Weak Red Emission Research Articles

Optical temperature sensing properties of novel RE3+ (RE = Er, Ho) doped BaLa2Ti3O10 phosphors

A novel luminescent material of BaLa2Ti3O10:RE3+ was synthesized by the high-temperature solid phase method, with a typical layered structure belonging to a special crystal system. Under the excitation of 980 nm, BaLa2Ti3O10:4 %Er3+ exhibits characteristic emissions centered at 531 nm, 551 nm and 668 nm. It is noteworthy that the color of BaLa2Ti3O10:3 %Ho3+ shows a strong green emission at 551 nm and a weak red emission near 664 nm, also represents adjustable yellow-green light with the change of 980 nm laser pumped powers. The optical temperature sensing properties were checked by employing different strategies, relating to the thermally-coupled-levels (TCLs) and nonthermally-coupled-levels (NTCLs). The results show that the maximum relative sensitivity of TCLs based on BaLa2Ti3O10:Er3+ is 0.68 % K−1 (305 K). Similarly, the maximum sensitivity of TCLs is 0.89 % K−1 (313 K) in BaLa2Ti3O10:Ho3+, which performs well from 313 K to 513 K. It has been found the samples using FIRs of TCLs can produce higher absolute (Sa) and relative (Sr) sensitivities compared with those using Fluorescence Intensity Ratios (FIRs) of NTCLs. The multiple FIRs also achieved superior levels of temperature resolution and repeatability in all cases. Generally, this work provides favorable candidates for the temperature sensors.

Laser Characteristics of Er3+/Yb3+:K-BaF2-Al-Phosphate Glasses.

Er3+ and Er3+/Yb3+-doped phosphate-based glasses have been synthesized by melt quenching technique and are characterized by absorption spectra, infrared emission, decay curves, Fourier transform infrared spectrum and up-conversion studies. From the absorption spectra, intensity parameters and radiative properties have been derived utilizing the Judd-Ofelt theory. Er3+-doped glass is found to have larger radiative lifetime for the laser originating from 4I13/2 level at 1537 nm. Infrared and visible characteristic emissions have been measured by exciting at 790 nm through down- and up-conversion, respectively. The up-conversion spectra consist of intense green emission at around 525 and 545 nm ascribed to the 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions, respectively, and a weak red emission at around 656 nm due to the 4F9/2 → 4I15/2 transition of Er3+ ions. Various spectroscopic and laser characteristics of these glasses have been calculated and compared with those of similar reported ones.

Preparation, upconversion/downshifting emissions, temperature sensing, and thermochromic properties of one-dimensional Y2Zr2O7:Er3+/Yb3+ tube-in-tube nanostructures via single-nozzle electrospinning

One-dimensional (1D) Y2Zr2O7:Er/Yb tube-in-tube nanostructures were prepared via a simple electrospinning technique with a single nozzle. The diameter of the outer tube of the Y2Zr2O7:Er/Yb tube-in-tube nanostructures is 190–170 nm, the thickness of the outer wall is 22–20 nm, the diameter of the inner tube is 120–100 nm, and the wall thickness of the inner tube is 17–14 nm. The optical properties of the Y2Zr2O7:Er/Yb tube-in-tube nanostructures, including the up-conversion and downshifting luminescence spectra, temperature sensitivity, and thermochromic properties, were studied in detail. Under 980 nm excitation, two weak green emissions at 528 nm and 550 nm, as well as a strong red emission at 650 nm of Er ions, are presented. When excited at 378 nm, the Er ions exhibit strong green emission at 545 nm, two weak red emission peaks at 650 and 680 nm, and near-infrared emission peaks at 1400–1600 nm. With increasing environmental temperature, the luminescence color of the 1D Y2Zr2O7:Er/Yb tube-in-tube nanostructures exhibited a transition from “orange→yellow→ green” when excited at 980 nm. For the 1D Y2Zr2O7:xEr/yYb tube-in-tube nanostructures (x = 0.01, 0.02, 0.03; y = 0.05, 0.10, 0.15), the maximum values of Sr are 2.3 % K−1 under 980 nm excitation and 2.1%K−1 under 378 nm excitation within the temperature range of 303–723 K. This work develops integrated multifunctional optical materials and provides an alternative approach for the fabrication of nanoscale smart platforms, advanced displays, and applications in information security.

