“…This causes the red and green UCL compete to each other. This experimental phenomenon is similar to our previous literature reported that the highly-Yb 3+ doped NaYF4:Er microcrystals always tend to generate red UCL color under 980 nm excitation [23]. However, for lowly Yb 3+ -doped NaYF4:2%Er microcrystal, there is no CR processes occurrence because of the relatively far distance between Yb 3+ and Er 3+ ions.…”
Section: Resultssupporting
confidence: 90%
“…The β-NaYbF4:Er microcrystals were synthesized by the similar hydrothermal method procedure according to our previous study [23]. In a typical procedure, for instance, synthesis of the β-NaYbF4:2%Er (mol%) microcrystals: firstly, the Yb(NO3)3 and Er(NO3)3 powders were dissolved in deionized water yielding a clear solution of Ln(NO3)3 (0.2 M); then the EDTA-2Na (1 mmol) and NaOH (5 mmol) were mixed with 12.5 mL deionized water under continuously stirring in a beaker; following, 5 mL of Ln(NO3)3 (0.2 M) aqueous solutions (the total Ln 3+ is 1 mmol), 8 mL of NH4F (2.0 M) aqueous solutions and 7 mL of dilute hydrochloric acid (1 M) were added into the beaker; finally, the above mixtures were stirred for 1.5 hour and transferred into a 50 mL Teflon-lined autoclave and heated at 200°C for 40 hours.…”
Section: Synthesis Of β-Naybf4 Microcrystalsmentioning
Controlling the upconversion luminescence (UCL) intensity ratio, especially pumped at 808 nm, is of fundamental importance in biological applications due to the water molecules exhibiting low absorption at this excitation wavelength. In this work, a series of β-NaYbF4:Er microrods were synthesized by a simple one-pot hydrothermal method and their intense green (545 nm) and red (650 nm) UCL were experimentally investigated based on single particle level under the excitation of 808 nm continuous-wave (CW) laser. Interestingly, the competition between the green and red UCL can be observed in highly Yb3+-doped microcrystals as the excitation intensity gradually increases, which leads to the UCL color changes from green to orange. However, the microcrystals doped with low Yb3+ concentration keep green color which is independent on the excitation power. Further investigations demonstrate that the cross-relaxation (CR) processes between Yb3+ and Er3+ ions result in the UCL competition.
“…This causes the red and green UCL compete to each other. This experimental phenomenon is similar to our previous literature reported that the highly-Yb 3+ doped NaYF4:Er microcrystals always tend to generate red UCL color under 980 nm excitation [23]. However, for lowly Yb 3+ -doped NaYF4:2%Er microcrystal, there is no CR processes occurrence because of the relatively far distance between Yb 3+ and Er 3+ ions.…”
Section: Resultssupporting
confidence: 90%
“…The β-NaYbF4:Er microcrystals were synthesized by the similar hydrothermal method procedure according to our previous study [23]. In a typical procedure, for instance, synthesis of the β-NaYbF4:2%Er (mol%) microcrystals: firstly, the Yb(NO3)3 and Er(NO3)3 powders were dissolved in deionized water yielding a clear solution of Ln(NO3)3 (0.2 M); then the EDTA-2Na (1 mmol) and NaOH (5 mmol) were mixed with 12.5 mL deionized water under continuously stirring in a beaker; following, 5 mL of Ln(NO3)3 (0.2 M) aqueous solutions (the total Ln 3+ is 1 mmol), 8 mL of NH4F (2.0 M) aqueous solutions and 7 mL of dilute hydrochloric acid (1 M) were added into the beaker; finally, the above mixtures were stirred for 1.5 hour and transferred into a 50 mL Teflon-lined autoclave and heated at 200°C for 40 hours.…”
Section: Synthesis Of β-Naybf4 Microcrystalsmentioning
Controlling the upconversion luminescence (UCL) intensity ratio, especially pumped at 808 nm, is of fundamental importance in biological applications due to the water molecules exhibiting low absorption at this excitation wavelength. In this work, a series of β-NaYbF4:Er microrods were synthesized by a simple one-pot hydrothermal method and their intense green (545 nm) and red (650 nm) UCL were experimentally investigated based on single particle level under the excitation of 808 nm continuous-wave (CW) laser. Interestingly, the competition between the green and red UCL can be observed in highly Yb3+-doped microcrystals as the excitation intensity gradually increases, which leads to the UCL color changes from green to orange. However, the microcrystals doped with low Yb3+ concentration keep green color which is independent on the excitation power. Further investigations demonstrate that the cross-relaxation (CR) processes between Yb3+ and Er3+ ions result in the UCL competition.
