氨基酸功能化石墨烯量子点的制备及性能研究

发布时间：2018-01-21 00:51

本文关键词： 石墨烯量子点氨基酸功能化光学传感酶促反应活性染料降解　出处：《江南大学》2017年博士论文　论文类型：学位论文

【摘要】：作为石墨烯家族的最新成员,准零维的石墨烯量子点克服了石墨烯片层之间因较强分子间作用力而导致的堆积和聚集现象,还因显著的量子限域效应和边界效应而展现出优异的光致发光性能。石墨烯量子点同时兼具石墨烯和量子点的优异性能,加上发光明亮而稳定、水溶性好和生物毒性低的优势,使其在化学传感、生物成像、医学治疗和能源相关领域具有更加诱人的前景。然而现有石墨烯量子点发光效率低、性能单一和功能性差的缺陷限制了其应用的拓展,因此需要制备新的具有特殊功能的石墨烯量子点来满足不同的需求并拓展石墨烯量子点的应用领域。为此,本论文开展了氨基酸功能化石墨烯量子点的制备、结构对性能影响及复合材料制备等领域应用研究。以20种氨基酸为功能化试剂制备20种氨基酸功能化石墨烯量子点,合成机理研究发现氨基酸的组成和空间结构会显著影响功能化石墨烯量子点的形成。空间位阻较大的氨基酸倾向于分布在石墨烯量子点的边缘,而简单的氨基酸则会部分掺杂到石墨烯量子点内部。此外,光学性质研究发现氨基酸功能化基团中氮元素的引入使石墨烯量子点的荧光量子产率有明显的提高,通常量子点边缘氮原子能够增加石墨烯量子点的电子密度,使荧光发射红移,而内部氮原子较强的吸电子性质则会导致荧光发射的蓝移。石墨烯量子点的表面基团组成和结构显著影响其光致发光性能。缬氨酸功能化石墨烯量子点实现了更灵敏和快速的重金属汞离子荧光检测,发现缬氨酸功能基团引入显著提高了汞离子对量子点的荧光猝灭性能,该方法的灵敏性是未功能化石墨烯量子点的14倍,响应速度提高近10倍。甲硫氨酸功能化石墨烯量子点对环境中pH值的变化表现出极为灵敏的荧光线性响应,基于此开发了一种宽范围的pH荧光传感器。当体系pH在1~14范围内,石墨烯量子点的荧光强度随着pH的增大逐渐增强,在其它缓冲体系中表现出相同的pH荧光响应性。与现有方法相比,新方法在灵敏度、选择性或响应范围等主要分析性能上有明显提高,并成功应用于实际水样中汞离子和pH值的检测,在生物细胞RBL-2H3 pH依赖荧光成像中也获得较好的效果。以H_2O_2氧化降解孔雀石绿染料为模型反应,考察石墨烯量子点结构对染料降解应用中催化性能的影响。结果表明20种氨基酸功能化石墨烯量子点的吸附和催化协同作用均能显著提高H_2O_2氧化降解孔雀石绿效率。筛选发现组氨酸功能化石墨烯量子点其富氮咪唑环提供更多的碱性活性位点,具有最高的催化活性。通过考察影响降解效率的各种因素,得到降解孔雀石绿的最佳条件(50 mg/L孔雀石绿、0.5 mg/mL组氨酸功能化石墨烯量子点、15 mmol/L H_2O_2、35℃),在此条件下,5 min即可降解93%。此外,该过程不需要使用特殊的光照或其它辅助条件,催化剂重复9次后活性没有明显的减少。分别以辣根过氧化物酶(HRP)催化H_2O_2氧化四甲基联苯胺和假单胞菌脂肪酶(PCL)催化L-薄荷醇与乙酸酐合成L-乙酸薄荷酯为模型反应,考察石墨烯量子点作为修饰剂对酶促反应活性调控性能。结果发现修饰剂的尺寸、表面基团性质和空间构型对生物酶行为有很大影响。HRP在以氧化石墨为前驱体制备的GO-GQD和半胱氨酸功能化石墨烯量子点(Cys-GQD)为修饰剂时分别表现出酶活性和稳定性促进和抑制的相反作用效果。圆二色谱研究结果表明,HRP在亲水基团较少的GO-GQD作用下结构有序程度增加,有助于酶活性的发挥。TMB氧化反应产生的蓝色物质能够显著猝灭石墨烯量子点的荧光,基于GO-GQD能够提高HRP活性和四甲基联苯胺氧化产物对GO-GQD荧光猝灭作用建立了一种检测H_2O_2的方法。PCL在Cys-GQD修饰剂作用下的活性和稳定性优于氧化石墨修饰,在最佳条件下,L-薄荷醇的转化率达97.3%,酶的半衰期为224 h,重复使用10次后活性没有明显下降。怎样将石墨烯量子点与其它材料结合,实现它们的优势互补,已逐渐成为研究的热点。首先以氨基酸功能化石墨烯量子点为还原剂和稳定剂一步制备金/石墨烯量子点纳米复合材料并考察功能化基团结构对还原性能的影响,发现石墨烯量子点功能基团组成显著影响其还原性,脯氨酸因是20种中唯一含二级胺结构的氨基酸,脯氨酸功能化石墨烯量子点其与金离子较强的亲和性使其具有最高的还原能力,复合材料的制备在1min内即可完成。复合材料洁净的表面以及高共轭程度石墨烯量子点负载使复合材料具有更好的电子传导能力。以复合材料制备的修饰电极在5.0 mmol/L K4[Fe(CN)6]中的ks值为15.58±0.43 cm/s,电子传递速率为裸电极的2.86倍,采用差分脉冲伏安方法检测对乙酰氨基酚进一步研究修饰电极的电化学特性,得到对乙酰氨基酚的检测下限为0.02μmol/L。论文最后以双锥形纳米金(BPGN)和石墨烯量子点构建了集表面增强拉曼散射(SERS)和荧光双光谱于一体的双模探针。首先采用改进方法以少量十二烷基苯磺酸钠(SDBS)为添加剂、减半十六烷基三甲基溴化铵(CTAB)用量制备BPGN作为SERS基底材料,两种表面活性剂间的协同作用有助于得到单分散性好且光学性质稳定的BPGN。将BPGN与发光性和生物相容性更优的石墨烯量子点组装于二氧化硅壳层内外两层制备双模探针,如此组装的优势简单可控,通过更改两种类型探针可以显著提高光谱编码能力。最后采用夹心免疫光学传感方式实现微囊藻毒素-CL的SERS和荧光方法双重检测。
[Abstract]:As the newest member of the family of graphene, graphene quantum dots of quasi zero dimension between the graphene layers due to strong intermolecular force caused by the accumulation and aggregation phenomenon, but also because of the obvious quantum confinement effect and boundary effect and show excellent optical luminescence properties of graphene quantum dots at the same time. With the excellent properties of graphene and quantum dots, with bright and stable, good water solubility and low toxicity advantages, the chemical sensing, biological imaging, has a more attractive prospect of medical treatment and energy related fields. However, the luminous efficiency of the existing graphene quantum dots is low, and the performance of single function the deficiency of low limit the expansion of its application, so we need gqds preparation with special functions to meet different needs and expand the application field of graphene quantum dots. Therefore, this thesis has carried out the amino Acid functionalized graphene quantum dots preparation, effect of structure on performance and preparation of composite materials and other fields. Research