Pub Date : 2026-03-24DOI: 10.1021/acs.jpcc.5c08577
Zhen Xu,Na Li,Yuanyuan Zhao,Yongqing Qiu
Perovskite solar cells (PSCs) have emerged as promising candidates for next-generation photovoltaics, yet their commercial viability is hindered by concerns over lead toxicity and stability. Herein, we systematically investigate the structural, electronic, optical, and thermodynamic properties of lead-free perovskites with the general formula (2-CEA)2BBr4–xIx (B = Sn, Ge; x = 0–4) and (2-CEA)2PbBr4 using density functional theory. The results reveal that 11 perovskite systems exhibit remarkable thermodynamic stability with negative formation enthalpies and sustained structural integrity during ab initio molecular dynamics simulations at 300 K. Substitution of Pb with Sn or Ge substantially reduces the bandgap, and it shows a further decreasing trend with increasing iodine doping concentration. Electronic structure analyses reveal that Sn/Ge substitution and iodine doping increase bond covalency and orbital hybridization, which collectively contribute to the narrowing of the bandgap. Optical property calculations demonstrate that both Sn- and Ge-based systems extend the spectral absorption range and enhance the absorption coefficient across the visible and near-ultraviolet regions. Notably, (2-CEA)2SnI4 and (2-CEA)2GeI4 exhibit the highest dielectric responses and strongest visible absorption. Our computational study not only validates the promising optoelectronic performance of lead-free (2-CEA)2BBr4–xIx (B = Sn, Ge; x = 0–4) perovskites but also provides theoretical guidance for the rational design of efficient, stable, and environmentally friendly PSC materials.
钙钛矿太阳能电池（PSCs）已成为下一代光伏电池的有希望的候选者，但其商业可行性受到铅毒性和稳定性的担忧的阻碍。本文采用密度泛函理论，系统地研究了无铅钙钛矿的结构、电子、光学和热力学性质，其通式为（2-CEA） 2BBr4-xIx （B = Sn, Ge; x = 0-4）和（2-CEA）2PbBr4。结果表明，在300 K从头算分子动力学模拟中，11个钙钛矿体系表现出显著的热力学稳定性，具有负生成焓和持续的结构完整性。用Sn或Ge取代Pb可显著降低带隙，并随着碘掺杂浓度的增加，带隙进一步减小。电子结构分析表明，Sn/Ge取代和碘掺杂增加了键共价和轨道杂化，共同有助于缩小带隙。光学性质计算表明，锡基和锗基体系都扩大了光谱吸收范围，提高了可见光和近紫外区的吸收系数。值得注意的是，（2-CEA）2SnI4和（2-CEA）2GeI4表现出最高的介电响应和最强的可见光吸收。我们的计算研究不仅验证了无铅（2-CEA） 2BBr4-xIx （B = Sn, Ge; x = 0-4）钙钛矿具有良好的光电性能，也为合理设计高效、稳定、环保的PSC材料提供了理论指导。
{"title":"A DFT Study on Tunable Optoelectronic Properties and Stability of (2-CEA)-Based Perovskites for Solar Cells","authors":"Zhen Xu,Na Li,Yuanyuan Zhao,Yongqing Qiu","doi":"10.1021/acs.jpcc.5c08577","DOIUrl":"https://doi.org/10.1021/acs.jpcc.5c08577","url":null,"abstract":"Perovskite solar cells (PSCs) have emerged as promising candidates for next-generation photovoltaics, yet their commercial viability is hindered by concerns over lead toxicity and stability. Herein, we systematically investigate the structural, electronic, optical, and thermodynamic properties of lead-free perovskites with the general formula (2-CEA)2BBr4–xIx (B = Sn, Ge; x = 0–4) and (2-CEA)2PbBr4 using density functional theory. The results reveal that 11 perovskite systems exhibit remarkable thermodynamic stability with negative formation enthalpies and sustained structural integrity during ab initio molecular dynamics simulations at 300 K. Substitution of Pb with Sn or Ge substantially reduces the bandgap, and it shows a further decreasing trend with increasing iodine doping concentration. Electronic structure analyses reveal that Sn/Ge substitution and iodine doping increase bond covalency and orbital hybridization, which collectively contribute to the narrowing of the bandgap. Optical property calculations demonstrate that both Sn- and Ge-based systems extend the spectral absorption range and enhance the absorption coefficient across the visible and near-ultraviolet regions. Notably, (2-CEA)2SnI4 and (2-CEA)2GeI4 exhibit the highest dielectric responses and strongest visible absorption. Our computational study not only validates the promising optoelectronic performance of lead-free (2-CEA)2BBr4–xIx (B = Sn, Ge; x = 0–4) perovskites but also provides theoretical guidance for the rational design of efficient, stable, and environmentally friendly PSC materials.","PeriodicalId":61,"journal":{"name":"The Journal of Physical Chemistry C","volume":"59 1","pages":""},"PeriodicalIF":4.126,"publicationDate":"2026-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147506246","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-24DOI: 10.1021/acs.jpcc.6c00879
Alexander V. Yakimov,Alexander Guda,Sergey Guda,Bogdan Protsenko,Elena Groppo,Felipe Morais Bolner,Sebastien Norsic,Jean Raynaud,Vincent Monteil,Christophe Copéret
