Influence of pH value on the quality of sol-gel derived ZnO films

In sol-gel derived ZnO films the pH value of the sol plays an important role in controlling their properties. In this study, the influence of adding monoethanolamine to zinc acetate solution in methanol on structural, surface morphology and optical properties has been investigated. Addition of monoethanolamine to zinc acetate solution transforms the nature of the sol from acidic to alkaline by changing the pH value from 6.4 to 10.6. The investigations indicate that high quality ZnO films are obtained by using sol having monoethanolamine to zinc acetate ratio of 1:1 and pH value of 10.6.     

二氧四胺大环配合物光谱特性与其催化活性关系的研究

测量并研究了二氧四胺大环配体 1,4,7,10 四氮杂环十三烷 11,13 二酮及其Cu(Ⅱ )、Co(Ⅱ )、Ni(Ⅱ )配合物在不同 pH值下的常规荧光谱和激光诱导荧光谱 ,发现配合物的荧光量子产率满足 ΦCuL5<ΦCoL5<ΦNiL5的关系 ,并对其作了解释。与此同时 ,分析了其作为模拟超氧歧化酶的催化活性和荧光光谱特性的关系 ,由三种配合物的荧光量子产率 ,推测出其催化活性的关系可能是CuL5>CoL5>NiL5。     

VO (Ⅱ)-天冬氨酸-π受体三元混配络合物的结构及其ESR波谱研究

测定了VOSO₄与天冬氨酸(asp)和邻菲罗啉(phen)及联吡啶(bipy)三元体系在不同酸度(pH=1-14)的乙二醇-水(1:1)溶液中低温ESR波谱,发现不同pH下生成不同组成和结构的络合物,利用Johnson加合规则并配合IR推测了它们的可能结构,利用电子光谱数据,计算了络合物晶体场参数。     

Improved techniques for in-situ monitoring and control of pH in the cane sugar manufacturing process

A pH sensor has been improved by using a pair of glass electrodes, appropriately fitted in a suitable assembly fabricated from a polymer material. An interface has been designed and developed for processing the signal from the pH sensor. The improved pH sensor and the interface forms the improved pH sensing system. The performance of the system is good and is a cost effective solution over pH measurement errors and problems. Details of the pH sensor, interface and the results of the field trials are presented in this paper.     

Experimental Studies on the Response of the Fiber Optic Evanescent Field Absorption Sensor

In the present study the response of the fiber optic evanescent field absorption sensor has been analyzed experimentally. The dependence of evanescent absorbance on sample (dye) concentration has been found to be nonlinear, in contradiction to theoretical predictions. The amount of nonlinearity as well as evanescent absorbance has been found to depend on the pH of the sample. As the pH decreases, the amount of nonlinearity and evanescent absorbance decrease. It has been shown that the nonlinearity and high evanescent absorbance at high pH value occur because of the adsorption of the positively charged dye molecules on the surface of the silica core of the plastic-clad silica (PCS) fiber, which is generally used for the sensor. A linear response has been obtained at pH close to 2.0, at which the presence of a tremendous amount of H ions in the sample restricts the adsorption of the dye molecules. The following empirical relation has been found to fit the experimental data: gamma 1.1C 1.6(pH)32C 1 3, where gamma is the evanescent absorption coefficient and C is the concentration of the dye. The first term is due to the simple Beer's law while the second term is the contribution of the pH dependent dye adsorption. In addition, we have found that the increase in core diameter increases the contribution of adsorption.     

Fabrication of bovine serum albumin nanotubes through template-assisted layer by layer assembly

One-dimensional protein nanostructures have many potential applications in the biomedical field. In this article, protein nanotubes have been fabricated via sequential filtration of bovine serum albumin (BSA) solution at pH 3.8 and 7.0 through the nanochannels of anodic aluminum oxide templates. The morphology of the nanostructures has been examined using scanning electron microscopy and transmission electron microscopy. Circular dichroism and UV/Vis spectroscopy have been used to select experimental conditions such as the pH values and the etching solution to release the fabricated protein nanotubes to minimize potential damage to the bioactivity of BSA. These results indicate that much more study needs to be done to strengthen the mechanical stability of the protein nanotubes and to better control their morphology.     

