层状粘土负载的金催化剂制备及其常温催化氧化活性

为了研究粘土的性质对其负载的金催化剂在CO常温氧化反应中的催化活性的影响,将金溶胶分别负载到类水滑石(LDHs)和经过壳聚糖改性的蒙脱石(CS-MMT)表面,得到纳米金颗粒呈高度分散状态的金催化剂样品.通过XRD、XRF、TEM、XPS等手段表征了金催化剂样品的物相、金的含量、金颗粒的粒径分布及金的存在价态,测试了催化剂样品对CO的常温转化率.结果表明:Au0是粘土负载的金催化剂对CO常温氧化反应的主要活性物种,碱性载体LDHs负载的金催化剂样品1.83%Au/Mg Al-CO32--LDHs表面只检测到Au0,金颗粒的平均粒径为2.6 nm,对CO的常温转化率能够达到100%,而酸性载体CS-MMT负载的金催化剂样品1.71%Au/CS-MMT表面同时存在氧化态和金属态的金,且Auδ+/Au0=1.1,金颗粒的平均粒径为2.1 nm,对CO的常温转化率仅为25%.     

预处理条件对Au/ZnO催化剂CO氧化性能的影响

采用沉积沉淀法制备了用于CO氧化的Au/ZnO催化剂, 并用程序升温还原(TPR), X射线衍射(XRD)和透射电镜(TEM)技术对催化剂进行了表征. 结果表明: 采用沉积沉淀法可制备出高度分散的Au/ZnO催化剂; 提高焙烧温度导致金颗粒聚集长大, 样品经533, 673, 773 K焙烧后金物种的颗粒尺寸分别为2.7, 3.5, 3.7 nm. 催化剂的TPR表征结果中发现部分还原态的金物种在室温就可被氧化, 催化剂预先用流动空气处理可提高其氧化还原性, 样品经多次氧化还原循环后, 其氧化循环性能没有明显下降. CO的氧化反应结果表明, 焙烧温度强烈影响催化剂对CO的氧化活性, 533 K焙烧后的催化剂活性最高. 即使在反应气中含水3.1%(体积比)的湿气条件下, 反应300 h后, CO的转化率仍然保持在95%.     

钙钛矿型氧化物负载纳米金属催化剂结构的动态调变及其催化氧化CO反应性能

研究了钛酸钡和钛酸钙担载的Ag和Pt纳米催化剂的表面结构随氧化-还原处理过程的动态变化及其对CO完全氧化反应性能的影响.发现氧化物担载的Ag催化剂在氧化处理后其催化活性较还原处理的高; X射线衍射(XRD)和X射线光电子能谱(XPS)表征结果表明,氧化处理能够提高载体表面Ag颗粒的分散度,而还原处理导致Ag颗粒的聚集,从而降低了催化氧化CO反应的活性.氧化-还原处理改变了担载Ag纳米粒子的尺寸并影响其CO氧化反应活性.与此相反,氧化物担载的Pt催化剂在还原处理后所表现出的CO氧化反应活性较氧化处理的高; 对比研究发现,氧化和还原处理后Pt纳米粒子的尺寸基本相同,但是氧化处理的样品中Pt表面物种以氧化态为主,而还原处理后Pt表面物种主要为金属态.Pt纳米粒子表面化学状态随氧化-还原处理的调变是导致表面催化活性差异的主要原因.     

Au/Ti-SBA-15的制备及其催化CO氧化性能

采用气相键合法制备了表面经二氧化钛单层分布修饰的SBA-15材料,并以该材料为载体,用改进的原位沉积沉淀法制备了Au负载量为1%的系列催化剂(Au/Ti-SBA15),考察了它们在CO氧化反应中的催化性能.采用透射电镜、X射线衍射、N2吸附-脱附、紫外-可见漫反射吸收光谱、X射线荧光分析和电感耦合等离子体发射光谱等方法对修饰的载体及其负载金催化剂进行了表征.结果表明,SBA-15孔道对Au颗粒的生长起到很好的限制作用.制得的催化剂在广谱温度范围内均有良好的催化CO氧化活性,不仅在低温具有氧化活性,而且在高达500oC时CO转化率还能达到100%,催化剂的存储稳定性和重现性都较好.     

