Review on recent progress in on-line monitoring technology for atmospheric pollution source emissions in China

Emissions from mobile sources and stationary sources contribute to atmospheric pollution in China,and its components,which include ultrafine particles(UFPs),volatile organic compounds(VOCs),and other reactive gases,such as NH3and NOx,are the most harmful to human health.China has released various regulations and standards to address pollution from mobile and stationary sources.Thus,it is urgent to develop online monitoring technology for atmospheric pollution source emissions.This study provides an overview of the main progress in mobile and stationary source monitoring technology in China and describes the comprehensive application of some typical instruments in vital areas in recent years.These instruments have been applied to monitor emissions from motor vehicles,ships,airports,the chemical industry,and electric power generation.Not only has the level of atmospheric environment monitoring technology and equipment been improving,but relevant regulations and standards have also been constantly updated.Meanwhile,the developed instruments can provide scientific assistance for the successful implementation of regulations.According to the potential problem areas in atmospheric pollution in China,some research hotspots and future trends of atmospheric online monitoring technology are summarized.Furthermore,more advanced atmospheric online monitoring technology will contribute to a comprehensive understanding of atmospheric pollution and improve environmental monitoring capacity.

Co_3O_4 nanosheet-built hollow dodecahedrons via a two-step self-templated method and their multifunctional applications

TheCo3O4 nanosheet-built hollow dodecahedrons(Co3 O4 NSHDs) were fabricated via a controllable twostep self-templated method. The ZIF-67 dodecahedrons were prepared as first self-template to synthesize the Co-LDH hollow dodecahedrons, which were further used as self-template to fabricateCo3O4 NSHDs by a controlled calcination.The proposed two-step self-templated method not only brings hollow structures without auxiliary template, ultrathin nanosheet, ultrafine grains, and large surface areas, but also allows the easy and uniform surface modification, as demonstrated of PdO modification. TheCo3O4 NSHDs with above features could show multifunctional applications, such as sensing and catalysis. Experiments suggest that theCo3O4 NSHDs show good gas sensing performances to trimethylamine at a low operating temperature(100 oC). They can be further enhanced by PdO surface modification, which have a low detection limit(250 ppb) and a short response time(4.5 s).In addition, theCo3O4 NSHDs exhibited excellent oxygen evolution reaction performances with a low overpotential of359 mV, low Tafel slope of 80.7 mV dec-1 and low electrochemical impedance, which was superior to those for theCo3O4 NCs obtained by directly calcinating the ZIF-67 templates,Ni foam and most common metal oxides catalysts.

Controllable Synthesis of Well-aligned ZnO Nanorod Arrays on Varying Substrates via Rapid Electrodeposition

A facile and rapid electrodeposition route was developed to controllably synthesize well-aligned ZnO nanorod arrays on diverse substrates, such as seed-layer pre-formed, pristine indium tin oxide （ITO） and Si, using Zn（NO3）2·6H2O and hexamethylenetetramine （HMT） as the precursors. X-ray diffraction （XRD） and transmission electron microscopy （TEM） results indicated that seed-layer pre-modified of ZnO nanorod arrays （ZNRs） possessed single crystalline, a wurtzite crystal structure with preferential growth orientation along [0001] direction. The ZNRs on pre-modified ZnO seed-layer （ZSL） had diameters of 30-50 nm, and aligned vertically to the substrates. ZNRs on ZSL/ITO substrate exhibited a high transmittance （above 80%） in visible wavelength range and the red-shift of band gap energy. An electrochemical reaction model was proposed to explain the growth process of ZnO nanorods. Importantly, the rapid synthesis of ZNRs provided the feasibility of preparation of SERS （surface enhanced Raman scattering） nanocomposite within shorter time by a subsequent electrochemical etching.

Hf-doped ZnO transistor with high bias stability and high field-effect mobility by modulation of oxygen vacancies and interfaces

ZnO-based thin film transistors(TFTs)with high bias stability are challenging due to the intrinsic defects and overhigh interface trap density.In this work,we fabricated Hf-doped ZnO films with different cycle ratio of Zn/Hf via atomic layer deposition and subsequent annealing treatment.The results show that the cycle ratio of Zn/Hf is optimized to be 10:1,and the corresponding atomic ratio is 2.24%.The threshold voltage and subthreshold swing of the devices are improved as the annealing temperature increases,owning to the decrease of the oxygen vacancies and interface trap density.Furthermore,we developed Hf-doped ZnO TFT with high bias stability by introducing HfO_(2)intermediate layer between the active layer and SiO_(2)dielectric layer,and the shift of threshold voltage is as low as-0.273 V,showing high bias stability.Also,the device has the high field-effective mobility of 52.4 cm^(2)/Vs,low subthreshold swing of 0.68 V/dec and high Ion/Ioff of 3.6×10^(8).The results indicate a promising fabrication method for highperformance ZnO-based TFTs,which may be applied in logic circuits,radio frequency identification and so on.