Search Results (12)

This work reports the light-to-heat conversion (LHC) behavior of NaNdF₄ doped with Sm³⁺. Due to the cross-relaxation between Nd³⁺ and Sm³⁺, the improved LHC is obtainable by introducing 5% Sm³⁺. When the laser power density is only 1.72 W/cm², the spot temperature of NaNdF₄:5%Sm³⁺ powder reaches as high as 138.7 ± 4.04 °C. More importantly, the photoheating response to the pump laser has favorable linear characteristics within a specific power range. A simple physical model is applied to analyze the relationship between photothermal heating and pump power. Finally, the temperature-responsive luminescence anti-counterfeiting is designed by combining the LHC material with the NaYF₄:Yb³⁺/Ho³⁺/Ce³⁺ microcrystals. This novel strategy only requires two laser beams, and thus is more convenient to apply. Full article

YF₃: (Eu³⁺, Nd³⁺) nanoparticles (orthorhombic phase, D~130 nm) were synthesized via the co-precipitation method, with subsequent hydrothermal treatment and annealing. The Eu³⁺ τ_decay linearly descends with the increase of temperature in the 80–320 K range. The τ_decay (T) slope values of the annealed YF₃: Eu³⁺ (2.5 and 5.0 mol.%) nanoparticles were the highest (110·10⁻⁴ and 67·10⁻⁴, μs/K) in the whole 80–320 K range, respectively. Thus, these samples were chosen for further doping with Nd³⁺. The maximum S_a and S_r values based on the LIR (I_Eu/I_Nd) function were 0.067 K⁻¹ (at 80 K) and 0.86%·K⁻¹ (at 154 K), respectively. As mentioned above, the single-doped YF₃: Eu³⁺ (2.5%) nanoparticles showed the linearly decreasing τ_decay (T) function (⁵D₀–⁷F₁ emission). The main idea of Nd³⁺ co-doping was to increase this slope value (as well as the sensitivity) by increasing the rate of τ_decay (T) descent via the addition of one more temperature-dependent channel of ⁵D₀ excited state depopulation. Indeed, we managed to increase the slope (S_a) to 180·10⁻⁴ K⁻¹ at 80 K. This result is one of the highest compared to the world analogs. Full article

This study synthesized the NaGdF₄@NaGdF₄: Yb, Tm@NaGdF₄: Yb, Nd upconversion nanoparticles (UCNPs), combined with another three-layer structure NaYF₄@NaYF₄: Yb, Er@NaYF₄ UCNPs, with a core-shell-shell structure, effectively suppressing fluorescence quenching and significantly improving upconversion luminescence efficiency. Two types of modified UCNPs were coupled with antibodies against fenpropathrin and procymidone to form signal probes, and magnetic nanoparticles were coupled with antigens of fenpropathrin and procymidone to form capture probes. A rapid and sensitive fluorescence immunoassay for the simultaneous detection of fenpropathrin and procymidone was established based on the principle of specific binding of antigen and antibody and magnetic separation technology. Under the optimal competitive reaction conditions, different concentrations of fenpropathrin and procymidone standards were added to collect the capture probe-signal probe complex. The fluorescence values at 542 nm and 802 nm were measured using 980 nm excitation luminescence. The results showed that the detection limits of fenpropathrin and procymidone were 0.114 µg/kg and 0.082 µg/kg, respectively, with sensitivities of 8.15 µg/kg and 7.98 µg/kg, and they were applied to the detection of fenpropathrin and procymidone in tomatoes, cucumbers, and cabbage. The average recovery rates were 86.5~100.2% and 85.61~102.43%, respectively, with coefficients of variation less than 10%. The results showed good consistency with the detection results of high-performance liquid chromatography, proving that this method has good accuracy and is suitable for the rapid detection of fenpropathrin and procymidone in food. Full article

