Physiochemical characterization of highly biocompatible, and colloidal LaF3:Yb/Er upconversion nanoparticles

Highly colloidal upconversion nanoparticles (UCNPs) were synthesized at low temperatures by the thermal decomposition process. The structure, morphology, crystallinity, surface chemistry, and optical properties were systematically optimized and studied through various spectroscopic techniques. X-ray diffraction (XRD) patterns have shown the formation of single-phase, highly purified, well-crystalline, hexagonal LaF₃ NPs, while the TEM micrographs show small, irregular sizes, spherically shaped, and aggregated polycrystalline UCNPs with an average crystalline size of about 8-15 nm. The Negative Zeta Potential value exhibits good biocompatibility of the UCNPs, which supports the idea that surface-anchored hydroxyl groups facilitate the stabilization of the NPs in aqueous media, as well as enhance biomolecules' tagging efficiency. The absorption spectrum, Zeta Potential, and hydrodynamic size that were measured in aqueous media illustrate excellent dispersibility, colloidal stability, biocompatibility, and cytotoxicity character of the UCNPs. Zeta potential and MTT assay studies illustrated high biocompatibility, it could be due to the surface-anchored hydroxyl groups. The nanoproduct demonstrates an excellent UC luminescence spectrum (i.e., prominent green emission ⁴S_3/2 → ⁴I/_15/2) upon irradiation by the 980-nm laser diode. TEM micrographs, further, revealed that this optically active material with aqueous sensitivities, porous crystal structure, and excellent UCNPs, could be a favorable candidate for potential photonics-based bio-related applications.

Up-converting nanoparticles synthesis using hydroxyl-carboxyl chelating agents: Fluoride source effect

The synthesis of lanthanide doped up-converting nanoparticles (UCNPs), whose morphological, structural, and luminescence properties are well suited for applications in optoelectronics, forensics, security, or biomedicine, is of tremendous significance. The most commonly used synthesis method comprises decomposition of organometallic compounds in an oxygen-free environment and subsequent infliction of a biocompatible layer on the particle surface. In this work, hydroxyl-carboxyl (-OH/-COOH) type of chelating agents (citric acid and sodium citrate) are used in situ for the solvothermal synthesis of hydrophilic NaY_0.5Gd_0.3F₄:Yb,Er UCNPs from rare earth nitrate salts and different fluoride sources (NaF, NH₄F, and NH₄HF₂). X-ray powder diffraction showed crystallization of cubic and hexagonal NaY_0.5Gd_0.3F₄:Yb,Er phases in nano- and micro-sized particles, respectively. The content of the hexagonal phase prevails in the samples obtained when Na-citrate is used, while the size and shape of the synthesized mesocrystals are affected by the choice of fluoride source used for precipitation. All particles are functionalized with citrate ligands and emit intense green light at 519 nm and 539 nm (²H_11/2, ⁴S_3/2 → ⁴I_15/2) under near infrared light. The intensity of this emission is distressed by the change in the origin of phonon energy of the host matrix revealed by the change in the number of the excitation photons absorbed per emitted photon.

Synthesis and characterization of LiLuF4:Er3+ and LiLuF4:Yb3+,Er3+ exhibiting upconversion fluorescence pumped by a 1560 nm laser

The UC emission at ∼1 μm could be enhanced by doping Yb³⁺ ions in LiLuF₄:Er microcrystals under 1560 nm excitation.

Development of ultrasensitive and As(iii)-selective upconverting (NaYF4:Yb3+,Er3+) platform

Solid-phase, LRET-based NaYF₄:Yb³⁺,Er³⁺ platform for the ultrasensitive (1 nM) detection of arsenic.

