Gold nanoparticles assembled with dithiocarbamate-anchored molecular wires

Charge-transfer plasmons of complex nanoparticle arrays connected by conductive molecular bridges

Charge-transfer plasmons (CTP) in complexes of metal nanoparticles bridged by conductive molecular linkers are theoretically analysed using a statistic approach. The applied model takes into account the kinetic energy of...

Hollow Porous Gold Nanoshells with Controlled Nanojunctions for Highly Tunable Plasmon Resonances and Intense Field Enhancements for Surface-Enhanced Raman Scattering

Plasmonic metal nanostructures with nanogaps have attracted great interest owing to their controllable optical properties and intense electromagnetic fields that can be useful for a variety of applications, but precise and reliable control of nanogaps in three-dimensional nanostructures remains a great challenge. Here, we report the control of nanojunctions of hollow porous gold nanoshell (HPAuNS) structures by a facile oxygen plasma-etching process and the influence of changes in nanocrevices of the interparticle junction on the optical and sensing characteristics of HPAuNSs. We demonstrate a high tunability of the localized surface plasmon resonance (LSPR) peaks and surface-enhanced Raman scattering (SERS) detection of rhodamine 6G (R6G) using HPAuNS structures with different nanojunctions by varying the degree of gold sintering. As the neck region of the nanojunction is further sintered, the main LSPR peak shifts from 785 to 1350 nm with broadening because the charge transfer plasmon mode becomes more dominant than the dipolar plasmon mode, resulting from the increase of conductance at the interparticle junctions. In addition, it is demonstrated that an increase in the sharpness of the nanojunction neck can enhance the SERS enhancement factor of the HPAuNS by up to 4.8-fold. This enhancement can be ascribed to the more intense local electromagnetic fields at the sharper nanocrevices of interparticle junctions. The delicate change of nanojunction structures in HPAuNSs can significantly affect their optical spectrum and electromagnetic field intensity, which are critical for their practical use in a SERS-based analytical sensor as well as multiple-wavelength compatible applications.

A dithiocarbamate anchoring group as a flexible platform for interface engineering

The molecular organization and electronic properties of dithiocarbamate (DTC) anchored self-assembled monolayers (SAMs) linked to Au(111) substrates are studied by a combination of X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, and state-of-the-art density functional theory calculations. For that, several piperidine/piperazine precursors with different architecture and substitution patterns are selected. The presented data show that the DTC anchor provides a useful building block for monomolecular self-assembly on coinage metals with both sulfur atoms bonded to the substrate in a way similar to what is usually observed for the more commonly applied thiolate docking group. The combination of the DTC group with the quite flexible piperidine/piperazine cyclic linkers results in a dense molecular packing with an upright orientation of the terminal moieties. The latter comprise phenyl rings bearing various substituents, which enables tuning the interfacial dipole over a wide range. Simulations on two prototypical DTC-docked SAMs help to better understand the experimental observations and provide insight into the local origin of the SAM-induced shifts in the electrostatic energy. In particular, a comparison of measured and simulated XP spectra reveals the significant contribution of the DTC group to the interfacial dipole.

Dithiocarbamates: Challenges, Control, and Approaches to Excellent Yield, Characterization, and Their Biological Applications

Progresses made in previous researches on syntheses of dithiocarbamates led to increase in further researches. This paper reviews concisely the challenges experienced during the synthesis of dithiocarbamate and mechanisms to overcome them in order to obtain accurate results. Aspects of its precursor's uses to synthesize adducts, nanoparticles, and nanocomposites are reported. Some common characterization techniques used for the synthesized products were assessed. Biological applications are also reported.

Morphological transformation of gold nanoparticles on graphene oxide: effects of capping ligands and surface interactions

This article presents the influence of capping ligand and surface interaction types on the coarsening or reshaping behavior of surface-immobilized gold nanoparticles with different core size and shape. The morphological transformation of gold nanoparticles and nanorods on graphene oxide upon heating at temperatures ranging from 50 to 200 °C was investigated. The aggregation and coarsening behaviors of spherical nanoparticles on graphene oxide were slightly affected by the core size of nanoparticles (~ 1, 3, and 10 nm). The comparison of two different surface ligands revealed that glutathione ligands provide much better protection than cetyltrimethylammonium bromide ligands against the morphological transformation of nanoparticles. In addition, the evaluation of surface binding interactions indicated that the attachment of nanoparticles and nanorods onto graphene oxide with additional thiol functional groups could improve the immobilization of particles and therefore decelerate coarsening and reshaping of nanoparticle and nanorods.