To prepared fluorescent chitosan capsules by in situ polyelectrolyte coacervation on poly(methacrylic acid)-doped porous calcium carbonate microparticles

To prepare hollow microcapsules composed of native chitosan (CS), a templating method is developed using poly(methacrylic acid) (PMAA)-doped porous calcium carbonate (CaCO₃) microparticles as sacrificial templates. At first, CS was adsorbed onto PMAA-doped porous CaCO₃ microparticles, and then the adsorbed CS was covalently cross-linked with each other by using glutaraldehyde. After the dissolution of the templates, the resultant CS capsules ranged from 2 to 5???m in diameter. Nitrogen adsorption?Cdesorption analysis are applied to characterize the porous CaCO₃ templates, the BET surface area and total pore volume are 160 and 0.50?cm³/g. The structure and morphology of the CS capsules are characterized by FESEM and TEM. Confocal laser scanning microscopy images reveal that the capsules have been labeled with green FITC. The gradual capsule invagination in response to bulk osmotic pressure created by CS solutions has also been discussed.     

Chitosan reinforced with modified CaCO<Subscript>3</Subscript> nanoparticles to enhance thermal,hydrophobicity properties and removal of cu(II) and cd(II) ions

The role of nanoparticles (NPs) in the enhancement of thermal, wettability and adsorption properties of chitosan (CS) was inspired by loading of CaCO₃ modified with diacid (DA) based on L- phenyl aniline (2–8 wt%) within the CS by ultrasound agitation. The diameter of CaCO₃-DA into the CS extended from 40 to 70 nm. A thermal test on the CS/CaCO₃-DA nanocomposite (NC) 2 wt% revealed that T ₅ (temperature with 5% weight loss) was increased up to 312 °C, which is twice the value of the pure polymer. The wettability property of the CS/CaCO₃-DA NCs was transformed from hydrophilicity to hydrophobicity as the CaCO₃-DA NPs concentration was increased. It is due to decrease of the accessibility of the CS polar groups to water. The CS/CaCO₃-DA NC 5 wt% was selected as the adsorbent for uptake of metal ions from the wastewater. It showed maximum adsorption capacity of 21.74 and 29.41 mg.g^?1 for Cu(II) and Cd(II), respectively. These are attributed to strong complexation reaction between the metal ions and functional groups in the obtained NC.     

Construction of pH-responsive drug delivery platform with calcium carbonate microspheres induced by chitosan gels

Construction of simple and convenient platforms for controlled delivery of anti-cancer drugs is of great importance for medical science and pharmaceutics. Here, chitosan (CS) gels were used to induce the growth of calcium carbonate (CaCO₃) microspheres, and the resulting CaCO₃ microspheres were well dispersed within the three-dimensional (3D) network framework of the CS gels. The synthesized CaCO₃/CS composites were then examined by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FT-IR) and X-ray diffractometry (XRD). Finally, the designed CaCO₃/CS composites were used for loading and controlled delivery of methotrexate (MTX), an anti-cancer drug. The encapsulation ratio of MTX calculated by UV–vis spectroscopy was approximately 78.8%. In addition, pH-responsive delivery of MTX from the CaCO₃/CS composites was successfully achieved due to the pH-sensitive property of CS, and the cumulative release of MTX could reach 93.3%, 86.6% and 77.6% at pH 8.5, 7.4 and 5.8, respectively.     

Porous aromatic frameworks of co-cured diethynylbenzene (DEB) and vinyltrimethoxysilane (VTMS) with good thermo-oxidative stability

A series of new porous aromatic frameworks (PAA-VTMS) co-cured by diethynylbenzene (DEB) and vinyltrimethoxysilane (VTMS) have been described. Thermally treated PAA-VTMS were also investigated. When the ratio of DEB to VTMS was 1:1 (PAA-VTMS-4), it showed characteristic pores with uniform diameter, confirmed by scanning electron microscope (SEM) and transmission electron microscopy (TEM) analyses. The surface area of PAA-VTMS-4 was up to 457 m²/g and its pore size was 7 nm, related to the hyper-cross-linked structure with plentiful benzene units. The co-cured PAA-VTMS samples whose DEB/VTMS ratios were higher or less than 1:1 showed low surface area. CO₂ uptake of PAA-VTMS-4 was 83 cm³/g at 0 °C and 72 cm³/g at 25 °C. The temperature of 5% weight loss of PAA-VTMS-4 was 388 °C in nitrogen and 346 °C in air. The surface area of the thermally treated sample (OPAA-VTMS-4) was decreased, but its CO₂ uptake was as high as 115 cm³/g at 0 °C and 105 cm³/g at 25 °C. The OPAA-VTMS-4 sample almost did not decompose in N₂, and the temperature of its 5% weight loss was 450 °C in air. It showed that PAA-VTMS with its new porous aromatic framework can be used at high temperature.     

