Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, PR China.
Langmuir. 2013 Jan 29;29(4):1199-205. doi: 10.1021/la304558r. Epub 2013 Jan 14.
Silver nanoclusters capped by hyperbranched polyethylenimine (PEI) have been developed as a highly sensitive fluorescent and colorimetric pH sensor. The probe responds rapidly to pH fluctuations and has such absorption characteristics that the color changes from the colorless or a nearly colorless state to a colored state with increasing acidity, so PEI-capped Ag nanoclusters could be used as a color indicator for colorimetric pH detection. Quantitatively, the fluorescence intensity of PEI-capped Ag nanoclusters exhibits a linear fashion over the pH range of 5.02-7.96 and increases by around 10-fold approximately with greater fluorescence at higher pH values. The repulsion development and conformational change of PEI with decreasing pH induce the aggregation of Ag nanoclusters, leading to an obvious color change and fluorescence quenching of Ag nanoclusters at low pH values. As expected, the pH probe is also sensitive to the different buffer solutions, except for those containing some anions that could react with Ag nanoclusters. Besides, the ionic strength of the buffers has a little influence on the pH-responsive behavior. Our pH sensor with nanoscaled physical dimensions would be a promising candidate in the applications in biological, medical, and pharmaceutical fields.
用超支化聚乙烯亚胺（PEI）包覆的银纳米簇已被开发为一种高灵敏度的荧光和比色 pH 传感器。该探针对 pH 波动响应迅速，且具有这样的吸收特性：颜色从无色或近乎无色状态变为随着酸度增加而呈现有色状态，因此 PEI 包覆的 Ag 纳米簇可用作比色 pH 检测的颜色指示剂。定量地说，PEI 包覆的 Ag 纳米簇的荧光强度在 pH 值为 5.02-7.96 的范围内呈线性变化，并且在较高 pH 值下荧光强度增加约 10 倍左右。随着 pH 值的降低，PEI 的斥力发展和构象变化会导致 Ag 纳米簇的聚集，从而导致 Ag 纳米簇在低 pH 值下发生明显的颜色变化和荧光猝灭。正如预期的那样，该 pH 探针除了对那些能与 Ag 纳米簇反应的阴离子存在的缓冲溶液不敏感外，还对不同的缓冲溶液敏感。此外，缓冲液的离子强度对 pH 响应行为的影响较小。我们的纳米级物理尺寸的 pH 传感器将是生物、医学和制药领域应用的有前途的候选者。
