The preparation and characterization graphene-cross-linked phenol–formaldehyde hybrid carbon xerogels

A new synthesis route based on polycondensation of phenol and formaldehyde cross-linked by graphene oxide (GO) was developed. Wet gel after gelation was converted into an organic xerogel by ambient pressure drying to obtain GO-cross-linked phenol–formaldehyde (PF) organic xerogels (GOCPFOX). Graphene-cross-linked PF carbon xerogels (GCPFCX) were produced by carbonization. The morphology and chemical structure of GOCPFOX and GCPFCX were analyzed. The electrochemical behavior of GCPFCX as an electrode material in electric double-layer capacitors (EDLCs) was investigated. Results show that the high mechanical strength of GO increased the gel skeleton strength; thus, organic xerogels exhibit very low drying shrinkage. Scanning electron micrographs indicated that addition of GO altered the gel structure. Thus, when GO was added into the PF solution, the PF molecular chains were anchored on the surface of GO by chemical and physical interaction. The GCPFCX-10 sample achieved the highest specific surface area, mesoporous volume, and specific capacity with 378 m²/g, 0.56 cm³/g, and 116 F/g, respectively. Hence, GCPFCX is a potential material for EDLCs owing to its low production cost and ability to avoid supercritical drying.     

Elementary Photoelectronic Processes at a Porphyrin Dye/Single‐Walled TiO2 Nanotube Hetero‐interface in Dye‐Sensitized Solar Cells: A First‐Principles Study

A unique one‐dimensional (1D) sandwich single‐walled TiO₂ nanotube (STNT) is proposed as a photoanode nanomaterial with perfect morphology and large specific surface area. We have thoroughly examined the elementary photoelectronic processes occurring at the porphyrin dye/STNT hetero‐interface in dye‐sensitized solar cells (DSSCs) by theoretical simulation. It is desirable to investigate the interfacial photoelectronic processes to elucidate the electron transfer and transport mechanism in 1D STNT‐based DSSCs. We have found that the photoexcitation and interfacial charge separation mechanism can be described as follows. A ground‐state electron of the dye molecule (localized around the electron donor) is first promoted to the excited state (distributed electron donor), and then undergoes ultrafast injection into the conduction band of the STNT, leaving a hole around the oxidized dye. Significantly, the injected electron in the conduction band is transported along the STNT by means of Ti 3d orbitals, offering a unidirectional electron pathway toward the electrode for massive collection without the observation of trap states. Our study not only provides theoretical guidelines for the modification of TiO₂ nanotubes as a photoanode material, but also opens a new perspective for the development of a novel class of TiO₂ nanotubes with high power‐generation efficiency.     

Osteopontin: A Uranium Phosphorylated Binding‐Site Characterization

Herein, we describe the structural investigation of one possible uranyl binding site inside a nonstructured protein. This approach couples spectroscopy, thermodynamics, and theoretical calculations (DFT) and studies the interaction of uranyl ions with a phosphopeptide, thus mimicking a possible osteopontin (OPN) hydroxyapatite growth‐inhibition site. Although thermodynamical aspects were investigated by using time‐resolved laser fluorescence spectroscopy (TRLFS) and isothermal titration calorimetry (ITC), structural characterization was performed by extended X‐ray absorption fine structure (EXAFS) at the U L_III‐edge combined with attenuated total reflection Fourier transform infrared (ATR‐FTIR) spectroscopy. From the vibrational and fluorescence spectra, several structural models of a UO₂²⁺/peptide complex were developed and subsequently refined by using theoretical calculations to fit the experimental EXAFS obtained. The structural effect of the pH value was also considered under acidic to moderately acidic conditions (pH 1.5–5.5). Most importantly, the uranyl/peptide coordination environment was similar to that of the native protein.     

Strong Morphological Effect of Mn3O4 Nanocrystallites on the Catalytic Activity of Mn3O4 and Au/Mn3O4 in Benzene Combustion

Gold nanoparticles (3–4 nm) were deposited on Mn₃O₄ nanocrystallites with three distinct morphologies (cubic, hexagonal, and octahedral). The resulting structures were characterized, and their activities for benzene combustion were evaluated. The dominant exposed facets for the three kinds of Mn₃O₄ polyhedrons show the activity order: (103)≈(200)>(101). A similar activity order was derived for the interfaces between the Au and the Mn₃O₄ facet: Au/(200)≈Au/(103)>Au/(101). The metal–support interactions between the Au nanoclusters and specific facets of the Mn₃O₄ polyhedrons lead to a unique interfacial synergism in which the electronic modification of the Au nanoparticles and the morphology of the Mn₃O₄ substrate have a joint effect that is responsible for a significant enhancement in the catalytic activity of the Au/Mn₃O₄ system.     

