Search

Silicon photonics enables wafer-scale integration of optical functionalities on chip. Silicon-based laser frequency combs can provide integrated sources of mutually coherent laser lines for terabit-per-second transceivers, parallel coherent light detection and ranging, or photonics-assisted signal processing. We report heterogeneously integrated laser soliton microcombs combining both indium phospide/silicon (InP/Si) semiconductor lasers and ultralow-loss silicon nitride (Si3N4) microresonators on a monolithic silicon substrate. Thousands of devices can be produced from a single wafer by using complementary metal-oxide-semiconductor-compatible techniques. With on-chip electrical control of the laser-microresonator relative optical phase, these devices can output single-soliton microcombs with a 100-gigahertz repetition rate. Furthermore, we observe laser frequency noise reduction due to self-injection locking of the InP/Si laser to the Si3N4 microresonator. Our approach provides a route for large-volume, low-cost manufacturing of narrow-linewidth, chip-based frequency combs for next-generation high-capacity transceivers, data centers, space and mobile platforms.

Cerenkov luminescence imaging (CLI) is a novel optical imaging technique that has been applied in clinic using various radionuclides and radiopharmaceuticals. However, clinical application of CLI has been limited by weak optical signal and restricted tissue penetration depth. Various fluorescent probes have been combined with radiopharmaceuticals for improved imaging performances. However, as most of these probes only interact with Cerenkov luminescence (CL), the low photon fluence of CL greatly restricted it’s interaction with fluorescent probes for in vivo imaging. Therefore, it is important to develop probes that can effectively convert energy beyond CL such as β and γ to the low energy optical signals. In this study, a Eu3+ doped gadolinium oxide (Gd2O3:Eu) was synthesized and combined with radiopharmaceuticals to achieve a red-shifted optical spectrum with less tissue scattering and enhanced optical signal intensity in this study. The interaction between Gd2O3:Eu and radiopharmaceutical were investigated using 18F-fluorodeoxyglucose (18F-FDG). The ex vivo optical signal intensity of the mixture of Gd2O3:Eu and 18F-FDG reached 369 times as high as that of CLI using 18F-FDG alone. To achieve improved biocompatibility, the Gd2O3:Eu nanoparticles were then modified with polyvinyl alcohol (PVA), and the resulted nanoprobe PVA modified Gd2O3:Eu (Gd2O3:Eu@PVA) was applied in intraoperative tumor imaging. Compared with 18F-FDG alone, intraoperative administration of Gd2O3:Eu@PVA and 18F-FDG combination achieved a much higher tumor-to-normal tissue ratio (TNR, 10.24 ± 2.24 vs. 1.87 ± 0.73, P = 0.0030). The use of Gd2O3:Eu@PVA and 18F-FDG also assisted intraoperative detection of tumors that were omitted by preoperative positron emission tomography (PET) imaging. Further experiment of image-guided surgery demonstrated feasibility of image-guided tumor resection using Gd2O3:Eu@PVA and 18F-FDG. In summary, Gd2O3:Eu can achieve significantly optimized imaging property when combined with 18F-FDG in intraoperative tumor imaging and image-guided tumor resection surgery. It is expected that the development of the Gd2O3:Eu nanoparticle will promote investigation and application of novel nanoparticles that can interact with radiopharmaceuticals for improved imaging properties. This work highlighted the impact of the nanoprobe that can be excited by radiopharmaceuticals emitting CL, β, and γ radiation for precisely imaging of tumor and intraoperatively guide tumor resection.

Two-dimensional (2D) π-stacked layered metal-organic frameworks (MOFs) are permanently porous and electrically conductive materials with easily tunable crystal structures. Here, we provide an accurate examination of the correlation between structural features and electronic properties of Ni3(HITP)2, HITP = 2,3,6,7,10,11-hexaiminotriphenylene, as an archetypical 2D MOF. The main objective of this work is to unravel the responsive nature of the layered architecture to external stimuli such as temperature and show how the layer flexibility translates to different conductive behaviors. To this end, we employ a combination of quantum mechanical tools, ab initio molecular dynamics (AIMD) simulations, and electronic band structure calculations. We compare the band structure and projected density of states of equilibrated system at 293 K to that of the 0 K optimized structure. Effect of interlayer π-π and intralayer d-π interactions on charge mobility is disentangled and studied by increasing the distance between layers of Ni3(HITP)2 and comparison to an exemplary case of Zn3(HITP)2 2D MOF. Our findings show how a structural change, which can be deformations along the layers, slipping of layers, or change of the interlayer distance, can induce metal-to-semiconductor or indirect-to-direct semiconductor transition, suggesting a way to adjust or even switch between the intralayer vs interlayer conductive anisotropy in Ni3(HITP)2, in particular, and 2D MOFs in general.

The van der Waals heterojunction involving graphene (Gr) with transition metal dichalcogenides (TMDs) is regarded as a promising structure for its outstanding performance in optoelectronic response. The electron-hole thermalization has been deemed to be the main reason for the subband gap excitation charge transfer from Gr to TMDs. However, the role of the intricate interlayer interaction of Gr and TMDs still requires intensive investigation. Here, we have investigated the photocarrier dynamics in a five-layer PtSe2/Gr heterojunction by using time-resolved optical pump and terahertz probe spectroscopy. Interestingly, after photoexcitation, electron transfer from PtSe2 to Gr has been demonstrated successfully in the PtSe2/Gr/substrate heterojunction; by contrast, no observable charge transfer occurs in the Gr/PtSe2/substrate heterostructure. The prominent difference for the different stacking sequences between Gr and PtSe2 can be ascribed to the effective electric field introduced by the fused silica substrate. A physical picture accounting for the effective electric field introduced by the substrate has been proposed to interpret the charge transfer process in the TMD/Gr heterostructure. More importantly, the electric field induced by the substrate plays a dominant role in controlling the charge transfer pathway in the TMDs/Gr heterojunction. This study not only sheds light on the substrate engineering of the van der Waals heterojunction but also provides new insight into the layer interaction dynamics in the Gr/TMD heterojunction.

