Green, Solvent-Free Mechanochemical Synthesis of Nano Ag2O/MnO2/N-Doped Graphene Nanocomposites: An Efficient Catalyst for Additive-Base-Free Aerial Oxidation of Various Kinds of Alcohols

Herein, we report a solvent-less, straightforward, and facile mechanochemical technique to synthesize nanocomposites of Ag2O nanoparticles-doped MnO2, which is further codoped with nitrogen-doped graphene (N-DG) [i.e., (X %)N-DG/MnO2-(1% Ag2O)] using physical milling of separately prepared N-DG and Ag2O NPs-MnO2 annealed at 400 °C over an eco-friendly ball-mill process. To assess the efficiency in terms of catalytic performance of the nanocomposites, selective oxidation of benzyl alcohol (BlOH) to benzaldehyde (BlCHO) is selected as a substrate model with an eco-friendly oxidizing agent (O2 molecule) and without any requirements for the addition of any harmful additives or bases. Various nanocomposites were prepared by varying the amount of N-DG in the composite, and the results obtained highlighted the function of N-DG in the catalyst system when they are compared with the catalyst MnO2-(1% Ag2O) [i.e., undoped catalyst] and MnO2-(1% Ag2O) codoped with different graphene dopants such as GRO and H-RG for alcohol oxidation transformation. The effects of various catalytic factors are systematically evaluated to optimize reaction conditions. The N-DG/MnO2-(1% Ag2O) catalyst exhibits premium specific activity (16.0 mmol/h/g) with 100% BlOH conversion and <99.9% BlCHO selectivity within a very short interval. The mechanochemically prepared N-DG-based nanocomposite displayed higher catalytic efficacy than that of the MnO2-(1% Ag2O) catalyst without the graphene dopant, which is N-DG in this study. A wide array of aromatic, heterocyclic, allylic, primary, secondary, and aliphatic alcohols have been selectively converted to respective ketones and aldehydes with full convertibility without further oxidation to acids over N-DG/MnO2-(1% Ag2O). Interestingly, it is also found that the N-DG/MnO2-(1% Ag2O) can be efficiently reused up to six times without a noteworthy decline in its effectiveness. The prepared nanocomposites were characterized using various analytical, microscopic, and spectroscopic techniques such as X-ray diffraction, thermogravimetric analysis, Fourier-transform infrared spectroscopy, Raman, field emission scanning electron microscopy, and Brunauer-Emmett-Teller.

A-site defective La2-xCuO4 perovskite-type oxides for efficient oxidation of cyclohexylbenzene

Phenol production through the oxidation of cyclohexylbenzene (CHB) and the subsequent decomposition of tertiary hydroperoxide has attracted more and more attention. In this study, defective La2-xCuO4 perovskite-type oxide catalysts with tunable A-site deficient structures and abundant surface oxygen vacancies were developed for the liquid phase oxidation of CHB to produce cyclohexylbenzene-1-hydroperoxide (CHBHP). By tuning the amount of A-site La ions in the perovskite structure, more surface oxygen vacancies and Cu+ species were formed in catalysts. The A-site-deficient La1.9CuO4 catalyst achieved significant catalytic efficiency along with a high CHBHP yield of 27.6% at 48.6% CHB conversion under reaction conditions (i.e., 120 °C and 12 h), outperforming those of other transition metal-based catalysts previously reported in the literature. A series of structural characterization methods and catalytic reactions highlighted the crucial roles of surface oxygen vacancies and metal La and Cu ions in the oxidation process. It was revealed that metal ions favored CHB adsorption and activation, while surface oxygen vacancies facilitated the creation of active adsorbed oxygen species. The present study offers an opportunity for the future design of new high-efficiency heterogeneous catalyst systems for CHB oxidation to obtain phenol.