“…These new UC emissions can be detected both in Mn-free and highly Mn 2+ -doped microcrystals. As demonstrated in our previous study [35], these new UC emissions originate from the transitions of 4 G 11/2 → 4 I 15/2 (382 nm), 4 F 5/2 → 4 I 15/2 (457 nm), 2 K 15/2 → 4 I 13/2 (472 nm), 4 G 11/2 → 4 I 15/2 (506 nm), 2 H 9/2 → 4 I 13/2 (560 nm), and 4 G 11/2 → 4 I 11/2 (618 nm) in Er 3+ , respectively. It is noteworthy that the newly emerged UC emissions can be observed regardless of the Mn 2+ concentration and the new 560 nm emission is always stronger than the traditional green (545 nm) emission.Fig.…”
Section: Resultssupporting
confidence: 67%
“…In comparison with these three UC emissions, other UC emissions are rarely observed in Yb/Er co-doped materials. Previously, we have observed a newly emerged 560 nm ( 2 H 9/2 → 4 I 13/2 ) emission from a single β-NaYF 4 :Yb/Er microcrystal under saturated excitation [ 35 ]. As excitation intensity increases, the 560-nm emission increases rapidly and further exceeds the traditional green emission (545 nm).…”
The presence of manganese ions (Mn2+) in Yb/Er-co-doped nanomaterials results in suppressing green (545 nm) and enhancing red (650 nm) upconversion (UC) emission, which can achieve single-red-band emission to enable applications in bioimaging and drug delivery. Here, we revisit the tunable multicolor UC emission in a single Mn2+-doped β-NaYF4:Yb/Er microcrystal which is synthesized by a simple one-pot hydrothermal method. Excited by a 980 nm continuous wave (CW) laser, the color of the single β-NaYF4:Yb/Er/Mn microrod can be tuned from green to red as the doping Mn2+ ions increase from 0 to 30 mol%. Notably, under a relatively high excitation intensity, a newly emerged emission band at 560 nm (2H9/2 → 4I13/2) becomes significant and further exceeds the traditional green (545 nm) emission. Therefore, the red-to-green (R/G) emission intensity ratio is subdivided into traditional (650 to 545 nm) and new (650 to 560 nm) R/G ones. As the doped Mn2+ ions increase, these two R/G ratios are in lockstep with the same tunable trends at low excitation intensity, but the tunable regions become different at high excitation intensity. Moreover, we demonstrate that the energy transfer (ET) between Mn2+ and Er3+ contributes to the adjustment of R/G ratio and leads to tunable multicolor of the single microrod. The spectroscopic properties and tunable color from the single microrod can be potentially utilized in color display and micro-optoelectronic devices.
“…[46] Changing the excitation wavelength and power, or utilizing pulse excitation with tunable pulse width and frequency obviously affects the excitation process and thus the emission properties, not only intensity and color, but also decay time. Similar exploratory work by other groups has extended the upconversion excitation wavelength from 980 to 800 and 1532 nm, and achieved multicolor upconversion luminescence through controlling the excitation wavelength [48][49][50][51] ; Yuan et al [52] observed and intensified the silent upconversion emission bands of Er 3+ at 382, 472, 506, 560, and 618 nm from a single NaYF 4 :Yb/Er microcrystal via increasing the excitation power. Similar exploratory work by other groups has extended the upconversion excitation wavelength from 980 to 800 and 1532 nm, and achieved multicolor upconversion luminescence through controlling the excitation wavelength [48][49][50][51] ; Yuan et al [52] observed and intensified the silent upconversion emission bands of Er 3+ at 382, 472, 506, 560, and 618 nm from a single NaYF 4 :Yb/Er microcrystal via increasing the excitation power.…”
Versatile manipulation of lanthanide photoluminescence not only enables a more thorough understanding of the luminescent mechanism, but also promotes their widespread applications including advanced display and security, bioimaging and biotherapy, and sensors. The traditional chemical methods, engineering of composition, concentration, size, morphology, and surface defects, can easily tune the excitation, energy transfer and emission processes and have been frequently used. Despite the powerful ability to control luminescence intensity and selectivity, these chemical approaches suffer from cumbersome synthesis processes and are usually time consuming and irreversible. Recently, there have been numerous examples of physical approaches realizing in situ, real time, and reversible luminescence manipulation for certain materials under a given excitation. Herein, the existing physical strategies comprising temperature, magnetic field, electric field, and mechanical stress are summarized. For each approach, the action mechanism, material design, applications, as well as current challenges are discussed, and possible development directions and broadening of the potential application areas are considered.
Applying Magnetic FieldMagneto-optic interaction, here mainly refers to the effect of applied magnetic field during luminescence measurement, was also widely utilized to regulate luminescence emission of not
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