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We investigate the preparation of nearly monodisperse gold nanoparticles by heat treatment in different conditions. The effects of various solvents, heating temperature, and heating time length on the monodispersity of gold nanoparticles were studied systematically and a general route to generate gold nanoparticles with uniform size was determined. The first step was to prepare gold nanoparticles with less than 3 nm and the following operation was to heat the gold nanoparticles in the present of thiolated solvents where monodispersed gold nanoparticles could be obtained easily. Our approach has enriched synthesis of monodisperse gold nanoparticles, and may provide some valuable experimental data about how the heating process affects the size evolution of gold nanoparticles. [ABSTRACT FROM AUTHOR]

Mesoporous silica microspheres in the 1-2 μm range with good size monodispersivity were synthesized by ammonia catalysed hydrolysis and condensation of tetraethylorthosilicate using methanol as solvent and cetyltrimethylammonium bromide as surfactant porogen. The mesopore diameter was subsequently expanded from <20 Å to ~200 Å by a postsynthesis hydrothermal treatment in a water-amine emulsion system followed by controlled dissolution in aqueous alkali. XRD, TEM, and N sorption measurements were used to characterize pore properties. Particle size measurements in conjunction with SEM were used to establish morphology and size distribution. Preliminary chromatographic results are presented which demonstrate the applicability of these particles in High Performance Liquid Chromatography (HPLC). The particle size, porosity and chromatographic performance of the particles are compared to commercial HPLC silicas. [ABSTRACT FROM AUTHOR]

Abstract: This article describes the preparation and characterization of fluorescent and magnetic composite particles of poly(styrene-co-methacrylic acid-co-2-naphthyl methacrylate) (poly(St/MAA/NMA)). First, monodisperse (Dw /Dn <1.1) and fluorescent poly(St/MAA/NMA) submicron particles were prepared using emulsifier-free emulsion polymerization by varying the concentration of the fluorescent comonomer, i.e., NMA. Composition of the particles was characterized by 1H NMR, FT-IR, GPC, and DSC analyses. The molecular weights and particle size of the particles were dependent on the NMA concentration. Second, Fe3O4 nanoparticles were immobilized onto the poly(St/MAA/NMA) submicron particles to give rise to multifunctional properties. The morphology and particles size were characterized by FE-SEM and CHDF. These poly(St/MAA/NMA)/Fe3O4 composite particles exhibited both fluorescent properties under UV irradiation at 365nm and magnetic properties. Photo-luminescent (PL) intensity of the particles showed linear dependence with NMA concentration. [Copyright &y& Elsevier]

A one-step method was presented for the controlled synthesis of highly monodisperse vinyl functionalized silica spheres (VFSSs), which could be self-assembled into three-dimensional (3D) fcc colloidal photonic crystals on a horizontal glass slide by a gravity sedimentation process. One precursor (vinyltriethoxysilane) and one solvent (water) were used in the experiment. The size of VFSSs could be adjusted from 420 to 650 nm with relative standard deviation below 2% by controlling the dripping speed of diluted ammonia catalyst, without changing the concentration of precursor/catalyst. SEM and TEM images illustrate the copiousness in quantity and the uniformity in size/shape of the VFSSs. 29Si nuclear magnetic resonance (NMR) spectrum confirms the surfaces of VFSSs have abundant vinyl groups (–CH=CH2) which connect to the silicon atoms. Optical characterizations of the transmission spectra reveal that the periodic arrays exhibit a photonic band gap in the (1 1 1) direction of the fcc lattice in consistent with the Bragg diffraction theory. This work has also been extended to prepare other monodisperse surface-modified silica spheres and fabricate organic functionalized colloidal templates. [Copyright &y& Elsevier]

We report a novel and facile method for fabricating coaxial microfluidic devices processing various dimensions at low cost, in which polypropylene hollow fibers or glass capillaries are used as the tip of the dispersed phase injection tube. With this coaxial microfluidic device, monodisperse biocompatible microspheres ranging from 300 to 800 μm were obtained by collecting oil-in-water or water-in-oil emulsions and solidifying the suspended microspheres. Microsphere size could be controlled by changing the tips or tuning the concentrations of the dispersed and continuous phases. By adding functional nanoparticles into the dispersed phase, it was demonstrated that fluorescent and magnetic microspheres can be fabricated easily using these microfluidic devices. [ABSTRACT FROM AUTHOR]

Abstract: A simple and effective approach to aqueous based biosynthesis of silver nanoparticles was demonstrated and the effect of temperature on controlling size of silver nanoparticles was studied. The morphology and uniformity of silver nanoparticles were investigated by UV–Vis spectroscopy, X-ray diffraction and HrTEM. The functional group of protein molecule was identified using FTIR. Increase in reaction temperature leads to decrease in size of silver nanoparticles and increase in monodispersity. [Copyright &y& Elsevier]

