Downconversion Emission Research Articles

Calcination-assisted hydrothermal crystallization and comparative up-/down-conversion luminescence of RE3+ (RE=Ho, Er and Tm)-doped YbNbO4 and Yb3NbO7

The RE3+ doped YbNbO4 and Yb3NbO7 nanophosphors (RE=Ho, Er and Tm) were synthesized via a calcination-assisted hydrothermal procedure. YbNbO4 intensified almost the whole up-conversion (UC)/down-conversion (DC) emissions of RE3+ by ∼2 times when compared with Yb3NbO7 components, indicating that a lower symmetry environment in the former case is more favorable for photoluminescence. UC luminescence in each case was dominated by a green band at ∼539 nm for Ho3+ and a NIR band at ∼803 nm for Tm3+, while doping YbNbO4 and Yb3NbO7 with Er3+ separately yielded the slightly stronger green 556 nm and red 658 nm emissions. The UC/DC luminescence mechanisms were elaborated via Yb3+ → RE3+ forward/backward energy transfer and cross relaxation.

Fluoride Hafnium/Zirconium-Softened Nanoprobes for Near-Infrared-IIb and CT Dual-Mode Bioimaging.

Fluoride-based lanthanide-doped nanoparticles (LDNPs) featuring second near-infrared (NIR-II, 1000-1700 nm) downconversion emission for bioimaging have attracted extensive attention. However, conventional LDNPs cannot be degraded and eliminated from organisms because of an inert lattice, which obstructs bioimaging applications. Herein, the core-shell LDNPs of Na3HfF7:Yb,Er@CaF2:Ce,Zr(Hf) [labeled as Zr(Hf)Ce-HC] with pH-selective and tunable degradability were synthesized for dual-modal bioimaging. Notably, the "softening" lattice of the Na3HfF7 matrix and different Zr4+(Hf4+) doping amounts in the shell enable Zr(Hf)Ce-HC with acidity-dependent and tunable degradability. After coating of an optimized Ce3+-doped CaF2:Zr shell, the near-infrared-IIb (NIR-IIb, 1500-1700 nm) luminescence intensity of ZrCe-HC is enhanced by 5.2 times compared with that of Na3HfF7:Yb,Er. The Hf element with high X-ray attenuation allows ZrCe-HC as the contrast agent for computed tomography (CT) bioimaging. The modification of oxidized sodium alginate endows ZrCe-HC with satisfying biocompatibility for NIR-IIb/CT dual-modal bioimaging. These findings would benefit the bioimaging applications of degradable fluoride-based LDNPs.

A bright Ce-based downshifting luminescence nanoprobe for NIR-IIb vessel imaging

Nanomaterials with unique emission in the second near-infrared window (NIR-II, 1000–1700 nm) are regarded as the promising probes for visualization of tumor vessels and cerebrovascular architecture, because of their superior features such as deep tissue penetration and large imaging resolution. Herein, the new Ce-based fluoride nanoparticles (NPs) with high-efficiency NIR-IIb emission were explored for high-resolution vascular imaging and tumor associated vessel detection. Under the same synthesis conditions, the Ce-based fluoride present the preferential formation CeF3 host and low upconversion (UC) emission, but possess more strong (1.45 times) NIR-IIb downconversion (DC) emission centered at 1525 nm under the irradiation of a 980 nm laser, which is significantly different from the traditional NaYF4:Yb/Er host. Through the efficient cross relaxation between Ce3+ and Er3+, intense NIR-IIb luminescence from Er3+ with high quantum yields were achieved, which make sure the entire mouse body and brain blood vessel imaging with supernal resolution (47.6 μm) were demonstrated. Moreover, the optical imaging in NIR-IIb region guided tumorous vascular visualization was successfully achieved. Therefore, the explored CeF3 NPs with boosting NIR-IIb emission can be employed as new diagnostic bio-probes used in high spatial resolution tumorous vessel detection.