The efficiency of antimony selenide (Sb2Se3) solar cells has been improved from 10% within only 7 years, but fundamental properties at the heterojunction interface such as the charge carrie...

Perovskite nanocrystals (NCs) can achieve blue stimulated emission readily by the halide stoichiometry mixing method compared with the traditional metal chalcogenide NCs. However, most perovskite materials can obtain stimulated emission only at low temperatures because nonradiative recombination associated with defects predominates at room temperature. Here, by adjusting the composition and controlling crystallization, a series of CsPbClxBr3−x NCs glasses with large particle size were prepared by traditional melt-quenching to overcome the obstacles, which demonstrated low-threshold stimulated emission from blue to cyan (blue: ∼1.02–0.55 mJ/cm2, cyan: ∼1.59–1.34 mJ/cm2) under two-photon excitation at room temperature. And the CsPbClxBr3-x NCs glasses showed excellent thermostability, which suggested a new opportunity for ultra-stable nonlinear photonics and lasers.

Molecular dynamics simulations combined with periodic electronic structure calculations are performed to decipher structural, thermodynamical and dynamical properties of the interfaced vs. confined water adsorbed in hexagonal 1D channels of the 2D layered electrically conductive Cu3(HHTP)2 and Cu3(HTTP)2 metal-organic frameworks (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene and HTTP = 2,3,6,7,10,11-hexathiotriphenylene). Comparing water adsorption in bulk vs. slab models of the studied 2D MOFs shows that water is preferentially adsorbed on the framework walls via forming hydrogen bonds to the organic linkers rather than by coordinating to the coordinatively unsaturated open-Cu2+ sites. Theory predicts that in Cu3(HTTP)2 the van der Waals interactions are stronger which helps the MOF maintain its layered morphology with allowing very little water molecules to diffuse into the interlayer space. Data presented in this work are general and helpful in implementing new strategies for preserving the integrity as well as electrical conductivity of porous materials in aqueous solutions.

Capturing the photolysis process of archetypal perovskite materials (such as methylammonium lead triiodide, MAPbI3) into metallic Pb0 is fundamentally important to understand the photodegradation pathway of organic–inorganic hybrid perovskites (OIHPs). In this study, the photodecomposition pathway of a MAPbI3 film in an atmospheric argon (Ar) gas environment was quasi-in situ studied comprehensively. Under light illumination, the decomposition of the perovskite film is first triggered at the grain boundaries, along with an obvious generation of metallic lead (Pb0) nanoparticles. Then, the degradation sites extend into the inner MAPbI3 grains. By calculating the growth kinetics of the Pb0 enriched nanoparticles, we can find that it strictly obeys an interfacial diffusion-controlled growth model. Atomic resolution high angle annular dark-field (HAADF) characterization confirms that the Pb0 enriched nanoparticles are with Pb@PbI2−x (x ≈ 0.4) core–shell structures, while the interface between crystalline MAPbI3 and amorphous PbI2−x controls the photodegradation pathway of perovskite films. To the best of our knowledge, this is the first time to directly observe the photolysis process of perovskite films in a practical environment (Ar gas and light illumination), particularly with nano or even atomic-scale resolution. Furthermore, the discovery of the interfacial-controlled photodegradation pathway of MAPbI3 into amorphous PbI2−x and then into Pb@PbI2−x aggregates has never been elucidated before.

The flexible and ever-changing layered structure of electrically conductive 2D metal–organic frameworks (MOFs) poses a formidable challenge for establishing any structure–application relationship. ...

To provide technical support and theoretical guarantee for the prevention and control of soil heavy metal pollution, the main types of topsoil and parent material in Jilin Province were systematica...

Along with the boost of drugs’ exploitation, drug delivery has been a common concern among researchers and patients. As an emerging strategy, the micro- and nano-needle (MNN) is a single or an array of micro/nanoneedles, and promises to be a robust technology for efficient, noninvasive and convenient drug delivery. Compared with the conventional injection, MNN can pierce the bio-membranes to transfer cargos without any damage of tissue or nerves. And regarding the topical drug release, MNN is more efficient than oral administration and topical cream. More specifically, microneedle, a powerful technique, has been widely applied in different diseases such as diabetes, anti-obesity and contraception through skin and ocular surface. Correspondingly, many novel microneedles and optimization methods have been developed recently to improve the drug delivery efficacy. Nanoneedle, much smaller than microneedle, can minimize the skin damages caused by the repeated use of microneedles. Nanoneedles with nanoscaled size are usually used to penetrate the cell membrane. And recently many stimulus-aided methods like electrical and magnetic force have been invented to deepen penetration and improve transfer effects. The aim of this review is to introduce the recent advances of MNN-based drug delivery, including their types, application locations and diseases, optimization of delivery strategies and future development prospects.

Photonic integrated circuits (PICs) have enabled numerous high performance, energy efficient, and compact technologies for optical communications, sensing, and metrology. One of the biggest challenges in scaling PICs comes from the parasitic reflections that feed light back into the laser source. These reflections increase noise and may cause laser destabilization. To avoid parasitic reflections, expensive and bulky optical isolators have been placed between the laser and the rest of the PIC leading to large increases in device footprint for on-chip integration schemes and significant increases in packaging complexity and cost for lasers co-packaged with passive PICs. This review article reports new findings on epitaxial quantum dot lasers on silicon and studies both theoretically and experimentally the connection between the material properties and the ultra-low reflection sensitivity that is achieved. Our results show that such quantum dot lasers on silicon exhibit much lower linewidth enhancement factors than any quantum well lasers. Together with the large damping factor, we show that the quantum dot gain medium is fundamentally dependent on dot uniformity, but through careful optimization, even epitaxial lasers on silicon can operate without an optical isolator, which is of paramount importance for the future high-speed silicon photonic systems.

