Ultrasound-assisted Liquid-phase Exfoliation Research Articles

Sub-nanosecond single mode-locking pulse generation in an intracavity KTP optical parametric oscillator with a few-layer Bi2Te3 topological insulator saturable absorber

By utilizing the ultrasound-assisted liquid phase exfoliation process, Bi2Te3 nanosheets are synthesized and deposited onto a quartz plate to form a saturable absorber (SA), in which nonlinear absorption characteristics around 1 μm are investigated with a home-made Q-switched laser. With the as-prepared Bi2Te3 SA employed, a sub-nanosecond KTiOPO4 (KTP) based intracavity optical parametric oscillator (IOPO) pumped by a dual-loss-modulated Q-switched and mode-locked (QML) laser is successfully realized. With a short duration of sub-nanosecond and a repetition rate of several kilohertz (kHz), the signal wave’s single mode-locking pulse existed underneath a Q-switched envelope can be formed. At an incident pump power of 8.92 W and an acousto-optic modulator (AOM) repetition rate of 2 kHz, a signal wave’s single mode-locking pulse underneath a Q-switching envelope with a measured minimum pulse duration of 520 ps is accomplished. It is the first demonstration of such Bi2Te3 SA utilized in a solid-state QML IOPO laser, to the best of our knowledge. According to the experimental results, this provides an efficient and straightforward approach to acquire sub-nanosecond OPO signal wave pulses. Additionally, the relevant coupled rate equations are established, and the simulation results match the experimental results, revealing the potential of Bi2Te3 as a nanomaterial for optoelectronic applications.

2D Ti3AlC2 and Ti3C2 nanosheets: Excellent optical limiting materials for laser protection

MXenes have important research value in the field of photonics. In this work, Ti3C2 MXene was obtained by etching the Ti3AlC2 MAX phase with hydrofluoric acid, Ti3AlC2 and Ti3C2 nanosheets with a thickness of several nanometers were prepared by ultrasound-assisted liquid-phase exfoliation using anhydrous ethanol as the exfoliation solvent. The nonlinear absorption properties of the two nanosheets at 1064, 532 and 355 nm excitation wavelengths (infrared to ultraviolet band), especially the optical limiting behavior, were systematically investigated with the help of open aperture Z-scan technique. Interestingly, Ti3C2 MXene, obtained from Ti3AlC2 MAX by a simple hydrofluoric acid etching operation only, exhibits different nonlinear optical properties from Ti3AlC2 MAX under the same experimental conditions. Ti3AlC2 nanosheets exhibited excellent two-photon absorption behavior in the visible light band, while the two-photon absorption behavior of Ti3C2 nanosheets is better in the ultraviolet band. The excellent nonlinear absorption properties exhibited by Ti3AlC2 and Ti3C2 nanosheets demonstrate their advantages as OL materials with great potential for applications in laser protection.

Facile and environmentally friendly synthesis of highly efficient two-dimensional hematene nanosheets for photocatalytic applications

Exfoliation of bulk hematite (α-Fe2O3), as an environmentally friendly, nontoxicity, and low-cost semiconductor oxide, exhibited greater photocatalytic activity under visible light irradiation. Herein, we described two preparation methods of novel two-dimensional non-van der Waals hematene (2D-Hm) nanosheets including ultrasound-assisted liquid-phase exfoliation (US-Hm) and chemical-assisted liquid-phase exfoliation (CH-Hm). The photocatalytic activity of 2D-Hm nanosheets was evaluated for the decomposition of Tetracycline (TC). Various advanced analyses were used to investigate the physical and chemical properties of the exfoliated samples. SEM and TEM analyses confirmed the layered structures of 2D-Hm. The crystalline structure of 2D-Hm samples was confirmed successfully by XRD analyses. After exfoliation of bulk hematite, the surface area increased remarkably from 5.73 m2/g to 24.16, and 15.26 m2/g using US-Hm, and CH-Hm exfoliation methods, respectively. The photoelectrochemical photocurrent and electrochemical impedance spectroscopy (EIS) analysis indicate that 2D-Hm samples have higher charge-transfer efficiency than bulk hematite. Additionally, the formation of hydroxyl (•OH) radicals was approved using the o-phenylenediamine (OPD) and photoluminescence (PL) analysis. The leaching iron concentration in the aqueous phase was measured within five consecutive examinations. To recognize the intermediates formed during the degradation process, gas chromatography-mass spectrometry (GC–MS) was employed.

