Recent studies show that dual-atom catalysts (DACs) on GDY enhance catalytic efficiency. However, selecting DACs structures that are easy to synthesize and suitable for large-scale applications remains a significant challenge. We used density functional theory (DFT) and the computational hydrogen electrode (CHE) model for screening of GDY-anchoring transition metals, aiming to reduce precious metal use. Through screening, we have discovered that Pd2@GDY exhibited an HER overpotential as low as 0.09 V, demonstrating satisfactory HER performance. Ni2@GDY exhibited a higher adsorption affinity for the second hydrogen atom, facilitating the HER through the Volmer-Tafel mechanism, thereby enhancing the HER rate. Additionally, we have found that the interaction between the two transition metals in this structural configuration enhanced adsorption strength and synergistically promoted the HER. Our research has the potential to advance the rational design of highly efficient DACs.

AbstractBulk black phosphorous (bP) exhibits excellent infrared (IR) optoelectronic properties, but most reported bP IR photodetectors are fabricated from single exfoliated flakes with lateral sizes of < 100 µm. Here, scalable thin films of bP suitable for IR photodetector arrays are realized through a tailored solution‐deposition method. The properties of the bP film and their protective capping layers are optimized to fabricate bP IR photoconductors exhibiting specific detectivities up to 4.0 × 108 cm Hz1/2 W−1 with fast 30/60 µs rise/fall times under λ = 2.2 µm illumination. The scalability of the bP thin film fabrication is demonstrated by fabricating a linear array of 25 bP photodetectors and obtaining 25 × 25 pixel IR images at ≈203 ppi with good spatial fidelity. This research demonstrates a commercially viable method of fabricating scalable bP thin films for optoelectronic devices including room temperature‐operable IR photodetector arrays.

Homojunctions are key elements in many mainstream electronic devices. However, conventional dopant-based "pn" homojunctions are not easily achievable in new material families, such as the 2D materials. Several recent 2D material studies have shown that lateral pn homojunctions can instead be electrostatically induced using back gates localized to either the source or drain contacts. Here, a hBN-encapsulated black phosphorus dual-gate device containing a lateral pn homojunction, whose orientation can be switched via application of back gate voltages, is demonstrated. Importantly, this study extends the state-of-the-art for this architecture by characterizing the photoresponse under infrared (lambda = 2.2 mu m) illumination. It is shown that when biased to form a homojunction, the device exhibits the photovoltaic effect, resulting in a specific detectivity of 8.5 x 108 cm Hz1/2 W-1 at 77 K under short-circuit conditions, and an open circuit photovoltage up to 175 mV at 77 K. Further, it is shown that the device can be operated in photoconductive mode, allowing a high responsivity of 0.55 A W-1. This device is thus highly reconfigurable as it can be switched between photovoltaic and photoconductive modes of operation to prioritize low noise and fast response or high responsivity. Black phosphorus dual-gate devices are shown to form electrostatically induced pn-homojunctions when asymmetric gate biases are applied. This allows the demonstration of photodiodes with specific detectivities of 8.5 x 108 cm Hz1/2 W-1 and open circuit photovoltages of 175 mV, under infrared illumination. This development extends the application of dual-gate van der Waals materials photodetectors into the short-wave infrared range. image

Abstract Superhydrophobic surfaces have been extensively studied for their self-cleaning properties. However, most of the constructed superhydrophobic surfaces have problems of changing the surface morphology and color of paper/cloth. An extremely dilute superhydrophobic solution was prepared by hybrid assembly of aminated nano SiO 2 and high fluorine epoxy polymer P(FOEMA- r -GMA). The preparation of superhydrophobic cotton (SHC) and superhydrophobic book paper (SHBP) were studied through the optimal construction conditions of solution impregnation method. The optimal construction conditions for SHC were as follows: the concentration of fluorinated epoxy polymer was 3 mg/mL, the soaking time was 5 hours, the drying time was 8 hours, and the drying temperature was 120 o C. The maximum WCA is 158 ° ± 3 o , and the minimum WRA is 4 o ± 3 o . SHC surface had good hydrophobic effect, acid and alkali resistance, self-cleaning effect, and its surface morphology remains basically unchanged. SHC could be used for oil water separation with a maximum oil water separation rate of 98.4%. The optimal construction conditions for SHBP were: the concentration of fluorinated epoxy polymer was 3 mg/mL, the soaking time was 9 hours, the drying time was 6 hours, the maximum WCA was 155 o ± 3 o , and the minimum WRA was 6 o ± 1 o . The hydrophobicity of SHBP was significantly improved, it would selective adsorbing oil from the oil water mixture and slightly reduce its smoothness.

