Synthesis and characterization of silica microsphere-based mesoporous materials

In this paper is described the synthesis of silica microspheres of low dimensionality, that is, with diameters ranging from ca. 200 to 450 nm. The structure and essential features of these materials have been studied by electron microscopy and analysis of isotherms of physical adsorption and, in contrast of the previously established, the presence of a mesoporous structure within the silica spheres has been unambiguously demonstrated.     

单分散性sio2胶体微球自组装光子晶体的实验研究

光子晶体是一种周期性电介质材料,具有光子带隙和光子局域等一系列优异的光学特性。制备了多种不同直径的单分散二氧化硅胶体微球,采用垂直沉积法将不同直径,以及同一直径不同浓度的二氧化硅胶体微球自组装成多种光子晶体薄膜,并用扫描电子显微镜和紫外—可见—近红外分光光度计对其微观结构和光学特性进行了表征,结果表明所得晶体薄膜具有三维有序结构,其表面存点、线缺陷。自组装得到的光子晶体薄膜存在明显的光子带隙特征,带隙位置与二氧化硅胶体微球直径有关,带隙中心波长与理论值一致。随着二氧化硅胶体微球浓度的增加,光子带隙深度增加,特性更好,但是,当浓度大于10%时,光子带隙的深度反而减小。     

二氧化硅微球颗粒解团聚研究

二氧化硅微球颗粒在无水和水相介质中都极易发生团聚现象,进而严重影响该颗粒的特性研究。为了更好地使用和研究二氧化硅微球颗粒,需要进行解团聚工艺研究。实验研究了不同尺度的颗粒的团聚特性和现象,提出了一种工艺,该工艺方法可以很好地实现大团聚的二氧化硅微球颗粒的解团聚。经过尼康显微镜观察,显示该工艺不仅很好地完成了二氧化硅微球的解团聚,而且提高了颗粒的分散性和稳定性。     

Multifunctional Mesostructured Silica Microspheres from an Ultrasonic Aerosol Spray

Multifunctional mesostructured silica microspheres are prepared using ultrasonic aerosol spray in conjunction with solvent evaporation‐induced assembly. Rare earth ion–phenanthroline complexes, magnetite particles, photoacid generators, and pH‐sensitive dyes are chosen as luminescent, magnetic, and photosensitive components. The incorporation of these functional components into mesostructured silica microspheres can be readily realized by dispersing them in the precursor solution of the aerosol spray process. Luminescent microspheres that can emit at multiple wavelengths when excited at a single wavelength are produced by the addition of multiple rare earth complexes into the precursor solution. The addition of magnetite particles leads to the production of magnetic luminescent microspheres. Photoacid generators and pH‐sensitive dyes are further employed to produce magnetic photosensitive microspheres that can release acid and change color upon UV light illumination. Such multifunctional microspheres could have exciting potential for many optical and biotechnological applications, such as multiplexed labeling, diagnosis, simultaneous imaging and therapy, cell capture and separation, targeted delivery, and optical data storage.     

硅烷偶联剂对制备纳米SiO2粒子形态的影响

硅烷偶联剂作为一种具有特殊性质的分散剂，对从正硅酸乙酯水解制得的SiO2微球形态会产生很大的影响。除因不同硅烷偶联剂的不同水解速度可获得不同尺寸的单分散SiO2微球外，还可得到由SiO2纳米粒子组装成的一维粒子链结构，特别是在高pH值条件下，硅烷偶联剂不仅发生水解，同时还发生自身缩聚反应，所得产物就可能起软模板作用，诱导SiO2纳米粒子的规则定向生长。     

Multiscale Colloidal Assembly of Silica Nanoparticles into Microspheres with Tunable Mesopores

Colloidal assembly of silica (nano)particles is a powerful method to design functional materials across multiple length scales. Although this method has enabled the fabrication of a wide range of silica‐based materials, attempts to design and synthesize porous materials with a high level of tuneability and control over pore dimensions have remained relatively unsuccessful. Here, the colloidal assembly of silica nanoparticles into mesoporous silica microspheres (MSMs) is reported using a discrete set of silica sols within the confinement of a water‐in‐oil emulsion system. By studying the independent manipulation of different assembly parameters during the sol–gel process, a design strategy is outlined to synthesize MSMs with excellent reproducibility and independent control over pore size and overall porosity, which does not require additional ageing or post‐treatment steps to reach pore sizes as large as 50 nm. The strategy presented here can provide the necessary tools for the microstructural design of the next generation of tailor‐made silica microspheres for use in separation applications and beyond.     

