首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 62 毫秒
1.
通过激光溅射法产生了V2On+ (n=1, 2), V3On+ (n=1, 2, 3)和V4O3+等缺氧的钒氧团簇,并采用532和266 nm波长的激光对它们进行了光解研究. 利用密度泛函理论计算与激光光解实验相结合确定了这些团簇的几何结构和可能的光解通道. 激光光解实验表明V相似文献   

2.
本文通过一个简单的、温和的方案制备了平均尺寸为120 nm,介孔结构的纳米粒子MnSiO3@Fe3O4@C. 粒子的细胞毒性微小,可以用作T1-T2*双模MRI造影剂. 酸性条件下MnSiO3@Fe3O4@C释放出大量的Mn2+缩短T1弛豫时间,提高成像分辨率. 超顺磁性的Fe3O4可以增强T2对比成像,检测病变组织. 类似于肿瘤微环境/细胞器的酸性PBS(pH=5.0)中Mn2+的释放率达到31.66%,约为中性条件(pH=7.4)下的7倍. 释放的Mn2+通过内吞作用被细胞摄取,经肾脏排出,细胞毒性实验表明,MnSiO3@Fe3O4@C具有低的细胞毒性,即使高浓度的200 ppm MnSiO3@Fe3O4@C对HeLa细胞的毒性也相对较小. 对荷瘤小鼠静脉注射定量MnSiO3@Fe3O4@C后,可以观察到一个快速增强的对比成像,给药24 h后,T1MRI信号显著增强,达到132%,而T2信号则明显降低至53.8%,活体MR成像证明了MnSiO3@Fe3O4@C可以同时作为阳性和阴性造影剂. 此外,得益于介孔MnSiO3优秀的酸敏感性,MnSiO3@Fe3O4@C可以作为一种潜在的药物载体,实现肿瘤的诊疗一体化.  相似文献   

3.
本文介绍了棒状NiCo_2O_4的制备,并将其修饰玻碳电极作为无酶葡萄糖传感器.通过简单的水热反应合成了NiCo_2O_4,然后在商用微波炉中对NiCo_2O_4进行处理,以消除水热合成过程中可能引入的残存水.扫描电镜、透射电镜、X射线衍射谱和X射线光电子能谱分析表明,微波处理前后结构无变化.通过EDS对Ni,Co,O原子比例的分析,证明微波处理对残存水的消除作用.微波处理的NiCo_2O_4(MNiCo_2O_4)作为葡萄糖传感器的灵敏度高达431.29μA mM~(-1) cm~(-2).最后,将M-NiCo_2O_4在水中浸泡不同时间后,其对葡萄糖的感应性能下降.结果表明,水热过程中引入的残存水对其电化学性能有很强的影响,微波预处理对其电化学性能也有着重要的影响.  相似文献   

4.
 采用溶胶-凝胶工艺和高温高压实验技术,制备了纳米CoFe2O4/SiO2复合材料。利用X射线衍射仪、扫描电子显微镜和振动样品磁强计,对样品的结构、微观形貌和磁性进行了研究,并对CoFe2O4中阳离子的占位情况进行了讨论。结果表明,随着处理压力的升高,样品的晶粒尺寸增大,晶格常数减小,比饱和磁化强度增大。通过计算结果可以推断,压力的升高导致CoFe2O4中的部分Fe3+从A位移向了B位,而部分Co2+则从B位移向了A位。  相似文献   

5.
高潭华  刘慧英  张鹏  吴顺情  杨勇  朱梓忠 《物理学报》2012,61(18):187306-187306
采用基于密度泛函理论的第一性原理方法, 在广义梯度近似(GGA)和GGA+U方法下对尖晶石型LiMn2O4及其Al掺杂 的尖晶石型LiAl0.125Mn1.875O4晶体的结构和电子性质进行了计算. 结果表明: 采用GGA方法得到尖晶石型LiMn2O4是立方晶系结构, 其中的Mn离子为+3.5价, 无法解释它的Jahn-Teller 畸变. 给出的LiMn2O4能带结构特征也与实验结果不符. 而采用GGA+U方法得到在低温下的LiMn2O4和其掺杂 体系LiAl0.125Mn1.875O4的晶体都是正交结构, 与实验一致. 也能明确地确定Mn的两种价态Mn3+/Mn4+的分布并且能够说明Mn3+O6z方向有明显的Jahn-Teller 畸变, 而Mn4+O6则没有畸变. LiMn2O4的能带结构与实验比较也能够符合. 采用GGA+U方法对Al掺杂体系的LiAl0.125Mn1.875O4的研究表明, 用Al替换一个Mn不会明显地改变晶体的电子性质, 但可以有效地消除Al3+O6 八面体的Jahn-Teller畸变, 从而改善正极材料LiMn2O4的性能, 这与电化学实验的观察结果相一致.  相似文献   

6.
Gd2O3:Eu3+纳米晶的燃烧合成及光致发光性质   总被引:1,自引:0,他引:1       下载免费PDF全文
采用柠檬酸作燃烧剂用燃烧合成法制备了Gd2O3:Eu3+纳米晶.用X射线衍射仪(XRD)、高分辨透射电子显微镜(HRTEM)和荧光分光光度计等对Gd2O3:Eu3+纳米晶的结构、形貌和发光性能进行了分析.结果表明:不同柠檬酸与稀土离子配比(C/M)制备的样品经800℃ 退火1 h后,均得到了纯立方相的Gd2O3:Eu3+纳米晶,晶粒尺寸约为30 nm,尺寸分布较窄,其中以C/M=1.0时制备的纳米晶结晶性最好,发光强度最大.Gd2O3:Eu3+纳米晶主发射峰位置均在612 nm处 (5D07F2跃迁),激发光谱中电荷迁移态发生红移,观察到Gd3+向Eu3+的有效能量传递.对柠檬酸与稀土离子配比(C/M)对结晶度、发光性质等的影响也进行了分析和讨论.  相似文献   

