Novel graphene electrochemical transistors incorporating zirconia inorganic molecular imprinted layer：Design, construction and application for highly sensitive and selective detection of acetaminophen.

Owing to their intrinsic amplifying effect together with chemical stability, graphene electrochemical transistor sensors (GECTs) are gaining momentum for sensing applications. However, the surface of GECTs for different detection substances must be modified with different recognition molecules, which was cumbersome and lack a universal method. Molecularly imprinted polymer (MIP) is a kind of polymer with specific recognition function for given molecules. Here, MIP and GECTs were combined to effectively solve the problem of weak selectivity of GECTs, and achieve the high sensitivity and selectivity of MIP-GECTs equipment in detecting acetaminophen (AP) in complex urine environment. A novel molecular imprinting sensor based on Au nanoparticles modified zirconia (ZrO2) inorganic molecular imprinting membrane on reduced graphene oxide (ZrO2-MIP-Au/rGO) was proposed. ZrO2-MIP-Au/rGO was synthesized by one-step electropolymerization using AP as template, ZrO2 precursor as the functional monomer. The -OH group on ZrO2 and the -OH/-CONH- group on AP were easily bonded by hydrogen bonding to form a MIP layer on the surface, which allows the sensor to have a large number of imprinted cavities for AP specific adsorption. As a proof of method, the GECTs based on ZrO2-MIP-Au/rGO functional gate electrode has the characteristics of wide linear range (0.1 nM-4 mM), low detection limit (0.1 nM) and high selectivity for AP detection. These achievements highlight the introduction of specific and selective MIP to GECTs with unique amplification function, which could effectively solve the problem of selectivity of GECTs in complex environments, suggesting the potential of MIP-GECTs in real-time diagnosis.

Core-shell architectured NH2-UiO-66@ZIF-8/multi-walled carbon nanotubes nanocomposite-based sensitive electrochemical sensor towards simultaneous determination of Pb2+ and Cu2.

Amino functionalized zirconium-based metal-organic framework (NH2-UiO-66) and zinc-based zeolitic imidazolate framework (ZIF-8) were integrated to develop a core-shell architectured hybrid material (NH2-UiO-66@ZIF-8, NU66@Z8). The morphology and structure evolutions of core-shell NU6@Z8 were investigated by FE-SEM, XRD, FTIR, and XPS. The NU66@Z8 combined with carboxylated multi-walled carbon nanotubes (CMWCNT) was deposited on a glassy carbon electrode (GCE) for fabricating an electrochemical platform towards detecting Pb2+ and Cu2+. The NU66@Z8/CMWCNT/GCE revealed significantly improved electrochemical performance for determination of Pb2+ and Cu2+ compared with the individual components, which can be attributed to the strong adsorption capacity, unique core-shell structure, and large electrochemical active surface area of NU66@Z8/CMWCNT. Under the optimal conditions, the developed sensor exhibited excellent sensing capability with a low limit of detection (Pb2+,1 nM; Cu2+, 10 nM) and a wide determination range (Pb2+,0.003-70 µM; Cu2+, 0.03-50 µM). The sensor showed high selectivity towards common interfering ions and good repeatability. The real sample recoveries of proposed sensor were in the range 95.0-103% for Pb2+ (RSD ≤ 5.3%) and 94.2-106% for Cu2+ (RSD ≤ 5.9%), suggesting that the NU66@Z8/CMWCNT is suitable for examining trace heavy metals in natural environment.