The synthetic chemistry and spectroscopy of sulfur-protected gold surfaces and nanoparticles is analyzed, indicating that the electronic structure of the interface is Au(0)–thiyl, with Au(I)–thiolates identified as high-energy excited surface states. Density-functional theory indicates that it is the noble character of gold and nanoparticle surfaces that destabilizes Au(I)–thiolates. Bonding results from large van der Waals forces, influenced by covalent bonding induced through s–d hybridization and charge polarization effects that perturbatively mix in some Au(I)–thiolate character. A simple method for quantifying these contributions is presented, revealing that a driving force for nanoparticle growth is nobleization, minimizing Au(I)–thiolate involvement. Predictions that Brust–Schiffrin reactions involve thiolate anion intermediates are verified spectroscopically, establishing a key feature needed to understand nanoparticle growth. Mixing of preprepared Au(I) and thiolate reactants always produces Au(I)–thiolate thin films or compounds rather than monolayers. Smooth links to O, Se, Te, C, and N linker chemistry are established. Significance Synthetic design strategies for gold surface protection and nanoparticle formation require knowledge of how protectant ligands bind. Sulfur compounds may protect gold surfaces using a weakly bound (physisorbed) form or a strongly bound (chemisorbed) one often assumed to be Au(I)–thiolate. However, chemical reaction conditions optimized for Au(I)–thiolate protection instead etch surfaces to produce molecular thin films. All experimental and calculated evidence indicates that chemisorbed surface species are actually bound mainly by strong van der Waals (aurophilic-like) forces. This understanding unifies gold–sulfur surface chemistry with that of all other ligands and also with that of gold compounds, forming the basis for future methodological developments. It is applied to predict intermediate species during the Brust–Schiffrin nanoparticle synthesis that are subsequently observed spectroscopically.

Recent progress on two-dimensional layered nanomaterials supported wearable biomedical sensors and power devices is comprehensively reviewed.