Correlation between biomedical and structural properties of Zn/Sr modified calcium phosphates.

This study investigates the correlation between the biomedical and structural properties of Zn/Sr-modified Calcium Phosphates (ZnSr-CaPs) synthesized via the sol-gel combustion method. X-ray diffraction (XRD) analysis revealed the presence of Ca10(PO4)6(OH)2 (HAp), CaCO3, and Ca(OH)2 phases in the undoped sample, while the additional phase, Ca3(PO4)2 (ß-TCP) was formed in modified samples. X-ray absorption near-edge structure (XANES) analysis demonstrated the incorporation of Sr into the lattice, with a preference for occupying the Ca1 sites in the HAp matrix. The introduction of Zn, furthermore, led to the formation of ZnO and CaZnO2 species. The ZnSr-CaPs exhibited significant antibacterial activity attributed to the generation of reactive oxygen species by ZnO, the oxidation reaction of CaZnO2, and the presence of Sr ions. Cytotoxicity tests revealed a correlation between the variation in ZnO content and cellular viability, with lower ZnO concentrations corresponding to higher cell viability. Additionally, the cooperative effects of Zn and Sr ions were found to enhance the bioactivity of CaPs, despite ZnO hindering the apatite formation process. These findings contribute to the deep understanding of the diverse role in modulating the antibacterial, cytotoxic, and bioactive properties of ZnSr-CaPs, offering potential applications in the field of biomaterials.

Controlling the Photocatalytic Activity and Benzylamine Photooxidation Selectivity of Bi2WO6 via Ion Substitution: Effects of Electronegativity.

Doping or ion substitution is often used as an effective strategy to improve photocatalytic activities of several semiconductors. Most frequently, the dopants provide extra states to increase light absorption, alter the electronic structure, or lower the carrier recombination. This work focuses on ion substitution in Bi2WO6, where the dopants modify band-edge potentials of the catalysts. Specifically, we investigate how the electronegativity (EN) of the dopant could be used to tune the band-edge potentials and how such changes influence the photocatalytic mechanism. Compared to Te that has a lower EN, I lowers the band-edge potentials. While substitutions with both ions enhance Rh B photodegradation and benzylamine photooxidation, the modified band potentials of I-doped Bi2WO6 influence the benzylamine photooxidation pathway, resulting in higher selectivity. Additionally, substitution of I7+ in the Bi2WO6 lattice improves the morphologies, decreases the band-gap energy, and reduces the carrier recombination. As a result, I-doped Bi2WO6 shows almost 3 times higher %conversion while maintaining 100% selectivity in the oxidative coupling of benzylamine. The findings here signify the importance of the choices of dopants on the photocatalytic reactions and would benefit the design of other related materials for such applications.

Heterojunction α-Fe2 O3 /ZnO Films with Enhanced Photocatalytic Properties Grown by Aerosol-Assisted Chemical Vapour Deposition.

Type I heterojunction films of α-Fe2 O3 /ZnO are reported here as a non-titania based photocatalyst, which shows remarkable enhancement in the photocatalytic properties towards stearic acid degradation under UVA-light exposure (λ=365 nm), with a quantum efficiency of ξ=4.42±1.54×10-4 molecules degraded/photon, which was about 16 times greater than that of α-Fe2 O3 , and 2.5 times greater than that of ZnO. Considering that the degradation of stearic acid requires 104 electron transfers for each molecule, this represents an overall quantum efficiency of 4.60 % for the α-Fe2 O3 /ZnO heterojunction. Time-resolved transient absorption spectroscopy (TAS) revealed the charge-carrier behaviour responsible for this increase in activity. Photogenerated electrons, formed in the ZnO layer, were transferred into the α-Fe2 O3 layer on the pre-µs timescale, which reduced electron-hole recombination. This increased the lifetime of photogenerated holes formed in ZnO, which oxidise stearic acid. The heterojunction α-Fe2 O3 /ZnO films grown herein show potential environmental applications as coatings for self-cleaning windows and surfaces.