Photothermal therapy operated in the second near-infrared (NIR-II, 1000–1700 nm) window and fluorescence imaging in the NIR-IIb (1500–1700 nm) region have become the most promising techniques in phototheranostics. Their combination enables simultaneous high-resolution optical imaging and deep-penetrating phototherapy, which is essential for high-performance phototheranostics. Herein, carboxyl-functionalized small organic photothermal molecules (Se-TC) and multi-layered NIR-IIb emissive rare-earth-doped nanoparticles (NaYF₄:Yb,Er,Ce@NaYF₄:Yb,Nd@NaYF₄, RENP) were rationally designed and successfully synthesized. Then, high-performance hybrid phototheranostic nanoagents (Se-TC@RENP@F) were easily constructed through the coordination between Se-TC and RENP and followed by subsequent F127 encapsulation. The carboxyl groups of Se-TC can offer strong binding affinity towards rare-earth-doped nanoparticles, which help improving the stability of Se-TC@RENP@F. The multilayered structure of RENP largely enhance the NIR-IIb emission under 808 nm excitation. The obtained Se-TC@RENP@F exhibited high 1064 nm absorption (extinction coefficient: 24.7 L g⁻¹ cm⁻¹), large photothermal conversion efficiency (PCE, 36.9%), good NIR-IIb emission (peak: 1545 nm), as well as great photostability. Upon 1064 nm laser irradiation, high hyperthermia can be achieved to kill tumor cells efficiently. In addition, based on the excellent NIR-IIb emission of Se-TC@RENP@F, in vivo angiography and tumor detection can be realized. This work provides a distinguished paradigm for NIR-IIb-imaging-guided NIR-II photothermal therapy and establishes an artful strategy for high-performance phototheranostics. Full article

In this study, we synthesized NaYF₄-based downshifting nanophosphors (DSNPs), and fabricated DSNP-polydimethylsiloxane (PDMS) composites. Nd³⁺ ions were doped into the core and shell to increase absorbance at 800 nm. Yb³⁺ ions were co-doped into the core to achieve intense near-infrared (NIR) luminescence. To further enhance the NIR luminescence, NaYF₄:Nd,Yb/NaYF₄:Nd/NaYF₄ core/shell/shell (C/S/S) DSNPs were synthesized. The C/S/S DSNPs showed a 3.0-fold enhanced NIR emission at 978 nm compared with core DSNPs under 800 nm NIR light. The synthesized C/S/S DSNPs showed high thermal stability and photostability against the irradiation with ultraviolet light and NIR light. Moreover, for application as luminescent solar concentrators (LSCs), C/S/S DSNPs were incorporated into the PDMS polymer, and the DSNP-PDMS composite containing 0.25 wt% of C/S/S DSNP was fabricated. The DSNP-PDMS composite showed high transparency (average transmittance = 79.4% for the visible spectral range of 380–750 nm). This result demonstrates the applicability of the DSNP-PDMS composite in transparent photovoltaic modules. Full article

Nd³⁺ (0.3 mol.%), Yb³⁺ (0, 1, 2, 3 and 5 mol.%): LiYF₄ phosphors were grown by the Bridgman–Stockbarger technique. The luminescence intensity ratio (LIR) of Nd³⁺ (⁴F_3/2–⁴I_9/2, ~866 nm) and Yb³⁺ emission (²F_5/2–²F_7/2, ~980 nm) was taken as a parameter. The energy exchange between ⁴F_3/2 (Nd³⁺) and ²F_5/2 (Yb³⁺) occurs via phonons, which elucidates the LIR temperature dependence. The influence of the cross-relaxation process on the temperature sensitivity was estimated as negligible. The LIR function depends on the Yb³⁺ concentration at a fixed 0.3 mol.% Nd³⁺. The maximum S_a and S_r value were reached for Nd³⁺ (0.3%), Yb³⁺ (1.0%): LiYF₄ (S_a = 0.007 K⁻¹ at 320 K) and Nd³⁺ (0.3%), Yb³⁺ (5.0%): LiYF₄ (S_r = 1, 1.03%*K⁻¹ at 260 K), respectively. Full article

