Modes conversion due to plasmons induced transparency

We investigate simulated and theoretically the optical properties of the metamaterial, composed of two bigger split ring resonators and one smaller split ring resonator in unit cell. We observe the magic phenomena that one mode B is inhibited from strong to weak then disappears while another mode A appears and becomes stronger and stronger as asymmetric degree increases. The results show the mode A originates from the destructive interference between the dipole mode and the quadrapole mode, and its strength is proportional to the cross coupling coefficient of near-field. The disappearance of the mode B is due to the competition between the mode B and the mode A, and the variation of strength is proportional to the frequency shift of the dark mode. That is, with asymmetric degree increasing, the mode B converts into the mode A. These phenomena are explained very well by the temporal coupled-mode theory. Our metamaterial provides a kind of new design for understanding the interaction between light and matter.     

Multiple morphologies of the aggregates from self‐assembly of diblock copolymer with relatively long corona‐forming block in dilute aqueous solution

Reported here is self‐assembly behavior in selective solvent of diblock copolymers with relatively long corona‐forming block compared to core‐forming block. Three diblock copolymers, poly(ethylene glycol) monomethyl ether‐b‐poly(methacryloyl‐L ‐leucine methyl ester), also denoted as MPEG‐b‐PMALM copolymer, were prepared by fixing MPEG block with an average number of repeating units of 115, whereas varying PMALM block with an average number of repeating unit of 44, 23, 9, respectively. Multiple morphologies, such as sphere, cylinder, vesicle, and their coexisted structures from self‐assembly of these diblock copolymers in aqueous media by changing block nonselective solvent and initial polymer concentration used in preparation, were demonstrated directly via TEM observation. These results herein might, therefore, demonstrate as an example that a wide range of morphologies can be accessed not only from “crew‐cut micelles” but also from “star‐micelles” by controlling over preparation strategies. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 364–371, 2010     

A novel spectrogram visual security encryption algorithm based on block compressed sensing and five-dimensional chaotic system

Based on block compressed sensing theory, combined with a five-dimensional chaotic system, we propose and analyze a novel spectrogram visual security encryption algorithm. This research is devoted to solving the compression, encryption and steganography problems of spectrograms involving large data volumes and high complexity. First, the discrete wavelet transform is applied to the spectrogram to generate the coefficient matrix. Then, block compressed sensing is applied to compress and preencrypt the spectrogram. Second, we design a new five-dimensional chaotic system. Then, several typical evaluation methods, such as the phase diagram, Lyapunov exponent, bifurcation diagram and sample entropy, are applied to deeply analyze the chaotic behavior and dynamic performance of the system. Moreover, the corresponding Simulink model has been built, which proves the realizability of the chaotic system. Importantly, the measurement matrix required for compressed sensing is constructed by the chaotic sequence. Third, dynamic Josephus scrambling and annular diffusion are performed on the secret image to obtain the cipher image. Finally, an improved least significant bit embedding method and alpha channel synchronous embedding are designed to obtain a steganographic image with visual security properties. To make the initial keys of each image completely different from other images, the required keys are produced using the SHA-256 algorithm. The experimental results confirm that the visual security cryptosystem designed in this study has better compression performance, visual security and reconstruction quality. Furthermore, it is able to effectively defend against a variety of conventional attack methods, such as statistical attacks and entropy attacks.

     

Fluorometric determination of water in organic solvents using europium ion-based luminescent nanospheres

Microchimica Acta - Luminescent nanospheres with strong red fluorescence were prepared from a europium(III) mixed complex with 2-thenoyltrifluoroacetone and 1,10-phenanthroline, and characterized...     

A non-enzyme hydrogen peroxide sensor based on core/shell silica nanoparticles using synchronous fluorescence spectroscopy

In our previous study, we have prepared aminated fluorescent silica nanoparticles doped with fluorescein isothiocyanate (FITC) (FSNPs) for the sensing of γ-globulin. Compared with conventional organic dyes, FSNPs show superiorities such as excellent photostability, good water solubility, and biocompatibility, which are in favor of improving the stability and sensitivity of sensors. To extend the application of FSNPs, a convenient and effective method for non-enzyme fluorescent sensor of hydrogen peroxide (H₂O₂) is introduced based on the synchronous fluorescence technique. The sensor includes two-step reactions, typical redox reaction between KI and H₂O₂ and iodination reaction between I₂ produced by the first step reaction and FITC doped in the network of silica nanoparticles, which induce the fluorescence quenching of FSNPs. The results show that the fluorescence signal of FSNPs linearly decreases with the trace amounts of hydrogen peroxide added in the range 5–80 μM with a detection limit of 0.8 μM under the optimal experimental conditions. The method is simple and sensitive and can be applied to the determination of trace amounts of H₂O₂. Good recovery data were obtained for the assay of H₂O₂ in river water by standard addition method with high accuracy and reliability.     