Killing Three Birds with One Stone: Energy Transfer Inducing Efficient, Zero Thermal Quenching, and Emission‐Color Tunable Phosphors

AbstractRed emission phosphors with high efficiency and excellent thermal stability are essential for phosphor‐converted light‐emitting diodes (pc‐LEDs). Na2MgPO4F: Mn2+ shows a very weak red emission peak at 615 nm due to 3d–3d forbidden transition. And it exhibits a normal thermal quenching behavior. Blue‐emitting Eu2+ with anti‐thermal quenching (ATQ) is introduced to tune the emission color, emission efficiency, and thermal stability of Mn2+ in Na2MgPO4F. The emission color of Na2MgPO4F: Eu2+, Mn2+ phosphors can be tuned by increasing the Mn2+ content. The internal and external quantum efficiencies of Na2MgPO4F:0.03Eu2+, 0.05Mn2+ are 89.3% and 41.1%, respectively, which are much higher than those of the Mn2+‐doped ones. Furthermore, the ATQ effect of Eu2+ is also transferred to Mn2+ via energy transfer, which results in Na2MgPO4F: Eu2+, Mn2+ phosphors with zero thermal quenching (ZTQ). The cooperation of energy transfer, enhanced absorption, and increased defects amount promotes the achievement of ZTQ in the co‐doped samples. Two white pc‐LEDs with a color rendering index of more than 90 are manufactured by using the as‐synthesized Na2MgPO4F: Eu2+, Mn2+ phosphors combined with near‐UV chips. This study not only provides high‐performance Eu2+, Mn2+ co‐doped phosphors suitable for high‐quality solid‐state lighting, but also exhibits a killing‐three‐birds‐with‐one‐stone strategy to obtain efficient, thermally stable, and color‐tunable phosphors.

Solid-state reaction synthesis of LuPO4:Yb3+, Tb3+ phosphors and the ultraviolet/near-infrared responsive spectra performances

Yb3+/Tb3+ co-doped LuPO4 phosphors were prepared by solid-state reaction method. The effects of Yb3+/Tb3+ doping concentrations on the downshifting and upconversion spectral performances of the synthesized phosphors were investigated. Upon the ultraviolet light excitation, the phosphors show obvious visible light emission, which can be assigned to the 5D4→7FJ (J=6, 5, 4, and 3) transitions of Tb3+ ions respectively, the green light emission at 543 nm is dominant. Upon 980 nm excitation, the phosphors display intense green and blue light emission, and weak yellow and red light emission, which originates from the cooperative energy transfer process between Yb3+ and Tb3+ ions. The synthesized LuPO4:Yb3+, Tb3+ phosphors show good ultraviolet/near-infrared responsive spectra, color-tunable and thermal-stability performances and may have potential applications in the related fields.

Investigation of diodic behavior in p-NiO/n-SnO2 bilayer heterojunctions fabricated via DC magnetron reactive sputtering

