Core-shell Au@Ag nanodendrites supported on TiO₂ nanowires for blue laser beam-excited SERS-based pH sensing

The blue laser beam-excited surface-enhanced Raman scattering (SERS)-based pH sensing holds great promise for avoiding undesired thermal heating effect on some special temperature-vulnerable molecules, as compared to the vast majority studies by exciting in the red or near-infrared (NIR). Herein, we report an ingenious approach to support core-shell Au@Ag nanodendrites (NDs) on TiO₂ nanowires, which can possess enhanced SERS activity under 473 nm laser excitation, owing to the improved charge-transfer effect on modified TiO₂ support by inserting plasmonic Au@Ag. By using pH-indicating 4-mercaptobenzoic acid (4-MBA), the obtained TiO₂/Au@Ag NDs can not only exhibit high sensitive linear-responses of pH changes ranging from pH 4.0 to 9.0 in different solutions (deionized water, NaCl, CaCl₂, and MgCl₂) but also provide excellent temperature stability under 4°C, 25°C and 37°C temperatures as well as good time stability after storage for 10 days. The established SERS-pH sensing by using shorter wavelength laser excitation is highly desirable for understanding physiological process in temperature-vulnerable microenvironment.