Atanu Kotal

Novel ascorbic acid based ionic liquids for the in situ synthesis of quasi-spherical and anisotropic gold nanostructures in aqueous medium.

A series of newly designed ascorbic acid based room temperature ionic liquids were successfully used to prepare quasi-spherical and anisotropic gold nanostructures in an aqueous medium at ambient temperature. The synthesis of these room temperature ionic liquids involves, first, the preparation of a 1-alkyl (such as methyl, ethyl, butyl, hexyl, octyl, and decyl) derivative of 3-methylimidazolium hydroxide followed by the neutralization of the derivatised product with ascorbic acid. These ionic liquids show significantly better thermal stability and their glass transition temperature (Tg) decreases with increasing alkyl chain length. The ascorbate counter anion of these ionic liquids acts as a reducing agent for HAuCl4 to produce metallic gold and the alkylated imidazolium counter cation acts as a capping/shape-directing agent. It has been found that the nature of the ionic liquids and the mole ratio of ionic liquid to HAuCl4 has a significant effect on the morphology of the formed gold nanostructures. If an equimolar mixture of ionic liquid and HAuCl4 is used, predominantly anisotropic gold nanostructures are formed and by varying the alkyl chain length attached to imidazolium cation of the ionic liquids, various particle morphologies can formed, such as quasispherical, raspberry-like, flakes or dendritic. A probable formation mechanism for such anisotropic gold nanostructures has been proposed, which is based on the results of some control experiments.

Interparticle interaction and size effect in polymer coated magnetite nanoparticles

The value of the surface anisotropy constant Ks as obtained from equation (5) in the 11th line from the top of page 9098 should be Ks= 0.15 × 10-4 Jm-2.

Ultrasound-Induced In Situ Formation of Coordination Organogels from Isobutyric Acids and Zinc Oxide Nanoparticles

The discovery of ultrasound-induced in-situ formation of coordination organogels using various isobutyric acids (such as isobutyric acid or 2-methylisobutyric acid or 2-bromoisobutyric acid) and zinc oxide nanoparticles was described. FTIR and XRD results suggest that ultrasound irradiation triggers the quick dissolution of zinc oxide nanoparticles by isobutyric acids, resulting in the in-situ formation of zinc isobutyrate complexes that undergoes fast sonocrystallization into gel fibers. FESEM results clearly demonstrate the formation of well-defined networks of fibers with several micrometers in length, but the average diameter of the fiber ranges from 30 to 65 nm, depending upon the nature of the isobutyric acids used. A combination of single-crystal structure analysis and powder XRD result was used to envisage the molecular packing present in the gel state. This is probably a very rare case of ultrasound-induced organogelation where metal oxide NPs are used as the precursor.

Free radical polymerization of alkyl methacrylates with N,N-dimethylanilinium p-toluenesulfonate at above ambient temperature: a quasi-living system

N,N-Dimethylanilinium p-toluenesulfonate (PTSA-DMA) has been successfully used as a versatile initiator for the quasi-living free radical polymerization of several alkyl methacrylate monomers such as methyl, ethyl, n-butyl, tert-butyl, and benzyl methacrylates (MMA, EMA, n-BuMA, t-BuMA and BzMA respectively) at 60 °C in dry THF. The initiator, PTSA-DMA was prepared by a simple complexation reaction of readily available p-toluenesulfonic acid (PTSA) and N,N-dimethylaniline (DMA). The yield of this polymerization system was moderate to good (60–75%). The produced poly(alkyl methacrylates) had narrow polydispersities (PDIs) (Mw/Mn = 1.16–1.45). Although, this polymerization follows first order kinetics but the obtained molecular weight remains almost unchanged with conversion. This polymerization proceeds through radical mechanism as confirmed by electron paramagnetic resonance spectroscopy. The ‘quasi-living’ nature of this polymerization was verified from the chain extension experiment as well as the successful synthesis of a block copolymer, poly(methyl methacrylate)-b-poly(methyl methacrylate-co-benzyl methacrylate), by the sequential addition of the respective monomers. The obtained block copolymer was characterized by 1H NMR, differential scanning calorimetric and atomic force microscopic studies.