Preparation Of Micro Research Articles

Activated carbon xerogels with a cellular morphology derived from hydrothermally carbonized glucose-graphene oxide hybrids and their performance towards CO2 and dye adsorption

We report the preparation of micro-/mesoporous carbon monolithic xerogels by means of a two-step approach that comprises (1) hydrothermal carbonization of glucose in the presence of graphene oxide (GO) sheets as morphology-directing agents and (2) chemical activation of the resulting hydrothermal carbon (HTC) xerogels with KOH. The as-prepared HTC xerogels were made up of a random assembly of thin (<30nm) carbon platelets, which were interpreted to arise via dehydration and condensation reactions of glucose at catalytically active (acidic) sites present on the surface of GO. The chemical activation afforded xerogels with large surface areas and pore volumes (up to ∼2000m2g−1 and 1.15cm3g−1, respectively) and a cellular morphology, which could be attributed to the combined effect of the activating agent and the unusual, compliant nature of the HTC xerogel. Additionally, the use of different activation conditions allowed fine-tuning the porous texture of the activated xerogels. Finally, the activated carbon xerogels displayed CO2 uptake capacities up to 4.9mmolg−1 at 0°C and 1bar, as well as an efficient performance (between 600 and 700mgg−1) in the adsorption of bulky dyes, thus demonstrating their application potential.

Preparation of Micro-/Macroporous Carbons and Their Gas Sorption Properties

Micro-/macroporous carbons (MMCs) were prepared using a hollow mesoporous silica capsule (HMSC) as a sacrificial hard template. The carbonization process after the infiltration of furfuryl alcohol into the template-free HMSC material afforded MMC materials in high yield. The hard template HMSC could be removed by HF etching without deteriorating the structure of MMC. The MMC materials were fully characterized by SEM, TEM, PXRD, XPS, and Raman spectroscopy. The replication processes were so successful that MMCs exhibited a hollow capsular structure with multimodal microporosity. Detailed textural properties of MMC materials were investigated by volumetric <TEX>$N_2$</TEX> adsorption-desorption analysis at 77 K. To explore the gas sorption abilities of MMCs for other gases, <TEX>$H_2$</TEX> and <TEX>$CO_2$</TEX> sorption analyses were also performed at various temperatures. The multimodal MMC materials were found to be good sorbents for both <TEX>$H_2$</TEX> and <TEX>$CO_2$</TEX> at low pressure.

Particles from preformed polymers as carriers for drug delivery.

Biodegradable and biocompatible polymers are widely used for the encapsulation of drug molecules. Various particulate carriers with different sizes and characteristics have been prepared by miscellaneous techniques. In this review, we reported the commonly used preformed polymer based techniques for the preparation of micro and nano-structured materials intended for drug encapsulation. A description of polymer-solvent interaction was provided. The most widely used polymers were reported and described and their related research studies were mentioned. Moreover, principles of each technique and its crucial operating conditions were described and discussed. Recent applications of all the reported techniques in drug delivery were also reviewed.

