銅離子是調節人類中樞神經系統功能的重要元素，根據研究結果顯示不只阿茲海默症、帕金森症、威爾遜症、門克斯症等主要神經疾病，還有糖尿病和骨質疏鬆症都與銅離子濃度息息相關，因此使用精確和快速的方法監測銅離子濃度非常重要。而傳統的檢測方法通常耗時且操作複雜，所以光致發光傳感器因為操作簡單、靈敏度高和檢測限低而被視為一種很有前景的銅離子檢測方法，引起了研究學者們的極大興趣。表面增強拉曼散射是一種增強拉曼訊號的技術，可以對低濃度的分析物進行高靈敏度檢測。最近的研究中常使用貴重金屬奈米粒子作為表面增強拉曼散射的活性基材，利用電磁增強以及化學增強機制來提高增強效率。本研究提供了一種自下而上的方法，通過大氣常壓微電漿輔助法藉由調控金前驅物和半胱胺酸的莫爾濃度比合成具有多功能的發射光可調金奈米團簇，應用於光致發光傳感和表面增強拉曼散射。而金奈米團簇透過一系列材料鑑定後可以發現到金屬核的大小會影響光致發光的波長，並在雷射光激發下能夠產生表面電漿子共振的現象。對於銅離子的光致發光感測的部分，金奈米團簇和銅離子具有高親和力可形成金奈米團簇和銅離子的複合物以降低光致發光強度，進而推測出主要猝滅機製為靜態猝滅，並在優化的條件下可以達到13 nM濃度偵測極限。在表面增強拉曼散射的研究中而除金屬核大小，金奈米團簇表面含氫官能基能提供氫建和凡德瓦力來提升材料的吸附效能和電子遷移率，應用於羅丹明6G染劑與生物分子葉酸的偵測下可以達到10 nM和1 μM濃度偵測極限。因此本研究藉由微電漿提供了一種簡便、低反應時間和環保的方法合成具有高靈敏度和寬線性範圍的多功能應用的金奈米團簇並探討各應用的感測機制。

The detection of copper ion is important for monitoring the central nervous diseases. However, conventional detection methods are usually time-consuming and involve complex operation. Recently, photoluminescent (PL) sensors have garnered great interest due to operational simplicity, high sensitivity, and low detection limits and have been reported as a promising method for copper ion detection. Moreover, surface enhanced Raman spectroscopy (SERS) is a powerful technique to perform highly sensitive detection of analytes at low concentrations. A recent study demonstrates that metal clusters with the core size less than 3 nm exhibit unique molecule-like electronic transition properties can be used for PL-based sensing and SERS-based applications. In this work, we report a bottom-up method to synthesize photoluminescent Au clusters at ambient conditions by atmospheric-pressure microplasma. The highly energetic electron and free radicals generated by microplasma can promote the growth of Au clusters in the liquid phase. The copper ion is the electron acceptor, the fluorescence of Au clusters is effectively quenched upon the addition of copper ion. As a result, a linear relationship between copper ion concentration and PL intensity ratio was obtained starting from 0.04-50 µM with a limit of detection (LoD) of 13 nM. In the SERS part, through control the charge transfer by controlling the fluorescence emission of Au clusters. The red-Au clusters show LoDs as low as 10 nM and 1 µM for R6G and folic acid, respectively. Overall, our work provides a facile and environmental-friendly synthesis of Au clusters for copper ion detection with high sensitivity, and wide linear range, and the uniform and sensitive SERS substrates.

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