New non-rare-earth-based oxide red phosphor discovery is of great interest in the field of energy-efficient LED lighting. In this work, a novel blue-light activated CaMg2Al16O27:Mn4+ (CMA:Mn4+) ...phosphor, showing strong red emission peaked at ∼655 nm under 468 nm excitation, is prepared by a solid-state reaction route. The microstructure and luminescent performance of this red-emitting phosphor are investigated in detail with the aids of X-ray diffraction refinement, diffuse reflection spectra, steady-state photoluminescence spectra and temperature-dependent PL/decay measurements. The crystal field strength (Dq) and the Racah parameters (B and C) are carefully calculated to evaluate the nephelauxetic effect of Mn4+ suffering from the CMA host. After incorporating CMA:Mn4+ and YAG:Ce3+ phosphor microcrystals into the glass host via a “phosphor-in-glass (PiG)” approach, warm white-light is achieved in the assembled high-powered w-LED device, thanks to the improved correlated color temperature and color rendering index.
Many technological nanomaterials are intentionally doped by introducing appropriate amounts of foreign elements into hosts to impart electronic, magnetic and optical properties. In fact, impurity ...doping was recently found to have significant influence on nucleation and growth of many functional nanocrystals (NCs), and provide a fundamental approach to modify the crystallographic phase, size, morphology, and electronic configuration of nanomaterials. In this feature article, we provide an overview of the most recent progresses in doping-induced control of phase structures, sizes, shapes, as well as performances of functional nanomaterials for the first time. Two kinds of impurity doping strategies, including the homo-valence ion doping and hetero-valence ion doping, are discussed in detail. We lay emphases on impurity doping induced modifications of microstructures and optical properties of upconversion (UC) lanthanide (Ln
3+
) NCs, but do not limit to them. In addition, we also illustrate the control of Ln
3+
activator distribution in the core@shell architecture, which has recently provided scientists with new opportunities for designing and tuning the multi-color emissions of Ln
3+
-doped UC NCs. Finally, the challenges and future perspectives of this novel impurity doping strategy are pointed out.
This feature article reviews a novel and facile impurity-doping strategy for modifying phase structures, sizes, shapes as well as performances of functional nanomaterials for the first time.
In this work, a novel thermometry strategy based on the diversity in thermal quenching behavior of two intervalence charge transfer (IVCT) states in oxide crystals is proposed, which provides a ...promising route to design self‐referencing optical temperature sensing material with superior temperature sensitivity and signal discriminability. Following this strategy, uniform Tb3+/Pr3+:NaGd(MoO4)2 micro‐octahedrons are directionally synthesized. Originated from the diverse thermal responses between Tb3+‐Mo6+ and Pr3+‐Mo6+ IVCT states, fluorescence intensity ratio of Pr3+ to Tb3+ in this material displays excellent temperature sensing property in a temperature range from 303 to 483 K. The maximum absolute and relative sensitivity reaches as high as 0.097 K−1 and 2.05% K−1, respectively, being much higher than those of the previously reported optical thermometric materials. Excellent temperature sensing features are also demonstrated in the other Tb3+/Pr3+ codoped oxide crystals having d0 electron configured transition metal ions (Ti4+, V5+, Mo6+, or W6+), such as scheelite NaLu(MoO4)2 and NaLu(WO4)2, and monazite LaVO4 and perovskite La2Ti3O9, evidencing the universal validity of the proposed strategy. This work exploits an effective pathway for developing new optical temperature sensing materials with high performance.
A novel thermometry strategy based on the diversity in thermal quenching behavior of two intervalence charge transfer states is proposed in this work. Following this strategy, several self‐referencing optical temperature sensing materials with excellent performance are fabricated.
