含铅聚合物微凝胶与硫化氢反应前后在良溶剂中的分子扩散行为

用溶液聚合法制备出轻度交联的含铅微凝胶,用光子相关光谱技术测定其在良溶剂中与H2S反应前、后的扩散行为,由外推法得到在浓度无限稀时的分子扩散系数,给出微凝胶的流体力学半径。结果表明:相同量的含铅微凝胶在不同的初始浓度下与H2S反应,生成含PbS纳米微粒的凝胶；但其体积增大不同,这说明H2S与含铅微凝胶的反应既可以在分子内也可以在分子间进行,分子间的反应使含硫化铅微凝胶扩散系数随浓度的变化曲线的线性范围变小。     

基于4-氨基-1, 8萘酰亚胺的双光子荧光H2S探针光学性质与响应机理分析

基于密度泛函理论水平上的解析响应函数方法,采用极化连续模型(PCM)研究了两种新型的截断型双光子荧光H₂S探针AcHS-1, 2的单双光子吸收及荧光发射性质,并对其响应机制进行了理论分析.计算结果表明, AcHS-1, 2在与H₂S反应后,生成物的单双光子吸收性质特别是荧光发射性质发生了明显的变化,它们的吸收峰都有较大的红移.此外,不同末端基团对探针分子的光学性质也有一定的影响.分析了探针分子AcHS-1, 2与H₂S反应前后的Mulliken布居及电荷转移过程,反应后分子内电荷转移量增大,从而改变了分子的光学性质,实现了对H₂S的探测.     

检测硫化氢分子的荧光探针

硫化氢（H₂S）是继一氧化碳和一氧化氮之后,第三种可在生命体内发挥生理作用的内源性气体信号分子。该气体分子在心血管和神经系统中担负着重要的生理病理调节作用。因此,选择性识别和高灵敏检测生物体内的H₂S具有十分重要的生物医学意义。在生物检测技术手段中,荧光探针法具有选择性好、灵敏度高、对生物样品损伤小以及可实现实时原位检测等独特的优势,故应用荧光探针法检测细胞内H₂S浓度的变化是近年来研究热点之一。本文依据荧光探针与H₂S之间的化学反应类型,将近三年来所研发的H₂S荧光探针按照其母体荧光团进行分类和总结,综述了H₂S荧光探针的研究进展,概述了相关荧光探针的设计理念、检测机理及生物应用,探讨了探针的结构和性能之间的关系,最后展望了H₂S荧光探针的发展趋势和应用前景。     

用于光催化分解硫化氢制氢的金属硫化物

硫化氢(H₂S)作为一种剧毒、恶臭的强腐蚀性气体,广泛来源于人类活动和自然界,对动植物生存和环境都具有较大的危害。光催化分解H₂S制氢是一种理想的H₂S处理技术,可以同时实现H₂S的转移和清洁能源氢气的产生。近年来,金属硫化物由于其优异的可见光响应、恰当的能带结构和对H₂S有高的稳定性,因此被广泛地应用于光催化分解H₂S制氢。本文对近年来国内外金属硫化物驱动H₂S资源化利用制氢领域取得的重要进展进行了概述和总结,探讨了不同反应媒介下光催化分解H₂S制氢机制;特别关注了一些为实现高效稳定光催化H₂S资源化利用制氢的优异调控策略;最后,对H₂S资源化利用的挑战和前景进行了展望。     

硼氮掺杂的碳纳米管对硫化氢气敏性能的理论研究

应用密度泛函理论研究了纯(8, 0)单壁碳纳米管(SWCNT)和B原子、N原子以及BN原子对掺杂的(8, 0) SWCNTs对硫化氢气体分子的传感性质. 计算结果表明, 与纯碳纳米管相比, B原子掺杂的SWCNT显示了对H₂S分子的敏感性, 其几何结构和电子性质在吸附H₂S分子后发生了显著变化; 而N原子和BN原子对的掺杂没有改善SWCNT对H₂S分子的吸附性能, 因此我们建议B原子掺杂的SWCNT作为检测H₂S分子的新型气相传感器.     

