Catalytic Activity Of Nanocomposites Research Articles

Highly operative removal of amoxicillin (AMX) from aqueous solution by MnFe2O4 nanoparticles and carboxy methyl cellulose (CMC) composite

In recent work, manganese ferrite (MnFe2O4) nanoparticles and manganese ferrite carboxy methyl cellulose (MnFe2O4/CMC) composite were synthesized using Salvadora persica extract (SPE). Characterization of green synthesized nanoparticles and composite was performed by different techniques such as FTIR, SEM, UV–visible spectroscopy, XRD, and EDX. These techniques evaluated the size, shape, composition, morphology, and crystallinity of bimetallic nanoparticles (BMNPs) and nano-composites (NCs). These techniques demonstrated the presence of oxygen with metals, 3.28 nm size of MnFe2O4 and CMC hump between the 22-26° and the spherical, cubic, and mostly irregular shape of MnFe2O4 nanoparticles and rougher surface of MnFe2O4/CMC composite. Nanoparticles and nanocomposites were utilized for the degradation of Amoxicillin (AMX). The maximum degradation of AMX occurred at optimum conditions such as adsorbent dosage (6 mg MnFe2O4, 2 mg MnFe2O4/CMC), pH (4,6) within 60 min at 5 mg/L initial AMX concentration. Results revealed that the catalytic activity of NCs (97 %) was more than BMNPs (93 %) which may be attributed to the incorporation of reduced Carboxy Methyl Cellulose (CMC). It reduced the e-hole recombination rate and enhanced the AMX degradation at ambient conditions. The nature of adsorption was illustrated by Langmuir and Freundlich models and results demonstrated that the Freundlich model followed more closely. Thermodynamics parameters described the endothermic and spontaneous nature of the adsorption process, negative Gibbs energy variation, and positive entropy and enthalpy change. The recovery and reusability of BMNPs and NCs were investigated and concluded that MnFe2O4 and NCs can be used many times for the AMX adsorption process.

Thermo‐sensitive ionic hydrogels synthesis via post quaternization cross‐linking: A highly efficient reusable catalytic thermo‐responsive nanoreactors

Radical polymerization reactions were employed to synthesize thermo‐responsive poly(N‐isopropylacrylamide‐co‐1‐vinylimidazole), p (NIPAM‐co‐VIm), hydrogels at room temperature. A postquaternized cross‐linking strategy was reported to fabricate thermo‐sensitive quaternized‐p (NIPAM‐co‐VIm) ionic hydrogels, Q‐p (NIPAm‐co‐VIm). Combination of methods (high‐resolution X‐ray photoelectron spectroscopy, dynamic light scattering, and atomic absorption spectroscopy) was employed to characterize the composite material. Following the concept of a “green chemistry,” the oxidation of alcohols/olefins was carried out in aqueous solution by using nanocomposites, p (NIPAM‐co‐VIm) and Q‐p (NIPAM‐co‐VIm). It was found that the catalytic activity of the metal nanocomposite can be modulated by the lower critical solution temperature (LCST) of particles. The catalyst showed improved catalytic activity above LCST. Quaternized composites showed higher catalytic activity than unquaternized counterparts, due to their high hydrophobicity, effective interactions between substrates and catalyst, and high flexibility. In addition, we demonstrated that the catalytic activity of the nanocomposites can be tuned by the volume phase transition within the hydrogel by using the catalytic reduction of 4‐nitrophenol/nitrobenzene, NP/NB, as the hydrophilic/hydrophobic substrates model. For 4‐NP, with an increase in temperature from 25°C to 35°C (<LCST), the apparent rate constant values had a downward trend. On the contrary, for NB, this value had an upward trend. These results revealed that different changes in rate constant for 4‐NP and NB with temperature should be attributed to significant differences in NP/NB affinity to interact with Ag‐NPs in the hydrogel. Moreover, the catalysts could efficiently be recycled four times without losing their quality. FT‐IR spectra and atomic absorption spectroscopy also proved that the catalysts were recyclable, durable, and leaching‐resistant.