The ratiometric fluorescence technique is believed to hold promise as the most important non-contact thermometry technique for future mass application due to the reliability and convenience ...originating from self-referencing. The discovery of thermally coupled levels in lanthanide ions initiated and boosted the fast development of the ratiometric fluorescence technique for temperature sensing in the past decades. However, the dilemma in the energy spacing between the two thermally coupled levels sets a limitation for further improvement of thermometric performance, which can be addressed by novel strategies other than thermally coupled level routes. The unique electronic structure of Ln
3+
ions offers great opportunities for conceiving such strategies. In this review, we have summarized recent progress in novel strategy design for ratiometric fluorescence temperature sensing, with the focus on the Ln
3+
luminescence involving dual emission construction. Various features of Ln
3+
luminescence dynamics have been described to play critical roles in judicious strategy design.
State-of-the-art progress in strategy design based on the Ln
3+
luminescence involving dual emission construction for ratiometric luminescence thermometry is reviewed.
Ruddlesden-Popper type perovskite Na2La1.96Pr0.04Ti3O10 is explored to be one of the most promising optical temperature sensing materials. The mechanism of its optical temperature sensing property is ...revealed by the configurational coordinate analysis. Sequentially, a novel temperature sensing strategy is proposed, and demonstrated to be universally valid for some Pr3+ doped oxides.
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•Pr:Na2La2Ti3O10 is explored to be a very promising optical thermometric materials.•Temperature sensing mechanism for this material is revealed relating to Pr-Ti IVCT.•A novel thermometric strategy utilizing IVCT interfered Pr3+ emission is proposed.•This strategy is universally valid for other Pr doped oxides with suitable IVCT.
In this study, the Ruddlesden-Popper type perovskite Na2La1.96Pr0.04Ti3O10 micro-crystals are synthesized and demonstrated to be one of the most promising optical temperature sensing materials. The measured maximal absolute temperature sensitivity of this phosphor reaches as high as 0.40K−1, remarkably superior to those of the inorganic optical thermometric materials reported previously; while the relative sensitivity is 1.96%K−1, ranking among the highest ones for the inorganic optical thermometric materials. Analysis of the configurational coordinate diagram indicates that thermo-induced relaxation between the Pr3+ 3Px and 1D2 levels through Pr3+-Ti4+ intervalence charge transfer state is the primary cause for the temperature sensing characteristics. Based on these results, a novel temperature sensing strategy utilizing the intervalence charge transfer state interfered Pr3+ luminescence to perform optical thermometry is proposed, which is further demonstrated to be universally valid for the Pr3+ doped oxides containing d0 configured transition metal ions, as long as energy of the intervalence charge transfer state is moderate. This work may provide useful inspiration for developing high sensitive optical thermometric materials.
The high-powered alternating current (AC) light-emitting diode (LED) (AC-LED), featuring low cost, high energy utilization efficiency, and long service life, will become a new economic growth point ...in the field of semiconductor lighting. However, flicker of AC-LED in the AC cycles is not healthy for human eyes, and therefore need to be restrained. Herein we report an innovation of persistent “phosphor-in-glass” (PiG) for the remote-type AC-LED, whose afterglow can be efficiently activated by the blue light. It is experimentally demonstrated that the afterglow decay of PiG in the microsecond range can partly compensate the AC time gap. Moreover, the substitution of inorganic glass for organic resins or silicones as the encapsulants would bring out several technological benefits to AC-LED, such as good heat-dissipation, low glare, and excellent physical/chemical stability.
Currently, the development of efficient red-emitting persistent phosphor is still an ongoing challenge. Herein, a novel red-emitting LPL phosphor Ca3Ti2O7:Pr3+ is successfully prepared by a ...high-temperature solid-state method. XRD Rietveld refinement analyses demonstrate the high phase purity of the sample which crystallizes in an orthorhombic Ccm21 space group with lattice parameters of a = 5.7702(5) Å, b = 19.4829(7) Å, and c = 5.1214(2) Å. Electronic structure of the host matrix is analyzed by the first-principle calculation using CASTEP code. The calculation results show that Ca3Ti2O7 has a direct band gap with CB and VB mainly composed of the Ti-3d and O-2p states, respectively. On the basis of the DR spectrum, the band gap is determined to be 3.6 eV. It is demonstrated that the 612 nm red-emitting persistent luminescence of Ca3Ti2O7:Pr3+ can be either activated by Ti4+–O2– → Ti3+–O– host absorption and Pr3+–O–Ti4+ → Pr4+–O–Ti3+ IVCT in the UV region, or Pr3+:3H4 → 3P J transition in the blue region. The red afterglow can last for ∼5 min observed by the naked eyes in the dark after ceasing the irradiation source. On the basis of the TL analyses, the trap is found exponentially distributed in the host with the depth of 0.69–0.92 eV. Finally, a possible LPL mechanism for Ca3Ti2O7:Pr3+ is proposed.
