Chemically selective membrane optode for Cr(VI) determination in aqueous samples

A methodology for simultaneous preconcentration and determination of Cr(VI) from aqueous samples was developed using a membrane optode formed by physical inclusion of a Cr(VI) selective chromophore 1,5-diphenylcarbazide (DPC) into a plasticized cellulose triacetate matrix. The inclusion of an anion exchanger (Aliquat-336) was found to be effective for immobilization of both DPC and Cr(VI)-DPC complex in the optode matrix itself. The proportionality in intensity of the magenta color on the optodes loaded with varying amounts of Cr(VI) suggests its potential applications for screening of Cr(VI) in aqueous samples by visual colorimetry. On loading high amounts of Cr(VI) in the membrane optode, its color changes from magenta to yellow, which indicates the possibility of using it as a threshold detector for Cr(VI). The membrane optode was optimized in terms of obtaining maximum preconcentration efficiency for Cr(VI) and subsequent stable optical response proportional to the amount of Cr(VI) in the membrane optode sample. The membrane optodes were tested for Cr(VI) determination in tap water and seawater samples. Using this optode, Cr(VI) even at levels of 13.6 ppb could be quantitatively detected. The optodes developed in the present work were found to be stable, cost effective, easy to prepare and efficient for direct preconcentration and determination of Cr(VI) in a variety of aqueous samples using spectrophotometry. However, this membrane optode is for one time use only as the reaction of Cr(VI) with DPC is irreversible.     

Rhodium catalyzed three-component reaction of aldehyde,boronic acid,and sulfonamides: a facile one-pot synthesis of diarylmethylamines

Rhodium(I) catalyzed three-component reaction for the one pot synthesis of diarylmethylamines in excellent yields were achieved by using aldehyde, boronic acid, and sulfonamides. The use of hyper-valent bis(trifluoroacetoxy)iodobenzene as an additive plays a key role in the chemo selective formation of amines instead of alcohols.     

Probing the microstructure of Nafion-117 using positron annihilation spectroscopy

We report a new result on positron annihilation studies in acid- and cation-neutralized (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, UO₂²⁺, Ni²⁺) Nafion membranes using positron lifetime and Doppler-broadened annihilation radiation (DBAR) measurements. The free-volume structure is characterized using a simple quantum mechanical model of positronium (Ps) in a spherical well. Our studies indicate that formation and expansion of clusters is always associated with a change in free-volume structure resulting in smaller free-volume holes. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 771–776, 1997     

Controllable states in compressible elastic dielectrics

Zusammenfassung Ein kontrollierter Zustand ist definiert als einer, in welchem eine endliche statische Verformung und entweder das elektrische Feld oder das dielektrische Verschiebungsfeld anfänglich vorgeschrieben sind. Es kann gezeigt werden, dass der resultierende Zustand ohne Volumkräfte oder Ladungen in jedem homogenen, isotropen und zusammendrückbaren Dielektrikum hervorgerufen werden kann.Es wird gezeigt, dass die einzig möglichen kontrollierten Zustände aus reinen homogenen Verschiebungen bestehen, kombiniert mit einheitlichen Feldern.     

A systematic scheme of qualitative analysis for anions. part I

A new and comprehensive scheme for the systematic detection of anions has been put forward. This scheme is based on the precipitation of difficultly soluble salts of anions in groups by basic group reagents in sodium carbonate solution and the subsequent analysis of cach group precipitate or filtrate for the detection of individual members of the group     

General Synthesis of Two‐Dimensional Patterned Conducting Polymer‐Nanobowl Sheet via Chemical Polymerization

Summary: A general method for the generation of two‐dimensional (2D) ordered, large‐area, and liftable conducting polymer‐nanobowl sheet has been demonstrated via chemical polymerization for the first time. The sheet is made using the monolayer self‐assembled from polystyrene (PS) spheres at the aqueous/air interface as template, followed by depositing conducting polymer on the part of PS monolayer submerging in the aqueous phase via chemical polymerization, and core extraction. During the process of polymerization, no substrate is required, which caused the as‐prepared patterned conducting polymer sheet can be easily lifted‐off and deposited, in full size, on any flat substrate. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectrum were used to characterize the products.

Morphology of the polyaniline‐CSA nanobowl sheet.