Combined In Situ Spectroscopies Reveal the Ligand Ordering-Modulated Photoluminescence of Upconverting Nanoparticles

Abstract

Clear understanding of the complicated interfacial effect of luminescent nanoparticles is of vital importance for their practical applications. Here, combined in situ spectroscopies based on sum-frequency generation and photoluminescence characterization of lanthanide-doped upconversion nanoparticles are established to distinguish the interfacial quenching effects from ligands and solvents. We provide clear spectroscopic evidence to demonstrate that the ligand conformation significantly influences the extent of luminescence quenching from both the ligands and solvents. Moreover, the ligand disordering induced by an enlarged surface curvature is proved to be one of the major reasons for the notorious size-dependent luminescence quenching of the upconversion nanoparticles. Finally, a conformational entropy-driven strategy is provided to increase the luminescence intensity of the upconversion nanoparticles via capping with mixed layers of oleic and dodecanoic acids. Our findings may open up new avenues for clarifying the complex interfacial photophysical issues regarding inorganic luminescent nanoparticles and promoting their practical applications.

Nanoparticle Assembly Induced Ligand Interactions for Enhanced Electrocatalytic CO2 Conversion

“…Therefore, the SFG intensity ratio between d + and r + (or dand r -) can be used to gauge the structural order of ligands on NP surfaces. 18,20 8 SFG spectra of TDPA-capped Ag NPs in the CH-stretch region (2800-3000 cm -1 ) exhibited four C-H stretch bands: methylene symmetric stretch (d + ), methylene asymmetric stretch (d -), methyl symmetric stretch (r + ), and methyl asymmetric out-of-plane stretch (rop) (Figure 4a, b).…”

“…However, when gauche defects along the alkyl chain are present as part of ligand disorder, the inversion symmetry is broken, allowing signals at the methylene stretch modes. Therefore, the SFG intensity ratio between d + and r + (or d – and r – ) can be used to gauge the structural order of ligands on NP surfaces. , …”

In Vivo Monitoring of Hydrogen Polysulfide via a NIR-Excitable Reversible Fluorescent Probe Based on Upconversion Luminescence Resonance Energy Transfer

“…Lanthanide-doped upconversion nanoparticles (UCNPs) are a kind of luminescent material with NIR excitation, which can sequentially absorb two or more low-energy photons and emit one high-energy photon. − In addition, the superior chemical stability and photostability of UCNPs make them in favor of long-term tracking in living systems. − Herein, we developed an upconversion nanoprobe based on the luminescence resonance energy transfer (LRET) principle for reversible detection of H 2 S n in vivo . As illustrated in Scheme , an SiR1 dye, as the reversible recognition unit for H 2 S n , served as the energy acceptor of UCNPs and was loaded onto the surface of UCNPs through coating with an amphiphilic polymer DSPE-PEG.…”

Improvement in Luminescence Intensity of β-NaYF4: 18%Yb3+, 2%Er3+@β-NaYF4 Nanoparticles as a Result of Synthesis in the Presence of Stearic Acid

“…However, one of the most important effects that SA, playing the role of ligands, can introduce is the lowering of surface quenching by replacing OA molecules. It was recently demonstrated that the capping ligands' conformation significantly influences the luminescence quenching from both ligand and solvent molecules and can be a major reason for the size-dependent luminescence quenching of the UCNPs [24].…”