Electroluminescence quenching mechanism in Rubrene doped host-guest system

In this paper, the electroluminescence quenching mechanism in a 5,6,11,12-tetraphenylnaphthacene （Rubrene） doped host-guest system is studied by utilizing a specially designed organic light-emitting diode with an emission layer consisting of a few periodic host/guest structures. Tris-（8-hydroxyquinoline） aluminium （Alq3） and Rubrene are used as the host and the guest, respectively. The thickness variation of the guest layer in each period enables the study of the effect of molecule aggregation, and the thickness variation of the host layer suggests a long range quenching mechanism of dipole-dipole interaction. The long range quenching mechanism is a Forster process, and the FSrster radius of Rubrene is between 3 and 10 nm.

Effect of Direct Quenching and Partitioning Treatment on Mechanical Properties of a Hot Rolled Strip Steel

Three different online heat treatment processes were designed to study the effects on the mechanical properties of a 0.19C-1.6Si-1.6Mn（wt%） hot rolled strip steel.The microstructures were characterized by means of SEM,TEM,EPMA,and XRD.The mechanical properties were estimated by tensile tests.Results showed that a satisfying combination of strength and ductility could be obtained through the ferrite relaxation and direct quenching and partitioning process.Analysis was also focused on this process.The microstructure contained proeutectoid ferrite grains,martensite packets and blocky or interlath retained austenite,and also contained carbide-free bainite in the case of relatively high quench temperatures.The retained austenite fraction was increased through proeutectoid ferrite and partial bainite transformation,while the tensile strength was also consequently decreased.The most of retained austenite transformed to ferrite under deformation and the elongation was obviously improved.

Microstructural evolution and mechanical properties of a low-carbon quenching and partitioning steel after partial and full austenitization

In this work, low-carbon steel specimens were subjected to the quenching and partitioning process after being partially or fully austenitized to investigate their microstructural evolution and mechanical properties. According to the results of scanning electron microscopy and transmission electron microscopy observations, X-ray diffraction analysis, and tensile tests, upper bainite or tempered martensite appears successively in the microstructure with increasing austenitization temperature or increasing partitioning time. In the partially austenitized specimens, the retained austenite grains are carbon-enriched twice during the heat treatment, which can significantly stabilize the phases at room temperature. Furthermore, after partial austenitization, the specimen exhibits excellent elongation, with a maximum elongation of 37.1%. By contrast, after full austenitization, the specimens exhibit good ultimate tensile strength and high yield strength. In the case of a specimen with a yield strength of 969 MPa, the maximum value of the ultimate tensile strength reaches 1222 MPa. During the partitioning process, carbon partitioning and carbon homogenization within austenite affect interface migration. In addition, the volume fraction and grain size of retained austenite observed in the final microstructure will also be affected.

A Phenyl Sulfide Functionalized Luminescent Sensors for Efficient Fe3+ and Cr2O72- Ions Detection

A new complex, {[Cd（BIDPT）（NBA）]}n（1）, was synthesized from the selfassembly of BIDPT（BIDPT = 4,4?-bis（imidazol-l-yl）diphenyl thioether） and H2NBA（H2 NBA = 4,4?-azanediyldibenzoic acid） ligands with Cd（Ⅱ）. 1 was characterized by infrared spectroscopy, powder X-ray diffraction, elemental analysis, and thermogravimetry measurement. 1 crystallizes in monoclinic system, space group P21/c with a = 8.8204（1）, b = 29.835（3）, c = 10.3813（1） ?, β = 96.180（2）°, V = 2730.7（5） ?3, Z = 4, C32H22CdN5O4S, Mr = 685.01, Dc = 1.666 g/cm3, μ = 0.926 mm-1, R = 0.0548 and wR = 0.1528. 1 features a parallel structure with 3-connected hcb network and the adjacent 2 D networks are stacked together via C–H···π interaction to form a 3 D network. Its application in detecting metal cations and inorganic anions was explored. 1 exhibits excellent photoluminescence sensing for Fe3+ and Cr2O72- ions. And the mechanism of quenching is also studied.

Mechanism of mechanical quenching and mechanoluminescence in phosphorescent CaZnOS:Cu

This article reports a new phosphorescent material,CaZnOS:Cu,that exhibits two types of mechano-optical conversion:mechanical quenching and mechanoluminescence.An intense mechanical quenching of phosphorescence corresponding to mechanical stimuli can be achieved in CaZnOS:Cu within a short decay time period.Over time,it gradually changes to mechanoluminescence when a mechanical load is applied.We propose that the mechanical quenching and mechanoluminescence arise from the different roles of shallow and deep traps in CaZnOS:Cu.CaZnOS:Cu has promising applications in monitoring mechanical stress in industrial plants,structures,and living bodies.

