Liquid-phase Exfoliation Method Research Articles

A green approach to water‐based graphene ink with reverse coffee ring effect

In printing electronics, graphene is used as a functional material due to its excellent physical properties. Therefore, to prepare a conductive graphene ink that contains non-toxic and environment-friendly solvent is very important. Direct preparation of graphene from graphite using liquid-phase exfoliation process is beneficial since it is simple and easy to use. Here in this work, we have synthesized the graphene dispersion using ethanol and water by liquid-phase exfoliation method and prepared a conductive graphene ink that shows an absence of coffee ring formation during the evaporation of solvents. A film has been prepared using the prepared ink which shows the electrical resistivity 1.06 Ω-cm at temperature 300 °C.

Nickel-vanadium layered double hydroxide nanosheets as the saturable absorber for a passively Q-switched 2 µm solid-state laser

Nickel-vanadium (NiV)-layered double hydroxide (LDH) was fabricated into a novel saturable absorber (SA) by the liquid phase exfoliation method and utilized as the laser modulator for the first time, to our best knowledge. We investigated a passive Q-switched Tm:YAG ceramic laser at 2 µm with the NiV-LDH SA. Under an absorbed pump power of 7.2 W, the shortest pulse width of 398 ns was obtained with an average output power of 263 mW and a pulse repetition frequency of 101.8 kHz, corresponding to a single pulse energy at 2.30 µJ. The results indicate that the NiV-LDH SA has great research potential in the field of laser modulation.

Optical and electrical characterization of WS2 multilayer on flexible PET substrate

WS2 is two-dimensional layered material which the electronic band gap is dependent on the number of layers. From application point of view, the WS2 few layers are good candidate for nano scale flexible electronics . In this study, the WS2 number of layers is modified using liquid phase exfoliation method. The blue shift of WS2 supernatant absorption peaks suggested the change of layer thickness compare to the non-exfoliated one. This supernatant is further deposited on Polyethylene terephthalate (PET) to create a flexible multilayer WS2 thin films. The morphology and the content of the thin film are confirmed by scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS), respectively. The Raman and photoluminescence spectroscopy show typical characteristics of WS2 multilayers which are dominated by W-S vibrations, exciton contributions, as well as the local defect and strain effects. Furthermore, the electrical characterization reveals the robustness of the WS2 electronic properties again the mechanical stretching. This study highlights the abundant optical and electrical characterization of WS2 multilayer which are applicable for flexible electronic devices.

Continuous and semi-continuous industrial production of lubricants modified with graphene nanostructures

This article proposes one of the options for the production of graphene-containing suspensions and their modification of lubricants. It is based on the technology of obtaining graphene nanostructures by the method of liquid-phase shear exfoliation of graphite. The proposed technological scheme can operate in both semi-continuous and continuous modes. The main advantages of this technology are simplicity and reliability of equipment, as well as environmental friendliness of production.

Ta2NiSe5 nanosheets as a novel broadband saturable absorber for solid-state pulse laser generation

Two-dimensional (2D) ternary chalcogenides have attracted great attentions because of their novel chemical and physical properties arising from the synergistic effect and stoichiometric variation with the additional third element compared with their binary counterparts. Here, high-quality 2D tantalum nickel selenide (Ta2NiSe5) nanosheets are successfully fabricated by a liquid-phase exfoliation (LPE) method. The ultrafast excited carrier relaxation time and nonlinear optical absorption response are investigated and reveal that the prepared 2D Ta2NiSe5 nanosheets have excellent broadband saturable absorption properties, which are further illustrated by three passively Q-switched (PQS) all-solid-state lasers operating at 1.0, 2.0 and 2.8 µm with the Ta2NiSe5 nanosheet-based saturable absorber (SA). Furthermore, mode-locked laser operation with the pulse width as short as 356 fs is also realized at 1.0 µm. This work not only demonstrates the excellent nonlinear optical proprieties and optical modulation performance of Ta2NiSe5, but also paves the way for exploring the photonic and optoelectronic proprieties of ternary chalcogenide materials.

Excellent ultraviolet optical limiting properties of 2D chromium nanosheets

Successfully fabricated 2D chromium nanosheets through the liquid phase exfoliation method and investigated the broadband nonlinear optical properties employed the open aperture Z-scan technique.

Two-dimensional tellurium saturable absorber for ultrafast solid-state laser

Two-dimensional (2D) Te nanosheets were successfully fabricated through the liquid-phase exfoliation (LPE) method. The nonlinear optical properties of 2D Te nanosheets were studied by the open-aperture Z-scan technique. Furthermore, the continuous wave mode-locked Nd:YVO4 laser was successfully realized by using 2D Te as a saturable absorber (SA) for the first time, to the best of our knowledge. Ultrashort pulses as short as 5.8 ps were obtained at 1064.3 nm with an output power of 851 mW. This primary investigation indicates that the 2D Te SA is a promising photonic device in the fields of ultrafast solid-state lasers.

