Effect Of Irradiation Time Research Articles

Photocatalytic degradation of an azo textile dye (C.I. Reactive Red 195 (3BF)) in aqueous solution over copper cobaltite nanocomposite coated on glass by Doctor Blade method

The degradation of C.I. Reactive Red 195 (3BF) in aqueous solution using copper cobaltite nanocomposite coated on glass by Doctor Blade method was studied. Structural, optical and morphological properties of nanocomposite coatings were characterized by X-ray powder diffractometry (XRD), diffuse reflectance spectroscopy (DRS) and field emission scanning electron microscopy (FESEM). The nanoparticles exhibit a particle size of 31nm, showing a good nanoscale crystalline morphology. The photocatalytic activity of copper cobaltite nanocomposite coated on glass was studied by performing the photocatalytic degradation of 3BF at different irradiation time. The effect of irradiation time on the degradation of 3BF was studied and the results showed that more than 85% of the 3BF was degraded in 45min of irradiation. The pseudo-first-order kinetic models were used and the rate constants were evaluated with pseudo first order rate constants of 4.10×10−2min−1. The main advantage of the photocatalyst coated on glass overcomes the difficulties in separation and recycle of photocatalyst suspensions.

Polyethylene-g-poly(cyclohexene oxide) by Mechanistic Transformation from ROMP to Visible Light-Induced Free Radical Promoted Cationic Polymerization

A novel polymerization mechanism transformation strategy, combining ring-opening metathesis polymerization (ROMP) and visible light induced cationic polymerization, is successfully applied for the synthesis of polyethylene-graft-poly(cyclohexene oxide) (PE-g-PCHO). First, cis-cyclooctene (COE) was polymerized via ROMP in the presence of a chain transfer agent and quantitatively hydrobrominated to give bromo functional polyethylene (PE-Br). Subsequent irradiation of PE-Br in the visible range using dimanganese decacarbonyl (Mn2(CO)10) and diphenyl iodonium hexafluorophosphate (Ph2I+PF6–) as radical generator and oxidant, respectively, initiated cationic polymerization of cyclohexene oxide (CHO) resulting in the formation of PE-g-PCHO. The effect of irradiation time and Mn2(CO)10 concentration on the grafting density and efficiency was evaluated. Both the precursor polymers and the corresponding graft copolymers were characterized by 1H NMR and Fourier transform infrared (FT-IR) spectroscopy, gel-permeation chromatography (GPC), and differential scanning calorimetric (DSC) analyses.

Evaluation of UV-A and solar light photocatalytic hydrogen gas evolution from olive mill wastewater

This work presents the results obtained in using olive mill wastewater (OMW) as sacrificial agent for the photocatalytic H2 evolution from water, at ambient temperature and pressure. The effects of irradiation time, catalyst amount, pH, and OMW concentration have been investigated. Under the best experimental conditions (4 h UV-A irradiation, 2 g L−1 Pt/TiO2, OMW 3.3% v/v, COD 944 mg L−1, pH 3) up to 44 μmol H2 were generated from aqueous samples. Consecutive irradiation cycles (4 × 4 h) on the same sample provided ca. 280 μmol H2, corresponding to 82% of the yield observed, under the same conditions and COD value, by using glucose as test sacrificial agent. H2 evolution was strongly improved (+81%) by pre-treating OMW with magnesium silicate (125 g L−1, 6 h contact), achieving a production of ca. 80 μmol H2 by 4 h UV-A irradiation. The possibility to exploit sunlight in the photocatalytic process was gained by using Eosin Y/Pt/TiO2. Under solar light the H2 yield resulted to be 66% with respect to that obtained by UV-A radiation. Beside some general mechanistic aspects of the photocatalytic process, benefits and drawbacks in recycling OMW for photocatalytic H2 evolution from water have been highlighted.

Investigation of optimum conditions and costs estimation for degradation of phenol by solar photo-Fenton process

In this study, solar photo-Fenton reaction using compound parabolic collectors reactor was assessed for removal of phenol from aqueous solution. The effect of irradiation time, initial concentration, initial pH, and dosage of Fenton reagent were investigated. H2O2 and aromatic intermediates (catechol, benzoquinone, and hydroquinone) were quantified during the reaction to study the pathways of the oxidation process. Complete degradation of phenol was achieved after 45 min of irradiation when the initial concentration was 100 mg/L. However, increasing the initial concentration up to 500 mg/L inhibited the degradation efficiency. The dosage of H2O2 and Fe+2 significantly affected the degradation efficiency of phenol. The observed optimum pH for the reaction was 3.1. Phenol degradation at different concentration was fitted to the pseudo-first order kinetic according to Langmuir–Hinshelwood model. Costs estimation for a large scale reactor based was performed. The total costs of the best economic condition with maximum degradation of phenol are 2.54 €/m3.

