Transition Metal Dichalcogenide Nanomaterials Research Articles

The futuristic applications of transition metal dichalcogenides for cancer therapy.

The second-most common cause of death resulting from genetic mutations in DNA sequences is cancer. The difficulty in the field of anticancer research is the application of the traditional methods, which also affects normal cells. Mutations, genetic replication alterations, and chromosomal abnormalities have a direct impact on the effectiveness of anticancer drugs at different stages. Presently, therapeutic techniques utilize nanotechnology, transition metal dichalcogenides (TMDCs), and robotics. TMDCs are being increasingly employed in tumor therapy and biosensing applications due to their biocompatibility, adjustable bandgap, versatile functionality, exceptional photoelectric properties, and wide range of applications. This study reports the advancement of nanoplatforms based on TMDCs that are specifically engineered for responsive and intelligent cancer therapy. This article offers a thorough examination of the current challenges, future possibilities for theranostic applications using TMDCs, and recent progress in employing TMDCs for cancer therapy. Currently, there is significant interest in two-dimensional (2D) TMDCs nanomaterials as ultrathin unique physicochemical properties. These materials have attracted attention in various fields, including biomedicine. Due to their inherent ability to absorb near-infrared light and their exceptionally large surface area, significant efforts are being made to prepare multifunctional nanoplatforms based on 2D TMDCs.

Synthesis and Formulation of Ternary Transition Metal Dichalcogenide Alloys for Additive Electronic Manufacturing

Compared with the most investigated graphene, layered transition metal dichalcogenides (TMDs) have received significant attention due to their various chemical compositions and great potential electronic application. In order to tailor and engineer properties of TMDs and therefore enhance their efficiency toward commercial applications, several methods have been employed including reducing dimensionality, creating inter and intra-heterostructures, introducing inter stain, and alloying. Among these, alloying via chemical vapor transport (CVT) is scalable, cost- efficient, and controllable method of tuning TMD bulk crystal properties. Alloying of TMDs can be categorized into several types including metal replacement, dichalcogenide replacement, and both metal and dichalcogenide replacement. In a typical TMD CVT reaction, high-purity precursors are mixed in a desired stochiometric ratio, vacuumed, and sealed in an ampoule to form a closed system. The resulting TMD crystal can then be used for additional processes, e.g., exfoliation to yield 2D TMD nanosheets. Additive electronics manufacturing is a promising technique for the scalable fabrication of electronic devices, including sensors and energy storage devices. For an ink to be compatible for different printing modalities the ink rheology including viscosity, surface tension, and solid requires to be tuned to obtain suitable fluid dynamic parameters for jetting the ink. This work summarizes the development, synthesis, characterization, and formulation of two-dimensional ternary TMDCs ink for aerosol jet printing (AJP) technology. Ball milling assisted liquid exfoliation is utilized for synthesizing ternary TMDs nanomaterials under controlled condition. The resulting nanomaterial is developed into nanomaterial ink compatible with AJP. Detailed analysis of the material characterization and ink properties are required to optimize the fluid dynamics and properties of the ink. After printing the formulated ink using AJP on various substrates, post-printing process techniques is required to be investigated for printed nanomaterials inks to achieve bulk-like performance for the printed structures. Our results highlight the innovations in synthesis and formulation of ternary transition metal dichalcogenide nanomaterial inks for additive manufacturing of electronic devices such as sensors, solar cells, and energy storage devices.

Covalently Functionalized MoS2 Initiated Gelation of Hydrogels for Flexible Strain Sensing.

