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Hollow polycrystalline structures and noble-metal coating endow ternary sulfides with promising light absorption and electrical properties for solar energy conversion applications. We developed a facile one-pot solvothermal chemical route to synthesize hollow Cu3SbS4 microspheres with an opening. Meanwhile, four phase-pure Cu-Sb-S high-quality nanocrystals can be produced in a selectable way by the same route. The detailed evolution process and self-driven breakage mechanism were proposed in detail. Subsequently, in situ reduction of Ag-ion precursor was conducted and Ag clusters was uniformly deposited on the providential hollow spherical architecture with nanoparticles-textured surface and interior to mitigate the oxidization of Cu3SbS4 nanoparticles. The created hollow metal-semiconductor nanocomposite opened up a favorable new situation. The nanocomposites exhibited a remarkably enhanced absorption over 2×105 cm-1 covering the UV and visible regions of the electromagnetic spectrum. The electric resistivity decreased drastically 90% by coating of noble metal. A reduction in the band gap energy for addition of Ag to Cu3SbS4 was confirmed from extrapolated optical results and theoretical validation. The synthetic effect of hollow structures and nanocomposites results in the superior performance of Cu-Sb-S compounds, thus, highlighting their potential applications in light absorbers and energy conversion technologies.

The as-extruded Mg-10Al2Y master alloy was chosen as a novel grain refiner for as-cast Mg-3Y alloy. Contrast samples of cast Mg-3Y alloy added with pure Al and Mg-Zr master alloy grain refiners were prepared under the same conditions. In this study, the influence of addition amounts of Al2Y and holding time on grain refinement efficiency as well as tensile properties was investigated. And the grain refining ability of the Al2Y particles was systematically evaluated in terms of the addition amounts, number density of the Al2Y particles and holding time. The finest grains are achieved at 2 wt% Al2Y addition amount, which corresponds to number density of the polygonal Al2Y particles of 420–460 mm–2. The Mg-10Al2Y master alloy has significant refinement performance and no refining recession occurs at the holding time within 60 min, or the settling time up to 180 min. Grain refinement and the second phase strengthening of uniformly distributed Al2Y particles contribute to the simultaneous enhancement on both strength and elongation of Mg-3Y alloy.

Wearable and implantable pressure sensors are in great demand for personalized health monitoring. Pressure sensors with low operation voltage and low power-consumption are desired for energy-saving devices. Organic iontronic devices, such as organic electrochemical transistors (OECTs), have demonstrated great potential for low power-consumption bioelectronic sensing applications. The ability to conduct both electrons and ions, in addition to their low-operation voltage has enabled the widespread use of OECTs in different biosensing fields. However, despite these merits, OECTs have not been demonstrated for pressure sensing applications. This is because most OECTs are gated with aqueous electrolyte, which fails to respond to external pressure. Here, a low power-consumption iontronic pressure sensor is presented based on an OECT, in which an ionic hydrogel is used as a solid gating medium. The resultant iontronic device operated at voltages less than 1 V, with a power-consumption between ~ 101– $10^{3} \mu \text{W}$ , while maintaining a tunable sensitivity between 1 ~ 10 kPa−1. This work places OECTs on the frontline for developing low power-consumption iontronic pressure sensors and for biosensing applications.

We use coarse-grained molecular dynamics simulations to study the self-assembly behavior of polyoxometalate (POM) nanoparticles (NPs) decorated with mobile polymer ligands under melt conditions. We demonstrate that due to the mobile nature of the grafted ligands on the NP surface, NPs have the ability to expose a part of their surfaces, leading to a block-copolymer-like self-assembly behavior. The exposed NP surface serves as one block and the grafted ligand polymers as another. This system has a strong ability to self-assemble into long-range ordered structures such as block copolymers due to large incompatibility between POM and ligand polymers, i.e., POM NPs can form lamellar, cylindrical, and spherical structures, which are consistent with previous experimental results. More importantly, these ordered structures are on the sub-10 nm scale, which is an important requirement for many applications. At low graft density, we find a new inverse-cylindrical structure formation where polymers form cylinders and POMs form a continuous network structure. A full self-assembly phase diagram is constructed which illustrates rules to manipulate the self-assembly structures of NPs decorated with mobile polymer ligands. We hope that these computational results will be useful for the new design of nanostructures with improved optical or electronic functions.

Effects of Ca addition on as-cast microstructure, mechanical and corrosion properties of Mg–2Zn–0.3Sr alloy were investigated for biodegradable implant application. First, a comparison between Ca a...

In this work, 8mol% yttria-stabilized zirconia (8YSZ) ripple-shaped electrolytes have been prepared by digital light processing (DLP) 3D printing and their electrochemical performances have been investigated. The total conductivities of flat samples printed at different angles were tested firstly to confirm that there is no huge influence on the electrochemical performance from the printing itself. Then, by using ripple-shaped electrolytes, primary cells were assembled and their electrochemical performance were investigated. Compared with the reference flat cell, an improvement of ~32% was achieved in the power density for the same thickness of the electrolyte (~200 µm) at 800 °C.

