Intensity Decay Curves Research Articles

Luminescence properties and thermal stability of Dy3+/Eu3+co-doped single-component BaZn2(PO4)2 glass-ceramic phosphors

Highly thermally stable BaZn2(PO4)2: Dy3+/Eu3+ glass-ceramic (GC) phosphors were synthesized using a high-temperature solid-state reaction and controlled-temperature pre-crystallization method. It is found that Dy3+-doped BaZn2(PO4)2 GC phosphors produce cold white light emission at 484 nm and 575 nm under 350 nm excitation with the optimal Dy3+ doping concentration of 0.25 mol%. The theoretical analysis indicates that the dipole-dipole interaction might be the origin of the concentration quenching mechanism of phosphor. The Eu3+-doped BaZn2(PO4)2 GC phosphors produce orange-red emission at 592, 616, 654 and 700 nm under 395 nm excitation. More than that, tunable white light emission can be achieved by optimize the co-doped concentration of Eu3+ on BaZn2(PO4)2: 0.25Dy3+ GC phosphor. The emission spectral intensity and luminescence decay curves from BaZn2(PO4)2: 0.25Dy3+/yEu3+ (range of y) GC phosphors show the energy transfer from Dy3+ to Eu3+ and the emission color can be tuned from cool white to warm white region with the color correlated temperatures (CCTs) reduction from 7299 K to 2520 K. The typical BaZn2(PO4)2: 0.25Dy3+/1Eu3+ GC phosphors have a high thermal stability with an activation energy of 0.30641 eV. Finally, the white LED devices were fabricated by coupling a 363 nm UV light-emitting diode chip with the BaZn2(PO4)2: 0.25Dy3+/yEu3+ GC phosphors. These results suggest that BaZn2(PO4)2: Dy3+/Eu3+ GC phosphors may be suitable candidates for single-component white light-emitting phosphors for application in UV-WLEDs.

Study on Urban Spatial Function Mixture and Individual Activity Space From the Perspectives of Resident Activity

The research on the relationship between residents’ daily activities and urban spatial structure is of considerable significance to urban planning engineering and the organization of urban functions. However, little research considers the perspective of micro-spatial scale or resident perception. The increasing user-generated activity check-in data in social networks provides a database for this research. In this study, we first divided the urban space into nine functions that satisfy the residents’ activities, then used the small-scale grid to divide the city blocks and used information entropy to evaluate the mixed degree of land use functions. We then introduced the latent Dirichlet allocation (LDA) topic model to identify 15 mixed patterns of land use functions and each spatial unit’s topic distribution. Moreover, the JS divergence index was employed to measure spatial units’ similarity, fit the distance-activity intensity decay curve, and studied the influence of the individual spatial function distribution choice. We demonstrate that in urban space, residents’ daily activities mold the blending of urban area functions and shift single-function urban planning to mixed-use, consisting of single-function dominant and multi-function mixed. Besides, the functional complementarity between the activity units weakens the distance attenuation effect of the activity-space interaction intensity to some extent. The research on the interaction between active space and spatial activities expect to support the combination of urban land use types, the layout of facilities, and the guidance of residents’ activities.

Optical thermometry based on upconversion luminescence of Yb3+-Er3+ and Yb3+-Ho3+ doped Y6WO12 phosphors.

The Yb3+-Er3+ and Yb3+-Ho3+ co-doped Y6WO12 (YWO) luminescent materials were synthesized successfully using the solid-state reaction method, and their phase purity, upconversion (UC) spectra, and optical temperature sensing properties were studied. Upon 980nm excitation, the dominant emission peak around 660nm is found in the YWO:Yb3+,Er3+ sample, which could be attributed to the Er3+F49/2-I415/2 electronic transition. Two green emission peaks of Er3+ appear in the range from 515-575nm. For the YWO:Yb3+,Ho3+ phosphor, there are three emission peaks found at 548, 667, and 758nm, which can be ascribed to the (F45,S52)-I58, F55-I58, and (F45,S52)-I57 transitions of Ho3+, respectively. By studying the emission intensity dependence of the pumping power, the result suggests that the two-photon process is involved for all the above emissions. In the temperature range of 293-553K, the temperature sensing behavior of the typical YWO:10%Yb3+,1%Er3+ and YWO:10%Yb3+,1%Ho3+ phosphors was investigated in detail, and the results have been shown by using the fluorescence intensity ratio technique and decay curves. The above investigations indicate that the present UC phosphors could be promising phosphor materials for temperature sensor.

