Ultraviolet Light Intensity Research Articles

Uniform and Gaussian Ultraviolet Light Intensity Distribution on Droplet for Selective Area Deposition of Particles

Abstract Particle transport through Marangoni convection inside a sessile droplet can be controlled by the ultraviolet (UV) light distribution on the surface. The photosensitive solution changes the surface tension gradient on the droplet surface and can induce clockwise and counterclockwise circulations depending on the incident light distribution. In this paper, the stream function in the sessile drop has been evaluated in toroidal coordinates by solving the biharmonic equation. Multiple primary clockwise and counterclockwise circulations are observed in the droplet under various concentric UV light profiles. The downward dividing streamlines are expected to deposit the particles on the substrate, thus matching the number of deposited rings on the substrate with the number of UV light rings. Moffatt eddies appear near the contact line or centerline of the droplet depending on the UV light profile and its distance from the contact line.

Combinatıon of a Box-Behnken design technique with response surface methodology for optimization of the photocatalytic mineralization of C.I. Basic Red 46 dye from aqueous solution

The photodegradation of an industrial azo dye C.I Basic Red 46 was examined in a fixed-bed photoreactor using UV-lamps simulated to the solar irradiation. In our photodecolorization study, the UV/TiO2 process was optimized using the Box-Behnken approach to evaluate the synergistic effects of three independent parameters (initial concentration of the dye, flow rate, and UV intensity) on mineralization effectiveness. The response surface methodology was in good promise with the prediction model (coefficients of determination of decolorization and mineralization were R2Dec = 0.997 and R2TOC = 0.994, respectively). The effects of the factors could be estimated from a second–order polynomial equation and student’s t-test. The optimal parameters of decolorization and mineralization were as follows: initial concentration of colorant 25 mg L−1, rate of fluid flow 0.3 L min−1, and ultraviolet light intensity 38.1 W m−2. The decolorization and mineralization removal efficiency under these optimal conditions were 100% and 57.63% respectively. These results indicate that optimization using response surface methodology, based on the Box-Behnken approach, is an excellent tool for determining the optimal conditions, and the process can be easily extrapolated for a specific treatment of real waste water containing the azo dye C.I Basic Red 46. Also, the intermediates that were produced during photodegradation process of Basic Red 46 were determined by GC/MS.

Numerical verification for a new type of UV disinfection reactor

Abstract The traditional biological method applied to the CFD (Computational Fluid Dynamics) analyses of ultraviolet (UV) disinfection reactor associates problems such as the long experimental period and complicated process. However, the paper proposes a CFD verification for a new UV disinfection reactor. The UV dose of UV disinfection reactor in different inlet flow rates and diverse UV powers are simulated and analyzed by the ANSYS-Fluent; a separate Fortran program is made for UV dose calculations. The H2O2 solution is added to the reactor model for the · O H (hydroxyl radical)absorbance experiment and numerical results of reactor are evaluated. It is concluded that the method of detecting · O H absorbance photolysis products by imposing H2O2 solution can verify the accuracy of CFD simulation. It can be applied to the design process of UV disinfection equipment. The radiation intensity near the light source is the strongest parameter. With an increase of radial distance, the UV light intensity shows an exponential decay. The UV dose can be increased by reducing the inlet flow and increasing the lamp power. However, results indicate that the adjustment of flow rate at the entrance is superior to increasing the power of UV lamp.

Preparation of Biomass-Based Carbon Dots with Aggregation Luminescence Enhancement from Hydrogenated Rosin for Biological Imaging and Detection of Fe3.

Fluorescent carbon dots (CDs) have numerous important applications, but enhancing the fluorescence emission and overcoming fluorescence quenching are still big challenges. Here, fluorescence-enhanced carbon dots (named hr-CDs) were prepared from sustainable hydrogenated rosin, using a simple hydrothermal method in a water solvent. The hr-CDs were mainly composed of graphitized carbon cores with surface functional groups. With the increase in the concentration to hr-CDs aqueous solutions, the distance between the carbon cores decreased, which resulted in the formation of J aggregates and the enhanced blue fluorescence emission. Even in the solid state, the hr-CDs show fluorescence emission because the surface functional groups could prevent π–π stacking interactions between the carbon cores. The hr-CDs show excellent resistance to photobleaching under intense ultraviolet light (200 mW/cm2). Vibrations and rotations of graphitized carbon core are restricted by low temperature and high viscosity, leading to increased radiative transition and thus increase in fluorescence intensity. The pH value in the range of 3.99–9.87 and anions have little effect on the fluorescence emission of hr-CDs. The fluorescence emission of the hr-CDs was selectively quenched by Fe3+ and can thus be used to detect Fe3+. The hr-CDs also have good biocompatibility and show the same ability in cell nuclear staining as 4′,6-diamidino-2-phenylindole (DAPI).

