UV Power Research Articles

Ag-ZnO nanoreactor grown on FTO substrate exhibiting high heterogeneous photocatalytic efficiency.

This Research Article reports an unusually high efficiency heterogeneous photodegradation of methyl orange (MO) in the presence of Ag nanoparticle-loaded ZnO quasi-nanotube or nanoreactor (A-ZNRs) nanocatalyst grown on FTO substrate. In typical process, photodegradation efficiency of as high as 21.6% per μg per Watts of used catalyst and UV power can be normally obtained within only a 60-min reaction time from this system, which is 10(3) order higher than the reported results. This is equivalent to the turnover frequency of 360 mol mol(-1) h(-1). High-density hexagonal A-ZNRs catalysts were grown directly on FTO substrate via a seed-mediated microwave-assisted hydrolysis growth process utilizing Ag nanoparticle of approximately 3 nm in size as nanoseed and mixture aqueous solution of Zn(NO3)·6H2O, hexamethylenetetramine (HMT), and AgNO3 as the growth solution. A-ZNRs adopts hexagonal cross-section morphology with the inner surface of the reactor characterized by a rough and rugged structure. Transmission electron microscopy imaging shows the Ag nanoparticle grows interstitially in the ZnO nanoreactor structure. The high photocatalytic property of the A-ZNRs is associated with the highly active of inner side's surface of A-ZNRs and the oxidizing effect of Ag nanoparticle. The growth mechanism as well as the mechanism of the enhanced-photocatalytic performance of the A-ZNRs will be discussed.

파 에너지 (자외선, 초음파)/과황산나트륨을 이용한 이부프로펜 분해특성 연구

Abstract In this study, ibuprofen(IBP) degradation by the photochemical (UV/S 2 O 82- ) and sonochemical (US/S 2 O 82- ) processes was examined under various parameters, such as UV (10~40±5 W/L) and US (50~90±5 W/L) power density, optimum dosage of persulfate ion (S 2 O 82- ), temperature (20~60℃) and anions effect (Cl - , HCO 3- , CO 32- ). The pseudo‐first‐order degradation rate constants were in the order of 10 -1 to 10 -5 min -1 depending on each processes. The synergistic effect of IBP degradation in UV/S 2 O 82- and US/S 2 O 82- processes could investigated, due to the generation of SO 4- radical. This result can confirm from the produced H 2 O 2 and SO 42- concentration in each processes. IBP degradation rate affected by the S 2 O 82- dosage, temperature, power and anion existence parameters. In particular, IBP degradation rate increased with the increase of the temperature (60℃) and applied power density (UV:40±5 W/L, US:90±5 W/L). On the other hand, anions effect on the IBP degradation was negative, due to the anion play as a the scavenger of radical.

Yb-fiber-laser-pumped, high-repetition-rate picosecond optical parametric oscillator tunable in the ultraviolet.

We report a compact tunable 240-MHz picosecond source for the ultraviolet based on intra-cavity frequency doubling of a signal-resonant MgO:sPPLT optical parametric oscillator (OPO), synchronously pumped at 532 nm in the green by the second harmonic of a mode-locked Yb-fiber laser at 80-MHz repetition rate. By deploying a 30-mm-long multi-grating MgO:sPPLT crystal for the OPO and a 5-mm-long BiB(3)O(6) crystal for internal doubling, we have generated tunable UV radiation across 317-340.5 nm, with up to 30 mW at 334.5 nm. The OPO also provides tunable visible signal in the red, across 634-681 nm, and mid-infrared idler radiation over 2429-3298 nm, with as maximum signal power of 800 mW at 642 nm. The signal pulses have a temporal duration of 12 ps at 665 nm and exhibit high spatial beam quality with Gaussian profile. The signal power is recorded to be naturally stable with a fluctuation of 1.4% rms over 14 hours, while UV power degradation has been observed and studied.

