Pub Date : 2025-03-27DOI: 10.1021/acs.jpclett.5c00225
Frédéric A. Perras, Frédéric Mentink-Vigier, Svetlana Pylaeva
This mini-review summarizes the evolving debate regarding the origins of the absorptive features seen in the dynamic nuclear polarization (DNP) spectra of certain monoradicals when they are irradiated at their electron Larmor frequency. This feature has drawn attention due to its reverse scaling with respect to the magnetic field strength and potential for high-field DNP. Two competing hypotheses have been introduced to explain the DNP feature based on (1) the Overhauser effect and low-temperature molecular dynamics and (2) radical clustering and a thermal mixing mechanism. Since the original discovery, a large number of experimental observations have been made in attempts to understand and ultimately leverage the mechanism. We summarize these observations and provide critical assessments of how the competing hypotheses approach them.
{"title":"Perspectives on the Dynamic Nuclear Polarization Mechanisms of Monoradicals: Overhauser Effect or Thermal Mixing?","authors":"Frédéric A. Perras, Frédéric Mentink-Vigier, Svetlana Pylaeva","doi":"10.1021/acs.jpclett.5c00225","DOIUrl":"https://doi.org/10.1021/acs.jpclett.5c00225","url":null,"abstract":"This mini-review summarizes the evolving debate regarding the origins of the absorptive features seen in the dynamic nuclear polarization (DNP) spectra of certain monoradicals when they are irradiated at their electron Larmor frequency. This feature has drawn attention due to its reverse scaling with respect to the magnetic field strength and potential for high-field DNP. Two competing hypotheses have been introduced to explain the DNP feature based on (1) the Overhauser effect and low-temperature molecular dynamics and (2) radical clustering and a thermal mixing mechanism. Since the original discovery, a large number of experimental observations have been made in attempts to understand and ultimately leverage the mechanism. We summarize these observations and provide critical assessments of how the competing hypotheses approach them.","PeriodicalId":62,"journal":{"name":"The Journal of Physical Chemistry Letters","volume":"57 1","pages":""},"PeriodicalIF":6.475,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143713764","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-27DOI: 10.1021/acs.jpclett.4c03625
Michael Odelius, Sarai Dery Folkestad, Thanit Saisopa, Yuttakarn Rattanachai, Wutthigrai Sailuam, Hayato Yuzawa, Nobuhiro Kosugi, Alexander C. Paul, Henrik Koch, Denis Céolin
Nitrogen K-edge X-ray absorption (XA) spectroscopy of aqueous ammonia reveals a splitting in the main-edge, which through theoretical modeling is shown to be related to symmetry breaking in hydrogen bonding. The XA main-edge of NH3 is formed by a pair of degenerate core-excitations into extended molecular orbitals. In aqueous solution, these form an antibonding mixture with orbitals of the surrounding water molecules. Although the spectral response to distortions is complex, we show that the degeneracy of the core-excitations is lifted by asymmetry in hydrogen bond donation (NH···O). A quantitative relation between asymmetry in the hydration shell and splitting in the main-edge of the nitrogen K-edge XA spectrum is established from systematic symmetry breaking in well-defined cluster models and through molecular dynamics sampling of simulated XA spectra of aqueous ammonia. The finding indicates that XA spectroscopy is a sensitive probe of asymmetry in solvation also around functional groups in biomolecules.
