Synthesis of high-concentration Cu nanoparticles in aqueous CTAB solutions

Pure metallic Cu nanoparticles at a high concentration (up to 0.2 M) have been synthesized by the reduction of cupric chloride with hydrazine in the aqueous CTAB solution. The input of extra inert gases was not necessary. The use of ammonia solution for the adjustment of solution pH up to 10 and the use of hydrazine as a reducing agent in a capped reaction bottle are crucial for the synthesis of pure Cu nanoparticles. The reaction solution finally became wine-reddish and its UV/vis absorption spectrum exhibited an absorption band at 574 nm, revealing the formation of metallic Cu nanoparticles. By the analysis of electron diffraction pattern, EDS, XRD, and XPS, the resultant particles were confirmed to be pure Cu with a face-centered cubic (fcc) structure. From the TEM analysis, it was found that the mean diameter of Cu nanoparticles first decreased and then approached a constant with the increase of hydrazine concentration. In addition, the CTAB concentration had not significant influence on the size of Cu nanoparticles. Also, TG analysis indicated that there were two weight-loss steps for the CTAB-capped Cu nanoparticles. It was suggested that a bilayer structure of CTAB was formed on the surface of Cu nanoparticles to prevent from the particle agglomeration. The synthesis method reported in this work might be helpful for the large-scale production of Cu nanoparticles.     

Adsorption of CTAB onto perlite samples from aqueous solutions

In this study, the adsorption properties of unexpanded and expanded perlite samples in aqueous cetyltrimethylammonium bromide (CTAB) solutions were investigated as a function of ionic strength, pH, and temperature. It was found that the amount of cetyltrimethylammonium bromide adsorbed onto unexpanded perlite was greater than that onto expanded perlite. For both perlite samples, the sorption capacity increased with increasing ionic strength and pH and decreasing temperature. Experimental data were analyzed by Langmuir and Freundlich isotherms and it was found that the experimental data were correlated reasonably well by the Freundlich adsorption isotherm. Furthermore, the isotherm parameters (KF and n) were also calculated. The adsorption enthalpy was determined from experimental data at different temperatures. Results have shown that the interaction between the perlite surface and CTAB is a physical interaction, and the adsorption process is an exothermic one.     

Occurrence of shear thickening in aqueous micellar solutions of CTAB with some added organic counterions

 In this experimental work we carefully investigate the influence of some organic counterions (having similarities): sodium salicylate (NaSal), sodium tosylate (NaTos) and sodium benzoate (NaBz) on the rheological properties of two aqueous solutions (0.1 and 0.05 M) of cetyltrimethylammonium bromide (CTAB). Here we are particularly interested in the occurrence of the shear thickening effect corresponding to shear induced structures (SIS). All the rheological measurements presented in this work are realized with the same geometrical device (plan-cone) with controlled imposed shear stress. Conditions of occurrence and evolutions of the characteristics of the obtained shear thickening are given. Received: 30 June 1997 Accepted: 20 October 1997     

On the shape of giant micelles in aqueous solutions of cetyltrimetylammoniumbromide (CTAB)

Low-temperature electron microscopy was used to image fracture faces of shock-frozen aqueous solutions containing the very large micelles of CTAB existing in the presence of N-methyl-N,N-diphenylamine (MDPA) and 9-anthracene carboxylic acid (9-AC) as solubilizates. When MDPA is present, large globular micelles are formed which have total aggregation numbers of the order of 10⁵ and are seen to be clusters of smaller disc-like structures containing some thousand CTAB-units. Thread-like features are visualized in solutions containing 9-AC which is known to induce the formation of micellar rods.     

SDS和CTAB水溶中胶束扩散系数及第一、第二CMC测定

在无探针条件下用循环伏安法测定了不同形状SDS和CTAB胶束的扩散系数，进而得到第一CMC和第二CMC（SDS：第一CMC和第二CMC分别为8．0×10－3和5．6×10－2mol·L-1;CTAB：第一CMC和第二CMC分别为8．9×10－4和2．1×10－2mol·L－1）．此法为表面活性剂体系物理化学性质的研究，特别是为第二CMC测定提供了一个新的研究方法．     