A method to evaluate the mechanical performance of the corroded steel cable based on the strength condition is proposed. The corrosion safety factor (nα) was introduced, and the evaluation model was established. The eccentric effect as a result of the local corrosion was also considered. Then, the axial tensile experiment on steel-strand specimens was carried out. Furthermore, the mechanical properties, including the ultimate bearing capacity and limited strain, were analyzed. The results show that the properties of locally corroded specimens deteriorate more than uniformly corroded specimens. It is verified that the experimental data are in good agreement with the proposed theoretical model when the corrosion degree α is less than 0.35. Based on the experimental data and the related specification of the stayed cable, the relationship between nα and α was precisely determined. Besides, the level of nα or the safety redundancy can be characterized by the evaluation score δ. The lower the score δ, the less safe is the cable structure. This method also provides significant application prospects for safety evaluation research in civil engineering.

Formamidinium (FA) perovskites have exhibited outstanding optoelectronic properties in solar cells and light-emitting diodes. However, their development on nanolaser application have rarely been ex...

Novel high-quality thin film nanocomposite (TFN) membranes for enhanced forward osmosis (FO) were first synthesized through organic phase controlled interfacial polymerization by utilizing functional multi-walled carbon nanotubes (MWCNTs). As 3-aminopropyltriethoxysilane (APTES) grafted MWCNTs via an amidation reaction significantly promoted the dispersion in organic solution, MWCNTs-APTES with better compatibility effectively restricted the penetration of trimesoyl chloride (TMC), thus adjusting the morphology and characters of TFN membranes. Various techniques such as Fourier transform infrared spectra (FTIR), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), sessile droplet analysis and FO experiments and reverse osmosis (RO) operation were taken to characterize and evaluate the performance of nanocomposites and membranes. The prepared TFN FO membranes exhibited good hydrophilicity and separation efficiency, in which water flux was about twice those of thin film composite (TFC) membranes without MWCNTs-APTES in both AL-DS and AL-FS modes. Compared with the original TFC membrane, the membrane structural parameter of the novel TFN FO membrane sharply was cut down to 60.7%. Based on the large number of low mass-transfer resistance channels provided by functional nanocomposites, the progresses may provide a facile approach to fabricate novel TFN FO membranes with advanced selectivity and permeability.

Hole transport layer is one of the primary factors that improve the optical-electric properties of perovskite solar cells. Spiro-OMeTAD is frequently utilized as hole transport materials in PSCs. However, pristine or oxygen oxidized spiro-OMeTAD has low mobility and conductivity. Herein, cumene hydroperoxide is introduced to accelerate the oxidation of spiro-OMeTAD, which improves the carrier mobility, declines the trap-state density and optimizes the energy match with perovskite layer, leading to the enhancement of the performance of device. Kelvin probe force microscopy images and Atomic force microscopy images show the improvement of interface morphology. Multiple electrochemical characterizations demonstrate the acceleration of spiro-OMeTAD oxidation, the enhancement of conductivity of the doped hole transport material, and the decline of trap-state density and carrier annihilation in hole transport layer/perovskite interface after the modification. The perovskite solar cell doped with optimal concentration acquires a power conversion efficiency of 20.33%, while the undoped device gets an efficiency of 18.00%.

Super-hydrophobic films were synthesized on the Mg alloy AZ31 by modifying in-situ grown Mg-Al layered double hydroxide (LDH) films with stearic acid (SA), sodium laurate (SL), myristic acid (MA) and 1H, 1H, 2H, 2H–perfluorodecyltrimethoxysilane (PFDTMS). These films exhibited a static water contact angle of 150.6°, 153.7°, 152° and 145.5°, respectively. Mg-Al LDH-SA, Mg-Al LDH-SL and Mg-Al LDH-MA films were produced by the neutralization reaction of the fatty acid and Mg(OH)2 whereas the Mg-Al LDH-PFDTMS film was produced by the hydrolysis reaction of PFDTMS along with the condensation polymerization reaction. The electrochemical impedance spectroscopy (EIS), the hydrogen evolution data as well as long-term immersion tests indicated that Mg-Al LDH-PFDTMS provided better barrier protection to improve the corrosion resistance of AZ31 Mg compared with the Mg-Al LDH-SA, Mg-Al LDH-SL and Mg-Al LDH-MA films, because the Si OH groups and the hydroxyl groups on the surface of the film were combined to form CF3(CF2)7(CH2)2Si(O-Surface)3, which decreased the surface energy and improved the corrosion resistance.

Mg-Al layered double hydroxides (LDHs) were deposited on the anodized magnesium alloy AZ31 via an easy in-situ method, and the surfaces of MgAl-LDHs were modified with myristic acid (MA) and 1H, 1H, 2H, 2H-Perfluorodecyltrimethoxysilane (PFDTMS). The obtained results showed that LDHs with the biggest flakes were preferential sites for absorption of MA, while unfavorable for the adsorption of PFDTMS. All of films modified with MA were superhydrophobic. The corrosion behavior of the AZ31 with modified LDH films was evaluated using hydrogen collection, electrochemical impedance spectroscopy (EIS), polarization potentiodynamic curves and the immersion tests. The superhydrophobic films considerably improved the corrosion performance of the LDH films on the AZ31 substrate.

