Raspberry-Like Microspheres of Core-Shell Cr2 O3 @TiO2 Nanoparticles for CO2 Photoreduction.
ABSTRACT: To promote the interaction of p-n semiconductors, raspberry-like microspheres of core-shell Cr2 O3 @TiO2 nanoparticles have been fabricated through a five-step process. Raman spectroscopy of products calcined at various temperatures reveal that the titania shell causes crystal distortion of the Cr2 O3 core, without changing the microstructures of the fabricated core-shell microspheres. In situ and time-resolved synchrotron-based powder XRD reveals the formation of monoclinic TiO2 in the fourth step, but these monoclinic TiO2 nanocrystals undergo a phase transition when the applied calcination temperature is above 550?°C. As a result, TiO2 (B), a magnéli phase of Ti4 O7 and Cr2 Ti6 O15 compounds, resulting from inner doping between Cr2 O3 and TiO2 , is formed. The close interaction of Cr2 O3 and TiO2 forms a p-n junction that decreases the recombination of photogenerated electron-hole pairs, leading to enhanced production of CH4 by photocatalytic reduction of CO2 .
Project description:Core-shell particles with integration of ferromagnetic core and dielectric shell are attracting extensive attention for promising microwave absorption applications. In this work, CoNi microspheres with conical bulges were synthesized by a simple and scalable liquid-phase reduction method. Subsequent coating of dielectric materials was conducted to acquire core-shell structured CoNi@TiO2 composite particles, in which the thickness of TiO2 is about 40?nm. The coating of TiO2 enables the absorption band of CoNi to effectively shift from Ku to S band, and endows CoNi@TiO2 microspheres with outstanding electromagnetic wave absorption performance along with a maximum reflection loss of 76.6?dB at 3.3?GHz, much better than that of bare CoNi microspheres (54.4?dB at 17.8?GHz). The enhanced EMA performance is attributed to the unique core-shell structures, which can induce dipole polarization and interfacial polarization, and tune the dielectric properties to achieve good impedance matching. Impressively, TiO2 coating endows the composites with better microwave absorption capability than CoNi@SiO2 microspheres. Compared with SiO2, TiO2 dielectric shells could protect CoNi microspheres from merger and agglomeration during annealed. These results indicate that CoNi@TiO2 core-shell microspheres can serve as high-performance absorbers for electromagnetic wave absorbing application.
Project description:Biodegradable polymer microparticles are promising delivery depots for protein therapeutics due to their relatively simple fabrication and facile administration. Double-wall microspheres (DWMS) comprising a core and shell made of two distinct polymers may provide enhanced control of the drug release profiles. Using precision particle fabrication (PPF) technology, monodisperse DWMS were fabricated with model protein bovine serum albumin (BSA)-loaded poly(lactide-co-glycolide) (PLG) core and drug-free poly(d,l-lactic acid) (PDLL) shell of uniform thickness. Monolithic single-wall microspheres were also fabricated to mimic the BSA-loaded PLG core. Using ethyl acetate and dichloromethane as shell- and core-phase solvents, respectively, BSA was encapsulated selectively in the core region within DWMS with higher loading and encapsulation efficiency compared to using dichloromethane as core and shell solvents. BSA in vitro release rates were retarded by the presence of the drug-free PDLL shell. Moreover, increasing PDLL shell thickness resulted in decreasing BSA release rate. With a 14-?m thick PDLL shell, an extended period of constant-rate release was achieved.
Project description:Polymeric composite microspheres consisting of a poly(D,L-lactic-co-glycolic acid) (PLGA) core surrounded by a poly(D,L-lactic acid) (PDLLA) shell layer were successfully fabricated by coaxial electrohydrodynamic atomization (CEHDA) process. Process conditions, including nozzle voltage and polymer solution flow rates, as well as solution parameters, such as polymer concentrations, were investigated to ensure the formation of composite microspheres with a doxorubicin-loaded PLGA core surrounded by a relatively drug-free PDLLA shell layer. Various microsphere formulations were fabricated and characterized in terms of their drug distribution, encapsulation efficiency and in vitro release. Numerical simulation of CEHDA process was performed based on a computational fluid dynamics (CFD) model in Fluent by employing the process conditions and fluid properties used in the experiments. The simulation results were compared with the experimental work to illustrate the capability of the CFD model to predict the production of consistent compound droplets, and hence, the expected core-shell structured microspheres.
