Synergistic adsorption and photocatalytic degradation of tetracycline using a Z-scheme kaolin/g-C3N4/MoO3 nanocomposite: A sustainable approach for water treatment

This research focuses on the synthesis and application of a novel kaolin-supported g-C3N4/MoO3 nanocomposite for the degradation of tetracycline, an important antibiotic contaminant in water systems. The nanocomposite was prepared through a facile and environmentally friendly approach, leveraging the adsorption and photocatalytic properties of kaolin, g-C3N4 and MoO3 nanoparticles, respectively. Comprehensive characterization of the nanocomposite was conducted using techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and optical spectra. The surface parameters were studied using N2 adsorption-desorption isotherm. The elemental composition was studied using X-ray photoelectron spectroscopy. The efficiency of the developed nanocomposite in tetracycline degradation was evaluated and the results revealed an efficient tetracycline degradation exhibiting the synergistic effects of adsorption and photocatalytic degradation in the removal process. The tetracycline degradation was achieved in 60 min. Kinetic studies and thermodynamic analyses provided insights into the degradation mechanism, suggesting potential applications for the nanocomposite in wastewater treatment. Additionally, the recyclability and stability of the nanocomposite were investigated, demonstrating its potential for sustainable and long-term application in water treatment.

Microwave synthesis of molybdenene from MoS2

Dirac materials are characterized by the emergence of massless quasiparticles in their low-energy excitation spectrum that obey the Dirac Hamiltonian. Known examples of Dirac materials are topological insulators, d-wave superconductors, graphene, and Weyl and Dirac semimetals, representing a striking range of fundamental properties with potential disruptive applications. However, none of the Dirac materials identified so far shows metallic character. Here, we present evidence for the formation of free-standing molybdenene, a two-dimensional material composed of only Mo atoms. Using MoS2 as a precursor, we induced electric-field-assisted molybdenene growth under microwave irradiation. We observe the formation of millimetre-long whiskers following screw-dislocation growth, consisting of weakly bonded molybdenene sheets, which, upon exfoliation, show metallic character, with an electrical conductivity of ~940 S m-1. Molybdenene when hybridized with two-dimensional h-BN or MoS2, fetch tunable optical and electronic properties. As a proof of principle, we also demonstrate applications of molybdenene as a surface-enhanced Raman spectroscopy platform for molecular sensing, as a substrate for electron imaging and as a scanning probe microscope cantilever.

Highly Mesoporous MoO3 Catalysts for Electrophilic Aromatic Substitution

Herein, a straightforward synthesis method for highly mesoporous molybdenum oxide has been demonstrated via use of inverse micelles and molybdenum-oxo cluster formation. The synthesized catalyst is stable, crystalline, and MoO₃ phase pure, as confirmed through thermogravimetric analysis, X-ray diffraction, and X-ray photoelectron spectroscopy. Further results from electron paramagnetic resonance, Raman spectroscopy, and UV-vis spectroscopy confirm the MoO₃ phase purity. Chemisorption studies reveal that the synthesized material is 65 times more active than its commercial parts. The quantitative value of ammonia chemisorption for the synthesized catalyst is 1270 μmol/g, whereas the commercial catalyst only gives 22 μmol/g. These materials were tested for electrophilic substitution reactions since they are excellent solid acid. Electrophilic substitution of benzyl alcohol with toluene gives a >99% conversion with ∼80% of selectivity toward the methyl diphenylmethane product. The turnover number and turnover frequency values were calculated to be as high as 115 and 38, respectively. A substrate scope study shows that the reaction has preference toward electron-donating groups, whereas electron-withdrawing groups block the reaction. Based on the obtained results, a mechanism has been proposed.

