Ultrathin gold films with chemiresistive functionality

The growing demand for monitoring and detecting biochemical changes is driving the development of scalable, easy-to-fabricate, and low-power consuming sensor technologies. In particular, chemiresistors are simple and cost-effective platforms that transduce chemical interactions into measurable electrical signals. Due to the large high surface-to-volume ratio, ultrathin metal films (UTMFs) have the potential for highly sensitive transducing materials. In this study, we investigate the suitability of gold (Au) UTMFs as chemiresistive transducing material by quantifying how film thickness influences their resistive response. As a prototypical detection target, we use self-assembled monolayers (SAMs) that can be easily functionalized on the Au UTMF surface. Real-time resistance measurements during SAM formation demonstrate that the thinner the Au UTMFs, the higher the sensitivity and the faster the response. In addition, we present a proof-of-concept biosensor using SH-PEG-Biotin SAMs for the detection of streptavidin, comparing the responses between shorter and longer PEG chains. The results show that shorter PEG chains forming SAMs provide greater sensitivity and a lower limit of detection. These results highlight the potential use of Au UTMF-based chemiresistors with SAMs as scalable and tunable biosensing platforms, where sensitivity and performance can be tailored via surface molecular engineering.