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Title: The role of analyte concentration in accelerated reaction rates in evaporating droplets
Accelerated reactions in microdroplets have been reported for a wide range of reactions with some microdroplet reactions occurring over a million times faster than the same reaction in bulk solution. Unique chemistry at the air–water interface has been implicated as a primary factor for accelerated reaction rates, but the role of analyte concentration in evaporating droplets has not been as well studied. Here, theta-glass electrospray emitters and mass spectrometry are used to rapidly mix two solutions on the low to sub-microsecond time scale and produce aqueous nanodrops with different sizes and lifetimes. We demonstrate that for a simple bimolecular reaction where surface chemistry does not appear to play a role, reaction rate acceleration factors are between 10 2 and 10 7 for different initial solution concentrations, and these values do not depend on nanodrop size. A rate acceleration factor of 10 7 is among the highest reported and can be attributed to concentration of analyte molecules, initially far apart in dilute solution, but brought into close proximity in the nanodrop through evaporation of solvent from the nanodrops prior to ion formation. These data indicate that analyte concentration phenomenon is a significant factor in reaction acceleration where droplet volume throughout the experiment is not carefully controlled.  more » « less
Award ID(s):
2203907
PAR ID:
10423030
Author(s) / Creator(s):
;
Date Published:
Journal Name:
Chemical Science
Volume:
14
Issue:
18
ISSN:
2041-6520
Page Range / eLocation ID:
4704 to 4713
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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