Facile fabrication of hollow mesoporous silica nanospheres for superhydrophilic and visible/near-IR antireflection coatings

A series of hierarchically mesostructured silica nanoparticles (MSNs) less than 100 nm in size were fabricated by means of a one-step synthesis using dodecanethiol (C(12)-SH) and cetyltrimethylammonium bromide (CTAB) as the dual template, and trimethylbenzene (TMB) as the swelling agent. Silica nanoparticles with varied morphologies and structures, including mesoporous silica nanoparticles with tunable pore size, mesoporous silica nanoparticles with a thin solid shell, hollow mesoporous silica nanoparticles with tunable cavity size, and hollow mesoporous silica nanoparticles with a thin solid shell, were obtained by regulating the TMB/CTAB molar ratio and the stirring rate with the assistance of C(12)-SH. Silica particulate coatings were successfully fabricated by using MSNs with varied morphologies and structures as building block through layer-by-layer dip-coating on glass substrates. The thickness and roughness of the silica particulate coatings could be tailored by regulating the deposition cycles of nanoparticles. The silica particulate coatings composed of hollow mesoporous silica nanoparticles with a thin shell (S2) increased the maximum transmittance of slide glass from 90 to 96%, whereas they reduced its minimum reflection from 8 to 2% at the optimized wavelength region that could be adjusted from visible to near-IR with a growing number of deposition cycles. The coatings also exhibited excellent superhydrophilic and antifogging properties. These mesostructured silica nanoparticles are also expected to serve as ideal scaffolds for biological, medical, and catalytic applications.     

Formation of grafted surface layers on silicon dioxide particles and their investigation by means of thermoprogrammed oxidation

Silica nanoparticles are obtained according to the Stober–Fink–Bohn method, and their surfaces are chemically modified with 1H,1H,2H,2H-perfluorodecyltriethoxysilane. It is estimated that sols of porous silica nanoparticles (average sizes, 50–200 nm) form during primary chemical process; the average size of the particles can be increased to 400–500 nm by consecutive growth. Oxythermography (thermoprogrammed oxidation) measurements reveal a stepped dependence between the content of organic substance of nanoparticles and the duration of chemical modification reaction exists. It is concluded that this could be due to the formation of dense shell (or shells) as a result of sols aging between the cycles of growth; such shells impose diffusive restrictions when molecules penetrate into the pores of the internal volume of the particles.

     

Applying different types of artificial neural network for modeling thermal conductivity of nanofluids containing silica particles

Journal of Thermal Analysis and Calorimetry - Nanofluids are widely applicable in thermal devices with porous structures. Silica nanoparticles have been dispersed in different heat transfer fluids...     

Bright luminescent, colloidal stable silica coated CdSe/ZnS nanocomposite by an in situ, one-pot surface functionalization

In this article, a systematic study of the design and development of surface-modification schemes for silica coated nanocomposite via an in situ, one-pot way is presented. Silica coated CdSe/ZnS nanoparticles were prepared in a water-in-oil microemulsion and subsequently surface modified via addition of various organosilane reagents to the microemulsion system. The resulting functionalized composite nanoparticles were characterized by different techniques like Transmission Electron Microscopy (TEM), photoluminescence spectroscopy and zeta-potential measurements. The results demonstrate that depending on the sequence of addition of silica precursors and organosilanes the product can show bright luminescence or considerable colloidal stability. The organosilanes molecules which are used here, act both as a stabilizer of the microemulsion system (regarding the charge compensation) and as a functional group the final product on top of silica shell. Using these surface-modification process, silica coated nanoparticles can be more readily conjugated with biomolecules and used as highly luminescent, sensitive, and reproducible labels in bioanalytical applications. Most importantly such surface functionalization could pave the way for controlled multi-mixed nanoparticles encapsulation (for example magnetic and QD nanoparticles).     

Highly selective and sensitive chromo-fluorogenic detection of the Tetryl explosive using functional silica nanoparticles

Silica nanoparticles containing polyamines and thiol groups have been used as probes for the selective detection of Tetryl.     

Chromogenic silica nanoparticles for the colorimetric sensing of long-chain carboxylates

Silica nanoparticles functionalized with chromogenic spirobenzopyran and thiourea subunits show selective colour changes in the presence of certain long-chain carboxylates.     