We demonstrate the first multi-stage 8 × 8 silicon photonic switch with switching elements based on dual add-drop microrings with a compact footprint of 4 mm2. This device leverages co-design of the switch architecture and the switching elements with a well-balanced set of performance metrics. The switching elements are designed to have a 3-dB optical passband of 165 GHz, exhibiting off- and on-resonance losses of 0.67 dB and 2 dB, respectively. Full characterization of all switch paths shows an end-to-end on-chip loss between 4.4 and 9.6 dB, with worst-case crosstalk leakage averaged at −16 dB. Owing to the efficient doped waveguide thermo-optic phase shifters, the device features a tuning efficiency of 48.85 GHz/mW. The reconfiguration time of the switch fabric is measured to be 1.2 μs and 0.5 μs at the rise and fall edge, respectively. The dual-microring switching element together with the multi-stage architecture preserves an end-to-end passband over 55 GHz. We validate the switch performance with optical paths of varying numbers of on- and off-resonance switching elements – less than 2 dB power penalties are obtained for all data routings at 32 Gbps.

In this work, a superhydrophobic material was successfully prepared with a water contact angle of about 155.5° and a rolling-off angle of about 6.8°, which showed superior UV resistance (365 nm, 5.0 ± 0.6 mW cm-2) for an illumination period of 30 h. The degradation of organic dyes, such as Nile red, methyl blue and orange, could be also achieved with our prepared surface. Anti-UV water-repellency was combined with photocatalysis to realize a self-cleaning surface for both dirt removal and organic degradation. Moreover, the reversible changes with superhydrophobicity and superhydrophilicity were induced by the self-healing property on such a surface, contributing to heavy and light oils/water separation. Because of ultra-long UV-resistance, photocatalysis, self-cleaning, self-healing and oil/water separation functions, our reported surface has potential for application in a variety of fields.

The rapid development of modern society has increased the demand for high-performance geo-materials. As an advanced cementitious composite, fiber-reinforced concrete has attracted much attention and has been widely applied to various buildings and civil infrastructure. A basalt fiber-reinforced concrete is proposed as an advanced geo-material and the mechanical and thermal properties were investigated in this study. The basalt fiber-reinforced concrete was compared with ordinary concrete to confirm its superiority by determination of the physical parameters, static compressive test, and dynamic compressive test. The static compressive test was performed using the YAW-2000C constant stress pressure experimental machine under different heating temperatures and cooling methods, while the dynamic compressive test was performed using the 75-mm split-Hopkinson pressure bar under different loading rates, heating temperatures, and cooling methods. For the basic physical parameters, it was found that the mass loss and wave velocity of concrete decrease with the increase of the temperature. In the static compressive test, the static compressive strength for both the ordinary concrete and the fiber-reinforced concrete decreased with the increase of the temperature, and greater strength was observed with the air-cooled compared to the water-cooled method. It was found that the strength of basalt fiber-reinforced concrete is greater than that of ordinary concrete. In the dynamic compressive test, the strength increased with an increasing loading rate and descended with an increasing temperature, while for the same heating temperature and loading rate, water cooling produced more irregular and smaller fragments than air cooling. The dynamic compressive strength of basalt fiber-reinforced concrete was bigger than that of ordinary concrete.

By using coarse-grained molecular dynamics simulations, we have investigated the structure and dynamics of supercooled single-chain cross-linked nanoparticle (SCNP) melts having a range of cross-linking degrees ϕ. We find a nearly linear increase in glass-transition temperature (Tg) with increasing ϕ. Correspondingly, we have also experimentally synthesized a series of polystyrene-based SCNPs and have found that the measured Tg estimated from differential scanning calorimetry is qualitatively consistent with the trend predicted by our simulation estimates. Experimentally, an increase in Tg as large as ΔTg = 61 K for ϕ = 0.36 is found compared with their linear chain counterparts, indicating that the changes in dynamics with cross-links are quite appreciable. We attribute the increase in Tg to the enlarged effective hard-core volume and the corresponding reduction in the free volume of the polymer segments. Topological constraints evidently frustrate the local packing. In addition, the introduction of intra-molecular cross-linking bonds slows down the structural relaxation and simultaneously enhances the local coupling motion on the length scales within SCNPs. Consequently, a more pronounced dynamical heterogeneity (DH) is observed for larger ϕ, as quantified by measuring the dynamical correlation length through the four-point susceptibility parameter, χ4. The increase in DH is directly related to the enhanced local cooperative motion derived from intra-molecular cross-linking bonds and structural heterogeneity derived from the cross-linking process. These results shed new light on the influence of intra-molecular topological constraints on the segmental dynamics of polymer melts.

To further reveal the mechanism of graphite migration in copper based graphite composites sliding against 45 steel, the particle Flow Code in 2 Dimensions (PFC2D) was employed to simulate and analysis the relationship between internal force chain and graphite migration in the composites. The simulation results show that a migrated graphite particle layer is formed on the composite surface during friction, and maintains dynamic equilibrium relying on “self-consumption”. The graphite migration displacement to the friction surface is affected by the force chain. The greater the force chain strength is, the smaller the graphite migration displacement is. When the force chain angle is in the range of 75° to 95°, the migration of the graphite particles can not occur; when the angle is 95° to 135°, the graphite migration displacement increases with the increase of the angle. And the greater force chain strength corresponds to the less worn particles and the less migrated graphite particles. The simulation results are significant for optimizing material design and improving the friction performances of copper based graphite composites.

