紫外光辐照法制备金纳米盘及其反应机理

用紫外光辐照氯金酸、聚乙烯吡咯烷酮(PVP)和纳米金种子的混合溶液, 在室温下用30 min制备出尺度小于100 nm的截角三角形或六边形金纳米盘. X射线能谱和衍射分析表明粒子是以{111}面为盘状面的高纯面心立方金单晶, 红外透射光谱表明金粒子与PVP之间存在作用. 产物的可见吸收光谱表现出纳米盘的各向异性表面等离子体共振吸收峰. 不同实验条件下产物的吸收光谱分析表明: PVP起还原剂和包覆剂的作用; 高强度紫外光加速了反应进行; 种子对反应具有催化作用; 种子的加入量有最佳值, 在该值下纳米盘平均尺度最大(达80 nm), 吸收谱上的面内偶极共振峰位于950 nm处; 种子的加入量超过该值时, 纳米盘尺度变小, 面内偶极共振峰发生蓝移.     

IR-change and yellowing of polyurethane as a result of UV irradiation

In this investigation IR-change and yellowing of polyurethane as a result of UV radiation were studied. In the presence of UV radiation (200 h, λ > 300 nm), the synthesized aromatic polyurethane undergoes photodegradation with gradual change of its colour. The photochemical degradation of the polyurethane is associated with the scission of the urethane group and photooxidation of the central CH₂ group between the aromatic rings. These reactions are combined with the yellowing of the polyurethane surface. Analysis of the colour changes in PU surface during photodegradation was carried out by measuring CIEL^∗a^∗b^∗ colour components (L^∗,a^∗,b^∗ and ΔE_a,b^∗). FT-IR spectroscopy was used to study the chemical changes caused by UV irradiation. The colour difference of yellowing Δ_a,b^∗ exhibits a systematic tendency to higher values with increasing irradiation time. Overall, ΔE_a,b^∗ colour change correlates well with photodegradation of polyurethane by relative increase of the concentration of carbonyl group. Our results are in agreement with the quinone (yellow colour) formation as the chromophoric reaction product of polyurethane degradation.     

Facile Synthesis of Gold Nanoplates by Citrate Reduction of AuCl4^- at Room Temperature

Metal and semiconductor nanoparticles with nonspherical shapes, such as wires1, cubes2,3 and belts4, have been drawing a great interest in scientific community as a result of their physical and chemical properties being distinctly different from conventio…     

Electrochemical biosensing for dsDNA damage induced by PbSe quantum dots under UV irradiation

<正>An electrochemical sensor for the detection of the natural double-stranded DNA(dsDNA) damage induced by PbSe quantum dots(QDs) under UV irradiation was developed.The biosensing membranes were prepared by successively assembling 3- mercaptopropionic acid,polycationic poly(diallyldimethyl ammonium) and dsDNA on the surface of the gold electrode.Damage of dsDNA was fulfilled by immersing the sensing membrane electrode in PbSe QDs suspension and illuminating it with an UV lamp. Cyclic voltammetry was utilized to detect dsDNA damage with Co(phen)_3~(3+) as the electroactive probe.The UV irradiation,Pb~(2+) ions liberated from the PbSe QDs under the UV irradiation and the reactive oxygen species(ROS) generated in the presence of the PbSe QDs also under the UV irradiation were the three factors of inducing the dsDNA damage.The synergistic effect of the three factors might dramatically enhance the damage of dsDNA.This electrochemical sensor provided a simple method for detecting DNA damage,and may be used for investigating the DNA damage induced by other QDs.     

Effects of solar UV irradiation on the tensile properties and structure of PPTA fiber

This paper comprehensively studied the effects of simulated solar ultraviolet irradiation on the mechanical and structural properties of the Twaron2000 para-aramid fiber by use of mechanical test, SEM, XRD, DSC, DMA and ATR-IR measurements. The results showed that after UV irradiation, the mechanical properties of the fiber were decreased obviously, and UV irradiation deteriorated the surface and defect areas of the fiber severely by photo-induced chain scission and end group oxidation in air with the crystalline structure remained almost unchanged although some local rearrangement of the crystalline area might occur. It was found that surface etching and shortening of the crystalline correlation length along the fiber axis were the main causes of the mechanical loss induced by UV irradiation.     

Modification of polysulfone ultrafiltration membranes with UV irradiation and hydrophilicity increasing agents

Hydrophobic polysulfone UF membranes were modified with UV irradiation and hydrophilicity increasing agents. The modifications were tested with 0.5% whey-protein solution and 0.05% lysozyme solution at pH 6 and with 0.05% bovine serum albumin solution at various pH values. UV irradiation increased flux and the hydrophilicity of the membranes. The flux increases obtained varied with pH and modification agents used and could be more than 400% compared to unmodified conditions without any loss in retention. The best retentions were obtained at pH values, where both the protein and the membrane had the same charge, and a strong electrostatic repulsion was obtained. The pores enlarged to fixed sizes, which depended on the sizes of the proteins and the range of double layer forces between proteins and membranes at different states of charge density.     