Iron fatty acid complexes (IFACs) are prepared via the dissolution of porous hematite powder in hot unsaturated fatty acid. The IFACs are then decomposed in five different organic solvents under reflux conditions in the presence of the respective fatty acid. The XRD analysis results indicate that the resulting NPs comprise a mixture of wustite, magnetite, and maghemite phases. The solvents with a higher boiling point prompt the formation of larger NPs containing wustite as the major component, while those with a lower boiling point produce smaller NPs with maghemite as the major component. In addition, it is shown that unstable NPs with a mixed wustite–magnetite composition can be oxidized to pure maghemite by extending the reaction time or using an oxidizing agent. [ABSTRACT FROM AUTHOR]

Abstract: The present paper discusses block copolymers with segments of either poly(ethylene oxide), poly(propylene oxide), or mixtures of poly(ethylene oxide)/poly(propylene oxide) and monodisperse aramide segments. The length of the polyether segments as well as the concentration of polyethylene oxide was varied. The synthesized copolymers were analyzed by DSC, FTIR, AFM and DMTA. In addition, the hydrophilicity was studied. The crystallinity of the monodisperse aramide segments was found to be high and the crystals, dispersed in the polyether phase, displayed a nano-ribbon morphology. The PEO segments were able to crystallize and this crystalline phase reduced the low-temperature flexibility. The PEO crystallinity and melting temperature could be strongly reduced by copolymerization with PPO segments. By using mixtures of PEO and PPO segments, hydrophilic copolymers with decent low-temperature properties could be obtained. [Copyright &y& Elsevier]

Abstract: Cadmium sulphide (CdS) nanowires with a monodisperse diameter of 3.6 nm and an aspect ratio of 10–170 were successfully synthesized using a simple and reproducible hot coordinating solvents method. The morphology and optical properties of the CdS nanocrystals were investigated using transmission electron microscopy (TEM), high-resolution TEM (HRTEM) ultraviolet–visible (UV–Vis) absorption spectroscopy and photoluminescence (PL) spectroscopy. It was found that using a long alkyl chain phosphonic acid-octadecylphosphonic acid (ODPA) causes a low diffusion rate and low reactivity which help to control the morphology of the nanocrystals. The timing of the injection process was also found to have critical effect on the morphology of the nanocrystals. Sharp peaks in both the UV–Vis absorption and PL spectra indicate that the size distribution of the diameter is nearly monodisperse. The photovoltaic properties of photovoltaic devices made with a blend of our nanowires and poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) were also investigated. Devices made with the nanowires were found to have double the I sc observed in devices made with lower aspect ratio CdS nanorods. The possible reason of low photocurrent and high V oc is maybe due to the presence of ligand in the nanocrystals. [Copyright &y& Elsevier]

Abstract: Monodisperse CeO2 nanocubes have been fabricated via an acrylamide-assisted hydrothermal route. NH3 and acrylic acid from the hydrolysis of acrylamide act as OH− provider and capping reagent, respectively. The structure and morphology of the products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), field-emission scanning electron microscopy (FE-SEM) and Fourier transformed infrared (FT-IR). The products have a cubic morphology with a mean size of 200 nm. The possible formation mechanism has been discussed based on the experimental results. [Copyright &y& Elsevier]

Abstract: We describe a method for the synthesis of phase-separated polymer latex with a monodisperse and multilayer core–shell (MMLCS) morphology by surface cross-linking emulsion polymerization. Poly(butyl acrylate)(PBA) was used for the seed and the core of the latex, the inner shell was poly(butyl acrylate-styrene) cross-linked with divinylbenzene (DVB) to avoid phase inversion, and the poly(methyl methacrylate-butyl acrylate-glycidyl methacrylate) was the outer shell. TEM, DSC, DLS were used to characterize this MMLCS emulsion. The multilayer core–shell structure was clearly shown in TEM micrographs, and the three-phase separation was confirmed by DSC analysis. DLS analysis showed that the average diameters and shell thicknesses of MMLCS latex were about 127 nm, 13 nm and 12 nm, which agreed with TEM micrograph measurements of 126 nm, 14 nm, and 14 nm, respectively. [Copyright &y& Elsevier]

Abstract: This paper demonstrates a proof-of-concept approach for producing genipin-gelatin microcapsules of precisely controlled and monodisperse size distributions by the microfluidic channels. We have demonstrated that one could control the size of emulsions from 130 μm to 580 μm in diameter (with a variation of less than 5%) by altering the relative sheath/sample flow rate ratio. In addition, Results show that the encapsulation and in vitro release of a model drug, 5-fluorouracil, to enhance the effect of controlled release. We demonstrated that the appropriate particle size for different release patterns is predictable, enabling better application of genipin-gelatin microcapsules as a drug carrier. The proposed microfluidic chip is capable of generating relatively uniform micro-droplets with well controllable diameter, and it has the added advantages of being a simple, low cost, and high throughput process. [Copyright &y& Elsevier]

