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Huang-Fu ZC, Tkachenko NV, Qian Y, Zhang T, Brown JB, Harutyunyan A, Chen G, Rao Y. Conical Intersections at Interfaces Revealed by Phase-Cycling Interface-Specific Two-Dimensional Electronic Spectroscopy (i2D-ES). J Am Chem Soc 2024. [PMID: 39037260 DOI: 10.1021/jacs.4c06035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/23/2024]
Abstract
Conical intersections (CIs) hold significant stake in manipulating and controlling photochemical reaction pathways of molecules at interfaces and surfaces by affecting molecular dynamics therein. Currently, there is no tool for characterizing CIs at interfaces and surfaces. To this end, we have developed phase-cycling interface-specific two-dimensional electronic spectroscopy (i2D-ES) and combined it with advanced computational modeling to explore nonadiabatic CI dynamics of molecules at the air/water interface. Specifically, we integrated the phase locked pump pulse pair with an interface-specific electronic probe to obtain the two-dimensional interface-specific responses. We demonstrate that the nonadiabatic transitions of an interface-active azo dye molecule that occur through the CIs at the interface have different kinetic pathways from those in the bulk water. Upon photoexcitation, two CIs are present: one from an intersection of an optically active S2 state with a dark S1 state and the other from the intersection of the progressed S1 with the ground state S0. We find that the molecular conformations in the ground state are different for interfacial molecules. The interfacial molecules are intimately correlated with the locally populated excited state S2 being farther away from the CI region. This leads to slower nonadiabatic dynamics at the interface than in bulk water. Moreover, we show that the nonadiabatic transition from the S1 dark state to the ground state is significantly longer at the interface than that in the bulk, which is likely due to the orientationally restricted configuration of the excited state at the interface. Our findings suggest that orientational configurations of molecules manipulate reaction pathways at interfaces and surfaces.
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Affiliation(s)
- Zhi-Chao Huang-Fu
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
| | - Nikolay V Tkachenko
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
| | - Yuqin Qian
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
| | - Tong Zhang
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
| | - Jesse B Brown
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
| | - Avetik Harutyunyan
- Honda Research Institute, USA, Inc., San Jose, California 95134, United States
| | - Gugang Chen
- Honda Research Institute, USA, Inc., San Jose, California 95134, United States
| | - Yi Rao
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
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2
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Zeng WW, Luo T, Xu P, Zhou C, Yang X, Ren Z. Vibronic coupling of Rhodamine 6G molecules studied by doubly resonant sum frequency generation spectroscopy with narrowband infrared and broadband visible. J Chem Phys 2024; 160:024705. [PMID: 38205850 DOI: 10.1063/5.0179871] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Accepted: 11/30/2023] [Indexed: 01/12/2024] Open
Abstract
Doubly resonant sum frequency generation (DR-SFG) serves as a potent characteristic technique for probing the electronic spectra and vibronic coupling of molecules on surfaces. In this study, we successfully developed a novel infrared (IR)-white light (WL) DR-SFG spectroscopy based on narrowband IR and tunable broadband WL. This novel method was employed to explore the excitation spectrum and vibronic couplings of sub-monolayer Rhodamine 6G molecules. Our findings elucidate that the xanthene skeleton vibrational modes exhibit strong coupling with the S0-S1 electronic transition. Notably, we observed not only the 0-0 transition of the S0-S1 electronic continuum but also the 0-1 transition, a first time observation in the realm of DR-SFG spectroscopy. This advanced DR-SFG spectroscopy methodology facilitates a more sensitive examination of electronic spectra and the coupling between electronic transitions and vibrational modes, heralding a significant advancement in the understanding of molecular interactions on surfaces.