Transition metal dichalcogenides (TMDs), with superior mechanical and electrical conductivity, are one of the most promising two-dimensional materials for creating a generation of intelligent and flexible electronic devices. However, due to the high van der Waals and electrostatic attraction, TMD nanomaterials tend to aggregate in dispersants to achieve a stable state, thus severely limiting their further applications. Surface chemical modification is a common strategy for improving the dispersity of TMD nanomaterials; however, there are still constraints such as limited functionalization methods, low grafting rate, and difficult practice application. Thus, it is challenging to develop innovative surface modification systems. Herein, we covalently modify an olefin molecule on surface-inert MoS2, and the modified MoS2 can be used as not only a catalyst for hydrogel polymerization, but also a cross-linker in the hydrogel network. Specifically, allyl is covalently grafted onto chemically exfoliated MoS2, and this modified MoS2 can be uniformly dispersed in polar solvents (such as acetone, N,N-dimethylformamide, and ethanol), remaining stable for more than 2 weeks. The allyl-modified MoS2 can catalyze the polymerization of polyacrylamide hydrogel and then integrate in the network, which increases the tensile strength of the composite hydrogel. The flexible sensor based on the composite hydrogel exhibits an ideal operating range of 600% and a quick response time of 150 ms. At the same time, the flexible device can also track the massive axial stretching movements of human joints, making it a reliable option for the next wave of wearable sensing technology.

WSe2 nanowires-based nanofluids for concentrating solar power

Tungsten selenide belongs to the family of inorganic compounds denominated transition metal dichalcogenides (TMDCs). There is emerging interest in these compounds in the field of optoelectronics, catalysis, sensing or energy storage, among others. Most works focus on the use of these materials in their 2D form but there is scarce research on the study of TMDCs nanomaterials with one-dimensional morphology. In this work, we explore the thermophysical properties of nanofluids based on 1D-WSe2 nanostructures with the aim of studying the feasibility of these nanofluids as heat transfer fluids in concentrating solar power plants. In this respect, nanofluids with a high heat transfer rate could increase the thermal efficiency of solar power plants, which would reduce the energy dependence on fossil fuels. Nanofluids of 0.02 wt%, 0.05 wt% and 0.10 wt% WSe2 concentrations have been prepared by the two-step method considering a thermal fluid used in solar power plants as the base fluid. The results of extinction coefficient evolution, ζ potential and particle size in suspension show a high colloidal stability over time of the prepared nanofluids mainly because of the high aspect ratio of the 1D-WSe2 nanomaterial. Additionally, the one-dimensionality and length of the synthesized nanowires favors the transport of heat in controlled directions, obtaining increases in thermal conductivity with respect to the base fluid of up to 16.8% in the highest concentration nanofluid. Improvements in isobaric specific heat of up to 15.7% and heat transfer of up to 20.8% compared to the base fluid have also been found. The results of this paper provide evidence that the presence of WSe2 nanowires induces increases in the thermal properties of the fluid commonly used in concentrating solar power plants without inducing agglomeration or sedimentation problems. Therefore, the nanofluids based on 1D-WSe2 nanostructures prepared in this work have a high potential to be used as heat transfer fluids in concentrating solar power plants based on parabolic trough collectors.

Triboelectric Pressure Sensors Using Laser-Directed Synthesis of Strain-Induced Crumpled MoS2

Two-dimensional (2D) transition metal dichalcogenide (TMDC) nanomaterials are currently regarded as next generation electronic materials for future flexible, transparent, and wearable electronics. Due to the lack of compatible synthesis and study, however, the characteristic influences of 2D TMDC nanomaterials have been little investigated in the field of triboelectric nanogenerator (TENG) devices that are currently one of the main technologies for mechanical energy harvesting. In this report, we demonstrate a fast, non-vacuum, wafer-scale, and patternable synthesis method for 2D MoS2 using pulsed laser-directed thermolysis. The laser-based synthesis technique that we have developed can apply internal stress to MoS2 crystal by adjusting its morphological structure, so that a surface-crumpled MoS2 TENG device generates ~40% more power than a flat MoS2 one. Compared to other MoS2-based TENG devices, it shows high-performance energy harvesting (up to ~25 V and ~1.2 μA) without assistance from other materials, even when the counterpart triboelectric surface has a slightly different triboelectric series. This enhanced triboelectrification is attribute to work function change as well as enlarged surface roughness. Finally, the direct-synthesized MoS2 patterns are utilized to fabricate a self-powered flexible haptic sensor array. The technique we propose here is intended to stimulate further investigation of the triboelectric effects and applications of 2D TMDC nanomaterials.

