Study of Photoluminescence and Thermoluminescence Properties of Tb3+ Doped Green Emitting YPO4 Nanophosphors

YPO4 nanophosphors doped with different concentrations of Tb3+ were synthesized using conventional co-precipitation method. The crystalline as well structural features were studied by using powder X-ray diffraction (PXRD) as well as Transmission electron microscope (TEM) images, which revealed highly crystalline nature of the prepared samples having particle sizes of around 40 nm. EDAX spectrum also shows the elemental composition of the synthesized nanoparticles which contain Y, P, O, Tb3+as expected. Prepared samples showed emission peaks at 491, 545, 588 and 624 nm under UV excitation having excitation wavelengths of 223 and 320 nm. The Commission International de I'Eclairage (CIE)study shows the chromaticity co-ordinates for the 600oC annealed samples to be x = 0.239, y = 0.4 which corresponds to cool greenish light suggesting the potential applications of the prepared nanophosphor in white light emitting diodes converted from green phosphors, optical display setups and PDP applications. Thermoluminescence (TL) study was carried out after exposing the samples 5at.wt% Tb3+ doped YPO4 to gamma radiations. Kinetic parameters were calculated using Deconvolution method.

Formation and aspect ratio control of rhabdophane-type yttrium orthophosphate hexagonal prism particles synthesized by a citrate-assisted hydrothermal process

The rhabdophane-type YPO4 particles have been synthesized in the presence of citrate ions under systematically varied reaction conditions.

The study of the influence of pH on the structural and spectroscopic properties of nanocrystalline Eu3+ ion-doped yttrium orthovanadate

In this study, it has been presented the influence of pH conditions on the evolution of the size, morphology and spectroscopic properties of yttrium orthovanadate during synthesis. A thorough research on the spectroscopic properties was performed. A series of highly crystalline 1 mol% Eu3+:YVO4 has been synthesized via the co-precipitation method. In addition, to improve the crystallinity, the materials were heat-treated at 800 °C, and the structural and morphological properties of the particles were studied using XRD (X-ray powder diffraction) and SEM (Scanning Electron Microscopy) techniques. In order to investigate the spectroscopic properties of 1 mol% Eu3+:YVO4, emission spectra and luminescence kinetics were measured. It was found that alkaline pH manifests in smaller particles compared to acidic pH conditions. In addition, superior spectroscopic properties were observed in materials obtained in alkaline pH.

Near-infrared excited luminescence and in vitro imaging of HeLa cells by using Mn2+ enhanced Tb3+ and Yb3+ cooperative upconversion in NaYF4 nanocrystals

Advanced biodetection and bioimaging require fluorescent labels which exhibit many, easily distinguishable colors to identify or study numerous biotargets in a single sample. Although numerous different colors have been demonstrated with lanthanide doped nanoparticles, these colors usually originate from various ratios of overlapping multiple emission bands from activators, which severely limits the number of available labels. As a consequence, different lanthanide doped labels cannot be easily distinguished from each other (e.g. Er3+ from Ho3+) in a quantitative way, when such labels are co-localized during microscopy wide-field imaging. It is therefore reasonable to expand the available choice of spectral signatures and not rely on just different colors. Other ions, such as Tb3+ or Eu3+, can offer new possibilities and unique spectral features in upconversion mode in this respect. For example, despite partial overlap with Er3+ or Ho3+ emission spectra, Tb3+ ions display also unique and easily distinguishable spectral features at 580 nm. Unfortunately, in terms of brightness, Tb3+ emission in upconversion mode is typically too weak to be useful. To improve the Tb3+ upconversion emission intensity, a new approach, i.e. Mn2+ co-doping, has been proposed and verified in this work. A versatile optimization of Tb3+, Yb3+ and Mn2+ ion concentrations has been performed based on luminescence spectra and lifetime studies. The most intense emission was achieved for nanoparticles doped with 10% Mn2+ ions, with over 30 times brighter intensity of Tb3+ ions compared to the emission of nanocrystals without the addition of Mn2+ ions. Additionally, as a proof of the concept, the surface of nanoparticles was coated with proteins and conjugated with folic acid, and such biofunctionalized nanoparticles were subsequently used for bioimaging of HeLa cells.

Multifunctional Optical Sensors for Nanomanometry and Nanothermometry: High-Pressure and High-Temperature Upconversion Luminescence of Lanthanide-Doped Phosphates-LaPO4/YPO4:Yb3+-Tm3

Upconversion luminescence of nano-sized Yb³⁺ and Tm³⁺ codoped rare earth phosphates, that is, LaPO₄ and YPO₄, 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 Tm³⁺ 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 Tm³⁺ band ratio (³F_2,3 → ³H₆/³H₄ → ³H₆), 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).

Tb3+- and Yb3+-doped novel KBaLu(MoO4)3 crystals with disordered chained structure showing down- and up-conversion luminescence

Tb³⁺/Yb³⁺ co-doped KBaLu(MoO₄)₃ with a highly disordered structure consisting of chains induces high color purity of primary green luminescence.

Dual-mode, tunable color, enhanced upconversion luminescence and magnetism of multifunctional BaGdF5:Ln3+ (Ln = Yb/Er/Eu) nanophosphors

BaGdF₅:Yb³⁺,Er³⁺/Eu³⁺ nanophosphors were prepared by a hydrothermal method, and the energy transfer, color-tunable dual-mode emissions and magnetic properties were studied, which could have promising applications in the fields of LEDs, MRI, biolabels, and so on.

Synthesis and spectroscopic properties of Yb3+ and Tb3+ co-doped GdBO3 materials showing down- and up-conversion luminescence

Gadolinium orthoborates doped with Yb³⁺ and Tb³⁺ ions, showing dual-mode luminescence (down- and up-conversion), were synthesised by the sol–gel Pechini method and analysed.

Multifunctional MWCNTs–NaGdF4:Yb3+,Er3+,Eu3+ hybrid nanocomposites with potential dual-mode luminescence, magnetism and photothermal properties

Novel multifunctional MWCNTs–NaGdF₄:Yb³⁺,Er³⁺,Eu³⁺ hybrid nanocomposites can simultaneously take advantage of up- and down-conversion luminescence, magnetism and photothermal properties.