Influence of Yb3+/Ho3+ codoping on optical and thermal properties of TeO2-ZnO glass

This paper reports the effect of incorporation of Yb3+ ions on the frequency downconversion luminescence and thermal properties of triply ionised Ho3+ doped zinc tellurite (TZ) glasses. The photoluminescence spectra of both the Ho3+/Yb3+ doped and codoped glasses have been recorded and observed a green emission band corresponding to the 5F4, 5S2 → 5I8 (∼550 nm) transition upon various excitations. In the downconversion (DC) emission process, the back energy transfer (BET) mechanism from Ho3+ ions to Yb3+ ions has also been explored. The colour emitted in the downconversion process is found to be non-tunable at different excitations. Thus, the Ho3+:TZ glass can be utilised for non-colour tunable optical devices under various UV excitations. Also the glass transition (Tg) and crystallisation (Tc) temperatures have been measured for both the doped and codoped glasses and found to be increased in the codoped glass. The singly Ho3+ions doped TZ glass shows better optical downconversion and glass forming ability.

Nd3+-sensitized multilayered rare-earth nanocrystals with enhanced NIR-IIb luminescence for high resolution optical imaging

Luminescence imaging in the second near-infrared (NIR-II) window, particularly within the NIR-IIb (1500–1700 nm) sub-window, has been utilized for both fundamental research and clinical applications due to its exceptional spatiotemporal resolution. Nevertheless, efficient contrast agents designed for NIR-IIb imaging are still scarce. Herein, a multilayered rare-earth nanocrystal (NaYF4:Yb,Er,Ce@NaYF4:Yb,Nd@NaYF4) with strong NIR-IIb luminescence was designed and synthesized. The doping of Ce3+ ions in the core effectively suppresses the upconversion and boosts the downconversion luminescence by populating the Er 4I13/2 level. Additionally, by separating the sensitizer (Nd3+) and the activator (Er3+) in different layers, we are able to maximize the light absorption around 800 nm and reduce the cross relaxations between rare-earth elements, which leads to a strong downconversion emission around 1530 nm under 808 nm excitation. After passivation with NaYF4 shell and phase transfer with highly PEGylated mesoporous silica layer, the nanocomposites with excellent colloidal stability and bright NIR-IIb emission were obtained. With long blood circulation time in vivo, the fabricated nanocomposites enable high resolution and contrast luminescence imaging of the blood vessels and tumors in living mice. Moreover, the rare-earth nanocrystals with superior optical properties also hold great promise for various applications in optical sensing and biomedical imaging.

Up-converted white light emission in Er3+ doped MgAl2O4 nanocrystals

This work presents the influence of host defect centers on the photoluminescence characteristics of Mg1−xErxAl2O4 (x = 0.005, 0.01, and 0.03) nanocrystals under UV and near-infrared (NIR) excitations. The spinel-structured nanocrystals are synthesized through the combustion method. The Rietveld refinement and nuclear magnetic resonance analyses estimated the Er3+ ion occupancy at octahedral and other random sites of the MgAl2O4 lattice, and the existence of various lattice defects. Diffuse reflectance spectra showed broad bands attributed to oxygen vacancies as well as antisite defects and sharp peaks attributed to f–f transitions of Er3+ ions. The upconversion luminescence spectra consisted of sharp emission lines, ascribed to Er3+ ions, in the green and red wavelength regions, which overlapped over the broad curve attributed to intrinsic defects. Further, the UV excited downconversion luminescence spectra showed two broad emission bands in blue–violet and red-NIR regions with a very weak Er3+ ion emission feature. This up- and downconversion emission revealed energy transfer between host and Er3+ ions via intrinsic defects. As a result, the emission color changes from bluish purple to white by varying the excitation wavelength from UV to NIR. This rare earth activated luminescence from MgAl2O4 nanocrystals would exhibit potential applications in display devices and solid-state lighting.

