POTENTIAL USE OF PLASMA-DEPOSITION TECHNIQUES IN THE PREPARATION OF RECOGNITION COATINGS FOR MASS SENSORS

The potential use of plasma-deposition techniques for the preparation of recognition coatings for mass sensors was investigated. Ethylenedia mine and 4-vinylpyridine plasma-produced coatings and solution-deposit ed coatings from commercially available polyethyleneimine and poly(4-v inylpyridine) on quartz crystal microbalances (QCMs) were examined for the detection of acetic acid and other vapors. Freshly prepared QCM p lasma-deposited recognition coatings from both ethylenediamine and 4-v inylpyridine were found to be very sensitive to acetic acid vapors. Ho wever the sensitivity decreased rapidly with time. Aging effects with solution deposited polymers films were noted as well. It was concluded that plasma-deposition of recognition coatings has great potential in the preparation of recognition coatings. In addition to well known ad vantages of the use of plasmas for surface film preparation or modific ation, the technique offers a one-step process of synthesizing and dep ositing high molecular weight films from volatile compounds not polyme rizable by conventional means. A major disadvantage is that the chemic al nature of the resulting coating is not easily predictable. However, careful choice of carrier gas and recognition film precursor can do m uch to simplify the design of effective recognition coatings.