New Approaches for Measuring Accelerated Chemical Reactions in Single Aerosol Particles

测量单个气溶胶颗粒中加速化学反应的新方法

• 批准号: EP/W009528/2
• 负责人: Michael Cotterell
• 金额: $ 21.53万
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FW009528%2F2
• 关键词: New; Approaches; Measuring; Accelerated; Chemical

Aerosols are liquid or solid particles suspended in a gas such as air. They are used in advanced manufacturing, freeze-drying, and inhaled medications, are implicated in the spread of respiratory diseases, and are pervasive in our natural world. Indeed, the role of aerosols in atmospheric processes represents one of the largest uncertainties in predicting climate change. Environmental aerosols also degrade air quality and are strongly linked to respiratory and cardiovascular illnesses. Yet, carefully designed aerosols are often utilised to deliver inhaled drugs to the lungs to treat disease, and to manufacture new materials.Recent studies have reported that chemical reactions can speed up by factors of up to a million in aerosols compared to reactions in beaker-scale solutions currently used to synthesise a range of chemicals, including pharmaceuticals such as benzopyridines (used in anaesthetics and vasodilators). The potential generality of reaction enhancement upon aerosolization may remove the need for expensive catalysts in many industrial synthetic processes for the manufacture of pharmaceuticals, agrochemicals, and other fine chemicals. Accelerated reactions have also been harnessed in analytical techniques, providing rapid degradation of bulky proteins for fast characterisations of monoclonal antibodies. Moreover, accelerated aerosol reactions may greatly affect the chemistry of atmospheric aerosols, with tremendous impacts on climate, air quality and human health. For example, the enhanced in-aerosol chemistry forming sunlight-absorbing organic molecules in air influences the warming of the Earth's atmosphere, and hence changes to the climate.Despite the potential socioeconomic impacts of reaction acceleration via aerosolization, the generality and underlying mechanisms of these enhanced chemistries are unknown. Electrospray ionisation mass spectrometry is the dominant measurement tool used to study accelerated aerosol reactions. High levels of electrical charge are deliberately imparted to generated aerosol droplets to enable analysis in a mass spectrometer. While electrical charge is known to drive chemistry in microdroplets, the impact of charge and the associated high electric field strengths on accelerated in-aerosol reactions is not understood or quantified. Moreover, such approaches probe evolving properties for an aerosol ensemble comprising tens of thousands of particles per cubic centimetre and therefore provide highly averaged properties. Yet an ensemble will exhibit a considerable level of particle-to-particle variability in chemical composition, mixing state and size. Consequently, measurements on aerosol samples containing hundreds or thousands of microdroplets prevent clear links being made between aerosol properties and reaction rate enhancements. Indeed, there are a range of physical phenomena that are unique to aerosols that could be driving enhanced chemistries, but new measurement approaches are needed to understand the causes.Advances in optical spectroscopy on single aerosols levitated in an optical trap allow the measurement of the physical and chemical properties of aerosol droplets with superior accuracy and sensitivity, on unlimited timescales, and under highly controlled conditions. In this project, we will build and benchmark a new integrated instrument combining three proven technologies to detect the formation of the products of in-aerosol reactions, using optical spectroscopy approaches in combination with laser based optical trapping of single particles. Through a comprehensive series of laboratory experiments, we will quantify reaction rates for an exemplar class of reaction that forms light absorbing products, and connect these rates to in-droplet reactant concentrations (including supersaturated solutions unique to aerosols), particle acidity, and the role of heterogeneous processes at the aerosol particle surface.

气溶胶是悬浮在空气等气体中的液体或固体颗粒。它们被用于先进的制造、冷冻干燥和吸入药物，与呼吸道疾病的传播有关，在我们的自然界中无处不在。事实上，气溶胶在大气过程中的作用是预测气候变化的最大不确定性之一。环境气溶胶还会降低空气质量，并与呼吸系统和心血管疾病密切相关。然而，精心设计的气雾剂经常被用来将吸入的药物输送到肺部治疗疾病，并制造新的材料。最近的研究报告称，与目前用于合成一系列化学品的烧杯规模的溶液中的反应相比，气雾剂中的化学反应可以加快高达100万倍，包括药物，如苯并吡啶(用于麻醉剂和血管扩张剂)。气雾化后反应增强的潜在普遍性可能会消除在制药、农用化学品和其他精细化学品制造的许多工业合成过程中对昂贵催化剂的需求。分析技术中也利用了加速反应，提供了体积庞大的蛋白质的快速降解，以快速鉴定单克隆抗体。此外，加速的气溶胶反应可能会极大地影响大气气溶胶的化学成分，对气候、空气质量和人类健康产生巨大影响。例如，空气中形成吸收阳光的有机分子的气溶胶化学增强会影响地球大气变暖，从而影响气候变化。尽管通过气雾化加速反应的潜在社会经济影响，但这些增强化学作用的共性和潜在机制尚不清楚。电喷雾电离质谱仪是用于研究加速气溶胶反应的主要测量工具。高水平的电荷被故意赋予产生的气溶胶液滴，以便在质谱仪中进行分析。虽然已知电荷推动微滴中的化学作用，但电荷和相关的高电场强度对加速气溶胶内反应的影响尚不清楚或量化。此外，这种方法探测每立方厘米包含数万个颗粒的气溶胶整体的演变特性，因此提供了高度平均的特性。然而，在化学成分、混合状态和大小方面，总体将表现出相当程度的颗粒到颗粒的可变性。因此，对含有数百或数千个微滴的气溶胶样品的测量阻止了气溶胶特性与反应速率增强之间的明确联系。事实上，有一系列气溶胶特有的物理现象可能会推动化学作用的增强，但需要新的测量方法来了解其原因。关于悬浮在光学陷阱中的单个气溶胶的光学光谱的进展使人们能够在无限的时间尺度和高度受控的条件下，以更高的精度和灵敏度测量气溶胶液滴的物理和化学性质。在这个项目中，我们将建造一台新的集成仪器并对其进行基准测试，该仪器结合了三项成熟的技术，使用光学光谱学方法结合基于激光的单颗粒光学捕获来检测气溶胶反应产物的形成。通过一系列全面的实验室实验，我们将量化形成光吸收产品的一类典型反应的反应速率，并将这些速率与液滴内反应物浓度(包括气溶胶特有的过饱和溶液)、颗粒酸度以及气溶胶颗粒表面的非均质过程的作用联系起来。