Preparation of porous polyvinyl acetate materials using concentrated emulsion templates

This paper is devoted to the preparation of highly porous polyvinyl acetate (PVAc) materials using concentrated emulsion templates. Stable concentrated emulsions were obtained by introducing colloidal silica to the aqueous phase, which was absorbed at the interface of the emulsion preventing the coalescence of the dispersed phase. The prepared samples were characterized by Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), N₂ adsorption (BET), thermo-gravimetric and differential thermal techniques. SEM measurement revealed that cell diameter of the resulting foams was controlled from 1 to 10 μm by altering the emulsion composition, such as the content of colloidal silica, and the volume fraction of the dispersed phase. FT-IR revealed the presence of SiO₂ and PVAc in the resulting foams. The nitrogen adsorption analysis showed that the samples possessed mesoporous structure with surface areas lager than 62 m² g^?1. Porous PVAc materials, which are biocompatible, will have potential applications in area of life science.     

Pore size-controlled synthesis of 3D hierarchical porous carbon materials for lithium-ion batteries

3D hierarchical porous carbons (3DCs) with different pore size distributions are prepared by using Ni(OH)₂ as template. The morphology, crystalline features, pore structure and surface composition of the hierarchical porous carbons are characterized using various analytic techniques including scanning electron microscopy, transmission electron microscopy, N₂ physical adsorption, powder X-ray diffraction and X-ray photoelectron spectroscopy. It is found that the pore size distributions of the 3DCs play an important role in the lithium-storage capacity when they are used as anode materials for rechargeable lithium-ion batteries. The typical sample 3DC-20 has a specific reversible capacity of 630 mAh g^??1 in the first cycle and and 363 mAh g^??1 after 50 cycles. The high capacity of 3DC-20 can be attributed to the existence of the largest amount of micropores with 0.6–0.9 nm pore width, which increase the lithium storage capacity; in addition, the existence of mesoporous and macroporous effectively shortens the distance for charge diffusion, the turbostratic graphite structure low resistance for electron conduction.     

Microcellular foaming of low‐density polyethylene using nano‐CaCo3 as a nucleating agent

In this study, microcellular foaming of low‐density polyethylene (LDPE) using nano‐calcium carbonate (nano‐CaCO₃) were carried out. Nanocomposite samples were prepared in different content in range of 0.5–7 phr nano‐CaCO₃ using a twin screw extruder. X‐ray diffraction and scanning electron microscopy (SEM) were used to characterize of LDPE/nano‐CaCO3 nanocomposites. The foaming was carried out by a batch process in compression molding with azodicarbonamide (ADCA) as a chemical blowing agent. The cell structure of the foams was examined with SEM, density and gel content of different samples were measured to compare difference between nanocomposite microcellular foam and microcellular foam without nanomaterials. The results showed that the samples containing 5 phr nano‐CaCO₃ showed microcellular foam with the lowest mean cell diameter 27 μm and largest cell density 8 × 10⁸ cells/cm³ in compared other samples. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Synthesis and characterization of porous TiO<Subscript>2</Subscript> with wormhole-like framework structure

A fast and reliable synthetic route for preparing contaminant-free porous TiO₂ with a wormhole-like framework and close packed macropores is demonstrated based on a sol-gel process involving acid hydrolysis of an alkoxide in the presence of a cationic surfactant. Powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements have been used to characterize the porous structure and the crystallinity. The XRD patterns, TEM and scanning electron microscopy (SEM) images confirm that these materials have disordered wormhole-like topology with close-packed nearly hexagonal macropores. The mesopore diameters and surface area of titanium dioxide, evaluated from the N₂-sorption isotherms, indicate average pore diameters of about 7 and 6 nm and surface areas of about 100 and 335 m²/g, for as-prepared and calcined samples at 400°C.     

