production. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zinc oxide nanostructures and its nano-compounds for efficient visible light photo-catalytic processes

NASA Astrophysics Data System (ADS)

Adam, Rania E.; Alnoor, Hatim; Elhag, Sami; Nur, Omer; Willander, Magnus

2017-02-01

Zinc oxide (ZnO) in its nanostructure form is a promising material for visible light emission/absorption and utilization in different energy efficient photocatalytic processes. We will first present our recent results on the effect of varying the molar ratio of the synthesis nutrients on visible light emission. Further we will use the optimized conditions from the molar ration experiments to vary the synthesis processing parameters like stirring time etc. and the effect of all these parameters in order to optimize the efficiency and control the emission spectrum are investigated using different complementary techniques. Cathodoluminescence (CL) is combined with photoluminescence (PL) and electroluminescence (EL) as the techniques to investigate and optimizes visible light emission from ZnO/GaN light emitting diodes. We will then show and discuss our recent finding of the use of high quality ZnO nanoparticles (NPs) for efficient photo-degradation of toxic dyes using the visible spectra, namely with a wavelength up to 800 nm. In the end, we show how ZnO nanorods (NRs) are used as the first template to be transferred to bismuth zinc vanadate (BiZn2VO6). The BiZn2VO6 is then used to demonstrate efficient and cost effective hydrogen production through photoelectrochemical water splitting using solar radiation.

Probing the electronic structure and photoactivation process of nitrogen-doped TiO2 using DRS, PL, and EPR.

PubMed

Zhang, Zizhong; Long, Jinlin; Xie, Xiuqiang; Lin, Huan; Zhou, Yangen; Yuan, Rusheng; Dai, Wenxin; Ding, Zhengxin; Wang, Xuxu; Fu, Xianzhi

2012-04-23

The electronic structure and photoactivation process in N-doped TiO(2) is investigated. Diffuse reflectance spectroscopy (DRS), photoluminescence (PL), and electron paramagnetic resonance (EPR) are employed to monitor the change of optical absorption ability and the formation of N species and defects in the heat- and photoinduced N-doped TiO(2) catalyst. Under thermal treatment below 573 K in vacuum, no nitrogen dopant is removed from the doped samples but oxygen vacancies and Ti(3+) states are formed to enhance the optical absorption in the visible-light region, especially at wavelengths above 500 nm with increasing temperature. In the photoactivation processes of N-doped TiO(2), the DRS absorption and PL emission in the visible spectral region of 450-700 nm increase with prolonged irradiation time. The EPR results reveal that paramagnetic nitrogen species (N(s)·, oxygen vacancies with one electron (V(o)·), and Ti(3+) ions are produced with light irradiation and the intensity of N(s)· species is dependent on the excitation light wavelength and power. The combined characterization results confirm that the energy level of doped N species is localized above the valence band of TiO(2) corresponding to the main absorption band at 410 nm of N-doped TiO(2), but oxygen vacancies and Ti(3+) states as defects contribute to the visible-light absorption above 500 nm in the overall absorption of the doped samples. Thus, a detailed picture of the electronic structure of N-doped TiO(2) is proposed and discussed. On the other hand, the transfer of charge carriers between nitrogen species and defects is reversible on the catalyst surface. The presence of oxygen-vacancy-related defects leads to quenching of paramagnetic N(s)· species but they stabilize the active nitrogen species N(s)(-). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of visible light on the optical properties of a-(Ge2Sb2Te5)90Ag10 thin film

NASA Astrophysics Data System (ADS)

Singh, Palwinder; Thakur, Anup

2018-05-01

(Ge2Sb2Te5)90Ag10 (GST-Ag) bulk alloy was prepared using melt quenching technique. GST-Ag thin film was deposited on glass substrate using thermal evaporation method. The prepared thin films were exposed to visible light (intensity of 105 Lux for 2, 8, 20 and 30 hours) using 25W LED lamp. Transmission spectra were taken using UV-vis-NIR spectrophotometer in the wavelength range 800-3200 nm. Optical band gap of as-deposited and light exposed thin films was determined using Tauc's plot. Optical band gap was found to be decreasing on light exposure upto 8 hours and after that no significant change was observed.

The synergistic effect of phase heterojunction and surface heterojunction to improve photocatalytic activity of VO •-TiO2: the co-catalytic effect of H3PW12O40

NASA Astrophysics Data System (ADS)

Li, Haiyan; Cai, Shengnan; Yang, Pengfei; Bai, Yan; Dang, Dongbin

2018-06-01

With nanotube titanic acid (abbreviated as NTA) and the 12-tungstophosphoric acid (H3PW12O40• xH2O, denoted as HPW) as start materials, respectively, according to a simple hydrothermal process in acid medium, we successfully prepared HPW modified VO •-TiO2 composite photocatalysts. During heat treatment companied by the transformation of NTA to TiO2, a kind of single-electron-trapped oxygen vacancy (VO •) could be formed contributing to the visible light absorption of catalysts. The morphology, phase and chemical structure, optical and electronic properties, and so on of the produced catalysts with various HPW loadings are characterized. The size range of synthesized photocatalyst nanoparticles are about 10 50 nm. Taking aqueous rhodamine B (RhB) dye as model pollutant, we carried out photocatalytic activity test of the achieved catalysts, revealing that the hybrid photocatalysts display significantly enhanced visible light-driven ( λ ≥ 420 nm) photocatalytic activity for degradation of RhB. Among various catalysts, HPWN-0.1-120 composite with nominal loading of 0.1 g HPW and heat treatment temperature of 120 °C possesses the highest photocatalytic performance in visible light, which is closely related to the co-effect of phase heterojunction of rutile/anatase, surface heterojunction of anatase/HPW, and oxygen vacancy (VO •). The two types of heterojunction promote greatly the separation efficiency of photoelectrons and photoholes and oxygen vacancy lures response of catalysts to visible light.

Visible Light-Assisted High-Performance Mid-Infrared Photodetectors Based on Single InAs Nanowire.

PubMed

Fang, Hehai; Hu, Weida; Wang, Peng; Guo, Nan; Luo, Wenjin; Zheng, Dingshan; Gong, Fan; Luo, Man; Tian, Hongzheng; Zhang, Xutao; Luo, Chen; Wu, Xing; Chen, Pingping; Liao, Lei; Pan, Anlian; Chen, Xiaoshuang; Lu, Wei

2016-10-12

One-dimensional InAs nanowires (NWs) have been widely researched in recent years. Features of high mobility and narrow bandgap reveal its great potential of optoelectronic applications. However, most reported work about InAs NW-based photodetectors is limited to the visible waveband. Although some work shows certain response for near-infrared light, the problems of large dark current and small light on/off ratio are unsolved, thus significantly restricting the detectivity. Here in this work, a novel "visible light-assisted dark-current suppressing method" is proposed for the first time to reduce the dark current and enhance the infrared photodetection of single InAs NW photodetectors. This method effectively increases the barrier height of the metal-semiconductor contact, thus significantly making the device a metal-semiconductor-metal (MSM) photodiode. These MSM photodiodes demonstrate broadband detection from less than 1 μm to more than 3 μm and a fast response of tens of microseconds. A high detectivity of ∼10 12 Jones has been achieved for the wavelength of 2000 nm at a low bias voltage of 0.1 V with corresponding responsivity of as much as 40 A/W. Even for the incident wavelength of 3113 nm, a detectivity of ∼10 10 Jones and a responsivity of 0.6 A/W have been obtained. Our work has achieved an extended detection waveband for single InAs NW photodetector from visible and near-infrared to mid-infrared. The excellent performance for infrared detection demonstrated the great potential of narrow bandgap NWs for future infrared optoelectronic applications.

A visible light-curable yet visible wavelength-transparent resin for stereolithography 3D printing

NASA Astrophysics Data System (ADS)

Park, Hong Key; Shin, Mikyung; Kim, Bongkyun; Park, Jin Woo; Lee, Haeshin

2018-04-01

Herein, a new polymeric resin for stereolithography (SLA) three-dimensional printing (SLA-3DP) is reported. An ultraviolet (UV) or visible (VIS) light source is critical for SLA printing technology. UV light can be used to manufacture 3D objects in SLA-3DP, but there are significant occupational safety and health issues (particularly for eyes). These issues prevent the widespread use of SLA-3DP at home or in the office. Through the use of VIS light, the safety and health issues can largely be solved, but only non-transparent 3D objects can be manufactured, which prevents the application of 3DP to the production of various common transparent consumer products. For these reasons, we developed a VIS light-curable yet visibly transparent resin for SLA-3DP, which also retains UV curability. The key was to identify the photoinitiator diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (DPTBP). DPTBP was originally designed as a UV photoinitiator, but we found that VIS light irradiation is sufficient to split DPTBP and generate radicals due to its slight VIS light absorption up to 420 nm. The cured resin displays high transparency and beautiful transparent colors by incorporating various dyes; additionally, its mechanical properties are superior to those of commercial resins (Arario 410) and photoinitiators (Irgacure 2959).

Conversion of far ultraviolet to visible radiation: absolute measurements of the conversion efficiency of tetraphenyl butadiene

NASA Astrophysics Data System (ADS)

Vest, Robert E.; Coplan, Michael A.; Clark, Charles W.

Far ultraviolet (FUV) scintillation of noble gases is used in dark matter and neutrino research and in neutron detection. Upon collisional excitation, noble gas atoms recombine into excimer molecules that decay by FUV emission. Direct detection of FUV is difficult. Another approach is to convert it to visible light using a wavelength-shifting medium. One such medium, tetraphenyl butadiene (TPB) can be vapor-deposited on substrates. Thus the quality of thin TPB films can be tightly controlled. We have measured the absolute efficiency of FUV-to-visible conversion by 1 μm-thick TPB films vs. FUV wavelengths between 130 and 300 nm, with 1 nm resolution. The energy efficiency of FUV to visible conversion varies between 1% and 5%. We make comparisons with other recent results. Work performed at the NIST SURF III Synchrotron Ultraviolet Radiation Facility,.

High efficient photocatalytic selective oxidation of benzyl alcohol to benzaldehyde by solvothermal-synthesized ZnIn2S4 microspheres under visible light irradiation

NASA Astrophysics Data System (ADS)

Chen, Zhixin; Xu, Jingjing; Ren, Zhuyun; He, Yunhui; Xiao, Guangcan

2013-09-01

Hexagonal ZnIn2S4 samples have been synthesized by a solvothermal method. Their properties have been determined by X-ray diffraction, ultraviolet-visible-light diffuse reflectance spectra, field emission scanning electron microscopy, nitrogen adsorption-desorption and X-ray photoelectron spectra. These results demonstrate that ethanol solvent has significant influence on the morphology, optical and electronic nature for such marigold-like ZnIn2S4 microspheres. The visible light photocatalytic activities of the ZnIn2S4 have been evaluated by selective oxidation of benzyl alcohol to benzaldehyde using molecular oxygen as oxidant. The results show that 100% conversion along with >99% selectivity are reached over ZnIn2S4 prepared in ethanol solvent under visible light irradiation (λ>420 nm) of 2 h, but only 58% conversion and 57% yield are reached over ZnIn2S4 prepared in aqueous solvent. A possible mechanism of the high photocatalytic activity for selective oxidation of benzyl alcohol over ZnIn2S4 is proposed and discussed.

Synthesis and visible-light-induced catalytic activity of Ag2S-coupled TiO2 nanoparticles and nanowires

NASA Astrophysics Data System (ADS)

Xie, Yi; Heo, Sung Hwan; Kim, Yong Nam; Yoo, Seung Hwa; Cho, Sung Oh

2010-01-01

We present the synthesis and visible-light-induced catalytic activity of Ag2S-coupled TiO2 nanoparticles (NPs) and TiO2 nanowires (NWs). Through a simple wet chemical process from a mixture of peroxo titanic acid (PTA) solution, thiourea and AgAc, a composite of Ag2S NPs and TiO2 NPs with sizes of less than 7 nm was formed. When the NP composite was further treated with NaOH solution followed by annealing at ambient conditions, a new nanocomposite material comprising Ag2S NPs on TiO2 NWs was created. Due to the coupling with such a low bandgap material as Ag2S, the TiO2 nanocomposites could have a visible-light absorption capability much higher than that of pure TiO2. As a result, the synthesized Ag2S/TiO2 nanocomposites exhibited much higher catalytic efficiency for the decomposition of methyl orange than commercial TiO2 (Degussa P25, Germany) under visible light.

Smart windows based on cholesteric liquid crystals (Conference Presentation)

NASA Astrophysics Data System (ADS)

Khandelwal, Hitesh; Debije, Michael G.; Schenning, Albert P. H. J.

2017-02-01

With increase in global warming, use of active cooling and heating devices are continuously increasing to maintain interior temperature of built environment, greenhouses and cars. To reduce the consumption of tremendous amount of energy on cooling and heating devices we need an improved control of transparent features (i.e. windows). In this respect, smart window which is capable for reflecting solar infrared energy without interfering with the visible light would be very attractive. Most of the technologies developed so far are to control the visible light. These technologies block visual contact to the outside world which cause negative effects on human health. An appealing method to selectively control infrared transmission is via utilizing the reflection properties of cholesteric liquid crystals. In our research, we have fabricated a smart window which is capable of reflecting different amount of solar infrared energy depending on the specific climate conditions. The reflection bandwidth can be tuned from 120 nm to 1100 nm in the infrared region without interfering with the visible solar radiations. Calculations reveal that between 8% and 45% of incident solar infrared light can be reflected with a single cell. Simulation studies predicted that more than 12% of the energy spent on heating, cooling and lighting in the built environment can be saved by using the fabricated smart window compared to standard double glazing window.

Effective nitrogen doping into TiO2 (N-TiO2) for visible light response photocatalysis.

PubMed

Yoshida, Tomoko; Niimi, Satoshi; Yamamoto, Muneaki; Nomoto, Toyokazu; Yagi, Shinya

2015-06-01

The thickness-controlled TiO2 thin films are fabricated by the pulsed laser deposition (PLD) method. These samples function as photocatalysts under UV light irradiation and the reaction rate depends on the TiO2 thickness, i.e., with an increase of thickness, it increases to the maximum, followed by decreasing to be constant. Such variation of the reaction rate is fundamentally explained by the competitive production and annihilation processes of photogenerated electrons and holes in TiO2 films, and the optimum TiO2 thickness is estimated to be ca. 10nm. We also tried to dope nitrogen into the effective depth region (ca. 10nm) of TiO2 by an ion implantation technique. The nitrogen doped TiO2 enhanced photocatalytic activity under visible-light irradiation. XANES and XPS analyses indicated two types of chemical state of nitrogen, one photo-catalytically active N substituting the O sites and the other inactive NOx (1⩽x⩽2) species. In the valence band XPS spectrum of the high active sample, the additional electronic states were observed just above the valence band edge of a TiO2. The electronic state would be originated from the substituting nitrogen and be responsible for the band gap narrowing, i.e., visible light response of TiO2 photocatalysts. Copyright © 2015 Elsevier Inc. All rights reserved.

New Proof-of-Concept in Viral Inactivation: Virucidal Efficacy of 405 nm Light Against Feline Calicivirus as a Model for Norovirus Decontamination.

PubMed

Tomb, Rachael M; Maclean, Michelle; Coia, John E; Graham, Elizabeth; McDonald, Michael; Atreya, Chintamani D; MacGregor, Scott J; Anderson, John G

2017-06-01

The requirement for novel decontamination technologies for use in hospitals is ever present. One such system uses 405 nm visible light to inactivate microorganisms via ROS-generated oxidative damage. Although effective for bacterial and fungal inactivation, little is known about the virucidal effects of 405 nm light. Norovirus (NoV) gastroenteritis outbreaks often occur in the clinical setting, and this study was designed to investigate potential inactivation effects of 405 nm light on the NoV surrogate, feline calicivirus (FCV). FCV was exposed to 405 nm light whilst suspended in minimal and organically-rich media to establish the virucidal efficacy and the effect biologically-relevant material may play in viral susceptibility. Antiviral activity was successfully demonstrated with a 4 Log 10 (99.99%) reduction in infectivity when suspended in minimal media evident after a dose of 2.8 kJ cm -2 . FCV exposed in artificial faeces, artificial saliva, blood plasma and other organically rich media exhibited an equivalent level of inactivation using between 50-85% less dose of the light, indicating enhanced inactivation when the virus is present in organically-rich biologically-relevant media. Further research in this area could aid in the development of 405 nm light technology for effective NoV decontamination within the hospital environment.

Visible light-induced insulin aggregation on surfaces via photoexcitation of bound thioflavin T.

PubMed

Chouchane, Karim; Pignot-Paintrand, Isabelle; Bruckert, Franz; Weidenhaupt, Marianne

2018-04-01

Insulin is known to form amyloid aggregates when agitated in a hydrophobic container. Amyloid aggregation is routinely measured by the fluorescence of the conformational dye thioflavin T, which, when incorporated into amyloid fibers, fluoresces at 480 nm. The kinetics of amyloid aggregation in general is characterized by an initial lag-phase, during which aggregative nuclei form on the hydrophobic surface. These nuclei then lead to the formation of fibrils presenting a rapid growth during the elongation phase. Here we describe a novel mechanism of insulin amyloid aggregation which is surprisingly devoid of a lag-time for nucleation. The excitation of thioflavin T by visible light at 440 nm induces the aggregation of thioflavin T-positive insulin fibrils on hydrophobic surfaces in the presence of strong agitation and at physiological pH. This process is material surface-induced and depends on the fact that surface-adsorbed insulin can bind thioflavin T. Light-induced insulin aggregation kinetics is thioflavin T-mediated and is based on an energy transfer from visible light to the protein via thioflavin T. It relies on a constant supply of thioflavin T and insulin from the solution to the aggregate. The growth rate increases with the irradiance and with the concentration of thioflavin T. The supply of insulin seems to be the limiting factor of aggregate growth. This light-induced aggregation process allows the formation of local surface-bound aggregation patterns. Copyright © 2018 Elsevier B.V. All rights reserved.

n/p-Type changeable semiconductor TiO2 prepared from NTA

NASA Astrophysics Data System (ADS)

Li, Qiuye; Wang, Xiaodong; Jin, Zhensheng; Yang, Dagang; Zhang, Shunli; Guo, Xinyong; Yang, Jianjun; Zhang, Zhijun

2007-10-01

A novel kind of nano-sized TiO2 (anatase) was obtained by high-temperature (400-700°C) dehydration of nanotube titanic acid (H2Ti2O4(OH)2, NTA). The high-temperature (400-700°C) dehydrated nanotube titanic acids (HD-NTAs) with a unique defect structure exhibited a p-type semiconductor behavior under visible-light irradiation (λ≥420 nm, E photon=2.95 eV), whereas exhibited an n-type semiconductor behavior irradiated with UV light (λ=365 nm, E photon=3.40 eV).

Multi-wavelength Characterization of Brown and Black Carbon from Filter Samples

NASA Astrophysics Data System (ADS)

Johnson, M. M.; Yatavelli, R. L. N.; Chen, L. W. A. A.; Gyawali, M. S.; Arnott, W. P.; Wang, X.; Chakrabarty, R. K.; Moosmüller, H.; Watson, J. G.; Chow, J. C.

2014-12-01

Particulate matter (PM) scatters and absorbs solar radiation and thereby affects visibility, the Earth's radiation balance, and properties and lifetimes of clouds. Understanding the radiative forcing (RF) of PM is essential to reducing the uncertainty in total anthropogenic and natural RF. Many instruments that measure light absorption coefficients (βabs [λ], Mm-1) of PM have used light at near-infrared (NIR; e.g., 880 nm) or red (e.g., 633 nm) wavelengths. Measuring βabs over a wider wavelength range, especially including the ultraviolet (UV) and visible, allows for contributions from black carbon (BC), brown carbon (BrC), and mineral dust (MD) to be differentiated. This will help to determine PM RF and its emission sources. In this study, source and ambient samples collected on Teflon-membrane and quartz-fiber filters are used to characterize and develop a multi-wavelength (250 - 1000 nm) filter-based measurement method of PM light absorption. A commercially available UV-visible spectrometer coupled with an integrating sphere is used for quantifying diffuse reflectance and transmittance of filter samples, from which βabs and absorption Ǻngström exponents (AAE) of the PM deposits are determined. The filter-based light absorption measurements of laboratory generated soot and biomass burning aerosol are compared to 3-wavelength photoacoustic absorption measurements to evaluate filter media and loading effects. Calibration factors are developed to account for differences between filter types (Teflon-membrane vs. quartz-fiber), and between filters and in situ photoacoustic absorption values. Application of multi-spectral absorption measurements to existing archived filters, including specific source samples (e.g. diesel and gasoline engines, biomass burning, dust), will also be discussed.

Visible light assisted degradation of organic dye using Ag{sub 3}PO{sub 4}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dhanabal, R.; Bose, A. Chandra, E-mail: acbose@nitt.edu; Velmathi, S.

2015-06-24

The study of visible light photodegradation of organic dye Methylene Blue (MB) have been investigated using silver phosphate (Ag{sub 3}PO{sub 4}) as a photocatalyst which is good efficient material for photocatalytic reaction. The simple ion-exchange method is used to prepare Ag{sub 3}PO{sub 4}. The structure of the material have been confirmed using X-ray diffraction which shows cubic structure of Ag{sub 3}PO{sub 4}. The functional group of the Ag{sub 3}PO{sub 4} has been verified by Fourier transform infrared spectroscopy. The bandgap of Ag{sub 3}PO{sub 4} is calculated using kubelka-munk function from the ultra violet-visible diffuse reflectance spectroscopy, the absorption of Ag{submore » 3}PO{sub 4} starts from 470 nm. Under simulated visible light irradiation, Ag{sub 3}PO{sub 4} catalyst exhibits good catalytic ability for degrading MB dye.« less

Microwave heating synthesis and formation mechanism of chalcopyrite structured CuInS{sub 2} nanorods in deep eutectic solvent

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Jianjun, E-mail: zhangjianjun7110@163.com; Chen, Jun; Li, Qiang

2015-03-15

Graphical abstract: Chalcopyrite structured CuInS{sub 2} nanorods were synthesized by an environmentally friendly microwave heating method in deep eutectic solvent. Results show that microwave heating time plays an important role in the formation of CuInS{sub 2} nanostructure phase. The SEM results indicated that the obtained CuInS{sub 2} nanostructures display rod-like morphology with diameters of about 40 nm and lengths of about 400 nm. The UV–vis spectrum results indicated that the CuInS{sub 2} nanorods exhibit strong absorption from the entire visible light region to the near-infrared region beyond 1100 nm. The possible growth mechanism of CuInS{sub 2} nanorods was discussed. -more » Abstract: Chalcopyrite structured CuInS{sub 2} nanorods were synthesized by an environmentally friendly microwave heating method in deep eutectic solvent. The as-synthesized CuInS{sub 2} nanorods were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), respectively. The results indicated that the obtained CuInS{sub 2} nanostructures display rod-like morphology with diameters of about 40 nm and lengths of about 400 nm. The influences of microwave heating time on the formation of CuInS{sub 2} phase were discussed. Ultraviolet–visible (UV–vis) and photoluminescence (PL) spectra were utilized to investigate the optical properties of CuInS{sub 2} nanorods. The results showed that the as-synthesized CuInS{sub 2} nanorods exhibit strong absorption from the entire visible light region to the near-infrared region beyond 1100 nm. PL spectrum of the as-synthesized CuInS{sub 2} nanorods displays an emission peak centered at 580 nm under excitation wavelength of 366 nm at room temperature. The possible growth mechanism of CuInS{sub 2} nanorods was discussed.« less

A Noninvasive and Speculative Method of Visualizing Latent Fingerprint Deposits on Thermal Paper.

PubMed

Bond, John W

2015-07-01

Latent fingerprint deposits on thermal paper have been visualized noninvasively at visible wavelengths when illuminated with a UV-A light source (peak 365 nm). A higher intensity UV source (250 W/m(2) at 0.38 m) gave superior fingerprint visibility when compared with a 60 W/m(2) (at 0.4 m) source. Removing the visible (blue) component of the light source emission did not adversely affect the visibility of the fingerprint. Sample fingerprints from 100 donors, when examined 24 h after deposition, produced identifiable fingerprints from nearly 34% of fingerprint deposits. A mechanism for the observed visibility is proposed based on low emission of visible wavelengths from areas of thermal paper coincident with the fingerprint deposit, when illuminated with UV. This is likely due to a weak color change in the thermal paper dye arising from protonated amino acid components of the sweat. This effect was not observed on nonthermal paper. © 2015 American Academy of Forensic Sciences.

Interference-enhanced infrared-to-visible upconversion in solid-state thin films sensitized by colloidal nanocrystals

NASA Astrophysics Data System (ADS)

Wu, Mengfei; Jean, Joel; Bulović, Vladimir; Baldo, Marc A.

2017-05-01

Infrared-to-visible photon upconversion has potential applications in photovoltaics, sensing, and bioimaging. We demonstrate a solid-state thin-film device that utilizes sensitized triplet-triplet exciton annihilation, converting infrared photons absorbed by colloidal lead sulfide nanocrystals (NCs) into visible photons emitted from a luminescent dopant in rubrene at low incident light intensities. A typical bilayer device consisting of a monolayer of NCs and a doped film of rubrene is limited by low infrared absorption in the thin NC film. Here, we augment the bilayer with an optical spacer layer and a silver-film back reflector, resulting in interference effects that enhance the optical field and thus the absorption in the NC film. The interference-enhanced device shows an order-of-magnitude increase in the upconverted emission at the wavelength of λ = 610 nm when excited at λ = 980 nm. At incident light intensities above 1.1 W/cm2, the device attains maximum efficiency, converting (1.6 ± 0.2)% of absorbed infrared photons into higher-energy singlet excitons in rubrene.

Human retinal imaging using visible-light optical coherence tomography guided by scanning laser ophthalmoscopy

PubMed Central

Yi, Ji; Chen, Siyu; Shu, Xiao; Fawzi, Amani A.; Zhang, Hao F.

2015-01-01

We achieved human retinal imaging using visible-light optical coherence tomography (vis-OCT) guided by an integrated scanning laser ophthalmoscopy (SLO). We adapted a spectral domain OCT configuration and used a supercontinuum laser as the illumating source. The center wavelength was 564 nm and the bandwidth was 115 nm, which provided a 0.97 µm axial resolution measured in air. We characterized the sensitivity to be 86 dB with 226 µW incidence power on the pupil. We also integrated an SLO that shared the same optical path of the vis-OCT sample arm for alignment purposes. We demonstrated the retinal imaging from both systems centered at the fovea and optic nerve head with 20° × 20° and 10° × 10° field of view. We observed similar anatomical structures in vis-OCT and NIR-OCT. The contrast appeared different from vis-OCT to NIR-OCT, including slightly weaker signal from intra-retinal layers, and increased visibility and contrast of anatomical layers in the outer retina. PMID:26504622

Quantifying solar spectral irradiance in aquatic habitats for the assessment of photoenhanced toxicity

USGS Publications Warehouse

Barron, M.G.; Little, E.E.; Calfee, R.; Diamond, S.

2000-01-01

The spectra and intensity of solar radiation (solar spectral irradiance [SSI]) was quantified in selected aquatic habitats in the vicinity of an oil field on the California coast. Solar spectral irradiance measurements consisted of spectral scans (280–700 nm) and radiometric measurements of ultraviolet (UV): UVB (280–320 nm) and UVA (320–400 nm). Solar spectral irradiance measurements were taken at the surface and at various depths in two marsh ponds, a shallow wetland, an estuary lagoon, and the intertidal area of a high-energy sandy beach. Daily fluctuation in SSI showed a general parabolic relationship with time; maximum structure–activity relationship (SAR) was observed at approximate solar noon. Solar spectral irradiance measurements taken at 10-cm depth at approximate solar noon in multiple aquatic habitats exhibited only a twofold variation in visible light and UVA and a 4.5-fold variation in UVB. Visible light ranged from 11,000 to 19,000 μW/cm2, UVA ranged from 460 to 1,100 μW/cm2, and UVB ranged from 8.4 to 38 μW/cm2. In each habitat, the attenuation of light intensity with increasing water depth was differentially affected over specific wavelengths of SSI. The study results allowed the development of environmentally realistic light regimes necessary for photoenhanced toxicity studies.

Perovskite photodetectors with both visible-infrared dual-mode response and super-narrowband characteristics towards photo-communication encryption application.

PubMed

Wu, Ye; Li, Xiaoming; Wei, Yi; Gu, Yu; Zeng, Haibo

2017-12-21

Photo-communication has attracted great attention because of the rapid development of wireless information transmission technology. However, it is still a great challenge in cryptography communications, where it is greatly weakened by the openness of the light channels. Here, visible-infrared dual-mode narrowband perovskite photodetectors were fabricated and a new photo-communication encryption technique was proposed. For the first time, highly narrowband and two-photon absorption (TPA) resultant photoresponses within a single photodetector are demonstrated. The full width at half maximum (FWHM) of the photoresponse is as narrow as 13.6 nm in the visible range, which is superior to state-of-the-art narrowband photodetectors. Furthermore, these two merits of narrowband and TPA characteristics are utilized to encrypt the photo-communication based on the above photodetectors. When sending information and noise signals with 532 and 442 nm laser light simultaneously, the perovskite photodetectors only receive the main information, while the commercial Si photodetector responds to both lights, losing the main information completely. The final data are determined by the secret key through the TPA process as preset. Such narrowband and TPA detection abilities endow the perovskite photodetectors with great potential in future security communication and also provide new opportunities and platforms for encryption techniques.

[Light, laser and PDT therapy for acne].

PubMed

Borelli, C; Merk, K; Plewig, G; Degitz, K

2005-11-01

In recent years, a number of studies have evaluated the treatment of acne using electromagnetic waves, such as lasers, photodynamic therapy, visible light or radio waves. While the efficacy of laser treatment is still uncertain, photodynamic therapy shows promising results, but with marked side-effects, as destruction of sebaceous glands. Treatment with blue light (405-420 nm wavelength) also appears effective and can be regarded as an treatment option for inflammatory acne.

Towards combined optical coherence tomography and hyper-spectral imaging for gastrointestinal endoscopy

NASA Astrophysics Data System (ADS)

Attendu, Xavier; Crunelle, Camille; de Sivry-Houle, Martin Poinsinet; Maubois, Billie; Urbain, Joanie; Turrell, Chloe; Strupler, Mathias; Godbout, Nicolas; Boudoux, Caroline

2018-04-01

Previous works have demonstrated feasibility of combining optical coherence tomography (OCT) and hyper-spectral imaging (HSI) through a single double-clad fiber (DCF). In this proceeding we present the continued development of a system combining both modalities and capable of rapid imaging. We discuss the development of a rapidly scanning, dual-band, polygonal swept-source system which combines NIR (1260-1340 nm) and visible (450-800 nm) wavelengths. The NIR band is used for OCT imaging while visible light allows HSI. Scanning rates up to 24 kHz are reported. Furthermore, we present and discuss the fiber system used for light transport, delivery and collection, and the custom signal acquisition software. Key points include the use of a double-clad fiber coupler as well as important alignments and back-reflection management. Simultaneous and co-registered imaging with both modalities is presented in a bench-top system

Photochemical preparation of pyrimidin-2(1H)-ones by rhenium(I) complexes with visible light.

PubMed

Liu, Qiang; Li, Ya-Nan; Zhang, Hui-Hui; Chen, Bin; Tung, Chen-Ho; Wu, Li-Zhu

2011-03-04

With visible light irradiation (λ > 400 nm) of rhenium(I) complexes (P1-P4), a photochemical conversion from 3,4-dihydropyrimidin-2(1H)-ones to pyrimidin-2(1H)-ones at room temperature has been achieved with good to excellent yields in CH(3)CN-H(2)O solution containing CCl(4) and K(2)CO(3). Luminescence quenching study and product analysis reveal that photoinduced electron transfer between rhenium(I) complex P and 3,4-dihydropyrimidin-2(1H)-ones plays an important role in the initial event.

Hyperlens-array-implemented optical microscopy

NASA Astrophysics Data System (ADS)

Iwanaga, Masanobu

2014-08-01

Limit of resolution of conventional optical microscopes has never reached below 100 nm under visible light illumination. We show that numerically designed high-transmittance hyperlens array (HLA) is implemented in an optical microscope and works in practice for achieving one-shot-recording optical images of in-situ placed objects with sub 50 nm resolution in lateral direction. Direct resolution test employing well-defined nanopatterns proves that the HLA-implemented imaging is super-resolution optical microscopy, which works even under nW/mm2 visible illumination for objects. The HLA implementation makes the resolution of conventional microscopes one-scale higher, leading to the 1/10 illumination wavelength range, that is, mesoscopic range.

Comparative investigation of the penetration of different wavelength visible LED radiation into dental tissue

NASA Astrophysics Data System (ADS)

Uzunov, Tz.; Uzunova, P.; Angelov, I.; Gisbrecht, A.

2008-12-01

In this paper we report the results of measurement of the penetration of the radiation from different visible light emitting diodes (LEDs) inside dental tissue. The experiments are made using several different LEDs with wavelengths between 450 nm and 800 nm and power densities between 50 and 250 mW/cm2, which are the most frequently used in the clinical practice with proved clinical effect. The experimental results show that the penetration depends on the wavelength and the type of tissue. The results can be employed in the clinical practice for determining radiation dosage in the treatment of periodontal diseases.

Construction of plasmonic Ag modified phosphorous-doped ultrathin g-C3N4 nanosheets/BiVO4 photocatalyst with enhanced visible-near-infrared response ability for ciprofloxacin degradation.

PubMed

Deng, Yaocheng; Tang, Lin; Feng, Chengyang; Zeng, Guangming; Wang, Jiajia; Zhou, Yaoyu; Liu, Yani; Peng, Bo; Feng, Haopeng

2018-02-15

To realize the full utilization of solar energy, the design of highly efficient photocatalyst with improved visible-near-infrared photocatalysis performance has attracted great attentions for environment pollutant removal. In this work, we rationally employed the surface plasmon resonance effect of metallic Ag in the phosphorus doped ultrathin g-C 3 N 4 nanosheets (PCNS) and BiVO 4 composites to construct a ternary Ag@PCNS/BiVO 4 photocatalyst. It was applied for the photodegradation of ciprofloxacin (CIP), exhibiting 92.6% removal efficiency under visible light irradiation (λ>420nm) for 10mg/L CIP, and presenting enhanced photocatalytic ability than that of single component or binary nanocomposites under near-infrared light irradiation (λ>760nm). The improved photocatalytic activity of the prepared Ag@PCNS/BiVO 4 nanocomposite can be attributed to the synergistic effect among the PCNS, BiVO 4 and Ag, which not only improves the visible light response ability and hinders the recombination efficiency of the photogenerated electrons and holes, but also retains the strong the redox ability of the photogenerated charges. According to the trapping experiment and ESR measurements results, OH, h + and O 2 - all participated in the photocatalytic degradation process. Considering the SPR effect of metallic Ag and the established local electric field around the interfaces, a dual Z-scheme electrons transfer mechanism was proposed. Copyright © 2017 Elsevier B.V. All rights reserved.

A Simple Approach to the Visible-Light Photoactivation of Molecular Metal Oxides.

PubMed

Fujimoto, Satomi; Cameron, Jamie M; Wei, Rong-Jia; Kastner, Katharina; Robinson, David; Sans, Victor; Newton, Graham N; Oshio, Hiroki

2017-10-16

This study explores a new method to maximize the visible-light-driven photocatalytic performance of organic-inorganic hybrid polyoxometalates (POMs). Experimental and theoretical investigations of a family of phosphonate-substituted POMs show that modification of grafted organic moieties can be used to tune the electronic structure and photoactivity of the metal oxide component. Unlike fully inorganic polyoxotungstates, these organic-inorganic hybrid species are responsive to visible light and function as photocatalysts (λ > 420 nm) in the decomposition of a model environmental pollutant. The degree of photoactivation is shown to be dependent on the nature of the inductive effect exerted by the covalently grafted substituent groups. This study emphasizes the untapped potential that lies in an orbital engineering approach to hybrid-POM design and helps to underpin the next generation of bespoke, robust, and cost-effective molecular metal oxide photoactive materials and catalysts.

Hydrothermal synthesis of Bi2WO6 and photocatalytic reduction of aqueous Cr(VI) under visible light irradiation

NASA Astrophysics Data System (ADS)

Li, Jing; Shi, Qingzhu; Chen, Yan; Song, Ming

2017-12-01

Bi2WO6 was synthesized via a facile hydrothermal method using different inorganic acid or alkali varied pH of the solution at 180℃ for 12 h, and characterized by X-ray diffraction, FESEM and photocurrent. Furthermore, the photocatalytic activity of Bi2WO6 was investigated in the reduction of aqueous Cr(VI) under visible light (λ > 420 nm) irradiation. As a result, assynthesized Bi2WO6 was an orthorhombic phase, and well-crystallized with 3D hierarchical structure constructed by arranged 2D layers of nanoplates. All the as-synthesized Bi2WO6 exhibited the visible light photocatalytic activities on aqueous Cr(VI), and Bi2WO6-(2) exhibited the highest photocatalytic reduction efficiency based on much higher separation and transfer efficiency of photogenerated electrons and holes.

Light absorption properties of brown carbon over the southeastern Tibetan Plateau.

PubMed

Zhu, Chong-Shu; Cao, Jun-Ji; Huang, Ru-Jin; Shen, Zhen-Xing; Wang, Qi-Yuan; Zhang, Ning-Ning

2018-06-01

We present a study of the light-absorbing properties of water-soluble brown carbon (WS-BrC) and methanol-soluble brown carbon (MeS-BrC) at a remote site (Lulang, 3326m above sea level) in the southeastern Tibetan Plateau during the period 2015-2016. The light absorption coefficients at 365nm (b abs365 ) of WS-BrC and MeS-BrC were the highest during winter and the lowest during monsoon season. MeS-BrC absorbs about 1.5 times higher at 365nm compared to WS-BrC. The absorption at 550nm appears lower compared to that of 365nm for WS-BrC and MeS-BrC, respectively. Higher average value of the absorption Ångström exponent (AAE, 365-550nm) was obtained for MeS-BrC (8.2) than that for WS-BrC (6.9). The values of the mass absorption cross section at 365nm (MAC 365 ) indicated that BrC in winter absorbs UV-visible light more efficiently than in monsoon. The results confirm the importance of BrC in contributing to light-absorbing aerosols in this region. The understanding of the light absorption properties of BrC is of great importance, especially in modeling studies for the climate effects and transport of BrC in the Tibetan Plateau. Copyright © 2017 Elsevier B.V. All rights reserved.

Iris biometric system design using multispectral imaging

NASA Astrophysics Data System (ADS)

Widhianto, Benedictus Yohanes Bagus Y. B.; Nasution, Aulia M. T.

2016-11-01

An identity recognition system is a vital component that cannot be separated from life, iris biometric is one of the biometric that has the best accuracy reaching 99%. Usually, iris biometric systems use infrared spectrum lighting to reduce discomfort caused by radiation when the eye is given direct light, while the eumelamin that is forming the iris has the most flourescent radiation when given a spectrum of visible light. This research will be conducted by detecting iris wavelengths of 850 nm, 560 nm, and 590 nm, where the detection algorithm will be using Daugman algorithm by using a Gabor wavelet extraction feature, and matching feature using a Hamming distance. Results generated will be analyzed to identify how much differences there are, and to improve the accuracy of the multispectral biometric system and as a detector of the authenticity of the iris. The results obtained from the analysis of wavelengths 850 nm, 560 nm, and 590 nm respectively has an accuracy of 99,35 , 97,5 , 64,5 with a matching score of 0,26 , 0,23 , 0,37.

Importance of Plasmonic Heating on Visible Light Driven Photocatalysis of Gold Nanoparticle Decorated Zinc Oxide Nanorods

PubMed Central

Bora, Tanujjal; Zoepfl, David; Dutta, Joydeep

2016-01-01

Herein we explore the role of localized plasmonic heat generated by resonantly excited gold (Au) NPs on visible light driven photocatalysis process. Au NPs are deposited on the surface of vertically aligned zinc oxide nanorods (ZnO NRs). The localized heat generated by Au NPs under 532 nm continuous laser excitation (SPR excitation) was experimentally probed using Raman spectroscopy by following the phonon modes of ZnO. Under the resonant excitation the temperature at the surface of the Au-ZnO NRs reaches up to about 300 °C, resulting in almost 6 times higher apparent quantum yield (AQY) for photocatalytic degradation of methylene blue (MB) compared to the bare ZnO NRs. Under solar light irradiation the Au-ZnO NRs demonstrated visible light photocatalytic activity twice that of what was achieved with bare ZnO NRs, while significantly reduced the activation energy required for the photocatalytic reactions allowing the reactions to occur at a faster rate. PMID:27242172

Growth Chambers on the International Space Station for Large Plants

NASA Technical Reports Server (NTRS)

Massa, G. D.; Wheeler, R. M.; Morrow, R. C.; Levine, H. G.

2016-01-01

The International Space Station (ISS) now has platforms for conducting research on horticultural plant species under LED lighting, and those capabilities continue to expand. The 'Veggie' vegetable production system was deployed to the ISS as an applied research platform for food production in space. Veggie is capable of growing a wide array of horticultural crops. It was designed for low power usage, low launch mass and stowage volume, and minimal crew time requirements. The Veggie flight hardware consists of a light cap containing red (630 nm), blue, (455 nm) and green (530 nm) LEDs. Interfacing with the light cap is an extendable bellows/baseplate for enclosing the plant canopy. A second large plant growth chamber, the Advanced Plant Habitat (APH), is will fly to the ISS in 2017. APH will be a fully controllable environment for high-quality plant physiological research. APH will control light (quality, level, and timing), temperature, CO2, relative humidity, and irrigation, while scrubbing any cabin or plant-derived ethylene and other volatile organic compounds. Additional capabilities include sensing of leaf temperature and root zone moisture, root zone temperature, and oxygen concentration. The light cap will have red (630 nm), blue (450 nm), green (525 nm), far red (730 nm) and broad spectrum white LEDs (4100K). There will be several internal cameras (visible and IR) to monitor and record plant growth and operations. Veggie and APH are available for research proposals.

Morpho-Structural Effects Caused by 660 nm Laser Diode in Epimastigotes Forms of Trypanosoma cruzi: In Vitro Study

NASA Astrophysics Data System (ADS)

Barbosa, Artur F. S.; Soares, Luiz G. P.; Aciole, Jouber M. S.; Aciole, Gilberth T. S.; Pitta, Ivan R.; Galdino, Suely L.; Pinheiro, Antonio L. B.

2011-08-01

Parasitic diseases represent a major public health problems in Latin America, in particular, Chagas disease or American trypanosomiasis, caused by the protozoan parasite Trypanosoma cruzi, infects more than 18 million people in all countries of Latin America. Visible light induces a photochemical reaction, that induces the activation of enzymes used mainly in the respiratory chain, and that light has the primary targets lysosomes and mitochondria of cells, increasing, the mitochondrial ATP production. The purpose of this study was to assess the morpho-structural generated in the epimastigote form of Trypanosoma cruzi, after irradiation with a semiconductor laser InGaAlP, at a wavelength (λ) equal to 660 nm±10 nm, 40 mW optical Power, emitting red light in the visible spectrum, with a dose of 6 J/cm2 in continuous mode. Then the parasites that have undergone irradiation were analyzed by optical microscopy and compared to untreated. It found the increase in size of the kinetoplast (structure with high concentration of extracellular DNA-kDNA, whose main function is to encode the respiratory chain enzymes such as ATPase and citocromoxidase), the cell nucleus and the cell volume of the parasite, leaving the more rounded.

Visible light scattering properties of irregularly shaped silica microparticles using laser based laboratory simulations for remote sensing and medical applications

NASA Astrophysics Data System (ADS)

Boruah, Manash J.; Ahmed, Gazi A.

2018-01-01

Laser based experimental light scattering studies of irregularly shaped silica microparticles have been performed at three incident wavelengths 543.5 nm, 594.5 nm and 632.8 nm supported by laboratory based computations and 3D realistic simulations, using an indigenously fabricated light scattering setup. A comparative analysis of the computational and experimentally acquired results is done and a good agreement is found in the forward scattering lobes in all cases for each of the measured scattering parameters. This study also provides an efficient way of detecting and measuring particle size distribution for irregular micro- and nanoparticles and is highly applicable in remote sensing, atmospheric, astrophysical, and medical applications and also for finding potential health hazards in the form of inhalable and respirable small particulate matter.

A metallic metal oxide (Ti5O9)-metal oxide (TiO2) nanocomposite as the heterojunction to enhance visible-light photocatalytic activity

NASA Astrophysics Data System (ADS)

Li, L. H.; Deng, Z. X.; Xiao, J. X.; Yang, G. W.

