【作者】 时伟杰；

【导师】 朱鲁生；

【作者基本信息】 山东农业大学 ， 土壤学， 2015， 博士

【摘要】 木质素是自然界中除纤维素之外的第二大丰富的天然可再生原料,也是纸浆和造纸工业的主要副产物。从造纸工业排放到河流中的造纸黑液含有大量的木质素,会造成水质污染和水生环境中化学需氧量(COD)的增加。由于木质素的化学结构非常复杂,不易分解制备成有用的材料。目前,虽然对木质素的应用进行了研究,但木质素相当复杂的化学结构仍限制了其广泛应用。考虑到木质素的三维网状结构,可利用其特点制备多孔碳材料。腐植酸(HA)是腐殖质的主要组成部分,广泛存在于土壤、底泥、河湖海沉积物、风化煤和褐煤中,是动、植物残体经微生物和化学过程分解后形成的天然有机高分子化合物。HA主要由碳、氧、氢以及少量的氮、磷和硫元素组成,它含有多种功能基团,如羧基、羰基、醇羟基、酚羟基和甲氧基等。因此,HA可以作为碳源来制备各种新型功能材料。值得一提的是,近年来,从秸秆和工业废液(如制浆废液和发酵废水)中获得HA取得了很大的进步,它为HA的生产提供了可再生且价廉易得的资源。本文对H2O2作为氧化剂氧化造纸黑液木质素制备腐植酸进行了初步的探讨,并以来源丰富,价格便宜的木质素和腐植酸为碳源,制备了新型功能化的碳材料,构建了两种新型的过氧化物模拟酶传感器,对血样中的胆固醇和尿样中的黄嘌呤进行了分析检测。同时,将制备的功能化碳材料用于细胞成像的研究。主要分为以下四个方面:(1)腐植酸具有优良的化学活性和生物活性,广泛应用于医疗、农业、工业等领域。本文初步探讨了以造纸黑液中提取的木质素为原料,采用常见的氧化剂H2O2氧化制备腐植酸,并通过红外、紫外、荧光、高效液相色谱等手段对产物进行了表征,表征结果发现,H2O2氧化木质素的产物中除了含有腐植酸外,还有其他的氧化物质。同时,试验对H2O2的浓度进行了探讨,得出H2O2的最佳浓度为6%。(2)以造纸黑液中提取的木质素和尿素作为前驱体,利用高温煅烧法制备了蜂窝状氮掺杂多孔碳(PCN)。然后利用乙二醇还原氯铂酸将Pt纳米粒子负载到PCN上,得到蜂窝状的Pt/PCN材料。制备的Pt/PCN利用扫描电子显微镜(SEM),透射电子显微镜(TEM),X射线粉末衍射(XRD)和X射线光电子能谱(XPS)进行了表征。结果表明,平均粒径为4 nm的Pt纳米粒子均匀的分散在蜂窝状PCN的表面。试验发现,Pt/PCN表现出优于Pt纳米粒子和PCN的过氧化物模拟酶活性,能够催化H2O2氧化3,3’,5,5’-四甲基联苯胺(TMB)的反应,从而生成蓝色的ox TMB,因此可以对H2O2进行检测,检测限为1.7×10-6 mol?L-1。胆固醇在胆固醇氧化酶的作用下能够生成H2O2,基于此原理,建立了一种快速,灵敏且选择性高的方法对胆固醇进行检测,检测限为8.3×10-6 mol?L-1。以造纸黑液中提取的木质素为主要原料制备Pt/PCN材料,其方法简便,成本低廉,原料丰富,且Pt/PCN显示出优异的过氧化物模拟酶活性,可对胆固醇实现快速灵敏的检测。因此,这项工作不仅有效利用了造纸黑液木质素,而且为人体中胆固醇的检测提供了一个新的方法。(3)以腐植酸和硫脲为前驱体制备了氮,硫掺杂的三维碳纳米片层级结构材料(N-S-CS),并通过乙二醇还原氯化钯将Pd纳米粒子沉积在N-S-CS上,得到了Pd/N-S-CS材料。通过TEM,XRD,EDX和XPS等对Pd/N-S-CS材料进行了表征,结果表明,制备的Pd/N-S-CS材料呈现由纳米片构成的三维层级结构,平均粒径为6 nm的Pd纳米粒子均匀的分布在纳米片的表面。此外,制备的Pd/N-S-CS具有优异的过氧化物模拟酶活性,可以催化H2O2和TMB发生蓝色反应。基于此原理,建立了一个简单、灵敏、高选择性比色方法,对H2O2和黄嘌呤进行检测,并且应用于尿样中实际样品的测定。H2O2和黄嘌呤的检测限分别为3.3×10-6 mol?L-1和2.9×10-7 mol?L-1。这项工作有望为人体中的黄嘌呤的检测提供一个新颖且有效的方法。(4)以腐植酸作为原材料,通过一步水热法制备了石墨烯量子点(GQDs)。TEM图像显示,GQDs平均粒径为4 nm,且具有较好的晶型。傅里叶变换红外光谱(FT-IR)和XPS表明,GQDs的表面存在着羧基和羟基等功能性基团,这使得制备的GQDs具有良好的水溶性。GQDs的光学性质通过光致发光(PL)光谱和紫外-可见(UV-VIS)光谱进行了确定。结果表明,GQDs显示了稳定的,优良的依赖于激发波长的光致发光性能,可作为荧光探针应用于生物成像。细胞成像结果表明,GQDs能够在细胞内明显成像。这项工作不仅建立了一种简便,价廉的合成GQDs的方法,而且有望在生物医学领域得到广泛应用。更多还原

【Abstract】 Lignin is known as the second most abundant natural and renewable raw material after cellulose. It is also the main by-product in the pulp and paper industries. Black liquor pouring into the rivers from paper industries contains a great deal of lignin, causing water pollution and the increase of chemical oxygen demand(COD) in aquatic environments。Due to the rather complex chemical structure, lignin is not easily degraded to useful materials. Although some applications have been researched, the rather complex chemical structure of lignin limited its wide applications. Considering the three dimensional structure of lignin, it may have the advantages to prepare porous carbon materials. Humic acid(HA) is one of the major components of humic substances, which is commonly present in soils, brown and brown-black coals, natural waters, river, lake and sea sediments and other natural materials as a product of degradation of plant, algal, and microbial material. HA