Green synthesis of bentonite/cellulose@lead oxide bio-nanocomposite with assistance of Pistacia Atlantica extract for efficient photocatalytic degradation of ciprofloxacin

In this study, a novel bentonite/cellulose@lead oxide (BT-CL-PbO) bio-nanocomposite was synthesized via a green route. For this proposal, the extracted cellulose from barley waste and natural bentonite were bonded together by covalent bonding, and finally the biosynthesized lead oxide nanoparticles were immobilized on them. Then, due to the destructive impacts of antibiotic contaminants on the environment and ecosystem, the catalytic activity of nanocomposite was investigated for the photodegradation of ciprofloxacin. The BT-CL-PbO exhibited excellent catalytic activity over CIP degradation under sunlight. Effect of initial pH, ciprofloxacin concentration, BT-CL-PbO dosage, and the existence of anions on photocatalytic activity was studied. The photodegradation process of CIP fitted the pseudo-first-order kinetic model, and the rate constants in the presence of BT-CL-PbO reached 0.1309 min−1, which was about 2.3 times higher than that of bare PbO nanoparticles. The scavenging experiments confirmed that photoexcited holes (h+) played the prominent role in the photodegradation of CIP. The BT-CL-PbO showed high stability and reusability after three cycles of photodegradation. The obtained results found that the BT-CL-PbO is a cost-effective and recyclable photocatalyst for the photodegradation of CIP and can be used for the treatment of other pharmaceutical contaminants.

An efficient chemiluminescence system based on mimic CuMOF/Co3O4 nanoparticles composite for the measurement of glucose and cholesterol

The development of novel non-enzyme mimics for (bio)sensing applications is of great practical importance. Herein, an efficient chemiluminescence (CL) system is presented according to the significant mimetic behavior of the copper metal-organic framework decorated with cobalt oxide nanoparticles (Co3O4@CuMOF). The catalytic activity of nanocomposite was proved by its strengthening effect on the CL emission of rhodamine B (RB)-hydrogen peroxide (H2O2) reaction. More documents were also obtained using colorimetric and fluorometric peroxidase substrates. The presence of Cu and Co in the Co3O4@CuMOF structure, as well as the high porosity and great surface area of the obtained composite, was responsible for the observed synergetic catalytic activity. The Michaelis-Menten constant (Km) for the composite (0.108 mM) was remarkably lower than that of pristine CuMOF and Co3O4 NPs, illustrating its superior affinity towards H2O2. A linear correlation was found between the CL intensity and H2O2 concentration in the extensive range of 1–250 nM, with a detection limit (3S) of 0.244 nM. Furthermore, the developed system was exploited as a reliable sensing device for individual measurement of cholesterol and glucose after their enzymatic oxidations. The obtained data verified the high sensitivity and selectivity of the probe, which could be linked to the presence of high-performance Co3O4@CuMOF and the accompanying enzymes, respectively. The designed method was appropriately applied to measure cholesterol and glucose levels in human serum samples, and its accuracy was validated by analyzing the standard materials.

Modified ultradispersed diamonds based catalytic systems in cross-coupling reactions

Methods for preparation of nanocomposites of modified detonation nanodiamonds (DND) with metallic palladium have been developed and their catalytic activity in the Suzuki-Miyaura cross-coupling reaction in various reaction media has been studied. Methods for the regeneration of palladium-containing nanocomposites from the reaction mixture have been developed. The high catalytic activity of nanocomposites is confirmed by kinetic analysis based on the results of chromatographic analysis of the reaction mixture and is comparable to the literature data about similar catalytic systems. Regenerated nanocomposites showed the retention of catalytic activity for 3 consecutive cross-coupling cycles on model systems.

Palladium nanoparticlesin situsynthesized onCyclea barbatapectin as a heterogeneous catalyst for Heck coupling in water, the reduction of nitrophenols and alkynes

This study develops an effective method forin situsynthesis of PdNPs usingCyclea barbatapectin as green reducing and stabilizing reagent. The catalytic activity of nanocomposite was evaluated for Heck coupling reaction, reduction of nitrophenols and reduction of alkynes.

Efficient solar heterogeneous photocatalytic degradation of metronidazole using heterojunction semiconductors hybrid nanocomposite, layered double hydroxides.

This study focuses on the synthesis of various nanocomposites with heterojunction structures, MgAl-LDH (LDH = layered double hydroxides) hybrid with semiconductor such as MoO3 and CuO. These solids were synthesized by co-precipitation method at constant pH and have been characterized extensively using atomic absorption spectroscopy (AAS), X-ray diffraction (XRD), Fourier transform infrared (FTIR) and transmission electron microscopy-energy dispersive X-ray (TEM-EDX) methods. The catalytic activity of nanocomposites was tested in the photocatalytic degradation under solar irradiation of emerging pollutants as the pharmaceutical metronidazole (MNZ). The experimental parameters, including initial MNZ concentration, the nature of oxide incorporate in the photocatalyst, catalyst loading were explored. All the synthesized samples showed high photocatalytic performances; the highest photocatalysis efficiency was achieved with the photocatalyst dose 1.5 g/L and initial MNZ concentration of 10 mg/L at neutral pH. The photocatalytic experimental results were fitted very well to the Langmuir-Hinshelwood model. From the obtained results the calcined LDH/semiconductors could be efficient for the photocatalytic process under solar irradiation of pharmaceuticals and may contribute in environmental remediation.

