MoS2 and MoS2 Nanocomposites for Adsorption and Photodegradation of Water Pollutants: A Review

Intermixing of MoS2 and WS2 photocatalysts toward methylene blue photodegradation

Visible-light-driven photocatalysis using layered materials has garnered increasing attention regarding the degradation of organic dyes. Herein, transition-metal dichalcogenides MoS2 and WS2 prepared by chemical vapor deposition as well as their intermixing are evaluated for photodegradation (PD) of methylene blue under solar simulator irradiation. Our findings revealed that WS2 exhibited the highest PD efficiency of 67.6% and achieved an impressive PD rate constant of 6.1 × 10-3 min-1. Conversely, MoS2 displayed a somewhat lower PD performance of 43.5% but demonstrated remarkable stability. The intriguing result of this study relies on the synergetic effect observed when both MoS2 and WS2 are combined in a ratio of 20% of MoS2 and 80% of WS2. This precise blend resulted in an optimized PD efficiency and exceptional stability reaching 97% upon several cycles. This finding underscores the advantageous outcomes of intermixing WS2 and MoS2, shedding light on the development of an efficient and enduring photocatalyst for visible-light-driven photodegradation of methylene blue.

Amphi-Luminescent MoS2 nanostructure for photocatalytic splitting of water and removal of Methylene Blue

Chemical dyes used in the textile industries are one of the major pollutants in water. Methylene blue (MB) is a commonly seen dye that creates hazardous health problems. In this article the photocatalytic degradation of MB by the nanocatalyst MoS2 (Nano-MoS2) and carbon dot (C Dots) incorporated MoS2 (Nano-CD-MoS2) is reported. The photocatalytic degradation of MB is analyzed based on the electron-hole recombination rate of the catalyst. Photoluminescence emission exhibited by the catalyst is used as a key indicator to probe the electron-hole recombination rate. Nano-MoS2 was synthesized hydrothermally at 180 0C for 8 h from ammonium tetra thiomolybdate (ATTM). C Dot was prepared following a green root from ash guard extract which later mixed with Nano-MoS2 and kept in an autoclave at a temperature 140 °C for 4 h to get Nano-CD-MoS2. The photoluminescence (PL) and photocatalytic behavior of Nano-MoS2 and Nano-CD-MoS2 and their application for water splitting and water purification are reported. The incorporation of graphene and artificial C Dot into MoS2 nanostructures are reported to increase the conductivity and active edge sites of MoS2 that enhances the photocatalytic action. Since green C Dots are eco-friendly and easily synthesizable than artificial C Dots, as a novel study, this article investigated the influence of green C Dots on the PL and photocatalytic performance of nanosized MoS2. Nano-MoS2 and Nano-CD-MoS2 exhibited both upconversion and downconversion PL; accordingly the nanostructures were termed as amphi-luminescent. The amphi-luminescence property widens the photon absorption range and hence enhances the catalytic degradation of dyes. Nano-MoS2 which exhibited lesser intensity of amphi-luminescence emission compared to Nano-CD-MoS2 showed better results in degradation of MB. C Dots may bind with the valence band electrons of MoS2, resulting in the reduction of dangling bonds. Dangling bonds can trap photo-induced excitons to hinder the rate of electron-hole recombination. So, fast electron-hole recombination occurs in Nano-CD-MoS2 than Nano-MoS2. Fast electron-hole recombination supports radiative electron-hole recombination while suppresses the non-radiative energy transfer of electrons and causes high PL intensity. However, according to the energy level diagram, Nano-MoS2 with minimal electron-hole recombination rate is more favorable for O2/O2-,.OH/ OH- and.OH/H2O reactions that facilitate MB degradation. Photocatalytic activity of catalysts were confirmed by measuring the photocurrent from a simple custom-made two-electrode water photolysis cell where the nanocatalysts were dispersed in electrolyte. Lead and steel rods were used as electrodes. Multimeter was used to measure current. Nano-MoS2 exhibited better performance with a maximum photocurrent of 141 µA. Influence of green C Dots in energy levels, PL and photocatalysis of MoS2 and mechanisms of PL and degradation of MB are thoroughly investigated in this article.

