Guna Doķe- PhD in physics
- Researcher at University of Latvia
Guna Doķe
- PhD in physics
- Researcher at University of Latvia
Recently defended PhD thesis devoted to red and near-infrared persistent luminescence of Cr and Mn doped germanates.
About
38
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Introduction
Current institution
Publications
Publications (38)
In this study, we report broadband near-infrared persistent luminescence of a novel MgGeO3: Cr³⁺ material. The luminescence can be excited by the ultraviolet radiation and detected for more than 16 hours. Optical and electron paramagnetic resonance spectroscopy experiments suggest that the observed bands appear as a result of interaction between Cr...
In this work novel garnet persistent luminescence phosphor Mg3Y2Ge3O12: Tb³⁺ (MYG: Tb³⁺) with bright blue to green tuneable emission is reported.
MYG: Tb³⁺ samples with Tb³⁺ content ranging from 0 to 100% were analysed. X-ray absorption spectroscopy analysis showed that Tb³⁺ ions incorporate in the garnet structure by replacing Y³⁺ ions. Optimal do...
Currently, extensive research activities are devoted to developing persistent phosphors which extend beyond the visible range. In some emerging applications, long-lasting emission of high-energy photons is required; however, suitable materials for the shortwave ultraviolet (UV–C) band are extremely limited. This study reports a novel Sr2MgSi2O7 pho...
Persistent luminescence or afterglow or long-lasting phosphorescence is a luminescence characterised by the emission of radiation lasting from a few seconds to several days after the excitation source is turned off. Most of the persistent luminescence materials have emission in the visible part of the spectrum, especially in green. Despite great po...
In this work, we report the synthesis of Eu2+-doped alpha-tricalcium phosphate (α-TCP, α-Ca3(PO4)2) via a phase transformation of Eu3+-doped CaHPO4 ∙ 2H2O. The phase conversion accompanied by a reduction of...
The study provides an in-depth analysis of the structure and luminescence properties of Mg₄Ga₈Ge₂O₂₀: Mn²⁺ (MGGO) materials, focusing particularly on their dynamic color-changing capabilities. A series of single-phase MGGO: xMn2+...
Persistent luminescence (PersL), also called long-lasting phosphorescence or simply afterglow, is a luminescence characterised by the emission of radiation from a few seconds to several days after the excitation source has been switched off. Over the past two decades, research on PersL materials, both in fundamental and applied physics, has develop...
For the last few decades, there has been extensive research on the materials that persist to emit optical radiation long after any type of charging has stopped. Most of the established persistent luminescence (PersL) materials emit light in the visible part of the spectrum; however, in recent years, there has been a growing interest in UV-emitting...
Garnet-based materials are widely investigated for applications in optics. In this research, we report the structure and spectroscopic properties of novel Mg3Lu2Ge3O12: Pr3+ garnet that exhibits orange persistent luminescence. The atomic positions of Mg3Lu2Ge3O12 were calculated using Rietveld refinement. The local structure analysis using extended...
Persistent luminescence (PersL) is a phenomenon when a material continues to emit light for a period of time, usually several minutes or hours after the removal of the excitation source. Although it is possible to find several hundred different materials suitable for the observation of PersL in the visible part of the spectrum, only a handful of th...
The origin of bright cyan persistent luminescence in La³⁺-doped Ca2SnO4 is investigated by optical and electron paramagnetic resonance spectroscopy methods. The incorporation of La³⁺ ions in the material stimulates the formation of Sn²⁺ emission centers and charge trap centers. After exposure of the material to UV radiation, charge transfer process...
Materials with long persistent luminescence (PersL) have caused widespread interest among scientists and industry for decades. Currently, there is widely available information on the long persistent luminescence materials with emission in the blue and green spectral range, while the number of publications on the afterglow in the red and near-infrar...
