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Novel Mode-Locked Fiber Lasers with Broadband Saturable Absorbers
Published in Sam Zhang, Jyh-Ming Ting, Wan-Yu Wu, Functional Thin Films Technology, 2021
In recent years, transition metal sulfide semiconductor materials have gradually become a research hotspot in the field of lasers because of their unique photoelectric properties. Similar to graphene, transition metal sulfides are also layered materials. In a single-layer transition metal sulfide structure, a single transition metal layer is sandwiched between two layers of chalcogen elements. Because of the 2D constraint of specific electron movement and the lack of interlayer coupling perturbation, 2D transition metal sulfides have the following unique optical physical characteristics: (1) The energy band characteristics have adjustable value (usually in 1–2 eV range) related to the number of layers. (2) With a decrease in the number of layers, there is a transition from an indirect band gap to a direct band gap. (3) They have better photoluminescence and electroluminescence properties. (4) They have stable laser characteristics, such as high binding energy, high vibrator strength, and long life. (5) They have ultrafast carrier characteristics. It is these excellent properties that cause transition metal sulfide materials to have application potential in the production of high-performance SA devices.
Tailoring Two-Dimensional Semiconductor Oxides by Atomic Layer Deposition
Published in Sumeet Walia, Krzysztof Iniewski, Low Power Semiconductor Devices and Processes for Emerging Applications in Communications, Computing, and Sensing, 2018
Mohammad Karbalaei Akbari, Serge Zhuiykov
A large number of ultra-thin layered materials can be synthesized by mechanical and chemical exfoliation, as well as deposition and growth techniques [15,35,36]. Achieving freely suspended, large-area 2D films is extremely challenging since the structural stability and molecular integrity of 2D films can be easily destroyed. Accordingly, one of the main challenges is the versatile and conformal deposition of these quasi-2D oxide nanostructures on convenient substrates including conducting, semiconducting and dielectric sublayers [37–45]. Precise control of thickness, monitoring of conformity and continuity of 2D oxide films over the substrate are among the major technical challenges, especially when the wafer-scale growth of 2D nanostructures is the main scope of discussion [46]. The growth of 2D oxides is achievable by using high-tech deposition techniques mostly exploiting the benefits of physical vapor and chemical vapor deposition (CVD) approaches by exerting ultra-high vacuum conditions during the fabrication process [46–48]. Since thin film growth is inherently a non-equilibrium process, discussion of the stoichiometry of deposited 2D oxide films, the stabilization of meta-stable oxide phases, the structural controllability and phase complexities of oxide–metal interface systems are of vital importance.
New advances in 2D electrochemistry—Catalysis and Sensing
Published in Craig E. Banks, Dale A. C. Brownson, 2D MATERIALS, 2018
Tharangattu N. Narayanan, Ravi K. Biroju, Thazhe Veettil Vineesh
Unlike the case of other conventional materials used in electrochemistry, the applicability of a 2D material in electrochemistry highly relies on the method of synthesis adopted, since the method mostly determines the amount and nature of defects in the layer (this includes surface/edge states, vacancy defects, point and line defects, etc.). Numerous physical and chemical methods are reported for the synthesis of layered materials.16–18 This includes both top-down and bottom-up approaches. Here, some of the important methods are briefed, and later, the layers developed through these methods are discussed for their electrocatalytic applications. A schematic of various methods available for graphene synthesis is shown in Fig. 1,19 and it is to be noted that many of these techniques are applicable to other conventional layered materials too.
Adsorption of anionic dye from aqueous environment using surface-engineered Zn/Cu hydroxy double salt-based material: mechanistic, equilibrium and kinetic studies
Published in Journal of Environmental Science and Health, Part A, 2023
Bhamini Pandey, Poonam Singh, Vinod Kumar
During the last few years, layered materials having two-dimensional (2D) structures have garnered enormous attention owing to their exceptional physiochemical and optical properties giving rise to potential applications in the field of catalysis, photonics, electronics, drug delivery, energy storage, etc.[1–4] Among these, the materials based on layered double hydroxides (LDHs) are widely explored owing to their distinctive layered structure having a large surface area, presence of different divalent and trivalent ions in the lattice, and high anion exchangeability for numerous organic, polymeric and inorganic species. In general, LDHs are characterized by the formulation [MII1-aMIIIa(OH)2]a+ Ax−a/x. yH2O where MII is the divalent cation (Zn2+, Mn2+, Mg2+, etc.), MIII is the trivalent cation (Ni3+, Fe3+, Ga3+, etc.), Ax− is the anion in interlayer region of valency x (CO32−, CH3COO−, SO42−, etc.) and a is the molar ratio (M3+/M2++ M3+). LDH possesses a brucite-like structure in which there is an isomorphous replacement of a part of MII ion by MIII ion resulting in an additional positive charge on the brucite layers, counterbalanced by the existence of anionic species in the interlamellar region.[5,6]
Highly sensitive gold-film surface plasmon resonance (SPR) sensor employing germanium selenide (GeSe) nanosheets
Published in Instrumentation Science & Technology, 2022
Ze-Ying Hao, Yao Liu, Zhou-Hao Zhao, Qi Wang
Graphene, transition metal disulfides (TMDC), and black phosphorus (BP) are examples of layered materials. However, GeSe, a group IV monothionide, is gaining interest for its unique features and prospective uses in electronics, spintronics, and photovoltaics.[21–23] With its extreme anisotropy and ultrahigh carrier mobility, GeSe has been hypothesized to exhibit characteristics that are comparable to those of black phosphorus.[24] Although the use of GeSe in SPR sensors is still uncommon, Zhao et al. developed a novel sensor that outperforms standard SPR sensors by 80% by spin-coating GeSe nanosheets on the surface of noble metals in a prismatic structure, with an optimal sensitivity of 3581.2 nm/RIU.[25] GeSe monolayers are direct band gap semiconductors with better characteristics in comparison to GeSe multilayers.[26,27] The light energy absorbed by monolayer GeSe may enhance electron transmission by forming a strong coupling on the Au film’s surface and therefore increasing the surface electric field.
Organic modification of layered zirconium phosphate/phosphonate for controlled release of therapeutic inorganic ions
Published in Science and Technology of Advanced Materials, 2021
Jin Nakamura, Ryoya Ito, Ryohei Kozaki, Ayae Sugawara-Narutaki, Chikara Ohtsuki
Layered materials have structures wherein heterolayers with a thickness of a few atomic layers are stacked via weak interactions, such as electrostatic forces with counter-charged ions or hydrogen bonding with water molecules. Because of the structural flexibility at the interlayer, organic drug molecules and inorganic ions of various sizes can be inserted between the layers on the basis of ion-exchange chemistry. Organically modified LZPs have been explored as excellent host materials to incorporate guest organic molecules via intercalation [22–24] or ion exchange [15,25,26]. The availability of acidic groups such as phosphate and sulfonate (SO3H) groups in the organically modified LZP is key for the uptake of inorganic ions caused by the ion-exchange property. Organically modified LZP with available acidic groups has been prepared using a mixture of phosphoric and aromatic phosphonic acids as the starting materials [15] and through post-synthesis sulfonation of the aromatic groups [26]. Here, phenyl-modified zirconium phosphate/phosphonate was prepared using a mixture of phosphoric and phenylphosphonic acids at various molar fractions.