and application of functional reagents preparation of 20 kinds of amino functionalized graphene quantum dots with 20 kinds of amino acids, synthesis mechanism study found that the composition and structure of amino acid can significantly influence the formation of functionalized graphene quantum dots. Sterically hindered amino acids tend to be distributed in the gqds edge, and simple amino acids will be part of the internal doped graphene quantum dots. In addition, the research found that the introduction of optical properties of amino acid nitrogen functional groups in the fluorescence quantum yield of graphene quantum dots have significantly improved generally, quantum dot edge nitrogen atom can increase the electron density of graphene quantum dots, the fluorescence emission redshift, and internal nitrogen atoms strong electron withdrawing properties will result in the blue shift of fluorescence emission The surface groups. The composition and structure of graphene quantum dots had significant influence on the photoluminescence properties. Valine functionalized graphene quantum dots to achieve a more rapid and sensitive fluorescence detection of mercury ion, found that valine introduced functional groups can significantly improve the performance of mercury ions on the fluorescence quenching of quantum dots, the sensitivity of the method is 14 times non functionalized graphene quantum dots, to improve the response speed of nearly 10 times. Methionine functionalized graphene quantum dots on the changes in the environment of pH value exhibit extremely linear fluorescence sensitive response, based on the development of pH fluorescence sensor with a wide range of pH. When the system is in the range of 1~14, fluorescence intensity gqds gradually increased with the increase of pH in the other buffer system showed the same pH fluorescence response. Compared with the existing methods, the new method in sensitivity, selectivity and response range of the Lord To analyze the performance has improved significantly, and successfully applied to the detection of mercury ion and pH in actual sample value, in biological cells RBL-2H3 pH dependent fluorescence imaging but also to obtain better results. The degradation of malachite green dye H_2O_2 oxidation as a model reaction of graphene quantum dot structure influence on the catalytic performance of dye degradation application the results show that the adsorption and catalysis. 20 kinds of amino functionalized graphene quantum dots synergy can significantly improve H_2O_2 oxidative degradation of malachite green. The efficiency of screening of histidine functionalized graphene quantum dots of the nitrogen rich alkaline imidazole ring provide more active sites, with the highest catalytic activity. The factors influencing degradation efficiency the optimal conditions of the degradation of malachite green (50 mg/L malachite green, 0.5 mg/mL histidine functionalized graphene quantum dots, 15 mmol/L H_2O_2,35 C), in this article Under 5 min can degrade 93%. in addition, the process does not require the use of special lighting or other auxiliary conditions, repeated 9 times after the catalyst activity was not significantly reduced. With horseradish peroxidase (HRP) catalytic oxidation of H_2O_2 four methyl benzidine and Pseudomonas lipase (PCL) catalyzed L- menthol and acetic anhydride synthesis of L- menthyl acetate as the model reaction of graphene quantum dots as modification agent to promote activity