Search

Luminescent nanothermometers have shown competitive superiority for contactless and noninvasive temperature probing especially at the nanoscale. Herein, we report the inherently Eu2+ /Eu3+ codoped Sc2 O3 nanoparticles synthesized via a one-step and controllable thermolysis reaction where Eu3+ is in-situ reduced to Eu2+ by oleylamine. The stable luminescence emission of Eu3+ as internal standard and the sensitive response of Eu2+ emission to temperature as probe comprise a perfect ratiometric nanothermometer with wide-range temperature probing (77-267 K), high repeatability (>99.94%), and high relative sensitivity (3.06% K-1 at 267 K). The in situ reduction of Eu3+ to Eu2+ ensures both uniform distribution in the crystal lattice and simultaneous response upon light excitation of Eu2+ /Eu3+ . To widen this concept, Tb3+ is codoped as additional internal reference for tunable temperature probing range.

Thermally stimulated current (TSC) measurements were carried out in as-grown TlGaSeS layered single crystals. The investigations were performed in temperatures ranging from 10 to 160 K with heating rate of 0.8 K s −1 . The analysis of the data revealed three electron trap levels at 13, 20 and 50 meV. The activation energies of the traps have been determined using various methods of analysis, and they agree with each other. The calculation for these traps yielded 3.3 × 10 −24 , 1.0 × 10 −24 , and 1.1 × 10 −24 cm 2 for capture cross-sections and 1.9 × 10 12 , 2.9 × 10 11 and 4.5 × 10 10 cm −3 for the concentrations, respectively. It was concluded that in these centers retrapping was negligible, as confirmed by the good agreement between the experimental results and the theoretical predictions of the model that assumes slow retrapping. An exponential distribution of electron traps was also revealed from the analysis of the TSC data obtained at different light excitation temperatures. This experimental technique provided values of 9 and 77 meV/decade for traps distribution of peaks A and C, respectively.

Charge carrier traps in as-grown TlGaSeS layered single crystals were studied using thermally stimulated current measurements. The investigations were performed in temperatures ranging from 10 to 100 K. The experimental evidences were found for the presence of one shallow hole trapping center in TlGaSeS, located at 12 meV from the valence band. The trap parameters have been calculated using various methods of analysis, and these agree well with each other. Its capture cross-section and concentration have been found to be 8.9 × 10 −26 cm 2 and 2.0 × 10 14 cm −3 , respectively. Analysis of the thermally stimulated current data at different light excitation temperatures leads to a value of 19 meV/decade for the shallow hole traps distribution.

As-grown Tl2In2S3Se layered single crystals were studied by thermally stimulated current measurements in the temperature range of 10–170 K with different heating rates. Experimental data were analyzed according to various methods such as curve fitting and initial rise. The analysis of thermally stimulated current spectra registered at light excitation temperature T0=10 K revealed the trap level located at 30 meV. Attempt-to-escape frequency, concentration and capture cross section of the traps were determined as 4.2 s−1, 2.4×109 cm−3 and 1.7×10−24 cm2, respectively. It was concluded that slow retrapping (monomolecular condition) occurs for the traps in Tl2In2S3Se crystals. By the analysis of thermally stimulated current data at different light excitation temperatures, the value of 39 meV/decade was obtained for traps distribution.

CaTiO3:Pr3+,Bi3+,B3+ red phosphor particles were prepared by a peroxide-based route. X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL) were utilized to characterize the resulting phosphors. Bi3+ codoping improves the excitation properties, especially under near-UV (370–400 nm) light excitation. A small amount of B2O3 can act as a flux to accelerate the formation of CaTiO3 host lattice and improve the PL properties of CaTiO3:Pr3+,Bi3+ phosphor. Under UV excitation, the strongest red emission is obtained from CaTiO3:0.05%Pr3+, 1.0%Bi3+,0.3B3+. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Photoemission electron microscopy (PEEM) is a unique surface-sensitive instrument capable of providing real-time images with high spatial resolution. While similar to the more common electron microscopies, scanning electron microscopy and transmission electron microscopy, the imaging technology relies on the photogeneration of electrons emitted from a sample through light excitation. This imaging technique has found prominence in surface and materials sciences, being well suited for imaging flat surfaces, and changes that occur to that surface as various parameters are changed (e.g. temperature, exposure to reactive gases). Biologically focused PEEM received significant attention in the 1970s, but was not aggressively advanced since that pioneering work. PEEM is capable of providing important insights into biological systems that extend beyond simple imaging. In this article, we identify and establish important issues that affect the acquisition and analysis of biological samples with PEEM. We will briefly review the biological impact and importance of PEEM with respect to our work. The article also concludes with a discussion of some of the current challenges that must be addressed to enable PEEM to achieve its maximum potential with biological samples.