CeO2对抗烧结Au₲MgGa2O4催化剂用于水汽变换和催化燃烧反应的促进作用

自上世纪八十年代在多相催化研究领域兴起纳米金催化淘金热以来,负载型纳米金催化剂的优越性和局限性都得到了广泛的研究.负载型纳米金催化剂活性强烈依赖于其晶粒尺寸和载体性质,一般认为,金纳米颗粒只有在一定的尺寸范围(2-5 nm)且负载在"活性"载体表面才能发挥出其优异的催化活性.然而,小尺寸纳米金颗粒热稳定性差的弱点阻碍了其工业化应用的进程.因此,如何实现小尺寸金纳米颗粒的高温稳定以及构筑金与"活性"载体间有效的接触界面是发挥纳米金优异催化性能的关键.我们曾利用MgGa_2O_4尖晶石载体与金纳米颗粒形成金属-氧化物"异质孪晶"结构,从而实现了将～3 nm的金颗粒稳定在块体金的熔点(1064°C)以上,为小尺寸纳米金的高温稳定提供了新的思路.但MgGa_2O_4尖晶石是一种非氧化还原性载体,对水分子或氧气分子的辅助活化作用较弱,因而限制了具有优异高温抗烧结性能的Au?MgGa_2O_4催化剂在水汽变换和催化燃烧反应中的应用.本文采用等体积浸渍法在高温800°C焙烧5 h后的Au?MgGa_2O_4-800℃-5h样品上进行CeO_2助剂的修饰,以提高其对水分子和氧气分子的活化能力.利用STEM, XRD和EDS-Mapping表征对CeO_2/[Au?MgGa_2O_4-800°C-5h]样品进行结构分析,发现该样品中纳米Au具有优异的高温抗烧结性能, 800°C焙烧5 h并经CeO_2修饰后其颗粒尺寸仍保持在3.1 nm左右,样品中CeO_2的晶粒尺寸约为6 nm,且Au纳米颗粒与CeO_2助剂间形成了有效的接触界面.利用H_2-TPR和XPS表征对该样品的氧化还原性能及电子性质进行分析,发现CeO_2/[Au?MgGa_2O_4-800°C-5h]样品中CeO_2的还原温度相比于CeO_2/MgGa_2O_4对比样品显著降低, XPS结果显示CeO_2添加后Au的化学价态由金属态变为氧化态,表明Au与CeO_2助剂间具有显著的电子转移.同时, CeO_2的添加显著提高了800°C老化后Au?MgGa_2O_4催化水汽变换(CO转化率由～1.5%升到～34.0%, 450°C)、甲烷燃烧(T50降低80°C)和CO氧化(T50降低100°C)等反应活性.为理解CeO_2对Au?MgGa_2O_4的催化性能促进机制,我们选取水汽变换反应为例,利用DRIFTs表征发现CeO_2促进了反应物H_2O的活化,并结合小尺寸Au对CO的活化能力,从而使水汽变换反应顺利进行.本文在MgGa_2O_4尖晶石稳定纳米金的基础上,利用具有优异氧传输性能的CeO_2作为助剂,提高了该催化剂对水分子和氧气分子的活化能力,从而获得了对水汽变换反应和催化燃烧反应具有高稳定性和高活性的CeO_2/[Au?MgGa_2O_4]催化剂.这种"先稳定-后活化"的催化剂设计思路也为今后高稳定性、高催化活性的纳米金催化剂的设计和制备提供了借鉴.     

Au/CeO2催化剂的制备及其对CO催化氧化性能的研究

采用水溶液沉淀法和沉积-沉淀法分别制备了CeO2载体及相应Au/CeO2催化剂,以CO氧化反应为表征反应,考察了载体制备条件,催化剂的焙烧温度、预处理温度和气氛以及活性组分负载量对催化剂性能的影响,并对催化剂进行了BET、XRD和TEM表征,分析了影响催化剂活性的原因.结果表明,载体的制备条件对催化剂的活性有一定影响,经微波处理的载体负载活性组分后,由于活性组分和载体的接触较紧密,因此有利于催化剂活性的提高.催化剂的最佳焙烧温度为300℃,最佳活化温度为300℃,气氛为空气,最佳金负载量为4%.     

