Novel splitting of excitation and emission spectra of K 2 TiF 6 :Mn 4+ phosphors induced by graphene quantum dots
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Novel splitting of excitation and emission spectra of K2TiF6:Mn4+ phosphors induced by graphene quantum dots Yuelan Li1, Youmiao Liu1, Haoran Huang1, Sen Liao1,2,* Huaxin Zhang1 1 2
, Yingheng Huang1,2, and
School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004, Guangxi, China School of Resources, Environment and Materials, Guangxi University, Nanning 530004, Guangxi, China
Received: 15 August 2020
ABSTRACT
Accepted: 3 November 2020
A series of K2TiF6:0.03Mn4?@GQDsymg/mol (KTF:0.03Mn4?@GQDsymg/mol, GQDs: Graphene quantum dots) was prepared by a simple coating method. Multiple enhanced effects on excitation (PLE) & emission (PL) spectra inducing by coating of GQDs are observed: (a) The intensities of PLE&PL are greatly enhanced, (b) PLE&PL spectra have large split, (c) Emission peaks of as-v4, as-v6, s-v4 and s-v3 are selectively enhanced to produce four strong peaks with almost the same intensity. Furthermore, the experimental results indicate that the appearance of the strong as-v4 and as-v6 helps to improve the red light quality of the sample. The mechanism of the enhanced effects is proposed: the coordination of GQDs with Ti4? and Mn4? ions leads to the splitting of the crystal field, which further results to enhancement and the large splitting of PLE and PL spectra. Prototype white light-emitting diodes (WLEDs) with low correlated color temperature and high color-rendering index are obtained using the optimal sample.
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1 Introduction Recently, Mn4?-doped phosphors A2XF6:Mn4? (X = Si, Ge, Zr, Sn, or Ti ; A = K, Na, Cs, or NH4) with narrowband red emission have received lots of attention [1–8], due to their ability to make blue lightbased WLEDs have high color-rendering index (CRI, Ra [ 80) and low correlated color temperature (CCT \ 4500 K). To obtain Mn4?-doped fluoride
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https://doi.org/10.1007/s10854-020-04823-4
phosphors with much better performances, many research efforts have been devoted to synthesize new Mn4?-doped fluoride phosphors via different methods. For example, Adachi et al. [9–11] synthesized a series of red-emitting fluoride phosphors, A2XF6:Mn4? (A = K, Na, NH4, X = Si, Ge, Zr, Sn, Ti) through a wet chemical etching route in aqueous KMnO4 and HF mixed solution. Liu et al. [12–15] prepared Na2SiF6:Mn4?, K2SiF6:Mn4?, K2GeF6:Mn4? and Rb2SiF6:Mn4? by a co-precipitation method. Pan
J Mater Sci: Mater Electron
et al. [16–18] reported a hydrothermal method was used for the synthesis of BaSiF6:Mn4?, BaTiF6:Mn4? and K2TiF6:Mn4? phosphors. Chen et al. [19] successfully prepared K2TiF6:Mn4? and K2SiF6:Mn4? red-emitting phosphors by the ion exchange method in room temperature with K2MnF6, K2TiF6 and K2SiF6 as raw materials. Recently, we also studied the novel luminescence enhancement and splitting of excitation and emission bands of Na2SiF6:Mn4?,Li? phosphors prepared by the ion exchange method [20]. Among the above-mentioned methods, the ion excha
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