Ramsey interferometry of Rydberg ensembles inside microwave cavities

We study ensembles of Rydberg atoms in a confined electromagnetic environment such as is provided by a microwave cavity. The competition between standard free space Ising type and cavity-mediated interactions leads to the emergence of different regimes where the particle−particle couplings range from the typical van der Waals r−6 behavior to r−3 and to r-independence. We apply a Ramsey spectroscopic technique to map the two-body interactions into a characteristic signal such as intensity and contrast decay curves. As opposed to previous treatments requiring high-densities for considerable contrast and phase decay (Takei et al 2016 Nat. Comms. 7 13449; Sommer et al 2016 Phys. Rev. A 94 053607), the cavity scenario can exhibit similar behavior at much lower densities.

A soft chemistry-based route to enhanced photoluminescence of terbium ions and tin oxide nanocrystals codoped silica thin films

Tb3+ ions and SnO2 nanocrystals (NCs) codoped silica films are fabricated by a soft chemistry-based approach. Via precise adjustment of Sn amounts in precursors, the size and number density of SnO2 NCs can be well controlled by a restrictive crystallization process. The characteristic emission intensity of Tb3+ ions at 541 nm can be greatly enhanced by two orders of magnitude if sensitized by SnO2 NCs with optimized size and number density. Photoluminescence excitation spectra of the films containing different Sn amounts indicate the non-radiative energy transfer process that takes place between Tb3+ ions and surface of SnO2 NCs. The photoluminescence intensity decay curves suggest two kinds of possible occurrence states of Tb3+ ions in codoped samples. All these results suggest the SnO2 NCs represent ideal sensitizers to effectively promote photoluminescence efficiency of Tb3+ ions. Particularly, the soft chemistry-based method reported here is very flexible for the fabrication of rare earth ions doped amorphous thin films, permitting the precise control of size and number density of NCs as sensitizers. We anticipate this fabrication strategy greatly enriches the techniques for the preparation of thin films, providing great promise for the realization of on-chip integration of silica-based optical lasers and amplifiers.

Phase evolution and photoluminescence in Er3+ doped glass ceramics containing lutetium oxyfluoride nanocrystals

Crystalline phase evolution through merely adjusting composition was achieved in silicate glass ceramics containing LunOn-1Fn+2 (n = 5–10) nanocrystals. Orthorhombic or cubic phase nanocrystals were precipitated in the aluminosilicate glass matrix after thermal treatment together with varying the Na2O/NaF ratio. Oxyfluoride nanocrystals with quasi-spherical shape show homogenous and dense distribution in glass matrix by transmission electron microscopy measurement. Intense upconversion and mid-infrared emissions were realized in these glass ceramics compared to the precursor glass, and the emission spectral shapes, relative emission intensity and fluorescence decay curves of Er3+ in cubic LuOF embedded samples exhibit remarkable differences due to the crystal phase dependent effect in glass ceramics. These results indicate that the crystallization and luminescence properties of oxyfluoride glass ceramics could be modified through the alteration of glass composition, which could be used for the development of novel glass ceramics and design of luminescent properties.

Neurotoxic Side Effects of Calcineurin Inhibitors in Patients After Liver Transplantation: Preliminary Results of a Quantitative MRI Study of the Brain

