Band gap tuning of Sn1-xCexO2 nanoflower for improved SERS activity of bioassay

Metal oxide-based surface-enhanced Raman scattering (SERS) platforms have attracted considerable interest, which show potentials for biomolecule detection due to their wide bandgap tuning range, stable properties, high electron mobility and good optical properties. However, the types and enhancement factor (EF) of metal oxide SERS substrates are limited. And the band-matched efficient photo-induced charge transfer (PICT) is the important process to further improve the EF. In this study, one efficient SERS substrate Sn1-xCexO2 was synthesized by varying concentrations of Ce ions with band gap tuning and oxygen vacancies introducing. As a result, the charge transfer pathway and strong interaction between the Sn1-xCexO2 nanoflowers (NFs) and methylene blue (MB) molecules are promoted, and the enhancement factor (EF) of this Sn1-xCexO2 (x = 0.03) NF is as high as 1.80 x 106. Then, we constructed a biosensor based on hybridization chain reaction (HCR) strategy combining with Mg2+-dependent DNAzyme cleavage nucleic acid cascade signal amplification to achieve sensitive and quantitative detection of microRNA 21 (miRNA 21). The limit of detection (LOD) was 0.72 fM with a detection linearity ranged from 1 fM to 10 nM. This study gives an approach for preparation of new SERS substrates which can be used in bioanalysis.