耐硫甲烷化中H2S浓度对MoO3/Al2O3和CoO-MoO3/Al2O3催化剂的影响

在0 到12 mL·L^-1 (体积分数φ=0.00%-1.20%) 范围内考察了不同H₂S 浓度对25% (质量分数, w)MoO₃/Al₂O₃和5% (w) CoO-25%MoO₃/Al₂O₃催化剂甲烷化性能的影响. 结果表明, 5%CoO-25%MoO₃/Al₂O₃的甲烷化活性随H₂S浓度的增加单调上升, 而25%MoO₃/Al₂O₃对H₂S浓度并不敏感. 对比这两种催化剂发现, 只有在H₂S浓度高于0.40% (φ) 时, 在25%MoO₃/Al₂O₃中添加Co助剂才会有促进作用; H₂S浓度低于0.40% (φ)时, Co助剂会抑制25%MoO₃/Al₂O₃催化剂的甲烷化活性. 分别对反应前后的催化剂表征发现, H₂S浓度的改变不会对两种催化剂的物理结构产生明显的影响, 而是通过影响催化剂表面的金属硫化物活性位来影响催化剂的甲烷化性能. 耐硫甲烷化反应体系中较高的硫含量下Co助剂才表现出对25%MoO₃/Al₂O₃催化剂的促进作用. 该研究明确了在MoO₃/Al₂O₃催化剂中添加Co助剂的硫化氢浓度范围, 为工业上选择合适的催化剂提供了依据.     

光催化分解硫化氢制取氢气的研究

以连续流动进H₂S气体系统,在室温条件下研究了用Xe灯照射含有催化剂的NaOH水溶液时,H₂S光催化分解为H₂气和元素S的反应。分别采用CdS、V₂O₅/TiO₂和V₂O₅/Al₂O₃为催化剂,考察了产氢量与介质中NaOH含量及照射时间的关系,讨论了光催化分解H₂S的反应机理。结果表明,连续流动通入H₂S气体进行光催化分解的方法是可行的,并接近实际可能应用的情况。     

新型室温硫化氢纳米传感器的制备及性能

采用溶胶-凝胶法在叉指金电极表面制备纳米二氧化钛(TiO₂)多孔薄膜, 并用浓度为2.5×10⁴ mol/L的花青素对其进行敏化, 制备了一种能在室温条件下检测硫化氢(H₂S)的高灵敏度传感器. 从材料的光谱特性、 微观结构和传感器的灵敏度等方面对该传感器的性能进行了评价, 并讨论了传感器的响应机理以及温度和湿度对灵敏度的影响. 结果表明, 材料表面的可见吸收光谱比花青素红移了约50 nm, 吸收能力有所提高; 纳米TiO₂颗粒呈层状堆积排列, 颗粒之间具有较多缝隙, 比表面积大. 在室温下, 该气体传感器对浓度为5~50 mL/m³的H₂S具有良好的敏感特性, 传感器灵敏度与H₂S浓度呈线性相关, 相关系数为0.939, 响应时间为50~70 s, 恢复时间为160~180 s. 计算和测试结果表明, 环境湿度约为50%时传感器的灵敏度最佳; 在10~50 ℃范围内, 温度与传感器的灵敏度存在负相关性. 该方法为简单、 经济制备室温条件下工作的气体传感器提供了新思路和新方法.     

TiO2光催化消除H2S的研究

在TiO₂上进行了气相H₂S光催化氧化消除的研究.氧对H₂S的光催化氧化消除过程是不可缺少的,对含量为560mg/m³的H₂S,当加入的氧气与原料气中H₂S的分子比为42:1,空速为28000h^-1时,去除率达到97%.在H₂S光催化氧化消除过程中,单质硫的产生可使TiO₂失活,经光照再生单质硫转化为SO₄^2-后,TiO₂活性恢复,而且SO₄^2-的生成对催化剂的中毒有抑制作用.     