Background: Calcineurin inhibitors (CNI) are the most often used immunosuppressive drugs for the prevention of graft rejection after liver transplantation (LT). Long-term CNI treatment, however, is associated with cardiovascular disease and renal dysfunction. Considering the high frequency of neurotoxic side effects during the first weeks after treatment onset, long-term effects upon brain tissue structure and brain function must be expected. Aiming to estimate the long-term influence of CNI on cerebral microstructure and function after LT we carried out this quantitative MR study. Methods: Ninety patients (mean age: 58 ± 8) with a history of at least 3 years after liver transplantation were studied. They were divided into three groups according to their medication of the last two years: 23 patients without CNI, 36 patients with reduced dose of CNI (stable tacrolimus blood trough levels below 5 μg/l or stable cyclosporine A blood trough levels below 50 μg/l) and 31 patients with standard dose of CNI. Four patients were excluded due to incomplete examinations or artefacts. Thirty-two healthy gender- and age-adjusted volunteers served as reference group. All subjects underwent neuropsychological testing with the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) and MR examinations at 3 T (Verio, Siemens, Erlangen). The MR protocol included a T1 weighted GRE with 2 flip angles, a T2 weighted TSE with three echoes, a T2* weighted GRE with triple TE. Quantitative T1, relative proton density (PD, in ratio to water phantom), T2 and T2* maps were obtained on-the-fly on the MR system with an extended image reconstruction provided by the manufacturer, using monoexponential fitting to the signal intensity decay curves of the T1 GRE, T2 TSE and T2 GRE sequences, respectively, for region of interest (ROI) measurements, which were made in 18 ROIs located in cerebellum, brainstem, and cerebral gray and white matter. One-way ANOVA with Bonferroni corrected post hoc tests (α = 0.05) were used to compare the qMRI data and Kruskal–Wallis test to compare the RBANS scores between groups. Results: RBANS scores revealed that patients receiving CNI owned a significantly worse visuospatial/constructional ability, and patients with low dose CNI an overall impaired cognitive function compared to controls. qMRI revealed significant microstructural changes, especially in frontal white matter, with higher PD and T2 (CNI free) and higher T2* (CNI free and low dose), indicating increased free water (PD and T2) and reduced metabolism (T2*) within brain tissue of these patients compared to controls. Interestingly, little change has been found in patients with standard CNI dose, indicating probably different phenotypes between patients, by considering that the CNI dose was applied depending on patients’ tolerability to CNI medication. Conclusion: These preliminary results showed that long term medication with CNI affects tissue microstructure in human brain and the brain function after liver transplantation (Figure 1). The authors have none to declare.

Late bronze age pottery as indicator of the deposition temperatures of the Minoan pyroclastic products, Santorini, Greece.

The Minoan eruption of Santorini volcano (Greece) took place in the Late Bronze Age (17th century BC) and produced a great volume of volcanic products that covered the whole island and buried every human settlement under meters of pyroclastic deposits. In this study we used thermal analysis of the magnetic remanence carried by pottery fragments buried under the pyroclastic deposits in order to estimate the thermal effect of the Minoan volcanic products on the pre-eruption habitation level. A total of 70 samples, prepared from 45 independent pottery fragments, have been studied. Samples were collected from three different sites, situated at the southern part of the island. Stepwise thermal demagnetizations reveal that the pottery fragments generally carry a two-component remanent magnetization. Interpretation of the demagnetization results using the normalised intensity decay curves and the orthogonal projection diagrams indicates that most samples were re-heated at temperatures around 160-260o C. The obtained results represent the equilibrium temperatures reached after the deposition of the pyroclastic fall and show that the pyroclastic fall deposits at distances around 6 to 9 km from the eruption vent were still hot enough to reheat the buried pottery at such temperatures.

Body diffusion kurtosis imaging: Basic principles, applications, and considerations for clinical practice.

Technologic advances enable performance of diffusion-weighted imaging (DWI) at ultrahigh b-values, where standard monoexponential model analysis may not apply. Rather, non-Gaussian water diffusion properties emerge, which in cellular tissues are, in part, influenced by the intracellular environment that is not well evaluated by conventional DWI. The novel technique, diffusion kurtosis imaging (DKI), enables characterization of non-Gaussian water diffusion behavior. More advanced mathematical curve fitting of the signal intensity decay curve using the DKI model provides an additional parameter Kapp that presumably reflects heterogeneity and irregularity of cellular microstructure, as well as the amount of interfaces within cellular tissues. Although largely applied for neural applications over the past decade, a small number of studies have recently explored DKI outside the brain. The most investigated organ is the prostate, with preliminary studies suggesting improved tumor detection and grading using DKI. Although still largely in the research phase, DKI is being explored in wider clinical settings. When assessing extracranial applications of DKI, careful attention to details with which body radiologists may currently be unfamiliar is important to ensure reliable results. Accordingly, a robust understanding of DKI is necessary for radiologists to better understand the meaning of DKI-derived metrics in the context of different tumors and how these metrics vary between tumor types and in response to treatment. In this review, we outline DKI principles, propose biostructural basis for observations, provide a comparison with standard monoexponential fitting and the apparent diffusion coefficient, report on extracranial clinical investigations to date, and recommend technical considerations for implementation in body imaging.