Miniaturized laser sources recently attracted considerable interests as their potential applications in optical communication, data storage, and imaging. However, high cavity losses induced by size reduction from the gain medium would lead high lasing threshold. In this work, the enhanced optical properties of CsPbBr3 perovskite nanocubes by using localized surface plasmonic effect of Au nanoparticles (NPs) were investigated. The integration of Au NPs in the poly (3, 4-ethylenedioxy-thiophene): poly (styrenesulfonate) PEDOT: PSS layer induces obviously enhancement both in the absorption and photoluminescence (PL) of CsPbBr3 perovskite nanocubes. Importantly, the lasing threshold of CsPbBr3 perovskite nanocubes is significantly reduced by ~ 33%. This study suggests that the lead halide perovskites hybridized with plasmonic nanomaterials would be promising candidates for laser devices and other optoelectronic devices with high efficiency.

Detecting deep tumors inside living subject is still challenging for Cerenkov luminescence imaging (CLI). In this study, a high-sensitivity endoscopic CLI (ECLI) system was developed with a dual-mode deep cooling approach to improve the imaging sensitivity. System was characterized through a series of ex vivo studies. Furthermore, subcutaneous and orthotropic human hepatocellular carcinoma (HCC) mouse models were established for ECLI guided tumor resection in vivo. The results showed that the ECLI system had spatial resolution (62.5 μm) and imaging sensitivity (6.29 × 10−2 kBq/μl 18F-FDG). The in vivo experimental data from the HCC mouse models demonstrated that the system was effective to intraoperatively guide the surgery of deep tumors such as liver cancer. Overall, the developed system exhibits promising potential for the applications of tumor precise resection and novel nanoprobe based optical imaging.

Heat is a ubiquitous energy resource, which is easily accessible from the environment. The pyroelectric effect, a phenomenon that converts temperature variation into electricity, enables a material to be operated like a heat engine between high and low temperatures and electric fields, producing electrical work. However, current literature focuses on material performances, with no energy stored by operating in such conversion cycles. This work presents a complete pyroelectric management system that both realized cycled energy conversion and a maximum harvested power up to 13.1 μW. We achieved this by integrating a laser heat source, an advanced pyroelectric device, a practical power interface, and an energy storage component together. A thin film Lead Zirconate Titanate device was fabricated to achieve very fast temperature response (∼0.1 ms). Thus, the energy conversion can be achieved in a much higher thermodynamic frequency (1 kHz), leading to a larger power density. The proposed power interface manages an optimized pyroelectric conversion cycle while recharging a battery, or a storage capacitor (up to 2.1 V). The results provide a promising method to harvest energy from waste-heat and have shown great potential to supply power to small-scale, distributed devices. In addition, the application of the laser source has also enabled the system to achieve wireless power transmission, which would enable a more flexible way to supply power to multiple devices.

Polymers : Molecular Diversity Preservation International 13(7), 1083 (2021). doi:10.3390/polym13071083 special issue: "Special Issue "Recycling and Resource Recovery from Polymers" / Special Issue Editors: Dr. Sheila Devasahayam, Guest Editor; Prof. Dr. Raman Singh, Guest Editor; Prof. Dr. Vladimir Strezov, Guest Editor", Published by MDPI, Basel

Funder: ERC Starting Grant (No. 717026), Bright and efficient blue emission is key to further development of metal halide perovskite light-emitting diodes. Although modifying bromide/chloride composition is straightforward to achieve blue emission, practical implementation of this strategy has been challenging due to poor colour stability and severe photoluminescence quenching. Both detrimental effects become increasingly prominent in perovskites with the high chloride content needed to produce blue emission. Here, we solve these critical challenges in mixed halide perovskites and demonstrate spectrally stable blue perovskite light-emitting diodes over a wide range of emission wavelengths from 490 to 451 nanometres. The emission colour is directly tuned by modifying the halide composition. Particularly, our blue and deep-blue light-emitting diodes based on three-dimensional perovskites show high EQE values of 11.0% and 5.5% with emission peaks at 477 and 467 nm, respectively. These achievements are enabled by a vapour-assisted crystallization technique, which largely mitigates local compositional heterogeneity and ion migration.

Luminescence lifetime-based nanosensors for chloride ions were designed by incorporating a luminescent ruthenium dye [Ru(1,10-phenanthroline)3] inside silica nanoparticles and chemically labelling their outer surface with chloride ion-sensitive fluorescent dyes (N,N'-bis(carboxypropyl)-9,9'-biacridine). The nanosensor surface was further functionalized with positively charged amino groups to facilitate intracellular uptake via endocytosis and target lysosomes. The nanosensors have an average diameter of 52 nm and are monodispersed in aqueous solutions. Because of the long lifetime of the reference ruthenium dye, the sensor response can be analyzed using the time-domain dual-lifetime referencing (td-DLR) approach. The use of pulsed excitation in td-DLR rather than intense continuous illumination in ratiometric measurements greatly prevents the dye from photobleaching which significantly improves its measurement stability and reproducibility for long-term monitoring. At optimum conditions, the sensor can measure chloride concentration in the range of 0-200 mM with a large ratiometric signal change from 140.9 to 40.2. Combined with our custom-built microscopic td-DLR system, variations of intracellular chloride concentration in lysosomes were imaged quantitatively with a high spatial resolution and accuracy.

This paper proposes a novel hybrid PWM mode for braking control of the brushless dc motor in the electric vehicle drive applications. To simplify the hardware circuit topology and reconstruct the real-time motor currents, a single dc-link current sensor sampling method is employed. However, in small duty ratio applications, the current signals cannot be sampled accurately under the conventional unipolar PWM mode due to the limitation of amplifier bandwidth and analog to digital converter sampling time. Therefore, a hybrid PWM mode based on unipolar-bipolar switching is used to obtain the current signals in a wide duty ratio range. The method proposed in this paper combines the advantages of unipolar and bipolar PWM, and realizes the real-time current control of brushless dc motor in the braking process. Simulation and experimental results verify the feasibility of the proposed control mode.

