Linear and nonlinear optical properties of Au/SiO2 nanocomposite prepared by P123

Mesoporous silica thin films loaded with gold nanoparticles are synthesized in the presence of EO20PO70EO20（P123）.Transmission electron microscope images show that the matrix of the nanocomposite is an ordered porous structure with a two-dimensional hexagonal phase.The wide-angle X-ray diffraction pattern implies that the nanocomposite contains gold crystals.These metallic nanoparticleembedded solid thin films show some linear and nonlinear optical properties due to their special structure and composition.Gold nanoparticles bring about surface plasmon resonance,and an absorption peak stemming from this effect has been observed.The linear absorption property is analyzed by a quantum mechanism,and the results show that it is influenced by the size and volume fraction of gold nanoparticles. Furthermore,it shows an obviously clear nonlinear optical property measured by the z-scan technique.The magnitude of the nonlinear refractive index of the nanocomposite is estimated to be about 10？ 10 cm 2 /W.     

Single electron transistor with programmable tunnelling structure

A single electron transistor based on the ordered nanodot arrays was reported. The gold nanoparticles self-assembled in the ordered mesoporous silica thin films were used as the Coulomb islands. The Coulomb blockade and Coulomb oscillation are demonstrated at room temperature, and the SIMON simulations are consistent with the experimental results.     

Dual roles of amphiphilic triblock copolymer P123 in synthesis of α-Fe nanoparticle/ordered mesoporous silica composites

A simple and effective method for in situ synthesis of α-Fe nanoparticle/ordered mesoporous silica (OMS) composites is reported. Evaporation induced self-assembly (EISA) and carbothermal reduction (CR) are strategically combined by using amphiphilic triblock copolymer P123 as not only a template and but also a precursor of carbon material. P123 plays dual roles in assembly of mesostructure and reduction of ferric species. Thermogravimetric analysis-mass spectrometer was used to investigate the pyrolysis process of the wet gels. The synthesized composites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscope (XPS) and N₂ adsorption. The results showed that the composites possess ordered hexagonal mesoporous structure and the α-Fe nanoparticles with about 16 nm were well dispersed in mesoporous matrix. The carbon material resulting from P123 can reduce ferric species to α-Fe nanoparticles at 800 °C. Moreover, the formation mechanism for Fe nanoparticles in OMS matrix is proposed.     

An overview of engineered porous material for energy applications: a mini-review

The ordered porous materials, developed using various templating materials, have generated huge interest among the electrochemist community due to their plenty of unique properties and functionalities that can be effectively applied in optoelectronic devices. Mesoporous materials possess excellent opportunities in energy storage and energy conversion applications due to their extraordinarily high surface area and large pore size. These properties may enhance the performance of porous materials in terms of lifetime and stability, energy and power density. In this review, we have tried to club the fields of optoelectronics and mesoporous materials. Also, we have summarised the primary methods for preparing mesoporous materials using various templates and described their applications as electrodes and catalysts in fuel cells, solar fuel production, dye-sensitised solar cells, perovskite, supercapacitors and rechargeable batteries. Finally, we have highlighted the research and development challenges of mesoporous materials those need to be overcome to enhance their contribution in renewable energy applications.     

Ordered mesoporous silica materials (SBA-15) with good heat-resistant magnetism

A series of highly ordered mesoporous materials (CF-SBA-15) with heat-resistant magnetism have been successfully prepared from impregnation of cobalt salt, iron salt, and citric acid with as-synthesized SBA-15. XRD and N₂ isotherms indicate that these materials have highly ordered hexagonal mesoporous symmetry and open pore systems. The measurement of magnetic property shows that these materials are ferromagnetic even if calcined at 550 °C for 10 h in air, indicating their good heat-resistant magnetism. These results would be very important for recycle and regeneration of adsorbents and catalysts in practical applications. Moreover, this method may be useful for other mesoporous materials with thermally stable magnetism from a combination of other mesoporous materials such as MCM-41 with magnetic nanoparticles of MnFe₂O₄ and NiFe₂O₄.     

