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State-of-the-Art Physical Chemistry and Chemical Physics in Korea

A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Physical Chemistry and Chemical Physics".

Deadline for manuscript submissions: closed (30 April 2023) | Viewed by 24097

Special Issue Editors

1. Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
2. Director, Center for Advanced Reaction Dynamics, Institute for Basic Science, Daejeon 34141, Republic of Korea
Interests: molecular structural dynamics; protein structural dynamics; time-resolved scattering; time-resolved spectroscopy; X-ray liquidography; femtochemistry; ultrafast phenomena
Special Issues, Collections and Topics in MDPI journals
Department of Chemistry, Yonsei University, Seoul 03722, Republic of Korea
Interests: ultrafast dynamics; structural dynamics; time-resolved X-ray spectroscopy; solar-fuel generation; photocatalyst; photoelectrochemistry
Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea
Interests: computational chemistry; multiscale modeling; materials simulation; electrified interface; electrochemistry
Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea
Interests: quantum dynamics; exciton transfer; molecular dynamics; simulation; organic

Special Issue Information

Dear Colleagues, 

In this International Journal of Molecular Sciences (IJMS) special issue, new and original research that has broad readership from all aspects of physical chemistry and chemical physics is published. For publication here, research must provide significant new innovation and insight in the physical chemistry and chemical physics fields with a focus on molecular research. The submitted articles will be judged by the Editors and peer-reviewers. Topics include, but are not limited to, the following:

  1. Intermolecular forces that act upon the physical properties of materials
  2. Reaction kinetics on the rate of a reaction
  3. The identity of ions and the electrical conductivity of materials
  4. Surface science and the electrochemistry of cell membranes
  5. Probing the structure and dynamics of ions, free radicals, polymers, clusters, and molecules
  6. Chemical structures and reactions at the quantum mechanical level
  7. The structure and reactivity of gas-phase ions and radicals
  8. Energy/charge transfer dynamics in organic/inorganic materials
  9. Physical processes in nanomaterials

Prof. Dr. Hyotcherl Ihee
Prof. Dr. Tae Kyu Kim
Prof. Dr. Hyungjun Kim
Prof. Dr. Young Min Rhee 
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. International Journal of Molecular Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. There is an Article Processing Charge (APC) for publication in this open access journal. For details about the APC please see here. Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • heterogeneous structures
  • alignment and surface phenomena
  • quantum theory
  • mathematical physics
  • statistical and classical mechanics
  • molecular structure
  • chemical kinetics
  • laser physics
  • dynamics
  • kinetics
  • photochemistry
  • spectroscopy
  • exciton dynamics
  • statistical mechanics
  • thermodynamics
  • electrochemistry
  • catalysis
  • surface science
  • quantum mechanics
  • theoretical developments
  • fundamental aspects of catalysis
  • solar energy conversion
  • polymer dynamics

Published Papers (13 papers)

