Two-dimensional Nanostructures Research Articles

Propolis polyphenol nanosheet for synergistic cancer chemo-photothermal therapy

Two-dimensional (2D) carbon-based nanostructures hold great promise as near-infrared (NIR) photothermal materials, yet their widespread use has been hindered by labor-intensive and costly fabrication processes. Here, a novel, cost-effective approach is presented to produce photothermal materials derived from the polyphenolic fraction of propolis (PFP) for the first time. The method involves the pyrolysis of PFP under a neutral atmosphere, resulting in the formation of 2D PFP-based nanosheets (PFPNS) measuring 50–100 nm in size with efficient photothermal properties. Then, a layer-by-layer nanohybrid structure comprising PFPNS, polydopamine (PDA), mesoporous silica (MS), and polyethyleneimine (PEI) layers (PFPNS@PDA@MS-PEI) was designed as a versatile platform for drug delivery. Specifically, the anticancer drug doxorubicin (DOX) was loaded onto the nanohybrid (PFPNS@PDA@MS(DOX)-PEI) for targeted delivery to cancerous cells. Each layer of the nanohybrid serves a distinct purpose, enhancing functionality and efficacy. The NIR-responsive PFPNS@PDA component facilitates accelerated drug release and induces hyperthermic effects on cancer cells upon NIR irradiation. The MS structure enables high drug loading capacity (approximately 83.3%), while the pH-responsive PEI layer promotes cellular uptake and facilitates drug release within the acidic microenvironment of cancer cells. Combining NIR irradiation with chemotherapy results in a synergistic effect, leading to the eradication of 67% of MCF-7 breast cancer cells. The demonstrated efficacy, coupled with the non-toxic nature of the nanohybrid, positions it as a promising candidate for synergistic chemo-photothermal therapy of tumor tissues.

Continuously Adjustable Thickness of Bi2MoO6 Nanosheets Enhances Photocatalytic Oxidation.

In this study, two-dimensional (2D) nanosheet photocatalysts of Bi2MoO6 with varying thicknesses were synthesized by adjusting the temperature during the hydrothermal reaction. The thinnest Bi2MoO6 nanosheet reached an approximate thickness of ∼4 nm, while the thickest nanosheet measured only ∼16 nm. The photocatalytic performance for Rhodamine B (RhB) degradation was found to be the most effective for the thinnest Bi2MoO6 nanosheet, displaying a degradation rate constant of 0.11 min-1. This rate was 2.5 times higher than that observed for the ∼16 nm thick Bi2MoO6 photocatalyst. The enhanced performance of the thinner two-dimensional nanostructure can be attributed to improved separation and migration of photogenerated charges. Additionally, the study identified hydroxyl radicals (•OH) and superoxide radicals (•O2-) as crucial oxidative species, contributing to the efficient mineralization of RhB dye. This work highlights the controllable synthesis of 2D materials with varying thicknesses and their specific applications in photocatalytic oxidation.

Hydrothermal Synthesis and Characterization of WSe2 Nanosheets: A Promising Approach for Wearable Photodetector Applications.

The two-dimensional (2D) WSe2 nanostructure was successfully synthesized via the hydrothermal method and subjected to comprehensive characterization using various spectroscopic techniques. X-ray diffraction (XRD) analysis confirmed the formation of nanosheets with a hexagonal crystal structure having a space symmetry of P63/mmc. Scanning electron microscopy (SEM) images showed irregular and nonuniform morphology. The size of the 2D nanosheets was determined using transmission electron microscopy (TEM) providing insights intotheir physical characteristics. The optical spectrum analysis yielded a discernible band gap value of 2.1 eV, as determined by the Tauc equation. Photoluminescence (PL) spectra display an emission at a wavelength of 610 nm, showing a broad emission associated with self-trapped excitons. Under excitation at λexc = 360 nm, PL emission spectra displayed a distinct peak at 610 nm, demonstrating the ability of the nanostructure to emit vivid red light. Photometric analysis underscored the potential of this nanostructure as a prominent red-light source for diverse display applications. The optimized photodetection performance of a device showcases a photoresponsivity of approximately 1.25 × 10-3 AW-1 and a detectivity of around 5.19 × 108 Jones at a wavelength of 390 nm. Additionally, the quantum efficiency is reported to be approximately 6.99 × 10-3 at a wavelength of 635 nm. These findings highlight the capability of the device for efficient photoconversion at specified wavelengths, indicating potential applications in sensing, imaging, and optical communication. The combination of structural, morphological, and optical characterizations highlights the suitability of 2D WSe2 nanostructure for practical optoelectronic applications, particularly in display technologies.

