Green Oxidant Research Articles

A Green Oxidation Process of p-Xylene to Terephthalic Acid through the UV Irradiation-Enhanced Ozonation Process

A Green Oxidation Process of <i>p</i>-Xylene to Terephthalic Acid through the UV Irradiation-Enhanced Ozonation Process

One-Pot Synthesis Green Zinc Oxide Nanoparticles immobilized on Activated Carbon derived from Pineapple Peel for Adsorption of Pb(II)

One-Pot Synthesis Green Zinc Oxide Nanoparticles immobilized on Activated Carbon derived from Pineapple Peel for Adsorption of Pb(II)

A study on the oxidative property using thermogravimetric analysis of NiO nanoparticles prepared by a simple wet chemical method

Nanosized NiO particles were synthesised by chemical co-precipitation technique and the particle has been characterized morphologically, elementally, structurally and thermally using High Resolution Scanning Electron Microscopy (HR-SEM), Energy Dispersive X-ray Spectroscopy (EDAX), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD) and Thermogravimetric Analysis (TGA). A green precipitated Nickel Oxide Nanoparticles (NiO NPs) was prepared and the size of the particle was found to be 45 nm and the presence of Ni and O elements were confirmed using the elemental analytic tools like EDX and FTIR in which the existence of water molecules was confirmed from the absorption spectrum. The generated sample's crystal structure was face-centered cubic, and Scherer's equation was used to compute its size, which was found to be 43 nm. Crystal characteristics including crystal parameters (a), interatomic distance (dh,k,l), atomic radius (r) and cell volume (Vc) were also calculated. The weight loss observed from TGA curve signifies the oxidative property of NiO NPs and there is a steady increase in the weight difference versus time difference. The calcination temperature of NiO was determined to be 700⁰C via analysis at the TGA curve's peaks. The activation energy (Ea) was determined using Coats-Redfern method by solving the slope of the graph between log[−log(1−α)T2] and 1000T. With respect to its highly effective capacity, which can be seen when treating with an increase in temperature, NiO may be used as an oxidising and reducing agent in oxidation and reduction processes.

Unleashing the power of non-edible oil seeds of Ipomoea cairica for cleaner and sustainable biodiesel production using green Molybdenum Oxide (MoO3) nano catalyst

This research aims to conduct a thorough analysis of the novel and cost-effective use of Ipomoea cairica L. seeds as a potential feedstock for green energy technologies. Ipomoea cairica L. seeds (42 % oil, 0.67 % free fatty acid content) were used as a promising source for producing sustainable biodiesel using novel green Molybdenum Oxide (MoO3) nanocatalyst. The Ipomoea cairica seeds utilized in this study serve a dual purpose: they provide feedstock for the future energy mix, and their seed shells (considered waste) are used as a starting material for synthesizing green nanocatalysts. The highest biodiesel yield of 95 % was achieved under optimal reaction conditions of 1:15 oil to methanol molar ratio, 50 °C, 120 min, and 0.4 (wt.%) catalyst loading. In order to evaluate the quality and characteristics of the resultant biodiesel and synthesized nanocatalyst, a detailed examination was conducted utilizing analytical techniques such EDX, XRD, FTIR, SEM, NMR (1H, 13C) and GC–MS analysis. The phytofabricated nanocatalyst unveils highest recyclability (up to 5 cycles), reactivity, stability and efficiency during transesterification operations. The produced biodiesel was also optimized using response surface methodology (Box-Behnken Design). When compared to conventional diesel, the biodiesel made from Ipomoea cairica L. seed oilshowed better oxidative stability and reduced viscosity, suggesting that it might be a viable replacement for conventional fuel without compromising engine performance. Moreover, using untamed, uncultivated, and non-edible seed plants to produce biodiesel presents a chance to move toward a more sustainable and environmentally friendly energy plan.