7.
以传统的浸渍法,在不同焙烧温度下制备了用于CO氧化反应的Co3O4/SiO2催化剂.通过激光拉曼光谱(Raman)、X射线光电子能谱(XPS)、X射线衍射(XRD)、程序升温还原(TPR)和X射线吸收精细结构谱(XAFS)表征了该系列催化剂的结构.在所有的催化剂中,XRD和Raman光谱都只检测到了Co3O4晶相的存在.与Co3O4体相相比,XPS结果表明在200 oC焙烧的(Co3O4(200)/SiO2)催化剂中Co3O4表面上存在着过量的Co2+.与XPS的结果一致,TPR结果表明Co3O4(200)/SiO2催化剂中Co3O4表面上存在氧缺陷, 并且XAFS结果也表明Co3O4(200)/SiO2催化剂中Co3O4具有更多的Co2+.提高焙烧温度使得过量的Co2+进一步氧化为Co3+,同时降低了表面氧缺陷浓度,从而得到计量比的Co3O44/SiO2催化剂.在所有的负载催化剂中Co3O4(200)/SiO2催化剂表现出了最好的CO氧化催化性能,表明过量Co2+和表面氧缺陷的存在能够促进Co3O4催化CO氧化反应的活性.  相似文献   

8.
本文利用脉冲激光溅射-超声分子束载带离子源在气相中产生了HC2nO+ (n=3-6)正离子. 通过对贴附CO的络合物离子的红外光解离光谱实验获得了HC2nO+正离子在1600∽3500 cm-1范围内的红外光谱. 通过比较实验光谱和理论模拟光谱确定了HC2nO+正离子具有端接氢和氧的直线型碳链衍生物结构,基态为三重态,单重态比三重基态能量高10∽15 kcal/mol. 成键分析表明HC2nO+中的碳链具有连烯的结构特征.  相似文献   

9.
用微波辅助水热-煅烧法成功合成了花状NaY(MoO4)2颗粒,用XRD、XPS、FESEM进行了表征,提出了花状NaY(MoO4)2颗粒可能的形成机理. 采用相同的方法合成了NaY(MoO4)2:Eu3+荧光体,该荧光材料在612 nm处有一个强的发射峰,可用作白色发光二极管的红色磷光剂. 此外,微波辅助水热-煅烧法可能发展成为制备其他花状稀土钼酸盐的有效途径.  相似文献   

10.
本文采用化学湿磨法,首次将金属氧化物Mn3O4包覆于LiNi0.5Mn1.5O4颗粒表面,使得电极材料的电子电导率从1.53×10-7 S/cm 提高到3.15×10-5 S/cm. 电化学测试结果表明Mn3O4包覆大大提高LiNi0.5Mn1.5O4正极材料的倍率性能和高温循环稳定性. 最佳包覆样品为2.6wt% Mn3O4包覆的LiNi0.5Mn1.5O4,在10 C倍率下具有108 mAh/g的高放电容并且在55 °C下100次循环后仍有78%的容量保持率,远大于未包覆样品67%的容量保持率.  相似文献   

11.
Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.  相似文献   

12.
A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.  相似文献   

13.
The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.  相似文献   

14.
A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.  相似文献   

15.
16.
Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·104 Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.  相似文献   

17.
A transient suppression method for piezoelectric ceramic transducer is presented. By adding some special pedestal pulses to the original transmitted signal, the transient effects in the output of the transducer can be just precisely transmission by use of a narrowband transducer. canceled, thereby achieving the broadband The experimental results show that the transient responses of the sinusoid pulses and coded signals are suppressed successfully and the acoustic waveforms radiated into the surrounding water are improved significantly.  相似文献   

18.
We experimentally demonstrate amplitude squeezed soliton utilizing intensity-dependent self-phase modulation in an asymmetric Sagnac interferometer.The system.whose components are connected via ferrule connector/physical connection(FC/PC)fiber connectors,constitutes all-fiber configuration to generate squeezed soliton.Soliton amplitude reduction measured by homodyne detection is near 4.0 dB below the shot-noise level.Optimal squeezing fields in both simple and compact all-fiber configuration are obtained.  相似文献   

19.
The(2 1)-dimensional nonlinear Schr(o)dinger(NLS)equation with spatially inhomogeneous nonlinearities is investigated,which describes propagation of light in(2 1)-dimensional nonlinear optical media with inhomogeneous nonlinearities.New types of optical modes and nonlinear effects in optical media are presented numerically.The results reveal that the regular split of beam can be obtained in (2 1)-dimensional nonlinear optical media with inhomogeneous nonlinearities,by adjusting the guiding parameter.Furthermore,the stability of beam regular split is discussed numerically,and the results reveal that the beam regular split is stable to the finite initial perturbations.  相似文献   

20.
In the real-world application of face recognition system, owing to the difficulties of collecting samples or storage space of systems, only one sample image per person is stored in the system, which is so-called one sample per person problem. Moreover, pose and illumination have impact on recognition performance. We propose a novel pose and illumination robust algorithm for face recognition with a single training image per person to solve the above limitations. Experimental results show that the proposed algorithm is an efficient and practical approach for face recognition.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号