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A two-dimensional (2D) van der Waals material composed only of tellurium (Te) atoms—tellurene—is drawing attention because of its high intrinsic electrical conductivity and strong interaction with gas molecules, which could allow the development of high-performance chemiresistive sensors. However, the correlation between the morphologies and gas detection properties of tellurene has not yet been studied in depth, and few reports exist on tellurene-based hydrogen sulfide (H2S) chemiresistive sensors in spite of their strong interaction with H2S molecules. Here, we investigate the morphology-dependent H2S gas detection properties of tellurene synthesized using a hydrothermal method. To tailor the morphologies of tellurene, the molecular weight of the surfactant was controlled, revealing that a 1D or 2D form was synthesized and also accompanied with the high crystallinity. The 1D tellurene-based chemiresistive sensor presented superior H2S detection properties compared to the 2D form, achieving a gas response (Rg/Ra) of ~38, even at room temperature. This outstanding performance was attributed to the high intrinsic electrical conductivity and high specific surface area of the resultant 1D tellurene. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) molybdenum disulfide (MoS2) is a promising material for constructing high-performance visible photosensor arrays because of its high mobility and scale-up process. These distinct properties enable the construction of practical optoelectrical sensor arrays. However, contact engineering for MoS2 films is not still optimized. In this work, we inserted a graphene interlayer between the MoS2 films and Au contacts (graphene/Au) via the wet-transfer method to boost the device performance. Using graphene/Au contacts, outstanding electrical properties, namely field-effect mobility of 12.06 cm2/V∙s, on/off current ratio of 1.0 × 107, and responsivity of 610 A/W under illumination at 640 nm, were achieved. These favorable results were from the Fermi-level depinning effect induced by the graphene interlayer. Our results may help to construct large-area photonic sensor arrays based on 2D materials. [ABSTRACT FROM AUTHOR]

Modulation of the electrical properties of graphene is of significant importance in advancing graphene electronics: it can be achieved by a Fermi level shift induced by electron acceptor/donor doping. Suitable doping methods involving low-temperature processes and offering long-term stability are imperative to practical applications for such materials. Here, we demonstrate a two-step chemical vapor deposition (CVD) technique for direct synthesis of N-doped graphene film from a pyridine feed-stock at 300 °C under ambient pressure. We extended the synthesis—classified into nucleation and lateral growth steps—by controlling the carbon partial pressure in the processing gases. This led to large-area, continuous N-doped graphene films of excellent quality with full surface coverage: for example, a film size of 2 in2, optical transmittance of 97.6%, and electron mobility of 1400 cm2 V−1 s−1. Our modified CVD method is expected to facilitate the direct synthesis of N-doped graphene in device manufacturing processes toward practical applications while keeping the underlying devices intact. Image 1 [ABSTRACT FROM AUTHOR]

Defect engineering of 2D transition metal dichalcogenides (TMDCs) is essential to modulate their optoelectrical functionalities, but there are only a few reports on defect‐engineered TMDC device arrays. Herein, the atomic vacancy control and elemental substitution in a chemical vapor deposition (CVD)‐grown molybdenum disulfide (MoS2) monolayer via mild photon irradiation under controlled atmospheres are reported. Raman spectroscopy, photoluminescence, X‐ray, and ultraviolet photoelectron spectroscopy comprehensively demonstrate that the well‐controlled photoactivation delicately modulates the sulfur‐to‐molybdenum ratio as well as the work function of a MoS2 monolayer. Furthermore, the atomic‐resolution scanning transmission electron microscopy directly confirms that small portions (2–4 at% corresponding to the defect density of 4.6 × 1012 to 9.2 × 1013 cm−2) of sulfur vacancies and oxygen substituents are generated in the MoS2 while the overall atomic‐scale structural integrity is well preserved. Electronic and optoelectronic device arrays are also realized using the defect‐engineered CVD‐grown MoS2, and it is further confirmed that the well‐defined sulfur vacancies and oxygen substituents effectively give rise to the selective n‐ and p‐doping in the MoS2, respectively, without the trade‐off in device performance. In particular, low‐percentage oxygen‐doped MoS2 devices show outstanding optoelectrical performance, achieving a detectivity of ≈1013 Jones and rise/decay times of 0.62 and 2.94 s, respectively. [ABSTRACT FROM AUTHOR]

