Free-electron-based nanoscopy enables the study of optical excitations in materials with deep-subwavelength spatial resolution, with cathodoluminescence (CL) being one of the most useful signals. When combined with an optical collection system, CL measurements can access multidimensional information on light; yet the phase of the emitted optical fields has remained largely elusive. Here, we demonstrate a reference-free phase retrieval approach for far-field CL wavefronts using the Gerchberg–Saxton algorithm implemented with real-space and angular-space CL intensity data. Applying this approach to representative nanostructures, including a planar surface, nanosphere, plasmonic crystal, and nanowire, we reconstructed distinct phase distributions that revealed their underlying radiation mechanisms. This reference-free framework offers a robust and flexible route for retrieving the phase of electron beam-excited optical fields without relying on a reference wave, making it readily extendable to a wide range of nanostructures.
{"title":"Cathodoluminescence Wavefront Retrieval","authors":"Izzah Machfuudzoh,Ryoichi Horisaki,Takumi Sannomiya","doi":"10.1021/acs.nanolett.6c03354","DOIUrl":"https://doi.org/10.1021/acs.nanolett.6c03354","url":null,"abstract":"Free-electron-based nanoscopy enables the study of optical excitations in materials with deep-subwavelength spatial resolution, with cathodoluminescence (CL) being one of the most useful signals. When combined with an optical collection system, CL measurements can access multidimensional information on light; yet the phase of the emitted optical fields has remained largely elusive. Here, we demonstrate a reference-free phase retrieval approach for far-field CL wavefronts using the Gerchberg–Saxton algorithm implemented with real-space and angular-space CL intensity data. Applying this approach to representative nanostructures, including a planar surface, nanosphere, plasmonic crystal, and nanowire, we reconstructed distinct phase distributions that revealed their underlying radiation mechanisms. This reference-free framework offers a robust and flexible route for retrieving the phase of electron beam-excited optical fields without relying on a reference wave, making it readily extendable to a wide range of nanostructures.","PeriodicalId":53,"journal":{"name":"Nano Letters","volume":"291 1","pages":""},"PeriodicalIF":10.8,"publicationDate":"2026-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149221738","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-10-21DOI: 10.1021/acs.nanolett.6c01957
Patrick Grenzer,Fabian Lie,Klaus H. Eckstein,Tobias Hertel,Linn Leppert
Two-dimensional halide perovskites host strongly bound excitons whose fine structure governs polarization selection rules and radiative recombination, yet spectral features in phenethylammonium lead iodide ((PEA)2PbI4) remain controversially assigned. Here, polarization-resolved low-temperature photoluminescence (PL) combined with first-principles G0W0+BSE calculations probes the intralayer and interlayer excitonic fine structure of this Ruddlesden–Popper perovskite. The low-energy multiplet is consistent with the intralayer excitonic fine structure governed by electron–hole exchange, crystal symmetry, and layer inequivalence in the two-layer unit cell, without requiring Rashba effects or exciton–polaron mechanisms as its primary origin. The weak doublet about 40 meV higher is best accounted for by interlayer excitons based on its energetics, splitting, and real-space character. Distortion-induced mixing of interlayer excitons with bright intralayer excitons provides a plausible explanation for the observed interlayer PL intensities and nearly orthogonal polarizations. These results support a layer-resolved excitonic picture encompassing both intralayer and interlayer states in (PEA)2PbI4.
{"title":"Intra- and Interlayer Excitonic Fine Structure of the Two-Dimensional Perovskite (PEA)2PbI4","authors":"Patrick Grenzer,Fabian Lie,Klaus H. Eckstein,Tobias Hertel,Linn Leppert","doi":"10.1021/acs.nanolett.6c01957","DOIUrl":"https://doi.org/10.1021/acs.nanolett.6c01957","url":null,"abstract":"Two-dimensional halide perovskites host strongly bound excitons whose fine structure governs polarization selection rules and radiative recombination, yet spectral features in phenethylammonium lead iodide ((PEA)2PbI4) remain controversially assigned. Here, polarization-resolved low-temperature photoluminescence (PL) combined with first-principles G0W0+BSE calculations probes the intralayer and interlayer excitonic fine structure of this Ruddlesden–Popper perovskite. The low-energy multiplet is consistent with the intralayer excitonic fine structure governed by electron–hole exchange, crystal symmetry, and layer inequivalence in the two-layer unit cell, without requiring Rashba effects or exciton–polaron mechanisms as its primary origin. The weak doublet about 40 meV higher is best accounted for by interlayer excitons based on its energetics, splitting, and real-space character. Distortion-induced mixing of interlayer excitons with bright intralayer excitons provides a plausible explanation for the observed interlayer PL intensities and nearly orthogonal polarizations. These results support a layer-resolved excitonic picture encompassing both intralayer and interlayer states in (PEA)2PbI4.","PeriodicalId":53,"journal":{"name":"Nano Letters","volume":"11 1","pages":""},"PeriodicalIF":10.8,"publicationDate":"2026-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149221737","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Flexible photonic devices and soft microlasers have attracted increasing attention for wearable sensing, biomedical monitoring, and deformable optoelectronic systems. Their mechanical compliance enables intimate contact with soft biological tissues, allowing optical signals to be modulated by external mechanical stimuli. Such characteristics make flexible laser-based platforms particularly suitable for mechanical sensing and physiological signal detection. In this work, we present a flexible microlaser array-based photonic platform designed for mechanical sensing and pulse monitoring. By integrating microscale laser emitters into a soft, transparent matrix with a microstructured architecture, the device maintains stable laser emission while responding to external pressure and dynamic strain. The optical response of the microlaser array exhibits sensitivity to mechanical perturbations, enabling the detection of periodic signals associated with the human pulse. This work highlights the potential of flexible laser photonics as a versatile tool for noninvasive mechanical and physiological sensing in wearable healthcare applications.
