基于MAX-DOAS的被动光谱测量重庆地区HCHO的研究

甲醛（HCHO）对人体、气候、环境影响巨大,也是大气光化学反应的重要中间产物。重庆市作为我国西南工业重地,是全国人口最多、面积最大的直辖市。其以燃煤为主的能源结构与环保设施的落后,以及特殊的地形与气候特征,导致空气污染极为严重。因此研究重庆地区大气中的甲醛浓度变化规律,具有重要意义。于2018年12月,在中国重庆市江北区凤凰座区域搭建了地面多轴差分吸收光谱监测系统(MAX-DOAS)。结合光谱处理软件QDOAS利用非线性最小二乘拟合算法反演甲醛的差分斜柱浓度(DSCD),并通过几何近似的方法得到大气质量因子(AMF),然后将甲醛的斜柱浓度（SCD）转换为柱浓度(VCD)。分析显示,甲醛的日平均变化和周平均变化相似。甲醛VCD的最小和最大平均浓度值分别为0.982×1016和9.221×1016 molecule·cm-2。其平均日变化较为明显,表现为早晚较高,中午最低。从甲醛VCD的平均周变化可以看出,基本趋势与平均日变化基本一致。周一整体偏低,周二中午出现明显高值,但无明显的周末效应,也没有任何明显的周循环。对比地基MAX-DOAS测量数据与 (臭氧监测仪器)卫星产品TROPOMI观测值,二者的一致性较好,且相关系数为0.84。但是,TROPOMI观测值平均比MAX-DOAS 的甲醛VCD低21.5％。研究表明,地基MAX-DOAS可以对城市区域污染气体如甲醛的实时快速监测及变化规律的研究分析提供一种有效手段,也可以对卫星数据来源进行有效校验。     

Intrinsic V vacancy and large magnetoresistance in V1-δSb2 single crystal

The binary pnictide semimetals have attracted considerable attention due to their fantastic physical properties that include topological effects, negative magnetoresistance, Weyl fermions, and large non-saturation magnetoresistance. In this paper, we have successfully grown the high-quality V_1-δSb₂ single crystals by Sb flux method and investigated their electronic transport properties. A large positive magnetoresistance that reaches 477% under a magnetic field of 12 T at T = 1.8 K was observed. Notably, the magnetoresistance showed a cusp-like feature at the low magnetic fields and such feature weakened gradually as the temperature increased, which indicated the presence of a weak antilocalization effect (WAL). In addition, based upon the experimental and theoretical band structure calculations, V_1-δSb₂ is a research candidate for a flat band.     

Electroreduction of CO2 on Au(310)@Cu High-index Facets

The chemical selectivity and faradaic efficiency of high-index Cu facets for the CO₂ reduction reaction (CO₂RR) is investigated. More specifically, shape-controlled nanoparticles enclosed by Cu {hk0} facets are fabricated using Cu multilayer deposition at three distinct layer thicknesses on the surface facets of Au truncated ditetragonal nanoprisms (Au DTPs). Au DTPs are shapes enclosed by 12 high-index {310} facets. Facet angle analysis confirms DTP geometry. Elemental mapping analysis shows Cu surface layers are uniformly distributed on the Au {310} facets of the DTPs. The 7 nm Au@Cu DTPs high-index {hk0} facets exhibit a CH₄ : CO product ratio of almost 10 : 1 compared to a 1 : 1 ratio for the reference 7 nm Au@Cu nanoparticles (NPs). Operando Fourier transform infrared spectroscopy spectra disclose reactive adsorbed *CO as the main intermediate, whereas CO stripping experiments reveal the high-index facets enhance the *CO formation followed by rapid desorption or hydrogenation.     

Proton Intercalation/De-intercalation Chemistry in Phenazine-based Anode for Hydronium-ion Batteries

Hydronium-ion batteries have received significant attention owing to the merits of extraordinary sustainability and excellent rate abilities. However, achieving high-performance hydronium-ion batteries remains a challenge due to the inferior properties of anode materials in strong acid electrolyte. Herein, a hydronium-ion battery is constructed which is based on a diquinoxalino [2,3-a:2’,3’-c] phenazine (HATN) anode and a MnO₂@graphite felt cathode in a hybrid acidic electrolyte. The fast kinetics of hydronium-ion insertion/extraction into HATN electrode endows the HATN//MnO₂@GF battery with enhanced electrochemical performance. This battery exhibits an excellent rate performance (266 mAh g⁻¹ at 0.5 A g⁻¹, 97 mAh g⁻¹ at 50 A g⁻¹), attractive energy density (182.1 Wh kg⁻¹) and power density (31.2 kW kg⁻¹), along with long-term cycle stability. These results shed light on the development of advanced hydronium-ion batteries.     

Polymer Multi-Block and Multi-Block+ Strategies for the Upcycling of Mixed Polyolefins and Other Plastics

Due to a continued rise in the production and use of plastic products, their end-of-life pollution has become a pressing global issue. One of the biggest challenges in plastics recycling is the separation of different polymers. Multi-block copolymers (MBCPs) represent an efficient strategy for the upcycling of mixed plastics via induced compatibilization, but this approach is limited by difficulties associated with synthesis and structural modification. In this contribution, several synthetic strategies are explored to prepare MBCPs with tunable microstructures, which were then used as compatibilizer additives to upcycle mixtures of polyolefins with other plastics. A multi-block⁺ strategy based on a reactive telechelic block copolymer platform was introduced, which enabled block extension during the in situ melt blending of mixed plastics, leading to better compatibilizing properties as well as better 3D printing capability. This strategy was also applicable to more complex ternary plastic blends. The polymer multi-block strategy enabled by versatile MBCPs synthesis and the multi-block⁺ strategy enabled by in situ block extension show exciting opportunities for the upcycling of mixed plastics.     

Laser cooling and trapping of metastable helium: towards Bose–Einstein condensation

Metastable triplet helium is an interesting atom, next to the alkalis and atomic hydrogen, to pursue Bose–Einstein condensation. In this paper an overview of the relevant physics of triplet helium and experimental progress in Amsterdam towards reaching Bose–Einstein condensation is described.     

Solid sampling electrothermal atomic absorption spectrometry for analysis of high-purity tungsten trioxide and high-purity tungsten blue oxide

A solid sampling ETAAS method for the direct determination of Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni and Zn in high-purity tungsten trioxide and tungsten blue oxide powders using a modern spectrometer with transversely heated graphite tube and a solid sampling system is described. The extremely high background caused by the vaporizing tungsten oxides could be eliminated by the reduction to tungsten metal using hydrogen as purge gas during pyrolysis. Quantification of all elements was performed using calibration curves measured with aqueous standard solutions. The analyte contents determined were between 0.033 (Cu) and 12.6 (Fe) μg/g for tungsten trioxide and between 0.001 (Co) and 0.5 (Na) μg/g for tungsten blue oxide. The accuracy was checked by comparing the results with those obtained by ETAAS in analysis of HF/HNO₃ sample digests and by other methods. Extremely low limits of detection being between 0.07 (Mg, Na, Zn) - 2 (Ni) and 0.01 (Mg, Na, Ni) - 1.7 (Fe) ng/g for tungsten trioxide and tungsten blue oxide, respectively, could be achieved due to almost complete freedom of blank and unusually high applicable sample amounts (5–15 mg for tungsten trioxide and 5–70 mg for tungsten blue oxide).