Green in water sonochemical synthesis of tetrazolopyrimidine derivatives by a novel core-shell magnetic nanostructure catalyst

A green approach for the one-pot four-component sonochemical synthesis of 5-methyl-7-aryl-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylic esters from the reaction of 2-cyano-guanidine, sodium azide, various aromatic aldehydes and methyl or ethyl acetoacetate in the presence of a catalytic amount of Fe₂O₃@SiO₂-(CH₂)₃NHC(O)(CH₂)₂PPh₂ as a new hybrid organic–inorganic core–shell nanomagnetic catalyst is described. This is the first design, preparation, characterization and application of the present nanomaterial and also the first ultrasound irradiated synthesis of the biologically and pharmaceutically important heterocyclic compounds in water as a green solvent. This novel sonocatalysis/nanocatalysis protocol offers several advantages such as high yields, short reaction times, environmentally-friendly reaction media, easily isolation of the products, simple preparation, full characterization and recoverability of the nanocatalyst by an external magnet and reusing several times without significant loss of activity.     

CO2-enhanced dehydrogenation of ethane over sonochemically synthesized Cr/clinoptilolite-ZrO2 nanocatalyst: Effects of ultrasound irradiation and ZrO2 loading on catalytic activity and stability

CO₂-enhanced oxidative dehydrogenation of ethane was investigated over sonochemically synthesized Cr/clinoptilolite-ZrO₂ nanocatalyst with the aim of assessing the effect of composite support and ultrasonic irradiation on the nanocatalyst reactivity and stability. To this aim, ZrO₂ promoted clinoptilolite supports varying in zirconia content (0, 25, 50 wt%) were synthesized by hydrothermally precipitation method and impregnated with chromium nitrate under ultrasound irradiation. The samples were characterized by XRD, FESEM, EDX, TEM, ICP, BET, FTIR, TPR-H₂ and TPD-NH₃ techniques. The characterization results indicated that ultrasound irradiation could not only reduce the formation of Cr₂O₃ and decrease submicron particle size of chromium oxide to nanometer scale, but also promote the distribution of metallic particles and strengthen the chromium-support interaction. As a result, utilizing ultrasound irradiation in the synthesis of Cr/Clinoptilolite helped to maintain a high and stable catalytic activity. These features were more prominent in the presence of zirconia. It was found that the metal oxide nanoparticles with about 4–8 nm are dispersed uniformly on the surface of composite support containing 25 wt% ZrO₂ (CLT-Z25). Moreover, the addition of ZrO₂ resulted in the formation of new strong acid sites and a significant modification in the reducibility of chromium species, which alongside homogenous and small Cr nanoparticles account for the superior catalytic performance of ZrO₂ containing samples. However, excessive loading of ZrO₂ (50 wt%) severely covered the surface of clinoptilolite, afforded the aggregations of metallic particles and thereupon, weakened the contact between clinoptilolite and ZrO₂, which together with more acid strength seriously resulted in the deactivation of catalyst. In spite of superior initial activity of ZrO₂-rich sample among the catalysts tested, ultrasonic synthesized Cr/CLT-Z25 nanocatalyst showed the best catalytic performance after 5 h-catalytic reaction.     

Ultrasonic accelerated coupling reaction using magnetically recyclable bis (propyl molononitril) Ni complex nanocatalyst: A novel,green and efficient synthesis of biphenyl derivatives

A novel, green and rapid sonochemical research to preparation of the biphenyls was carried out through the coupling reaction between various aryl halides and phenylboronic acid by using bis(propyl malononitrile) Ni (0) complex (NiFe₂O₄@SiO₂-BPMN-Ni) as an efficient nano catalyst. The catalyst can be recycled via an external magnet and reused several times without considerable loss of its catalytic activity. Compare to the previous works, this procedure has advantages such as easy workup, high yields of products, environmentally benign and short reaction times. The novel nickel catalyst prepared and characterized by FT-IR, XRD, SEM, EDX, TGA and VSM techniques.     

Novel ionic liquid supported on Fe3O4 nanoparticles and its application as a catalyst in Mannich reaction under ultrasonic irradiation

A family of novel ionic liquid with l-alanine and choline chloride as environmentally benign materials have been synthesized and grafted on Fe₃O₄ nanoparticles using easy preparation techniques. The structure of ionic liquid supported on Fe₃O₄ nanoparticles (IL-Fe₃O₄ NPs) characterized by various analyses such as FE-SEM, EDX, XRD, NMR, FTIR and VSM. The catalytic activities of this catalyst are examined in the Mannich reaction for synthesis of β-aminocarbonyl compounds under ultrasonic irradiation. The recyclability of catalyst is investigated, and the results have indicated that the catalyst can be recycled six times without obvious activity decreasing.     