Project description:Most previous studies of perovskite core/shell structures have been based on ZnO/TiO2 nanowires (NWs), which are not suitable for high photoelectric conversion efficiency. Here, core/shell ZnO/TiO2 NWs with AgCl-doped CdSe quantum dots were fabricated as an electron transport layer (ETL) for perovskite solar cells, based on ZnO/TiO2 arrays. We designed CdSe with AgCl dopants that were synthesized by a colloidal process. An improvement of the recombination barrier (Rct1), due to shell supplementation with AgCl-doped CdSe quantum dots, improved the open circuit voltage, the fill factor, and the adsorption capacity of CH3NH3PbI3 perovskite with NWs. The enhanced cell steady state was attributable to TiO2 with AgCl-doped CdSe QD supplementation. A maximum power conversion efficiency of 15.12% was attained in an atmospheric environment. The mechanism of the recombination and electron transport in the perovskite solar cells becoming the basis of ZnO/TiO2 core/shell arrays was investigated to represent the merit of ZnO/TiO2 core/shell arrays as an electron transport layer in effective devices. These results showed an uncomplicated approach for restraining non-radiative recombination loss in hetero-structure core/shell arrays to significantly improve perovskite solar cell performance and increase the effectiveness of photovoltaics.
Project description:Biodegradable polymer double-wall microspheres (DWMS) are promising vehicles for macromolecular therapeutics such as proteins and peptides. Using precision particle fabrication (PPF) technology, uniform DWMS with outer diameter approximately 55 ?m were fabricated comprising poly(lactide-co-glycolide) cores encapsulating bovine serum albumin (BSA) and approximately 10 ?m thick, drug-free, poly(lactic acid) (PLA) shells of varying PLA molecular weight. Also, monolithic single-wall microspheres (SWMS) were fabricated to mimic the BSA-loaded core. The use of relatively fast-extracting ethyl acetate and slowly extracting dichloromethane as shell- and core-phase solvents, respectively, was found to produce DWMS with well-defined core-shell structure, high BSA encapsulation efficiency, and the desired localization of protein in the particle core. Initial protein distribution, particle erosion, and in vitro protein release from DWMS and SWMS were examined. The presence of a BSA-free shell in DWMS decreased the protein release rate and extended the duration of release from approximately 50 days to 70-80 days, demonstrating the capacity of such DWMS to provide enhanced control of protein delivery rates.
Project description:Hemisphere-like gold nanoparticles (NPs) were loaded on TiO2 (Au/TiO2) by the deposition-precipitation method. Subsequent photodeposition of CdS on the Au surface of Au/TiO2 at 50 °C yields Au(core)-CdS(shell) hybrid quantum dots with a heteroepitaxial (HEPI) junction on TiO2 (Au@#CdS/TiO2), whereas nonHEPI Au@CdS/TiO2 was formed by CdS photodeposition at 25 °C. In the HEPI system, the shape of the Au core changes to an angular shape, whereas it remains in a hemisphere-like shape in the nonHEPI system. The hot photodeposition technique was applied to the Au NP-loaded mesoporous TiO2 nanocrystalline film (Au/mp-TiO2). Using Au@CdS/mp-TiO2 and Au@#CdS/mp-TiO2 as the photoanodes, two-electrode quantum dot-sensitized photoelectrochemical cells were fabricated for hydrogen (H2) generation from water, and the performances of the cells were evaluated under illumination of simulated sunlight. In the photocurrent and the rate of H2 evolution, the Au@#CdS/mp-TiO2 photoanode cell surpasses the CdS/mp-TiO2 and Au@CdS/mp-TiO2 ones. Three-dimensional finite-difference time-domain calculations for the model systems indicated that the angular shape Au core generates an intense electric field at the corners and edges, extending the electric field distribution over the Au core-CdS shell interface. The striking shape effect on the cell performances can originate from the promotion of the CdS excitation and charge separation due to the near-field enhancement by the deformed Au core.