Choosing an appropriate interlayer (IL) is still a crucial challenge for charge balance and exciton regulation in ultra-thin doping-free white organic light-emitting diodes (WOLEDs). Herein, for the first time, the blue thermally activated delayed fluorescence (TADF) 10, 10, 10-(4, 4, 4-Phosphoryltris (benzene-4, 1-diyl)) tris (10Hphenoxazine) (TPXZPO) was selected as the n-type inter-layer (IL) switch. The monochromatic and white light device achieved maximum external quantum efficiencies (EQE) of 24.47% and 14.96%, respectively. More importantly, all devices exhibited extremely low turn-on voltage and stable electroluminescent spectra, with CIE coordinates Δ (x, y) varying only by (0.01, 0.01) in the luminance range of 100 to 10,000 cd/m2. The results showed that new-type IL plays a crucial role in regulating charge and exciton distribution, which could effectively control of the emission zone and the triplet exciton density. This excellent performance demonstrates that the introduction of TADF IL is a promising prospect in the application of high-performance ultra-thin doping-free WOLEDs.

Besides enhancing thermoelectric performance of the existing thermoelectric materials, many efforts have been focused on the exploration of novel thermoelectric materials with potentially high performance typically. This is largely guided by the concept of the intrinsic low lattice thermal conductivity, which is arisen from various mechanisms, such as intrinsic vacancy, low sound velocity, complex crystal structure and lattice anharmonicity. Motivated by the inherent feature of highly disorder cations and intrinsic vacancies introducing strong lattice anharmonicity, this work focuses on a semiconducting compound, ZnIn2Se4, as a potential thermoelectric material. Pristine ZnIn2Se4 shows an n-type conduction and a low carrier concentration of 2.8 × 1018 cm−3. A lattice thermal conductivity as low as ∼0.9 W/m*K at high temperature is obtained, due to the additional phonon scattering by highly disorder cations and intrinsic vacancies. Thus, a peak zT of ∼0.23 is demonstrated in pristine ZnIn2Se4 even with the carrier concentration far deviating from the optimum. This work not only indicates this compound as a promising n-type thermoelectric material, but also provides a direction for enhancement of zT.

Benefited from hierarchical porous structure of Loofah sponge (LS) fibers, a 3D electrically and thermally conductive network structure termed conductive cellulose skeleton (Cellulose-RGO-TDI) was fabricated. In addition, PA6 molecular chains were covalently bonded with conductive cellulose skeleton by reaction between imino groups of PA6 and isocyanate groups of Cellulose-RGO-TDI. As a result, PA6/Cellulose-RGO-TDI nano-composite with high electrical and thermal conductivity was fabricated via reactive melt processing. Both RGO outside the fiber and RGO inside the 3D-bundled micro-channel work together to assemble omnibearing trans-scale conductive networks in the whole hierarchical porous structure of the cellulose skeleton. Finally, more integral conductive pathways are established by RGO along the cellulose fiber, which is more beneficial to transmission of charge carrier and phonons in the whole cellulose skeleton. Exfoliated RGO nano-sheets homogeneously dispersed between matrix and cellulose skeleton and a good interface forms, which promoted formation of electrically and thermally conductive network, resulting in the remarkably improved electrically conductivity of 5.8 × 10−1 S/m and thermally conductivity of 0.419 W m−1 K−1 of the composite with 1.2 vol% RGO loading.

The origin of guided-wave behavior is presented for the case of slabs and for thin films of dielectric materials. The discussion examines the origin of the guided wave using a classical optics approach and that of Maxwell’s equations, as well as the matching of fields at the interfaces of dielectric layers. The chapter also includes various approximations and graphical methods for waveguides with abrupt and diffused geometry.

Electro-optic modulators are based on the control of guided waves using electro-optic variation of the phase or amplitude using an applied electric field. Different theoretical approaches can be used to describe electro-optic control including coupled-mode theory. Phase retardation of the guided light enables polarization splitting, optical switching, and wavelength-selective coupling. Two model–material systems, which are extensively used for E/O devices: GaAs (or other III–V semiconductor material) and lithium niobate. In addition, secondary material systems are mentioned throughout.

Controlling the state of polarization for a propagating mode on an integrated optical chip is a particularly challenging aspect of integrated optical engineering. A significant aspect of that challenge is the need for fabrication with several different forms of materials. In fact in many cases the use of a hybrid approach is required. In this chapter, a wide variety of approaches from simple metal over layers to complex layered structure, and carefully fabricated optical nanostructures are examined for their use in polarization control.

The materials technology for integrated optics is complex and thus this chapter examines the optical properties, the electronic properties, the fabrication, and pattering of a set of the most common materials. These include polymers, crystalline silicon, epitaxial three-five thin films, and doped titanium dioxide. In the discussion, the relative importance of each material is described.