A photocalibrated NO donor based on N-nitrosorhodamine 6G upon UV irradiation

A N-nitrosated rhodamine 6G acid (NOG) was designed for monitoring the kinetics and the dose of NO release in a real-time fashion with UV irradiation.     

UV irradiation enhances the bonding strength between citric acid-crosslinked gelatin and stainless steel

The effect of ultraviolet ray (UV) irradiation on the bonding strength between low carbon stainless steel 316 (SUS316L) and trisuccinimidyl citrate (TSC)-crosslinked alkali-treated gelatin (AlGelatin-TSC) was investigated. The UV irradiation effectively generated hydroxyl groups on the surface of SUS316L. The bonding strength between AlGelatin-TSC and SUS316L before UV irradiation was 0.345±0.007 MPa, and upon UV irradiation it increased to 0.750±0.069 MPa. In order to explain this enhanced bonding strength, the surface of SUS316L was examined using its water contact angle and X-ray photoelectron spectroscopy. Furthermore, the N 1s peaks derived from the TSC succinimidyl group were assigned to the surface of SUS316L after the immobilization of the TSC. This indicates that ester bond formation between the TSC active esters and the SUS316L hydroxyl groups contributed to the enhanced bonding strength. Therefore, UV irradiation and subsequent TSC immobilization is a simple way to functionalize biometal surfaces with various structures. This has practical applications for medical devices such as drug-eluting stents, dental implants, and metallic artificial bone.     

Photodegradation of dye pollutants on TiO_2 pillared bentonites under UV light irradiation

TiO2 pillared bentonite samples dried under different conditions are used to degrade 2,4-dichlorophenol and orange II under UV light irradiation. The supercritical dried sample exhibits a high activity for the photodegradation of 2,4-dichlorophenol and orange II due to its structural features. TOC and COD are measured during the degradation of 2,4-dichlorophenol under UV light irradiation using P25 and TiO2 pillared bentonite samples dried under different conditions. The clay-based catalysts can be readily separated by filtration or sedimentation.     

Effects of UV irradiation on tribological properties of nano‐TiO2 thin films

One‐layer and two‐layer nano‐TiO₂ thin films were prepared on the surface of common glass by sol–gel processing. Water contact angle, surface morphology, tribological properties of the films before and after ultraviolet (UV) irradiation were investigated using DSA100 drop shape analyzer, scanning probe microscopy (SPM), SEM and universal micro‐materials tester (second generation) (UMT‐2MT) friction and wear tester, respectively. The stored films markedly resumed their hydrophilicity after UV irradiation. But UV irradiation worsened tribological properties of the films. After the film was irradiated by UV, the friction coefficient between the film and GCr15 steel ball increased about 10–50% and its wear life shortened about 20–90%. Abrasive wear, brittle break and adherence wear are the failure mechanisms of nano‐TiO₂ thin films. It was believed that UV irradiation increased surface energy of the film and then aggravated adherence wear of the film at initial stage of friction process leading to severe brittle fracture and abrasive wear. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of UV irradiation on mechanical properties and structure of poly(1,3,4-oxadiazole) fibers

The accelerated ultraviolet aging behavior of poly(1,3,4-oxadiazole) fibers (POD fibers) exposed to artificial environment for different durations were studied. The influence of ultraviolet light on the intrinsic viscosity, structure, appearance and morphology, mechanical properties of POD fibers were investigated during aging by ATR-FTIR and UV-spectra, XPS, WXRD, SEM and tensile strength tester. The results revealed that the structure and properties of POD fibers were affected by UV light. Tensile strength and breaking elongation of POD fibers were severely decreased after 48 h UV light irradiation, and the change of intrinsic viscosity indicated that only degradation but not crosslink occurred. Disruption of oxadiazole rings and formation of carbonyl and amide were observed. UV aging process in nitrogen atmosphere suggested that the oxygen was indispensable and the essence of POD UV aging was photo-oxidation process. POD was amorphous and the recrystallization on surface was present after UV aging due to degradation. Morphology of POD fiber surface was damaged after UV aging.     

Stabilization of electronic properties of (1R)-(−)-10-camphorsulfonic acid doped polyaniline by UV irradiation

Stability of electronic parameters of conducting polymers affects the overall performance of organic electronics. We show that UV light (254 nm) treatment of polyaniline (PANI) films, containing camphorsulfonic acid (CSA) as a dopant and cast from formic acid, decreases the film resistance and keeps their improved resistance stable for at least 4 months. It has been found that due to the different origins of these electronic properties, the resistance and work function of the PANI·CSA films are affected differently by the UV treatment. The long-term stability of the resistance is governed by morphological changes of the material. On the other hand the stability of the threshold voltage of the field-effect transistor (FET) which is an indirect measure of the work function, originates from the charge density equilibration at the PANI·CSA film/insulator interface. The FT-IR, UV-vis and circular dichroism data provide the evidence that after the UV treatment the polymer molecular structure remains intact, but some secondary structural re-arrangements of the PANI·CSA take place. These re-arrangements are resulting from the strong donor-acceptor interactions between the imine and/or amine groups of the PANI chains and the CO and SO₃⁻ groups of the doping CSA-anion. These interactions enhance significantly the mechanical rigidity of the PANI matrix. The increasing broad absorption band of the “free-carrier tail” in the FT-IR spectra correlates with the conductivity increase of the UV treated PANI·CSA film.     

