Ninawe Pranay, Jain Anil, Sangole Mayur, Anas Mohd, Ugale Ajay, Malik Vivek K, Yusuf Seikh M, Singh Kirandeep, Ballav Nirmalya
Department of Chemistry, Indian Institute of Science Education and Research (IISER), Pune, 411008, India.
Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai, 400085, India.
Chemistry. 2024 Jan 16;30(4):e202303718. doi: 10.1002/chem.202303718. Epub 2023 Nov 27.
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 (HHTP) (HHTP - 2,3,6,7,10,11-hexahydroxytriphenylene), containing Cu(II) S= 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 (HHTP) crystallites onto diamagnetic reduced graphene oxide (rGO) sheets, resulting in the formation of electron-doped Cu (HHTP) -rGO composite which exhibited a characteristic semiconducting behavior (5 K to 300 K) with high electrical conductivity of 70 S ⋅ m and a carrier density of ~1.1×10 cm at 300 K. Remarkably, no magnetic transition in the Cu (HHTP) -rGO composite was observed down to 1.5 K endorsing the robust spin liquidity of the 2D MOF Cu (HHTP) . 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 (HHTP) and Cu (HHTP) -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).
一方面，量子自旋液体（QSL）的电子或空穴掺杂可能会开启高温超导性，另一方面，它会破坏自旋流动性，产生磁有序基态。最近，一种二维金属有机框架Cu（HHTP）（HHTP为2,3,6,7,10,11-六羟基三亚苯），在Kagome晶格中含有Cu（II）S = 受挫自旋，正成为一种有前景的QSL候选物。在此，我们展示了一种将Cu（HHTP）微晶原位锚定在抗磁性还原氧化石墨烯（rGO）片上的优雅氧化还原化学策略，从而形成电子掺杂的Cu（HHTP）-rGO复合材料，该复合材料在5 K至300 K范围内表现出典型的半导体行为，在300 K时具有70 S·m的高电导率和约1.1×10 cm的载流子密度。值得注意的是，在低至1.5 K的温度下，未观察到Cu（HHTP）-rGO复合材料中的磁转变，这证实了二维金属有机框架Cu（HHTP）具有强大的自旋流动性。比热容测量结果表明，原始Cu（HHTP）和Cu（HHTP）-rGO复合材料的残余熵值分别为理论预期值的28％和34％，这表明在低至1.5 K的温度下存在强烈的量子涨落（比交换相互作用J的值小两倍）。
