Electrochemical Investigations of 3-(3-Thienyl) Acrylic Acid Protected Nanoclusters and Planar Gold Surfaces

Abstract

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.

Single‐Molecule Conductance Studies of Organometallic Complexes Bearing 3‐Thienyl Contacting Groups

“…In seeking to further explore the electrical properties of oligophenyleneethynylene (OPE), and trans ‐bis(alkynyl) complexes of platinum and ruthenium, we have turned to such a systematic study here. Here, the 3‐thienyl moiety, which is readily introduced into both organic and organometallic structures, is used as a contacting group for the ready attachment of organic, ruthenium and platinum‐based organometallic complexes within Au|molecule|Au junctions and electrical characterisation by using both the I ( s ) (measuring the tunnelling current ( I ) as a function of distance ( s )) and STM‐BJ methods. The conductance results are interpreted with the aid of DFT level calculations and junction simulations.…”

Control of Stripelike and Hexagonal Self-Assembly of Gold Nanoparticles by the Tuning of Interactions between Triphenylene Ligands

“…28 Many groups are interested in the π-π interaction of organic protective agents to control various types of assembly of NPs, 29 for example, spherical aggregates by terthiophene 30 and 2D assembly by pyrene units 31,32 or by thiophene ligands. 33 1D assemblies of NPs can also be realized by fixation on the 1D matrix by π-π interactions. 34 To the best of our knowledge, no report has appeared yet for the 1D stripelike arrangement of NPs induced by interactions of organic protective agents.…”

“…We succeeded in arranging small Au NPs (less than 2 nm diameter) in 2D by the aid of π−π interaction of bisimidazole pyridine ligand in 2000 . Many groups are interested in the π−π interaction of organic protective agents to control various types of assembly of NPs, for example, spherical aggregates by terthiophene and 2D assembly by pyrene units , or by thiophene ligands . 1D assemblies of NPs can also be realized by fixation on the 1D matrix by π−π interactions .…”