Ziegler–Natta catalysts, discovered in the 1950s, are still central to the industrial production of polyethylene and polypropylene. Despite being the workhorse of the polymer industry and years of extensive research, the improvements in Ziegler–Natta catalysts have been mostly empirical. In particular, the coordination surroundings of the Ti sites in precatalysts, key for the formation of active sites upon AlEt3 activation, have been highly debated. Notably, quantification of different Ti sites on the MgCl2 surface has not been possible thus far, hindering the development of quantitative structure–activity relationships. In this work, we prepared a series of precatalysts with increasing concentrations of the BCl3 modifier during the catalyst synthesis, known to affect the number of Cl and alkoxo ligands in the Ti local surroundings, as well as the activity in ethylene polymerization. We developed a methodology, relying on a library of theoretical X-ray absorption spectroscopy (XAS) lines computed from the density functional theory (DFT)-optimized structural models, benchmarked on a series of well-defined molecular compounds. A quantitative analysis of the XAS data allows us to evaluate the relative fractions of Ti sites in the Cl surrounding, as well as containing alkoxide and O-donor ligands. The analysis shows that the number of Ti–O bonds (initially mostly present in their alkoxo form) decreases upon treatment with BCl3 up to the B/Ti ratio of 2, in agreement with earlier proposals, and increases afterward, due to O-donor ligands, likely related to B-alkoxo species coordinated to Ti. The catalytic activity of these precatalysts after activation with AlEt3 in ethylene polymerization passes through a maximum at a B/Ti ratio of ∼2, pointing to its relation to the detrimental effect of O-based ligands on the activity. This approach allows one to address and quantify the metal speciation in the complex Ziegler–Natta precatalysts and relate this to their catalytic activity, a first step toward establishing quantitative structure–activity relationships.
{"title":"Nature of Surface Sites in Ziegler–Natta Precatalysts from a Quantitative Analysis of the Ti K-Edge X-ray Absorption Spectra","authors":"Alexander V. Yakimov,Alexander Guda,Sergey Guda,Bogdan Protsenko,Elena Groppo,Felipe Morais Bolner,Sebastien Norsic,Jean Raynaud,Vincent Monteil,Christophe Copéret","doi":"10.1021/acs.jpcc.6c00879","DOIUrl":"https://doi.org/10.1021/acs.jpcc.6c00879","url":null,"abstract":"Ziegler–Natta catalysts, discovered in the 1950s, are still central to the industrial production of polyethylene and polypropylene. Despite being the workhorse of the polymer industry and years of extensive research, the improvements in Ziegler–Natta catalysts have been mostly empirical. In particular, the coordination surroundings of the Ti sites in precatalysts, key for the formation of active sites upon AlEt3 activation, have been highly debated. Notably, quantification of different Ti sites on the MgCl2 surface has not been possible thus far, hindering the development of quantitative structure–activity relationships. In this work, we prepared a series of precatalysts with increasing concentrations of the BCl3 modifier during the catalyst synthesis, known to affect the number of Cl and alkoxo ligands in the Ti local surroundings, as well as the activity in ethylene polymerization. We developed a methodology, relying on a library of theoretical X-ray absorption spectroscopy (XAS) lines computed from the density functional theory (DFT)-optimized structural models, benchmarked on a series of well-defined molecular compounds. A quantitative analysis of the XAS data allows us to evaluate the relative fractions of Ti sites in the Cl surrounding, as well as containing alkoxide and O-donor ligands. The analysis shows that the number of Ti–O bonds (initially mostly present in their alkoxo form) decreases upon treatment with BCl3 up to the B/Ti ratio of 2, in agreement with earlier proposals, and increases afterward, due to O-donor ligands, likely related to B-alkoxo species coordinated to Ti. The catalytic activity of these precatalysts after activation with AlEt3 in ethylene polymerization passes through a maximum at a B/Ti ratio of ∼2, pointing to its relation to the detrimental effect of O-based ligands on the activity. This approach allows one to address and quantify the metal speciation in the complex Ziegler–Natta precatalysts and relate this to their catalytic activity, a first step toward establishing quantitative structure–activity relationships.","PeriodicalId":61,"journal":{"name":"The Journal of Physical Chemistry C","volume":"49 