Synthesis and solid state NMR characterization of novel peptide/silica hybrid materials

The successful synthesis and solid state NMR characterization of silica-based organic–inorganic hybrid materials is presented. For this, collagen-like peptides are immobilized on carboxylate functionalized mesoporous silica (COOH/SiO_x) materials. A pre-activation of the silica material with TSTU (O-(N-Succinimidyl)-N,N,N′,N′-tetramethyluronium tetrafluoroborate) is performed to enable a covalent binding of the peptides to the linker. The success of the covalent immobilization is indicated by the decrease of the ¹³C CP-MAS NMR signal of the TSTU moiety. A qualitative distinction between covalently bound and adsorbed peptide is feasible by ¹⁵N CP-MAS Dynamic Nuclear Polarization (DNP). The low-field shift of the ¹⁵N signal of the peptide's N-terminus clearly identifies it as the binding site. The DNP enhancement allows the probing of natural abundance ¹⁵N nuclei, rendering expensive labeling of peptides unnecessary.     

Fabrication and characterization of amorphous silica nanostructures

Large-scale amorphous silica nanostructures, including nanowires, nanotubes and flowerlike nanowire bunches depending on the position, have been fabricated on silicon wafer through a cheap route under the assistance of gold and germanium. Accompanying the observation of blue-green light emission, comprehensive micro-structural characterization reveals that the growth of nanostructures is catalyzed only by gold whereas the final morphology of nanostructures depends on the location to germanium ball. Au₂Si, a compound of gold and silicon, is also disclosed as an intermediate state during the catalysis. Correspondingly, a growth scheme is proposed based on the experimental results and the vapor-liquid-solid mechanism.     

Fabrication and performances of an optical sensor system constructed by a novel Cu(I) complex embedded on silica matrix

In this paper, a novel diamine ligand of 2-(pyridin-2-yl)-5-p-tolyl-1.3.4-oxadiazole (PTO) and its corresponding Cu(I) complex of [Cu(PTO)(PPh₃)₂]BF₄ with triphenylphosphine (PPh₃) as the auxiliary ligand are synthesized. Single crystal analysis confirms its identity. Its photophysical properties, including UV–vis absorption, emission spectrum, and luminescence decay dynamics, are measured and studied. The room temperature luminescence is a yellow one with long excited state lifetime of 64.4 μs under pure nitrogen atmosphere. Combined with density functional calculation on the cation of the Cu(I) complex, the yellow emission is assigned as a phosphorescent character of metal-to-ligand-charge-transfer, whose excited state is expected to be sensitive towards molecular oxygen. [Cu(PTO)(PPh₃)₂]BF₄ is then doped into a silica supporting matrix of MCM-41 to construct an oxygen-sensitive probe of [Cu(PTO)(PPh₃)₂]BF₄/MCM-41, which shows a maximum sensitivity (luminescence intensity in O₂ medium/intensity in N₂ medium) of 5.95 towards oxygen with short response time of 10 s. This sensing system shows a good photodurability upon continuous excitation radiation.     

Chaos generation by a hybrid integrated chaotic semiconductor laser

We design a hybrid integrated chaotic semiconductor laser with short-cavity optical feedback. It can be assembled in a commercial butterfly shell with just three micro-lenses. One of them is coated by a transflective film to provide the optical feedback for chaos generation while insuring regular laser transmission. We prove the feasibility of the chaos generation in this compact structure and provide critical external parameters for the fabrication by theoretical simulations. Rather than the usual changeless internal parameters used in previous simulation research, we extract the real parameters of the chip by experiment. Moreover, the maps of the largest Lyapunov exponent with varying bias current and feedback intensity K_(ap) demonstrate the dynamic characteristics under different external-cavity conditions. Each laser chip has its own optimal external cavity length(L) and feedback intensity(K_(ap)) to generate chaos because of the different internal parameters. We have acquired two ranges of optimal parameters(L = 4 mm, 0.12 K_(ap) 0.2 and L = 5 mm, 0.07 K_(ap) 0.12) for two different chips.     

石墨烯-硅基混合光子集成电路

近年来硅基光子学已经慢慢走向成熟,它被认为是未来取代电子集成电路,实现下一代更高性能的光子集成电路的关键技术.这得益于硅基光子器件与现代的互补金属氧化物半导体工艺相兼容,能够实现廉价的大规模集成.然而,由于受硅材料本身的光电特性所限,在硅基平台上实现高性能的有源器件仍然存在着巨大挑战.石墨烯-硅基混合光子集成电路的发展为解决这一问题提供了可行的方案.这得益于石墨烯作为一种兼具高载流子迁移率、高电光系数和宽带吸收等优点的二维光电材料,能够方便地与现有硅基器件相集成,并充分发挥自身的光电性能优势.本文结合我们课题组在该领域研究的一些最新成果,介绍了国际上在石墨烯-硅基混合光子集成电路上的一些重要研究进展,涵盖了光源、光波导、光调制器和光探测器四个重要组成部分.     

