Tunable Narrow Band Emissions from Dye-Sensitized Core/Shell/Shell Nanocrystals in the Second Near-Infrared Biological Window

Abstract

We introduce a hybrid organic–inorganic system consisting of epitaxial NaYF4:Yb3+/X3+@NaYbF4@NaYF4:Nd3+ (X = null, Er, Ho, Tm, or Pr) core/shell/shell (CSS) nanocrystal with organic dye, indocyanine green (ICG) on the nanocrystal surface. This system is able to produce a set of narrow band emissions with a large Stokes-shift (>200 nm) in the second biological window of optical transparency (NIR-II, 1000–1700 nm), by directional energy transfer from light-harvesting surface ICG, via lanthanide ions in the shells, to the emitter X3+ in the core. Surface ICG not only increases the NIR-II emission intensity of inorganic CSS nanocrystals by ~4-fold but also provides a broadly excitable spectral range (700–860 nm) that facilitates their use in bioapplications. We show that the NIR-II emission from ICG-sensitized Er3+-doped CSS nanocrystals allows clear observation of a sharp image through 9 mm thick chicken breast tissue, and emission signal detection through 22 mm thick tissue yielding a better imaging profile than from typically used Yb/Tm-codoped upconverting nanocrystals imaged in the NIR-I region (700–950 nm). Our result on in vivo imaging suggests that these ICG-sensitized CSS nanocrystals are suitable for deep optical imaging in the NIR-II region.

Confining Excitation Energy in Er3+‐Sensitized Upconversion Nanocrystals through Tm3+‐Mediated Transient Energy Trapping

“…[6] As ar esult of this inherent limitation, ar elatively low doping level of lanthanide activators is generally implemented. [9] However, Figure 1. 10 6 Wcm À2 )h as been demonstrated to effectively alleviate luminescence concentration quenching in nanoparticles with heavily doped activators (ca.…”

“…10 6 Wcm À2 )h as been demonstrated to effectively alleviate luminescence concentration quenching in nanoparticles with heavily doped activators (ca. [9] However, Figure 1. [8] Another general strategy to prevent the concentration quenching is to implement ac ore-shell design by which the dominant luminescence quenching through energy migration to surface defects can be effectively blocked ( Figure 1a).…”

Recent Advance in Near‐Infrared (NIR) Imaging Probes for Cancer Theranostics

“…D) Photographs of tumor from different groups of mice at the end of cancer therapy. [77] More importantly, the www.advancedsciencenews.com www.advtherap.com modified ICG not only increases the NIR-II luminescence but provides a broad excitation spectral range from 700-860 nm, which facilitates their use in bioapplications. [93] Copyright 2018, Wiley-VCH.…”

Physical Manipulation of Lanthanide‐Activated Photoluminescence

“…[27] Thanks to the robust chemical synthesis methodologies developed for both bulk and micro/nanoscale materials, it is comparatively easy to manipulate the luminescent properties by means of modulating the composition, crystallographic parameters, sensitizer and activator ions distribution, size, morphology, and surface defects of luminescent materials. By integrating organic dye, indocyanine green (ICG), onto the surface of NaYF 4 :Yb 3+ /X 3+ @NaYbF 4 @NaYF 4 :Nd 3+ (X = null, Er, Ho, Tm, or Pr) core/shell/shell nanocrystals, Shao et al [41] broadened successfully the excitation spectral range (700-860 nm) and increased a set of narrow band emissions located within 1000-1700 nm taking advantage of the large absorption cross section of organic dye and subsequently improved energy transfer efficiency to lanthanide ions; Wisser et al [42] utilized dye ATTO 542 to decorate the surfaces of hexagonal-phase Na(Y/Gd/Lu) 0.8 F 4 :Yb 0.18 Er 0.02 upconverting nanoparticles to enhance the luminescence intensity and also tune the emission color and lifetime, where the Förster resonance energy transfer from Er 3+ to dye and the high radiative rate of the dye play a key role for luminescence manipulation. For example, co-doping of Ce 3+ with Tb 3+ and Eu 3+ at different concentrations within ScPO 4 ·2H 2 O microparticles allows manipulation of the emission wavelengths, intensity, and lifetime [37] ; Increasing the concentration of Tm 3+ /Er 3+ in NaYbF 4 nanoparticles could impact the energy transfer process between sensitizer Yb 3+ and activator Tm 3+ /Er 3+ , leading to the upconversion color tuning from blue/green to red [38] ; Zhuo et al [39] distributed multiple activators (Tm 3+ , Er 3+ , and Ho 3+ ) into spatially separated layers in one single KSc 2 F 7 nanorod to effectively restrain the deleterious energy transfer between these activators and enhance their www.advancedsciencenews.com www.ann-phys.org upconversion luminescence.…”