Synthesis of Graphene from a Used Battery Electrode

Graphene was produced by electrochemical exfoliation of a used battery electrode. Aqueous solutions of cationic (cetyltrimethylammonium bromide), anionic (sodium dodecyl sulphate), and nonionic (poly vinyl pyrrolidone) surfactants, along with NaCl and combinations of these surfactants with NaCl, were used as the electrolyte. The following observations were made: (I) up to several micrometer sized graphene sheets were produced, (II) the addition of NaCl into the electrolytes significantly enhanced the yield of the exfoliated graphene, (III) the type of surfactant affected the defect density of the exfoliated product, and (IV) electrochemical impedance spectroscopy provided insight into the reason for the changes in the defect density ratio between the graphene samples.

Role of spacer length in interaction between novel gemini imidazolium surfactants and Rhizopus oryzae lipase

An insight into the effects of new ionic liquid-type gemini imidazolium cationic surfactants on the structure and function of the lipases is of prime importance for their potential application. Changes in the activity, stability and structure of Rhizopus ouzae lipase in the presence of novel gemini surfactants, C-16-3-C(16)im]Br-2 and C-16-12-C(16)im]Br-2 were probed in the present study. Surfactant with shorter spacer length, C-16-3-C(i6)im]Br-2 was found to be better in improving the hydrolytic activity and thermal stability of the lipase. For both the surfactants, activation was concentration dependent. CD spectroscopy results showed a decrease in a-helix and an increase in beta-sheet content in the presence of these surfactants. A higher structural change observed in presence of C-16-12-C(16)im]Br-2 correlated with lower enzyme activity. Isothermal titration calorimetric studies showed the binding to be spontaneous in nature based on sequential two site binding model. The forces involved in binding were found to differ for the two surfactants proving that the spacer length is an important factor which governs the interaction. These surfactants could be used as promising components both in enzyme modification and media engineering for attaining the desired goals in biocatalytic reactions. (C) 2015 Elsevier B.V. All rights reserved.

Heterostructure composites of rGO/GeO2/PANI with enhanced performance for Li ion battery anode material

A novel solvothermal method has been used for the synthesis of porous ellipsoidal GeO2 particles with oleic acid and oleylamine as solvent and co-surfactant, respectively and its performance has been studied as an anode material for Li ion battery applications. The presence of highly hydrophobic oleic acid and oleylamine on the surface of the as synthesized sample imparts a detrimental effect on its performance. Although removal of the capping agents with glacial acetic acid improves the performance to some extent, a drastic enhancement in both the specific capacity and cycling stability is observed when the nanoparticles are wrapped with rGO/PANI composites at low temperature. (C) 2015 Elsevier B.V. All rights reserved.

Modulation of Buckling Dynamics in Nanoparticle Laden Droplets Using External Heating

Dynamics of contact free (levitated) drying of nanofluid droplets is ubiquitous in many application domains ranging from spray drying to pharmaceutics. Controlling the final morphology (macro to micro scales) of the dried out sample poses some serious challenges. Evaporation of solvent and agglomeration of particles leads to porous shell formation in acoustically levitated nanosilica droplets. The capillary pressure due to evaporation across the menisci at the nanoscale pores causes buckling of the shell which leads to ring and bowl shaped final structures. Acoustics plays a crucial role in flattening of droplets which is a prerequisite for initiation of buckling in the shell: Introduction of mixed nanocolloids (sodium dodecyl sulfate + nanosilica) reduces evaporation rate, disrupts formation of porous shell, and enhances mechanical strength of the shell, all of which restricts the process of buckling. Although buckling is completely arrested in such surfactant added droplets, controlled external heating using laser enhances evaporation through the pores in the shell due to thermally induced structural changes and rearrangement of SDS aggregates which reinitializes buckling in such droplets, Furthermore, inclusion of anilinium hydrochloride into the nanoparticle laden droplets produces ions which adsorb and modify the morphology of sodium dodecyl sulfate crystals and reinitializes buckling in the shell (irrespective of external heating conditions). The kinetics of buckling is determined by the combined effect of morphology of the colloidal particles, particle/aggregate diffusion rate within the droplet, and the rate of evaporation of water. The buckling dynamics leads to cavity formation which grows subsequently to yield final structures with drastically different morphological features. The cavity growth is controlled by evaporation through the nanoscate pores and exhibits a universal trend irrespective of heating rate and nanoparticle type.