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Research

Jump to: Review

8 pages, 3304 KiB  
Article
Interfacial-Water-Modulated Photoluminescence of Single-Layer WS2 on Mica
by Yanghee Kim, Haneul Kang, Myeongin Song, Hyuksang Kwon and Sunmin Ryu
Int. J. Mol. Sci. 2023, 24(4), 3492; https://doi.org/10.3390/ijms24043492 - 09 Feb 2023
Cited by 1 | Viewed by 1464
Abstract
Because of their bandgap tunability and strong light–matter interactions, two-dimensional (2D) semiconductors are considered promising candidates for next-generation optoelectronic devices. However, their photophysical properties are greatly affected by their surrounding environment because of their 2D nature. In this work, we report that the [...] Read more.
Because of their bandgap tunability and strong light–matter interactions, two-dimensional (2D) semiconductors are considered promising candidates for next-generation optoelectronic devices. However, their photophysical properties are greatly affected by their surrounding environment because of their 2D nature. In this work, we report that the photoluminescence (PL) of single-layer WS2 is substantially affected by interfacial water that is inevitably present between it and the supporting mica substrates. Using PL spectroscopy and wide-field imaging, we show that the emission signals from A excitons and their negative trions decreased at distinctively different rates with increasing excitation power, which could be attributed to the more efficient annihilation between excitons than between trions. By gas-controlled PL imaging, we also prove that the interfacial water converted the trions into excitons by depleting native negative charges through an oxygen reduction reaction, which rendered the excited WS2 more susceptible to nonradiative decay via exciton–exciton annihilation. Understanding the role of nanoscopic water in complex low-dimensional materials will eventually contribute to devising their novel functions and related devices. Full article
(This article belongs to the Special Issue State-of-the-Art Physical Chemistry and Chemical Physics in Korea)
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11 pages, 1615 KiB  
Article
Excited State Intramolecular Proton Transfer Dynamics of Derivatives of the Green Fluorescent Protein Chromophore
by Junghwa Lee, Pyoungsik Shin, Pi-Tai Chou and Taiha Joo
Int. J. Mol. Sci. 2023, 24(4), 3448; https://doi.org/10.3390/ijms24043448 - 09 Feb 2023
Viewed by 1621
Abstract
Excited state intramolecular proton transfer (ESIPT) dynamics of the o-hydroxy analogs of the green fluorescent protein (GFP) chromophore have been investigated by time-resolved spectroscopies and theoretical calculations. These molecules comprise an excellent system to investigate the effect of electronic properties on the [...] Read more.
Excited state intramolecular proton transfer (ESIPT) dynamics of the o-hydroxy analogs of the green fluorescent protein (GFP) chromophore have been investigated by time-resolved spectroscopies and theoretical calculations. These molecules comprise an excellent system to investigate the effect of electronic properties on the energetics and dynamics of ESIPT and to realize applications in photonics. Time-resolved fluorescence with high enough resolution was employed to record the dynamics and the nuclear wave packets in the excited product state exclusively in conjunction with quantum chemical methods. The ESIPT are ultrafast occurring in 30 fs for the compounds employed in this work. Although the ESIPT rates are not affected by the electronic properties of the substituents suggesting barrierless reaction, the energetics, their structures, subsequent dynamics following ESIPT, and possibly the product species are distinct. The results attest that fine tuning of the electronic properties of the compounds may modify the molecular dynamics of ESIPT and subsequent structural relaxation to achieve brighter emitters with broad tuning capabilities. Full article
(This article belongs to the Special Issue State-of-the-Art Physical Chemistry and Chemical Physics in Korea)
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13 pages, 4135 KiB  
Article
Formation and Thermal Stability of Ordered Self-Assembled Monolayers by the Adsorption of Amide-Containing Alkanethiols on Au(111)
by Young Ji Son, Jin Wook Han, Hungu Kang, Sicheon Seong, Seulki Han, Shoichi Maeda, Shunta Chikami, Tomohiro Hayashi, Masahiko Hara and Jaegeun Noh
Int. J. Mol. Sci. 2023, 24(4), 3241; https://doi.org/10.3390/ijms24043241 - 07 Feb 2023
Cited by 4 | Viewed by 1982
Abstract
We examined the surface structure, binding conditions, electrochemical behavior, and thermal stability of self-assembled monolayers (SAMs) on Au(111) formed by N-(2-mercaptoethyl)heptanamide (MEHA) containing an amide group in an inner alkyl chain using scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and cyclic [...] Read more.
