Decay Lifetime Research Articles

Key Components Degradation in Proton Exchange Membrane Fuel Cells: Unraveling Mechanisms through Accelerated Durability Testing

In the process of promoting the commercialization of proton exchange membrane fuel cells, the long-term durability of the fuel cell has become a key consideration. While existing durability tests are critical for assessing cell performance, they are often time-consuming and do not quickly reflect the impact of actual operating conditions on the cell. In this study, improved testing protocols were utilized to solve this problem, which is designed to shorten the testing cycle and evaluate the degradation of the cell performance under real operating conditions more efficiently. Accelerated durability analysis for evaluating the MEA lifetime and performance decay process was carried out through two testing protocols—open circuit voltage (OCV)-based accelerated durability testing (ADT) and relative humidity (RH) cycling-based ADT. OCV-based ADT revealed that degradation owes to a combined mechanical and chemical process. RH cycling-based ADT shows that degradation comes from a mainly mechanical process. In situ fluoride release rate technology was employed to elucidate the degradation of the proton exchange membrane during the ADT. It was found that the proton exchange membrane suffered more serious damage under OCV-based ADT. The loss of F− after the durability test was up to 3.50 × 10−4 mol/L, which was 4.3 times that of the RH cycling-based ADT. In addition, the RH cycling-based ADT had a significant effect on the catalyst layer, and the electrochemically active surface area decreased by 48.6% at the end of the ADT. Moreover, it was observed that the agglomeration of the catalysts was more obvious than that of OCV-based ADT by transmission electron microscopy. It is worth noting that both testing protocols have no obvious influence on the gas diffusion layer, and the contact angle of gas diffusion layers does not change significantly. These findings contribute to understanding the degradation behavior of proton exchange membrane fuel cells under different working conditions, and also provide a scientific basis for developing more effective testing protocols.

Spectra and decay properties of higher lying BC meson states

In this work, the spectra and decay properties of [Formula: see text] mesons [Formula: see text]) have been investigated using a nonrelativistic potential model incorporating corrections from LQCD. The nonrelativistic Schrödinger wave equation is solved numerically using the Matrix Numerov Method. Using the obtained masses and wave functions, decay widths, lifetime, branching ratios and radiative decay widths are computed for the [Formula: see text] system. Influence of the bound state effect on decay width of [Formula: see text] mesons is also analyzed. We compare the obtained results with the experimental data and with other theoretical models.

Generation of singlet oxygen inside living cells: correlation between phosphorescence decay lifetime, localization and outcome of photodynamic action

Photodynamic therapy (PDT) is a promising alternative treatment for localized lesions and infections, utilizing reactive oxygen species (ROS) generated by photosensitizers (PS) upon light activation. Singlet oxygen (1O2) is a key ROS responsible for photodynamic damage. However, the effectiveness of PS in biological systems may not correlate with the efficiency of singlet oxygen generation in homogeneous solutions. This study investigated singlet oxygen generation and its decay in various cellular microenvironments using liposome and ARPE-19 cell models. Rose Bengal (RB), methylene blue (MB), and protoporphyrin IX (PpIX) were employed as selected PS. Lifetimes of singlet oxygen generated by the selected photosensitizers in different cellular compartments varied, indicating different quenching rates with singlet oxygen. RB, located near cell membranes, exhibited the highest phototoxicity and lipid/protein peroxidation, followed by PpIX, while MB showed minimal cytotoxicity in similar conditions. Singlet oxygen decay lifetimes provide insights into PS localization and potential phototoxicity, highlighting the importance of the lipid microenvironment in PDT efficacy, providing useful screening method prior to in vivo applications.Graphical abstract

The highly efficient and stable near-infrared phosphor Ca3MgSnGe3O12: Cr3+ for multifunctional application

