A SERS Biosensor Constructed by Calcined ZnO Substrate with High-Efficiency Charge Transfer for Sensitive Detection of Pb2+

•Calcined ZnO submicron flowers (ZnO SFs) with narrow band gap exhibited admirable SERS effect for the Raman signal of methyl blue (MB).•Free-legged DNA walker amplification strategy was utilized to construct a SERS biosensor for sensitive detection of target Pb2+ by combining ZnO SFs substrate.•The biosensor achieved a low detection limit of 3.55 pM for target Pb2+.