Sustainable and cost-effective edge oxidized graphite/PEDOT:PSS nanocomposites with improved electrical conductivity

Poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) is a soft and conjugated polymer whose conductive properties can be properly tuned through doping with various additives or solvents, preserving its excellent processability. In this work PEDOT:PSS was combined with a cost-effective graphite derivative named Edge Oxidized Graphite (EOG) for developing a nanocomposite with improved electrical conductivity, with respect to the pristine PEDOT:PSS, through an easy and environmentally friendly doping process. Firstly, the EOG powders, produced by a green oxidation process of graphite, were deeply characterized through Fourier transform infrared (FT-IR), Thermogravimetric (TGA), and Wide-angle X-ray scattering (WAXD) analysis, showing that this nanofiller has oxygenated functional groups on the sheet edges. The quality and the stability of the EOG dispersions within PEDOT:PSS were investigated at different carbon-filler concentrations, up to high loading of 25 %wt/V of EOG through rheological analyses, demonstrating pseudo-plastic behavior and excellent long-term stability of the inks due to the absence of inhomogeneities and aggregates over time; in fact, the same inks were tested under the same rheological conditions after 21 days, showing the same viscosity trend for all EOG concentrations (%wt/V). Transmission electron microscopy (TEM) and (Scanning Electron microscopy) SEM investigation of spin-coated samples onto glass substrates were performed to morphologically evaluate the nanocomposites and estimate the average size of the sheets, particularly the mean length of 1.2 μm and an approximated thickness of 26 nm of the EOG sheets dispersed into the polymer matrix (PEDOT:PSS) was determined, while WAXD analysis allowed to identify the average layer number of the EOG sheets, obtaining thus, a direct measurement of the EOG sheets aspect ratio equal to 45. Finally, sheet resistance tests showed that the increasing concentration of EOG leads to a significant improvement in the electrical conductivity of the nanocomposites, from 1.1 S/cm for pristine PEDOT:PSS to 21.9 S/cm for nanocomposites with the highest EOG content (25 %wt/V). This work demonstrates the successful development of nanocomposite based on PEDOT:PSS doped with carbon-based filler synthesized through a green and cost-effective process, promoting their use in the production of bio/electrochemical sensors or optoelectronic devices.

Intensifying Photocatalytic Baeyer-Villiger Oxidation of Ketones with the Introduction of Ru Metalloligands and Bimetallic Units in POM@MOF.

The synthesis of visible light-responsive and efficient photocatalysts toward green Baeyer-Villiger oxidation organic synthesis is of extraordinary significance. In this work, we have synthesized two examples of visible light responsive crystalline polyoxometalate@metal-organic framework materials Ru-NiMo and Ru-CoMo by introducing Ru metalloligands and {CdM3O12} bimetallic units (M = Ni or Co). This is the first report of metalloligand-modified polyoxometalate@metal-organic framework materials with bimetallic nodes, and the materials form a three-dimensional framework directly through coordination bonds between {CdM3O12} bimetallic units and metalloligands. In particular, Ru-NiMo can achieve efficient photocatalytic conversion of cyclohexanone to ε-caprolactone in yields as high as 95.5% under visible light excitation in the range of λ > 400 nm, achieving a turnover number and turnover frequency of 955 and 440 h-1, respectively, which are the best known photocatalysts for Baeyer-Villiger oxidation, while apparent quantum yield measured at 485 nm is 4.4%. Moreover, Ru-NiMo exhibited excellent structural stability and recyclability, producing a 90.8% yield after five cycles of recycling.

