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Lanthanide-activated alkaline earth aluminate phosphors are excellent luminescent materials that are designed to overcome the limitations of conventional sulfide-based phosphors. The increasing research attention on these phosphors over the past decade has led to a drastic improvement in their phosphorescence efficiencies and resulted in a wide variety of phosphorescence colors, which can facilitate applications in various areas. This review article discusses the development of lanthanide-activated alkaline earth aluminate phosphors with a focus on the various synthesis methods, persistent luminescence mechanisms, activator and coactivator effects, and the effects of compositions. Particular attention has been devoted to alkaline earth aluminate phosphors that are extensively used, such as strontium-, calcium-, and barium-based aluminates. The role of lanthanide ions as activators and coactivators in phosphorescence emissions was also emphasized. Finally, we address recent techniques involving nanomaterial engineering that have also produced lanthanide-activated alkaline earth aluminate phosphors with long-persistent luminescence. [ABSTRACT FROM AUTHOR]

A series of CaF 2 -doped phosphors was synthesized in situ in hydrothermal conditions (in a DAB- 2 reactor), in the presence of sodium citrate as a complexing agent preventing premature precipitation. The materials were doped with Yb3+/Er3+ pair of ions, which resulted in up-conversion emission. Additionally, Mn2+ ions were incorporated into the structure of the CaF 2 to analyse their influence on the chromaticity of the luminescence colour, in view of their application in bioimaging. Detailed structural analysis showed that the structure of the nanoparticles obtained resembled the core@shell like structure. Finally, the emission colour was tuned from green to orange – red. It was confirmed that the quantity of Mn2+ ions incorporated in the CaF 2 matrix definitely differs from the expected one. The real concentration of Mn2+ ions in the structure is frequently ignored, which leads to incorrect conclusions. For this reason, a detailed structural and spectroscopic analysis was conducted and the effect of Mn2+ ions on the structure and the average size of the CaF 2 -doped phosphors was studied. Moreover, the in vitro cytotoxicity of the nanoparticles was evaluated. Obtained results showed that CaF 2 :15%Yb3+, 2%Er3+, 2.6%Mn2+ reduces cell viability of fibroblast at lower concentrations (50, 100 and 200 μg/ml) than CaF 2 :15%Yb3+, 2%Er3+ (200 μg/ml). Moreover, CaF 2 :15%Yb3+, 2%Er3+ caused increase of the fibroblast proliferation rate at the lowest tested concentration (10 μg/ml). Image 1 • Structural analysis of CaF 2 -doped phosphors showed the core@shell like structure. • The Mn2+ ions' quantity in the CaF 2 matrix definitely differs from the expected. • The emission colour of CaF 2 -doped materials was tuned from green to orange – red. • Two various type of excitation source resulted in different effect of colour tuning. [ABSTRACT FROM AUTHOR]

In biomedical and optical applications, multifunctional upconverting nanoparticles (UCNPs) play an essential role where non‐invasive temperature sensing and imaging are necessary. UCNPs smaller than 20 nm, which can be excited under 808 nm wavelength, are particularly promising in this area and can be implemented in humans or other mammals. However, new versatile nanoprobes are still needed for biology, especially for challenging studies of small aquatic invertebrates. Such tools allow better monitoring and understanding of their physiology, biochemistry, and ecological responses, which is crucial due to the growing pollution of water reservoirs and climate change. Herein, multifunctional NaYF4:Yb3+, Er3+@NaNdF4:Yb3+ core@shell NPs (15 nm), forming stable aqueous colloids, exhibiting intense emissions under excitation in the first biological window (808 nm), and presenting high thermal sensitivity and resolution related to the thermally coupled energy levels of Er3+ ions, are designed and synthesized. Such properties of UCNPs are further utilized for optical imaging of aquatic invertebrates (Daphnia magna) and temperature detection inside their bodies under 808 nm excitation. This pioneering application of NaYF4:Yb3+, Er3+@NaNdF4:Yb3+ demonstrates the high potential of developed UCNPs for multifunctional applications, especially for bioimaging and temperature sensing within whole organisms. [ABSTRACT FROM AUTHOR]

An amendment to this paper has been published and can be accessed via a link at the top of the paper. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel properties of upconverting nanoparticles (UCNPs) for biomedical applications. • Comparison of various UCNPs in real conditions for penetration depth of excitation light. • Deep penetration of near-infrared light (808, 975, 1208, and 1532 nm) in human blood. • Advantages of core/shell NaErF 4 /NaYF 4 UCNPs for luminescence detection through a blood layer using a 1532 nm laser. The properties of upconverting nanoparticles (UCNPs) are crucial for their applications in biomedicine. For studies of organisms and biological materials, the penetration depth of excitation light is also essential as the depth from which the luminescence can be detected. Currently, many researchers are trying to obtain UCNPs with intense emission under excitation wavelengths from the biological transparency windows to increase the penetration depth. However, studies comparing the properties of various types of UCNPs in real conditions are rare. This article shows how deep the 808, 975, 1208, and 1532 nm laser radiation penetrates human blood. Moreover, we determined how thick a layer of blood still permits for observation of the luminescence signal. The measured luminescence properties indicated that the near-infrared light could pass through the blood even to a depth of 7.5 mm. The determined properties of core/shell NaErF 4 /NaYF 4 materials are the most advantageous, and their emission is detectable through 3.0 mm of blood layer using a 1532 nm laser. We prove that the NaErF 4 /NaYF 4 UCNPs can be perfect alternatives for the most studied NaYF 4 :Yb3+,Er3+/NaYF 4. Additionally, the setup proposed in this article can potentially decrease reliance on animal testing in initial biomedicine research. [ABSTRACT FROM AUTHOR]

• Enhanced Tm emission intensity by double TiO 2 modification. • Formation of new Tm-f states below the CB of TiO 2 during the synthesis process. • Bathochromic shift of absorption for Tm-TiO 2 samples. • Enhanced photocatalytic activity under Vis irradiation for Tm-TiO 2. • Higher electronic density in the TiO 2 band gap region. The utilization of solar light to induce a photocatalytic reaction in the presence of wide band gap semiconductors requires the modification of their surface and optical properties. The Vis-to-UV up-conversion process (UCP) that occurs in lanthanide ions could be employed to induce TiO 2. Thus, having in mind solar-forced photocatalysis, nanostructured TiO 2 co-modified with Tm and Li was prepared via a hydrothermal method. In addition to the exhaustive surface characterization of the as-prepared samples, the partial density of states (PDOS) was computed to better understand the electronic structure and physicochemical properties of the prepared photocatalysts. It was demonstrated that Tm ions were beneficial for phenol degradation in the aqueous phase under visible irradiation, whereas the co-presence of Tm and Li ions was profitable for enhanced luminescence. Although action spectra revealed that excitation of Tm-TiO 2 in the range from 400 to 490 nm led to the photodegradation of phenol and 2-propanol, the UCP was not responsible for the photocatalytic activity under Vis irradiation. Therefore, it is proposed that the formation of sub-band gap states from the lanthanide 4f level played a key role in the phenol degradation process. [ABSTRACT FROM AUTHOR]