Studies on Structure and Properties of HDPE Functionalized Through Ultraviolet Irradiation and Its Blends with CaCO3

Abstract

The structure and properties of high-density polyethylene (HDPE) functionalized through ultraviolet irradiation in air and its blends with CaCO₃ were studied by Fourier transfer infrared (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), contact angle measurement, Molau test, and mechanical properties test. The experimental results reveals that oxygen-containing groups such as C = O and C - O were introduced onto the molecular chains of HDPE through ultraviolet irradiation in air, and the groups' concentration increases with irradiation time. After irradiation, the water contact angle of HDPE becomes smaller, showing that the hydrophilicity of irradiated HDPE increases. Compared with those of HDPE/CaCO₃ blend, the dispersion of CaCO₃ particles in irradiated HDPE/CaCO₃ blend, the interface interaction between CaCO₃ particles and irradiated HDPE matrix, and the mechanical properties of irradiated HDPE/CaCO₃ blend are improved due to the introduction of polar groups.     

Synthesis,characterization, and evaluation of unsupported porous NiS submicrometer spheres as a cathode material for lithium batteries

Synthesis of a nanostructured pure phase nickel sulfide in a single step is a challenge. In this work, a new method for direct synthesis of uniform NiS–SiO₂ submicrospheres was developed by ultrasonic spray pyrolysis. Colloidal silica was used as a sacrificial template to create the porous structure. After silica removal, hollow, porous pure phase NiS nanospheres were obtained. The product was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, transmission electron microscopy, and N₂ adsorption/desorption isotherm. The results confirmed the formation of single phase millerite NiS porous nanospheres with a high surface area of 312 m² g^?1. The NiS spheres were tested as cathode for lithium batteries. A discharge capacity of 340 mAh g^?1 with good capacity retention during multiple cycles was obtained.     

Effect of Nano-CaCO3 on Mechanical and Thermal Properties of Polyamide Nanocomposites

Polyamide-CaCO₃ nanocomposites were prepared by melt intercalation on twin-screw extruder. Various particle sizes (23, 17 and 11 nm) of CaCO₃ were synthesized by in-situ deposition technique. The shape and sizes of nano-CaCO₃ particles were confirmed by transmission electron microscopy (TEM). Nano-CaCO₃ was added from 1 to 4 wt% in the polyamide. Properties such as Tensile strength, Elongation at break, Hardness, and Flame retardency were studied. These results were compared with commercial CaCO₃ filled composites. Nano-CaCO₃ filled in polyamide shows, 3 fold improvement in Young's modulus in comparison to commercial CaCO₃ and 4–7 folds to virgin polyamide. Besides that, a polyamide nanocomposite shows 2 times improvements in flame retarding and vicat softening properties compared to commercial CaCO₃. Moreover, thermal degradation was studied on TGA and found to be improved compared to commercial CaCO₃. This was due to uniform dispersion of nano-CaCO₃ with greater surface area in comparison to commercial CaCO₃ in the polyamide matrix. Extent of dispersion of nano-CaCO₃ was studied along with microcracks generated during tensile testing using scanning electron microscope (SEM).     

Ag nanowires and its application as electrode materials in electrochemical capacitor

Silver nanowires were synthesized on a large scale by using anodic aluminum oxide (AAO) film as templates and serving ethylene glycol as reductant. Their morphological and structural characterizations were characterized with field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and selected area electron diffraction (SAED). The electrochemical properties of silver nanowires as electrode materials for electrochemical capacitors were investigated by cyclic voltammetry (CV) and galvanostatic charge/discharge technique in 6 M KOH aqueous electrolyte. The Ag₂O/Ag coaxial nanowires were formed by the incomplete electrochemical oxidation during the charge step. The maximum specific capacitance of 987 F g^?1 was obtained at a charge–discharge current density of 5 mA cm^?2.     

Design of intelligent chitosan/heparin hollow microcapsules for drug delivery

In this study, a novel strategy has been developed for the assembly of polyelectrolyte multilayer (PEM) on CaCO₃ templates in acidic pH solutions, where consecutive polyelectrolyte layers (heparin/poly(allylamine hydrochloride) or heparin/chitosan) were deposited on PEM hollow microcapsules established previously on CaCO₃ templates. The PEM build‐up, hollow capsule characterization and successful encapsulation of fluorescein 5(6)‐isothiocyanate (FITC)‐Dextran by coprecipitation with CaCO₃ are demonstrated. Improvement by the removal of CaCO₃ core was achieved while the depositions. In the course of the release profile, high retardation for encapsulated FITC‐Dextran was observed. The combined shell capsules system is a significant trait that has potential use in tailoring functional layer‐by‐layer capsules as intelligent drug delivery vehicles where the preliminary in vitro tests showed the responsiveness on the enzymes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44425.     