{"title":"Symmetry Breaking around Aqueous Ammonia Revealed in Nitrogen K-edge X-ray Absorption","authors":"Michael Odelius, Sarai Dery Folkestad, Thanit Saisopa, Yuttakarn Rattanachai, Wutthigrai Sailuam, Hayato Yuzawa, Nobuhiro Kosugi, Alexander C. Paul, Henrik Koch, Denis Céolin","doi":"10.1021/acs.jpclett.4c03625","DOIUrl":"https://doi.org/10.1021/acs.jpclett.4c03625","url":null,"abstract":"Nitrogen K-edge X-ray absorption (XA) spectroscopy of aqueous ammonia reveals a splitting in the main-edge, which through theoretical modeling is shown to be related to symmetry breaking in hydrogen bonding. The XA main-edge of NH<sub>3</sub> is formed by a pair of degenerate core-excitations into extended molecular orbitals. In aqueous solution, these form an antibonding mixture with orbitals of the surrounding water molecules. Although the spectral response to distortions is complex, we show that the degeneracy of the core-excitations is lifted by asymmetry in hydrogen bond donation (NH···O). A quantitative relation between asymmetry in the hydration shell and splitting in the main-edge of the nitrogen K-edge XA spectrum is established from systematic symmetry breaking in well-defined cluster models and through molecular dynamics sampling of simulated XA spectra of aqueous ammonia. The finding indicates that XA spectroscopy is a sensitive probe of asymmetry in solvation also around functional groups in biomolecules.","PeriodicalId":62,"journal":{"name":"The Journal of Physical Chemistry Letters","volume":"61 1","pages":""},"PeriodicalIF":6.475,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143713583","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-26DOI: 10.1021/acs.jpclett.5c00434
Agustín J. Colussi
Orders-of-magnitude reaction accelerations and the formation of H2O2 in aerosolized water microdroplets are in search of explanation. These processes are not overall spontaneous as generally assumed because they are preceded by the forced aerosolization of water. Nor are they caused by internal electric fields because the electrical activation of chemical reactions requires external static fields vectorially aligned with transition state dipoles. The formation of H2O2 is enabled by the partial dehydration of HO– and H+ ions in low-density interfacial water, a process that raises their free energies of formation and lifts the endoergicity of the prerequisite electron transfer HO– + H+ = HO• + H• in bulk water. The lack of unimolecular reaction accelerations suggests the accelerations of bimolecular reactions are due to the higher frequencies of molecular encounters, fewer transition state recrossings, and smaller entropy losses for expanding solvent cavities to hold their transition states in interfacial vs bulk water.
{"title":"Physical Chemistry of Water Microdroplets","authors":"Agustín J. Colussi","doi":"10.1021/acs.jpclett.5c00434","DOIUrl":"https://doi.org/10.1021/acs.jpclett.5c00434","url":null,"abstract":"Orders-of-magnitude reaction accelerations and the formation of H<sub>2</sub>O<sub>2</sub> in aerosolized water microdroplets are in search of explanation. These processes are not overall spontaneous as generally assumed because they are preceded by the forced aerosolization of water. Nor are they caused by internal electric fields because the electrical activation of chemical reactions requires external static fields vectorially aligned with transition state dipoles. The formation of H<sub>2</sub>O<sub>2</sub> is enabled by the partial dehydration of HO<sup>–</sup> and H<sup>+</sup> ions in low-density interfacial water, a process that raises their free energies of formation and lifts the endoergicity of the prerequisite electron transfer HO<sup>–</sup> + H<sup>+</sup> = HO<sup>•</sup> + H<sup>•</sup> in bulk water. The lack of unimolecular reaction accelerations suggests the accelerations of bimolecular reactions are due to the higher frequencies of molecular encounters, fewer transition state recrossings, and smaller entropy losses for expanding solvent cavities to hold their transition states in interfacial vs bulk water.","PeriodicalId":62,"journal":{"name":"The Journal of Physical Chemistry Letters","volume":"18 1","pages":""},"PeriodicalIF":6.475,"publicationDate":"2025-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143703608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
It is challenging to predict optical properties of fluorescent dyes, especially in the crystalline state, owing to the uncertainty in conformation, packing, and coupling. Herein, we elucidate the decisive role of molecular conformation and molecular packing in the fluorescence emissions of some crystalline materials based on experimental results and theoretical calculations. Two homologous fluorophores (Ph-MP and Ph-HP) were synthesized, and they both exhibited interesting crystallization-induced emission enhancement and quenching. Although the homologues show almost the same fluorescence behavior in the solid state, on–off emission of their crystals depends upon different factors. Emission of the Ph-MP crystals is governed by the twisted intramolecular charge transfer effect, while emission of the Ph-HP crystals relied on π–π stacking. Based on this understanding, application of single-molecule-based versatile crystals in information encryption was demonstrated. It is believed that the evidence and unveiled mechanism for the effect of crystallization on emission will contribute to development in high-performance luminescent materials.
