MoO3 Nanorods Research Articles

Greener assembling of MoO3 nanoparticles supported on gum arabic: cytotoxic effects and catalytic efficacy towards reduction of p-nitrophenol

An economical and easy one-step method for the biosynthesis of highly stable molybdenum trioxide (MoO3) nanoparticles was developed using gum arabic as a bio-template; ensuing nanoparticles (NP) were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, UV–visible spectroscopy, transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX). The crystallinity and purity of MoO3 nanoparticles in the orthorhombic phase were confirmed by XRD analysis, and their rod-shaped identity (average sizes ranging from 7.5 to 42 nm) were observed by TEM. Cytotoxic effects of the NP were monitored using Hep G2 (human liver cancer) and HEK 293 (human embryonic kidney) cell lines via 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide assays. The results of this study revealed that MoO3 nanoparticles are nontoxic towards Hep G2 cell lines and displayed negligible toxicity, even at very high concentrations (1000 ppm), although had moderate toxicity towards HEK 293 cells. Furthermore, their catalytic activity was evaluated for the reduction of p-nitrophenol to p-aminophenol. Synopsis: Green synthesis of MoO3 nanorods using gum arabic demonstrated as an eco-friendly catalyst for the conversion of p-nitrophenol with negligible toxicity towards Hep G2 cell lines.

Improved electrochemical performance of rGO-wrapped MoO3 nanocomposite for supercapacitors

A low-cost hydrothermal method has been employed to synthesize phase pure α-MoO3 and MoO3/rGO nanocomposite electrodes with novel structures for high-performance supercapacitors. Both nanocomposites exhibited orthorhombic layered structure. Pure MoO3 exhibited nanorod-like morphology, whereas MoO3/rGO nanocomposite showed flower-like structure. The TEM studies reveal that the GO reduced to rGO and wrapped to the MoO3 nanorods. The pure MoO3 nanorods electrode demonstrated a specific capacitance of 331 F/g at a current density of 1 A/g. The MoO3/rGO nanocomposite electrode with unique flower-like structure showed enhanced electrochemical performance with a specific capacitance of 486 F/g at a current density of 1 A/g with 92% capacity retention even after 1000 discharge cycles.

One-dimensional MoO3/Pd nanocomposite electrodes for high performance supercapacitors

One-dimensional (1D) nanostructures are the exemplary host for fabricating active electrode material for supercapacitors as they have large specific surface area, robust adsorption/desorption capability and outstanding thermal stability, which could assist as support and promoter to anchor noble metal nanoparticles with enhanced electrochemical properties. Herein, pure and MoO3/Pd nanocomposites have been synthesized by simple hydrothermal method. The XRD spectrum of synthesized powder exhibited orthorhombic α-MoO3 structure and the calculated average crystallite sizes are 42 nm and 33 nm for pure and MoO3/Pd nanocomposites respectively. The Pd nanoparticles plays a crucial role in controlling the structure. The SEM images showed 1D nanorods like structure with a size of about 100 nm dia and few micrometer length. The TEM images confirm the Pd nanoparticles are incorporated into the 1D MoO3 nanorods. The electrochemical properties of pure and MoO3/Pd 1D nanocomposite electrodes showed pseudocapacitive nature. The MoO3/Pd electrode exhibited high specific capacitance of 501 F g−1 at a current density of 1 mA g−1 with good cycling stability. The high specific capacitance of newly fabricated MoO3/Pd nanocomposite electrode is mainly associated with the synergetic effect between Pd nanoparticles and MoO3 nanorods.

Graphene and diglyme assisted improved Al3+ ion storage in MoO3 nanorod: steps for high-performance aqueous aluminum-ion battery

An approach to improve the Al3+ ion storage capacity of MoO3 in aqueous electrolyte is illustrated here. Graphene as conductive additive and diglyme as electrolyte additive play a pivotal and synergistic role in the improvement. Graphene-MoO3 composite exhibits stable capacity of 160 mAh g−1 over 100 cycles in diglyme mixed aqueous electrolyte with v/v mixing ratio of 50:50, whereas it delivers a capacity of only 75 mAh g−1 at the 100th cycle in pristine aqueous electrolyte. Besides, pristine MoO3 also demonstrates improved stability in diglyme mixed aqueous electrolyte.

