介绍一个与材料相关的研究型综合化学实验——壳聚糖的制备与表征

在中国科学技术大学夏季学期的研究型实验课程"化学科研基础训练"中开设"壳聚糖的制备与表征"综合实验,以龙虾壳为原料,通过除蛋白、脱盐、脱色、脱乙酰等一系列反应,制备得到目标产物壳聚糖。运用红外光谱、核磁共振仪、黏度法、滴定等对产品的结构及性能进行表征。     

ZnO nanowire lines and bundles: Template-deformation-guided alignment for patterned field-electron emitters

One-dimensional ZnO materials have been promising for field-emission (FE) application, but how to facially control the alignment of ZnO emitters is still a great challenge especially for patterned display application. Here, we report the fabrication of novel ZnO nanowire (NW) line and bundle arrays for patterned field-electron emitters. The effects of PS template size and heating time on the resulted ZnO nanoarrays were systematically studied. The deformation degree of PS templates was controlled and hence utilized to adjust the alignment of electrochemically deposited ZnO arrays. It was found that the length of NW lines and the density of NW bundles can effectively tuned by the PS template heating time. The optimal FE performance with turn-on electric field as low as of 4.4 V μm⁻¹ and the field-enhancement factor as high as of 1450 were achieved through decreasing the screening effect among the patterned field-electron emitters.     

Path integral quantization corresponding to the deformed Heisenberg algebra

In this paper, the deformation of the Heisenberg algebra, consistent with both the generalized uncertainty principle and doubly special relativity, has been analyzed. It has been observed that, though this algebra can give rise to fractional derivative terms in the corresponding quantum mechanical Hamiltonian, a formal meaning can be given to them by using the theory of harmonic extensions of function. Depending on this argument, the expression of the propagator of the path integral corresponding to the deformed Heisenberg algebra, has been obtained. In particular, the consistent expression of the one dimensional free particle propagator has been evaluated explicitly. With this propagator in hand, it has been shown that, even in free particle case, normal generalized uncertainty principle and doubly special relativity show very much different result.     

Elongating the area of plasma/fluid interaction of surface nanosecond pulsed discharges

Plasma-assisted flow control is of high industrial interest, but practical applications at full scale require a large surface of interaction. Nanosecond pulsed Dielectric Barrier Discharge (DBD) have demonstrated promising results of flow control, but their interacting region is limited to only a few cm². In this paper, the conditions to extend a surface nanosecond DBD are documented. It is shown that a sliding discharge regime can fully fill an inter-electrode distance of 40 mm. This discharge regime promotes the formation of two hemispheric pressure waves originating from both air-exposed electrodes while an horizontal region of pressure gradient is also observed.     

Studies on metabolism of total glucosides of paeony from Paeoniae Radix Alba in rats by UPLC‐Q‐TOF‐MS/MS

Total glucosides of paeony are the active constituents of Paeoniae Radix Alba. In this study, a novel strategy was proposed to find more metabolites and the differences between paeoniflorin, albiflorin and total glucosides of paeony (TGP). This strategy was characterized as follows: firstly, the animals were divided into three groups (paeoniflorin, albiflorin and TGP) to identify the source of TGP metabolites from paeoniflorin or albiflorin; secondly, a generic information‐dependent acquisition scan for the low‐level metabolites was triggered by the multiple mass defect filter and dynamic background subtraction; thirdly, the metabolites were identified with a combination of data‐processing methods including mass defect filtering, neutral loss filtering and product ion filtering; finally, a comparative study was used in the metabolism of paeoniflorin, albiflorin and TGP. Based on the strategy, 18 metabolites of TGP, 10 metabolites of paeoniflorin and 13 metabolites of albiflorin were identified respectively. The results indicated that the hydrolysis, conjugation reaction and oxidization were the major metabolic pathways, and the metabolic sites were the glycosidic linkage, the ester bond and the benzene ring. This study is first to explore the metabolism of TGP, and these findings enhance our understanding of the metabolism and the interactions of paeoniflrin and albiflorin in TGP. Copyright © 2015 John Wiley & Sons, Ltd.     

Thermal gradient induced sidebranching in directional solidification

The polycrystalline perovskitelike manganese oxides La_1-xA_xMnO (A = Na, and K, ) have been fabricated by sol-gel technique. For all the compositions explored in this work, the average manganese oxidation state is practically constant, at for A = Na, and for A = K, respectively. A close relationship is confirmed to hold between the Curie temperature (T_c) and the bond distance of Mn-O. Results of magnetic measurements show that these materials can be utilized as suitable candidates for magnetic refrigerants with wide applied temperature span, for their significant entropy change and the easily tuned Curie temperature. Received: 12 September 1997 / Revised: 18 December 1997 / Accepted: 21 January 1998     

Surface structures formed by individual adsorption and coadsorption of Mn and Bi on Cu(0 0 1), studied by LEED

We have studied the individual adsorption of Mn and Bi, and their coadsorption on Cu(0 0 1) by low-energy electron diffraction (LEED). For Mn, we have determined the c(2 × 2) structure formed at 300 K, whose structure had been determined by several methods. We reconfirmed by a tensor LEED analysis that it is a substitutional structure and that a previously reported large corrugation (0.30 Å) between substitutional Mn and remaining surface Cu atoms coincides perfectly with the present value. In the individual adsorption of Bi, we have found a c(4 × 2) structure, which is formed by cooling below ∼250 K a surface prepared by Bi deposition of ∼0.25 ML coverage at 300 K where streaky half-order LEED spots appear. The c(4 × 2) structure has been determined by the tensor LEED analysis at 130 K and it is a substitutional structure. In the coadsorption, we found a c(6 × 4) structure, which has been determined by the tensor LEED analysis. It is very similar to the previously determined structure of the c(6 × 4) formed by coadsorption of Mg and Bi, and embedded MnBi₄ clusters are arranged in the top Cu layer instead of MgBi₄. Large lateral displacements of Bi atoms in the c(6 × 4)-(Mn + Bi) suggest that the Mn atoms undergo the size-enhancement caused by their large magnetic moment.