Surface characterization of TEMPO‐oxidized bacterial cellulose

In this study, we focused on the surface character of bacterial cellulose (BC) before and after oxidation mediated by 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO).Solid‐state ¹³C NMR, XPS, SEM, contact angle and surface free energy analyses were performed to investigate the effects of various parameters (reaction time and oxidant and catalyst concentrations) on the surface composition, morphology and polarity of the BC. The results provided by the combined use of these techniques showed that hydrogen bonds were disrupted on the BC surface after carboxylation occurred; therefore, the surface of oxidized BC was rougher than that of the original BC, and the surface free energy, especially the polar components, increased after oxidation. Copyright © 2013 John Wiley & Sons, Ltd.     

Novel Synthesis of some Spiro Heterocycles Derived from 3-Hydroxy-3(2-Oxocyclohexyl)-Indolin-2-One

The reaction of 3-hydroxy-3(2-oxocyclohexyl)indolin-2-one 1 with some active methylene, bidentates, phenylisocyanate, phenylisothiocyanate, carbon disulfide, benzaldehyde, ketoketene S,S-acetal, cyanoketene S,S-acetal, active halo compounds or benzylidenemalononitrile affords a series of new spiro heterocyclic systems.     

The Electronic Nature of the 1,4‐β‐Glycosidic Bond and Its Chemical Environment: DFT Insights into Cellulose Chemistry

The molecular understanding of the chemistry of 1,4‐β‐glucans is essential for designing new approaches to the conversion of cellulose into platform chemicals and biofuels. In this endeavor, much attention has been paid to the role of hydrogen bonding occurring in the cellulose structure. So far, however, there has been little discussion about the implications of the electronic nature of the 1,4‐β‐glycosidic bond and its chemical environment for the activation of 1,4‐β‐glucans toward acid‐catalyzed hydrolysis. This report sheds light on these central issues and addresses their influence on the acid hydrolysis of cellobiose and, by analogy, cellulose. The electronic structure of cellobiose was explored by DFT at the BB1 K/6‐31++G(d,p) level. Natural bond orbital (NBO) analysis was performed to grasp the key bonding concepts. Conformations, protonation sites, and hydrolysis mechanisms were examined. The results for cellobiose indicate that cellulose is protected against hydrolysis not only by its supramolecular structure, as currently accepted, but also by its electronic structure, in which the anomeric effect plays a key role.     

Electro‐optical cells using a cellulose derivative and cholesteric liquid crystals

A cellulose derivative/liquid crystal composite‐type electro‐optical cell using a commercial cholesteric liquid crystal (CLC) was investigated. The electro‐optical properties of the system were examined, i.e. the dependence on applied voltage of the reflected wavelength and the minimum and maximum transmissions. A thin film of the CLC was dispersed with a cross‐linked cellulose film of 25 µm thickness. In the voltage dependence of the reflected wavelength it was verified that there is a hysteresis in the reflected wavelength. The variation of the reflected wavelength with temperature was also determined. The results are analysed in the framework of similar systems described in the literature for CLC dispersed in a polymer matrix.     

Adsorption of Hg(II) Ions onto Binary Biopolymeric Beads of Carboxymethyl Cellulose and Alginate

The removal of Hg(II) ions from aqueous solution by adsorption onto cross-linked polymeric beads of carboxymethyl cellulose (CMC) and sodium alginate was studied at fixed pH (6) and room temperature 28 ± 0.2°C. The cross-linked polymeric beads were characterized by FTIR spectra. Sorption capacity of the polymer for the mercury ions was investigated in aqueous media consisting different amounts of mercury ions (2.5 to 100 mg dm^?3) and at different pH values (2 to 8). Adsorption behavior of Hg(II) ions could be modeled using both the Langmuir and Freundlich isotherms. The dynamic nature of adsorption was quantified in terms of several kinetic constants such as rate constants for adsorption (k₁) and Lagergreen rate constant (K_ad). The influence of various experimental parameters such as effect of pH, contact time, solid-to-liquid ratio, salt effect, and temperature effect etc. were investigated on the adsorption of Hg(II) ions.     

