聚乙烯亚胺对氧化锌纳米阵列形貌的影响

采用化学沉淀法,以硝酸锌和六次亚甲基四胺的水溶液为生长溶液,在涂覆氧化锌晶种层的玻璃衬底上制备了定向生长的氧化锌纳米棒阵列,并研究了添加剂聚乙烯亚胺的浓度对氧化锌纳米棒形貌和结构的影响.X射线衍射和场发射扫描电镜的结果表明,合成的氧化锌纳米棒阵列较为均匀致密,具有六方纤锌矿结构,且有沿(002)晶面择优生长的特性;随着聚乙烯亚胺浓度的增加,氧化锌纳米棒的直径减小,直径分布趋于均匀,且氧化锌纳米棒的形貌也从锥状转变为柱状结构;另外,聚乙烯亚胺的加入对氧化锌的生长速度具有抑制作用,当聚乙烯亚胺的浓度增加至0.012 mol·L-1时,无氧化锌阵列生长.对氧化锌纳米棒阵列进行了拉曼光谱表征,结果表明,随着溶液中聚乙烯亚胺浓度的增加,氧化锌纳米棒的氧空位缺陷减少.最后,对聚乙烯亚胺浓度对氧化锌纳米阵列影响的机理进行了探讨.     

溶剂效应对DCM发光特性的影响

有机发光二极管利用有机半导体光电功能材料的电致发光效应,具有许多优异性能,是新一代有发展前途的平板显示器件及光源。有机发光材料的光电特性、光物理、光化学过程直接决定了有机发光二极管的性能。利用荧光光谱方法观察典型高效有机小分子激光染料DCM在不同溶剂中的发光特性,研究其与溶剂分子的相互作用,即溶剂效应对其发光特性的影响。结果表明DCM溶液的荧光光谱中心波长随溶剂极性增大而红移,相对发光强度基本上随溶剂极性增大。同时,还观察了不同浓度DCM溶液的发光特性,研究DCM分子间相互作用导致的浓度猝灭效应,结果表明DCM溶液浓度为10^-6mol／L时,DCM溶液相对发光强度最大。     

花状的氧化锌纳米结构的制备及其光学性能

以氢氧化钠和六水合硝酸锌为反应物,在未使用任何表面活性剂的简单反应体系中制得了玫瑰花状ZnO纳米结构,采用X射线衍射(XRD)、扫描电子显微镜(SEM)和室温荧光光谱对产物的晶体结构、形貌和发光性质进行了表征和分析.测试结果表明,所得产物为六方纤锌矿结构ZnO纳米材料,产物结晶完整,尺寸较均匀.这种简单水热法制备的ZnO纳米材料仅在384nm处具有一个较强的紫外发光峰,而在黄绿区几乎没有发光峰,进一步证明了所得样品结晶良好,没有缺陷和空位.以上结果表明所制备的氧化锌纳米材料具有优异的紫外光发射能力.     

Synthesis and Solvent Polarity-Sensitive Photoluminescent Property of 4-Phenylethynyl-4'-Dimethylaminochalcone

以4-溴-4'-二甲氨基查尔酮和苯乙炔为原料,通过Sonogashira钯催化偶联反应合成了4-苯乙炔基-4'-二甲氨基查尔酮,并通过红外光谱和核磁共振氢谱对其结构进行了表征.进一步研究了4-苯乙炔基-4’-二甲氨基查尔酮在不同极性的溶剂中的紫外可见吸收光谱和荧光光谱,结果表明该化合物具有极性敏感的发光特性.     