Surface Plasmon Resonance-Mediated Photocatalytic H2 Generation

The limited yield of H2 production has posed a significant challenge in contemporary research. To address this issue, researchers have turned to the application of surface plasmon resonance (SPR) materials in photocatalytic H2 generation. SPR, arising from collective electron oscillations, enhances light absorption and facilitates efficient separation and transfer of electron-hole pairs in semiconductor systems, thereby boosting photocatalytic H2 production efficiency. However, existing reviews predominantly focus on SPR noble metals, neglecting non-noble metals and SPR semiconductors. In this review, we begin by elucidating five different SPR mechanisms, covering hot electron injection, electric field enhancement, light scattering, plasmon-induced resonant energy transfer, and photo-thermionic effect, by which SPR enhances photocatalytic activity. Subsequently, a comprehensive overview follows, detailing the application of SPR materials-metals, non-noble metals, and SPR semiconductors-in photocatalytic H2 production. Additionally, a personal perspective is offered on developing highly efficient SPR-based photocatalysis systems for solar-to-H2 conversion in the future. This review aims to guide the development of next-gen SPR-based materials for advancing solar-to-fuel conversion.

MoS2-based nanocomposites and aerogels for antibiotic pollutants removal from wastewater by photocatalytic degradation process: A review

Photocatalytic technologies based on molybdenum disulfide (MoS2) catalysts are effective, eco-friendly, and promising for antibiotic pollutants treatment. The technologies used by MoS2-based nanocomposites and aerogels for efficient degradation of antibiotics are reviewed in detail for the first time in this paper. The fundamental aspects of MoS2 were comprehensively scrutinized, encompassing crystal structure, optical properties, and photocatalytic principle. Then, the main synthesized methods and advantages/disadvantages for the preparation of MoS2-based nanocomposites and aerogels were systematically presented. Besides, a comprehensive overview of diverse MoS2-based nanocomposites and aerogels photo-degradation systems that enhanced the degradation of antibiotic pollutants were revealed. Meanwhile, the photo-degradation mechanism concentrated on the photoelectron transfer pathways and reactive oxygen species (ROS) were systematically evaluated. Finally, the challenges and perspectives for deeply development of MoS2-based nanocomposites and aerogels were discussed. This review may help researchers to deeply understand the research status of MoS2-based nanocomposites and aerogels for antibiotics removal, and makes clear the photo-degradation mechanism from photoelectron transfer pathways and ROS aspects of MoS2-based nanocomposites and aerogels.

Progress of disinfection catalysts in advanced oxidation processes, mechanisms and synergistic antibiotic degradation

Human diseases caused by pathogenic microorganisms make people pay more attention to disinfection. Meanwhile, antibiotics can cause microbial resistance and increase the difficulty of disease treatment, resulting in risk of triggering a vicious circle. Advanced oxidation process (AOPs) has been widely studied in the field of synergistic treatment of the two contaminates. This paper reviews the application of catalytic materials and their modification strategies in the context of AOPs for disinfection and antibiotic degradation. It also delves into the mechanisms of disinfection such as the pathways for microbial inactivation and the related influencing factors, which are essential for understanding the pivotal role of catalytic materials in disinfection principles by AOPs. More importantly, the exploratory research on the combined use of AOPs for disinfection and antibiotic degradation is discussed, and the potential and prospects in this field is highlighted. Finally, the limitations and challenges associated with the application of AOPs in disinfection and antibiotic degradation are summarized. It aims to provide a starting point for future research efforts to facilitate the widespread use of advanced oxidation processes in the field of public health.

Ultrasound assisted electrodeposition of photocatalytic antibacterial MoS2-Zn coatings controlled by sodium dodecyl sulfate

