High refractive index nanocomposite cover-layer for optical storage media

A nanocomposite cover-layer consisting of a UV curable resin and TiO₂ nanoparticles, a dielectric cover-layer, and a hybrid cover-layer for near-field optical recording media are prepared and characterized. The dielectric and the nanocomposite cover-layers with a refractive index of about 1.95 showed a rough surface, which yields collisions between a solid immersion lens and a cover-layer during the near-field gap servo test. A smooth surface with a nanocomposite cover-layer can be obtained by reducing the refractive index to less than 1.86, which results in a successful gap servo without the collision.     

Refractive index of silver nanoparticles dispersed in polyvinyl pyrrolidone nanocomposite

A silver nanoparticles/polymer composite was fabricated by reduction of silver nitrate in the presence of the polymer polyvinyl pyrrolidone. The plasmonic resonance of silver nanoparticles leads to a remarkable change of the dielectric dispersion of the polymer in the visible range. The refractive indexes of the nanocomposite with different fractions of the precursor silver nitrate at the wavelengths of 488, 532, and 633 nm were investigated by using reflectometry. At a fraction larger than 0.122, the refractive index change was larger than 0.1, and the maximal refractive index change of 0.84 was achieved at a wavelength of 488 nm with a fraction of 0.422. The experimental results were consistent with the prediction of Maxwell Garnett theory. The solid-state nanocomposite with a strong refractive index dispersion and tunability has promising applications in optics and communication devices.     

Spectral relationship of photoinduced refractive index and absorption changes in fulgide films

Fulgides are one kind of organic photochromic compound, which are famous for their thermal irreversibility. In this report, from the difference spectra of the absorption ΔA(λ) of one kind of pyrrylfulgide, the spectral refractive index change Δn(λ) was calculated by the Kramers–Kronig relation (KKR), and a good correlation of theoretically derived values and the experimental values of the Δn measured by a modified Michelson interferometer was found. Further, it is demonstrated that it was possible to calculate the spectral dependence of diffraction efficiency from the easily accessible absorption changes. This method will be a useful tool for the characterization and optimization of fulgide films. The results show that the diffraction efficiency is high at 488 and 750 nm, where the absorption is very small, so we can realize non-destructive reconstruction.     

红外光学材料硫化锌衬底上沉积金刚石膜的研究

采用微波等离子体化学气相沉积法,在预镀陶瓷过渡层的硫化锌衬底上沉积金刚石膜。在以前的实验中,我们发现在陶瓷过渡层上沉积金刚石膜极其困难,但采用金刚石诱导形核方法后,我们已经在过渡层／硫化锌试样表面获得了很小面积（约1mm宽的环状区域）的金刚石形核。本文对前期的诱导形核工作进行了一定改进,目前已经使形核生长范围大大增加,沉积面积超过原来10倍。此外,本文对金刚石／过渡层／硫化锌试样的红外透过特性以及金刚石膜质量等进行了评价。     

Near-field optical recording with nanocomposite cover-layer for numerical aperture of 1.85

Near-field optical recording media with a nanocomposite cover-layer were prepared and tested using a gap servo, near-field recording system with an effective numerical aperture of 1.85. The refractive index of the nanocomposite cover-layer, which has a smooth surface, is 1.86, yielding a successful gap servo operation. However, the recording density cannot be maximized due to the refractive index of the cover-layer being lower than the required value for the effective numerical aperture. A recording density of 95?GB per disc can be achieved with a nanocomposite cover-layer having a refractive index of 1.86. The readout signal from 110?GB is not clear due to the reduced eventual numerical aperture in conjunction with the limited refractive index of the cover-layer.     