[Display omitted] Photon upconversion is an intensively investigated phenomenon in the materials sciences due to its unique applications, mainly in biomedicine for disease prevention and treatment. This study reports the synthesis and properties of tetragonal LiYbF 4 :Tm3+@LiYF 4 core@shell nanoparticles (NPs) and their applications. The NPs had sizes ranging from 18.5 to 23.7 nm. As a result of the energy transfer between Yb3+ and Tm3+ ions, the synthesized NPs show intense emission in the ultraviolet (UV) range up to 347 nm under 975 nm excitation. The bright emission in the UV range allows for singlet oxygen generation in the presence of hematoporphyrin on the surface of NPs. Our studies show that irradiation with a 975 nm laser of the functionalized NPs allows for the production of amounts of singlet oxygen easily detectable by Singlet Oxygen Sensor Green. The high emission intensity of NPs at 800 nm allowed the application of the synthesized NPs in an upconversion-linked immunosorbent assay (ULISA) for highly sensitive detection of the nucleoprotein from SARS-CoV-2, the causative agent of Covid-19. This article proves that LiYbF 4 :Tm3+@LiYF 4 core@shell nanoparticles can be perfect alternatives for the most commonly studied upconverting NPs based on the NaYF 4 host compound and are good candidates for biomedical applications. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO 2 ) nanoparticles (NPs) modified with neodymium (Nd) in the range between 0.1 and 1.0 mol% were prepared via the hydrothermal method. The samples obtained were characterized by diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), X-ray fluorescence (EDX), Brunauer–Emmett–Teller (BET) method, X-ray powder diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL). The photocatalytic activity of the obtained samples was evaluated by photodegradation of phenol in aqueous solution under ultraviolet–visible (UV–Vis, λ > 350 nm) and visible (Vis, λ > 420 nm) irradiation. Experimental results showed that the photocatalysts exhibited high photocatalytic activity under Vis light. The sample showing the highest photoactivity under Vis irradiation was in the form of anatase; its surface area equalled 124 m 2 /g (1.16 times larger than that of pristine TiO 2 ). The average crystal size was 10.9 nm, and it was modified with 0.1 mol% of Nd 3+ (28% of phenol was degraded after 60 min of irradiation). The photocatalytic tests of phenol degradation in the presence of scavengers confirm that e − and were responsible for the visible light degradation of organic compounds in the aqueous phase. Action spectra analysis revealed that although Nd-modified TiO 2 could be excited under visible light in the range of 400–480 nm, the up-conversion process is not responsible for the degradation of phenol under Vis irradiation. [ABSTRACT FROM AUTHOR]

A series of Er-, Yb-, Ho-, Tb-, Gd-, Pr-TiO 2 nanotubes (RE-NTs) was prepared via an electrochemical method. The as-prepared photocatalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis absorption, scanning electron microscopy (SEM) and luminescent spectroscopy. The experiments demonstrated that toluene in the gas phase was successfully degraded under visible light (LEDs λ max = 465 nm) using RE-NTs. In the presence of the most active sample (Ho-NTs), the photodegradation of toluene reached 30% after 60 min of vis irradiation. To investigate the localization of RE in the TiO 2 structure, computer simulations were performed using the plane-wave-based Vienna ab-initio simulation package (VASP) implementing spin-polarized density-functional theory (DFT) and the generalized gradient approximation (GGA). It is proposed that during the electrochemical process, TiO 2 systems with new Ho-f states below the conduction band of TiO 2 is formed. The photocatalytic activity under Vis irradiation is attributable not to OH but to other forms of reactive oxygen species (O 2 − , HO 2 , H 2 O 2 ). [ABSTRACT FROM AUTHOR]

Lithium lanthanum praseodymium tetraphosphates nanopowders, LiLa 1−x Pr x (PO 3 ) 4 , where x = 0.01–1, were prepared by wet-chemistry synthesis route. The structure and morphology of phosphates were analyzed by collecting X-ray diffraction patterns, Raman and FT-IR spectra. The obtained materials were composed of submicron crystals in the elongated forms and plates. The monoclinic structure of the crystals with the space group C 2/ c was assigned for all investigated compositions. The decrease of unit cell parameters with the increase of praseodymium concentration, due to the lower ionic radius of the Pr 3+ as compared to the La 3+ cations, was evidenced. Spectroscopic properties of the LiLa 1−x Pr x (PO 3 ) 4 powders were analyzed in details on the basics of the absorption, excitation, and emission spectra with luminescence lifetimes measurements. The intraconfigurational 4 f 2 transitions were observed under blue (λ = 440 nm) and UV (λ = 212 nm) excitation. The luminescence characteristic of the samples was dependent on the concentration of the Pr 3+ ions in the host material. Significant concentration quenching in the whole range of investigated samples was observed leading to barely seen emission of the LiPr(PO 3 ) 4 crystals. [ABSTRACT FROM AUTHOR]

In this paper, the UV sensitive optically active cellulose fibers contained of 0.5% w/w Sr 2 CeO 4 , Gd 4 O 3 F 6 :5%Eu 3+ and CeF 3 :5%Tb 3+ with respectively blue, red and green emission are described. The fibers were formed from an 8% by weight cellulose spinning solution in N-methylmorpholine-N-oxide (NMMO). The modifiers were chosen because of their specific color of emitted light. Photoluminescent particles were introduced into the polymer matrix during the dissolution process of cellulose in NMMO. The emission intensity and excitation energy of the final cellulosic luminescent products were examined by photoluminescence spectroscopy. The degree of dispersion of the nanoparticles in the polymer matrix was evaluated using transmission electron microscopy (TEM). The influence of modifier's particles on the mechanical properties of the fibers was determined. [ABSTRACT FROM AUTHOR]

Soils are major reservoirs of plastic particles, an issue that agricultural activities have aggravated. Thus, devising eco-friendly, safe, and cost-effective strategies for enhanced degradation of plastic particles in soil and arable land has been a landmark over the last couple of years. Rot fungi are being used as cleaning agents for plastic-laden soils due to their ability to recycle organic matter and degrade toxic compounds. This article systematizes and outlines the metabolic and biochemical processes of rot fungi in the degradation of plastic particles. It provides a framework for soil policies addressing microbiota's role in soil resilience, emphasizes the potential accumulation of plastic particles on plants' edible parts, and frames the role of rot fungi in this pertinent issue. It also highlights the potential boost that advanced computational tools may provide to this research field. • The metabolic and biochemical processes of rot fungi during degradation of plastic particles are outlined. • Soil policies and the sources of nano(micro)plastics on soil were addressed. • Hydrophobins allow rot fungi to colonize nano(micro)plastic particles. • The rot fungi secretome promotes the breakdown of polymer homo-or heteroatom backbone structures. • Membrane-bound proteins (P450's) play a role in the assimilation and mineralization of plastic degradation products. [ABSTRACT FROM AUTHOR]

• UC emission of NaYF 4 :Er3+ and NaYF 4 :Yb3+,Er3+ were investigated under pressure. • Laser power density dependencies under pressure were analyzed for the first time. • The number of photons involved in population of the excited state was calculated. • Changes in emission bands in the compression cycle were compared. • Pressure sensing performance - relative sensitivity was estimated as ≈20 % GP−1. Inorganic nanomaterials doped with lanthanide ions and exhibiting upconversion (UC) luminescence are leading in research of nonlinear optical materials. Extreme conditions, such as high-pressure compression (in the GPa range), may influence the physicochemical properties of various compounds. In this work, we investigated the optical properties of upconverting NaYF 4 :Er3+@NaYF 4 and NaYF 4 :Yb3+,Er3+@NaYF 4 core@shell nanoparticles (NPs), focusing on the impact of high pressure on the number of photons involved in the UC mechanism. We measured the UC emission spectra of the synthesized NPs under high-pressure conditions, which allowed us to observe the pressure-induced intensity changes, band centroids spectral shifts, and band intensity ratios alterations. Importantly, by measuring the power-dependent UC emission spectra as a function of pressure, we determined and analyzed the number of photons (n) involved in the UC processes for the first time. It turned out that the n value changes with pressure as a result of diverse multi-phonon relaxation processes enhanced under high-pressure conditions. The results show potential adjustment of UC mechanisms with the use of high-pressure. The calculated band intensity ratios were also used for pressure sensing applications, resulting in the relative sensitivity reaching almost ≈20 % GPa−1 for the Er3+-doped core@shell NPs. [Display omitted] [ABSTRACT FROM AUTHOR]

