【作者】 张新生；

【导师】 陈建峰；

【作者基本信息】 北京化工大学 ， 化学工艺， 2011， 博士

【摘要】 海洋生物污损是人类开发和利用海洋过程中碰到的突出难题,海洋防污涂料是诸多防治措施中较为经济、有效的办法,而其中的防污剂是影响防污效果的关键成分之一。传统的防污剂是通过对附着生物进行毒杀达到防污目的,有的还可能进入食物链影响人类健康和生态安全,因此,新型、高效、环境友好的防污剂是当前研究的热点。基于此,本课题拟利用银超强的抗菌性,借助二氧化硅多孔的壳结构,设计、组装核壳结构纳米Ag@SiO2;在深入研究其杀菌动力学、杀菌机理、防腐蚀性能的基础上尝试摸索可行的防污涂料配方。本文的主要研究内容和结论归纳如下：首先,制备出了形貌可控、大小均匀、分散良好的核壳结构纳米Ag@SiO2。在阳离子表面活性剂CTAB的保护下,先用水合联氨还原硝酸银,随后利用TEOS的水解和聚合反应,最终在银纳米颗粒表面包覆上一层二氧化硅。通过深入研究TEOS加入时间、TEOS加入量、CTAB加入量、氨水加入量、无水乙醇加入量对样品结构形貌的影响,总结了较优的制备条件,该条件下得到的纳米Ag@SiO2球的直径大小在70nm以下,其中银核的大小在15-20 nm,纳米二氧化硅壳层的厚度约为20-25 nm。研究发现,核壳结构纳米Ag@SiO2制备过程中,要等到硝酸银同水合联氨的反应时间进行到7-10分钟再加入TEOS,且加入量控制在二氧化硅与银的质量比等于2.5较合适；CTAB起到分散纳米银和定向二氧化硅的作用,加入量也要适当；适量的氨水有利于形成Si02微球,而与水体积比为1／4的无水乙醇能够使其表面更加平滑。其次,研究了核壳结构纳米Ag@SiO2对革兰氏阴性菌(大肠杆菌)和革兰氏阳性菌(金黄色葡萄球菌)的杀菌性能。杀菌动力学实验表明对革兰氏阴性菌和革兰氏阳性菌均显示了超强的杀菌能力,浓度为18.17 mg/L的纳米Ag@SiO2在25分钟内使7 log大肠杆菌完全失活,彻底杀死同量的金黄色葡萄球菌需要39分钟。TEM观察进一步证实了杀菌过程中细胞形态的破坏,表现在细胞壁的破损或细胞内部物质的流失。在纳米Ag@SiO2体系中利用ESR测试没有发现产生·OH自由基和·02自由基等活性氧物种,但杀菌过程中银离子浓度却有明显降低,由此提出了纳米Ag@SiO2杀菌机理,即银核通过多孔的二氧化硅壳层不断释放出银离子导致了杀菌效果,而不是产生了ROS所引起的催化杀菌理论。以上三部分实验一致证实,由于金黄色葡萄球菌拥有相对较厚的细胞壁,因此较大肠杆菌而言对纳米Ag@SiO2具有更强的抵御力。再次,进一步研究了添加纳米Ag@SiO2对其环氧树脂涂层在不同介质中防腐性能的影响。测试了颜基比为0、0.1%和0.3%的环氧树脂涂层分别在大肠杆菌和金黄色葡萄球菌溶液中浸泡前和浸泡110h后的EIS,提出了其等效电路模型并进行了解析与拟合；同时,利用AFM观察了涂层在菌液中浸泡前的表面微观结构,比较了涂层在菌液中浸泡前和浸泡850h后的表面形貌。结果发现,未添加纳米Ag@SiO2的涂层在两个体系中浸泡后阻抗下降了96%和94%,颜基比为0.3%的涂层分别下降了73%和96%,两个涂层表面都出现了明显的锈斑,尤其以后者涂层腐蚀锈斑比较严重;而颜基比为0.2%的涂层阻抗和形貌浸泡前后基本保持不变。EN测试结果也显示,纳米Ag@SiO2的添加显著提高了其环氧树脂涂层耐无机盐腐蚀的能力,基本上都在88%以上,最高可达到99%；而对涂层抗微生物腐蚀能力的提高也都在80%以上。最后,在传统氧化亚铜防污涂料配方基础上,尝试摸索了以纳米Ag@SiO2作为防污剂的新型海洋防污涂料配方。基本思想是将氧化亚铜用纳米Ag@SiO2和其它颜填料替代,根据漆膜呈现的物理化学性质,进一步优化匹配防污剂、树脂、油脂、颜填料和各种溶剂、助剂,并最终确定防污涂料配方。通过反复实验给出了一个基本的涂料配方,添加2.5%纳米Ag@SiO2作为防污剂,加入40%左右的丙烯酸树脂,确定了颜填料和混合溶剂的比例,其常规物理性能检测结果为：外观光滑,附着力为4级,铅笔硬度HB,强度和柔韧性有所欠缺。该防污涂料配方有待进一步优化和改进。更多还原

