Disulfide Nanoplates Research Articles

Nanoscale Imaging of Palladium-Enhanced Photocatalytic Reduction of 4-Nitrothiophenol on Tungsten Disulfide Nanoplates.

Two-dimensional (2D) dichalcogenides are modern nanomaterials with unique physical and chemical properties. These materials possess band gaps in the infrared and visible regions of the electromagnetic spectrum that can be tuned by their molecular composition. Excitons generated as a result of such light-matter interactions are capable of catalyzing chemical reactions in molecular analytes present on the dichalcogenide surfaces. However, the photocatalytic properties of such nanomaterials remain poorly understood. In the current study, we utilize tip-enhanced Raman spectroscopy (TERS) to examine photocatalytic reduction of 4-nitrothiophenol (4-NTP) to p,p'-dimercaptoazobisbenzene (DMAB) on tungsten disulfide (WS2) nanoplates and WS2 coupled with palladium nanoparticles (WS2@PdNPs). Our results indicate that although both WS2 and WS2@Pd were capable of reducing 4-NTP into DMAB, the metallic hybrid demonstrated much greater yield and rates of DMAB formation compared to WS2 nanoplate. These results indicate that coupling of catalytic metals to dichalcogenides could be used to enhance their catalytic properties.

Synthesis of degradable titanium disulfide nanoplates for photothermal ablation of tumors

Inorganic nanomaterials with high photothermal effects have received immense interest for photothermal therapy of tumors, while most of them suffer from long-term safety concerns due to their non-degradability. To address this issue, we have reported the PEGylated titanium disulfide (TiS2-PEG) nanoplates as degradable photothermal agents. The oleylamine-capped TiS2 nanoplates with an average size of ∼200 nm have been prepared via a high-temperature liquid-phase route, and they can be easily dispersed in nonpolar solvents and remain high stability for at least one month. To confer hydrophilicity, the oleylamine-capped TiS2 nanoplates are then surface-modified with amphiphilic PEGylated lipids through Van der Waals interactions. When dispersed in saline solution at 37 °C, the TiS2-PEG are unstable and they can be gradually decomposed into Ti(OH)4/TiO2 sol ultrasmall particles (<5 nm) within 72 h, indicating the suitable degradable feature. In addition, the TiS2-PEG nanoplates exhibit a strong near-infrared photoabsorption with a high photothermal conversion efficacy of 36.3% upon 808 nm laser irradiation. The in vitro and in vivo experiments confirm the low cytotoxicity of TiS2-PEG and high photothermal ablation ability towards cancer cells by the combination of TiS2-PEG and 808 nm laser. Importantly, owing to the degradability and size reduction, part of TiS2-PEG can be excreted from mice bodies via urine and feces, thus alleviating safety concerns. Therefore, the present TiS2-PEG nanoplates can act as a safe and degradable photothermal agent for tumor therapy, which also provides some insights into developing other degradable inorganic nanoagents.

A sensitive and selective approach for detection of tetracyclines using fluorescent molybdenum disulfide nanoplates

The wide use of tetracyclines (TCs) for prevention and therapy of animal diseases may result in excessive residues in animal products, which could pose serious risks to human health. A novel molybdenum disulfide nanoplates (MoS2 NPs)-based fluorescent sensor for tetracycline (TET) is reported. The MoS2 NPs, synthesized via a facile bottom-up hydrothermal route, showed blue fluorescence at 430 nm in aqueous solution. Interestingly, its fluorescence was quenched significantly upon addition of TET, which is mainly due to a combination of the inner filter effect and electron transfer. Thus, the MoS2 NPs based fluorescence sensor was delineated for the detection of TET. The methodology here presented showed a low detection limit of 0.032 μM and satisfied recoveries from 88.46% to 108.62% in spiked milk, milk powder and bovine muscle samples.

