Total Luminescence Intensity Research Articles

Novel high-sensitivity optical thermometry based on fluorescence intensity ratio of <inline-formula><tex-math id="Z-20240425115725">\begin{document}${\text{VO}}_4^{3 - } $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240012_Z-20240425115725.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240012_Z-20240425115725.png"/></alternatives></inline-formula> to Pr<sup>3+</sup>

It is noteworthy that since 2010, the number of published and cited scientific papers on optical thermometry has increased exponentially. Optical thermometry technology is about to make a significant process in sensing, therapy, diagnosis, and imaging. The current research mainly focuses on optical thermometry that is developing towards high-sensitivity thermometry. In this work, a new thermometry strategy is proposed based on the different temperature-dependent behaviors between the host ions and the doped ions. Firstly, YVO<sub>4</sub>:<i>x</i>Pr<sup>3+</sup>(<i>x</i> = 0%–1.5%) phosphors are successfully synthesized by the solid-state method. Then, the structure and luminescence properties of the samples are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and fluorescence spectrophotometer. The XRD results show that Pr<sup>3+</sup> ions are successfully incorporated into the YVO<sub>4</sub> host, and the sample has a tetragonal phase crystal structure with space group <i>I</i>41/<i>amd</i>. The SEM results show that the samples are rectangular-shaped micron particles with smooth surfaces, and the average grain size is about 2.1 μm. Under the excitation of 320 nm, the sample mainly exhibits broadband blue emission around 440 nm and red emission at 606 nm, which are attributed to the charge transfer transition of <inline-formula><tex-math id="M2">\begin{document}${\text{VO}}_4^{3 - }$\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240012_M2.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240012_M2.png"/></alternatives></inline-formula> and the <sup>1</sup>D<sub>2</sub>→<sup>3</sup>H<sub>4</sub> transition of Pr<sup>3+</sup>, respectively. The relationship between the luminescence of the sample and the concentration of Pr<sup>3+</sup> is studied. It is found that the optimal doping concentration of Pr<sup>3+</sup> is 0.5%, and a higher doping concentration will cause concentration to be quenched. The reason for quenching concentration is the electric dipole-quadrupole interaction. The luminescence peak position of the temperature-dependent spectrum of YVO<sub>4</sub>:0.5%Pr<sup>3+</sup> is consistent with that at room temperature. As the temperature increases, the total luminescence intensity gradually decreases, which is caused by thermal quenching, and the mechanism of thermal quenching is analyzed. Since the temperature-dependent behaviors of luminescence of <inline-formula><tex-math id="M3">\begin{document}${\text{VO}}_4^{3 - }$\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240012_M3.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240012_M3.png"/></alternatives></inline-formula> and Pr<sup>3+</sup> are significantly different from each other, a new fluorescence intensity ratio thermometry strategy is realized. Temperatures range is 303–353 K, and the maximum absolute sensitivity and relative sensitivity are 0.651 K<sup>–1</sup> and 3.112×10<sup>–2</sup> K<sup>–1</sup> at 353 K, respectively, much higher than the traditional thermally coupled level thermometry strategy. In addition, there is no obvious overlap between the emission peaks of <inline-formula><tex-math id="M4">\begin{document}${\text{VO}}_4^{3 - }$\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240012_M4.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240012_M4.png"/></alternatives></inline-formula> and Pr<sup>3+</sup>, which provides a good discrimination capability for signal detection. The above results show that this work provides a promising path for designing self-reference optical thermometry materials with excellent temperature sensitivity and signal discrimination.

