Tailoring Lanthanide Upconversion Luminescence through Material Designs and Regulation Strategies

Abstract

The anti‐Stokes upconversion luminescence (UCL) generated from lanthanide‐doped upconversion nanoparticles (UCNPs) has been highly favorable. Nevertheless, the future success of UCNPs is critically reliant on efficient tailoring of UCL, which has always been intensively focused and comprehensively studied. Notably, in recent years, several reports propose paradigm‐shifting techniques and strategies in tailoring UCL, which greatly accelerate the development of the field. Therefore, the authors feel there is an urge to conduct an essential review and discussion on recent advances in tailoring UCL via internal material designs and external regulation strategies. The review starts with explicit discussions on the intricate material design of UCNPs, including orthogonal UCNP designs, hybrid upconversion systems, and highly doped designs. Subsequently, tailoring UCL via remote regulation strategies will be reviewed, including the upconversion manipulation with a microcavity, near‐field effect, excitation power density, heat, and polarization angle. The innovations in the UCL tailoring strategies have significantly contributed to the progression of the field. The results demonstrated in these studies can potentially trigger new experimental designs in lots of other areas and further promote the future practical application of UCNPs.

Comparison of Quantum Yield of Upconversion Nanocrystals Determined by Absolute and Relative Methods

“…In general, the use of the 3M experimental method and the three correction factors a, b, and c in Equation ( 5 where ϕ ða,expÞ UC is the experimental value of UCQY, a is a correction factor due to reabsorption of UC emission in the integrating sphere (Figure S7, Supporting Information), while b is a correction factor due to the finite thickness of the sample changing the excitation power with depth into the sample and the nonlinear origin of UC (Figure S8, Supporting Information) and c is As NCs are the most intensively investigated class of UC materials, [33,34] a NC-based UC system is chosen for a comparison of the absolute method and the relative method; the latter using the reference SrF 2 :1%Yb 3þ ,1%Er 3þ single crystal. The NC sample, with a α-NaYF 4 :18%Yb 3þ ,2%Er 3þ @CaF 2 core@shell structure, is chosen for a number of reasons.…”

“…As NCs are the most intensively investigated class of UC materials, [ 33,34 ] a NC‐based UC system is chosen for a comparison of the absolute method and the relative method; the latter using the reference SrF 2 :1%Yb 3+ ,1%Er 3+ single crystal. The NC sample, with a α‐NaYF 4 :18%Yb 3+ ,2%Er 3+ @CaF 2 core@shell structure, is chosen for a number of reasons.…”

Multifunctionality of luminescent molecular nanomagnets based on lanthanide complexes

“…[1][2][3][4] Among the desired physical functionalities, one can count, for example, super-ionic conductivity, ferroelectricity, non-linear optical (NLO) effects, luminescence, ferromagnetism and electrochemical activity, and the responsivity of these effects to physical and chemical stimuli. [5][6][7][8][9][10] The combination of at least two of the abovelisted properties in a multifunctional material can be realized in composite systems that are built of functional units, e.g., magnetic nanoparticles covered by luminescent shells. [11][12][13] An alternative is offered by single-phase multifunctional materials whose various physical properties are designed at the molecular level within the homogenous matter.…”

Bright and Stable Nanomaterials for Imaging and Sensing

“…Most nanomaterials can be easily internalized into cells and tissues, and their surface chemistry can be tuned to target specific biological sites. Many different types of photoluminescent nanomaterials are described in the literature [11,25], from polymer chains of well-controlled size and architecture containing multiple dyes to dye-loaded polymer nanoparticles (PNPs) that cover the size range from tens to hundreds of nanometers, dye-loaded silica nanoparticles (SNPs) obtained by condensation polymerization of different alcoxisilanes [26,27], semiconductor nanoparticles (quantum dots, QDs), [28] aggregation-induced emission (AIE) fluorescent nanoparticles, [29,30] conjugated polymer nanoparticles (CPNPs) [31], lanthanide-doped upconverting nanoparticles (UCNPs) [32]. Other less common types include silicon quantum dots, [33] dye-loaded dendrimers, [34] lipid nanoparticles [35], etc.…”