2015-06-01

Coupling titanium dioxide (TiO2) with other semiconductors is a popular method to extend the optical response range of TiO2 and improve its photon quantum efficiency, as coupled semiconductors can increase the separation rate of photoinduced charge carriers in photocatalysts. Differing from normal semiconductors, metallic oxides have no energy gap separating occupied and unoccupied levels, but they can excite electrons between bands to create a high carrier mobility to facilitate kinetic charge separation. Here, we propose the first metallic metal oxide-metal oxide (Ti5O9-TiO2) nanocomposite as a heterojunction for enhancing the visible-light photocatalytic activity of TiO2 nanoparticles and we demonstrate that this hybridized TiO2-Ti5O9 nanostructure possesses an excellent visible-light photocatalytic performance in the process of photodegrading dyes. The TiO2-Ti5O9 nanocomposites are synthesized in one step using laser ablation in liquid under ambient conditions. The as-synthesized nanocomposites show strong visible-light absorption in the range of 300-800 nm and high visible-light photocatalytic activity in the oxidation of rhodamine B. They also exhibit excellent cycling stability in the photodegrading process. A working mechanism for the metallic metal oxide-metal oxide nanocomposite in the visible-light photocatalytic process is proposed based on first-principle calculations of Ti5O9. This study suggests that metallic metal oxides can be regarded as partners for metal oxide photocatalysts in the construction of heterojunctions to improve photocatalytic activity.

A metallic metal oxide (Ti5O9)-metal oxide (TiO2) nanocomposite as the heterojunction to enhance visible-light photocatalytic activity.

PubMed

Li, L H; Deng, Z X; Xiao, J X; Yang, G W

2015-01-26

Coupling titanium dioxide (TiO2) with other semiconductors is a popular method to extend the optical response range of TiO2 and improve its photon quantum efficiency, as coupled semiconductors can increase the separation rate of photoinduced charge carriers in photocatalysts. Differing from normal semiconductors, metallic oxides have no energy gap separating occupied and unoccupied levels, but they can excite electrons between bands to create a high carrier mobility to facilitate kinetic charge separation. Here, we propose the first metallic metal oxide-metal oxide (Ti5O9-TiO2) nanocomposite as a heterojunction for enhancing the visible-light photocatalytic activity of TiO2 nanoparticles and we demonstrate that this hybridized TiO2-Ti5O9 nanostructure possesses an excellent visible-light photocatalytic performance in the process of photodegrading dyes. The TiO2-Ti5O9 nanocomposites are synthesized in one step using laser ablation in liquid under ambient conditions. The as-synthesized nanocomposites show strong visible-light absorption in the range of 300-800 nm and high visible-light photocatalytic activity in the oxidation of rhodamine B. They also exhibit excellent cycling stability in the photodegrading process. A working mechanism for the metallic metal oxide-metal oxide nanocomposite in the visible-light photocatalytic process is proposed based on first-principle calculations of Ti5O9. This study suggests that metallic metal oxides can be regarded as partners for metal oxide photocatalysts in the construction of heterojunctions to improve photocatalytic activity.

Light Absorptive Properties of Articular Cartilage, ECM Molecules, Synovial Fluid, and Photoinitiators as Potential Barriers to Light-Initiated Polymer Scaffolding Procedures.

PubMed

Finch, Anthony J; Benson, Jamie M; Donnelly, Patrick E; Torzilli, Peter A

2017-06-01

Objective Many in vivo procedures to repair chondral defects use ultraviolet (UV)-photoinitiated in situ polymerization within the cartilage matrix. Chemical species that absorb UV light might reduce the effectiveness of these procedures by acting as light absorption barriers. This study evaluated whether any of the individual native biochemical components in cartilage and synovial fluid interfered with the absorption of light by common scaffolding photosensitizers. Materials UV-visible spectroscopy was performed on each major component of cartilage in solution, on bovine synovial fluid, and on four photosensitizers, riboflavin, Irgacure 2959, quinine, and riboflavin-5'-phosphate. Molar extinction and absorption coefficients were calculated at wavelengths of maximum absorbance and 365 nm. Intact articular cartilage was also examined. Results The individual major biochemical components of cartilage, Irgacure 2959, and quinine did not exhibit a significant absorption at 365 nm. Riboflavin and riboflavin-5'-phosphate were more effectual light absorbers at 365 nm, compared with the individual native species. Intact cartilage absorbed a significantly greater amount of UV light in comparison with the native species. Conclusion Our results indicate that none of the individual native species in cartilage will interfere with the absorption of UV light at 365 nm by these commonly used photoinitiators. Intact cartilage slices exhibited significant light absorption at 365 nm, while also having distinct absorbance peaks at wavelengths less than 300 nm. Determining the UV absorptive properties of the biomolecules native to articular cartilage and synovial fluid will aid in optimizing scaffolding procedures to ensure sufficient scaffold polymerization at a minimum UV intensity.

Polarization dependent color switching by extra-ordinary transmission in H-slit plasmonic metasurface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mandal, P.; Anantha Ramakrishna, S.; Patil, Raj

2013-12-14

An array of H-shaped subwavelength slits in a plasmonic film has a polarization dependent extra-ordinary transmission due to shape anisotropy. Non-overlapping extra-ordinary transmission bands for the orthogonal linear polarization states of the input light are used to demonstrate a polarization dependent color switch. The fabricated array of submicron sized H-slits on a gold film displayed two transmission bands for the linear x- and y-polarized light at visible (650–850 nm) and near-infra-red (1150–1450 nm) bands, respectively. The relative transmitted light in these two bands can be controlled by changing the linear polarization state of the input radiation from 0° to 90°.

White light emitting diode as potential replacement of tungsten-halogen lamp for visible spectroscopy system: a case study in the measurement of mango qualities

NASA Astrophysics Data System (ADS)

Chiong, W. L.; Omar, A. F.

2017-07-01

Non-destructive technique based on visible (VIS) spectroscopy using light emitting diode (LED) as lighting was used for evaluation of the internal quality of mango fruit. The objective of this study was to investigate feasibility of white LED as lighting in spectroscopic instrumentation to predict the acidity and soluble solids content of intact Sala Mango. The reflectance spectra of the mango samples were obtained and measured in the visible range (400-700 nm) using VIS spectroscopy illuminated under different white LEDs and tungsten-halogen lamp (pro lamp). Regression models were developed by multiple linear regression to establish the relationship between spectra and internal quality. Direct calibration transfer procedure was then applied between master and slave lighting to check on the acidity prediction results after transfer. Determination of mango acidity under white LED lighting was successfully performed through VIS spectroscopy using multiple linear regression but otherwise for soluble solids content. Satisfactory results were obtained for calibration transfer between LEDs with different correlated colour temperature indicated this technique was successfully used in spectroscopy measurement between two similar light sources in prediction of internal quality of mango.

Influence of multiple light-scattering on TiO2 nanoparticles imbedded into stratum corneum on light transmittance in UV and visible wavelength regions

NASA Astrophysics Data System (ADS)

Popov, Alexey P.; Priezzhev, Alexander V.; Lademann, Jürgen; Myllylä, Risto

2007-05-01

This paper focuses on the simulation of propagation of radiation in UV and visible wavelength regions within a superficial skin layer (stratum corneum, SC) partially filled with titanium dioxide (TiO II) nanoparticles. Volume concentrations of the particles (0.67% - 2.25%) correspond to the maximal concentrations of the considered particles in the frames of independent scattering. Transmittance of 307-, 400-, and 500-nm light through a 20-μm thick SC is calculated. The effect of the TiO II nanoparticles on the contribution of photons undergone different numbers of scattering acts into transmittance is considered. It is shown that administration of the nanoparticles results in the broadening of the distribution of transmitted photons over undergone scattering acts. It also results in the shift of the maximum location of this distribution to larger number of scattering acts for the wavelengths of 400 and 500 nm being the latter the most pronounced. The increase of undergone scattering acts leads to the elongation of photon trajectories within the medium and results in the increase of the diffuse reflected light and the transmittance decrease.

Hybrid GaN LED with capillary-bonded II-VI MQW color-converting membrane for visible light communications

NASA Astrophysics Data System (ADS)

Santos, Joao M. M.; Jones, Brynmor E.; Schlosser, Peter J.; Watson, Scott; Herrnsdorf, Johannes; Guilhabert, Benoit; McKendry, Jonathan J. D.; De Jesus, Joel; Garcia, Thor A.; Tamargo, Maria C.; Kelly, Anthony E.; Hastie, Jennifer E.; Laurand, Nicolas; Dawson, Martin D.

2015-03-01

The rapid emergence of gallium-nitride (GaN) light-emitting diodes (LEDs) for solid-state lighting has created a timely opportunity for optical communications using visible light. One important challenge to address this opportunity is to extend the wavelength coverage of GaN LEDs without compromising their modulation properties. Here, a hybrid source for emission at 540 nm consisting of a 450 nm GaN micro-sized LED (micro-LED) with a micron-thick ZnCdSe/ZnCdMgSe multi-quantum-well color-converting membrane is reported. The membrane is liquid-capillary-bonded directly onto the sapphire window of the micro-LED for full hybridization. At an injection current of 100 mA, the color-converted power was found to be 37 μW. At this same current, the -3 dB optical modulation bandwidth of the bare GaN and hybrid micro-LEDs were 79 and 51 MHz, respectively. The intrinsic bandwidth of the color-converting membrane was found to be power-density independent over the range of the micro-LED operation at 145 MHz, which corresponds to a mean carrier lifetime of 1.9 ns.

Enhancement in visible light photocatalytic activity by embedding Cu nanoparticles over CuS/MCM-41 nanocomposite

NASA Astrophysics Data System (ADS)

Sohrabnezhad, Sh.; Karamzadeh, M.

2017-07-01

This article indicate the biogenic synthesis of copper nanoparticles (Cu NPs) using the borage flowers extract of Borago officinalis over CuS/MCM-41 nanocomposite (NC). No external reducing was utilized in the developed method. The CuS-MCM-41 NC was used as stabilizing agent. The synthesis of CuS nanostructure in MCM-41 material has been realized by hydrothermal method. Their physiochemical properties have been characterized by X-ray diffraction, transmission electron microscopy (TEM), UV-Visible diffuse reflectance spectroscopy, and Fourier transform infrared spectroscopy. On the basis of TEM images, a layer of Cu NPs has been located over CuS/MCM-41 NC with average diameter of 60-80 nm. The results revealed the spherical nature of the prepared Cu NPs with diameter less than 10 nm. The DR spectra of Cu NPs in MCM-41 and CuS-MCM-41 NCs showed surface plasmon resonance bands at 570 and 500-600 nm, respectively. The photocatalytic activity was evaluated under visible light irradiation using the photocatalytic degradation of methylene blue (MB) as a model reaction. The prepared Cu/CuS/MCM-41 nanocomposite microspheres showed higher photodegradation ability for MB than CuS/MCM-41. The degradation of MB achieved up to 80% after 60 min and the nanocomposite could be recycled and reused.

Light alters nociceptive effects of magnetic field shielding in mice: intensity and wavelength considerations

PubMed Central

Prato, Frank S; Desjardins-Holmes, Dawn; Keenliside, Lynn D; McKay, Julia C; Robertson, John A; Thomas, Alex W

2008-01-01

Previous experiments with mice have shown that repeated 1 hour daily exposure to an ambient magnetic field-shielded environment induces analgesia (antinociception). The exposures were carried out in the dark (less than 2.0×1016 photons s−1 m−2) during the mid-light phase of the diurnal cycle. However, if the mice were exposed in the presence of visible light (2.0×1018 photons s−1 m−2, 400–750 nm), then the analgesic effects of shielding were eliminated. Here, we show that this effect of light is intensity and wavelength dependent. Introduction of red light (peak at 635 nm) had little or no effect, presumably because mice do not have photoreceptors sensitive to red light above 600 nm in their eyes. By contrast, introduction of ultraviolet light (peak at 405 nm) abolished the effect, presumably because mice do have ultraviolet A receptors. Blue light exposures (peak at 465 nm) of different intensities demonstrate that the effect has an intensity threshold of approximately 12% of the blue light in the housing facility, corresponding to 5×1016 photons s−1 m−2 (integral). This intensity is similar to that associated with photoreceptor-based magnetoreception in birds and in mice stimulates photopic/cone vision. Could the detection mechanism that senses ambient magnetic fields in mice be similar to that in bird navigation? PMID:18583276

Efficiently Visible-Light Driven Photoelectrocatalytic Oxidation of As(III) at Low Positive Biasing Using Pt/TiO2 Nanotube Electrode

NASA Astrophysics Data System (ADS)

Qin, Yanyan; Li, Yilian; Tian, Zhen; Wu, Yangling; Cui, Yanping

2016-01-01

A constant current deposition method was selected to load highly dispersed Pt nanoparticles on TiO2 nanotubes in this paper, to extend the excited spectrum range of TiO2-based photocatalysts to visible light. The morphology, elemental composition, and light absorption capability of as-obtained Pt/TiO2 nanotubes electrodes were characterized by FE-SEM, energy dispersive spectrometer (EDS), X-ray photoelectron spectrometer (XPS), and UV-vis spectrometer. The photocatalytic and photoelectrocatalytic oxidation of As(III) using a Pt/TiO2 nanotube arrays electrode under visible light ( λ > 420 nm) irradiation were investigated in a divided anode/cathode electrolytic tank. Compared with pure TiO2 which had no As(III) oxidation capacity under visible light, Pt/TiO2 nanotubes exhibited excellent visible-light photocatalytic performance toward As(III), even at dark condition. In anodic cell, As(III) could be oxidized with high efficiency by photoelectrochemical process with only 1.2 V positive biasing. Experimental results showed that photoelectrocatalytic oxidation process of As(III) could be well described by pseudo-first-order kinetic model. Rate constants depended on initial concentration of As(III), applied bias potential and solution pH. At the same time, it was interesting to find that in cathode cell, As(III) was also continuously oxidized to As(V). Furthermore, high-arsenic groundwater sample (25 m underground) with 0.32 mg/L As(III) and 0.35 mg/L As(V), which was collected from Daying Village, Datong basin, Northern China, could totally transform to As(V) after 200 min under visible light in this system.

Visible-light-driven N-TiO2@SiO2@Fe3O4 magnetic nanophotocatalysts: Synthesis, characterization, and photocatalytic degradation of PPCPs.

PubMed

Kumar, Ashutosh; Khan, Musharib; Fang, Liping; Lo, Irene M C

2017-07-24

TiO 2 -based photocatalysis offers certain advantages like rapid degradation and mineralization of organic compounds. However, the practical applicability of photocatalysts in degradation of pharmaceuticals and personal care products (PPCPs) is still restricted by challenges including their limited photocatalytic activity under visible light and difficulty in their separation from suspension. To overcome these challenges, a visible-light-driven magnetic N-TiO 2 @SiO 2 @Fe 3 O 4 nanophotocatalyst was developed through fine-tuning the pertinent factors (calcination temperature, Fe 3 O 4 loading, and nitrogen doping) involved during synthesis process, on the basis of degradation of ibuprofen (a typical PPCP). The TEM-EDX, XRD and XPS analyses confirmed the successful synthesis of nanophotocatalyst. By comparing nanophotocatalyst's performance on ibuprofen under two visible light sources, i.e., compact fluorescent lamps (CFLs) and light emitting diodes (LEDs) of similar irradiance, CFLs of irradiance 320μWcm -2 and peak emissive wavelength 543nm served as a better source, resulting in 94% degradation. Furthermore, 93% of benzophenone-3 within 5h and 71% of carbamazepine within 9h was degraded under visible light emitted by CFLs. The superparamagnetic behavior of the nanophotocatalyst enabled its successful magnetic separation (95% efficiency) from the suspension within 20-25min under an electromagnetic field of ∼200mT. Copyright © 2017 Elsevier B.V. All rights reserved.

Semi-transparent all-oxide ultraviolet light-emitting diodes based on ZnO/NiO-core/shell nanowires

NASA Astrophysics Data System (ADS)

Shi, Zhi-Feng; Xu, Ting-Ting; Wu, Di; Zhang, Yuan-Tao; Zhang, Bao-Lin; Tian, Yong-Tao; Li, Xin-Jian; Du, Guo-Tong

2016-05-01

Semi-transparent all-oxide light-emitting diodes based on ZnO/NiO-core/shell nanowire structures were prepared on double-polished c-Al2O3 substrates. The entire heterojunction diode showed an average transparency of ~65% in the ultraviolet and visible regions. Under forward bias, the diode displayed an intense ultraviolet emission at ~382 nm, and its electroluminescence performance was remarkable in terms of a low emission onset, acceptable operating stability, and the ability to optically excite emissive semiconductor nanoparticle chromophores.Semi-transparent all-oxide light-emitting diodes based on ZnO/NiO-core/shell nanowire structures were prepared on double-polished c-Al2O3 substrates. The entire heterojunction diode showed an average transparency of ~65% in the ultraviolet and visible regions. Under forward bias, the diode displayed an intense ultraviolet emission at ~382 nm, and its electroluminescence performance was remarkable in terms of a low emission onset, acceptable operating stability, and the ability to optically excite emissive semiconductor nanoparticle chromophores. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07236k

Visible Light Responsive Catalysts Using Quantum Dot-Modified Ti02 for Air and Water Purification

NASA Technical Reports Server (NTRS)

Coutts, Janelle L.; Levine, Lanfang H.; Richards, Jeffrey T.; Hintze, paul; Clausen, Christian

2012-01-01

The method of photocatalysis utilizing titanium dioxide, TiO2, as the catalyst has been widely studied for trace contaminant control for both air and water applications because of its low energy consumption and use of a regenerable catalyst. Titanium dioxide requires ultraviolet light for activation due to its band gap energy of 3.2 eV. Traditionally, Hg-vapor fluorescent light sources are used in PCO reactors and are a setback for the technology for space application due to the possibility of Hg contamination. The development of a visible light responsive (VLR) TiO2-based catalyst could lead to the use of solar energy in the visible region (approx.45% of the solar spectrum lies in the visible region; > 400 nm) or highly efficient LEDs (with wavelengths > 400 nm) to make PCO approaches more efficient, economical, and safe. Though VLR catalyst development has been an active area of research for the past two decades, there are few commercially available VLR catalysts; those that are available still have poor activity in the visible region compared to that in the UV region. Thus, this study was aimed at the further development of VLR catalysts by a new method - coupling of quantum dots (QD) of a narrow band gap semiconductor (e.g., CdS, CdSe, PbS, ZnSe, etc.) to the TiO2 by two preparation methods: 1) photodeposition and 2) mechanical alloying using a high-speed ball mill. A library of catalysts was developed and screened for gas and aqueous phase applications, using ethanol and 4-chlorophenol as the target contaminants, respectively. Both target compounds are well studied in photocatalytic systems serve as model contaminants for this research. Synthesized catalysts were compared in terms of preparation method, type of quantum dots, and dosage of quantum dots.

High performance sulfur, nitrogen and carbon doped mesoporous anatase-brookite TiO₂ photocatalyst for the removal of microcystin-LR under visible light irradiation.

PubMed

El-Sheikh, Said M; Zhang, Geshan; El-Hosainy, Hamza M; Ismail, Adel A; O'Shea, Kevin E; Falaras, Polycarpos; Kontos, Athanassios G; Dionysiou, Dionysios D

2014-09-15

Carbon, nitrogen and sulfur (C, N and S) doped mesoporous anatase-brookite nano-heterojunction titania photocatalysts have been synthesized through a simple sol-gel method in the presence of triblock copolymer Pluronic P123. XRD and Raman spectra revealed the formation of anatase and brookite mixed phases. XPS spectra indicated the presence of C, N and S dopants. The TEM images demonstrated the formation of almost monodisperse titania nanoparticles with particle sizes of approximately 10nm. N2 isotherm measurements confirmed that both doped and undoped titania anatase-brookite materials have mesoporous structure. The photocatalytic degradation of the cyanotoxin microcystin-LR (MC-LR) has been investigated using these novel nanomaterials under visible light illumination. The photocatalytic efficiency of the mesoporous titania anatase-brookite photocatalyst dramatically increased with the addition of the C, N and S non-metal, achieving complete degradation (∼ 100 %) of MC-LR. The results demonstrate the advantages of the synthetic approach and the great potential of the visible light activated C, N, and S doped titania photocatalysts for the treatment of organic micropollutants in contaminated waters under visible light. Copyright © 2014 Elsevier B.V. All rights reserved.

Enhanced photocathodic protection performance of Ag/graphene/TiO2 composite for 304SS under visible light.

PubMed

Li, Hong; Wang, Xiutong; Wei, Qinyi; Liu, Xueqing; Qian, Zhouhai; Hou, Baorong

2017-06-02

Ag and graphene co-sensitized TiO 2 composites were successfully fabricated and used as photoanodes for photogenerated cathodic protection of 304 stainless steel (304SS) under visible light. Graphene films was firstly deposited onto the TiO 2 nanotube (NT) films via cyclic voltammetric electrodeposition. Ag/graphene/TiO 2 films were then fabricated via dipping and photoreduction method. The morphology, composition and optical response of the Ag/graphene/TiO 2 NT composites were characterized by scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, UV-vis diffusion reflectance spectroscopy, respectively. The photocathodic protection performance of the Ag/graphene/TiO 2 composites were systematically studied through open-circuit potential and potentiodynamic polarization measurements in 3.5 wt% NaCl solution under visible light (λ > 400 nm). The composites exhibited enhanced photogenerated cathodic protection performance for 304SS under visible light irradiation compared to pure TiO 2 . Graphene and Ag have a synergistic effect on the enhancement of photocathodic protection performance of TiO 2 . The composites prepared with 30-cycle graphene film and 15 mM AgNO 3 solution showed the optimal corrosion protection performance.

Enhanced photocathodic protection performance of Ag/graphene/TiO2 composite for 304SS under visible light

NASA Astrophysics Data System (ADS)

Li, Hong; Wang, Xiutong; Wei, Qinyi; Liu, Xueqing; Qian, Zhouhai; Hou, Baorong

2017-06-01

Ag and graphene co-sensitized TiO2 composites were successfully fabricated and used as photoanodes for photogenerated cathodic protection of 304 stainless steel (304SS) under visible light. Graphene films was firstly deposited onto the TiO2 nanotube (NT) films via cyclic voltammetric electrodeposition. Ag/graphene/TiO2 films were then fabricated via dipping and photoreduction method. The morphology, composition and optical response of the Ag/graphene/TiO2 NT composites were characterized by scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, UV-vis diffusion reflectance spectroscopy, respectively. The photocathodic protection performance of the Ag/graphene/TiO2 composites were systematically studied through open-circuit potential and potentiodynamic polarization measurements in 3.5 wt% NaCl solution under visible light (λ > 400 nm). The composites exhibited enhanced photogenerated cathodic protection performance for 304SS under visible light irradiation compared to pure TiO2. Graphene and Ag have a synergistic effect on the enhancement of photocathodic protection performance of TiO2. The composites prepared with 30-cycle graphene film and 15 mM AgNO3 solution showed the optimal corrosion protection performance.

Engineering the Complex-Valued Constitutive Parameters of Metamaterials for Perfect Absorption

NASA Astrophysics Data System (ADS)

Wang, Pengwei; Chen, Naibo; Tang, Chaojun; Chen, Jing; Liu, Fanxin; Sheng, Saiqian; Yan, Bo; Sui, Chenghua

2017-04-01

We theoretically studied how to directly engineer the constitutive parameters of metamaterials for perfect absorbers of electromagnetic waves. As an example, we numerically investigated the necessary refractive index n and extinction coefficient k and the relative permittivity ɛ and permeability μ of a metamaterial anti-reflection layer, which could cancel the reflection from a hydrogenated amorphous silicon (α-Si:H) thin film on a metal substrate, within the visible wavelength range from 300 to 800 nm. We found that the metamaterial anti-reflection layer should have a negative refractive index ( n < 0) for short-wavelength visible light but have a positive refractive index ( n > 0) for long-wavelength visible light. The relative permittivity ɛ and permeability μ could be fitted by the Lorentz model, which exhibited electric and magnetic resonances, respectively.

Rough gold films as broadband absorbers for plasmonic enhancement of TiO2 photocurrent over 400–800 nm

PubMed Central

Tan, Furui; Li, Tenghao; Wang, Ning; Lai, Sin Ki; Tsoi, Chi Chung; Yu, Weixing; Zhang, Xuming

2016-01-01

Recent years have witnessed an increasing interest in highly-efficient absorbers of visible light for the conversion of solar energy into electrochemical energy. This study presents a TiO2-Au bilayer that consists of a rough Au film under a TiO2 film, which aims to enhance the photocurrent of TiO2 over the whole visible region and may be the first attempt to use rough Au films to sensitize TiO2. Experiments show that the bilayer structure gives the optimal optical and photoelectrochemical performance when the TiO2 layer is 30 nm thick and the Au film is 100 nm, measuring the absorption 80–90% over 400–800 nm and the photocurrent intensity of 15 μA·cm−2, much better than those of the TiO2-AuNP hybrid (i.e., Au nanoparticle covered by the TiO2 film) and the bare TiO2 film. The superior properties of the TiO2-Au bilayer can be attributed to the rough Au film as the plasmonic visible-light sensitizer and the photoactive TiO2 film as the electron accepter. As the Au film is fully covered by the TiO2 film, the TiO2-Au bilayer avoids the photocorrosion and leakage of Au materials and is expected to be stable for long-term operation, making it an excellent photoelectrode for the conversion of solar energy into electrochemical energy in the applications of water splitting, photocatalysis and photosynthesis. PMID:27608836

Scatter Measurements Made With Ultraviolet Light

NASA Astrophysics Data System (ADS)

Anthon, Erik W.

1985-09-01

The quality of optical surfaces is generally evaluated by how much light (normally visible light) is scattered by the surface. Most optical glasses and many coating materials are completely opaque to ultraviolet light (253.7 nm). Ultraviolet light tends to scatter much more than visible light. Scatter measurements made with ultraviolet light are therefore very sensitive and the scatter from second surfaces and from the interior (bulk) of the optical material is eliminated by the opacity. A novel scattermeter that operates with ultraviolet light has been developed. The construction and operation of this scattermeter will be described. Cleaning soon becomes the limiting factor when measuring the surfaces with very low level of scatter. Sensitivity to repeated cleaning has been investigated. Different surfaces are compared and uniformity of surfaces is measured by mapping a surface area with an x-y stage. Polished glass surfaces generally have much higher scatter than natural glass surfaces (fire polished, drawn or floated surfaces). Very low scatter levels have been found on thin drawn glass.

Pd-MnO2 nanoparticles/TiO2 nanotube arrays (NTAs) photo-electrodes photo-catalytic properties and their ability of degrading Rhodamine B under visible light.

PubMed

Thabit, Mohamed; Liu, Huiling; Zhang, Jian; Wang, Bing

2017-10-01

Pd-MnO 2 /TiO 2 nanotube arrays (NTAs) photo-electrodes were successfully fabricated via anodization and electro deposition subsequently; the obtained Pd-MnO 2 /TiO 2 NTAs photo electrodes were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and characterized accordingly. Moreover, the light harvesting and absorption properties were investigated via ultraviolet-visible diffuse reflectance spectrum (DRS); photo degradation efficiency was investigated via analyzing the photo catalytic degradation of Rhodamine B under visible illumination (xenon light). The performed analyses illustrated that Pd-MnO 2 codoped particles were successfully deposited onto the surface of the TiO 2 nanotube arrays; DRS results showed significant improvement in visible light absorption which was between 400 and 700nm. Finally, the photo catalytic degradation efficiency results of the designated organic pollutant (Rhodamine B) illustrated a superior photocatalytic (PC) efficiency of approximately 95% compared to the bare TiO 2 NTAs, which only exhibited a photo catalytic degradation efficiency of approximately 61%, thus it indicated the significant enhancement of the light absorption properties of fabricated photo electrodes and their yield of OH radicals. Copyright © 2017. Published by Elsevier B.V.

Demonstrating Basic Properties of Spectroscopy Using a Self-Constructed Combined Fluorimeter and UV-Photometer

ERIC Educational Resources Information Center

Kvittingen, Eivind V.; Kvittingen, Lise; Melø, Thor Bernt; Sjursnes, Birte Johanne; Verley, Richard

2017-01-01

This article describes a combined UV-photometer and fluorimeter constructed from 3 LEDs and a few wires, all held in place with Lego bricks. The instrument has a flexible design. In its simplest version, two UV-LEDs (355 nm) are used as light source and to detect absorption, and a third LED, in the visible spectrum (e.g., 525 nm), is used to…

Quasi-periodic photonic crystal Fabry–Perot optical filter based on Si/SiO2 for visible-laser spectral selectivity

NASA Astrophysics Data System (ADS)

Qi, Dong; Wang, Xian; Cheng, Yongzhi; Chen, Fu; Liu, Lei; Gong, Rongzhou

2018-06-01

We report on a 1D quasi-periodic photonic crystal Fabry–Perot optical filter Cs(Si/SiO2)3(SiO2/Si)3 for spectral selectivity of visible light and 1.55 µm laser. A material transparency interval of 1.03–2.06 µm makes Si a unique choice of high refractive index material. Owing to the CIE 1931 standard and equal inclination interference, the designed structure can be successfully fabricated with a certain color (brown, khaki, or blue) corresponding to the different Cs physical thickness d and response R(λ). In addition, the peak transmittance T max of the proposed structure can reach as high as 92.56% (Cs  =  20 nm), 90.83% (Cs  =  40 nm), and 88.85% (Cs  =  60 nm) with a relatively narrow full width at half maximum of 4.4, 4.6, and 4.8 nm at 1.55 µm. The as-prepared structure indicates that it is feasible for a photonic crystal Fabry–Perot optical filter to achieve visible-laser (1.55 µm) spectral selectivity.

Infrared reflective coatings for building and automobile glass windows for heat protection

NASA Astrophysics Data System (ADS)

Butt, M. A.; Fomchenkov, S. A.; Kazanskiy, N. L.; Ullah, A.; Ali, R. Z.; Habib, M.

2017-04-01

Sunlight can be used a source of light in buildings and automobiles, however infrared wavelengths in sunlight result in heating. In this work, Infrared Reflective Coatings are designed using thin films to transmit visible wavelengths 400 700 nm while reflecting infrared wavelengths above 700 nm. Three different design approaches have been used, namely single layer of metal, sandwich structure and multilayer design. Four metals (Ag, Au, Al and Cu) and two dielectrics (TiO2 and SiO2) are used in this study. Designs with Ag show maximum reflection of Infrared wavelengths in all designs. Sandwich structures of TiO2-Ag-TiO2 on substrate with 22 nm of thickness for each layer show the maximum transmission of 87% in the visible region and maximum reflection of Infrared wavelengths.

High power fiber coupled diode lasers for display and lighting applications

NASA Astrophysics Data System (ADS)

Drovs, Simon; Unger, Andreas; Dürsch, Sascha; Köhler, Bernd; Biesenbach, Jens

2017-02-01

The performance of diode lasers in the visible spectral range has been continuously improved within the last few years, which was mainly driven by the goal to replace arc lamps in cinema or home projectors. In addition, the availability of such high power visible diode lasers also enables new applications in the medical field, but also the usage as pump sources for other solid state lasers. This paper summarizes the latest developments of fiber coupled sources with output power from 1.4 W to 120 W coupled into 100 μm to 400 μm fibers in the spectral range around 405 nm and 640 nm. New developments also include the use of fiber coupled multi single emitter arrays at 450 nm, as well as very compact modules with multi-W output power.

Exposure to Visible Light Emitted from Smartphones and Tablets Increases the Proliferation of Staphylococcus aureus: Can this be Linked to Acne?

PubMed Central

Taheri, M.; Darabyan, M.; Izadbakhsh, E.; Nouri, F.; Haghani, M.; Mortazavi, S.A.R.; Mortazavi, G.; Mortazavi, S.M.J.; Moradi, M.

2017-01-01

Background: Due to rapid advances in modern technologies such as telecommunication technology, the world has witnessed an exponential growth in the use of digital handheld devices (e.g. smartphones and tablets). This drastic growth has resulted in increased global concerns about the safety of these devices. Smartphones, tablets, laptops, and other digital screens emit high levels of short-wavelength visible light (i.e. blue color region in the visible light spectrum). Material and Methods: At a dark environment, Staphylococcus aureus bacteria were exposed to the light emitted from common tablets/smartphones. The control samples were exposed to the same intensity of light generated by a conventional incandescent light bulb. The growth rate of bacteria was examined by measuring the optical density (OD) at 625 nm by using a spectrophotometer before the light exposure and after 30 to 330 minutes of light exposure. Results: The growth rates of bacteria in both smartphone and tablet groups were higher than that of the control group and the maximum smartphone/control and tablet/control growth ratios were observed in samples exposed to digital screens’ light for 300 min (ratios of 3.71 and 3.95, respectively). Conclusion: To the best of our knowledge, this is the first study that investigates the effect of exposure to light emitted from digital screens on the proliferation of Staphylococcus aureus and its association with acne pathogenesis. Our findings show that exposure to short-wavelength visible light emitted from smartphones and tablets can increase the proliferation of Staphylococcus aureus. PMID:28580338

Optimized fan-shaped chiral metamaterial as an ultrathin narrow-band circular polarizer at visible frequencies

NASA Astrophysics Data System (ADS)

He, Yizhuo; Wang, Xinghai; Ingram, Whitney; Ai, Bin; Zhao, Yiping

2018-04-01

Chiral metamaterials have the great ability to manipulate the circular polarizations of light, which can be utilized to build ultrathin circular polarizers. Here we build a narrow-band circular polarizer at visible frequencies based on plasmonic fan-shaped chiral nanostructures. In order to achieve the best optical performance, we systematically investigate how different fabrication factors affect the chiral optical response of the fan-shaped chiral nanostructures, including incident angle of vapor depositions, nanostructure thickness, and post-deposition annealing. The optimized fan-shaped nanostructures show two narrow bands for different circular polarizations with the maximum extinction ratios 7.5 and 6.9 located at wavelength 687 nm and 774 nm, respectively.

Visible-infrared achromatic imaging by wavefront coding with wide-angle automobile camera

NASA Astrophysics Data System (ADS)

Ohta, Mitsuhiko; Sakita, Koichi; Shimano, Takeshi; Sugiyama, Takashi; Shibasaki, Susumu

2016-09-01

We perform an experiment of achromatic imaging with wavefront coding (WFC) using a wide-angle automobile lens. Our original annular phase mask for WFC was inserted to the lens, for which the difference between the focal positions at 400 nm and at 950 nm is 0.10 mm. We acquired images of objects using a WFC camera with this lens under the conditions of visible and infrared light. As a result, the effect of the removal of the chromatic aberration of the WFC system was successfully determined. Moreover, we fabricated a demonstration set assuming the use of a night vision camera in an automobile and showed the effect of the WFC system.

In vivo high-resolution cortical imaging with extended-focus optical coherence microscopy in the visible-NIR wavelength range

NASA Astrophysics Data System (ADS)

Marchand, Paul J.; Szlag, Daniel; Bouwens, Arno; Lasser, Theo

2018-03-01

Visible light optical coherence tomography has shown great interest in recent years for spectroscopic and high-resolution retinal and cerebral imaging. Here, we present an extended-focus optical coherence microscopy system operating from the visible to the near-infrared wavelength range for high axial and lateral resolution imaging of cortical structures in vivo. The system exploits an ultrabroad illumination spectrum centered in the visible wavelength range (λc = 650 nm, Δλ ˜ 250 nm) offering a submicron axial resolution (˜0.85 μm in water) and an extended-focus configuration providing a high lateral resolution of ˜1.4 μm maintained over ˜150 μm in depth in water. The system's axial and lateral resolution are first characterized using phantoms, and its imaging performance is then demonstrated by imaging the vasculature, myelinated axons, and neuronal cells in the first layers of the somatosensory cortex of mice in vivo.

Fabrication of white light-emitting diodes based on UV light-emitting diodes with conjugated polymers-(CdSe/ZnS) quantum dots as hybrid phosphors.

PubMed

Jung, Hyunchul; Chung, Wonkeun; Lee, Chang Hun; Kim, Sung Hyun

2012-07-01

White light-emitting diodes (LEDs) were fabricated using GaN-based 380-nm UV LEDs precoated with the composite of blue-emitting polymer (poly[(9,9-dihexylfluorenyl-2,7-diyl)-alt-co-(2-methoxy-5-{2-ethylhexyloxy)-1 ,4-phenylene)]), yellow green-emitting polymer (poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-{2,1',3}-thiadiazole)]), and 605-nm red-emitting quantum dots (QDs). CdSe cores were obtained by solvothermal route using CdO, Se precursors and ZnS shells were synthesized by using diethylzinc, and hexamethyldisilathiane precursors. The optical properties of CdSe/ZnS QDs were characterized by UV-visible and photoluminescence (PL) spectra. The structural data and composition of the QDs were transmission electron microscopy (TEM), and EDX technique. The quantum yield and size of the QDs were 58.7% and about 6.7 nm, respectively. Three-band white light was generated by hybridizing blue (430 nm), green (535 nm), and red (605 nm) emission. The color-rendering index (CRI) of the device was extremely improved by introducing the QDs. The CIE-1931 chromaticity coordinate, color temperature, and CRI of a white LED at 20 mA were (0.379, 0.368), 3969 K, and 90, respectively.

Estimating Leaf Water Status from Vis-Nir Reflectance and Transmittance

NASA Technical Reports Server (NTRS)

Vanderbilt, Vern; Daughtry, Craig; Dahlgren, Robert

2017-01-01

Remotely sensing the water status of plant canopies remains a long term goal of remote sensing research. Established approaches involve measurements in the thermal infrared and the 900-2000nm reflective infrared. Less popular UV-visible-NIR techniques presumably deserve research attention, because photochemical changes linked to plant water status manifest spectral light scattering and absorption changes. Here we monitored the visible and NIR light reflected from the leaf interior as well as the leaf transmittance as the relative water content of corn (Zeamays L.) leaves decreased. Our results highlight the importance of both scattering effects and effects due to absorption by leaf pigments.

Anti-reflective coating for visible light using a silver nanodisc metasurface with a refractive index of less than 1.0

NASA Astrophysics Data System (ADS)

Yasuda, Hideki; Matsuno, Ryo; Koito, Naoki; Hosoda, Hidemasa; Tani, Takeharu; Naya, Masayuki

2017-12-01

Suppression of visible-light reflection from material surfaces is an important technology for many applications such as flat-panel displays, camera lenses, and solar panels. In this study, we developed an anti-reflective coating design based on a silver nanodisc metasurface. The effective refractive index of a 10-nm-thick monolayer of silver nanodiscs was less than 1.0, which enabled strong suppression of reflection from the underlying substrate. The nanodisc structure was easy to fabricate using a conventional roll-to-roll wet-coating method. The anti-reflective structure was fabricated over a large area.

Visible Light Responsive Liquid Crystal Polymers Containing Reactive Moieties with Good Processability.

PubMed

Liu, Yuyun; Wu, Wei; Wei, Jia; Yu, Yanlei

2017-01-11

Two types of novel reactive linear liquid crystal polymers (LLCPs) with different azotolene concentrations have been synthesized and processed into films and fibers by solution and melting processing methods. Then, the LLCPs in the obtained monodomain fiber and polydomain film were easily cross-linked with difunctional primary amines. The resulted cross-linked liquid crystal polymers (CLCPs) underwent reversible photoinduced bending and unbending behaviors in response to 445 and 530 nm visible light at room temperature, respectively. The post-cross-linking method provides a facile way to prepare the CLCP films and fibers with different shapes from LLCPs, which can be processed by traditional melting and solution methods.

AgBr/MgBi2O6 heterostructured composites with highly efficient visible-light-driven photocatalytic activity

NASA Astrophysics Data System (ADS)

Zhong, Liansheng; Hu, Chaohao; Zhuang, Jing; Zhong, Yan; Wang, Dianhui; Zhou, Huaiying

2018-06-01

AgBr/MgBi2O6 heterostructured photocatalysts were synthesized by the deposition-precipitation method. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and UV-Visible diffuse reflectance spectroscopy (UV-Vis DRS) were employed to examine the phase structure, morphology and optical properties of the as-prepared samples. The photocatalytic activity was investigated by decomposing methylene blue (MB) solution under visible light irradiation (λ > 420 nm). AgBr/MgBi2O6 composites exhibited significantly enhanced visible-light-driven photocatalytic properties in comparison with pure MgBi2O6 and AgBr. When the molar ratio of AgBr to MgBi2O6 was 3:1, the composite catalyst showed the optimal photocatalytic activity and excellent stability. The enhanced photocatalytic activity of AgBr/MgBi2O6 composites was attributed to the formation of p-n heterojunction between AgBr and MgBi2O6, thereby resulting in the effective separation and transfer of photogenerated electrons-hole pairs.

Multispectral Near-Infrared Imaging of Composite Restorations in Extracted Teeth.

PubMed

Logan, Cooper M; Co, Katrina U; Fried, William A; Simon, Jacob C; Staninec, Michal; And, Daniel Fried; Darling, Cynthia L

2014-02-20

One major advantage of composite restoration materials is that they can be color matched to the tooth. However, this presents a challenge when composites fail and they need to be replaced. Dentists typically spend more time repairing and replacing composites than placing new restorations. Previous studies have shown that near-infrared imaging can be used to distinguish between sound enamel and decay due to the differences in light scattering. The purpose of this study was to use a similar approach and exploit differences in light scattering to attain high contrast between composite and tooth structure. Extracted human teeth with composites (n=16) were imaged in occlusal transmission mode at wavelengths of 1300-nm, 1460-nm and 1550-nm using an InGaAs image sensor with a tungsten halogen light source with spectral filters. All samples were also imaged in the visible range using a high definition 3D digital microscope. Our results indicate that NIR wavelengths at 1460-nm and 1550-nm, coincident with higher water absorption yield the highest contrast between dental composites and tooth structure.

Multispectral near-infrared imaging of composite restorations in extracted teeth

NASA Astrophysics Data System (ADS)

Logan, Cooper M.; Co, Katrina U.; Fried, William A.; Simon, Jacob C.; Staninec, Michal; Fried, Daniel; Darling, Cynthia L.

2014-02-01

One major advantage of composite restoration materials is that they can be color matched to the tooth. However, this presents a challenge when composites fail and they need to be replaced. Dentists typically spend more time repairing and replacing composites than placing new restorations. Previous studies have shown that near-infrared imaging can be used to distinguish between sound enamel and decay due to the differences in light scattering. The purpose of this study was to use a similar approach and exploit differences in light scattering to attain high contrast between composite and tooth structure. Extracted human teeth with composites (n=16) were imaged in occlusal transmission mode at wavelengths of 1300-nm, 1460-nm and 1550-nm using an InGaAs image sensor with a tungsten halogen light source with spectral filters. All samples were also imaged in the visible range using a high definition 3D digital microscope. Our results indicate that NIR wavelengths at 1460-nm and 1550-nm, coincident with higher water absorption yield the highest contrast between dental composites and tooth structure.

High-resolution light microscopy of nanoforms

NASA Astrophysics Data System (ADS)

Vodyanoy, Vitaly; Pustovyy, Oleg; Vainrub, Arnold

2007-09-01

We developed a high resolution light imaging system. Diffraction gratings with 100 nm width lines as well as less than 100 nm size features of different-shaped objects are clearly visible on a calibrated microscope test slide (Vainrub et al., Optics Letters, 2006, 31, 2855). The two-point resolution increase results from a known narrowing of the central diffraction peak for the annular aperture. Better visibility and advanced contrast of the smallest features in the image are due to enhancement of high spatial frequencies in the optical transfer function. The imaging system is portable, low energy, and battery operated. It has been adapted to use in both transmitting and reflecting light. It is particularly applicable for motile nanoform systems where structure and functions can be depicted in real time. We have isolated micrometer and submicrometer particles, termed proteons, from human and animal blood. Proteons form by reversible seeded aggregation of proteins around proteon nucleating centers (PNCs). PNCs are comprised of 1-2nm metallic nanoclusters containing 40-300 atoms. Proteons are capable of spontaneous assembling into higher nanoform systems assuming structure of complicated topology. The arrangement of complex proteon system mimics the structure of a small biological cell. It has structures that imitate membrane and nucleolus or nuclei. Some of these nanoforms are motile. They interact and divide. Complex nanoform systems can spontaneously reduce to simple proteons. The physical properties of these nanoforms could shed some light on the properties of early life forms or forms at extreme conditions.

Effect of LED light spectra on starvation-induced oxidative stress in the cinnamon clownfish Amphiprion melanopus.