Evaluating the effect of unidirectional loading on the piezoresistive characteristics of carbon nanoparticles

The piezoresistive effect of materials can be adopted for a plethora of sensing applications, including force sensors, structural health monitoring, motion detection in fabrics and wearable, etc. Although metals are the most widely adopted material for sensors due to their reliability and affordability, they are significantly affected by temperature. This work examines the piezoresistive performance of carbon nanoparticle (CNP) bulk powders and discusses their potential applications based on strain-induced changes in their resistance and displacement. The experimental results are correlated with the characteristics of the nanoparticles, namely, dimensionality and structure. This report comprehensively characterizes the piezoresistive behavior of carbon black (CB), onion-like carbon (OLC), carbon nanohorns (CNH), carbon nanotubes (CNT), dispersed carbon nanotubes (CNT-D), graphite flakes (GF), and graphene nanoplatelets (GNP). The characterization includes assessment of the ohmic range, load-dependent electrical resistance and displacement tracking, a modified gauge factor for bulk powders, and morphological evaluation of the CNP. Two-dimensional nanostructures exhibit promising results for low loads due to their constant compression-to-displacement relationship. Additionally, GF could also be used for high load applications. OLC’s compression-to-displacement relationship fluctuates, however, for high load it tends to stabilize. CNH could be applicable for both low and high loading conditions since its compression-to-displacement relationship fluctuates in the mid-load range. CB and CNT show the most promising results, as demonstrated by their linear load-resistance curves (logarithmic scale) and constant compression-to-displacement relationship. The dispersion process for CNT is unnecessary, as smaller agglomerates cause fluctuations in their compression-to-displacement relationship with negligible influence on its electrical performance.

Topology selectivity of a conformationally flexible precursor through selenium doping

Conformational arrangements within nanostructures play a crucial role in shaping the overall configuration and determining the properties, for example in covalent/metal organic frameworks. In on-surface synthesis, conformational diversity often leads to uncontrollable or disordered structures. Therefore, the exploration of controlling and directing the conformational arrangements is significant in achieving desired nanoarchitectures. Herein, a conformationally flexible precursor 2,4,6-tris(3-bromophenyl)−1,3,5-triazine is employed, and a random phase consisting of C3h and Cs conformers is firstly obtained after deposition of the precursor on Cu(111) at room temperature to 365 K. At low coverage (0.01 ML) selenium doping, we achieve the selectivity of the C3h conformer and improve the nanopore structural homogeneity. The ordered two-dimensional metal organic nanostructure can be fulfilled by selenium doping from room temperature to 365 K. The formation of the conformationally flexible precursor on Cu(111) is explored through the combination of high-resolution scanning tunneling microscopy and non-contact atomic force microscopy. The regulation of energy diagrams in the absence or presence of the Se atom is revealed by density functional theory calculations. These results can enrich the on-surface synthesis toolbox of conformationally flexible precursors, for the design of complex nanoarchitectures, and for future development of engineered nanomaterials.

Weyl Node-Participated Magnetoresistance and Nonreciprocal Transport in Two-Dimensional Tellurene Nanostructures

Weyl Node-Participated Magnetoresistance and Nonreciprocal Transport in Two-Dimensional Tellurene Nanostructures

One-time mass production of AlN nanosheets: Synergistic effect of high-energy shear and effective collision in a sanding mill

