Crosslinked hydrogel-derived carbons activated by trace amounts of aqueous potassium carbonate for carbon dioxide adsorption.

A new method for green synthesis of activated carbon using chitosan-based hydrogel precursors is reported. Chitosan-based hydrogel materials are designed to absorb trace amounts of non-toxic and non-corrosive activating agent K2CO3 from dilute aqueous solution. The K2CO3 impregnated hydrogels are further freeze-dried and converted to activated carbons with tuneable pore structure by a single-step pyrolysis. Activated carbon with highest pore volume of 0.76 cm3/g and surface area of 2026 m2/g is obtained by using K2CO3 as low as 0.23 g per gram of chitosan hydrogel. It can adsorb maximum CO2 of 4.2 mmol/g at 25 °C and 1 bar. This study demonstrates that biopolymer hydrogels impregnated with trace amounts of K2CO3 are excellent precursor materials to design high surface area carbons for CO2 capture.

Design and synthesis of mixed-ligand architectured Zn-based coordination polymers for energy storage.

In this work, a Zn-based 1D coordination polymer [Zn(H2O)(C10H8N2)(C9H4O6)]·2H2O, denoted as Zn-CP, has been designed and synthesized by a slow diffusion mediated multi-ligand approach at room temperature. The Zn-CP material is characterized by single crystal analysis and other spectroscopic methods. A heteronanocomposite (Zn-CP/rGO) is prepared by mixing Zn-CP with conductive rGO nanosheets through ultrasonication and is used as a battery-type material for supercapacitor application. The Zn-CP/rGO hybrid nanostructure material delivers a specific capacity of 188.5 C g-1 (377 F g-1) at a current density of 1 A g-1 with good cycling stability (85% capacity retention upon 6000 charge-discharge cycles at 6 A g-1) and a high coulombic efficiency of 97% while a pure Zn-CP electrode delivers only 135.5 C g-1 (261 F g-1) at the same current density. Furthermore, a hybrid supercapacitor device (Zn-CP/rGO∥AC) is fabricated, which delivers a maximum energy density of 13.3 W h kg-1 and a power density of 7446 W kg-1. The suitable power density and long standing endurance of the hybrid device show promising potential for battery-type supercapacitor application.

Design of ZIF-67 nanoflake derived NiCo-LDH/rGO hybrid nanostructures for aqueous symmetric supercapattery application under alkaline condition.

Well-defined polyhedral ZIF-67 metal-organic frameworks (MOFs) are usually synthesized using methanol as solvent. In this work, methanol is replaced with deionized water as a solvent to synthesize ZIF-67 MOFs with unique nanoflake morphology. The ZIF-67 nanoflakes are synthesized directly byin situmethod on reduced graphene oxide (rGO) to obtain ZIF-67/rGO-xprecursors which are further transformed into NiCo-layered double hydroxide nanocomposites (NiCo-LDH/rGO-x,x = 10, 30, 50 and 90 mg of rGO). The NiCo-LDH/rGO-xnanostructured composites are found to be excellent materials for battery type supercapacitor (supercapattery) applications. Among these samples, the NiCo-LDH/rGO-30 composite gives maximum specific capacity of 829 C g-1(1658 F g-1) at a current density of 1 A g-1and high rate capability. The as fabricated 2-electrode symmetric Swagelok deviceNiCo-LDH/rGO-30NiCo-LDH/rGO-30delivered a high energy density of 49.2 Wh kg-1and a power density of 4511 W kg-1, and enabled us to glow red, blue and white LED bulbs using three coin cells. The device can show good capacity retention even after 3000 continuous charge-discharge cycles. The NiCo-LDH/rGO-30 composite,in situderived from ZIF-67 MOF in combination with optimal amount of rGO, is an excellent material to deliver both high energy density and high power density in supercapattery devices.

The corrosion inhibition of stainless steel by ferrocene-polyoxometalate hybrid molecular materials - experimental and first principles studies.

