Gallium Complexes in Three‐Layer Organic Electroluminescent Devices

Organic light‐emitting diodes fabricated by subsequently spin‐coating two layers—a hole‐transporting followed by a metal chelate emissive layer—onto poly(3,4‐ethylenedioxythiophene)/poly(styrenesulfonate) are presented for the first time. The electron–hole recombination occurs in a layer consisting of Ga complexes (see Figure), which exhibit high fluorescence quantum yields, and their emission spectra are blue‐shifted relative to that of tris(8‐hydroxyquinoline) aluminum. By doping this spin‐coated emission layer with fluorescent emitters the emission band can be shifted within the visible spectral range.     

Mechanical Behavior of Particle Reinforced Metal Matrix Composites

Metal matrix composites provide significantly enhanced properties — like higher strength, stiffness and weight savings — in comparison to conventional monolithic materials. Particle reinforced MMCs are attractive due to their cost‐effectiveness, isotropic properties, and their ability to be processed using similar technology used for monolithic materials. This review captures the salient features of experimental as well as analytical and computational characterization of the mechanical behavior of MMCs. The main focus is on wrought particulate reinforced light alloy matrix systems, with a particular emphasis on tensile, creep, and fatigue behavior.     

Dynamic mechanical analysis of heat,microwave and visible light cure denture base resins

The clinical durability and performance of a denture are limited by the properties of the denture base resins used in the fabrication of the prosthesis. Among the properties considered important for denture base resins are viscoelastic properties such as storage modulus, damping and glass transition. In this study, dynamic mechanical analysis using a flexural mode of deformation in the temperature range 25–180°C has been used to characterize the viscoelastic properties of three denture base resins with different curing modes including conventional thermal cure, microwave cure and visible light cure. The resins studied were popular commercial systems. The results indicate that the microwave cure and conventional thermal cure resins are significantly different in their viscoelastic properties from the current visible light cure resin system. The latter resin is characterized by higher flexural modulus and loss modulus across the entire range of temperatures investigated and in addition shows higher glass transition temperature relative to the other resins studied. The results indicate that filler loading and crosslinking effects may be responsible for this behaviour of the visible light cure resin and may indicate a potential brittle behaviour not desirable in a permanent denture.     

Optical Pliers: Micrometer-Scale,Light-Driven Tools Grown on Optical Fibers

The ability to grip and handle small objects, from sub-millimeter electronic components to single-micrometer living cells, is vital for numerous ever-shrinking technologies. Mechanical grippers, powered by electric, pneumatic, hydraulic or piezoelectric servos, are well suited for the job at larger scales, but their complexity and need for force transmission prevent their miniaturization and remote control in tight spaces. Using liquid crystal elastomer microstructures that can change shape quickly and reversibly in response to light, a light-powered gripping tool—optical pliers—is built by growing two bending jaws on the tips of optical fibers. By delivering UV light to trigger polymerization via a micrometer-size fiber core, structures of similar size can be made without resorting to any microfabrication technology, such as laser photolithography. The tool is operated using visible light energy supplied through the fibers, with no force transmission. The elastomer growth technique readily offers micrometer-scale, remotely controlled functional structures with different modes of actuation as building blocks for the microtoolbox.     

Nanomechanical and Charge Transport Properties of Two‐Dimensional Atomic Sheets

The materials properties of graphene and other two‐dimensional atomic sheets are influenced by atomic‐scale defects, mechanical deformation, and microstructures. Thus, for graphene‐based applications, it is essential to uncover the roles of atomic‐scale defects and domain structures of two‐dimensional layers in charge transport properties. This review highlights recent studies of nanomechanical and charge transport properties of two‐dimensional atomic sheets, including graphene, MoS₂, and boron nitrides. Because of intrinsic structural differences, two‐dimensional atomic sheets give rise to unique nanomechanical properties, including a dependence on layer thickness and chemical modification that is in contrast to three‐dimensional continuum media. Mapping of local conductance and nanomechanical properties on a graphene layer can be used to image the domain and microstructures of two‐dimensional atomic layers. This paper also reviews recent experimental and theoretical findings on the role of bending, defects, and microstructures on nanomechanical and transport properties of graphene‐derived materials.     