Metal oxide charge transfer complex for effective energy band tailoring in multilayer optoelectronics

Metal oxides are intensively used for multilayered optoelectronic devices such as organic light-emitting diodes (OLEDs). Many approaches have been explored to improve device performance by engineering electrical properties. However, conventional methods cannot enable both energy level manipulation and conductivity enhancement for achieving optimum energy band configurations. Here, we introduce a metal oxide charge transfer complex (NiO:MoO₃-complex), which is composed of few-nm-size MoO₃ domains embedded in NiO matrices, as a highly tunable carrier injection material. Charge transfer at the finely dispersed interfaces of NiO and MoO₃ throughout the entire film enables effective energy level modulation over a wide work function range of 4.47 – 6.34 eV along with enhanced electrical conductivity. The high performance of NiO:MoO₃-complex is confirmed by achieving 189% improved current efficiency compared to that of MoO₃-based green OLEDs and also an external quantum efficiency of 17% when applied to blue OLEDs, which is superior to 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile-based conventional devices.

One pathway for improving the performance of optoelectronics is the tailoring energy bands of the charge transport layer. Here, Kim et al present a charge transfer complex composed out of nanodomains of MoO₃ embedded within an NiO matrix, significantly improving green and blue OLED performance.

Development of Sustainable Heterogeneous Catalysts for the Photocatalytic Treatment of Effluents

The inadequate discharge of effluents from different sources without prior treatment can impact the characteristics of soil and water, which reflect serious environmental problems. Advanced oxidative processes (AOP) appear as a viable alternative for environmental remediation, including wastewater treatment. Herein, α-MoO3 and α-Fe2O3 semiconductors were synthesized at low temperature by a Pechini-based method and then applied in photocatalysis. The catalytic efficiency was performed under visible light toward the degradation of an organic persistent pollutant (Rhodamine B dye, RhB), commonly present in industries wastewater. The results indicated that the synthesized α-MoO3 or α-Fe2O3 photocatalysts presented a pronounced activity and promoted an efficient RhB degradation after 15 min of reaction. α-MoO3 had a degradation efficiency of 93% and 98%, while α-Fe2O3 showed 67% and 100% RhB degradation without and with the addition of H2O2, respectively. These results suggest that the synthesized oxides have high oxi-reductive capacity, which can be used for a fast and effective photodegradation of RhB and other organic persistent pollutants to minimize environmental impacts.

Multi-amine-assisted crystal growth of large-sized α-MoO3 elongated nano-plates

Large-sized α-MoO₃ elongated nano-plates were synthesized by the introduction of multi-amines such as ethylene di-amine and diethylene tri-amine (DETA) in the conventional hydrothermal reaction. DETA made large hexagonal rods with an h-MoO₃ intermediate phase containing H₂O, NH₄OH, and DETA ions. During the hydrothermal reaction, the hexagonal rods were transformed to elongated α-MoO₃ nano-plates by the re-dissolution of h-MoO₃ and re-growth to α-MoO₃ because DETA retarded the preferred growth reaction of the MoO₆ octahedra to the [001] direction and helped the MoO₆ octahedra to grow in the [100] direction. In addition, DETA promoted α-MoO₃ nano-belts to be assembled into elongated nano-plates by oriented attachment because the multi-ammonium groups in the DETA backbone could adhere to the α-MoO₃ nano-belts due to attractive Coulomb interactions.

Amorphous MoO3-x nanosheets prepared by the reduction of crystalline MoO3 by Mo metal for LSPR and photothermal conversion

Amorphous MoO3-x with enhanced LSPR has been fabricated successfully by introducing Mo atoms into the interlayers of MoO3 nanosheets via a hydrothermal method. The inserted Mo atom could bond with inherent Mo atoms and further form a distorted atomic configuration structure. Thus, the amorphous MoO3-x possesses a relatively excellent photothermal conversion efficiency of 61.79%.

