Low-dimensional Nanomaterials Research Articles

The Formation and Transformation of Low-Dimensional Carbon Nanomaterials by Electron Irradiation.

Low-dimensional materials based on graphene or graphite show a large variety of phenomena when they are subjected to irradiation with energetic electrons. Since the 1990s, electron microscopy studies, where a certain irradiation dose is unavoidable, have witnessed unexpected structural transformations of graphitic nanoparticles. It is recognized that electron irradiation is not only detrimental but also bears considerable potential in the formation of new graphitic structures. With the availability of aberration-corrected electron microscopes and the discovery of techniques to produce monolayers of graphene, detailed insight into the atomic processes occurring during electron irradiation became possible. Threshold energies for atom displacements are determined and models of different types of lattice vacancies are confirmed experimentally. However, experimental evidence for the configuration of interstitial atoms in graphite or adatoms on graphene remained indirect, and the understanding of defect dynamics still depends on theoretical concepts. This article reviews irradiation phenomena in graphene- or graphite-based nanomaterials from the scale of single atoms to tens of nanometers. Observations from the 1990s can now be explained on the basis of new results. The evolution of the understanding during three decades of research is presented, and the remaining problems are pointed out.

Controlling On-Surface Photoactivity: The Impact of π-Conjugation in Anhydride-Functionalized Molecules on a Semiconductor Surface.

On-surface synthesis has become a prominent method for growing low-dimensional carbon-based nanomaterials on metal surfaces. However, the necessity of decoupling organic nanostructures from metal substrates to exploit their properties requires either transfer methods or new strategies to perform reactions directly on inert surfaces. The use of on-surface light-induced reactions directly on semiconductor/insulating surfaces represents an alternative approach to address these challenges. Here, exploring the photochemical activity of different organic molecules on a SnSe semiconductor surface under ultra-high vacuum, we present a novel on-surface light-induced reaction. The selective photodissociation of the anhydride group is observed, releasing CO and CO2. Moreover, we rationalize the relationship between the photochemical activity and the π-conjugation of the molecular core. The different experimental behaviour of two model anhydrides was elucidated by theoretical calculations, showing how the molecular structure influences the distribution of the excited states. Our findings open new pathways for on-surface synthesis directly on technologically relevant substrates.

Superatom-assembled boranes, carboranes, and low-dimensional boron nanomaterials based on aromatic icosahedral B12 and C2B10

Superatom-assembled boranes, carboranes, and low-dimensional boron nanomaterials based on aromatic icosahedral B12 and C2B10

Synthesis of low dimensional nanomaterials by pulsed laser ablation in liquid

With the increasing application of functional nanomaterials in numerous fields, considerable effort has been devoted to exploring simple and efficient methods for their synthesis. Pulsed laser ablation in liquid (PLAL) is one such novel technique for producing colloidal nanomaterials. It is simple to setup, easy to operate, and can be carried out at room temperature and under atmosphere. This method employs a pulsed laser beam to ablate bulk targets or powders within different liquids, thereby creating colloidal nanomaterials. As a result, it holds significant promise for scalable processing. However, most prior research on PLAL has focused on the synthesis of larger spherical nanoparticles, even though low-dimensional nanomaterials, including zero-dimensional quantum dots, one-dimensional nanowires and nanotubes, and two-dimensional nanosheets and nanobelts, find more usage in various applications, such as optoelectronic devices, catalysis, and biomedicine. In the PLAL process, the high-intensity laser pulses not only fragment the illuminated solids to produce nanomaterials but also interact with liquid molecules, generating multiple reactive ions for chemical reactions. Consequently, various low-dimensional nanomaterials can also be generated. This study provides a comprehensive review of low-dimensional nanomaterials synthesized via PLAL, including their formation mechanisms and applications.

Low-dimensional antimicrobial nanomaterials in anti-infection treatment and wound healing

Low-dimensional antimicrobial nanomaterials in anti-infection treatment and wound healing

Microheater Chips with Carbon Nanotube Resistors.