• Flow regime presenting various flow process in microfluidic. • Effect of Qc/Qd, µc/µd, and Ca c number on the ratio of the droplet size to the junction size. • Dimensionless correlation of droplet size in the narrowing jetting and tip-streaming state. • Systematic studies on the jetting regime, especially the narrowing jetting and tip streaming regimes. • Monodisperse droplet preparation with predictable and controllable size. The formation of water-in-oil (W/O) emulsion droplets in a microfluidic flow-focusing device was investigated under the wide selection of operating parameters together with liquid materials. This is not only to demonstrate the obtained flow regimes and droplet outcomes but also to propose a predictive correlation among droplet size and operating dimensionless numbers. Data were collected from two etched channels of 100 and 190 µm depth. Experimental results of 12 data sets from over 100 experiments in two different-sized channels were assessed. Under the certain range of studied conditions, the stable narrowing jet and tip streaming regime noticeably created monodisperse droplet formation with high throughput. In addition, droplet size and junction size have been found to correlate with the flow rate ratio (Q c /Q d), viscosity ratio (µ c /µ d) and capillary number (Ca) following the correlation equation proposed in this work. This correlation will be beneficial in delivering predictable and controllable monodisperse droplets in a high flow process regime. Graphical Abstract [Display omitted]. [ABSTRACT FROM AUTHOR]

Abstract: Monodisperse rare-earth ion (Eu3+, Ce3+, Tb3+) doped LaPO4 particles with oval morphology were successfully prepared through a facile solvothermal process without further heat treatment. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), Fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) spectra and the kinetic decays were performed to characterize these samples. The XRD results reveal that all the doped samples are well crystalline at 180°C and assigned to the monoclinic monazite-type structure of the LaPO4 phase. It has been shown that all the as-synthesized samples show perfectly oval morphology with narrow size distribution. The possible growth mechanism of the LaPO4:Ln has been investigated as well. Upon excitation by ultraviolet radiation, the LaPO4:Eu3+ phosphors show the characteristic 5 D 0−7 F 1–4 emission lines of Eu3+, while the LaPO4:Ce3+, Tb3+ phosphors demonstrate the characteristic 5 D 4−7 F 3–6 emission lines of Tb3+. [Copyright &y& Elsevier]

Abstract: In this paper, we report a facile method to prepare nearly monodisperse Pd nanoparticles by heating Pd(II) ions in 4-tert-butyltoluene solvent, in the presence of oleylamine and trioctylphosphine (TOP) ligands. It has been found the concentration of TOP ligand was highly pivotal for the formation of Pd nanoparticles. Without TOP, only aggregated Pd particles were obtained due to the reduction of Pd(II) by oleylamine. When the molar ratio of TOP to Pd(II) was less than two, well-protected Pd nanoparticles were obtained. However, when the molar ratio reached to two, only Pd(II)–TOP coordination complexes were obtained as the final product. Also, the addition of excess oleylamine as a supplementary protecting ligand has proven to be very important. By controlling the experimental conditions, Pd nanoparticles were obtained by this simple synthetic process, and the average size controllable in the range of 9.5–14.9nm, with standard deviation in the range of 8–13%. [Copyright &y& Elsevier]

High resolution mobility analysis of an electrosprayed sample of the ΦX174 bacteriophage reveals an exceptionally narrow size distribution (relative diameter full width at half maximum below 0.7%) centered at a mean mobility diameter d p = 28.9 nm. These icosahedral particles are commercially available in solution at concentrations in excess of 109/mL. Here they are simply dialyzed into 10 mM aqueous ammonium acetate, before being atomized in a bipolar electrospray. • An inexpensive commercial bacteriophage is identified as a 29 nm size standard for aerosol studies. • The original saline virus solution is readily purified by dialysis and is stable in a common electrospraying buffer (10 mM aqueous ammonium acetate). • The size distribution is the narrowest reported to date (relative full width at half maximum of 0.7% in diameter) for an aerosol size standard above 5 nm. [ABSTRACT FROM AUTHOR]

The size and composition of nanoparticles are instrumental to many catalytic processes; for example, their controlled synthesis is key to achieving high yield and quality in aerosol chemical vapor deposition (CVD) of carbon nanotubes (CNTs). Using a custom-built atmospheric pressure DC microplasma reactor, we synthesize sub-3 nm iron nanoparticle aerosols at high number concentration (> 1 0 9 #/cm 3) with narrow size distribution ( σ g < 1. 3) from a ferrocene vapor precursor. We demonstrate precise diameter control down to 1.1 nm and maximum yield near unity. We invoke a charge-mediated formation mechanism to show that the ∼ 10 μ s plasma residence time is sufficient to dissociate the precursor and partially ionize the resulting iron vapor, yet too short for the aggregation of clusters beyond 10 atoms. Thus, particle growth occurs primarily downstream of the plasma domain through aggregation of neutral and ionized vapor and clusters. This model closely reproduces the observed particle size distributions with the selection of an appropriate fractional ionization, yet is insufficient to entirely explain the rapid growth rate observed experimentally. This mechanism is different from that of existing microplasma processes, which have a longer residence time allowing particle formation to occur within the plasma, and may explain the demonstrated capability to co-optimize nanoparticle yield, throughput, and diameter control at a level exceeding the performance of previously published thermal and microplasma methods. • Designed and fabricated atmospheric pressure microplasma reactor for synthesis of nanoparticles. • Synthesized Fe aerosol with 1.1–3.0 nm diameter at high number concentration and yield. • Tuned particle size and diameter via precursor concentration and carrier gas flow rates. • Charge-mediated mechanism explains rapid particle formation and narrow size distribution. [ABSTRACT FROM AUTHOR]

