Microwave-assisted synthesis of GdOF: Eu3+/Tb3+ ultrafine phosphor powders suitable for advanced forensic and security ink applications

The rare-earth-doped inorganic ultrafine oxyfluoride host matrices in forensic science, especially in latent fingerprint detection and anti-counterfeiting applications, were still unexplored and may replace the existing technology owing to its high sensitivity. Herein, GdOF: Eu³⁺/Tb³⁺ ultrafine red and green phosphors were synthesized via a rapid, green microwave-assisted hydrothermal method at 150 °C. The phosphors synthesized by this novel method possess good luminescent intensity for the hypersensitive ⁵D₀→⁷F₂ transition of Eu³⁺ and ⁵D₄→⁷F₅ transition of Tb³⁺ ions as compared to the phosphors prepared via other conventional methods such as co-precipitation synthesis, sol-gel synthesis, and microwave-assisted co-precipitation synthesis. Further, an enhancement in the luminescent intensity of the ultrafine phosphor was noticed when the microwave parameters and pH values were tuned. The optimized red and green phosphors having high luminescence intensity, good color purity, and high quantum yields of 89.3%, and 71.2%, respectively, were used for the visualization of latent fingerprints on various substrates. These promising phosphors exhibited excellent visualization regardless of the background interference and limit the risk of duplication and are highly reliable. The security inks developed using these phosphors are highly efficient for anti-counterfeiting applications. These multifunctional properties of investigated phosphors can be explored for security applications.

The synthesis and multicolor luminescence of lanthanide doped Vernier lutetium oxyfluorides

We report a facile hydrothermal method followed by heat treatment for synthesizing monodispersed V-LuOF nanorods through which multicolor emissions are achieved in V-LuOF:Tb³⁺,xEu³⁺.

Applications of nanoparticles in biomedical imaging

An urgent need for early detection and diagnosis of diseases continuously pushes the advancements of imaging modalities and contrast agents. Current challenges remain for fast and detailed imaging of tissue microstructures and lesion characterization that could be achieved via development of nontoxic contrast agents with longer circulation time. Nanoparticle technology offers this possibility. Here, we review nanoparticle-based contrast agents employed in most common biomedical imaging modalities, including fluorescence imaging, MRI, CT, US, PET and SPECT, addressing their structure related features, advantages and limitations. Furthermore, their applications in each imaging modality are also reviewed using commonly studied examples. Future research will investigate multifunctional nanoplatforms to address safety, efficacy and theranostic capabilities. Nanoparticles as imaging contrast agents have promise to greatly benefit clinical practice.

Morphology/phase controllable synthesis of monodisperse ScVO4 microcrystals and tunable multicolor luminescence properties in Sc(La)VO4(PO4):Bi3+,Ln3+ phosphors

A facile one-pot hydrothermal approach was employed to prepare novel chocolate-like ScVO₄ microcrystals using polyethylene glycol as an additive.

Size of the rare-earth ions: a key factor in phase tuning and morphology control of binary and ternary rare-earth fluoride materials

An IL based solvothermal route to prepare RE ion doped luminescent binary/ternary fluoride nanomaterials. Size of the RE ions tunes the nature of the product, crystal phase, lattice strain and morphology, effecting the luminescence properties.

Controllable Synthesis of Monodisperse Er3+-Doped Lanthanide Oxyfluorides Nanocrystals with Intense Mid-Infrared Emission

Monodisperse lanthanide oxyfluorides LnOF (Ln = Gd, Y) with mid-infrared emissions were controllably synthesized via a mild co-precipitation route and a subsequent heat-treatment. The detailed composition and morphology were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and high resolution transmission electron microscopy (HRTEM). The results showed that monodisperse GdOF:Er³⁺ were nano-riced shape with length about 350 nm and width about 120 nm, while the quasi-spherical YOF:Er³⁺ were uniform nanocrystals with an average size around 100 nm. The influence of calcination temperature on the size and phase transition of LnOF nanocrystals was also investigated. The photoluminescence (PL) spectra indicated that the 2.7 μm emission of Er³⁺ had achieved in both GdOF and YOF nanocrystals, which were calcined at different temperatures. In addition, the decay time of both ⁴I_13/2 and ⁴I_13/2 energy levels corresponding to Er³⁺ in YOF nanocrystals were also studied in detail. The results suggested that both rice-shaped GdOF nanocrystals and YOF nanocrystals could provide suitable candidate materials for nanocrystals-glass composites, which could be a step forward to the realization of mid-infrared laser materials.