We demonstrate an elastic multi-wavelength selective switch with up to two wavelength switching capability per crosspoint. We fabricated the switch in a silicon photonics foundry and demonstrated a 17 nm tuning range for ring resonators, with a mean path loss of 2.43 dB. This is a 70% reduction in path loss as compared to previous generations, and we demonstrate a high-speed pulse-amplitude-modulation-4 transmission at 111 Gbps through different paths of the switch.

This work experimentally investigates the impact of p-doping on the relative intensity noise (RIN) properties and subsequently on the modulation properties of semiconductor quantum dot (QD) lasers epitaxially grown on silicon. Owing to the low threading dislocation density and the p-modulation doped GaAs barrier layer in the active region, the RIN level is found very stable with temperature with a minimum value of − 150 d B / H z . The dynamical features extracted from the RIN spectra show that p-doping between zero and 20 holes/dot strongly modifies the modulation properties and gain nonlinearities through increased internal losses in the active region and thereby hinders the maximum achievable bandwidth. Overall, this Letter is important for designing future high-speed and low-noise QD devices integrated in future photonic integrated circuits.

Carbon dioxide is a green and sustainable one-carbon source, which could be utilized in the production of various fine chemicals. In recent studies, the light-mediated carboxylation employing CO2 has received considerable attention. The photocarboxylation of substrates with CO2 to build novel C-C bonds is introduced in this Minireview. The article is arranged based on the light-driven reactive intermediates, including CO2 radical anion, substrate radical anions, carbanions, and M-C species. Most of the cases are under the topic of photoredox catalysis, with single electron transfer as the main driving force. Some non-catalytic examples are also discussed to provide more mechanistic insights.

This paper describes a theory for mode locking and frequency comb generation by four-wave mixing in a semiconductor quantum-dot active medium. The derivation uses a multimode semiclassical laser theory that accounts for fast carrier collisions within an inhomogeneous distribution of quantum dots. Numerical simulations are presented to illustrate the role of active medium nonlinearities in mode competition, gain saturation, carrier-induced refractive index and creation of combination tones that lead to locking of beat frequencies among lasing modes in the presence of cavity material dispersion.

Surface defects of titanium strip need to be removed by local grinding, but local cracking or band breaking then occurs during subsequent cold rolling. Tensile properties and deformation resistance of 3 mm thick commercially pure titanium strip with grinding pits on the surface were simulated by a finite-element method using a multi-pass cold-rolling deformation process. The stress and strain of grinding pits with depths of 0.25&ndash, 2 mm were analyzed. During cold-rolling deformation, the stress and strain in the center of a grinding pit were larger than at the edge region. The strip was first subjected to tensile stress in the rolling direction, which then decreased and gradually changed to compressive stress. Partial stress was larger in the rolling direction than in the transverse direction. When the tensile stress and true strain both exceeded the stress and strain limits during second-pass rolling, the strip with a grinding depth of 2 mm cracked, but shallower grinding pits were repaired. The criterion for cracking during rolling after grinding is that the maximum tensile strain at the bottom of the pit must be less than the critical strain of the material: ln(1+h/H)&le, &epsilon, Crln(1+h/H)&le, Cr. Results of numerical simulation were verified by the data for cold-rolling tests.

An ohmic contact to a single GaAs nanowire is achieved by sulfide passivation and rapid annealing. The device exhibits a low dark current of hundreds of pA and good photoresponsivity of 13 mA/W. © 2020 The Author(s)

Hypothesis Conventional strategies for strengthening silica aerogels through polymer modification always lead to a significant density increase and an obvious sacrifice of thermal insulation performance. In this work, we propose a facile one-pot method for the preparation of polymer-reinforced silica aerogels via polymerization of water-in-oil high internal phase emulsion (HIPE) templates. Experiments Hyperbranched vinyl-modified polyethoxysiloxane (VPEOS) is used as both emulsion stabilizer and silica source. FT-IR spectra of VPEOS are recorded to confirm the successful incorporation of vinyl groups. The pore structure of polymer-functionalized silica aerogels is characterized by a scanning electron microscope (SEM), nitrogen adsorption–desorption and mercury intrusion porosimetry. Findings The Young’s modulus is increased from 0.69 to 19.28 MPa, nearly 28 times that of unmodified silica aerogels. Moreover, the silica aerogels present a superhydrophobicity with a water contact angle of 152.4° and good thermal insulation. The superior performance properties of the polymer-reinforced silica aerogels over pure silica aerogels may guarantee their wide applications in energy and aerospace fields.

Viscosity is one of the most important properties for many scientific and technological applications, and therefore it has been the subject of an enormous effort of measurement, correlation, and interpretation. Reliable reference data can be of great help to improve viscosity accuracy, while for viscosity, the only accepted standard is the viscosity of pure water at 20 °C (the reference value recommended by ISO is 1.0016 mPa·s). With the technology and industry advancing, there is a new requirement for reference materials of viscosity covering wide temperature, pressure, and viscosity ranges in order to face the challenge that the order of magnitude of viscosity turns to 1014. Considering the dissatisfaction of the only standard, we put forward these candidates to meet the need of appropriate viscosity standard materials: dimethyl adipate (DMA), diethyl adipate (DEA), dipropyl adipate (DPA), and dibutyl adipate (DBA). These materials have the characteristics of easy to obtain, high purity, high thermal chemical stability, and especially larger viscosity value. In this work, the viscosity was experimentally measured by the vibrating wire viscometer over the temperature range of (283 to 363) K and at pressures up to 40 MPa. The combined expanded uncertainty of the reported viscosity is about 2 % with a confidence level of 0.95 (k = 2). The empirical Andrade–Tait equation was used to correlate the experimental results.

