Flower-like ceria (CeO2) architectures consisting of well aligned nanosheets were first synthesized by a glycol solvothermal method. The size of CeO2 architectures is about 5?μm in width and 10?μm in length, with the nanosheets thickness below 100?nm. Subsequently, the adsorbed Ag ions on the surface of CeO2 were in situ reduced to form Ag nanoparticles (NPs), leading to the fabrication of Ag/CeO2 hybrid architectures (HAs). The formed Ag NPs with sizes of 20–40?nm were uniformly loaded on the surface of the CeO2 sheets. The antibacterial properties of Ag/CeO2 HAs against Gram-negative E. coli and Gram-positive S. aureus were evaluated by minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and a filter paper inhibition zone method. The results demonstrated that Ag/CeO2 HAs displayed excellent antibacterial activity toward S. aureus and E. coli, which were attributed to the synergistic antibacterial effect between Ag NPs and CeO2 in HAs. Here, CeO2 nanoflowers as a new substrate could restrict Ag NPs aggregations and improve their antibacterial activities. Therefore, the resulted Ag/CeO2 HAs would be considered as a promising antibacterial agent.
The aim of this work was an investigation of structural and electrical properties of ZnO/Zn2-xFexTiO4 (x?=?0.7, 1, 1.4) powders. The compounds obtained by sol-gel method are characterized by several techniques: X-ray diffraction (XRD), N2 adsorption–desorption isotherms, scanning and transmission electron microscopy (SEM and TEM), X-ray photoelectron spectroscopy (XPS), electrical and dielectrical measurements. The XRD, SEM and XPS analysis confirmed the formation of ZnFeTiO4 inverse spinel structure. The electrical and dielectrical properties of ZnO/Zn2-xFexTiO4 (x?=?0.7, 1, 1.4) were measured by impedance spectroscopy, revealing a decrease in the electrical conductivity and the dielectric constant with Fe content.
Pure and Ag-doped zinc oxide sol–gel thin films were prepared by spin-coating process. Pure and Ag–ZnO films, containing 2–8% Ag, were annealed at 500?°C for 2?h. All thin films were prepared and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and UV–visible spectroscopy. X-ray diffraction studies show the polycrystalline nature with hexagonal wurtzite structure of ZnO and Ag:ZnO thin films. The crystallite size of the prepared samples reduced with increasing Ag doping concentrations. AFM and SEM results indicated that the average crystallite size decreased as Ag doping concentration increased. The transmittance spectra were then recorded at wavelengths ranging from 300 to 1000?nm. The films produced yielded high transmission at visible regions. The optical band gap energy of spin-coated films also decreased as Ag doping concentration increased. In particular, their optical band gap energies were 3.75, 3.55, 3.4, 3.3, and 3.23?eV at 0%, 2%, 4%, 6%, and 8%, respectively. Antibacterial activity of pure and Ag-doped zinc oxide against Escherichia coli and Staphylococcus aureus was evaluated by international recognized test (JIS Z 2801). The results showed that pure and Ag-doped ZnO thin film has an antibacterial inhibition zone against E. coli and S. aureus. Gram-positive bacteria seemed to be more resistant to pure and Ag-doped ZnO thin film than gram-negative bacteria. The test shows incrementally increasing in antibacterial activity of the thin films when dopant ratio increased under UV light.
BaTiO3 (BTO) and BaTi1?xMnxO3 (x?=?0.25, 0.50, 0.75?mol%) ceramic materials have been prepared by the sol–gel combustion method. X-ray diffraction (XRD) has been carried out to characterize the phase purity and crystal structure of the prepared compounds, and all XRD patterns suggest tetragonal structure with the phase group of P4mm. The variation in the estimated lattice parameters confirms the incorporation of Mn atoms at Ti site of BTO. Raman spectroscopy studies under various temperatures suggest a phase transition from tetragonal to cubic phase at ~433?K, identified by a distinct Raman mode at 308?cm?1. As Raman modes are getting softened by Mn doping, phase transition temperature of the Mn-doped compounds is significantly decreased from 473?K (x?=?0%) to 433?K (x?=?0.75%). Dielectric properties such as permittivity and dielectric loss as the function of frequency under various temperatures have two distinct dielectric anomalies (i) at 393?K associated to tetragonal to cubic phase transition and (ii) at 550?K due to oxygen vacancy defect in the samples. Observation of weak ferromagnetism at 2, 300, and 400?K in the M (H) and ZFC-FC curve, suppose its origin due to an intriguing exchange interaction between Mn and oxygen vacancies.
