石墨烯量子点-金纳米簇比率荧光传感器用于海水pH检测

表层海洋pH正以约每年0.002的速度下降，这种变化将会对地球的化学循环和气候变化的物理化学参数产生潜在的影响。为了准确了解海洋的酸化程度，本文建立了一种快速准确检测海水pH的方法。采用柠檬酸热解法合成石墨烯量子点（GQDs）,以谷胱甘肽（GSH）为模板合成金纳米簇（GSH-AuNCs）,将GQDs和GSH-AuNCs结合制成GQDs-AuNCs比率荧光传感器，用于海水pH的检测。在酸性条件下，由于GSH-AuNCs表面的羧基发生质子化，GSH-AuNCs分子之间的静电斥力减弱因而发生聚集，荧光强度随之降低。在碱性条件下，GSH-AuNCs表面的羧基脱质子化，GSH-AuNCs分子之间的静电斥力增强，荧光强度也随之增强。在pH 2～11范围内，GQDs-AuNCs比率荧光探针的荧光强度比值(I₅₆₅/I₄₄₀)与pH之间呈线性相关。将该方法用于海水的pH检测，得到较好的实验结果。

Graphene quantum dots-gold nanoclusters ratiometric fluorescence sensor for seawater pH detection

The pH of the surface ocean is decreasing at a rate of about 0. 002 per year, which will have a potential impact on the chemical cycle of the earth and the physicochemical parameters of climate change. In order to accurately understand the degree of ocean acidification, we established a rapid and accurate method to detect seawater pH. Graphene quantum dots (GQDs) were synthesized by citric acid pyrolysis method, and gold nanoclusters (GSH-AuNCs) were synthesized using glutathione (GSH) as template. GQDs and GSH-AuNCs were combined to fabricate a GQDs-AuNCs ratio metric fluorescence sensor for seawater pH detection. Under acidic conditions, the electrostatic repulsion between GSH-AuNCs is weakened due to the protonation of carboxyl groups on the surface of GSH-AuNCs, which leads to the aggregation of GSH-AuNCs and the decrease of fluorescence intensity. Under alkaline conditions, the carboxyl groups on the surface of GSH-AuNCs are deprotonated, the electrostatic repulsion between GSH-AuNCs molecules increases, and the fluorescence intensity also increases. When the pH is in the range of 2 ~ 11, the fluorescence intensity ratio (I565 / I440 ) of GQDs-AuNCs ratiometric fluorescent probe is linearly correlated with the pH value. This method was used for pH detection of seawater, and good experimental results were obtained.