Measuring Electric Charge and Molecular Coverage on Electrode Surface from Transient Induced Molecular Electronic Signal (TIMES)

Abstract

Charge density and molecular coverage on the surface of electrode play major roles in the science and technology of surface chemistry and biochemical sensing. However, there has been no easy and direct method to characterize these quantities. By extending the method of Transient Induced Molecular Electronic Signal (TIMES) which we have used to measure molecular interactions, we are able to quantify the amount of charge in the double layers at the solution/electrode interface for different buffer strengths, buffer types, and pH values. Most uniquely, such capabilities can be applied to study surface coverage of immobilized molecules. As an example, we have measured the surface coverage for thiol-modified single-strand deoxyribonucleic acid (ssDNA) as anchored probe and 6-Mercapto-1-hexanol (MCH) as blocking agent on the platinum surface. Through these experiments, we demonstrate that TIMES offers a simple and accurate method to quantify surface charge and coverage of molecules on a metal surface, as an enabling tool for studies of surface properties and surface functionalization for biochemical sensing and reactions.

Detecting Protein–Ligand Interaction from Integrated Transient Induced Molecular Electronic Signal (i-TIMES)

“…All experimental data presented in this paper as well as the results in our earlier publication show the surface charge signal have piecewise linear dependence on the logarithmic molecular concentration. 27 The slope of the curve and the turning point(s) of the piecewise linear curve contain important information about the molecular behaviors on the electrode surface, which we will use to determine the K d . We can treat the slopes and the turning points between sections of different slopes as the fingerprint of each type of molecule.…”

Design of 150‐μV input‐referred voltage 1‐GHz comparison frequency dual offset cancelation comparator for pH biomarker system‐on‐chip

“…When the ions approach to in-plane electrode plate, the ions will absorb part of electrical field, denoted as C_delta illustrated in Figure 2 To read the pH value is very difficult since the ions surround around the molecular is just in the size around nanometer; the sensing capacitance change raised from ion is less than femto farad or the induced current is nanoscale. 36,37 Therefore, it is very important to design an extremely low offset comparator for the SoC sensor array. In order to reduce input referred voltage (noise) in comparator circuits, it often to design digitally time-sequence switch and very complex techniques to overcome the kickback noise and input offset voltage [38][39][40][41][42] in comparator, and assisted with calibration scheme.…”

“…To read the pH value is very difficult since the ions surround around the molecular is just in the size around nanometer; the sensing capacitance change raised from ion is less than femto farad or the induced current is nanoscale 36,37 . Therefore, it is very important to design an extremely low offset comparator for the SoC sensor array.…”