A dual-excited and dual near-infrared emission phosphor Mg 14 Ge 5 O 24 :Cr 3+ ,Cr 4+ with a super broad band for biological detection

Recently, near-infrared phosphors that can be applied in many fields such as night vision, agriculture, and bio-applications have attracted considerable interest in the research field worldwide. Herein, a multi-functional and dual-excited near-infrared phosphor Mg Ge O :Cr ,Cr which provides two emission bands ranging from 700 nm to 1100 nm and 1100 nm to 1700 nm has been obtained via the traditional high-temperature solid state reaction. The presence of six and four coordination ions in the olivine structure of Mg Ge O provides a favorable environment for the coexistence of Cr and Cr . Under blue light excitation, a super broad emission band ranging from 650 nm to 1100 nm with a full-width at half maximum (FWHM) of 266 nm is assigned to the spin-allowed T (4F) → A transition of Cr in a weak crystal-field environment. With the increase in the concentration of Cr ions, more and more Cr preferentially occupies four coordinated Ge sites, and the other broad emission band ranging from 1100 nm to 1600 nm with a FWHM of 256 nm that comes from the T → A transition of Cr is observed. The phenomenon of NIR I region excitation and NIR II region emission appears. The transmission experiment of a biological tissue proves that the Mg Ge O :Cr ,Cr phosphor has potential applications in the field of near-infrared light-emitting diodes for biological detection.