Synthesis and investigation of SnS2/RGO nanocomposites with different GO concentrations: structure and optical properties, photocatalytic performance

In this study, we report the synthesis of tin disulfide/reduced graphrene oxide (SnS2/RGO) nanocomposites by a simple one-step hydrothermal method. In order to investigate the effect of RGO on the structure and optical properties and photocatalytic activity of the products a series of nanocomposites was prepared with different concentrations of GO. The samples were examined using X-ray diffraction, field emission scanning electron microscopy (FESEM), Raman spectroscopy, UV–Vis spectroscopy and photoluminescence techniques. The results confirmed the growth of SnS2 with the hexagonal phase. FESEM analysis showed that the hexagonal tin disulfide nanoplates are uniformly dispersed on the surface of the graphene oxide sheets. The optical examination of SnS2 and SnS2/RGO nanocomposites indicated that the band gaps of all nanocomposites are greater than that of SnS2 due to the quantum confinement effect. The photocatalytic activity of the SnS2/RGO nanocomposites was investigated for degradation of the acid orange 7 dye under visible light. It was observed that all nanocomposites have a higher photocatalytic activity for the degradation in comparison with pure SnS2. The optimum concentration of GO in SnS2/RGO nanocomposite for achieving the highest photocatalytic efficiency (81%) was determined as 2 mg ml−1 during 180 min.

(101) Plane-Oriented SnS2 Nanoplates with Carbon Coating: A High-Rate and Cycle-Stable Anode Material for Lithium Ion Batteries.

Tin disulfide is considered to be a promising anode material for Li ion batteries because of its high theoretical capacity as well as its natural abundance of sulfur and tin. Practical implementation of tin disulfide is, however, strongly hindered by inferior rate performance and poor cycling stability of unoptimized material. In this work, carbon-encapsulated tin disulfide nanoplates with a (101) plane orientation are prepared via a facile hydrothermal method, using polyethylene glycol as a surfactant to guide the crystal growth orientation, followed by a low-temperature carbon-coating process. Fast lithium ion diffusion channels are abundant and well-exposed on the surface of such obtained tin disulfide nanoplates, while the designed microstructure allows the effective decrease of the Li ion diffusion length in the electrode material. In addition, the outer carbon layer enhances the microscopic electrical conductivity and buffers the volumetric changes of the active particles during cycling. The optimized, carbon coated tin disulfide (101) nanoplates deliver a very high reversible capacity (960 mAh g-1 at a current density of 0.1 A g-1), superior rate capability (796 mAh g-1 at a current density as high as 2 A g-1), and an excellent cycling stability of 0.5 A g-1 for 300 cycles, with only 0.05% capacity decay per cycle.

Exploring co-catalytic graphene frameworks for improving photocatalytic activity of Tin disulfide nanoplates

The exploration of high efficient photocatalysts for water-splitting is a challenge as well as an opportunity for future applications in renewable sustainable energy. In this paper, a two dimensional photocatalytic Tin disulfide/graphene hybrid nanosheets (SnS2/rGO HNs) with identically 2D structural configurations have been prepared via a facile hydrothermal route. The as-prepared SnS2/rGO HNs photoanode demonstrates improved photoelectrochemical (PEC) performance when compared to bare SnS2 electrodes. X-ray diffraction pattern and Raman spectra are carried out and confirm that the as-prepared SnS2/rGO HNs are pure and well crystalized. Additional morphological and microstructural tests verify a high yield of SnS2/rGO HNs with good quality, indicating the relatively stability of graphene platform with high specific surface area. Further PEC measurements demonstrate the photocurrent density of SnS2/rGO HNs attain maximum under 100mW/cm2 when the applied potential is 0V and varies from 321nA/cm2 to 244nA/cm2 while the applied potential increase from 0V to 1.0V. Besides that, the duration test exhibits no detectable distinction after processing 25 cycles. The PEC improvement is proposed to derive from the positive synergetic effect between SnS2 and co-catalytic graphene framework. We hope this work can provide fundamental illustration about the PEC performance of two-dimensional SnS2/rGO HNs, offering extendable availabilities for its potential application into high-performance PEC and photovoltaic devices.