Individuals automatically mimic a wide range of different behaviors, and such mimicking behavior has several social benefits. One of the landmark findings in the literature is that being mimicked increases liking for the mimicker. Research in cognitive neuroscience demonstrated that mentally simulating motor actions is neurophysiologically similar to engaging in these actions. Such research would predict that merely imagining being mimicked produces the same results as actually experiencing mimicry. To test this prediction, we conducted two experiments. In Experiment 1, being mimicked increased liking for the mimicker only when mimicry was directly experienced, but not when it was merely imagined. Experiment 2 replicated this finding within a high-powered online sample: merely imagining being mimicked does not produce the same effects as being actually mimicked. Theoretical and practical implications of these experiments are discussed. [ABSTRACT FROM AUTHOR]

Nanophosphors based on yttrium orthoborates doped with Eu3+ or Tb3+ were obtained by the wet chemical synthesis Pechini method with ethylene glycol and citric acid as the reagents promoting copolymerization. Optimal synthesis conditions were found. Crystal structure, morphology and grain size of the nanoproducts were determined on the basis of XRD (X-ray diffraction), EDX (Energy-dispersive X-ray spectroscopy) and TEM (transmission electron microscopy) analysis. Spectroscopic properties were investigated using excitation and emission spectra and luminescence decay curves. Judd-Ofelt intensity parameters were calculated and analysed. The influence of calcination temperature on the physicochemical properties was also examined in order to define the optimum conditions of synthesis. [ABSTRACT FROM AUTHOR]

People have the automatic tendency to mimic their interaction partners. Mimicry theories propose that such mimicking behavior is beneficial for the mimicker as mimicked persons tend to like, trust and help the mimicker more. Yet an open question remains as to whether prosocial effects translate to parties other than the mimicker. To test for the presence of such a spillover effect, we ran two field experiments (total N = 460). In all experiments, participants interacted with an experimenter. The experimenter either verbally mimicked the participants or behaved naturally. Afterwards, either the experimenter or another person asked participants to donate to a charity. Across all experiments, our results indicate that irrespective of whether a donation request is made by the mimicker or another person, mimicry increases the likelihood to donate to a charity, but not the amount that participants are willing to donate. Bayesian analyses suggest that this effect is less strongly pronounced than assumed by previous research and theories. • Mimicry leads to higher charity donations. • Participants (in two field experiments) were mimicked (or not) and asked to donate. • A donation request was made by the mimicker or a stranger. • Mimicry increased the likelihood of donating, but not the amount, irrespective of who asked for donations. [ABSTRACT FROM AUTHOR]

Modification with rare-earth (RE) metals has emerged as an important approach for enhancing the properties of titanium dioxide. Herein, the visible-light photocatalytic activity of RE-TiO 2 (RE: Tm, Er, Nd, Dy, Lu, La, Ho, Pr, Tb, Sc, Ce, Yb, Sm, Gd, Y, or Eu) was investigated using a combination of computer simulations and experimental techniques. The RE-TiO 2 photocatalysts were characterised using advanced experimental techniques, including X-ray diffraction, X-ray photoelectron spectroscopy, luminescence, diffuse reflectance spectroscopy, and specific surface area measurements. Furthermore, a quantitative structure–activity relationship analysis was conducted by applying a partial least-squares machine learning algorithm. The Ho-TiO 2 sample exhibited the highest photocatalytic activity under visible-light irradiation. Notably, the observed activity was not due to an up-conversion process, originating instead from slight bandgap narrowing caused by new sub-bandgap states from the RE 4 f levels. [Display omitted] • The visible-light photoactivity of rare-earth-metal-doped TiO 2 was investigated. • Photocatalysts based on all rare-earth elements, except Pm, were synthesised. • A combination of computational and experimental techniques was applied. • Ho-TiO 2 achieved the highest photocatalytic activity under visible-light irradiation. • Sub-bandgap states from the 4 f levels of the doped metal caused bandgap narrowing. [ABSTRACT FROM AUTHOR]

[Display omitted] The right choice of synthesis route for upconverting nanoparticles (UCNPs) is crucial for obtaining a well-defined product with a specific application capability. Thus we decided to compare the physicochemical, cytotoxic, and temperature-sensing properties of UCNPs obtained from different rare earth (RE) ions, which has been made for the first time in a single study. The core/shell NaYF 4 :Yb3+,Er3+/NaYF 4 UCNPs were obtained by reaction in a mixture of oleic acid and octadecene, and their highly stable water colloids were prepared using the ligand-free modification method. Both oleate-capped and ligand-free UCNPs exhibited a bright upconversion emission upon 975 nm excitation. Moreover, slope values, emission quantum yields, and luminescence lifetimes confirmed an effective energy transfer between the Yb3+ and Er3+ ions. Additionally, the water colloids of the UCNPs showed temperature-sensing properties with a good thermal sensitivity level, higher than 1 % K−1 at 358 K. Evaluation of the cytotoxicity profiles of the obtained products indicated that cell viability was decreased in a dose-dependent manner in the analyzed concentration range. [ABSTRACT FROM AUTHOR]

Water-dispersible up-converting nanoparticles (UCNPs) are known to be very effective in biomedical applications. Research groups have paid special attention to the synthesis of hydrophilic UCNPs with good physicochemical properties. Being aware of this, we decided to improve the ligand-free modification method of OA-capped NaYF4:Yb3+,Er3+/NaYF4 UCNPs prepared by precipitation in high-boiling-point solvents as the thus-far reported methods do not provide satisfactory results. Different molarities of hydrochloric acid and various mixing times were selected to remove the organic ligand from the NPs' surface and to discover the most promising modification approach. Highly water-stable colloids were obtained with a very high reaction yield of up to 96%. Moreover, the acid treatment did not affect the morphology and the size of the product. All of the crystals exhibited a bright up-conversion emission under 975-nm excitation, which confirmed the two-photon excitation and effective energy transfer between the used dopant ions. Thus, we could establish the most successful ligand-free modification procedure. [ABSTRACT FROM AUTHOR]

Great interest has been placed on studying algicidal bacteria to control cyanobacterial outbreaks in freshwater ecosystems. However, the mechanism of changes at the molecular and cellular level in cyanobacteria stressed by algicidal bacteria requires better exploration. Here, the physiological stress of Microcystis aeruginosa and Aphanizomenon gracile strains, two well-known bloom-forming cyanobacteria, was described when exposed to algicidal bacteria Morganella morganii SU7S0818 and Bacillus pumilus SU8S0818 (isolated from a eutrophic reservoir). The results indicated that both bacteria induced a strong algicidal activity, although Aphanizonmenon strains were more sensitive than Microcystis. Studied cyanobacterial strains accumulated high amounts of reactive oxygen species (ROS) contributing to almost complete cell death after six days of co-culture. Gene expression analysis based on the upregulation of the psb A and rec A genes for photosynthesis and DNA repair mechanisms, respectively, showed that A. gracile strains responded slower to cellular stress (24–30 h) than M. aeruginosa strains (12 h). Microscopic analyses revealed the increase of cyanophycin granules in affected cyanobacterial cells, which may indicate the development of a survival mechanism under algicidal stress conditions. These findings are critical to understanding and managing the problem of global expansion of harmful algal blooms caused by different species of cyanobacteria. [Display omitted] • Bacillus pumilus SU8S0818 and Morganella morganii SU7S0818 disrupt cyanobacteria. • Aphanizomenon gracile was more sensitive than Microcystis aeruginosa. • Photosynthesis and DNA damage/repair stress signal was slower for A. gracile. • Cyanobacterial ultrastructure cell damage was associated to ROS accumulation. • Cyanophicyn granules in damaged cells was regarded as a survival mechanism. [ABSTRACT FROM AUTHOR]