The specific and excellent properties of the low-dimensional nanomaterials have made them promising building blocks to be integrated into microelectromechanical systems with high performances. Here, we present a new microheater chip for in situ TEM, in which a cross-stacked superaligned carbon nanotube (CNT) film resistor is located on a suspended SiNx membrane via van der Waals (vdW) interactions. The CNT microheater has a fast high-temperature response and low power consumption, thanks to the micro/nanostructure of the CNT materials. Moreover, the membrane bulging amplitude is significantly reduced to only ∼100 nm at 800 °C for the vdW interaction between the CNTs and the SiNx membrane. An in situ observation of the Sn melting process is successfully conducted with the assistance of a customized flexible temperature control system. The uniform wafer-scaled CNT films enable a high level of consistency and cost-effective mass production of such chips. The as-developed in situ chips, as well as the related techniques, hold great promise in nanoscience, materials science, and electrochemistry.

Generalized strategy to construct multifunctional inorganic nanomaterials/silicone rubber composite aerogels: Taking CNTs as an example for smart sensing

The structure and characteristics of carbon nanotubes (CNTs) aerogel (CNTA) make it capable of only compression, lacking the necessary toughness, flexural, and tensile properties. These limitations restrict its application. To overcome these obstacles, this study employed an interface modification and the Pickering emulsion strategy, using water-soluble CNTs as the continuous phase while silicone rubber (SR) as the dispersed phase, to successfully achieve the organic–inorganic combination and prepare the SR-CNTs composite aerogel (SRC). Benefiting from the synergistic effect of the “soft-hard” phase combination of SR (soft) and CNTs (hard), SRC exhibited good conductivity (1.23 S/m) and superior multi-axial mechanical properties such as compression (90 %), bending (360°), twisting (360°), and stretching (110 %), making it broad prospects in the field of flexible sensing. Importantly, the strategy employed in this study offers an innovative approach for a transition from low-dimensional nanomaterials to three-dimensional macroscopic overall structures. This approach effectively addresses common issues in traditional aerogel materials, such as mechanical brittleness and structural instability, which also allows for functionalization and customization, opening up new possibilities for the research and application of high-performance aerogels.

Biphase Pd Nanosheets with Atomic-Hybrid RhOx/Pd Amorphous Skins Disentangle the Activity-Stability Trade-Off in Oxygen Reduction Reaction.

The activity-stability trade-off relationship of oxygen reduction reaction (ORR) is a tricky issue that strikes the electrocatalyst population and hinders the widespread application of fuel cells. Here neoteric biphase Pd nanosheets that are structured with ultrathin two-dimensional crystalline Pd inner cores and ≈1 nm thin atomic-hybrid RhOx/Pd amorphous skins, named c/a-Pd@PdRh NSs, for disentangling this trade-off dilemma for alkaline ORR are developed. The superthin amorphous skins significantly amplify the quantity of flexibly low-coordinated atoms for electrocatalysis. An in situ selected oxidation of the top-surface Rh dopants creates atomically hybrid RhOx/Pd disorder surfaces. Detailed energy spectra and theoretical simulation confirm that these RhOx/Pd interfaces can arouse a surface charge redistribution, causing significant electron deficiency and lowered d-band center for surface Pd. Meanwhile, anticorrosive Rh/RhOx species can thermodynamically passivate the neighboring Pd atoms from oxidative dissolution. Thanks to these amplified interfacial effects, the biphase c/a-Pd@PdRh NSs simultaneously exhibit a superhigh ORR activity (5.92 A mg-1, 22.8 times that of Pt/C) and an outstanding long-lasting stability after 100k cycles of accelerated durability test, showcasing unprecedented electrocatalysts for breaking the activity-stability trade-off relationship of ORR. This work paves a bran-new strategy for designing high-performance electrocatalysts through creating modulated amorphous skins on low-dimensional nanomaterials.

Atomic Scale Structure of Self-Assembled Lipidated Peptide Nanomaterials.