Tin oxide (SnOx) thin films at varying oxygen flow rates and Nickel oxide (NiO) thin films were deposited by reactive dc magnetron sputtering on glass substrates. Structural, chemical, morphological, optical and electrical properties of the deposited films were studied. XRD studies confirmed that the deposited films were polycrystalline in nature. SnOx thin films have shown two phases such as SnO and SnO2. AFM and SEM were used to analyse the morphology of the films and EDS confirmed the presence of Sn and Ni in the respective films. The examination of the x-ray photoelectron spectrum showed that the sputtered SnOx films contain both Sn2+ and Sn4+ oxidation states and NiO films contain Ni+2 and Ni+3 oxidation states. Photoluminescence study shows strong violet and weak red emission peaks for SnOx films and NiO showed strong emission peaks in the orange-red region. The optical results demonstrate that the films were transparent. The bandgap of SnOx and NiO samples were ∼3.3 eV and − 3.42 eV, respectively. Further we constructed a p-NiO/n-SnO2 heterojunction diode and its electrical characteristics were thoroughly assessed. Using dark current–voltage measurements, electrical characteristics such saturation current, ideality factor and barrier height were determined. The increase in oxygen flow rate led to reduction in the rectification of the devices. Our findings support the creation of high-performance metal oxide heterojunction for optoelectronic devices.

Thermal enhanced upconversion luminescent of Sc2W3O12:Yb3+/Er3+ for optical temperature measurement

In recent years, people have higher requirements for temperature measurement with the development of optical temperature measurement. Meanwhile, the emission intensity of most fluorescent materials is quenched by thermal effects as the temperature rises, making it challenging to meet the specifications of fluorescent materials employed in the field of pyrometry. In this work, the pure phase of Yb3+/Er3+ ions co-doped Sc2W3O12 phosphor was successfully prepared. Sc2W3O12: Yb3+, Er3+ samples showed strong green emission and weak red emission. The optimal doping concentrations of Yb3+ and Er3+ ions are 0.3 and 0.02, respectively. The potential upconversion luminescence (UCL) mechanism was investigated by analyzing the UCL spectra, downshift emission spectra and power dependence spectra of Yb3+/Er3+ ions co-doped Sc2W3O12. The upconversion emission excitation path is mainly through Er3+ ions from 4I11/2 absorption photon excitation to 4F7/2 energy level, then the photons of 4F7/2 relaxes to green and red emission energy levels and returns to ground state for emitting green and red light. In addition, according to the UCL green light intensity increasing with temperature, it serves as an optical temperature sensor. The temperature sensitivity of the sample was explored in the temperature range of 298 K–673 K. This study provides new materials and ideas for non-contact temperature sensing.

Carbon dots with enhanced red emission for ratiometric sensing and encryption applications.

The excitation-dependent emission properties of carbon dots (Cdots) are extensively reported, but their red emission is often weak, limiting their wider application. Here we introduce ethidium bromide, asa functional precursor with red emission, to enhance the red emission for Cdots, with comparable intensity at a broad wavelength range to multi-emission Cdots (M-Cdots). We found that Cdots prepared with ethidium bromide/ethylenediamine exhibited strong blue and red emission at 440 and 615nm, with optimal excitation at 360 and 470 nm as M-Cdots, respectively, but the Cdots from single ethidium bromide (EB-Cdots) possessed weak red emission. M-Cdots exhibited a broad absorption band at 478 nm, but a bandblue-shifted to 425 nm was observed for EB-Cdots, while no absorption was observed at 478-425 nm for the Cdots prepared with citric acid and ethylenediamine. Thus, we proposed that C=O and C=N formed a π-conjugation structure as the absorption band at 478 nm for the red emission of M-Cdots, as also confirmed with the excitation at 470 nm. Moreover, the π-conjugation structure is fragile and sensitive to harsh conditions, so red emission was difficult to observe for the Cdots prepared with citric acid/ethylenediamine or single ethidium bromide. M-Cdots possess two centers for blue and red emission with different structures. The dual emission was therefore used for ratiometric sensing with dichromate (Cr2O72-) and formaldehyde (HCHO) as the targets using the intensity ratio of the emissions at 615 and 440nm. Due to the comparable intensity at a broad wavelength range, we designed encryption codes with five excitations at 360, 400, 420, 450, and 470 nm as the inputs, and the emission colors were used for information decoding. Thus, we determined why red emission was difficult to realize for Cdots, and our results could motivate the design of red-emission Cdots for extensive applications.