Pulsed cathodoluminescence and Raman spectra of MoS2 and WS2 nanocrystals and their combination MoS2/WS2 produced by self-propagating high-temperature synthesis

Molybdenum and tungsten disulfide nanoplates were produced by self-propagating high-temperature synthesis in argon atmosphere. This method provides an easy way to produce MoS2 and WS2 from nanoplates up to single- and several layers. The Raman peak intensities corresponding to in-plane E12g and out-of-plane A1g vibration modes and their shifts strongly depend on the thicknesses of the MoS2 and WS2 platelets indicating size-dependent scaling laws and properties. An electron beam irradiation of MoS2 and WS2 powders leads to an occurrence of pulsed cathodoluminescence (PCL) spectra at 575 nm (2.15 eV) and 550 nm (2.25 eV) characteristic to their intrinsic band gaps. For the combination of MoS2 and WS2 nanopowders, a PCL shoulder at 430 nm (2.88 eV) was observed, which is explained by the radiative electron-hole recombination at the MoS2/WS2 grain boundaries. The luminescence decay kinetics of the MoS2/WS2 nanoplates appears to be slower than for individual MoS2 and WS2 platelets due to a spatial separation of electrons and holes at MoS2/WS2 junction resulting in extension of recombination time.

Tin Disulfide Nanoplates on Graphene Nanoribbons for Full Lithium Ion Batteries.

A nanocomposite material made of layered tin disulfide (SnS2) nanoplates vertically grown on reduced graphene oxide nanoribbons (rGONRs) has been successfully developed as an anode in lithium ion batteries by a facile method. At a rate of 0.4 A/g, the material exhibits a high discharge capacity of 823 mAh/g even after 800 cycles. It shows excellent rate stability when the current density varies from 0.1 to 3.0 A/g with a Coulombic efficiency larger than 99%. In order to demonstrate the anode material for practical applications, SnS2-rGONR/LiCoO2 full cells were constructed. To the best of our knowledge, this is the first time that a full cell has been successfully developed using metal chalcogenides as an anode. The full cell delivers a high capacity of 642 mAh/g at 0.2 A/g, superior rate, and cycling stability after long-term cycling. Moreover, the full cell has a high output working voltage of 3.4 V. These excellent lithium storage performances in half and full cells can be mainly attributed to the synergistic effect between the highly conductive network of rGONRs and the high lithium-ion storage capability of layered SnS2 nanoplates.

Microfiber-coupler-assisted control of wavelength tuning for Q-switched fiber laser with few-layer molybdenum disulfide nanoplates.

Based on the liquid exfoliated method, we obtained the few-layer molybdenum disulfide (MoS2) nanoplates solution. By thermal evaporation method, we directly deposited MoS2 thin film onto the facet of a fiber patch cord. The modulation depth of the film is as high as 29%, and a Q-switched fiber laser was achieved. We also provided a new method to continuously tune the output laser with a tuning sensitivity of ∼5.5 nm/(1% strain) by controlling the cavity loss with a strained microfiber coupler (MFC).

Structure and catalytic properties of hexagonal molybdenum disulfide nanoplates

Molybdenum disulfide (MoS2) is a compound very useful for its properties; it is used as a lubricant, catalyst in hydrodesulfurization, in hydrogen fuel storage, etc. In this work MoS2 hexagonal nanoplates were synthesized at different temperatures and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy and high resolution transmission electron microscopy (HRTEM). These nanoplates have a size of 25–35 nm as revealed by SEM. With aberration corrected STEM it was possible to measure the interatomic distance of Mo–Mo, which was found to be 2.8 A. The catalytic properties of the nanoplates were measured in the hydrodesulfurization of dibenzothiophene, showing high activity and high direct desulfurization pathway (DDS) selectivity for an unpromoted MoS2 catalyst. Theoretical calculations were performed in 2H-MoS2 as well as 2H-MoS2 with a rotation of 16° and 19° which was applied to the two S planes in the crystalline structure. The results obtained on the rotated 2H-MoS2 yielded indication of a small gap semiconductor of Eg = 0.38 eV when compared to the unrotated 2H-MoS2, which is a semiconductor of Eg = 2.00 eV. This tendency of the rotated crystalline 2H-MoS2 toward metallicity could be responsible for the enhancement of the catalytic properties observed in the material in question, compared to other MoS2-based catalysts.