One-dimensional architecture with reduced graphene oxide supporting ultrathin MoO2 nanosheets as high performance anodes for lithium-ion batteries

Two-dimensional (2D) materials have been widely studied and used as anode materials for lithium ion batteries (LIBs) because of their high specific surface area and intrinsic mechanical flexibility which could offer numerous active sites and protect effect for LIBs. However, 2D nanosheets are easy to stack and partially lose surface area for Li-ion storage thus greatly affecting their electrochemical performance. Here, we develop a simple strategy to obtain a nanosheets-based one-dimensional structure hybrid by in situ reduction from MoO3 nanorods to MoO2 nanosheets and nanoparticles which are anchored on a 1D reduced graphene oxide skeleton (MoO2-rGO). It was demonstrated that the primary MoO2 nanosheets and nanoparticles are uniformly dispersed on the reduced graphene oxide nanosheets, which are further assembled into a 1D loosened nanostructure. The loosened nanosheets offer more accessible surface area and facilitate transport of electrons and Li-ions. Moreover, MoO2 nanoparticles effectively avoid agglomeration from nanosheets. Results show that MoO2-rGO hybrid demonstrates an enhanced cyclic life, high stability and prominent rate performance when evaluated as anode material for LIBs. The first discharge capacity can reach 1256.4 mAh g−1 and provide a highly reversible capacity of 1003.7 mA h g−1 after 100 cycles at 0.1 A g−1, which makes MoO2-rGO a promising candidate for LIBs. The excellent performance can be attributed to the unique 1D loosened structure consists of MoO2 and conducting rGO nanosheets, which facilitates fast transfer of Li-ion and electron, and the reduced graphene oxide nanosheets acting as a skeleton provide a continuous conductive network and simultaneously strengthen the structural stability.

Porous Mo2C nanorods as an efficient catalyst for the hydrogen evolution reaction

Generate hydrogen fuel from electrochemical water splitting has been considered as a promising approach. However, to obtain the low-cost and high performance catalysts towards hydrogen evolution reaction (HER) which can be applied in both alkaline and acid solution remains a challenge. Herein, we synthesized an active and stable HER catalyst composed of Mo2C nanocrystals embedded in the nanocarbon layers (Mo2C@C) by using MoO3 nanorods as precursor. Benefiting from the porous one dimensional structure and ultrafine Mo2C nanocrystals, Mo2C@C exhibits high HER catalytic activity for 10 mA cm−2with the overpotential of 119 mV in 1 M KOH solution and 170 mV in 0.5 M H2SO4solution, respectively. Moreover, Mo2C@C displays long durability during the HER process with almost no decay and maintains the porous one dimensional architecture after the HER stability test. This study offers the guideline for the further design and fabrication of the nanostructured HER electrocatalysts in wide pH range.

Green tide biomass templated synthesis of molybdenum oxide nanorods supported on carbon as efficient nanozyme for sensitive glucose colorimetric assay

The nanozymes, alternative for natural enzymes, have become popular in many research fields because they exhibit relatively high activity and stability. Herein, we utilize abundant, renewable ocean green tide (Enteromorpha prolifera, EP) waste as a biotemplate to facilely prepare MoO3 nanorods supported on EP derived carbon (MoO3/C). The as-prepared MoO3/C exhibited excellent peroxidase-like activity with Km of 0.13 mM and Vmax of 0.292 μM s−1 (H2O2 as the substrate), superior to most mimetic peroxidases reported so far. The catalytic mechanism of the as-synthesized MoO3/C is proven to be a Ping-pong BiBi electron transfer mechanism. Further, the MoO3/C was used for non-enzymatic measurement of H2O2 sensitively, with the linear H2O2 concentration range of 1–100 μM and a low limit of detection (LOD) of 0.181 μM (S/N = 3). Based on its excellent catalytic activity and stability, the MoO3/C was coupled with glucose oxidase to apply for the colorimetrically sensing glucose sensitively and selectively, with two linear parts, 0.02–0.5 mM as well as 0.5–6.0 mM glucose and a LOD of 10 μM glucose (S/N = 3). Moreover, the detection of blood glucose in real human serums was realized successfully. Thus, the green tide biomass waste templated strategy opens up an avenue to develop nanozymes for many applications, which is simple, cost-effective and environmentally friendly.