Directed self-assembly of functionalized silica nanoparticles on molecular printboards through multivalent supramolecular interactions

Silica nanoparticles functionalized with beta-cyclodextrin (CD) host molecules (5) have been prepared by reacting carboxylic active ester-terminated silica nanoparticles (4) with CD heptamine. Silica nanoparticles functionalized with glucosamine (6), having similar surface properties as 5 but lacking the host-guest recognition motif, were used to perform blank experiments. The CD-functionalized silica nanoparticles 5 were determined by TEM to be 55 +/- 6 nm in size. They exhibited pH-dependent aggregation, which is explained by the presence of free amino and carboxylic acid groups on the particle surface, which was corroborated by zeta potential measurements. The functionalization with CD was further confirmed by host-guest studies in solution and at CD-functionalized silicon substrates. The addition of an adamantyl-terminated dendrimer, capable of multivalent host-guest binding with CD, led to strong aggregation of the CD particles 5, but not of the glucosamine-functionalized 6. Furthermore, 5 gave strong adsorption to CD monolayers on silicon onto which adamantyl-terminated dendrimers were adsorbed, whereas 6 did not. The good discrimination between dendrimer-covered and uncovered areas of the CD monolayer substrates allowed the directed self-assembly of the silica particles 5 onto dendrimer-patterned areas created by microcontact printing.     

Facile preparation of superhydrophobic silica nanoparticles by hydrothermal-assisted sol–gel process and effects of hydrothermal time on surface modification

Journal of Sol-Gel Science and Technology - Superhydrophobic silica nanoparticles were prepared by hydrothermal-assisted sol–gel process using a two-step synthesis route. Silica nanoparticles...     

Surface modification of silica nanoparticles to reduce aggregation and nonspecific binding

In this article, a systematic study of the design and development of surface-modification schemes for silica nanoparticles is presented. The nanoparticle surface design involves an optimum balance of the use of inert and active surface functional groups to achieve minimal nanoparticle aggregation and reduce nanoparticle nonspecific binding. Silica nanoparticles were prepared in a water-in-oil microemulsion and subsequently surface modified via cohydrolysis with tetraethyl orthosilicate (TEOS) and various organosilane reagents. Nanoparticles with different functional groups, including carboxylate, amine, amine/phosphonate, poly(ethylene glycol), octadecyl, and carboxylate/octadecyl groups, were produced. Aggregation studies using SEM, dynamic light scattering, and zeta potential analysis indicate that severe aggregation among amine-modified silica nanoparticles can be reduced by adding inert functional groups, such as methyl phosphonate, to the surface. To determine the effect of various surface-modification schemes on nanoparticle nonspecific binding, the interaction between functionalized silica nanoparticles and a DNA chip was also studied using confocal imaging/fluorescence microscopy. Dye-doped silica nanoparticles functionalized with octadecyl and carboxylate groups showed minimal nonspecific binding. Using these surface-modification schemes, fluorescent dye-doped silica nanoparticles can be more readily conjugated with biomolecules and used as highly fluorescent, sensitive, and reproducible labels in bioanalytical applications.     

纳米粒子毛细管电泳/微流控芯片新技术及其在手性分离中的应用

纳米粒子因其具有较大的比表面积和良好的生物相容性等特点,已广泛应用于分离科学领域。纳米粒子毛细管电泳/微流控芯片技术是纳米材料技术与毛细管电泳/微流控芯片技术相结合的产物。纳米粒子可以被吸附或键合到毛细管壁作为固定相与被分析物发生相互作用;也可以作为假固定相参与样品在柱内的分配和保留,从而提高柱效,改善分离。手性是自然界的本质属性之一,开发新的快速、高效、灵敏的手性分离分析方法对于对映体的立体选择性合成、药理研究、手性纯度检测和环境检测都具有重要的意义。本文主要综述了近些年来几种不同类型纳米粒子(聚合物纳米粒子、磁性纳米粒子、金纳米粒子、碳纳米管和其他类型纳米粒子)用于毛细管电泳/微流控芯片进行手性分离的现状,并对该领域今后的发展进行了展望。     

Palladium magnetic nanoparticle‐polyethersulfone composite membrane as an efficient and versatile catalytic membrane reactor

Developing polymer catalytic membrane reactors is an aim due to its outstanding advantages. In this paper, a novel catalytic membrane containing palladium‐supported magnetic nanoparticles is introduced. Silica‐iron oxide core shell nanoparticles were first prepared and functionalized by phosphine ionic liquid functionalized poly(ethylene glycol). The modified magnetic nanoparticles were used as support for immobilization of palladium. The final palladium‐immobilized nanoparticles were used as active filler for the preparation of membrane reactor. The prepared membranes were characterized, and their activities were tested in carbon‐carbon bond formation and catalytic reduction. The catalytic membrane showed good performance in the mentioned reactions.     

