Sonochemistry of organic compounds in homogeneous aqueous oxidising systems

The influence of ultrasound on the degradation of trichloroethylene, o-chlorophenol and 1,3-dichloro-2-propanol in some Fenton type aqueous systems was investigated. Kinetic analysis of the results revealed that the ultrasonic waves do not really enhance the reactivity of the system, but rather add their own degradation mechanism to the chemical degradation. This effect is comparable to the well known sonochemical switching effect. As a consequence, the degradation rate of the combined systems is the sum of the pure sonochemical degradation rate and the silent chemical degradation rate. The only exception to this rule is the degradation of o-chlorophenol in the presence of hydrogen peroxide, in the absence of catalysts. Care had to be taken in order to avoid artifacts that may arise, e.g., when neglecting temperature effects.     

痕量挥发性有机物的高场不对称波形离子迁移谱研究

高场不对称波形离子迁移谱(high-field asymmetric waveform ion mobility spectrometry,FAIMS)技术是一种快速、高灵敏的痕量物质检测技术.利用自制的高场不对称波形离子迁移谱仪分别对丙酮、苯和甲苯样品进行了检测,结果表明三种挥发性物质在谱图中的分离效果优于传统离子迁...     

Electrical conductivity and dielectric properties of sulfamic acid doped polyaniline

The temperature and frequency dependence of dielectric constant (ε′) and dielectric loss (ε″) is studied for different samples of polyaniline (PANI), doped with different concentration of sulfamic acid in the frequency range (10–100 kHz) and temperature range (300–400 K). The dc conductivity has also been measured to see the effect of sulfamic acid and the conduction mechanism has been explained by the propagation of polaron through a conjugated polymer chain due to shifting of double bonds (alternation), which gives rise to electrical conduction.     

Real-time and online screening method for materials emitting volatile organic compounds

In the semiconductor industry, volatile organic compounds (VOCs) in the cleanroom air work as airborne molecular contamination, which reduce the production yield of semiconductor chips by forming nanoparticles and haze on silicon wafers and photomasks under ultraviolet irradiation during photolithography processes. Even though VOCs in outdoor air are removed by gas filters, VOCs can be emitted from many kinds of materials used in cleanrooms, such as organic solvents and construction materials (e.g., adhesives, flame retardants and sealants), threatening the production of semiconductors. Therefore, finding new replacements that emit lower VOCs is now essential in the semiconductor industry. In this study, we developed a real-time and online method to screen materials for developing the replacements by converting VOCs into nanoparticles under soft X-ray irradiation. This screening method was applied to measure VOCs emitted from different kinds of organic solvents and adhesives. Our results showed good repeatability and high sensitivity for VOCs, which come from aromatic compounds, some alcohols and all tested adhesives (Super glue and cleanroom-use adhesives). In addition, the overall trend of measured VOCs from cleanroom-use adhesives was well matched with those measured by a commercial thermal desorption–gas chromatography–mass spectrometry, which is a widely used off-line method for analyzing VOCs. Based on the results, this screening method can help accelerate the developing process for reducing VOCs in cleanrooms.     

Preparation and measurements of electrical and spectroscopic properties of sodium thiosulphate doped polyaniline

Polyaniline has been synthesized and is doped with sodium thiosulphate. The doping of polyaniline (PANI) is done at two different time periods and DC conductivity is measured to see the effect of dopant. It has been observed that the crystallinity of PANI increases through doping which ultimately increases the conductivity. The conductivity result shows that the conduction is taking place through hopping process due to wide range of localized states present near the fermi level. Structural changes due to interaction of dopant species with PANI are studied through FTIR.     

Porous FeVO4 nanorods: synthesis,characterization, and gas-sensing properties toward volatile organic compounds

Herein, we describe a multifunctional anti-cancer prodrug system based on water-dispersible carbon nanotube (CNT); this prodrug system features active targeting, pH-triggered drug release, and photodynamic therapeutic properties. For this prodrug system (with the size of ~100–300 nm), an anti-cancer drug, doxorubicin (DOX), was incorporated onto CNT via a cleavable hydrazone bond; and a targeting ligand (folic acid) was also coupled onto CNT. This prodrug can preferably enter folate receptor (FR)-positive cancer cells and undergo intracellular release of the drug triggered by the reduced pH. The targeted CNT-based prodrug system can cause lower cell viability toward FR-positive cells compared to the non-targeted ones. Moreover, the CNT carrier exhibits photodynamic therapeutic (PDT) action; and the cell viability of FR-positive cancer cells can be further reduced upon light irradiation. The dual effects of pH-triggered drug release and PDT increase the therapeutic efficacy of the DOX–CNT prodrug. This study may offer some useful insights on designing and improving the applicability of CNT for other drug delivery systems.

