MoSe2/Montmorillonite Composite Nanosheets: Hydrothermal Synthesis, Structural Characteristics, and Enhanced Photocatalytic Activity

Deep-Learning-Assisted Discriminative Detection of Vitamin B12 and Vitamin B9 by Fluorescent MoSe2 Quantum Dots

A facile and environmentally mindful approach for the synthesis of MoSe2 QDs was developed via the hydrothermal method from bulk MoSe2. In this, the exfoliation of MoSe2 was enhanced with the aid of an intercalation agent (KOH), which could reduce the exfoliation time and increase the exfoliation efficiency to form MoSe2 QDs. We found that MoSe2 QDs display blue emission that is suitable for different applications. This fluorescence property of MoSe2 QDs was harnessed to fabricate a dual-modal sensor for the detection of both vitamin B12 (VB12) and vitamin B9 (VB9), employing fluorescence quenching. We performed a detailed study on the fluorescence quenching mechanism of both analytes. The predominant quenching mechanism for VB12 is via Förster resonance energy transfer. In contrast, the recognition of VB9 primarily relies on the inner filter effect. We applied an emerging and captivating approach to pattern recognition, the deep-learning method, which enables machines to "learn" patterns through training, eliminating the need for explicit programming of recognition methods. This attribute endows deep-learning with immense potential in the realm of sensing data analysis. Here, analyzing the array-based sensing data, the deep-learning technique, "convolution neural networks", has achieved 93% accuracy in determining the contribution of VB12 and VB9.

Preparation of C3N4/montmorillonite composite photocatalyst for effective removal of organic pollutants

Due to the good photocatalytic performance, which ensures the decomposition of pollutants under light, g-C₃N₄ is considered as an ideal photocatalytic material. Montmorillonite has a high adsorption capacity and layered structure, which has positive effects on increasing the specific surface area of g-C₃N₄ and avoid its polymerization agglomeration. In this paper, montmorillonite was used as carrier for g-C₃N₄ to obtain a new photocatalytic composite g-C₃N₄/Mt. Then the morphological and (micro)structural properties were characterized. The well-characterized materials were evaluated for the photocatalytic activity in degradation of methylene blue and Bisphenol A. The effects of the mass fraction of g-C₃N₄, light irradiation time, and pollutant concentration on the photocatalytic performance of g-C₃N₄/Mt composites were studied. Under the optimal experimental plan, the rate of photocatalytic degradation can reach to 99.3% within 120 min. Through the MS spectrum, it can be found that methylene blue molecule were catalysed and degraded into many harmless substances with low-molecular weight. Finally, based on the obtained reaction products, the mechanism by which the pollutants are removed was proposed. This study provides a new strategy to improve the photocatalysis ability of g-C₃N₄, which is of great significance for a sustainable pollution treatment.

MoSe2-WS2 Nanostructure for an Efficient Hydrogen Generation under White Light LED Irradiation

In this work, MoSe2-WS2 nanocomposites consisting of WS2 nanoparticles covered with few MoSe2 nanosheets were successfully developed via an easy hydrothermal synthesis method. Their nanostructure and photocatalytic hydrogen evolution (PHE) performance are investigated by a series of characterization techniques. The PHE rate of MoSe2-WS2 is evaluated under the white light LED irradiation. Under LED illumination, the highest PHE of MoSe2-WS2 nanocomposite is 1600.2 µmol g-1 h-1. When compared with pristine WS2, the MoSe2-WS2 nanostructures demonstrated improved PHE rate, which is 10-fold higher than that of the pristine one. This work suggests that MoSe2-WS2 could be a promising photocatalyst candidate and might stimulate the further studies of other layered materials for energy conversion and storage.

Synergetic contribution of enriched selenium vacancies and out-of-plane ferroelectric polarization in AB-stacked MoSe2 nanosheets as efficient piezocatalysts for TC degradation

Novel MoSe2 piezocatalysts with surface selenium vacancies and out-of-plane ferroelectric polarization exhibit ultrafast degradation of the antibiotic tetracycline.

