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Near-infrared (NIR)-II light-excitable photonic agents capable of generating tumor hyperthermia and cytotoxic free radicals are promising for synergistic phototherapy of tumors. However, the lack o...

With the rapid development of the internet of things, light-excited gas sensors have aroused great attention to meet the increasing demand for room-temperature devices with high portability and low power consumption. However, there are still many issues that need to be addressed, especially the lack of tailored structures specifically designed for light-excited gas sensors. In this work, ∼2600 PIC micron-scaled gas sensors and LED UVC light sources were integrated on a 2-inch sapphire wafer. The integrated microchip exhibited an excellent gas-sensing response to NO2 under in situ light excitation. The response of the device to 500 ppb NO2 was S = 1.12 and its response to an ultra-low concentration of 10 ppb NO2 was S = 1.01. The device exhibited a low resistance at the kΩ-level and fast response and recovery time of 30 s and 88 s, respectively, to 500 ppb NO2, making it ideal for portable applications at room temperature. Moreover, its sensing properties could be tuned by adjusting the wavelength and irradiance of the LED layer. This work lays the foundation for the fabrication of integrated multi-functional devices.

Optimizing the stability and improving photoluminescence quantum yields (PLQYs) of all-inorganic halide perovskite nanocrystals has become an urgent and challenging task to promote its application ...

Photoelectrochemical (PEC) cells offer a promising approach for developing a solar energy conversion system to resolve the increasingly serious energy crisis and environmental issues. However, the lack of stable and eco-friendly electrodes hampers their practical applications. Herein, we prepare an eco-friendly photoanode with enhanced PEC performance embedding AgInS2 quantum dots (QDs) into three-dimensional (3D) graphene nanowalls (GNWs). AgInS2 QDs with tunable PL emissions are synthesized using a facile hydrothermal method and then deposited on GNWs directly grown on silica by a catalyst-free method. Benefitting from the interconnected 3D conductive network, GNWs act as an outstanding electron acceptor to transport the photogenerated carriers of AgInS2 QDs. The experimental results demonstrate that the AgInS2/GNWs photoanodes exhibit rapid photoresponse upon light excitation with comparable short rise-time (0.23 s) and decay-time (0.41 s). By optimizing the reaction temperature of the QDs, a photo-current density of 145 μA cm−2 can be achieved due to the effective separation of the photogenerated carriers. Meanwhile, the as-prepared photoanodes exhibit excellent stability of the photoresponse for more than 4000 s of on–off switching and one-month duration. Our study provides a new strategy to construct an eco-friendly PEC system with high performance which shows potential applications for PEC-type devices.

Two new oxysulfides, AeGeS2O (Ae = Sr, Ba), were successfully synthesized via the molten salt method. The two isostructural compounds crystallize in the noncentrosymmetric space group P212121. Their structures feature 1∞[GeS2O]2- one-dimensional helical chains which are built up by [GeS2O2]4- heteroanionic tetrahedra via corner sharing of O atoms. The two oxysulfides are typical semiconductors with wide bandgaps (SrGeS2O: 3.9 eV and BaGeS2O: 4.1 eV) that are perfectly consistent with the first-principles calculation results. They show typical band emissions under UV light excitation (SrGeS2O: 375 nm and BaGeS2O: 360 nm). In addition, SrGeS2O also possesses an orange-yellow light emission (572 nm). SrGeS2O and BaGeS2O exhibit moderate second harmonic generation (SHG) intensities of 0.4 × AgGaS2 and 0.5 × AgGaS2, respectively.

We report on a strong persistent photoconductivity (PPC) induced appearance of conductor‑like behaviour in zinc-tin-oxide (ZTO) photo-thinfilm transistors (TFT). The active ZTO channel layer was prepared by remote-plasma reactive sputtering and possesses an amorphous structure. Under sub-bandgap excitation of ZTO with UV light, the photocurrent reaches as high as ~10-4 A (a photo-to-dark current ratio of ~107) and remains close to this high value after switching off the light. During this time, the ZTO TFT exhibits strong PPC with long-lasting recovery time, which leads the appearance of the conductor‑like behaviour in ZTO semiconductor. In the present case, the conductivity changes over six orders of magnitude, from ~10-7 to 0.92 Ω-1cm-1. After UV exposure, the ZTO compound can potentially remain in the conducting state for up to a month. The underlying physics of the observed PPC effect is investigated by studying defects (deep-states and tail-states) by employing a discharge current analysis (DCA) technique. Findings from the DCA study reveal direct evidence for the involvement of sub-gap tail-states of the ZTO in the strong PPC, while deep-states contribute to mild PPC.