     

Investigations on the electrical and structural properties of polyaniline doped with camphor sulphonic acid

Polyaniline is chemically synthesised and doped with camphor sulphonic acid. FTIR studies carried out on these samples indicate that the aromatic rings are retained after polymerisation. The percentage of crystallinity for polyaniline doped with camphor sulphonic acid has been estimated from the X-ray diffraction studies and is around 56% with respect to polyaniline emeraldine base. The change in dielectric permittivity with respect to temperature and frequency is explained on the basis of interfacial polarisation. AC conductivity is evaluated from the observed dielectric permittivity. The values of AC and DC conductivity and activation energy are calculated. The activation energy values suggested that the hopping conduction is the prominent conduction mechanism in this system.     

挥发性有机物同分异构体光电离-离子迁移谱检测研究

自行研制的紫外光电离-离子迁移谱装置,对碳链异构、官能团异构和官能团位置异构的11种同分异构体挥发性有机物进行了实验研究,结果表明,这些有机同分异构体能够在离子迁移谱中实现分离。得到了11种挥发性有机物离子的约化迁移率,对实验所研究的同分异构体而言,迁移率大小符合以下规律:直链<分支<环状,一级<二级<三级,对位<间位<邻位,醇类<酮类<芳香类。实验中用指数稀释法对11种样品进行了定量分析,利用该方法得到装置检测限达到ppb～ppm量级。其中对丙醛、叔丁醇、乙苯、乙醚等同分异构体的光电离离子迁移谱研究均为首次报道。     

稀土Eu3+掺杂纳米TiO2-SiO2发光材料的制备和发光性质的研究

采用溶胶-凝胶法制备了稀土Eu3+掺杂于不同比例的纳米TiO2-SiO2复合体系,研究了基质中钛、硅摩尔配比对发光性能的影响.样品的FTIR谱图显示:纳米复合氧化物SiO2-TiO2之间发生了键合作用,形成了Ti-O-Si键;TEM显示样品的颗粒大小约为35 nm,是具有一定的单分散性的球形颗粒;XRD和SAED结果表明,样品退火至700℃后仍为单一的锐钛矿相,这说明微量硅的加入对二氧化钛的锐钛矿相有热稳定的作用.当微量的Si4+进入TiO2的晶格,取代部分Ti4+的位置时,形成了结构等电子陷阱.通过对样品的激发光谱、发射光谱分析,发现这种结构有利于将基质吸收的能量传递到发光中心,使Eu3+的465nm处7F0→5D2激发效率最高,成为最灵敏的激发线.     

Preparation and properties of Er and Yb doped InP-based semiconductor compounds

In this paper we pursue the effect of the erbium and ytterium addition during the liquid phase epitaxial (LPE) growth on physical properties of thin InP layers. Series of InP layer samples were prepared by LPE from the melts containing 0–0.3 wt.% of Er and Yb. The grown layers were examined by the Hall effect andC-V measurements, photoluminescence spectroscopy and Rutherford backscattering spectrometry (RBS). We have found that only Yb impurity was incorporated into the lattice of InP layer. With increasing Yb content in the growth melt the layer’s conductivity smoothly changed from n to p type when Yb admixture exceeded certain limit. On the basis of these results we prepared p-n junctions in the InP layers directly doped by Yb, and tested then byC-V measurements. Presented at the 1st Czech-Chinese Workshop “Advanced Materials for Optoelectronics”, Prague, Czech Republic, June 13–17, 1998. This work has been supported by the Grant Agency of the Czech Republic, project No. 102/99/0341.     

The study of optical,dielectric and optoelectronic properties of dodecylbenzene sulfonic acid doped polyaniline

Soluble polyaniline (PANI) doped with dodecylbenzene sulfonic acid (DBSA) was synthesized by chemical oxidation method and was cast on glass using homemade spray, a simple technology used for coating thin film in order to replace other costly complicated techniques. The PANI–DBSA was characterized by FTIR, XRD and UV–vis techniques. The TGA results illustrated that they are three major stages of weight loss of the PANI–DBSA sample. D.C. and A.C. study was performed by pelletizing the sample. D.C. conductivity obtained at room temperature was 3.753 × 10⁻³ S/cm. The A.C. conductivity and dielectric properties was analyzed in the frequency range 100–1000 kHz which indicates that the value of dielectric constant and loss tangent increases with increase in temperature and decreases with increase in frequency and in addition it supports the hopping mechanism. Current density–voltage (J–V) measurements was used to characterize ITO/PANI–DBSA/Al device. The value of various junction parameters such as ideality factor, barrier height and saturation current density was calculated.     

Electrical properties of Li-based NASICON compounds doped with yttrium oxide

In the present study, the electrical properties of lithium-based Li_1.3Al_0.3???x Y _x Ti_1.7(PO₄)₃ (LAYTP) system is reported. Yttrium is a rare earth element and has been found to be an excellent sintering aid in ceramic electrode materials. Earlier attempts to replace the tetravalent Ti⁴⁺ using trivalent cations like Al³⁺, Y³⁺, In³⁺, and Sc³⁺ in rhombohedral NASICON structure have resulted in enhanced electrical conductivity. The effect of trivalent cation Y³⁺ doping in an optimized system Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) is discussed. The electrical properties of this ceramic compound in temperature range of 303 to 423 K and in the microwave frequency range of 20 MHz to 1 Hz were studied for the LAYTP system using impedance spectroscopy. The role of yttrium to improve the density of the material and thereby the study of the grain and grain boundary is explored.     

