Advances in the photon avalanche luminescence of inorganic lanthanide-doped nanomaterials.

Photon avalanche (PA)-where the absorption of a single photon initiates a 'chain reaction' of additional absorption and energy transfer events within a material-is a highly nonlinear optical process that results in upconverted light emission with an exceptionally steep dependence on the illumination intensity. Over 40 years following the first demonstration of photon avalanche emission in lanthanide-doped bulk crystals, PA emission has been achieved in nanometer-scale colloidal particles. The scaling of PA to nanomaterials has resulted in significant and rapid advances, such as luminescence imaging beyond the diffraction limit of light, optical thermometry and force sensing with (sub)micron spatial resolution, and all-optical data storage and processing.

Bifunctional Luminescent Thermometer-Manometer Based on Cr-Cr Pair Emission.

Pressure dependence of spectral positions of the E → A and T → A bands of Cr ions, resulting from changes in Cr-O covalency and variations in crystal field strength, respectively, is commonly utilized in luminescence manometry. However, as demonstrated in this paper, the luminescence of Cr-Cr pairs shows insensitivity to pressure changes, making this signal suitable as a luminescence reference. The significant difference in the thermal and pressure dependences of luminescence with Cr occupying different crystallographic positions in CaAlO:Cr enables the development of a dual-function luminescence thermometer that operates in both ratiometric and lifetime-based readout modes.

Investigating the Potential of Cr-Doped Pyroxene for Highly Sensitive Optical Pressure Sensing.

Luminescent manometry has gained significant popularity in recent years due to its capability to provide in situ pressure measurements in a remote manner. Therefore, there is a growing need to identify phosphors with pressure-dependent spectroscopic properties that can be utilized to develop highly sensitive pressure sensors operating over a wide pressure range. Hence, we present a novel temperature-invariant luminescent manometer based on Cr ion emission in pyroxene CaSrMgSiO:Cr.

Pressure-Induced Remarkable Spectral Red-Shift in Mn -Activated NaY (SiO ) O Red-Emitting Phosphors for High-Sensitive Optical Manometry.

To settle the low sensitivity of luminescent manometers, the Mn -activated NaY (SiO ) O red-emitting phosphors with splendid pressure sensing performances are developed. Excited by 408 nm, the resulting products emit bright red emission originating from T ( G) → A transition of Mn , in which the optimal concentration of the activator ion is ≈1 mol%. Moreover, the admirable thermal stability of the developed phosphors is studied and confirmed by the temperature-dependent emission spectra, based on which the activation energy is derived to be 0.

Frontiers of Deep-Red Emission of Mn Ions with Ruddlesden-Popper Perovskites.

It is well-known that the chemical composition of the host material significantly affects the spectroscopic performance of transition metal ions. However, it is worth noting that also the structure and symmetry of crystallographic sites play significant roles in transition metal ion luminescence. In this study, we demonstrate three perovskite structures of strontium titanate forming so-called Ruddlesden-Popper phases doped with Mn ions.

Mn-activated CaBa(PO)O near-infrared phosphor and its application in luminescence thermometry.

The near-infrared luminescence of CaBa(PO)O:Mn is demonstrated and explained. When excited into the broad and strong absorption band that spans the 500-1000 nm spectral range, this phosphor provides an ultranarrow (FWHM = 5 nm) emission centered at 1140 nm that originates from a spin-forbidden E → A transition with a 37.5% internal quantum efficiency and an excited-state lifetime of about 350 μs.

Influence of the Synthesis Conditions on the Morphology and Thermometric Properties of the Lifetime-Based Luminescent Thermometers in YPO:Yb,Nd Nanocrystals.

An increase in the accuracy of remote temperature readout using luminescent thermometry is determined, among other things, by the relative sensitivity of the thermometer. Therefore, to increase the sensitivity, intensive work is carried out to optimize the host material composition and select the luminescent ions accordingly. However, the role of nanocrystal morphology in thermometric performance is often neglected.

Quantitative Comparison of the Light-to-Heat Conversion Efficiency in Nanomaterials Suitable for Photothermal Therapy.

