Al-doped α-MnO2 coated by lignin for high-performance rechargeable aqueous zinc-ion batteries

Zn/MnO₂ batteries, one of the most widely studied rechargeable aqueous zinc-ion batteries, suffer from poor cyclability because the structure of MnO₂ is labile with cycling. Herein, the structural stability of α-MnO₂ is enhanced by simultaneous Al³⁺ doping and lignin coating during the formation of α-MnO₂ crystals in a hydrothermal process. Al³⁺ enters the [MnO₆] octahedron accompanied by producing oxygen vacancies, and lignin further stabilizes the doped Al³⁺via strong interaction in the prepared material, Al-doped α-MnO₂ coated by lignin (L + Al@α-MnO₂). Meanwhile, the conductivity of L + Al@α-MnO₂ improves due to Al³⁺ doping, and the surface area of L + Al@α-MnO₂ increases because of the production of nanorod structures after Al³⁺ doping and lignin coating. Compared with the reference α-MnO₂ cathode, the L + Al@α-MnO₂ cathode achieves superior performance with durably high reversible capacity (∼180 mA h g⁻¹ at 1.5 A g⁻¹) and good cycle stability. In addition, ex situ X-ray diffraction characterization of the cathode at different voltages in the first cycle is employed to study the related mechanism on improving battery performance. This study may provide ideas of designing advanced cathode materials for other aqueous metal-ion batteries.

Al³⁺ doping combined with lignin coating improves the structural stability and electrochemical performance of the modified α-MnO₂, L + Al@α-MnO₂.     

Removal of manganous dithionate (MnS2O6) with MnO2 from the desulfurization manganese slurry

Manganese desulfurization has been increasingly explored, but the generated manganous dithionate (MD) by-product affects the valuable use of the desulfurized slurry. In this study, α-MnO₂, β-MnO₂, γ-MnO₂, and δ-MnO₂ were prepared for MD removal in desulfurization manganese slurry. Results showed that δ-MnO₂ had the best activity among the four because of its porosity and favorable surface properties. The operation conditions showed that 12.00 g L⁻¹ MD can be removed by more than 80.00% under the conditions of 1.4 mol L⁻¹ sulfuric acid, 100 g L⁻¹ δ-MnO₂ dosage, and reaction at 90 °C for 3 h. The MD removal with MnO₂ followed the decomposition–oxidation pass and direct oxidation–reduction reaction and consequently induced structure destruction and crystalline transfer. MD removal with natural MnO₂ ore was also examined, and natural MnO₂ ore in the δ type was found to have prominent activity. Thus, this type of natural MnO₂ may serve as a good alternative to pure MnO₂ for decreasing the cost of MD removal from desulfurization manganese slurry.

The manganous dithionate by-product of the desulfurized slurry could be oxidized with MnO₂ without any impurity. σ-MnO₂ showed the best activity due to its high surface area and expose much more surface-active oxygen.     

Fabrication of novel electrochemical sensors based on modification with different polymorphs of MnO2 nanoparticles. Application to furosemide analysis in pharmaceutical and urine samples

