日光辐射光还原合成左旋多巴胺功能化的荧光发射的银纳米簇和铁离子检测

以左旋多巴胺(L-3,4-dihydroxyphenylalanine,DOPA)为稳定剂,采用日光辐射光还原法,合成了强荧光发射的银纳米簇(silver nanoclusters,Ag NCs)。透射电镜分析表明,所合成的Ag NCs表现亚纳米非晶态结构。Ag NCs在可见-近红外波长范围内(400~750 nm)有明显光吸收带,最大荧光激发和发射峰分别为550和630 nm,荧光量子产率为2.3%(相对于罗丹明B)。Ag NCs的荧光强度与合成时的日光辐射时间、DOPA浓度以及pH值等因素有关。进一步优化了合成Ag NCs的条件。基于荧光猝灭原理,所合成的DOPA功能化的Ag NCs能选择性地灵敏响应Fe3+。修饰在Ag NCs表面的配体DOPA能够选择性地结合Fe3+,导致Ag NCs显著聚集,伴随荧光猝灭。Ag NCs具有的较高量子产率和红荧光发射特性,有利于提高Fe3+的分析灵敏度。

Synthesis of DOPA-Functionalized Fluorescent Silver Nanoclusters via Sunlight Photo-Reduction for Ferric Ion Assay

Highly fluorescent silver nanoclusters (Ag NCs) are synthesized by a facile sunlight photo-reduction approach where L-3, 4-dihydroxyphenylalanine (DOPA) serves as stabilizers. TEM analyses reveal that the as-prepared Ag NCs is subnanoscaled and noncrystalline. Such Ag NCs possess significant absorption in visible and near-infrared wavelength range of 400~750 nm, and fluoresce at 630 nm (maximum emission) when excited at 550 nm with a quantum yield (QY) of 2.3% (referred to Rhodamine B). The fluorescence intensity highly depends on the synthesis conditions, such as sunlight irradiation time, the DOPA concentration and pH value. Thus the conditions for synthesis of Ag NCs have been further optimized. Moreover, such DOPA-functionalized Ag NCs can sensitively and selectively response ferric ions on the basis of fluorescence quenching. The specific coordination between ferric ions and the DOPA ligands, which stabilizes the as-prepared Ag NCs, allows aggregation of the silver nanoclusters and concomitant significant fluorescence quenching. Both the high brightness and the red-emission of the as-formed Ag NCs provide higher sensitivity for Fe³⁺ assay.