Utilization of Montmorillonite-Modified Earthenware from Bentonite-Ca as a Microbial Fuel Cell (MFC) Membrane Based on Tempe Liquid Waste as a Substrate

Modifications of the Microbial Fuel Cell (MFC) membrane need to be carried out to increase its electric potential energy. This research aims to determine the effect of montmorillonite from bentonite-Ca as a composite in modified earthenware (GT), which is then used as a membrane of the MFC-based on tempe wastewater as substrate. The results obtained were compared to MFC that used pure earthenware membrane (GM). The ratio of bentonite-Ca and clay in GT was 50:50, while GM used 100% of clay. Characterizations of GT dan GM were performed using FTIR, XRD, and SAA. MFC testing was carried out for 24 hours, where every 2 hours, measurements of potential difference (V), current (A), and power density (W/cm2) were carried out. FTIR and XRD data showed an increase in montmorillonite content in GT, while SAA data showed a decrease in pore volume in GT. The decrease in pore volume GT occurs due to an increase in the number of trivalent cations (Al3+, Fe3+) and bivalent (Mg2+). These cations help transfer protons from the anode to the cathode, which causes a decrease in the potential difference and an increase in the current strength and the MFC-GT power density. The average difference between the decrease in potential difference from MFC-GM to MFC-GT is 0.043 V, while the increase in current is 0.022 mA, and the increase in power density is 0.163 mW/cm2.

Emerging One-/Two-Dimensional Heteronanostructure Integrating SiC Nanowires with MoS2 Nanosheets for Efficient Electrocatalytic Hydrogen Evolution

MoS₂ has emerged as a good application prospect in the electrocatalytic hydrogen evolution reaction (HER). Nevertheless, the catalytic activity of MoS₂ is greatly restricted by its inferior electrical conductivity, inadequate exposure of active edge sites, and sluggish water dissociation dynamics. Herein, a 1D/2D heteronanostructure composed of SiC nanowires wrapped with MoS₂ nanosheets was prepared via the hydrothermal synthesis of MoS₂ on highly connected SiC nanowires (SiCnw). The nanocomposites exhibit an emerging tectorum-like morphology with interface connections of C-Mo bonds, which benefit the efficient interfacial transmission of electrons. Due to the synergetic catalytic effects of MoS₂ nanosheets and SiC nanowires, the MoS₂/SiCnw nanocomposites possess efficient catalytic performance with a low Tafel slope (55 mV/dec). SiC nanocrystals could reduce the activated water dissociation energy barrier, and the morphologies of connected nanowires could improve the active site exposure and charge transport. The nanocomposites possess favorable hydrogen adsorption free energy from density functional theory (DFT) calculations. The electrocatalytic performance of MoS₂/SiCnw nanocomposites could be further improved by assembling the nanocomposites on a carbon fiber paper to enhance the electronic transmission efficiency.

Controllable incorporation of oxygen in MoS2 for efficient adsorption of Hg2+ in aqueous solutions

Molybdenum disulfide (MoS₂) was incorporated controllably by oxygen in order to modify the hydrophobic surfaces and thus to improve the adsorption of Hg²⁺ on MoS₂ in aqueous solutions in this work. The experimental results indicated that the incorporation of oxygen could dramatically improve the adsorption of Hg²⁺ on MoS₂. With 11% oxygen atom incorporation, the adsorption rate and capacity increased over 17 times and 21 folds, respectively, compared with that without oxygen incorporation. This vast improvement was found to be contributed to that the incorporation of oxygen would greatly enhance the complexation between S atoms and Hg²⁺ on MoS₂ surfaces, resulting in the great increase of the Hg²⁺ adsorption. The increase of the adsorption capacity with increasing incorporated oxygen reached a plateau, which might be due to the saturation of covalent bond. In addition, the incorporation of oxygen atom greatly enhanced the hydrophilicity of MoS₂ surfaces, facilitating the hydrated Hg²⁺ ions to approach to MoS₂ surfaces. This finding might provide a highly potential adsorbent for efficiently removing Hg²⁺ from water.

