Project

Advanced Functional Nanomaterials for Optical Thermometry

Goal: Sensitive detection of temperature using changes in optical emission from nanomaterials

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Miroslav D Dramicanin
added a research item
Judd–Ofelt theory is a cornerstone of lanthanides’ spectroscopy given that it describes 4fn emissions and absorptions of lanthanide ions using only three intensity parameters. A self-referenced technique for computing Judd–Ofelt intensity parameters from the excitation spectra of Eu3+-activated luminescent materials is presented in this study along with an explanation of the parametrisation procedure and free user-friendly web application. It uses the integrated intensities of the 7F0 → 5D2, 7F0 → 5D4, and 7F0 → 5L6 transitions in the excitation spectrum for estimation and the integrated intensity of the 7F0 → 5D1 magnetic dipole transition for calibration. This approach facilitates an effortless derivation of the Ω6 intensity parameter, which is challenging to compute precisely by Krupke’s parametrisation of the emission spectrum and, therefore, often omitted in published research papers. Compared to the parametrisation of absorption spectra, the described method is more accurate, can be applied to any material form, and requires a single excitation spectrum.
Miroslav D Dramicanin
added a research item
The figures of merit of luminescence intensity ratio (LIR) thermometry for Er3+ in 40 different crystals and glasses have been calculated and compared. For calculations, the relevant data has been collected from the literature while the missing data were derived from available absorption and emission spectra. The calculated parameters include Judd-Ofelt parameters, refractive indexes, Slater integrals, spin-orbit coupling parameters, reduced matrix elements (RMEs), energy differences between emitting levels used for LIR, absolute and relative sensitivities. We found a slight variation of RMEs between hosts as a result of variations in values of Slater integrals and spin-orbit coupling parameters, and we calculated their average values over 40 hosts. The calculations showed that crystals perform better than glasses in Er3+ based thermometry, and we identified hosts that have large values of both absolute and relative sensitivity.
Miroslav D Dramicanin
added a research item
This work demonstrates the luminescence of Mn4+ activated cubic spinel Li4Ti5O12 (LTO) powders. One-step solid-state method was used to obtain eleven samples with different quantities of Mn4+. The deep red emission centered at around 696 nm originates from 2Eg → 4A2g spin forbidden electronic transitions from 3 d3 electron configuration of Mn4+ ion. The concentration quenching of emission is also observed in values of excited-state lifetimes, ranging from 212 μs to 143 μs. Such emission in the red spectral region which can be excited by blue light is suitable for the plant growth LEDs. The exchange charge model (ECM) of crystal field was used to calculate the Mn4+ energy levels in the LTO host. The temperature dependence of the Mn4+ emission in LTO was measured in the 10–350 K temperature range. Excited-state lifetime strongly changes with temperature. A very large value of relative sensitivity of 2.6% K−1 is found at 330 K, which facilitates temperature measurements with the temperature resolution of about 0.26 K. A low concentration of Nb5+ co-doping sensitizes the Mn4+ optical center effectively showing a relative increment of emission intensity.
Miroslav D Dramicanin
added a research item
Following astonishing growth in the last decade, the field of luminescence thermometry has reached the stage of becoming a mature technology. To achieve that goal, further developments should resolve inherent problems and methodological faults to facilitate its widespread use. This perspective presents recent findings in luminescence thermometry, with the aim of providing a guide for the reader to the paths in which this field is currently directed. Besides the well-known temperature read-out techniques, which are outlined and compared in terms of performance, some recently introduced read-out methods are discussed in more detail. These include intensity ratio measurements that exploit emissions from excited lanthanides levels with large energy differences, dual-excited and time-resolved single-band ratiometric methods, and phase-angle temperature read-outs. The necessity of the extension of theoretical models and a careful re-examination of those currently in use is emphasized. Regarding materials, the focus of this perspective is on dual-activated probes for luminescence intensity ratio (LIR), and transition-metal-ion-activated phosphors for both lifetime and LIR thermometry. Several particularly important applications of luminescence thermometry are presented. These include temperature measurement in catalysis, in-situ temperature mapping for microfluidics, thermal history measurement, thermometry at extremely high temperatures, fast temperature transient measurement, low-pressure measurement via up-conversion nanoparticle emission intensity ratios, evaluation of the photothermal chirality of noble metal clusters, and luminescence thermometry using mobile devices. Routes for the development of primary luminescence thermometry are discussed in view of the recent redefinition of the kelvin.
