Facile Liquid-phase Exfoliation Research Articles

A practical fluorometric and colorimetric dual-mode sensing platform based on two-dimensional porous organic nanosheets for rapid determination of trifluralin.

Trifluralin, a widely used dinitroaniline herbicide, poses significant toxic risks, necessitating the development of rapid detection methods for food safety. In this study, we prepared ultrathin two-dimensional triphenylamine porous organic nanosheets (TPA-PONs) through a facile liquid-phase exfoliation process. The TPA-PONs, characterized by their exceptional fluorescence properties and nanoscale thickness (1.65 ± 0.3 nm), demonstrated a remarkable fluorescence quenching response upon exposure to trifluralin. Spectroscopic analysis combined with DFT calculations revealed that the quenching mechanism is driven by electron and energy transfer. TPA-PONs-based fluorescence sensor exhibited a linear response to trifluralin concentrations ranging from 0.01 to 10.0 μmol L-1 with a limit of detection as low as 3.50 nmol L-1. Additionally, the sensor was applied to detect trifluralin residues in vegetables, achieving recoveries of 89.08-102.84%. To facilitate on-site detection, a novel TPA-PONs-based colorimetric film sensor has been developed, enabling visual analysis of trifluralin using a smartphone. This dual-mode sensing platform holds significant potential for enhancing food safety monitoring.

Liquid Phase Exfoliation of Few-Layer Non-Van der Waals Chromium Sulfide.

Exfoliation of 2D non-Van der Waals (non-vdW) semiconductor nanoplates (NPs) from inorganic analogs presents many challenges ahead for further exploring of their advanced applications on account of the strong bonding energies. In this study, the exfoliation of ultrathin 2D non-vdW chromium sulfide (2D Cr2S3) by means of a combined facile liquid-phase exfoliation (LPE) method is successfully demonstrated. The morphology and structure of the 2D Cr2S3 material are systematically examined. Magnetic studies show an obvious temperature-dependent uncompensated antiferromagnetic behavior of 2D Cr2S3. The material is further loaded on TiO2 nanorod arrays to form an S-scheme heterojunction. Experimental measurements and density functional theory (DFT) calculations confirm that the formed TiO2@Cr2S3 S-scheme heterojunction facilitates the separation and transmission of photo-induced electron/hole pairs, resulting in a significantly enhanced photocatalytic activity in the visible region.

Bionanoengineered 2D monoelemental selenene for piezothrombolysis

Thrombosis-related diseases represent the leading causes of disability or death worldwide. However, conventional thrombolytic therapies are subjected to narrow therapeutic window, short circulation half-life and bleeding. Herein, we rationally design and develop a safe and efficient nonpharmaceutical thrombolysis strategy based on a specific piezocatalytic effect arising from platelet membrane (PM)-conjugated two-dimensional (2D) piezoelectric selenene, Se-PM nanosheets (NSs). The 2D selenene is fabricated from nonlayered bulk selenium powder by a facile liquid-phase exfoliation method, and the PM conjugation confers selenene with the distinct thrombus-homing feature. Under ultrasonic activation, the piezoelectric characteristic of selenene triggers electrons and holes separation, resulting in generation of reactive oxygen species (ROS) by reacting with surrounding H2O and O2 in the thrombosis microenvironment for thrombolysis. Both systematic in vitro and in vivo assessments demonstrate that the biocompatible Se-PM NSs efficiently degrade erythrocytes, fibrin and artificial blood clots under ultrasound irradiation. Compared to the clinical thrombolytic drug urokinase plasminogen activator, the engineered Se-PM NSs possess excellent thrombolytic efficacy by single treatment in the tail thrombosis animal model without bleeding risk. The engineered Se-PM nanoplatform marks an exciting jumping-off point for research into the application of piezocatalysis in clinical treatment of thrombosis.

Unraveling the Photoluminescence Properties of a Boron Nitride Nanosheet Dispersed in Different Solvents and Its Application to Generate White Light.

