{"title":"The effect of samarium substitution on the structure, conduction mechanism, and dielectric relaxation of MnNi-nanospinel ferrites","authors":"B. Ünal,A. Baykal,M. A. Almessiere,E. Mojtahedi","doi":"10.1039/d6cp03090d","DOIUrl":"https://doi.org/10.1039/d6cp03090d","url":null,"abstract":"The incorporation of Sm into Mn–Ni spinel ferrites to form Mn0.5Ni0.5SmxFe2−xO4 (x ≤ 0.10) nanospinel ferrites (Sm → MnNi (x ≤ 0.10) NSFs) was achieved via the sol–gel method. The product was subjected to different characterization techniques to investigate its structure and morphology. A cubic crystal structure and a sphere morphology were confirmed by X-ray Powder Diffractometry (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM), respectively. The electrical and dielectric spectra of the Sm → MnNi (x ≤ 0.10) NSFs were systematically examined using dielectric spectroscopy, electrical conductivity, and complex impedance analyses. The AC conductivity spectra reveal both frequency- and temperature-dependent dispersions, which are consistent with Jonscher's power law (JPL), whereas the Arrhenius analysis of the DC conductivity discloses two thermally activated regimes dominated by localized and long-range small polaron-hopping processes. The calculated activation energies ranged from 10 to 190 meV in the LT region and 420 to 530 meV in the HT region, confirming the dual conduction mechanism. Furthermore, dielectric constant and loss spectra demonstrated Maxwell–Wagner interfacial polarization and Koop's phenomenological behavior, with Sm3+ ion-substitution ratios most strongly influencing the grain boundary resistance and polarization dynamics. In addition, the complex electrical modulus and Nyquist plots reveal single semicircular arcs, indicating grain-boundary-dominant conduction and non-Debye relaxation. Interestingly, moderate Sm3+ ion-substitution ratios, ranging from 0.050 to 0.075, improve lattice distortion, lower the activation energy (EA), and enhance hopping conduction; conversely, excessive substitution ratios, such as 0.10, lead to defect clustering, significantly reducing electrical performance. All these findings strongly highlight the critical role of rare earth (RE) element substitution in shaping conduction and dielectric relaxation in Mn–Ni NSFs.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"31 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149173167","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}
{"title":"Synthesis and self-assembly of new quinuclidinolium-based surfactants: enhanced activity of cytochrome <i>c</i> and efficient antimicrobial activity.","authors":"Muskan Kondal, Rajwinder Kaur, Kanica Sharma, Manpreet Singh, Navdeep Kaur, Pratap Kumar Pati, Sugam Kumar, Vinod Kumar Aswal, Tejwant Singh Kang","doi":"10.1039/d6cp01935h","DOIUrl":"https://doi.org/10.1039/d6cp01935h","url":null,"abstract":"<p><p>Bio-based surfactants are a great alternative to conventional surfactants owing to their low toxicity and minimal environmental impact. Herein, four new 3-quinuclidinol-based surfactants, namely, [C<sub>16</sub>Qui][Br], [C<sub>12</sub>Qui][Br], [C<sub>12</sub>AQui][Br] and [C<sub>8</sub>Qui][Br], have been synthesized and characterized for the first time. The thermal stability of all the surfactants at higher than 250 °C makes them suitable for high-temperature applications. The self-assembly behavior of these surfactants is thoroughly characterized using various techniques. The interactions between relatively hydrophobic bulky head groups, along with other hydrophobic interactions, drive micelle formation. Small-angle neutron scattering (SANS) measurements provide insights into the micellar structures of all surfactants: [C<sub>16</sub>Qui][Br] assembles into spherical micelles, [C<sub>12</sub>Qui][Br] and [C<sub>12</sub>AQui][Br] form prolate ellipsoidal structures, and [C<sub>8</sub>Qui][Br] arranges into loosely packed, random polymer-like micelles. The micellar structure of short-chain surfactants is solely driven by interactions between head groups, while more compact micellar structures are observed for long-chain surfactants. The presence of an amide functionality near the quinuclidinolium head group further governs the characteristics and properties of the micelles. The interlocking of head groups in the self-assembled structure and distinct structural arrangement of surfactant ions are studied through <sup>1</sup>H-NMR spectroscopy and 2D <sup>1</sup>H-<sup>1</sup>H correlation and nuclear Overhauser effect spectroscopies (COSY and NOESY). The aqueous solutions of these surfactants are employed as a catalytic reactor to enhance the enzymatic activity of cytochrome <i>c</i>. The synergistic effect of hydrophobic and electrostatic interactions enhances the enzymatic activity in both monomeric and micellar forms. Interestingly, these surfactants exhibit good microbial inhibition depending upon their structural features and net charge. The present study provides additional understanding of the synthesis of bio-based surfactants and their utilization in diverse biocatalytic and medical applications.