Designing Black Phosphorus and Heptazine-Based Crystalline Carbon Nitride Composites for Photocatalytic Water Splitting

Black phosphorus (BP) and heptazine-based crystalline carbon nitride (KPHI) composite photocatalysts were synthesized by molten salt and ultrasound-assisted liquid phase exfoliation methods. The structure, morphology and optical properties of the as-prepared BP/KPHI composites were evaluated by various characterization techniques. In addition, the photocatalytic performance of BP/KPHI composites for hydrogen production was investigated. The photocatalytic activity of BP/KPHI composite catalysts could be modulated by changing the loading mass ratio of BP. The BP/KPHI composite photocatalyst with a mass ratio of 10% exhibited the highest photocatalytic activity with the hydrogen production rate of 4.3 mmol g−1 h−1, about three times higher than that of pristine KPHI. Benefiting from the advantages of simplicity, rapidity, high yield and good controllability, this nanocomposite photocatalyst has the potential to serve as an excellent photocatalytic material for solar energy conversion.

Novel cyclic ultrasound-assisted liquid phase exfoliation of graphene in deionized water: A parameter study

In this study, a novel cyclic ultrasound-assisted liquid phase exfoliation method for graphene in deionized water (DIW) was studied. A cyclic apparatus that can control temperature was developed. The size, thickness, number of layers of as-prepared graphene suspensions were characterized and quantified based on this apparatus covering the frequency range of 20 kHz to 35 kHz. The statistics shown that the prepared graphene has a surface area of 9.77 μm2 and a composite conductivity of 1.45 × 104 S/m at a frequency of 35 kHz. This study offers a potential pathway for its large-scale production at a low cost.

Nanometer-Thin Stacks of MXenes (Ti3C2Tx and Ta4C3Tx) for Applications as Nonlinear Photonic Devices

Two-dimensional (2D) carbides of transition metals, so called “MXenes”, maintain excellent optical properties and unique layer stacking form via hydrogen bonds in contrast to other low-dimensional materials. These promising features have attracted increasingly research interest in the field of ultrafast photonics. In this work, titanium carbide (Ti3C2Tx) and tantalum carbide (Ta4C3Tx), as two promising MXene materials for photonic applications, are experimentally synthesized by the ultrasound-assisted liquid phase exfoliation technique. The morphology of prepared few-layer Ti3C2Tx and Ta4C3Tx has been systematically characterized by transmission electron microscopy and X-ray diffraction analysis. Density functional theory is performed to obtain their electronic band structures, demonstrating metallic properties and verifying their optical absorption at 1 μm. Their tempting optical modulation properties for multi-gigahertz pulsed laser emission are demonstrated by using them as saturable absorbers in a waveguide laser cavity. Particularly, high-performance Q-switched mode-locked lasers with/without laser mirrors are realized based on the hybrid waveguide laser configuration, delivering 1 μm laser pulses with durations as short as 30 ps. The results presented in this work show the great potential of metallic MXenes and waveguide structures for applications in functional photonic devices.

Broadband saturable absorption responses of few-layered MoSe2 nanosheets for all-solid-state Q-switched lasers

Few-layered molybdenum diselenide (MoSe2) nanosheets were successfully fabricated by the ultrasound-assisted liquid phase exfoliation (UALPE) method. It exhibits broadband nonlinear optical (NLO) responses with optical modulation depths of 12.4% and 9.3% at 1.3 and 2 μm, respectively. Based on this, it was transferred onto a quartz substrate, acting as a saturable absorber (SA) to initiate solid-state pulsed lasers. The Q-switched Nd: GdVO4 laser with a minimum pulse duration of 366 ns and a repetition rate of 196 kHz was generated at around 1.3 μm. Meanwhile, the Q-switched Tm: YLF laser with a minimum pulse duration of 200 ns and a repetition rate of 43 kHz was obtained at around 2 μm. The experimental results indicate that few-layered MoSe2 nanosheets have a significant development prospect as a SA in optical modulation with a broad spectral band range at the near-infrared (NIR) band.

