Multilayered Microspheres Research Articles

Germanium recovery using polyphenol microspheres prepared by horseradish peroxidase reaction

AbstractBACKGROUND: The formation of polyphenol microspheres by the polymerization of 3‐methylcatechol was performed in a methanol/phosphate buffer solution using horseradish peroxidase (HRP), without the use of a surfactant or a water/oil interface, to be used for germanium recovery.RESULTS: The polyphenol microspheres were of diameter 1 mm. The functional group density of phenol group in the polymer was approximately 15 mol kg−1 determined by the Folin‐Denis method. In batchwise experiments, the amount of germanium adsorbed was 0.23 mol kg−1.CONCLUSION: Because germanium is a rare metal, a system for its recovery is required. Using the proposed system, continuous recovery of germanium can be achieved using multilayered microspheres. Copyright © 2011 Society of Chemical Industry

Processing and characterization of chitosan microspheres to be used as templates for layer-by-layer assembly

Chitosan (Ch) microspheres have been developed by precipitation method, cross-linked with glutaraldehyde and used as a template for layer-by-layer (LBL) deposition of two natural polyelectrolytes. Using a LBL methodology, Ch microspheres were alternately coated with hyaluronic acid (HA) and Ch under mild conditions. The roughness of the Ch-based crosslinked microspheres was characterized by atomic force microscopy (AFM). Morphological characterization was performed by environmental scanning electron microscopy (ESEM), scanning electron microscopy (SEM) and stereolight microscopy. The swelling behaviour of the microspheres demonstrated that the ones with more bilayers presented the highest water uptake and the uncoated cross-linked Ch microspheres showed the lowest uptake capability. Microspheres presented spherical shape with sizes ranging from 510 to 840 mum. ESEM demonstrated that a rougher surface with voids is formed in multilayered microspheres caused by the irregular stacking of the layers. A short term mechanical stability assay was also performed, showing that the LBL procedure with more than five bilayers of HA/Ch over Ch cross-linked microspheres provide higher mechanical stability.

TiO2‐Coated Multilayered SnO2 Hollow Microspheres for Dye‐Sensitized Solar Cells

TiO2-coated multilayered SnO2 hollow microspheres exhibit a high overall photoconversion efficiency of ∼5.65% when used for dye-sensitized solar-cell photoelectrodes due to multiple reflecting and scattering of incident light in the hierarchical hollow spherical structure.

Preparation of nanoplates assembled 4CaO·5B 2O 3·7H 2O oval-like microspheres via a hydrothermal method

4CaO·5B 2O 3·7H 2O uniform oval-like microspheres morphology has been prepared at 120 °C by a simple hydrothermal method with the help of the surfactant polyethylene glycol(PEG-300). The result indicates that 4CaO·5B 2O 3·7H 2O oval-like microspheres are constructed by ladder-like layers, and each layer is made up of numerous densely packed nanoplates with the thickness of 50–100 nm and the diameter of several microns. The nanoplates in each layer are interconnected with the nanoplates in next layer, which leads to form the multilayered structural oval-like microspheres. The PEG-300 plays an important role in the formation of this oval-like microspheres morphology.

Encapsulation of Levitated Microparticles

Multi-layered polymer microspheres with diameters of order 10 μm were produced by polymerizing monomer droplets levitated in an electrodynamic balance. The polymer spheres were subsequently coated with additional monomer by combining the levitated particle with a charged droplet of opposite polarity, and the monomer coating was photochemically polymerized to form a solid shell. The thickness of the shell was determined by comparing the angular light scattering with Mie theory. A polymer coating was also applied to levitated NaNO3particles, and Raman spectroscopy was used to explore the effect of the polymer shell on the Raman signal associated with the salt core. The coating significantly reduced the Raman signal from the salt core, and these results are shown to be consistent with a decrease in the internal electromagnetic field in the salt core computed using Mie theory.

One‐step preparation of double‐walled microspheres

Multilayered microspheres for drug delivery can be produced by several methods, but most techniques involve several stages and often lead to layers of non‐uniform thickness. The solcent evaporation method of producing double‐layered microspheres described here svoids these difficulties, a single step yielding micrespheres consisting of an inner core of polymer surrounded by a second polymer. The theory is presented and the characterization of the microspheres discussed.