Excitation wavelength and pumping power dependent temperature sensing property of Nd3+/Yb3+/Er3+ triply-doped LaNbO4 phosphor

Optical thermometry based on the fluorescence intensity ratio technology between the thermally coupled energy levels of Er3+ has become a research hotspot, but it is often limited by excitation conditions, which reduces its universality and reliability. In this work, Nd3+/Yb3+/Er3+ triply-doped LaNbO4 phosphor with excellent up-conversion (UC) luminescence characteristic and reliable temperature sensing sensitivity has been prepared by solid-state reaction method. Intense green and weak red UC emissions were gained under 808 nm and 980 nm excitations. The temperature dependent UC luminescence property and temperature sensing behavior of the sample has been investigated. The results demonstrated that the intensity ratio of the two green emissions was insensitive to the excitation wavelength and pumping power of the lasers, and the maximum absolute sensitivity was derived to be 0.91 % K−1 at 481 K. This work provides a new material with reliable and high temperature sensing sensitivity for optical thermometers.

Non-invasive thermal sensing and improved recoverable energy storage density of Bi0.5Na0.5TiO3: Er3+ doped multifunctional ferroelectric ceramic

In this work, Er3+ substituted bismuth sodium titanate ceramics with the chemical composition Bi0.5-xErxNa0.5TiO3 (x = 0.00, 0.01, 0.02, 0.03, 0.04, and 0.05) were synthesized using conventional solid state technique. The influence of Er3+ ions on structural, optical, ferroelectric, and temperature sensing properties have been investigated. The prepared ceramic powders were initially heated at a calcination temperature 850 °C to form single phase Bi0.5-xErxNa0.5TiO3 and finally sintered at temperature 1050 °C. Formation of pure phase compositions with rhombohedral crystal structure is confirmed through X-ray diffraction studies. The typical FTIR bands near 540, 860, 910 cm−1 confirmed the presence of Ti–O stretching of octahedral groups in the perovskite structure. The decent squared shaped saturated P-E hysteresis are obtained under an electric field of 60 ≤ E ≤ 70 kV/cm, and the loops become slimmer at higher Er3+ concentrations (x = 0.04). The efficiency of energy storage density increases with Er3+ doping and an improved recoverable energy storage (Wr = 2.73 J/cm3) and a higher efficiency (η = 70.77%) are obtained for Er content, x = 0.04. The photoluminescence spectra were recorded at two excitation wavelengths (488 nm and 980 nm). Two distinct green emission bands (529 nm and 550 nm) and one weak red emission band (670 nm) were observed at both excitation wavelengths. Increasing Er3+ content beyond (x > 0.03) leads to significant quenching of light emission due to cross relaxation process and non-radiative relaxations. The pump power dependency revealed that two photons were involved in the light upconversion process. The time-resolved fluorescence spectroscopy confirmed the decrease in lifetime with increasing Er3+ concentration. The absolute and relative sensitivity of the prepared ceramic at Er3+ concentration (x = 0.03) were found to be 0.47% K−1 at 523 K and 1.1% K−1 at 303 K, respectively. These optical and electrical properties open the possibility of realizing multifunctionality in the field of energy storage and opto-electronic applications.

Down- and up-conversion luminescence processes in olivine-type ceramic phosphors Li2AGeO4:Er3+ (A = Zn, Mg)

Luminescence properties of olivine-type germanate phosphors with general formula Li2AGeO4:0.5Er3+ (A = Zn, Mg) have been studied. Olivine-type materials prepared via conventional solid-state reaction method were examined for down- and up-conversion luminescence processes. In the down-conversion process after 381 nm excitation, two strong green emission bands due to 2H11/2/4S3/2 → 4I15/2 transitions of Er3+ were registered, with a change in the intensity ratio depending on the ceramic matrix. Weak red emission bands related to 4F9/2 → 4I15/2 transition were also recorded. In contrast, luminescence bands behaved completely differently for the up-conversion process after infrared excitation at λexc = 980 nm. Red emission bands were much more significant than green emission bands. These effects are stronger for Li2MgGeO4:0.5Er3+ than Li2ZnGeO4:0.5Er3+. In the red and green spectral range, slope values for both matrices Li2AGeO4:0.5Er3+ (A = Zn, Mg) confirmed two-photon process.

