Magnesium Oxide Nanoparticles Reinforced Electrospun Alginate-Based Nanofibrous Scaffolds with Improved Physical Properties.

Mechanically robust alginate-based nanofibrous scaffolds were successfully fabricated by electrospinning method to mimic the natural extracellular matrix structure which benefits development and regeneration of tissues. Alginate-based nanofibres were electrospun from an alginate/poly(vinyl alcohol) (PVA) polyelectrolyte complex. SEM images revealed the spinnability of the complex composite nanofibrous scaffolds, showing randomly oriented, ultrafine, and virtually defects-free alginate-based/MgO nanofibrous scaffolds. Here, it is shown that an alginate/PVA complex scaffold, blended with near-spherical MgO nanoparticles (⌀ 45 nm) at a predetermined concentration (10% (w/w)), is electrospinnable to produce a complex composite nanofibrous scaffold with enhanced mechanical stability. For the comparison purpose, chemically cross-linked electrospun alginate-based scaffolds were also fabricated. Tensile test to rupture revealed the significant differences in the tensile strength and elastic modulus among the alginate scaffolds, alginate/MgO scaffolds, and cross-linked alginate scaffolds (P < 0.05). In contrast to cross-linked alginate scaffolds, alginate/MgO scaffolds yielded the highest tensile strength and elastic modulus while preserving the interfibre porosity of the scaffolds. According to the thermogravimetric analysis, MgO reinforced alginate nanofibrous scaffolds exhibited improved thermal stability. These novel alginate-based/MgO scaffolds are economical and versatile and may be further optimised for use as extracellular matrix substitutes for repair and regeneration of tissues.Peer Reviewe

Nano-MgO reinforced chitosan nanocomposites for high performance packaging applications with improved mechanical, thermal and barrier properties

Chitosan nanocomposite thin films were fabricated by incorporating MgO nanoparticles to significantly improve its physical properties for potential packaging applications. A novel in-situ method was developed to synthesise spherical shaped MgO nanoparticles by heat-treating magnesium carbonate/poly(methyl methacrylate) (PMMA) composite precursor. Optimum mechanical properties of chitosan composites were yielded at 5 (w/w%) of MgO concentration, where tensile stress and elastic modulus significantly improved by 86% and 38%, respectively, compared to those of pure chitosan films. These improvements are due to the interaction of hydroxyl and amine groups of chitosan with MgO as confirmed by FTIR spectroscopy. Fracture surface morphology indicated the interplay between MgO dispersion and aggregation on the mechanical properties at different MgO concentrations. Furthermore, the chitosan/MgO nanocomposites displayed remarkable thermal stability, flame retardant properties (satisfied V0 rating according to the UL-94 standards), UV shielding and moisture barrier properties, which could certainly add value to the packaging material

Photocatalytic activity of electrospun MgO nanofibres: Synthesis, characterization and applications

One dimensional MgO nanofibres with high photocatalytic activity were fabricated using the electrospinning method via a polyvinyl alcohol (PVA)/magnesium precursor based system and the dye degradation efficacy of MgO nanofibres was compared with MgO nanospheres. Optimum electrospinning parameters including suitable magnesium precursors were investigated and the formation of MgO nanofibres were confirmed with scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) mapping. Furthermore, the crystalline lattice structure and surface roughness of fabricated nanofibres were evaluated using transmission electron microscopic-electron diffraction mode (TEM-SAED) and atomic force microscopy (AFM), respectively. Fabricated MgO nanofibres exhibited excellent photocatalytic degradation activity against widely used model reactive dye, Reactive Yellow (RY). In contrast to MgO nanospheres, electrospun MgO nanofibres completely degraded the reactive dye under UV irradiation. These photocatalytic MgO nanofibres show a great potential to be used in efficient treatment of industrial dye effluents

Cost effective, industrially viable production of Fe<inf>2</inf>O<inf>3</inf> nanoparticles from laterites and its adsorption capability

