Blue Laser Illumination Research Articles

Advanced photodegradation and antimicrobial performance: A comparative study of Al/Ag-Co-doped ZnO synthesis via laser assist chemical bath

This study utilizes a novel laser-assisted chemical bath synthesis (LACBS) approach to dope zinc oxide (ZnO) nanostructures with aluminum (Al) and silver (Ag), examining enhancements in photocatalytic and antimicrobial capabilities. The configurations tested include undoped ZnO, singly-doped ZnO(0.05) and ZnO(0.05), and co-doped ZnO:[Ag(0.025), Al(0.025)]. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses reveal shifts in lattice orientations and novel morphologies such as crumpled nano-flakes and interlocked flower-like formations. UV–visible spectroscopy results show a reduction in optical band gaps from 3.39 eV in undoped ZnO to 2.89 eV in co-doped samples. Photocatalytic activity testing under UV light reveals that undoped ZnO reaches a 68 % degradation efficiency of methylene blue over 10 min, while co-doped ZnO exhibits a superior 78.93 % efficiency under blue laser illumination. Antimicrobial assays indicate that co-doped ZnO inhibits Escherichia coli and Klebsiella pneumonia growth with zones of inhibition up to 40 mm, significantly larger than those observed with singly-doped or undoped samples. The integration of Al and Ag significantly enhances the crystalline structure, reduces the optical band gap by up to 0.50 eV, and increases both photocatalytic and antimicrobial effectiveness, marking substantial progress in the functional applications of ZnO nanostructures.

Yellow YAG-Ag/Al2O3 film applied to blue laser illumination

The most popular light-emitting component for laser illumination right now is phosphor in glass (PiG), however its major weakness is the poor heat conductivity. In this research, the yellow YAG:Ce phosphor and Ag paste were co-fired on an Al2O3 substrate using the blade-coating approach to create a PiM (phosphor in metal) film. Due to the ultra-high thermal conductivity of Ag, the highest blue laser power density that YAG-Ag PiM can achieve is 9.2 W·mm−2, and the maximal luminous flux, lumen efficiency and CCT (correlated color temperature) are 620 lm, 172 lm·W−1 and 6244 K, respectively.

Facile Synthesis of Ni-Doped ZnO Nanostructures via Laser-Assisted Chemical Bath Synthesis with High and Durable Photocatalytic Activity

Pure and Ni-doped (1%, 2%, and 3%) nanostructures were synthesized using a novel laser-assisted chemical bath synthesis (LACBS) technique. For the first time, LACBS was used to create a doping solution utilizing a 7 W blue laser with a 444.4 nm wavelength and a continuous beam. The Ni-doping concentration was varied by changing the amount of Ni precursor added. All samples were analyzed using XRD, SEM, EDX, FTIR, UV–Vis, and photocatalysis tests for photodegradation under blue laser illumination. XRD was used to confirm that the tested ZnO had a hexagonal wurtzite structure. The crystallite size decreased as the Ni-doping concentration rose. EDX experiments were conducted to analyze the elemental characteristics of the pure and Ni-doped (1%, 2%, and 3%) nanostructures. The existence of nanoscale hexagonal structures was confirmed through SEM studies. The band gap values of the pure and Ni-doped ZnO nanostructures decreased as the doping concentration increased. FTIR studies were conducted to examine the functional groups of the pure and doped samples. The produced materials exhibited excellent photocatalytic performance toward the degradation of MB organic dye, an example of a pollutant found in wastewater.

Holographic colour prints for enhanced optical security by combined phase and amplitude control

Conventional optical security devices provide authentication by manipulating a specific property of light to produce a distinctive optical signature. For instance, microscopic colour prints modulate the amplitude, whereas holograms typically modulate the phase of light. However, their relatively simple structure and behaviour is easily imitated. We designed a pixel that overlays a structural colour element onto a phase plate to control both the phase and amplitude of light, and arrayed these pixels into monolithic prints that exhibit complex behaviour. Our fabricated prints appear as colour images under white light, while projecting up to three different holograms under red, green, or blue laser illumination. These holographic colour prints are readily verified but challenging to emulate, and can provide enhanced security in anti-counterfeiting applications. As the prints encode information only in the surface relief of a single polymeric material, nanoscale 3D printing of customised masters may enable their mass-manufacture by nanoimprint lithography.

