Iron Oxide Nanoparticles Modified with Carbon Quantum Nanodots for the Stabilization of Palladium Nanoparticles: An Efficient Catalyst for the Suzuki Reaction in Aqueous Media under Mild Conditions

Magnetic ethylene-based periodic mesoporous organosilica supported palladium: An efficient and recoverable nanocatalyst for Suzuki reaction

In the present study, a novel magnetic ethylene-based periodic mesoporous organosilica supported Pd-Schiff base complex (Fe₃O₄@PMO/SB-Pd) was prepared, characterized and applied as a recoverable nanocatalyst for green synthesis of Suzuki products. Chemical composition, magnetic and thermal behavior, morphology and particle size of Fe₃O₄@PMO/SB-Pd were investigated by using FT-IR, TGA, EDX, VSM, PXRD, TEM and Scanning electron microscopy (SEM) analyses. The Fe₃O₄@PMO/SB-Pd nanocomposite was applied as an efficient nanocatalyst in the Suzuki reaction under ultrasonic conditions giving corresponding products in high yield. Some advantages of this study are simple purification of products, the use of water solvent, easy catalyst separation, short reaction time and high catalyst efficiency and recoverability.

N-substituted CQDs impregnated by Fe3O4 heterostructure: Bifunctional catalyst for electro-catalytic and photo-catalytic detection of an environmental hazardous organic pollutant

ortho-Nitroaniline (o-NA) compounds are deemed to be a strongly toxic pollutant in nature and potentially carcinogenic; however, they are frequently utilized to synthesize dyes, pesticides, medicines, fungicides, pigments, and other organic chemicals. Their detection in an aqueous medium is fundamentally required to avoid the potential hazardous being created by these compounds. In this study, a novel sensor based on an Iron oxide (Fe3O4) containing highly dispersed nitrogen-doped carbon quantum dots (N-CQDs@Fe3O4 NFs) was demonstrated for the electrochemical detection of o-NA using differential pulse voltammetry (DPV) and cyclic voltammetry (CV) techniques. N-CQDs@Fe3O4 NFs were synthesized by hydrothermal method and studied by various analytical and spectroscopy techniques, which collectively reveal that the as-prepared composite has superior physical and chemical properties. The DPV study indicated that the o-NA sensor had a good limit of detection, linear range, and sensitivity in the range of 1.2 nm, 0.03-386.84 μM, and 36.5575 μA μM-1 cm-2, respectively, along with the sensor showed superior sensitivity when compared to the previously reported modified electrodes. Further, N-CQD/Fe3O4 NFs worked as heterogeneous catalysts for the photocatalytic reduction of o-NA to o-phenylenediamine (o-PD) in an aqueous medium. The reaction was examined under UV-Visible spectroscopy, and the complete photocatalytic reduction was observed for the N-CQD/Fe3O4 NFs in about 6 min with 96% as compared to other control samples; thus, authenticating the superiority of the synthesized composite in rendering the real-time applications.

Sustainable synthesis of biomass-derived carbon quantum dots and their catalytic application for the assessment of α,β-unsaturated compounds

Herein, we demonstrate a simple, reproducible, and environment-friendly strategy for the synthesis of carbon quantum dots (CQDs) utilizing the mango (Mangifera indica) kernel as a renewable green carbon source. Various analytical tools characterized the as-prepared CQDs. These fluorescent CQDs showed significant water solubility with a uniform size of about 6 nm. The as-synthesized CQDs show significantly enhanced catalytic activity for the production of α,β-unsaturated compounds from the derivatives of aromatic alkynes and aldehydes under microwave irradiation in aqueous media. A potential mechanistic pathway and role of carboxylic functionalities were also revealed via various control experiments. The protocol shows outstanding selectivity towards the assessment of α,β-unsaturated compounds over other possible products. A comparative evaluation suggested the as-synthesized CQDs show higher catalytic activity under microwave radiation as compared to the conventional ways. These recyclable CQDs represent a sustainable alternative to metals in synthetic organic chemistry. A cleaner reaction profile, low catalyst loading, economic viability and recyclability of the catalyst, atom economy, and comprehensive substrate applicability are additional benefits of the current protocol according to green chemistry.