Despite the outstanding optoelectronic properties of MoS2 and its analogues, synthesis of such materials with desired features including fewer layers, arbitrary hollow structures, and particularly specifically customized morphologies, via inorganic reactions has always been challenging. Herein, using predesigned lanthanide‐doped upconversion luminescent materials (e.g., NaYF4:Ln) as templates, arbitrary MoS2 hollow structures with precisely defined morphologies, widely variable dimensions, and very small shell thickness (≈2.5 nm) are readily constructed. Most importantly, integration of the near‐infrared‐responsive template significantly improves the photoresponse of up to 600 fold in device made of NaYF4:Yb/Er@MoS2 compared with that of MoS2 nanosheets under 980 nm laser illumination. Multichannel optoelectronic device is further fabricated by simply changing luminescent ions in the template, e.g., NaYF4:Er@MoS2, operating at 1532 nm light excitation with a 276‐fold photoresponse enhancement. The simple chemistry, easy operation, high reliability, variable morphologies, and wide universality represent the most important advantages of this novel strategy that has not been accessed before., A facile template‐based strategy for reliable construction of arbitrary MoS2 hollow architectures with widely varied morphologies and dimensions is reported. An up to 600‐fold improvement of photoresponse to 980 nm light illumination is obtained in the representative optoelectronic device made of NaYF4:Yb/Er@MoS2 composite, compared with that of MoS2 nanosheets.

We designed and realized non-concentric magnetoplasmonic-diskplasmonic-ring nanocavities. Free-space light excitation and hybridization of multipolar modes in the plasmonic nanoring with the dipolar plasmon of the magnetoplasmonic disk produce an unprecedented amplification of the magneto-optic response.

The photon activated quantum states yielding resonant tunneling characteristics have been studied from the electrical properties of CdSe nanosheets grown in solvothermal technique. Using metal-semiconductor junction properties, the observed current density –voltage (J-V) behaviors have been analyzed under ultra-violet (UV) light excitation. In comparison to the dark behavior, the J-V property under UV shows a peak bound feature attributed to quantum controlled resonant tunneling effect.

In this paper we report the photo-trapping effect of photogenerated charge in a few numbers of silicon nanocrystals (Si-NCs) embedded in SiO2 layer tunnel oxide of small area single electron photodetector (Photo-SET or nanopixel). Using Current-Voltage measurements under illumination (photo-I–V) we find the photo-active traps effect in inversion zone at room temperature. Random Telegraphic Signal under illumination (photo-RTS analysis) confirms that is a photo-generated active trap inside into tunnel oxide layer (Ephoto-act∼ 0.2 eV) and capture section: σ∼8.72 × 10−17 cm2). Moreover, an increasing about 10 pF in capacity’s values in the inversion region for inverse high voltage applied under photo-excitation at low temperature have been marked using photo-Capacitance-Voltage (photo-C–V) measurements. This result confirms the contribution of photo-active traps to better dots photo-charged. The increase of light excitation time-duration, increase the hysteresis width. At 100 μW optical power and 595 nm wavelength, the hysteresis width has their saturation for a 0,05V/s romp speed, and consequently, SiO2 will not behave a dielectric, but as a metal. So we make think that total capacity of structure no more corresponds to the capacity related to the oxide, but to all structure capacity values. The nanopixel photo-detection time (∼400 s) estimated from the flat band evolution in time is affected by photo-active oxide traps presence.

