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Laser-induced graphene (LIG) has been extensively explored for various applications due to its low cost, simple preparation, and excellent physical and chemical properties. Compared to non-degradable polymers such as polyamide (PI), bio-based precursors offer immense advantages for more sustainable development. In this study, folate was innovatively proposed as the precursor for high-quality LIG synthesis, which was further used for the development of strain sensors and electrochemical catalysis. The folate-based LIG strain sensor demonstrated a broad operating range (0–12%), high sensitivity (with a gauge factor up to 361), exceptional stability, and reliability (exhibiting a consistent response over 10,000 repeated stretching cycles). Moreover, it exhibited precise detection capabilities for subtle deformations induced by human respiration, speech, swallowing, pulse beating, and joint movements. In terms of electrochemical catalysis, folate-based LIG demonstrated a remarkable enhancement in increasing the degradation rate of pollutants like Rhodamine B through the electro-Fenton process. The findings of this study suggest that LIG derived from folate processes shows huge promise for applications such as medical monitoring, micromotion recognition, and water pollutant remediation. [ABSTRACT FROM AUTHOR]

Hybrid water electrolyzers that use facile organic oxidation reactions (OOR) as an alternative to the sluggish oxygen evolution reaction (OER) are projected as high-value electrolyzers due to the simultaneous production of H2 and value-added chemicals. In the present study, electro-oxidative dehydrogenation of benzylamine (BAm) to benzonitrile (BN) is carried out as an alternate oxidation reaction to OER, coupled with the hydrogen evolution reaction (HER), in a hybrid water electrolysis system. For this, heterostructures of Ni2Co layered double hydroxide (LDH) and reduced graphene oxide (rGO) are synthesized by using flocculation of oppositely surface-charged nanosheets and used for the benzylamine oxidation reaction (BAmOR). The Ni2Co-LDH/rGO heterostructures require 1.35 V vs RHE to achieve a current density of 10 mA cm–2 in the presence of BAm, compared to 1.61 V vs RHE without BAm, indicating that BAmOR can be a potential alternate to OER. Upon utilizing Ni2Co-LDH/rGO heterostructures as the anode and commercial Pt as the cathode in a hybrid water splitting cell, faradaic efficiencies of ∼94% and ∼85% are achieved for H2 and BN production, respectively. Additionally, the hybrid electrolysis cell is capable of producing 38.6 μmol cm–2 h–1 H2 even at a cell voltage of 1.39 V, whereas the traditional water electrolysis cell requires a cell voltage of 1.68 V to yield a similar (34.7 μmol cm–2 h–1) amount of H2. This clearly suggests that substituting the OER with BAmOR is beneficial for not only achieving high efficiency in H2 production but also producing value-added BN. [ABSTRACT FROM AUTHOR]

Achieving dispersions of antimony sulfide (Sb2S3) in environmentally friendly solvents is of paramount importance for safer and sustainable processing due to its wide range of applications. The efficacy of liquid-phase exfoliation (LPE) depends on the choice of solvents, and the determination of the Hansen solubility parameters (HSP) is crucial. In this work, employing the Hansen solubility sphere method, the HSP values of Sb2S3 are determined to be 20.8, 10.8, and 13.4 MPa1/2, which correspond to dispersive, polar, and hydrogen-bonding interactions, respectively. Environmentally friendly solvents, such as 2-butanol and isopropyl alcohol (IPA), have been identified as good solvents for exfoliation. Subsequently, the stability of the dispersions is investigated using an analytical centrifuge. Through the in situ visualization of transmission profiles and various stability parameters like the instability index, sedimentation velocity, and decay time constants, 2-butanol is found to have excellent dispersion stability. To further explain the observed stability, density functional theory (DFT) calculations are carried out. The adsorption energy of 2-butanol on the surface of Sb2S3 is higher than that of IPA, leading to better solute–solvent interactions and, hence, better dispersion stability. Subsequently, the dispersions are utilized to fabricate thin films using the spray-coating method. The solution-processed Sb2S3 photodetector exhibits an impressive responsivity of 68 mA/W, noise-equivalent power (NEP) of 0.3 pW/Hz–1/2, and detectivity of 2.4 × 1011 Jones. [ABSTRACT FROM AUTHOR]

The utilization of two-dimensional (2D) materials in optoelectronic devices has witnessed a surge. Production of 2D ultrathin molybdenum disulfide (MoS2) nanosheets without the use of toxic precursors and without altering the phase of the material is still a task. We developed a cost-effective liquid-phase exfoliation method that is free of additives, utilizing ultrasound to produce a significant amount of nearly single-layered MoS2 nanosheets by employing isopropyl alcohol and deionized water as a cosolvent. This work addresses the deficiencies in the current state-of-the-art studies by exploring the mechanism governing ultrasonic cavitation, resulting in MoS2 nanosheets. Various sonication durations were altered to investigate the relationship between the duration of sonication and the dimensionality of the resulting nanosheets. The findings revealed that prolonged sonication durations yielded bilayered and trilayered nanosheets. The reduction in layer thickness was confirmed by Raman modes as the sonication time increased. Size-dependent optical studies indicated that the optical properties have enhanced as the sonication time increased. An open-aperture Z-scan investigation was conducted to explore the size-dependent nonlinear optical features of MoS2 nanosheets, employing a 532 nm neodymium-doped yttrium aluminum garnet pulsed laser in a nanosecond pulsed regime. The optical limiting performance of the nanosheets sonicated at various time intervals was accessed and it was observed that as the nanosheets' thickness decreases, the optical limiting behavior improves. Due to two-photon absorption, MoS2 nanosheets display optical limiting behaviors through reverse saturable absorption. Optical limiting thresholds as low as 2.98 × 1012 W/m2 are attained. This significant enhancement suggests that these ultrathin MoS2 nanosheets are suitable for applications in laser shielding. [ABSTRACT FROM AUTHOR]