The investigation of efficient and stable near-infrared (NIR) luminescent materials is crucial for rapidly developing near-infrared spectroscopic techniques. Herein, NIR phosphors Ca3MgSnGe3O12: Cr3+ with ultra thermal stability and high internal quantum yield (IQY) are explored. The emission intensity remained at 91.75 %@423 K of room temperature and the IQY/EQE reaches 91.41 %/34.04 % after doping the H3BO3 flux agent for optimization. Moreover, a single luminescence center was identified by cryogenic photo luminescence spectroscopy (PL) from 4 K to 300 K and lifetime decay curve. Importantly, NIR light can easily removes all kinds of background interference that cannot be easily eliminated by visible light, which is not only widely used in night vision and biological tissue penetration, but also has higher application prospects in NIR fingerprint detection. Moreover, it clearly displays high level of fingerprint details under high temperature conditions and after water immersion, thus it is perfectly suited for using in Automatic Fingerprint Identification System (AFIS) systems. Therefore, Ca3MgSnGe3O12: Cr3+ NIR pc-LEDs have great potential for latent fingerprint detection at actual crime scenes.

Synthesis and photoluminescent spectroscopic analysis of lanthanum (III) coordinated with 1,10-Phenanthroline: A study of its thermally stable behavior

A blue-emitting phosphor designed by lanthanum (III) coordinated with two 1,10-Phenanthroline and three nitrate ligands, [La(Phen)2(NO3)3], was obtained by an effective and simple precipitation method. Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffraction (PXRD) revealed the coordination modes in the compound and the chemical structure, crystallizing in a monoclinic system in the C2/c space group. The luminescence properties, absolute quantum yield (ϕ), and luminescence lifetime decay (τ) were determined by photoluminescence spectroscopy. Under a 350 nm excitation, the sample presents three emission bands corresponding to the π* → π transitions belonging to the organic ligand. The luminescence lifetime (τ) was determined through a monoexponentially fit, obtaining a value of 5616 ns. The [La(Phen)2(NO3)3] complex exhibits an absolute quantum yield of 3 % with the same excitation conditions. In addition, the photometric analysis shows that the luminescent response to a 350 nm excitation is that of a blue-emitting high-purity phosphor with 96 % and chromatic coordinates of 0.15, 0.05. The temperature-dependent luminescence properties revealed considerable thermal stability in the 20–150 °C range with a signal loss of 47 % and an activation energy of thermal quenching (ΔE) of 0.13 eV, the first value reported for a lanthanum complex based on 1,10-Phenanthroline.

Hard X-ray nanoprobe to study the emission properties of Ce-doped YAG wafer by using XEOL and TR-XEOL

In this study, the valent state, emission properties, and decay lifetime of Ce-doped yttrium aluminum garnet (Y3Al5O12, YAG) wafer have been probed using X-ray absorption (XAS), X-ray excited optical luminescence (XEOL), and time-resolved XEOL (TR-XEOL). The XAS spectrum demonstrates that Ce ions are in the trivalent state, and the XEOL spectrum exhibits typical 5 d1-4f1(2F5/2) and 5 d1-4f1(2F7/2) transitions of Ce3+ ions, with emission peaks at ∼528 nm and 582 nm, respectively. From the TR-XEOL measurements, the decay lifetimes of 5 d1-4f1(2F5/2) and 5 d1-4f1(2F7/2) transitions are about ∼90 ns and ∼100 ns, respectively. We found that the reabsorption effects will not only make the 5 d1-4f1(2F7/2) transitions have longer decay lifetime, but also the higher emission intensity. By comparison with photoluminescence (PL) and time-resolved PL using a pulsed laser at 375 nm, we found that the emission spectra and decay lifetime of Ce-doped YAG (111) wafer are different when using X-ray irradiation. The longer decay lifetime measured by TR-XEOL compared TR-PL are caused by high X-ray dose irradiation. In addition, high X-ray doses provided by the nano-focus X-ray beam will be influenced the emission behaviors of Ce-doped YAG (111) wafer. Which phenomena have been demonstrated by using time-dependent XEOL with irradiation for 10 h. These peculiar emission behaviors observed with a hard X-ray nanoprobe may be able to provide important information on quantum technologies and scintillators used in hard X-ray detectors.