A novel method for the thermal analysis of GaN/AlGaN back-illuminated high power UV LEDs

We report a novel method for the thermal analysis of high-power multi-quantum well GaN/AlGaN UV LEDs of λ ∼ 330 nm. 3D modeling and simulations of chip-on-plate (COP) have been investigated for the packaging of UV LEDs. Steady state thermal analysis of COP packaged devices were carried out using finite element method (FEM). Different heat sinks’ designs such as plate-fins, and pin-fins were modeled to determine device junction temperatures (Tj). We also employed thermal resistance circuit (TRC) model to determine the Tj considering both conductive and convective methods of heat transfer. Results were in good agreement both for the FEM and TRC models. For the fine plate-fin dense and the less-dense large-fins heat sinks, calculated Tj values were ∼37 °C, and ∼46 °C for a corresponding operating power of ∼1.5 W, respectively. On other hand, similar power level junction temperatures of 33 °C and 41 °C were determined respectively for high- and low-density pin-fins heat sinks. Furthermore, thermal flux analysis of these heat sinks was also performed. A comparative study of on–substrate un-packaged and two different (COP) packaged devices was also performed. It was found that our COP based packaged devices are thermally more stable with improved photoluminescence (PL) intensity. As much as around 30% enhancement in the PL intensity of the packaged devices along with a noticeable decrease in the red-shift (about 7 nm) of the spectrum was determined.

개선된 플라즈마 공정을 이용한 Ralstonia Solanacearum 불활성화에 관한 연구

Abstract Effect of improvement of the dielectric barrier discharge (DBD) plasma system on the inactivation performance of bacteria were investigated. The improvement of plasma reactor was performed by combination with the basic plasma reactor and UV process or combination with the basic plasma reactor and circulation system which was equipped with gas-liquid mixer. Experimental results showed that tailing effect was appeared after the exponential decrease in basic plasma reactor. There was no enhancement effect on the Ralstonia Solanacearum inactivation with combination of basic plasma process and UV process. The application of gas-liquid mixing device on the basic plasma reactor reduced inactivation time and led to complete sterilization. The effect existence of gas-liquid mixing device, voltage, air flow rate (1 1E 5 L/min), water circulation rate (2.8 1E 9.4 L/min) in gas  liquid mixing plasma, plasma voltage and UV power of gas  liquid mixing plasma+UV process were evaluated. The optimum air flow rate, water circulation rate, voltage of gas-liquid mixing system were 3 L/min, 3.5 L/min and 60 V, respectively. There was no enhancement effect on the Ralstonia Solanacearum inactivation with combination of gas-liquid mixing plasma and UV process.Key words : Dielectric barrier discharge plasma, Ralstonia solanacearum, Gas-liquid mixer, Inactivation

Heterogeneous photo-assisted Fenton catalytic removal of tetracycline using Fe-Ce pillared bentonite

In the present work, a novel heterogeneous photo-Fenton catalyst was prepared by iron and cerium pillared bentonite. The catalyst Fe-Ce/bentonite was characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), Brunauer-Emmett-Teller (BET) and scanning electron microscopy (SEM) methods. It is found that Fe and Ce intercalate into the silicate layers of bentonite successfully. Tetracycline was removed by heterogeneous photo-Fenton reaction using the catalyst in this work. The effects of different reaction systems, hydrogen peroxide concentration, initial pH, catalyst dosage, UV power and introduction of different anions on degradation were investigated in details. The stability of catalyst was investigated through recycling experiment. The results show that removal rate of tetracycline is 98.13% under the conditions of 15 mmol/L H2O2, 0.50 g/L catalyst dosage, initial pH 3.0, 11 W UV lamp power and 60 min reaction time. However, the removal rate decreases after adding some anions. The hydroxyl radical plays an important role in heterogeneous photo-assisted Fenton degradation of tetracycline. The catalyst is very stable and can be recycled many times.

