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University of Washington realizes single redox molecules in nanoelectrochemical cells

2019-03-27 来源:亚科官网
Single-molecule detection can study the individual behavior of individual molecules in the system, and thus can reach the limit of analytical chemical detection, which has attracted more and more attention. The use of electrochemical methods to directly detect electrical signals generated by single molecules for redox is a significant challenge because one or several electrons are minimally generated and cannot be directly detected at room temperature using current electrochemical instruments.
In order to overcome this difficulty, methods such as redox cycle, fluorescence detection, and Raman spectroscopy have been developed. Among them, the fluorescence detection method is a very sensitive and effective method for detecting the fluorescent signal emitted by a single molecule in different states of redox. In single-molecule fluorescence detection, in order to achieve a higher signal-to-noise ratio, one needs to minimize the detection volume to minimize the background signal. Total internal reflection fluorescence microscopy, confocal microscopy, and nanopore electrode arrays can all be used to reduce the detection volume. However, these methods are difficult to estimate the efficiency of single molecule detection, that is, the ratio of the number of single molecules detected to the number of single molecules generated by actual redox.
Redox activity detection of single molecules
Recently, Professor Zhang Bo of the University of Washington designed a new strategy to detect single molecules with redox activity and successfully estimated the efficiency of single molecule detection. The authors used Pt bipolar electrochemical nanocells (Pt nanocells) and epifluorescence microscopy to observe the formation of resorufin in Pt nanocells. The main body of the Pt nanocell is a nanopipet with a 100 nm diameter nozzle plated with a platinum nanoparticle that completely separates the internal solution of the pipette from the external solution to form a two-pole isolated bipolar electrode (Closed bipolar electrode). Thereafter, they filled the interior of the Pt nanocell with a resazurin solution, placed horizontally on a sample stage of an inverted fluorescence microscope, and immersed in a FcMeOH solution. A pair of drive electrodes are also inserted into the inner and outer solutions of the nanocell, respectively, for controlling the voltage across the bipolar electrodes. When the voltage difference across the bipolar electrode reaches a certain value, the FcMeOH oxidation reaction on the outer surface of the platinum nanoparticle and the resazurin reduction reaction on the inner surface can be coupled to generate a highly fluorescent resorufin molecule, which is then captured by a CCD camera.
The advantages of Platinum bipolar nanoelectrochemical cell detection single molecule
First, the fluorescent molecules are only formed inside the nanopipette, and the inner diameter of the straw is only about 100 nanometers, and the portion irradiated by the laser is only 6 micrometers. Therefore, the sample is positively small (0.24 fL), and the background fluorescence signal is extremely low, and it can be observed by total internal reflection fluorescence microscopy without fluorescence single crystal; second, the inner space of the tiny nanopipette limits the free diffusion of fluorescent molecules, increasing the probability of single molecules being captured by the camera; and third, due to the redox reaction inside and outside of Pt nanocell is coupled, and only by knowing the concentration of the external FcMeOH molecule and the number of internal fluorescent molecules recorded by the camera, the detection efficiency of the single molecule can be estimated. In this way, it is possible to detect a single redox reaction that does not generate fluorescence outside the nanocell by using the fluorescent molecules observed inside the nanocell, and it is of great significance for the study of single molecule electrochemistry.
Edited by Suzhou Yacoo Science Co., Ltd.