Dependence Of Upconversion Emission Research Articles

Upconversion Luminescence and Optical Temperature-Sensing Properties of LaNbO4:Yb3+/Er3+ Phosphors

In recent years, upconversion (UC) luminescence has attracted considerable attention because of its potential application in temperature measurement. In this work, LaNbO4:Er3+/Yb3+ phosphors are synthesized using a solid-state method. The x-ray diffraction patterns show that the phosphors obtained exhibit a single monoclinic structure, and doping does not change the crystal structure. Intense green and red emissions are observed upon 980-nm excitation. The emission intensity varies with the doping concentration, and the best doping concentrations are 1 mol.% and 10 mol.% for Er3+ and Yb3+ ions, respectively. The possible luminescence mechanism is investigated based on the UC emission dependence on pump power. The temperature-sensing ability is also investigated based on the fluorescence intensity ratio between two thermally coupled levels 2H11/2 and 4S3/2. The maximum sensitivity achieved is 0.81% K−1 at around 430 K, suggesting that the phosphor is a potential candidate for temperature sensing applications.

Excitation spectra and temperature dependence of upconversion emission for Er3+/Yb3+ co-doped Nb2O5 nanocrystals

ABSTRACTEr3+/Yb3+ co-doped Nb2O5 nanocrystals were studied for upconversion efficiency and temperature dependence. Under 975 and 1550 nm excitation, the upconversion emissions of the Er3+/Yb3+ co-doped Nb2O5 nanocrystals were studied. The luminescent characteristics of the materials were found to be closely related to environment temperature, Er3+ concentration, pumping power and wavelength. The materials can be applied to fluorescence imaging and fluorescence probe, and so on.

Dependence of upconversion emission and optical temperature sensing behavior on excitation power in Er3+/Yb3+ co-doped BaMoO4 phosphors

BaMoO4: Er3+/Yb3+ phosphors with different concentrations have been fabricated by a facile hydrothermal method. The morphology observation shows that the shape and size of BaMoO4 powders change after Er3+/Yb3+ doping. The upconversion luminescence spectra consist of intense green bands centered at 536 and 558 nm and a weak red emission band peaked at 668 nm upon 980 nm excitation. The excitation power and doping concentration have little impacts on the color emitted from the samples. Applying the fluorescence intensity ratio (FIR) technique, the temperature sensing behaviors are investigated based on thermally coupled levels (2H11/2 and 4S3/2) and non-thermally coupled levels (4F9/2 and 4S3/2), respectively. The thermometry is sensitive to the excitation power for 4F9/2 and 4S3/2 levels, leading to large measurement errors caused by the power variation. Such a problem can be solved by using the power-insensitive FIR between 2H11/2 and 4S3/2 levels, which also shows the advantage of high absolute sensitivity with the maximum of 110.7 × 10−4 K−1. So, the developed BaMoO4:Er3+/Yb3+ phosphors can be applied in green light upconverters, display devices and temperature sensors.

Tunable reddish to magenta upconversion luminescence in Tm3+-doped glass

Generation of the color-tunable reddish to magenta upconversion luminescence in Tm3 + -single-doped glasses under near-infrared (1.1 to 1.3 μm) excitation is reported. Upconversion emission in the ultraviolet, blue- and red-spectral regions due to D21-H63, D21-F43, G41-H63, G41-F43, and F2,33-H63 transitions, respectively, was observed. The dependence of upconversion emission upon excitation power and Tm3 + content was also investigated. Adjusting the excitation power and Tm3 + concentration, the overall fluorescence emission can be tuned across the reddish to magenta color in the international commission on illumination color chromaticity diagram. The CIE-1931 color coordinates move from red toward the bluish region occupying the magenta region with an increase in the excitation power.

Manipulation of microstructures and the stability of white emissions in NaLuF4:Yb3+, Ho3+, Tm3+ upconversion crystals

A series of Yb3+, Ho3+, Tm3+ doped NaLuF4-based nanostructures and microstructures with controllable crystalline phases and morphologies were designed via adjusting the parameters of the oleic acid-assisted hydrothermal method. It is found that increasing the NH4F content and prolonging the reaction time to conduce the formation of β-NaLuF4 and the possible evolution process was proposed. Besides, the dependence of upconversion emission on sensitizer (Yb3+) concentration and pump power in Yb3+-Ho3+ and Yb3+-Tm3+ codoped β-NaLuF4 was investigated. On this basis, a tunable multicolor was achieved in NaLuF4:Yb3+/Ho3+/Tm3+ microrods. It is worth mentioning that white-light output with the calculated CIE color coordinate of (0.333, 0.330) was realized in the microrods, and the triply doped samples presented an outstanding capacity for color controlling and satisfactory color stability in the white region as well as lower threshold pump power density and lower optimal excitation pump power density for white-emission, which present great potential applications in the field of color display and white light-emitting diodes.

Codopant ion-induced tunable upconversion emission in β-NaYF4:Yb3+/Tm3+nanorods

An innovative route to tune upconversion (UC) emission in β-NaYF(4):Yb(3+)/Tm(3+) nanorods through codoping a third rare-earth ion upon continuous wave excitation near 976 nm is reported. The dependence of UC emission on codopant concentration and environment temperature shows that tailored local environment and readjustable depopulation of excited-state ions are responsible for the tuning of UC luminescence. Codopant ions introduce a new distribution of active ions and a modified distance between Tm(3+) and Yb(3+) ions, making UC systems more sensitive to impurity ions than downconversion systems.

Blue Upconversion Emission in Yb3+ and Tm3+ CodopedLead–Germanate–Tellurite Glasses

Intense blue and red upconversion emissions have been observed inYb3+/Tm3+ co-doped0.05 K2O-0.1ZnO-0.1BaO-0.2PbO-0.2GeO2-0.35TeO2glasses under the pump of 976-nm laser diode. The dependence of theintensity of the upconversion emissions on the Tm3+concentration has been studied in order to determine the ionconcentration and the involved mechanism. The blue emission centred at476 nm decreases and the 792-nm red emission increases with theincreasing Tm3+ concentration. Subsequently, the dependence ofupconversion emission intensity on the excitation power isinvestigated. It is found that the intensity ratio between the 792-nmred and 476-nm blue emissions decreases with the increasing pumpenergy.