consists of carbon, oxygen, hydrogen and sometimes small amounts of nitrogen and occasionally phosphorous and sulphur, and contains many chemical functional groups such as carboxylic, carbonyl, phenolic, and hydroxyl groups connected with the aliphatic or aromatic carbons in the macromolecules structures. Therefore, HA can be used as carbon source to prepare all kinds of new functional materials. It is worth mentioning that the methods to extract HA from straw and industrial waste liquid(such as pulping waste liquor and fermentation wastewater) have made a great progress in recent years, which provides the new renewable, easily available and very cheap resources for the production of HA.In this paper, we preliminarily discussed the synthesis of humic acid by oxidation of the common oxidant H2O2 using lignin extracted from alkaline black liquor as raw material. After that, we prepared the new functional materials using inexpensive and earth-abundant materials of lignin and HA. Based on these materials, the simple, sensitive and selective colorimetric methods for the determination of cholesterol in serum samples and xanthine in urine samples were developed. In addition, the prepared functional material was applied on bioimaging. The main contents could be divided into four aspects as follow:(1) Humic acid has excellent chemical and biological activities, widely used in medical, agricultural, industrial and other fields. This paper preliminarily discussed the synthesis of humic acid by oxidation of the common oxidant H2O2 using lignin extracted from alkaline black liquor as raw material. The products were characterized by fourier transform infrared spectrum(FT-IR), ultraviolet-visible(UV-Vis) spectra, photoluminescence(PL) spectra and.high-performance liquid chromatography(HPLC). Results indicated that there are also other oxidizing substances in addition to the main product of humic acid. Meanwhile, the concentration of H2O2 on the influence of product was also discussed, the optimal concentration of H2O2 was 6%.(2) Lignin obtained from black liquor and urea have been successfully used as the precursors to prepare honeycomb-like nitrogen-doped porous carbon(PCN). Then Pt nanoparticles were uniformly dispersed on honeycomb-like PCN by glycol reduction to form Pt nanoparticles/PCN(Pt/PCN). The obtained Pt/PCN was characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray powder diffraction(XRD) and X-ray photoelectron spectroscopy(XPS), which showed that Pt nanoparticles with an average size of 4 nm were uniformly dispersed on the surface of honeycomb-like PCN. The prepared Pt/PCN was found to have much higher catalytic activity than individual Pt nanoparticles and PCN, which can catalyze oxidation of the peroxidase substrate 3, 3′, 5, 5′-tetramethylbenzidine(TMB) in the presence of H2O2 to produce a blue color reaction, the detection limit of H2O2 can be reached to 1.7×10-6 mol?L-1. Cholesterol oxidase(COx) is the enzyme