Aging effect of a molecularly imprinted polymer on a quartz tuning fork sensor for detection of volatile organic compounds

The sensing stability and sensitivity of a molecularly imprinted polymer (MIP) selective to the adsorption of hydrocarbons was studied. The MIP was deposited on a quartz crystal tuning fork (QTF) resonator, whose chemical and physical properties were monitored over time, using Scanning Electron Microscopy (SEM), Brunauer–Emmett–Teller adsorption isotherm analysis (BET), and Fourier transform infrared spectroscopy (FTIR). In addition, kinetic binding analysis of the MIP-modified QTF sensor was carried out for the sensors stored and operated under ambient conditions (740 mmHg, 20–23 °C). Although the polymer was able to maintain its physical and chemical properties at microscopic, BET adsorption, and spectroscopic levels, the intrinsic adsorption properties of hydrocarbons onto MIP binding sites altered over time, which suggest that the 3-D conformational changes of the polymer binding sites occurring at nanoscopic/angstrom level may cause the sensitivity degradation in MIP. The changes were significantly reduced by stabilizing the polymer under low storage temperatures.