Luminescence properties of Ammonium Silicon Fluoride films prepared by vapour etching technique

Photoluminescence (PL) properties of Ammonium Silicon Fluoride samples prepared by vapour etching technique are investigated with respect to excitation energy, excitation intensity and temperature. Ageing effect at ambient conditions is also examined by Fourier Transform Infrared Spectroscopy. PL peak maximum blue shifts as the excitation intensity increases and saturates at 2.106 eV. Temperature-dependent variations in PL peak energies and intensities cannot be thoroughly elucidated via Quantum Confinement model alone and require consideration of recombination rates at Si–SiO_x interface. Temperature dependence of integrated PL intensity is treated by a three-component functional form.Infrared absorption bands at 1060 cm^− 1, 1113 cm^− 1 and 1230 cm^− 1 attain saturation with time. Agreement between the saturation time of SiO_x longitudinal optic mode at 1230 cm^− 1 and that deduced from PL measurements in literature is noted. It is shown that PL emissions are intrinsic in nature and have a significant excitonic contribution.     

外界条件对爆轰制备纳米氧化铁的影响研究

爆轰法合成纳米氧化铁,具有工艺设备简单、成本低、操作方便等优点.不同的外界条件对生成产物的形状、性质以及晶粒大小有一定影响.本文基于相同实验材料及实验温度的基础上,使反应物在不同压力环境中爆轰反应,并利用透射电镜以及XRD衍射分析等方式,对两种情况下制得的γ-Fe2O3产物的性质、形貌以及晶粒粒径大小进行对比与分析.结果表明,外界压力变化后,反应生成的纳米氧化铁的表面形貌有所差异,如圆整度降低,分散性提高等.     

Ion adsorption studies of micro and nano acrylic fibers modified by ethanolamine

Micro and nano polyacrylonitrile fibers were modified to polyacrylonitrile‐monoethanolamine (PAN‐MEA) through reaction PAN with ethanolamine. The modified PAN fiber was prepared by conversion nitrile groups into hydroxyle groups using ethanolamine solution with different concentration under refluxing at 91°C. Modified raw acrylic fibers (RAF) with submicrometer diameters ranging from 120 to 300 nm were produced using electrospinning in N,N‐dimethyl formamide (DMF). The PAN‐MEA micro and nano fibers were examined as chelating material in a series of batch adsorption experiments for removal of Cu (II), Pb (II) and Ni (II) ions. The fiber structure has been investigated by different experimental techniques of characterization such as Fourier transform infrared spectroscopy (FT‐IR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Also, the physical and mechanical properties has been investigated in this study. Nano fibers show adsorption metal ions more than the usual fiber because of high ratio of surface to mass.     

Magnetic properties of iron nanoparticles prepared by exploding wire technique

Nanoparticles of iron were prepared in distilled water using very thin iron wires and sheets, by the electro-exploding wire technique. Transmission electron microscopy reveals the size of the nanoparticles to be in the range 10 to 50 nm. However, particles of different sizes can be segregated by using ultrahigh centrifuge. X-ray diffraction studies confirm the presence of the cubic phase of iron. These iron nanoparticles were found to exhibit fluorescence in the visible region in contrast to the normal bulk material. The room temperature hysteresis measurements upto a field of 1.0 tesla were performed on a suspension of iron particles in the solution as well as in the powders obtained by filtration. The hysteresis loops indicate that the particles are superparamagnetic in nature. The saturation magnetizations was approximately 60 emu/gm. As these iron particles are very sensitive to oxygen a coating of non-magnetic iron oxide tends to form around the particles giving it a core-shell structure. The core particle size is estimated theoretically from the magnetization measurements. Suspensions of iron nanoparticles in water have been proposed to be used as an effective decontaminant for ground water.     

Kinetics and thermodynamics of cadmium ion removal by adsorption onto nano zerovalent iron particles

Nano zerovalent iron (nZVI) is an effective adsorbent for removing various organic and inorganic contaminants. In this study, nZVI particles were used to investigate the removal of Cd(2+) in the concentration range of 25-450 mg L(-1). The effect of temperature on kinetics and equilibrium of cadmium sorption on nZVI particles was thoroughly examined. Consistent with an endothermic reaction, an increase in the temperature resulted in increasing cadmium adsorption rate. The adsorption kinetics well fitted using a pseudo second-order kinetic model. The calculated activation energy for adsorption was 54.8 kJ mol(-1), indicating the adsorption process to be chemisorption. The intraparticle diffusion model described that the intraparticle diffusion was not the only rate-limiting step. The adsorption isotherm data could be well described by the Langmuir as well as Temkin equations. The maximum adsorption capacity of nZVI for Cd(2+) was found to be 769.2 mg g(-1) at 297 K. Thermodynamic parameters (i.e., change in the free energy (ΔG(o)), the enthalpy (ΔH(o)), and the entropy (ΔS(o))) were also evaluated. The overall adsorption process was endothermic and spontaneous in nature. EDX analysis indicated the presence of cadmium ions on the nZVI surface. These results suggest that nZVI could be employed as an efficient adsorbent for the removal of cadmium from contaminated water sources.     