Antimony emerges as one of the interesting monoelemental graphene analogs, having unique properties and a wide range of applications. Among the solution-processing routes, liquid-phase exfoliation (LPE) offers various advantages. However, the choice of solvent greatly influences the exfoliation efficiency. Here, detailed work has been carried out on the LPE of antimony and its dispersion stability. By employing the Hansen solubility sphere method, the Hansen solubility parameters of antimony are determined to be 22.53, 14.03, and 18.31 MPa1/2, corresponding to the dispersion interactions, polar interactions, and hydrogen bonding interactions, respectively. To further understand the solute–solvent interactions, the stability of the dispersions is investigated both qualitatively and quantitatively using an accelerated centrifuge-based technique employing space-time-resolved extinction profiles (STEP). The sedimentation kinetics of the dispersions are studied using various metrics like instability index, integral extinction, and cumulative sedimentation velocity distribution. Among the solvents studied, isopropyl alcohol, ε-caprolactone, N-methyl pyrrolidone, dimethyl sulfoxide, and ethanol are found to have better dispersion stability. Interestingly, some of the solvents with high dispersion concentrations appear to be relatively less stable. Combining Hansen solubility parameters with stability analysis helped in identifying the efficient solvents for obtaining the stable antimonene dispersions. Furthermore, antimonene nanosheets embedded in the carbon nanotubes matrix are used as anode materials for lithium-ion battery applications. The excellent cyclic stability exhibited by antimonene indicates it to be a promising candidate for next-generation energy storage systems. [ABSTRACT FROM AUTHOR]

Nonaqueous dispersions of graphene nanoplatelets (GrNPs) can be used to prepare thin films and coatings free of surfactants, but typically involve polar organic solvents with high boiling points and low exposure limits. Here, we describe the mechanochemical exfoliation and dispersion of GrNPs in volatile aprotic solvents such as ethyl acetate (EtOAc) and acetone, which rank favorably in green solvent selection guides. GrNPs in powder form were exfoliated with a solvent on a horizontal ball mill for 48 h and then sonicated at moderate power to produce suspensions in excess of 300 μg/mL with minimum loss of dispersion stability over 7 weeks at room temperature. Atomic force microscopy of individual particles indicates a median thickness and lateral width of 8–10 layers and 180 nm, respectively. GrNP films can be deposited by conventional airbrush equipment with a dry time of seconds and applied as layers and coatings that enhance the reproducibility and performance of electronic devices. We demonstrate the utility of spray-coated GrNPs as contact layers for low-cost electrochemical sensing with improvements in intrabatch reproducibility and as conformal coatings on metal heat sinks with enhanced rates of heat dissipation. [ABSTRACT FROM AUTHOR]

In this work, we apply liquid cascade centrifugation to highly concentrated graphene dispersions produced by liquid-phase exfoliation in water with an insoluble bis-pyrene stabilizer to obtain fractions containing nanosheets with different lateral size distributions. The concentration, stability, size, thickness, and the cytotoxicity profile are studied as a function of the initial stabilizer concentration for each fraction. Our results show that there is a critical initial amount of stabilizer (0.4 mg/mL) above which the dispersions show reduced concentration, stability, and biocompatibility, no matter the lateral size of the flakes. [ABSTRACT FROM AUTHOR]

Developing a general strategy to efficiently exfoliate transition metal dichalcogenide (TMD) electrocatalysts would be significantly beneficial for the electrocatalytic hydrogen evolution reaction (HER) from water splitting. However, there are several challenges in the production of two-dimensional (2D) TMDs, including the complicated fabrication process, high defect rate, and low production yield. Herein, we developed a general applicable mild organic molecular intercalator-assisted liquid-phase exfoliation method to produce TMD nanosheets in a large scale. The as-prepared ultrathin WSe2, MoSe2, WS2, and MoS2 nanosheets have a 2D nanosheet structure with a thickness of ∼3 nm and lateral size in a few hundred nanometers. This mild intercalation method can avoid introducing harsh exfoliation conditions used in conventional liquid-phase exfoliation, electrochemistry exfoliation, and lithium intercalation, thus resulting in high-quality exfoliation of TMD crystals. Additionally, benefiting from superior intrinsic electrical conductivity, unique 2D structure, and highly exposed active sites, the exfoliated WSe2 and MoSe2 nanosheets exhibited excellent catalytic activity for HER in acid with overpotentials of 223 and 225 mV at a current density of 10 mA cm–2 and low Tafel slopes of 64 and 65 mV dec–1, respectively. [ABSTRACT FROM AUTHOR]

The absence of scalable and environmentally sustainable methods for producing electronic-grade graphene nanoplatelets remains a barrier to the industrial-scale application of graphene in printed electronics and conductive composites. To address this unmet need, here we report the utilization of carboxylated cellulose nanocrystals (CNCs) extracted from the perennial tall grass Miscanthus × giganteus as a biorenewable dispersant for the aqueous liquid-phase exfoliation of few-layer graphene nanoplatelets. This CNC-based exfoliation procedure was optimized using a Bayesian machine learning model, resulting in a significant graphite-to-graphene conversion yield of 13.4% and a percolating graphene thin-film electrical conductivity of 3.4 × 10 4 S m -1 . The as-exfoliated graphene dispersions were directly formulated into an aerosol jet printing ink using cellulose-based additives to achieve high-resolution printing (∼20 μm line width). Life cycle assessment of this CNC-based exfoliation method showed substantial improvements for fossil fuel consumption, greenhouse gas emissions, and water consumption compared to incumbent liquid-phase exfoliation methods for electronic-grade graphene nanoplatelets. Mechanistically, potential mean force calculations from molecular dynamics simulations reveal that the high exfoliation yield can be traced back to the favorable surface interactions between CNCs and graphene. Ultimately, the use of biorenewable CNCs for liquid-phase exfoliation will accelerate the scalable and eco-friendly manufacturing of graphene for electronically conductive applications.

Graphite is one of only a few layered materials that can be exfoliated into nanosheets with semimetallic properties, which limits the applications of nanosheet-based electrodes to material combinations compatible with the work function of graphene. It is therefore important to identify additional metallic or semimetallic two-dimensional (2D) nanomaterials that can be processed in solution for scalable fabrication of printed electronic devices. Metal diborides represent a family of layered non-van der Waals crystals with semimetallic properties for all nanosheet thicknesses. While previous reports show that the exfoliated nanomaterial is prone to oxidation, we demonstrate a readily accessible inert exfoliation process to produce quasi-2D nanoplatelets with intrinsic material properties. For this purpose, we demonstrate the exfoliation of three representative metal diborides (MgB 2 , CrB 2 , and ZrB 2 ) under inert conditions. Nanomaterial is characterized using a combination of transmission electron microscopy, scanning electron microscopy, atomic force microscopy, IR, and UV-vis measurements, with only minimal oxidation indicated postprocessing. By depositing the pristine metal diboride nanoplatelets as thin films using a Langmuir-type deposition technique, the ohmic behavior of the networks is validated. Furthermore, the material decomposition is studied by using a combination of electrical and optical measurements after controlled exposure to ambient conditions. Finally, we report an efficient, low-cost approach for sample encapsulation to protect the nanomaterials from oxidation. This is used to demonstrate low-gauge factor strain sensors, confirming metal diboride nanosheets as a suitable alternative to graphene for electrode materials in printed electronics.