Ferroelectric, magnetoelectric and photoelectric properties of BiFeO3 /LaNiO3 heterostructure

BiFeO3/LaNiO3 (BFO/LNO) heterostructure was fabricated on quartz substrate via RF sputtering method. The microstructure and surface morphology of the BFO/LNO heterostructure was demonstrated. BFO layer shows good ferroelectric and weak ferromagnetic characters at room temperature. The dielectric constants of the heterostructure under an applied magnetic field 1.2T and zero field are both decreased with increasing frequency at room temperature and the dielectric constant under the applied magnetic field is larger, which is attributed to the coupling between the electric and magnetic dipoles, and further demonstrated in the framework of the Ginzburg-Landau theory for second phase transition. Additionally, the photoconductivity of the heterostructure under blue-laser illumination was observed, and the photoconductivity increase with the enhanced power of the blue-laser.

In situ investigations of laser and thermally modified As2S3 nanolayers: Synchrotron radiation photoelectron spectroscopy and density functional theory calculations

As-deposited, annealed, and in situ As2S3 nanolayers, illuminated by blue (405 nm) and red (650 nm) laser light, were studied using synchrotron radiation photoelectron spectroscopy and DFT electronic structure calculations. Changes in composition and local atomic coordination occurring in the irradiated region of As2S3 films were monitored by analysis of As 3d and S 2p core levels. These studies show that both the thermal treatment and the red laser illumination of As2S3 nanolayers decrease the concentration of homopolar (As-As and S-S) bonds. From the other hand, an increasing concentration of As-rich structural units (s.u.) with a homopolar As-As bond was observed under in situ blue laser illumination of As2S3 nanolayers. Molecular orbital energies were calculated for different As- and S-centered s.u. and used for the interpretation of the core levels and valence band spectra. The surface local structure of the As2S3 nanolayers and its photoinduced transformation are discussed in detail.

Origin of photovoltaic effect in superconducting YBa2Cu3O6.96 ceramics.

We report remarkable photovoltaic effect in YBa2Cu3O6.96 (YBCO) ceramic between 50 and 300 K induced by blue-laser illumination, which is directly related to the superconductivity of YBCO and the YBCO-metallic electrode interface. There is a polarity reversal for the open circuit voltage Voc and short circuit current Isc when YBCO undergoes a transition from superconducting to resistive state. We show that there exists an electrical potential across the superconductor-normal metal interface, which provides the separation force for the photo-induced electron-hole pairs. This interface potential directs from YBCO to the metal electrode when YBCO is superconducting and switches to the opposite direction when YBCO becomes nonsuperconducting. The origin of the potential may be readily associated with the proximity effect at metal-superconductor interface when YBCO is superconducting and its value is estimated to be ~10–8 mV at 50 K with a laser intensity of 502 mW/cm2. Combination of a p-type material YBCO at normal state with an n-type material Ag-paste forms a quasi-pn junction which is responsible for the photovoltaic behavior of YBCO ceramics at high temperatures. Our findings may pave the way to new applications of photon-electronic devices and shed further light on the proximity effect at the superconductor-metal interface.

Flexible phototransistors based on graphene nanoribbon decorated with MoS2 nanoparticles

This paper presents highly efficient, flexible, and low-cost photo-transistors based on graphene nanoribbon (GNR) decorated with MoS2 nanoparticles (NPs). Due to high carrier mobility, GNR has been used as carrier transport channel and MoS2 NPs provide strong advantage of high gain absorption and the generation of electron-hole pairs. These pairs get separated at the interface between GNR and MoS2 NPs, which leads to electron transfer from NPs towards GNR. The fabricated devices based on GNR-MoS2 hybrid material show a high photo-responsivity of 66AW−1 and fast rise-time (tr) and decay-time (td) of 5ms and 30ms, respectively, under blue laser illumination with a wavelength of 385nm and power density of 2.1μW. The achieved photo-responsivity is 1.3×105 and 104 times larger than that of the first reported pristine graphene and MoS2 photo-transistors, respectively. Furthermore, fabricated devices show a high stability for bending radii larger than 6mm. The simple solution based process, high gain and reproducible operation of fabricated photo-transistors indicate potential applications of them in state of the art photo-detectors and imaging systems.

Light-Induced Increase of Electron Diffusion Length in a p-n Junction Type CH3NH3PbBr3 Perovskite Solar Cell.