Sunlight-promoted photocatalytic hydrogen gas evolution from water-suspended cellulose: a systematic study.

This work presents a systematic study of cellulose (CLS) as a sacrificial biomass for photocatalytic H2 evolution from water. The idea is indeed to couple a largely available and not expensive biomass, and water, with a renewable energy like solar radiation. An aqueous CLS suspension irradiated either at 366 nm (UV-A) or under sunlight in the presence of Pt/TiO2 behaves as a H2 evolving system. The effects of irradiation time, catalyst and CLS concentrations, pH and water salinity are studied. Addition of CLS to the sample significantly improved H2 evolution from water splitting, with yields up to ten fold higher than those observed in neat water. The mechanism of the photocatalytic process relies on the TiO2-mediated CLS hydrolysis, under irradiation. The polysaccharide depolymerisation generates water-soluble species and intermediates, among them 5-hydroxymethylfurfural (HMF) was identified. These intermediates are readily oxidized following the glucose photoreforming, thus enhancing water hydrogen ion reduction to give gas-phase H2. The formation of "colored" by-products from HMF self-polymerization involves a sort of "in situ dye sensitization" that allows an effective photoreaction even under solar light. The procedure is evaluated and successfully extended on cellulosic biomasses, i.e. rice husk and alfalfa (Medicago sativa) stems, not previously investigated for this application.

Preparation and photocatalytic properties of graphene/TiO2 nanotube arrays photoelectrodes

Graphene/TiO2 Nanotube Arrays (GR/TNAs) photoelectrodes were fabricated by in-situ anodization and electro-deposition method. The surface morphology, structure, photoluminescence spectra (PL), and photocatalytic activity of the samples were investigated. The as-prepared graphene/TNAs (GR/TNAs) photoelectrodes showed significant improvement in the separation of photogenerated carriers and excellent photocatalytic stability. The effects of irradiation time, initial concentration, ionic strength and bias potential on the removal of rhodamine B (Rh.B) by TNAs and GR/TNAs were studied. Results showed that degradation rate of Rh.B for GR/TNAs photoelectrodes reached 75% after 60min illumination at pH of 6.0. The GR/TNAs exhibited significantly enhanced photocatalytic activity compared to unmodified TNAs. When the bias potential was applied, Rh.B degradation rate increased to 90% at 0.5V. NO3−, Ca2+ and Mg2+ in the solution promoted the degradation of Rh.B, while SO42−, Cl− and F− suppressed the removal rate.

One Step Photopolymerization of N, N-Methylene Diacrylamide and Photocuring of Carboxymethyl Starch-Silver Nanoparticles onto Cotton Fabrics for Durable Antibacterial Finishing

The PI/UV system ((4-trimethyl ammonium methyl) benzophenone chloride/UV) was used to synthesize carboxymethyl starch- (CMS-) stabilized silver nanoparticles (AgNPs). AgNPs so prepared had round shape morphology with size of 1–7 nm. The prepared AgNPs were utilized to impart antibacterial finishing for cotton fabrics. The PI/UV system was further utilized to fix AgNPs onto cotton fabrics by photocrosslinking of AgNPs-CMS composite onto cotton fabrics to impart durable antibacterial properties. Effect of irradiation time and incorporating N, N-methylene diacrylamide (MDA) in different concentrations on antibacterial performance before and after repeated washing cycles was studied.S. aureusandE. coliwere used to evaluate the antibacterial performance of finished fabrics. The antibacterial performance was directly proportional to the irradiation time and concentration of MDA but inversely proportional to the number of washing cycles. The inhibition zone ofS. aureusandE. coliis the same although they are different in the cell wall structure and mode of action due to the nanosize structure formed.

Photo induced crystallization of CaF_2 from a Na_2O/K_2O/CaO/CaF_2/Al_2O_3/SiO_2 glass

A new photo thermal refractive glass system is introduced. Glasses in the system Na2O/K2O/CaO/CaF2/Al2O3/SiO2 were doped with Ag2O, CeO2, KBr, SnO2 and Sb2O3. They were irradiated with UV light and subsequently thermally annealed at 530 °C, a temperature just above Tg. This led to a slightly yellow coloration. A second thermal annealing step at a temperature of 560 °C led to the crystallization of cubic CaF2 as proved by x-ray diffraction. Samples, annealed in a two step process at 530 °C for 1 h and 560 °C for 20 h without previous irradiation did not show crystallization. Furthermore, the effect of irradiation time on crystallization behavior and the role of KBr in the photoinduced crystallization process were also investigated.

