石墨碳纳米材料光学性质在生化传感领域的应用

石墨碳纳米材料因其特殊的光学性质而受到广泛关注。石墨碳纳米材料最引人注目的光学性质之一是其独特的拉曼性质,作为拉曼探针,石墨碳纳米材料在对于复杂生物样品,极端测试条件和定量拉曼检测方面都有很好的应用;除了拉曼性质以外,单壁碳纳米管(SWNTs)独特的近红外二区(NIR-II,1000-1700 nm)荧光性质,具有穿透深度大、分辨率高的荧光成像特点,在生物活体成像领域也得到了很好的应用。除了光致发光特性,石墨碳纳米材料还具有优异的光热转换效应,同时具有比表面积大的特点,被广泛应用在针对肿瘤的热疗及其它疗法协同治疗当中。除此之外,石墨碳纳米材料还是一种高效的信号传导基底,可以猝灭激发态的染料和光敏剂,利用该类性质设计的生物传感器和纳米药物,显现出高灵敏、高选择性的特点。本文主要结合本课题组的工作,总结和探讨了石墨碳纳米材料作为光学探针、光热材料和信号传递基底在生化传感领域的应用。     

A novel silk‐based segmented block copolymer containing GlyAlaGlyAla β‐sheets templated by phenoxathiin

A novel segmented block copolymer, containing polyethylene glycol segment and GlyAlaGlyAla sequence derived from B. mori silk, has been prepared as a model for silk‐based materials using both solution and interfacial techniques. Inherent viscosity, size exclusion chromatography, and light‐scattering measurements gave molecular weight between M_w 34,000–39,000. Evidence for phase separation was provided by differential scanning calorimetry, which gave two T_g's at −57 °C and 111 °C, and transmission electron microscopy, which showed a morphology in which the peptide domain, estimated to be about 20–50 nm, was dispersed in the continuous polyether phase. Solid‐state FTIR spectroscopic results showed that the polymer contained both parallel and antiparallel β‐sheet stacks, and that the solution‐polymerized material has the higher β‐sheet content. This was further confirmed by ¹³C NMR, which gave about 80% total β‐sheet content for the solution‐polymerized product and about 40% for the polymer obtained by interfacial polymerization. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 352–366, 2000     

Precise determination of residual stresses in FeSi3 electrical sheets in the vicinity of laser scratches with high lateral resolution

States of residual stress in laser scribed FeSi3 electrical sheets in the vicinity of the laser scratch have been investigated. The influence of the laser treatment on the distortion of the crystal lattice was not only determined qualitatively but also quantitatively. Residual stresses of third kind were determined. Residual stress maps of the vicinity of the laser scratch were recorded showing clearly the influence of the laser treatment on the stress state as well as on the formation of the domain structure in FeSi3. The dislocation densities and stress states could be determined on spots of micrometer size. This was made possible by coupling the KOSSEL and electron backscatter diffraction (EBSD) techniques in one device at high lateral resolution. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

