Arsenite oxidation and arsenate determination by the molybdene blue method

Based on the similarity in properties of arsenate and phosphate, the colorimetric method using the molybdene blue complex was tested in order to determine low As(V) concentration in waters. The influence of complex formation time, daylight, temperature and competitive anions (silicate and sulphate) upon complex formation was determined. Optimal complex formation was reached in 1 h at 20±1 °C and was slightly favoured when developed in daylight. The formation rate declined with decreasing reaction temperature and no influence of any of the competitive anions tested (at concentrations usually found in natural waters of granitic areas) was noted. The detection limit of this method was 20 μg As(V) l⁻¹. This simple, fast and sensitive arsenic determination method is suitable for field analysis, especially for waters containing low levels of phosphate and organic matter. Through arsenate determination, this colorimetric method allowed the arsenite oxidation efficiency of five common industrial oxidants to be compared. H₂O₂ and MnO_2(s) were not considered as effective oxidants as a high excess was necessary to ensure As(III) oxidation. NaOCl and KMnO₄ were promising oxidants as they allowed complete arsenite oxidation with a small excess for NaOCl or even less than the electron stoichiometric ratio in the case of KMnO₄. FeCl₃ was the most effective oxidant among the reagents tested here.     

The effect of nanosized titania-silica film composition on the photostability of adsorbed methylene blue dye

The effect of nanosized porous films (average density 10 g/m²) of TiO₂. TiO₂/SiO₂, and SiO₂ on the photostability of adsorbed methylene blue (MB) dye during UV irradiation in air was investigated by optical spectroscopy and laser-induced mass spectrometry. The effectiveness of the photodecomposition of MB decreases in the order TiO₂ > TiO₂/SiO₂ > SiO₂ with rate constants 1E-2, 0.6E-2, and 0.3E-2 min⁻¹ respectively. A mechanism including the participation of both excited states of the dye molecules and photoexcited titanium dioxide is proposed for the photodecolorization of MB adsorbed on the surface of the investigated films. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 4, pp. 220–225, July–August, 2007.     

阿利新蓝的合成

阿利新蓝 (ＡｌｃｉａｎＢｌｕｅ)是一种从植物中提取出的天然物。于 1 944年由Ｈａｄｄｏｃｋ和Ｗｏｏｄ在实验室通过多次实验后所发现。它的水溶液呈天蓝色 ,着色性好而且吸光系数很大。又因它较好的水溶性。所以可以作为高效的生物染色剂[1,2 ] ,用于粘蛋白染色、细菌染色及聚酯、纤维素等人造和天然纤维的染料[3 ] 。基于它的重大应用前景和较高的商业价值 ,探索出一条合理的工业化合成路线就非常重要了。有关阿利新蓝的应用虽然有很多 ,但始终未见合成阿利新蓝的文献报道。在设计它的有机合成时必然涉及酞菁铜 (ＰｃＣｕ)的氯甲基化反…     

等色染料离子对萃取光度法研究：Ⅰ.溴酚蓝·亚甲蓝体系

研究了溴酚蓝（ＢＰＢ）·亚甲蓝（ＭＢ）等色染料离子对萃取光度测定银、汞和铜的方法。首先将被测金属离子形成［Ｍｅ（ｐｈｅｎ）３］ＢＰＢ的二氯乙烷萃取液，用ＫＣＮ解析并反萃入水相，而后加入和溴酚蓝等色的亚甲蓝溶液继续萃取。由于等色染料离子对和Ｍｅ（ＣＮ）ｎＢＰＢ三元络合物同时进入二氯乙烷中而提高了灵敏度、测定Ａｇ、Ｈｇ和Ｃｕ的摩尔吸光系数均在１０５Ｌ·ｍｏｌ（－１）·ｃｍ（－１）以上。     

镓-铬蓝黑R络合吸附波的研究及应用

在0.012mol/L HAc-0.10mol/L NaAc缓冲溶液中pH5.60,铬蓝黑R于-0.34V(vs.SCE)处有一极谱波P_1,加入Ga(Ⅲ),在-0.55V(vs.SCE)处产生一灵敏的极谱波P_2。i_p_2与Ga(Ⅲ)浓度在0.20～15.0μg/25ml范围内呈线性关系。试验表明,该极谱波属络合吸附波。本法用于测定铝箔、铅锌矿中微量镓,结果满意。     

