Shreyasi Chattopadhyay

Electrochemical energy storage in montmorillonite K10 clay based composite as supercapacitor using ionic liquid electrolyte.

Exploring new electrode materials is the key to realize high performance energy storage devices for effective utilization of renewable energy. Natural clays with layered structure and high surface area are prospective materials for electrical double layer capacitors (EDLC). In this work, a novel hybrid composite based on acid-leached montmorillonite (K10), multi-walled carbon nanotube (MWCNT) and manganese dioxide (MnO2) was prepared and its electrochemical properties were investigated by fabricating two-electrode asymmetric supercapacitor cells against activated carbon (AC) using 1.0M tetraethylammonium tetrafluroborate (Et4NBF4) in acetonitrile (AN) as electrolyte. The asymmetric supercapacitors, capable of operating in a wide potential window of 0.0-2.7V, showed a high energy density of 171Whkg(-1) at a power density of ∼1.98kWkg(-1). Such high EDLC performance could possibly be linked to the acid-base interaction of K10 through its surface hydroxyl groups with the tetraethylammonium cation [(C2H5)4N(+) or TEA(+)] of the ionic liquid electrolyte. Even at a very high power density of 96.4kWkg(-1), the cells could still deliver an energy density of 91.1Whkg(-1) exhibiting an outstanding rate capability. The present study demonstrates for the first time, the excellent potential of clay-based composites for high power energy storage device applications.

Extremely fast Au–Ag alloy–dealloy associated reversible plasmonic modifications in SiO2 films

We report a unique alloy–dealloy phenomenon of Au–Ag nanoparticles inside SiO2 films with clear plasmonic modifications between the absorptions of Ag (∼415 nm) and Au (∼524 nm). An Au–Ag (1 : 1) alloy nanoparticles (average size: 4.5 nm)-incorporated transparent SiO2 film is prepared on a glass substrate using mercaptosuccinic acid capped Au nanoparticles and Ag+ co-doped hybrid sol. The Au–Ag (1 : 1) alloy-originated plasmon band (465 ± 1 nm) is gradually red-shifted with increasing temperature (50 to 400 °C) due to the partial oxidation of Ag, causing a systematic modification of the alloy composition. The 1 : 1 alloy, however, reverted very quickly, showing its original plasmon band in the presence of a small amount of H2 due to re-reduction of the oxidized Ag and instantaneous re-alloying. During the Ag oxidation, the Si–OH groups associated with the embedded SiO2 matrix exchange Ag+ to form Ag–O–Si linkages; they subsequently release Ag very quickly in H2 and dissolve again into the parent alloy. As a result, the films exhibit reversible and rapid optical changes while cycling in 0.1% to 1% H2 (balance Ar) and air in the temperature range from 50 to 400 °C. This unique reversible alloy–dealloy phenomenon clearly demonstrates the mechanism of plasmonic modification associated with Au–Ag nanoparticles embedded in the sol–gel SiO2 film matrix.

In Situ Mg/MgO-Embedded Mesoporous Carbon Derived from Magnesium 1,4-Benzenedicarboxylate Metal Organic Framework as Sustainable Li–S Battery Cathode Support

Development of advanced carbon cathode support with the ability to accommodate high sulfur (S) content as well as effective confinement of the sulfur species during charge–discharge is of great importance for sustenance of Li–S battery. A facile poly(vinylpyrrolidone)-assisted solvothermal method is reported here to prepare Mg–1,4-benzenedicarboxylate metal organic framework (MOF) from which mesoporous carbon is derived by thermal treatment, where the hexagonal sheetlike morphology of the parent MOF is retained. Existence of abundant pores of size 4 and 9 nm extended in three dimensions with zigzag mazelike channels helps trapping of S in the carbon matrix through capillary effect, resulting in high S loading. When tested as a cathode for lithium–sulfur battery, a reversible specific capacity of 1184 mAh g–1 could be achieved at 0.02 C. As evidenced by X-ray photoelectron spectroscopy, in situ generated Mg in the carbon structure enhances the conductivity, whereas MgO provides support to S immobilization through chemical interactions between Mg and sulfur species for surface polarity compensation, restricting the dissolution of polysulfide into the electrolyte, the main cause for the “shuttle phenomenon” and consequent capacity fading. The developed cathode shows good electrochemical stability with reversible capacities of 602 and 328 mAh g–1 at 0.5 and 1.0 C, respectively, with retentions of 64 and 67% after 200 cycles. The simple MOF-derived strategy adopted here would help design new carbon materials for Li–S cathode support.

Fabrication of a cubic zirconia nanocoating on a titanium dental implant with excellent adhesion, hardness and biocompatibility

A crystalline cubic zirconia (ZrO2) nanocoating was fabricated in situ on commercially pure titanium metal (cpTi) as a superior dental implant with enhanced biocompatibility. The crystallinity of the nanocoating was achieved at a moderately lower annealing temperature (350 °C) in air using a simple sol–gel method applying a successive layer-by-layer dip-coating technique. Such a procedure facilitates the growth of cubic phase zirconia without noticeable deterioration of the metallic Ti. The bioactivity and biocompatibility of this ZrO2 coated cpTi (Z-cpTi) were assessed in terms of apatite precipitation through immersion in simulated body fluid, and cell proliferation, respectively for several periods of time. The newly designed Z-cpTi showed unique apatite forming ability, better biocompatibility and tissue attachment properties, and is expected to reduce inflammatory response compared to the bare Ti implants. Moreover, the chemical inertness, corrosion and wear resistant properties, high strength, and appearance of this ZrO2 nanocoating suggest the probable expediency of Z-cpTi as an advanced oral implant for long-standing performance.

Influence of C–S interactions on the electrochemical performance of –COOH functionalized MWCNT/S composites as lithium-sulfur battery cathode

Effective trapping of polysulfides within the carbon cathode host strongly depends on intrinsic C–S interactions. We report herein a systematic study of the influence of S-loading process on C–S interactions in MWCNT/S composites prepared by three commonly used industry-friendly methods, namely, mechanical solid-state mixing, infiltration method from a solution of S in CS

Electrospun TiO2–rGO Composite Nanofibers with Ordered Mesopores by Molecular Level Assembly: A High Performance Anode Material for Lithium-Ion Batteries

_{2}

Low Temperature Fabrication of Photoactive Anatase TiO2 Coating and Phosphor from Water–Alcohol Dispersible Nanopowder

2, and chemical deposition by disproportionation reaction of sodium sulfide and sodium thiosulfate. FESEM and TEM studies reveal strikingly different morphologies of the resulting MWCNT/S composites. XPS and Raman studies indicate different extents of recovery of