Determination of uric acid in serum by SERS system based on VO-MnCo2O4/Ag nanozyme

The level of uric acid is crucial to human health. Octahedral oxygen vacancy MnCo₂O₄/Ag (V_O-MnCo₂O₄/Ag) nanozyme was successfully prepared by simple hydrothermal, calcination and self-reduction methods. V_O-MnCo₂O₄/Ag nanozyme is rich in Mn²⁺/Mn³⁺ and C_O²⁺/C_O³⁺ redox electron pairs, large specific surface area and oxygen vacancies. V_O-MnCo₂O₄/Ag nanozyme showed high uricase-like activity and peroxidase-like activity. At the same time, the SERS signal of the detected molecule could be significantly enhanced after the catalytic reaction of the V_O-MnCo₂O₄/Ag nanozyme. The K_m values of V_O-MnCo₂O₄/Ag nanozyme for H₂O₂ and TMB were 0.04 mM and 0.027 mM respectively. Based on the uric acid oxidase-like and peroxidase-like activities of V_O-MnCo₂O₄/Ag, we developed a label-free, sensitive, and reliable SERS uric acid detection system. The detection linear range of uric acid is 0.01 μM-1000 μM and the detection of limit is 7.8 × 10^-9 M. The results show that the sensing system has good accuracy, sensitivity, selectivity, and stability. It can be applied to the determination of samples under different conditions. This study provides profound insights into the design of enzyme-like activity regulation and SERS properties regulation of nanozymes, provides guidance for the study of reaction kinetics and catalytic mechanism of nanozymes, and has broad application prospects in the field of nanozymes and SERS sensing analysis.

Investigation of Sulfur Doping in Mn-Co Oxide Nanotubes on Surface-Enhanced Raman Scattering Properties

Doping engineering is an efficient strategy to manipulate the optoelectronic properties of metal oxides for sensing, catalysis, and energy applications. Herein, we have demonstrated the fabrication of sulfur (S)-doped Mn-Co oxides to regulate their band and surface electronic structures, which is beneficial to enhancing the charge transfer (CT) between the metal oxides and their adsorbed molecules. As expected, significantly enhanced SERS signals are achieved on S-doped Mn-Co oxide nanotubes, and the minimum detection concentration can reach as low as 10^-8 M. Furthermore, the change in the electronic structure caused by S-doping provides different microelectric fields to influence the orientation of the interaction between the probe molecules and the substrate. Additionally, the evaluation of the oxidase-like catalytic activity of the substrate proved that, with an increase in the ratio of Co²⁺/Co³⁺ content, the number of electrons on the substrate increases, which promotes the CT process and further increases the degree of CT. The nonmetallic doping route in semiconducting metal oxides can provide effective and stable SERS activity; moreover, it provides a new strategy for exploring the relationship between CT in catalysis and SERS performance of semiconductors.

Advances in Graphene/Inorganic Nanoparticle Composites for Catalytic Applications

Graphene-based nanocomposites with inorganic (metal and metal oxide) nanoparticles leads to materials with high catalytic activity for a variety of chemical transformations. Graphene and its derivatives such as graphene oxide, highly reduced graphene oxide, or nitrogen-doped graphene are excellent support materials due to their high surface area, their extended π-system, and variable functionalities for effective chemical interactions to fabricate nanocomposites. The ability to fine-tune the surface composition for desired functionalities enhances the versatility of graphene-based nanocomposites in catalysis. This review summarizes the preparation of graphene/inorganic NPs based nanocomposites and their use in catalytic applications. We discuss the large-scale synthesis of graphene-based nanomaterials. We have also highlighted the interfacial electronic communication between graphene/inorganic nanoparticles and other factors resulting in increased catalytic efficiencies.

Regio- and Stereoselective Syn-Boronation of Terminal Alkynes Catalyzed by Copper Nanospheres on Graphene Nanosheets

Evenly distributed copper nanospheres on reduced graphene oxide were prepared and showed high heterogeneous catalytic activity in converting varying terminal alkynes into (E)-β-styrene boronate esters. The excellent catalytic performance was achieved through the synergistic catalysis between Cu nanospheres and rGO. This work not only is a supplement for preparing (E)-β-styrene boronate esters but also provides a way for the rational designing of high-performance graphene-based catalysts. Meanwhile, the advancement of graphene-based nanomaterials will be motivated to promote their applications in the development of green catalytic chemistry.

