Seed-mediated growth method for electroless deposition of AgNPs on glass substrates for use in SERS measurements

摘要

In this work, an electroless deposition method for silver nanoparticles (AgNPs) on glass substrates was developed for use in surface-enhanced Raman scattering (SERS) measurements. To obtain evenly distributed AgNPs of suitable size on the glass substrates, a seeding procedure was utilized as a pretreatment before the electroless deposition of AgNPs. The AgNPs thus formed were affected by both the seeding and growing procedures. To optimize the procedures for preparation of SERS substrates, several factors, including reaction time, the concentration of silver ions, and the concentration of reducing agents (glucose) for seeding and growing procedures, were varied. The morphologies of the seeds and the resulting AgNPs on the glass substrates were characterized by field-emission scanning electron microscopy (FE-SEM) and correlated with the SERS signals from probing with para-nitrothiophenol (pNTP). The results indicated that only the seeding time and the concentration of silver ions significantly influenced the distribution and sizes of the Ag seeds on the substrates. In the growing procedures, both the concentration of silver nitrate and the reducing agent affected the morphologies of the resulting AgNPs and, hence, the SERS signals. The substrates prepared using this newly developed method offer 2-5 times improvement of the SERS signals compared to substrates prepared without seed treatment. Also, the AgNPs prepared by this method can be easily controlled to designated sizes with even spatial and size distributions.