【摘要】：環(huán)境污染與能源短缺等問題使得再生資源的開發(fā)與利用受到人們的廣泛關(guān)注。半纖維素來自植物的細(xì)胞壁,是自然界中含量豐富、價格低廉的天然多糖,已被廣泛應(yīng)用在造紙、能源、食品以及生物醫(yī)藥等領(lǐng)域,逐漸成為一種可取代石化產(chǎn)品、無毒、可降解、環(huán)境友好的新型原料。但是,半纖維素復(fù)雜的糖組分、較高的分枝度以及無定形結(jié)構(gòu)使得其只能進(jìn)行低附加值利用。為了實現(xiàn)半纖維素的高值化利用,本研究采用半纖維素的模型物—木聚糖作為基材,一方面將木聚糖與另一種天然多糖(殼聚糖)進(jìn)行結(jié)構(gòu)組裝,另一方面將木聚糖與無機納米貴金屬材料有效復(fù)合,發(fā)展了木聚糖基復(fù)合功能材料,并考察了其性能,主要研究內(nèi)容包括:1、木聚糖/殼聚糖復(fù)合物的制備與性能探討為了避免分別溶于堿性和酸性溶液的木聚糖和殼聚糖在混合時產(chǎn)生沉淀,使得兩者之間的反應(yīng)不能順利進(jìn)行,本研究將木聚糖和殼聚糖溶于同一種離子液體后進(jìn)行美拉德反應(yīng),使得殼聚糖中的氨基與木聚糖中的還原性末端醛基接枝,最終生成大分子物質(zhì)類黑精,即木聚糖-殼聚糖美拉德反應(yīng)產(chǎn)物。結(jié)果證明,當(dāng)木聚糖和殼聚糖兩者質(zhì)量比為1:1時更容易發(fā)生美拉德反應(yīng),此時得到的美拉德反應(yīng)產(chǎn)物具有較高的抗氧化性能,有望用作食品抗氧化劑。另外,為了改善殼聚糖膜的性能,將殼聚糖膜浸入到不同濃度的木聚糖NaOH溶液中。在此過程中,木聚糖分子進(jìn)入殼聚糖膜的縫隙中形成小的球結(jié),隨著木聚糖濃度的增加球結(jié)逐漸增大,并且木聚糖與殼聚糖之間也形成了較強的分子間相互作用力,當(dāng)木聚糖濃度為3%時,得到致密光滑的木聚糖/殼聚糖復(fù)合膜。結(jié)果表明,此復(fù)合膜的拉伸強度、斷裂伸長率以及抗紫外能力均隨著木聚糖溶度的增加而增加,復(fù)合膜的水蒸汽透過率、吸水性以及氧氣阻隔性能均優(yōu)于殼聚糖膜,此復(fù)合膜也具有較好的疏水性。因此該復(fù)合膜與單純殼聚糖膜相比更適用于食品包裝膜。2、木聚糖綠色制備納米金屬材料及其性能研究以木聚糖作為還原劑和穩(wěn)定劑,在微波條件下進(jìn)行Tollens反應(yīng)制備了納米銀,并得到木聚糖/納米銀復(fù)合材料,在加熱條件下制備了納米金,并得到木聚糖/納米金復(fù)合材料。其中納米銀的最佳制備條件為:微波加熱溫度60~70°C,微波功率800 W,微波時間30 min,氨水濃度2%,木聚糖與AgNO3的比例50 mg:0.13 mmol,在此條件下生成的納米銀被木聚糖包裹、分散均勻、粒徑分布為20~35 nm;納米金的最佳制備條件為:木聚糖與HAu Cl4?4H2O的質(zhì)量比0.15 g:15 mg,反應(yīng)溫度80°C,反應(yīng)時間40 min,在此條件下得到的納米金的粒徑為10~30 nm,具有較窄的粒徑分布。探討得到的木聚糖綠色合成納米貴金屬的反應(yīng)機理為:木聚糖的還原性末端基能將貴金屬離子還原為貴金屬單質(zhì),其本身也被氧化為羰基,在此過程中,木聚糖的主鏈只有輕微水解,但側(cè)鏈有部分脫落;其后納米貴金屬的晶核不斷長大,最終形成納米粒子,而木聚糖中的羥基具有很高的電負(fù)性,能夠包裹在納米貴金屬粒子表面成為穩(wěn)定劑。此外,木聚糖/納米銀和木聚糖/納米金復(fù)合材料分別能夠?qū)x子和半胱氨酸進(jìn)行高靈敏度和特異性檢測;其中木聚糖/納米銀復(fù)合材料對汞離子的最低檢測限(LOD)能達(dá)到4.6 n M,在實際水樣中對汞離子也有較好的檢測效果;木聚糖/納米金復(fù)合材料對半胱氨酸的檢測限(LOD)為0.57μM,在血漿環(huán)境中也能對半胱氨酸進(jìn)行檢測。本研究一方面為納米貴金屬的綠色合成提供了新的途徑,另一方面也將得到的納米貴金屬用于汞離子以及半胱氨酸的檢測,從而實現(xiàn)了半纖維素的高值化利用。3、木聚糖-點擊-殼聚糖季銨鹽聚合物(Xylan-click-QCS)的合成及在納米金屬材料制備中的應(yīng)用基于以上研究,本文將木聚糖與殼聚糖和納米貴金屬同時結(jié)合,以實現(xiàn)木聚糖的進(jìn)一步高值化利用。在本研究中,首先將溴代丙炔與木聚糖反應(yīng)生成丙炔基木聚糖;并將殼聚糖季銨化生成殼聚糖季銨鹽,其6位羥基被對甲苯磺�；〈笈c疊氮鈉反應(yīng)生成疊氮化殼聚糖季銨鹽,隨后在銅(I)的催化下利用點擊化學(xué)合成Xylan-click-QCS。然后利用Xylan-click-QCS制備了納米銀與納米金,其中木聚糖中的還原性末端基以及殼聚糖季銨鹽中的季銨基作為還原性基團(tuán)能將金屬離子還原成金屬單質(zhì),而點擊化學(xué)產(chǎn)物中的三唑環(huán)不僅能夠為納米貴金屬粒子的生長提供原始位點,也能鈍化生成的納米金屬粒子表面使其穩(wěn)定存在。其中生成的納米銀粒徑分布有兩個范圍:10~20 nm和2~5 nm,這說明除了納米顆粒,此反應(yīng)也生成了納米銀簇,將兩者分離后可大大拓寬產(chǎn)物的應(yīng)用范圍;而生成的納米金粒徑分布為20~30 nm,與木聚糖合成的納米金相比粒徑分布更加均一。
文內(nèi)圖片：
圖片說明：常見半纖維素糖單元[8]
[Abstract]:The problems of environment pollution and energy shortage make the development and utilization of renewable resources widely concerned. The hemicellulose comes from the cell wall of the plant, is a natural polysaccharide which is abundant in nature and low in cost, and has been widely used in the fields of paper making, energy, food and biological medicine, and has gradually become a novel raw material which can be substituted for petrochemical products, non-toxic, degradable and environment-friendly. However, a semi-cellulose complex sugar component, a higher degree of branching, and an amorphous structure makes it possible to make only low-value-added