One-pot synthesis of gold nanorods via autocatalytic growth of sonochemically formed gold seeds: The effect of irradiation time on the formation of seeds and nanorods

A one-pot synthesis for gold nanorods was developed using sonochemical reduction of gold ions in an aqueous solution in the presence of cetyltrimethylammonium bromide, silver nitrate, and ascorbic acid, where we focused on the autocatalytic growth of gold seeds formed by ultrasonic irradiation for short times. In growth experiments with these sonochemically formed gold seeds, sigmoidal shape growth curves were observed, and the induction period before growth began was longer for shorter irradiation times. This result indicated that the number of sonochemically formed gold seeds increased with increasing irradiation time. The average aspect ratio of the gold nanorods produced changed from 2.0 at an irradiation time of 0.5min to 3.6 at 15min. The gold nanorods produced were longer and wider when the irradiation time was shorter.

Evaluation of Modified Poly by UV-Induced Graft Polymerization as a Novel Hydrophilic Films

In order to improve the hydrophilic performances, the surface of poly films was modified through grafting polymerization of styrene (ST) initiated by ultraviolet (UV) in ethanol/water mixture solution. The effects of irradiation time, concentration of inhibitor (ferrous ammonium sulfate) on the grafting degree of ST will be investigated. The original and grafted poly films were characterized by scanning electron microscopy (SEM) and Static contact angle (CA), to characterize the chemical changes of the poly film surface. The results showed that the hydrophilic of poly films was improved significantly than that of the original film. The contact angle of PO-g-ST increased from 70° to 120.4° over a critical grafting degree of 26.35%, the hydrophilic of PP membranes improved dramatically.

Photosynthesis of Carboxymethyl Starch-Stabilized Silver Nanoparticles and Utilization to Impart Antibacterial Finishing for Wool and Acrylic Fabrics

The water soluble photoinitiator (PI) 4-(trimethyl ammonium methyl) benzophenone chloride/UV system is used in the synthesis of silver nanoparticles (AgNPs). Green synthesis method involved using PI/UV system, carboxymethyl starch (CMS), silver nitrate, and water. AgNPs obtained had a spherical shape morphology and a size of 1–7 nm. To impart antibacterial properties, wool and acrylic fabrics were treated with AgNPs obtained. The PI/UV system was further utilized to fix AgNPs onto wool and acrylic fabrics by photocrosslinking to impart durable antibacterial properties. The effect of irradiation time on the antibacterial performance before and after repeated washing cycles was studied. S. aureus (as G +ve) and E. coli (as G −ve) were used to estimate the antibacterial performance of the finished fabrics. The antibacterial performance was directly proportional to the irradiation time but inversely proportional to the number of washing cycles. However, after the 15th washing cycle, samples still have bacteriostatic effect; that is, although they show zero inhibition zone, they cannot be attacked by the bacterial growth and do not inhibit the bacterial growth. AgNPs finished wool fabrics showed more antibacterial activity than those of AgNPs finished acrylic fabrics.

Effect of irradiation time on riboflavin–ultraviolet-A collagen crosslinking in rabbit sclera

To determine the effect of the duration of irradiation on the biomechanical parameters of combined riboflavin-ultraviolet-A (UVA) collagen crosslinking (CXL) in rabbit sclera. Department of Ophthalmology, Provincial Hospital affiliated with Shandong University, Shandong, China. Experimental study. Thirty-six New Zealand rabbits were divided into 6 groups based on the duration of irradiation (10, 20, 30, 40, 50, or 60 minutes). After the application of riboflavin 0.1% drops (without dextran) as a photosensitizer, the animals were irradiated with 3 mW/cm(2) UVA at 365 nm. Only the left eye of each rabbit was treated. All the animals were humanely killed 24 hours postoperatively. One eye in each treated group was used for light microscopy. The other treated eye and all control eyes were prepared for biomechanical testing. The biomechanical parameters were ultimate stress, Young modulus, and the physiological modulus. The eyes irradiated for 10 or 20 minutes did not differ significantly from the control eyes. Stress-strain measurement of scleral strips irradiated for 40 minutes or longer showed a significant increase in the ultimate stress, Young modulus, and the physiological modulus. There was a significant increase in the physiological modulus of scleral strips irradiated for 30 minutes or longer. Eyes that were irradiated for 50 minutes and 60 minutes had retinal damage. Riboflavin-UVA CXL can lead to a noticeable increase in the biomechanical stiffness of the sclera. The physiological modulus is the most sensitive tool to measure stiffness. In this study, the optimum duration of irradiation was 40 minutes.