EPR and optical study of erbium-doped CeO2 and CeO2 / CeF3 nanoparticles

Here, the facile dry synthesis of composite CeO2/CeF3 nanoparticles doped with Er3+ probe ions using ammonium bifluoride (NH4HF2) is reported. This method allows synthesizing composite nanoparticles with different ratio of СеО2 and CeF3. The structural properties of the composite nanoparticles were studied using XRD, SEM, and TEM techniques, which confirmed the formation of composite CeO2/CeF3 nanoparticles. The luminescence spectra show that the intensity of the Ce3+ peak increases after fluorination procedure, revealing the fact that the amount of Ce3+ is increased. In particular, the total 4f-4f luminescence intensity of CeO2/CeF3:Er3+(0.1 at.%) nanoparticles is 3.5 time higher compared to CeO2:Er3+(0.1 at.%) ones under both UV or resonant pumping. Probably it can be associated with the increased concentration of trivalent rare-earth ions in a cubic-distorted environment. The same tendency is observed for the excitation spectra. EPR measurements showed that fluorination of CeO2 nanoparticles doped with different concentration of Er3+ ions leads to the formation of trigonal sites in ceria nanoparticles.

Monolithically integrated photonic chips with asymmetric MQWs structure for suppressing Stokes shift

An asymmetric (ASY) multiple quantum wells (MQWs) structure consisting of emission and detection regions with different In components and thicknesses is presented for suppressing the Stokes shift in monolithically integrated photonic chips. Compared with conventional MQWs, the total luminescence intensity of ASY MQWs is improved due to the action of the potential field for transferring more holes to the quantum well near the n-GaN side. Meanwhile, resulted from about 25–30 nm redshift in response spectra, a 4.5-fold increase in the overlap of luminescence-detection spectra is realized. A photodetector exhibits a photo-to-dark current ratio of up to 107 at 0 V bias. Furthermore, the reported ASY MQWs diode shows a maximum bandwidth (−3 dB) of 173 MHz, suggesting that a monolithically integrated chip has tremendous potential on the application of the on-chip visible light communication.

DISBALANCE OF BIORADICAL PROCESSES AS THE MAIN CAUSE OF DISORGANIZATION OF CONNECTIVE TISSUE STRUCTURES IN EXPERIMENTAL PERIODONTITIS

Abstract: Relevance. The features of the dynamics of free radical processes, as well as the metabolism of collagen structures of the connective tissue matrix against the background of periodontitis will reveal deeper pathogenetic mechanisms and application points for the introduction of new therapeutic and diagnostic technologies into practice. The purpose of the study. Assessment and establishment of interrelations between the intensity of bio-radical processes and collagen metabolism in dynamics in experimental periodontitis. Materials and methods. The study used 45 white nonlinear rats, on which the model of periodontitis proposed by Shkolnaya K. D., Atrushkevich V.G. (Patent RU No. 2625295 dated 12.07.2017) was reproduced. The total activity of free radical oxidation and the antioxidant potential of the body were monitored by the biochemiluminescence method, and markers of collagen metabolism were recorded. Results. The study revealed a sharp predominance of oxidative processes and the inability of the antioxidant potential to suppress free radical peroxidation, as evidenced by the persistently high levels of total luminescence intensity and biohemiluminescence light sum that persist throughout the experiment, despite dynamic changes. Reactive oxygen species in conditions of progressive chronic inflammation have a damaging effect on collagen fibers, which means they lead to the inevitable destruction of the periodontal complex, which is expressed in the growth of CO and PSO. In addition, there is a significant direct correlation between the dynamics of the intensity of free radical oxidation and the indicators of collagen metabolism. Conclusion. Thus, oxidative stress, progressing against the background of periodontitis, leads to disorganization of connective tissue structures of the periodontal. In turn, the study confirms the validity of the use of markers of the intensity of free radical oxidation and collagen metabolism to diagnose the severity of the disease and prognosis, as well as the need for the use of antioxidant drugs as part of complex therapy.

Thermal enhancement of 2H11/2→4I15/2 up-conversion luminescence of BaLu6(Si2O7)2(Si3O10):Er3+/Yb3+ phosphors