光学活性两亲性嵌段共聚物的合成与表征

以溴封端聚乙二醇单甲醚(MPEG-Br)为大分子引发剂,三(2-二甲氨基乙基)胺(Me6TREN)/溴化亚铜(CuBr)为催化体系,通过原子转移自由基聚合(ATRP)反应制备了不同嵌段比例且分子量分布较窄的光学活性聚乙二醇单甲醚嵌段聚(N-甲基丙烯酰-L-亮氨酸甲酯)(MPEG-b-PMALM)聚合物.以1H-NMR表征了其化学结构以及两嵌段的比例.通过热重分析(TGA)和示差扫描量热仪(DSC)研究了嵌段共聚物的热学性能.相对于单体的旋光度,共聚物在聚合过程中旋光度发生了反转,其旋光度的绝对值显著增加,且随着PMALM嵌段含量的增加而增加.圆二色谱法(CD)结果表明,嵌段共聚物分子主链形成了一种无规卷曲的二级构象结构,其光学活性亦随PMALM含量的增加而增强.     

高温超导GdBa2Cu3O7-δ薄膜双晶晶界结特性研究

在晶界夹角为24°的YSZ人工双晶基片上,采用原位直流磁控溅射法制备了高温超导双晶GdBa₂Cu₃O_7-δ超导薄膜。采用光刻技术在晶界上刻出了尺寸5×5μm²的双晶晶界结。在77K下观测了结的直流I-V特性和在10GHz微波辐射下结的Shapiro台阶。这表明我们的人工双晶晶界结具有约瑟夫森弱连接行为。对结的特性进行了初步的理论分析和在实验基础上的数值模拟,模拟结果与RSJ理论符合较好,表明我们的双晶晶界结基本符合RSJ模型。     

高Tc超导GdBa_2Cu_3O_(7-δ)薄膜双晶晶界结及双晶结光探测器

在晶界夹角分别为 2 4°,3 2°的 YSZ双晶基片上 ,制备了高 Tc Gd Ba2 Cu3O7-δ双晶超导薄膜 ,采用光刻技术在晶界上刻出了两种不同尺寸的双晶晶界结 ,在液氮温度下观测了结的直流 I-V特性 ,用 1 0 GHz微波辐照双晶结结区 ,观察到了结临界电流的压缩和 Shapiro台阶 ,表明双晶结具有约瑟夫逊弱连接行为。用上述双晶结进行光探测 ,用波长为 0 .63 2 8μm的 He-Ne激光器辐照结区 ,系统的观测了其光响应特性 ,结果如下 :噪声等效功率 NEP =1 .9× 1 0 - 1 3W,归一化探测率 D*=5.3× 1 0 9cm Hz12 W- 1 ,响应率 Rv =4 .2× 1 0 7V/W,响应时间 τ<6.3 5× 1 0 - 7s     

Chiroptical aggregates from block copolymer bearing amino acid moieties in aqueous solution

Optically active poly(ethylene glycol) monomethyl ether‐b‐poly(methacryloyl‐L ‐leucine methyl ester) (denoted as MPEG‐b‐PMALM) copolymers were prepared via atom transfer radical polymerization (ATRP), using bromine (Br) end‐capped poly(ethylene glycol) monomethyl ether (denoted as MPEG‐Br) as macroinitiator in the presence of CuBr/tris(2‐dimethylaminoethy1)amine (Me₆TREN) as catalytic system. Broad range of morphologies, such as spherical, cylindrical, and vesicular micelles, which were prepared by initially dissolving prepared polymer in organic solvent at different concentration followed by addition various amount of water before dialysis against water to remove any added solvent, was observed by transmission electron microscope (TEM). More detailed chiroptical properties of the micelles/aggregates in aqueous solution were evaluated by circular dichroism (CD) spectroscopy as a function of micelles morphologies, polymer concentration, solvents employed, temperature, etc. The micellar solutions exhibit almost the same CD spectra regardless of its morphologies. The intensity of the CD spectra of the cylindrical micelles decreased in the molar ellipticities as the micellar concentration in water was increased. The Cotton effect was markedly changed when the solvent hydrophobicity was changed by addition of trifluoromethyl ethanol (TFME) to water. The intensity of the CD spectra decreased not too much within the temperature range from 20 °C to 90 °C, indicating good stability of the micelles upon temperature variation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1345–1355, 2009     

Existence of periodic solutions for a Liénard type p-Laplacian differential equation with a deviating argument

By means of Mawhin’s continuation theorem, a class of p-Laplacian type differential equation with a deviating argument of the form

(_φp(x^′(t)))^′+f(x(t))x^′(t)+β(t)g(t,x(t−τ(t,_|x|∞)))=e(t)${\left({\phi }_p\left(x^{\prime }\left(t\right)\right)\right)}^{\prime }+f\left(x\left(t\right)\right)x^{\prime }\left(t\right)+\beta \left(t\right)g(t,x(t-\tau (t,{\left|x\right|}_{\infty })))=e\left(t\right)$