Zhuang Wen-Chang,Zhang Hai-Yue,Chen Zhen-Yang,Cheng Wen-Jing,Na Wei-Dan,Li Zhao,Tian Lin
Paper-based sensing platform is a point of need analytical toolkit for safety testing. However, the sensitivity, specificity, and simplicity are still challenging. Herein, we report a novel strategy (Au/δ-MnO 2 hollow nanosphere and 3,3′,5,5′-tetramethylbenzidine (TMB) induced test strips for signal-on detection) that can be utilized for hexavalent chromium (Cr 6+ ) detection. Interestingly, Cr 6+ (CrO 4 2− ) as a smart switch can remarkably enhance the oxidase-like activity of Au/δ-MnO 2 hollow nanosphere. The presence of Cr 6+ can regulate the surface electronic redistribution of Au/δ-MnO 2 and adjust the geometric configuration, which leads to the improvement in oxidase-like activity of Au/δ-MnO 2 . As a proof-of-concept application, a visual paper-based sensing platform of Cr 6+ along with quantitative analysis by the test strips was successfully constructed. This paper-based sensing platform exhibits a linear range with excellent selectivity for other interfering substances and lower limit of detection of 0.09 μmol·L −1 , providing a promising toolkit at-home Cr 6+ measurement and environmental monitoring. Graphical abstract
Lu Ji,Fang Li,Conghui Che,Wei Xue,Qiusheng Yang,Xiaoshu Ding,Dongsheng Zhang,Xinqiang Zhao,Yanji Wang
In the reaction of dimethyl carbonate (DMC) and 2,4-diaminotoluene (TDA), Au/CeO 2 exhibits higher selectivity than CeO 2 for dimethyl toluene-2,4-dicarbamate (TDC). However, its catalytic activity drops after H 2 reduction (denoted as Au/CeO 2 -R). The characterization results illustrate that Au exists as a single atom with the primary species as Au δ+ in Au/CeO 2 , forming Ce x Au 1−x O 2 structure similar to solid solution. Whereas for Au/CeO 2 -R catalyst, Au mainly exists as Au 0 , forming the Au-O-Ce structure on CeO 2 surface. Significantly, the strong interaction between Au and CeO 2 increases Ce 3+ and oxygen vacancies content, as well as modulates their acidic property. However, the catalytic activity of Au/CeO 2 -R is found to be lower than Au/CeO 2 as the species formed by DMC dissociation on its surface are not easily desorbed. Other transition metals supported on CeO 2 are also prepared, wherein Pt/CeO 2 and Pd/CeO 2 exhibit good TDC selectivity. In the end, the electronegativity and catalytic activity of metals are correlated.
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