Investigating the effect of nanoparticle on phenanthrene biodegradation by Labedella gwakjiensis strain KDI

Polycyclic aromatic hydrocarbons (PAHs), as persistent organic contaminants, are a major source of concern due to their toxic effect on ecosystems and human health. This study attempted to isolate halotolerant PAHs degrading bacteria from saline oil-contaminated soils. Among the isolates, strain KDI with the highest 16S rRNA gene sequence similarity to Labedella gwakjiensis was able to reduce surface tension (ST) from 65.42 to 26.60 mN m^-1 and increase the emulsification index to 81.04%, as a result of significant biosurfactant production. Response Surface Methodology (RSM) analysis was applied to optimize the factors, i.e. PAHs concentration and NaCl concentration as well as to determine the effect of these important variables on PAHs biodegradation. The Carbon Quantum Dots. Iron Oxide (CQDs.Fe₃O₄) nanoparticles were characterized by several popular analytical techniques, after which the effect of CQD.Fe₃O₄ nanoparticles on biodegradation was examined. PAHs biodegradation rate and efficiency of strain KDI to degrade PHE in the presence of CQD.Fe₃O₄ nanoparticles was analyzed by GC. According to the results during biodegradation both the concentration of PAHs and the amount of NaCl were effective. The biodegradation rate significantly increased in the presence of CQD.Fe₃O₄. The highest biodegradation of PHE occurred in the presence of 0.5 g/L of CQD.Fe₃O₄ which was 63.63% and 81.77% after 48 and 72 h of incubation. To the best of our knowledge, this is the first report on optimization of PAHs concentration and salinity by RSM and nanobioremediation of PHE using a bacterial strain in the presence of CQD.Fe₃O₄ nanoparticles.

Synthesis, properties and catalysis of quantum dots in C–C and C-heteroatom bond formations

Luminescent quantum dots (QDs) represent a new form of carbon nanomaterials which have gained widespread attention in recent years, especially in the area of chemical sensing, bioimaging, nanomedicine, solar cells, light-emitting diode (LED), and electrocatalysis. Their extremely small size renders some unusual properties such as quantum confinement effects, good surface binding properties, high surface‐to‐volume ratios, broad and intense absorption spectra in the visible region, optical and electronic properties different from those of bulk materials. Apart from, during the past few years, QDs offer new and versatile ways to serve as photocatalysts in organic synthesis. Quantum dots (QD) have band gaps that could be nicely controlled by a number of factors in a complicated way, mentioned in the article. Processing, structure, properties and applications are also reviewed for semiconducting quantum dots. Overall, this review aims to summarize the recent innovative applications of QD or its modified nanohybrid as efficient, robust, photoassisted redox catalysts in C–C and C-heteroatom bond forming reactions. The recent structural modifications of QD or its core structure in the development of new synthetic methodologies are also highlighted. Following a primer on the structure, properties, and bio-functionalization of QDs, herein selected examples of QD as a recoverable sustainable nanocatalyst in various green media are embodied for future reference.

Magneto-Luminescent Nanocomposites Based on Carbon Dots and Ferrite with Potential for Bioapplication

Multifunctional nanocomposites that combine both magnetic and photoluminescent (PL) properties provide significant advantages for nanomedical applications. In this work, a one-stage synthesis of magneto-luminescent nanocomposites (MLNC) with subsequent stabilization is proposed. Microwave synthesis of magnetic carbon dots (M-CDs) was carried out using precursors of carbon dots and magnetic nanoparticles. The effect of stabilization on the morphological and optical properties of nanocomposites has been evaluated. Both types of nanocomposites demonstrate magnetic and PL properties simultaneously. The resulting MLNCs demonstrated excellent solubility in water, tunable PL with a quantum yield of up to 28%, high photostability, and good cytocompatibility. Meanwhile, confocal fluorescence imaging showed that M-CDs were localized in the cell nuclei. Consequently, the multifunctional nanocomposites M-CDs are promising candidates for bioimaging and therapy.

Green Synthesis of Pd Nanoparticles for Sustainable and Environmentally Benign Processes

Among transition metal nanoparticles, palladium nanoparticles (PdNPs) are recognized for their high catalytic activity in a wide range of organic transformations that are of academic and industrial importance. The increased interest in environmental issues has led to the development of various green approaches for the preparation of efficient, low-cost and environmentally sustainable Pd-nanocatalysts. Environmentally friendly solvents, non-toxic reducing reagents, biodegradable capping and stabilizing agents and energy-efficient synthetic methods are the main aspects that have been taken into account for the production of Pd nanoparticles in a green approach. This review provides an overview of the fundamental approaches used for the green synthesis of PdNPs and their catalytic application in sustainable processes as cross-coupling reactions and reductions with particular attention afforded to the recovery and reuse of the palladium nanocatalyst, from 2015 to the present.