Tensile behavior and deformation mechanism of quenching and partitioning treated steels at different deforming temperatures

The effects of deforming temperatures on the tensile behaviors of quenching and partitioning treated steels were investigated. It was found that the ultimate tensile strength of the steel decreased with the increasing temperature from 25 to 100 ℃, reached the maximum value at 300 ℃, and then declined by a significant extent when the temperature further reached 400 ℃. The total elongations at 100, 200 and 300 ℃are at about the same level. The steel achieved optimal mechanical properties at 300 ℃due to the proper transformation behavior of retained austenite since the stability of retained austenite is largely dependent on the deforming temperature. When tested at 100 and 200 ℃, the retained aus tenite was reluctant to transform, while at the other temperatures, about 10 vol. % of retained aus- tenite transformed during the tensile tests. The relationship between the stability of retained austenite and the work hardening behavior of quenching and partitioning treated steels at different deforming temperatures was also studied and discussed in detail. In order to obtain excellent mechanical properties, the stability of retained austenite should be carefully controlled so that the effect of transforma tion-induced plasticity could take place continuously during plastic deformation.

Fluorescent probe gold nanodots to quick detect Cr(VI) via oxidoreduction quenching process

A method is described here for the quickly(<30 s) accurate determination of Cr(VI)(Cr_2O_7^(2-)), based on fluorescent probes gold nanodots(AuNDs, excitation/emission peaks at 395/604 nm) coated with glutathione(GSH). The fluorescence of the AuNDs responses linearly to Cr(VI) concentrations, ranging widely from 1 nM to 10 m M with detection limit as low as 0.35 nM. At the same time, the AuNDs is demonstrated highly selective for Cr(VI) detection over other acid group ions and metal ions without any masking reagent. These make probability for practical use. The quenching mechanism is investigated deeply via fluorescent lifetime, XPS and TEM analysis. Different from most reported quenching explanation of aggregation derived from charge attraction, these results verify the redox reaction between Cr_2O_7^(2-)and sulfhydryl(–S) of GSH. The Au(I)–S bonds of AuNDs broke, accompanies with the oxidation of –S to form S–S bonds. As a result, AuNDs cross linked to each other. In the end, the fluorescence quenched. Attractively, the present study provides a new strategy for pollutant detection, such as from harmful Cr(VI) of Cr_2O_7^(2-)to nontoxic Cr(III).

Microstructure and Tensile Properties of a Nb–Mo Microalloyed 6.5Mn Alloy Processed by Intercritical Annealing and Quenching and Partitioning

The transformation behavior, microstructural evolution and mechanical properties were compared in a coldrolled Nb–Mo microalloyed 6.5Mn alloy after intercritical annealing（IA） and quenching and partitioning（Q ＆ P）,respectively. The thermodynamic calculation and theoretical analysis were used to determine the optimal heat treatment parameters. The Q ＆ P samples exhibited relatively higher strength with relatively low ductility, mainly due to the hard martensite matrix, which resulted in continuous yielding behavior upon loading, whereas the IA samples showed the significantly improved ductility, which benefited from the more sufficient transformation-induced plasticity（TRIP） effects and the softer ultrafine ferrite matrix. The dependence of yield point elongation（YPE） of IA samples on grain size demonstrated that the YPE value was in the reverse proportional relationship to the average grain size, which agreed well with theoretical analysis.

B-GQDs@GSH as a Highly Selective and Sensitive Fluorescent Probe for the Detection of Fe^(3+) in Water Samples and Intracellular

Owing to the excellent stability,biocompatibility and photoluminescence property,graphene quantum dots(GQDs)are emerging as a kind of potential materials to be applied in a series of fields ranging from sensor to drug delivery.As the growing concern for human and environmental safety,selective detection of metal ions has been paid more and more attention.GQDs,as nanoparticles with superior optical properties,have been attracting growing attention in the field of metal ions detection.In this work,glutathione(GSH)functionalized boron doped graphene quantum dots(B-GQDs@GSH)were successfully synthesized with stable bright blue fluorescence and has been used for the detection of Fe^(3+).A good linear relationship between 1/(F_(0)-F)and 1/c with the concentration ranging from 0.70 to 53μmol/L was obtained with a detection limit of 5.5 nmol/L.The application of B-GQDs@GSH for Fe^(3+)detection in water samples was demonstrated and the quenching mechanism was further explored.Due to low cytotoxicity and favorable biocompatibility,B-GQDs@GSH were successfully applied for cell fluorescence imaging and intracellular determination of Fe^(3+).

Europium Activated Aluminum Organic Frameworks for Highly Selective and Sensitive Detection of Fe and Cr(Ⅵ) in Aqueous Solution

The aluminum based MOFs compound, MIL-96(Al), has been studied as a luminescence sensor by incorporating of Eu3+ ions, which renders the compound strong red-light emission. The as-synthesized MIL-96(Al):Eu3+ nanocrystals exhibit water dispersibility and environmental stability, which are general requirement for an ideal sensing material. The MIL-96(Al):Eu3+ nanocrystals show excellent selective detection ability on Fe3+ ions in aqueous solution with value of low detection limit 20 μM. Meanwhile, it also exhibits excellent selective detection ability on CrO42- and Cr2O72- in aqueous solution with value of low detection limit 10 and 22 μM, respectively. The results of this study show that MIL-96(Al):Eu3+ nanocrystals could be used as a multi-responsive luminescent senor for Fe3+ and Cr(Ⅵ) species in aqueous solution. The possible luminescence quenching mechanism has also been discussed.