ED‐XRF set‐up for size‐segregated aerosol samples analysis

The knowledge of size‐segregated elemental concentrations in atmospheric particulate matter (PM) gives a useful contribution to the complete chemical characterisation; this information can be obtained by sampling with multi‐stage cascade impactors. In this work, samples were collected using a low‐pressure 12‐stage Small Deposit Impactor and a 13‐stage rotating Micro Orifice Uniform Deposit Impactor^?. Both impactors collect the aerosol in an inhomogeneous geometry, which needs a special set‐up for X‐ray analysis. This work aims at setting up an energy dispersive X‐ray fluorescence (ED‐XRF) spectrometer to analyse quantitatively size‐segregated samples obtained by these impactors. The analysis of cascade impactor samples by ED‐XRF is not customary; therefore, as additional consistency test some samples were analysed also by particle‐induced X‐ray emission (PIXE), which is more frequently applied to size‐segregated samples characterised by small PM quantities. A very good agreement between ED‐XRF and PIXE results was obtained for all the detected elements in samples collected with both impactors. The good inter‐comparability proves that our methodology is reliable for analysing size‐segregated samples by ED‐XRF technique. The advantage of this approach is that ED‐XRF is cheaper, easier to use, and more widespread than PIXE, thus promoting an intensive use of multi‐stage impactors. Copyright © 2011 John Wiley & Sons, Ltd.     

Characterization of Nano‐Particles Using Laser‐Induced Incandescence

Laser‐induced incandescence (LII) is introduced as a valuable tool for the characterization of nanoparticles. This optical measurement technique is based on the heating of the particles by a short laser pulse and the subsequent detection of the thermal radiation. It has been applied successfully for the investigation of soot in different fields of application, which is described here in the form of an overview with a focus on work done at the LTT‐Erlangen during the last 10 years. In laboratory flames the soot primary particle size, volume concentration, and relative aggregate size have been determined in combination with the number density of primary particles. Furthermore, the primary particle sizes of carbon blacks have been measured in situ and online under laboratory conditions and also in production reactors. Measurements with different types of commercially available carbon black powders, which were dispersed in a measurement chamber yielded a good correlation between LII results and the specified product properties. Particle diameters determined by LII in a furnace black reactor correlate very well with the CTAB‐absorption number, which is a measure for the specific surface area. It turned out that the LII method is not affected by variations of the aggregate structure of the investigated carbon blacks. The LII signal also contains information on the primary particle size distribution, which can be reconstructed by the evaluation of the signal decay time at, at least, two different time intervals. Additionally, soot mass concentrations have been determined inside diesel engines and online measurements were performed in the exhaust gas of such engines for various engine conditions simultaneously providing information about primary particle size, soot volume, and number concentration. The LII results exhibit good correlation with traditional measurement techniques, e.g., filter smoke number measurements. In addition to the soot measurements, primarily tests with other nanoparticles like TiO₂ or metal particles are encouraging regarding the applicability of the technique for the characterization of such different types of nanoparticles.     

Quantitative elemental analysis of individual particles with the use of micro‐beam X‐ray fluorescence method and Monte Carlo simulation

The aim of the work was to develop a Monte Carlo (MC) method and combine it with micro‐beam X‐ray fluorescence (XRF) technique for determination of chemical composition of individual particles. A collection of glass micro‐spheres, made of NIST (National Institute of Standards and Technoly) K3089 material of known chemical composition, with diameters in the range of 25–45 µm was investigated. The micro‐spheres were measured in a scanning micro‐beam XRF spectrometer utilising X‐ray tube as a source of primary radiation. Results obtained for low Z elements showed high dependence on particle size. It was found that the root mean square of concentration uncertainty, for the all elements present in the particle, increases with growing sample size. More accurate results were obtained for high Z elements such as Fe–Pb, as compared to others. The elemental percentage uncertainty did not exceed 14% for any particular sample and 6% for the whole group of the measured micro‐spheres as an average. Results obtained by the Monte Carlo method were compared with other analytical approaches. Copyright © 2009 John Wiley & Sons, Ltd.     

Simple method to prepare size‐controllable gold nanoparticles in solutions and their applications on surface‐enhanced Raman scattering

We report here, for the first time, a simple method to prepare size‐controllable Au nanoparticles (NPs) in aqueous solutions from bulk Au substrates. First, chitosan (Ch)‐capped Au‐containing complexes were prepared by electrochemical oxidation–reduction cycles in 0.1 N NaCl and 1 g/l Ch solutions. Then the solutions were heated from room temperature to boiling at different heating rates to synthesize size‐controllable Au NPs. The particle sizes of the prepared Au(111) NPs could be controlled from 5 to 30 nm with an increase of the heating rate during preparation. Experimental results indicate that the prepared Au(111) NPs with diameters ranging from 10 to 30 nm can serve as surface‐enhanced Raman scattering active probes for molecules of rhodamine 6G. Copyright © 2010 John Wiley & Sons, Ltd.     