{"title":"Crystallization-Induced Emission Enhancement or Quenching? Elucidating the Mechanism behind Using Single-Molecule-Based Versatile Crystals","authors":"Yutong Shang, Yalei Ma, Qiangbazhuoma, Baimaquzhen, Liping Ding, Jing Liu, Shiwei Yin, Rong Miao, Yu Fang","doi":"10.1021/acs.jpclett.5c00774","DOIUrl":"https://doi.org/10.1021/acs.jpclett.5c00774","url":null,"abstract":"It is challenging to predict optical properties of fluorescent dyes, especially in the crystalline state, owing to the uncertainty in conformation, packing, and coupling. Herein, we elucidate the decisive role of molecular conformation and molecular packing in the fluorescence emissions of some crystalline materials based on experimental results and theoretical calculations. Two homologous fluorophores (Ph-MP and Ph-HP) were synthesized, and they both exhibited interesting crystallization-induced emission enhancement and quenching. Although the homologues show almost the same fluorescence behavior in the solid state, on–off emission of their crystals depends upon different factors. Emission of the Ph-MP crystals is governed by the twisted intramolecular charge transfer effect, while emission of the Ph-HP crystals relied on π–π stacking. Based on this understanding, application of single-molecule-based versatile crystals in information encryption was demonstrated. It is believed that the evidence and unveiled mechanism for the effect of crystallization on emission will contribute to development in high-performance luminescent materials.","PeriodicalId":62,"journal":{"name":"The Journal of Physical Chemistry Letters","volume":"9 1","pages":""},"PeriodicalIF":6.475,"publicationDate":"2025-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143713766","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-26DOI: 10.1021/acs.jpclett.5c00305
Pierre-Marie Deleuze, Bruno Domenichini, Hélène Magnan, Mathieu G. Silly, Antoine Barbier, Sylvie Bourgeois, Céline Dupont
In this work, we determine the electronic structure and charge carrier dynamics of α-Fe2O3(0001) ultrathin film deposited on Pt(111) as a function of water pressure by combined near ambient pressure–time-resolved photoelectron spectroscopy (NAP-TR-PES) measurements and DFT calculations. Under ultrahigh vacuum (UHV) α-Fe2O3 exhibits the expected typical n-type semiconductor behavior with a surface photovoltage (SPV) shift of 31 meV. Surprisingly, when exposed to water a completely different comportment appears. At a partial pressure of water of PH2O = 0.02 hPa, a much smaller SPV (7 meV) appears that is shifted in the opposite direction, which is thus characteristic of a p-type semiconductor. Finally, at PH2O > 0.1 hPa, SPV is canceled, which is consistent with a layer of metallic nature. DFT calculations explain these experimental findings well as originating from a modification of the surface structure and electronic properties of the layer consecutive to water adsorption. It is shown that the Fermi level position in the band gap of hematite depends on the quantity of adsorbed water, giving rise to the ambipolar behavior of the surface, which is able to transport both negative and positive charges when exposed to the appropriate water pressure.
