In-situ synthesis of ultrasmall ZnCoS nanoparticles on bimetallic metal-organic framework for enhanced electrochemical sensing of dopamine

Abstract Integrating bimetallic sulfides into metal-organic frameworks (MOFs) crystal materials to develop MOF-based composites was an effective strategy to enhance the electrochemical performance of MOFs. Herein, bimetallic MOF zinc/cobalt-porphyrin (ZnCo-TCPP) nanosheets were firstly prepared using a facile surfactant-assisted method, and then ZnCoS/ZnCo-TCPP was synthesized by in-situ sulfidation of ZnCo-TCPP with thioacetamide (TAA) under different vulcanization times. Subsequently, a novel dopamine (DA) sensing method was established based on these materials. The morphologies, compositions and structures of these compounds were characterized by Transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and N2 adsorption/desorption isotherm. The characterization results indicated that ZnCoS with a size of about 5 nm were uniformly dispersed on the surface of ZnCo-TCPP without agglomeration. The electrochemical results demonstrated that ZnCoS/ZnCo-TCPP had the highest current response to DA oxidation with the vulcanization time of 3 h. The linear range of the sensor based on ZnCoS/ZnCo-TCPP was 0.01-327.8 μM, the detection limit was determined to be 3 nM (S/N＝3), and the sensitivity was 379.3 μA mM−1 cm−2. Compared with analogous types DA sensors reported in previous literature, the linear range of this sensor had been expanded by at least an order of magnitude, and the detection limit had been reduced by at least an order of magnitude. Furthermore, the fabricated sensor was used to detect DA in human serum with the recoveries ranged from 96.26% to 103.6%. The acceptable recoveries rate proved that the sensor had the potential for the efficient determination of DA. The proposed strategy provided a discriminative and sensitive analytical platform for DA clinical diagnostics and drug screening. Keywords: Electrochemical sensing, Bimetallic MOF, Bimetallic sulfides, Dopamine.摘要 将双金属硫化物引入金属有机框架（metal-organic frameworks, MOFs）晶体材料以制备MOF基复合材料，是提升MOFs电化学性能的有效策略。本文首先采用简便的表面活性剂辅助法制备了双金属MOF锌/钴卟啉（ZnCo-TCPP）纳米片，随后通过不同硫化时间下硫代乙酰胺（thioacetamide, TAA）对ZnCo-TCPP进行原位硫化，合成了ZnCoS/ZnCo-TCPP复合材料。基于上述材料，本文构建了一种新型的多巴胺（dopamine, DA）检测方法。采用透射电子显微镜、X射线光电子能谱、X射线衍射以及氮气吸附-脱附等温线对上述化合物的形貌、组成与结构进行了表征。表征结果显示，粒径约5 nm的ZnCoS均匀分散在ZnCo-TCPP表面，未出现团聚现象。电化学测试结果表明，当硫化时间为3 h时，ZnCoS/ZnCo-TCPP对多巴胺氧化反应的电流响应最高。基于ZnCoS/ZnCo-TCPP制备的传感器线性范围为0.01~327.8 μM，检出限为3 nM（信噪比S/N=3），灵敏度可达379.3 μA·mM⁻¹·cm⁻²。与已有文献报道的同类多巴胺传感器相比，本传感器的线性范围至少扩大了一个数量级，检出限至少降低了一个数量级。此外，将所制备的传感器应用于人血清中多巴胺的检测，回收率为96.26%~103.6%。该回收率结果表明，本传感器具备高效检测多巴胺的应用潜力。本研究提出的策略为多巴胺的临床诊断与药物筛选提供了一种特异性强、灵敏度高的分析平台。 关键词：电化学传感、双金属MOF、双金属硫化物、多巴胺。