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Affiliation(s)
- Wei-Wang Zeng
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, People's Republic of China
- University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049, People's Republic of China
| | - Ting Luo
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, People's Republic of China
- Research Center for Industries of the Future and School of Engineering, Westlake University, Hangzhou 310030, People's Republic of China
| | - Peng Xu
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, People's Republic of China
- Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, People's Republic of China
| | - Chuanyao Zhou
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, People's Republic of China
| | - Xueming Yang
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, People's Republic of China
- Department of Chemistry, Southern University of Science and Technology, 1088 Xueyuan Road, Guangdong, Shenzhen 518055, People's Republic of China
| | - Zefeng Ren
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, People's Republic of China
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Brown JB, Qian Y, Huang-Fu ZC, Zhang T, Wang H, Rao Y. In Situ Probing of the Surface Properties of Droplets in the Air. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023. [PMID: 37497860 DOI: 10.1021/acs.langmuir.3c00875] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/28/2023]
Abstract
Surface properties of nanodroplets and microdroplets are intertwined with their immense applicability in biology, medicine, production, catalysis, the environment, and the atmosphere. However, many means for analyzing droplets and their surfaces are destructive, non-interface-specific, not conducted under ambient conditions, require sample substrates, conducted ex situ, or a combination thereof. For these reasons, a technique for surface-selective in situ analyses under any condition is necessary. This feature article presents recent developments in second-order nonlinear optical scattering techniques for the in situ interfacial analysis of aerosol droplets in the air. First, we describe the abundant utilization of such droplets across industries and how their unique surface properties lead to their ubiquitous usage. Then, we describe the fundamental properties of droplets and their surfaces followed by common methods for their study. We next describe the fundamental principles of sum-frequency generation (SFG) spectroscopy, the Langmuir adsorption model, and how they are used together to describe adsorption processes at planar liquid and droplet surfaces. We also discuss the history of developments of second-order scattering from droplets suspended in dispersive media and introduce second-harmonic scattering (SHS) and sum-frequency scattering (SFS) spectroscopies. We then go on to outline the developments of SHS, electronic sum-frequency scattering (ESFS), and vibrational sum-frequency scattering (VSFS) from droplets in the air and discuss the fundamental insights about droplet surfaces that the techniques have provided. Finally, we describe some of the areas of nonlinear scattering from airborne droplets which need improvement as well as potential future directions and utilizations of SHS, ESFS, and VSFS throughout environmental systems, interfacial chemistry, and fundamental physics. The goal of this feature article is to spread knowledge about droplets and their unique surface properties as well as introduce second-order nonlinear scattering to a broad audience who may be unaware of recent progress and advancements in their applicability.
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Affiliation(s)
- Jesse B Brown
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
| | - Yuqin Qian
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
| | - Zhi-Chao Huang-Fu
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
| | - Tong Zhang
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
- Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Hui Wang
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
| | - Yi Rao
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
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4
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Shulenberger KE, Jilek MR, Sherman SJ, Hohman BT, Dukovic G. Electronic Structure and Excited State Dynamics of Cadmium Chalcogenide Nanorods. Chem Rev 2023; 123:3852-3903. [PMID: 36881852 DOI: 10.1021/acs.chemrev.2c00676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
Abstract
The cylindrical quasi-one-dimensional shape of colloidal semiconductor nanorods (NRs) gives them unique electronic structure and optical properties. In addition to the band gap tunability common to nanocrystals, NRs have polarized light absorption and emission and high molar absorptivities. NR-shaped heterostructures feature control of electron and hole locations as well as light emission energy and efficiency. We comprehensively review the electronic structure and optical properties of Cd-chalcogenide NRs and NR heterostructures (e.g., CdSe/CdS dot-in-rods, CdSe/ZnS rod-in-rods), which have been widely investigated over the last two decades due in part to promising optoelectronic applications. We start by describing methods for synthesizing these colloidal NRs. We then detail the electronic structure of single-component and heterostructure NRs and follow with a discussion of light absorption and emission in these materials. Next, we describe the excited state dynamics of these NRs, including carrier cooling, carrier and exciton migration, radiative and nonradiative recombination, multiexciton generation and dynamics, and processes that involve trapped carriers. Finally, we describe charge transfer from photoexcited NRs and connect the dynamics of these processes with light-driven chemistry. We end with an outlook that highlights some of the outstanding questions about the excited state properties of Cd-chalcogenide NRs.