A novel MnO₂ nanoparticles/chitosan-modified pencil graphite electrode (MnO₂ NPs/CS/PGE) was constructed using two different MnO₂ polymorphs (γ-MnO₂ and ε-MnO₂ nanoparticles). X-ray single phases of these two polymorphs were obtained by the comproportionation reaction between MnCl₂ and KMnO₄ (molar ratio of 5 : 1). The temperature of this reaction is the key factor governing the formation of the two polymorphs. Their structures were confirmed by powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) and energy dispersive X-ray (EDX) analysis. Scanning electron microscopy (SEM) was employed to investigate the morphological shape of MnO₂ NPs and the surface of the bare and modified electrodes. Moreover, cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were used for surface analysis of the modified electrodes. Compared to bare PGE, MnO₂ NPs/CS/PGE shows higher effective surface area and excellent electrocatalytic activity towards the oxidation of the standard K₃[Fe(CN)₆]. The influence of different suspending solvents on the electrocatalytic activity of MnO₂ was studied in detail. It was found that tetrahydrofuran (THF) is the optimum suspending solvent regarding the peak current signal and electrode kinetics. The results reveal that the modified γ-MnO₂/CS/PGE is the most sensitive one compared to the other modified electrodes under investigation. The modified γ-MnO₂/CS/PGE was applied for selective and sensitive determination of FUR. Under the optimized experimental conditions, γ-MnO₂/CS/PGE provides a linear response over the concentration range of 0.05 to 4.20 μmol L⁻¹ FUR with a low limit of detection, which was found to be 4.44 nmol L⁻¹ (1.47 ng mL⁻¹) for the 1^st peak and 3.88 nmol L⁻¹ (1.28 ng mL⁻¹) for the 2^nd one. The fabricated sensor exhibits a good reproducibility and selectivity and was applied successfully for the determination of FUR in its dosage forms and in spiked urine samples with good accuracy and precision.

A novel MnO₂ nanoparticles/chitosan-modified pencil graphite electrode (MnO₂ NPs/CS/PGE) was constructed using two different MnO₂ polymorphs (γ-MnO₂ and ε-MnO₂ nanoparticles).     

CNT modified layered α-MnO2 hybrid flame retardants: preparation and their performance in the flame retardancy of epoxy resins

In this paper, CNT modified layered α-MnO₂ hybrid flame retardants (α-MnO₂–CNTs) were synthesized through one-pot preparation. The structure and composition of the α-MnO₂–CNTs hybrid flame retardants were investigated by X-ray diffraction, TEM and SEM. Subsequently, the α-MnO₂–CNTs hybrids were then incorporated into epoxy resin (EP) to improve the fire safety properties. Compared with pure EP and the composites with CNTs or α-MnO₂, EP/α-MnO₂–CNTs composites exhibited improved flame retardancy and smoke suppression properties. With the incorporation of only 2.0 wt% of α-MnO₂–CNTs hybrid flame retardants, the peak heat release rate and total heat release of the composites showed 34% and 10.7% reduction respectively. In addition, the volatile gases such as CO and CO₂ were reduced and the smoke generation was also effectively inhibited. The improved fire safety of the composites is generally due to the network structures and the synergistic effect of α-MnO₂ and CNTs, the catalyzing charring effect, smoke suppression and the physical barrier effect of α-MnO₂ nanosheets.

In this paper, CNT modified layered α-MnO₂ hybrid flame retardants (α-MnO₂–CNTs) were synthesized through one-pot preparation.     

A first-principles investigation of α, β, and γ-MnO2 as potential cathode materials in Al-ion batteries

An inexpensive and eco-friendly alternative energy storage solution is becoming more in demand as the world moves towards greener technology. We used first principles calculations to investigate α, β, and γ-MnO₂ and their Al-ion intercalation mechanism in potential applications for aluminum batteries. We explored these complexes through investigating properties such as volume change, binding/diffusion energy, and band gap to gauge each material. α-MnO₂ had almost no volume change. γ-MnO₂ had the lowest binding energy and diffusion barrier. Our study gives insight into the feasibility of using MnO₂ in aluminum batteries and guides investigation of the material within its different phases.

An inexpensive and eco-friendly alternative energy storage solution is becoming more in demand as the world moves towards greener technology.     

The effects of Fe-doping on MnO2: phase transitions,defect structures and its influence on electrical properties