PubMed

Choi, Cheol Young; Shin, Hyun Suk; Choi, Young Jae; Kim, Na Na; Lee, Jehee; Kil, Gyung-Suk

2012-11-01

The present study aimed to test starvation-induced oxidative stress in the cinnamon clownfish Amphiprion melanopus illuminated by light-emitting diodes (LEDs): red (peak at 630 nm), green (peak at 530 nm), and blue (peak at 450 nm) within a visible light. We investigated the oxidative stress induced by starvation for 12 days during illumination with 3 LED light spectra through measuring antioxidant enzyme (superoxide dismutase [SOD] and catalase [CAT]) mRNA expression and activity; CAT western blotting; and measuring lipid peroxidation [LPO]), plasma H(2)O(2), lysozyme, glucose, alanine aminotransferase (AlaAT), aspartate aminotransferase (AspAT), and melatonin levels. In green and blue lights, expression and activity of antioxidant enzyme mRNA were significantly lower than those of other light spectra, results that are in agreement with CAT protein expression level by western blot analysis. Also, in green and blue lights, plasma H(2)O(2), lysozyme, glucose, AlaAT, AspAT, and melatonin levels were significantly lower than those in other light spectra. These results indicate that green and blue LEDs inhibit oxidative stress and enhance immune function in starved cinnamon clownfish. Copyright © 2012 Elsevier Inc. All rights reserved.

Biocompatibility and antibacterial activity of nitrogen-doped titanium dioxide nanoparticles for use in dental resin formulations

PubMed Central

Zane, Andrew; Zuo, Ranfang; Villamena, Frederick A; Rockenbauer, Antal; Digeorge Foushee, Ann Marie; Flores, Kristin; Dutta, Prabir K; Nagy, Amber

2016-01-01

The addition of antibacterial functionality to dental resins presents an opportunity to extend their useful lifetime by reducing secondary caries caused by bacterial recolonization. In this study, the potential efficacy of nitrogen-doped titanium dioxide nanoparticles for this purpose was determined. Nitrogen doping was carried out to extend the ultraviolet absorbance into longer wavelength blue light for increased biocompatibility. Titanium dioxide nanoparticles (approximately 20–30 nm) were synthesized with and without nitrogen doping using a sol–gel method. Ultraviolet–Visible spectroscopy indicated a band of trap states, with increasing blue light absorbance as the concentration of the nitrogen dopant increased. Electron paramagnetic resonance measurements indicated the formation of superoxide and hydroxyl radicals upon particle exposure to visible light and oxygen. The particles were significantly toxic to Escherichia coli in a dose-dependent manner after a 1-hour exposure to a blue light source (480 nm). Intracellular reactive oxygen species assay demonstrated that the particles caused a stress response in human gingival epithelial cells when exposed to 1 hour of blue light, though this did not result in detectable release of cytokines. No decrease in cell viability was observed by water-soluble tetrazolium dye assay. The results show that nitrogen-doped titanium dioxide nanoparticles have antibacterial activity when exposed to blue light, and are biocompatible at these concentrations. PMID:27980404

Biocompatibility and antibacterial activity of nitrogen-doped titanium dioxide nanoparticles for use in dental resin formulations.

PubMed

Zane, Andrew; Zuo, Ranfang; Villamena, Frederick A; Rockenbauer, Antal; Digeorge Foushee, Ann Marie; Flores, Kristin; Dutta, Prabir K; Nagy, Amber

The addition of antibacterial functionality to dental resins presents an opportunity to extend their useful lifetime by reducing secondary caries caused by bacterial recolonization. In this study, the potential efficacy of nitrogen-doped titanium dioxide nanoparticles for this purpose was determined. Nitrogen doping was carried out to extend the ultraviolet absorbance into longer wavelength blue light for increased biocompatibility. Titanium dioxide nanoparticles (approximately 20-30 nm) were synthesized with and without nitrogen doping using a sol-gel method. Ultraviolet-Visible spectroscopy indicated a band of trap states, with increasing blue light absorbance as the concentration of the nitrogen dopant increased. Electron paramagnetic resonance measurements indicated the formation of superoxide and hydroxyl radicals upon particle exposure to visible light and oxygen. The particles were significantly toxic to Escherichia coli in a dose-dependent manner after a 1-hour exposure to a blue light source (480 nm). Intracellular reactive oxygen species assay demonstrated that the particles caused a stress response in human gingival epithelial cells when exposed to 1 hour of blue light, though this did not result in detectable release of cytokines. No decrease in cell viability was observed by water-soluble tetrazolium dye assay. The results show that nitrogen-doped titanium dioxide nanoparticles have antibacterial activity when exposed to blue light, and are biocompatible at these concentrations.

High-power visible laser effect on a Boston Micromachines' MEMS deformable mirror

NASA Astrophysics Data System (ADS)

Norton, Andrew; Gavel, Donald; Dillon, Daren; Cornelissen, Steven

2010-07-01

Continuous-facesheet and segmented Boston Micromachines Corporations' (BMC) Micro-Electrical Mechanical Systems (MEMS) Deformable Mirrors (DM) have been tested for their response to high-power visible-wavelength laser light. The deformable mirrors, coated with either protected silver or bare aluminum, were subjected to a maximum of 2 Watt laser-light at a wavelength of 532 nanometers. The laser light was incident on a ~ 3.5×3.5 cm area for time periods from minutes to 7 continuous hours. Spot heating from the laser-light is measured to induce a local bulge in the surface of each DM. For the aluminum-coated continuous facesheet DM, the induced spot heating changes the surface figure by 16 nm rms. The silver-coated continuous-facesheet and segmented (spatial light modulator) DMs experience a 6 and 8 nm surface rms change in surface quality with the laser at 2 Watts. For spatial frequencies less than the actuator spacing (300 mm), the laser induced surface bulge is shown to be removable, as the DMs continued to be fully functional during and after their exposure. Over the full 10 mm aperture one could expect the same results with a 15 Watt laser guide star (LGS). These results are very promising for use of the MEMS DM to pre-correct the outgoing laser light in the Laboratory for Adaptive Optics' (LAO) laser uplink application.

Novel development of nanocrystalline kesterite Cu2ZnSnS4 thin film with high photocatalytic activity under visible light illumination

NASA Astrophysics Data System (ADS)

Apostolopoulou, Andigoni; Mahajan, Sandip; Sharma, Ramphal; Stathatos, Elias

2018-01-01

Cu2ZnSnS4 (CZTS) represents a promising p-type direct band gap semiconductor with large absorption coefficient in the visible region of solar light. In the present study, a kesterite CZTS nanocrystalline film, with high purity, was successfully synthesized via the combination of successive ionic layer adsorption and reaction (SILAR) and chemical bath deposition (CBD) technique. The morphology and structural properties of the CZTS films were characterized by FE-SEM microscopy, porosimetry in terms of Brunauer-Emmett-Teller (BET) technique, X-ray diffraction and Raman spectroscopy. The as-prepared films under mild heat treatment at 250 °C in the presence of sulfur atmosphere exhibited fine nanostructure with 35 nm average particle size, high specific surface area of 53 m2/g and 9 nm pore diameter. The photocatalytic activity of the films was examined to the degradation of Basic Blue 41 (BB-41) and Acid Orange 8 (AO-8) organic azo dyes under visible light irradiation, demonstrating 97.5% and 70% discoloration for BB-41 and AO-8 respectively. Reusability of the CZTS films was also tested proving good stability over several repetitions. The reduction of photocatalyst's efficiency after three successive repetitions didn't exceed 5.6% and 8.5% for BB-41 and AO-8 respectively.

WO{sub 3} nanoplates, hierarchical flower-like assemblies and their photocatalytic properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Jianhua, E-mail: jhhuang@zstu.edu.cn; Xiao, Liang; Yang, Xiaolong

Graphical abstract: WO{sub 3} nanoplates, hierarchical flower-like assemblies and their visible light-driven photocatalytic properties for degradation of rhodamine B. - Highlights: • Preparation of monoclinic WO{sub 3} by a hydrothermal reaction of PbWO{sub 4} in the presence of HNO{sub 3}. • Single-crystalline WO{sub 3} nanoplates were formed when 4 M HNO{sub 3} solution was used. • WO{sub 3} flowers were assembled by nanoplates when 15 M HNO{sub 3} solution was used. • The products showed excellent visible light-driven photodegradation of rhodamine B. - Abstract: Monoclinic WO{sub 3} was prepared by a hydrothermal reaction of PbWO{sub 4} in the presence ofmore » HNO{sub 3}. WO{sub 3} rectangular nanoplates with a side length of 50–150 nm and a thickness of about 25 nm were obtained at 4 M HNO{sub 3} solution. And the single crystal nature was confirmed by the selected area electron diffraction. Whereas WO{sub 3} hierarchical flower-like assemblies with 3–5 μm in diameter were self-organized by nanoplates in the presence of 15 M HNO{sub 3} solution. Compared with commercial WO{sub 3} particles, our products showed an enhancement of photocatalytic properties for the degradation of rhodamine B under visible light irradiation.« less

Effect of gamma radiation on the optical and structural properties of ZnO nanowires with various diameters

NASA Astrophysics Data System (ADS)

Reyhani, A.; Gholizadeh, A.; vahedi, V.; Khanlary, M. R.

2018-01-01

The effects of gamma-irradiation are studied on the morphology and structural properties of ZnO nanowire with various diameters. The ZnO nanowires are grown using Zn thin films at various initial thicknesses including 125, 250 and 500 nm in air ambient. The results illustrate dramatic effects of Gamma-irradiation on the deformation of ZnO nanowires. Thus, radiation induce ripple ZnO surfaces instead ZnO nanowires. Gamma-irradiation has also been effective on the optical and crystalline properties of the nanowires. X-ray diffraction attests that size of the ZnO nano-structures has changed and (l00) crystalline direction related to Zn metal has been created after irradiation. UV-Visible spectra display two areas for transmittance of irradiated ZnO nanowires, one in the Visible-light and the other in IR sub-region. In the Visible-light area, the layer gets thicker from 125 to 500 nm; the difference between the layer transmittance spectra is reduced before and after gamma irradiation. In the IR-light region, with increasing of ZnO initial thickness, the difference between the layer transmittance spectra is increased before and after gamma irradiation. The photoluminescence spectroscopy displays that intensity of green-yellow band improves in compared to near-band-edge emission due to formation of Zn metal and oxygen vacancies after gamma irradiation.

Fe-N co-doped SiO2@TiO2 yolk-shell hollow nanospheres with enhanced visible light photocatalytic degradation

NASA Astrophysics Data System (ADS)

Wan, Hengcheng; Yao, Weitang; Zhu, Wenkun; Tang, Yi; Ge, Huilin; Shi, Xiaozhong; Duan, Tao

2018-06-01

SiO2@TiO2 yolk@shell hollow nanospheres (STNSs) is considered as an outstanding photocatalyst due to its tunable structure and composition. Based on this point, we present an unprecedentedly excellent photocatalytic property of STNSs toward tannic acid via a Fe-N co-doped strategy. Their morphologies, compositions, structure and properties are characterized. The Fe-N co-doped STNSs formed good hollow yolk@shell structure. The results show that the energy gap of the composites can be downgraded to 2.82 eV (pure TiO2 = 3.2 eV). Photocatalytic degradation of tannic acid (TA, 30 mg L-1) under visible light (380 nm < λ < 780 nm) irradiation is used to evaluate the photocatalytic activity of the composites. Compared with pure TiO2 nanospheres, non-doped STNSs and N-doped STNSs, the Fe-N co-doped STNSs exhibits the highest activity, which can degrade 99.5% TA into CO2 and H2O in 80 min. The probable degradation mechanism of the composites is simultaneously proposed, the band gap of STNSs becomes narrow by co-doping Fe-N, so that the TiO2 shell can stimulate electrons under visible light exposure, generate the ions of radOH and radO2- with a strong oxidizing property. Therefore this approach works is much desired for radioactive organic wastewater photocatalytic degradation.

Flame Imaging System

NASA Technical Reports Server (NTRS)

Barnes, Heidi L. (Inventor); Smith, Harvey S. (Inventor)

1998-01-01

A system for imaging a flame and the background scene is discussed. The flame imaging system consists of two charge-coupled-device (CCD) cameras. One camera uses a 800 nm long pass filter which during overcast conditions blocks sufficient background light so the hydrogen flame is brighter than the background light, and the second CCD camera uses a 1100 nm long pass filter, which blocks the solar background in full sunshine conditions such that the hydrogen flame is brighter than the solar background. Two electronic viewfinders convert the signal from the cameras into a visible image. The operator can select the appropriate filtered camera to use depending on the current light conditions. In addition, a narrow band pass filtered InGaAs sensor at 1360 nm triggers an audible alarm and a flashing LED if the sensor detects a flame, providing additional flame detection so the operator does not overlook a small flame.

Photocarcinogenesis by methoxypsoralen, neutral red, proflavine, and long UV radiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Santamaria, L.; Bianchi, A.; Arnaboldi, A.

1985-01-01

A study of the photosensitizing effects of 8-methoxypsoralen (MOP), neutral red (NR), and proflavine (PF) on the skin of female Swiss albino mice, strain 955, was carried out using fractionated exposure to long ultraviolet light (300-400 nm) and visible light (tungsten emission). The results (1) confirmed MOP photocarcinogenicity, (2) demonstrated that both NR and PF are photocarcinogens, and, further, (3) showed that the above UV light with 2.6% of fluence at 313 nm is a long-term carcinogenic agent even though the total dose of 313 nm was 100 times less than the minimal UV tumorigenic dose in mice. The tumorsmore » were mammary adenocarcinomas, carcinomas of skin appendages, carcino-mixo-sarcomas, lymphomas, and one case of thyroid adenocarcinoma. The implications of the above data regarding the controversy about oncogenic risks in photochemotherapy are discussed.« less

Photocatalysis using a Wide Range of the Visible Light Spectrum: Hydrogen Evolution from Doped AgGaS2.

PubMed

Yamato, Kohei; Iwase, Akihide; Kudo, Akihiko

2015-09-07

Doping of nickel into AgGaS2 yields a new absorption band, at a wavelength longer than the intrinsic absorption band of the AgGaS2 host. The doped nickel forms an electron donor level in a forbidden band of AgGaS2 . The nickel-doped AgGaS2 with rhodium co-catalyst shows photocatalytic activity for sacrificial H2 evolution under the light of up to 760 nm due to the transition from the electron donor level consisting of Ni(2+) to the conduction band of AgGaS2 . Apparent quantum yields for the sacrificial H2 evolution at 540-620 nm are about 1 %. Moreover, the nickel-doped AgGa0.75 In0.25 S2 also responds to near-IR light, up to 900 nm. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Infrared Radiative Properties of Food Materials

USDA-ARS?s Scientific Manuscript database

Precisely, infrared radiation is electromagnetic radiation whose wavelength is longer than that of visible light, but shorter than that of terahertz radiation and microwaves. The infrared portion of the electromagnetic spectrum spans roughly three orders of magnitude (750 nm to 100 µm) and has been...

The effects of wavelength on photodegradation depth profiles in Japanese cedar (Cryptomeria japonica D. Don) earlywood

Treesearch

Yutaka Kataoka; Makoto Kiguchi; R. Sam Williams; Philip D. Evans

2006-01-01

FT-IR microscopy was used to depth profile the photodegradation of Japanese cedar earlywood exposed to monochromatic light in the UV and visible ranges (band pass: 20nm). Parallel experiments assessed the transmission of the light through thin sections of Japanese cedar. The depth of photodegradation increased with wavelength up to and including the violet region of...

A possible mechanism for visible-light-induced skin rejuvenation

NASA Astrophysics Data System (ADS)

Longo, Leonardo; Lubart, Rachel; Friedman, Harry; Lavie, R.

2004-09-01

In recent years there has been intensive research in the field of non-ablative skin rejuvenation. This comes as a response to the desire for a simple method of treating rhytids caused by aging, UV exposure and acne scars. In numerous studies intense visible light pulsed systems (20-30J/cm2) are used. The mechanism of action was supposed to be a selective heat induced denaturalization of dermal collagen that leads to subsequent reactive synthesis. In this study we suggest a different mechanism for photorejuvenation based on light induced Reactive Oxygen Species (ROS) formation. We irradiated collagen in-vitro with a broad band of visible light, 400-800 nm, 12-22J/cm2, and used the spin trapping coupled with electron paramagnetic resonance (EPR) spectroscopy to detect ROS. In vivo, we used dose 30 J in average (35 for acnis scars, 25 for wrinkles and redness). Irradiated collagen results in hydroxyl and methyl radicals formation. We propose, as a new concept, that visible light at the intensity used for skin rejuvenation, 20-30J/cm2, produces high amounts of ROS which destroy old collagen fibers encouraging the formation of new ones. On the other hand at inner depths of the skin, where the light intensity is much weaker, low amounts of ROS are formed which are well known to stimulate fibroblast proliferation.

Plasmonic active spectral filter in VIS-NIR region using metal-insulator-metal (MIM) structure on glass plate

NASA Astrophysics Data System (ADS)

Oshikane, Yasushi; Murai, Kensuke; Higashi, Takaya; Yamamoto, Fumihiko; Nakano, Motohiro; Inoue, Haruyuki

2012-10-01

Interaction between surface plasmons at two interfaces inside a meta-insulator-metal (MIM) structure is one of the interesting physical phenomena in nanophotonics. We have started to create a plasmonic active spectral filter based on the MIM structure for a developing white light-emitting diode (LED) visible-light communication. An optical active filter at visible region assisted by surface plasmon resonance (SPR) in MIM structure of vacuum-deposited thin films on glass substrate has been studied both experimentally and theoretically. Interface between the first thin silver layer (M1, around 50 nm-thick) and bulk glass slide is appropriate for excitation of SPR at particular wavelength and incident angle of illumination light. And spatial extension of the SPR wave may cause an effective propagating mode confined in the insulator layer (I, around 150 nm-thick) by both M1 and the second thick silver layer (M2, around 200 nm-thick). Such an energy conversion from the illuminating light to the propagating SPR modes corresponds to an evident absorption dip on spectral reflectance curve of the MIM structure, and the shape of dip may vary widely in response to material and configuration of the MIM. The spectral and angular reflectance of the prototypical MIM structure has been measured by spectrophotometer for P- and S-polarized light because the plasmonic effect inside the MIM structure depends strongly on the polarization of light. Such the characteristic reflection feature has also been studied by using both the usual transfer matrix method and 2D electromagnetic simulation based on the finite element method. In this talk, several striking and preliminary MIM prototypes will be introduced and discussed.

Silver nanocube aggregation gradient materials in search for total internal reflection with high phase sensitivity

NASA Astrophysics Data System (ADS)

König, Tobias A. F.; Ledin, Petr A.; Russell, Michael; Geldmeier, Jeffrey A.; Mahmoud, Mahmoud. A.; El-Sayed, Mostafa A.; Tsukruk, Vladimir V.

2015-03-01

We fabricated monolayer coatings of a silver nanocube aggregation to create a step-wise optical strip by applying different surface pressures during slow Langmuir-Blodgett deposition. The varying amount of randomly distributed nanocube aggregates with different surface coverages in gradient manner due to changes in surface pressure allows for continuous control of the polarization sensitive absorption of the incoming light over a broad optical spectrum. Optical characterization under total internal reflection conditions combined with electromagnetic simulations reveal that the broadband light absorption depends on the relative orientation of the nanoparticles to the polarization of the incoming light. By using computer simulations, we found that the electric field vector of the s-polarized light interacts with the different types of silver nanocube aggregations to excite different plasmonic resonances. The s-polarization shows dramatic changes of the plasmonic resonances at different angles of incidence (shift of 64 nm per 10° angle of incidence). With a low surface nanocube coverage (from 5% to 20%), we observed a polarization-selective high absorption of 80% (with an average 75%) of the incoming light over a broad optical range in the visible region from 400 nm to 700 nm. This large-area gradient material with location-dependent optical properties can be of particular interest for broadband light absorption, phase-sensitive sensors, and imaging.We fabricated monolayer coatings of a silver nanocube aggregation to create a step-wise optical strip by applying different surface pressures during slow Langmuir-Blodgett deposition. The varying amount of randomly distributed nanocube aggregates with different surface coverages in gradient manner due to changes in surface pressure allows for continuous control of the polarization sensitive absorption of the incoming light over a broad optical spectrum. Optical characterization under total internal reflection conditions combined with electromagnetic simulations reveal that the broadband light absorption depends on the relative orientation of the nanoparticles to the polarization of the incoming light. By using computer simulations, we found that the electric field vector of the s-polarized light interacts with the different types of silver nanocube aggregations to excite different plasmonic resonances. The s-polarization shows dramatic changes of the plasmonic resonances at different angles of incidence (shift of 64 nm per 10° angle of incidence). With a low surface nanocube coverage (from 5% to 20%), we observed a polarization-selective high absorption of 80% (with an average 75%) of the incoming light over a broad optical range in the visible region from 400 nm to 700 nm. This large-area gradient material with location-dependent optical properties can be of particular interest for broadband light absorption, phase-sensitive sensors, and imaging. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr06430e

Short-term Responses of Posidonia australis to Changes in Light Quality

PubMed Central

Strydom, Simone; McMahon, Kathryn M.; Kendrick, Gary A.; Statton, John; Lavery, Paul S.

2018-01-01

Seagrass meadows are highly productive ecosystems that provide ecosystem services to the coastal zone but are declining globally, particularly due to anthropogenic activities that reduce the quantity of light reaching seagrasses, such as dredging, river discharge and eutrophication. Light quality (the spectral composition of the light) is also altered by these anthropogenic stressors as the differential attenuation of wavelengths of light is caused by materials within the water column. This study addressed the effect of altered light quality on different life-history stages of the seagrass Posidonia australis, a persistent, habitat-forming species in Australia. Aquarium-based experiments were conducted to determine how adult shoots and seedlings respond to blue (peak λ = 451 nm); green (peak λ = 522 nm); yellow (peak λ = 596 nm) and red (peak λ = 673 nm) wavelengths with a control of full-spectrum light (λ = 400 – 700 nm, at 200 μmol photons m-2 s-1). Posidonia australis adults did not respond to changes in light quality relative to full-spectrum light, demonstrating a capacity to obtain enough photons from a range of wavelengths across the visible spectrum to maintain short-term growth at high irradiances. Posidonia australis seedlings (<4 months old) grown in blue light showed a significant increase in xanthophyll concentrations when compared to plants grown in full-spectrum, demonstrating a pigment acclimation response to blue light. These results differed significantly from negative responses to changes in light quality recently described for Halophila ovalis, a colonizing seagrass species. Persistent seagrasses such as P. australis, appear to be better at tolerating short-term changes in light quality compared to colonizing species when sufficient PPFD is present. PMID:29387070

Novel solar light driven photocatalyst, zinc indium vanadate for photodegradation of aqueous phenol

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mahapure, Sonali A.; Rane, Vilas H.; Ambekar, Jalindar D.

2011-05-15

Graphical abstract: Novel photocatalyst, zinc indium vanadate (ZnIn{sub 2}V{sub 2}O{sub 9}) demonstrated and showed an excellent photocatalytic activity for phenol degradation under visible light. Research highlights: {yields} Designing and identification of a photocatalyst having prospective potential application to be used in visible light (400-800 nm). {yields} Successful synthesis of novel ZnIn{sub 2}V{sub 2}O{sub 9} by solid state route. {yields} Confirmation of the designed product using characterization techniques. {yields} Application study comprising photodegradation of aqueous phenol at visible light despite of UV radiations. -- Abstract: In the present investigation, we have demonstrated the synthesis of novel photocatalyst, zinc indium vanadate (ZIV)more » by solid-solid state route using respective oxides of zinc, indium and vanadium. This novel photocatalyst was characterized using XRD, FESEM, UV-DRS and FTIR in order to investigate its structural, morphological and optical properties. XRD clearly shows the formation of phase pure ZIV of triclinic crystal structure with good crystallinity. FESEM micrographs showed the clustered morphology having particle size between 0.5 and 1 {mu}m. Since, optical study showed the band gap around 2.8 eV, i.e. in visible region, we have performed the photocatalytic activity of phenol degradation under visible light irradiation. The photodecomposition of phenol by ZIV is studied for the first time and an excellent photocatalytic activity was obtained using this novel photocatalyst. Considering the band gap of zinc indium vanadate in visible region, it will also be the potential candidate for water splitting.« less

Effects of N precursor on the agglomeration and visible light photocatalytic activity of N-doped TiO2 nanocrystalline powder.

PubMed

Hu, Yulong; Liu, Hongfang; Rao, Qiuhua; Kong, Xiaodong; Sun, Wei; Guo, Xingpeng

2011-04-01

N-doped TiO2 nanocrystalline powders were prepared by the sol-gel method using various N precursors, including triethylamine, hydrazine hydrate, ethylenediamine, ammonium hydroxide, and urea. The samples were characterized by X-ray diffraction, N2 adsorption isotherms, transmission electron microscopy, ultraviolet-visible diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The photocatalytic activities of as-prepared samples under irradiation of visible light (lambda > 405 nm) were evaluated by photodecomposition of methyl orange. The alkalinity of N precursor was found to play a key role in the gel process. The N precursor with moderate alkalinity causes TiO2 nanoparticles to be sol-transformed into a loosely agglomerated gel. This transformation facilitates the preparation of an N-doped TiO2 powder with small nanocrystal size, large specific surface area, and high N doping level and results in high visible light photocatalytic activity. The N in TiO2 with N is binding energy at 399-400 eV may be assigned to the N-H species located in interstitial sites of TiO2 lattice which is the active N species responsible for the visible light photocatalytic activity. The N species of N 1s peak at 402 and 405 eV are ineffective to the visible light photocatalytic activity and may inhibit the photocatalytic activity. Moreover, a TiO2 nanoparticle powder with large specific area can be achieved by using urea as a template and then by using ammonium hydroxide to transform the sol into gel.

Ag3PO4 nanocrystals deposited on monoclinic olive-like BiVO4 with efficient photodegradation of organic dyes under visible light irradiation

NASA Astrophysics Data System (ADS)

Chen, Jingshuai; Jiang, Liang-Liang; Liu, Xing-Pei; Mao, Chang-Jie; Song, Ji-Ming; Niu, Helin; Zhang, Shengyi

2017-05-01

Olive-like BiVO4 microstructures with lengths of 600-1000 nm and widths of 300-600 nm have been synthesized via a facile and additive-free solvothermal method. Studies find that the type of solvent plays an important role in the morphology of the final products. Furthermore, Ag3PO4 nanocrystals are successfully deposited on monoclinic olive-like BiVO4 via in situ precipitation method. The as-synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), photoluminescence (PL) spectra, and UV-vis diffuse reflectance spectra (DRS). The photocatalytic activities of the catalysts are evaluated by degradation of rhodamine B (RhB) and methylene blue (MB) under visible light (≥420 nm) irradiation. The experimental results suggest that catalytic activity of the composite photocatalysts is greatly influenced by the loading level of Ag3PO4. The molar ratio of 0.8:1.0 Ag3PO4-loaded BiVO4 exhibits higher photocatalytic activity in both the decolorization of RhB and MB than that of individual BiVO4 and P25. The observed improvement in photocatalytic activity is associated with the extended absorption in the visible light region resulting from the Ag3PO4 nanoparticles, and the effective separation of photogenerated carriers at the Ag3PO4/BiVO4 interfaces through the formation of heterojunction structure. The study provides a general and effective method in the fabrication of composite with sound heterojunctions that may show a variety of applications.

Ease synthesis of mesoporous WO3-TiO2 nanocomposites with enhanced photocatalytic performance for photodegradation of herbicide imazapyr under visible light and UV illumination.

PubMed

Ismail, Adel A; Abdelfattah, Ibrahim; Helal, Ahmed; Al-Sayari, S A; Robben, L; Bahnemann, D W

2016-04-15

Herein, we report the ease synthesis of mesoporous WO3-TiO2 nanocomposites at different WO3 contents (0-5wt%) together with their photocatalytic performance for the degradation of the imazapyr herbicide under visible light and UV illumination. XRD and Raman spectra indicated that the highly crystalline anatase TiO2 phase and monoclinic and triclinic of WO3 were formed. The mesoporous TiO2 exhibits large pore volumes of 0.267cm(3)g-1 and high surface areas of 180m(2)g(-1) but they become reduced to 0.221cm(3)g(-1) and 113m(2)g(-1), respectively upon WO3 incorporation, with tunable mesopore diameter in the range of 5-6.5nm. TEM images show WO3-TiO2 nanocomposites are quite uniform with 10-15nm of TiO2 and 5-10nm of WO3 sizes. Under UV illumination, the overall photocatalytic efficiency of the 3% WO3-TiO2 nanocomposite is 3.5 and 6.6 times higher than that of mesoporous TiO2 and commercial UV-100 photocatalyst, respectively. The 3% WO3-TiO2 nanocomposite is considered to be the optimum photocatalyst which is able to degrade completely (100% conversion) of imazapyr herbicide along 120min with high photonic efficiency ∼8%. While under visible light illumination, the 0.5% WO3-TiO2 nanocomposite is the optimum photocatalyst which achieves 46% photocatalytic efficiency. Copyright © 2015 Elsevier B.V. All rights reserved.

Carbon and nitrogen co-doped bowl-like Au/TiO2 nanostructures with tunable size for enhanced visible-light-driven photocatalysis

NASA Astrophysics Data System (ADS)

Li, Yayuan; Cao, Shubo; Zhang, Ang; Zhang, Chen; Qu, Ting; Zhao, Yongbin; Chen, Aihua

2018-07-01

It is of great importance to extend the UV response of anatase TiO2 into the visible light range for the practical applications. Here, a facile rout to carbon and nitrogen co-doped, Au loaded bowl-like TiO2 nanostructures with tunable size are proposed by using self-assembled polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer (BCP) spherical micelles as templates. Amphiphilic PS-b-P4VP self-assembles to form PS@P4VP core-shell spherical micelles with P4VP as the out layer in an evaporable mixed solvents of ethanol/tetrahydrofuran (THF). The size of uniform PS@P4VP spherical micelles can be precisely tuned in the range of a few nm to several hundred nm by controlling the molecular composition of the BCPs. Bowl-like TiO2 nanostructures with a replicate size loaded with highly dispersed Au nanoparticles (NPs) of ∼5 nm in diameter are fabricated from these spherical micelles because of strong complex ability of pyridine groups. PS-b-P4VP provides carbon and nitrogen sources to dope the resulting samples simultaneously. The special carbon and nitrogen co-doped bowl-like Au/TiO2 nanostructures exhibit much higher photocatalytic activity in the photodegradation of rhodamine B (RhB) compared to Au/P25 under visible light irradiation. Furthermore, the photocatalytic activity is significantly influenced by the BCP molecular composition due to different surface area and loading capacity of the resulting samples. This study provides a facile way to synthesize multi-element doped hollow or bowl-like nanoparticles with tunable size in the nanometer range which have potential application at photocatalysis, oxygen reduction reaction, etc.

Characterization and photocatalytic performance evaluation of various metal ion-doped microstructured TiO2 under UV and visible light.

PubMed

Sahoo, Chittaranjan; Gupta, Ashok K

2015-01-01

Commercially available microcrystalline TiO2 was doped with silver, ferrous and ferric ion (1.0 mol %) using silver nitrate, ferrous sulfate and ferric nitrate solutions following the liquid impregnation technology. The catalysts prepared were characterised by FESEM, XRD, FTIR, DRS, particle size and micropore analysis. The photocatalytic activity of the prepared catalysts was tested on the degradation of two model dyes, methylene blue (3,7-bis (Dimethylamino)-phenothiazin-5-ium chloride, a cationic thiazine dye) and methyl blue (disodium;4-[4-[[4-(4-sulfonatoanilino)phenyl]-[4-(4-sulfonatophenyl)azaniumylidenecyclohexa-2,5-dien-1-ylidene]methyl]anilino]benzene sulfonate, an anionic triphenyl methane dye) under irradiation by UV and visible light in a batch reactor. The efficiency of the photocatalysts under UV and visible light was compared to ascertain the light range for effective utilization. The catalysts were found to have the anatase crystalline structure and their particle size is in a range of 140-250 nm. In the case of Fe(2+) doped TiO2 and Fe(3+) doped TiO2, there was a greater shift in the optical absorption towards the visible range. Under UV light, Ag(+) doped TiO2 was the most efficient catalyst and the corresponding decolorization was more than 99% for both the dyes. Under visible light, Fe(3+) doped TiO2 was the most efficient photocatalyst with more than 96% and 90% decolorization for methylene blue and methyl blue, respectively. The kinetics of the reaction under both UV and visible light was investigated using the Langmuir-Hinshelwood pseudo-first-order kinetic model. Kinetic measurements confirmed that, Ag(+) doped TiO2 was most efficient in the UV range, while Fe(3+) doped TiO2 was most efficient in the visible range.

Point-of-use water disinfection using ultraviolet and visible light-emitting diodes.

PubMed

Lui, Gough Yumu; Roser, David; Corkish, Richard; Ashbolt, Nicholas J; Stuetz, Richard

2016-05-15

Improvements in point-of-use (POU) drinking water disinfection technologies for remote and regional communities are urgently needed. Conceptually, UV-C light-emitting diodes (LEDs) overcome many drawbacks of low-pressure mercury tube based UV devices, and UV-A or visible light LEDs also show potential. To realistically evaluate the promise of LED disinfection, our study assessed the performance of a model 1.3 L reactor, similar in size to solar disinfection bottles. In all, 12 different commercial or semi-commercial LED arrays (270-740 nm) were compared for their ability to inactivate Escherichia coli K12 ATCC W3110 and Enterococcus faecalis ATCC 19433 over 6h. Five log10 and greater reductions were consistently achieved using the 270, 365, 385 and 405 nm arrays. The output of the 310 nm array was insufficient for useful disinfection while 430 and 455 nm performance was marginal (≈ 4.2 and 2.3-log10s E. coli and E. faecalis over the 6h). No significant disinfection was observed with the 525, 590, 623, 660 and 740 nm arrays. Delays in log-phase inactivation of E. coli were observed, particularly with UV-A wavelengths. The radiation doses required for >3-log10 reduction of E. coli and E. faecalis differed by 10 fold at 270 nm but only 1.5-2.5 fold at 365-455 nm. Action spectra, consistent with the literature, were observed with both indicators. The design process revealed cost and technical constraints pertaining to LED electrical efficiency, availability and lifetime. We concluded that POU LED disinfection using existing LED technology is already technically possible. UV-C LEDs offer speed and energy demand advantages, while UV-A/violet units are safer. Both approaches still require further costing and engineering development. Our study provides data needed for such work. Copyright © 2016 Elsevier B.V. All rights reserved.

A multichannel visible spectroscopy system for the ITER-like W divertor on EAST.

PubMed

Mao, Hongmin; Ding, Fang; Luo, Guang-Nan; Hu, Zhenhua; Chen, Xiahua; Xu, Feng; Yang, Zhongshi; Chen, Jingbo; Wang, Liang; Ding, Rui; Zhang, Ling; Gao, Wei; Xu, Jichan; Wu, Chengrui

2017-04-01

To facilitate long-pulse high power operation, an ITER-like actively cooled tungsten (W) divertor was installed in Experimental Advanced Superconducting Tokamak (EAST) to replace the original upper graphite divertor in 2014. A dedicated multichannel visible spectroscopic diagnostic system has been accordingly developed for the characterization of the plasma and impurities in the W divertor. An array of 22 lines-of-sight (LOSs) provides a profile measurement of the light emitted from the plasma along upper outer divertor, and the other 17 vertical LOSs view the upper inner divertor, achieving a 13 mm poloidal resolution in both regions. The light emitted from the plasma is collected by a specially designed optical lens assembly and then transferred to a Czerny-Turner spectrometer via 40 m quartz fibers. At the end, the spectra dispersed by the spectrometer are recorded with an Electron-Multiplying Charge Coupled Device (EMCCD). The optical throughput and quantum efficiency of the system are optimized in the wavelength range 350-700 nm. The spectral resolution/coverage can be adjusted from 0.01 nm/3 nm to 0.41 nm/140 nm by switching the grating with suitable groove density. The frame rate depends on the setting of LOS number in EMCCD and can reach nearly 2 kHz for single LOS detection. The light collected by the front optical lens can also be divided and partly transferred to a photomultiplier tube array with specified bandpass filter, which can provide faster sampling rates by up to 200 kHz. The spectroscopic diagnostic is routinely operated in EAST discharges with absolute optical calibrations applied before and after each campaign, monitoring photon fluxes from impurities and H recycling in the upper divertor. This paper presents the technical details of the diagnostic and typical measurements during EAST discharges.

Photoactive platinum(ii) β-diketonates as dual action anticancer agents.

PubMed

Raza, Md Kausar; Mitra, Koushambi; Shettar, Abhijith; Basu, Uttara; Kondaiah, Paturu; Chakravarty, Akhil R

2016-08-16

Platinum(ii) complexes, viz. [Pt(L)(cur)] (1), [Pt(L)(py-acac)] (2) and [Pt(L)(an-acac)] (3), where HL is 4,4'-bis-dimethoxyazobenzene, Hcur is curcumin, Hpy-acac and Han-acac are pyrenyl and anthracenyl appended acetylacetone, were prepared, characterized and their anticancer activities were studied. Complex [Pt(L)(acac)] (4) was used as a control. Complex 1 showed an absorption band at 430 nm (ε = 8.8 × 10(4) M(-1) cm(-1)). The anthracenyl and pyrenyl complexes displayed bands near 390 nm (ε = 3.7 × 10(4) for 3 and 4.4 × 10(4) M(-1) cm(-1) for 2). Complex 1 showed an emission band at 525 nm (Φ = 0.017) in 10% DMSO-DPBS (pH, 7.2), while 2 and 3 were blue emissive (λem = 440 and 435, Φ = 0.058 and 0.045). There was an enhancement in emission intensity on glutathione (GSH) addition indicating diketonate release. The platinum(ii) species thus formed acted as a transcription inhibitor. The released β-diketonate base showed photo-chemotherapeutic activity. The complexes photocleaved plasmid DNA under blue light of 457 nm forming ∼75% nicked circular (NC) DNA with hydroxyl radicals and singlet oxygen as the ROS. Complexes 1-3 were photocytotoxic in skin keratinocyte HaCaT cells giving IC50 of 8-14 μM under visible light (400-700 nm, 10 J cm(-2)), while being non-toxic in the dark (IC50: ∼60 μM). Complex 4 was inactive. Complexes 1-3 generating cellular ROS caused apoptotic cell death under visible light as evidenced from DCFDA and annexin-V/FITC-PI assays. This work presents a novel way to deliver an active platinum(ii) species and a phototoxic β-diketone species to the cancer cells.

A multichannel visible spectroscopy system for the ITER-like W divertor on EAST

NASA Astrophysics Data System (ADS)

Mao, Hongmin; Ding, Fang; Luo, Guang-Nan; Hu, Zhenhua; Chen, Xiahua; Xu, Feng; Yang, Zhongshi; Chen, Jingbo; Wang, Liang; Ding, Rui; Zhang, Ling; Gao, Wei; Xu, Jichan; Wu, Chengrui

2017-04-01

To facilitate long-pulse high power operation, an ITER-like actively cooled tungsten (W) divertor was installed in Experimental Advanced Superconducting Tokamak (EAST) to replace the original upper graphite divertor in 2014. A dedicated multichannel visible spectroscopic diagnostic system has been accordingly developed for the characterization of the plasma and impurities in the W divertor. An array of 22 lines-of-sight (LOSs) provides a profile measurement of the light emitted from the plasma along upper outer divertor, and the other 17 vertical LOSs view the upper inner divertor, achieving a 13 mm poloidal resolution in both regions. The light emitted from the plasma is collected by a specially designed optical lens assembly and then transferred to a Czerny-Turner spectrometer via 40 m quartz fibers. At the end, the spectra dispersed by the spectrometer are recorded with an Electron-Multiplying Charge Coupled Device (EMCCD). The optical throughput and quantum efficiency of the system are optimized in the wavelength range 350-700 nm. The spectral resolution/coverage can be adjusted from 0.01 nm/3 nm to 0.41 nm/140 nm by switching the grating with suitable groove density. The frame rate depends on the setting of LOS number in EMCCD and can reach nearly 2 kHz for single LOS detection. The light collected by the front optical lens can also be divided and partly transferred to a photomultiplier tube array with specified bandpass filter, which can provide faster sampling rates by up to 200 kHz. The spectroscopic diagnostic is routinely operated in EAST discharges with absolute optical calibrations applied before and after each campaign, monitoring photon fluxes from impurities and H recycling in the upper divertor. This paper presents the technical details of the diagnostic and typical measurements during EAST discharges.

Energy efficiency for the removal of non-polar pollutants during ultraviolet irradiation, visible light photocatalysis and ozonation of a wastewater effluent.

PubMed

Santiago-Morales, Javier; Gómez, María José; Herrera-López, Sonia; Fernández-Alba, Amadeo R; García-Calvo, Eloy; Rosal, Roberto

2013-10-01

This study aims to assess the removal of a set of non-polar pollutants in biologically treated wastewater using ozonation, ultraviolet (UV 254 nm low pressure mercury lamp) and visible light (Xe-arc lamp) irradiation as well as visible light photocatalysis using Ce-doped TiO2. The compounds tracked include UV filters, synthetic musks, herbicides, insecticides, antiseptics and polyaromatic hydrocarbons. Raw wastewater and treated samples were analyzed using stir-bar sorptive extraction coupled with comprehensive two-dimensional gas chromatography (SBSE-CG × GC-TOF-MS). Ozone treatment could remove most pollutants with a global efficiency of over 95% for 209 μM ozone dosage. UV irradiation reduced the total concentration of the sixteen pollutants tested by an average of 63% with high removal of the sunscreen 2-ethylhexyl trans-4-methoxycinnamate (EHMC), the synthetic musk 7-acetyl-1,1,3,4,4,6-hexamethyltetrahydronaphthalene (tonalide, AHTN) and several herbicides. Visible light Ce-TiO2 photocatalysis reached ~70% overall removal with particularly high efficiency for synthetic musks. In terms of power usage efficiency expressed as nmol kJ(-1), the results showed that ozonation was by far the most efficient process, ten-fold over Xe/Ce-TiO2 visible light photocatalysis, the latter being in turn considerably more efficient than UV irradiation. In all cases the efficiency decreased along the treatments due to the lower reaction rate at lower pollutant concentration. The use of photocatalysis greatly improved the efficiency of visible light irradiation. The collector area per order decreased from 9.14 ± 5.11 m(2) m(-3) order(-1) for visible light irradiation to 0.16 ± 0.03 m(2) m(-3) order(-1) for Ce-TiO2 photocatalysis. The toxicity of treated wastewater was assessed using the green alga Pseudokirchneriella subcapitata. Ozonation reduced the toxicity of treated wastewater, while UV irradiation and visible light photocatalysis limited by 20-25% the algal growth due to the accumulation of reaction by-products. Three transformation products were identified and tracked along the treatments. Copyright © 2013 Elsevier Ltd. All rights reserved.

Route towards cylindrical cloaking at visible frequencies using an optimization algorithm

NASA Astrophysics Data System (ADS)

Rottler, Andreas; Krüger, Benjamin; Heitmann, Detlef; Pfannkuche, Daniela; Mendach, Stefan

2012-12-01

We derive a model based on the Maxwell-Garnett effective-medium theory that describes a cylindrical cloaking shell composed of metal rods which are radially aligned in a dielectric host medium. We propose and demonstrate a minimization algorithm that calculates for given material parameters the optimal geometrical parameters of the cloaking shell such that its effective optical parameters fit the best to the required permittivity distribution for cylindrical cloaking. By means of sophisticated full-wave simulations we find that a cylindrical cloak with good performance using silver as the metal can be designed with our algorithm for wavelengths in the red part of the visible spectrum (623nm <λ<773nm). We also present a full-wave simulation of such a cloak at an exemplary wavelength of λ=729nm (ℏω=1.7eV) which indicates that our model is useful to find design rules of cloaks with good cloaking performance. Our calculations investigate a structure that is easy to fabricate using standard preparation techniques and therefore pave the way to a realization of guiding light around an object at visible frequencies, thus rendering it invisible.

Broadband full-color monolithic InGaN light-emitting diodes by self-assembled InGaN quantum dots

PubMed Central

Li, Hongjian; Li, Panpan; Kang, Junjie; Ding, Jiianfeng; Ma, Jun; Zhang, Yiyun; Yi, Xiaoyan; Wang, Guohong

2016-01-01

We have presented broadband full-color monolithic InGaN light-emitting diodes (LEDs) by self-assembled InGaN quantum dots (QDs) using metal organic chemical vapor deposition (MOCVD). The electroluminescence spectra of the InGaN QDs LEDs are extremely broad span from 410 nm to 720 nm with a line-width of 164 nm, covering entire visible wavelength range. A color temperature of 3370 K and a color rendering index of 69.3 have been achieved. Temperature-dependent photoluminescence measurements reveal a strong carriers localization effect of the InGaN QDs layer by obvious blue-shift of emission peak from 50 K to 300 K. The broadband luminescence spectrum is believed to be attributed to the injected carriers captured by the different localized states of InGaN QDs with various sizes, shapes and indium compositions, leading to a full visible color emission. The successful realization of our broadband InGaN QDs LEDs provide a convenient and practical method for the fabrication of GaN-based monolithic full-color LEDs in wafer scale. PMID:27734917

Gravity-induced absorption changes in Phycomyces blakesleeanus during parabolic flights: first spectral approach in the visible.

