Throughout history, the fate of the countries of the Western Balkans was mainly determined by political factors, and their inclusion in the integration processes represents an attempt to give primacy ...to economic factors and sustainable development, in relation to political factors. Today, we encounter a large number of comments, statements by experts and representatives of political organizations about the potential effects of the "Open Balkans" initiative, but also the lack of serious theoretical and empirical research on its progress and potential effects on the sustainable development of the region. Precisely because of the above, the authors of this paper devote their attention to finding an answer to the question of how this initiative developed and what are its potential effects on sustainable development, i.e. to what extent it contributes to increasing the well-being of the members and neighboring countries. Empirical evidence for the acceptability of the most important views and conclusions presented in the paper was provided through research in which the first author of this paper participated, and based on data collected by the Faktor Plus Agency in all countries that signed the initiative.
We report the procedure for hydrothermal synthesis of ultrasmall Yb3+/Tm3+ co-doped Sr2LaF7 (SLF) upconversion phosphors. These phosphors were synthesized by varying the concentrations of Yb3+ (x = ...10, 15, 20, and 25 mol%) and Tm3+ (y = 0.75, 1, 2, and 3 mol%) with the aim to analyze their emissions in the near IR spectral range. According to the detailed structural analysis, Yb3+ and Tm3+ occupy the La3+ sites in the SLF host. The addition of Yb3+/Tm3+ ions has a huge impact on the lattice constant, particle size, and PL emission properties of the synthesized SLF nanophosphor. The results show that the optimal dopant concentrations for upconversion luminescence of Yb3+/Tm3+ co-doped SLF are 20 mol% Yb3+ and 1 mol% Tm3+ with EDTA as the chelating agent. Under 980 nm light excitation, a strong upconversion emission of Tm3+ ions around 800 nm was achieved. In addition, the experimental photoluminescence lifetime of Tm3+ emission in the SLF host is reported. This study discovered that efficient near IR emission from ultrasmall Yb3+/Tm3+ co-doped SLF phosphors may have potential applications in the fields of fluorescent labels in bioimaging and security applications.
Abstract
The near-infrared luminescence of Ca
6
Ba(PO
4
)
4
O:Mn
5+
is demonstrated and explained. When excited into the broad and strong absorption band that spans the 500–1000 nm spectral range, ...this phosphor provides an ultranarrow (FWHM = 5 nm) emission centered at 1140 nm that originates from a spin-forbidden
1
E →
3
A
2
transition with a 37.5% internal quantum efficiency and an excited-state lifetime of about 350 μs. We derived the crystal field and Racah parameters and calculated the appropriate Tanabe–Sugano diagram for this phosphor. We found that
1
E emission quenches due to the thermally-assisted cross-over with the
3
T
2
state and that the relatively high Debye temperature of 783 K of Ca
6
Ba(PO
4
)
4
O facilitates efficient emission. Since Ca
6
Ba(PO
4
)
4
O also provides efficient yellow emission of the Eu
2+
dopant, we calculated and explained its electronic band structure, the partial and total density of states, effective Mulliken charges of all ions, elastic constants, Debye temperature, and vibrational spectra. Finally, we demonstrated the application of phosphor in a luminescence intensity ratio thermometry and obtained a relative sensitivity of 1.92%K
−1
and a temperature resolution of 0.2 K in the range of physiological temperatures.