We study the interfacial structure and dynamics of a polymer nanocomposite (PNC) composed of octaaminophenyl polyhedral oligomeric silsesquioxane (OAPS) and poly(2-vinylpyridine) (P2VP) by performing full atomistic molecular dynamics simulations. There are eight aminophenyl groups grafted on the surface of the OAPS particle and the particle has a size comparable to the Kuhn segment of P2VP. These aminophenyl groups can form hydrogen bonds (HBs) with pyridine rings from surrounding P2VP chains. We found that OAPS can form ∼2 HBs on average with surrounding polymer chains. The effect of the HBs is investigated in detail by either switching on or off these HBs in our simulation. By analyzing the interfacial static packing structure and dynamic properties, we demonstrate that the system has an ∼1 nm interface width, similar to the OAPS particle size. We also found that HBs can prevent the further penetration of polymers into the inner zone (grafting layer) of the OAPS, and therefore keep the P2VP chains in the outer layer (>1 nm), remaining bulk-like, which is well consistent with experimental results. In addition, we found that NP diffusion is coupled to the absorbed polymer chains, which also dramatically slows down the diffusion of polymer segments in return. The core–shell model in which the NP and absorbed polymers diffuse as a single object is validated here at the full atomistic level. These results provide atomistic insights into the unique structure and dynamics in the small attractive NP–polymer interfacial region. We hope these results will be helpful for the understanding of peculiar phenomena in attractive polymer nanocomposites containing small NPs.

Ion gating is strategic to the development of low-voltage, printable, and flexible transistors. Tin dioxide (SnO2) is an attractive material for ion-gated transistors due to its good conductivity and low processing temperature. Solution-processed SnO2 ion-gated transistors were demonstrated on rigid and flexible substrates. The mode of transistor operation of the charge carriers can be controlled by the rational processing and patterning of the metal oxide.

We presented new physical insights into designing resonator-assisted photonic interleavers. The robust flat-top transmission spectra of the devices can be achieved and interpreted through rigorous mathematical models based on quasi Fourier series.

A novel silicon photonic circuit for simultaneous Mode and Wavelength Division (De)Multiplexing is demonstrated via advanced simulation. This compact Si circuit uses optical phase shifters based on asymmetric waveguides.

The combination of biomimetic nanochannels and nanostructures provided a new idea for bioanalytical purposes. In this paper, we reported a self-assembled system based on the integration of anodic aluminum oxide (AAO) membranes and CuO method to fabricate CuO nanostructures in the confined area of AAO membranes. Furthermore, we investigated morphologies of the self-assembly systems by field emission scanning electron microscopy (FESEM) and characterized the type and content of microelements by energy dispersive spectrometer. Transmembrane ion current through nanochannels was tested by an electrochemical workstation, and optical properties of the self-assembly systems were characterized by ultraviolet–visible spectrophotometer. We could conclude from the results that the morphology and distribution status of CuO nanostructures are controllable, while ionic current through nanochannels and optical properties of self-assembled systems could be regulated by changing experimental parameters such as electrodeposition time, electrodeposition voltage or annealing temperature. On this base, we utilized the synergistic effect of nanochannels and nanostructures to enhance the sensitivity of biological molecules response. This study not only prepared CuO nanostructures in biomimetic nanochannels controllably, but also provided a novel application paradigm for nanochannels-nanostructures self-assembled system, which could be used for biological analysis and detection.

Adding small nanoparticles (NPs) into polymer melt can lead to a non-Einstein-like decrease in viscosity. However, the underlying mechanism remains a long-standing unsolved puzzle. Here, for an all-polymer nanocomposite formed by linear polystyrene (PS) chains and PS single-chain nanoparticles (SCNPs), we perform large-scale molecular dynamics simulations and experimental rheology measurements. We show that with a fixed (small) loading of the SCNP, viscosity reduction (VR) effect can be largely amplified with an increase in matrix chain length \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$N$$\end{document}N, and that the system with longer polymer chains will have a larger VR. We demonstrate that such \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$N$$\end{document}N-dependent VR can be attributed to the friction reduction experienced by polymer segment blobs which have similar size and interact directly with these SCNPs. A theoretical model is proposed based on the tube model. We demonstrate that it can well describe the friction reduction experienced by melt polymers and the VR effect in these composite systems., Addition of small nanoparticles into polymer melt can lead to decrease in viscosity but the underlying mechanism for such viscosity reduction remains unclear. Here, the authors investigate the reduction in viscosity by large-scale molecular dynamics simulation and experimental rheology measurements for an all-polymer nanocomposite formed by linear polystyrene chains and PS single-chain nanoparticle.

Exploration of novel thermoelectric materials is of great significance for thermoelectric development. AB2X2 Zintl compounds with rich chemical constitute, have been frequently demonstrated as promising thermoelectric materials because of their low lattice thermal conductivity and tunable band structure. This motivates the current work to focus on the experimental evaluation of thermoelectric potential on SrCd2Sb2, a new member of Zintl compounds. Na-substitution at Sr site leads to an effective increase in Hall carrier concentration from ~ 2.6 × 1018 to ~ 1.1 × 1020 cm−3, enabling a well estimation of transport properties by a single parabolic band (SPB) model with acoustic scattering. This reveals a multi-band transporting behavior in SrCd2Sb2 thermoelectrics with heavy-doping or elevated-temperature, ensuring a 150%-improvement in thermoelectric figure of merit (zT). On the basis of model, a peak zT of ~ 1.4 is achievable by minimizing lattice thermal conductivity, which not only demonstrates this compound as a promising thermoelectric material, but also provides a guidance for further advancements.