Transition metal dichalcogenide nanospheres for high-refractive-index nanophotonics and biomedical theranostics

Recent developments in the area of resonant dielectric nanostructures have created attractive opportunities for concentrating and manipulating light at the nanoscale and the establishment of the new exciting field of all-dielectric nanophotonics. Transition metal dichalcogenides (TMDCs) with nanopatterned surfaces are especially promising for these tasks. Still, the fabrication of these structures requires sophisticated lithographic processes, drastically complicating application prospects. To bridge this gap and broaden the application scope of TMDC nanomaterials, we report here femtosecond laser-ablative fabrication of water-dispersed spherical TMDC (MoS2 and WS2) nanoparticles (NPs) of variable size (5 to 250 nm). Such NPs demonstrate exciting optical and electronic properties inherited from TMDC crystals, due to preserved crystalline structure, which offers a unique combination of pronounced excitonic response and high refractive index value, making possible a strong concentration of electromagnetic field in the NPs. Furthermore, such NPs offer additional tunability due to hybridization between the Mie and excitonic resonances. Such properties bring to life a number of nontrivial effects, including enhanced photoabsorption and photothermal conversion. As an illustration, we demonstrate that the NPs exhibit a very strong photothermal response, much exceeding that of conventional dielectric nanoresonators based on Si. Being in a mobile colloidal state and exhibiting superior optical properties compared to other dielectric resonant structures, the synthesized TMDC NPs offer opportunities for the development of next-generation nanophotonic and nanotheranostic platforms, including photothermal therapy and multimodal bioimaging.

Defect-Rich Molybdenum Sulfide Quantum Dots for Amplified Photoluminescence and Photonics-Driven Reactive Oxygen Species Generation.

Transition metal dichalcogenide (TMD) quantum dots (QDs) with defects have attracted interesting chemistry due to the contribution of vacancies to their unique optical, physical, catalytic, and electrical properties. Engineering defined defects into molybdenum sulfide (MoS2 ) QDs is challenging. Herein, by applying a mild biomineralization-assisted bottom-up strategy, blue photoluminescent MoS2 QDs (B-QDs) with a high density of defects are fabricated. The two-stage synthesis begins with a bottom-up synthesis of original MoS2 QDs (O-QDs) through chemical reactions of Mo and sulfide ions, followed by alkaline etching that creates high sulfur-vacancy defects to eventually form B-QDs. Alkaline etching significantly increases the photoluminescence (PL) and photo-oxidation. An increase in defect density is shown to bring about increased active sites and decreased bandgap energy; which is further validated with density functional theory calculations. There is strengthened binding affinity between QDs and O2 due to lower gap energy (∆EST ) between S1 and T1 , accompanied with improved intersystem crossing (ISC) efficiency. Lowered gap energy contributes to assist e- -h+ pair formation and the strengthened binding affinity between QDs and 3 O2 . Defect engineering unravels another dimension of material properties control and can bring fresh new applications to otherwise well characterized TMD nanomaterials.

Oxygenic Enrichment in Hybrid Ruthenium Sulfide Nanoclusters for an Optimized Photothermal Effect.