Influence of Pr3+ co-doping on the luminescent properties of CGA:2 at.% Ho single crystal fibers

Ho3+, Pr3+ co-doped CaGdAlO4 (Ho,Pr:CGA) crystal fibers were successfully grown by the micro-pulling-down (μ-PD) technique for the first time. Detailed investigations were conducted on the polarized absorption spectra, fluorescence spectra, and lifetime decay curves. The 2 at.% Ho, 0.4 at.% Pr:CGA crystal fiber exhibits a broad absorption band at 1147 nm with full width at half maximum (FWHM) of 25.5 nm and 64.5 nm for σ and π polarization, respectively. Increasing the concentration of Pr3+ led to a decrease in emission intensity at 2001 nm and an increase in emission intensity at 2861 nm. The FWHMs of the crystal fiber containing 2 at.% Ho and 0.4 at.% Pr:CGA at 2861 nm were 44.5 nm for σ polarization and 24.3 nm for π polarization. Additionally, the lifetime ratio (5I7/5I6) decreases from 25.18 to 2.85 in the crystal fibers containing 2 at.% Ho:CGA and 2 at.% Ho, 0.4 at.% Pr:CGA, respectively. These findings suggest that the presence of deactivated Pr3+ ions can significantly reduce the lifetime gap between the 5I6 and 5I7 energy levels, potentially mitigating the self-termination phenomenon on the ∼3 μm emission.

Hybrid metal halide family with color-time-dual-resolved phosphorescence for multiplexed information security applications

Luminescent materials with engineered optical properties play an important role in anti-counterfeiting and information security technology. However, conventional luminescent coding is limited by fluorescence color or intensity, and high-level multi-dimensional luminescent encryption technology remains a critically challenging goal in different scenarios. To improve the encoding capacity, we present an optical multiplexing concept by synchronously manipulating the emission color and decay lifetimes of room-temperature phosphorescence materials at molecular level. Herein, we devise a family of zero-dimensional (0D) hybrid metal halides by combining organic phosphonium cations and metal halide tetrahedral anions as independent luminescent centers, which display blue phosphorescence and green persistent afterglow with the highest quantum yields of 39.9 % and 57.3 %, respectively. Significantly, the luminescence lifetime can be fine-tuned in the range of 0.0968–0.5046 μs and 33.46–125.61 ms as temporary time coding through precisely controlling the heavy atomic effect and inter-molecular interactions. As a consequence, synchronous blue phosphorescence and green afterglow are integrated into one 0D halide platform with adjustable emission lifetime acting as color- and time-resolved dual RTP materials, which realize the multiple applications in high-level anti-counterfeiting and information storage. The color-lifetime-dual-resolved encoding ability greatly broadens the scope of luminescent halide materials for optical multiplexing applications.

Cu-Fe bimetallic MOFs with long lifetime separated-state charge for enhancing selectivity for CO2 photoreduction to CH4

Improving the CO2 to CH4 conversion efficiency of Cu metal-organic frameworks (Cu-MOFs) catalysts is important for promoting carbon capture and utilization. In this work, a series of novel Cu-Fe bimetallic MOFs photocatalysts (Cu-BTB-Fe with 0.5 wt%, 1.0 wt%, 2.0 wt%, and 4.0 wt% of Fe; H3BTB = 1,3,5-tris(4-carboxyphenyl) benzene) were synthesized by a bimetallic site (Cu and Fe) design strategy in order to improve the electron-hole separation efficiency and CO2 adsorption activation. Findings indicated that the as-synthesized Cu-BTB-2 wt% Fe catalyst exhibited excellent catalytic performance for the conversion of CO2 to CH4 and CO under simulated sunlight irradiation, providing a yield of 32.20 μmol∙g−1∙h−1 and a selectivity of 69.24 % for CO2 to CH4 conversion as well as a yield of 14.29 μmol∙g−1∙h−1 for CO2 to CO conversion without liquid phase products. This is because the Cu-Fe bimetallic sites can continuously supply photoinduced electrons with long separated-state decay lifetime to efficiently activate CO2. Specifically, the Cu-BTB-Fe catalysts provided a high proportion of effective photoinduced electrons with long decay lifetime for the CO* hydrogenation process through a unique electron transfer mechanism, while the strong affinity between CO2 and [Cu2(COO)4]-Fe active units enabled high CO2 adsorption activation and rapid CO2 reduction. The present approach, hopefully, would help to establish feasible pathway for the development of novel highly selective Cu-based MOFs photocatalysts for CO2 photocatalytic reduction yielding CH4.

