Polymeric Carbon Nitride-based Single Atom Photocatalysts for CO2 Reduction to C1 Products

Photocatalytic CO₂ reduction to C₁ fuels is considered to be an important way for alleviating increasingly serious energy crisis and environmental pollution. Due to the environment-friendly, simple preparation, easy formation of highly-stable metal-nitrogen(M-N_x) coordination bonds, and suitable band structure, polymeric carbon nitride-based single-atom catalysts(C₃N₄-based SACs) are expected to become a potential for CO₂ reduction under visible-light irradiation. In this review, we summarize the recent advancement on C₃N₄-based SACs for photocatalytic CO₂ reduction to C₁ products, including the reaction mechanism for photocatalytic CO₂ reduction to C₁ products, the structure and synthesis methods of C₃N₄-based SACs and their applications toward photocatalytic CO₂ reduction reaction(CO₂RR) for C₁ production. The current challenges and future opportunities of C₃N₄-based SACs for photoreduction of CO₂ are also discussed.     

Structure and Mechanical Stability of Epoxy Modified Polyurethane Foam Under Heat and Stress

A series of phenolic epoxy resin (PEP) modified polyurethane foams (PUF) were prepared via an in-situ polymerization, one step process. It was found that the epoxy modified PUF foam exhibited a perforated network structure with larger cell size, higher open cell porosity and enhanced ovality compared with pure PUF. With increasing content of PEP, the tensile strength, elongation at break and low temperature modulus of PUF decreased. A single T_g was observed for PEP modified PUF, indicating that the two component phases of the polyurethane-epoxy were miscible. With increasing PEP content, the T_g of PUF shifted slightly to higher temperature, tan δ_max dropped to lower values, and the retention value of the storage modulus at ?20 and ?10?°C increased. For pure PUF, the cell walls degraded and the structure became disordered after aging under heat and stress, while for PUF/20wt%PEP, the degradation degree was obviously reduced, and an orientation of the cells along the stress direction and a density increase was observed. During aging at 200?°C, the retention of the mechanical properties of PUF/20wt% PEP was much higher than that of pure PUF, and it showed superior stability under heat and stress, attributed to incorporation of the thermally resistant oxazolidone rings and benzene rings in the PU backbones, the highly cross-linked networks of the polyurethane-epoxy systems and the obvious orientation of the cells under stress.     

纳米银改性树脂基托机械性能的初步研究

采用磁控溅射技术在聚甲基丙烯酸甲酯(PMMA)树脂基托表面沉积一层纳米银(Ag NPs)涂层.研究了纳米银改性PMMA树脂基托的机械性能,为改性材料的临床应用提供理论基础.根据国际标准ISO2409:2007描述的划格法对涂层与基底的附着力强度进行测试,各组试件的接触角采用静态液滴法测量,三点弯曲法检测试件的弯曲强度.结果显示,各组涂层与PMMA基底材料结合良好,各组试件的表面润湿性变化不大,其中PMMA-Ag NPs80s组疏水性略有提高,各组试件的弯曲强度均符合国家标准.     

静电纺丝法制备酚醛纤维研究进展

酚醛树脂是一种广泛使用的合成树脂,包括热固性和热塑性两类,具有良好的阻燃性、耐热性和耐腐蚀性。酚醛纤维是由酚醛树脂所制成的交联纤维,传统的酚醛纤维制备方法有熔融纺丝法和湿法纺丝法,后来出现了静电纺丝法。本文根据酚醛树脂的种类分别介绍了热固性、热塑性和热塑/热固混合酚醛树脂三类材料静电纺丝的研究进展。在改善酚醛纤维特性方面,综述了四种优化措施,包括加入无机盐、微波辐射辅助固化、非匀速阶梯式加热固化、氧化石墨烯修饰的静电纺丝法等。此外,对本实验室制备酚醛纤维的研究也进行了概述,阐述了酚醛纤维当前存在的问题及未来发展方向。     