一种新型集成光学微位移传感器的研究

本文采用数值孔径(N.A)法首次计算了光纤-波导端面的耦合效率和器件的响应特性;全面测试了器件的性能,其理论分析与实验结果符合较好;还讨论了进一步提高器件的探测灵敏度及其实用化的途径.     

Fabrication of hybrid surface-modified titania-epoxy nanocomposite films

This work reports the preparation of well-dispersed surface-modified titiania nanoparticles in organic solvents. Different types of surface-modified titania nanoparticles can be incorporated into epoxy matrix to form hybrid nanocomposites. The hybrid nanocomposite films have higher refractive index than pure epoxy system. The refractive index can be tuned by using different forms of titania nanoparticles and by changing the titania solid content. The titania solid content in the epoxy matrix can be more than 70 wt% without affecting the optical transparency of the hybrid film.     

基于硅基槽波导的单纤三向滤波器的研究

设计了基于硅基槽波导的微环谐振型单纤三向滤波器。基于电磁场理论得到了二维情形下的硅基槽波导的模场及有效折射率随波长的变化关系,在此基础上,利用硅基槽微环谐振腔谐振波长与微环半径的关系,优化得到了可将1490nm和1550nm两个下载波长分开的谐振环半径,并同时将1310nm波长上传,三个波长信号从不同端口输出,成功地实现了三向器滤波功能。利用传递函数法模拟了所设计的硅基槽微环谐振型三向滤波器的输出光谱,结果显示其串扰可低至-16.9dB。     

Fabrication of integrated waveguide grating in azo polymers

In this Letter, we have introduced a technique, new to our knowledge, to fabricate gratings on a waveguide of azo-functionalized polymeric films using a slit mask and a fast, direct-writing method. To prevent the destruction of the waveguide by the grating formation on the waveguide, we placed a slit mask on the waveguide. By properly adjusting the resonance, this grating can be used as an integrated wavelength filter. We have produced an attenuation of 13.4?dB at 1562?nm with a FWHM of 3.45?nm. The grating has been fabricated as narrow as the width of the waveguide to couple filtered light into the waveguide by using a slit mask. Any light shifted from the resonance will pass through the waveguide undisturbed.     

用一种新的装配方式制备单畴GdBCO超导块材

在顶部籽晶熔渗生长工艺(TSIG)的基础上,采用一种新的装配方式制备单畴Gd-Ba-Cu-O(GdBCO)超导块材,并对所得样品的形貌、微观结构以及超导性能进行了研究.结果表明,应用新的装配方式可以提高液相源块的支撑能力,有效避免样品在热处理过程中的倾斜或坍塌现象,从而提高了样品制备过程的稳定性和可重复性.此外,应用新的装配方式还有助于GdBCO样品的完整生长. 关键词： 熔渗生长 新的装配方式 GdBCO     

Fabrication of superhydrophobic cotton fabrics by silica hydrosol and hydrophobization

Superhydrophobic cotton fabrics were prepared by the incorporation of silica nanoparticles and subsequent hydrophobization with hexadecyltrimethoxysilane (HDTMS). The silica nanoparticles were synthesized via sol-gel reaction with methyl trimethoxy silane (MTMS) as the precursor in the presence of the base catalyst and surfactant in aqueous solution. As for the resulting products, characterization by particle size analyzer, scanning electron microscopy (SEM), scanning probe microscopy (SPM), X-ray photoelectron spectroscopy (XPS), and thermal gravimetric analysis (TGA) were performed respectively. The size of SiO₂ nanoparticles can be controlled by adjusting the catalyst and surfactant concentrations. The wettability of cotton textiles was evaluated by the water contact angle (WCA) and water shedding angle (WSA) measurements. The results showed that the treated cotton sample displayed remarkable water repellency with a WCA of 151.9° for a 5 μL water droplet and a WSA of 13° for a 15 μL water droplet.     

Laser-induced high-quality etching of fused silica using a novel aqueous medium

Laser-induced backside wet etching of fused-silica plates using an aqueous solution of naphthalene-1,3,6-trisulfonic acid trisodium salt (Np(SO₃Na)₃) is reported. A KrF excimer laser was employed as a light source. The etch rate varied greatly with the concentration of the solution and the laser fluence. For lower concentration solutions, the etch rate increased linearly with laser fluence. For highly concentrated solutions, however, the etch rate increased abruptly at higher fluence. Well-defined line-and-space and grid micropatterns were fabricated using a low etch rate. The etched surface was as flat as the surface of the virgin plates and the etched pattern was free of debris and microcracks. The formation and propagation of shockwaves and bubbles in the solution during the etch process were monitored. High pressure, as well as the high temperature generated by the photothermal process, plays a key role in the etching process. Received: 8 April 2002 / Accepted: 12 April 2002 / Published online: 19 July 2002     

High-pressure effects on nanometric hybrid xerogels, p-phenylenediamine/silica and p-anisidine/silica