Facile synthesis of novel ultrathin α‐MoO 3 square nanosheets with excellent adsorptive capacity and photocatalytic performance for efficient treatment of Rhodamine B

Novel ultrathin α-MoO3 square nanosheets with the width of 200–400 nm and the thickness of ∼50 nm were synthesised successfully via a facile and efficient solid sintered method using the carbon@MoS2 nanocomposites as precursor. The as-prepared products were characterised by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, and tested in adsorption and photocatalysis to remove Rhodamine B (RhB). Compared with commercial MoO3 and/or MoO3 nanorods, α-MoO3 square nanosheets exhibit greater adsorptive capacity and photocatalytic performance for degrading RhB. Moreover, this combination of adsorption and photocatalysis using α-MoO3 could be promising is demonstrated as a more pressing technique for contaminant removal from wastewater.

A simple approach for synthesis of hollow mesoporous nanotubes loaded with metallic and magnetic nanoparticles: Only one step is required

Hollow mesoporous polypyrrole (PPy)@Pd‐Fe3O4 nanotubes were prepared using MoO3 nanorods as hard templates in one step, in which construction of PPy nanotubes, preparation of Pd nanoparticles, synthesis of Fe3O4 nanoparticles and removal of MoO3 nanorods were combined together. To the best of our knowledge, this is the simplest approach for the synthesis of nanomaterials with catalytic activity, magnetic property and hollow mesoporous structure simultaneously. Although the preparation procedure was simplified, the catalytic activity and magnetic property were not sacrificed. In the catalytic reduction of 4‐nitrophenol, both reaction rate constant and turnover frequency were higher than those of previous reports. Importantly, the nanotubes could be easily separated from the reaction solution in the presence of a magnetic field, and saturation magnetization could be controlled by the amount of pyrrole monomer. After six recycles, the catalytic activity maintained 94.8% of that of the first run, indicating good stability and reusability.

3D multiporous Co,N co-doped MoO2/MoC nanorods hybrids as improved electrode materials for highly sensitive simultaneous determination of acetaminophen and 4-aminophenol

3D multiporous Co, N co-doped MoO2/MoC (3D Co,N-MoO2/MoC) nanorods hybrids were successfully synthesized via carburizing core-shell ZIF-67-cladded MoO3 nanorods precursor at high temperature. As-fabricated Co,N-MoO2/MoC nanorods coated glassy carbon electrodes (GCE) was demonstrated to possess superior electrocatalytic activity for the electro-oxidation of acetaminophen (AC) and 4-aminophenol (4-AP). Such excellent electrochemical performance was largely attributed to the synergistic effect of the unique multiporous structure, the optimal component and abundant active sites of the nanorods. The corresponding electrode reaction mechanisms were studied in detail in this article. Under optimal conditions, the linear detection ranges were 0.05–200.0 μmol/L for AC and 0.05–140.0 μmol/L for 4-AP, respectively, with the low detection limits of 0.013 μmol/L and 0.012 μmol/L. Furthermore, the 3D Co,N-MoO2/MoC/GCE revealed excellent sensitivity, good reproducibility, stability and anti-interference ability. The developed electrode was evaluated towards the detecting AC and 4-AP in biological fluids, environment water and pharmaceutical formulations with satisfactory recovery, which had a broad application prospect.