Microwave Assisted Short-Time Alkaline Extraction of Birch Xylan

Efficacy of microwave energy for the extraction of xylan from birch wood as an alternative to conventional method of extraction was investigated. Effect of irradiation time and microwave power input on the solubilization of wood and yield of extracted xylan was studied. The maximum yield of xylan obtained at the higher power level was significantly lesser compared to the lower power level indicating the molecular degradation of the polymer. The highest yield of xylan (60 % of the original xylan) was obtained at the lowest power level studied, 110 W, for an irradiation time of 10 min. Comparison with conventional extraction showed that 10 min of microwave extraction provided a similar wood dissolution to that at 90 °C for 1.5 h, but with a higher yield of xylan. Characterization of the precipitated xylan indicated that the extracted xylan contained 68–88 % of xylose with the major chemical structure consisting of a linear backbone of (1-4) β-d-xylopyransoyl residues. Molecular mass of the extracted xylan indicated that the xylan extracted using microwave contained 60–70 % of high molecular weight fraction, and about 30–40 % of low molecular weight fraction, whereas xylan extracted using conventional method showed a reverse trend. Molecular mass of non-aggregated xylan was reported to be 6,000 Da (in terms of dextran equivalents). Crystallinity of wood fibers increased irrespective of the method of extraction indicating no degradation of the strength of the fibers occurred during the extraction.

COD Removal of Textile Printing and Dyeing Wastewater by Photocatalysis

Degradation of printing and dyeing wastewater after aerobic biochemical treatment by photocatalysis is studied by using a rotating photoreactor and TiO2photocatalyst of Degussa P25. Effects of irradiation time and pH value on removing efficiency are investigated. The results show that the COD down to about 80mg/L can be achieved at the irradiation time of about 4-5 hours at mild pH values. At the pH value from 1.5 to 3.2, the COD down to about 80mg/L can be achieved at the irradiation time less than 1 hour, and the COD down to about 20mg/L could be achieved at the irradiation time of about 4 hours at a pH value of about 3.2.

Photocatalytic conversion of CO2 into value-added hydrocarbon (methanol) with high selectivity over ZnS nanoparticles driven by 355-nm pulsed laser

In the present investigation, monochromatic 355-nm pulsed laser radiations generated by third harmonic of Nd:YAG laser (1,060 nm) were applied as an excitation light source for conversion of CO2 into value-added hydrocarbon (methanol) with high selectivity over ZnS particles through photo-catalytic process. The microstructure and optical band absorption of as-prepared ZnS nanoparticles were characterized by means of XRD, UV–Vis absorption spectrum, TEM, SAED, and EDX spectrum. The effect of irradiation time as well as the pulsed laser energy on methanol yield and photoefficiency were investigated and discussed in detail. Furthermore, a possible mechanism for such conversion process is also discussed based on the band edge of ZnS semiconductor and the unique monochromatic characteristic of the adopted 355-nm pulsed laser.

Controlled and rapid growth of MTT zeolite crystals with low-aspect-ratio in a microwave reactor

The nucleation and growth of MTT zeolite, an important 10-membered ring (10 MR) zeolite, was controlled by a microwave-assisted hydrothermal synthesis. The effect of irradiation time (12,18, and 24h), seed-assisted synthesis with 1wt.% seeds for 6h and desilication under microwave irradiation on crystallinity and porosity were investigated. Under microwave-assisted synthesis, uniform crystal size, with lower crystal aspect-ratio and suppressed phase-impurity has been obtained. The tendency of column-like crystal to form bundle of columns was reduced significantly. Seeded growth further reduced synthesis time to 6h. Post-synthetic treatment was used to obtain larger pore volume of MTT zeolites. Some of the protonated MTT samples were tested in n-hexane cracking as model reaction. Characterization techniques such as XRD, FE-SEM, N2 adsorption–desorption, 27Al MAS NMR and NH3-TPD have been carried out to obtain insight in the physico-chemical properties of zeolite catalysts.

