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Photon Correlation Spectroscopy (photon + correlation_spectroscopy)
Kinds of Photon Correlation Spectroscopy Selected AbstractsPotential MRI Contrast Agents Based on Micellar Incorporation of Amphiphilic Bis(alkylamide) Derivatives of [(Gd,DTPA)(H2O)]2,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 16 2003Kristof Kimpe Abstract DTPA-bisamide derivatives with alkyl chains containing 14, 16 and 18 carbon atoms were synthesized and complexes of various trivalent lanthanide ions (Ln = Gd, La, Pr, Eu) were formed. Variable temperature proton NMR spectroscopy of paramagnetic praseodymium(III) and europium(III) complexes revealed that long aliphatic substituents considerably increase the energy barrier for the intramolecular rearrangement around the lanthanide ion. The gadolinium(III) complexes were incorporated into mixed micelles, and photon correlation spectroscopy showed that the mean sizes of all the micelles were within the same range. The NMRD curves of all three DTPA-bisamide-gadolinium complexes incorporated in mixed micelles display higher relaxivity values than the commercially available Gd,DTPA contrast agent. The higher relaxivity obtained for the micellar DTPA-bisamide-gadolinium complexes with C14 and C16 chains relative to the micellar DTPA-bisamide-GdIII C18 chain complex could be attributable to the fact that the alkyl chain containing 18 carbon atoms is longer than the alkyl chain of the major component of the micelles, DPPC, in which it is inserted. This would allow increased mobility of the polar head and hence a lower relaxivity. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] The dynamic behavior of magnetic colloids in suspensionJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2007Tina Autenrieth The dynamic behavior of magnetic colloidal particles in suspension is investigated. The particles of the core,shell colloid consist of a cobalt ferrite core embedded in a silica shell and are stabilized by surface charges. As the suspension is strongly opaque to visible light, it can not be probed by dynamic light scattering techniques as a result of strong multiple scattering as well as absorption effects. Therefore, the static and dynamic behavior is probed with small-angle X-ray scattering and X-ray photon correlation spectroscopy (XPCS), respectively. Using XPCS, we are able to study the diffusion coefficient of an opaque colloidal system as a function of the scattering vector. In this paper, we report on the behavior of the colloidal system in the absence of an external magnetic field, meaning that the magnetic moments of the particles are oriented randomly. We find no evidence for magnetic interactions in the static data, while the dynamic XPCS data deviate very significantly from the predictions of model calculations. [source] Transmission electron microscopy and electron diffraction study of BSA-loaded quaternized chitosan nanoparticlesJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2008A-jun Wan Abstract Chitosan nanoparticles, O -(2-hydroxyl) propyl-3-trimethyl ammonium chitosan chloride (O -HTCC) nanoparticles and bovine serum albumin (BSA) loaded chitosan and O -HTCC nanoparticles of a size (about 200,600 nm) were obtained through the process of ionic gelation between chitosan or O -HTCC and sodium tripolyphosphate (TPP). The physicochemical properties of nanoparticles made from chitosan, O -HTCC, BSA loaded chitosan, and BSA loaded O -HTCC were determined by transmission electron microscopy (TEM), polarized optical microscopy (POM), photon correlation spectroscopy (PCS), and X-ray diffraction (XRD) pattern. Zeta potential was also performed to understand the surface properties of nanoparticles and their ability to bind negatively charged BSA. TEM, POM, and XRD suggested that ionic-gelation process significantly influenced the crystallinity of BSA, and greater chain realignment in the BSA-loaded chitosan and O -HTCC nanoparticles. PCS revealed that BSA-loaded chitosan nanoparticles were bigger than chitosan nanoparticles in size and BSA-loaded O -HTCC nanoparticles were smaller than O-HTCC nanoparticles in size. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008 [source] PARTICLE SIZE DETERMINATION OF FOOD SUSPENSIONS: APPLICATION TO CLOUDY APPLE JUICEJOURNAL OF FOOD PROCESS ENGINEERING, Issue 6 2000D.B. GENOVESE ABSTRACT Three different techniques were applied to determine particle size distribution (PSD) of cloudy apple juice: sedimentation-photometry (S-F), scanning electron microscopy (SEM) and photon correlation spectroscopy (PCS). All the three techniques found particles in a range from about 0.05 to 3 micrometers (,m = 10,6m). While calculation of PSD by SEM was based on particle number, calculation of PSD by PCS and S-F were based on intensity of scattered light, and both weight (or volume) and projected area (or absorbed light), respectively. In order to compare results from these techniques, appropriate equations were used to convert distributions from one base to another. Three characteristic diameters were also obtained from each distribution: mean, median and modal. Characteristic diameters range from 0.88 to 2.50 ,m in weight basis, 0.77 to 2.50 ,m in projected area basis and 0.08 to 0.23 ,m in number basis. Differences between these diameters were due to asymmetry in the distributions. [source] ,-Carotene-Loaded Nanostructured Lipid CarriersJOURNAL OF FOOD SCIENCE, Issue 2 2008A. Hentschel ABSTRACT:, Nanostructured lipid carriers (NLC) technology was used to disperse hydrophobic ,-carotene in an aqueous phase. NLC are lipid nanoparticles with a particle matrix consisting of a blend of a liquid and solid lipid. They were