{"title":"Ambipolar Behavior of Hematite Surface Induced by Water Adsorption Revealed under Environmental Conditions","authors":"Pierre-Marie Deleuze, Bruno Domenichini, Hélène Magnan, Mathieu G. Silly, Antoine Barbier, Sylvie Bourgeois, Céline Dupont","doi":"10.1021/acs.jpclett.5c00305","DOIUrl":"https://doi.org/10.1021/acs.jpclett.5c00305","url":null,"abstract":"In this work, we determine the electronic structure and charge carrier dynamics of α-Fe<sub>2</sub>O<sub>3</sub>(0001) ultrathin film deposited on Pt(111) as a function of water pressure by combined near ambient pressure–time-resolved photoelectron spectroscopy (NAP-TR-PES) measurements and DFT calculations. Under ultrahigh vacuum (UHV) α-Fe<sub>2</sub>O<sub>3</sub> exhibits the expected typical <i>n</i>-type semiconductor behavior with a surface photovoltage (SPV) shift of 31 meV. Surprisingly, when exposed to water a completely different comportment appears. At a partial pressure of water of <i>P</i><sub>H<sub>2</sub>O</sub> = 0.02 hPa, a much smaller SPV (7 meV) appears that is shifted in the opposite direction, which is thus characteristic of a <i>p</i>-type semiconductor. Finally, at <i>P</i><sub>H<sub>2</sub>O</sub> > 0.1 hPa, SPV is canceled, which is consistent with a layer of metallic nature. DFT calculations explain these experimental findings well as originating from a modification of the surface structure and electronic properties of the layer consecutive to water adsorption. It is shown that the Fermi level position in the band gap of hematite depends on the quantity of adsorbed water, giving rise to the ambipolar behavior of the surface, which is able to transport both negative and positive charges when exposed to the appropriate water pressure.","PeriodicalId":62,"journal":{"name":"The Journal of Physical Chemistry Letters","volume":"88 1","pages":""},"PeriodicalIF":6.475,"publicationDate":"2025-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143703624","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-26DOI: 10.1021/acs.jpclett.4c03593
Lucian A. Constantin, Eduardo Fabiano, Fabio Della Sala
We present a nonempirical strategy to construct a correlation functional rooted in the Møller–Plesset (MP) adiabatic connection (AC) formalism for the strong-interaction regime, which satisfies both the weak- and strong-interaction limits and describes accurately the uniform electron gas (UEG) model. The functional is based on Hartree–Fock (HF) orbitals and employs only the UEG and helium atom as model systems; thus, it can be considered a nonempirical and nonlinear generalization of post-HF approaches based on the second-order perturbation theory (MP2) correlation. The functional describes the correlation of atoms with 1 mHa/electron accuracy, and it is also accurate for jellium surface energies. Accurate tests using a nearly complete basis set on diverse systems and properties (atomization/interaction energies, dispersion forces, and ionization potentials) have shown an excellent performance of the functional that corrects the MP2 overbinding without error cancellation. The present investigation can open the way for the development of a new generation of post-HF functionals based on nonlinear MP2 contributions and strong-correlation ingredients.
{"title":"Nonempirical Adiabatic Connection Correlation Functional from Hartree–Fock Orbitals","authors":"Lucian A. Constantin, Eduardo Fabiano, Fabio Della Sala","doi":"10.1021/acs.jpclett.4c03593","DOIUrl":"https://doi.org/10.1021/acs.jpclett.4c03593","url":null,"abstract":"We present a nonempirical strategy to construct a correlation functional rooted in the Møller–Plesset (MP) adiabatic connection (AC) formalism for the strong-interaction regime, which satisfies both the weak- and strong-interaction limits and describes accurately the uniform electron gas (UEG) model. The functional is based on Hartree–Fock (HF) orbitals and employs only the UEG and helium atom as model systems; thus, it can be considered a nonempirical and nonlinear generalization of post-HF approaches based on the second-order perturbation theory (MP2) correlation. The functional describes the correlation of atoms with 1 mHa/electron accuracy, and it is also accurate for jellium surface energies. Accurate tests using a nearly complete basis set on diverse systems and properties (atomization/interaction energies, dispersion forces, and ionization potentials) have shown an excellent performance of the functional that corrects the MP2 overbinding without error cancellation. The present investigation can open the way for the development of a new generation of post-HF functionals based on nonlinear MP2 contributions and strong-correlation ingredients.","PeriodicalId":62,"journal":{"name":"The Journal of Physical Chemistry Letters","volume":"183 1","pages":""},"PeriodicalIF":6.475,"publicationDate":"2025-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143713763","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-25DOI: 10.1021/acs.jpclett.5c00123