Graphene oxide reinforced polyamide nanocomposite coated on paper as a novel layered sorbent for microextraction by packed sorbent

ABSTRACT

In this work, a novel layered sorbent for microextraction by packed sorbent (MEPS) was introduced, which has been prepared by coating graphene oxide/polyamide (GO/PA) nanocomposite (NC) onto cellulose paper through solvent exchange method. Scanning electron microscopy (SEM) was applied to investigate the surface characteristic and morphology of PA and GO/PA NC coated on cellulose paper. The prepared MEPS device was used for extraction of organophosphorous pesticides (OPPs) including chlorpyrifos, fenthion, fenithrothion, ethion, edifenphos and phosalone in environmental aqueous samples followed by detection using gas chromatography-flame ionisation detector (GC-FID). Important parameters affecting the MEPS method including pH of sample solution, extraction draw-discard cycles, sorbent layers, desorption solvent volume and desorption draw-eject number were studied and optimised using central composite design (CCD). Based on the method validation, limits of detection (LODs) were in the range of 0.2–1 µg L^?1. The calibration graphs for chlorpyrifos, fenthion and edifenphos are linear in the concentration range of 1 to 500 µg L^?1; for ethion and phosalone are linear in the range of 1–1000 µg L^?1 and for fenithrothion is linear in the range of 3–1000 µg L^?1. The method precision (RSD %) with six replicates determinations was in the range of 3 to 9.4 % and 3.9 to 11.9% for distilled water and spiked river water sample, respectively, at the concentration level of 300 µg L^?1 . The developed method was applied successfully to determine OPP compounds in river, dam and tap water samples; accordingly, the relative recoveries (RR%) were obtained in the range of 77.8 to 113.3%.     

以阴离子交换纤维素膜作基质室温燐光法测定痕量2,6-二氨基嘌呤的研究

本文对2,6-二氨基嘌呤(DAP)在不同的基质上和不同的重原子微扰剂存在下的室温燐光(RTP)强度进行比较,结果表明,NaI-NaAc是有效的重原子体系。适宜的固体基质为阴离子交换纤维素(二乙氨基乙基纤维素)膜(DEAE)和慢速定量滤纸。前者对酸度的变化具有较好的缓冲能力,本文提出了以DEAE为固体基质,测定痕量DAP的RTP法。     

可再生纤维素/环糊精聚合物对水中亚甲基蓝吸附行为

利用甘蔗渣提取纤维素修饰环糊精聚合物,成功制备可再生纤维素/环糊精聚合物（SUG-EPI-CDP）吸附剂。采用傅利叶红外光谱仪（FT-IR）与热重分析仪（TGA）对材料进行表征,同时考察了该材料对水中亚甲基蓝（MB）吸附特性和机理的影响。结果表明：在溶液pH值为7、温度为30 ℃的条件下,SUG-EPI-CDP可在120 min内有效去除MB,去除率达80.9%。通过模型拟合发现,SUG-EPI-CDP对MB的吸附是自发且吸热的过程,符合准二阶动力学方程和Langmuir等温线模型。该吸附剂实验最大吸附量达8.1 mg/g,远高于其他废料所制备的吸附剂。结果表明,利用可再生纤维素修饰可有效提高环糊精聚合物的吸附性能,同时为甘蔗渣资源化利用提供了新途径。     

Self-assembly on natural cellulose: Towards high-efficient catalysts

Nanoarchitectures based on the layer-by-layer self-assembly technique hold great potential for the availability and applicability of bio-inspired functional materials. The introduction of various specific functional building blocks onto the nanofibers of natural cellulose substances (e.g., commercial filter paper, cotton, etc.) through the self-assembly approach provides a facile strategy for the fabrication of artificial nanomaterials. This review summarizes a series of cellulose-based catalytic materials fabricated by utilizing the natural cellulose substance as the structural scaffolds or templates through the LbL self-assembly process. The unique three-dimensional network porous structures and high surface areas of the cellulose substances were maintained by the resultant cellulose-derived catalysts, while the excellent mechanical strength of the cellulose-based membrane catalysts was inherited from the initial cellulose substrates. When employed for the photodegradation of organic dyes, the photocatalytic hydrogen production from water splitting, and the antibiosis, these cellulose-based catalysts exhibited high activities and excellent cycling stabilities.     

药用缓释辅料——羟丙基甲基纤维素的合成及其缓释性能的研究

本文研究了药物缓释材料HPMC的合成方法,探讨了碱纤维素制备,醚化剂浓度,混合醚化剂配经以及产品后处理对高粘度HPMC的影响。本文还初步对KCl,氨茶碱,硝酸异山梨醇酯等药物采用合成的HPMC作辅料,进行了缓释制剂的研究,结果表明合成的HPMC具有满意的缓释性能。