We examined the surface structure, binding conditions, electrochemical behavior, and thermal stability of self-assembled monolayers (SAMs) on Au(111) formed by N-(2-mercaptoethyl)heptanamide (MEHA) containing an amide group in an inner alkyl chain using scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV) to understand the effects of an internal amide group as a function of deposition time. The STM study clearly showed that the structural transitions of MEHA SAMs on Au(111) occurred from the liquid phase to the formation of a closely packed and well-ordered β-phase via a loosely packed α-phase as an intermediate phase, depending on the deposition time. XPS measurements showed that the relative peak intensities of chemisorbed sulfur against Au 4f for MEHA SAMs formed after deposition for 1 min, 10 min, and 1 h were calculated to be 0.0022, 0.0068, and 0.0070, respectively. Based on the STM and XPS results, it is expected that the formation of a well-ordered β-phase is due to an increased adsorption of chemisorbed sulfur and the structural rearrangement of molecular backbones to maximize lateral interactions resulting from a longer deposition period of 1 h. CV measurements showed a significant difference in the electrochemical behavior of MEHA and decanethiol (DT) SAMs as a result of the presence of an internal amide group in the MEHA SAMs. Herein, we report the first high-resolution STM image of well-ordered MEHA SAMs on Au(111) with a (3 × 2√3) superlattice (β-phase). We also found that amide-containing MEHA SAMs were thermally much more stable than DT SAMs due to the formation of internal hydrogen networks in MEHA SAMs. Our molecular-scale STM results provide new insight into the growth process, surface structure, and thermal stability of amide-containing alkanethiols on Au(111). Full article
(This article belongs to the Special Issue State-of-the-Art Physical Chemistry and Chemical Physics in Korea)
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13 pages, 3082 KiB  
Article
Investigating the Photodissociation Dynamics of CF2BrCF2I in CCl4 through Femtosecond Time-Resolved Infrared Spectroscopy
by Seongchul Park, Juhyang Shin and Manho Lim
Int. J. Mol. Sci. 2023, 24(2), 1319; https://doi.org/10.3390/ijms24021319 - 10 Jan 2023
Viewed by 1189
Abstract
The photodissociation dynamics of CF2BrCF2I in CCl4 at 280 ± 2 K were investigated by probing the C−F stretching mode from 300 fs to 10 μs after excitation at 267 nm using time-resolved infrared spectroscopy. The excitation led [...] Read more.
The photodissociation dynamics of CF2BrCF2I in CCl4 at 280 ± 2 K were investigated by probing the C−F stretching mode from 300 fs to 10 μs after excitation at 267 nm using time-resolved infrared spectroscopy. The excitation led to the dissociation of I or Br atoms within 300 fs, producing the CF2BrCF2 or CF2ICF2 radicals, respectively. All nascent CF2ICF2 underwent further dissociation of I, producing CF2CF2 with a time constant of 56 ± 5 ns. All nascent g-CF2BrCF2 isomerized into the more stable a-CF2BrCF2 with a time constant of 47 ± 5 ps. Furthermore, a-CF2BrCF2 underwent a bimolecular reaction with either itself (producing CF2BrCF2Br and CF2CF2) or Br in the CCl4 solution (producing CF2BrCF2Br) at a diffusion-limited rate. The secondary dissociation of Br from a-CF2BrCF2 was significantly slow to compete with the bimolecular reactions. Overall, approximately half of the excited CF2BrCF2I at 267 nm produced CF2BrCF2Br, whereas the other half produced CF2CF2. The excess energies in the nascent radicals were thermalized much faster than the secondary dissociation of I from CF2ICF2 and the observed bimolecular reactions, implying that the secondary reactions proceeded under thermal conditions. This study further demonstrates that structure-sensitive time-resolved infrared spectroscopy can be used to study various reaction dynamics in solution in real time. Full article
(This article belongs to the Special Issue State-of-the-Art Physical Chemistry and Chemical Physics in Korea)
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13 pages, 3259 KiB  
Article
Effect of Water Vapor on Oxidation Processes of the Cu(111) Surface and Sublayer
by Young Jae Kim, Daeho Kim, Yongman Kim, Yongchan Jeong, Beomgyun Jeong and Jeong Young Park
Int. J. Mol. Sci. 2023, 24(1), 810; https://doi.org/10.3390/ijms24010810 - 03 Jan 2023
Cited by 4 | Viewed by 2335
Abstract
Copper-based catalysts have different catalytic properties depending on the oxidation states of Cu. We report operando observations of the Cu(111) oxidation processes using near-ambient pressure scanning tunneling microscopy (NAP-STM) and near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS). The Cu(111) surface was chemically inactive to [...] Read more.
Copper-based catalysts have different catalytic properties depending on the oxidation states of Cu. We report operando observations of the Cu(111) oxidation processes using near-ambient pressure scanning tunneling microscopy (NAP-STM) and near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS). The Cu(111) surface was chemically inactive to water vapor, but only physisorption of water molecules was observed by NAP-STM. Under O2 environments, dry oxidation started at the step edges and proceeded to the terraces as a Cu2O phase. Humid oxidation of the H2O/O2 gas mixture was also promoted at the step edges to the terraces. After the Cu2O covered the surface under humid conditions, hydroxides and adsorbed water layers formed. NAP-STM observations showed that Cu2O was generated at lower steps in dry oxidation with independent terrace oxidations, whereas Cu2O was generated at upper steps in humid oxidation. The difference in the oxidation mechanisms was caused by water molecules. When the surface was entirely oxidized, the diffusion of Cu and O atoms with a reconstruction of the Cu2O structures induced additional subsurface oxidation. NAP-XPS measurements showed that the Cu2O thickness in dry oxidation was greater than that in humid oxidation under all pressure conditions. Full article