聚二甲基二烯丙基氯化铵及其与CTAB混合物水溶液 的吸附动力学

用最大泡压法分别测定了聚二甲基二烯丙基氯化铵,十六烷基三甲基溴化铵以及两者混合物水溶液的动表面张力。十六烷基三甲基溴化铵的吸附服从扩散-动力学控制机理。发现聚二甲基二烯丙基氯化铵水溶液的表面张力具有独特的时间相关性。吸附的前期服从扩散控制机理,而在吸附的后期,即接近吸附平衡时服从扩散-动力学控制机理。混合物水溶液的整个吸附过程受扩散控制。     

Promoting photochromism on flavylium derived 2-hydroxychalcones in aqueous solutions by addition of CTAB micelles

A strategy to obtain photochromism from the network of chemical reactions originated by flavylium compounds in solution is described. This strategy is particularly useful for flavylium salts bearing amino groups which give rise to a variety of beautiful colors but lack photochemistry in water. The trans-chalcone of 7-(N,N-diethylamino)-4'-hydroxyflavylium interacts strongly with CTAB micelles defining a yellow dark state. Upon irradiation, the system switches to a pink-red state emerging from the flavylium cation that is formed inside the micelle and ejected to the bulk aqueous phase. The photochemical product reverts back to the trans-chalcone adduct with the micelle in the dark. The thermodynamics as well as the kinetics of the photochromic system were studied in detail. The best color contrast is obtained at pH = 4.25 with Phi = 0.001 and a recovery lifetime of approximately 3 h. This photochromic system works with no need of changing the pH, which constitutes an important improvement over previously described systems dependent on pH jumps.     

Experimental study of contact plating of metals from aqueous solutions

Experimental data on the contact displacement of metals from aqueous solutions are shown. Experimental chronopotentiograms are compared with those calculated based on an earlier proposed model.     

Dose determination of nickel implantations in silicon wafers

Summary The dose of nickel ions implanted with an energy of 300 keV or 6 MeV, respectively, into silicon wafers was measured by X-ray fluorescence analysis (XRFA) after the implantation process. Dose values for Ni were determined within the range from 5×10¹⁵ to 1×10¹⁸ ions/cm². The detection limit of this simple and non-destructive procedure amounts to about 10¹⁴ atoms/cm². The accuracy was confirmed by flame atomic absorption spectrometry (FAAS), total-reflection X-ray fluorescence analysis (TXRFA), and by Rutherford-backscattering spectroscopy (RBS). The study confirms XRFA to be a suitable method for dose determinations after the implantation process.     

双十八烷基二甲基氯化铵水溶液CMC值的测定

采用电导法和荧光法测定了阳离子表面活性剂-双十八烷基二甲基氯化铵(DODAC)的临界胶束浓度(CMC), 在温度为14 ℃时, 电导法测得DODAC溶液的临界胶束浓度为5.24×10-5 mol/L, 荧光法测得DODAC溶液的临界胶束浓度为9.67×10-5 mol/L.     

Specific features of the bulk etching of single-crystal semiconducting silicon in aqueous KOH solutions

Bulk chemical etching of single-crystal semiconducting silicon in aqueous alkaline solutions of KOH was studied at various solution temperatures, alkaline component concentrations, and microscopic amounts of a potassium ferricyanide additive. Specific effects of these factors on the process of silicon etching are explained by comparing the corresponding activation energies. The possibility of using alkaline aqueous solutions of KOH with a potassium ferricyanide additive for fabrication of elements in microsystem technology devices is assessed.     

Effects of added nonionic surfactant and inorganic salt on the rheology of sugar surfactant and CTAB aqueous solutions

The effect of adding tri(oxyethylene) dodecyl ether (C₁₂EO₃) on the phase and rheological behavior of sucrose hexadecanoate and CTAB aqueous solutions in the presence of added salt (NaBr) was investigated. Viscoelastic solutions are formed in CTAB and C₁₆SE systems upon addition of lipophilic nonionic surfactant C₁₂EO₃. The zero-shear viscosity shows a maximum at a certain mixing fraction of C₁₂EO₃, except in the case of the aqueous CTAB/C₁₂EO₃ system in the absence of salt. The rheological properties are strongly affected by the addition of salt to the CTAB systems but they remain unaltered in the case of C₁₆SE systems. In ionic systems, the mixing fraction of C₁₂EO₃ for the maximum viscosity depends on salt concentration.     

