1
|
Doan-Nguyen TP, Crespy D. Advanced density-based methods for the characterization of materials, binding events, and kinetics. Chem Soc Rev 2022; 51:8612-8651. [PMID: 36172819 DOI: 10.1039/d1cs00232e] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Investigations of the densities of chemicals and materials bring valuable insights into the fundamental understanding of matter and processes. Recently, advanced density-based methods have been developed with wide measurement ranges (i.e. 0-23 g cm-3), high resolutions (i.e. 10-6 g cm-3), compatibility with different types of samples and the requirement of extremely low volumes of sample (as low as a single cell). Certain methods, such as magnetic levitation, are inexpensive, portable and user-friendly. Advanced density-based methods are, therefore, beneficially used to obtain absolute density values, composition of mixtures, characteristics of binding events, and kinetics of chemical and biological processes. Herein, the principles and applications of magnetic levitation, acoustic levitation, electrodynamic balance, aqueous multiphase systems, and suspended microchannel resonators for materials science are discussed.
Collapse
Affiliation(s)
- Thao P Doan-Nguyen
- Max Planck-VISTEC Partner Laboratory for Sustainable Materials, Vidyasirimedhi Institute of Science and Technology (VISTEC), Rayong 21210, Thailand. .,Department of Materials Science and Engineering, School of Molecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology (VISTEC), Rayong 21210, Thailand
| | - Daniel Crespy
- Max Planck-VISTEC Partner Laboratory for Sustainable Materials, Vidyasirimedhi Institute of Science and Technology (VISTEC), Rayong 21210, Thailand. .,Department of Materials Science and Engineering, School of Molecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology (VISTEC), Rayong 21210, Thailand
| |
Collapse
|
2
|
Chang YP, Devi Y, Chen CH. Micro-droplet Trapping and Manipulation: Understanding Aerosol Better for a Healthier Environment. Chem Asian J 2021; 16:1644-1660. [PMID: 33999498 DOI: 10.1002/asia.202100516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Indexed: 11/09/2022]
Abstract
Understanding the physicochemical properties and heterogeneous processes of aerosols is key not only to elucidate the impacts of aerosols on the atmosphere and humans but also to exploit their further applications, especially for a healthier environment. Experiments that allow for spatially control of single aerosol particles and investigations on the fundamental properties and heterogeneous chemistry at the single-particle level have flourished during the last few decades, and significant breakthroughs in recent years promise better control and novel applications aimed at resolving key issues in aerosol science. Here we propose graphene oxide (GO) aerosols as prototype aerosols containing polycyclic aromatic hydrocarbons, and GO can behave as two-dimensional surfactants which could modify the interfacial properties of aerosols. We describe the techniques of trapping single particles and furthermore the current status of the optical spectroscopy and chemistry of GO. The current applications of these single-particle trapping techniques are summarized and interesting future applications of GO aerosols are discussed.
Collapse
Affiliation(s)
- Yuan-Pin Chang
- Department of Chemistry, National Sun Yat-sen University, No. 70 Lien-hai Rd., Kaohsiung, 80424, Taiwan.,Aerosol Science Research Center, National Sun Yat-sen University, No. 70 Lien-hai Rd., Kaohsiung, 80424, Taiwan
| | - Yanita Devi
- Department of Chemistry, National Sun Yat-sen University, No. 70 Lien-hai Rd., Kaohsiung, 80424, Taiwan
| | - Chun-Hu Chen
- Department of Chemistry, National Sun Yat-sen University, No. 70 Lien-hai Rd., Kaohsiung, 80424, Taiwan
| |
Collapse
|
3
|
Wexler AS, Patel K, Gen M, Chan CK. Reconciling Measurement and Prediction of Free and Solvated Water in Solution. ACS OMEGA 2020; 5:8754-8765. [PMID: 32337437 PMCID: PMC7178779 DOI: 10.1021/acsomega.0c00311] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 03/18/2020] [Indexed: 06/11/2023]
Abstract
In 2019, Wexler showed that, by applying Raoult's law rigorously to aqueous solutions and properly accounting for hydration of solutes, equations can be derived that accurately describe solute and solvent activity over the full range of concentrations from infinitely dilute to pure solutes. One feature of this theory is that it also predicts the amount of water that is free and the amount that is bound to the solute. In 2004 and 2005, Choi and co-workers used an electrodynamic balance to measure (i) the concentration of a range of organic and electrolyte solutes as a function of water activity and (ii) the amount of free and bound water in these solutions using the fluorescence of pyranine as a probe. In the current work, we compare the predictions of Wexler's theory to the measurements of Choi. After the adjustments to the amount of free water obtained by these measurements, the predictions of Wexler's theory match the measurements of Choi. The potential reasons for the adjustments are discussed.
