Volume 2, Issue 6, December 2011

Frontiers In Bio-nanocomposites

Ashutosh Tiwari

Advanced Materials Letters, 2011, Volume 2, Issue 6, Pages 377-377
DOI: 10.5185/amlett.2011.12001

In today’s world, bio- nanocomposites are becoming increasingly prevalent owing to the extraordinary properties that they possess. Scientists learn to select suitable matrix (e.g. aliphatic polyesters, polypeptides and proteins, polysaccharides, and polynucleic acids) and fillers (e.g. nanotubes, nanofibers, clay nanoparticles, hydroxyapetite and metal nanoparticles) and alter their chemistry and structure to suit the target field. A critical challenge in the design and development of bio- nanocomposites is the adhesion of filler and matrix at their nanointerface. Also, bio- nanocomposites in addition to providing enhanced properties such as mechanical and thermal are biocompatible and/or biodegradable. This makes them one of the most versatile materials available today and thus can be prominently applied to biomedical technologies such as bone restructuring/repair, tissue engineering, dental applications, and controlled drug delivery.

Green, formaldehyde-free, foams for thermal insulation

Maria C. Basso; Xinjun Li; Vanessa Fierro; Antonio Pizzi; Samuele Giovando; Alain Celzard

Advanced Materials Letters, 2011, Volume 2, Issue 6, Pages 378-382
DOI: 10.5185/amlett.2011.4254

New, green and cheap rigid foams presenting outstanding performances for thermal insulation are described. Such ultra-lightweight cellular materials are mainly based on renewable chemicals: tannin and furfuryl alcohol, are very easy to produce and have thermal conductivity as low as 38 mW/m/K. Compared to previously reported tannin-based foams, these new materials are much “greener” and present improved resistance to compression and to water. Especially the formaldehyde, formerly used as cross-linking agent of tannins but known as a volatile and harmful chemical, could be successfully removed from the formulation. The as-obtained, 2nd generation, tannin-based foams are totally stable and have an expected interest for thermal insulation of buildings.

Microwave assisted preparation and characterization of biopolymer-clay composite material and its application for chromium detoxification from industrial effluent

A. Santhana Krishna Kumar; S. Kalidhasan; Vidya Rajesh; N. Rajesh

Advanced Materials Letters, 2011, Volume 2, Issue 6, Pages 383-391
DOI: 10.5185/amlett.2011.2224

The microwave assisted preparation and characterization of chitosan-surfactant modified NaMMT clay composite material is discussed, followed by its interesting application to detoxify heavy metal chromium. Cr(VI) could be effectively adsorbed in a weakly acidic medium (pH 5) from a large sample volume. The composite material before and after the adsorption of chromium was scrupulously characterized using FT-IR, SEM, XRD and EDX techniques. The XRD study revealed the crystalline nature of the composite material with sharp and symmetric peaks. The bichromate ion forms an ion-pair with the protonated amine group in chitosan and this is reflected in the appearance of a Cr=O peak at 916 cm -1 in IR study. The surface hydroxyl groups in clay can be protonated and this could also serve as a source of electrostatic interaction with the bichromate oxyanion. The material exhibited a superior adsorption capacity of 133 mg g -1 and the adsorption data fitted well with Langmuir and Freundlich isotherm models. The composite adsorbent material exhibits a pore size of 3.5 nm at a maximum pore volume of 0.16 cm 3 g -1 . The BET surface area of the material obtained from N2 adsorption was found to be 52 m 2 g -1 . The experimental data also showed a good correspondence to the pseudo-second-order kinetics and the sorption thermodynamics correlated to the endothermic nature of the adsorption. The adsorbent could be regenerated using ascorbic acid or sodium sulfite which is indicative of the greener aspect in the methodology.

