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Limited by large transmission loss, the development of transverse electric (TE) mode silicon-on-insulator (SOI) based on-chip long length chirped grating waveguide faces many difficulties now. To overcome this problem, multi-mode waveguide with a measured transmission loss of 0.7 dB/cm is applied in this paper, and a chirped spiral Bragg grating waveguide (SBGW) is proposed and experimentally demonstrated. The length of the chirped SBGW reaches 2.7 cm, which is the longest SOI based grating reported so far. The total group delay is measured to be 628 ps, with a structure size of only 0.3 mm2 due to the application of spiral configuration. The slope of the linear dispersion is -27.7 ps/nm. This integrated chirped SBGW shows great compatibility with frequently used TE mode SOI devices and has great potential for applications in microwave photonics requiring dispersion control.

The electrochemical performances of reduced graphene oxide (RGO)/poly-3,4-dioxyethylenethiophene (PEDOT) aerogels as supercapacitor electrode materials were evaluated. The PEDOT was synthesized by oxidative polymerization of 3,4-dioxyethylenethiophene (EDOT). It was doped by nonylphenol polyoxyethylene ether sulfate (NPES) in order to become a flowable material (F-PEDOT) at or near room temperature. Hydrothermal treatment of a mixture of graphene oxide (GO) and F-PEDOT led to reduced graphene oxide (RGO) and dedoped PEDOT (RGO/PEDOT) aerogels which possessed a high specific surface area and a good compressive modulus. When used as a supercapacitor electrode material, it exhibited a high capacitance of 400 F·g−1 at a current density of 0.5 A·g−1, and 234 F·g−1 at a high current density of 20 A·g−1 in the three-electrode test system. It retained almost its initial capacitance over 6000 charge–discharging cycles even at a current density of 10 A·g−1. Moreover, the RGO/PEDOT//RGO asymmetric supercapacitor (ASc) exhibits a maximum energy density of 14.16 W h·kg−1 at a power density of 1.53 kW·kg−1 and displays an acceptable cycle stability with 83.4% of the initial capacitance retention after 8000 charging–discharging cycles at a high rate of 6.25 A·g−1.

The unique geometry of screw extruders allows handling very viscous media; thus, they can be used as continuous reactors to conduct polymerization reactions without using any solvents. This is call...

A microwave photonic phase shifter based on four cascaded tunable silicon nitride microring resonators is proposed. The phase shifts and RF power variations of the microwave photonic phase shifter were investigated theoretically and experimentally. Good overall performances with full phase tuning range of 400°, low RF power variations of ± 1.5 dB with a broad bandwidth of 11 GHz, fiber to fiber insertion loss about 5.2 dB were achieved. The maximum frequency can be extended to about 40 GHz, which is limited by the MRR’s free spectra range.

Flexographic printing is promising for large-area electronics due to high print-speed and roll-to-roll capability. There have been recent attempts in using graphene as an active pigment in inks, most notably for slower techniques such as inkjet and screen printing. However, formulation of graphene-enhanced inks for high-speed printing and its effect on key metrics have never been investigated. Herein, graphene nanoplatelets (GPs) are incorporated to a conductive flexographic ink without compromising the rheological properties. An industrial scale at 100 m min−1 is printed on paper and polyethylene terephthalate (PET) substrates using a commercial flexographic press, and statistical performance variations are investigated across entire print runs. It is shown that GP-incorporation improves sheet-resistance (Rs) and uniformity, with up to 54% improvement in average Rs and 45% improvement in the standard-deviation on PET. The adhesion on both the substrates improves with GP-incorporation, as verified by tape/crosshatch tests. The durability of GP-enhanced samples is probed with a 1000 cyclic bend-test, with 0.31% average variation in resistance in the flat state on PET between the first and last 100 bends, exhibiting a robust print. The statistically scalable results show that GP-incorporation offers a cost-performance advantage for flexographic printing of large-area conductive patterns without modifications to traditional high-speed graphics printing presses. Published version We acknowledge funding from the Engineering and Physical Sciences Research Council (EP/L016087/1) and Alphasense Limited in United Kingdom.

Nonpolar Si-doped AlGaN with high electron concentration (EC) and superior surface morphology (SM) layers were successfully grown on r-plane sapphire substrates for the first time with metal organic chemical vapor deposition technology. X-ray diffraction, cross-sectional scanning electron microscope, ultraviolet–visible absorption spectroscopy, atomic force microscopy, and Hall measurements were used to examine the influence of indium surfactant and an extra AlGaN buffer on crystalline quality (CQ), SM, and electrical characteristics of the nonpolar Si-doped n-AlGaN, respectively. The characterization results revealed that the anisotropy in CQ of the nonpolar Si-doped n-AlGaN epi-layers was suppressed effectively, and the SM, as well as the electrical properties including EC, electron mobility (EM), and electron resistivity (ER), had been significantly improved by using indium surfactant and an extra AlGaN buffer layer. In fact, an EC as high as 4.8 × 1017 cm−3, an EM up to 3.42 cm2/V s, an ER down to 4.78 $$\Omega \bullet $$cm , and a root-mean-square value as small as 8.2 nm for surface roughness was achieved for the nonpolar Si-doped n-AlGaN with a relatively high Al composition of 50%.

