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Crop types have significant impacts (p < 0.05) on the background nitrous oxide emissions (BNE) from soils. The annual BNE for China when considering the proportion of planting area is 0.69 ± 1.52 kg N–N2O ha−1.

Metal–organic frameworks (MOFs) have attracted extensive interest owing to their tunable compositions and large specific surface areas. Herein, Fe3O4@carbon and Fe3C@carbon composites were fabricated from iron-based MOFs (MIL-53(Fe)) via a facile hydrothermal and calcination process. Based on the Gibbs free energy theory, nanocrystal transformation from Fe3O4 to Fe3C can be well controlled when the calcination temperature is above 689 °C, revealing that the temperature plays key roles in improving the electromagnetic parameters and microwave absorbing performance. Using elaborately designed MIL-53(Fe) as a precursor for carbon-based lightweight microwave absorbers, a minimum reflection loss (RLmin) value of −30.48 dB at a very thin matching thickness of only 1.4 mm and an effective microwave bandwidth of 4.40 GHz (from 13.6 to 18 GHz) can be achieved. It is believed that this work can arouse interest to further exploit metal–organic frameworks for lightweight carbon-based microwave absorbers.

In this study, in situ sulfur-doped carbon nitride nanosheets (S-g-C3N4 NSs) are used as the signal readout for the sensitive and selective sensing of L-cysteine (L-Cys) in human serum samples based on the competitive coordination chemistry of Cu2+ between L-Cys and S-g-C3N4 NSs. S-g-C3N4 NSs are prepared by using trithiocyanuric acid as a precursor for the first time, which exhibits stronger electrogenerated chemiluminescence (ECL) intensity compared with pristine graphitic carbon nitride nanosheets (g-C3N4 NSs). The ECL signals of the S-g-C3N4 NSs can be quenched by Cu2+ and the subsequent presence of L-Cys can recover the ECL signals of the S-g-C3N4 NSs. These changes are ascribed to the higher coordination ability between Cu2+ and L-Cys than that between Cu2+ and the S-g-C3N4 NSs. On the basis of this, the concentration of L-Cys can be quantitatively determined. Under optimized conditions, the ECL intensity recovery shows a linear relationship with the L-Cys concentration range from 30 nM to 0.2 mM with a lower detection limit of 5 nM (S/N = 3). The proposed method is highly sensitive and selective and is thus particularly useful for fast and simple clinical diagnosis of diseases, such as Alzheimer's disease and cardiovascular disease.

In recent years, two-dimensional inorganic materials (MoS2) have been promising candidates for EM wave absorber because of their high specific surface area, excellent electronic properties and dielectric loss caused by polymorphism. Nevertheless, the poor impedance matching of individual MoS2 limited its microwave absorption performance. Optimizing the impedance matching of microwave absorber can be an effective way to achieve electromagnetic wave attenuation. In this study, we deposited CoFe2O4 magnetic nanoparticles on the surface of MoS2 nanosheets using reasonable hydrothermal reactions to optimize its poor impedance and enhance interfacial polarization. The MC-6 composite (mMoS2 : mCoFe2O4 = 6 : 1) exhibited excellent microwave absorption capability. The minimum reflection loss (RL) reached −55.3 dB at 16.24 GHz (Ku band) and the effective absorption bandwidth (

In the present work, polydopamine (PDA) modified reduced graphene oxide (pRGO)/SnO2/Au nanoparticles (NPs) were synthesized. SnO2/AuNPs were prepared through the redox reaction between reductive stannous(II) ions and oxidative auric(III) ions without any other reagents, and then the as-prepared graphene oxide (GO) was reduced and stabilized with the help of DA followed by decorating with SnO2/AuNPs. The morphology and structure of the hybrid nanomaterials were characterized by Raman spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction analysis. Then we constructed electrochemical sensors based on the hybrid nanomaterials for the determination of dopamine (DA). Cyclic voltammetry (CV) results showed that the hybrid nanomaterials had better sensing performance than pRGO/AuNPs and pRGO. Differential pulse voltammetry (DPV) showed that the separation of oxidation peak potentials for ascorbic acid (AA)–DA, uric acid (UA)–DA and UA–AA was about 200 mV, 100 mV and 300 mV, respectively. The linear range for the detection of DA was from 0.008 μM to 20 μM with a coefficient of 0.9986. The detection limit was 5 nM (S/N = 3). These indicate the selective and sensitive detection of DA. Finally, the constructed sensors were also applied to detect DA in human real samples.