In this study, pure titanium dioxide (TiO2), Ta-doped TiO2, S-doped TiO2, and Ta-S-codoped rutile TiO2 photocatalysts were prepared by a sol-gel method. To evaluate the properties of the synthesized samples, X-ray diffraction analysis (XRD) and X-ray photoelectron spectroscopy (XPS) were applied. XRD detection results showed that the samples contained rutile phase basically. Scanning electron microscope observation showed that the morphology of Ta-S-TiO2 was nearly spherical. Transmission electron microscope investigation indicated that Ta-S-TiO2 had a flower-shaped structure consisting of many nanorods. The measurement of Brunauer-Emmett-Teller (BET)-specific surface areas (SBET) showed that tantalum and sulfur codoping can effectively increase the SBET of TiO2. XPS results indicated that Ta was in the form of Ta5+ in the TiO2 structure. Finally, the photocatalytic activities of synthesized photocatalyst samples were measured for the degradation of methylene blue in ultraviolet and visible light irradiation. The results demonstrated that the Ta-S-codoped rutile TiO2 photocatalyst had better photocatalytic performance than pure rutile TiO2, Ta-doped rutile TiO2 and S-doped rutile TiO2 photocatalyst.
Effects of pure TiO2, Ta-TiO2, S-TiO2, and Ta-S-TiO2 on degradation of MB under visible light irradiation (a) and ultraviolet (UV) irradiation (b) were studied. Ta-S-TiO2 exhibited a good photocatalytic performance under UV and visible light irradiation.
The effect of Nb as a support modifier on the NiMo6/Al2O3–Nb2O5(x) (x?=?0, 1, 4, and 8?wt% Nb) catalysts was studied. The supports were prepared by one-pot coprecipitation from soluble precursors. The XRF analysis of the catalysts showed that the contents of Mo and Ni increased slightly with the presence of Nb. Micropore area and pore volume augmented importantly with Nb content, resulting in pore diameters between 5.3 and 9.3?nm. XPS analysis showed that the presence of Nb decreases the active metal–support interaction, improving the Mo and Ni sulfidation degree. The Raman spectra of sulfided catalysts suggested an increase in the number of layers of MoS2 in the presence of Nb. Generally, the thiophene HDS activity at normal pressure of sulfided NiMo6/Al2O3–Nb2O5(8) was greater than that of the sulfided catalysts with x?=?0, 1, and 4?wt% Nb, which can be attributed to the Nb promotion that would have an effect on the type of active site (Brønsted or Lewis acidic sites), since the number of sites by CO chemisorption for sulfided NiMo6/Al2O3–Nb2O5(x) did not show correlation with the catalytic activity. The high-pressure HDS activity of dibenzothiophene was also greater in the presence of Nb, and the hydrogenation route was preferred for the Nb-promoted solid, while the unpromoted one showed a larger yield of direct desulfurization products.
TiO2/WO3 nanocomposite with nanodisk morphology was prepared and successfully used as a photocatalyst. The nanocomposite was obtained via sonochemical and hydrothermal methods, using pomegranate juice as a capping agent. The products were characterized by FE-SEM imaging, BET, EDAX spectroscopy, X-ray diffraction, DRS, and FT-IR spectroscopy. TiO2/WO3 nanocomposite showed high sensitivity to absorb visible light in compared to TiO2. In an optimized condition, the yield of the aerobic photocatalytic oxidation of benzyl alcohol derivatives reached to 65% for the TiO2/WO3 nanocomposite, while the conversion percent of the derivatives was less than 8% and 50% on the TiO2 and WO3 nanoparticles, respectively. Experimental results were supported by density functional theory (DFT) calculations. The DFT results in several solvents of different dielectric constants, confirmed the strong dependence of light absorption and photocatalytic activity to adsorption energy of the substrates on the surface of the nanoparticles (Ead). In addition, the theoretical results showed an inverse correlation between the adsorption energy of benzyl alcohol and its conversion percent, accordance to the experimental trend.
CaMn7O12 precursor sol was prepared by using Ca(NO3)2·4H2O and Mn(CH3COO)4·4H2O as the raw materials, acetylacetone (AcAcH) as the chelating agent, and methyl alcohol (MeOH) as the solvent. The CaMn7O12 crystalline film was obtained via dip-coating and annealing treatment on the LaAlO3 (001) single-crystal substrate. XRD θ-2θ scan indicated that the as-prepared CaMn7O12 film had strong preferred orientation along the c-axis. In addition, the results of the ω and ? scans demonstrated that the film exhibited outstanding out-of-plane and in-plane texture characteristics. The SEM characterization showed that the CaMn7O12 film was dense and free of cracks. The grain size was uniform with an average size of ~180?nm. Vibrating sample magnetometer (VSM) test results indicated the CaMn7O12 film was antiferromagnetic and had a saturation magnetization of 114.2?emu/cm3 at 50?K.