UV Radiation Effects on SiO2 Gels Doped with Organic Dyes

Silica gels prepared by the sol-gel method with TEOS as a precursor and doped with the organic dyes rhodamine B, Na fluoresceine and eosine G were exposed to UV radiation pulses from a nitrogen laser. The absorption, luminescence and IR spectra were taken as a function of the exposure time. The absorption and the luminescence curves show successive maxima and minima. The same response is observed when the exposure procedure is repeated. These results are explained in terms of the cyclic filling and depletion of the long-lived triplet excited electronic state. At short exposure times, the data can be fitted with a Lorentzian curve and the corresponding parameters are given.     

UV light‐mediated alkylation of inorganic selenium

In the presence of low molecular weight organic acids (formic, acetic, propionic and malonic), inorganic selenium(IV) is converted by UV irradiation to volatile selenium carbonyl, dimethylselenide and diethylselenide, depending on the acid used. Gas chromatography–mass spectrometry analysis of the volatile products shows that, in 0.7 M formic acid solution, approximately 60–70% (v/v) SeH₂ and 30–40% (v/v) SeCO are formed. The presence of nitrate ion appears to increase threefold the formation of SeCO while completely suppressing formation of SeH₂. Copyright © 2003 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.     

紫外光照射对掺铝氧化锌薄膜导电和透光性质的影响

本文采用光助溶胶—凝胶法制备了掺铝氧化锌(AZO)透明导电薄膜.研究了紫外光照射对薄膜导电性和透光性质的影响.结果表明:光照使薄膜的导电性显著提高,且光照后薄膜方阻的降低幅度随薄膜晶粒尺寸的减小而逐渐增加;而随着紫外光照射时间延长,薄膜的紫外吸收边蓝移,近红外区透光率降低.以上实验现象可能与表面吸附氧解吸引起的载流子浓度增加、迁移率升高以及分层退火处理形成的薄膜结构有关.     

Gamma radiation induced synthesis of gold nanoparticles in aqueous polyvinyl pyrrolidone solution and its application for hydrogen peroxide estimation

Gold nanoparticles (Au nps) have been synthesized in aqueous solution of polyvinyl pyrrolidone (PVP) by gamma radiolysis from HAuCl₄·3H₂O precursor and in presence of small concentrations of Ag⁺, 2-propanol and acetone. The effect of different experimental parameters, such as concentration of reactant, molecular weight of PVP on nanoparticle formation was studied. TEM image confirmed that spherical Au nps were formed when PVP of molecular weight 360,000 Da was used as capping agent. H₂O₂ is a reactant in the enzyme catalyzed reaction of o-phenylene diamine (o-PDA). The reaction product has a weak absorption in the yellow region of the spectrum. When this product interacts with Au nps, it leads to enhancement of the absorption peak. The nanoparticles synthesized by radiation method were used for estimation of H₂O₂. The absorbance value of this peak at λ_max was observed to change with H₂O₂ concentration, which was monitored for estimation of H₂O₂. The response is linear in the range of 2.5×10⁻⁶ mol dm⁻³ to 2×10⁻⁴ mol dm⁻³ and 1×10⁻⁷ mol dm⁻³ to 3×10⁻⁶ mol dm⁻³ H₂O₂ in two separate sets of experimental parameters with detection limit 1×10⁻⁷ mol dm⁻³.     

紫外光照下尿嘧啶在磷酸盐水溶液中的新型光化学反应研究

在中压汞灯光照下,无机磷酸盐能促进尿嘧啶水溶液(pH=8)的光解作用(磷酸盐效应),发生嘧啶碱基的光解取代反应,主要光解产物为6-磷酸基尿嘧啶(C₄H₅N₂O₆P).通过元素分析,UV,IR,EIMS,¹HNMR,¹³CNMR,³¹PNMR等测试手段和方法,确定了光解产物的组成和结构.实验表明,在中压汞灯的发射光谱(连续光谱)中,对磷酸盐效应起作用的波长为190～220nm.     

聚三甲硅基丙炔的紫外辐照研究I．聚三甲硅基丙炔均质膜在空气中的紫外辐照

聚１－三甲硅基丙炔膜经紫外线辐照后其氧氮选择性提高，用ＸＰＳ及水接触角法研究了膜的表面组成对透气性的影响。     

RNA is more UV resistant than DNA: the formation of UV-induced DNA lesions is strongly sequence and conformation dependent

DNA and RNA hairpins, which represent well-folded oligonucleotide structures, were irradiated and the amount of damaged hairpins was directly quantified by using ion-exchange HPLC. The types of photoproducts formed in the hairpins were determined by ESI-HPLC-MS/MS experiments. Irradiation of hairpins with systematically varied sequences and conformations (A versus B) revealed remarkable differences regarding the amount of photolesions formed. UV-damage formation is, therefore, a strongly sequence and conformation dependent process.