Hexagonal boron nitride (h-BN) is an influential 2D nanomaterial; however, its practical optoelectronic applications rely primarily on controlling the structural defects. The photoluminescence depends explicitly on the developed vacancies and substitutional defects. The present work utilizes the concept of facile liquid-phase exfoliation of hexagonal (h) boron nitride (BN) powder in common organic solvents and cosolvent mixtures to obtain a layered boron nitride nanosheet (BNNS). Although the literature concerning the layered structure of BNNS obtained by different methods is substantial, what is lacking is a detailed photoluminescence study of the layered structure obtained by changing the solvent and cosolvent mixtures, and here lies the novelty of our work. The obtained layered structure was subjected to a detailed photoluminescence study by varying the temperature. We tried to correlate how the defects originating upon changing the solvent and cosolvent affected the photoluminescence of the layered BNNS. The obtained layered structure is suitably supported by optical and electron microscopy images. High-resolution transmission electron microscopy confirm the presence of a few layers, and X-ray photoelectron spectroscopy studies give an idea of the atomic composition of the obtained BNNS. The photoluminescence properties of the obtained BNNS in water were modulated by the addition of two different classes of block copolymers, e.g., Pluronic (F-68, P-407, and P-123) and Tetronic (T-904, T-908, and T-90R4) copolymers. As an application, we were successful in constructing a nanocomposite material made up of a BNNS-copolymer-organic fluorophore to check the possibilities of generating white light.

Efficient Fluoride Removal from Aqueous Solution Using Graphene/Ce Composite Supported on Activated Carbon

Background: More than 260 million people worldwide are affected by excess fluoride (F- > 1.5 mg/L) in their drinking water. Fluorosis of the teeth and skeleton, among other health issues, is caused by it. Objective: The aim of this study is to evaluate the fluoride removal from contaminated water using graphene-based new adsorbent material. Method: Graphene (G) was prepared by a facile liquid-phase exfoliation method. CeO2 nanoparticles (NPs) were synthesized by the co-precipitation method. G was treated with CeO2 NPs in a probe sonicator to generate G/Ce material in solution. Finally, the impregnation evaporation process synthesized the G/Ce supported on activated carbon composite (G/Ce/AC). Results: FE-SEM analysis shows that the crumpling and scrolling sheets of G, the nanosized spherical shape of CeO2 NPs and a thick layer of nano-sized spherical particles has built up on the surface of graphene in G/Ce/AC composite. After conversion to G/Ce/AC Composite, the specific surface area of graphene was increased from 3.08 to 485.3621 m2/g. The adsorption of fluoride on G/Ce/AC was investigated using batch systems (effects of pH, contact time, adsorbent dosage and the initial fluoride concentration), adsorption isotherm and kinetic studies. The pseudo-second order was the one that best described the kinetic data, while the Langmuir isotherm best described the equilibrium data with a maximum adsorption capacity equal to 27.9 mg/g. Conclusion: Therefore, the results show that the G/Ce/AC composite was well synthesized and has excellent fluoride adsorption capacity compared to other materials already evaluated for this purpose.

Development of a Smart and Ultrafast Flexible Humidity Sensor Using the 0D/2D Au/GeS Heterostructure for Human Respiration Rate Monitoring

We have developed a smart, Internet of Things (IoT)-enabled, intelligent, and flexible humidity sensor for human respiration rate monitoring by using a heterostructure of two-dimensional (2D) germanium(II) sulfide (GeS) and zero-dimensional (0D) gold nanoparticles (Au NPs). The 2D GeS was synthesized by a facile liquid-phase exfoliation process, followed by the post-functionalization of Au NPs. Furthermore, the chemical and structural integrities of the heterostructure were corroborated by microscopic and spectroscopic techniques. The as-prepared heterostructure (termed Au-GeS) exhibited a maximum sensor response of 7102% at 90% of relative humidity (RH) level compared to the pristine GeS sensor response of 2700% at the same RH level. Finally, we demonstrate the use of the Au-GeS flexible humidity sensor for human respiration rate monitoring. The sensor showed an ultrafast response and recovery times of 0.69 and 0.73 s, respectively, during exhalation and inhalation. The sensor was further integrated into a portable electronic system to facilitate IoT-enabled real-time wireless sensing at the smartphone application interface. In our study, the excellent sensor performance with a simple fabrication process offers utilization of the flexible sensor in personal health monitoring.

