Nirmal R G, Kavitha A L, Berchmans Sheela, Yegnaraman V
Central Electrochemical Research Institute, Karaikudi 630006, Tamilnadu, India.
J Nanosci Nanotechnol. 2007 Jun;7(6):2116-24. doi: 10.1166/jnn.2007.780.
Formation of self assembled monolayers on gold surface by thiols and disulphides is a well known phenomenon and extensive research work has been carried out in this area with envisaged applications in the area of sensors, molecular electronics, lithography, device fabrication using bottom-up approach, etc. Recently, it has been established that thiophene molecules can self assemble on gold surface due to Au-S interactions. 3-(3-thienyl) acrylic acid, a bifunctional ligand is used in this work to form self-assembled monolayers on planar gold surfaces (two dimensional assemblies) and to prepare monolayer protected gold nano clusters (three-dimensional assemblies). The electron transfer blocking properties of the two-dimensional monolayers were evaluated by using standard redox probes like ferrocyanide anions and Ruthenium hexamine cations. The functionalisation of the two-dimensional and three-dimensional assemblies has been carried out with ferrocene carboxylic acid and the functionalised monolayers were characterized by Cyclic voltammetry. The formation of thienyl acrylic acid protected nanoclusters has been verified by TEM and surface plasmon resonance absorption. It has been observed that when thiophene based ligands are used as stabilizers for the formation of metal nanoparticles, they tend to aggregate as a result of pi-pi interactions between adjacent thiophene ligands. In this case it is found that aggregation is prevented. The substituent at the thiophene ring hinders pi-pi interactions. The quantised nature of electrochemical charging of these nanoparticles has been demonstrated by differential pulse voltammetry (DPV), which exhibit peak like features (coulomb's staircase). This work also explores the possibility of using 3-(3-thienyl) acrylic acid as building blocks or spacers on planar and colloidal gold surfaces for potential applications in the field of sensors and devices.
硫醇和二硫化物在金表面形成自组装单分子层是一种众所周知的现象，并且在该领域已经开展了广泛的研究工作，其设想应用于传感器、分子电子学、光刻、自下而上方法的器件制造等领域。最近，已经确定噻吩分子由于金 - 硫相互作用可以在金表面自组装。在这项工作中，使用双功能配体3 - （3 - 噻吩基）丙烯酸在平面金表面形成自组装单分子层（二维组装）并制备单分子层保护的金纳米簇（三维组装）。通过使用标准氧化还原探针如亚铁氰化物阴离子和六胺钌阳离子来评估二维单分子层的电子转移阻断性能。二维和三维组装体已用二茂铁羧酸进行功能化，并且通过循环伏安法对功能化的单分子层进行了表征。通过透射电子显微镜（TEM）和表面等离子体共振吸收验证了噻吩基丙烯酸保护的纳米簇的形成。已经观察到，当基于噻吩的配体用作形成金属纳米颗粒的稳定剂时，由于相邻噻吩配体之间的π - π相互作用，它们倾向于聚集。在这种情况下，发现聚集被阻止。噻吩环上的取代基阻碍了π - π相互作用。通过差分脉冲伏安法（DPV）证明了这些纳米颗粒电化学充电的量子化性质，其表现出类似峰的特征（库仑台阶）。这项工作还探索了在平面和胶体金表面上使用3 - （3 - 噻吩基）丙烯酸作为构建块或间隔物在传感器和器件领域潜在应用的可能性。
