A highly dispersed Pt/copper modified-MnO_(2)catalyst for the complete oxidation of volatile organic compounds:The effect of oxygen species on the catalytic mechanism

Manganese oxide(MnO_(2))exhibits excellent activity for volatile organic compound oxidation.However,it is currently unknown whether lattice oxygen or adsorbed oxygen is more conducive to the progress of the catalytic reaction.In this study,novel hollow highly dispersed Pt/Copper modified-MnO_(2)catalysts were fabricated.Cu^(2+)was stabilized into theδ-MnO_(2)cladding substituting original K+,which produced lattice defects and enhance the content of adsorbed oxygen.The 2.03 wt%Pt Cu_(0.050)-MnO_(2)catalyst exhibited the highest catalytic activity and excellent stability for toluene and benzene oxidation,with T_(100)=160℃under high space velocity(36,000 mL g^(-1)h^(-1)).The excellent performance of catalytic oxidation of VOCs is attributed to the abundant adsorbed oxygen content,excellent low-temperature reducibility and the synergistic catalytic effect between the Pt nanoparticles and Cu_(0.050)-MnO_(2).This study provides a comprehensive understanding of the Langmuir-Hinshelwood(L-H)mechanism occurring on the catalysts.

A mini-review on ZnIn_(2)S_(4)-Based photocatalysts for energy and environmental application

As one of the most attractive and eco-friendly technologies,semiconductor photocatalysis is demonstrated as a potential strategy to solve global energy shortage environmental pollution problems.Regarding semiconductor-based photocatalysts,Zinc indium sulfide(ZnIn_(2)S_(4)) with various morphological structures has become research hotspots owing to its superior visible light absorption,high chemical durability and low cost.Nevertheless,the photocatalytic activity of pristine ZnIn_(2)S_(4) is unsatisfactory due to limited range of visible light absorption and fast recombination rate of light-induced electrons and holes.Different modification strategies,such as metal deposition,element doping,vacancy engineering and semiconductor combination,have been systematically developed for enhancing the photocatalytic performance of ZnIn_(2)S_(4) materials.In order to promote further developments of ZnIn_(2)S_(4) in photocatalytic applications,this mini-review summarizes the progress of recent research works for the construction of highly activity ZnIn_(2)S_(4)-based photocatalysts for the first time.In addition,the typical applications of ZnIn_(2)S_(4)-based photocatalytic materials have been critically reviewed and described such as in hydrogen evolution from photocatalytic water splitting,carbon dioxide photoreduction,and treatment of water pollution.The current challenges and further prospects for the development of ZnIn_(2)S_(4) semiconductor photocatalysts are finally pointed out.

Pt–Pd bimetallic nanoparticles anchored on uniform mesoporous MnO_(2) sphere as an advanced nanocatalyst for highly efficient toluene oxidation

Improving catalytic performance is a yet still challenge in thermal catalytic oxidation.Herein,uniform mesoporous MnO_(2) nanospheresupported bimetallic Pt–Pd nanoparticles were successfully fabricated via a SiO_(2) template strategy for the total catalytic degradation of volatile organic compounds at low temperature.The introduction of mesopores into the MnO_(2) support induces a large specific surface area and pore size,thus providing numerous accessible active sites and enhanced diffusion properties.Moreover,the addition of a secondary noble metal can adjust the O_(ads)/O_(latt) molar ratios,resulting in high catalytic activity.Among them,the catalyst having a Pt/Pd molar ratio of 7:3 exhibits optimized catalytic activity at a weight hourly space velocity of 36,000 mL g^(-1) h^(-1),reaching 100%toluene oxidation at 175℃ with a lower activation energy(57.0 kJ mol^(-1))than the corresponding monometallic Pt or non-Pt-based catalysts(93.8 kJ mol^(-1) and 214.2 kJ mol^(-1)).Our findings demonstrate that the uniform mesoporous MnO_(2) nanosphere-supported bimetallic Pt–Pd nanoparticles catalyst is an effective candidate for application in elimination of toluene.