The composition of Mn_1−xFe_xO₂ (x = 0–0.15) was synthesized by a hydrothermal method at 140 °C for 5 hours of reaction time. Investigations were carried out including XRD, FTIR, Raman spectroscopy, FESEM, and TEM for crystallographic phase analysis. Furthermore, XPS and XAS were used to analyze the oxidation states of Mn and dopant Fe in the octahedron sites. For electrical characterizations, an impedance analyzer was used to explore the conductivity and dielectric properties. It was discovered that the undoped MnO₂ possessed an α-MnO₂ structure performing (2 × 2) tunnel permitting K⁺ insertion and had a nanorod morphology. The Fe ion that was doped into MnO₂ caused a phase transformation from α-MnO₂ to Ramsdellite R-MnO₂ after x = 0.15 was reached and the tunnel dimension changed to (2 × 1). Furthermore, this caused increased micro-strain and oxygen vacancies. An oxidation state analysis of Mn and substituted Fe in the octahedron sites found mixed 3+ and 4+ states. Electrical characterization revealed that the conductivity of Fe-doped MnO₂ is potentially electron influenced by the oxidation state of the cations in the octahedron sites, the micro-strain, the dislocation density, and the movement of K⁺ ions in the tunnel.

Phase transformation from initially α-MnO₂ to R-MnO₂ due to Fe-doping cause modification of interatomic distances affects to the electrical properties.     

Biofunctional hollow γ-MnO2 microspheres by a one-pot collagen-templated biomineralization route and their applications in lithium batteries

γ-MnO₂ nanomaterials play an essential role in the development of advanced electrochemical energy storage and conversion devices with versatile industrial applications. Herein, novel dandelion-like hollow microspheres of γ-MnO₂ mesocrystals have been fabricated for the first time by a one-pot biomineralization route. Recombinant collagen with unique rod-like structure has been demonstrated as a robust template to tune the morphologies of γ-MnO₂ mesocrystals, and a very low concentration of collagen can alter the nanostructures of γ-MnO₂ from nanorods to microspheres. The as-prepared γ-MnO₂ mesocrystals formed well-ordered hollow microspheres composed of delicate nanoneedle-like units. Among all the reported γ-MnO₂ with various nanostructures, the γ-MnO₂ microspheres showed the most prowess to maintain high discharge capacities after 100+ cycles. The superior electrochemical performance of γ-MnO₂ likely results from its unique hierarchical micro-nano structure. Notably, the γ-MnO₂ mesocrystals display high biocompatibility and cellular activity. Collagen plays a key dual role in mediating the morphology as well as endowing the biofunction of the γ-MnO₂ mesocrystals. This environmentally friendly biomineralization approach using rod-like collagen as the template, provides unprecedented opportunity for the production of novel nanostructured metal oxides with superior biocompatibility and electrochemical performance, which have great potential in advanced implantable and wearable health-care electronic devices.

Recombinant collagen with unique rod-like structure has been demonstrated as a robust template to create novel dandelion-like hollow microspheres of γ-MnO₂ mesocrystals, which display superior biocompatibility and electrochemical performance.     

A p-type multi-wall carbon nanotube/Te nanorod composite with enhanced thermoelectric performance

In this study, multi-walled carbon nanotube (MWCNT)/tellurium (Te) nanorod composites with various MWCNT contents are prepared and their thermoelectric properties are investigated. The composite samples are prepared by mixing Te nanorods with surface-treated MWCNTs. Te nanorods are synthesized by solution phase mixing using polyvinylpyrrolidone (PVP). The MWCNTs used in this study are surface-treated with a solution consisting of H₂SO₄ and HNO₃. With increasing MWCNT content, the composite samples exhibit a reduction in the Seebeck coefficient and enhanced electrical conductivity. The maximum power factor of 5.53 μW m K⁻² is observed at 2% MWCNT at room temperature. The thermal conductivity of the composite reduced after the introduction of MWCNTs into the Te nanorod matrix; this is attributed to the generation of heterostructured interfaces between MWCNTs and the Te nanorods. At room temperature, the composites containing 2% MWCNTs exhibited the maximum thermoelectric figure of merit (ZT), which is ∼3.91 times larger than that of pure Te nanorods.

In this study, multi-walled carbon nanotube (MWCNT)/tellurium (Te) nanorod composites with various MWCNT contents are prepared and their thermoelectric properties are investigated.     