硫化氢对活性炭脱除单质汞的影响

H₂S是煤气中的含硫成分,活性炭能否催化氧化煤气中的H₂S形成活性硫,以促进H₂S和Hg⁰的协同脱除是值得研究的。 本文首先通过程序升温脱附和热力学分析了低温情况下H₂S对活性炭脱除Hg⁰的影响。 在较低吸附温度130 ℃下,H₂S不仅不能作为硫源,还使活性炭对Hg⁰的吸附显著减弱,这主要是由于H₂S对活性炭表面的吸附氧的消耗以及H₂S对含氧官能团的氧的取代反应造成的。 在此基础上,进一步研究了高温下H₂S对活性炭的影响,高温也不能使活性炭有效渗入单质硫。 所以无论低温还是高温情况下,利用H₂S作为硫源使Hg⁰以HgS的形式脱除并不是活性炭脱汞的可行手段。 本文揭示了较宽的温度范围内H₂S对单纯的活性炭脱除Hg⁰的影响机理,能为用于煤气脱汞的活性炭的设计以及作为负载时机理研究提供支持作用。     

铅离子敏感N-异丙基丙烯酰胺共聚物微凝胶的制备

采用对N-异丙基丙烯酰胺-丙烯酸共聚微凝胶进行改性的方法合成了含苯并18-冠-6功能基团的PNIPAM微凝胶.红外和核磁光谱等手段证明苯并18-冠-6基团被引入到微凝胶中.改性后的微凝胶仍具有很好的温敏性,但是相转变温度由改性前的30℃提高到42℃,并且溶胀度也大大增加.在不控制离子强度的条件下微凝胶的粒径随Na+浓度增加而减小,但是随Pb2+浓度增加微凝胶粒径先减后增.在控制离子强度不变的条件下Na+浓度对微凝胶的粒径影响很小,但是随Pb2+浓度增加微凝胶粒径明显增大,显示较强的铅离子敏感性。     

UV cured transparent films including non‐aqueous conductive microgels

UV cured transparent films containing non‐aqueous conductive microgels coated with poly(aniline)/dodecyl benzenesulfonic acid(DBSA) were obtained. The conductive microgels were prepared by interface polymerization of aniline/DBSA in the presence of non‐aqueous polymeric microgels. The electrical conductivity and the particle size of the prepared conductive microgel were 0.5 S/cm and 58 nm, respectively. The prepared conductive microgels were easily blended with a UV curable coating formulation, and then were cured to make highly optically transparent films. For the UV cured film containing about 35 wt% of the conductive microgels, a surface resistance in the range of 10⁷ to 10⁸ Ω/square was obtained. In a polar cosolvent, such as NMP and m‐cresol, the critical volume was shifted to the lower range, with a value of 10 wt%. The UV cured films containing the conductive microgels exhibited good electrical stability against the thermal aging and humidity. Copyright © 2002 John Wiley & Sons, Ltd.     

Equilibrium and kinetic aspects of the uptake of poly(ethylene oxide) by copolymer microgel particles of N-isopropylacrylamide and acrylic acid

The use of microgels for controlled uptake and release has been an area of active research for many years. In this work copolymer microgels of N-isopropylacrylamide (NIPAM) and acrylic acid (AAc), containing different concentrations of AAc and also cross-linking monomer, have been prepared and characterized. These microgels are responsive to pH and temperature. As well as monitoring the equilibrium response to changes in these variables, the rates of swelling/de-swelling of the microgel particles, on changing either the pH or the temperature, have also been investigated. It is shown that the rate of de-swelling of the microgel particles containing AAc is much faster than the rate of swelling, on changing the pH appropriately. This is explained in terms of the relative mobilities of the H(+) and Na(+) ions, in and out of the particles. It was observed that the microgels containing AAc, at pH 8, de-swelled relatively slowly on heating to 50 degrees C from 20 degrees C. This is attributed to the resistance to collapse associated with the large increase in counterion concentration inside the microgel particles. The swelling and de-swelling properties of these copolymer microgels have also been investigated in aqueous poly(ethylene oxide) (PEO) solutions, of different MW (2000-300 000). The corresponding absorbed amounts of PEO from solution onto the microgels have also been determined using a depletion method. The results, as a function of AAc content, cross-linker concentration, PEO MW, pH, and temperature, have been rationalized in terms of the ease and depth of penetration of the PEO chains into the various microgel particles and also the H-bonding associations between PEO and either the -COOH of the AAc moeities and/or the H of the amide groups (much weaker). Finally, the adsorption and desorption of the PEO molecules in to and out of the microgel particles have been shown to be extremely slow compared to normal diffusion time scales for polymer adsorption onto rigid surfaces.     