1","pages":""},"PeriodicalIF":4.126,"publicationDate":"2026-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147506201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The electrode potential of alkali metals is a critical parameter for battery performance, but its dependence on electrolyte compositions remains poorly understood, particularly for sodium metal, because of its high reactivity with electrolytes. Here, we systematically evaluated the sodium electrode potentials (ENa) in various electrolytes composed of sodium bis(fluorosulfonyl)imide, which enables stable measurements by forming a robust solid electrolyte interphase. The coordination state around Na+ in each electrolyte was analyzed by using Raman spectroscopy and 23Na NMR. In a low-concentration regime, ENa strongly correlates with 23Na chemical shifts that reflect the electron-donating ability of solvents, indicating that the solvating ability is the primary determinant of ENa. At a higher concentration, ab initio molecular dynamics simulations revealed that the 23Na chemical shifts reflected the ion-pairing state, as well as solvation. Leveraging these insights, we developed a simple yet powerful predictive model for the ENa. By using only 23Na chemical shifts and salt-to-solvent molar ratios, the model can accurately predict ENa across diverse electrolytes. This work identifies a new descriptor of ENa and provides a platform for rational electrolyte design for advanced sodium batteries.
{"title":"23Na NMR Chemical Shift as a Descriptor of Sodium Electrode Potential","authors":"Hiroshi Takida,Yasuyuki Kondo,Yu Katayama,Kazuhisa Hirata,Tsuyoshi Yamashita,Yuki Yamada","doi":"10.1021/acs.jpcc.5c08725","DOIUrl":"https://doi.org/10.1021/acs.jpcc.5c08725","url":null,"abstract":"The electrode potential of alkali metals is a critical parameter for battery performance, but its dependence on electrolyte compositions remains poorly understood, particularly for sodium metal, because of its high reactivity with electrolytes. Here, we systematically evaluated the sodium electrode potentials (ENa) in various electrolytes composed of sodium bis(fluorosulfonyl)imide, which enables stable measurements by forming a robust solid electrolyte interphase. The coordination state around Na+ in each electrolyte was analyzed by using Raman spectroscopy and 23Na NMR. In a low-concentration regime, ENa strongly correlates with 23Na chemical shifts that reflect the electron-donating ability of solvents, indicating that the solvating ability is the primary determinant of ENa. At a higher concentration, ab initio molecular dynamics simulations revealed that the 23Na chemical shifts reflected the ion-pairing state, as well as solvation. Leveraging these insights, we developed a simple yet powerful predictive model for the ENa. By using only 23Na chemical shifts and salt-to-solvent molar ratios, the model can accurately predict ENa across diverse electrolytes. This work identifies a new descriptor of ENa and provides a platform for rational electrolyte design for advanced sodium batteries.","PeriodicalId":61,"journal":{"name":"The Journal of Physical Chemistry C","volume":"9 1","pages":""},"PeriodicalIF":4.126,"publicationDate":"2026-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147506207","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-24DOI: 10.1021/acs.jpcc.6c00625
Yiwei He,Dongrun Xu,Zhen Ma,Xingfu Tang
Electronic structures of active components play a pivotal role in determining catalytic activity in heterogeneous catalysis, and modulating electronic metal–support interactions is an efficient protocol to improve catalytic activity of supported metal nanoparticles. Herein, we tune the electronic metal–support interactions by supporting platinum nanoparticles on anatase TiO2(101) and TiO2(001) facets with different work functions to get Pt/TiO2(101) and Pt/TiO2(001), respectively. Owing to the lower work function of TiO2(101) than that of TiO2(001), the supported Pt nanoparticles on TiO2(101) are mainly at a metallic state via support→metal electron transfer, whereas the Pt nanoparticles on TiO2(001) preserve at the oxidation states. Compared with Pt/TiO2(001), the richer high-level electrons around the Fermi level of Pt/TiO2(101) more efficiently facilitate O2 activation and inhibit CO adsorption poisoning, simultaneously, thus lowering the activation energy of the reaction and enhancing the CO oxidation rates. This work provides a reasonable strategy for designing supported metal nanoparticle catalysts by modulating the electronic metal–support interactions via simple facet effects of supports.
