纳米Fe_2O_3作为润滑油添加剂的摩擦磨损性能

采用烧结方法制备得到纳米α-Fe_2O_3,利用X射线衍射仪(XRD)和透射电镜(TEM)对样品进行了表征,研究了纳米α-Fe_2O_3作为液体石蜡添加剂的摩擦磨损性能。结果表明,添加纳米添加剂后,润滑油摩擦系数改变不明显,但磨损率显著降低。磨损率与纳米α-Fe_2O_3添加剂的表面积和添加量密切相关,当纳米材料的表面积为47m~2/g时磨损率最低,磨损率值降低为3.78×10~(-15) m~2/g;添加量为1.0wt%,润滑油磨损率最低。     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

CoCr2O4纳米晶的制备及其磁性研究

通过高分子金属络合物热解法制备了COCr2O4纳米晶，并对它的表面微结构和磁性能进行了表征。通过高分辨电镜和傅立叶红外光谱的研究发现在平均粒径为12nm的纳米晶表面不仅有晶格炔陷，而且吸附有大量聚合物分解后的有机碎片，这些有机碎片对纳米晶表面磁矩的钉扎以及纳米晶自身的表面晶格缺陷．导致自旋无序的表面和相对自旋有序的核之间产生强的交换耦合作用．从而使得纳料晶呈现出奇特的磁性能，如低温下存在较走的矫顽力和偏置场等。     

Structural studies of pulsed-laser deposited nanocomposite metal-oxide films

Pulsed laser deposition in vacuum has been used to develop metal-oxide nanocomposite films with well controlled structural quality. Results for the copper–aluminium oxide (Cu:Al₂O₃) system are used to illustrate the main morphological and structural features of these films. High resolution transmission electron microscopy (TEM) analysis shows that the films consist of Cu nanocrystals with average dimensions that can be controlled between 2 nm and 10 nm embedded in an amorphous Al₂O₃ matrix. It is observed that the in-plane shape of the nanocrystals evolves from circular to elongated, and the number of nanocrystals per unit area decreases as their size increases. This evolution is explained in terms of nucleation at the substrate surface and coalescence during the later stages of growth. The thermal stability of the films has been studied by in situ TEM annealing and no transformation could be observed up to about 800 °C when partial crystallization of the Al₂O₃ starts.     

Surface and defect modifications in mixture of ZnO and carbon nanocrystals at mechanical processing

The Raman scattering and photoluminescence (PL) spectra, PL temperature dependences and scanning electronic microscopy (SEM) images have been studied in the mixture of ZnO+1.0%C nanocrystals (NCs) before and after intensive mechanical processing (MP). The study reflects the diversity of physical processes occurring at MP: the amorphization of the ZnO NC surface, transforming an amorphous graphite into graphene monolayers covered of ZnO NCs, changing the ZnO NC shape owing to the plastic deformation and crushing the individual ZnO NCs, the partial oxidation of graphene layers with the formation of graphene oxide passivating ZnO NCs, the formation of graphite oxide when temperature increasing at MP, as well as the ZnO defect modification near the surface of ZnO NCs, etc. Additionally the new ‘blue” PL band peaked at 2.82–2.92 eV has been revealed in PL spectra after MP, which is assigned to emission of graphite (graphene) oxides. All mentioned processed have been studied and discussed in details.     

An Injectable Hydrogel for Simultaneous Photothermal Therapy and Photodynamic Therapy with Ultrahigh Efficiency Based on Carbon Dots and Modified Cellulose Nanocrystals

The convenience of injectable hydrogels that can provide high loading of diverse phototherapy agents and further long-time retention at the tumor site has attracted tremendous interest in simultaneous photothermal and photodynamic cancer therapies. However, to incorporate the phototherapy agents into hydrogels, complex modifications are generally unavoidable. Moreover, these phototherapy agents usually suffer from low efficiency and work at different irradiation wavelengths outside the near infrared windows. Hence, a method for the fabrication of an injectable hydrogel for simultaneous photothermal therapy and photodynamic therapy, through the Schiff-base reaction between amido modified carbon dots (NCDs) and aldehyde modified cellulose nanocrystals is proposed. The NCDs act as both phototherapy agents and crosslinkers to form hydrogels. Significantly, the NCDs demonstrate an extremely high photothermal conversion efficiency of 77.6% which is among the highest levels for photothermal agents and a high singlet quantum yield of 0.37 under a single 660 nm light-emitting diode irradiation. The hydrogels are examined through in vitro and in vivo animal experiments which show nontoxic and effectively tumor inhibition. Thus, the strategy of direct reaction of phototherapy agents and the matrix not only provides new strategies for injectable hydrogel fabrication but paves a new road for advanced tumor treatment.