Modulated upconversion luminescence of WO3: Yb3+/Ho3+ through non-equivalence substitution of Bi3+ ions

The upconversion luminescence (UCL) of inorganic materials doped with activators and sensitizers has great application, but its luminescence intensity always impose restrictions on its development. Herein, an obvious enhancement in luminescence intensity of the WO3: Yb3+, Ho3+ phosphor was realized through non-equivalence substitution of Bi3+ ions. The single pure phase of the synthesized WO3: Yb3+, Ho3+, and Bi3+ phosphors has been confirmed by the XRD pattern. The morphology of phosphors and valence state of elements have been performed by SEM and XPS techniques. The sample on excitation with 980 nm performs forceful green emission and weak red emission at 543 nm and 662 nm, separately. The concentrations for doped Yb3+ and Ho3+ to obtain the optimal UCL in WO3 are 8% and 1%, respectively. The optimized doping concentration for Bi3+ ions is 3%. Compared to samples without Bi3+ ions, the Yb3+/Ho3+/Bi3+ doped WO3 obtains 1.59 and 2.33 times increase in emission intensity of green and red, respectively. We also explored the UCL mechanism and enhancement mechanism on the basis of the power dependency, the UCL and the downshift luminescence. These results based on Yb3+/Ho3+ UCL phosphors research is of great significance.

Effect of Al Incorporation on the Structural and Optical Properties of Sol-Gel AZO Thin Films.

ZnO and Al-doped ZnO (AZO) thin films were prepared using the sol-gel method and deposited on a Silicon (Si(100)) substrate using the dipping technique. The structure, morphology, thickness, optical constants in the spectral range 300-1700 nm, bandgap (Eg) and photoluminescence (PL) properties of the films were analyzed using X-ray diffractometry (XRD), X-ray fluorescence (XRF), atomic force microscopy (AFM), scanning electron microscopy (SEM), spectroscopic ellipsometry (SE), Raman analysis and PL spectroscopy. The results of the structure and morphology analyses showed that the thin films are polycrystalline with a hexagonal wurtzite structure, as well as continuous and homogeneous. The PL background and broader peaks observable in the Raman spectra of the AZO film and the slight increase in the optical band gap of the AZO thin film, compared to undoped ZnO, highlight the effect of defects introduced into the ZnO lattice and an increase in the charge carrier density in the AZO film. The PL emission spectra of the AZO thin film showed a strong UV line corresponding to near-band-edge ZnO emission along with weak green and red emission bands due to deep-level defects, attributed to the oxygen-occupied zinc vacancies (OZn lattice defects).

Electrical, luminescent properties and electronic structure of (Ho, Nb) co-doped BNT-based multifunctional ceramics

The effects of (Ho, Nb) co-doping on the electrical, luminescent properties and electronic structure of Bi0.5(Na0.82K0.18)0.5Ti1-x(Ho0.5Nb0.5)xO3 (x = 0, 0.010, 0.015, 0.020, 0.025, and 0.030, abbreviated as BNKT-xHN) ceramics were investigated. XRD analysis showed that Ho3+ and Nb5+ ions completely entered the crystal structure of BNT-based ceramics, forming a stable perovskite structure. SEM confirmed the polycrystalline nature and relatively uniform grain structure of the samples. The doping of (Ho, Nb) destroyed the long-range ferroelectricity of BNT-based ceramics, resulting in the transition from ferroelectric phase to relaxor ferroelectric phase. The maximum unipolar strain of 0.32% was obtained by introducing (Ho, Nb) with a concentration of x = 0.020. Under excitation at 453 nm, a strong green emission peak appears at 550 nm, corresponding to the energy level transition of 5S2→5I8, while the weak red emission centered at 658 nm is due to the energy level transition from 5F5→5I8. As the amount of doping increases, the luminous intensity first increases and then decreases. The first-principle method based on density functional theory was used to calculate the energy band structure and density of the system states. The calculated results show that the band gap width (Eg) decreases with the increase of doping amount, and the electron cloud density distribution of the energy level orbit is very stable. Reducing the band gap makes it easier for electrons to absorb photon energy, which may explain the micro-mechanism of changing luminous intensity.