Different pathways for the degradation of rhodamine (RhB) as well as different activity order for the degradation of RhB and methyl orange (MO) were observed over hexagonal ZnIn2S4 microspheres and ...cubic ZnIn2S4 nanoparticles. A detailed study of the physicochemical and surface properties of these two ZnIn2S4 polymorphs has been carried out to elucidate these phenomena. The results reveal that hexagonal ZnIn2S4 microspheres are composed of nanolamella petals growing in the ab plane, i.e., the negative (0001) S plane. This negative (0001) S plane not only is favorable for the adsorption of the cationic dye RhB via N(Et)2 groups but also can accumulate the photogenerated holes. These make the hole-directed photocatalytic de-ethylation of RhB more expedient over hexagonal ZnIn2S4 microspheres. This negative (0001) S plane of hexagonal ZnIn2S4 microspheres also shows promoting effect for the degradation of cationic dye like MB, but not for the degradation of anionic dye like MO. Our result provides some new insights in how the surface facet can take effect on influencing the performance of a photocatalyst and why different polymorphs can exhibit different photocatalytic performance.
Monodisperse Er(3+):NaGdF(4)@Ho(3+):NaGdF(4)@NaGdF(4) active-core/active-shell/inert-shell nanocrystals, which can extend the near-infrared wavelength excitable range for upconversion (UC) emissions, ...were successfully fabricated for the first time. Importantly, doping of Er(3+) and Ho(3+) into the core and shell respectively suppresses adverse energy transfers between them, resulting in intense UC emissions for both Er(3+) and Ho(3+) dopants.
The commercially dominant phosphor-converted illumination white light-emitting-diodes (w-LEDs) generally suffer from red deficiency and the poor thermal stability of the organic encapsulants, ...resulting in cool white light, luminous degradation and chromatic aberration for the embedded YAG:Ce 3+ phosphors after long-term working. Aiming to solve these problems, herein, a chromaticity-tunable robust phosphor-in-glass (PiG) inorganic color converter was successfully fabricated by co-sintering YAG:Ce 3+ ,Mn 2+ ,Si 4+ phosphor particles and the innovatively-designed TeO 2 –B 2 O 3 –ZnO–Na 2 O–Al 2 O 3 low-melting precursor glass. At first, the spectrally-modified YAG:Ce 3+ ,Mn 2+ ,Si 4+ phosphor was prepared by doping Mn 2+ as the red emitter and doping Si 4+ as the charge compensator through a solid-state reaction route. Then, the YAG:Ce 3+ ,Mn 2+ ,Si 4+ powder was incorporated into a specifically prepared precursor glass to form the PiG composite at 550 °C. Owing to the density and the refractive index matches for the phosphor particles and the glass matrix, the particle dispersion in PiG is quite homogeneous and the adverse light-scattering is depressed. The high-power warm w-LED was constructed by coupling a PiG plate with an InGaN blue chip. Remarkably, the chromaticity coordinate of such a w-LED can be well tuned to follow along the Planckian locus with the correlated color temperature evolving from cool white (5541 K) to warm white (3050 K) and a color rendering index around 70, under a driving current of 350 mA. Moreover, the PiG-based warm w-LED presents much superior thermal stability to the traditional phosphor-in-silicone (PiS)-based one. This work highlights the practical applications of the PiG luminescent material in the long-lifetime high-power warm w-LEDs.
