Madhurya Chandel

A simple ‘in situ’ co-precipitation method for the preparation of multifunctional CoFe2O4–reduced graphene oxide nanocomposites: excellent microwave absorber and highly efficient magnetically separable recyclable photocatalyst for dye degradation

Here, an ‘in situ’ co-precipitation reaction method has been reported for the preparation of CoFe2O4–RGO (CF–RGO) nanocomposites. To the best of our knowledge, this is the first time a simple synthetic method is reported for the preparation of CoFe2O4–RGO nanocomposites where a hydrothermal technique was not used. The novelty of this technique lies in its simplicity, cost-effectiveness, and the capability of large scale production of CoFe2O4–RGO nanocomposites. The synthesized CoFe2O4–RGO nanocomposites possess excellent microwave absorbing properties as well as high photocatalytic activity towards the degradation of various dyes under visible light irradiation. 85CF–15RGO (85 wt% CF and 15 wt% RGO) showed excellent microwave absorption properties with a Reflection Loss (RL) of −31.31 dB (∼99.94% absorption) at 9.05 GHz with an 8.2–10.92 GHz effective band width range. To the best of our knowledge 85CF–15RGO nanocomposite exhibited comparable and even superior microwave absorption properties in the X-band region than most of the ferrite based composites. 75CF–25RGO (75 wt% CF and 25 wt% RGO) acted as a very good magnetically separable photocatalyst for the degradation of various synthetic dyes (such as methyl orange, methylene blue, rhodamine B and a mixture of these dyes) under visible light irradiation emitted from a 100 W reading lamp. Moreover, CoFe2O4–RGO catalyst also showed easy magnetic separation with high reusability. The photocatalytic activity of 75CF–25RGO was found to be comparable and in some cases better than the various reported RGO–ferrite composites. The simple method of preparation and multifunctional character make CF–RGO nanocomposites attractive materials for application in the area of photocatalysis as well as microwave absorption.

Synthesis of a Ni0.8Zn0.2Fe2O4–RGO nanocomposite: an excellent magnetically separable catalyst for dye degradation and microwave absorber

A Ni0.8Zn0.2Fe2O4 reduced graphene oxide nanocomposite has been synthesized by a simple ‘in situ co-precipitation’ technique. This composite exhibited an ability to act as an excellent magnetically separable catalyst towards the degradation of various dyes as well as a toxic herbicide (trifluralin). It also demonstrated very good microwave absorption properties.

CuO Nanoparticle Immobilised Mesoporous TiO2–Cobalt Ferrite Nanocatalyst: A Versatile, Magnetically Separable and Reusable Catalyst

Here, synthesis and catalytic activity of a novel nanocatalyst (CuO@mTiO2@CF), consisting of CuO nanoparticles, mesoporous titanium oxide and Cobalt ferrite have been reported for the first time. The catalyst was synthesized using a simple aqueous solution based chemical methodology. Synthesized CuO@mTiO2@CF showed excellent catalytic activity towards various organic reactions such as (i) Epoxidation of styrene, (ii) Click reaction, (iii) Biginelli reaction, (iv) Reduction of 4-Nitrophenol and trifluralin in presence of excess NaBH4. Moreover, this novel nanocatalyst offered easy magnetic separation after the catalysis reaction and excellent reusability. Easy synthesis methodology, versatility, good reusability and easy separation make the nanocatalyst attractive in the field of heterogeneous catalysis.Graphical Abstract

Synthesis of a BiFeO3 nanowire-reduced graphene oxide based magnetically separable nanocatalyst and its versatile catalytic activity towards multiple organic reactions

Herein, we report for the first time synthesis of a BiFeO3 nanowire-reduced graphene oxide nanocatalyst (BFO–RGO) using a hydrothermal method. The BFO–RGO nanocatalyst exhibited excellent catalytic activity towards Biginelli reaction, Click reaction, styrene epoxidation, 4-NP reduction and a herbicide, (trifluralin) reduction. The novelty of this catalyst lies in its high catalytic efficiency towards many organic reactions, easy separation and good reusability.

