In vivo optical bioimaging by using Nd-doped LaF3 luminescent nanorods in the second near-infrared window

Blue to Red Emission Tunable Bi3+ co-doped YPO4:Eu3+: Host Emission and Phase Change

Bi3+(0, 1, 3, 5, 7, 10, 12 and 15 at.%) co-doped YPO4:Eu3+ have been hydrothermally synthesized. Bi3+ (x ≥ 1 at.%) co-doping in YPO4:Eu3+ renders mixed crystalline phase of tetragonal to hexagonal. Pure tetragonal phase of Bi3+ co-doped YPO4:Eu3+ could be achieved upon annealing at 900 °C. The luminescence intensity is improved significantly upon annealing at 900 °C. This is due to the reduction of quenching pathways such as water molecules, dangling bonds, etc. The probability of magnetic dipole and electric dipole transitions is observed to be altered. As-prepared samples show near blue emission, while 900 °C annealed samples exhibit red emission, which could be a potential candidate for display, sensing and biological labelling, etc.

Synthesis, Structure and Near Infrared Fluorescence Property of a New Nd-MOF Based on a Triangular Benzylamine Ligand

A new 3D metal-organic framework (Nd-MOF) {[Nd₂L₂]·2NH₂(CH₃)₂·3H₂O} was successfully established via a solvothermal method with Nd³⁺ ion and 5-(bis(4-carboxybenzyl) amino)-isophthalicacid (H₄L), and has also been characterized by X-ray diffraction, powder X-ray diffraction (PXRD), IR and photoluminescence(PL)spectrum. The neodymium ions are free of coordinated solvents, and the Nd-MOF exhibits strong near-infrared (NIR) fluorescence. Besides, Its NIR fluorescence property shows low temperature resistance, which is favorable for being used in the low temperature environment. Besides, the fluorescence lifetime of Nd-MOF is 6.03 μs, and the quantum yield is 1.2%. The small quantum yield may owe to large energy gap between the T1 of the ligand H₄L and the resonance energy level ⁴F_3/2 of the Nd³⁺ ion, or due to large crystal size of the Nd-MOF.

Photoluminescence Investigations of Dy3+-Doped Silicate Xerogels and SiO2-LaF3 Nano-Glass-Ceramic Materials

In this work, the series of Dy³⁺-doped silicate xerogels were synthesized by sol-gel technique and further processed at 350 °C into SiO₂-LaF₃:Dy³⁺ nano-glass-ceramic materials. The X-ray diffraction (XRD) measurements, along with the thermal analysis, indicated that heat-treatment triggered the decomposition of La(TFA)₃ inside amorphous sol-gel hosts, resulting in the formation of hexagonal LaF₃ phase with average crystal size at about ~10 nm. Based on the photoluminescence results, it was proven that the intensities of blue (⁴F_9/2 → ⁶H_15/2), yellow (⁴F_9/2 → ⁶H_13/2), and red (⁴F_9/2 → ⁶H_11/2) emissions, as well as the calculated yellow-to-blue (Y/B) ratios, are dependent on the nature of fabricated materials, and from fixed La³⁺:Dy³⁺ molar ratios. For xerogels, the emission was gradually increased, and the τ(⁴F_9/2) lifetimes were elongated to 42.7 ± 0.3 μs (La³⁺:Dy³⁺ = 0.82:0.18), however, for the sample with the lowest La³⁺:Dy³⁺ molar ratio (0.70:0.30), the concentration quenching was observed. For SiO₂-LaF₃:Dy³⁺ nano-glass-ceramics, the concentration quenching effect was more visible than for xerogels and started from the sample with the highest La³⁺:Dy³⁺ molar ratio (0.988:0.012), thus the τ(⁴F_9/2) lifetimes became shorter from 1731.5 ± 5.7 up to 119.8 ± 0.4 μs. The optical results suggest, along with an interpretation of XRD data, that Dy³⁺ ions were partially entered inside LaF₃ phase, resulting in the shortening of Dy³⁺-Dy³⁺ inter-ionic distances.

Application of rare earth-doped nanoparticles in biological imaging and tumor treatment

Rare earth-doped nanoparticles have been widely used in disease diagnosis, drug delivery, tumor therapy, and bioimaging. Among various bioimaging methods, the fluorescence imaging technology based on the rare earth-doped nanoparticles can visually display the cell activity and lesion evolution in living animals, which is a powerful tool in biological technology and has being widely applied in medical and biological fields. Especially in the band of near infrared (700–1700 nm), the emissions show the characteristics of deep penetration due to low absorption, low photon scattering, and low autofluorescence interference. Furthermore, the rare earth-doped nanoparticles can be endowed with the water solubility, biocompatibility, drug-loading ability, and the targeting ability for different tumors by surface functionalization. This confirms its potential in the cancer diagnosis and treatment. In this review, we summarized the recent progress in the application of rare earth-doped nanoparticles in the field of bioimaging and tumor treatment. The luminescent mechanism, properties, and structure design were also discussed.