Transition-metal dichalcogenide (TMD)-based nanomaterials have been extensively explored for the photonic therapy. To the best of our knowledge, near-infrared (NIR) light is a requirement for the photothermal therapy (PTT) to achieve the feature of deep-tissue penetration, whereas no obvious absorption peaks existing in the NIR region for existing TMD nanomaterials limit their therapeutic efficacy. As one category of TMD nanomaterials, ruthenium sulfide-based nanomaterials have been less exploited in biomedical applications including tumor therapy so far. Here, we develop a facile biomineralization-assisted bottom-up strategy to synthesize oxygenic hybrid ruthenium sulfide nanoclusters (RuSx NCs) by regulating the oxygen amounts and sulfur defects for the optimized PTT. By regulating the increasing initial molar ratios of Ru to S, RuSx NCs with small sizes were endowed with increasing oxygen contents and sulfur defects, leading to the photothermal conversion efficiency (PCE) increasing from 32.8 to 41.9%, which were higher than that of most small-sized inorganic photothermal nanoagents. In contrast to commercial indocyanine green, these RuSx NCs exhibited higher photostability under NIR laser irradiation. The high PCE and superior photostability allowed RuSx NCs to effectively and completely ablate cancer cells. Thus, the proposed defect engineering strategy endows RuSx NCs with an excellent photothermal effect for the PTT of tumors of living mice, which also proves the potential of further exploring the properties of RuSx NCs for future biomedical applications.

In-Situ X-Ray Absorption Spectroscopy Study of Electrocatalytic Reduction of Carbon Dioxide with Molybdenum Disulfide

Electrocatalytic reactions offer alternative routes for the conversion and storage of energy. For instance, the electrocatalytic reduction of carbon dioxide could lead to energy-rich syngas, methanol, or even hydrocarbons. Layered transition metal dichalcogenide nanomaterials, such as MoS2, have emerged as electrocatalysts towards CO2 reduction with high efficiency and low overpotentials. However, the underlying chemical and electronic states defining the catalytic activity have not yet been completely defined. These key states can be probed for both metals and ligands in selected MX2 (M=W, Mo; X=S, Se) using synchrotron-based X-ray absorption spectroscopy (XAS). In recent work we performed in-situ XAS measurements at Mo K-edge and S K-edge for MoS2 nanosheets. Measurements at the S K-edge showed drastic changes at the pre-edge and edge indicating changes in number of available unoccupied states and Zeff respectively. On the other hand, only a small shift of the Mo K-edge was observed. Metal d-states are found to be the active site for catalysis, yet the ligand K-edge presents a better method to examine catalytic processes. Since the pre-edge reflects a transition to metal-ligand hybridized states, its intensity and position gives direct insight into the activity and changes of d-states. Given the vast compositional space of metal and ligand for MX2, the knowledge of how d-state activity will serve to pave the way to a better study of metal and chalcogenide combinations to improve the electrocatalytic performance. Figure 1

Synthesis of biocompatible chitosan functionalized Ag decorated biocomposite for effective antibacterial and anticancer activity

The transition-metal dichalcogenides (TMDCs) like MoS2 and WS2 are a new and interesting class of materials and show considerable promise for use in a wide variety of fields, including nanomedicine for cancer. The eco-friendly, biodegradability, toxicity, and antimicrobial activity remain an open issue. Herein, we focused on the current demands of two dimensional (2D) TMDCs and produced high-quality, few-layered MoS2 nanosheets. Noble metal Ag incorporated into the 2D-CS/MoS2 NC by the liquid exfoliated process. The manufactured CS/MoS2/Ag hybrid NC showed excellent antibacterial activity against two microorganisms such as Gram-positive (21, 27, and 33 mm) and Gram-negative bacteria (23, 30, and 39 mm). The CS/MoS2/Ag hybrid NC was designed to have significant antibacterial activity against E.coli bacteria than S.aureus. Furthermore, the hybrid NC has a 74.18% cell inhibition against MCF-7 cancer cells. According to the literature relevant, it is the first extensive experimental analysis on the nano-bio interaction of 2D TMDCs nanomaterials in MCF-7 breast cancer cells.