Abstract: Monodisperse ellipsoids were synthesized by continuous coating of silica on hematite spindle cores. Spindle cores with decreasing aspect ratio were obtained by decreasing the molar ratio of Fe3+ and H2PO4 −. Using PVP molecules as the surface stabilizer for silica coating, the aspect ratio of the ellipsoids can also be tuned by altering the amount of added TEOS. These monodisperse ellipsoids with well controlled sizes and aspect ratios can be regarded as the potential building blocks for self-assembly. [Copyright &y& Elsevier]

Abstract: This study presented an approach to prepare monodisperse immobilized Ti4+ affinity chromatography (Ti4+-IMAC) microspheres for specific enrichment of phosphopeptides in phosphoproteome analysis. Monodisperse polystyrene seed microspheres with a diameter of ca. 4.8μm were first prepared by a dispersion polymerization method. Monodisperse microspheres with a diameter of ca. 13μm were prepared using the seed microspheres by a single-step swelling and polymerization method. Ti4+ ion was immobilized after chemical modification of the microspheres with phosphonate groups. The specificity of the Ti4+-IMAC microspheres to phosphopeptides was demonstrated by selective enrichment of phosphopeptides from mixture of tryptic digests of α-casein and bovine serum albumin (BSA) at molar ratio of 1 to 500 by MALDI-TOF MS analysis. The sensitivity of detection for phosphopeptides determined by MALDI-TOF MS was as low as 5fmol for standard tryptic digest of β-casein. The Ti4+-IMAC microspheres were compared with commercial Fe3+-IMAC adsorbent and homemade Zr4+-IMAC microspheres for enrichment of phosphopeptides. The phosphopeptides and non-phosphopeptides identified by Fe3+-IMAC, Zr4+-IMAC and Ti4+-IMAC methods were 26, 114, 127 and 181, 11, 11 respectively for the same tryptic digest samples. The results indicated that the Ti4+-IMAC had the best performance for enrichment of phosphopeptides. [Copyright &y& Elsevier]

Abstract: A nonhydrolytic hot solution synthesis technique was used to grow monodisperse ternary oxide nanocrystals of ZnGa2O4:Eu3+. The shape of ZnGa2O4:Eu3+ nanocrystals was a function of the type of precursor, and their size was controlled by changing the concentration ratio of Zn precursor to surfactant. The crystal structure of synthesized ZnGa2O4 nanocrystals was a cubic spinel with no detectable secondary phases. Photoluminescence of red-emitting ZnGa2O4:Eu3+ nanocrystals resulted in a high (5D0–7F2)/(5D0–7F1) intensity ratio, suggesting that the Eu3+ ions occupy tetrahedral Zn2+ sites or distorted octahedral Ga3+ sites with no inversion symmetry in ZnGa2O4 nanocrystals. [Copyright &y& Elsevier]

Abstract: In this paper a series of perpendicular rupturing flow routes with differing angles ranging from 30° to 150° between the entrance channels were used to control the gas–liquid phase dispersed flow in T-junction microfluidic devices. Uniform gas bubble plugs were produced in consistent, two-phase flows within the channels of the microfluidic devices. Both the gas–liquid flow and the size of the gas bubbles, which ranged from 800 to 3100μm in length, depended on several influential factors including the flow rates, the physical properties of the liquid phase, and the angle between entrance channels. Considering these factors and the equilibrium between the shear force and interfacial tension within the microfluidic channels, an equation was derived in the form of L/w =1/2(Q G /Q L sin θ +2/5cot θ)1/2 Ca −1/5 relating the angle between the entrance channels of the two phases to the gas bubble plug length within the microfluidic device. The relationship allows for the prediction of gas bubble plug length in T-junction microfluidic devices employing intersection angles ranging from 30° to 150° and is thus potentially useful for the controllable preparation of monodisperse gas bubbles. [Copyright &y& Elsevier]

Abstract: Monodisperse Y2O3:Er and Y2O3:Er,Yb microspheres with diameter of 1.5–3μm, which are composed of nanoparticles with size of about 50nm, were prepared by a simple solvothermal method followed by further heat treatment. The structural properties of samples were investigated by X-ray diffraction; field emission scanning electron microscopy, Raman spectroscopy and Fourier transform infrared spectroscopy. Especially, the effect of CH3COONa on the formation of microspheres was investigated. Under 980nm laser excitation, strong green (518–570nm), strong red (645–686nm) and weak violet (405–420nm) upconversion emissions have been observed in Y2O3:Er and Y2O3:Er,Yb microspheres. The upconversion mechanisms were studied through laser power and concentration dependence of the upconverted emissions. The upconversion properties indicate that Y2O3:Er and Y2O3:Er,Yb microspheres may be used in upconversion phosphors. [Copyright &y& Elsevier]

