By realizing in thin films a tensile stress state, superconductivity of 13 K was introduced into FeTe, a nonsuperconducting parent compound of the iron pnictides and chalcogenides, with a transition temperature higher than that of its superconducting isostructural counterpart FeSe. For these tensile stressed films, superconductivity is accompanied by a softening of the first-order magnetic and structural phase transition, and also, the in-plane extension and out-of-plane contraction are universal in all FeTe films independent of the sign of the lattice mismatch, either positive or negative. Moreover, the correlations were found to exist between the transition temperatures and the tetrahedra bond angles in these thin films.
It
is well known that the calcium ion is essential for maintaining
life activities in living organisms, and it is of great significance
to detect the intracellular calcium concentration. For the detection
of calcium ions, we developed a new type of fluorescent carbon dots
(CDs), whose surface was modified by ethylenebis(oxyethylenenitrilo)tetraacetic
acid (EGTA) through a secondary hydrothermal method. This is a simple
and convenient chemical preparation method because all reactions are
carried out in the same autoclave, and the final product is directly
the EGTA-modified CDs. The CDs exhibit bright blue fluorescence, and
as the calcium concentration increases, the fluorescence intensity
drops sharply. The fluorescence quenching correlates with the concentration
of calcium ions and has a good linearity in the range of 15–300
μM with a detection limit of 0.38 μM. The experimental
results confirmed that the detection of calcium ions by CDs is a static
fluorescence quenching process. Also, cytotoxicity test and cellular
imaging experiments have shown that the CDs are nontoxic and biocompatible.
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