The hybrid molecular materials [Fe(C5H5)2]3[PW12O40]·(H2O)4 and [Fe(C5H5)2]3[PMo12O40]·(H2O)6, denoted respectively as FcPW and FcPMo, are synthesized via a co-precipitation method under acidic conditions (pH: ∼2-3). The molecular properties of these compounds are investigated via various analytical methods. UV-vis diffuse reflectance and photoluminescence studies confirm that these compounds are charge-transfer salts. Stainless steel plates (SS, 316 grade) coated with these hybrid compounds and dipped in 0.5 M H2SO4 and Ringer's solutions show significantly inhibited corrosion. The corrosion inhibition properties of these materials are studied via weight loss, electrochemical impedance spectroscopy, and potentiodynamic polarization studies. The reproducibility of the corrosion inhibition results is ensured via repeat measurements, and error values are reported. The surfaces of the corroded steel plates are examined via scanning electron and atomic force microscopy techniques. It is found that the corrosion is of uniform type. The Tafel extrapolation method shows that the inhibition efficiency is 74% for SS@FcPMo and 65% for SS@FcPW. The corrosion inhibition mechanism is explained based on the redox nature of the hybrid materials. The experimental results are corroborated through computational studies carried out using a first principles approach with the optimized geometries and frontier molecular orbitals of the hybrid molecular materials.

Facile hydrothermal synthesis of urchin-like cobalt manganese spinel for high-performance supercapacitor applications.

A facile hydrothermal method has been adopted to synthesize the spherical urchin-like hierarchical CoMn2O4 nanostructures on the nickel foam substrate. The as-synthesized urchins have an average diameter of ∼3-7µm with numerous self-assembled nanoneedles grown radically in all the directions from its center with a huge void space between them. For comparison, we have also studied the electrochemical as well as other physicochemical properties of parent simple Co3O4 and MnO2 materials, which were also synthesized by a similar hydrothermal method. The results show that CoMn2O4 electrode displayed significantly higher (more than two times) areal and specific capacitances compared to Co3O4 and MnO2 electrodes with excellent capacitance retention and Coulombic efficiency. Moreover, the energy and power densities obtained for CoMn2O4 electrode are also far higher than the parent Co3O4 and MnO2. Long-term cycling tests of CoMn2O4 electrode shows the improved capacitance with high rate capability up to 6000 cycles indicating their potential for high performance supercapacitor applications. The better electrochemical performance of CoMn2O4 electrode can be attributed to the smart urchin-like nanostructures, which has several advantages like, more electroactive sites for faradic reactions emerging from the two metal ions, higher electronic/ionic conductivity and fast electrolyte transportation kinetics promoted by unique morphology.

Charge storage, electrocatalytic and sensing activities of nest-like nanostructured Co3O4.

We synthesized nanostructured Co3O4 samples using anionic (SDS), cationic (CTAB) and nonionic (Triton X-100) surfactant molecules in hydrothermal conditions and subsequent calcination. This approach facilitates the synthesis of porous Co3O4 material with bundle-like-sheet, nest-like and flake-like morphologies with specific surface areas in the range of 50-77m2g-1. Among these materials, the nest-like nanostructured Co3O4 material has unique pore architecture, larger pore volume, low solution and charge transfer resistance, and found to be an active material for charge storage, electrocatalytic and sensing applications. The specific capacitance value of the nest-like Co3O4 is 404Fg-1 at a current density of 2Ag-1 with 80% specific capacitance retention. The electrocatalytic oxidation of methanol occurs at lower onset potential on this material with good electrochemical stability. It has good sensing ability for glucose with high sensitivity of 929µAcm-2mM-1, fast response time of ∼0.5s and detection limit as low as ∼1µM. These results show that the nest-like nanostructured Co3O4 material is a versatile candidate for various applications.

A Vanadium(V) Oxide Nanorod Promoted Platinum/Reduced Graphene Oxide Electrocatalyst for Alcohol Oxidation under Acidic Conditions.

A Pt-V2 O5 /rGO ternary hybrid electrocatalyst was designed by using active vanadium(V) oxide (V2 O5 ) nanorods and reduced graphene oxide (rGO) components. The V2 O5 nanorods were synthesized by a simple polyol-assisted solvothermal method and were incorporated uniformly onto rGO sheets by intermittent microwave heating. Subsequently, Pt nanoparticles (2-3 nm in size) were deposited over the V2 O5 /rGO composite by the conventional polyol reflux method. The electrocatalytic performance of the Pt-V2 O5 /rGO ternary hybrid and bare Pt/rGO catalysts towards the oxidation of simple alcohols was evaluated in acidic media. The ternary hybrid catalyst exhibited higher electrocatalytic activity than bare Pt/rGO and also showed good stability. The higher electrocatalytic activity of the Pt-V2 O5 /rGO ternary hybrid was attributed to a synergistic effect among the Pt, V2 O5 , and rGO components. In addition, oxygen-containing species, such as OH groups, were generated on V2 O5 at lower potentials. These groups were able to scavenge intermediate species such as COads on the Pt surfaces and helped to regenerate the active sites on the Pt surface more effectively for the routine alcohol oxidation reaction.