Abstract: An effective and reproducible method of preparing highly monodisperse organic–inorganic hybrid silica spheres was studied. One process, one precursor (organosilane) and one solvent (water) were used in our experiments. The size of hybrid silica spheres could be adjusted from 360 to 770 nm with relative standard deviation below 2% by controlling the concentration of the organosilane precursor and the ammonia catalyst. The increasing of the precursor concentration increases the particle size while the catalyst concentration has a reverse effect on the particle size. The concept of homogeneous nucleation and growth processes are introduced to explain the formation mechanism and the effect of reaction conditions. The scanning electron microscopy (SEM) images illustrate the copiousness in quantity and the uniformity in size/shape of the particles that could be routinely accomplished in this synthesis. Fourier transform infrared (FT-IR) and 29Si nuclear magnetic resonance (NMR) spectra confirm the structure of vinyl hybrid silica spheres, where the vinyl group (ph name="dbnd" />CH2) exists and connects to the silicon atom. This method has also been extended to design and prepare other organic–inorganic hybrid materials especially in monodisperse surface-modified silica spheres. [Copyright &y& Elsevier]

Abstract: Monodisperse copolymer particles of styrene, n-butyl acrylate, and methacrylic acid were prepared by emulsion copolymerization using a polymerizable poly(ethylene glycol)-ethyl ether methacrylate (PEG-EEM) macromonomer. The good uniformity of the copolymer particles indicated that the aggregation of the unstable precursor particles during the particle nucleation period was uniform and no coagulation of the prepared copolymer particles suggested that the PEG-EEM macromonomer acted as an effective stabilizer in the replacement of surfactant in emulsion polymerization. The particle size and molecular weight of the copolymer particles increased with increasing PEG-EEM concentration up to 4wt.%, and decreased at 6wt.%, which was attributed to its solubility. The rate of polymerization increased with increasing reaction temperature due to increases in the rate of initiator decomposition, propagation rate, and diffusion rate of radicals and monomers. The size and molecular weight of the copolymer particles decreased with increasing temperature. The effects of the initiator concentration, monomer ratio, and concentration of chain transfer agent on the properties of the copolymer particles were also investigated. [Copyright &y& Elsevier]

The capillarity-driven ascent of liquid through certain elementary assemblies of equal spherical particles held in a neutrally wetted container is considered and the conditions for liquid to flow are established. For flow through the assembly to be possible, critical contact angles of the liquid on the spheres must not be exceeded. These critical angles are considerably lower than the 90° which the Washburn equation predicts. Finally, the effect of sphere size disparity (or polydispersity) is considered in an Appendix. It is shown that wetting of the assembly may be controlled by manipulation of size distributions as well as by change in the contact angle. Experimental evidence in support of these ideas is presented for a two-dimensional array. [ABSTRACT FROM AUTHOR]

Abstract: Nearly monodispersed populations of microbubbles were produced using flow focusing with a food grade emulsifier. The microbubbles produced by this technique have diameters in the range of 120–200 μm. The flow focusing device uses metered streams of air and liquid to produce a jet that periodically pinches to make individual microbubbles. The size of the microbubbles can be controlled by changing the relative flow rates of the gas and the liquid. The emulsifier consists of a mixture of monoglycerides, diglycerides and sodium stearoyl lactylate in combination with polyethylene glycol (PEG)-40 stearate. The emulsifier forms a thin shell that stabilizes the microbubbles. The microbubbles are stable over time with their sizes remaining roughly constant over 2 h. Such stability allows suspensions of microbubbles to be formed and their rheological properties tested. The sizes of the microbubbles are also monitored off-line while testing, examining the effect of shearing on the bubble sizes, as well as their stability over time. These results show that the microbubble suspensions are viscoelastic and exhibit power law behavior. The relationship between the air fraction of the suspension and fluid viscosity is determined. [Copyright &y& Elsevier]

Abstract: In this paper, we reported a method to prepare monodisperse magnetite nanoparticles at mild temperature using cheap and non-toxic precursors. It overcomes the shortages of chemical co-precipitation method and thermal decomposition method and combines the advantages of facile, cheap, large-scale, monodisperse, nanosize, and low synthesis temperature and low toxic. In this method, FeCl3 ·6H2O, FeCl2 ·4H2O and sodium oleate were mixed in toluene/ethanol/water mixture solvent and refluxed at 74°C to prepare magnetite nanoparticles directly. The nanoparticles were characterized by transmission electron microscopy, dynamic light scattering, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectrometer and thermogravimetric analysis. The magnetic properties of nanoparticles were measured by superconducting quantum interference device. The results showed that the nanoparticles are well-monodisperse with about 4–5nm of average diameter. The nanoparticles were proved to be superparamagnetic with saturated magnetization 23.6emu/g and blocking temperature 24.4K. A possible formation mechanism of monodisperse magnetite nanoparticles was presented at the same time. [Copyright &y& Elsevier]

