Narrow Results

In the quest of extending isostructural hybridization approach to organic–inorganic nanocomposite-based photocatalytic systems, a unique strategy of replacing the traditional inorganic semiconductors with naturally produced mycosporine-like amino acids (MAA) is proposed. The main motivation of incorporating MAA in symbiotically configured nanocomposites is with regard to MAA green, nontoxic nature, UV absorption and photostability. Our facile one-pot solvothermal method is to facilitate the amalgamation of MAA and molybdenum disulfide-graphene (MG) composite at the molecular/nanoscale level to endow better photocatalytic functionality. It is observed that the rate of photocatalytic dye degradation of Rhodamine 6G (R6G) becomes consistently enhanced with an incremental increase in the concentration of MAA in MG. The combination of MG-MAA leads up to 81.2% quenching of the PL emission, as compared with MG. Noticeable decrease in PL lifetime from 280 ps (MG) to 77ps (MG-MAA) explicitly implies fast charge extraction and transport of the charge carriers.

Nanoparticles (NPs) with high uniformity have been extensively investigated for their excellent chemical stability. Near-monodisperse globular MoS₂ NPs were prepared with sulphur powders (SPs) as a sulphur source by a one-pot polyol-mediated process without surfactants, transfer agents and toxic agents at 170–190${}^{\circ }$C. The as-processed SPs greatly affected the formation of the MoS₂ NPs after low-activity sulphur (S₈)_n was reassembled from common SPs (S${}_8)$. The average size of MoS₂ NPs can be reduced remarkably from 100–200nm to 50nm by introducing low amounts of MnCl₂. A preliminary four-step growth mechanism based on the aggregation-coalescence model was also proposed. This green and simple method may be an alternative to the common hot-injection and heating-up methods for the preparation of monodisperse NPs, particularly transition metal dichalogenides.

To improve the high charge carrier recombination rate and low visible light absorption of {001} facets exposed TiO₂ [TiO₂(001)] nanosheets, few-layered MoS₂ nanoparticles were loaded on the surfaces of TiO₂(001) nanosheets by a simple photodeposition method. The photocatalytic activities towards Rhodamine B (RhB) were investigated. The results showed that the MoS₂–TiO₂(001) nanocomposites exhibited much enhanced photocatalytic activities compared with the pure TiO₂(001) nanosheets. At an optimal Mo/Ti molar ratio of 25%, the MoS₂–TiO₂(001) nanocomposites displayed the highest photocatalytic activity, which took only 30min to degrade 50mL of RhB (50mg/L). The active species in the degradation reaction were determined to be h${}^{+}$ and ${}^{•}$OH according to the free radical trapping experiments. The reduced charge carrier recombination rate, enhanced visible light utilization and increased surface areas contributed to the enhanced photocatalytic performances of the 25% MoS₂–TiO₂(001) nanocomposites.

Three-dimensional reduced graphene oxide (RGO) matrix decorated with nanoflowers of layered MoS₂ (denoted as 3D MoS₂/RGO) have been synthesized via a facile one-pot stepwise hydrothermal method. Graphene oxide (GO) is used as precursor of RGO and a 3D GO network is formed in the first-step of hydrothermal treatment. At the second stage of hydrothermal treatment, nanoflowers of layered MoS₂ form and anchor on the surface of previously formed 3D RGO network. In this preparation, thiourea not only induces the formation of the 3D architecture at a relatively low temperature, but also works as sulfur precursor of MoS₂. The synthesized composites have been investigated with XRD, SEM, TEM, Raman spectra, TGA, N₂ sorption technique and electrochemical measurements. In comparison with normal MoS₂/RGO composites, the 3D MoS₂/RGO composite shows improved electrochemical performance as anode material for lithium-ion batteries. A high reversible capacity of 930mAh$\cdot$g${}^{-1}$ after 130 cycles under a current density of 200mA$\cdot$g${}^{-1}$ as well as good rate capability and superior cyclic stability have been observed. The superior electrochemical performance of the 3D MoS₂/RGO composite as anode active material for lithium-ion battery is ascribed to its robust 3D structures, enhanced surface area and the synergistic effect between graphene matrix and the MoS₂ nanoflowers subunit.

Based on U-g-C₃N₄ (U-gCN) and T-g-C₃N₄ (T-gCN) prepared with urea and thiourea as raw materials, respectively, a visible-light-driven MoS₂-modified U-gCN/T-gCN/MoS₂ (UTM) ternary heterojunction photocatalyst was successfully prepared using a sonication and bathing method. The photocatalytic activity of as-prepared photocatalyst was evaluated through the degradation of tetracycline hydrochloride (TC) and Rhodamine B (RhB) under the visible light irradiation. The UTM ternary heterojunction showed remarkably enhanced photocatalytic activity. For the degradation of TC and RhB, the degradation rates of 93.9% and 99.9% have been achieved after being irradiated under visible light for 2h and 1h, respectively. The enhanced photocatalytic performance can be ascribed to the role of loaded MoS₂ cocatalyst and the well-formed interfaces between U-gCN and T-gCN, which not only enhance the light absorption, but also accelerate the separation and transfer of photogenerated electron–hole pairs. Furthermore, UTM ternary heterojunction has excellent recyclability and chemical stability. The photodegradation rates of 89.9% and 96.78% of TC and RhB have been obtained, respectively, after being reused for five times. Sacrificial agent tests demonstrate that $•$${\mathrm{\text{O}}}_2^{-}$ is the major reactive species in the photocatalytic reaction system.