Black phosphorus (BP) attracts huge interest in photonic and optoelectronic applications ranging from passive switch for ultrafast lasers to photodetectors. However, the instability of chemically unfunctionalized BP in ambient environment due to oxygen and moisture remains a critical barrier to its potential applications. Here, the parylene-C layer was used to protect inkjet-printed BP-saturable absorbers (BP-SA), and the efficacy of this passivation layer was demonstrated on the stable and continuous operation of inkjet-printed BP-SA in harsh environmental conditions. BP-SA was integrated in an erbium-doped ring laser cavity and immersed in water at ~60°C during operation for investigation. Mode-locked pulses at ~1567.3 nm with ~538 fs pulse width remained stable for >200 h. The standard deviation of spectral width, central wavelength, and pulse width were 0.0248 nm, 0.0387 nm, and 2.3 fs, respectively, in this period, underscoring the extreme stability of BP-SA against high temperature and humidity. This approach could enable the exploitation of BP-based devices for photonic applications when operating under adverse environmental conditions.

A silicon nitride waveguide crossing based on multimode-interference is designed and fabricated. By optimizing the structure parameters with finite difference time domain method, 0.3 dB insertion loss and −75 dB crosstalk at 1550 nm are obtained. Then the designed waveguide crossing is fabricated based on the double strip silicon nitride waveguide. The measured results show the insertion loss and crosstalk are about 0.6 dB and below −42 dB, respectively, in the wavelength range of 1520 nm ∼ 1640 nm with low polarization dependence. The waveguide crossing could be a key building block for the silicon nitride waveguide platform.

Cellulose contains abundant oxygen-containing functional groups and can be used to fabricate hydrogel matrixes for supercapacitors (SCs). However, conventional bacterial cellulose-based SCs need a ...

A continuously tunable optical delay line with low delay ripple based on four cascaded tunable silicon nitride microring resonators for Ka-band beamforming network is proposed. The delay responses of the tunable optical delay line were investigated theoretically and experimentally. And a maximum delay tuning range of 300.3 ps, 169.4 ps and 88.6 ps were achieved when the delay bandwidth is set as 2 GHz, 5 GHz and 10 GHz respectively. In addition, low delay ripple about 8.5 ps and low additional loss less than 3.6 dB were obtained. Moreover, the maximum delay tuning range was increased to about 395 ps by combining the off-resonance region of the cascaded MRRs.

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Thermoplastic vulcanizate (TPV) have been widely used in industry, and injection molding is one of the most widely used technique to produce TPV products. In this study, effects of shear during injection molding on the anisotropic microstructure and properties of EPDM/PP TPV containing rubber nanoparticle agglomerates was systematically studied by using quantitative nanomechanical mapping of atomic force microscopy (AFM-QNM) for the first time. The shear of injection molding induced break-up of the EPDM nanoparticles agglomerates, and a significant decrease in the size of the latter with increasing shear rate was observed. Meanwhile, the shear orients both PP crystals and EPDM nanoparticle agglomerates, and their orientation degree along the shear direction, and the crystallinity of PP increase with increasing the shear rate. As a result, whatever the anisotropy, the Young's moduli at nanoscale of PP obtained by AFM-QNM, and the tensile strength and elastic modulus of TPV increase with increasing shear rate till the shear-induced PP chain degradation becomes important. Moreover, the tensile strength and elastic modulus of TPV parallel to the shear direction are much higher than those perpendicular to it, while the elongation at break and elasticity are the opposite. Interestingly, for TPV perpendicular to the shear direction, despite of the higher crystallinity and elastic modulus of TPV prepared under moderate shear rate than that under very low shear rate, the elasticity of the former is even much higher than the latter. The mechanisms on effects of shear on the anisotropy of microstructure, mechanical properties and elasticity of EPDM/PP TPV were revealed. This study provides guidance for optimizing process conditions in order to control the microstructure of the TPV and best balance their effects on mechanical properties and elasticity of TPV.

Epoxy (EP) composites with comprehensive good processability, low coefficient of thermal expansion (CTE), and high thermal conductivity, but electrical insulation properties are largely demanded in the higher power electric devices. However, micro-fillers have a positive effect on maintaining the good flowability of epoxy composites, while do not bring high thermal conductivity enhancement per unit mass. While nano-fillers with high specific surfaces offer very promising opportunities for heat-conducting network construction, but the nano-fillers dispersion is difficult to control and will cause increased viscosity and processing difficulties. Herein, we expect that the addition of small amounts of silver nanowires (AgNWs) at 0.5 vol% into the EP/S-Al2O3 composites could largely enhance the thermal conductivity but not sacrifice their processability. Owing to the bridging effects of rigid nanowires between the main spherical particles, the thermal conductivity of the micro-nano EP/AgNWs/S-Al2O3 composites with 40 vol% S-Al2O3 and 0.5 vol% AgNWs exhibits a 106.5% increment comparing to that without AgNWs. The limitation of both single micro or nano-sized thermal conductive fillers can be offset by the micro-nano filler network structure. The best combination properties of the EP/AgNWs/S-Al2O3 composites can reach the high thermal conductivity (1.602 W/m·K), low viscosity (55.6 Pa s), low CTE (37.1 ppm/°C), and high glass transition temperature (Tg, 152.1 °C). These results demonstrate that adding multiscale fillers into epoxy composites may solve the tradeoff between thermal conductivity and processability performances and fit the applications in high-power density electronic devices.

