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MoS2 is widely used in many fields including spin-valleytronics, logic transistors, light emitting devices, clean energy and biology. However, controllable synthesis of two-dimensional MoS2 sheets remains a great challenge. We report the formation of round-shaped monolayer MoS2 domains with a tunable size and the shape transformation from triangle...
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... 2D materials and Si Nanocomposites: Since the first realization of graphene in 2004 [367], various graphene like 2D materials such as transition metal dichalcogenides, black phosphorus, metallic sulfide compounds and etc have been explored for several applications including antibacterial [79,368] 2D material systems exhibit interesting energy band structure, photo-electronics, electrical and magnetic properties which may provide new opportunities for advanced medical applications. [369][370][371] Notably, some 2D materials also found to be lethal to microorganism and fungi. [79] These materials possess several advantages such as ultra large specific area for drug loading, chemically and physically neutralizing bacteria, high density of active site and outstanding photothermal/photocatalyst properties compared to other materials and their topology [372,373]. ...
Silicon (Si) nanomaterials are extensively explored to address the multidrug resistance bacteria/diseases and to enable developments of novel and innovative approaches for next-generation highly efficient, cost-effective, and reliable multifunctional biomedical tools. This article reviews the contemporary developments in the utilization of Si nanostructures (Si-NSs) and nanocomposites for antibacterial surfaces and theranostic agents as powerful instruments to tackle pathogenic bacteria and diseases related to them. Realization of nature-inspired antibacterial surfaces, photoresponsive smart antibacterial surfaces, and selective functionality of Si-NSs has been discussed by biomedical imaging and drug delivery applications of Si-NSs. Photoresponsive Si nanocomposite systems enable in-situ non-invasive process monitoring utilizing surface-enhanced Raman spectroscopy (SERS) or photothermal imaging phenomenon is also addressed. Finally, crucial challenges and several research trends of implementing Si-NSs and their hybrid systems as multifunctional platforms for advanced biomedical tools and their clinical translation are highlighted.
... Exposure to many active sites by exfoliation in multiple layers or a single layer using ultrasonic Liquidphase exfoliation (LPE) can easily be done [34] . For example, bulk MoSx obtained by thermal decomposition of (NH4)2MoS4 can be exfoliated in a suitable polar micromolecular solvent into monolayers or individual nanoflakes using ultrasonic radiation [62,63] . This process creates a force greater than the Van der Waals attraction between the layers, causing the bulk structure to crumble and be sliced into single-layer nanotubes that can easily be dispersed in polar micromolecular solvents. ...
... Thus, it is crucial to investigate materials with neuromorphic behaviors and potential compatibility with Si technology, as well as to elucidate their underlying mechanism for further SNN applications. Recently, two-dimensional (2D) materials have come to the fore in materials science research, which demonstrate their superior fine-tuning electronic properties enabling the feasible device structure design [21][22][23][24][25][26][27][28][29] . Silicon nanosheets (SiNSs) are 2D thin films of Si which have different crystalline structures than bulk Si, while are potentially compatible with well-developed Si technology. ...
Silicon is vital for its high abundance, vast production, and perfect compatibility with the well-established CMOS processing industry. Recently, artificially stacked layered 2D structures have gained tremendous attention via fine-tuning properties for electronic devices. This article presents neuromorphic devices based on silicon nanosheets that are chemically exfoliated and surface-modified, enabling self-assembly into hierarchical stacking structures. The device functionality can be switched between a unipolar memristor and a feasibly reset-able synaptic device. The memory function of the device is based on the charge storage in the partially oxidized SiNS stacks followed by the discharge activated by the electric field at the Au-Si Schottky interface, as verified in both experimental and theoretical means. This work further inspired elegant neuromorphic computation models for digit recognition and noise filtration. Ultimately, it brings silicon - the most established semiconductor - back to the forefront for next-generation computations.
