<title>Smart chemical sensors using ZnO semiconducting thin films for freshness detection of foods and beverages</title>

ABSTRACT The sensitivity ofthe chemical sensor, based on the resistance change ofAl2O3-doped and &i02-doped ZnO(ZnO:A1 and ZnO:Sn02) thin film, is studied for exposure to various gases. It is found that the ZnO:A1 andZnO:Sn thin film chemical sensor has a high sensitivity and excellent selectivity for amine (TMA and DMA) gas and ethanol gas, respectively. The ZnO:A1 (5.Owt%) thin film chemical sensor which exhibit a highsensitivity for exposure to odors from rotten sea foods, such as salmon, sea lweam, oyster, squid and sardine,responds to the freshness change ofthese sea foods. The ZnO:Sn02 (78wt%) thin film chemical sensor which exhibit a high sensitivity for exposure to aroma from alcohols, such as wine, Japanese sake, and vthisky, responds to the freshness change ofthese alcohols.Keywords: ZnO, thin films, chemical sensor, gas sensor, freshness detection, foods, beverages 1. DTRODUCTION Recently, the detection of freshness of foods and beverages has become an important task in many fields offood and drink industiy, such as food and drink processing andtechnology. It is ofurgent necessity to developa rapid and non-destructive method capable of detecting the freshness of foods and beverages. In order todevelop the smart chemical sensor suitable for freshness detection offoods or beverages, wehave prepared ZnO