A Pd/Cr2O3 hybrid catalyst for cyanation reaction of some aryl halides was synthesized and characterized by XRD, SEM/EDS and TEM. The porous structure of the catalyst was also investigated by BET ...analysis. All XRD characteristic lines were obtained for Cr2O3 and Pd/Cr2O3 hybrid in good agreement with the reference XRD data. It was found that average particle size of Pd/Cr2O3 composite was about 22 nm. The catalytic efficiency of the Pd/Cr2O3–catalyzed cyanation reaction was evaluated for some m- and p-substituted aryl halides. The influence of solvent, reaction time, and base on the activity of the Pd/Cr2O3 catalyst was investigated, and the optimal reaction conditions were systematically obtained. Catalytic investigations showed that Pd/Cr2O3 hybrid can exhibit very good catalytic performance for cyanation reaction of aryl halides with a high yield of around 90%, and retained its catalytic activity throughout successive 5 cycles. Comparative TEM images of Pd/Cr2O3 hybrid catalyst, as-synthesized and after 5th cycle, showed that nano-sized structure of Pd/Cr2O3 catalyst was protected without significant change.
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In the presented paper, the influence of the molecular weight and the type of polyamino acid functional groups on the electrokinetic properties and the stability of chromium (III) oxide suspension ...were examined. Analysis of the data obtained from the adsorption, potentiometric titration, zeta potential, and stability measurements allows to propose stabilization or destabilization mechanism of the studied systems. In the studies, there were used polyamino acids with different ionic characters: anionic polyaspartic acid and cationic polylysine. The measurements showed that the zeta potential depends on the concentration and molecular weight of the applied polymer. Stability of the chromium (III) oxide suspensions in the presence of ionic polyamino acids increases compared to the results obtained in the absence of polymers. The exception is LYS 4,900 at pH = 10. Under these conditions, the decrease in stability is observed due to formation of polymer bridges between the polymer chains adsorbed on different colloidal particles. Determination of the stabilization/destabilization mechanism of the polyamino acid/chromium (III) oxide system and examination of the effects of polymer molecular weight on the stabilization properties can contribute to a wider use of this group of compounds as potential stabilizers or flocculants in many industrial suspensions.
Spectrally selective solar absorbers based on Cr2O3/Cr/Cr2O3 multilayered coatings were deposited onto stainless steel substrates by using an electron beam physical vapor deposition technique. The ...structural investigations of the multilayered coatings showed crystalline phase of Cr2O3 after annealing the coatings at 500 °C in air for 2 h. The Raman analysis revealed vibrational modes corresponding to Eg and A1g symmetries in Cr2O3. The gradual appearance of absorption bands associated with of CrO bond stretching was also observed from the attenuated total reflectance measurement. The Morphology investigations of the coatings by SEM showed presence of nanoparticles with size ranging from 40 to 50 nm in diameter. The AFM also revealed a columnar growth with an average surface roughness of 16 nm. The optical analysis of the coatings showed a combination of good solar absorptance of 0.89 and low thermal emittance of 0.25 at 100 °C. These optical properties could arise from a combination of interference, and intrinsic effects that occur in the multilayered solar absorber structure. These results indicate that a Cr2O3/Cr/Cr2O3 multilayered coating deposited by e-beam evaporation is an excellent thin films material for selective solar absorbers application.
•A Cr2O3/Cr/Cr2O3 solar absorber was deposited by the e-beam evaporation method.•The deposited solar absorber exhibited good solar absorptance of 0.89 at 100 °C.•The Cr2O3/Cr/Cr2O3 solar absorber showed low thermal emittance of 0.25 at 100 °C.
Thermophysical analysis of acrylic pyramid solar still with and without Zn2+ substituted Cr2O3 nanoparticles had been analysed. Synthesised pure and Zn2+ doped Cr2O3 nanoparticle with different ...dopant concentrations is used along with the black absorber paint as an additional source in enhancing the heat transfer in the solar still. Heat transfer modes, efficiency (instantaneous and overall) and thermophysical properties are predicted for solar still with and without Zn2+ substituted Cr2O3 nanoparticles.