Effect of modulated irradiation time on the degree of conversion and the amount of elutable substances from nano-hybrid resin-based composites

The aim of our study was to analyse whether the irradiation time and/or the modulation of irradiation time influence the degree of conversion (DC) and the amount of elutable substances from modern nano-hybrid resin-based composites (RBCs). The DC was recorded in real time for 5min by means of attenuated total reflectance-Fourier transform infrared spectroscopy (n = 5) on the lower surface of 2-mm-thick samples irradiated with continuous and modulated irradiation times for 20s and 40s. The modulated times comprise a short polymerisation (2s or 5s) followed by a rest period of 1min and an additional polymerisation to complete 20s and 40s of polymerisation (2s + 18s, 5s + 15s, 2s + 38s and 5s + 35s). After storing the specimens in ethanol/water for 7days at 37°C, the eluates were analysed by gas chromatography-mass spectrometry. Results were statistically analyzed using a one-way ANOVA analysis (α = 0.05). The effect of irradiation time on DC is similar in all three analyzed materials, showing a significant increase in DC by increasing irradiation time from 20s to 40s, while the DC is not influenced within one irradiation time (20s or 40s) by the modulation of time. The type and amount of eluates are strongly dependent from the material and the irradiation protocol. An interrupt irradiation of RBCs is clinically feasible, reducing in general the amount of elutable substances at similar DC as the corresponding continuous polymerisation.

高重频CO2激光损伤HgCdTe晶体的数值分析

To obtain thermal damage characteristics of the HgCdTe crystal irradiated by a CO2 laser,the theoretical model of Hg0. 784Cd0. 216Te crystal damaged by the high repetition frequency CO2 laser was developed,and then the damage thresholds of Hg0. 784Cd0. 216Te crystal irradiated by a single pulse laser and a high repetition frequency laser were calculated based on the finite element method. Finally,the effect of irradiation time and laser repetition frequency on the damage thresholds was analyzed. The results show that the damage threshold of the crystal radiated by a single pulse laser is 64. 5 J / cm2. In the high repetition frequency( f 1 kHz) CO2laser irradiation,the damage threshold of the crystal mainly depends on the laser average power density and irradiation time,and is independent of the laser repetition frequency. With the increase of irradiation time,the damage threshold can effectively be reduced. When the laser average power density is less than1. 95 kW / cm2,the crystal damage will not occur. The conclusions have a reference value for laser processing and protection.

赤色電球形蛍光ランプによる暗期中断時間と光強度がスプレーギクの開花と花房の形状に及ぼす影響

赤色電球形蛍光ランプによる暗期中断時間と光強度がスプレーギクの開花と花房の形状に及ぼす影響について，秋ギク‘ゴールドストックダークリネカー’および夏秋ギク‘コイアローム’を用いて調べた．光源として，市販の白熱電球（対照光源，75 W）および660 nmの波長をピークにもち，赤色光を多く含む赤色電球形蛍光ランプ（21 W，試作品）を用いた．その結果，いずれの品種とも，商品価値の高い整った花房の形状を示す花芽分化抑制可能な光合成有効光量子束密度（PPFD）の下限値は，同じ暗期中断時間で比較すると，赤色電球形蛍光ランプを使用した場合に白熱電球を使用した場合より低かった．秋ギク品種では，赤色電球形蛍光ランプを使用して1時間の暗期中断を行った場合，花芽分化抑制可能なPPFDの下限値が示されたが，白熱電球を使用した場合では示されなかった．さらに，いずれの品種においても，赤色電球形蛍光ランプを使用した場合の花芽分化抑制可能なPPFDの下限値と，これに対応する暗期中断時間の積の値がほぼ一定になったことから，花芽分化抑制可能なPPFDの下限値と暗期中断時間は反比例の関係にあり，ブンセン-ロスコーの相反則が成り立っていると考えられた．

Preparation and Characterization of Commercial Polyethyleneterephthalate Membrane for Fuel Cell Applications

Commercial Polyethyleneterephthalate (PET) based proton exchange membrane was prepared by UV-radiation grafting of styrene onto PET films. The effect of irradiation time and different concentrations of the monomer on the degree of grafting (D.G.) has been studied. It was found that the DG increases linearly with increasing the irradiation time and monomer concentration, reaching a maximum at a certain level. The effect of chlorosulfonic acid concentrations on ion exchange capacity (IEC) and tensile strength also studied to find the optimum concentration of chlorosulfonic acid for using in the sulfonation process. The range of IEC, 0.2 to 0.775 m mol/g, resulting from treating styrene grafted and sulfonated PET (PET-g-PSSA) membranes with different chlorosulfonic acid levels showed that chlorosulfonic acid is an effective tool to control IEC. Fourier transform infrared (FTIR) spectroscopic analysis confirmed grafting and sulfonation onto PET Films. In addition, thermogravimetric analysis was used to investigate the behavior of the original PET film and PET-g-PSSA membranes. The methanol permeability and the proton conductivity of PET-g-PSSA film with D.G. 166% were found to be 1.2×10-8 and 58 m S/cm, respectively, better than those of Nafion 212 membrane measured with the same instruments under the same conditions. Since they have lower cost, higher conductivity and lower methanol permeability, PET-g-PSSA could be better used instead of Nafion in direct methanol fuel cells.