It has been reported that the dispersing ability of a given surfactant in surfactant-assisted liquid-phase exfoliation of graphite is extremely affected by its adsorption energy on graphene nanosheets. This study employs computational and experimental techniques to analyze the true relationship between adsorption energy and the dispersing ability of a group of surfactants in the surfactant-assisted liquid-phase exfoliation of graphite. In the first section, adsorption energies computed for a group of homologous surfactants with different hydrocarbon tail lengths are used to predict dispersing-ability trends. It is found that the adsorption energy of the surfactants correlates directly with their tail length. In light of the literature, it is therefore expected that the surfactant with the highest adsorption energy is most effective at dispersing. The experimental section examines this expectation and shows that this is not guaranteed as a general rule. Based on the experimental results, this expectation can be met when surfactant concentrations are quite below surfactants' critical micelle concentrations (CMCs) but fails at concentrations near or exceeding CMCs. Finally, quantum computation and molecular dynamics simulations are employed to justify the dispersing-ability trend observed at higher concentrations. Results demonstrate that the molecular size of the surfactants becomes considerable at these concentrations. In view of this, a new quantity, "adsorption energy per molecular volume", is proposed to explain the behavior of the surfactants at high concentrations. Using this new quantity, the dispersing-ability trend observed at higher concentrations is explained. [ABSTRACT FROM AUTHOR]

Here, we demonstrate the production of 2D nanosheets of arsenic disulfide (As 2 S 3 ) via liquid-phase exfoliation of the naturally occurring mineral, orpiment. The resultant nanosheets had mean lateral dimensions and thicknesses of 400 and 10 nm, and had structures indistinguishable from the bulk. The nanosheets were solution mixed with carbon nanotubes and cast into nanocomposite films for use as anodes in potassium-ion batteries. These anodes exhibited outstanding electrochemical performance, demonstrating an impressive discharge capacity of 619 mAh/g at a current density of 50 mA/g. Even after 1000 cycles at 500 mA/g, the anodes retained an impressive 94% of their capacity. Quantitative analysis of the rate performance yielded a capacity at a very low rate of 838 mAh/g, about two-thirds of the theoretical capacity of As 2 S 3 (1305 mAh/g). However, this analysis also implied As 2 S 3 to have a very small solid-state diffusion coefficient (∼10 -17 m 2 /s), somewhat limiting its potential for high-rate applications.

Lithium-ion batteries are the leading energy storage technology for portable electronics and vehicle electrification. However, demands for enhanced energy density, safety, and scalability necessitate solid-state alternatives to traditional liquid electrolytes. Moreover, the rapidly increasing utilization of lithium-ion batteries further requires that next-generation electrolytes are derived from earth-abundant raw materials in order to minimize supply chain and environmental concerns. Toward these ends, clay-based nanocomposite electrolytes hold significant promise since they utilize earth-abundant materials that possess superlative mechanical, thermal, and electrochemical stability, which suggests their compatibility with energy-dense lithium metal anodes. Despite these advantages, nanocomposite electrolytes rarely employ kaolinite, the most abundant variety of clay, due to strong interlayer interactions that have historically precluded efficient exfoliation of kaolinite. Overcoming this limitation, here we demonstrate a scalable liquid-phase exfoliation process that produces kaolinite nanoplatelets (KNPs) with high gravimetric surface area, thus enabling the formation of mechanically robust nanocomposites. In particular, KNPs are combined with a succinonitrile (SN) liquid electrolyte to form a nanocomposite gel electrolyte with high room-temperature ionic conductivity (1 mS cm -1 ), stiff storage modulus (>10 MPa), wide electrochemical stability window (4.5 V vs Li/Li + ), and excellent thermal stability (>100 °C). The resulting KNP-SN nanocomposite gel electrolyte is shown to be suitable for high-rate rechargeable lithium metal batteries that employ high-voltage LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA) cathodes. While the primary focus here is on solid-state batteries, our strategy for kaolinite liquid-phase exfoliation can serve as a scalable manufacturing platform for a wide variety of other kaolinite-based nanocomposite applications.

Two-dimensional (2D) wide bandgap materials are gaining significant interest for next-generation optoelectronic devices. However, fabricating electronic-grade 2D nanosheets from non-van der Waals (n-vdW) oxide semiconductors poses a great challenge due to their stronger interlayer coupling compared with vdW crystals. This strong coupling typically introduces defects during exfoliation, impairing the optoelectronic properties. Herein, we report the liquid-phase exfoliation of few-atomic-layer thin, defect-free, free-standing ZnO nanosheets. These micron-sized, ultrathin ZnO structures exhibit three different orientations aligned along both the polar c -plane as well as the nonpolar a - and m -planes. The superior crystalline quality of the ZnO nanosheets is validated through comprehensive characterization techniques. This result is supported by density functional theory (DFT) calculations, which reveals that the formation of oxygen vacancies is energetically less favorable in 2D ZnO and that the c -plane loses its polarity upon exfoliation. Unlike bulk ZnO, which is typically dominated by defect-induced emission, the exfoliated nanosheets exhibit a strong, ambient-stable excitonic UV emission. We further demonstrate the utility of solution processing of ZnO nanosheets by their hybrid integration with organic components to produce stable light emitting diodes (LEDs) for display applications.

The heterogeneous nature of mass-produced 2D material's nanoflakes requires analysis of size and shape parameters: their distributions around the desired values are essential for production and characterization. In this work, we obtain analytical expressions and behaviors of statistical distributions of experimentally extracted size and shape parameters of nanoflakes obtained by liquid-phase exfoliation. The collected data are open and can be mathematically handled to be analyzed through different associations in different scales, such as the logarithm of the length/thickness (r) and length/width (rL) aspect ratios. We find that ln-(r), a shape parameter, follows nearly Gaussian distributions, being an efficient fingerprint to characterize the material type and processing. On the other hand, the logarithms of thickness and volume follow asymmetric distributions with specific asymptotic behaviors, called exponential-power-Gaussian functions, but centrifugation turns both nearly Gaussian-distributed. Finally, the logarithm of the length/width aspect ratio, ln-(rL), an in-plane shape parameter, was found to follow the single-parameter probability density distribution xe–λx2. The method detected that centrifugation enhances, by up to threefold, the percentage of flakes with large length/width ratios. This statistical methodology can be incorporated into the quality control of mass production of 2D nanoflakes, whose target applications can be found across the fast-growing nanomaterials' industry. [ABSTRACT FROM AUTHOR]