Flexible optoelectronics is a rapidly growing field, with a wide range of potential applications. From wearable sensors to bendable solar cells, curved displays, and curved focal plane arrays, the possibilities are endless. The criticality of flexible photodetectors for many of these applications is acknowledged, however, devices that are demonstrated thus far are limited in their spectral range. In this study, flexible photodetectors are demonstrated using a VO x nanoparticle ink, with an extremely broad operating wavelength range of 0.4 to 20 µm. This ink is synthesized using a simple and scalable wet‐chemical process. These photodetectors operate at room temperature and exhibit minimal variance in performance even when bent at angles of up to 100 ° at a bend radius of 6.4 mm. In addition, rigorous strain testing of 100 bend and release cycles revealed a photoresponse with a standard deviation of only 0.55%. This combination of mechanical flexibility, wide spectral response, and ease of fabrication makes these devices highly desirable for a wide range of applications, including low‐cost wearable sensors and hyperspectral imaging systems.

2D materials, with distinct characteristics compared to their conventional bulk counterparts, have been a popular topic in various optoelectronic research fields. Herein, indium selenide (InSe), a monochalcogenide van der Waals layered semiconductor, which has been studied due to its thickness dependent optical characteristics is explored. For InSe to be used as a versatile light source, enhancing the emission of InSe is required. Here, enhanced photoluminescence (PL) from multi‐layer InSe is demonstrated using a gap plasmon induced between Ag nanocube dimer and an Au substrate. Such plasmonic structures support multiple resonances, one of those overlapping with InSe's band edge PL emission. The calculated Purcell factor shows a 200‐fold increase on the short edge of nanocube dimers. Experimentally, PL enhancement of 6‐fold is demonstrated at room temperature. In addition, a method for determining the thickness of 2D materials via dark‐field spectroscopy using white light illumination is shown. This study paves the way for the incorporation of 2D InSe into nanophotonic structures.

Flexible optoelectronics is a rapidly growing field, with a wide range of potential applications. From wearable sensors to bendable solar cells, curved displays, and curved focal plane arrays, the possibilities are endless. The criticality of flexible photodetectors for many of these applications is acknowledged, however, devices that are demonstrated thus far are limited in their spectral range. In this study, flexible photodetectors are demonstrated using a VOx nanoparticle ink, with an extremely broad operating wavelength range of 0.4 to 20 & mu;m. This ink is synthesized using a simple and scalable wet-chemical process. These photodetectors operate at room temperature and exhibit minimal variance in performance even when bent at angles of up to 100 & DEG; at a bend radius of 6.4 mm. In addition, rigorous strain testing of 100 bend and release cycles revealed a photoresponse with a standard deviation of only 0.55%. This combination of mechanical flexibility, wide spectral response, and ease of fabrication makes these devices highly desirable for a wide range of applications, including low-cost wearable sensors and hyperspectral imaging systems.

