Engineering large-scaled electrochromic semiconductor films as reproductive SERS substrates for operando investigation at the solid/liquid interfaces

Although surface-enhanced Raman spectroscopy (SERS) has been applied for gathering fingerprint information, even in single molecule analysis, the decayed Raman signals in aqueous solutions largely obstruct the on-site insight reaction process. In this study, large-scaled semiconductor films with multi-walled (TiO2/WO3/TiO2) nanopore distribution are fabricated by combining electrochemical anodization and sputtering technique, and then employed as the SERS substrates for detection of molecules at the solid/liquid interfaces. Given the remarkably improved electrochromic property of the multi-walled film, such SERS substrates were endowed with tunable oxygen vacancy (VO) density and distribution via simply applying electrochemical bias voltage, which enabled one to achieve an enhanced charge transfer efficiency and thus a remarkably increased Raman signal even in solution. The VO-rich SERS substrate is highly repeatable, thus providing a reliable platform for in-situ monitoring of the target molecules or intermediates at the solid/liquid interfaces. [Display omitted] A large-scaled semiconductor films with multi-walled (TiO2/WO3/TiO2) nanopore distribution is developed for gaining enhanced Raman signals at the solid/liquid surface. Benefiting from the remarkably improved electrochromic property of the multi-walled nanopore films, the SERS substrate can be controllably filled with oxygen vacancies (VO) via a simple electrochemical approach, which enables us to achieve a remarkably increased Raman signal even in the solution.