XRD confirms the rhombohedral phase with average particle size of pure and Zn doped Cr2O3 around ± 14 nm and ± 12 nm respectively. Surface morphology showed nearly spherical shape with loosely agglomerated and the presence of Cr and Zn was confirmed by EDAX analysis. Dielectric measurements showed enhanced dielectric constant and electrical conductivity as the function of temperature at different frequency range. Performance ratio observed during the study is in the range of 2.11 to 10.125 for solar still alone, 2.38 to 11.9 % for solar still with pure Cr2O3 nanomaterial, 2.38 % to 12.87 % for solar still with 2.5 mol.% Zn2+ doped Cr2O3 nanomaterial, 2.46 % to 13.22 % for solar still with 5 mol.% Zn2+ doped Cr2O3 nanomaterial and 2.54 % to 13.67 % for solar still combined with 7.5 mol.% Zn2+ doped Cr2O3 nanomaterial.
Average daily output of solar still was found to be 2.366 L/day, 3.147 L/day, 3.299 L/day, 3.3761 L/day and 3.628 L/day for pyramid solar still under five modes of study. Efficiency of the still was calculated as 18.29%, 21.15%, 21.88%, 22.32% and 23.48% for pyramid solar still under five modes of study. It is found that the productivity yield of solar still with 7.5 mol.% Zn2+ doped Cr2O3 nanomaterial is increased to higher level due to the increased absorption of solar radiation when compared to other modes of study.
The adsorption mechanism of different polymers containing ionic polyamino acids monomers in the chain structure at the solid-liquid interface was investigated. Initially, the influence of molecular ...weight and solution pH on simple polyamino acids (poly(L-aspartic acid) and poly(L-lysine) binding was determined. Considering the obtained dependencies, the polymer adsorption layer conformation was proposed in the systems containing block copolymers (both diblock and symmetrical triblock) consisting of polypeptide as well as poly(ethylene glycol) fragments. The presented studies focused on the application of two experimental methods. The polymer adsorption was carried out using the batch method and the adsorbate concentration was determined spectrophotometrically. Then, the turbidimetric measurements were taken. The analysis of the obtained results showed that the adsorption process of block copolymers depends on two factors. Firstly, the solution pH determines both the nature of the interactions of the copolymer structural units with the solid surface and the conformation of the polypeptide chains. The second parameter influencing the adsorption layer structure is the ratio of the lengths of both blocks. Introducing a short PEG fragment into the polymer main chain may improve the polymer adsorption properties by increasing the number of interactions with the adsorbent surface.
This contribution reports on novel physical properties of specific oxides in their nano scaled configuration. This includes the ultrafast optical limiting of VO2 thin films, the magneto-optical ...tunability of the ESR response of α-Cr2O3 nano-spheres, and the reversible control of the surface tension of ZnO oriented nano-rods as well as the validation of the synthesis of high crystalline stoichiometric of rare earth nanostructures by the so called local gas feeding beam pulsed laser deposition.
•Photo-induced and photo-tunable phenomena in nano-structured oxides are reported.•VO2 nano-coating exhibit ultrafast optical limiting.•α-Cr2O3 nano-spheres exhibit magneto-optical tunability and enhanced ESR response.•ZnO oriented nano-rods exhibit reversible photo-controlled the surface tension.•High crystalline RE2O3 nanostructures by local gas feeding/pulsed laser deposition.
The Cr2O3/carbon nanocomposites synthesized by directly carbonizing glycine–CrCl3 gel precursor exhibit superior cycling and rate performances as lithium-ion battery anode materials. Display omitted
...•The Cr2O3/carbon nanocomposites were prepared by directly carbonizing the glycine–CrCl3 gel precursor.•The prepared Cr2O3 nanoparticles were embedded in carbon sheets.•The Cr2O3/carbon nanocomposites displayed superior cycling performance and rate performances.•The carbon sheets improved the electrical conductivity of Cr2O3 and buffered the volume change.