Graphene Nanosheets Stabilized by P3HT Nanoparticles for Printable Metal-Free Electrocatalysts for Oxygen Reduction

The development of metal-free electrocatalysts with efficient catalytic performance and long-term stability is highly desirable for fuel cell applications. In this study, a solution-processable graphene-based electrocatalyst for the oxygen reduction reaction (ORR) is developed using a facile liquid-phase exfoliation process. An aqueous dispersion of poly(3-hexylthiophene-2,5-diyl) (P3HT) nanoparticles is prepared via a simple miniemulsion process and used as a medium for graphite exfoliation, where the interfacial interaction between P3HT nanoparticles and graphene is utilized to simultaneously stabilize the exfoliated graphene flakes and induce efficient intermolecular charge transfer to accelerate the ORR. Neutron scattering with contrast variation was carried out to study the colloidal architecture of the produced dispersions and the interactions at the interface between graphene and P3HT nanoparticles. The nanoparticle-stabilized graphene (G/P3HT) dispersions were employed for printing of flexible conductive circuits (∼180 Ω sq–1) and fabrication of metal-free electrocatalyst layers for the ORR, which reduces O2 molecules to OH– ions via the highly efficient four-electron pathway and exhibits superior stability (∼97% retention after 10,000 cycles). This printable graphene electrocatalyst provides a breakthrough in green chemistry and advanced techniques for the fabrication of low-cost and sustainable fuel cells.

Ultrahigh stable laminar graphene membranes for effective ionic and molecular nanofiltration with a machine learning-assisted study.

Graphene oxide (GO) membranes have gained great attention for water purification due to the formation of stacked nanosheets giving nanocapillary channels. Unlike graphene, the interlayer spacing of GO membranes gets readily expanded in aqueous solution due to their high oxygen content, resulting in poor ion rejection. Herein, we prepared ultralow oxygen-containing graphene (∼1 at%) via facile liquid-phase exfoliation which was formed as membrane laminates. The graphene membranes exhibited ultrahigh stability with no observed swelling or deformation of the laminar structure when kept in water, aqueous salt solutions, and various pH solutions for over one week. The membranes with a high degree of tortuous nanocapillary channels can efficiently reject the ions found in seawater as well as various charged dye molecules. This indicates that the graphene membranes exhibited ionic and molecular sieving properties due to the effect of size exclusion obtained from the narrow nanocapillary channel and electrostatic repulsion from negatively charged graphene nanosheets. Moreover, we also demonstrated machine learning to gain insights into the membrane performance, which allowed us to obtain membrane optimization as a model for water purification technology.

High-efficiency photocatalytic candidate material: Zinc phosphorus trisulfide

• Facile synthesis of ZnPS 3 material. • ZnPS 3 material has high specific surface area and more active sites. • ZnPS 3 material exhibit an excellent photocatalytic performance. Layered metal phosphorus trichalcogenides (MPX 3 ) has been attracting more and more attention for its optical and electronic properties. As a member of MPX 3 family, ZnPS 3 is a candidate material for photocatalytic hydrogen production. Herein, the exfoliated ZnPS 3 was obtained by a facile liquid-phase exfoliation from its bulk crystals, which shown an excellent photocatalytic performance with a hydrogen production rate up to 640 μmol g −1 h −1 . This work not only provides a facile synthesis of ZnPS 3 , but also demonstrates the application prospect of layered ZnPS 3 materials using solar energy to produce clean fuels.

