The Effect of Novel Synthetic Methods and Parameters Control on Morphology of Nano-alumina Particles

A new samarium complex of 1,3-bis(pyridin-3-ylmethyl)thiourea on boehmite nanoparticles as a practical and recyclable nanocatalyst for the selective synthesis of tetrazoles

Boehmite is a natural and environmentally friendly compound. Herein boehmite nanoparticles were primarily synthesized and, then, their surface were modified via 3-choloropropyltrimtoxysilane (CPTMS). Afterwards, a new samarium complex was stabilized on the surface of the modified boehmite nanoparticles (Sm-bis(PYT)@boehmite). The obtained nanoparticles were characterized using thermogravimetric analysis (TGA), energy dispersive X-ray spectroscopy (EDS), Brunauer-Emmett-Teller (BET), wavelength dispersive X-ray spectroscopy (WDX), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), Inductively coupled plasma mass spectrometry (ICP-MS), dynamic light scattering (DLS), and X-ray diffraction (XRD) pattern. Sm-bis(PYT)@boehmite was used as an environmentally friendly, efficient, and organic-inorganic hybrid nanocatalyst in the homoselective synthesis of tetrazoles in polyethylene glycol 400 (PEG-400) as a green solvent. Notably, Sm-bis(PYT)@boehmite is stable and has a heterogeneous nature. Thus, it can be reused for several runs without any re-activation.

Synthesis of tetrazoles catalyzed by a new and recoverable nanocatalyst of cobalt on modified boehmite NPs with 1,3-bis(pyridin-3-ylmethyl)thiourea

In the first part of this work, boehmite nanoparticles (BNPs) were synthesized from aqueous solutions of NaOH and Al(NO₃)₃·9H₂O. Then, the BNPs surface was modified using 3-choloropropyltrimtoxysilane (CPTMS) and then 1,3-bis(pyridin-3-ylmethyl)thiourea ((PYT)₂) was anchored on the surface of the modified BNPs (CPTMS@BNPs). In the final step, a complex of cobalt was stabilized on its surface (Co-(PYT)₂@BNPs). The final obtained nanoparticles were characterized by FT-IR spectra, TGA analysis, SEM imaging, WDX analysis, EDS analysis, and XRD patterns. In the second part, Co-(PYT)₂@BNPs were used as a highly efficient, retrievable, stable, and organic-inorganic hybrid nanocatalyst for the formation of organic heterocyclic compounds such as tetrazole derivatives. Co-(PYT)₂@BNPs as a novel nanocatalyst are stable and have a heterogeneous nature; therefore, they can be recovered and reused again for several consecutive runs without any re-activation.

Coloured hybrid materials: exploiting an emergent surface property of fluorinated Al2O3 containing anthocyanins and betacyanins

Two fluorinated γ-Al₂O₃ series were synthesized by a sol-gel method with two solvents (2-propanol and 2-butanol), two aluminium sources (ATB and ATP) and one fluorine source (Na₃AlF₆). The resulting inorganic matrixes were evaluated to characterize aluminium and fluorine species ([AlO₄^5-], [AlO₅^7-], [AlO₆^9-], [AlF₄^-], [AlF₅^2-] and [AlF₆^3-]) by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ²⁷Al magic angle spinning nuclear magnetic resonance (²⁷Al MAS-NMR) and infrared spectroscopy (IR-ATR). BET and BJH analyses using the nitrogen isotherms of these materials allowed identifying a clear trend in some textural parameters such as specific surface area and fluorine content. These results were confirmed by scanning electron microscopy (SEM). Chemical affinity and acid surface properties were evidenced with colour shifts in two groups of hybrid pigments, prepared with natural anthocyanins (Brassica oleracea) and betacyanins (Bougainvillea glabra).

Designable assembly of atomically precise Al4O4 cubane supported mesoporous heterometallic architectures

Heterometallic cluster-based framework materials are of interest in terms of both their porous structures and multi-metallic reactivity. However, such materials have not yet been extensively investigated because of difficulties in their synthesis and structural characterization. Herein, we reported the designable synthesis of atomically precise heterometallic cluster-based framework compounds and their application as catalysts in aldol reactions. By using the synergistic coordination protocol, we successfully isolated a broad range of compounds with the general formula, [Al₄M₄O₄(L)₁₂(DABCO)₂] (L = carboxylates; DABCO = 1,4-diazabicyclo[2.2.2]-octane; M²⁺ = Co²⁺, Mn²⁺, Zn²⁺, Fe²⁺, Cd²⁺). The basic heterometallic building blocks contain unprecedented main-group γ-alumina moieties and surrounding unsaturated transition metal centers. Interestingly, the porosity and interpenetration of these frameworks can be rationally regulated through the unprecedented strategy of increment of the metal radius in addition to general introduction of sterically bulky groups on the ligand. Furthermore, these porous materials are effective catalysts for aldol reactions. This work provides a catalytic molecular model platform with accurate molecular bonding between the supporters and catalytically active metal ions.