Kaolinite/TiO2 composites were prepared by using sol-gel method and raw kaolin, pretreated kaolinite and tetrabutyl titanate as the main raw materials. X-ray diffractometer, field-emission scanning electron microscope and infrared spectrometer analysis were carried out to characterize the phase composition and microstructure of the samples. The photocatalytic performance of the kaolinite/TiO2 composites were evaluated by degrading the methylene blue (MB) and phenol aqueous solution, respectively. The results show that intercalation and exfoliation reduced the size and thickness of kaolinite particles. Acid treatment improved the distribution and the loading quantity of TiO2 grains. When the kaolinite/TiO2 composites were calcined at 500?°C, the tetragonal structure of anatase particles of 30–100?nm in size were obtained, but the exfoliated kaolinite crystals were damaged. The degradation rate of MB increased gradually with the extension of photocatalytic reaction time and the enhancement of photocatalyst dosage. The adsorption performance of acid-treated kaolinite/TiO2 composite (AKT) was nearly the same as that of raw kaolin/TiO2 composite (RKT), but that of the exfoliated kaolinite/TiO2 composite (EKT) was the most excellent. The photocatalytic performance of AKT and EKT were better than that of RKT, and AKT exhibited the optimum property. Under a certain photocatalyst dosage and photocatalysis time, the absorption rate and the degradation rate decreased gradually with the enhancement of initial concentration of MB. Similar result was also acquired for the degradation of phenol. Both the acid treating and the exfoliating to kaolinite enhanced the photocatalytic performance of the kaolinite/TiO2 composite photocatalysts, but acid treatment may be more helpful to the preparation of high performance kaolinite/TiO2 composite photocatalyst.
Bismuth ferrite (BiFeO3) nanopowder have been successfully synthesized for the first time via a microwave-assisted sol-gel combustion method by using citric acid as fuel. The resulting nanopowder was characterized using FT-IR, TG-DTA, XRD, EDX, VSM, SEM, and UV-Vis DRS. A ferromagnetic hysteresis loop with a saturation magnetization (MS) of 0.66?emu?g?1 has been observed at room temperature in the sample. The optical properties of the nanosized BiFeO3 showed its small band gap (=2.08?eV) indicates a possibility of utilizing much visible light for photocatalysis.
Bone infections in human beings are an essentially destructive problem with crucial clinical and economic effects; thus, incorporation of antibiotics such as amoxicillin (AMX) into the scaffold was developed as an effective treatment for bone infections. In this respect, we develop new nanostructured bredigite (Bre; Ca7MgSi4O16)–amoxicillin (AMX; α-amino-hydroxybenzyl-penicillin) scaffolds containing different concentrations of amoxicillin (0, 3, 5, and 10%) by using space holder method to assure bactericidal properties. The result depicted that the Bre–AMX scaffolds possess porosity of 80–82% with high compressive strength of 1.2–1.4?MPa and controlled antibiotic release for prevention of infection. Bre–(3–10%)AMX scaffolds were able to destroy Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) bacteria, as well as effectively inhibit the growth of bacterial cells; in addition, the antibacterial activity of the AMX-loaded scaffolds augmented with the increase of the AMX concentration. Sustained drug release was detected from Bre–AMX scaffolds accompanied by initial burst release of 20% for 8?h, followed by a sustained release, which is favorable for bone infection treatment. These new Bre–(3–5%)AMX scaffolds possess excellent mechanical properties and antibacterial activity with no cytotoxicity suggested as an appropriate alternative for bone infection treatment.
Dual-network aerogels (HPSA) with improved mechanical property and thermal insulation were prepared by vacuum impregnation of HNTs/PVA aerogels (the first network aerogel, HPA) in tetraethoxysilane (TEOS). Scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, and N2 adsorption–desorption analysis were used to study micromorphology and microstructure of HPSA, while compression tests and thermal conductivity tests were used to investigate related properties. The results showed that the dual-network frame was successfully constructed, this enabled HPSA to display enhanced compressive properties with increased HNTs content. The addition of silica sol improved the mesoporous characteristics including specific surface area and pore volume and also reduced the thermal conductivities. The first network made it possible for HPSA to possess good mechanical property, while SiO2 aerogel allowed HPSA greater thermal insulation. The obtained aerogel samples exhibited a high compressive strength (i.e., 1.36?MPa) and a low thermal conductivity (i.e., 0.022?W/(m?K)). HNTs/SiO2 dual-network aerogels with improved strength and thermal insulation could show great potential in a wide variety of applications.
