A spray-freezing approach to reduced graphene oxide/MoS2 hybrids for superior energy storage

A spray-freezing approach to reduced graphene oxide/MoS2 hybrids for superior energy storage

Tao Cheng, Jin Xu, Ziqi Tan, Jianglin Ye, Zhuchen Tao, Zhenzhen Du, Ying Wu, Shuilin Wu, Hengxing Ji, Yan Yu. Yanwu Zhu

Abstract

A three-dimensional (3D) architectural hybrid, composed of reduced graphene oxide (RGO) and ultrathin MoS2 layers, is fabricated by a facile spray-freezing method. The spray-freezing to liquid nitrogen rapidly freezes the precursor droplets which avoids phase separation and restacking of MoS2 and RGO platelets, and the following drying/annealing results in the porous 3D structure. The as-prepared 3D architectural RGO/MoS2 hybrid has a high surface area of 128 m2 g−1, a porous structure and a good electrical conductivity. In LIBs, the capacity of RGO/MoS2 anode (with an optimized MoS2 content of 55 wt%) remains 1197 mAh g−1 after 400 cycles of measurement at a current density of 1 A g−1 and it remains 892 mAh g−1 over 400 cycles at a current density of 2 A g−1. A capacity of 723 mAh g−1 is obtained at a current of 10 A g−1. As for the anode (with an optimized MoS2 content of 74 wt%) in SIBs, a high initial discharge capacity of 1315 mAh g−1, a superior rate capacity of 470 mAh g−1 at 1 A g−1 and an excellent cycling stability (518 mAh g−1 after 200 cycles at 0.5 A g−1) are demonstrated.

Keywords

Reduced graphene oxide, Molybdenum disulfide, Lithium ion batteries, Sodium ion  batteries, Electrochemistry

Development of Inhalable Dry Powder Formulations Loaded with Nanoparticles Maintaining Their Original Physical Properties and Functions

Development of Inhalable Dry Powder Formulations Loaded with Nanoparticles Maintaining Their Original Physical Properties and Functions

Okuda T

Abstract

Functional nanoparticles, such as liposomes and polymeric micelles, are attractive drug delivery systems for solubilization, stabilization, sustained release, prolonged tissue retention, and tissue targeting of various encapsulated drugs. For their clinical application in therapy for pulmonary diseases, the development of dry powder inhalation (DPI) formulations is considered practical due to such advantages as: (1) it is noninvasive and can be directly delivered into the lungs; (2) there are few biocomponents in the lungs that interact with nanoparticles; and (3) it shows high storage stability in the solid state against aggregation or precipitation of nanoparticles in water. However, in order to produce effective nanoparticle-loaded dry powders for inhalation, it is essential to pursue an innovative and comprehensive formulation strategy in relation to composition and powderization which can achieve (1) the particle design of dry powders with physical properties suitable for pulmonary delivery through inhalation, and (2) the effective reconstitution of nanoparticles that will maintain their original physical properties and functions after dissolution of the powders. Spray-freeze drying (SFD) is a relatively new powderization technique combining atomization and lyophilization, which can easily produce highly porous dry powders from an aqueous sample solution. Previously, we advanced the optimization of components and process conditions for the production of SFD powders suitable to DPI application. This review describes our recent results in the development of novel DPI formulations effectively loaded with various nanoparticles (electrostatic nanocomplexes for gene therapy, liposomes, and self-assembled lipid nanoparticles), based on SFD.

