ZnO nanorods comprised of biosensors with Au nanoparticles are described in this study for detecting Hepatitis C virus (HCV). The biosensor device was constructed on a glass substrate with silver and ...gold electrodes. The ZnO nanorods were grown by microwave hydrothermal synthesis, and the Au nanoparticles were deposited by the sputtering method. The Au nanoparticles were deposited because of the right efficient of anti-HCV antibodies with cystamine and glutaraldehyde. The ZnO nanorods were evaluated using SEM images. The electrochemical biosensor shows a sensitive response to HCV with a detection limit of 0.25 μg/μL. The proposed sensor characteristics of high specificity, good reproducibility and remarkable stability will provide a sensitive, selective, and convenient approach for the detection of HCV.
Currently, numerous properties of semiconducting oxides are correlated to their morphological characteristics resulting from their exposed surfaces. In the present work, the relationship between the ...following morphologies rod, bean, hexagon, and rod/cube of CeO2 with the exposure of (111), (110), (100), and (311) surfaces and the main charge carriers generated by the photochemical processes was investigated. This was done in regard to the degradation of ciprofloxacin and rhodamine-B. The initial stages of the degradation of the two types of molecules were evaluated, allowing the determination of where the charge carriers generated in the semiconductor preferentially acted on the molecules. Therefore, the active species in each photocatalyst were identified by scavenger tests and correlated to the computational simulations using the density functional theory. Accordingly, the relationships between the morphology, surface exposure in the particles, surface defects, photochemically generated species, and preferential attack on the micropollutant molecule were shown. Specific surface area analyses demonstrate an effective relationship between photocatalytic activity and the exposed surface of the particle. This will allow rationalization of the relation between the catalytic and electronic properties of semiconductor surfaces.
Present theoretical and experimental work provides an in-depth understanding of the morphological, structural, electronic, and optical properties of hexagonal and monoclinic polymorphs of bismuth ...phosphate (BiPO
). Herein, we demonstrate how microwave irradiation induces the transformation of a hexagonal phase to a monoclinic phase in a short period of time and, thus, the photocatalytic performance of BiPO
. To complement and rationalize the experimental results, first-principles calculations have been performed within the framework of density functional theory. This was aimed at obtaining the geometric, energetic, and structural parameters as well as vibrational frequencies; further, the electronic properties (band structure diagram and density of states) of the bulk and corresponding surfaces of both the hexagonal and monoclinic phases of BiPO
were also acquired. A detailed characterization of the low vibrational modes of both the hexagonal and monoclinic polymorphs is key to explaining the irreversible phase transformation from hexagonal to monoclinic. On the basis of the calculated values of the surface energies, a map of the available morphologies of both phases was obtained by using Wulff construction and compared to the observed scanning electron microscopy images. The BiPO
crystals obtained after 16-32 min of microwave irradiation provided excellent photodegradation of Rhodamine B under visible-light irradiation. This enhancement was found to be related to the surface energy and the types of clusters formed on the exposed surfaces of the morphology. These findings provide details of the hexagonal-to-monoclinic phase transition in BiPO
during microwave irradiation; further, the results will assist in the design of electronic devices with higher efficiency and reliability.
One-dimensional nanostructures of KNbO3 have attracted a great interest in the scientific community, mainly because of their promising application as nanoelectromechanical systems (NEMS). However, ...the synthesis of KNbO3 structures becomes complex due to the natural tendency to form non-stoichiometric potassium niobates. In this context, we report on the crystallization of one-dimensional KNbO3 nanostructures through the reaction between Nb2O5 and KOH under microwave-assisted hydrothermal synthesis (M-H). The use of this synthesis method made possible a very fast synthesis of singlecrystalline powders. Based on SEM, TEM and XRD characterizations, the influence of the synthesis time and the reactants concentration in the structure and morphology of the resultant KNbO3 was established. The conditions that favor the crystallization of nanofingers were determined to be small amounts of Nb2O5 and short reaction times.