In this study, we demonstrate the fabrication of a novel 2D transition metal dichalcogenide, VTe 2 , into a saturable absorber (SA) by using the liquid phase exfoliation method. Furthermore, the first-principles calculations were conducted to elucidate the electronic band structures and absorption spectrum. The nonlinear optical absorption properties of VTe 2 at 1.0, 2.0, and 3.0 μm were measured using open-aperture Z-scan and P-scan methods, which showed saturation intensities and modulation depths of 95.57 GW/cm 2 and 9.24%, 3.11 GW/cm 2 and 7.26%, and 15.8 MW/cm 2 and 17.1%, respectively. Furthermore, in the realm of practical implementation, the achievement of stable passively Q-switched (PQS) lasers employing SA composed of few-layered VTe 2 nanosheets has manifested itself with broadband operating wavelengths from 1.0 to ∼3.0 μm. Specifically, PQS laser operations from near-infrared to mid-infrared with pulse durations of 195 and 563 ns for 1.0 and 2.0 μm solid-state lasers, respectively, and 749 ns for an Er 3+ -doped fluoride fiber laser at 3.0 μm were obtained. Our experimental results demonstrate that VTe 2 is a potential broadband SA device for achieving PQS lasers. To the best of our knowledge, this is the first demonstration of using VTe 2 as an SA in PQS lasers in the near- and mid-infrared regions, which highlights the potential of VTe 2 for future research and applications in optoelectronic devices.

Tetracyanonickelate (TCN)-based metal-organic frameworks (MOFs) show great potential in electrochemical applications such as supercapacitors due to their layered morphology and tunable structure. This study reports on improved electrochemical performance of exfoliated manganese tetracyanonickelate (Mn-TCN) nanosheets produced by the heat-assisted liquid-phase exfoliation (LPE) technique. The structural change was confirmed by the Raman frequency shift of the C≡N band from 2177 to 2182 cm -1 and increased band gap from 3.15 to 4.33 eV in the exfoliated phase. Statistical distribution obtained from atomic force microscopy (AFM) shows that 50% of the nanosheets are single-to-four-layered and have an average lateral size of ∼240 nm 2 and thickness of ∼1.2-4.8 nm. High-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) patterns suggest that the material maintains its crystallinity after exfoliation. It exhibits an almost 6-fold improvement in specific capacitance (from 13.0 to 72.5 F g -1 ) measured at a scan rate of 5 mV s -1 in 1 M KOH solution. Galvanostatic charge-discharge (GCD) measurement shows a capacity enhancement from ∼18 F g -1 in the bulk phase to ∼45 F g -1 in the exfoliated phase at a current density of 1 A g -1 . Bulk crystals exhibit an increasing trend of capacitance retention by ∼125% over 1000 charge-discharge cycles attributed to electrochemical exfoliation. Electrochemical impedance spectroscopy (EIS) demonstrates a 5-fold reduction in the total equivalent series resistance (ESR) from 4864 Ω (bulk) to 1089 Ω (exfoliated). The enhanced storage capacity in the exfoliated phase results from the combined effect of the electrochemical double-layer charge storage mechanism at the nanosheet-electrolyte interface and the Faradic process characteristic of the pseudocapacitive charge storage behavior.

As a metal-free and visible-light-responsive photocatalyst, graphitic carbon nitride (g-C 3 N 4 ) has emerged as a new research hotspot and has attracted broad attention in the field of solar energy conversion and thin-film transistors. Liquid-phase exfoliation (LPE) is the best-known method for the synthesis of 2D g-C 3 N 4 nanosheets. In LPE, bulk g-C 3 N 4 is exfoliated in a solvent via high-shear mixing or sonication in order to produce a stable suspension of individual nanosheets. Two parameters of importance in gauging the performance of a solvent in LPE are the free energy required to exfoliate a unit area of layered materials into individual sheets in the solvent (Δ G exf ) and the solvation free energy per unit area of a nanosheet (Δ G sol ). While approximations for the free energies exist, they are shown in our previous work to be inaccurate and incapable of capturing the experimentally observed efficacy of LPE. Molecular dynamics (MD) simulations can provide accurate free-energy calculations, but doing so for every single solvent is time- and resource-consuming. Herein, machine learning (ML) algorithms are used to predict Δ G exf and Δ G sol for g-C 3 N 4 . First, a database for Δ G exf and Δ G sol is created based on a series of MD simulations involving 49 different solvents with distinct chemical structures and properties. The data set also includes values of critical descriptors for the solvents, including density, surface tension, dielectric constant, etc. Different ML methods are compared, accompanied by descriptor selection, to develop the most accurate model for predicting Δ G exf and Δ G sol . The extra tree regressor is shown to be the best performer among the six ML methods studied. Experimental validation of the model is conducted by performing dispersibility tests in several solvents for which the free energies are predicted. Finally, the influence of the selected descriptors on the free energies is analyzed, and strategies for solvent selection in LPE are proposed.

Few-atomic-layer nanoflakes of liquid-phase exfoliated semiconducting transition metal dichalcogenides (TMDs) hold promise for large-area, high-performance, low-cost solar energy conversion, but their performance is limited by recombination at defect sites. Herein, we examine the role of defects on the performance of WSe2 thin film photocathodes for solar H2 production by applying two separate treatments, a pre-exfoliation annealing and a post-deposition surfactant attachment, designed to target intraflake and edge defects, respectively. Analysis by TEM, XRD, XPS, photoluminescence, and impedance spectroscopy are used to characterize the effects of the treatments and photoelectrochemical (PEC) measurements using an optimized Pt-Cu cocatalyst (found to offer improved robustness compared to Pt) are used to quantify the performance of photocathodes (ca. 11 nm thick) consisting of 100-1000 nm nanoflakes. Surfactant treatment results in an increased photocurrent attributed to edge site passivation. The pre-annealing treatment alone, while clearly altering the crystallinity of pre-exfoliated powders, does not significantly affect the photocurrent. However, applying both defect treatments affords a considerable improvement that represents a new benchmark for the performance of solution-processed WSe2: solar photocurrents for H2 evolution up to 4.0 mA cm-2 and internal quantum efficiency over 60% (740 nm illumination). These results also show that charge recombination at flake edges dominates performance in bare TMD nanoflakes, but when the edge defects are passivated, internal defects become important and can be reduced by pre-annealing. [ABSTRACT FROM AUTHOR]

