Increase Of UV Irradiation Time Research Articles

Study on enhanced photoluminescence properties of Au surface-modified ZnO NRAs composites

Au nanoparticles were deposited on the surface of ZnO nanorods arrays (NRAs) by photoreduction method under different UV irradiation time. The content and size of Au nanoparticles deposited on ZnO nanorods become larger with the increase of UV irradiation time. In addition, When the UV irradiation time is 40 min, the UV emission peak and UV–visible ratio of the prepared Au surface-modified ZnO NRAs are relatively largest, and the visible emission peak of that is relatively smallest, indicating that its photoluminescence performance is relatively best. The study indicates the Au surface-modified ZnO NRAs composites are promising candidate for light emitting applications.

Photocatalytic Properties of Co-precipitated Bismuth Cobalt Ferrite

Bismuth substituted cobalt ferrite nanoparticle is studied for photocatalytic in this paper. Bismuth cobalt ferrite has been synthesized by the coprecipitation method and low-temperature annealing treatment. The characterization results showed that the XRD spectral pattern is consistent with ICDD 221086. The crystallite size of bismuth cobalt ferrite increases with increasing annealing temperature. FTIR results confirm the available metal-oxide at number wave around 570/cm and 475/cm which is the appearance of octahedral and tetrahedral sites owing cobalt ferrite. The photocatalyst test was carried out by varying the catalyst mass and UV irradiation time. The absorption spectrum decreases with increasing catalyst mass. The increase in UV irradiation time causes the formation of more holes (h+) and electrons (e-). So that the hydroxide reaction occurs that produces free radicals. The results of this study indicate that cobalt ferrite-based nanoparticles have potential as photocatalyst materials.

Effect of UV irradiation on microbial structure, metabolic pathways and functional genes of nitrogen metabolism in highland wastewater

<p>In this experiment, in the background of the plateau environment, the effects of ultraviolet irradiation on the microbial community structure, metabolic pathways and nitrogen metabolism function genes of sewage were studied at 0 (control group), 5, 10, 30, and 180 min. The results showed that the increase of UV irradiation time promoted the microbial richness of sewage, but decreased the microbial diversity. In terms of community structure, the increase of ultraviolet irradiation time will inhibit or promote some bacterial genera, for example, it has a promoting effect on Bacteroidota, norank_f_ Saprospiraceae, etc., and an inhibitory effect on Phreatobacter. The relative abundance of metabolic pathways changed significantly with the increase of UV irradiation time, and the change trends at different metabolic levels were the same. In nitrogen metabolism pathways, the relative abundance of genes involved in nitrification and denitrification functions was inhibited by the duration of UV irradiation.</p>

Stability of a calibrant as certified reference material for determination of trans-zearalenone by high performance liquid chromatography-diode array detection-triple quadrupole tandem mass spectrometry.

In this study, a trans-zearalenone (trans-ZEN) calibrant in acetonitrile as certified reference material (CRM) was prepared and intensively investigated the stability by high performance liquid chromatography coupled diode array detection and triple quadrupole tandem mass spectrometry (HPLC-DAD-MS/MS). The photoisomerization and degradation of main component and related impurities in trans-ZEN calibrant CRM was studied in detail under different light conditions such as UV light (254nm), sunlight, and visible light. Trans-ZEN in acetonitrile was confirmed a significant shift toward cis-ZEN up to a 52% cis-isomerization rate after exposing to UV light (254nm) in transparent ampule for 1day. The unsaturated double bond photosensitive groups of trans-ZEN and cis-ZEN will further undergo photoreaction to generate more isomers and related products with the increase of UV irradiation time. The calibrant in amber ampules was relatively stable after exposing to sunlight for 28days, with only 0.35% cis-isomer observed. The results indicated that trans-ZEN solution calibrant should be packed in amber ampules to avoid UV rays. Thermal stability test exhibited this calibrant was stable over 6weeks even at 60°C. Trans-ZEN was found to be more stable in acetonitrile than in methanol since an unknown impurity was observed in methanol after 6weeks placed at 25°C. The stability study of trans-ZEN calibrant provided a basis for the usage, storage, and transportation of the CRM. A concentration and expanded uncertainty of the trans-ZEN calibrant CRM of 11.01 ± 0.18µg/mL was developed.

