File Name: nanomaterials synthesis properties and applications .zip
Metrics details. In recent years, 2-dimensional 2D materials such as graphene and h-BN have been spotlighted, because of their unique properties and high potential applicability. Among these 2D materials, transition metal dichalcogenides TMDs have attracted a lot of attention due to their unusual electrical, optical, and mechanical properties.
Metrics details. In recent years, 2-dimensional 2D materials such as graphene and h-BN have been spotlighted, because of their unique properties and high potential applicability. Among these 2D materials, transition metal dichalcogenides TMDs have attracted a lot of attention due to their unusual electrical, optical, and mechanical properties. Also, TMDs have virtually unlimited potential in various fields, including electronic, optoelectronic, sensing, and energy storage applications. For these various applications, there are many methods for sample preparation, such as the mechanical, liquid exfoliation and chemical vapor deposition techniques.
In this review, we introduce the properties, preparation methods and various applications of TMDs materials. In the last few years, a great deal of attention has been dedicated to layered two-dimensional 2D materials, such as graphene and hexagonal boron nitride h-BN , owing to their potential applications in various fields [ 1 - 5 ]. The great potential of graphene has stimulated a lot of interest in the exploration of other layered 2D nanomaterials, which can complement the requirements associated with graphene.
It is well known that graphene generally exhibits semi-metallic properties, and, therefore, semiconducting and insulating 2D layered nanomaterials having structural properties akin to graphene are needed in order to integrate them into nano-electronic devices for different applications.
TMDs have received significant attention because they exhibit unique electrical [ 6 , 7 ], optical [ 8 - 15 ], and mechanical [ 16 , 17 ] properties. Layered 2D nanostructures with atomic scale thicknesses may exhibit peculiar and fascinating properties in contrast with those of their bulk parent compounds. Both the experimental and theoretical results have shown that 2D semiconductors have exceptional properties that can result in novel and important breakthroughs in the field of nanomaterials and nanodevices.
Because of these attractive properties, there are many potential applications of TMDs materials, such as electronic devices [ 6 , 18 - 25 ], optoelectronic devices [ 26 - 29 ], gas sensing [ 18 , 30 - 34 ] and energy storage devices [ 35 - 42 ].
The bonding length of the M-X atom lies between 3. There are a number of possible layered structure TMDs materials consist of 16 transition metals and three chalcogen atoms. In the case of Co, Rh, Ir and Ni, only a few layered structures are observed, for example NiS 2 forms an apyrite structure, however NiTe 2 forms layered structure [ 43 ].
Castellanos-Gomez et al. Another experimental work also showed the mechanical properies of suspended MoS 2 nanosheets. Bertolazzi et al. This results show that single-layer MoS 2 could be suitable for a variety of applications, such as reinforcing elements in composites and for the fabrication of flexible electronic devices [ 17 ].
Mechanical propertis of MoS 2. The inset graph shows the same graph on a linear scale [ 16 ]. Acquired force versus z-piezo extension curves for the suspended membrane and the substrate right. The various electronic properties of TMDs arise from the filling of the non-bonding d bands from the group 4 to group 10 species. When the orbitals are partially occupied, the TMDs display metallic properties, whereas when they are fully occupied, they exhibit semiconducting ones.
The influence of the chalcogen atoms on the electronic structure is minor compared with that of the metal atoms, however it is observed that the broadening of the d bands decreases the bandgap by increasing the atomic number of the chalcogen [ 43 ].
The bulk TMDs material has an indirect bandgap according to both the theoretical calculations and experimental results [ 8 - 15 ]. It also shown that the PL intensity of inversely dependent on the number of MoS 2 layers. Especially, single-layer MoS 2 shows very strong PL intensity [ 11 , 13 ]. Lee et al. They clearly observed signal in-plane E 1 2g and out-of-plane A 1g modes for the MoS 2 sample with number of layers varying from 1 to 6. The frequency of E 1 2g decreases and that of A 1g increases with increasing number of MoS 2 layers.
The reason for the opposite direction of the frequency shift is the partially Columbic interaction and possible stacking-induced charge of the intra-layer bonding [ 14 ]. Optical absorption is another important characteristic of TMDs materials and is related to the band structure of these semiconducting layered materials.
Benameur et al. Recently, Li et al. The grayscale image of the R channel shows distinct layers ranging from single-layer to tri-layers of MoS 2 nanohseets. Also, the intensity difference between the MoS 2 nanosheets and SiO 2 can be used to distinguish the number of MoS 2 layers.
