Preparation and photocatalytic properties of hybrid core–shell reusable CoFe2O4–ZnO nanospheres

Magnetically separable and reusable core–shell CoFe₂O₄–ZnO photocatalyst nanospheres were prepared by the hydrothermal synthesis technique using glucose derived carbon nanospheres as the template. The morphology and the phase of core–shell hybrid structure of CoFe₂O₄–ZnO were assessed via TEM, SEM and XRD. The magnetic composite showed high UV photocatalytic activity for the degradation of methylene blue in water. The photocatalytic activity was found to be ZnO shell thickness dependent. Thicker ZnO shells lead to higher rate of photocatalytic activity. Hybrid nanospheres recovered using an external magnetic field demonstrated good repeatability of photocatalytic activity. These results promise the reusability of the hybrid nanospheres for photocatalytic activity.     

Observation of bulk like magnetic ordering below the blocking temperature in nanosized zinc ferrite

We investigated the magnetic behavior of nanosized zinc ferrite with the help of vibrating sample magnetometry and in-field Mössbauer spectroscopy. The nanoparticles of zinc ferrite with crystallite size ranging from 10 to 62 nm were synthesized by a nitrate method. The structure and phase were determined with the help of X-ray diffraction. Attributes of cation inversion were found with the calculated values of lattice parameter. The saturation magnetization decreases with the increase in crystallite size at room temperature, while these values are almost the same at 10 K for all the samples except the one with crystallite size of 10 nm. The thermal magnetization measurement shows a decrease in blocking temperature with increase in particle size for these samples. The synthesized samples exhibit the presence of antiferromagnetic ordering below the blocking temperature as investigated by in-field Mössbauer spectroscopy.     

One pot glucose detection by [Fe(III)(biuret-amide)] immobilized on mesoporous silica nanoparticles: an efficient HRP mimic

An [Fe(III)(biuret-amide)] complex has been immobilized onto mesoporous silica nanoparticles via Cu(I) catalyzed azide-alkyne click chemistry. This hybrid material functions as an efficient peroxidase mimic and was successfully used for the quantitative determination of hydrogen peroxide and glucose via a one-pot colorimetric assay.     

An organocatalytic direct Mannich-cyclization cascade as [3+2] annulation: asymmetric synthesis of 2,3-substituted pyrrolidines

A new method for asymmetric synthesis of 2,3-substituted pyrrolidines from N-PMP aldimines and succinaldehyde via formal [3+2] cycloaddition is reported. This reaction involves proline catalyzed direct Mannich reaction and acid catalyzed reductive cyclization with high yields (up to 78%) and excellent enantioselectivities (up to >99%).     

Study of dielectric and ac impedance properties of citrate-gel synthesized Li0.35Zn0.3Fe2.35O4 ferrite

Nano-crystals of Li_0.35Zn_0.3Fe_2.35O₄ ferrite have been synthesized using citrate precursor method. The sample synthesized was sintered at different temperatures in order to vary their crystallite size. The average crystallite size was found in the range 24?C57?nm by varying the temperature from 300 to 1,100?°C. X-ray diffraction measurements confirmed the formation of cubic spinel structure at all the sintering temperatures in this work. The high frequency performance of the ferrite samples were estimated by measuring the frequency dispersion of the dielectric constant, dielectric loss and ac electrical conductivity. The dielectric constant has been observed to show normal behavior with frequency and decreases with the decrease in crystallite size. It is also observed that decrease in dielectric constant depends on sintering temperature because of lithium evaporation at higher temperature. A low value of dielectric constant and dielectric loss has been found, which makes them applicable for high frequency applications by decreasing the skin effect. The impedance spectroscopy technique has been used to study the effect of grain and grain boundary on the electrical properties of Li_0.35Zn_0.3Fe_2.35O₄ ferrite. The analysis of data shows only one semi-circle corresponding to the grain boundary volume suggesting that the conduction mechanism takes place predominantly through grain boundary volume in the prepared samples.     