丝网印刷普鲁士蓝修饰电极催化还原测定过氧化氢

制备了普鲁士蓝修饰的丝网印刷过氧化氢传感器,研究了过氧化氢在该修饰电极上的电催化还原特性,考察了有关修饰膜制备和试验条件对传感器性能的影响。结果表明,pH4.0的0.2mol·L-1KH2PO4 K2HPO4缓冲溶液(PBS)中,修饰电极对过氧化氢显示出快速的电化学响应,较高的稳定性、重现性和催化活性,测定的线性范围为1.0×10-5～1.0×10-3mol·L-1,相关系数为0.999,检出限为6.0×10-6mol·L-1(3σ)。电极制作方法简便,可用于实际样品的测定。     

On the mechanism of electroluminescence emission by porous silicon layers

The analytical treatment of a model considering the electrooxidation of p-porous silicon layers under galvanostatic conditions is able to give account of experimental facts such as the shape and location of the electroluminescence peak as well as of the spectral shift of the electroluminescence peak produced by oxidation. The proposed model considers electroluminescence to be the result of electron injection into the conduction band by an adsorbed intermediate produced by electrooxidation of the surface coverage with hydrogen or siloxene of the silicon nanocrystallites. The access of holes to the surface is made possible by low accumulation layer conditions and is the rate determining step in the electroluminescence mechanism. In this way it is possible to give a satisfactory explanation to the shift towards the blue experimented by the electroluminiscence emission maximum as a consequence of electrooxidation.     

Spectrophotometric and titrimetric determination of gallium in minerals and ores using semimethylthymol blue

The composition, overall stability constant and molar absorptivity of the chelate of gallium(III) ion with semimethylthymol blue, SMTB, were determined spectrophotometrically in acetate buffer (pH 4.5–5). A violet Ga(SMTB) chelate was formed with logarithmic overall stability constant of 18.0±0.1 (I=0.1) and molar absorptivity of 4.25×10⁴l mol^–1cm^–1 (_max 580 nm). SMTB is proposed as a new reagent for the spectrophotometric determination of micro-molar amounts of gallium(III). The colour development depends on time, temperature, pH and buffer species. The interference of different cations, anions and organic acids on gallium(III) determination was also investigated. Beer's law was obeyed for 3.5–31.3 gGa(III)/25ml (0.14–1.25 g ml^–1). SMTB was used for the spectrophotometric determination of gallium in different grade minerals and ores and the results were of acceptable error and relative standard deviation. Comparison between the two suggested methods and atomic absorption spectrometry for Ga(III) determination was carried out.     

The Photopolymerization Kinetics of Acryl amide Sensitized with Toluidine Blue-Alcoholamine Induced by He-Ne Laser

Toluidine blue(TB) is a good sensitizer for the polymerization of acrylnmide(AM) induced by He-Ne laser. With TB as a sensitizer and various alcoholamine as donors, the photoredox of TB and the polymerization kinetics of AM induced by He-Ne laser were investigated. It was found that either for the photoredox of TB or for the polymerization of AM, the activity of alcoholamine increases in the order of EOA相似文献   

Photolithographic Patterning and Doping of Silica Xerogel Films

This study shows that conventional photolithography can be applied for patterning native or organic dye-doped silica films (0.5 m thick) obtained via a base-catalyzed sol-gel process. Photoresist was spin-coated onto high optical quality xerogel films, soft-baked, exposed to UV irradiation through a photomask, and developed with a commercial photoresist developing solution. Etching away of the photoresist-unprotected areas of the silica films was carried out with a dilute HF solution, while the remaining unexposed photoresist was removed with acetone. Interdigitated array patterns with features as small as 0.5 mm show a smooth surface and extremely sharp interfaces. Densification of the films at 550°C for 2 h decreases the film thickness by 11%, increases the refractive index from 1.420 to 1.456, and allows for well-defined patterning down to length scales of 10 m. Since the densification conditions are incompatible with organic dopants, it is demonstrated that sol-gel films can be doped after pattering (post-doping) by adsorption of cationic dyes from solution. Scanning electron microscopy reveals that the microstructure of patterned sol-gel films is similar to that of bulk monoliths, indicating that the photolithographic procedure is not harmful to the film quality. All patterned films demonstrate highly regular light diffraction patterns.