Characterization of the metallic phase in nanocrystalline ZnAl2O4-supported Pt catalysts

In this study several complementary methods as XRD, HRTEM, O₂ and H₂ adsorption, as well as H₂-O₂ titration were used for characterization of the metallic phase in 0.5-3.0 wt.% Pt/ZnAl₂O₄ catalysts. Three nanocrystalline ZnAl₂O₄ spinels used as a supports were prepared by the solvothermal and co-precipitation method. It was found that irrespective of the preparation method they form very good support materials with a high capacity to achieve high platinum dispersion. O₂ and H₂ chemisorption data showed metal dispersion up to 90% and good correspondence with HRTEM results was observed. The H₂-O₂ titration method may be applied for determination of Pt dispersion only in the high-loaded Pt/ZnAl₂O₄ catalysts. The catalytic performances of Pt supported on the prepared spinels were evaluated in the propane total oxidation reaction.     

Sonochemically preparation and characterization of bimetallic Ni-Co/Al2O3-ZrO2 nanocatalyst: Effects of ultrasound irradiation time and power on catalytic properties and activity in dry reforming of CH4

The catalytic performance of nanostructured Ni-Co/Al₂O₃-ZrO₂ catalysts, prepared by ultrasound-assisted impregnation method was examined in the dry reforming of methane. The effect of irradiation power and irradiation time have been studied by changing time (0, 20, 80 min) and power of the sonication (30, 60, 90 W) during the synthesis which resulted in different physiochemical properties of the nanocatalyst. The nanocatalysts were characterized by XRD, FESEM, PSD, EDX, TEM, TPR-H₂, BET, FTIR and TG analyses. Based on the characterization results, ultrasound treatment endowed the sample with more uniform and smaller nanoparticles; higher surface area, stronger metal-support interaction and more homogenous dispersion. Moreover, the analyses exhibited smaller particles with higher surface area and less population of particle aggregates at longer and highly irradiated nanocatalysts. The nanocatalyst irradiated at 90 W for 80 min (the longest irradiation time and the most intense power) showed a uniform morphology and a very narrow particles size distribution. More than 65% of particles of this nanocatalyst were in the range of 10–30 nm. Activity tests demonstrated that employing ultrasound irradiation during impregnation improves feed conversion and products yield, reaching values close to equilibrium. Among sonicated nanocatalysts, with increasing power and time of irradiation, the nanocatalyst represents higher activity. The superior performance amongst the various bimetallic catalysts tested was observed over the catalyst with 90 W and 80 min ultrasonic irradiation which is stable in 24 h time on stream test. The excellent anti-coking performance of this bimetallic catalyst, confirmed by TG and FESEM analyses of spent catalyst, is closely related to the promoting effect of sonication on the metal-support interaction, Ni dispersion and particle size; and probably, the synergy between metallic species.     

Characterization and applications of Ag nanoparticles in waveguides

This work reports the preparation, characterization and applications of silver nanoparticles synthesized through the chemical reduction of AgNO₃ and protected by surface modifier. In order to characterize the formation of nanoparticles and the role of synthesis parameters (time, temperature) several studies were made, such as UV-vis spectroscopy, TEM and AFM. We present the incorporation of Ag nanoparticles in sol-gel obtained matrix, because this technique allows the incorporation of larger concentrations of active optical agents and the obtainment of full-dense films at lower temperature than those possible by other methods. The final goal of this work is the preparation of 80SiO₂·20B₂O₃ films for active optical waveguides doped with Ag nanoparticles and Erbium. We are looking for the reinforcement of the fluorescence intensity due to the effect of the resonant coupling of both optical agents (Er and nanoparticles) to produce optical amplifiers.     

Synthesis of rod and lath-shaped CuSe and tremella-shaped Cu<Subscript>2−<Emphasis Type="Italic">x</Emphasis></Subscript>Se nanostructures at room temperature,and their optical properties

The research for tunable synthesis and characterization techniques is important for the investigation of nanomaterials. Herein we developed old precipitation reaction for the morphology- and phase-tunable synthesis of copper selenides nanostructures at room temperature, avoiding tedious preparation of selenium precursors, such as selenite or selenosulfate. The molar ratio of Cu²⁺ and Se sources served the function of a switch for selectively synthesis of stoichiometric CuSe and non-stoichiometric Cu_2−x Se. Nanorod and lath-like CuSe formed with excess of selenium source, while tremella-shaped Cu_2−x Se responded to the 1:1 of Cu²⁺/Se or excess of copper source. The structures of nanocrystals, especially the lifelike surface, were characterized in detail by electron microscopy techniques, such as STEM. Novel nanostructures put up the excellent absorption properties in the visible light region, respectively, and could bear potential applications in solar cell devices in the future. This strategy offered a convenient, mild and energy-efficient route for the preparation of other mental chalcogenides nanocrystals with different morphologies or tunable phases.     

