An Extended Gate Field Effect Transistor-based (EGFET-based) Urea Microbiosensor Based on Polypyrrole

Here, an extended – gate field effect transistor (EGFET) urea microsensor based on modified polypyrrole (PPy) is reported for the quantitative detection of urea in aqueous solution. the EGFET urea sensor was made by integrating a small and cheap metal oxide semiconductor field - effect transistor (MOSFET) with a Au microelectrode modified with urease and pH sensitive PPy. First, the urease was added to a pyrrole solution and then pyrrole/urease solution was electropolymerized on the surface of gold microelectrode in galvostanic mode to produce a urea sensitive microelectrode. The microsensor was imaged using a stereo microscope to confirm the polymerization of pyrrole/urease. The EGFET urea microsensor was tested in deionized water containing various concentrations of urea. The electrode showed a linear response for a wide concentration range of urea from 10−9 to 10−5 M with a sensitivity of 35.5 mV/decade urea.

Synthesis and Characterization of Ru-MOFs on Microelectrode for Trace Mercury Detection

Mercury ions (Hg2+) pollution in the water environment can cause serious harm to human health. Trace Hg2+ detection is of vital importance for environmental monitoring. Herein, we report a novel design of Ru-MOFs modified gold microelectrode for Hg2+ determination. Ru-MOFs are synthesized directly by the cathodic method on gold microelectrode, with the covered area accurately controlled. Cathodic synthesized Ru-MOFs show good conductivity and are suitable to be used as the electrode surface material directly. The synergy of the pre-deposition process and the adsorption process of Ru-MOFs can effectively improves the performance of the sensor. The results show good linearity (R2 = 0.996) from 0.1 ppb to 5 ppb, with a high sensitivity of 0.583 μA ppb−1 mm−2. The limit of detection is found to be 0.08 ppb and the test process is within 6 min. Most importantly, the senor has a good anti-interference ability and the recoveries are satisfactory. This miniature electrochemical sensor has the potential for on-site detection of trace mercury in the field.