A single photodetector capable of switching its peak spectral photoresponse between two wavelength bands is highly useful, particularly for the infrared (IR) bands in applications such as remote sensing, object identification, and chemical sensing. Technologies exist for achieving dual-band IR detection with bulk III-V and II-VI materials, but the high cost and complexity as well as the necessity for active cooling associated with some of these technologies preclude their widespread adoption. In this study, we leverage the advantages of low-dimensional materials to demonstrate a bias-selectable dual-band IR detector that operates at room temperature by using lead sulfide colloidal quantum dots and black phosphorus nanosheets. By switching between zero and forward bias, these detectors switch peak photosensitive ranges between the mid- and short-wave IR bands with room temperature detectivities of 5 × 109 and 1.6 × 1011 cm Hz1/2 W-1, respectively. To the best of our knowledge, these are the highest reported room temperature values for low-dimensional material dual-band IR detectors to date. Unlike conventional bias-selectable detectors, which utilize a set of back-to-back photodiodes, we demonstrate that under zero/forward bias conditions the device's operation mode instead changes between a photodiode and a phototransistor, allowing additional functionalities that the conventional structure cannot provide.

Atomically thin two-dimensional (2D) transition metal dichalcogenides (TMDs) are promising materials for photovoltaic (PV) applications. Their self-terminated nature and strong absorption characteristics introduce an unprecedented possibility for high voltages to bandgap ratios, with secondary benefits including the potential for high internal quantum efficiencies/low recombination and strong absorption coefficients coupled with stability in a range of environments. However, despite the promise of such material systems, their PV performances still lag behind the conventional 3D materials. In principle, one possible way to manipulate the behavior of a 2D heterobilayer structure is to change its interlayer twist angle. In this study, the effects of twist angle between vertically stacked type-II MoS2/WS2 heterobilayers on fundamental optical properties such as light absorbance, excess carrier lifetime, and diffusion are reported. These properties can have a direct effect on the final PV performance of these heterobilayers. It is found that the interlayer twist in MoS2/WS2 heterobilayers does not affect their absorbance. However, the carrier lifetime and photon emission across the heterobilayers are modulated with the interlayer twist. These findings could be useful to facilitate the optimization of monolayer TMD-based optoelectronic devices.

The self-terminated, layered structure of van der Waals materials introduces fundamental advantages for infrared (IR) optoelectronic devices. These are mainly associated with the potential for low noise while maintaining high internal quantum efficiency when reducing IR absorber thicknesses. In this study, we introduce a new van der Waals material candidate, zirconium germanium telluride (ZrGeTe4), to a growing family of promising IR van der Waals materials. We find the bulk form ZrGeTe4 has an indirect band edge around ∼0.5 eV, in close agreement with previous theoretical predictions. This material is found to be stable up to 140 °C and shows minimal compositional variation even after >30 days storage in humid air. We demonstrate simple proof-of-concept broad spectrum photodetectors with responsivities above 0.1 AW-1 across both the visible and short-wave infrared wavelengths. This corresponds to a specific detectivity of ∼109 cm Hz1/2 W-1 at λ = 1.4 μm at room temperature. These devices show a linear photoresponse vs illumination intensity relationship over ∼4 orders of magnitude, and fast rise/fall times of ∼50 ns, also verified by a 3 dB roll-off frequency of 5.9 MHz. As the first demonstration of photodetection using ZrGeTe4, these characteristics measured on a simple proof-of-concept device show the exciting potential of the ZrGeTe4 for room temperature IR optoelectronic applications.

Long-wave infrared (LWIR) photodetection is of high technological importance, having a wide range of applications that include thermal imaging and spectroscopy. Two-dimensional (2D) noble-transition-metal dichalcogenides, platinum diselenide (PtSe2) in particular, have recently shown great promise for infrared detection. However, previous studies have mainly focused on wavelengths up to the short-wave infrared region. In this work, we demonstrate LWIR photodetectors based on multilayer PtSe2. In addition, we present an optical cavity substrate that enhances the light-matter interaction in 2D materials and thus their photodetection performance in the LWIR spectral region. The PtSe2 photoconductors fabricated on the TiO2/Au optical cavity substrate exhibit responsivities up to 54 mA/W to LWIR illumination at a wavelength of 8.35 μm. Moreover, these devices show a fast photoresponse with a time constant of 54 ns to white light illumination. The findings of this study reveal the potential of multilayer PtSe2 for fast and broadband photodetection from visible to LWIR wavelengths.