Three-dimensional (3D) GeO2 nanowire networks were fabricated by using germanium as both a source material and catalyst in an oxygen-rich growth environment. The branches within one network show very regular orientation relationships: either perpendicular or parallel to each other. The nanowires follow a base-growth model and the growth direction is along . The GeO2 nanowire networks exhibit strong violet emission peaked at 404 nm under a 265 nm UV light excitation.

The intensity dependent absorption and transparency of Ce:BaTiO3 is examined in relation to the two trap model of the photorefractive effect. At wavelengths of both 532 nm and 633 nm, the material exhibits intensity dependent absorption, while at a wavelength of 790 nm, intensity dependent transparency is observed, with a transition between absorption and transparency at approximately 650 nm. Experimental data is matched to the two trap theoretical model with good agreement. Analysis of this match shows that the light excitation cross-section of the shallow traps are the main contributors to the observed intensity dependent transition.

Superfine powder of Tb3+ ion-doped aluminates phosphors, GdSrAl3O7:Tb3+ was synthesized with a precursor prepared by an EDTA-sol–gel method at 900 °C. Field-emission scanning electron-microscopy (FE-SEM) observation indicated a narrow size-distribution of about 150–300 nm for the particles with elliptical shape. Upon excitation with vacuum ultraviolet (VUV) and near UV light excitation, the phosphors show a strong emission line at around 542 nm corresponding to the 5D4 → 7F5 transition of Tb3+, and the highest PL intensity at 542 nm was found at a content of about 12 mol% Tb3+. As the Tb3+ concentration increases, Tb ions strongly cross-relaxation interact resulting in a decrease of the lifetime. The results reveal that GdSrAl3O7:Tb3+ would be a promising green phosphor for PDP application.

The bottom-up construction and operation of machines and motors of molecular size is a topic of great interest in nanoscience, and a fascinating challenge of nanotechnology. Researchers in this field are stimulated and inspired by the outstanding progress of molecular biology that has begun to reveal the secrets of the natural nanomachines which constitute the material base of life. Like their macroscopic counterparts, nanoscale machines need energy to operate. Most molecular motors of the biological world are fueled by chemical reactions, but research in the last fifteen years has demonstrated that light energy can be used to power nanomachines by exploiting photochemical processes in appropriately designed artificial systems. As a matter of fact, light excitation exhibits several advantages with regard to the operation of the machine, and can also be used to monitor its state through spectroscopic methods. In this review we will illustrate the design principles at the basis of photochemically driven molecular machines, and we will describe a few examples based on rotaxane-type structures investigated in our laboratories.

A portable multifunction amperometric transducer for monitoring bioactive material has been designed to operate with a wide range of electrogenic biosamples. The system realized is innovative, being designed to be flexible, modular and small, with two independent not-interfering sensing cells equipped with programmable optical excitation, current measurement system and automated flow system. Each of the two cells is provided with screen printed electrodes to measure the generated biocurrent and features different optical sources (LEDs with emission peak at 470nm and 660nm) to activate the photosynthetic electron transfer of various biomediators from plants and/or microrganisms. Target applications belong to the agro-food, pharmaceutical and biomedical fields. To demonstrate the large applicability of the transducer, experimental measurements were conducted with Photosystem II protein and tyrosinase to detect four different pesticides and cathecol, respectively. Further applications in environmental water monitoring and food analysis are envisaged for such biosensors.

The paper is concerned with applications of multimode interference structures (MMI) as the elements of integrated optic circuits. Investigations of MMI produced by ion-exchange in glass, obtained by visualization method of light propagation in gradient structures, using fluorescence of the substance covering the MMI section, are presented. Experimental results concern the self-imaging phenomena for symmetrical and paired interference for TE, TM and unpolarized light excitation. On the base of investigations and BPM simulations the applications of MMI are proposed.

