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In this paper, PS (polystyrene)/Au/ZIF-8 (zeolite imidazole framework-8) hybrid structures were synthesized for the first time as novel SERS active substrates. A series of substrates were successfully prepared by changing the Au sputtering time (5 min, 8 min, 10 min, 15 min and 20 min). When the sputtering time of Au was 10 min, the 4-mercaptobenzoic acid (4-MBA) molecules on the PS/Au/ZIF-8 substrate exhibited the maximum SERS enhancement. Meanwhile, the hybrid SERS substrate exhibited good SERS reproducibility, and we successfully obtained an ultrahigh enhancement factor of 1.67 × 106. Probe molecules can be easily enriched on the surface of the PS/Au/ZIF-8 composite due to their large pore volume and the high surface area of metal organic framework (MOF) materials. ZIF-8 also guides the probe molecules to the "hot-spots" to enhance the SERS signals. Moreover, the detection limit of R6G molecules achieved was 10−12 M when PS/Au(10 min)/ZIF-8 was used as a highly sensitive SERS sensor. This strategy has brought new insights to SERS research, and has also provided a new idea for the application and development of SERS in MOF-based SERS materials and ultra-sensitive analyses. [ABSTRACT FROM AUTHOR]

This work reports on the effect of the morphology of ZIF-67 on its performance as a non-enzymatic electrochemical uric acid sensor. Three different structures were prepared using a simple co-precipitation method with different solvents. The characterization studies on ZIF-67 were carried out by several techniques including X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The characterization results showed that ZIF-67 which was prepared using methanol, water, and a mixture of methanol and water displayed dodecahedral, microplate, and irregular shapes, respectively. The three different structures are denoted as Me-ZIF-67, W-ZIF-67, and M-ZIF-67, respectively. The uric acid sensor performances were evaluated by conducting Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV) measurements in PBS solution with a pH of 7.4 containing uric acid. The test results show that W-ZIF-67 has the highest electrocatalytic activity compared to the other two materials possessing the highest current and the lowest overpotential. As a uric acid sensor, W-ZIF-67 has a sensitivity of 0.0377 μA μM−1 cm−2 with a relatively wide linear detection range of 20–1000 μM, and a detection limit of 3.04 μM. W-ZIF-67 also has good reproducibility and is stable against interfering species such as urea, glucose, ascorbic acid, and NaCl. [ABSTRACT FROM AUTHOR]