研究目的
To demonstrate a new technique called ES-SERS for probing the surface chemical compositions of atmospherically relevant particles, including the detection of surface aqueous sulfate and adsorbed water, and to apply this technique to characterize submicron ambient particulate matter.
研究成果
The ES-SERS technique successfully probes the surface chemical compositions of atmospherically relevant particles, demonstrating the availability of aqueous sulfate anions on the surface and the presence of surface-adsorbed water. The technique's insensitivity to particle size in the range studied and its application to ambient PM reveal the potential for future studies on submicron particles and the internal structure of individual particles.
研究不足
The chemical enhancement resulting in a peak shift could pose an obstacle to tracing the phase transition as well as identifying functional groups. The technique's sensitivity to particle size and the need for particles to be at least 1 μm in size for analysis due to the Abbe diffraction limit are also noted limitations.
1：Experimental Design and Method Selection:
The study employs electrospray-surface enhanced Raman spectroscopy (ES-SERS) to measure the surface chemical compositions of atmospherically relevant particles. Ag nanoparticle aerosols are electrosprayed over analyte particles to realize surface-sensitive SERS.
2：Sample Selection and Data Sources:
Laboratory-generated supermicron particles of ammonium sulfate (AS), AS mixed with succinic acid (AS/SA), and AS mixed with sucrose (AS/sucrose), as well as submicron ambient aerosol particles collected in Hong Kong, are used as samples.
3：List of Experimental Equipment and Materials:
Equipment includes a piezoelectric particle generator, a sputtering device for gold coating, an electrospray system for Ag nanoparticle deposition, a Raman spectroscope, and a differential mobility analyzer for particle size distribution measurements. Materials include ammonium sulfate, succinic acid, sucrose, and Ag nanoparticles.
4：Experimental Procedures and Operational Workflow:
Analyte particles are deposited on a substrate, dried, and then exposed to a controlled relative humidity environment. Ag nanoparticles are electrosprayed onto the analyte particles, and Raman measurements are conducted to observe spectral features.
5：Data Analysis Methods:
Raman spectra are analyzed to identify chemical compositions and interactions, with enhancement factors calculated to compare normal Raman and SERS measurements.
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