Collapse
Affiliation(s)
- Anthony S. Wexler
- Air
Quality Research Center and Departments of Mechanical and Aerospace
Engineering, Civil and Environmental Engineering, and Land, Air and
Water Resources, University of California, Davis, California 95616, United States
| | - Kunal Patel
- Department
of Chemical Engineering, University of California, Davis, California 95616, United States
| | - Masao Gen
- Faculty
of Frontier Engineering, Institute of Science and Engineering, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
| | - Chak K. Chan
- School
of Energy and Environment, City University
of Hong Kong, Kowloon, Hong Kong, China
| |
Collapse
|
4
|
Tang M, Cziczo DJ, Grassian VH. Interactions of Water with Mineral Dust Aerosol: Water Adsorption, Hygroscopicity, Cloud Condensation, and Ice Nucleation. Chem Rev 2016; 116:4205-59. [DOI: 10.1021/acs.chemrev.5b00529] [Citation(s) in RCA: 228] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Mingjin Tang
- Department
of Chemistry, University of Iowa, Iowa City, Iowa 52242, United States
| | - Daniel J. Cziczo
- Department
of Earth, Atmospheric and Planetary Sciences and Civil and Environmental
Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Vicki H. Grassian
- Department
of Chemistry, University of Iowa, Iowa City, Iowa 52242, United States
- Departments
of Chemistry and Biochemistry, Nanoengineering and Scripps Institution
of Oceanography, University of California San Diego, La Jolla, California 92093, United States
| |
Collapse
|
5
|
Eom HJ, Gupta D, Li X, Jung HJ, Kim H, Ro CU. Influence of Collecting Substrates on the Characterization of Hygroscopic Properties of Inorganic Aerosol Particles. Anal Chem 2014; 86:2648-56. [DOI: 10.1021/ac4042075] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Hyo-Jin Eom
- Department
of Chemistry, Inha University, 253 Yonghyun-dong, Nam-gu, Incheon 402-751, Republic of Korea
| | - Dhrubajyoti Gupta
- Department
of Chemistry, Inha University, 253 Yonghyun-dong, Nam-gu, Incheon 402-751, Republic of Korea
| | - Xue Li
- Department
of Chemistry, Inha University, 253 Yonghyun-dong, Nam-gu, Incheon 402-751, Republic of Korea
| | - Hae-Jin Jung
- Department
of Chemistry, Inha University, 253 Yonghyun-dong, Nam-gu, Incheon 402-751, Republic of Korea
| | - HyeKyeong Kim
- Department
of Chemistry, Inha University, 253 Yonghyun-dong, Nam-gu, Incheon 402-751, Republic of Korea
| | - Chul-Un Ro
- Department
of Chemistry, Inha University, 253 Yonghyun-dong, Nam-gu, Incheon 402-751, Republic of Korea
| |
Collapse
|
6
|
In-situ FTIR-ATR spectroscopic observation on the dynamic efflorescence/deliquescence processes of Na2SO4 and mixed Na2SO4/glycerol droplets. Chem Phys 2014. [DOI: 10.1016/j.chemphys.2013.12.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
|
7
|
Zeng G, Kelley J, Kish JD, Liu Y. Temperature-dependent deliquescent and efflorescent properties of methanesulfonate sodium studied by ATR-FTIR spectroscopy. J Phys Chem A 2014; 118:583-91. [PMID: 24387240 DOI: 10.1021/jp405896y] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Modeling of aerosols and cloud formation processes in the marine boundary layer (MBL) require extensive data on hygroscopic properties of relevant methanesulfonate particles, which are currently scarce. In this work, methanesulfonate sodium (CH3SO3Na, MSA-Na), the most abundant methanesulfonate salt, was selected, and its deliquescent and efflorescent properties at temperatures relevant to the lower troposphere were studied using an ATR-FTIR flow system. To validate the approach, we investigated hygroscopic properties of NaCl particles, and our measured deliquescent relative humidity (DRH) and efflorescent relative humidity (ERH) of the NaCl particles obtained from the changes in integrated absorbance of water peaks in infrared spectra agreed with literature data well. We then reported DRH and ERH of MSA-Na particles as a function of temperature for the first time using both the changes in integrated absorbance of water peaks and the changes in peak position and shape of CH3SO3(-) symmetric and asymmetric vibrational modes. Our experiments showed that MSA-Na particles present quite different temperature-dependent hygroscopic behaviors from NaCl. Both the DRH and ERH of MSA-Na particles increase with decreasing temperatures. Due to the significant differences in temperature-dependent DRH and ERH, NaCl particles, if processed in MBL by methanesulfonic acid, are expected to deliquesce slightly earlier during a hydration process but effloresce at a much earlier stage during a dehydration process, especially at lower temperatures. This could considerably influence phase, size, and water content of sea salt aerosols and consequently their reactivity, lifetime, and impacts on atmospheric chemistry and climate systems.
