Synthesis and surface chemistry of nano silver particles

In this report, we present a simple wet chemical route to synthesize nano-sized silver particles, and their surface properties are discussed in detail. Silver nano particles of the size 40–80 nm are formed in the process of oxidation of glucose to gluconic acid by amine in the presence of silver nitrate, and the gluconic acid caps the nano silver particle. The presence of gluconic acid on the surface of nano silver particles was confirmed by XPS and FTIR studies. As the nano silver particle is encapsulated by gluconic acid, there was no surface oxidation, as confirmed by XPS studies. The nano silver particles have also been studied for their formation, structure, morphology and size using UV–Visible spectroscopy, XRD and SEM. Further, the antibacterial properties of these nano particles show promising results for E. Coli. The influence of the alkaline medium towards the particle size and yield was also studied by measuring the pH of the reaction for DEA, NaOH and Na₂CO₃.     

First synthesis of 1,3-oxaselenepanes

The first synthesis of 1,3-oxaselenepane derivatives by the reaction of aryl isoselenocyanates with 4-bromobutanol in the presence of sodium hydride in THF as a one-pot reaction is described. The Z/E isomerism for the exocyclic carbon-nitrogen double bond in the selenium heterocycles was observed for the first time.     

Heterogeneous catalysis by new bead‐shaped polymer‐supported multisite phase transfer catalysts

Three different new insoluble bead‐shaped polymer‐supported multisite phase transfer catalysts containing two, four and six active sites have been prepared and characterized by FTIR, TGA, [chloride ion] and SEM analyses. The presence of number of active sites in each catalyst and their corresponding catalytic ability were studied by determining pseudo‐first order rate constants for C‐alkylation of phenylacetonitrile (PAN) and four different substituted PAN as the substrate using a low concentration of NaOH (25% w/w) at 50 °C. The observed rate constants were compared with rate constants of same reactions catalyzed by single‐site catalyst under identical reaction conditions. From comparative study, the efficiency of catalysts were found to be in the order six‐site>four‐site>two‐site>single‐site thus confirming number of active sites in each catalyst. Further, the detailed kinetic profile of C‐alkylation of PAN has been investigated using the superior six‐site catalyst by varying stirring speed, [substrate], [catalyst], [NaOH], and temperature. Based on the observed kinetic and activation parameters, an interfacial mechanism was proposed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 771–785, 2009     

One-pot multi-component synthesis of N,N′-alkylidene bisamides and imidazoles using heteropoly-11-tungsto-1-vanadophosphoric acid supported on natural clay as catalyst: A green approach

One-pot multi-component synthesis of N,N′-alkylidene bisamides, 2,4,5-trisubstituted imidazoles and 1,2,4,5-tetrasubstituted imidazoles in the presence of catalytic material heteropoly-11-tungsto-1-vanadophosphoric acid (HPV) supported on activated natural clay for about 20% (HPVAC-20) under solvent-free reaction condition have been achieved. Green heterogeneous reaction condition, simple workup procedure, short reaction time, high yield of products, and reusability of the catalyst are the advantages of this protocol.     

Volatile oil composition of Pogostemon heyneanus and comparison of its composition with patchouli oil

The volatile oil of the leaves of Pogostemon heyneanus Benth. (Lamiaceae) was analyzed by GC and GC-MS. Twenty-six components representing 96.0% of the oil were identified. The major components of the oil were acetophenone (51.0%), beta-pinene (5.3%), (E)-nerolidol (5.4%), and patchouli alcohol (14.0%). Comparison of the compositions of the oils of P. heyneanus and P. cablin (Blanco) Benth. (Patchouli oil) showed wide variation between them. Though 13 sesquiterpenes and oxygenated sesquiterpenes were detected in both oils, their concentrations in the oils differed widely. Acetophenone, benzoyl acetone and (E)-nerolidol present in the oil of P. heyneanus were not detected in patchouli oil.     

A mathematical model to predict the grain size of nanocrystalline CdS thin films based on the deposition condition used in the sol–gel spin coating method

Design of experiment (DOE) based on central composite design (CCD) has been employed for the development of a mathematical model correlating the important process parameters like thiourea concentration (U), annealing temperature (A), rotational speed (S), and annealing time (T) of the spin coating process for the preparation of CdS thin films. The experiments were conducted as per the design matrix. Nanocrystalline CdS thin films have been prepared using cadmium nitrate and thiourea as precursors by sol gel spin coating method using the results of the mathematical model. The prepared CdS films have been characterized and the crystal structure and grain size of the samples were analyzed using X-ray diffraction technique. The adequacy of the developed models was checked by analysis of variance (ANOVA) technique. The accuracy of prediction has been carried out by conducting confirmation test. Using this model, the main effect of process parameters on grain size of CdS films have been studied. These parameters were optimized to obtain minimum grain size using the Microsoft excel solver. The results have been verified by depositing CdS films using the optimized conditions. These films have been characterized using X-ray diffraction technique and the grain size is found to be 8.8 nm. The high resolution transmission electron microscopy (HRTEM) analysis showed the grain size of the prepared CdS film to be ∼7 nm. UV–vis spectroscopy analysis revealed that CdS films exhibited quantum confinement effect.     

Instabilities in free-surface electroosmotic flows

Instability of a thin electrolyte film undergoing a direct current electroosmotic flow has been investigated. The film with a compliant electrolyte–air interface is flowing over a rigid charged substrate. Unlike previous studies, inclusion of the Maxwell stresses in the formulation shows the presence of a new finite wavenumber shear-flow mode of instability, alongside the more frequently observed long-wave interfacial mode. The shear mode is found to be the dominant mode of instability when the electrolyte–solid and electrolyte–air interfaces are of opposite charge or of same charge but have very large zeta-potential at the electrolyte–air interface. The conditions for mode-switch (interfacial to shear) and the direction of the travelling waves are discussed through stability diagrams. Interestingly, the analysis shows that when the interfaces are of nearly same zeta potential, the ‘free’ electrolyte–air interface behaves more like a ‘stationary’ wall because of the ion transport in the reverse direction of the flow.     

Multi-band phase shifter design using modified slotline configuration

In this paper, an analog multiband phase shifter using slotline configuration is proposed. To implement the design, a pair of modified Split Ring Resonator (SRR) is employed. The periodic property of SRR provides multiband characteristics, whether the coupling slot gives the phase variations over the bands. The operation is well explained with an equivalent circuit model and its characteristics have been studied both in simulation and measurement. The prototype operates in 1.77–2.16, 3.5–3.97, 5.08–5.33, 6.43–6.93, and 8.01–8.59 GHz frequency bands which can be utilized for GSM, GPS, WLAN, C-band, and X-band applications, respectively.