金属化合物对煤岩显微组分所制活性炭吸附性能的影响

研究了Ni2O3,Fe2O3等金属化合物对太西无烟煤和大同烟煤分离富集镜质组、丝质组所制活性炭吸附性能的影响。研究结果表明：金属化合物能显著加快太西无烟煤显微组份的活化反应速度，部分金属化合物可以提高太西无烟煤显微组分所制活性炭的吸附性能，但对大同烟煤显微组分所制活性炭的性能影响不大，其因在于大同烟煤的反应性高于太西无烟煤。加入金属化合物提高无烟煤显微组份活化反应速度的主要原由是金属化合物对碳与水蒸气活化反应有一定的催化作用，使活化活性点增加，进而提高了活化反应效率；而能否提高活性炭的吸附性能则与金属化合物和煤岩显微组分的性质有关。     

Microcolumn studies of dye adsorption onto manganese oxides modified diatomite

The method described here cannot fully replace the analysis of large columns by small test columns (microcolumns). The procedure, however, is suitable for speeding up the determination of adsorption parameters of dye onto the adsorbent and for speeding up the initial screening of a large adsorbent collection that can be tedious if a several adsorbents and adsorption conditions must be tested. The performance of methylene blue (MB), a basic dye, Cibacron reactive black (RB) and Cibacron reactive yellow (RY) was predicted in this way and the influence of initial dye concentration and other adsorption conditions on the adsorption behaviour were demonstrated. On the basis of the experimental results, it can be concluded that the adsorption of RY onto manganese oxides modified diatomite (MOMD) exhibited a characteristic "S" shape and can be simulated effectively by the Thomas model. It is shown that the adsorption capacity increased as the initial dye concentration increased. The increase in the dye uptake capacity with the increase of the adsorbent mass in the column was due to the increase in the surface area of adsorbent, which provided more binding sites for the adsorption. It is shown that the use of high flow rates reduced the time that RY in the solution is in contact with the MOMD, thus allowing less time for adsorption to occur, leading to an early breakthrough of RY. A rapid decrease in the column adsorption capacity with an increase in particle size with an average 56% reduction in capacity resulting from an increase in the particle size from 106-250 microm to 250-500 microm. The experimental data correlated well with calculated data using the Thomas equation and the bed depth-service time (BDST) equation. Therefore, it might be concluded that the Thomas equation and the BDST equations can produce accurate predication for variation of dye concentration, mass of the adsorbent, flow rate and particle size. In general, the values of adsorption isotherm capacity obtained in a batch system show the maximum values and are considerably higher than those obtained in a fixed-bed.     

In situ comparative studies of self-assembly adsorption of bovine serum albumin on nano films by atomic force microscopy

The self-assembly adsorption of function protein on crystal surfaces, as a common phenomenon, broadly takes place in many applications of biosensors, biocapsules and bioMEMS/bioNEMS. To systematically investigate the different adsorption characteristic of the same function protein on two different crystal surfaces under the identical environment, a hybrid surface composing silica and discontinuous Gold Nano Film (GNF) was fabricated by Physical Vapor Deposition (PVD) and ultrasonic cleaning method, where the dynamic process of the self-assembly adsorption of Bovine Serum Albumin (BSA) was in situ observed by Atomic Force Microscope (AFM). The variations on the junction area of the two different surfaces were studied in the aqueous solution before and after injecting BSA with 0.05 mg/ml concentration. It was found that silica, compared with same hydrophilic GNF, took on a fairly weak adsorption force. The results indicated that the adsorption strength of BSA on the hydrophilic crystal surface was determined not only by hydrophilic property, but also other interaction forces, like Van der Waals and so on. Moreover, observed under the contact mode of AFM, BSA adsorbed on GNF had great tendency to forming a ridge-like topography. These results may be helpful in the application of immunosensors and other areas.     