TiO2-SiO2系统凝胶玻璃薄膜折射率的研究

应用光度法研究了溶胶－凝胶系统组成、热处理温度对iO2-SiO2系统凝胶玻璃薄膜折射率的影响规律。随薄膜中TiO2含量的增加以及热处理温度的升高,薄膜的折射率逐渐增大。通过调整TiO2-SiO2系统的组成及适当的热处理温度,可实现TiO2-SiO2系统薄膜折射率在1．5－2．4之间的连续变化。     

折射率可调SiO_2薄膜及耐环境性宽频增透膜的制备

通过溶胶-凝胶法制备了折射率连续可调的SiO2薄膜,并将其应用于制备双层宽频增透膜。以正硅酸乙酯为前驱体,分别以盐酸和氨水为催化剂制备酸催化SiO2溶胶和碱催化SiO2溶胶;将酸催化和碱催化的SiO2溶胶按不同比例进行混合制得酸碱混合SiO2溶胶,最后通过浸渍-提拉法在K9玻璃上制备SiO2薄膜。椭偏仪测试结果表明SiO2薄膜的折射率在1.18~1.44之间连续可调,折射率随着酸催化SiO2溶胶比例的增加而增加。分别以折射率为1.41和1.18的SiO2薄膜为底层和上层,成功制备出在527和1053nm处同时高增透的双层宽频增透膜。最后,以六甲基二硅氮烷为修饰剂,通过增透膜表面的有机修饰,提高了宽频增透膜的疏水性和耐环境性。     

Synthesis and photoluminescent properties of doped ZnS nanocrystals capped by poly(vinylpyrrolidone)

Zinc sulfide semiconductor nanocrystals doped with selected transition metal ions (Mn²⁺, Cu²⁺, and Ni²⁺) have been synthesized via a solution-based method utilizing low dopant concentrations (0–1%) and employing poly(vinylpyrrolidone) (PVP) as a capping agent. UV/Vis absorbance spectra for all of the synthesized nanocrystals show an exitonic peak at around 310 nm, indicating that the introduction of the dopant does not influence the particle size. Calculated particle sizes for undoped and doped nanocrystals are in the 4.3 nm size range. Photoluminescence spectra recorded for undoped ZnS nanocrystals, using an excitation wavelength of 310 nm, exhibit an emission peak centered at around 460 nm. When a dopant ion is included in the synthesis, peaks in the corresponding photoluminescence spectra are red-shifted. For Mn-doped nanocrystals, an intense peak centered at approximately 590 nm is found and is seen to increase in photoluminescence intensity with an increase in dopant concentration. In contrast, for Cu-doped and Ni-doped nanocrystals, weaker peaks centered at around 520 and 500 nm, respectively, are observed and are noticed to decrease in photoluminescence intensity with an increase in dopant concentration. These results clearly show that careful control of synthetic conditions must be employed in the synthesis of doped semiconductor nanocrystals in order to obtain materials with optimized properties.     

Evolution of graded refractive index in squid lenses.

A lens with a graded refractive index is required for vision in aquatic animals with camera-type eyes. This optical design entails a radial gradient of protein density, with low density in external layers and high density in internal layers. To maintain the optical stability of the eye, different material properties are required for proteins in different regions of the lens. In low-density regions of the lens where slight protein aggregation causes significant light scattering, aggregation must be minimized. Squid lens S-crystallin proteins are evolutionarily derived from the glutathione S-transferase protein family. We used biochemistry, optical modelling and phylogenetics to study the evolution and material properties of S-crystallins. S-crystallins are differentially expressed in a radial gradient, suggesting a role in refractive index. This gradient in S-crystallin expression is correlated with their evolutionary history and biochemistry. S-crystallins have been under positive selection. This selection appears to have resulted in stabilization of derived S-crystallins via mutations in the dimer interface and extended electrostatic fields. These derived S-crystallins probably cause the glassy organization and stability of low refractive index lens layers. Our work elucidates the molecular and evolutionary mechanisms underlying the production and maintenance of camera-like optics in squid lenses.     

