The Quartz Crystal Microbalance (QCM) is an exciting tool for the electrochemist. With it, the researcher can now follow not only the current that flows, but the weight changes of the electrode, too! This is a valuable tool when studying reactions which involve films, adsorbates, metal deposition, corrosion, or monolayer formation. It is sensitive enough Read more about Quartz Crystal Microbalance[…]
Being able to scan rapidly does not insure that the results will be meaningful! The speed of the current measurement circuitry is often the limiting factor!
The key to finding the practical limit for obtaining meaningful fast scan cyclic voltammograms is nearly always finding the speed of the current measurement. Here the researcher has an important role to play: It is the researcher who must select the current range to use for fast cyclic voltammetry. The autoranging capability of many modern computer controlled potentiostats generally cannot be used because the decisions cannot be made and implemented fast enough.
Because of stray (and deliberately added) capacitances, the current measuring circuitry generally becomes slower as the full scale current decreases. Obtaining the fastest scan requires a tradeoff of scan rate, electrode size, analyte concentration, current range, and acceptable noise in the measurement. It is often better to use a less sensitive current scale (larger full scale current) coupled with a larger pre-amplification factor on the ADC, data recorder, or oscilloscope used. Although this approach is likely to increase the noise in the measurement, it does allow a higher scan rate to be realized.
The speed or frequency response of each current range can sometimes be found in the manufacturer’s data sheet under “Current Measurement” or sometimes as a “System Specification” if a specific current range is quoted along with the bandwidth.
This number can be roughly translated into a scan rate by looking at Figure 1.
Several times I have been asked a question about whether potentiostat Model XYZZY can scan at xyz V/s. Rarely is the answer in the data sheet for the instrument. Often, however, enough information is given to assess the limits. The path I follow to arrive at an answer is outlined here. An important fact about Read more about How Fast Can My Potentiostat Scan?[…]
One guideline that I have heard recommended (although I cannot give a reference for it) is that data over a decade range of frequency is required to support each circuit component.
All curve-fitting software should report some measure of the “goodness of fit.” Often this is the chi-squared parameter ( X2 ) or a value related to it. Boukamp makes the recommendation that the value of X2 should decrease by tenfold if a new circuit element is introduced into the circuit model. The tenfold decrease provides the justification for including the new circuit element. If the inclusion of an additional circuit element does not substantially improve the goodness-of-fit (as evidenced by the decrease in the X2 value), then based on Occam’s Razor, you should keep the simpler model, or continue your search for an improved one.
The old joke about the ability to “fit an elephant” if you use enough parameters is all too true with impedance data. Each component added to the model should have a physical explanation. Adding components only because they make the fit look better (smaller X2) without a physical interpretation is the equivalent to “fitting an elephant.”
For DNA Electrochemical Detection on Microfluidic Gene Chip On the microfluidic gene chip, due to high difficulty in temperature changes frequently and products detecting equipment miniaturize, the conventional methods of DNA detection can’t meet the requirements. In this paper, a newly electrochemical method, cyclic voltammetry, basing on a set of special electrodes and the Loop-mediated Read more about Development of a Cyclic Voltammetry Method[…]
The Center for Electrochemical Engineering at Ohio Univ.’s Russ College of Engineering and Technology has received a National Science Foundation (NSF) award to establish a new industry university cooperative research center in Athens, Ohio, with partner site Washington University-St. Louis.
Led by Russ Professor of Chemical Engineering and Center for Electrochemical Engineering Director Gerri Botte, research at the new Center for Electrochemical Processes and Technology (CEProTECH) will focus on electrochemical alternatives to conventional chemical and biological processes, with the goal of enhancing advanced production capabilities, via a consortium model.
Consortium members will have access to pre-competitive, industry-driven research results and a dedicated 20,000-square-foot facility, located on Mill Street in Athens, Ohio, with more than $7 million in state-of-the-art equipment and infrastructure; students with specialized expertise in electrochemical engineering; and relationships with faculty, government labs and agencies, and other industry members.
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