This work is devoted to the study of thermometric performances of Nd³⁺ (0.1 or 0.5 mol.%), Yb³⁺ (X%):YF₃ nanoparticles. Temperature sensitivity of spectral shape is related to the phonon-assisted nature of energy transfer (PAET) between Nd³⁺ and Yb³⁺). However, in the case of single-doped Nd³⁺ (0.1 or 0.5 mol.%):YF₃ nanoparticles, luminescence decay time (LDT) of ⁴F_3/2 level of Nd³⁺ in Nd³⁺ (0.5 mol.%):YF₃ decreases with the temperature decrease. In turn, luminescence decay time in Nd³⁺ (0.1 mol.%):YF₃ sample remains constant. It was proposed, that at 0.5 mol.% the cross-relaxation (CR) between Nd³⁺ ions takes place in contradistinction from 0.1 mol.% Nd³⁺ concentration. The decrease of LDT with temperature is explained by the decrease of distances between Nd³⁺ with temperature that leads to the increase of cross-relaxation efficiency. It was suggested, that the presence of both CR and PAET processes in the studied system (Nd³⁺ (0.5 mol.%), Yb³⁺ (X%):YF₃) nanoparticles provides higher temperature sensitivity compared to the systems having one process (Nd³⁺ (0.1 mol.%), Yb³⁺ (X%):YF₃). The experimental results confirmed this suggestion. The maximum relative temperature sensitivity was 0.9%·K⁻¹ at 80 K. Full article

In this study. a novel near-infrared fluorescent-driven contrast agent (Ag-doped NaYF₄:Yb³⁺/Er³⁺@NaYF₄:Nd³⁺@NaGdF₄) was synthesized using a coprecipitation-hydrothermal-solvothermal-solvothermal (CHSS) method. The results shows that hexagonal NaYF₄:Yb³⁺/Er³⁺ with a diameter of 300 nm was successfully synthesized by the CHSS method. The new contrast agent was characterized using scanning electron microscopy, fluorescence spectrometry, transmission electron microscopy, energy-dispersive spectrometry and ultraviolet-visible light diffuse reflectance absorption spectroscopy. Even at low concentrations (0.2 M), this proposed contrast agent can be excited by near-infrared light with a wavelength of 980 nm and emits a dazzling green light with a wavelength of 540 nm, and the comparison of the luminescence intensity proves that doping with silver increases the luminescence intensity of the upconverted nanomaterial by nearly 13 times based on the calculated quantum yield. TEM images show the successful preparation of silver nanoparticles with a diameter of 30 nm, and the energy spectrum shows the successful doping of silver nanoparticles and the successful preparation of the core-shell structure of NaYF₄:Yb³⁺/Er³⁺@NaYF₄:Nd³⁺@NaGdF₄. Furthermore, the mechanism of the increased luminous intensity has been studied using simulation calculations. Finally, cytotoxicity tests were used to test material which was modified by 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[amino(polyethylene glycol)-2000] (DSPE-PEG_2K), and the biocompatibility was significantly improved, meeting the standard for biological applications. Full article

Lanthanide (Ln³⁺)–doped upconversion nanoparticles (UCNPs) offer an ennormous future for a broad range of biological applications over the conventional downconversion fluorescent probes such as organic dyes or quantum dots. Unfortunately, the efficiency of the anti−Stokes upconversion luminescence (UCL) process is typically much weaker than that of the Stokes downconversion emission. Albeit recent development in the synthesis of UCNPs, it is still a major challenge to produce a high−efficiency UCL, meeting the urgent need for practical applications of enhanced markers in biology. The poor quantum yield efficiency of UCL of UCNPs is mainly due to the fol-lowing reasons: (i) the low absorption coefficient of Ln³⁺ dopants, the specific Ln³⁺ used here being ytterbium (Yb³⁺), (ii) UCL quenching by high−energy oscillators due to surface defects, impurities, ligands, and solvent molecules, and (iii) the insufficient local excitation intensity in broad-field il-lumination to generate a highly efficient UCL. In order to tackle the problem of low absorption cross-section of Ln3+ ions, we first incorporate a new type of neodymium (Nd³⁺) sensitizer into UCNPs to promote their absorption cross-section at 793 nm. To minimize the UCL quenching induced by surface defects and surface ligands, the Nd³⁺-sensitized UCNPs are then coated with an inactive shell of NaYF₄. Finally, the excitation light intensity in the vicinity of UCNPs can be greatly enhanced using a waveguide grating structure thanks to the guided mode resonance. Through the synergy of these three approaches, we show that the UCL intensity of UCNPs can be boosted by a million−fold compared with conventional Yb³⁺–doped UCNPs. Full article