Eu3+, Tb3+- and Er3+, Yb3+-Doped α-MoO3 Nanosheets for Optical Luminescent Thermometry

Here we report a novel synthesis approach for the preparation of α-MoO₃:Ln³⁺ materials employing a two-step synthesis. Additionally, in this work the α-MoO₃:Ln³⁺ materials are reported as potential optical thermometers for the first time. In this synthesis approach, first MoS₂ 2D nanosheets were prepared, which were further heat treated to obtain α-MoO₃. These materials were fully characterized by powder X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray fluorescence (XRF), thermogravimetry (TG) and differential thermal analysis (DTA), transmission electron microscopy (TEM), and luminescence spectroscopy. Temperature-dependent luminescence measurements were carried out to determine the optical thermometric properties of two different types of α-MoO₃:Ln³⁺ materials (Eu³⁺/Tb³⁺ downshifting and Er³⁺/Yb³⁺ upconversion luminescence systems). We demonstrate in this study that this class of material could be a potential candidate for temperature-sensing applications.

Novel Red Emission from MoO3/MoS2-MoO2-MoO3 Core-Shell Belt Surface

Electrically driven red emission from MoS₂-MoO₂-MoO₃ (MS-MO) hybrid-based metal-semiconductor-metal (MSM) devices is reported for the first time. MoO₃ belts with high crystal quality and sufficient size are synthesized by thermal deposition. A layer of MS-MO hybrid is then produced on the belt surface to form MoO₃/MS-MO core-shell by sulfurization. The devices exhibit unique electrical properties, a nonlinear I- V curve, and electric hysteresis characteristics at high applied biases (>2.4 V), where MS-MO hybrids act as electron transport channels. The electroluminescent current of the device increases to a set current limit over time when a constant bias is applied. The novel characteristics of the device are attributed to the space charge limited conduction (SCLC) mechanism occurring in MS-MO hybrids. The strong light emission is from recombination of excitons within the MoS₂ phase. This work develops a simple and effective method to drive MoS₂ to emit light on a large scale without using monolayer MoS₂ and vertical p-n junctions, indicating great potential for future 2D optoelectronics and photonics applications.

Soft chemistry of ion-exchangeable layered metal oxides

Disassembly and re-assembly of layered metal oxides by soft chemical approaches can be used to tailor functionalities in artificial photosynthesis, energy storage, optics, and piezoelectrics.

Highly dispersed Au nanoparticles decorated WO3 nanoplatelets: Laser-assisted synthesis and superior performance for detecting ethanol vapor

Loading of noble metal nanoparticles (NPs) on the surfaces of semiconductor oxides to form a hybrid nanostructure is an effective strategy to improve gas-sensing performance. In this study, WO₃ nanoplatelets decorated with Au NPs were prepared by laser ablation in liquids (LAL) with subsequent aging and annealing treatments. Results indicated that Au NPs with an average size of 7.8 ± 2.5 nm were highly dispersed on the surface of WO₃ nanoplatelets. As gas-sensing materials, the obtained Au-decorated WO₃ nanoplatelets showed lower operating temperature of 320 °C and higher response value of 3.5-fold in detecting ethanol molecules compared with pure WO₃ nanoplatelets. Moreover, Au-decorated WO₃ nanoplatelets displayed good selectivity toward ethanol compared with other tested vapors and excellent stability within several cycled measurements. These results can be ascribed to the supported Au NPs, which promote the adsorption and dissociation of oxygen species, eventually resulting in accelerated electron depletion on the surface of Au-WO₃ hybrids.

MoS2 Nanosheets Supported on Hollow Carbon Spheres as Efficient Catalysts for Electrochemical Hydrogen Evolution Reaction

Hybridizing structured carbon materials with MoS₂ has been demonstrated to be an effective method to increase the electrochemical hydrogen evolution reaction (HER) activity and durability of MoS₂. In this study, we report the growth of MoS₂ nanosheets on the surface of uniform hollow carbon spheres (HCS) to form a hydrangea-like nanocomposite. The HCS were formed through carbonization of a phenol formaldehyde template, and the MoS₂ nanosheets were grown on the HCS surfaces through a hydrothermal method. The nanocomposites have the advantages of significantly improved electrical conductivity, ease of varying the MoS₂ loading, and minimizing stacking of MoS₂ nanosheets, which are manifested by their remarkably improved HER performance. The well-tuned carbon-MoS₂ composite shows a Tafel slope of 48.9 mV dec^-1, an onset potential of -0.079 V (vs reversible hydrogen electrode), and an overpotential of 126 mV at the current density of 10 mA cm^-2 after 1000 potential cycles.