酸化膨润土负载金催化剂用于CO氧化

用盐酸和硫酸对膨润土（Ben）进行改性处理,采用浸渍法（IMP）、沉积-沉淀法（DP）和阳离子吸附法(CA)制备改性膨润土负载的金催化剂,以CO氧化作为探针反应对催化剂的催化性能进行了研究,采用BET、XRD、TEM和TPD等对催化剂进行表征。 结果表明,经过简单的酸处理后的膨润土比表面积和孔体积有了大幅度的提高,硫酸酸化的膨润土作为载体较之盐酸酸化土更容易得到活性较高的金催化剂,XRD粒径计算结果和TEM观察结果证明,硫酸酸化的膨润土作为载体相比盐酸酸化土可以得到Au颗粒度更小的催化剂。 不同制备方法中,阳离子吸附法能较好的将Au负载于膨润土载体上,得到小颗粒的金催化剂,且在吸附48 h、450 ℃焙烧、150 ℃下H2还原的预处理条件下得到的催化剂活性最好。     

活性炭负载金催化分解空气中低浓度臭氧

采用等体积浸渍法制备了以煤质活性炭为载体的负载金催化剂,并运用N2吸附-脱附法和X射线光电子能谱对样品进行了表征.考察了该催化剂催化分解低浓度臭氧的活性,并研究了载体预处理方法和催化剂后处理方法对催化剂活性的影响.在常温,相对湿度为60%,臭氧浓度为45 mg/m3,空速为60 000 h-1的条件下,1.6 g活性炭经HNO3和NaBH4处理后负载金再经H2还原后的催化剂在反应最初的16 h内臭氧去除率稳定在100%,反应100 h后对臭氧的去除率仍在97%以上.表征结果表明,NaBH4还原处理使得活性炭比表面积、孔体积及石墨碳含量增加,含氧官能团下降,从而提高了催化剂的活性.载金后,催化剂比表面积和孔体积进一步增大,但石墨碳含量下降,C-O和COO-等含氧官能团增加.经臭氧氧化后,催化剂的比表面积和孔体积减小,石墨碳含量下降,C-O,COO-和C=O等含氧官能团增加,而金的粒径和价态并未改变,表明活性炭在金催化下被臭氧氧化.     

载金微孔分子筛催化剂研究进展

长期以来金被认为是化学惰性的,虽然早期对它的催化活性有所研究,但直到20世纪80年代中期,才相继出现了两个突破性的进展:1985年,英国威尔士大学的Hutchings教授,发现Au-Pd催化剂能够催化乙炔氢氯化反应~([1]);日本首都东京大学的Haruta教授发现,负载型纳米金催化剂具有优异的低温催化CO氧化活性~([2]).之后纳米金催化剂吸引了众多学者的目光,它的应用范围也越来越广泛.研究表明,影响纳米金催化剂催化性能的因素主要有载体的种类和性质、纳米金粒子的尺寸(常小于10 nm)形貌、氧化状态等,如何制备较小纳米金颗粒以及控制其粒径长大是获得高活性高稳定性金催化剂的关键~([3～5]).     

具有良好热稳定性的Al2O3改性Fe2O3基金催化剂

通过共沉淀法和沉积-沉淀法制备出了具有良好热稳定性的Al2O3改性Fe2O3基金催化剂, 并通过透射电镜(TEM)、X射线衍射(XRD)、N2吸附-脱附及热重和差示扫描量热(TG-DSC)分析等表征手段对催化剂的结构与表面形貌进行了研究分析. TEM测试结果表明: 500 ℃焙烧后, 未掺杂Al2O3的催化剂中金颗粒粒径分布较宽, 平均粒径约为7.0 nm, 载体颗粒尺寸在50-100 nm范围内; 而掺杂Al2O3的催化剂中金颗粒粒径分布变窄, 平均粒径约为5.0 nm, 且载体颗粒大小也明显小于未掺杂Al2O3的催化剂, 保持在30-50 nm的范围内. N2吸附-脱附测试结果表明, Al2O3的掺杂有利于保持催化剂的介孔结构和比表面积, 从而提高了载体的热稳定性. XRD和TG-DSC测试结果表明, Al2O3的掺杂可以有效地抑制Fe2O3的结晶, 进而抑制了高温焙烧过程中金颗粒的长大. 选用CO低温氧化反应对催化剂的活性进行了评价, 即使在500 ℃高温下焙烧12 h, 掺杂了Al2O3的催化剂仍然可在26.7 ℃将CO完全转化, 而未掺杂Al2O3的催化剂CO最低完全转化温度(T100)高达61.6 ℃. Al2O3的掺杂显著提高了催化剂的热稳定性能.     

