Facile microwave-assisted synthesis of Zn2GeO4:Mn2+, Yb3+ uniform nanorods and near-infrared down-conversion properties

Germanates have potential applications in electroluminescent fields. Herein, we report a simple strategy for the rapid synthesis of near-infrared (NIR) down-conversion Zn1.96-x,GeO4+1/2x:Mn0.04Ybx phosphors using the microwave-assisted hydrothermal method. This method is facile, rapid, surfactant-free and environmentally friendly. In the Zn2GeO4 lattice, intrinsic defect transitions and Mn2+ ions act as broadband spectral sensitizers by absorbing UV Vis (280-500 nm) photons and transferring the absorbed energy to Yb3+ centers in a cooperative down-conversion process. Efficient energy transfer is reflected by a sharp decrease in the excited state lifetime and green photoluminescence (PL) from tetrahedrally coordinated Mn2+ with increasing Yb3+ concentration. The possible formation mechanism for Zn1.96-xGeO4+1/2x:Mn0.04Ybx nanorods has been presented. PL spectroscopic characterizations show that pure Zn2GeO4 sample shows a blue emission due to defects, while zn(2)ceO(4):Mn2+ phosphors exhibit a green emission corresponding to the characteristic transition of Mn2+ (T-4(1) -> (6)A(1)) under the excitation of UV. The Yb3+ acceptor is then the source of NIR emission at a wavelength of similar to 1000 nm. These phosphors are promising for applications in solar spectral down-conversion. (C) 2016 Elsevier B.V. All rights reserved.