Nd3+/Yb3+ cascade-sensitized single-band red upconversion emission in active-core/active-shell nanocrystals

Introduce Ce3+ Ions to Realize Enhancement of C+L Band Luminescence of KMnF3: Yb, Er Nanoparticles

Polymer-based waveguide amplifiers are essential components in integrated optical systems, as their gain bandwidths directly determine the operating wavelength of optical circuits. However, development of the wideband gain media has been challenging, making it difficult to fabricate devices with broadband amplification capability. Rare earth ion-doped nanoparticles (NPs) are a key component in the gain media, and their full width at half maximum (FWHM) of the emission peak decides the final gain bandwidth of the gain media. Here, KMnF3: Yb, Er, Ce@KMnF3: Yb NPs with the broad full width at half maximum (FWHM) of the emission peak covering the S+C band was prepared. The NPs were synthesized using a hydrothermal method, and the FWHM of the emission peak of NPs reached 76 nm under the excitation of a 980 nm laser. The introduction of Ce3+ ions and a core-shell structure coating greatly enhanced the emission intensity of NPs at C band. Since KMnF3: Yb, Er, Ce@KMnF3: Yb NPs have exceptional broadband luminescence properties at C band, KMnF3: Yb, Er, Ce@KMnF3: Yb NPs can be the potential gain medium in the future polymer-based waveguide amplifiers.

-808nm-Activated Ca2+Doped Up-conversion Nanoparticles That Release NO Inducing Liver Cancer Cell (HepG2) Apoptosis

A near-infrared (NIR) light-triggered release method for nitric oxide (NO) was developed utilizing core/shell NaYF4: Tm/Yb/Ca@NaGdF4: Nd/Yb up-conversion nanoparticles (UCNPs) bearing a mesoporous silica (mSiO2) shell loaded with the NO donor S-nitroso-N-acetyl-DL-penicillamine (SNAP). To avoid overheating in biological samples, Nd3+ was chosen as a sensitizer, Yb3+ ions as the bridging sensitizer, and Tm3+ ions as UV-emissive activator while co-doping with Ca2+ was done to enhance the luminescence of the activator Tm3+. NO release from SNAP was triggered by an NIR-UV up-conversion process, initiated by 808 nm light absorbed by the Nd3+ ions. NO release was confirmed by the Griess method. Under 808 nm irradiation, the viability of the liver cancer cell line HepG2 significantly decreased with increasing UCNPs@mSiO2-SNAP concentration. For a UCNPs@mSiO2-SNAP concentration of 200 μg/ml, the cell survival probability was 47 %. These results demonstrate that UCNPs@mSiO2-SNAP can induce the release of apoptosis-inducing NO by NIR irradiation.

Huge upconversion luminescence enhancement by a cascade optical field modulation strategy facilitating selective multispectral narrow-band near-infrared photodetection

Since selective detection of multiple narrow spectral bands in the near-infrared (NIR) region still poses a fundamental challenge, we have, in this work, developed NIR photodetectors (PDs) using photon upconversion nanocrystals (UCNCs) combined with perovskite films. To conquer the relatively high pumping threshold of UCNCs, we designed a novel cascade optical field modulation strategy to boost upconversion luminescence (UCL) by cascading the superlensing effect of dielectric microlens arrays and the plasmonic effect of gold nanorods, which readily leads to a UCL enhancement by more than four orders of magnitude under weak light irradiation. By accommodating multiple optically active lanthanide ions in a core-shell-shell hierarchical architecture, developed PDs on top of this structure can detect three well-separated narrow bands in the NIR region, i.e., those centered at 808, 980, and 1540 nm. Due to the large UCL enhancement, the obtained PDs demonstrate extremely high responsivities of 30.73, 23.15, and 12.20 A W^-1 and detectivities of 5.36, 3.45, and 1.91 × 10¹¹ Jones for 808, 980, and 1540 nm light detection, respectively, together with short response times in the range of 80-120 ms. Moreover, we demonstrate for the first time that the response to the excitation modulation frequency of a PD can be employed to discriminate the incident light wavelength. We believe that our work provides novel insight for developing NIR PDs and that it can spur the development of other applications using upconversion nanotechnology.

Improved Red Emission and Short-Wavelength Infrared Luminescence under 808 nm Laser for Tumor Theranostics

In this research, a multimodal imaging platform guided photodynamic theranostics under 808 nm was designed using a NaErF₄:Tm@NaYF₄:Yb@NaLuF₄:Nd,Yb-ZnPc structure. Unlike conventional codoped Yb³⁺/Er³⁺ system, Er³⁺ ions as activator and sensitizer were used to improve the up-conversion energy transfer processes. Furthermore, higher energy transfer processes between Er³⁺ ions could be obtained through doped 1% Tm³⁺ ions as an energy trapping center in the NaErF₄. This platform could emit much brighter upconversion luminescence (UCL) (124-fold enhancement for red emission) and short wavelength infrared (SWIR) emission under single 808 nm laser excitation. Importantly, the SWIR imaging with higher resolution and better signal-to-noise ratio can pass the blood-brain barrier to see the brain vessels. Because of the enhanced red emission, the UCL nanoparticles were combined with ZnPc agent to exhibit photodynamic therapy (PDT) effect, and its distribution and excretion could be detected by the photoacoustic (PA) imaging under single near-infrared (NIR) laser. Thus, this platform could be used as multimodal imaging (SWIR, PA, CT, and UCL) guided PDT agent under single 808 nm laser.