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Metal–organic frameworks (MOFs) have unique potential in the field of gas sensing due to their ultra-high specific surface area and abundant mesoporous structure. In this paper, a mesoporous Co3O4 hollow polyhedron structure with high specific surface area (141.6 m2 g−1) was synthesized by annealing at the optimum temperature. The gas response of the mesoporous Co3O4 hollow polyhedron structure to volatile organic compounds such as xylene, ethanol, methanol and acetone was systematically tested. The experimental results show that the mesoporous Co3O4 hollow polyhedron structure has the highest sensitivity (21.33) and excellent stability for xylene gas, and the detection limit is low (1 ppm). The excellent sensing performance benefits from large surface area, high oxygen defect concentration and mesoporous structure. [ABSTRACT FROM AUTHOR]

The development of sensors with high sensitivity, selectivity, long-term stability and other excellent performances is still the focus of current research on gas sensors. In this paper, biomorphic zinc oxide composite reduced graphene oxide nanomaterials (C–Z–ZnO–rGO) based on a metal–organic framework are synthesized by an impregnation calcination method using cotton as a biological template. The microscopic morphologies and structural composition of the composites are characterized. The response value of C–Z–ZnO–rGO to acetic acid gas is much higher than that of other gas sensors. At an operating temperature of 350 °C, the C–Z–ZnO–rGO gas-sensitive sensors have a response value of 410 for 100 ppm acetic acid, a response time of 43 s, and a recovery time of 18 s, and have good repeatability and long-term stability. The response value of 2.614 for 1 ppm of acetic acid gas further indicates that the C–Z–ZnO–rGO sensor has a low detection limit. The hollow structure of the C–Z–ZnO–rGO composites has the advantages of high specific surface area, multiple pores, diverse structures and abundant active sites, which improves the adsorption performance on acetic acid gas. [ABSTRACT FROM AUTHOR]

The current luminescent metal-organic framework (MOF) based fluorescence detection mostly focuses on achiral molecules. The stereospecific recognition and determination of MOF-based detection remain challenging. A novel luminescent terbium-based MOF (Tb-MOF) based biosensing system with excellent performance for stereoselective detection of D-amino acids (D-AAs) was introduced in this paper. D-Amino acid oxidase catalyzes stereospecific oxidative deamination of D-AAs, producing H2O2. The generated H2O2 effectively quenches the fluorescence of Tb-MOF. Under optimum conditions, the D-AAs were detected with excellent efficiency. The linear working range was 0.5-100 mM for D-Alanine (D-Ala) and 0. 5-5 mM for D-Proline (D-Pro), respectively. The limit of detection (Ksv detection) for D-Ala and D-Pro was 0.09 mM and 0.14 mM, respectively. The detection can be performed within 30 min with high selectivity and long-term stability. The fluorescent sensing platform required simple fabrication and operation and was free from complicated reaction processes and expensive reagents. The present sensing system was successfully applied in D-AA detection in human serum with good recovery, indicating its potential application in detection in biological samples. [ABSTRACT FROM AUTHOR]

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]