TiO
2
/SrTiO
3
heterojunction powders were obtained and characterized, and their photocatalytic potential was evaluated. The formation of the solid–solid interface was evidenced by secondary-phase ...formation in the interface region, which was observed using transmission electron microscopy. The photocatalytic efficiency of the TiO
2
/SrTiO
3
heterojunction was higher than that of pure TiO
2
and SrTiO
3
samples. The photocatalytic behavior was investigated via scavenger experiments, which indicated that the mechanism of charge transfer for the heterojunction was the direct transfer of the electrons at the interface. A surface compositional analysis of the materials revealed that effective electronic-transfer properties of the materials are more important than the content of pre-adsorbed species on the surface for redox reactions. Photoluminescence spectroscopy analyses showed a reduction in the photoluminescent intensity for the heterojunction and emission in distinct regions depending on the defects formed in the heterojunction. These differences in behavior may be related to the different photocatalytic responses observed for pure compounds and heterojunctions; a broad analysis indicates that the mono (
V
O
·
) and double (
V
O
·
·
) ionized vacancies affect the performance of the photocatalyst in the degradation of micropollutants.
•Auto-combustion route was optimized to obtain pure BiFeO3 powder without calcination.•Magnetization of powders and composites originate from Fe3O4 nanoparticles.•Auto-combustion synthesis of BiFeO3 ...with glycine fuel forms Fe3O4 as a by-product.•Dopants influence the properties in a more complex way than only by charge and size.•Y3+ and Zr4+ as dopants led to best improvement in electrical properties.
Bismuth ferrite (BiFeO3) powders were synthesized by auto-combustion method using glycine as a fuel. Doping ions of different valence were used to study the influence on electrical conductivity and ferroelectric properties. Powders were mixed and hot-pressed with α-PVDF to form flexible composite samples. Composites endured significantly higher electrical fields with lower leakage and retained the weak ferromagnetism present in powders. Dielectric properties were improved by doping with Zr4+, Y3+ and Ca2+ as well as the electrical resistivity. Flexible composites exhibited improved electrical resistivity and modified conduction mechanism. Relatively high magnetization of powders completely originates from magnetite particles formed during the combustion, while sintered samples exhibited typical antiferromagnetic behaviour.
In this research, ZnO nanorods - Au nanoparticles nanohybrids have been fabricated and employed to sensitive electrochemical strategy for the specific detection of the ovarian cancer antigen ...CA-125/MUC126. The microdevice was developed in our lab based on gold and silver electrodes sputtered on glass substrate. The ZnO nanorods arrays were grown on working electrode using assisted microwave hydrothermal synthesis than gold nanoparticles (Au NPs) were deposited by sputtering. The Au NPs onto ZnO nanorods surface provides a favorable platform for efficient loading of anti-CA-125 antibody via binding with cystamine and glutaraldehyde. The effective loading of the biological material (CA-125 antibody and antigen) on the matrix was observed by SEM images. The electrochemical immunosensor shows a sensitive response to ovarian cancer antigen recombinant human CA-125/MUC126 with detection of 2.5ng/μL, 100 times lower than immunoblot system. Due to high specificity, reproducibility and noteworthy stability, the developed sensor will provide a sensitive, selective and convenient approach to be used to detect CA-125/MUC126.
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•Development of simple methodology to prepare an electrochemical immunosensor based on ZnO nanorods (NRs)-Au NPs nanohybrids;•Study of effective loading of the biological material on the ZnO nanorods (NRs)-Au NPs nanohybrids matrix by SEM•Electrochemical immunosensor with detection limit 100 times lower than immunoblotting test
Titanate nanotubes were successfully synthesized using the microwave-assisted hydrothermal method from commercial TiO2-anatase powder. Several samples were obtained at varying temperatures and time. ...Powder samples containing titanate nanotube (Na2Ti6O13) single phase were obtained at 130°C for 4h and 150°C for 2h, demonstrating the kinetics dependence of reaction temperature. Through XRD analysis and electron diffraction pattern, the nanotube structures were found to be composed of a short range ordering, thus giving rise to a broad XRD peak profile. The higher time and temperature (150°C for 4h) led to the formation of more organized structures. The nanotubes UV–vis spectra showed a band gap of 3.90eV and a shoulder on the curve which led to another band gap value 3.25eV. The photoluminescence spectrum emission peak presented a significant decrease, indicating the reduction of surface or structural defects of titanate nanotubes due to longer hydrothermal treatment duration. All structural, electronics and morphologics transformation led to an improvement on photocatalytic activities for nanotubes, especially the sample obtained at 150°C for 1h that rate of decolorization is 0.01879min−1, 2.25 times faster than TiO2-anatase (starting phase).
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