Multichannel Control of PersL/Upconversion/Down-Shifting Luminescence in a Single Core-Shell Nanoparticle for Information Encryption

Persistent luminescence (PersL) has been attracting substantial attention in diverse frontier applications such as optical information security and in vivo bioimaging. However, most of the reported PersL emissions are based on the dopants instead of the host matrix, which also plays an important role. In addition, there are few works on the PersL-based multifunctional nanoplatform in nanosized materials. Here, we report a class of novel nanostructure designs with PersL, upconversion, and down-shifting luminescence to realize the fine-tuning of emission colors under different excitation modes including steady-state irradiation, time-gating, and PersL generation. Blue, orange, and green emissions were easily achieved in such a single nanoparticle under suitable excitation modes. Moreover, the physical origin of the PersL of the CaF₂ matrix was discussed by simulating the energy band structure with Ca_xF_y defects. Our results provide new opportunities for the design of a new class of multifunctional materials, showing great promise in the field of information encryption security and multilevel anticounterfeiting.

Dye-sensitized lanthanide containing nanoparticles for luminescence based applications

Due to their exceptional luminescent properties, lanthanide (Ln) complexes represent a unique palette of probes in the spectroscopic toolkit. Their extremely weak brightness due to forbidden Ln electronic transitions can be overcome by indirect dye-sensitization from the antenna effect brought by organic ligands. Despite the improvement brought by the antenna effect, (bio)analytical applications with discrete Ln complexes as luminescent markers still suffers from low sensitivity as they are limited by the complex brightness. Thus, there is a need to develop nano-objects that cumulate the spectroscopic properties of multiple Ln ions. This review firstly gives a brief introduction of the spectral properties of lanthanides both in complexes and in nanoparticles (NPs). Then, the research progress of the design of Ln-doped inorganic NPs with capping antennas, Ln-complex encapsulated NPs and Ln-complex surface functionalized NPs is presented along with a summary of the various photosensitizing ligands and of the spectroscopic properties (excited-state lifetime, brightness, quantum yield). The review also emphasizes the problems and limitations encountered over the years and the solutions provided to address them. Finally, a comparison of the advantages and drawbacks of the three types of NP is provided as well as a conclusion about the remaining challenges both in the design of brighter NPs and in the luminescence based applications.

Hybrid photoluminescent material from lanthanide fluoride and graphene oxide with strong luminescence intensity as a chemical sensor for mercury ions

In this work, we employed NaxLiyGdF4:Tb3+@PMA@Phen@GO nanocomposite as chemical sensor for selective and sensitive luminescence sensing of toxic Hg2+ metal ion.

Ligand-Sensitised LaF3 :Eu3+ and SrF2 :Eu3+ Nanoparticles and in Vitro Haemocompatiblity Studies

Luminescent Ln³⁺ -doped nanoparticles (NPs) functionalised with the desired organic ligand molecules for haemocompatibility studies were obtained in a one-pot synthesis. Chelated aromatic organic ligands such as isophthalic acid, terephthalic acid, ibuprofen, aspirin, 1,2,4,5-benzenetetracarboxylic acid, 2,6-pyridine dicarboxylic acid and adenosine were applied for surface functionalisation. The modification of the nanoparticles is based on the donor-acceptor character of the ligand-nanoparticle system, which is an alternative to covalent functionalisation by peptide bonding as presented in our recent report. The aromatic groups of selected ligands absorb UV light and transfer their excited-state energy to the dopant Eu³⁺ ions in LaF₃ and SrF₂ NPs. Herein, we discuss the structural and spectroscopic characterisation of the NPs and the results of haemocompatibility studies. Flow cytometry analysis of the nanoparticles' membrane-binding is also presented.

Infrared Photon Pair-Production in Ligand-Sensitized Lanthanide Nanocrystals

This report details spectroscopic characterizations of rare-earth, core-shell nanoparticles decorated with the f-element chelator 3,4,3-LI(1,2-HOPO). Evidence of photon downconversion is corroborated through detailed power dependence measurements, which suggest two-photon decay paths are active in these materials, albeit only representing a minority contribution of the sum luminescence, with emission being dominated by normal, Stokes' shifted fluorescence. Specifically, ultraviolet ligand photosensitization of Nd³⁺ ions in a NaGdF₄ host shell results in energy transfer to a Nd³⁺/Yb³⁺-doped NaGdF₄ nanoparticle core. The population and subsequent decay of core, Yb³⁺²F_5/2 states result in a spectral shift of 620 nm, manifested in a NIR emission displaying luminescence profiles diagnostic of Yb³⁺ and Nd³⁺ excited state decays. Emphasis is placed on the generality of this material architecture for realizing ligand-pumped, multi-photon downconversion, with the Nd³⁺/Yb³⁺ system presented here functioning as a working prototype for a design principle that may be readily extended to other lanthanide pairs.

Bimodal Visualization of Endogenous Nitric Oxide in Lysosomes with a Two-Photon Iridium(III) Phosphorescent Probe

Nitric oxide (NO) is a fundamental signaling molecule that shows complex effects on the catabolic autophagy process, which is closely linked with lysosomal function. In this study, a new lysosome-targeted, pH-independent, and two-photon phosphorescent iridium(III) complex, Ir-BPDA, has been investigated for endogenous NO detection and imaging. The rational design of the probe, as the addition of the morpholine moieties and the substitution of a benzyl group in the amino group in Ir-BPDA, facilitates its accumulation in lysosomes and makes the reaction product with NO, Ir-BPDA-NO, insusceptible in its phosphorescence intensity and lifetime against pH changes (pH 4-10), well suited for lysosomal NO detection (pH 4-6). Furthermore, Ir-BPDA exhibits a fast and 50-fold response to NO in phosphorescence intensity and a two-photon cross-section as high as 60 GM after the reaction, as well as a notably increased phosphorescence lifetime from 200.1 to 619.6 ns. Thus, accompanied by its photostability, Ir-BPDA enabled the detection of NO in the lipopolysaccharide-stimulated macrophages and zebrafish model, revealing the endogenous lysosomal NO distribution during inflammation in vivo by means of both TPM and PLIM imaging techniques.