Solid-phase photodegradation of polystyrene by nano TiO2 under ultraviolet radiation

Solid phase photodegradation of polystyrene (PS) and Polystyrene – titanium dioxide nano composite (PS-TiO2) was studied under ultraviolet radiation of wavelength of 253 nm. Titanium dioxide (TiO2) photocatalyst was synthesized via sol-gel method and characterized using SEM, EDX and XRD. Photodegradation of PS and PS-TiO2 was monitered using GPC, FTIR spectroscopy, UV-DRS, SEM and weight loss measurements. An appreciable decrease in the values of average molecular weights were observed from the GPC data with the increase in the UV exposure time for PS as well as PS-TiO2 composites. FTIR and UV–vis spectra revealed that the photodegradation of PS and PS-TiO2 composite was accelerated by the increase in UV irradiation time and also with the increase in the percentage of TiO2. It was also evident from the FTIR spectra that photooxidative degradation was the possible mechanism of degradation. Band gap energies of PS and PS-TiO2 determined using Tauc plot decreased upon increase in UV irradiation. The change in surface morphology of the irradiated samples compared to the pristine ones were clearly observed in their SEM images. Weight loss of the polymer samples increased upon increase in UV irradiation time. Mechanical properties (tensile and flexural) of raw as well as irradiated samples of PS and PS-TiO2 composites showed an appreciable decrease in their values with increase in irradiation time. The values of dielectric constant of the UV irradiated polymer specimens showed higher values compared to that of non irradiated specimens at varying frequencies. Dielectric strength of the polymer specimens decreased with the increase in UV irradiation time.

Reductive transformation of profenofos with nanoscale Fe/Ni particles.

Profenofos is an abundantly used organophosphate pesticide in agriculture but its excessive use may lead to hazardous effects on environment. Thus, the present study focused on the reductive transformation of this pesticide in the presence of Fe/Ni bimetallic nanoparticles by optimizing the process parameters such as stirring time, nanoparticles dose, pH, and initial pesticide concentration. The results of reductive transformation were compared with photodegradation studies. It was found that with the increase in UV irradiation time, the percent degradation was increased. After 660min, a 78% photodegradation of 100μM solution of pesticide was observed. On increasing the initial pesticide concentration to 200μM, the maximum degradation was achieved in 570min, but here, only 73% degradation was observed. The rates of photodegradation observed with 100 to 400μM solutions were 1.4 × 10-3, 1.5 × 10-3, 1.5 × 10-3, and 5 × 10-4min-1 respectively.In case of reductive transformation carried out in the presence of Fe/Ni bimetallic nanoparticles, the degradation was observed to be increased from 78 to 93.9% in only 180min. A further increase in pesticide concentration led to a decrease in degradation. Under these conditions, the rate of reaction was found to be 1.09 × 10-2min-1. A 93% degradation of profenofos was further increased to 98% when the quantity of nanoparticles was increased twice; hence, a significant reduction in time of irradiation was observed. Reductive transformation of pesticide thus provided an efficient and cheaper method for reducing the burden of profenofos from the environment.

Study on photoluminescence and thermoluminescence properties of UV-irradiated CaSrAl2SiO7:Ce3+ phosphors

This paper reports synthesis of CaSrAl2SiO7:Ce3+ phosphors via traditional high temperature solid state reaction method. The phase analysis of the phosphors was carried out using powder X-ray diffraction (XRD) technique which indicates that all these compounds are of single phase of CaSrAl2SiO7 with tetragonal crystal structure. Average grain size of the phosphor was determined by using Scherrer formula. The photoluminescence (PL) study was carried out using spectrofluorophotometer. PL Excitation (PLE) spectra consist of two peaks at around 253 and 290 nm. CaSrAl2SiO7:Ce3+ emits strong violet emission located at 418 nm when excited with 290 nm. Emission is associated with 5D→4F transition of Ce3+ ions. Thermoluminescence (TL) properties of UV-irradiated phosphor were measured. Effect of different heating rates on TL glow curve was recorded and 5 °C/s is found to be optimum heating rate. There is no shift in glow peak position with increase in UV-irradiation time. TL intensity increases with increase in UV exposure time up to 35 min and then saturates. To analyse kinetic study, glow curve was deconvoluted into four different traps and their activation energies were determined by using peak shape method. Concentration dependence on PL and TL was investigated; concentration quenching in PL occurs at 1 mol% of Ce3+ and quenching in TL arises at 0.5 mol% of Ce3+. TL spectra and decay characteristic were also carried out. This paper deals with possible mechanism of PL and TL.