Ethanol dehydration over Keggin type tungstophosphoric acid and its potassium salts supported on carbon

The current study reports the synthesis, characterization and catalytic activity of tungstophosphoric acid (HPW) and its potassium salts (KH2PW and K3PW) supported on activated carbon (AC). Because potassium salts of tungstophosphoric acid are insoluble, the carbon supported KH2PW and K3PW were prepared by a two step impregnation method. The synthesized catalysts were characterized by various physicochemical methods such as Fourier transform infrared and Raman spectroscopy, differential thermal analysis, thermogravimetric analysis, X-ray diffraction, scanning electron microscopy and nitrogen physisorption. It is observed that all active phases keep their Keggin-type structure after being supported on AC, while their specific surface area is considerably increased by deposition on this porous substrate. The results also indicated that the synthesized materials retained the morphology specific for the support as well as its thermal properties. The adsorption behaviour of the nanocomposites towards nicosulfuron pesticide was found to be particulary good and even slightly improved when compared to pure activated carbon. The catalytic activity of the prepared catalysts was probed for the vapor phase dehydration of ethanol at 300 °C. The conversion of ethanol and selectivity toward ethylene and diethyl ether of nanocomposites were compared with the values of bare HPW, KH2PW and K3PW. Results revealed that catalytic activity depends on the catalyst type and active phase loading. The conversion over unsupported catalysts decreased by increasing the cation content per Keggin unit. The nanocomposites with 30 wt% loading of HPW achieved the best conversion of nearly 100% and the highest and stable selectivity toward ethylene. The catalytic activity of nanocomposites with acidic KH2PW showed lower catalytic activity of about 70%, while the nanocomposites of neutral K3PW and AC showed negligible activity.

Polydopamine-graphene/Ag–Pd nanocomposite as sustainable catalyst for reduction of nitrophenol compounds and dyes in environment

In this work, for the first time a new nanocomposite Ag–Pd-PDA/rGO was prepared in order to lower the consumption of palladium and to increase the catalytic activity of Pd with synergic effect. The prepared nanocomposite (Ag–Pd-PDA/rGO) was characterized using several analytical techniques such as FT-IR, XRD, TEM, SEM, EDX map, and BET. The effect of PDA and molar ratio of bimetal were investigated in morphology, size and catalytic activity of nanocomposite. The SEM and TEM showed that surface of PDA/rGO was decorated with Ag–Pd nanoparticles with cluster form in average diameter of 60 nm. The prepared nanocomposite was used as a new catalyst for reduction of nitro aromatic compounds such as 4-nitrophenol (4-NP) to 4-aminophenil (4-AP) and reduction of anionic and cationic dyes at 25 °C. Fortunately, the obtained results showed that the catalytic activity of Ag–Pd-PDA/rGO has been increased about 10 times in comparison to the Ag–Pd/rGO. The apparent kinetics of reduction has pseudo-first-order kinetics and the rate constant and TOF value was found to be 5.4×10−3 and 84741 h−1, respectively. The obtained catalyst showed high stability, leading to substrate conversion 98% after 5 cycles which supports the promising reduction of 4-NP.

Nanocatalysts of Palladium on Combined Matrices-Supports for Portable Sources of Electric Current

Palladium nanocomposites on combined supporting matrices (Nafion–carbon nanotubes (CNT)) are synthesized. The functional characteristics of the materials are studied by the methods of cyclic voltammetry and atomic force microscopy. The physicochemical characteristics of palladium/Nafion–CNT nanocomposites obtained by chemical reduction using anionic and nonionic surfactants are compared. Nanocatalysts formed showed high activity in the oxidation of formic acid. The effect of preparation conditions on the catalytic activity of nanocomposites is shown.

