Surface-enhanced Raman scattering (SERS) active substrate from gold nanoparticle-coated porous silicon for sensitive detection of horseradish peroxidase enzyme

The sensitive detection of horseradish peroxidase (HRP) enzyme using a gold nanoparticle/porous silicon (AuNPs/PSi) active substrate via surface-enhanced Raman scattering (SERS) is demonstrated. Electrochemical porosification via galvanostatic anodization in hydrofluoric acid (HF) mixed with ethanol was used to fabricate mesopore-size PSi layers onto a p-type Si (100) wafer. The AuNPs were reduced onto the meso-PSi surface through a spontaneous galvanic displacement reaction by dipping the substrates in a simple plating bath. The structural features and morphology of the designed frameworks were elucidated by X-ray diffraction (XRD) analysis, field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). The SERS performance of the AuNPs/PSi substrate was firstly examined and evaluated using crystal violet dye as the target analyte, where it exhibited enhanced SERS response. Moreover, the active substrate displayed an extremely sensitive and reproducible SERS response toward the HRP enzyme as a reactive analyte. The active substrate exhibited excellent detectable performance with a very low concentration of 10-8 M HRP and an enhancement factor (EF) of approximately 4.8 x 105. The analytical enhancement of Raman signals in response to Au plasmonic nanoparticles signifies the combination of the charge-transfer mechanism and electromagnetic amplification because of the formed density of hotspot regions. Therefore, the current newly fabricated AuNPs/PSi substrates have optimistic prospects in biophysical, biochemical, and biomedical applications as highly active SERS substrates.