A series of BaLu6(Si2O7)2(Si3O10):Er3+/Yb3+ phosphors were manufactured by high temperature solid phase reaction method. The X-ray diffraction (XRD) and vary temperature up-conversion luminescence (UCL) under 980 nm laser excitation were measured to analyze the structure and optical thermal behaviors. When the fixed Er3+ concentration is 0.1, the brightest sample appears at Yb3+ concentration 3.0. By adjusting the doping concentration of Er3+ and Yb3+ respectively, the thermal enhancement UCL times of 2H11/2→4I15/2 transitions of Er3+ attain the maximum point while Er3+/Yb3+ is 0.01/3.0. And the thermal enhancement UCL of 2H11/2→4I15/2 transitions of Er3+ is 4.12 times, and the total green luminescence intensity increases 1.97 times at the range of 303–723 K. Additionally, based on fluorescence intensity ratio (FIR) technique, the maximum absolute sensitivity is 0.00645 K−1. The single doped 1.0Er3+ sample has the thermal enhancement UCL of 2H11/2→4I15/2 transitions of Er3+, however the single doped 4.0Er3+ sample does not have, and this indicates that the cross relaxation between Er3+ is unfavorable to thermal enhancement of 2H11/2→4I15/2. The possible vary temperature UCL mechanism was expound. The results manifest that the BaLu2.99Er0.01Yb3.0(Si2O7)2(Si3O10) phosphor can be a good candidate for optical thermometer at high temperature.

Achieving tunable luminescence in Eu2+ and Eu3+ codoped MAl2B2O7:Eu (M = Ca2+, Sr2+, and Ba2+) phosphor by structure defect designing and site symmetry controlling

Eu2+ and Eu3+ codoped alkaline-earth aluminum borates MAl2B2O7:Eu (M = Ca2+, Sr2+, and Ba2+) phosphors were prepared by a conventional high-temperature solid-state method. The phosphor exhibits strong absorption in the spectral range of ∼200–450 nm and bright tunable emission in the blue region, white region, and red region. The effect of composition, excitation wavelength, and doping concentration of europium ion on luminescence behavior of the phosphors were investigated systematically. Upon 254 nm excitation, SrAl2B2O7:Eu exhibits blue and bluish-green emission of Eu2+ and red emission of Eu3+. Ca2+ substitution for Sr2+ promoted the optimization of luminescence quality, and even the emergence of white light with chromatic coordination (0.382, 0.234), and Ba2+ substitution for Sr2+ increased the total luminescence intensity by ∼12.5 times. The changes in luminescence behavior were explained according to the structural defect of the phosphor and the site symmetry of the europium ions. The tunable luminescence and white-light emission upon 254 nm excitation imply that the phosphors have potential application prospects in cold cathode fluorescent lamps.

Highly-increased photoluminescence of Pr3+ due to the Eu2+→ Pr3+ energy transfer in Al2O3 coatings formed by plasma electrolytic oxidation

In this paper, photoluminescence (PL) properties of Pr3+ single doped and Pr3+/Eu2+ co-doped Al2O3 coatings formed by plasma electrolytic oxidation of aluminum were investigated. The PL spectra of Al2O3:Pr3+ coatings feature bands ascribed to 4f-4f transitions of Pr3+. PL excitation spectra contain three broad bands in the violet and blue regions which correspond to the direct excitation of the Pr3+ ground state 3H4 into higher levels 3PJ (J = 0, 1, 2), while PL emission spectra contain several bands attributed to transitions of Pr3+ from excited levels 3P0 and 3P1 to the lower multiplets 3HJ (J = 4, 5, 6) and 3FJ (J = 2, 3, 4). Among these transitions, 3P0→3F2 transition in the red region (644 nm) is the most intense. PL emission intensity of Pr3+ increases by co-doping Eu2+ into Al2O3:Pr3+ coatings due to the energy transfer from Eu2+ to Pr3+, occurring due to the overlap between PL emission spectra of Eu2+, excited by middle ultraviolet radiation, and PL excitation spectra of Pr3+ in Al2O3 host. Under middle ultraviolet excitation, 3P0→3F2 transition of Pr3+ in Al2O3:Pr3+/Eu2+ coatings is 62 times more intense than without co-doping and 16 times if comparison is made with Al2O3:Pr3+ excited by 446 nm. The total luminescence intensity of Al2O3 co-doped with Pr3+/Eu2+ and doped with Pr3+ is 3.6 times more intense of the former if both samples are excited by 446 nm. The gains are linearly increasing with Eu2+ doping concentration. Al2O3:Pr3+/Eu2+ poses as an alternative phosphor to YAG:Ce3+ for the creation of neutral white LEDs by excitation with InGaN semiconductors.