Aluminum nitride (AlN) has attracted huge attention in new energy vehicle, communication equipment fields, due to the high-thermal conductivity and reliable insulating ability. One of the most crucial factors is the preparation of high-performance AlN powders, and more significantly, the two-dimensional nanostructure would change the phonon vibration mode and transport process, bringing in the novel heat conduction and electricity properties. In this paper, kilogram of two-dimensional aluminum nitride nanosheets (AlNNS) with thicknesses around 30 nm and particle sizes around 400 nm were prepared by a new strategy for the nano sanding process, in which they still keep high purity (impurity content ppm grade) without further purification. Furthermore, the technological parameters of the sanding time and line speed are found as the key factors, that would affect the transformation process from hexagonal AlN into super-thin AlNNS. The morphology of the nanosheets is more complete at the line speed of 8 m/s. In addition, AlNNS have an increase of 7% in thermal conductivity (at 50 °C) compared to that of raw powders. Moreover, AlNNS have stronger sintering activity due to the larger specific surface area, in which show an increase of 16.8% in shrinkage. Therefore, AlNNS would represent excellent physical properties more than thermal conductivity, providing a new dimension research in high-thermal conductivity ceramics. Last but not least, nano sanding strategy as a purely physical process, avoids the subsequent chemical purification process, and has the advantages of simple and efficient, low energy consumption and environmental protection.

A hybrid MLP-CNN model based on positional encoding for daytime radiative cooler

Radiative cooling is a groundbreaking technology for sustainable temperature regulation to combat global warming and the urban heat island effect. Traditional optimization algorithms for cooling system structures are often brute-force and even limited to local optimal solutions. Here, we propose a joint simulation method based on a multilayer perceptron (MLP) and a convolutional neural network (CNN) with position encoding (PE), namely the hybrid MLP-CNN model with PE. This method can significantly reduce simulation time, avoid getting trapped in local optima, and accurately predict the optical response and radiative cooling power of the structure. Applying PE enables the MLP model to learn the relationship between structural parameters and optical response more quickly and effectively, reducing loss during training and more minor root mean square error (RMSE) and mean relative error (MRE) during testing. In addition, the residual network can reduce the problem of overfitting in the network. Compared to using only an MLP, the hybrid MLP-CNN with PE model can effectively reduce loss and achieve more accurate prediction outputs. The hybrid model is much faster than traditional electromagnetic simulations, taking only 1% of the time, and the model dramatically reduces the time needed to predict the optical response of structures and effectively decreases the cost of designing optical devices. Utilizing this hybrid model not only avoids the potential drawbacks of being limited to suboptimal solutions and significantly reduces the simulation time, but also effectively predicts the optical response of the device. This approach can demonstrate remarkable adaptability in optimizing geometric parameters of various optical apparatuses, including polarization converters, beam splitters, metalens, and other two-dimensional nanostructures.

A study on sensitivity to an embedded nanostructure in a micrometer-channel-length Si MOSFET

Nano-artifact metrics (NAM) is an information security technology that uses a nano-scale random structure as a unique identifier, and is expected to provide secure authentication in the Internet of Things era. For electrical discrimination of the two-dimensional random nanostructure in terms of NAM, we investigated the sensitivity to the nanostructure in a Si MOSFET with micrometer channel length in a simulation and experiment. The device simulation showed that the sensitivity was increased by decreasing the channel length and increasing the height of the nano-convex structures. It also showed that a device with a 10 μm channel length could detect a nano-convex. On the other hand, the fabricated Si MOSFET with a 50 nm height nano-convex showed lower nanostructure sensitivity than that expected in the simulation. A detailed analysis indicated that the degradation of the sensitivity was attributed to fabrication process issues, including the unintentional reduction of the convex size and high source and drain resistance.

Progress in Electronic, Energy, Biomedical and Environmental Applications of Boron Nitride and MoS2 Nanostructures.

In this review, we examine recent progress using boron nitride (BN) and molybdenum disulfide (MoS2) nanostructures for electronic, energy, biomedical, and environmental applications. The scope of coverage includes zero-, one-, and two-dimensional nanostructures such as BN nanosheets, BN nanotubes, BN quantum dots, MoS2 nanosheets, and MoS2 quantum dots. These materials have sizable bandgaps, differentiating them from other metallic nanostructures or small-bandgap materials. We observed two interesting trends: (1) an increase in applications that use heterogeneous materials by combining BN and MoS2 nanostructures with other nanomaterials, and (2) strong research interest in environmental applications. Last, we encourage researchers to study how to remove nanomaterials from air, soil, and water contaminated with nanomaterials. As nanotechnology proceeds into various applications, environmental contamination is inevitable and must be addressed. Otherwise, nanomaterials will go into our food chain much like microplastics.