Green valley galaxies

The ?green valley? is a wide region separating the blue and the red peaks in the ultraviolet-optical color magnitude diagram, first revealed using GALEX UV photometry. The term was coined by Christopher Martin (Caltech), in 2005. Green valley highlights the discriminating power of UV to very low relative levels of ongoing star formation, to which the optical colors, including u?r, are insensitive. It corresponds to massive galaxies below the star-forming, ?main? sequence, and therefore represents a critical tool for the study of the quenching of star formation and its possible resurgence in otherwise quiescent galaxies. This article reviews the results pertaining to (predominantly disk) morphology, structure, environment, dust content and gas properties of green valley galaxies in the local universe. Their relationship to AGN is also discussed. Attention is given to biases emerging from defining the ?green valley? using optical colors. We review various evolutionary scenarios and we present evidence for a new one, the quasi-static view of the green valley, in which the majority (but not all) of galaxies currently in the green valley were only partially quenched in the distant past and now participate in a slow cosmic decline of star formation, which also drives down the activity on the main sequence, presumably as a result of the dwindling accretion/cooling onto galaxy disks. This emerging synthetic picture is based on the findings from Fang et al. (2012), Salim et al. (2012) and Martin et al. (2007), as well as other results.

Photoreduction and light-induced triplet-state formation in a single-site fluoroalkylated zinc phthalocyanine

Electron-withdrawing perfluoroalkyl peripheral substituents enhance the photosensitizing properties of metal phthalocyanines while increasing their solubility, thus providing opportunities for advanced characterization of their catalytically-relevant excited states. Optical absorption and electron paramagnetic resonance (EPR) spectroscopy experiments reveal that red light induces the reduction of perfluoroisopropyl-substituted zinc(ii) phthalocyanine (F64PcZn) dissolved in ethanol. A similar photoreduction does not occur in toluene. Furthermore, intense UV irradiation causes the photodegradation of F64PcZn in ethanol, but low power UV illumination favours the formation of the triplet excited state, a prerequisite for new photocatalytic applications. The UV-induced triplet state of F64PcZn is characterized using a combination of transient EPR experiments and DFT computations.

Investigation into the fluorescence quenching behaviors and applications of carbon dots

Carbon dots (CDs) are novel fluorescent materials with low toxicity and good biocompatibility. Herein, the collisional/dynamic and photoluminescence (PL) center destruction quenching behaviors of a novel type of CDs were investigated. Moreover, the quenching behaviors of the CDs were exploited in applications. Firstly, dynamic PL quenching was achieved by Fe(3+) ions, which was proved by the Stern-Volmer equation, temperature dependent quenching and fluorescence lifetime measurements. Furthermore, a hemin sensor based on the Fe(3+)/CDs system was achieved. Secondly, quenching induced by PL center destruction was caused by hydroxyl radicals (˙OH), which were produced by high power UV light or the H2O2/Fe(2+) system; thus an H2O2 sensor with a low detection limit (0.9 ppb) was realized. Finally, we assumed that the CDs are really composed of cross-linked molecular clusters, and that the PL centers of the as prepared CDs are certain molecular/chemical groups.

관로형 UV 소독기를 위한 세척 및 모니터링 시스템 개발

In this paper, an integrated control system is proposed for automatic control and remote monitoring of pipeline type UV sterilizer. The proposed system can control the cleaning wiper in the sterilizer with various cleaning motions, and periodically check the contamination level of the UV lamps with the UV power sensors. Therefore, sterilizer repair and maintenance can be more effectively done. In addition, the control system based on the open-source processor can communicate with external smart devices via Bluetooth, and thus wirelessly exchange control commands and sensor data. Furthermore, the system is able to flexibly cope with changes of cleaning motions and sensors since its firmware can be wirelessly upgraded by using the smart device. Consequently, the proposed system is suitable to construct a smart sewage treatment system in small towns.