Spectral properties of transverse Laguerre-Gauss modes in parametric down-conversion

The first color photos of the parametric down-conversion (PDC) emission cone illustrate the correlation of longitudinal and transverse momentum in the process, i.e., wavelength-dependent emission angles of PDC photons. However, current experiments and applications are more conveniently described in terms of discrete mode sets, with the most suitable choice depending on the propagation symmetries of the experimental setting. Remarkably, despite the fact that experiments with PDC sources are becoming ever more demanding, e.g., in terms of brightness or state fidelity, a description of spectral-spatial coupling in parametric down-conversion for the case of discrete modal decompositions remains elusive. We present a comprehensive study, in theory and experiment, of the spectral dependence of the transverse Laguerre-Gauss modes in parametric down-conversion. Moreover, we show how the spectral and spatial coupling can be harnessed to tune the purity of the well-known orbital angular momentum entanglement. This paper has implications for efficient collection of entangled photons in a transverse single mode, quantum imaging, and engineering pure states for high-dimensional quantum information processing. Published by the American Physical Society 2024

Intense green up/down conversion emission and high-sensitivity optical thermometry of NaYb(WO4)2:Er3+ stoichiometric phosphors

Optical thermometry based on fluorescence intensity ratio (FIR) has garnered significant interest among researchers due to its rapid, non-contact, and high sensitivity characteristics. In this study, stoichiometric NaYb(WO4)2 phosphors, doped with varying concentrations of Er3+, were successfully synthesized using the high-temperature solid-state method. Under both 980 nm and 266 nm excitation, the samples exhibited strong green and very weak red upconversion (UC) and downconversion (DC) luminescence. The structural and morphological properties of the prepared samples were thoroughly characterized using techniques such as X-ray diffraction (XRD), XRD Rietveld refinement, scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) spectroscopy. The phosphors demonstrated high-purity UC and DC emission, with maximum green-to-red ratios of 60.9 and 77.0, respectively. This discovery opens up vast possibilities for their application as pure green color converters. The UC emission of Er3+ ions in the stoichiometric NaYb(WO4)2 phosphor was identified as a two-photon UC process, as evidenced by the relationship between the luminescence intensity and the excitation power of the sample. Moreover, the temperature-dependent emission spectra of UC and DC were monitored, and investigated the fluorescence intensity ratios (FIRs) of 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions of Er3+ ions to assess the optical temperature sensing behavior of NaYb(WO4)2:Er3+. The experimental results revealed that the maximum absolute sensitivities (SA) of NaYb(WO4)2 phosphors were 0.0120 K-1 (UC) and 0.0077 K-1 (DC), and the maximum relative sensitivities (SR) were 0.0089 K-1 (UC) and 0.0092 K-1 (DC), respectively. These findings highlight the promising of Er3+-doped Yb3+ stoichiometric NaYb(WO4)2 phosphors in optical temperature sensors.

Enhancement of luminescence properties of Sm3+ doped tellurite glass embedded with gold nanoparticles: Heat treatment

Various compositions of tellurite glasses doped with samarium ions embedded with gold nanoparticles are prepared by the melt quenching method, the chemical glass compositions 78.6TeO2-20Na2O-1Sm2O3-0.4AuCl3 are heat-treated at different annealing time and temperature. The absorption spectra reveal nine transitions. The surface plasmon resonance was detected at two bands located at ∼ 552 nm and ∼ 595 nm, which are observed from the absorption spectrum. The down-conversion emission under excitation 404 nm showed four emission transitions from the 4G5/2 state to 6H5/2, H7/2, 6H9/2, and 6H11/2. The green and red emission intensity is enhanced due to the formation of the Au NPs along the annealing time and temperature process. At 325 °C heat treatment, the emission intensities of the glass samples increased by a factor of 1.88:1.33:1.54:2.16 corresponding to the emissions transitions, respectively. Transmission electron microscopy (TEM) image of the sample at 325 °C heat treatment, confirmed the existence of Au nanoparticles with a size of ∼ 11.25 nm. The cromacity diagram shows the highest color purity (CP) values TSNA-6 glass sample which is 99.684 %.Results indicate the favorable of tellurite glass nanocomposites for developing nanophotonics applications.