Organic two-dimensional (2D) crystals are fundamentally important for development of future devices. Despite that more than a half of man-made products contain polymers, 2D crystals consisting of long linear chains have yet to be explored. Here we report on the fabrication of 2D polyaniline (PANI) crystals via rational electrochemical polymerization followed by liquid-phase exfoliation. The 2D PANI is molecularly thin (∼0.8 nm) and composed of PANI chains with a number-average molecular weight of ∼31,000. The chains are parallel to each other with the benzene rings standing almost vertically to the surface, implying a face-to-face arrangement of the neighboring chains held together by abundant π-π interactions augmented with hydrogen bonds. The 2D PANI can be readily transferred to various solid surfaces and exhibit interesting electrical and optical properties, suggesting that they would be potentially useful in photoelectronic devices and other applications. [ABSTRACT FROM AUTHOR]

Tumors have become the biggest obstacle to human health, and there are various treatment methods at present. Photothermal therapy (PTT) is usually ineffective and does not inhibit tumor progression due to the inability of the lasers to penetrate deeply. Therefore, most existing studies chose a 1064 nm laser with stronger penetrating power; meanwhile, studies have shown that the inclusion of harmful free radicals can significantly improve the antitumor efficacy. Herein, TiO nanosheets (NSs) were creatively prepared and encapsulated with an alkyl radical generator {2,2'-azobis[2-(2-imidazoline-2-yl)propane] dihydrochloride, [AIPH]} in sodium alginate (ALG) hydrogel for effective tumor killing by PTT and pairing with dangerous free radicals. TiO NSs were obtained by the liquid-phase exfoliation method, together with AIPH, which were in situ coencapsulated multifunctional hydrogels formed by the combination of Ca 2+ and ALG. This ALG hydrogel could enrich TiO NSs and AIPH at the tumor site for a long time, and through the excellent photothermal properties of TiO NSs, AIPH could slowly and effectively generate alkyl radicals at the tumor site, which, in turn, gave it a better antitumor effect compared with that of TiO NSs in the deep hypoxic environment of the tumor. The AIPH + TiO + ALG hydrogel has distinctive anticancer capabilities based on the results of both in vivo and in vitro experiments. This material also has good biosafety. By combining PTT and free radical treatment, this work provides a novel therapeutic method to achieve oxygen-independent free radical production and enhance therapeutic efficacy.

Isopycnic density gradient ultracentrifugation (iDGU) has been widely applied to sort nanomaterials by their physical and electronic structure. However, the commonly used density-gradient medium iodixanol has a finite maximum buoyant density that prevents the use of iDGU for high-density nanomaterials. Here, we overcome this limit by adding cesium chloride (CsCl) to iodixanol, thus increasing its maximum buoyant density to the point where the high-density two-dimensional nanomaterial rhenium disulfide (ReS2) can be sorted in a layer-by-layer manner with iDGU. The resulting aqueous ReS2 dispersions show photoluminescence at ∼1.5 eV, which is consistent with its direct bandgap semiconductor electronic structure. Furthermore, photocurrent measurements on thin films formed from solution-processed ReS2 show a spectral response that is consistent with optical absorbance and photoluminescence data. In addition to providing a pathway for effective solution processing of ReS2, this work establishes a general methodology for sorting high-density nanomaterials via iDGU. [ABSTRACT FROM AUTHOR]

Magnetism and the existence of magnetic order in a material is determined by its dimensionality. In this regard, the recent emergence of magnetic layered van der Waals (vdW) materials provides a wide playground to explore the exotic magnetism arising in the two-dimensional (2D) limit. The magnetism of 2D flakes, especially antiferromagnetic ones, however, cannot be easily probed by conventional magnetometry techniques, being often replaced by indirect methods like Raman spectroscopy. Here, we make use of an alternative approach to provide direct magnetic evidence of few-layer vdW materials, including antiferromagnets. We take advantage of a surfactant-free, liquid-phase exfoliation (LPE) method to obtain thousands of few-layer FePS 3 flakes that can be quenched in a solvent and measured in a conventional SQUID magnetometer. We show a direct magnetic evidence of the antiferromagnetic transition in FePS 3 few-layer flakes, concomitant with a clear reduction of the Néel temperature with the flake thickness, in contrast with previous Raman reports. The quality of the LPE FePS 3 flakes allows the study of electron transport down to cryogenic temperatures. The significant through-flake conductance is sensitive to the antiferromagnetic order transition. Besides, an additional rich spectra of electron transport excitations, including secondary magnetic transitions and potentially magnon-phonon hybrid states, appear at low temperatures. Finally, we show that the LPE is additionally a good starting point for the mass covalent functionalization of 2D magnetic materials with functional molecules. This technique is extensible to any vdW magnetic family.

A 2D van der Waals (vdW) magnet can get rid of the constraints of lattice matching and compatibility and then create a variety of vdW heterostructures, which provides a opportunity for spintronic devices. However, the ability to reliably exfoliate large, high-quality vdW ferromagnetic Fe 3 GeTe 2 (FGT) nanoflakes in scaled-up production is severely limited. Herein, an efficient and stable three-stage sonication-assisted liquid-phase exfoliation was developed for mass preparation of high-structural-integrity few- and single-layer FGT nanoflakes with a greatly enhanced intrinsic exchange bias. The three stages include slicing crystals, weakening interlayer vdW forces, and using ultrasonic cavitation. The highest yield of FGT nanoflakes is 22.3 wt % with single layers accounting for 6%. The size is controllable, and several micrometers, tens of micrometers, and a maximum of 103 μm are available. The 200 mg level output has overcome the limitations of mechanical exfoliation and molecular beam epitaxy in economically amplificated production. An intrinsic exchange bias is observed in the restacked nanoflakes due to the magnetic proximity on the interface of the FGT/natural surface oxide layer. The material reaches 578 Oe (2 K) and 2300 Oe after further oxidation, at least 250% higher than other precisely tailored vdW magnetic heterostructures. In addition, the unusual semiconductivity of the liquid-phase exfoliated FGT nanoflakes is reported. This work skillfully utilizes oxidation to enhance the potential of FGT for large-scale spintronics, optoelectronics, efficient data storage, and various extended applications, and it is beneficial for exfoliating other promising magnetic vdW materials.

