Nd³⁺-Sensitized Upconversion Nanostructure as a Dual-Channel Emitting Optical Probe for Near Infrared-to-Near Infrared Fingerprint Imaging

Abstract

Lanthanide upconversion nanophosphors (Ln-UCNPs) have attracted great attention in a variety of fields, benefiting from low background fluorescence interference and a high signal-to-noise ratio of upconversion luminescence. However, the establishment of Ln-UCNPs with dual near-infrared (NIR) emission channels still remains challenging. Herein, we report the design and synthesis of Nd-sensitized NaYbF:Tm@NaYF:Yb@NaNdF:Yb hierarchical-structured nanoparticles that emit NIR luminescence at 696 and 980 nm under excitation at 808 nm. The sensitizer-rich NaYbF core promotes efficient energy transfer to Tm. The interlayer of NaYF:Yb effectively prevents the cross-relaxation process from Tm to Nd and thus enhances the luminescence emission. The introduction of Nd ion as the sensitizer transforms the excitation wavelength from 980 to 808 nm, which subtly averts the laser-induced thermal effect and offers a new pathway for the NIR emission channel at 980 nm. The as-prepared nanoparticles were further applied in developing latent and blood fingerprint images, which exhibited high signal-to-noise ratio and distinguishable details under 808 nm excitation with negligible thermal damage to the sample. Our work provides a promising strategy to realize NIR-to-NIR dual-channel emissions in Ln-UCNPs. With further functionalization, such nanoparticles are expected to have great potential in forensic and biological sciences.

Broadband Plasmonic Antenna Enhanced Upconversion and Its Application in Flexible Fingerprint Identification

“…Photoluminescence using quantum dots and fluorescence dyes is one of the most sensitive techniques for fingerprint detection, but it suffers from background fluorescence . In contrast to traditional fingerprint identification technology based on fluorescence dyes and quantum dots, UC fingerprint identification using NIR excited UCNCs has the exceptional stability, and can remove the interference of background fluorescence and excitation light, owing to unique nonlinear UC property and large anti‐Stokes shift,[5e,22] but it also suffers from the low quantum efficiency of UCNCs, leading to the low emission intensity of UCNCs. The broadband plasmon antenna enhanced UC device is promised to solve the above issue.…”

Rising Stars in Science and Technology: Luminescent Lanthanide Materials

“…Moreover, sophisticated hexagonal nanorods encompassing various NaYF 4 :Yb,Ln phosphors enable the design of different RGB combinations for specific nanomarking (Figure b) . Fingerprints that are otherwise difficult to reveal can also be mapped with UCNPs (Figure c).…”

“…(b) Epitaxially grown hexagonal NaYF 4 :Yb,Ln microrods encompassing different combinations of UC phosphors (R: Yb/Er 50:0.05 mol‐%; G: Yb/Er 5:0.05 mol‐%; B: Yb/Tm 20:0.2 mol‐%); adapted with permission from ref . (c) Fingerprint on a polyethylene bag revealed by UCNP luminescence; reproduced with permission from ref . (d) SrAl 2 O 4 :Eu II sensor (beige zone) detecting a crack in a concrete beam; redrawn with permission after ref …”

Nanoparticles used for fingermark detection—A comprehensive review

“…Li et al conducted a study with the core‐shell NPs—NaYF 4 :Tm@NaYF 4 :Yb@NaNdF 4 :Yb that has dual NIR emission at 696 and 980 nm (J. Li et al, ). These NPs were coated with citrate and Tween 20 was added to the working solution to detect sebaceous‐rich fingermarks.…”