Collapse
Affiliation(s)
- Guang Zeng
- Department of Chemistry, University of Colorado Denver , Denver, Colorado 80217, United States
| | | | | | | |
Collapse
|
8
|
Krieger UK, Marcolli C, Reid JP. Exploring the complexity of aerosol particle properties and processes using single particle techniques. Chem Soc Rev 2012; 41:6631-62. [DOI: 10.1039/c2cs35082c] [Citation(s) in RCA: 247] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
9
|
State of water and its implications for supersaturated structures in Mg(NO3)2 aerosols. Sci Bull (Beijing) 2009. [DOI: 10.1007/s11434-008-0508-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
10
|
Zhao LJ, Zeng QX, Zhang YH. State of Water in Supersaturated Nitrate Aerosols Disclosed by the Raman Difference Spectra. J Phys Chem A 2008; 113:215-20. [DOI: 10.1021/jp8084974] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Li-Jun Zhao
- The Institute of Chemical Physics, School of Science, and School of Aerospace Science and Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Qing-Xuan Zeng
- The Institute of Chemical Physics, School of Science, and School of Aerospace Science and Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Yun-Hong Zhang
- The Institute of Chemical Physics, School of Science, and School of Aerospace Science and Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
| |
Collapse
|
11
|
Wang F, Zhao L, Zhang Y. Crystallization dynamics of supersaturated NaClO4 aerosols studied by high-speed photography. Sci Bull (Beijing) 2008. [DOI: 10.1007/s11434-008-0284-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
12
|
Li XH, Zhao LJ, Dong JL, Xiao HS, Zhang YH. Confocal Raman Studies of Mg(NO3)2 Aerosol Particles Deposited on a Quartz Substrate: Supersaturated Structures and Complicated Phase Transitions. J Phys Chem B 2008; 112:5032-8. [DOI: 10.1021/jp709938x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Xiao-Hong Li
- The Institute of Chemical Physics, School of Science, and School of Aerospace Science and Engineering, Beijing Institute of Technology, Beijing 100081, People's Republic of China
| | - Li-Jun Zhao
- The Institute of Chemical Physics, School of Science, and School of Aerospace Science and Engineering, Beijing Institute of Technology, Beijing 100081, People's Republic of China
| | - Jin-Ling Dong
- The Institute of Chemical Physics, School of Science, and School of Aerospace Science and Engineering, Beijing Institute of Technology, Beijing 100081, People's Republic of China
| | - Han-Shuang Xiao
- The Institute of Chemical Physics, School of Science, and School of Aerospace Science and Engineering, Beijing Institute of Technology, Beijing 100081, People's Republic of China
| | - Yun-Hong Zhang
- The Institute of Chemical Physics, School of Science, and School of Aerospace Science and Engineering, Beijing Institute of Technology, Beijing 100081, People's Republic of China
| |
Collapse
|
13
|
Zhao LJ, Wang F, Zhang K, Zeng QX, Zhang YH. Deliquescence and Efflorescence Processes of Aerosol Particles Studied byin situFTIR and Raman Spectroscopy. CHINESE J CHEM PHYS 2008. [DOI: 10.1088/1674-0068/21/01/1-11] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
14
|
FTIR-ATR in situ observation on the efflorescence and deliquescence processes of Mg(NO3)2 aerosols. ACTA ACUST UNITED AC 2008. [DOI: 10.1007/s11426-007-0059-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
15
|