Bismuth telluride halides (BiTeX) are Rashba-type crystals with several potential applications ranging from spintronics and nonlinear optics to energy. Their layered structures and low cleavage energies allow their production in a two-dimensional form, opening the path to miniaturized device concepts. The possibility to exfoliate bulk BiTeX crystals in the liquid represents a useful tool to formulate a large variety of functional inks for large-scale and cost-effective device manufacturing. Nevertheless, the exfoliation of BiTeI by means of mechanical and electrochemical exfoliation proved to be challenging. In this work, we report the first ultrasonication-assisted liquid-phase exfoliation (LPE) of BiTeI crystals. By screening solvents with different surface tension and Hildebrandt parameters, we maximize the exfoliation efficiency by minimizing the Gibbs free energy of the mixture solvent/BiTeI crystal. The most effective solvents for the BiTeI exfoliation have a surface tension close to 28 mN m -1 and a Hildebrandt parameter between 19 and 25 MPa 0.5 . The morphological, structural, and chemical properties of the LPE-produced single-/few-layer BiTeI flakes (average thickness of ∼3 nm) are evaluated through microscopic and optical characterizations, confirming their crystallinity. Second-harmonic generation measurements confirm the non-centrosymmetric structure of both bulk and exfoliated materials, revealing a large nonlinear optical response of BiTeI flakes due to the presence of strong quantum confinement effects and the absence of typical phase-matching requirements encountered in bulk nonlinear crystals. We estimated a second-order nonlinearity at 0.8 eV of |χ (2) | ∼ 1 nm V -1 , which is 10 times larger than in bulk BiTeI crystals and is of the same order of magnitude as in other semiconducting monolayers (e.g., MoS 2 ).

The emergence of attractive properties in materials at atomically thin regimes has seen an ongoing interest in two-dimensional (2D) materials. An aspect that has lacked focused attention is the effect of 2D material thickness on its crystal structure. As several layered materials naturally exist in mixed metastable phases, it raises an important question of whether a specific polymorph of these mixed-phase materials will be favored at atomically thin limits. This work attempts to address this issue by employing lead monoxide as a model 2D polymorphic system. We propose a reactive oxygen species (ROS) sequestration-mediated liquid-phase exfoliation (LPE) strategy for the facile synthesis of ultrathin PbO. This is followed by a suite of microscopic and spectroscopic analyses of the PbO nanosheets that reveals the polymorphic transformation of orthorhombic (β) PbO to its tetragonal (α) analogue with reduction in nanosheet thickness. The transformation process reveals an interesting crystal structure of ultrathin 2D PbO where [001]-oriented domains of α-PbO coexist alongside [100]-oriented regions of β-PbO. Density functional theory (DFT) calculations support our experimental data by revealing a higher thermodynamic stability of the tetragonal phase in PbO monolayers. These findings are likely to instigate interest in carefully evaluating the crystal structures of ultrathin 2D materials while promoting research in understanding the phase transformation across a range of 2D crystals.

A gold-doped zinc oxide (Au-ZnO)/exfoliated tungsten diselenide (exfoliated WSe 2 ) nanocomposite-based gas sensor toward benzene with high sensing properties was demonstrated. Epoxy resin was used as the matrix of the Au-ZnO/exfoliated WSe 2 nanocomposite sensor. The straw-shaped Au-ZnO was synthesized by the hydrothermal method, and WSe 2 nanosheets (NSs) were prepared via hydrothermal and liquid-phase exfoliation methods. The properties of Au-ZnO/exfoliated WSe 2 nanoheterostructures constructed by self-assembly technology have been confirmed via a series of characterization methods. The benzene-sensing performances of sensors were tested at 25 °C. Compared with Au-ZnO, WSe 2, and their composites, the Au-ZnO/exfoliated WSe 2 sensor has a significant performance improvement, including a higher response and linear fit degree, better selectivity and repeatability, and faster detection rate. The significantly enhanced sensing properties of the Au-ZnO/exfoliated WSe 2 sensor can be ascribed to the doping of Au nanoparticles, the increase in the specific surface area and adsorption sites of NSs after exfoliation, and the cooperative interface combination of the ZnO/WSe 2 heterojunction. Furthermore, the sensitivity mechanism of the composite sensor to benzene was explored by density functional theory simulations.

We designed functionalized hexagonal boron nitride (FhBN) nanoflakes with high proton conductivity in both in- and through-plane directions as next generation polymer electrolyte membranes (PEMs) for energy storage and conversion systems. The synthesis and functionalization of hBN nanoflakes with sulfonic acid (SA) groups are obtained by one-step and in situ liquid-phase exfoliation with excellent dispersibility and stability over a period of three months. The physico/chemical properties of FhBN nanoflakes were investigated by different spectroscopic and microscopic characterization, confirming chemical interactions between hBN lattice and SA groups. High concentrations (65 and 75 wt %) of FhBN nanoflakes composed with Nafion solution formed stable FhBN-Nafion nanocomposite PEMs, offering extra proton conduction sites, doubling ion-exchange capacity, and reducing the swelling ratio compared to those of Nafion. Our results demonstrate that both the in-plane and through-plane proton conductivities of FhBN-Nafion PEMs significantly improve under various conditions comparative to that of Nafion. The maximum values of both in- and through-plane conductivities for FhBN75%-Nafion PEM at 80% of humidity and 80 °C are 0.41 and 0.1 S·cm -1 , respectively, which are 7 and 14 times higher than those of Nafion. The bidirectional superionic transport in highly concentrated FhBN PEMs is responsible for outstanding properties, useful for electrochemical energy devices.

Over the past 15 years, two-dimensional (2D) materials have been studied and exploited for many applications. In many cases, 2D materials are formed by the exfoliation of layered crystals such as transition-metal disulfides. However, it has recently become clear that it is possible to exfoliate nonlayered materials so long as they have a nonisotropic bonding arrangement. Here, we report the synthesis of 2D-platelets from the earth-abundant, nonlayered metal sulfide, iron pyrite (FeS 2 ), using liquid-phase exfoliation. The resultant 2D platelets exhibit the same crystal structure as bulk pyrite but are surface passivated with a density of 14 × 10 18 groups/m 2 . They form stable suspensions in common solvents and can be size-selected and liquid processed. Although the platelets have relatively low aspect ratios (∼5), this is in line with the anisotropic cleavage energy of bulk FeS 2 . We observe size-dependent changes to optical properties leading to spectroscopic metrics that can be used to estimate the dimensions of platelets. These platelets can be used to produce lithium ion battery anodes with capacities approaching 1000 mAh/g.

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 NO 2 (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 NO 2 adsorption because of the interfacial electron transfer from tellurene to NO 2 , revealing an underlying explanation for tellurene-based gas sensors. These results indicate that tellurene is eminently promising for detecting NO 2 with superior sensitivity, favorable selectivity, an ultralow DL, fast response-recovery, and high stability.