In recent years, nanotechnology has found widespread applications in environmental monitoring, medical applications, plant fertilisers, cosmetics and others. Therefore, it is important to study nanomaterials' influence and subsequent risks to the environment and organisms (from production to disposal). Therefore, in the present study, the toxic effects of two surface modifications (poly (ethylene glycol)-neridronate, PEG-Ner and poly (acrylic acid), PAA) in comparison to unmodified, 26 nm- and 52 nm-sized core@shell lanthanide-doped upconverting nanoparticles (UCNPs, NaYF 4 :Yb3+,Er3+@NaYF 4) were analysed. Wheat seedlings (Triticum aestivum L.) were chosen as a model organism since this species is one of the most widely cultivated crops. The influence of UCNPs (at concentrations of 0, 10, 50, and 100 μg/mL) on germination percentage, germination rate and growth was studied based on morphological parameters such as root number, root and hypocotyl length, and root and hypocotyl mass. In addition, an assay based on Evans blue staining was conducted to analyse damaged cell membranes and cell death. The type, size and concentration of UCNPs influenced the growth but not the germination of wheat. 52-nm-sized ligand-free UCNPs and the 26-nm-sized UCNPs/PAA decreased plant growth. Moreover, the ligand-free 26-nm-sized UCNPs interacted with the root cell membranes of seedlings. No significant changes were observable regarding viability (tetrazolium chloride reduction assay), oxidative stress and electrolyte leakage from root cells in plants incubated with ligand-free 26-nm-sized UCNPs. Overall, we have shown that the ligand-free UCNPs (of both sizes) had the strongest toxic effect; PAA-modified UCNPs were toxic only at smaller sizes and PEG-Ner-modified UCNPs had no toxic impact. Therefore, PEG-Ner was identified as the safest surface compound among the UCNPs investigated in the study, which may neutralise the harmful effects of nanoparticles on plants. [Display omitted] • The phytotoxicity of NaYF 4 :Yb3+,Er3+@NaYF 4 upconverting nanoparticles (UCNPs) depends on surface modification and size. • Surface modification with PEG-Ner renders UCNPs non-toxic and PAA reduces the toxic effects of larger UCNPs (52 nm). • The UCNPs were visualised simultaneously in various parts of the plants without background autofluorescence. [ABSTRACT FROM AUTHOR]

This paper reports the spectroscopic properties of up-converting NaLuF 4 materials doped with Yb3+, Er3+ and with different amount of Ho3+ ions. The products were synthesized by simple hydrothermal route and their structural properties were carefully examined by using X-ray diffraction and scanning electron microscopy. The relation between the changing amount of Ho3+ ions and spectroscopic properties was investigated by luminescence measurements. The recorded emission spectra exhibited seven characteristic bands under excitation with 975 nm laser beam, with the most intense peaks at 550 and 650 nm. The observed in the emission spectra peaks resulted from overlapped emission of Er3+ and Ho3+ ions. The dependencies between laser power density and integral luminescence intensity were measured. Determined on their basis number of photons responsible for the observed up-conversion and calculated luminescence lifetimes allowed determining the mechanism of the up-conversion process, in detail. Image 1 • The synthesis and spectroscopic properties of NaLuF 4 :Yb3+,Er3+,Ho3+ are reported. • The different amount of Ho3+ dopant influenced luminescence properties. • The energy transfer and cross-relaxation between Er3+ and Ho3+ were studied. • Mechanism of the up-conversion process was proposed. [ABSTRACT FROM AUTHOR]

Abstract The article describes the properties of LuF 3 and NaLuF 4 fluorides doped with Yb3+ and Er3+ or Tm3+ ions, their comparison and application in latent fingermarks imaging. The single-phase materials were successfully synthesized by the hydrothermal method. They exhibited up-conversion (UC) phenomenon under excitation by the near-infrared (NIR) radiation at 975 nm. Under excitation, the energy transfer between Yb3+ and Er3+ or Tm3+ ions occurred and emissions in the visible range were recorded (green or blue for Er3+ or Tm3+ dopants respectively). The luminescence decays of as-prepared samples were measured allowing the calculation of luminescence lifetimes. The dependencies of integrated UC intensity on laser power density were measured for the obtained samples, revealing up to three-photon process for Yb3+ and Tm3+ co-doped and two-photon process for Yb3+ and Er3+ co-doped materials. Furthermore, up-converting lutetium fluorides synthesized in this report were successfully used to visualize latent fingermarks on various non-porous surfaces. Graphical abstract Image 1 Highlights • LuF 3 and β-NaLuF 4 doped with lanthanide ions were prepared by a hydrothermal method. • Doping by 20% Yb3+ and 0.5% Er3+ or 0.5% Tm3+ ions resulted in intense up-conversion. • Prepared materials revealed latent fingermarks on various non-porous surfaces. [ABSTRACT FROM AUTHOR]

Novel rare earth-doped K 2 Ta 2 O 6 (RE-K 2 Ta 2 O 6 ) photocatalysts were successfully synthesized by one-step hydrothermal method. The effect of dopant type (RE = Y, Yb, Ho, Pr, Er) and amount of rare earth precursor (2, 4, 8 and 10 mol%) on the physicochemical and photocatalytic properties of RE-K 2 Ta 2 O 6 have been investigated. All as-prepared materials were subsequently characterized by UV–vis diffuse reflectance spectroscopy (DRS), Brunauer-Emmett-Teller (BET) specific surface area measurement, scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, mass magnetic susceptometry and photoluminescence (PL) emission spectroscopy. The photocatalytic activity under UV–vis light irradiation was estimated in phenol degradation in aqueous phase, toluene removal in gas phase and H 2 generation from formic acid solution. The experimental results show that, novel RE-K 2 Ta 2 O 6 exhibits greatly improved degradation efficiency under UV–vis light irradiation compared with pristine K 2 Ta 2 O 6 . The Er-K 2 Ta 2 O 6 and Pr-K 2 Ta 2 O 6 , obtained by introducing of 2 mol% of RE ions during synthesis, reveal the highest photocatalytic activity among prepared samples in aqueous phase (33% of phenol decomposition after 90 min of irradiation) and gas phase (45% of toluene removal after 60 min of irradiation), respectively. Moreover, both photocatalysts present good stability after subsequent three cycles. The active species trapping test shows that OH and O 2 − radicals are significantly involved in phenol oxidation under UV–vis light irradiation. The amount of H 2 evolution increases with increasing addition of Er dopant into K 2 Ta 2 O 6 lattice. The highest H 2 production is obtained for 10 mol% Er-K 2 Ta 2 O 6 after 240 min of UV–vis light irradiation (15.40 μmol/min). Enhanced photoactivity performance can be attributed to incorporation of RE ions at K + lattice site in RE-K 2 Ta 2 O 6 , probably leading to formation of new RE 4f states below the conduction band of K 2 Ta 2 O 6 structure. To investigate the localization of RE ions in K 2 Ta 2 O 6 structure, the band structure and partial density of the states (PDOS) have been investigated. Computer simulations were performed using plane-wave based Vienna ab-initio simulation package (VASP) with the generalized gradient approximation (GGA) by Perdew-Burke-Ernzerhof (PBE). Moreover, inclusion of RE ions in K 2 Ta 2 O 6 causes predominance pyrochlore phase formation over perovskite in regular cubic structure. Summarized, RE-doped K 2 Ta 2 O 6 is promising material in photocatalytic degradation of organic pollutants and H 2 generation processes. Our work may provide valuable information for rare earth doping semiconductor with improved photocatalytic performance. [ABSTRACT FROM AUTHOR]

