Fabrication of Cu-doped molybdenum oxide for bifunctional SERS and photothermal conversion

Heavily-doped semiconductor materials have attracted great attentions owing to their tunable localized surface plasmon resonance (LSPR) in the visible or near-infrared (NIR) range, which is expected to own excellent performance comparable to that of precious metals. However, the current strategies of doping MoO3 are usually tedious and not environmental-friendly, and the synergistic effects of oxygen vacancies and metal ion doping on the LSPR are rarely investigated. Herein, we report a facile supercritical CO2-assisted method to synthesize Cu-doped MoO3 nanoparticles (Cu–MoO3-x NPs) with tunable LSPR properties, and the morphology, doped Cu ion concentration and oxygen vacancies density can be modulated as the control of supercritical CO2 pressure from 10 to 16 MPa. Moreover, the Cu–MoO3-x NPs possess outstanding surface enhanced Raman spectroscopy (SERS) performance (with the enhancement factor of 3.48 × 107 and the limit of detection of 10−9 M) and relatively high photothermal conversion efficiency (62.4%). This work provides an efficient route for the fabrication of heavily-doped metal oxide semiconductors with superior LSPR performance in various light utilization fields.