Silver nanoplates have been used in the colorimetric
sensing of
analytes through various mechanisms. Herein, we proposed the use of
single-particle inductively coupled plasma mass spectrometry (SP-ICP-MS)
for providing additional information on changes in nanoparticles during
the colorimetric sensing of analytes. The information on equivalent
spherical diameter and the number of particles obtained from SP-ICP-MS
was employed for tracking the changes in silver nanoparticles during
their synthesis process under various synthesis conditions and also
during the colorimetric sensing of mercury. By comparing the edge
size of triangular nanoplates observed by transmission electron microscopy,
the information on the plate thickness of triangular silver nanoplates
was also estimated by the size information from SP-ICP-MS. Four types
of silver nanoplates were examined including bare silver nanoplates,
silver nanoplates capped with glutathione, silver nanoplates capped
with glutathione mixed with 0.05 mg L–1 mercury
and bromide ions, and silver nanoplates capped with glutathione mixed
with 1 mg L–1 mercury and bromide ions. The information
on equivalent spherical diameter and the number of particles was used
for understanding the sensing mechanism of the silver nanoplates toward
mercury ions. The information from SP-ICP-MS was combinedly used with
plasmon absorption data, as well as the information from field-flow
fractionation-ICP-MS (FFF-ICP-MS), in order to study the changes in
silver nanoparticles at various concentrations of mercury ions. A
linear increase in particle concentrations was observed by SP-ICP-MS
for the concentration range of 0.001–0.01 mg L–1 mercury ions. The particle concentrations were highest at 0.01 mg
L–1 mercury ions and decreased to the same numbers
as for the bare silver nanoplates without bromide etching. This study
shows the potential use of SP-ICP-MS to provide additional information
for tracking silver nanoparticles during their synthesis and colorimetric
sensing of mercury ions. In addition, for SP-ICP-MS analysis of particle
concentrations for the diluted silver nanoplates in contact with mercury
ions before etching with diluted bromide ions, the limit of detection
for mercury was pushed down to approximately 0.01 μg L–1, which would be very useful for the analysis of real samples under
environmentally relevant conditions.
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