A series of lanthanide doped yttrium vanadates were prepared by Pechini's method (sol-gel process). The as-prepared precursors, in the presence of citric acid, were calcined in the temperature range of 600–900 °C. The obtained products were composed of small nanoparticles, in the size range of 20–50 nm, depending on the annealing temperature, exhibiting a bright green up-conversion emission, under NIR laser irradiation, and emission lifetimes in the range of 4.7–18.3 μs. Their structural, morphological and spectroscopic properties were investigated in detail by XRD, HR-TEM including FFT analysis, EDX and spectroscopic techniques (emission, power dependence and emission kinetics). The luminescence quenching phenomenon, manifested in a decrease of up-conversion intensity and shortening of emission lifetime, was observed with increasing of the Yb 3+ ion concentration and decreasing the particle size. The optimal concentration of the Yb 3+ ions was found to be 15 mol% (YVO 4 : Yb 3+ 15 mol%, Er 3+ 2 mol%). [ABSTRACT FROM AUTHOR]

• The toxicity of lanthanide-doped nanocrystals, bare or PEG-coated, was evaluated. • Overall, SrF2:Yb3+,Er3+@PEG NPs were slightly more toxic. • Hydra viridissima was the species showing the highest sensitivity to the NPs. • Both NPs were found to accumulate in daphnia's digestive tract. Various types of nanoparticles (NPs) have been widely investigated recently and applied in areas such as industry, the energy sector, and medicine, presenting the risk of their release into the environment. The ecotoxicity of NPs depends on several factors such as their shape and surface chemistry. Polyethylene glycol (PEG) is one of the most often used compounds for functionalisation of NP surfaces, and its presence on the surfaces of NPs may affect their ecotoxicity. Therefore, the present study aimed to assess the influence of PEG modification on the toxicity of NPs. As biological model, we chose freshwater microalgae, a macrophyte and invertebrates, which to a considerable extent enable the assessment of the harmfulness of NPs to freshwater biota. SrF 2 :Yb3+,Er3+ NPs were used to represent the broad group of up-converting NPs, which have been intensively investigated for medical applications. We quantified the effects of the NPs on five freshwater species representing three trophic levels: the green microalgae Raphidocelis subcapitata and Chlorella vulgaris , the macrophyte Lemna minor , the cladoceran Daphnia magna and the cnidarian Hydra viridissima. Overall, H. viridissima was the most sensitive species to NPs, which affected its survival and feeding rate. In this case, PEG-modified NPs were slightly more toxic than bare ones (non-significant results). No effects were observed on the other species exposed to the two NPs at the tested concentrations. The tested NPs were successfully imaged in the body of D. magna using confocal microscopy; both NPs were detected in the D. magna gut. The results obtained reveal that SrF 2 :Yb3+,Er3+ NPs can be toxic to some aquatic species; however, the structures have low toxicity effects for most of the tested species. [Display omitted] [ABSTRACT FROM AUTHOR]

The luminescent GdVO 4 :Eu 3+ 5%@SiO 2 @NH 2 core@shell nanomaterials were obtained via co-precipitation method, followed by hydrolysis and co-condensation of silane derivatives: tetraethyl orthosilicate and 3-aminopropyltriethoxysilane. Their effect on human erythrocytes sedimentation and on proliferation of human lung microvascular endothelial cells was examined and discussed. The luminescent nanoparticles were synthesized in the presence of polyacrylic acid or glycerin in order to minimalize the agglomeration and excessive growth of nanostructures. Surface coating with amine functionalized silica shell improved their biocompatibility, facilitated further organic conjugation and protected the internal core. Magnetic measurements revealed an enhanced T 1 -relaxivity for the synthesized GdVO 4 :Eu 3+ 5% nanostructures. Structure, morphology and average grain size of the obtained nanomaterials were determined by X-ray diffraction, transmission electron microscopy and dynamic light scattering analysis. The qualitative elemental composition of the nanomaterials was established using energy-dispersive X-ray spectroscopy. The spectroscopic characteristic of red emitting core@shell nanophosphors was completed by measuring luminescence spectra and decays. The emission spectra revealed characteristic bands of Eu 3+ ions related to the transitions 5 D 0 - 7 F 0,1,2,3,4 and 5 D 1 - 7 F 1 . The luminescence lifetimes consisted of two components, associated with the presence of Eu 3+ ions located at the surface of the crystallites and in the bulk. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lanthanide-doped core@shell nanoparticles for luminescent cellulose fibers production. • Dual-range excitation of luminescent materials with 975 and 1532 nm laser radiation. • Luminescent fibers as anti-counterfeiting agents for documents, clothes and valuable products. • '3-level' protection system resulting from a unique optical activity of the nanoparticles. The increasingly wide-spreading falsification of documents, clothing, and packaging has a negative impact on every aspect of the global markets. Therefore, the development of high-quality strategies for materials protection has become a big challenge. Thus, this work presents novel anti-counterfeiting lyocell fibres, exhibiting bright green or yellowish up-conversion emission upon dual-range excitation, using either 975-nm or 1532-nm NIR laser radiation. The up-converting cellulose fibers were prepared by introducing lanthanide-doped core@shell nanoparticles β-NaYF 4 : Yb3+, Er3+@β-NaYF 4 into the cellulose matrix. The spinning process of fibres was based on N-methylmorpholine N-oxide method, environmentally friendly because of the reusable reagents used. The prepared fibres were incorporated into the paper mass, forming a luminescent paper as a proof of concept for the multi-modal protection of documents. The luminescent fibres have considerable application potential as anti-counterfeiting composite materials with excellent performance, which are very difficult to imitate or copy, providing a very high level of security. [ABSTRACT FROM AUTHOR]

[Display omitted] • CeO 2 /ZnO composites more active in ciprofloxacin (CIP) degradation than ZnO or CeO 2. • Improved activity of CeO 2 /ZnO results from formation of Z-scheme heterojunction. • Degradation of CIP proceeds via two parallel pathways initiated by h+ and/or HO•. • Main oxidative species responsible for degradation of CIP are photo-generated holes. The aim of this study was to provide deep insight into photocatalytic degradation of ciprofloxacin (CIP) over CeO 2 /ZnO nanocomposites. Catalysts used in this work were synthesized by a simple co-precipitation method and fully characterized by means of XRD, nitrogen physisorption, TEM, UV–vis, PL and XPS. Degradation of CIP was tracked by UV–vis and LC-MS techniques and the mineralization efficiency was determined by TOC analyses. It was documented that CeO 2 /ZnO nanocomposites were ca. twice more active than undoped ZnO and ca. 10 times more active than pristine CeO 2. The improved activity of the nanocomposites resulted from the formation of a Z-scheme heterojunction in which photo-excited electrons from the conduction band of ZnO migrate to the valence band of CeO 2. Photocatalytic degradation of CIP over the nanocomposites was found to be a surface reaction in which CIP molecules adsorbed onto ZnO are directly oxidized by photogenerated holes (h+). Degradation of the antibiotic proceeded through two parallel pathways: i) pathway I (dominant) in which piperazine moiety of CIP molecules was selectively oxidized by h+, and ii) pathway II in which both fluoroquinolone and piperazine moieties of the antibiotic were degraded. The latter pathway required participation of both h+ and hydroxyl radicals (HO•). [ABSTRACT FROM AUTHOR]

