Layer-by-layer assembly of low-temperature-imprinted poly(methacrylic acid)/gold nanoparticle hybrids for gaseous formaldehyde mass sensing

Abstract

The designing of gas-phase molecular recognition elements capable of detecting the sub-ppm levels of indoor air pollutants, e.g. formaldehyde at room temperature with substantially low cross-sensitivity and fast response and recovery kinetics is a challenge. In an effort to realize such a device, low-temperature formaldehyde imprinting and layer-by-layer assembly of imprinted poly(methacrylic acid) and core–shell gold nanoparticles to fabricate imp-PMAA/Au-NP hybrids or sandwich structures are reported. 10 MHz quartz microbalance (QMB) coated with imp-PMAA/Au-NPs hybrid layer (optimized thickness: 100 ± 20 nm) is used as a transducer. Control measurements performed at 25 °C and 50% relative humidity (RH) reveal 2–9 fold increase in the sensor response of imp-PMAA/Au-NPs hybrid layer towards gaseous formaldehyde (1 ppm) as compared to other tested materials. Imp-PMAA/Au-NPs hybrid sensor exhibits the high selectivity towards formaldehyde due to a combination of the non-covalent dispersion interactions of formaldehyde with the molecular recognition sites and enhanced surface area. Further experiments reveal fast response and recovery times (28 and 13 s, respectively) for the imp-PMAA/Au-NPs hybrid sensor with low detection limit (152 ppb). Furthermore, excellent sensor characteristics such as complete reversibility, repeatability, and minimal humidity effect indicate that the layer-by-layer assembled imp-PMAA/Au-NPs hybrid sensor is useful for potential applications in monitoring indoor air quality.