UV sensitivity of the vegetative and reproductive tissues of two Antarctic brown macroalgae was compared. Photosynthesis as well as the content and localization of phenolic substances were determined. Responses to UV radiation were quantified as chlorophyll fluorescence (Fv /Fm ). Ascoseira mirabilis showed high UV tolerance, while in Cystosphaera jacquinotii Fv /Fm decreased by 15-21%, the receptacles being more tolerant than the vegetative blades. The phlorotannin contents showed an opposite pattern: the soluble fraction dominated in C. jacquinotii while in A. mirabilis the insoluble fraction was more abundant. Soluble phlorotannins were higher in the reproductive than in vegetative tissues in both species. Images of tissue cross-sections under violet-blue light excitation confirmed a high allocation of phenolic compounds (as blue autofluorescence) in C. jacquinotii, both in reproductive and vegetative blades. The allocation and proportions of the soluble and insoluble phlorotannins could be related with the observed UV tolerance of the vegetative and reproductive tissues.

Luminescence properties of YAl 3 (BO 3 ) 4 (YAB) and Y 1-x Sc x Al 3 (BO 3 ) 4 (YSAB) have been investigated under vacuum ultraviolet (VUV) light excitation. In YAB, two emission bands peaking at 3.2 and 3.9 eV are observed. On the other hand, there appear two emission bands at 3.2 eV and about 4.1 eV in YSAB. The origins of these emission bands are ascribed to two kinds of BO 3 atomic groups. We suppose that the shift of the peak around 4 eV band is deeply related to the fact that one kind of BO 3 atomic groups of YSAB are significantly distorted compared to that of YAB.

We have studied photoluminescence (PL) spectrum and dynamics of Cu- and Al-doped ZnS (ZnS:Cu,Al) nanocrystals fabricated by sequential implantation of Zn +, S + , Cu + , and Al + ions into Al 2 O 3 matrices. These samples exhibit intense green PL under UV light excitation. The space- and time-resolved PL measurements show that the broad green PL is due to the donor-acceptor (DA) pair luminescence of single ZnS:Cu,Al nanocrystals.

Photoluminescence (PL) of poly(vinyl pyrrolidone) (PVP) and silica/PVP hybrid films was investigated. The transparent PVP film was found to exhibit bluish PL centered at approximately 440 nm in response to ultraviolet (UV) light excitation. This PL behavior was made good use of in preparing luminescent silica/PVP hybrid films with high thermal stability at temperatures up to 250 °C. Europium-doped hybrid films exhibited white PL upon UV excitation, resulting from mixing of broadband PVP emissions and 5 D 0 → 7 F 2 emissions of Eu 3+ . Emission colors could be finely tuned by changing excitation wavelengths.

We present a method to include the effects of light excitation on two different models of resonant-tunneling-diode-based devices. Our approach takes into account both photoconductive and charge accumulation effects responsible for shifting the static I–V curve when the structure is under light excitation. Computational simulations led to good agreement between the model and experimental results.

Novel one-component phosphors, Cd1-xDyxSiO3, which emit white color long-lasting phosphorescence upon UV light excitation, are prepared by the conventional high-temperature solid-state method and t...

We study the effect of interband light excitation on hopping conductivity in dense arrays of Ge/Si quantum dots. Both negative and positive photoeffects depending on dot occupations with holes were observed. Long-time conductivity dynamics (typically, 102 − 104 sec at T = 4.2 K) has been revealed as well as after switch on and switch off the illumination, displaying a sluggish temporal dependence. Our observation is explained by spatial separation of electrons and holes due to the presence of potential barriers created by positively charged Ge quantum dots. The time-dependent equalization of barrier heights as a result of hole trapping into the dots was proposed as an additional effect explaining persistent photoconductivity. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Combinatorial chemistry was applied to the optimization of red phosphors used for plasma display panels. Quaternary and ternary combinatorial libraries were developed for (Y, Gd, Lu, Sc)BO3 and (Y, Gd)(BO3 PO4) systems. Our combinatorial chemistry system consists of solution-based combinatorial synthesis and characterization, enabling the swift scanning of luminance and of Commission Internationale de l'Eclairage (CIE) chromaticity under vacuum ultraviolet light excitation. As a consequence of the combinatorial approach, several new candidates were found to show higher luminance than the commercially available red phosphor for plasma display panels.