Superhydrophilic surfaces without the need of other stimuli are usually realized by constructing a rough morphology. However, constructing rough surfaces usually require specialized equipment or complicated processing. Besides, rough surfaces can cause undesirable scattering, which strongly limits the use in optical devices. In this article, we prepared superhydrophilic TiO2 films with ultra-smooth surfaces using simple sol-gel dip-coating method. The hydrophilicity of the TiO2 films varied with different post-heat treatments. The films heat-treated at 400?°C exhibited a durable superhydrophilicity and anti-fogging property. This superhydrophilicity was attributed to the decrease of surface hydrophobic alkoxy groups and the formation of point defects, i.e., Ti3+ and oxygen vacancies, which are favourable for dissociative water adsorption. The amount of surface organic groups was influenced by autophobicity effects, further hydrolysis and decomposition of residual alkoxy groups. Additionally, the wettability behaviours of the films were also explained from the perspective of the surface energy. These results can benefit the design and manufacture of anti-fogging and self-cleaning superhydrophilic TiO2 films.
A robust synthesis approach to Ni2+-substituted Mg0.25-xNixCu0.25Zn0.5Fe2O4 (0?≤?x?≤?0.25?mol.) ferrimagnetic oxides using citrate assisted sol–gel process is reported. The route utilizes simple metal nitrate precursors in aqueous solution, thus eliminating the need for organometallic precursors. Citric acid acts as a fuel for the combustion reaction and forms stable complexes with metal ions preventing the precipitation of hydroxilated compounds to yield the composite ferrite structure by auto-combustion process. The XRD signatures, especially (3 1 1) plane, confirmed the formation of spinel structure. The linear growth of lattice constant from 8.385 to 8.409?Å was observed by Ni2+ substitution from 0 to 0.25. The dense microstructure is observed with the average grain size of 0.42–2.18?µm. The transport properties revealed the semiconducting behavior of as-prepared ferrite material, with an increase in the DC-electrical resistivity by the incorporation of nickel. The magnetic properties viz. initial permeability (µi) and magnetic moment (nB) are explained, based on the deviation in saturation magnetization (Ms), anisotropy constant (K1), density values, and exchange interactions. Furthermore, the effect of adding Ni2+ on the Curie temperature, frequency-dependent dielectric properties of the ferrite material are also discussed.
Metal nanoparticles synthesis using the biological material offers a simple, biocompatible, cost-effective and nontoxic in character. A number of plant materials have been utilized as resource material for the most favorable biosynthesis of active nanomaterials. This study involves the synthesis of active silver nanoparticles (Ag NPs) using the Carissa carandas (Karonda) berry water extract at room temperature. The nanoparticles characterized at several parameters including shape, size, mass and charge with help of electron microscopy (TEM), Fourier transforms IR (FTIR), UV-VIS spectroscopy and Raman spectroscopy which proved the efficient silver nanoparticles to be useful in several practical applications. The UV-visible spectra showed the surface plasmon resonance peak at ~440?nm, which is weel recognized attribute peak in case of silver nanoparticles. Avarage size of the biogenic silver nanoparticles ranged from ~10–60?nm, predominantly spherical in shape. The suggested possible mechanisms for the synthesis of silver nanoparticles relies on reduction of AgNO3 due to occurrence of carinol (and related resonant compounds) in the berry extract with inductive effect of the proton of methoxy and allyl groups, present at ortho and para positions of the compounds. The biologically synthesized Ag NPs also showed efficient antibacterial activity against different pathogenic and non-pathogenic bacteria at par with the generic antibiotics.
A novel ZrCO composite aerogel is synthesized using zirconium oxychloride and resorcinol–formaldehyde (RF) as precursors through the sol–gel route and carbothermal reduction process. The effects of different Zr/R molar ratios and calcination temperatures on the physical chemistry properties of ZrCO aerogels are investigated. The ZrCO composite aerogel consists of the C/ZrO2/ZrC ternary aerogel. The results show that with the increase of R/Zr molar ratios, the specific surface area and bulk density increase with calcination temperature up to 1300?°C, but decrease at even temperature (1500?°C). The specific surface area is as high as 637.4?m2/g for ZrCO composite aerogel (R:Zr?=?2:1), which was higher than ever reported. As the heat-treatment temperature increases to 1500?°C, the ZrC crystalline phase occurs and the t-ZrO2 phase still appears within the composite. The thermal conductivity of the carbon fiber mat-reinforced composite aerogel is as low as 0.057?W/m/K at room temperature (25?°C).
