辛醇对LiBr水溶液汽液界面的影响

采用分子动力学方法分析303.15 K时,添加不同量异辛醇的水或溴化锂水溶液汽液界面的微观结构,发现;未吸收水蒸气时,当异辛醇较少时,醇分子在界面处分布不均匀;当异辛醇较多时,异辛醇在界面处均匀分布,但排列比较松散;随着异辛醇数目的继续增加,异辛醇在界面处形成双层结构。异辛醇亲水羟基中的氢与阴离子存在氢键作用,而阳离子与异辛醇的氧之间存在着较强的静电相互作用。在非平衡条件下,采用分子动力学方法对添加或未添加正辛醇的溴化锂水溶液吸收水蒸气的动态过程模拟0到100ps,发现;加有正辛醇的溴化锂水溶液与未添加正辛醇的溴化锂水溶液相比,吸收的水分子数目明显增多。     

Properties of aqueous NaCl solutions in external electromagnetic fields

Molecular dynamics simulations are performed to investigate the effects of an external electromagnetic field on aqueous NaCl electrolyte solutions at a temperature of 298 K. The simulations assume that the electromagnetic waves propagate in the x-axis direction with a frequency of 50, 100 or 200 GHz. The intensity of the electromagnetic field is assumed to vary in the range 0.1–0.3 V/Å. The simulations are conducted for two different NaCl solution concentrations, namely 1 m and 5 m (molality). The results indicate that as the intensity of the electromagnetic field is increased, the re-orientation of the water molecules becomes more pronounced and the diffusion coefficient of the aqueous NaCl solution increases. It is also shown that in both the low-concentration and high-concentration solutions, the diffusion coefficients of water molecules and ions increase as the frequency and intensity of the electromagnetic field increase.     

Microscopic dynamics in water and ionic aqueous solutions: velocity cross-correlations

The microscopic momentum transfer between distinct particles in water and ionic aqueous solutions has been investigated by molecular dynamics simulation. The time correlation functions between the initial velocity of a central molecule and later velocities of molecules within different coordination shells were calculated for liquid water. Special attention was paid to the influence of the intermolecular hydrogen bonds on the exchange of momentum among water molecules and on the power spectra of the velocity autocorrelation functions. The velocity cross-correlations between ions in an aqueous NaCl solution also were calculated. It was observed that the difference between the results for the Na⁺ and Cl^? ions are associated mainly with the different sizes of the ions.     

气相界面活性剂对溴化锂水溶液吸收水蒸气的影响

目前在溴化锂吸收式制冷机/热泵中被广泛采用的界面活性剂是2-ethyl-1-hexanol(2EH)和1-octanol。传统的界面活性剂的添加方式是,将界面活性剂以液相形式投入到溴化锂溶液中。如果在三效循环中仍采用这样的方式将2EH加入到溴化锂溶液中,由于发生器的温度较高,势必有界面活性剂被蒸发而进入冷媒系统。为探讨三效循环界面活性剂的可能添加方式,同时试图研究界面活性剂以气相形式投入对溴化锂溶液吸收水蒸气的影响,本文针对几种可能有效的界面活性剂,做了界面活性剂的气相添加对吸收速度影响的测试实验。经过对2-ethyl-1-hexanol、1-heptanol和1-hexanol等添加剂的静态池实验,结果表明,气相添加的效果与液相投入没有明显的差别,同样可以大大提高溴化锂溶液吸收水蒸气的速度。     

银/二氧化硅复合材料对硝酸钠红外吸收光谱特性影响

对海洋营养盐进行快速检测是海洋污染监控中的一项重要任务。测量了硝酸钠溶液蒸发过程中的红外光谱,发现表面增强红外光谱法在营养盐的快速检测中有重要的应用价值。采用Stober方法制备了二氧化硅纳米颗粒,然后采用银氨溶液与二氧化硅溶液混合的方法制备银/二氧化硅(Ag/SiO₂)复合材料,并利用扫描电镜(SEM)、X射线衍射(XRD)以及紫外-可见(UV-Visible)吸收光谱对其进行表征。研究了硝酸钠水溶液干燥过程中Ag/SiO₂复合材料对硝酸钠红外吸收光谱的影响,结果表明硝酸根反对称伸缩振动吸收峰的吸收强度得到增强,这可能来自Ag/SiO₂薄膜材料的界面效应。     