First Principles Study and Experimental Investigation of Graphene-Molybdenum Disulphide Nanocomposites Based Passive Saturable Absorber

Research on hybrid graphene with other two-dimensional materials has gained considerable attention owing to their potential applications beyond single components. Through our first principles analysis via density functional theory, graphene-molybdenum disulphide (MoS2) demonstrated a band gap opening by 2 meV, from gapless graphene when MoS2 layer is introduced into the structure. The simulated graphene-MoS2 has a direct band gap situated at K point of Brillouin zone with preserved Dirac properties of graphene. The experimental studies on graphene-MoS2 also have been performed by preparing graphene-MoS2-chitin nanocomposite through facile liquid-phase exfoliation method. Apart from energy gap using Tauc relation, the physical morphology and nonlinear properties of the material were systematically characterized. Graphene-MoS2-chitin exhibits a modulation depth of 10.5%, which is lower than individual graphene but higher than individual MoS2. Further investigation on the material’s performance was done by integrating the fabricated film into Erbium-doped fiber laser. Stable nanosecond pulse laser operation was realized with graphene-MoS2-chitin hybrid saturable absorber. The pulse width was measured to be 156.4 ns with repetition rate of 1.89 MHz, corresponding to a peak power of 56.13 mW and pulse energy of 8.78 nJ.

Crumpled graphene oxide/spinel cobalt oxide composite based high performance supercapacitive energy storage device

Crumpled graphene oxide (cGO) was synthesized using a facile liquid phase exfoliation technique mediated by OHˉ cutter; followed by the synthesis of cGO/Co3O4 composite through hydrothermal route involving the as-synthesized cGO and cobalt salt precursors. Co3O4 is a mixed oxide of cobalt that exhibits good redox and charge cycling attributes owing to the presence of Co(II) and Co(III) oxidation states within it. This report includes thorough investigation on the electrochemical and charge storage properties of the fabricated electrodes using cyclic voltammetry, charge – discharge and impedance analyses, and also by endurance test. The report also describes detailed evaluation of the structural properties of the products (cGO and cGO/Co3O4 composites). Two sets of prototype ‘symmetric’ supercapacitors were fabricated using aqueous and gel KOH based electrolytes that successfully lit up LED and run a DC motor. The gel KOH electrolyte based device showed best performance and yielded 44 Wh/Kg specific energy and 1202 W/Kg specific power. The results are quite promising which open up a new avenue for using cGO/Co3O4 composite as a low cost alternative for conventional and costly carbon nanomaterial based supercapacitors.

H2S sensor based on two-dimensional MoO3 nanoflakes: Transition between sulfidation and oxidation

H2S is a flammable, explosive, and highly toxic gas; consequently, a high-performance H2S sensor based on metal oxides is required. In this study, two-dimensional MoO3 nanoflakes were synthesized through facile liquid-phase exfoliation. The thickness of the prepared MoO3 is approximately 4.2 nm. High-performance was obtained using a gas sensor based on two-dimensional MoO3 nanoflakes at a working temperature of 300 °C. In addition, the lowest detection limit can be in the range of parts per billion, and the sensor exhibits high resistance to humidity. The sensing mechanism is discussed based on the results of ex situ characterizations of the sensing process and computation of the electronic structure. The results indicate that the chemically reversible sensing process is based on the transition between sulfidation and oxidation, where sulfidation promotes the mobility of electrons and increases the conductivity of MoO3. This novel sensing mechanism provides a new perspective for the study of H2S sensors based on metal oxides.

PbSe Nanocrystals Produced by Facile Liquid Phase Exfoliation for Efficient UV–Vis Photodetectors

AbstractLead selenide (PbSe)‐based nanomaterials have been extensively investigated as building blocks for next‐generation optoelectronic devices owing to their unique properties. In this work, PbSe nanocrystals (NCs) have been successfully fabricated by a facile liquid phase exfoliation approach and directly applied as active materials for photo‐electrochemical (PEC)‐type photodetectors (PDs). Taking advantage of broadband absorption and fast carrier dynamics, the PbSe NCs‐based PDs exhibit excellent photo‐current density (11.88 μA cm−2), photo‐responsivity (12.37 mA W−1), response/recovery time (0.12/0.13 s), and long‐term cycling stability. The working mechanism of PbSe NCs‐based PDs is explored by density functional theory calculations based on their structural and electronic properties under various conditions. It is anticipated that this contribution paves the way to readily fabricate low‐dimensional PbSe NCs and extend their practical applications in PEC‐type PDs.