水杨酸与人血清白蛋白相互作用的荧光光谱研究

在ｐＨ９．５０含０．０１ｍｏｌ／ＬＫＣｌ的硼砂缓冲溶液中,人血清白蛋白（ＨＳＡ）与水杨酸发生相互作用,而导致两者的荧光谱发生变化。采用不同的方法测得这一反应的解离常数。     

A study of the adsorption of the amphiphilic penicillins cloxacillin and dicloxacillin onto human serum albumin using surface tension isotherms

The interaction of human serum albumin (HSA) with two structurally similar anionic amphiphilic penicillins, cloxacillin and dicloxacillin, at 25 °C has been examined by surface tension measurements under conditions at which the HSA molecule was positively (pH 4.5) or negatively charged (pH 7.4). Measurements were at fixed HSA concentrations (0.0125 and 0.125% w/v) and at drug concentrations over a range including, where possible, the critical micelle concentration (cmc). Interaction between anionic drugs and positively charged HSA at pH 7.4 resulted in an increase of the cmc of each drug as a consequence of its removal from solution by adsorption. Limited data for cloxacillin at pH 4.5 indicated an apparent decrease of the cmc in the presence of HSA suggesting a facilitation of the aggregation by association with the protein. Changes in the surface tension-log (drug concentration) plots in the presence of HSA have been discussed in terms of the adsorption of drug at the air-solution and protein-solution interfaces. Standard free energy changes associated with the micellization of both drugs and their adsorption at the air-solution interface have been calculated and compared.     

固体废弃物的酸碱度与浸提剂pH值的相关性研究

本文对固体废弃物的酸碱度与浸提剂pH值的相关性进行了初步的研究。研究结果表明：不同酸碱度的固体废弃物在不同pH值的浸提剂浸提下，金属元素的溶出量大为不同。酸性固体废弃物在pH值较低（pH=2-4)的浸提剂浸提时，金属元素的溶出量较大，在pH=4-8时，其重金属元素的溶出量趋于恒值，中性固体废弃物浸提剂的pH值对其金属元素的溶出量变化不大。碱性固体废弃物不受浸提剂pH值的影响，金属元素几乎没有溶出。另外，固体废弃物中，金属元素以不同化合物形态的存在也直接影响到浸提率。提出了固体废弃物的任意堆放和填埋，会在酸雨的冲淋浸泡下，对环境造成极大的危害，并根据当地降水的pH值制定出相应的地方监测标准。     

Charged Porphyrin – dopa Melanin Interaction at Varied pH: Fluorescence Lifetime and Photothermal Studies

The influence of pH on the spectral forms of negatively and positively charged porphyrin dyes: tetrakis(4-sulfonatophenyl)porphyrin (TPPS₄) and tetra(4-N, N, N, N-trimethylanilinium) porphyrin (TAP) in the presence of dopa melanin is investigated. The interaction between dyes and dopa melanin is shown to be dependent on the kind of dye spectral forms and on environmental pH. The creation of different forms, deactivation of their electronic excited states, and their interaction with dopa melanin have been monitored by absorption, fluorescence, and photoacoustic spectroscopy in the pH range of 2–9. This article demonstrates that the TAP–dopa melanin complex is destroyed at the lowest pH because of competition between positively charged peripheral groups of TAP and protons, which interact with negative centers of dopa melanin. Otherwise, dopa melanin affects photothermal and fluorescence properties of monomeric dications (TAP and TPPS₄) rather weakly. It has also been suggested that the aggregated dicationic of TPPS₄ can serve as an acceptor in the energy transfer from dopa melanin. Presented results seem to be applicable to a photodynamic therapy of cancer.     