利用红外光谱分析有机羧酸在均相反应中的配位作用机理

利用红外(IR)光谱、X射线衍射(XRD)及透射电子显微镜(TEM)等手段,对有机羧酸在尿素及硝酸铈的均相反应混合溶液中所起的配位作用进行了分析,并对产品的物相和形貌进行了测试与表征.实验结果表明:在尿素及硝酸铈的混合溶液中分别加入一元羧酸硬脂酸,二元羧酸酒石酸和三元羧酸柠檬酸时,一元羧酸硬脂酸在混合溶液中只起表面活性剂的作用,其产物为斜方晶系的单晶Ce2O(CO3)2·H2O微粉,且表面活性剂硬脂酸的加入使得晶体的晶化程度明显提高;而二元羧酸酒石酸与三元羧酸柠檬酸在均相反应中则起螯合剂的作用,分别与Ce3 形成螯合物酒石酸铈和柠檬酸铈,这些结果的造成是由于其反应机理的不同所导致的.     

网络状表面结构纳米氧化锌的发光特性

为研究表面形貌对微纳结构氧化锌晶体光学特性的影响,利用气相传输法制备了一种具有特殊表面结构的纳米氧化锌颗粒状样品.应用X射线衍射谱、电子能量散射谱和扫描电镜等对样品结构和形貌进行了分析,结果表明样品具有三种层次结构组成的网络状表面形貌|室温下以波长355 nm激光激发样品,观察到紫外峰明显被抑制的发光谱.基于样品表面周期性微结构,用时域有限差分法和严格耦合波分析法对样品发光谱特性及成因进行仿真研究.结果表明,发光谱中紫外峰的被削弱与材料能级结构无关,其形成机理缘于样品表面类蝴蝶翅膀表面微结构,类似于光子晶体表面结构颜色.     

水热法制备形貌可控的ZnMoO4微晶及其光致发光性能

以Zn(Ac)2和(NH4)6Mo7O24.4H2O为原料,分别以CTAB、SDS、PVP-K30作为辅助剂,采用水热法合成了不同形貌和结构的ZnMoO4微晶。使用X射线衍射(XRD)、扫描电镜(SEM)及光致发光光谱(PL)等分析手段对所得材料的结构、形貌及发光性能进行了分析和表征。测试结果表明:通过改变辅助剂的种类、用量和反应时间可以合成形貌可控的ZnMoO4微晶,不同形貌的样品发光强度不同,但发射中心均在565 nm左右。     

掺钴氧化锌稀磁半导体的SEM及X射线能谱微分析研究

采用水热法,以CoCl2·6H2O为前驱物,KOH作为矿化剂合成了掺钴氧化锌稀磁半导体晶体.利用扫描电子显微镜(SEM)及X射线能谱仪(XREDS)对合成晶体的微观形貌、表面及内部掺杂元素Co的相对含量和分布的均匀性进行了研究.研究结果表明:水热法合成的掺Co氧化锌晶体具有多种微观形貌,较大的晶体具有极性生长特性.随晶体形貌不同,显露面也发生了相应改变.不同微观形貌的晶体其Co含量有所差异,较大的晶体掺杂Co元素相对含量大于较小的晶体,+c(1011)显露面Co元素的含量比+c(1010)面高,锥柱状晶体其区别尤为明显.大的晶体内部存在着少量的氧化钴团簇,晶体表面与晶体内部Co元素分布相对均匀.由于Co2+具有磁性,因此,氧化钴团簇的存在将对氧化锌稀磁半导体晶体的磁性产生一定的影响.     

多孔ZnO微米球的制备及其优异的丙酮敏感特性

以六水合硝酸锌、尿素为原料,以六亚甲基四胺为表面活性剂,利用水热法合成了多孔氧化锌微米球.通过X射线衍射仪、扫描电子显微镜和吸附仪对样品的结构、形貌、比表面积和孔径进行了表征.利用所得多孔微米球氧化锌制备了气敏元件,并对其气敏特性进行了测试.结果表明:在280℃的工作温度下,表面多孔氧化锌微米球气敏元件对50 ppm的丙酮气体的灵敏度为26.8,响应时间和恢复时间分别约为4 s和10 s,并具有良好的选择性.     