Improvement of O2 adsorption for α-MnO2 as an oxygen reduction catalyst by Zr4+ doping

Zr⁴⁺ doped α-MnO₂ nanowires were successfully synthesized by a hydrothermal method. XRD, SEM, TEM and XPS analyses indicated that Mn³⁺ ions, Mn⁴⁺ ions, Mn^4+δ ions and Zr⁴⁺ ions co-existed in the crystal structure of synthesized Zr⁴⁺ doped α-MnO₂ nanowires. Zr⁴⁺ ions occupied the positions originally belonging to elemental manganese in the crystal structure and resulted in a mutual action between Zr⁴⁺ ions and Mn³⁺ ions. The mutual action made Mn³⁺ ions tend to lose their electrons and Zr⁴⁺ ions tend to get electrons. Cathodic polarization analyses showed that the electrocatalytic activity of α-MnO₂ for oxygen reduction reaction (ORR) was remarkably improved by Zr⁴⁺ doping and the Zr/Mn molar ratio notably affected the ORR performance of the air electrodes prepared by Zr⁴⁺ doped α-MnO₂ nanowires. The highest ORR current density of the air electrodes prepared by Zr⁴⁺ doped α-MnO₂ nanowires in alkaline solution appeared at Zr/Mn molar ratio of 1 : 110, which was 23% higher than those prepared by α-MnO₂ nanowires. EIS analyses indicated that the adsorption process of O₂ molecules on the surface of the air electrodes prepared by Zr⁴⁺ doped α-MnO₂ nanowires was the rate-controlling step for ORR. The DFT calculations revealed that the mutual action between Zr⁴⁺ and Mn³⁺ in Zr⁴⁺ doped α-MnO₂ nanowires enhanced the adsorption process of O₂ molecules.

O₂ adsorption was enhanced after doping Zr⁴⁺ into MnO₂ nanowires subsequently led to the improvement of ORR catalytic performance.     

3D zinc@carbon fiber composite framework anode for aqueous Zn–MnO2 batteries

Rechargeable aqueous batteries are one of the most promising large-scale energy storage devices because of their environment-friendly properties and high safety advantages without using flammable and poisonous organic liquid electrolyte. In addition, rechargeable Zn–MnO₂ batteries have great potential due to their low-cost resources as well as high energy density. However, dendritic growth of the zinc anode hinders the exertion of cycling stability and rate capacity in an aqueous Zn–MnO₂ battery system. Here we use an electrochemical deposition method to in situ form a three-dimensional (3D) zinc anode on carbon fibers (CFs). This 3D Zn@CFs framework has lower charge transfer resistance with larger electroactive areas. Batteries based on the 3D zinc framework anode and α-MnO₂ nanowire cathode present enhanced rate capacity and long cycling stability, which is promising for utilization in other zinc anode based aqueous batteries as an effective way to solve dendrite formation.

Synthesis of a 3D Zn@CFs anode through constant voltage electrodeposition to realize a dendrite-free cycling performance in an aqueous Zn/MnO₂ battery.     

Critical behavior near room temperature in La0.75Ca0.05Na0.20MnO3 sample

The critical behavior of La_0.75Ca_0.05Na_0.20MnO₃ was studied at around room temperature via magnetization measurements. From the relative slope, we deduced that the Tricritical Mean-Field model was the most suitable model. The estimated critical exponents were found to be β = 0.24 ± 0.004, γ = 0.98 ± 0.065 and δ = 5.08 at T_C = 300 K. These critical exponents satisfied the Widom scaling relation δ = 1 + γ/β, implying the reliability of our values. Based on the critical exponents, the magnetization–field–temperature (M–μ₀H–T) data around T_C collapsed into two curves, obeying the single scaling equation with ε = (T − T_C)/T_C being the reduced temperature. These results suggest short-range interaction in our sample.

A set of typical M²vs. μ₀H/M for La_0.75Ca_0.05Na_0.20MnO₃ sample.     