use. In order to realize the high-level utilization of hemicellulose, the research adopts a model of hemicellulose as a base material, and on the one hand, the xylan is structurally assembled with another natural polysaccharide (chitosan), and on the other hand, the xylan is effectively compounded with the inorganic nano-noble metal material, The preparation and properties of the xylan-based composite functional material were studied. The main contents of this study were as follows:1. The preparation and the properties of the xylan/ chitosan complex were discussed in order to avoid the precipitation of the xylan and the chitosan in the basic and acidic solution, so that the reaction between the chitosan and the chitosan is not carried out smoothly, and the xylan and the chitosan are dissolved in the same ionic liquid to carry out Maillard reaction, so that the amino groups in the chitosan are grafted with the reducing terminal aldehyde groups in the xylan, and finally the macromolecular substance type black essence is generated, Namely a xylan-chitosan Maillard reaction product. The results show that Maillard reaction is more likely to occur when the mass ratio of the xylan and the chitosan is 1:1, and the obtained Maillard reaction product has high antioxidant performance and is expected to be used as a food antioxidant. In addition, in order to improve the performance of the chitosan membrane, the chitosan membrane was immersed in a different concentration of the xylan NaOH solution. In the process, the xylan molecules enter into the gap of the chitosan membrane to form a small spherical junction, and as the increase of the concentration of the xylan increases gradually, a stronger intermolecular interaction force is formed between the xylan and the chitosan, when the concentration of the xylan is 3 percent, And a dense and smooth xylanase/ chitosan composite membrane is obtained. The results show that the tensile strength, elongation at break and the ultraviolet resistance of the composite membrane are increased with the increase of the solubility of the xylan, and the water vapor transmission rate, the water absorption and the oxygen barrier properties of the composite membrane are superior to that of the chitosan membrane, and the composite membrane also has good hydrophobicity. Therefore, the composite membrane is more suitable for the food packaging film than the pure chitosan membrane. And the xylan/ nano-silver composite material is obtained, and the nano-gold is prepared under the heating condition, and the xylan/ nano-gold composite material is obtained. The preparation conditions of the nano silver are as follows: the microwave heating temperature is 60 to 70 DEG C, the microwave power is 800W, the microwave time is 30 minutes, the ammonia concentration is 2 percent, the proportion of the xylan and the AgNO3 is 50 mg to 0.13 mmol, the nano silver generated under the condition is wrapped by the xylan, the dispersion is uniform, and the particle size distribution is 20 to 35 nm; The optimum