Metal-Ligand Interactions and Their Roles in Controlling Nanoparticle Formation and Functions

Conspectus Functional nanoparticles (NPs)have been studied extensively inthe past decades for their unique nanoscale properties and their promisingapplications in advanced nanosciences and nanotechnologies. One criticalcomponent of studying these NPs is to prepare monodisperse NPs sothat their physical and chemical properties can be tuned and optimized.Solution phase reactions have provided the most reliable processesfor fabricating such monodisperse NPs in which metal-ligandinteractions play essential roles in the synthetic controls. Theseinteractions are also key to stabilizing the preformed NPs for themto show the desired electronic, magnetic, photonic, and catalyticproperties. In this Account, we summarize some representative organicbipolar ligands that have recently been explored to control NP formationand NP functions. These include aliphatic acids, alkylphosphonic acids,alkylamines, alkylphosphines, and alkylthiols. This ligand group coversmetal-ligand interactions via covalent, coordination, and electrostaticbonds that are most commonly employed to control NP sizes, compositions,shapes, and properties. The metal-ligand bonding effects onNP nucleation rate and growth can now be more thoroughly investigatedby in situ spectroscopic and theoretical studies.In general, to obtain the desired NP size and monodispersity requiresrational control of the metal/ligand ratios, concentrations, and reactiontemperatures in the synthetic solutions. In addition, for multicomponentNPs, the binding strength of ligands to various metal surfaces needsto be considered in order to prepare these NPs with predesigned compositions.The selective ligand binding onto certain facets of NPs is also keyto anisotropic growth of NPs, as demonstrated in the synthesis ofone-dimensional nanorods and nanowires. The effects of metal-ligandinteractions on NP functions are discussed in two aspects, electrochemicalcatalysis for CO2 reduction and electronic transport acrossNP assemblies. We first highlight recent advances in using surfaceligands to promote the electrochemical reduction of CO2. Several mechanisms are discussed, including the modification ofthe catalyst surface environment, electron transfer through the metal-organicinterface, and stabilization of the CO2 reduction intermediates,all of which facilitate selective CO2 reduction. Thesestrategies lead to better understanding of molecular level controlof catalysis for further catalyst optimization. Metal-ligandinteraction in magnetic NPs can also be used to control tunnelingmagnetoresistance properties across NPs in NP assemblies by tuningNP interparticle spacing and surface spin polarization. In all, metal-ligandinteractions have yielded particularly promising directions for tuningCO(2) reduction selectivity and for optimizing nanoelectronics,and the concepts can certainly be extended to rationalize NP engineeringat atomic/molecular precision for the fabrication of sensitive functionaldevices that will be critical for many nanotechnological applications.

Automated summary

Functional nanoparticles have been extensively studied for their unique properties and promising applications in nanosciences and nanotechnologies. The preparation of monodisperse nanoparticles is crucial for tuning and optimizing their physical and chemical properties. Metal-ligand interactions play essential roles in synthesizing and stabilizing nanoparticles, and recent research has focused on using organic bipolar ligands to control nanoparticle formation and functions. By understanding and controlling metal-ligand interactions, researchers have made significant progress in improving catalysis and electronic transport across nanoparticles.