Vivien L. Cherrette, David Zeitz, Mariam Khvichia, Jason K. Cooper, Yuan Ping, Jeremy Lake Barnett, Jin Z. Zhang
CsPbBr3 perovskite quantum dot (PQD) films enriched with 208Pb (I = 0) or 207Pb (I = 1/2) isotope were used to study the effect of nuclear spin on the photoexcited carrier spin relaxation using circularly polarized femtosecond transient absorption spectroscopy at 293 and 77 K. At 293 K, the short carrier spin relaxation lifetimes of 208Pb-enriched PQDs (2.0 ps) and natPb PQDs (0.70 ps) indicate that electron–phonon interactions dominate. At 77 K, the 207Pb-enriched PQD carrier spin relaxation lifetime was not detectible within the instrumental limit (<0.30 ps). However, the carrier spin relaxation lifetime increased to 5.0 ps for natPb PQDs and 170 ps for 208Pb-enriched PQDs. The dramatic increase in the 208Pb-enriched PQD carrier spin relaxation lifetime suggests that decreasing the concentration of 207Pb in the PQDs can reduce spin decoherence from nuclear spin–carrier spin coupling and enhance the lifetime.
{"title":"Enhancing the Photoexcited Carrier Spin Relaxation Lifetime in CsPbBr3 Perovskite Quantum Dots by 208Pb Isotope Enrichment","authors":"Vivien L. Cherrette, David Zeitz, Mariam Khvichia, Jason K. Cooper, Yuan Ping, Jeremy Lake Barnett, Jin Z. Zhang","doi":"10.1021/acs.jpclett.5c00123","DOIUrl":"https://doi.org/10.1021/acs.jpclett.5c00123","url":null,"abstract":"CsPbBr<sub>3</sub> perovskite quantum dot (PQD) films enriched with <sup>208</sup>Pb (<i>I</i> = 0) or <sup>207</sup>Pb (<i>I</i> = 1/2) isotope were used to study the effect of nuclear spin on the photoexcited carrier spin relaxation using circularly polarized femtosecond transient absorption spectroscopy at 293 and 77 K. At 293 K, the short carrier spin relaxation lifetimes of <sup>208</sup>Pb-enriched PQDs (2.0 ps) and <sup>nat</sup>Pb PQDs (0.70 ps) indicate that electron–phonon interactions dominate. At 77 K, the <sup>207</sup>Pb-enriched PQD carrier spin relaxation lifetime was not detectible within the instrumental limit (<0.30 ps). However, the carrier spin relaxation lifetime increased to 5.0 ps for <sup>nat</sup>Pb PQDs and 170 ps for <sup>208</sup>Pb-enriched PQDs. The dramatic increase in the <sup>208</sup>Pb-enriched PQD carrier spin relaxation lifetime suggests that decreasing the concentration of <sup>207</sup>Pb in the PQDs can reduce spin decoherence from nuclear spin–carrier spin coupling and enhance the lifetime.","PeriodicalId":62,"journal":{"name":"The Journal of Physical Chemistry Letters","volume":"23 1","pages":""},"PeriodicalIF":6.475,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143695787","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Aqueous batteries, such as aqueous zinc-ion batteries (AZIB), have garnered significant attention because of their advantages in intrinsic safety, low cost, and eco-friendliness. However, aqueous electrolytes tend to freeze at low temperatures, which limits their potential industrial applications. Thus, one of the core challenges in aqueous electrolyte design is optimizing the formula to prevent freezing while maintaining good ion conductivity. However, the experimental trial-and-error approach is inefficient for this purpose, and existing simulation tools are either inaccurate or too expensive for high-throughput phase transition predictions. In this work, we employ a small amount of experimental data and differentiable simulation techniques to develop a multimodal optimization workflow. With minimal human intervention, this workflow significantly enhances the prediction power of classical force fields for electrical conductivity. Most importantly, the simulated electrical conductivity can serve as an effective predictor of electrolyte freezing at low temperatures. Generally, the workflow developed in this work introduces a new paradigm for electrolyte design. This paradigm leverages both easily measurable experimental data and fast simulation techniques to predict properties that are challenging to access by using either approach alone.