Access to Advanced Functional Materials through Postmodification of Biomimetic Assemblies via Click Chemistry.

The design, synthesis, and fabrication of functional nanomaterials with specific properties remain a long-standing goal for many scientific fields. The self-assembly of sequence-defined biomimetic synthetic polymers presents a fundamental strategy to explore the chemical space beyond biological systems to create advanced nanomaterials. Moreover, subsequent chemical modification of existing nanostructures is a unique approach for accessing increasingly complex nanostructures and introducing functionalities. Of these modifications, covalent conjugation chemistries, such as the click reactions, have been the cornerstone for chemists and materials scientists. Herein, we highlight some recent advances that have successfully employed click chemistries for the postmodification of assembled one-dimensional (1D) and two-dimensional (2D) nanostructures to achieve applications in molecular recognition, mineralization, and optoelectronics. Specifically, biomimetic nanomaterials assembled from sequence-defined macromolecules such as peptides and peptoids are described.

Highly efficient alkaline aqueous MXene-based asymmetric supercapacitors developed by corrugation-like MoS2 and WS2 modified CMX electrodes

The preparation of superior performance supercapacitors to achieve high energy density, fast charge-discharge speed and long cycle stability characteristics has become the focus of attention to realize their potential as practical energy storage devices. In this paper, a cross-linking CNTs@MXene (CMX) architecture is selected as the negative electrode to increase the contact area with electrolyte, and corrugation-like morphologies MoS2 and WS2 nanoparticles modified CMX (Mo/W-CMX) two-dimensional nanostructure as the positive electrode to provide multiple ion diffusion through its channels structure, which presents good electrochemical performance with high specific capacitance and high energy density in 1 M KOH alkaline electrolyte. CNTs introduced into MXene interface by bridges can effectively impede the re-stacking of MXene, meanwhile, CMX as a matrix can also alleviate the properties degradation caused by the agglomeration and volume strain for sulfides. Benefiting from the facilitate accessibility of ions and high ability of electron transfer, the prepared Mo/W-CMX electrode exhibits a dramatic specific capacitance of 1160 F g−1 at 1 A g−1 and excellent capacitance retention of 88.67% at 25 A g−1 after 10,000 cycles. Meanwhile, the assembled asymmetric supercapacitor (Mo/W-CMX // CMX) presents an ultrahigh energy density of 28.1 Wh kg−1 at the power density of 697.3 W kg−1 and maintains 81.25% cycle stability at 15 A g−1 for 10,000 charge-discharge cycles. It is essential to highlight that the superior performance fabricated asymmetric supercapacitor holds a wide application prospect and very competitive energy-storage values in the upgrading of new high-performance devices.

Engineering large nanoporous networks with size and shape selected by appropriate precursors

Large domains of two-dimensional supramolecular porous nanostructures are interesting for various applications from electronics to biology. Here, we investigate the formation of Cu-coordinated networks on Cu(111) using scanning tunneling microscopy and density functional theory (DFT). We consider two molecules with three pyridyl end groups connected to a central benzene ring by either one or two phenyl groups, namely 1,3,5-tris[4-(pyridin)phenyl]benzene (TPyPB) and 1,3,5-tris[4-(pyridin)-[1,1’-biphenyl]benzene (TPyPPB), respectively. Upon deposition of TPyPB at room temperature, a honeycomb nanostructure forms, which is stabilized by Cu adatoms, as previously seen. Upon deposition at 400 K, the growth dynamics change, and molecules become trapped in the hexagonal pores. In contrast, deposition of TPyPPB at room temperature leads to vitreous structures, which rearrange at 400 K forming a low-defect and extended ordered honeycomb phase, which is also stabilized only in the presence of Cu adatoms. The DFT calculations for both honeycomb phases show an impressive agreement with the experimental results, considering the size of such structures. After annealing at 420 K, a complex flower-like structure composed of a mix of two- and three-fold coordinated Cu centers emerges. Further annealing to above 420 K leads to another new phase composed of a high molecular density motif, the so-called diamond phase.

