Surface-enhanced Raman scattering (SERS) signals strongly rely on the interactions and distance between analyte molecules and metallic nanostructures. In this work, the use of a gold nanoparticle (AuNP)-embedded metal-organic framework was introduced for the highly sensitive SERS detection. The AuNPs were in situ grown and encapsulated within the host matrix of MIL-101 by a solution impregnation strategy. The as-synthesized AuNPs/MIL-101 nanocomposites combined the localized surface plasmon resonance properties of the gold nanoparticles and the high adsorption capability of metal-organic framework, making them highly sensitive SERS substrates by effectively preconcentrating analytes in close proximity to the electromagnetic fields at the SERS-active metal surface. We discussed the fabrication, physical characterization, and SERS activity of our novel substrates by measuring the Raman signals of a variety of model analytes. The SERS substrate was found to be highly sensitive, robust, and amiable to several different target analytes. A SERS detection limit of 41.75 and 0.54 fmol for Rhodamine 6G and benzadine, respectively, was demonstrated. The substrate also showed high stability and reproducibility, as well as molecular sieving effect thanks to the protective shell of the metal-organic framework. Subsequently, the potential practical application of the novel SERS substrate was evaluated by quantitative analysis of organic pollutant p-phenylenediamine in environmental water and tumor marker alpha-fetoprotein in human serum. The method showed good linearity between 1.0 and 100.0 ng/mL for p-phenylenediamine and 1.0-130.0 ng/mL for alpha-fetoprotein with the correlation coefficients of 0.9950 and -0.9938, respectively. The recoveries ranged from 80.5% to 114.7% for p-phenylenediamine in environmental water and 79.3% to 107.3% for alpha-fetoprotein in human serum. These results foresee promising application of the novel metal-organic framework based composites as sensitive SERS-active substrates in both environmental and clinical samples.

A facile and efficient strategy about the synthesis of a novel kind of hybrid magnetic metal-organic framework (MOF)-5 via chemical bonding assembly was reported. The covalent bonding established between the amino functionalized Fe3O4 nanoparticles and the surface of the metal organic framework improved the chemical stability and structure uniformity of the hybrid microcrystals. Combination of MOF-5 with Fe3O4 nanoparticles allows for facile withdrawal of the porous materials by magnetic decantation. The powder X-ray diffraction patterns of the hybrid magnetic MOF-5 showed the structure of the metal organic framework was not disturbed with the decoration of magnetic nanoparticles. The as-synthesized materials combine the favorable attributes of both magnetic characteristics of Fe3O4 nanoparticles and high porosity of metal organic framework, making them excellent candidates as adsorbents for magnetic enrichment of trace analytes. Their potential applications were explored by preconcentrating polycyclic aromatic hydrocarbons and gibberellic acids from environmental, food, and plant samples prior to gas chromatography-mass spectrometry (GC/MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS), respectively. The results showed that the magnetic MOF-5 exhibited superior enrichment capacity for both of these nonpolar and polar analytes. The method demonstrated good precision (relative standard deviations (RSDs) of 1.7-9.7%), low detection limits (0.91-1.96 ng·L(-1) for polycyclic aromatic hydrocarbons and 0.006-0.08 μg L(-1) for gibberellic acid), and good linearity (correlation coefficients higher than 0.9949). The RSDs of batch-to-batch extraction were 2.9-11.2%. The magnetic MOF-5 was robust enough for repeatable use without damage of extraction performance.