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Affiliation(s)
| | - Madison R Jilek
- Department of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Skylar J Sherman
- Department of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Benjamin T Hohman
- Department of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Gordana Dukovic
- Department of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States.,Renewable and Sustainable Energy Institute (RASEI), University of Colorado Boulder, Boulder, Colorado 80309, United States.,Materials Science and Engineering, University of Colorado Boulder, Boulder, Colorado 80303, United States
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5
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Two-dimensional electronic-vibrational sum frequency spectroscopy for interactions of electronic and nuclear motions at interfaces. Proc Natl Acad Sci U S A 2021; 118:2100608118. [PMID: 34417312 DOI: 10.1073/pnas.2100608118] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Interactions of electronic and vibrational degrees of freedom are essential for understanding excited-states relaxation pathways of molecular systems at interfaces and surfaces. Here, we present the development of interface-specific two-dimensional electronic-vibrational sum frequency generation (2D-EVSFG) spectroscopy for electronic-vibrational couplings for excited states at interfaces and surfaces. We demonstrate this 2D-EVSFG technique by investigating photoexcited interface-active (E)-4-((4-(dihexylamino) phenyl)diazinyl)-1-methylpyridin-1- lum (AP3) molecules at the air-water interface as an example. Our 2D-EVSFG experiments show strong vibronic couplings of interfacial AP3 molecules upon photoexcitation and subsequent relaxation of a locally excited (LE) state. Time-dependent 2D-EVSFG experiments indicate that the relaxation of the LE state, S 2, is strongly coupled with two high-frequency modes of 1,529.1 and 1,568.1 cm-1 Quantum chemistry calculations further verify that the strong vibronic couplings of the two vibrations promote the transition from the S 2 state to the lower excited state S 1 We believe that this development of 2D-EVSFG opens up an avenue of understanding excited-state dynamics related to interfaces and surfaces.
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6
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Premadasa UI, Bible AN, Morrell-Falvey JL, Doughty B, Ma YZ. Spatially co-registered wide-field nonlinear optical imaging of living and complex biosystems in a total internal reflection geometry. Analyst 2021; 146:3062-3072. [PMID: 33949432 DOI: 10.1039/d1an00129a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Nonlinear optical microscopy that leverages an objective based total internal reflection (TIR) excitation scheme is an attractive means for rapid, wide-field imaging with enhanced surface sensitivity. Through select combinations of distinct modalities, one can, in principle, access complementary chemical and structural information for various chemical species near interfaces. Here, we report a successful implementation of such a wide-field nonlinear optical microscope system, which combines coherent anti-Stokes Raman scattering (CARS), two-photon fluorescence (TPF), second harmonic generation (SHG), and sum frequency generation (SFG) modalities on the same platform. The intense optical fields needed to drive these high order nonlinear optical processes are achieved through the use of femtosecond pulsed light in combination with the intrinsic field confinement induced by TIR over a large field of view. The performance of our multimodal microscope was first assessed through the experimental determination of its chemical fidelity, intensity and polarization dependences, and spatial resolution using a set of well-defined model systems. Subsequently, its unique capabilities were validated through imaging complex biological systems, including Hydrangea quercifolia pollen grains and Pantoea sp. YR343 bacterial cells. Specifically, the spatial distribution of different molecular groups in the former was visualized via vibrational contrast mechanisms of CARS, whereas co-registered TPF imaging allowed the identification of spatially localized intrinsic fluorophores. We further demonstrate the feasibility of our microscope for wide-field CARS imaging on live cells through independent characterization of cell viability using spatially co-registered TPF imaging. This approach to TIR enabled wide-field imaging is expected to provide new insights into bacterial strains and their interactions with other species in the rhizosphere in a time-resolved and chemically selective manner.