전기분사법에 의한 다공성 실크 피브로인 미세입자의 제조

실크 피브로인은 뛰어난 생체적합성 및 생분해성으로 인해 의료용 천연고분자소재로 각광받고 있으며 다양한 형태로 제조되어 이용되고 있다. 전기분사법은 고분자 용액에 고전압을 적용하여 미세입자를 제조하는 방법으로 진행과정이 간단하고 첨가제를 필요로 하지 않는다는 장점을 지닌다. 본 연구에서는 실크 피브로인 다공성 미세입자를 제조하기 위하여 폴리(에틸렌 글리콜)(PEG)을 첨가한 후 전기분사를 실시하였다. PEG를 첨가함으로써 분사원액의 전도도는 감소하였고 점도는 증가하였다. 제조된 미세입자의 크기는 PEG 첨가에 따라 감소하였는데 이는 분사용액의 전도도 및 점도보다는 피브로인과 PEG간의 상분리에 의한 효과인 것으로 보인다. 제조된 실크 피브로인 미세입자를 물에 침지한 결과 PEG가 제거되었으며 최종적으로 실크 피브로인 다공성 입자를 제조할 수 있었다. 제조된 다공성 실크 피브로인 미세입자는 약물전달체 및 조직공학용 세포전달체로 이용가능성이 높을 것으로 기대된다. Nowadays, silk fibroin receives a lot of attention as novel natural biomaterials due to its excellent biocompatibility and biodegradability. Electrohydrodynamic spraying (EHDS) is one of the method for the preparation of micro or nanoparticles by applying high voltage to the polymer solution. In this research, we fabricated silk fibroin porous microparticles by electrohydrodynamic spraying. Poly(ethylene glycol) (PEG) was added to the fibroin solution to give pores to silk fibroin microparticles. By the addition of PEG, the microparticle size was decreased despite of the decrease in conductivity and the increase of viscosity of the spraying solution. It seems that the immiscibility of silk fibroin and PEG affected much more to the microparticle size than the conductivity and viscosity. Immersing the as-sprayed microparticles into the water removed the phase-separated PEG, and finally, porous silk fibroin microparticles were prepared. The porous silk fibroin microparticles are expected to be applied as drug carriers in drug delivery or cell carriers in tissue engineering.

Preparation of micro- and crypto-tephras for quantitative microbeam analysis

Abstract The smallest tephra grains present special challenges in their preparation for quantitative microbeam chemical analysis by EPMA and LA-ICP-MS. High-quality polished surfaces are an essential pre-requisite for the collection of high quality quantitative chemical data, as these shards also present significant difficulties for analysis. A method for the preparation of tephra grains as small as 10–50 µm is described in detail. This method uses inexpensive, widely available materials and is easily implemented in facilities in which polished geological samples are prepared for microanalysis. Samples prepared in this way reduce or eliminate the difficulties in microbeam analysis associated with small grains, when appropriate analytical protocols are used.

Research on Progress and Possibility of Electrospining of Native Cellulose and Preparation of Copper-Based Antimicrobial Fiber

Electrostatic spinning is now recognized as a versatile and easily feasible method for the preparation of micro and nanofibrous materials. Because of their high specific surface area and highly porous structure electrospun materials can find application as wound dressings that provide good draining and good air permeability [. By adding various types of material or chemical modification in electrospun materials, we can prepare a polymer with excellent antibacterial properties of nanomaterials. Copper, an inorganic antibacterial agent, is also called the second silver. The antibacterial research of copper series attracted great concern in recent years. First, the paper introduced the progress and mechanism of electrostatic spinning of native cellulose and Cu (II) ion antimicrobial fibres, and then did a brief presentation of copper ion antibacterial fibers on the bases of electrostatic spinning of native cellulose.

Fluorescent Films Based on Molecular-Gel Networks and Their Sensing Performances

A pyrene-capped terthiophene of cholesteryl derivative (CholG-3T-Py) was designed, synthesized, and utilized for the fabrication of a fluorescent film. Unlike the commonly adopted direct-coating method, the film was fabricated by the physical immobilization of the fluorophore, CholG-3T-Py, onto a glass plate surface via preformed low-molecular-mass gelator (LMMGs)-based molecular-gel networks. The photophysical behavior of the film as prepared and its sensing performances to nitrobenzene (NB) were conducted after activation with toluene. It was found that the film as prepared and activated is sensitive to the presence of NB, and the sensing process is fully reversible. Furthermore, the effects of commonly found interferents, including structural analogues, raw materials, which are commonly used for the production of NB, and other nitroaromatics (NACs), on the sensing process were also tested. It was shown that only aniline and phenol possess slight interference. The present work not only extends the applications of LMMGs-based molecular gels but also provids a new approach for preparation of micro- and nano-structure-based fluorescent sensing films.

Preparation of micro and nanostructured titania compounds from ilmenite concentrates

Preparation of titania compounds by double-reductive hydrochloric acid leaching of ilmenite concentrate is reported. A rod-shaped nanostructure titania compound was obtained via centrifugation of leach liquors as a by-product. The liquors of leaching experiments were subjected to zetasizer test. The suspended particles in leach liquors were investigated using SEM and TEM analysis. The results revealed that the rod-shaped particles were smaller than 100nm in width. The XRD analysis verified the formation of rutile and pseudorutile phases as main phases. Regarding to the XRF analysis, The TiO2 content of ilmenite increased from 33% in ilmenite concentrate to about 80% in the products containing some constituents such as Fe2O3, SiO2 and Al2O3.