PubMed

Schmidt, Werner

2006-12-01

Gravity-induced absorption changes as experienced during a series of parabolas on the Airbus 300 Zero-G have been measured previously pointwise on the basis of dual-wavelength spectroscopy. Only the two wavelengths of 460 and 665 nm as generated by light-emitting diodes have been utilised during our first two parabolic-flight campaigns. In order to gain complete spectral information throughout the wavelength range from 400 to 900 nm, a miniaturized rapid scan spectrophotometer was designed. The difference of spectra taken at 0 g and 1.8 g presents the first gravity-induced absorption change spectrum measured on wild-type Phycomyces blakesleeanus sporangiophores, exhibiting a broad positive hump in the visible range and negative values in the near infrared with an isosbestic point near 735 nm. The control experiment performed with the stiff mutant A909 of Phycomyces blakesleeanus does not show this structure. These results are in agreement with those obtained with an array spectrophotometer. In analogy to the more thoroughly understood so-called light-induced absorption changes, we assume that gravity-induced absorption changes reflect redox changes of electron transport components such as flavins and cytochromes localised within the plasma membrane.

Broadband optical properties of biomass burning aerosol and identification of brown carbon chromophores

NASA Astrophysics Data System (ADS)

Rudich, Y.; Bluvshtein, N.; Lin, P.; Flores, J. M.; Segey, L.; Tas, E.; Snider, G.; Weagle, C. L. M.; Brown, S. S.; Laskin, J.; Laskin, A.

2017-12-01

Accurate modeling of the radiative effects of smoke aerosols requires wavelength-dependent measurements and parameterizations of their optical properties in the UV and visible spectral ranges along with improved description of their chemical composition. To address this issue, we used a recently developed approach to retrieve the time- and spectral-dependent optical properties of ambient biomass burning aerosols from 300 to 650 nm wavelengths during a regional nighttime bonfire festival in Israel. During the biomass burning event, the overall absorption at 400 nm increased by about two orders of magnitude, changing the single scattering albedo from a background level of 0.95 to 0.7. In addition, PM2.5 filter samples were collected for detailed chemical analysis of the water soluble organics that contribute to light absorption. Nitroaromatic compounds were identified as major organic species responsible for the 50-80% of the total visible light absorption (> 400 nm). Typical chromophores include 4-nitrocatechol, 4-nitrophenol, nitro-syringol and nitro-guaiacol; oxidation-nitration products of methoxyphenols, and known products of lignin pyrolysis. Our results suggests that night time chemistry of nitrogen oxides with particles may play a significant role in atmospheric transformations of brown carbon.

Hydrogen incorporation by plasma treatment gives mesoporous black TiO 2 thin films with visible photoelectrochemical water oxidation activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Islam, Syed Z.; Reed, Allen; Nagpure, Suraj

2018-05-01

In this work, we use neutron reflectometry (NR) to investigate the roles of hydrogen in plasma treated hydrogen doped mesoporous black titania thin films in their visible light absorption and enhanced photoactivity for water oxidation. The cubic ordered mesoporous TiO2 thin films are prepared by a surfactant-templated sol-gel method and are treated with hydrogen plasma, an approach hypothesized to capitalize on the high degree of disorder in the material and the high energy of the plasma species to achieve efficient hydrogen doping. UV-vis absorbance spectra indicate that H2 plasma treatment makes TiO2 films black, with broad-spectrum enhancement of visible lightmore » absorption, and XPS analysis shows peak for Ti3+ state in treated films. The presence of hydrogen in black mesoporous titania (H-TiO2) films is confirmed by the scattering length density (SLD) profiles obtained from neutron reflectometry measurements. The H-TiO2 shows ca. 28 times and 8 times higher photocurrent for photoelectrochemical water oxidation compared to undoped TiO2 films under UV (365 nm) and blue (455 nm) LED irradiation, respectively. These findings provide the first direct evidence that the dramatic change in visible light absorbance of H-treated black TiO2 is accompanied by significant hydrogen uptake and not just Ti3+ generation or surface disordering.« less

CdSe nanorod/TiO2 nanoparticle heterojunctions with enhanced solar- and visible-light photocatalytic activity

PubMed Central

Laatar, Fakher; Moussa, Hatem; Alem, Halima; Balan, Lavinia; Girot, Emilien; Medjahdi, Ghouti; Ezzaouia, Hatem

2017-01-01

CdSe nanorods (NRs) with an average length of ≈120 nm were prepared by a solvothermal process and associated to TiO2 nanoparticles (Aeroxide® P25) by annealing at 300 °C for 1 h. The content of CdSe NRs in CdSe/TiO2 composites was varied from 0.5 to 5 wt %. The CdSe/TiO2 heterostructured materials were characterized by XRD, TEM, SEM, XPS, UV–visible spectroscopy and Raman spectroscopy. TEM images and XRD patterns show that CdSe NRs with wurtzite structure are associated to TiO2 particles. The UV–visible spectra demonstrate that the narrow bandgap of CdSe NRs serves to increase the photoresponse of CdSe/TiO2 composites until ≈725 nm. The CdSe (2 wt %)/TiO2 composite exhibits the highest photocatalytic activity for the degradation of rhodamine B in aqueous solution under simulated sunlight or visible light irradiation. The enhancement in photocatalytic activity likely originates from CdSe sensitization of TiO2 and the heterojunction between these materials which facilitates electron transfer from CdSe to TiO2. Due to its high stability (up to ten reuses without any significant loss in activity), the CdSe/TiO2 heterostructured catalysts show high potential for real water decontamination. PMID:29354345

CdSe nanorod/TiO2 nanoparticle heterojunctions with enhanced solar- and visible-light photocatalytic activity.

PubMed

Laatar, Fakher; Moussa, Hatem; Alem, Halima; Balan, Lavinia; Girot, Emilien; Medjahdi, Ghouti; Ezzaouia, Hatem; Schneider, Raphaël

2017-01-01

CdSe nanorods (NRs) with an average length of ≈120 nm were prepared by a solvothermal process and associated to TiO 2 nanoparticles (Aeroxide ® P25) by annealing at 300 °C for 1 h. The content of CdSe NRs in CdSe/TiO 2 composites was varied from 0.5 to 5 wt %. The CdSe/TiO 2 heterostructured materials were characterized by XRD, TEM, SEM, XPS, UV-visible spectroscopy and Raman spectroscopy. TEM images and XRD patterns show that CdSe NRs with wurtzite structure are associated to TiO 2 particles. The UV-visible spectra demonstrate that the narrow bandgap of CdSe NRs serves to increase the photoresponse of CdSe/TiO 2 composites until ≈725 nm. The CdSe (2 wt %)/TiO 2 composite exhibits the highest photocatalytic activity for the degradation of rhodamine B in aqueous solution under simulated sunlight or visible light irradiation. The enhancement in photocatalytic activity likely originates from CdSe sensitization of TiO 2 and the heterojunction between these materials which facilitates electron transfer from CdSe to TiO 2 . Due to its high stability (up to ten reuses without any significant loss in activity), the CdSe/TiO 2 heterostructured catalysts show high potential for real water decontamination.

Near infrared photoluminescence properties of porous silicon prepared under the influence of light illumination

NASA Astrophysics Data System (ADS)

Hamadeh, H.; Naddaf, M.; Jazmati, A.

2008-12-01

Porous silicon (PS) has been prepared by anodic etching of boron doped silicon under the influence of monochromatic light illumination. The optical properties of the PS samples have been investigated using temperature dependent photoluminescence (PL) spectroscopy. An overall enhancement of the infrared luminescence yield is caused by the light illumination. In the visible spectral range, changes at the low energy side of the broad PL band were observed. In the near infrared spectral range, a new PL band at 850 nm, which is strongly correlated with light illumination, was detected. The new PL band disappears once blue light is used, whereas an increase in its intensity is observed, when the etching is performed under the illumination of light with wavelengths close to the band gap. By increasing the temperature, the 850 nm transition band grows at the expense of the main near infrared transition at 1100 nm. The recombination characteristics of this PL band are indicative of its extrinsic nature. The macroscopic morphology shows strong dependence on the wavelength of the illumination light. Photoassisted preparation could provide a tool for the control of the optical and structural properties of PS.

A study on a portable fluorescence imaging system

NASA Astrophysics Data System (ADS)

Chang, Han-Chao; Wu, Wen-Hong; Chang, Chun-Li; Huang, Kuo-Cheng; Chang, Chung-Hsing; Chiu, Shang-Chen

2011-09-01

The fluorescent reaction is that an organism or dye, excited by UV light (200-405 nm), emits a specific frequency of light; the light is usually a visible or near infrared light (405-900 nm). During the UV light irradiation, the photosensitive agent will be induced to start the photochemical reaction. In addition, the fluorescence image can be used for fluorescence diagnosis and then photodynamic therapy can be given to dental diseases and skin cancer, which has become a useful tool to provide scientific evidence in many biomedical researches. However, most of the methods on acquiring fluorescence biology traces are still stay in primitive stage, catching by naked eyes and researcher's subjective judgment. This article presents a portable camera to obtain the fluorescence image and to make up a deficit from observer competence and subjective judgment. Furthermore, the portable camera offers the 375nm UV-LED exciting light source for user to record fluorescence image and makes the recorded image become persuasive scientific evidence. In addition, when the raising the rate between signal and noise, the signal processing module will not only amplify the fluorescence signal up to 70 %, but also decrease the noise significantly from environmental light on bill and nude mouse testing.

Dispersed-nanoparticle loading synthesis for monodisperse Au-titania composite particles and their crystallization for highly active UV and visible photocatalysts.

PubMed

Sakamoto, Takeshi; Nagao, Daisuke; Noba, Masahiro; Ishii, Haruyuki; Konno, Mikio

2014-06-24

Submicrometer-sized amorphous titania spheres incorporating Au nanoparticles (NPs) were prepared in a one-pot synthesis consisting of a sol-gel reaction of titanium(IV) isopropoxide in the presence of chloroauric acid and a successive reduction with sodium borohydride in a mixed solvent of ethanol/acetonitrile. The synthesis was allowed to prepare monodisperse titania spheres that homogeneously incorporated Au NPs with sizes of ca. 7 nm. The Au NP-loaded titania spheres underwent different crystallization processes, including 500 °C calcination in air, high-temperature hydrothermal treatment (HHT), and/or low-temperature hydrothermal treatment (LHT). Photocatalytic experiments were conducted with the Au NP-loaded crystalline titania spheres under irradiation of UV and visible light. A combined process of LHT at 80 °C followed by calcination at 500 °C could effectively crystallize titania spheres maintaining the dispersion state of Au NPs, which led to photocatalytic activity higher than that of commercial P25 under UV irradiation. Under visible light irradiation, the Au NP-titania spheres prepared with a crystallization process of LHT at 80 °C for 6 h showed photocatalytic activity much higher than a commercial product of visible light photocatalyst. Structure analysis of the visible light photocatalysts indicates the importance of prevention of the Au NPs aggregation in the crystallization processes for enhancement of photocatalytic activity.

Spectroscopic signatures of ozone at the air–water interface and photochemistry implications

PubMed Central

Anglada, Josep M.; Martins-Costa, Marilia; Ruiz-López, Manuel F.; Francisco, Joseph S.

2014-01-01

First-principles simulations suggest that additional OH formation in the troposphere can result from ozone interactions with the surface of cloud droplets. Ozone exhibits an affinity for the air–water interface, which modifies its UV and visible light spectroscopic signatures and photolytic rate constant in the troposphere. Ozone cross sections on the red side of the Hartley band (290- to 350-nm region) and in the Chappuis band (450–700 nm) are increased due to electronic ozone–water interactions. This effect, combined with the potential contribution of the O3 + hν → O(3P) + O2(X3Σg−) photolytic channel at the interface, leads to an enhancement of the OH radical formation rate by four orders of magnitude. This finding suggests that clouds can influence the overall oxidizing capacity of the troposphere on a global scale by stimulating the production of OH radicals through ozone photolysis by UV and visible light at the air–water interface. PMID:25071195

Pentosan-derived water-soluble carbon nano dots with substantial fluorescence: Properties and application as a photosensitizer

NASA Astrophysics Data System (ADS)

Wu, Qiong; Li, Wei; Wu, Yanjiao; Huang, Zhanhua; Liu, Shouxin

2014-10-01

The hydrothermal carbonization of monosaccharides and polysaccharides is widely used in the production of carbonaceous material with a desired structure. However, the liquid products are regarded as waste and discarded. Here, we report a facile approach for the synthesis of water-soluble carbon nano dots (CNDs) with substantial fluorescence from the liquid by-products of the hydrothermal carbonization of pentosan, thus the by-products of pulp refining. The synthesized CNDs are monodispersed spheres with abundant oxygen-containing groups and they have an average size of 30 nm. Quantum yield measurements revealed CNDs with substantial green photoluminescence (PL) without passivation. Additionally, excitation was independent, pH-sensitive and stable. The use of CNDs as a photosensitizer in the CNDs/TiO2 system for methylene blue (MB) degradation under visible light irradiation is attractive. The spectral response range of the CNDs/TiO2 system can be widened from the UV region to a part of the visible light region (400-550 nm).

White light generation using photonic crystal fiber with sub-micron circular lattice

NASA Astrophysics Data System (ADS)

Saghaei, Hamed; Ghanbari, Ashkan

2017-08-01

In this paper, we study a photonic crystal fiber (PCF) with circular lattice and engineer linear and nonlinear parameters by varying the diameter of air-holes. It helps us obtain low and high zero dispersion wavelengths in the visible and nearinfrared regions. We numerically demonstrate that by launching 100 fs input pulses of 1, 2, and 5 kW peak powers with center wavelength of 532 nm from an unamplified Ti:sapphire laser into a 100 mm length of the engineered PCF, supercontinua as wide as 290, 440 and 830 nm can be obtained, respectively. The spectral broadening is due to the combined action of self-phase modulation, stimulated Raman scattering and parametric four-wave-mixing generation of the pump pulses. The third and the widest spectrum covers the entire visible range and a part of near infrared region making it a suitable source for both white light applications and optical coherence tomography to measure retinal oxygen metabolic response to systemic oxygenation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patil, B. N.; Acharya, S. A., E-mail: saha275@yahoo.com

In the present work ZnS-CdS composite was prepared by hydrothermal method. The prepared samples were characterized by X-ray diffraction (XRD) to confirm formation of nano particles, Scanning electron microscopy (SEM) images exhibit nanoscale dimensions of as synthesized individual phases. UV/VIS spectra were recorded for evaluation of photophysical properties. The composite was explored as photocatalysts to study dye degradation using methylene blue in aqueous slurry under irradiation of 663 nm wavelength and congo red under irradiation of 493 nm wavelength. Under the same conditions the photocatalytic activity of the individual phases ZnS and CdS were also examined. The ZnS-CdS composite is found inmore » enhancing the rate of photo degradation of toxic dyes as compare to ZnS and CdS individually in presence of visible light. This ZnS based metal sulphide/oxide semiconductor nanocomposites are high potential material for Photo-degradation of toxic dyes, and act as good photocatalyst in visible light.« less

Rapid water disinfection using vertically aligned MoS 2 nanofilms and visible light

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Chong; Kong, Desheng; Hsu, Po -Chun

Here, solar energy is readily available in most climates and can be used for water purification. However, solar disinfection of drinking water (SODIS) mostly relies on ultraviolet light, which represents only 4% of total solar energy, and this leads to slow treatment speed. The development of new materials that can harvest visible light for water disinfection, and speed up solar water purification, is therefore highly desirable. Here, we show that few-layered vertically aligned MoS 2 (FLV-MoS 2) films can be used to harvest the whole spectrum of visible light (~ 50% of solar energy) and achieve highly efficient water disinfection.more » The bandgap of MoS 2 was increased from 1.3 eV to 1.55 eV by decreasing the domain size, which allowed the FLV-MoS 2 to generate reactive oxygen species (ROS) for bacterial inactivation in water. The FLV-MoS 2 showed ~15 times better log inactivation efficiency of indicator bacteria compared to bulk MoS 2, and much faster inactivation of bacteria under both visible light and sunlight illumination compared to widely used TiO 2. Moreover, by using a 5 nm copper film on top of the FLV-MoS 2 as a catalyst to facilitate electron-hole pair separation and promote the generation of ROS, the disinfection rate was further increased 6 fold. With our approach, we achieved water disinfection of >99.999% inactivation of bacteria in 20 minutes with a small amount of material (1.6 mg/L) under simulated visible light.« less

Rapid water disinfection using vertically aligned MoS 2 nanofilms and visible light

DOE PAGES

Liu, Chong; Kong, Desheng; Hsu, Po -Chun; ...

2016-08-15

Here, solar energy is readily available in most climates and can be used for water purification. However, solar disinfection of drinking water (SODIS) mostly relies on ultraviolet light, which represents only 4% of total solar energy, and this leads to slow treatment speed. The development of new materials that can harvest visible light for water disinfection, and speed up solar water purification, is therefore highly desirable. Here, we show that few-layered vertically aligned MoS 2 (FLV-MoS 2) films can be used to harvest the whole spectrum of visible light (~ 50% of solar energy) and achieve highly efficient water disinfection.more » The bandgap of MoS 2 was increased from 1.3 eV to 1.55 eV by decreasing the domain size, which allowed the FLV-MoS 2 to generate reactive oxygen species (ROS) for bacterial inactivation in water. The FLV-MoS 2 showed ~15 times better log inactivation efficiency of indicator bacteria compared to bulk MoS 2, and much faster inactivation of bacteria under both visible light and sunlight illumination compared to widely used TiO 2. Moreover, by using a 5 nm copper film on top of the FLV-MoS 2 as a catalyst to facilitate electron-hole pair separation and promote the generation of ROS, the disinfection rate was further increased 6 fold. With our approach, we achieved water disinfection of >99.999% inactivation of bacteria in 20 minutes with a small amount of material (1.6 mg/L) under simulated visible light.« less

Conversion of visible light to electrical energy - Stable cadmium selenide photoelectrodes in aqueous electrolytes

NASA Technical Reports Server (NTRS)

Wrighton, M. S.; Ellis, A. B.; Kaiser, S. W.

1977-01-01

Stabilization of n-type CdSe to photoanodic dissolution is reported. The stabilization is accomplished by the competitive oxidation of S(--) or S(n)(--) at the CdSe photoanode in an electrochemical cell. Such stabilized cells are shown to sustain the conversion of low energy (not less than 1.7 eV) visible light to electricity with good efficiency and no deterioration of the CdSe photoelectrode or of the electrolyte. The electrolyte undergoes no net chemical change because the oxidation occurring at the photoelectrode is reversed at the cathode. Conversion of monochromatic light at 633 nm to electricity is shown to be up to approximately 9% efficient with output potentials of approximately 0.4 V. Conversion of solar energy to electricity is estimated to be approximately 2% efficient.

Metal-free organic sensitizers for use in water-splitting dye-sensitized photoelectrochemical cells

PubMed Central

Swierk, John R.; Méndez-Hernández, Dalvin D.; McCool, Nicholas S.; Liddell, Paul; Terazono, Yuichi; Pahk, Ian; Tomlin, John J.; Oster, Nolan V.; Moore, Thomas A.; Moore, Ana L.; Gust, Devens; Mallouk, Thomas E.

2015-01-01

Solar fuel generation requires the efficient capture and conversion of visible light. In both natural and artificial systems, molecular sensitizers can be tuned to capture, convert, and transfer visible light energy. We demonstrate that a series of metal-free porphyrins can drive photoelectrochemical water splitting under broadband and red light (λ > 590 nm) illumination in a dye-sensitized TiO2 solar cell. We report the synthesis, spectral, and electrochemical properties of the sensitizers. Despite slow recombination of photoinjected electrons with oxidized porphyrins, photocurrents are low because of low injection yields and slow electron self-exchange between oxidized porphyrins. The free-base porphyrins are stable under conditions of water photoelectrolysis and in some cases photovoltages in excess of 1 V are observed. PMID:25583488

Visible near-infrared light scattering of single silver split-ring structure made by nanosphere lithography.

PubMed

Okamoto, Toshihiro; Fukuta, Tetsuya; Sato, Shuji; Haraguchi, Masanobu; Fukui, Masuo

2011-04-11

We succeeded in making a silver split-ring (SR) structure of approximately 130 nm in diameter on a glass substrate using a nanosphere lithography technique. The light scattering spectrum in visible near-infrared region of a single, isolated SR was measured using a microscope spectroscopy optical system. The electromagnetic field enhancement spectrum and distribution of the SR structure were simulated by the finite-difference time-domain method, and the excitation modes were clarified. The long wavelength peak in the light scattering spectra corresponded to a fundamental LC resonance mode excited by an incident electric field. It was shown that a single SR structure fabricated as abovementioned can operate as a resonator and generate a magnetic dipole. © 2011 Optical Society of America

Broadband image sensor array based on graphene-CMOS integration

NASA Astrophysics Data System (ADS)

Goossens, Stijn; Navickaite, Gabriele; Monasterio, Carles; Gupta, Shuchi; Piqueras, Juan José; Pérez, Raúl; Burwell, Gregory; Nikitskiy, Ivan; Lasanta, Tania; Galán, Teresa; Puma, Eric; Centeno, Alba; Pesquera, Amaia; Zurutuza, Amaia; Konstantatos, Gerasimos; Koppens, Frank

2017-06-01

Integrated circuits based on complementary metal-oxide-semiconductors (CMOS) are at the heart of the technological revolution of the past 40 years, enabling compact and low-cost microelectronic circuits and imaging systems. However, the diversification of this platform into applications other than microcircuits and visible-light cameras has been impeded by the difficulty to combine semiconductors other than silicon with CMOS. Here, we report the monolithic integration of a CMOS integrated circuit with graphene, operating as a high-mobility phototransistor. We demonstrate a high-resolution, broadband image sensor and operate it as a digital camera that is sensitive to ultraviolet, visible and infrared light (300-2,000 nm). The demonstrated graphene-CMOS integration is pivotal for incorporating 2D materials into the next-generation microelectronics, sensor arrays, low-power integrated photonics and CMOS imaging systems covering visible, infrared and terahertz frequencies.

Synthesis of visible-light responsive graphene oxide/TiO(2) composites with p/n heterojunction.

PubMed

Chen, Chao; Cai, Weimin; Long, Mingce; Zhou, Baoxue; Wu, Yahui; Wu, Deyong; Feng, Yujie

2010-11-23

Graphene oxide/TiO(2) composites were prepared by using TiCl(3) and graphene oxide as reactants. The concentration of graphene oxide in starting solution played an important role in photoelectronic and photocatalytic performance of graphene oxide/TiO(2) composites. Either a p-type or n-type semiconductor was formed by graphene oxide in graphene oxide/TiO(2) composites. These semiconductors could be excited by visible light with wavelengths longer than 510 nm and acted as sensitizer in graphene oxide/TiO(2) composites. Visible-light driven photocatalytic performance of graphene oxide/TiO(2) composites in degradation of methyl orange was also studied. Crystalline quality and chemical states of carbon elements from graphene oxide in graphene oxide/TiO(2) composites depended on the concentration of graphene oxide in the starting solution. This study shows a possible way to fabricate graphene oxide/semiconductor composites with different properties by using a tunable semiconductor conductivity type of graphene oxide.

Characterization of the thin layer photocatalysts TiO2 and V2O5- and Fe2O3- doped TiO2 prepared by the sol-gel method

NASA Astrophysics Data System (ADS)

Loc Luu, Cam; Nguyen, Quoc Tuan; Thoang Ho, Si; Nguyen, Tri

2013-09-01

The catalysts TiO2 and TiO2 doped with Fe and V were prepared using the sol-gel method. TiO2-modified samples were obtained in the form of a thick film on pyrex glass sticks and tubes and were used as catalysts in the gas phase photo-oxidation of p-xylene. The physico-chemical characteristics of the catalysts were determined using the methods of Brunauer-Emmett-Teller adsorption, x-ray diffraction, and infrared, ultraviolet and visible and Raman spectroscopies. The experimental results show that the introduction of V did not expand the region of light absorption, but slightly reduced the size of the TiO2 particles, and reduced the number of OH-groups, which should decrease the photocatalytic activity and efficiency of the obtained catalysts compared to those of pure TiO2. The Fe-doped TiO2 samples, in contrast, are characterized by an extension of the spectrum of photon absorption to the visible region with wavenumbers λ up to 464 nm and the values of their band gap energy decreased to lower quantities (up to 2.67 eV), therefore they should have higher catalytic activity and conversion efficiency of p-xylene in the visible region than the original sample. For these catalysts, a combined utilization of radiation by ultraviolet (λ = 365 nm) and visible (λ = 470 nm) light increased the activity and the yield in p-xylene conversion by a factor of around 2-3, as well as making these quantities more stable in comparison with those of TiO2-P25 Degussa.

High-performance ultraviolet detection and visible-blind photodetector based on Cu{sub 2}O/ZnO nanorods with poly-(N-vinylcarbazole) intermediate layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perng, Dung-Ching, E-mail: dcperng@ee.ncku.edu.tw; Center for Micro/Nano Science and Technology, National Cheng Kung University, One University Road, Tainan 701, Taiwan; Lin, Hsueh-Pin

This study reports a high-performance hybrid ultraviolet (UV) photodetector with visible-blind sensitivity fabricated by inserting a poly-(N-vinylcarbazole) (PVK) intermediate layer between low-cost processed Cu{sub 2}O film and ZnO nanorods (NRs). The PVK layer acts as an electron-blocking/hole-transporting layer between the n-ZnO and p-Cu{sub 2}O films. The Cu{sub 2}O/PVK/ZnO NR photodetector exhibited a responsivity of 13.28 A/W at 360 nm, a high detectivity of 1.03 × 10{sup 13} Jones at a low bias of −0.1 V under a low UV light intensity of 24.9 μW/cm{sup 2}. The photo-to-dark current ratios of the photodetector with and without the PVK intermediate layer at a bias of −0.5 V are 1.34 × 10{supmore » 2} and 3.99, respectively. The UV-to-visible rejection ratios (R{sub 360 nm}/R{sub 450 nm}) are 350 and 1.735, respectively. Several features are demonstrated: (a) UV photo-generated holes at the ZnO NRs can effectively be transported through the PVK layer to the p-Cu{sub 2}O layer; (b) the insertion of a PVK buffer layer significantly minimizes the reverse-bias leakage current, which leads to a larger amplification of the photocurrent; and (c) the PVK buffer layer greatly improves the UV-to-visible responsivity ratio, allowing the device to achieve high UV detection sensitivity at a low bias voltage using a very low light intensity.« less

Photoassisted photoluminescence fine-tuning of gold nanodots through free radical-mediated ligand-assembly

NASA Astrophysics Data System (ADS)

Tseng, Yu-Ting; Cherng, Rochelle; Harroun, Scott G.; Yuan, Zhiqin; Lin, Tai-Yuan; Wu, Chien-Wei; Chang, Huan-Tsung; Huang, Chih-Ching

2016-05-01

In this study, we have developed a simple photoassisted ligand assembly to fine-tune the photoluminescence (PL) of (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide-capped gold nanodots (11-MUTAB-Au NDs). The 11-MUTAB-Au NDs (size: ca. 1.8 nm), obtained from the reaction of gold nanoparticles (ca. 3 nm) and 11-MUTAB, exhibited weak, near-infrared (NIR) PL at 700 nm with a quantum yield (QY) of 0.37% upon excitation at 365 nm. The PL QY of the Au NDs increased to 11.43% after reaction with 11-mercaptoundecanoic acid (11-MUA) for 30 min under ultraviolet (UV) light, which was accompanied by a PL wavelength shift to the green region (~520 nm). UV-light irradiation accelerates 11-MUA assembly on the 11-MUTABAu NDs (11-MUA/11-MUTAB-Au NDs) through a radical-mediated reaction. Furthermore, the PL wavelength of the 11-MUA/11-MUTAB-Au NDs can be switched to 640 nm via cysteamine under UV-light irradiation. We propose that the PL of the Au NDs with NIR and visible emissions was originally from the surface thiol-Au complexes and the Au core, respectively. These dramatically different optical properties of the Au NDs were due to variation in the surface ligands, as well as the densities and surface oxidant states of the surface Au atoms/ions. These effects can be controlled by assembling surface thiol ligands and accelerated by UV irradiation.In this study, we have developed a simple photoassisted ligand assembly to fine-tune the photoluminescence (PL) of (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide-capped gold nanodots (11-MUTAB-Au NDs). The 11-MUTAB-Au NDs (size: ca. 1.8 nm), obtained from the reaction of gold nanoparticles (ca. 3 nm) and 11-MUTAB, exhibited weak, near-infrared (NIR) PL at 700 nm with a quantum yield (QY) of 0.37% upon excitation at 365 nm. The PL QY of the Au NDs increased to 11.43% after reaction with 11-mercaptoundecanoic acid (11-MUA) for 30 min under ultraviolet (UV) light, which was accompanied by a PL wavelength shift to the green region (~520 nm). UV-light irradiation accelerates 11-MUA assembly on the 11-MUTABAu NDs (11-MUA/11-MUTAB-Au NDs) through a radical-mediated reaction. Furthermore, the PL wavelength of the 11-MUA/11-MUTAB-Au NDs can be switched to 640 nm via cysteamine under UV-light irradiation. We propose that the PL of the Au NDs with NIR and visible emissions was originally from the surface thiol-Au complexes and the Au core, respectively. These dramatically different optical properties of the Au NDs were due to variation in the surface ligands, as well as the densities and surface oxidant states of the surface Au atoms/ions. These effects can be controlled by assembling surface thiol ligands and accelerated by UV irradiation. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00795c

On the accuracy of aerosol photoacoustic spectrometer calibrations using absorption by ozone

NASA Astrophysics Data System (ADS)

Davies, Nicholas W.; Cotterell, Michael I.; Fox, Cathryn; Szpek, Kate; Haywood, Jim M.; Langridge, Justin M.

2018-04-01

In recent years, photoacoustic spectroscopy has emerged as an invaluable tool for the accurate measurement of light absorption by atmospheric aerosol. Photoacoustic instruments require calibration, which can be achieved by measuring the photoacoustic signal generated by known quantities of gaseous ozone. Recent work has questioned the validity of this approach at short visible wavelengths (404 nm), indicating systematic calibration errors of the order of a factor of 2. We revisit this result and test the validity of the ozone calibration method using a suite of multipass photoacoustic cells operating at wavelengths 405, 514 and 658 nm. Using aerosolised nigrosin with mobility-selected diameters in the range 250-425 nm, we demonstrate excellent agreement between measured and modelled ensemble absorption cross sections at all wavelengths, thus demonstrating the validity of the ozone-based calibration method for aerosol photoacoustic spectroscopy at visible wavelengths.

A novel plasmonic interferometry and the potential applications

NASA Astrophysics Data System (ADS)

Ali, J.; Pornsuwancharoen, N.; Youplao, P.; Aziz, M. S.; Chiangga, S.; Jaglan, J.; Amiri, I. S.; Yupapin, P.

2018-03-01

In this article, we have proposed the plasmonic interferometry concept and analytical details given. By using the conventional optical interferometry, which can be simply calculated by using the relationship between the electric field and electron mobility, the interference mobility visibility (fringe visibility) can be observed. The surface plasmons in the sensing arm of the Michelson interferometer is constructed by the stacked layers of the silicon-graphene-gold, allows to characterize the spatial resolution of light beams in terms of the electron mobility down to 100-nm scales, with measured coherence lengths as low as ∼100 nm for an incident wavelength of 1550 nm. We have demonstrated a compact plasmonic interferometer that can apply to the electron mean free paths measurement, from which the precise determination can be used for the high-resolution mean free path measurement and sensing applications. This system provides the practical simulation device parameters that can be fabricated and tested by the experimental platform.

Research on spectrum broadening covering visible light of a fiber femtosecond optical frequency comb for absolute frequency measurement

NASA Astrophysics Data System (ADS)

Xing, Shuai; Wu, Tengfei; Li, Shuyi; Xia, Chuanqing; Han, Jibo; Zhang, Lei; Zhao, Chunbo

2018-03-01

As a bridge connecting microwave frequency and optical frequency, femtosecond laser has important significance in optical frequency measurement. Compared with the traditional Ti-sapphire femtosecond optical frequency comb, with the advantages of compact structure, strong anti-interference ability and low cost, the fiber femtosecond optical frequency comb has a wider application prospect. An experiment of spectrum broadening in a highly nonlinear photonic crystal fiber pumped by an Er-fiber mode-locked femtosecond laser is studied in this paper. Based on optical amplification and frequency doubling, the central wavelength of the output spectrum is 780nm and the average power is 232mW. With the femtosecond pulses coupled into two different photonic crystal fibers, the coverage of visible spectrum is up to 500nm-960nm. The spectral shape and width can be optimized by changing the polarization state for satisfying the requirments of different optical frequencies measurement.

Study of resonance light scattering for remote optical probing

NASA Technical Reports Server (NTRS)

Penney, C. M.; Morey, W. W.; St. Peters, R. L.; Silverstein, S. D.; Lapp, M.; White, D. R.

1973-01-01

Enhanced scattering and fluorescence processes in the visible and UV were investigated which will enable improved remote measurements of gas properties. The theoretical relationship between scattering and fluorescence from an isolated molecule in the approach to resonance is examined through analysis of the time dependence of re-emitted light following excitation of pulsed incident light. Quantitative estimates are developed for the relative and absolute intensities of fluorescence and resonance scattering. New results are obtained for depolarization of scattering excited by light at wavelengths within a dissociative continuum. The experimental work was performed in two separate facilities. One of these utilizes argon and krypton lasers, single moded by a tilted etalon, and a 3/4 meter double monochromator. This facility was used to determine properties of the re-emission from NO2, I2 and O3 excited by visible light. The second facility involves a narrow-line dye laser, and a 3/4 meter single monochromator. The dye laser produces pulsed light with 5 nsec pulse duration and 0.005 nm spectral width.

Colloidal silver nanoparticles prepared by UV-light induced citrate reduction technique for the quantitative detection of uric acid

NASA Astrophysics Data System (ADS)

Maity, Anupam; Panda, Sovan Kumar

2018-04-01

Reddish-yellow color colloid consisting of silver nanoparticles (Ag NPs) has been synthesized by reducing aqueous AgNO3 solution by photo-induced citrate reduction technique under UV light. As prepared colloid exhibits single and intense plasmonic absorption peak in the violet region of the visible spectra with the peak centered at 405 nm. The NPs are fine and spherical with diameter ranging from 5 to 10 nm. These colloidal NPs have been used for the quantitative detection of uric acid by UV-VIS spectroscopy. A linear red shifting of the characteristics Plasmonic absorption peak of Ag NPs is observed with uric acid concentration. Uric acid can be detected by UV-VIS spectroscopy down to 5 nM limit using the prepared colloid.

Hydrogen generation from water/methanol under visible light using aerogel prepared strontium titanate (SrTiO3) nanomaterials doped with ruthenium and rhodium metals

NASA Astrophysics Data System (ADS)

Kuo, Yenting; Klabunde, Kenneth J.

2012-07-01

Nanostructured strontium titanate visible-light-driven photocatalysts containing rhodium and ruthenium were synthesized by a modified aerogel synthesis using ruthenium chloride and rhodium nitrate as dopant precursors, and titanium isopropoxide and strontium metal as the metal sources. The well-defined crystalline SrTiO3 structure was confirmed by means of x-ray diffraction. After calcination at 500 °C, diffuse reflectance spectroscopy shows an increase in light absorption at 370 nm due to the presence of Rh3 + ; however an increase of the calcination temperature to 600 °C led to a decrease in intensity, probably due to a loss of surface area. An increase in the rhodium doping level also led to an increase in absorption at 370 nm however, the higher amounts of dopant lowered the photocatalytic activity. The modified aerogel synthesis allows greatly enhanced H2 production performance from an aqueous methanol solution under visible light irradiation compared with lower surface area conventional materials. We believe that this enhanced activity is due to the higher surface areas while high quality nanocrystalline materials are still obtained. Furthermore, the surface properties of these nanocrystalline aerogel materials are different, as exhibited by the higher activities in alkaline solutions, while conventional materials (obtained via high temperature solid-state synthesis methods) only exhibit reasonable hydrogen production in acidic solutions. Moreover, an aerogel synthesis approach gives the possibility of thin-film formation and ease of incorporation into practical solar devices.

Nature of light scattering in dental enamel and dentin at visible and near-infrared wavelengths

NASA Astrophysics Data System (ADS)

Fried, Daniel; Glena, Richard E.; Featherstone, John D. B.; Seka, Wolf

1995-03-01

The light-scattering properties of dental enamel and dentin were measured at 543, 632, and 1053 nm. Angularly resolved scattering distributions for these materials were measured from 0 deg to 180 deg using a rotating goniometer. Surface scattering was minimized by immersing the samples in an index-matching bath. The scattering and absorption coefficients and the scattering phase function were deduced by comparing the measured scattering data with angularly resolved Monte Carlo light-scattering simulations. Enamel and dentin were best represented by a linear combination of a highly forward-peaked Henyey-Greenstein (HG) phase function and an isotropic phase function. Enamel weakly scatters light between 543 nm and 1.06 mu m, with the scattering coefficient ( mu s) ranging from mu s = 15 to 105 cm-1. The phase function is a combination of a HG function with g = 0.96 and a 30-60% isotropic phase function. For enamel, absorption is negligible. Dentin scatters strongly in the visible and near IR ( mu s approximately equals 260 cm-1) and absorbs weakly ( mu a approximately equals 4 cm-1). The scattering phase function for dentin is described by a HG function with g = 0.93 and a very weak isotropic scattering component ( approximately 2%).

Surface exciton emission of MgO crystals

NASA Astrophysics Data System (ADS)

Kuang, Wen-Jian; Li, Qing; Chen, Yu-Xiang; Hu, Kai; Wang, Ning-Hui; Xing, Fang-Li; Yan, Qun; Sun, Shuai-Shuai; Huang, Yan; Tao, Ye; Tolner, Harm

2013-09-01

MgO crystals have been exposed to vacuum ultraviolet (VUV) radiation from a synchrotron, with energies up to 9 eV, and the emitted light, at wavelengths above 200 nm, was observed. It is concluded that bulk excitons, play an important role in the diffusion of energy inside MgO crystals, resulting in 5.85 eV (212 nm) emission from the MgO terraces of large (0.2-2 µm) MgO : F crystals. In the case of aliovalent impurity doping, then the bulk exciton energy is also transferred to the Vk centres and 5.3 eV (235 nm) light is emitted. Both fluorine and silicon doping appear to promote UV surface emission, acting similarly to an ns2 ion inside MgO, while strong scandium doping is killing the surface emission completely. The 212 nm surface UV emission and the 235 nm bulk UV emission can be excited only at the bandgap edge. Broadband visible light, centred around 400 nm, is also emitted. Contrary to the UV emission, this is not generated when excited at the bandgap edge; instead, we find that it is only excited at sub-bandgap energies, with a maximum at the 5C surface excitation energy of 5.71 eV (217 nm) for the MgO terraces.

Wavelength-dependent photoresponse of biological and aqueous model systems using the photodynamic plant pigment hypericin.

PubMed

Kubin, A; Alth, G; Jindra, R; Jessner, G; Ebermann, R

1996-11-01

Photodynamic eradication of tumour cells in vivo depends on the presence of a photosensitizer, light delivery to the cells, and an oxygen supply. Hypericin, a polycyclic quinone with absorption maxima in the ultraviolet and visible ranges, was prepared for clinical use as a photosensitizer. Due to antitumoral and antineoplastic activities as well as the generation of singlet oxygen after photoexcitation, hypericin was applied in clinical oncology and photodynamic therapy. Hypericin was administered subcutaneously (20 micrograms hypericin in 200 microliters Nacl/pyridine solution) into the ante brachium (forearm) of two volunteers. After the diffusion and equilibration of 120 min phototesting was carried out using outdoor light exposure, halogen lamp, laser 514 nm (argon), laser 632 nm (argon dye) and laser 670 nm (diode laser), from 60 to 120 J cm-2. Positive phototests to outdoor light exposure, halogen lamp and laser 514 nm were characterized by rubescence, oozing, vesiculation and darting pain. Phototests with laser 632 nm and 670 nm showed no effects after irradiation. When hypericin was administered topically on skin, erythema and flaring could not be induced by any irradiation. These results suggest that hypericin is a potent photosensitizer only within the UV and green light ranges. This characteristic photoresponse could also be obtained in guinea pig papillary muscle (GPPM) bioassay, which may be established as a model for photosensitizer testing. Irradiation of hypericin-incubated GPPM with 514 nm (20 J cm-2) led to a decrease of the contractile force of about 31%. However, excitation with 632 nm and 670 nm did not cause inotropic effects on GPPM. In addition, hypericin and Photosan 3 were shown to be capable of sensitizing the photo-oxidation of sodium linoleate. This assay should be established for testing interactions between photosensitizers and light sources in vitro.

Vertically integrated visible and near-infrared metasurfaces enabling an ultra-broadband and highly angle-resolved anomalous reflection.

PubMed

Gao, Song; Lee, Sang-Shin; Kim, Eun-Soo; Choi, Duk-Yong

2018-06-21

An optical device with minimized dimensions, which is capable of efficiently resolving an ultra-broad spectrum into a wide splitting angle but incurring no spectrum overlap, is of importance in advancing the development of spectroscopy. Unfortunately, this challenging task cannot be easily addressed through conventional geometrical or diffractive optical elements. Herein, we propose and demonstrate vertically integrated visible and near-infrared metasurfaces which render an ultra-broadband and highly angle-resolved anomalous reflection. The proposed metasurface capitalizes on a supercell that comprises two vertically concatenated trapezoid-shaped aluminum antennae, which are paired with a metallic ground plane via a dielectric layer. Under normal incidence, reflected light within a spectral bandwidth of 1000 nm ranging from λ = 456 nm to 1456 nm is efficiently angle-resolved to a single diffraction order with no spectrum overlap via the anomalous reflection, exhibiting an average reflection efficiency over 70% and a substantial angular splitting of 58°. In light of a supercell pitch of 1500 nm, to the best of our knowledge, the micron-scale bandwidth is the largest ever reported. It is noted that the substantially wide bandwidth has been accomplished by taking advantage of spectral selective vertical coupling effects between antennae and ground plane. In the visible regime, the upper antenna primarily renders an anomalous reflection by cooperating with the lower antenna, which in turn cooperates with the ground plane and produces phase variations leading to an anomalous reflection in the near-infrared regime. Misalignments between the two antennae have been particularly inspected to not adversely affect the anomalous reflection, thus guaranteeing enhanced structural tolerance of the proposed metasurface.

Broadband operation of rolled-up hyperlenses

NASA Astrophysics Data System (ADS)

Schwaiger, Stephan; Rottler, Andreas; Bröll, Markus; Ehlermann, Jens; Stemmann, Andrea; Stickler, Daniel; Heyn, Christian; Heitmann, Detlef; Mendach, Stefan

2012-06-01

This work is related to an earlier publication [Schwaiger , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.102.163903 102, 163903 (2009)], where we demonstrated by means of fiber-based transmission measurements that rolled-up Ag-(In)GaAs multilayers represent three-dimensional metamaterials with a plasma edge which is tunable over the visible and near-infrared regime by changing the thickness ratio of Ag and (In)GaAs, and predicted by means of finite-difference time-domain simulations that hyperlensing occurs at this frequency-tunable plasma edge. In the present work we develop a method to measure reflection curves on these structures and find that they correspond to the same tunable plasma edge. We find that retrieving the effective parameters from transmission and reflection data fails, because our realized metamaterials exceed the single-layer thicknesses of 5nm, which we analyze to be the layer thickness limit for the applicability of effective parameter retrieval. We show that our realized structures nevertheless have the functionality of an effective metamaterial by supplying a detailed finite-difference time-domain study which compares light propagation through our realized structure (17-nm-thick Ag layers and 34-nm-thick GaAs layers) and light propagation through an idealized structure of the same total thickness but with very thin layers [2-nm-thick Ag layers and 4-nm-thick (In)GaAs layers]. In particular, our simulations predict broadband hyperlensing covering a large part of the visible spectrum for both the idealized and our realized structures.

