Adsorption Kinetics of Phosphonic Acids and Proteins on Functionalized Indium Tin Oxide Surfaces using Electrochemical Impedance Spectroscopy
Phosphonic acids (PAs) are known to have a spontaneous affinity for chemisorption onto several metal oxide surfaces. The self-assembled monolayer (SAM) of phosphonates provides a platform for further surface modifications using biomolecules that can be adopted for the development of sensors and biosensors. With this in view, we studied adsorption kinetics of different phosphonic acids of short chain lengths such as phosphonopropionic acid (PPA), aminobenzylphosphonic acid (ABPA), benzylphosphonic acid (BPA), butylphosphonic acid (BuPA), and a long chain decylphosphonic acid (DecPA) on ITO surface using electrochemical impedance spectroscopy (EIS) at short and long time scales. The dependence of solution concentration on formation kinetics is studied and the existence of two discrete kinetics was revealed. We show from our studies that the rate of adsorption is controlled by diffusion at small time scales. Furthermore, the phosphonic acid modified surface is also used as a substrate for the adsorption of cytochrome C (CytC) (a heme protein) and urease (an enzyme) and the kinetics of their adsorption has been studied.
R. V. Jagadeesh is presently a Senior Research Fellow at the Soft Condensed Matter Laboratory in the Raman Research Institute, India. Jagadeesh received his Masters degree in Dyes, Drugs, Pharmaceuticals and Pesticides from the National Institute of Technology (NIT), Warangal and joined the Raman Research Institute as Research Fellow during 2011. He is pursuing his PhD degree with Jawaharlal Nehru University, New Delhi in the area of chemically modified electrodes primarily based on graphene and indium tin oxide surfaces. More specifically his research studies involve development of noble metal incorporated integral graphene electrodes for alcohol oxidation as well as silane and phosphonate modified ITO surfaces for electrochemical sensing. He is presently working on his thesis and is expecting it to be completed by the end of this year.
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