Sustainable antimicrobial finishing of cotton fabrics by chitosan UV-grafting: from laboratory experiments to semi industrial scale-up

The topic of the present study was the antibacterial finishing of cotton fabrics by ultraviolet grafting of chitosan biopolymer on fiber surface. A first part, carried out at laboratory level, deals with the optimization of process parameters, followed by a deep characterization of treated samples, revealing the effectiveness of the treatment. Therefore, the applied method was carefully monitored, laboratory apparatus were used and just samples of small surface were prepared by UV-grafting of pure chitosan in inert atmosphere, on dried samples, as recommended for radical curing.To test the feasibility of the proposed treatment even at semi-industrial level, in the second step of the study larger fabric samples were impregnated by foulard with a commercial chitosan solution and then were irradiated, both dried and wet, with an high power UV lamp, in air. Moreover, samples add-on was significantly reduced in order to hold down the finishing cost. White and dyed samples were treated and evaluated in terms of conferred antibacterial activity, yellowing or color changes and final hand. Eventually, treatment fastness to domestic laundering was tested.Obtained results confirmed the previous laboratory results: a strong antibacterial activity with good washing fastness was achieved by irradiation of the samples even wet and in air. It was obtained with a chitosan add-on percentage lowered till 0.3 wt% with a negligible affection of color or hand properties of the fabric.

Nanosecond-pulsed dielectric barrier discharges in Kr/Cl2 for production of ultraviolet radiation

In this paper, we present a study of nanosecond-pulsed, coaxial dielectric barrier discharges for generation of UV radiation in Kr/Cl2 mixtures with total pressures of 25 and 50 mbar. This study is based on an ensemble of experimental and modeling results and aims to identify the dominant physical mechanisms leading to the production of KrCl* (B state). The emission band of KrCl* is peaked at 222 nm, which is in the wavelength range of interest for applications in microbial decontamination. We find that for the same energy per pulse deposited in the discharge, more UV radiation is emitted at higher pressures where relatively more of the energy deposited in the gas goes into heating the electrons, with less going to heating the ions in the sheath. The Cl2 partial pressure significantly affects the KrCl* time-averaged, spatial profiles, leading to different optimal conditions for average and for peak UV power densities. Model results show that the highest KrCl* number density occurs near the walls and is associated with the development of cathode sheaths during the voltage pulse.

Nanoporous SnO2 prepared by a photochemical strategy: Controlling of specific surface area and photocatalytic activity in degradation of dye pollutants

Nanoporous SnO2 fine particles with controlled specific surface area were prepared in the SnSO4 and H2SO4 mixed solutions by a simple photochemical method for the first time. Compared with other solution methods, the controlling of surface area can be manipulated at room temperature without the addition of any surfactant or template. Only by controlling the concentration of H2SO4, the specific surface area of the product could be tuned in the range of 13–203m2g−1. They showed high activity and can be applied to efficient photocatalytic degradation of dye pollutants under a low power (8W 254nm) UV lamp. It was found the activity gradually increased with the increase of the specific surface area or the increase of the concentration of H2SO4 employed in the preparation process. The formation of SnO2 and pore structures, the morphologies, the compositions and the photocatalytic degradation mechanisms were systematically studied.

Fuzzy clustering evaluation of the discrimination power of UV–Vis and (±) ESI-MS detection system in individual or coupled RPLC for characterization of Ginkgo Biloba standardized extracts