Transition Experiences: Perilous Passages or New Challenges? Theoretical and Practical Understanding of Transitions for People With Autistic Spectrum Conditions

The aim of this paper is to present a theoretical and practical understanding of transitions in young people with an Autistic Spectrum Condition (ASC) and to discuss ways in which support can be provided at different stages of their lives. It aims to propose and highlight some practical initiatives which can be adopted in the preparation of micro and macro transitions thus ensuring an understanding of the criteria behind such practices which can further support practitioners in the long-term aim of positive and empowering outcomes. Ashforth (2001, Role transitions in organizational life: An identity based perspective. Mahwah, NJ: Lawrence Earlbaum Associate) proposes four motives: identity, meaning, control and belonging, which are discussed in the context of role-transitions. These transitions can often require an adjustment in an individual’s behaviour and relationships with their environment as well as people around them. Transitions occur throughout our lives and these key times can cause high levels of disorientation and anxiety more so in people with ASC. The impact of a range of transitions is also discussed and suggestions of ways in which individuals with ASC can be supported are also presented through examples of key resources which can be tailored to each individual’s needs.

Preparation of micro- and nano-emulsions of soybean oil and removal of sorbed phenanthrene from sandy soil

Soybean oil was used as a biodegradable extracting agent for the removal of sorbed phenanthrene (PHE) in sandy soil. In this study, several methods of forming emulsions using soybean oil and their extraction properties were investigated. The stable and homogeneous oil emulsions were formed more effectively by ultrasonication (U1) than by homogenization (H1). Moreover, homogenization before ultrasonication (HU1) established more stable emulsions than U1 alone. The mean diameter of oil droplets in U1 or HU1 was reduced to the nanometer range (approximately 70 nm) by U1 with 750W using a high-power sonic tip operated at 33% amplitude and 20 kHz frequency for 5 min. The extraction efficiency of sorbed PHE from soil by oil emulsions increased with decreasing size of droplets of oil emulsions; the maximum extraction of PHE was achieved with HU1. Thus, nano-emulsions of vegetable oil made by U1 could be an environmentally benign alternative for effectively washing soil.

Hierarchically structured zeolites: synthesis, mass transport properties and applications

Zeolites with hierarchically porous structures have garnered much attention due to their highly attractive properties. Hierarchically structured zeolites integrate at least two levels of porosity and present the advantages associated with each level of porosity, from selectivity to mass transport. They are categorized into three distinctly different types according to their hierarchical porosities: mesostructured zeolites, macrostructured zeolites, and micro–meso–macroporous structured zeolites. Most importantly, hierarchically structured zeolites offer an effective solution to the mass transport problem associated with conventional zeolites in catalysed reactions because they combine the catalytic features of micropores and the improved accessibility and increased molecular transport related to the addition of several porosities within a single body. In recent years, many strategies have been successfully developed to synthesize hierarchically structured zeolitic materials. This feature article thoroughly summarizes recent developments that have been achieved in the field of hierarchically structured zeolites, with the main focus on the synthesis strategies that are available, with examples given from the literature. Available approaches are reviewed for the preparation of micro–mesoporous structured zeolites, micro–macroporous structured zeolites and micro–meso–macroporous structured zeolites. Furthermore, the enhanced mass transport properties of hierarchically structured zeolites, featuring additional larger pores in addition to the crystalline micropores, have also been described. The significant improvement in catalytic properties in a range of important reactions resulting from enhanced mass transport properties have also been discussed through several representative cases. It is the intent of this work to stimulate intuition into the optimal design of related hierarchically organized zeolites with desired characteristics.

