Effect Of Ultraviolet Illumination Research Articles

Effect of ultraviolet illumination on corrosion resistance of 304 austenitic stainless steel in molybdate-containing solution

This study investigates the effect of ultraviolet (UV) illumination on the corrosion resistance of 304 stainless steel in molybdate-containing solution. The UV illumination was found to reduce the passivation and pitting resistance of the passive films. In addition, the passive film exhibited n-type semiconductor characteristics. Under UV illumination, the content of Cr2O3 within the passive film decreased. Moreover, the formation of a built-in electric field inhibited the absorption of MoO42− on the substrate surface, thereby weakening the corrosion inhibition of Na2MoO4. This leads to a reduction in the corrosion resistance of the passive film.

Effect of Ultraviolet Illumination on the Fixation of Silver Ions on Zinc Oxide Films and Their Photocatalytic Efficiency

This study focuses on the fabrication and characterization of nanostructured zinc oxide films deposited on glass substrates using sol–gel dip-coating methods. The thin films are functionalized with silver ions at various Ag+ concentrations (10−2, 10−3, 10−4 M) through room temperature ion fixation process with and without ultraviolet (UV) illumination. Physicochemical characterization techniques, such as employing Scanning Electron Microscopy with Energy-dispersive X-ray spectroscopy (SEM-EDX), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Ultraviolet–Visible Spectroscopy and Electron Paramagnetic Resonance (EPR) techniques. The SEM-EDX and XRD confirmed a characteristic ganglia-like structure with a hexagonal crystalline structure. The photocatalytic performance and available surface area of the pure and Ag films are investigated in the removal of methylene blue dye under UV and visible light illumination and in darkness. It is observed that the photocatalytic activity increases proportionally to the Ag+ ion concentration: ZnO < Ag(10−4 M)/ZnO, < Ag(10−3 M)/ZnO < Ag(10−2 M)/ZnO. Moreover, the catalysts modified under UV illumination during the fixation treatment (Ag-UV/ZnO) exhibited a higher photocatalytic efficiency and degraded the dye in comparison with those without a light source (Ag/ZnO). The experimental results are confirmed using total organic carbon (TOC) analysis. The optimal silver concentration (10−2 M) is established, which shows the highest photocatalytic efficiency (in both cases of ion fixation treatment). The results can be used as a guideline for the development of co-catalyst-functionalized semiconductor photocatalysts.

Effects of Ultraviolet Illumination on Oxygen Interstitial Injection from TiO2 under Liquid Water

Effects of Ultraviolet Illumination on Oxygen Interstitial Injection from TiO₂ under Liquid Water

CsPbBr3 Nanoplatelets: Synthesis and Understanding of Ultraviolet Light-Induced Structural Phase Change and Luminescence Degradation

CsPbBr3 perovskite nanocrystals (mainly nanoplatelet morphology) have attracted attention due to their promising applications in optoelectronic devices. However, ultraviolet (UV) light exposure to these materials is one of the major factors for the degradation of halide perovskite nanocrystals, which needs to be studied to improve stability and boost performance. In this study, we synthesized CsPbBr3 perovskite nanoplatelets utilizing a hot injection method. The UV illumination effect on luminescence and structural properties of perovskite CsPbBr3 nanoplatelets were studied in detail. Under UV light illumination, less-emissive phases like CsPb2Br5 were observed within 10 h. However, long-term (i.e., 48 h) illumination of UV light resulted in the formation of some trace of PbCO3 and PbO phases that causes further degradation of perovskite CsPbBr3 nanoplatelets. This was verified by a significant decrease in photoluminescence (PL) intensity. Interestingly, UV light treated samples exhibited a stable CsPb2Br5 phase, which was observed after aging for a long period (∼9 months) of time that showed no further degradation. Furthermore, X-ray diffraction and full-width half maxima results confirmed an increase in crystalline size with illumination time increase. Obtained results strongly indicate that the UV light-induced PL degradation and trap state formation causes a synergistic effect of photo annealing in the presence of oxygen and moisture.

Hydrodynamic Snaring Array for Trapping and Perfusion Culture of Single Cell

A hydrodynamic snare and well array were developed to accomplish single-cell trapping and stem-cell perfusion culture. Directed streamline distribution is induced using unique V-shaped weir to load single bone marrow stem cell into U-shaped dwelling weir. The voids decrease flow speed in the dwelling area and enable a stable perfusion culture. The hydrodynamic snaring array was integrated with an on-line temperature control and monitoring system, and the ultraviolet illumination effect on a microscope is eliminated that is suitable for the long-term growth of single bone marrow stem cell with minimal external interventions.

