02422nas 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-oxide01803nas a2200241 4500008004100000022001400041245011400055210006900169260000900238300001200247490000800259520100700267100001701274700001901291700001501310700001701325700001301342700001801355700001801373700002201391700002101413856012701434 2021 eng d a2469-995000aPossible electron doping of geometrically perfect spin-1/2 kagome-lattice barlowite by reduced graphene oxide0 aPossible electron doping of geometrically perfect spin12 kagomel cSEP  aL1004180 v1043 aDoping of quantum spin liquid (QSL) insulators by electron or hole leads to intriguing phase transitions to metallic and superconducting states. The barlowite family with geometrically perfect S = 1/2 kagome planes and tunable interkagome coupling is an emerging platform to realize spin-ordered, valence bond crystal, QSL states. Theoretical investigations on electron doping revealed localized states in the band gap of barlowite unlike metallicity in cuprate (Nd2CuO4). We present successful anchoring of phase-pure barlowite crystallites onto reduced graphene oxide (rGO). The resulting barlowite-rGO system was found to be an electrical semiconductor with Arrhenius activation energy of 0.07 eV. Semiconducting properties of the barlowite-rGO system were further modulated with retention of structural integrity. We have attributed such a transformation of electrical transport response to plausible electron doping thereby making charge-doping experiments on barlowite and its analogs propitious.1 aGupta, Kriti1 aNinawe, Pranay1 aJain, Anil1 aDadwal, Arun1 aAnas, M.1 aMalik, V., K.1 aYusuf, S., M.1 aJoy, Pattayil, A.1 aBallav, Nirmalya uhttps://library.ncl.res.in/content/possible-electron-doping-geometrically-perfect-spin-12-kagome-lattice-barlowite-reduced02192nas 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-dimensional02272nas a2200289 4500008004100000022001400041245009400055210006900149260000900218490000700227520134800234653003101582653002001613653002701633653001601660653002101676100001901697700001501716700001901731700001501750700001601765700002101781700002101802700002101823700002101844856011701865 2024 eng d a0947-653900aRobust spin liquidity in 2D metal-organic framework Cu3 (HHTP)2 with S=1/2 kagome lattice0 aRobust spin liquidity in 2D metalorganic framework Cu3 HHTP2 wit cJAN 0 v303 a

On one hand electron or hole doping of quantum spin liquid (QSL) may unlock high-temperature superconductivity and on the other hand it can disrupt the spin liquidity, giving rise to a magnetically ordered ground state. Recently, a 2D MOF, Cu-3(HHTP)(2) (HHTP - 2,3,6,7,10,11-hexahydroxytriphenylene), containing Cu(II) S = 1/2 frustrated spins in the Kagome lattice is emerging as a promising QSL candidate. Herein, we present an elegant in situ redox-chemistry strategy of anchoring Cu-3(HHTP)(2) crystallites onto diamagnetic reduced graphene oxide (rGO) sheets, resulting in the formation of electron-doped Cu-3(HHTP)(2)-rGO composite which exhibited a characteristic semiconducting behavior (5 K to 300 K) with high electrical conductivity of 70 S . m(-1) and a carrier density of similar to 1.1 x 10(18) cm(-3) at 300 K. Remarkably, no magnetic transition in the Cu-3(HHTP)(2)-rGO composite was observed down to 1.5 K endorsing the robust spin liquidity of the 2D MOF Cu-3(HHTP)(2). Specific heat capacity measurements led to the estimation of the residual entropy values of 28 % and 34 % of the theoretically expected value for the pristine Cu-3(HHTP)(2) and Cu-3(HHTP)(2)-rGO composite, establishing the presence of strong quantum fluctuations down to 1.5 K (two times smaller than the value of the exchange interaction J).

10a2D Metal-organic Framework10aElectron doping10aReduced graphene oxide10aSpin Liquid10aSpin-frustration1 aNinawe, Pranay1 aJain, Anil1 aSangole, Mayur1 aAnas, Mohd1 aUgale, Ajay1 aMalik, Vivek, K.1 aYusuf, Seikh, M.1 aSingh, Kirandeep1 aBallav, Nirmalya uhttps://library.ncl.res.in/content/robust-spin-liquidity-2d-metal-organic-framework-cu3-hhtp2-s12-kagome-lattice04907nas a2200229 4500008004100000245007800041210007000119260000800189490000600197520417400203100001804377700001904395700002204414700001704436700001704453700001704470700001604487700002104503700002204524700002104546856011004567 2024 eng d00aUnconventional hole doping of S = ½ kagome antiferromagnet CoCu3(OH)6Cl20 aUnconventional hole doping of S ½ kagome antiferromagnet CoCu3OH cSEP0 v33 a

Geometrically perfect S = ½ kagome lattices with frustrated magnetism are typically electrical insulators. Electron or hole doping is predicted to induce an exotic conducting state including superconductivity. Herein, an unconventional strategy of doping an S = ½ kagome lattice CoCu3(OH)6Cl2 is adopted – a structural analogue of a well-known quantum spin liquid (QSL) candidate herbertsmithite (ZnCu3(OH)6Cl2) – by integrating it with reduced graphene oxide (rGO) via in situ redox chemistry. Such an integration drastically enhances the electrical conductivity, resulting in the transformation of an insulator to a semiconductor, corroborating the respective density of states obtained from the density functional theory calculations. Estimation of the magnetic moments, data on the Hall-effect measurements, Bader charge analysis, and photoemission signals, altogether provide a bold signature of remote hole doping in CoCu3(OH)6Cl2 by rGO. The remote doping provides an alternative to the site doping approach to impart exotic electronic properties in spin liquid candidates, specifically, the generation of topological states like Dirac metal is envisioned.

1 aMandal, Rimpa1 aNinawe, Pranay1 aAnanthram, K., S.1 aMhase, Akash1 aGupta, Kriti1 aSaha, Sauvik1 aUgale, Ajay1 aSingh, Kirandeep1 aTarafder, Kartick1 aBallav, Nirmalya uhttps://library.ncl.res.in/content/unconventional-hole-doping-s-%C2%BD-kagome-antiferromagnet-cocu3oh6cl2