Preparation of micro- and nanospheres with superamphiphobic surfaces by dispersion polymerization

Micro- and nanospheres with superamphiphobic surfaces were prepared by a simple method that employed the conventional dispersion polymerization of perfluoroalkyl methacrylates in methanol. The polymerizations of 2,2,2-trifluoroethyl methacrylate (TFMA) produced microspheres with an average 4.12-μm diameter, while that of 2-(perfluorooctyl)ethyl methacrylate (POMA) provided nanospheres with a 679-nm diameter. An X-ray photoelectron spectroscopy analysis revealed that the fluorine atoms were highly concentrated on the top of the sphere surfaces. It was found that the surface coated with the spheres had a superamphiphobicity. The water contact angles were 150° for the PTFMA microspheres and 173° for the PPOMA nanospheres, while the diiodomethane contact angles were 159° for the microspheres and 160° for the nanospheres. The synergistic effect of the spherical structure and the high concentration of fluorine on the top of the surface produced the superamphiphobicity.

Facile Fabrication of Polysiloxane Nanorods on Magnesium Surface in the Presence of 1,6-diphosphono-hexane to Obtain a Superhydrophobic Surface

Superhydrophobic surfaces have been the focus of both industry and academic research. The high water repellency exhibited by these surfaces is based on a natural phenomenon (i.e. Lotus effect). Superhydrophobicity is explained by the Wenzel and Cassie-Baxter model. According to this model, the air trapped in micro-/nano-scale rough surfaces is a key factor in making these surfaces superhydrophobic. The trapped air and the micro-/nano-scale rough surface act to suspend the water droplet on the tops of the surface microstructure. In nature, there are many examples of plants and animals utilizing superhydrophobicity for various purposes. There are two factors that determine the superhydrophobicity of a surface. The first one is the chemical composition on the surface, which for superhydrophobicity, must have low surface energy. The second factor is the geometrical structure of the surface. Surface roughness is a key factor controlling wettability because it determines the contact area between a water droplet and the surface. One of the criteria for superhydrophobicity is that the water contact angle of the surface should be more than 150. A water droplet on even a slightly tilting superhydrophobic surface will not remain on it but will roll off. This property can be exploited to remove contaminants on a superhydrophobic surface using water droplets. The lotus leaf possesses this self-cleaning property, which originates from the wax-covered microstructures on its surface. This self-cleaning effect has been exploited for various applications such as for developing water repellency coatings, preventing snow sticking, and enhancing the lubricity of micro-fluidic devices. However, the fabrication of superhydrophobic surfaces requires the preparation of micro-/nano-scale rough surfaces, and thus many methods have been developed to fabricate such surfaces; these methods include metal atom deposition, the sol-gel method, and etching process. However, these methods are generally complex and require the use of expensive devices. Therefore, a simple and inexpensive approach for obtaining industrially feasible superhydrophobic surface is required. Polysiloxane is a well-known hybrid organic-inorganic material, and it has been studied extensively. Polysiloxane is prepared by the hydrolysis and condensation of alkyl triethoxysilanes. A series of reactions are carried out to finally produce oligomers and polymers. There are many complex reactions that produce many different polysiloxanes. Mabry et al. prepared the fluorinated polyhedral oligomeric silsesquinoxane using one-pot synthetic method. The surface that was coated with this fluorinated polyhedral compound exhibited hydrophobic property whose effectiveness was dependent on the length of the fluoroalkyl chain. Fluorinated alkyl silane and alkyl silane have been used to coat micro/nano-scale rough surfaces to obtain a superhydrophobic surface. This coating layer is transparent. Generally, the alkyl silane derivative used as the coating layer is a flexible amorphous polysiloxane or a transparent self-assembled monolayer. In 1997, Parikh et al. obtained the crystalline structure of polymerized octadesylsiloxane (PODS). Li et al. obtained a superhydrophobic surface with liquid n-octadecyl trichlorosilane. A nanosheet of PODS was obtained by coating a glass surface with liquid PODS and then dipping the glass surface in an organic solvent. The nanosheet was obtained by the forming of a self-assembled structure that then underwent polycondensation. In the present study, we have demonstrated the facile synthesis of nano-rode structures of polysiloxane on a metal surface achieved by simply dipping Mg piece in a mixture solution of alkyltriethoxysilane and 1,6-diphosphonohexane. The prepared rough surface of the Mg piece was coated with a solution of stearic acid in alcohol to obtain superhydrophobic surface.