Exploring the sensitivity of pristine and Al-doped boron nitride biphenylene nanosheets towards COx (x = 1, 2) gas using density functional theory

Two-dimensional (2D) nanostructures are of great interest for environmental monitoring, industrial safety, and medical diagnostics due to their unique physicochemical properties. Therefore, it is important to design and develop new 2D materials. This research aims to investigate the sensitivity of pristine and Al-doped boron nitride biphenylene (BNBP) nanosheets towards CO/CO2 gas using the density functional theory method. The study provides insightful information regarding the properties of nanosheets, which goes beyond conventional graphene samples containing carbon rings of different sizes that affect their reactivity and sensitivity. The study used the M06-2X functional and the 6-31G(d,p) basis set to perform all calculations, including geometry optimization, vibrational frequency, and thermochemical quantities of interacting species. The results show that Al-doped BNBP nanosheets exhibit higher sensitivity towards CO2 molecules than pristine BNBP nanosheets. Also, Al-BNBP may be used as a selective detector of CO in the presence of CO2 gas molecules. The study's findings suggest that Al-doped BNBP nanosheets could serve as highly sensitive and selective detectors for CO gas, which could be beneficial in environmental monitoring, industrial safety, and medical diagnostics. Further studies can focus on optimizing the design and fabrication of Al-doped BNBP nanosheets for gas sensing applications, including exploring different doping concentrations, functionalization, and device configurations.

Controlled self-assembly of the perylene bisimides into rectangular and ribbon-like nanostructures

Fabricating nanostructures by the perylene bisimides (PBIs) has attracted great interests, but control over the shapes and sizes is still challenge. Herein, two chiral PBIs synthesized by 3,4,9,10-perylene tetracarboxylic dianhydride, D-alanine (or L-alanine) and triethylene glycol monomethyl ether have been developed. A serious of H-aggregated two-dimensional (2D) nanostructures from rectangular nanostructures to ribbon-like nanostructures are self-assembled by the two PBIs through a heating, cooling and aging process in alcoholic solvents and deionized water. The aspect ratios, shapes and sizes of the 2D nanostructures could be controlled by tailoring the dissolving capacity of the solvents. The van der Waals' force and the π-π stacking interaction play key roles in the formation of the 2D nanostructures. The optical properties of the 2D nanostructures are observably influenced by the dissolving capacity of the solvents. The S0-1 vibronic transition of the perylene skeletons is confirmed to generate a strong non-radiative energy transfer in deionized water. The maximum phosphorescence lifetime is greater than 2.2 ms in deionized water. This study will offer a new view to prepare the 2D nanostructures which could be used as sensors and photocatalysts.

Numerical Evaluation of the Elastic Moduli of AlN and GaN Nanosheets.

Two-dimensional (2D) nanostructures of aluminum nitride (AlN) and gallium nitride (GaN), called nanosheets, have a graphene-like atomic arrangement and represent novel materials with important upcoming applications in the fields of flexible electronics, optoelectronics, and strain engineering, among others. Knowledge of their mechanical behavior is key to the correct design and enhanced functioning of advanced 2D devices and systems based on aluminum nitride and gallium nitride nanosheets. With this background, the surface Young's and shear moduli of AlN and GaN nanosheets over a wide range of aspect ratios were assessed using the nanoscale continuum model (NCM), also known as the molecular structural mechanics (MSM) approach. The NCM/MSM approach uses elastic beam elements to represent interatomic bonds and allows the elastic moduli of nanosheets to be evaluated in a simple way. The surface Young's and shear moduli calculated in the current study contribute to building a reference for the evaluation of the elastic moduli of AlN and GaN nanosheets using the theoretical method. The results show that an analytical methodology can be used to assess the Young's and shear moduli of aluminum nitride and gallium nitride nanosheets without the need for numerical simulation. An exploratory study was performed to adjust the input parameters of the numerical simulation, which led to good agreement with the results of elastic moduli available in the literature. The limitations of this method are also discussed.

Controlling thermal emission with metasurfaces and its applications

Abstract Thermal emission caused by the thermal motion of the charged particles is commonly broadband, un-polarized, and incoherent, like a melting pot of electromagnetic waves, which makes it unsuitable for infrared applications in many cases requiring specific thermal emission properties. Metasurfaces, characterized by two-dimensional subwavelength artificial nanostructures, have been extensively investigated for their flexibility in tuning optical properties, which provide an ideal platform for shaping thermal emission. Recently, remarkable progress was achieved not only in tuning thermal emission in multiple degrees of freedom, such as wavelength, polarization, radiation angle, coherence, and so on but also in applications of compact and integrated optical devices. Here, we review the recent advances in the regulation of thermal emission through metasurfaces and corresponding infrared applications, such as infrared sensing, radiative cooling, and thermophotovoltaic devices.