The detection of light in the longwave infrared (LWIR) region is crucial for many applications such as environmental monitoring, thermal imaging and surveillance. Many commercial LWIR photodetectors involve complex fabrication processes, require cryogenic temperatures or exhibit slow photoresponse. Hence, there is a continuous pursuit of developing room-temperature, on-chip LWIR photodetectors, using simple fabrication processes [1] . Metal-organic charge transfer complexes typically have a narrow bandgap, which allows them to absorb LWIR wavelengths [2] . Here, we report room temperature LWIR photoresponse in one such charge transfer complex, ie. copper 7,7,8,8-tetracyano-2,3,5,6-tetraflouroquinodimethane (CuTCNQF 4 ), achieved via simple synthesis and fabrication processes.

Thin two-dimensional (2D) material absorbers have the potential to reduce volume dependent thermal noise in infrared detectors. However, any reduction in noise must be balanced against lower absorption from the thin layer, which necessitates advanced optical architectures. Such architectures can be particularly effective for applications that require detection only within a specific narrow wavelength range. This study presents a Fabry-Pérot cavity enhanced bP/MoS2 mid-wave infrared (MWIR) photodiode. This simple structure enables tunable narrow-band (down to 0.42 µm full-width-half-maximum) photodetection in the 2-4 µm range by adjusting the thickness of the Fabry-Pérot cavity resonator. This is achieved whilst maintaining room temperature performance metrics comparable to previously reported 2D MWIR detectors. Zero bias specific detectivity and responsivity values of up to 1.7 × 109 cm Hz1/2 W-1 and 0.11 A W-1 at λ = 3.0 µm are measured, with a response time of less than 3 ns. These results introduce a promising family of 2D detectors with applications in MWIR spectroscopy.

Oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) are two important processes for electrochemical energy storage and conversion. Herein, we describe the preparation of carbon-supported Pd nanocubes@Mo core@shell nanostructures as efficient dual catalysts for both ORR and HER. The core@shell structure was manifested by high resolution transmission electron microscopy measurements, including high angle angular dark field-scanning transmission electron microscopy and elemental mapping analysis. Further structural insights were obtained in X-ray diffraction and X-ray photoelectron spectroscopy measurements. The nanostructures exhibited apparent electro-catalytic activity toward both ORR and HER, and the performances were markedly higher than those without the deposition of a Mo overlayer. In ORR, the activity was even better than that of commercial Pt/C within the context of onset potential, specific and mass activities; whereas in HER, the performance of Pd nanocubes@Mo core@shell nanostructures remained subpar as compared to that of Pt/C in terms of the overpotential to reach the current density of 10 mA cm(-2), the Tafel slope was comparable and the stability was excellent. The excellent electrocatalytic performance can be attributed to the Pd-Mo synergistic effects imparted from the core-shell structure. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

A simple approach for preparing recycled poly(ethylene terephthalate) (r-PET) with excellent processability and melt strength has been developed in this research. To increase the intrinsic viscosity of r-PET, a two-step chain extension process using a combination of SAG-008 and tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM) was investigated. To evaluate the chain extension degree of the modified r-PET, its intrinsic viscosity (IV) and rheological properties were characterized, and found to be correlated to the long-chain branches and molecular weight. The results indicated that the combination of SAG-008 and TGDDM at the optimized conditions provided the highest IV of 1.18 dl/g while controlling the gel formation to a low value. The increases in storage modulus, loss modulus and complex viscosity revealed the enhancement of melt strength and viscoelasticity of r-PET. The differential scanning calorimetry results showed that the crystallinity was reduced with the addition of chain extenders. On the other hand, stepwise annealing method from room temperature to crystal melting temperature promoted the crystallization, which was confirmed by wide-angle X-ray diffraction measurement.

Peptide-capped nanoparticles represent a unique type of nanomaterials with emergent optical and electrochemical properties. Herein, a series of peptide capped palladium nanoparticles have been prepared and employed as highly efficient catalysts for oxygen electroreduction. The peptide sequence was tuned by substituting amino acid residues at specialized positions, and strong surface effects were observed between the peptide sequence and the electrocatalytic activity. The findings corresponded well with the previously reported CC coupling catalytic reactions, indicating that the residue-specific binding effects but not the overall binding strength governed the electrocatalytic activity. The results may shed light on the rational design of bio-inspired nanomaterials with optimized electrocatalytic properties.