Solid phase synthesis of two muramyl pentapeptide derivatives

Solid phase peptide synthesis (SPPS) of two selected muramyl pentapeptide derivatives is described. The simplicity of removing the protecting groups via one-step deprotection and cleavage from the resin is the biggest advantage of SPPS. Using this method, two muramyl pentapeptide derivatives, D-MurN₃-L-Ala-D-iGlu-L-Lys-D-Ala-D-Ser (5) and D-MurN₃-L-Ala-D-iGlu-L-Lys-D-Ala-D-Ala (6), were obtained. Their chemical structures were confirmed by high-resolution mass spectrometry (HRMS) and nuclear magnetic resonance (NMR) spectroscopy. To determine the absolute configuration of the carbon atom in the side chain of the muramic acid derivative, single-crystal X-ray diffraction measurements were recorded.     

Control of chain ends of polyesters in polycondensation of AA and BB monomers by use of solid‐phase reagent

For selective synthesis of linear polyester having a functional group at one end, polycondensation between 1,4‐butanediol ( 1a ) and sebacoyl chloride ( 2a ) and between 1,12‐dodecanediol ( 1b ) and isophthaloyl chloride ( 2b ) was conducted in the presence of oxime resin or oxime silica gel, followed by cleavage of the formed polyester from the solid‐phase support with aniline. Matrix‐assisted laser desorption ionization time‐of‐flight mass spectra and ¹H NMR spectra of the cleaved polyester showed that the products contained not only polyester with anilide at one end ( poly 1 ), but also polyester with anilides at both ends ( poly 2 ). The product ratio of poly 1 to poly 2 ( poly 1 / poly 2 ) was dependent on monomers, monomer concentration, feed ratio of monomer to oxime moiety in the support, oxime content in the support, reaction solvent, and the nature of the support. Polyester with a high poly 1 / poly 2 ratio of 81/21 and moderate molecular weight (M_n = 1430 g/mol) was obtained by polycondensation of 1b and 2b in the presence of oxime silica gel in dichloromethane. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1379–1386     

新郑西亚斯东周玉器材料属性与加工工艺的科技分析

中国玉文化源远流长，治玉工艺经过各个时代的不断发展和完善，在一定程度上能反映古代社会生产力发展水平及文化、贸易、技术交流等信息。利用能量色散型X射线荧光光谱（EDXRF）、激光拉曼光谱（LRS）、超景深光学显微系统（OM）等分析技术，结合硅胶覆膜微痕复制技术，对河南省新郑西亚斯东周墓地出土的一批玉器进行科技分析。首先利用化学成分和物相结构分析技术确定了玉器材质的矿物属性，其次利用显微分析技术表征了玉器表面及穿孔内部和印模的加工痕迹，特别是阴刻纹饰和穿孔微痕特征，最后探讨了玉器样品的材料属性和加工工艺两者之间的联系。化学成分和物相结构分析结果表明，所分析的西亚斯东周玉器材质丰富，主要矿物组成有滑石、透闪石、水晶、云母等。玉器表面纹饰微痕特征分析表明，所分析玉器阴刻工艺采用了两种加工工具，分别是砣具和手持硬质工具。穿孔微痕分析特征表明，钻孔包括单面钻孔和双面/多面钻孔两种方式，钻孔工艺则有实心钻、管钻等。部分玉器钻孔形状和内部微痕特征表明，尽管均采用了实心钻工艺，但所采用的实心钻头在形状上存在差异，同时，也存在是否配合解玉砂进行钻孔的差异。不同材料属性的玉器采用了不同的加工工艺。滑石质玉器，莫氏硬度1，器型主要为玉片饰，其表面阴刻纹饰主要采用手持硬质工具进行刻画，钻孔主要采用了双面钻孔方式，并使用了实心钻头未添加解玉砂进行加工，钻头形状可能为圆锥状；云母质玉器，莫氏硬度2~3，器型主要为玉玦片饰，纹饰采用了砣具添加解玉砂的加工工艺，钻孔方式为单面钻孔，采用了管钻工艺。透闪石型玉器，莫氏硬度5~6，器型主要为玉片饰，表面纹饰采用砣具配合解玉砂砣刻，以双面钻孔的方式为主，钻孔工艺为实心钻头配合解玉砂工艺，钻头形状与滑石类样品一致，为圆锥状。水晶质玉器，莫氏硬度7，均为珠饰，表面无纹饰，钻孔方式为双面/多面钻孔，钻孔工艺为实心钻配合解玉砂工艺，且钻头可能为圆柱形。研究结果表明，玉器表面纹饰所采用的阴刻工艺和钻孔工艺，与玉器本身的材料属性、器型等存在密切关系。     