Unsaturated Mn(II)-Centered [Mn(BDC)] n Metal-Organic Framework with Strong Water Binding Ability and Its Potential for Dehydration of an Ethanol/Water Mixture.

An unsaturated Mn(II)-centered metal-organic framework was synthesized. The presence of an unsaturated Mn(II) center, together with a guest-responsive structural changing feature, plays a crucial role for strong binding with water, leading to its potential application for water/ethanol separation. In addition, the present framework is thermally stable up to 400 °C, which is beneficial for the regeneration process after adsorption.

Double network structure via ionic bond and covalent bond of carboxymethyl chitosan and poly(ethylene glycol): Factors affecting hydrogel formation.

The factors were studied that affect the formation of DN hydrogel, which was prepared using a water-based, environmental-friendly system. The DN hydrogel was designed and prepared based on a cross-linked, polysaccharide-based, polymer carboxymethyl chitosan (CMCS) via an ionic crosslinking reaction for the first network structure. UV irradiation created a radical crosslinking reaction of poly(ethylene glycol) from a double bond at the chain end for the second network structure. It was found that the optimum hydrogel was produced using 9.5 %v/v of 1000PEGGMA, CMCS 5%w/v, and CaCl2 3%w/v. The results showed the highest percentage of the gel fraction was 87.84 % and the hydrogel was stable based on its rheological properties. Factors affecting the hydrogel formation were the concentration and molecular weight of PEGGMA and the concentrations of CMCS and calcium chloride (CaCl2). The DN hydrogel had bioactivity due to its octacalcium phosphate (OCP) hydroxyapatite crystal form. In addition, the composite DN scaffold with a conductive polymer of chitosan-grafted-polyaniline (CS-g-PANI) had conduction of 2.33 × 10-5 S/cm when the concentration of CS-g-PANI was 3 mg/ml, confirming the semi-conductive nature of the material. All the results indicated that DN hydrogel could be a candidate to apply in tissue-engineering applications.

Structural studies and electrical properties of Cs/Al/Te/O phases with the pyrochlore structure.

A series of polycrystalline and single crystal cesium aluminum tellurates with the pyrochlore structure have been prepared and characterized. The variations in cell edge for the Cs/Al/Te/O phases range from 10.06 Å for the Al rich limit to 10.14 Å for the Te rich limit. Rietveld structural analyses based on both X-ray and neutron diffraction data were performed on 5 different compositions. Single crystals of 3 compositions were prepared and studied by X-ray diffraction. The anharmonic component of the thermal motion for Cs was small but became significant on replacing Cs with Rb. A maximum in the electrical conductivity of about 0.1 S/cm is found in the middle of this range close to the ideal composition of CsAl(1/3)Te(5/3)O(6). The conductivity is attributed to filled Te 5s states associated with Te(4+) lying just below the conduction band based on empty Te 5s states associated with Te(6+). The relatively large Te(4+) ion is compressed by the lattice, and as this compression increases the filled 5s states approach the conduction band and thereby increases conductivity.

CsTe2O(6-x): novel mixed-valence tellurium oxides with framework-deficient pyrochlore-related structure.

Structures of CsTe2O(6-x) phases were investigated by single-crystal X-ray diffraction and neutron powder diffraction. Stoichiometric CsTe2O6 is a mixed-valence Cs2Te4⁺Te36⁺O12 compound with a rhombohedral pyrochlore-type structure where there is complete order of Te4⁺ and Te6⁺. On heating, this compound develops significant electrical conductivity. As CsTe2O6 becomes oxygen deficient above 600 °C, the rhombohedral pyrochlore-type structure is replaced by a cubic pyrochlore-type structure with disordered Te4⁺/Te6⁺ and oxygen vacancies. However, for CsTe2O(6-x) phases prepared at 500 °C, the observed pyrochlore-type structure has symmetry. The Te4⁺ and O vacancies are all on chains running along the b axis, and the maximum value of x observed is about 0.3. At still higher values of x a new compound was discovered with a structure related to that reported for Rb4Te34⁺Te56⁺O23.

