Plasmonic hot electron transfer-induced multicolor MoO 3-x -based chromogenic system for visual and colorimetric determi

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Plasmonic hot electron transfer-induced multicolor MoO3-x-based chromogenic system for visual and colorimetric determination of silver(I) Jiayan Du 1 & Junren Wang 2 & Yuequan Deng 1 & Yi He 2 Received: 10 December 2019 / Accepted: 1 January 2020 # Springer-Verlag GmbH Austria, part of Springer Nature 2020

Abstract A plasmonic hot electron transfer-induced multicolor chromogenic system is described for label-free visual colorimetric determination of silver(I). The chromogenic system consists of plasmonic MoO3-x nanosheets with oxygen vacancies and Ag(I). Under white light-emitting diode (LED) excitation, energetic hot hole-electron pairs are formed on the surface of the blue MoO3-x nanosheets. The resulting hot electrons are transferred to Ag(I) upon which it becomes reduced. This results in the generation of yellow silver nanoparticles. Simultaneously, the hot holes lead to the oxidation of the MoO3-x nanosheets to yield colorless MoO3 nanosheets. Similarly, energetic hot hole-electron pairs can also be generated on the surface of AgNPs under white LED irradiation, which contributes to the reduction of Ag(I) and the oxidation of MoO3-x. Overall, a colorful transition from blue to green and finally to yellow can be observed. This multicolor chromogenic system was applied to the colorimetric determination of Ag(I) in the 33–200 μM concentration range and a 0.66 μM limit of detection, at analytical wavelengths of 430 and 760 nm. The method also is amenable to semi-quantitative visual determination of Ag(I). Keywords Colorimetry . Water sample . Photo-oxidation . Nanosheet

Introduction Plasmonic nanomaterials are featured by their powerful lightmaterial interactions because of the excitation of localized surface plasmon resonance (LSPR) [1, 2]. The LSPR excitation occurs when the oscillation frequency of valence electrons of nanomaterials matches the frequency of the incident light [3]. The decay of the LSPR usually produces high concentration of energetic charge-carriers (hot hole-electron

Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00604-020-4108-z) contains supplementary material, which is available to authorized users. * Yi He [email protected] 1

School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang 621010, People’s Republic of China

2

State Key Laboratory of Environment-friendly Energy Materials, School of National Defence Science & Technology, Southwest University of Science and Technology, Mianyang 621010, People’s Republic of China

pairs), which can activate chemical reactions on the surface of plasmonic nanomaterials [4, 5]. To date, plasmonic nanomaterials such as silver, gold, and copper have been applied to drive a diverse range of chemical reactions, including oxidation reactions of NH3 and CO, water splitting, methylene blue reduction, and N2 fixation [6–12], in which the plasmonic noble metal nanoparticles serve as photocatalysts. The achievements in the photochemical transformations i