Ultrafine Ag-coated Cu (Cu@Ag) nanoparticles (NPs) less than 20 nm in diameter were prepared. After synthesizing ultrafine Cu NPs using a solvothermal method to serve as the core particles, Cu@Ag NPs were fabricated with different initial Ag precursor concentrations, resulting in different thicknesses, densities, and uniformities of Ag shells. The average thickness and density of the Ag shell increased with increasing initial Ag precursor concentration in a Cu:Ag atomic ratio from 6:1 to 1:1. However, excessive Ag precursor concentrations induced homogeneous nucleation and growth of surplus fine pure NPs. Ag dewetting behavior and Cu oxidation in the Cu 4 @Ag 1 NPs were observed, they occurred during heating at 200 and 250 °C, respectively. The electrical resistivities of sintered Cu 4 @Ag 1 films decreased with increasing temperature from 200 to 240 °C. The resistivity after washing the OA and sintering for 60 min at 240 °C in air was measured to be 4.96 × 10 −3 Ω cm. The film was sintered in nitrogen using the ink containing non-washed Cu 4 @Ag 1 NPs indicated the lower resistivity of 2.70 × 10 −3 Ω cm owing to the non-oxidation atmosphere, although the chemically capped oleylamine in the core-shell NPs hindered the sintering behavior. [ABSTRACT FROM AUTHOR]

Sn nanoparticles (NPs) were synthesised via chemical reduction. Trisodium citrate dihydrate and mixtures of trisodium citrate dihydrate and 1,10-phenanthroline monohydrate were used as capping agents for the synthesis. When a specific amount of trisodium citrate dihydrate (3.4 × 10mM) was solely added, very fine particle sizes and excellent suppression of aggregation were achieved in the dried samples. When 5 mM of 1,10-phenanthroline monohydrate was used in combination with trisodium citrate dihydrate (at the optimum concentration of 3.4 × 10mM), the particle refining and the suppression of aggregation were further improved. The nano-solder paste prepared by mixing the synthesised Sn NPs with a commercial flux exhibited stable reflow soldering characteristics. The formation of an intermetallic layer, similar to that observed when commercial solder pastes containing micron-sized powders were used, was seen when soldering was carried out with the solder paste containing the synthesised Sn NPs. [ABSTRACT FROM AUTHOR]

Abstract: Ultrafine Sn nanoparticles (NPs) (diameter<10nm) exhibiting a remarkable depression in their melting point were synthesized at room temperature by a modified polyol process. For the synthesis, low-grade Sn(II) 2-ethylhexanoate and sodium borohydride were used as the precursor and reducing agent in a diethylene glycol medium. Further, polyvinyl pyrrolidone was used as a capping agent during the synthesis. The synthesized crystalline Sn NPs showed an average diameter of 7.98nm and an extremely low melting point of 128°C. To test the applicability of the synthesized ultrafine Sn NPs to practical systems, an Ag-based composite ink containing the Sn NPs was prepared. The ink was easily sintered through local liquid-phase sintering by melting of the ultrafine Sn NPs added as a metal binder. Therefore, despite the low-temperature (170°C) sintering with a short duration (~15min), the composite ink exhibited excellent sheet resistance. [Copyright &y& Elsevier]

Transition Metal Dichalcogenides: Atomic Vacancy Control and Elemental Substitution in a Monolayer Molybdenum Disulfide for High Performance Optoelectronic Device Arrays (Adv. Funct. The atomic-resolution scanning transmission electron microscopy directly confirms that sulfur vacancies and oxygen substituents are generated in the MoS SB 2 sb monolayer, and its device shows outstanding optoelectronic performances. Defect engineering, elemental substitution, molybdenum disulfides, transition metal dichalcogenides, vacancy control. [Extracted from the article]

A forward osmosis membrane consisting of graphene oxide (GO) nanosheets cooperatively cross-linked by ethylenediamine (EDA) molecule and poly(acrylic acid) (PAA) polymer chain is proposed. Desirable GO-based nanocomposite membrane must satisfy the conflicting requirements of high water flux and salt rejection simultaneously, which is yet to be achieved. In this study, the GO/EDA/PAA nanocomposite structure demonstrates that good water flux (52 LMH) and salt rejection (97%) can be achieved simultaneously by cooperatively employing the short monomer molecule EDA and the long PAA polymer chain within the channel region of the GO nanocomposite membrane structure. It is suggested that the membrane-wide network of hydrogen bonds between the GO nanosheets and the PAA chains aligned parallel to them is supplemented by anchoring carbon-nitrogen covalent bonds between GO and EDA molecules to form the nanocomposite structure. The nanocomposite structure resulting from the configurations of EDA molecules and PAA chains within the channel region provide an optimal condition for blocking hydrated salt ions while allowing the flow of water molecules. Also, it functions as a reinforcement of the membrane structure for the improved structural integrity. Image 1 • The GO nanosheets are cooperatively cross-linked by EDA and PAA simultaneously. • The configurations of EDA molecules and PAA chains in the membrane form a nanocomposite structure. • The GO/EDA/PAA 8.1:0.9:1 membrane overcomes the trade-off relationship between the flux and rejection. • The d -spacing and performance of membrane can be controlled by its compositions. • A good structural stability is achieved by incorporating the cross-linkers to GO. [ABSTRACT FROM AUTHOR]