Fabrication of Three-Dimensionally Ordered Macroporous TiO2 Films with Enhanced Photovoltaic Conversion Efficiency

Negative-charged polystyrene (PS) microspheres were prepared through a soap-free emulsion polymerization method using potassium persulfate as initiator. Three-dimensionally ordered macroporous TiO₂ films were fabricated using the high-quality PS colloidal crystals templates obtained via a horizontal deposition method. The as-prepared macroporous TiO₂ films were applied as the photoanodes in dye-sensitized solar cell (DSSC). The microstructure of the products were characterized by X-ray diffractometer, fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption–desorption analyzer. The results showed that the macroporous TiO₂ films replicated well the 3D ordered structure derived from PS colloidal crystal templates and revealed a relatively large specific surface area (69.99 m²/g), which could increase the capacity of TiO₂ film anode for absorbing dyes and scattering light. The photocurrent–voltage (I–V) characteristics of DSSC were measured by a digital source meter under simulated solar light. The results indicated that the introduction of an ordered macroporous TiO₂ interfacial layer increased the photovoltaic conversion efficiency, which was improved by 68 % from 3.61 to 6.08 %, as compared to a device using a bare P25 TiO₂ photoanode. Our results showed that the hierarchically ordered macroporous TiO₂ bilayer films photoanode for DSSC could be helpful to improve the photovoltaic conversion efficiency.     

Hydrothermal Biotemplated Synthesis of Biomorphic Porous CeO2 and Their Catalytic Performance

Biomorphic porous CeO₂ powder was synthesized by the hydrothermal method using stems of clover as biotemplates. Thermogravimetric and differential thermal analysis, X-ray diffraction, N₂ adsorption–desorption, field emission scanning electron microscopy and Fourier transfer infrared spectroscopy were applied to characterize the samples. The oxygen storage/release capacity (OSC) and catalytic oxidation performance of the biomorphic porous CeO₂ for acid magenta were also investigated. Results show that the as-synthesized CeO₂ powders exhibit a cubic phase and have porous structures with pore size ranging from several to dozens of micrometers. The results of N₂ adsorption–desorption measurement suggest that the biomorphic CeO₂ contains a large number of mesopores on the surface of CeO₂ framework; and, the pore diameter is from 15–35 nm. The OSC value of the biomorphic porous CeO₂ is 174.6 μmol O₂/g ceria, which is two-times higher than powdered CeO₂. After catalytic oxidation for 300-min by the biomorphic porous CeO₂, the decolorizing rate of acid magenta is close to 95 %, which is higher than for powdered CeO₂ (64 %).     

Template-directed synthesis of porous alumina particles with precise wall thickness control via atomic layer deposition

Highly porous alumina particles with precise wall thickness control were synthesized by atomic layer deposition (ALD) of alumina on highly porous poly(styrene-divinylbenzene) (PS-DVB) particle templates. Alumina ALD was carried out using alternating reactions of trimethylaluminum and water at 33 °C. The growth rate of alumina was ∼0.3 nm per coating cycle. The wall thickness can be precisely controlled by adjusting the number of ALD coating cycles. Thermo-gravimetric analysis, X-ray diffraction, nitrogen adsorption, scanning electron microscopy, and transmission electron microscopy were used to characterize the fabricated porous alumina particles. The effect of number of ALD coating cycles and calcination temperature on the mesoporous structure of the alumina particles was investigated. γ-Alumina was formed at temperature above 600 °C. Porous alumina particles with a surface area of 80-100 m²/g were obtained and thermally stable at 800 °C. The pore volume of the porous particles can be as high as 1 cm³/g after calcination at 800 °C. Such porous alumina particles may find wide application in nanotechnology and catalysis.     

Magnetic porous carbon microspheres synthesized by simultaneous activation and magnetization for removing methylene blue

Magnetic porous carbon microspheres (MPCMs) based on Fe₃O₄-encapsulating carbon composites for removing methylene blue (MB) in aqueous solutions were synthesized by simultaneous activation and magnetization. A series of MPCMs were prepared by combining hydrothermal and annealing treatment with α-Fe₂O₃ nanoparticles as iron source, glucose as carbon source and ZnCl₂ as porogen. The phase structure, specific surface area, porosity, thermostability, magnetic property, as well as morphology of as-prepared MPCMs were verified by X-ray diffraction, Brunauer–Emmeltt–Teller surface area analysis, thermogravimetric analysis, vibrating sample magnetometry, field emission scanning electron microscopy and high resolution transmission electron microscopy. The results indicate that the maximum specific surface area of MPCMs is up to 480.32 m²/g when the mass ratio of ZnCl₂/glucose is 0.25, which is designated as MPCMs-0.25. The saturation magnetism of MPCMs-0.25 is 30.16 emu/g. Adsorption properties of MPCMs were detected by using MPCMs-0.25 as adsorbent to remove MB from aqueous solution. The outcomes suggest that the adsorption reaches equilibrium within 35 min and physical adsorption is involved in the whole adsorption processes. The results of adsorption isotherm reveal that the adsorption process might include monolayer and porous adsorption, meanwhile, various adsorption sites exist on the surfaces of MPCMs-0.25. The reusability and stability of MPCMs-0.25 were also confirmed by five adsorption–desorption cycle experiments.     

