Chenyi Yuan

Air pollutants from residential solid fuel combustion are attracting growing public concern. Field measured emission factors (EFs) of various air pollutants for solid fuels are close to the reality and urgently needed for better emission estimations. In this study, emission factors of particulate matter (PM), organic carbon (OC), elemental carbon (EC), and various polycyclic aromatic hydrocarbons (PAHs) from residential combustions of coal briquette, coal cake, and wood were measured in rural Heshun County, China. The measured EFs of PM, OC, and EC were 8.1-8.5, 2.2-3.6, 0.91-1.6 g/kg for the wood burnt in a simple metal stove, 0.54-0.64, 0.13-0.14, 0.040-0.0041 g/kg for the briquette burned in an improved stove with a chimney, and 3.2-8.5, 0.38-0.58, 0.022-0.052 g/kg for the homemade coal cake combusted in a brick stove with a flue, respectively. EFs of 28 parent PAHs, 4 oxygenated PAHs, and 9 nitro-PAHs were 182-297, 7.8-10, 0.14-0.55 mg/kg for the wood, 14-16, 1.7-2.6, 0.64-0.83 mg/kg for the briquette, and 168-223, 4.7-9.5, 0.16-2.4 mg/kg for the coal cake, respectively. Emissions from the wood and coal cake combustions were much higher than those for the coal briquette, especially true for high molecular weight PAHs. Most EFs measured in the field were higher than those measured in stove combustions under laboratory conditions.

With the development of internet of things and artificial intelligence electronics, metal oxide semiconductor (MOS)-based sensing materials have attracted increasing attention from both fundamental research and practical applications. MOS materials possess intrinsic physicochemical properties, tunable compositions, and electronic structure, and are particularly suitable for integration and miniaturization in developing chemiresistive gas sensors. During sensing processes, the dynamic gas-solid interface interactions play crucial roles in improving sensors' performance, and most studies emphasize the gas-MOS chemical reactions. Herein, from a new view angle focusing more on physical gas-solid interactions during gas sensing, basic theory overview and latest progress for the dynamic process of gas molecules including adsorption, desorption, and diffusion, are systematically summarized and elucidated. The unique electronic sensing mechanisms are also discussed from various aspects including molecular interaction models, gas diffusion mechanism, and interfacial reaction behaviors, where structure-activity relationship and diffusion behavior are overviewed in detail. Especially, the surface adsorption-desorption dynamics are discussed and evaluated, and their potential effects on sensing performance are elucidated from the gas-solid interfacial regulation perspective. Finally, the prospect for further research directions in improving gas dynamic processes in MOS gas sensors is discussed, aiming to supplement the approaches for the development of high-performance MOS gas sensors.

With the rapid development of nanotechnology and catalysis science, numerous enzyme-mimicking nanomaterials have been rationally designed as the substitutes for natural enzymes. Herein, the Pt-loaded hollow mesoporous carbon nanospheres (Pt-HMCNs) were proposed as the peroxidase mimic for the first time. The monodispersed HMCNs with huge hollow cavity and mesoporous carbon skeleton were first synthesized via high-temperature carbonization and NaOH etching of core–shell structured SiO2@RF/SiO2 (RF = resorcinol–formaldehyde resin) nanospheres, which were prepared through a simple surfactant-free strategy in a one-pot system only containing three main raw chemicals as tetraethyl orthosilicate, resorcinol, and formaldehyde. And then the Pt-HMCNs were obtained through surface graft of −NH2 groups and loading of as-synthesized ultrasmall Pt nanoparticles (NPs) in size of 1–3 nm on the HMCNs. The prepared Pt-HMCNs nanocomposites exhibited superior peroxidase-like catalytic activity toward the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) substrate, which owned stronger affinity to H2O2 and TMB as substrates than the natural enzyme (horseradish peroxidase). The outstanding peroxidase-mimic performance of the Pt-HMCNs is due to the unique hollow mesoporous structure as well as the interfacial effect between Pt NPs and carbon skeleton. A simple and general colorimetric approach was established to accurately detect ascorbic acid (AA) and glucose, and their detection limits were calculated to be 3.29 and 35.4 μM, respectively. Besides, wide linear range and high selectivity against interfering substances were also achieved in this assay during AA and glucose detection based on the Pt-HMCNs catalyst. The colorimetric method built on Pt-HMCNs in this work could be applied to biomedicine, food science, environment monitoring, and other fields for accurately detecting ascorbic acid, glucose, and other important substances in some complex systems.