电场条件下氧化锌结晶特性及极化产物的拉曼光谱分析

开展高压电场调控纳米材料结构形貌和性能研究在功能材料领域具有重要的理论和实际意义.本文在高压电场条件下合成了氧化锌纳米粉体,并对粉末试片进行了后期电场极化处理,研究了电场对氧化锌的结构形貌、点缺陷、拉曼光谱的影响.以X射线衍射仪(XRD)、扫描电镜(SEM)和拉曼光谱仪对产物的结构形貌、拉曼位移、缺陷分布等进行了表征.结果表明,高压电场条件下氧化锌的完全晶化时间和温度比未施加电场时明显延长和升高,直流电场能够显著促进前驱物中氧化锌的形核,并降低晶化速度.不同电场强度下氧化锌具有不同的显微形貌.纳米氧化锌粉末试片在直流电场中极化后,其阴极面和阳极面的拉曼光谱表现出明显的差异.有明显漏电电流的情况下,阳极面在1050 cm~(–1)处的二级光学声子模A_1(LO)的强度显著提高,且拉曼强度I_1=438 cm~(–1)和I_2=1050 cm~(–1)的比值与极化电场的场强呈线性关系.当调转试片正反面进行二次极化时,原来在阳极面尖锐的1050 cm~(–1)峰经过阴极极化而消失.阳极面1050 cm~(–1)拉曼峰的锐化与氧化锌晶粒内的缺陷重新分布和双肖脱基势垒有关.     

Self-organization of five species in a cyclic competition game

Cyclic competition game models, particularly the “rock–paper–scissors” model, play important roles in exploring the problem of multi-species coexistence in spatially ecological systems. We propose an extended “rock–paper–scissors” game to model cyclic interactions among five species, and find that two of the five can coexistent when biodiversity disappears, which is different from the “rock–paper–scissors” game. As the number of fingers is five, we named the new model the “fingers” game, where the thumb, forefinger, middle finger, ring finger, and little finger cyclically dominate their subsequent species and are dominated by their former species. We investigate the “fingers” model in two ways: direct simulations and nonlinear partial differential equations. An important finding is that the number of species in a cyclic competition game has an influence on the emergence of biodiversity. To be specific, the “rock–paper–scissors” model is in favor of maintaining biodiversity in comparison with the “fingers” model when the variables (population size, reproduction rate, selection rate, and migration rate) are the same. It is also shown that the mobility and reproduction rate can promote or jeopardize biodiversity.     

Experimental study on downstep in Chinese intonation

Downstep in pitch contour of Chinese Putonghua is examined using subtly designed sentences by controlling tone combinations. The results show both automatic and nonautomatic downstep phenomena exist in Chinese. In non-automatic downstep, low tones compress downwards the pitch range of the following syllables. and the main influence of downstep is on topline. Low tone not only lower the topline behind it, but also raise the high tones before it, the effects are compatible with each other. In automatic downstep, the topline of pitch contour in intonational phrase is presented as a linear downtrend, but it differs among speakers due to the effect of personal stress practice. In comparison with downstep phenomenon in other tone or non-tone languages, the downstep ratio in Chinese is not constant, and the domain of downstep is not limited within the adjacent tones.     

Contrastive analysis on tone between Putonghua and Taiwan Mandarin

The differences of the pitch and duration of Chinese syllables between Putonghua （PTH） and Taiwan Mandarin （TM） were studied. The speech materials to be used are not only isolated syllables, but also sentences. The results reveal that： For the isolated syllables, T1 and T2 in TM are influenced by Minnan dialect, therefore their pitch are lower than those in PTH. T3 is fall-rise in PTH, while it is fall in TM. Moreover, the syllable duration sequence for different tone is T3〉T2〉T1〉T4 in PTH, while it is T1〉T2〉T3〉T4 in TM. For the syllables in sentences, T2 is mid-rise in PTH, while it is mid-level in TM. And the T3 is longer than T4 but shorter than T1 or T2 in PTH, while it is the shortest in TM. Furthermore the effects of prosodic phrase boundary on duration for different tones are almost the same in PTH, but the lengthening part of T1 or T2 is longer than that of T3 or T4 in TM.     