Indocyanine green (ICG) emits fluorescence in the far-red domain under light excitation. ICG video angiography (ICG-VA) has been established as a useful method to evaluate blood flow in the operative field. We report the usefulness of ICG-VA for Sylvian fissure dissection in patients with subarachnoid hemorrhage (SAH). Subjects comprised 7 patients who underwent ICG-VA before opening the Sylvian fissure during neck clipping for ruptured cerebral aneurysm. We observed contrasted Sylvian veins before opening the Sylvian fissure using surgical microscopes. This procedure was termed "Sylvian ICG". We observed ICG fluorescence quickly in all cases. Sylvian veins that appeared unclear in the standard microscopic operative field covered with subarachnoid hemorrhage were extremely clearly depicted. These Sylvian ICG findings were helpful in identifying entry points and the dissecting course of the Sylvian fissure. At the time of clipping, no residual fluorescence from Sylvian ICG was present, and aneurysm clipping was not impeded. Sylvian ICG for SAH patients is a novel technique to facilitate dissection of the Sylvian fissure. We believe that this technique will contribute to improved safety of clipping surgery for ruptured aneurysms.

To study chemical and biological processes, spatially resolved determination of the concentrations of one or more analyte species is of distinct interest. With a light-addressable potentiometric sensor (LAPS), chemical images can be created, which visualize the concentration distribution above the sensor plate. One important challenge is to achieve a good lateral resolution in order to detect events that take place in a small and limited region. LAPS utilizes a focused light spot to address the measurement region. By moving this light spot along the semiconductor sensor plate, the concentration distribution can be observed. In this study, we show that utilizing a pulse as light excitation instead of a traditionally used continuously modulated light excitation, the lateral resolution can be improved by a factor of 6 or more.

The ability of plasmonic nanoparticles to harness visible light can be being combined with their catalytic activity to drive photocatalytic transformations. This Review introduces the promise of this new class of photocatalysts for fulfilling the quest for sunlight-driven recycling of CO2 into transportable liquid fuels. We discuss the prospects and challenges of such an approach. Despite considerable advances, a selective, stable, and efficient CO2 reduction reaction (CO2RR) catalyst has been elusive. These open challenges may be addressable by the strategic utilization of plasmonic light excitation. Plasmonic catalysts have exhibited the ability to drive a rich milieu of CO2RR processes under visible light excitation. At this stage, improved mechanistic understanding and reaction control are needed. To motivate rational design of photocatalytic materials and processes by a future generation of researchers, we suggest potential pathways by which plasmonic-assisted CO2RR can take place. We describe unique...

Fluorescence-guided surgery represents an evolution in the intraoperative assessment of physiology and anatomy during precision surgery. Fluorophores with known light excitation and emission profiles are used to specifically target tissues or pharmacological processes. These photophysical properties can be harnessed to improve tissue penetration compared with visible light. There is a growing body of evidence on the clinical effectiveness of fluorescence-guided surgery in several domains ranging from benign to neoplastic disease across multiple disciplines.

Low-temperature-grown GaAs (LT-GaAs)-based Fabry-Perot cavity photoconductors, designed for RF and THz optoelectronics applications using1550 nm lasers, are studied. The sub-sampling of continuous waves at frequencies up to 300 GHz is presented. The duty-cycle-limited conversion losses measured up to 67 GHz show that this GaAs-based photoconductor behaves as a nearly perfect photoswitch controlled by a 1550 nm pulsed laser.

Single-molecule detection commonly requires focused laser beams because of the small absorption cross-sections of dye molecules. Now, researchers have shown that thousands of dye molecules in nanoparticles can transfer light excitation to a single acceptor dye, enabling single-molecule detection at sunlight excitation power.

Cu2O nanowires decorated with Au nanoparticles (Cu2O–Au NWs) were synthesized by a facile solution method. Due to light excited plasmonic hot carrier transfer from Au nanoparticles into Cu2O nanowires, under 360 and 420 nm light excitation, the fluorescence emissions of Cu2O–Au NWs, compared with that of Cu2O nanowires, were enhanced 4.03 and 3.35 times, respectively. The decay time of Cu2O–Au NWs is 4.85 times longer than that of Cu2O NWs under 337 nm light excitation. The results indicate that hot carrier transfer can effectively modulate the optical properties of Cu2O NWs.

In this work, multiple color emitting solid-state carbon dots with europium (III) complexes hybrid material has been prepared through in situ synthesis within the confined interlayer of the host clay. The emission color of the resulting hybrid material can be tuned from red to blue through changing the excitation wavelength, where the white emission (CIE-(0.27, 0.28)) can be achieved under 302 nm UV light excitation. Therefore, the as-prepared material possesses a promising prospect in the area of optics, especially in white light-emitting diodes (WLEDs).