A refractive index sensor based on all-grating racetrack resonators is proposed and demonstrated in this paper. The structure consists of two subwavelength grating (SWG) waveguide-based racetrack resonators, a straight SWG bus waveguide and a SWG waveguide-based open racetrack. A sharp Fano resonance can be obtained by the mutual coupling of the two SWG racetrack resonators. Theoretical analysis and numerical simulations show that the introduction of grating can enhance the interaction between the sensor and the measured liquid analyte, thus increasing the sensitivity of the device. Calculated sensitivity of 500 nm/RIU around wavelength 1550 nm is achieved, and the figure of merit is 2000 RIU−1. The extinction ratio of this device can reach 21.53 dB.

A stopband and passband switchable microwave photonic filter based on the integrated tunable dual ring coupled Mach–Zehnder interferometer has been demonstrated. By using the optical single sideband modulation, the switchable stopband and passband optical responses of the optical filter are one-to-one mapping to the RF spectra. The center frequency and bandwidth of the switchable microwave photonic filter are both reconfigurable. A frequency tuning range of 4–25 GHz is obtained, and the bandwidth tuning ranges of the passband and stopband MPFs are 4.54–9.72 GHz and 3.65–6.35 GHz, respectively. In addition, a RF rejection ratio about 20 dB is achieved. Compared with the switchable MPFs implemented by nonintegrated devices, the proposed switchable MPF provides a simple and low cost method to process radiofrequency signals.

Most graphene electro-optic modulators based on the electro-refractive modulation are composed of Mach-Zehnder interferometer or microring resonator structures and have a relative compact size comparing with dielectric ones. To further shrink the footprint, we use the localized surface plasmon resonance of a chain of three metal disks to realize a submicron graphene modulator, whose length can be reduced to less than 1 μm. The proposed graphene modulator has an extinction ratio of 5.5 dB with a length of only 740 nm. And the insertion loss, 3-dB bandwidth, and power consumption of the modulator are 1.9 dB, 83.4 GHz, and 8.55 fJ/bit respectively.

A simplified beamforming architecture using a wavelength-selective optical true time delay (OTTD) module is proposed for phased array antenna (PAA) systems. Based on diffraction order multiplexing of an arrayed waveguide grating (AWG), the beamformer can realize multiple simultaneous time delays with only one OTTD module. We design, fabricate, and characterize a compact integrated optical beamformer using this structure for an eight-element X -band PAA system. The time delays generated by the fabricated beamformer are measured to be in the range from 0 to 278 ps in 5.7 ps increments of eight diffraction orders. The measured overall variation in the insertion loss of this device is less than 1.85 dB from 1527 to 1607 nm. The experimental results demonstrate that the proposed architecture can offer many advantages, such as multibeam capability, low insertion loss, a small footprint, and high resolution.

The effects of the modulation in the NH3 flow duty-ratio in a three-way pulsed-flow epitaxial growth process on the structural and optical properties of non-polar a-plane Al0.34Ga0.66N epi-layers were studied intensively. It was revealed that the typical pyramidal defects originated from the anisotropy in growth rate could be evidently reduced with an optimized NH3 flow duty-ratio. In fact, the root-mean-square value determined with atomic force microscope was decreased from 12.8 to 3.1 nm when the NH3 flow duty-ratio was increased from 0 to 0.57. Moreover, the LO-phonon-assisted exciton emission observed in the photoluminescence (PL) spectrum was remarkably suppressed, and the linewidth of the near band edge PL emission peak was decreased by 47%, implying the significantly enhanced optical properties of the non-polar a-plane Al0.34Ga0.66N epi-layer.

A tunable microwave photonic notch filter with ultrahigh radio frequency (RF) rejection ratio is achieved by using a dual-drive Mach-Zender modulator and a microring resonator. In addition, we dedicated to clarify the mechanisms of the microwave photonic notch filters based on a microring resonator under both overcoupled and undercoupled states and the performance differences between these two situations are investigated in detail. Furthermore, the experimental results show that the cancellation microwave photonic notch filter with ultrahigh RF rejection ratio can be achieved with both undercoupled and overcoupled microring resonators. Besides, an RF rejection ratio exceeding 50 dB was achieved for a microring resonator with an optical extinction ratio of only 4 dB, where a 46-dB enhancement from optical to RF response is obtained. Also, the bandwidth of the microwave photonic filter can tuned from 0.65 to 2.2 GHz by adjusting the coupling ratio of the ring resonator. Meanwhile, by tuning the wavelength of the optical carrier, the filtering frequency can be tuned and a tuning range of about 25 GHz was achieved. The implementation is much simpler and more economical compared with previous reports and has great potential in monolithic integration of microwave photonic filters on chip.

