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The effect of pressure on the properties of nanoparticles is a growing area of investigation. These measurements are typically performed in a colloidal suspension, however, the pressure-induced changes of the interactions between the nanoparticle surface and the solvent are often neglected. Here, we report vibrational spectroscopy of a common nanoparticle ligand, 1-dodecanethiol, and a common solvent, toluene, under pressure. We find that the pressure-induced phase change of the 1-dodecanethiol is altered by the presence of toluene, and that change depends on the concentration of free ligand in the solution. At near-equal concentrations, phase segregation is observed, and the dodecanethiol crystallizes independently from the toluene. On the other hand, at unequal concentrations, concerted phase transitions are observed in the dodecenethiol and toluene, and a disordered conformation of dodecanethiol is maintained to much higher pressures. These results shed light on the pressure-induced changes in intermolecular interactions between nanoparticle ligands and solvents, which must be considered in designing high pressure investigations of colloidal nanoparticles. 

Abstract We report a new class of hydrophobic polymer ligands with quaternary ammonium head groups for surface modification of noble metal nanoparticles (NPs). Quaternary ammonium ligands bind NPs through non‐covalent electrostatic interactions, producing polymer‐grafted NPs with high colloidal and chemical stability. These polymers having charged head groups offer powerful strategies to tailor the structure and function of metal‐electrolyte interfaces in electrocatalytic systems. The ammonium head groups serve as ionic reservoirs that preconcentrate bicarbonate counterions at the surface of nanocatalysts, while the hydrophobic polymer backbones restructure local hydrogen‐bonding networks, modulating water and ion transport dynamics. These interfacial effects promote CO₂electroreduction, particularly under diffusion‐limited conditions, resulting in a CO Faradaic efficiency (FE) exceeding 90%. 

We report a new design of polymer phenylacetylene (PA) ligands and the ligand exchange methodology for colloidal noble metal nanoparticles (NPs). PA-terminated poly(ethylene glycol) (PEG) can bind to metal NPs through acetylide (M-CC-R) that affords a high grafting density. The ligand−metal interaction can be switched between σ bonding and extended π backbonding by changing grafting conditions. The σ bonding of PEG−PA with NPs is strong and it can compete with other capping ligands including thiols, while the π backbonding is much weaker. The σ bonding is also demonstrated to improve the catalytic performance of Pd for ethanol oxidation and prevent surface absorption of the reaction intermediates. Those unique binding characteristics will enrich the toolbox in the control of colloidal surface chemistry and their applications using polymer ligands.