Strong light coupling effect for a glancing-deposited silver nanorod array in the Kretschmann configuration

PubMed Central

2014-01-01

In this work, three slanted silver nanorod arrays (NRAs) with different thicknesses are fabricated using the glancing angle deposition method. Each silver NRA in the Kretschmann configuration is arranged to form a prism/NRA/air system. Attenuated total reflection occurs over the visible wavelengths and wide incident angles of both s- and p-polarization states. The extinctance is inversely proportional to the thickness of the Ag NRA. The thinnest NRA, with a thickness of 169 nm, exhibits strong extinctance of more than 80% over the visible wavelengths. The associated forward scatterings from the three NRAs are measured and compared under illumination with a laser beam with a wavelength of 632.8 nm. PMID:25352769

Detecting technology of biophotons

NASA Astrophysics Data System (ADS)

Ma, Junfu; Zhu, Zhaohui; Zhu, Yanbin

2002-03-01

A key technique of detecting the ultra-weak photon emission from biological system (UPE) is to change the light signal of an extremely weak level into electric signal of a considerable level when the photo-electric detecting system were be applied. This paper analyzed the difficult for detecting the ultra-weak photon emission from biological system (UPE) mainly is in the absence of high sensitivity detector in UV-visible-infra spectra region. An experimental setup for testing UPE in different spectral region was designed. Using the experimental setup the test data of different several spectral regions from 300 nm to 1060 nm has were tested. The test result show the UPE of living biological system exists in wide spectra region from UV- visible to infrared.

In situ glow discharge plasma electrolytic synthesis of reduced TiO2 for enhanced visible light photocatalysis

NASA Astrophysics Data System (ADS)

Feng, Guang; Wu, Botao; Qayyum Khan, Abdul; Zeng, Heping

2018-05-01

Reduced titanium dioxide (TiO2‑x) due to its extraordinary visible light absorption has been widely investigated in photodegradation and water splitting nowadays. However, conventional routes to synthesize reduced TiO2 usually demand multiple preparation steps, harsh controlled conditions or expensive facilities. Here we developed a single-step in situ approach to prepare the gray TiO2‑x nanoparticles (sub-10 nm) effectively by the glow discharge plasma electrolysis (GDPE) under atmospheric pressure. The co-existence of self-doped oxygen vacancies and Ti3+ in the generated TiO2‑x nanoparticles is demonstrated by electron paramagnetic resonance (EPR). The tunable ratio of bulk/surface defect can be realized by controlling the glow discharge power directly. It should be noticed that Ti3+ in the synthesized TiO2‑x are quite stable in ambient air. The UV–vis spectra of gray TiO2‑x show an enhanced visible light absorption, which leads to high visible-light photocatalytic activity. Moreover, the as-prepared TiO2‑x after 6 months storage still shows excellent stability during photocatalytic reactions. Owing to its simplicity and effectivity, this preparation method with GDPE should provide a large-scale production for TiO2‑x with high photoactivity.

UV-visible light photocatalytic properties of NaYF4:(Gd, Si)/TiO2 composites

NASA Astrophysics Data System (ADS)

Mavengere, Shielah; Kim, Jung-Sik

2018-06-01

In this study, a new novel composite photocatalyst of NaYF4:(Gd, Si)/TiO2 phosphor has been synthesized by two step method of solution combustion and sol-gel. The photocatalyst powders were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), UV-vis spectroscopy and photoluminescence (PL) spectroscopy. Raman spectroscopy confirmed the anatase TiO2 phase which remarkably increased with existence of yttrium silicate compounds between 800 cm-1 and 900 cm-1. Double-addition of Gd3+-Si4+ ions in NaYF4 host introduced sub-energy band levels with intense absorption in the ultraviolet (UV) light region. Photocatalytic activity was examined by exposing methylene blue (MB) solutions mixed with photocatalyst powders to 254 nm UV-C fluorescent lamp and 200 W visible lights. The UV and visible photocatalytic reactivity of the NaYF4:(Gd, 1% Si)/TiO2 phosphor composites showed enhanced MB degradation efficiency. The coating of NaYF4:(Gd, 1% Si) phosphor with TiO2 nanoparticles creates energy band bending at the phosphor/TiO2 interfaces. Thus, these composites exhibited enhanced absorption of UV/visible light and the separation of electron and hole pairs for efficient photocatalysis.

Structural, thermal and optical investigations of Dy3+ ions doped lead containing lithium fluoroborate glasses for simulation of white light

NASA Astrophysics Data System (ADS)

Zulfiqar Ali Ahamed, Sd.; Madhukar Reddy, C.; Deva Prasad Raju, B.

2013-05-01

Lead containing barium zinc lithium fluoroborate (LBZLFB) glasses doped with different concentrations of trivalent dysprosium ions were synthesized by conventional melt quenching method and characterized through the XRD, DSC, FTIR, FT-Raman, optical absorption, photoluminescence and decay curve analysis. X-ray diffraction studies revealed amorphous nature of the studied glass matrices. The thermal behavior has been reported by recording DSC thermograms. Coexistence of trigonal BO3 and tetrahedral BO4 units was evidenced by IR and Raman spectroscopy. Judd-Ofelt intensity parameters have been evaluated for 1.0 mol% Dy3+ ions doped LBZLFB glass. The measuring branching ratios are reasonably high for transitions 4F9/2 → 6H15/2 and 6H13/2 suggesting that the emission at 486 and 577 nm, respectively can give rise to lasing action in the visible region. From the visible emission spectra, the yellow to blue (Y/B) intensity ratios and chromaticity color coordinates were estimated. A combination of blue and yellow emissions has emerged in the glasses, which allows the observation of white light when the glasses are excited by the ultraviolet/blue light. These Dy3+ doped glasses are studied for their utility for white light generation under 454 nm excitation and the present LBZLFB glass is more suitable for generation of white light for blue LED chips.

Polypyrrole coated phase-change contrast agents for sono-photoacoustic imaging (Conference Presentation)

NASA Astrophysics Data System (ADS)

Li, David S.; Yoon, Soon Joon; Matula, Thomas J.; O'Donnell, Matthew; Pozzo, Lilo D.

2017-03-01

A new light and sound sensitive nanoemulsion contrast agent is presented. The agents feature a low boiling point liquid perfluorocarbon core and a broad light spectrum absorbing polypyrrole (PPy) polymer shell. The PPy coated nanoemulsions can reversibly convert from liquid to gas phase upon cavitation of the liquid perfluorocarbon core. Cavitation can be initiated using a sufficiently high intensity acoustic pulse or from heat generation due to light absorption from a laser pulse. The emulsions can be made between 150 and 350 nm in diameter and PPy has a broad optical absorption covering both the visible spectrum and extending into the near-infrared spectrum (peak absorption 1053 nm). The size, structure, and optical absorption properties of the PPy coated nanoemulsions were characterized and compared to PPy nanoparticles (no liquid core) using dynamic light scattering, ultraviolet-visible spectrophotometry, transmission electron microscopy, and small angle X-ray scattering. The cavitation threshold and signal intensity were measured as a function of both acoustic pressure and laser fluence. Overlapping simultaneous transmission of an acoustic and laser pulse can significantly reduce the activation energy of the contrast agents to levels lower than optical or acoustic activation alone. We also demonstrate that simultaneous light and sound cavitation of the agents can be used in a new sono-photoacoustic imaging method, which enables greater sensitivity than traditional photoacoustic imaging.

Broadband All-Polymer Phototransistors with Nanostructured Bulk Heterojunction Layers of NIR-Sensing n-Type and Visible Light-Sensing p-Type Polymers

PubMed Central

Han, Hyemi; Nam, Sungho; Seo, Jooyeok; Lee, Chulyeon; Kim, Hwajeong; Bradley, Donal D. C.; Ha, Chang-Sik; Kim, Youngkyoo

2015-01-01

We report ‘broadband light-sensing’ all-polymer phototransistors with the nanostructured bulk heterojunction (BHJ) layers of visible (VIS) light-sensing electron-donating (p-type) polymer and near infrared (NIR) light-sensing electron-accepting (n-type) polymer. Poly[{2,5-bis-(2-ethylhexyl)-3,6-bis-(thien-2-yl)-pyrrolo[3,4-c]pyrrole-1,4-diyl}-co-{2,2′-(2,1,3-benzothiadiazole)]-5,5′-diyl}] (PEHTPPD-BT), which is synthesized via Suzuki coupling and employed as the n-type polymer, shows strong optical absorption in the NIR region (up to 1100 nm) in the presence of weak absorption in the VIS range (400 ~ 600 nm). To strengthen the VIS absorption, poly(3-hexylthiophene) (P3HT) is introduced as the p-type polymer. All-polymer phototransistors with the BHJ (P3HT:PEHTPPD-BT) layers, featuring a peculiar nano-domain morphology, exhibit typical p-type transistor characteristics and efficiently detect broadband (VIS ~ NIR) lights. The maximum corrected responsivity (without contribution of dark current) reaches up to 85 ~ 88% (VIS) and 26 ~ 40% (NIR) of theoretical responsivity. The charge separation process between P3HT and PEHTPPD-BT components in the highest occupied molecular orbital is proposed as a major working mechanism for the effective NIR sensing. PMID:26563576

Surface Plasmon Enhanced Photocatalysis of Au/Pt-decorated TiO2 Nanopillar Arrays

NASA Astrophysics Data System (ADS)

Shuang, Shuang; Lv, Ruitao; Xie, Zheng; Zhang, Zhengjun

2016-05-01

The low quantum yields and lack of visible light utilization hinder the practical application of TiO2 in high-performance photocatalysis. Herein, we present a design of TiO2 nanopillar arrays (NPAs) decorated with both Au and Pt nanoparticles (NPs) directly synthesized through successive ion layer adsorption and reaction (SILAR) at room temperature. Au/Pt NPs with sizes of ~4 nm are well-dispersed on the TiO2 NPAs as evidenced by electron microscopic analyses. The present design of Au/Pt co-decoration on the TiO2 NPAs shows much higher visible and ultraviolet (UV) light absorption response, which leads to remarkably enhanced photocatalytic activities on both the dye degradation and photoelectrochemical (PEC) performance. Its photocatalytic reaction efficiency is 21 and 13 times higher than that of pure TiO2 sample under UV-vis and visible light, respectively. This great enhancement can be attributed to the synergy of electron-sink function of Pt and surface plasmon resonance (SPR) of Au NPs, which significantly improves charge separation of photoexcited TiO2. Our studies demonstrate that through rational design of composite nanostructures one can harvest visible light through the SPR effect to enhance the photocatalytic activities initiated by UV-light, and thus realize more effectively utilization of the whole solar spectrum for energy conversion.

Facile synthesis of flake-like TiO2/C nano-composites for photocatalytic H2 evolution under visible-light irradiation

NASA Astrophysics Data System (ADS)

Yan, Baolin; Zhou, Juan; Liang, Xiaoyu; Song, Kainan; Su, Xintai

2017-01-01

The production of H2 by photocatalytic water splitting has become a promising approach for clean, economical, and renewable evolution of H2 by using solar energy. In spite of tremendous efforts, the present challenge for materials scientists is to build a highly active photocatalytic system with high efficiency and low cost. Here we report a facile method for the preparation of TiO2/C nano-flakes, which was used as an efficient visible-light photocatalyst for H2 evolution. This composite material was prepared by using a phase-transfer strategy combined with salt-template calcination treatment. The results showed that anatase TiO2 nanoparticles with the diameter of ∼10 nm were uniformly dispersed on the carbon nano-flakes. In addition, the samples prepared at 600 °C (denoted as T600) endowed a larger surface area of 196 m2 g-1 and higher light absorption, resulting in enhanced photocatalytic activity. Further, the T600 product reached a high H2 production rate of 57.2 μmol h-1 under visible-light irradiation. This unusual photocatalytic activity arose from the positive synergetic effect between the TiO2 and carbon in this hybrid catalyst. This work highlights the potential of TiO2/C nano-flakes in the field of photocatalytic H2 evolution under visible-light irradiation.

Ultraviolet and visible light spectrophotometric approach to blood typing: objective analysis by agglutination index.

PubMed

Narayanan, S; Orton, S; Leparc, G F; Garcia-Rubio, L H; Potter, R L

1999-10-01

A new blood typing technology based on ultraviolet (UV) and visible light spectroscopy (UV/visible spectroscopy) has been developed. Blood groups and types are determined by quantifying reproducible changes in the UV and visible light spectra of blood in the presence of agglutinating antibodies. Samples of red cells in the presence and absence of agglutinating antibodies were examined by UV/visible spectroscopy. Blood groups and types were determined by comparing the optical density spectra obtained between 665 and 1000 nm. These comparisons generate numbers (agglutination index) ranging from 0 to 100, with smaller numbers corresponding to lack of agglutination and larger numbers corresponding to agglutination. The optical density of agglutinated blood is dramatically different from that of unagglutinated blood. The agglutination index derived from the relative slopes of the spectra is an objective indicator of agglutination strength. An agglutination index greater than 17 consistently and accurately established blood group- and type-specific agglutination. The method accurately predicted A, B, and O blood groups, and D type in over 275 samples. Scattering theory-based calculations of relative volumes of red cells before and after agglutination show a direct correlation with the agglutination index and provide the theoretical basis of the analysis. This quantitative technique is reproducible and has the potential for automation.

Multifunctional Eu3+- and Er3+/Yb3+-doped GdVO4 nanoparticles synthesized by reverse micelle method

PubMed Central

Gavrilović, Tamara V.; Jovanović, Dragana J.; Lojpur, Vesna; Dramićanin, Miroslav D.

2014-01-01

Synthesis of Eu3+- and Er3+/Yb3+-doped GdVO4 nanoparticles in reverse micelles and their multifunctional luminescence properties are presented. Using cyclohexane, Triton X-100, and n-pentanol as the oil, surfactant, and co-surfactant, respectively, crystalline nanoparticles with ~4 nm diameter are prepared at low temperatures. The particle size assessed using transmission electron microscopy is similar to the crystallite size obtained from X-ray diffraction measurements, suggesting that each particle comprises a single crystallite. Eu3+-doped GdVO4 nanoparticles emit red light through downconversion upon UV excitation. Er3+/Yb3+-doped GdVO4 nanoparticles exhibit several functions; apart from the downconversion of UV radiation into visible green light, they act as upconvertors, transforming near-infrared excitation (980 nm) into visible green light. The ratio of green emissions from 2H11/2 → 2I15/2 and 4S3/2 → 4I15/2 transitions is temperature dependent and can be used for nanoscale temperature sensing with near-infrared excitation. The relative sensor sensitivity is 1.11%K−1, which is among the highest sensitivities recorded for upconversion-luminescence-based thermometers. PMID:24572638

Multifunctional Eu3+- and Er3+/Yb3+-doped GdVO4 nanoparticles synthesized by reverse micelle method

NASA Astrophysics Data System (ADS)

Gavrilović, Tamara V.; Jovanović, Dragana J.; Lojpur, Vesna; Dramićanin, Miroslav D.

2014-02-01

Synthesis of Eu3+- and Er3+/Yb3+-doped GdVO4 nanoparticles in reverse micelles and their multifunctional luminescence properties are presented. Using cyclohexane, Triton X-100, and n-pentanol as the oil, surfactant, and co-surfactant, respectively, crystalline nanoparticles with ~4 nm diameter are prepared at low temperatures. The particle size assessed using transmission electron microscopy is similar to the crystallite size obtained from X-ray diffraction measurements, suggesting that each particle comprises a single crystallite. Eu3+-doped GdVO4 nanoparticles emit red light through downconversion upon UV excitation. Er3+/Yb3+-doped GdVO4 nanoparticles exhibit several functions; apart from the downconversion of UV radiation into visible green light, they act as upconvertors, transforming near-infrared excitation (980 nm) into visible green light. The ratio of green emissions from 2H11/2 --> 2I15/2 and 4S3/2 --> 4I15/2 transitions is temperature dependent and can be used for nanoscale temperature sensing with near-infrared excitation. The relative sensor sensitivity is 1.11%K-1, which is among the highest sensitivities recorded for upconversion-luminescence-based thermometers.

Cd/In-Codoped TiO2 nanochips for high-efficiency photocatalytic dye degradation.

PubMed

Liu, Dongliang; Huang, Peng; Liu, Yong; Wu, Zhou; Li, Dongsheng; Guo, Jun; Wu, Tao

2018-05-01

Titanium dioxide has been widely investigated in the field of photocatalysis research. However, the wide bandgap (3.2 eV) greatly limits its practical applications because only ultraviolet light can be absorbed by bare TiO2. Herein, we report a facile approach to prepare Cd/In-codoped TiO2 nanochips with the capability of visible light absorption. Such bimetallic-doped TiO2 was synthesized through a two-step process: Cd/In/S-TiO2 gels were first synthesized by mixing the preformed Cd-In-S supertetrahedral nanoclusters with a titanium source, and the subsequent pyrolytic process effectively converted the gels into Cd/In-TiO2 nanochips with a thickness of ∼2.19 nm and a uniform diameter of ∼10.60 nm. Interestingly, the absorption band of Cd/In-TiO2 nanochips was adjusted by pyrolysis temperature, which further regulated the photocatalytic efficiency of dye degradation under visible light. Current research demonstrates that doping TiO2 by multimetallic sulfide nanoclusters opens up a new door to further enrich the dopants in TiO2 and broaden their potential applications.

Multifunctional Eu3+- and Er3+/Yb3+-doped GdVO4 nanoparticles synthesized by reverse micelle method.

PubMed

Gavrilović, Tamara V; Jovanović, Dragana J; Lojpur, Vesna; Dramićanin, Miroslav D

2014-02-27

Synthesis of Eu(3+)- and Er(3+)/Yb(3+)-doped GdVO4 nanoparticles in reverse micelles and their multifunctional luminescence properties are presented. Using cyclohexane, Triton X-100, and n-pentanol as the oil, surfactant, and co-surfactant, respectively, crystalline nanoparticles with ~4 nm diameter are prepared at low temperatures. The particle size assessed using transmission electron microscopy is similar to the crystallite size obtained from X-ray diffraction measurements, suggesting that each particle comprises a single crystallite. Eu(3+)-doped GdVO4 nanoparticles emit red light through downconversion upon UV excitation. Er(3+)/Yb(3+)-doped GdVO4 nanoparticles exhibit several functions; apart from the downconversion of UV radiation into visible green light, they act as upconvertors, transforming near-infrared excitation (980 nm) into visible green light. The ratio of green emissions from (2)H11/2 → (2)I15/2 and (4)S3/2 → (4)I15/2 transitions is temperature dependent and can be used for nanoscale temperature sensing with near-infrared excitation. The relative sensor sensitivity is 1.11%K(-1), which is among the highest sensitivities recorded for upconversion-luminescence-based thermometers.

Charon's light curves, as observed by New Horizons' Ralph color camera (MVIC) on approach to the Pluto system

NASA Astrophysics Data System (ADS)

Howett, C. J. A.; Ennico, K.; Olkin, C. B.; Buie, M. W.; Verbiscer, A. J.; Zangari, A. M.; Parker, A. H.; Reuter, D. C.; Grundy, W. M.; Weaver, H. A.; Young, L. A.; Stern, S. A.

2017-05-01

Light curves produced from color observations taken during New Horizons' approach to the Pluto-system by its Multi-spectral Visible Imaging Camera (MVIC, part of the Ralph instrument) are analyzed. Fifty seven observations were analyzed, they were obtained between 9th April and 3rd July 2015, at a phase angle of 14.5° to 15.1°, sub-observer latitude of 51.2 °N to 51.5 °N, and a sub-solar latitude of 41.2°N. MVIC has four color channels; all are discussed for completeness but only two were found to produce reliable light curves: Blue (400-550 nm) and Red (540-700 nm). The other two channels, Near Infrared (780-975 nm) and Methane-Band (860-910 nm), were found to be potentially erroneous and too noisy respectively. The Blue and Red light curves show that Charon's surface is neutral in color, but slightly brighter on its Pluto-facing hemisphere. This is consistent with previous studies made with the Johnson B and V bands, which are at shorter wavelengths than that of the MVIC Blue and Red channel respectively.

Charon's Light Curves, as Observed by New Horizons' Ralph Color Camera (MVIC) on Approach to the Pluto System.

NASA Technical Reports Server (NTRS)

Howett, C. J. A.; Ennico, K.; Olkin, C. B.; Buie, M. W.; Verbiscer, A. J.; Zangari, A. M.; Parker, A. H.; Reuter, D. C.; Grundy, W. M.; Weaver, H. A.;

Emerging Techniques for Vicarious Calibration of Visible Through Short Wave Infrared Remote Sensing Systems

NASA Technical Reports Server (NTRS)

Ryan, Robert E.

2006-01-01

Simple field-portable white light LED calibration source shows promise for visible range (420-750 nm) 1) Prototype demonstrated <0.5% drift over 10-40 C temperature range; 2) Additional complexity (more LEDs) will be necessary for extending spectral range into the NIR and SWIR; 3) LED long lifetimes should produce at least several hundreds of hours or more stability, minimizing need for expensive calibrations and supporting long-duration field campaigns; and 4) Enabling technology for developing autonomous sites.

Reflectance differences between Target and Torch rape cultivars

NASA Technical Reports Server (NTRS)

Gausman, H. W.; Leamer, R. W. (Principal Investigator)

1982-01-01

Spectroradiometric reflectance measurements were made on Target and Torch plants (four and five leaves, respectively) that were growing in 0.09 m2 soil-containing flats. Torch's spectrophotometric single leaf reflectance was consistently lower than Target's at the 650-nm chlorophyll absorption band because Torch's chlorophyll concentration was larger than Target's, which caused more red light absorption. Spectroradiometric measurements indicate that: wet soil strongly absorbs visible light (500 to 700 nm) so that Target's soil-containing flat with 60% plant cover has less reflectance than Torch's soil-containing flat with 75% plant cover; Torch (most foiliage) has higher near-infrared (750 to 1,350 nm) reflectance than Target (least foliage); and the 2,200-nm wavelength is a candidate band to distinguish Target from Torch. The difference in chlorophyll concentrations between Target and Torch, compared with leaf structural differences, is apparently the most important factor that would affect the infrared color film's tonal response to vegetation in the photographic sensitive region (500 to 900 nm).

Effect of 710 nm visible light irradiation on neurite outgrowth in primary rat cortical neurons following ischemic insult

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choi, Dong-Hee; Department of Medical Science, Konkuk University School of Medicine, Seoul; Lee, Kyoung-Hee

2012-06-01

Highlights: Black-Right-Pointing-Pointer 710 nm wavelength light (LED) has a protective effect in the stroke animal model. Black-Right-Pointing-Pointer We determined the effects of LED irradiation in vitro stroke model. Black-Right-Pointing-Pointer LED treatment promotes the neurite outgrowth through MAPK activation. Black-Right-Pointing-Pointer The level of synaptic markers significantly increased with LED treatment. Black-Right-Pointing-Pointer LED treatment protects cell death in the in vitro stroke model. -- Abstract: Objective: We previously reported that 710 nm Light-emitting Diode (LED) has a protective effect through cellular immunity activation in the stroke animal model. However, whether LED directly protects neurons suffering from neurodegeneration was entirely unknown. Therefore, wemore » sought to determine the effects of 710 nm visible light irradiation on neuronal protection and neuronal outgrowth in an in vitro stroke model. Materials and methods: Primary cultured rat cortical neurons were exposed to oxygen-glucose deprivation (OGD) and reoxygenation and normal conditions. An LED array with a peak wavelength of 710 nm was placed beneath the covered culture dishes with the room light turned off and were irradiated accordingly. LED treatments (4 min at 4 J/cm{sup 2} and 50 mW/cm{sup 2}) were given once to four times within 8 h at 2 h intervals for 7 days. Mean neurite density, mean neurite diameter, and total fiber length were also measured after microtubule associated protein 2 (MAP2) immunostaining using the Axio Vision program. Synaptic marker expression and MAPK activation were confirmed by Western blotting. Results: Images captured after MAP2 immunocytochemistry showed significant (p < 0.05) enhancement of post-ischemic neurite outgrowth with LED treatment once and twice a day. MAPK activation was enhanced by LED treatment in both OGD-exposed and normal cells. The levels of synaptic markers such as PSD 95, GAP 43, and synaptophysin significantly increased with LED treatment in both OGD-exposed and normal cells (p < 0.05). Conclusion: Our data suggest that LED treatment may promote synaptogenesis through MAPK activation and subsequently protect cell death in the in vitro stroke model.« less

Multispectral cross-polarization reflectance measurements suggest high contrast of demineralization on tooth surfaces at wavelengths beyond 1300 nm due to reduced light scattering in sound enamel.

PubMed

Chan, Kenneth H; Fried, Daniel

2018-06-01

The enamel scattering coefficient decreases markedly with increasing wavelength from the visible to the near-infrared (NIR). However, beyond 1300 nm, the scattering coefficient is difficult to measure, and it is not known whether light scattering continues to decrease significantly at longer wavelengths. It is hypothesized that water absorption is a major contributor to the contrast between sound and demineralized enamel beyond 1300 nm since deeply penetrating photons in sound enamel are likely absorbed by water. Reflectance images of demineralization on tooth surfaces were acquired at wavelengths near 1450, 1860, 1880, and 1950 nm. The magnitude of water absorption is similar at 1450 and 1880 nm but varies markedly between 1860, 1880, and 1950 nm. Multispectral comparisons of lesion contrast provide insight into the mechanism responsible for higher contrast at longer NIR wavelengths. The highest contrast was at 1950 nm; however, the markedly higher contrast at 1880 compared to 1450 nm and similar contrast between 1860 and 1880 nm suggests that the enamel scattering coefficient continues to decrease beyond 1300 nm, and that reduced light scattering in sound enamel is most responsible for the higher lesion contrast at longer NIR wavelengths. This has important implications for the choice of wavelengths for caries detection and diagnostic devices, including the performance of optical coherence tomography beyond 1300 nm. (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Red Light Combined with Blue Light Irradiation Regulates Proliferation and Apoptosis in Skin Keratinocytes in Combination with Low Concentrations of Curcumin

PubMed Central

Cai, Qing; Ren, Qu; Wei, Lizhao

2015-01-01

Curcumin is a widely known natural phytochemical from plant Curcuma longa. In recent years, curcumin has received increasing attention because of its capability to induce apoptosis and inhibit cell proliferation as well as its anti-inflammatory properties in different cancer cells. However, the therapeutic benefits of curcumin are severely hampered due to its particularly low absorption via trans-dermal or oral bioavailability. Phototherapy with visible light is gaining more and more support in dermatological therapy. Red light is part of the visible light spectrum, which is able to deeply penetrate the skin to about 6 mm, and directly affect the fibroblast of the skin dermis. Blue light is UV-free irradiation which is fit for treating chronic inflammation diseases. In this study, we show that curcumin at low concentrations (1.25–3.12 μM) has a strong anti-proliferative effect on TNF-α-induced psoriasis-like inflammation when applied in combination with light-emitting-diode devices. The treatment was especially effective when LED blue light at 405 nm was combined with red light at 630 or 660 nm, which markedly amplified the anti-proliferative and apoptosis-inducing effects of curcumin. The experimental results demonstrated that this treatment reduced the viability of human skin keratinocytes, decreased cell proliferation, induced apoptosis, inhibited NF-κB activity and activated caspase-8 and caspase-9 while preserving the cell membrane integrity. Moreover, the combined treatment also down-regulated the phosphorylation level of Akt and ERK. Taken together, our results indicated that the combination of curcumin with LED blue light united red light irradiation can attain a higher efficiency of regulating proliferation and apoptosis in skin keratinocytes. PMID:26382065

Metal Nanoshells for Plasmonically Enhanced Solar-to-Fuel Photocatalytic Conversion

DTIC Science & Technology

2014-05-09

Final 3. DATES COVERED (From - To) 04/16/2013 – 04/15/2014 4. TITLE AND SUBTITLE Metal Nanoshells for Plasmonically Enhanced Solar -to...following experiments, the core-shell of nanoshell@SiO2, as well as the nanostructure of photocatalyst, were further investigated. Solar energy in the...nanoshells as the core can absorb the solar energy in the IR and visible-light region ranging from 500 nm to 900 nm. Our data showed that the plasmonic

Solar Water Splitting at λ=600 nm: A Step Closer to Sustainable Hydrogen Production.

PubMed

Zhang, Jinshui; Wang, Xinchen

2015-06-15

Overall water splitting with a semiconductor photocatalyst under visible-light irradiation is considered as a "dream reaction" in chemistry. The development of a 600 nm photocatalyst for solar water splitting highlighted here is not only an important milestone towards sustainable hydrogen production, but also a new starting point for artificial photosynthesis. STH=solar-to-hydrogen energy conversion efficiency. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

OP09O-OP404-9 Wide Field Camera 3 CCD Quantum Efficiency Hysteresis

NASA Technical Reports Server (NTRS)

Collins, Nick

2009-01-01

The HST/Wide Field Camera (WFC) 3 UV/visible channel CCD detectors have exhibited an unanticipated quantum efficiency hysteresis (QEH) behavior. At the nominal operating temperature of -83C, the QEH feature contrast was typically 0.1-0.2% or less. The behavior was replicated using flight spare detectors. A visible light flat-field (540nm) with a several times full-well signal level can pin the detectors at both optical (600nm) and near-UV (230nm) wavelengths, suppressing the QEH behavior. We are characterizing the timescale for the detectors to become unpinned and developing a protocol for flashing the WFC3 CCDs with the instrument's internal calibration system in flight. The HST/Wide Field Camera 3 UV/visible channel CCD detectors have exhibited an unanticipated quantum efficiency hysteresis (QEH) behavior. The first observed manifestation of QEH was the presence in a small percentage of flat-field images of a bowtie-shaped contrast that spanned the width of each chip. At the nominal operating temperature of -83C, the contrast observed for this feature was typically 0.1-0.2% or less, though at warmer temperatures contrasts up to 5% (at -50C) have been observed. The bowtie morphology was replicated using flight spare detectors in tests at the GSFC Detector Characterization Laboratory by power cycling the detector while cold. Continued investigation revealed that a clearly-related global QE suppression at the approximately 5% level can be produced by cooling the detector in the dark; subsequent flat-field exposures at a constant illumination show asymptotically increasing response. This QE "pinning" can be achieved with a single high signal flat-field or a series of lower signal flats; a visible light (500-580nm) flat-field with a signal level of several hundred thousand electrons per pixel is sufficient for QE pinning at both optical (600nm) and near-UV (230nm) wavelengths. We are characterizing the timescale for the detectors to become unpinned and developing a protocol for flashing the WFC3 CCDs with the instrument's internal calibration system in flight. A preliminary estimate of the decay timescale for one detector is that a drop of 0.1-0.2% occurs over a ten day period, indicating that relatively infrequent cal lamp exposures can mitigate the behavior to extremely low levels.

Femtosecond Visible Transient Absorption Spectroscopy of Chlorophyll f-Containing Photosystem I.

PubMed

Kaucikas, Marius; Nürnberg, Dennis; Dorlhiac, Gabriel; Rutherford, A William; van Thor, Jasper J

2017-01-24

Photosystem I (PSI) from Chroococcidiopsis thermalis PCC 7203 grown under far-red light (FRL; >725 nm) contains both chlorophyll a and a small proportion of chlorophyll f. Here, we investigated excitation energy transfer and charge separation using this FRL-grown form of PSI (FRL-PSI). We compared femtosecond transient visible absorption changes of normal, white-light (WL)-grown PSI (WL-PSI) with those of FRL-PSI using excitation at 670 nm, 700 nm, and (in the case of FRL-PSI) 740 nm. The possibility that chlorophyll f participates in energy transfer or charge separation is discussed on the basis of spectral assignments. With selective pumping of chlorophyll f at 740 nm, we observe a final ∼150 ps decay assigned to trapping by charge separation, and the amplitude of the resulting P700 +• A 1 -• charge-separated state indicates that the yield is directly comparable to that of WL-PSI. The kinetics shows a rapid 2 ps time constant for almost complete transfer to chlorophyll f if chlorophyll a is pumped with a wavelength of 670 nm or 700 nm. Although the physical role of chlorophyll f is best supported as a low-energy radiative trap, the physical location should be close to or potentially within the charge-separating pigments to allow efficient transfer for charge separation on the 150 ps timescale. Target models can be developed that include a branching in the formation of the charge separation for either WL-PSI or FRL-PSI. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

In vitro near-infrared imaging of natural secondary caries.

PubMed

Simon, Jacob C; Lucas, Seth; Lee, Robert; Darling, Cynthia L; Staninec, Michal; Vanderhobli, Ram; Pelzner, Roger; Fried, Daniel

2015-02-24

Secondary caries stands as the leading reason for the failure of composite restorations and dentists spend more time replacing existing restorations than placing new ones. Current clinical strategies, and even modern visible light methods designed to detect decay, lack the sensitivity to distinguish incipient lesions, are confounded by staining on the surface and within the tooth, or are limited to detecting decay on the tooth surface. Near-IR (NIR) imaging methods, such as NIR reflectance and transillumination imaging, and optical coherence tomography are promising strategies for imaging secondary caries. Wavelengths longer than 1300-nm avoid interference from stain and exploit the greater transparency of sound enamel and dental composites, to provide increased contrast with demineralized tissues and improved imaging depth. The purpose of this study was to determine whether NIR transillumination (λ=1300-nm) and NIR cross-polarized reflectance (λ=1500-1700-nm) images can serve as reliable indicators of demineralization surrounding composite restorations. Twelve composite margins (n=12) consisting of class I, II & V restorations were chosen from ten extracted teeth. The samples were imaged in vitro using NIR transillumination and reflectance, polarization sensitive optical coherence tomography (PS-OCT) and a high-magnification digital visible light microscope. Samples were serially sectioned into 200- μ m slices for histological analysis using polarized light microscopy (PLM) and transverse microradiography (TMR). The results presented demonstrate the utility of NIR light for detecting recurrent decay and suggest that NIR images could be a reliable screening tool used in conjunction with PS-OCT for the detection and diagnosis of secondary caries.

In-vitro near-infrared imaging of natural secondary caries

NASA Astrophysics Data System (ADS)

Simon, Jacob C.; Lucas, Seth; Lee, Robert; Darling, Cynthia L.; Staninec, Michal; Vanderhobli, Ram; Pelzner, Roger; Fried, Daniel

2015-02-01

Secondary caries stands as the leading reason for the failure of composite restorations and dentists spend more time replacing existing restorations than placing new ones. Current clinical strategies, and even modern visible light methods designed to detect decay, lack the sensitivity to distinguish incipient lesions, are confounded by staining on the surface and within the tooth, or are limited to detecting decay on the tooth surface. Near-IR (NIR) imaging methods, such as NIR reflectance and transillumination imaging, and optical coherence tomography are promising strategies for imaging secondary caries. Wavelengths longer than 1300-nm avoid interference from stain and exploit the greater transparency of sound enamel and dental composites, to provide increased contrast with demineralized tissues and improved imaging depth. The purpose of this study was to determine whether NIR transillumination (λ=1300-nm) and NIR crosspolarized reflectance (λ=1500-1700-nm) images can serve as reliable indicators of demineralization surrounding composite restorations. Twelve composite margins (n=12) consisting of class I, II and V restorations were chosen from ten extracted teeth. The samples were imaged in vitro using NIR transillumination and reflectance, polarization sensitive optical coherence tomography (PS-OCT) and a high-magnification digital visible light microscope. Samples were serially sectioned into 200-μm slices for histological analysis using polarized light microscopy (PLM) and transverse microradiography (TMR). The results presented demonstrate the utility of NIR light for detecting recurrent decay and suggest that NIR images could be a reliable screening tool used in conjunction with PS-OCT for the detection and diagnosis of secondary caries.

Blue-light emitting electrochemical cells comprising pyrene-imidazole derivatives

NASA Astrophysics Data System (ADS)

Lee, Hyeonji; Sunesh, Chozhidakath Damodharan; Subeesh, Madayanad Suresh; Choe, Youngson

2018-04-01

Light-emitting electrochemical cells (LECs), the next-generation lighting sources are the potential replacements for organic light-emitting diodes (OLEDs). In recent years, organic small molecules (SMs) have established the applicability in solid-state lighting, and considered as prospective active materials for LECs with higher device performance. Here, we describe the synthesis of pyrene-imidazole based SMs, PYR1, and PYR2 that differ by one pyrene unit and their characterization by various spectroscopic methods. To investigate the thermal, photophysical, and electrochemical properties of the two synthesized compounds, we performed thermogravimetric, UV-visible, photoluminescence (PL), and voltammetric measurements. The photoluminescence (PL) emission spectra of PYR1 and PYR2 measured in the acetonitrile solution, where PYR1 and PYR2 emit in the blue spectral region with peaks aligned at 383 nm and 389 nm, respectively. The fabricated LEC devices exhibited broader electroluminescence (EL) spectra with a significant red shift of the emission maxima to 446 nm and 487 nm, with CIE coordinates of (0.17, 0.18) and (0.18, 0.25) for PYR1 and PYR2, respectively. The LECs based on PYR1 and PYR2 produced maximum brightness values of 180 and 72 cd m-2 and current densities of 55 and 27 mA cm-2, respectively.

Room-temperature synthesis of Zn(0.80)Cd(0.20)S solid solution with a high visible-light photocatalytic activity for hydrogen evolution.

PubMed

Wang, Dong-Hong; Wang, Lei; Xu, An-Wu

2012-03-21

Visible light photocatalytic H(2) production from water splitting is of great significance for its potential applications in converting solar energy into chemical energy. In this study, a series of Zn(1-x)Cd(x)S solid solutions with a nanoporous structure were successfully synthesized via a facile template-free method at room temperature. The obtained solid solutions were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS) and N(2) adsorption-desorption analysis. The solid solutions show efficient photocatalytic activity for H(2) evolution from aqueous solutions containing sacrificial reagents S(2-) and SO(3)(2-) under visible-light irradiation without a Pt cocatalyst, and loading of the Pt cocatalyst further improves the visible-light photocatalytic activity. The optimal photocatalyst with x = 0.20 prepared at pH = 7.3 displays the highest activity for H(2) evolution. The bare and 0.25 wt% Pt loaded Zn(0.80)Cd(0.20)S nanoparticles exhibit a high H(2) evolution rate of 193 μmol h(-1) and 458 μmol h(-1) under visible-light irradiation (λ ≥ 420 nm), respectively. In addition, the bare and 0.25 wt% Pt loaded Zn(0.80)Cd(0.20)S catalysts show a high H(2) evolution rate of 252 and 640 μmol h(-1) under simulated solar light irradiation, respectively. Moreover, the Zn(0.80)Cd(0.20)S catalyst displays a high photocatalytic stability for H(2) evolution under long-term light irradiation. The incorporation of Cd in the solid solution leads to the visible light absorption, and the high content of Zn in the solid solution results in a relatively negative conduction band, a modulated band gap and a rather wide valence bandwidth, which are responsible for the excellent photocatalytic performance of H(2) production and for the high photostability. This journal is © The Royal Society of Chemistry 2012

Study of white light emission from ZnS/PS composite system

NASA Astrophysics Data System (ADS)

Wang, Caifeng; Li, Qingshan; Lu, Lei; Zhang, Lichun; Qi, Hongxia

2007-09-01

ZnS films were deposited by pulsed laser deposition (PLD) on porous silicon (PS) substrates formed by electrochemical anodization of p-type (100) silicon wafer. The photoluminescence (PL) spectra of ZnS/PS composites were measured at room temperature. Under different excitation wavelengths, the relative integrated intensities of the red light emission from PS layers and the blue-green emission from ZnS films had different values. After samples were annealed in vacuum at different temperatures (200, 300, and 400 Celsius degree) for 30 min respectively, a new green emission located at around 550 nm appeared in the PL spectra of all ZnS/PS samples, and all of the ZnS/PS composites had a broad PL band (450-700 nm) in the visible region, exhibiting intensively white light emission.

Formation of 2D bright spatial solitons in lithium niobate with photovoltaic response and incoherent background

NASA Astrophysics Data System (ADS)

Pustozerov, A.; Shandarov, V.

2017-12-01

The influence of incoherent background illumination produced by light-emitting diodes (LED's) of different average wavelengths and laser diode emitting in blue region of visible on diffraction characteristics of narrow coherent light beams of He-Ne laser due to refractive index changes of Fe-doped lithium niobate sample are studied. It has been experimentally demonstrated that nonlinear diffraction of red beams with wavelength 633 nm and diameters on full width of half maximum (FWHM) near to 15 μm may be totally compensated using background light with average wavelengths 450 - 465 nm. To provide the necessary intensity of incoherent background, the combinations of spherical and cylindrical concave lenses with blue LED and laser diode module without focusing its beam have been used.

MoS2-InGaZnO Heterojunction Phototransistors with Broad Spectral Responsivity.

PubMed

Yang, Jaehyun; Kwak, Hyena; Lee, Youngbin; Kang, Yu-Seon; Cho, Mann-Ho; Cho, Jeong Ho; Kim, Yong-Hoon; Jeong, Seong-Jun; Park, Seongjun; Lee, Hoo-Jeong; Kim, Hyoungsub

2016-04-06

We introduce an amorphous indium-gallium-zinc-oxide (a-IGZO) heterostructure phototransistor consisting of solution-based synthetic molybdenum disulfide (few-layered MoS2, with a band gap of ∼1.7 eV) and sputter-deposited a-IGZO (with a band gap of ∼3.0 eV) films as a novel sensing element with a broad spectral responsivity. The MoS2 and a-IGZO films serve as a visible light-absorbing layer and a high mobility channel layer, respectively. Spectroscopic measurements reveal that appropriate band alignment at the heterojunction provides effective transfer of the visible light-induced electrons generated in the few-layered MoS2 film to the underlying a-IGZO channel layer with a high carrier mobility. The photoresponse characteristics of the a-IGZO transistor are extended to cover most of the visible range by forming a heterojunction phototransistor that harnesses a visible light responding MoS2 film with a small band gap prepared through a large-area synthetic route. The MoS2-IGZO heterojunction phototransistors exhibit a photoresponsivity of approximately 1.7 A/W at a wavelength of 520 nm (an optical power of 1 μW) with excellent time-dependent photoresponse dynamics.

Tunable UV-visible absorption of SnS2 layered quantum dots produced by liquid phase exfoliation.

PubMed

Fu, Xiao; Ilanchezhiyan, P; Mohan Kumar, G; Cho, Hak Dong; Zhang, Lei; Chan, A Sattar; Lee, Dong J; Panin, Gennady N; Kang, Tae Won

2017-02-02

4H-SnS 2 layered crystals synthesized by a hydrothermal method were used to obtain via liquid phase exfoliation quantum dots (QDs), consisting of a single layer (SLQDs) or multiple layers (MLQDs). Systematic downshift of the peaks in the Raman spectra of crystals with a decrease in size was observed. The bandgap of layered QDs, estimated by UV-visible absorption spectroscopy and the tunneling current measurements using graphene probes, increases from 2.25 eV to 3.50 eV with decreasing size. 2-4 nm SLQDs, which are transparent in the visible region, show selective absorption and photosensitivity at wavelengths in the ultraviolet region of the spectrum while larger MLQDs (5-90 nm) exhibit a broad band absorption in the visible spectral region and the photoresponse under white light. The results show that the layered quantum dots obtained by liquid phase exfoliation exhibit well-controlled and regulated bandgap absorption in a wide tunable wavelength range. These novel layered quantum dots prepared using an inexpensive method of exfoliation and deposition from solution onto various substrates at room temperature can be used to create highly efficient visible-blind ultraviolet photodetectors and multiple bandgap solar cells.

Facile fabrication of an efficient BiVO4 thin film electrode for water splitting under visible light irradiation.

PubMed

Jia, Qingxin; Iwashina, Katsuya; Kudo, Akihiko

2012-07-17

An efficient BiVO(4) thin film electrode for overall water splitting was prepared by dipping an F-doped SnO(2) (FTO) substrate electrode in an aqueous nitric acid solution of Bi(NO(3))(3) and NH(4)VO(3), and subsequently calcining it. X-ray diffraction of the BiVO(4) thin film revealed that a photocatalytically active phase of scheelite-monoclinic BiVO(4) was obtained. Scanning electron microscopy images showed that the surface of an FTO substrate was uniformly coated with the BiVO(4) film with 300-400 nm of the thickness. The BiVO(4) thin film electrode gave an excellent anodic photocurrent with 73% of an IPCE at 420 nm at 1.0 V vs. Ag/AgCl. Modification with CoO on the BiVO(4) electrode improved the photoelectrochemical property. A photoelectrochemical cell consisting of the BiVO(4) thin film electrode with and without CoO, and a Pt counter electrode was constructed for water splitting under visible light irradiation and simulated sunlight irradiation. Photocurrent due to water splitting to form H(2) and O(2) was confirmed with applying an external bias smaller than 1.23 V that is a theoretical voltage for electrolysis of water. Water splitting without applying external bias under visible light irradiation was demonstrated using a SrTiO(3)Rh photocathode and the BiVO(4) photoanode.

Differential response of human dermal fibroblast subpopulations to visible and near-infrared light: Potential of photobiomodulation for addressing cutaneous conditions.