The direct identification method is a very simple and non-destructive technique for distinguishing the number of MoS 2 layers and MoS 2 based devices. Optical properties of MoS 2. In , Novoselov et al. This method is typically adopted to prepare single-layer TMDs samples. The single crystal TMDs samples prepared by the mechanical exfoliation method are of good quality, and can be used for studying their basic properties [ 26 , 30 , 46 ] by optical microscopy, atomic force microscopy AFM , scanning tunneling microscopy STM , transmission electron microscopy TEM and so on.
However, the size of the TMDs material prepared by the mechanical exfoliation method is quite small approximately on the tens of microns scale, posing a limitation to real device applications. Mechanical and liquid exfoliation method. The red dotted squares represent the subsequent AFM scan areas [ 45 ].
S indicates SiO 2 substrate [ 45 ]. To exploit the extraordinary potential of these layered materials, large quantities of TMDs nanosheets are required.
To obtain large amounts of single- or few-layer TMDs nanosheets, a solution processing strategy would be more appropriate. The first report on the liquid phase exfoliation of sheets of clay materials in the early s [ 47 ] has inspired many studies into methods of exfoliating sheets of TMDs [ 48 - 52 ]. Seo et al. The resulting single sheets of 2D WS 2 can further assemble together via van der Waals interactions to form nanosheets containing a number of layers.
However, the lateral dimension of the WS 2 sheets is restricted by the size of the rods. Due to their layered structures, TMDs bulk materials can be intercalated by various kinds of intercalates such as organic molecules, transition metal halides and lithium ions [ 50 ]. The resulting intercalated compounds can be exfoliated to single and few-layer 2D TMDs nanosheets by ultrasonication [ 54 - 58 ]. For example, Ramakrishna Matte et al. However, this method is time-consuming and the degree of lithium insertion is not controllable, which limits it feasibility.
Zheng et al. By incorporating the layered TMDs bulk materials, such as MoS 2 , WS 2 , TiS 2 , and ZrS 2 , as the cathode in an electrochemical cell, the lithium intercalation in these materials can be monitored and finely controlled during the discharge process. The obtained intercalated compounds can be ultrasonicated and exfoliated in water or ethanol to achieve high-grade TMDs single-layer materials in large amounts. In another work, Coleman et al.
Based on their theoretical investigation, Coleman et al. These images and associated Fourier transforms illustrate that no substantial deviation from the hexagonal symmetry of these materials is observed, unlike the MoS 2 and WS 2 nanosheets exfoliated by lithium intercalation [ 27 , 60 ].
To apply TMDs materials to real devices, their large scale growth is essential. The chemical vapor deposition CVD method is the most effective way to achieve large-area growth.
This method can be divided into two tyes, the sulfurization or selenization of metal thin films and vapor phase reaction of metal oxides with chalcogen precursor. Attempts to synthesis MoS 2 layers by the simple sulfurization of Mo metal thin films have been reported.
Zhan et al. The size and thickness of the pre-deposited Mo film determine the size and thickness of the MoS 2 thin film, respectively. The direct sulfurization of the Mo metal thin film provides a quick and easy way to access atomically thin MoS 2 layers on insulating substrates.
However, it is challenging to deposit a uniform Mo film. Kong et al. Uniform TMDs edge-terminated films with densely packed, strip-like grains can be produced on various substrates including glassy carbon, quartz and oxidized silicon. To produce wafer-scale MoS 2 thin films, an MoO 3 thin layer with the desired thickness is prepared by thermal evaporation on a sapphire substrate. The as-grown MoS 2 thin film can be transferred to an arbitrary substrate for the fabrication of electronic devices [ 63 ].
A similar technique has also been adopted for the synthesis of large-area WS 2 sheets with controllable thickness [ 64 ]. However, the synthesis of TMDs by the direct sulfurization or selenization of a metal oxide thin film has several limitations, such as the difficulty to control the thickness of the pre-deposited metal oxide or metal thin film, which affects the wafer-scale uniformity.
To obtain high quality TMDs with the desired number of layers, the thickness of the metal oxide needs to be precisely controlled. Recently attempts have been made to improve the synthetic process by depositing metal oxide layers via atomic layer deposition ALD [ 65 ].
Song et al. Sulfurization or selenization of metal or metal oxide thin film. A layer of MoO 3 3. The MoO 3 was then converted to MoS 2 by a two-step thermal process [ 63 ]. Wang et al. The surface sulfurization of the crystalline MoO 2 micro-plates produces a top MoS 2 layer with a high degree of crystallinity However, the MoS 2 growth is still determined by the crystal size of the MoO 2 flakes, where the MoS 2 single crystal obtained is randomly distributed as an isolated island.