Ultrasound-assisted synthesis of graphene@MXene hybrid: A novel and promising material for electrochemical sensing

To date, multiple graphene@MXene hybrids have been reported via various synthesis approaches, but almost all the graphene@MXene hybrids inevitably used the reduced graphene oxide that prepared by chemical oxidation/reduction method, which generally involved the complex and dangerous operation procedure, and the highly toxic chemical reagent. How to prepare graphene@MXene hybrid through a simple, safe and eco-friendly synthetic route is highly desired. Compared with traditional synthesis technology, ultrasound synthesis strategy displays the merits of simplicity, low cost and environment protection. Herein, MXene (Ti3C2Tx) nanoflakes coupled with graphene nanosheets (graphene@MXene) were prepared in N-methylpyrrolidone (NMP) by simple ultrasound-assisted liquid-phase exfoliation method for the first time. Besides, the effect of types of solvent with different viscocity, sonication temperature and sonication duration time on the property of graphene@MXene hybrids were systematacially investigated. It is found the liquid-phase exfoliated graphene owned excellent electron transfer ability and the MXene (Ti3C2Tx) nanoflakes possessed outstanding adsorption property, the as-synthesized graphene@MXene hybrid exhibited significant signal synergistic enhancement effect toward the oxidation of hazardous veterinary drug residue compound (chlorpromazine) and food additives (rhodamine B). Based on this, a novel and sensitive electrochemical sensor was fabricated, the linear detection ranges were 5 nM to 0.5 μM for chlorpromazine with sensitivity of 1090 µA μM−1 cm−2, and 10 nM to 2.5 μM for rhodamine B with sensitivity of 440 and 102.14 µA μM−1 cm−2. Besides, the detection limits were evaluated to be as low as 1.25 nM and 2.45 nM for chlorpromazine and rhodamine B, respectively.

Fabrication of bentonite nanosheets from natural bentonite using ultrasonic-assisted liquid phase exfoliation method and its application for adsorptive removal of Methylene Blue from water

Clays (especially bentonite) are widely used as barriers in landfills to prevent contamination of subsoil and groundwater by leachate containing heavy metals or toxic organics. However, the future application of bentonite nanomaterials is still limited due to complicated and expensive preparation process requiring several steps, toxic chemical agents, or additional surfactants. In this study, a green approach was proposed to produce bentonite nanoplatelets by an ultrasound-assisted liquid-phase exfoliation method using natural clay minerals containing bentonite as a precursor. The materials were then characterized by SEM, BET, AFM and XRD. The produced material was used to remove methylene blue (MB) from aqueous solution by batch adsorption. Results showed that the bentonite nanoplatelets gave high adsorption ability with Langmuir maximum adsorption capacity of 312.50 mg/g, which could be a good adsorbent for removing dyes and other toxic organics in wastewater.

SiP Nanosheets: A Metal-Free Two-Dimensional Photocatalyst for Visible-Light Photocatalytic H2 Production and Nitrogen Fixation.

Two-dimensional (2D) semiconductors for photocatalysis are more advantageous than the other photocatalytic materials since the 2D semiconductors generally have large specific surface area and abundant active sites. Phosphorus silicon (SiP), with an indirect bandgap in bulk and a direct bandgap in the monolayer, has recently emerged as an attractive 2D material because of its anisotropic layered structure, tunable bandgap, and high charge carrier mobility. However, the utilization of SiP as a photocatalyst for photocatalysis has been scarcely studied experimentally. Herein, we reported the synthesis of SiP nanosheets (SiP NSs) prepared from bulk SiP by an ultrasound-assisted liquid-phase exfoliation approach which can act as a metal-free, efficient, and visible-light-responsive photocatalyst for photocatalytic H2 production and nitrogen fixation. In a half-reaction system, the maximal H2 and NH3 generation rate under visible light irradiation achieves 528 and 35 μmol·h-1·g-1, respectively. Additionally, the apparent quantum yield for H2 production at 420 nm reaches 3.56%. Furthermore, a Z-scheme photocatalytic overall water-splitting system was successfully constructed by using Pt-loaded SiP NSs as the H2-evolving photocatalyst, Co3O4/BiVO4 as the O2-evolving photocatalyst, and Co(bpy)33+/2+ as an electron mediator. Notably, the highest H2 and O2 generation rate with respect to Pt/SiP NSs achieves 71 and 31 μmol·h-1·g-1, respectively. This study explores the potential application of 2D SiP as a metal-free visible-light-responsive photocatalyst for photocatalysis.

