天然茶葉黑色素作為薄膜半導體特性之研究

Abstract

黑色素是屬於生物高分子的一種，存在於植物、動物和微生物的獨特色素。黑色素主要功能在於保護生物免於太陽輻射的直接照射。黑色素是個具有清除自由機活性功能的抗氧化劑，亦是重金屬的螯合劑，也對有毒有機分子具有強吸收性。黑色素本身無毒且具有生物親和力，是對抗有毒化學物和重金屬的天然保護劑。黑色素是從茶葉中大量萃取出來。我們可以利用掃描式電子顯微鏡、能量分散式光譜儀、光學顯微鏡、傅立葉轉換紅外線光譜儀，去分析確認黑色素的導電性、組成、物理特性。非晶質的黑色素薄膜具有半導體特性。透過碘元素的摻雜可以增加其導電性。由我們結果知道從茶葉萃取出來的黑色素，是具有低毒性天然的材料，可以當作低溫製程下的電子元件，且從以前的結果報告也知道黑色素薄膜具有開關特性。透過半導體製程的黑色素薄膜，也可以製作成有機薄膜電晶體，為具有開關特性的元件。茶葉黑色素製作的有機薄膜電晶體表現出漸增式P型通道特性。利用氧化處理也可以加強茶葉薄膜的導電性，從黑色素薄膜具有導電性，也許可以提供更進一步了解黑色素在生物體內所扮演的生物性功能。

Melanins belong to a family of pigmented biopolymers that occur widely in nature from plant, animal, to microbe. Their main function is to protect living organisms against UV radiation. Melanin is a strong antioxidant with free radical scavenging activity, a strong heavy-metal chelator, a strong organic toxin absorber, and bio-compatibility; thus, it serves as a natural guardian against hostile chemical and heavy-metal environments. Melanin was extracted from tea in large and economic scale. We also characterized the conductivity, composition, and physical properties of melanins by SEM, EDS, OM, and FTIR. An amorphous thin film of melanin exhibited semiconductor properties.Iodine-doping enhanced this conductivity. Our results indicated that melanin extracted from tea is an abundant resource of low-toxic and natural material for low temperature processing of electronic devices. Melanin thin film also presented a second switching voltage different from previous reports. Organic thin film transistors (OTFTs) based on semiconducting tea melanin films were fabricated, which acted as switch devices. Tea melanin OTFTs showed a p-channel enhancement property. Oxidation enhanced tea melanin films conductivity. The conductive properties for the tea melanin films might provide further insight into the biological function of tea melanin devices. Tea melanin OTFTs showed a p-channel enhancement property.Oxidation enhanced tea melanin films conductivity. The conductive properties for the tea melanin films might provide further insight into the biological function of tea melanin.