Experimental Studies of UV Irradiation Induced Changes in Optical, Mechanical and Microstructural Properties of PVA/Modified Cellulose Composite

Poly(vinyl alcohol) (PVA)/modified Cellulose composite films with 85:15 wt.% were prepared by solution casting method and subjected to UV irradiation for different intervals of time. The UV irradiation induced modifications in optical, mechanical and morphological properties were studied. The FTIR results confirm the chemical interaction between PVA and Cellulose. The optical absorption also supports the formation of crosslinked network in the polymer composite. The XRD result shows an increase in the amorphousness with increase in UV irradiation time. The Young’s modulus (YM), tensile strength (TS), stiffness and percentage (%) elongation at break (% EB) of the composite films increase with increase in UV irradiation time. The Scanning Electron microscope (SEM) images confirm the

Electron Paramagnetic Resonance Examination of Free Radical Formation in Salicylic Acid and Urea Exposed to UV Irradiation

Free radicals formed by UV irradiation of the two magistral formulas applied on the skin, salicylic acid and urea, were examined by X-band (9.3 GHz) EPR spectroscopy. The influence of the time of UVA (315–400 nm) irradiation on free radical properties and concentrations in the drug samples was determined. The nonirradiated magistral formula did not contain free radicals. Amplitudes (A) and linewidths (ΔBpp) of EPR spectra were analysed. Fast spin-lattice relaxation process existed in the tested drugs. UV irradiation did not change spin-lattice interactions in the tested magistral formula. Concentrations of free radicals formed by UV irradiation in salicylic acid and urea were ~1017–1018 spins/g. The strongest formation of free radicals under UV irradiation was observed for salicylic acid than for urea. Free radical concentration in salicylic acid increased with the increase of UV irradiation time from 15 minutes to 30 minutes, and after its value remained unchanged. The increase of free radical concentration in urea with UV irradiation time was stated. Salicylic acid is characterized with higher photosensitivity than urea. Salicylic acid, urea, and the skin treated by them should not be stored on UV exposure. The usefulness of EPR spectroscopy to optimize storage conditions of recipe drugs was conformed.

Effect of UV irradiation on the proportion of organic chloramines in total chlorine in subsequent chlorination.

This study investigated the changes of chlorine species and proportion of organic chloramines during the chlorination process after UV irradiation pretreatment in drinking water. It was found that the UV pretreatment could enhance the percentage of organic chloramines by increasing free chlorine consumption in the chlorination of raw waters. The percentage of organic chloramines in total chlorine increased with UV intensity and irradiation time in raw waters. However, for the humic acid synthesized water, the percentage of organic chloramines increased first and then decreased with the increase of UV irradiation time. The value of SUVA declined in both raw and humic acid synthesized waters over the UV irradiation time, which indicated that the decomposition of aromatic organic matter by UV could be a contributor to the increase of free chlorine consumption and organic chloramine proportion. The percentage of organic chloramines during chlorination of raw waters after 30-min UV irradiation pretreatment varied from 20.2% to 41.8%. Total chlorine decreased obviously with the increase of nitrate concentration, but the percentage of organic chloramines increased and was linearly correlated to nitrate concentration.