Intense photoluminescence (PL) has been observed at room temperature from the polycrystalline SiC samples prepared from carbon-saturated Si melt at a temperature ranging from 1500 to 1650°C. Composition and structure of the samples have been confirmed by means of X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy. PL measurements with 325 nm UV light excitation revealed that the room temperature PL spectrum of the samples consists of 3 luminescent bands, the peak energies of which are 2.38 eV, 2.77 eV and 3.06 eV, respectively. The 2.38 eV band is much stronger than the others. It is suggested that some extrinsic PL mechanisms associated with defect or interface states would be responsible to the intensive PL observed at room temperature.

Conjugated polymers have recently attracted a great deal of attention for applications in photodynamic therapy (PDT) because of their light-harvesting capability, efficient energy transfer, and singlet oxygen generation properties. This review describes recent advances in PDT development, including therapeutic mechanisms of PDT in cancer treatments, light excitation methods, and especially recent advances of conjugated polyelectrolytes and conjugated polymer nanoparticles as photosensitizers. The future direction on PDT and further development of conjugated polymer photosensitizers are discussed. The aim of this review is to stimulate innovative ideas to synthesize a new generation of conjugated polymer photosensitizers and promote their translation to clinical applications of PDT.

A visible/near-infrared optical sensor based on an ITO/SiOx/n-Si structure with internal gain is presented. This surface-barrier structure was fabricated by a low-temperature processing technique. The interface properties and carrier transport were investigated from dark current–voltage and capacitance–voltage characteristics. Examination of the multiplication properties was performed under different light excitation and reverse bias conditions. The spectral and pulse response characteristics are analyzed. The current amplification mechanism is interpreted by the control of electron current by the space charge of photogenerated holes near the SiOx/Si interface. The optical sensor output characteristics and device applications are discussed.

The impact of long-term light excitation on YBa 2 Cu 3 O x (YBCO) ( x ≈6.4) thin films grown on “wedged” SrTiO 3 substrates was studied at several temperatures between 50 and 275 K. From the anisotropic resistance of the films, the in-plane ( ρ ab ) and the out-of-plane ( ρ c ) resistivities were calculated. The electrical anisotropy ρ c / ρ ab increased substantially during the light excitation at all studied temperatures. At 50 K, an increase of more than a factor of two was observed, whereas at higher temperatures the increases were smaller. At 275 K, ρ c / ρ ab showed a slightly falling tendency after about 1 h of illumination indicating oxygen ordering. The results strongly support our previously proposed two-mechanism picture of persistent photoconductivity in YBCO.

Lanthanide-doped photon upconversion nanoparticles (UCNPs) are capable of converting low-intensity near-infrared light to UV and visible emission through the synergistic effects of light excitation ...

Background Cotton is an important domesticated fiber used to manufacture a variety of products and industrial goods. During harvesting with cotton strippers and cotton pickers, it is contaminated with foreign matter from botanical and non-botanical sources which adversely affect the quality and consistency of cotton, and therefore reduces its market value. To improve the current grading done by the High Volume Instrument (HVI) and human inspectors, it was explored whether fluorescence imaging can be used for cotton foreign matter detection. Results Eight types of botanical foreign matter (bark, bract, brown leaf, green leaf, hull, seed coat, seed, stem), and four types of non-botanical foreign matter (paper, twine, plastic bale packaging, plastic bag) were subjected to a fluorescence spectroscopy analysis to determine their optimal excitation and emission wavelength range. Matrix 3D scans were performed in the excitation range from 300 nm to 500 nm, and emission range from 320 nm to 700 nm, and the results indicated the photo-excitable fluorescence in the aforementioned excitation range for all the selected foreign matter categories. Consequently, the blue and the UV LEDs were selected as the excitation sources. The blue LED light provided optimal excitation light for bark, brown leaf, bract, green leaf, hull, and stem, while the UV LED light provided optimal excitation light for paper, plastic bag, plastic packaging, seed, seed coat, and twine. Conclusions UV and blue light induces fluorescence in 12 types of botanical and non-botanical cotton foreign matter. An imaging apparatus with blue and UV light excitation sources, and a consumer grade SLR camera was successfully developed to capture and characterize fluorescent images of cotton foreign matter. Based on the results, fluorescent imaging could be a promising method for cotton foreign matter detection. Future studies will focus on the classification of cotton foreign matter categories and to further refine the image processing sequence. Electronic supplementary material The online version of this article (doi:10.1186/1754-1611-8-29) contains supplementary material, which is available to authorized users.