Simultaneous determination of methadone and morphine at a modified electrode with 3D β-MnO2 nanoflowers: application for pharmaceutical sample analysis

The present research synthesized manganese dioxide nano-flowers (β-MnO₂-NF) via a simplified technique for electro-catalytic utilization. Moreover, morphological characteristics and X-ray analyses showed Mn in the oxide form with β-type crystallographic structure. In addition, the research proposed a new efficient electro-chemical sensor to detect methadone at the modified glassy carbon electrode (β-MnO₂-NF/GCE). It has been found that oxidizing methadone is irreversible and shows a diffusion controlled procedure at the β-MnO₂-NF/GCE. Moreover, β-MnO₂-NF/GCE was considerably enhanced in the anodic peak current of methadone related to the separation of morphine and methadone overlapping voltammetric responses with probable difference of 510 mV. In addition, a linear increase has been observed between the catalytic peak currents gained by the differential pulse voltammetry (DPV) of morphine and methadone and their concentrations in the range between 0.1–200.0 μM and 0.1–250.0 μM, respectively. Furthermore, the limits of detection (LOD) for methadone and morphine were found to be 5.6 nM and 8.3 nM, respectively. It has been found that our electrode could have a successful application for detecting methadone and morphine in the drug dose form, urine, and saliva samples. Thus, this condition demonstrated that β-MnO₂-NF/GCE displays good analytical performances for the detection of methadone.

Electrochemical sensor based on β-MnO₂ nanoflower-modified glassy carbon electrode for the simultaneous detection of methadone and morphine was fabricated.     

Highly selective colorimetric determination of catechol based on the aggregation-induced oxidase–mimic activity decrease of δ-MnO2

Multiple enzyme-like activities of manganese oxides (MnO₂) have been reported and applied in catalysis, biosensors, and cancer therapy. Here, we report that catechol can be determined colorimetrically based on the 3,3′,5,5′-tetramethylbenzidine (TMB) oxidase-like activity of δ-MnO₂. The detection was based on pre-incubation of catechol containing water samples with δ-MnO₂, and then the residual TMB oxidase-like activity of reacted δ-MnO₂ was linearly dependent on the catechol concentration in the range of 0.5 to 10 μM. This determination method was stable at pH 3.73–6.00 and was not affected by ion strength up to 200 μM. Common co-solutes in water bodies (50 μM) have negligible effects and excellent selectivity of catechol among various phenolic compounds (15 μM) was facilitated. Both reduction and aggregation of δ-MnO₂ were observed during the incubation process with catechol, and aggregation-induced TMB oxidase–mimic activity decrease was the main factor for this colorimetric determination.

A new determination mechanism for catechol: aggregation-induced oxidase-mimic activity decrease of δ-MnO₂.     

Theoretical study on NOx adsorption properties over the α-MnO2(110) surface

Herein, α-MnO₂ was studied as an adsorbent for the removal of NO_x (NO, NO₂) derived from flue gas. First-principles calculations based on the density functional theory (DFT) were performed to investigate the NO_x adsorption properties over the α-MnO₂(110) surface. NO strongly adsorbed over the α-MnO₂(110) surface via chemisorption spontaneously under 550 K. The NO₂ molecules adsorbed over the surface via chemisorption and physisorption when the terminal N- and O atoms approached the surface, respectively. The joint adsorption of NO_x was more stable than the isolated adsorption system. Furthermore, the net charge was transferred from the molecule to the surface. The surface and temperature affected the entropy, enthalpy, NO adsorption and NO₂ desorption in the temperature range of 300–550 K. The equilibrium constants decreased with an increase in temperature, which reduced the conversion rate.

NO adsorbs over the α-MnO₂(110) surface initially and then NO₂ in the isolated system at low temperature. Joint adsorption is more stable than the isolated system.     