Curing behavior and properties of high biosourced epoxy resin blends based on a triepoxy monomer and a tricarboxylic acid hardener from 10-undecenoic acid

Renewable propane-1,2,3-triyl tris(9-(oxiran-2-yl) nonanoate) (EGU, 100 wt% biogenic) and a tricarboxylic acid triglyceride (CGTU) hardener (85.7 wt% biogenic) were synthesized from 10-undecenoic acid (10-UDA) and used to produce epoxy resins with 52–92 wt% biobased carbon. CGTU was prepared by thermally activated thiol-ene coupling of thioglycolic acid onto propane-1,2,3-triyl tris(undec-10-enoate), (GUD) in the absence of solvent. The characterized CGTU was used as a green hardener of blends based on EGU and a conventional bisphenol A-based epoxy pre-polymer (DGEBA) at various mass percentages (0–100 wt%) with an stoichiometric epoxy/acid equivalent ratio. Calorimetric studies revealed higher peak temperature, lower reaction heats, and longer gelation times in resins with high EGU proportion, evidencing the lower reactivity of aliphatic EGU compared with aromatic DGEBA. Cured resins were yellowish transparent rubber-like materials with glass transition temperatures (Tg) varying from −14 °C to −42 °C and tensile strength in the range of 1750 kPa–790 kPa, for 0 and 100 wt % EGU, respectively. The soluble fraction of all resins was less than 4.3%, reflecting a high level of crosslinking. Thermosets with high biobased content showed both UV-light protection and visible light transparency.     

Synergistic effect of thermoplastic phenolic resin and multiwalled carbon nanotubes on the crystallization of polyoxymethylene

To reduce the crystallization rate of polyoxymethylene (POM) to meet the requirement of thick-walled and large-sized articles production, and maintain high crystallinity as well as obtain refined crystalline grains to ensure the strength and stiffness simultaneously, thermoplastic phenolic resin (PF) and multiwalled carbon nanotubes (MWCNTs) were used as crystal growth inhibitor and nucleating agent, respectively, and their effects on the crystallization of POM were studied in details. The results showed that PF is an effective inhibitor and MWCNTs exhibits excellent nucleation effect on POM. Based on the obtained results, their synergistic influences on the crystallization process of POM were investigated. It is found that the objective of decreasing the crystallization rate while maintaining high crystallinity and forming fine crystalline grains can be realized. The 97/3/1 wt% POM/PF/MWCNTs, compared with those of neat POM, The T _c shifts by 3.3°C to a lower temperature, the crystallization enthalpy increases by 16.1 J/g and the full width at half-maximum widens by 48.5%. The modulation effect of PF and MWCNTs on the crystallization is closely related to the PF content and dispersion, the distribution and dispersion of MWCNTs in the PF and POM phases.     

电感耦合等离子体质谱(ICP-MS)法测定土壤中的碘

通过电感耦合等离子体质谱法(ICP-MS)测定土壤中的碘。样品预处理采用艾斯卡试剂熔融、热水提取和阳离子树脂静态交换,试验加入了不同剂量的阳离子交换树脂在不同程度上降低了溶液中Na+ 和Zn2+^{等阳离子的盐效应干扰。研究了乙醇在}ICP-MS中对碘元素的增强效应,用3%的氨水溶液清洗进样系统,有效减少的碘的记忆效应和清洗时间。该方法线性范围宽,方法灵敏度高,检出限低,试剂用量少,环境友好。对苏州及周边区域若干非污染土壤点位进行采样、制备和测试,碘平均含量为2.7μg.g_-1^;同步测试国家有证标准物质,精密度和准确度良好。