{"title":"Modulating Metal–Support Electronic Interactions Enhances CO Oxidation Activity on Pt/TiO2","authors":"Yiwei He,Dongrun Xu,Zhen Ma,Xingfu Tang","doi":"10.1021/acs.jpcc.6c00625","DOIUrl":"https://doi.org/10.1021/acs.jpcc.6c00625","url":null,"abstract":"Electronic structures of active components play a pivotal role in determining catalytic activity in heterogeneous catalysis, and modulating electronic metal–support interactions is an efficient protocol to improve catalytic activity of supported metal nanoparticles. Herein, we tune the electronic metal–support interactions by supporting platinum nanoparticles on anatase TiO2(101) and TiO2(001) facets with different work functions to get Pt/TiO2(101) and Pt/TiO2(001), respectively. Owing to the lower work function of TiO2(101) than that of TiO2(001), the supported Pt nanoparticles on TiO2(101) are mainly at a metallic state via support→metal electron transfer, whereas the Pt nanoparticles on TiO2(001) preserve at the oxidation states. Compared with Pt/TiO2(001), the richer high-level electrons around the Fermi level of Pt/TiO2(101) more efficiently facilitate O2 activation and inhibit CO adsorption poisoning, simultaneously, thus lowering the activation energy of the reaction and enhancing the CO oxidation rates. This work provides a reasonable strategy for designing supported metal nanoparticle catalysts by modulating the electronic metal–support interactions via simple facet effects of supports.","PeriodicalId":61,"journal":{"name":"The Journal of Physical Chemistry C","volume":"60 1","pages":""},"PeriodicalIF":4.126,"publicationDate":"2026-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147506202","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Metal halide-based absorbents of ammonia are promising materials for developing new separation methods for ammonia production. In this study, the ammonia absorption/desorption behaviors of single metal halide salts and mixed metal halides composed of different cations were investigated. The mixed metal halides were prepared via mechanochemical (MC) treatment. The ammonia absorption/desorption behaviors of the MC-treated mixed metal halides were completely different from those of the individual single salts, as well as a simple mixture of the corresponding metal halides prepared using a mortar and pestle. After ammonia absorption, the mixed metal halides formed a single-phase crystal structure with no phase segregation. Fourier-transform infrared analysis revealed that the samples containing specific metal cations (Mn2+) had the same position for the infrared peak (1415 cm–1) assigned to ammonia coordinated to metal cations. These results demonstrate that ammonia preferentially coordinates to specific metal cations (Mn2+) within the mixed metal halides.
