When Design Meets Function: The Prodigious Role of Surface Ligands in Regulating Nanoparticle Chemistry

Abstract

The underlying power of "interplay of forces" in controlling the properties and functions at the nanoscale is highlighted in this perspective. This interplay is achieved by installing attractive and repulsive forces, via proper ligand chemistry, which will guide the nanomaterials to interact with their surroundings as per the need. Along with improving the existing properties, the balancing of attractive and repulsive forces holds the prospects of imparting newer functions as well. The concept of "ligand-directed interplay of forces" is extensively practiced by our group and others for addressing many challenges in the areas of self-assembly, catalysis, light harvesting, and nanomedicine. The journey has been rewarding so far in terms of achieving many important feats in nanoscience, such as selfassembly under equilibrium and nonequilibrium regimes, outplaying ligand poisoning in nanocatalysis, channelizing the flow of energy and electron in donor−acceptor systems, multicolor photopatterning using a single nanohybrid system, biospecific targeting and therapy, and so on. As evident from this perspective, the diversity of the areas benefited showcases the breadth and depth of the impact that surface ligands and interplay of forces can have in material science. Furthermore, the implementation of the "ligand of choice" approach is one way to realize distinct and specific functions from a limited set of nanomaterials. All the examples of "liganddirected studies" mentioned in this perspective are based on the regulation of, primarily, electrostatic forces emanating from the charged surface ligands. Thus, it will be logical to try various combinations of ligands and forces, which means that the area of "ligand-directed nanochemistry" will keep on advancing beyond our predictions. Looking forward, there is plenty of room at the NP surface.

Deciphering the Role of Light Excitation Attributes in Plasmonic Photocatalysis: The Case of Nicotinamide Cofactor Regeneration

“…A widely used electron mediator, [Cp*Rh(bpy)(H 2 O)] 2+ , was incorporated to enhance the charge transfer rate for a better comparison of the reaction yields under different excitations as well as to regenerate the enzymatically active 1,4-NADH. 43−45 Moreover, the incorporation of a positively charged electron mediator allowed us to use electrostatic forces as a tool to install the concept of "catalyst−reactant interaction" 11,12,46 in our study. A favorable catalyst−reactant interaction will channelize the diffusion and increase the local concentration of the reactants close to the surface of the catalyst, thereby enhancing the possibility of the charge transfer process.…”

“…A favorable catalyst−reactant interaction will channelize the diffusion and increase the local concentration of the reactants close to the surface of the catalyst, thereby enhancing the possibility of the charge transfer process. 11,12,46 Accordingly, the surface of the AuNRs was appropriately functionalized with negatively charged ligands to achieve electrostatic attraction with the positively charged electron mediator. Detailed wavelengthdependent experiments showed that hot charge carriers generated through selective interband transitions (via excitation at ∼450 nm) yielded the best photocatalytic regeneration of the NADH cofactor, compared to selective intraband (via excitation at ∼808 nm) and inter + intraband transitions (via excitation at ∼532 nm).…”

“…Our selection of AuNRs to photocatalyze the regeneration of the NADH cofactor satisfies the fundamental requirements that a catalyst–reactant system should possess to gain conclusive insights into the role of light excitations in plasmonic photocatalysis. A widely used electron mediator, [Cp*Rh­(bpy)­(H 2 O)] 2+ , was incorporated to enhance the charge transfer rate for a better comparison of the reaction yields under different excitations as well as to regenerate the enzymatically active 1,4-NADH. − Moreover, the incorporation of a positively charged electron mediator allowed us to use electrostatic forces as a tool to install the concept of “catalyst–reactant interaction” ,, in our study. A favorable catalyst–reactant interaction will channelize the diffusion and increase the local concentration of the reactants close to the surface of the catalyst, thereby enhancing the possibility of the charge transfer process. ,, Accordingly, the surface of the AuNRs was appropriately functionalized with negatively charged ligands to achieve electrostatic attraction with the positively charged electron mediator.…”

“…A widely used electron mediator, [Cp*Rh­(bpy)­(H 2 O)] 2+ , was incorporated to enhance the charge transfer rate for a better comparison of the reaction yields under different excitations as well as to regenerate the enzymatically active 1,4-NADH. − Moreover, the incorporation of a positively charged electron mediator allowed us to use electrostatic forces as a tool to install the concept of “catalyst–reactant interaction” ,, in our study. A favorable catalyst–reactant interaction will channelize the diffusion and increase the local concentration of the reactants close to the surface of the catalyst, thereby enhancing the possibility of the charge transfer process. ,, Accordingly, the surface of the AuNRs was appropriately functionalized with negatively charged ligands to achieve electrostatic attraction with the positively charged electron mediator. Detailed wavelength-dependent experiments showed that hot charge carriers generated through selective interband transitions (via excitation at ∼450 nm) yielded the best photocatalytic regeneration of the NADH cofactor, compared to selective intraband (via excitation at ∼808 nm) and inter + intraband transitions (via excitation at ∼532 nm).…”

(NHC-olefin)-nickel(0) nanoparticles as catalysts for the (Z)-selective semi-hydrogenation of alkynes and ynamides

“…To achieve this, different strategies have been explored, including the use of: surfactants and micellar catalysis, various supports (with different metal-support interactions) or organic ligands. 1 Although the latter strategy was initially achieved through the use of ligands such as thiols, amines, cyanides, disulfides, thioethers or phosphines, 2 N-heterocyclic carbene (NHC) ligands, which are now privileged ligands in organometallic chemistry and homogeneous catalysis, have been established as novel promising stabilisation agents for metal NPs. 3 Thus, several studies have demonstrated the versatility of N-heterocyclic carbene ligands in stabilising and structuring NPs of metals like Ru, 4 Rh, 5 or Pd 6 for significant applications in catalysis, such as the hydrogenation of alkenes and alkynes, the Buchwald–Hartwig amination or the oxidation of alcohols.…”