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Er3+,Yb3+-doped oxyfluorotellurite glassesa??Impact of temperature on spectroscopic properties and optical sensor qualities
摘要： Oxyfluorotellurite glasses co-doped with erbium (0.5%) and ytterbium (2%, 5%) were manufactured from high purity reagents at 840 °C in air. Differential thermal analysis was used to estimate the temperatures of glass transition and glass crystallization of 2% and 5%Yb co-doped glasses. The effect of Yb3+ co-doping on relaxation dynamics of erbium excited states was demonstrated by the means of excitation, emission and fluorescence lifetime spectroscopy. Up-conversion luminescence spectra were studied in a function of temperature in the 295–675 K range, yielding information on thermal quenching of the emission and a temperature sensing model based on 2H11/2–4I15/2 to 4S3/2–4I15/2 erbium fluorescence intensity ratio. Application potential of the investigated material in optical sensor thermometry was evaluated. Maximum absolute and relative sensitivities were established at 6.45 × 10?3 K?1 at T = 675 K and 0.46 %K?1 at T = 400 K, respectively.
关键词： Oxyfluorotellurite glass,(Er3+,Yb3+) Upconversion,Temperature sensor
更新于2025-09-23 15:19:57
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Engineering Efficient Photon Upconversion in Semiconductor Heterostructures
摘要： Photon upconversion is a photophysical process in which two low-energy photons are converted into one high-energy photon. Photon upconversion has broad appeal for a range of applications from biomedical imaging and targeted drug-release to solar energy harvesting. Current upconversion nanosystems, including lanthanide-doped nanocrystals and triplet-triplet annihilation (TTA) molecules, have achieved upconversion quantum yields of order 10-30%. However, the performance of these materials is hampered by inherently narrow absorption cross-sections and fixed energy levels originating in atomic, ionic, or molecular states. Semiconductors, on the other hand, have inherently wide absorption cross-sections. Moreover, recent advances enable the synthesis of colloidal semiconductor nanoparticles with complex heterostructures that can control band alignments and tune optical properties. We synthesize and characterize a three-component heterostructure that successfully upconverts photons under continuous-wave (CW) illumination and solar-relevant photon fluxes. The heterostructure is composed of two cadmium selenide (CdSe) quantum dots (QDs), an absorber and emitter, spatially separated by a cadmium sulfide (CdS) nanorod (NR). We demonstrate that the principles of semiconductor heterostructure engineering can be applied to engineer improved upconversion efficiency. We first eliminate electron trap-states near the surface of the absorbing QD and then tailor the bandgap of the NR such that charge carriers are funneled to the emitting QD. When combined, these two changes result in a 100-fold improvement in photon upconversion performance.
关键词： solar energy,semiconductors,upconversion,coupled quantum dots,nanostructures,core/rod/emitter
更新于2025-09-23 15:19:57
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Engineering efficient upconverting nanothermometers using Eu <sup>3+</sup> ions
摘要： Upconversion nanothermometry combines the possibility of optically sensing temperatures in very small areas, such as microfluidic channels or on microelectronic chips, with a simple detection setup in the visible spectral range and reduced heat transfer after near-infrared (NIR) excitation. We propose a ratiometric strategy based on Eu3+ ion luminescence activated through upconversion processes. Yb3+ ions act as a sensitizer in the NIR region (980 nm), and energy is transferred to Tm3+ ions that in turn excite Eu3+ ions whose luminescence is shown to be thermally sensitive. Tridoped SrF2:Yb3+,Tm3+,Eu3+ nanoparticles (average size of 17 nm) show a relative thermal sensitivity of 1.1% K-1 at 25.0 °C, in the range of the best ones reported to date for Ln3+-based nanothermometers based on upconversion emission. The present nanoparticle design allows us to exploit upconversion of lanthanide ions that otherwise cannot be directly excited upon NIR excitation and that may provide operational wavelengths with a highly stable read out to fill the spectral gaps currently existing in upconversion-based nanothermometry.
关键词： nanothermometry,nanoparticles,upconversion,ratiometric strategy,lanthanide ions,Eu3+
更新于2025-09-19 17:15:36
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Bi <sub/>2</sub> SiO <sub/>5</sub> @g-SiO <sub/>2</sub> upconverting nanoparticles: a bismuth-driven core–shell self-assembly mechanism
摘要： Core–shell systems have attracted increasing interest among the research community in recent years due to their unique properties and structural features, and the development of new synthetic strategies is still a challenge. In this work, we have investigated lanthanide-doped Bi2SiO5 nanocrystal formation inside mesoporous silica nanoparticles (MSNs). The role of both synthesis temperature and concentration of the bismuth precursor impregnated into the MSNs is discussed, showing an unprecedented strategy for the simultaneous stabilization of a crystalline core and a glassy shell. Temperature dependent synchrotron radiation X-ray powder diffraction (SR-XRPD) and high resolution transmission electron microscopy (HR-TEM) analyses allow one to follow the crystalline core growth. A mechanism for the formation of a Bi2SiO5@g-SiO2 core–shell nanosystem is proposed. In addition, the easy tunability of the color output of the upconverting system is demonstrated by means of suitable doping lanthanide ions with potential applications in several fields.
关键词： upconversion luminescence,mesoporous silica,core–shell nanoparticles,bismuth silicate,Bi2SiO5
更新于2025-09-19 17:15:36
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Enhanced Conversion Process in a Sub-wavelength Thin Upconversion Layer by Using Metamaterial Mirror
摘要： Because of finite bandgap, useful spectral ranges of semiconductors are limited for photovoltaic applications. The upconversion (UC) process is one of alternatives to extend the useful spectral range by converting long wavelength photons to short wavelength photons. For example, NaYF4 codoped Yb3+/Er3+ converts photons from near-infrared (970 nm) to visible (660 nm). However, in the form of a thin layer on a flat metal mirror, which is a representative structure to add UC layer into photovoltaic devices, the UC material exhibits low efficiency in optical devices because of its low absorption and conversion efficiencies. In this paper, the UC process is highly enhanced by a metamaterial mirror consisting of grooved silver surfaces. The absorption of UC material is improved by a factor of 5.3 due to increased light-matter interaction because the electric field is highly concentrated in the UC layer near the metal surface. The surface plasmon polariton (SPP) modes induced by a dipole emitter to a metal grooved surface enhance the spontaneous emission (SE) rate of the emission wavelength of UC material by a factor of 65 compared with a thin UC layer on flat mirror. Consequently, total efficiency of the UC process is 400 times more enhanced than the reference structure by magnetic mirror property and SPP modes of metamaterial mirror.
关键词： Metamaterial,Upconversion,Thin film
更新于2025-09-19 17:15:36
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APTES modified GO-PEI-Er3+/Yb3+: NaYF4 Upconverting Nanoparticles Hybrid Film Based Optical pH Sensor and NIR Photoelectric Response
摘要： The APTES modified GO-PEI-Er3+/Yb3+: NaYF4 upconverting nanoparticles hybrid film has been developed. The developed films have been structurally and optically characterized. The upconversion (UC) emission based pH dependent study to sense pH upon excitation at 980 nm diode laser radiation has been performed. The UC emission intensity is significantly reduced for pH ~ 9 and explained due to strong interaction between graphene oxide and PEI-APTES-Er3+/Yb3+:NaYF4 UC NPs. The developed film is also found more sensitive to the urine as observed from the UC emission measurement. The developed film exhibits good repeatability and high stability. The UC emission intensity for both the green and red bands arising from the Er3+ ion in the developed film shows a decreasing trend with increase in pH values (pH range of 5-9). The photocurrent response of the developed films (i.e. film 2 and film 3) coated on FTO glass plate upon excitation at 980 nm laser radiation shows the increment in current values by ~ 17% and ~ 14% respectively when the pump power density of the excitation source reaches to 1.5 W/mm2.
关键词： pH sensor,Upconversion,Rare earth,Graphene oxide,Photoelectric response
更新于2025-09-19 17:15:36
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Enhanced upconversion and downshifting emissions from Tm3+, Yb3+ co-doped CaZrO3 phosphor in the presence of alkali ions (Li+, Na+ and K+)
摘要： The Tm3+, Yb3+ co-doped CaZrO3 phosphor samples have been synthesized through solid state reaction method in the absence and presence of alkali metal ions (i.e. Li+, Na+, K+). The X-ray diffraction (XRD) study shows the formation of CaZrO3 crystal with orthorhombic phase. The Tm3+, Yb3+ co-doped CaZrO3 phosphor emits intense upconversion emission in blue (474 nm) and NIR (799 nm) regions due to 1G4 → 3H6 and 3H4 → 3H6 transitions of Tm3+ ions, respectively on excitation with 980 nm radiation. The emission intensity is significantly enhanced in the presence of alkali ions due to charge compensation and asymmetry in the crystal field. The emission intensity in the case of Na+ co-doped phosphor is maximum and at 1 W pump power, it is increased by ~ 44 and ~ 31 times in blue and NIR regions, respectively as compared to without alkali ions co-doped phosphor. The downshifting emission in blue region has been observed due to oxygen vacancy and Tm3+ ions on excitation with 277 and 360 nm radiations which is enhanced significantly in the presence of alkali ions. Thus, the intense blue emission by this material is suitable for blue and white light emitting phosphors.
关键词： Calcium Zirconate,Downshifting,Alkali ions,Upconversion,Rare earth
更新于2025-09-19 17:15:36
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Near-infrared and upconversion luminescence of Tm3+ and Tm3+/Yb3+-doped oxyfluorosilicate glasses
摘要： Oxyfluorosilicate glasses-doped with different concentrations of Tm3+ and Tm3+/Yb3+ ions have been synthesized and characterized their absorption, photoluminescence, luminescence decay and upconversion properties. The Judd-Ofelt intensity parameters have been obtained from the absorption spectrum of Tm3+ single-doped glass and are in turn used to calculate radiative properties such as transition probabilities, branching ratios and lifetimes for the fluorescent levels of Tm3+ ions. Visible and near-infrared emission spectra of Tm3+ and Tm3+/Yb3+-doped glasses have been measured under 473 nm laser excitation. The quenching of emission intensities at higher concentrations of Tm3+ ions has been found to be due to cross-relaxation mechanisms. The Tm3+/Yb3+ co-doped glasses show upconverted emissions under 975 nm laser excitation. The mechanism of upconversion has been explained based on the pump power dependence of upconversion luminescence. The results reveal that the co-doped glasses are promising for optical fiber amplifiers operating at the relatively low-loss wavelength regions.
关键词： Glasses,Optical properties,1.2 μm emission,Upconversion,Judd-Ofelt theory,Tm3+ and Tm3+/Yb3+
更新于2025-09-19 17:15:36
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Enhanced UV-Vis-NIR activated photocatalytic activity from Fe <sup>3+</sup> -doped BiOBr:Yb <sup>3+</sup> /Er <sup>3+</sup> upconversion nanoplates: synergistic effect and mechanism insight
摘要： Upconversion (UC) materials are recognized as promising candidates to harvest solar energy for photocatalysis. In this work, a simple strategy for simultaneously enhancing the UC luminescence and photocatalytic efficiency of BiOBr:Yb3+/Er3+ nanoplates through Fe3+ ion doping is reported. Compared to the Fe3+-free sample, the UC emission intensity was significantly enhanced through tailoring of the crystal symmetry by Fe3+ ions. Experiment and DFT calculations reveal that the introduction of Fe3+ ions resulted in the formation of an impurity energy level, extending to the light absorption region. As expected, the Fe3+-doped BiOBr:Yb3+/Er3+ nanoplates exhibit a wide photoresponse from the UV to NIR regions, good stability, and obviously enhanced photocatalytic activities compared with the BiOBr:Yb3+/Er3+ nanoplates in the degradation of RhB. The boosted photocatalytic activity can be attributed to the synergic effect of the efficient utilization of UC luminescence and Fe3+ doping, where Fe3+ doping could improve the light harvesting capacity, enhance the separation efficiency of electron and hole (e?/h+) pairs, and promote the production of highly oxidative species. This work not only provides a promising system for the efficient utilization of solar light, but also offers a feasible guideline for the further design of broad-spectrum active photocatalysts.
关键词： Enhanced UV-Vis-NIR activated photocatalytic activity,mechanism insight,Fe3+-doped BiOBr:Yb3+/Er3+ upconversion nanoplates,synergistic effect
更新于2025-09-19 17:15:36
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Real-time naked-eye recognizable temperature monitoring based on Ho <sup>3+</sup> (or Tm <sup>3+</sup> )-activated NaYF <sub/>4</sub> upconversion nanowires <i>via</i> visual multicolor alteration
摘要： Non-contact thermometry for real-time temperature monitoring is a challenging research topic. Advances in microelectronics and biotechnology demand precise temperature monitoring with novel materials and approaches, where conventional thermometers are burdensome because of employing expensive additional equipment (e.g. spectrometers) and further data processing. Lanthanide-doped upconversion nanomaterials that can convert single near-infrared excitation into multicolor visible emissions open the door for a novel strategy to thermometry. Herein, a real-time naked-eye recognizable color change was achieved based on Ho3+ (or Tm3+)-activated NaYF4 upconversion nanowires, depending on the different spectral sensitivities of the blue, green and red upconversion emissions to temperature. Furthermore, the luminescence color can be also directly modulated by only using 975 nm laser radiation, which extended their application scope. These desirable properties make upconversion nanomaterials promising for temperature monitoring, anti-counterfeiting, and multicolor temperature probing applications with the advantages of being simple, convenient and unreplicable.
关键词： nanowires,naked-eye recognizable,upconversion,temperature monitoring,multicolor alteration
更新于2025-09-19 17:15:36