The chromium(III) oxide (Cr2O3) nanoparticles embedded in the carbon sheets are fabricated by combining a sol–gel approach with an efficient carbonization process using glycine as carbon precursor. These Cr2O3/carbon nanocomposites serving as anode materials for lithium-ion batteries (LIBs) have been tested, exhibiting higher cycling (reversible capacity of 465.5mAhg−1 after 150 cycles at a current density of 100mAg−1) and rate performances (the discharge capacities of 448.7, 287.2, and 144.8mAhg−1 at a current density of 200, 400, and 800mAg−1, respectively) than pure Cr2O3 (reversible capacity of 71.2mAhg−1 after 150 cycles at a current density of 100mAg−1 and the discharge capacities of 174.4, 60.5, 29.5, and 13.6mAhg−1 at a current density of 100, 200, 400, and 800mAg−1, respectively) due to the presence of carbon sheets, which efficiently buffer the volume change during the lithiation/delithiation and improve the electrical conductivity between Cr2O3 nanoparticles.
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In this work, we present the design and fabrication of a novel nanocomposite based on noble metal and metal oxide nanoparticles dispersed on highly porous carbon obtained via the ...pyrolysis of an inorganic complex and metal-organic frameworks. This nanocomposite is prepared by a two-step procedure: first, the composite support of nanoporous carbon (NPC) is obtained by the direct carbonization of the Cr-benzene dicarboxylic ligand (BDC) MOF in an Argon atmosphere at 500 °C (Cr2O3-NPC). A mixture containing Cr2O3-NPC and PtCl(SnCl3)(SMe2)2 is then prepared, and underflow of Argon is heated to 380 °C. Finally, Pt-SnO2 nanoparticles are loaded on the Cr2O3-NPC support, and the obtained nanocomposite was denoted as Pt-SnO2/Cr2O3-NPC. The morphology and crystalline structure of the prepared nanocomposites were characterized using XRD, SEM, EDX, FT-IR, and XPS. In addition, the prepared nanocomposite was examined as a novel electrocatalyst for the ethanol electro-oxidation reaction (EOR). The obtained results demonstrated that, compared with Pt/Cr2O3-NPC, Pt-SnO2/Cr2O3-NPC showed higher electrocatalytic activity, lower onset potential, and a higher level of poisoning tolerance toward of ethanol oxidation in acidic media. The overall results corroborate the predominant role of SnO2 as an excellent catalytic-enhancing agent thorough facilitating the charge transfer process and increasing the CO poisoning oxidation by the spillover of OHads to the Pt surface. Thus, the prepared Pt-SnO2/Cr2O3-NPC catalyst could be considered a promising anode catalyst for direct ethanol fuel cells.
Chromium (III) oxide nanoparticles (NPs) have a wide range of industrial applications, particularly in the production of lithium-ion batteries; however, the toxicity of these NPs has not been studied ...extensively. The phytotoxicity and genotoxicity of chromium (III) oxide NPs have not been assessed, and only one study reported their cytotoxicity, underscoring the need to perform comprehensive toxicity studies on these NPs. Here, we showed that chromium (III) oxide NPs had no effect on germination rates, and only decreased root elongation in L. sativa as determined by root elongation and biomass studies. Chromium (III) oxide NPs had no phytotoxic effects under environmental realistic conditions, whereas they had cytotoxic effects against HK-2 and Raw 264.7 cells in vitro. However, the cytotoxicity of chromium (III) oxide NPs did not occur under environmentally realistic conditions. The genotoxicity of chromium (III) oxide NPs was not significant in HK-2 cells, suggesting that the potential environmental cytotoxicity of chromium (III) oxide NPs is limited. This study proposes comprehensive phytotoxicity, cytotoxicity, and genotoxicity testing tools that would be easy, safe, and effective for evaluating the toxicity of NPs. This integrated testing system could be an accurate and stable method for evaluating the toxicity of other nanomaterials.
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