We have demonstrated a low threshold and tunable flexible random laser (RL) in dye-doped poly ethylene glycol diacrylate (PEG-DA) hydrogel, which was prepared by crosslinking polymerization using PEG-DA monomer and photoinitiator. The random lasering is attributed to the light scattering from the porous structure of hydrogels, and the wavelength of random lasing can be tuned by ~3.2 nm in the temperature range from 30 °C to 70 °C. Under the continuous increasing and decreasing temperature cycle, the random lasing tunable phenomenon can still be observed, which proves that this flexible material can be used as a new temperature sensor. In addition, we also explored the application of flexible laser in phototherapy. Considering the good elasticity and transparency of hydrogels, this thermo-responsive property will be of great significance to the biomedical applications of flexible material.

Rhombohedral GeTe can be approximated as the directional distortion of the cubic GeTe along [111]. Such a symmetry-breaking of the crystal structure results in an opposite arrangement in energy of the L and Σ valence bands, and a split of them into 3L+1Z and 6Σ+6η, respectively. This enables a manipulation of the overall band degeneracy for thermoelectric enhancements through a precise control of the degree of crystal structure deviating from a cubic structure for the alignment of the split bands. Here, we show the effect of AgBiSe2-alloying on the crystal structure as well as thermoelectric transport properties of rhombohedral GeTe. AgBiSe2-alloying is found to not only finely manipulate the crystal structure for band convergence and thereby an increased band degeneracy, but also flatten the valence band for an increased band effective mass. Both of them result in an increased density of state effective mass and therefore an enhanced Seebeck coefficient along with a decreased mobility. Moreover, a remarkably reduced lattice thermal conductivity of ∼0.4 W/m-K is obtained due to the introduced additional point defect phonon scattering and bond softening by the alloying. With the help of Bi-doping at the Ge site for further optimizing the carrier concentration, thermoelectric figure of merit, zT, of ∼1.7 and average zTave of ∼0.9 are achieved in 5% AgBiSe2-alloyed rhombohedral GeTe, which demonstrates this material as a promising candidate for low-temperature thermoelectric applications.

Made available in DSpace on 2019-10-04T12:38:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-07-24 NSERC DG MESI PSIIRI 936 China Scholarship Council Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Trottier Energy Institute FRQNT-RQMP Ion-gated transistors employ ionic gating media (e.g. ionic liquids, polymer electrolytes, aqueous saline solutions) to modulate the density of the charge carriers in the transistor channel. Not only they operate at low voltages (ca 0.5-1 V) but they can also feature printability, flexibility and easy integration with chemo- and bio-sensing platforms. Metal oxides are transistor channel materials interesting for their processability in air, at low temperature. Among metal oxides, tungsten oxide (band gap ca 2.5-2.7 eV) stands out for its electrochromic, gas sensing and photocatalytic properties. Here we demonstrate ion-gated tungsten oxide transistors and phototransistors working in different ion gating media, such as one hydrophobic ionic liquid and an aqueous electrolyte, fabricated both on rigid and flexible substrates. Ion-gated tungsten oxide phototransistors operating in aqueous media could be used as photocatalytic sensors in portable applications. Polytech Montreal, Dept Genie Phys, CP 6079,Succ Ctr Ville, Montreal, PQ H3C 3A7, Canada Univ Fed Minas Gerais, Dept Fis, BR-30123970 Belo Horizonte, MG, Brazil Polytech Montreal, Dept Genie Chim, CP 6079,Succ Ctr Ville, Montreal, PQ H3C 3A7, Canada Univ Estadual Paulista, Dept Fis Quim, Rua Prof Degni 55, BR-14800060 Araraquara, Brazil Univ Montreal, Dept Chim, CP 6128,Succ Ctr Ville, Montreal, PQ H3C 3J7, Canada Univ Bologna, Dipartimento Chim Giacomo Ciamician, Via Selmi 2, I-40126 Bologna, Italy Univ Estadual Paulista, Dept Fis Quim, Rua Prof Degni 55, BR-14800060 Araraquara, Brazil FAPESP: 2014/27079-9 FAPESP: 2015/50526-4 FAPESP: 2016/09033-7

There is an increasing need to develop conducting hydrogels for bioelectronic applications. In particular, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hydrogels have become a research hotspot due to their excellent biocompatibility and stability. However, injectable PEDOT:PSS hydrogels have been rarely reported. Such syringe-injectable hydrogels are highly desirable for minimally invasive biomedical therapeutics. Here, an approach is demonstrated to develop injectable PEDOT:PSS hydrogels by taking advantage of the room-temperature gelation property of PEDOT:PSS. These PEDOT:PSS hydrogels form spontaneously after syringe injection of the PEDOT:PSS suspension into the desired location, without the need of any additional treatments. A facile strategy is also presented for large-scale production of injectable PEDOT:PSS hydrogel fibers at room temperature. Finally, it is demonstrated that these room-temperature-formed PEDOT:PSS hydrogels (RT-PEDOT:PSS hydrogel) and hydrogel fibers can be used for the development of soft and self-healable hydrogel bioelectronic devices.