Synthesis of RGO/Cu8S5/PPy Composite Nanosheets with Enhanced Peroxidase‐Like Activity for Sensitive Colorimetric Detection of H2O2 and Phenol

In this paper, a novel strategy for the fabrication of reduced graphene oxide (rGO)/Cu₈S₅/polypyrrole (PPy) composite nanosheets with Cu₈S₅ nanoparticles and PPy layer anchored on the surface of rGO as peroxidase‐like nanocatalyst is reported. During the synthesis, graphene oxide (GO)/CuO composite nanosheets are prepared first and used as templates, then the sulfuration of CuO and polymerization of pyrrole are accompanied with the reduction of GO, resulting in ternary rGO/Cu₈S₅/PPy composite nanosheets. The synthesized Cu₈S₅ nanoparticles with a diameter in the range from tens to hundreds of nanometers are dispersed within PPy decorated rGO nanosheets. The resultant ternary rGO/Cu₈S₅/PPy composite nanosheets exhibit a higher peroxidase‐like catalytic activity toward the oxidation of 3,3′,5,5′‐tetramethylbenzidine in the presence of H₂O₂ than GO/CuO and rGO/CuS composite nanosheets, revealing a synergistic effect on their activity. The as‐prepared rGO/Cu₈S₅/PPy platform provides a simple colorimetric approach for the detection of H₂O₂ and phenol with a high sensitivity. This work offers a new way for the fabrication of rGO‐based nanocomposite with superior enzyme‐like activity, which displays great potential applications in biocatalysis and environmental monitoring.     

Ultrasonic assisted synergetic green synthesis of polycyclic imidazo(thiazolo)pyrimidines by using Fe3O4@clay core-shell

A practical and green approach for the ultrasound-enhanced one-pot multicomponent synthesis of tetraheterocyclic imidazo(thiazolo)pyrimidines is described via the condensation of an 2-aminobenzimidazole or 2-aminobenzothiazole, dimedone and various aldehydes in the presence of Fe₃O₄@clay as an environmentally benign and reusable core/shell nanocomposite catalyst in relatively quantitative yields. This novel eco-friendly protocol includes several advantages such as avoiding hazardous solvents, reusability of the catalyst, easy work-up, short reaction times, room temperature and mild reaction conditions. Furthermore, ultrasonic irradiation and synergistic catalyst showed considerable superiority vs. traditional heating or stirring conditions.     

A high-voltage lithium-ion battery prepared using a Sn-decorated reduced graphene oxide anode and a LiNi<Subscript>0.5</Subscript>Mn<Subscript>1.5</Subscript>O<Subscript>4</Subscript> cathode

This paper describes the preparation and characterization of a high-voltage lithium-ion battery based on Sn-decorated reduced graphene oxide and LiNi_0.5Mn_1.5O₄ as the anode and cathode active materials, respectively. The Sn-decorated reduced graphene oxide is prepared using a microwave-assisted hydrothermal synthesis method followed by reduction at high temperature of a mixture of (C₆H₅)₂SnCl₂ and graphene oxide. The so-obtained anode material is characterized by thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, and electron diffraction spectroscopy. The LiNi_0.5Mn_1.5O₄ is a commercially available product. The two materials are used to prepare composite electrodes, and their electrochemical properties are investigated by galvanostatic charge/discharge cycles at various current densities in lithium cells. The electrodes are then used to assemble a high-voltage lithium-ion cell, and the cell is tested to evaluate its performance as a function of discharge rate and cycle number.     

Role of precursor alloy phases and intermediate oxides in the preparation of Raney and Urushibara iron

⁵⁷Fe Mössbauer spectroscopy and scanning electron microscopy measurements of precursor phases formed during catalyst preparation and of the catalysts, themselves, demonstrate that the preparation of Raney iron from iron aluminum alloys involves the formation of Fe(OH)₂ and Fe₃O₄ as intermediate phases. The metallic Fe is formed from subsequent reduction of Fe₃O₄ by hydrogen generated by the oxidation of aluminum metal by hydroxide ions. Precursors to Urushibara iron U?Fe (III) are found to consist of Fe?Zn alloys when Zn is used as a reductant and of epitaxial deposits of Fe on aluminum when Al is the reductant. The material resulting from the reduction of the iron salt by aluminum is not a hydrogenation catalyst; the absence of catalytic activity is related to the absence of any alloying of the iron and aluminum. A consideration of the preparation of Raney iron, Urushibara iron, ammonia synthesis and Fischer-Tropsch catalysts leads to the conclusions that catalytic activity is highly correlated to the existence of intermediate mixed-crystals phases and the presence of intimate mixtures of at least two phases in the final catalyst.     