ПОЛУЧЕНИЕ ГРАФЕНОВЫХ СТРУКТУР И НАНОПОЛИМЕРОВ С ИСПОЛЬЗОВАНИЕМ УЛЬТРАЗВУКОВЫХ КОЛЕБАНИЙ

Graphene-based polymer nanocomposites are considered a promising class of future materials. The degree of filling, the filler and binder nature, and the shape, size, and mutual arrangement of filler particles determine the properties of a polymer composite material. The destruction of nanoparticles aggregates occurs most effectively in liquid media under the action of ultrasonic vibrations. The authors proposed the technique and designed laboratory equipment for ultrasonic treatment of the finely-dispersed graphite suspension, carried out the ultrasonic treatment (UST) of finely-dispersed graphite powder. The suspensions based on graphite with a solvent were obtained. The authors carried out the experiments on producing graphene using the graphite liquid-phase exfoliation method at the ultrasonic treatment with different ultrasonic treatment times, analyzed experimental data, and selected the UST optimal time. The paper contains the results of the study of the effect of the graphite suspension base on the degree of ultrasonic liquid-phase exfoliation of graphite. The most effective synthesis of graphene structures using UST is synthesis from graphite suspensions based on dichloroethane, benzol, and dichlorobenzene. Graphene structures’ output ratio amounts to up to 66 %. The authors developed the technology for producing polymers modified with graphene structures using ultrasonic dispersion. Based on graphene synthesized by the graphite liquid-phase exfoliation, the authors obtained nanopolymers using ultrasonic vibrations, carried out DSC measurements, and studied their strength properties. The limit strength of elastic polymers is from 1.9 to 3.6 MPa at different concentrations of graphene inclusions. The residual elongation of samples within the deviation did not change and amounted to 200 %.

Boron quantum dots all-optical modulator based on efficient photothermal effect

All-optical devices without external electronic components have drawn extraordinary attentions in all-optical communication. In this work, boron quantum dots (BQDs) were synthesized by a facile liquid-phase exfoliation method. The as-prepared BQDs showed good structural homogeneity and crystallinity, broadband optical absorption as well as excellent photothermal properties. Femtosecond-resolved transient absorption further revealed the short carrier relaxation time of BQDs. Inspired by the outstanding photothermal properties and ultrafast carrier dynamic of BQDs, we fabricated BQDs-based all-optical modulator. The phase shift with a slope efficiency of 0.032 π/mW and response time of 0.97 ms can be achieved. The modulator was used in laser resonance cavity to achieve all-optical actively Q-switched laser operation with control repetition rate. This prototypical BQDs-based all-optical modulator shows a great potential to be applied in all-optical information processing and communication.

Exfoliated Molybdenum Disulfide-Wrapped CdS Nanoparticles as a Nano-Heterojunction for Photo-Electrochemical Water Splitting.

We developed a heterojunction photocathode, MoS2@CdS, based on the wrapping of CdS nanoparticles by the MoS2 nanocrystals. The liquid-phase exfoliation method was adopted for preparing few-layer MoS2 nanocrystals of a layer thickness of ∼7.9 nm, whereas CdS nanoparticles of an average diameter of ∼17 nm were synthesized by the one-step hydrothermal process. The synthesized nanocrystals and nanoparticles were characterized by AFM, FESEM, HRTEM, STEM, XRD, GIXRD, UV-vis absorption, fluorescence emission, and Raman spectroscopy. The difference between two modes in the Raman spectrum of MoS2 indicates the formation of few-layer MoS2. The photoelectrochemical performance of the heterojunction photocathode was excellent. The MoS2@CdS heterostructure photocathode increased the photocurrent density (JPh) under 100 mW/cm2 illumination. We obtained the maximum applied biased photoconversion efficiency (ABPE) of ∼1.2% of the MoS2@CdS heterojunction photocathode in optimum device configuration. The production of H2 was measured as ∼72 μmol/h for the MoS2@CdS heterostructure with a cyclic stability of up to 7500 s.

