Direct measurement of the pH of aerosol particles using carbon quantum dots
Direct measurement of the pH of aerosol particles using carbon quantum dots
复制标题
使用碳量子点直接测量气溶胶颗粒的 pH 值
DOI：
10.1039/d2ay01005d
复制
发表时间：
2022
影响因子：
3.1
通讯作者：
Freedman, Miriam Arak
中科院分区：
文献类型：
--
作者：
Tackman, Emma C.;Grady, Rachel S.;Freedman, Miriam Arak
气溶胶颗粒的pH值测量仍然具有挑战性，因为它们的尺寸小，成分复杂，酸度高。在大气中大量存在的含水气溶胶颗粒的酸性影响了从反应速率到云形成的许多化学过程。目前只有一种技术-- pH试纸--可以直接测定气溶胶颗粒的pH值，而且仅限于测量整个颗粒群的平均酸度。用于评估气溶胶pH值的其他方法包括过滤器样品、颗粒进液采样、拉曼光谱、有机染料和热力学模型，但这些方法要么在较高的pH值范围内操作，要么无法评估某些化学物质或复杂性。在这里，我们提出了一种新的方法来确定酸度的单个颗粒和颗粒相使用碳量子点作为一种新的原位荧光团。碳量子点易于合成、储存稳定，并且在与环境气溶胶颗粒相关的pH 0至pH 3的高酸性范围内对pH敏感。为了建立该方法，由雾化标准溶液的比率荧光强度形成校准曲线，相关系数（R2）为0.99。此外，还测定了代表环境气溶胶的含有复杂有机混合物（COM）的气溶胶颗粒的pH值，证明了使用碳量子点作为复杂系统的pH敏感荧光团的有效性。在正确的pH值范围内直接测量气溶胶粒子和相酸度的能力有助于参数化大气模型，并改善对其他气溶胶特性及其对健康和气候影响的预测。
The pH of aerosol particles remains challenging to measure because of their small size, complex composition, and high acidity. Acidity in aqueous aerosol particles, which are found abundantly in the atmosphere, impacts many chemical processes from reaction rates to cloud formation. Only one technique – pH paper – currently exists for directly determining the pH of aerosol particles, and this is restricted to measuring average acidity for entire particle populations. Other methods for evaluating aerosol pH include filter samples, particle-into-liquid sampling, Raman spectroscopy, organic dyes, and thermodynamic models, but these either operate in a higher pH range or are unable to assess certain chemical species or complexity. Here, we present a new method for determining acidity of individual particles and particle phases using carbon quantum dots as a novel in situ fluorophore. Carbon quantum dots are easily synthesized, shelf stable, and sensitive to pH in the highly acidic regime from pH 0 to pH 3 relevant to ambient aerosol particles. To establish the method, a calibration curve was formed from the ratiometric fluorescence intensity of aerosolized standard solutions with a correlation coefficient (R2) of 0.99. Additionally, the pH of aerosol particles containing a complex organic mixture (COM) representative of environmental aerosols was also determined, proving the efficacy of using carbon quantum dots as pH-sensitive fluorophores for complex systems. The ability to directly measure aerosol particle and phase acidity in the correct pH range can help parametrize atmospheric models and improve projections for other aerosol properties and their influence on health and climate.