{"title":"Preferential Coordination of Ammonia to Specific Cations in Mixed Metal Halides","authors":"Ryota Fujisawa,Manabu Tokushige,Ryosuke Omae,Junichi Ryu","doi":"10.1021/acs.jpcc.5c08662","DOIUrl":"https://doi.org/10.1021/acs.jpcc.5c08662","url":null,"abstract":"Metal halide-based absorbents of ammonia are promising materials for developing new separation methods for ammonia production. In this study, the ammonia absorption/desorption behaviors of single metal halide salts and mixed metal halides composed of different cations were investigated. The mixed metal halides were prepared via mechanochemical (MC) treatment. The ammonia absorption/desorption behaviors of the MC-treated mixed metal halides were completely different from those of the individual single salts, as well as a simple mixture of the corresponding metal halides prepared using a mortar and pestle. After ammonia absorption, the mixed metal halides formed a single-phase crystal structure with no phase segregation. Fourier-transform infrared analysis revealed that the samples containing specific metal cations (Mn2+) had the same position for the infrared peak (1415 cm–1) assigned to ammonia coordinated to metal cations. These results demonstrate that ammonia preferentially coordinates to specific metal cations (Mn2+) within the mixed metal halides.","PeriodicalId":61,"journal":{"name":"The Journal of Physical Chemistry C","volume":"3 1","pages":""},"PeriodicalIF":4.126,"publicationDate":"2026-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147506208","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sliding ferroelectricity holds great promise for enabling low-power, high-density nanoscale devices, yet most studies have focused on two-dimensional (2D) homobilayer systems. Using first-principles calculations, we construct MX/NY (M, N = Al, Ga, Si; X, Y = C, N) heterobilayer structures and show that both interlayer sliding and biaxial compressive strain could trigger polarization reversal in all these configurations, suggesting a consistent trend across the six studied III–IV graphene-like heterobilayers within the present periodic first-principles framework. Moreover, the polarization magnitudes surpass those of well-known 2D homobilayer sliding ferroelectrics. Further analysis shows that the stacking-pattern modulation induced by sliding and the local out-of-plane atomic distortion induced by strain within the periodic heterobilayer model are identified as key factors associated with polarization reversal. These results provide a first-principles design perspective for sliding- and strain-responsive ferroelectricity in asymmetric 2D heterobilayers, particularly for supported or mechanically constrained device configurations.
滑动铁电在实现低功耗、高密度纳米级器件方面具有很大的前景，但大多数研究都集中在二维（2D）均匀层系统上。利用第一性原理计算，我们构建了MX/NY （M, N = Al, Ga, Si； X, Y = C， N）异质层结构，并表明在所有这些结构中，层间滑动和双轴压缩应变都可以触发极化反转，这表明在目前的周期性第一性原理框架内，所研究的六种III-IV类石墨烯异质层具有一致的趋势。此外，极化幅度超过了众所周知的二维均匀层滑动铁电体。进一步分析表明，滑动引起的叠加模式调制和应变引起的局部面外原子畸变是引起周期性异质层模型极化反转的关键因素。这些结果为非对称二维异质层中的滑动和应变响应铁电性提供了第一性原理设计视角，特别是对于支持或机械约束的器件配置。
{"title":"Dual-Mode Polarization Reversal via Coupled Sliding and Strain in 2D Heterobilayers","authors":"Yan-Dong Guo,Shao-Jin Xia,Haoran Hu,Liyan Lin,Yue Jiang,Lin-Dong Zhang,Ye-Wei Chen,Man-Jun Jiang,Hong-Li Zeng,Xiao-Hong Yan","doi":"10.1021/acs.jpcc.5c07809","DOIUrl":"https://doi.org/10.1021/acs.jpcc.5c07809","url":null,"abstract":"Sliding ferroelectricity holds great promise for enabling low-power, high-density nanoscale devices, yet most studies have focused on two-dimensional (2D) homobilayer systems. Using first-principles calculations, we construct MX/NY (M, N = Al, Ga, Si; X, Y = C, N) heterobilayer structures and show that both interlayer sliding and biaxial compressive strain could trigger polarization reversal in all these configurations, suggesting a consistent trend across the six studied III–IV graphene-like heterobilayers within the present periodic first-principles framework. Moreover, the polarization magnitudes surpass those of well-known 2D homobilayer sliding ferroelectrics. Further analysis shows that the stacking-pattern modulation induced by sliding and the local out-of-plane atomic distortion induced by strain within the periodic heterobilayer model are identified as key factors associated with polarization reversal. These results provide a first-principles design perspective for sliding- and strain-responsive ferroelectricity in asymmetric 2D heterobilayers, particularly for supported or mechanically constrained device configurations.","PeriodicalId":61,"journal":{"name":"The Journal of Physical Chemistry C","volume":"18 1","pages":""},"PeriodicalIF":4.126,"publicationDate":"2026-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147506247","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-24DOI: 10.1021/acs.jpcc.6c00841
Hubert King,Ryan Murphy,Avery Baumann,Robert Dalgliesh,Dirk Honecker,Greg Smith
Small-angle neutron scattering (SANS) and polarization-modulation infrared reflection–absorption spectroscopy (PM-IRRAS) were used to investigate the coupled evolution of nanometer water films and carbonation products in Ca(OH)2 and Mg(OH)2 under humidified CO2. Quantitative SANS modeling demonstrates that subnanometer adsorbed films on Ca(OH)2 and thicker (≈1–2 nm) D2O films on Mg(OH)2 mediate ion transport and isotopic exchange at buried interfaces. Infrared spectra confirm H–D exchange on Mg(OH)2 but not on Ca(OH)2, revealing distinct surface accessibility. In situ, both hydroxides initially form amorphous hydrated carbonates─ACC and AMC─but diverge as Ca(OH)2 spontaneously dehydrates to CaCO3 at room temperature while Mg(OH)2 remains hydrated. This divergence reflects the higher hydration affinity of Mg2+ and links isotope-dependent water-film stability to the persistence of amorphous phases. Together, these findings show that interfacial water films dictate whether carbonation proceeds by porosity generation (Calcium) or densification (Magnesium), providing mechanistic insight into mineral carbonation, cement durability, and low-temperature CO2 alteration processes.