Localized Charge Transfer in Two-Dimensional Molybdenum Trioxide

Molybdenum trioxide is an interesting inorganic system in which the empty 4d states have potential to hold extra electrons and therefore can change states from insulating opaque (MoO₃) to colored semimetallic (H_xMoO₃). Here, we characterize the local electrogeneration and charge transfer of the synthetic layered two-dimensional 2D MoO₃-II (a polymorph of MoO₃ and analogous to α-MoO₃) in response to two different redox couples, i.e., [Ru(NH₃)₆]³⁺ and [Fe(CN)₆]^3- by scanning electrochemical microscopy (SECM). We identify the reduction of [Ru(NH₃)₆]³⁺ to [Ru(NH₃)₆]²⁺ at the microelectrode that leads to the reduction of MoO₃-II to conducting blue-colored molybdenum bronze H_xMoO_3. It is recognized that the dominant conduction of the charges occurred preferentially at the edges active sites of the sheets, as edges of the sheets are found to be more conducting. This yields positive feedback current when approaching the microelectrode toward 2D MoO₃-II-coated electrode. In contrast, the [Fe(CN)₆]^4-, which is reduced from [Fe(CN)₆]^3-, is found unfavorable to reduce MoO₃-II due to its higher redox potential, thus showing a negative feedback current. The charge transfer on MoO₃-II is further studied as a function of applied potential. The results shed light on the charge transfer behavior on the surface of MoO₃-II coatings and opens the possibility of locally tuning of their oxidation states.

Substrate-Friendly Growth of Large-Sized Ni(OH)2 Nanosheets for Flexible Electrochromic Films

Large-area, 2D, anisotropic, direct growth of nanostructures is considered an effective and straightforward way to readily fulfill transparent, flexible technology requirements. In addition, formation of thin hybrid structures by combining with another 2D material brings about dimensional advantages, such as intimate heterostructure functionalities, large specific area, and optical transparency. Here, we demonstrate 2D planar growth of thin Ni(OH)₂ nanosheets on arbitrary rigid and soft supports, by exploiting the growth strategies of oriented attachment induced by interfacial chemistry and the intrinsic driving force of layered structure constitution. Moreover, large-scale 2D heterohybrids have successfully been prepared by direct conformal growth of Ni(OH)₂ nanosheets overlying MoO₃ nanobelts. Unlike the exfoliation and transfer of 2D materials technique, this approach minimizes multiple process contamination and physical-handling structural defects. Accordingly, proof-of-concept flexible electrochromism is demonstrated in view of its prerequisite to the access of a large homogeneous material coating. The as-synthesized 2D layered structure affirms its optical and electrochemical superiority through the display of wide optical modulation, high coloration efficiency, good cyclic stability, and flexibility.

Construction of a new ternary α-MoO3–WO3/CdS solar nanophotocatalyst towards clean water and hydrogen production from artificial wastewater using optimal design methodology

Facile construction of ternary α-MoO_3(0.03)–WO_3(0.36)/CdS_(0.61) nanophotocatalyst for generation of renewable clean water and energy from synthetic wastewater under solar irradiation.

CeO2-modified α-MoO3 nanorods as a synergistic support for Pt nanoparticles with enhanced COads tolerance during methanol oxidation

A new type of Ce-doped α-MoO₃ (Ce_0.2Mo_0.8O_3−δ) nanorod support was synthesized using a two-step hydrothermal method.

MoOx–pyridine organic–inorganic hybrid wires as a reusable and highly selective catalyst for the oxidation of alcohols: a comparison study between reaction-controlled phase-transfer catalysis and heterogeneous catalysis

The different catalytic behaviors of Mo₃O₁₀(C₅H₆N)₂·H₂O wires (MoO_x–pyridine) in the selective oxidation of alcohols by means of molecular oxygen (O₂) and hydrogen peroxide (H₂O₂) as green oxidants were investigated.