Ceramifiable flame-retardant silicone rubber composites were prepared by silicone rubber (SR) as the base polymer, and ammonium polyphosphate, calcium carbonate, sericite mica, and glass frits were utilized as additives. The flammability and thermal stability properties of ceramifying silicone rubber composites were studied by the limiting oxygen index (LOI), microscale combustion calorimetry (MCC), and thermogravimetric analysis (TG). The ceramic residues formed at various temperatures were studied by mechanical testing, scanning electron microscopy (SEM), and X-ray diffraction (XRD). The results indicated that the ceramifying silicone rubber achieved a LOI value of 31.2% and the flexural strength of ceramic residues formed at 1000 °C was 19.7 MPa. Moreover, the MCC results demonstrated that the heat release rate and total release rate of the composites were reduced significantly compared to the corresponding value of neat SR. The TG showed that the residue of composites was approximately 61.5% at 700 °C, as significantly higher than that the residue of neat SR. The XRD results demonstrated that fluoroapatite and Ca2SiO4 crystals were produced in the ceramic residue at high temperatures. The SEM analysis depicted that the number of holes was reduced and a dense structure was formed as the sintering temperature increased, leading to the excellent mechanical properties of formed ceramics at high temperatures.

Nanocomposites based on Co@Pt core@shell nanoparticles encapsulated in nitrogen-doped porous carbons were prepared as a new type of high-performance electrocatalysts for oxygen reduction reaction (ORR). Controlled pyrolysis of zeolitic imidazolate framework 67 (ZIF-67) led to the formation of Co nanoparticles encapsulated in nitrogen-doped porous carbon (Co-NC), which underwent galvanic replacement reactions with K2PtCl4 forming Co@Pt core@shell nanoparticles. The surface microstructure and composition of the resulting Co@Pt-NC nanocomposite were examined by electron microscopic as well as X-ray photoelectron spectroscopic (XPS) measurements. With the Co@Pt particles encapsulated in nitrogen-doped porous carbon, the hybrids exhibited a high specific surface area and abundant catalytically active sites for ORR. Electrochemically, the specific activity and mass activity of the Co@PtNC composite at +0.85 V (0.145 mA cm(-2) and 71.9 A g(-1)) were superior to those of commercial Pt/C (0.123 mA cm(-2) and 38.4 A g(-1)). Furthermore, the Co@Pt-NC composite also exhibited remarkably higher durability and more robust tolerance against methanol crossover than commercial Pt/C. (C) 2017 Elsevier B.V. All rights reserved.

Vinyltrimethoxysilane‐grafted ethylene vinyl acetate copolymer (EVA‐g‐VTMS) was synthesized and applied to compatibilize ethylene‐propylene‐diene copolymer (EPDM)/methyl vinyl silicone rubber (MVQ) blends. The silane‐grafting was successfully proved by differential scanning calorimetry, FTIR spectroscopy and XPS spectroscopy. The additive amount of the compatibilizer (EVA‐g‐VTMS) was optimized to be 10 phr (parts per hundred of rubber in weight) based on analysis of scanning electron microscopy, mechanical properties, aging properties, dynamic mechanical properties, rheological properties and thermal properties. Compared with the blend without EVA‐g‐VTMS, results show that the blend with 10 phr of EVA‐g‐VTMS exhibits the finest morphology. Tensile strength, elongation at break, modulus at 100% elongation, tear strength and TE index increase by 82.5%, 16.9%, 60.0%, 40.9%, and 41.9%, respectively. Dynamic mechanical analysis reveals storage modulus increase and glass transition temperatures of EPDM and MVQ move closer to each other. Rheological analysis shows a decrease in complex modulus and complex viscosity, and the processibility of the blend was improved. Furthermore, thermogravimetric analysis shows enhancement of thermal stability. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers