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Here, we demonstrate room temperature NO2 sensors based on ZnO/rGO nanocomposites by a facile hydrothermal method. The ZnO nanoparticles (20 ~ 50 nm) were wrapped by film-like rGO with different contents (0.5, 1.0, 2.0, 3.0 wt %). They all exhibit p-type sensing toward NO2 at room temperature. The content of rGO shows an obvious effect on the sensing properties. The ZnO NPs-1% rGO has a high response of 5.21 to 10 ppm NO2 with a response/recovery time of 198/144 s. The sensing mechanism is discussed. The gas-sensitive properties are derived from the strong synergistic effect between the smaller particles of ZnO and rGO. [ABSTRACT FROM AUTHOR]

Summary An improved nanocomposite-based packaging material (NCP) was prepared by blending polyethylene with nano-Ag, nano-TiO2 and attapulgite. And its effect on preservation quality of green tea (Biluochun and Qingfeng) during one-year ambient storage was investigated. The results showed that adding nanoparticles to the polyethylene could significantly improve the barrier property. After one-year ambient storage, the moisture of Biluochun and Qingfeng with NCP was decreased by 10.3% and 6.1% compared with the normal packaging material. Meanwhile, the contents of amino acid, tea polyphenols, chlorophyll and ascorbic acid were increased by 22.8%, 9.4%, 30.4% and 9.5% for Biluochun and 19.2%, 9.3%, 27.3% and 21.6% for Qingfeng, respectively, compared with the normal packaging material. Moreover, the sensory quality of NCP was also superior to that with the control. Therefore, the improved NCP material probably provides an attractive alternative to maintain the preservation quality of green tea at a high level during storage. [ABSTRACT FROM AUTHOR]

Abstract: A novel nanocomposite-based packaging (NCP) was prepared by blending polyethylene (PE) with nano-Ag, nano-TiO2 and montmorillonite. The effects of NCP on the quality parameters of ethylene-treated mature kiwifruit were investigated during the 42d of storage at 4°C. The results showed that adding nanoparticles to the PE significantly decreased the oxygen, water vapor permeability and longitudinal strength, and inhibited spore germination. The weight loss, softening, color variation and soluble solid content of kiwifruit were significantly inhibited by 22.67%, 124.84%, 23.46% and 14.42% respectively, which indicated that NCP could delay the ripening of kiwifruit. However, ascorbic acid and total phenols contents in NCP-treated fruit were increased compared with the controls. Additionally, kiwifruit in NCP exhibited 57.44% lower headspace ethylene concentration, 29.44% for malondialdehyde (MDA), lower polyphenol oxidase (PPO) activity and higher peroxidase (POD) activity than the controls. These results suggest that NCP may be a useful technique to reduce fruit decay and maintain quality in kiwifruits during postharvest storage. [Copyright &y& Elsevier]

Magnetic NiFe 2 O 4 /SBA-15 nanocomposites were synthesized by a facile impregnation method, and NiFe 2 O 4 nanoparticles presented spinel phase structure and existed in the mesopores of SBA-15. Partial mesopores were blocked by NiFe 2 O 4 nanoparticles and micropores formed, which the capillarity of micropores played a decisive role for methylene blue (MB) adsorption. The saturation magnetization increased from 2.34 emu g −1 to 10.03 emu g −1 with the NiFe 2 O 4 content, while the specific surface area decreased from 552.18 m 2 g −1 to 260.40 m 2 g −1 and pore volume decreased from 1.13 cm 3 g −1 to 0.49 cm 3 g −1 . MB adsorption could be improved by optimizing the NiFe 2 O 4 content of the nanocomposites. MB could be adsorbed completely in 60 min with the optimum nanocomposites and could be separated easily from water by magnetic separation technique. [ABSTRACT FROM AUTHOR]

Meso-tetrakis(4-carboxyphenyl)-porphyrin-functionalized γ-Fe 2 O 3 nanoparticles (H 2 TCPP-γ-Fe 2 O 3 ) were successfully prepared by one-pot method under hydrothermal conditions and were found to possess intrinsic peroxidase-like activity. The H 2 TCPP-γ-Fe 2 O 3 nanocomposites can catalytically oxidize peroxidase substrate 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H 2 O 2 to produce a blue color reaction, which can be easily observed by the naked eye. Furthermore, kinetic studies indicate that the H 2 TCPP-γ-Fe 2 O 3 nanocomposites have an even higher affinity to TMB than that of the natural enzyme, horseradish peroxidase (HRP). On the basis of the high activity, the reaction provides a simple, sensitive and selective method for colorimetric detection of H 2 O 2 over a range of 10–100 μM with a minimum detection limit of 1.73 μM. Moreover, H 2 TCPP-γ-Fe 2 O 3 /glucose oxidase (GOx)/TMB system provides a novel colorimetric sensor for glucose and shows good response toward glucose detection over a range of 5–25 μM with a minimum detection limit of 2.54 μM. The results indicated that it is a simple, cheap, convenient, highly selective, sensitive and easy handling colorimetric assay. Results of a fluorescent probe suggest that the catalase-mimic activity of the H 2 TCPP-γ-Fe 2 O 3 nanocomposites effectively catalyze the decomposition of H 2 O 2 into H 2 O and O 2 . [ABSTRACT FROM AUTHOR]

5,10,15,20-Tetrakis(4-carboxyphenyl)-porphyrin-functionalized Fe3O4 nanocomposites (H2TCPP-Fe3O4) were successfully prepared by a simple two-step method. These nanocomposites exhibited ultra-high peroxidase-like activity compared with pure Fe3O4 nanoparticles. Colorless peroxidase substrate 3,3,5,5-tetramethylbenzidine (TMB) was changed by H2O2 to its blue oxidized state. Kinetic studies indicated that the H2TCPP-Fe3O4 nanocomposites exhibited enhanced affinity toward H2O2 with a higher catalytic activity than Fe3O4 nanoparticles alone. Results of a fluorescent probe suggested that the catalase-mimic activity of the H2TCPP-Fe3O4 nanocomposites effectively catalyzed the decomposition of H2O2 into hydroxyl radicals. A simple, sensitive, and selective visual and colorimetric method with TMB as the substrate was designed to detect glucose when combined with glucose oxidase. This colorimetric method can be used for colorimetric detection of H2O2 with a minimum detection limit of 1.07×10−6 M and a dynamic range of 5×10−6 mol·L−1 to 8×10−5 mol·L−1. This method can also be used to detect glucose at a minimum detection limit of 2.21×10−6 M and a dynamic range of 25×10−6 mol·L−1 to 5×10−6 mol·L−1. Furthermore, the robustness of the nanocomposites makes them suitable for a wide range of applications in biomedicine and environmental chemistry fields. [ABSTRACT FROM AUTHOR]