Micro- and nano-scale hollow TiO 2 fibers by coaxial electrospinning: Preparation and gas sensing

We report the preparation of micro- and nano-scale hollow TiO 2 fibers using a coaxial electrospinning technique and their gas sensing properties in terms of CO. The diameter of hollow TiO 2 fibers can be controlled from 200 nm to several micrometers by changing the viscosity of electrospinning solutions. Lower viscosities produce slim hollow nanofibers. In contrast, fat hollow microfibers are obtained in the case of higher viscosities. A simple mathematical expression is presented to predict the change in diameter of hollow TiO 2 fibers as a function of viscosity. The successful control over the diameter of hollow TiO 2 fibers is expected to bring extensive applications. To test a potential use of hollow TiO 2 fibers in chemical gas sensors, their sensing properties to CO are investigated at room temperature.

Dissolution rate improvement of valsartan by low temperature recrystallization in compressed CO 2: Prevention of excessive agglomeration

In this study, the recrystallization of valsartan by ASES (Aerosol Solvent Extraction System), a supercritical micronization process, using compressed CO 2 was carried out to improve the bioavailability of valsartan through preparation of micro sized particles without excessive agglomeration. Fine valsartan particles from an ethyl acetate (EA) solution were precipitated using compressed CO 2 as an antisolvent at low temperature. The EA was considered a proper organic solvent to prevent agglomeration of the prepared valsartan associating to the solubility parameters of the solvents. Ultra fine valsartan particles with a mean diameter of 0.1 μm were obtained without excessive agglomeration at the subcritical CO 2 of 70 bar and 5 °C. When the supercritical CO 2 was at 100 bar and 40 °C, valsartan was precipitated to fine particles that tended to agglomerated due to the melting point depression produced by CO 2. During the agglomeration process, particles were sintered by the Ostwald ripening mechanism, which resulted in an increase in particle size. Agglomeration of the particles was shown to be prevented at low temperature, where re-melting of the precipitated valsartan particles is minimized. Hence, processed valsartan with compressed CO 2 at a low temperature improved its dissolution rate due to the small size of the particles attributing to low level of particle agglomeration.

Laser assisted electrochemical preparation of micro and nanopores in Ga x In1−x P

We report on the preparation of Ga(x)In(1−x)P/GaAs lattice matched heterostructures by liquid phase epitaxy and their electrochemical etching to prepare porous networks. We show that the process of formation of pores strongly depends on the electrolyte, on the applied current/voltage anodization regime, and that illumination is a crucial factor in obtaining fine porous structures with a high degree of self-organization.

Nanocrystalline silicon in biological studies

AbstractPorous silicon and similar materials, like micro‐ and nanocrystalline silicon, are nowadays studied not only in physical research (e.g. optical gain studies, electro‐optical devices, solar energy conversion), but they are very promising also in biological research as fluorescent labels, biological sensors, drug delivery systems or scaffold for various tissues. We are giving an overview of various approaches of preparation of micro‐ and nanocrystalline silicon and current studies of applications with main focus on biology and medicine. In contrast to other nanomaterials used in biological studies (e.g. carbon nanotubes, fullerenes, cadmium containing quantum dots) silicon based nanomaterials show very good biocompatibility and low cytotoxicity. Therefore, these materials have potential to become powerful tools for in vivo investigation of life processes on subcellular and molecular level. Our group concentrates on developing of gentle florescent label based on porous silicon for single molecule detection in the cell. (© 2011 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

