Improving the SERS enhancement and reproducibility of inkjet-printed Au NP paper substrates by second growth of Ag nanoparticles

The fabrication of paper-based SERS substrates, which provided the advantages of active Raman signal enhancement with good reproducibility is still a challenge for real-world applications. In this report, we showed how the SERS enhancement and reproducibility of Au NP paper substrates prepared by inkjet-printed method could be improved significantly by second growth of Ag NPs. The Au/Ag NP paper substrates fabricated with the improved protocol had a much higher SERS enhancement (about 1.356✕10³ times) compared with printed Au NP paper substrates. Moreover, the reaction parameters affected the SERS enhancement of Au/Ag NP paper substrates were optimized by collecting rhodamine 6G (R6G) SERS spectra. Further, the reproducibility of Au/Ag NP paper substrates were evaluated on random spots of single substrate and batch to batch substrates by recording the intensity of R6G at 611 cm⁻¹. The SERS intensities at 611 cm⁻¹ showed small relative standard deviation, which indicated the good reproducibility of Au/Ag NP paper substrates. This improved method enabled the printed Au NP paper substrates to possess the practical applicability for the on-site SERS sensing.