Uncovering the origin of enhanced field emission properties of rGO–MnO2 heterostructures: a synergistic experimental and computational investigation

The unique structural merits of heterostructured nanomaterials including the electronic interaction, interfacial bonding and synergistic effects make them attractive for fabricating highly efficient optoelectronic devices. Herein, we report the synthesis of MnO₂ nanorods and a rGO/MnO₂ nano-heterostructure using low-cost hydrothermal and modified Hummers'' methods, respectively. Detailed characterization and confirmation of the structural and morphological properties are done via X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM). Compared to the isolated MnO₂ nanorods, the rGO/MnO₂ nano-heterostructure exhibits impressive field emission (FE) performance in terms of the low turn-on field of 1.4 V μm⁻¹ for an emission current density of 10 μA cm⁻² and a high current density of 600 μA cm⁻² at a relatively very low applied electric field of 3.1 V μm⁻¹. The isolated MnO₂ nanorods display a high turn-on field of 7.1 for an emission current density of 10 μA cm⁻² and a low current density of 221 μA cm⁻² at an applied field of 8.1 V μm⁻¹. Besides the superior FE characteristics of the rGO/MnO₂ nano-heterostructure, the emission current remains quite stable over the continuous 2 h period of measurement. The improvement of the FE characteristics of the rGO/MnO₂ nano-heterostructure can be ascribed to the nanometric features and the lower work function (6.01 and 6.12 eV for the rGO with 8% and 16% oxygen content) compared to the isolated α-MnO₂(100) surface (Φ = 7.22 eV) as predicted from complementary first-principles electronic structure calculations based on density functional theory (DFT) methods. These results suggest that an appropriate coupling of rGO with MnO₂ nanorods would have a synergistic effect of lowering the electronic work function, resulting in a beneficial tuning of the FE characteristics.

The unique structural merits of heterostructured nanomaterials including the electronic interaction, interfacial bonding and synergistic effects make them attractive for fabricating highly efficient optoelectronic devices.     

Microstructure and electrochemical properties of high performance graphene/manganese oxide hybrid electrodes

Hybrids consisting of 2D ultra-large reduced graphene oxide (RGO) sheets (∼30 μm long) and 1D α-phase manganese oxide (MnO₂) nanowires were fabricated through a versatile synthesis technique that results in electrostatic binding of the nanowires and sheets. Two different hybrid (RGO/MnO₂) compositions had remarkable features and performance: 3 : 1 MnO₂/RGO (75/25 wt%) denoted as 3H and 10 : 1 MnO₂/RGO (90/10 wt%) denoted as 10H. Characterization using spectroscopy, microscopy, and thermal analysis provided insights into the microstructure and behavior of the individual components and hybrids. Both hybrids exhibited higher specific capacitance than their individual components. 3H demonstrated excellent overall electrochemical performance with specific capacitance of 225 F g⁻¹, pseudocapacitive and electrochemical double-layer capacitance (EDLC) contributions, charge-transfer resistance <1 Ω, and 97.8% capacitive retention after 1000 cycles. These properties were better than those of 10H; this was attributed 3H''s more uniform distribution of nanowires enabling more effective electronic transport. Thermal annealing was used to produce reduced graphene oxide (RGO) that exhibited significant removal of oxygen functionality with a resulting interlayer spacing of 0.391 nm, higher D/G ratio, higher specific capacitance, and electrochemical properties representing more ideal capacitive behavior than GO. Integrating ultra-large RGO with very high surface area and MnO₂ nanowires enables chemical interactions that may improve processability into complex architectures and electrochemical performance of electrodes for applications in electronics, sensors, catalysis, and deionization.

Tuning the microstructure of ultra-large reduced graphene oxide (RGO) 2D sheets and manganese oxide (MnO₂) 1D nanowires to produce a hybrid material enabled achieving excellent electrochemical capacitive behavior for energy storage.     