Solventless Mechanochemical Fabrication of ZnO–MnCO3/N-Doped Graphene Nanocomposite: Efficacious and Recoverable Catalyst for Selective Aerobic Dehydrogenation of Alcohols under Alkali-Free Conditions

Catalytic efficacy of metal-based catalysts can be significantly enhanced by doping graphene or its derivatives in the catalytic protocol. In continuation of previous work regarding the catalytic properties of highly-reduced graphene oxide (HRG), graphene-oxide (GO) doped mixed metal oxide-based nanocomposites, herein we report a simple, straightforward and solventless mechanochemical preparation of N-doped graphene (NDG)/mixed metal oxide-based nanocomposites of ZnO–MnCO3 (i.e., ZnO–MnCO3/(X%-NDG)), wherein N-doped graphene (NDG) is employed as a dopant. The nanocomposites were prepared by physical milling of separately fabricated NDG and ZnO–MnCO3 calcined at 300 °C through eco-friendly ball mill procedure. The as-obtained samples were characterized via X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FT-IR), Raman, Field emission scanning electron microscopy (FESEM), Energy-dispersive X-ray spectroscopy (EDX) and surface area analysis techniques. To explore the effectiveness of the obtained materials, liquid-phase dehydrogenation of benzyl alcohol (BOH) to benzaldehyde (BH) was chosen as a benchmark reaction using eco-friendly oxidant (O2) without adding any harmful surfactants or additives. During the systematic investigation of reaction, it was revealed that the ZnO–MnCO3/NDG catalyst exhibited very distinct specific-activity (80 mmol/h.g) with a 100% BOH conversion and <99% selectivity towards BH in a very short time. The mechanochemically synthesized NDG-based nanocomposite showed remarkable enhancement in the catalytic performance and increased surface area compared with the catalyst without graphene (i.e., ZnO–MnCO3). Under the optimum catalytic conditions, the catalyst successfully transformed various aromatic, heterocyclic, allylic, primary, secondary and aliphatic alcohols to their respective ketones and aldehydes with high selectively and convertibility without over-oxidation to acids. In addition, the ZnO–MnCO3/NDG was also recycled up to six times with no apparent loss in its efficacy.

2G waste lignin to fuel and high value-added chemicals: Approaches, challenges and future outlook for sustainable development

Lignin is produced as a byproduct in cellulosic biorefinery as well in pulp and paper industries and has the potential for the synthesis of a variety of phenolics chemicals, biodegradable polymers, and high value-added chemicals surrogate to conventional petro-based fuels. Therefore, in this critical review, we emphasize the possible scenario for lignin isolation, transformation into value addition chemicals/materials for the economic viability of current biorefineries. Additionally, this review covers the chemical structure of lignocellulosic biomass/lignin, worldwide availability of lignin and describe various thermochemical (homogeneous/heterogeneous base/acid-catalyzed depolymerization, oxidative, hydrogenolysis etc.) and biotechnological developments for the production of bio-based low molecular weight phenolics, i.e. polyhydroxyalkanoates, vanillin, adipic acid, lipids etc. Besides, some functional chemicals applications, lignin-formaldehyde ion exchange resin, electrochemical and production of few targeted chemicals are also elaborated. Finally, we examine the challenges, opportunities and prospects way forward related to lignin valorization.

Aerobic oxidation of 5-hydroxymethylfurfural into 2,5-diformylfuran using manganese dioxide with different crystal structures: A comparative study

Aerobic oxidation of 5-Hydroxymethylfurfural (HMF) to 2,5-Diformylfuran (DFF) using O₂ gas represents a sustainable approach for valorization of lignocellulosic compounds. As manganese dioxide (MnO₂) is validated as a useful oxidation catalyst and many crystalline forms of MnO₂ exist, it is critical to explore how the crystalline structures of MnO₂ influence their physical/chemical properties, which, in turn, determine catalytic activities of MnO₂ crystals for HMF oxidation to DFF. In particular, six MnO₂ crystals, α-MnO₂, β-MnO₂, γ-MnO₂, δ-MnO₂, ε-MnO₂, and λ-MnO₂ are prepared and investigated for their catalytic activities for HMF oxidation to DFF. With different morphologies and crystalline structures, these MnO₂ crystals possess very distinct surficial chemistry, redox capabilities, and textural properties, making these MnO₂ exhibit different catalytic activities towards HMF conversion. Especially, β-MnO₂ can produce much higher DFF per surface area than other MnO₂ crystals. β-MnO₂ could achieve the highest C_HMF = 99% and Y_DFF = 97%, which are much higher than the reported values in literature, possibly because the surficial reactivity of β-MnO₂ appears to be highest in comparison to other MnO₂ crystals. Especially, β-MnO₂ could exhibit Y_DFF > 90% over 5 cycles of reusability test, and maintain its crystalline structure, revealing its advantageous feature for aerobic oxidation of HMF to DFF. Through this study, the relationship between morphology, surface chemistry, and catalytic activity of MnO₂ with different crystal forms is elucidated for providing scientific insights into design, application and development of MnO₂-based materials for aerobic oxidation of bio-derived molecules to value-added products.