Strong clockwise block rotation of the Ali-Sabieh/Aïsha Block: evidence for opening of the Afar Depression by a ‘saloon-door’ mechanism

Abstract Palaeomagnetic investigations were carried out on tilted Jessoma sandstones in the Aïsha block. The average natural remanent magnetization intensity was 0.026A m −1 with good behaviour on demagnetization both by thermal and alternating fields. The normalized magnetization intensity decay curves indicated that fine-grained, Ti-poor titanomagnetites were the carriers of magnetization. A well-defined single-component magnetization with a poorly defined secondary component was found. The latter was removed at temperatures below 300°C or at 10 mT. After these steps, a straight-line segment directed towards the origin was identified, which was interpreted as the characteristic remanent magnetization. Site mean direction coordinates of Dec g =227.8°, Inc g =–33.9° ( n =7, α 95 =2.8°, K =478) ( in situ ) and Dec s =225.6°, Inc s =0.4° ( n =7, α 95 =2.8°, K =478) (tilt-corrected) were obtained. Corresponding mean virtual geomagnetic pole coordinates of Lon g =117.5° E, Lat g =43.3° N ( A 95 =3.2°, n =7) ( in situ ) and Lon s =143.5° E, Lat s =43.3° N ( A 95 =2.8°, n =7) (tilt-corrected) were obtained. The corrected in situ mean pole position was compared with the African apparent polar wander path curve and a deposition age for the sandstone of 60±5 Ma was determined, which is consistent with previous reports. A vertical axis rotation ( R ±Δ R ) of the Aïsha block of 29.1±4.06° was obtained, which is equivalent to an inferred 30° counterclockwise rotation of the Danakil block, in agreement with a ‘saloon-door’ mechanism for the opening of the Afar Depression.

Concentration effect on the spectroscopic behavior of Tb3+ ions in zinc phosphate glasses

Zinc phosphate glasses (PZABPTb) in the compositional system: P2O5–ZnO–Al2O3–BaO–PbO doped with variable Tb3+ concentrations (1–5wt% Tb2O3) were prepared and characterized through absorption, excitation, emission and intensity decay rate measurements. The Judd–Ofelt model has been adopted to evaluate the radiative properties of the 5D4→7F6–3 emission transitions. The effect of Tb3+ ion concentration on the emissions from the 5D3,4 excited levels is discussed in detail. Analysis of the intensity decay curves corresponding to blue and green emissions from levels 5D3 and 5D4, respectively, allowed determination of effective lifetimes, which confirmed the Tb3+ ion concentration quenching of the blue emission in these glasses. The decay curves for the 5D3 level are found to be non-exponential in nature for all the studied concentrations due to ion–ion energy transfer through cross-relaxation. In an attempt to identify the origin of the energy transfer mechanism, the decay curves were well fitted to the Inokuti–Hirayama model for S=6, which indicates that the energy transfer process is of dipole–dipole type. The optical band gap energy (Eopt) has been evaluated taking into account the ultraviolet edge of absorption spectra.

Luminescence properties of silk cocoon derived carbonaceous fluorescent nanoparticles/PVA hybrid film

Carbonaceous fluorescent nanoparticles (CFNs) with broad particle distribution were synthesized by thermal-treatment using carbonation of silk cocoon as raw materials. The experimental results showed tunable emission wavelength of the nanoparticles. The quantum yield of the CFNs was calculated to be 23%. A CFNs/PVA hybrid thin film was prepared from a blend of the CFNs with polyvinyl alcohol (PVA) showing interesting green afterglow which could be observed by naked eyes. The afterglow spectrum revealed that the CFNs/PVA thin film had a broad afterglow emission peak located at 520nm. The afterglow intensity decay curve of the film showed visually recognizable period longer than 140s. The PVA–PVA hydrogen bonding in the PVA matrix may play a key role for the afterglow.

Experimental and Computational Study of BODIPY Dye-Labeled Cavitand Dynamics

Understanding the distance distribution and dynamics between moieties attached to the walls of a resorcin[4]arene cavitand, which is switchable between an expanded kite and a contracted vase form, might enable the use of this molecular system for the study of fundamental distance-dependent interactions. Toward this goal, a combined experimental and molecular dynamics (MD) simulation study on donor/acceptor borondipyrromethene (BODIPY) dye-labeled cavitands present in the vase and kite forms was performed. Direct comparison between anisotropy decays calculated from MD simulations with experimental fluorescence anisotropy data showed excellent agreement, indicating that the simulations provide an accurate representation of the dynamics of the system. Distance distributions between the BODIPY dyes were established by comparing time-resolved Förster resonance energy transfer experiments and MD simulations. Fluorescence intensity decay curves emulated on the basis of the MD trajectories showed good agreement with the experimental data, suggesting that the simulations present an accurate picture of the distance distributions and dynamics in this molecular system and provide an important tool for understanding the behavior of extended molecular systems and designing future applications.