Photoswitching of the [Fe(Htrz)2(trz)](BF4) spin crossover polymeric material has been investigated by means of confocal Raman spectroscopy upon continuous laser irradiation outside and inside its thermal hysteresis loop. In both cases, the evolution of HS and LS Raman marker bands show that light excitation can trigger the LS to HS transition, but the long-lived HS state can be populated only within the hysteresis loop. Local sample heating can explain this light-induced effect leading to a narrowing of the thermal hysteresis loop for laser intensities higher than 0.02 mW/μm2, in strong accordance with previous time-resolved pump-probe experiments on similar materials.

A visible/near-infrared optical sensor based on an ITO/SiOx/n-Si structure with internal gain is presented. This surface-barrier structure was fabricated by a low-temperature processing technique. The interface properties and carrier transport were investigated from dark current–voltage and capacitance–voltage characteristics. Examination of the multiplication properties was performed under different light excitation and reverse bias conditions. The spectral and pulse response characteristics are analysed. The current amplification mechanism is interpreted by the control of electron current by the space charge of photogenerated holes near the SiOx/Si interface. The optical sensor output characteristics and some possible device applications are presented.

Several methods for determination of the antenna heterogeneity of Photosystem II from fluorescence rise curves measured with DCMU have been developed so far. Using these methods, two, three or four types of Photosystem II with respect to the antenna heterogeneity were determined. However, the accuracy of some of these methods is under debate. Here, we present a new method for the determination of the antenna heterogeneity of Photosystem II. The method is based on direct simultaneous fitting of several fluorescence rise curves measured with DCMU at different intensities of light excitation. As several curves measured under different light conditions are fitted simultaneously by the same model, reliability and accuracy in determination of model parameters increase. Our method was applied to two plant materials with different structure of the thylakoid membrane: wheat leaves and cells of green alga Chlamydomonas reinhardtii.

F-centers in an additively colored KCl crystals were excited by light of the L1-band (3371 A). The emission spectrum of the main bands were measured at several temperatures ranging from 47 to 171 K. At least three bands were clearly identified, the F*-band, the K-band, and the M-band. A mechanism for the electron decay which leads to an interpretation of the data is proposed. In addition, the experiment suggests that under L1-light excitation, the luminiscence lifetime may contain at least three lifetimes: the lifetime of F* (∼600 ns), the lifetime for the K-band (335 ns) (Da Silva, Phy. Stat. Sol. (b) 169 (1992) K119–122) and the one corresponding to the M-center (30 ns).

This paper deals with researches of output characteristics of a field-controlled phototransistor with light excitation in a light-activated mode. Optical signal transformation mechanisms in a channel are determined, considering processes in a drain-gate junction. Criteria of base region effective modulation are specified. Obtained results can be used in design of new generation transistors.

We report the investigation of the steady-state Hall mobility and carrier concentration behavior depending on extrinsic light excitation intensity, wavelength and temperature in n-type liquid-encapsulated Czochralski (LEC) GaAs crystals. The carrier concentration of the samples measured in the dark ranged from 108 to 3×1011 cm−3, and the Hall mobility showed a pronounced minimum in the concentration region 109–1011 cm−3. The measured dependencies demonstrated peculiarities in this region which could not be explained by a homogeneous semiconductor model. We demonstrate that the observed effects are caused by the complex influence of the deep levels in the band gap and of the defect inhomogeneities related to the cellular structure of dislocations. The effect of inhomogeneities is intensified in the samples from the intermediate concentration region 109–1011 cm−3. It is related to the specific compensation conditions, which take place when the Fermi level appears between the EL2 level and the negative-U dou...

