Switching to the brighter lane: pathways to boost the absorption of lanthanide-doped nanoparticles

Abstract

The use of organic dyes, semiconductors, and plasmonic nanostructures are three of the most promising strategies to make lanthanide-doped nanoparticles brighter by means of increasing their absorption capabilities.

Near infrared bioimaging and biosensing with semiconductor and rare-earth nanoparticles: recent developments in multifunctional nanomaterials

“…Nevertheless, this comes at a cost in the form of low radiative transition probabilities, yielding poor Ln 3+ molar extinction coefficients in the order of 0.1-10 M −1 cm −1 . 85 Although different strategies aimed to improve the absorption (that translates to brightness) of RENPs have been developed, it still represents an important bottleneck for these nanomaterials. 85,86 Generally, RENPs are the result of embedding Ln 3+ within the crystalline structure of a proper dielectric host material which has three main fundamental roles: i) crystal structure asymmetry and crystal field can be used to increase the probability of the 4f-4f transitions; ii) low cutoff phonon energies reduce non-radiative quenching of the excited states, and iii) host matrix serves as a platform where different sensitizers and activators can be combined to achieve specific luminescent features.…”

“…85 Although different strategies aimed to improve the absorption (that translates to brightness) of RENPs have been developed, it still represents an important bottleneck for these nanomaterials. 85,86 Generally, RENPs are the result of embedding Ln 3+ within the crystalline structure of a proper dielectric host material which has three main fundamental roles: i) crystal structure asymmetry and crystal field can be used to increase the probability of the 4f-4f transitions; ii) low cutoff phonon energies reduce non-radiative quenching of the excited states, and iii) host matrix serves as a platform where different sensitizers and activators can be combined to achieve specific luminescent features. [87][88][89] Page 22 of 48 Nanoscale Advances RENPs can be produced by multiple approaches, which can be generally split into syntheses performed in organic solvents, or in aqueous media.…”

Multiphoton Upconversion Materials for Photocatalysis and Environmental Remediation

“…In that regard, the absorption cross‐section of lanthanide sensitizers can be principally enhanced by coupling UCNPs with NIR‐absorbing dyes or quantum dots. Tethered NIR dyes harvest NIR excitation and transfer it to lanthanides via Föster or Dexter energy transfer mechanisms (Figure 6a) [107] . In addition, organic dyes radiatively decay much faster than lanthanide‐doped UCNPs with inherently forbidden optical transitions.…”

Enhancing Dye‐Triplet‐Sensitized Upconversion Emission Through the Heavy‐Atom Effect in CsLu2F7:Yb/Er Nanoprobes

“…Recently, triplet energy transfer (TET) from the triplet excited state (T 1 ) of NIR dye has been proposed as an ideal strategy to directly and efficiently enhance the UC emissions of Yb 3+ ‐doped UCNCs without the requirement of the complicated core/multishell structure [11] . Nearly 100 % energy transfer efficiency from long‐lived T 1 to Ln 3+ activators can be achieved, [12] which is difficult to realize based on the short‐lived S 1 of organic dyes [13] . Nevertheless, triplet state exciton concentration of NIR dye is usually low due to the forbidden nature of intersystem crossing (ISC) from S 1 to T 1 and the optical absorption transition between the spin‐zero ground state and the spin‐one triplet levels [12, 14] .…”