Down-conversion emission of Er3+ doped sulfophosphate glass: The role of TiO2 and Ag nanoparticles co-embedment

In this study, Er3+-doped sulfophosphate glasses containing titanium nanoparticles (TiO2 NPs) with 0.0, 0.01, 0.02, 0.03, 0.04, and 0.05 mol% of silver (Ag) nanoparticles (AgNPs) were synthesized using the melt-quenching technique. The impact of AgNPs on the physical and structural characteristics, optical absorption and emission features, and photocatalytic activity of the glasses were investigated. The density and molar volume of the glasses were determined. Transmission electron microscopy (TEM) was used to study the existence of both AgNPs and TiO2 NPs in the glass matrix. The absorption spectra of the glasses revealed several bands of absorption in the UV–Vis–NIR region, with peaks at 1534, 977, 795, 650, 544, 520, 487, 450, 406, 378, and 364 nm. The SPR peaks of silver were observed at 553 and 588 nm, while those of TiO2 NPs were located around 409 and 849 nm. The intensity of emission was found to be enhanced by increasing the concentration of AgNPs. According to the findings of Judd-Ofelt theory, the system containing of 0.04 mol% of AgNPs has also the optimal performance which can be applied to the function of a broadband amplifier by having a high emission cross section of 70.18 × 10−22 cm2. Finally, the photocatalytic performance of the glasses was evaluated by conducting a degradation experiment with methylene blue (MB). The results validated their light-activated self-cleaning properties in the presence of Ag/TiO2 NPs.

A NIR Programmable In Vivo miRNA Magnifier for NIR‐II Imaging of Early Stage Cancer

AbstractAberrant expressions of biomolecules occur much earlier than tumor visualized size and morphology change, but their common measurement strategies such as biopsy suffer from invasive sampling process. In vivo imaging of slight biomolecule expression difference is urgently needed for early cancer detection. Fluorescence of rare earth nanoparticles (RENPs) in second near‐infrared (NIR‐II) region makes them appropriate tool for in vivo imaging. However, the incapacity to couple with signal amplification strategies, especially programmable signal amplification strategies, limited their application in lowly expressed biomarkers imaging. Here we develop a 980/808 nm NIR programmed in vivo microRNAs (miRNAs) magnifier by conjugating activatable DNAzyme walker set to RENPs, which achieves more effective NIR‐II imaging of early stage tumor than size monitoring imaging technique. Dye FD1080 (FD1080) modified substrate DNA quenches NIR‐II downconversion emission of RENPs under 808 nm excitation. The miRNA recognition region in DNAzyme walker is sealed by a photo‐cleavable strand to avoid “false positive” signal in systemic circulation. Upconversion emission of RENPs under 980 nm irradiation activates DNAzyme walker for miRNA recognition and amplifies NIR‐II fluorescence recovery of RENPs via DNAzyme catalytic reaction to achieve in vivo miRNA imaging. This strategy demonstrates good application potential in the field of early cancer detection.

A NIR Programmable In Vivo miRNA Magnifier for NIR-II Imaging of Early Stage Cancer.

Aberrant expressions of biomolecules occur much earlier than tumor visualized size and morphology change, but their common measurement strategies such as biopsy suffer from invasive sampling process. In vivo imaging of slight biomolecule expression difference is urgently needed for early cancer detection. Fluorescence of rare earth nanoparticles (RENPs) in second near-infrared (NIR-II) region makes them appropriate tool for in vivo imaging. However, the incapacity to couple with signal amplification strategies, especially programmable signal amplification strategies, limited their application in lowly expressed biomarkers imaging. Here we develop a 980/808 nm NIR programmed in vivo microRNAs (miRNAs) magnifier by conjugating activatable DNAzyme walker set to RENPs, which achieves more effective NIR-II imaging of early stage tumor than size monitoring imaging technique. Dye FD1080 (FD1080) modified substrate DNA quenches NIR-II downconversion emission of RENPs under 808 nm excitation. The miRNA recognition region in DNAzyme walker is sealed by a photo-cleavable strand to avoid "false positive" signal in systemic circulation. Upconversion emission of RENPs under 980 nm irradiation activates DNAzyme walker for miRNA recognition and amplifies NIR-II fluorescence recovery of RENPs via DNAzyme catalytic reaction to achieve in vivo miRNA imaging. This strategy demonstrates good application potential in the field of early cancer detection.

