To conveniently monitor and remove toxic Hg 2+ and S 2− in food samples, Au Ag quantum-dot nanozyme (Au-Ag@FA QDs) was identified. The strong synergistic effect among folic acid (FA), Ag and Au endowed Au-Ag@FA QDs with superior peroxidase-mimic activity to accelerate 3,3′,5,5′-tetramethylbenzidine (TMB) redox with K m / V max of 0.28 mmol·L −1 /6.40 × 10 −8 mol·L −1 ·s −1 . Trace Hg 2+ or S 2− could selectively alter its peroxidase-like activity and inherent fluorescence performance, with obvious hyperchromic/“turn-on” fluorescent effect for Hg 2+ or hypochromic/“turn-off” one for S 2− . And red-green-blue (RGB) values analyzed from smartphones changed regularly with c Hg 2+ or c S 2− . Under the optimized conditions, Au-Ag@FA QDs were successfully applied for multi-mode UV–vis, fluorescent, and RGB monitoring of Hg 2+ or S 2− in food samples. The detection limits were 7.38 × 10 −7 /5.74 × 10 −8 /4.93 × 10 −6 g·L −1 and 1.99 × 10 −6 /4.48 × 10 −8 /5.79 × 10 −6 g·L −1 respectively. Importantly, over 93.8 % Hg 2+ or 90.5 % S 2− could be removed by simple centrifugal-separation after detection. The selective recognition mechanisms to Hg 2+ and S 2− were also proposed.
In this work, Ag quantum dot-modified AgInS2/In2S3/TNR nanoarray photocatalysts were prepared by a secondary hydrothermal and wet chemical method. Compared with the unmodified TNR arrays, the modified Ag-AgInS2/In2S3/TNR samples showed a significant increase in light absorption and could utilize more solar energy. In addition, the Ag-AgInS2/In2S3/TNR samples can effectively promote the separation and transfer of electron-hole pairs to enhance the photoelectrochemical and photocatalytic performance of the composites, and the degradation rate of the optimal Ag-AgInS2/In2S3/TNR samples can reach 95.73% for TC-HCl, which is of great importance for environmental protection. The main reasons for the enhanced catalytic performance are: the presence of surface Ag quantum dots and AgInS2 sensitizers greatly increases the absorption of sunlight, allowing more energy to enter the catalytic system; the stepped energy level arrangement of AgInS2/In2S3/TNR nanoarrays can spatially separate electrons and holes, improving the separation efficiency and enhancing the overall performance of the material.
Zhuangzhuang Yin,Shihan Qi,Shangkun Deng,Kang Xu,Zhu Liu,Miao Zhang,Zhaoqi Sun
In this study, a Bi 2 MoO 6 /TiO 2 heterojunction photocatalyst modified with Ag quantum dots was successfully synthesized. The results demonstrated that Ag–Bi 2 MoO 6 /TiO 2 exhibited excellent photoelectrochemical performance and photocatalytic activity for the degradation of tetracycline hydrochloride. The catalyst had the best photocurrent density with a maximum value of 103.0 µA/cm 2 , which was 11.7 times higher than that of unmodified TiO 2 nanorods. Ag–Bi 2 MoO 6 /TiO 2 significantly increased the absorption intensity and red-shifted with a bandgap of 1.88 eV, which is substantially narrower than that of TiO 2 . Furthermore, it exhibited extremely high photocatalytic activity for the degradation of tetracycline hydrochloride with a degradation rate of 90.8% at 120 min. A photocatalytic mechanism was proposed to explain the principle of tetracycline hydrochloride degradation using this catalyst.
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