Keywords

aerosol delivery; dry powder inhaler; powder-particle design; reconstituted nanoparticle; spray-freeze drying

Shrinkage of spray-freeze-dried microparticles of pure protein for ballistic injection by manipulation of freeze-drying cycle

Shrinkage of spray-freeze-dried microparticles of pure protein for ballistic injection by manipulation of freeze-drying cycle

Straller G, Lee G

Abstract

Spray-freeze-drying was used to produce shrivelled, partially-collapsed microparticles of pure proteins that may be suitable for use in a ballistic injector. Various modifications of the freeze drying cycle were examined for their effects on collapse of the pure protein microparticles. The use of annealing at a shelf temperature of up to +10°C resulted in no visible particle shrinkage. This was because of the high Tg’ of the pure protein. Inclusion of trehalose or sucrose led to particle shrinkage because of the plasticizing effects of the disaccharides on the protein. Only by extending the duration of primary drying from 240 to 2745min at shelf temperatures in the range -12 to -8°C were shrivelled, wrinkled particles of bSA and bCA of reduced porosity obtained. Manipulation of the freeze-drying cycle used for SFD can therefore be used to modify particle morphology and increase particle density.

Keywords

Ballistic injector; Collapse; Protein; Spray-freeze-drying

Mechanical particle coating using polymethacrylate nanoparticle agglomerates for the preparation of controlled release fine particles: The relationship between coating performance and the characteristics of various polymethacrylates.

Mechanical particle coating using polymethacrylate nanoparticle agglomerates for the preparation of controlled release fine particles: The relationship between coating performance and the characteristics of various polymethacrylates.

Kondo K, Kato S, Niwa T

Abstract

We aimed to understand the factors controlling mechanical particle coating using polymethacrylate. The relationship between coating performance and the characteristics of polymethacrylate powders was investigated. First, theophylline crystals were treated using a mechanical powder processor to obtain theophylline spheres (<100μm). Second, five polymethacrylate latexes were powdered by spray freeze drying to produce colloidal agglomerates. Finally, mechanical particle coating was performed by mixing theophylline spheres and polymethacrylate agglomerates using the processor. The agglomerates were broken under mechanical stress to coat the spheres effectively. The coating performance of polymethacrylate agglomerates tended to increase as their pulverization progressed. Differences in the grindability of the agglomerates were attributed to differences in particle structure, resulting from consolidation between colloidal particles. High-grindability agglomerates exhibited higher pulverization as their glass transition temperature (Tg) increased and the further pulverization promoted coating. We therefore conclude that the minimization of polymethacrylate powder by pulverization is an important factor in mechanical particle coating using polymethacrylate with low deformability. Meanwhile, when product temperature during coating approaches Tg of polymer, polymethacrylate was soften to show high coating performance by plastic deformation. The effective coating by this mechanism may be accomplished by adjusting the temperature in the processor to the Tg.

Keywords

Dry fine particle coating; Glass transition temperature; Grindability; Mechanical powder processing; Polymethacrylate; Spray freeze drying

Preparation and Characterization of Pentoxyverine Citrate Micro-Nano Particle Aggregations

Preparation and Characterization of Pentoxyverine Citrate Micro-Nano Particle Aggregations

Bo Chen, Hui Tang, Yong Peng Huang, Jian Lan Jiao, Chuan Pin Zou

Abstract

Micro-nano drug particle aggregations were prepared by shearing emulsification, high pressure homogenization and spray freeze drying, particle formational process and optimization of preparation conditions were analyzed, and micro-morphologies, particle size distributions, aerodynamic properties, release performances, inhalation and deposition properties were characterized. Results show that the optimum condition is drug supersaturation 2 and liquid feeding rate 800 mL/h. Micro morphologies of aggregations are porous spherical foamy structure formed by flaky micro-nano particles. The aggregations obtain both of the advantages of low density and large porous particles and micro-nano superficial particles. Tap density is only 0.062 g mL-1, mass median aerodynamic diameter is 0.93μm, aerosol availability is 59.8%, fine particle fraction is 15.80%, and more than 99% drugs dissolve within 5 min. All above properties are effective for drug delivery and release of DPI.