preparation conditions of the nano-gold are as follows: the mass ratio of the xylan and the HAuCl4-4H2O is 0.15 g:15 mg, the reaction temperature is 80 DEG C, the reaction time is 40 min, the particle size of the nano-gold obtained under the condition is 10-30 nm, and the nano-gold has a narrow particle size distribution. The reaction mechanism of the obtained xylan green synthetic nano-noble metal is that the reductive end group of the xylan can reduce the noble metal ions into a noble metal simple substance, and the noble metal ion is also oxidized into a metal base, in which the main chain of the xylan is only slightly hydrolyzed, but the side chain is partially shed; And finally, the nano-particles are formed, and the hydroxyl groups in the xylan have high electronegativity and can be coated on the surface of the nano-noble metal particles to be a stabilizer. in addition, that xylan/ nano-silver and the xylan/ nano-gold composite material can carry out high-sensitivity and specific detection on the mercury ion and the cysteine, wherein the minimum detection limit (LOD) of the xylan/ nano-silver composite material to the mercury ion can reach 4.6 n-M, The detection limit of cysteine (LOD) was 0.57. m u.M, and cysteine was also detected in the plasma environment. on the one hand, the invention provides a new way for green synthesis of the nano-noble metal, and on the other hand, the obtained nano-noble metal is used for the detection of the mercury ions and the cysteine, The synthesis of xylan-click-chitosan quaternary salt-salt polymer (Xylan-click-QCS) and its application in the preparation of nano-metal materials are based on the above research. in the present study, first, the bromopropyne and the xylan are reacted to form the propargyl-xylan, and the chitosan quaternary salt is generated by the chitosan quaternary salt, and the 6-position hydroxyl group is replaced by the toluene sulfo-base and reacts with the sodium azide to generate the azido chitosan quaternary salt, Xylan-click-QCS is then chemically synthesized under the catalysis of copper (I). then the nano-silver and the nano-gold are prepared by using the Xylan-click-QCS, And the three-ring ring in the chemical product can not only provide the original site for the growth of the nano-noble metal particles, but also can passivate the surface of the generated nano metal particles to make the surface of the nano metal particle stable. wherein the generated nano-silver particle size distribution has two ranges of 10-20 nm and 2-5 nm, which indicates that the nano-silver cluster is formed in addition to the nano-particles, and the application range of the product can be greatly expanded after the nano-silver clusters are separated; and the generated nano-silver particle size distribution is 20-30 nm, Compared with the nano-gold synthesized by the xylan, the particle size distribution is more uniform.
【學(xué)位授予單位】：華南理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：O636.1;TB332

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本文編號：2512327