</p>","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149178076","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}
{"title":"New insights into fragmentation chemistry of dihydropyran (DHP): a multiscale computational study from neutral dissociation to electron-impact mass spectrometry.","authors":"Bartosz Majewski, Marta Łabuda","doi":"10.1039/d6cp03002e","DOIUrl":"10.1039/d6cp03002e","url":null,"abstract":"<p><p>In this work, we present a multiscale computational investigation of the fragmentation chemistry of 3,4-dihydro-2<i>H</i>-pyran (DHP) by combining complementary quantum chemical calculations, <i>ab initio</i> molecular dynamics, potential energy surface analysis, QCxMS simulations, and machine-learning methods. First, the intrinsic fragmentation pathways of neutral DHP are investigated. Electronic structure calculations characterize the molecular properties, while molecular dynamics simulations reveal the dominant fragmentation channels and their dependence on internal excitation energy. The underlying reaction mechanisms are further elucidated by automated exploration of the potential energy surface identifying key intermediates, transition states, and activation barriers. In the second part, electron-ionization (EI) mass spectra are predicted using QCxMS and three machine-learning models (NEIMS, RASSP, and a developed by us HYBRID GNN-ResNet architecture) and compared with available experimental data. The results highlight the complementary roles of physics-based and data-driven approaches in describing different aspects of DHP fragmentation. The neutral-state molecular dynamics and potential-energy-surface calculations provide mechanistic insight into intrinsic dissociation pathways, whereas QCxMS and machine-learning models enable direct comparison with the experimental EI mass spectrum. Together, these approaches provide a multiscale description of DHP fragmentation while also defining the limits of correspondence between neutral-state dynamics and electron-impact fragmentation.</p>","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":" ","pages":"24557-24569"},"PeriodicalIF":3.0,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149035611","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}
{"title":"Dipole-constrained variational Hirshfeld for electrostatically faithful atomic charges.","authors":"Leila Pujal, Farnaz Heidar-Zadeh","doi":"10.1039/d6cp02598f","DOIUrl":"https://doi.org/10.1039/d6cp02598f","url":null,"abstract":"<p><p>Density-based atomic partitioning methods provide atomic electron densities that enable the consistent derivation of atomic properties used to model non-bonded interactions, but their atomic charges often fail to accurately reproduce molecular electrostatics. We develop dipole-constrained additive variational Hirshfeld (d-AVH), a partitioning method that exactly reproduces the reference molecular dipole using atomic charges alone. The method extends the AVH framework by introducing dipole constraints into the variational optimization of promolecular densities, which are represented as linear combinations of neutral and charged proatom densities. Two variants are studied: the computationally efficient minimal-basis d-AVH-M and the more flexible bound-proatom d-AVH-B. Across a diverse dataset of more than 760 compounds, d-AVH systematically improves the accuracy of point-charge approximations to the electrostatic potential (ESP) relative to AVH while preserving the conformational stability and interpretability of Hirshfeld-based atomic densities. For several chemically distinct subsets, d-AVH matches the accuracy of ESP-fitted charges and surpasses Charge Model 5. These results establish d-AVH as a broadly applicable density-based framework for constructing electrostatically faithful atomic charges.</p>","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149177889","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}