(This article belongs to the Special Issue State-of-the-Art Physical Chemistry and Chemical Physics in Korea)
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16 pages, 3470 KiB  
Article
Conformational Structures of Neutral and Cationic Pivaldehyde Revealed by IR-Resonant VUV-MATI Mass Spectroscopy
by Sung Man Park, Yu Ran Lee and Chan Ho Kwon
Int. J. Mol. Sci. 2022, 23(23), 14777; https://doi.org/10.3390/ijms232314777 - 26 Nov 2022
Cited by 3 | Viewed by 1199
Abstract
Pivaldehyde, which is an unwanted by-product released with engine exhaust, has received considerable research attention because of its hydrocarbon oxidations at atmospheric temperature. To gain insight into the conformer-specific reaction dynamics, we investigated the conformational structures of the pivaldehyde molecule in neutral (S [...] Read more.
Pivaldehyde, which is an unwanted by-product released with engine exhaust, has received considerable research attention because of its hydrocarbon oxidations at atmospheric temperature. To gain insight into the conformer-specific reaction dynamics, we investigated the conformational structures of the pivaldehyde molecule in neutral (S0) and cationic (D0) states using the recently invented IR-resonant VUV-MATI mass spectroscopy. Additionally, we constructed the two-dimensional potential energy surfaces (2D PESs) associated with the conformational transformations in the S0 and D0 states to deduce the conformations corresponding to the measured vibrational spectra. The 2D PESs indicated the presence of only the eclipsed conformation in the global minima of both states, unlike those in propanal and isobutanal. However, comparing the IR-dip VUV-MATI spectra from two intense peaks in the VUV-MATI spectrum with the anharmonic IR simulations revealed the correspondence between the gauche conformer on the S0 state and the measured IR spectra. Furthermore, Franck–Condon analysis confirmed that most peaks in the VUV-MATI spectrum are attributed to the adiabatic ionic transitions between the neutral gauche and cationic eclipsed conformers in pivaldehyde. Consequently, electron removal from the highest occupied molecular orbital, consisting of the nonbonding orbital of the oxygen atom in pivaldehyde, promoted the formyl-relevant modes in the induced cationic eclipsed conformer. Full article
(This article belongs to the Special Issue State-of-the-Art Physical Chemistry and Chemical Physics in Korea)
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7 pages, 1539 KiB  
Article
Ultrafast Continuum IR Generation and Its Application in IR Spectroscopy
by Chaiho Lim, Kwanghee Park, Yeongseok Chae, Kyungwon Kwak and Minhaeng Cho
Int. J. Mol. Sci. 2022, 23(21), 13245; https://doi.org/10.3390/ijms232113245 - 31 Oct 2022
Cited by 1 | Viewed by 1702
Abstract
The spectral range of femtosecond time-resolved infrared spectroscopy is limited by the bandwidth of mid-IR pulses (100~400 cm−1) generated from the combination of Ti:Sapphire amplifier, Optical Parametric Amplifier (OPA), and Difference Frequency Generation (DFG). To overcome this limitation, we implement a [...] Read more.
The spectral range of femtosecond time-resolved infrared spectroscopy is limited by the bandwidth of mid-IR pulses (100~400 cm−1) generated from the combination of Ti:Sapphire amplifier, Optical Parametric Amplifier (OPA), and Difference Frequency Generation (DFG). To overcome this limitation, we implement a compact continuum mid-IR source producing ultrafast pulses that span the frequency range from 1000 to 4200 cm−1 (from 10 to 2.4 μm), which utilize the mixing of fundamental, second-harmonic, and third-harmonic of 800 nm pulse in the air. After building an IR spectrometer with continuum IR and a monochromator, we found that the distortion of the measured IR spectrum originated from the contamination of higher-order diffraction. We used bandpass filters to eliminate the higher-order contributions and correct the measured IR spectrum. We further characterized the spectral properties of fundamental, second-harmonic, and third-harmonic fields after the plasmonic filamentation process, which helps to improve the efficiency of the continuum IR generation. Using the generated continuum IR pulses, we measured the IR absorption spectrum of a water–benzonitrile mixture, which was found to be consistent with the spectrum obtained with a commercial FT-IR spectrometer. The present work will be useful for the efficient generation of continuum IR pulses for IR pump-probe and two-dimensional IR spectroscopy experiments in the future. Full article
(This article belongs to the Special Issue State-of-the-Art Physical Chemistry and Chemical Physics in Korea)
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13 pages, 2473 KiB  
Article
Thermodynamics of π–π Interactions of Benzene and Phenol in Water
by Dooam Paik, Hankyul Lee, Hyungjun Kim and Jeong-Mo Choi
Int. J. Mol. Sci. 2022, 23(17), 9811; https://doi.org/10.3390/ijms23179811 - 29 Aug 2022
Cited by 2 | Viewed by 1950
Abstract
