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Abstract: MoO3 nanoflowers were successfully synthesized on a Si substrate by a facility microwave hydrothermal method. The nanoflowers consisted of tens of nanobelts and the nanobelts were about several micrometers in length, several tens to several hundreds of nanometers in width, and tens of nanometers in thickness. Field-emission measurements showed that the nanoflowers had a relatively low turn-on field of ∼4.3V/μm and their emission was a barrier tunneling quantum-mechanical process. The fluctuations of the emission current were less than 10% over 3h. The low turn-on field and high stability of emission current indicate that the as-grown MoO3 nanobelts exhibit a good field-emission property and have great potential for applications in field-emission devices. [Copyright &y& Elsevier]

Abstract: Cubic and hexagonal NaYF4:Ln3+ (Ln=Eu and Yb/Tm) microcrystals were separately synthesized by an EDTA-assisted solvothermal method. Under 393-nm excitation, the emission spectra of NaYF4:Eu3+ microcrystals show the characteristic Eu3+ emissions. In the excitation spectra of the 610-nm emission, the 7F0 → 5D3 is dominant for the cubic microcrystals, while the 7F0 → 5L6 is dominant for the hexagonal sample. In addition, unusually strong ultraviolet emissions (1I6 → 3H6, 1I6 → 3F4, and 1D2 → 3H6) were observed in the hexagonal NaYF4:Yb3+/Tm3+ microcrystals under 980-nm excitation. In comparison with a cubic sample having the same chemical compositions, the hexagonal microcrystals had a markedly enhanced ability of emitting ultraviolet up-conversion luminescence. [Copyright &y& Elsevier]