Correction to: Performance evaluation of microbial fuel cell fabricated using green nano-graphene oxide as coating anode material

Correction to: Performance evaluation of microbial fuel cell fabricated using green nano-graphene oxide as coating anode material

Green Oxidation of Amines Using Salicylic Acid Derivatives as Organocatalysts and Its Application to One-pot Synthesis of Pharmaceutical Molecules

Green Oxidation of Amines Using Salicylic Acid Derivatives as Organocatalysts and Its Application to One-pot Synthesis of Pharmaceutical Molecules

Highly efficient oxidative degradation of organic dyes by using magnetically recyclable nanocatalyst based on manganese-porphyrin

This study reports the attachment of meso-tetrakis-(4-carboxyphenyl)porphyrinato manganese(III) acetate (Mn(TCPP)OAc) to the surface of amine-functionalized iron oxide magnetic nanoparticle (Fe3O4@SiO2@NH2) by amide bonds. To characterize the structure and morphology of the prepared nanocatalyst (Fe3O4@SiO2@NH2@(Mn(TCPP)OAc)), various techniques such as FT-IR, ultraviolet–visible spectroscopy, flame atomic absorption spectroscopy, X-ray powder diffraction, scanning electron microscopy, vibration sample magnetometry and thermogravimetric analysis were applied. In the following, the catalytic efficiency of the prepared nanocatalyst were also investigated for the oxidative degradation of various organic dyes with hydrogen peroxide (as a green oxidant) in water and the effect of various parameters which may affect the catalytic efficiency were optimized. In addition, the prepared nanocatalyst showed little deactivation with time, was easily recovered by an external magnet, and could be reused at least five times with no significant loss in the activity.

Cavity-Directed Synthesis of Labile Polyoxometalates for Catalysis in Confined Spaces.

The artificial microenvironments inside coordination cages have gained significant attention for performing enzyme-like catalytic reactions by facilitating the formation of labile and complex molecules through a "ship-in-a-bottle" approach. Despite many fascinating examples, this approach remains scarcely explored in the context of synthesizing metallic clusters such as polyoxometalates (POMs). The development of innovative approaches to control and influence the speciation of POMs in aqueous solutions would greatly advance their applicability and could ultimately lead to the formation of elusive clusters that cannot be synthesized by using traditional methods. In this study, we employ host-guest stabilization within a coordination cage to enable a novel cavity-directed synthesis of labile POMs in aqueous solutions under mild conditions. The elusive Lindqvist [M6O19]2- (M=Mo or W) POMs were successfully synthesized at room temperature via the condensation of molybdate or tungstate building blocks within the confined cavity of a robust and water-soluble Pt6L4(NO3)12 coordination cage. Importantly, the encapsulation of these POMs enhances their stability in water, rendering them efficient catalysts for environmentally friendly and selective sulfoxidation reactions using H2O2 as a green oxidant in a pure aqueous medium. The approach developed in this paper offers a means to synthesize and stabilize the otherwise unstable metal-oxo clusters in water, which can broaden the scope of their applications.

Cavity‐Directed Synthesis of Labile Polyoxometalates for Catalysis in Confined Spaces

AbstractThe artificial microenvironments inside coordination cages have gained significant attention for performing enzyme‐like catalytic reactions by facilitating the formation of labile and complex molecules through a “ship‐in‐a‐bottle” approach. Despite many fascinating examples, this approach remains scarcely explored in the context of synthesizing metallic clusters such as polyoxometalates (POMs). The development of innovative approaches to control and influence the speciation of POMs in aqueous solutions would greatly advance their applicability and could ultimately lead to the formation of elusive clusters that cannot be synthesized by using traditional methods. In this study, we employ host–guest stabilization within a coordination cage to enable a novel cavity‐directed synthesis of labile POMs in aqueous solutions under mild conditions. The elusive Lindqvist [M6O19]2− (M=Mo or W) POMs were successfully synthesized at room temperature via the condensation of molybdate or tungstate building blocks within the confined cavity of a robust and water‐soluble Pt6L4(NO3)12 coordination cage. Importantly, the encapsulation of these POMs enhances their stability in water, rendering them efficient catalysts for environmentally friendly and selective sulfoxidation reactions using H2O2 as a green oxidant in a pure aqueous medium. The approach developed in this paper offers a means to synthesize and stabilize the otherwise unstable metal‐oxo clusters in water, which can broaden the scope of their applications.

Photocatalyzed Aerobic Cross-Dehydrogenative Coupling of Diarylphosphine Oxides with Alcohols and Phenols.