Synthesis of CuO/g-C3N4 Composite with High Anti-Interference Ability for Enhanced Fenton-Like Catalysis

The combination of semiconductors and transition metal compounds for Fenton-like application has been widely reported. However, there are still some problems that can be further studied such as the optimization of metal species and in-depth research of mechanism. In this paper, using melamine and copper acetate as raw materials, a kind of composite of copper oxide and graphitic carbon nitride (CuO/g-C₃N₄) is synthesized by a facile hydrothermal method. The synthetic conditions such as type of transition metal salt and ratio of raw material are further optimized. With the presence of H₂O₂, the CuO/g-C₃N₄ composite shows exceptional broad-spectrum Fenton-like catalytic performance against the organic dyes in aqueous solution within a wide pH range, and the highest degradation rate of organic dyes can reach 99% within 10 min. After eight times of recycling, the catalytic activity of the composite can still remain more than 85%. More importantly, the CuO/g-C₃N₄ composite presented excellent anti-interference ability toward heavy metal ions and complex pollutants. Finally, the enhanced Fenton-like catalytic mechanism is illustrated in detail.     

Preparative treatment with NaOH to selectively concentrate iron oxides of a Chilean volcanic soil?material to produce effective heterogeneous Fenton catalyst

A Chilean volcanic Ultisol material was first size-fractionated so as to obtain the fraction with mean particle sizes ??<?53 ??m. This sample was then sequentially treated three or five times with 5 mol L^???1 NaOH, in an attempt to evaluate the effectiveness of the selective chemical dissolution to concentrate iron oxides, as a preparation procedure before using the materials as heterogeneous Fenton catalysts. The effects of those treatments on the iron oxides mineralogy were monitored with Mössbauer spectroscopy. The NaOH-treated samples were tested as catalysts towards the H₂O₂ decomposition. Three or five sequential NaOH treatments were found to be comparably effective, by concentrating nearly the same proportion of iron oxides in the remaining solid phase (25.1 ± 0.4 and 23.3 ± 0.2 mass%, respectively). 298 K-Mössbauer patterns were similar for both samples, with a central (super)paramagnetic Fe^3?+? doublet and a broad sextet, assignable to several closely coexisting magnetically ordered forms of iron oxides. Despite of this nearly similar effect of the two treatments, the Ultisol material treated three times with NaOH presents higher heterogeneous catalytic efficiency and is more suitable to decompose H₂O₂ than that with five treatments.     

Ultrasound mediation for one-pot multi-component synthesis of amidoalkyl naphthols using new magnetic nanoparticles modified by ionic liquids

The ionic liquid 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium acetate was immobilized on the Fe₃O₄ nanoparticles (MNPs-IL-OAc) and used as an efficient new heterogeneous nanocatalyst for the one-pot multi-component synthesis of 1-amidoalkyl-2-naphthols under ultrasound irradiation. The advantages of present combined method are the use of a low scale catalyst, easier work-up procedure, waste-free, green and efficient synthetic entry to excellent yield of products in a high reusability and a short reaction time.     

Mössbauer study of nanodimensional nickel ferrite – mechanochemical synthesis and catalytic properties

Iron–nickel spinel oxide NiFe₂O₄ nanoparticles have been prepared by the combination of chemical precipitation and subsequent mechanical milling. For comparison, their analogue obtained by thermal synthesis is also studied. Phase composition and structural properties of iron–nickel oxides are investigated by X-ray diffraction and Mössbauer spectroscopy. Their catalytic behavior in methanol decomposition to CO and methane is tested. An influence of the preparation method on the reduction and catalytic properties of iron–nickel samples is established.     