PubMed

Mignon, Charles; Uzunbajakava, Natallia E; Castellano-Pellicena, Irene; Botchkareva, Natalia V; Tobin, Desmond J

2018-04-17

The past decade has witnessed a rapid expansion of photobiomodulation (PBM), demonstrating encouraging results for the treatment of cutaneous disorders. Confidence in this approach, however, is impaired not only by a lack of understanding of the light-triggered molecular cascades but also by the significant inconsistency in published experimental outcomes, design of the studies and applied optical parameters. This study aimed at characterizing the response of human dermal fibroblast subpopulations to visible and near-infrared (NIR) light in an attempt to identify the optical treatment parameters with high potential to address deficits in aging skin and non-healing chronic wounds. Primary human reticular and papillary dermal fibroblasts (DF) were isolated from the surplus of post-surgery human facial skin. An in-house developed LED-based device was used to irradiate cell cultures using six discrete wavelengths (450, 490, 550, 590, 650, and 850 nm). Light dose-response at a standard oxygen concentration (20%) at all six wavelengths was evaluated in terms of cell metabolic activity. This was followed by an analysis of the transcriptome and procollagen I production at a protein level, where cells were cultured in conditions closer to in vivo at 2% environmental oxygen and 2% serum. Furthermore, the production of reactive oxygen species (ROS) was accessed using real-time fluorescence confocal microscopy imaging. Here, production of ROS in the presence or absence of antioxidants, as well as the cellular localization of ROS, was evaluated. In terms of metabolic activity, consecutive irradiation with short-wavelength light (⇐530 nm) exerted an inhibitory effect on DF, while longer wavelengths (>=590 nm) had essentially a neutral effect. Cell behavior following treatment with 450 nm was biphasic with two distinct states: inhibitory at low- to mid- dose levels (<=30 J/cm 2 ), and cytotoxic at higher dose levels (>30 J/cm 2 ). Cell response to blue light was accompanied by a dose-dependent release of ROS that was localized in the perinuclear area close to mitochondria, which was attenuated by an antioxidant. Overall, reticular DFs exhibited a greater sensitivity to light treatment at the level of gene expression than did papillary DFs, with more genes significantly up- or down- regulated. At the intra-cellular signaling pathway level, the up- or down- regulation of vital pathways was observed only for reticular DF, after treatment with 30 J/cm 2 of blue light. At the cellular level, short visible wavelengths exerted a greater inhibitory effect on reticular DF. Several genes involved in the TGF-β signaling pathway were also affected. In addition, procollagen I production was inhibited. By contrast, 850 nm near-infrared (NIR) light (20 J/cm 2 ) exerted a stimulatory metabolic effect in these cells, with no detectable intracellular ROS formation. Here too, reticular DF were more responsive than papillary DF. This stimulatory effect was only observed under in vivo-like low oxygen conditions, corresponding to normal dermal tissue oxygen levels (approximately 2%). This study highlights a differential impact of light on human skin cells with upregulation of metabolic activity with NIR light, and inhibition of pro-collagen production and proliferation in response to blue light. These findings open-up new avenues for developing therapies for different cutaneous conditions (e.g., treatment of keloids and fibrosis) or differential therapy at distinct stages of wound healing. Lasers Surg. Med. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

Filter-based measurements of UV-vis mass absorption cross sections of organic carbon aerosol from residential biomass combustion: Preliminary findings and sources of uncertainty

NASA Astrophysics Data System (ADS)

Pandey, Apoorva; Pervez, Shamsh; Chakrabarty, Rajan K.

2016-10-01

Combustion of solid biomass fuels is a major source of household energy in developing nations. Black (BC) and organic carbon (OC) aerosols are the major PM2.5 (particulate matter with aerodynamic diameter smaller than 2.5 μm) pollutants co-emitted during burning of these fuels. While the optical nature of BC is well characterized, very little is known about the properties of light-absorbing OC (LAOC). Here, we report our preliminary findings on the mass-based optical properties of LAOC emitted from the combustion of four commonly used solid biomass fuels - fuel-wood, agricultural residue, dung-cake, and mixed - in traditional Indian cookstoves. As part of a pilot field study conducted in central India, PM2.5 samples were collected on Teflon filters and analyzed for their absorbance spectra in the 300-900 nm wavelengths at 1 nm resolution using a UV-Visible spectrophotometer equipped with an integrating sphere. The mean mass absorption cross-sections (MAC) of the emitted PM2.5 and OC, at 550 nm, were 0.8 and 0.2 m2 g-1, respectively, each with a factor of ~2.3 uncertainty. The mean absorption Ångström exponent (AǺE) values for PM2.5 were 3±1 between 350 and 550 nm, and 1.2±0.1 between 550 and 880 nm. In the 350-550 nm range, OC had an AǺE of 6.3±1.8. The emitted OC mass, which was on average 25 times of the BC mass, contributed over 50% of the aerosol absorbance at wavelengths smaller than 450 nm. The overall OC contribution to visible solar light (300-900 nm) absorption by the emitted particles was 26-45%. Our results highlight the need to comprehensively and accurately address: (i) the climatic impacts of light absorption by OC from cookstove emissions, and (ii) the uncertainties and biases associated with variability in biomass fuel types and combustion conditions, and filter-based measurement artifacts during determination of MAC values.

Visible light controls cell adhesion on a photoswitchable biointerface.

PubMed

Ming, Zunzhen; Hua, Xin; Xue, Yuan; Lin, Qiuning; Bao, Chunyan; Zhu, Linyong

2018-05-04

Bioactive surfaces with specific interactions with cells have been greatly interested due to their potential applications in biosensors and tissue engineering. Herein, we fabricated a dopamine contained photoswitch molecule (compound 1) which could form self-assembled monolayer (SAM) on substrates. The SAM showed a good photoswitch ability and manifested excellent fatigue resistance, which displayed its potential application as a biologically friendly surface coating. Contact angle analysis and cell experiments exhibited that the SAM surface was hydrophobic before irradiation which favored cell adhesion, while, it turned hydrophilic and induced cell unfouling or detachment after light irradiation. The uses of visible light stimulation (λ ex  = 530 nm) and the reversible regulation on cell adhesion and detachment should open up new avenues for bioacitve surfaces in biomedical applications. Copyright © 2018 Elsevier B.V. All rights reserved.

Metal-free organic sensitizers for use in water-splitting dye-sensitized photoelectrochemical cells

DOE PAGES

Swierk, John R.; Méndez-Hernández, Dalvin D.; McCool, Nicholas S.; ...

2015-01-12

Solar fuel generation requires the efficient capture and conversion of visible light. In both natural and artificial systems, molecular sensitizers can be tuned to capture, convert, and transfer visible light energy. We demonstrate that a series of metal-free porphyrins can drive photoelectrochemical water splitting under broadband and red light (λ > 590 nm) illumination in a dye-sensitized TiO 2 solar cell. Here, we report the synthesis, spectral, and electrochemical properties of the sensitizers. Despite slow recombination of photoinjected electrons with oxidized porphyrins, photocurrents are low because of low injection yields and slow electron self-exchange between oxidized porphyrins. As a result,more » the free-base porphyrins are stable under conditions of water photoelectrolysis and in some cases photovoltages in excess of 1 V are observed.« less

Ultraviolet/visible photodiode of nanostructure Sn-doped ZnO/Si heterojunction

NASA Astrophysics Data System (ADS)

Kheirandish, N.; Mortezaali, A.

2013-05-01

Sn doped ZnO nanostructures deposited on Si substrate with (100) orientation by spray pyrolysis method at temperature 450 °C. Sn/Zn atomic ratio varies from 0% to 5%. The scanning electron microscope measurements showed that size of particles reduce with increasing the doping concentration. The X-ray diffraction analysis revealed formation of the wurtzite phase of ZnO. I-V curves of Sn doped ZnO/Si were investigated in dark and shows diode-like rectifying behavior. Among doped ZnO/Si, sample with atomic ratio of Sn/Zn = 5% is a good candidate to study photodiode properties in UV/visible range. Photoelectric effects have been observed under illumination monochromatic laser light with a wavelength of 325 nm and halogen lamp. Measurements demonstrate that the photodiode has high sensitivity and reproducibility to halogen light respect to laser light.

Construction of AgBr nano-cakes decorated Ti3+ self-doped TiO2 nanorods/nanosheets photoelectrode and its enhanced visible light driven photocatalytic and photoelectrochemical properties

NASA Astrophysics Data System (ADS)

Deng, Xiaoyong; Zhang, Huixuan; Guo, Ruonan; Cheng, Xiuwen; Cheng, Qingfeng

2018-05-01

In the study, AgBr nano-cakes decorated Ti3+ self-doped TiO2 nanorods/nanosheets (AgBr-Ti3+/TiO2 NRs/NSs) photoelectrode with enhanced visible light driven photocatalytic (PC) and photoelectrochemical (PECH) performance has been successfully fabricated by hydrothermal reaction, followed by sodium borohydride reduction and then successive ionic layer adsorption and reaction (SILAR) treatment. Afterwards, series of characterizations were conducted to study the physicochemical properties of AgBr-Ti3+/TiO2 NRs/NSs photoelectrode. Results indicated that AgBr nano-cakes with sizes varying from 110 to 180 nm were uniformly decorated on the surface of Ti3+/TiO2 NRs/NSs to form AgBr-Ti3+/TiO2 NRs/NSs photoelectrode. Moreover, PC activity of AgBr-Ti3+/TiO2 NRs/NSs photoelectrode was measured by degradation of methylene blue (MB). It was found that AgBr-Ti3+/TiO2 NRs/NSs photoelectrode exhibited higher PC activity (98.7%) than that of other samples within 150 min visible light illumination, owing to the enhancement of visible light harvesting and effective separation of photoproduced charges. Thus, AgBr nano-cakes and Ti3+ exerted a huge influence on the PC and PECH properties of AgBr-Ti3+/TiO2 NRs/NSs photoelectrode. Furthermore, the possible enhanced visible light driven PC mechanism of AgBr-Ti3+/TiO2 NRs/NSs was proposed and confirmed.

Light-Regulated Polymerization under Near-Infrared/Far-Red Irradiation Catalyzed by Bacteriochlorophyll a.

PubMed

Shanmugam, Sivaprakash; Xu, Jiangtao; Boyer, Cyrille

2016-01-18

Photoregulated polymerizations are typically conducted using high-energy (UV and blue) light, which may lead to undesired side reactions. Furthermore, as the penetration of visible light is rather limited, the range of applications with such wavelengths is likewise limited. We herein report the first living radical polymerization that can be activated and deactivated by irradiation with near-infrared (NIR) and far-red light. Bacteriochlorophyll a (Bachl a) was employed as a photoredox catalyst for photoinduced electron transfer/reversible addition-fragmentation chain transfer (PET-RAFT) polymerization. Well-defined polymers were thus synthesized within a few hours under NIR (λ=850 nm) and far-red (λ=780 nm) irradiation with excellent control over the molecular weight (M(n)/M(w)<1.25). Taking advantage of the good penetration of NIR light, we showed that the polymerization also proceeded smoothly when a translucent barrier was placed between light source and reaction vessel. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhancing the Photovoltaic Performance of Perovskite Solar Cells with a Down-Conversion Eu-Complex.

PubMed

Jiang, Ling; Chen, Wangchao; Zheng, Jiawei; Zhu, Liangzheng; Mo, Li'e; Li, Zhaoqian; Hu, Linhua; Hayat, Tasawar; Alsaedi, Ahmed; Zhang, Changneng; Dai, Songyuan

2017-08-16

Organometal halide perovskite solar cells (PSCs) have shown high photovoltaic performance but poor utilization of ultraviolet (UV) irradiation. Lanthanide complexes have a wide absorption range in the UV region and they can down-convert the absorbed UV light into visible light, which provides a possibility for PSCs to utilize UV light for higher photocurrent, efficiency, and stability. In this study, we use a transparent luminescent down-converting layer (LDL) of Eu-4,7-diphenyl-1,10-phenanthroline (Eu-complex) to improve the light utilization efficiency of PSCs. Compared with the uncoated PSC, the PSC coated with Eu-complex LDL on the reverse of the fluorine-doped tin oxide glass displayed an enhancement of 11.8% in short-circuit current density (J sc ) and 15.3% in efficiency due to the Eu-complex LDL re-emitting UV light (300-380 nm) in the visible range. It is indicated that the Eu-complex LDL plays the role of enhancing the power conversion efficiency as well as reducing UV degradation for PSCs.

Image sensor pixel with on-chip high extinction ratio polarizer based on 65-nm standard CMOS technology.

PubMed

Sasagawa, Kiyotaka; Shishido, Sanshiro; Ando, Keisuke; Matsuoka, Hitoshi; Noda, Toshihiko; Tokuda, Takashi; Kakiuchi, Kiyomi; Ohta, Jun

2013-05-06

In this study, we demonstrate a polarization sensitive pixel for a complementary metal-oxide-semiconductor (CMOS) image sensor based on 65-nm standard CMOS technology. Using such a deep-submicron CMOS technology, it is possible to design fine metal patterns smaller than the wavelengths of visible light by using a metal wire layer. We designed and fabricated a metal wire grid polarizer on a 20 × 20 μm(2) pixel for image sensor. An extinction ratio of 19.7 dB was observed at a wavelength 750 nm.

Rapid water disinfection using vertically aligned MoS2 nanofilms and visible light

NASA Astrophysics Data System (ADS)

Liu, Chong; Kong, Desheng; Hsu, Po-Chun; Yuan, Hongtao; Lee, Hyun-Wook; Liu, Yayuan; Wang, Haotian; Wang, Shuang; Yan, Kai; Lin, Dingchang; Maraccini, Peter A.; Parker, Kimberly M.; Boehm, Alexandria B.; Cui, Yi

2016-12-01

Solar energy is readily available in most climates and can be used for water purification. However, solar disinfection of drinking water mostly relies on ultraviolet light, which represents only 4% of the total solar energy, and this leads to a slow treatment speed. Therefore, the development of new materials that can harvest visible light for water disinfection, and so speed up solar water purification, is highly desirable. Here we show that few-layered vertically aligned MoS2 (FLV-MoS2) films can be used to harvest the whole spectrum of visible light (∼50% of solar energy) and achieve highly efficient water disinfection. The bandgap of MoS2 was increased from 1.3 to 1.55 eV by decreasing the domain size, which allowed the FLV-MoS2 to generate reactive oxygen species (ROS) for bacterial inactivation in the water. The FLV-MoS2 showed a ∼15 times better log inactivation efficiency of the indicator bacteria compared with that of bulk MoS2, and a much faster inactivation of bacteria under both visible light and sunlight illumination compared with the widely used TiO2. Moreover, by using a 5 nm copper film on top of the FLV-MoS2 as a catalyst to facilitate electron-hole pair separation and promote the generation of ROS, the disinfection rate was increased a further sixfold. With our approach, we achieved water disinfection of >99.999% inactivation of bacteria in 20 min with a small amount of material (1.6 mg l-1) under simulated visible light.

Space beam combiner for long-baseline interferometry

NASA Astrophysics Data System (ADS)

Lin, Yao; Bartos, Randall D.; Korechoff, Robert P.; Shaklan, Stuart B.

1999-04-01

An experimental beam combiner (BC) is being developed to support the space interferometry program at the JPL. The beam combine forms the part of an interferometer where star light collected by the sidestats or telescopes is brought together to produce white light fringes, and to provide wavefront tilt information via guiding spots and beam walk information via shear spots. The assembly and alignment of the BC has been completed. The characterization test were performed under laboratory conditions with an artificial star and optical delay line. Part of each input beam was used to perform star tracking. The white light interference fringes were obtained over the selected wavelength range from 450 nm to 850 nm. A least-square fit process was used to analyze the fringe initial phase, fringe visibilities and shift errors of the optical path difference in the delay line using the dispersed white-light fringes at different OPD positions.

Ponderomotive electron acceleration in a silicon-based nanoplasmonic waveguide.

PubMed

Sederberg, S; Elezzabi, A Y

2014-10-17

Ponderomotive electron acceleration is demonstrated in a semiconductor-loaded nanoplasmonic waveguide. Photogenerated free carriers are accelerated by the tightly confined nanoplasmonic fields and reach energies exceeding the threshold for impact ionization. Broadband (375 nm ≤ λ ≤ 650  nm) white light emission is observed from the nanoplasmonic waveguides. Exponential growth of visible light emission confirms the exponential growth of the electron population, demonstrating the presence of an optical-field-driven electron avalanche. Electron sweeping dynamics are visualized using pump-probe measurements, and a sweeping time of 1.98 ± 0.40 ps is measured. These findings offer a means to harness the potential of the emerging field of ultrafast nonlinear nanoplasmonics.

A simple fiber-optic microprobe for high resolution light measurements: application in marine sediment

NASA Technical Reports Server (NTRS)

Jorgensen, B. B.; Des Marais, D. J.

1986-01-01

A fiber-optic microphobe is described which is inexpensive and simple to build and use. It consists of an 80-micrometers optical fiber which at the end is tapered down to a rounded sensing tip of 20-30-micrometers diameter. The detector is a hybrid photodiode/amplifier. The probe has a sensitivity of 0.01 microEinst m-2 s-1 and a spectral range of 300-1,100 nm. Spectral light gradients were measured in fine-grained San Francisco Bay sediment that had an undisturbed diatom coating on the surface. The photic zone of the mud was only 0.4 mm deep. Measured in situ spectra showed extinction maxima at 430-520, 620-630, 670, and 825-850 nm due to absorption by chlorophyll a, carotenoids, phycocyanin, and bacterio-chlorophyll a. Maximum light penetration in the visible range was found in both the violet and the red < or = 400 and > or = 700 nm.

Synthesis of Cr3+-doped TiO2 nanoparticles: characterization and evaluation of their visible photocatalytic performance and stability.

PubMed

Mendiola-Alvarez, Sandra Yadira; Guzmán-Mar, Jorge Luis; Turnes-Palomino, Gemma; Maya-Alejandro, Fernando; Caballero-Quintero, Adolfo; Hernández-Ramírez, Aracely; Hinojosa-Reyes, Laura

2017-09-28

Cr 3+ -doped TiO 2 nanoparticles (Ti-Cr) were synthesized by microwave-assisted sol-gel method. The Ti-Cr catalyst was characterized by X-ray diffraction, ultraviolet-visible diffuse reflectance spectroscopy, N 2 adsorption-desorption analysis, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, photoluminescence spectroscopy, X-ray photoelectron spectroscopy (XPS) and zetametry. The anatase mesoporous Ti-Cr material exhibited a specific surface area of 54.5 m 2 /g. XPS analysis confirmed the proper substitution of Ti 4+ cations by Cr 3+ cations in the TiO 2 matrix. The particle size was of average size of 17 nm for the undoped TiO 2 but only 9.5 nm for Ti-Cr. The Cr atoms promoted the formation of hydroxyl radicals and modified the surface adsorptive properties of TiO 2 due to the increase in surface acidity of the material. The photocatalytic evaluation demonstrated that the Ti-Cr catalyst completely degraded (4-chloro-2-methylphenoxy) acetic acid under visible light irradiation, while undoped TiO 2 and P25 allowed 45.7% and 31.1%, respectively. The rate of degradation remained 52% after three cycles of catalyst reuse. The higher visible light photocatalytic activity of Ti-Cr was attributed to the beneficial effect of Cr 3+ ions on the TiO 2 surface creating defects within the TiO 2 crystal lattice, which can act as charge-trapping sites, reducing the electron-hole recombination process.

A heterojunction photocatalyst composed of zinc rhodium oxide, single crystal-derived bismuth vanadium oxide, and silver for overall pure-water splitting under visible light up to 740 nm.

PubMed

Kobayashi, Ryoya; Takashima, Toshihiro; Tanigawa, Satoshi; Takeuchi, Shugo; Ohtani, Bunsho; Irie, Hiroshi

2016-10-12

We recently reported the synthesis of a solid-state heterojunction photocatalyst consisting of zinc rhodium oxide (ZnRh 2 O 4 ) and bismuth vanadium oxide (Bi 4 V 2 O 11 ), which functioned as hydrogen (H 2 ) and oxygen (O 2 ) evolution photocatalysts, respectively, connected with silver (Ag). Polycrystalline Bi 4 V 2 O 11 (p-Bi 4 V 2 O 11 ) powders were utilized to form ZnRh 2 O 4 /Ag/p-Bi 4 V 2 O 11 , which was able to photocatalyze overall pure-water splitting under red-light irradiation with a wavelength of 700 nm (R. Kobayashi et al., J. Mater. Chem. A, 2016, 4, 3061). In the present study, we replaced p-Bi 4 V 2 O 11 with a powder obtained by pulverizing single crystals of Bi 4 V 2 O 11 (s-Bi 4 V 2 O 11 ) to form ZnRh 2 O 4 /Ag/s-Bi 4 V 2 O 11 , and demonstrated that this heterojunction photocatalyst had enhanced water-splitting activity. In addition, ZnRh 2 O 4 /Ag/s-Bi 4 V 2 O 11 was able to utilize nearly the entire range of visible light up to a wavelength of 740 nm. These properties were attributable to the higher O 2 evolution activity of s-Bi 4 V 2 O 11 .

Nonlinear optics in the LP(02) higher-order mode of a fiber.

PubMed

Chen, Y; Chen, Z; Wadsworth, W J; Birks, T A

2013-07-29

The distinct disperion properties of higher-order modes in optical fibers permit the nonlinear generation of radiation deeper into the ultraviolet than is possible with the fundamental mode. This is exploited using adiabatic, broadband mode convertors to couple light efficiently from an input fundamental mode and also to return the generated light to an output fundamental mode over a broad spectral range. For example, we generate visible and UV supercontinuum light in the LP(02) mode of a photonic crystal fiber from sub-ns pulses with a wavelength of 532 nm.

Quantum interference of highly-dispersive surface plasmons (Conference Presentation)

NASA Astrophysics Data System (ADS)

Tokpanov, Yury S.; Fakonas, James S.; Atwater, Harry A.

2016-09-01

Previous experiments have shown that surface plasmon polaritons (SPPs) preserve their entangled state and do not cause measurable decoherence. However, essentially all of them were done using SPPs whose dispersion was in the linear "photon-like" regime. We report in this presentation on experiments showing how transition to "true-plasmon" non-linear dispersion regime, which occurs near SPP resonance frequency, will affect quantum coherent properties of light. To generate a polarization-entangled state we utilize type-I parametric down-conversion, occurring in a pair of non-linear crystals (BiBO), glued together and rotated by 90 degrees with respect to each other. For state projection measurements, we use a pair of polarizers and single-photon avalanche diode coincidence count detectors. We interpose a plasmonic hole array in the path of down-converted light before the polarizer. Without the hole array, we measure visibility V=99-100% and Bell's number S=2.81±0.03. To study geometrical effects we fabricated plasmonic hole arrays (gold on optically polished glass) with elliptical holes (axes are 190nm and 240nm) using focused ion beam. When we put this sample in our system we measured the reduction of visibility V=86±5% using entangled light. However, measurement using classical light gave exactly the same visibility; hence, this reduction is caused only by the difference in transmission coefficients of different polarizations. As samples with non-linear dispersion we fabricated two-layer (a-Si - Au) and three-layer (a-Si - Au - a-Si) structures on optically polished glass with different pitches and circular holes. The results of measurements with these samples will be discussed along with the theoretical investigations.

A visible-light-excited europium(III) complex-based luminescent probe for visualizing copper ions and hydrogen sulfide in living cells

NASA Astrophysics Data System (ADS)

Wang, Yiren; Wang, Huan; Yang, Mei; Yuan, Jingli; Wu, Jing

2018-01-01

Development of visible-light-excited lanthanide (III) complex-based luminescent probes is highly appealing due to their superiority of less damage to the living biosystems over the conventional UV-light-excited ones. In this work, a visible-light-excited europium (III) complex-based luminescent probe, BPED-BHHCT-Eu3+-BPT, has been designed and synthesized by conjugating the Cu2+-binding N,N-bis(2-pyridylmethyl)ethanediamine (BPED) to a tetradentate β-diketone ligand 4,4‧-bis(1″,1″,1″,2″,2″,3″,3″-heptafluoro-4″,6″-hexanedione-6″-yl)chlorosulfo-o-terphenyl (BHHCT) and coordinating with a coligand 2-(N,N-diethylanilin-4-yl)-4,6-bis(pyrazol-1-yl)-1,3,5-triazine) (BPT) for the time-gated luminescence detection of Cu2+ ions and hydrogen sulfide (H2S) in living cells. BPED-BHHCT-Eu3+-BPT exhibited a sharp excitation peak at 407 nm and a wide excitation window extending to beyond 460 nm. Upon its reaction with Cu2+ ions, the luminescence of BPED-BHHCT-Eu3+-BPT was efficiently quenched, which could be reversibly restored by the addition of H2S due to the strong affinity between Cu2+ ions and H2S. The "on-off-on" type luminescence behavior of BPED-BHHCT-Eu3+-BPT towards Cu2+ ions and H2S enabled the sensing of the two species with high sensitivity and selectivity. The performances of BPED-BHHCT-Eu3+-BPT for visualizing intracellular Cu2+ ions and H2S were investigated, and the results have demonstrated the practical applicability of the probe for molecular imaging of cells.

Visible red and infrared light alters gene expression in human marrow stromal fibroblast cells.

PubMed

Guo, J; Wang, Q; Wai, D; Zhang, Q Z; Shi, S H; Le, A D; Shi, S T; Yen, S L-K

2015-04-01

This study tested whether or not gene expression in human marrow stromal fibroblast (MSF) cells depends on light wavelength and energy density. Primary cultures of isolated human bone marrow stem cells (hBMSC) were exposed to visible red (VR, 633 nm) and infrared (IR, 830 nm) radiation wavelengths from a light emitting diode (LED) over a range of energy densities (0.5, 1.0, 1.5, and 2.0 Joules/cm2) Cultured cells were assayed for cell proliferation, osteogenic potential, adipogenesis, mRNA and protein content. mRNA was analyzed by microarray and compared among different wavelengths and energy densities. Mesenchymal and epithelial cell responses were compared to determine whether responses were cell type specific. Protein array analysis was used to further analyze key pathways identified by microarrays. Different wavelengths and energy densities produced unique sets of genes identified by microarray analysis. Pathway analysis pointed to TGF-beta 1 in the visible red and Akt 1 in the infrared wavelengths as key pathways to study. TGF-beta protein arrays suggested switching from canonical to non-canonical TGF-beta pathways with increases to longer IR wavelengths. Microarrays suggest RANKL and MMP 10 followed IR energy density dose-response curves. Epithelial and mesenchymal cells respond differently to stimulation by light suggesting cell type-specific response is possible. These studies demonstrate differential gene expression with different wavelengths, energy densities and cell types. These differences in gene expression have the potential to be exploited for therapeutic purposes and can help explain contradictory results in the literature when wavelengths, energy densities and cell types differ. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

METIS: the visible and UV coronagraph for solar orbiter

NASA Astrophysics Data System (ADS)

Romoli, M.; Landini, F.; Antonucci, E.; Andretta, V.; Berlicki, A.; Fineschi, S.; Moses, J. D.; Naletto, G.; Nicolosi, P.; Nicolini, G.; Spadaro, D.; Teriaca, L.; Baccani, C.; Focardi, M.; Pancrazzi, M.; Pucci, S.; Abbo, L.; Bemporad, A.; Capobianco, G.; Massone, G.; Telloni, D.; Magli, E.; Da Deppo, V.; Frassetto, F.; Pelizzo, M. G.; Poletto, L.; Uslenghi, M.; Vives, S.; Malvezzi, M.

2017-11-01

METIS coronagraph is designed to observe the solar corona with an annular field of view from 1.5 to 2.9 degrees in the visible broadband (580-640 nm) and in the UV HI Lyman-alpha, during the Sun close approaching and high latitude tilting orbit of Solar Orbiter. The big challenge for a coronagraph is the stray light rejection. In this paper after a description of the present METIS optical design, the stray light rejection design is presented in detail together with METIS off-pointing strategies throughout the mission. Data shown in this paper derive from the optimization of the optical design performed with Zemax ray tracing and from laboratory breadboards of the occultation system and of the polarimeter.

High-power fiber-coupled 100W visible spectrum diode lasers for display applications

NASA Astrophysics Data System (ADS)

Unger, Andreas; Küster, Matthias; Köhler, Bernd; Biesenbach, Jens

2013-02-01

Diode lasers in the blue and red spectral range are the most promising light sources for upcoming high-brightness digital projectors in cinemas and large venue displays. They combine improved efficiency, longer lifetime and a greatly improved color space compared to traditional xenon light sources. In this paper we report on high-power visible diode laser sources to serve the demands of this emerging market. A unique electro-optical platform enables scalable fiber coupled sources at 638 nm with an output power of up to 100 W from a 400 μm NA0.22 fiber. For the blue diode laser we demonstrate scalable sources from 5 W to 100 W from a 400 μm NA0.22 fiber.

Comparison of elliptical and spherical mirrors for the grasshopper monochromators at SSRL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Waldhauer, A. P.

1989-07-01

A comparison of the performance of a spherical and elliptical mirror in the grasshopper monochromator is presented. The problem was studied by ray tracing and then tested using visible (/lambda/=633 nm) laser light. Calculations using ideal optics yield an improvement in flux by a factor of up to 2.7, while tests with visible light show an increase by a factor of 5 because the old spherical mirror is compared to a new, perfect elliptical one. The FWHM of the measured focus is 90 /mu/m with a spherical mirror, and 25 /mu/m with an elliptical one. Elliptical mirrors have been acquiredmore » and are now being installed in the two grasshoppers at SSRL.« less

High efficient light absorption and nanostructure-dependent birefringence of a metal-dielectric symmetrical layered structure

NASA Astrophysics Data System (ADS)

Jen, Yi-Jun; Jhang, Yi-Ciang; Liu, Wei-Chih

2017-08-01

A multilayer that comprises ultra-thin metal and dielectric films has been investigated and applied as a layered metamaterial. By arranging metal and dielectric films alternatively and symmetrically, the equivalent admittance and refractive index can be tailored separately. The tailored admittance and refractive index enable us to design optical filters with more flexibility. The admittance matching is achieved via the admittance tracing in the normalized admittance diagram. In this work, an ultra-thin light absorber is designed as a multilayer composed of one or several cells. Each cell is a seven-layered film stack here. The design concept is to have the extinction as large as possible under the condition of admittance matching. For a seven-layered symmetrical film stack arranged as Ta2O5 (45 nm)/ a-Si (17 nm)/ Cr (30 nm)/ Al (30 nm)/ Cr (30 nm)/ a-Si (17 nm)/ Ta2O5 (45 nm), its mean equivalent admittance and extinction coefficient over the visible regime is 1.4+0.2i and 2.15, respectively. The unit cell on a transparent BK7 glass substrate absorbs 99% of normally incident light energy for the incident medium is glass. On the other hand, a transmission-induced metal-dielectric film stack is investigated by using the admittance matching method. The equivalent anisotropic property of the metal-dielectric multilayer varied with wavelength and nanostructure are investigated here.

Human phase response curve to a single 6.5 h pulse of short-wavelength light

PubMed Central

Rüger, Melanie; St Hilaire, Melissa A; Brainard, George C; Khalsa, Sat-Bir S; Kronauer, Richard E; Czeisler, Charles A; Lockley, Steven W

2013-01-01

The photic resetting response of the human circadian pacemaker depends on the timing of exposure, and the direction and magnitude of the resulting shift is described by a phase response curve (PRC). Previous PRCs in humans have utilized high-intensity polychromatic white light. Given that the circadian photoreception system is maximally sensitive to short-wavelength visible light, the aim of the current study was to construct a PRC to blue (480 nm) light and compare it to a 10,000 lux white light PRC constructed previously using a similar protocol. Eighteen young healthy participants (18–30 years) were studied for 9–10 days in a time-free environment. The protocol included three baseline days followed by a constant routine (CR) to assess initial circadian phase. Following this CR, participants were exposed to a 6.5 h 480 nm light exposure (11.8 μW cm−2, 11.2 lux) following mydriasis via a modified Ganzfeld dome. A second CR was conducted following the light exposure to re-assess circadian phase. Phase shifts were calculated from the difference in dim light melatonin onset (DLMO) between CRs. Exposure to 6.5 h of 480 nm light resets the circadian pacemaker according to a conventional type 1 PRC with fitted maximum delays and advances of −2.6 h and 1.3 h, respectively. The 480 nm PRC induced ∼75% of the response of the 10,000 lux white light PRC. These results may contribute to a re-evaluation of dosing guidelines for clinical light therapy and the use of light as a fatigue countermeasure. PMID:23090946

Synergistic interactions between temporal coupling of complex light and magnetic pulses upon melanoma cell proliferation and planarian regeneration.

PubMed

Murugan, Nirosha J; Karbowski, Lukasz M; Persinger, Michael A

2017-01-01

Synergisms between a physiologically patterned magnetic field that is known to enhance planarian growth and suppress proliferation of malignant cells in culture and three light emitting diode (LED) generated visible wavelengths (blue, green, red) upon planarian regeneration and melanoma cell numbers were discerned. Five days of hourly exposures to either a physiologically patterned (2.5-5.0 μT) magnetic field, one of three wavelengths (3 kLux) or both treatments simultaneously indicated that red light (680 nm), blue light (470 nm) or the magnetic field significantly facilitated regeneration of planarian compared to sham field exposed planarian. Presentation of both light and magnetic field conditions enhanced the effect. Whereas the blue and red light diminished the growth of malignant (melanoma) cells, the effect was not as large as that produced by the magnetic field. Only the paired presentation of the blue light and magnetic field enhanced the suppression. On the other hand, the changes following green light (540 nm) exposure did not differ from the control condition and green light presented with the magnetic field eliminated its effects for both the planarian and melanoma cells. These results indicate specific colors affect positive adaptation that is similar to weak, physiologically patterned frequency modulated (8-24 Hz) magnetic fields and that the two forms of energy can synergistically summate or cancel.

Advancing spaceborne tools for the characterization of planetary ionospheres and circumstellar environments

NASA Astrophysics Data System (ADS)

Douglas, Ewan Streets

This work explores remote sensing of planetary atmospheres and their circumstellar surroundings. The terrestrial ionosphere is a highly variable space plasma embedded in the thermosphere. Generated by solar radiation and predominantly composed of oxygen ions at high altitudes, the ionosphere is dynamically and chemically coupled to the neutral atmosphere. Variations in ionospheric plasma density impact radio astronomy and communications. Inverting observations of 83.4 nm photons resonantly scattered by singly ionized oxygen holds promise for remotely sensing the ionospheric plasma density. This hypothesis was tested by comparing 83.4 nm limb profiles recorded by the Remote Atmospheric and Ionospheric Detection System aboard the International Space Station to a forward model driven by coincident plasma densities measured independently via ground-based incoherent scatter radar. A comparison study of two separate radar overflights with different limb profile morphologies found agreement between the forward model and measured limb profiles. A new implementation of Chapman parameter retrieval via Markov chain Monte Carlo techniques quantifies the precision of the plasma densities inferred from 83.4 nm emission profiles. This first study demonstrates the utility of 83.4 nm emission for ionospheric remote sensing. Future visible and ultraviolet spectroscopy will characterize the composition of exoplanet atmospheres; therefore, the second study advances technologies for the direct imaging and spectroscopy of exoplanets. Such spectroscopy requires the development of new technologies to separate relatively dim exoplanet light from parent star light. High-contrast observations at short wavelengths require spaceborne telescopes to circumvent atmospheric aberrations. The Planet Imaging Concept Testbed Using a Rocket Experiment (PICTURE) team designed a suborbital sounding rocket payload to demonstrate visible light high-contrast imaging with a visible nulling coronagraph. Laboratory operations of the PICTURE coronagraph achieved the high-contrast imaging sensitivity necessary to test for the predicted warm circumstellar belt around Epsilon Eridani. Interferometric wavefront measurements of calibration target Beta Orionis recorded during the second test flight in November 2015 demonstrate the first active wavefront sensing with a piezoelectric mirror stage and activation of a micromachine deformable mirror in space. These two studies advance our "close-to-home'' knowledge of atmospheres and move exoplanetary studies closer to detailed measurements of atmospheres outside our solar system.

Self-service kiosk for testing sunglasses.

PubMed

Mello, Marcio M; Lincoln, Victor A C; Ventura, Liliane

2014-04-25

Sunglasses users may only be assured on their ultraviolet protection by purchasing certified products, however they are not able to check if sunglasses are still ultraviolet (UV) protected as they age, unless they resort themselves to a professional who is qualified for using a spectrophotometer and is acknowledged on the standards for providing a report for the user. Current literature establishes safe limits on the exposure of the eyes relatively to the ultraviolet radiation exposure for the UVA and UVB ranges (280 nm - 400 nm). The UV protection is category dependent. Sunglasses are categorized from 0 to 4 and the categories are determined by the lenses transmission's percentage on the visible range (380 nm - 780 nm). In order to overcome inaccessibility of such measurements on sunglasses, a prototype for testing ultraviolet protection on sunglasses, according to Brazilian Standards, has been developed for amateur use. The system consists of assembling UVA and UVB light sources and two UV responsive photodiode sensors, with Erythema action response for measuring UV protection; for categories measurements, combination of white light and LEDs were used for the visible range, as well as a light sensor having spectral response similar to the human eye. Electronics has been developed for controlling the measurements and software has been implemented for providing the report as well as for the user's interface. All the system was embedded as a self-service touch screen kiosk and provides transmittance measurements that are within the deviation limit required by NBR15111, i.e., 0.25%. Measurements were performed in over 45 sunglasses and compared to CARY 5000 - VARIAN spectrophotometer and present a good correlation for the measurements of transmittance in the visible spectral range (r2 = 0.9999) and in the ultraviolet range (r2 = 0.9997). The prototype identifies the UV protection, for non-corrective sunglasses, according to category of the lens and is available for the public. In addition to educating the population about the importance of wearing protected sunglasses, the prototype has also allowed the public to have access to information about the quality of protection of their own sunglasses in an easy and free testing method.

Spectral transmittance of intraocular lenses under natural and artificial illumination: criteria analysis for choosing a suitable filter.

PubMed

Artigas, Jose M; Felipe, Adelina; Navea, Amparo; Artigas, Cristina; García-Domene, Maria C

2011-01-01

To compare the spectral transmission of different intraocular lenses (IOLs) with either ultraviolet (UV) or blue-light filters, and to analyze the performance of these filters with artificial light sources as well as sunlight. Experimental study. The spectral transmission curve of 10 IOLs was measured using a PerkinElmer Lambda 800 UV/VIS spectrometer (Waltham, MA). Different filtering simulations were performed using the D65 standard illuminant as daylight and standard incandescent lamp and fluorescent bulb illuminants. Spectral transmittance of the IOLs. All the IOLs studied provide good UVC (200-280 nm) and UVB (280-315 nm) protection, except for one that presented an appreciable window at 270 nm. Nevertheless, both natural and artificial sources have practically no emission under 300 nm. In the UVA (315-380 nm) range the curves of the different IOLs manifested different degrees of absorption. Not all the UV filters incorporated in different IOLs protect equally. The filters that provide greater photoprotection against UV radiation, even blue light, are yellow and orange. Then, yellow and orange IOL filters may be best suited for cases requiring special retinal protection. The filters that favor better photoreception of visible light (380-780 nm) are those that transmit this radiation close to 100%. Artificial illumination practically does not emit in the UV range, but its levels of illumination are very low when compared with solar light. A possible balance between photoprotection and photoreception could be a sharp cutoff filter with the cutoff wavelength near 400 nm and a maximum transmittance around 100%. Copyright © 2011 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

Honing the accuracy of extreme-ultraviolet optical system testing: at-wavelength and visible-light measurements of the ETS Set-2 projection optic

NASA Astrophysics Data System (ADS)

Goldberg, Kenneth A.; Naulleau, Patrick P.; Bokor, Jeffrey; Chapman, Henry N.

2002-07-01

As the quality of optical systems for extreme ultraviolet lithography improves, high-accuracy wavefront metrology for alignment and qualification becomes ever more important. To enable the development of diffraction-limited EUV projection optics, visible-light and EUV interferometries must work in close collaboration. We present a detailed comparison of EUV and visible-light wavefront measurements performed across the field of view of a lithographic-quality EUV projection optical system designed for use in the Engineering Test Stand developed by the Virtual National Laboratory and the EUV Limited Liability Company. The comparisons reveal that the present level of RMS agreement lies in the 0.3-0.4-nm range. Astigmatism is the most significant aberration component for the alignment of this optical system; it is also the dominant term in the discrepancy, and the aberration with the highest measurement uncertainty. With EUV optical systems requiring total wavefront quality in the (lambda) EUV/50 range, and even higher surface-figure quality for the individual mirror elements, improved accuracy through future comparisons, and additional studies, are required.

Two-dimensionally grown single-crystal silicon nanosheets with tunable visible-light emissions.

PubMed

Kim, Sung Wook; Lee, Jaejun; Sung, Ji Ho; Seo, Dong-jae; Kim, Ilsoo; Jo, Moon-Ho; Kwon, Byoung Wook; Choi, Won Kook; Choi, Heon-Jin

2014-07-22

Since the discovery of graphene, growth of two-dimensional (2D) nanomaterials has greatly attracted attention. However, spontaneous growth of atomic two-dimensional (2D) materials is limitedly permitted for several layered-structure crystals, such as graphene, MoS2, and h-BN, and otherwise it is notoriously difficult. Here we report the gas-phase 2D growth of silicon (Si), that is cubic in symmetry, via dendritic growth and an interdendritic filling mechanism and to form Si nanosheets (SiNSs) of 1 to 13 nm in thickness. Thin SiNSs show strong thickness-dependent photoluminescence in visible range including red, green, and blue (RGB) emissions with the associated band gap energies ranging from 1.6 to 3.2 eV; these emission energies were greater than those from Si quantum dots (SiQDs) of the similar sizes. We also demonstrated that electrically driven white, as well as blue, emission in a conventional organic light-emitting diode (OLED) geometry with the SiNS assembly as the active emitting layers. Tunable light emissions in visible range in our observations suggest practical implications for novel 2D Si nanophotonics.

The Enhanced Photo-Electrochemical Detection of Uric Acid on Au Nanoparticles Modified Glassy Carbon Electrode

NASA Astrophysics Data System (ADS)

Shi, Yuting; Wang, Jin; Li, Shumin; Yan, Bo; Xu, Hui; Zhang, Ke; Du, Yukou

2017-07-01

In this work, a sensitive and novel method for determining uric acid (UA) has been developed, in which the glassy carbon electrode (GCE) was modified with electrodeposition Au nanoparticles and used to monitor the concentration of UA with the assistant of visible light illumination. The morphology of the Au nanoparticles deposited on GCE surface were characterized by scanning electron microscope (SEM) and the nanoparticles were found to be well-dispersed spheres with the average diameter approaching 26.1 nm. A series of cyclic voltammetry (CV) and differential pulse voltammetry (DPV) measurements have revealed that the introduction of visible light can greatly enhance both the strength and stability of response current due to the surface plasmon resonance (SPR). Specifically, the DPV showed a linear relationship between peak current and UA concentration in the range of 2.8 to 57.5 μM with the equation of I pa (μA) = 0.0121 c UA (μM) + 0.3122 ( R 2 = 0.9987). Herein, the visible light illuminated Au/GCE possesses a potential to be a sensitive electrochemical sensor in the future.

Sentinel Node Mapping Using a Fluorescent Dye and Visible Light During Laparoscopic Gastrectomy for Early Gastric Cancer: Result of a Prospective Study From a Single Institute.

PubMed

Lee, Chang Min; Park, Sungsoo; Park, Seong-Heum; Jung, Sung Woo; Choe, Jung Wan; Sul, Ji-Young; Jang, You Jin; Mok, Young-Jae; Kim, Jong-Han

2017-04-01

The aim of this study was to investigate the feasibility of sentinel node mapping using a fluorescent dye and visible light in patients with gastric cancer. Recently, fluorescent imaging technology offers improved visibility with the possibility of better sensitivity or accuracy in sentinel node mapping. Twenty patients with early gastric cancer, for whom laparoscopic distal gastrectomy with standard lymphadenectomy had been planned, were enrolled in this study. Before lymphadenectomy, the patients received a gastrofiberoscopic peritumoral injection of fluorescein solution. The sentinel basin was investigated via laparoscopic fluorescent imaging under blue light (wavelength of 440-490 nm) emitted from an LED curing light. The detection rate and lymph node status were analyzed in the enrolled patients. In addition, short-term clinical outcomes were also investigated. No hypersensitivity to the dye was identified in any enrolled patients. Sentinel nodes were detected in 19 of 20 enrolled patients (95.0%), and metastatic lymph nodes were found in 2 patients. The latter lymph nodes belonged to the sentinel basin of each patient. Meanwhile, 1 patient (5.0%) experienced a postoperative complication that was unrelated to sentinel node mapping. No mortality was recorded among enrolled cases. Sentinel node mapping with visible light fluorescence was a feasible method for visualizing sentinel nodes in patients with early gastric cancer. In addition, this method is advantageous in terms of visualizing the concrete relationship between the sentinel nodes and surrounding structures.