Effect of UV irradiation on optical, mechanical and microstructural properties of PVA/NaAlg blends

Poly(vinyl alcohol) (PVA)/Sodium alginate (NaAlg) blend films with 60:40wt% were prepared by solution casting method and subjected to UV irradiation for different intervals of time. The optical, mechanical and morphological properties of the blend films were modified after UV irradiation. The FTIR and FT-Raman results show the chemical interaction between PVA and NaAlg. The UV–vis absorption peak at 278nm shifts slightly towards longer wavelength and the absorption increases with irradiation time, indicate the increase in crosslinking network. The XRD results show an increase in amorphous nature with increase in UV irradiation time. The DSC/TGA results show a single glass transition temperature (Tg), which confirm that the blends are completely miscible and thermally stable up to 250°C. The Young׳s modulus, tensile strength and stiffness of the blend films increase with increase in UV irradiation time. The SEM images confirm that the surface of 48h UV irradiated PVA:NaAlg blend is more photo-resistant than unirradiated blend.

Combined Biological and Advanced Oxidation Treatment Processes for COD and Color Removal of Sewage Water

Wastewater (WW) generation is inevitable in rapidly growing and urbanizing societies resulting in significant damage to the quality and quantity of fresh water resources. The study was intended to harness the reuse potential of sewage WW using integrated wastewater treatment process. Composite sample of sewage WW was collected from inlet of sewage wastewater treatment plant. The WW sample was batch wise subjected to activated sludge process (ASP), ozonation, UV irradiation, H 2 O 2 oxidation and sand filtration separately for different time intervals (i.e. 0 to 60 min) and concentrations of H 2 O 2 (0.1 to 1.0 mlL -1 ), followed by the integration of all the processes at their optimum conditions. Batch experiments were performed in pyrex containers using 1.5L sample except for ASP that is 20L. Efficiencies were measured in terms of COD, color and TSS removal along with changes in pH and temperature. Biological diversity of WW was also determined using cultural techniques followed by biochemical tests. Color reduction was much higher and faster than COD in all the tested treatment processes. Ozonation was the fastest process to remove 78% color in 30 minutes however, ASP was more economical for the same efficiency but requires high hydraulic retention time (HRT). Increase in UV irradiation time reduced COD and color by 54 and 69% after 60min respectively. Sand filter efficiently removed 97% TSS with marginal reduction in COD. Integration of 4 hr ASP, 24 min ozonation and 10 min UV exposure with 1 ml L -1 H 2 O 2 dose yielded 98 and 100% COD and Color reduction respectively.

Investigation of Structure and Properties of PET Multifilament Irradiated with UV in Different Atmosphere

Changes of mechanical properties and chemical structure of polyester (PET) fibers are studied through UV simulated accelerated ageing experiments with N2, air and O3 as the atmosphere. The structure, thermal stabilities and tensile strength are obtained by FTIR, DTA-TG, XRD, SEM and micro-mechanics test. The difference of degradation process in various atmospheres is discussed in this paper. The results show that the fracture tensile strength of PET multifilament decreases with the increase of UV irradiation time. And oxidation and then decarbonylation take place on the surface. Besides, Melting temperature (Tm), the temperature of quality loss by 10% (T10) and the crystallization also decrease. However, in O3 atmosphere the oxidation develops very quickly and fully, therefore, the carbonyl on the surface is eliminated and decreases significantly, and the tensile strength decreases much faster than those in N2 and air. The skin layer of irradiated fibers appears serious damaged. The mechanism of chemical degradation for samples irradiated in N2 environments is similar to those irradiated in air.

Bioactivity of L-b-L Self-Assembly TiO<sub>2</sub> Hollow Spheres by UV Irradiation Enhanced

Using nano-TiO2 particles obtained by hydrolysis of titanium oxysulfate (TiOSO4) as the precursor, and polystyrene (PS) spheres as the template, TiO2 hollow spheres were successfully deposited on CPTi substrates through layer-by-layer self-assembly technology. After ultraviolet light (UV) irradiation, the TiO2 coatings were soaked in simulated body fluid (SBF) to explore their bioactivities. The effects of UV irradiation time and UV irradiation media on the bioactivities of nano TiO2 coatings were investigated. The results show that bone-like apatite can be formed on the surface of nano TiO2 coating irradiated by UV, and this reveals that the irradiated coating has good bioactivity. The amount of apatite formed on the surface of the coating increases with the increase of UV irradiation time. UV-irradiated media also influence the bioactivity of the coating. The bioactivities of nano TiO2 coatings irradiated in air and SBF are better than that in water.