Biomorphic Cellular Ceramics

Biotemplating—a new concept for preparation of ceramic composite materials with biomorphic microstructures will be described. Biological carbon preforms (C_B‐templates) were derived from different wood structures by high‐temperature pyrolysis at temperatures between 800 and 1800 °C and used as templates for infiltration with gaseous or liquid Si to form SiC‐ and SiSiC‐ceramics. During high‐temperature processing, the microstructural details of the bioorganic preforms were retained. Cellular ceramic composites with unidirectional porous morphologies and anisotrophic mechanical properties were obtained. The cellular composites show low density, but high specific strength and excellent high temperature stability.     

TbDyFe中稀土元素的烧损对组织和性能的影响

在模拟实验低真空环境下,将Tb,Dy及Fe合金元素经过熔炼、定向凝固、热处理后,制备了Tb_(0.27)Dy_(0.73)Fe_(1.91)合金棒。测试合金棒的磁致伸缩性能,研究材料的组织结构,分析组织中缺陷产生的原因。结果表明:在低真空环境下,大量的孪生枝晶片层和普通孪晶组织产生,其中片层状孪晶具有良好的压磁效应和力学性能,而普通孪晶的产生对材料磁致伸缩性能产生不利影响。合金基体主要相为REFe_2与REFe_3耦合相,烧损导致合金的成分偏离,造成包晶REFe_2相和初生REFe3相的耦合生长。与此同时,存在由于热应力产生的微裂纹和稀土元素偏聚烧损后产生的孔洞。这些组织和缺陷对TbDyFe合金棒的磁致伸缩性能和力学性能产生不利影响。     

Tuning the Photoinduced Electron Transfer in a Zr‐MOF: Toward Solid‐State Fluorescent Molecular Switch and Turn‐On Sensor

The immobilization of fluorescent photoinduced electron transfer (PET) switches/sensors into solid state, which usually cannot maintain their identical properties in solution, has remained a big challenge. Herein, a water‐stable anthracene and maleimide appended zirconium‐based‐metal–organic framework (Zr‐MOF; UiO‐68‐An/Ma) is reported. Unlike the regular intramolecular “fluorophore–spacer–receptor” format, the separated immobilization of fluorescent (anthracene) and acceptor (maleimide) groups into the framework of a multivariate MOF can also favor a pseudo‐intramolecular fluorescent PET process, resulting in UiO‐68‐An/Ma with very weak fluorescence. Interestingly, after Diels–Alder reaction or thiol‐ene reaction of maleimide groups, the pseudo‐intramolecular fluorescent PET process in UiO‐68‐An/Ma fails and the solid‐state fluorescence of the crystals is recovered. In addition, UiO‐68‐An/Ma shows an interesting application as solid‐state fluorescent turn‐on sensor for biothiols, with the naked eye response at a low concentration of 50 µmol L^?1 within 5 min. This study represents a general strategy to enable the efficient tuning of fluorescent PET switches/sensors in solid state, and considering the fluorescence of the PET‐based MOFs can be restored after addition of analyte/target species, this research will definitely inspire to construct stimuli‐responsive fluorescent MOFs for interesting applications (e.g., logic gate) in future.     

Photoreversible Fluorescent Modulation of Nanoparticles via One‐Step Miniemulsion Polymerization