Crystalline Nd-substituted Bi4Ti3O12 (BNT) nanopowder was directly produced from a stoichiometric oxide mixture by intense milling. During the milling, mechanical alloying between the constituent oxides occurred, resulting in a sequential phase transformation from metastable fluorite to BNT with increasing milling time. The formation of the BNT phase was complete after 9h of milling. The resulting powder consisted of nearly monodisperse crystallites of ∼18nm average size, exhibiting a zeta potential of +50mV at pH∼2. [Copyright &y& Elsevier]

Abstract: The pore structure of monodisperse mesostructured silica spheres has been investigated by a combination of X-ray diffraction, nitrogen sorption isotherms and transmission electron microscopy (TEM). The radial dependence of the mesostructure has been obtained by TEM analysis of thin microtomed slices taken at different distance from the particle core. A structural model is proposed based on the TEM observations where bundles of the hexagonally ordered cylindrical channels bend and twist, without any preferred direction, close to the particle core and attain a radially extended structure closer to the particle surface. Thermal calcination results in a pore shrinkage of about 16% and some loss of the long-range mesostructure while radiative disintegration and partial removal of the organic template by an UV/Ozone treatment had a negligible effect on the inorganic framework in terms of pore size or spatial pore arrangement. [Copyright &y& Elsevier]

Abstract: Silver nanoparticles were synthesized by UV irradiation of [Ag(NH3)2]+ aqueous solution using poly(N-vinyl-2-pyrrolidone) (PVP) as both reducing and stabilizing agents. The formation of silver nanoparticles was confirmed from the appearance of surface plasmon absorption maxima around 420nm. It was found that the formation rate of silver nanoparticles from Ag2O was much quicker than that from AgNO3, and the absorption intensity increased with PVP concentration as well as irradiation time. The maximum absorption wavelength (λ max) was blue shift with increasing PVP content until 8 times concentration of [Ag(NH3)2]+ (wt%). The transmission electron microscopy (TEM) showed the resultant particles were 4–6nm in size, monodisperse and uniform particle size distribution. X-ray diffraction (XRD) demonstrated that the colloidal nanoparticles were the pure silver. In addition, the silver nanoparticles prepared by the method were stable in aqueous solution over a period of 6 months at room temperature (∼25°C). [Copyright &y& Elsevier]

Abstract: Nearly monodisperse antimony pentoxide with a mean diameter of 2 nm and polydispersity of 0.047 was prepared through a simple method based on reflux oxidization system. By adjusting the synthetic parameters (kinds of stabilizing agents, size and purity of original Sb2O3 etc.), the controllable synthesis of ultrafine Sb2O5 can be easily achieved. Detailed investigations about the effects of experimental parameters on the colloid stability and size distribution of the final products were carried out. The particles were characterized using various experimental techniques such as transmission electron microscopy (TEM), X-ray diffraction (XRD) and particle size distributions. [Copyright &y& Elsevier]

Abstract: A simple, but efficient method for preparation of water-soluble iron oxide nanoparticles has been developed. Monodisperse Fe3O4 nanoparticles were synthesized by thermal decomposition of iron-oleate. Surface double-exchange of oleic acid capped monodisperse Fe3O4 nanoparticles with a familiar 2,3-dimercaptosuccinnic acid (HOOC–CH(SH)–CH(SH)–COOH, DMSA) was first performed in chloroform in the presence of triethylamine, and then this process was repeated in ethanol under the same conditions. The resulting Fe3O4 nanoparticles could be transferred into water to form stable magnetic fluid without post-treatment processes such as filtration and re-concentration. TEM images show that water-soluble Fe3O4 nanoparticles remain monodisperse and even form a monolayer of ordered assembly, and the results of TGA, VSM show that Fe3O4 nanoparticles via surface double-exchange possess more DMSA molecules through intermolecular disulfide cross-linking between DMSA, as confirmed by Raman spectra. Zeta potential measurements show that nanoparticles after surface double-exchange are negatively charged in the range of pH=1–14, and stability assays exhibit their excellent stability in water and other physiological environments. [Copyright &y& Elsevier]

Abstract: This paper presents a new symmetrical flow route of perpendicular rupturing to realize the controllable preparation of monodisperse O/W and W/O emulsions by using a cross-junction microfluidic device. Uniform plugs ranging from 300 to 1800μm were successfully prepared. The effect of surfactants on two-phase flow performance, two-phase flow patterns under different continuous phase and dispersed phase flow, and the influences of flow rates and the viscosity of continuous phase on plug length were studied. The formation mechanisms of plug flow have been discussed. Considering both the equilibrium between shear force of the continuous flow and interfacial tension, the wetting property between dispersed phase and walls of microchannel, and the influence of oil/water flow ratio on the shape of the interface, a quantitative equation was developed to predict the plug length, which is consistent with the experimental results. [Copyright &y& Elsevier]