{"title":"Studies of Water Films and Carbonation via Neutron Scattering and Infrared Adsorption: In Situ Studies of Mg(OH)2 and Ca(OH)2","authors":"Hubert King,Ryan Murphy,Avery Baumann,Robert Dalgliesh,Dirk Honecker,Greg Smith","doi":"10.1021/acs.jpcc.6c00841","DOIUrl":"https://doi.org/10.1021/acs.jpcc.6c00841","url":null,"abstract":"Small-angle neutron scattering (SANS) and polarization-modulation infrared reflection–absorption spectroscopy (PM-IRRAS) were used to investigate the coupled evolution of nanometer water films and carbonation products in Ca(OH)2 and Mg(OH)2 under humidified CO2. Quantitative SANS modeling demonstrates that subnanometer adsorbed films on Ca(OH)2 and thicker (≈1–2 nm) D2O films on Mg(OH)2 mediate ion transport and isotopic exchange at buried interfaces. Infrared spectra confirm H–D exchange on Mg(OH)2 but not on Ca(OH)2, revealing distinct surface accessibility. In situ, both hydroxides initially form amorphous hydrated carbonates─ACC and AMC─but diverge as Ca(OH)2 spontaneously dehydrates to CaCO3 at room temperature while Mg(OH)2 remains hydrated. This divergence reflects the higher hydration affinity of Mg2+ and links isotope-dependent water-film stability to the persistence of amorphous phases. Together, these findings show that interfacial water films dictate whether carbonation proceeds by porosity generation (Calcium) or densification (Magnesium), providing mechanistic insight into mineral carbonation, cement durability, and low-temperature CO2 alteration processes.","PeriodicalId":61,"journal":{"name":"The Journal of Physical Chemistry C","volume":"16 1","pages":""},"PeriodicalIF":4.126,"publicationDate":"2026-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147506203","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-24DOI: 10.1021/acs.jpcc.5c08676
Amit Kumar,Fengbo Ma,Xianyan Chen,Yiping Zhao
Surface-enhanced Raman scattering (SERS) enables ultrasensitive molecular detection, yet systematic variations in spectral shape (not just signal intensity) often limit reproducibility and interpretation. Here, we present a combined experimental and chemometric study that elucidates how substrate optical response and molecular adsorption orientation jointly govern SERS spectral variability. Using 1,2-bis(4-pyridyl) ethylene (BPE) on oblique-angle-deposited silver nanorod (AgNR) substrates as a model system, we constructed a comprehensive spectral data set spanning six controlled experimental conditions, including defect mapping, batch-to-batch variation, nanorod length tuning, concentration-dependent drop-casting, static immersion, and real-time immersion measurements. Hierarchical cluster analysis (HCA) partitions the spectra into seven reproducible clusters with distinct average spectral shapes, separating low- and high-signal-to-noise regimes and revealing systematic evolution of relative intensities among the five characteristic BPE modes. By correlating cluster membership with experimental metadata, we show that specific spectral shapes are strongly associated with defined physical conditions, including surface defects, nanorod geometry, analyte concentration, and adsorption dynamics. To interpret the cluster-dependent spectral shapes, we introduce intensity web plots under three normalization strategies that isolate different governing physics: absolute intensities emphasize overall electromagnetic enhancement and analyte coverage; normalization by the sum of the five peak intensities suppresses global scaling and highlights substrate-dependent optical reweighting of Raman bands; and normalization to the 1015 cm–1 mode provides an internal reference that accentuates orientation-selective enhancement. Together, these results establish a physics-informed, data-driven framework for better understanding the origins of SERS spectral shape changes under complex experimental conditions.
