Preparation and structure of amino-acid films based on vacuum deposition processing with and without an irradiation of inductively coupled plasma

Amino acids are capable of constructing supramlecular networks through the multiple hydrogen bonds. Dry processing can produce amino-acid films withou t the influence of polar solvents, which are usually used for dissolving am ino acids in wet processing. In this study, D-phenylalanine (D-Phe) films a re prepared by vacuum vaporization methods with and without the assistance of irradiation of inductively coupled plasma (ICP). The vaporized film with out ICP irradiation (Vap film) consists of round sponge-like masses (2- to 6-mu m diameter) and the content of raw material D-Phe is 72%. Infrared and X-ray photoelectron spectroscopies clarified that there exists little diff erences between the raw D-Phe and the Vap film. ICP irradiation during vapo rization of D-Phe flattened the resultant film surface extremely well and r educed the content of D-Phe to 1.7%. The ICP-treated films have the unpaire d electrons at their concentrations of several 10(4) spins/cm(3). Slight re duction of atomic ratios of oxygen in these vaporized films may have been c aused by the dehydration and decarboxylation reactions. However, the differ ences in atomic ratios between these vaporized films and the raw D-Phe are quite small.