Topic 5 min read

Scanning probes & sensor research

Latest updated: December 2, 2019

Overview:

Scanning probe electrochemistry (SECM) is particular suited to sensor research.  SECM has been and continues to be, employed in a variety of sensor and biosensor studies. Through the use of SECM, it is possible to answer a number of questions about sensor systems, as outlined in the table below.

 

Question Technique Information Measured Example
Can surface functionalization be detected? dc-SECM dc-SECM detects the activity of a surface towards the redox mediator. The functionalization of a surface changes the activity of the surface towards a mediator, which changes the current measured when the probe is near the surface. By measuring approach curves to the surface before and after functionalization changes in the activity of the surface to the redox mediator will be detected. N. Ndebele, J. Mack, T. Nyokong, Electroanalysis 31 (2019) 137-145
Can membrane ion-selectivity be investigated? dc-SECM dc-SECM can be used to detect ionic flow through a membrane by connecting the probe as the CE on one side of the membrane and having a separate WE on the other side of the membrane. The current during the approach to the membrane can be monitored. Increasing current with decreasing probe to sample distance indicates ion flow across the membrane. T. J. Jackson, J. M. Sanderson, R. Kataky, Sensors and Actuators B 130 (2008) 630–637
Can sensor arrays be formed? SECM The x, y, z scanning of the SECM instruments can be used in the formation of biosensor arrays. This can be achieved with the sample submerged in solution by biasing the probe near the sample surface to cause electrochemical deposition. Another method is to use a microcapillary probe filled with a solution, which contacts the sample surface to deposit the array. J. Holmes, et al. Analytica Chimica Acta 741 (2012) 1– 8
Can specific binding of antigens in biosensors be investigated? dc-SECM The activity of a surface towards a redox mediator can be detected. When the specific binding of antigens to a biosensor occurs, there will be a noticeable change in the activity of the biosensor to the redox mediator compared to the biosensor prior to exposure to the antigen. In some cases, the change in current measured scales with changing antigen concentration. J. Holmes, et al. Analytica Chimica Acta 741 (2012) 1– 8
Can information about the sensor substructure be determined? dc-SECM While bulk electrochemical measurements give an average of the entire sensor response, dc-SECM measurements are local. Changes in the dc-SECM signal reflect changes in the local substructure of the sensor such as differences in enzyme activity, the influence of neighboring sites, etc. M. Maciejewska et al. Electrochemistry Communications 8 (2006) 1119–1124
Can the concentration profile of reactants/products near a sensor be determined? dc-SECM dc-SECM is a chemically selective measurement with the measured current signal directly related to the concentration of the measured species (i.e. redox mediator). It is possible, therefore, to relate the probe current at different distances from the sensor to the concentration of the species, allowing a concentration profile to be produced. B. Csóka et al.  Biosensors and Bioelectronics 18 (2003) 141-149

 

Glossary:

  • Scanning ElectroChemical Microscopy (SECM): Measurement of local electrochemical activity of a sample with chemical selectivity. The local impedance of a sample can also be measured.
  • Localized Electrochemical Impedance Spectroscopy (LEIS): Measurement of local impedance differences and point-by-point Electrochemical Impedance Spectroscopy
  • Scanning Kelvin Probe (SKP): Local non-contact measurement of sample work function. Topography can also be measured.
  • Scanning Vibrating Electrode Technique (SVET): Measurement of the local current distribution of a sample in electrolyte. Also known as Vibrating Probe.
  • Scanning Droplet Cell (SDS): Local electrochemical and impedance measurements of a sample within a droplet.
  • Optical Surface Profiler (OSP): Non-contact measurement of the local sample topography.