Fostered by the success of photodynamic therapy (PDT), light activation of transition metal complexes has raised notable interest for applications in biology and in medicine. The rich photochemistry of metal complexes and the arsenal of chemical reactions accessible via light excitation have been exploited for developing therapeutic agents which exert their biological action through novel mechanisms. This chapter aims to provide an overview of the concepts and strategies adopted by leading scientists in the design and development of photoactivatable metal complexes with potential use in cancer therapy. In particular, we focus on the anticancer properties of Pt, Rh, and Ru complexes which have been demonstrated to be amongst the most promising classes of compounds.

The radical-pair mechanism is understood to underlie the magnetic navigation capability of birds and possibly other species. Experiments with birds have provided indirect and in cases conflicting evidence on the actual existence of this mechanism. We here propose a new experiment that can unambiguously identify the presence of the radical-pair magnetoreceptor in birds and unravel some of its basic properties. The proposed experiment is based on modulated light excitation with a pulsed laser, combined with delayed radio-frequency magnetic field pulses. We predict a resonance effect in the birds' magnetic orientation versus the rf-pulse delay time. The resonance's position reflects the singlet-triplet mixing time of the magnetoreceptor., Comment: 5 pages, 5 figures

Silica submicron rods were conveniently synthesized through a simple sol-gel method at room temperature. The SEM images demonstrated that the obtained silica submicron rods had high purity and uniform diameter of about 380-400 nm. The XRD results showed the obtained silica submicron rods were amorphous. Furthermore, the silica submicron rods exhibited blue emission under UV light excitation, which is relevant to the surface-associated defects.

Biocompatible luminescent materials have received much attention for the development of novel bioprobes. In the present work, we have synthesized the flower-like hydroxyapatite (HA) nanostructure from eggshell biowaste via a simple and rapid microwave conversion process. The synthesized product is identified as Mg containing B-type carbonated HA. It showed an intense blue emission between 360 nm to 550 nm with maximum around 430 nm under UV light excitation (λex= 344 nm). This blue emission might result from the carbonate related impurities present in the structure of HA and it can be a potential luminescent material for the development biocompatible probes.

Photostructural changes in thin films of amorphous selenium have been studied in situ at 30 K using EXAFS. A dynamical increase in coordination is observed in the excited state accompanied by an increase in disorder. The observed change is attributed to the formation of dynamical interchain bonds under light excitation.

Operational features of excitable Belousov–Zhabotinsky-type light-sensitive media that can be used to implement image-processing operations are discussed. They embrace (i) the main primitive responses of such media to light excitation as a function of medium acidity, temperature and light exposure, (ii) the characteristics of temporal evolution of stored media and (iii) the resolution and information content inherent in images stored by excitable media. It is shown that controlling the acidity of the medium, its temperature and the duration of light exposure enables one to get reproducible results.

Fluorescence optical imaging of molecular and cellular structures has been pursued with great interest over the last years. The methodology, which was originally introduced in the microscopy field, is now avery important tool in several preclinical research fields which use living laboratory animals. Today, dedicated fluorescence imaging systems are also being tested for first introduction into the clinical situation. These investigations are driven by the advantage that the methodology is a non-invasive one, that images can be obtained in real-time and with high-resolution, and that molecular informationis available at comparatively low costs compared to PET and SPECT. Nevertheless, the limited penetration of light into tissues is one of the main challenges. Consequently, the implementation of fluorescence optical imaging into the clinical practice will prospectively be confined to dedicated parts of the body using specialized light excitation, detection systems. Moreover, special attention must also be devoted to the design of corresponding fluorooptical probes. The signaling moiety of optical probes is normally much larger compared to optical tracer with corresponding impact on pharmacokinetics and dynamics. In this article we will discuss the potential and current challenges in optical imaging in diagnostic radiology.

Flow cytometry (FC) is a technique for the rapid analysis of multiple parameters of individual cells. One of the limitations of conventional methods for the analysis of cell populations is the determination of a single value for each cell parameter, which is considered representative of the whole cell population. In contrast, FC aims to obtain segregated data, corresponding to different cell subpopulations. In flow cytometers, single cells or particles pass through a light source in a directed fluid stream, and the interaction of the individual cells with the light source can be recorded and analysed, using the principles of light scattering, light excitation and the emission from fluorescent stains. Thus, the data obtained can provide useful information on the distribution of specific characteristics in cell populations.