Size‐Dependent Structural and Optical Characteristics of Glucose‐Derived Graphene Quantum Dots

It is of scientific importance to obtain graphene quantum dots (GQDs) with narrow‐size distribution in order to unveil their size‐dependent structural and optical properties, thereby further to explore the energy band diagram of GQDs. Here, a soft‐template microwave‐assisted hydrothermal method to prepare GQDs with diameters less than 5 nm ± 0.55 nm is reported. The size‐dependent photoluminescence (PL) quantum yield (QY) decay lifetime and electron energy loss spectroscopy (EELS) of the GQDs are studied systematically. The QY of the GQDs with an average diameter of 2 nm is the highest (15%) among all the samples investigated and the QY decreases with increasing diameter of the GQDs. The size‐dependence of the PL decay lifetime is also observed. The result suggests that spatial confinement effects related to radiative relaxation play an important role in the size‐dependent decay lifetime. A realistic energy band diagram of the GQDs is deduced from the experimental results.     

Thermomagnetically Responsive γ‐Fe2O3@Wax@SiO2 Sub‐Micrometer Capsules

A three steps synthesis route is proposed to generate thermosensitive and magnetically responsive γ‐Fe₂O₃@Wax@SiO₂ sub‐micrometer capsules with a paraffinic core and a solid and brittle shell. The process integrates Pickering‐based emulsions, inorganic and sol–gel chemistries to promote monodisperse in size wax droplets, γ‐Fe₂O₃ nanoparticles and mineralization of the wax/water interfaces. Hybrid capsules are obtained with an average size around 800 nm, representing the first example of sub‐micrometer capsules generated employing Pickering emulsions as templates. Cetyltrimethylammonium bromide (CTAB) cationic surfactant added during mineralization at concentrations between 0.17 and 1.0 wt% impacts the shell density. The shell density seems to improve its mechanical strength while affording a low wax expansion volume without breaking for CTAB concentrations above 1.0 wt%. At lower CTAB concentration (0.17 wt%), the silica shell becomes less bulky and cannot resist the wax dilatation induced by the solid‐to‐liquid phase transition imposed by hyperthermia. The magnetically induced heating provided by the internal magnetic moments is sufficient to melt the wax core, expanding its volume, inducing thereby the surrounding silica shell rupture. Such γ‐Fe₂O₃@Stearic Acid@Wax@SiO₂ sub‐micrometer capsules allow a sustained wax release with time, whereby 20% of the wax is released after 50 min of alternating magnetic field treatment.     

Focused ion beam preparation of samples for X‐ray nanotomography

The preparation of hard material samples with the necessary size and shape is critical to successful material analysis. X‐ray nanotomography requires that samples are sufficiently thin for X‐rays to pass through the sample during rotation for tomography. One method for producing samples that fit the criteria for X‐ray nanotomography is focused ion beam/scanning electron microscopy (FIB/SEM) which uses a focused beam of ions to selectively mill around a region of interest and then utilizes a micromanipulator to remove the milled‐out sample from the bulk material and mount it on a sample holder. In this article the process for preparing X‐ray nanotomography samples in multiple shapes and sizes is discussed. Additionally, solid‐oxide fuel cell anode samples prepared through the FIB/SEM technique underwent volume‐independence studies for multiple properties such as volume fraction, average particle size, tortuosity and contiguity to observe the characteristics of FIB/SEM samples in X‐ray nanotomography.     

Radiation damage to protein specimens from electron beam imaging and diffraction: a mini‐review of anti‐damage approaches,with special reference to synchrotron X‐ray crystallography

Recent research progress using X‐ray cryo‐crystallography with the photon beams from third‐generation synchrotron sources has resulted in recognition that this intense radiation commonly damages protein samples even when they are held at 100 K. Other structural biologists examining thin protein crystals or single particle specimens encounter similar radiation damage problems during electron diffraction and imaging, but have developed some effective countermeasures. The aim of this concise review is to examine whether analogous approaches can be utilized to alleviate the X‐ray radiation damage problem in synchrotron macromolecular crystallography. The critical discussion of this question is preceded by presentation of background material on modern technical procedures with electron beam instruments using 300–400 kV accelerating voltage, low‐dose exposures for data recording, and protection of protein specimens by cryogenic cooling; these practical approaches to dealing with electron radiation damage currently permit best resolution levels of 6 Å (0.6 nm) for single particle specimens, and of 1.9 Å for two‐dimensional membrane protein crystals. Final determination of the potential effectiveness and practical value of using such new or unconventional ideas will necessitate showing, by experimental testing, that these produce significantly improved protection of three‐dimensional protein crystals during synchrotron X‐ray diffraction.     