Polyvinylalcohol (PVA)-Assisted Exfoliation of ReS2 Nanosheets and the Use of ReS2-PVA Composites for Transparent Memristive Photosynapse Devices.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have attracted significant attention for their outstanding optoelectrical properties. Unlike most TMDs with layer-dependent photoresponsivity, rhenium disulfide (ReS2) shows excellent thickness-independent photoresponsivity. Herein, we show a surfactant-free polyvinyl alcohol (PVA)-assisted exfoliation method for 2D-TMDs in aqueous solution and a transparent photosensitive memristor synapse device based on ReS2 nanosheets composited with PVA. ReS2 nanosheets are obtained via PVA-assisted exfoliation. After exfoliation, the ReS2-PVA dispersion solution is spin-coated on a substrate and dried to form a nanocomposite film without additional processing. Transparent memristors are then fabricated on plastic or glass substrates to demonstrate the applicability of the ReS2-PVA film. The devices show "write once, read many" memory behavior with a high ON/OFF current ratio (1.0 × 104 at 0.5 V) during electrical operation. In the high resistive state, synaptic functions with long-term memory behavior are successfully mimicked by applying photonic stimuli to the transparent ReS2-PVA memristors. The excitatory postsynaptic current stimulated by the photosignal is gradually reduced by electric stimuli. The proposed PVA-assisted exfoliation method is cost-effective, environmentally friendly, and applicable to various TMD nanomaterials. Furthermore, the ReS2-PVA nanocomposite film obtained via a simple solution-based process demonstrates excellent photosynaptic behavior.

Illuminating the Electronic Properties of WS2 Polytypism with Electron Microscopy

AbstractTailoring the specific stacking sequence (polytypes) of layered materials represents a powerful strategy to identify and design novel physical properties. While nanostructures built upon transition‐metal dichalcogenides (TMDs) with either the 2H or 3R crystalline phases have been routinely studied, knowledge of TMD nanomaterials based on mixed 2H/3R polytypes is far more limited. In this work, mixed 2H/3R free‐standing WS2 nanostructures displaying a flower‐like configuration are fingerprinted by means of state‐of‐the‐art transmission electron microscopy. Their rich variety of shape‐morphology configurations is correlated with relevant local electronic properties such as edge, surface, and bulk plasmons. Machine learning is deployed to establish that the 2H/3R polytype displays an indirect band gap of . Further, high resolution electron energy‐loss spectroscopy reveals energy‐gain peaks exhibiting a gain‐to‐loss ratio greater than unity, a property that can be exploited for cooling strategies of atomically‐thin TMD nanostructures and devices built upon them. The findings of this work represent a stepping stone towards an improved understanding of TMD nanomaterials based on mixed crystalline phases.

Metallic 1T Phase Enabling MoS2 Nanodots as an Efficient Agent for Photoacoustic Imaging Guided Photothermal Therapy in the Near‐Infrared‐II Window

Transition metal dichalcogenide (TMD) nanomaterials, specially MoS2 , are proven to be appealing nanoagents for photothermal cancer therapies. However, the impact of the crystal phase of TMDs on their performance in photoacoustic imaging (PAI) and photothermal therapy (PTT) remains unclear. Herein, the preparation of ultrasmall single-layer MoS2 nanodots with different phases (1T and 2H phase) is reported to explore their phase-dependent performances as nanoagents for PAI guided PTT in the second near-infrared (NIR-II) window. Significantly, the 1T-MoS2 nanodots give a much higher extinction coefficient (25.6Lg-1 cm-1 ) at 1064nm and subsequent photothermal power conversion efficiency (PCE: 43.3%) than that of the 2H-MoS2 nanodots (extinction coefficient: 5.3Lg-1 cm-1 , PCE: 21.3%). Moreover, the 1T-MoS2 nanodots also give strong PAI signals as compared to negligible signals of 2H-MoS2 nanodots in the NIR-II window. After modification with polyvinylpyrrolidone, the 1T-MoS2 nanodots can be used as a highly efficient agent for PAI guided PTT to effectively ablate cancer cells in vitro and tumors in vivo under 1064nm laser irradiation. This work proves that the crystal phase plays a key role in determining the performance of nanoagents based on TMD nanomaterials for PAI guided PTT.