{"title":"Screening and Design of Aqueous Zinc Battery Electrolytes Based on the Multimodal Optimization of Molecular Simulation","authors":"Wei Feng, Luyan Zhang, Yaobo Cheng, Jin Wu, Chunguang Wei, Junwei Zhang, Kuang Yu","doi":"10.1021/acs.jpclett.5c00341","DOIUrl":"https://doi.org/10.1021/acs.jpclett.5c00341","url":null,"abstract":"Aqueous batteries, such as aqueous zinc-ion batteries (AZIB), have garnered significant attention because of their advantages in intrinsic safety, low cost, and eco-friendliness. However, aqueous electrolytes tend to freeze at low temperatures, which limits their potential industrial applications. Thus, one of the core challenges in aqueous electrolyte design is optimizing the formula to prevent freezing while maintaining good ion conductivity. However, the experimental trial-and-error approach is inefficient for this purpose, and existing simulation tools are either inaccurate or too expensive for high-throughput phase transition predictions. In this work, we employ a small amount of experimental data and differentiable simulation techniques to develop a multimodal optimization workflow. With minimal human intervention, this workflow significantly enhances the prediction power of classical force fields for electrical conductivity. Most importantly, the simulated electrical conductivity can serve as an effective predictor of electrolyte freezing at low temperatures. Generally, the workflow developed in this work introduces a new paradigm for electrolyte design. This paradigm leverages both easily measurable experimental data and fast simulation techniques to predict properties that are challenging to access by using either approach alone.","PeriodicalId":62,"journal":{"name":"The Journal of Physical Chemistry Letters","volume":"47 1","pages":""},"PeriodicalIF":6.475,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143695693","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-25DOI: 10.1021/acs.jpclett.5c00500
Daria M. Cegiełka, Łukasz Bodek, Michael Zharnikov, Piotr Cyganik
Self-assembled monolayers (SAMs) are broadly used for molecular engineering of surfaces and interfaces, which demands control over their structure and properties. An important tool in this context is the so-called odd–even effects exploiting the dependence of the SAM structure on the parity of the number of building blocks forming the backbone of SAM-building molecules. Even though these effects influence parameters crucial for SAM applications, they have been mainly studied on coinage metals (Au and Ag) until now. Here, using the series of biphenyl-substituted carboxylic acids (BPnCOO, n = 0–4), we show that structural odd–even behavior occurs as well on technologically relevant surface of naturally oxidized aluminum (representative of other oxide surfaces), with the even-numbered monolayers exhibiting higher packing density and lower molecular inclination than the odd-numbered analogs. Despite these structural changes, the SAM desorption energy remains nearly constant at a high value (∼1.5 eV) making BPnCOO/AlOx a promising system for organic electronics applications.
