Scanning Electrochemical Microscopy

Scanning electrochemical microscopy (SECM) involves the measurement of electrochemically active species through an ultramicroelectrode (UME) (an electrode with a diameter of the order a few nm to 25 micrometers) when it is held or moved in a solution in the vicinity of a substrate. Since the electrochemical current is proportional to the concentration of a redox species at the substrate, which can be live cells or metal alloys, any change in their chemical activities will perturb the electrochemical responses of the probe. This perturbation provides information about the nature and activities at the substrate. For instance, reactive oxygen species (ROS) released from a single live cell have been found by us to be a good molecular probe for its physiology and pathophysiology. SECM has been also applied to various metallic materials very important to our daily life. We have constructed grain microstructure maps of Ti metal alloys, UO2+x (x=0.001 to 0.33) and Zr alloys based on reactivity images from SECM, providing insights into relationship between their structures and reactivities.

While the SECM has become a very powerful tool to determine fast heterogeneous kinetics, image chemical and biological activity, fabricate interdigitated arrays, its power would be increased if it was combined with other techniques. Only a few attempts have been reported on nanoelectrode fabrication and combinations of SECM with other techniques: SECM/photoelectrochemical microscopy, SECM/ atomic force microscopy (AFM), and SECM /AFM /near-field scanning optical microscopy (NSOM).

We are working hard in the aspects of probe fabrication, probe displacement, scanning speeds, and probe-to-substrate distance adjustment for further development of SECM. We have found a novel strategy to perform constant-distance AC SECM imaging: negative AC feedback is independent on the nature of the substrate. This is significant since the probe-to-substrate distance can be kept constant by simply setting up the constant AC current. Simultaneous AC and DC SECM images will discriminate topographical from chemical information.

  1. Nowierski, C.; Noël, J. J.; Shoesmith, D. W.; Ding, Z., Pathways for Hydrogen Absorption into Zircaloy-2 under Cathodic Polarization Assessed by Scanning Electrochemical Microscopy, Scanning Electron Microscopy, and Electrochemical Impedance Spectroscopy. J Electrochem Soc 2012, 159 (12), C590-C596.
  2. Zhang, M. M. N.; Long, Y.-T.; Ding, Z., Cisplatin effects on evolution of ROS from single human bladder cancer cells investigated by SECM. J Inorg Biochem 2012, 108, 115-122.
  3. Zhao, X.; Diakowski, P. M.; Ding, Z., Deconvoluting Topography and Spatial Physiological Activity of Live Macrophage Cells by SECM in Constant-Distance Mode. Anal Chem 2010, 82 (20), 8371-8373.
  4. Zhao, X.; Lam, S.; Jass, J.; Ding, Z., SECM of single human urinary bladder cells using reactive oxygen species as probe of inflammatory response. Electrochem Commun 2010, 12 (6), 773-776.
  5. Zhao, X.; Zhang, M.; Long, Y.; Ding, Z., Redox reactions of reactive oxygen species as the probe for SECM of single live T24 cells. Can J Chem 2010, 88 (6), 569-576.
  6. He, H.; Zhu, R. K.; Qin, Z.; Keech, P.; Ding, Z.; Shoesmith, D. W., Determination of Local Corrosion Kinetics on Hyper-Stoichiometric UO2+x by Scanning Electrochemical Microscopy. J Electrochem Soc 2009, 156 (3), C87-C94.
  7. Nowierski, C.; Noel, J. J.; Shoesmith, D. W.; Ding, Z., Correlating surface microstructures with reactivity on zirconium using SECM and SEM. Electrochem Commun 2009, 11 (6), 1234-1236.
  8. Zhu, R.; Qin, Z.; Noel, J. J.; Shoesmith, D. W.; Ding, Z., Analyzing the influence of alloying elements and impurities on the localized reactivity of titanium 7 by SECM. Anal Chem 2008, 80 (5), 1437-1447.
  9. Diakowski, P. M.; Ding, Z., Novel strategy for constant-distance imaging using alternating current scanning electrochemical microscopy. Electrochem Commun 2007, 9 (10), 2617-2621.
  10. Diakowski, P. M.; Ding, Z., Interrogation of living cells using alternating current scanning electrochemical microscopy (AC-SECM). Phys Chem Chem Phys 2007, 9 (45), 5966-5974.
  11. Zhao, X.; Petersen, N. O.; Ding, Z., Comparison study of live cells by atomic force microscopy, confocal microscopy, and scanning electrochemical microscopy. Can J Chem 2007, 85 (3), 175-183.
  12. Zhu, R.; Nowierski, C.; Ding, Z.; Noel, J. J.; Shoesmith, D. W., Insights into grain structures and their reactivity on grade-2 Ti alloy surfaces by scanning electrochemical microscopy. Chem Mater 2007, 19 (10), 2533-2543.