Highly Sensitive LSPR Sensor Chips Based on Crystalline Gold Nanoparticles Grown on Silica

In this paper, we demonstrate the fabrication of LSPR sensor chips consisting of crystalline gold nanoparticles (AuNPs) over a large area. These crystalline AuNPs were grown on a heated silica substrate via thermal evaporation in a simple single-step fabrication process. To the best of our knowledge, the fabrication of LSPR sensor chips via the growth of crystalline AuNPs has not been demonstrated earlier. We present a process of AuNP growth wherein nanoparticles have been successfully formed for deposition thicknesses up to 40 nm at comparatively lower temperatures than what has been demonstrated earlier. The crystalline AuNPs are formed during the evaporation process, without the requirement of any additional annealing time. The growth of crystalline AuNPs, as proposed in this paper, enables the formation of AuNPs for larger values of equivalent QCM film thicknesses, going up to 40 nm, and possibly even higher. The AuNPs from different values of film thicknesses also allow the tuning of LSPR peak wavelength over a wider range of the visible spectrum. Increased crystallinity was also obtained in the nanoparticles grown at high temperatures and for larger thicknesses. The evaluation of the LSPR sensor chips containing these crystalline AuNPs showed that high surface sensitivity of 28.89 nm/nm was obtained for a conformal thin film layer of Al2O3 over the AuNPs, which is higher than what has been demonstrated earlier. These sensor chips containing crystalline AuNPs also show higher bulk sensitivity than what has been reported previously for AuNPs nanoparticles formed by template-free methods and annealing.