In this study, a facile and environment-friendly method for the preparation of bovine serum albumin (BSA) capped fluorescent Cu nanoclusters (BSA-CuNCs) was adopted. The as-prepared BSA-CuNCs were characterized by ultraviolet-visible spectroscopy (UV-Vis), fluorescent spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM). The fluorescence excitation and emission wavelength of BSA-CuNCs appeared at 325 and 406 nm, respectively. The as-synthesized BSA-CuNCs can be utilized as a bi-functional nanomaterial for pH sensing and dopamine (DA) detection with good performance. The fluorescence intensity decreased linearly with decrease in pH from 12 to 5 and increased linearly with increase in DA concentration from 0.5 to 50 μM. TEM measurements proved that the decrease in the pH value resulted in the aggregation of BSA-CuNCs, leading to color change and the quenching of fluorescence. The FT-IR spectra, fluorescent spectra, UV-Vis spectra and zeta potential measurements demonstrated that DA can be combined with Cu²⁺ and the Cu²⁺ would be removed from the surface of BSA-CuNCs. As a result, the fluorescence was recovered owing to the formation of the highly stable compound CuH₂(DA)₂. The pH value of five water samples was determined by the proposed method with relative errors of less than 0.91%. Furthermore, DA in human urine samples was also analyzed by BSA-CuNCs with good recoveries ranging from 90.4% to 104.7% using the standard addition method. It is believed that the bi-functional BSA-CuNCs will show great potential in bio-systems.

中文翻译：

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BSA封盖双功能荧光铜纳米簇作为pH传感器并选择性检测多巴胺

在这项研究中，采用了一种简便且环保的方法来制备牛血清白蛋白（BSA）封端的荧光铜纳米簇（BSA-CuNCs）。所制备的BSA-CuNC通过紫外-可见光谱（UV-Vis），荧光光谱，傅立叶变换红外（FT-IR）光谱和透射电子显微镜（TEM）表征。BSA-CuNCs的荧光激发和发射波长分别出现在325和406 nm。合成后的BSA-CuNCs可以用作具有良好性能的用于pH传感和多巴胺（DA）检测的双功能纳米材料。荧光强度随着pH值从12降低到5线性下降，并且随着DA浓度从0.5到50μM线性增加。TEM测量证明，pH值降低导致BSA-CuNCs聚集，导致颜色变化和荧光猝灭。FT-IR光谱，荧光光谱，UV-Vis光谱和zeta电位测量结果表明DA可以与Cu结合使用²⁺和Cu ²⁺将从BSA-CuNCs的表面去除。结果，由于形成了高度稳定的化合物CuH ₂（DA） ₂而恢复了荧光。通过提出的方法测定了五个水样品的pH值，相对误差小于0.91％。此外，BSA-CuNC还使用标准添加方法对人尿样品中的DA进行了分析，回收率在90.4％至104.7％之间。据信，双功能BSA-CuNCs将在生物系统中显示出巨大的潜力。