Construction Of Ordered Noble Metalic Micro/Nanostructure Arrays And Their Optical Properties

An interesting and simple strategy to prepare noble metal nanoparticles(NPs)arrays with different morphologies and size on a substrate was developed by using monolayer colloidal crystal as a template,followed by depositing a layer of prepare precious film and annealing at different temperatures.Hat-shaped,cup-shaped,rice-shaped and sphere-shaped Pt NPs arrays were obtained after annealing the PS template with Pt film at 300?,500?,700? and 900?,respectively.Different sizes of Au nanoparticles were prepared with deposition time is 60s-120 s.The extiction spectra of different Au nanoparticles arrays presented three obvious peaks.Assigning to localized surface plasmon resonances(LSPR)and array diffraction peak of the Au NPs.The LSPR peaks blue shifted with increase of particles.The extinction spectra of hat-shaped,cup-shaped and rice-shaped Pt NPs arrays presented two obvious peaks,assigning to transverse and longitudinal LSPR of the Pt NPs.The transverse and longitudinal LSPR peaks both blue shifted when geometrical morphology changed from hat-shaped to cup-shaped,and then to rice-shaped due to increasing annealing temperatures.The transverse LSPR peaks blue shifted from ca.487 nm to ca.453 nm,and the longitudinal LSPR peaks blue shifted from ca.1201 nm to ca.898 nm.Compared with hat-shaped,cup-shaped and rice-shaped Pt NPs arrays,there was only one localized surface plasmon resonance peak in extinction spectra of sphere-shaped Pt NPs arrays because of their symmetrical nanostructure.But it presented a peak at ca.635 nm,which is assigned to Bragg diffraction of the highly ordered structure of the Pt nanosphere arrays.Moreover,the extinction spectra of sphere-shaped Pt NPs arrays with different dimater were studied.The results show that there was no obvious shift of the LSPR and diffraction with the increase of dimater of nanosphere.This method would motivate more research efforts in developing new methods to fabricate asymmetrical nanostructures.Additionally,these novel properties originating from the anisotropic nanostructures may open up new applications in many fields.Based on the above technologies,periodic alloyed(Au-Ag,Au-Cu,Au-Ag-Cu)nanoparticles(NPs)arrays with uniform size,controllable composition and center-to-center spacing were fabricated by a novel and facile strategy based on physical vapor deposition on monolayer colloidal crystal template and further heat treatment.The composition and center-to-center spacing were manipulated by adjusting the sputtering target in deposition process and the size of colloidal spheres of the template,respectively.Shadow effect and dewetting model were employed to analyze the whole process of the evolution from metallic thin film to spherical nanoparticle with uniform size.Localized surface plasmon resonance(LSPR)and diffraction peaks of these alloyed arrays were systematically measured.The variety of dielectric constant has an important influence on the LSPR peak and diffraction peak.Both the LSPR and diffraction peaks of Au-Ag alloyed NPs arrays exhibit blue shift due to their lower dielectricconstant than that of pure Au NPs.However,compared with Au element,Cu element possesses a higher dielectric constant,leading to red shift of the LSPR and diffraction peaks of Au-Cu alloyed NPs arrays.With increase of NP size,the diffraction peaks of both binary alloyed NPs exhibit red shift slightly.Moreover,the LSPR absorption peaks were more sensitive to the composition of NPs than the diffraction peaks.This work would open up a novel strategy in the production of alloyed NPs arrays with tunable LSPR peak and diffraction peaks,which would be highly helpful to improve their practical applications in various fields.