In recent years, intensive research has focused on lanthanide-doped nanoparticles (NPs) used as noncontact temperature sensors, particularly in nanomedicine. These NPs must be capable of excitation and emission within biological windows, where biological materials usually show better transparency for radiation. In this article, we propose that NPs sensitized with Er 3+ ions can be applied as temperature sensors in biological materials. We synthesized the NPs through a reaction in high-boiling solvents and confirmed their crystal structure and the formation of core@shell NPs by using X-ray diffraction, high-resolution transmission electron microscopy, and element distribution mapping within the NPs. NaErF 4 @NaYF 4 , NaYF 4 :12.5% Er 3+ , 2.5% Tm 3+ @NaYF 4 , NaYF 4 :7.5% Er 3+ @NaYF 4 , and NaYF 4 :12.5% Er 3+ , 2.5% Ho 3+ @NaYF 4 exhibited intense upconversion (UC) emission under 1532 nm laser excitation detectable also in the whole human blood. We propose that this UC results from energy transfer between Er 3+ ions and from Er 3+ to Tm 3+ or Ho 3+ codopants. To determine the mechanism of UC, we measured the dependence of the emission band intensities on the laser power densities. Importantly, we also analyzed the temperature-dependent emission of the NPs within the 295-360 K range. Based on the collected emission spectra, we calculated the luminescence intensity ratios (LIRs) of the emission bands to assess their potential for optical temperature sensing. The temperature-sensing properties varied with the concentration of Er 3+ ions and the presence of additional Tm 3+ or Ho 3+ codopants. Depending on the NP composition and the emission bands used for luminescence ratio calculations, the maximum relative temperature sensitivity ranged from 4.55%·K -1 to 1.12%·K -1 , with temperature resolution between 0.05 and 2.53 K at room temperature. Finally, as proof of using NPs as temperature sensors in biomedicine, we successfully measured the temperature-dependent emission of NaYF 4 :7.5% Er 3+ @NaYF 4 NPs dispersed in whole blood under 1532 nm excitation. We demonstrated that the ratio of Er 3+ ion emission bands changes with temperature, indicating that these NPs have potential applications in temperature sensing within biological environments. We also confirmed the properties of NPs as temperature sensors by measuring the temperature reading uncertainty and the repeatability of the LIR readings during heating-cooling cycles, thereby confirming the excellent properties of the studied systems as temperature sensors.

The authors are proposing a theoretical model explaining the behavior of individuals tested through experiments on obedience toward authority conducted according to Milgram's paradigm. Their assumption is that the participant faces typical avoidance-avoidance conflict conditions. Participant does not want to hurt the learner in the adjacent room but he or she also does not want to harm the experimenter. The solution to this conflict, entailing hurting on of the two, may be different depending on the spatial organization of the experiment. In the study, experimental conditions were modified, so that the participant was (vs. was not) in the same room as the experimenter and was (vs. was not) in the same room as the learner. Forty individuals (20 women and 20 men) were tested in each of the four experimental conditions. It turns out that the physical presence of the experimenter was conducive to obedience, while the physical presence of the learner reduced it.

The upconversion phenomenon allows for the emission of nanoparticles (NPs) under excitation with near-infrared (NIR) light. Such property is demanded in biology and medicine to detect or treat diseases such as tumours. The transparency of biological systems for NIR light is limited to three spectral ranges, called biological windows. However, the most frequently used excitation laser to obtain upconversion is out of these ranges, with a wavelength of around 975 nm. In this article, we show an alternative - Tm 3+ /Er 3+ -doped NPs that can convert 1208 nm excitation radiation, which is in the range of the 2 nd biological window, to visible light within the 1 st biological window. The spectroscopic properties of the core@shell NaYF 4 :Tm 3+ @NaYF 4 and NaYF 4 :Er 3+ ,Tm 3+ @NaYF 4 NPs revealed a complex mechanism responsible for the observed upconversion. To explain emission in the studied NPs, we propose an energy looping mechanism: a sequence of ground state absorption, energy transfers and cross-relaxation (CR) processes between Tm 3+ ions. Next, the excited Tm 3+ ions transfer the absorbed energy to Er 3+ ions, which results in green, red and NIR emission at 526, 546, 660, 698, 802 and 982 nm. The ratio between these bands is temperature-dependent and can be used in remote optical thermometers with high relative temperature sensitivity, up to 2.37%/°C at 57 °C. The excitation and emission properties of the studied NPs fall within 1 st and 2 nd biological windows, making them promising candidates for studies in biological systems.

Recently, materials revealing the upconversion (UC) phenomenon, which is a conversion of low-energy photons to higher-energy ones, have attracted considerable attention in luminescence thermometry due to the possibility of precise and remote optical thermal sensing. The most widely studied type of luminescent thermometry uses a ratiometric approach based on changes in the UC luminescence intensity, mainly of lanthanide ions' thermally coupled energy levels. In this work, NaYF 4 :Ho 3+ @NaYF 4, and NaYF 4 :Ho 3+ , Er 3+ @NaYF 4 nanoparticles (NPs) were synthesized by the controlled reaction in oleic acid and octadecene at 573 K. The obtained nanoparticles had hexagonal structures, oval shapes, and average sizes of 22.5 ± 2.2 nm and 22.2 ± 2.0 nm, respectively. The spectroscopic properties of the products were investigated by measurements of the UC emission under 1151 nm laser excitation in the temperature range between 295 to 378 K. The sample doped with Ho 3+ and Er 3+ ions showed unique behavior of enhancing emission intensity with the temperature. The relative sensitivity determined for the NPs containing Ho 3+ and Er 3+ ions, reached the maximum value of 1.80%/K at 378 K. Here, we prove that the NaYF 4 :Ho 3+ , Er 3+ @NaYF 4 system presents unique and excellent optical temperature sensing properties based on the luminescence intensity ratios of the near-infrared bands of both Ho 3+ and Er 3+ ions., (© 2023. Springer Nature Limited.)

A lot of people are interested in optical thermometry, especially the new single-band ratiometric (SBR) technology for measuring temperature. But since SBR thermometry is still in its infancy, it is highly constrained when compared to the conventional dual-band ratiometric approach. In this paper, we propose a new SBR thermometry technique that is based on both the ground and excited state absorption processes. When these two different processes occur, the green emission of Tb 3+ in the low-cost host of NaSrGd(MoO 4 ) 3 (NSGM) responds to changes in temperature in a way that is the exact opposite of what you would expect. The maximum luminescence intensity was obtained for an optimum terbium concentration of 40% mol. The resulting chromaticity coordinates ( x , y ) and high correlated color temperature (CCT) values of the doped phosphors give a thermally stable cold emission in the green region with a color purity of about 92%. Using this intriguing characteristic as a foundation, sensitive SBR thermometry has been successfully developed, and the optical properties of the material have also been thoroughly researched. At room temperature, the relative sensitivity reaches its maximum value of 10.9% K -1 . These findings may give important information that may be used in the design of new luminescent thermometers that have excellent performance.