Laser-directed synthesis of strain-induced crumpled MoS2 structure for enhanced triboelectrification toward haptic sensors

Two-dimensional (2D) transition metal dichalcogenide (TMDC) nanomaterials are currently regarded as next-generation electronic materials for future flexible, transparent, and wearable electronics. Due to the lack of compatible synthesis and study, however, the characteristic influences of 2D TMDC nanomaterials have been little investigated in the field of triboelectric nanogenerator (TENG) devices that are currently one of the main technologies for mechanical energy harvesting. In this report, we demonstrate a fast, non-vacuum, wafer-scale, and patternable synthesis method for 2D MoS 2 using pulsed laser-directed thermolysis. The laser-based synthesis technique that we have developed can apply internal stress to MoS 2 crystal by adjusting its morphological structure, so that a surface-crumpled MoS 2 TENG device generates ~40% more power than a flat MoS 2 one. Compared to other MoS 2 -based TENG devices, it shows high-performance energy harvesting (up to ~25 V and ~1.2 μA) without assistance from other materials, even when the counterpart triboelectric surface has a slightly different triboelectric series. This enhanced triboelectrification is attribute to work function change as well as enlarged surface roughness. Finally, the direct-synthesized MoS 2 patterns are utilized to fabricate a self-powered flexible haptic sensor array. The technique we propose here is intended to stimulate further investigation of the triboelectric effects and applications of 2D TMDC nanomaterials. • Fast, non-vacuum, large-scale and patternable synthesis of 2D MoS 2 is developed by laser-directed thermolysis. • Surface morphology of MoS 2 is intentionally controlled by tuning laser synthesis mechanism. • Surface-crumpled MoS 2 shows high-performance triboelectric energy harvesting signals. • Improved triboelectrification is attributable to work function change, surface area enlargement, and secondary effects. • Self-powered flexible haptic sensor array is fabricated using directly patterned MoS 2 .

2D transition metal dichalcogenide nanomaterials: advances, opportunities, and challenges in multi-functional polymer nanocomposites

The functionalized TMD nanolayers have the potential to introduce multi-functionalities into polymer matrices, thus leading to the development of high-performance multi-functional composites/nanocomposites.

The Study of Atmospheric Pressure CVD Growth Process of MoxW1-xTe2 Nanobelts for Tuneable Chemical Composition

Transition metal dichalcogenides nanomaterials with topological semimetallic phase (MoTe2, WTe2 and MoxW1-xTe2) are expected to realize no-consumption electronic transportation due to its Dirac point. Especially, the various structure existence in MoxW1-xTe2, like hexagonal (2H), monoclinic (1T’) and othorombic (Td), provides opportunities for phase engineering, which is beneficial for future novel electronic and spintronic devices. Plenty works have focused on the synthesis of MoTe2, WTe2 and MoxW1-xTe2 nanomaterials. Unfortunately, the understanding of the growth process of MoxW1-xTe2 nanomaterials is still absent and the exact control of the atomic ratio between Mo and W in MoxW1-xTe2 nanomaterials is still a huge task up to now. Here, we study the growth process of MoxW1-xTe2 nanomaterials by the growing of binary MoTe2 and WTe2 nanomaterials. Through detailed structural and compositional characterization, same growth mode, crystallography, and morphology have been observed among MoTe2, WTe2 and MoxW1-xTe2 nanomaterials. Through analysis, we suggest that the heating temperature of Mo and W precursors during the CVD process is the key parameters to achieve the tuneable chemical composition of MoxW1-xTe2 nanomaterials. This study dissected the growth process of MoxW1-xTe2 nanomaterials and provided a possible method to control the chemical composition of MoxW1-xTe2 nanomaterials by APCVD, which is beneficial to realize the phase engineering in Mo-W-Te system and also for future topological application.