Facile preparation of nanoporous platinum and its high electrocatalytic performances

Jiagang Hou; Haoran Geng; Caixia Xu; Xiaolei Mu; Jinshui Yao

Advanced Materials Letters, 2011, Volume 2, Issue 6, Pages 392-396
DOI: 10.5185/amlett.2011.2225

Nanoporous platinum was fabricated by a simple dealloying method. Electron microscope characterizations show that selectively etching Al from PtAl alloy precursors in alkali or acid solution can both easily prepare three-dimensional bicontinuous network nanostructures of Pt. The resulted nanostructure exhibited much enhanced catalytic performance towards methanol electrooxidation compared with commercial Pt/C catalyst. More importantly, CO stripping and potentiostatic tests demonstrated that nanoporous Pt has much higher long-term catalytic stability and CO resistance than the Pt/C catalyst.

Morphology and electrical conductivity of self- doping polyanilines synthesized via self- assembly process

S.R. Kargirwar; S.R. Thakare; M.D. Choudhary; S.B. Kondawar; S.R. Dhakate

Advanced Materials Letters, 2011, Volume 2, Issue 6, Pages 397-401
DOI: 10.5185/amlett.2011.4245

Copolymerization of self doping monomer aniline and oxalic acid (OA)/ acetic acid (AA) in different molar ratio via the self-assembly process were conducted to prepare self-doping polyanilines (SD-PANIs). In this polymerization process, AA or OA plays the roles of surfactant and dopant for the self-doping PANIs. The morphology, UV–Vis absorption behaviour, crystalline density and electrical conductivity of self-doped PANIs are investigated. Depending on molar ratio of aniline to OA/AA, nanotubes structure of polyaniline (PANI) can be formed. Higher concentration of OA leads to increase in the diameter of the tubes in which micelles act as the template in the self-assembly of PANI to form nanotube structures, whereas increase in concentration of AA leads to change the structure of polyaniline from microspheres to nanotubes. The nanotubular structure aggregates to form a bundle structure as the concentration of AA increases. More uniform structure is observed in case of OA than that of AA, which may be due to the bulky structure of OA than AA. Higher absorption intensity in UV-Vis spectra of self-doping PANIs was observed for lower concentration of OA/AA. The crystal structure for the synthesized self-doped PANIs is orthorhombic and the C-N-C angle is larger. High electrical conductivity of the self-doped PANIs was observed as a function of degree of doping.

Microstructure, phase formations and optical bands in nanostructured alumina

Jitendra Gangwar; Kajal Kumar Dey; Surya Kant Tripathi; Avanish Kumar Srivastava

Advanced Materials Letters, 2011, Volume 2, Issue 6, Pages 402-408
DOI: 10.5185/amlett.2011.3233

We report the synthesis of nano-scaled alumina of varied dimensions through a novel optimized processing of aluminum nitrate. The X-ray diffractometry confirmed the formation of X- and γ- phases of alumina particles in the nano region, depending on the annealing conditions during processing. Subsequently, a detailed microscopic investigation revealed the morphological alterations and crystallographic information even at lattice scale. The presence of different bonds and band energies were investigated by employing infra-red and photoluminescence spectrometry, respectively. The evolution of fascinating microstructure, phase formations and optical bands has been presented and discussed to elucidate the systematic evolution of different crystalline phases (α and γ) from an amorphous alumina with increased annealing temperature.

Liquid-Phase Synthesis of Nickel Nanoparticles stabilized by PVP and study of their structural and magnetic properties

Mandeep Singh; Manish Kumar; Frantisek Stipanek; Pavel Ulbrich; Pavel Svoboda; Eva Santava; M.L. Singla

Advanced Materials Letters, 2011, Volume 2, Issue 6, Pages 409-414
DOI: 10.5185/amlett.2011.4257

We have synthesized nickel nanoparticles using nickel chloride as a precursor in ethanol using PVP (Poly Vinyl Pyrrolidone) as a surfactant and hydrazine hydrate as reducing agent at 60 °C in a facile manner. The structural analysis showed that particles are face-centered cubic and monodisperse within the PVP matrix with average size about 3 nm. The magnetic analysis shows the superparamagnetism of the single-domain nickel nanoparticles with the blocking temperature (Tb) exists around 14 K with clear hysteretic effect observation below this blocking temperature.