Upconverting SrF2 nanoparticles doped with Yb3+/Ho3+, Yb3+/Er3+ and Yb3+/Tm3+ ions - optimisation of synthesis method, structural, spectroscopic and cytotoxicity studies

For a number of years nanomaterials have been continuously devised and comprehensively investigated because of the growing demand for them and their multifarious applications, especially in medicine. This paper reports on the properties of SrF₂ nanoparticles (NPs) for applications in biomedicine, showing effective ways of their synthesis and luminescence under near infrared radiation - upconversion. NPs doped with lanthanide, Ln³⁺ ions (where Ln = Yb, Ho, Er, Tm) were prepared by the hydrothermal method and subjected to comprehensive studies, from determination of their structure and morphology, revealing small, 15 nm structures, through spectroscopic properties, to cytotoxicity in vitro. The effects of such factors as the reaction time, type and amount of precipitating compounds and complexing agents on the properties of products were characterized. The cytotoxicity of the synthesized and functionalized NPs was investigated, using human fibroblast cell line (MSU-1.1). The synthesized structures may decrease cells' proliferation in a dose-dependent manner in the measured concentration range (up to 100 µg/mL). However, the cells remain alive according to the fluorescent assay. Moreover, the treated cells were imaged using confocal laser scanning microscopy. Cellular uptake was confirmed by the presence of upconversion luminescence in the cells.

Wide spectrum photocatalytic activity in lanthanide-doped upconversion nanophosphors coated with porous TiO2 and Ag-Cu bimetallic nanoparticles

Approaches towards maximum utilization of solar light spectrum for photocatalysis have currently attracted great interest. The combination of profoundly different properties, such as, upconversion, semiconducting and plasmonic properties can produce a favorable path in efficient utilization of the different regions of solar light reaching to earth. In this regard, design and fabrication of microstructures consisting of upconverting lanthanide doped nanophosphors coated with porous semiconducting material, TiO₂ and decorated with plasmonic Ag-Cu bimetallic nanoparticles is presented in this work. These microstructures display great stability and exceptional photocatalytic activity by absorbing wide spectrum from ultraviolet to near infrared. The photocatalytic activity could be attributed to the synergistic effects between the different components and the efficient energy transfer between them. The development of such sort of hybrid microstructures could pave way for the development of new materials for the efficient utilization of the wide spectrum of sunlight.

Tuning the Catalytic Properties of Copper-Promoted Nanoceria via a Hydrothermal Method

Copper-cerium mixed oxide catalysts have gained ground over the years in the field of heterogeneous catalysis and especially in CO oxidation reaction due to their remarkable performance. In this study, a series of highly active, atomically dispersed copper-ceria nanocatalysts were synthesized via appropriate tuning of a novel hydrothermal method. Various physicochemical techniques including electron paramagnetic resonance (EPR) spectroscopy, X-ray diffraction (XRD), N2 adsorption, scanning electron microscopy (SEM), Raman spectroscopy, and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) were employed in the characterization of the synthesized materials, while all the catalysts were evaluated in the CO oxidation reaction. Moreover, discussion of the employed mechanism during hydrothermal route was provided. The observed catalytic activity in CO oxidation reaction was strongly dependent on the nanostructured morphology, oxygen vacancy concentration, and nature of atomically dispersed Cu2+ clusters.

Focal photodynamic intracellular acidification as a cancer therapeutic

Cancer cells utilize an array of proton transporters to regulate intra- and extracellular pH to thrive in hypoxic conditions, and to increase tumor growth and metastasis. Efforts to target many of the transporters involved in cancer cell pH regulation have yielded promising results, however, many productive attempts to disrupt pH regulation appear to be non-specific to cancer cells, and more effective in some cancer cells than others. Following a review of the status of photodynamic cancer therapy, a novel light-activated process is presented which creates very focal, rapid, and significant decreases in only intracellular pH (pHi), leading to cell death. The light-activation of the H⁺ carrier, nitrobenzaldehyde, has been effective at initiating pH-induced apoptosis in non-cancerous and numerous cancerous cell lines in vitro, to include breast, prostate, and pancreatic cancers. Also, this intracellular acidification technique caused significant reductions in tumor growth rate and enhanced survival in mice bearing triple negative breast cancer tumors. The efficacy of an NBA-upconverting nanoparticle to kill breast cancer cells in vitro is described, as well as a discussion of the potential intracellular mechanisms underlying the pH-induced apoptosis.

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.

Facile hydrothermal synthesis of Tb2(MoO4)3:Eu3+ phosphors: controllable microstructures, tunable emission colors, and the energy transfer mechanism

Microsphere-like Tb₂(MoO₄)₃ structures have been successfully synthesized by a facile hydrothermal method with the subsequent calcination treatment.