Laterite is an iron-rich earth material containing naturally occurring minerals such as hematite (Fe2O3), magnetite (Fe3O4), goethite (Fe3+O(OH)), gibbsite (Al(OH)3) and kaolinite (Al2Si2O5(OH)4). Even though these laterites are negligibly used as a cheap raw material in the brick manufacturing industry, they could be used in the synthesis of advanced materials including iron oxide nanoparticles and nanocomposites for a broad range of applications. Therefore, for the first time, this study focuses on the synthesis of iron oxide nanoparticles using laterites as a cheap raw material. In this method, first, iron and aluminium components of laterites were extracted into hydrochloric acid as their corresponding metallic ions. The extracted solution was then, mixed with sodium dodecyl sulphate (SDS) and the mixture was added dropwise to a basic solution maintaining the pH around 14 while stirring. The obtained ferric hydroxide nanoparticles were calcined to obtain iron oxide nanoparticles. The obtained nanoparticles were spherical shaped particles in the particle size range of 20-50 nm. These nanoparticles are characterized using x-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Scanning Electron Microscopy (SEM) and inductively coupled plasma mass spectrometry (ICP-MS). Furthermore, these synthesized nanoparticles showed superior adsorption capacity of Cr3+ ions from an aqueous solution, demonstrating its ability to remove heavy metals, which is a crucial factor for water filtration applications

Combined Zr and Y phosphate coatings reinforced with chemically anchored B<inf>2</inf>O<inf>3</inf> for the oxidation inhibition of carbon fiber

The use of carbon fiber-based composites in high-temperature environments has been hindered due to the inferior oxidation resistance of standard carbon fiber. Protective coatings comprised of refractory ceramics have served in enhancing the thermal endurance of carbon fiber significantly. Although zirconium and yttrium-based materials have been highly studied on their refractory characteristics, phosphate-based thermal barrier systems are scarce. Herein, we report the oxidation retardation capability of a B2O3-chemically anchored, Zr3(PO4)4/YPO4 coating system on carbon fiber. In-situ, sol-gel-developed coatings with varying thicknesses and constructs were investigated for morphology, crystallography, composition, mechanical properties and thermal integrity. A uniquely consolidated B2O3@Zr3(PO4)4/YPO4 molecular arrangement was indicated in coatings by infra-red and X-ray spectroscopy. Ultimately, superior oxidation protection with an enhancement of ~180 °C over uncoated fiber was exhibited by the integrated nanocoatings, indicating its potential suitability for thermal shielding of carbon-based composites at temperatures in the range of 900–1000 °C. The exhibited improvement in thermal performance was attributed to the fortification provided by the coordinated B2O3 network on the fundamental Zr3(PO4)4/YPO4 system

Carbon quantum dots-decorated nano-zirconia: A highly efficient photocatalyst

A unique and efficient composite material was synthesized by incorporating carbon quantum dots on to the surface of zirconia (ZrO2) nanoparticles. ZrO2 nanoparticles with an average diameter of 40 nm were synthesized by a sol-gel process with zirconium oxychloride as the precursor. Carbon quantum dots (CQDs) were synthesized via a facile method by calcining a solution of ammonium citrate. Synthesized CQDs suspended in absolute ethanol emitted a green glow under UV irradiation. A convenient one-step process involving mixing in absolute ethanol under sonication was adopted for the formation of CQD-decorated ZrO2 nanoparticles (CQDZ). The dried final composite was characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Fourier transform infrared (FT-IR) spectroscopy. The photocatalytic performance of CQDZ was evaluated by quantifying the removal efficiency of methylene blue dye. CQDZ managed to remove methylene blue by 66.5%, 76.5%, 84.3% and 95.0% under UV-irradiation of 10, 20, 40 and 60 min respectively. Under the same experimental conditions, pure ZrO2 nanoparticles managed to remove only 34% of the dye under 60 min of UV irradiation. The produced composite showed promise as a formidable contender to be used in industrial dye removal from waste water

Facile and low-cost synthesis of pure hematite (α-Fe<inf>2</inf>O<inf>3</inf>) nanoparticles from naturally occurring laterites and their superior adsorption capability towards acid-dyes