High-performance and environment-friendly biomass-based composite films have drawn much attention recently. Here, bio-nanocomposites of TEMPO-oxidized cellulose nanofibrils (TOCNs) reinforced with layered double hydroxides (LDHs) were prepared through an environmentally benign pathway by aqueous dispersion. The results showed that LDHs could be uniformly dispersed in the cellulose nanofibril matrix to form an intercalated nanolayered structure due to good compatibility and the formation of ionic and hydrogen bonds between LDHs with positive charges and TOCNs with negative charges. The TOCN-LDH composite films exhibited high light transmittance, which exceeded 80% with an LDHs content of less than 10%. Moreover, the incorporation of LDHs improved not only the mechanical properties of the cellulose nanofibrils, but also their thermal stability, flame retardancy and hydrophobicity. More specifically, the highest Young's modulus and tensile strength reached 39.3 GPa of TOCN-LDH20 and 358 MPa of TOCN-LDH5, which were 364% and 178% of the neat TOCN film, respectively. The water contact angle and limiting oxygen index of the TOCN-LDH composite film increased from 46° to 103°, and from 25 to 31, respectively, with the LDH content increase from 0 to 20 wt%.

Microwave photonic technologies have been introduced for achieving broadband radio-frequency signal measurement. However, few of the proposed schemes mention the low-power radio-frequency signal detection, which stringently limits their practical applications in certain areas. In this paper, we designed and demonstrated a wideband low-power radio-frequency signal measurement system with optoelectronic oscillator. Here, the unknown radio-frequency signal matched the potential oscillation mode is allowable to be detected, amplified and estimated. The key component in the tunable optoelectronic oscillator is a silicon nitride micro-disk resonator with a very high Q-factor, which is utilized to achieve frequency selection as a microwave filter. A frequency measurement system range from 1 ~ 20 GHz with radio frequency power as low as -105 dBm, measurement errors of ±375 MHz and the maximum gain of 61.7 dB were realized experimentally.

Aiming at high-strength damping elastomers, the pre-cross-linked sliding graft copolymer (SGC) is incorporated into a nitrile rubber (NBR). The microstructure characterizations reveal that SGC phas...

N-polar AlGaN epi-layer was realized on AlN seeding layer grown with a novel flow-modulation method. The polarity reversion from Al(Ga)-polar to N-polar for AlGaN/AlN films was confirmed by KOH etching and subsequent observation with optical microscope as well as high-resolution X-ray diffraction (HR-XRD) measurement. In particular, the dependence of crystalline quality and defect size in the N-polar AlGaN epi-layers on the Ⅴ/Ⅲ ratio was investigated with HR-XRD and scanning electron microscopy (SEM). It was found that as the full width at half maximum (FWHM) value of the X-ray rocking curve (XRC) varied with the Ⅴ/Ⅲ ratio in a "W-shape" for the N–polar AlGaN epi-layers, and a FWHM value as small as 450 arcsec was achieved for the sample grown with a V/III ratio of 988. Moreover, it was revealed by the SEM measurement that the maximum diagonal length of hexagonal cone on the surface of the N-polar AlGaN epi-layers decreased sharply when a Ⅴ/Ⅲ ratio of 1,236 was used although the crystalline quality and the surface morphology of the N-polar AlGaN epi-layers were not improved simultaneously. The peculiar migration of the group-III atoms on the surface of the N-polar AlGaN epi-layer associated with the molar ratio of TMA/(TMA+TMG) was considered to be responsible for this result.

Cellulose is the most earth-abundant natural polymer resource, which with combined eco-friendly and extraordinary sustainable properties such as renewability, biodegradability, low cost and excellent biocompatibility has been widely used by humans for thousands of years. In the past few years, many novel cellulosic materials and their unique applications have been developed including the recent research focus on energy harvesting. The high crystallization and plentiful polar hydroxyl groups endow cellulose with a large number of dipoles and strong electron donating capacity, resulting in a promising potential of piezoelectric and triboelectric effects. However, there is no review about cellulose-based nanogenerators until now. In this paper, the most recent developments of designing, modification, processing and integration of cellulose-based piezoelectric nanogenerators (PENGs), triboelectric nanogenerators (TENGs) and hybrid piezo/triboelectric nanogenerators (PTENGs) for energy harvesting and other applications are reviewed in detail. For cellulose-based PENGs, representative basic piezoelectric cellulose and recent research on PENG devices are discussed. For cellulose-based TENGs, several effective strategies including rough modification of contact surface, addition of electronic functional fillers and chemical modification for improving the output performance are further summarized. Meanwhile, the latest cellulose-based hybrid PTENG is also introduced from the fundamental design to the investigations on enhanced strategies. The opportunities and challenges of these cellulose-based nanogenerator devices are put forward in the final part, which could enable this up-to-date and state-of-the-art review to be an effective guidance for the future research on cellulose-based nanogenerators in energy harvesting.

This work presents a method for the synthesis of a liquid-like polythiophene (L-Pth) by chemical oxidative polymerization of thiophene in dichloromethane. FeCl3 was used as an initiator and nonylphenol polyoxyethylene ether (NPES) as a dopant. The structures and physicochemical properties of the L-Pth were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), fluorescence spectroscopy and ultraviolet-visible photometer (UV–vis). Unlike conventional polythiophene, L-Pth is composed of NPES and polythiophene, and part of NPES is doped on the thiophene backbone. It exhibits a liquid-like behavior at room temperature. It is typical of a semiconductor with a relatively high electric conductivity of 1.2 S m−1. Moreover, it turns high-energy blue light (in the ranges of 400–480 nm) into relative low-energy green light (peak at 515 nm), which makes it a potential filler for preparing a blue light protection film for eyes protection. The combination of the liquid behavior, excellent solubility and good electric conductivity also makes it a promising precursor for applications such as lightweight battery, super capacitor and anti-corrosion of metals.

