The Preparation And Characterization Of Sulfhydryl Compound SAMs On Gold Surface

The biosensor is a rapid development and wide range of applications of modern analytical techniques in recent years. The immobilization of active biological macromolecule is one of the most imporant technologies of the biosensor. Self-assembled monolayers (SAMs) technology provides an ideal platform for protein immobilized, such as enzymes, antigens, antibodies, DNA and other biological macromolecules. However, the carboxylic or amino groups on the surface of the SAMs easily form intermolecular hydrogen bonds, adversely affect the immobilization of protein molecules. In this paper, we use Fourier transform reflection-absorption infrared spectroscopy (PM-FT-IRRAS), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) to characterise three different mixed self-assembled monolayers (SAMs) and protein films. We have found the method to prevent the formation of hydrogen bonds in (MUA) SAMs. Successfully, the conditions of fixing protein has been optimized. The effects of the alkaline solution on L-cysteine (L-Cys) SAM structure was researched. The preparation of1-mercaptopyrene and interaction with grapheme was studied. The results have significants for research and application in the area of biosensor.The major contents in this thesis are described as follows:1. A study on the mixed MUA-containing SAMs to control intermolecular hydrogen bondsMercaptoundecanoic acid (MUA), respectively with mercaptoundecanol (MUOH), mercapto-heptane (C6CH3) and mercapto-hexanol (C6OH) formed the mixed thiols SAMs. The mixed thiol molecules was used to increase the distance between the MUA that prevent the formation of hydrogen bonds. And bovine serum albumin (BSA) was used as a model protein to study the effect of hydrogen in immobilizition of the protein. Infrared characterization of the three different mixed thiols SAMs show that, to use the fractional step method, three mixed thiols SAMs can effectively prevent MUA from generating intermolecular hydrogen bonds. The structure of mixed SAMs MUA/MUOH is the most compact to immobilize large amount of BSA.2. Influence of variety and acidity on L-cysteine SAMs structureThe conditions, such as variety, acidity and concentration of the Self-assembled solution, as well as the assembling time and concentration of L-Cys solution have a significant impact on the structure of L-Cys SAMs. To construct the biosensor that perform more excellently, we prepared L-Cys SAMs/Au in hydrochloric acid and sodium hydroxide, acetate buffer solution (ABS) and phosphate buffer solution (PBS), respectively. The results show that, L-Cys SAMs prepared in HCl/NaOH solution that fixed maximum amount of BSA at pH value of6.0. L-Cys SAMs prepared in ABS that fixed maximum amount of BSA at pH value of5.0. And L-Cys SAMs prepared in PBS that fixed maximum amount of BSA at pH value of8.5. With the change of ionic strength in phosphate buffer solution, between the L-Cys molecules can form a bilayer through amide bond on the surface of the gold. In PBS buffer,with the range of concentration in0.04～0.16mol/L, the formation of L-Cys SAMs exists the amide bond. When the concentration is0.08M, a number of amide bonds was the largest.3. The synthesis of1-mercaptopyrene and interaction with graphene1-Pyrenesulfonyl chloride is synthesized by sulfonation reaction and acylation reaction respectively from pyrene. After further reduction of zinc dust and concentrated hydrochloric acid, we got1-mercaptopyrene.1-Mercaptopyrene and graphene have similar structure, so that they can get together to improve the dispersibility of graphene, and then fix the graphene on the surface of the gold. The results show the amount of fixed graphene via the fractional step and mixing method obviously different, fractional step was better than mixing method.