Facile molten salt synthesis of Cs-MnO2 hollow microflowers for supercapacitor applications.

A facile molten salt technique is an interesting preparation method as it enables mass production of materials. With the use of CsNO3 salt, Cs-intercalated MnO2 hollow microflowers are obtained in this work. δ-MnO2 with a layered structure, instead of other allotropes with smaller structural cavities, is formed and stabilized by large Cs+ ions. Formation of the hollow microflowers is explained based on the Ostwald ripening process. The salt to starting agent ratio has little effect on the crystal structure and morphologies of the products but does influence the crystallinity, the interlayer distance, and the intercalating Cs+ content. The capacity of Cs+ in the structure and the interlayer distance are maximized when the weight ratio of CsNO3 : MnSO4 is 7 : 1. Cs-MnO2 obtained from this optimum ratio has most suitable crystallinity and interlayer distance, and consequently shows a highest specific capacitance of 155 F g-1 with excellent cycling performance. The obtained specific capacitance is comparable to that of other alkaline-intercalated MnO2, suggesting that Cs-MnO2 could be another interesting candidate for supercapacitor electrodes.

Low-Cost One-Step Fabrication of Highly Conductive ZnO:Cl Transparent Thin Films with Tunable Photocatalytic Properties via Aerosol-Assisted Chemical Vapor Deposition.

Low-cost, high-efficiency, and high quality Cl-doped ZnO (ZnO:Cl) thin films that can simultaneously function as transparent conducting oxides (TCOs) and photocatalysts are described. The films have been fabricated by a facile and inexpensive solution-source aerosol-assisted chemical vapor deposition technique using NH4Cl as an effective, cheap, and abundant source of Cl. Successful ClO substitutional doping in the ZnO films was evident from powder X-ray diffraction, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry results, while scanning electron microscopy reveals the impact of Cl doping on the ZnO thin film morphology. All ZnO:Cl films deposited were transparent and uncolored; optical transmittance in the visible region (400-700 nm) exceeded 80% for depositions using 5-20 mol % Cl. Optimal electrical properties were achieved when using 5 mol % Cl with a minimum measured resistivity of (2.72 ± 0.04) × 10-3 Ω·cm, in which the charge carrier concentration and mobility were measured at (8.58 ± 0.16) × 1019 cm-3 and 26.7 ± 0.1 cm2 V-1 s-1 respectively, corresponding to a sheet resistance (R sh) of 41.9 Ω□-1 at a thickness of 650 nm. In addition to transparent conducting properties, photocatalytic behavior of stearic acid degradation in the ZnO:Cl films was also observed with an optimal Cl concentration of 7 mol % Cl, with the highest formal quantum efficiency (ξ) measured at (1.63 ± 0.03) × 10-4 molecule/photon, while retaining a visible transparency of 80% and resistivity ρ = (9.23 ± 0.13) × 10-3 Ω·cm. The dual functionality of ZnO:Cl as both a transparent conductor and an efficient photocatalyst is a unique combination of properties making this a particularly unusual material.

Economical and green biodiesel production process using river snail shells-derived heterogeneous catalyst and co-solvent method.

River snail shells-derived CaO was used as a heterogeneous catalyst to synthesize biodiesel via transesterification of palm oil with methanol. The shell materials were calcined in air at 600-1000°C for 3h. Physicochemical properties of the resulting catalysts were characterized by TGA-DTG, XRD, SEM, BET, XRF, FT-IR and TPD. CaO catalyzed transesterification mechanism of palm oil into biodiesel was verified. The effects of adding a co-solvent on kinetic of the reaction and %FAME yield were investigated. %FAME yield of 98.5%±1.5 was achieved under the optimal conditions of catalyst/oil ratio of 5wt.%; methanol/oil molar ratio of 12:1; reaction temperature of 65°C; 10%v/v of THF in methanol and reaction time of 90min. The results ascertained that river snail shells is a novel raw material for preparation of CaO catalyst and the co-solvent method successfully decreases the reaction time and biodiesel production cost.