Microwave-assisted synthesis and upconversion luminescence of NaYF4:Yb, Gd, Er and NaYF4:Yb, Gd, Tm nanorods

Anisotropic rare-earth ion (RE3+) doped fluoride upconversion particles are emerging as a potential candidate in diverse areas, ranging from biomedical imaging to photonics. Here, we develop a facile strategy to synthesize NaYF4:Yb, Er, Gd and NaYF4:Yb, Tm, Gd upconversion nanorods via microwave synthesis route by controlling the synthesis time and compared the optical properties of similar nanorods prepared via solvothermal technique. With the increase in synthesis time, the phase of the particle was found to change from mixed-phase to purely hexagonal and the morphology of the particles change the mixed phase of spherical and rod-shaped particles to completely nanorods for a synthesis time of 60 minutes. Further, the intrinsically hydrophobic particles changed to hydrophilic by removal of oleic capping via acid treatment and the amine-functionalized silica coating. The upconversion luminescence, as well as laser power-dependent emission properties of the surface-modified particles, elucidate that the surface modification route influence the upconversion luminescence as well as solvent-dependent emission properties. Moreover, the laser power-dependent studies elucidate that the upconversion process in a multi-photon process.

Nanoparticle impregnated self-supporting protein gel for enhanced reduction in oxidative stress: A molecular dynamics insight for lactoferrin-polyphenol interaction

In the present work, lactoferrin (Lf) based nanoparticle incorporated self-supporting gel encapsulating a flavonoid, quercetin (Q), was developed. The complex formation between Lf and Q was assessed using molecular docking and dynamics simulation that lactoferrin and quercetin showed strong interaction and binding supporting hydrophobic interaction. The microscopic, spectroscopic, and x-ray techniques were used to characterize the gel extensively. In vitro drug release was studied to understand the release pattern of quercetin from the protein gel. The viscosity of the gel and its rheological characteristics were determined using a Brookfield viscometer. Ex vivo skin permeation studies using vertical diffusion cells were carried out to understand its skin permeation properties. The gel showed strong anti-oxidant activity using the DPPH scavenging assay. The enhanced effect of the Lf-Q complex on antioxidant enzyme activity (superoxide dismutase, catalase, and malondialdehyde), was supported by molecular dynamics, surface hydrophobicity, and in vitro studies. To investigate the effect of the gel on angiogenesis, the chorioallantoic membrane assay was performed and its compatibility with erythrocytes was also assessed. Suitability for topical administration was assessed using skin irritation studies performed on Sprague Dawley rats. The overall results suggest that the developed NiPG is suitable for cutaneous localization of quercetin with enhanced antioxidant activity.

Subcellular imaging and diagnosis of cancer using engineered nanoparticles

The advances in the synthesis of nanoparticles with engineered properties are reported to have profound applications in oncological disease detection via optical and multimodal imaging and therapy. Among various nanoparticle-assisted imaging techniques, engineered fluorescent nanoparticles show great promise from high contrast images and localized therapeutic applications. Of all the fluorescent nanoparticles available, the gold nanoparticles, carbon dots, and upconversion nanoparticles are emerging recently as the most promising candidates for diagnosis, treatment, and cancer monitoring. This review addresses the recent progress in engineering the properties of these emerging nanoparticles and their application for cancer diagnosis and therapy. In addition, the potential of these particles for subcellular imaging is also reviewed here.

Post annealing induced manipulation of phase and upconversion luminescence of Cr3+ doped NaYF4:Yb,Er crystals

The role of post synthesis annealing at different temperatures (200–600 °C) on the structural as well as luminescence properties of NaY_80%F₄:Yb_17%,Er_3% prepared via a coprecipitation method was found to change the structure from a cubic to hexagonal phase with a concomitant increase in upconversion luminescence by 12 times for the green region and 17 times for the red region. Addition of the Cr³⁺ ions (5–20 mol%) into the host followed by post annealing at 200–600 °C causes that the samples to exhibit phase dependent and upconversion luminescence behavior that depend upon the doping concentration as well as the annealing temperature. The inductively coupled optical emission spectroscopy reveals that only 1/600 times of the desired volume of the co-dopant goes to the lattice and it can manifest visible spectral changes in the diffuse reflectance spectra of the samples. The samples co-doped with Cr³⁺ ion concentrations of 10–15% and post-annealed at 600 °C were found to have maximum emission with an enhancement factor of 24 for the green region and 33 for the red region. In addition, the laser power dependent studies reveal that even for the power density levels 3.69 W cm⁻² to 32.14 W cm⁻², the samples are in the saturation regime and most of the samples investigated here follow a single photon process, and a few samples show a slope value less than 1 for laser power dependent intensity plots. The results show the remarkable promise of controlled tailoring of the properties of upconversion crystals via post annealing and co-doping.

Co-dopant (Cr³⁺ ion) concentration as well as post annealing found to change the structural as well as luminescence properties of Cr³⁺ ion doped NaY_80%F₄:Yb_17%,Er_3% prepared via a co-precipitation method.