Creating cellulose fibres with excellent UV protective properties using moist CF4 plasma and ZnO nanoparticles

Weakly ionised gaseous plasma created in a moist tetrafluoromethane gas at a low pressure with an electrodeless radiofrequency discharge was applied to modify the surface properties of cellulose fibres. The plasma was used to increase the adsorption of zinc oxide (ZnO) nanoparticles such that cellulose fibres with good ultraviolet (UV) protective properties could be created. The UV protection factor (UPF) values of the ZnO-functionalised fibres were determined as a function of the plasma treatment time. The chemical and physical surface properties of the plasma-treated fibres were examined using scanning electron microscopy, X-ray photoelectron spectroscopy, and wettability tests. The quantity of zinc on the fibres was determined using inductively coupled plasma mass spectroscopy. The results indicated that 30 s of plasma treatment resulted in ZnO-functionalised samples with lower UPF values than samples without plasma treatment due to the creation of fluorine-rich functional groups on cellulose fibres and the agglomeration of ZnO nanoparticles. The highest UPF values (50+) were obtained when samples were treated with plasma for 10 s. These high UPF values were a result of the increased adsorption of uniformly distributed ZnO nanoparticles caused by fibres surface functionalization and roughening upon plasma treatment. Furthermore, the mechanical properties of textiles treated with moist CF₄ plasma for 10 s were slightly improved.     

Effect of thymol on the antibacterial efficiency of plasma-treated cotton fabric

In this research, the effect of thymol on the antibacterial activity of cotton fabric when modified by low-temperature plasma was investigated. The modification consisted of plasma pre-functionalization followed by one-step wet treatment with thymol. Oxygen and nitrogen were used as the working gases in the plasma reactor. The results showed that plasma-treated samples can absorb more thymol than untreated samples. Thus, the antibacterial activity of the samples in this case, which was analyzed by the bacteria counting test, was increased considerably. Durability of the antibacterial property was also assessed. It was concluded that loading thymol on plasma-treated cotton fabric produced effective durable antibacterial textiles.     

Surface Activation of Poly(Methyl methacrylate) by Plasma Treatment: Stable Antibody Immobilization for Microfluidic Enzyme-Linked Immunosorbent Assay

With the aim of obtaining stable antibody immobilization on the poly(methyl methacrylate), PMMA channel surface, PMMA substrates were activated with O₂ plasma treatment to introduce surface polar groups on it. The plasma-treated PMMA surfaces were characterized using water contact angle measurement, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). It was observed that plasma treatment significantly improved the surface wettability with changing surface chemistry and topography. The strategy of immobilization of a model antibody, anti-goat IgG on plasma-treated PMMA involved two steps. First the plasma-treated PMMA was functionalized with (3-aminopropyl)thriethoxy silane, APTES off-chip which facilitated covalent capturing of antibody via a crosslinking agent in the inner surface of PMMA channel in the second step. The antibody immobilization on plasma-treated PMMA was also confirmed using AFM, XPS, and fluorescence microscopy. The anti-IgG covalently captured on channel surface was evaluated with sandwich ELISA protocol on-chip using fluorescence microscopy. The observed results demonstrate that this technique could be extended to integrate the current diagnostic techniques into the plastic chip for important biomarker diagnosis.     

The Effects of Non-thermal Plasma on the Morphology of Ce-doped ZnO: Synthesis,Characterization and Photocatalytic Activity of Hierarchical Nanostructures

ZnO nanoparticles with and without 8 mol % Ce dopant were synthesized by precipitation method and the prepared samples were treated with various types of non-thermal plasma in order to study their effects on the morphology and photocatalytic activity of the samples. As-prepared Ce-doped ZnO has a hexagonal wurtzite structure and the crystal system was not changed by the plasma treatment. The morphology of Ce-doped ZnO was changed from spherical particle to flower and rod-like shapes by the plasma treatment. The particle size of the treated Ce-doped ZnO is smaller in comparison with that of untreated sample. The photodegradation of methylene blue by the plasma-treated Ce-doped ZnO in aqueous solution is higher than that of the untreated Ce-doped ZnO. The enhancement of the photocatalytic activity by the plasma-treated samples may come from the particle size reduction, enhancement in charge separation efficiency and increase of the surface area.     

Preparation and Characterization of Chitosan-Coated DBD Plasma-Treated Natural Rubber Latex Medical Surgical Gloves with Antibacterial Activities

The natural rubber latex (NRL) film taken from medical surgical gloves was surface-modified with a dielectric barrier discharge (DBD) plasma treatment under an air environment. The results showed that surface hydrophilicity of the NRL film increased after the plasma treatment due to the presence of oxygen-containing polar groups on the plasma-treated surface. An increase in plasma treatment time increased the surface roughness of the NRL film, and eventually decreased the mechanical properties. From the obtained results, the optimum plasma treatment time of 20?s was chosen. After immersion in a chitosan solution, the amount of chitosan deposited on the plasma-treated NRL film increased with increasing chitosan concentrations. The chitosan coating smoothed the surface of the plasma-treated NRL film and also improved the mechanical properties. The highest antibacterial activities of the chitosan-coated DBD plasma-treated NRL film against both Staphylococcus aureus and Escherichia coli were achieved when a 2?%(w/v) chitosan solution was used for the coating.     