Phosphotungstic acid impregnated niobium coated superparamagnetic iron oxide nanoparticles as recyclable catalyst for selective isomerization of terpenes

Conversion efficiency as high as 80-100% and 50% selectivity for camphene and limonene was achieved with low production of polymeric byproducts (18-28%), easy recovery with a magnet and reuse for up to five cycles maintaining similar activity and distribution of products, using a new magnetically recyclable catalyst based on niobium oxide coated on superparamagnetic iron oxide nanoparticles (SPION) impregnated with phosphotungstic acid (HPW). The catalyst was demonstrated to be effective in the selective conversion of alpha and beta-pinenes into valuable terpenes, under ultrasonic probe activation and with toluene as solvent. A unique synergic effect between the components generating more active and selective catalytic sites was demonstrated, indicating that the SPION covered with 30 wt% of Nb2O5 gives the best performance when impregnated with HPW as co-catalyst. The materials were fully characterized by XRD, EDX, XPS, TEM, BET, VSM and FTIR.

The Use of Carbon Quantum Dot as Alternative of Stannous Chloride Application in Radiopharmaceutical Kits

Even today, technetium-99m is a radionuclide choice for diagnostic in nuclear medicine. The unique chemical and physical properties of technetium-99m make it suitable as an available radionuclide in many centers. In this study, we examined the potential of CQD as a reducing agent in the MDP kit. Citric acid-derived CQD was synthesized and confirmed by FT-IR, TEM, UV-Vis, XPS, and surface analysis. No cytotoxicity was observed by the MTT assay. They were reducing properties of the CQD confirmed by fluorescence microscopy. The MDP kit is prepared by evaluating different parameters that affect the radiolabeling yield, including ligand, time, and CQD. The optimum amount of each parameter is obtained by Box–Behnken software. Finally, fluorescent spectroscopy, SPECT imaging, and biodistribution study showed that CQD reduces technetium-99m. Accumulation of radiotracer in the femur showed that CQD could be used in a radiopharmaceutical kit.

Pd Catalyst Based on Hyperbranched Polypyridylphenylene Formed In Situ on Magnetic Silica Allows for Excellent Performance in Suzuki-Miyaura Reaction

Here, for the first time, we developed a catalytic composite by forming a thin layer of a cross-linked hyperbranched pyridylphenylene polymer (PPP) on the surface of mesoporous magnetic silica (Fe₃O₄-SiO₂, MS) followed by complexation with Pd species. The interaction of Pd acetate (PdAc) with pyridine units of the polymer results in the formation of Pd²⁺ complexes which are evenly distributed through the PPP layer. The MS-PPP-PdAc catalyst was tested in the Suzuki-Miyaura cross-coupling reaction with four different para-Br-substituted arenes, demonstrating enhanced catalytic properties for substrates containing electron withdrawing groups, and especially, for 4-bromobenzaldehyde. In this case, 100% selectivity and conversion were achieved with TOF of >23 000 h^-1 at a very low Pd loading (0.032 mol %), a remarkable performance in this reaction. We believe these exceptional catalytic properties are due to the hyperbranched polymer architecture, which allows excellent stabilization of catalytic species as well as a favorable space for reacting molecules. Additionally, the magnetic character of the support allows for easy magnetic separation during the catalyst synthesis, purification, and reuse, resulting in energy and materials savings. These factors and excellent reusability of MS-PPP-PdAc in five consecutive uses make this catalyst promising for a variety of catalytic reactions.