Miroslav D Dramicanin
added a research item
A promising way to improve the performance of luminescent materials is to combine them with noble metal nanoparticles. Herein, a set of silver/europium-doped lanthanum orthophosphate (Ag/La 0.95 Eu 0.05 PO 4) nanostructures with different concentrations of silver nanoparticles were prepared and investigated. The presented overlap between the strongest europium (Eu 3+) excitation line and the broad silver nanoparticle surface plasmon resonance makes the combination prospective for coupling. X-ray powder diffraction confirmed the monoclinic monazite structure. The transmission electron microscopy revealed particles with a rod-like shape and~4 aspect ratio. Photoluminescence spectra show characteristic Eu 3+ ion red emission. One of the requirements for an enhanced luminescence effect is the precise control of the distance between the noble metal nanoparticles and the emitter ion. The distance is indirectly varied throughout the change of Ag nanoparticle concentration in the La 0.95 Eu 0.05 PO 4 host. The emission intensity increases with the increase in Ag nanoparticles up to 0.6 mol %, after which the luminescence decreases due to the nanoparticles' close packing and aggregation leading to the displacement of La 0.95 Eu 0.05 PO 4 from the vicinity of the metal particles and reabsorption of the emitted light. The emission intensity of La 0.95 Eu 0.05 PO 4 increases more than three times when the Eu 3+ excitation is supported by the localized surface plasmon resonance in the Ag/La 0.95 Eu 0.05 PO 4 nanostructures.
Prashanthi Kovur
added a research item
A strategy for optical nanothermometry using the negative thermal quenching behavior of intrinsic BiFeO3 semiconductor nanoparticles has been reported here. X-ray diffraction measurement shows polycrystalline BiFeO3 nanoparticles with a rhombohedral distorted perovskite structure. Transmission electron microscopy shows agglomerated crystalline nanoparticles around 20 nm in size. Photoluminescence measurements show that intensity of the defect level emission increases significantly with temperature, while the intensity of near band emission and other defect levels emissions show an opposite trend. The most important figures of merit for luminescence nanothermometry: the absolute (Sa) and the relative sensor sensitivity (Sr) and the temperature resolution (ΔTm) were effectively resolved and calculated. The relative sensitivity and temperature resolution values are found to be 2.5% K⁻¹ and 0.2 K, respectively which are among the highest reported values observed so far for semiconductors.
Prashanthi Kovur
added a research item
This report focuses on fabrication, characterization, and fundamental optical properties of Eu³⁺- and Sm³⁺-doped GdVO4 luminescent thin films. Films were uniformly grown on three different substrates: single crystal sapphire (0001), thermally grown silicon oxide (Si/SiO2 ~ 500 nm) on silicon and fused quartz using pulsed laser deposition technique. Thin films’ structure, morphology, and photoluminescent properties were investigated by X-ray diffraction, atomic force and scanning electron microscopy, diffuse reflectance and photoluminescence spectroscopy. Thin films’ structure characterized by X-ray diffraction showed that for all substrates highly crystalline, zircon-type pure phase films were formed. Films’ thickness and internal morphology were determined by cross-sectional scanning electron microscopy showing completely dense, pore-free film with an average thickness of ~ 390 nm. Atomic force microscopy revealed that the average crystallite size of both Eu³⁺- and Sm³⁺-doped GdVO4 thin films deposited on fused quartz is higher as compared to the single crystal sapphire (0001) and thermally grown silicon oxide (Si/SiO2 ~ 500 nm) and that the surface roughness increases with the increase in the grain size. Energy band gap values, estimated from diffuse reflectance spectra were 3.57 and 3.53 eV for Eu³⁺- and Sm³⁺-doped GdVO4 thin films, respectively. Photoluminescent properties were investigated in detail in both steady state and lifetime domain. The emission spectra show clear orange–red emission in the Sm³⁺-doped GdVO4 thin films and red emission in Eu³⁺-doped ones.
Miroslav D Dramicanin
added 2 research items
In this chapter, we discuss the basics behind the fluorescence of organic compounds and explain differences in fluorescence response to temperature changes as a result of differences between the structures of compounds. We show that important properties of fluorescent organic materials, such as their strong and wide absorption bands, in many cases in the visible spectral range, their large Stokes shifts, and the great sensitivity of their electronic excited states on the environment, make them excellent fluorescence temperature probes. The chapter gives several examples of luminescence thermometry with different types of organic and organic–inorganic probes. These include organic dyes and pigments, dyes incorporated in functional polymers (including semiconducting polymers), discrete metal–organic complexes, and metal–organic frameworks (MOFs).
Miroslav D Dramicanin
added a research item
The binary luminescence thermometry probe is prepared from Y2O3:Ho3+ and Mg2TiO4:Mn4+ powders. This probe facilitates self‐referencing temperature readouts with excellent repeatability from both emission intensity ratio and excited state lifetimes. The ratio of intensities of Mn4+ deep red emission from 2E, 4T2→4A2 electronic transitions, and Ho3+ green emission from 5F4,5S2 →5I8 electronic transitions provides temperature measurements over the room temperature to 100 °C temperature range with a superior relative sensitivity of 4.6% °C−1 and temperature resolution of 0.1 °C. Over the same temperature range, the temperature readout from the Mn4+ emission lifetime offers measurements with relative sensitivity better than 0.5% °C−1 and better than 0.2 °C in resolution.
