A gas sensor based on natural dye-sensitized TiO 2 thin film for pork-borne amines monitor

China is the world's biggest market for pork in terms of production as well as consumption. The concentration of amines is a quality criterion for pork freshness. To detect the pork-borne amines quickly and noninvasively, a dye-sensitized TiO 2 thin film gas sensor was developed in this article. Firstly, TiO 2 films were deposited on glass by DC magnetron sputtering method. About 0.5μm thick of TiO 2 depositions were performed from 6mm thick targets with a diameter of 100 mm onto glass substrates with a sputtered-Au counter electrode. Secondly, the natural dyes were extracted from spinach (Spinacia oleracea), red radish (Raphanus sativus L), winter jiasmine (Jasminum nudiflorum), and black rice (Oryza sativa L. indica) by ethanol, and kept as sensitizing compounds. Thirdly, the TiO 2 film was immersed in an ethanol solution containing a natural dye for 24 h to absorb the dye on TiO 2 film adequately. Therefore, a TiO 2 thin film gas sensor was prepared. The dye sensitized TiO 2 thin film gas-sensitivity to spermine was examined at room temperature. The results indicated that, the black-rice dye, which has the highest anthocyanin among the four nature dyes, sensitized film showed excellent gas-sensitivity to spermine of 500ppb, and had good selectivity to analogy gases such as spermidine, putrscine, and cadaverine that will increase during storage. The film is good for monitoring the freshness of pork.