The rational design of high-performance flexible pressure sensors with both high sensitivity and wide linear range attracts great attention because of their potential applications in wearable electronics and human-machine interfaces. Here, polyaniline nanofiber wrapped nonwoven fabric was used as the active material to construct high performance, flexible, all fabric pressure sensors with a bottom interdigitated textile electrode. Due to the unique hierarchical structures, large surface roughness of the polyaniline coated fabric and high conductivity of the interdigitated textile electrodes, the obtained pressure sensor shows superior performance, including ultrahigh sensitivity of 46.48 kPa&minus, 1 in a wide linear range (&lt, 4.5 kPa), rapid response/relaxation time (7/16 ms) and low detection limit (0.46 Pa). Based on these merits, the practical applications in monitoring human physiological signals and detecting spatial distribution of subtle pressure are demonstrated, showing its potential for health monitoring as wearable electronics.

Creating vertically aligned 2D nanostructures is a promising approach to achieving advanced electronic and optoelectronic materials. In this study, Mg2Si nanosheet bundles were synthesized by Ca atom extraction from CaSi2 microwalls grown on Si substrates via thermal annealing in a MgCl2/Mg mixed vapor. The nanosheet bundle structure was modified to compound nanosheet bundles from previously reported Si nanosheet bundles. The observed Mg2Si nanosheets consist of thin Mg2Si layers, and well-defined fine-scale Mg2Si superlattice-like structures were achieved in the nanosheet bundles. In addition, the Raman scattering and photoluminescence properties were examined, and structural and electronic modifications of the nanosheet bundle compared with the bulk crystals were suggested. To obtain tailored properties and functionalities of the nanosheet bundles, structural modification of layered crystals is a useful technique.

The regulation of charge and exciton distribution play a significant role in ultra-thin non-doped white organic light-emitting diodes (WOLEDs). Herein, the exciplex is selected as an interlayer (IL) switch to adjust the charge balance and regulate exciton distribution in ultra-thin non-doped WOLEDs. The optimal device achieved a maximum external quantum efficiency (EQE) of 22.42 %, a maximum current efficiency of 63.41 cd/A and a maximum power efficiency of 83.04 lm/W. The time‐resolved photoluminescence of different exciplexes has been systematically investigated to reveal the intrinsic luminance mechanism of high-efficiency WOLEDs. In addition, kelvin probe force microscopy (KFPM) results provide new insights in exciplex interlayer switch surface charge effect. These results demonstrate the potential of exciplex IL for exciton confinement, charge balance and carrier transport, which prevent energy loss and reduce triplet-triplet annihilation. Therefore, the utilization of exciplex IL is a promising approach for the development of next-generation WOLEDs.

Ensuring stable red and blue emission from white organic light-emitting devices (WOLEDs) with complementary colors is a major challenge. Here, a novel exciplex systems were used to solve this problem, where a thermally activated delayed fluorescence (TADF) material 10, 10, 10-(4, 4, 4-Phosphoryltris (benzene-4,1-diyl)) tris (10Hphenoxazine) (TPXZPO) and a common hole transporting material N,N′-dicarbazolyl-3,5-benzene (MCP) were mixed with an electron-transporting material (1,3,5-Triazine-2,4,6-triyl)tris(benzene-3,1-diyl)) tris(diphenylphosphineoxide) (PO-T2T) to form exciplex host for red and blue phosphorescent materials, respectively. Benefitted from the high triplet energy of donor and accepter were select to form exciplex host which ensures that excitons are excellent confined to the EMLs. Matched exciplex host-guest systems and a multichannel reverse intersystem crossing reduces energy loss during energy transfer processes and prevents triplet-triplet annihilation. The use of stepped energy transfer channels and exciplex interlayer switch ensures WOLEDs have greater stability. The devices exhibited a maximum power efficiency, current efficiency, and external quantum efficiency of 69.25 lm/W, 56.69 cd/A and 24.55%, respectively. More importantly, the devices exhibited extremely stable color rendering index ranging from 74 to 76 with luminance ranging from 102 to 104 cd/m2. These results indicate that the exciplex are promising for use in developing high performance complementary color WOLEDs.

Selection of non-toxic elements existed in human body or certified for tissue regeneration is considered for multifunctional biodegradable metals. The effect of Sr addition on microstructure, mechanical properties, and degradation behavior of biodegradable Mg–2Zn-0.3Ca alloy was studied as an example to gain insight into the Mg–Zn–Ca alloy series. The average grain size of alloys became smaller and more homogeneous distinctly by increasing Sr content. The second phases on the grain boundaries and the interdendritic interstices were also refined with small amount of Sr addition. More concentration of Sr element was detected evidentially at the interface between grains and the second phases. Mg–2Zn-0.3Ca-0.3Sr alloy shows the optimal flexural and compressive strength of (441 ± 18) MPa and (317 ± 13) MPa, respectively. The electrochemical measurement in simulated body fluid showed that addition of Sr would slightly deteriorate the corrosion resistance of Mg–Zn–Ca–Sr alloys. The in-vitro immersion tests were conducted and analyzed in detail by three different immersion stages and got a distinctive corrosion performance compared with the electrochemical measurements. Homogenization annealing was conducted for Mg–2Zn-0.3Ca-0.3Sr alloy, which can reduce dendrite segregation and significantly improve the corrosion resistance of alloy. The degradation process of alloys in simulated body fluid was summarized in detail for Mg–Zn–Ca–Sr alloys. This work not only provides the relationship between microstructure and properties of biodegradable Mg alloys, but also a comprehensive discussion of degradation behavior of Mg–Zn–Ca alloys for orthopedic application.