The hybrid xerogels p-phenylenediamine/silica and p-anisidine/silica were prepared with different surface areas and porosities and they were processed at high pressure (7.7 GPa or ∼76000 atm) in a quasi-hydrostatic medium at room temperature. The morphologies of the materials were studied before and after the high-pressure treatment by using N₂ adsorption–desorption isotherms, scanning electron microscopy and infrared thermal analysis. The porous hybrid p-phenylenediamine /silica presented after the high-pressure treatment a surface-area reduction and an entrapment of organics in closed pores. However, the less porous hybrid p-anisidine /silica showed a surprising behavior, a pressure-induced increase in surface area with opening of pores. We propose a mechanism based on the inhibition of the cold sintering process by the organics to explain these results. PACS 81.20.-n; 81.40.Vw; 81.05.-t     

紫外光固化丙烯酸酯/二氧化硅杂化光学增透膜的研制

采用旋转镀膜工艺和紫外光固化技术在石英基片上制备出了快速固化的丙烯酸酯/二氧化硅有机/无机杂化单层宽带光学增透膜,考察了丙烯酸酯与正硅酸乙酯的物质的量之比对薄膜增透性能等的影响。实验结果表明,该比值为2.0时,增透膜的最大透射率为99.0%,采用旋转镀膜工艺制备的有机/无机杂化单层增透膜在425～1060nm的较宽波段范围内透射率均达98%以上。     

紫外光固化丙烯酸酯/二氧化硅杂化光学增透膜的研制

 采用旋转镀膜工艺和紫外光固化技术在石英基片上制备出了快速固化的丙烯酸酯/二氧化硅有机/无机杂化单层宽带光学增透膜，考察了丙烯酸酯与正硅酸乙酯的物质的量之比对薄膜增透性能等的影响。实验结果表明，该比值为2.0时，增透膜的最大透射率为99.0%，采用旋转镀膜工艺制备的有机/无机杂化单层增透膜在425～1060nm的较宽波段范围内透射率均达98%以上。     

Trap-state-assisted white light emission from a CdSe nanocrystal integrated hybrid light-emitting diode

This Letter reports on the fabrication of hybrid white-light-emitting diodes made of semiconductor nanocrystals (NCs) integrated on InGaN/GaN LEDs. Using core type and core/shell type CdSe NCs, the white light properties are systematically engineered for white light generation with high color rendering index (CRI). Unlike CdSe/ZnS core/shell NCs, which exhibited a unique narrowband edge emission, core type CdSe NCs offered extended broad emission toward orange/red wavelengths associated with deep trap states. Consequently, the light-emitting properties of the devices showed strong dependence on the type of NCs used, and devices with CdSe NCs offered admirable characteristics, such as Commission Internationale d'Eclairage coordinates of (0.356, 0.330) and a CRI as high as 87.4.     

Fabrication and characterization of epoxy/silica functionally graded composite material

Increased use of composites in aerospace and defense application induces the search for heat resistant material. In present study silica reinforced epoxy functionally graded material using quartz fabric is prepared with different thickness. The gradation in silica : epoxy matrix is maintained with one side pure epoxy to opposite side pure silica. Thermal and mechanical behaviour of the composites were studied. It was found that the temperature gradient of 350°C to 950°C could be maintained for 2 to 5 min if the thickness of insulating silica layer is increased from 0.5 mm to 16 mm. Mechanical properties such as flexural modulus and strength of FGM composites were also evaluated. Strength and modulus decreased with increase of insulating layer.     

Thermal nonlinear effects in hybrid silica/polymer microdisks

The linear and thermal nonlinear spectral responses of silica and hybrid silica/polymer microdisk resonators are investigated. Both types of resonators can be fabricated using the same technological procedure with only slight modification. An extra polymer layer results in opposite sign of the nonlinear thermal optical response of the hybrid microdisks compared to the pure silica ones, which can be explained by the different thermorefractive coefficients of silica and polymer. A full compensation of eigen frequency shift, caused by thermal nonlinearity, has been demonstrated experimentally.     

Fabrication of well-defined individual dislocations in SiGe as a novel one-dimensional system

We show a new way to fabricate well-defined individual dislocations in SiGe. We started with a fully pseudomorphic but metastable SiGe layer grown on Si(0 0 1) by molecular beam epitaxy. Next, elongated (1 mm) mesa stripes with various widths (0.5–3 μm) were fabricated by a combination of isotropic and anisotropic etching. For smaller stripes, elastic relaxation of the strained SiGe layer can occur, transforming the originally biaxial strained layer into uniaxial strained subsystems. Subsequent strain relaxation caused by high temperature treatments leads to the formation of individual dislocation along the mesa stripes. The number of parallel dislocation can be adjusted by the original strain (Si:Ge ratio and layer thickness) and the mesa widths. We were able to fabricate structures with exactly one dislocation. Finally, contact pads were added to the stripes enabling the electrical characterization of individual dislocation.