Collective Total Synthesis of Englerin A and B,Orientalol E and F,and Oxyphyllol: Application of the Organocatalytic [4+3] Cycloaddition Reaction

The concise collective total synthesis of englerin A and B, orientalol E and F, and oxyphyllol has been accomplished in 10–15 steps, with the total synthesis of orientalol E and oxyphyllol being achieved for the first time. The success obtained was enabled by the realization of the [4+3] cycloaddition reaction of 9 and 10 . Other features of the synthesis include 1) the intramolecular Heck reaction to access the azulene core, 2) the epoxidation–S_N2′ reduction sequence to access the allylic alcohol, 3) the efficient regioselective and stereoselective formal hydration of the bridging C?C bond in the synthesis of englerins, and 4) the late‐stage chemo‐ and stereoselective C? H oxidation in the synthesis of orientalol E. The total synthesis of these natural products has enabled the structural revision of oxyphyllol and established the absolute stereochemical features of the organocatalytic [4+3] cycloaddition reaction. The identification of 5 as the natural product oxyphyllol, the success in converting 5 to orientalol E, along with the fact that englerins and oxyphyllol were isolated from plants of the same genus Phyllanthus gives support to our proposed biosynthetic pathways. This work may enable detailed biological evaluations of these natural products and their analogues and derivatives, especially of their potential in the fight against renal cell carcinoma (RCC).     

Durable antimicrobial cotton fabrics containing stable quaternarized N-halamine groups

A novel N-halamine precursor with tertiary amino group (5,5-dimethylhydantoinyl-3-ylethyl)-dimethylamine (DEADH), was synthesized and then covalently bonded onto cotton fabrics modified by 3-chloropropyltrimethoxysilane to form quaternarized N-halamine precursor grafted cotton fabrics which could be transferred to N-halamine structure upon exposure to dilute sodium hypochlorite solution. The grafted cotton fabrics were characterized by FT-IR, X-ray photoelectron spectroscopy, and field emission scanning electron microscope. The antimicrobial test showed that the cotton fabrics grafted with the quaternarized N-halamine were capable of 7-log inactivation of Staphylococcus aureus and Escherichia coli O157:H7 within 1 min of contact time. Very interestingly, it was found that the grafting process and following chlorination had almost no adverse effect on the tensile strength of cotton fabrics. Furthermore, the antimicrobial cotton fabrics exhibited good washing durability and stability.     

稀土镧在腈纶纤维化学镀银中的应用及其电化学性能

采用化学镀法(镀液中加入适量的稀土镧)在硅烷偶联剂改性后的腈纶纤维表面沉积金属银,由粒径分析、X射线衍射、扫描电子显微镜、阴极极化曲线以及循环伏安曲线等方法对其进行表征,研究了硝酸镧对化学镀银沉积速度、镀层质量和电化学性能的影响。结果表明,镀银液中加入适宜的硝酸镧,银的沉积速率和腈纶纤维表面银镀层的表面质量均有不同程度的提高。电化学测试表明,镀银液中增大硝酸镧的浓度(0～0.01 g/L),阴极极化曲线极化度增大,氧化还原峰的电流上升,电沉积的速度加快。     

化学发光分析与高效液相色谱联用检测酪氨酸

在强碱性条件下,KMnO4氧化酪氨酸产生自由基,自由基氧化Luminol产生强化学发光,酪氨酸浓度与相对发光强度呈线性关系。选用C18反相色谱柱、CH3OH、KH2PO4混合液为流动相,酪氨酸能很好分离。基于此,建立CL-HPLC检测酪氨酸的新方法,线性范围为1.2×10-3～5.0×10-2g/L、线性相关系数为0.9994、RSD为2.37%、检测限为3.3×10-4g/L。方法已于检测实际样品氨基酸口服液,并与UV光度法,结果一致。本文探讨了酪氨酸增强KMnO4-Luminol化学发光机理。     

建筑用梳形共聚物分散剂溶液行为的光散射研究

采用激光光散射研究了一种主链为聚丙烯酸侧链为聚乙二醇的梳形共聚物分散剂的一些溶液行为.从静态光散射得出了较为合理的表观重均分子量、均方旋转半径等参数.动态光散射给出了流体力学半径分布及其角度和浓度依赖性.结合静态和动态光散射,上述梳形共聚物分散剂在溶液中的构象也得到初步的表征.通过与描述梳形聚合物的Gay-Raphae模型进行比较表明,这类梳形共聚物溶液在低盐离子和低pH值条件下存在聚集行为,形成以PAA主链为核PEG为壳层的类胶束聚集.