Structural and optical properties of composite phosphor Thx(MoO4)2/Bi2(1-x)Mo2O9; [formula omitted] doped with Ho3+/Yb3+ as a multifunctional materials

Composite phosphor’s, Thx(MoO4)2/Bi2(1-x)Mo2O9:2Ho3+/5Yb3+ have been synthesized cumulatively by facile co-precipitation process in ethylene glycol (EG) medium and subsequently placed for calcinations. Rietveld refinement of XRD patterns and FTIR analysis confirms the phase formation with a systematic variation of individual phases in dual-phase composite system [Th(MoO4)2-Orthorhombic; β-Bi2Mo2O9-Mononclinic]. Phase-dependent UV-Vis absorption of REs ions (Ho3+/Yb3+) has been observed and the difference between the optical bandgap of both phases leads to show the different aspect of the efficacy of optical properties. PL emission spectra of these phosphors show a strong green, relatively weak red and NIR emissions under λexci= 450 nm. The Yb3+ ions in the phosphor act as sensitizer and responsible for commencing the efficient UC emission, which shows nearly identical emission behavior under 980 nm excitation. Drastic changes in emission intensity (UC/DC) are observed with a relative dual-phase variation. Basically, the different crystal field scenarios around REs ions pertaining to both phases are responsible for the changes in emission intensity. The properties like dual-mode emission, phase dependent emission, color tuning properties, make them multifarious, that can be used for biological cell imaging, phototherapy, optical switching, display devices, solar cells, LEDs, etc.

Luminescence properties of Pr3+ doped high density germanate scintillating glasses for fast-event X-ray detection

Pr 3+ doped high density germanate glasses were prepared by the melt-quenching method. The physical and luminescent properties were investigated. The glass containing BaF 2 represented maximum phonon energy of 810 cm −1 , and the glass density was greater than 6 g/cm 3 . The glass exhibited good radiation resistance under 2 h of X-ray irradiation. Intense blue, green emissions and weak red emissions were observed when the glass was excited by X-ray, and the blue fluorescence lifetimes were in the range of 9.15–12.59 μs The results show that Pr 3+ doped germanate glass could be a potential scintillating material in the field of X-ray detection for fast events.

Sensitive Detection of BRCA1 Gene Based on Target Proximity Induced Quenching of the Fluorescence of Copper Nanoclusters

The mutations of breast cancer susceptibility gene 1 (BRCA1) play an important role in inherited breast cancers. Thus, the sensitive assay of the BRCA1 gene is extremely important for disease diagnosis and human health. Herein, a fast, sensitive and selective assay technique has been constructed based on fluorescent copper nanoclusters (CuNCs). The CuNCs were successfully formed with poly(AT-TA) double stranded DNA (dsDNA) as template. In the absence of the target, a strong red emission was observed under 365 nm ultraviolet (UV) lamp and a big fluorescence response was obtained. However, in the presence of BRCA1 gene, there was only weak red emission and a low response signal was produced because of the target-proximity induced quenching of the fluorescence of CuNCs. The linear range for the BRCA1 gene assay was 2-600 nM, and the limit of detection was 2 nM. The assay technique showed good selectivity, good stability and satisfactory recoveries for the detection of BRCA1 gene in diluted serum samples. Moreover, by integrating a UV lamp and a smartphone, the fluorescence sensor would be transferred to a microfluidic chip, providing a prospective application in point-of-care for monitoring breast cancer risk.

