Shape and size control of Cu nanoparticles by tailoring the surface morphologies of TiN-coated electrodes for biosensing applications.

A method for controlling the shapes and sizes of Cu nanoparticles during electrodeposition has been developed by tailoring the surface morphologies of TiN-coated electrodes. Larger octahedral Cu NPs grew on a granular TiN film; smaller, irregular Cu NPs formed on a pyramidal TiN film. The surface morphology of the TiN film affected the accumulation of Cu(2+) and hexadecyltrimethylammonium (CTA(+)) ions, leading to the different shapes and sizes of the resulting Cu NPs. The significant steric effect of the CTA(+) ions was confirmed when using the film of pyramidal TiN as the electrode in the CTAB-containing electrolyte; it contributed to the growth of the smaller, irregular Cu NPs. The sensitivity of the smaller, irregular Cu NPs in the detection of glucose was better than that of the larger, octahedral Cu NPs because of the former's greater increase in the Cu(2+)-to-Cu(0) ratio.

Monte Carlo simulation of atom diffusion via vacancies in nanofilms with a model simple cubic lattice system.

Monte Carlo simulation was employed to investigate correlation factors of atoms (f(A)) diffusing via vacancies in nanofilms possessing a simple cubic lattice that was selected as a model system. The correlation factors change significantly with varying the film thickness, as well as jump frequency ratios. When the film thickness is sufficiently large, f(A) approaches 0.6531, a limiting value for the 3D bulk lattice. As the film thickness is considerably small, f(A) converges to 0.4669, a limiting value for the 2D square lattice. A minimum of the factors, corresponding to 2/3 x f(A)(3D-SC) (= 0.4354), occurred in a specific nanofilm regime ranging from about 100 to 500 atomic layers, which was mainly due to confinement of atoms movement to nanofilms. Correlation factors of vacancy diffusion (f(v)) were also investigated and exhibited similar trend of the relations between the factors and the film thickness in a certain nanofilm regime. The relation between the correlation factors and the film thickness is analyzed and discussed.