Guiding Properties of Silica/Air Hollow-Core Bragg Fibers

The guiding properties of realistic silica/air hollow-core Bragg fibers have been investigated by calculating the dispersion curves, the confinement loss spectrum, and the field distribution of the guided modes through a full-vector modal solver based on the finite-element method. In particular, the silica bridge influence on the fundamental mode has been analyzed by comparing the properties of an ideal structure, without the silica nanosupports, and of two realistic fibers, with squared off and rounded air-holes. Simulation results have demonstrated the presence of anticrossing points in the dispersion curves, associated to the transition of the fundamental mode into a surface mode. It has been shown that surface modes are responsible for the sharp loss peaks, also experimentally measured, which pollute the loss spectrum of the fundamental mode and of the higher order modes. Then, the influence on the guiding properties of each geometric characteristic in the hollow-core Bragg fiber cross-section has been deeply investigated, thus showing which parameter it is better to change in order to properly modify the loss values or its spectral behavior. Moreover, in order to improve the loss properties of hollow-core Bragg fibers, the number of silica and air layers in the fiber cladding has been increased, and the layer thickness has been modified. Results have shown that the first change is more effective for the loss reduction, while the second is useful for a spectral shift. Finally, among the different possible applications, the feasibility of a DNA biosensor based on a hollow-core Bragg fiber has been demonstrated.      

Cover Picture: Generation of Monodisperse Mesoporous Silica Microspheres with Controllable Size and Surface Morphology in a Microfluidic Device (Adv. Funct. Mater. 24/2008)

A one‐step in situ method, termed microfluidic diffusion‐induced self‐assembly, for the synthesis of monodisperse ordered mesoporous silica microspheres, is reported. The method combines microfluidic generation of uniform droplets and subsequent in situ rapid solvent diffusion‐induced self‐assembly within the microfluidic channel. The mesoporous silica microspheres prepared in this way reveal well‐ordered 2D hexagonal mesostructures with unprecedented corrugated surface morphology of disordered mesopores that are larger than 15 nm. It is speculated that the formation of an interfacial subphase and rapid diffusion of solvent to oil are attributed to the formation of the unique surface morphology. It is also shown that the surface morphology and the particle size of the mesoporous silica microspheres can be systematically controlled by adjusting fluidic conditions.     

Generation of Monodisperse Mesoporous Silica Microspheres with Controllable Size and Surface Morphology in a Microfluidic Device

A one‐step in situ method, termed microfluidic diffusion‐induced self‐assembly, for the synthesis of monodisperse ordered mesoporous silica microspheres, is reported. The method combines microfluidic generation of uniform droplets and subsequent in situ rapid solvent diffusion‐induced self‐assembly within the microfluidic channel. The mesoporous silica microspheres prepared in this way reveal well‐ordered 2D hexagonal mesostructures with unprecedented corrugated surface morphology of disordered mesopores that are larger than 15 nm. It is speculated that the formation of an interfacial subphase and rapid diffusion of solvent to oil are attributed to the formation of the unique surface morphology. It is also shown that the surface morphology and the particle size of the mesoporous silica microspheres can be systematically controlled by adjusting fluidic conditions.     