High band gap, high open-circuit voltage solar cells with methylammonium lead tribromide (MAPbBr3) perovskite absorbers are of interest for spectral splitting and photoelectrochemical applications, because of their good performance and ease of processing. The physical origin of high performance in these and similar perovskite-based devices remains only partially understood. Using cross-sectional electron-beam-induced current (EBIC) measurements, we find an increase in carrier diffusion length in MAPbBr3(Cl)-based solar cells upon low intensity (a few percent of 1 sun intensity) blue laser illumination. Comparing dark and illuminated conditions, the minority carrier (electron) diffusion length increases about 3.5 times from Ln = 100 ± 50 nm to 360 ± 22 nm. The EBIC cross section profile indicates a p-n structure between the n-FTO/TiO2 and p-perovskite, rather than the p-i-n structure, reported for the iodide derivative. On the basis of the variation in space-charge region width with varying bias, measured by EBIC and capacitance-voltage measurements, we estimate the net-doping concentration in MAPbBr3(Cl) to be 3-6 × 10(17) cm(-3).

Optical schemes for speckle suppression by Barker code diffractive optical elements

A method for speckle suppression based on Barker code and M-sequence code diffractive optical elements (DOEs) is analyzed. An analytical formula for the dependence of speckle contrast on the wavelength of the laser illumination is derived. It is shown that speckle contrast has a wide maximum around the optimal wavelength that makes it possible to obtain large speckle suppression by using only one DOE for red, green, and blue laser illumination. Optical schemes for implementing this method are analyzed. It is shown that the method can use a simple liquid-crystal panel for phase rotation instead of a moving DOE; however, this approach requires a high frequency of liquid-crystal switching. A simple optical scheme is proposed using a 1D Barker code DOE and a simple 1D liquid-crystal panel, which does not require a high frequency of liquid-crystal switching or high-accuracy DOE movement.

Optogenetic manipulation of cerebellar Purkinje cell activity in vivo.

Purkinje cells (PCs) are the sole output neurons of the cerebellar cortex. Although their anatomical connections and physiological response properties have been extensively studied, the causal role of their activity in behavioral, cognitive and autonomic functions is still unclear because PC activity cannot be selectively controlled. Here we developed a novel technique using optogenetics for selective and rapidly reversible manipulation of PC activity in vivo. We injected into rat cerebellar cortex lentiviruses expressing either the light-activated cationic channel channelrhodopsin-2 (ChR2) or light-driven chloride pump halorhodopsin (eNpHR) under the control of the PC-specific L7 promoter. Transgene expression was observed in most PCs (ChR2, 92.6%; eNpHR, 95.3%), as determined by immunohistochemical analysis. In vivo electrophysiological recordings showed that all light-responsive PCs in ChR2-transduced rats increased frequency of simple spike in response to blue laser illumination. Similarly, most light-responsive PCs (93.8%) in eNpHR-transduced rats decreased frequency of simple spike in response to orange laser illumination. We then applied these techniques to characterize the roles of rat cerebellar uvula, one of the cardiovascular regulatory regions in the cerebellum, in resting blood pressure (BP) regulation in anesthetized rats. ChR2-mediated photostimulation and eNpHR-mediated photoinhibition of the uvula had opposite effects on resting BP, inducing depressor and pressor responses, respectively. In contrast, manipulation of PC activity within the neighboring lobule VIII had no effect on BP. Blue and orange laser illumination onto PBS-injected lobule IX didn't affect BP, indicating the observed effects on BP were actually due to PC activation and inhibition. These results clearly demonstrate that the optogenetic method we developed here will provide a powerful way to elucidate a causal relationship between local PC activity and functions of the cerebellum.

Confocal laser endoscopy for diagnosing intraepithelial neoplasias and colorectal cancer in vivo

A confocal laser endoscopy system has recently been developed that may allow subsurface imaging of living cells in colonic tissue in vivo. The aim of the present study was to assess its potential for prediction of histology during screening colonoscopy for colorectal cancer. Twenty-seven patients underwent colonoscopy with the confocal endoscope using acriflavine hydrochloride or fluorescein sodium with blue laser illumination. Furthermore, 42 patients underwent colonoscopy with this system using fluorescein sodium. Standardized locations and circumscript lesions were examined by confocal imaging before taking biopsy specimens. Confocal images were graded according to cellular and vascular changes and correlated with conventional histology in a prospective and blinded fashion. Acriflavine hydrochloride and fluorescein sodium both yielded high-quality images. Whereas acriflavine hydrochloride strongly labeled the superficial epithelial cells, fluorescein sodium offered deeper imaging into the lamina propria. Fluorescein sodium was thus used for the prospective component of the study in which 13,020 confocal images from 390 different locations were compared with histologic data from 1038 biopsy specimens. Subsurface analysis during confocal laser endoscopy allowed detailed analysis of cellular structures. The presence of neoplastic changes could be predicted with high accuracy (sensitivity, 97.4%; specificity, 99.4%; accuracy, 99.2%). Confocal laser endoscopy is a novel diagnostic tool to analyze living cells during colonoscopy, thereby enabling virtual histology of neoplastic changes with high accuracy. These newly discovered diagnostic possibilities may be of crucial importance in clinical practice and lead to an optimized rapid diagnosis of neoplastic changes during ongoing colonoscopy.