{"title":"<i>Ab initio</i> kinetics and thermochemistry of hydrogen atom abstraction from solketal by hydroxyl radicals.","authors":"Solmaz Nadiri, Yuxiang Zhu, Chong-Wen Zhou","doi":"10.1039/d6cp01808d","DOIUrl":"https://doi.org/10.1039/d6cp01808d","url":null,"abstract":"<p><p>As oxygenated biofuels gain prominence in sustainable energy strategies, understanding their reaction kinetics with hydroxyl (˙OH) radicals is essential for predicting combustion behavior. In this work, all six hydrogen-atom abstraction (HAA) pathways in the solketal (2,2-dimethyl-1,3-dioxolane-4-methanol) + ˙OH reaction were characterized using high-level <i>ab initio</i> calculations and variational transition state theory (VTST). Molecular geometries and vibrational frequencies were obtained at the M06-2X/6-311++G(d,p) level, with single-point energies refined at the QCISD(T)/CBS level. Low-frequency torsional modes were treated using one-dimensional hindered rotor scans. All abstraction channels proceed through low or partially submerged transition states (-3.1 to 3.2 kcal mol<sup>-1</sup>), necessitating a variational treatment. VTST calculations with asymmetric Eckart tunneling corrections were performed over 300-2000 K. At 298 K, the α (hydroxymethyl C-H) and r<sub>1</sub> (ring methine C-H) channels dominate the reactivity, yielding a total rate coefficient of <i>k</i><sub>total</sub> (298 K) ≈ 1.4 × 10<sup>13</sup> cm<sup>3</sup> mol<sup>-1</sup> s<sup>-1</sup>. With increasing temperature, the ring-centered channels (r<sub>1</sub> and r<sub>2</sub>) become dominant, while O-H abstraction becomes increasingly competitive, reaching ∼24% of the total flux at 2000 K. A systematic sensitivity analysis shows that the β<sub>1</sub>, β<sub>2</sub>, and O-H channels are strongly influenced by the treatment of low-frequency vibrational modes, leading to variations in the predicted rate coefficients of up to several orders of magnitude. In contrast, the α, r<sub>1</sub>, and r<sub>2</sub> channels are comparatively robust. Temperature-dependent thermochemical properties (Δ<sub>f</sub><i>H</i>°, <i>S</i>°, ) were computed and fitted to NASA polynomials, and modified Arrhenius parameters were derived for all channels. The resulting dataset provides a consistent foundation for incorporation into detailed combustion models and highlights the importance of entropic and variational effects in hydrogen abstraction from multifunctional oxygenates.</p>","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149177896","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}
Ruobing Han, Chenrui Zhang, Tianzhen Yang, Yuquan Zhu, Jingyu Sun, Rufang Zhao, Yang Wang
{"title":"Rational design and mechanistic elucidation of Pt-based alloy-supported Fe<sub>1</sub>(OH)<sub>3</sub> interfaces for superior CO oxidation catalysis.","authors":"Ruobing Han, Chenrui Zhang, Tianzhen Yang, Yuquan Zhu, Jingyu Sun, Rufang Zhao, Yang Wang","doi":"10.1039/d6cp02797k","DOIUrl":"https://doi.org/10.1039/d6cp02797k","url":null,"abstract":"<p><p>The development of active and stable CO oxidation catalysts is critical for PEMFCs, as they purify hydrogen fuel and mitigate cathode poisoning, determining cell efficiency and operational lifetime. In this work, we present a rational design strategy for such catalysts <i>via</i> first-principles calculations. We constructed well-defined Fe<sub>1</sub>(OH)<sub>3</sub>/M<sub>1</sub>Pt interfaces by anchoring Fe<sub>1</sub>(OH)<sub>3</sub> clusters onto transition-metal-doped Pt surfaces. A multi-step screening strategy was implemented to screen sixteen transition metals, identifying Cu, Zn, Ag, and Au as optimal dopants that fine-tune *CO adsorption strength into a favorable range. These catalysts exhibit moderate *CO adsorption energies and significantly reduced Gibbs free-energy barriers for the rate-determining step compared to the Fe<sub>1</sub>(OH)<sub>3</sub>/Pt reference. The activity originates from a balance between moderate *CO adsorption and hydrogen-bond stabilization of *COOH by the Fe<sub>1</sub>(OH)<sub>3</sub> site. Alloying the Pt support with Cu, Zn, Ag, or Au leads to more exothermic *COOH formation and enhances the reaction kinetics by lowering the kinetic barriers. Electronic analysis reveals that the cohesive energy of the dopant metal and the number of unpaired d-electrons serve as key descriptors for *CO adsorption strength. This work provides a comprehensive design strategy and fundamental insights for developing highly active and stable single-site catalysts for CO oxidation in PEMFCs.</p>","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149178114","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}