The π–π interaction is a major driving force that stabilizes protein assemblies during protein folding. Recent studies have additionally demonstrated its involvement in the liquid–liquid phase separation (LLPS) of intrinsically disordered proteins (IDPs). As the participating residues in IDPs are exposed to water, [...] Read more.
The π–π interaction is a major driving force that stabilizes protein assemblies during protein folding. Recent studies have additionally demonstrated its involvement in the liquid–liquid phase separation (LLPS) of intrinsically disordered proteins (IDPs). As the participating residues in IDPs are exposed to water, π–π interactions for LLPS must be modeled in water, as opposed to the interactions that are often established at the hydrophobic domains of folded proteins. Thus, we investigated the association of free energies of benzene and phenol dimers in water by integrating van der Waals (vdW)-corrected density functional theory (DFT) and DFT in classical explicit solvents (DFT-CES). By comparing the vdW-corrected DFT and DFT-CES results with high-level wavefunction calculations and experimental solvation free energies, respectively, we established the quantitative credibility of these approaches, enabling a reliable prediction of the benzene and phenol dimer association free energies in water. We discovered that solvation influences dimer association free energies, but not significantly when no direct hydrogen-bond-type interaction exists between two monomeric units, which can be explained by the enthalpy–entropy compensation. Our comprehensive computational study of the solvation effect on π–π interactions in water could help us understand the molecular-level driving mechanism underlying the IDP phase behaviors. Full article
(This article belongs to the Special Issue State-of-the-Art Physical Chemistry and Chemical Physics in Korea)
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18 pages, 4035 KiB  
Article
Mechanism of Ir(ppy)3 Guest Exciton Formation with the Exciplex-Forming TCTA:TPBI Cohost within a Phosphorescent Organic Light-Emitting Diode Environment
by Jae Whee Park, Kwang Hyun Cho and Young Min Rhee
Int. J. Mol. Sci. 2022, 23(11), 5940; https://doi.org/10.3390/ijms23115940 - 25 May 2022
Cited by 3 | Viewed by 2150
Abstract
Cohosts based on hole transporting and electron transporting materials often act as exciplexes in the form of intermolecular charge transfer complexes. Indeed, exciplex-forming cohosts have been widely developed as the host materials for efficient phosphorescent organic light-emitting diodes (OLEDs). In host–guest systems of [...] Read more.
Cohosts based on hole transporting and electron transporting materials often act as exciplexes in the form of intermolecular charge transfer complexes. Indeed, exciplex-forming cohosts have been widely developed as the host materials for efficient phosphorescent organic light-emitting diodes (OLEDs). In host–guest systems of OLEDs, the guest can be excited by two competing mechanisms, namely, excitation energy transfer (EET) and charge transfer (CT). Experimentally, it has been reported that the EET mechanism is dominant and the excitons are primarily formed in the host first and then transferred to the guest in phosphorescent OLEDs based on exciplex-forming cohosts. With this, exciplex-forming cohosts are widely employed for avoiding the formation of trapped charge carriers in the phosphorescent guest. However, theoretical studies are still lacking toward elucidating the relative importance between EET and CT processes in exciting the guest molecules in such systems. Here, we obtain the kinetics of guest excitation processes in a few trimer model systems consisting of an exciplex-forming cohost pair and a phosphorescent guest. We adopt the Förster resonance energy transfer (FRET) rate constants for the electronic transitions between excited states toward solving kinetic master equations. The input parameters for calculating the FRET rate constants are obtained from density functional theory (DFT) and time-dependent DFT. The results show that while the EET mechanism is important, the CT mechanism may still play a significant role in guest excitations. In fact, the relative importance of CT over EET depends strongly on the location of the guest molecule relative to the cohost pair. This is understandable as both the coupling for EET and the interaction energy for CT are strongly influenced by the geometric constraints. Understanding the energy transfer pathways from the exciplex state of cohost to the emissive state of guest may provide insights for improving exciplex-forming materials adopted in OLEDs. Full article
(This article belongs to the Special Issue State-of-the-Art Physical Chemistry and Chemical Physics in Korea)
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7 pages, 1173 KiB  
Communication
Photoelectron Spectroscopy of OH-Anion–Water Clusters Generated by Ultrasonic Nebulizer
by Minchae Kang, Chang Jun Park, Hyung Min Kim and Sang Hak Lee
Int. J. Mol. Sci. 2022, 23(8), 4175; https://doi.org/10.3390/ijms23084175 - 10 Apr 2022
Viewed by 1469
Abstract
Investigating molecules in the gas phase is the only way to discover their intrinsic molecular properties; however, it is challenging to produce the gaseous phase of large-molecule chemicals. Thermal evaporation is typically used to convert molecules into gases, but it is still challenging [...] Read more.
