Special Issue "Luminescent Rare-Earth-Based Nanomaterials"

A special issue of Nanomaterials (ISSN 2079-4991).

Deadline for manuscript submissions: 31 December 2020.

Special Issue Editor

Dr. Łukasz Marciniak
Website
Guest Editor
Institute of Low Temperature and Structure Research of the Polish Academy of Sciences, Wroclaw, Poland
Interests: nanomaterials; luminescence; luminescent thermometry; multifunctional nanoparticles; up-conversion; light-to-heat conversion; luminescent imaging

Special Issue Information

Dear Colleagues,

Rare-earth-doped inorganic phosphors have been an exciting subject of research for decades due to their unique and fascinating luminescent properties, such as a strong emission intensity with sharp emission lines and long luminescent lifetimes. Their wide range of applications, including lighting, displays, scintillators, solid-state lasers, and optical storage, confirms their great importance. Doping lanthanide ions into nanoparticles not only extends the list of potential applications of rare-earth-doped phosphors but enables, among other things, the development of diagnostic and theranostic tools with unprecedented functionality. An appropriate composition, stoichiometry, and architecture of such nanoparticles will allow for the creation of multifunctional materials that combine optical temperature, pressure, and pH sensing with luminescence imaging and light-to-heat conversion. Although unparalleled and impressive, their capabilities have yet to be fully explored and understood.

To respond to the expectations of our readers and provide a picture of recent progress in the field of lanthanide nanocrystalline phosphors, we have established a Special Issue of Nanomaterials entitled “Luminescent Rare-Earth-Based Nanomaterials”.

Dr. Łukasz Marciniak
Guest Editor

Manuscript Submission Information

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Keywords

  • luminescence
  • lanthanides
  • rare earth
  • optical properties
  • down shifting
  • down conversion
  • up conversion
  • luminescent thermometry
  • bioimaging
  • all optical sensors
  • light-to-heat convertors.

Published Papers (4 papers)