Several robust titania (TiO₂) coated core/multishell trivalent lanthanide (Ln) upconversion nanoparticles (UCNPs) hybrid architecture designs have been reported for use in photodynamic therapy (PDT) against cancer, utilizing the near-infrared (NIR) excited energy down-shifting and up-conversion chain of Nd³⁺ (λ_{793-808 nm}) → Yb³⁺ (λ_{980 nm}) → Tm³⁺(λ_{475 nm}) → TiO₂ to produce reactive oxygen species (ROS) for deep tissue-penetrating oxidative cytotoxicity, e.g., NaLnF₄:Yb,Tm (Ln = Y, Gd). Herein, we demonstrate that by doping the Tm³⁺ emitter ions in the outer shell and the Nd³⁺ sensitizer ions in the core, the newly designed NaYF₄:Nd,Yb@Yb@Yb,Tm@TiO₂ hybrid UCNPs exert more ROS production than the reference NaYF₄:Yb,Tm@Yb@Nd,Yb@ TiO₂ with the Tm³⁺ ions in the core and the Nd³⁺ ions in the outer shell, upon 793 nm laser irradiation, primarily due to the shortening of the Tm³⁺-TiO₂ distance of the former with greater Förster resonance energy transfer (FRET) efficiency. After coating with polyallylamine hydrochloride (PAH)/polyethylene glycol folate (PEG-FA), the resulting NaYF₄:Nd,Yb@Yb@Yb,Tm@TiO₂-PAH-PEG-FA hybrid nanocomposites could be internalized in MDA-MB-231 cancer cells, which also show low dark cytotoxicity and effective photocytotoxicity upon 793 nm excitation. These nanocomposites could be further optimized and are potentially good candidates as nanotheranostics, as well as for other light-conversion applications. Full article

Hexagonal NaYF₄:Nd³⁺/Yb³⁺/Er³⁺ microcrystals and nanocrystals with well-defined morphologies and sizes have been synthesized via a hydrothermal route. The rational control of initial reaction conditions can not only result in upconversion (UC) micro and nanocrystals with varying morphologies, but also can produce enhanced and tailored upconversion emissions from the Yb³⁺/Er³⁺ ion pairs sensitized by the Nd³⁺ ions. The increase of reaction time converts the phase of NaYF₄:Nd³⁺/Yb³⁺/Er³⁺ particles from the cubic to the hexagonal structure. The added amount of oleic acid plays a critical role in the shape evolution of the final products due to their preferential attachment to some crystal planes. The adjustment of the molar ratio of F⁻/Ln³⁺ can range the morphologies of the β-NaYF₄:Nd³⁺/Yb³⁺/Er³⁺ microcrystals from spheres to nanorods. When excited by 808 nm infrared laser, β-NaYF₄:Nd³⁺/Yb³⁺/Er³⁺ microplates exhibit a much stronger UC emission intensity than particles with other morphologies. This phase- and morphology-dependent UC emission holds promise for applications in photonic devices and biological studies. Full article

In this paper, Nd³⁺–Yb³⁺–Er³⁺-doped β-NaYF₄ nanocrystals with different Nd³⁺ concentrations are synthesized, and the luminescence properties of the upconversion nanoparticles (UCNPs) have been studied under 808-nm excitation for sensitive biological applications. The upconversion luminescence spectra of NaYF₄ nanoparticles with different dopants under 808-nm excitation proves that the Nd³⁺ ion can absorb the photons effectively, and the Yb³⁺ ion can play the role of an energy-transfer bridging ion between the Nd³⁺ ion and Er³⁺ ion. To investigate the effect of the Nd³⁺ ion, the decay curves of the ⁴S_3/2 → ⁴I_15/2 transition at 540 nm are measured and analyzed. The NaYF₄: 20% Yb³⁺, 2% Er³⁺, 0.5% Nd³⁺ nanocrystals have the highest emission intensity among all samples under 808-nm excitation. The UC (upconversion) mechanism under 808-nm excitation is discussed in terms of the experimental results. Full article