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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.
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Reaction Acceleration at Solid/Solution Interfaces: Katritzky Reaction Catalyzed by Glass Particles
Abstract The Katritzky reaction in bulk solution at room temperature is accelerated significantly by the surface of a glass container compared to a plastic container. Remarkably, the reaction rate is increased by more than two orders of magnitude upon the addition of glass particles with the rate increasing linearly with increasing amounts of glass. A similar phenomenon is observed when glass particles are added to levitated droplets, where large acceleration factors are seen. Evidence shows that glass acts as a “green” heterogeneous catalyst: it participates as a base in the deprotonation step and is recovered unchanged from the reaction mixture. Reaction acceleration at two separate interfaces is recognized in this study: i) air/solution phase acceleration, as is well known in microdroplets; ii) solid/solution phase, where such acceleration appears to be a new phenomenon.
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- Award ID(s):
- 1905087
- PAR ID:
- 10237074
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 60
- Issue:
- 6
- ISSN:
- 1433-7851
- Page Range / eLocation ID:
- p. 2929-2933
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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