• Synthesis of Ti 3 C 2 T X -EDA composite by hydrothermal reaction for adapting as an active layer of nanofiltration membrane. • Controllable surface Zeta potential and active layer thickness. • High pure water flux as a nanofiltration membrane. • High rejection performance against various heavy metal ions. • Stable continuous nanofiltration performance. In a situation in which a huge amount of industrial wastewater is being generated worldwide, developing technology to effectively remove various types of heavy metal ions in wastewater is crucial. To achieve this goal, in this study, a material functionalized with ethylenediamine on Ti 3 C 2 T X is used as the active layer of a nanofiltration membrane to provide excellent rejection against six types of heavy metal ions (Mn2+, Zn2+, Cd2+, Cu2+, Ni2+, and Pb2+). When this Ti 3 C 2 T X -EDA membrane is applied to the nanofiltration system, a heavy metal rejection of greater than 93% is demonstrated, regardless of the heavy metal type with high pure water permeance of 21.1 LMH bar−1 at optimized operating conditions. In particular, for Mn2+, the Ti 3 C 2 T X -EDA membrane demonstrates a high heavy metal rejection of 99.8%. In addition, this membrane exhibit excellent continuous nanofiltration performance for various heavy metal solutions. Because this material can be deposited onto various support membranes, using it as an active layer provides a very efficient approach to achieving heavy metal removal from industrial wastewater. [ABSTRACT FROM AUTHOR]

In a situation facing the limitations of previous renewable energy systems, salinity gradient power (SGP), which is not affected by climate and time, can be a new alternative. SGP can generate electricity by salt concentration difference between two feeds without pollutant emission. One of the representative SGP systems is reverse electrodialysis (RED). An essential part of the RED system is the ion exchange membrane (IEM). However, the research on IEMs for RED, with low areal resistance and high permselectivity, is still lacking. This study proposes a cation exchange membrane (CEM) with engineering nanostructure and introducing new material. Nafion@MXene/Cellulose acetate (CA) composite CEM is fabricated by inspiration from the concrete structure of the building. The electrospun MXene/CA nanofiber is a framework, and the Nafion ionomer is a filler in structure. As a result, the Nafion@MXene/CA CEM shows better physical/electrochemical properties than the casted Nafion and layered membrane. In addition, the Nafion@MXene/CA CEM exhibits a higher power density (2.30 W m−2) in the RED system than the commercial membrane, casted Nafion, and layered membrane. High power generation through structural/material engineering. [Display omitted] • The MXene/CA nanofiber acts as a framework, and the Nafion ionomer is a filler of the concrete-structured NMC CEM. • The MXene nanosheets improve the physical/electrochemical properties of the cellulose acetate nanofiber-based CEM. • The concrete-structured NMC is strong even if the thickness is reduced due to its unique structure. • High power density (2.30 W m−2) was obtained due to the thin membrane and the high permselectivity affected by MXene. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) molybdenum disulfide (MoS2) is the most mature material in 2D material fields owing to its relatively high mobility and scalability. Such noticeable properties enable it to realize practical electronic and optoelectronic applications. However, contact engineering for large-area MoS2 films has not yet been established, although contact property is directly associated to the device performance. Herein, we introduce graphene-interlayered Ti contacts (graphene/Ti) into large-area MoS2 device arrays using a wet-transfer method. We achieve MoS2 devices with superior electrical and photoelectrical properties using graphene/Ti contacts, with a field-effect mobility of 18.3 cm2/V∙s, on/off current ratio of 3 × 107, responsivity of 850 A/W, and detectivity of 2 × 1012 Jones. This outstanding performance is attributable to a reduction in the Schottky barrier height of the resultant devices, which arises from the decreased work function of graphene induced by the charge transfer from Ti. Our research offers a direction toward large-scale electronic and optoelectronic applications based on 2D materials. [ABSTRACT FROM AUTHOR]