Effect of Ag nanoparticles growth on the downconversion emissions of erbium in TeO2-Nb2O5-ZnO-Ag2O glass system

TeO2 based glasses containing silver and doped by erbium ions were synthesized via the melting-quenching process. These glasses were subjected to an annealing treatment during different times above the glass temperature transition Tg. Transmission electron microscope (TEM) and X-ray diffraction (XRD) revealed the growth of silver nanoparticles inside the tellurite glass host. Raman analysis was conducted to examine the structural characteristics of the glass systems and to detect any effects brought by the heat-treatment. Using 488 nm excitation, the down-conversion luminescence properties of erbium ions were studied and the processes implicated in the near-infrared emission (NIR) at 1530 nm were analysed. It was found that the heat-treatment enhanced the Raman signal and the downconversion emission of Er3+ ions. Especially, annealing for long time (at 440°C) resulted in an improvement of NIR emission intensity to the detriment of green emissions, as well as a considerable enhancement in the quantum yield and measured lifetime of the 1530 nm emission. The results indicate that the proposed glasses could be appropriate down-converting materials for improving the spectral response of some photovoltaic (PV) cells having bandgaps in the range 0.7–0.9eV.

In situ synthesis of polychromic up/down-conversion carbon dots/YF3 composites for information encryption and security

Polychromic up/down-conversion emissions in carbon dots (CDs) system play a key role in advanced information encryption and security. However, it is difficult to simultaneously achieve tunable up/down-conversion emissions in CDs system owing to the difficulty in preparation of red down-conversion emission and the poor absorption of CDs to near-infrared excitation sources. Herein, red fluorescence (FL) and room-temperature phosphorescence (RTP) emissions are obtained by establishing energy transfer processes from blue CDs to the Eu3+/Mn2+. Color-tunable upconversion luminescence (UCL) is achieved by in situ preparation process of rare-earth (Er3+/Yb3+, Tm3+/Yb3+, and Tm3+/Er3+) co-doped YF3 upconversion nanoparticles on CDs/boric acid composites. Based on the mold-filling, deposition, handwriting and screen-printing methods, various stable security patterns and characters composed of multicolor emissions of FL, UCL and RTP by switching excitation wavelength and external thermal stimulation, showing great potential for information encryption and security. This work paves the way for the color conversion of FL, RTP and UCL in CDs system and the construction of advanced information encryption and security technologies.

Structure, morphology, photonconversion and energy transfer characteristics of Er3+/Yb3+:BaYF5 nanocrystals synthesized by hydrothermal method for photovoltaics

Lanthanide doped nanocrystalline fluoride optical materials have been explored for diverse applications in the solar energy harvesting, industry, medical, forensic and biological fields because of high photoluminescence quantum yield and low phonon energy. In this manuscript, Er3+/Yb3+:BaYF5 nanocrystals were synthesized by hydrothermal process. These nanocrystals were investigated through X-ray diffraction (XRD), SEM/TEM, Raman, quantum yield, photoluminescence upconversion (UC) and downconversion (DC) studies. XRD patterns exhibited the cubic phase and no phase deviation with the addition of Er3+ and Yb3+ ions. The TEM images illustrate the cubic-like morphologies of the obtained nanocrystals. Raman spectrum unveils the characteristic vibrational bands with an intense band at 498 cm−1, which is considered the phonon energy of the BaYF5 matrix. Under 488 nm excitation, the near infrared (NIR) emission of Er3+ increases up to 5 mol% and then decreases for a 10 mol% doped sample. Photoluminescence DC quantum yield of Er3+/Yb3+:BaYF5 sample is measured by using integrating sphere in the visible region under 488 nm (Xe flash lamp) excitation, is 4.25%. Under 900 nm laser excitation, intense NIR emissions at 978 and 1550 nm corresponding to Yb3+ (2F5/2 → 2F7/2) and Er3+ (4I13/2 → 4I15/2) ions, respectively, were observed. With the increase of Yb3+ concentration, the NIR emissions of both Er3+ and Yb3+ increase to 5 mol% and then decrease to 10 mol%. The strength of green UC emission of Er3+ decreases with increase of Er3+ concentration, whereas it enhances with the rise of Yb3+ concentration under 980 nm laser excitation. Two-photon UC process is confirmed as the slopes of the green, and red intensities are 2 and 2. These nanocrystals exhibit intense UC and DC emissions under 980 nm and 480 nm, respectively, which can be suitable for improving the efficiency of solar cells.

Rare earth ions doped Bi2MoO6 luminescent materials: Pechini sol-gel synthesis, down-conversion and up-conversion multicolor emissions, and potential applications

A series of rare earth ions (Eu3+, Sm3+, Yb3+/Er3+, Yb3+/Ho3+, Yb3+/Tm3+) doped bismuth molybdate (Bi2MoO6) phosphors with excellent multicolor luminescence have been synthesized by a facile Pechini sol-gel method. XRD, EDX, and XPS results confirm the highly crystalline orthorhombic phase of Bi2MoO6 and verify that the rare earth ions (RE3+) are effectively integrated into the Bi2MoO6 matrix. During the synthesis process, the calcination conditions play an important role in obtaining the luminescent host matrix, and the optimal calcination condition for the Bi2MoO6 products is determined of 800 °C for 2 h. The Eu3+ and Sm3+ doped Bi2MoO6 samples display intense red and orange-red light under UV/visible excitation whereas the Yb3+/Ln3+ (Ln = Er, Ho, and Tm) doped Bi2MoO6 materials emit green, green, and blue colors when excited by NIR light. Both down-conversion (DC) and up-conversion (UC) multicolor luminescence are obtained by doping the proper Ln3+ activators into the Bi2MoO6 host. The doping concentrations of various RE3+ ions are optimized to generate advantageous phosphors and the luminescence mechanisms of RE3+ ions are systematically studied. The LED devices fabricated by Bi2MoO6:Yb3+/Ln3+ UC phosphors exhibit dazzling multicolor emissions under an injection current, which directly discloses that the as-prepared materials may be of great potential in LEDs and optoelectronic devices. Interestingly, the Bi2MoO6:Yb3+/Er3+/Eu3+ phosphors can simultaneously exhibit red and yellow-green DC emissions and green UC light under excitation of 464, 488, and 980 nm. The multi-mode emission features illustrate that the as-synthesized phosphors may have application prospects in anti-counterfeiting applications.

Enhanced green up/down-conversion emissions through phase transformation in Ho3+/Yb3+ co-doped Y2O3:ZrO2 phosphors in presence of Na+ ions

This study reports the intense green upconversion and downconversion emissions from Ho3+/Yb3+/Na+ co-doped Y2O3:ZrO2 phosphor prepared by traditional solid-state reaction technique for fixed concentration of Ho3+/Yb3+ ions and different concentrations of Na+ ion. The phosphor samples exhibit a multiphase crystalline structure in the absence of Na+ ions. However, with co-doping of Na+ ions (at 20 mol%), it almost turns into Y4Zr3O12 with single rhombohedral phase. When Na + ions are present in the sample, the SEM image reveals a growth in particle size. The UV–Vis–NIR measurements show an enhancement in the absorbance of doped REs ions (Ho3+/Yb3+) on Na+ co-doping. The Ho3+/Yb3+ co-doped Y2O3:ZrO2 phosphor shows an intense green upconversion (UC) emission at 549 nm due to Ho3+ ions on the excitation with 980 nm radiation. In the presence of Na + ions, a modification of the crystallinity, growth in crystallite size (particle size) and an increase in the asymmetry of the crystalline structure around the REs ions led to an enhancement in the intensity of the UC emission almost about ∼8.5 times. The Log-Log plot demonstrates the involvement of two photons in the UC process. The lifetime of the 5F4/5S2 level decreases with increasing the concentration of Na + ion. Thus, the prepared phosphor could be an excellent candidate for source of green light, finger printing, optoelectronic devices etc.

Visible DC approach by controlling the UV light in (Eu3+/Tb3+) co-activated TBZN glasses for w-LEDs and a-Si solar cells