An all-subwavelength grating waveguide-based sensing structure for figure of merit (FOM) improvement on a silicon-on-insulator platform is proposed and demonstrated. Four racetrack resonators are applied to narrow the spectrum from the drop port of a single racetrack resonator for lower full width at half-maximum, and the FOM is therefore higher through the spectrum-narrowing operation. Numerical simulation and analysis illustrate that the proposed structure is able to raise the FOM more than twice compared to a single racetrack resonator, and a high FOM of 1850.57/refractive index unit is achieved.

Early diagnosis in exhaled breath is a key technology for next-generation personal healthcare monitoring. Current chemiresistive sensors, primarily based on metal oxide (MOx) thin films, have limited applicability in such portable systems due to their high power consumption, long recovery time, poor device-to-device consistency, and baseline drifts. To address these challenges for ammonia ($${{\rm{NH}}}_{3}$$ NH 3 ) detection in exhaled breath, a critical biomarker for a variety of kidney and liver problems, we present a formulation of a graphene–MOx functional ink-based sensing platform. We integrate our sensing layer directly onto miniaturized CMOS microhotplates (μHP) via inkjet printing, potentially enabling scalability and device-to-device performance repeatability. Using stage-by-stage temporal analysis, and a temperature-pulsed modulation (TM) strategy, we achieve ultrahigh responsivity (1500% at 10 ppm pure $${{\rm{NH}}}_{3}$$ NH 3 ), fast response and recovery time (28 and 43 s), ultralow power consumption (~6 mW), negligible baseline drift ($${{\rm{WO}}}_{3}$$ WO 3 ) device as part of the sensor array. Our dual graphene–MOx formulations and their integration with ultralow power CMOS through inkjet printing represent a significant step towards reliable and portable multi-analyte breath diagnostics.

We demonstrate an all-fiber, thulium-doped, mode-locked laser using a black phosphorus (BP) saturable absorber (SA). The BP-SA, exhibiting strong nonlinear response, is fabricated by inkjet printing. The oscillator generates self-starting 139 fs dispersion-managed soliton pulses centered at 1859nm with 55.6 nm spectral bandwidth. This is the shortest pulse duration and widest spectral bandwidth achieved directly from an all-fiber thulium-doped fiber laser mode-locked with a nanomaterial saturable absorber to date. Our findings demonstrate the applicability of BP for femtosecond pulse generation at 2 µm spectral region.

The N-polar AlGaN epi-layers were successfully grown on (0001) c-plane sapphire substrates by using the reformed metal-organic chemical vapor deposition technology featured with an optimized pulsed NH3-flow supplying scheme. In order to reduce the hexagonal defects in the N-polar AlGaN epi-layers, the conventional NH3 pulsed-flow technology was reformed. Particular attention should be paid on the impacts of the variation in the duty ratio and the NH3-purge term within each growth cycle on the surface morphology and crystalline quality of the grown N-polar AlGaN epi-layers. A smooth surface morphology with a root-mean-square value as small as 5.7 nm was obtained. On the other hand, the significantly decreased density of the hexagonal defects confirmed with microscope and X-ray diffraction measurements implies a remarkable improvement in crystalline quality of the N-polar AlGaN epi-layers. These results indicate that the reformed pulsed-flow technology with an optimized source supplying scheme plays a crucial role in improving the surface morphology and crystalline quality of the N-polar AlGaN epi-layers.

International audience; The kinetic developments of the free-radical bulk polymerization of styrene in the presence of recycled rubber tire particles are studied by isothermal differential scanning calorimetry (DSC). Two different chemical initiators, namely benzoyl peroxide (BPO) and 2,2'-Azobis(2methylbutyronitrile) (AMBN), are tested in a series of variable-composition experiments, under three different polymerization temperatures, in order to selectively address the role of the different species on the evolution of the polymerization reaction. The variation of the overall effective kinetic rate constant and activation energy of the polymerization are also calculated to quantify the effect of the addition of the particulate filler. The results of the study demonstrate that the combination of the peroxide initiator agent with a composition of the reacting mixture in the order of 30 mass%, in terms of the rubber tire particles, results in a significant deviation of the evolution of the rate of polymerization and monomer conversion, with respect to that of the pure homopolymerization system in the absence of tire particles. The observed phenomena are consistent with previous studies reported in the literature and are mainly attributed to the chemical interactions taking place between the initiator agent and additives of the formulation of the tire particles.

Theoretically, transition metal oxide/carbon nanofibril aerogels are promising candidates for lithium-ion battery anode materials as they combine the high stability and electrical conductivity of the carbon matrix and the high theoretical specific capacity of transition metal oxide (TMO). However, challenges still exist to embed TMO nanoparticles into thin carbon nanofibril absolutely and tightly, limiting further improvements in electrochemical performances of the composites. Herein, necklace-like Fe3O4/carbon nanofibril aerogel (Fe3O4/CNF) was constructed by crosslinking alginate with Fe3+, followed by carbonization of the obtained ferric alginate aerogel. Based on an “egg-box” helical structure resulting from strong coordination between the Fe3+ and the carboxylate groups of alginate, three-dimensional interconnected carbon aerogel was facilely fabricated with Fe3O4 nanoparticles (~11 nm in diameter) firmly embedded in ultrafine carbon nanofibrils (~18 nm in diameter), exhibiting a special necklace-like structure. Consequently, the composite exhibits a high reversible capacity and stability of 1176 mAh g−1 over 200 cycles at 1 A g−1 and a high rate performance of 615 mAh g−1 at 4 A g−1. These Fe3O4/CNF aerogels may have potential applications for enhanced lithium storage of electrochemical devices.

