Extended Near-Infrared Photoactivity of Bi₆Fe1.9Co0.1Ti₃O18 by Upconversion Nanoparticles

High-efficiency upconversion process in cobalt and neodymium doped graphene QDs for biomedical applications

Multiphoton absorbing upconversion nanoparticles are emerging as bioimaging materials but are limited by the low quantum yield of their visible fluorescence. This article contains colloids of graphene quantum dots (GQDs), Neodymium, and Cobalt doped Graphene Quantum dots (Co-GQDs and Nd-GQDs) surrounded by carboxylic acids are synthesized which especially are suitable for bio applications; in this way, carboxylic acid groups exchanged by Amoxicillin as an antibiotic with bactericidal activity. The XRD diffraction method, TEM microscope, UV-Vis, and photoluminescence spectroscopies characterize the synthesized materials. The synthesized Quantum dots (QDs) exhibit upconversion properties and their emission is centered at 480 nm, but a red shift was observed with the increase of the excitation wavelength. In the emission spectra of synthesized QDs that can be related to the defect levels introduced by passivation of the QDs in the structure, the results show that with the interaction of the surface QDs with more carboxylic groups, the redshift is not observed. As the results indicate an increase in the intensity of upconversion emission is recorded for Co-GQDs and Nd-GQDs. The absolute quantum efficiency (QY) for Co-GQDs and Nd-GQDs were determined to be 41% and 100% more than GQDs respectively. DFT calculations indicate a strong bond between graphene and cobalt and Neodymium atoms. In doped materials, there are trap levels between the band gap of the GQDs which are responsible for increasing the intensity of the upconversion phenomenon.

Progress and Perspectives on Aurivillius-Type Layered Ferroelectric Oxides in Binary Bi4Ti3O12-BiFeO3 System for Multifunctional Applications

Driven by potentially photo-electro-magnetic functionality, Bi-containing Aurivillius-type oxides of binary Bi4Ti3O12-BiFeO3 system with a general formula of Bin+1Fen−3Ti3O3n+3, typically in a naturally layered perovskite-related structure, have attracted increasing research interest, especially in the last twenty years. Benefiting from highly structural tolerance and simultaneous electric dipole and magnetic ordering at room temperature, these Aurivillius-phase oxides as potentially single-phase and room-temperature multiferroic materials can accommodate many different cations and exhibit a rich spectrum of properties. In this review, firstly, we discussed the characteristics of Aurivillius-phase layered structure and recent progress in the field of synthesis of such materials with various architectures. Secondly, we summarized recent strategies to improve ferroelectric and magnetic properties, consisting of chemical modification, interface engineering, oxyhalide derivatives and morphology controlling. Thirdly, we highlighted some research hotspots on magnetoelectric effect, catalytic activity, microwave absorption, and photovoltaic effect for promising applications. Finally, we provided an updated overview on the understanding and also highlighting of the existing issues that hinder further development of the multifunctional Bin+1Fen−3Ti3O3n+3 materials.

Recent progress in the development of upconversion nanomaterials in bioimaging and disease treatment

Multifunctional lanthanide-based upconversion nanoparticles (UCNPs), which feature efficiently convert low-energy photons into high-energy photons, have attracted considerable attention in the domain of materials science and biomedical applications. Due to their unique photophysical properties, including light-emitting stability, excellent upconversion luminescence efficiency, low autofluorescence, and high detection sensitivity, and high penetration depth in samples, UCNPs have been widely applied in biomedical applications, such as biosensing, imaging and theranostics. In this review, we briefly introduced the major components of UCNPs and the luminescence mechanism. Then, we compared several common design synthesis strategies and presented their advantages and disadvantages. Several examples of the functionalization of UCNPs were given. Next, we detailed their biological applications in bioimaging and disease treatment, particularly drug delivery and photodynamic therapy, including antibacterial photodynamic therapy. Finally, the future practical applications in materials science and biomedical fields, as well as the remaining challenges to UCNPs application, were described. This review provides useful practical information and insights for the research on and application of UCNPs in the field of cancer.

Modification of Bi6Fe1.9Co0.1Ti3O18/SiO2/NaGdF4:Yb3+,Er3+ nanocomposites with different SiO2 thicknesses for tunable upconversion luminescent and ferromagnetic properties

Modification of Bi₆Fe_1.9Co_0.1Ti₃O₁₈/SiO₂/NaGdF₄:Yb³⁺,Er³⁺ nanocomposites with different SiO₂ thickness for tunable upconversion emission and ferromagnetic properties.