A photocatalytic cross-dehydrogenative coupling of diarylphosphine oxides with alcohols and phenols has been developed. Using organic dye Rose Bengal as the photocatalyst and air as the oxidant, the reaction proceeded smoothly at room temperature. Both alcohols and phenols were feasible, affording various organophosphinates in high yields. The absence of a halogenating reagent, the absence of a transition-metal catalyst, a green oxidant, and mild conditions make this strategy environmentally benign and sustainable. Mechanistic studies indicated that the reaction is enabled by the cooperation of photoredox catalysis and photosensitization.

Green redox separation and efficient extraction of vanadium and chromium from leaching solution of chrome-vanadium slag

Green separation and efficient extraction of vanadium and chromium from vanadium-chromium leaching solution are serious challenges for the utilization of chrome-vanadium slag. A green sucrose reduction-H2O2 selective oxidation route is proposed for deep separation of vanadium and chromium from vanadium-chromium leaching solution based on different redox properties. Eh-pH diagram of V-Cr-H2O system and existence forms of vanadium and chromium ions are calculated. Obvious difference of redox properties between V(V) and Cr(VI) exists in acidic environment. The dependences of selective separation on pH for reduction, temperature, m(sucrose)/m(Cr(VI)) and n(H2O2)/n(V(V)) are studied. The concentration ratio of vanadium to chromium in solution after selective separation of chromium decreases from 1.6 to 0.06. The extraction ratios of Cr2O3 and V2O5 are 96.3% and 93.8%, respectively. The redox behavior of V(V) and Cr(VI) is revealed. Cr(VI) and V(V) are reduced to Cr(Ⅲ) and V(IV) by 5-hydroxymethylfurfural, a hydrolysate of sucrose, and then V(IV) is selectively oxidized to V(V) by H2O2. Cr2O3·n(H2O) and ammonium polyvanadate obtained by hydrolysis and ammonium precipitation are calcined to Cr2O3 and V2O5, respectively. Cr2O3 with the purity of 99.4% can be used as high-quality pigment. The purity of V2O5 meets the requirements of YB/T 5304–2011 for 98 V2O5.

Cascade Electrochemical Aerobic Oxygenation of 2-Substituted Indoles and Electrochemical [5 + 3] Annulation with Amidines: Access to Eight-Membered Benzo[1,3,5]triazocin-6(5H)-ones.

The cascade electrochemical C3-selective aerobic oxygenation of 2-substituted indoles and electrochemical [5 + 3] annulation with amidines through an undivided cell galvanostatic method employing molecular oxygen and "electricity" as green oxidants was developed. This protocol provides an efficient and direct approach to eight-membered benzo[1,3,5]triazocin-6(5H)-ones. Mechanistic studies suggested that two subsequent electrochemical processes both proceeded through radical pathways.

The effects of green and chemically-synthesized copper oxide nanoparticles on the production and gene expression of morphinan alkaloids in Oriental poppy

Oriental poppy (Papaver orientale L.) belonging to the Papaveraceae family, has the capacity to synthesize a wide range of benzylisoquinoline alkaloids (BIAs). This experiment was conducted to investigate the effects of green and chemical copper oxide nanoparticles (CuO NPs) elicitors on oxidative stress and the BIAs biosynthesis pathway in the cell suspension culture of P. orientale. This research shows that both green and chemical CuO NPs at concentrations of 20 mg/L and 40 mg/L, induce oxidative stress in the cell suspension of P. orientale by increasing the production of H2O2 and the activity of antioxidant enzymes. The comparison of treatments revealed that utilizing a lower concentration of CuO NPs (20 mg/L) and extending the duration of cell suspension incubation (up to 48 h) play a more influential role in inducing the expression of the BIAs biosynthesis pathway genes (PsWRKY, TYDC, SalSyn, SalR, SalAT, T6ODM, COR and CODM) and increasing the production of morphinan alkaloids (thebaine, codeine, and morphine). The overarching results indicate that the concentration of CuO NPs and the duration of cell treatment have a more significant impact than the nature of CuO NPs in inducing oxidative stress and stimulating the expression of the BIAs pathway genes.

