Rapid one-pot synthesis and photoelectrochemical properties of copper vanadates

Solution combustion synthesis (SCS) is shown to be versatile for the rapid-one-pot synthesis of three compounds and four polymorphs in the Cu-V-0 ternary family: alpha-CuV2O6, alpha- and beta-Cu2V2O7, and gamma-Cu3V2O8. These compounds feature copper/vanadium stoichiometric ratios ranging from 1:1 to 3:1; their structural, electronic, optoelectronic, and photoelectrochemical attributes were comprehensively characterized by a combination of theoretical and experimental techniques. The main contribution of the present study is the demonstration that a range of stoichiometries in this compound family can be derived simply by tuning the precursor mole ratio in the SCS procedure. The Cu-V-O family of samples, derived by SCS, is shown to exemplify the strong effect of compound stoichiometry on the optoelectronic and photoelectrochemical properties. Overall, alpha-CuV2O6 showed the best performance, rooted in the direct nature of the optical transition in this material. Finally, SCS is very time-efficient and the various compositions can be obtained in a matter of minutes, as opposed to hours or even days in classical solution-based or ceramic synthesis routes2428372847COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES88881.131530/2016-0C.J. and A.K. acknowledge the support of the“Széchenyi 2020”program within the framework of the GINOP-2.3.2-15-2016-00013 project. M.T.G. and C.L. acknowledge CAPES-PDSE(Process#88881.131530/2016-0) for partial financial supportunder the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior Program. M.N.H. was supported by the National Science Foundation (Award No. DMR-1609811).M.N.H. and H.P.S. thank the Texas Advanced ComputingCenter (Austin, TX) facility for their computational needs.The authors thank the three anonymous reviewers forperceptive comments on an earlier version of this manuscrip

Fermionic versus bosonic descriptions of one-dimensional spin-gapped antiferromagnets

In terms of spinless fermions and spin waves, we describe magnetic properties of a spin-1/2 ferromagnetic-antiferromagnetic bond-alternating chain which behaves as a Haldane-gap antiferromagnet. On one hand, we employ the Jordan-Wigner transformation and treat the fermionic Hamiltonian within the Hartree-Fock approximation. On the other hand, we employ the Holstein-Primakoff transformation and modify the conventional spin-wave theory so as to restore the sublattice symmetry. We calculate the excitation gap, the specific heat, the magnetic susceptibility, magnetization curves, and the nuclear spin-lattice relaxation rate with varying bond alternation. These schemes are further applied to a bond-alternating tetramerized chain which behaves as a ferrimagnet. The fermionic language is particularly stressed as a useful tool to investigate one-dimensional spin-gapped antiferromagnets, while the bosonic one works better for ferrimagnets.Comment: 10 pages, 5 figure