A two-step synthetic route to GdOF:Ln3+ nanocrystals with multicolor luminescence properties

GdOF:Ln³⁺ (Ln = Eu, Tb, Eu/Tb, Ce/Tb, Yb/Er, and Yb/Tm) nanocrystals with multicolor emissions have been synthesized by a novel topotactic transformation route.

Lanthanide doped Bi2O3 upconversion luminescence nanospheres for temperature sensing and optical imaging

The facile synthesis and surface modification of lanthanide doped Bi₂O₃ nanospheres, and their applications for temperature sensing and optical imaging.

Yb³⁺/Er³⁺-Codoped Bi₂O₃ Nanospheres: Probe for Upconversion Luminescence Imaging and Binary Contrast Agent for Computed Tomography Imaging

In this work, water-soluble Yb(3+)/Er(3+) codoped Bi2O3 upconversion (UC) nanospheres with uniform morphology have been successfully synthesized via a solid-state-chemistry thermal decomposition process. With 980 nm near-infrared irradiation, the Bi2O3:Yb(3+)/Er(3+) nanospheres have bright UC luminescence (UCL). Moreover, multicolor UC emissions (from green to red) can be tuned by simply changing the Yb(3+) ions doping concentration. After citric acid molecules were grafted on the surface of Bi2O3:20% Yb(3+)/2% Er(3+) nanospheres, the MTT assay on HeLa cells and CCK-8 assay on osteoblasts show that the UC nanospheres exhibit excellent stability and biocompatibility. The possibility of using these nanoprobes with red UCL for optical imaging in vivo has been demonstrated. Furthermore, Bi(3+) and Yb(3+) containing nanospheres as binary contrast agent also exhibited significant enhancement of contrast efficacy than iodine-based contrast agent via X-ray computed tomography (CT) imaging at different voltage setting (80-140 kVp), indicating they have potential as CT imaging contrast agent. Thus, Yb(3+)/Er(3+) codoped Bi2O3 nanospheres could be used as dual modality probe for optical and CT imagings.

Size/morphology induced tunable luminescence in upconversion crystals: ultra-strong single-band emission and underlying mechanisms

In this work, we present a two-step method to controllably synthesize novel and highly efficient upconversion materials, Lu5O4F7:Er(3+),Yb(3+) nano/micro-crystals, and investigate their size/morphology induced tunable upconversion properties. In addition to the common phenomenon aroused by a surface quenching effect, direct experimental evidence for the regulation of phonon modes is obtained in nanoparticles. The findings in this work advance the existing mechanisms for the general explanation of size/morphology induced upconversion features. Because of the adjustment of phonon energy and density as well as the surface quenching effect, the biocompatible Lu5O4F7:Er(3+),Yb(3+) nanoparticles exhibit an ultra-strong single-band red upconversion, rendering them promising for biomedical applications.

Phase transition, morphology transformation and highly enhanced luminescence properties of YOF:Eu3+ crystals by Gd3+ doping

We report the crystal phase transition, morphology transformation, and greatly enhanced luminescence properties of YOF crystals by Gd³⁺ doping.

Upconversion luminescence mechanisms of Er3+ ions under excitation of an 800 nm laser

The green/red emission mechanisms of Er³⁺ ions are studied by comparing PL properties upon excitation by CW and fs lasers.

The crystal structure and upconversion properties of Yb3+, Er3+/Ho3+ codoped BaLiF3 microcrystals with different morphologies

A series of x mol% Yb³⁺, 1 mol% Ho³⁺/1 mol% Er³⁺ (0 ≤ x ≤ 25) codoped BaLiF₃ microcrystals with different cubic morphologies and sizes (1.52 μm–3.83 μm) were synthesized by a facile surfactant-assisted hydrothermal-microemulsion approach for the first time.