An efficient water-assisted liquid exfoliation of layered MXene (Ti3C2Tx) by rationally matching Hansen solubility parameter and surface tension

Two-dimensional (2D) transition metal carbides and nitrides (MXenes) have spurred great attention in many applications due to their outstanding electronic or mechanical properties. The exfoliation into single and fewer layer nanosheets of MXene is a requisite step for performance study in many cases. Herein this study aims to propose a facile and convenient liquid phase exfoliation (LPE) method to fabricate fewer-layer MXene nanosheets in large scale. The Hansen solubility parameters (HSPs) and surface tension component ratio are estimated and further applied to detect a green low-boiling-point water/acetone cosolvent for the better exfoliation of MXene. It has been found that the exfoliation efficiency is improved efficiently by matching HSPs and surface tension component ratio of MXene to that of solvents. A high concentrated MXene dispersion up to 1.727 mg/ml in the optimum composition of the water/acetone mixture which is approximately 78 and 5 times higher than that in pure acetone and water, respectively. Detailed characterization of morphology and suspension stability of exfoliated MXene are implemented which exhibit that the high quality and more stable MXene nanosheets are obtained in the suitable cosolvent. In addition, the determined HSPs and surface tension component ratio of MXene here will make a contribution to finding other new efficient solvents for MXene conveniently in specific fields.

Passively Q-switched Nd:YVO4 laser with few-layered MoSe2 saturable absorber

We fabricated few-layered MoSe2 nanosheets via the simple ultrasonic-assisted liquid phase exfoliation (UALPE) method. Typical characterizations and testing were exploited to confirm the nonlinear absorption properties of MoSe2 nanoflakes. A passively Q-switched Nd:YVO4 laser emitting 1 [Formula: see text]m wavelength was demonstrated with the as-prepared MoSe2 saturable absorber (SA). The stable pulses were generated with a maximum output power of 215 mW and a shortest pulse width of 192 ns. The experimental data provided a solid base for the photonics applications of MoSe2 nanomaterials.

Fast high-shear exfoliation of natural flake graphite with temperature control and high yield

High-shear exfoliation of graphite is a cost-effective liquid-phase exfoliation (LPE) method for producing few-layer graphene dispersions. However, the drawbacks of LPE such as low graphene concentrations, long processing times and solvent residuals hamper the scalability of the process and applicability of the dispersions. Here, we demonstrate a fast graphene synthesis where concentrations as high as 3 mg/ml with a 3% yield are produced only after 2 h of shear exfoliation in environmentally friendly aqueous medium using sodium cholate as surfactant. The produced graphene is of high quality and mostly less than 5 layers thick. The high concentration is attributed to a proper choice of effective mixing parameters, low exfoliation temperature (10 °C) and an appropriate surfactant concentration. In addition, we noticed that larger graphite flakes (250 μm-1 mm) increased the lateral dimensions of the exfoliated sheets while the yield and concentration were independent of the flake size. Furthermore, using larger graphite flakes improved the conductivity of the subsequent graphene films. Prior to film fabrication, dialysis removed excess surfactant from the dispersions improving the film conductivity (17 000 S/m) by ca 40%.

Graphene Synthesis by Ultrasound Energy-Assisted Exfoliation of Graphite in Various Solvents

The liquid-phase exfoliation (LPE) method has been gaining increasing interest by academic and industrial researchers due to its simplicity, low cost, and scalability. High-intensity ultrasound energy was exploited to transform graphite to graphene in the solvents of dimethyl sulfoxide (DMSO), N,N-dimethyl formamide (DMF), and perchloric acid (PA) without adding any surfactants or ionic liquids. The crystal structure, number of layers, particle size, and morphology of the synthesized graphene samples were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), ultraviolet visible (UV–vis) spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM). XRD and AFM analyses indicated that G-DMSO and G-DMF have few layers while G-PA has multilayers. The layer numbers of G-DMSO, G-DMF, and G-PA were determined as 9, 10, and 21, respectively. By DLS analysis, the particle sizes, polydispersity index (PDI), and zeta potential of graphene samples were estimated in a few micrometers. TEM analyses showed that G-DMSO and G-DMF possess sheet-like fewer layers and also, G-PA has wrinkled and unordered multilayers.

MXene Ti3C2Tx (T = F, O, or OH) saturable absorber for a 2 μm doubly Q-switched laser with AOM

MXene Ti3C2Tx (T = F, O, or OH) was fabricated by aqueous acid etching and liquid phase exfoliation method. Its appearance, the spectra and the saturated absorption characteristics were measured. By using MXene Ti3C2Tx as saturable absorber (SA) and an acousto-optic modulator (AOM), a doubly Q-switched Tm:LuAG laser at 2 μm waveband was realized. Under the incident pump power of 9.5 W at modulated repetition rate 1 kHz of AOM, the narrowest laser pulse width of 178 ns was obtained, corresponding to the highest pulse peak power of 1062 W. To our knowledge, this is the shortest pulse width and highest peak power obtained in the Q-switched lasers with MXene Ti3C2Tx as SA. In comparison to the singly Q-switched laser with only MXene Ti3C2Tx or AOM, the doubly Q-switched laser can generate shorter pulse width and higher peak power. The maximum compression ratio of pulse width 6.0 and the highest enhancement factor of peak power 205 were achieved. The experimental results show that MXene Ti3C2Tx is an excellent SA in 2 μm waveband laser system and the doubly Q-switched laser can compress pulse width and improve pulse peak power.