Electrochemical formation and characterisation of poly(3-methylthiophene)/WO3 nanocomposite films

Stable poly(3-methylthiophene)/WO₃ (PMeT/WO₃) nanocomposite films have been prepared by a two-step electrochemical method. At first the WO₃ film was grown by a potentiostatic method in tungsten electrolytes, and then PMeT was deposited on the WO₃ film by a potentiodynamic polymerisation method in 2?M solutions of 3-methylthiophene in 1-butyl-3-metyllimidazolium hexafluorophosphate ([BMIM]PF₆). The products are characterised in detail by multiform techniques: scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDS) and Fourier-transform infrared spectroscopies (FTIR). The obtained PMeT/WO₃ film displays a significant enhancement of electrochemical activity and a higher stability than that of pure PMeT films.     

Automated tracking of liquid velocities in a refractive index matched porous medium

Abstract

Particle tracking velocimetry is applied to flow inside a porous column at Reynolds number Re = 28. The column is composed of refractive‐index‐matched solid and liquid materials, allowing seeding particles to be tracked in a laser‐illuminated axial slice. To complement earlier results acquired for 7 mm spheres, we conduct new experiments with larger 12 mm spheres. By improving the image acquisition and analysis, we are able to process the new experiments using fully automated algorithms instead of manual tracking. As a result, greater vector yields, more accurate velocity data, and a more complete spatial coverage are achieved.     

三元体系化学水浴法制备ZnS薄膜结晶性能的研究

太阳薄膜电池ZnS缓冲层一般以氨水为主络合剂、水合肼为辅助络合剂二元络合体系化学水浴法制备。实验发现以氨水为主络合剂、水合肼和柠檬酸为辅助络合荆三元体系制备的ZnS薄膜质量明显要比氨水、水合肼二元体系的ZnS薄膜好。薄膜表面更加光亮、平整，光透过率能得到明显提高。从实验现象和测试结果来看，随柠檬酸浓度增加，在反应溶液中无定形态白色沉淀明显减少，ZnS薄膜结晶性能也得到明显提高，ZnS薄膜光透过率升高。柠檬酸浓度为0．15mol／L时，薄膜光透过率达到85％左右，完全满足太阳能电池的要求；继续增加柠檬酸的量，薄膜光透过率趋于一致，光透过率略有回落。     

高折光率环氧/ZrO2纳米杂化材料的制备

采用溶胶-凝胶法在环氧E51中原位生成无机纳米ZrO₂团簇,并利用有机环氧分子链上的侧羟基与无机纳米团簇间形成化学键,以增加有机无机组分间的相容性,并防止无机纳米团簇在体系中团聚。采用红外光谱、X射线衍射、扫描电镜、原子力显微镜和透射电镜等对其结构进行了表征,证明成功地在体系中原位生成了ZrO₂纳米粒子且分布均匀,所制备的薄膜材料具有很好的平整度。环氧/ZrO₂纳米杂化光学材料的折光率随着体系中无机纳米粒子含量的增加而呈线性增加,并实现折光率在1.512~1.749间连续可调;在可见光波长范围内,环氧/ZrO₂纳米杂化光学薄膜的透过率普遍维持在85%以上,当纳米粒子的含量增至25%后,透光率也能保持在80%以上。     

Ultrathin ZnS nanosheet/carbon nanotube hybrid electrode for high-performance flexible all-solid-state supercapacitor

Flexible and easily reconfigurable supercapacitors show great promise for application in wearable electronics.In this study,multiwall C nanotubes (CNTs) decorated with hierarchical ultrathin zinc sulfide (ZnS) nanosheets (ZnS@CNT) are synthesized via a facile method.The resulting ZnS@CNT electrode,which delivers a high specific capacitance of 347.3 F·g-1 and an excellent cycling stability,can function as a high-performance electrode for a flexible all-solid-state supercapacitor using a polymer gel electrolyte.Our device exhibits a remarkable specific capacitance of 159.6 F·g-1,a high energy density of 22.3 W·h·kg-1 and a power density of 5 kW·kg-1.It also has high electrochemical performance even under bending or twisting.The all-solid-state supercapacitors can be easily integrated in series to power different commercial light-emitting diodes without an external bias voltage.     