Investigating molecules in the gas phase is the only way to discover their intrinsic molecular properties; however, it is challenging to produce the gaseous phase of large-molecule chemicals. Thermal evaporation is typically used to convert molecules into gases, but it is still challenging to study ionic molecules in solutions in the gas phase. Electrospray ionization is one of the best methods to generate molecules in the gas phase, and it is uniquely capable of studying large biomolecules, including proteins. However, the molecular temperature required to study the spectroscopic properties of the molecules is very high. In this study, we developed a new, simple evaporation method using an ultrasonic nebulizer to obtain gas-phase molecules. Using this new equipment, we observed OH anions and their water clusters in the gas phase and obtained their photoelectron spectra. We observed that the vertical electron-detachment energy (VDE) of OH was 1.90 ± 0.05 eV and the VDEs of its water clusters and OH (H2O)n (n = 1–2) decreased to 1.50 ± 0.05 eV (n = 1) and 1.30 ± 0.05 eV (n = 2), respectively. Full article
(This article belongs to the Special Issue State-of-the-Art Physical Chemistry and Chemical Physics in Korea)
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17 pages, 5286 KiB  
Article
Mechanistic Insights into the Polymorphic Associations and Cross-Seeding of Aβ and hIAPP in the Presence of Histidine Tautomerism: An All-Atom Molecular Dynamic Study
by Abbas Salimi, Sompriya Chatterjee and Jin Yong Lee
Int. J. Mol. Sci. 2022, 23(4), 1930; https://doi.org/10.3390/ijms23041930 - 09 Feb 2022
Cited by 2 | Viewed by 1695
Abstract
Hundreds of millions of people around the world have been affected by Type 2 diabetes (T2D) which is a metabolic disorder. Clinical research has revealed T2D as a possible risk factor for Alzheimer’s disease (AD) development (and vice versa). Amyloid-β (Aβ) and human [...] Read more.
Hundreds of millions of people around the world have been affected by Type 2 diabetes (T2D) which is a metabolic disorder. Clinical research has revealed T2D as a possible risk factor for Alzheimer’s disease (AD) development (and vice versa). Amyloid-β (Aβ) and human islet amyloid polypeptide are the main pathological species in AD and T2D, respectively. However, the mechanisms by which these two amyloidogenic peptides co-aggregate are largely uninvestigated. Herein, for the first time, we present the cross-seeding between Amylin1-37 and Aβ40 considering the particular effect of the histidine tautomerism at atomic resolution applying the all-atom molecular dynamics (MD) simulations for heterodimeric complexes. The results via random seed MD simulations indicated that the Aβ40(δδδ) isomer in cross-talking with Islet(ε) and Islet(δ) isomers could retain or increase the β-sheet content in its structure that may make it more prone to further aggregation and exhibit higher toxicity. The other tautomeric isomers which initially did not have a β-sheet structure in their monomeric forms did not show any generated β-sheet, except for one seed of the Islet(ε) and Aβ40(εεε) heterodimers complex that displayed a small amount of formed β-sheet. This computational research may provide a different point of view to examine all possible parameters that may contribute to the development of AD and T2D and provide a better understanding of the pathological link between these two severe diseases. Full article
(This article belongs to the Special Issue State-of-the-Art Physical Chemistry and Chemical Physics in Korea)
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14 pages, 18361 KiB  
Article
Intramolecular Charge Transfer of Curcumin and Solvation Dynamics of DMSO Probed by Time-Resolved Raman Spectroscopy
by Myungsam Jen, Sebok Lee, Gisang Lee, Daedu Lee and Yoonsoo Pang
Int. J. Mol. Sci. 2022, 23(3), 1727; https://doi.org/10.3390/ijms23031727 - 02 Feb 2022
Cited by 5 | Viewed by 2136
Abstract
Intramolecular charge transfer (ICT) of curcumin in dimethyl sulfoxide (DMSO) solution in the excited state was investigated by femtosecond electronic and vibrational spectroscopy. Excited-state Raman spectra of curcumin in the locally-excited and charge-transferred (CT) state of the S1 excited state were separated [...] Read more.
Intramolecular charge transfer (ICT) of curcumin in dimethyl sulfoxide (DMSO) solution in the excited state was investigated by femtosecond electronic and vibrational spectroscopy. Excited-state Raman spectra of curcumin in the locally-excited and charge-transferred (CT) state of the S1 excited state were separated due to high temporal (<50 fs) and spectral (<10 cm−1) resolutions of femtosecond stimulated Raman spectroscopy. The ultrafast (0.6–0.8 ps) ICT and subsequent vibrational relaxation (6–9 ps) in the CT state were ubiquitously observed in the ground- and excited-state vibrational modes of the solute curcumin and the νCSC and νS=O modes of solvent DMSO. The ICT of curcumin in the excited state was preceded by the disruption of the solvation shells, including the breakage of hydrogen bonding between curcumin and DMSO molecules, which occurs at the ultrafast (20–50 fs) time scales. Full article
(This article belongs to the Special Issue State-of-the-Art Physical Chemistry and Chemical Physics in Korea)
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Review