Demonstration of 4H-SiC Thyristor Triggered by 100-mW/cm2 UV Light

In this letter, a silicon carbide (SiC) thyristor, with an 80- $\mu \text{m}$ thick p-type blocking base, is fabricated and triggered by a 365-nm ultraviolet light-emitting diode (UV LED). In the fabricated thyristor, a thin double-layer n-base structure is designed to improve the poor hole-injection capacity of p+n emitter junction and reduce the triggering ultraviolet light intensity. The UV-LED-triggered performance of the fabricated light-triggered SiC thyristor (LTT) is tested by a resistive load circuit. The results indicate that the fabricated SiC LTT can be triggered by a UV LED with an intensity of 100 mW/cm2. Also, it is shown that the turn-on delay time ( ${t}_{\text {d}}$ ) has the highest proportion in the turn-on time ( ${t}_{\text {on}}$ ) and affects the turn-on performance of the SiC LTT most significantly.

Photocatalytic degradation of organic dye via atomic layer deposited TiO2 on ceramic membranes in single-pass flow-through operation

Photocatalytic membranes operating under flow-through conditions are promising for continuous single-pass water treatment, while factors influencing pollutant removal require further understanding. In this work, anodized aluminium oxide membranes with pore sizes of 20 nm and 200 nm were coated with a titanium dioxide (TiO2) photocatalyst via atomic layer deposition. The impact of operational parameters on the photocatalytic efficiency of these membranes was examined. The convective flow through the coated membrane pores enhanced the accessibility of the model pollutant methylene blue (MB) resulting in effective mass transfer and, hence, significant photodegradation. The MB removal increased up to 50% with increasing coating thickness (up to 6 nm) and ultraviolet (UV, 365 nm) light intensity (2 mW/cm2). Above these values, the degradation was no longer limited by these parameters. The high degradation achieved below the UV content of terrestrial sunlight signifies the applicability of TiO2. Experiments demonstrate that the convective MB molar flux, under low membrane flux or low MB concentration, limits the reaction rate, but results in a high removal (up to 80%). Thus, a continuous process in photocatalysis coupled with membrane filtration exhibits significant potential for treating polluted water.

High-performing self-driven ultraviolet photodetector by TiO2/Co3O4 photovoltaics

Ultraviolet (UV) may provide the essential to maintain the human body and metabolism, however, excessive exposure to UV light is absolutely harmful. We may take advantage of the strong UV energy for energy conversion devices. A stable, simple and scalable heterojunction (TiO2/Co3O4) thin film was developed for UV-absorbing and visible-blind photovoltaic. Effective hole transport layer (HTL, NiO) insertion established photovoltaics, having a power conversion efficiency of 15.8%. The heterojunction exhibits the improved carrier lifetime from 1.94 ms to 9 ms, resulting in the enhancement of both photovoltage and photocurrent from 0.17 V to 0.78 V and from 0.54 mA cm−2 to 13.5 mA cm−2, respectively. The TiO2/Co3O4 device exhibits a photoresponse to a UV light intensity of 60 μW cm−2 in the presence of sunlight and works stable for over a year. The results indicate metal oxide heterojunction (TiO2/Co3O4) photovoltaic device could be useful for monitoring UV radiation exposure and cost-effective self-powered UV optoelectronics. The functional utilization of metal oxide layers would provide strong benefits for photoelectric devices, such as photodetectors and transparent solar cells.

