938 research outputs found
Universal linear-temperature resistivity: possible quantum diffusion transport in strongly correlated superconductors
The strongly correlated electron fluids in high temperature cuprate
superconductors demonstrate an anomalous linear temperature () dependent
resistivity behavior, which persists to a wide temperature range without
exhibiting saturation. As cooling down, those electron fluids lose the
resistivity and condense into the superfluid. However, the origin of the
linear- resistivity behavior and its relationship to the strongly correlated
superconductivity remain a mystery. Here we report a universal relation
, which bridges the slope of the
linear--dependent resistivity () to the London penetration depth
at zero temperature among cuprate superconductor
BiSrCaCuO and heavy fermion superconductors
CeCoIn, where is vacuum permeability, is the Boltzmann
constant and is the reduced Planck constant. We extend this scaling
relation to different systems and found that it holds for other cuprate,
pnictide and heavy fermion superconductors as well, regardless of the
significant differences in the strength of electronic correlations, transport
directions, and doping levels. Our analysis suggests that the scaling relation
in strongly correlated superconductors could be described as a hydrodynamic
diffusive transport, with the diffusion coefficient () approaching the
quantum limit , where is the quasi-particle effective
mass.Comment: 8 pages, 2 figures, 1 tabl
A ratiometric Al³⁺ ion probe based on the coumarin-quinoline FRET system
A coumarin-quinoline based fluorescence resonance energy transfer (FRET) system (TCQ) has been synthesized and employed as a ratiometric fluorescence probe. The selective fluorescent response of the probe TCQ toward Al³⁺ was devised by employing a quinoline moiety as a FRET energy donor with a coumarin moiety as an energy acceptor. The quinoline emission at 390 nm decreased and the coumarin emission at 480 nm increased concurrently on addition of Al³⁺ under excitation wavelength at 253 nm. The TCQ probe exhibited high selectivity for Al³⁺ as compared to other tested metal ions and the ratiometric sensing of Al³⁺ was determined by plotting the fluorescence intensity ratio at 480 nm and 390 nm versus Al³⁺ ion concentration. Moreover, test strips based on TCQ were fabricated, which were found to act as a convenient and efficient Al³⁺ ion detection kit. Furthermore, this system has been used for imaging of Al³⁺ in living cells
Characterization of the aggregation-induced enhanced emission of N,N'-bis(4-methoxysalicylide)benzene-1,4-diamine
© 2015 Springer Science+Business Media New York. N,N′-bis(4-methoxysalicylide)benzene-1,4-diamine (S1) was synthesized from 4-methoxysalicylaldehyde and p-phenylenediamine and it was found to exhibit interesting aggregation-induced emission enhancement (AIEE) characteristics. In aprotic solvent, S1 displayed very weak fluorescence, whilst strong emission was observed when in protic solvent. The morphology characteristics and luminescent properties of S1 were determined from the fluorescence and UV absorption spectra, SEM, fluorescence microscope and grading analysis. Analysis of the single crystal diffraction data infers that the intramolecular hydrogen bonding constitutes to a coplanar structure and orderly packing in aggregated state, which in turn hinders intramolecular C-N single bond rotation. Given that the three benzene rings formed a large plane conjugated structure, the fluorescence emission was significantly enhanced. The absolute fluorescence quantum yield and fluorescence lifetime also showed that radiation transition was effectively enhanced in the aggregated state. Moreover, the AIEE behavior of S1 suggests there is a potential application in the fluorescence sensing of some volatile organic solvents
Synthesizing and characterization of hole doped nickel based layer superconductor (LaSr)ONiAs
We report the synthesizing and characterization of the hole doped Ni-based
superconductor (. By substituting La with Sr, the
superconducting transition temperature is increased from 2.75 K of the
parent phase to 3.7 K at the doping levels x= 0.1 - 0.2. The curve
versus hole concentration shows a symmetric behavior as the electron
doped samples . The normal state resistivity in Ni-based
samples shows a good metallic behavior and reveals the absence of an anomaly
which appears in the Fe-based system at about 150 K, suggesting that this
anomaly is not a common feature for all systems. Hall effect measurements
indicate that the electron conduction in the parent phase is
dominated by electron-like charge carriers, while with more Sr doping, a
hole-like band will emerge and finally prevail over the conduction, and
accordingly the superconducting transition temperature increases.Comment: 4 pages, 5 figure
Gap Structure of the Overdoped Iron-Pnictide Superconductor Ba(FeNi)As: A Low-Temperature Specific-Heat Study
Low-temperature specific heat (SH) is measured on the postannealed
Ba(Fe_{1-x}Ni_x)_2As_2 single crystal with x = 0.058 under different magnetic
fields. The sample locates on the overdoped sides and the critical transition
temperature is determined to be 14.8 K by both the magnetization and SH
measurements. A simple and reliable analysis shows that, besides the phonon and
normal electronic contributions, a clear T2 termemerges in the low temperature
SH data.Our observation is similar to that observed in the Co-doped system in
our previous work and is consistent with the theoretical prediction for a
superconductor with line nodes in the energy gap.Comment: 5 pages, 4 figure
A readily accessible multifunctional probe: simultaneous recognition of the cation ZN²⁺ and the anion F⁻ via distinguishable wavelengths
The probe 1 was readily prepared via condensation of 8-formyl-7-hydroxy-coumarin and carbonic dihydrazide in a one-step procedure. Probe 1 exhibited high sensitivity and selectivity towards Zn²⁺ and F⁻ through a “turn-on” fluorescence response and/or ratiometric colorimetric response with low detection limits of the order of 10-8 M. The complex behaviour was fully investigated by spectral titration, isothermal titration calorimetry, 1H NMR spectroscopic titration and mass spectrometry. Interestingly, probe 1 not only recognizes the cation Zn²⁺ and the anion F⁻, but can also distinguish between these two ions via the max wavelength in their UV-vis spectra (360 nm for 1-Zn²⁺ versus 400 nm for 1-F⁻ complex) or their fluorescent spectra (λₑₓ / λₑm = 360 nm/ 454 nm for 1-Zn²⁺ versus λₑₓ / λₑm = 400 nm/ 475 nm for 1-F⁻ complex) due to their differing red-shifts. Additionally, probe 1 has been further explored in the detection of Zn²⁺ in living cells
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