{"title":"Understanding SERS Spectral Shape Variability through Substrate Optics, Molecular Orientation, and Unsupervised Clustering","authors":"Amit Kumar,Fengbo Ma,Xianyan Chen,Yiping Zhao","doi":"10.1021/acs.jpcc.5c08676","DOIUrl":"https://doi.org/10.1021/acs.jpcc.5c08676","url":null,"abstract":"Surface-enhanced Raman scattering (SERS) enables ultrasensitive molecular detection, yet systematic variations in spectral shape (not just signal intensity) often limit reproducibility and interpretation. Here, we present a combined experimental and chemometric study that elucidates how substrate optical response and molecular adsorption orientation jointly govern SERS spectral variability. Using 1,2-bis(4-pyridyl) ethylene (BPE) on oblique-angle-deposited silver nanorod (AgNR) substrates as a model system, we constructed a comprehensive spectral data set spanning six controlled experimental conditions, including defect mapping, batch-to-batch variation, nanorod length tuning, concentration-dependent drop-casting, static immersion, and real-time immersion measurements. Hierarchical cluster analysis (HCA) partitions the spectra into seven reproducible clusters with distinct average spectral shapes, separating low- and high-signal-to-noise regimes and revealing systematic evolution of relative intensities among the five characteristic BPE modes. By correlating cluster membership with experimental metadata, we show that specific spectral shapes are strongly associated with defined physical conditions, including surface defects, nanorod geometry, analyte concentration, and adsorption dynamics. To interpret the cluster-dependent spectral shapes, we introduce intensity web plots under three normalization strategies that isolate different governing physics: absolute intensities emphasize overall electromagnetic enhancement and analyte coverage; normalization by the sum of the five peak intensities suppresses global scaling and highlights substrate-dependent optical reweighting of Raman bands; and normalization to the 1015 cm–1 mode provides an internal reference that accentuates orientation-selective enhancement. Together, these results establish a physics-informed, data-driven framework for better understanding the origins of SERS spectral shape changes under complex experimental conditions.","PeriodicalId":61,"journal":{"name":"The Journal of Physical Chemistry C","volume":"6 1","pages":""},"PeriodicalIF":4.126,"publicationDate":"2026-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147506206","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To address current energy challenges, solid-state proton conductors for proton exchange membrane fuel cells have attracted significant attention. Understanding and improving proton conduction requires insights into both overall and local structure/molecular dynamics. However, the local structure and molecular dynamics of molecular crystal-based materials have not been explored sufficiently. In this study, we synthesized a novel proton-conducting molecular crystal with a stoichiometric acid–base pair, viz. bisimidazolium 1,5-pentylenediphosphonate (5DPA-2Im), which is a typical composition for molecular crystal-based proton conductors. We also investigated the effect of local structure and molecular dynamics on proton conduction by this molecular crystal. Upon heating, the proton conductivity of 5DPA-2Im increased and continued to increase over time when its temperature was maintained at 413 K. Thermogravimetric (TG) and nuclear magnetic resonance (NMR) analyses revealed that one imidazole molecule is removed from the 5DPA-2Im structure upon heating, which accelerates the molecular motion of other imidazole and 5DPA molecules. Furthermore, proton exchange between two phosphonic acid moieties in 5DPA occurs due to the generation of and H2PO3 in the presence of substoichiometric amounts of imidazole, which are expected to play crucial roles in enhancing proton conductivity. These results suggested that, similar to polymer proton conductors, the local structures and molecular dynamics are also important in molecular crystalline proton conductors.
