Heavy-metal-free I–III–VI₂ quantum dots (QDs) have recently emerged as favorable alternatives to toxic II–VI QDs for optoelectronic and biological applications, but low fluorescence efficiency is a key issue related to the promising nanocrystals. In this work, we demonstrate big enhancement of two-photon fluorescence efficiency and low threshold two-photon pumped amplification of spontaneous emission (ASE) of Zn-processed CuInS₂ (CIS) QDs for the first time. The change of two-photon process caused by Zn²⁺ cation exchange in CIS QDs is systematically investigated. Two-photon ASE in Zn-processed CIS QDs films is achieved with a record of low threshold fluence of 5.7 μJ/cm². With high two-photon fluorescence quantum yields and low threshold ASE, the Zn-processed CIS QDs could become a promising candidate for two-photon bioimaging, nonlinear optical and novel QDs laser devices.

中文翻译：

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Zn处理的CuInS ₂量子点的双光子荧光增强和自发发射的低阈值放大

不含重金属的I–III–VI ₂量子点（QD）最近已成为光电和生物应用中有毒II–VI QD的有利替代品，但低荧光效率是与有前途的纳米晶体相关的关键问题。在这项工作中，我们首次展示了锌处理的CuInS ₂（CIS）QD的双光子荧光效率的大幅提高和低阈值双光子泵浦的自发发射（ASE）。系统地研究了CIS量子点中Zn ²⁺阳离子交换引起的双光子过程的变化。Zn处理的CIS QDs薄膜中的双光子ASE实现了5.7μJ/ cm ²的低阈值通量记录。Zn具有高的双光子荧光量子产率和低阈值ASE，经过Zn处理的CIS QD可能成为双光子生物成像，非线性光学和新型QDs激光设备的有希望的候选者。