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Affiliation(s)
- Uvinduni I Premadasa
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
| | - Amber N Bible
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | | | - Benjamin Doughty
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
| | - Ying-Zhong Ma
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
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7
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Cotton DE, Roberts ST. Sensitivity of sum frequency generation experimental conditions to thin film interference effects. J Chem Phys 2021; 154:114704. [PMID: 33752341 DOI: 10.1063/5.0039897] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Sum-frequency generation (SFG) spectroscopy has furthered our understanding of the chemical interfaces that guide key processes in biology, catalysis, environmental science, and energy conversion. However, interpreting SFG spectra of systems containing several internal interfaces, such as thin film electronics, electrochemical cells, and biofilms, is challenging as different interfaces within these structures can produce interfering SFG signals. One potential way to address this issue is to carefully select experimental conditions that amplify the SFG signal of an interface of interest over all others. In this report, we investigate a model two-interface system to assess our ability to isolate the SFG signal from each interface. For SFG experiments performed in a reflective geometry, we find that there are few experimental conditions under which the SFG signal originating from either interface can be amplified and isolated from the other. However, by performing several measurements under conditions that alter their interference, we find that we can reconstruct each signal even in cases where the SFG signal from one interface is more than an order of magnitude smaller than its counterpart. The number of spectra needed for this reconstruction varies depending on the signal-to-noise level of the SFG dataset and the degree to which different experiments in a dataset vary in their sensitivity to each interface. Taken together, our work provides general guidelines for designing experimental protocols that can isolate SFG signals stemming from a particular region of interest within complex samples.
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Affiliation(s)
- Daniel E Cotton
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Sean T Roberts
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, USA
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8
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Deng GH, Wei Q, Qian Y, Zhang T, Leng X, Rao Y. Development of interface-/surface-specific two-dimensional electronic spectroscopy. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2021; 92:023104. [PMID: 33648131 DOI: 10.1063/5.0019564] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Accepted: 01/26/2021] [Indexed: 06/12/2023]
Abstract
Structures, kinetics, and chemical reactivities at interfaces and surfaces are key to understanding many of the fundamental scientific problems related to chemical, material, biological, and physical systems. These steady-state and dynamical properties at interfaces and surfaces require even-order techniques with time-resolution and spectral-resolution. Here, we develop fourth-order interface-/surface-specific two-dimensional electronic spectroscopy, including both two-dimensional electronic sum frequency generation (2D-ESFG) spectroscopy and two-dimensional electronic second harmonic generation (2D-ESHG) spectroscopy, for structural and dynamics studies of interfaces and surfaces. The 2D-ESFG and 2D-ESHG techniques were based on a unique laser source of broadband short-wave IR from 1200 nm to 2200 nm from a home-built optical parametric amplifier. With the broadband short-wave IR source, surface spectra cover most of the visible light region from 480 nm to 760 nm. A translating wedge-based identical pulses encoding system (TWINs) was introduced to generate a phase-locked pulse pair for coherent excitation in the 2D-ESFG and 2D-ESHG. As an example, we demonstrated surface dark states and their interactions of the surface states at p-type GaAs (001) surfaces with the 2D-ESFG and 2D-ESHG techniques. These newly developed time-resolved and interface-/surface-specific 2D spectroscopies would bring new information for structure and dynamics at interfaces and surfaces in the fields of the environment, materials, catalysis, and biology.
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Affiliation(s)
- Gang-Hua Deng
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, USA
| | - Qianshun Wei
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, USA
| | - Yuqin Qian
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, USA
| | - Tong Zhang
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, USA
| | - Xuan Leng
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, USA
| | - Yi Rao
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, USA
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9
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Blake MJ, Colon BA, Calhoun TR. Leaving the Limits of Linearity for Light Microscopy. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2020; 124:24555-24565. [PMID: 34306294 PMCID: PMC8301257 DOI: 10.1021/acs.jpcc.0c07501] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Nonlinear microscopy has enabled additional modalities for chemical contrast, deep penetration into biological tissues, and the ability to collect dynamics on ultrafast timescales across heterogenous samples. The additional light fields introduced to a sample offer seemingly endless possibilities for variation to optimize and customize experimentation and the extraction of physical insight. This perspective highlights three areas of growth in this diverse field: the collection of information across multiple timescales, the selective imaging of interfacial chemistry, and the exploitation of quantum behavior for future imaging directions. Future innovations will leverage the work of the studies reviewed here as well as address the current challenges presented.