{"title":"Cage-Dependent Raman Bands of O2 Molecules Confined in Clathrate Hydrate Structures","authors":"Yusuke Jin,Satoshi Takeya,Jiro Nagao","doi":"10.1039/d6cp03509d","DOIUrl":"https://doi.org/10.1039/d6cp03509d","url":null,"abstract":"The vibrational properties of guest molecules confined within clathrate hydrate (hydrate) cages are strongly influenced by the local positions of the guests within the cage framework. Herein, we report the O-O stretching Raman bands of O₂ molecules en-caged in structure-I, structure-II, and structure-H hydrates. Unexpectedly, the O-O stretching bands assigned to the larger 5¹²6² and 5¹²6⁴ cages are blue-shifted relative to that of the smaller 5¹² cage. This observation contrasts with the conventional loose-cage/tight-cage model, in which the vibrational frequencies of smaller guest molecules confined in smaller cages generally appear at higher wavenumbers compared to those in larger cages.To clarify the origin of this anomalous Raman behavior, density functional theory (DFT) calculations were performed for O₂, N₂, and CH₄ molecules confined within representative hydrate cages. The optimized structures and guest-position potential energy profiles reveal that O₂ exhibits more pronounced cage-wall-proximal localization than N₂ and CH₄, particularly in the 5¹²6² and 5¹²6⁴ cages. The combined Raman and DFT results indicate that O₂ confined within these larger cages experiences a more repulsive local environment than that in the smaller cage. These findings indicate that the unusual Raman behavior of O₂ is associated not only with cage size but also with cagewall-proximal localization.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"14 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149173153","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}
{"title":"Cluster defect Zn + Si in KHPO crystals: effects on electronic structure and optical properties","authors":"Yu Ren,Haixiu Gan,Fang Xie,Ning Meng,Tingyu Liu","doi":"10.1039/d6cp02841a","DOIUrl":"https://doi.org/10.1039/d6cp02841a","url":null,"abstract":"First-principles calculations were implemented to explore the performance evolution of paraelectric (PE) and ferroelectric (FE) KH2PO4 (KDP) crystals induced by the cluster defect ZnK + SiP. The Freysoldt–Neugebauer–Vande Walle (FNV) finite-size correction was employed to calculate accurate defect formation energies (DFEs). This study systematically investigates the lattice configurations, electronic features, as well as optical absorption and luminescence spectra. Our calculations directly connect atomic-scale defect physics to experimentally measurable macroscopic properties. We find that the negatively charged defect (ZnK + SiP)′ causes the most drastic local lattice deformation (34.59%) and orbital reconstruction, which quantitatively explains the experimentally observed sub-bandgap absorption and provides a microscopic mechanism for laser-induced damage. Specifically, the in-gap localized defect states promote multi-photon absorption, a key precursor to irreversible lattice damage under long-term laser irradiation. Considerable electron–phonon coupling leads to a high Huang–Rhys factor in PE-KDP, indicating phonon-dominated non-radiative energy dissipation. This non-radiative pathway quantitatively accounts for the thermal load that ultimately reduces the laser-induced damage threshold (LIDT). The simulated absorption peak at 3.08 eV (403 nm) matches the experimental absorption signal at 395 nm. Remarkable Stokes redshifts confirm that most photoexcitation energy transforms into lattice heat, which directly correlates with the reduced operational lifetime of KDP optical components in high-power laser systems, particularly for inertial confinement fusion (ICF) applications.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"6 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149173163","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}
Siyi Wang, Jie Yang, Yongchun Li, Abduhalik Kadir, Bumaliya Abulimiti, Mei Xiang