A Facile Liquid Phase Exfoliation of Tungsten Diselenide using Dimethyl Sulfoxide as Polar Aprotic Solvent to Produce High‐quality Nanosheets

AbstractTwo‐dimensional (2D) ultra‐thin nanosheets of semiconducting layered structure of transition metal dichalcogenides (TMDs) are in high demand for fundamental studies as well as potential applications in optoelectronic devices, advanced display devices and many more. The real challenge in this area is to produce large scale nanosheets with a single stable phase.Herein, we report a top‐down strategy for liquid‐phase exfoliation of bulk tungsten diselenide (WSe2) powder to produce hexagonal (2H) few layers (2–3 layers) of nanosheets by ultra‐sonication method using a highly‐efficient dimethyl sulfoxide (DMSO) as polar aprotic solvent. As produced nanosheets are further characterized by different spectroscopic techniques such as Raman and ultraviolet‐visible (UV‐Vis) spectroscopy to validate the quality of exfoliated WSe2 nanosheets and estimated the direct optical band gap after exfoliation of WSe2. Further, the Raman spectroscopy evidences the transition from bulk to few layers of WSe2 nanosheets. The TEM/HRTEM images and XPS results also confirm the good quality and efficient exfoliation of WSe2 nanosheets. Moreover, the estimated optical band gap from UV‐Vis and Tauc plot confirm the transition occurs from indirect band gap (∼1.27 eV) to direct optical band gap ∼1.55 eV after exfoliation of WSe2 nanosheets. Hence, the proposed method provides a simple, large scale and inexpensive exfoliation approach to produce high‐quality single phase 2H‐WSe2 nanosheets.

Ultra‐Small 2D PbS Nanoplatelets: Liquid‐Phase Exfoliation and Emerging Applications for Photo‐Electrochemical Photodetectors

2D PbS nanoplatelets (NPLs) form an emerging class of photoactive materials and have been proposed as robust materials for high-performance optoelectronic devices. However, the main drawback of PbS NPLs is the large lateral size, which inhibits their further investigations and practical applications. In this work, ultra-small 2D PbS NPLs with uniform lateral size (11.2± 1.7nm) and thickness (3.7± 0.9nm, ≈6 layers) have been successfully fabricated by a facile liquid-phase exfoliation approach. Their transient optical response and photo-response behavior are evaluated by femtosecond-resolved transient absorption and photo-electrochemical (PEC) measurements. It is shown that the NPLs-based photodetectors (PDs) exhibit excellent photo-response performance from UV to the visible range, showing extremely high photo-responsivity (27.81mA W-1 ) and remarkable detectivity (3.96 × 1010 Jones), which are figures of merit outperforming currently reported PEC-type PDs. The outstanding properties are further analyzed based on the results of first-principle calculations, including electronic band structure and free energies for the oxygen evolution reaction process. This work highlights promising applications of ultra-small 2D PbS NPLs with the potential for breakthrough developments also in other fields of optoelectronic devices.

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.

Ultrafast humidity sensor based on liquid phase exfoliated graphene

Humidity sensing is important to a variety of technologies and industries, ranging from environmental and industrial monitoring to medical applications. Although humidity sensors abound, few available solutions are thin, transparent, compatible with large-area sensor production and flexible, and almost none are fast enough to perform human respiration monitoring through breath detection or real-time finger proximity monitoring via skin humidity sensing. This work describes chemiresistive graphene-based humidity sensors produced in few steps with facile liquid phase exfoliation followed by Langmuir–Blodgett assembly that enables active areas of practically any size. The graphene sensors provide a unique mix of performance parameters, exhibiting resistance changes up to 10% with varying humidity, linear performance over relative humidity (RH) levels between 8% and 95%, weak response to other constituents of air, flexibility, transparency of nearly 80%, and response times of 30 ms. The fast response to humidity is shown to be useful for respiration monitoring and real-time finger proximity detection, with potential applications in flexible touchless interactive panels.