Degradation of diclofenac sodium using UV/biogenic selenium nanoparticles/H2O2: Optimization of process parameters

The resistance of diclofenac (DCF), one of the most popular nonsteroidal anti-inflammatory drugs, to biodegradation processes and its abundance in the aquatic environment made it an environmental concern. Degradation by ultraviolet (UV) irradiation in the presence of various catalysts has possibility to eliminate DCF from water resources. In the present study, optimization of DCF degradation under UV light irradiation using biogenic selenium nanoparticles (Se NPs) in the presence of H2O2 (assisted by central composite design) in a photoreactor followed by identification of the produced metabolites (using GC-MS (EI) technique) was evaluated. To assess the influence of parameters on the UV/Se NPs/H2O2-assisted degradation efficiency of DCF, four main factors including light intensity (W/m2), Se NPs concentration (μg/mL), pH, and H2O2 concentration (mM) were chosen. Predicted values of degradation efficiency were found to be in good agreement with experimental values (Pre-R2 = 0.9982 and Adj-R2 = 0.9953). Optimization results showed that maximum degradation efficiency (97.43%) was achieved at the optimum conditions including Se NPs concentration of 32 μg/mL, UV light intensity of 30 W/m2, pH 7.5, and H2O2 concentration of 0.05 mM. 1-(2, 6-dichlorophenyl)-2-indolinone was found to be the main product among several peaks in the GC-MS chromatogram of the DCF treated sample.

Design of a Wireless Sensor Network for Optimal Deployment of Sensor Nodes in a Cocoa Crop

In this study, factorial experiments were conducted in two different scenarios to design a Wireless Sensor Network for monitoring a cocoa crop in a rural area in Colombia. Node sensors measured temperature, relative humidity, soil moisture, Ultra-Violet light, and visible light intensity. The factors considered in the experiments were distance between node sensors, height from the ground, and type of antenna; in turn, Received Signal Strength Indicator and data transfer time were the outputs. The wireless sensor network was deployed in the crop, covering approximately 3 % of the area and using 7 different nodes in a cluster tree topology. First, an open field scenario with line of sight was used to determine the appropriate height of the node sensors. Second, a scenario in the actual cocoa crop was utilized to find the appropriate distance between modules and type of antenna. We found, based on our calculations and experimental data, that a height of 1.25 m was required to avoid the Fresnel zone and improve the RSSI of the network. Furthermore, we determined that a distance below 35 m was needed to guarantee signal reception and avoid long data transfer times. The wire antenna exhibited a better performance. Finally, the proposed methodology and monitoring system can be used for agronomic applications in rural areas in Colombia to increase crop yield.

Micro-particle grafted eco-friendly polymer filaments for 3D printing technology

One of the most common polymers used in material extrusion 3D printing is Acrylonitrile Butadeine Styrene (ABS). The research presented here explores the effect of reinforcing metallic powders on the tensile strength as well as the photo-degradation of ABS printing polymer. A comparison is made between pure ABS, three blends of ABS/TiO2 microparticles with the idea to see the effect of the additives on the tensile as well as its photo-degradation properties. Tensile tests on the specimens made with different percentages of infill showed that ABS reinforced with 10% TiO2 (by weight) resulted in the highest Strength of 20.54 MPa. The compounding of the ABS polymer with TiO2 and the irradiation to different intensities of ultraviolet (UV) light has confirmed photo-degradation of the polymer. The highest reduction in weight recorded being 0.081 g in 240 min at 64 W intensity. This promises a substantial reduction in the carbon footprint of the ABS polymer which is widely used for 3D printing but is non-biodegradable. The pilot experiments confirm that grafting TiO2 microparticles into the feedstock can improve the strength as well as degrade the polymer components by exposing them to UV light making them Eco-friendly.

Sensing Characteristics of Fiber Fabry-Perot Sensors Based on Polymer Materials

A simple optic-fiber Fabry-Perot (FP) sensing technique was proposed and experimentally investigated by using polymer material to connect the ends of two singlemode fibers. Four different polymer materials (benzocyclobutene (BCB), UV88 (Relentless, China), Loctite3525 (HenKel, Germany), and NOA68 (Norland, USA)) filling the FP cavity were used to comparatively study the sensing performance of temperature, strain and refractive index. The result shows that the FP sensor with BCB has excellent repeatability with good linear response to temperature in a wide range from room temperature to 250 °C, which is much larger than that of other three materials (<; 90 °C), while UV88 with a cost of less than 1/10 of the other three polymer materials has the best sensitivity to strain and temperature. In addition, the FP sensor was firstly applied to measure ultraviolet (UV) light intensity. The test results demonstrate that the proposed FP sensor structure has a good linear response and repeatability to UV intensity for all four polymer materials, and Loctite3525 has the highest sensitivity (0.0087 nm/(mw/cm 2 )) and the best repeatability among the four polymer materials.