Development of a novel RAFT-UV grafting technique to modify polypropylene membrane used for NOM removal

Surface modification of polypropylene microporous membrane was conducted by reversible addition-fragmentation chain transfer (RAFT) polymerization under UV irradiation. Dibenzyltrithiocarbonate was used as a RAFT agent. Attenuated total reflection-Fourier transform infrared spectroscopy and filed emission scanning electron microscopy were used to characterize the structural and morphological changes on the membrane surface. The degree of grafting of poly(acrylic acid) (PAAc) on the membrane surface increased with the increase of UV irradiation time, and decreased with the increase of the concentration of chain transfer agent. Surface-initiated block graft copolymerization with acrylamide was carried out on the PAAc modified membrane surface in the presence of free radical initiator, 2,2′-azobisisobutyronitrile. The degree of grafting of polyacrylamide (PAAm) increased with the reaction time. These results demonstrated that block graft copolymer of PAAc and PAAm on the membrane surface was accomplished by the combination of UV irradiation and the surface-initiated RAFT method. The pure water flux through the PAAc grafted membranes increased with the degree of grafting up to 0.67 wt.%, and then it decreased. The membrane filtration of natural organic matter from the Yangtze River showed that the degree of grafting played a very important role. Reduction from pure water flux was lower, the flux recoveries after water and caustic cleaning and flux ratios after fouling were higher for the modified membrane than those of the unmodified membrane. The PAAc grafted PPMM with a degree of grafting of 2.51 wt.% possessed the best antifouling characteristics. The high hydrophilicity, high permeability, and low fouling character of the modified membranes make microporous polypropylene membranes desirable for water treatment.

Synthesis and Characterization of Silver/Clay/Chitosan Bionanocomposites by UV-Irradiation Method

Problem statement: Silver/Montmorillonite/Chitosan Bionanocomposites (Ag/MMT/Cts BNCs) have been synthesized by UV-irradiation reduction method in the absence of any reducing agent or heat treatment which is used to antibacterial application and medical devices. Approach: MMT, Chitosan and AgNO3 were used as a solid support, stabilizer and silver precursor, respectively. The properties of Ag/MMT/Cts BNCs were studied as a function of UV-irradiation times. The crystalline structure, d-spacing of interlayer of MMT, the size distributions and surface plasmon resonance of synthesized silver nanoparticles (Ag-NPs) were characterized using Powder X-Ray Diffraction (PXRD), Transmission Electron Microscopy (TEM) and UV-vis spectroscopy. The functional groups of prepared BNCs were also determined by Fourier Transform Infrared (FT-IR). Results: The results obtained from UV-vis spectroscopy of synthesized Ag-NPs showed that the intensity of the maximum wavelength of the plasmon peaks were increased with the increasing in the UV-irradiation times. Results from UV-visible spectroscopy and Transmission Electron Microscopy (TEM) microphotographs show that particles size of Ag-NPs decrease with the increase of UV-irradiation time. Conclusion: UV-irradiation disintegrated the Ag-NPs into smaller size until a relatively stable size and size distribution were achieved. Ag/MMT/Cts BNCs could be suitable to antimicrobial applications and medical devices.

Fouling control in a submerged membrane‐bioreactor by the membrane surface modification