具有高电催化活性的g-C3N4-ZnS-DNA纳米复合材料的制备及应用

g-C3N4作为丰富的可见光光催化剂,具有独特的二维结构,优异的化学稳定性和可调的电子结构;但因其激子结合能高和结晶度较低,导致其光催化过程量子效率偏低,限制了光催化剂的推广应用.根据g-C3N4独特的可调电子结构,将其与半导体材料进行耦合,形成异质结构,通过调控半导体的能带结构,优化其光吸收能力,促进光生电子-空穴对的快速分离,从而抑制光生载流子的复合,提高其光催化效率.目前,人们已发展了许多g-C3N4与窄禁带和宽禁带半导体耦合形成的二元纳米复合材料,广泛应用于光催化降解污染物、光催化水解产氢和光催化还原将温室气体CO2转换成有用的碳氢燃料等方面,但关于g-C3N4基的三元复合光催化剂,尤其与天然纳米材料DNA复合,研究其电催化性能的却鲜有报道.近年来,随着环境污染日益严重,被称为环境激素的五氯酚(PCP)、壬基酚(NP)等一系列环境激素在水体和土壤等环境介质中长期残留,难以降解,且容易聚集在生物体内,通过空气循环和食物链等方式进入人体,对环境和人体产生极大的危害,所以越来越多的人致力于环境激素的高效筛选和检测的研究.常规的分析方法已经很难满足人们对环境激素的高灵敏检测的要求,而电化学方法因其操作简单、成本低廉、选择性好、灵敏度高、样品前处理简单等特点而备受关注.本文成功设计和制备了g-C3N4-ZnS-DNA三元纳米复合材料.首先,采用水热法制备了ZnS半导体纳米片,采用热解法制备了g-C3N4纳米片,接着将它们与DNA复合,成功制备了g-C3N4-ZnS-DNA纳米复合材料,通过苯胺聚合法修饰到玻碳电极表面,成功构建了NP和PCP环境激素新型的电化学传感器.通过透射电镜、X射线衍射、紫外-可见漫反射光谱和X射线光电子能谱等对其形貌、结构及组分进行了表征.采用CHI660C仪器对新型的电化学传感器的电催化性能进行了系统研究.通过循环伏安法(CV)和示差脉冲伏安法(DPV)研究了NP和PCP在g-C3N4-ZnS-DNA-GCE修饰电极的上的电化学行为.电化学阻抗谱表明,g-C3N4-ZnS-DNA纳米复合材料大大促进了修饰电极的电子传递能力,与g-C3N4膜相比,ZnS和DNA共掺杂的g-C3N4膜对NP和PCP的电化学响应明显提高,峰电流是g-C3N4膜的2倍,电催化活性明显增强.在最优化条件下,NP和PCP检测的线性范围分别为2.0×10–5–1.0×10–8和1.0×10–5–1.0×10–8 mol L–1,检出限均为3.3×10–9 mol L–1.将g-C3N4-ZnS-DNA-GCE修饰电极用于湖水中NP和PCP的测定,其回收率均高于90%,证明g-C3N4-ZnS-DNA纳米复合材料修饰电极可应用实际水样中痕量环境激素的测定.同时,我们分析了电催化活性增强的原因:(1)DNA分子通过C-O-C键连接到g-C3N4表面,导致ZnS纳米片组装成线性超结构,形成稳定的g-C3N4-ZnS-DNA纳米复合材料;(2)由于DNA和PCP或NP之间的相互作用使得电极表面上的PCP和NP的浓度增加;(3)纳米复合材料聚苯胺膜可促进电子转移和加速PCP或NP向电极表面的扩散;并提出了Z型g-C3N4-ZnS-DNA纳米复合材料的电子转移路径,以及PCP和NP的可能的电催化氧化机理.     

缺陷工程调控石墨相氮化碳及其光催化空气净化应用进展

Since the pioneering work on polychlorinated biphenyl photodegradation by Carey in 1976, photocatalytic technology has emerged as a promising and sustainable strategy to overcome the significant challenges posed by energy crisis and environmental pollution. In photocatalysis, sunlight, which is an inexhaustible source of energy, is utilized to generate strongly active species on the surface of the photocatalyst for triggering photo-redox reactions toward the successful removal of environmental pollutants, or for water splitting. The photocatalytic performance is related to the photoabsorption, photoinduced carrier separation, and redox ability of the semiconductor employed as the photocatalyst. Apart from traditional and noble metal oxide semiconductors such as P25, bismuth-based compounds, and Pt-based compounds, 2D g-C₃N₄ is now identified to have enormous potential in photocatalysis owing to the special π-π conjugated bond in its structure. However, some inherent drawbacks of the conventional g-C₃N₄, including the insufficient visible-light absorption ability, fast recombination of photogenerated electron-hole pairs, and low quantum efficiency, decrease its photocatalytic activity and limit its application. To date, various strategies such as heterojunction fabrication, special morphology design, and element doping have been adopted to tune the physicochemical properties of g-C₃N₄. Recent studies have highlighted the potential of defect engineering for boosting the light harvesting, charge separation, and adsorption efficiency of g-C₃N₄ by tailoring the local surface microstructure, electronic structure, and carrier concentration. In this review, we summarize cutting-edge achievements related to g-C₃N₄ modified with classified non-external-caused defects (carbon vacancies, nitrogen vacancies, etc.) and external-caused defects (doping and functionalization) for optimizing the photocatalytic performance in water splitting, removal of contaminants in the gas phase and wastewater, nitrogen fixation, etc. The distinctive roles of various defects in the g-C₃N₄ skeleton in the photocatalytic process are also summarized. Moreover, the practical application of 2D g-C₃N₄ in air pollution control is highlighted. Finally, the ongoing challenges and perspectives of defective g-C₃N₄ are presented. The overarching aim of this article is to provide a useful scaffold for future research and application studies on defect-modulated g-C₃N₄.      

