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Laser-Generated BiVO4 Colloidal Particles with Tailoring Size and Native Oxygen Defect for Highly Efficient Gas Sensing
摘要： To alleviate the poor sensing performance of BiVO4, developing new strategies for the fabrication of unique device with improved sensing properties is very necessary and has great practical significance. In this work, size-tailored and uniform black BiVO4 colloids with abundant oxygen vacancy were synthesized by a unique method of pulsed laser irradiation of colloidal nanoparticles (PLICN). The corresponding laser irradiation effects on the sensing properties are comparatively investigated. The results indicate that the BiVO4 nanospheres with average size of 50 nm shows best sensing properties with high sensitivity, superior selectivity, low detection limit (44 ppb) to H2S at low working temperature (75 oC). Its sensing response is over 4 times higher when comparing with that of the raw material. Further investigation manifests that laser irradiation could induce quantity of the oxygen vacancy and decrease the resistance of the sensing device, which is mainly responsible for the enhanced sensing performance. Moreover, the density functional theories (DFT) calculations suggest that the oxygen vacancies can greatly decrease the surface absorption energy with enhanced H2S absorption capability on BiVO4 surface and lower the bader charger transfer from the absorbed H2S molecules to the BiVO4, thus enabling the implementation for the enhanced gas-sensing properties.
关键词： Pulsed laser irradiation,Hydrogen sulfide,Bismuth vanadate,Nanosphere,Gas sensor
更新于2025-09-23 15:19:57
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Designed synthesis of microstructure and defect-controlled Cu-doped ZnO-Ag nanoparticles: exploring high-efficiency sunlight-driven photocatalysts
摘要： Cu-doped ZnO nanoparticles composited with Ag were synthesized by one-step sol-gel method in this work, aiming at highly photocatalytic activity and possible application under sunlight (especially near ultraviolet and visible light regions, 300-760 nm) irradiation. Scanning electron microscopy (SEM) shows that the introduction of Cu inhibits particle aggregation. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) reveal that Zn(Cu)O-Ag nanoparticles (CZA NPs) are composed of metallic Ag (Ag0) and Zn(Cu)O nanocrystals; while at the Cu concentration of higher than 2%, a little CuO nanocrystals appear. Transmission electron microscopy (TEM) results evidenced the well-defined formation of Zn(Cu)O-Ag and/or CuO-ZnO-Ag heterojunctions. UV–vis spectra display that the visible absorption of the samples is obviously enhanced after the Cu introduction. At a low Cu doping level (0.2%) and moderate Cu concentration (3~5%), the blue and green photoluminescence (PL) emission strength of the samples become very weak in comparison to other samples, indicative of the high separation of photogenerated electron-hole pairs. Reasonably, the higher photocatalytic degradation (complete degradation of methylene blue (MB) and methyl orange (MO) within 40 minutes under the simulated sunlight irradiation) are achieved in these cases: low Cu doping level (0.2%) and moderate Cu concentration (3~5%) in CZA NPs. Further, we checked the effects of other factors on the photocatalytic degradation for possible application. Our results suggest that one well-designed composite type such as element-doped Zn(M)O-Ag nano-heterojunction or complicated metal oxide-ZnO-Ag nanocomposites possessing suitable band structures for the separation and utilization of photo-generated carriers, will remarkably improve the photocatalytic performance of nano-ZnO under sunlight irradiation.
关键词： ZnO-Ag nanocomposites,heterojunction,sunlight irradiation,Cu-doped ZnO,photocatalytic degradation
更新于2025-09-23 15:19:57
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Femtosecond-laser-irradiation-induced structural organization and crystallinity of Bi2WO6
摘要： controlling the structural organization and crystallinity of functional oxides is key to enhancing their performance in technological applications. in this work, we report a strong enhancement of the structural organization and crystallinity of Bi2Wo6 samples synthetized by a microwave-assisted hydrothermal method after exposing them to femtosecond laser irradiation. X-ray diffraction, UV-vis and Raman spectroscopies, photoluminescence emissions, energy dispersive spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy were employed to characterize the as-synthetized samples. To complement and rationalize the experimental results, first-principles calculations were employed to study the effects of femtosecond laser irradiation. Structural and electronic effects induced by femtosecond laser irradiation enhance the long-range crystallinity while decreasing the free carrier density, as it takes place in the amorphous and liquid states. these effects can be considered a clear cut case of surface-enhanced Raman scattering.
