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Issue 44, 2016
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Exploring Mn2+-location-dependent red emission from (Mn/Zn)–Ga–Sn–S supertetrahedral nanoclusters with relatively precise dopant positions

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Abstract

Mn2+-Doped semiconductor nanocrystals or quantum dots have been extensively studied as potential yellow/orange/red phosphors due to the stable Mn2+-related emission tuned by its tetrahedral coordination environment in host lattices. However, it is still very difficult to objectively explore the location–performance relationship in conventional Mn2+-doped nanomaterials since the precise location information on Mn2+ dopants is generally unavailable due to their random distribution in host lattices. Herein, we purposely selected a specific supertetrahedral-nanocluster-based molecular crystal (OCF-40-ZnGaSnS, composed of isolated supertetrahedral T4-ZnGaSnS nanoclusters (NCs) with the formula [Zn4Ga14Sn2S35]12−) as a host lattice, and effectively controlled the relatively precise position of Mn2+ dopants in host lattices of T4-ZnGaSnS NCs by in situ substitution of Zn2+ sites by Mn2+ ions, and investigated the Mn2+-location-dependent red emission properties. The current study clearly indicates that a long-lifetime (∼170 μs) red emission centred at 625 nm at room temperature for lightly-doped [Zn3MnGa14Sn2S35]12− NCs with one Mn2+ dopant in its surface centre is very sensitive to temperature and dramatically red-shifts to 645 nm at 33 K upon the excitation of 474 nm. However, heavily-doped OCF-40-MnGaSnS (composed of T4-MnGaSnS NCs with the formula [Mn4Ga14Sn2S35]12−, in which four Mn2+ dopants are accurately located at its core in the form of Mn4S) gives the temperature-insensitive red emission with a longer wavelength (641 nm) and a shorter lifetime (42 μs) at room temperature. This phenomenon is pretty uncommon compared to other heavily Mn2+-doped semiconductors. Such differences in their PL properties are ascribed to Mn2+-location-induced lattice strain to different degrees in two Mn2+-doped supertetrahedral NCs. In addition, the Mn2+-related red emission of both samples can be predominantly induced by the direct excitation of Mn2+ ions and secondarily by indirect excitation through exciton energy transfer from host lattices to Mn2+ dopants. Consistently, the DFT calculations suggest that the emission of NCs originated from the transition from the low spin excited state of Mn2+ (4T1) to its high spin ground state (6A1). The calculation results also revealed that the emission wavelength of lightly-doped [Zn3MnGa14Sn2S35]12− NCs is not obviously affected by the temperature-induced thermal effect, but by temperature-induced structural contraction, while that of heavily-doped [Mn4Ga14Sn2S35]12− NCs is affected by both effects. The total temperature cooling effect on the emission of [Zn3MnGa14Sn2S35]12− NCs is the red-shift, while that on the emission of [Mn4Ga14Sn2S35]12− NCs is negligible, which is akin to the experimental results. This research opens up a new perspective and provides a feasible method to explore the location–performance relationship of other Mn2+-doped NCs.

Graphical abstract: Exploring Mn2+-location-dependent red emission from (Mn/Zn)–Ga–Sn–S supertetrahedral nanoclusters with relatively precise dopant positions

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Publication details

The article was received on 05 Sep 2016, accepted on 26 Sep 2016 and first published on 26 Sep 2016


Article type: Paper
DOI: 10.1039/C6TC03844A
Citation: J. Mater. Chem. C, 2016,4, 10435-10444
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    Exploring Mn2+-location-dependent red emission from (Mn/Zn)–Ga–Sn–S supertetrahedral nanoclusters with relatively precise dopant positions

    Q. Zhang, J. Lin, Y. Yang, Z. Qin, D. Li, S. Wang, Y. Liu, X. Zou, Y. Wu and T. Wu, J. Mater. Chem. C, 2016, 4, 10435
    DOI: 10.1039/C6TC03844A

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