Intense blue-upconversion in Tm3+∕Yb3+-codoped gallate–bismuth–lead glasses has been achieved under an excitation from a commercially available 980nm laser diode. Energy transfer processes and excited-state absorption account for the population of the G41 emitting level of the Tm3+. Although the addition of GeO2 has enhanced the glass thermal stability, the phonon mode associated with vibration of GeO2 has almost no influence on the blue-upconversion intensity and the radiative lifetime of H43 level. The dependence of the phonon energy of the host on contributions from multiphonon decay on the fluorescence has been discussed. Significant enhancement of the blue-upconversion has also been observed in gallate–bismuth–lead glasses with the incorporation of PbF2 content.

Nucleation of crystals from solution is fundamental to many natural and industrial processes. In this work, the molecular mechanism of conformational polymorphism nucleation and the links between the molecular conformation in solutions and in crystals were investigated in detail by using 5-nitrofurazone as the model compound. Different polymorphs were prepared, and the conformations in solutions obtained by dissolving different polymorphs were analysed and compared. The solutions of 5-nitrofurazone were proven to contain multiple conformers through quantum chemical computation, Raman spectra analysis, 2D nuclear Overhauser effect spectroscopy spectra analysis and molecular dynamics simulation. The conformational evolution and desolvation path was illustrated according to the 1H NMR spectra of solutions with different concentrations. Finally, based on all the above analysis, the molecular conformational evolution path during nucleation of 5-nitrofurazone was illustrated. The results presented in this work shed a new light on the molecular mechanism of conformational polymorphism nucleation in solution.

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