Photoelectrochemical behaviour of a dye-grafted nanocrystalline SnO 2 powder

A perylene-based dye was synthesized and covalently bound to undoped SnO 2 nanosized powder. Because of the grafted dye, film sintering is not a straightforward process. In a preliminary step, it is proposed to check the photoactivity of this new powdered material directly by means of the cavity microelectrode technique under green or blue laser illumination through an optical microscope. Taking advantage of the chemical stability of the Sn–C bond, aqueous redox electrolytes were considered. Two types of microcavities were used, a laser-ablated with a residual Pt-coating on the overall cavity inner side, and a chemically etched with the rear Pt contact at the bottom only. Voltammetry and electrochemical impedance spectroscopy (EIS) were used to characterize the response of the SnO 2 powder inserted in the cavity. From the results presented here, two contributions have been identified: (i) that of the light insensitive Pt|electrolyte interface due to the Pt-coated inner side when present; (ii) that of the dye-grafted SnO 2|electrolyte photoactive interface. It is shown that direct information on available photopotentials for a given redox electrolyte can be readily obtained. From this point of view, a 600 mV open-circuit voltage has been obtained with the new dye-sensitized SnO 2 powder in contact with an aqueous bromide-containing electrolyte.

Extended and Point Defects in Diamond Studied with the Aid of Various Forms of Microscopy.

It is shown that star disclinations can be a significant source of stress in chemical vapor deposited (CVD) diamond. This purely geometrical origin contrasts with other sources of stress that have been proposed previously. The effectiveness is demonstrated of the use of electron irradiation using a transmission electron microscope (TEM) to displace atoms from their equilibrium sites to investigate intrinsic defects and impurities in CVD diamond. After irradiation, the samples are studied by low temperature photoluminescence microscopy using UV or blue laser illumination. Results are given that are interpreted as arising from isolated <100> split self-interstitials and positively charged single vacancies. Negatively charged single vacancies can also be revealed by this technique. Nitrogen and boron impurities may also be studied similarly. In addition, a newly developed liquid gallium source scanned ion beam mass spectrometry (SIMS) instrument has been used to map out the B distribution in B doped CVD diamond specimens. The results are supported by micro-Raman spectroscopy.

Extended and Point Defects in Diamond Studied with the Aid of Various Forms of Microscopy

AbstractIt is shown that star disclinations can be a significant source of stress in chemical vapor deposited (CVD) diamond. This purely geometrical origin contrasts with other sources of stress that have been proposed previously. The effectiveness is demonstrated of the use of electron irradiation using a transmission electron microscope (TEM) to displace atoms from their equilibrium sites to investigate intrinsic defects and impurities in CVD diamond. After irradiation, the samples are studied by low temperature photoluminescence microscopy using UV or blue laser illumination. Results are given that are interpreted as arising from isolated &lt;100&gt; split self-interstitials and positively charged single vacancies. Negatively charged single vacancies can also be revealed by this technique. Nitrogen and boron impurities may also be studied similarly. In addition, a newly developed liquid gallium source scanned ion beam mass spectrometry (SIMS) instrument has been used to map out the B distribution in B doped CVD diamond specimens. The results are supported by micro-Raman spectroscopy.

Extended and Point Defects in Diamond Studied with the Aid of Various Forms of Microscopy

Abstract It is shown that star disclinations can be a significant source of stress in chemical vapor deposited (CVD) diamond. This purely geometrical origin contrasts with other sources of stress that have been proposed previously. The effectiveness is demonstrated of the use of electron irradiation using a transmission electron microscope (TEM) to displace atoms from their equilibrium sites to investigate intrinsic defects and impurities in CVD diamond. After irradiation, the samples are studied by low temperature photoluminescence microscopy using UV or blue laser illumination. Results are given that are interpreted as arising from isolated &lt;100&gt; split self-interstitials and positively charged single vacancies. Negatively charged single vacancies can also be revealed by this technique. Nitrogen and boron impurities may also be studied similarly. In addition, a newly developed liquid gallium source scanned ion beam mass spectrometry (SIMS) instrument has been used to map out the B distribution in B doped CVD diamond specimens. The results are supported by micro-Raman spectroscopy.