responsible for oxidizing cholesterol to H2O2, therefore, a rapid, selective and sensitive colorimetric method for the cholesterol detection was developed with the detection limit of 8.3×10-6 mol?L-1. The method used lignin as the main raw material to prepare Pt/PCN is facile, low cost and rich in resource, and the prepared Pt/PCN was successfully applied as enzyme mimic for colorimetric detection of cholesterol sensitively. It is believed that this work not only provides a potential way to utilize the black-liquor lignin, but also puts forward a novel method for the detection of cholesterol in human body.(3) Pd nanoparticles supported on nitrogen, sulfur-doped three-dimentional hierarchical nanostructures(Pd/N-S-CS) was successfully prepared by glycol reduction of Pd on nitrogen, sulfur-doped three-dimentional hierarchical nanostructures(N-S-CS) using humic acid(HA) and thiourea as the precursors. Transmission electron microscopy(TEM), X-ray diffraction(XRD), energy-dispersive X-ray spectra(EDX) and X-ray photoelectron spectra(XPS) were employed to confirm the characterizations of Pd/N-S-CS. The results showed that the obtained Pd/N-S-CS had interesting three-dimensional hierarchical nanostructures which were composed of nanosheets, and Pd nanoparticles with average diameter of 6 nm were distributed on the surface of nanosheets. Furthermore, the Pd/N-S-CS exhibited excellent peroxidase-like activity and it can effectively catalyze the classical peroxidase substrate 3,3′,5,5′-tetramethylbenzidine(TMB) by H2O2 to produce a color reaction. Based on this finding, a simple, sensitive, and selective colorimetric method for H2O2 and xanthine detection was developed and applied to detect xanthine in urine samples. The detection limit of H2O2 and xanthine were 3.3 × 10-6 M and 2.9 × 10-7 mol?L-1, respectively. This work is expected to provide a novel and efficient method for the detection of xanthine in human body.(4) Humic acid as a raw material was applied for the preparation of graphene quantum dots(GQDs) by a simple one-step hydrothermal method. The transmission electron microscopy(TEM) images show that GQDs are well-crystalline with an average size of 4 nm. Fourier transform infrared spectrum(FT-IR) and X-ray photoelectron spectra(XPS) suggest the existence of functional groups such as hydroxyl and carboxylic groups on GQDs surface which makes the synthesized GQDs water-soluble. Optical properties of GQDs were characterized by photoluminescence(PL) spectra and ultraviolet-visible(UV-Vis) spectroscopy. It turns out that GQDs show a stable, excellent excitation-dependent photoluminescence. Therefore, the as-prepared GQDs can be applied as fluorescent materials for bioimaging. The cellular imaging studies indicate that GQDs can obviously imaging the cells. This work provides a novel low-cost raw material for the synthesis of fluorescent quantum dots by a facile method, which may have wide applications in the biomedical fields.更多还原