Miroslav D Dramicanin
added 4 research items
Temperature has an essential role in biological systems, affecting a variety of their properties. It is not strange then that temperature measurements in biomedicine, especially those at an intracellular and intercellular level, are of paramount importance. The use of luminescent nanothermometers opens the way for accurate and even real-time temperature monitoring in many biomedical applications. This chapter begins with a discussion of the optical properties of tissues. Emphasis is given to the absorption, reflection, and scattering properties of tissues which govern light propagation. The term “biological windows,” which is commonly used to describe spectral ranges in which light propagates through tissues with low attenuation, is related to tissue properties. The chapter then goes on to describe the fluorescence of tissue components in different spectral regions. Several biomedical applications of luminescence thermometry are depicted: intracellular and intercellular temperature measurements, in-tumor temperature monitoring during thermal therapy, and the diagnosis of ischemia using thermal imaging.
This chapter describes the physical phenomena that govern the luminescence of lanthanide and transition metal ion doped materials and highlights their characteristics relevant to luminescence thermometry. Mechanisms behind down-shifting, up-converting, scintillating, and quantum cutting are depicted, and the most relevant phosphors mentioned. Common routes for preparation of single crystals, powders, thin films, and coatings of these materials are concisely presented in a separate section. Detail is given about luminescence thermometry using the intensity ratio of emissions from thermally coupled excited states of lanthanide ions, including a discussion of the energy levels of each lanthanide ion, emission colors, temperature measurement ranges, and measurement sensitivities. Temperature readings from emission decay times and rise times, and emission intensity ratios from doubly activated materials (both lanthanide and transition ion doped), are presented. The chapter also contains an extensive overview of the literature (with 117 references) on lanthanide and transition metal ion doped materials, for which luminescence thermometry has been demonstrated.
This introductory chapter of the book aims to familiarize readers with the importance of temperature and measurements of temperature. It starts with several examples which illustrate why we measure temperature, and explains that temperature sensors account for about 80% of all the sensors worldwide. It then goes on to give basic information on the temperature sensor market, including data on present market value and estimated growth, key market drivers, and key products. Finally, a brief history of thermometry is presented, mainly focusing on the development of the first instruments and temperature scales.
Prashanthi Kovur
added a research item
Wide-bandgap semiconductor nanowires with surface defect emission centers have the potential to be used as sensitive thermometers and optical probes. Here, we show that the green luminescence of multiferroic BiFeO3 (BFO) nanowires shows an anomalous negative thermal quenching (NTQ) with increasing temperatures. The release of trapped carriers from localized surface defect states is suggested as the possible mechanism for the increased green luminescence which was experimentally observed at elevated temperatures. A reasonable interpretation of the photoluminescence (PL) processes in BFO nanowires is achieved, and the activation energies of the PL quenching and thermal hopping are deduced. Negative thermal quenching of BFO nanowires provides a new strategy for optical thermometry at higher temperatures.
Miroslav D Dramicanin
added a research item
Luminescence Thermometry: Methods, Materials, and Applications presents the state-of-the art applications of luminescence thermometry, giving a detailed explanation of luminescence spectroscopic schemes for the read-out of temperature, while also describing the diverse materials that are capable of sensing temperature via luminescence. Chapters cover the fundamentals of temperature, traditional thermometers and their figures of merit, a concise description of optical thermometry methods, luminescence and instrumentation, and an explanation of the ways in which increases in temperature quench luminescence. Additional sections focus on materials utilized for luminescence thermometry and the broad range of applications for luminescence thermometry, including temperature measurement at the nanoscale and the application of multifunctional luminescent materials. Key Features Provides an overview of luminescence thermometry applications, including high-temperature, biomedical, nanoscale and multifunctional Delves into luminescence thermometry by materials group, including Rare-earth and transition Metal Ion Doped, Semiconductors, Quantum Dots and Organic materials Gives a concise introduction of the latest methods of temperature measurement, including luminescence spectroscopic schemes and methods of analysis Table of Contents: 1.Introduction to Measurements of Temperature 2. Temperature and Ways of Measuring It 3. Luminescence: basics, methods and instrumentation 4. Schemes for the Read-out of Temperature from Luminescence 5. Methods of Analysis for Luminescence Thermometry Measurements 6. Lanthanide and Transition Metal Ion doped Materials for Luminescence Temperature Sensing 7. Luminescence Temperature Sensing Using Semiconductor Quantum Dots 8. Luminescence Temperature Sensing using Organic Materials 9. Applications of Luminescence Thermometry in Engineering 10. Bio-medical Applications of Luminescence Thermometry 11. Temperature measurements at the nanoscale 12. Achieving multi-functionality by combining thermometry with other luminescence applications
Prashanthi Kovur
added a research item
Transparent, luminescent thin films of Dy3 +-doped GdVO4 were fabricated by pulsed laser deposition technique on quartz substrates. Thin film structure, morphology and optical properties were investigated and discussed in detail. X-ray analysis shows relatively intense reflection peaks confirming that as-deposited films are highly crystalline with strong (200) preferred orientation. Cross-sectional scanning electron microscopy shows relatively dense film with an average thickness of ~ 340 nm. Band gap of Dy3 +-doped GdVO4 thin film, estimated from diffuse reflectance spectrum, is 3.61 eV. Refractive index and extinction coefficient of thin films as a function of wavelength are extracted from ellipsometric spectra. The photoluminescent emission spectra have two dominant bands: one in the yellow (~ 573 nm, ⁴F9/2 → ⁶H13/2 transition) followed by the other in the blue (~ 484 nm, ⁴F9/2 → ⁶H15/2 transition) region resulting in the emission color placed in the white light region.