Hierarchically ordered carbon tube-sheet superstructure via template-directed self-assembly of polyimide

In this work, we report a template-directed self-assembly strategy towards the gram-level synthesis of hierarchically ordered carbon tube-sheet superstructure (CTSS) by using MoO3 nanorod as the template and polyimide (PI) as the carbon source. Even in large quantities, MoO3 nanorods can guide the assembly of PI in solution into vertically oriented nanosheet arrays with periodic patterns, which can be converted to nitrogen-doped porous CTSS after the removal of template and thermal carbonization. Possessing hierarchically ordered architecture, rich porosity and high nitrogen content, CTSS is an appealing material for energy storage and conversion devices such as high-performance lithium ion battery anode and water splitting catalyst support. More importantly, the results in this work highlight an avenue for the controllable synthesis of hierarchically ordered carbon superstructures with diversified functions and applications.

Rational interaction between the aimed gas and oxide surfaces enabling high-performance sensor: The case of acidic α-MoO3 nanorods for selective detection of triethylamine

The rational interaction between the oxide surfaces and aimed gas is favorable for enhancement in gas-sensing (including rapid response and recovery rate, remarkable response value, and excellent selectivity). Herein, we have prepared acidic α-MoO3 nanorods through a facile hydrothermal route. The as-obtained MoO3 nanorods possess about 10 μm in length and around 200–300 nm in diameter, respectively. The gas sensor fabricated using these MoO3 nanorods exhibits an apparent response to triethylamine (TEA) vapor with an actual detection concentration as low as 0.1 ppm at its optimal working temperature of 300 °C. The response time for detecting 100 ppm TEA is only 4 s, and the recovery time is less than 2 min (88 s). Moreover, the sensor shows an extremely remarkable selectivity towards TEA against other interfering gases, such as methanol, ethanol, isopropanol, acetone, toluene, and ammonia. The impressive TEA sensing of these MoO3 nanorods could be determined by suitable interaction between TEA molecules and the MoO3 surfaces (including base/acid attractive force, highly active lattice oxygen for catalytical oxidation of TEA, and fast adsorption/desorption kinetics at certain temperature). This paper provides an avenue for designing high-performance gas sensor from perspective of understanding the interaction between aimed gas and material surfaces.

One-Dimensional Porous Hybrid Structure of Mo2C-CoP Encapsulated in N-Doped Carbon Derived from MOF: An Efficient Electrocatalyst for Hydrogen Evolution Reaction over the Entire pH Range.

The development of outstanding noble-metal-free electrocatalysts for the hydrogen evolution reaction (HER) has attracted broad interest. Herein, a novel one-dimensional (1D) HER hybrid catalyst consisted of cobalt phosphide (CoP) and molybdenum carbide (Mo2C) nanoparticles wrapped by nitrogen-doped graphitic carbon (called CoP/Mo2C-NC) was successfully fabricated by a facile continuous-flow method and a simple two-step annealing process. During these processes, the successful synthesis of the MoO3 nanorods coated with cobalt zeolitic imidazolate frameworks (Co-ZIF-67) (Co-ZIF-67@MoO3) through the continuous-flow method plays a key role. The as-synthesized CoP/Mo2C-NC hybrid electrocatalyst exhibits a significantly enhanced HER electrocatalytic activity over the entire pH range relative to that of the control materials CoP, Mo2C-NC, and physically mixed CoP and Mo2C-NC. The outstanding HER catalytic performance is mainly due to the fact that the electron cloud transfers from Co to Mo in CoP/Mo2C-NC through the Co-P-Mo bond, resulting in the formation of a high valence state for Co (Co3+) species and lower valence states for Mo (i.e., Mo2+, Mo3+) species, providing the abundant HER active sites. Moreover, the Gibbs free energy (Δ GH*) of CoP/Mo2C-NC obtained by the density function theory calculations indicates a good balance between the Volmer and Heyrovsky/Tafel steps in HER kinetics. Such a cobalt zeolitic imidazolate framework-mediated strategy depicted in this work offers an interesting perspective for developing highly efficient noble-metal-free electrocatalysts for hydrogen production.

