Construction of hierarchical NCMTs@MoO2/FeNi3 tubular heterostructures for enhanced performance in catalysis and protein adsorption

A new type of hybrid material (NCMTs@MoO2/FeNi3) with a multi-layer heterostructure was designed and fabricated via a one-step pyrolysis process using FeOOH/NiMoO4@PDA as the precursor. FeOOH/NiMoO4@PDA was prepared by the solvothermal method, followed by the nickel-ion etching method coupled with the polymerization of dopamine (DA). The as-obtained material was made of nitrogen-doped carbon nanotubes embedded with FeNi3 and MoO2 nanoparticles (NPs). Notably, the FeNi3 NPs exhibited significantly improved performance in the reduction of 4-nitrophenol (4-NP) and adsorption of histidine-rich protein as well as provided appropriate magnetism resources. The MoO2 NPs imparted a metallic nature with excellent conductivity, and the N-doped mesoporous carbon microtubes also improved conductivity and facilitated mass transfer, thus leading to enhanced performance in catalysis. Benefiting from the 1D hierarchical porous structure and compositional features, the NCMTs@MoO2/FeNi3 composites exhibited excellent performance in 4-NP reduction and protein adsorption via specific metal affinity between the polyhistidine groups of proteins and the FeNi3 NPs. The result presented here indicates that the strategy of combining tailored components, heterostructuring, and carbon integration is a promising way to obtain high-performance composites for other energy-related applications.

Plasma-liquid synthesis of MoOx and WO3 as potential photocatalysts

Plasmas in contact with liquids represent a green chemistry method for the synthesis of metal oxides. In this work, underwater plasma was used for the synthesis of molybdenum and tungsten oxides. The obtained samples were analyzed by various techniques. Results showed that underwater plasma with Mo electrodes allows obtaining non-stoichiometric molybdenum oxide (MoOx). In the case of tungsten electrodes, monoclinic WO3 was formed. The synthesized oxides have a wide band gap (3.21 eV for MoOx and 3.27 eV for WO3). The photocatalytic and sorption activities of the synthesized oxides towards the decomposition of cationic and anionic dyes (Methylene Blue, Rhodamine B, and Reactive Red 6C) were studied. MoOx shows excellent photocatalytic performance under UV and visible light irradiation. The photocatalytic activity of WO3 under visible light is less than that under UV irradiation.

Engineering MoS2 nanostructures from various MoO3 precursors towards hydrogen evolution reaction

MoS₂, MoO₂–MoS₂-B and MoO₂–MoS₂-R nanoflowers were prepared using α-MoO₃ particles, α-MoO₃ nanobelts and h-MoO₃ microrods, respectively; larger exposure of Mo–S and lower amounts of Mo–O were responsible for the higher HER performance.

Revealing the role of the 1T phase on the adsorption of organic dyes on MoS2 nanosheets

Herein, different phases of MoS₂ nanosheets were synthesized, characterized and tested for dye removal from water. The influence of the MoS₂ phases as well as the 1T concentration on the adsorption performance of organic dyes MO, RhB and MB was deeply investigated. The results revealed that the 1T-rich MoS₂ nanosheets have superior adsorption performance compared to other 2H and 3R phases. The kinetic results of the adsorption process demonstrate that the experimental data followed the pseudo-second order equation. Meanwhile, the adsorption of dyes over the obtained materials was fitted with several isotherm models. The Langmuir model gives the best fitting to the experimental data with maximum a adsorption capacity of 787 mg g⁻¹. The obtained capacity is significantly higher than that of all previous reports for similar MoS₂ materials. Computational studies of the 2H and 1T/2H-MoS₂ phases showed that the structural defects present at the 1T/2H grain boundaries enhance the binding of hydroxide and carboxyl groups to the MoS₂ surface which in turn increase the adsorption properties of the 1T/2H-MoS₂ phase.

The high adsorption capacity of dyes onto the 1T-rich MoS₂ samples is due to the strong binding between the hydroxide/carboxyl groups and the 1T active sites. The capacity can be tuned by controlling the ratio between 1T and 2H phases of MoS₂ nanosheets.

Adsorption behavior of isocyanate/ethylenediamine tetraacetic acid-functionalized graphene oxides for Cu2+ removal

A special adsorption of Cu²⁺ removal is demonstrated using specifically functionalized graphene oxide (GO)/isocyanate (MDI) composites, on which ethylenediamine tetraacetic acid (EDTA) is grafted via amidation and carbamate reaction. The structure and morphology of GO and functionalized composites (EDTA/MDI/GO) were characterized by scanning electron microscope (SEM), Fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Thermogravimetric analysis (TGA). This study investigated the adsorption and desorption behaviors of heavy metal cations and the effects of solution conditions such as pH on Cu²⁺ removal. The experimental results illustrated that after introducing EDTA and MDI into the GO, the maximum adsorption capacity reached 254.2 ± 10.4 mg/g within 180 min, obviously higher than the GO prepared without these additions (136.5 ± 7.2 mg/g). The EDTA/MDI/GO adsorption kinetics and equilibrium adsorption isotherm fitted the pseudo-second-order kinetic model (R² = 0.995) and Langmuir isotherm model (R² = 0.986) well, respectively. Furthermore, EDTA/MDI/GO also displayed good reusability for the efficient removal of Cu²⁺ after being washed with HCl, suggesting potential application in Cu²⁺ cleanup.

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.