A highly sensitive and selective antioxidant probe based on a bi-modally functionalized conjugated polyelectrolyte

A new water-soluble anionic conjugated polyelectrolyte with a nitroxide radical covalently linked to the sulfonated poly(phenylene ethynylene) backbone (PPE-SO(3)) is reported. This radical-functionalized PPE-SO(3) (RF-PPE-SO(3)) demonstrates fluorescence and electron spin resonance (ESR) bimodal signaling function and shows sensitive and selective response to antioxidants.Ministry of Science and Technology of China[2011CB910403]; National Natural Science Foundation of China[20835005, 20975086, J1030415

Quantum dot-Eu3+ conjugate as a luminescence turn-on sensor for ultrasensitive detection of nucleoside triphosphates

We report a conjugate of thioglycolic acid (TGA) capped CdTe quantum dot and Eu3+ ion (TGA-CdTe QD-Eu3+) that can be used as an ultrasensitive luminescence turn-on sensor for nucleoside triphosphates (NTPs). The TGA-CdTe QD-Eu3+ conjugate is a weakly luminescent species as a result of the strong quenching effect of Eu3+ ion on the luminescence of TGA-CdTe QDs. The conjugate's luminescence can be readily restored by its reaction with adenosine triphosphate (ATP) and other NTPs, and thus gives an ultrasensitive detection of NTPs, with a detection limit of 2 nM. The sensing mechanism has also been explored, and the effective quenching of TGA-CdTe QDs emission by Eu3+ ions has been attributed to photoinduced electron transfer (PET). ATP, as the representative of NTP's, can remove Eu3+ from the surface of TGA-CdTe QDs, leading to restoration of the TGA-CdTe QDs luminescence. (C) 2012 Elsevier B.V. All rights reserved.Ministry of Science and Technology of China [2011CB910403]; National Natural Science Foundation of China [20835005, 20975086, J1030415

Quantum dot-Eu3 conjugate as a luminescence turn-on sensor for ultrasensitive detection of nucleoside triphosphates

We report a conjugate of thioglycolic acid (TGA) capped CdTe quantum dot and Eu3 ion (TGA-CdTe QD-Eu3) that can be used as an ultrasensitive luminescence turn-on sensor for nucleoside triphosphates (NTPs). The TGA-CdTe QD-Eu3 conjugate is a weakly luminescent species as a result of the strong quenching effect of Eu3 ion on the luminescence of TGA-CdTe QDs. The conjugate's luminescence can be readily restored by its reaction with adenosine triphosphate (ATP) and other NTPs, and thus gives an ultrasensitive detection of NTPs, with a detection limit of 2 nM. The sensing mechanism has also been explored, and the effective quenching of TGA-CdTe QDs emission by Eu3 ions has been attributed to photoinduced electron transfer (PET). ATP, as the representative of NTPs, can remove Eu3 from the surface of TGA-CdTe QDs, leading to restoration of the TGA-CdTe QDs luminescence. 漏 2012 Elsevier B.V

The Comparation of Arrhenius-Type and Modified Johnson–Cook Constitutive Models at Elevated Temperature for Annealed TA31 Titanium Alloy

Constitutive models play a significant role in understanding the deformation behavior of materials and in optimizing the manufacturing process. In order to improve the reliability of calculation results, the high temperature flow behavior of TA31 titanium alloy obtained from an annealed hot-rolled plate has been investigated by a Gleeble-3500 thermo-mechanical simulator. The isothermal hot compression tests are conducted in the temperature range of 850 to 1050 °C and the strain rate range from 0.001 to 10 s−1 with a height reduction of 60%. The annealed TA31 shows a dynamic recovery characteristic during thermo-mechanical processing. The experimental data have been used to develop an Arrhenius-type constitutive model and a modified Johnson–Cook model under the consideration of coupling effect on strain, temperature, and strain rate, as well as the strain-softening phenomenon. The material parameters are determined by a global optimization method based on the initial values by means of a regression method. A comparation of the predicted results has been performed based on the modified Johnson–Cook model and those acquired from the Arrhenius-type model. The correlation coefficient and average absolute relative error of the modified Johnson–Cook model are 4.57% and 0.9945, respectively. However, when the optimization method has been applied, they are 15.77% and 0.9620 for the Arrhenius-type model, respectively. These results indicate that the modified Johnson–Cook model is more accurate and efficient in predicting the flow stress of annealed TA31 titanium alloy under a set of model material parameters. Furthermore, the simple mathematical expression of this model is helpful to incorporate it into the finite element software to obtain detailed and valuable information during the thermo-mechanical processing simulation for TA31 in further work

Electron transfer quenching by nitroxide radicals of the fluorescence of carbon dots

Ministry of Science and Technology of China [2011CB910403]; National Science Foundation of China [20835005, 20975086, J1030415]Blue fluorescent carbon dots (CDs) were synthesized by a microwave assisted one-step procedure without surface passivation. The intermolecular interactions between the CDs and nitroxide radicals in aqueous and aprotic solution were investigated. The fluorescence of the CDs was found to be efficiently quenched by the paramagnetic nitroxide radical. A SOMO (singly occupied molecular orbital) facilitated electron transfer was proposed to account for the quenching of the fluorescence of the CDs in the CD@TEMPO conjugate, formed via electrostatic interactions between the negatively charged CDs and the cationic 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide free radical (4-AT). Covalently spin-labeled CDs by the paramagnetic nitroxide radical yield a weakly fluorescent spin-labeled conjugate (CD-TEMPO), which exhibits sensitive fluorescence and electron spin resonance (ESR) bimodal response towards ascorbic acid (AA) at the mu M level. The fluorescence intensity of the spin-labeled CDs was also found to be sensitive to paramagnetic factors and thus establishes its promising potential for constructing a bimodal responsive sensor with off-on fluorescence and on-off ESR signaling for the detection of antioxidants and carbon-centered radicals

Effect of Gd and Ti co-doping on electrical performance of Bi2O3 oxygen ion conductor

In this study, a new oxygen ion conductor electrolyte material with high conductivity was reported. Bi _2 O _3 was co-doped with Gd _2 O _3 and TiO _2 by solid-phase synthesis method to obtain Bi _1–3x Gd _2x Ti _x O _1.5+ _δ and Bi _0.76 Gd _0.18−x Ti _x O _1.5+ _δ (TGSB) ceramics. The phase composition, surface morphology and electrical properties of TGSB samples were characterized by x-ray diffraction (XRD), scanning electron microscope (SEM) and AC impedance respectively. XRD results show that only 6T12GSB has a single cubic fluorite structure, and impurity phases appear in other samples. The SEM results show that only when the doping concentrations of Gd and Ti are 12 mol% and 6 mol% respectively, the particle size is relatively smaller and there are no obvious pores. From the analysis of electrical properties, Gd dopant is helpful to the stability of the Bi _2 O _3 phase than Ti dopant, but not beneficial to higher conductivity. When the doping concentration of Gd is higher than 16 mol%, it becomes more stable. The conductivity of the 6T12GSB sample is relatively high. The conductivity of the TGSB samples is higher than that of the TLSB samples under the lower temperature condition (<450 °C), and the electrical performance of Bi _2 O _3 -based materials are enhanced especially at low temperature