Recoverable and thermally stable superhydrophobic silica coating

A facile route to methyltrimethoxysilane (MTMS) based recoverable superhydrophobic silica coatings with dual-scale roughness obtained through the single step base catalyst sol–gel process. Superhydrophobic silica coatings have shown static water contact angle near about 170 ± 1° and dynamic water contact angle up to 2 ± 1°. Superhydrophobic-superhydrophilic switching feature also achieved by alternating heat treatment and bath surface modification with Trimethylchlorosilane (TMCS) at room temperature (26 °C). Furthermore, the superhydrophobic state could be transformed into superhydrophilic state by slow rate heat treatment. These studies present a very simple strategy for the fabrication of recoverable superhydrophobic surfaces.     

Transition metal complexes enslaved in the supercages of zeolite-Y: DFT investigation and catalytic significance

A series of zeolite-Y encapsulated hybrid catalysts, [M(STCH)·xH₂O]-Y have been prepared by encapsulating Schiff base complexes [where M?=?Mn(II), Fe(II), Co(II), Ni(II); (x?=?3) and Cu(II); (x?=?1); H₂STCH?=?salicylaldehyde thiophene-2-carboxylic hydrazone] in zeolite-Y matrix by flexible ligand method. These hybrid materials have been characterized by various physico-chemical techniques such as ICP-OES, elemental analyses, (FT-IR and electronic) spectral studies, BET, scanning electron micrographs, thermal analysis and X-ray powder diffraction patterns. X-ray powder diffraction analysis reveals that the structural integrity of the mother zeolite in the hybrid material remained intact upon immobilization of the complex. Density functional theory is employed to calculate the relaxed structure, bond angle, bond distance, dihedral angle, difference of highest occupied molecular orbital and lowest unoccupied molecular orbital energies gap and electronic density of states of ligand and their neat transition metal complexes. The hybrid materials are active catalysts for the hydroxylation of phenol using hydrogen peroxide (30% H₂O₂) as an oxidant in order to selectively synthesize catechol or hydroquinone, amongst them [Cu(STCH)·H₂O]-Y shown the highest % of selectivity towards catechol (81.3%).     

Recent advances in ZnO nanostructures and thin films for biosensor applications: Review

Biosensors have shown great potential for health care and environmental monitoring. The performance of biosensors depends on their components, among which the matrix material, i.e., the layer between the recognition layer of biomolecule and transducer, plays a crucial role in defining the stability, sensitivity and shelf-life of a biosensor. Recently, zinc oxide (ZnO) nanostructures and thin films have attracted much interest as materials for biosensors due to their biocompatibility, chemical stability, high isoelectric point, electrochemical activity, high electron mobility, ease of synthesis by diverse methods and high surface-to-volume ratio. ZnO nanostructures have shown the binding of biomolecules in desired orientations with improved conformation and high biological activity, resulting in enhanced sensing characteristics. Furthermore, compatibility with complementary metal oxide semiconductor technology for constructing integrated circuits makes ZnO nanostructures suitable candidate for future small integrated biosensor devices. This review highlights recent advances in various approaches towards synthesis of ZnO nanostructures and thin films and their applications in biosensor technology.     

Influence of hole mobility on the response characteristics of p-type nickel oxide thin film based glucose biosensor

RF sputtered p-type nickel oxide (NiO) thin film exhibiting tunable semiconductor character which in turns enhanced its functional properties. NiO thin film with high hole mobility is developed as a potential matrix for the realization of glucose biosensor. NiO thin film prepared under the optimized deposition conditions offer good electrical conductivity (1.5 × 10⁻³ Ω⁻¹-cm⁻¹) with high hole mobility (2.8 cm² V⁻¹ s⁻¹). The bioelectrode (GO_x/NiO/ITO/glass) exhibits a low value of Michaelis–Menten constant (K_m = 1.05 mM), indicating high affinity of the immobilized GO_x toward the analyte (glucose). Due to the high surface coverage (2.32 × 10⁻⁷ mol cm⁻²) of the immobilized enzyme on to the NiO matrix and its high electrocatalytic activity, the prepared biosensor exhibits a high sensitivity of 0.1 mA (mM⁻¹-cm⁻²) and a good linearity from 25 to 300 mg dL⁻¹ of glucose concentration with fast response time of 5 s. Various functional properties of the material (mobility, crystallinity and stress) are found to influence the charge communication feature of NiO thin film matrix to a great extent, resulting in enhanced sensing response characteristics.