Aeromagnetic Compensation Algorithm Based on Levenberg-Marquard Neural Network

The magnetic compensation of aeromagnetic survey is an important calibration work,which has a great impact on the accuracy of measurement.In an aeromagnetic survey flight,measurement data consists of diurnal variation,aircraft maneuver interference field,and geomagnetic field.In this paper,appropriate physical features and the modular feedforward neural network(MFNN)with Levenberg-Marquard(LM)back propagation algorithm are adopted to supervised learn fluctuation of measuring signals and separate the interference magnetic field from the measurement data.LM algorithm is a kind of least square estimation algorithm of nonlinear parameters.It iteratively calculates the jacobian matrix of error performance and the adjustment value of gradient with the regularization method.LM algorithm’s computing efficiency is high and fitting error is very low.The fitting performance and the compensation accuracy of LM-MFNN algorithm are proved to be much better than those of TOLLES-LAWSON(T-L)model with the linear least square(LS)solution by fitting experiments with five different aeromagnetic surveys’data.

口腔诊室不同通风状态下气溶胶类污染物喷溅情况研究

目的研究在独立空间内进行口腔诊疗操作时,不同通风状态下气溶胶类污染物的喷溅情况,为降低医患感染风险提供依据。方法选取独立口腔诊室,在3种不同通风状态(自然开窗通风、新风系统和新风系统及空气消毒机)下开展3种不同口腔诊疗操作(龈上洁治、根管预备和牙体预备),定义为9种工况。测定不同位点在不同时点的菌落总数,定量分析不同通风状态的气溶胶类污染物在时间和空间上的轨迹分布。采用Spearman秩相关分析、广义线性混合模型、方差分析和Wilcoxon秩和检验,以及秩次转换后进行多重比较以分析菌落总数的差异和平衡状态。结果方差分析结果表明,各位点的菌落总数差异无统计学意义(F=1.45,P=0.182),即各位点的菌落总数分布在各位点较为均匀。相对于自然开窗通风,开启新风系统进行龈上洁治和牙体预备,菌落总数(N_(工况1)=25.8 CFU/cm^(2);N_(工况2)=10.4 CFU/cm^(2);N_(工况7)=35.7 CFU/cm^(2);N_(工况8)=6.5 CFU/cm^(2))均随着时间的增加呈现降低的趋势(t_(龈上洁治)=2.27,P_(龈上洁治)=0.024;t_(牙体预备)=2.30,P_(牙体预备)=0.022)。所有工况治疗结束后30~60 min内与治疗结束后60~120 min内的菌落总数均无明显差异,即喷溅操作结束30 min后菌落总数趋于动态平衡的状态,且符合《医院消毒卫生标准GB 15982-2012》中的Ⅳ类环境要求。结论开启新风系统能在口腔诊疗喷溅操作中一定程度上有效降低特定空间的气溶胶类污染物。上一患者治疗结束后30 min下一患者方进入该区域进行治疗较安全。

2D/2D hierarchical Co_(3)O_(4)/ZnIn_(2)S_(4)heterojunction with robust builtin electric field for efficient photocatalytic hydrogen evolution

Because of its importance in enhancing charge separation and transfer,built-in electric field engineering has been acknowledged as an effective technique for improving photocatalytic performance.Herein,a stable p–n heterojunction of 2D/2D(2D:twodimensional)Co_(3)O_(4)/ZnIn_(2)S_(4)with a strong built-in electric field is precisely constructed.The Co_(3)O_(4)/ZnIn_(2)S_(4)heterojunction exhibits a higher visible-light photocatalytic hydrogen(H2)evolution rate than the individual components,which is primarily attributed to the synergy effect of improved light absorption,abundant active sites,short charge transport distance,high separation efficiency of photogenerated carriers.Furthermore,the photoelectrochemical studies and density functional theory(DFT)calculation results demonstrate that the enhanced interfacial charge separation and migration induced by the generated built-in electric field are the critical reasons for the boosted photocatalytic performance.This research might pave the way for the rational design and manufacturing of 2D/2D heterojunction photocatalysts with extremely efficient photocatalytic performance for solar energy conversion.