Luminescence performance of Cr3+ doped and Cr3+, Mn4+ co-doped La2ZnTiO6 phosphors

Cr3+ doped and Cr3+, Mn4+ co-doped La2ZnTiO6 phosphors were prepared using solid-state reaction method and their luminescence performance has been investigated. La2ZnTiO6: Cr3+ phosphor exhibits red luminescence band centred at 740 nm when excited with light in spectral range from ultraviolet to blue and green (300 nm–500 nm). Both emissions at 740 nm (Cr3+) and at 710 nm (Mn4+) can be observed in the Cr3+, Mn4+ co-doped phosphor and its total luminescence intensity excited at 337 nm is enhanced to 1.6 times with the introduction of Mn4+ ions. The ratio of emission intensity at 710 nm to that at 740 nm in the co-doped phosphor increases monotonically as excitation wavelength increases from 330 to 400 nm. The performance of the developed phosphors in present work indicates that they might be used in indoor cultivation of LEDs and wavelength detection.

A Spectral Shift-Based Electrochemiluminescence Sensor for Hydrogen Sulfide.

Classic electrochemiluminescence (ECL) assays relying on the change in luminescence intensity face a challenge in the quantitative analysis of complex samples. Here, we report the design and implementation of a new sensing strategy, using the maximum luminescence wavelength (λmax) shift as the readout to achieve quantitative detection. This approach includes an ECL luminophore (RuSiO2@GO) and a H2S-sensitive inner filter absorber (CouMC). The absorbance of CouMC illustrates a dependence on the H2S concentration, which induces a change in the maximum luminescence wavelength (Δλmax) of the ECL luminophore. Both experimental and simulated results suggest that the spectral shift of ECL effectively avoids the interference of the total luminescence intensity fluctuations, enabling a highly reliable quantitative analysis. This spectral shift-based ECL assay strategy offers a wide application potential by extending types of ECL luminophores and absorptive chemodosimeters, based on an inner filter effect.

Spectral change of intermediate band luminescence in GaP:N due to below‐gap excitation: Discrimination from thermal activation

As an intermediate band (IB) originating from discrete nitrogen (N) levels is formed in GaP:N with increasing N concentration, GaP1−xNx alloy is considered to be a promising candidate for IB‐type solar cells. We studied the IB luminescence of a GaP1−xNx with 0.56% N and detected carrier recombination (CR) levels by superposing a below‐gap excitation (BGE) light of 1.17 eV. We resolved a high‐energy component of 2.15 eV in the IB luminescence, Ihigh, from total luminescence intensity Iall. With increasing the BGE density at fixed temperature of 5 K, the amount of decrease in Ihigh was distinctly smaller than that of simple temperature rise without the BGE at the same Iall value. We conclude that the observed intensity change of the IB luminescence due to the BGE comes not from thermal activation, but from optical excitation among the IB, conduction band, and CR levels in GaP1−xNx. It is of primal importance to understand CR levels toward determining their origins and eliminating them for realization of efficient IB‐type solar cells.

High color purity red emission of Y2Ti2O7:Yb3+, Er3+ under 1550 and 980 nm excitation

Red emission with high color purity in Y2Ti2O7:Yb3+,Er3+ material is successfully obtained by high-concentration doping of Yb3+ and Er3+ under 980 and 1550nm excitation based on the special layer structure of pyrochlore crystal. It shows that Yb3+ ion content and excitation wavelength greatly influence the red emission percent of total up-conversion luminescence intensity of Y2Ti2O7:Yb3+,Er3+. Y2Ti2O7:Yb3+,Er3+ shows much better red color purity at 1550nm excitation than at 980nm. Furthermore, the co-doping of Yb3+ ions considerably boosts the red emission under 980 or 1550nm pumping with different luminescence mechanisms compared with Y2Ti2O7:Er3+ sample. The red emission percent of total up-conversion luminescence intensity gradually increases with the increment of Yb3+ concentration at both excitation sources. The red-to-green emission ratio of the sample is 6.97 (980nm) and 23.26 (1550nm) when the Yb3+ content is 30mol%.

