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

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

A single chemosensor for multiple analytes: fluorogenic and ratiometric absorbance detection of Zn²⁺, Mg²⁺ and F⁻, and its cell imaging

A simple coumarin based sensor 1 has been synthesized from the condensation reaction of 7-hydroxycoumarin and ethylenediamine via the intermediate 7-hydroxy-8-aldehyde-coumarin. As a multiple analysis sensor, 1 can monitor Zn²⁺ with the fluorescence enhanced at 457 nm, and ratiometric detection at 290 nm, 350 nm and 420 nm in DMF/H₂O (1/4, v/v) medium. Sensor 1 can also monitor Mg²⁺ with the fluorescence enhanced at 430 nm, and ratiometric detection at 290 nm, 370 nm and 430 nm in DMF medium through the interaction of chelation enhance fluorescence (CHEF) with metal ions. Furthermore, 1 also can monitor F⁻ with the fluorescence enhanced at 460 nm, and ratiometric detection at 290 nm and 390 nm in DMF medium simultaneously via hydrogen bonding and deprotonation with F− anion. Spectral titration, isothermal titration calorimetry and mass spectrometry revealed that the sensor formed a 1:1 complex with Mg²⁺, Zn²⁺ or F⁻, with stability constants of 4.5 × 10⁶, 3.4 × 10⁶, 8.0 × 10⁴ M⁻1 respectively. The complexation of the ions by 1 was an exothermic reaction driven by entropy processes. Furthermore, the sensor exhibits good membrane-permeability and was capable of monitoring at the intracellular Zn²⁺ level in living cells

High-order squeezing of the quantum electromagnetic field and the generalized uncertainty relations in two-mode squeezed states

It is found that two-mode output quantum electromagnetic field in two-mode squeezed states exhibits higher-order squeezing to all even orders. And the generalized uncertainty relations are also presented for the first time. The concept of higher-order squeezing of the single-mode quantum electromagnetic field was first introduced and applied to several processes by Hong and Mandel in 1985. Lately Li Xizeng and Shan Ying have calculated the higher-order squeezing in the process of degenerate four-wave mixing and presented the higher-order uncertainty relations of the fields in single-mode squeezed states. In this paper we generalize the above work to the higher-order squeezing in two-mode squeezed states. The generalized uncertainty relations are also presented for the first time

Higher-Order Squeezing of Quantum Field and the Generalized Uncertainty Relations in Non-Degenerate Four-Wave Mixing

It is found that the field of the combined mode of the probe wave and the phase-conjugate wave in the process of non-degenerate four-wave mixing exhibits higher-order squeezing to all even orders. And the generalized uncertainty relations in this process are also presented