For lithium ion batteries, fast charging technology is one of the most important research topics in current society. Transition metal oxides show broad application prospects due to their obvious pseudocapacitive effect. We choose Fe3O4 as the template to design the enhanced pseudocapacitance effect considering of its high theoretical specific capacity and superior structural adjustability. The nanohybrid materials with multiple ionically bonded interfaces accumulated the giant pseudocapacitive effect to obtain superior specific capacity. As a result, the nanohybrid shows a ranking specific capacity over 800 mAh g−1 at 1 A g−1 for 1000 cycles as well as excellent rate capabilities. The existence of interfacial pseudocapacitive effect was confirmed by the kinetic analysis calculating from CV curves. Furthermore, the computation simulation based on the density functional theory (DFT) highly corresponded with our viewpoint about interfacial lithium storage. Our findings pave a novel path for designing novel electrode materials and could further advance the development of lithium-ion batteries with long-term stability and superhigh capacity.

We demonstrate an all-fiber Tm-doped mode-locked fiber laser utilizing a black phosphorus saturable absorber. The oscillator delivers self-starting, 139 fs pulses centered at 1859 nm with 55.6 nm spectral bandwidth.

The creation of crystal phase heterostructures of transition metal chalcogenides, e.g., the 1T/2H heterostructures, has led to the formation of metal/semiconductor junctions with low potential barriers. Very differently, post-transition metal chalcogenides are semiconductors regardless of their phases. Herein, we report, based on experimental and simulation results, that alloying between 1T-SnS2 and 1T-WS2 induces a charge redistribution in Sn and W to realize metallic Sn0.5W0.5S2 nanosheets. These nanosheets are epitaxially deposited on surfaces of semiconducting SnS2 nanoplates to form vertical heterostructures. The ohmic-like contact formed at the Sn0.5W0.5S2/SnS2 heterointerface affords rapid transport of charge carriers, and allows for the fabrication of fast photodetectors. Such facile charge transfer, combined with a high surface affinity for acetone molecules, further enables their use as highly selective 100 ppb level acetone sensors. Our work suggests that combining compositional and structural control in solution-phase epitaxy holds promises for solution-processible thin-film optoelectronics and sensors., Controlling the composition and crystal phase of layered heterostructures is important. Here, the authors report the liquid-phase epitaxial growth of Sn0.5W0.5S2 nanosheets with 83% metallic phase on SnS2 nanoplates, which are used as 100 ppb level chemiresistive gas sensors at room temperature.

Dependence of the nonlinear and linear viscoelastic behaviors of thermoplastic vulcanizates (TPV) on the content (φ) of rubber nanoparticle agglomerates (NPAs) was explored by dynamic oscillation shear tests. Under a large strain, TPV exhibit a φ-dependent yield stress ( σ y ) as σ y ∝ φ 1.53 ± 0.87 . As φ increases, the rubber NPAs network becomes stronger, and the elastic modulus and viscosity of TPV increase. φ-dependent modulus ( G 0 ' ) of TPV is G 0 ' ∝ φ 3.18 ± 0.24 in the low-ω region. Rubber NPs agglomerate to form a network more easily than rigid particles. The fractal dimension df (=1.65 ± 0.09) of the rubber NPAs in TPV is lower than the universal df (~1.8) of rigid particles aggregates. The φ-dependent modulus G 0 ' of TPV in the linear viscoelastic region shows G 0 ' ~ { ( φ c − φ ) 1 , f o r i s o l a t e d r u b b e r N P A s , φ ≤ φ c ( φ − φ c ) 2.15 ± 0.12 , f o r r u b b e r N P A s n e t w o r k , φ ≥ φ c , where φc is the percolation threshold of φ. This study provides an understanding of the viscoelasticity of TPV containing rubber NPAs and their network structure.

Graphene modulators based on surface plasmonic waveguides enable a strong interaction between light and graphene because great electric field enhancement occurs in the sub-wavelength region. However, a tight field confinement will cause a large metal absorption of light. Thus, graphene modulator base on hybrid plasmonic waveguide has a tradeoff between the propagation loss and the modulation depth. Here, we achieved a good balance between them by designing and optimizing an electro-optic modulator based on hybrid plasmonic waveguide with four graphene layers. The structure of the waveguide is metal/insulator/Si/insulator/metal. The modulation depth and the propagation loss of the modulator are 0.524 and 0.05 dB/μm respectively, which make a relatively high figure of merit about 10.5. Also the obtained modulation bandwidth and power consumption are 150 GHz and 0.607 pJ/bit, respectively.

Traditional dielectric polymers are nonbiodegradable and nonrenewable petroleum-derived synthetic ones. Here, we report on flexible and 2D nanolayer-structured nanocomposite dielectric films which ...