Swelling Kinetics of Microgels Embedded in a Polyacrylamide Hydrogel Matrix

Composite hydrogels—macroscopic hydrogels with embedded microgel particles—are expected to respond to external stimuli quickly because microgels swell much faster than bulky gels. In this work, the kinetics of the pH‐induced swelling of a composite hydrogel are studied using turbidity measurements. The embedded microgel is a pH‐ and thermosensitive poly(N‐isopropylacrylamide‐co‐acrylic acid) microgel and the hydrogel matrix is polyacrylamide. A rapid pH‐induced swelling of the embedded microgel particles is observed, confirming that composite hydrogels respond faster than ordinary hydrogels. However, compared with the free microgels, the swelling of the embedded microgel is much slower. Diffusion of OH^? into the composite hydrogel film is identified as the main reason for the slow swelling of the embedded microgel particles, as the time of the pH‐induced swelling of this film is comparable to that of OH^? diffusion into the film. The composition of the hydrogel matrix does not significantly change the characteristic swelling time of the composite hydrogel film. However, the swelling pattern of the film changes with composition of the hydrogel matrix.     

Preparation of spherical nanostructured poly(methacrylic acid)/PbS composites by a microgel template method

Spherical poly(methacrylic acid)/PbS (PMAA/PbS) composites with a fishnet-like surface and core-shell structure were prepared by a microgel template method. The composites were prepared in two steps. Pb(Ac)(2) was dissolved in MAA solution before it was polymerized into microgels in an inverse suspension system. In this way, Pb(2+) was trapped within the microgel network. Then, H(2)S was introduced slowly into the system, and the metal ions were deposited within the microgels as PbS. The presence of PbS was confirmed by X-ray diffraction (XRD) and thermogravimetric measurements, and the morphology of the composites was characterized by scanning electron microscopy (SEM). It was found that the surface structure of the microparticles depends largely on the nature of the continuous phase of the system. The microparticles from xylene have a fishnet-like surface structure, and the inner structure and composition of the particles are different from the outer structure and composition. The surface of the particles from cyclohexane, however, appears smoother and denser than the surface of the particles from xylene. The different structure of the particle surfaces from the two systems has been attributed to the differences in template structure.     

Water‐dispersible microgel modified with methacryloyl groups by ionic bonding on the surface and the photopolymer microgel

A novel water‐dispersible reactive microgel, which had a diameter of 40–90 nm, was synthesized for photopolymer materials. The microgels have segments with substituted ammonium groups, to provide water solubility, in their polymer networked structure. It has unsaturated groups connected to the quaternary nitrogens by ionic bonding (I‐type microgel). The I‐type microgel was compared with one that has methacryloyl groups connected with the quaternary nitrogens of the microgel by covalent bonding (C‐type microgel). The I‐type microgels were able to separately control the modified amount of quaternary nitrogen and methacryloyl group. In the presence of 2,4‐diethylthioxantone as a photoinitiator and pentaerthritol triacrylate as a crosslinker, the photopolymer containing the C‐type or I‐type microgels had sensitivity high enough for practical use. Not only the amount of the methacryloyl group of the microgel but the amount of the quaternary nitrogen affected the sensitivity and the rate of polymerization of the water‐dispersible photopolymer containing the I‐type microgels. Copyright © 2000 John Wiley & Sons, Ltd.     