We have performed the temporally-averaged photovoltage measurements under intermittent light excitation on Cu(In,Ga)Se 2 [CIGS] solar cells by means of photo-assisted Kelvin probe force microscopy, which we originally proposed, and evaluated a time constant τ for photovoltage decay and a contribution ratio r of fast carrier recombination, the former of which is considered to represent a time constant required for the carrier movement across the potential barriers at the hetero-interfaces in the cell structure.

Tunable white light emission is obtained from γ-irradiated Ag/Eu co-doped 65NaPO3—30Al(PO3)3—5SiO2 phosphate glass under 320—394 nm excitation.

International audience; We have investigated the mechanisms of photoelectron tunneling into gold from tipless, nitridized, gallium arsenide microcantilevers through thin polymers. A study of the tunnel bias, tunnel distance, and light excitation power dependence of the tunneling photo-current reveals the tunneling process to be Fowler-Nordheim like. Both the value of the dielectric constant and the sign of the tunneling photocurrent at low excitation power suggest the important role of polymer defects.

Photocatalysis phenomena in TiO 2 have been under intense investigation for its potential applications in pollution abatement and in production of hydrogen for green energy. Present study shows that surface modification is a potential technique to achieve efficient and stable plasmonic assisted sun light driven photocatalyst with TiO 2 thin films. A few layers (of different thicknesses) of metallic silver have been deposited (by DC magnetron sputtering technique and subsequently annealed) on the surface of sol-gel processed and spin coated TiO 2 thin films. The photocatalytic activity (PCA) has been measured with 254 nm, 352 nm and actual sun light excitations, aqueous Rhodamine B (RhB) dye is used to estimate the photocatalytic oxidation. The photocatalytic activity has been expressed as the number of RhB molecules oxidized for a given photon flux at the excitation wavelength, also rate constants have been evaluated. It is observed that (i) silver exists in the metallic state on the surface of TiO 2 thin films, (ii) the surface work function of TiO 2 thin films is modified by the silver as revealed by Kelvin probe measurements and (iii) the PCA of silver modified TiO 2 thin films is higher in comparison with unmodified surface. An attempt has been made to explain the higher activity of the surface modified Ag/TiO 2 thin film photocatalyst through the plasmon assisted photocatalytic process. The present study clearly establishes the view that surface modification of TiO 2 is a viable approach towards achieving an efficient sun light photocatalyst. � 2012 Elsevier B.V. All rights reserved.

Laser-flash-illuminated, dried chloroplast samples produce a fast electric response signal. We show that this signal is due to the light gradient effect. Two phenomena are observed when an external electric field is applied to the samples: (1) a large electric signal, obtained on light excitation, which is very different from the signal due to the light gradient effect; (2) an electric field due to polarization in the chloroplast layers which remains for hours when the sample is illuminated in an electric field. We attribute the two effects in the electric field to the motion and trapping of electrons due to light excitation in the thylakoid membranes.

Many Ru and Os systems display photoactive (3)MLCT states. Systems activated by therapeutic window light in the absence of O(2) remain elusive. [(bpy)(2)Os(dpp)RhCl(2)(phen)](3+) photobinds and photocleaves DNA under red light in an oxygen independent manner, due to molecular design involving one Os chromophore coupled to a photoactive cis-Rh(III)Cl(2) moiety.

We theoretically demonstrate optical pulsation based on optical near-field interactions at the nanoscale. We observe pulsation in populations pumped by continuous-wave light excitation based on optical energy transfer from smaller to larger quantum dots. This will provide critical insights toward the design and implementation of experimental nanophotonic pulse generating devices.

NAD(P)H fluorescence was investigated by spectrally-resolved lifetime detection, while individual NAD(P)H fluorescence components were resolved by spectral linear unmixing approach. Photobleaching was induced by excitation of a defocused elliptical spot with a 375nm picosecond laser for 30s repeated every 60s for 7min. Our data indicate presence of three individual components in cardiac cell autofluorescence (AF), and we recorded comparable photobleaching of the two resolved NAD(P)H components ("bound" and "free"). Decrease in photon counts during photobleaching was induced by lowering of the component amplitudes, without modification in the fluorescence lifetimes, while the ratio of the two amplitudes remained unchanged. Gathered results are crucial for choosing appropriate light excitation and fluorescence acquisition for prolonged studies of endogenous fluorescence aiming to investigate changes in metabolic oxidative state in living cardiac cells during their contraction.