A hybrid plasmonic modulator based on graphene on channel plasmonic polariton waveguide was proposed to overcome the difficulty in achieving high-speed modulation on the nanometric plasmonic waveguide platform. The extinction ratio and the figure of merit of the proposed modulator were analyzed in detail, and a tradeoff between them was found due to the intrinsic loss of the channel plasmonic polariton waveguide. And an optimized hybrid plasmonic modulator with large modulation bandwidth of 0.662 THz, low power consumption of 118.7 fJ/bit, and short device length of 7.680 μm was obtained theoretically. In addition, the proposed hybrid plasmonic modulator based on graphene on channel plasmonic polariton waveguide is easy to fabricate and provides a potential solution for the high-speed plasmonic modulator.

A polarization-insensitive 2 × 2 multimode interference coupler based on double strip silicon nitride waveguides is proposed and optimized by using the three-dimensional finite difference time domain method. By optimizing the device’s structure parameters in detail, polarization independent excess loss of −0.32dB is obtained, and negligible output uniformities of −0.02dB and −0.03dB could be achieved for the TE and TM mode, respectively. The optimized polarization-insensitive 2 × 2 multimode interference coupler could be served as a building block on the double strip silicon nitride waveguides platform.

Quasi-ordered semi-polar 11 2 2 plane AlGaN multiple-quantum-well (MQW) nanorod (NR) arrays with a period of 400 nm were successfully fabricated by a self-assembly technique using polystyrene spheres. The diameter and height of the NRs were about 360 and 600 nm, respectively. The photoluminescence (PL) peak wavelengths of both NR and planar MQWs were located at 266 nm at room temperature, demonstrating that the quantum-confined Stark effect was negligible in the semi-polar AlGaN MQWs. The PL integral intensity of the MQW NR arrays was enhanced by 1.5 times compared to that of planar MQWs. Moreover, the degree of polarization was increased from 15.9% to 26.2% when fabricating the NR arrays, demonstrating enhanced polarized emission. The finite-difference time-domain method was used to explain the enhancement of PL intensity, which was mainly due to the modified light extraction by the quasi-ordered NR arrays.

An ultra-compact TE-mode-pass power splitter, using subwavelength gratings (SWGs) and hybrid plasmonic waveguides (HPWs) on silicon-on-insulator (SOI) platform is proposed and demonstrated. In the present design, the SWGs are embedded in one input tapered waveguide and two adjacent inverse-tapered waveguides in the bottom layer to form a power splitter for the TE mode. As to the injected TM mode, it is radiated into the claddings and absorbed by two segmented HPWs, located above the bottom layer. Therefore, both polarization handling and power splitting can be realized Simulation results show that, an ultra-compact TE-mode-pass power splitter with length of only 2.7 μ m is achieved, which is so far the shortest one. Moreover, low insertion loss (IL) of 0.64 dB and high extinction ratio (ER) of 20.56 dB are obtained, together with return loss (RL) are 26.60 dB and 23.16 dB for the TE and TM modes at the wavelength of 1.55 μ m, respectively. Besides, the working bandwidth is up to 167 nm (1477 nm ∼ 1644 nm) when ER > 12 dB and IL

In this article, the effect of ammonia (NH3) flow-modulation on the crystalline quality and morphology of the nonpolar a-plane AlGaN epilayer grown on the r-plane sapphire substrate was reported. The as-grown metal-organic chemical vapor deposition (MOCVD) epilayers have been diagnosed with high-resolution X-ray diffraction, atomic force microscopy, and scanning electron microscopy techniques. It was found that with the introduction of proper interruption of NH3-flow during the MOCVD growth process, enormous reduction in the threading dislocation density (TDD) and significant improvements in the crystalline quality and surface morphology could be realized. By optimizing the NH3-flow interruption time to 30 s during the growth of the nonpolar AlGaN intermediate layer, a small root-mean-square value of 1.8 nm for the surface roughness and a TDD of 2 × 1010 cm−2 were achieved. Moreover, the full width at half maximum values determined from the X-ray rocking curves were reduced from 2410 to 1512 arcsec and 2355 to 1645 arcsec along c- and m-plane directions, respectively.

The ability to achieve low phase noise single-mode oscillation within an optoelectronic oscillator (OEO) is of fundamental importance. In the frequency-tunable OEO, the wide microwave photonic filter (MPF) bandwidth is detrimental to select single-mode among the large number of cavity modes, thus leading to low signal quality and spectral purity. Stable single–mode oscillation can be achieved in a large time delay OEO system by harnessing the mechanism from parity-time (PT) symmetry. Here, a PT-symmetric tunable OEO based on dual-wavelength and cascaded phase-shifted fiber gratings (PS-FBGs) in a single-loop is proposed and experimentally demonstrated. Combining the merits of wide frequency tuning of PS-FBG-based MPF and single mode selection completed by the PT-symmetric architecture of the OEO, where the gain and loss modes carried by dual-wavelengths to form two mutually coupled resonators in a single-loop, signals range from 1 GHz to 22 GHz with the low phase noise distributed in −122∼ −130 dBc/Hz at 10 kHz offset frequency are obtained in the experiment.

The random laser from sheared dye-doped polymer-dispersed liquid crystal (DDPDLC) is investigated. As the emission intensity weakens, the threshold of random laser from DDPDLC increases from 2.0 mJ/pulse to 4.0 mJ/pulse, and the degree of polarization (DOP) increases from 0.1 to 0.78, obviously when the shear distance increases from 0 mm to 4 mm. As the liquid crystal droplets are gradually oriented in the shear direction caused by alignment direction of polymer chain and anisotropy of droplet shape, the scattering intensity perpendicular to the shear direction gradually decreases and that parallel to the shear direction gradually increases. The anisotropic absorption of the laser dye also plays a certain role as the shear distance is 0 mm. The controllable intensity and polarization degree of random laser have a huge potential for sensing applications.

