The formation of covalently linked composites of multi-walled carbon nanotubes (MWCNT) and glucose oxidase (GOD) with high-function density for use as a biosensing interface is described. The reaction intermediates and the final product were characterized by using FT-IR spectroscopy, and the MWCNT-coated GOD nanocomposites were examined by atomic force microscopy (AFM) and transmission electron microscopy (TEM). Interestingly, it was found that the GOD-MWCNT composites are highly water soluble. Electrochemical characterization of the GOD-MWCNT composites that were modified on a glassy carbon electrode shows that the covalently linked GOD retains its bioactivity and can specifically catalyze the oxidation of glucose. The oxidation current shows a linear dependence on the glucose concentration in the solution in the range of 0.5-40 mM with a detection limit of 30 microM and a detection sensitivity of 11.3 microA/mMcm2. The present method may provide a way to synthesize MWCNT related composites with other biomolecules and for the construction of enzymatic reaction-based biofuel cells and biosensors.

Gold films with various nanostructures on porous silicon substrates have been created in one step by using a galvanic exchange reaction approach. In this approach, the formation of gold films is initiated by the formation of metal nuclei via an exchange reaction in which both the oxidation of silicon and reduction of gold complex occur simultaneously. Results show that the deposition of gold film is diffusion controlled, and its apparent activation energy was determined to be 28.57 kJ mol−1. Therefore, gold nanostructures with text structure, clusters, and dendrites with leaf-like or branch-like structure can be prepared by adjusting the diffusion conditions such as system temperature, concentration of gold salt, ultrasonic vibration, and addition of additives. The SERS activity of the various porous silicon supported gold nanostructures was evaluated using pyridine and adenine as molecular probes. Amongst the various porous silicon supported gold nanostructures, the gold films with leaf-like structures show the highest SERS activity due to the presence of surface active sites in the nanostructures. The present method is promising for the fabrication of stable gold nanostructures for ultrasensitive analytical measurements.

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