Highly Sensitive Lanthanide-Doped Nanoparticles-Based Point-of-Care Diagnosis of Human Cardiac Troponin I

Introduction

Methods

Results

Conclusion

High performance FIR thermometry on the basis of the redshift of CTB by dual-wavelength alternative excitation in Eu3+:YVO4

Compared with the forbidden 4f transition of rare earth ions, the strong absorption of the charge transfer band (CTB) enabled fluorescence thermometry to have high luminescence efficiency. Based on the temperature induced redshift of CTB, a high performance fluorescence intensity ratio (FIR) thermometry performed by dual-wavelength alternative excitation was studied. By way of the rising and falling edges of CTB in Eu³⁺ doped YVO₄, monochrome sensitivity as a function of excitation wavelength was studied in the range of 303-783 K. The excitation wavelength with the highest positive monochrome sensitivity was determined, as well as that with the negative one. The optimum FIR temperature sensing strategy is proposed, and the theoretical highest relative sensitivity (S_r) is calculated to be 1.86% K^-1, with the lowest uncertainty (ΔT) of 0.1 K at 783 K.

Stably and highly sensitive FIR thermometry over a wide temperature range of 303-753 K based on the GdVO4:Eu3+ and Al2O3:Cr3+ hybrid particles

Fluorescence intensity ratio (FIR) temperature sensors provide an effective method to control or study fine variations in physical and biological research because of their high sensitivity, accuracy, and spatial resolution. However, it is difficult to maintain high sensitivity over a wide temperature range using FIR temperature sensors because of the limits of the Boltzmann distribution law. In this study, sensitivity amplification for a wide temperature range in FIR thermometry based on GdVO₄:Eu³⁺ and Al₂O₃:Cr³⁺ hybrid particles is achieved. The mechanism of the non-monotonic temperature dependence of the relative sensitivity (S_r) is studied. The results demonstrate that the S_r stably keeps ∼2.4% per K over a wide temperature range of 303-753 K, thus providing a basis for the extensive application of FIR temperature sensors.

Efficient Photoreduction of Hexavalent Chromium Using the Reduced Graphene Oxide-Sm2MoO6-TiO2 Catalyst under Visible Light Illumination

In past years, the presence of toxic heavy metal ions in water and soil has caused major health problems. The ternary type semiconductor material, reduced graphene oxide (rGO)-Sm₂MoO₆-TiO₂, has been investigated as a photocatalyst for the reduction of soluble chromium(VI) into (III) for the first time. The as-synthesized rGO-Sm₂MoO₆-TiO₂ catalyst was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy, X-ray photoelectron spectroscopy, FT-Raman, Fourier transform infrared, and optical spectroscopy. The maximum Cr(VI) reduction of 96% was achieved within 70 min under visible light illumination. The powder XRD analysis confirmed the formation of anatase TiO₂. Field-emission SEM images depicted well-dispersed rGO sheets, and TiO₂ and Sm₂MoO₆ particles are randomly distributed onto rGO. The reduction of Cr(VI) by rGO-Sm₂MoO₆-TiO₂ was considerably greater than the reduction by Sm₂MoO₆, TiO₂, Sm₂MoO₆-rGO, TiO₂-rGO, and Sm₂MoO₆-TiO₂. Sm₂MoO₆ acts as an effective cocatalyst to TiO₂ to enhance the separation of photo-generated electron-holes. Even after six consecutive cycles, the photoreduction of Cr(VI) was more than 85%, which reveals that the excellent reusability performance of the catalyst for practical applications. The photogenerated electron plays an important role in the reduction of Cr(VI) into nontoxic Cr(III), and the synergistic effect of rGO greatly improved the separation of h⁺ and e^- pairs.

Synthesis and luminescent properties of uniform monodisperse LuPO4:Eu3+/Tb3+ hollow microspheres

Uniform monodisperse LuPO4:Eu3+/Tb3+ hollow microspheres with diameters of about 2.4 µm have been successfully synthesized by the combination of a facile homogeneous precipitation approach, an ion-exchange process and a calcination process. The possible formation mechanism for the hollow microspheres was presented. Furthermore, the luminescence properties revealed that the LuPO4:Eu3+ and LuPO4:Tb3+ phosphors show strong orange-red and green emissions under ultraviolet excitation, respectively, which endows this material with potential application in many fields, such as light display systems and optoelectronic devices. Since the synthetic process can be carried out at mild conditions, it should be straightforward to scale up the entire process for large-scale production of the LuPO4 hollow microspheres. Furthermore, this general and simple method may be of much significance in the synthesis of many other inorganic materials.

Pulsed Laser Deposited Dysprosium-Doped Gadolinium-Vanadate Thin Films for Noncontact, Self-Referencing Luminescence Thermometry

Lanthanide-doped vanadate thin films offer (i) a promising platform for luminescence-based noncontact temperature sensing; (ii) ratiometric/self-referencing absolute measurements; (iii) exceptional repeatability and reversibility for multirun uses and a long life cycle; (iv) 2% K(-1) maximum temperature sensitivity (among the highest recorded for inorganic nanothermometers); (v) a temperature resolution greater than 0.5 K; and (vi) the potential for high-resolution 2D temperature mapping.