SIMS depth profile analysis of particles collected in an urban environment

AbstractAnalytical procedures of collection and sample preparation of micro‐ and nanoparticles from urban environment as well as results of analyses are presented. Particulate matter is collected from indoor and outdoor urban air by several methods using mechanical collectors: personal cascade impactor and quartz filters. The other method treats human organisms as collectors: the method is based on induced sputum. Elemental analysis of the collected material performed by spark‐source mass spectrometry (SSMS) on magnetic sector JEOL JMS‐1BM2 mass analyzer, gives concentration of over 20 elements with ppb sensitivity. SIMS depth profile analysis is performed on SAJW‐05 apparatus with quadrupole QMA‐410 analyzer and Physical Electronics ion gun. Indium substrate covered with particulate matter is scanned with 100 µm diameter 5 keV Ar+ ion beam. Particles collected by cascade impactor were deposited at indium substrates. Four aerodynamic diameter classes were analyzed, i.e. 10–2.5 µm, 2.5–1 µm, 1–0.5 µm and 0.5–0.25 µm. Depth profile analysis was performed up to 100 nm depth of eroded material. Results were obtained on sets of particles, and the measured secondary ion currents gave integral values of the analyzed material. Assuming average surface composition of the analyzed particles some hints on the compositional morphology of the type of ‘core‐shell’ are extracted. Obtained data on the bulk elemental composition and SIMS depth profile results show the dependence on the grain size. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Facile fabrication of nanoporous composite separator membranes for lithium-ion batteries: poly(methyl methacrylate) colloidal particles-embedded nonwoven poly(ethylene terephthalate)

Highly-ordered nanoparticle arrangements have drawn substantial attention as an ideal starting template for the preparation of micro- and nanostructured porous materials. In the present study, by exploiting the concept of these unusual colloidal structures, we demonstrate facile fabrication of novel nanoporous composite separator membranes for high-safety and high-power lithium-ion batteries. This is based on the introduction of close-packed poly(methyl methacrylate) (PMMA) colloidal particle arrays to a poly(ethylene terephthalate) (PET) nonwoven support. Herein, the nanoparticle arrangement, driven by the self-assembly of PMMA colloidal particles provides a highly-ordered nanoporous structure, i.e. well-connected interstitial voids formed between the close-packed PMMA nanoparticles, in the composite separator membrane. The nonwoven PET serves as a mechanical support to mitigate the thermal shrinkage of the nonwoven composite separator membrane. Performance benefits of the nonwoven composite separator membrane, as compared to a commercialized polyethylene (PE) separator membrane, are elucidated in terms of thermal shrinkage, liquid electrolyte wettability, and ionic transport. Based on comprehensive characterization of the nonwoven composite separator membrane, the effect of the nanoporous structure on the electrochemical performance, such as self-discharge, discharge capacity, discharge C-rate capability, and cyclability of cells is investigated.

Octadecyl acrylate – Methyl methacrylate block and gradient copolymers from ATRP: Comb-like stabilizers for the preparation of micro- and nano-particles of poly(methyl methacrylate) and poly(acrylonitrile) by non-aqueous dispersion polymerization

Three random and three block copolymers of methyl methacrylate (MMA) and octadecyl acrylate (ODA) were synthesized by atom transfer radical polymerization. These copolymers were assessed for their application as stabilizers in the one-step non-aqueous dispersion (NAD) polymerization of MMA and of acrylonitrile (AN) in a non-polar solvent mixture of hexane and dodecane. In all cases stable spherical micro-particle colloidal dispersions were formed with particle diameters in the range of 62–2725 nm for PMMA. Uniform monodisperse PMMA particles with standard deviations in size distributions of less than 5% were obtained in two cases demonstrating the utility of ODA:MMA copolymers as replacement preformed stabilizers in the one-step synthesis of MMA micro-spheres. Overall the block copolymer PMMA64-block-PODA36 gave greater control over size when varying the solvent:monomer ration than a related gradient PMMA–PODA copolymer. These copolymers were further used as stabilizers in the one-step NAD polymerization of MMA with ethylene glycol dimethacrylate (EGDMA) under similar conditions allowing for the preparation of monodisperse cross-linked PMMA particles with diameters ranging from 110 to 1700 nm. The general utility of the copolymers as stabilizers was demonstrated by the NAD polymerization of acrylonitrile (AN) in non-polar solvent mixture of hexane and dodecane giving ‘crumpled’ latex dispersions with particle diameters in the range 85–483 nm.