Functional colloidal nanoparticles capable of converting between various energy types are finding an increasing number of applications. One of the relevant examples concerns light-to-heat-converting colloidal nanoparticles that may be useful for localized photothermal therapy of cancers. Unfortunately, quantitative comparison and ranking of nanoheaters are not straightforward as materials of different compositions and structures have different photophysical and chemical properties and may interact differently with the biological environment.

Correction: Synthesis and characterizations of YZ-BDC:Eu,Tb nanothermometers for luminescence-based temperature sensing.

[This corrects the article DOI: 10.1039/D2RA01759H.].

Synthesis and characterizations of YZ-BDC:Eu,Tb nanothermometers for luminescence-based temperature sensing.

In the present work, nanothermometers based on amorphous zirconium metal-organic frameworks co-doped with rare-earth ions (YZ-BDC:Eu,Tb nanothermometers) with sizes of about 10-30 nm were successfully synthesized a microwave-assisted hydrothermal method at 120 °C for 15 min. The determined BET surfaces area, total pore volume and average pore diameter were ∼530 m g, 0.45 cm g and 3.

All near-infrared multiparametric luminescence thermometry using Er, Yb-doped YAG nanoparticles.

This paper presents four new temperature readout approaches to luminescence nanothermometry in spectral regions of biological transparency demonstrated on Yb/Er-doped yttrium aluminum garnet nanoparticles. Under the 10 638 cm excitation, down-shifting near infrared emissions (>10 000 cm) are identified as those originating from Yb ions' F → F (∼9709 cm) and Er ions' I → I (∼6494 cm) electronic transitions and used for 4 conceptually different luminescence thermometry approaches. Observed variations in luminescence parameters with temperature offered an exceptional base for studying multiparametric temperature readouts.

Boltzmann-distribution-dominated persistent luminescence ratiometric thermometry in NaYF:Pr.

A novel, to the best of our knowledge, optical temperature measurement method is proposed, i.e., persistent luminescence intensity ratio (PLIR) thermometry.

Self-referenced method for the Judd-Ofelt parametrisation of the Eu excitation spectrum.

Judd-Ofelt theory is a cornerstone of lanthanides' spectroscopy given that it describes 4f 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 Eu-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 F → D, F → D, and F → L transitions in the excitation spectrum for estimation and the integrated intensity of the F → D magnetic dipole transition for calibration.

Standardization of Methodology of Light-to-Heat Conversion Efficiency Determination for Colloidal Nanoheaters.

Localized photothermal therapy (PTT) has been demonstrated to be a promising method of combating cancer, that additionally synergistically enhances other treatment modalities such as photodynamic therapy or chemotherapy. PTT exploits nanoparticles (called nanoheaters), that upon proper biofunctionalization may target cancerous tissues, and under light stimulation may convert the energy of photons to heat, leading to local overheating and treatment of cancerous cells. Despite extensive work, there is, however, no agreement on how to accurately and quantitatively compare light-to-heat conversion efficiency (η) and rank the nanoheating performances of various groups of nanomaterials.

Highly NIR-emitting ytterbium complexes containing 2-(tosylaminobenzylidene)-N-benzoylhydrazone anions: structure in solution and use for bioimaging.

Solution behaviour in DMSO using 1D and 2D NMR spectroscopy was performed for lanthanide complexes Ln(L)(HL) and Ln(HL)Cl, containing non-macrocyclic 2-(tosylamino)-benzylidene-N-benzoylhydrazone (HL), and the structure of [Yb(L)] cation in solution was determined. Based on the NMR data, the possibility to obtain novel complexes containing [Ln(L)] was predicted, which was successfully synthesized, and the crystal structure of K(CHOH)[Yb(L)] was determined. Thanks to its high quantum yield of NIR luminescence (1.

Gallato Zirconium (IV) Phtalocyanine Complex Conjugated with SiO2 Nanocarrier as a Photoactive Drug for Photodynamic Therapy of Atheromatic Plaque.

A new conjugate of gallato zirconium (IV) phthalocyanine complexes (PcZrGallate) has been obtained from alkilamino-modified SiO nanocarriers (SiO-(CH)-NHNPs), which may potentially be used in photodynamic therapy of atherosclerosis. Its structure and morphology have been investigated. The photochemical properties of the composite material has been characterized.