Reinforcement of recycled PP polymers by nanoparticles incorporation

Recycling process seems to be the most efficient way to reduce ecological impacts of used polymers. Nevertheless, the properties of the recycled PP polymer are proved to be insufficient during its reuse, particularly with regard to its thermo-mechanical and rheological behaviors. The incorporation of nanoparticles as fillers into polymer matrix seems to be one of the most successful solutions to upgrade recycled PP polymer. This paper presents an overview on the application of different nanofillers such as clay, calcium carbonate (CaCO₃), Silica (SiO₂), Zinc Oxide (ZnO), carbon black (CB), carbon nanotubes (CNT), antioxidizers and others into recycled PP matrix. Literature works on the effects of nanofillers on obtained nanocomposites are extensively studied. The first section deals with PP recycling and its impact on thermal, mechanical and rheological properties of the polymer. Then, the second part summarizes recent studies on the effects of nanoparticles incorporation on thermo-mechanical and rheological properties of recycled PP. Finally, recyclability of PP-based nanocomposites is discussed.     

Electroanalysis based on stand-alone matrices and electrode-modifying films with silica sol-gel frameworks: a review

Silica sol-gel matrices and its organically modified analogues that contain aqueous electrolytes, ionic liquids, or other ionic conductors constitute stand-alone solid-state electrochemical cells when hosting electrodes or serve as modifying films on working electrodes in conventional cells. These materials facilitate a wide variety of analytical applications and are employed in various designs of power sources. In this review, analytical applications are the focus. Solid-state cells that serve as gas sensors, including in chromatographic detectors of gas-phase analytes, are described. Sol-gel films that modify working electrodes to perform functions such as hosting electrochemical catalysts and acting as size-exclusion moieties that protect the electrode from passivation by adsorption of macromolecules are discussed with emphasis on pore size, structure, and orientation. Silica sol-gel chemistry has been studied extensively; thus, factors that control its general properties as frameworks for solid-state cells and for thin films on the working electrode are well characterized. Here, recent advances such as the use of dendrimers and of nanoscale beads in conjunction with electrochemically assisted deposition of silica to template pore size and distribution are emphasized. Related topics include replacing aqueous solutions as the internal electrolyte with room-temperature ionic liquids, using the sol-gel as an anchor for functional groups and modifying electrodes with silica-based composites.

     

喷涂法构筑二氧化硅纳米粒子涂层及其光学和润湿性质

采用Stöber方法,通过调节反应温度及乙醇和水的体积,合成了不同粒径的二氧化硅纳米粒子.以合成的粒径为20 nm的二氧化硅纳米粒子为原料,采用简单、方便的喷涂方法在玻璃片上构筑了纳米粒子涂层.在550 ℃煅烧二氧化硅纳米粒子涂层,增强了二氧化硅纳米粒子在玻璃片上的附着力.用1H, 1H, 2H, 2H-全氟辛基三乙氧基硅烷修饰之后,二氧化硅纳米粒子涂层的表面润湿性由亲水性转变为疏水性.通过喷涂法制备的二氧化硅纳米粒子涂层具有减反增透效果,当二氧化硅纳米粒子质量分数为0.48%、循环喷涂沉积数为3时,涂层在可见光范围内的最大透光率可达95.5%.用扫描电子显微镜观测涂层表面形貌发现,喷涂法制备的涂层是均匀的、可控的.喷涂技术构筑纳米粒子涂层具有简单快速、可大面积应用等优点.     

Synthesis and characterization of diazonium functionalized nanoparticles for deposition on metal surfaces

Silica nanoparticles were surface-functionalized with diazonium groups. The reaction steps leading to the formation of the diazonium functionality were followed with IR and XPS, and the structure of the diazonium-functionalized nanoparticle was confirmed with solid state NMR. Nanoparticle size distribution was determined with DLS, SEM, and TEM. The nanoparticles were then covalently bonded to gold and iron surfaces. Their spatial distribution over the metal surface was analyzed by SEM. Diazonium modification of nanoparticles represents a new method for the covalent attachment of nanoparticles to metal surfaces.     

