Tiantian Zhou,Haonan Zhang,Xiaoming Ma,Xin Zhang,Yuanna Zhu,Aiyu Zhang,Yongqiang Cao,Ping Yang
The AgI/Bi 2 MoO 6 /AgBi(MoO 4 ) 2 (ABM) multi-heterostructure nanosheet composite system for visible-light photocatalysis have been successfully constructed by a simple one-step calcination method. The ABM multi-heterostructure composite photocatalysts exhibited the obviously improved photocatalytic performance than the pristine Bi 2 MoO 6 , AgBi(MoO 4 ) 2 , and AgI for the degradation of both Tetracycline hydrochloride (TC) and Rhodamine B (RhB). The apparent degradation rate for the ABM sample with the highest photocatalytic activity is 5.4 (TC) and 23.4 times (RhB) that of Bi 2 MoO 6 , 4.0 (TC) and 4.9 times (RhB) that of AgBi(MoO 4 ) 2 , and 1.9 (TC) and 2.4 times (RhB) that of AgI, respectively. This ABM sample with the highest activity showed a Bi 2 MoO 6 /AgBi(MoO 4 ) 2 composite nanosheet morphology (lateral size: 1–5 u m, thickness: 90−130 nm) with a large amounts of small AgI nanocrystals (diameter: 2−25 nm) uniformly distributed on the surface of composite sheet. The outstanding performance of the ABM composite photocatalysts should be ascribed to the effective separation of photoinduced electron-hole pairs via the multi-heterostructure in ABM, the enhanced visible-light absorption, as well as the two-dimensional (2D) morphology benefitting to the exposure of plenty of surface reactive sites and significant reduction of migration distances of photogenerated carriers. It is hoped that this facile method for the fabrication of multi-heterostructure in our work could promote and inspire the other multicomponent functional nanomaterials used in the fields of not only photocatalysis, but also solar cells, sensors, catalysis, and so on, in the future.
This work begins with a study of the synthesis of multi-color luminescence phosphors, which is followed by a discussion of the temperature sensitivity of AgBi(MoO4)2:Yb3+/Er3+. Uniform and approximately spherical particles of AgBi(MoO4)2-based phosphors were prepared by a simple one-step hydrothermal method without adding any surfactant. We obtained a series of rich green, yellow, blue, and white luminescence phosphors by doping Ln3+ (Ln3+ = Yb3+, Er3+, Ho3+, Tm3+) into the AgBi(MoO4)2 matrix, and an analysis of various correlative factors was made, especially for the amounts of doping ions. Furthermore, the investigation of the temperature sensitivity of AgBi(MoO4)2:Yb3+/Er3+ revealed that the fluorescence intensity becomes lower with increasing temperature from 323 to 573 K. The fluorescence intensity ratio (FIR) of the two thermal coupling energy levels (2H11/2, 4S3/2) of Er3+ was calculated, and the absolute sensitivity of the obtained phosphor reached a maximum value of 1.32% K−1 at 463 K, as obtained by fitting the FIR as a function of temperature, which is a relatively high level compared with other related materials. This material is expected to be used as a highly sensitive FIR thermometer.
Silver nanoparticles (NPs) and related semiconductors are a family of very important and widely applied photocatalysts. However, the preparation of high stability and activity of this photocatalyst is still a challenge. In this work, we report a stable Ag/AgCl/AgBi(MoO 4 ) 2 heterojunction photocatalyst fabricated via a simple in situ anion-exchange reaction followed by the photoreduction treatment. In the treatment of tetracycline (TC) wastewater under visible light, the AC-0.4 sample (prepared with 0.4 mmol KCl) exhibits the significantly improved activity (degradation ratio, DR of 71.3%) compared with the pristine AgBi(MoO 4 ) 2 (30% DR) and Ag/AgCl sample (synthesized by the photoreduction of AgCl) (37% DR) under identical experimental conditions. This activity promotion is from the fast interfacial electron transfer between the heterojunction phases of AgCl/AgBi(MoO 4 ) 2 and the SPR effect of Ag NPs. After five successive recycles, the AC-0.4 sample still maintains good stability and activity for TC degradation, which shows a great potential to be used in practical application. Through the ESR and controlled scavenged experiments, we found the • OH and • O 2 − are the major reactive intermediate species in the TC photodegradation reaction. Our work provides a new insight into the synthesis of stable and high efficient Ag-based heterojunction photocatalysts for the application of wastewater treatment.
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