Fabrication Of Metallic Nanostructures Based On Colloidal Lithography And Their Applications In Sers

Fabrication of metal nanostructures has attracted increasing attention due to theirdiverse applications in photonics, electronics, biosensing, medical diagnostics andtherapies. It is well appreciated that the optical, electronic, and catalytic properties ofmetal nanostructures can be tuned by controlling their size, shape, and composition.Colloidal Lithography is one of the controllable, inexpensive and versatile methodsfor fabricating periodic arrays of metallic nanostructures.Based on the above considerations, we have fabricated three kinds of metallicnanostructures based on colloidal lithography combined with nanoimprint lithography(NIL), electrochemical deposition and thermal evaporation. We investigated theapplications of the fabricated metallic nanostructures. This thesis includes thefollowing three parts.Firstly, a simple and efficient method for fabricating gold nanoparticle (AuNP)arrays is developed. With this method, the AuNP arrays are fabricated by taking anelectrochemical deposition (ECD) process on the ITO substrate, which is initiallypatterned with NIL. The stamp for NIL is fabricated by the cost-efficient colloidallithography. The size of the AuNPs can be adjusted by varying the potential andduration of ECD; the periodicity can be changed by applying polystyrene spheres withdifferent sizes. In this work, the diameters of AuNPs are varied from130to420nm.The AuNP arrays can be readily extended to other conductive substrates, which maybe applied for detecting and sensing.Secondly, elevated nanoantenna arrays are fabricated to achieve excellentsurface-enhanced Raman scattering (SERS) performance. The position of hot spotscan be shifted from bottom to top by changing the thickness of deposited silver. Theshift and the hydrophobicity of silver increase the possibility for probe moleculesaccess to hot spots, which provides higher SERS sensitivities. A maximum SERSenhancement factor (EF) of9.8×109is achieved on the optimal elevated nanoantennaarrays with detection limit of as low as10-12mol/L and fine reproducibility that themaximum RSD is15.45%. The combination of the shift of hot spots and the wettability of surface provides an approach to improve the SERS performance.Thirdly, silver nanocone arrays are fabricated to achieve SERS-active substrateswith high reproducibility by the combination of colloidal lithography and thermalevaporation. By varying the angle of slope and height of silver nanocone, the intensityof SERS can be optimized. The fabricated silver nanocone arrays are expected to beapplied to detecting and sensing.