A nitrobenzoxadiazolyl(NBD)‐based fluorescent dye and a photochromic spiropyran derivative are incorporated into polymeric nanoparticles via a one‐step miniemulsion polymerization. The diameter of the nanoparticles can be varied from approximately 40 nm to 80 nm by adjusting the polymerization conditions. The prepared nanoparticles exhibit the spectral properties of both NBD dye and spiropyran, indicating that the two chromophores are incorporated into the nanoparticles. The determined amount of NBD and spiropyran in the nanoparticles are about ≈85–90% of the feed amount, while the determined weight ratios of spiropyran to NBD in nanoparticles are very close to that of feed ratios, suggesting the miniemulsion polymerization is a suitable approach for incorporating multiple chromophores into individual nanoparticles with controlled amounts (content) and ratio. UV and visible light can be applied to modulate the fluorescence emission of NBD dye in nanoparticles. Upon UV irradiation, the spiropyran moieties in nanoparticles are converted to the open‐ring (McH form) structure and upon visible‐light irradiation they return to the closed‐ring (SP form) structure; as a result, the fluorescence of NBD can be reversibly “switched off” and “switched on”. Fluorescence resonance energy transfer from the excited NBD dye molecules to the McH form of the spiropyran moieties is the drives the fluorescence modulation. The nanoparticles display fairly good photoreversibility, photostability, and relatively fast photoresponsivity upon alternate UV/Vis irradiation. This class of photoresponsive nanoparticles may find applications in biological fields, such as labeling and imaging, as well as in optical fields, for example, individually light‐addressable nanoscale devices.     

Tunable Luminescent Carbon Nanospheres with Well‐Defined Nanoscale Chemistry for Synchronized Imaging and Therapy

In this work, we demonstrate the significance of defined surface chemistry in synthesizing luminescent carbon nanomaterials (LCN) with the capability to perform dual functions (i.e., diagnostic imaging and therapy). The surface chemistry of LCN has been tailored to achieve two different varieties: one that has a thermoresponsive polymer and aids in the controlled delivery of drugs, and the other that has fluorescence emission both in the visible and near‐infrared (NIR) region and can be explored for advanced diagnostic modes. Although these particles are synthesized using simple, yet scalable hydrothermal methods, they exhibit remarkable stability, photoluminescence and biocompatibility. The photoluminescence properties of these materials are tunable through careful choice of surface‐passivating agents and can be exploited for both visible and NIR imaging. Here the synthetic strategy demonstrates the possibility to incorporate a potent antimetastatic agent for inhibiting melanomas in vitro. Since both particles are Raman active, their dispersion on skin surface is reported with Raman imaging and utilizing photoluminescence, their depth penetration is analysed using fluorescence 3D imaging. Our results indicate a new generation of tunable carbon‐based probes for diagnosis, therapy or both.     

Untersuchungen zum Verschleißverhalten von Metall/Metall – Gleitpaarungen aus CoCrMo‐Legierungen

Investigation of the Wear Behaviour of Metal/Metal Bearings of Co Cr Mo – Alloys CoCrMo‐alloys are successfully used for long‐term implants, because of their corrosion and wear resistance as well as their mechanical properties. In order to improve CoCrMo‐alloys for metal‐on‐metal bearings the influence of carbon content on wear behaviour is investigated. Casted or forged CoCrMo‐alloys with a carbon content from 0.008 to 0.48 wt % were studied in ring on disc oscillating tests. Friction torque, weight loss and surface roughness, as well as light and scanning electron microscopic investigations of the sample surface were used to characterize the wear behaviour. – All alloys show similar friction torque and weight loss. But the surface roughness and the wear mechanisms are depended on the carbon content.     

The relationship between the electrical and mechanical properties of polymer–nanotube nanocomposites and their microstructure

A range of polymer–nanotube nanocomposites were produced using different processing routes. Both polymer-grafted and as-grown nanotubes were used and latex and polystyrene matrices investigated. The microstructures of the nanocomposites were studied, mainly by electron microscopy, in terms of the dispersion state of the nanotubes and the polymer–nanotube interface. The mechanical and electrical properties of the composites were also measured. The relationship between the microstructures observed and the resulting physical properties are discussed. It is found that composites with apparently similar microstructures can exhibit similar mechanical properties but very different electrical behaviours. Moreover, the nanocomposites produced using polymer-grafted nanotubes exhibit a clear improvement of the stress at large deformation. Thus, from our results, it appears that the mechanical and electrical properties do not necessarily depend on the same microstructural parameters. However it is still a challenge to simultaneously improve both physical properties.     

