Real-Time Monitoring of Competing Nanoparticle Formation Pathways during Cation Exchange Using Benchtop Light Scattering
Real-Time Monitoring of Competing Nanoparticle Formation Pathways during Cation Exchange Using Benchtop Light Scattering
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DOI：
10.1021/acs.chemmater.0c04938
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发表时间：
2021-06
影响因子：
8.6
通讯作者：
Gabriella A. Di Domizio;Lucas T. Alameda;J. Fanghanel;Robert W. Lord;JenniferR. Miller;R. Schaak
中科院分区：
文献类型：
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作者：
Gabriella A. Di Domizio;Lucas T. Alameda;J. Fanghanel;Robert W. Lord;JenniferR. Miller;R. Schaak
阳离子交换是合成纳米粒子的一种越来越常见的途径，因为它以可控的方式改变组成，同时保持其他关键特征，包括晶体结构和形貌。然而，根据体系和反应条件的不同，阳离子交换途径可以与其他纳米颗粒形成途径竞争。因此，监测这类反应的简单策略可以提供信息。在这里，我们使用激光指示器的台式光散射作为一种简单的工具来监控假定的阳离子交换反应，并帮助实时区分涉及阳离子交换的途径和涉及溶解和再沉淀的途径。我们以闪锌矿硫化铜矿转化为硫化锰为模型体系。当激光指示器穿过反应瓶时，当闪锌矿硫化铜纳米颗粒与Mn2+在100°C反应时，连续观察到光散射，表明纳米颗粒存在于整个反应过程中，这是阳离子交换途径所必需的。在较高的温度下，光散射消失，然后重新出现，这表明纳米颗粒并不总是存在的，而且涉及溶解和再沉淀的不同途径是可行的。使用这种方法，再加上额外的对照实验，我们能够确定闪锌矿的门槛温度，低于这个温度，闪锌矿是一种亚稳定的多晶型，通过阳离子交换途径形成。我们还能够确定，在更高的温度下，热力学上有利的产物岩盐MnS通过溶解/再沉淀途径形成。这些结果为模型阳离子交换反应的温度依赖性提供了有用的见解，并表明光散射可以在台面上实时提供对纳米颗粒反应路径的高水平洞察，这些反应路径涉及合成后修饰，其中可能有多个竞争路径。
Cation exchange is an increasingly common pathway for nanoparticle synthesis, as it modifies the composition in a controllable way while maintaining other key features, including crystal structure and morphology. However, cation exchange pathways can compete with other nanoparticle formation pathways, depending on the system and reaction conditions. Simple strategies for monitoring such reactions can therefore be informative. Here, we use benchtop light scattering with a laser pointer as a simple tool to monitor putative cation exchange reactions and to help differentiate, in real time, between pathways that involve cation exchange versus pathways that involve dissolution and reprecipitation. We use the transformation of digenite copper sulfide into manganese sulfide as a model system. When a laser pointer shines through the reaction flask as digenite copper sulfide nanoparticles react with Mn2+at 100 °C, light scattering is observed continuously, indicating that nanoparticles are present during the entire reaction as would be required for a cation exchange pathway. At higher temperatures, light scattering disappears and then reappears, indicating that nanoparticles are not always present and that a different pathway involving dissolution and reprecipitation is operable. Using this approach, along with additional control experiments, we were able to identify the threshold temperature below which zincblende MnS, a metastable polymorph, forms through a cation exchange pathway. We were also able to establish that at higher temperatures, the thermodynamically favored product, rocksalt MnS, forms through a dissolution/reprecipitation pathway. These results provide useful insights into the temperature dependence of a model cation exchange reaction and suggest that light scattering could provide high-level insights, in real time on the benchtop, into nanoparticle reaction pathways that involve postsynthetic modifications where multiple competing pathways could be possible.