改性耐晒蓝与铜离子形成的配合物吸光性质研究

在乙醇与水体积比为1∶1的混合溶剂中将工业级染料耐晒蓝(FRL)用重结晶法提纯,提纯后的FRL用亚硝酸钠(NaNO₂)进行重氮化,再与邻菲咯啉(Phen)进行偶合,得到改性耐晒蓝(FRLP)。FRLP与Cu2+反应形成配合物。利用退色分光光度法结合等摩尔连续变化法测定Cu2+与FRLP的组成,在pH 6～9的条件下得到1∶2的配合物。在pH 8.8的B-R缓冲溶液中测得该配合物的摩尔吸光系数ε_{590 nm}为9.5×104 L·mol-1·cm-1,表观稳定常数K_表为5.12×1012。研究了该配合物在紫外区的谱学性质,发现在200～305 nm区域内其水溶液对紫外光具有很强的吸收作用。将该配合物与聚乙烯醇共混制成偏光膜,对紫外光同样具有较强的吸收作用,在可见光区最大吸收波长处与光轴平行时单片膜的透过率为45%～50％,两片垂直放置的膜在200～325 nm范围内透过率为零,325～400 nm范围内的平均透过率约10%。     

Synthesis and Photocatalytic Activity of Nanosized Powder of Zn-Doped Titanium Dioxide

Nanosized powder materials made Zn-doped titanium dioxide with concentration of 0.1, 0.5, and 1.0 mol % Zn²⁺ have been synthesized from aqueous solutions of inorganic compounds of titanium modified with zinc(II) ions. The materials obtained have been studied by electron microscopy, thermogravimetric analysis, and powder X-ray diffraction. It has been found that if zinc ions introduced in titanium dioxide the stabilization of anatase modification takes place retaining size and morphology of particles. The materials synthesized have shown photocatalytic activity under ultraviolet and visible light irradiation. The highest photocatalytic activity has been found for material containing 0.1 mol % Zn²⁺ and calcined at 600°С.     

氯化钠溶液中纳米银胶的紫外-可见光谱研究

考察了纳米银胶制备中的一系列影响因素。用TEM和UV-Vis表征了水溶性高分子PVP,PVA和强电解质NaCl对纳米银胶的影响,发现不同制备方法和不同介质中得到的纳米银胶的分散性质和粒径大小不同,吸收光谱有差别。NaCl的加入对纳米银胶的吸收光谱影响显著,尤其是对于没有PVP,PVA保护的体系,当溶液中NaCl浓度达到某一临界值时,纳米银胶的吸收光谱出现突变。     

Measurement of the optical absorption coefficient for liquid based on optical microfiber

An inline measuring method of the optical absorption coefficient for liquid based on optical microfiber (OM) is studied. If an OM is immersed into absorptive liquid, the additional loss of the OM will increase. We have analyzed the relationship between the additional loss of the OMs and the absorption coefficients of the liquids, and found that the OM with determinate construction will be useful for measuring the absorption coefficients of the liquid whose refractive index is lower than that of the OM. Two OM samples are prepared to measure the absorption coefficient of pure water. A supercontinuum source is launched into the OM sample which is immersed into pure water, and absorption spectrum from 1400 to 1700 nm has been achieved by monitoring the additional loss. The trend of the absorption spectrum is similar with that of the reported result, showing that the inline measurement of the optical absorption coefficient is a feasible method for those lower refractive index liquids.     

Electronic Spectra and the Mechanism of Complexing of Uranyl Nitrate in Water–Acetone Solutions

Based on the analysis of electronic absorption and luminescence spectra, the processes of complexing in an aqueous solution of uranyl nitrate hexahydrate (UO₂(NO₃)₂·6H₂O) on gradual addition of small amounts of acetone have been investigated. In a pure aqueous solution, uranyl exists as the UO₂·5H₂O complex. It is shown that addition of acetone to the solution leads to displacement of some water molecules from the first coordination sphere of uranyl and formation of uranyl nitrate dihydrate complexes, UO₂(NO₃)₂·2H₂O. It has been established that the stability of these complexes is determined by the decrease in both the water activity and the degree of hydration of uranyl and nitrate. This is the result of the local increase in the concentration of the molecules of acetone (due to its hydrophobicity) in those regions of the solution in which there are uranyl and nitrate ions. The experimental facts supporting the proposed mechanism are given.     