Experiments on obedience to authority conducted under the paradigm developed by Milgram have demonstrated that empathy plays either no or a very limited role in determining participants' behaviors. This study proposes that this occurs due to participants empathizing with both "learners" and experimenters. Empathy with learners makes participants withdraw from the experiment, while empathy with experimenters makes them continue. Therefore, the more that participants are characterized by dispositional empathy, the more they are reluctant to hurt learners but, at the same time, the more they try not to disappoint experimenters. This study investigates the effects of empathy being situationally directed toward learners. After manipulating the alleged similarities between "teachers" and "learners" in terms of crucial attitudes and values, the degree to which teachers obeyed experimenters and were willing to electrocute learners was measured. The results confirm that situationally directed empathy reduces participants' obedience to experimenters., Competing Interests: Declaration of competing interest We have no conflicts of interest to disclose. All authors declare that they have no conflicts of interest., (Copyright © 2023 The Author(s). Published by Elsevier B.V. All rights reserved.)

Numerous experiments have proven that mimicry is highly beneficial (mainly to the mimicker but also to the mimickee). Some studies have shown initial data suggesting the potential of applying this knowledge to business settings. In the present paper we unpack this issue in two ways. First, by presenting potential benefits stemming from mimicry for the mimicking dyad, and second for the business environment represented by the mimicker. Two consecutive studies: a Pretest and a Main Experiment run in natural settings showed great potential in improving the assessments of quality of service provided by verbally mimicking (or not). The results of both studies showed that mimicry offers benefits for the mimicker (increased employee kindness and employee evaluation), and also spillover to the organization/company represented by the mimicking employee (increased opinion of and willingness to return to the shop/hotel). Future research directions and limitations are discussed., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Kulesza, Dolinski, Muniak, Borkowska, Bibikova and Grzyb.)

The COVID-19 crisis requires fast and highly sensitive tests for the early stage detection of the SARS-CoV-2 virus. For detecting the nucleocapsid protein (N protein), the most abundant viral antigen, we have employed upconversion nanoparticles that emit short-wavelength light under near-infrared excitation (976 nm). The anti-Stokes emission avoids autofluorescence and light scattering and thus enables measurements without optical background interference. The sandwich upconversion-linked immunosorbent assay (ULISA) can be operated both in a conventional analog mode and in a digital mode based on counting individual immune complexes. We have investigated how different antibody combinations affect the detection of the wildtype N protein and the detection of SARS-CoV-2 (alpha variant) in lysed culture fluid via the N protein. The ULISA yielded a limit of detection (LOD) of 1.3 pg/mL (27 fM) for N protein detection independent of the analog or digital readout, which is approximately 3 orders of magnitude more sensitive than conventional enzyme-linked immunosorbent assays or commercial lateral flow assays for home testing. In the case of SARS-CoV-2, the digital ULISA additionally improved the LOD by a factor of 10 compared to the analog readout.

Pollution of the environment with plastic is an important concern of the modern world. It is estimated that annually over 350 million tonnes of this material are produced, wherein, despite the recycling methods, a significant part is deposited in the environment. The plastic has been detected in the industrial areas, as well as farmlands and gardens in many world regions. Larger plastic pieces degraded in time into smaller pieces including microplastic (MP) and nanoplastic particles (NP). Nanoplastic is suggested to pose the most serious danger as due to the small size, it is effectively taken up from the environment by the biota and transported within the organisms. An increasing number of reports show that NP exert toxic effects also on plants. One of the most common plant response to abiotic stress factors is the accumulation of reactive oxygen species (ROS). On the one hand, these molecules are engaged in cellular signalling and regulation of genes expression. On the other hand, ROS in excess lead to oxidation and damage of various cellular compounds. This article reviews the impact of NP on plants, with special emphasis on the oxidative response., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Ekner-Grzyb, Duka, Grzyb, Lopes and Chmielowska-Bąk.)

Recently, the up-converting (UC) materials, containing lanthanide ions (Ln 3+ )have attracted considerable attention because of the multitude of their potential applications. The most frequently investigated are UC systems based on the absorption of near-infrared (NIR) radiation by Yb 3+ ions at around 975-980 nm and emission of co-dopants, usually Ho 3+ , Er 3+ or Tm 3+ ions. UC can be observed also upon excitation with irradiation with a wavelength different than around 980 nm. The most often studied systems capable of UC without the use of Yb 3+ ion are those based on the properties of Er 3+ ions, which show luminescence resulting from the excitation at 808 or 1532 nm. However, also other Ln 3+ ions are worth attention. Herein, we focus on the investigation of the UC phenomenon in the materials doped with Ho 3+ ions, which reveal unique optical properties upon the NIR irradiation. The SrF 2 NPs doped with Ho 3+ ions in concentrations from 4.9% to 22.5%, were synthesized by using the hydrothermal method. The structural and optical characteristics of the obtained SrF 2 :Ho 3+ NPs are presented. The prepared samples had crystalline structure, were built of NPs of round shapes and their sizes ranged from 16.4 to 82.3 nm. The NPs formed stable colloids in water. Under 1156 nm excitation, SrF 2 :Ho 3+ NPs showed intense UC emission, wherein the brightest luminescence was recorded for the SrF 2 :10.0%Ho 3+ compound. The analysis of the measured lifetime profiles and dependencies of the integral luminescence intensities on the laser energy allowed proposing the mechanism, responsible for the observed UC emission. It is worth mentioning that the described SrF 2 :Ho 3+ samples are one of the first materials for which the UC luminescence induced by 1156 nm excitation was obtained., (Creative Commons Attribution license.)

The study provides deep insight into the origin of photocatalytic deactivation of Nb 2 O 5 after modification with ceria. Of particular interest was to fully understand the role of ceria species in diminishing the photocatalytic performance of CeO 2 /Nb 2 O 5 heterostructures. For this purpose, ceria was loaded on niobia surfaces by wet impregnation. The as-prepared materials were characterized by powder X-ray diffraction, nitrogen physisorption, UV-visible spectroscopy, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and photoluminescence measurements. Photocatalytic activity of parent metal oxides (i.e., Nb 2 O 5 and CeO 2 ) and as-prepared CeO 2 /Nb 2 O 5 heterostructures with different ceria loadings were tested in methanol photooxidation, a model gas-phase reaction. Deep insight into the photocatalytic process provided by operando -IR techniques combined with results of photoluminescence studies revealed that deactivation of CeO 2 /Nb 2 O 5 heterostructures resulted from increased recombination of photo-excited electrons and holes. The main factor contributing to more efficient recombination of the charge carriers in the heterostructures was the ultrafine size of the ceria species. The presence of such highly dispersed ceria species on the niobia surface provided a strong interface between these two semiconductors, enabling efficient charge transfer from Nb 2 O 5 to CeO 2 . However, the ceria species supported on niobia exhibited a high defect site concentration, which acted as highly active recombination centers for the photo-induced charge carriers., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