Keywords

Characterization, Dry Powder Inhalation, Micro-Nano Particle Aggregation, Pentoxyverine Citrate, Spray Freeze Drying

Structured emulsion-templated porous copolymer based on photopolymerization for carbon capture

Structured emulsion-templated porous copolymer based on photopolymerization for carbon capture

Dariush Nikjoo, Farid Akhtar

Abstract

Porous hydrogel copolymers of acrylamide (AAM) and acrylic acid (AAC) were structured in the form of monoliths and granules. AAM-co-AAC porous copolymer monoliths were synthesized using high internal phase emulsion (HIPE) as template and photopolymerization. For granulation, photopolymerization was used for the fabrication of the AAM-co-AAC hydrogel, which was subsequently freeze-granulated. The structural analysis (FTIR and XRD) confirmed the successful synthesis of hydrogel copolymers. The CO2 uptake capacity of structured AAM-co-AAC copolymers was evaluated through adsorption and absorption mechanisms by volumetric and gravimetric methods, respectively. The granules exhibited the CO2 adsorption uptake of 0.8 mmol g−1 at 25 kPa and 298 K. The CO2 and N2 adsorption data demonstrated that the hydrogel copolymers were selective for CO2. Furthermore, the granules were capable of capturing CO2 in the presence of water. The results of absorption of CO2 on water-swollen granules demonstrated that CO2-uptake capacity increases with increasing water content up to 1.8 mmol g−1.

Keywords

Porous polymer, Photopolymerization, Adsorption, Absorption, Carbon capture

Phase change and droplet dynamics for a free falling water droplet

Phase change and droplet dynamics for a free falling water droplet

K.R. Sultana, K. Pope, L.S. Lam, Y.S. Muzychka

Abstract

This paper numerically examines phase change of free falling droplets in a sub-zero environment. The model is based on the solution of the Navier-Stokes equations coupled with the Volume of Fluid (VOF) methodology for tracking the droplet-air interface. A 2D axisymmetric model is adopted to implement the influential numerical parameters. The phase change phenomenon of fresh and salt water droplets with constant and variable properties are considered in this model. Current results reveal that the internal circulation enhances heat transfer to the surrounding air and increases the nucleation phenomenon. Furthermore, larger sized droplets have a higher nucleation temperature than the smaller sized droplets. The computational results are compared to previously published experimental data for nucleation and droplet dynamics. The results of this paper provide new insights on phase change and droplet dynamics and contribute to the understanding of mechanisms involved with spray freezing applications.

Keywords

Computational fluid dynamics, Droplet, Nucleation, Sub-zero environment, Thermophysical properties

Improving quercetin dissolution and bioaccessibility with reduced crystallite sizes through media milling technique

Improving quercetin dissolution and bioaccessibility with reduced crystallite sizes through media milling technique

Muwen Lu, Chi-Tang Ho, Qingrong Huang

Abstract

Quercetin (QC) is a common bioflavonoid with low water solubility, which limits its oral bioavailability and in vivo beneficial functions. To enhance QC bioaccessibility, QC nanoparticles were produced using the media milling technology. Hydrophobically modified starch (HMS) was added with the ratio of 1:1 to QC as a stabilizer to prevent the agglomeration of QC particles. The QC nanodispersions were either spray-dried or freeze-dried after media milling process. Physicochemical characteristics of dried QC powders were measured through dynamic light scattering (DLS), Fourier Transform-Infrared spectroscopy (FTIR), dissolution test and X-ray diffraction (XRD). The detailed crystallite structures were carefully analyzed. The TNO dynamic gastro-intestinal model-1 (TIM-1) was utilized to study the in vitro QC bioaccessibility by simulation of the digestive processes in the upper GI tract. This study suggests that media milling technique combined with spray/freeze-drying treatment is an efficient processing method for the development of crystalline nutraceuticals-based functional food products with reduced crystallite sizes and enhanced metastable equilibrium solubility, dissolution and bioaccessibility.

