Inkjet-Printed Functional Surface Enhanced Raman Scattering (SERS) Sensors for Aerosol Detection

Recent advances in Inkjet-printing of advanced materials have provided a versatile platform for the rapid development and prototyping of sensor devices. We have recently demonstrated inkjet-printed surface enhanced Raman scattering (SERS) sensors on flexible substrates for the detection of small chemical molecules. (Tay et al., J Raman Spectrosc., 2021, 52, 563-572) These flexible SERS sensors have good batch-to-batch uniformity and many advantages for performing point-of-sampling testing such as liquid or aerosol filtration and swabbing capabilities. These simple sampling and separation attributes make these inkjet-printed paper-based sensors ideal for field applications. The SERS effect relies upon the electromagnetic field enhancement that results from coupling of plasmonic nanostructures (e.g. silver or gold nanoparticles). SERS exploits the unique vibrational signature of an analyte molecule and in practice, it is often coupled with spectral recognition software for the detection of molecules of interest. In this presentation, we will highlight the kinetically controlled seed-mediated nanoparticle synthesis and ink preparation for inkjet-jet printing process. Although SERS effect scales with the size and aggregates of the nanoparticles, our results show larger nanoparticles and larger aggregates also produce very high background. The high background comes from carbonaceous materials in the ambient and becomes adsorbed onto the sensor surface. For the detection of molecular analyte with poor affinity towards the nanoparticle surfaces, carbonaceous molecules cannot be easily displaced. In this presentation, we will present strategies to improve the sensor performance towards analytes with poor affinity towards nanoparticle surfaes. We will compare the SERS sensors produced through a customized piezo-electric inkjet printer and a high-precision materials printer.