Tunable photoluminescence and magnetic properties of Dy(3+) and Eu(3+) doped GdVO4 multifunctional phosphors

A series of Dy(3+) or/and Eu(3+) doped GdVO4 phosphors were successfully prepared by a simple hydrothermal method and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectrometry (EDS), photoluminescence (PL) spectroscopy and vibrating sample magnetometry (VSM). The results indicate that the as-prepared samples are pure tetragonal phase GdVO4, taking on nanoparticles with an average size of 45 nm. Under ultraviolet (UV) light excitation, the individual Dy(3+) or Eu(3+) ion activated GdVO4 phosphors exhibit excellent emission properties in their respective regions. The mechanism of energy transfer from the VO4(3-) group and the charge transfer band (CTB) to Dy(3+) and Eu(3+) ions is proposed. Color-tunable emissions in GdVO4:Dy(3+),Eu(3+) phosphors are realized through adopting different excitation wavelengths or adjusting the appropriate concentration of Dy(3+) and Eu(3+) when excited by a single excitation wavelength. In addition, the as-prepared samples show paramagnetic properties at room temperature. This kind of multifunctional color-tunable phosphor has great potential applications in the fields of photoelectronic devices and biomedical sciences.

Biomolecule-assisted route for shape-controlled synthesis of 3D flower-like CdWO4 microstructures

Plausible mechanism for the formation of 3d hierarchical flower-like structures.

Reddish-orange-emitting and paramagnetic properties of GdVO4:Sm3+/Eu3+ multifunctional nanomaterials

The as-prepared samples are short and rod-like in shape with a diameter of about 10 nm and length of about 20–30 nm. The excitation spectra indicate that Sm³⁺ ions transfer energy to Eu³⁺ ions, which increases the color purity of Eu³⁺ ions in the GdVO₄ system.

Structural, spectroscopic, and magnetic properties of Eu3+-doped GdVO4 nanocrystals synthesized by a hydrothermal method

New interesting aspects of the spectroscopic properties, magnetism, and method of synthesis of gadolinium orthovanadates doped with Eu(3+) ions are discussed. Gd(1-x)Eu(x)VO4 (x = 0, 0.05, 0.2) bifunctional luminescent materials with complex magnetic properties were synthesized by a microwave-assisted hydrothermal method. Products were formed in situ without previous precipitation. The crystal structures and morphologies of the obtained nanomaterials were analyzed by X-ray diffraction and transmission and scanning electron microscopy. Crystallographic data were analyzed using Rietveld refinement. The products obtained were nanocrystalline with average grain sizes of 70-80 nm. The qualitative and quantitative elemental composition as well as mapping of the nanocrystals was proved using energy-dispersive X-ray spectroscopy. The spectroscopic properties of red-emitting nanophosphors were characterized by their excitation and emission spectra and luminescence decays. Magnetic measurements were performed by means of vibrating sample magnetometry. GdVO4 and Gd0.8Eu0.2VO4 exhibited paramagnetic behavior with a weak influence of antiferromagnetic couplings between rare-earth ions. In the substituted sample, an additional magnetic contribution connected with the population of low-lying excited states of europium was observed.

Multifunctional Eu3+- and Er3+/Yb3+-doped GdVO4 nanoparticles synthesized by reverse micelle method

Synthesis of Eu³⁺- and Er³⁺/Yb³⁺-doped GdVO₄ nanoparticles in reverse micelles and their multifunctional luminescence properties are presented. Using cyclohexane, Triton X-100, and n-pentanol as the oil, surfactant, and co-surfactant, respectively, crystalline nanoparticles with ~4 nm diameter are prepared at low temperatures. The particle size assessed using transmission electron microscopy is similar to the crystallite size obtained from X-ray diffraction measurements, suggesting that each particle comprises a single crystallite. Eu³⁺-doped GdVO₄ nanoparticles emit red light through downconversion upon UV excitation. Er³⁺/Yb³⁺-doped GdVO₄ nanoparticles exhibit several functions; apart from the downconversion of UV radiation into visible green light, they act as upconvertors, transforming near-infrared excitation (980 nm) into visible green light. The ratio of green emissions from ²H_11/2 → ²I_15/2 and ⁴S_3/2 → ⁴I_15/2 transitions is temperature dependent and can be used for nanoscale temperature sensing with near-infrared excitation. The relative sensor sensitivity is 1.11%K⁻¹, which is among the highest sensitivities recorded for upconversion-luminescence-based thermometers.

Temperature dependence of emission and lifetime in Eu(3+)- and Dy(3+)-doped GdVO4

Eu(3+)- and Dy(3+)-doped GdVO(4) samples synthesized by a high-temperature solid-state method are investigated by fluorescence spectroscopy at 298-750 K. They demonstrate potential for development as thermographic phosphors because the experimental and theoretical temperature dependence of the intensity ratio of the two lines agrees well. Experimental lifetime measurements recorded at 10-750 K were fitted using three theoretical models: multiphonon relaxation, temperature quenching through the charge transfer (CT) region, and our modified CT model (TDCT), which considers the temperature dependence of CT energy. The TDCT model yields the best results with good agreement between experimental and fitted lifetime data.