Woods E, Kim HS, Wivagg CN, Dotson SJ, Broekhuizen KE, Frohardt EF. Phase transitions and surface morphology of surfactant-coated aerosol particles. J Phys Chem A 2007; 111:11013-20. [PMID: 17929784 DOI: 10.1021/jp074848m] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Probe molecule spectroscopy and hygroscopic growth curves characterize the morphology of surfactant-coated aerosol particles as a function of relative humidity (RH). This study focuses on particles composed of either potassium iodide or sodium chloride and sodium dodecyl sulfate (SDS). At high RH, these mixed particles assume a reverse micelle type structure, and at low RH, they comprise a solid core of either KI or NaCl coated with SDS and water. The deliquescence relative humidity (DRH) and efflorescence relative humidity (ERH) of the inorganic fraction of the mixed particles are very similar to those of the pure salts. The surface polarity and morphology sampled by the coumarin 314 probe molecule ranges from that of a water-organic interface to that of an ionic surface and depends strongly on the RH and the amount of SDS. When the SDS coverage of the droplet just prior to efflorescence reaches approximately one monolayer, a thin soap film persists on the surface to values of RH much lower than the ERH. Both the electronic spectroscopy and photoelectric charging efficiency show a separate efflorescence for this layer at RH < 5%. The spectroscopy further reveals that there is a hysteresis associated with this low RH phase transition for both KI and NaCl cores.
Collapse
Affiliation(s)
- Ephraim Woods
- Department of Chemistry, Colgate University, 13 Oak Drive, Hamilton, New York 13346, USA.
| | | | | | | | | | | |
Collapse
|
16
|
Reid JP, Meresman H, Mitchem L, Symes† R. Spectroscopic studies of the size and composition of single aerosol droplets. INT REV PHYS CHEM 2007. [DOI: 10.1080/01442350601081899] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
|
17
|
Li XH, Wang F, Lu PD, Dong JL, Wang LY, Zhang YH. Confocal Raman Observation of the Efflorescence/Deliquescence Processes of Individual NaNO3 Particles on Quartz. J Phys Chem B 2006; 110:24993-8. [PMID: 17149921 DOI: 10.1021/jp064221o] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Confocal Raman spectroscopy was used to study the structural changes of bulk NaNO3 solutions with molar water-to-solute ratios (WSRs) of 54.0-12.3 and NaNO3 droplets (10-100 microm) with WSRs of 9.5-1.0 on a quartz substrate. Upon reduction of the WSR, a blue shift of the symmetric stretching band (nu(1)(NO3-)) from approximately 1048 to approximately 1058 cm(-1) was observed in the confocal Raman spectra with high signal-to-noise ratios. Accordingly, the full width at half-height of the nu(1)(NO3-) band increased from approximately 8.4 cm-1 for the dilute solution (WSR = 54.0) to approximately 15.6 cm-1 for the extremely supersaturated droplet (WSR = 1.0), suggesting the formation of contact ion pairs with different structures. For the O-H stretching band, the ratio of weak hydrogen-bonding components to strong ones, i.e., I(3488)/I(3256), increased from approximately 1.2 at WSR = 54.0 to approximately 7.3 at WSR = 1.0, indicating that the strong hydrogen bonds were heavily destroyed between water molecules especially in the supersaturated droplets. In the humidifying process, two hygroscopic behaviors were observed depending on the morphology of solid NaNO3 particles. No surface water was detected for a solid NaNO3 particle with rhombohedral shape at relative humidities (RHs) below 86%. When the RH increased from 86% to 93%, it suddenly absorbed water and turned into a solution droplet. For a maple-leaf-shaped NaNO3 particle with a rough surface, however, a trace of residual water originally remained on the rough surface even at very low RH according to its Raman spectrum. Its initial water uptake from the ambient occurred at approximately 70% RH. The small amount of initially adsorbed water induced surface rearrangement of the maple-leaf-shaped particle. A further increase of RH made the particle gradually turn into a regular solid core swathed in a solution layer. Eventually, it completely deliquesced in the RH region of 86-93%, similar to the case of the NaNO3 particle with rhombohedral shape.
