S. Umapathy

SYNTHESIS AND CHARACTERIZATION OF NANOSIZED Mg(OH)2 AND ITS NANOCOMPOSITE WITH POLY (VINYL ALCOHOL)

Nano-Mg(OH)2 was synthesized by co-precipitation method. Peaks between 500 and 1250 cm-1 in FTIR spectroscopy confirmed the presence of metal hydroxide stretching. TGA inferred that above 600°C, 50% of residue weight remained. HRTEM of nanocomposite gave an idea about the nonspherical morphology of particles of size 25 nm to 30 nm. SEM inferred that flower-like morphology for pristine Mg(OH)2 and higher % weight of aniline-intercalated Mg(OH)2 had agglomerated structure. UV visible spectrum inferred the presence of Mg2+ ion at 275 nm and the presence of amino-group-intercalated Mg(OH)2, which had a sharp peak at 193 nm and the intensity of which increases with the increase in % weight of aniline. PL inferred that aniline-intercalated Mg(OH)2 showed a lower intensity of which increased with higher wavelength value than the pristine and nanocomposite with PVA.

Polymerization of acrylamide in the presence of ultrasound and peroxomonosulfate

Polymerization of acrylamide (M) in the presence of ultrasound and peroxomonosulfate (PMS) was carried out for the first time for various concentration ranges of monomer and initiator and various temperatures at a constant frequency of 1 Mhz. The rate of polymerization R p was found to increase with increase in the concentration of monomer and initiator and found to depend on [M] and [PMS] 1/2 . The rate of disappearance of initiator (-d[PMS/dt) was also followed simultaneously under the experimental conditions and found to increase linearly with increase in [PMS]. A probable reaction mechanism was proposed on the basis of the observed results, and the individual rate constant were evaluated.

Polymerization of acrylamide in the presence of peroxodisulfate and ultrasound

Polymerization of acryamide was specifically performed under conditions wherein no polymerization could occur in the absence of ultrasound and initiator. Polymerizations were carried out in the presence of peroxodisulfate and ultrasound. The rate of polymerization and the rate of peroxodisulfate disappearance were followed under various conditions to arrive at the rate dependencies. The observed results were adequately explained in terms of the proposed mechanism. The rate parameters were evaluated and provided as evidence for the polymerization which can occur in the presence of ultrasound.

Sonochemical cyclopolymerization of diallylamine

Abstract Cyclopolymerization of a symmetrical nonconjugated diolefin, diallylamine was found possible in the presence of ultrasound and peroxodisulphate. The rate of polymerization, Rp showed first- and half-order dependencies on diallylamine and peroxodisulphate concentration, respectively. The results are explained through a proposed mechanism involving alternating intramolecular and intermolecular propagation reactions. The rate parameters for the cyclopolymerization are evaluated. The role of ultrasound in initiating the cyclopolymerization is discussed.

Spectroscopic Studies on Pure and Histidine-Functionalized Multiwalled Carbon Nanotubes

ABSTRACT Electron paramagnetic resonance, Fourier transform infrared, and ultraviolet-visible studies were carried out for pure and histidine-functionalized multiwalled carbon nanotubes. Electron paramagnetic resonance absorption spectral data were found to be the best fit for the Gaussian lineshape. The g-values indicate the presence of magnetic impurities in the samples and the interaction between the localized electrons and delocalized electrons in the nanotubes trapped at defects or magnetic ion sites. The electron spin concentration decreases with increasing concentration of histidine, which implies that the unpaired electrons undergo a reduction process in the histidine-functionalized multiwalled carbon nanotubes. Fourier transform infrared study confirms the presence of functional groups in pure and histidine-functionalized multiwalled carbon nanotubes. Ultraviolet-visible study reveals the formation of a charge transfer complex in histidine-functionalized multiwalled carbon nanotubes.

