CHED 367 |
| The gold electrode can be used as support in self-assembled monolayers (SAMs) where certain molecules can adsorb spontaneously to the surface through covalent bonds forming a well-ordered and oriented layer. Gold is a desirable support because of its relative inertness which permits the formation of reproducible well-ordered SAMs and because it is easy to clean due to its stable oxide, in contrast with platinum and other substrates which are difficult to clean and take a longer time. Modification of gold surface with aromatic thiols has not received much attention compared to alkane thiols but the former has proved to form rigid layers with unique packing structure. The modification of gold with molecules like 4-aminothiolphenol (4-ATP), can provide a substrate with the desire properties for different uses as corrosion inhibitors, derivatization, biosensor and other functions. Electrochemical characterization of gold substrate with 4-ATP monolayers was studied. Different concentrations (10mM and 20mM) of 4-ATP solutions for immobilization were prepared in ethanol. Before and after immobilization, the gold electrodes were electrochemically evaluated with cyclic voltammetry in 1M H2SO4. After the immobilization, an anodic peak appears at approximately 0.85V which evidences an organic monolayer, in this case 4-ATP monolayer oxidation. Also desorption studies were analyzed in 0.1M potassium hydroxide (KOH) in aqueous solution. A desorption peak for 4-ATP in 0.1M KOH appeared at -1.0V. Desorption studies revealed a surface coverage of 8.3x10-10±3.8x10-11moles/cm2 when a concentration of 10mM was used while a concentration of 20mM revealed a surface coverage of 1.5x10-9±1.3x10-10moles/cm2. This agrees with literature where thiols are found to have a surface coverage between 10-9 and 10-10 moles/cm2. Cyclic voltammetry and desorption with KOH are simple methods to study the SAMs formation of 4-ATP. |
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Undergraduate Research Poster Session: Analytical Chemistry
11:00 AM-1:00 PM, Monday, March 26, 2007 Hyatt Regency Chicago -- Riverside Center, Poster
Division of Chemical Education |