A new molecular silver precursor for the preparation of thin conductive silver films

The synthesis and characterization of a new molecular silver precursor is reported. The presented complex [Ag(DioxoNic)₂]NO₃ (DioxoNic=(2,2-Dimethyl-1,3-dioxolan-4-yl)methyl nicotinate) can be obtained by the reaction of silver(I) nitrate and (2,2-Dimethyl-1,3-dioxolan-4-yl)methyl nicotinate in ethanol. The product crystallizes in the monoclinic space group P21/c (No. 14). Concentrated ethanolic solutions allow the fabrication of thin films via dip coating. Using UV-irradiation and subsequent moderate temperature treatment compact films of elemental silver can be obtained. The resulting silver films show excellent electrical properties with sheet resistances down to 0.7 Ω/sq at a film thickness of 25 nm corresponding to a specific electrical resistance of 1.75×10⁻⁸ Ωm very close to the value of bulk silver. For the potential application in optoelectronic devices, the complex was tested as an ink in a soft printing process for the preparation of patterned silver films.     

Ultrasound assisted co-precipitation of nanostructured CuO–ZnO–Al2O3 over HZSM-5: Effect of precursor and irradiation power on nanocatalyst properties and catalytic performance for direct syngas to DME

Nanostructured CuO–ZnO–Al₂O₃/HZSM-5 was synthesized from nitrate and acetate precursors using ultrasound assisted co-precipitation method under different irradiation powers. The CuO–ZnO–Al₂O₃/HZSM-5 nanocatalysts were characterized using XRD, FESEM, BET, FTIR and EDX Dot-mapping analyses. The results indicated precursor type and irradiation power have significant influences on phase structure, morphology, surface area and functional groups. It was observed that the acetate formulated CuO–ZnO–Al₂O₃/HZSM-5 nanocatalyst have smaller CuO crystals with better dispersion and stronger interaction between components in comparison to nitrate based nanocatalysts. Ultrasound assisted co-precipitation synthesis method resulted in nanocatalyst with more uniform morphology compared to conventional method and increasing irradiation power yields smaller particles with better dispersion and higher surface area. Additionally the crystallinity of CuO is lower at high irradiation powers leading to stronger interaction between metal oxides. The nanocatalysts performance were tested at 200–300 °C, 10–40 bar and space velocity of 18,000–36,000 cm³/g h with the inlet gas composition of H₂/CO = 2/1 in a stainless steel autoclave reactor. The acetate based nanocatalysts irradiated with higher levels of power exhibited better reactivity in terms of CO conversion and DME yield. While there is an optimal temperature for CO conversion and DME yield in direct synthesis of DME, CO conversion and DME yield both increase with the pressure increase. Furthermore ultrasound assisted co-precipitation method yields more stable CuO–ZnO–Al₂O₃/HZSM-5 nanocatalyst while conventional precipitated nanocatalyst lost their activity ca. 18% and 58% in terms of CO conversion and DME yield respectively in 24 h time on stream test.     

Solvent-free synthesis of new spiropyrroloindole compounds using Fe3O4/TiO2/MWCNTs MNCs via multicomponent reactions: assessment of new spiropyrroloindole antioxidant activity

In this study, water extract of Spinacia oleracea leaves was used for the synthesis of Fe₃O₄/TiO₂/MWCNTs magnetic nanocomposites and high performance of this catalyst was confirmed by employing it in the solvent-free multicomponent reactions of anilines, oxalyl chloride, diamines or hydroxyamines, electron-deficient acetylenic ester, α-haloketones and Et₃N at room temperature for the generation of new spiropyrroloindoles in high yields. This catalyst could be utilized several times and has a significant role in the yield of product. The synthesized spiropyrroloindoles have NH and OH group in their structure and for this reason have good antioxidant activity. Also, by employing Gram-positive and Gram-negative bacteria and the disk diffusion procedure confirmed the antimicrobial effect of some spiropyrroloindole derivatives. The results showed that synthesized spiropyrroloindoles prevented the bacterial growth. This used process for preparation of new spiropyrroloindoles has some improvements such as low reaction time, product with high yields, and simple separation of catalyst and products.

Graphical abstract

     

Synthesis of AuNPs@RGO nanosheets for sustainable catalysis toward nitrophenols reduction

A facile, green and one-pot synthesis strategy for the convenient preparation of well-dispersed gold nanoparticles (AuNPs) decorated reduced graphene oxide (RGO) without using any other toxic chemicals and reductants is reported herein. The synthesized AuNPs@RGO hybrid nanomaterials were characterized by UV–visible absorption spectroscopy, FT-IR, XRD, Raman, SEM, TEM and EDX analysis. The AuNPs@RGO acts as an efficient catalyst for the reduction of organic nitroaromatics (2- & 4-nitro phenols) in the presence of NaBH₄. This newly synthesized hybrid AuNPs@RGO has superior catalytic activity over any other Au-nanomaterials ever reported. The rate of nitro aromatics reduction is found to be dependent on concentrations of substrate, reductant and catalyst. The mechanisms for the synthesis and catalytic reduction have been studied and discussed.