Binding Materials for MOF Monolith Shaping Processes: A Review towards Real Life Application

Metal–organic frameworks (MOFs) could be utilized for a wide range of applications such as sorption, catalysis, chromatography, energy storage, sensors, drug delivery, and nonlinear optics. However, to date, there are very few examples of MOFs exploited on a commercial scale. Nevertheless, progress in MOF-related research is currently paving the way to new industrial opportunities, fostering applications and processes interconnecting fundamental chemistry with engineering and relevant sectors. Yet, the fabrication of porous MOF materials within resistant structures is a key challenge impeding their wide commercial use for processes such as adsorptive separation. In fact, the integration of nano-scale MOF crystallic structures into bulk components that can maintain the desired characteristics, i.e., size, shape, and mechanical stability, is a prerequisite for their wide practical use in many applications. At the same time, it requires sophisticated shaping techniques that can structure nano/micro-crystalline fine powders of MOFs into diverse types of macroscopic bodies such as monoliths. Under this framework, this review aims to bridge the gap between research advances and industrial necessities for fostering MOF applications into real life. Therefore, it critically explores recent advances in the shaping and production of MOF macro structures with regard to the binding materials that have received little attention to date, but have the potential to give new perspectives in the industrial applicability of MOFs. Moreover, it proposes future paths that can be adopted from both academy and industry and can further boost MOF exploitation.

In Situ Low-Temperature Growth and Superior Luminescent Property of Well-Aligned, High-Quality Cubic CsPbBr3 Micrometer-Scale Single Crystal Arrays on Transparent Conductive Substrates

Direct assembly of high-quality single-crystal perovskite microarrays on transparent conductive substrates and carrier injection layers is vital to realize high-performance optoelectronic devices. Although cubic-phase CsPbBr₃ is considered to have a higher structural and optical quality than the orthorhombic one, obtaining a well-aligned assembly directly on the aforementioned substrates is still challenging. Here we developed a solvent-assisted crystallization strategy with the assistance of surface modifiers, through which the in situ low-temperature growth of well-aligned cubic single-crystal CsPbBr₃ microarray with a preferential out-of-plane [100] orientation is achieved for the first time on commercial transparent conductive substrates. As compared with the control orthorhombic samples, the cubic CsPbBr₃ single crystals possess superior properties including a higher photoluminescence internal quantum efficiency, fewer defect states, a weaker scattering by phonons, and an appearance of lasing. The results presented here can pave the way for future design and applications of optoelectronic devices based on perovskite microarrays.

Spherical core-shell alumina support particles for model platinum catalysts

γ- and δ-alumina are popular catalyst support materials. Using a hydrothermal synthesis method starting from aluminum nitrate and urea in diluted solution, spherical core-shell particles with a uniform particle size of about 1 μm were synthesized. Upon calcination at 1000 °C, the particles adopted a core-shell structure with a γ-alumina core and δ-alumina shell as evidenced by 2D and 3D electron microscopy and 27Al magic angle spinning nuclear magnetic resonance spectroscopy. The spherical alumina particles were loaded with Pt nanoparticles with an average size below 1 nm using the strong electrostatic adsorption method. Electron microscopy and energy dispersive X-ray spectroscopy revealed a homogeneous platinum dispersion over the alumina surface. These platinum loaded alumina spheres were used as a model catalyst for bifunctional catalysis. Physical mixtures of Pt/alumina spheres and spherical zeolite particles are equivalent to catalysts with platinum deposited on the zeolite itself facilitating the investigation of the catalyst components individually. The spherical alumina particles are very convenient supports for obtaining a homogeneous distribution of highly dispersed platinum nanoparticles. Obtaining such a small Pt particle size is challenging on other support materials such as zeolites. The here reported and well-characterized Pt/alumina spheres can be combined with any zeolite and used as a bifunctional model catalyst. This is an interesting strategy for the examination of the acid catalytic function without the interference of the supported platinum metal on the investigated acid material.