Herein, we investigate the performance of single- and multiparametric luminescence thermometry founded on the temperature-dependent spectral features of Ca6BaP4O17:Mn5+ near-infrared emission. The ...material was prepared by a conventional steady-state synthesis, and its photoluminescence emission was measured from 7500 to 10,000 cm−1 over the 293–373 K temperature range in 5 K increments. The spectra are composed of the emissions from 1E → 3A2 and 3T2 → 3A2 electronic transitions and Stokes and anti-Stokes vibronic sidebands at 320 cm−1 and 800 cm−1 from the maximum of 1E → 3A2 emission. Upon temperature increase, the 3T2 and Stokes bands gained in intensity while the maximum of 1E emission band is redshifted. We introduced the procedure for the linearization and feature scaling of input variables for linear multiparametric regression. Then, we experimentally determined accuracies and precisions of the luminescence thermometry based on luminescence intensity ratios between emissions from the 1E and 3T2 states, between Stokes and anti-Stokes emission sidebands, and at the 1E energy maximum. The multiparametric luminescence thermometry involving the same spectral features showed similar performance, comparable to the best single-parameter thermometry.
The binary luminescence thermometry probe is prepared from Y2O3:Ho3+ and Mg2TiO4:Mn4+ powders. This probe facilitates self‐referencing temperature readouts with excellent repeatability from both ...emission intensity ratio and excited state lifetimes. The ratio of intensities of Mn4+ deep red emission from 2E, 4T2→4A2 electronic transitions, and Ho3+ green emission from 5F4,5S2 →5I8 electronic transitions provides temperature measurements over the room temperature to 100 °C temperature range with a superior relative sensitivity of 4.6% °C−1 and temperature resolution of 0.1 °C. Over the same temperature range, the temperature readout from the Mn4+ emission lifetime offers measurements with relative sensitivity better than 0.5% °C−1 and better than 0.2 °C in resolution.
The combination of Mn4+ and Ho3+ emissions facilitates highly sensitive and repeatable luminescence thermometry. It shows a superior temperature resolution which can be realized using cheap blue LED sources and which covers the most relevant temperature range from room temperature to 100 °C.
Herein, we demonstrate the photoluminescence properties of Dy
3+
-activated YNbO
4
, LuNbO
4,
and mixed Y
x
Lu
1−
x
NbO
4
:Dy
3+
(
x
= 0.25, 0.5, 0.75) phosphors. For this purpose, five samples ...with a fixed Dy
3+
concentration (2 mol%) were prepared by the solid-state reaction method. X-ray diffraction measurements showed that all phosphors crystallize in a monoclinic fergusonite-beta-(Y) structure with a C2/c space group. Scanning electron microscopy clearly shows that samples are composed of dense, well-developed micron-sized, cube-shaped grains with rounded edges. The photoluminescent emission spectra feature Dy
3+
peaks at standard positions corresponding to transitions from the
4
F
9/2
excited emitting level to the
6
H
J
(
J
= 15/2; 13/2; 11/2 and 9/2) lower levels with two dominant emission bands placed in the blue (~ 479 nm, B) and yellow (~ 576 nm, Y) spectral region. It is observed that with Lu increase in the host lattice Y/B ratio decreases toward the desired ratio of unity to obtain white light. To evaluate the suitability of these phosphors for use in solid-state lighting, their photoluminescence emission was analyzed in detail by calculating CIE coordinates, correlated color temperature (CCT) and Delta u,v (DUV). It is shown that CIE chromaticity coordinates of all Dy
3+
-activated Y
x
Lu
1−
x
NbO
4
samples (
x
= 0, 0.25, 0.5, 0.75, and 1) fall into the white portion of the diagram and that with the increase of Lu in the host lattice color becomes whiter. CCT values for all samples are in the cooler 4000–4500 K range with positive DUVs indicating that color points are placed above the black body curve. The average lifetime of
4
F
9/2
level is calculated to be ~ 0.2 ms for all Dy
3+
-activated Y
x
Lu
1−x
NbO
4
samples, indicating that there is no influence of the Y-to-Lu ratio in the host niobate material on the luminescence kinetics.