Hematite nanoparticles have a broad range of outstanding applications such as in wastewater treatment, electrolytic studies, and photoelectrochemical and superparamagnetic applications. Therefore, the development of facile and novel methods to synthesize hematite nanoparticles using low-cost raw materials is an important and timely requirement. In this study, we have developed a facile economical route to synthesize hematite nanoparticles, directly from the naturally occurring material laterite. Laterite is a rock that is rich in Fe and Al with extensive distribution in large mineable quantities in many countries around the world, though not yet utilized for major industrial applications. In this method, ferric ions in the laterite were leached out using acid and the solution obtained was hydrolyzed with slow-release hydroxyl ions which were acquired by aqueous decomposition of urea. The resulted precursor was calcined to obtain hematite nanoparticles. Characterization data shows that the final product is comprised of spherical hematite nanoparticles with a narrow particle size vs. frequency distribution with an average particle diameter of 35 nm. The synthesized product has a purity of over 98%. Furthermore, the synthesized nanoparticles show an excellent adsorption percentage as high as 70%, even when the initial dye concentration in water is 5000 ppm and the amount of material is minimal, towards acid dyes which are excessively used in textile based industries. Such acid dyes are a threat to the environment when they are released into water bodies by industries in massive quantities. Therefore synthesized hematite nanoparticles are ideal to treat dye wastewater in industrial effluents because such nanoparticles are low cost and economical, and the synthesis procedure is rather facile and effective

Drug-Loaded Halloysite Nanotube-Reinforced Electrospun Alginate-Based Nanofibrous Scaffolds with Sustained Antimicrobial Protection

Halloysite nanotube (HNT)-reinforced alginate-based nanofibrous scaffolds were successfully fabricated by electrospinning to mimic the natural extracellular matrix (ECM) structure which is beneficial for tissue regeneration. An antiseptic drug, cephalexin (CEF)-loaded HNT, was incorporated into the alginate-based matrix to obtain sustained antimicrobial protection and robust mechanical properties, the key criteria for tissue engineering applications. Electron microscopic imaging and drug release studies revealed that CEF had penetrated into the lumen space of the HNT and also deposited on the outer walls, with a total loading capacity of 30 wt %. Moreover, the diameter of alginate-based nanofibers of the scaffolds ranged from 40 to 522 nm with well-aligned HNTs, resulting in superior mechanical properties. For instance, the addition of 5% (w/w) HNT improved the tensile strength (σ) and elastic modulus by 3-fold and 2-fold, respectively, compared to those of the alginate-based scaffolds without HNT. The fabricated scaffolds exhibited remarkable antimicrobial properties against both Gram-negative and Gram-positive bacteria, and the cytotoxicity studies confirmed the nontoxicity of the fabricated scaffolds. Drug release kinetics showed that CEF inside HNTs diffuses within 24 h and that the diffusion of the drug is delayed by 7 days once the CEF-loaded HNTs are incorporated into the alginate-based nanofibers. These fabricated alginate-based electrospun scaffolds with enhanced mechanical properties and sustained antimicrobial protection hold great potential to be used as artificial ECM scaffolds for tissue engineering applications

Industrial and environmental significance of photonic zirconia nanoflakes: Influence of boron doping on structure and band states

A unique zirconia nanomorphology possessing an enhanced photocatalytic efficiency was developed utilizing a convenient single-sol synthesis process which involved in-situ doping of zirconia by boron. The boron-doped zirconia exhibited a flake morphology as opposed to the spherical pure form and subsequent crystallographic investigations implied the phase conversion from binary to single-phase along with the shape due to the doping. Optical characterization indicated a modified band structure with newly generated isolated impurity states within the principle zirconia band edges. As per the X-ray spectroscopy data, boron was detected as chemically bound to oxygen while electron paramagnetic resonance indicated the presence of an adsorbed oxygen lattice. During UV and simulated solar irradiation trials, respective removal capabilities of 90% and 93% of the model compound were accomplished, hence the effectiveness of the photocatalyst was confirmed. The enhanced photoactivity observed in the UV region was attributed to combined effects of the boron-induced isolated impurity states within principle band edges of zirconia, the defect-rich planer morphology, favorable interfacial interactions and the greater availability of oxygen on the lattice. Developed nanoflakes are stable, inert, and efficient hence exhibiting compelling suitability in the remediation of harmful industrial organic compounds