Mg–Ti substituted strontium hexa-ferrites nanopowders (SrFe12?x(MgTi)x/2O19, x?=?0–3) were prepared by the sol–gel method. The morphology, structure and composition of the nanostructures were examined by field emission scanning electron microscopy (FESEM) and X-ray diffraction. The effect of Mg–Ti doping on the magnetic properties of the powders was investigated by vibrating sample magnetometry (VSM) and ferromagnetic resonance (FMR) at ambient temperature. Experimental results showed that the materials exhibit hexagonal structures with tunable magnetic properties. The saturation magnetization and the coercive field (Hc) decreased through the Mg and Ti substitution. FMR proved that by incorporation of Mg and Ti in strontium ferrite lattice, crystalline anisotropy, and microwave absorption can be tuned. SrFe12?x(MgTi)x/2O19 ferrites are good candidate for applications at X-band microwave frequencies. A low field absorption signal was observed with the same phase as the FMR absorption in all doped ferrites.
Light-activated antimicrobial coatings were obtained by the covalently immobilizing photo-sensitizers in a hybrid organic/inorganic matrix. These coatings were deposited via sol-gel chemistry using epoxy and methyl functional silanes. The light-activated chromophores used in this study were Methylene Blue, Toluidine Blue O, and Rose Bengal. The immobilized photo-sensitizers did not leach from the coatings. The mechanically durable hybrid coatings comprising 2.5% by weight of Rose Bengal had a good adhesion to the glass surface. These coatings were tested for the photo-deactivation of Escherichia coli and Staphylococcus aureus using illumination by a commercial fluorescent lamp. Log reduction of E. coli and S. aureus were >4 when illuminated by the fluorescent lamp in 1 and 3?h, respectively. Due to its high mechanical durability and chemical resistance, such light-activated hybrid coatings are promising candidates for indoor applications in healthcare facilities.
BaM hexaferrites substituted with both Ca2+ and Mg2+ ions, namely, Ba1-2×CaxMgxFe12O19 (0.0?≤?x?≤?0.1), synthesized during a sol–gel auto-combustion route. The hexaferrite phase and morphology of all samples were investigated using X-ray powder diffraction, a field emission scanning electron microscope, a high-resolution transmission microscope, and Fourier transform infrared spectroscopy. In addition, an M-type hexagonal structure was confirmed using XRD for all samples. FE-SEM and TEM revealed the shape of the hexagonal plate. Measurements of the magnetization versus the field M(H) of Ba1-2×CaxMgxFe12O19 (0.0?≤?x?≤?0.1) nanohexaferrites were conducted at 300 and 10?K. A hard-ferrimagnetic behavior at both 300 and 10?K was noted for the different products produced. The squareness ratio indicates the uniaxial anisotropy for various products. The deduced values of saturation magnetization (Ms) in all substituted samples are higher than in the pristine sample (x?=?0). The Ba0.96Ca0.02Mg0.02Fe12O19 nanosized hexaferrite showed the highest values of Ms, remanence Mr, magneton number (nB), and magnetocrystalline anisotropy constant (Keff). In contrast, the values of the coercive field (Hc) and intrinsic coercivity (Hci) diminish with the increase in the amount of the substituted Ca and Mg elements.
Brick-shaped zinc tungstate nanoparticles have been synthesized by ecofriendly solvent-free process using molten salts. Zinc tungstate nanobricks (ZnWO4 Nbs) were characterized by powder x-ray diffraction (PXRD), FTIR, Raman, energy dispersive and electron microscopic studies. ZnWO4 Nbs are used as the multifunctional electrode materials to oxygen generation reactions (OGR), oxygen reduction reactions (ORR) and supercapacitors (SCs) as well as photo-catalysts in the waste-water treatment by the degradation of organic dyes. Low overpotential (?10?=?0.475?V), low tafel slope (140?mV/dec), high current density (~70?mA/cm2) and good stability of the electrodes are the key results of the present studies for water electrolysis (OGR/ORR). ZnWO4 Nbs have also shown great interest in supercapacitors with efficient charge–discharge activities in 1?M KOH. The specific capacitance and energy density of ZnWO4 Nbs were found to be 250?F/g and 80?Wh/kg, respectively, at 5?mV/s, these values are relatively higher than that of previously reported specific capacitance and energy density value of metal tungstate nanoparticles. ZnWO4 Nbs as the photo-catalysts work very significantly for photocatalytic degradation of aqueous MB dye solution (~85 % in 3?h) in neutral medium.
ZnWO4 Nanobricks show significant multifunctional electro-chemical activities in alkaline medium and photocatalytic degradation of organic dye in neutral medium.