We study low-temperature-grown, GaAs-based Fabry-Perot cavity photoconductors, designed for RF and THz optoelectronics applications using 1550 nm lasers. We present here the sub-sampling of continuous waves at frequencies up to 300 GHz with a SNR of 70 dB.

The Tb3+/Sm3+ codoped Sr2LiSiO4F white emitting phosphors were synthesized by a solid-state reaction technique at high temperature. The X-ray diffraction patterns, photoluminescence properties, and decay behaviors have been investigated. The Tb3+ emissions (blue and green) and Sm3+ emissions (orange) are both observed in the codoped samples Sr2LiSiO4F: 0.05Sm3+, xTb3+ by near-UV light (370 nm) exciting. The white emission has been obtained by adjusting Tb3+ doping concentration at 5% (x = 0.05). These luminescent powders are expected to be a potential candidate as white emitting phosphor for near-ultraviolet InGaN-based white light-emitting diodes.

The dynamic of nonequilibrium charge carriers, involving trapping centers, in conditions of joint action the stationary light excitation and alternate deformation on semiconductor is investigated.

Tunable white light was realized in samples Ba2(1−x)TiP2O9:2xEu (x = 0–0.80) by introducing orange-red light emitting Eu3+ in self-activated blue-green light emitting matrix Ba2TiP2O9. The sample Ba2(1−x)TiP2O9:2xEu is a multiphase system consisting of Ba2TiP2O9, EuPO4 and TiO2 when x is greater than or equal to 0.20. The tunable light from blue-green to bluish-white, to white, and eventually to pinky-white of samples Ba2(1−x)TiP2O9:2xEu under UV light excitation is attributed to the light mixture of tunable blue-green light from Ti4+–O2− charge transfer transition in Ba2TiP2O9 and orange-red light from Eu3+ 4f–4f transition mostly in EuPO4. The Commission International de l’Eclairage chromaticity coordinates, correlated color temperature and color rendering index were tuned from (0.262, 0.339), 9492 K and 74 for matrix sample Ba2TiP2O9 to (0.324, 0.346), 5876 K and 87 for sample Ba2(1−x)TiP2O9:2xEu (x = 0.40) under UV light excitation. Therefore, a kind of promising UV-excited white light emitting multiphase phosphor was obtained.

This paper provides the theory, mathematics analysis and experiments in support of the Infrared thermal-wave inspection on the subsurface defects in a solid using linear frequency modulated light excitation (LFMTWI). The specimen is heated by the heat flux of linear frequency modulation for launching thermal-wave into the sample in a desired range of frequency. The more thermal wave responses characters are obtained, and the IR thermal-wave imaging shows much more advantages for subsurface defects detection. The simulation and experimental results from steel sample are presented in support of this technique.

A kind of Tm3+/Dy3+ co-doped fluorphosphate glass was prepared by the melt quenching method for continuous tunable multi-chromatic phosphors. The emission and excitation spectra of the glass showed that the color of luminescence can be tuned from blue/cold white to warm white/yellow by controlling the wavelength of exciting light. White light emission can be achieved under 353 nm and 362 nm UV light excitation. In addition, energy transfer mechanisms between Tm3+ and Dy3+ were also analyzed. The relationship between the color coordinate and the excited wavelength was also established. The Tm3+/Dy3+ co-doped fluorphosphate glass may be potential candidates for tunable multi-chromatic phosphor application.

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.

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.

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.

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...

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.

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.

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.

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.

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...

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.

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.

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.

Investigation of some light-matter interactions in Multi-Interface Novel Devices (MIND) containing a nanoscale Si-layered system have led to a method for predicting free-carrier density dependent nonlinear optical properties as a function of doping, light excitation intensity and carrier injection. The approach is based on the well-known t-matrix approximation. A simplified a few-layer optical model has been constructed that will reproduce the main features/parameters of real systems. The degree of model and simulation self-consistency is discussed using basic physical functions and published experimental data. Near perfect agreement between the simulated model and the corresponding experimental results has been obtained. In this way, the simulation allowed us to determine the main origins/components of the strong optical nonlinearity characteristic of one of the most specific MIND behaviours.

In this work we report on the development of a fluorescence molecular imager based on patterned light excitation operating in the time-domain.