Poly(dibutyl itaconate-co-isoprene-co-methacrylic acid) (PDIM)/halloysite nanotubes (HNTs) nanocomposites with strong interfacial interaction were prepared by co-coagulation of PDIM latex and HNTs aqueous suspension, followed by mechanical kneading with rubber additives. The interfacial interaction, thermal properties, morphology, and mechanical properties of the nanocomposites were investigated. The hydrogen bonds were confirmed in the nanocomposites. Morphology investigation showed uniform and individual dispersion of HNTs in the PDIM matrix. With the incorporation of HNTs into the PDIM matrix, the tensile strength and the fracture energy were significantly improved without sacrificing the extensibility. The improved mechanical properties were correlated to the co-coagulation and the strong hydrogen bonds. Especially, the morphology investigation of tensile fracture surfaces revealed a mechanism for the improved mechanical performance, in which the stress was efficiently transferred from PDIM to HNTs via hydrogen bonds and then the dissociation of the hydrogen bonds dissipated energy to increase the fracture energy of the nanocomposites.

The structural and optical properties of the non-polar a-plane (11 2 0) AlN template grown on semi-polar r-plane (1 1 02) sapphire substrate with three-step pulsed flow growth method in a metalorganic chemical vapor deposition system were investigated extensively. It was found that the crystalline quality, optical property, and surface morphology of the a-plane AlN template grown by the three-step pulsed flow growth method featured with variable temperature were greatly improved as compared with the a-plane AlN template grown by conventional one-step pulsed flow growth method with a fixed temperature. In fact, besides the remarkably reduced full width at half maximum values of both the symmetrical X-ray rocking curve and the A1(TO) Raman scattering peak, strong relative light transmittance and steep absorption edge were observed in the ultraviolet-visible absorption spectrum for the a-plane AlN template grown by the three-step pulsed flow growth method. Furthermore, a superior surface morphology and a decreased surface deformation were achieved with a root mean square value as small as 3.4 nm in an atomic force microscope detection area of 5 × 5 µm2. These results reveal that the three-step pulsed flow growth method should be powerful to grow high crystalline quality non-polar a-plane AlN template which plays a crucial role in the epitaxial growth of the AlGaN-based III-nitrides.

The intrinsic spin-valleys in monolayer transition metal dichalcogenides make them promising for exploring new-generation valleytronic and spintronic devices. However, it is very challenging to detect and manipulate a specific valley with off resonance electromagnetic fields at room temperature due to their ultrashort lifetimes and phonon-assisted intervalley scattering. Here, utilizing the sputtering and the focused ion beam milling methods, we fabricate a quasi-three-dimensional chiral microstructure using molybdenum disulfide. Based on chirality and double plasmonic resonances, we realize off resonance wavelength control of valley-polarized photoluminescence at room temperature. Furthermore, we find that the chiral field excitation enhancement (13) and chiral quantum yield amplification (1.35 times) contribute to the huge differences in the photoluminescence of valleys. These results reported here may pave the way for further development of on-chip photonic integration of two-dimensional materials.

Compared to polyvinylidene fluoride (PVDF) and its copolymers, castor-oil-derived nylon-11 has been less explored over the past decades, despite its excellent piezoelectric properties at elevated temperatures. To utilize nylon-11 for future sensor or vibrational energy harvesting devices, it is important to control the formation of the electroactive δ′ crystal phase. In this work, nylon-11 films were first fabricated by solution-casting and were then uniaxially stretched at different stretching ratios (SR) and temperatures (Ts) to obtain a series of stretched films. The combination of two-dimensional wide-angle X-ray diffraction (2D-WAXD) and differential scanning calorimetry (DSC) techniques showed that the fraction of the δ′ crystal phase increased with the stretching ratio and acquired a maximum at a Ts of 80 °C. Further, it was found that the ferroelectric and piezoelectric properties of the fabricated nylon-11 films could be correlated well with their crystalline structure. Consequently, the stretched nylon-11 film stretched at an SR of 300% and a Ts of 80 °C showed maximum remanent polarization and a remarkable piezoelectric coefficient of 7.2 pC/N. A simple piezoelectric device with such a nylon-11 film was made into a simple piezoelectric device, which could generate an output voltage of 1.5 V and a current of 11 nA, respectively.

We report on the successful growth of non-polar a-plane p-type Mg-doped AlGaN epi-layers with various Al compositions by metal organic chemical vapor deposition (MOCVD). The p-AlGaN epi-layers with the Al composition varied from 0 to 0.41 were studied comprehensively. In particular, a novel MOCVD growth process featured with pulsed mass flow supply (PMFS) of the metal organic-source was applied for the fabrication of the Mg-doped AlGaN with various Al compositions. It was revealed that a significant enhancement in electrical conductivity was induced owing to the application of the newly-developed PMFS technique during the growth of the Mg-doped AlGaN. In fact, a hole concentration up to 7.0 × 1016 cm−3 was realized for the p-Al0.41Ga0.59N epi-layer sample grown with the PMFS technique.