Preparation And Application Of Free-standing,Conductive Metallic Nanoparticle Film Prepared By Light Welding

Nanostructured metallic thin films have emerged as new functional nanomaterials and have been widely used in diverse fields,such as chemical sensors,catalysis,and optoelectronic devices.Bottom-up assembly of nanomaterials,using isolated,disordered nanomaterials as building blocks,could offer a simple,low-cost strategy for large-scale preparation of conductive metallic thin films.However,such solution-processed thin films are often plagued by excessive inter-particle resistance and only exhibit limited current delivering capability.Until now,many strategies have been developed,aiming to minimize inter-particle resistance and to enhance the current delivering capability of the thin nanoparticle film.This thesis has developed a new light welding strategy.It,when combing with interfacial self-assembly of nanoparticles(NPs),can offer a solution-processable approach to metallic thin films,allowing regulating its diverse properties,including conductivity.The main research contents of this thesis are outlined as below:1.Fabricate self-supported,highly conductive metallic thin films by combining interfacial self-assembly of NPs and light welding process.It was found that the light from a xenon lamp can weld adjacent Ag and Au NPs assembled at the water-air interface,forming a highly interconnected,free-standing metallic thin film with excellent electrical transport properties.This thesis further examines the influence of particle type,particle size,illumination duration,light intensity,and light source on the welding extent and thus the current delivering capability of the metallic thin film.Moreover,this thesis also reveals that the mechanism of light welding is light-driven Ostwald ripening.In detail,the giant field created as a result of plasmon(oscillation of conductive electrons in metal induced light)excitation accelerates the dissolution and movement of atoms,forming a local supersaturated solution.As a result,the dissolved atoms deposit and fill in the inter-particle gaps because they are energetically favorable locations owing to their negative curvatures.2.Demonstrate the application of high conductive metallic film as electrode in functional electronic and optoelectronic devices.Perovskite photodetectors were constructed using conductive Ag NP thin film as interdigital electrodes and perovskite(CH3NH3PbI3)film as the light-absorbing active layer.Compared with traditional ITO electrode,the perovskite photodetector constructed from the Ag NP thin film showed notably improved photoelectric performance.3.Investigate the electrocatalytic properties of the highly conductive Au NP film for methanol oxidation.The as-prepared thin nanoparticle film is in fact a type of two-dimensional nanoporous gold film.This thesis shows the welded nanoparticle film,thanks to its high current delivering capability,shows excellent eletrocatalytic activity for methanol oxidation,higher than that from bulk gold electrode and self-assembled,unwelded Au NP film(without light treatment).