{"title":"Odd–Even Effects in the Structure and Thermal Stability of Carboxylic Acid Anchored Monolayers on Naturally Oxidized Aluminum Surface","authors":"Daria M. Cegiełka, Łukasz Bodek, Michael Zharnikov, Piotr Cyganik","doi":"10.1021/acs.jpclett.5c00500","DOIUrl":"https://doi.org/10.1021/acs.jpclett.5c00500","url":null,"abstract":"Self-assembled monolayers (SAMs) are broadly used for molecular engineering of surfaces and interfaces, which demands control over their structure and properties. An important tool in this context is the so-called odd–even effects exploiting the dependence of the SAM structure on the parity of the number of building blocks forming the backbone of SAM-building molecules. Even though these effects influence parameters crucial for SAM applications, they have been mainly studied on coinage metals (Au and Ag) until now. Here, using the series of biphenyl-substituted carboxylic acids (BPnCOO, <i>n</i> = 0–4), we show that structural odd–even behavior occurs as well on technologically relevant surface of naturally oxidized aluminum (representative of other oxide surfaces), with the <i>even-numbered</i> monolayers exhibiting higher packing density and lower molecular inclination than the <i>odd-numbered</i> analogs. Despite these structural changes, the SAM desorption energy remains nearly constant at a high value (∼1.5 eV) making BPnCOO/AlO<sub><i>x</i></sub> a promising system for organic electronics applications.","PeriodicalId":62,"journal":{"name":"The Journal of Physical Chemistry Letters","volume":"6 1","pages":""},"PeriodicalIF":6.475,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143695695","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-25DOI: 10.1021/acs.jpclett.5c00400
Sophia Vadachkoria, Qingqing Lei, Timothy C. Steimle, Michael C. Heaven
YbNH2 has been recognized as a suitable platform for observations of parity and time-reversal symmetry violations. Gas phase electronic spectra for YbNH2 were obtained for the Ã2B2-X̃2A1 and B̃2B1-X̃2A1 band systems. Both upper states are derived from the Yb+(4f146s)NH2– → Yb+(4f146p)NH2– electron promotion. Laser excitation and dispersed fluorescence measurements yielded band origins, vibrational constants and rotational band contours. Data for the Ã-X̃ system show a Franck–Condon distribution that is favorable for laser cooling. An upper bound for the vibrational branching fraction for the 000 transition in emission was found to be 0.94, assuming negligible radiation to the low-energy Yb+(4f136s2)NH2– states. Quantum chemical calculations for the ÖX̃ vibronic bands are reported.
{"title":"Electronic Spectroscopy of YbNH2 and the Potential for Laser Cooling","authors":"Sophia Vadachkoria, Qingqing Lei, Timothy C. Steimle, Michael C. Heaven","doi":"10.1021/acs.jpclett.5c00400","DOIUrl":"https://doi.org/10.1021/acs.jpclett.5c00400","url":null,"abstract":"YbNH<sub>2</sub> has been recognized as a suitable platform for observations of parity and time-reversal symmetry violations. Gas phase electronic spectra for YbNH<sub>2</sub> were obtained for the <i>Ã</i><sup>2</sup><i>B</i><sub>2</sub>-<i>X̃</i><sup>2</sup><i>A</i><sub>1</sub> and <i>B̃</i><sup>2</sup><i>B</i><sub>1</sub>-<i>X̃</i><sup>2</sup><i>A</i><sub>1</sub> band systems. Both upper states are derived from the Yb<sup>+</sup>(4f<sup>14</sup>6s)NH<sub>2</sub><sup>–</sup> → Yb<sup>+</sup>(4f<sup>14</sup>6p)NH<sub>2</sub><sup>–</sup> electron promotion. Laser excitation and dispersed fluorescence measurements yielded band origins, vibrational constants and rotational band contours. Data for the <i>Ã</i>-<i>X̃</i> system show a Franck–Condon distribution that is favorable for laser cooling. An upper bound for the vibrational branching fraction for the 0<sub>0</sub><sup>0</sup> transition in emission was found to be 0.94, assuming negligible radiation to the low-energy Yb<sup>+</sup>(4f<sup>13</sup>6s<sup>2</sup>)NH<sub>2</sub><sup>–</sup> states. Quantum chemical calculations for the <i>Ã</i>–<i>X̃</i> vibronic bands are reported.","PeriodicalId":62,"journal":{"name":"The Journal of Physical Chemistry Letters","volume":"71 1","pages":""},"PeriodicalIF":6.475,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143695694","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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