of the enzyme. The results show that the control performance of modified size, surface group properties and spatial configuration of.HRP has a great influence on the graphite oxide was prepared by GO-GQD and cysteine functionalized graphene quantum dots on the biological behavior of enzyme (Cys-GQD) as modification agent were shown to promote enzyme activity and stability and suppression of the opposite effect. Round two chromatography results showed that HRP in hydrophilic groups with less GO-GQD node The orderly degree of increase, contribute to enzyme activity play blue substance produced.TMB oxidation reaction to graphene quantum dot fluorescence quenching was graphite, GO-GQD can improve the activity of HRP and four methyl benzidine oxidation products of GO-GQD fluorescence quenching.PCL method was established for detecting H_2O_2 activity and stability is better than that of modified graphite oxide modifier under the action of Cys-GQD based on L- under the optimum conditions, conversion of menthol rate reached 97.3%, the half-life of the enzyme was 224 h, after 10 times of repeated use without apparent loss of activity. How to combine it with the graphene quantum dot materials, realize their complementary advantages, has gradually become a hot research topic. Firstly, using amino acid functionalized graphene quantum dots as a step in the preparation of gold / graphene quantum dot nanocomposites and study the functional groups structure influence on the reducing capability of reducing agent and stabilizer, found Gqds functional group composition has significant effect on reducing, because it is only 20 proline containing two amine amino acids, proline functionalized graphene quantum dots and its strong affinity for gold ions has the highest reducing ability, preparation of composite materials can be completed within 1min. The composite the material has better electronic conductivity of composite surface clean and high degree of conjugation of gqds load. With composite material prepared modified electrode in 5 K4[Fe mmol/L (CN) 6] in KS was 15.58 + 0.43 cm/s, electron transfer rate was 2.86 times higher than the bare electrode, the electrochemical properties of acetaminophen further study of phenol modified electrode by differential pulse voltammetry method to detect the detection limit by acetaminophen for 0.02 mol/L. in the end to double cone gold nanoparticles (BPGN) and graphene quantum dots are set up The surface enhanced Raman scattering (SERS) dual-mode probe and fluorescence double spectrum in one of the first. The improved method is used with a small amount of twelve sodium dodecyl benzene sulfonate (SDBS) as additive, half sixteen alkyl three methyl bromide (CTAB) dosage of preparation of BPGN as SERS substrate material, two kinds of surface active agent of the synergetic effect of help get well dispersed and stable optical properties of the BPGN. BPGN and the luminescent properties and biocompatibility of superior graphene quantum dots assembled on the silica shell inside and outside the two preparation of dual-mode probe, so the advantages of simple assembly controlled by changing the two types of probes can significantly improve the spectral encoding ability. Finally realize the dual detection of SERS and the fluorescence method of microcystin -CL by sandwich immune optical sensing.

【学位授予单位】：江南大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O613.71;TB383.1

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