Modulating Interfacial Properties in Pseudoternary Microemulsions via Urea Addition: Impact of Cosurfactant on the Reverse Micellar Structure and Interactions.

We have studied the structural and interfacial properties of CTAB/isooctane/alcohol/aqueous urea reverse micelles (RMs) for the first time using time-resolved fluorescence and small-angle X-ray scattering techniques. The chain length of alcohol, used as cosurfactant, has been varied to design three microemulsion systems: CTAB/1-butanol, CTAB/1-hexanol, and CTAB/1-octanol/isooctane/water, at a fixed water loading ratio, w0 = 12. Time-resolved fluorescence anisotropy studies indicate that urea induces micellar aggregation in CTAB/1-butanol and CTAB/1-hexanol RMs but breaks down RM aggregates in CTAB/1-octanol RMs. Urea addition slows down solvation dynamics inside RMs at higher urea concentrations, evident from the longer lifetimes of solvent correlation decay. The underlying changes in microemulsion structure and intermicellar interactions are studied using small-angle X-ray scattering studies. The significant intermicellar interactions were modeled using the sticky hard sphere (SHS) for the CTAB/1-butanol and CTAB/1-hexanol RMs and by using the Macroion model for the CTAB/1-octanol RMs. The two different structural factors highlight the dominance of attractive and repulsive forces, respectively. Although there is no change in RM shape, the combination of urea addition and chain length variation in cosurfactants significantly alters the size and interface in these pseudoternary RMs.

Ln3+ Induced Thermally Activated Delayed Fluorescence of Chiral Heterometallic Clusters Ln2Ag28.

A series of TADF-active compounds: 0D chiral Ln-Ag(I) clusters L-/D-Ln2Ag28-0D (Ln=Eu/Gd) and 2D chiral Ln-Ag(I) cluster-based frameworks L-/D-Ln2Ag28-2D (Ln=Gd) has been synthesized. Atomic-level structural analysis showed that the chiral Ag(I) cluster units {Ag14S12} in L-/D-Ln2Ag28-0D and L-/D-Ln2Ag28-2D exhibited similar configurations, linked by varying numbers of [Ln(H2O)x]3+ (x=6 for 0D, x=3 for 2D) to form the final target compounds. Temperature-dependent emission spectra and decay lifetimes measurement demonstrated the presence of TADF in L-Ln2Ag28-0D (Ln=Eu/Gd) and L-Gd2Ag28-2D. Experimentally, the remarkable TADF properties primarily originated from {Ag14S12} moieties in these compounds. Notably, {Ag14S12} in L-Eu2Ag28-0D and L-Gd2Ag28-2D displayed higher promote fluorescence rate and shorter TADF decay times than L-Gd2Ag28-0D. Combined with theoretical calculations, it was determined that the TADF behaviors of {Ag14S12} cluster units were induced by 4 f perturbation of Ln3+ ions. Specially, while maintaining ΔE(S1-T1) small enough, it can significantly increase k(S1→S0) and reduce TADF decay time by adjusting the type or number of Ln3+ ions, thus achieving the purpose of improving TADF for cluster-based luminescent materials.

Ln3+ Induced Thermally Activated Delayed Fluorescence of Chiral Heterometallic Clusters Ln2Ag28

AbstractA series of TADF‐active compounds: 0D chiral Ln−Ag(I) clusters L‐/D‐Ln2Ag28‐0D (Ln=Eu/Gd) and 2D chiral Ln−Ag(I) cluster‐based frameworks L‐/D‐Ln2Ag28‐2D (Ln=Gd) has been synthesized. Atomic‐level structural analysis showed that the chiral Ag(I) cluster units {Ag14S12} in L‐/D‐Ln2Ag28‐0D and L‐/D‐Ln2Ag28‐2D exhibited similar configurations, linked by varying numbers of [Ln(H2O)x]3+ (x=6 for 0D, x=3 for 2D) to form the final target compounds. Temperature‐dependent emission spectra and decay lifetimes measurement demonstrated the presence of TADF in L‐Ln2Ag28‐0D (Ln=Eu/Gd) and L‐Gd2Ag28‐2D. Experimentally, the remarkable TADF properties primarily originated from {Ag14S12} moieties in these compounds. Notably, {Ag14S12} in L‐Eu2Ag28‐0D and L‐Gd2Ag28‐2D displayed higher promote fluorescence rate and shorter TADF decay times than L‐Gd2Ag28‐0D. Combined with theoretical calculations, it was determined that the TADF behaviors of {Ag14S12} cluster units were induced by 4 f perturbation of Ln3+ ions. Specially, while maintaining ΔE(S1–T1) small enough, it can significantly increase k(S1→S0) and reduce TADF decay time by adjusting the type or number of Ln3+ ions, thus achieving the purpose of improving TADF for cluster‐based luminescent materials.