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Affiliation(s)
- Marea J Blake
- Department of Chemistry, University of Tennessee, Knoxville, TN 37996
| | - Brandon A Colon
- Department of Chemistry, University of Tennessee, Knoxville, TN 37996
| | - Tessa R Calhoun
- Department of Chemistry, University of Tennessee, Knoxville, TN 37996
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10
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Qian Y, Deng GH, Rao Y. In Situ Spectroscopic Probing of Polarity and Molecular Configuration at Aerosol Particle Surfaces. J Phys Chem Lett 2020; 11:6763-6771. [PMID: 32787224 DOI: 10.1021/acs.jpclett.0c02013] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The growth of aerosol particles in the atmosphere is related to chemical reactions in the gas and particle phases and at aerosol particle surfaces. While research regarding the gas and particle phases of aerosols is well-documented, physical properties and chemical reactivities at aerosol particle surfaces have not been studied extensively but have long been recognized. In particular, in situ measurements of aerosol particle surfaces are just emerging. The main reason is a lack of suitable surface-specific analytical techniques for direct measurements of aerosol particles under ambient conditions. Here we develop in situ surface-specific electronic sum frequency scattering (ESFS) to directly identify spectroscopic behaviors of molecules at aerosol particle surfaces. As an example, we applied an ESFS probe, malachite green (MG). We examined electronic spectra of MG at aerosol particle surfaces and found that the polarity of the surfaces is less polar than that in bulk. Our quantitative orientational analysis shows that MG is orientated with a polar angle of 25°-35° at the spherical particle surfaces of aerosols. The adsorption free energy of MG at the aerosol surfaces was found to be -20.75 ± 0.32 kJ/mol, which is much lower than that at the air/water interface. These results provide new insights into aerosol particle surfaces for further understanding the formation of secondary organic aerosols in the atmosphere.
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Affiliation(s)
- Yuqin Qian
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
| | - Gang-Hua Deng
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
| | - Yi Rao
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
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11
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Doughty B, Premadasa UI, Cahill JF, Webb AB, Morrell-Falvey JL, Khalid M, Retterer ST, Ma YZ. Total internal reflection enabled wide-field coherent anti-Stokes Raman scattering microscopy. OPTICS LETTERS 2020; 45:3087-3090. [PMID: 32479466 DOI: 10.1364/ol.45.003087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 04/23/2020] [Indexed: 06/11/2023]
Abstract
Wide-field coherent anti-Stokes Raman scattering (CARS) microscopy offers an attractive means for the rapid and simultaneous acquisition of vibrationally resolved images across a large field of view. A major challenge in the implementation lies in how to achieve sufficiently strong excitation fields necessary to drive the third-order optical responses over the large focal region. Here, we report a new wide-field CARS microscope enabled by a total internal reflection excitation scheme using a femtosecond Ti:Sapphire oscillator to generate pump and broadband near-infrared Stokes pulses. The spectrally broad Stokes pulse, in combination with its inherent chirp, offers not only access to a wide range of Raman modes spanning ∼1000 to ∼3500cm-1 but also a straightforward means to select vibrational transitions within this range by simply varying the time delay between the pulses. The unique capabilities of this wide-field CARS microscope were validated by acquiring high-quality CARS images from the model and complex biological samples on conventional microscope coverslips.
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12
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Colon BA, Hassan MR, Saleheen A, Baker CA, Calhoun TR. Total Internal Reflection Transient Absorption Microscopy: An Online Detection Method for Microfluidics. J Phys Chem A 2020; 124:4160-4170. [PMID: 32338897 DOI: 10.1021/acs.jpca.9b12046] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Microreactors have garnered widespread attention for their tunability and precise control of synthetic parameters to efficiently produce target species. Despite associated advances, a lack of online detection and optimization methods has stalled the progression of microfluidic reactors. Here we employ and characterize a total internal reflection transient absorption microscopy (TIRTAM) instrument to image excited state dynamics on a continuous flow device. The experiments presented demonstrate the capability to discriminate between different chromophores as well as in differentiating the effects of local chemical environments that a chromophore experiences. This work presents the first such online transient absorption measurements and provides a new direction for the advancement and optimization of chemical reactions in microfluidic devices.