During the MoS 2 growth, MoO 3 in the vapor phase undergoes a two-step reaction, the first of which involves the formation of MoO 3-x that further reacts with the sulfur vapor to grow MoS 2 layers. The growth of singlecrystalline MoS 2 flakes directly on arbitrary substrates is quite possible by this method and, hence, it has been widely used for producing synthetic TMDs single-layers.
The growth of MoS 2 is very sensitive to the substrate treatment prior to the growth [ 67 ]. Facilitating the nucleation by seeding the substrate with graphene-like species has also been explored [ 69 - 71 ]. Vaporization of metal oxide with chalcogen precursor. The inset plot is the height profile along the black line shown in the image, demonstrating its single-layer thickness [ 70 ].
Typical optical images of single-layer triangles and continuous film. Small bilayer domains with a darker color can be observed in the lower left and right [ 78 ]. Najmaei et al. The triangular-shaped MoS 2 crystals are observed to be nucleated and formed on the step edges. Using substrate patterning by lithography processes, the nucleation of the MoS 2 layers can be controlled.
The observed catalytic process along the edges is due to the significant reduction in the nucleation energy barrier of MoS 2 at the step edges as compared with the flat surface [ 72 ]. Further experiments revealed that small triangular MoS 2 domains are preferentially nucleated at the step edges and then continue to grow and form boundaries with other domains.
Their coalescence finally results in the formation of a continuous MoS 2 film [ 73 ].
Nanotechnology focuses on the development of novel, functional materials at an atomic, molecular, and macromolecular scale at sizes ranging from 1 to nm. In recent years, studies related to the synthesis of nanomaterials and nanoparticles with unique and desired properties have attracted growing attention due to their small size, multifucntionality, surface tailorability, and biocompatibility. These features have led to increasing numbers of applications in which nanomaterials for various branches of science, industry, and daily life have emerged; however their use in biotechnology is of particular importance. This rapidly growing, cross-disciplinary field of science gives the possibility to design and develop novel solutions that include application of multifunctional nanoparticles in biomedicine, cancer diagnosis, the food industry, or heterogenous catalysts as well as support for biocatalysts. The widespread application of nanomaterials acts as a driving force for research and development of nanomaterials-based systems in biotechnology. This special Issue welcomes contributions which report on the synthesis, characterization, and application of nanomaterials of various origins in all areas of biotechnology. We hope to attract original research articles related to the fundamental science and practical use of nanomaterials in biotechnology as well as review articles which describe the current state of the art.
Carbon nanodots C-dots have generated enormous excitement because of their superiority in water solubility, chemical inertness, low toxicity, ease of functionalization and resistance to photobleaching. In this review, by introducing the synthesis and photo- and electron-properties of C-dots, we hope to provide further insight into their controversial emission origin particularly the upconverted photoluminescence and to stimulate further research into their potential applications, especially in photocatalysis, energy conversion, optoelectronics, and sensing. If you are not the author of this article and you wish to reproduce material from it in a third party non-RSC publication you must formally request permission using Copyright Clearance Center. Go to our Instructions for using Copyright Clearance Center page for details. Authors contributing to RSC publications journal articles, books or book chapters do not need to formally request permission to reproduce material contained in this article provided that the correct acknowledgement is given with the reproduced material.
Colloidal semiconductor nanocrystals or quantum dots have evolved during the last few decades from fundamental theoretical concepts to real commercial products one recent example is a line of Samsung QLED TVs in which quantum dots are employed as color converters , owing to intensive efforts by a plethora Colloidal semiconductor nanocrystals or quantum dots have evolved during the last few decades from fundamental theoretical concepts to real commercial products one recent example is a line of Samsung QLED TVs in which quantum dots are employed as color converters , owing to intensive efforts by a plethora of research groups worldwide. These nanomaterials benefit on the one hand from their unique size-dependent optoelectronic properties, based on quantum confinement. On the other hand, their solution-based synthesis is a remarkably simple process that can be implemented in nearly any chemistry lab. Both these factors greatly promote investigation of semiconductor nanocrystals, making this field truly interdisciplinary. Among the main players involved are chemists, physicists, biologists, material researchers, and engineers.
Nanomaterials research takes a materials science -based approach to nanotechnology , leveraging advances in materials metrology and synthesis which have been developed in support of microfabrication research. Materials with structure at the nanoscale often have unique optical, electronic, thermo-physical or mechanical properties. Nanomaterials are slowly becoming commercialized  and beginning to emerge as commodities. This includes both nano-objects , which are discrete pieces of material, and nanostructured materials , which have internal or surface structure on the nanoscale; a nanomaterial may be a member of both these categories. Engineered nanomaterials have been deliberately engineered and manufactured by humans to have certain required properties.
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