H.T. Wu

A fast-response, highly sensitive and selective fluorescent probe for the ratiometric imaging of hydrogen peroxide with a 100 nm red-shifted emission

Recently, growing attention has been paid to the accurate determination of hydrogen peroxide (H2O2) for elucidating its detailed biological function in physiology and pathology. A fluorescence method with the help of a fluorescent probe is the preferred technique for in situ visualization of biologically important species in vivo, even in single living cells. In the present manuscript, we developed a simple, fast response and highly selective fluorescent probe (1) with a receptor of the boronate moiety for the ratiometric imaging of H2O2 in living cells. Probe 1 could quantifiably detect H2O2 in the range of 18–540 μM by a ratiometric fluorescence spectroscopy method with a detection limit of 4 μM. Importantly, probe 1 exhibited 81 nm red-shifted absorption spectra accompanied by the color changes from colorless to yellow, and 100 nm red-shifted emission spectra upon addition of H2O2. Thus, 1 can serve as a “naked-eye” probe for H2O2. Preliminary bioimaging application and low cytotoxicity investigations further demonstrated that the proposed probe would be of great benefit to biomedical researchers for investigating the detailed biological function of H2O2 in biological systems.

Crystal structure and microwave dielectric characteristics of Co-substituted Zn1−xCoxZrNb2O8 (0 ≤ x ≤ 0.1) ceramics

Wolframite structure Zn1−xCoxZrNb2O8 (x = 0, 0.02, 0.04, 0.06, 0.08, 0.10) ceramics were prepared by the conventional solid state method. The crystal structures were studied via X-ray diffraction, and lattice vibrational modes were obtained by Raman spectroscopy. It could be found that all the A-site (Zn2+/Co2+, Zr4+) and B-site (Nb5+) cations were octahedrally coordinated with oxygen anions from the diagrammatic sketch of the crystal structure. Rietveld refinement was used to analyze the crystal structure and the lattice parameters were obtained. Based on the complex chemical bond theory and lattice parameters, intrinsic factors such as the bond ionicity, lattice energy, bond energy and coefficient of thermal expansion were calculated. Based on the results, Nb–O bonds played an important role in affecting the microwave dielectric proprieties of Zn1−xCoxZrNb2O8 ceramics. Co2+ substitution would affect the crystal structure and influence the microwave dielectric properties. The tendency of the dielectric constant (er) could be predicted by the polarizability and bond ionicity of Nb–O bonds, and the er showed the same tendency with Raman shifts of Nb–O vibration modes. The variation of the quality factor (Qf) could be explained by the change of the lattice energy of Nb–O bonds and the full width at half maximum (FWHM) values of Nb-site Raman modes. The temperature coefficient of resonant frequency (τf) showed the same tendency with the bond energy, octahedral distortion and bond valence of Nb–O bonds, and the opposite tendency with the thermal expansion coefficient.