Self‐Assembling Nanoparticles at Surfaces and Interfaces

Nanoparticles are the focus of much attention due to their astonishing properties and numerous possibilities for applications in nanotechnology. For realising versatile functions, assembly of nanoparticles in regular patterns on surfaces and at interfaces is required. Assembling nanoparticles generates new nanostructures, which have unforeseen collective, intrinsic physical properties. These properties can be exploited for multipurpose applications in nanoelectronics, spintronics, sensors, etc. This review surveys different techniques, currently employed and being developed, for assembling nanoparticles in to ordered nanostructures. In this endeavour, the principles and methods involved in the development of assemblies are discussed. Subsequently, different possibilities of nanoparticle‐based nanostructures, obtained in multi‐dimensions, are presented.     

MPS‐Modified Silica Nanoparticles Linked with Cd2+ Ions

Silica nanoparticles were linked by using 3‐mercaptopropyltrimethoxysilane (MPS) as a coupling agent and Cd²⁺ as bridging ions. The TEM micrographs showed approximately linear linkage between the silica nanoparticles rather than dense packing. The UV‐visible absorption spectra confirmed the formation of S‐Cd‐S bonds between the silica nanoparticles. The alternative films of MPS‐modified SiO₂ nanoparticles and Cd²⁺ ions were also prepared using the layer‐by‐layer self‐assembly technique and characterized by AFM.     

Synthesis of tubular gold and silver nanoshells using silica nanowire core templates

We report the synthesis of tubular gold and silver nanoshells on silica nanowire core templates in solution. Silica nanowires were synthesized and characterized with optical and NMR methods. Gold nanoparticle seeds (2 to 3 nm) with weak repulsive surfactants such as tetrakis-hydroxymethyl-phosphonium chloride (THPC) were conjugated to the surface of these nanowires. A regrowth process was initiated from these nanoparticles on the surface of the silica nanowires dispersed in gold or silver stock solutions in the presence of reducing agents. Micrometers-long gold and silver tubular nanoshells (80-150 nm o.d.) were made, fully covering the silica nanowires.     

Conjugated polyelectrolyte amplified fluorescent assays with probe functionalized silica nanoparticles for chemical and biological sensing

Low-cost sensors with high sensitivity and selectivity for chemical and biological detection are of high scientific and economic importance. Silica nanoparticles (NPs) have shown vast promise in sensor applications by virtue of their controllable surface modification, good chemical stability, and biocompatibility. This mini-review summarizes our recent development of silica NP-based assays for chemical and biological detection, where silica NPs serve as the substrate for probe immobilization, target recognition, and separation. The assay performance is further improved through the introduction of conjugated polyelectrolyte to amplify the detection signal. The assays have been demonstrated to be successful for the detection of DNA, small molecules, and proteins. They could be generalized for other targets based on specific interactions, such as DNA hybridization, antibody-antigen recognition, and target-aptamer binding.     

Preparation of Silica/Poly(tert‐butylmethacrylate) Core/Shell Nanocomposite Latex Particles

Nanocomposite latex particles, with a silica nanoparticle as core and crosslinked poly(tert‐butylmethacrylate) as shell, were prepared in this work. Silica nanoparticles were first synthesized by a sol‐gel process, and then modified by 3‐(trimethoxysilyl)propyl methacrylate (MPS) to graft C?C groups on their surfaces. The MPS‐modified silica nanoparticles were characterized by elemental analysis, FTIR, and ²⁹Si NMR and ¹³C‐NMR spectroscopy; the results showed that the C?C groups were successfully grafted on the surface of the silica nanoparticles and the grafted substance was mostly the oligomer formed by the hydrolysis and condensation reaction of MPS. Silica/poly(tert‐butylmethacrylate) core/shell nanocomposite latex particles were prepared via seed emulsion polymerization using the MPS‐modified silica nanoparticle as seed, tert‐butylmethacrylate as monomer and ethyleneglycol dimethacrylate as crosslinker. Their core/shell nanocomposite structure and chemical composition were characterized by means of TEM and FTIR, respectively, and the results indicated that silica/poly(tert‐butylmethacrylate) core/shell nanocomposite latex particles were obtained.