Liquid- phase exfoliation (LPE) is the principal method of producing two-dimensional (2D) materials such as graphene in large quantities with a good balance between quality and cost and is now widely adopted by both the academic and industrial sectors. The fragmentation and exfoliation mechanisms involved have usually been simply attributed to the force induced by ultrasound and the interaction with the solvent molecules. Nonetheless, little is known about how they actually occur, i.e. , how thick and large graphite crystals can be exfoliated into thin and small graphene flakes. Here, we demonstrate that during ultrasonic LPE the transition from graphite flakes to graphene takes place in three distinct stages. First, sonication leads to the rupture of large flakes and the formation of kink band striations on the flake surfaces, primarily along zigzag directions. Second, cracks form along these striations, and together with intercalation of solvent, lead to the unzipping and peeling off of thin graphite strips that in the final stage are exfoliated into graphene. The findings will be of great value in the quest to optimize the lateral dimensions, thickness, and yield of graphene and other 2D materials in large-scale LPE for various applications.

Flexible perovskite solar cells (PSCs) are currently one of the most attractive flexible thin-film photovoltaic technologies. Despite achieving remarkable progress in power conversion efficiencies (PCEs), flexible PSCs have not yet kept pace with rigid PSCs. Defect passivation is of crucial importance to further enhance the PCEs of flexible PSCs. Here, highly dispersed fluorographene quantum dots (FGQDs) are exfoliated from graphite fluoride with the aid of stirring and sonication and used to passivate the grain boundaries and surface of the perovskite films for high-performance flexible PSCs. Photoluminescence spectroscopy (PL) and time-resolved PL decays indicate that the FGQDs are beneficial for suppressing carrier recombination. Space-charge-limited current measurements prove that the passivated perovskite film exhibits reduced trap densities. As a result, a best PCE of 20.40% is achieved from the flexible PSCs, owing to significantly reduced charge recombination. Moreover, the champion device delivers an outstanding steady-state PCE exceeding 20%. The flexible PSCs with the FGQDs also exhibit enhanced thermal stability and environmental stability. Our work not only highlights the importance of passivating the defects within the perovskite films for high-efficiency flexible PSCs but also offers a promising future for the commercialization of flexible PSCs.

Few-layered InSe nanosheets were fabricated by the simple liquid-phase exfoliation method. The morphology and crystal structure features of InSe nanosheet sample were characterized comprehensively. The photoluminescence (PL) spectrum indicated that the liquid-phase exfoliated InSe nanosheets contained variously layered nanoflakes, where eight layers nanosheets dominate. In addition, the first-principle simulation was carried out to describe the electron density of states (DOS) and the electronic band structures. Moreover, the few-layered InSe nanosheets performed excellent nonlinear absorption properties in a broad spectral band. As an application, the stable passively Q-switched (PQS) lasers with few-layered InSe nanosheets saturable absorbers (SAs) were realized with the operating wavelengths at 1.06, 1.34, and 1.91 μm. The shortest pulse durations were 599, 520, and 210 ns, respectively. Our results confirmed that the few-layered InSe nanosheets could be an excellent candidate for pulsed lasers in wide spectral bands.

Semiconducting two-dimensional (2D) transition-metal dichalcogenides (TMDCs) are considered promising sensing materials due to the high surface-to-volume ratio and active sensing sites. However, the reported strategies for 2D TMDCs toward sensing of volatile organic compounds (VOCs) present with some drawbacks. These include high operation temperatures, low gas response, and complex fabrication, limiting the development of room-temperature gas sensors. In this study, 2D MoS 2 nanoflakes were prepared by liquid-phase exfoliation, and their surface was functionalized with Au nanoparticles (NPs) through a facile solution mixing method. MoS 2 decorated with Au NPs with an average size of 10 nm was used as a material platform for an electrochemical sensor to detect a wide variety of VOCs at room temperature. Through dynamic sensing tests, the enhancement of gas-sensing performance in terms of response and selectivity, especially in detecting oxygen-based VOCs (acetone, ethanol, and 2-propanol), was demonstrated. After Au functionalization, the response of the gas sensor to acetone improved by 131% (changing from 13.7% for pristine MoS 2 to 31.6% for MoS 2 -Au(0.5)). Sensing tests under various relative humidity values (10-80%), bending or long-term conditions, indicated the sound robustness and flexibility of the sensor. Density functional theory simulations suggested that the adsorption energy of VOC molecules on MoS 2 -Au is significantly higher than that on pristine MoS 2 , contributing to the gas-sensing enhancement; a VOC-sensing mechanism for Au-decorated MoS 2 nanoflakes was proposed for the first time for the highly sensitive and selective detection of oxygen-based VOCs.

Photothermal therapy (PTT) based on two-dimensional (2D) nanomaterials has shown significant potential in cancer treatment. However, developing 2D nanomaterial-based theranostic agents with good biocompatibility and high therapeutic efficiency remains a key challenge. Bulk titanium (Ti) has been widely used as biomedical materials for their reputable biocompatibility, whereas nanosized Ti with a biological function remains unexplored. In this work, the 2D Ti nanosheets (NSs) are successfully exfoliated from nonlayer bulk Ti and utilized as an efficient theranostic nanoplatform for dual-modal computed tomography/photoacoustic (CT/PA) imaging-navigated PTT. Besides the excellent biocompatibility obtained by TiNSs as expected, they are found to show strong absorption ability with an extinction coefficient of 20.8 L g -1 cm -1 and high photothermal conversion ability with an efficiency of 61.5% owing to localized surface plasmon resonances, which exceeds most of other well-known photothermal agents, making it quite promising for PTT against cancer. Furthermore, the metallic property and light-heat-acoustic transformation endow 2D Ti with the strong CT/PA imaging signal and efficient cancer therapy, simultaneously. This work highlights the enormous potential of nanosized Ti in both the diagnosis and treatment of cancer. As a paradigm, this study also paves a new avenue for the elemental transition-metal-based cancer theranostics.

