Friday, October 8, 2010, 11:00 am — Chemistry Bldg. 555, Room 300
Electrochemical experiments in small conﬁned volumes presents an interesting avenue to explore fundamental questions regarding the behavior of ions and redox-active molecules in solution in the vicinity of an electrode. These studies are also vitally important for development of lab-on-a-chip type applications which rely on electro-chemical detection.
Using microfabrication methods we have developed electrochemical devices that conÃƒâ€šÃ‚Â¬sist of two plane-parallel electrodes that are embedded in a nanoﬂuidic channel. The electrode spacings can be reliably adjusted during the fabrication process to be ∼ 50 nm. The volume enclosed by the active area of the device is ca. 1 femtoliter (10−15 L). Redox-active molecules are capable of freely diﬀusing in and out of the nanochanÃƒâ€šÃ‚Â¬nel. When the electrodes are suitably biased, the molecules can repeatedly shuttle multiple electrons between the electrode, leading to an ampliﬁcation in the measured electrical current.
Because of the small volume of the detection area, statistical ﬂuctuations in the number of molecules in it give rise to corresponding ﬂuctuations in the measured current which can be readily observed as electrical noise. As the absolute number of molecules decreases with decreasing detection volume, these ﬂuctuations become an increasingly prominent feature in nanoscale devices. We recently introduced a new technique called Electrochemical Correlation Spectroscopy (ECS). Much like its optical counterpart, Fluoresence Correlation Spectroscopy (FCS), ECS relies on an autocorrelation analysis of these ﬂuctuations. This yields new information about adÃƒâ€šÃ‚Â¬sorption dynamics of molecules in the channel, hitherto unavailable through other electrochemical means -a direct consequence of performing electrochemical experiÃƒâ€šÃ‚Â¬ments in such small volumes.
Recently, we have also been able to detect ﬂuctuations corresponding to th
Hosted by: John Miller
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