Multimetallic AuPd@Pd@Pt core-interlayer-shell icosahedral electrocatalysts for highly efficient oxygen reduction reaction

Incorporating Pt with core metals into Pt-based core-shell catalysts is regarded as a promising strategy to substantially enhance the catalytic properties towards oxygen reduction reaction(ORR) in fuel cells due to the synergetic effect between distinct metals. In this wok, ultrathin Pt skins with two atomic layers were epitaxially coated on as-prepared icosahedral Au_50Pd_50, Au_60Pd_40 and Au_66Pd_34 nanocrystal seeds,which are constructed with alloyed cores and Pd shells with different thickness. Through electron microscopic characterizations, Pd interlayers with tunable thickness of 3, 6, and 12 atomic layers can be found in the Au_66Pd_34@Pt, Au_60 Pd_40@Pt and Au_50Pd_50@Pt icosahedra, respectively. These icosahedral Au Pd@Pd@Pt nanocrystals show substantially enhanced activities and durabilities in electrocatalytic measurements towards ORR compared to Au_75Pd_25@Pt icosahedra without Pd interlayer and commercial Pt/C catalysts. Specifically, Au_60Pd_40@Pt icosahedra with 6 atomically thick Pd interlayer display the best electrocatalytic performances, whose mass activities before and after durability tests of 50,000 cycles are11.6 and 30.2 times, respectively, as high as that of the commercial Pt/C.

Zeolitic Imidazolate Framework 8-Derived Au@ZnO for Efficient and Robust Photocatalytic Degradation of Tetracycline

Summary of main observation and conclusion Tetracycline (TC) and other antibiotics accumulated in groundwater and soil pollute ecological environment and threaten human health. Gold nan oparticles doped on photocatalysts are able to enhance the photodegradation efficiency during removing these antibiotics, but preparation of Au nanoparticles of well-dispersion on photocatalysts remains challenging. In this work, zeolite imidazolate (ZIF-8) was employed as the precursor to prepare Au@ZnO photocatalyst via impregnation and in-situ reduction method to efficiently degrade the tetracycline in the aqueous solution. Au nanoparticles are of 10 nm in size and uniformly dispersed on the surfaces of ZnO microstructures. The as-prepared Au@ZnO is able to remove 85.5% of TC of 0.010 mg/mL within 2h, presenting higher photocatalytic activity than pure ZnO catalyst. Most importantly, the catalyst shows its superior stability after five cycles without structure and activity changing. The mechanism of the photocatalytic degradation was discussed in detail.

Synthesis of poly(pyridine-imide)s and their electronic memory performances

In this paper,poly(pyridine-imide)s,PI-Ph and PI-Naphth,were successfully synthesised and fabricated for use as memory devices.The Al/PI-Ph/indium tin oxide(ITO)device showed dynamic random access memory characteristics,whereas Al/PI-Naphth/ITO showed rewritable(FLASH)memory characteristics.Characterisation of their UV,cyclic voltammograms,and density functional theory,were used to illustrate the different memory behaviours.The results show that the stability of electric-field-induced-charge-transfer complexes can affect memory performance.