Inspection of lithographic mask blanks for defects

DOEpatents

Sommargren, Gary E.

2001-01-01

A visible light method for detecting sub-100 nm size defects on mask blanks used for lithography. By using optical heterodyne techniques, detection of the scattered light can be significantly enhanced as compared to standard intensity detection methods. The invention is useful in the inspection of super-polished surfaces for isolated surface defects or particulate contamination and in the inspection of lithographic mask or reticle blanks for surface defects or bulk defects or for surface particulate contamination.

A new nano-TiO2 immobilized biodegradable polymer with self-cleaning properties.

PubMed

Sökmen, Münevver; Tatlıdil, Ilknur; Breen, Chris; Clegg, Francis; Buruk, Celal Kurtuluş; Sivlim, Tuğba; Akkan, Senay

2011-03-15

This study concentrated on the direct immobilization of anatase nano titanium dioxide particles (TiO(2), 10nm particle size) into or onto a biodegradable polymer, polycaprolactone, by solvent-cast processes. The self-cleaning, namely photocatalytic properties of the produced materials were tested by photocatalytic removal of methylene blue as model compound and antimicrobial properties were investigated using Candida albicans as model microorganism. Produced TiO(2) immobilized polymer successfully removed methylene blue (MB, 1 × 10(-5)M) from aqueous solution without additional pH arrangement employing a UV-A light (365 nm) source. Almost 83.2% of dye was removed or decomposed by 5 wt% TiO(2) immobilized into PCL (0.08 g) and removal percentage reached to 94.2% with 5 wt% TiO(2) immobilized onto PCL after a 150 min exposure period. Although removal percentage decrease with increased ionic strength and usage of a visible light source, produced materials were still effective. TiO(2) immobilized onto PCL (5 wt%) was quite effective killing almost 54% of C. albicans (2 × 10(6)CFU/mL) after only 60 min exposure with a near visible light source. Control experiments employing PCL alone in the presence and absence of light were ineffective under the same condition. Copyright © 2011 Elsevier B.V. All rights reserved.

Enhanced near-infrared to visible upconversion nanoparticles of Ho³⁺-Yb³⁺-F⁻ tri-doped TiO₂ and its application in dye-sensitized solar cells with 37% improvement in power conversion efficiency.

PubMed

Yu, Jia; Yang, Yulin; Fan, Ruiqing; Liu, Danqing; Wei, Liguo; Chen, Shuo; Li, Liang; Yang, Bin; Cao, Wenwu

2014-08-04

New near-infrared (NIR)-to-green upconversion nanoparticles of Ho(3+)-Yb(3+)-F(-) tridoped TiO2 (UC-F-TiO2) were designed and fabricated via the hydrosol-hydrothermal method. Under 980 nm NIR excitation, UC-F-TiO2 emit strong green upconversion fluorescence with three emission bands at 543, 644, and 751 nm and convert the NIR light in situ to the dye-sensitive visible light that could effectively reduce the distance between upconversion materials and sensitizers; thus, they minimize the loss of the converted light. Our results show that this UC-F-TiO2 offers excellent opportunities for the other types of solar cells applications, such as organic solar cells, c-Si solar cells, multijunction solar cells, and so on. When integrating the UC-F-TiO2 into dye-sensitized solar cells (DSSCs), superior total energy conversion efficiency was achieved. Under AM1.5G light, open-circuit voltage reached 0.77 ± 0.01 V, short-circuit current density reached 21.00 ± 0.69 mA cm(-2), which resulted in an impressive overall energy conversion efficiency of 9.91 ± 0.30%, a 37% enhancement compared to DSSCs with pristine TiO2 photoanode.

FT-Raman study of dehydrogenation polymer (DHP) lignins

Treesearch

Umesh P. Agarwal; Noritsugu Terashima

2003-01-01

Compared to conventional Raman spectroscopy where samples are excited using visible light lasers, 1064 nm-excited FT-Raman technique has the single most important advantage that the sample-fluorescence is significantly suppressed for samples that are strongly fluorescent. DHPs are difficult to analyze in conventional Raman because small amounts of chromophores present...

The effects of 405-nm visible light on the survival of Campylobacter on chicken skin and stainless steel

USDA-ARS?s Scientific Manuscript database

Campylobacter spp. are major food-borne pathogens responsible for a significant portion of the human cases of bacterial mediated gastrointestinal disease, and poultry products are an important source of infections. Reducing the numbers of this pathogen on poultry products should lower the incidence...

Enhanced optical discrimination system based on switchable retroreflective films

NASA Astrophysics Data System (ADS)

Schultz, Phillip; Heikenfeld, Jason

2016-04-01

Reported herein is the design, characterization, and demonstration of a laser interrogation and response optical discrimination system based on large-area corner-cube retroreflective films. The switchable retroreflective films use light-scattering liquid crystal to modulate retroreflected intensity. The system can operate with multiple wavelengths (visible to infrared) and includes variable divergence optics for irradiance adjustments and ease of system alignment. The electronic receiver and switchable retroreflector offer low-power operation (<4 mW standby) on coin cell batteries with rapid interrogation to retroreflected signal reception response times (<15 ms). The entire switchable retroreflector film is <1 mm thick and is flexible for optimal placement and increased angular response. The system was demonstrated in high ambient lighting conditions (daylight, 18k lux) with a visible 10-mW output 635-nm source out to a distance of 400 m (naked eye detection). Nighttime demonstrations were performed using a 1.5-mW, 850-nm infrared laser diode out to a distance of 400 m using a night vision camera. This system could have tagging and conspicuity applications in commercial or military settings.

In situ photodeposition of cobalt on CdS nanorod for promoting photocatalytic hydrogen production under visible light irradiation

NASA Astrophysics Data System (ADS)

Chen, Wei; Wang, Yanhong; Liu, Mei; Gao, Li; Mao, Liqun; Fan, Zeyun; Shangguan, Wenfeng

2018-06-01

Non-noble metal Co were loaded on CdS for enhancing photocatalytic activity of water splitting by a simple and efficient in situ photodeposition method. The Co particles with diameter ca. 5 nm were photoreduced and then loaded on the surface of CdS. The loading of Co can not only effectively promote the separation of electrons and holes photoexcited by CdS, but reduce the overpotential of hydrogen evolution as well, thus enhancing photocatalytic activity of water splitting. The highest photocatalytic H2 evolution rate of Co/CdS reaches up to 1299 μmol h-1 under visible light irradiation(λ > 420 nm) when the amount of loading is 1.0 wt%, which is 17 times of that of pure CdS and achieves 80% of that of 0.5 wt%Pt/CdS. This work not only exhibits a pathway to obtain photocatalysts with high photocatalytic activity for hydrogen production, but provides a possibility for the utilization of low cost Co as a substitute for noble metals in photocatalytic hydrogen production.

Transmittance of MCF-7 breast tumor cell line through visible and near infrared spectrum

NASA Astrophysics Data System (ADS)

Tabakoǧlu, H. Ã.-zgür

2016-03-01

In this study, light transmittance of MCF-7 tumor cells from 450 nm to 1100 nm has been measured in their growing medium and evaluated. Transmittance differences have been tried to be put forward in cancer cell line on visible (VIS) and near infrared (NIR) spectrum as well as in between different numbers of cells in medium. An absorption-reflection spectrophotometer was used in the experiments. System has a tungsten light source, optical chopper, a monochromator, sample chamber, silicon detectors, lock-in amplifier and computer. System was controlled by software in order to adjust scan range, scan steps and grating configuration. Cells were grown in medium, and measurements were taken from cells while they were in 5 ml medium. According to our findings, there are significant differences between VIS and NIR regions for the same number of cells. There were found no statistical difference among different numbers of cells. Increasing number of cells has not affected the transmittance. Transmittance of medium is not significantly different from different concentration of cells.

One-pot synthesis of metal-organic framework@SiO2 core-shell nanoparticles with enhanced visible-light photoactivity.

PubMed

Li, Zong-Qun; Wang, Ai; Guo, Chun-Yan; Tai, Yan-Fang; Qiu, Ling-Guang

2013-10-14

This paper presents a novel strategy to prepare Cu3(BTC)2@SiO2 core-shell nanoparticles in the size range of 200-400 nm using a new one-pot strategy under ultrasonic irradiation at room temperature. In this approach, the silica shell thickness could be finely tuned in the size range of 12-60 nm for various reaction times. Nanocomposite thin films were fabricated on the glass substrates by Sol-Gel spin coating using the products for 1.5 h, 2 h and 2.5 h, respectively, and heat treated using an infrared lamp heating system in air. The photocatalytic degradation of phenol in aqueous solution using Cu2(BTC)3@SiO2 thin films was investigated under visible light irradiation at pH 4. After a 45 min reaction with phenol, the degradation rate was up to 93.1%. Moreover, the thin film photocatalysts could be reused 5 times without appreciable loss of photocatalytic activity for degradation of phenol. The present work clearly shows that the films as photocatalysts showed higher photocatalytic performance.

Fabrication of a TiO2@porphyrin nanofiber hybrid material: a highly efficient photocatalyst under simulated sunlight irradiation

NASA Astrophysics Data System (ADS)

La, Duong Duc; Rananaware, Anushri; Phuong Nguyen Thi, Hoai; Jones, Lathe; Bhosale, Sheshanath V.

2017-03-01

The solar spectrum consists of 8% UV radiation, while 45% of solar energy is from visible light. It is therefore desirable to fabricate a hybrid material which is able to harvest energy from a wide range of photons from the sun for applications such as solar cells, photovoltaics, and photocatalysis. In this study we report on the fabrication of a TiO2@porphyrin hybrid material by surfactant-assisted co-assembly of monomeric porphyrin molecules with TiO2 nanoparticles. The obtained TiO2@porphyrin composite shows excellent integration of TiO2 particles with diameters of 15-30 nm into aggregated porphyrin nanofibers, which have a width of 70-90 nm and are several µm long. SEM, XPS, XRD, FTIR, UV-Vis and fluorescence spectroscopy were employed to characterize the TiO2@TCPP hybrid material. This material exhibits efficient photocatalytic performance under simulated sunlight, due to synergistic photocatalytic activities of the porphyrin aggregates in visible light and TiO2 particles in the UV region. A plausible mechanism for photocatalytic degradation is also proposed and discussed.

Supercontinuum white light lasers for flow cytometry

PubMed Central

Telford, William G.; Subach, Fedor V.; Verkhusha, Vladislav V.

2009-01-01

Excitation of fluorescent probes for flow cytometry has traditionally been limited to a few discrete laser lines, an inherent limitation in our ability to excite the vast array of fluorescent probes available for cellular analysis. In this report, we have used a supercontinuum (SC) white light laser as an excitation source for flow cytometry. By selectively filtering the wavelength of interest, almost any laser wavelength in the visible spectrum can be separated and used for flow cytometric analysis. The white light lasers used in this study were integrated into a commercial flow cytometry platform, and a series of high-transmission bandpass filters used to select wavelength ranges from the blue (~480 nm) to the long red (>700 nm). Cells labeled with a variety of fluorescent probes or expressing fluorescent proteins were then analyzed, in comparison with traditional lasers emitting at wavelengths similar to the filtered SC source. Based on a standard sensitivity metric, the white light laser bandwidths produced similar excitation levels to traditional lasers for a wide variety of fluorescent probes and expressible proteins. Sensitivity assessment using fluorescent bead arrays confirmed that the SC laser and traditional sources resulted in similar levels of detection sensitivity. Supercontinuum white light laser sources therefore have the potential to remove a significant barrier in flow cytometric analysis, namely the limitation of excitation wavelengths. Almost any visible wavelength range can be made available for excitation, allowing access to virtually any fluorescent probe, and permitting “fine-tuning” of excitation wavelength to particular probes. PMID:19072836

Photochemistry and reactivity of the phenyl radical-water system: a matrix isolation and computational study.

PubMed

Mardyukov, Artur; Crespo-Otero, Rachel; Sanchez-Garcia, Elsa; Sander, Wolfram

2010-08-02

The reaction of the phenyl radical 1 with water has been investigated by using matrix isolation spectroscopy and quantum chemical calculations. The primary thermal product of the reaction between 1 and water is a weakly bound complex stabilized by an OH...pi interaction. This complex is photolabile, and visible-light irradiation (lambda>420 nm) results in hydrogen atom transfer from water to radical 1 and the formation of a highly labile complex between benzene and the OH radical. This complex is stable under the conditions of matrix isolation, however, continuous irradiation with lambda>420 nm light results in the complete destruction of the aromatic system and formation of an acylic unsaturated ketene. The mechanisms of all reaction steps are discussed in the light of ab initio and DFT calculations.

Solution epitaxy of gallium-doped ZnO on p-GaN for heterojunction light-emitting diodes

NASA Astrophysics Data System (ADS)

Le, H. Q.; Lim, S. K.; Goh, G. K. L.; Chua, S. J.; Ang, N. S. S.; Liu, W.

2010-09-01

We report white light emission from a Ga-doped ZnO/p-GaN heterojunction light-emitting diode which was fabricated by growing gallium-doped ZnO film on the p-GaN in water at 90°C. As determined from Ga-doped ZnO films grown on (111) oriented MgAl2O4 spinel single crystal substrates, thermal treatment at 600°C in nitrogen ambient leads to a carrier concentration of 3.1×1020 cm-3 (and carrier mobility of 28 cm2/Vs) which is two orders of magnitude higher than that of the undoped films. Electroluminescence emissions at wavelengths of 393 nm (3.155 eV) and 529.5 nm (2.4 eV) were observed under forward bias in the heterojunction diode and white light could be visibly observed. The high concentration of electrons supplied from the Ga-doped ZnO films helped to enhance the carrier recombination and increase the light-emitting efficiency of the heterojunction diode.

AlGaInN laser diode technology for GHz high-speed visible light communication through plastic optical fiber and water

NASA Astrophysics Data System (ADS)

Najda, Stephen P.; Perlin, Piotr; Suski, Tadek; Marona, Lucja; Leszczyński, Mike; Wisniewski, Przemek; Czernecki, Robert; Kucharski, Robert; Targowski, Grzegorz; Watson, Malcolm A.; White, Henry; Watson, Scott; Kelly, Antony E.

2016-02-01

AlGaInN ridge waveguide laser diodes are fabricated to achieve single-mode operation with optical powers up to 100 mW at ˜420 nm for visible free-space, underwater, and plastic optical fiber communication. We report high-frequency operation of AlGaInN laser diodes with data transmission up to 2.5 GHz for free-space and underwater communication and up to 1.38 GHz through 10 m of plastic optical fiber.

Atmospheric skin aging-Contributors and inhibitors.

PubMed

McDaniel, David; Farris, Patricia; Valacchi, Giuseppe

2018-04-01

Cutaneous aging is a complex biological process consisting of 2 elements: intrinsic aging, which is primarily determined by genetics, and extrinsic aging, which is largely caused by atmospheric factors, such as exposure to sunlight and air pollution, and lifestyle choices, such as diet and smoking. The role of the solar spectrum, comprised of ultraviolet light, specifically UVB (290-320 nm) and UVA (320-400) in causing skin damage, including skin cancers, has been well documented. In recent years, the contribution of visible light (400-700 nm) and infrared radiation (above 800 nm) in causing skin damage, similar to the photodamage caused by UV light, is also being elucidated. In addition, other atmospheric factors such as air pollution (smog, ozone, particulate matter, etc.) have been implicated in premature skin aging. The skin damage caused by environmental exposure is largely attributable to a complex cascade of reactions inside the skin initiated by the generation of reactive oxygen species (ROS), which causes oxidative damage to cellular components such as proteins, lipids, and nucleic acids. These damaged skin cells initiate inflammatory responses leading to the eventual damage manifested in chronically exposed skin. Novel therapeutic strategies to combat ROS species generation are being developed to prevent the skin damage caused by atmospheric factors. In addition to protecting skin from solar radiation using sunscreens, other approaches using topically applied ingredients, particularly antioxidants that penetrate the skin and protect the skin from within, have also been well documented. This review summarizes current knowledge of atmospheric aggressors, including UVA, UVB, visible light, infrared radiation (IR), and ozone on skin damage, and proposes new avenues for future research in the prevention and treatment of premature skin aging caused by such atmospheric factors. New therapeutic modalities currently being developed are also discussed. © 2018 Wiley Periodicals, Inc.

The effect of metal cluster deposition route on structure and photocatalytic activity of mono- and bimetallic nanoparticles supported on TiO2 by radiolytic method

NASA Astrophysics Data System (ADS)

Klein, Marek; Nadolna, Joanna; Gołąbiewska, Anna; Mazierski, Paweł; Klimczuk, Tomasz; Remita, Hynd; Zaleska-Medynska, Adriana

2016-08-01

TiO2 (P25) was modified with small and relatively monodisperse mono- and bimetallic clusters (Ag, Pd, Pt, Ag/Pd, Ag/Pt and Pd/Pt) induced by radiolysis to improve its photocatalytic activity. The as-prepared samples were characterized by X-ray fluorescence spectrometry (XRF), photoluminescence spectrometry (PL), diffuse reflectance spectroscopy (DRS), X-ray powder diffractometry (XRD), scanning transition electron microscopy (STEM) and BET surface area analysis. The effect of metal type (mono- and bimetallic modification) as well as deposition method (simultaneous or subsequent deposition of two metals) on the photocatalytic activity in toluene removal in gas phase under UV-vis irradiation (light-emitting diodes- LEDs) and phenol degradation in liquid phase under visible light irradiation (λ > 420 nm) were investigated. The highest photoactivity under Vis light was observed for TiO2 co-loaded with platinum (0.1%) and palladium (0.1%) clusters. Simultaneous addition of metal precursors results in formation of larger metal nanoparticles (15-30 nm) on TiO2 surface and enhances the Vis-induced activity of Ag/Pd-TiO2 up to four times, while the subsequent metal ions addition results in formation of metal particle size ranging from 4 to 20 nm. Subsequent addition of metal precursors results in formation of BNPs (bimetallic nanoparticle) composites showing higher stability in four cycles of toluene degradation under UV-vis. Obtained results indicated that direct electron transfer from the BNPs to the conduction band of the semiconductor is responsible for visible light photoactivity, whereas superoxide radicals (such as O2rad- and rad OOH) are responsible for pollutants degradation over metal-TiO2 composites.

Path length and spectrum of single-cycle mid-IR light bullets in transparent dielectrics

NASA Astrophysics Data System (ADS)

Chekalin, S. V.; Kompanets, V. O.; Dormidonov, A. E.; Kandidov, V. P.

2018-04-01

Filamentation of femtosecond laser radiation with a wavelength of 800 – 3900 nm and a power slightly exceeding the critical self-focusing power is studied using the spectral method and the method of laser coloration in LiF crystal. It is found that the length of a filament formed in the single-pulse regime increases with increasing excitation wavelength from a few tens of micrometres at 80 nm to hundreds of micrometres at 3900 nm. In the spectral region of anomalous group velocity dispersion, starting from 2600 nm, the initially smooth luminescence profile of the long-lived induced colour centres acquires a periodic structure, demonstrating the formation of a light bullet with a duration of about one cycle of the light field oscillation and a diameter smaller than 10 μm. The path length of such bullets does not exceed 0.5 mm in the single-pulse regime and 2.7 mm in the waveguide regime. A consequence of periodic modulation of the bullet light field in the process of propagation, observed experimentally and confirmed by calculations, is the appearance of sidebands near the excitation wavelength, as well as the appearance of visible spectral components in the supercontinuum radiation, whose angular divergence increases with increasing wavelength.

[Spectral Analysis of CdZnSe Ternary Quantum Dots Sensitized TiO2 Tubes and Its Application in Visible-Light Photocatalysis].

PubMed

Han, Zhi-zhong; Ren, Li-li; Pan, Hai-bo; Li, Chun-yan; Chen, Jing-hua; Chen, Jian-zhong

2015-11-01

In this work, cadmium nitrate hexahydrate [Cd(NO₃)₂ · 6H₂O] is as a source of cadmium, zinc nitrate [Zn(NO₃)₂] as a source of zinc source, and NaHSe as a source of selenium which was prepared through reducing the elemental selenium with sodium borohydride (NaBH₄). Then water-soluble Cd₁₋xZnxSe ternary quantum dots with different component were prepared by colloid chemistry. The as-prepared Cd₁₋xZnx Se ternary quantum dots exhibit stable fluorescent property in aqueous solution, and can still maintain good dispersivity at room temperature for four months. Powder X-ray diffraction (XRD) and high resolution transmission electron microscope (HRTEM) were used to analyze crystal structure and morphology of the prepared Cd₁₋xZnxSe. It is found that the as-prepared ternary quantum dots are cubic phase, show as sphere, and the average of particle size is approximate 4 nm. The spectral properties and energy band structure of the as-prepared ternary quantum dots were modulated through changing the atom ratio of elements Zn and Cd. Compared with binary quantum dots CdSe and ZnSe, the ultraviolet-visible (UV-Visible) absorption spectrum and fluorescence (FL) emission spectrum of ternary quantum dots are both red-shift. The composites (Cd₀.₅ Zn₀.₅ Se@TNTs) of Cd₀.₅ Zn₀.₅ Se ternary quantum dots and TiO₂ nanotubes (TNTs) were prepared by directly immerging TNTs into quantum dots dispersive solution for 5 hours. TEM image shows that the Cd₀.₅ Zn₀.₅ Se ternary quantum dots were closely combined to nanotube surface. The infrared spectra show that the Ti-Se bond was formed between Cd₀.₅ Zn₀.₅ Se ternary quantum dots and TiO₂ nanotubes, which improve the stability of the composite. Compared to pristine TNTs, UV-Visible absorption spectrum of the composites is significantly enhanced in the visible region of light. And the absorption band edge of Cd₀.₅Zn₀.₅ Se@TNTs red-shift from 400 to 700 nm. The recombination of the photogenerated electron-hole pairs was restrained with the as-prepared ternary quantum dots. Therefore, the visible-light photocatalytic efficiency was greatly improved. After visible-light irradiation for 60 min, the degradation of Cd₀.₅ Zn₀.₅ Se@TNTs photocatalysts for RhB is nearly 100%, which is about 3. 3 times of that of pristine TNTs and 2. 5 times of that of pure Cd₀.₅ Zn₀.₅ Se ternary quantum dots, respectively.

Synthesis of nano-TiO2 photocatalysts with tunable Fe doping concentration from Ti-bearing tailings

NASA Astrophysics Data System (ADS)

Sui, Yulei; Liu, Qingxia; Jiang, Tao; Guo, Yufeng

2018-01-01

In this work, highly pure nano-TiO2 photocatalysts with varying Fe doping concentration were successfully synthesized from low-cost Ti-bearing tailings by an acidolysis-hydrothermal route. The effects of H2SO4 concentration, leaching temperature, acid/tailings ratio and leaching time on the recovery of TiO2 from the tailings were investigated. Synthesized samples were characterized by XRD, TEM, EDS, XPS, and UV-vis spectroscopy. The results showed that the material prepared is characteristic anatase with the average size of 20 nm and the Fe doping concentration in the synthesized nano-TiO2 is tunable. The photocatalytic activity of synthesized nano-TiO2 photocatalyst was also evaluated by the photodegradation of Rhodamine B under visible light and UV light irradiation. Our study demonstrates a low-cost approach to synthesize highly efficient and visible light responsive catalysts.

Development of UV-curable liquid for in-liquid fluorescence alignment in ultraviolet nanoimprint lithography

NASA Astrophysics Data System (ADS)

Ochiai, Kento; Kikuchi, Eri; Ishito, Yota; Kumagai, Mari; Nakamura, Takahiro; Nakagawa, Masaru

2018-06-01

We studied a fluorescent UV-curable resin suitable for fluorescence alignment in UV nanoimprinting. The addition of a cationic fluorescent dye caused radical photopolymerization of a UV-curable resin by exposure to visible excitation light for fluorescence microscope observation. The microscope observation of a resin film prepared by pressing resin droplets on a silica substrate with a fluorinated silica superstrate revealed that the cationic dye molecules were preferably adsorbed onto the silica surface. It was indicated that the dye molecules concentrated on the silica surface may cause the photocuring. A nonionic fluorescent dye was selected owing to its low polar symmetrical structure and its solubility parameter close to monomers. The fluorescent UV-curable resin with the nonionic dye showed uncured stability to exposure to visible excitation light for 30 min with a light intensity of 8.5 mW cm‑2 detected at 530 nm.

Preparation and Application of Immobilized Surfactant-Modified PANi-CNT/TiO2 under Visible-Light Irradiation

PubMed Central

Yuan, Ching; Hung, Chung-Hsuang; Yuan, Chung-Shin; Li, Huei-Wen

2017-01-01

Hydrothermally and sol-gel-synthesized immobilized surfactant-modified polyaniline-carbon nanotubes/TiO2 (PANi-CNT/TiO2) photocatalysts were prepared and their application in the degradation of diethyl phthalate (DEP) under visible light at 410 nm was investigated in this sturdy. To improve the dispersion of nanoparticles and the transfer of electrons, the TiO2 surface was modified with both sodium dodecyl sulfate (SDS) and functionalized carbon nanotubes (CNT-COOH and CNT-COCl). With the addition of PANi, which was increased from 1–5%, the adsorption edge of the prepared photocatalysts shifted to 442 nm. The SDS linked the PANi polymers to achieve a thickness of coating of the film of up to 314–400 nm and 1301–1600 nm for sol-gel hydrolysis and hydrothermally-synthesized photocatalysts, respectively. An appropriate film thickness would extend the transfer path of the electrons and inhibit the recombination of the electrons and the electron-holes. The photo-degradation performance of DEP by the hydrothermally-synthesized photocatalysts was better than those by sol-gel hydrolysis. The results revealed that the hydroxyl radicals were the key oxidant in the degradation of DEP using hydrothermally-synthesized PANi-CNT/TiO2 photocatalysts. The morphology and functional groups of the raw materials of photocatalysts were characterized and a comparison of photocatalytic activity with other TiO2-based photocatalysts was also provided. PMID:28773238

Broadband white light emission from Ce:AlN ceramics: High thermal conductivity down-converters for LED and laser-driven solid state lighting

NASA Astrophysics Data System (ADS)

Wieg, A. T.; Penilla, E. H.; Hardin, C. L.; Kodera, Y.; Garay, J. E.

2016-12-01

We introduce high thermal conductivity aluminum nitride (AlN) as a transparent ceramic host for Ce3+, a well-known active ion dopant. We show that the Ce:AlN ceramics have overlapping photoluminescent (PL) emission peaks that cover almost the entire visible range resulting in a white appearance under 375 nm excitation without the need for color mixing. The PL is due to a combination of intrinsic AlN defect complexes and Ce3+ electronic transitions. Importantly, the peak intensities can be tuned by varying the Ce concentration and processing parameters, causing different shades of white light without the need for multiple phosphors or light sources. The Commission Internationale de l'Eclairage coordinates calculated from the measured spectra confirm white light emission. In addition, we demonstrate the viability of laser driven white light emission by coupling the Ce:AlN to a readily available frequency tripled Nd-YAG laser emitting at 355 nm. The high thermal conductivity of these ceramic down-converters holds significant promise for producing higher power white light sources than those available today.

Two-dimensional photonic crystal arrays for polymer:fullerene solar cells.

PubMed

Nam, Sungho; Han, Jiyoung; Do, Young Rag; Kim, Hwajeong; Yim, Sanggyu; Kim, Youngkyoo

2011-11-18

We report the application of two-dimensional (2D) photonic crystal (PC) array substrates for polymer:fullerene solar cells of which the active layer is made with blended films of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). The 2D PC array substrates were fabricated by employing a nanosphere lithography technique. Two different hole depths (200 and 300 nm) were introduced for the 2D PC arrays to examine the hole depth effect on the light harvesting (trapping). The optical effect by the 2D PC arrays was investigated by the measurement of optical transmittance either in the direction normal to the substrate (direct transmittance) or in all directions (integrated transmittance). The results showed that the integrated transmittance was higher for the 2D PC array substrates than the conventional planar substrate at the wavelengths of ca. 400 nm, even though the direct transmittance of 2D PC array substrates was much lower over the entire visible light range. The short circuit current density (J(SC)) was higher for the device with the 2D PC array (200 nm hole depth) than the reference device. However, the device with the 2D PC array (300 nm hole depth) showed a slightly lower J(SC) value at a high light intensity in spite of its light harvesting effect proven at a lower light intensity.

Identification of cyanobacteriochromes detecting far-red light

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rockwell, Nathan C.; Martin, Shelley S.; Lagarias, J. Clark

The opacity of mammalian tissue to visible light and the strong attenuation of infrared light by water at ≥900 nm have contributed to growing interest in the development of far-red and near-infrared absorbing tools for visualizing and actuating responses within live cells. Here we report the discovery of cyanobacteriochromes (CBCRs) responsive to light in this far-red window. CBCRs are linear tetrapyrrole (bilin)-based light sensors distantly related to plant phytochrome sensors. Our studies reveal far-red (λ max = 725–755 nm)/orange (λ max = 590–600 nm) and far-red/red (λ max = 615–685 nm) photoswitches that are small (<200 amino acids) and canmore » be genetically reconstituted in living cells. Phylogenetic analysis and characterization of additional CBCRs demonstrated that far-red/orange CBCRs evolved after a complex transition from green/red CBCRs known for regulating complementary chromatic acclimation. Incorporation of different bilin chromophores demonstrated that tuning mechanisms responsible for red-shifted chromophore absorption act at the A-, B-, and/ or C-rings, whereas photoisomerization occurs at the D-ring. Two such proteins exhibited detectable fluorescence extending well into the near-infrared region. In conclusion, this work extends the spectral window of CBCRs to the edge of the infrared, raising the possibility of using CBCRs in synthetic biology applications in the far-red region of the spectrum.« less

Identification of cyanobacteriochromes detecting far-red light

DOE PAGES

Rockwell, Nathan C.; Martin, Shelley S.; Lagarias, J. Clark

2016-06-13

The opacity of mammalian tissue to visible light and the strong attenuation of infrared light by water at ≥900 nm have contributed to growing interest in the development of far-red and near-infrared absorbing tools for visualizing and actuating responses within live cells. Here we report the discovery of cyanobacteriochromes (CBCRs) responsive to light in this far-red window. CBCRs are linear tetrapyrrole (bilin)-based light sensors distantly related to plant phytochrome sensors. Our studies reveal far-red (λ max = 725–755 nm)/orange (λ max = 590–600 nm) and far-red/red (λ max = 615–685 nm) photoswitches that are small (<200 amino acids) and canmore » be genetically reconstituted in living cells. Phylogenetic analysis and characterization of additional CBCRs demonstrated that far-red/orange CBCRs evolved after a complex transition from green/red CBCRs known for regulating complementary chromatic acclimation. Incorporation of different bilin chromophores demonstrated that tuning mechanisms responsible for red-shifted chromophore absorption act at the A-, B-, and/ or C-rings, whereas photoisomerization occurs at the D-ring. Two such proteins exhibited detectable fluorescence extending well into the near-infrared region. In conclusion, this work extends the spectral window of CBCRs to the edge of the infrared, raising the possibility of using CBCRs in synthetic biology applications in the far-red region of the spectrum.« less

2D Measurements of the Balmer Series in Proto-MPEX using a Fast Visible Camera Setup

NASA Astrophysics Data System (ADS)

Lindquist, Elizabeth G.; Biewer, Theodore M.; Ray, Holly B.

2017-10-01

The Prototype Material Plasma Exposure eXperiment (Proto-MPEX) is a linear plasma device with densities up to 1020 m-3 and temperatures up to 20 eV. Broadband spectral measurements show the visible emission spectra are solely due to the Balmer lines of deuterium. Monochromatic and RGB color Sanstreak SC1 Edgertronic fast visible cameras capture high speed video of plasmas in Proto-MPEX. The color camera is equipped with a long pass 450 nm filter and an internal Bayer filter to view the Dα line at 656 nm on the red channel and the Dβ line at 486 nm on the blue channel. The monochromatic camera has a 434 nm narrow bandpass filter to view the Dγ intensity. In the setup, a 50/50 beam splitter is used so both cameras image the same region of the plasma discharge. Camera images were aligned to each other by viewing a grid ensuring 1 pixel registration between the two cameras. A uniform intensity calibrated white light source was used to perform a pixel-to-pixel relative and an absolute intensity calibration for both cameras. Python scripts that combined the dual camera data, rendering the Dα, Dβ, and Dγ intensity ratios. Observations from Proto-MPEX discharges will be presented. This work was supported by the US. D.O.E. contract DE-AC05-00OR22725.

Investigation of Electrical and Optical Properties of Highly Transparent TCO/Ag/TCO Multilayer.

PubMed

Kim, Sunbo; Lee, Jaehyeong; Dao, Vinh Ai; Ahn, Shihyun; Hussain, Shahzada Qamar; Park, Jinjoo; Jung, Junhee; Lee, Chan; Song, Bong-Shik; Choi, Byoungdeog; Lee, Youn-Jung; Iftiquar, S M; Yi, Junsin

2015-03-01

Transparent conductive oxides (TCOs) have been widely used as transparent electrodes for opto-electronic devices, such as solar cells, flat-panel displays, and light-emitting diodes, because of their unique characteristics of high optical transmittance and low electrical resistivity. Among various TCO materials, zinc oxide based films have recently received much attention because they have advantages over commonly used indium and tin-based oxide films. Most TCO films, however, exhibit valleys of transmittance in the wavelength range of 550-700 nm, lowering the average transmittance in the visible region and decreasing short-circuit current (Isc) of solar cells. A TCO/Ag/TCO multi-layer structure has emerged as an attractive alternative because it provides optical characteristics without the valley of transmittance compared with a 100-nm-thick single-layer TCO. In this article, we report the electrical, optical and surface properties of TCO/Ag/TCO. These multi-layers were deposited at room temperature with various Ag film thicknesses from 5 to 15 nm while the thickness of TCO thin film was fixed at 40 nm. The TCO/Ag/TCO multi-layer with a 10-nm-thick Ag film showed optimum transmittance in the visible (400-800 nm) wavelength region. These multi-layer structures have advantages over TCO layers of the same thickness.

Spitzer Space Telescope Mid-IR Light Curves of Neptune

NASA Technical Reports Server (NTRS)

Stauffer, John; Marley, Mark S.; Gizis, John E.; Rebull, Luisa; Carey, Sean J.; Krick, Jessica; Ingalls, James G.; Lowrance, Patrick; Glaccum, William; Kirkpatrick, J. Davy;

Visible-Infrared Hyperspectral Image Projector

NASA Technical Reports Server (NTRS)

Bolcar, Matthew

2013-01-01

The VisIR HIP generates spatially-spectrally complex scenes. The generated scenes simulate real-world targets viewed by various remote sensing instruments. The VisIR HIP consists of two subsystems: a spectral engine and a spatial engine. The spectral engine generates spectrally complex uniform illumination that spans the wavelength range between 380 nm and 1,600 nm. The spatial engine generates two-dimensional gray-scale scenes. When combined, the two engines are capable of producing two-dimensional scenes with a unique spectrum at each pixel. The VisIR HIP can be used to calibrate any spectrally sensitive remote-sensing instrument. Tests were conducted on the Wide-field Imaging Interferometer Testbed at NASA s Goddard Space Flight Center. The device is a variation of the calibrated hyperspectral image projector developed by the National Institute of Standards and Technology in Gaithersburg, MD. It uses Gooch & Housego Visible and Infrared OL490 Agile Light Sources to generate arbitrary spectra. The two light sources are coupled to a digital light processing (DLP(TradeMark)) digital mirror device (DMD) that serves as the spatial engine. Scenes are displayed on the DMD synchronously with desired spectrum. Scene/spectrum combinations are displayed in rapid succession, over time intervals that are short compared to the integration time of the system under test.

Optical analysis of nanoparticles via enhanced backscattering facilitated by 3-D photonic nanojets

NASA Astrophysics Data System (ADS)

Li, Xu; Chen, Zhigang; Taflove, Allen; Backman, Vadim

2005-01-01

We report the phenomenon of ultra-enhanced backscattering of visible light by nanoparticles facilitated by the 3-D photonic nanojet a sub-diffraction light beam appearing at the shadow side of a plane-waveilluminated dielectric microsphere. Our rigorous numerical simulations show that backscattering intensity of nanoparticles can be enhanced up to eight orders of magnitude when locating in the nanojet. As a result, the enhanced backscattering from a nanoparticle with diameter on the order of 10 nm is well above the background signal generated by the dielectric microsphere itself. We also report that nanojet-enhanced backscattering is extremely sensitive to the size of the nanoparticle, permitting in principle resolving sub-nanometer size differences using visible light. Finally, we show how the position of a nanoparticle could be determined with subdiffractional accuracy by recording the angular distribution of the backscattered light. These properties of photonic nanojets promise to make this phenomenon a useful tool for optically detecting, differentiating, and sorting nanoparticles.

Ultrafast Graphene Light Emitters.

PubMed

Kim, Young Duck; Gao, Yuanda; Shiue, Ren-Jye; Wang, Lei; Aslan, Ozgur Burak; Bae, Myung-Ho; Kim, Hyungsik; Seo, Dongjea; Choi, Heon-Jin; Kim, Suk Hyun; Nemilentsau, Andrei; Low, Tony; Tan, Cheng; Efetov, Dmitri K; Taniguchi, Takashi; Watanabe, Kenji; Shepard, Kenneth L; Heinz, Tony F; Englund, Dirk; Hone, James

2018-02-14

Ultrafast electrically driven nanoscale light sources are critical components in nanophotonics. Compound semiconductor-based light sources for the nanophotonic platforms have been extensively investigated over the past decades. However, monolithic ultrafast light sources with a small footprint remain a challenge. Here, we demonstrate electrically driven ultrafast graphene light emitters that achieve light pulse generation with up to 10 GHz bandwidth across a broad spectral range from the visible to the near-infrared. The fast response results from ultrafast charge-carrier dynamics in graphene and weak electron-acoustic phonon-mediated coupling between the electronic and lattice degrees of freedom. We also find that encapsulating graphene with hexagonal boron nitride (hBN) layers strongly modifies the emission spectrum by changing the local optical density of states, thus providing up to 460% enhancement compared to the gray-body thermal radiation for a broad peak centered at 720 nm. Furthermore, the hBN encapsulation layers permit stable and bright visible thermal radiation with electronic temperatures up to 2000 K under ambient conditions as well as efficient ultrafast electronic cooling via near-field coupling to hybrid polaritonic modes under electrical excitation. These high-speed graphene light emitters provide a promising path for on-chip light sources for optical communications and other optoelectronic applications.

Pyrolytic carbon coated black silicon

NASA Astrophysics Data System (ADS)

Shah, Ali; Stenberg, Petri; Karvonen, Lasse; Ali, Rizwan; Honkanen, Seppo; Lipsanen, Harri; Peyghambarian, N.; Kuittinen, Markku; Svirko, Yuri; Kaplas, Tommi

2016-05-01

Carbon is the most well-known black material in the history of man. Throughout the centuries, carbon has been used as a black material for paintings, camouflage, and optics. Although, the techniques to make other black surfaces have evolved and become more sophisticated with time, carbon still remains one of the best black materials. Another well-known black surface is black silicon, reflecting less than 0.5% of incident light in visible spectral range but becomes a highly reflecting surface in wavelengths above 1000 nm. On the other hand, carbon absorbs at those and longer wavelengths. Thus, it is possible to combine black silicon with carbon to create an artificial material with very low reflectivity over a wide spectral range. Here we report our results on coating conformally black silicon substrate with amorphous pyrolytic carbon. We present a superior black surface with reflectance of light less than 0.5% in the spectral range of 350 nm to 2000 nm.

Plant photomorphogenesis and canopy growth

NASA Technical Reports Server (NTRS)

Ballare, Carlos L.; Scopel, Ana L.

1994-01-01

An important motivation for studying photomorphogenesis is to understand the relationships among plant photophysiology in canopies, canopy productivity, and agronomic yield. This understanding is essential to optimize lighting systems used for plant farming in controlled environments (CE) and for the design of genetically engineered crop strains with altered photoresponses. This article provides an overview of some basic principles of plant photomorphogenesis in canopies and discusses their implications for (1) scaling up information on plant photophysiology from individual plants in CE to whole canopies in the field, and (2) designing lighting conditions to increase plant productivity in CE used for agronomic purposes (e.g. space farming in CE Life Support Systems). We concentrate on the visible (lambda between 400 and 700 nm) and far-infrared (FR; lambda greater than 700 nm) spectral regions, since the ultraviolet (UV; 280 to 400 nm) is covered by other authors in this volume.

Plant photomorphogenesis and canopy growth

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ballare, C.L.; Scopel, A.L.

1994-12-31

An important motivation for studying photomorphogenesis is to understand the relationships among plant photophysiology in canopies, canopy productivity, and agronomic yield. This understanding is essential to optimize lighting systems used for plant farming in controlled environments (CE) and for the design of genetically engineered crop strains with altered photoresponses. This article provides an overview of some basic principles of plant photomorphogenesis in canopies and discusses their implications for (1) scaling up information on plant photophysiology from individual plants in CE to whole canopies in the field, and (2), designing lighting conditions to increase plant productivity in CE used for agronomicmore » purposes [e.g. space farming in CE Life-Support-Systems]. We concentrate on the visible ({lambda} between 400 and 700 nm) and far red (FR; {lambda} > 700 nm) spectral regions, since the ultraviolet (UV; 280 to 400 nm) is covered by other authors in this volume.« less

10 m/25 Gbps LiFi transmission system based on a two-stage injection-locked 680 nm VCSEL transmitter.

PubMed

Lu, Hai-Han; Li, Chung-Yi; Chu, Chien-An; Lu, Ting-Chien; Chen, Bo-Rui; Wu, Chang-Jen; Lin, Dai-Hua

2015-10-01

A 10  m/25  Gbps light-based WiFi (LiFi) transmission system based on a two-stage injection-locked 680 nm vertical-cavity surface-emitting laser (VCSEL) transmitter is proposed. A LiFi transmission system with a data rate of 25 Gbps is experimentally demonstrated over a 10 m free-space link. To the best of our knowledge, it is the first time a two-stage injection-locked 680 nm VCSEL transmitter in a 10  m/25  Gbps LiFi transmission system has been employed. Impressive bit error rate performance and a clear eye diagram are achieved in the proposed systems. Such a 10  m/25  Gbps LiFi transmission system provides the advantage of a communication link for higher data rates that could accelerate the deployment of visible laser light communication.

Broadband Measurement of Aerosol Extinction in the Visible Range

NASA Astrophysics Data System (ADS)

He, Quanfu; Bluvshtein, Nir; Segev, Lior; Flores, Michel; Rudich, Yinon; Washenfelder, Rebecca; Brown, Steven

2017-04-01

Atmospheric aerosols influence the Earth's radiative budget directly by scattering and absorbing incoming solar radiation. Aerosol direct forcing remains one of the largest uncertainties in quantifying the role that aerosols play in the Earth's radiative budget. The optical properties of aerosols vary as a function of wavelength, but few measurements reported the wavelength dependence of aerosol extinction cross section and complex refractive indices, particularly in the blue and visible spectral range. There is also currently a large gap in our knowledge of how the optical properties evolve as a function of atmospheric aging in the visible spectrum. In this study, we constructed a new and novel laboratory instrument to measure aerosol extinction as a function of wavelength, using cavity enhanced spectroscopy with a white light source. This broadband cavity enhanced spectroscopy (BBCES) covers the 395-700 nm spectral region using a broadband light source and a grating spectrometer with charge-coupled device detector (CCD). We evaluated this BBCES by measuring extinction cross section for aerosols that are pure scattering, slightly absorbing and strongly absorbing atomized from standard materials. We also retrieved the refractive indices from the measured extinction cross sections. Secondary organic aerosols from biogenic and anthropogenic precursors were "aged" to differential time scales (1 to 10 days) in an Oxidation Flow Reactor (OFR) under the combined influence of OH, O3 and UV light. The new BBCES was used to online measure the extinction cross sections of the SOA. This talk will provide a comprehensive understanding of aerosol optical properties alerting during aging process in the 395 - 700 nm spectrum.

Relevance of sunscreen application method, visible light and sunlight intensity to free-radical protection: A study of ex vivo human skin.