... Next, growth occurs during the temperature ramp down process on the surface of Cu in contact with sapphire, and a mix of triangular and round crystal edges can be observed as shown in the optical image in figure 1(a). Although the triangular geometry is thermodynamically favorable, the abundance of precursor Cu and high reaction temperature may push to a kinetically controlled rapid growth, leading to some round crystal edges [26,27]. Random, non-uniform distribution of crystals throughout the copper surface suggests saturation via the molten catalyst. ...
Transition metal dichalcogenides (TMDs) are known for their layered structure and tunable functional properties. However, a unified understanding on other transition metal chalcogenides (i.e., M2X) is still lacking. Here, the relatively new class of copper-based chalcogenides Cu2X (X=Te, Se, S) is thoroughly reported. Cu2X are synthesized by an unusual vapor-liquid assisted growth on a Al2O3/Cu/W stack. Liquid copper plays a significant role in synthesizing these layered systems, and sapphire assists with lateral growth and exfoliation. Similar to traditional TMDs, thickness dependent phonon signatures are observed, and high-resolution atomic images reveal the single phase Cu2Te that prefers to grow in lattice-matched layers. Charge transport measurements indicate a metallic nature at room temperature with a transition to a semiconducting nature at low temperatures accompanied by a phase transition, in agreement with band structure calculations. These findings establish a fundamental understanding and thrust Cu2Te as a flexible candidate for wide applications from photovoltaics and sensors to nanoelectronics.
... The stabilization energies of these three edges increase successively because of the increase in kink density [62][63][64]. Because the interfacial interaction between graphene and the Ru(0001) surface is significantly weakened by near-surface Ar nanobubbles, graphene overlayers are quasi-freestanding and display intrinsic properties [20,65]. Ru(0001) surfaces adopt a high catalytic activity for the decomposition of O 2 into O atoms, which provides sufficient etching agents [54]. ...
The synthesis of high-quality ultrathin overlayers is critically dependent on the surface structure of substrates, especially involving the overlayer-substrate interaction. By using in situ surface measurements, we demonstrate that the overlayer-substrate interaction can be tuned by doping near-surface Ar nanobubbles. The interfacial coupling strength significantly decreases with near-surface Ar nanobubbles, accompanying by an “anisotropic to isotropic” growth transformation. On the substrate containing near-surface Ar, the growth front crosses entire surface atomic steps in both uphill and downhill directions with no difference, and thus, the morphology of the two-dimensional (2D) overlayer exhibits a round-shape. Especially, the round-shaped 2D overlayers coalesce seamlessly with a growth acceleration in the approaching direction, which is barely observed in the synthesis of 2D materials. This can be attributed to the immigration lifetime and diffusion rate of growth species, which depends on the overlayer-substrate interaction and the surface catalysis. Furthermore, the “round to hexagon” morphological transition is achieved by etching-regrowth, revealing the inherent growth kinetics under quasi-freestanding conditions. These findings provide a novel promising way to modulate the growth, coalescence, and etching dynamics of 2D materials on solid surfaces by adjusting the strength of overlayer-substrate interaction, which contributes to optimization of large-scale production of 2D material crystals.
... This process creates a force greater than the Van der Waals attraction between the layers, causing the bulk structure to crumble and be sliced into single-layer nanotubes that can easily be dispersed in polar micromolecular solvents. The criteria for selecting a surfactant or solvent are based on the similarity between the liquid's surface tension and the absorbent surface's free energy [54]. LPE results in high exfoliation success on materials with low surface energy and can prevent agglomeration of MS NSs [55] in contrast to mechanical exfoliation, where much of the resulting MSs are multilayer structures, which still blocked the efficient active sites in comparison with that in the well-dispersed single-layer structure [3]. ...
... Precursors (usually molybdenum trioxide (MoO 3 ) or Mo metal and organic sulfides, respectively) containing Mo and S decompose, and the Mo and S atoms then combine via chemical reactions to form a MoS 2 layer on the substrate, usually at temperatures between 700 and 1000 • C, in the Chemical Vapor Deposition (CVD) process [12,54]. However, the temperature range is reduced to 150-300 • C with a modified version of CVD, called the Plasma Enhanced CVD (PECVD) technique, which allows the deposition of NMs on plastic and flexible substrates [75]. ...