{"title":"Molecular twisting, donor engineering, and BF<sub>2</sub> coordination in chalcone-coumarin sensitizers for DSSCs.","authors":"Siyi Wang, Jie Yang, Yongchun Li, Abduhalik Kadir, Bumaliya Abulimiti, Mei Xiang","doi":"10.1039/d6cp02505f","DOIUrl":"https://doi.org/10.1039/d6cp02505f","url":null,"abstract":"<p><p>Efficient organic sensitizers for dye-sensitized solar cells (DSSCs) need to absorb light effectively while maintaining good charge separation and dye regeneration. In this work, twelve chalcone-coumarin-based D-π-A sensitizers were designed to study the effects of donor structure and BF<sub>2</sub> coordination on their electronic, excited-state, and photovoltaic properties. Benchmark calculations using experimentally reported parent dyes showed that CAM-B3LYP gives a suitable description of the charge-transfer excitations in these systems. Increasing the strength of the D unit raises the HOMO energy and reduces the HOMO-LUMO gap. BF<sub>2</sub> coordination mainly lowers the LUMO energy and increases polarization on the acceptor side. The energy gap decreases from 1.843 to 1.327 eV for the AX1 dyes and from 1.632 to 1.136 eV for the AX2 dyes. These changes are accompanied by red shifts of the absorption bands of up to 186 nm. Hole-electron and interfragment charge-transfer analyses show that stronger donors promote charge transfer within the molecule, while BF<sub>2</sub> coordination increases the contribution of the acceptor region. All of the sensitizers have favorable electron-injection driving forces. The strength of the D unit also affects the thermodynamics of dye regeneration. Based on the calculated electronic, optical, and photovoltaic properties, 2-AX2, 3-AX2, and 2-BX2 show the most favorable overall properties.</p>","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149178108","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}
{"title":"Vacancy-engineered electronic reconstruction for spin-polarized photocurrent with signal enhancement in Ti<sub>2</sub>CO<sub>2</sub> MXene.","authors":"Yufei Huang, Chuan Xie, Meiqi Wang, Qifeng Li, Fangqi Liu, Sicong Zhu","doi":"10.1039/d6cp02479c","DOIUrl":"10.1039/d6cp02479c","url":null,"abstract":"<p><p>Polarization-sensitive and spin-polarized photocurrent generation paves a critical path for constructing multifunctional integrated optoelectronic devices. However, two-dimensional material systems that simultaneously possess intrinsic tunable electronic structures and strong polarization-dependent photoresponse remain extremely scarce. Herein, we systematically investigate the modulation mechanisms of vacancy engineering on the electronic structures, optical properties, and device photoelectric transport performance of Ti<sub>2</sub>CO<sub>2</sub> MXene with different layer thicknesses using first-principles calculations combined with the nonequilibrium Green's function method. At the material level, our investigations reveal that oxygen vacancies primarily induce bandgap narrowing and significantly enhance the optical absorption of the material in the low-energy region. In contrast, titanium vacancies in monolayer Ti<sub>2</sub>CO<sub>2</sub> and carbon vacancies in the upper layer of bilayer Ti<sub>2</sub>CO<sub>2</sub> strongly break the parity-time (PT) symmetry of the crystal lattice, leading to bandgap closure, the introduction of defect states near the Fermi level, and pronounced spin-splitting effects. Device-level simulations further confirm that vacancy engineering can effectively modulate polarization-dependent photocurrents and achieve a substantial enhancement of the extinction ratio in specific photon energy ranges. Among all the studied configurations, bilayer Ti<sub>2</sub>CO<sub>2</sub> with an upper-layer carbon vacancy exhibits the optimal optoelectronic performance: its maximum photocurrent approaches 90<i>a</i><sub>0</sub><sup>2</sup> per photon near 0.7 eV, and the extinction ratio reaches as high as 1.5 × 10<sup>3</sup> near 1.0 eV. Notably, both the titanium-vacancy and upper-layer carbon-vacancy configurations can generate highly spin-polarized photocurrents with a maximum spin polarization approaching 100%. These findings highlight that vacancy-engineered Ti<sub>2</sub>CO<sub>2</sub> is a highly promising candidate for high-performance polarization-sensitive photodetectors and spin-polarized optoelectronic devices.</p>","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":" ","pages":"24467-24474"},"PeriodicalIF":3.0,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149035575","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}