Photocatalytic MoS2 with visible light response is considered as a promising bactericidal material owing to its non-toxicity and high antibacterial efficiency. However, photocatalysts always exist as powder, so it is difficult to settle photocatalysts on the metal surface, which limits their application in aqueous environments. To solve this problem, ultrasound and sodium dodecyl sulfate (SDS) were introduced into the co-deposition process of MoS2 and zinc matrix, so that novel MoS2-Zn coatings were obtained. In this process, ultrasound and SDS strongly promoted the dispersion and adsorption of MoS2 on the co-depositing surfaces. Then MoS2 were proved to be composited into the Zn matrix with effective structures, and the addition of SDS effectively increased the loading content of MoS2 in the MoS2-Zn coatings. Besides, the antibacterial performance of the MoS2-Zn coatings was evaluated with three typical fouling bacteria E.coli, S.aureus and B.wiedmannii. The MoS2-Zn coating showed high and broad-spectrum antibacterial properties with over 98 % inhibition rate against these three bacteria. Furthermore, it is proved that the MoS2-Zn coatings generated superoxide (·O2-) and hydroxyl radicals (·OH) under visible light, which played the dominant and subordinate roles in the antibacterial process, respectively. The MoS2-Zn coatings also showed high antibacterial stability after four "light-dark" cycles. According to the results of the attached bacteria, the MoS2-Zn coatings were considered to effectively repel the living pelagic bacteria instead of killing the attached ones, which was highly environmentally friendly. The obtained MoS2-Zn coatings were considered promising in biofilm inhibiting and marine antifouling fields.

A Comprehensive Ecotoxicity Study of Molybdenum Disulfide Nanosheets versus Bulk form in Soil Organisms

The increasing use of molybdenum disulfide (MoS2) nanoparticles (NPs) raises concerns regarding their accumulation in soil ecosystems, with limited studies on their impact on soil organisms. Study aim: To unravel the effects of MoS2 nanosheets (two-dimensional (2D) MoS2 NPs) and bulk MoS2 (156, 313, 625, 1250, 2500 mg/kg) on Enchytraeus crypticus and Folsomia candida. The organisms' survival and avoidance behavior remained unaffected by both forms, while reproduction and DNA integrity were impacted. For E. crypticus, the individual endpoint reproduction was more sensitive, increasing at lower concentrations of bulk MoS2 and decreasing at higher ones and at 625 mg/kg of 2D MoS2 NPs. For F. candida, the molecular endpoint DNA integrity was more impacted: 2500 mg/kg of bulk MoS2 induced DNA damage after 2 days, with all concentrations inducing damage by day 7. 2D MoS2 NPs induced DNA damage at 156 and 2500 mg/kg after 2 days, and at 1250 and 2500 mg/kg after 7 days. Despite affecting the same endpoints, bulk MoS2 induced more effects than 2D MoS2 NPs. Indeed, 2D MoS2 NPs only inhibited E. crypticus reproduction at 625 mg/kg and induced fewer (F. candida) or no effects (E. crypticus) on DNA integrity. This study highlights the different responses of terrestrial organisms to 2D MoS2 NPs versus bulk MoS2, reinforcing the importance of risk assessment when considering both forms.

Molybdenum disulfide, exfoliation methods and applications to photocatalysis: a review

This review provides a deep analysis of the mechanical and optoelectronic characteristics of MoS2. It offers a comprehensive assessment of diverse exfoliation methods, encompassing chemical, liquid-phase, mechanical, and microwave-driven techniques. The review also explores MoS2's versatile applications across various domains and meticulously examines its significance as a photocatalyst. Notably, it highlights key factors influencing the photocatalytic process. Indeed, the enhanced visible light responsiveness of materials like MoS2 holds immense potential across a wide range of applications. MoS2's remarkable photocatalytic response to visible light, coupled with its notable stability, opens up numerous possibilities in various fields. This unique combination makes MoS2 a promising candidate for applications that require efficient and stable photocatalytic processes, such as environmental remediation, water purification, and energy generation. Its attributes contribute significantly to addressing contemporary challenges and advancing sustainable technologies.

Ultrasensitive detection of crystal violet using a molybdenum sulfide-silver nanostructure-based sensing platform: roles of the adsorbing semiconductor in SERS signal enhancement

