Aninda J. Bhattacharyya

High lithium storage in micrometre sized mesoporous spherical self-assembly of anatase titania nanospheres and carbon

Composite of anatase titania (TiO2) nanospheres and carbon grown and self-assembled into micron-sized mesoporous spheres via a solvothermal synthesis route are discussed here in the context of rechargeable lithium-ion battery. The morphology and carbon content and hence the electrochemical performance are observed to be significantly influenced by the synthesis parameters. Synthesis conditions resulting in a mesoporous arrangement of an optimized amount carbon and TiO2 exhibited the best lithium battery performance. The first discharge cycle capacity of carbon-titania mesoporous spheres (solvothermal reaction at 150 degrees C at 6 h, calcination at 500 degrees C under air, BET surface area 80 m(2)g(-1)) was 334 mAhg(-1) (approximately 1 Li) at current rate of 0.066 Ag-1. High storage capacity and good cyclability is attributed to the nanostructuring of TiO2 (mesoporosity) as well as due to formation of a percolation network of carbon around the TiO2 nanoparticles. The micron-sized mesoporous spheres of carbon-titania composite nanoparticles also show good rate cyclability in the range (0.066-6.67) Ag-1.

Influence of surface chemistry of mesoporous alumina with wide pore distribution on controlled drug release

The crucial role of the drug carrier surface chemical moeities on the uptake and in vitro release of drug is discussed here in a systematic manner. Mesoporous alumina with a wide pore size distribution (2-7 nm) functionalized with various hydrophilic and hydrophobic surface chemical groups was employed as the carrier for delivery of the model drug ibuprofen. Surface functionalization with hydrophobic groups resulted in low degree of drug loading (approximately 20%) and fast rate of release (85% over a period of 5 h) whereas hydrophilic groups resulted in a significantly higher drug payloads (21%-45%) and slower rate of release (12%-40% over a period of 5 h). Depending on the chemical moiety, the diffusion controlled ( proportional, varianttime(-)(0.5)) drug release was additionally observed to be dependent on the mode of arrangement of the functional groups on the alumina surface as well as on the pore characteristics of the matrix. For all mesoporous alumina systems the drug dosages were far lower than the maximum recommended therapeutic dosages (MRTD) for oral delivery. We envisage that the present study would aid in the design of delivery systems capable of sustained release of multiple drugs.

Improved Lithium Cyclability and Storage in Mesoporous SnO2 Electronically Wired with Very Low Concentrations (≤1 %) of Reduced Graphene Oxide

On the wire: Mesoporous tin dioxide (SnO(2)) wired with very low amounts (≤1 %) of reduced graphene oxide (rGO) exhibits a remarkable improvement in lithium-ion battery performance over bare mesoporous or solid nanoparticles of SnO(2). Reversible lithium intercalation into SnO(2)/SnO over several cycles was demonstrated in addition to conventional reversible lithium storage by an alloying reaction.

Study of ion transport in lithium perchlorate-succinonitrile plastic crystalline electrolyte via ionic conductivity and in situ cryo-crystallography.

Ion transport mechanism in lithium perchlorate (LiClO(4))-succinonitrile (SN), a prototype of plastic crystalline soft matter electrolyte is discussed in the context of solvent configurational isomerism and ion solvation. Contributions of both solvent configurational isomerism and ion solvation are reflected in the activation energy for ion conduction in 0-1 M LiClO(4)-SN samples. Activation energy due to solvent configurational changes, that is, trans-gauche isomerism is observed to be a function of salt content and decreases in presence of salt (except at high salt concentrations, e.g. 1 M LiClO(4)-SN). The remnant contribution to activation energy is attributed to ion-association. The X-ray diffraction of single crystals obtained using in situ cryo-crystallography confirms directly the observations of the ionic conductivity measurements. Fourier transform infrared spectroscopy and NMR line width measurements provide additional support to our proposition of ion transport in the prototype plastic crystalline electrolyte.

Utilizing an ionic liquid for synthesizing a soft matter polymer “gel” electrolyte for high rate capability lithium-ion batteries

A cross-linked polymer “gel” electrolyte obtained from free radical polymerization of a vinyl monomer (acrylonitrile; AN) in a room temperature ionic liquid electrolyte (N,N-methyl butyl pyrrolidinium-bis(trifluoromethanesulphonyl)imide-lithium bis(trifluoromethanesulphonyl)imide; LiTFSI-[Py1,4-TFSI]) for application in high rate capability rechargeable lithium-ion batteries is discussed here. This is a novel alternative compared to the often employed approach of using a molecular liquid as the medium for performing the polymerization reaction. The polymer “gel” electrolytes (AN:Py1,4-TFSI = 0.16–0.18, w/w) showed remarkable compliable mechanical strength and higher thermal stability compared to LiTFSI-[Py1,4-TFSI]. Despite two orders increase in magnitude of viscosity of polymer “gels”, the room temperature ionic conductivity of the “gels” (1.1 × 10−3–1.7 × 10−3 Ω−1 cm−1) were nearly identical to that of the ionic liquid (1.8 × 10−3 Ω−1 cm−1). The present “gel” electrolytes did not exhibit any ageing effects on ionic conductivity similar to the conventional polymer gel electrolytes (e.g. high molecular weight polymer + salt + high dielectric constant molecular solvent). The disorder (ionic liquid) to a relative order (cross-linked polymer electrolyte) transformation does not at all influence the concentration of conducting species. The polymer framework is still able to provide efficient pathways for fast ion transport. Unlike the ionic liquid which is impossible to assemble without a conventional separator in a cell, the polymer “gel” electrolyte could be conveniently assembled without a separator in a Li|lithium iron phosphate (LiFePO4) cell. Compared to the ionic liquid, the “gel” electrolyte showed exceptional cyclability and rate capability (current density: 35–760 mA g−1 with LiFePO4 electronically wired with carbon (amorphous or multiwalled nanotube [MWCNT]).