Optical and structural properties of PbI<Subscript>2</Subscript> thin film produced via chemical dipping method

PbI₂ thin films were deposited on glass substrates via chemical bath deposition. The characteristics of PbI₂ thin films were examined through their structural and optical properties. X-ray diffraction spectra showed the presence of rhombohedral structure and atom planes were subject to change with the pH of the bath. Scanning electron microscope indicated uniform distribution of grains. Optical properties were examined via UV–VIS; optical spectrum of the thin films was measured at the range of 200–1100 nm wavelength. Optimum pH levels for producing thin films were found to be pH 4–5. It has been observed that transmission and optical band gap (E _g) increased with the pH of the bath, which varied between 66–95 and 2.24–2.50 %, respectively; on the other hand film thickness of PbI₂ thin films was decreased with the pH of the bath. Energy-dispersive X-ray spectroscopy analysis were in accordance with theoretical value of PbI₂ at pH = 4 and 5. Refractive index was negatively correlated with pH of the chemical bath; it has been calculated as 1.97, 1.40, 1.29 and 1.24 for the films produced at pH 2, 3, 4 and 5. The results of the study were compared with similar studies in the literature.     

Rundtischgespräche

Separation of cesium and cobalt from simulated medium active waste (MAW) by coprecipitation with hexacyanocobaltate (III) salts has been discussed. It has been found that coprecipitation of cesium or cobalt from MAW can be carried out successfully by using only potassium hexacyanocobaltate (III). The retention of cesium and cobalt has been studied over a wide range of pH, from zero to 12. A comparison of cobalti-, ferro- and ferricyanide complexes towards the retention of cesium at different pH values has also been made. The retention capacity of cobalticyanide precipitates for cesium and cobalt at pH 1.6 has been reported.     

VO2+-谷氨酸-π受体三元混配配合物的结构与波谱研究

测定了VOSO₄-谷氨酸(Glu)-邻菲啉(phen)及VOSO₄-谷氨酸-联吡啶(bipy)三元混配配合物在不同酸度下(pH=1~14)的乙二醇/水(1:1)溶液中的低温(173K)ESR谱.发现随pH的变化形成各种结构和组成的配合物,利用Johnson的加合规则、结合配合物的IR光谱推测了各种配合物的可能结构;利用电子光谱数据计算了配合物的晶体场多数;讨论了谷氨酸、π受体配合物的成配规律。     

Polyelectrolyte Complexes of Homo- and Copolymers of Vinyl Ether of Monoethanolamine with Poly(Acrylic Acid) in Aqueous Solutions

The complexation of homo- and copolymers of vinyl ether of monoethanolamine with poly(acrylic acid) has been studied in aqueous solutions. The effect of pH on the complexation has been shown. In acidic media (pH 2.4), the polyelectrolyte complex is enriched by anionic polymer units. In weakly acidic media (pH 4–6), the formation of stoichiometric polyelectrolyte complex is observed. In higher pH media (pH 6–8), the polycomplex contains an excessive amount of cationic polymer. The stability of the polyelectrolyte complexes is affected by the addition of inorganic salts and dimethylformamide.     

吡啶酮系偶氮染料腙式—偶氮式互变异构的研究——Ⅰ核磁共振波谱在构型测定中的应用

测定了七个吡啶酮系偶氮染料的~(13)C NMR波谱.借助于选择性非灵敏核极化转移增强法(SELINEPT)完成了谱带归属。从pH值对~(13)C化学位移的影响,~1H NMR谱和紫外-可见吸收光谱,指出这类染料的酸-碱变色现象是由腙式和偶氮式构型互变平衡的移动引起的.介质酸性或碱性的增强分别有利于染料以腙式或偶氮式的构型存在.不同结构的吡啶酮染料,其变色pH值是相当不同的.     

CdSe/ZnS Fluorescent Nanoparticles as Nanoprobes of Local pH in Diagnostics of Oncology

We discuss the fluorescence spectra from a set of points in histological sections of colon tissue with different levels of pathology that were stained with hydrophilic semiconductor CdSe/ZnS nanoparticles that were modified by a unique method at the phase interface. The shifts in the fluorescence spectra that were recorded for stained cells at different pathologies are described using the electrochromism of the nanoparticles. Aqueous solutions of the CdSe/ZnS nanoparticles with different pH values are used as systems that model the acidity of a biological medium. It has been shown that the shifts of the fluorescence bands of the CdSe/ZnS nanoparticles are caused by a change in the local electrical field that is induced by solvated ions near their surface at different pH values of the solutions. The application of the CdSe/ZnS nanoparticles as nanoprobes for the local pH in biological tissue is discussed in the context of this model.     