Au@MoS₂-CdS, as ternary composite structure, was successfully synthesized by a facile process combining hydrothermal and seed-growth methods. The introduction of Au nanoparticles (NPs) into MoS₂ spheres, forming a core–shell structure, demonstrates strong plasmonic absorption enhancement. The incorporation of CdS NPs into the Au@MoS₂ core–shell structure further extends the absorption range of visible light and enhances exciton dissociation. The resultant composite structure exhibits the highest photocatalytic activity in photocatalytic degradation of rhodamine B (RhB) solution, compared with Au NPs, MoS₂ spheres, Au@MoS₂ core–shell and MoS₂-CdS heterostructures. The above phenomena are supported by a series of characterization results such as SEM, TEM, XRD, EDS and UV-Vis, etc. Based on structural and morphological analyses, we propose the synthesis method of ternary composite structure photocatalysts, which is helpful for the synthesis of future multicomponent photocatalytic materials.

Constructing van der Waals (vdW) heterostructures with various-layered two-dimensional (2D) materials is attractive to design various materials and devices. For controllable fabrication of vdW heterostructures, it is very important to make the growth process clear. In this work, SnS₂/MoS₂ vertical heterostructures were synthesized by the one-step chemical vapor deposition (CVD) method. The bottom MoS₂ triangle layers can be partially or completely covered by SnS₂ layers. The interlayer charge separation was also observed in the heterostructures by photoluminescence (PL) spectroscopy. The growth mechanism of SnS₂/MoS₂ vertical heterostructures was also discussed for the first time. MoS₂ triangle layers form on the substrates at first and then grow a top layer of SnS₂. This study will provide an important and practical method, as a guidance to prepare high-quality vertical heterostructures.

A surfactant system L64 and alcohol mixture was employed to exfoliate MoS₂. To reduce the impact of surfactant on the quality of the nanosheet, the concentration of L64 was decreased to an extremely low value 0.0325 mM. Utilize common ultrasonic bath, the production yield of the nanosheet was increased to about 5% per hour, and statistical results from AFM showed that 40% of the nanosheet were less than 4 nm thick. Rheology characterization showed that surfactant alcohol mixtures were shear thinning fluid, yet the viscosity of L64 system varies directly with the shear rate in the high-speed shear region (higher than 400 s⁻¹), and further affect the shear strength, therefore viscosity at high-speed shear can be considered as an indicator of the effectiveness for the exfoliation system. Exfoliated MoS₂ was evaluated by hydrogen evolution reaction, and compared to the bulk MoS₂, the 4 wt% Pt/FL-MoS₂ improved the overpotential from 366 mV to 273 mV at 10 mA$•$cm${}^{-2}$. This study presented a facile and effective route to fabricate 2D MoS₂ with much less residue, and bring more opportunities to exploit clean and nontoxic system to exfoliate 2D materials.

In molybdenum disulfide (MoS₂), cobalt (Co) doping is an effective way to introduce catalytic active sites on the basal plane. For improving their capability of electrocatalytic hydrogen evolution reaction (HER), it is desirable to produce more active sites and endow them with highly electrocatalytic activity. In this work, we used silicon dioxide (SiO₂) nanospheres as template to prepare porous Co-doped MoS₂ with different Co content. We found that the prepared porous catalyst has improved the catalytic performance. Furthermore, the increase in Co content not only increases the number of active sites, but also can improve the activity for each Co atom. First-principle calculations based on density functional theory (DFT) suggest that this mutually enhanced activity originates from the shift of the density of state (DOS) of the vertical d${}_{z2}$ orbital near the Fermi energy level caused by the interaction among the Co atoms.

Layered g-C₃N₄ was obtained through secondary calcination, and the MoS₂–Ag/g-C₃N₄ catalyst was prepared via hydrothermal and light deposition methods. XRD, SEM and TEM results proved that the MoS₂–Ag/g-C₃N₄ sandwich biscuit structure was successfully obtained, and the sharper diffraction peak of MoS₂–Ag/g-C₃N₄ than g-C₃N₄ or MoS₂ is attributed to the synergistic crystallinity effect. SPR effect of Ag increases the electron transport time, which effectively prolonging the survival time of electron–hole pairs. Compared the degradation performance of 10mg/L rhodamine B (RhB) with different ratios of materials, 10wt.% MoS₂–Ag/g-C₃N₄ has the highest degradation property. The degradation rate remains at 87.2% under the best condition after four cycles proved that the MoS₂–Ag/g-C₃N₄ composite possesses good stability.

In this paper, a simple method has been used to synthesize silver-molybdenum disulfide nanoparticles (Ag-MoS₂ NPs) with photothermal and physical inhibition of bacteria. The MoS₂ nanocarriers were obtained by an environment-friendly liquid-phase separation method. The coated Ag NPs with high antibacterial activity and fluorescence property endowed the synthesized Ag-MoS₂ NPs with the ability to be traced. The Ag-MoS₂ NPs had photothermal properties with a maximum photothermal increase of $72^{\circ }$C. The results of the dual photothermal–chemical antibacterial activity using Ag-MoS₂ NP carriers showed that Ag-MoS₂ NPs had broad-spectrum inhibition activity with MIC values up to $5.2\pm 0.3$$\mu$g/mL against Escherichia coli. The Ag-MoS₂ NPs were also used to destroy cell integrity by disrupting cell membranes and cell walls to achieve the inhibition of cell survival. The toxicity test in mice demonstrated the nontoxicity of Ag-MoS₂ NPs. Ag-MoS₂ NPs were studied for dual photothermal–chemical antibacterial activity, and the material reduced the amount of Ag NPs used, resulting in lower biotoxicity, hence providing a possible avenue for the clinical application of Ag NPs.