Study Of Biochemical Surface Modification Of Porous Silicon

This experimental study includes the following contents:1. Electrochemical detection of ascorbic acid by porous silicon electrode Porous silicon prepared by electrochemical anodic oxidation and modified through biofunctionalization surfaces has been used to detect ascorbic acid. The relationship between ascorbic acid concentration and voltage, current, pH has been analyzed, respectively, by measuring Tafel curve, linear sweep curves with electrochemical workstation LK-2005. Experimental studies have shown that current increases with the concentration of ascorbic acid at a given voltage, Tafel curves shift toward positive potential with increase of ascorbic acid concentration. The current increases with decrease of pH values, but there was not a goog linear relationship. Surface modification of porous silicon has been conducted by silver layer and the modified electrode showed greater current than non-modifited electrode at same ascorbic acid concentration and same potential from the measurement of Tafel curve.2.Biological function of porous silicon on the biological sensing of urea solutionA unique electrode based on aminopropyl-triethoxysilane ( APTS)-coated porous silicon(PS) substrate has been fabricared and used as a urea-sensitive electrode after urease immobilization. PS substrate was formed by electrochemical anodization in an etching solution composed of HF and ethanol. APTS layer was formed on the PS surface by coating and heating at 780℃in argon atmosphere. Urease immobilization was carried out by immersing the APTS/PS in urease solution. The immobilized system gives linear response for concentrations of urea ranging in values between 3.6×10^-3 and 8.0×10^-3 mol dm^-3 , studied with voltammetry. The surface of biofunctionized porous silicon has thus provided a suitable environment for urease with 15 days retention of its activity. The molecular structure on the PS surface was characterized with Fourier-transform infrared (FTIR) technique. The change in the surface morphology has been studied by scanning electron microscopy and it is observed that the immobilized system has successfully retained urease. The eleperimental results showed that porous silicon with biofunctionalization surfaces could give a good sensitivity and repeatability to detect urea solution.3. porous silicon enzyme electrode biosensors solution of Glucose.Porous siicon(PS) is provided with characteristics of nanometer size, large specific surface and bio-compatibility. Photoelectrochemical etching technique has been used to prepare a porous silicon substrate which then modified by aminopropyl-triethoxysilane(APTS) to realize biofunctionalization of the surface. Glucose oxidase(GOD) immobilization was carried out by glutaraldehyde(Gluta) cross-linking to the porous silicon and to form GOD-Gluta-APTS-PS composite structure. The GOD-Gluta-APTS-PS structure was used as working electrode mou nted in a measuring cell sealed by an O-ring. A saturated calomel electrode(SCE) and platinum dish was used as reference electrode and counter electrode, respectively. Chrononamperemeter and logarithmic current-popential measurements were performed to detect a glucose solution. Under the selected conditions,the enzyme composite electreode offered a liner response in the glucose concentration range of 10×10-6—55×10-6 mol dm^-3. The sensor remained good response after 20 days through 5 days interval measurements.