A Magnetic Reduced Graphene Oxide Nanocomposite: Synthesis, Characterization, and Application for High-Efficiency Detoxification of Aflatoxin B1.

(1) Background: Safety problems associated with aflatoxin B1 (AFB1) contamination have always been a major threat to human health. Removing AFB1 through adsorption is considered an attractive remediation technique. (2) Methods: To produce an adsorbent with a high AFB1 adsorption efficiency, a magnetic reduced graphene oxide composite (Fe3O4@rGO) was synthesized using one-step hydrothermal fabrication. Then, the adsorbent was characterized using a series of techniques, such as SEM, TEM, XRD, FT-IR, VSM, and nitrogen adsorption-desorption analysis. Finally, the effects of this nanocomposite on the nutritional components of treated foods, such as vegetable oil and peanut milk, were also examined. (3) Results: The optimal synthesis conditions for Fe3O4@rGO were determined to be 200 °C for 6 h. The synthesis temperature significantly affected the adsorption properties of the prepared material due to its effect on the layered structure of graphene and the loading of Fe3O4 nanoparticles. The results of various characterizations illustrated that the surface of Fe3O4@rGO had a two-dimensional layered nanostructure with many folds and that Fe3O4 nanoparticles were distributed uniformly on the surface of the composite material. Moreover, the results of isotherm, kinetic, and thermodynamic analyses indicated that the adsorption of AFB1 by Fe3O4@rGO conformed to the Langmuir model, with a maximum adsorption capacity of 82.64 mg·g-1; the rapid and efficient adsorption of AFB1 occurred mainly through chemical adsorption via a spontaneous endothermic process. When applied to treat vegetable oil and peanut milk, the prepared material minimized the loss of nutrients and thus preserved food quality. (4) Conclusions: The above findings reveal a promising adsorbent, Fe3O4@rGO, with favorable properties for AFB1 adsorption and potential for food safety applications.

Penetration and spreading of graphene oxide ink in rice paper enabling its unique expressiveness in Chinese paintings

Abstract In Chinese paintings, the marriage of rice paper and ink is the soul of this art. Ink possesses a highly distinctive “color” expressiveness. By employing ink, various shades of black and diverse color effects can be portrayed, making the image more rich, vibrant, and three-dimensional on a rice paper. However, when used in traditional ink wash painting, the flow and penetration of conventional ink is difficult to control, and its carbon black particles make it a challenge to achieve multiple transparent gradients. Considering the water solubility and two-dimensional nanostructure of graphene oxide (GO), the authors of this paper has developed and proposed the use of water-based GO ink for Chinese ink wash painting, aiming to endow it with new aesthetic forms and unique expressive potentials.

Self-assembled π-conjugated chromophores: preparation of one- and two-dimensional nanostructures and their use in photocatalysis.

Photocatalytic systems have attracted research interest as a clean approach to generate energy from abundant sunlight. In this context, developing efficient and robust photocatalytic structures is crucial. Recently, self-assembled organic chromophores have entered the stage as alternatives to both molecular systems and (in)organic semiconductors. Nanostructures made of self-assembled π-conjugated dyes offer, on the one hand, molecular customizability to tune their optoelectronic properties and activities and on the other hand, provide benefits from heterogeneous catalysis that include ease of separation, recyclability and improved photophysical properties. In this contribution, we present recent achievements in constructing supramolecular photocatalytic systems made of chromophores for applications in water splitting, H2O2 evolution, CO2 reduction, or environmental remediation. We discuss strategies that can be used to prepare ordered photocatalytic systems with an emphasis on the effect of packing between the dyes and the resulting photocatalytic activity. We further showcase supramolecular strategies that allow interfacing the organic nanostructures with co-catalysts, molecules, polymers, and (in)organic materials. The principles discussed here are the foundation for the utilization of these self-assembled materials in photocatalysis.