Luminescence properties of erbium and europium doped NaLaF4 with different oxygen content have been studied. Vacuum ultraviolet (VUV) excitation luminescence spectroscopy technique has been applied by using synchrotron radiation excitation. It was found that oxygen impurity leads to significant degradation of Er3+ or Eu3+ emission under VUV excitat...
Angular dependency of electron paramagnetic resonance, optically detected by UV-excited recombination luminescence (RL-EPR), was measured for nominally pure ZnO single crystals. Observed magnetic resonances belong to the broad yellow RL band with slow decay centred at 610 nm, which is characteristic of untreated ZnO crystals. In the sample, irradia...
Complex fluorides, especially rare-earth doped NaREF4 (RE = Y3+, La3+ or Gd3+), are promising materials for the upconversion luminescence mostly due to low phonon energy of their matrices and multisite nature of the crystalline lattice. Although multisite formation in hexagonal NaREF4 structures has generally been proved, the actual number of the a...
In this work, NaLaF4 doped with Er3+ of different concentrations was synthesized. The luminescence spectrum for NaLaF4:Er3+ (0.2 mol%) at 489 nm excitation reveals characteristic Er3+ luminescence bands in the green (540 nm), red (660 nm) and infrared (980 nm) spectral regions. The green luminescence band originated from the 4S3/2 ? 4I15/2 transiti...
Energy transfer from Nd 3þ to Er 3þ in NaLaF 4 :Er 3þ , Nd 3þ samples has been observed. Er 3þ luminescence bands appear as result of different energy transfer mechanisms. Possible luminescence and energy transfer mechanisms have been offered. a b s t r a c t In the course of this research several NaLaF 4 samples doped with different Er 3þ and Nd 3...
Oxyfluoride glasses 49SiO2·6Al2O3·24Li2O·20LaF3 activated with Tb, Ce, Eu have been synthesized and studied. After heating at 580°C and 750°C crystalline phases were obtained. The samples were studied by DTA (Differential thermal analyzer), CL (cathodoluminescence), XRD (X-ray diffraction), SEM (scanning electron microscope), EDS (energy dispersive...
Up-conversion luminescence process, which is related to absorption of several light photons (usually infrared) followed by emission of light in the visible or even ultraviolet spectral regions, has attracted interest of scientists due to its potential practical use in various applications including biolabels, temperature sensors, light sources etc....
In this work Er3+ doped NaLaF4 material has been synthesized Along with the description of the synthesis route, luminescence spectra and decay kinetics of both traditional and up-conversion luminescence of Er3+ will be presented for different Er3+ doping levels. It will be shown that the main mechanisms involved in the creation of the up-conversion...
In this work we tried to achieve multicolor up-conversion luminescence in low phonon energy material NaLaF4 doped with different Er3+ Tm3+ and Yb3+ concentrations. Up-conversion luminescence was measured and main luminescence bands from Er3+ and Tm3+ in red, green and blue spectral regions were observed. The relative intensities of the luminescence...
In this work, we used Mn2+ as a dopant in the oxyfluoride glasses with various fluoride compounds. Electron paramagnetic resonance (EPR) measurements were carried out before and after a heat treatment of the material. In both cases, a well pronounced hyperfine (hf) structure of the EPR spectra characteristic to the Mn2+ ion have been observed. EPR...
Up-conversion luminescence of oxyfluoride glass and glass ceramics containing LaF3 crystallites doped with Yb3+ and Er3+ was investigated at low temperature. Excitation of Yb3+ in the IR region revealed the fast and the slow components of Er3+ up-conversion luminescence originating from both glass and crystalline phases. The temporal differences of...
Oxyfluoride silicate glass SiO2–Al2O3–Na2CO3–NaF–LaF3–ErF3 was synthesized. The glass transition and crystallization temperatures were determined by differential thermal analysis. Glass ceramics containing LaF3:Er3+ crystallites of size ∼20nm were formed in the glass matrix after the heat treatment of the precursor glass in the vicinity of the crys...
