https://libjncir.jncasr.ac.in/xmlui/handle/10572/1542 2026-04-04T05:39:41Z 2026-04-04T05:39:41Z Lingampalli, S. R. Dileep, K. Datta, Ranjan Gautam, Ujjal K. https://libjncir.jncasr.ac.in/xmlui/handle/10572/2530 2017-02-21T10:25:25Z 2014-01-01T00:00:00Z

Tuning the Oxygen Release Temperature of Metal Peroxides over a Wide Range by Formation of Solid Solutions Lingampalli, S. R.; Dileep, K.; Datta, Ranjan; Gautam, Ujjal K. Metal peroxides, with a labile peroxy bond, constitute a distinct class of inorganic compounds that can generate singlet oxygen species and works as versatile reagents in many important industrial processes such as in polymer initiation reactions. Even after several decades after their discovery, the number of metal peroxides yet is few and their utility is severely limited by the corresponding decomposition temperatures (T-dec), which cannot be tuned to suit the most desirable condition for a particular reaction. One way of overcoming this would have been to obtain solid solutions of two peroxides with different decomposition temperatures. Surprisingly, in contrast to the vast majority of extended solids such as the oxide, hydroxide, and perovskite families, solid solutions of metal peroxides have remained so far nonexistent. Here, we explore and demonstrate that peroxides of Zn and Mg, ZnO2 (T-dec similar to 200 degrees C), and MgO2 (T-dec = 300 degrees C) can form solid solutions in the entire solubility range. Importantly, the decomposition temperatures of the solid solutions lie between that for the constituent phases and changes the composition systematically. These findings provide the first genuine chemical system that can potentially be tuned to decompose at different predesigned temperatures to generate reactive oxygen species. Restricted Access

2014-01-01T00:00:00Z Nityashree, N. Gautam, Ujjal K. Rajamathi, Michael https://libjncir.jncasr.ac.in/xmlui/handle/10572/2529 2017-02-21T10:25:23Z 2014-01-01T00:00:00Z

Synthesis and thermal decomposition of metal hydroxide intercalated saponite Nityashree, N.; Gautam, Ujjal K.; Rajamathi, Michael Chlorite-like nanocomposites in which the anionic clay layers are intercalated between the cationic clay layers were prepared by mixing an aqueous colloidal dispersion of exfoliated layers of copper hydroxysalt or alpha-cobalt hydroxide with an aqueous colloidal dispersion of exfoliated saponite layers. The nanocomposites showed a different thermal decomposition behavior compared to the parent layered solids. The thermal decomposition of the chlorite-like nanocomposites resulted in nanocomposites in which metal oxide (CuO/Co3O4) nanoparticles are uniformly distributed in saponite matrix. The particle size of the oxide nanoparticles in the nanocomposite could be varied by varying the decomposition parameters such as the temperature and duration of decomposition. (C) 2013 Elsevier B.V. All rights reserved. Restricted Access

2014-01-01T00:00:00Z Nethravathi, C. Rajamathi, Catherine R. Rajamathi, Michael Wang, Xi Gautam, Ujjal K. Golberg, Dmitri Bando, Yoshio https://libjncir.jncasr.ac.in/xmlui/handle/10572/2526 2017-02-21T10:25:27Z 2014-01-01T00:00:00Z

Cobalt Hydroxide/Oxide Hexagonal Ring-Graphene Hybrids through Chemical Etching of Metal Hydroxide Platelets by Graphene Oxide: Energy Storage Applications Nethravathi, C.; Rajamathi, Catherine R.; Rajamathi, Michael; Wang, Xi; Gautam, Ujjal K.; Golberg, Dmitri; Bando, Yoshio The reaction of beta-Co(OH)(2) hexagonal platelets with graphite oxide in an aqueous colloidal dispersion results in the formation of beta-Co(OH)(2) hexagonal rings anchored to graphene oxide layers. The interaction between the basic hydroxide layers and the acidic groups on graphene oxide induces chemical etching of the hexagonal platelets, forming beta-Co(OH)(2) hexagonal rings. On heating in air or N-2, the hydroxide hybrid is morphotactically converted to porous Co3O4/CoO hexagonal ring graphene hybrids. Porous NiCo2O4 hexagonal ring graphene hybrid is also obtained through a similar process starting from beta-Ni0.33Co0.67(OH)(2) platelets. As electrode materials for supercapacitors or lithium-ion batteries, these materials exhibit a large capacity, high rate capability, and excellent cycling stability. Restricted Access

2014-01-01T00:00:00Z Rana, Moumita Bharathanatha, R. R. Gautam, Ujjal K. https://libjncir.jncasr.ac.in/xmlui/handle/10572/2527 2017-02-21T10:25:30Z 2014-01-01T00:00:00Z

Kinetically stabilized C-60-toluene solvate nanostructures with a discrete absorption edge enabling supramolecular topotactic molecular exchange Rana, Moumita; Bharathanatha, R. R.; Gautam, Ujjal K. Nanosized fullerene solvates have attracted widespread research attention due to recent interesting discoveries. A particular type of solvate is limited to a fixed number of solvents and designing new solvates within the same family is a fundamental challenge. Here we demonstrate that the hexagonal closed packed (HCP) phase of C-60 solvates, formed with m-xylene, can also be stabilized using toluene. Contrary to the notion on their instability, these can be stabilized from minutes up to months by tuning the occupancy of solvent molecules. Due to high stability, we could record their absorption edge, and measure excitonic life-time, which has not been reported for any C-60 solvate. Despite being solid, absorbance spectrum of the solvates is similar in appearance to that of C-60 in solution. A new absorption band appears at 673 nm. The fluorescence lifetime at 760 nm is similar to 1.2 ns, suggesting an excited state unaffected by solvent-C-60 interaction. Finally, we utilized the unstable set of HCP solvates to exchange with a second solvent by a topotactic exchange mechanism, which rendered near permanent stability to the otherwise few minutes stable solvates. This is also the first example of topotactic exchange in supramolecular crystal, which is widely known in ionic solids. (C) 2014 Elsevier Ltd. All rights reserved. Restricted Access

2014-01-01T00:00:00Z