β-Peptides have great potential as novel biomaterials and therapeutic agents, due to their uniqueability to self-assemble into low dimensional nanostructures,and their resistance to enzymatic degradationin vivo. However, the self-assembly mechanisms of β-peptides, which possess increased flexibility due to the extra backbone methylene groups present within the constituent β-amino acids, are not well understood due to inherent difficulties of observing their bottom-up growth pathway experimentally. A computational approach is presented for the bottom-up modelling of the self-assembledlipidated β3-peptides, from monomers, to oligomers, to supramolecular low-dimensional nanostructures, in all-atom detail. The approach is applied to elucidate the self-assembly mechanisms of recently discovered, distinct structural morphologies of low dimensional nanomaterials, assembled from lipidated β3-peptide monomers. The resultant structures of the nanobelts and the twisted fibrils are stable throughout subsequent unrestrained all-atom molecular dynamics simulations, and these assemblies display good agreement with the structural features obtained from X-ray fiber diffraction and atomic force microscopy data.This is the first reported, fully-atomistic model of a lipidated β3-peptide-based nanomaterial, and the computational approach developed here, in combination with experimental fiber diffraction analysis and atomic force microscopy, will be useful in elucidating the atomic scale structure of self-assembled peptide-based and other supramolecular nanomaterials.

Improvement of isopropanol sensing performance by surface sensitization of CdSnO3 nanocubes with CdS quantum dots

Perovskite oxides are promising gas-sensing materials due to the stable chemical properties and suitable energy band structure. Quantum dots are low-dimensional nanomaterials with large specific surface areas and rich active sites, which are beneficial to sensing process. Here, the surface of porous CdSnO3 nanocubes were sensitized with CdS quantum dots via a chemical bath deposition strategy and applied to isopropanol sensor. The novel CdS-modified CdSnO3 porous cubes had a large specific surface area. In addition, DFT calculations show that the adsorption of isopropanol by CdS contributes to the recognition of isopropanol among alcohols by CdS/CdSnO3 composite. Combined with the catalytic action of CdS on the oxidation of isopropanol and the formation of n-n heterojunction between CdSnO3 and CdS, the sensor possessed enhanced performance in isopropanol detection. The response of the CdS/CdSnO3 sensor was 20.12 to 100 ppm isopropanol, which was about three times higher than that of pure CdSnO3. And the sensor also possessed superior selectivity to isopropanol, fast response and recovery speed (5/22 s) and low optimum operating temperature (138 °C). This work has reference significance for the construction and understanding of isopropanol-sensing nanomaterials.

Four-phonon scattering of so-As and improvement of the thermoelectric properties by increasing the buckling height.

In recent years, more and more thermoelectric (TE) materials have been discovered as the research boom of TE materials advances. However, due to the low conversion efficiency, most of the current TE materials cannot meet the commercial demand. The low-dimensional nanomaterials are promising to break the current status quo of low conversion efficiency of TE materials. Here, we predicted a stable two-dimensional TE material, namely so-As, based on density functional theory. The so-As has an ultra-low lattice thermal conductivity,κl= 1.829 W m-1K-1at 300 K, and when the temperature rises to 700 K theκlis only 0.788 W m-1K-1. This might be caused by the strong anharmonic interaction among the so-As phonon and the out-of-plane vibration of the low-frequency acoustic modes. Moreover, the maximumZTvalue of thep-type so-As is 0.18 at room temperature (0.45 at 700 K), while that of then-type can even reach 0.75 at 700 K. In addition, we have also studied the difference between the four- and three-phonon scattering rates. The increase of scattering channels leads to the ultra-lowκl, which is only 3.33 × 10-4W m-1K-1at room temperature, showing an almost adiabatic property. Finally, we adjust the TE properties of so-As by changing the buckling height. With the buckling height is increased by 2%, the scattering rate of so-As is extremely high. WhenTis 700 K, the maximumZTof then-type is 0.94 (p-type can also reach 0.7), which is 25% higher than the pristine one. Our work reveals the impact of buckling height on the TE figure of merit, which provides a direction for future search and regulation of the highZTTE materials.

