A sonochemical approach for a silver particle layer SERS substrates preparation and subsequent application in qualitative analysis

We present an easy and efficient method for silver particle layer SERS substrate preparation that combines a modified Tollens’ approach with using ultrasound to obtain unique reaction conditions by generating high-energy hot-spots as the arising acoustic cavities implode. The silver layers were deposited on various substrates in a one-step reduction process of silver nitrate. Three different reductants (maltose, glucose, ascorbic acid) were used to obtain silver particle layers with different particle sizes, morphologies, and inter-particle distances. To further optimize the properties of the silver particles for SERS and to provide higher signal enhancement, all the prepared nanoparticle layers were activated in 4 M Cl− solution. The size of silver particles was in most samples under 100 nm and the particles formed clusters, but they were also present on the surface individually. In some of the activated substrates, bigger particles (0.5–1 μm) occur as well. The activated as well as non-activated substrates were tested as SERS substrates using 10−5 M adenine as a model analyte. Laser wavelengths of 455 nm, 532 nm, 633 nm, 780 nm, and 785 nm were used for the SERS measurements. High enhancement factors up to 3.5·105 and 2.8·105 were obtained for SERS measurements using lasers of 532 nm and 780 nm, respectively.