巰基苯甲酸異構物對銅奈米團簇的製備及其螢光性質的影響

Abstract

本篇論文主要開發一步合成法在70 °C利用巰基苯甲酸（mercaptobenzoic acid）與銅離子反應30分鐘來合成發光銅奈米團簇聚集體（copper nanocluster aggregates），且藉由使用不同的巰基苯甲酸異構物，可合成出具有不同物理及光學性質的銅奈米團簇。以鄰、對巰基苯甲酸分別可合成出具有藍色及紅色放光性質的銅奈米團簇，其量子產率分別為13.2% 和 0.5%。另一方面，以間巰基苯甲酸合成的銅奈米團簇雖具放紅光性質，但十分微弱。隨著 pH 值的提高，鄰巰基苯甲酸與對巰基苯甲酸合成的銅奈米團簇，其螢光分別有上升以及下降的趨勢，其中對巰基苯甲酸之銅奈米團簇具有聚集誘導放光的性質，相較之下，由於鄰巰基苯甲酸之銅奈米團簇具有在水溶液分散性好、穩定以及高量子產率的特性，其可透過分析物誘導消光作用（analyte-induced fluorescence quenching）用於氰離子的偵測，其偵測極限（limit of detection）為 5 nM。

An one-pot approach has been developed to synthesize copper nanoclusters (Cu NCs) aggregates from copper nitrate and mercaptobenzoic acid (MBA) at 70 °C within 30 min. Cu NCs prepared separately from the three isomers of MBA exhibit different physical and optical properties. 2-Mercaptobenzoic acid (thiosalicylic acid, TA) and 4-mercaptobenzoic acid (4-MBA) allow preparation of blue- and red-emissive Cu NCs aggregates when excited at 338 and 324 nm, with quantum yields of 13.2% and 0.5%, respectively. On the other hand, Cu NCs aggregates prepared from 3-mercaptobenzoic acid (3-MBA) have very weak red-emission properties. Upon increasing pH values from 3.0 to 11.0, the fluorescence intensity of TA-Cu NCs and 4-MBA-Cu NCs aggregates increases and decreases, respectively. Unlike TA-Cu NCs aggregates, 4-MBA-Cu NCs aggregates show strong aggregation-induced emission. The water-dispersible, stable, and highly fluorescent TA-Cu NCs aggregates allow detection of CNˉ down to 5 nM, based on analyte-induced fluorescence quenching.