Abstract: The influence of particle size on the poisoning of ethylene hydrogenation by CO was studied over a series of catalysts composed of nearly monodisperse Pt nanoparticles (1.7–7.1 nm) encapsulated in mesoporous silica (SBA-15). The turnover frequency at 403 K in the presence of 0.5 Torr CO was ∼2 × 10−2 s−1 (compared with ∼102 s−1 in the absence of CO). The apparent activation energy in the absence and presence of 0.2 Torr CO was ∼10 and 20 kcal mol−1, respectively. The pressure dependency changes significantly in the presence of CO; reaction orders in hydrogen were 1/2 in the presence of CO at 403 K and noncompetitive with regard to co-adsorption with C2H4. In the absence of CO at similar temperatures, H2 adsorption was primarily irreversible (first-order dependence), and H2 and C2H4 compete for the same sites. Ethylene orders at 403 K were first order in the presence of 0.2 Torr CO and remained unity with increasing CO pressure. At similar reaction conditions in the absence of CO, ethylene had an inhibitory effect (negative reaction order) on the overall hydrogenation reaction. The change in C2H4 and H2 kinetics suggests strong competitive adsorption between C2H4 and CO for the same type of site, whereas H2 apparently adsorbs on distinct surface sites due either to steric hindrance or H2-induced CO desorption. Incorporation of a quasi-equilibrated CO adsorption step into a noncompetitive Langmuir–Hinshelwood mechanism predicts the experimentally observed pressure dependencies and a doubling of the apparent activation energy. Hydrogenation of ethylene in the presence of 1 Torr CO was examined under reaction conditions at 403 K by infrared spectroscopy; the only surface species identified under reaction conditions was linear-bound CO. The hydrogenation of ethylene on clean Pt catalysts was structure-insensitive and remains insensitive in the presence of CO; rates decreased only by a factor of two with increasing particle size. [Copyright &y& Elsevier]

Abstract: The synthesis and characterisation of segmented block copolymers based on mixtures of hydrophilic poly(ethylene oxide) and hydrophobic poly(tetramethylene oxide) polyether segments and monodisperse crystallisable bisester tetra-amide segments are reported. The PEO length was varied from 600 to 8000g/mol and the PTMO length was varied from 650 to 2900g/mol. The influence of the polyether phase composition on the thermal mechanical and the elastic properties of the resulting copolymers was studied. The use of high melting monodisperse tetra-amide segments resulted in a fast and almost complete crystallisation of the rigid segment. The copolymers had only one polyether glass transition temperature, which suggests that the amorphous polyether segments were homogenously mixed. Thermal analysis of the copolymers showed one polyether melting temperature that was lower than in the case of ideal co-crystallisation between the two polyether segments. However, at PEO or PTMO lengths larger than 2000g/mol two polyether melting temperatures were observed. The copolymer with the best low temperature properties was based on a mixture of PEO and PTMO segments, both having a molecular weight of 1000g/mol, at a weight ratio of 30/70. [Copyright &y& Elsevier]

Abstract: The monodisperse zirconia-coated polystyrene core–shell spheres were prepared in mixed solvents. The influence of the different catalyst with deionized water or ammonia and the volume fraction of acetonitrile in the mixture were investigated systematically with TEM and SEM. The shell thickness of the zirconia-coated polystyrene spheres was found to be correlated in a quasilinear fashion with the concentration of zirconium n-propoxide. The corresponding zirconia hollow particles were obtained through calcinations. XRD results showed that calcination promoted the transformation of amorphous zirconia into monoclinic phase. And the ZrO2 hollow spheres retained spherical shape up to 900°C. [Copyright &y& Elsevier]

Abstract: Monodispersed Pickering emulsion droplets were prepared by self-assembling of sulfonated polystyrene (SPS) latex particles at droplet interface. The stability of emulsion was obviously improved by pre-dispersing the latex particles in oil–water two phase and then mixing them into emulsion. For oil-in-water emulsion, the optimal stability was obtained by pre-dispersing 0.33 weight fraction of the latex particles in oil phase initially. Several parameters were considered during the preparation, including sulfonation time of the SPS latex particles, the dispersed percent of the latex particles in oil–water two phases, the pre-dispersion time of water phase dispersate and oil–water volume ratio. When sulfonation time of the latex particles was close to 60h, the stability of the particles stabilized emulsion droplets was the best. The increase of pre-dispersion time of water phase dispersate and oil–water volume ratio could obviously decrease the dispersity of emulsion droplets. Finally, monodisperse emulsion droplets were obtained with average droplet diameter 7.4μm and standard deviation 0.37. The emulsion droplets could re-assemble into ordered array. [Copyright &y& Elsevier]

