Detection of Ultra-Low Concentration of Methylene Blue by Porous Silicon Photonic Crystals Covered With Siver Nanoparticles as Efficient Sers Substrate

 In this work, porous silicon photonic crystals (PSi PhCs) covered by silver nanoparticles (AgNPs) were prepared as surface-enhanced Raman scattering (SERS) substrate to detect methylene blue (MB) at low concentrations. The limit of MB detection in water by the SERS substrate is evaluated to be 10\(^{-10}\) mol/L. The SERS signal intensities of 446 cm\(^{-1}\) and 1623 cm\(^{-1}\) peaks in SERS spectra of MB are fit in exponential functions of concentrations ranging from 10\(^{-4}\) to 10\(^{-10}\) mol/L. These results show that the AgNPs on PSi PhCs substrates could be applied in environmental sensing.