Magnetic behaviour of a magnetite/silicon nanocomposite

Mesoporous silicon is utilized to infiltrate quite monodisperse iron oxide nanoparticles into the pores. This semiconducting matrix exhibits oriented pores, clearly separated from each other, with an average pore diameter of 55 nm. Iron oxide nanoparticles of 8 nm and 5 nm in size which are coated with a surfactant are prepared by high temperature decomposition in the presence of an organic precursor. The achieved nanocomposite consists of dispersed Fe₃O₄-nanoparticles within the pores and offers magnetic properties which are determined by the morphology of the silicon matrix as well as by the distribution of the particles within the individual pores. Thus, the change of regime between a superparamagnetic and a blocked state of the system can be tuned. Furthermore, magnetic anisotropy between the two magnetization directions, normal and parallel to the sample surface, is observed due to the oriented and separated pores of the template which are quasi-regular arranged. This porous silicon/magnetite composite with its adjustable magnetic properties is also of interest for possible applications in biomedicine due to the low toxicity of both materials.     

A study on the structural and mechanical properties of ordered mesoporous Al2O3 film

Ordered mesoporous aluminum oxide films with a porosity range of 40-48% were synthesized by an evaporation-induced self-assembly (EISA) process using surfactant templating. To investigate the role of the hydrolysis reaction in the formation of a mesoporous structure, the changes of pore structure properties according to a variation of aging time and water molar ratio were monitored. From the tendencies of pore structure properties, the optimized condition for a high porosity and a highly ordered pore structure in ordered mesoporous alumina film was determined. This alumina film maintained the mesoporous structure even though it annealed at high temperatures, up to 1200 °C. Therefore, the ordered mesoporous alumina films synthesized in this study could be applicable as a material used at high temperature.     

Novel synthesis of highly ordered mesoporous Fe2O3/SiO2 nanocomposites for a room temperature VOC sensor

The controlled synthesis of mesoporous silica and metal oxide nanocomposites with a highly ordered porous structure and large specific surface area for specific applications has been an attractive topic in the field of porous materials. Herein, we introduce a novel method for the fabrication of highly ordered mesoporous structured and large specific surface area Fe₂O₃/SiO₂ nanocomposites, and consider their application in room temperature gas sensors. The mesoporous Fe₂O₃/SiO₂ nanocomposites were synthesised by a two-step method, which combines the hydrothermal growth of Fe₂O₃ nanoparticles and the microemulsion phase of Brij 56 (C₁₆EO₁₀) surfactant as templates in instantly direct-templating synthesis. This synthesis method enables the fabrication of mesoporous Fe₂O₃/SiO₂ nanocomposites without distortion of the ordered porous structure after calcination at high temperature. The synthesised materials were found to be efficient in a room temperature VOC sensor application, with good recovery.     

Exclusive T2 MRI contrast enhancement by mesoporous carbon framework encapsulated manganese oxide nanoparticles

Single mode (either T₁ or T₂) contrast agents employed during magnetic resonance imaging owe their advantage over their dual counterparts to the fact that they do not involve any quenching caused by interference between the two modes. The chemistry involving oxides of manganese is highly significant due to their applicability as MRI contrast agents. Manganese oxides are usually known to display a dominant T₁ relaxation enhancement. But, in this work, an engineered structure of manganese oxide (Mn₂O₃) nanoparticles encapsulated within mesoporous carbon frameworks was developed which exhibited dominant T₂ contrast enhancement, through regulation of contact between the magnetic ion and water. Microstructural characterization revealed that the mesoporous carbon frameworks were spherical in shape and the nanoparticles within them had an average size of 40–50 nm. Relaxivity measurement, MRI experiments and cell viability assay convincingly established the system as a new class of biocompatible T₂ based magnetic resonance imaging agent.     

Ordering and growth of Langmuir–Blodgett films: X-ray scattering studies

The interplay of ordering, confinement and growth in ultrathin films gives rise to various interesting phenomena not observed in bulk materials. The nature of ordering and interfacial morphology present in these films, in turn, depends on their growth mechanism. Well-ordered metal–organic films, deposited using an enigmatic Langmuir–Blodgett (LB) technique, are not only ideal systems for understanding the interplay between growth and structure of ultrathin films but also for studying chemical reactions and phase transitions in confined geometries. Studies on these LB films also enhance our understanding of the fundamental interactions of amphiphilic molecules important for biological systems. Advent of grazing incidence X-ray scattering techniques has enabled us to probe the interfacial structure of these multilayer films at very high resolution and as a result has improved our knowledge about the mechanism of growth processes and about physical/chemical properties of ultrathin films. In this review we will focus our attention on recent results obtained using these X-ray scattering techniques to understand the mechanism of growth leading to formation of remarkably well-ordered LB films after giving a brief outline of these scattering techniques. In addition, we also review recent results on growth and structure of nanoparticles formed by suitable chemical processes within the ordered matrix of LB films. Finally, we will discuss the work done on melting of LB films and its implications in our understanding of melting process in lower dimensions. In all these studies, especially those on as-deposited LB films results of atomic force microscopy measurements have provided important complementary morphological information.     