Bimetallic Pt-Co Nanoparticle Deposited on Alumina for Simultaneous CO and Toluene Oxidation in the Presence of Moisture

Carbon monoxide (CO) and hydrocarbons (HCs) generally have competitive adsorption on the active site of noble-metal nano-catalysts, thus developing an effective way to reduce the passivation of competitive reaction with each other is an urgent problem. In this study, we successfully synthesized transition metal-noble metal (Pt-M) alloys via introducing inexpensive metal elements (M = Ni, Co and Cu) into Pt particles and then deposited on alumina support to form Pt-based catalysts. Subsequently, we choose CO and toluene as polluting gases to evaluate the catalytic activities of Pt-M/Al2O3 catalysts. Introducing inexpensive metal elements (M = Ni, Co, and Cu) significantly changed the physicochemical properties and catalytic activities of these Pt-based catalysts. It can be found that the Pt-Co/Al2O3 catalyst exhibited outstanding catalytic activity for CO and toluene oxidation under mixed gas atmosphere, compared with other Pt-based catalysts, which is due to the higher dispersity, more surface adsorption oxygen, and well redox ability. Surprisingly, H2O could promote the catalytic activities for CO/toluene co-oxidation over the Pt-Co/Al2O3 catalyst. Thus, the present synthetic strategy not only opens an avenue towards the synthesis of noble metal-based catalysts, but also provides an excellent tolerance to H2O in the catalytic process.

Eco-Friendly and Solvent-Less Mechanochemical Synthesis of ZrO2–MnCO3/N-Doped Graphene Nanocomposites: A Highly Efficacious Catalyst for Base-Free Aerobic Oxidation of Various Types of Alcohols

In recent years, the development of green mechanochemical processes for the synthesis of new catalysts with higher catalytic efficacy and selectivity has received manifest interest. In continuation of our previous study, in which graphene oxide (GRO) and highly reduced graphene oxide (HRG) based nanocomposites were prepared and assessed, herein, we have explored a facile and solvent-less mechanochemical approach for the synthesis of N-doped graphene (NDG)/mixed metal oxide (MnCO3–ZrO2) ((X%)NDG/MnCO3–ZrO2), as the (X%)NDG/MnCO3–ZrO2 nano-composite was synthesized using physical grinding of separately synthesized NDG and pre-calcined (300 °C) MnCO3–ZrO2 via green milling method. The structures of the prepared materials were characterized in detail using X-ray powder diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive X-Ray Analysis (EDX), Fourier-transform infrared spectroscopy (FTIR), Raman, Thermogravimetric analysis (TGA), and N2 adsorption-desorption isotherm analysis. Besides, the obtained nanocomposites were employed as heterogeneous oxidation catalyst for the alcohol oxidation using green oxidant O2 without involving any surfactants or bases. The reaction factors were systematically studied during the oxidation of benzyl alcohol (PhCH2OH) as the model reactant to benzaldehyde (PhCHO). The NDG/MnCO3–ZrO2 exhibits premium specific activity (66.7 mmol·g−1·h−1) with 100% conversion of PhCH2OH and > 99.9% selectivity to PhCHO after only 6 min. The mechanochemically prepared NDG based nanocomposite exhibited notable improvement in the catalytic efficacy as well as the surface area compared to the pristine MnCO3–ZrO2. Under the optimal circumstances, the NDG/MnCO3–ZrO2 catalyst could selectively catalyze the aerobic oxidation of a broad array of alcohols to carbonyls with full convertibility without over-oxidized side products like acids. The NDG/MnCO3–ZrO2 catalyst were efficiently reused for six subsequent recycling reactions with a marginal decline in performance and selectivity.