Improving the Sensitivity of Fluorescence‐Based Immunoassays by Photobleaching the Autofluorescence of Magnetic Beads

In fluorescence‐based assays, usually a target molecule is captured using a probe conjugated to a capture surface, and then detected using a second fluorescently labeled probe. One of the most common capture surfaces is a magnetic bead. However, magnetic beads exhibit strong autofluorescence, which often overlaps with the emission of the reporter fluorescent dyes and limits the analytical performance of the assay. Here, several widely used magnetic beads are photobleached and their autofluorescence is reduced to 1% of the initial value. Their autofluorescence properties, including their photobleaching decay rates and autofluorescence spectra pre‐ and post‐photobleaching, and the stability of the photobleaching over a period of two months are analyzed. The photobleached beads are stable over time and their surface functionality is retained. In a high‐sensitivity LX‐200 system using photobleached magnetic beads, human interleukin‐8 is detected with a threefold improvement in detection limit and signal‐to‐noise ratio over results achievable with nonbleached beads. Since many contemporary immunoassays rely on magnetic beads as capture surfaces, prebleaching the beads may significantly improve the analytical performance of these assays. Moreover, nonmagnetic beads with low autofluorescence are also successfully photobleached, suggesting that photobleaching can be applied to various capture surfaces used in fluorescence‐based assays.     

Highly Fluorescent Magnetic Nanobeads with a Remarkable Stokes Shift as Labels for Enhanced Detection in Immunoassays

Fluorescence immunoassays are popular for achieving high sensitivity, but they display limitations in biological samples due to strong absorption of light, background fluorescence from matrix components, or light scattering by the biomacromolecules. A powerful strategy to overcome these problems is introduced here by using fluorescent magnetic nanobeads doped with two boron‐dipyrromethane dyes displaying intense emission in the visible and near‐infrared regions, respectively. Careful matching of the emission and absorption features of the dopants leads to a virtual Stokes shift larger than 150 nm achieved by an intraparticle Förster resonance energy transfer (FRET) process between the donor and the acceptor dyes. Additionally, the magnetic properties of the fluorescent beads allow preconcentration of the sample. To illustrate the usefulness of this approach to increase the sensitivity of fluorescence immunoassays, the novel nanoparticles are employed as labels for quantification of the widely used Tacrolimus (FK506) immunosuppressive drug. The FRET‐based competitive inhibition immunoassay yields a limit of detection (LOD) of 0.08 ng mL^?1, with a dynamic range (DR) of 0.15–2.0 ng mL^?1, compared to a LOD of 2.7 ng mL^?1 and a DR between 4.1 and 130 ng mL^?1 for the immunoassay carried out with direct excitation of the acceptor dye.     

Particle‐Based Optical Sensing of Intracellular Ions at the Example of Calcium – What Are the Experimental Pitfalls?

Colloidal particles with fluorescence read‐out are commonly used as sensors for the quantitative determination of ions. Calcium, for example, is a biologically highly relevant ion in signaling, and thus knowledge of its spatio‐temporal distribution inside cells would offer important experimental data. However, the use of particle‐based intracellular sensors for ion detection is not straightforward. Important associated problems involve delivery and intracellular location of particle‐based fluorophores, crosstalk of the fluorescence read‐out with pH, and spectral overlap of the emission spectra of different fluorophores. These potential problems are outlined and discussed here with selected experimental examples. Potential solutions are discussed and form a guideline for particle‐based intracellular imaging of ions.     

Tetragonal Single‐Crystalline Boron Nanowires with Strong Anisotropic Light Scattering Behaviors and Photocurrent Response in Visible‐Light Regime

Boron is a narrow‐bandgap (1.56 eV) semiconductor with high melting‐point, low‐density, large Young's modulus and very high refractive index (3.03) close to silicon. Therefore, boron nanostructures is expected to possess strong visible‐light scattering properties. However, photonic and optoelectronic properties of the boron nanostructures are seldom studied until now. In this paper, we have successfully prepared single‐crystalline boron nanowire (BNW) arrays with high‐density on Si substrate. All the BNWs are found to possess strong light‐scattering behaviors in the visible regime. Most of all, the scattered light is found to polarize along the longitudinal direction of the nanowire. They also have excellent second‐harmonic generation (SHG) properties under ultrafast laser irradiation. Further optoelectronic measurements show that an individual BNW device exhibits notable photocurrent responses in the visible‐light range at ambient conditions, which can be attributed to the strong coupling effect between individual BNW and the visible light. The maximum photoresponsivity of an individual BNW can reach up to 12.12 A W^–1 at a voltage of 10 V, and the response time is only 18 ms. Therefore, it unveils that the BNWs have a promising future in visible‐light communications and detections.     

