Improved multiphoton ultraviolet upconversion photoluminescence in ultrasmall core-shell nanocrystals

Diffraction-Unlimited Photomanipulation at the Plasma Membrane via Specifically Targeted Upconversion Nanoparticles

Engineered UCNP are used to trigger rapid photoconversion of the fluorescent protein Dendra2 with nanoscopic precision and over longer distances in mammalian cells. By exploiting the synergy of high-level thulium doping with core-shell design and elevated excitation intensities, intense UCNP emission is achieved, allowing fast photoconversion of Dendra2 with <10 nm resolution. A tailored biocompatible surface coating and functionalization with a derivate of green fluorescent protein (GFP) for recognition of antiGFP nanobodies are developed. Highly specific targeting of UCNP to fusion proteins of antiGFP on the surface of mammalian cells is demonstrated. UCNP bound to extracellular Dendra2 enable rapid photoconversion selectively in molecular proximity and thus unambiguous detection of cytokine receptor dimerization in the plasma membrane and in endosomes. Remarkably, UCNPs are also suited for manipulating intracellular Dendra2 across the plasma membrane. This study thus establishes UCNP-controlled photomanipulation with nanoscale precision, opening exciting opportunities for bioanalytical applications in cell biology.

Nanoscale "fluorescent stone": Luminescent Calcium Fluoride Nanoparticles as Theranostic Platforms

Calcium Fluoride (CaF2) based luminescent nanoparticles exhibit unique, outstanding luminescent properties, and represent promising candidates as nanoplatforms for theranostic applications. There is an urgent need to facilitate their further development and applications in diagnostics and therapeutics as a novel class of nanotools. Here, in this critical review, we outlined the recent significant progresses made in CaF2-related nanoparticles: Firstly, their physical chemical properties, synthesis chemistry, and nanostructure fabrication are summarized. Secondly, their applications in deep tissue bio-detection, drug delivery, imaging, cell labeling, and therapy are reviewed. The exploration of CaF2-based luminescent nanoparticles as multifunctional nanoscale carriers for imaging-guided therapy is also presented. Finally, we discuss the challenges and opportunities in the development of such CaF2-based platform for future development in regard to its theranostic applications.

Mechanisms of the blue emission of NaYF4:Tm3+ nanoparticles excited by an 800 nm continuous wave laser

Simultaneous multiwavelength excitation and the quantum transition principle are utilized to study the blue emission mechanisms of NaYF₄:Tm³⁺ UCNPs under 800 nm CW laser excitation.

Photon Upconversion Through Tb(3+) -Mediated Interfacial Energy Transfer

A strategy of interfacial energy transfer upconversion is demonstrated through the use of a terbium (Tb(3+) ) dopant as energy donor or energy migrator in core-shell-structured nanocrystals. This mechanistic investigation presents a new pathway for photon upconversion, and, more importantly, contributes to the better control of energy transfer at the nanometer length scale.

Up/down conversion switching by adjusting the pulse width of red laser beams in LaF₃:Tm³⁺ nanocrystals

We demonstrate a versatile approach to fine-tuning the ratio of blue to near-infrared emission intensity from Tm3+ ions in LaF3 nanocrystals by adjusting the pulse widths and excitation wavelengths of red laser beams. The mechanism of color-tunable Tm3+ emission by pulse widths is explored, and a mechanism based on promoting the population of some luminescence levels and cutting off the population of others by suitably adjusting pulse duration is proposed. The underlying reason of excitation wavelength-modulated emission is ascribed to tuning absorption probability ratio of ground state absorption to excited state absorption by tuning the matching degree between the energies of excitation wavelength and ground (excited) state absorption of Tm3+. The ability of our LaF3:Tm3+ nanocrystals to emit variable emissions on demand in response to pulse width and excitation wavelength provides keen insights into controlling the population processes of luminescent levels and offers a versatile approach for tuning the spectral output.