Advanced Li-Ion Hybrid Supercapacitors Based on 3D Graphene-Foam Composites

Li-ion hybrid supercapacitors (LIHSs) have recently attracted increasing attention as a new and promising energy storage device. However, it is still a great challenge to construct novel LIHSs with high-performance due to the majority of battery-type anodes retaining the sluggish kinetics of Li-ion storage and most capacitor-type cathodes with low specific capacitance. To solve this problem, 3D graphene-wrapped MoO₃ nanobelt foam with the unique porous network structure has been designed and prepared as anode material, which delivers high capacity, improved rate performance, and enhanced cycle stability. First-principles calculation reveals that the combination of graphene dramatically reduces the diffusion energy barrier of Li⁺ adsorbed on the surface of MoO₃ nanobelt, thus improving its electrochemical performance. Furthermore, 3D graphene-wrapped polyaniline nanotube foam derived carbon is employed as a new type of capacitor-type cathode, demonstrating high specific capacitance, good rate performance, and long cycle stability. Benefiting from these two graphene foam-enhanced materials, the constructed LIHSs show a wide operating voltage range (3.8 V), a long stable cycle life (90% capacity retention after 3000 cycles), a high energy density (128.3 Wh·kg^-1), and a high power density (13.5 kW·kg^-1). These encouraging performances indicate that the obtained LIHSs may have promising prospect as next-generation energy-storage devices.

Doping-free bandgap tuning in one-dimensional Magnéli-phase nanorods of Mo4O11

We synthesized one-dimensional (1D) Magnéli-phase nanorods of Mo4O11 using the hot filament metal-oxide vapor deposition technique. The 1D Magnéli-phase Mo4O11 nanorods synthesized at 1000, 1050, 1100, 1150, and 1200 °C contain varying combinations of two orthorhombic (α) and monoclinic (η) phases, and various mixtures of Mo(4+), Mo(5+) and Mo(6+) cations, while those synthesized at a higher temperature look bluer. The shifts of the transmittance maximum and absorbance minimum of the 1D Magnéli-phase Mo4O11 nanorods are inversely and linearly proportional to the elevated temperature, verifying that the bandgaps (Eg) are inversely proportional to the elevated temperature. The bandgap (Eg) of the 1D Magnéli-phase Mo4O11 nanorods can be tuned by simply controlling the synthesis temperature without doping with other materials, giving the 1D Magnéli-phase Mo4O11 nanorods good potential for use in optoelectronic nanodevices and bandgap engineering.

Systematic synthesis and analysis of change in morphology, electronic structure and photoluminescence properties of 2,2′-dipyridyl intercalated MoO3 hybrid nanostructures and investigation of their photocatalytic activity

An organic–inorganic hybrid was synthesized using 2,2′-dipyridyl and MoO₃ nanorods via simple hydrothermal method. Here, dipyridyl has acted as stretching molecule and bonded the MoO₃ nanorods together along the length to form hybrid micro crystals.

Synthesis and characterization of alkali metal molybdates with high catalytic activity for dye degradation

In this contribution, the synthesis and catalytic activity of alkali metal molybdates for the degradation of cationic dyes under ambient conditions were systematically studied.

Microwave assisted fast formation of Sn(MoO4)2 nano-assemblies on DNA scaffold for application in lithium-ion batteries

Self-assembled aggregated Sn(MoO₄)₂ nanomaterials on DNA scaffolds exhibit enhanced capability as anode materials in lithium-ion battery (LIB) applications.

An ultraselective and ultrasensitive TEA sensor based on α-MoO3 hierarchical nanostructures and the sensing mechanism

Flower-like α-MoO₃ hierarchical nanostructures were successfully synthesized via a single-step solvothermal route. A sensor based on α-MoO₃ flowers manifested superior gas sensing performance towards TEA at 170 °C.

Facile fabrication and enhanced gas sensing properties of hierarchical MoO3 nanostructures

Hierarchical MoO₃ nanostructures, synthesized through oxidization conversion of hydrothermally synthesized MoS₂ precursors, show superior gas sensing performance toward ethanol.