Project description:We have designed and evaluated a dual anticancer delivery system to provide combined gene therapy and chemotherapy. Double-walled microspheres consisting of a poly(d,l-lactic-co-glycolic acid) (PLGA) core surrounded by a poly(lactic acid) (PLA) shell were fabricated via the precision particle fabrication (PPF) technique. We make use of the advantages of double-walled microspheres to deliver chitosan-DNA nanoparticles containing the gene encoding the p53 tumor suppressor protein (chi-p53) and/or doxorubicin (Dox), loaded in the shell and core phases, respectively. Different molecular weights of PLA were used to form the shell layer for each formulation. The microspheres were monodisperse with a mean diameter of 65 to 75 ?m and uniform shell thickness of 8 to 17 ?m. Blank and Dox-loaded microspheres typically exhibited a smooth surface with relatively few small pores, while chi-microspheres containing p53 nanoparticles, with and without Dox, presented rough and porous surfaces. The encapsulation efficiency of Dox was significantly higher when it was encapsulated alone compared to co-encapsulation with chi-p53 nanoparticles. The encapsulation efficiency of chi-p53 nanoparticles, on the other hand, was not affected by the presence of Dox. As desired, chi-p53 nanoparticles were released first, followed by simultaneous release of chi-p53 nanoparticles and Dox at a near zero-order rate. Thus, we have demonstrated that the PPF method is capable of producing double-walled microspheres and encapsulating dual agents for combined modality treatment, such as gene therapy and chemotherapy.
Project description:Yolk-shell TiO2 microspheres were synthesized via a one-pot template-free solvothermal method building on the aldol condensation reaction of acetylacetone. This unique structure shows superior light scattering ability resulting in power conversion efficiency as high as 11%. This work provided a new synthesis system for TiO2 microspheres from solid to hollow and a novel material platform for high performance solar cells.
Project description:Recently, K-ion batteries (KIBs) have attracted attention for potential applications in next-generation energy storage devices principally on the account of their abundancy and lower cost. Herein, for the first time, we report an anatase TiO2-derived Magnéli phase Ti6O11 as a novel anode material for KIBs. We incorporate pristine carbon nanotube (CNT) on the TiO2 host materials due to the low electronic conductivity of the host materials. TiO2 transformed to Magnéli phase Ti6O11 after the first insertion/deinsertion of K ions. From the second cycle, Magnéli phase Ti6O11/CNT composite showed reversible charge/discharge profiles with ?150 mA h g-1 at 0.05 A g-1. Ex situ X-ray diffraction and transmission electron microscopy analyses revealed that the charge storage process of Magnéli phase Ti6O11 proceeded via the conversion reaction during potassium ion insertion/deinsertion. The Magnéli phase Ti6O11/CNT composite electrode showed long-term cycling life over 500 cycles at 200 mA g-1, exhibiting a capacity retention of 76% and a high Coulombic efficiency of 99.9%. These salient results presented here provide a novel understanding of the K-ion storage mechanisms in the extensively investigated oxide-based material for Li-ion batteries and Na-ion batteries, shedding light on the development of promising electrode materials for next-generation batteries.
Project description:Multicomponent polymer particles with specific morphology are promising materials exhibiting novel functionality which cannot be obtained with single-component polymer particles. Particularly, the preparation of such kinds of polymer particles involving electrically or optically active conjugated polymers with uniform size is a challenging subject due to their intense demands. Here, microspheres of binary polymer blend consisting of poly(4-butyltriphenylamine) (PBTPA)/poly(methyl methacrylate) (PMMA) (1:1 in weight) were produced via a microfluidic emulsification with a Y-shaped microreactor, and a subsequent solvent evaporation method. The flow rate of the dispersed phase (polymer solution) was fixed to 7 µL/min, and 140 or 700 µL/min of the flow rate of the continuous phase (aqueous 0.6 wt % of poly(vinyl alcohol) (PVA) solution) was utilized to produce the dispersion with different diameter. The concentration of dispersed phase was adjusted to 0.1 or 1.0 w/v%. Core-shell, Janus and dumbbell type microspheres were obtained dependent on the flow rate of continuous phase. Incomplete core-shell type microspheres were produced for the blend involving low molecular weight PMMA. Complex Janus and core-shell type microspheres were fabricated by the addition of sodium dodecyl sulfate (SDS) to continuous phase. It is found that final morphologies are strongly dependent on the initial conditions of dispersion including the particle size suggesting that the morphologies are governed by the kinetical factors together with the conventionally accepted thermodynamic ones.