02382nas a2200241 4500008004100000022001400041245016300055210006900218260000800287300001200295490000800307520150800315100002301823700002401846700001701870700001801887700002701905700001901932700001701951700002401968700002101992856012702013 2019 eng d a0008-622300aIn-situ generated Mn3O4-reduced graphene oxide nanocomposite for oxygen reduction reaction and isolated reduced graphene oxide for supercapacitor applications0 aInsitu generated Mn3O4reduced graphene oxide nanocomposite for o cDEC a285-2910 v1543 a

We have generated in situ nanocomposite of Mn3O4 and reduced graphene oxide (rGO) upon employing wet-chemical reduction of graphene oxide (GO) by Mn(II) salt as mild-reducing agent for the first time and examined the oxygen reduction reaction (ORR) activity in 0.1 M KOH electrolyte. The half-wave potential (E-1/2) of the nanocomposite catalyst (20% Mn3O4-rGO/C) was found to be around -0.153 V which is only similar to 87 mV negative from the commercially available catalyst (20% Pt/C). Remarkably, after 5000 linear sweep voltammetry cycles the E-1/2 shifted marginally by 20 mV; and the number of electrons transferred during ORR was estimated to be close to 4. Such an efficient electrocatalytic performance of the nanocomposite was primarily attributed to the synergistic interaction between Mn3O4 and rGO. The fabricated all-solid-state supercapacitor of rGO (extracted from the nanocomposite) in aqueous polyvinyl alcohol-sulfuric acid (PVA-H2SO4) gel polymer electrolyte (GPE) showed C-s value of similar to 310 F/g at a current density of 1 A/g along with long durability (10,000 charge-discharge cycles). All-solid-state flexible rGO supercapacitor exhibited high-flexibility and excellent durability (30,000 cycles with 100% retention of C-s). Our results provide an enormous opportunity in designing transition metal oxides decorated semiconducting reduced graphene oxide nanocomposite platforms for various electrochemical applications. (C) 2019 Elsevier Ltd. All rights reserved.

1 aJha, Plawan, Kumar1 aKashyap, Varchaswal1 aGupta, Kriti1 aKumar, Vikash1 aDebnath, Anil, Krishna1 aRoy, Debashree1 aRana, Shammi1 aKurungot, Sreekumar1 aBallav, Nirmalya uhttps://library.ncl.res.in/content/situ-generated-mn3o4-reduced-graphene-oxide-nanocomposite-oxygen-reduction-reaction-and02422nas a2200193 4500008004100000022001400041245008600055210006900141260000800210300001600218490000800234520177600242100001702018700001702035700001902052700002202071700002102093856011402114 2020 eng d a1932-744700aIntegrating structurally perfect s=1/2 kagome-lattice with reduced graphene oxide0 aIntegrating structurally perfect s12 kagomelattice with reduced  cSEP a19753-197590 v1243 a

S = 1/2 kagome-lattice hydroxychlorides are promising candidates for realizing the elusive quantum spin liquid (QSL) state. Herbertsmithite [Cu3Zn(OH)(6)Cl-2], a naturally occurring hydroxychloride mineral from the class of atacamites {[Cu-4-xMx(OH)(6)X-2] where M = Zn, Cu, Co, Ni and X = Cl, Br, I}, is one of the most appealing systems to study the QSL state because of the presence of a structurally perfect S = 1/2 kagome-lattice. It is an electrical insulator. However, realizing phase-pure herbertsmithite without imposing harsh reaction conditions remained synthetically challenging. In this work, for the first time, we have synthesized phase-pure herbertsmithite as well as its structural analogue paratacamite, [ZnxCu4-x(OH)(6)Cl-2; 0.33 = x < 1], at ambient reaction conditions. Furthermore, taking graphene oxide (GO) as an additional precursor in the reaction mixture, we have successfully integrated phase-pure crystallites of herbertsmithite (H) and paratacamite (P) with nanosheets of semiconducting and diamagnetic reduced graphene oxide (rGO) by in situ oxidation-reduction reaction. The isolated H-rGO and P-rGO systems were found to be magnetic semiconductors inheriting strong spin frustration from H and P, and semiconductivity from rGO. The H-rGO system in particular exhibited negative Seebeck coefficient (n-type semiconductor) with a thermoelectric power factor of 0.1 mu W center dot m(-1)center dot K-2 at 400 K. We anticipate the simple chemical principles outlined in this work to be useful for studying a variety of complex QSLs including electron doping. Also, semiconducting and rather unconventional materials of such metal oxochlorides with rGO isolated here need further exploration in view of thermoelectric applications.

1 aGupta, Kriti1 aDadwal, Arun1 aNinawe, Pranay1 aJoy, Pattayil, A.1 aBallav, Nirmalya uhttps://library.ncl.res.in/content/integrating-structurally-perfect-s12-kagome-lattice-reduced-graphene-oxide02192nas a2200217 4500008004100000022001400041245012900055210007000184260000800254300001400262490000700276520142900283100001601712700001901728700001501747700001901762700001801781700002101799700002101820856013301841 2024 eng d a0020-166900aIntertwining of localized (d) and delocalized (π) spins in magnetically frustrated two-dimensional metal-organic frameworks0 aIntertwining of localized d and delocalized π spins in magnetica cFEB a3675-36810 v633 a

Two-dimensional metal-organic frameworks (2D MOFs) are emerging as a new class of multifunctional materials for diversified applications, although magnetic properties have not been widely explored. The metal ions and organic ligands in some of the 2D MOFs are arranged in the well-known Kagome lattice, leading to geometric spin frustration. Hence, such systems could be the potential candidates to exhibit an exotic quantum spin liquid (QSL) state, as was observed in Cu-3(HHTP)(2) (HHTP = hexahydroxytriphenylene), with no magnetic transition down to 38 mK. Hereto, we have investigated the spin intertwining in a bimetallic 2D MOF system, M-3(HHTP)(2) (M = Cu/Zn)(,) arising from the localized (d-electron) and delocalized (pi-electron) S = 1/2 spins from the Cu(II) ions and the HHTP radicals, respectively. The origin of the spin frustration (down to 5K) was critically examined by varying the metal composition in bimetallic systems, CuxZn3-x(HHTP)(2) (x = 1, 1.5, 2), containing both S = 1/2 and S = 0 spins. Additionally, to gain a deeper understanding, we studied the spin interaction in the pristine Zn-3(HHTP)(2) system containing only S = 0 Zn(II) ions. In view of the quantitative estimate of the localized and delocalized spins, the d-pi spin correlation appears essential in understanding the unusual magnetic and/or other physical properties of such hybrid organic-inorganic 2D crystalline solids

1 aUgale, Ajay1 aNinawe, Pranay1 aJain, Anil1 aSangole, Mayur1 aMandal, Rimpa1 aSingh, Kirandeep1 aBallav, Nirmalya uhttps://library.ncl.res.in/content/intertwining-localized-d-and-delocalized-%CF%80-spins-magnetically-frustrated-two-dimensional