Defect engineered bioactive transition metals dichalcogenides quantum dots

Transition metal dichalcogenide (TMD) quantum dots (QDs) are fundamentally interesting because of the stronger quantum size effect with decreased lateral dimensions relative to their larger 2D nanosheet counterparts. However, the preparation of a wide range of TMD QDs is still a continual challenge. Here we demonstrate a bottom-up strategy utilizing TM oxides or chlorides and chalcogen precursors to synthesize a small library of TMD QDs (MoS2, WS2, RuS2, MoTe2, MoSe2, WSe2 and RuSe2). The reaction reaches equilibrium almost instantaneously (~10–20 s) with mild aqueous and room temperature conditions. Tunable defect engineering can be achieved within the same reactions by deviating the precursors’ reaction stoichiometries from their fixed molecular stoichiometries. Using MoS2 QDs for proof-of-concept biomedical applications, we show that increasing sulfur defects enhanced oxidative stress generation, through the photodynamic effect, in cancer cells. This facile strategy will motivate future design of TMDs nanomaterials utilizing defect engineering for biomedical applications.

Using ligands to control reactivity, size and phase in the colloidal synthesis of WSe2 nanocrystals.

Colloidal chemistry is leveraged for size- and phase-tuning of transition metal dichalcogenide nanomaterials. Specifically, nucleation and growth of colloidal WSe2 nanocrystals are controlled via mixtures of oleic acid (OA) and trioctylphosphine oxide. Increased OA yields slower nucleation, larger nanocrystals and a shift from the 2H to 1T' phase.

Polyphenol-Assisted Exfoliation of Transition Metal Dichalcogenides into Nanosheets as Photothermal Nanocarriers for Enhanced Antibiofilm Activity.

Transition metal dichalcogenide (TMD) nanosheets have evoked enormous research enthusiasm and have shown increased potentials in the biomedical field. However, a great challenge lies in high-throughput, large-scale, and eco-friendly preparation of TMD nanosheet dispersions with high quality. Herein, we report a universal polyphenol-assisted strategy to facilely exfoliate various TMDs into monolayer or few-layer nanosheets. By optimizing the exfoliation condition of molybdenum disulfide (MoS2), the yield and concentration of as-exfoliated nanosheets are up to 60.5% and 1.21 mg/mL, respectively. This is the most efficient aqueous exfoliation method at present and is versatile for the choices of polyphenols and TMD nanomaterials. The as-exfoliated MoS2 nanosheets possess superior biomedical stability as nanocarriers to load antibiotic drugs. They show a high photothermal conversion effect and thus induce a synergetic effect of chemotherapy and photothermal therapy to harvest enhanced antibiofilm activity under near-infrared (NIR) light. All these results offer an appealing strategy toward the synthesis and application of ultrathin TMD nanosheets, with great implications for their development.

The Phases of WS2 Nanosheets Influence Uptake, Oxidative Stress, Lipid Peroxidation, Membrane Damage, and Metabolism in Algae.

Application of transition metal dichalcogenide (TMDC) nanosheets with different phases have attracted much attention in various fields. However, the effects of TMDC phases on environmental biology remain largely unknown. In this study, chemically exfoliated WS2 nanosheets (Ce-WS2, mainly the 1T phase) and annealed exfoliated WS2 nanosheets (Ae-WS2, 2H phase) were fabricated to serve as representative TMDC nanomaterials. Ce-WS2 showed higher levels of cellular uptake, oxidative stress, lipid peroxidation, membrane damage, and inhibition of photosynthesis than Ae-WS2 in Chlorella vulgaris. These differences were attributed to the higher electron conductivity and higher separation efficiency of electrons and holes in the 1T phase, a typical feature of Ce-WS2. Correspondingly, 2H-phase Ae-WS2 exhibited lower photooxidation/reduction activity and a lower ability to generate reactive oxygen species (mainly •OH) under visible-light irradiation. 1T-phase Ce-WS2 dissolved more readily than Ae-WS2 and released more W ions into aqueous environments, but the W ions exhibited negligible toxicity. Metabolomic analysis revealed that Ce-WS2 induced more obvious alterations in metabolites (e.g., amino acids and fatty acids) and metabolic pathways (e.g., starch and sucrose metabolism) than Ae-WS2. These alterations correlated with cell membrane damage, oxidative stress and photosynthesis inhibition. The present work provides insights into the environmentally friendly design of two-dimensional TMDCs.