Urate oxidase-loaded MOF electrodeposited on boron nanosheet-doxorubicin complex as multifunctional nano-enzyme platform for enzymatic and ratiometric electrochemical biosensing

In this work, a novel multifunctional nano-enzyme platform was developed and used for enzymatic and ratiometric electrochemical biosensing of uric acid (UA). Boron nanosheets (BNSs) were prepared through ultrasound-assisted liquid-phase exfoliation, followed by the loading of doxorubicin (DOX) to form BNSs-DOX complex. The complex was drop-casted on glassy carbon electrode (GCE) surface to prepare BNSs-DOX/GCE. Cobalt-based metal-organic framework (MOF) with encapsulation of urate oxidase (UOx) was in-situ copolymerized and electrodeposited on the BNSs-DOX surface to construct UOx@MOF/BNSs-DOX nanohybrid-modified GCE. The modified electrode serves as an artificial nano-enzyme sensing platform and presents multifunctional functions, including DOX-loaded BNSs carrier, UOx-enzyme immobilization, enzymatic redox and ratiometric electrochemical sensing of UA. The platform was explored as a new ratiometric electrochemical biosensor to detect UA in the concentration range of 0.1–200 μM, with a low limit of detection of 0.025 μM. Experimental results testify high selectivity, sensitivity and stability toward efficient detection of UA over potential interferents, revealing high detection accuracy and repeatability. The explored biosensor shows superior detection performances in real biological samples, together with high detection recoveries. Excellent properties and functions endow the biosensor with great prospects for precise screening and early diagnosis of UA-relevant malignant diseases in clinic.

Sulfur nanoparticle-encapsulated MOF and boron nanosheet-ferrocene complex modified electrode platform for ratiometric electrochemical sensing of adriamycin and real-time monitoring of drug release

This work developed a modified electrode platform for dual-channel applications in ratiometric electrochemical sensing and real-time monitoring of drug release. In the presence of cobalt ions and sulfur nanoparticles (SNPs), 2-methylimidazole was polymerized to form SNPs-encapsulated cobalt metal–organic framework (MOF), SNPs@MOF. Boron nanosheets (BNSs) were prepared through ultrasound-assisted liquid-phase exfoliation, followed by loading ferrocene (Fc) to form BNSs-Fc complex. A clean glassy carbon electrode (GCE) was modified with Nafion on the surface, followed by drop-casting of BNSs-Fc and SNPs@MOF to construct a modified electrode platform, SNPs@ MOF/BNSs-Fc/GCE. The morphologies, microstructures, spectra and properties of products were characterized systematically. The platform was used as a new ratiometric electrochemical sensor to detect adriamycin (ADR), due to stable Fc signal output and content-dependent ADR signal output during the electrochemical redox process of Fc and ADR. Under optimal conditions, the sensor can perform effective detection of ADR in a broad range of 0.01–10 μM, with a low limit of detection of 2 nM. The sensor was verified to possess high detection selectivity, sensitivity and stability, and enabled successful detection of ADR in biological fluid samples, indicating potential reliability and practicability. Besides, the prepared BNSs-ADR carriers in electrolyte solution have the capability of spontaneous and pH-regulatable release of ADR. By means of the platform-based sensor, linear relationships of ADR/Fc redox-peak current ratio (or concentration of released ADR) versus release time were well constructed, which thus realized ratiometric electrochemical real-time monitoring of ADR release by the sensor.

Effect of Temperature and Acoustic Pressure During Ultrasound Liquid-Phase Processing of Graphite in Water

Ultrasound-assisted liquid-phase exfoliation is a promising method for manufacturing two-dimensional materials. Understanding the effect of ultrasonication parameters such as the temperature and input power on the developed pressure field is pivotal for optimization of the process. Limited research has been carried out to determine the optimal temperature for exfoliation, with some data generating disputed results. Simply maximizing the sonication power does not necessarily produce a higher yield because of shielding. In this study, a high-temperature calibrated cavitometer was used to measure the acoustic pressure generated in different graphite solutions in deionized water at various temperatures (from 10°C to 70°C) and input power conditions (from 20% to 100%). In addition, high-speed optical imaging provided insight on the shock wave generation from transient bubble collapses under different sonication conditions. The optimal sono-exfoliation parameters were determined to be 20% input power at 10°C for graphite flake solution, and 100% input power at 40°C to 50°C for graphite powder solution.