Excited State Absorption for Ratiometric Thermal Imaging.

Luminescence thermometry, an alternative to thermal imaging using the thermovision technique, requires the development of new approaches and a thorough understanding of the physical phenomena involved, in order to improve the temperature readout parameters. A phenomenon that has recently been shown to cause an extremely strong increase in the emission intensity for the temperature elevation is the thermally induced excited state absorption. This work demonstrates that taking advantage of the strong thermal dependence of the thermally induced excited state absorption process, the limitation associated with the two thermally coupled excited levels usually involved in the ratiometric temperature readout can be overcome, improving the thermometric properties of the luminescent thermometer.

Synergy between NIR luminescence and thermal emission toward highly sensitive NIR operating emissive thermometry.

There are many figures of merit, which determine suitability of luminescent thermometers for practical applications. These include thermal sensitivity, thermal accuracy as well as ease and cost effectivness of technical implementation. A novel contactless emission thermometer is proposed, which takes advantage of the coexistence of photoluminescence from Nd doping ions and black body emission in transparent Nd doped-oxyfluorotellurite glass host matrix.

Cr based nanocrystalline luminescent thermometers operating in a temporal domain.

Cr3+ doped nanocrystals were examined as a noncontact temperature sensor in a lifetime-based approach. The impact of both the analysis protocols and host materials on the lifetime-based approach was systematically investigated. Temperature-dependent luminescence decay curves were analyzed according to three different procedures (average lifetime approach, double exponential fit and time-gated ratiometric approach).

Thermochromic Luminescent Nanomaterials Based on Mn/Tb Codoping for Temperature Imaging with Digital Cameras.

A new thermographic nanocrystalline SrAlO:Mn,Tb phosphor was developed, and the concentrations of both dopants and the synthesis conditions were optimized. The combination of the thermally quenched luminescence from the Mn ions to the almost temperature-independent emission from Tb provides a sensitive luminescent thermometer ( = 2.8%/°C at 150 °C) with strong emission color variability.

Fabrication and characterization of up-converting β-NaYF:Er,Yb@NaYF core-shell nanoparticles for temperature sensing applications.

This paper presents the use of soft template method to synthesize core and core-shell up-converting nanoparticles usefull for temperature sensing applications. Based on the stock solutions of core β-NaYF:Er,Yb nanoparticles and involving soft template method without any additional process of surface functionalization, it is possible to directly design the core-shell β-NaYF:Er,Yb@NaYF nanoparticles, which can be perfectly dispersed in cyclohexane and surfactants like oleic acid (OA), triethanolamine (TEA) or Cetyltrimethylammonium bromide (CTAB). The morphological, crystalline and elemental characteristics of samples were investigated by Field Emission Scanning Electron Microscopy, X-Ray Diffraction, High Resolution Transmission Electron Microscopy, Selected Area Electron Diffraction patterns and Energy-Dispersive X-Ray Spectroscopy (EDX) measurements.

Implementing Defects for Ratiometric Luminescence Thermometry.

In luminescence thermometry enabling temperature reading at a distance, an important challenge is to propose new solutions that open measuring and material possibilities. Responding to these needs, in the nanocrystalline phosphors of yttrium oxide YO and lutetium oxide LuO, temperature-dependent emission of trivalent terbium Tb dopant ions was recorded at the excitation wavelength 266 nm. The signal of intensity decreasing with temperature was monitored in the range corresponding to the D → F emission band.

Enhancement of the sensitivity of single band ratiometric luminescent nanothermometers based on Tb ions through activation of the cross relaxation process.

The description of luminescent processes and their thermally induced changes, that may be also influenced by the optically active ions concentration, and thus by the various inter-ionic processes, is the key to the improved development of luminescence thermometry. A phosphor doped with only trivalent terbium ions was described, which, by using two excitation lines fitted to the F → D and F → D transitions, shows a luminescent signals with the opposite characteristics of intensity changes as a function of temperature. By modifying the concentration of Tb ions, the probability of {D, F} ↔ {D, F} cross-relaxation was being altered, which turned out to have a beneficial effect on the properties of the described nanothermometers.