Miroslav D Dramicanin
added 2 research items
Temperature is important because it has an effect on even the tiniest elements of daily life and is involved in a broad spectrum of human activities. That is why it is the most commonly measured physical quantity. Traditional temperature measurements encounter difficulties when used in some emerging technologies and environments, such as nanotechnology and biomedicine. The problem may be alleviated using optical techniques, one of which is luminescence thermometry. This paper reviews the state of luminescence thermometry and presents different temperature read-out schemes with an emphasis on those utilizing the downshifting emission of lanthanide-doped metal oxides and salts. The read-out schemes for temperature include those based on measurements of spectral characteristics of luminescence (band positions and shapes, emission intensity and ratio of emission intensities), and those based on measurements of the temporal behavior of luminescence (lifetimes and rise times). This review (with 140 references) gives the basics of the fundamental principles and theory that underlie the methods presented, and describes the methodology for the estimation of their performance. The major part of the text is devoted to those lanthanide-doped metal oxides and salts that are used as temperature probes, and to the comparison of their performance and characteristics.
Sensitive detection of temperature in a non-contact fashion has applications in many diverse areas and disciplines. Immediate need exists for non-contact temperature measurement of moving or contact sensitive objects, hardly accessible bodies, or objects in hazardous locations. Materials and sensor platforms used for non-contact temperature measurements often limits their use in certain environments. The changes of luminescence properties of materials with temperature (such as changes of absolute and relative emission intensities, lifetime values of excited states, emission rise times, peak positions, and emission bandwidths) allow some materials to act as sensitive thermometers. The phenomenon become the basis of a new arm in the field of luminescence spectroscopy commonly termed as a luminescence thermometry. This lecture presents an overview of different modalities of luminescence thermometry, such as the use of materials with a single- or multi- emission centers, the selection of the reference emission, and advantages or disadvantages of the emission intensity measurements versus measurements of temporal changes in emission. Then, different classes of materials commonly utilized for luminescence thermometry are listed along with their figures of merit (temperature sensitivities, resolutions, measurement ranges. These include rare earth doped optical fibers, phosphors in forms of powders, thin films and ceramics, organic-inorganic hybrids etc. Finally, several state-of-the-art applications of remote temperature sensing with luminescence are shown.
Prashanthi Kovur
added a research item
Here we report on preparation of Eu3+-doped Gd2Ti2O7 pyrochlore luminescent thin films by pulsed laser deposition technique and their structural, morphological and optical characterization. The influence of annealing temperature and background gas (air vs. argon) on film photoluminescence is examined for the optimization of post-deposition annealing conditions. As-deposited amorphous films become pure pyrochlore crystalline after calcination at temperatures higher than 1000 °C. Atomic force microscopy showed increase in the grain size from ∼20 nm in the as-deposited to ∼60 nm in the crystalline sample annealed at 1100 °C. Scanning electron microscopy showed dense films with the uniform thickness of about 700 nm. Luminescence spectra of crystalline films were complex and composed of better resolved emission lines than in the amorphous sample. Emission spectra showed that symmetry of Eu3+ sites become disturbed in annealed films due to the extrinsic thermal stress. Films treated in argon displayed similar emission and excitation spectral features like air-treated ones, but with better resolved emission lines. Calculated quantum efficiency of emission showed that optimization of annealing conditions led to an enhancement of films luminescence. The highest quantum efficiency of emission and the longest lifetime is found for the sample annealed at 1100 °C in presence of argon.
Prashanthi Kovur
added a project goal
Sensitive detection of temperature using changes in optical emission from nanomaterials