Ultrafast synchrotron X-ray imaging and multiphysics modelling of liquid phase fatigue exfoliation of graphite under ultrasound

Ultrasound-assisted liquid phase exfoliation is a promising method for manufacturing of 2D materials in large scale and sustainable manner. A large number of studies using ex-situ nano/micro structural characterization techniques have been made to investigate the underlying mechanisms, aiming to understand the exfoliation dynamics. Due to the complex multiphysics and multi-length nature of the process, those ex-situ methods cannot provide the real-time and in-situ dynamic information for understanding how exactly layer exfoliation starts and grows under ultrasound. Here, we used the ultrafast synchrotron-X-ray phase-contrast imaging (a combined temporal resolution of 3.68 μs and a spatial resolution of 1.9 μm/pixel) to study the exfoliation dynamics in real time and operando condition. We revealed, for the first time, the fatigue exfoliation phenomenon at the graphite surface caused by the imploding ultrasonic bubbles occurring cyclically in line with the ultrasound frequency. A multiphysics numerical model was also developed to calculate the shock wave produced at bubble implosion and the resulting cyclic and impulsive tensile and shear stresses acting on the graphite surface. Our research reveals that the graphite layer exfoliation rate and efficiency are predominantly determined by the number of imploding bubbles inside the effective cavitation bubble zone. The findings are valuable for developing industrial upscaling strategies for ultrasound processing of 2D materials.

A stable nanosilver decorated phosphorene nanozyme with phosphorus-doped porous carbon microsphere for intelligent sensing of 8-hydroxy-2′-deoxyguanosine

Nanozyme based on the silver nanoparticles (AgNPs) decorated highly water-oxygen stable phosphorene (BP) nanohybrid with phosphorus-doped porous carbon microspheres (P-PCMs) is applied as an intelligent sensing platform for the electrochemical detection of 8-hydroxy-2′-deoxyguanosine (8-OHdG) as a biomarker of oxidative DNA damage in human urine sample. The density functional theory (DFT) is use for investigating the effect of silver on the conductivity level of BP and discussing a possible mechanism for the electrocatalytic oxidation of 8-OHdG. The Ag+ is in-situ reduced as AgNPs that grows onto the BP surface for the controllable preparation of BP-AgNPs with effective surface passivation among different metal ions decorated BP. P-PCMs with 4.9-fold enhancement in specific surface area (1636.73 m2 g−1) are prepared by hydrothermal carbonization of α-cyclodextrin as carbon sources, then calcinate in the presence of phosphoric acid as an activator and dopant. P-PCMs-BP-AgNPs are prepared by the ultrasound-assisted liquid-phase exfoliation with the addition of Ag+, and both P-PCMs and black phosphorus crystals are sufficiently grinded. The P-PCMs-BP-AgNPs nanohybrid displays good long-term water-oxygen stability, extraordinary specific surface area, superior electrocatalytic capacity with 303-fold enhancement, enzyme-like characteristics with Imax of 100 μA and Km of 29 μM. The machine learning (ML) model with artificial neural network (ANN) algorithm is employed for the intelligent output of 8-OHdG in real sample with acceptable recovery in work range from 0.2 to 125 μM.

Efficient and Direct Exfoliation of High-Quality Graphene Layers in Water from Different Graphite Sources and Its Electrical Characterization

Green and efficient mass production of graphene sheets with high quality and electrical conductivity is intriguing for both academic scientists and industry. Among numerous production methods suffering from complexity or harsh chemical media, direct and high-yield exfoliation of graphite in water seems to be the best choice. In this study, efforts were made to prepare high-quality and stable graphene dispersions with the highest possible concentrations through an ultrasound-assisted liquid-phase exfoliation (LPE) in water directly from two types of natural graphites. The rigorous structural, morphological and electrical analyses were conducted on both graphite and graphene samples to quantitatively identify the effect of graphite sources on the LPE yield and the quality of the graphene nanosheets produced in the presence of an ionic surfactant. The results obtained by TEM, AFM, XRD and Raman spectroscopy indicated the successful and efficient production of single and few layer graphene sheets with the remarkable concentration of 3.18[Formula: see text]mg.ml[Formula: see text] in water. Moreover, the results signified that the structural quality, electrical conductivity and production yield of the graphene layers undoubtedly depend on the structural properties of graphite source. In fact, the graphite source greatly influences the final properties and potential applications of the produced graphene layer and the results are so important for the future graphene industry.