Elucidating the Mechanism of Efficient Eu(III) and Yb(III) Sensitisation from a Re(I) Tetrazolato Triangular Assembly.

The reaction of Re(CO)5Br with deprotonated 1H-(5-(2,2':6',2''-terpyridine)pyrid-2-yl)tetrazole yields a triangular assembly formed by tricarbonyl Re(I) vertices. Photophysical measurements reveal blue-green emission with a maximum at 520 nm, 32 % quantum yield, and 2430 ns long-lived excited state decay lifetime in deaerated dichloromethane solution. Coordination of lanthanoid ions to the terpyridine units red-shifts the emission to 570 nm and also reveals efficient (90 %) and fast sensitisation of both Eu(III) and Yb(III) at room temperature, with a similar rate constant kET on the order of 107 s-1. Efficient sensitisation of Eu(III) from Re(I) is unprecedented, especially when considering the close proximity in energy between the donor and acceptor excited states. On the other hand, comparative measurements at 77 K reveal that energy transfer to Yb(III) is two orders of magnitude slower than that to Eu(III). A two-step mechanism of sensitisation is therefore proposed, whereby the rate-determining step is a thermally activated energy transfer step between the Re(I) centre and the terpyridine functionality, followed by rapid energy transfer to the respective Ln(III) excited states. At 77 K, the direct Re(I) to Eu(III) energy transfer seems to proceed via a ligand-mediated superexchange Dexter-type mechanism.

Mechanical Tuning of Fluorescence Lifetime and Bandgap in an Elastically Flexible Molecular Semiconductor Crystal.

Despite having superior transport properties, lack of mechanical flexibility is a major drawback of crystalline molecular semiconductors as compared to their polymer analogues. Here single crystals of an organic semiconductor are reported that are not only flexible but exhibit systematic tuning of bandgaps, fluorescence lifetime, and emission wavelengths upon elastically bending. Spatially resolved fluorescence lifetime imaging and confocal fluorescence microscopy reveals systematic trends in the lifetime decay across the bent crystal region along with shifts in the emission wavelength. From the outer arc to the inner arc of the bent crystal, a significant decrease in the lifetime of ≈1.9ns is observed, with a gradual bathochromic shift of ≈10nm in the emission wavelength. For the crystal having a bandgap of 2.73eV, the directional stress arising from bending leads to molecular reorientation effects and variations in the extent of intermolecular interactions- which are correlated to the lowering of bandgap and the evolution of the projected density of states. The systematic changes in the interactions quantified using electron density topological analysis in the compressed inner arc and elongated outer arc region are correlated to the non-radiative decay processes, thus rationalizing the tuning of fluorescence lifetime.

One- and Two-Photon Photophysical Properties, Ultrafast Dynamics, and DFT Study of Three Modified Zinc Phthalocyanines.

As two-photon absorption (TPA) materials, phthalocyanine molecules have promising application prospects due to their large TPA absorption cross-section, high third-order nonlinear optical susceptibility, and ultrafast response characteristics. In this work, optical properties and the ultrafast response of three modified zinc phthalocyanine molecules (P-HPcZn, Pc-P-Pc, and (DR1)4PcZn) were analyzed. No obvious side-shoulder absorption peaks in the Q-band can be observed from the steady-state absorption spectra of the three molecules, confirming the lack of aggregation products in the solutions of our measurement. Open-aperture Z-scan results show relatively large TPA cross-section values of 136.4 and 55.3 GM for Pc-P-Pc and (DR1)4PcZn, respectively. The nonlinear optical results show that the absorption process observed under the excitation of femtosecond pulses is a reverse saturable absorption (RSA) mechanism. Up-conversion fluorescence spectra of (DR1)4PcZn in THF solution indicate that the fluorescence emission mechanism is TPA. In the study of ultrafast dynamics, the transient absorption spectra were investigated and the decay lifetime of the dynamic traces corresponding to some representative probe wavelengths was obtained through data fitting with a multi-exponential function. Finally, the charge transfer and excited state properties of the modified zinc phthalocyanine molecules were discussed in depth by the DFT method. The energy gaps of P-HPcZn, Pc-P-Pc, and (DR1)4PcZn are 2.16, 1.39, and 2.13 eV, respectively. The results indicate that the Pc-P-Pc of donor-acceptor-donor (D-A-D) structure has the smallest energy gap as well as the best charge transfer properties.

AIE-active large Stokes-shift BODIPY Functionalized with Carbazolyl for Lysosome-Targeted Imaging in Living Cells

A large number of studies have shown that lysosomal microcircumstances changes can affect many physiological and pathological processes at the cellular level. However, the visual detection of lysosomal microcircumstances is relatively difficult due to low pH (4.5–6.0) value in lysosomal that require the probe not only stable under acidic condition but also has a good localization effect to lysosomal. Obviously, novel fluorescent which possessed both acidic stability and lysosomal-target property together with lysosomal viscosity active is highly demanded. Herein, a novel BODIPY molecular CarBDP based on carbazole group was rationally designed and synthesized for the lysosomal imaging. CarBDP exhibited AIE feature with a large Stokes shift of up to 157 nm. More importantly, co-localization assay of the CarBDP-treated MCF-7 cells indicated that CarBDP has a good localization effect on lysosomal (Rr = 0.7109) due to the carbazole group while the normal BODIPY that without carbazole group (PhBDP) shows poor localization performance, this was the first time that a small molecule can locate lysosomes only based on carbazole group. CarBDP exhibits strong solid emission with long fluorescence decay lifetime (τ = 44.54 ns) and was stable under acid condition.The probe CarBDP assembled with carbazole group was successfully utilized for lysosomal localization and mapping lysosomal viscosity in live cells, which provides a novel candidate tool for the determination of lysosomal microcircumstances.

Dazzling red-emitting Ca2EuMO6 (M = Sb, Nb, Ta) double-perovskite phosphors with potential application in phosphor-converted white light-emitting diodes

In this paper, three new efficient Eu3+-activated Ca2EuMO6 (M = Sb, Nb, and Ta) red-emitting phosphors with outstanding luminescence properties were prepared by using the high-temperature solid-state reaction method. X-ray diffraction and Rietveld refinements revealed the double-perovskite structure of Ca2EuMO6 (M = Sb, Nb, and Ta) compounds. Photoluminescent excitation and emission spectra, decay lifetimes, CIE chromaticity coordinates, color purity values, internal quantum efficiency, and thermal stability were discussed in detail. Under the excitation of 395 nm near-ultraviolet light, these Ca2EuMO6 (M = Sb, Nb, and Ta) phosphors demonstrated bright narrow-band red emissions with peaks at 592, 620, 656, and 703 nm due to the 5D0→7FJ (J = 1–4) transitions of Eu3+ ions. The internal quantum efficiencies of the Ca2EuSbO6, Ca2EuNbO6, and Ca2EuTaO6 samples were determined to be 39.3%, 41.6%, and 40.4%, respectively. Impressively, the emission intensity of Ca2EuNbO6 is about 1.25 times higher than that of commercial Y2O3:Eu3+ red phosphor. CIE color coordinates of Ca2EuMO6 (M = Sb, Nb, and Ta) phosphors were calculated to be (0.6748, 0.3250), (0.6800, 0.3198), and (0.6790, 0.3208), respectively; along with high color purity of 90.7%, 93.2%, and 92.7%. Besides, their thermal stability was also investigated, and the corresponding emission intensities of Ca2EuMO6 (M = Sb, Nb, and Ta) at 423 K were respectively maintained at 73%, 86%, and 80% of that at 303 K. All results show that these newly developed red-emitting Ca2EuMO6 (M = Sb, Nb, and Ta) phosphors possess potential applications in white light-emitting diodes.