书页搭接之摩擦力研究

将两本书以一页搭一页的方式联接在一起,然后向水平方向两侧拉伸,纸张间会产生机理复杂的摩擦力,摩擦力的总和可以使搭接结构的极限拉力达到很大.本文在不同搭接长度及不同搭接页数的条件下,对极限拉力进行了实测,得到了搭接长度与搭接页数对极限拉力的影响关系.对摩擦力产生机理进行了分析,给出了理论模型的公式,并通过MATLAB对相关系数进行了与实测数据的最小二乘法拟合,得到了半理论半经验的摩擦力计算公式.计算公式可以为这种特殊联接工艺的最大承载拉力计算提供参考.     

An asymptotic variational problem modeling a thin elastic sheet on a liquid,lifted at one end

We discuss a 1D variational problem modeling an elastic sheet on water, lifted at one end. Its terms include all forces that are relevant in the experiment. By studying a suitable Gamma-limit, we identify a parameter regime in which the sheet is inextensible, and the bending energy of the sheet is negligible. In this regime, the problem simplifies to one with an explicit solution. In order to prove $\mathrm{\Gamma }-$ convergence, we introduce a retardation argument in order to deal with the possibly infinite bending energy of the ansatz. This model involves a variational problem set in an unbounded domain and non reflexive topology, and hence requires special care.     

Cellulose acetate composite films fabricated with zero-valent iron nanoparticles and its use in the degradation of persistent organic pollutants

Cellulose acetate (CA), and CA blended with Nicotiana tabacum ash (ACA) membranes have synthesized and fabricated with zero-valent Fe NPs (ZVI) and named as CA@Fe⁰ and ACA@Fe⁰. The as-synthesized membranes were inspected for the removal and detoxification of toxic organic pollutants. Comparative studies of CA@Fe⁰ and ACA@Fe⁰ NPs were investigated for five model pollutants, such as 4-nitrophenol (4NP), methyl orange (MO), Congo red (CR), methylene blue (MB), and bromocresol green (BCG). The kinetic model indicated that the apparent rate constant K_app value of ACA@Fe⁰ was highest for all model pollutants compared to CA@Fe⁰ NPs. The K_app value is derived from pseudo-first-order kinetics. The K_app value of MO discoloration was 8.17 × 10⁻¹ min⁻¹ with ACA@Fe⁰ which is highest than CA@Fe⁰ (3.08 × 10⁻¹ min⁻¹). The turnover frequency (TOF) was highest for ACA@Fe⁰ for all the pollutants compared to CA@Fe⁰ and the highest TOF value was found for CR dye with ACA@Fe⁰ which is 0.523 h⁻¹. Both the membranes also showed promising antibacterial activity against Salmonella typhi. Furthermore, CA, ACA membrane and CA@Fe⁰ and ACA@Fe⁰ NPs were characterized through FESEM, EDS, XRD, FTIR and TGA analysis.     

Layer-by-layer assembly and tribological property of multilayer ultrathin films constructed by modified graphene sheets and polyethyleneimine

A series of graphene sheets (GS)-based multilayer films was constructed in virtue of layer-by-layer electrostatic self-assembly technique based on the negatively charged poly(sodium 4-styrenesulfonate) (PSS) mediated GS (PSS-GS) and the positively charged polyethyleneimine (PEI). High-resolution transmission electron microscope, atomic force microscope and micro-Raman spectrum characterizations demonstrated that the PSS-GS has been synthesized and could be assembled on the single-crystal silicon substrate. Ellipsometric thickness measurement and ultraviolet-visible absorption spectroscope confirmed the successive assemblies of GS. Finally, the macrotribological behaviors of different multilayer films were evaluated on a ball-on-plate macrotribometer and the results indicated that the prepared three- and five-layer films had high load affording ability and long anti-wear life, which could be highly dependent upon the high coverage and excellent self-lubricant properties that the GS owns intrinsically.