Optical ammonia sensor based on Yb3+, Er3+, Tm3+ co-doped NaYF4 up-conversion material/phenol red composites

Abstract

In this paper, optical ammonia sensor based on Yb3+, Er3+, Tm3+ co-doped NaYF4 up-conversion material/phenol red composites was proposed. Phenol red and Yb3+, Er3+, Tm3+ co-doped NaYF4 were mixed thoroughly and transferred into PE conical shell to form ammonia sensitive unit. The epoxy resin was coated onto two end sides of PE conical shell to fix ammonia sensitive composite. The absorption intensity of up-conversion luminescence located at 663 nm will be affect by the concentration of ammonia attribute to the reaction between ammonia and phenol red. The detected intensity near 663 nm decreases exponentially with the increasing ammonia concentration. The water absorption of epoxy resin benefit for the detection of ammonia. The signal wavelength will not be affected by the background visible light due to the 980 nm wavelength of excitation is far from the signal wavelength. The response time and recover time of the sensor also were measured and discussed.