Influence of hexagonal boron nitride nanosheets on phase transformation, microstructure evolution and mechanical properties of Si3N4 ceramics

Fully dense Si3N4 materials with 1 wt.% (∼ 1.5 vol.%) and 2 wt.% (∼ 3.0 vol.%) h-BN nanosheets were prepared by spark plasma sintering at 1750 °C with the dwell of 7 min under a pressure of 50 MPa in a vacuum. BN nanosheets with different dimensions were prepared by ultrasound-assisted liquid phase exfoliation of h-BN powder, followed by centrifugation at different speeds (1000 rpm and 3000 rpm). The addition of BN nanosheets hindered the particle rearrangement stage of sintering, which resulted in the delayed α→β phase transformation of Si3N4. To study a direct effect of BN nanosheets on the mechanical properties of Si3N4, the results were compared to the monolithic Si3N4 with similar grain size and α/β-Si3N4 ratio. The addition of 2 wt.% h-BN nanosheets (1000 rpm) increased both the fracture toughness (∼ 26 %) and the strength (∼ 45 %) of Si3N4, when compared to the monolithic Si3N4 with similar microstructure.

Few-layer TaSe2 as a saturable absorber for passively Q-switched erbium-doped fiber lasers

TaSe2 nanosheets are prepared by means of ultrasound-assisted liquid phase exfoliation (LPE) and the nonlinear saturable absorption properties are experimentally investigated. The TaSe2-polyvinyl alcohol (PVA) film is then manufactured and a TaSe2-based saturable absorber (SA) is fabricated for demonstrating a Q-switched erbium-doped fiber laser (EDFL) for the first time. Taking advantage of the saturable absorption properties of the TaSe2-based SA, the obtained shortest Q-switched pulse duration is 1.53 µs with a pulse energy of 65.5 nJ. The results indicate that TaSe2 is a competent candidate for use as SA in promoting stable and flexible ultrafast lasers. The work may pave the way to researches and applications for photonics in the mid-infrared band.

Fabrication of graphitic carbon nitride films by inkjet printing

Graphitic carbon nitride (g‐C3N4) has recently arisen at the forefront of researching in many areas. For this reason, the establishment of attractive and functional methodologies for the preparation of g‐C3N4 films and coatings to develop novel applications is very important. Therefore, this paper is focused on taken advantage of the functionalities of ultrasound-assisted liquid-phase exfoliation (UALPE) process and inkjet printing (IJP) technique for the fabrication of g‐C3N4 films. By an integral analysis, a stable and printable colloidal ink containing exfoliated g‐C3N4 with an average particle size of 263 nm was formulated. Reproducible and well-defined g‐C3N4 films with 10, 20 and 30 printing-passes have been obtained where the distinctive characteristic related to the automatic droplets’ deposition provided by IJP technique allowed an easy control on the spatial uniformity, thickness and transparency. Additionally, the inkjet printed g‐C3N4 films were evaluated as a fluorescence sensor exhibiting a good response to the presence of Ag+ in aqueous solution. The strategy here reported can be exploited for the deposition of large-area and complex patterns of g‐C3N4 onto a variety of rigid and flexible substrates through the simple and low-cost UALPE and IJP approaches.

Toxicity evaluation of bulk and nanosheet MoS2 catalysts using battery bioassays

Herein, the main aim is to study the influence of the materials’ structural properties on their ecotoxicological properties. The acute toxicity of the bulk (molybdenum disulfide) MoS2 and 2D nanosheet MoS2 was investigated using organisms of four different taxonomic groups. Ultrasound-assisted liquid-phase exfoliation method was used for preparing 2D nanosheets from bulk MoS2. Bulk and nanosheet MoS2 were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD) analyses. The acute toxicity of the bulk and nanosheet MoS2 catalysts was evaluated with four different bioassays using the test organisms Vibrio fischeri (a marine photobacterium), Pseudokirchnerialla subcapitata (a freshwater microalga), Daphnia magna (a freshwater crustacean) and the freshwater duckweed Spirodela polyrhiza. The toxic effect of the materials depended on their structural/size features and the type/sensitivity of the test organism. Generally speaking, bulk MoS2 was more toxic than its nanosheet form. The freshwater crustacean Daphnia magna appeared to be the most suitable, easy-to-handle, and at the same time sensitive test organism for bulk and nanosheet MoS2 among the tested organisms.