A novel porous Au@MIL-100 (Fe) core-shell structure in which a Au nanoparticle (AuNP) core is coated with a controllable uniform metal-organic framework shell has been fabricated by using a facile step-by-step procedure. The as-synthesized Au@MIL-100 (Fe) takes advantage of the high adsorption capability of the MIL-100 (Fe) shell and the localized surface plasmon resonance properties of the AuNP core, and was used as a hybrid surface enhanced Raman scattering (SERS) substrate. We discussed the fabrication, physical characterization, and SERS activity of our novel substrate, and found that this new substrate had controllable shell thickness, high stability and good SERS activity. The potential practical application of the novel SERS substrate was firstly evaluated by quantitative analysis of malachite green in aquaculture water. The method showed good linearity between 3.0 × 10(-8)-1.0 × 10(-6) mol L(-1) for malachite green with a correlation coefficient of 0.9945. The limit of detection (LOD) was 8.0 × 10(-9) mol L(-1). Then the applicability of Au@MIL-100 (Fe) as the SERS substrate for in situ detection of malachite green on the fish body indicated its great potential as a rapid and on-site detection analytical strategy. In addition, the preliminary investigation also shows that the Au@MIL-100 (Fe) has SERS activity toward carbon disulfide which would be a new strategy for SERS-based gas sensors.

Toxicity issues and biocompatibility concerns with traditional classical chemical cross-linking processes prevent them from being universal approaches for hydrogel fabrication for tissue engineering. Physical cross-linking methods are non-toxic and widely used to obtain cross-linked polymers in a tunable manner. Therefore, in the current study, argon micro-plasma was introduced as a neutral energy source for cross-linking in fabrication of the desired gelatin-graphene oxide (gel-GO) nanocomposite hydrogel scaffolds. Argon microplasma was used to treat purified gelatin (8% w/v) containing 0.1∼1 wt% of high-functionality nano-graphene oxide (GO). Optimized plasma conditions (2,500 V and 8.7 mA) for 15 min with a gas flow rate of 100 standard cm3/min was found to be most suitable for producing the gel-GO nanocomposite hydrogels. The developed hydrogel was characterized by the degree of cross-linking, FTIR spectroscopy, SEM, confocal microscopy, swelling behavior, contact angle measurement, and rheology. The cell viability was examined by an MTT assay and a live/dead assay. The pore size of the hydrogel was found to be 287 ± 27 µm with a contact angle of 78° ± 3.7°. Rheological data revealed improved storage as well as a loss modulus of up to 50% with tunable viscoelasticity, gel strength, and mechanical properties at 37 °C temperature in the microplasma-treated groups. The swelling behavior demonstrated a better water-holding capacity of the gel-GO hydrogels for cell growth and proliferation. Results of the MTT assay, microscopy, and live/dead assay exhibited better cell viability at 1% (w/w) of high-functionality GO in gelatin. The highlight of the present study is the first successful attempt of microplasma-assisted gelatin-GO nano composite hydrogel fabrication that offers great promise and optimism for further biomedical tissue engineering applications.

Electrically conductive nanocomposites composed of a zirconium-based metal−organic framework (MOF) and nanocarbons are synthesized by in situ growth of MOF nanocrystals in the presence of graphene nanoribbons (GNRs) or graphene oxide (GO). The electrical conductivity and porosity of the obtained MOF-based nanocomposites are highly tunable by adjusting the MOF-to-carbon ratio as well as the type of nanocarbons used during the synthesis. Redox-active manganese sites are thereafter decorated in the MOF structure in these nanocomposites to render redox hopping in MOF under electrochemical conditions, and the pseudocapacitive behaviors of these MOF−GNR and MOF−GO nanocomposites are investigated in aqueous electrolytes. With the electrical conductivity provided by nanocarbons and the high-density redox-active manganese sites supported by the porous framework, the Mndecorated nanocomposites exhibit better performances as the materials for pseudocapacitors than the pristine Mn-decorated MOF and nanocarbons.

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A novel and mild Cu-catalyzed oxidative dual arylation of carbon−carbon double bonds in acrylamides with 3aminoindazoles is proposed for the synthesis of cyanoarylated oxindoles. Notably, 3-aminoindazoles are employed as efficient arylating agents via the cleavage of two C−N bonds. This oxidative dual arylation of active alkenes involves a radical process and undergoes a sequence of 3-aminoindazole oxidation, two-C−Nbond cleavage, cyanoaryl radical addition, and intramolecular cyclization.