Cerenkov luminescence (CL) is a novel imaging modality that has recently been used in biomedical imaging field. However, there are plenty of limitations for the clinical transactions of Cerenkov luminescence imaging (CLI), due to the properties of CL. The newly developed europium-doped gadolinium oxide (Gd 2 O 3 :Eu) nanoparticles can interact with the CL and γ-radiation as well, generating a stronger red-shifted light, which is of great benefits for biomedical application and clinical transaction.

On-chip photonic information processing systems require great research efforts toward miniaturization of the optical components. However, when approaching the classical diffraction limit, conventional dielectric lasers with all dimensions in nanoscale are difficult to realize due to the ultimate miniaturization limit of the cavity length and the extremely high requirement of optical gain to overcome the cavity loss. Herein, we have succeeded in reducing the laser size to subwavelength scale in three dimensions using an individual CsPbBr3 perovskite nanocuboid. Even though the side length of the nanocuboid laser is only ∼400 nm, single-mode Fabry–Perot lasing at room temperature with laser thresholds of 40.2 and 374 μJ/cm2 for one- and two-photon excitation has been achieved, respectively, with the corresponding quality factors of 2075 and 1859. In addition, temperature-insensitive properties from 180 to 380 K have been demonstrated. The physical volume of a CsPbBr3 nanocuboid laser is only ∼0.49λ3 (where ...

Based on the natural graphene-structure in the raw asphaltene material, a graphene-polyurethane sponge (GPU) oil-absorption material was prepared via a facile and inexpensive route of dip-coated sp...

The interplay among ferroelectric, magnetic and elastic degrees of freedom in multiferroics is the key issues in condensed matters, which has been widely investigated by various methods. Here, using ultrafast two-color pump-probe spectroscopy, the picosecond electron-phonon and spin-lattice coupling process in Dysprosium doped-BiFeO3 (BDFO) films on SrTiO3 (STO) substrate have been investigated systematically. The Dy-doping induced structural transition and magnetic enhancement in BDFO is observed by ultrafast electron-phonon and spin-lattice interaction, respectively. The elastic anomalies in BDFO films are revealed by the photo-induced coherent acoustic phonon. With increasing the Dy doping ratio, the frequencies of the acoustic phonon in the films are modulated, and the phonon transmission coefficient between films and substrate is found to approach unity gradually. The ultrafast observation of the tunability of the ferroelectric, magnetic and the elastic properties in the morphotropic phase boundary of rare-earth doped BFO films provides new insights into the integration of BFO in next-generation high frequency electro-magnetic and electroacoustic devices.

Pyroelectric materials are promising for thermal energy scavenging from waste-heat sources and new materials with exotic properties are constantly being discovered. Antiferroelectrics (AFE) are of particular interest since such materials have been observed to possess both conventional, negative pyroelectricity and inverse, positive pyroelectricity. In this study, we compare direct and indirect measurements of the pyroelectric coefficient and use the temperature dependence on the dielectric constant to show the inverse pyroelectric regime arises primarily from field-induced pyroelectricity. Energy conversion cycles are performed in both pyroelectric regimes using a 1 kHz pulsed laser heat source, realizing a maximum power density of 2.25 W cm−3 in the conventional regime and 0.68 W cm−3 in the inverse regime. A new pyroelectric energy conversion model, using parameters taken from direct measurements of the pyroelectric coefficient, capacitance, loss tangent, and leakage current agrees with the energy conversion experiments, showing both the validity of the model and the origin of pyroelectricity in the inverse regime. Finally, a resonant circuit for pyroelectric energy harvesting is proposed that takes full advantage of the bi-directional functionality of AFE materials. This work clarifies the debate on the origin of pyroelectric features in AFE materials and demonstrates the potential for future energy conversion applications.

Quantum dot lasers epitaxially grown on Si are promising for an efficient light source for silicon photonics. Recently, considerable progress has been made to migrate 1.3 μm quantum dot lasers from off-cut Si to on-axis (001) Si substrates. Here, we report significantly improved performance and reliability of quantum dot lasers enabled by a low threading dislocation density GaAs buffer layer. Continuous-wave threshold currents as low as 6.2 mA and output powers of 185 mW have been achieved at 20 °C. Reliability tests after 1500 h at 35 °C showed an extrapolated mean-time-to-failure of more than a million hours. Direct device transparency and amplified spontaneous emission measurements reveal an internal optical loss as low as 2.42 cm–1 and injection efficiency of 87%. This represents a significant stride toward efficient, scalable, and reliable III–V lasers on on-axis Si substrates for photonic integrate circuits that are fully compatible with CMOS foundries.

In vivo fluorescence imaging in the near-infrared II window (NIR-II, 1000–1700 nm) has great improvements in imaging quality compared with the visible (400–700 nm) and the NIR-I (700–900 nm) window due to the low autofluorescence and the reduced scattering. To date, a variety of NIR-II fluorophores have been synthesized and applied in vivo imaging and disease diagnosis. Multifunction is believed as one of the developing trends. In this study, we report a liposome-coated lanthanide nanoparticle, named as NPs@Lips, which can emit three-wavelengths fluorescence (1000–1100 nm (NIR-II), 1300–1350 nm (NIR-IIa), 1500–1700 nm (NIR-IIb) simultaneously under an 808 nm laser excitation. The imaging results demonstrated that the images in longer wavelengths provided a higher resolution and enhanced signal-to-noise (S/N) ratio than the ones in shorter wavelengths. Then, the NPs@Lips were studied for in vivo multifunctional biological imaging, including brown adipose tissue imaging, vascular imaging and lymph node localization biopsy. Interestingly, NPs@Lips can accumulate in brown adipose tissue without any targeting molecules, which provided an alternative sensitive and non-radiation method for brown adipose tissue imaging in the field of metabolic disorders. Overall, the NPs@Lips were potential NIR-II probe for multifunctional nanomedicine applications.