Creation of Au nanoparticles decorated MoO3 nanorods using CoSP and the application as hole transport layer (HTL) in plasmonic-enhanced organic photovoltaic devices

Surfactant free MoO3 nanorods (50 nm–5 µm long and 50–300 nm diameter) with Au nanoparticles with varying nanorod dimensions and Au fraction have been synthesized in-situ by using inexpensive continuous spray pyrolysis (CoSP) technique. In-situ grown gold nanoparticles (∼10–20 nm) with MoO3 nanorods (Au/MoO3) were obtained which proved useful in getting the additional effect due to plasmonics. The CoSP- synthesized Au/MoO3 nanorods have been used as anode buffer layers in organic photovoltaic devices (OPVs). The resulting devices exhibit a remarkable enhancement in power conversion efficiency (from 2.22% to 3.71%) when Au/MoO3 nanorods were used in the device which can be attributed to the strong localized surface plasmon resonance (LSPR) absorption.

Synthesis and Characterization of 1D-MoO3 Nanorods Using Abutilon indicum Extract for the Photoreduction of Hexavalent Chromium

In this present work, we report a novel green synthesis of MoO3 nanorods (NRs) utilizing Abutilon Indicum (A. Indicum) plant extract, containing palmitric, linoleic, linolinic acids and their derivatives which might be acting as both reducing and stabilizing agents. The synthesized catalyst has been employed to reduce toxic Cr(VI) to Cr(III) in the aqueous solution which was continuously monitored by UV–Vis absorbance spectroscopy. The structural, optical and morphological characterizations are performed using PXRD, UV-DRS, PL, FESEM, TEM, FT-IR and EDAX. The optical properties were precisely investigated by calculating the Tauc’s relation. The band gap of as synthesized MoO3 was found to be 2.57 eV (483 nm) which falls under visible region, thus catalyst can be activated under solar light which could be cost effective. Biologically synthesized MoO3 NRs showed highest activity, i.e., almost 99% toward reduction of Cr(VI) under solar light. In addition to this, the photo firmness and reusability test showed that the catalyst can be reused upto five cycles without waning its activity.

Investigations of Interfacial Electric Field on Reduced‐Graphene‐Oxide‐Supported Molybdenum Oxide @ Silver Phosphate Ternary Hybrid Composite: Highly Efficient Visible‐Light‐Driven Photocatalyst

AbstractReduced graphene oxide supported molybdenum oxide @ silver phosphate (RGO‐MoO3@Ag3PO4) ternary hybrid composite was prepared by simple mixing of RGO supported MoO3 nanorods into Ag3PO4 nanosphere. Upon visible light exposure, the photocatalytic degradation of MB revealed that the 30 wt.% RGO‐MoO3@Ag3PO4 photocatalyst led to 2.9 times higher activities than pure Ag3PO4, 6.2 and 8.7 times compared to RGO‐MoO3 and pure MoO3, respectively. Degradation of MB using 30 wt.% RGO‐MoO3@Ag3PO4 is 2.9 and 15 times higher compared to RhB and MO respectively. The downward band bending of Ag3PO4 at the interface of RGO‐MoO3@Ag3PO4 was investigated based on the electric field formed. The formed electric field at the interface of RGO‐MoO3@Ag3PO4 is found to be 50 mV which avoids the recombination rate of electron‐hole pairs at the interfaces. This formed electric field promotes the higher separation efficiency of electrons‐holes pairs and longer life time of photoexcited electrons in the RGO‐MoO3@Ag3PO4 resulting higher efficiency and stability. RGO act as an electron acceptor and transporter during charge transfer process between MoO3 and Ag3PO4.