Collapse
Affiliation(s)
- Xiao-Hong Li
- The Institute for Chemical Physics, Beijing Institute of Technology, Beijing, China 100081
| | | | | | | | | | | |
Collapse
|
18
|
Mitchem L, Buajarern J, Hopkins RJ, Ward AD, Gilham RJJ, Johnston RL, Reid JP. Spectroscopy of Growing and Evaporating Water Droplets: Exploring the Variation in Equilibrium Droplet Size with Relative Humidity. J Phys Chem A 2006; 110:8116-25. [PMID: 16805498 DOI: 10.1021/jp061135f] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
We demonstrate that the thermodynamic properties of a single liquid aerosol droplet can be explored through the combination of a single-beam gradient force optical trap with Raman spectroscopy. A single aqueous droplet, 2-6 microm in radius, can be trapped in air indefinitely and the response of the particle to variations in relative humidity investigated. The Raman spectrum provides a unique fingerprint of droplet composition, temperature, and size. Spontaneous Raman scattering is shown to be consistent with that from a bulk phase sample, with the shape of the OH stretching band dependent on the concentration of sodium chloride in the aqueous phase and on the polarization of the scattered light. Stimulated Raman scattering at wavelengths commensurate with whispering gallery modes is demonstrated to provide a method for determining the size of the trapped droplet with nanometer precision and with a time resolution of 1 s. The polarization dependence of the stimulated scatter is consistent with the dependence observed for the spontaneous scatter from the droplet. By characterizing the spontaneous and stimulated Raman scattering from the droplet, we demonstrate that it is possible to measure the equilibrium size and composition of an aqueous droplet with variation in relative humidity. For this benchmark study we investigate the variation in equilibrium size with relative humidity for a simple binary sodium chloride/aqueous aerosol, a typical representative inorganic/aqueous aerosol that has been studied extensively in the literature. The measured equilibrium sizes are shown to be in excellent agreement with the predictions of Köhler theory. We suggest that this approach could provide an important new strategy for characterizing the thermodynamic properties and kinetics of transformation of aerosol particles.
Collapse
Affiliation(s)
- Laura Mitchem
- School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom
| | | | | | | | | | | | | |
Collapse
|
19
|
Abstract
▪ Abstract Aerosols play a critical role in a diverse range of scientific disciplines. To characterize and quantify their role, it is essential that the fundamental details of mass and heat transfer between the aerosol particle and surrounding medium, the properties of multiphase droplets, and the coagulation of aerosol droplets be more fully explored. Elastic and inelastic light scattering can provide information on particle size, composition, morphology, and temperature. In addition, spatial inhomogeneities in composition and temperature can be probed. We review how such techniques can be used to develop an understanding of the chemical and physical dynamics of a single aerosol droplet.
Collapse
Affiliation(s)
- Jonathan P Reid
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, United Kingdom.
| | | |
Collapse
|
20
|
Hopkins RJ, Reid JP. A Comparative Study of the Mass and Heat Transfer Dynamics of Evaporating Ethanol/Water, Methanol/Water, and 1-Propanol/Water Aerosol Droplets. J Phys Chem B 2006; 110:3239-49. [PMID: 16494335 DOI: 10.1021/jp056523g] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The mass and heat transfer dynamics of evaporating multicomponent alcohol/water droplets have been probed experimentally by examining changes in the near surface droplet composition and average droplet temperature using cavity-enhanced Raman scattering (CERS) and laser-induced fluorescence (LIF). The CERS technique provides a sensitive measure of the concentration of the volatile alcohol component in the outer shell of the droplet, due to the exponential relationship between CERS intensity and species concentration. Such volatile droplets, which are probed on a millisecond time scale, evaporate nonisothermally, resulting in both temperature and concentration gradients, as confirmed by comparisons between experimental measurements and quasi-steady state model calculations. An excellent agreement between the experimental evaporation trends and quasi-steady state model predictions is observed. An unexpectedly slow evaporation rate is observed for the evaporation of 1-propanol from a multicomponent droplet when compared to the model; possible explanations for this observation are discussed. In addition, the propagation depth of the CERS signal, and, therefore, the region of the droplet from which compositional measurements are made, can be estimated. Such measurements, when considered in conjunction with quasi-steady state theory, can allow droplet temperature gradients to be measured and vapor pressures and activity coefficients of components within the droplet to be determined.
Collapse
Affiliation(s)
- Rebecca J Hopkins
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
| | | |
Collapse
|