Stable and tunable plasmon resonance of molybdenum oxide nanosheets from the ultraviolet to the near-infrared region for ultrasensitive surface-enhanced Raman analysis

Jinhu Wang; Yinhua Yang; Hua Li; Jun Gao; Ping He; Liang Bian; Faqin Dong; Yi He

doi:10.1039/c9sc02202c

Stable and tunable plasmon resonance of molybdenum oxide nanosheets from the ultraviolet to the near-infrared region for ultrasensitive surface-enhanced Raman analysis

Chem Sci. 2019 May 23;10(25):6330-6335. doi: 10.1039/c9sc02202c. eCollection 2019 Jul 7.

Authors

Jinhu Wang¹, Yinhua Yang², Hua Li², Jun Gao³, Ping He³, Liang Bian⁴, Faqin Dong⁴, Yi He¹

Affiliations

¹ State Key Laboratory of Environment-friendly Energy Materials , Sichuan Co-Innovation Center for New Energetic Materials , Southwest University of Science and Technology , Mianyang 621010 , P. R. China . Email: yhe2014@126.com.
² Materials Characterization & Preparation Center , Southern University of Science and Technology , Shenzhen 518055 , China.
³ School of Materials Science and Engineering , Southwest University of Science and Technology , Mianyang , 621010 , P. R. China.
⁴ Key Laboratory of Solid Waste Treatment and Resource Recycle , Ministry of Education , State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials , Southwest University of Science and Technology , Mianyang 621010 , Sichuan , China.

Abstract

Preparation of color-tunable and stable plasmonic MoO₃ nanomaterials remains challenging, due to the lack of an effective preparation strategy and surface protection in heavily doped MoO₃. Herein, we report a facile and reliable method for synthesis of oxygen-deficient MoO₃ (MoO_3-x ) nanosheets using dopamine as the reducing agent and precursor for the formation of a polydopamine (PDA) surface coating. The PDA-coated MoO_3-x nanosheets show stable and tunable localized surface plasmon resonance (LSPR) from the ultraviolet to the near-infrared region (361-809 nm) via altering the pH value of the medium, accompanying the generation of multicolor nanosheet dispersions, such as deep blue, faint bluish, orange, yellow and black. Importantly, the resulting PDA-coated MoO_3-x nanosheets are quite stable even in the presence of oxidants, and they can be used as an ultrasensitive surface-enhanced Raman scattering (SERS) substrate. The limit of detection for rhodamine 6G (R6G) dye is down to 0.3 fM concentration, and the corresponding Raman enhancement factor reaches 1 × 10¹⁰. The coupling of charge transfer between R6G and PDA-coated MoO_3-x nanosheets and molecular resonances may be responsible for the strong SERS effect.