Fabrication of poly(N-isopropylacrylamide) nanoparticles using a simple spray-coating method and applications for a QCM-based HCl gas sensor coating

- Fabrication of PNIPAM nanoparticles by a novel spray-coating method for a HCl gas sensor coating was proposed.
- Nanoparticles were successfully formed on the resonator surface and their mean diameter was ∼100 nm.
- The sensor response was three times larger than that of the sensor created with the former method.
- The value of the recovery was unexpectedly less than 90%.
- Higher temperature led to a reduction of the influence of humidity on the HCl gas sensor response.

We propose a new simplified fabrication process for poly(N-isopropylacrylamide) (PNIPAM) nanoparticles for a quartz crystal microbalance (QCM)-based HCl gas sensor coating. PNIPAM solution, synthesized via atom transfer radical polymerization (ATRP) below a lower critical solution temperature (LCST), is simply sprayed onto a heated quartz resonator surface at 50 °C; nanoparticles with a mean diameter of 100 nm were successfully formed with this method. The PNIPAM nanoparticles produced exhibited a large HCl gas sensor response, and the magnitude of the response increased linearly with PNIPAM loading on the resonator. However, the value of the recovery was unexpectedly less than 90%. The hydrogen-bonding structure of the nanoparticles produced was characterized by water vapor adsorption measurement and FT-IR analysis in a humid atmosphere.