AbstractTo improve the antifouling characteristics, polypropylene microporous membranes (PPHFMMs) were surface‐modified by the sequential photoinduced graft polymerization of acrylic acid and acrylamide. The grafting density and the grafting chain length, which played important roles in the antifouling characteristics, were controlled in the first and the second step, respectively. The ATR/FTIR results clearly indicated the successful modification on the membrane surface. The static water contact angle of the modified membrane reduced obviously with the increase of the grafting chain length. The contact angle of the acrylic acid modified membranes was lower than that of the acrylamide modified membrane with similar grafting chain length. The grafting chain length increased with the increase of UV irradiation time and monomer concentration. The grafting chain length of poly(acrylic acid) (PAAc) was lower than that of the polyacrylamide (PAAm) under the same polymerization conditions. Pure water flux for the modified membranes increased with the increase of grafting chain length, and had maximums. The antifouling characteristics of the modified membranes in a submerged membrane‐bioreactor (SMBR) were evaluated. The modified membranes showed better filtration performances in the SMBR than the unmodified membrane, and the acrylic acid grafted membrane presented better antifouling characteristics than acrylamide modified membranes. The results demonstrated that the surface carboxyl‐containing membranes were better than the surface amido‐containing membranes. The results of Pearson correlations demonstrated that the PAAc modified membranes with longer grafting chain length had higher flux recoveries, while the PAAm modified membranes with longer grafting chain length had lower flux recoveries. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Thermo- and pH-responsive polypropylene microporous membrane prepared by the photoinduced RAFT-mediated graft copolymerization

Thermo- and pH-responsive polypropylene microporous membrane prepared by photoinduced reversible addition–fragmentation chain transfer (RAFT) graft copolymerization of acrylic acid and N-isopropyl acrylamide by using dibenzyltrithiocarbonate as a RAFT agent. Attenuated total reflection-Fourier transform infrared spectroscopy (ATR/FT-IR), X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (FE-SEM) were used to characterize the structural and morphological changes on the membrane surface. Results of ATR/FT-IR and XPS clearly indicated that poly(acrylic acid) (PAAc) and poly(N-isopropyl acrylamide) (PNIPAAm) were successfully grafted onto the membrane surface. The grafting chain length of PAAc on the membrane surface increased with the increase of UV irradiation time, and decreased with the increase of the concentration of chain transfer agent. The PAAc grafted membranes containing macro-chain transfer agents, or the living membrane surfaces were further functionalized via surface-initiated block copolymerization with N-isopropyl acrylamide in the presence of free radical initiator, 2,2′-azobisisobutyronitrile. It was found that PNIPAAm can be grafted onto the PAAc grafted membrane surface. The results demonstrated that polymerization of AAc and NIPAAm by the RAFT method could be accomplished under UV irradiation and the process possessing the living character. The PPMMs with PAAc and PNIPAAm grafting chains exhibited both pH- and temperature-dependent permeability to aqueous media.

UV-irradiation-induced bioactivity on TiO 2 coatings with nanostructural surface

Titania (TiO 2) coatings with nanostructural surface prepared using plasma spraying technology were irradiated by ultraviolet light in simulated body fluids to improve their bioactivity. The in vitro bioactivity of the coatings was evaluated by investigating the formation of apatite on their surfaces in simulated body fluids. Bone-like apatite was observed to precipitate on the UV-irradiated TiO 2 coating with nanostructural surface after it was immersed in simulated body fluid for a certain period, but not on the as-sprayed and UV-irradiated TiO 2 coatings without nanostructural surface. The results indicate that the nano-TiO 2 surface can be activated by UV-irradiation to induce its bioactivity. The ability of apatite formation on the nano-TiO 2 surface was improved with the increase of UV-irradiation time. The in vivo results reveal that the as-prepared TiO 2 coating with nanostructural surface cannot induce the formation of new bones during the implantation period, but the UV-irradiated TiO 2 coating with nanostructural surface could do so during an implantation time longer than 2 months. Our results indicate that the osseointegration ability of the plasma-sprayed TiO 2 coating with nanostructural surface can be improved by UV irradiation.

Control of Luminescence Intensity from Rare Earth Ion (EU 3+, TU 3+)-DOPED POLYIMIDE NANOPARTICLES BY UV-IRRADIATION AND THERMAL TREATMENT

The control of luminescence intensity from rare earth ion(Eu3+, Tu3+)-doped polyimide(PI)nanoparticle film by UV-irradiation and thermal treatment is reported. In the system, it was observed that luminescence intensity assigned to rare earth ion increased with increase of UV-irradiation time, whereas the intensity decreased with elevation of thermal treatment temperature. It was estimated that the mechanism of the above phenomena is based on a reversible change in an energy transfer probability from PI to rare earth ion by the UV-irradiation and the thermal treatment.