Docetaxel‐Loaded Nanoparticles of Dendritic Amphiphilic Block Copolymer H40‐PLA‐b‐TPGS for Cancer Treatment

A dendritic amphiphilic block copolymer H40‐poly(d,l ‐lactide)‐block‐d‐α‐tocopheryl polyethylene glycol 1000 succinate (H40‐PLA‐b‐TPGS) is synthesized, which is then employed to develop a system of nanoparticles (NPs) loaded with docetaxel (DTX) as a model drug for cancer treatment due to its higher drug‐loading content and drug encapsulation efficiency, smaller particle size, faster drug release, and higher cellular uptake in comparison to the linear PLA polymer NPs and PLA‐b‐TPGS copolymer NPs. The drug‐loaded NPs are prepared by a modified nanoprecipitation method and characterized in terms of size and size distribution, surface morphology, drug release profile, and physical state of DTX. Cellular uptake of coumarin 6‐loaded NPs by MCF‐7 cancer cells is determined by flow cytometry and confocal laser scanning microscopy. The antitumor efficacy of the drug‐loaded NPs is investigated in vitro by MTT assay and in vivo by xenograft tumor model. The 72 h IC50 of the drug formulated in the PLA, PLA‐b‐TPGS, and H40‐PLA‐b‐TPGS NPs is found to be, 1.5 ± 0.3, 0.9 ± 0.1, and 0.15 ± 0.06 μg mL^?1, which are 7.3, 12.2, and 73.3‐fold effective than 11.0 ± 1.2 μg mL^?1 for Taxotere, respectively. Such advantages are further confirmed by the measurement of the tumor size and weight.     

Preparation,Characterization and Optimization of Egg Albumin Nanoparticles as Low Molecular‐Weight Drug Delivery Vehicle

Protein nanoparticles have been recognized as carriers to deliver low molecular‐weight drugs, anticancer drug, DNA, vaccines, oligonucleotides, peptides and etc. The purpose of this research was preparation of Egg Albumin (EA) nanoparticle with suitable size/size distribution and good surface properties for drug delivery application based on simple coacervation method along with optimization of the nanoparticles by employing Taguchi method. Several synthesis parameters were examined to characterize their impacts on nanoparticle size and topography. These variables were including temperature, EA concentration, desolvating agent volume, pH value and agitation speed. In addition, size and morphology of prepared nanoparticles were analyzed by photon correlation spectroscopy (PCS) as well as atomic force microscopy (AFM). As result of Taguchi analysis in this research, desolvating agent volume and pH were most influencing factors on particle size. The minimum size of nanoparticles (～51 nm) were obtained at Temperature 55 °C, 30 mg/ml EA concentration, desolvating agent volume 50 ml, agitation speed of 500 rpm and pH 4. The mechanistic of optimum conditions for preparing protein nanoparticles from Egg Albumin for the first time and their characterization as delivering nano system are discussed.     

A Multi‐Electrode Approach for On‐Line Characterisation of Size and Shape

A multi‐electrode approach is proposed for on‐line characterisation of particle size and shape in dilute particulate suspensions. Based on an electrozone principle, the approach uses four electrodes in a tube rather than two electrodes across an aperture employed in conventional methods. The outer two electrodes are used for current injection, while the inner two electrodes yield voltage measurement. A sensor designed in this way can reduce errors of false counts and oversizing that may occur in conventional methods, thus providing more accurate particle sizing. It is also possible to use the signal slope along with signal peak for particle size and shape characterisation. Both theoretical modelling and experiments were conducted, showing that particle aspect ratio along with particle diameter can be obtained, for example, for cylindrical particles.     