Passive photonic diodes based on natural van der Waals heterostructures

AbstractVan der Waals heterostructures are composed of stacked atomically thin two-dimensional (2D) crystals to provide unprecedented functionalities and novel physics. Franckeite, a naturally occurring van der Waals heterostructure consisting of superimposed SnS2-like and PbS-like layers alternately, shows intriguing potential in versatile optoelectronic applications. Here, we have prepared the few-layer franckeite via liquid-phase exfoliation method and characterized its third-order nonlinearity and ultrafast dynamics experimentally. We have found that the layered franckeite shows low saturable intensity, large modulation depth and picosecond ultrafast response. We have designed the passive photonic diodes based on the layered franckeite/C60cascaded film and suspension configuration and found that the passive photonic diodes exhibit stable nonreciprocal transmission of light. The experimental results show the excellent nonlinear optical performance and ultrafast response of the layered franckeite, which may make inroad for the cost effective and reliable high-performance optoelectronic devices.

2 µm passively Q-switched all-solid-state laser based on a Ta2NiSe5 saturable absorber

In this paper, a novel 2D ternary chalcogenide Ta2NiSe5 is fabricated into a saturable absorber by using the liquid phase exfoliation (LPE) method and successfully applied to the passive Q-switching experiment of Tm:YAP all-solid-state laser at 2 µm. The nonlinear optical absorption (NOA) properties of Ta2NiSe5 at 2 µm was measured by using an open-aperture Z-scan method, showing saturation fluence and modulation depth of 400 µJ/cm2 and 24%, respectively. By using Ta2NiSe5 as saturable absorber, the shortest pulse width of 740 ns and maximum repetition frequency of 71 kHz are obtained, respectively. This results prove that the Ta2NiSe5 is an excellent saturable absorber to achieve passively Q-switched laser at 2 µm, for the first time to the best of our knowledge.

Simultaneous Preparation and Functionalization of Ultrathin Few−layer Black Phosphorus Nanosheets and Their Electrocatalytic OER and HER Performance

AbstractA convenient liquid phase exfoliation method is reported here to prepare functionalized few−layer black phosphorus (BP) nanosheets by using succinic acid (SA) or L−ascorbic acid (L−AA) −assisted tip−ultrasonicated exfoliation. The thickness of the obtained nanosheets is about 2–2.5 nm, which is equivalent to 4–5 layers of BP atoms. And SA−BP−1 : 3 exhibits a best OER and HER performance in the group of SA−BP with different weight ratios, requiring an overpotential of 369.8 mV for OER and 235 mV for HER to achieve the current density of 10 mA cm−2, respectively. Meantime, L−AA−BP‐1 : 1 presents a great OER and HER performance in the group of L−AA−BP with different weight ratios, requiring an overpotential of 459.5 mV for OER and 224 mV for HER to achieve the current density of 10 mAcm−2, respectively. And two groups of the samples significantly enhance the OER and HER performance of few−layer BP nanosheets (550 mV and 431 mV). In addition, both the consecutive cyclic voltammetry and chronoamperometric measurements reveal the outstanding electrocatalytic stability of the samples.

Starting monomer of graphdiyne–hexakis[(trimethylsilyl)ethynyl]benzene: a superior nonlinear absorption material

Graphdiyne (GDY) is an emerging carbon allotrope consisting of sp- and sp2-hybrid carbon atoms. The sp-hybrid carbon–carbon triple bond structure with strong d–π interaction has endowed GDY special nonlinear absorption (NLA) properties, which is different from graphene. As a starting monomer for synthesizing GDY, hexakis[(trimethylsilyl)ethynyl]benzene (HEB-TMS) also owns the carbon–carbon triple bond (sp-) and the benzene ring (sp2-) structures (similar to GDY), which stimulates us to explore the NLA properties of HEB-TMS. In this work, two-dimensional (2D) nanosheets of HEB-TMS are successfully prepared using a liquid-phase exfoliation method with the thicknesses of 3.49 ~ 4.47 nm. And the broadband NLA properties are researched using an open-aperture Z-scan method (from ultraviolet to infrared waveband). The results demonstrate that HEB-TMS owns excellent NLA characteristics in visible light waveband. The excellent optical limiting properties of HEB-TMS provide the possibility of application in the protection of human eyes and precision optical component in visible light.

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.