Influence of Alumina Precursor Properties on Cu-Fe Alumina Supported Catalysts for Total Toluene Oxidation as a Model Volatile Organic Air Pollutant

The structure–property relationship of catalytic supports for the deposition of redox-active transition metals is of great importance for improving the catalytic efficiency and reusability of the catalysts. In this work, the role of alumina support precursors of Cu-Fe/Al2O3 catalysts used for the total oxidation of toluene as a model volatile organic air pollutant is elucidated. Surface characterization of the catalysts revealed that the surface area, pore volume and acid site concentration of the alumina supports are important but not the determining factors for the catalytic activity of the studied catalysts for this type of reaction. The determining factors are the structural order of the support precursor, the homogeneous distribution of the catalytic sites and reducibility, which were elucidated by XRD, NMR, TEM and temperature programed reduction (TPR). Cu–Fe/Al2O3 prepared from bayerite and pseudoboehmite as highly ordered precursors showed better catalytic performance compared to Cu-Fe/Al2O3 derived from the amorphous alumina precursor and dawsonite. Homogeneous distribution of FexOy and CuOx with defined Cu/Fe molar ratio on the Al2O3 support is required for the efficient catalytic performance of the material. The study showed a beneficial effect of low iron concentration introduced into the alumina precursor during the alumina support synthesis procedure, which resulted in a homogeneous metal oxide distribution on the support.

Thermal Conductivity and Stability of Novel Aqueous Graphene Oxide–Al2O3 Hybrid Nanofluids for Cold Energy Storage

Thermal ice storage has gained a lot of interest due to its ability as cold energy storage. However, low thermal conductivity and high supercooling degree have become major issues during thermal cycling. For reducing the cost and making full use of the advantages of the graphene oxide–Al2O3, this study proposes heat transfer enhancement of thermal ice storage using novel hybrid nanofluids of aqueous graphene oxide–Al2O3. Thermal conductivity of aqueous graphene oxide–Al2O3 nanofluid was measured experimentally over a range of temperatures (0–70 °C) and concentrations. Thermal conductivity of ice mixing with the hybrid nanoparticles was tested. The influences of pH, dispersant, ultrasonic power and ultrasonic time on the stability of the hybrid nanofluids were examined. A new model for the effective thermal conductivity of the hybrid nanofluids considering the structure and Brownian motion was proposed. The results showed that pH, dispersant, ultrasonic power level and ultrasonication duration are important factors affecting the stability of the hybrid nanofluids tested. The optimum conditions for stability are pH = 11, 1% SDS, 375 W ultrasonic power level and 120 min ultrasonic application time. The thermal conductivity of hybrid nanofluids increases with the increase of temperature and mass fraction of nanoparticles. A newly proposed thermal conductivity model considering the nanofluid structure and Brownian motion can predict the thermal conductivity of hybrid nanofluids reasonably well.

Nanomaterials for the Removal of Heavy Metals from Wastewater

Removal of contaminants in wastewater, such as heavy metals, has become a severe problem in the world. Numerous technologies have been developed to deal with this problem. As an emerging technology, nanotechnology has been gaining increasing interest and many nanomaterials have been developed to remove heavy metals from polluted water, due to their excellent features resulting from the nanometer effect. In this work, novel nanomaterials, including carbon-based nanomaterials, zero-valent metal, metal-oxide based nanomaterials, and nanocomposites, and their applications for the removal of heavy metal ions from wastewater were systematically reviewed. Their efficiency, limitations, and advantages were compared and discussed. Furthermore, the promising perspective of nanomaterials in environmental applications was also discussed and potential directions for future work were suggested.

Comparative Study Between Aluminum Monolith and Foam as Carriers for The Intensification of The CO Water Gas Shift Process

A comparison between the effect of different highly thermal conductive carriers on the performance of Pt/CeO2/Al2O3-based structured catalysts in a water–gas shift reaction, was reported. The structured catalysts were prepared by means of washcoating two carriers, a flow through aluminum monolith and an open cell aluminum foam, with the same contact surface and the same chemical composition of the washcoat. The experiments were carried out under stressful conditions (no dilution and high space velocity), so as to minimize the thermal dispersions and to highlight the effect of the thermal conductivity of the carriers and the material transport phenomena. Both of the catalysts showed a substantially flat thermal profile, while the carbon monoxide conversion was higher with the foam-based catalyst, as a result of the higher temperatures reached. The experimental results were validated with a computational fluid dynamics (CFD) simulation by using the finite elements software, COMSOL Multiphysics®. Through the simulation results, it was also possible to investigate the effects of transport phenomena on the two catalytic systems, such as mass and heat transfer.