关键词： structural organization,Bi2WO6,femtosecond laser irradiation,crystallinity,microwave-assisted hydrothermal method
更新于2025-09-23 15:19:57
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Long-term effect of low-level diode laser irradiation on proliferation of stem cells from human exfoliated deciduous teeth after cryopreservation protocol
摘要： Low-level laser irradiation (LLLI) could be useful for the stimulation of stem-cell proliferation. LLLI has important physiological properties which increase the mitochondrial activity of cells. This study aimed to evaluate the biological effect of LLLI on cryopreserved stem cell from human exfoliated deciduous teeth (SHEDs). Cryopreserved and characterised SHEDs from a previous study were used for this study. The SHEDs were exposed to GaAlAs diode laser with energy densities of 1.2 (Group 2) and 2 J cm?2 (Group 3). For the control group (Group 1), SHEDs were cultured in culture medium including Dulbecco’s modified Eagle’s Medium supplemented with 15% foetal bovine serum, 1% L-glutamine, 1% penicillin-streptomycin, 1% gentamycin, and amphotericin-B. The cells in the experimental groups were irradiated as previously indicated, and after the irradiation were incubated for 0, 24, 48, and 72 h at 37 °C in 5% CO2. Proliferation of SHEDs was analysed by 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide assay at incubation periods of 0, 24, 48, and 72 h after the single-laser irradiation. The effects of laser irradiation on apoptosis of SHEDs at the last incubation period (72 h) were detected with the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labelling (TUNEL) method. Group 2 showed increased TUNEL-positive cells compared to Groups 1 and 3, but no significant differences between the three groups were observed (p > 0.05). Comparing Groups 2 and 3 to Group 1, the proliferation of SHEDs significantly increased after 24, 48, and 72 h (p < 0.05), but no significant differences were observed between the groups at 0 h (p > 0.05). In addition to this, at 72 h, Group 3 showed significantly higher proliferative effect on SHEDs compared to Group 2 (p > 0.05). In terms of clinical usage of long-term cryopreserved SHEDs, we can recommend to clinicians and researchers that prior to their use, LLLI may be used to increase the proliferation rate.
关键词： cryopreserved stem cells,low-level diode laser irradiation (LLLI),apoptosis,proliferation
更新于2025-09-23 15:19:57
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Effect of irradiation time in the synthesis of Au-Ag nanoalloys by femtosecond laser
摘要： The synthesis of metallic nanoparticles can be performed by femtosecond laser-induced photoreduction of the metallic ion solution. Due to hydrogen radical and the solvated electron generated through the interaction of ultrafast laser and water medium, the dissolved metallic ion in the medium can be converted to their respective metallic atom and then precipitated into nanoparticles. When there is more than one metallic ion available in the solution, alloy nanoparticles can be generated. One parameter that affects this laser-based synthesis was the duration of laser irradiation time that has an advantage for size modification of nanoparticles. In this work, we have synthesized Au-Ag nanoalloys from the mixture of Au and Ag ion in water medium added with 0.01wt% polyvinylpyrrolidone (PVP) as a capping agent and irradiated for 5 and 10 minutes. The result showed that there was linear shifting in surface plasmon resonance (SPR) of the nanoalloys in respect with their volume fraction of the ions. The results also revealed that the nanoparticle size was indeed reduced as the laser irradiation was prolonged, i.e., Au50Ag50 has a particle size of 7.98 nm and 5.18 nm for 5 and 10 minutes irradiation time, respectively.
关键词： irradiation time,Au-Ag nanoalloys,surface plasmon resonance,femtosecond laser,nanoparticle size
更新于2025-09-23 15:19:57
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Effect of Light-Emitting Diode Irradiation on Chronic Nonhealed Wound After Below-Knee Amputation
摘要： Chronic nonhealed wound after below-knee amputation is a serious problem that is faced by the health care team; therefore, there is a need to find an adjuvant therapy to address this problem. The aim of the study is to evaluate the therapeutic efficacy of light-emitting diode (LED) irradiation on chronic nonhealed wound after below-knee amputation using a digitalized method of evaluation by Adobe Photoshop CS5 aided by magnetic lasso tool. Thirty patients with chronic nonhealed wound (≥4 weeks) after below-knee amputation were randomly divided into 2 equal groups, with 15 participants in each. Group A received the LED irradiation for 24 sessions (3 sessions per week) in addition to the standard medical treatment, and the second experimental group (group B) received the standard medical treatment for 8 weeks. Methods of evaluation included the wound surface area: for tracing the wound perimeter using a computerized software. Results showed that both LED irradiation therapy and standard medical treatment were effective in healing the chronic nonhealed wound, but the LED was more effective than standard medical treatment alone. A clear improvement in the results of wound healing surface area was found in group A, with an improvement percentage of 50.63%, when compared with group B, which used the standard medical treatment alone, with an improvement percentage of 43.96%.