Effects of ultraviolet illumination on 4H-SiC Schottky barrier diodes irradiated by swift heavy ions

In this study, the capacitance-voltage (C-V) and current-voltage (I-V) characteristics of 4H-SiC Schottky barrier diode (SBD) irradiated by swift heavy ions (SHI) are studied under different ultraviolet (UV) conditions. The effective carrier concentration (ND), reverse current (IR), series resistance (RS), ideal factor (n) and Schottky barrier height (SBH) are calculated and analyzed. Furthermore, by analyzing the parameters, especially, ND, IR and n, a physical model is built. The UV illumination dependence of the recombination center states for defects or defect-states is presented.

Unraveling the mechanism of ultraviolet-induced optical gating in Zn1−xMgxO nanocrystal solid solution field effect transistors

We report ultraviolet (UV)-induced optical gating in a Zn1−xMgxO nanocrystal solid solution (NCSS) field effect transistor (FET) through a systematic study in which UV-induced charge transport properties are probed as a function of Mg composition. Change in the electrical properties of Zn1−xMgxO NCSS associated with electronic traps is investigated by field effect-modulated current–voltage characteristic curves in the dark and under illumination. Under UV illumination, significant threshold voltage shift to a more negative value in an n-channel Zn1−xMgxO NCSS FET is observed. Importantly, as the Mg composition increases, the effect of UV illumination on the threshold voltage shift is alleviated. We found that threshold voltage shift as a function of Mg composition in the dark and under illumination is due to difference in the deep trap density in the Zn1−xMgxO NCSS. This is supported by Mg composition dependent photoluminescence intensity in the visible range and reduced FET mobility with Mg addition. The presence of the deep traps and the corresponding trap energy levels in the Zn1−xMgxO NCSS are ensured by photoelectron spectroscopy in air.

Ultraviolet illumination effect on monolayer graphene-based resistive sensor for acetone detection

In this study, a room-temperature acetone gas sensor based on monolayer graphene is proposed with the improvement by ultraviolet (UV) illumination. The monolayer graphene film was grown by low pressure chemical vapor deposition and then transferred to the interdigital gold electrode by the standard transferred method. To test the acetone sensing properties, the concentration of 300, 600 and 900 ppb acetone provided by a gas standards generator is applied in the testing chamber. The resistance changes following a doping type modification of graphene between illumination and acetone gas. A 1.9% change in short time illumination on graphene could be obtained at 600 ppb and room temperature, which could make this a candidate for biomedical application in the future. In the meantime, a mechanism is proposed to explain whole behavior based on photo-induced molecular desorption.

Effect of ultraviolet illumination on metal oxide resistive memory

We investigate the photoelectrical and resistive switching properties of Pt/ZnO/Pt capacitor operated in unipolar mode under ultraviolet (UV) illumination. The oxygen photodesorption under UV illumination explains the photoconduction observed in initial and high resistance states. Meanwhile, oxygen readsorption at surface-related defects justifies the different photoresponses dynamics in both states. Finally, UV illumination significantly reduces the variations of resistance in high resistance state, set voltage and reset voltage by 58%, 33%, and 25%, respectively, stabilizing Pt/ZnO/Pt capacitor. Our findings in improved switching uniformity via UV light give physical insight into designing resistive memory devices.

Controlling the Carrier Concentration of Epitaxial Graphene by Ultraviolet Illumination

Silicon carbide (SiC) is a well-known material for UV detection however the effect of UV illumination on the electron donation between the substrate, interfacial (or buffer layer) and graphene is not well understood. The effect of ultraviolet (UV) illumination on the carrier concentration of an epitaxial graphene hall bar device is investigated by scanning Kelvin probe microscopy (SKPM) and transport measurements in ambient and vacuum conditions. Modulation of the carrier concentration is demonstrated and shown to be due to both substrate and environmental effects.

Effect of UV Illumination on the NaCl-Induced Atmospheric Corrosion of Pure Zinc

The effect of ultraviolet (UV) illumination on the NaCl-induced atmospheric corrosion of pure zinc was investigated in this work. UV illumination affects the atmospheric corrosion morphology and corrosion rate of zinc. The NaCl-induced atmospheric corrosion rate of zinc increases significantly under UV illumination, which can be attributed to the photovoltaic effect of the corrosion products with semiconductor properties. The photoinduced electrons and holes, which are generated by the corrosion products with semiconductor properties under UV illumination, participate in the corrosion reactions and thus affect the atmospheric corrosion rate of zinc.