Synthesis of multifunctional CuFe2O4–reduced graphene oxide nanocomposite: an efficient magnetically separable catalyst as well as high performance supercapacitor and first-principles calculations of its electronic structures

Here, we report an ‘in situ’ co-precipitation reduction based synthetic methodology to prepare CuFe2O4 nanoparticle–reduced graphene oxide (CuFe2O4–RGO) nanocomposites. First principles calculations based on Density Functional Theory (DFT) were performed to obtain the electronic structures and properties of CuFe2O4, graphene and CuFe2O4–graphene composites, and to understand the interfacial interaction between CuFe2O4 and graphene in the composite. The synergistic effect, which resulted from the combination of the unique properties of RGO and CuFe2O4 nanoparticles, was exploited to design a magnetically separable catalyst and high performance supercapacitor. It has been demonstrated that the incorporation of RGO in the composite enhanced its catalytic properties as well as supercapacitance performance compared with pure CuFe2O4. The nanocomposite with 96 wt% CuFe2O4 and 4 wt% RGO (96CuFe2O4–4RGO) exhibited high catalytic efficiency towards (i) reduction of 4-nitrophenol to 4-aminophenol, and (ii) epoxidation of styrene to styrene oxide. For both of these reactions, the catalytic efficiency of 96CuFe2O4–4RGO was significantly higher than that of pure CuFe2O4. The easy magnetic separation of 96CuFe2O4–4RGO from the reaction mixture and good reusability of the recovered catalyst also showed here. 96CuFe2O4–4RGO also demonstrated better supercapacitance performance than pure CuFe2O4. 96CuFe2O4–4RGO showed specific capacitance of 797 F g−1 at a current density of 2 A g−1, along with ∼92% retention for up to 2000 cycles. To the best of our knowledge, this is the first investigation on the catalytic properties of CuFe2O4–RGO towards the reduction of 4-nitrophenol and the epoxidation reaction, and DFT calculations on the CuFe2O4–graphene composite have been reported.

Synthesis of Various Ferrite (MFe2O4) Nanoparticles and Their Application as Efficient and Magnetically Separable Catalyst for Biginelli Reaction

Herein, we reports the application of various spinel ferrite nanoparticles, MFe2O4 (M = Co, Ni, Cu, Zn), as efficient catalyst for Biginelli reaction. All ferrite nanoparticles were synthesized using a novel aqueous solution based method. It was observed that, the catalytic activity of the ferrite nanoparticles followed the decreasing order of CoFe2O4 > CuFe2O4 > NiFe2O4 > ZnFe2O4. The most important feature of these ferrite nanocatalysts is that, these nanoparticles can directly be used as catalyst and no surface modification or functionalization is required. These ferrite nanoparticles are easily separable from reaction mixture after reaction by using a magnet externally. Easy synthesis methodology, high catalytic activity, easy magnetic separation and good reusability make these ferrite nanoparticles attractive catalysts for Biginelli reaction.

Barium Hexaferrite (BaFe12O19) Nanoparticles as Highly Active and Magnetically Recoverable Catalyst for Selective Epoxidation of Styrene to Styrene Oxide

Herein, we are reporting the use of pure single phase barium hexaferrite (BaFe12O19) nanoparticles as an efficient catalyst for epoxidation of styrene. BaFe12O19 nanocatalysts exhibit high conversion of styrene with excellent selectivity of styrene oxide formation. Easy method of preparation, capability of catalyzing the epoxide reaction of styrene to styrene oxide with excellent styrene conversion (~91%) and high styrene oxide selectivity (~86.5%), easy magnetic separation and very good reusability make the synthesized BaFe12O19 nanocatalyst an excellent catalyst for this reaction. To the best of our knowledge, this is the first time the use of BaFe12O19 as catalyst for this reaction has been reported.