Luminescent PEO Coatings on Aluminum

Results show the possibilities of pore filling approach to modify alumina coatings with various materials in order to enhance coating optical (or other) properties and develop new functional materials; as well as demonstrate novel alumina phase transition detection approach. Luminescent PEO coatings were produced on aluminum surface using pore-filling method. Three stage process was developed to modify alumina coating in order to enhance its luminescent properties. Eu3+ recharging to Eu2+ followed by significant (up to 10 times) total luminescence intensity increase was observed, Eu ion presence evaluated in final coating by measuring fast decay kinetics. Structure of obtained coatings was analyzed using XRD and FTIR spectroscopy indicating presence of η-alumina phase.

Luminescence characteristics of Lu2SiO5:Ce3+ (LSO:Ce) ceramic scintillators under VUV–UV excitation

The luminescent properties of LSO:Ce (1mol%) scintillators were characterized systematically under vacuum ultraviolet (VUV)–UV excitation. Under 185nm VUV excitation, a broad emission band was detected in the wavelength range from 350nm to 600nm at different temperatures, which is ascribed to the 5d→4f electron transitions of Ce3+. Excitation wavelength and temperature effects on luminescent properties of LSO:Ce ceramic scintillators were investigated in this paper. At 50K, the emission intensity of Ce1 (Ce3+ locating in seven-oxygen-coordinated site) was much stronger than that of Ce2 (Ce3+ locating in six-oxygen-coordinated site), and the total emission intensity excited by 355nm (Ce1) was higher than that excited by 185nm (host). The total luminescence intensity increases as the rising temperature in the temperature range of 150–300K, which is originated from thermal enhancement of transportation of free carriers dominating Ce1 emission.

Luminescent Properties of Polycrystalline Cerium-Doped Lutetium Pyrosilicate Powders

Single phase LPS powders with nanosize particles were synthesized by a sol-gel process. Temperature and calcination temperature dependence of luminescence of the synthetic LPS:Ce powders were investigated under vacuum ultraviolet (VUV)-UV excitation. Luminescence intensity of LPS:Ce powders increase with calcination temperature, but it reaches the maximum at 1250 °C. Decay time of the LPS:Ce powders also slightly increasing from 27.1 to 30.5 ns as calcining temperature elevating. Both of them attribute to improved crystallization of LPS:Ce powders. Total luminescence intensity of LPS:Ce powder calcined at 1350 °C for 2 h has no noteworthy variation as the temperature rising in temperature 30-260 K range, this luminescence stability suggests that LPS:Ce would also be a good scintillator for high energy radiation detection in low temperature condition with temperature variation.

Influence of Parameters of a Printing Plate on Photoluminescence of Nanophotonic Printed Elements of Novel Packaging

In order to produce nanophotonic elements for smart packaging, we investigated the influence of the parameters of screen and offset gravure printing plates on features of printed application of coatings with nanophotonic components and on parameters of their photoluminescence. To determine the dependence of luminescence intensity on the thickness of solid coating, we carried out the formation of nanophotonic solid surfaces by means of screen printing with different layer thickness on polypropylene film. The obtained analytical dependencies were used to confirm the explanation of the processes that occur during the fabrication of nanophotonic coverings with offset gravure printing plates. As a result of experimental studies, it was determined that the different character of the dependency of total luminescence intensity of nanophotonic elements from the percentage of a pad is explained by the use of different types of offset gravure printing plates, where the size of raster points remains constant in one case and changes in the other case, while the depth of the printing elements accordingly changes or remains constant. To obtain nanophotonic areas with predetermined photoluminescent properties, the influence of investigated factors on changes of photoluminescent properties of nanophotonic printed surfaces should be taken into consideration.