{"title":"Annealing-Induced Local Structure and Molecular Dynamics Effects Enhance the Proton Conductivity of a Bisimidazolium Diphosphonate Salt","authors":"Yasuhiro Shigeta, Masashi Annen, Nanaka Hosoe, Takuya Kurihara, Shogo Amemori, Tomonori Ida, Motohiro Mizuno","doi":"10.1021/acs.jpcc.5c08405","DOIUrl":"https://doi.org/10.1021/acs.jpcc.5c08405","url":null,"abstract":"To address current energy challenges, solid-state proton conductors for proton exchange membrane fuel cells have attracted significant attention. Understanding and improving proton conduction requires insights into both overall and local structure/molecular dynamics. However, the local structure and molecular dynamics of molecular crystal-based materials have not been explored sufficiently. In this study, we synthesized a novel proton-conducting molecular crystal with a stoichiometric acid–base pair, viz. bisimidazolium 1,5-pentylenediphosphonate (5DPA-2Im), which is a typical composition for molecular crystal-based proton conductors. We also investigated the effect of local structure and molecular dynamics on proton conduction by this molecular crystal. Upon heating, the proton conductivity of 5DPA-2Im increased and continued to increase over time when its temperature was maintained at 413 K. Thermogravimetric (TG) and nuclear magnetic resonance (NMR) analyses revealed that one imidazole molecule is removed from the 5DPA-2Im structure upon heating, which accelerates the molecular motion of other imidazole and 5DPA molecules. Furthermore, proton exchange between two phosphonic acid moieties in 5DPA occurs due to the generation of <i></i><math display=\"inline\"><msubsup><mrow><mi>HPO</mi></mrow><mrow><mn>3</mn></mrow><mrow><mo>−</mo></mrow></msubsup></math> and H<sub>2</sub>PO<sub>3</sub> in the presence of substoichiometric amounts of imidazole, which are expected to play crucial roles in enhancing proton conductivity. These results suggested that, similar to polymer proton conductors, the local structures and molecular dynamics are also important in molecular crystalline proton conductors.","PeriodicalId":61,"journal":{"name":"The Journal of Physical Chemistry C","volume":"14 1","pages":""},"PeriodicalIF":4.126,"publicationDate":"2026-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147496535","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-23DOI: 10.1021/acs.jpcc.6c00118
Debayan Mondal, Priya Mahadevan
Two-dimensional halide perovskites have been found to have unusual optoelectronic properties. The members which have the organic molecule sandwiched between single inorganic layers are found to exhibit a dual excitonic feature, with the one associated with the surface at higher energy than the feature emerging from the interior of the crystal. Surface calculations do not capture this effect. In this work, we show that neutral defects involving a molecule-halogen unit have a small formation energy and hence form easily at the edges/surface. This is a consequence of the weak interactions between the organic cations and the anions. The states introduced by these defects are responsible for the higher band gap state associated with the dual emission that has been observed in experiments. In contrast, these defects are difficult to form in three-dimensional (3D) perovskites, with their formation energy following the molecule-inorganic layer interaction strength. The stronger interactions in MAPbI3 lead to the larger formation energy for the defect, while the weaker interactions in FAPbI3 reduce the formation energy of these defects. Apart from providing the microscopic origin of the dual emission, the present study also provides a route to reduce the concentration of these defects.
{"title":"Why Do We Have Dual Emission in Two-Dimensional Hybrid Perovskites?","authors":"Debayan Mondal, Priya Mahadevan","doi":"10.1021/acs.jpcc.6c00118","DOIUrl":"https://doi.org/10.1021/acs.jpcc.6c00118","url":null,"abstract":"Two-dimensional halide perovskites have been found to have unusual optoelectronic properties. The members which have the organic molecule sandwiched between single inorganic layers are found to exhibit a dual excitonic feature, with the one associated with the surface at higher energy than the feature emerging from the interior of the crystal. Surface calculations do not capture this effect. In this work, we show that neutral defects involving a molecule-halogen unit have a small formation energy and hence form easily at the edges/surface. This is a consequence of the weak interactions between the organic cations and the anions. The states introduced by these defects are responsible for the higher band gap state associated with the dual emission that has been observed in experiments. In contrast, these defects are difficult to form in three-dimensional (3D) perovskites, with their formation energy following the molecule-inorganic layer interaction strength. The stronger interactions in MAPbI<sub>3</sub> lead to the larger formation energy for the defect, while the weaker interactions in FAPbI<sub>3</sub> reduce the formation energy of these defects. Apart from providing the microscopic origin of the dual emission, the present study also provides a route to reduce the concentration of these defects.","PeriodicalId":61,"journal":{"name":"The Journal of Physical Chemistry C","volume":"17 1","pages":""},"PeriodicalIF":4.126,"publicationDate":"2026-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147496537","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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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