High-quality SiO2 Colloidal Crystal Fabricated by Controllable Vertical Deposition Method

Monodispersed silica microspheres with diameter of 353 nm were assembled into photonic crystal in ethanol colloidal suspensions of varied silica volume fraction at different temperature and humidity by means of controllable vertical deposition method. The surface morphology and optical properties were studied by SEM and UV-Vis-NIR. It was found that the high quality silica colloidal photonic crystals were obtained from ethanol solutions with environment temperature between 45℃ and 55℃, humidity between 66% and 76%, the volume fraction of microspheres is between 0.8% and 1.5%, The ordered close-packed photonic crystal fabricated by controllable vertical deposition method had the two photonic bandgaps in the visible light band and near infrared band,     

“Ship‐in‐a‐Bottle” Growth of Noble Metal Nanostructures

Noble metal nanostructures are grown inside hollow mesoporous silica microspheres using “ship‐in‐a‐bottle” growth. Small Au seeds are first introduced into the interior of the hollow microspheres. Au nanorods with synthetically tunable longitudinal plasmon wavelengths and Au nanospheres are obtained through seed‐mediated growth within the microspheres. The encapsulated Au nanocrystals are further coated with Pd or Pt shells. The microsphere‐encapsulated bimetallic core/shell nanostructures can function as catalysts. They exhibit high catalytic performance and their stability is superior to that of the corresponding unencapsulated core/shell nanostructures in the catalytic oxidation of o‐phenylenediamine with hydrogen peroxide. Therefore, these hollow microsphere‐encapsulated metal nanostructures are promising as recoverable and efficient catalysts for various liquid‐phase catalytic reactions.     

偏振分光膜中节瘤的激光损伤特性

研究了1 064 nm HfO2/SiO2偏振分光膜中节瘤的损伤特性。为了研究偏振分光膜中节瘤缺陷种子源粒径大小与损伤阈值之间的关系,在熔石英基板上植入了尺寸和密度可控的单分散性的SiO2小球,并采用电子束蒸发技术在熔石英基板上制备了1 064 nm HfO2/SiO2偏振分光膜。为了便于损伤测试,节瘤缺陷密度控制在20~40 mm2左右,并采取旋涂的措施防止了SiO2小球团聚的现象。为了获得人工节瘤损伤能量的统计值,用脉宽为10 ns的1 064 nm脉冲激光进行了光栅扫描式损伤测试。实验结果表明在偏振分光膜中节瘤缺陷的损伤阈值随着种子源粒径的增大而单调下降。     

Liquid Metal-Enabled Microspheres with High Drug Loading and Multimodal Imaging for Artery Embolization

The drug-eluting microspheres that have been widely used in clinical treatments such as chemoembolization commonly suffer from inadequate drug loading and tracking difficulties. With inherent high density and excellent biocompatibility, liquid metal (LM) has been explored at the frontiers of medical imaging and clinical therapy. Herein, multifunctional microspheres (SA/LM/DOX) are reported with high drug loading and multimodal imaging by adsorbing silanized LM particles on sulfonated agarose microspheres (SA), which are capable of heating and accelerating drug release under an 808 nm near-infrared (NIR) laser. The negative SA microspheres can adsorb more positive drugs such as doxorubicin (DOX) up to 104 mg DOX per mL microspheres. It deserves to be mentioned that SA/LM/DOX microspheres have the function of multimodal imaging under computed tomography (CT), magnetic resonance imaging (MRI), and B-scan ultrasonography (US), which significantly facilitate location tracking during the embolization process. In rabbit ear central artery embolization, these microspheres are smoothly injected into the intended location of the vessel and successfully blocked blood flow, and eventually led to necrosis of rabbit ear. Overall, these microspheres with high drug loading capacity and multimodal contrast properties are promising candidates to be developed as new products for future clinical medicine.     

Si02光子晶体的制备及其自组装带隙特性研究

首先运用Stober溶胶凝胶法制备单分散Si02球形颗粒,通过扫描电镜研究各种反应条件如氨水浓度、无水乙醇的量、TEOS的浓度、温度等对二氧化硅的颗粒大小和形貌的影响,并通过SEM对样品的表面形貌进行了表征。通过研究改变垂直沉积法的各种条件对组装成的Si02光子晶体的带隙特性的影响。分析微球粒径、悬浮液中微球的体积分数、基片与液面之间所成的角度对光子晶体带隙性能的影响,并总结了较佳的垂直沉积法条件。     

Genetic algorithm-based characterization of the optical properties of flame-hydrolysis deposited silica waveguides

Genetic algorithms have been demonstrated to be a robust method for the calculation of the refractive-index profile of annealed germanium-doped flame-hydrolysis deposited (FHD) silica layers using measurements of the effective refractive indexes of the different modes of propagation. A nonuniform refractive-index profile in depth was obtained, which agrees well with the germanium concentration and density profiles measured for the films.     