Innovative approach to tailoring upconversion luminescence in Yb3+/Eu3+ doped CaZrO3 perovskite host matrix

This study presents the synthesis and characterization of upconverter nanostructures consisting of a perovskite host matrix, CaZrO3, co-doped with trivalent ytterbium (Yb3+) and europium (Eu3+), denoted as CaZrO3:Yb3+/Eu3+. Single-doped CaZrO3:Eu3+ samples were excited using a 394 nm UV source, while CaZrO3:Yb3+/Eu3+ samples were excited with a 980 nm diode laser source. Yb3+ ions efficiently absorb the 980 nm light and transfer the absorbed energy to the nearby ion Eu3+ ions, leading to the emission of visible light around 590, 614, and 655 nm, respectively. The emission spectra of Eu3+ ions exhibit an initial increase with increasing Yb3+ concentration, peaking at 7 mol%, followed by a decrease due to luminescence quenching. The decay lifetime of Eu3+ ions under 300 nm excitation decreases simultaneously with increasing Yb3+ concentration, indicating energy migration between Yb3+ and Eu3+. Detailed explanations of the energy transfer mechanism between Yb3+ and Eu3+ ions are provided, supported by equations and diagrams. This study provides valuable insights into the optimization of dopant concentrations for enhancing upconversion luminescence in CaZrO3:Yb3+/Eu3+ nanostructures, with 3 mol% Eu3+ concentration identified as optimal based on preliminary experiments. The findings presented in this paper contribute to the understanding of energy transfer processes in luminescence upconversion materials and highlight the potential of CaZrO3:Yb3+/Eu3+ nanostructures for applications in lighting, displays, and bio-imaging. This work represents a significant advancement in the field of upconversion luminescence emission, particularly in the utilization of CaZrO3 codoped with Yb3+ and Eu3+, and lays the foundation for further research in this area.

Up-Conversion Luminescence and Optical Temperature Sensing Properties of NaLuF4:Yb3+/Ho3+ Micron-Sized Crystals at Low Temperature.

Non-contact temperature sensors utilising the fluorescence intensity ratio and the unique up-conversion (UC) luminescence of rare-earth ions have numerous benefits; however, their operational temperature range has remained limited. In this study, NaLuF4:Yb3+/Ho3+ samples were prepared by the hydrothermal method. The samples exhibited exceptional UC luminescence properties at low temperatures. The intensity of the green emission (with peak wavelengths of 540 and 546 nm) gradually decreased with increasing temperature, and the green emissions showed a unique change at low temperatures. In addition, we studied the dependence of the UC luminescence intensity on the excitation power and the variation in the decay lifetime with temperature. The experiments revealed excellent luminous performance and significantly enhanced sensitivity at low temperatures; the maximum absolute sensitivity Sa and relative sensitivity Sr of the 540 and 546 nm thermally coupled energy levels were 1.02% and 0.55% K-1, respectively. The potential temperature sensing properties of Yb3+/Ho3+-co-doped NaLuF4 makes it suitable for temperature sensing applications at temperatures as low as 30 K. This study offers a novel approach for the advancement of temperature sensing technology at low temperatures.

Copper Iodide Hybrid with Unique Cu3I3 Trimeric Inorganic Functional Unit and Far‐red/Near‐infrared Emission

AbstractIn this paper, a neutral copper iodide hybrid with unique Cu3I3 trimeric inorganic functional unit is successfully fabricated using 5,6,7,8‐tetrahydroquinoxaline (L) with large steric‐hindrance group as the organic ligand. The hybrid owns a one‐dimensional (1D) extended polymeric structure in the form of Cu3I3(L)2. As a CuI‐based hybrid, 1D‐Cu3I3(L)2 has an infrequent far‐red/near‐infrared emission, exhibiting the potential application prospects in the field of display and night vision. Moreover, the luminescence mechanism is carefully studied by decay lifetime measurement and calculation of density of states, which is verified to be the combination of metal‐to‐ligand charge transfer and halide‐to‐ligand charge transfer.