Investigation of metal absorption and antibacterial activity on cotton fabric modified by low temperature plasma

In this work, the silver particle absorption and antibacterial activity of cotton fabric when modified by low temperature plasma were investigated. The modification consisted of plasma pre-functionalization followed by one-step wet treatment with silver nitrate solution. Oxygen and nitrogen were used as the working gases in the system, and the results were compared. The results showed that nitrogen plasma-treated samples can absorb more silver particles than oxygen-treated samples, and thus the antibacterial activity of the samples in this case, which was analyzed by the counting bacteria test, was increased considerably.     

等离子体改性聚氯乙烯的TiO2光催化降解研究

聚氯乙烯(PVC)是一种通用型塑料,无论采用挤出、注射或浸渍等方法均有优异的成型性能,至今仍是大量使用的弹性体.……     

Optical diode effect of nematic liquid crystal induced by plasma-treated surface

We reported an optical diode effect of a nematic liquid crystal (LC) sample induced by a plasma-treated surface. The LC sample whose one of the substrates was plasma treated transmitted or blocked the incident light depending on the sign of the applied electric field. On the other hand, the LC samples whose both substrates were plasma treated or none of the substrates were plasma treated showed the same transmittance regardless of the sign of the electric field. The optical diode effect was shown when the nematic LC materials contain strong dipole moments, while the same effect was not observed when the weak polar LC was used. A thin polar LC layer formed near the plasma-treated surface makes the net field in the positive and the negative frame to be different, resulting in the optical diode effect.     

Surface modification of acrylate intraocular lenses with dielectric barrier discharge plasma at atmospheric pressure

Surface modification with dielectric barrier discharge (DBD) plasma was carried out at atmospheric pressure (argon as the discharge gas) to improve the biocompatibility of hydrophobic acrylate intraocular lens (IOL). Changes of the plasma-treated IOL surface in chemical composition, morphology and hydrophilicity were comprehensively evaluated by X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and water contact angle (WCA) measurements. The surface biocompatibility of the untreated and plasma-treated IOLs was compared with the adhesion behavior of platelets, macrophages and lens epithelial cells (LECs) in vitro. After DBD plasma treatment, the hydrophilicity of the IOL surface was obviously improved. The changes in WCA with treatment extension may be attributed to both the introduction of oxygen or/and nitrogen-containing polar groups and the increase of surface roughness induced by plasma etching effect. The existence of low molecular weight oxidized material (LMWOM) was proved on the plasmatreated IOL which was caused by the chain scission effect of the plasma treatment. The plasma-treated IOLs resisted the adhesion of platelets and macrophages significantly. The LECs spreading and proliferation were postponed on the IOLs plasma-treated for more than 180 s, with a well maintained epithelial phenotype of LECs. The IOL biocompatibility was improved after the DBD plasma treatment. We speculate that slighter foreign-body reaction and later incidence of anterior capsule opacification (ACO) may be expected after implantation of the argon DBD plasma-treated IOL. Supported by the Zhejiang Natural Science Foundation of China (Grant No. 2004C23003)     

A comparison of plasma and electron beam-sterilization of PU catheters

Polyurethane (PU) catheters made of Pellethane 2363-80AE^® were treated in two different ways: a new treatment with low temperature plasma that could be used to decontaminate reusable polymer devices in hospitals, and an e-beam (EB) irradiation. Polymer structure and bulk properties were studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), infrared spectroscopy (FTIR) and size exclusion chromatography (SEC). Although PU was strongly modified by the e-beam irradiation leading to branching of polymer chains, it had no or little impact on the thermo-mechanical properties of the catheters and on the hard/soft segment organization of PU. For plasma-treated samples, no modification in the polymer bulk was observed, confirming that plasma treatment might be considered as an alternative to e-beam irradiation. The analysis of surface modifications showed an evolution of superficial topology and chemical composition (grafting of oxygen and nitrogen species) of the catheters after treatment, with a more polar and hydrophilic surface.