Anomalous heating rate effect in thermoluminescence intensity using a simplified semi-localized transition (SLT) model

During thermoluminescence (TL) measurements carried out with different heating rates, one expects the total number of emitted photons to be constant. However, for many luminescence materials one observes a decreased intensity of luminescence at elevated temperatures, due to the presence of the well-known phenomenon of thermal quenching. Recent experimental work on the dosimetric material YPO4 double doped with lanthanides demonstrated the exact opposite behavior, in which the total luminescence intensity increases with the heating rate during the TL experiments. This anomalous TL behavior was recently explained by using the Mandowski model of semi-localized transitions (SLTs). In this paper it is shown that this anomalous heating rate or “anti-quenching” phenomenon can also be described by using a simplified SLT model of TL with approximated kinetic equations. The simulated glow curves show that as the probability of the non-radiative processes increases, the anomalous heating rate effect becomes dominant. The dependence of the anomalous heating rate effect on the values of the kinetic parameters in the model is examined by allowing random variations of the parameters in the model, within wide ranges of physically reasonable values covering several orders of magnitude. It is shown by simulation that the variable heating rate method can systematically underestimate the value of the activation energy E, while by contrast the initial rise method of analysis almost always yields the correct E value. These simulated results are discussed in relation to recent experimental work on the double doped dosimetric material YPO4.

Luminescent Property of Al<sub>2</sub>O<sub>3</sub>:Ce<sup>3+</sup> Thin Films

The Al2O3 films doped with Ce3 + were deposited on slides by the medium-frequency reaction magnetron sputtering process, to which the power is constant, Ar flow rate 70 sccm, O2 flow rate 25~45sccm and sputtering time 90min at room temperature. The relationship between the luminescent properties of Al2O3:Ce3 + films and the doped amount of Ce3 + in the films was studied. The presence of Ce3 + and stoichiometry of those films were determined. It was observed that the total luminescence intensity increases and the peak positions are strongly dependent on Ce3+ concentration in the films. The analysis of luminescent excitation spectra showed that the luminance is due to the Ce3+ concentration in the cerium chloride aggregate formed in the films.

Revisiting with Updated Hardware an Old Spectroscopic Technique: Circularly Polarized Luminescence

Among the various chiroptical spectroscopic techniques available today, circularly polarized luminescence (CPL) plays a minor role and is still used by a limited number of specialists. The cost of the few commercial instruments available and the complexity of homemade apparatuses have strongly limited the widespread application of this technique. New technological approaches, such as the use of light-emitting diode (LED) sources, may significantly simplify the required instrumentation and encourage new potential users. Calibration procedure and the quantitative determination of CPL and total luminescence intensity as well as the corresponding g ratio are described.

Indirect optical transition due to surface band bending in ZnO nanotubes

ZnO nanotubes (ZNTs) have been successfully evolved from ZnO nanorods (ZNRs) by a simple chemical etching process. Two peaks located at 382 and 384 nm in the UV emission region has been observed in the room temperature photoluminescence (PL) spectrum of ZNTs since the surface band bending in ZNTs induces the coexistence of indirect and direct transitions in their emission process. In addition, a strong enhancement of total luminescence intensity at room temperature in ZNTs has also be observed in comparison with that of ZNRs. Both temperature-dependent PL and time-resolved PL results not only further testify the coexistence of indirect and direct transitions due to the surface band bending but also reveal that less nonradiative contribution to the emission process in ZNTs finally causes their stronger luminescence intensity.

Mechanochromic Luminescence Quenching: Force-Enhanced Singlet-to-Triplet Intersystem Crossing for Iodide-Substituted Difluoroboron−Dibenzoylmethane−Dodecane in the Solid State

A lipid derivative of difluoroboron-iododibenzoylmethane (BF(2)dbm(I)OC(12)H(25)) was synthesized via Claisen condensation and boronation. Green photoluminescence is observed for the complex in the solid state. Unlike the previously reported difluoroboron-avobenzone (BF(2)AVB) complex, which exhibited significantly red-shifted fluorescence upon mechanical perturbation, the emission of a BF(2)dbm(I)OC(12)H(25) solid film is quenched when the sample is smeared under air but becomes orange under nitrogen. Spectroscopic and lifetime studies suggest that smearing brings the singlet excited state closer to the triplet state, thus increasing the coupling between the two states. As a result, intersystem crossing from the singlet to the triplet excited state is facilitated, and the total luminescence intensity is quenched at room temperature.