3-D mapping with ellipsometrically determined physical thickness/refractive index of spin coated sol-gel silica layer

Precursor sol for sol-gel silica layer was prepared from the starting material, tetraethylorthosilicate (TEOS). The sol was deposited onto borosilicate crown (BSC) glass by the spinning technique (rpm 2500). The gel layer thus formed transformed to oxide layer on heating to 450°C for ∼ 30 min. The physical thickness and the refractive index of the layer were measured ellipsometrically (Rudolph Auto EL II) at 632.8 nm. About 10 × 10 mm surface area of the silica layer was chosen for evaluation of thickness and refractive index values at different points (121 nos.) with 1 mm gap between two points. Those data were utilized in the Autolisp programme for 3-D mapping. Radial distribution of the evaluated values was also displayed.     

PF/MCM-41纳米复合材料的制备及其耐热性

采用原位聚合结合共混工艺制备了PF／MCM-41纳米复合材料，研究了耐热性．结果表明，当MCM-41粉的含量为20％时，PF／MCM-41纳米复合材料中MCM-41粉的分散性及有机-无机两相间的界面结合良好；与纯PF比较，复合材料的质量损失达到50％（质量分数）时的温度提高约70℃，分解结束时的温度提高约100℃．介孔MCM-41中的纳米级孔道能有效地限制其内树脂分子链的自由运动，是PF／MCM-41复合材料耐热性提高的机理．同时，其纳米级厚度的孔壁具有极好的耐热性和绝热性，在快速升温的条件下能延缓孔内树脂分子的热分解及分解产生的小分子产物的释放．     

Interfacial coupling in heteroepitaxial vertically aligned nanocomposite thin films: From lateral to vertical control

Very recently, vertically aligned nanocomposite (VAN) thin films have served as an intriguing platform to obtain significant insights of the fundamental physics and achieve novel functionalities for potential technological applications. In this review article, we have investigated the lattice mismatch and vertical interfacial coupling in representative VAN systems for probing strain engineering in the vertical direction. Systematic studies of ferroelectricity, low field magnetoresistance and magnetoelectric coupling in VAN architectures have been reviewed and compared. The enhancement and tunability of the physical properties are attributed to the effective strain-, phase- and interface- couplings in VAN films. In the end, important and promising research directions in this field are proposed, including understanding the growth mechanisms of VAN structures, and creating more effective couplings for enhanced functionalities and ultimate device applications.     

Experimental determination of refractive index of condensed reflectin in squid iridocytes

Loliginid squid dynamically tune the structural iridescence of cells in their skin for active camouflage and communication. Bragg reflectors in these cells consist of membrane-bound lamellae periodically alternating with low refractive index extracellular spaces; neuronal signalling induces condensation of the reflectin proteins that fill the lamellae, consequently triggering the expulsion of water. This causes an increase in refractive index within the lamellae, activating reflectance, with the change in lamellar thickness and spacing progressively shifting the wavelength of reflected light. We used micro-spectrophotometry to measure the functionally relevant refractive index of the high-index lamellae of the Bragg reflectors containing the condensed reflectins in chemically fixed dermal iridocytes of the squid, Doryteuthis opalescens. Our high-magnification imaging spectrometer allowed us to obtain normalized spectra of optically distinct sections of the individual, subcellular, multi-layer Bragg stacks. Replacement of the extracellular fluid with liquids of increasing refractive index allowed us to measure the reflectivity of the Bragg stacks as it decreased progressively to 0 when the refractive index of the extracellular medium exactly matched that of the reflectin-filled lamellae, thus allowing us to directly measure the refractive index of the reflectin-filled lamellae as n_{condensed lamellae} ≈ 1.44. The measured value of the physiologically relevant n_{condensed lamellae} from these bright iridocytes falls within the range of values that we recently determined by an independent optical method and is significantly lower than values previously reported for dehydrated and air-dried reflectin films. We propose that this directly measured value for the refractive index of the squid''s Bragg lamellae containing the condensed reflectins is most appropriate for calculations of reflectivity in similar reflectin-based high-index layers in other molluscs.