Assembly of Titanium‐oxo Clusters from Embonic Acid‐Modified {Ti2} Molecular Building Blocks with Efficient Sulfur‐Catalyzed Oxidation Activities

AbstractTo design and synthesize high‐nucleated titanium‐oxo clusters rationally based on molecular building blocks with potential coordination ability is still a great challenge. In this work, a family of titanium‐oxo clusters, including Ti2, Ti6, Ti12, and Ti20 clusters, have been assembled from large‐size ligand embonic acid‐modified {Ti2} molecular building blocks under solvothermal conditions. By modulating auxiliary linkers and solvent types, the {Ti2} building blocks exhibit varying degrees of polymerization to form high‐nuclear titanium‐oxo clusters. Notably, Ti20 with high nucleation, as the decamer containing {Ti2} building blocks, can act as a stable and heterogeneous catalyst to efficiently catalyze the oxidation of sulfides to sulfones and sulfoxides when using H2O2 as the green oxidant. This study provides a new approach for the design and synthesis of highly nucleated and homometallic TOCs based on {Ti2} units.

A novel approach to wound healing: Green synthetic nano-zinc oxide embedded with sodium alginate and polyvinyl alcohol hydrogels for dressings

Wound healing constitutes a formidable challenge within the healthcare system, attributable to infection risks and protracted recovery periods. The pressing need for innovative wound healing methods has spurred the urgency to develop novel approaches. This study sought to advance wound healing by introducing a novel approach employing a composite sponge dressing. The composite sponge dressing, derived from LFL-ZnO (synthesized through the green methodology utilizing Lactobacillus plantarum ZDY2013 fermentation liquid), polyvinyl alcohol (PVA), and sodium alginate (SA) via a freeze–thaw cycle and freeze-drying molding process, demonstrated notable properties. The findings elucidate the commendable swelling, moisturizing, and mechanical attributes of the SA/LFL-ZnO/PVA composite sponge dressing, characterized by a porous structure. Remarkably, the dressing incorporating LFL-ZnO exhibited substantial inhibition against both methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus aureus (S. aureus). Hemolysis and cytotoxicity tests corroborated the excellent biocompatibility of the sponge dressing. In vivo evaluation of the therapeutic efficacy of the 1 mg/mL LFL-ZnO composite dressing on scald wounds and S. aureus-infected wounds revealed its capacity to accelerate wound healing and exert pronounced antibacterial effects. Consequently, the composite sponge dressings synthesized in this study hold significant potential for application in wound treatment.

Bioinspired Stevia rebaudiana Green Zinc Oxide Nanoparticles for the Adsorptive Removal of Antibiotics from Water.

Green zinc oxide nanoparticles (ZnO NPs) synthesized using Stevia rebaudiana as a reducing agent were investigated as ecofriendly adsorbents for the removal of the antibiotics ciprofloxacin (CIP) and tetracycline (TET) from water. Green ZnO NPs were synthesized using a rapid novel approach that did not require annealing or calcination at high temperatures to produce mesoporous NPs with a size range of 37.36-71.33 nm, a specific surface area of 15.28 m2/g, and a negative surface charge of -15 mV at pH 5. The green ZnO NPs exhibited an antioxidant activity of 85.57% at 250 μg/mL and an antibacterial activity with MIC and MBC of 50 and 100 mg/mL, respectively, against both Escherichia coli and Staphylococcus aureus. The best adsorption performance was achieved using a 4 g/L dose and pH 5, yielding, respectively, 86.77 ± 0.82% removal and 27.07 ± 0.26 mg/g adsorption capacity for CIP at 10 mg/L and 67.86 ± 3.41% and 15.88 ± 0.37 mg/g for TET at 25 mg/L. The green ZnO NPs achieved 79.71% ± 0.28 and 61.55% ± 0.53 removal of 10 mg/L CIP and 25 mg/L TET, respectively, in a spiked tap water binary system of the two contaminants. Adsorption of CIP and TET occurred mainly via electrostatic interactions, whereby CIP was bound more strongly than TET by virtue of its charge and size. The synthesis and adsorption processes were evaluated by a stepwise regression statistical model to optimize their parameters. Lastly, the green ZnO NPs were regenerated and reused for 5 cycles, indicating their functionality as simple, reusable, and low-cost adsorbents for the removal of CIP and TET from wastewater, in accordance with SDGs #6 and 12 for the sustainable management of water.