Si nanosheets connected to Si nanowires were synthesized using a MnCl 2 /Si powder source with an Au catalyst. The synthesis method has benefits in terms of avoiding conventionally used air-sensitive SiH 4 or SiCl 4 . The existence of the Si nanosheets connected to the Si nanowires, like sprouts or leaves with petioles, was observed, and the surface of the nanosheets was Si{111}. The nanosheets were grown in the growth direction of perpendicular to that of the Si nanowires. It was evident from these structural features of the nanosheets that the nanosheets were formed by the twin-plane reentrant-edge mechanism. The feature of the observed lattice fringes, which do not appear for Si bulk crystals, of the Si(111) nanosheets obtained by high resolution transmission electron microscopy was clearly explained due to the extra diffraction spots that arose by the reciprocal lattice streaking effect.

Structural control and morphological modification of a series of Si-based nanostructures were studied from the viewpoint of modifying the catalyst’s characteristics. The catalyst was modified from a liquid to a solid during its growth. The growth evolution of the faceted Si nanowires occurred via a vapor–liquid–solid mechanism followed by a silicide vapor–solid–solid mechanism. The shapes of the catalysts defined the shapes of the nanowires during the vapor–solid–solid growth. The catalyst was further modified by the deposition of MnCl2. Only irregularly shaped Si particles or MnCl2 particles were observed on top of the Si nanowires. The characteristic modification of catalysts by liquid-phase crystal nucleation and deposition of liquid-phase droplets was discussed. In addition, the synthesis of a CrSi2 nanowire bundle by the formation of dense nanoparticles was studied.

Hybrid organic–inorganic perovskites, represented by materials in the CH3NH3PbI3 series, have become one of the most promising materials for solar cells with a high power conversion efficiency and low cost. The ordered Pb–I cage in such hybrid perovskites can induce the polarized cations to form a variety of polarization domains with long-range order, which will lead to the formation of specific atomic conformations or metastable crystalline phases, unique electronic band structures and optical absorption properties. Such domain-dependent characteristics play a critical role in the phase transition and service stability of such solar cells, and also open up the opportunity of tuning their electronic structure. In the present study, we systematically investigate the band structures and optical absorption properties of different electronically ordered domains in CH3NH3PbI3. By comparing different perovskites containing various cations, we have clarified the important influence of cation polarization on domain-dependent properties. Our results provide not only a possible pathway for the manipulation of band structure by applying an external field, but also a novel scheme for improving the performance and stability of hybrid perovskites.

Fatigue performance of hot-rolled ribbed-steel bar with the yield strength of 500 MPa (HRB500) was studied with bend-rotating fatigue test at a stress ratio of R = −1. It is determined by staircase method that its fatigue strength for 10 7 cycles is 451 MPa, which is higher than that of common carbon structural steel. This should be attributed to the fine-grain strengthening resulting from the high content of alloy element V and Thermo-Mechanical Control Process (TMCP). The S-N curve function is also obtained by nonlinear regression with three parameters power function. The fatigue fractures of the specimen were further analyzed with Scanning Electron Microscopy (SEM) and Energy Disperse Spectroscopy (EDS) to study the fracture mechanism. Taking into account microstructure, hardness and cleanliness of the material, it implies that the fatigue fractures of HRB500 rebar all arise from surface substrates in which many brittle inclusions are contained, and that the fatigue crack propagation is principally based on the mechanism of quasi-cleavage fracture, because of the intracrystalline hard spots leading to stress concentration and thus to the cracks. Moreover, the transient breaking area exhibits microvoid coalescence of ductile fracture due to the existing abundant inclusions.

Polymeric single-chain nanoparticles (SCNPs) are soft nano-objects synthesized by intramolecular crosslinking of isolated single polymer chains. Syntheses of such SCNPs usually need to be performed in a dilute solution. In such a condition, the bonding probability of the two active crosslinking units at a short contour distance along the chain backbone is much higher than those which are far away from each other. Such a reaction condition often results in local spheroidization and, therefore, the formation of loosely packed structures. How to inhibit the local spheroidization and improve the compactness of SCNPs is thus a major challenge for the syntheses of SCNPs. In this study, computer simulations are performed and the fact that a precollapse of the polymer chain conformation in a cosolvent condition can largely improve the probability of the crosslinking reactions at large contour distances is demonstrated, favoring the formations of closely packed globular structures. As a result, the formed SCNPs can be more spherical and have higher compactness than those fabricated in ultradilute good solvent solution in a conventional way. It is believed this simulation work can provide a insight into the effective syntheses of SCNPs with spherical conformations and high compactness.