Emerging WS2/montmorillonite composite nanosheets as an efficient hydrophilic photocatalyst for aqueous phase reactions

Tungsten disulfide (WS₂) as one of transition metal dichalcogenides exhibits excellent catalytic activity. However, its catalytic performances in aqueous phase reactions are limited by its hydrophobicity. Here, the natural hydrophilic two-dimensional clay was used to enhance the dispersibility of WS₂ in aqueous phase. WS₂/montmorillonite (WS₂/MMT) composite nanosheets were prepared via hydrothermal synthesis of WS₂ on the surface of montmorillonite from WCl₆ and CH₃CSNH₂. The microstructure and morphology show that WS₂ nanosheets are assembled parallelly on the montmorillonite with the interface interaction. Through the support of montmorillonite, WS₂/MMT possesses higher photocatalytic ability for aqueous phase reactions than WS₂, which could be due to the synergistic effect of higher adsorption property, higher hydrophilicity, dispersibility and more catalytic reaction site. The strategy could provide new ideas for obtaining novel hydrophilic photocatalyst with excellent performance.

Optimal Synthesis of Environment-Friendly Iron Red Pigment from Natural Nanostructured Clay Minerals

A series of environment-friendly clay minerals-α-Fe₂O₃ iron-red hybrid pigments-were prepared by a simple one-step hydrothermal reaction process using natural nanostructured silicate clay minerals as starting materials. The influence of structure, morphology and composition of different clay minerals on the structure, color properties, and stability of the pigments was studied comparatively by systematic structure characterizations with X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmittance electron microscope (TEM), X-ray fluorescence spectroscopy (XRF), X-ray photoelectron spectroscopy (XPS) and CIE-L*a*b* Colorimetric analyses. The results showed that the clay minerals act as green precipitants during the hydrothermal reaction to induce in-situ transformation of Fe(III) ions into Fe₂O₃ crystals. Meanwhile, they also act as the "micro-reactor" for forming Fe₂O₃ crystals and the supporter for inhibiting the aggregation of Fe₂O₃ nanoparticles. The color properties of iron-red hybrid pigments are closely related to the surface charges, surface silanol groups, and solid acid sites of clay minerals. The clay minerals with higher surface activity are more suitable to prepare iron-red pigments with better performance. The iron-red hybrid pigment derived from illite (ILL) clay showed the best red color performance with the color values of L* = 31.8, a* = 35.2, b* = 27.1, C* = 44.4 and h° = 37.6, and exhibited excellent stability in different chemical environments such as acid, alkaline, and also in high-temperature conditions.

TiO2 nanoparticles assembled on kaolinites with different morphologies for efficient photocatalytic performance

Natural kaolinite clays with different dimensionalities (including kaolinite nanoflakes and nanorods) supported TiO₂ nanoparticles were successfully prepared via a facile sol-gel method. Moreover, comparisons between FK/TiO₂ and RK/TiO₂ nanocomposites are conducted in terms of matrix morphology, surface property, energy band structure and interfacial interaction. The effects of kaolinite microstructure, morphology and dimensionality on the interfacial characteristics and photocatalytic properties of the nanocomposites were investigated in detail. The results showed that TiO₂ nanoparticles are more easily attached on the kaolinite nanoflakes, and possess more uniform distribution and smaller particle size than that of kaolinite nanorods. In particular, the FK/TiO₂ nanocatalysts exhibit higher photocatalytic activity for the degradation of tetracycline hydrochloride than that of RK/TiO₂ and bare TiO₂, which is attributed to the stronger surface adsorptivity, higher loading efficiency and smaller grain size. Additionally, FK/TiO₂ composites show excellent stability, which is ascribed to the intimate interfacial contact between two-dimensional kaolinite nanoflakes and TiO₂ nanoparticles. Overall, the enhanced catalytic performance for FK/TiO₂ composites is the synergistic effect of two-dimensional morphology, better adsorption capability and more active photocatalysis TiO₂ species.