Simultaneous measurement of SO2 and NO2 concentration using an optical fiber-based LP-DOAS system

SO2 and NO2 are the most important pollution in atmosphere. An optimized long path (LP) differential optical absorption spectroscopy (DOAS) system of high light intensity at an ultraviolet (UV) wavelength is proposed and used to measure the concentration of SO2 and NO2 simultaneously. In contrast to the traditional DOAS, the system adopted a Y-type optical fiber structure instead of a combination of mirrors in the telescope. The UV light intensity test shows that the light intensity of UV can arrive to above 80% of the max measuring range when the light path reaches 135 m, and the integral time of the spectrograph is only 15 ms. The system is proved to be efficacious through laboratory calibration. The maximum error of SO2 calibration is 4.19%, and is 5.22% for NO2. The error of the SO2 and NO2 mixture calibration is within 10%. Field measurement is implemented in a wastewater treatment plant in winter. The measurement light path is 738 m. The concentration of SO2 varies from 6 μg/m3 (2.26 ppb) to 20 μg/m3 (7.52 ppb), and the concentration of NO2 varies from 100 μg/m3 (53.2 ppb) to 200 μg/m3 (106.4 ppb) approximately. The results are in accordance with the data from a monitoring station nearby in magnitude order and variation tendency mostly.

Polyoxometalate-viologen photochromic hybrids for rapid solar ultraviolet light detection, photoluminescence-based UV probing and inkless and erasable printing.

In this work, a new crystalline polyoxometalate-viologen hybrid, (Pbpy)(Me2NH2)3[PW11ZnO40] (1: Pbpy = 1,1'-[1,4-phenylenebis-(methylene)]bis(4,4'-bipyridinium)), has been synthesized. It showed efficient ultraviolet light detection ability with an obvious colour change from pale yellow to blue and fast response with ultraviolet intensity as low as 0.006 mW cm-2 in narrow-band UV regions. The POM-viologen-based film of 1 has also been readily prepared on quartz substrates using a drop casting method and could exhibit different levels of colour changes under sunlight irradiation at different local times on a sunny day, indicating its potential to be used as a portable device for solar ultraviolet light detection. Ultraviolet light detection is not only reflected in colour changes, but also accompanies the photoluminescence phenomenon. The fluorescence intensity decreased with the increase of UV intensity, and when irradiated with an ultraviolet xenon lamp (8 mW cm-2) for about 5 min, the fluorescence intensity was almost completely quenched. The compound has the potential to achieve fluorescence based UV probing. The powdered sample of compound 1 could also be deposited in paper simply by coating it with a solution of ethanol. The paper can be used as an inkless and erasable print medium, which was found to remain clear for 11 d in the dark under an ambient atmosphere and was also reusable when erased.

Evaluating performance, degradation, and release behavior of a nanoform pigmented coating after natural and accelerated weathering

Pigments with nanoscale dimensions are added to exterior coatings to achieve desirable color and gloss properties. The present study compared the performance, degradation, and release behavior of an acrylic coating that was pigmented by a nanoform of Cu-phthalocyanine after both natural (i.e., outdoor) and accelerated weathering. Samples were weathered outdoors in three geographically distinct locations across the United States (Arizona, Colorado, Maryland) continuously for 15 months. Identically prepared samples were also artificially weathered under accelerated conditions (increased ultraviolet (UV) light intensity and elevated temperatures) for three months, in one-month increments. After exposure, both sets of samples were characterized with color, gloss, and infrared spectroscopy measurements, and selectively with surface roughness measurements. Results indicated that UV-driven coating oxidation was the principal degradation pathway for both natural and accelerated weathering samples, with accelerated weathering leading to an increased rate of oxidation without altering the fundamental degradation pathway. The inclusion of the nanoform pigment reduced the rate of coating oxidation, via UV absorption by the pigment, leading to improved coating integrity compared to non-pigmented samples. Release measurements collected during natural weathering studies indicated there was never a period of weathering, in any location, that led to copper material release above background copper measurements. Lab-based release experiments performed on samples weathered naturally and under accelerated conditions found that the release of degraded coating material after each type of exposure was diminished by the inclusion of the nanoform pigment. Release measurements also indicated that the nanoform pigment remained embedded within the coating and did not release after weathering.