关键词： wound surface area measurement,below-knee amputation,chronic nonhealed wound,light-emitting diode irradiation
更新于2025-09-23 15:19:57
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Effect of the spot size on ionization and degree of plasma shielding in plumes induced by irradiation of a copper target by multiple short laser pulses
摘要： The plasma plume expansion into argon background gas at atmospheric pressure induced by irradiation of a copper target with a burst of three short laser pulses at 266 nm wavelength is studied numerically for the laser spot diameters ranging from 20 μm to 500 μm. The computational model includes a thermal model of the irradiated target and a kinetic model of plume expansion. The kinetic model is implemented in the form of the direct simulation Monte Carlo method that is redesigned to account for ionization and absorption of laser radiation in the plume. The irradiation conditions are chosen to do not induce ionization and absorption during the first pulse in the burst independently of the laser spot size. During the second pulse, the ionization is initiated in the vicinity of the irradiated target behind the shock wave that is generated during that pulse and propagates through the vapor plume created by the preceding pulse. The simulations show that the degree of ionization and plasma shielding during the second and subsequent pulses strongly increases with increasing the laser spot size. It is explained by different rates of expansion between pulses in the plumes generated at various spot sizes. At a relatively small spot size, the rapid drop of density and temperature in the plume induced by the first pulse can preclude plasma ignition during the second and further pulses. These results suggest that the use of lasers with the spot sizes that are in the order of tens of micrometers can be favorable for mitigating the effect of plasma shielding in multi-pulse laser ablation when the plumes induced by individual laser pulses strongly interact with each other.
关键词： Plume expansion,Multi-pulse irradiation,Laser spot size,Laser ablation,Plasma shielding
更新于2025-09-23 15:19:57
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Thermal coagulum formation and hemostasis during repeated multipulse Nd:YAG laser treatment of cutaneous vascular lesions: animal experiment study
摘要： Laser therapy has been widely used to treat port-wine stain (PWS) and other cutaneous vascular lesions via selective photothermolysis. High incident laser fluence is always prohibited in clinic to prevent the thermal damage in normal skin tissue, leading to insufficient energy deposition on the target blood vessel and incomplete clearance of PWS lesion. In this study, repeated multipulse laser (RMPL) irradiation was proposed to induce acute thermal damage to target blood vessels with low incident fluence (40 J/cm2 for 1064-nm Nd:YAG laser). The feasibility of the method was investigated using animal models. Repeated multipulse irradiation cycles with 10-min intervals were performed in RMPL. A hamster dorsal skin chamber model with a visualization system was constructed to investigate the instant generation of thermal coagulum and relevant hemostasis by thrombus formation during and after irradiation under 1064 nm Nd:YAG single multipulse laser (SMPL) and RMPL irradiation. The diameter of the target blood vessel and the size of thermal coagula were measured before and after laser irradiation. The reflectance spectra of the dorsal skin were measured by a reflectance spectrometer during RMPL. Stasis thermal coagula that clogged the vessel lumen were generated during SMPL irradiation with low incident fluence. However, there was no acute thermal damage of blood vessels. Reflectance spectra measurement showed that the generation of thermal coagula and subsequent thrombus formation increases blood absorption by more than 10% within the first 10 min after laser irradiation. Acute vessel thermal damage could be induced in the target blood vessel by RMPL with low incident fluence of 40 J/cm2. Compared with our previous SMPL study, nearly 30% reduction in incident laser fluence was achieved by RMPL. Low fluence RMPL may be a promising approach to improve the therapeutic outcome for patients with cutaneous vascular lesions by improving energy deposition on the target blood vessel.
关键词： Thermal coagula,1064-nm Nd:YAG laser,Port-wine stain,Repeated multiple pulse laser irradiation,Thrombus formation
更新于2025-09-23 15:19:57
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Effect of Infrared Low-Intensity Laser Irradiation on Lipid Peroxidation under Conditions of Experimental Circulatory Hypoxia of Visual Analyzer
摘要： The physiological stress modeled by circulatory hypoxia activates LPO processes in various tissues. In posthypoxic period, the infrared low-intensity laser irradiation significantly decreased the chemiluminescence parameters in blood plasma, normalized the retinal levels of diene and triene conjugates, and decreased MDA in the rat brain attesting to the correcting effect of this irradiation during various types of physiological stresses.
关键词： infrared low-intensity laser irradiation,lipid peroxidation,rats,visual analyzer
更新于2025-09-23 15:19:57
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Effect of UV exposure of ITO/PEDOT:PSS substrates on the performance of inverted-type perovskite solar cells
摘要： We have fabricated inverted-type perovskite solar cells employing CH3NH3PbI3?xClx perovskite in the form of ITO/PEDOT:PSS/Perovskite/PCBM/Al. The effects of UV radiation on ITO/PEDOT:PSS substrates have been investigated for perovskite solar cells. ITO/PEDOT:PSS substrates were exposed to UV radiation for 5 to 15 min. The perovskite solar cells fabricated on UV-irradiated ITO/PEDOT:PSS substrates exhibited better performance as compared to those fabricated on substrates employing non-treated PEDOT:PSS. We used photovoltaic characterization, UV–VIS absorption, sheet resistance, X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), and external quantum efficiency (EQE) characterization techniques to investigate the effect of UV irradiation of ITO/PEDOT:PSS substrates on the performance of perovskite solar cells. The devices fabricated on ITO/PEDOT:PSS (UV irradiated for 10 min) exhibited the best device performance of all. We achieved a 9% increase in the overall power conversion efficiency for the devices fabricated on substrates exposed to UV radiation.
关键词： Power conversion efficiency,ITO,Perovskite solar cells,PEDOT:PSS,UV irradiation
更新于2025-09-23 15:19:57