Poly(o-anisidine) coatings on brass: Synthesis,characterization and corrosion protection

Poly(o-anisidine) (POA) coatings were synthesized on brass by electrochemical polymerization of o-anisidine in aqueous salicylate solution by using cyclic voltammetry. These coatings were characterized by cyclic voltammetry, UV–visible absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The corrosion protection aspects of POA coatings on brass in aqueous 3% NaCl solution were investigated by potentiodynamic polarization technique and electrochemical impedance spectroscopy (EIS). The potentiodynamic polarization measurements show that the POA coating has ability to protect the brass against corrosion. The corrosion potential was about 0.204 V versus SCE more positive for the POA coated brass than that of uncoated brass and reduces the corrosion rate of brass almost by a factor of 800. The corrosion behavior of the POA coatings was also investigated by EIS through immersion tests performed in aqueous 3% NaCl solution. The evolution of the impedance parameters with the immersion time was studied and the results show that the POA acts as a protective coating on brass against corrosion in 3% NaCl solution. The water uptake and delamination area were also determined to further support the corrosion protection performance of the POA coating.     

Effect of Water Vapor Absorption on Measurements of Atmospheric Nitrate Radical by LP-DOAS

利用长程差分吸收光谱技术进行大气NO3自由基测量时,水汽的强烈吸收叠加在测量光谱中,对NO3的精确反演和探测限带来较大的影响. 通过分析水汽吸收的非线性效应,建立了一种去除水汽影响的有效方法. 通过测量日间大气吸收谱,并考虑日间水汽与夜晚水汽变化量,一同参与数据拟合,结果表明该方法可以有效地去除水汽吸收的影响. 把该方法应用于在珠三角外场实验中,获得了好的效果,探测限达到3.6 ppt。     

Fluorescent silver nanoparticles via exploding wire technique

Aqueous solution containing spherical silver nanoparticles of 20–80 nm size have been generated using a newly developed novel electro-exploding wire (EEW) technique where thin silver wires have been exploded in double distilled water. Structural properties of the resulted nanoparticles have been studied by means of X-ray diffractometer (XRD) and transmission electron microscopy (TEM). The absorption spectrum of the aqueous solution of silver nanoparticles showed the appearance of a broad surface plasmon resonance (SPR) peak centered at a wavelength of 390 nm. The theoretically generated SPR peak seems to be in good agreement with the experimental one. Strong green fluorescence emission was observed from the water-suspended silver nanoparticles excited with light of wavelengths 340, 360 and 390 nm. The fluorescence of silver nanoparticles could be due to the excitation of the surface plasmon coherent electronic motion with the small size effect and the surface effect considerations     

Density Functional Theory Study of Infrared and Ultraviolet Spectra of Urea L-Malic Acid

用密度泛函理论研究了新型二阶非线性光学晶体-L苹果酸脲.采用一些密度泛函理论方法计算了分子结构,比较得出PBEPBE/6-31+G(d,p)是计算分子结构的一种最佳的方法,然后给出了其红外和紫外可见光谱,并与实验结果作了比较,还结合分子轨道布局分析了紫外可见光谱. 同时结合极化连续模型利用密度泛函理论方法研究了L苹果酸脲在水中的几何结构及红外和紫外可见光谱,并指出了溶剂化效应对其性质的影响.     

Preparation and colloidal behaviour of surface-modified EuF3

Surface-modified EuF₃ nanoparticles has been produced by mixing of NaF and Eu(NO₃)₃ aqueous solutions in the presence of sodium citrate as stabilizer. Transmission electron microscopy and dynamic light scattering has shown citric ions influence on the particle size and morphology. Modified and unmodified EuF₃ samples were characterized by X-ray diffraction, elemental analysis, IR and luminescence spectroscopy. The results indicate that citrate ions bond chemically with EuF₃ particle, forming a layer onto the surface. The layer stabilizes nanoparticle colloids and prevents their aggregation. In the case of modified EuF₃ colloids, reversible precipitation-peptization processes at varying pH values and Cu²⁺ chemosorption by citric layer are revealed.     