介孔二氧化钛光催化降解乙醛及其影响因素

"应用溶剂蒸发自组装的方法合成了具有蠕虫状孔道的介孔二氧化钛粉末和薄膜．考察了不同焙烧温度对材料介孔结构和光催化性能的影响．乙醛光催化降解实验用来表征不同焙烧温度下介孔材料的光催化性能．结果表明实验中合成的介孔二氧化钛材料的光催化活性明显高于颗粒二氧化钛(Degussa P25)．其中400 oC焙烧的样品具有平均孔径为6.0 nm的窄的孔径分布和117 m2/g的大的比表面积．通过对光催化活性结果的分析,发现介孔二氧化钛的活性主要受其比表面积和结晶性的共同影响．对介孔二氧化钛薄膜材料进行了同样的光催化表     

Magnetic nanoparticles as building blocks for high-performance magnetic materials

We report on the magnetic behaviour of films of Fe nanoparticles deposited from the gas phase with sizes in the range 2–3 nm embedded in Ag and Co matrices and Co nanoparticles of the same size embedded in Ag matrices. Magnetometry measurements, using a VSM, of very low volume fraction (1–2%) assemblies of Fe and Co in Ag show perfect superparamagnetism and enable us to confirm that the size distribution of the particles in the matrix is the same as that of the free particles prior to deposition. The hysteresis loops at 2 K, which is below the blocking temperature, show that the particles have a uniaxial anisotropy that is randomly oriented in three dimensions with the Co nanoparticles having a much higher anisotropy than the Fe particles. The soft magnetic behaviour of pure Fe and Co nanoparticle films with no matrix is well described by a random anisotropy model and is consistent with the formation of a correlated super-spin glass (CSSG) characteristic of amorphous materials. The Co nanoparticle films appear to have a lower random anisotropy than the Fe ones in contrast to the behaviour observed for the isolated particles. Films of Fe nanoparticles embedded in Co matrices, whose saturation magnetization exceeds the Slater–Pauling curve, also show magnetic behaviour consistent with a CSSG. At high volume fractions, the films of Fe nanoparticles embedded in Co matrices behave almost identically to films of pure Co nanoparticles.     

Photonic band gap thin films from mesoporous silica spheres acting as receptacles for species yielding added functionality

We demonstrate that mesoporous silica particles capable of acting as receptacles for functional nanoparticles may be readily synthesized and then assembled into photonic crystal thin films displaying well-defined Bragg diffraction features in the visible region. We show that it is possible to tailor not only the particle diameter, but also the pore diameters within the particles. As an example of the possible application of such particles in photonic crystal fabrication we show that it is possible to deposit Fe₂O₃ nanoparticles on the exterior of and inside the pores of hexagonal phase mesoporous silica spheres.     

Iron–cobalt nanocrystalline alloy supported on a cubic mesostructured silica matrix: FeCo/SBA-16 porous nanocomposites

A series of novel nanocomposites constituted of FeCo nanoparticles dispersed in an ordered cubic Im3m mesoporous silica matrix (SBA-16) have been successfully synthesized using the wet impregnation method. SBA-16, prepared using the non-ionic Pluronic 127 triblock copolymer as a structure-directing agent, is an excellent support for catalytic nanoparticles because of its peculiar three-dimensional cage-like structure, high surface area, thick walls, and high thermal stability. Low-angle X-ray diffraction, N₂ physisorption, and transmission electron microscopy analyses show that after metal loading, calcination at 500 °C, and reduction in H₂ flux at 800 °C, the nanocomposites retain the well-ordered structure of the matrix with cubic symmetry of pores. FeCo alloy nanoparticles with spherical shape and narrow size distribution (4–8 nm) are homogeneoulsy distributed throughout the matrix and they seem in a large extent to be allocated inside the pores.     