Synthesis of Self‐Stabilized Poly(N‐(3‐Amidino)‐Aniline) Particles and their CO2‐Responsive Properties

Novel CO₂‐responsive conductive polymer particles based on poly(N‐(3‐amidino)‐aniline) (or PNAAN) are reported in this work. A CO₂‐responsive N‐(3‐amidino)‐aniline (NAAN) monomer is firstly synthesized with the pendant amidine group at the meta‐position of aniline (AN) and subsequently polymerized into the PNAAN polymer by chemical oxidation. Self‐assembly of PNAAN in turn forms the polymer particles. In the strong or weak acid media, the amidine group protonates into cationic amidinium and self‐stabilizes the PNAAN particles without the use of any stabilizers. The reaction media are found to affect the polymerization rate and self‐assembly of particles, and hence the size and size distribution of the resultant particles. The particles synthesized in strong basic media show CO₂‐responsvie properties since the H⁺ released by dissolved CO₂ (dCO₂) can protonate the amidine group into hydrophilic amidinium group and result in swelling of the PNAAN particles. Zeta‐potential measurements show the reversible change of particle surface charges in the presence and absence of dCO₂. Dynamic light scattering (DLS) measurements show the particle size linearly changed with dCO₂ concentration in the range of 5 × 10^?4 and 2.5 × 10^?2 atm. This is the first reported CO₂‐responsive polyaniline (PANI) particles for dCO₂ sensing or reversible fixation of CO₂.     

Proton µ‐PIXE mapping,AFM imaging and size statistics of mineral granules in a dental composite

We applied proton microbeam particle‐induced X‐ray emission (µ‐PIXE) for mapping Ca, Zr, Ba and Yb, and atomic force microscopy (AFM) for imaging the surface landscape of a dental composite which releases Ca²⁺ and F^? for the protection of hard dental tissues. Three areas ～250 × 250 µm² located ～0.5–2 mm apart on a smooth surface specimen were mapped with 3.1 MeV protons focused to a ～3.0 µm spot and at ～3.9 µm pixel size sampling. The maps evidenced particles with diameters of 3.2–32 µm (Ca), 20–60 µm (Zr), ≤ 4 µm (Ba) and 10–50 µm (Yb). Cross‐section area histograms of Ca‐rich particles fitted with 2–6 Poisson functions revealed a polydisperse size distribution and substantial differences from an area to another, possibly implying large local variations of Ca²⁺ released in the hard tissue near a dental filling of a few millimeters in diameter. Such imbalances may lead to low local Ca²⁺ protection of the dental tissue, favoring the onset of secondary caries. Similarly, AFM images showed high zone‐dependent differences in the distributions of grains with apparent diameters of 1–4 µm, plausibly recognized as Ca‐ and Ba‐containing particles. In a simple model based on demineralization data, lateral diffusion of Ca²⁺ between adjacent domains containing high‐ and low‐area Ca‐rich grains is described by exponential concentration gradients. These gradients may generate appreciable electromotive forces, which may enhance electrochemically the local tissue demineralization. Similar effects are to be expected in the protective action of F^? ions released from microgranules of YbF₃ and of Ba fluoroaluminosilicate glass. Copyright © 2010 John Wiley & Sons, Ltd.     

Microcrystallography using single‐bounce monocapillary optics

X‐ray microbeams have become increasingly valuable in protein crystallography. A number of synchrotron beamlines worldwide have adapted to handling smaller and more challenging samples by providing a combination of high‐precision sample‐positioning hardware, special visible‐light optics for sample visualization, and small‐diameter X‐ray beams with low background scatter. Most commonly, X‐ray microbeams with diameters ranging from 50 µm to 1 µm are produced by Kirkpatrick and Baez mirrors in combination with defining apertures and scatter guards. A simple alternative based on single‐bounce glass monocapillary X‐ray optics is presented. The basic capillary design considerations are discussed and a practical and robust implementation that capitalizes on existing beamline hardware is presented. A design for mounting the capillary is presented which eliminates parasitic scattering and reduces deformations of the optic to a degree suitable for use on next‐generation X‐ray sources. Comparison of diffraction data statistics for microcrystals using microbeam and conventional aperture‐collimated beam shows that capillary‐focused beam can deliver significant improvement. Statistics also confirm that the annular beam profile produced by the capillary optic does not impact data quality in an observable way. Examples are given of new structures recently solved using this technology. Single‐bounce monocapillary optics can offer an attractive alternative for retrofitting existing beamlines for microcrystallography.     

Intra‐laser‐cavity microparticle sensing with a dual‐wavelength distributed‐feedback laser

An integrated intra‐laser‐cavity microparticle sensor based on a dual‐wavelength distributed‐feedback channel waveguide laser in ytterbium‐doped amorphous aluminum oxide on a silicon substrate is demonstrated. Real‐time detection and accurate size measurement of single micro‐particles with diameters ranging between 1 µm and 20 µm are achieved, which represent the typical sizes of many fungal and bacterial pathogens as well as a large variety of human cells. A limit of detection of ∼500 nm is deduced. The sensing principle relies on measuring changes in the frequency difference between the two longitudinal laser modes as the evanescent field of the dual‐wavelength laser interacts with micro‐sized particles on the surface of the waveguide. Improvement in sensitivity far down to the nanometer range can be expected upon stabilizing the pump power, minimizing back reflections, and optimizing the grating geometry to increase the evanescent fraction of the guided modes.     

