Development of an ultrafine aerosol particle mobility analyzer with separation and sensitivity enhancement and real-time monitoring

该项目的目标是开发一种新的仪器，以准确测量在各种环境应用中采样的纳米颗粒的尺寸分布。新仪器将提高超细颗粒的灵敏度、选择性和检测速度，最大尺寸可达100纳米，即PM0.1颗粒。这种小尺寸的颗粒物与产生较大颗粒物的自然或人工来源相同，但PM0.1颗粒物可能会构成特殊的健康威胁，因为它们很容易进入人体。改进的测量技术有助于检测和控制环境中的PM0.1颗粒。将要开发的仪器是离子迁移率光谱仪(IMS)。IMS将使用在空间上变化的电场来限制颗粒在气相中的扩散，因此将提高颗粒尺寸分布测量的分辨率。此外，IMS系统将与质谱仪耦合，以便粒子迁移率可以与粒子质量相关联。这一新仪器的使用将提高我们对气溶胶和纳米颗粒的表征和在气相中的传输的基本理解。研究小组将在夏令营中开展活动，向K-12年级的学生，特别是那些来自代表人数不足的群体的学生演示气溶胶科学原理。该小组还将通过K-12教师/导师意识研讨会交流气溶胶在气候变化和污染中的作用。气溶胶通常根据其在气相中的流动性获得的大小进行分类。大多数情况下，基于迁移率的气溶胶粒子尺寸分布函数是用扫描迁移率粒度仪(SMPS)测量的。虽然SMPS非常成功，但它也有几个缺点，可以通过采用不同的技术来解决。例如，扩散展宽导致大多数运行中的商业设备的分辨率下降。此外，开关电源通常需要几分钟才能完成电压扫描。这一持续时间限制了气溶胶样本在时间上迅速变化时可获得的信息，这种情况可能发生在飞机或道路附近采样时。对于气相中PM0.1颗粒的测量来说，这些挑战更加严重。尽管实验和理论上的兴趣仍在继续，但对自由分子区域(1-100 nm)中粒子的动量转移的理论理解仍然存在知识空白。这项拟议的研究预计将通过增加仪器分离/分辨率来影响气溶胶领域，方法是限制纳米颗粒的扩散展宽，通过质量-迁移率和尺寸关系对小型气溶胶进行分类，以及快速、低信噪比扫描以研究快速变化的气溶胶(对于小于10纳米的颗粒，每次扫描最多数十毫秒)。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The goal of this project is to develop a new instrument to measure accurately the size distribution of nanoparticles sampled in a variety of environmental applications. The new instrument will enhance the sensitivity, selectivity, and detection speed of ultrafine particles up to 100 nanometers in size, which are referred to as PM0.1 particles. Particles of this small size arise from the same natural or human-made sources that produce larger particles, but PM0.1 particles may pose special health threats because they readily enter the body. Improved measurement techniques could help with the detection and control of PM0.1 particles in the environment. The instrument that will be developed is an Ion Mobility Spectrometer (IMS). The IMS will use an electric field that varies spatially to restrict diffusion of particles in the gas phase and therefore will enhance the resolution of measurements of the particle size distribution. In addition, the IMS system will be coupled to a mass spectrometer so that particle mobility can be correlated with particle mass. The use of this new instrument will improve our fundamental understanding of aerosol and nanoparticle characterization and transport in the gas phase. The research team will conduct activities that demonstrate principles of aerosol science to K-12 students, especially those from underrepresented groups, in summer camps. The team will also communicate the role of aerosols in climate change and pollution through K-12 teacher/mentor awareness symposia.Aerosols are generally classified by size obtained from their mobility in the gas phase. Most often, mobility-based size distribution functions of aerosol particles are measured with a scanning mobility particle sizer (SMPS). While the SMPS has been highly successful, it has several shortcomings that could be addressed by employing different techniques. For example, diffusional broadening leads to a degradation in resolution for most operating commercial devices. Furthermore, SMPSs typically require minutes to complete voltage scans. This duration limits the information that can be obtained when aerosol samples vary rapidly in time, which can occur when sampling near aircraft or roadways. These challenges are exacerbated for measurements of PM0.1 particles in the gas phase. Despite continued experimental and theoretical interest, there is still a knowledge gap in the theoretical understanding of momentum transfer of particles that lie in the free molecular regime (1-100nm). The proposed research is expected to impact the aerosol field through increases in instrument separation/resolution by restricting diffusion broadening of nanoparticles, classifications of small aerosols through a mass-mobility and size relationship and quick, low signal-to-noise scans to study rapidly varying aerosols (up to tens of milliseconds per scan for particles smaller than 10 nanometers).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.