Chemiresistor array with nanocluster interfaces as a micro-GC detector

An integrated array of chemiresistor (CR) microsensors employing a novel set of Au-thiolate monolayer-protected nanoclusters (MPN) as interface materials has been developed and tested as an ultra-low-dead-volume detector for a micro gas chromatograph (/spl mu/GC). Six MPNs 3-5 nm in mean core diameter each with a different type of organo-thiolate ligand were synthesized by a single-phase method, spray cast onto interdigital electrodes, and exposed to several organic vapors. Four of these MPNs were coated onto the same CR array and used as a detector for a conventional GC to analyze a mixture of 15 vapors. The array provides characteristic vapor response patterns, linear calibration curves, and good overall sensitivity, which increases at lower temperatures and detector-cell flow rates. On the basis of injected mass, GC responses indicate that detection limits in the low part-per-trillion range are achievable from preconcentrated sample volumes of <1 L. Sensitivity does not vary significantly among similarly coated CRs having electrode spacings ranging from 0.1-15 /spl mu/m consistent with a response model based on bulk-film swelling.