Synthesis and study of polyaniline nanocomposites with metal oxides

A method for synthesizing a nanosized highly conductive polyaniline composite with tin and titanium oxides has been proposed. The synthesis of dioxides and polycondensation of aniline have been performed in one reactor, which makes it possible to control the sizes of SnO₂ and TiO₂ nanoparticles from 10 to 300 nm and change their content in the nanocomposite by varying the conditions of synthesis (temperature, pH, and reagent concentration). The morphology, composition, IR spectra, conductivity, and thermal stability of the synthesized samples have been studied.     

Photophysical characterization of pyrazino[2,3-c]-1,2,6-thiadiazine 2,2-dioxides in DMSO and acetonitrile solutions

Photophysical characterization of some pyrazino[2,3-c][1,2,6]thiadiazine 2,2-dioxides derivatives in DMSO and acetonitrile has been carried out. Acid-base processes have been found to occur in the ground and excited states. In DMSO and acetonitrile equilibrium between the neutral and deprotonated molecules is established in the ground state. In acetonitrile, a second equilibrium between the neutral and protonated form is also present at a lower pH, and can be treated independently of the first one. Absorption, emission, and excitation spectra of the species involved have been measured; data analysis allows us to calculate pK _aand quantum efficiencies. The change of the decay lifetimes with pH, along with steady state fluorescence measurements show the existence of communication between the excited states and enable us to estimate the excited state kinetic rate constants.A discussion about their possible use as laser dyes based on the energy threshold condition is also given.     

Ultrasound extraction optimization for bioactive molecules from Eucalyptus globulus leaves through antioxidant activity

Antioxidant products present a very high added value and are demanded in the market. The optimization of their extraction is a high-stakes matter for both economic and environmental points of view. Ultrasound extraction has been considered one of the most promising methods, so the relative importance of key parameters may have decisive economic significance. For this reason, different parameters that have influence on the extraction capacity such as ultrasound power, time, temperature, pH and % ethanol in water have been studied to know the relationships between the independent parameters and their influence on the extraction from Eucalyptus globulus leaves. An experimental Box-Behnken factorial design and subsequent analysis by neural networks have been used. The relative influence of each parameter varies according to the nature of the extracted compound. In this regard, the higher capacity of extraction of the selected antioxidant compounds by means of the variation of the operation conditions can be facilitated. For all the studied compounds, temperature has been the most important parameter for their extraction. The relative content (%) of bioactive compounds (terpenes) in the optimized Eucalyptus globulus extract has been performed by GC–MS analysis.     

Iminobiotin Binding Induces Large Fluorescent Enhancements in Avidin and Streptavidin Fluorescent Conjugates and Exhibits Diverging pH-Dependent Binding Affinities

The pH-dependent binding affinity of either avidin or streptavidin for iminobiotin has been utilized in studies ranging from affinity binding chromatography to dynamic force spectroscopy. Regardless of which protein is used, the logarithmic dependence of the equilibrium dissociation constant (K_d) on pH is assumed conserved. However a discrepancy has emerged from a number of studies which have shown the binding affinity of streptavidin for iminobiotin in solution to be unexpectedly low, with the K_d at values usually associated with non-specific binding even at strongly basic pH levels. In this work we have utilized a Bodipy fluorescent conjugate of avidin and an Oregon Green fluorescent conjugate of streptavidin to determine the K_d of the complexes in solution in the pH range of 7.0 to 10.7. The study was made possible by the remarkable fluorescent enhancement of the two fluorescent conjugates (greater than 10 fold) upon saturation with iminobiotin. The streptavidin-iminobiotin interaction exhibited almost no pH dependence over the range studied, with K_d consistently on the order of 10⁻⁵ M. In contrast, under identical experimental conditions the avidin-iminobiotin interaction exhibited the expected logarithmic dependence on pH. We discuss the possible origins for why these two closely related proteins would diverge in their binding affinities for iminobiotin as a function of pH.