Green Synthesis of Zinc Oxide Nanoparticles from Althaea officinalis Flower Extract Coated with Chitosan for Potential Healing Effects on Diabetic Wounds by Inhibiting TNF-α and IL-6/IL-1β Signaling Pathways.

Diabetes Mellitus is a multisystem chronic pandemic, wound inflammation, and healing are still major issues for diabetic patients who may suffer from ulcers, gangrene, and other wounds from uncontrolled chronic hyperglycemia. Marshmallows or Althaea officinalis (A.O.) contain bioactive compounds such as flavonoids and phenolics that support wound healing via antioxidant, anti-inflammatory, and antibacterial properties. Our study aimed to develop a combination of eco-friendly formulations of green synthesis of ZnO-NPs by Althaea officinalis extract and further incorporate them into 2% chitosan (CS) gel. First, develop eco-friendly green Zinc Oxide Nanoparticles (ZnO-NPs) and incorporate them into a 2% chitosan (CS) gel. In-vitro study performed by UV-visible spectrum analysis showed a sharp peak at 390 nm, and Energy-dispersive X-ray (EDX) spectrometry showed a peak of zinc and oxygen. Besides, Fourier transforms infrared (FTIR) was used to qualitatively validate biosynthesized ZnO-NPs, and transmission electron microscope (TEM) showed spherical nanoparticles with mean sizes of 76 nm and Zeta potential +30mV. The antibacterial potential of A.O.-ZnO-NPs-Cs was examined by the diffusion agar method against Gram-positive (Staphylococcus aureus and Bacillus subtilis) and Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa). Based on the zone of inhibition and minimal inhibitory indices (MIC). In addition, an in-silico study investigated the binding affinity of A.O. major components to the expected biological targets that may aid wound healing. Althaea Officinalis, A.O-ZnO-NPs group showed reduced downregulation of IL-6, IL-1β, and TNF-α and increased IL-10 levels compared to the control group signaling pathway expression levels confirming the improved anti-inflammatory effect of the self-assembly method. In-vivo study and histopathological analysis revealed the superiority of the nanoparticles in reducing signs of inflammation and wound incision in rat models. These biocompatible green zinc oxide nanoparticles, by using Althaea Officinalis chitosan gel ensure an excellent new therapeutic approach for quickening diabetic wound healing.

Cation Effects on the Acidic Oxygen Reduction Reaction at Carbon Surfaces.

Hydrogen peroxide (H2O2) is a widely used green oxidant. Until now, research has focused on the development of efficient catalysts for the two-electron oxygen reduction reaction (2e- ORR). However, electrolyte effects on the 2e- ORR have remained little understood. We report a significant effect of alkali metal cations (AMCs) on carbons in acidic environments. The presence of AMCs at a glassy carbon electrode shifts the half wave potential from -0.48 to -0.22 VRHE. This cation-induced enhancement effect exhibits a uniquely sensitive on/off switching behavior depending on the voltammetric protocol. Voltammetric and in situ X-ray photoemission spectroscopic evidence is presented, supporting a controlling role of the potential of zero charge of the catalytic enhancement. Density functional theory calculations associate the enhancement with stabilization of the *OOH key intermediate as a result of locally induced field effects from the AMCs. Finally, we developed a refined reaction mechanism for the H2O2 production in the presence of AMCs.