The poor stability, in particular with respect to temperature, moisture, and light exposure, remains a ubiquitous impediment virtually for metal halide perovskite materials and devices in their future practical application. Herein, from the perspective of precursor solution chemistry, ionic liquid solvent methylammonium acetate (MAAc) is introduced to prepare high-quality MAPbBr3 perovskite thin films in a one-step air-processing process without anti-solvent treatment. Due to formation of pinhole-free, uniform, and compact MAPbBr3 perovskite film, excellent amplified spontaneous emission (ASE) with high emission efficiency and low threshold is obtained under nanosecond laser. Furthermore, the prepared MAPbBr3 perovskite exhibits excellent two-photon induced ASE with a low threshold of 100 µJ cm-2 under 800 nm femtosecond laser excitation. More importantly, in comparison with the traditional MAPbBr3 films prepared with N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), the MAPbBr3 film prepared with MAAc shows excellent optical stability: no signs of degradation under more than 2 h pulsed laser excitation, stable ASE emission spectra under the humidity of 95% and ASE spectra can be stimulated when films are kept in air for more than 6000 h without encapsulation.

We describe the effectiveness of filter layers, which displace misfit dislocation (MD) formation away from the active region, in improving high temperature reliability of epitaxially integrated InAs quantum dot lasers on on-axis silicon substrates. We find that inserting these “trapping layer (TL)” filters at either 80 nm or 180 nm from the active region substantially reduces device degradation at 60 °C. After 3000 h of continuous operation, the best trapping-layer-free device shows a 55% increase in threshold current while the best trapping layer (TL) devices each show less than a 9% increase. We explain these findings by correlating changes in individual device performance to changes in misfit dislocation (MD) structure. All MDs in devices without TLs show evidence of recombination enhanced dislocation climb (REDC); in contrast, adding trapping layers at 180 nm or 80 nm reduces the fraction of electrically active MDs to 9% and 1%, respectively. Reliability data after 3000 hours suggest that incorporating trapping layers a shorter distance from the active region (80 nm) is more effective than incorporating these layers further away. We conclude by identifying the mutually and self-reinforcing failure processes associated with REDC that TLs significantly remediate: increasing dislocation line length, increasing point defect densities, and increasing junction temperature. Overall, understanding and controlling crystal defects continues to be the most impactful avenue toward integrating light sources on photonic integrated circuits and closing the gap with native-substrate lasers.

Thermodynamics and kinetics of O2 adsorption and its impacts on structural features and conductive behavior of 2D π-stacked layered metal–organic frameworks (MOFs) are studied using periodic PBE-D3 quantum mechanical calculations. Our computed O2 adsorption energies of Co3(HTTP)2 (HTTP = hexathiotriphenylene), as a representative of the 2D MOFs family, show that not only open-Co(II) sites but also redox-active HTTP linkers take part in chemisorption of O2 by forming strong S=O bonds. This is in contrast to conventional 3D Co2(OH)2(BBTA) and Fe2(dobdc) MOFs with similar hexagonal 1D channels where O2 adsorption occurs solely via coordination to the open-metal sites. Due to the adsorptive capability of its redox-active linkers, Co3(HTTP)2 is superior to the analogues 3D MOFs where the change in the oxidation state of the transition metal centers is suggested to result in hindering both the kinetics and thermodynamics of the adsorption process. Our calculated band structures and density of states show that the conductive behavior of the studied Co3(HTTP)2 2D MOF changes dramatically from metallic in the parent system to semiconducting under oxygen rich conditions, with direct bandgap openings that range from 123 to 251 meV. The results presented in this work are helpful in understanding the effects of different electroactive guest molecules on the structure and conductive behavior of 2D layered MOFs and related nonporous materials.

This study investigated the effects of cyclic nonlinear viscoelastic (NLVE) loads on the fatigue response of asphalt binder, and the damage accumulation law of asphalt binder under NLVE-LVE combined loads. The experimental results reported the difference in the fatigue characteristics of asphalt binder under cyclic NLVE and LVE loads. It was found that NLVE loads nonlinearly reduced the remaining fatigue life of asphalt binder, which demonstrated the inapplicability of the conventional Miner’s rule. In addition, good agreement between the proposed model (Oeser and Zhang (orz) model) and the experimental results indicated the reliability and effectiveness of the established damage accumulation model.

This paper explores the removal of natural organic matter (NOM) and disinfection by-products (DBPs) in drinking water by heterogeneous Fenton-like oxidation and granular activated carbon (GAC) filtration in a pilot scale test without adjusting pH of the water. pH of the used water in this study was from 7.5 to 8.7. Comparing with conventional water treatment processes, heterogeneous Fenton-like reaction and GAC filtration increased the removal rate of dissolved organic carbon (DOC), NOM with different apparent molecular weight (AMW) (F1-F7) and with different compositions (C1-C5) to 75.11%, 88.65% and 58.73%, respectively. Moreover, heterogeneous Fenton-like reaction and GAC filtration increased the removal rate of DBPs to 88.18%. The multivariate statistical analysis indicated that haloacetic acids (HAAs) and haloketones (HKs) mainly came from fulvic-like and humic-like NOM with AMW lower than 1.5 K Da. These substances with AMW between 1.5 K Da and 3.5 K Da were the main precursors of trihalomethanes (THMs). The main precursors of halonitriles (HANs) were soluble microbial byproduct-like (SMP-like), tyrosine-like and tryptophan-like substance with the AMW between 3.5 K Da and 4.5 K Da. Overall, without adjusting pH of water, heterogeneous Fenton-like reaction and GAC filtration improved the removal efficiency of NOM and DBPs, and controlled the genotoxicity of drinking water.