Highly efficient catalytic reduction and electrochemical sensing of hazardous 4-nitrophenol using chitosan/rGO/palladium nanocomposite

Designing and developing new catalytic materials is important in industrial and practical applications. Polysaccharide supported nanocomposites have gained increased attention due to the urgent need of non-toxic, environmental friendly and highly effective catalyst. Novel cross linked chitosan/rGO/palladium nanocomposites with different weight percentages of graphene and palladium were synthesized via simple and cost effective chemical reduction method. Electrostatic interaction between opposite charged groups of chitosan and palladium was analysed using FTIR and Raman spectroscopy. A mechanism for incorporation of palladium into the chitosan supported reduced graphene oxide (rGO) is proposed. Further, chitosan/rGO/palladium nanocomposites were characterized using FESEM and HRTEM. Size of the palladium nanoparticles was assessed to be 2–3 nm. XRD pattern confirms the presence of chitosan, graphene and (111) orientated Pd nanoparticles. Optical property of composites containing different weight percentages of rGO and Pd was analyzed using UV–Vis spectroscopy. Catalytic activity of nanocomposites, CS/rGO/Pd-5%, CS/rGO/Pd-10% and CS/rGO/Pd-15% was studied using 4-nitrophenol (4-NP) as the model reactant. Turn over frequency (TOF) of the catalyst, CS/rGO/Pd-15% was calculated to be 19.8 h−1. Concentration (wt% of) dependent catalytic behavior was observed. Chitosan/rGO/palladium nanocomposites modified glassy carbon electrode (GCE) was fabricated for the electrochemical determination of 4-nitrophenol using cyclic voltammetry. Limit of detection was found to be 86 nM. Sensitivity of the electrode was found to be 0.06875 μA μM−1 cm−2. It is concluded that the performance of this catalyst is an alternative technique for the sensing of 4-nitrophenol and catalytic hydrogenation to remove the toxic pollutants.

Mussel-Inspired Polydopamine Functionalized Plasmonic Nanocomposites for Single-Particle Catalysis.

Polydopamine functionalized plasmonic nanocomposites with well-distributed catalytically active small gold nanoislands around large gold core were fabricated without using any chemical reductant or surfactant. The optical properties, surface molecular structures, and ensemble catalytic activity of the gold nanocomposites were investigated by time-of-flight secondary ion mass spectrometry and UV-vis spectroscopy, respectively. Moreover, the considerable catalytic activity of the nanocomposites toward 4-nitrophenol reduction was real time monitored by dark-field spectroscopy techniques at the single-nanoparticle level avoiding averaging effects in bulk systems. According to the obtained plasmonic signals from individual nanocomposites, the electron charging and discharging rates for these nanocomposites during the catalytic process were calculated. Our results offer new insights into the design and synthesis of plasmonic nanocomposites for future catalytic applications as well as a further mechanistic understanding of the electron transfer during the catalytic process at the single-nanoparticle level.

Synthesis and characterization of new nanocomposite CTAB-PTA@CS as an efficient heterogeneous catalyst for oxidative desulphurization of gasoline

In order to obtain the clean gasoline fuel, a new nanocomposite, CTAB-PTA@CS has been introduced as an efficient and green catalyst for oxidative desulphurization (ODS) process. The nanocomposite was successfully prepared by reaction of cetyltrimethylammonium bromide (CTAB), phosphotungstic acid (PTA), and chitosan (CS) at room temperature under sonication condition. The organic-inorganic hybrid characterized by FT-IR, UV–vis, XRD, and SEM techniques. The catalytic activity of nanocomposite was tested on real gasoline fuel in the presence of CH3COOH/H2O2 in the volume ratio of 1/2 as oxidant system. Additionally, the results are compared with that oxidation process of prepared model sulphur compounds (MSCs) at the same conditions. After one hour, the results were shown that the removal of mercaptans and total sulphur content could be reduced to 98% and 95% at the temperature of 35°C. The main factors affecting the desulphurization efficiency, including catalyst dosage and temperature were investigated in detail. In addition, the kinetic parameters of oxidation of MSCs, reaction mechanism, and reusability of catalyst were discussed. This system provides an environmentally friendly, feasible and new catalytic method for the production of low-sulphur gasoline fuel.

Synthesis and catalytic activity of platinum/porous silicon nanocomposites

Physicochemical characteristics of the functional electrode nanocomposites based on porous silicon with platinum nanoparticles were investigated with the use of electron microscopy, X-ray diffraction, and cyclic voltammetry. It is established that a decrease in the platinum nanoparticle size leads to an increase in catalytic activity of nanocomposites in the reactions of electrocatalytic oxygen reduction and hydrogen oxidation.

