ABSTRACT
The modulation of luminescence via external stimuli such as temperature, mechanical stress, hydrostatic pressure, as well as electric and/or magnetic fields, has witnessed great progress, enabled the disclosure of new principles and energy transfer pathways, and widened applications. However, investigations on the luminescence modulation of lanthanide ions doped in semiconductors via an applied electric field are still absent. Herein, for the first time, we have demonstrated the in situ, real-time, and reversible modulation of the luminescence of Eu3+ doped in SnO2 nanocrystals by manipulating the recombination rate of photo-generated electrons and holes, and the accompanied energy transfer mode in terms of linear and quasi-sinusoidal, from semiconductor to lanthanide ions. Following the same principle, the modulation of near infrared responsive Er3+ in SnO2 and the visible luminescence of perovskite nanocrystals is further realized. This study offers extra methodologies for luminescence modulation, in addition to those already reported for ferro- and/or piezoelectric-hosted luminescent materials.
ABSTRACT
Scandium (Sc) sits at a unique position in the periodic table, i.e., the junction of the top of the rare earth column and the beginning of the transition metal row. Studies have shown that Sc-based nanomaterials are very sensitive to the surrounding chemical environment. A simple adjustment of the chemical reaction conditions such as temperature, surfactant molecules, and solvents (e.g., oleic acid (OA) or 1-octadecene (OD)) can easily lead to different products in terms of chemical composition and phase structure. Herein, under purposely adjusted reaction conditions, we have investigated the interconversion process between two representative Sc-based nanomaterials, that is, nanocrystals of orthorhombic KSc2F7:Yb/Er and cubic K2NaScF6:Yb/Er, both of which have characteristic red upconversion luminescence and high similarity in chemical composition and phase structure. Experimental results have indicated that conversion from KSc2F7:Yb/Er to K2NaScF6:Yb/Er may start from the edge of the nanocrystal where K+ in KSc2F7:Yb/Er was gradually substituted by the post-introduced Na+ in the solution and finally KSc2F7:Yb/Er nanorods were broken and K2NaScF6:Yb/Er nanocubes were formed. On the other hand, a simple variation of the OA : OD ratio facilitates the dissolution of K2NaScF6:Yb/Er and subsequent crystallization of KSc2F7:Yb/Er during the opposite conversion process. Possible chemical reaction mechanisms were further developed to elucidate the interconversion details. Meanwhile, the variation of the upconversion luminescence such as emission intensity, red to green ratio, and lifetime is interpreted to monitor the conversion progress at corresponding stages, which is highly consistent with the scenario discussed above.
ABSTRACT
Luminescent nanothermometers have shown competitive superiority for contactless and noninvasive temperature probing especially at the nanoscale. Herein, we report the inherently Eu2+ /Eu3+ codoped Sc2 O3 nanoparticles synthesized via a one-step and controllable thermolysis reaction where Eu3+ is in-situ reduced to Eu2+ by oleylamine. The stable luminescence emission of Eu3+ as internal standard and the sensitive response of Eu2+ emission to temperature as probe comprise a perfect ratiometric nanothermometer with wide-range temperature probing (77-267 K), high repeatability (>99.94%), and high relative sensitivity (3.06% K-1 at 267 K). The in situ reduction of Eu3+ to Eu2+ ensures both uniform distribution in the crystal lattice and simultaneous response upon light excitation of Eu2+ /Eu3+ . To widen this concept, Tb3+ is codoped as additional internal reference for tunable temperature probing range.
ABSTRACT
In the controlled synthesis of ScOOH nanomaterials, the surfactant molecule Na3 Cit not only helps to manipulate the crystallographic structures, but also to initiate the transfer from α-ScOOH to γ-ScOOH. Further annealing of ScOOH generates cubic Sc2 O3 with morphologies inherited from respective origins. When doped with lanthanide ions, both ScOOH and Sc2 O3 can be utilized for high-temperature probing and light-emitting-diode lighting.