Tellurene Nanoflake-Based NO2 Sensors with Superior Sensitivity and a Sub-Parts-per-Billion Detection Limit.

Industrial production, environmental monitoring, and clinical medicine put forward urgent demands for high-performance gas sensors. Two-dimensional (2D) materials are regarded as promising gas-sensing materials owing to their large surface-to-volume ratio, high surface activity, and abundant surface-active sites. However, it is still challenging to achieve facilely prepared materials with high sensitivity, fast response, full recovery, and robustness in harsh environments for gas sensing. Here, a combination of experiments and density functional theory (DFT) calculations is performed to explore the application of tellurene in gas sensors. The prepared tellurene nanoflakes via facile liquid-phase exfoliation show an excellent response to NO2 (25 ppb, 201.8% and 150 ppb, 264.3%) and an ultralow theory detection limit (DL) of 0.214 ppb at room temperature, which is excellent compared to that of most reported 2D materials. Furthermore, tellurene sensors present a fast response (25 ppb, 83 s and 100 ppb, 26 s) and recovery (25 ppb, 458 s and 100 ppb, 290 s). The DFT calculations further clarify the reasons for enhanced electrical conductivity after NO2 adsorption because of the interfacial electron transfer from tellurene to NO2, revealing an underlying explanation for tellurene-based gas sensors. These results indicate that tellurene is eminently promising for detecting NO2 with superior sensitivity, favorable selectivity, an ultralow DL, fast response-recovery, and high stability.

Liquid-phase exfoliation of black sesame to create a nanoplatform for in vitro photoluminescence and photothermal therapy.

Aim: The present study aims to apply the facile liquid-phase exfoliation (LPE) strategy to fabricate 2D organic materials and thus to broaden the family of biocompatible and multifunctional 2D materials. Materials & methods: 2D material-organic melanin and cellulose nanosheets were synthesized from black sesame hull using LPE. Photoluminescence and photothermal properties of the nanosheets were assessed, as well as stability and cell killing ability. Results: The prepared 2D nanoplatform exhibited broad and multiple photoluminescent emission bands. It also demonstrated efficient photothermal cancer therapy with excellent biocompatibility. Conclusion: The present study could open an avenue in exfoliating organic materials using the LPE strategy. This could make the fabrication of multifunctional 2D organic materials more efficient and broaden the family of biocompatible 2D nanomaterials.

TiO2 anchored on MoS2 nanosheets based on molybdenite exfoliation as an efficient cathode for enhanced Cr (VI) reduction in microbial fuel cell

MoS2 nanosheet-decorated TiO2 nanocomposites were prepared via facile liquid-phase exfoliation of natural molybdenite combined with in situ hydrolysis route. These materials were used as a photocathode for the first time in microbial fuel cell (MFC) to reduce hexavalent chromium (Cr (VI)). Results showed the maximum power density of 1 wt% MoS2/TiO2-based MFC was 3.7 and 1.9 times higher than that of blank graphite and TiO2-based MFC, respectively. This MFC achieved 99.57% removal of Cr (VI) with a concentration of 20 mg L−1 within 8 h under visible light illumination at pH 2 and high degradation rate of 2.49 g m−3 h−1. The introduction of MoS2 nanosheets as a cocatalyst can expand the absorption of visible light, thereby leading to increased electronic participation in Cr (VI) reduction. Moreover, the appropriate amounts of MoS2 nanosheets also contribute to electrons migration and additional active site. The enhanced power output and Cr (VI) reduction efficiency of MFC can be attributed to the synergistic coupling between bioanode and MoS2/TiO2 photocathode. On the basis of its facile and scalable synthetic strategy as well as its stable and outstanding photoelectrocatalytic performance for MFC, this MoS2/TiO2 nanocomposite showed potential in the efficient treatment of wastewater.