Mechanism of Improved Luminescence Intensity of Ultraviolet Light Emitting Diodes (UV-LEDs) Under Thermal and Chemical Treatments

In this work, the influences of thermal annealing and chemical passivation on the optical and electrical properties of ultraviolet light-emitting-diode (UV-LED) were investigated. The electroluminescence (EL) intensities of the LEDs under KOH treatment and thermal annealing increased by 48% and 81%, respectively compared to as-fabricated LED under current level of 10 mA. Cathodoluminescence (CL) mapping of UV-LEDs confirmed no variation of the density of the non-radiative recombination centers after surface treatments, and no obvious change in surface morphology was identified due to lacking of energy for surface atom migration. However, Raman spectroscopy indicates a relaxation of compressive strains inside the thin film after both thermal and chemical treatments, and conductive atomic force microscopy (c-AFM) also illustrated reduced leakage current after KOH passivation, which are responsible for the improved luminescence properties of UV-LEDs.

UV-photodetector based on heterostructured ZnO/(Ga,Ag)-co-doped ZnO nanorods by cost-effective two-step process

In the present work, we have fabricated, characterized and tested the hetero-structured zinc oxide/[gallium, silver]-co-doped zinc oxide (ZnO/[Ga,Ag]-co-doped ZnO) ultraviolet (UV)-photodetector (PD) using a cost-effective two-step process. In this, the results of our study are reported and discussed for the first time. X-ray diffraction (XRD) analysis ensures that the prepared samples are well-crystallized and show a hexagonal-wurtzite ZnO structure. The scanning electron microscopy (SEM) confirmed nanorods growth in a hexagonal shape on the film surface, which is the key point in the enhancement of the photoresponse. The fabricated UV-photodetector ZnO/[Ga,Ag]-co-doped ZnO achieved a phtotoresponse of 40% with a rapid switching rate that was three times greater than that of the pristine ZnO at UV light intensity of 13.5 mW/cm2 and proportional to the illumination intensity. The highest responsivity of Rp = 1424.5 A/W and photoconductive gain of G = 4800 were achieved at a UV light exposure of 13.5 mW/cm2 with applied voltage (bias) of 5 V. This could be ascribed to the clear substitution of Ga and Ag in the ZnO, which enhanced the UV sensing properties.

One-Step Coating Processed Phototransistors Enabled by Phase Separation of Semiconductor and Dielectric Blend Film.

Fabrication of organic thin-film transistors (OTFTs) via high throughput solution process routes have attracted extensive attention. Herein, we report a simple one-step coating method for vertical phase separation of the poly(3-hexylthiophene-2,5-diyl) (P3HT) and poly(methyl methacrylate) (PMMA) blends as semiconducting and dielectric layers in OTFTs. These OTFTs can be used as phototransistors for ultraviolet (UV) light detection, where the phototransistors exhibited great photosensitivity of 597.6 mA/W and detectivity of 4.25 × 1010 Jones under 1 mW/cm2 UV light intensity. Studies of the electrical properties in these phototransistors suggested that optimized P3HT contents in the blend film can facilitate the improvement of film morphology, and therefore form optimized vertical phase separation of the PMMA and P3HT. These results indicate that the simple one-step fabrication method creates possibilities for realizing high throughput phototransistors with great photosensitivity.

Concentration Distribution of Photosensitive Liquid in a Droplet Under Ultraviolet Light

Abstract A semi-analytical solution for the concentration of photosensitive suspension is developed in a hemispherical droplet illuminated with ultraviolet (UV) laser. A biharmonic equation in stream function is analytically solved using toroidal coordinates, which is used to solve the transport equation for concentration. Flow pattern and photosensitive material concentration are affected by the peak location of the UV light intensity, which corresponds to the surface tension profile. When the laser beam is moved from the droplet center to its edge, a rotationally symmetric flow pattern changes from a single counter clockwise circulation to a circulation pair and finally to a single clockwise circulation. This modulation in the orientation of circulation modifies the concentration distribution of the photosensitive material. The distribution depends on both diffusion from the droplet surface and the Marangoni convection. The region beneath the droplet surface away from the UV light intensity peak has low concentration, while the region near the downward dividing streamline has the highest concentration. When the UV light peak reaches the droplet edge, the concentration is high everywhere in the droplet.