Measurement of group birefringence and dispersion of polarisation maintaining erbium-doped silica fibre

The group birefringence and chromatic dispersion of a polarisation maintaining bow-tie erbium-doped silica fibre have been measured in the wavelength range 1.2-1.68 mu m by an interferometric measurement technique without any polarisers. The group birefringence is lower than that of a conventional bow-tie fibre and the zero dispersion wavelengths of the two polarisation modes are shifted to 1.613 and 1.630 mu m.<>     

Injectable Microfluidic Hydrogel Microspheres for Cell and Drug Delivery

Microfluidic hydrogel microspheres have been broadly studied across a wide range of industries and applications, and their use in the medical field, including control cells and drug delivery, is increasing. The usual design of these materials is intended to enable the efficient and smart encapsulation of cells and/or drugs in microspheres in which the functionalities and features are effectively controlled, lending itself some unique properties. These characteristics promote exchanges and cooperation in multiple disciplines and boost the development of precision medicine, new manufacturing technologies, and applied materials. This review begins with a discussion of microfluidic hydrogel microspheres and then introduces the preparation equipment, main principles, and related characteristics of the microspheres. Furthermore, the medical applications of microfluidic hydrogel microspheres for delivering cells and drugs are emphasized. Finally, this review discusses perspectives and future directions for accelerating the development and application of microfluidic hydrogel microspheres for controlled delivery.     

Combined Surface and Volume Templating of Highly Porous Nanocast Carbon Monoliths

Nanocast carbon monoliths exhibiting a three‐ or four‐modal porosity have been prepared by one‐step impregnation, using silica monoliths containing a bimodal porosity as the scaffold. Combined volume and surface templating, together with the controlled synthesis of the starting silica monoliths used as the scaffold, enables a flexible means of pore‐size control on several length scales simultaneously. The monoliths were characterized by nitrogen sorption, scanning electron microscopy, transmission electron microscopy, and mercury porosimetry. It is shown that the carbon monoliths represent a positive replica of the starting silica monoliths on the micrometer length scale, whereas the volume‐templated mesopores are a negative replica of the silica scaffold. In addition to the meso‐ and macropores, the carbon monoliths also exhibit microporosity. The different modes of porosity are arranged in a hierarchical structure‐within‐structure fashion, which is thought to be optimal for applications requiring a high surface area in combination with a low pressure drop over the material.     

Ultrabright Fluorescent and Lasing Microspheres from a Conjugated Polymer

Fluorescent microspheres are used for biomarkers, assay substrates, chemical diagnostics, flow cytometry, and biological imaging. These applications demand the highest fluorescence intensity achievable; however, concentration quenching limits the amount of dye that can be practically incorporated in conventional fluorescent microspheres. Conjugated polymers (CPs) can be less susceptible to concentration quenching, suggesting that they can be excellent candidates for a new class of light‐emitting microspheres. Due to their long‐chain‐conjugated backbone, however, CPs can be resistant to forming smoothly curved or spherical structures. Here, strongly fluorescent CP microspheres as large as 100 µm in diameter are synthesized. Whispering gallery modes (WGMs) appear in the fluorescence spectra, and the microspheres show clear evidence of lasing above a threshold pump intensity. These conjugated polymer beads are up to 50 times larger than CP microspheres obtained by other methods, and they exceed the emission intensity of conventional fluorescent microspheres by more than an order of magnitude.     

Design parameters for fluoride multimode fibers

Numerical calculations of losses due to polymer coatings and macrobending have been made for step-index multimode fluoride fibers. To minimize such losses, fiber parameters must be chosen to give a large value for V, the normalized frequency. Due to the long propagation wavelength (2.5 μm) for fluoride fiber, the parameters needed are very different from those of silica fiber. Using the criterion that ⩾90% of the modes have losses ⩽0.01 dB/km, it was found that the cladding diameters need to be rather large compared to step-index silica fiber parameters. Although the mode distributions are unknown for fluoride fiber, using a theoretical Gaussian distribution, losses were calculated for the various fiber parameters