Preparation and characterization of a photochromic hydrogel

Chen Mo; Lin Lin; Li Xiaoqiang

Advanced Materials Letters, 2011, Volume 2, Issue 6, Pages 415-418
DOI: 10.5185/amlett.2011.2227

A new type of photochromic hydrogel, spiropyran (SP)-Polyvinylpyrrolidone (PVP)-poly (N-isopropyl acrylamide) (PNIPAM) hydrogel with functionalized SP chemically incorporated, was synthesized. The molecular structure of synthesized products was given by nuclear magnetic resonance (NMR) spectra and infrared spectrum (IR). The photochromism of the hydrogel was evidenced by photography and characterized by ultraviolet-visible (UV-Vis) spectroscopy. The photochromic reversibility of the hydrogel was tested through observing its responses to the alternating UV irradiation to dark environment. The fluorescence micrographs showed the fluorescent effect as well as confirmed the photochromic properties of the hydrogel, and indicated that the chemical incorporation made the functionalized SP distribute well in the gel.

AC impedance spectroscopy and conductivity studies of Ba0.8Sr0.2TiO3 ceramics

Subrat K. Barik; R.N.P. Choudhary; A.K. Singh

Advanced Materials Letters, 2011, Volume 2, Issue 6, Pages 419-424
DOI: 10.5185/amlett.2011.2228

The AC impedance and conductivity properties of Ba0.8Sr0.2TiO3 ceramics in a wide frequency range at different temperatures have been studied. The compound was prepared by a high-temperature solid-state reaction technique. A preliminary structural analysis of the compound by X-ray diffraction technique confirmed its single phase. An ac impedance spectroscopic technique was used to correlate between the microstructure and electrical properties of the compound. The presence of both grain (bulk) and grain boundary effect in the compound was observed. The frequency-dependent electrical data were used to study the conductivity mechanism. An analysis of the electric impedance and modulus with frequency at different temperatures has provided some information to support suggested conduction mechanism.

Simulation study of influence of Al, Si and B on the growth of TiC

Haimin Ding; Kaiyu Chu; Jinfeng Wang

Advanced Materials Letters, 2011, Volume 2, Issue 6, Pages 425-428
DOI: 10.5185/amlett.2011.2230

The influence of Al, Si and B on the growth of TiC is studied in this article. It is found that the adsorption of Al is more favorable on TiC {111} than that on {001}. Therefore, under the influence of it, the growth rate of {111} will be accelerated and result in the decreasing of the relative growth rate between {001} and {111}. Therefore, TiC will grow into truncated-octahedron. But when TiC is formed under the influence of Si and B, they will grow into hexagonal platelets due to the preferential adsorption of Si and B on {011} and {001}.

Biosynthesis of silver nanoparticles using murraya koenigii (curry leaf): An investigation on the effect of broth concentration in reduction mechanism and particle size

Laura Christensen; Singaravelu Vivekanandhan; Manjusri Misra; Amar Kumar Mohanty

Advanced Materials Letters, 2011, Volume 2, Issue 6, Pages 429-434
DOI: 10.5185/amlett.2011.4256

Biological synthesis of silver nanoparticles using Murraya koenigii leaf extract was investigated and the effect of broth concentration in reduction mechanism and particle size is reported. The rapid reduction of silver (Ag + ) ions was monitored using UV-visible spectrophotometry and showed formation of silver nanoparticles within 15 minutes. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) analysis showed that the synthesized silver nanoparticle are varied from 10-25 nm and have the spherical shape. Further, the XRD analysis confirms the nanocrystalline phase of silver with FCC crystal structure. From this study, it was found that the increasing broth concentration increases the rate of reduction and decreases the particle size.