Instrumental neutron activation analysis of silicon wafers using the silicon matrix as the comparator

For the instrumental neutron activation analysis of trace impurities in high purity silicon wafer, a modified single comparator method has been applied. The energy distribution of the neutrons at the irradiation position was measured using the two flux monitors, Au and Co, and elemental contents were calculated using the silicon matrix in the wafer as a comparator. This has advantage of reducing the cross contamination from an external monitor during sample preparation and irradiation, the uncertainties from the non-homogeneity of the neutron flux and the error on the weight of comparators. Determination limits for 49 elements were presented under the condition of 72 hours irradiation at a neutron flux of 3.7·10¹³ n·cm^-2·s^-1 and 4000 s measurement. The analytical results obtained by this method and the conventional single comparator method were compared and were found to agree well within 5%.     

Helium-3 activation analysis of oxygen in silicon nitride films on silicon wafers

Oxygen in silicon nitride films on silicon wafers was analyzed by activation with the¹⁶O(³He, p)¹⁸F reaction. By³He bombardment of samples propertly arranged under consideration of the¹⁸F recoil effect, total oxygen was reliably determined and its predominant part was estimated to be located whether on film surface, in film interior, or on film-substrate interface. Sample films with 0.1 to 2 μm thicknesses were found to contain 0.2 to 2 μg/cm² of oxygen in locations varying with preparation conditions. This method has been compared with ESCA and other methods for surface analysis.     

Nonlinear rheology of CTAB/NaSal aqueous solutions: finite extensibility of a network of wormlike micelles

The nonlinear rheology of aqueous solutions of cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal) was investigated. The concentration of CTAB was fixed at 0.1 mol L(-1), and the concentration of NaSal was varied from 0.07 to 0.4 mol L(-1). For all test solutions, dynamic moduli were described with the Maxwell model having a single relaxation time, tau. Time evolutions of the shear stress, sigma, and the first normal stress difference, N(1), after inception of the steady shear flow were measured. For solutions having low NaSal concentrations, strain-hardening was observed and sigma and N(1) diverged at a certain strain when the shear rate, , exceeded tau(-1). For solutions with high NaSal concentrations, stress overshoot similar to that of ordinary entangled polymer solutions was observed at between tau(-1) and a certain critical rate, (C), while the strain-hardening was observed at > (C). A simple relationship for elastic solids, N(1)/sigma = gamma with gamma being the strain imposed by shear flow, held for all the solutions in the strain-hardening regime. The strain-hardening was attributable to the strain-dependent shear modulus and well described with the network theory considering the finite extensibility of network strands. The segment size of network strands was successfully determined. Thus, the stress-strain relationship obtained after the inception of fast flows is useful for characterizing the network properties.     

Neutron activation analysis of very pure silicon wafers

Procedure and results of instrumental neutron activation analysis of very pure silicon wafers of 12.5 and 15 cm diameter are described. It is shown that the determined contaminations are mainly present on the surface or in a surface layer of the wafers. With the method outlined here very low limits of detection for a large number of elements are obtained. The analyses also confirmed that two routine process cleaning procedures do not contaminate the surface of the waters.     

Chemical transformations in sodium chloride aqueous solutions under the action of low-temperature contact glow-discharge plasma

Changes in the composition of aqueous NaCl solutions during the course of their treatment with glow-discharge plasma in a gas-liquid plasma-chemical reactor have been studied. A mathematical model involving the steps of oxidation of water molecules and chloride ions and the steps of reduction of their chemical conversion products has been developed. For the first time, it has been found that the hydrogen peroxide content of the solution monotonically decreases with the concentration of NaCl and a change in chlorite, chlorate, and perchlorate concentrations has the appearance of an undulating curve with a maximum at c(NaCl) = 3 g/L. The predominant accumulation of hypochlorite ions in the solution has been detected only in the case of the plasma treatment of the NaCl solutions with concentrations higher than 5 g/L.     

Measurement of concentration of calcium-45 in aqueous solutions with a silicon photodiode as a beta-ray detector

It was found that a commercial silicon photodiode modified only by removing its window can be used as a low-background detector of -rays from⁴⁵Ca solutions. We built a test system which could count -rays from 0.21% hot CaCl₂ solutions in the concentration range of 10^–5–10^–8M with linear sensitivity. Such a system using a small photodiode for real-time detection of -rays from small amounts of assay solutions could have many applications in the field of biophysics, biochemistry and physiology, e.g., in the study of Ca-binding proteins. This photodiode was also found to be suitable for measurement of low-energy -rays from¹⁴C.