H-MoO3/Activated carbon nanocomposites for electrochemical applications

MoO3 nanorods were synthesized through the microwave method and the nanocomposites of MoO3/activated carbon were prepared for supercapacitor and hydrogen evolution reaction (HER). The XRD pattern revealed that the prepared MoO3 has a hexagonal phase (h-MoO3). The as-prepared h-MoO3 was composited with activated carbon (AC) and tested for supercapacitor studies. The fabricated supercapacitor exhibited an appreciable specific capacitance, power density, and energy densities. Further, dedoping of nitrogen in the doped AC creates defects on AC (DAC). These DAC/MoO3 nanocomposites were prepared and tested for its electrocatalytic activity towards hydrogen evolution reactions. DAC/MoO3 nanocomposite showed much higher electrocatalytic activity than the neat MoO3.

Laser-induced thermal effects in hexagonal MoO3 nanorods

Laser-induced thermal effects on the hexagonal MoO3 nanorods at different power density levels were studied using Raman spectroscopy and scanning electron microscopy techniques. The structural features of the nanorods were accompanied by varying the incident laser power from 8.0 to 600 mW by using a gradual increasing rate and a sudden increasing incident laser power. It was shown that the photoeffects observed on the MoO3 nanorods critically depends on the exposure rate. By gradually increasing the incident laser power up to 600 mW, morphology of the nanorods were completely preserved, and the observed thermal behavior was discussed on the basis of thermal contact at nanoscale. However, when the irradiation intensity was suddenly increased, it was observed that overheating of h-MoO3 nanorods at relatively lower laser powers (80 mW) sublimate the nanorods around the laser spot region. The MoO3 molecules on vapor-phase at high temperatures condense and crystallize next to the laser spot on the orthorhombic (α-MoO3) and monoclinic (β-MoO3) phases. Furthermore, the nanorods closest to the laser spot region undergo a structural phase (and morphological) transition from h-MoO3 phase to α-MoO3 phase.

From MoO2@MoS2 Core–Shell Nanorods to MoS2 Nanobelts

One‐dimensional (1D) atomically thin crystals have attracted considerable interests due to their unique properties and potential applications. For example, reducing graphene physical size down to nanoscale to nanoribbons opens up band gaps, which makes graphene useful in electronic devices. Here, a facile approach to produce single‐ and bi‐layered MoS2 nanobelts by PMMA assisted decoupling of MoO2@MoS2 core–shell nanorods is reported by the authors. Atomic force microscopy (AFM), Raman and photoluminescence (PL) results show that the decoupled monolayer staple‐like MoS2‐shells can fold into bilayer nanobelts during the PMMA removal process. Raman, high‐resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) results reveal that the left MoO2 nanorods exhibit high crystal‐quality. These findings provide a method to produce 1D MoS2 nanobelts, which have potential applications in electronics and catalysis.

Efficient and Cost-effective Photoelectrochemical Degradation of Dyes in Wastewater over an Exfoliated Graphite-MoO3 Nanocomposite Electrode

Herein, we prepared hexagonal MoO3 (h-MoO3) nanorods by homogenous co-precipitation and utilized them to fabricate a composite h-MoO3-exfoliated graphite (EG) electrode. The above composite was characterized by scanning electron microscopy, Raman spectroscopy, X-ray diffraction, and UV-Vis spectroscopy, and used for the degradation of cationic (methylene blue, MB) and anionic (methyl red, MR) dyes in synthetic wastewater. The efficiency of this degradation was assessed by UV-Vis spectroscopy and electrochemical techniques. Good dispersion of h-MoO3 in EG decreased the electron-hole recombination rate and enhanced the photon absorption efficiency of the EG-MoO3 electrode, which therefore exhibited a higher dye photodegradation efficiency than the bare EG one. Specifically, the efficiencies of 180-min MB photodegradation over EG and EG-MoO3 electrodes were 66.9 and 88.55%, respectively, whereas the corresponding values for MR were 68.0 and 92.22%, respectively, i.e., MR was degraded more effectively than MB. Furthermore, photoelectrochemical oxidation was shown to be more efficient than purely photolytic and electrochemical oxidation, which, together with the ease of preparation, low cost, and high photoactivity/stability of the fabricated nanocomposite electrode makes it potentially suitable for industrial wastewater treatment.