Effects of ultraviolet illumination and temperature on ionic motion in single-crystalline CuIn2Te3.5

Abstract A CuIn 2 Te 3.5 single crystal behaves as a mixed ionic and electronic conductor. Under application of a constant potential to a paint graphite/CuIn 2 Te 3.5 /paint graphite solid state device, a variation of the current intensity, I , with time is observed whereas the potential across the device, V m , remains constant in all measurements. An equivalent electrical circuit permits to understand this behaviour assuming that mobile ions are blocked at the CuIn 2 Te 3.5 /paint graphite interface, therefore changing the interface potential, whereas the electronic conduction is possible across that interface. Two ionic diffusion coefficients have been computed from σ(1/t) curves. Consecutive measurements have shown that the current intensity takes different values under identical electrical conditions whereas V m is constant. These changes have been explained by the formation of a residual interface potential. The ultraviolet (UV) illumination effect has been studied by comparison of measurements carried out under dark and UV illumination conditions. Lower values of I and the interface potential are observed under dark than under UV illumination conditions. The ratio between the diffusion coefficients under dark and UV illumination conditions is close to 2.2 for both diffusion coefficients. Cu bond-breaking can explain the decrease of the ionic diffusion coefficients under UV illumination. The temperature effect in the ionic motion has been analysed in the 293–383 K range. The increase of the number of free electronic carriers and mobile ions with temperature permits to compute their activation energies, 0.28 and 0.8 eV for the electronic carriers and mobile ions, respectively, whereas the two ionic diffusion coefficients do not vary. In the 338–348 K temperature range, the ionic resistance remains practically constant and the diffusion coefficients increase considerably; this behaviour would indicate that a reversible phase change is probably taking place.

Effects of Ultraviolet Illumination on Sol–Gel Synthesized Al-Doped ZnO Thin Films

Effects of Ultraviolet Illumination on Sol–Gel Synthesized Al-Doped ZnO Thin Films

Effect of Ultraviolet Illumination and Ambient Gases on the Photoluminescence and Electrical Properties of Nanoporous Silicon Layer for Organic Vapor Sensor

The purpose of this research, the nanoporous silicon layer were fabricated and investigated the physical properties such as photoluminescence and the electrical properties in order to develop organic vapor sensor by using nanoporous silicon. The Changes in the photoluminescence intensity of nanoporous silicon samples are studied during ultraviolet illumination in various ambient gases such as nitrogen, oxigen and vacuum. In this paper, the nanoporous silicon layer was used as organic vapor adsorption and sensing element. The advantage of this device are simple process compatible in silicon technology and usable in room temperature. The structure of this device consists of nanoporous silicon layer which is formed by anodization of silicon wafer in hydrofluoric acid solution and aluminum electrode which deposited on the top of nanoporous silicon layer by evaporator. The nanoporous silicon sensors were placed in a gas chamber with various organic vapor such as ethanol, methanol and isopropyl alcohol. From studying on electrical characteristics of this device, it is found that the nanoporous silicon layer can detect the different organic vapor. Therefore, the nanoporous silicon is important material for organic vapor sensor and it can develop to other applications about gas sensors in the future.

Effects of Ultraviolet Illumination on Resistive Switching Properties of CuxO Thin Film

The resistance of an Al/CuxO/Cu structure can reversibly switch between the high resistance state (HRS) and the low resistance state (LRS) with dc voltage application. The use of the conducting filament model was suggested to explain this behavior. The resistive switching from the HRS to the LRS can be induced by dc voltage application, ultraviolet (UV) illumination, or thermal heating. Therefore, the formation of conducting filaments was relative to power and unnecessary with the electric field. Effects of UV illumination and voltage stress on the resistive switching were also investigated to analyze the role of the electrostatic force. The resistive switching from the HRS to the LRS induced by dc voltage application should be dominated by thermochemical reaction and was partially helped by the electrostatic force.

Observation of coherent phonons in Ca-doped SrTiO3: Doping-induced ferroelectric phase transition and ultraviolet-illumination effect

Photo-induced effect in Ca-doped SrTiO3 was investigated by observing coherent phonons. Coherent phonons of soft modes were studied by using ultrafast polarization spectroscopy. Under an ultraviolet (UV) illumination, a shift of the ferroelectric phase transition point at 28 K toward the lower temperature side was observed, and a decrease of phonon frequencies after the UV illumination was found.

