Covalent coupling of nanoparticles with low-density functional ligands to surfaces via click chemistry

We demonstrate the application of the 1,3-dipolar cycloaddition (“click” reaction) to couple gold nanoparticles (Au NPs) functionalized with low densities of functional ligands. The ligand coverage on the citrate-stabilized Au NPs was adjusted by the ligand:Au surface atom ratio, while maintaining the colloidal stability of the Au NPs in aqueous solution. A procedure was developed to determine the driving forces governing the selectivity and reactivity of citrate-stabilized and ligand-functionalized Au NPs on patterned self-assembled monolayers. We observed selective and remarkably stable chemical bonding of the Au NPs to the complimentarily functionalized substrate areas, even when estimating that only 1–2 chemical bonds are formed between the particles and the substrate

Inkjet Stucturing on Electrode Surfaces

Alkanethiols spontaneously assembles from solution or vapour on oxide free metal surfaces resulting in a close-packed molecular stuctures with a high degree of orientation and molecular order. In this study, inkjet printing technique is used to immobilize monolayers of alkanethiols on gold electrodes. The quality of the inkjetted monolayers are analyzed by electrochemical methods, i.e. cyclic voltammetry and electrochemical impedance spectroscopy, and by Polarization Modulation Infrared Reflection-Absorption Spectroscopy (PM-IRRAS) which show a similar molecular quality to those produced by immersion technique, the standard technique. The kinetic and mass transfer behaviours of micro-scale structures of inkjetted monolayers, e.g. bands and dots array electrodes, are explored by electrochemical methods. The microscale inkjetted structures of monolayers are of interest in the fields of microelectronic devices (e.g. chemical and biosensors) and optoelectronic devices. Taking benefits from multichannel existing in the printhead, mixtures of SAMs are demonstrated. Mixing of monolayers differing in functional groups provides a model surface to study interface phenomena at molecular level such as ion permeation, selective chemical binding, and electron transfer kinetic

Fabrication of Hierarchically Porous Materials and Nanowires through Coffee Ring Effect

We report a versatile method for the fabrication of nanowires and hierarchical porous materials from a wide variety of ceramic materials such as CaCO₃, ZnO, CuO, Co₃O₄, Co-doped ZnO, and Ag₂O. The method consists of evaporation of CO₂-enriched water microdroplets (diameter ∼3 μm) deposited from an aerosol onto heated substrates (<i>T</i> = 120 °C). A variety of porous scaffolds with 1–3 μm sized pores can be generated by tuning the process conditions. Subsequent sintering of the scaffolds is shown to generate nanosized pores in the walls of the porous scaffold creating a dual hierarchy of pore sizes (∼50 nm and 1–3 μm). We propose a mechanism for the formation of scaffolds based on the coffee-ring effect during the evaporation of microdroplets. Ostwald-ripening of CaCO₃ scaffolds prepared without sintering yields scaffold structures consisting of two-dimensional crystals of CaCO₃ that are one unit cell thick. The favorable application of CaCO₃ scaffolds for the enhancement of bone healing around titanium implants with improved biocompatibility is also demonstrated