Development of uniquely patterned surfaces for multifunctional biosensing schemes

            The practical use of this interface in biosensing investigations will be limited to the quality and character of the monolayer in a variety of environments. As such, this research will focus on fundamental characterization studies first with an eye for applied studies in the future.
  
Current Projects:

1. Patterning polycrystalline electrodes with domains of different thiols. The reproducibility of the desorption-backfilling method will be tested using polycrystalline Au electrodes and simple straight chained thiols. The polycrystalline surface is composed of a number of surface facets and grain boundaries (e.g. 111, 100) which have reasonably separated desorption potentials. We will find conditions that result in the complete removal of thiol from the 111 face which results in a void that can then be backfilled with a different thiol. The conditions that we will vary will include, electrode incubation time, potential sweep rate, time spent at desorption and thiols of various solubility. The reproducibility of the backfilled SAM will be quantified with electrochemical characterization and some surface probe microscopy (SEM).
2. Introducing functional groups in the mixed SAM. The knowledge gained in the first project will lead to a more detailed study including the effects of the biological functional group. There can be a significant impact to the character of these monolayers when a bulky endgroup is introduced. To characterize the more complex interface, reductive desorption studies will be conducted on both single crystal electrodes such as Au(111) or Au(100) as well as polycrystalline surfaces. The functional group chosen will be selected for a specific biosensing problem and initial studies will be focused on that system. The biosensing strategy will be carried out after proper characterization of the ligand modified SAM is completed.
3. Spectroelectrochemical investigations. The combined knowledge that we obtain with polycrystalline electrodes coated with simple and complex thiols will be incorporated with Au nanoparticles that are tethered to a planar surface. Since Au nanoparticles are composed of well defined facets, the patterning process can be extended to this interface. These patterned NPs can then be coupled with surface plasmon resonance spectroscopy (SPR) for more enhanced detection of biomolecules that are difficult to recognize with electrochemistry alone.

List of Publications:

[14] Smith, S. R., Han, S., Zhe, W., Shepherd, J. L.; “An Electrochemical Approach to Fabricate a Heterogeneous Mixed Monolayer on Planar Polycrystalline Au and its Characterization with Lateral Force Microscopy” Journal of Electroanalytical Chemistry 666, (2012) 76-84. PDF

[13] Smith, S.R.; Guerra, E.; Siemann, S.; Shepherd J.L.; “Au dissolution during the anodic response of short-chain alkylthiols with polycrystalline Au electrodes.” Electrochimica Acta, 56, (2011) 8291-8298. PDF.

[12] Guerra, E.; and Shepherd, J. L.; “The effect of polytetrafluorethylene on pressure oxidation of nickelferous pyrrhotite.” Hydrometallurgy, 106 (3-4), (2011) 179-182. PDF.

[11] Scott, A. F.; Gray-Munro, J., Shepherd J. L.; “Influence of Coating Bath Chemistry on the Deposition of 3-Mercaptopropyltrimethoxysilane Films Deposited on Magnesium Alloy.” Journal of Colloid and Interface Science, 343, (2010) 474-483 PDF.

[10] Säbel, C. E., Shepherd, J. L., Siemann, S.; “A direct spectrophotometric method for the Simultaneous determination of zinc and cobalt in metalloproteins using 4-(2-pyridylazo)resorcinol.” Analytical Biochemistry 391, (2009) 74-76. PDF

[9] Rucareanu, S.; Maccarini, M.; Shepherd, J. L.; Lennox, R. B.; "Polymer-Capped Gold Nanoparticles by Ligand Exchange Reactions" Journal of Materials Chemistry. 18, (2008)5830-5834. PDF

[8] Lemay, D. M. and Shepherd J. L.; "Electrochemical Fabrication of a Heterogeneous Binary SAM on Polycrystalline Au" Electrochimica Acta 54 (2008) 388–393. PDF

[7] Shepherd, J. L. and Bizzotto, D. “Characterization of mixed alcohol monolayers adsorbed onto a Au(111) electrode using electro-fluorescence microscopy.” Langmuir 22(10), (2006) 4869-76. PDF

[6] Chung, E.; Shepherd, J. L.; Bizzotto, D.; Wolf, M. O., “Electrochemical dimerization of 2-(2'-Thienyl)pyridine adsorbed on Au(111) observed by in situ fluorescence.” Langmuir 20, (2004)8270-8278. PDF

[5] Shepherd, J. L.; Kell, A.; Chung, E.; Sinclar, C. W.; Workentin, M. S.; Bizzotto, D., “Selective reductive desorption of a SAM-coated gold electrode revealed using fluorescence microscopy”. Journal of the American Chemical Society 126, (2004) 8329-8335. PDF

[4] Bizzotto, D.; Yang, Y.; Shepherd, J. L.; Stoodley, R.; Agak, J.; Stauffer, V.; Lathuilliere, M.; Akhtar, A. S.; Chung, E., “Electrochemical and spectroelectrochemical characterization of lipid organization in an electric field.” Journal of Electroanalytical Chemistry 574, (2004) 167-184. PDF

[3] Shepherd, J. L.; Bizzotto, D., “On the apparent fluorescence recovery due to electrosorption.” Journal of Physical Chemistry B 107, (2003) 8524-8531. PDF

[2] Stoodley, R.; Shepherd, J.; Wasan, K. M.; Bizzotto, D., “Amphotericin B interactions with a DOPC monolayer. Electrochemical investigations.” Biochimica Biophysica Acta 1564, (2002) 289-297. PDF

[1] Shepherd, J.; Yang, Y.; Bizzotto, D., “Visualization of potential induced formation of water-insoluble surfactant aggregates by epi-fluorescence microscopy.” Journal of Electroanalytical Chemistry 524-525, (2002) 54-61. PDF

Book Chapters:

[1] Bizzotto, D. and Shepherd, J. L. “Epi-fluorescence microscopy studies of potential controlled changes of adsorbed thin organic films at electrode surfaces”. In Advances in Electrochemical Science and Engineering. Diffraction and Spectroscopic Methods in Electrochemistry. Richard C. Alkire, Dieter M. Kolb, Jacek Lipkowski, Philip N. Ross (Eds.). John Wiley & Sons. (2006). 

Refereed Conference Proceedings:

[3] Smith S.R., Guerra, E and Shepherd J. L. “Investigating Gold Dissolution During Oxidative Resorption of Alkylthiol Self-Assembled Monolayers”. ECS Transactions: Electrochemistry in Mineral and Metal Processing. 2010, 28(6), 249-258.

[2] Guerra E.; and Shepherd J.L. “Tapered Anodes for Copper Electrowinning”, Proceedings of the Copper-Cobre 2007 International Conference: August 25-30, (2007) - Toronto, Volume 5 - Electrowinning and Electrorefining, Edwards, J., and Houlachi, G. (Eds.), The Minerals, Metals & Materials Society, Montreal, QC, Canada.

[1] Guerra E.; and Shepherd J.L. “Cathode Guides for Conventional Copper Electrorefining Reactors Employing Starter Sheet Cathodes” ECS Transactions – Denver, Volume 2 Electrochemistry in Mineral and Metal Processing VII, 209th Meeting of The Electrochemical Society, Woods, R., Kelsall, G.H. and Doyle, F.M. (Eds.), Denver, Colorado, May 7-12 (2006), The Electrochemical Society, Pennington N.J. pp. 345.