Hot electron-driven SERS enhancement of non-SERS-active creatinine using Ag-decorated ZnO nanorods

The development of highly sensitive and selective Surface-Enhanced Raman Spectroscopy (SERS) substrates is crucial for biomedical applications. This study presents an advanced SERS substrate by integrating silver nanoparticles (AgNPs) with ZnO nanorods (NRs), leveraging hot electron dynamics to enhance the SERS signal for non-SERS-active creatinine detection. AgNPs were deposited onto ZnO NRs using silver nitrate (AgNO₃) concentrations ranging from 0.01 M to 0.16 M, resulting in distinct nanoparticle distributions optimized for hot electron generation. The structural and optical properties of the substrates were systematically analyzed using FESEM, EDX mapping, and UV–Vis spectroscopy. The AgZnO nanorods synthesized with 0.13 M AgNO₃ demonstrated the most favorable AgNPs distribution, achieving a high-density configuration that significantly enhanced the Raman signal, yielding an enhancement factor (EF) of 5.07 × 10 3 for 1.0 × 10 −2 M non-SERS-active creatinine molecules, representing a 56.90 % improvement in sensitivity. This enhancement is attributed to the synergistic effect of localized surface plasmon resonance (LSPR) and efficient hot electron transfer, facilitated by the optimized AgNPs distribution. Moreover, the substrate showed strong reproducibility (RSD < 30 %), short-term stability over five days, and uniform SERS activity across the surface. These findings establish a direct correlation between AgNPs arrangement and hot electron-driven SERS enhancement, highlighting the potential of AgZnO nanorods as a highly effective SERS substrate for biomedical applications. Hot Electron Transfer in AgZnO Nanorods: A Mechanism for Raman Enhancement of Non-Active Molecules. • The effect of AgNO 3 concentrations on AgNPs' nanostructural formation onto ZnO nanorods. • The influence of AgNPs' nanostructure on hot electrons generation and optoelectronic properties of AgZnO NR. • The correlation between AgNPs distribution density on ZnO NR and hot electron generation towards SERS enhancement. • The mechanism of hot electron transfer in AgZnO substrate in intensifying SERS signal of non-SERS-active creatinine molecules. • The analytical enhancement factor (EF) of 5.07 × 10 3 , achieving a 56.90 % increase in SERS intensity for creatinine detection at 1.0 × 10 −2 M.