Heavy metals pollution of aqueous solutions generates considerable concerns as they adversely impact the environment and health of humans. Among the remediation technologies, adsorption with metal sulfide nanomaterials has proven to be a promising strategy due to their cost-effective, environmentally friendly, surface modulational, and amenable properties. Their excellent adsorption characteristics are attributed to the inherently exposed sulfur atoms that interact with heavy metals through various processes. This work presents a comprehensive overview of the sequestration of heavy metals from water using metal sulfide nanomaterials. The common methods of synthesis, the structures, and the supports for metal sulfide nano-adsorbents are accentuated. The adsorption mechanisms and governing conditions and parameters are stressed. Practical heavy metal remediation application in aqueous media using metal sulfide nanomaterials is highlighted, and the existing research gaps are underscored.
... Such a growth process belongs to the thermodynamic control. 59,60 To further probe this growth process, we conducted a series of atomic force microscopy (AFM) observations. Figure S3a shows an AFM image of the γ-Fe 2 O 3 nanoflakes at the initial stage, where three branches grow in different directions by tiny triangular sheets. ...
... Such transformation reveals that the growth undergoes a transition from thermodynamically to kinetically dominated control, which successfully realizes morphology-tunable synthesis. 59,70 Moreover, the γ-Fe 2 O 3 nanoflakes are found to be air-stable, which can be stored in air for 3 months ( Figure S6). ...
... A wide variety of ex situ studies has investigated the role of growth parameters (pressure, temperature, precursor vapor concentration) [2,[25][26][27][28][29] and has postulated different nucleation and growth mechanisms. [30][31][32] More detailed understanding has been provided by recent in situ studies that have investigated chalcogenide growth dynamics in real time. ...
Layered metal chalcogenide materials, such as MoS 2 and Bi 2 Te 3 , have found important applications as 2D materials in emerging electronic devices. To create nanoscale layered chalcogenide materials with precisely controlled structures and properties, it is critical to understand and control how they evolve and transform under various conditions. This Minireview presents an overview of recent research focused on using in situ characterization to understand the atomic‐scale details of transformations during growth, under exposure to reactive chemical and thermal environments, and on interfacing with other materials. These efforts have used techniques including in situ transmission electron microscopy (TEM), X‐ray spectroscopy, and optical methods to understand nanoscale transformations. These in situ studies have provided a substantially improved understanding of transformation mechanisms in layered chalcogenide materials, which is an important step toward use of these interesting materials in a variety of electronic and electrochemical devices.
... The temperature of Se zone can change the Pd/Se vapor concentration ratio in the growth, resulting in various atomic structure of edge and eventually impacting the domain shape. This phenomenon has been observed in other 2D materials [40,[45][46][47][48][49]. ...
Palladium diselenide (PdSe2), a stable layered material with pentagonal structure, has attracted extensive interest due to its excellent electrical and optoelectronic performance. Here, we report a reliable process to synthesize PdSe2 via chemical vapor deposition (CVD) method. Through systematic regulation of temperature in the growth process, we can tune the thickness, size, nucleation density and morphology of PdSe2 nanosheets. Field-effect transistors based on PdSe2 nanosheets exhibit n-type behavior and present a high electron mobility of 105 cm2·V−1·s−1. The electrical property of the devices after 6 months keeping in the air show little change, implying outstanding air-stability of PdSe2. In addition, PdSe2 near-infrared photodetector shows a photoresponsivity of 660 A·W−1 under 914 nm laser. These performances are better than those of most CVD-grown 2D materials, making ultrathin PdSe2 a highly qualified candidate material for next-generation optoelectronic applications.
... Such a growth regime is achieved in the presence of a relatively low reactant concentration of Mo and S atoms. In this study, such a thermodynamic controlled growth regime occurred before the temperature reached 730 °C [72]. ...