Preparation and Properties of CdSiO<sub>3</sub>: Mn<sup>2+</sup>, Er<sup>3+</sup> Phosphor

CdSiO3: Mn2+, Er3+ long-lasting phosphor was prepared by the conventional high temperature solid-state method. Effects of the concentration of Mn2+ and Er3+ on the luminescent properties of phosphor CdSiO3: Mn2+, Er3+ were investigated by means of photoluminescence (PL) spectra and the afterglow intensity decay curves. It was found that when the Mn2+ and Er3+ dopant-concentrations were 0.2 mol% and 0.8 mol% of Cd2+ ions in CdSiO3, respectively, the luminescence of phosphor prepared had better luminescent property and longer afterglow time. The phosphorescence for it could be seen with the naked eye for more than 60 min in the dark after the removal of the 254 nm UV light. Role of Er3+ co-doped into CdSiO3: Mn2+ matrix was discussed in this paper.

Different dynamics of ultraviolet upconversion in Tm3+:ZBLAN glass under blue laser excitation

Ultraviolet upconversion luminescence around 292nm, 350nm and 363nm in Tm3+:ZBLAN glass was observed clearly by pulsed excitation at 464nm. Upconversion dynamics was discussed in detail by an analysis of the measured intensity dependence, decay curves and excitation spectra of upconversion luminescence, from which it was clarified that upconversion luminescence around 292nm and 350nm from 1I6 level was attributed to excited state absorption, while that around 363nm from 1D2 level was attributed to energy transfer process.

Kinetics of Photon Upconversion in Ionic Liquids: Time-Resolved Analysis of Delayed Fluorescence

Photon upconversion (UC) based on triplet-triplet annihilation (TTA) is an emerging wavelength shifting technology, which is applicable to sunlight. Previously we found that the quantum efficiency of TTA-UC (ΦUC) carried out in ionic liquids (ILs) is dependent on the type of IL employed. In this article we investigate the kinetics of the triplet emitter molecules (perylene) that implement TTA to determine the origin of the IL dependence of ΦUC. We measure the time-resolved delayed UC fluorescence intensities from samples made with five imidazolium-based ILs, and their intensity decay curves are analyzed with an analytical model. Consequently, several important aspects regarding both the first-order and second-order decays are elucidated. It is revealed that the IL dependence of ΦUC primarily originates from the IL dependence of the branching ratio toward TTA upon an encounter of two triplet emitter molecules. Additionally, a strong correlation between the viscosity of the ILs and the branching ratios toward TTA is found. This finding is supported by temperature-dependent measurements, from which ΦUC is found to be significantly affected by the viscosity of the IL. The results of this study should provide a clue for further improving ΦUC.

Depth-dependent C K-NEXAFS spectra for self-assembled monolayers of 4-methylbenzenethiol and 4-ethylbenzenethiol on Au(1 1 1)

Depth analysis using X-ray absorption fine-structure spectroscopy at the near carbon K-edge (C K-NEXAFS) was performed for self-assembled monolayers of 4-methylbenzenethiol (4-MBT) and 4-ethylbenzenethiol (4-EBT) on Au(111). On the basis of the polarization dependence of π* resonance intensity, the benzene rings of 4-MBT and 4-EBT were found to be tilted by 30±10° and 60±5° with respect to the Au(111) surface, respectively. The spectra were separated into two components according to their depth by fitting the intensity decay curves of the electrons emitted by X-ray absorption. The spectra for lower segments exhibited bands at almost identical energies with different intensities depending on the polarization between 4-MBT and 4-EBT. In contrast, the spectra for upper segments including the alkyl groups showed a marked difference in the location of the σCC* resonance. The σCC* resonance of the ethyl group predominantly observed in the 15° incidence spectrum of 4-EBT indicated that the ethyl group was directed perpendicularly.