Nanocomposite strain sensors, particularly those consisting of polymer-graphene composites, are increasingly common and are of great interest in the area of wearable sensors. In such sensors, application of strain yields an increase in resistance due to the effect of deformation on interparticle junctions. Typically, widening of interparticle separation is thought to increase the junction resistance by reducing the probability of tunnelling between conducting particles. However, an alternative approach would be to use piezoresistive fillers, where an applied strain modifies the intrinsic filler resistance and so the overall composite resistance. Such an approach would broaden sensing capabilities, as using negative piezoresistive fillers could yield strain-induced resistance reductions rather than the usual resistance increases. Here, we introduce nanocomposites based on polyethylene oxide (PEO) filled with MoS 2 nanosheets. Doping of the MoS 2 by the PEO yields nanocomposites which are conductive enough to act as sensors, while efficient stress transfer leads to nanosheet deformation in response to an external strain. The intrinsic negative piezoresistance of the MoS 2 leads to a reduction of the composite resistance on the application of small tensile strains. However, at higher strain the resistance grows due to increases in junction resistance. MoS 2 -PEO composite gauge factors are approximately -25 but fall to -12 for WS 2 -PEO composites and roughly -2 for PEO filled with MoSe 2 or WSe 2 . We develop a simple model, which describes all these observations. Finally, we show that these composites can be used as dynamic strain sensors.

As a source of clean and sustainable energy, reliable hydrogen production requires highly efficient and stable electrocatalysts. In recent years, molybdenum disulfide (MoS 2 ) has been demonstrated as a promising electrocatalyst for hydrogen evolution reactions (HERs). Here, we demonstrate that a three-dimensional (3D) MoS 2 quantum dot (MoS 2 QD) aerogel is an efficient cathode electrocatalyst that can be used to enhance the HER in acid, neutral, and alkaline (e.g., real seawater) environments. In studying the effects of the exfoliated MoS 2 dimension for the HER, we found that the biofunctionalized exfoliated MoS 2 QD shows much higher cathodic density, a more lower energy input, and a lower Tafel slope for the HER than the larger size of the chlorophyll-assisted exfoliated MoS 2 , highlighting the importance of the size of the MoS 2 aerogel support for accelerating the HER performance. Moreover, the electrocatalytic activity of MoS 2 QD-aerogel is superior to that of Pt in neutral conditions. In real seawater, the MoS 2 QD-aerogel sample exhibits stable HER performance after consecutive scanning for 150 cycles, while the HER activity of the Pt dramatically decreases after 50 cycles. These results showed for the first time how the 3D MoS 2 configuration in MoS 2 aerogel can be used to effectively produce hydrogen for clean energy applications.

The solar response ability and low-cost fabrication of the photoanode are important factors for the effective output of the photoelectrochemical system. Modification of the photoanode by which its ability to absorb irradiation can be manipulated has gained tremendous attention. Here, we demonstrated the MoSe 2 , WSe 2 , and MoSe 2 /WSe 2 nanocrystal thin films prepared by the liquid-phase exfoliated and electrophoresis methods. Atomic force microscopy and high-resolution transmission electron microscopy show that the liquid exfoliated nanocrystals have a few layered dimensions with good crystallinity. Scanning electron microscopy demonstrated uniform distribution and randomly oriented nanocrystals, having a homogeneous shape and size. X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectra confirm the equal contribution of MoSe 2 and WSe 2 nanocrystals in the formation of the MoSe 2 /WSe 2 heterojunction. Because of superior absorption of MoSe 2 /WSe 2 heterojunction in the visible region and type-II heterojunction band alignment, in situ measurement of heterojunction electrode shows almost 1.5 times incident photo-to-current conversion efficiency and photoresponsivity in comparison to individual material electrodes. Our result clearly indicates the influence of heterojunction formation between liquid exfoliated nanocrystals on effective separation of photogenerated exciton and enhances charge carrier transfer, which leads to the improvement in photoelectrochemical performance. Liquid exfoliated nanosheet-based heterojunction is attractive as efficient photoanodes for the photoelectrochemical systems.

Owing to the attractive energy band properties, a black phosphorus (BP)-analogue semiconductor, germanium selenide (GeSe), shows a promising potential applied for optoelectronic devices. Herein, ultrathin GeSe nanosheets were systematically prepared via a facile liquid-phase exfoliation approach, with controllable nanoscale thickness. Different from BP, ultrathin GeSe nanosheets exhibit good stability under both liquid and ambient conditions. Besides, its ultrafast carrier dynamics was probed by transient absorption spectroscopy. We showed that the GeSe nanosheet-based photodetector exhibits excellent photoresponse behaviors ranging from ultraviolet (UV) to the visible regime, with high responsivity and low dark current. Furthermore, the detective ability of such a device can be effectively modulated by varying the applied bias potential, light intensity, and concentration of the electrolyte. Generally, our present contribution could not only supply fundamental knowledge of a GeSe nanosheet-based photoelectrochemical (PEC)-type device, but also offer guidance to extend other possible semiconductor materials in the application of the PEC-type photodetector.

Black phosphorus (BP) nanosheets with unique biocompatibility and superior optical performance have attracted enormous attention in material science. However, their instability and poor solution-processability severely limit their clinical applications. In this work, we demonstrate the use of silk fibroin (SF) as an exfoliating agent to produce thin-layer BP nanosheets with long-term stability and facile solution-processability. Presence of SF prevents rapid oxidation and degradation of the resultant BP nanosheets, enhancing their performance in physiological environment. The SF-modified BP nanosheets exhibit subtle solution-processability and are fabricated into various BP-based material formats. As superior photothermal agents, BP-based wound dressings effectively prevent bacterial infection and promote wound repair. Therefore, this work opens new avenues for unlocking current challenges of BP nanosheet applications for practical biomedical purposes.

Although two-dimensional boron (B) has attracted much attention in electronics and optoelectronics due to its unique physical and chemical properties, in-depth investigations and applications have been limited by the current synthesis techniques. Herein, we demonstrate that high-quality few-layer B sheets can be prepared in large quantities by sonication-assisted liquid-phase exfoliation. By simply varying the exfoliating solvent types and centrifugation speeds, the lateral size and thickness of the exfoliated B sheets can be controllably tuned. Additionally, the exfoliated few-layer B sheets exhibit excellent stability and outstanding dispersion in organic solvents without aggregates for more than 50 days under ambient conditions, owing to the presence of a solvent residue shell on the B sheet surface that provides excellent protection against air oxidation. Moreover, we also demonstrate the use of the exfoliated few-layer B sheets for high-performance supercapacitor electrode materials. This as-prepared device exhibits impressive electrochemical performance with a wide potential window of up to 3.0 V, excellent energy density as high as 46.1 Wh/kg at a power density of 478.5 W/kg, and excellent cycling stability with 88.7% retention of the initial specific capacitance after 6000 cycles. This current work not only demonstrates an effective strategy for the synthesis of the few-layer B sheets in a controlled manner but also makes the resulting materials promising for next-generation optoelectronics and energy storage applications.