Luminescence property tuning of Yb3+-Er3+ doped oxysulfide using multiple-band co-excitation

Dual-wavelength enhanced upconversion luminescence properties of Li+-doped NaYF4:Er,Yb glass-ceramic for all-optical logic operations

Rare earth-doped oxyfluoride glass-ceramic (GC) demonstrate the physical, chemical, and mechanical stabilities of oxide glass and excellent optical properties of fluoride crystals and is regarded as a potential material for developing advanced optical devices. In the present study, Li⁺-doped NaYF₄:Er,Yb GC was prepared by the traditional melt-quenching method. Upon the excitation of single 980 and 1550 nm lasers, the upconversion (UC) luminescence intensities of green and red emission were enhanced due to the introduction of the crystal field symmetry reducing available Li⁺ ions of the use of dual-wavelength (980 and 1550 nm) co-excitation and could further enhance the UC luminescence intensity owing to its synergetic effect, which is suitable for the design of all-optical logic gates. The all-optical UC logic gates and complex logic operations ("YES + OR", "INH + YES", "XOR + YES", and "INH + AND + YES + OR") are designed by taking the two excitation sources as input signals and UC emission as output signals. The results provide a novel strategy to enhance UC luminescence and further information for the design of novel photonic logic devices for future optical computing technologies.

Enhancing red luminescence by doping Yb3+ into Er3+ self-sensitized Gd2O2S upconverting nanoparticles under excitation at 1530 nm

Red upconversion luminescence (UCL) nanoparticles are of significant importance for applications in the fields of deep tissue imaging, photothermal therapy and security ink. In this work, a highly efficient red emission was achieved by introducing Yb³⁺ ions as mediators in Er³⁺ self-sensitized Gd₂O₂S nanoparticles under excitation at 1530 nm. The results show that the Gd₂O₂S:Yb³⁺,Er³⁺ nanoparticles synthesized by a homogeneous precipitation method exhibit a uniform spherical shape and narrow size distribution with a mean particle diameter of ≈65 nm. Moreover, the integral emission intensity ratio of red to green of the Gd₂O₂S:Yb³⁺,Er³⁺ sample is significantly enhanced 3-fold compared with the Gd₂O₂S:Er³⁺ sample without Yb³⁺ doping. The enhancement mechanisms are discussed in detail on the basis of steady-state luminescence spectra and decay dynamics measurements under various excitations at 380, 808, 980 and 1530 nm, respectively. It has been demonstrated that the enhanced red luminescence is induced by cross-relaxation energy transfer from Er³⁺ to Yb³via⁴S_3/2 (Er³⁺) + ²F_7/2 (Yb³⁺) → ⁴I_13/2 (Er³⁺) + ²F_5/2 (Yb³⁺) and ⁴I_11/2 (Er³⁺) + ²F_7/2 (Yb³⁺) → ⁴I_15/2 (Er³⁺) + ²F_5/2 (Yb³⁺), and further followed by back energy transfer from Yb³⁺ to Er³⁺ through ⁴I_13/2 (Er³⁺) + ²F_5/2 (Yb³⁺) → ⁴F_9/2 (Er³⁺) + ²F_7/2 (Yb³⁺). The former cross-relaxation procedure effectively populates the red emission level of ⁴F_9/2 by depopulating the green emission level of ³S_3/2. Our findings provide a feasible way to enhance the red UCL and new insights into red UCL mechanisms in the Er³⁺ self-sensitized system under ≈1500 nm excitation, by combining with the nontoxic oxysulfide host, indicating their potential application as safe fluorescent nanoprobes in the bio-field.

Enhanced up-conversion luminescence and temperature-sensing of GdVO4:Ln3+ 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.