Assessing optical characteristics of nanoparticle inks for inkjet-printed electronics using UV-Vis-NIR spectroscopy

Printed electronics leverage diverse printing techniques to deposit functional materials on substrates, with inkjet printing emerging as a versatile and waste-minimizing approach. Metallic nanoparticle inks, notably silver and gold, offer stability and conductivity, despite oxidation challenges. Metal oxide nanoparticles exhibit distinct optical properties, including strong ultraviolet absorption and characteristic visible-light absorption. Such metal oxides are increasingly favored in printed electronics for their enhanced resistance to oxidation. UV-Vis spectroscopy provides insights into nanomaterial properties, including localized surface plasmon resonance, facilitating applications such as transparent electrodes and photocatalysis. The integration of inkjet nanoparticle inks with advanced characterization techniques enables development of novel electronic devices. This work used UV-Vis spectroscopy on various nanoparticles, Au, Ag, SiO₂, and BaTiO₃ NPs, in suitable solvents at different concentrations. Furthermore, both the ‘aged’ and the ‘fresh’ Ag ink dispersed in deionized (DI) water underwent syringe filtration using filters with pore sizes of 5 μm, 1 μm, and 0.22 μm, followed by their spectra measurement and analysis. The UV–Vis spectra revealed distinct plasmonic peaks for Au (⁓527 nm) and Ag (⁓398 nm) inks, with older Ag ink showing broader peaks due to agglomeration. Filtration with a 0.22 μm membrane virtually eliminated the absorbance of a fresh Ag ink (indicating most particles <0.22 μm), whereas an aged Ag ink clogged this filter, confirming severe aggregation. SEM images corroborated these findings, showing uniform nanoparticles in fresh ink vs. larger clusters in aged ink.