Search

This paper presents a strategy to convert hydrophilic cellulose nanofibrils (CNF) into a highly cross-linked hydrophobic network with inorganic nanoparticles to develop a gel ink suitable for gel 3D printing. The CNF were chemically modified initially through a single-electron transfer-living radical polymerization (SET-LRP) of stearyl acrylate (SA) in the presence of the surface-modified cobalt iron oxide (CoFe2O4, CFO) nanoparticles. The modified CFO nanoparticles provide their multifunctional properties, such as magnetic and electrochemical, to the CNF hybrid network and, at the same time, act as cross-linking agents between the nanocellulose fibrils, while the grafted poly-stearyl acrylate (PSA) introduces a strong hydrophobicity in the network. A suitable gel ink form of this CNF–PSA–CFO material for gel 3D printing was achieved together with a certain solvent. Some test structure prints were directly obtained with the CNF–PSA–CFO gel and were used to evaluate the consolidation of such 3D objects through solvent exchange and freeze-drying while also keeping the magnetic and electrochemical properties of CFO in the CNF-based composite intact. The pristine CNF and CFO particles and the CNF–PSA–CFO were characterized by FTIR, SEM, XPS, TGA, VSM, and CV measurements. [ABSTRACT FROM AUTHOR]

Though Pr 3+ doped LiYF 4 (LiYF 4 :Pr 3+ ) bulk crystals are a well-known laser gain material with several radiative transitions, their nanocrystal counterparts have not been investigated with regards to these. Through downsizing to the nanoscale, novel applications are expected, especially in composite photonic devices. For example, nanocrystals in stable colloidal form with narrow size distribution are highly desirable to reduce scattering in such composites. Herein, we synthesized monodispersed LiYF 4 :Pr 3+ nanocrystals having a size of 10 nm resulting in colorless clear stable colloidal dispersions and conducted an extensive optical characterization for the first time. We observed unexpected yet intense emission with excited state lifetimes comparable to bulk crystals in the visible spectrum through excitation at 444 nm and 479 nm. In macroscopic bulk crystals, this emission is only exploitable through excitation of a different, subjacent energy level. A comprehensive comparison to the bulk crystals provides deeper insight into the excitation mechanism and performance of these nanocrystals. The presented results pave the way for developing application-oriented LiYF 4 :Pr 3+ nanocrystals as emitters with tailored properties for quantum optics or biomedical applications., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

Yttrium oxide (Y 2 O 3 ) is considered as one of the best host lattices for europium (Eu 3+ ) based red emitting phosphors because of its unit cell and good photo-saturation properties. As a bulk material, it reaches nearly 100% quantum yield. However, providing high quality nanosized materials for the LED industry is still a challenge and not easily accomplished. Within this publication, a simple one pot, non-hydrolytic, solvent-based synthesis method for producing uniform and monodisperse red-emitting europium doped yttrium oxide (Y 2 O 3 :Eu) nanoparticles is provided. The synthesis is the cheapest and fastest reported yet, yields up to 80%, and offers good scalability, and the diameter of the produced nanodiscs is tunable from 7 nm to 30 nm. The dispersed nanomaterial shows bright red emission (607 nm) under UV excitation (273 nm) and a higher quantum yield (>30%) compared to other nanosized Y 2 O 3 :Eu materials. In order to shift the excitation wavelength towards the visible region we added Tb 3+ as the sensitizer. Thereby, it was also possible to tune the emission colour towards orange/yellow. Further, a distorted anisotropic cubic Y 2 O 3 phase is confirmed by XRD analysis, resulting in a distinct change in the intensities of red emission transitions. A calcination step transforms it into a highly crystalline cubic phase, known from the bulk material, and exhibiting a typical emission spectrum., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)