Discrimination power evaluation of UV-Vis and (±) electrospray ionization/mass spectrometric techniques, (ESI-MS) individually considered or coupled as detectors to reversed phase liquid chromatography (RPLC) in the characterization of Ginkgo Biloba standardized extracts, is used in herbal medicines and/or dietary supplements with the help of Fuzzy hierarchical clustering (FHC). Seventeen batches of Ginkgo Biloba commercially available standardized extracts from seven manufacturers were measured during experiments. All extracts were within the criteria of the official monograph dedicated to dried refined and quantified Ginkgo extracts, in the European Pharmacopoeia. UV-Vis and (±) ESI-MS spectra of the bulk standardized extracts in methanol were acquired. Additionally, an RPLC separation based on a simple gradient elution profile was applied to the standardized extracts. Detection was made through monitoring UV absorption at 220 nm wavelength or the total ion current (TIC) produced through (±) ESI-MS analysis. FHC was applied to raw, centered and scaled data sets, for evaluating the discrimination power of the method with respect to the origins of the extracts and to the batch to batch variability. The discrimination power increases with the increase of the intrinsic selectivity of the spectral technique being used: UV-Vis<MS(-)<MS(+), but it is strongly sensitive to chemometric transformation of data. Comparison with cluster analysis (CA) and principal components analysis (PCA) indicates that the FHC algorithm produces better classification. However, PCA and CA may be successfully applied to discriminate between the manufacturing sources of the standardized extracts, and at some extent, to monitor the inter-batch variability. Although the chromatographic dimension sensibly contributes to the discrimination power, spectral MS data may be used as the lone powerful holistic alternative in characterization of standardized Ginkgo Biloba extracts.

Separation of Selenite from Inorganic Selenium Ions using TiO2Magnetic Nanoparticles

A simple and quick separation technique for selenite in natural water was developed using @ nanoparticles. For the synthesis of nanoparticles, a polymer-assisted sol-gel method using hydroxypropyl cellulose (HPC) was developed to control particle dispersion in the synthetic procedure. In addition, titanium butoxide (TBT) precursor, instead of the typical titanium tetra isopropoxide, was used for the formation of the shell. The synthesized nanoparticles were used to separate selenite () in the presence of or selenium anions for the photocatalytic reduction to atom on the shell, followed by magnetic separation using nanoparticles. The reduction efficiency of the photocatalytic reaction was 81.4% at a UV power of 6W for 3 h with a dark adsorption of 17.5% to the nanoparticles, as determined by inductively coupled plasma-mass spectrometry (ICP-MS). The developed separation method can be used for the speciation and preconcentration of selenium cations in environmental and biological analysis.

Synthesis of GaN Nanoparticles by DC Plasma Enhanced Chemical Vapor Deposition

The unique optical properties of nanostructured GaN basically, turn it as a very important part of many electronic and optoelectronic devices such as high power transistors, UV detectors, solar cells, lasers and blue LED. The aim of the current study is GaN nanoparticle deposition at low temperature in preferred direction. In this work, GaN nanoparticles were prepared using direct current plasma enhanced chemical vapor deposition (DC-PECVD) method on Si (100) wafer as a substrate at 700°C. Gallium metal and nitrogen plasma were used as precursors. GaN nanoparticles were grown based on the direct reaction between gallium atoms and excited nitrogen species in the plasma. Structural and morphological characterizations of GaN nanoparticles were carried out using X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) and field emissions electron microscopy (FE-SEM). Preferred (100) direction of GaN nanostructures which obtained by careful control of processing parameters, were revealed by XRD. FE-SEM images show the average diameter of nanoparticles is 37 nm. The EDS results show the Ga to N ratio in the sample was 8.8 to 1.2 by weight which is very close to the Ga to N ratio of prefect GaN crystal. The deviance is related to the nitrogen vacancy of the sample. These results demonstrate a simple inexpensive method for GaN nanoparticle deposition at low temperature which is critical for many of applications.