Polymerization of methacrylamide in the presence of ultrasound and peroxomonosulphate

Polymerization of methacrylamide has been carried out in the presence of ultrasound and peroxomonosulphate for the first time. The rate of polymerization and the rate of disappearance of peroxomonosulphate were followed simultaneously. A first order dependence on monomer and half order dependence with respect to peroxomonosulphate were found towards rate of polymerization. However, a first-order dependence on peroxomonosulphate was noted with rate of peroxomonosulphate disappearance. A suitable reaction scheme is suggested to fit with the experimental results. The composite rate constants for the polymerization were evaluated and compared for acrylamide and methacrylamide polymerization in the presence of ultrasound.

Synthesis and Characterization of Nano-sized Zn(OH)2 and Zn(OH)2/PVA Nano-composite

Nano-sized Zn(OH)2 was synthesized by the co-precipitation method. Further, the structure and properties were tested with FTIR, UV-visible spectroscopy, XRD and TGA as analytical tools. The structural morphology and size of the Zn(OH)2 synthesized by the co-precipitation method were determined by using FESEM and HRTEM techniques. The effect of the synthesized nano-sized Zn(OH)2 on the structural and thermal properties of PVA matrix was tested and discussed.

Influence of α-amylase template concentration on systematic entrapment of highly stable and monodispersed colloidal gold nanoparticles

Nano gold / α-amylase colloidal dispersions of profound stability were made using simple procedure with a conventional reducing agent. The surface plasmon resonance of the gold nanocrystals was used to quantify the extent of the dispersion stability and functionalization. It is found that the reduced gold nanoparticles were trapped into the protein network without denaturation the structure of α-amylase protein. This kind of entrapment of particles into the protein network prevents clustering of individual gold nanoparticles (6.42 nm ± 0.92 nm) by acting as a natural spacer. Systematic entrapment was facilitated by the affinity of gold to the sulfur moieties (Au-S) in the protein structure.

Peptide assisted synthesis and functionalization of gold nanoparticles and their adsorption by chitosan particles in aqueous dispersion

We have reported a novel method of synthesis of gold nanoparticles (GNPs), using two different peptides, e.g. glutathione (GSH) and glycyl-glycine (GG), as reducing agents. The formation of GNPs was observed with the development of the surface plasmon resonance (SPR) peak in UV-visible spectrum. The nanoparticles phase has been investigated using powder x-ray diffraction (XRD) method and has been seen to be single phase. The as-synthesized GNPs were not fully covered by the used peptides as seen by the thermogravimetry analysis (TGA), and therefore, trisodium citrate (TSC) has been used further as a ‘filler’ agent for GNPs to become well dispersible in aqueous medium. The Fourier transform infrared (FTIR) spectroscopy method has confirmed the presence of peptides and TSC coatings on the nanoparticles’ surface. In comparison, the GNPs formed using GG have been observed to be more stable than those formed using GSH. The nanoparticle size was measured using XRD, dynamic light scattering (DLS) and transmission electron microscopy (TEM). These dispersions were further used to investigate the interaction between the GNPs and chitosan (CS) microparticles. The effects of this interaction were studied using UV-visible spectroscopy, DLS and FTIR. XRD and TEM showed that GNPs were uptaken by CS microparticles.

Sonochemical Synthesis of Poly (Methyl Acrylate)

Polymers are prepared by various methods. The method of preparation plays an important role in deciding many of the physical properties of polymers. In this work Poly (Methyl Acrylate), PMA, is synthesized by free radical addition polymerization in the presence a monomer, an initiator under the influence of ultrasound. Methyl Acrylate (E-Merck, India) of proper strength is mixed with aqueous sodium peroxodisulphate solution of known strength and the time of passage of ultrasound is varied in steps of 30 minutes and 10 samples of solid PMA are obtained for 10 different periods of passage of ultrasound. Solid PMA samples are purified and air-dried under clean environment. TGA, DTA measurements are done on all the 10 PMA samples. The thermal stability of PMA with the change in the time of passage of ultrasound is discussed quantitatively. The thermal stability of PMA, synthesized sonochemically shows better results over the thermal method of synthesis. However in this paper we report the measurements made on PMA samples synthesized at 30 and 300 minutes sonication periods respectively.