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Research

Open AccessArticle
Comparison of Three Ratiometric Temperature Readings from the Er3+ Upconversion Emission
Nanomaterials 2020, 10(4), 627; https://doi.org/10.3390/nano10040627 - 28 Mar 2020
Cited by 1
Abstract
The emission of Er3+ provides three combinations of emission bands suitable for ratiometric luminescence thermometry. Two combinations utilize ratios of visible emissions (2H11/24I15/2 at 523 nm/ 4S3/24I15/2 at 542 [...] Read more.
The emission of Er3+ provides three combinations of emission bands suitable for ratiometric luminescence thermometry. Two combinations utilize ratios of visible emissions (2H11/24I15/2 at 523 nm/ 4S3/24I15/2 at 542 nm and 4F7/24I15/2 at 485 nm/ 4S3/24I15/2 at 545 nm), while emissions from the third combination are located in near-infrared, e.g., in the first biological window (2H11/24I13/2 at 793 nm/ 4S3/24I13/2 at 840 nm). Herein, we aimed to compare thermometric performances of these three different ratiometric readouts on account of their relative sensitivities, resolutions, and repeatability of measurements. For this aim, we prepared Yb3+,Er3+:YF3 nanopowders by oxide fluorination. The structure of the materials was confirmed by X-ray diffraction analysis and particle morphology was evaluated from FE-SEM measurements. Upconversion emission spectra were measured over the 293–473 K range upon excitation by 980 nm radiation. The obtained relative sensitivities on temperature for 523/542, 485/542, and 793/840 emission intensity ratios were 1.06 ± 0.02, 2.03 ± 0.23, and 0.98 ± 0.10%K−1 with temperature resolutions of 0.3, 0.7, and 1.8 K, respectively. The study showed that the higher relative temperature sensitivity does not necessarily lead to the more precise temperature measurement and better resolution, since it may be compromised by a larger uncertainty in measurement of low-intensity emission bands. Full article
(This article belongs to the Special Issue Luminescent Rare-Earth-Based Nanomaterials)
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Open AccessArticle
Making Nd3+ a Sensitive Luminescent Thermometer for Physiological Temperatures—An Account of Pitfalls in Boltzmann Thermometry
Nanomaterials 2020, 10(3), 543; https://doi.org/10.3390/nano10030543 - 18 Mar 2020
Cited by 2
Abstract
Ratiometric luminescence thermometry employing luminescence within the biological transparency windows provides high potential for biothermal imaging. Nd3+ is a promising candidate for that purpose due to its intense radiative transitions within biological windows (BWs) I and II and the simultaneous efficient excitability [...] Read more.
Ratiometric luminescence thermometry employing luminescence within the biological transparency windows provides high potential for biothermal imaging. Nd3+ is a promising candidate for that purpose due to its intense radiative transitions within biological windows (BWs) I and II and the simultaneous efficient excitability within BW I. This makes Nd3+ almost unique among all lanthanides. Typically, emission from the two 4F3/2 crystal field levels is used for thermometry but the small ~100 cm−1 energy separation limits the sensitivity. A higher sensitivity for physiological temperatures is possible using the luminescence intensity ratio (LIR) of the emissive transitions from the 4F5/2 and 4F3/2 excited spin-orbit levels. Herein, we demonstrate and discuss various pitfalls that can occur in Boltzmann thermometry if this particular LIR is used for physiological temperature sensing. Both microcrystalline, dilute (0.1%) Nd3+-doped LaPO4 and LaPO4: x% Nd3+ (x = 2, 5, 10, 25, 100) nanocrystals serve as an illustrative example. Besides structural and optical characterization of those luminescent thermometers, the impact and consequences of the Nd3+ concentration on their luminescence and performance as Boltzmann-based thermometers are analyzed. For low Nd3+ concentrations, Boltzmann equilibrium starts just around 300 K. At higher Nd3+ concentrations, cross-relaxation processes enhance the decay rates of the 4F3/2 and 4F5/2 levels making the decay faster than the equilibration rates between the levels. It is shown that the onset of the useful temperature sensing range shifts to higher temperatures, even above ~ 450 K for Nd concentrations over 5%. A microscopic explanation for pitfalls in Boltzmann thermometry with Nd3+ is finally given and guidelines for the usability of this lanthanide ion in the field of physiological temperature sensing are elaborated. Insight in competition between thermal coupling through non-radiative transitions and population decay through cross-relaxation of the 4F5/2 and 4F3/2 spin-orbit levels of Nd3+ makes it possible to tailor the thermometric performance of Nd3+ to enable physiological temperature sensing. Full article
(This article belongs to the Special Issue Luminescent Rare-Earth-Based Nanomaterials)
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Open AccessArticle
Synthesis, Cytotoxicity Assessment and Optical Properties Characterization of Colloidal GdPO4:Mn2+, Eu3+ for High Sensitivity Luminescent Nanothermometers Operating in the Physiological Temperature Range
Nanomaterials 2020, 10(3), 421; https://doi.org/10.3390/nano10030421 - 28 Feb 2020
Cited by 1
Abstract
Herein, a novel synthesis method of colloidal GdPO4:Mn2+,Eu3+ nanoparticles for luminescent nanothermometry is proposed. XRD, TEM, DLS, and zeta potential measurements confirmed the crystallographic purity and reproducible morphology of the obtained nanoparticles. The spectroscopic properties of GdPO4 [...] Read more.
Herein, a novel synthesis method of colloidal GdPO4:Mn2+,Eu3+ nanoparticles for luminescent nanothermometry is proposed. XRD, TEM, DLS, and zeta potential measurements confirmed the crystallographic purity and reproducible morphology of the obtained nanoparticles. The spectroscopic properties of GdPO4:Mn2+,Eu3+ with different amounts of Mn2+ and Eu3+ were analyzed in a physiological temperature range. It was found that GdPO4:1%Eu3+,10%Mn2+ nanoparticles revealed extraordinary performance for noncontact temperature sensing with relative sensitivity SR = 8.88%/°C at 32 °C. Furthermore, the biocompatibility and safety of GdPO4:15%Mn2+,1%Eu3+ was confirmed by cytotoxicity studies. These results indicated that colloidal GdPO4 doped with Mn2+ and Eu3+ is a very promising candidate as a luminescent nanothermometer for in vitro applications. Full article
(This article belongs to the Special Issue Luminescent Rare-Earth-Based Nanomaterials)
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Open AccessArticle
LiAl5O8:Fe3+ and LiAl5O8:Fe3+, Nd3+ as a New Luminescent Nanothermometer Operating in 1st Biological Optical Window
Nanomaterials 2020, 10(2), 189; https://doi.org/10.3390/nano10020189 - 22 Jan 2020
Cited by 1
Abstract
New types of contactless luminescence nanothermometers, namely, LiAl5O8:Fe3+ and LiAl5O8:Fe3+, Nd3+ are presented for the first time, revealing the potential for applications in biological systems. The temperature-sensing capability of the nanocrystals [...] Read more.
New types of contactless luminescence nanothermometers, namely, LiAl5O8:Fe3+ and LiAl5O8:Fe3+, Nd3+ are presented for the first time, revealing the potential for applications in biological systems. The temperature-sensing capability of the nanocrystals was analyzed in wide range of temperature (−150 to 300 °C). The emission intensity of the Fe3+ ions is affected by the change in temperature, which induces quenching of the 4T1 (4G) → 6A1 (6S) Fe3+ transition situated in the 1st biological window. The highest relative sensitivity in the temperature range (0 to 50 °C) was found to be 0.82% °C (at 26 °C) for LiAl5O8: 0.05% Fe3+ nanoparticles that are characterized by long luminescent lifetime of 5.64 ms. In the range of low and high temperatures the Smax was calculated for LiAl5O8:0.5% Fe3+ to be 0.92% °C at −100 °C and for LiAl5O8:0.01% Fe3+ to be 0.79% °C at 150 °C. The cytotoxicity assessment carried out on the LiAl5O8:Fe3+ nanocrystals, demonstrated that they are biocompatible and may be utilized for in vivo temperature sensing. The ratiometric luminescent nanothermometer, LiAl5O8:Fe3+, Nd3+, which was used as a reference, possesses an Smax = 0.56%/°C at −80 °C, upon separate excitation of Fe3+ and Nd3+ ions using 266 nm and 808 nm light, respectively. Full article
(This article belongs to the Special Issue Luminescent Rare-Earth-Based Nanomaterials)
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