Vanadium pentoxide nanochains for high-performance electrochemical supercapacitors.

We have synthesized unique hierarchical one dimensional (1D) nanochains of V2O5 by employing simple hydrothermal method using cetyltrimethylammonium bromide (CTAB) as a soft template. The electrochemical performance of resulting V2O5 electrode materials was evaluated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy techniques. The V2O5 nanochains (V2O5-ctab) show maximum specific capacitance of 631 F g(-1) at a current density of 0.5 A g(-1) and retain 300 F g(-1) even at high current density of 15 A g(-1). In addition the V2O5 nanochains show good cyclic stability with 75% capacitance retention after 1200 charge-discharge cycles. The order of specific capacitance is commercial bulk-V2O5 (160 F g(-1))

Occurrence of insecticide residues in selected crops and natural resources.

Pesticide residue monitoring was taken up at Kothapally and Enkepally villages of Ranga Reddy district, Andhra Pradesh in food crops (rice, maize, pigeonpea), vegetables (tomato and brinjal), cotton besides soil and water during 2008-2009 seasons. Of the 80 food crop and cotton samples, only two rice grain samples (3 %) showed beta endosulfan residues and two (3 %) out of 80 soil samples of food crops and cotton showed alpha and beta endosulfan residues. Out of 75 tomato samples, 26 (35 %) were contaminated and 4 % had residues above maximum residue limit (MRLs). Out of the 50 soil samples from tomato fields, 13 (26 %) contained residues. Among the 80 brinjal samples, 46 (56 %) contained residues and 4 % of samples had residues above MRLs. Only 13 % of the soil samples from brinjal fields were contaminated. Water samples found free from residues. In general the incidence of residues was below MRL in food crops.

Isolation and characterization of baculoviruses from three major lepidopteran pests in the semi-arid tropics of India.

Baculoviruses were isolated from three major lepidopteran pests, Helicoverpa armigera, Spodoptera litura and Amsacta albistriga in the semi-arid tropics during natural epizootic conditions at ICRISAT fields, Patancheru, Andhra Pradesh, India. Biological, morphological and biochemical analysis identified these isolates as Nucleopolyhedroviruses (NPVs). Scanning electron microscopy of the occlusion bodies (OBs) purified from diseased larvae revealed polyhedral particles of size approximately 0.5-2.5 µm [Helicoverpa armigera Nucleopolyhedrovirus (HearNPV)], 0.9-2.92 µm [Spodoptera litura Nucleopolyhedrovirus (SpltNPV)] and 1.0-2.0 µm [Amsacta albistriga Nucleopolyhedrovirus (AmalNPV)] in diameter. Transmission electron microscopy of thin sections of OBs of the three isolates revealed up to 5-8 multiple bacilliform shaped particles packaged within a single viral envelope. The dimensions of these particles were 277.7 × 41.6 nm for HearNPV, 285.7 × 34.2 nm for SpltNPV and 228.5 × 22.8 nm for AmalNPV. Each of HearNPV and AmalNPV contained up to 6 nucleocapsids and SpltNPV contained up to 7 nucleocapsids per envelope. The estimated molecular weights of the purified OB (polyhedrin) protein of the three NPVs were 31.29-31.67 kDa. Virus yield (OBs/larva) was 5.18 ± 0.45 × 10(9) for HearNPV, 5.73 ± 0.17 × 10(9) for SpltNPV and 7.90 ± 0.54 × 10(9) for AmalNPV. The LC50 values of various NPVs against 2nd and 3rd instar larvae indicated 2.30 × 10(4) and 1.5 × 10(5) OBs/ml for HearNPV, 3.5 × 10(4) and 2.4 × 10(5) OBs/ml for SpltNPV and 5.6 × 10(4) and 3.96 × 10(5) OBs/ml for AmalNPV. The lethal time required to cause 50% mortality (LT50) for these three species were also defined. This study has shown that the NPVs infecting three major lepidopteran pests in India are multiple NPVs, and they have good potential to use as biocontrol agents against these important pests.