Different properties of two types of red fluorescent proteins in octocoral, Scleronephthya spp. as Akane families.

We report the different properties of two types of red fluorescent proteins (RFP), undescribed species, extracted from two octocorals, Scleronephthya sp. 1 (S. sp. 1) and S. sp, 2 (Alcyonacea, Nephtheidae). S. sp. 1, named Alc-Orange, emits strong green emission at 492 nm and weak red emission at 590 and 630 nm when excited at 449 and 574 nm, respectively. S. sp. 2, LS-Red, emits strong deep red at 642 nm and weak green at 480 and 510 nm when excited at 574 nm and 434 nm, respectively. LS-Red has a very large Stokes shift of about 208 nm emitting at 642 nm when excited at 434 nm. Interestingly, LS-Red shows some emissions at 480 (blue emission), 514 (green emission), 563 (orange emission), and 642 nm (deep red emission) continuously at pH 7.5, which means multicolored fluorescence protein by one excitation at 434 nm. In pH dependence of fluorescence of Alc-Orange (pH 13 to 3.5), no relation between 'green and red FPs' was observed, whereas LS-Red showed the interconversion between 'green and red forms' depending on pH (11.5 to 4.5).

Cr3+ ions improving the spectral properties of YAG: Ce3+ luminescent ceramics for white LD lighting

The lack of red light emission in Y3Al5O12:Ce3+ (YAG:Ce3+) luminescent ceramics has resulted in high color temperature and low color rendering index for solid state illumination, such as, LED or LD. Therefore, Y2.94Al5-xCrxO12:0.06Ce3+ (x = 0.004, 0.029, 0.054, 0.079, 0.104 mol) luminescent ceramics were prepared by vacuum sintering method. The doping of Cr3+ ions caused the weak red emission peaks between 675 nm and 720 nm, and the luminescence intensity of red light increased first and then decreased with the increase of Cr3+ ions doping content. The best doping concentration of Cr3+ ions is 0.054 mol. And in the co-doped system of ceramics, we confirmed the energy transfer from Ce3+ to Cr3+. YAG:Ce3+, Cr3+ series ceramics yielded a slight shift in color coordinates towards the red light area. Meanwhile, as the concentration of Cr3+ ions increasing, the color rendering index began to show an increasing trend with a maximum value of 79.4. The consequences display that Ce, Cr co-doped garnet luminescent ceramics are promising for red light supplementation and high CRI lighting applications of white LD.

Li+ aided self-activated [formula omitted] phosphors for efficient dual-mode emission and temperature sensing application

For the first time, lanthanide co-doped self-activated Ca9Y1−x−yErxYby(VO4)7 phosphors have been investigated for bearing dual-mode emission: downshifting and upconversion emission behavior. The Ca9Y1−x−yErxYby(VO4)7 phosphor, under 379 nm excitation evinces two bright green emission peaks at 525 nm and 553 nm, which corresponds to H11/22,S3/24→I15/24 transitions of Er3+ ion, this transition is sensitized by an efficient energy transfer from the (VO4)3− group to Er3+ ions. Irradiated with a 980 nm power tunable laser, it shows strong green and comparatively weak red emissions bands. The upconversion emission can be enhanced enormously with the introduction of Li+ ions in the optimized Ca9Y0.847Er0.003Yb0.15(VO4)7 phosphor. Furthermore, utilizing the well-known fluorescence intensity ratio (FIR) technique, optimized Ca9Y0.647Li0.20Er0.003Yb0.15(VO4)7 phosphor has been explored for optical temperature sensors also. The maximum absolute sensitivity and relative sensitivity are obtained to be 0.0125 K−1 at 513 K and 0.012 K−1 at 300 K, respectively. The acquired result reveals that the phosphor Ca9Y0.647Li0.20Er0.003Yb0.15(VO4)7 can be a worthy material for temperature sensing application.