Synthesis of nano particle of inorganic oxides by polymer matrix

Ultrafine (⩽ 150 nm) powders of spinels [MFe₂O₄ where M = Ni(II), Co(II) and Zn(II)]; rare-earth orthoferrites [RFeO₃ where R = Sm, Nd and Gd], and rare-earth garnets [R₃Fe₃O₁₂ where R = Sm, Nd and Gd] with good purity and chemical homogeneity were prepared through two new versatile chemical routes. The first route involved the coprecipitation of the desired metal nitrates from their aqueous solution, in presence of a water soluble polymer-polyvinyl alcohol (PVA), by triethyl ammonium carbonate solution. The other process involved complete evaporation of a mixture of optimum amounts of PVA and the desired aqueous metal nitrate solutions, with and without the addition of optimum amounts of urea when the mixture was evaporated to a pasty mass. In addition, detailed study on the reported potassium ferricyanide route was also carried out for the production of the rare-earth orthoferrite powders. The various precursor as well as the heat-treated mixed-oxide powders, prepared through each of the routes, were compared by the physical characterization studies involving thermal gravimetry and differential scanning calorimetry, infrared spectroscopy, X-ray powder diffraction, transmission electron microscopy, and room temperature magnetic measurements.     

Some properties of thin layers of silica containing carbon and iron oxides prepared by the sol-gel method

Thin layers of silica containing carbon and iron oxides have been prepared by the sol-gel method. The samples were investigated using Auger electron spectroscopy, energy loss, microhardness and Mössbauer effect measurements. It is shown that carbon is located in the pores of the silica network. The electrical conductivity depends on the temperature of heat treatment in the vacuum. The maximum value of conductivity was observed for an annealing temperature about 600 to 800° C. All samples exhibited low activation energy 0.12 eV. It is suggested that the mechanism of conductivity can be interpreted as a tunnelling process of electrons between carbon granules.     

Surface-enhanced Raman spectroscopy studies of surfactant adsorption to a hydrophobic interface

Surface-enhanced Raman spectroscopy is used to investigate the kinetics of adsorption of the cationic surfactant cetylpyridinium chloride (CPC) to hydrophobic surfaces from water. A hydrophobic surface, with stable and reproducible SERS activity, is produced by binding gold colloids to an amine-terminated glass slide and then modifying this surface with octadecyltrimethoxysilane. In situ SERS-detected adsorption of CPC from aqueous solution is found to follow a Frumkin isotherm. Interactions between the charged head groups could be detected in frequency shifts in the symmetric ring breathing mode, consistent with an interfacial surfactant environment similar to a CPC micelle. Rates of surfactant adsorption were determined by time-resolved SERS measurements and were found to be much slower than the diffusion-controlled limit, indicating a significant kinetic barrier to adsorption. Desorption kinetics were heterogeneous, consistent with the spectroscopic results. Alkylsilane-modified gold colloids were shown to be useful substrates for investigating amphiphile adsorption from aqueous solutions to hydrophobic surfaces, where the adsorption kinetics could also be used to determine analyte concentrations in solution.     

Strain induced anomalous red shift in mesoscopic iron oxide prepared by a novel technique

Nano magnetic oxides are promising candidates for high density magnetic storage and other applications. Nonspherical mesoscopic iron oxide particles are also candidate materials for studying the shape, size and strain induced modifications of various physical properties viz. optical, magnetic and structural. Spherical and nonspherical iron oxides having an aspect ratio, ∼2, are synthesized by employing starch and ethylene glycol and starch and water, respectively by a novel technique. Their optical, structural, thermal and magnetic properties are evaluated. A red shift of 0·24 eV is observed in the case of nonspherical particles when compared to spherical ones. The red shift is attributed to strain induced changes in internal pressure inside the elongated iron oxide particles. Pressure induced effects are due to the increased overlap of wave functions. Magnetic measurements reveal that particles are superparamagnetic. The marked increase in coercivity in the case of elongated particles is a clear evidence for shape induced anisotropy. The decreased specific saturation magnetization of the samples is explained on the basis of weight percentage of starch, a nonmagnetic component and is verified by TGA and FTIR studies. This technique can be modified for tailoring the aspect ratio and these particles are promising candidates for drug delivery and contrast enhancement agents in magnetic resonance imaging.     

静电自组装法制备的纳米多层膜的吸波性能

配制了钡铁氧体溶胶和PSS（聚苯乙烯磺酸钠）溶胶,并利用静电自组装的方法在硅片上组装了纳米多层膜。利用紫外-可见分光光度计测出了单层最佳组装时问及每个双层的层厚。用SEM和XPS考察了纳米多层膜的表面形貌和铁元素的价态。对纳米多层膜进行吸波测试,结果显示：总层数为45个双层、总厚度为300nm左右的纳米多层膜有显著的吸波效应,在频率为8～18GHz范围内,最大吸波率达到16．85dB。基于量子理论探讨了纳米多层膜的吸波机理。     

Effects of soil properties on surfactant adsorption

Abstract

The effects of surface area, soil organic matter (SOM) content, and cation exchange capacity (CEC) of natural soils and clays on the adsorption capacity of cationic, anionic, and nonionic surfactants in water‐solid systems were investigated based on the adsorption isotherm analysis. The sorption capacity for a cationic surfactant was proportional to the CEC of the solids. For both anionic and nonionic surfactants, the sorption capacity was related to the soil mineral fraction. However, other soil properties probably affect the practical sorption. The investigated soil properties were treated case by case.     