Synthesis and luminescent properties of PEO/lanthanide oxide nanoparticle hybrid films

In this study, we investigate the optical properties of lanthanide oxide nanoparticles dispersed in poly(ethylene oxide) (PEO) network as thermally stable polymeric films. The aim of this work is both to keep a good optical transparency in the visible domain and to obtain luminescent materials after incorporation of nanoparticles. For this purpose, we develop luminescent nanocrystals of oxides containing terbium ion as a doping element in Gd₂O₃. These sub-5-nm lanthanide oxides nanoparticles have been prepared by direct oxide precipitation in high-boiling polyalcohol solutions and characterized by luminescence spectroscopy. PEO/lanthanide oxide nanohybrid films are prepared by radical polymerization of poly(ethylene glycol) methacrylate after introduction of lanthanide oxide particles.As a first result; the obtained films present interesting luminescence properties with a very low lanthanide oxide content (up to 0.29 wt%). Furthermore, these films are still transparent and keep their original mechanical properties.Prior to describe the specific applications to optical use, we report here the dynamic mechanical analysis (DMA), X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM), and luminescent properties of. nanohybrid films.     

Nanosized iron and chromium oxides supported on mesoporous CeO2 and SBA-15 silica: Physicochemical and catalytic study

Mesoporous ceria and SBA-15 silica were modified with iron and chromium oxide nanoparticles and characterized by XRD, N₂-physisorption, FTIR, UV-vis, Moessbauer spectroscopy and TPR-TG in hydrogen. Their catalytic behaviour in methanol decomposition to CO and hydrogen was also studied. Stabilization of mono- and bi-chromate species, FeO_x patches or isolated iron ions as well as Fe₂O₃ and Cr₂O₃ nanoparticles in different ratio depending on the nature of the porous matrix was observed. The simultaneous presence of iron and chromium oxides lead to change in their dispersion, providing easier reducibility, higher catalytic activity and stability of the obtained materials in comparison with the corresponding mono-component ones. The “intimate contact” at the interface of both loaded metal oxide nanoparticles and the support was discussed with respect to explain the differences in the state of the active ingredient and its specific catalytic behaviour.     

Mesoporous silica-coated superparamagnetic particles prepared by pseudomorphic transformation and their application in purification of plasmid DNA

Abstract  

Mesoporous silica-coated superparamagnetic particles were prepared via pseudomorphic transformation of pre-made amorphous silica-coated Fe₃O₄–polymer composite particles using n-cetyltrimethylammonium bromide (CTAB) and 1,3,5-trimethyl benzene (MES) as template. The mesoporous particles presented almost the same size, shape, and magnetic property as the original amorphous particles but an ordered mesoporous shell with wormhole-like pore structure. The pore size of the shells increased from 2.4 to 3.1 and 4.2 nm as the molar ratio of MES/CTAB increased from 0 to 1.0 and 1.5. DNA extraction experiments showed the mesoporous particles were qualified for purification of plasmid DNA from bacterial lysate.     

Adsorptive removal and kinetics of methylene blue from aqueous solution using NiO/MCM-41 composite

Highly ordered mesoporous material MCM-41 was synthesized from tetraethylorthosilicate (TEOS) as Si source and cetyltrimethylammonium bromide (CTAB) as template. Well-dispersed NiO nanoparticles were introduced into the highly ordered mesoporous MCM-41 by chemical precipitation method to prepare the highly ordered mesoporous NiO/MCM-41 composite. X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and high-resolution TEM (HRTEM), and nitrogen adsorption–desorption measurement were used to examine the morphology and the microstructure of the obtained composite. The morphological study clearly revealed that the synthesized NiO/MCM-41 composite has a highly ordered mesoporous structure with a specific surface area of 435.9 m² g⁻¹. A possible formation mechanism is preliminary proposed for the formation of the nanostructure. The adsorption performance of NiO/MCM-41 composite as an adsorbent was further demonstrated in the removal azo dyes of methyl orange (MO), Congo red (CR), methylene blue (MB) and rhodaming B (RB) under visible light irradiation and dark, respectively. The kinetics and mechanism of removal methylene blue were studied. The results show that NiO/MCM-41 composite has a good removal capacity for organic pollutant MB from the wastewater under the room temperature. Compared with MCM-41 and NiO nanoparticles, 54.2% and 100% higher removal rate were obtained by the NiO/MCM-41 composite.