Ion Tracks and Nanohillocks Created in Natural Zirconia Irradiated with Swift Heavy Ions

Natural monoclinic zirconia (baddeleyite) was irradiated with 340 MeV Au ions, and the irradiation-induced nanostructures (i.e., ion tracks and nanohillocks) were observed using transmission electron microscopy. The diameter of the nanohillocks was approximately 10 nm, which was similar to the maximum molten region size calculated using the analytical thermal spike model. Ion tracks were imaged as strained regions that maintained their crystalline structure. The cross-sections of most of the ion tracks were imaged as rectangular contrasts as large as 10 nm. These results strongly indicated that the molten region was recrystallized anisotropically, reflecting the lattice structure. Furthermore, low-density track cores were formed in the center of the ion tracks. The formation of low-density track cores can be attributed to the ejection of molten matter toward the surface. A comparison of the ion tracks in the synthetic zirconia nanoparticles and those in larger natural zirconia samples showed that the interface between the strained track contrast and the matrix was less clear in the former than in the latter. These findings suggest that the recrystallization process was affected by the size of the irradiated samples.

Reusable nano-catalyzed green protocols for the synthesis of quinoxalines: an overview

Heterocyclic compounds are very widely distributed in nature and are essential for life activities. They play a vital role in the metabolism of all living cells, for example, vitamins and co-enzyme precursors thiamine, riboflavin etc. Quinoxalines are a class of N-heterocycles that are present in a variety of natural and synthetic compounds. The distinct pharmacological activities of quinoxalines have attracted medicinal chemists considerably over the past few decades. Quinoxaline-based compounds possess extensive potential applications as medicinal drugs, presently; more than fifteen drugs are available for the treatment of different diseases. Diverse synthetic protocols have been developed via a one-pot approach using efficient catalysts, reagents, and nano-composites/nanocatalysts etc. But the use of homogeneous and transition metal-based catalysts suffers some demerits such as low atom economy, recovery of catalysts, harsh reaction conditions, extended reaction period, expensive catalysts, the formation of by-products, and unsatisfactory yield of products as well as toxic solvents. These drawbacks have shifted the attention of chemists/researchers to develop green and efficient protocols for synthesizing quinoxaline derivatives. In this context, many efficient methods have been developed for the synthesis of quinoxalines using nanocatalysts or nanostructures. In this review, we have summarized the recent progress (till 2023) in the nano-catalyzed synthesis of quinoxalines using condensation of o-phenylenediamine with diketone/other reagents with plausible mechanistic details. With this review, we hope that some more efficient ways of synthesizing quinoxalines can be developed by synthetic chemists.

Structural, Morphological and Optical Properties of Nanostructured ZrO2 Films Obtained by an Electrochemical Process at Different Deposition Temperatures

This article focuses on the impact of the deposition temperature (in the range from 60 to 80 °C) in ZrO2 films obtained by the electrochemical deposition process on SnO2-covered glass substrates. The solution in which the deposition takes place is aqueous, containing ZrOCl2 with a concentration of 3 × 10−5 M and KCl with a concentration of 0.1 M. By implementing X-ray diffraction (XRD), optical profilometry, scanning electron microscopy (SEM), and UV-VIS-NIR spectroscopy, the temperature dependence of ZrO2 films properties was revealed. The X-Ray Diffraction XRD spectra showed six different diffraction maxima ((−111)М, (101)Т, (111)М, (112)М, (202)М, and (103)M) associated with the electrochemical ZrO2 layers, and the polycrystalline structure of the films was confirmed at all deposition temperatures. The determination of the average roughness did not indicate significant temperature dependence in the deposited layers. SEM micrographs showed that the layers were composed of grains, most of them of a regular shape, although their size increased slightly with an increased deposition temperature. The coarsest-grained structure was observed for the layers deposited at 80 °C. It was demonstrated that the deposition temperature weakly impacts the reflectance and transmittance spectra of the ZrO2 layers. Such layers with low values of specular and high values of diffuse transition, and reflection in the spectral range from 380 to 800 nm, can be applied to various optoelectronic devices such as thin-film solar cells.

Natural vs. Synthetic Phosphate as Efficient Heterogeneous Compounds for Synthesis of Quinoxalines

Natural phosphate (NP) and synthetic fluorapatite phosphate (SFAP) were proposed as stable, inexpensive, readily available and recyclable catalysts for the condensation of 1,2-diamines with 1,2-dicarbonyls in methanol to afford quinoxaline at room temperature. NP provided as high as 92-99% yield for quinoxalines in short reaction times (i.e., 1-45 min), while SFAP created quinoxalines with 87-97% yield in 60-120 min. From the chemical analyses, X-ray fluoresecency, X-ray diffraction, energy dispersive X-ray and Fourier-transform infrared spectroscopy methods, two main phases (CaO, P2O5) appeared in NP together with other low content phases (SiO2, Fe2O3). Compared to other phases, apatite (CaO and P2O5 as Ca10(PO4)6) played a major role in the catalytic activity of NP. SFAP with similar Ca/P atomic ratio showed a relatively lower catalytic activity than NP for the condensation of 1,2-diamine with 1,2-dicarbonyl in methanol at ambient temperature. To investigate the recyclability of catalysts, the surface properties of NP and 6-recycled NP were investigated using scanning electron microscopy, energy dispersive X-ray and Brunauer-Emmett-Teller and Barrett-Joyner-Halenda methods. Some differences were observed in NP and 6-recycled NP's particle size, surface area, the volume and size of pores, and the content of elements; nevertheless, the use-reuse process did not noticeably change the catalytic property of NP.

