Surface modification for thin film deposition, nanocable fabrication and molecular gates in nanoporous templates

This dissertation reports surface modification for novel fabrications of ultra flat Te thin films, Au-Te nanocables and guarding protein transport through nanoporous templates. The study of the growth of ultra thin films with ultra flat surfaces is of great importance not only for understanding the growth mechanisms but also for the fabrication of nanostructures. In the first part of this work, we first find that Cd ions act as a mediator for smooth growth of Te films during electrochemical deposition at a potential of 138 mV (vs. standard hydrogen electrode, SHE). Without Cd ions, Te films grow in an island mode with larger surface roughness. At a more negative applied potential (-350 mV vs. SHE), Cd acts as a co-deposition element to form CdTe films grown in island mode with rough surfaces. The growth of the thin films is investigated by in situ electrochemical atomic force microscopy (EC-AFM) and in situ electrochemical surface plasmon spectroscopy (EC-SPR).; In the second part of this work, we report a novel route to fabricate Au-Te nanocables. Using nanoporous polycarbonate tract-etching membrane (PCTE membrane) as a template, Au nanotubes are fabricated by electroless Au deposition inside the nanopores of the PCTE membrane. Using the Au nanotube membrane as a second template, Te is then deposited on the surfaces of the Au nanotubes to form Te nanowires by taking advantage of the surface modification from the Cd mediator. The deposition rate is sufficiently slow to radially grow Te nanowires coaxially within the Au nanotubes to form Au-Te nanocables.; In the third part of this work, the nanoporous template, surface-modified with self-assembled monolayers, is studied for molecular gates. A low ionic strength of I = 0.01 M in buffer solution causes a dramatic reduction of the molecular fluxes of bovine serum albumin (BSA) and bovine hemoglobin (BHb) through the nanoporous template when the pH values deviate from the isoelectric points of BSA and BHb. The molecular gating phenomena are therefore successfully demonstrated. The selectivity of BSA/BHb in a mixture is enhanced an order magnitude higher than if an ionic strength of I = 0.1 M is used.