SECM Scanning Electrochemical Microscopy

The SECM integrates a positioning system, a bipotentiostat, and an ultramicroelectrode tip. The positioning system moves the tip close to the surface of the sample. The bipotentiostat polarizes both the sample and the  tip independently and measures both resulting currents. The tip is an ultramicroelectrode with a specific tapered polish and active radius lower than 100 microns. The positioning system scans the measurement tip and charts position with measured electrochemical parameters, creating a data map of local current.

Approach Curves are used as an electrochemical means by which to position the probe in Z sufficiently close to the sample to be in the local imaging zone. Current at the tip is charted as the tip is incremented towards the sample. When the probe is sufficiently close to the sample (a distance of 2-4 times that of the probe diameter) the measured current at the tip transitions from a bulk response to a local response. Over a region of high conductivity, a Nerstian response provides a local current enhanced over that of the bulk current. However, local current is decreased relative to bulk value over areas of low conductivity of the sample as mass-transport is hindered to the tip.

The Soft Stylus Probe technology from LEPA-EPFL, Switzerland, offers a convenient method of controlling the tip – sample distance without the need for complicated feedback electronics. Constant distance measurements are especially important when sample topography can affect the electrochemical response such as rough and corrugated surfaces. In addition, the soft probe technique has been shown to be ideal for soft tissue samples and has been applied to the detection and staging of cancer.

A common experiment in SECM is Generator-Collector Mode. Here one channel of the bipotentiostat polarizes the sample; where the other channel polarizes the tip. Similar to a Rotating – Ring Disk Electrode (RRDE) experiment, one electrode generates an electrochemical reaction, the products of which are subsequently measured at the other electrode. A SECM does this while adding the extra dimension of spatial resolution to the data, and being able to change from Sample Generation – Tip Collection (SG-TC) to Tip Generation –Sample Collection (TG-SC) often by simply changing polarization levels.

Since the imaging mechanism is electrochemistry, the applications of a SECM are as varied as the applications of electrochemistry itself. Some key applications are biological sensors, reaction kinetics, porous membrane study, fuel cell catalysts, and corrosion mechanisms.

 

  • Documents +

  • Specifications +


    Potentiostats
    Compliance Voltage ±12V
    Polarizations Voltage ±10V
    Current Ranges & Resolutions
    VersaSTAT 4
    VersaSTAT 3F
    VersaSTAT 3

    4nA to 1A standard; 120fA on 4nA range
    4nA to 650mA standard; 120fA on 4nA range
    200nA to 650 mA standard; 6pA on 200nA range
    Compatible with Low Current Interface and Boosters to expand current measurement capability.
    EIS capable.
    *Please see Potentiostat's brochure for detailed specification on the model


    Probes
    Probe 10 micron Pt probe with RG ratio of ~ 10
  • Options +


    L-Cell VersaSCAN L-Cell
    • Screws into optical table of VersaSCAN
    • Approximately 1 Liter in volume
    • Level adjustment mechanism
    • Accepts large flat samples and 32-mm diameter mounted samples
    • Recommended for all techniques, particularly LEIS, SVET, SKP, SDC, OSP
    mL-Cell VersaSCAN mL-Cell
    • Screws into optical base of VersaSCAN
    • Approximately 7 mL in volume
    • Level adjustment mechanism
    • Accepts a range of samples including 32-mm diameter mounted samples and non-standard samples
    • Specifically engineered for low-volume SECM applications
    VersaCAM VersaCAM
    Long Working Distance Video Microscope
    • Camera:
      • Color
      • Number of pixels: 795 (H) x 596 (V)
      • Minimum illumination 0.02 lx. F1.2
      • Power: 12V DC ±10%
      • CS-mounted or C-mount with provided adapter
    • Lens:
      • C-Mount
      • Manual focus
    • Display:
      • 8 inch color TFT display
      • PAL & NTSC auto selection
      • 640x480 (307,200 pixels) screen resolution
  • Video +

    Watch video demonstrations of the SECM Scanning Electrochemical Microscopy

  • Experiments +


    Approach Curve Approach Curves measure current as the probe position is incremented in the Z-direction approaching the sample. Typically, these experiments are first ran over known areas of insulating nature to show negative feedback….then over areas of known conducting nature to show positive feedback. By comparing the results of these two experiments, you can successfully position the probe at the appropriate Z-distance for a SECM experiment.
    Line Scan SECM Line Scan experiments allow you to polarize either the probe or sample at a potential sufficient to cause an electrochemical reaction. Current is recorded as the probe’s position is scanned in either the X or Y direction. If the “Secondary Potentiostat” is connected Generator-Collector experiments are possible, as the probe and sample can be independently polarized.
    Area Scan SECM Area Scans are X-Line Scan experiments at incremented positions in the Y-direction. This XY plane is graphed as a map.
    Non-Scanning, Fundamental Experiments The VersaSTAT's can run a wide variety of non-scanning fundamental experiments with the VersaStudio environment. Please reference the brouchure or webpage of your specific model of potentiostat for complete details on its non-scanning experiments.