聚多巴胺原位还原银纳米增强碳点荧光自组装纳米复合膜用于检测葛根素研究

以胱氨酸和柠檬酸为碳源，采用一步水热法合成了氮硫掺杂结构的蓝色荧光碳点(FCDs)。FCDs在350 nm波长光源激发下，于455 nm出现最大的荧光发射峰。碳点水溶液在pH=6~11范围内都呈现稳定的荧光发射，具有61.7%的高荧光量子产率和10.75 ns的长荧光寿命。以此碳点为目标物，设计层层自组装膜的简易制备方案，探究银纳米复合基底对其荧光信号的增强效应，通过增强型荧光传感膜实现提高药物检测灵敏度的目的。实验过程中利用多巴胺碱性溶液的自聚合和还原效应，在玻璃基底上形成平整的聚多巴胺膜，同步进行硝酸银原位还原，可制得均匀分散的聚多巴胺复合银纳米膜基底。紫外光谱、荧光光谱、扫描电子显微镜和电子能谱检测结果表明，在多巴胺聚合膜形成过程中原位还原的银纳米，具有操作简便和稳定性能好优点，纳米颗粒不易被氧化。结合层层自组装多层膜技术(layer-by-layer self-assembled mutilayers, LBL SAMs)，在纳米复合膜表面组装聚电解质分子层，精确调控银纳米与碳点的间隔距离，构建荧光性自组装膜FTO/PDA-AgN/PDDA/PSS/PDDA]₃/FCDs，探究银纳米对碳点的荧光增强效应。研究结果表明，当聚多巴胺复合银纳米基底与碳点之间达到一定间隔距离时，银纳米粒子可增强自组装膜上碳点的荧光信号，荧光强度增加近3倍，相应的荧光寿命由6.084 ns减小至2.983 ns。这种荧光增强效应呈现出来的距离依赖性、辐射衰减加快和与银纳米还原程度相关性，表明增强荧光的机理可能为银纳米和碳点之间的局域表面等离子共振效应。葛根素的加入使传感膜上碳点的荧光信号发生猝灭，猝灭的程度和葛根素的含量在3.33×10-7~1.50×10-5 mol·L-1范围内呈现良好的线性关系，可建立荧光传感薄膜对葛根素的含量检测。线性回归方程为I₀/I=2.843×104c_Pue+1.068，相关系数r=0.9985 6，检出限QL=2.31×10-7 mol·L-1。相比于FTO/PDA/PDDA/PSS/PDDA]₃/FCDs，增强荧光型传感膜明显提高了对葛根素的响应灵敏度，检测限降低近一个数量级。

Self-Assembled Nanocomposite Film of AgN In-Situ Grown on Polydopamine With Enhanced Fluorescence of CDs for Detection of Puerarin

The S,N co-dopedcarbon dots was obtained through the one-step hydrothermal treatment of cystine and citric acid.The results suggested that the prepared carbon dot solution has fluorescence emission at 455 nm with an excitation wavelength of 350 nm.This fluorescent Carbon Dots(FCDs)showed stableemission performancein pH 6~11 and bright blueemission with a quantum yield of 61.7%and an average lifetime of 10.75 ns.In this article,a sample preparation scheme with self-assembled nanocomposite film of silver nanoparticle(AgN)was designed to enhanced the optically stimulated luminescence emission of FCDs.The enhance PL signal of FCDs grown on sensing film leading to a higher sensitivity of drug content detection.A uniform nanocomposite film substrate was prepared via the reduction in situ of silver ions in polydopamine(PDA).The Enhanced Fluorescence film FTO/PDA-AgN/PDDA/PSS/PDDA]3/FCDs was achieved by self-assembled the polyelectrolyte molecular Layer-by-Layer(LbL)on the nanocomposite film that was utilized to control the distance of silver nanoparticle(AgN)and fluorescent Carbon Dots(FCDs).The synchronous reduction method was easy to operate,and theresults of Ultraviolet,Fluorescence,Raman spectra and scanning electron microscopy revealed that the composite silver nanostructure in polydopamine film result in the AgN has the advantage of not being oxidized.The silver nanoparticles could enhance the optically stimulated luminescence emission of FCDs as the separation distance was optimally designed between FCDs and AgN surface,the fluorescent intensity of FCDs in SAMs increased by nearly 3 times with the corresponding fluorescence lifetime reduced from 6.08 to 2.98 ns.The characteristics of the AgN-enhanced fluorescence which has distance-dependence,accelerated radiation attenuation and correlation with the reduction degree of AgN were additional evidence for a local surface plasmon resonance effect between AgN and FCDs.The experimental results showed that the addition of puerarin(Pue)quenched the fluorescence signal of FCDs,and the degree of quenching had a good linear relationship with the content of puerarin in the range of 3.33×10^-7~1.50×10^-5 mol·L^-1.The linear regression equation is I0/I=2.843×10^4cPue+1.068,the correlation coefficient R=0.99856,and the detection limit QL=2.31×10^-7 mol·L^-1.This established AgN-enhanced fluorescence system based on the SAMs could increase the sensitivity of the detection for puerarin as the detection limit was reduced about an order of magnitude.