Photo excitation and laser detachment of C60− anions in a storage ring

We have studied the photo physics of C60(-) anions in the electrostatic storage ring ELISA with ions produced in a plasma source and cooled and bunched in a He filled ion trap. A previous study using delayed electron detachment as a signal of resonance-enhanced multiphoton electron detachment (REMPED) has been repeated both at room temperature and with the trap cooled to liquid nitrogen temperature. However, wavelength dependence of the overlap of the strongly focused laser beam with the ion beam introduces distortions of the absorption spectrum. We have therefore applied a new method, combining the IR light with a slightly delayed, powerful UV pulse (266 nm). After absorption of three UV photons, the ions decay by delayed (thermal) electron emission, and time spectra are recorded for varying wavelength. The fraction of ions heated by absorption of a single IR photon is then extracted from a principal component analysis of these spectra. In good agreement with the earlier REMPED experiment, an origin band for transitions between the two lowest electronic levels of the anion, with t1u and t1g symmetry, is observed at 9380 cm(-1), with strong sidebands from excitation of the two A(g) and eight H(g) vibrations. As before, a hot band is observed at about 9150 cm(-1) and assigned to a transition from an excited vibronic Jahn-Teller state. However, an earlier observed band at higher energy, interpreted as a transition from this excited state to an excited vibronic state in the t1g electronic level, is much weaker in the new measurements and could be an H(g) vibrational sideband. Also earlier studies of direct laser detachment from C60(-) in the storage ring ASTRID have been revisited, with ions cooled by liquid nitrogen in the ion trap. We confirm the previous measurement with a determination of the threshold for s-wave detachment at 2.664 ± 0.005 eV, slightly lower than a recent value of the electron binding, 2.683 ± 0.008 eV, obtained from the energy spectrum of photo electrons. The detachment yield is observed to increase sharply for photon energies above a threshold at 2.78 eV, maybe caused by either Feshbach resonances or a shape resonance due to the presence of a bound electron state in the continuum.

Surface modification of ABS by photocatalytic treatment for electroless copper plating

Surface roughness of acrylonitrile–butadiene–styrene (ABS) resin prior to metallization is treated generally with sulphuric/chromic acid system. However, the presence of chrominum (VI) ion imposes serious environmental problems. In this work, TiO2 photocatalytic treatment was used to enhance the adhesion strength between the ABS surface and the electroless copper film. Effects of the TiO2 content, irradiation time and UV power upon the surface topography, surface characterization and the adhesion strength were investigated. The results indicated that the surface hydrophilicity of ABS resin and the adhesion strength between the electroless copper film and ABS surface increased with an increase in the UV power and a prolongation in irradiation time, and did not increase linearly with an increase of TiO2 content. Though the surface topography of ABS changed little, the adhesion strength reached 1.25 kN/m, which was higher than that in the optimal H2SO4–MnO2 colloid. The surface chemistry results indicated that –COOH and –OH groups formed with the photocatalytic treatment and the absorption strengths increased with the UV power. XPS analysis results further demonstrated that the contents of C=O and –COOH reached 6.4 and 4.9% with the photocatalytic treatment, which was much higher than that of the H2SO4–MnO2 colloid (3.9 and 3.1%). The high contents of C=O and –COOH groups enhanced the surface hydrophilicity of the ABS resin and improved the adhesion strength between the electroless copper film and ABS resin. The results indicated that the photocatalytic treatment was an environment-friendly and effective method to replace the commercial wet chemical process for ABS surface modification.

Equipment based on high power UV and white light LEDs to collect and observe scorpions (Arachnida: Scorpiones) and other fluorescent organisms

We introduce a new, high quality, low cost and versatile LEDs-based handset device that emits high power UV and white light, which can be used interchangeably. It offers power control and has long battery life. Even though it is optimized to detect and collect scorpions under low light conditions, it can also be used with other groups of fluorescent organisms. The device achieved superior performance in field and laboratory trials when compared with a 12 LEDs low power UV flashlight, and a 46 W black fluorescent light lamp, to locate Tityus serrulatus Lutz & Mello, 1922.

High performance stretchable UV sensor arrays of SnO2 nanowires

A high performance, stretchable UV sensor array was fabricated based on an active matrix (AM) device that combined field effect transistors of SWCNTs and SnO2 nanowires. The AM devices provided spatial UV sensing via the individual sensors in the array. SnO2 NW UV sensors showed an average photosensitivity of ∼105 and a photoconductive gain of ∼106 under very low UV (λ = 254 nm) power intensities of 0.02–0.04 mW cm−2. The UV sensing performance was not deteriorated by a prestrain of up to 23% induced by radial deformation, consistent with the mechanical analysis.