One-Pot Magnetic Iron Oxide-Carbon Nanodot Composite-Catalyzed Cyclooxidative Aqueous Tandem Synthesis of Quinazolinones in the Presence of tert-Butyl Hydroperoxide

The development of synthetic protocols for biologically important molecules using biocompatible catalysts in aqueous medium holds the key in green and sustainable chemistry. Herein, a magnetically recoverable iron oxide-carbon dot nanocomposite has been demonstrated as an effective catalyst for cyclooxidative tandem synthesis of quinazolinones in aqueous medium using alcohols as starting materials. Fluorescent carbon dots, the newest entrant in the nanocarbon family, were used as the stabilizing agent for the iron oxide nanoparticles, and a continuous layer of carbon dots decorates the iron oxide nanoparticle surface as observed by transmission electron microscopy. The fluorescence studies demonstrated the effective electron transfer from carbon dots to the iron oxide nanoparticles resulting in complete quenching of emission owing to carbon dots, once it binds with iron oxide nanoparticles. The nanocatalyst showed high activity with significant reusability for the syntheses of quinazolinones in the presence of tert-butyl hydroperoxide (TBHP) in an aqueous medium. Controlled experiments revealed the synergistic effect of carbon dots in enhancing the catalytic activity of iron oxide, as they might influence the decomposition of TBHP into radicals owing to their peroxidase activity. These radicals stabilized over the nanoparticle surface are known to have increased lifetime compared to solution-based radicals. These surface-stabilized radicals then could catalyze the tandem reaction resulting in the formation of the quinazolinone derivatives in high yields.

Photo-Assisted Synthesis of a Pd-Ag@CQD Nanohybrid and Its Catalytic Efficiency in Promoting the Suzuki-Miyaura Cross-Coupling Reaction under Ligand-Free and Ambient Conditions

Supported bimetallic nanoparticles are very promising heterogeneous catalysts for carbon-carbon cross-coupling reactions, though reports focusing on their synergistic activity for promoting such reactions are very limited. In the current study, bimetallic Pd-Ag hybrid nanoparticles supported on carbon quantum dots (CQDs), Pd-Ag@CQDs, were synthesized by a facile and fast UV-light-driven (365 nm) one-pot protocol for the first time to investigate such a synergistic activity. The physico-chemical structural features of the Pd-Ag@CQD nanohybrid were evaluated by UV-vis, Fourier transform infrared, X-ray diffraction, electron-dispersive X-ray, and transmission electron microscopy analyses. The nanohybrid was found to have dimensions in the range of ca. 3-5 nm. The bimetallic Pd-Ag@CQD nanohybrid was utilized as an efficient heterogeneous catalyst for promoting the Suzuki-Miyaura coupling reaction with aryl bromides and aryl chlorides under ligand-free and ambient conditions. The synergistic activity of the components of the nanohybrid induced catalytic enhancement of the cross-coupling reaction in terms of short reaction times (<1 h) and high yields (>90%). The heterogeneous character of the nanohybrid system also enabled easy separation and recyclability (up to six cycles).

Boron Nitride Nanosheet-Anchored Pd-Fe Core-Shell Nanoparticles as Highly Efficient Catalysts for Suzuki-Miyaura Coupling Reactions

Boron nitride nanosheets (BNNS) were used to anchor bimetallic Pd-Fe nanoparticles for Suzuki-Miyaura coupling catalysts. The bimetallic nanoparticles were found to be core-shell in structure, and their formation was likely facilitated by their interactions with the BNNS. The Pd-Fe/BNNS catalysts were highly effective in representative Suzuki-Miyaura reactions, with performances matching or exceeding those of the state-of-the-art methods. Specifically, the superior catalytic activities were characterized by generally shortened reaction times, minimal Pd usage, excellent reusability of the catalysts and high or nearly quantitative conversion yields in a benign solvent system without the need for any special conditions, such as ligands and surfactants or inert gas protection. The obvious advantages of the Pd-Fe/BNNS over similar catalysts based on other supports, such as reduced graphene oxide (rGO), suggest that BNNS may be developed into a versatile platform for many other important catalytic reactions.

meso-Tetrakis[4-(methoxycarbonyl)phenyl]porphyrinatopalladium(ii) supported on graphene oxide nanosheets (Pd(ii)-TMCPP-GO): synthesis and catalytic activity

In this study, meso-tetrakis[4-(methoxycarbonyl)phenyl]porphynatopalladium(ii) as a macrocyclic palladium complex was covalently grafted to the surface of graphene oxide (Pd-TMCPP-GO). The prepared catalyst was checked in Suzuki reaction.

Palladium supported on phosphinite functionalized Fe3O4 nanoparticles as a new magnetically separable catalyst for Suzuki–Miyaura coupling reactions in aqueous media

Novel phosphinite functionalized magnetic (Fe₃O₄) nanoparticles having silica nanoshells containing an imidazolium ionic liquid moiety have been successfully synthesized and used as a support and stabilizer for palladium nanoparticles.