Surface functionalization of metallic and semiconducting 2D transition metal dichalcogenides (TMDs) have mostly relied on physi- and chemi-sorption at defect sites, which can diminish the potential applications of the decorated 2D materials, as structural defects can have substantial drawbacks on the electronic and optoelectronic characteristics. Here, we demonstrate a spontaneous defect-free functionalization method consisting of attaching Au single atoms to monolayers of semiconducting MoS2(1H) via S-Au-Cl coordination complexes. This strategy offers an effective and controllable approach for tuning the Fermi level and excitation spectra of MoS2 via p-type doping and enhancing the thermal boundary conductance of monolayer MoS2, thus promoting heat dissipation. The coordination-based method offers an effective and damage-free route of functionalizing TMDs and can be applied to other metals and used in single-atom catalysis, quantum information devices, optoelectronics, and enhanced sensing.

Traditional Feigl's spot tests can be greatly improved with the aid of gold nanoparticles and Raman probes, by monitoring the changes in the surface enhanced Raman scattering (SERS) of the analytes directly applied on a filter paper previously impregnated with the selective organic reagent. As a proof of concept, diphenylthiocarbazone (dithizone) was treated with citrate stabilized gold nanoparticles and employed in paper spot tests for a variety of transition and heavy metal ions. Below 10(-5) mol L(-1), only mercury(II) ions were able to displace the dithizone molecules from the "coordination shell" of the gold nanoparticles, leading to a systematic decay of the Raman signals. Because of the huge enhancement of the dithizone vibrational peaks, the SERS spot tests allowed the detection of picograms of Hg(2+) ions.

In this paper we show how surface coordination chemistry can elucidate one of the reproducibility issues related to the classical synthesis of gold nanoparticles by the Turkevich method.

We introduce a graphene oxide/gold nanorod nanocomposite as a surface-enhanced Raman spectroscopy (SERS) substrate that suppresses the usual temporal intensity fluctuations, commonly referred to as blinking. The temporal stability of the SERS spectra from the nanocomposite is statistically determined using the coefficient of variation of the integrated spectra. We demonstrate that, by introducing graphene oxide, the coefficient of variation from the nanocomposite is five times smaller when compared to gold nanorods without graphene oxide, which is attributed to the removal of the nanorod's surfactant from plasmonic hot spots due to graphene oxide−surfactant interaction. The resulting nanocomposite can, then, be used as a reliable substrate for precise SERS chemical analysis. The nanocomposite is, therefore, analyzed as a SERS substrate for the detection of Rhodamine 640, providing a 4-fold stability improvement relative to gold nanorods without graphene oxide, while the dye's Raman signal is enhanced both by SERS and by resonant excitation.