Abstract: Monodispersed BaSO4 micrometer and submicrometer sized particles were produced by a simple precipitation reaction in the presence of poly(methacrylic acid) (PMAA) at the ambient temperature. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and electron diffraction (ED) were used to characterize the obtained BaSO4 particles, and polycrystalline nature of the BaSO4 products was revealed. A “polymer–M in situ template” model was proposed to elucidate the formation process of such polycrystalline BaSO4 particles. [Copyright &y& Elsevier]

Abstract: The purpose of this study is to generate monodisperse TPP-chitosan microparticles using a cross-flow microfluidic chip coupled with external crosslinking reaction. We have demonstrated that one can control the size of TPP-chitosan emulsions from 180 to 680μm in diameter (with a variation of less than 10%) by altering the relative sheath/sample flow rate ratio. Our strategy is based on the sheath effect (focusing) to form uniform self-assembling sphere structures, the so-called water-in-oil (w/o) emulsions, in the cross-junction microchannel. These fine emulsions, consisting of aqueous 1% (w/v) chitosan, are then dripped into a solution containing 10% (w/v) tripolyphosphate (TPP). They then undergo an ionic-crosslinking reaction and create water-insoluble TPP-chitosan microparticles in an efficient manner. In addition, the size distribution of the resulting TPP-chitosan microspheres is narrow (about polyindex=1) which is suitable to provide the optimal release rate in the administration of controlled release drugs. The proposed microfluidic chip is capable of generating relatively uniform micro-droplets and has the advantages of actively controlling the droplet diameter, and having a simple and low cost process, with a high throughput. [Copyright &y& Elsevier]

Abstract: This article describes the fabrication of a rigid magnetic monodisperse bead (M-PGMA-TRI, 4.92μm) with polyglycidyl methacrylate (PGMA) cross-linked by trimethylolpropane trimethacrylate (TRI). This was realized by adding a proper amount (2%, w/w) of TRI after 3h of the dispersion-polymerization reaction with the monomer of GMA. The mono-sized microspheres were further processed to introduce magnetic granules by sulfonation and penetration-deposition approaches. The monodisperse bead (M-PGMA) without TRI addition was also fabricated for comparison. The morphology, size and magnetic characteristics of the microspheres were extensively characterized. The M-PGMA-TRI microspheres were nonporous, of smooth surface and superparamagnetic with a saturation magnetization of 13.0emu/g. Recycled use of the material for protein adsorption exhibited stability of the magnetic properties of the M-PGMA-TRI, as compared to the significant loss of the saturation magnetization of the M-PGMA. The chemical stability of the M-PGMA-TRI was also confirmed by examining its protein adsorption and magnetic properties after incubation in various solutions such as acidic buffer (pH 2.2) for 24h. The adsorption capacity of γ-globulin reached 287.2mg/g and kept stable in the repeated adsorption/desorption/regeneration cycles. The results indicated that the introduction of 2% TRI was promising for producing rigid magnetic mono-sized microspheres for protein adsorption. [Copyright &y& Elsevier]

Flow rate effect on droplet formation in a co-flowing microfluidic device is investigated numerically. Transition conditions are discovered that the droplet size is either approximately independent of or strongly dependent on the flow rate ratio. This phenomenon is explained by the relation between strain rate and droplet diameter. Regions of four drop patterns are demarcated and conditions that give polydisperse drops are described, which is helpful to assure the accuracy and efficiency in droplet production. [ABSTRACT FROM AUTHOR]

Abstract: Monodisperse ZnO nanoparticles were successfully prepared through the decomposition of zinc acetylacetonate precursor in oleylamine. The samples were characterized by transmission electron microscope, X-ray diffraction and infrared spectroscopy. The particle size and morphology could be modified through tuning the reaction temperature, reaction period and concentration of zinc acetylacetonate. The grain size of monodisperse ZnO could be obtained at 205 and 300 °C for 1 h with 1:100 molar ratio of acetylacetonate and oleylamine, respectively. The average grain size of ZnO nanoparticles increased and the shape of ZnO particles varied with the reaction period prolonging or reaction temperature increasing. Some ZnO particles had self-aggregated into a belt using a solution of 1:10 molar ratio of zinc acetylacetonate and oleylamine at 250 °C for 1 h. The oleylamine plays an important role in preventing aggregation of ZnO nanoparticles. [Copyright &y& Elsevier]

Abstract: Ionic polymerizable surfactants MOBS and MOTB were synthesized and used as emulsifier to synthesize monodisperse polystyrene microlatexes by emulsion polymerization induced by gamma rays. Transmission electron microscopy and X-ray fluorescence were used to characterize the prepared polystyrene. The results show that ionic polymerizable surfactants are effective in the preparation of monodisperse polystyrene microlatexes, and that emulsion polymerization induced by gamma rays has advantages over initiator-induced emulsion polymerization. A possible nucleation stage was suggested and the kinetics of the process was also analyzed. [Copyright &y& Elsevier]