Konservasi Koleksi Lukisan Museum Le Mayeur

As a result of human work, painting is a cultural heritage that has important values. The state of the structure of the paintings which is composed by organic materials makes the painting very vulnerable to the environmental influences and other causes of damage. This research aims to find out about the characteristics of the painting, the types of damage, the factors that cause damage, and its conservation techniques both preventive and and curative to painting collection of Le Mayeur Museum.The results of this research are expected to provide benefits and development of science in the field of archeology about the study of cultural heritage conservation. This study uses qualitative analysis, technology analysis, and comparative analysis. Data collection technique used are direct observation technique, interviews, and library reserach studies. The theories applied are Aesthetic Theory and Conservation Theory.The results obtained namely the characteristic of Le Mayeur’s paintings are representative with women’s theme and surroundings life, the coloring technique using plaque technique with oil paint, watercolor, traditional paint, and pastels color. Generally, there are several types of damage to the painting collection of Le Mayeur Museum, such as physical or mechanic damage, biotic damage, and chemical damage. Those types of damage are caused by physical factors,chemistry factors, biotic factors, and human factors. The conservation techniques carried out at the Le Mayeur Museum include preventive conservation and curative conservation. The preventive actions are carried out with control of temperature, air humidity, intensity of ultraviolet light, and control of air containing salt due to sea water vapor. The curative actions taken are semi-chemist medicine and painting restoration.

Novel nanotechnology and near-infrared photodynamic therapy to kill periodontitis-related biofilm pathogens and protect the periodontium

ObjectivePeriodontal tissue destruction and tooth loss are increasingly a worldwide problem as the population ages. Periodontitis is caused by bacterial infection and biofilm plaque buildup. Therefore, the objectives of this study were to: (1) develop a near-infrared light (NIR)-triggered core-shell nanostructure of upconversion nanoparticles and TiO2 (UCNPs@TiO2), and (2) investigate its inhibitory effects via antibacterial photodynamic therapy (aPDT) against periodontitis-related pathogens. MethodsThe core β-NaYF4:Yb3+,Tm3+ were synthesized via thermal decomposition and further modified with the TiO2 shell via a hydrothermal method. The core-shell structure and the upconversion fluorescence-induced aPDT treatment via 980nm laser were studied. Three periodontitis-related pathogens Streptococcus sanguinis (S. sanguinis), Porphyromonas gingivalis (P. gingivalis) and Fusobacterium nucleatum (F. nucleatum) were investigated. The killing activity against planktonic bacteria was detected by a time-kill assay. Single species 4-day biofilms on dentin were tested by live/dead staining, colony-forming units (CFU), and metabolic activity. ResultsThe hexagonal shaped UCNPs@TiO2 had an average diameter of 39.7nm. UCNPs@TiO2 nanoparticles had positively charged (+12.4mV) surface and were biocompatible and non-cytotoxic. Under the excitation of NIR light (980nm), the core NaYF4:Yb3+,Tm3+ UCNPs could emit intense ultraviolet (UV) light, which further triggered the aPDT function of the shell TiO2 via energy transfer, thereby realizing the remarkable antibacterial effects against planktons and biofilms of periodontitis-associated pathogens. NIR-triggered UCNPs@TiO2 achieved much greater reduction in biofilms than control (p<0.05). Biofilm CFU was reduced by 3–4 orders of magnitude via NIR-triggered aPDT, which is significantly greater than that of negative control and commercial aPDT control groups. The killing efficacy of UCNPs@TiO2-based aPDT against the three species was ranked to be: S. sanguinis<F. nucleatum=P. gingivalis. Metabolic activities of biofilms were also greatly reduced via NIR-triggered aPDT (p<0.05). SignificanceUpconversion fluorescence-based aPDT achieved strong inhibiting effects against all three species of periodontitis-related pathogens. This novel nanotechnology demonstrated a high promise to inhibit periodontitis, with exciting potential to combat other oral infectious diseases such as deep endodontic infections.