Burial of the Polymorphic Residue 129 in Amyloid Fibrils of Prion Stop Mutants

Misfolding of the natively α-helical prion protein into a β-sheet rich isoform is related to various human diseases such as Creutzfeldt-Jakob disease and Gerstmann-Sträussler-Scheinker syndrome. In humans, the disease phenotype is modified by a methionine/valine polymorphism at codon 129 of the prion protein gene. Using a combination of hydrogen/deuterium exchange coupled to NMR spectroscopy, hydroxyl radical probing detected by mass spectrometry, and site-directed mutagenesis, we demonstrate that stop mutants of the human prion protein have a conserved amyloid core. The 129 residue is deeply buried in the amyloid core structure, and its mutation strongly impacts aggregation. Taken together the data support a critical role of the polymorphic residue 129 of the human prion protein in aggregation and disease.

Use of Intravoxel Incoherent Motion MR Imaging to Assess Placental Perfusion in a Murine Model of Placental Insufficiency

The objectives of this study were to evaluate the potential of intravoxel incoherent motion (IVIM) magnetic resonance imaging at 4.7 T to distinguish decreased placental perfusion from normal perfusion in a controlled murine model and to determine the effect of transient maternal hyperoxygenation on placental microvascularization. The study was approved by our animal care committee. Ten pregnant rats underwent ligation of the left uterine vascular pedicle on the 17th embryonic day (E17). A multishot diffusion-weighted spin-echo echo-planar imaging sequence, using 14 b values (b10 to b800), was performed on the 19th embryonic day (E19) under room air and during maternal hyperoxygenation. For each placenta and its 2 layers, the signal intensity decay curve according to the b values was obtained. The following IVIM parameters were calculated using biexponential fitting: the diffusion coefficient (D), the pseudodiffusion coefficient (D*), and the perfusion fraction (f). Mixed regression modeling was used to analyze the effect of ligation status, oxygenation, and the placental layer on IVIM parameters. Seventy-three placentas were examined: 23 in the ligated horn and 50 in the nonligated control horn. The IVIM parameters were obtained for 67% of the placentas. In the control horn, the mean (SD) values on room air were 28% (13%), 9.6 (9) ×10(-3) mm(2)/s, and 0.88 (0.36) ×10(-3) mm(2)/s for the perfusion fraction, the pseudodiffusion coefficient, and the diffusion coefficient, respectively. The perfusion fraction was significantly decreased in the ligated horn (-6.7% [1.9%]; P = 0.001) and during maternal hyperoxygenation (-3.3 [1.64%]; P = 0.047). The diffusion coefficient increased significantly during the hyperoxygenation (0.26 [0.04] × 10(-3) mm(2)/s; P = 0.0001) and in the inner placental layer (0.21 [0.05] ×10(-3) mm(2)/s; P = 0.0001). The perfusion fraction is a sensitive marker of decreased placental perfusion. The perfusion fraction and the diffusion coefficient are modified during the hyperoxygenation. Our IVIM-based approach may help in the investigation and early diagnosis of vascular diseases during pregnancy.

Corneal respiratory function by FAD autofluorescence lifetime

AbstractPurpose We intend to develop an efficient method to assess in‐vivo the corneal respiratory function in order to diagnose corneal cells dysfunction prior to its pathologic expression.Methods Metabolic alterations can be assessed by measuring the amount of the metabolic co‐factors flavin adenine dinucleotide (FAD) and nicotinamide adenine dinucleotide (NADH). FAD has advantages over NADH, like being present only in the mitochondria. Furthermore, using fluorescence lifetime imaging microscopy (FLIM) we are able to discriminate between its free or protein‐bound states. We resorted to a PicoQuant MicroTime 100 (PicoQuant GmbH, Berlin, Germany) coupled to an Olympus BX51 Microscope (Olympus Corporation, Tokyo, Japan). This setup uses a pulsed blue diode laser with a trigger frequency of 40 MHz with an excitation filter of 440±10 nm. Intensity decay curves were processed with SymPhoTime v5.3 Software (PicoQuant GmbH). The instrument response function was acquired to improve data analysis precision.Results We successfully acquired ex‐vivo autofluorescence images of male Wistar rat and Bovine corneas. A bi‐exponential decay was observed in both cases with a fast decay around 1 ns and a longer one around 4 ns, which correspond to protein‐bound and free FAD, respectively. These results are in accordance with other studies, although there is some controversy regarding FAD lifetimes.Conclusion We showed that it is possible, with our apparatus, to acquire metabolic images of the cornea using FAD autofluorescence. We intend to modify the instrument optical setup in order to acquire reflectance and fluorescence lifetime images simultaneously for corneal layer identification.