Plasmonic metal nanostructures have been used as effective materials for enhancing the laser desorption ionization (LDI) efficiency in mass spectrometry analysis. But the ionization mechanism and the origin of initial charges have not been fully understood yet. Here we provided experimental evidence showing that the hot electron transfer in localized surface plasmon resonance (LSPR) plays a key role in ionizing molecules during the LDI process.
Volatile
organic compounds (VOCs) from exhaled breath (EB) are
considered to be promising biomarkers for lung diseases. A convenient
and sensitive point-of-care (POC) testing method for EB VOCs is essential.
Here, we developed a POC test paper for the analysis of EB aldehydes,
which are potential biomarkers for lung cancer. A probe molecule,
4-aminothiophenol (4-ATP), was anchored on a paper substrate to specifically
capture gas-phase aldehydes through the Schiff base reaction. Meanwhile,
thin-film reaction acceleration was utilized to increase capture efficiency.
By directly coupling the test paper to a mass spectrometer through
paper spray, high sensitivity (0.1 ppt) and a wide quantification
linear range (from 10 ppt to 1 ppm) were obtained. Analysis of EB
from lung cancer patients with the test paper showed a significant
increase in several reported aldehyde markers compared to EB from
healthy volunteers, indicating the potential of this method for sensitive,
low-cost, and convenient lung cancer screening and diagnosis.
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