Effect of Ultraviolet Light on Hybrid Zinc Oxide Polymer BulkHeterojunction Solar Cells

Compared to conjugated polymerpoly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene](MDMO-PPV) solar cells, bulk heterojunction solar cells composed ofzinc oxide (ZnO) nanocrystals and MDMO-PPV have a better energyconversion efficiency. However, ultraviolet (UV) light deteriorates theperformance of solar cells composed of ZnO and MDMO-PPV. We propose amodel to explain the effect of UV illumination on these ZnO:MDMO-PPVsolar cells. According to this model, the degradation from UVillumination is due to a decrease of exciton dissociation efficiency.Our model is based on the experimental results such as the measurementsof current density versus voltage, photoluminescence, and photocurrent.

Mechanism and Kinetics of the Sorption of Platinum, Palladium, and Gold on Activated Carbon from UV-Illuminated Chloride Solutions

The mechanism and kinetics of the sorption preconcentration of gold, platinum, and palladium on activated carbon from solutions exposed to ultraviolet (UV) radiation were studied. The thermodynamic parameters of sorption (sorption capacity and type of adsorption isotherm) were determined; the effect of pH was considered. An explanation of the mechanism of the effect of UV illumination on sorption preconcentration was proposed. It was demonstrated that UV illumination does not change thermodynamic parameters of sorption but significantly affects the kinetics of sorption preconcentration.

Effect of variable intensity ultraviolet radiation on passivity breakdown of AISI Type 304 stainless steel

The effect of ultraviolet illumination on passivity breakdown of a commercial grade (CG) of AISI Type 304 stainless steel and of a high purity heat (HPH) of the same material in neutral 0.5 M NaCl solution and in 0.025 M NaCl + 0.15 M H 3BO 3/0.007 M Na 2B 4O 7, pH = 7.5, solution was experimentally studied. Passivity breakdown on the CG, as indicated by the measured breakdown potential and the intensity of the noise observed in the current under potentiostatic conditions, was inhibited at low illumination intensities but was enhanced at high illumination intensities. The low intensity photo-inhibition of passivity breakdown (PIPB) is consistent with previous observations on Fe, Ni, Cu/Ni alloys, and stainless steels, and has been attributed to quenching of the electric field and a subsequent modification of the vacancy structure in the barrier layer. These processes inhibit the formation of a critical cation vacancy condensate at the metal/barrier layer interface. The breakdown sites are envisioned to be regions of inherently high cation vacancy flux, and to include the points of intersection of the barrier layer with inclusions (e.g., MnS) and second phase particles (e.g., Cr 2O 3). Thus, at low intensities (power densities less than 100 mW/cm 2, λ=325 nm), cation vacancy condensation/cap dissolution at the periphery of the inclusion is considered to be the fundamental breakdown event, even though, MnS dissolution eventually occurs, as an acidic crevice develops adjacent to the inclusion. On the other hand, under high intensity illumination conditions (power density > 100 mW/cm 2), enhancement of passivity breakdown is attributed to photoactivation and dissolution of the MnS inclusions, which occur in parallel with vacancy condensation. The HPH exhibited breakdown voltages that were about 0.5 V more positive than that for the commercial grade of AISI Type 304 SS, under identical experimental conditions. The breakdown voltage, V b was shifted in the positive direction, upon irradiation with super band-gap light at a high power density in 0.5 M NaCl, but no change in V b was noted when irradiated in 1.0 M NaCl.

Effects of ultraviolet illumination on dry etch rates of NiFe-based magnetic multilayers

NiFe and NiFeCo were dry etched in inductively coupled plasma Cl2/Ar and CO/NH3 discharges, either with or without concurrent UV illumination from a Hg arc lamp. No enhancement was observed for CO/NH3 etching of the two materials, or for Cl2/Ar etching of NiFe. However, enhancements in etch rate of up to a factor of three were observed for Cl2/Ar etching of NiFeCo when ultraviolet (uv) illumination was employed. The etched surface morphologies were similar both with and without the UV irradiation. The etch rates in Cl2/Ar discharges were strongly correlated with the amount of chlorinated residues detected on the surface by Auger electron spectroscopy, indicating that the desorption of the metal chloride reaction products was the rate-limiting step in the etching.