The diffusion dynamics of fullerene (C 60 ) in unentangled linear atactic polystyrene (PS) and polypropylene (PP) melts and the structure and dynamic properties of polymers in interface area are investigated by performing all-atom molecular dynamics simulations. The comparison of the results in two systems emphasises the influence of local interactions exerted by polymer side group on the diffusion dynamics of the nanoparticle. In the normal diffusive regime at long time scales, the displacement distribution function (DDF) follows a Gaussian distribution in PP system, indicating a normal diffusion of C 60 . However, we observe multiple peaks in the DDF curve for C 60 diffusing in PS melt, which indicates a diffusion mechanism of hopping of C 60 . The attractive interaction between C 60 and phenyl ring side groups are found to be responsible for the observed hopping diffusion. In addition, we find that the C 60 is dynamically coupled with a subsection of a tetramer on PS chain, which has a similar size with C 60 . The phenyl ring on PS chain backbone tends to have a parallel configuration in the vicinity of C 60 surface, therefore neighbouring phenyl rings can form chelation effect on the C 60 surface. Consequently, the rotational dynamics of phenyl ring and the translational diffusion of styrene monomers are found to be slowed down in this interface area. We hope our results can be helpful for understanding of the influence of the local interactions on the nanoparticle diffusion dynamics and interfacial properties in polymer/nanoparticle composites.

Electrolyte-gated transistors hold promise for applications in printable and flexible electronics. Metal oxide semiconductors are particularly interesting as electrolyte-gated channel materials for their abundance, thermodynamic stability and ease of processing under ambient conditions. In this work, we synthesized by sol–gel and hydrothermal methods different types of tungsten oxide to be used as channel materials in ion gel-gated transistors. X-ray diffraction and scanning and transmission electron microscopy revealed that the differently processed oxides show a different structure (hexagonal and monoclinic) and morphology (granular, nanofiber and nanoplate). We studied the electrochemical and transistor properties of the oxides using, as the gating media, two different ion gels prepared from the same ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM]TFSI), and two different block copolymers. We tentatively propose that for sufficiently high values of the gate–source bias, the doping results from chemical and electrochemical contributions.

Thermally activated delayed fluorescence (TADF) emitters have received much attention for the fabrication of white organic light-emitting diodes (WOLEDs); however, challenges remain owing to severe efficiency roll-off, poor color stability, and high cost. In this contribution, solution-processed hybrid WOLEDs were obtained by employing a blue TADF dendrimer, bis{4-[3,6-bis(3,6-di-tert-butylcarbazol-N-yl)carbazol-N-yl]phenyl}sulfone (BPS), combined with an orange iridium complex, bis(2-phenylbenzothiazolato)(acetylacetonate)iridium(III), Ir(bt)2 (acac), as a co-dopant. The devices achieved a maximum external quantum efficiency of 6.59 % and a maximum current efficiency of 17.34 cd A-1 . The results suggest that the TADF dendrimer serving as an assistant dopant were helpful in reducing the triplet populations by up-converting the triplet excitons to the singlet state and immediately transferring the singlet excitons to Ir(bt)2 (acac) (bt=2-phenylbenzothiazolato, acac=acetylacetonato) by virtue of the long-range Forster resonance energy transfer, thus significantly decreasing the triplet-triplet annihilation (TTA). Moreover, the emitters can act as shallow trapping centers to decrease charge and exciton aggregation. The resulting OLEDs exhibit stable electroluminescent spectra and low efficiency roll-off at relatively high current density. The CIE coordinates Δ(x, y) vary only (0.02, 0.02) in the luminance range of 100 to 10 000 cd m-2 .

Made available in DSpace on 2022-04-28T19:01:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-09-17 Electrolyte-gated (EG) transistors, based on electrolyte gating media, are powerful device structures to modulate the charge carrier density of materials by orders of magnitude, at relatively low operating voltages (sub-2 V). Tungsten trioxide (WO3) is a metal oxide semiconductor well investigated for applications in electrochromism, sensing, photocatalysis, and photoelectrochemistry. In this work, we report on EG transistors making use of mesoporous nanostructured WO3 thin films easily permeated by the electrolyte as the transistor channel and bis(trifluoromethylsulfonyl)imide ([TFSI])-based ionic liquids as the gating media. The WO3 EG transistors operate at ca. 1 V. Using a combination of cyclic voltammetry, X-ray diffraction, and transistor performance characterizations, complemented by spectroscopic (Raman and infrared) investigations, we correlate the metal oxidation state and the charge transport properties of the metal oxide, shedding light on the doping process in electrically biased WO3 nanostructured thin films exposed to electrolytes. Département de Génie Physique Polytechnique Montréal, C.P. 6079, Succ. Centre Ville Departamento de Físico-Química Universidade Estadual Paulista, Rua Professor Degni, 55 CNR-IENI Dipartimento di Scienze Chimiche Università di Padova, Via F. Marzolo 1 Département de Chimie Université de Montréal, C.P. 6128, Succ. Centre Ville Dipartimento di Chimica giacomo Ciamician Università di Bologna, Via Selmi, 2 Departamento de Físico-Química Universidade Estadual Paulista, Rua Professor Degni, 55