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Affiliation(s)
- Brandon A Colon
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Muhammad Redwan Hassan
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Amirus Saleheen
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Christopher A Baker
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Tessa R Calhoun
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
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13
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Kelley AM. Can second order nonlinear spectroscopies selectively probe optically “dark” surface states in small semiconductor nanocrystals? J Chem Phys 2020; 152:120901. [DOI: 10.1063/1.5139208] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Affiliation(s)
- Anne Myers Kelley
- Chemistry and Chemical Biology, University of California, Merced, 5300 North Lake Rd., Merced, California 95343, USA
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14
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Deng GH, Qian Y, Wei Q, Zhang T, Rao Y. Interface-Specific Two-Dimensional Electronic Sum Frequency Generation Spectroscopy. J Phys Chem Lett 2020; 11:1738-1745. [PMID: 32045523 DOI: 10.1021/acs.jpclett.0c00157] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
High even-order surface/interface specific spectroscopy has the potential to provide more structural and dynamical information about surfaces and interfaces. In this work, we developed a novel fourth-order interface-specific two-dimensional electronic sum frequency generation (2D-ESFG) for structures and dynamics at surfaces and interfaces. A translating wedge-based identical pulses encoding system (TWINs) was introduced to generate phase-locked pulse pairs for coherent pump beams in 2D-ESFG. As a proof-of-principle experiment, fourth-order 2D-ESFG spectroscopy was used to demonstrate couplings of surface states for both n-type and p-type GaAs (100). We found surface dark state within the bandgap of the GaAs in 2D-ESFG spectra, which could not be observed in one-dimensional ESFG spectra. To our best knowledge, this is a first demonstration of interface-specific two-dimensional electronic spectroscopy. The development of the 2D-ESFG spectroscopy will provide new structural probes of spectral diffusion, conformational dynamics, energy transfer, and charge transfer for surfaces and interfaces.
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Affiliation(s)
- Gang-Hua Deng
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
| | - Yuqin Qian
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
| | - Qianshun Wei
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
| | - Tong Zhang
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
| | - Yi Rao
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
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15
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Baturin V, Lepeshkin S, Bushlanova N, Uspenskii Y. Atomistic origins of charge traps in CdSe nanoclusters. Phys Chem Chem Phys 2020; 22:26299-26305. [PMID: 33175940 DOI: 10.1039/d0cp05139j] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Constructing trap-free nanomaterials is a challenge that requires a fundamental understanding of the trapping phenomenon, especially the structural features responsible for electronic localization. Previously, such trapping configurations were explored by manual insertion of surface defects according to researchers' intuition, e.g. Cd-Se-Cd moiety [Houtepen et al., Chem. Mater., 2017, 29, 752]. In this study we report new types of traps in CdSe nanoclusters, including the metal-based one, which were found using a novel, unbiased approach. Namely, we screened a vast number of globally optimized CdnSem clusters (n,m ≤ 15) for localized electronic states. These systems model the wide diversity of defects in unpassivated areas of a nanocluster surface, while still being accessible for ab initio global optimization. Despite this variety, all 39 traps we found fall into 3 types, including two new ones. Such a reduction shows the universal character of discovered traps, irrelevant to the global structure of a cluster. Many of these traps not only have newly reported atomic arrangements, but also original confinement mechanisms which are explained at the atomistic level. We found that the relaxation and global optimization of the cluster structure greatly reduce the number of traps and push the trap energies from midgap to the near-gap edge positions, which agrees with the spectral measurements of II-VI semiconductor nanocrystals.
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Affiliation(s)
- Vladimir Baturin
- Skolkovo Institute of Science and Technology, Bolshoy Boulevard 30, bld. 1, Moscow 121205, Russia.
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