Design,Synthesis and Characterization of Coordination Polymer from[Cu(DMF)_(4)(SCN)_(2)]as a Precursor

This paper is focused on investigation of coordination polymers constructed by Cu(II)and rigid pyridyl ligands,such as 4,4'-bipyridyl-1,2,4-triazole(Hpytz)and 1,10-phenanthroline(phen)from a mononuclear precursor[Cu(DMF)_(4)(NCS)_(2)](1).As expected,the complex was self-assembled with phen to form a 1D double-stranded chain of[Cu(phen)(μ-SCN)_(2)]∞(2),with Hpytz to form 1D zigzag chain of[Cu_(2)(μ-Hpytz)_(2)(NCS)_(2)(DMF)_(2)(μ-SCN)_(2)]∞(3)in which thiocyanate anion linked the Cu-μ-Hpytz-Cu chain into an infinite 2D network via weak Cu…S interaction.To treat 3 with the bridged anion dca,a novel 3D framework[Cu(μ-Hpytz)(μ-dca)(μ-SCN)]∞(4)was obtained in which Cu-μ-Hpytz-Cu chain is preserved and both thiocyanate anion and dicyanamide(dca)act as bridging ligands.In addition,complex 3 was applied as a metal catalyst in polymerization of MMA in aqueous solution at room temperature.

Negative effect on molecular planarity to achieve organic ternary memory: triphenylamine as the spacer

Adjusting the spacers between the electron-acceptor and the elector-donor is important to design organic ternary memory material but rarely reported. In this paper, two small molecules, ZIPGA and ZIPCAD with benzene ring or triphenylamine as the spacers,were designed and synthesized to fabricate memory devices. The Al/ZIPGA/indium-tin oxide (ITO) device showed ternary characteristics, whereas Al/ZIPCAD/ITO had no obvious memory characteristics. Density functional theory calculation, X-ray diffraction (XRD) and atomic force microscopy (AFM) were employed to interpret the different memory properties. ZIPGA thin film has the closer intermolecular packing and flatter surface morphology than ZIPCAD film, which was favorable to the electron migration. This work demonstrates the importance of spacers and reveals that triphenylamine may be not a good spacer in design of new memory material.

Study of Linear and Nonlinear Optical Properties of Four Derivatives of Substituted Aryl Hydrazones of 1,8-Naphthalimide

Four 1,8-naphthalimide hydrazone molecules with different electron-donating groups have been applied in the study of linear and nonlinear optical(NLO)properties.These compounds showed strong green emission in solution.Their NLO properties such as two-photon absorption(TPA)behavior with femtosecond laser pulses ca.800 nm and excited-state absorption(ESA)behavior with nanosecond laser pulses at 532 nm were investigated.Compound 4 presented the largest two-photon cross section(550 GM)among them due to two factors:the conjugated length of compound 4 is the longest and the electron-donating ability of compound 4 is the strongest.Different from TPA behavior,compound 2 showed the best nonlinear absorption properties at 532 nm and its nonlinear absorption coef-ficient and third-order nonlinear optical susceptibilitiesχ^(3)were up to 1.41×10^(−10) MKS and 4.65×10^(−12) esu,re-spectively.Through the modification of the structure,the nonlinear optical properties of these compounds at differ-ent wavelengths(532 and 800 nm)were well tuned.The great broad-band nonlinear optical properties indicate hy-drazones are good candidates for organic nonlinear optical absorption materials.

Preparation of Fluorescent Polystyrene via ATRP with Dimethylamino Chalcones as Initiator

4-(3-(4-(Dimethylamino)phenyl)acryloyl)phenyl-2-bromo-2-methylpropanoate(APPBr)was used for the heterogeneous atom transfer radical polymerization(ATRP)of styrene(St)with copper(I)bromide/N,N,N',N",N"-pentamethyldiethylenetriamine(PMDETA)catalytic system.The functional end group was characterized via UV-Vis and ^(1)H NMR spectra.The polymerization showed a first-order kinetic characteristic and each of the obtained polymers had well-controlled molecular weight and relatively low polydispersity index(PDI).Furthermore,the obtained end-functionalized polystyrene(PS)in solution showed strong green-light emission which is further affected by mixing different metal cations.In particular,the fluorescent intensity of the polymer was decreased in the presence of Ag^(+),Cu^(2+)and Fe^(3+).