Crystal violet (CV) is an organic dye that is stabilized by the extensive resonance delocalization of electrons over three electron-donating amine groups. This prevents the molecule from being linked to a metal surface, and therefore, reduces the sensitivity of surface-enhanced Raman scattering (SERS) sensors for this toxic dye. In this work, we improved the sensing performance of a silver-based SERS sensor for CV detection by modifying the active substrate. Molybdenum sulfide (MoS2) nanosheets were employed as a scaffold for anchoring electrochemically synthesized silver nanoparticles (e-AgNPs) through a single step of ultrasonication, leading to the formation of MoS2/Ag nanocomposites. As an excellent adsorbent, MoS2 promoted the adsorption of CV onto the surface of the substrate, allowing more CV molecules to be able to experience the SERS effect originating from the e-AgNPs. Hence, the SERS signal of CV was significantly enhanced. In addition, the effects of the MoS2 content of the nanocomposites on their SERS performance were also taken into account. Using MoS2/Ag with the most optimal MoS2 content of 10%, the SERS sensor exhibited the best enhancement of the SERS signal of CV with an impressive detection limit of 1.17 × 10-11 M in standard water and 10-9 M in tap water thanks to an enhancement factor of 2.9 × 106, which was 11.2 times higher than that using pure e-AgNPs.

Heteroatom-Doped Molybdenum Disulfide Nanomaterials for Gas Sensors, Alkali Metal-Ion Batteries and Supercapacitors

Molybdenum disulfide (MoS2) is the second two-dimensional material after graphene that received a lot of attention from the research community. Strong S-Mo-S bonds make the sandwich-like layer mechanically and chemically stable, while the abundance of precursors and several developed synthesis methods allow obtaining various MoS2 architectures, including those in combinations with a carbon component. Doping of MoS2 with heteroatom substituents can occur by replacing Mo and S with other cations and anions. This creates active sites on the basal plane, which is important for the adsorption of reactive species. Adsorption is a key step in the gas detection and electrochemical energy storage processes discussed in this review. The literature data were analyzed in the light of the influence of a substitutional heteroatom on the interaction of MoS2 with gas molecules and electrolyte ions. Theory predicts that the binding energy of molecules to a MoS2 surface increases in the presence of heteroatoms, and experiments showed that such surfaces are more sensitive to certain gases. The best electrochemical performance of MoS2-based nanomaterials is usually achieved by including foreign metals. Heteroatoms improve the electrical conductivity of MoS2, which is a semiconductor in a thermodynamically stable hexagonal form, increase the distance between layers, and cause lattice deformation and electronic density redistribution. An analysis of literature data showed that co-doping with various elements is most attractive for improving the performance of MoS2 in sensor and electrochemical applications. This is the first comprehensive review on the influence of foreign elements inserted into MoS2 lattice on the performance of a nanomaterial in chemiresistive gas sensors, lithium-, sodium-, and potassium-ion batteries, and supercapacitors. The collected data can serve as a guide to determine which elements and combinations of elements can be used to obtain a MoS2-based nanomaterial with the properties required for a particular application.

Functional Bimetal/Carbon Composites Co/Zr@AC for Pesticide Atrazine Removal from Water

Atrazine is a toxic and refractory herbicide that poses threats to human health and the ecological environment. In order to efficiently remove atrazine from water, a novel material, Co/Zr@AC, was developed. This novel material is prepared by loading two metal elements, cobalt and zirconium, onto activated carbon (AC) through solution impregnation and high-temperature calcination. The morphology and structure of the modified material were characterized, and its ability to remove atrazine was evaluated. The results showed that Co/Zr@AC had a large specific surface area and formed new adsorption functional groups when the mass fraction ratio of Co²⁺:Zr⁴⁺ in the impregnating solution was 1:2, the immersion time was 5.0 h, the calcination temperature was 500 °C, and the calcination time was 4.0 h. During the adsorption experiment on 10 mg/L atrazine, the maximum adsorption capacity of Co/Zr@AC was shown to be 112.75 mg/g and the maximum removal rate was shown to be 97.5% after 90 min of the reaction at a solution pH of 4.0, temperature of 25 °C, and Co/Zr@AC concentration of 60.0 mg/L. In the kinetic study, the adsorption followed the pseudo-second-order kinetic model (R² = 0.999). The fitting effects of Langmuir and Freundlich isotherms were excellent, indicating that the process of Co/Zr@AC adsorbing atrazine also conformed to two isotherm models, so the adsorption of atrazine by Co/Zr@AC had multiple effects including chemical adsorption, mono-molecular layer adsorption, and multi-molecular layer adsorption. After five experimental cycles, the atrazine removal rate was 93.9%, indicating that Co/Zr@AC is stable in water and is an excellent novel material that can be used repeatedly.