Influence of ultrasound pretreatment on wood physiochemical structure

As an initial step to increase the use of renewable biomass resources, this study was aimed at investigating the effects of ultrasound pretreatment on structural changes of wood. Samples were pretreated by ultrasound with the power of 300 W and frequency of 28 kHz in aqueous soda solution, aqueous acetic acid, or distilled water, then pretreated and control samples were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The results shown that ultrasound pretreatment is indeed effective in modifying the physiochemical structure of eucalyptus wood; the pretreatment decreased the quantity of alkali metals (e.g., potassium, calcium and magnesium) in the resulting material. Compared to the control group, the residual char content of samples pretreated in aqueous soda solution increased by 10.08%–20.12% and the reaction temperature decreased from 361 °C to 341 °C, however, in samples pretreated by ultrasound in acetic solution or distilled water, the residual char content decreased by 12.40%–21.45% and there were no significant differences in reactivity apart from a slightly higher maximum reaction rate. Ultrasound pretreatment increased the samples’ crystallinity up to 35.5% and successfully removed cellulose, hemicellulose, and lignin from the samples; the pretreatment also increased the exposure of the sample to the treatment solutions, broke down sample pits, and generated collapses and microchannels on sample pits, and removed attachments in the samples.     

A Novel “Turn On” Glucose-Based Rhodamine B Fluorescent Chemosensor for Mercury Ions Recognition in Aqueous Solution

A novel “turn-on” fluorescent sensor based on glucose and rhodamine B for detection of mercury ions was designed and synthesized. The fluorescent sensor showed an extreme specificity for mercury ions than for other metal ions in aqueous solution. On adding mercury ions to the solution of glucose-based rhodamine B sensor, the absorption and fluorescence signals enhanced remarkably at 567 and 587 nm, respectively. Titration of sensor with mercury ions showed 1:1 stoichiometric reaction. The cyclic voltammetric measurement of an increasing amount of mercury ions in the solution of glucose-based rhodamine B sensor commendably showed the change in the fluorescence characteristics. Furthermore, the successful detection of trace amount of mercury ions in water indicated that glucose-based rhodamine B sensor can be used for the detection of the limited mercury ions in drinking water.     

Chemical modification of glass surface with a monolayer of nonchromophoric and chromophoric methacrylate terpolymer

The methacrylate terpolymers, a nonchromophoric and chromophoric one, containing 2-hydroxyethyl groups were reacted with 3-isocyanatopropyltriethoxysilane to obtain reactive polymers able to form covalent bonding with -SiOH groups of the glass surface via triethoxysilane group condensation. Chemical modification of the Corning 2949 glass plates treated in this way resulted in increase of wetting angle from 11° to ca. 70-73°. Determination of ellipsometric parameters revealed low value of the substrate refractive index as compared with that of bulk Corning 2949 glass suggesting roughness of the surface. The AFM image of the bare glass surface and that modified with terpolymer monolayer confirmed this phenomenon. Modification of the glass with the terpolymer monolayer made it possible to create the substrate surface well suited for deposition of familiar chromophore film by spin-coating. The chromophore polymer film deposited onto the modified glass surface was found to be resistant to come unstuck in aqueous solution.     

Modified polypropylene fabrics and their metal ion sorption role in aqueous solution

Polypropylene non-woven fabrics were grafted with glycidyl methacrylate by the electron beam irradiation method and the introduced epoxide rings were chemically conversed to hydroxyl and thiol groups. The modified polypropylene fabrics showed sufficient hydrophilicity to adsorb the metal ions from the aqueous solutions. The modified fibers were examined as adsorbents for metal ions dissolved in seawater and its model solutions at various conditions. The amount of ions adsorbed on the fabrics was determined by a sequential plasma spectrometry. The modified polypropylene fabrics adsorbed extremely high amount of Au(III) and Hg(II) ions. The equilibrium adsorption of Au(III) was almost not disturbed, even if Cu(II), Cd(II), Pb(II) and the other ions coexisted in the same aqueous solution. Nowadays, the most widely advantages of this technique are the recovery of metal ions dissolved in water and the treatment of industrial wastewater systems.     

Ultrasonic absorption—a new technique

Ultrasonic absorption spectroscopy is described for investigating the biological and chemical damage caused by gamma irradiation on three solutions, namely erythrocyte solution, sodium salt DNA solution in distilled water and glucose solution in distilled water.