Nanoparticles (NPs) based on host compound NaYF 4 with core@shell structures were synthesised by the precipitation reaction in high-boiling point octadecene/oleic acid solvent. Four laser wavelengths were used (808, 975, 1208, or 1532 nm) for excitation of the obtained NPs. The resulting emission and mechanisms responsible for spectroscopic properties were studied in detail. Depending on NP compositions, i.e. type of doping ion (Er 3+ , Tm 3+ , or Yb 3+ ) or presence of dopants in the same or different phases, adjustable up-conversion (UC) could be obtained with emission peaks covering the visible to near-infrared range (475 to 1625 nm). The presented results demonstrated multifunctionality of the prepared NPs. NaYF 4 :2%Tm 3+ @NaYF 4 NPs exhibited emission at 700 and 1450 nm under 808 nm laser excitation or 800 and 1625 nm emission under 1208 nm laser radiation, as a result of ground- and excited-state absorption processes (GSA and ESA, respectively). However, NaYF 4 :5%Er 3+ ,2%Tm 3+ @NaYF 4 NPs showed the most interesting properties, as they can convert all studied laser wavelengths due to the absorption of Tm 3+ (808, 1208 nm) or Er 3+ ions (808, 975, 1532 nm), revealing a photon avalanche process under 1208 nm laser excitation, as well as GSA and ESA at other excitation wavelengths. The NaYF 4 :2%Tm 3+ @NaYF 4 :5%Er 3+ NPs revealed the resultant emission properties, as the dopant ions were separated within core and shell phases. The NaYF 4 :18%Yb 3+ ,2%Tm 3+ @NaYF 4 and NaYF 4 :18%Yb 3+ ,2%Tm 3+ @NaYF 4 :5%Er 3+ samples showed the brightest emission, around 800 nm, under 975 nm excitation, though other laser wavelengths allowed for observation of luminescence, as well, especially in NPs with Er 3+ in the outer shell, capable of UC under 1532 nm. The presented results highlight the unique and universal properties of lanthanide ions for designing luminescent NPs for a variety of potential applications, such as confocal microscopy.

Due to their photon up-converting capability, lanthanide ions are ideal candidates dopants for semiconductors for developing visible light-driven photocatalytic activity. Of particular relevance, the low luminescence efficiency of Ln-based nanoparticles is one of the main factors that limits their further applications. Carbon, which is present on the surface of all TiO 2 photocatalysts, can be responsible for luminescence quenching processes and, thus, decreasing the photocatalytic activity of TiO 2 . This article presents a systematic experimental and theoretical study of the effects of carbon on the photocatalytic performance of Ho 3+ -modified TiO 2 . Ho 3+ -TiO 2 photocatalysts modified with various carbon contents (from 0.5 to 20 mol.%) were successfully prepared using a simple hydrothermal method. As-obtained samples were characterized by UV-Vis diffuse reflectance spectroscopy (DRS/UV-Vis), X-ray diffraction (XRD), X-ray photoelectron emission spectroscopy (XPS), N 2 adsorption measurements, photoluminescent spectroscopy (PL), field-emission scanning electron microscopy (FE-SEM) and scanning transmission microscopy (STEM). The photodegradation efficiency of phenol was estimated for visible light (λ > 420 nm and λ > 455 nm). The XPS and XRD analyses and theoretical calculations revealed that the substitutional doping of holmium and carbon in the TiO 2 anatase structure resulted in the appearance of a new sub-band-gap. Changes in the material texture, BET surface area and pore volume can be easily controlled via carbon content in samples. Doping of the Ho 3+ -TiO 2 photocatalysts with carbon resulted in quenching of the emission of Ho 3+ and, thus, the photodegradation of phenol, was observed in samples containing smaller amounts of carbon. Sixty minutes of irradiation resulted in 89% of phenol degradation under visible light (λ > 420 nm)., (Copyright © 2019 Elsevier Inc. All rights reserved.)

For a number of years nanomaterials have been continuously devised and comprehensively investigated because of the growing demand for them and their multifarious applications, especially in medicine. This paper reports on the properties of SrF 2 nanoparticles (NPs) for applications in biomedicine, showing effective ways of their synthesis and luminescence under near infrared radiation - upconversion. NPs doped with lanthanide, Ln 3+ ions (where Ln = Yb, Ho, Er, Tm) were prepared by the hydrothermal method and subjected to comprehensive studies, from determination of their structure and morphology, revealing small, 15 nm structures, through spectroscopic properties, to cytotoxicity in vitro. The effects of such factors as the reaction time, type and amount of precipitating compounds and complexing agents on the properties of products were characterized. The cytotoxicity of the synthesized and functionalized NPs was investigated, using human fibroblast cell line (MSU-1.1). The synthesized structures may decrease cells' proliferation in a dose-dependent manner in the measured concentration range (up to 100 µg/mL). However, the cells remain alive according to the fluorescent assay. Moreover, the treated cells were imaged using confocal laser scanning microscopy. Cellular uptake was confirmed by the presence of upconversion luminescence in the cells.

Ultrasmall (9-30 nm) Yb 3+ /Er 3+ -doped, upconverting alkaline rare-earth fluorides that are promising for future applications were synthesized by the microwave-assisted hydrothermal method. The formation mechanism was proposed, indicating the influence of the stability of metal ions complexes with ethylenediaminetetraacetic acid on the composition of the product and tendency to form M 2 REF 7 (M 0.67 RE 0.33 F 2.33 ) cubic compounds in the M-RE-F systems. Their physicochemical properties (structure, morphology, and spectroscopic properties) are compared and discussed. The obtained nanoparticles exhibited emission of light in the visible spectra under excitation by 976 nm laser radiation. Excitation and emission spectra, luminescence decays, laser energy dependencies, and upconversion quantum yields were measured to determine the spectroscopic properties of prepared materials. The Yb 3+ /Er 3+ pair of ions used as dopants was responsible for an intense yellowish-green emission. The upconversion quantum yields determined for the first time for M 2 REF 7 -based materials were 0.0192 ± 0.001% and 0.0176 ± 0.001% for Sr 2 LuF 7 :Yb 3+ ,Er 3+ and Ba 2 LuF 7 :Yb 3+ ,Er 3+ respectively, the two best emitting samples. These results indicated the prepared materials are good and promising alternatives for the most studied NaYF 4 :Yb 3+ ,Er 3+ nanoparticles.

Upconversion luminescence of nano-sized Yb 3+ and Tm 3+ codoped rare earth phosphates, that is, LaPO 4 and YPO 4 , has been investigated under high-pressure (HP, up to ∼25 GPa) and high-temperature (293-773 K) conditions. The pressure-dependent luminescence properties of the nanocrystals, that is, energy red shift of the band centroids, changes of the band ratios, shortening of upconversion lifetimes, and so forth, make the studied nanomaterials suitable for optical pressure sensing in nanomanometry. Furthermore, thanks to the large energy difference (∼1800 cm -1 ), the thermalized states of Tm 3+ ions are spectrally well-separated, providing high-temperature resolution, required in optical nanothermometry. The temperature of the system containing such active nanomaterials can be determined on the basis of the thermally induced changes of the Tm 3+ band ratio ( 3 F 2,3 → 3 H 6 / 3 H 4 → 3 H 6 ), observed in the emission spectra. The advantage of such upconverting optical sensors is the use of near-infrared light, which is highly penetrable for many materials. The investigated nanomanometers/nanothermometers have been successfully applied, as a proof-of-concept of a novel bimodal optical gauge, for the determination of the temperature of the heated system (473 K), which was simultaneously compressed under HP (1.5 and 5 GPa).

The structure of gadolinium oxyfluoride nanoparticles was revised. Extensive studies including X-ray diffraction and Rietveld refinement as well as Fourier transform infrared spectroscopy and Raman spectroscopy confirmed the monoclinic P12/c1 crystal structure of Gd4O3F6. Morphological analysis using transmission electron microscopy showed the nanocrystallinity of the materials prepared via the sol-gel Pechini's method. The luminescent properties of the prepared materials with different concentrations of Eu(3+) ions were characterized by emission spectroscopy. The phosphors obtained were investigated in the vacuum ultraviolet range using synchrotron radiation. The Judd-Ofelt parameters (Ω2, Ω4) and emission efficiencies η were calculated and are discussed in detail.