Enhanced up-conversion luminescence and temperature-sensing of GdVO:Ln with dual-wavelength excitation.

There exists a tendency in the research of up-conversion materials to shift the excitation from 980 nm to multiple excitation wavelengths. A series of GdVO4:Ln3+ with similar sizes and irregular prism morphology were successfully prepared by a co-precipitation technique. A wide multi-color emission corresponding to different Ln3+ doping was also obtained under single excitation. It is worth pointing out that among all the studied samples, only the emission intensity of GdVO4:Yb3+/Er3+ excited at two-wavelengths (980 nm + 1550 nm) simultaneously was enhanced by a factor of 1.87, compared to the sum of emission intensities excited at two single-wavelengths separately. Moreover, to further enhance the up-conversion luminescence intensity, cation ions (Lu3+/Y3+) and anion ions (PO43-) were also doped into the host, and the luminous intensity was also improved to a certain extent. A possible mechanism for energy transfer and possible transitions were also suggested and discussed in detail using an energy level diagram. In addition, not only a high record value of Sa (0.0069 K-1) but also a high Sr (1.13% K-1) is achieved for GdVO4:Yb3+/Er3+ in the physiological temperature range (273-453 K). Combining a much intensified dual-wavelength up-conversion signal and good temperature-sensing properties, this work can be extended to the surges of other lanthanide ion doped systems pumped by using multiple-wavelength lasers, and can also open new possibilities for up-conversion color displays and anti-counterfeiting applications.