Jump to: Research

21 pages, 4646 KiB  
Review
Overcoming the Limitation of Spin Statistics in Organic Light Emitting Diodes (OLEDs): Hot Exciton Mechanism and Its Characterization
by Soo Wan Park, Dongwook Kim and Young Min Rhee
Int. J. Mol. Sci. 2023, 24(15), 12362; https://doi.org/10.3390/ijms241512362 - 02 Aug 2023
Cited by 4 | Viewed by 1479
Abstract
Triplet harvesting processes are essential for enhancing efficiencies of fluorescent organic light-emitting diodes. Besides more conventional thermally activated delayed fluorescence and triplet-triplet annihilation, the hot exciton mechanism has been recently noticed because it helps reduce the efficiency roll-off and improve device stability. Hot [...] Read more.
Triplet harvesting processes are essential for enhancing efficiencies of fluorescent organic light-emitting diodes. Besides more conventional thermally activated delayed fluorescence and triplet-triplet annihilation, the hot exciton mechanism has been recently noticed because it helps reduce the efficiency roll-off and improve device stability. Hot exciton materials enable the conversion of triplet excitons to singlet ones via reverse inter-system crossing from high-lying triplet states and thereby the depopulation of long-lived triplet excitons that are prone to chemical and/or efficiency degradation. Although their anti-Kasha characteristics have not been clearly explained, numerous molecules with behaviors assigned to the hot exciton mechanism have been reported. Indeed, the related developments appear to have just passed the stage of infancy now, and there will likely be more roles that computational elucidations can play. With this perspective in mind, we review some selected experimental studies on the mechanism and the related designs and then on computational studies. On the computational side, we examine what has been found and what is still missing with regard to properly understanding this interesting mechanism. We further discuss potential future points of computational interests toward aiming for eventually presenting in silico design guides. Full article
(This article belongs to the Special Issue State-of-the-Art Physical Chemistry and Chemical Physics in Korea)
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