PubMed

Haywood, Rachel

2006-01-01

With the continued rise in skin cancers worldwide there is a need for effective skin protection against sunlight damage. It was shown previously that sunscreens, which claimed UVA protection (SPF 20+), provided limited protection against UV-induced ascorbate radicals in human skin. Here the results of an electron spin resonance (ESR) investigation to irradiate ex vivo human skin with solar-simulated light are reported. The ascorbate radical signal in the majority of skin samples was directly proportional to the irradiance over relevant sunlight intensities (0.9-2.9 mW cm(-2)). Radical production (substratum-corneum) by UV (wavelengths < 400 nm) and visible components (> 400 nm) was approximately 67% and 33% respectively. Ascorbate radicals were in steady state concentration at low irradiance (approximately 1 mW cm(-2) equivalent to UK sunlight), but at higher irradiance (approximately 3 mW cm(-2)) decreased with time, suggesting ascorbate depletion. Radical protection by a four star-rated sunscreen (with UVA protection) was optimal when applied as a thin film (40-60% at 2 mg cm(-2)) but less so when rubbed into the skin (37% at 4 mg cm(-2) and no significant protection at 2 mg cm(-2)), possibly due to cream filling crevices, which reduced film thickness. This study validates ESR determinations of the ascorbate radical for quantitative protection measurements. Visible light contribution to radical production, and loss of protection when sunscreen is rubbed into skin, has implications for sunscreen design and use for the prevention of free-radical damage.

Efficient generation of 509 nm light by sum-frequency mixing between two tapered diode lasers

NASA Astrophysics Data System (ADS)

Tawfieq, Mahmoud; Jensen, Ole Bjarlin; Hansen, Anders Kragh; Sumpf, Bernd; Paschke, Katrin; Andersen, Peter E.

2015-03-01

We demonstrate a concept for visible laser sources based on sum-frequency generation of beam combined tapered diode lasers. In this specific case, a 1.7 W sum-frequency generated green laser at 509 nm is obtained, by frequency adding of 6.17 W from a 978 nm tapered diode laser with 8.06 W from a 1063 nm tapered diode laser, inside a periodically poled MgO doped lithium niobate crystal. This corresponds to an optical to optical conversion efficiency of 12.1%. As an example of potential applications, the generated nearly diffraction-limited green light is used for pumping a Ti:sapphire laser, thus demonstrating good beam quality and power stability. The maximum output powers achieved when pumping the Ti:sapphire laser are 226 mW (CW) and 185 mW (mode-locked) at 1.7 W green pump power. The optical spectrum emitted by the mode-locked Ti:sapphire laser shows a spectral width of about 54 nm (FWHM), indicating less than 20 fs pulse width.

Ultraviolet electroluminescence from hybrid inorganic/organic ZnO/GaN/poly(3-hexylthiophene) dual heterojunctions.

PubMed

Chen, Yungting; Shih, Hanyu; Wang, Chunhsiung; Hsieh, Chunyi; Chen, Chihwei; Chen, Yangfang; Lin, Taiyuan

2011-05-09

Based on hybrid inorganic/organic n-ZnO nanorods/p-GaN thin film/poly(3-hexylthiophene)(P3HT) dual heterojunctions, the light emitting diode (LED) emits ultraviolet (UV) radiation (370 nm - 400 nm) and the whole visible light (400 nm -700 nm) at the low injection current density. Meanwhile, under the high injection current density, the UV radiation overwhelmingly dominates the room-temperature electroluminescence spectra, exponentially increases with the injection current density and possesses a narrow full width at half maximum less than 16 nm. Comparing electroluminescence with photoluminescence spectra, an enormously enhanced transition probability of the UV luminescence in the electroluminescence spectra was found. The P3HT layer plays an essential role in helping the UV emission from p-GaN material because of its hole-conductive characteristic as well as the band alignment with respect to p-GaN. With our new finding, the result shown here may pave a new route for the development of high brightness LEDs derived from hybrid inorganic/organic heterojuctions.

Optimizing the withdrawal speed using dip coating for optical sensor

NASA Astrophysics Data System (ADS)

Samat, S. F. A.; Sarah, M. S. P.; Idros, M. Faizol Md; Rusop, M.

2018-05-01

The processing route of sol-gel has been used for many productions of thin film using metal oxide such as titanium dioxide, zinc oxide, carbon dioxide and so on. For this research the thin film phase was studied has high transmittance using dip coating technique with different withdrawal speed for optical sensing. The result obtained from optical transmittance spectra that transmits at 30nm and bend at 350nm to 800nm was in the visible light wavelength range. From the data, the withdrawal speed was low at 5s and 10s could give the highest transmittance which were 90.41% and 87.91% respectively.

In vitro evaluation of low-intensity light radiation on murine melanoma (B16F10) cells.

PubMed

Peidaee, P; Almansour, N M; Pirogova, E

2016-03-01

Changes in the energy state of biomolecules induced by electromagnetic radiation lead to changes in biological functions of irradiated biomolecules. Using the RRM approach, it was computationally predicted that far-infrared light irradiation in the range of 3500-6000 nm affects biological activity of proto-oncogene proteins. This in vitro study evaluates quantitatively and qualitatively the effects of selected far-infrared exposures in the computationally determined wavelengths on mouse melanoma B16F10 cells and Chinese hamster ovarian (CHO) cells by MTT (thiazolyl blue tetrazolium bromide) cell proliferation assay and confocal laser-scanning microscopy (CLSM). This paper also presents the findings obtained from irradiating B16F10 and CHO cells by the selected wavelengths in visible and near-infrared range. The MTT results show that far-infrared wavelength irradiation induces detrimental effect on cellular viability of B16F10 cells, while that of normal CHO cells is not affected considerably. Moreover, CLSM images demonstrate visible cellular detachment of cancer cells. The observed effects support the hypothesis that far-infrared light irradiation within the computationally determined wavelength range induces biological effect on cancer cells. From irradiation of selected visible and near-infrared wavelengths, no visible changes were detected in cellular viability of either normal or cancer cells.

Efficient visible-light photocatalytic degradation of sulfadiazine sodium with hierarchical Bi₇O₉I₃under solar irradiation.

PubMed

Xu, MengMeng; Zhao, YaLei; Yan, QiShe

2015-01-01

Bi₇O₉I₃, a kind of visible-light-responsive photocatalyst, with hierarchical micro/nano-architecture was successfully synthesized by oil-bath heating method, with ethylene glycol as solvent, and applied to degrade sulfonamide antibiotics. The as-prepared product was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-visible diffuse reflection spectra and scanning electron microscopy (SEM). XRD and XPS tests confirmed that the product was indeed Bi₇O₉I₃. The result of SEM observation shows that the as-synthesized Bi₇O₉I₃ consists of a large number of micro-sheets with parallel rectangle structure. The optical test exhibited strong photoabsorption in visible light irradiation, with 617 nm of absorption edges. Moreover, the difference in the photocatalytic efficiency of as-prepared Bi₇O₉I₃ at different seasons of a whole year was investigated in this study. The chemical oxygen demand removal efficiency and concentration of NO(3)(-) and SO(4)(2-) of solution after reaction were also researched to confirm whether degradation of the pollutant was complete; the results indicated a high mineralization capacity of Bi₇O₉I₃. The as-synthesized Bi₇O₉I₃exhibits an excellent oxidizing capacity of sulfadiazine sodium and favorable stability during the photocatalytic reaction.

Growth Chambers on the International Space Station for Large Plants

NASA Technical Reports Server (NTRS)

Massa, Gioia D.; Wheeler, Raymond M.; Morrow, Robert C.; Levine, Howard G.

2016-01-01

The International Space Station (ISS) now has platforms for conducting research on horticultural plant species under LED (Light Emitting Diodes) lighting, and those capabilities continue to expand. The Veggie vegetable production system was deployed to the ISS as an applied research platform for food production in space. Veggie is capable of growing a wide array of horticultural crops. It was designed for low power usage, low launch mass and stowage volume, and minimal crew time requirements. The Veggie flight hardware consists of a light cap containing red (630 nanometers), blue, (455 nanometers) and green (530 nanometers) LEDs. Interfacing with the light cap is an extendable bellowsbaseplate for enclosing the plant canopy. A second large plant growth chamber, the Advanced Plant Habitat (APH), is will fly to the ISS in 2017. APH will be a fully controllable environment for high-quality plant physiological research. APH will control light (quality, level, and timing), temperature, CO2, relative humidity, and irrigation, while scrubbing any cabin or plant-derived ethylene and other volatile organic compounds. Additional capabilities include sensing of leaf temperature and root zone moisture, root zone temperature, and oxygen concentration. The light cap will have red (630 nm), blue (450 nm), green (525 nm), far red (730 nm) and broad spectrum white LEDs (4100K). There will be several internal cameras (visible and IR) to monitor and record plant growth and operations. Veggie and APH are available for research proposals.

Development and applications of tunable, narrow band lasers and stimulated Raman scattering devices for atmospheric lidar

NASA Technical Reports Server (NTRS)

Wilkerson, Thomas D.

1993-01-01

The main thrust of the program was the study of stimulated Raman processes for application to atmospheric lidar measurements. This has involved the development of tunable lasers, the detailed study of stimulated Raman scattering, and the use of the Raman-shifted light for new measurements of molecular line strengths and line widths. The principal spectral region explored in this work was the visible and near-IR wavelengths between 500 nm and 1.5 microns. Recent alexandrite ring laser experiments are reported. The experiments involved diode injection-locking, Raman shifting, and frequency-doubling. The experiments succeeded in producing tunable light at 577 and 937 nm with line widths in the range 80-160 MHz.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shamirzaev, V. T., E-mail: tim@isp.nsc.ru; Gaisler, V. A.; Shamirzaev, T. S.

The spectrum of ultraviolet (UV) InGaN/GaN light-emitting diodes and its dependence on the current flowing through the structure are studied. The intensity of the UV contribution to the integrated diode luminescence increases steadily with increasing density of current flowing through the structure, despite a drop in the emission quantum efficiency. The electroluminescence excitation conditions that allow the fraction of UV emission to be increased to 97% are established. It is shown that the nonuniform generation of extended defects, which penetrate the active region of the light-emitting diodes as the structures degrade upon local current overheating, reduces the integrated emission intensitymore » but does not affect the relative intensity of diode emission in the UV (370 nm) and visible (550 nm) spectral ranges.« less

The Synthesis of a Core-Shell Photocatalyst Material YF3:Ho3+@TiO2 and Investigation of Its Photocatalytic Properties

PubMed Central

Xu, Xuan; Zhou, Shiyu; Long, Jun; Wu, Tianhu; Fan, Zihong

2017-01-01

In this paper, YF3:Ho3+@TiO2 core-shell nanomaterials were prepared by hydrolysis of tetra-n-butyl titanate (TBOT) using polyvinylpyrrolidone K-30 (PVP) as the coupling agent. Characterization methods including X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) under TEM, X-ray photoelectron spectroscopy (XPS), fluorescence spectrometry, ultraviolet-visible diffuse reflectance spectroscopy, and electron spin resonance (ESR) were used to characterize the properties and working mechanism of the prepared photocatalyst material. They indicated that the core phase YF3 nanoparticles were successfully coated with a TiO2 shell and the length of the composite was roughly 100 nm. The Ho3+ single-doped YF3:Ho3+@TiO2 displayed strong visible absorption peaks with wavelengths of 450, 537, and 644 nm, respectively. By selecting these three peaks as excitation wavelengths, we could observe 288 nm (5D4→5I8) ultraviolet emission, which confirmed that there was indeed an energy transfer from YF3:Ho3+ to anatase TiO2. In addition, this paper investigated the influences of different TBOT dosages on photocatalysis performance of the as-prepared photocatalyst material. Results showed that the YF3:Ho3+@TiO2 core-shell nanomaterial was an advanced visible-light-driven catalyst, which decomposed approximately 67% of rhodamine b (RhB) and 34.6% of phenol after 10 h of photocatalysis reaction. Compared with the blank experiment, the photocatalysis efficiency was significantly improved. Finally, the visible-light-responsive photocatalytic mechanism of YF3:Ho3+@TiO2 core-shell materials and the influencing factors of photocatalytic degradation were investigated to study the apparent kinetics, which provides a theoretical basis for improving the structural design and functions of this new type of catalytic material. PMID:28772662

Solar irradiance limits the long-term survival of Listeria monocytogenes in seawater.

PubMed

NicAogáin, K; Magill, D; O'Donoghue, B; Conneely, A; Bennett, C; O'Byrne, C P

2018-03-01

Seafood has often been implicated in outbreaks of food-borne illness caused by Listeria monocytogenes but the source of contamination is usually not known. In this study we investigated the possibility that this pathogen could survive in seawater for an extended time period. Freshly collected seawater samples were inoculated with 1 × 10 8  CFU per ml of L. monocytogenes EGD-e and survival was monitored by plate counting for up to 25 days. When incubated in the dark, either at ambient temperatures (4-14°C) or at 16°C, >10 4  CFU per ml survivors were present after 25 days. However, when the seawater cell suspensions were exposed to ambient light (solar irradiation) and temperatures, L. monocytogenes lost viability rapidly and no survivors could be detected after the 80 h time point. Both UV-A and visible light in the blue region of the spectrum (470 nm) were found to contribute to this effect. The stress inducible sigma factor σ B was found to play a role in survival of L. monocytogenes in seawater. Together these data demonstrate that solar irradiation is a critical determinant of L. monocytogenes survival in marine environments. The data further suggest the possibility of controlling this food-borne pathogen in food-processing environments using visible light. Listeria monocytogenes is a food-borne bacterial pathogen capable of causing the life-threatening infection, listeriosis. In seafood the route of contamination from the environment is often not well understood as this pathogen is not generally thought to survive well in seawater. Here we provide evidence that L. monocytogenes is capable of surviving for long periods of time in seawater when light is excluded. Sunlight is demonstrated to have a significant effect on the survival of this pathogen in seawater, and both visible (470 nm) and UV-A light are shown to contribute to this effect. © 2017 The Society for Applied Microbiology.

Broadband reflection of polymer-stabilized chiral nematic liquid crystals induced by a chiral azobenzene compound.

PubMed

Chen, Xingwu; Wang, Ling; Chen, Yinjie; Li, Chenyue; Hou, Guoyan; Liu, Xin; Zhang, Xiaoguang; He, Wanli; Yang, Huai

2014-01-21

A chiral nematic liquid crystal-photopolymerizable monomer-chiral azobenzene compound composite was prepared and then polymerized under UV irradiation. The reflection wavelength of the composite can be extended to cover the 1000-2400 nm range and also be adjusted to the visible light region by controlling the concentration of chiral compounds.

Highly efficient tandem polymer solar cells with a photovoltaic response in the visible light range.

PubMed

Zheng, Zhong; Zhang, Shaoqing; Zhang, Maojie; Zhao, Kang; Ye, Long; Chen, Yu; Yang, Bei; Hou, Jianhui

2015-02-18

Highly efficient polymer solar cells with a tandem structure are fabricated by using two excellent photovoltaic polymers and a highly transparent intermediate recombination layer. Power conversion -efficiencies over 10% can be realized with a photovoltaic response within 800 nm. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Continuous-wave ultraviolet generation at 320 nm by intracavity frequency doubling of red-emitting Praseodymium lasers

NASA Astrophysics Data System (ADS)

Richter, A.; Pavel, N.; Heumann, E.; Huber, G.; Parisi, D.; Toncelli, A.; Tonelli, M.; Diening, A.; Seelert, W.

2006-04-01

We describe a new approach for the generation of coherent ultraviolet radiation. Continuous-wave ultraviolet light at 320 nm has been obtained by intracavity frequency doubling of red-emitting Praseodymium lasers. Lasing at the 640-nm fundamental wavelength in Pr:LiYF4 and Pr:BaY2F8 was realized by employing an optically pumped semiconductor laser at 480 nm as pump source.Using LiB3O5 as nonlinear medium, ~19 mW of ultraviolet radiation with ~9% optical efficiency with respect to absorbed power was reached for both laser crystals; the visible-to-ultraviolet conversion efficiency was 26% and 35% for Pr:LiYF4 and Pr:BaY2F8, respectively.

Semiconducting polymer dot as a highly effective contrast agent for photoacoustic imaging

NASA Astrophysics Data System (ADS)

Yuan, Zhen; Zhang, Jian

2018-02-01

In this study, we developed a novel PIID-DTBT based semiconducting polymer dots (Pdots) that have broad and strong optical absorption in the visible-light region (500 nm - 700 nm). Gold nanoparticles (GNPs) and gold nanorods (GNRs) that have been verified as an excellent photoacoustic contrast agent were compared with Pdots based on photoacoustic imaging method. Both ex vivo and in vivo experiment demonstrated Pdots have a better photoacoustic conversion efficiency at 532 nm than GNPs and similar photoacoustic performance with GNRs at 700 nm at the same mass concentration. Our work demonstrates the great potential of Pdots as a highly effective contrast agent for precise localization of lesions relative to the blood vessels based on photoacoustic tomography imaging.

In0.15Ga0.85N visible-light metal-semiconductor-metal photodetector with GaN interlayers deposited by pulsed NH3

NASA Astrophysics Data System (ADS)

Wang, Hongxia; Zhang, Xiaohan; Wang, Hailong; Lv, Zesheng; Li, Yongxian; Li, Bin; Yan, Huan; Qiu, Xinjia; Jiang, Hao

2018-05-01

InGaN visible-light metal-semiconductor-metal photodetectors with GaN interlayers deposited by pulsed NH3 were fabricated and characterized. By periodically inserting the GaN thin interlayers, the surface morphology of InGaN active layer is improved and the phase separation is suppressed. At 5 V bias, the dark current reduced from 7.0 × 10-11 A to 7.0 × 10-13 A by inserting the interlayers. A peak responsivity of 85.0 mA/W was measured at 420 nm and 5 V bias, corresponding to an external quantum efficiency of 25.1%. The insertion of GaN interlayers also lead to a sharper spectral response cutoff.

Laser ablated hard coating for microtools

DOEpatents

McLean, II, William; Balooch, Mehdi; Siekhaus, Wigbert J.

1998-05-05

Wear-resistant coatings composed of laser ablated hard carbon films, are deposited by pulsed laser ablation using visible light, on instruments such as microscope tips and micro-surgical tools. Hard carbon, known as diamond-like carbon (DLC), films produced by pulsed laser ablation using visible light enhances the abrasion resistance, wear characteristics, and lifetimes of small tools or instruments, such as small, sharp silicon tips used in atomic probe microscopy without significantly affecting the sharpness or size of these devices. For example, a 10-20 nm layer of diamond-like carbon on a standard silicon atomic force microscope (AFM) tip, enables the useful operating life of the tip to be increased by at least twofold. Moreover, the low inherent friction coefficient of the DLC coating leads to higher resolution for AFM tips operating in the contact mode.

Extracting and focusing of surface plasmon polaritons inside finite asymmetric metal/insulator/metal structure at apex of optical fiber by subwavelength holes

NASA Astrophysics Data System (ADS)

Oshikane, Yasushi; Murai, Kensuke; Nakano, Motohiro

2013-09-01

We have been studied a finite asymmetric metal-insulator-metal (MIM) structure on glass plate for near-future visible light communication (VLC) system with white LED illuminations in the living space (DOI: 10.1117/12.929201). The metal layers are vacuum-evaporated thin silver (Ag) films (around 50 nm and 200 nm, respectively), and the insulator layer (around 150 nm) is composed of magnesium fluoride (MgF2). A characteristic narrow band filtering of the MIM structure at visible region might cause a confinement of intense surface plasmon polaritons (SPPs) at specific monochromatic frequency inside a subwavelength insulator layer of the MIM structure. Central wavelength and depth of such absorption dip in flat spectral reflectance curve is controlled by changing thicknesses of both insulator and thinner metal layers. On the other hand, we have proposed a twin-hole pass-through wave guide for SPPs in thick Ag film (DOI: 10.1117/12.863587). At that time, the twin-hole converted a incoming plane light wave into a pair of channel plasmon polaritons (CPPs), and united them at rear surface of the Ag film. This research is having an eye to extract, guide, and focus the SPPs through a thicker metal layer of the MIM with FIBed subwavelength pass-through holes. The expected outcome is a creation of noble, monochromatic, and tunable fiber probe for scanning near-field optical microscopes (SNOMs) with intense white light sources. Basic experimental and FEM simulation results will be presented.

SEMICONDUCTOR MATERIALS: White light photoluminescence from ZnS films on porous Si substrates

NASA Astrophysics Data System (ADS)

Caifeng, Wang; Qingshan, Li; Bo, Hu; Weibing, Li

2010-03-01

ZnS films were deposited on porous Si (PS) substrates using a pulsed laser deposition (PLD) technique. White light emission is observed in photoluminescence (PL) spectra, and the white light is the combination of blue and green emission from ZnS and red emission from PS. The white PL spectra are broad, intense in a visible band ranging from 450 to 700 nm. The effects of the excitation wavelength, growth temperature of ZnS films, PS porosity and annealing temperature on the PL spectra of ZnS/PS were also investigated.

Smartphone Based Platform for Colorimetric Sensing of Dyes

NASA Astrophysics Data System (ADS)

Dutta, Sibasish; Nath, Pabitra

We demonstrate the working of a smartphone based optical sensor for measuring absorption band of coloured dyes. By integration of simple laboratory optical components with the camera unit of the smartphone we have converted it into a visible spectrometer with a pixel resolution of 0.345 nm/pixel. Light from a broadband optical source is allowed to transmit through a specific dye solution. The transmitted light signal is captured by the camera of the smartphone. The present sensor is inexpensive, portable and light weight making it an ideal handy sensor suitable for different on-field sensing.

InGaN/GaN dot-in-nanowire monolithic LEDs and lasers on (001) silicon

NASA Astrophysics Data System (ADS)

Bhattacharya, P.; Hazari, A.; Jahangir, S.

2017-02-01

GaN-based nanowire arrays have been grown on (001)Si substrate by plasma-assisted molecular beam epitaxy and their structural and optical properties have been determined. InxGa1-xN disks inserted in the nanowires behave as quantum dots with emission ranging from visible to near-infrared. We have exploited these nanowire heterostructure arrays to realize light-emitting diodes and diode lasers in which the quantum dots form the active light emitting media. The fabrication and characteristics of 630nm light-emitting diodes and 1.3μm edge-emitting diode lasers are described.

On induced-modifications in optical properties of Makrofol® DE 1-1 SSNTD by UVB and UVA

NASA Astrophysics Data System (ADS)

Al-Amri, A.; El Ghazaly, M.; Abdel-Aal, M. S.

The induced modifications in the optical properties of Makrofol® DE 1-1 solid state nuclear track detectors upon irradiation by UVB (302 nm) and UVA (365 nm) were characterized and compared. Makrofol® DE 1-1 detectors were irradiated separately for different durations with UVB (302 nm) and UVA (365 nm). The measurements revealed insignificant changes were observed at all in UVA (365 nm)-irradiated Makrofol® DE 1-1, irrespective the irradiation time (dose). All UVB (302 nm)-irradiated Makrofol® DE 1-1 detectors show a substantial red shift in UV-Vis spectra and a continuous increase in absorbance as the exposure time (Dose) to UVB increases. UVC-irradiated Makrofol® DE 1-1 exhibits absorption bands at 315 ± 5 nm in UV-visible spectra. The absorption increases exponential with the increasing the UVB irradiation time gets saturated started from 75 h to 400 h. In the visible light range no significant changes were observed in Makrofol® DE 1-1 detector irrespective the exposure time to UVB of 302 nm. It is found that the direct band gap is higher than indirect band gap and both decrease with the increase in the irradiation time of UVB of 302 nm. The obtained results of the Urbach energy and carbon atoms per cluster indicate that both increase with the increase in the irradiation time to UVB (302 nm). The induced modification in the optical properties of Makrofol® DE 1-1 can be used in UVB dosimetry, meanwhile it is not applicable for UVA of 365 nm.

Ag/BiOBr Film in a Rotating-Disk Reactor Containing Long-Afterglow Phosphor for Round-the-Clock Photocatalysis.

PubMed

Yin, Haibo; Chen, Xiaofang; Hou, Rujing; Zhu, Huijuan; Li, Shiqing; Huo, Yuning; Li, Hexing

2015-09-16

Ag/BiOBr film coated on the glass substrate was synthesized by a solvothermal method and a subsequent photoreduction process. Such a Ag/BiOBr film was then adhered to a hollow rotating disk filled with long-afterglow phosphor inside the chamber. The Ag/BiOBr film exhibited high photocatalytic activity for organic pollutant degradation owing to the improved visible-light harvesting and the separation of photoinduced charges. The long-afterglow phosphor could absorb the excessive daylight and emit light around 488 nm, activating the Ag/BiOBr film to realize round-the-clock photocatalysis. Because the Ag nanoparticles could extend the light absorbance of the Ag/BiOBr film to wavelengths of around 500 nm via a surface plasma resonance effect, they played a key role in realizing photocatalysis induced by long-afterglow phosphor.

Green Synthesis and Characterization of SmVO4 Nanoparticles in the Presence of Carbohydrates As Capping Agents with Investigation of Visible-Light Photocatalytic Properties

NASA Astrophysics Data System (ADS)

Eghbali-Arani, Mohammad; Sobhani-Nasab, Ali; Rahimi-Nasrabadi, Mehdi; Pourmasoud, Saeid

2018-03-01

SmVO4 nanoparticles were synthesized through a fast and simple procedure (green method). The effects of three parameters including temperature, type of capping agent, and concentration on the size and morphology behavior of SmVO4 nanoparticles were explored. The analysis of SmVO4 nanoparticles was performed through some techniques including, Fourier transform infrared spectroscopy, x-ray diffraction, energy dispersive x-ray microanalysis, scanning electron microscopy, transmission electron microscopy, thermogravimetry, differential thermal analysis, ultraviolet-visible spectroscopy, and vibrating sample magnetometers. The study of photocatalytic behaviour of the SmVO4 nanoparticles in various conditions has been carried out. The impacts of different factors such as dosage, grain size, and kind of pollutant (methylene blue = MB and methyl orange = MO) on the photocatalytic property of SmVO4 nanoparticles were assessed. The photocatalytic activities of SmVO4 catalysts were studied for the degradation of dye under visible light (λ > 400 nm).

Development of Flight Slit-Jaw Optics for Chromospheric Lyman-Alpha SpectroPolarimeter

NASA Technical Reports Server (NTRS)

Kubo, Masahito; Suematsu, Yoshinori; Kano, Ryohei; Bando, Takamasa; Hara, Hirohisa; Narukage, Noriyuki; Katsukawa, Yukio; Ishikawa, Ryoko; Ishikawa, Shin-nosuke; Kobiki, Toshihiko;

Development of Flight Slit-Jaw Optics for Chromospheric Lyman-Alpha SpectroPolarimeter

NASA Technical Reports Server (NTRS)

Kubo, Masahito; Suematsu, Yoshinori; Kano, Ryohei; Bando, Takamasa; Hara, Hirohisa; Narukage, Noriyuki; Katsukawa, Yukio; Ishikawa, Ryoko; Ishikawa, Shin-nosuke; Kobiki, Toshihiko;

Energy transfer and visible-infrared quantum cutting photoluminescence modification in Tm-Yb codoped YPO(4) inverse opal photonic crystals.

PubMed

Wang, Siqin; Qiu, Jianbei; Wang, Qi; Zhou, Dacheng; Yang, Zhengwen

2015-08-01

YPO₄:  Tm, Yb inverse opal photonic crystals were successfully synthesized by the colloidal crystal templates method, and the visible-infrared quantum cutting (QC) photoluminescence properties of YPO₄:  Tm, Yb inverse opal photonic crystals were investigated. We obtained tetragonal phase YPO₄ in all the samples when the samples sintered at 950°C for 5 h. The visible emission intensity of Tm³⁺ decreased significantly when the photonic bandgap was located at 650 nm under 480 nm excitation. On the contrary, the QC emission intensity of Yb³⁺ was enhanced as compared with the no photonic bandgap sample. When the photonic bandgap was located at 480 nm, the Yb³⁺ and Tm³⁺ light-emitting intensity weakened at the same time. We demonstrated that the energy transfer between Tm³⁺ and Yb³⁺ is enhanced by the suppression of the red emission of Tm³⁺. Additionally, the mechanisms for the influence of the photonic bandgap on the energy transfer process of the Tm³⁺, Yb³⁺ codoped YPO₄ inverse opal are discussed.

Nitrogen-modified nano-titania: True phase composition, microstructure and visible-light induced photocatalytic NOx abatement

NASA Astrophysics Data System (ADS)

Tobaldi, D. M.; Pullar, R. C.; Gualtieri, A. F.; Otero-Irurueta, G.; Singh, M. K.; Seabra, M. P.; Labrincha, J. A.

2015-11-01

Titanium dioxide (TiO2) is a popular photocatalyst used for many environmental and anti-pollution applications, but it normally operates under UV light, exploiting ∼5% of the solar spectrum. Nitrification of titania to form N-doped TiO2 has been explored as a way to increase its photocatalytic activity under visible light, and anionic doping is a promising method to enable TiO2 to harvest visible-light by changing its photo-absorption properties. In this paper, we explore the insertion of nitrogen into the TiO2 lattice using our green sol-gel nanosynthesis method, used to create 10 nm TiO2 NPs. Two parallel routes were studied to produce nitrogen-modified TiO2 nanoparticles (NPs), using HNO3+NH3 (acid-precipitated base-peptised) and NH4OH (totally base catalysed) as nitrogen sources. These NPs were thermally treated between 450 and 800 °C. Their true phase composition (crystalline and amorphous phases), as well as their micro-/nanostructure (crystalline domain shape, size and size distribution, edge and screw dislocation density) was fully characterised through advanced X-ray methods (Rietveld-reference intensity ratio, RIR, and whole powder pattern modelling, WPPM). As pollutants, nitrogen oxides (NOx) are of particular concern for human health, so the photocatalytic activity of the NPs was assessed by monitoring NOx abatement, using both solar and white-light (indoor artificial lighting), simulating outdoor and indoor environments, respectively. Results showed that the onset of the anatase-to-rutile phase transformation (ART) occurred at temperatures above 450 °C, and NPs heated to 450 °C possessed excellent photocatalytic activity (PCA) under visible white-light (indoor artificial lighting), with a PCA double than that of the standard P25 TiO2 NPs. However, higher thermal treatment temperatures were found to be detrimental for visible-light photocatalytic activity, due to the effects of four simultaneous occurrences: (i) loss of OH groups and water adsorbed on the photocatalyst surface; (ii) growth of crystalline domain sizes with decrease in specific surface area; (iii) onset and progress of the ART; (iv) the increasing instability of the nitrogen in the titania lattice.

Surface Properties and Photocatalytic Activities of the Colloidal ZnS:Mn Nanocrystals Prepared at Various pH Conditions

PubMed Central

Heo, Jungho; Hwang, Cheong-Soo

2015-01-01

Water-dispersible ZnS:Mn nanocrystals (NC) were synthesized by capping the surface with mercaptoacetic acid (MAA) molecules at three different pH conditions. The obtained ZnS:Mn-MAA NC products were physically and optically characterized by corresponding spectroscopic methods. The UV-Visible absorption spectra and PL emission spectra showed broad peaks at 310 and 590 nm, respectively. The average particle sizes measured from the HR-TEM images were 5 nm, which were also supported by the Debye-Scherrer calculations using the X-ray diffraction (XRD) data. Moreover, the surface charges and the degrees of aggregation of the ZnS:Mn-MAA NCs were determined by electrophoretic and hydrodynamic light scattering methods, indicating formation of agglomerates in water with various sizes (50–440 nm) and different surface charge values accordingly the preparation conditions of the NCs (−7.59 to −24.98 mV). Finally, the relative photocatalytic activities of the ZnS:Mn-MAA NCs were evaluated by measuring the degradation rate of methylene blue (MB) molecule in a pseudo first-order reaction condition under the UV-visible light irradiation. As a result, the ZnS:Mn-MAA NC prepared at the pH 7 showed the best photo-degradation efficiency of the MB molecule with the first-order rate constant (kobs) of 2.0 × 10−3·min−1. PMID:28347105

3D laser printing by ultra-short laser pulses for micro-optical applications: towards telecom wavelengths

NASA Astrophysics Data System (ADS)

Ryu, Meguya; Mizeikis, Vygantas; Morikawa, Junko; Magallanes, Hernando; Brasselet, Etienne; Varapnickas, Simonas; Malinauskas, Mangirdas; Juodkazis, Saulius

2017-08-01

Three dimensional (3D) fast (< 0.5 hour) printing of micro-optical elements down to sub-wavelength resolution over 100 μm footprint areas using femtosecond (fs-)laser oscillator is presented. Using sub-1 nJ pulse energies, optical vortex generators made of polymerised grating segments with an azimuthally changing orientation have been fabricated in SZ2080 resist; width of polymerised rods was 150 nm and period 0.6-1 μm. Detailed phase retardance analysis was carried out manually with Berek compensator (under a white light illumination) and using an equivalent principle by an automated Abrio implementation at 546 nm. Direct experimental measurements of retardance was required since the period of the grating was comparable (or larger) than the wavelength of visible light. By gold sputtering, transmissive optical vortex generators were turned into reflective ones with augmented retardance, Δn × h defined by the form birefringence, Δn, and the height h = 2d where d is the thickness of the polymerised structure. Retardance reached 315 nm as measured with Berek compensator at visible wavelengths. Birefringent phase delays of π (or λ/2 in wavelength) required for high purity vortex generators can be made based on the proposed approach. Optical vortex generators for telecom wavelengths with sub-wavelength patterns of azimuthally oriented gratings are amenable by direct laser polymerisation.

NADH-fluorescence scattering correction for absolute concentration determination in a liquid tissue phantom using a novel multispectral magnetic-resonance-imaging-compatible needle probe

NASA Astrophysics Data System (ADS)

Braun, Frank; Schalk, Robert; Heintz, Annabell; Feike, Patrick; Firmowski, Sebastian; Beuermann, Thomas; Methner, Frank-Jürgen; Kränzlin, Bettina; Gretz, Norbert; Rädle, Matthias

2017-07-01

In this report, a quantitative nicotinamide adenine dinucleotide hydrate (NADH) fluorescence measurement algorithm in a liquid tissue phantom using a fiber-optic needle probe is presented. To determine the absolute concentrations of NADH in this phantom, the fluorescence emission spectra at 465 nm were corrected using diffuse reflectance spectroscopy between 600 nm and 940 nm. The patented autoclavable Nitinol needle probe enables the acquisition of multispectral backscattering measurements of ultraviolet, visible, near-infrared and fluorescence spectra. As a phantom, a suspension of calcium carbonate (Calcilit) and water with physiological NADH concentrations between 0 mmol l-1 and 2.0 mmol l-1 were used to mimic human tissue. The light scattering characteristics were adjusted to match the backscattering attributes of human skin by modifying the concentration of Calcilit. To correct the scattering effects caused by the matrices of the samples, an algorithm based on the backscattered remission spectrum was employed to compensate the influence of multiscattering on the optical pathway through the dispersed phase. The monitored backscattered visible light was used to correct the fluorescence spectra and thereby to determine the true NADH concentrations at unknown Calcilit concentrations. Despite the simplicity of the presented algorithm, the root-mean-square error of prediction (RMSEP) was 0.093 mmol l-1.

Two-Functional Direct Current Sputtered Silver-Containing Titanium Dioxide Thin Films

NASA Astrophysics Data System (ADS)

Musil, J.; Louda, M.; Cerstvy, R.; Baroch, P.; Ditta, I. B.; Steele, A.; Foster, H. A.

2009-04-01

The article reports on structure, mechanical, optical, photocatalytic and biocidal properties of Ti-Ag-O films. The Ti-Ag-O films were reactively sputter-deposited from a composed Ti/Ag target at different partial pressures of oxygen p_{O2} on unheated glass substrate held on floating potential U fl. It was found that addition of 2 at.% of Ag into TiO2 film has no negative influence on UV-induced hydrophilicity of TiO2 film. Thick ( 1,500 nm) TiO2/Ag films containing (200) anatase phase exhibit the best hydrophilicity with water droplet contact angle (WDCA) lower than 10° after UV irradiation for 20 min. Thick ( 1,500 nm) TiO2/Ag films exhibited a better UV-induced hydrophilicity compared to that of thinner ( 700 nm) TiO2/Ag films. Further it was found that hydrophilic TiO2/Ag films exhibit a strong biocidal effect under both the visible light and the UV irradiation with 100% killing efficiency of Escherichia coli ATCC 10536 after UV irradiation for 20 min. Reported results show that single layer of TiO2 with Ag distributed in its whole volume exhibits, after UV irradiation, simultaneously two functions: (1) excellent hydrophilicity with WDCA < 10° and (2) strong power to kill E. coli even under visible light due to direct toxicity of Ag.

The influence of femtosecond laser pulse wavelength on embryonic stem cell differentiation

NASA Astrophysics Data System (ADS)

Mthunzi, Patience

2012-10-01

Stem cells are rich in proteins, carbohydrates, deoxyribonucleic acid (DNA), ribonucleic acid (RNA) and various other cellular components which are responsible for a diversity of functions. Mostly the building blocks of these intracellular entities play an active role in absorbing ultra-violet (UV) and visible light sources. Light-matter interactions in biomaterials are a complex situation and subsequent damage may not always amount only from wavelength dependent effects but may also be driven by a wealth of other optical parameters which may lead to a variety photochemical reactions. Previously, literature has reported efficient photo-transfection and differentiation of pluripotent stem cells via near infrared (NIR) femtosecond (fs) laser pulses with minimum compromise to their viability. Therefore, in this study the influence of using different fs laser wavelengths on optical stem cell transfection and differentiation is investigated. A potassium titanyl phosphate (KTP) crystal was employed in frequency doubling a 1064 nm fs laser beam. The newly generated 532 nm fs pulsed beam was then utilized for the first time in transient photo-transfection of ES-E14TG2a mouse embryonic stem (mES) cells. Compared to using 1064 nm fs pulses which non-invasively introduce plasmid DNA and other macromolecules into mES cells, our results showed a significant decline in the photo-transfection efficiency following transfecting with a pulsed fs visible green beam.

Visible-light induced photocatalysis of AgCl@Ag/titanate nanotubes/nitrogen-doped reduced graphite oxide composites

NASA Astrophysics Data System (ADS)

Pan, Hongfei; Zhao, Xiaona; Fu, Zhanming; Tu, Wenmao; Fang, Pengfei; Zhang, Haining

2018-06-01

High recombination rate of photogenerated electron-hole pairs and relatively narrow photoresponsive range of TiO2-based photocatalysts are the remaining challenges for their practical applications. To address such challenges, photocatalysts consisting of AgCl covered Ag nanoparticles (AgCl@Ag), titanate nanotubes (TiNT), and nitrogen-doped reduced graphite oxide (rGON) are fabricated through alkaline hydrothermal process, followed by deposition and in situ surface-oxidation of silver nanoparticles. In the synthesized photocatalysts, the titanate nanotubes have average length of about 100 nm with inner diameters of about 5 nm and the size of the formed silver nanoparticles is in the range of 50-100 nm. The synthesized photocatalyst degrades almost all the model organic pollutant Rhodamine B in 35 min and remains 90% of photocatalytic efficiency after 5 degradation cycles under visible light irradiation. Since the oxidant FeCl3 applied for oxidation of surface Ag to AgCl is difficult to be completely removed due to the high adsorption capacity of TiNT and rGON, the effect of reside Fe atoms on photocatalytic activity is evaluated and the results reveal that the residue Fe atom only affect the initial photodegradation performance. Nevertheless, the results demonstrate that the formed composite catalyst is a promising candidate for antibiosis and remediation in aquatic environmental contamination.

Analysis of surgical smoke produced by various energy-based instruments and effect on laparoscopic visibility.

PubMed

Weld, Kyle J; Dryer, Stephen; Ames, Caroline D; Cho, Kuk; Hogan, Chris; Lee, Myonghwa; Biswas, Pratim; Landman, Jaime

2007-03-01

We analyzed the smoke plume produced by various energy-based laparoscopic instruments and determined its effect on laparoscopic visibility. The Bipolar Macroforceps, Harmonic Scalpel, Floating Ball, and Monopolar Shears were applied in vitro to porcine psoas muscle. An Aerodynamic Particle Sizer and Electrostatic Classifier provided a size distribution of the plume for particles >500 nm and <500 nm, and a geometric mean particle size was calculated. A Condensation Particle Counter provided the total particle-number concentration. Electron microscopy was used to characterize particle size and shape further. Visibility was calculated using the measured-size distribution data and the Rayleigh and Mie light-scattering theories. The real-time instruments were successful in measuring aerosolized particle size distributions in two size ranges. Electron microscopy revealed smaller, homogeneous, spherical particles and larger, irregular particles consistent with cellular components. The aerosol produced by the Bipolar Macroforceps obscured visibility the least (relative visibility 0.887) among the instruments tested. Particles from the Harmonic Scalpel resulted in a relative visibility of 0.801. Monopolar-based instruments produced plumes responsible for the poorest relative visibility (Floating Ball 0.252; Monopolar Shears 0.026). Surgical smoke is composed of two distinct particle populations caused by the nucleation of vapors as they cool (the small particles) and the entrainment of tissue secondary to mechanical aspects (the large particles). High concentrations of small particles are most responsible for the deterioration in laparoscopic vision. Bipolar and ultrasonic instruments generate a surgical plume that causes the least deterioration of visibility among the instruments tested.

Facile fabrication of CuO-Pb2O3 nanophotocatalyst for efficient degradation of Rose Bengal dye under visible light irradiation

NASA Astrophysics Data System (ADS)

Kamaraj, Eswaran; Somasundaram, Sivaraman; Balasubramani, Kavitha; Eswaran, Muthu Prema; Muthuramalingam, Rajarajan; Park, Sanghyuk

2018-03-01

A p-type CuO/n-type Pb2O3 heterojunction photocatalyst was prepared by a simple wet chemical process and the photocatalytic ability was evaluated for the degradation of Rose Bengal (RB) under visible light irradiation. Synthesized nanocatalysts were characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Energy-dispersive X-ray spectroscopy (EDS), Brunauer-Emmett-Teller (BET) surface area analysis, and X-ray photoelectron spectroscopy (XPS). The p-n heterojunction of CuO-Pb2O3 nanostructures can promote the light absorption capability of photocatalyst and charge separation of electron-hole pairs. Photodegradation assays showed that the addition of CuO effectively enhanced the photocatalytic activity of CuO-Pb2O3 under visible light irradiation (λmax > 420 nm). Compared with pure Pb2O3 and CuO, the CuO-Pb2O3 exhibited significantly enhanced photocatalytic degradation activity. The reaction rate constant of CuO-Pb2O3 is 0.092 min-1, which is much higher than those of CuO (0.073 min-1) and Pb2O3 (0.045 min-1).

Tuning Cu dopant of Zn 0.5 Cd 0.5 S nanocrystals enables high-performance photocatalytic H 2 evolution from water splitting under visible-light irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mei, Zongwei; Zhang, Bingkai; Zheng, Jiaxin

2016-08-01

Cu-doping into Zn1-xCdxS can greatly enhance the photocatalytic H2 evolution from water splitting under visible-light irradiation. However, it is still controversial for how the Cu-dopant improves this performance. Here, we report that appropriate Cu-doped Zn0.5Cd0.5S nanocrystals reach 21.4 mmol/h/g of H2 evolution rate without cocatalyst in the visible-light region, which is also 2.8 times as high as that of the undoped counterpart, and the corresponding apparent quantum efficiency is 18.8% at 428 nm. It is firstly confirmed that the Cu2+ changes into Cu+ after being doped by soft X-ray absorption spectroscopy (sXAS). We theoretically propose that the transformation of 2Cu2+more » to 2Cu+ results in one adjacent S2- vacancy (VS) in host during the doping process, while the Cu+-dopant and VS attract the photoexcited holes and electrons, respectively. Accordingly, the photocatalytic activity is improved due to the enhanced separation of photoexcited carriers accompanied with the enhanced light absorption resulting from the Cu+-dopant and 2Cu+/VS complex as possible active site for photocatalytic H2 evolution.« less

Harnessing structural darkness in the visible and infrared wavelengths for a new source of light.

PubMed

Huang, Jianfeng; Liu, Changxu; Zhu, Yihan; Masala, Silvia; Alarousu, Erkki; Han, Yu; Fratalocchi, Andrea

2016-01-01

Engineering broadband light absorbers is crucial to many applications, including energy-harvesting devices and optical interconnects. The performances of an ideal absorber are that of a black body, a dark material that absorbs radiation at all angles and polarizations. Despite advances in micrometre-thick films, the absorbers available to date are still far from an ideal black body. Here, we describe a disordered nanostructured material that shows an almost ideal black-body absorption of 98-99% between 400 and 1,400 nm that is insensitive to the angle and polarization of the incident light. The material comprises nanoparticles composed of a nanorod with a nanosphere of 30 nm diameter attached. When diluted into liquids, a small concentration of nanoparticles absorbs on average 26% more than carbon nanotubes, the darkest material available to date. By pumping a dye optical amplifier with nanosecond pulses of ∼100 mW power, we harness the structural darkness of the material and create a new type of light source, which generates monochromatic emission (∼5 nm wide) without the need for any resonance. This is achieved through the dynamics of light condensation in which all absorbed electromagnetic energy spontaneously generates single-colour energy pulses.