produced by melting the lipid blend at 80 °C and dispersing it into a hot emulsifier solution. The aim of this study was to extend the limited knowledge of melt-emulsified lipidic colloids in food systems and to evaluate the feasibility for further applications as functional ingredient in beverages. Physical stability of the NLC suspension was examined at 2 different storage temperatures by measuring the particle size with photon correlation spectroscopy (PCS) and laser diffractometry (LD). All particles containing sufficient amounts of emulsifier were smaller than 1 ,m (LD diameter 100%) at a mean particle size of around 0.3 ,m (LD) for 9 wk at 20 °C and at least 30 wk at 4 to 8 ° C. Differential scanning calorimetry (DSC) was used to study the solid state of the lipids both in the ,-carotene loaded PGMS and in the NLC particles. Propylene glycol monostearate (PGMS) when dispersed as NLC recrystallized up to 98% during storage time. Within the regarded period of 7 mo no polymorph transitions were observed. Furthermore, stability of the ,-carotene in water dependent on NLC concentration and tocopherol content was measured photospectrometrically to get an estimation of the behavior of NLC in beverages. [source] Preparation of monodisperse nanoparticles containing poly(propylene imine)(NH2)32 -polystyreneJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2009Hu Liu Abstract Polypropylenimine dendrimer (DAB-Am-32, generation 4.0) was converted into a macroinitiator DAB-Am-32-Cl via reaction with 2-chloropropionyl chloride. Monodisperse nanoparticles containing poly(propylene imine)(NH2)32 -polystyrene were prepared by emulsion atom transfer radical polymerization (ATRP) of styrene (St), using the DAB-Am-32-Cl/CuCl/bpy as initiating system. The structure of macroinitiator was characterized by FTIR spectrum, 1H NMR, and 13C NMR. The structure of poly(propylene imine)(NH2)32 -polystyrene was characterized by FT-IR spectrum and 1H NMR; the molecular weight and molecular weight distribution of poly(propylene imine)(NH2)32 -polystyrene were characterized by gel permeation chromatograph (GPC). The morphology, size and size distribution of the nanoparticles were characterized by photon correlation spectroscopy (PCS), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The effects of monomer/macroinitiator ratio and surfactant concentration on the size and size distribution of the nanoparticles were investigated. It was found that the diameters of the nanoparticles were smaller than 100 nm (30,80 nm) and monodisperse; moreover, the particle size could be controlled by monomer/macroinitiator ratios and surfactant concentration. With the increasing of the ratio of St/DAB-Am-32-Cl, the number-average diameter (Dn), weight-average diameter (Dw) were both increased gradually. With enhancing the surfactant concentration, the measured Dh of the nanoparticles decreased, while the polydispersity increased. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2892,2904, 2009 [source] Fast two-dimensional detection for X-ray photon correlation spectroscopy using the PILATUS detectorJOURNAL OF SYNCHROTRON RADIATION, Issue 5 2009Fabian Westermeier The first X-ray photon correlation spectroscopy experiments using the fast single-photon-counting detector PILATUS (Paul Scherrer Institut, Switzerland) have been performed. The short readout time of this detector permits access to intensity autocorrelation functions describing dynamics in the millisecond range that are difficult to access with charge-coupled device detectors with typical readout times of several seconds. Showing no readout noise the PILATUS detector enables measurements of samples that either display fast dynamics or possess only low scattering power with an unprecedented signal-to-noise ratio. [source] A Geiger-mode avalanche photodiode array for X-ray photon correlation spectroscopyJOURNAL OF SYNCHROTRON RADIATION, Issue 1 2009I. Johnson X-ray photon correlation spectroscopy (XPCS) provides an opportunity to study the dynamics of systems by measuring the temporal fluctuations in a far-field diffraction pattern. A two-dimensional detector system has been developed to investigate fluctuations in the frequency range of several Hz to kHz. The X-ray detector system consists of a thin 100,µm scintillation crystal coupled to a Geiger-mode avalanche photodiode array. In this article the elements of the system are detailed and the detector for XPCS measurements is demonstrated. [source] Fluorescent gel particles in the nanometer range for detection of metabolites in living cells,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 9-10 2006Kristoffer Almdal Abstract In this present work a research program that aims at the development of sensor particles based on ratiometric detection of fluorescence from two dyes was embarked on. Such particles can in principle be used to achieve spatially and time resolved measurements of metabolite concentrations in living cells. The dyes are chosen such that the fluorescence of one dye is a function of an analyte concentration whereas the fluorescence of the other dye is independent of variations in the medium. Methods have been investigated for synthesizing such particles based on crosslinked polyacrylamide in inverse micelles in oil microemulsions. Typical sizes of the particles are tens of nanometers. Characterization methods for such particles based on size exclusion chromatography, photon correlation spectroscopy, scanning electron microscopy, and atomic force microscopy have been developed. The stability of the sensor particles and their potential as an analytical tool will be discussed. Copyright © 2006 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||