Polypyrrole/poly(N‐isopropylacrylamide‐co‐acrylic acid) thermosensitive and electrically conductive composite microgels

The electrically conductive polypyrrole/dodecylbenzene sulfonic acid/poly(N‐isopropylacrylamide‐co‐acrylic acid) (PPy/DBSA/poly(NIPAAm‐co‐AA)) composite microgels were synthesized by a chemical oxidation of pyrrole in the presence of DBSA as the primary dopant, and poly(NIPAAm‐co‐AA) microgels as the polymeric codopant and template, in which APS was used as the oxidant. It was proposed to prepare “intelligent” polymer microgel particles containing both thermosensitive and electrically conducting properties. The polymerization of pyrrole took place directly inside the microgel networks, leading to formation of composite microgels and the morphology was observed by transmission electron microscope. PPy particles interacted strongly with microgels, as the acid groups of microgels acted as the polymeric codopant. The composite microgels thus formed showed electrically conducting behavior dependent on humidity and temperature. At temperatures lower than lower critical solution temperature, the conductivity decreased with increasing the humidity and a small hysteresis phenomenon was observed. The hysteresis became indistinct when temperature was near volume phase transition temperature. However, after the treatment of high temperature and high humidity, the conductivity increased surprisingly due to the structure reorganization inside the composite microgels. The distinctive functionality of the PPy composite microgels was expected to be utilized in many attractive applications. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1648–1659, 2006     

Polyurethane acrylate microgel synthesized by emulsion polymerization using unsaturated self-emulsified polymer

Polyurethane (PU) acrylate microgels were obtained by emulsion polymerization of self-emulsified PU acrylate terminated by 2-hydroxyethyl methacrylate without any extra emulsifier and crosslinker. Moreover, the PU acrylate was also used as stabilizer and crosslinker to synthesize poly(methyl methacrylate) (PMMA)–PU composite microgels via emulsion polymerization, which provided a new method to synthesize PU microgels and their composite microgels. The kinetics of microgel synthesis was studied by gel permeation chromatography. The dynamic rheological behaviors indicated that a crosslinked structure was formed. The frequency dependency of the loss tangent and complex viscosities showed strong relationships with the microgel structure. Those microgels with rigid PMMA core showed higher ability to slide than the soft PU acrylate microgel, which had influence on the changing of loss tangent with frequency. All the microgels swollen in tetrahydrofuran exhibited high viscosities and strong shear-thinning behaviors. As a sort of flexible microgel, the PU microgel was able to form a coherent film at room temperature, which was distinct from hard microgels.     

Highly regenerable ionic liquid microgels as inherently metal‐free green catalyst for H2 generation

Polymeric ionic liquid (PIL) microgel of poly([2‐(methacryloyloxy)ethyl]trimethylammonium chloride) (p(MTMA)) was synthesized by using an inverse suspension polymerization technique. The anion‐exchanged PIL microgels via chloride replacement from p(MTMA) were prepared as p(MTMA)‐potassium thiocyanate (p(MTMA)‐KSCN), p(MTMA)‐sodium tetrafluoroborate (p(MTMA)‐NaBF₄), and p(MTMA)‐sodium dicyanamide (p(MTMA)‐NaN(CN)₂) microgels by treatment with corresponding salts of potassium thiocyanate (KSCN), sodium tetrafluoroborate NaBF₄, and sodium dicyanamide NaN(CN)₂ in aqueous media. The prepared microgels were found to be efficient metal‐free catalysts, and their catalytic activity in H₂ production from the methanolysis of NaBH₄ was investigated. Moreover, various parameters affecting H₂ production such as the effect of microgel size, the concentration of NaBH₄, the effect of the anion in the microgel, the reusability of the microgel, and temperature were investigated. The Ea value calculated for the methanolysis reaction of NaBH₄ catalyzed by p(MTMA) microgels was found as 24.1 ± 0.7 kJ mol⁻¹ ranging from −15 to 45°C, and this Ea value is lower than some Ea values for the same reaction. Interestingly, 10‐time successive use of p(MTMA) microgel as catalyst in NaBH4 methanolysis reduced its catalytic activity to 49%, whereas the anion‐exchanged forms of p(MTMA) microgel, p(MTMA)‐KSCN, p(MTMA)‐NaBF₄, and p(MTMA)‐NaN(CN)₂ only reduced their catalytic activity to 89, 86, and 79%, respectively, after 10 consecutive uses. Therefore, these anion‐exchanged microgel catalysts are highly efficient in comparison with virgin p(MTMA) microgels for regenerable H₂ generation from the methanolysis of NaBH₄.