Synthesis and Characterization of CoxOy–MnCO3 and CoxOy–Mn2O3 Catalysts: A Comparative Catalytic Assessment Towards the Aerial Oxidation of Various Kinds of Alcohols

CoxOy–manganese carbonate (X%)(CoxOy–MnCO3 catalysts (X = 1–7)) were synthesized via a straightforward co-precipitation strategy followed by calcination at 300 °C. Upon calcination at 500 °C, these were transformed to CoxOy–dimanganese trioxide i.e., (X%)CoxOy–Mn2O3. A relative catalytic evaluation was conducted to compare the catalytic efficiency of the two prepared catalysts for aerial oxidation of benzyl alcohol (BzOH) to benzaldehyde (BzH) using O2 molecule as a clean oxidant without utilizing any additives or alkalis. Amongst the different percentages of doping with CoxOy (0–7% wt./wt.) on MnCO3 support, the (1%)CoxOy–MnCO3 catalyst exhibited the highest catalytic activity. The influence of catalyst loading, calcination temperature, reaction time, and temperature and catalyst dosage was thoroughly assessed to find the optimum conditions of oxidation of benzyl alcohol (BzOH) for getting the highest catalytic efficiency. The (1%)CoxOy–MnCO3 catalyst which calcined at 300 °C displayed the best effectiveness and possessed the largest specific surface area i.e., 108.4 m2/g, which suggested that the calcination process and specific surface area play a vital role in this transformation. A 100% conversion of BzOH along with BzH selectivity >99% was achieved after just 20 min. Notably, the attained specific activity was found to be considerably larger than the previously-reported cobalt-containing catalysts for this transformation. The scope of this oxidation reaction was expanded to various alcohols containing aromatic, aliphatic, allylic, and heterocyclic alcohols without any further oxidation i.e., carboxylic acid formation. The scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET) specific surface area analytical techniques were used to characterize the prepared catalysts. The obtained catalyst could be easily regenerated and reused for six consecutive runs without substantial decline in its efficiency.

Eco-Friendly Mechanochemical Preparation of Ag2O–MnO2/Graphene Oxide Nanocomposite: An Efficient and Reusable Catalyst for the Base-Free, Aerial Oxidation of Alcohols

Recently, the development of eco-friendly mechanochemical approaches for the preparation of novel catalysts with enhanced activity and selectivity has gained considerable attention. Herein, we developed a rapid and solvent-less mechanochemical method for the preparation of mixed metal oxide (Ag2O–MnO2) decorated graphene oxide (GRO)-based nanocomposites (Ag2O–MnO2/(X wt.%)GRO), as the Ag2O–MnO2/(X wt.%)GRO nanocomposite was fabricated by the physical grinding of freshly prepared GRO and pre-annealed (300 °C) mixed metal oxide nanoparticles (NPs) (Ag2O–MnO2) using an eco-friendly milling procedure. The as-prepared nanocatalysts were characterized by using various techniques. Furthermore, the nanocomposites were applied as a heterogeneous catalyst for the oxidation of alcohol by employing gaseous O2 as an eco-friendly oxidant under base-free conditions. The mechanochemically obtained GRO-based composite exhibited noticeable enhancement in the surface area and catalytic performance compared to the pristine Ag2O–MnO2. The results revealed that (1%)Ag2O–MnO2/(5 wt.%)GRO catalyst exhibited higher specific performance (13.3 mmol·g−1·h−1) with a 100% conversion of benzyl alcohol (BnOH) and >99% selectivity towards benzaldehyde (BnH) within 30 min. The enhancement of the activity and selectivity of GRO-based nanocatalyst was attributed to the presence of various oxygen-containing functional groups, a large number of defects, and a high specific surface area of GRO. In addition, the as-prepared nanocatalyst also demonstrated excellent catalytic activity towards the conversion of a variety of other alcohols to respective carbonyls under optimal conditions. Besides, the catalyst ((1%)Ag2O–MnO2/(5 wt.%)GRO) could be efficiently recycled six times with no noticeable loss in its performance and selectivity.