Emerging optoelectronic artificial synapses and memristors based on low-dimensional nanomaterials

The Von Neumann architecture has been the foundation of modern computing systems. Still, its limitations in processing large amounts of data and parallel processing have become more apparent as computing requirements increase. Neuromorphic computing, inspired by the architecture of the human brain, has emerged as a promising solution for developing next-generation computing and memory devices with unprecedented computational power and significantly lower energy consumption. In particular, the development of optoelectronic artificial synaptic devices has made significant progress toward emulating the functionality of biological synapses in the brain. Among them, the potential to mimic the function of the biological eye also paves the way for advancements in robot vision and artificial intelligence. This review focuses on the emerging field of optoelectronic artificial synapses and memristors based on low-dimensional nanomaterials. The unique photoelectric properties of these materials make them ideal for use in neuromorphic and optoelectronic storage devices, with advantages including high carrier mobility, size-tunable optical properties, and low resistor–capacitor circuit delay. The working mechanisms, device structure designs, and applications of these devices are also summarized to achieve truly sense-storage-computer integrated optoelectronic artificial synapses.

Inorganic Hydrogel Based on Low-Dimensional Nanomaterials.

Composed of three-dimensional (3D) nanoscale inorganic bones and up to 99% water, inorganic hydrogels have attracted much attention and undergone significant growth in recent years. The basic units of inorganic hydrogels could be metal nanoparticles, metal nanowires, SiO2 nanowires, graphene nanosheets, and MXene nanosheets, which are then assembled into the special porous structures by the sol-gel process or gelation via either covalent or noncovalent interactions. The high electrical and thermal conductivity, resistance to corrosion, stability across various temperatures, and high surface area make them promising candidates for diverse applications, such as energy storage, catalysis, adsorption, sensing, and solar steam generation. Besides, some interesting derivatives, such as inorganic aerogels and xerogels, can be produced through further processing, diversifying their functionalities and application domains greatly. In this context, we primarily provide a comprehensive overview of the current status of inorganic hydrogels and their derivatives, including the structures of inorganic hydrogels with various compositions, their gelation mechanisms, and their exceptional practical performance in fields related to energy and environmental applications.

Performance potential of transistors based on tellurium nanowire arrays: A quantum transport study

Low-dimensional nanomaterials provide promising material platforms for aggressively scaled transistor technologies. We assess the performance potential of transistors based on an array of Tellurium nanowires (TNWs), by parameterizing a machine-learning (ML) tight-binding model with quantum transport device simulations. It has been shown that a transistor based on a parallel array of carbon nanotubes (CNTs) can have excellent on-state performance, but the small bandgap limits the transistor scalability and off-state performance. Our results indicate that compared to the CNT array FETs, the TNW array FETs have significantly suppressed ambipolar transport and improved subthreshold characteristics. The TNW array FET has the potential to achieve a near-ideal subthreshold swing (SS) close to 60 mV/dec, a very large on–off ratio (>109), and low source-drain leakage current at a 10 nm-scale channel length, due to its excellent gate electrostatics with a gate-all-around (GAA) structure, larger band gap and reduced quantum–mechanical tunneling. The TNW array FET also shows excellent scalability with a SS below 100 mV/dec when the channel length is further scaled down to 5 nm. Its larger bandgap and heavier effective mass significantly reduce quantum tunneling. This mechanism contributes to improved subthreshold and lower leakage but also highlights the need to develop low Schottky barrier contacts for TNWs.

Materials-Driven Soft Wearable Bioelectronics for Connected Healthcare.

In the era of Internet-of-things, many things can stay connected; however, biological systems, including those necessary for human health, remain unable to stay connected to the global Internet due to the lack of soft conformal biosensors. The fundamental challenge lies in the fact that electronics and biology are distinct and incompatible, as they are based on different materials via different functioning principles. In particular, the human body is soft and curvilinear, yet electronics are typically rigid and planar. Recent advances in materials and materials design have generated tremendous opportunities to design soft wearable bioelectronics, which may bridge the gap, enabling the ultimate dream of connected healthcare for anyone, anytime, and anywhere. We begin with a review of the historical development of healthcare, indicating the significant trend of connected healthcare. This is followed by the focal point of discussion about new materials and materials design, particularly low-dimensional nanomaterials. We summarize material types and their attributes for designing soft bioelectronic sensors; we also cover their synthesis and fabrication methods, including top-down, bottom-up, and their combined approaches. Next, we discuss the wearable energy challenges and progress made to date. In addition to front-end wearable devices, we also describe back-end machine learning algorithms, artificial intelligence, telecommunication, and software. Afterward, we describe the integration of soft wearable bioelectronic systems which have been applied in various testbeds in real-world settings, including laboratories that are preclinical and clinical environments. Finally, we narrate the remaining challenges and opportunities in conjunction with our perspectives.