Synthesis of catalytic systems based on nanocomposites containing palladium and hydroxycarbonates of rare-earth elements

The preparation, characterization, and catalytic activity of nanocomposites containing palladium nanoparticles supported on yttrium and cerium hydroxycarbonates in the Suzuki cross-coupling reaction between phenylboronic acid and iodobenzene are described. All catalytic systems were characterized by means of SEM, EDS, and their surface areas were determined with N2 physisorption. The conversion degree of the Suzuki reaction was characterized with gas chromatography, and the reaction products were identified with 1H and 13C{1H}–NMR spectra. Nanocomposites Pd/Y(OH)CO3 and Pd/Ce(OH)CO3 were synthesized according to two methods: the first one—simultaneous production of nanoscale substrate and immobilization of palladium nanoparticles on its surface (nanocomposites 1), the second one—the prior synthesis of polyvinylpyrrolidone stabilized palladium nanoparticles followed by their immobilization on the nano-sized substrate surface (nanocomposites 2). Both groups of catalysts showed high catalytic activity with the highest TOF values 8.5 × 103 h–1 for nanocomposites 1 and 78.9 × 103 h–1 for nanocomposites 2 allowing to decrease the palladium content in the nanocomposites and, consequently, reduce the cost of the catalyst while maintaining its high catalytic activity.

Fabrication and characterization of Fe3O4@APTES@PAMAM-Ag highly active and recyclable magnetic nanocatalyst: Catalytic reduction of 4-nitrophenol

The surface of amine-fuctionalized magnetic nanoparticle was coated with polyamidoamine dendrimer via of alkylation of amine groups with methyl acrylate (Micheal addition route). Then silver nanoparticles were doped between the layers of dendrimer branches. The as-prepared nanocomposite is composed of a central magnetite core with a strong response to external fields, an interlayer of SiO2, polyamidoamine dendrimer (G1) and numerous highly dispersed Ag nanoparticles with a narrow size distribution. The crystallite size from XRD (9±2nm) and particle size from TEM analysis (11.6±0.2nm) are consistent with each other. The catalytic activity of nanocomposite was tested against 4-nitrophenol. It has well magnetic separability and excellent reusability without major loss and activity (it can be conveniently recycled from the reaction system by using a magnet) and no deactivation has been observed after at least 5 cycles of reaction.

Synthesis of graphene-based Co-B catalyst via simultaneous chemical reduction for hydrolysis of sodium borohydride

Co-B nanoparticles are deposited on graphene sheets by simultaneous chemical reduction of Co+2 and graphite oxides using NaBH4 as the reducing agent. The reduced Co−B/graphene nanocomposites were characterized by X-ray diffraction, Fourier transform infrared spectra, X-ray photoelectron spectroscopy, and thermogravimetric analysis. The results show that after reduction, not only considerable amount of functional groups has been removed but also exhibited formation of Co-B alloy on the graphene sheets. The catalytic activity of nanocomposites was investigated by the hydrolysis of NaBH4 in aqueous solution. Graphene support material greatly enhances the hydrolysis of NaBH4 with respect to graphite and active carbon supports, and chemical reduced graphene sheets can readily form stable aqueous colloids through electrostatic stabilization. The present method is promising for the synthesis of effective supported catalysts for hydrolysis of NaBH4.

Comparative study on oxidation desulphurization of actual gas oil and model sulfur compounds with hydrogen peroxide promoted by formic acid: Synthesis and characterization of vanadium containing polyoxometalate supported on anatase crushed nanoleaf

H7SiV3W9O40-TiO2 nanocomposite has been synthesized by reaction of Na10[α-SiW9O34] with sodium vanadate and then condensation with titanium tetraisopropoxide at 100°C via sol–gel method under oil-bath condition. The materials are characterized by IR, XRD, TEM and UV–vis techniques. TEM images depict that the crushed nanoleaf of anatase phase is 20nm in nature and fixing of H7SiV3W9O40 decreases its size. Indeed, the nanoparticles of H7SiV3W9O40-TiO2 are small with a size of about 10nm. The oxidative desulfurization (ODS) of several sulfur compounds with a mixture of hydrogen peroxide and formic acid was studied. On the other hand, catalytic activity of nanocomposite was tested on oxidative desulfurization of actual gas oil and results are compared with that of model sulfur compounds. This Keggin-type supported catalyst was shown to be able to have oxidative desulfurization of model sulfur compounds and actual gas oil with high yield. The addition of formic acid enhanced the conversion. This system provides an efficient, convenient and practical method for scavenging sulfur compound.