Isotherm, thermodynamic, kinetics and adsorption mechanism studies of methyl orange by surfactant modified silkworm exuviae

This paper reports on the development of organo-modified silkworm exuviae (MSE) adsorbent prepared by using hexadecyltrimethylammonium bromide (HDTMAB) for removing methyl orange (MO), a model anionic dye, from aqueous solution. The natural and modified samples were characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and Fourier transform infrared spectroscopy (FT-IR). Batch adsorption experiments were carried out to remove MO from its aqueous solutions using SE and MSE. It was observed that the adsorption capacity of MSE is 5-6 times of SE. The different parameters effecting on the adsorption capacity such as pH of the solution, initial dye concentration, temperature and contact time have been investigated. Analysis of adsorption results obtained at different temperatures showed that the adsorption pattern on the MSE can be described perfectly with Langmuir isotherm model compared with Freundlich and Dubinin-Radushkevich (D-R) isotherm models, and the characteristic parameters for each adsorption isotherm were also determined. The adsorption process has been found exothermic in nature and thermodynamic parameters have been calculated. The adsorption kinetic followed the pseudo-second order kinetic model. The results of FT-IR, EDS and desorption studies all suggest that methyl orange adsorption onto the MSE should be mainly controlled by the hydrophobic interaction mechanism, along with a considerable contribution of the anionic exchange mechanism. The results indicate that HDTMAB-modified silkworm exuviae could be employed as low-cost material for the removal of methyl orange anionic dye from wastewater.     

Characteristics of thin nitrided oxides prepared by an in-situ process

In this paper a new method of depositing silicon nitrided oxide by an in-situ process is introduced. Thin nitrided-oxide (NO) films were deposited on silicon by rapid thermal oxidation and rapid thermal chemical vapour deposition (RTCVD). Thin oxide films, 10.0 nm, were rapidly thermally grown in a dry oxygen ambient at 1000 °C and the silicon-nitride films were deposited on the oxide at 700–900 °C using an NH₃ and SiH₄ gaseous mixture. The effect of the NH₃/SiH₄ input ratio and the deposition temperature on the deposition rate and the electrical properties was studied. The experimental results show that the deposition rate increased with increasing deposition temperature and decreasing NH₃/SiH₄ input ratio. From the data for the Fourier-transform infrared spectroscopy (FTIR) and the C-V curves of the NO films, it was observed that the flat-band voltage is directly related to the N-H-bond peak intensity. The flat-band voltage shifts to the positive with increasing deposition temperature and to the negative with increasing NH₃/SiH₄ input ratio, and the breakdown field of NO films is higher than that of the RTP oxidation (RTO) films.     

Mechanism study of nitrate reduction by nano zero valent iron

This study investigates the fate of nitrogen species during nitrate reduction by nano-scale zero valent iron (NZVI) and related reaction mechanisms. The NZVI used for the experiments was prepared by chemical reduction without a stabilizing agent. NZVI has great ability to reduce nitrate. However, the question of what end-product results from nitrate reduction by NZVI has sparked controversy. Establishing nitrogen mass balance by quantitative analysis of aqueous phase and gas-phase nitrogen species, this study clearly determines that nitrate was converted to ammonium ion followed by ammonia stripping under a strong alkaline condition, which leads to a decrease in the total aqueous nitrogen amount. Moreover, some of the major reactions, which consisted of nitrate reduction, ammonia production, and ammonia stripping were modelled by pseudo first-order kinetics. According to the model estimation results, additional reaction mechanisms would exist in an early stage of reaction. This might be due to the adsorption and desorption reaction which could be explained by the core-shell structure model.     

Arsenic removal by adsorption on iron(III) phosphate

Under natural conditions, arsenic is often associated with iron oxides and iron(III) oxidative capacity towards As(III) is well known. In this study, As(III) and As(V) removal was performed using synthesised iron(III) phosphate, either amorphous or crystalline. This solid can combine (i) As(III) oxidation by iron(III) and (ii) phosphate substitution by As(V) due to their similar properties. Results showed that adsorption capacities were higher towards As(III), leading to Fe2+ and HAsO4(2-) leaching. Solid dissolution and phosphate/arsenate exchange led to the presence of Fe3+ and PO4(3-) in solution, therefore various precipitates involving As(V) can be produced: with Fe2+ as Fe3(AsO4)2.8H2O(s) and with Fe3+ as FeAsO4.2H2O(s). Such formations have been assessed by thermodynamic calculations. This sorbent can be a potential candidate for industrial waste treatment, although the high release of phosphate and iron will exclude its application in drinking water plants.