Nucleation and Crystallization Phenomena in Glass‐Ceramics

Glass‐ceramics are modern multiphase materials. Different types of glass‐ceramics can be fabricated and their properties tailored to meet specific requirements. It is possible, therefore, to produce glasses that combine desirable optical properties such as transparency and mechanical properties such as strength. Furthermore, this controlled development of glass‐ceramics also enables the fabrication of materials exhibiting properties that are unknown in conventional glasses and ceramics. In this article, the authors discuss nucleation and crystallization phenomena in the controlled development of various glass‐ceramics on the basis of their own work. The reaction mechanisms in the formation of glass‐ceramics and their microstructures are illustrated. In addition, the resulting properties of the glass‐ceramics and their particular applications are presented.     

Multifunctional FeCo/TiN Multilayer Thin Films with Combined Magnetic and Protective Properties

Coatings with thicknesses ranging from a few nanometer up to several micrometer produced by physical vapor deposition (PVD) processes have been established in engineering technologies since the early 1980s. In particular, magnetron sputtered wear resistance coatings are industrially established and capable to enhance tool lifetimes significantly. However, in cases where optical inspection of a coating in use is not possible, an intrinsic sensor function of the film would be beneficial. Therefore, the development of wear resistant coatings with an integrated sensor functionality based on the insertion of a magnetoelastic ferromagnetic phase is suggested. In combination with appropriate read‐out electronics such a film system would be ready for online monitoring of the coatings' actual state (e.g., strain, temperature, volume loss). This paper focuses on the development of wear resistance coatings which simultaneously supply beneficial mechanical properties as well as ferromagnetic properties optimized for online non‐contact read‐out applications. Multilayer coatings obtained through alternate stacking of magnetron sputtered TiN and FeCo layers with a nominal total thickness of 1000 nm were produced as a model system meeting the above conditions. The bilayer period was varied down to 2.6 nm while the individual layer thickness ratio t_TiN/t_FeCo was determined by the deposition rates and maintained constant at a value of about 3/1. The films were vacuum annealed ex situ in a static magnetic field subsequent to the deposition. The constitution of the as‐deposited and annealed coatings as well as their mechanical (nanohardness, Young's modulus) and magnetic properties (magnetization hysteresis, frequency‐dependent permeability) are described. Finally, the suitability of the coatings for the use in remote‐interrogable wear sensor applications is briefly discussed.     

Distinguishable Detection of Ultraviolet,Visible, and Infrared Spectrum with High‐Responsivity Perovskite‐Based Flexible Photosensors

Distinguishable detection of the ultraviolet, visible, and infrared spectrum is promising and significant for the super visual system of artificial intelligences. However, it is challenging to provide a photosensor with such broad spectral response ability. In this work, the ultraviolet, visible, and infrared spectrum is distinguished by developing serial photosensors based on perovskite/carbon nanotube hybrids. Oraganolead halide perovskites (CH₃NH₃PbX₃) possess remarkable optoelectronic properties and tunable optical band gaps by changing the halogens, and integration with single‐walled carbon nanotubes can further improve their photoresponsivities. The CH₃NH₃PbCl₃‐based photosensor shows a responsivity up to 10⁵ A W^?1 to ultraviolet and no obvious response to visible light, which is superior to that of most ultraviolet sensors. The CH₃NH₃PbBr₃‐based photosensor exhibits a high responsivity to visible light. Serial devices of the two hybrid photosensors with comparable electric and sensory performances can distinguish the spectrum of ultraviolet, visible, and infrared even with varying light intensities. The photosensors also demonstrate excellent mechanical flexibility and bending stability. By taking full advantages of the oraganolead halide perovskites, this work provides flexible high‐responsivity photosensors specialized for ultraviolet, and gives a simple strategy for distinguishable detection of ultraviolet, visible, and infrared spectrum based on the serial flexible photosensors.