Structural and Morphological Studies of V2O5/MWCNTs and ZrO2/MWCNTs Composites as Photocatalysts

The present study outlines the synthesis of transition metal oxide- (TMO-) multiwall carbon nanotubes- (MWCNTs-) based composites for photocatalytic application. MWCNTs were functionalized/purified by treating with H2SO4 and HNO3 to improve their dispersion in water. The TMOs (ZrO2, V2O5) were decorated on MWCNTs by the hydrothermal method to yield V2O5/MWCNTs and ZrO2/MWCNTs composites. Subsequently, these composites were characterized for their structural/morphological studies by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Photocatalytic activities of TMO/MWCNTs composites were investigated by degradation phenomenon of methylene blue (MB) dye in aqueous solution. It was observed that the prepared composites best performed in the presence of H2O2 under ultraviolet irradiation. The maximum observed degradation efficiencies for ZrO2/MWCNTs and V2O5/MWCNTs were 49% and 96%, respectively.

Ni-Doped ZrO2 nanoparticles decorated MW-CNT nanocomposite for the highly sensitive electrochemical detection of 5-amino salicylic acid

Ni-ZrO₂/MWCNT/GCE for highly sensitive electrochemical detection of 5-ASA in biofluids.

A decennary update on applications of metal nanoparticles (MNPs) in the synthesis of nitrogen- and oxygen-containing heterocyclic scaffolds

Heterocycles have been found to be of much importance as several nitrogen- and oxygen-containing heterocycle compounds exist amongst the various USFDA-approved drugs. Because of the advancement of nanotechnology, nanocatalysis has found abundant applications in the synthesis of heterocyclic compounds. Numerous nanoparticles (NPs) have been utilized for several organic transformations, which led us to make dedicated efforts for the complete coverage of applications of metal nanoparticles (MNPs) in the synthesis of heterocyclic scaffolds reported from 2010 to 2019. Our emphasize during the coverage of catalyzed reactions of the various MNPs such as Ag, Au, Co, Cu, Fe, Ni, Pd, Pt, Rh, Ru, Si, Ti, and Zn has not only been on nanoparticles catalyzed synthetic transformations for the synthesis of heterocyclic scaffolds, but also provide an inherent framework for the reader to select a suitable catalytic system of interest for the synthesis of desired heterocyclic scaffold.

Photocatalytic activity of ZrO2 composites with graphitic carbon nitride for hydrogen production under visible light

The synthesized ZrO₂/g-C₃N₄ composites exhibit superior performance in water splitting for hydrogen production due to the effective electron–hole separation at the composite interface.

A simple ultrasensitive electrochemical sensor for simultaneous determination of gallic acid and uric acid in human urine and fruit juices based on zirconia-choline chloride-gold nanoparticles-modified carbon paste electrode

The determination of gallic acid (GA) and uric acid (UA) is essential due to their biological properties. Numerous methods have been reported for the analysis of GA and UA in various real samples. However, the development of a simple, rapid and practical sensor still remains a great challenge. Here, a carbon paste electrode (CPE) was modified by nanocomposite containing zirconia nanoparticles (ZrO₂NPs), Choline chloride (ChCl) and gold nanoparticles (AuNPs) to construct ZrO₂-ChCl-AuNPs/CPE as electrochemical sensor for the simultaneous electro-oxidation of GA and UA. Characterization was performed by Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy and energy dispersive X-ray spectroscopy. The modified electrode was investigated by different methods including electrochemical impedance spectroscopy and cyclic voltammetry. Kinetic parameters such as charge transfer coefficient, standard heterogeneous electron transfer rate constant and other parameters were calculated via voltammetry techniques. Differential pulse voltammetry was used for simultaneous determination of GA and UA applying the ZrO₂-ChCl-AuNPs/CPE electrode. At the optimum conditions, this sensor showed a linear response in the ranges 0.22- 55 and 0.12-55 µM for GA and UA, respectively. In addition, low detection limits of 25 and 15 nM were obtained for GA and UA, respectively. Furthermore, ZrO₂-ChCl-AuNPs/CPE was successfully applied for the independent determination of GA in green tea and fruit juice as well as the simultaneous determination of GA and UA in human urine samples.

A cobalt Schiff base complex on TiO2nanoparticles as an effective synergistic nanocatalyst for aerobic C–H oxidation

A cobalt Schiff base complex on TiO₂nanoparticles possess excellent photocatalytic properties under visible light for the aerobic benzylic C–H oxidation.

Aerobic benzylic C–H oxidation catalyzed by a titania-based organic–inorganic nanohybrid

The visible light photocatalytic properties of TiO₂/AA/Co organic–inorganic nanohybrid in the aerobic benzylic C–H oxidation was exploited.

A synergistic effect of a cobalt Schiff base complex and TiO2 nanoparticles on aerobic olefin epoxidation

A cobalt Schiff base complex and TiO₂ nanoparticles exhibited a synergistic effect on the visible-light photocatalytic activity in the aerobic oxidation of various olefins in the absence of reducing agent.