Patterned growth of two-dimensional atomic layer semiconductors.

Transition metal dichalcogenides (TMDCs), which are representative of two-dimensional (2D) semiconductors, have attracted tremendous attention over the last two decades. TMDCs are regarded as potential candidates in modern nano- and optoelectronic applications due to their unique crystal structures and outstanding electronic and optoelectronic properties. For practical use, 2D semiconductors need to be fabricated with diverse morphologies for integration into electronic devices and to perform different functionalities. Controlled patterning synthesis with programmable geometries is therefore highly desired. We review state-of-the-art strategies for the patterned growth of atomic layer TMDCs and their heterostructures, including additive manufacturing and subtractive manufacturing for patterning single TMDC materials and the introduction of other low-dimensional nanomaterials as growth templates or hetero-atoms for element conversion in patterning TMDC heterostructures. The optoelectronic and electronic applications of the as-grown monolayer TMDC patterns are introduced. Future challenges and the prospects for the patterned growth of 2D semiconductors are discussed based on present achievements.

Recent advanced strategies for bimetallenes toward electrocatalytic energy conversion reactions.

Designing low-dimensional nanomaterials is vital to address the energy and environmental crisis by means of electrocatalytic conversion reactions. Bimetallenes, as an emerging class of 2D materials, present promise for electrocatalytic conversion reactions. By leveraging atomically thin layers, bimetallenes present unsaturated surface coordination, high specific surface area and high conductivity, which are all indispensable features for heterogeneous electrochemical reactions. However, the intrinsic activity and stability of bimetallenes needs to be improved further for bimetallene electrocatalysts, due to the higher demands of practical applications. Recently, many strategies have been developed to optimize the chemical or electronic structure to accommodate transfer of reactants, adsorption or desorption of intermediates, and dissociation of products. Considering that most such work focuses on adjusting the structure, this review offers in-depth insight into recent representative strategies for optimizing bimetallene electrocatalysts, mainly including alloying, strain effects, ligand effects, defects and heteroatom doping. Moreover, by summarizing the performance of bimetallenes optimized using various strategies, we provide a means to understand structure-property relationships. In addition, future prospects and challenges are discussed for further development of bimetallene electrocatalysts.

Low-dimensional nanomaterial-enabled efficient and stable perovskite light-emitting diodes: recent progress and challenges

This article reviews the research progress and challenges of multi-functional low-dimensional nanomaterials in advanced perovskite light-emitting diodes.

Review of Low-Dimensional Nanomaterials for Blue-Light Emission

Review of Low-Dimensional Nanomaterials for Blue-Light Emission

Nonequilibrium thermal rectification at the junction of harmonic chains.

A thermal diode or rectifier is a system that transmits heat or energy in one direction better than in the opposite direction. We investigate the influence of the distribution of energy among wave numbers on the diode effect for the junction of two dissimilar harmonic chains. An analytical expression for the diode coefficient, characterizing the difference between heat fluxes through the junction in two directions, is derived. It is shown that the diode coefficient depends on the distribution of energy among wave numbers. For an equilibrium energy distribution, the diode effect is absent, while for non-equilibrium energy distributions the diode effect is observed even though the system is harmonic. We show that the diode effect can be maximized by varying the energy distribution and relative position of spectra of the two harmonic chains. Conditions are formulated under which the system acts as an ideal thermal rectifier, i.e., transmits heat only in one direction. The results obtained are important for understanding the heat transfer in heterogeneous low-dimensional nanomaterials.