Temperature sensing from the photoluminescence of MgAl2O4:Cr3+ ceramic powder is systematically investigated. Material was prepared by self-propagating high temperature synthesis method. In this ...host, Cr3+ experiences the strong crystal field, so the overlapping emissions from 2E and 4T2 energy levels are observed. Emission and excitation spectra were recorded from 300 K to 540 K. The broad photoluminescence attributed to 4T2→4A2 emission gains in intensity with increase in temperature on account of 2E→4A2 emission intensity until 460 K when both emissions start quenching. The emissions were separated by deconvolution at each temperature and used for the luminescence intensity ratio temperature readout method. The obtained relative sensitivity exhibited high values in the physiological range, from 3.5 %K−1 at 300 K to 2.9 %K−1 at 330 K, above 2 %K−1 below 400 K and above 1 %K−1 between 400 K and 540 K.
The observation by scanning tunnelling spectroscopy of Abrikosov vortex cores in the high-temperature superconductor YBa2Cu3O7-δ (Y123) has revealed a robust pair of electron-hole symmetric states at ...finite subgap energy. Their interpretation remains an open question because theory predicts a different signature in the vortex cores, characterized by a strong zero-bias conductance peak. Here, we present scanning tunnelling spectroscopy data on very homogeneous Y123 at 0.4 K revealing that the subgap features do not belong to vortices: they are actually observed everywhere along the surface with high spatial and energy reproducibility, even in the absence of magnetic field. Detailed analysis and modelling show that these states remain unpaired in the superconducting phase and belong to an incoherent channel, which contributes to the tunnelling signal in parallel with the superconducting density of states.
In this work, the potential of Li1.8Na0.2TiO3:Mn4+ for the lifetime-based luminescence thermometry is assessed. The material is prepared by the solid-state reaction of Li2CO3, Na2CO3, and ...nanostructured TiO2 at 800 °C, and its monoclinic structure (space group C2/c) is confirmed by X-ray diffraction analysis. In this host, Mn4+ provides strong absorption around 330 nm and 500 nm due to 4A2g → 4T1g and 4A2g→ 4T2g electric dipole forbidden and spin-allowed electron transitions, respectively, and emits around 679 nm on account of 2Eg→4A2g spin forbidden electron transition. Temperature dependences of emission intensity and emission decay are measured over the 10–350 K range. Due to the low value of energy of 4T2g level (20000 cm−1), the strong emission quenching starts at low-temperatures which favors the use of this material for the luminescence thermometry. It is demonstrated that the quite large value of relative sensitivity (2.27% K−1@330 K) facilitates temperature measurements with temperature resolution better than 0.15 K, and with the excellent repeatability.
•Li1.8Na0.2TiO3:Mn4+ was synthesized by the solid-state reaction method in C2/c structure.•The material was used as a probe for the lifetime-based luminescence thermometry.•Mn4+ emits around 679 nm due to of 2Eg→4A2g spin forbidden electron transition.•The material exhibits a large value of relative sensitivity (2.27% K−1@330 K).•Excellent Mn4+ emission repeatability with temperature resolution of 0.15 K.
There is a worldwide trend of increasing interest in cultural tourism products, and the World Tourism Organization predicts that the cultural tourism market will be one of the five leading segments ...of the tourism market in the future. Local culture is an important feature of a tourist destination, and thanks to tourism, it becomes a flywheel of social and economic development. Cultural tourism is focused on cultural attractions and activities as the main reasons for traveling, and the participation of cultural tourism in all tourist movements is increasing. Thus in France, Italy, Spain, the United Kingdom, income from tourists whose primary goal is to get acquainted with cultural goods and cultural achievements exceed 1/3 of total tourism revenues. Starting from the above, this paper focuses on the analysis of the key problems of the development of cultural tourism and the possibilities of enriching tourist destinations with cultural offer through the development of a cultural product, as a way of increasing the value of a comprehensive tourist offer and attracting a large number of tourists. It concludes with a brief analysis of the key issues for this field of cultural policy in the Republic of Serbia and recommendations on how to make a tourist attraction from a cultural resource and to achieve greater satisfaction of the tourists with their stay in a destination.
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