Liu Ying, Zaffalon Matteo L, Zito Juliette, Cova Francesca, Moro Fabrizio, Fanciulli Marco, Zhu Dongxu, Toso Stefano, Xia Zhiguo, Infante Ivan, De Trizio Luca, Brovelli Sergio, Manna Liberato
Key Laboratory of Materials Physics of Ministry of Education, School of Physics and Microelectronics, Zhengzhou University, Daxue Road 75, Zhengzhou 450052, China.
Nanochemistry, Istituto Italiano di Tecnologia, via Morego 30, Genova 16163, Italy.
Chem Mater. 2022 Oct 11;34(19):8603-8612. doi: 10.1021/acs.chemmater.2c01578. Epub 2022 Sep 20.
In this work, we report the hot-injection synthesis of CsZnCl colloidal nanocrystals (NCs) with tunable amounts of Cu and Mn substituent cations. All the samples had a rodlike morphology, with a diameter of ∼14 nm and a length of ∼30-100 nm. Alloying did not alter the crystal structure of the host CsZnCl NCs, and Cu ions were mainly introduced in the oxidation state +1 according to X-ray photoelectron and electron paramagnetic resonance spectroscopies. The spectroscopic analysis of unalloyed, Cu-alloyed, Mn-alloyed, and Cu, Mn coalloyed NCs indicated that (i) the CsZnCl NCs have a large band gap of ∼5.35 eV; (ii) Cu(I) aliovalent alloying leads to an absorption shoulder/peak at ∼4.8 eV and cyan photoluminescence (PL) peaked at 2.50 eV; (iii) Mn(II) isovalent alloying leads to weak Mn PL, which intensifies remarkably in the coalloyed samples, prompted by an energy transfer (ET) process between the Cu and Mn centers, favored by the overlap between the lowest (A → T) transition for tetrahedrally coordinated Mn and the PL profile from Cu(I) species in the CsZnCl NCs. The efficiency of this ET process reaches a value of 61% for the sample with the highest extent of Mn alloying. The PL quantum yield (QY) values in these Cu, Mn coalloyed NCs are lower at higher Mn contents. The analysis of the Mn PL dynamics in these samples indicates that this PL drop stems from inter-Mn exciton migration, which increases the likelihood of trapping in defect sites, in agreement with previous studies.
在本工作中，我们报道了通过热注入法合成具有可调含量的铜（Cu）和锰（Mn）取代阳离子的CsZnCl胶体纳米晶体（NCs）。所有样品均呈棒状形态，直径约为14 nm，长度约为30 - 100 nm。合金化并未改变主体CsZnCl NCs的晶体结构，根据X射线光电子能谱和电子顺磁共振光谱，铜离子主要以 +1氧化态引入。对未合金化、Cu合金化、Mn合金化以及Cu、Mn共合金化的NCs进行光谱分析表明：（i）CsZnCl NCs具有约5.35 eV的大带隙；（ii）Cu（I）异价合金化导致在约4.8 eV处出现吸收肩/峰以及在2.50 eV处出现青色光致发光（PL）峰；（iii）Mn（II）等价合金化导致较弱的Mn PL，在共合金化样品中显著增强，这是由Cu和Mn中心之间的能量转移（ET）过程引起的，四面体配位的Mn的最低（A→T）跃迁与CsZnCl NCs中Cu（I）物种的PL谱之间的重叠有利于该过程。对于Mn合金化程度最高的样品，该ET过程的效率达到61%。在这些Cu、Mn共合金化的NCs中，较高Mn含量下的PL量子产率（QY）值较低。对这些样品中Mn PL动力学的分析表明，这种PL下降源于Mn间激子迁移，这增加了在缺陷位点捕获的可能性，与先前的研究一致。