A crosslinked “polymer–gel” rechargeable lithium-ion battery electrolyte from free radical polymerization using nonionic plastic crystalline electrolyte medium

A cross-linked polymer–gel soft matter electrolyte with superior electrochemical, thermal and mechanical properties obtained from free radical polymerization of vinyl monomers in a semi-solid organic nonionic plastic crystalline electrolyte for application in rechargeable lithium-ion batteries is discussed here.

Ionic conductivity, mechanical strength and Li-ion battery performance of mono-functional and bi-functional (“Janus”) “soggy sand” electrolytes

Influence of dispersion of uniformly sized mono-functional and bi-functional (“Janus”) particles on ionic conductivity of novel “soggy sand” electrolytes and its implications on mechanical strength and lithium-ion battery performance are discussed here.

Green ionothermal synthesis of hierarchical nanostructures of SnS2 and their Li-ion storage properties

Flower-like hierarchical architectures of layered SnS2 have been synthesized ionothermally for the first time, using a water soluble EMIM]BF4 ionic liquid (IL) as the solvent medium. At lower reaction temperatures, the hierarchical structures are formed of few-layered polycrystalline 2D nanosheet-petals composed of randomly oriented nanoparticles of SnS2. The supramolecular networks of the IL serve as templates on which the nanoparticles of SnS2 are glued together by combined effects of hydrogen bonding, electrostatic, hydrophobic and imidazolium stacking interactions of the IL, giving rise to polycrystalline 2D nanosheet-petals. At higher reaction temperatures, single crystalline plate-like nanosheets with well-defined crystallographic facets are obtained due to rapid inter-particle diffusion across the IL. Efficient surface charge screening by the IL favors the aggregation of individual nanosheets to form hierarchical flower-like architectures of SnS2. The mechanistic aspects of the ionothermal bottom-up hierarchical assembly of SnS2 nanosheets are discussed in detail. Li-ion storage properties of the pristine SnS2 samples are examined and the electrochemical performance of the sample synthesized at higher temperatures is found to be comparable to that reported for pristine SnS2 samples in the literature.

Electrochemical sensing and photocatalysis using Ag–TiO2 microwires

AbstractAnatase Ag–TiO2 microwires with high sensitivity and photocatalytic activity were synthesized via polyol synthesis route followed by a simple surface modification and chemical reduction approach for attachment of silver. The superior performance of the Ag–TiO2 composite microwires is attributed to improved surface reactivity, mass transport and catalytic property as a result of wiring the TiO2 surface with Ag nanoparticles. Compared to the TiO2 microwires, Ag–TiO2 microwires exhibited three times higher sensitivity in the detection of cationic dye such as methylene blue. Photocatalytic degradation efficiency was also found to be significantly enhanced at constant illumination protocols and observation times. The improved performance is attributed to the formation of a Schottky barrier between TiO2 and Ag nanoparticles leading to a fast transport of photogenerated electrons to the Ag nanoparticles. Graphical AbstractThe Ag–TiO2 composite micro-wires synthesized via polyol route followed by chemical functionalization approach showed improved current response and hence sensitivity for the detection of dyes. They also showed higher efficiency for photocatalytic degradation of dyes. Their performance remains unaffected for several cycles.

Composite of few-layer MoO3 nanosheets with graphene as a high performance anode for sodium-ion batteries

Identification of an appropriate anode material is one of the major challenges for rechargeable Na-ion batteries. Layered MoO3 is a potential alternative as it can reversibly store large amounts of sodium. However, MoO3 is a poor electronic conductor and undergoes large volume changes during repeated cycling. Ultrathin nanosheets of 1-3 bilayers of MoO3 are synthesized starting from the oxidation of few-layer MoS2 nanosheets. The MoO3 nanosheets are subsequently chemically tagged with optimum amounts of rGO leading to the formation of a 3D MoO3-rGO composite. The MoO3-rGO composite exhibits remarkable electrochemical stability, cyclability and high rate capability over a wide range of operating currents (0.05-1 C). This simple and novel material design strategy of MoO3-rGO provides the most optimum condition for buffering the volume changes during repeated cycling and provides facile pathways for Na-ion and electron transport in MoO3.