Effect of nickel ion doping in MnO2/reduced graphene oxide nanocomposites for lithium adsorption and recovery from aqueous media

Novel and effective reduced graphene oxide–nickel (Ni) doped manganese oxide (RGO/Ni-MnO₂) adsorbents were fabricated via a hydrothermal approach. The reduction of graphite to graphene oxide (GO), formation of α-MnO₂, and decoration of Ni-MnO₂ onto the surface of reduced graphene oxide (RGO) were independently carried out by a hydrothermal technique. The physical and morphological properties of the as-synthesized adsorbents were analyzed. Batch adsorption experiments were performed to identify the lithium uptake capacities of adsorbents. The optimized parameters for Li⁺ adsorption investigated were pH = 12, dose loading = 0.1 g, Li⁺ initial concentration = 50 mg L⁻¹, in 10 h at 25 °C. It is noticeable that the highest adsorption of Li⁺ at optimized parameters are in the following order: RGO/Ni3-MnO₂ (63 mg g⁻¹) > RGO/Ni2-MnO₂ (56 mg g⁻¹) > RGO/Ni1-MnO₂ (52 mg g⁻¹). A Kinetic study revealed that the experimental data were best designated pseudo-second order for each adsorbent. Li⁺ desorption experiments were performed using HCl as an extracting agent. Furthermore, all adsorbents exhibit efficient regeneration ability and to some extent satisfying selectivity for Li⁺ recovery. Briefly, it can be concluded that among the fabricated adsorbents, the RGO/Ni3-MnO₂ exhibited the greatest potential for Li⁺ uptake from aqueous solutions as compared to others.

Novel and effective reduced graphene oxide–nickel (Ni) doped manganese oxide (RGO/Ni-MnO₂) adsorbents were fabricated via a hydrothermal approach for lithium adsorption and recovery from aqueous media.     

Enhanced electrochemical performance of α-MoO3/graphene nanocomposites prepared by an in situ microwave irradiation technique for energy storage applications

Nanoparticles of α-molybdenum oxide (α-MoO₃) are directly grown on graphene sheets using a surfactant-free facile one step ultrafast in situ microwave irradiation method. The prepared α-MoO₃ and α-MoO₃/G nanocomposites are analysed by different characterization techniques to study their structural, morphological and optical properties. Transmission electron microscope images reveal the intercalation of three dimensional (3D) α-MoO₃ nanoparticles into 2D graphene sheets without any agglomeration. The electrochemical results exhibit improved performance for the α-MoO₃/G composite electrode compared to pristine α-MoO₃ owing to its structural superiority. The specific capacitance (C_s) values of the α-MoO₃/G composite and pristine α-MoO₃ are measured to be 483 and 142 F g⁻¹ respectively at a current density of 1 A g⁻¹. The α-MoO₃/G composite maintains a very strong cyclic performance after 5000 cycles. The capacitance retention of the composite electrode shows stable behavior without any degradation confirming its suitability as an enduring electrode material for high-performance supercapacitor applications.

Nanoparticles of α-molybdenum oxide (α-MoO₃) are directly grown on graphene sheets using a surfactant-free facile one step ultrafast in situ microwave irradiation method.     

Novel graphene-like two-dimensional bilayer germanene dioxide: electronic structure and optical properties

Using ab initio calculations, we present a two-dimensional (2D) α-2D-germanene dioxide material with an ideal sp³ bonding network which possesses a large band gap up to 2.50 eV. The phonon dispersion curves and molecular dynamics (MD) simulation under the chosen parameters suggest that the novel 2D structure is stable. The dielectric function and absorption spectrum also show the consistent band gap within the electronic structure diagram, suggesting possible application as an ultraviolet light optical detector. The calculated carrier mobility of 4.09 × 10³ cm² V⁻¹ s⁻¹ can be observed along the x direction, which is much higher than that of MoS₂ (∼3.0 cm² V⁻¹ s⁻¹). Finally, we found that α-2D-germanene dioxide could potentially act as an ideal monolayer insulator in so-called van der Waals (vdW) heterostructure devices. These findings expand the potential applications of the emerging field of 2D α-2D-germanene dioxide materials in nanoelectronics.

Using ab initio calculations, we present a two-dimensional (2D) α-2D-germanene dioxide material with an ideal sp³ bonding network which possesses a large band gap up to 2.50 eV.