Optical Trapping-Microspectroscopy of Single Aerosol Microdroplets in Air : Supercooling of Dimethylsulfoxide Microdroplets

We report temperature (T = +22.5 ∼ -57.0 °C)-controlled optical trapping of single dimethylsulfoxide (DMSO) droplets with the diameter (d) of 7-15 μm in air. Optically levitated DMSO microdroplets containing 0.1 mol/dm3 (=M) potassium iodide (KI) as an additive for reducing the vapor pressure of DMSO in air have been suggested to take supercooled liquid states even below the freezing temperature (fp) of the bulk DMSO liquid (fp = +18.4 °C in the presence of 0.1 M KI) as seen in bright-field microscopic observations of the droplet. Clear evidence for supercooling of an aerosol DMSO microdroplet below fp has been obtained by in situ optical trapping-polarized Raman microspectroscopy of the droplet down to -14.9 °C. Analysis of the polarized Raman spectral data of an aerosol DMSO droplet (d = ∼10 μm) has demonstrated that the droplet at +22.5, +0.2, or -14.9 °C is characterized by the rotational relaxation time (τrot) of a DMSO molecule in the droplet being 1.95, 2.58, or 3.90 ps, respectively. On the basis of the τrot values and the Stokes-Einstein equation (τrot = 8πa3η/kBT where a, η, kB are the radius (1.883 Å) of a DMSO molecule, the viscosity in DMSO, and the Boltzmann constant, respectively), the η values in the DMSO microdroplet in air at +22.5, +0.2, or -14.9 °C have been estimated to be 2.39, 2.94, or 4.20 cP, respectively, while that of bulk DMSO liquid at +20.5 °C is 1.98 cP. We also report the T-dependence (+22.5 > T > -14.9 °C) of the viscosity in a single aerosol DMSO microdroplet (d = ∼10 μm) and the effects of aerosolization in air on the viscosity in DMSO.

Medienart:

E-Artikel

Erscheinungsjahr:

2020

Erschienen:

2020

Enthalten in:

Zur Gesamtaufnahme - volume:124

Enthalten in:

The journal of physical chemistry. A - 124(2020), 43 vom: 29. Okt., Seite 9035-9043

Sprache:

Englisch

Beteiligte Personen:

Miura, Atsushi [VerfasserIn]
Nakajima, Ryosuke [VerfasserIn]
Abe, Sayaka [VerfasserIn]
Kitamura, Noboru [VerfasserIn]

Links:

Volltext

Themen:

Journal Article

Anmerkungen:

Date Completed 02.11.2020

Date Revised 02.11.2020

published: Print-Electronic

Citation Status PubMed-not-MEDLINE

doi:

10.1021/acs.jpca.0c06179

funding:

Förderinstitution / Projekttitel:

PPN (Katalog-ID):

NLM316238392