Gold Nanoparticle-Based Chemiresistors: Recognition of Volatile Organic Compounds Using Tunable Response Kinetics.

The development of sensors enabling the identification of volatile organic compounds (VOCs) and their mixtures is an ongoing challenge driven by many potential applications, such as breath analysis in medical diagnosis, food quality control, and environmental monitoring. In this context, hybrid materials of organically stabilized or cross-linked metal nanoparticles show great potential for the chemiresistive detection of VOCs. Here, we show that the unique nanostructure of these materials induces analyte-dependent response kinetics, which can be tuned and employed for analyte recognition. First, the response kinetics of different α,ω-alkanedithiol (ADT) cross-linked GNP film chemiresistors were measured by exposing them to vapors of toluene, 1-butanol, 1-propanol, 2-propanol, ethanol, water, 4-methylpentan-2-one, and different homologous alkanes. The t₈₀ response times and the integrated area below the response transients were used as characteristic features of the response kinetics. The response times depended strongly on the molecular volume of the analyte as opposed to the maximum sensor response, which was governed by the analytes' polarity and vapor pressure. We attribute the variation in response time to molecular transport of the analyte molecules entering the sensor film. Second, using different-sized cross-linkers, different film thicknesses, or by preexposing the sensors to deep ultraviolet radiation, it is possible to tune the kinetics of the sensors' responses to different analytes. Third, by employing linear discriminant analysis on data sets containing the maximum responses and kinetic response features of a GNP/ADT sensor array with adjusted response kinetics, it was possible to differentiate between very similar analytes over a broad range of concentrations (100–4000 ppm). Hence, the methods described herein will be very useful for various applications of nanoparticle-based chemiresistor arrays. [ABSTRACT FROM AUTHOR]