Borotellurite (TBZN: TeO2–B2O3–ZnO–Na2O) glasses co-activated with Eu3+ and Tb3+ ions were fabricated by a melt quenching method to know their ability for white light sources and solar converters. Amorphous nature, morphology, elemental mapping of the chemical composition, and functional groups of glasses were investigated. The down conversion (DC) process was studied on the luminescence characteristics of Eu3+/Tb3+ co-activated TBZN glasses by ultraviolet light (UV:351 & 378 nm) conversion and these glasses exhibit the characteristic red (5D0→7F1,2,3,4) luminescence of Eu3+ along with green (5D4→7F5) and blue (5D4→7F6) luminescence of Tb3+ ions in the visible region. Upon 378 nm of UV radiation, the co-activating of Tb3+ with Eu3+ ions improves the green and red DC emissions by 2 and 4 orders of magnitude due to energy transfer (ET) from Eu3+ to Tb3+, respectively. The evidence of ET: Eu3+ → Tb3+ is stated by the declining of red emission (%) and decay times from the 5D0 level of Eu3+ ions, and the reduction in decay times was confirmed to be dipole-dipole interaction in the means of Reisfeld and Dexter's ET process. The solar spectral performance of the excitation and de-excitation spectra of (Eu3+/Tb3+):TBZN glass system is imparted with the standard solar spectrum. Results are also discussed in terms of integrated intensity of red to green emission in (%), critical transfer distance (Rc), (x, y) color coordinates, correlated color temperatures (CCT), color purity (CP), and quantum efficiency (ηQE) values to discriminate the potentiality of (Eu3+/Tb3+):TBZN glass system in white light emitting diodes and solar cells.

Enhanced piezoelectricity and non-contact optical temperature sensing performance in Er3+ ion modified (K,Na)NbO3-based multifunctional ceramics

Rare earth ions doped ferroelectrics have attracted wide attentions due to their multifunction characteristics with both ferroelectric/piezoelectric properties and intriguing photoluminescence performance, which show great prospects for future multifunctional devices. In this work, a novel rare earth Er3+ ion modified potassium-sodium niobate (KNN) based ceramics were elaborately designed and prepared by the conventional solid-state reaction. The microstructure, phase structure, electric properties and photoluminescence performance of the Er3+ ion modified KNN-based ceramics were systematically investigated. Enhanced piezoelectricity (a considerable d33 of exceeding 300 pC/N and a large d33* up to 500 p.m./V) was realized through optimizing the substitution of BaZrO3 by (Er0.5,Na0.5)ZrO3. Both down-conversion and up-conversion photoluminescence emissions were detected in the optimal composition. The temperature-dependent upconversion emissions of the optimal Er3+ modified ceramic sample in the temperature range of 303–573K were verified to be applicable for non-contact optical temperature sensing with a maximum sensitivity Sa of 0.0028 K-1 and a peak relative sensitivity Sr of 0.96% K−1. Moreover, low-temperature sensing performance with a maximum Sr of 16.7% K−1 in the temperature range of 80–280K was also presented based on the temperature-dependent down-conversion emissions. With both decent electrical properties and intriguing photoluminescence performance, the Er3+-modified KNN-based ferroelectrics exhibit good application potential in the future multifunctional optoelectronic devices.

Optimized core-shell lanthanide nanoparticles with ultrabright Ce3+-modulated second near-infrared emission for "lighting" plants.

Second near-infrared (NIR-II, 1000-1700 nm) photon-mediated fluorescence imaging has attracted extensive interest in the field of bioimaging. However, NIR-II fluorescent nanoprobes competent for plant imaging have been rarely developed. Herein, lanthanide-doped nanoparticle (LDNP) optimal core-shell structure and ultrabright NIR-II emission were developed for "lighting" plants. The Ce3+-doped active shell coated on the NaErF4:Tm core enables dual-mode red upconversion (UC) and NIR-II downconversion (DC) emission of LDNPs upon 980 nm laser excitation. Under the optimized doping content, the intensities of red UC and NIR-II DC emission were respectively boosted by 5- and 19-fold those of the core nanoparticles, which endowed LDNPs with ideal NIR-II emissive capabilities for optical imaging of plants. Significantly, the NIR-II fluorescent signal affords much higher signal-to-noise rate than the red UC. LDNPs were modified with polyethyleneimine to enable outstanding hydrophilicty and facilitate their uptake by plants. Arabidopsis thaliana and Nicotiana benthamiana were chosen as plant models for NIR-II imaging studies. The toxic effect of LDNPs after being transported into Brassica rapa chinensis was systematically studied on mice. The NIR-II imaging strategy offers a promising method for studying the uptake and transport of nanoparticles in plants.