Successive,Seed‐Mediated Growth for the Synthesis of Single‐Crystal Gold Nanospheres with Uniform Diameters Controlled in the Range of 5–150 nm

A simple and robust route is described to the synthesis of single‐crystal Au nanospheres with diameters controlled in the range of 5 nm to 150 nm. The success of this synthesis relies on the use of single‐crystal Au spheres with different diameters as the seeds for successive growth and the use of a slow injection rate for the precursor to enable surface diffusion for the atoms added onto the surface of a seed. The diameters could be precisely controlled by varying the size and/or number of the seeds. The products exhibit excellent uniformity in terms of both size and shape and they are expected to find widespread use in a number of applications, including self‐assembly, fabrication of metallodielectric photonic crystals, plasmonics, and biomedical research.     

Characterization of TiO2 Smoke Prepared Using Gas‐Phase Hydrolysis of TiCl4

The formation of submicron TiO₂ smoke (a gas‐phase suspension) from titanium tetrachloride in a low‐pressure hydrolysis reaction in a simple reactor configuration has been studied. Particle size distribution, particle morphology and degree of crystallinity have been characterized as a function of reaction conditions. Highly crystalline anatase TiO₂ particles with narrow size distribution and smaller particle size were formed at high reactor temperature, while larger, amorphous particles were found at lower reactor temperatures. These results are consistent with literature studies. At 817 °C, small (450 nm), spherical, unagglomerated particles could be produced. A gas‐phase dispersion of these particles is intended for use as seeds in subsequent kinetic studies of titanium dioxide formation reactions involving a rapid compression methodology.     

Effect of high-intensity ultrasonic treatment on the emulsion of hemp seed oil stabilized with hemp seed protein

In this study, hemp seed oil (HSO) emulsions stabilized with hemp seed protein (HPI) were prepared and treated with high intensity ultrasonic (HIU). The effects of different treatment powers (0, 150, 300, 450, 600 W) on the properties, microstructure and stability of emulsions were investigated. HIU-treated emulsions showed improved emulsifying activity index and emulsifying stability index, reduced particle size, and increased absolute values of ζ-potential, with the extreme points of these indices occurring at a treatment power of 450 W. Here, the emulsion showed the best dispersion and the smallest particle size in fluorescence microscopy observation, with the highest adsorbed protein content (30.12%), and the highest tetrahydrocannabinol (THC) retention rate (87.64%). The best thermal and oxidative stability of the emulsions were obtained under HIU treatment with a power of 450 W. The D₄₃ and the peroxide values (POV) values after 30 d storage were the smallest at 985.74 ± 64.89 nm and 4.6 μmol/L, respectively. Therefore, 450 W was optimal HIU power to effectively improve the properties of HPI-stabilized HSO emulsion and promote the application of HSO and its derivatives in food processing production.     

Bone‐nanohydroxyapatite spheres interface evaluation by synchrotron radiation X‐ray microfluorescence

Hydroxyapatite (HA) is largely used as bone graft; it seems to be the most promising synthetic implant material, mainly because of its excellent biocompatibility. The crystallinity, particle and pore size of HA are important characteristics and can be modified by decreasing basic structural form below 100 nm and have evoked a great amount of attention for improving prevention, diagnosis, and disease treatment, besides improving bone repair through the biodegradation of the material. The aim of this study was to investigate bone mineral content in bone samples with nanohydroxyapatite and HA spheres, specially its spatial distribution on bone microarchitecture. Circular bone defects were made in both tibiae of 12 White New Zeland adult rabbits (Oryctolagus cuniculus) and were divided randomly into five groups – blood clot (control group), sintered HA, non‐sintered HA, sintered nanoHA and non‐sintered nanoHA – all materials in spherical shape, to smooth handling and accommodation of the surgical bed, and to minimize inflammatory response. The rabbits were euthanatized according to the experimental period of 1 and 4 weeks after surgery. The samples were evaluated by polarized microscopy as well as X‐ray microfluorescence in order to account the bone mineral content bone‐implant interfaces, through synchrotron radiation. Our results revealed greater newly formed bone area in the non‐sintered materials and control groups, and the used technique showed that the amount of calcium of new bone was consistent with both mature bone and HA spheres. In conclusion, the present findings suggest that HA‐based biomaterials are biocompatible, promote osteoconduction and favored bone repair. Copyright © 2011 John Wiley & Sons, Ltd.