Sonodynamic therapy is considered as a minimally invasive method for pathogen elimination and cancer therapy with high spatial and temporal accuracy. However, sonosensitizers with good biocompatibility and high efficiency are still urgently needed. Herein, we have developed a piezoelectric nanocomposite, barium titanate (BaTiO3, BTO) nanocubes with Schottky junction modified by Au nanoparticles (Au@BTO) as a new kind of sonosensitizer for high-efficient sonodynamic therapy. Ultrasound as an exogenous mechanical wave can trigger the piezotronic effect of Au@BTO to facilitate the separation and migration of charge carriers at the piezoelectric/metal interface, which further effectively increases reactive oxygen species (ROS) generation via redox reaction. Due to the high ROS generation efficiency, Au@BTO as the sonosensitizer shows a high antibacterial efficiency against representative Gram-negative and Gram-positive bacteria. Furthermore, the in vitro and in vivo results illustrate that the sonodynamic process also promotes fibroblast migration, which contributes to dermal wound healing in mice. The proposed piezoelectric nanocomposite as a new kind of sonosensitizer has great potential for sonodynamic therapy.

The exciton effect in two-dimensional (2D) transition metal dichalcogenides (TMDs) plays a dominating role in describing the optical and optoelectronic properties. However, the interplay between the excitons and free carriers has not yet been understood upon photoexcitation in 2D TMDs. Here, we first present a study of the dynamical interplay of excitons and unbound electron–hole pairs using time-resolved terahertz (THz) spectroscopy (TRTS) in a few-layer WS2 laminate. Our experimental results demonstrate that the Auger recombination is observed in the relaxation process of the mobile charge carriers rather than that of excitons upon photoexcitation. The transient complex THz photoconductivity spectroscopy of WS2 is well described by the Drude–Lorentz model of free carriers modulated by the exciton polarization field. Our results provide a comprehensive understanding of nonequilibrium carrier kinetics (both excitons and free carriers) in WS2 laminate, and should be applicable to other 2D systems.

Two series of membranes A and B were designed and prepared by the following synthesis protocols where the cross-linked membranes were composed of highly sulfonated poly(ether ether ketone) (SPEEK) as the acidic component and polyphosphazenes backbone as the basic component. Membrane A was synthesized based on the graft-onto reaction between brominated poly[(4-methoxyphenoxy)(4-methylphenoxy)phosphazenes] (PMMP-Br) and SPEEK3 polymers, while membranes B were obtained by the reaction of bromomethyl groups of polyphosphazenes with triethylamine and simultaneously combined with various amounts of SPEEK3. All the membranes were characterized chemically, thermally, and mechanically by a set of technical means. Polyphosphazenes were found to constrain to a large extent the water uptake and swelling when blended with highly sulfonated PEEK providing sufficient mechanical strength without over-swelling. Specially, the advent of sulfonated single-walled carbon nanotubes (SCNT) in the membrane A led to the hybrid membrane A2:1-SCNT with favorable properties. It exhibited a satisfying proton conductivity of 0.132 S cm −1 at 80 °C and a very low methanol permeability of 2.16×10 −7 cm 2 s −1 , and retained considerable thermal stability as well as mechanical strength. Also, the fuel cell performance of A2:1-SCNT at 25 °C was higher than that of recast membrane A2:1.

Wax-based additives can be used as flow improvers to enhance the workability of asphalt rubber (AR). Conventionally, warm asphalt rubber (WAR) is produced by preparing AR first and then blending it with warm mix asphalt (WMA) additive. However, directly mixing WMA additive, base asphalt and crumb rubber together may save more energy since the early incorporation of WMA additive also helps decrease the production temperature of AR. To assess the feasibility of incorporating wax-based additives at an earlier stage, this study investigates the influence of the mixing procedure on WAR prepared by two wax-based additives, i.e., commercial Sasobit and conventional paraffin wax. Rheological tests on WAR revealed no significant difference between WARs prepared by different procedures. However, the direct mixing method led to worse WAR workability compared to the traditional mixing procedure. Chemical analysis on the liquid phase of WARs (crumb rubber removed) indicated that independent of the type of wax-based additive, there is less wax in the liquid phase of WARs when the additive is added earlier, which may be caused by the absorption of wax by crumb rubber during the interacting process. Thus, it is not recommended to replace the traditional mixing procedure with the direct mixing method.

Graphene oxide (GO) is an attractive option for large scale production of graphene. On the other hand, the graphene obtained by the reduction of GO has inevitable structural defects, and the vacant lattice sites will significantly restrict its conductivity. It has been demonstrated that thermal annealing in hydrogen is an efficient method to reduce defects and heal the lattice in GO samples. However, it is still not clear how the defects and/or disordering influence the photoelectric conversion efficiency and the carrier relaxation pathway in GO. Herein, time-domain terahertz (THz) spectroscopy is employed to characterize the properties of the multilayer GO films which were annealed in hydrogen at various temperatures. Upon photoexcitation, a transient increase of the conductivity was observed for the reduced graphene oxide (RGO) samples. The ultrafast carrier relaxation process can be well assigned to the carrier–carrier scattering and carrier–phonon coupling. Our results demonstrated that the RGO films ...