Cobalt-impregnated biochar produced from CO2-mediated pyrolysis of Co/lignin as an enhanced catalyst for activating peroxymonosulfate to degrade acetaminophen

-While sulfate radical (SO₄^-)-based processes are useful to degrade acetaminophen (ACE), studies of using peroxymonosulfate (PMS) to degrade ACE are quite limited. In addition, although Co is validated as the most effective metal for activating PMS, very few Co catalysts have been developed and investigated for activating PMS to degrade ACE. Since carbon is a promising substrate to support Co nanoparticles (NPs) to form Co/carbon composite catalysts, most existing carbon substrates require delicate fabrications. As biochar is an easy-to-obtain but versatile carbon material, pyrolysis of Co/lignin affords an advantageous Co-impregnated biochar (CoIB) as an attractive catalyst for PMS activation. Specifically, as CO₂ substitutes N₂ as a reaction medium for pyrolysis of Co/lignin, the syngas production from pyrolysis can be substantially improved and a magnetic CoIB is afforded. This CoIB consists of evenly-distributed Co nanoparticles (NPs) impregnated in carbon matrices of biochar, and possesses several superior characteristics, such as high porosity, large surface area and magnetism, enabling CoIB a promising catalyst for activating PMS to degrade ACE. CoIB also shows a much higher catalytic activity of PMS activation than CoIBN₂, and Co₃O₄ for degrading ACE. CoIB is also recyclable for activating PMS to effectively degrade ACE for multiple cycles. The ACE degradation pathway by this CoIB-activated PMS is proposed according to the degradation products. These findings validate that CoIB is assuredly an advantageous heterogeneous catalyst, which can be easily prepared from pyrolysis of Co/lignin in CO₂ with concomitant enhanced syngas production for effectively activating PMS to degrade ACE.

Metal-Oleate Complex-Derived Bimetallic Oxides Nanoparticles Encapsulated in 3D Graphene Networks as Anodes for Efficient Lithium Storage with Pseudocapacitance

In this manuscript, we have demonstrated the delicate design and synthesis of bimetallic oxides nanoparticles derived from metal-oleate complex embedded in 3D graphene networks (MnO/CoMn₂O₄ ⊂ GN), as an anode material for lithium ion batteries. The novel synthesis of the MnO/CoMn₂O₄ ⊂ GN consists of thermal decomposition of metal-oleate complex containing cobalt and manganese metals and oleate ligand, forming bimetallic oxides nanoparticles, followed by a self-assembly route with reduced graphene oxides. The MnO/CoMn₂O₄ ⊂ GN composite, with a unique architecture of bimetallic oxides nanoparticles encapsulated in 3D graphene networks, rationally integrates several benefits including shortening the diffusion path of Li⁺ ions, improving electrical conductivity and mitigating volume variation during cycling. Studies show that the electrochemical reaction processes of MnO/CoMn₂O₄ ⊂ GN electrodes are dominated by the pseudocapacitive behavior, leading to fast Li⁺ charge/discharge reactions. As a result, the MnO/CoMn₂O₄ ⊂ GN manifests high initial specific capacity, stable cycling performance, and excellent rate capability.

Three-dimensional composite of Co3O4 nanoparticles and nitrogen-doped reduced graphene oxide for lignin model compound oxidation

3D composite of Co₃O₄ nanoparticles and N-doped reduced graphene oxide can effectively catalyze the oxidation of lignin model compounds.

Catalytic Oxidation of Vanillyl Alcohol Using FeMCM-41 Nanoporous Tubular Reactor

Iron containing nanoporous MCM-41 (FeMCM-41) with different Si/Fe ratios of 50, 100 and 150 was synthesized by hydrothermal synthesis process. The materials obtained from hydrothermal synthesis were characterized by various physico chemical techniques such as XRD, N2 adsorption, DR UV-vis, EPR and FTIR spectroscopy. XRD analyses of FeMCM-41 materials confirmed the presence of well-ordered crystalline structure. N2 isotherm of FeMCM-41 materials showed type IV adsorption isotherm. EPR and DR UV-vis analysis of FeMCM-41 samples indicates the presence of high tetrahedral coordination at the Si/Fe ratios of 100 and 150. The catalytic performance of FeMCM-41 nano tubular reactor was tested in the liquid phase oxidation of vanillyl alcohol into vanillin using H2O2 (50[Formula: see text]wt% in water). The reaction products were analyzed by gas chromatography in DB-5 capillary column with flame ionization detector. The products were confirmed by 1H NMR, [Formula: see text]C NMR and LC-Mass spectroscopy. The maximum conversion of vanillyl alcohol (85%) and selectivity towards vanillin (82%) were observed using the catalyst FeMCM-41(100) in 30[Formula: see text]min at 60[Formula: see text]C. The influence of reaction temperature, reaction time, reactants molar ratio, Si/Fe ratio and amount of catalyst were investigated.

Sonochemical oxidation of vanillyl alcohol to vanillin in the presence of a cobalt oxide catalyst under mild conditions

The heterogeneous oxidation of vanillyl alcohol to vanillin was investigated on new grounds under eco-friendly conditions in the presence of hydrogen peroxide as an oxidant and water as solvent, coupled with low frequency ultrasonic irradiation. The sono-Fenton-like-assisted vanillyl alcohol oxidation was performed with a high-surface area nanostructured spinel cobalt oxide catalyst exhibiting small crystallites size. The catalytic reaction was also carried out under conventional heating conditions for comparison purposes. The influence of the reaction parameters, namely catalyst loading and hydrogen peroxide concentration was studied with the aim of determining the optimum yield and selectivity to the desired vanillin product. The chemical effects of ultrasound (ability to generate hydroxyl radicals) along with increased mass transfer appeared to be key prerequisites for enhancing the efficiency of the process, while decreasing the overall energy consumption.

CuZrO3nanoparticles catalyst in aerobic oxidation of vanillyl alcohol

A highly crystalline, mesoporous and perovskite type CuZrO₃nanoparticles catalyst was preparedviaa simple and facile one pot solvent evaporation method.

A highly reduced graphene oxide/ZrOx–MnCO3 or –Mn2O3 nanocomposite as an efficient catalyst for selective aerial oxidation of benzylic alcohols

ZrOx(1%)–MnCO₃/HRG(1%) based nanocomposites material as an efficient oxidation catalyst.

Nanosized spinel Cu–Mn mixed oxide catalyst prepared via solvent evaporation for liquid phase oxidation of vanillyl alcohol using air and H2O2

Spinel Cu–Mn mixed oxide preparedviasolvent evaporation method demonstrating superior catalytic activity.

Composition, Electronic and Magnetic Investigation of the Encapsulated ZnFe2O 4 Nanoparticles in Multiwall Carbon Nanotubes Containing Ni Residuals

We report investigation on properties of multiwall carbon nanotubes (mCNTs) containing Ni residuals before and after encapsulation of zinc ferrite nanoparticles. The pristine tubes exhibit metallic character with a 0.3 eV reduction in the work function along with ferromagnetic behavior which is attributed to the Ni residuals incorporated during the preparation of tubes. Upon encapsulation of zinc ferrite nanoparticles, 0.5 eV shift in Fermi level position and a reduction in both the π band density of state along with a change in the hybridized sp(2)/sp(3) ratio of the tubes from 2.04 to 1.39 are observed. As a result of the encapsulation, enhancement in the σ bands density of state and coating of the zinc ferrite nanoparticles by the internal layers of the CNTs in the direction along the tube axis is observed. Furthermore, Ni impurities inside the tubes are attracted to the encapsulated zinc ferrite nanoparticles, suggesting the possibility of using these particles as purifying agents for CNTs upon being synthesized using magnetic catalyst particles. Charge transfer from Ni/mCNTs to the ZnFe2O4 nanoparticles is evident via reduction of the density of states near the Fermi level and a 0.3 eV shift in the binding energy of C 1 s core level ionization. Furthermore, it is demonstrated that encapsulated zinc ferrite nanoparticles in mCNTs resulted in two interacting sub-systems featured by distinct blocking temperatures and enhanced magnetic properties; i.e., large coercivity of 501 Oe and saturation magnetization of 2.5 emu/g at 4 K.

Graphene-supported metal/metal oxide nanohybrids: synthesis and applications in heterogeneous catalysis

This minireview outlines recent advances in the design and catalytic applications of graphene-supported metal/metal oxide nanohybrids.

Rational design of carbon support to prepare ultrafine iron oxide catalysts for air oxidation of alcohols

The efficient carbon supports change not only the physical but also the chemical properties of iron oxide and create new active sites for the enhancement of catalytic activity in the oxidation of alcohols with air as an oxygen source.

Structural properties, magnetic interactions, magnetocaloric effect and critical behaviour of cobalt doped La0.7Te0.3MnO3

The effect of cobalt doping on the structural, magnetic and magnetocaloric properties of electron-doped manganite La_0.7Te_0.3Mn_1−xCo_xO₃ (x = 0, 0.1, 0.2, 0.25, 0.3 and 0.5) has been investigated.