【Abstract】 Fouling caused by marine organisms is a critical problem when the human develop and utilize the ocean. Using marine antifouling coatings is a more economical and effective method, and biocides are one of key components which determine the coatings antifouling effect. Traditional biocides achieve the goal by poisoning the fouling organisms, and some are so likely to enter food chain as to pose a threat to the human health and ecological safety. So, novel, efficient and environment-friendly biocides are a hot problem studying currently. For this purpose, Ag@SiO2 core-shell nanoparticles (NPs) were designed and assembled in view of superior bactericidal properties of silver NPs and porous structure of silica NPs in this paper. The bactericidal kinetics, mechanism of killing bacteria, and anticorrosion properties of Ag@SiO2 NPs were studied deeply. Then a feasible formula of antifouling coating was tried to develop. The main contents and conclusions of this paper are induced as follows:Firstly, the monodisperse Ag@SiO2 core-shell NPs which the morphology is even and controllable had been successfully prepared. A series steps, such as the reaction between silver nitrate and hydrazine hydrate, hydrolysis and polycondensation of TEOS, and lastly the coating of silica NPs on silver NPs, were conducted in the presence of CTAB. Through studying the effects of the addition time of TEOS and the added quantity of TEOS, CTAB, ammonia and ethanol on the microstructure of the specimens, the optimal preparation condition of Ag@SiO2 NPs below to 70 nm in diameter with a 15～20 nm silver core encapsulated within a 20～25 nm thick silica shell was gained. The results showed that it is suitable for preparation of Ag@SiO2 NPs that TEOS is added at 7～10 min after the reaction of silver nitrate and hydrazine hydrate with the quantity meeting 2.5 ratio of silica to silver. CTAB plays a positive role in dispersing silver NPs and directing silica NPs and its added quantity should be appropriate. Similarly, the right amount of ammonia takes effect in formation of silica microspheres, and adding the volume ratio of ethanol to water attributes to its smooth surface. Secondly, the bactericidal properties of as-synthesized Ag@SiO2 NPs against both Gram-negative strain (E. coli) and Gram-positive strain (S. aureus) had been deeply studied. The bactericidal kinetics test showed extraordinary antibacterial properties, and when the concentration of Ag@SiO2 NPs was 18.17 mg/L, the time needed for destruction total approximate 7 log S. aureus was about 39 min, whereas the inactivation time was shortened to 25 min for E. coli. TEM measurement confirmed the cells were destructed upon treatment, with a leakage of the intracellular substances or the rupture of the cell wall. Because reactive oxygen species (ROS), such as·OH and·O2-, were not found in the Ag@SiO2 NPs system using electron spin resonance (ESR) spin-trap technique, and there was an obvious decrease of Ag+ in the suspension, it could be concluded that inactivation of the bacterial was not due to ROS in the case, but probably owing to Ag+ eluted from Ag@SiO2. The above three experiments confirmed E. coli were found to be more susceptible to the biocidal activity of Ag@SiO2 NPs comparing to S. aureus because of its thinner cell wall.Thirdly, the influences of Ag@SiO2 NPs additive with different P/B ratios on the corrosion resistance of the epoxy coatings in different media were further investigated. Electrochemical impedance spectroscopy (EIS) of the epoxy coatings pigmented with Ag@SiO2 NPs with P/B=0,0.1% and 0.3% before and after 110 h immersion in E. coli and S. aureus solution, respectively, and corresponding equivalent circuits for the coatings were proposed and analysed. Meanwhile, the surface microstructure of the coatings was observed by atomic force microscope (AFM) before immersion in bacterial solution, and the surface topography of the coatings was compared before and 850h immersion in bacterial solution. The results showed that the resistances of the coatings with P/B=0 were decreased by 96% after immersion in E. coli solution and 94% in S. aureus solution, while that of the coatings with P/B=0.3% were 73% and 96%. The obvious rusty spots were found in the surfaces of above two coatings. However, there was little change in both resistance and topography of the coating with P/B=0.1%.The results of electrochemical noise (EN) also showed that Ag@SiO2 NPs additive improves inorganic salt corrosion resistance of its epoxy coatings to a 88-99% degree, and microbiological corrosion resistance goes up by above 80%.Finally, on the basis of traditionally cuprous oxide antifouling paint formula, the author tried to find a new antifouling paint formula using Ag@SiO2 NP as biocides. The main idea is that firstly cuprous oxide is replaced with Ag@SiO2 NP, and other alternative fillers. Secondly, according to the physical and chemical properties of the paint film, the proportion of biocides, resins, oils, fillers, various solvents, and additives are further adjusted and optimized. In the end, the antifouling paint formula is determined. A basic paint formula was given by different processes and repeated experiments, in which adding 2.5% Ag@SiO2 NPs as the antifouling agent,40% acrylic resin, appropriate proportion of pigment, filler and mixed solvent. The physical performance test results showed that the paint film posesses the appearance of smooth, adhesion to 4, pencil hardness HB, bad strength and flexibility. So the antifouling paint formula will be further optimized and improved.更多还原