An analysis of absorption-desorption of volatile organic compounds by molecularly imprinted polymer films

A theoretical analysis of the experimental data on absorption (desorption) of volatile organic compounds by (from) molecularly imprinted polymer films was performed. The theoretical time dependences of the amount of absorbed analyte in a film were calculated using a system of equations with four kinetic parameters (Γ, K, K _sur , and C _eq ), which were determined by theoretically approximating the experimental data. The special features of the absorption-desorption process in a polymer film were suggested to be described using a parameter called the specificity coefficient. Specificity coefficients were determined for all the polymers and analytes studied. The specificity coefficients obtained from the chromatographing data were compared with the imprinting factors of chromatograms calculated from the experimental retention time values. An empirical linear dependence of specificity coefficients on imprinting factor values was obtained.     

Electric conductivity of siliconorganic polyhomoconjugated polymer films upon adsorption of volatile organic compounds

The electrophysical parameters of polyhomoconjugated organosilicon polymer films are studied, and variation of their conductivity under the action of water, toluene, and ammonia vapors is measured. Films 1–2 μm thick are prepared by the casting method from a solution of poly[2,2-dimethyl-2-sila-1,3-propylene-(4, 4′-biphenylene)]a (polymer I) and poly[2-n -butyl-2-phenyl-2-sila-1,3-propylene-(4, 4′-biphenylene)]a (polymer II). In the course of conductivity measurement, organic volatiles and water are adsorbed due to a stepwise rise in the pressure over the sample from 10⁻³ to 10⁻¹ Torr. The initial values of the resistivity of polymers I and II are estimated as 4 × 10⁹ Θ cm. Exposure of the films to organic volatile vapors and water vapor causes a reversible change in the conductivity of the films. For polymer-I films, the conductivity upon adsorption of ammonia, toluene, and water vapors exceeds the initial value by 150, 10, and 600 times, respectively. The sensitivity of polymer-II films is lower by a factor of 1.5–2.0. The time of conductivity variation as the vapors are injected and evacuated is within 10 and 30 s, respectively. The mechanisms of organic volatile and water adsorption on the surface of polyhomoconjugated organosilicon polymer films are compared with adsorption mechanisms on the surface of π-polyconjugated organic films.     

Synthesis, magnetic and dielectric properties of Er-Ni doped Sr-hexaferrite nanomaterials for applications in High density recording media and microwave devices

A sol-gel combustion method has been successfully employed for the synthesis of Sr-hexaferrite nanomaterials doped with Er³⁺ and Ni²⁺ at strontium and iron sites, respectively. The X-ray diffraction analysis confirmed the single magnetoplumbite phase and the crystallite size was found to be in the range of 14-16 nm, suitable for obtaining signal-to-noise ratio in the high density recording media. The magnetic properties such as saturation magnetization (M_s), remanence (M_r) and coercivity (H_c) were calculated from hysteresis loops. M_s, M_r and H_c are observed to increase with the Er-Ni content. The dielectric constant (ε´) and dielectric loss (tan δ) is found to decrease with the increase in frequency and is explained on the basis of Maxwell-Wagner and Koops theory. The decrease in dielectric constant and dielectric loss but increase in saturation magnetization and remanence with Er-Ni content suggests that the materials are suitable for applications in microwave devices and high density recording media .     

Electrical conductivity of mixed structures based on conjugated organic materials and metals oxides upon adsorption of volatile organic compounds

Physics of the Solid State - This paper reports on the results of investigations of the electrophysical characteristics of films based on conjugated organic molecules of copper phthalocyanine...     

Electrical,thermal and spectroscopic studies of Te doped polyaniline

In the present paper, we have reported the chemical synthesis and characterization of polyaniline doped with tellurium. The aniline was polymerized by chemical oxidation using ammonium persulphate as an oxidant and was doped with different concentrations of tellurium. Doped PANI was characterized by using FTIR, DSC and two-probe conductivity measurement. The dc conductivity has been measured to see the effect of tellurium and its mechanism has been explained by the formation of polarons and bipolarons that move along the polymer chain, and gives rise to the electrical conductivity. The observed increase in conductivity of polyaniline is attributed due to the incorporation of Te into the PANI chain. Glass transition temperature (T_g) and enthalpy (ΔH) have been calculated from DSC measurements. FTIR spectra suggest the structural changes after incorporation of Te in polymeric chain.     

一种新型光学多通池系统应用于烟雾箱内挥发性有机化合物探测

介绍了Chernin型多通池的原理、设计及应用,该系统稳定性好,调节简单,光程在3—330 m的范围内可调.通过对NO₂的痕量探测,验证了该系统的稳定性及可靠性,在37 m的吸收光程内,NO₂的探测极限达19.1 μg/m³.同时,利用该系统对烟雾箱内的邻、间、对-二甲苯,甲苯进行了痕量探测,在36 m的吸收光程内,探测极限分别达到42.6,15.1,9.9和19.7 μg/m³,该系统可以满足烟雾箱内挥发性有机化合物