Keywords

Quercetin, Nanoparticle, Wet milling, Dissolution, Bioaccessibility

Solid state stability of polyphenols from a plant extract after fluid bed atmospheric spray-freeze-drying

Solid state stability of polyphenols from a plant extract after fluid bed atmospheric spray-freeze-drying

Cristiane Cardoso Correia Teixeira, Tatiana Pereira de Freitas Cabral, Luciana, Alves Tacon, Isabel Lemos Villardi, Aurea Donizete Lanchote, Luis Alexandre Pedro deFreitas

Abstract

Dry powder extracts are the most suitable pharmaceutical forms of phytomedicines due to their greater physical and chemical stability in the solid state, in addition to the possibility of easy preparation of tablets and capsules. Recently, Baccharis dracunculifolia D.C. crops have been stimulated in Brazil to obtain the green propolis, which is derived from pollen harvesting of Baccharis by the Apis mellifera, and develop new phytomedicines from this plant. The aim of this work was to obtain stable powdered Baccharis dracunculifolia leaf extracts dried by fluidized-bed atmospheric spray-freeze-drying and study the stability of its chemical markers in the solid state. The drying was performed using D-mannitol, modified corn starch and their mixture as adjuvants. Physical characterization was performed by determining the dried extract powder size, morphology, flow and packing. Their chemical stability was evaluated by high performance liquid chromatography quantification of p-coumaric acid, cinnamic acid, artepillin C and baccharin. The antioxidant activity of the dried extract was determined using the stable free radical 2,2-diphenylpicrylhydrazil. The results showed that the four prenylated compounds are sensitive to drying at freezing temperatures, but D-mannitol could efficiently prevent their loss. The Baccharis spray-freeze-dried extracts showed a high yield, low moisture and excellent pharmacotechnical properties. The stability tests demonstrated a high loss of polyphenols at 40, 60 and 80 °C, especially artepillin C (the main marker) and showed high instability. The kinetics of polyphenols losses were measured, and their rates were used to fit three-dimensional diffusion models and the Arrhenius equation. The results demonstrate that the Baccharis dracunculifolia dried extract, using artepillin C as a reference, could achieve a shelf life as long as 10 years when stored at 4 °C and protected from light. The process of fluid-bed atmospheric spray-freeze-drying was shown to be an attractive alternative for drying of heat-sensitive and high value-added materials such as medicinal plant extracts.

Keywords

Polyphenols, Baccharis dracunculifolia, Fluid bed, Spray-freeze-drying, Degradation

Synthesis of high-performance Li2FeSiO4/C composite powder by spray-freezing/freeze-drying a solution with two carbon sources

Synthesis of high-performance Li2FeSiO4/C composite powder by spray-freezing/freeze-drying a solution with two carbon sources

Yukiko Fujita, Hiroaki Iwase, Kenji Shida, Jinsun Liao, Takehisa Fukui, Motohide Matsuda

Abstract

Li2FeSiO4 is a promising cathode active material for lithium-ion batteries due to its high theoretical capacity. Spray-freezing/freeze-drying, a practical process reported for the synthesis of various ceramic powders, is applied to the synthesis of Li2FeSiO4/C composite powders and high-performance Li2FeSiO4/C composite powders are successfully synthesized by using starting solutions containing both Indian ink and glucose as carbon sources followed by heating. The synthesized composite powders have a unique structure, composed of Li2FeSiO4 nanoparticles coated with a thin carbon layer formed by the carbonization of glucose and carbon nanoparticles from Indian ink. The carbon layer enhances the electrochemical reactivity of the Li2FeSiO4, and the carbon nanoparticles play a role in the formation of electron-conducting paths in the cathode. The composite powders deliver an initial discharge capacity of 195 and 137 mAh g−1 at 0.1 C and 1 C, respectively, without further addition of conductive additive. The discharge capacity at 1 C is 72 mAh g−1 after the 100th cycle, corresponding to approximately 75% of the capacity at the 2nd cycle.

Keywords

Lithium-ion battery, Cathode material, Li2FeSiO4/C, Spray-freezing/freeze-drying, Nanoparticle, Composite powder