Synthesis of macroporous ZrO2–Al2O3 mixed oxides with mesoporous walls, using polystyrene spheres as template

Macroporous ZrO₂–Al₂O₃ mixed oxides with mesoporous walls were synthesized. The three-dimensional interconnected macroporous structures, of inorganic zirconia–alumina mixed oxides containing different alumina compositions (25, 50, 100 wt%), were prepared by sol–gel method from inorganic precursors and using polystyrene microspheres with diameters of 685 and 1520 nm as templates. The final porous arrays with controllable pore size in the submicrometer range could be obtained by calcination of the organic template. The structural characteristics are discussed. The physicochemical characterization of the samples was carried out by N₂ physisorption (S_BET), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The shrinkage of pore diameter was approximately 35%, and the wall thickness of inorganic framework varied between 135 and 154 nm. The specific surface areas, of the samples, were between 123 and 287 m²/g, obtaining the largest surface area with the highest alumina contents and the smallest templates.     

Polystyrene/CaCO3 composites with different CaCO3 radius and different nano‐CaCO3 content—structure and properties

The Archimedes' principle and physical theory are attempted to analysis the densification and structure of the polystyrene (PS) composites by melt compounding with CaCO₃ having different particle size. The difference between the measured specific volume (ν) andthe theoretically calculated specific volume (ν_mix), Δν = ν−ν_mix, can reflect the densification of the composites. It is clearly demonstrated that the PS composites become more condensed with the reduction of the CaCO₃ particle size. Especially, when the content for nano‐CaCO₃ achieves 2 wt%, the Δν value of the composites reaches the least, which shows the best densification. Meanwhile, the glass transition temperature (T_g) reaches the maximum value of about 100°C by differential scanning calorimetry (DSC) and thermal mechanical analysis (TMA), which indirectly reveals the composites microstructure more condensed. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) reveal that 2 wt% nano‐CaCO₃ uniformly disperses in PS composites. The CaCO₃ selected in this experiment has certain toughening effect on PS. The impact and tensile strength increase with addition of nano‐CaCO₃, but the elongation at break decreases. When nano‐CaCO₃ content achieved 2 wt%, the impact and tensile strength present the maximum value of 1.63 KJ/m² and 44.5 MPa, which is higher than the pure PS and the composites filled with the same content of micro‐CaCO₃. POLYM. COMPOS., 31:1258–1264, 2010. © 2009 Society of Plastics Engineers     

Nanoporous rice husk derived carbon for gas storage and high performance electrochemical energy storage

We report on the gas storage behaviour and electrochemical charge storage properties of high surface area activated nanoporous carbon obtained from rice husk through low temperature chemical activation approach. Rice husk derived porous carbon (RHDPC) exhibits varying porous characteristics upon activation at different temperatures and we observed high gas uptake and efficient energy storage properties for nanoporous carbon materials activated even at a moderate activation temperature of 500 °C. Various experimental techniques including Fourier transform-infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, high resolution transmission electron microscopy and pore size analyser are employed to characterise the samples. Detailed studies on gas adsorption behaviour of CO₂, H₂ and CH₄ on RHDPCs have been performed at different temperatures using a volumetric gas analyser. High adsorption capacities of ~9.4 mmol g^?1 (298 K, 20 bar), 1.8 wt% (77 K, 10 bar) and ~5 mmol g^?1 (298 K, 40 bar) were obtained respectively for CO₂, H₂ and CH₄, superior to many other carbon based physical adsorbents reported so far. In addition, these nanoporous carbon materials exhibit good electrochemical performance as supercapacitor electrodes and a maximum specific capacitance of 112 F g^?1 has been obtained using aqueous 1 M Na₂SO₄ as electrolyte. Our studies thus demonstrate that nanoporous carbon with high porosity and surface area, obtained through an efficient approach, can act as effective materials for gas storage and electrochemical energy storage applications.