Abelian-Higgs phase of SU(2) QCD and glueball energy

It is shown that SU(2) QCD admits an dual Abelian-Higgs phase, with a Higgs vacuum of a type-Ⅱ superconductor. This is done by using a connection decomposition for the gluon field and the random-direction approximation. Using a bag picture with soft wall, we presented a calculational procedure for the glueball energy based on the recent proof for wall-vortices [Nucl. Phys. B 741(2006)1].     

High efficiency filtering using two-dimensional photonic crystal coupled cavity structures

Transmission spectra of coupled cavity structures (CCSs) in two-dimensional (2D) photonic crystals (PCs) are investigated using a coupled mode theory, and an optical filter based on CCS is proposed. The performance of the filter is investigated using finite-difference time-domain (FDTD) method, and the results show that within a very short coupling distance of about 3λ, where λ is the wavelength of signal in vacuum, the incident signals with different frequencies are separated into different channels with a contrast ratio of 20 dB. The advantages of this kind of filter are small size and easily tunable operation frequencies.     

Signal generation in an isotropic medium in scanning electron acoustic microscope

Based on the research in Ref. [5][Materials Science and Engineering, 1989; A122： 57 63], an improved model of heat source is set up, the different modes of Lamb wave in an isotropic sample generated by a chopped electron beam at frequency f are obtained with integral transform and normal function expansion method, and the output signal of PZT coupled at the back surface of the sample is found out. The generation mechanism of SEAM （Scanning Electron Acoustic Microscopy） signal is discussed. It shows that the SEAM is a near field imaging technique with high spatial resolution and its best lateral spatial resolution is about 2√2α （α is the radius of the focused electron beam）. Some of experimental results of SEAM images are presented in the paper and it shows that the spatial resolution of SEAM is better than 0.5 μm and smaller than the thermal diffusion length of the sample. Therefore the character of near field imaging in SEAM is also proved experimentally.     

Real-time restoration of rotational blurred image using gradient-loading

The key to the restoration of rotational motion blurred image is how to restore the image under a low cost and to correct the irreversibility of the degradation function matrix.Based on the special qualities of degradation function matrix and precise deduction in space-domain, we present a new approach using gradient-loading for restoration of rotational blurred image.By easily adding a gradient operator, the irreversibility of the original matrix is corrected and can be applied for inverse filtering then.Gradientloading is the optimized approach which combines the advantages of both the approaches using constrained least square filtering and traditional diagonal-loading.Compared with the approach using least square filtering, its peak signal-to-noise ratio (PSNR) is improved from 3.18 to 6.46dB, while the computing time is reduced to 1/2-1/3.Experimental results demonstrate the effectiveness, noise-resistibility, robustness, and low complexity of this approach, which make it more suitable for real-time environment.     

All-Optical Logic Device Using Bent Nonlinear Tapered Y-Junction Waveguide Structure

We propose an all-optical logic device made of a bent tapered Y-junction waveguide with a Kerr-type nonlinear interface. It could provide an AND gate, OR gate, and exclusive-OR (XOR) gate. We could obtain different transmission results by adjusting the bending angle. The numerical simulation results show that the device functions as AND, OR, and XOR gates.     

Real-time, continuous-wave terahertz imaging by a pyroelectric camera

Real-time, continuous-wave terahertz (THz) imaging is demonstrated. A 1.89-THz optically-pumped farinfrared laser is used as the illumination source, and a 124 × 124 element room-temperature pyroelectric camera is adopted as the detector. With this setup, THz images through various wrapping materials are shown. The results show that this imaging system has the potential applications in real-time mail and security inspection.