We report the preparation of mixed halide hybrid perovskites (CH3NH3PbI3‑x Br x ) using a solvent-less mechanosynthesis route. Compositional analysis using EDXRF microscopy has confirmed the production of the desired materials. As relative abundance of halogen (x) increases, the tetragonal phase gradually transforms to cubic phase and the band gap tunability of the material is observed.

No abstract

A promising method of micropropagation of Stevia rebaudiana Bertoni has been developed with an aim to increase the biomass, survivability of the plantlets and stevioside production, using chlorocholine chloride (CCC). Microshoots transferred to the MS medium containing different combinations CCC and IBA were found to be most effective in terms of growth pattern, hardening ability of the plantlets and stevioside content, compared to MS medium containing either IBA or CCC. Among other combinations tested, MS medium supplemented with 3 mg/l CCC and 3 mg/l IBA was found most effective in inducing significant changes like reduced shoot length, increased number of roots, higher leaf size, increased biomass and chlorophyll retaining capacity, higher survival percentage and most importantly the elevated stevioside content. Collectively, the major observations of this research indicate that application of CCC in micropropagation of S. rebaudiana Bertoni is a promising approach and has commercial prospects.

Co 3 O 4 with spinel structure shows CO oxidation activity at very low temperature under dry conditions. This study aims at finding the origin of the unique catalytic activity of Co species in Co 3 O 4 based oxides. Although, octahedral site Co 3+ species have been reported to be active in Co 3 O 4 based catalysts, there is no solid explanation as to why Co is so special as compared with other metals like Fe having similar redox states. In this study, mainly, three model spinel catalysts including MnCo 2 O 4 , MnFe 2 O 4 , and CoCr 2 O 4 have been chosen. A detailed analysis of bulk and crystal surface structure, surface properties of the catalysts, and redox properties of the active metals has been performed to understand the unusual catalytic activity. Low-temperature CO oxidation activity decreases in the following order: MnCo 2 O 4 ≫ MnFe 2 O 4 > CoCr 2 O 4 . It indicates that the Co 2+ species in a tetrahedral site (in CoCr 2 O 4 ) remains inactive for lowtemperature catalytic activity, while Co 3+ in an octahedral site (in MnCo 2 O 4 ) is active in Co 3 O 4 based catalysts. This result is corroborated with CoFe 2 O 4 which shows a higher activity than CoCr 2 O 4 , as it has partial occupation of the octahedral site. Fe, being a weak redox metal, does not show low-temperature activity, although crystallite facets of MnCo 2 O 4 and MnFe 2 O 4 catalysts are predominantly exposed in the (100) and (110) lattice planes, which contain quite similar concentrations of Co 3+ and Fe 3+ species in both. The intensity of the redox peak for CO oxidation involving a Co 3+ /Co 2+ couple in MnCo 2 O 4 indicates a highly favorable reaction, while a nonresponsive behavior of Co species is observed in CoCr 2 O 4 . As expected, MnFe 2 O 4 is proven to be weak, giving a much lower intensity of electrochemical CO oxidation. Both CO-and H 2 -TPR indicate a much higher reducibility of Co species in MnCo 2 O 4 as compared with Co species in CoCr 2 O 4 or Fe in MnFe 2 O 4 .

ZnO nanorods are synthesized at room temperature through a simple chemical process without using any template or capping agent.