Assessing the reproducibility and up-scaling of the synthesis of Er,Yb-doped NaYF4-based upconverting nanoparticles and control of size, morphology, and optical properties

Abstract

Lanthanide-based, spectrally shifting, and multi-color luminescent upconverting nanoparticles (UCNPs) have received much attention in the last decades because of their applicability as reporter for bioimaging, super-resolution microscopy, and sensing as well as barcoding and anti-counterfeiting tags. A prerequisite for the broad application of UCNPs in areas such as sensing and encoding are simple, robust, and easily upscalable synthesis protocols that yield large quantities of UCNPs with sizes of 20 nm or more with precisely controlled and tunable physicochemical properties from low-cost reagents with a high reproducibility. In this context, we studied the reproducibility, robustness, and upscalability of the synthesis of β-NaYF4:Yb, Er UCNPs via thermal decomposition. Reaction parameters included solvent, precursor chemical compositions, ratio, and concentration. The resulting UCNPs were then examined regarding their application-relevant physicochemical properties such as size, size distribution, morphology, crystal phase, chemical composition, and photoluminescence. Based on these screening studies, we propose a small volume and high-concentration synthesis approach that can provide UCNPs with different, yet controlled size, an excellent phase purity and tunable morphology in batch sizes of up to at least 5 g which are well suited for the fabrication of sensors, printable barcodes or authentication and recycling tags.

Topological Control of Lanthanide-Doped Upconversion Nanocrystals for Improved FRET Coupling Efficiency in Second Near-Infrared-Triggered Photodynamic Therapy

“…With the progression of epitaxial growth, a disk-shaped morphology eventually forms when more OA ligands are chosen to bond to the (001) facet. Interestingly, our results align with some aspects of the research conducted by Markus Haase, Ute Resch-Gengern, and Paul Alivisatos. ,, …”

Er3+-Doped Upconversion Nanoparticle Coatings for Thermometric Microscanning: Tackling Experimental Factors

“…The maximum slope was obtained by converting the values of Δ to T and the values of steps to micrometers. For this derivative, D x = 1.0(3) K μm −1 was calculated, which can be fed into eq 4 to estimate the spatial resolution obtaining σ X = 0.24 (7) μm, in close agreement with previously reported values. 44 A word of caution is needed here.…”

“…It was possible to resolve the thermal gradients produced by the Joule effect on the scale of microns. From temperature line profiles, it was possible to calculate the spatial resolution of the setup: σ X = 0.24 (7) μm. Similarly, the temperature resolution σ T = 0.24(2) K was obtained using the m-UCNPs that presented the highest thermal sensitivity 1.741 (% K −1 ) at 300 K. Given that all resolutions are strongly dependent on the relative sensitivity of the UCNPs used, efforts in the design and synthesis of highly sensitive particles are a key factor to improve the technique.…”

“…Studies of thermal processes in nanostructures, cell biology, and microfluidics require thermal probes for sensing heat exchange with high spatiotemporal resolution. , In microelectronics, the performance of devices is largely dependent on heat dissipation through the Joule effect, requiring accurate measurements of thermal profiles to identify hot spots and optimize heat dissipation. , In biomedical applications, precise temperature determination could be used for studies of cellular metabolism, tissue engineering, and drug delivery systems. Recent advances in the synthesis and control of upconversion nanoparticles (UCNPs) drove the development of optical-based thermometric methods that harvest the anti-Stokes emission of trivalent lanthanide ions (Ln 3+ ). − In particular, there has been extensive research over the past decade on Er 3+ -doped UCNPs focusing on their use in optical thermometry within the physiological temperature range. − The theoretical basis of the physical properties of Er 3+ -doped UCNPs has been detailed in several works. − Simultaneously, many research groups have explored the experimental details regarding the implementation of upconversion thermometry (UCT), resulting in major advances. Just to mention a few examples, Er 3+ -doped UCNPs were successfully applied for sensing temperatures up to 900 K, integrated into optical fibers for sensing heat generated within a battery, temperature reading of an electrical microheater, and applied in microfluidic devices .…”

Synthesis and emission dynamics of sub-3 nm single-emitter upconversion nanoparticles

“…3 nm luminescent UCNPs with 57% Yb encouraged us to carry out this strategy. As it has been reported that substantial variability in the average UCNP diameter could be observed for a defined synthetic protocol, 55,56 we simply repeated the abovementioned synthesis of Na(Yb57%-Gd42%)F4:Tm1%. While the PSD remained constant owing to our new heating method, we could achieve the preparation of ultrasmall UCNPs ranging from 3.86 nm down to 2.84 nm in diameter, the target size for single-Tm-ion UCNPs (Fig.…”