Quantitative Analysis of Weak Current Rectification in Molecular Tunnel Junctions Subject to Mechanical Deformation Reveals Two Different Rectification Mechanisms for Oligophenylene Thiols versus Alkane Thiols

Metal-molecule-metal junctions based on alkane thiol (CnT) and oligophenylene thiol (OPTn) self-assembled monolayers (SAMs) and Au electrodes are expected to exhibit similar electrical asymmetry, as both junctions have one chemisorbed...

Probing fibronectin adsorption on chemically defined surfaces by means of single molecule force microscopy

Atomic force microscope (AFM) based single molecule force spectroscopy (SMFS) and a quartz crystal microbalance (QCM) were respectively employed to probe interfacial characteristics of fibronectin fragment FNIII8–14 and full-length fibronectin (FN) on CH3–, OH–, COOH–, and NH2-terminated alkane-thiol self-assembled monolayers (SAMs). Force-distance curves acquired between hexahistidine-tagged FNIII8–14 immobilised on trisNTA-Ni2+ functionalized AFM cantilevers and the OH and COOH SAM surfaces were predominantly ‘loop-like’ (76% and 94% respectively), suggesting domain unfolding and preference for ‘end-on’ oriented binding, while those generated with NH2 and CH3 SAMs were largely ‘mixed type’ (81% and 86%, respectively) commensurate with unravelling and desorption, and ‘side-on’ binding. Time-dependent binding of FN to SAM-coated QCM crystals occurred in at least two phases: initial rapid coverage over the first 5 min; and variably diminishing adsorption thereafter (5–70 min). Loading profiles and the final hydrated surface concentrations reached (~ 950, ~ 1200, ~ 1400, ~ 1500 ng cm−2 for CH3, OH, COOH and NH2 SAMs) were consistent with: space-filling ‘side-on’ orientation and unfolding on CH3 SAM; greater numbers of FN molecules arranged ‘end-on’ on OH and especially COOH SAMs; and initial ‘side-on’ contact, followed by either (1) gradual tilting to a space-saving ‘end-on’ configuration, or (2) bi-/multi-layer adsorption on NH2 SAM.

Simulation Studies on the Interaction of Graphene and Gold Nanoparticle

In this computational study, the interaction between a single layer graphene sheet and a gold nanoparticle is investigated employing molecular dynamics (MD) simulation at room temperature. The interactions between the graphene and gold nanoparticle were explored for three different types of gold nanoparticle, namely, bare gold nanoparticle, methyl terminated alkane thiol-coated gold nanoparticle and hydroxy terminated alkane thiol-coated gold nanoparticle. The interactions between the graphene and gold nanoparticle have resulted in the adsorption of gold nanoparticle on the surface of graphene. The structural properties of the graphene–gold hybrid nanostructures were found to be influenced by the capping layer of the gold nanoparticle.

THE KINETICS OF THE AS GROWN AND ANNEALED SELF-ASSEMBLED MONOLAYER STUDIED BY FORCE SPECTROSCOPY

The growth of biological systems like DNA, peptides and proteins are accredited to the self-assembly processes from the molecular level to the nanoscale. The flawless immobilization of DNA on any surface is quite an important step to the development of DNA-based biosensors. The present paper reports the use of atomic force microscopy to determine the mechanical properties of the as grown and annealed self-assembled monolayer (SAM) as well as the mutated DNA immobilized on the SAM. The SAM of alkane thiol (16-mercapto-1-hexadecanol) was developed on Au surface, which was then annealed and analyzed for its structural and mechanical properties. The surface coverage, height and monolayer’s order was studied as a function of incubation time and annealing time. Excessive annealing led to the defragmentation and desorption of SAM structures due to breaking of hydrocarbon bonds. AFM was employed to determine the detach separation, pull-off and work of adhesion of the as grown and annealed SAM.

The significance of bromide in the Brust–Schiffrin synthesis of thiol protected gold nanoparticles

The mechanism of the two-phase Brust–Schiffrin synthesis of alkane thiol protected metal nanoparticles has been shown to be highly sensitive to the precursor species and reactant conditions.

The Hydrophobic Effect on Electrodeposition of Billirubin Oxidase CotA

The hydrophobic effect on electrodeposition of an enzyme CotA was investigated. The CotA was electrodeposited on a gold disc electrode modified with an alkane thiol self-assembled monolayer (SAM). The CotA immobilized hydrophobic SAM gold electrodes exhibited a larger electrochemical activity compared with the hydrophilic SAM and bare electrodes. In particular, large current responses were observed in an ethanethiol or a 1-butanethiol SAM gold electrode. In addition, effect of addition of non-ionic surfactant Triton X on the electrodeposition was checked using the SAM gold electrode. The addition of Triton X had a positive effect on the electrodeposition.