{"title":"Flexible Microlaser Emitter for Mechanical Sensing and Pulse Mapping","authors":"Ningyuan Nie,Zhiyi Yuan,Tian Zhou,Guocheng Fang,Bowen Fu,Xiyu Sun,Po-Hao Tseng,Yu-Cheng Chen","doi":"10.1021/acs.nanolett.6c03896","DOIUrl":"https://doi.org/10.1021/acs.nanolett.6c03896","url":null,"abstract":"Flexible photonic devices and soft microlasers have attracted increasing attention for wearable sensing, biomedical monitoring, and deformable optoelectronic systems. Their mechanical compliance enables intimate contact with soft biological tissues, allowing optical signals to be modulated by external mechanical stimuli. Such characteristics make flexible laser-based platforms particularly suitable for mechanical sensing and physiological signal detection. In this work, we present a flexible microlaser array-based photonic platform designed for mechanical sensing and pulse monitoring. By integrating microscale laser emitters into a soft, transparent matrix with a microstructured architecture, the device maintains stable laser emission while responding to external pressure and dynamic strain. The optical response of the microlaser array exhibits sensitivity to mechanical perturbations, enabling the detection of periodic signals associated with the human pulse. This work highlights the potential of flexible laser photonics as a versatile tool for noninvasive mechanical and physiological sensing in wearable healthcare applications.","PeriodicalId":53,"journal":{"name":"Nano Letters","volume":"11 1","pages":""},"PeriodicalIF":10.8,"publicationDate":"2026-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149221680","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Using two-dimensional (2D) van der Waals (vdW) ferromagnets in spintronic devices can enhance their performance through well-controlled vdW interfaces and reduced power consumption. Cr2Te3 appears as a promising candidate because of its strong perpendicular magnetic anisotropy, but the Curie temperature is limited to 180 K. In this work, we use annealing in air to uncover the magnetic phase diagram of Cr2Te3. We correlate magnetic properties with layer stacking and the interlayer distance; both depend strongly on the annealing temperature. In particular, disorder in layer stacking plays a key role in the magnetic properties of Cr2Te3 and more generally of vdW ferromagnets. By annealing at 375 °C, we can eventually raise the Tc of Cr2Te3 up to 303 K in the epitaxial Cr2Te3/WSe2 vdW heterostructure with in-plane magnetic anisotropy. This work provides a simple method to control the magnetic properties of 2D ferromagnets and incorporate them into spintronics devices.
{"title":"Magnetic Phase Diagram of Cr2Te3: The Hidden Role of Layer Stacking","authors":"Cyriack Jego,Thierry Sauvage,Nicolas Gauthier,Quentin Guillet,Jean-François Jacquot,Isabelle Gomes de Moraes,Damien Caliste,Pascal Pochet,Denis Jalabert,Hanako Okuno,Thomas Olsen,Alain Marty,Matthieu Jamet","doi":"10.1021/acs.nanolett.6c03322","DOIUrl":"https://doi.org/10.1021/acs.nanolett.6c03322","url":null,"abstract":"Using two-dimensional (2D) van der Waals (vdW) ferromagnets in spintronic devices can enhance their performance through well-controlled vdW interfaces and reduced power consumption. Cr2Te3 appears as a promising candidate because of its strong perpendicular magnetic anisotropy, but the Curie temperature is limited to 180 K. In this work, we use annealing in air to uncover the magnetic phase diagram of Cr2Te3. We correlate magnetic properties with layer stacking and the interlayer distance; both depend strongly on the annealing temperature. In particular, disorder in layer stacking plays a key role in the magnetic properties of Cr2Te3 and more generally of vdW ferromagnets. By annealing at 375 °C, we can eventually raise the Tc of Cr2Te3 up to 303 K in the epitaxial Cr2Te3/WSe2 vdW heterostructure with in-plane magnetic anisotropy. This work provides a simple method to control the magnetic properties of 2D ferromagnets and incorporate them into spintronics devices.","PeriodicalId":53,"journal":{"name":"Nano Letters","volume":"234 1","pages":""},"PeriodicalIF":10.8,"publicationDate":"2026-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149221740","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Upconverting lanthanide-doped particles are widely used as nanoscale temperature sensors, particularly in biological and photonic environments. However, extending their functionality to simultaneously measure temperature and light intensity remains a challenge, as the luminescent response is highly sensitive to both the environment composition and its temperature. In this work, we combine deep-learning methods with large-scale spectral data sets to investigate the reliability of Er/Yb-doped particles to function as dual sensors. Spectral data are collected from single particles levitating in vacuum and ensembles of particles in application-relevant wet and dry media. Although traditional ratiometric methods reliably retrieve temperature irrespective of the environment and specific experimental apparatus, they fail to disentangle the complex dependencies needed for dual sensing. Our trained models overcome these limitations, accurately predicting both temperature and laser power despite environmental variability. This approach opens a new route toward robust, data-driven sensing with upconverting particles in complex or fluctuating conditions.
{"title":"Deep-Learning-Driven Dual Sensors Based on Single-Trapped Upconverting Particles","authors":"Óscar Pérez-Benito,J. Ignacio Echavarría,Javier Hernandez-Rueda","doi":"10.1021/acs.nanolett.6c03652","DOIUrl":"https://doi.org/10.1021/acs.nanolett.6c03652","url":null,"abstract":"Upconverting lanthanide-doped particles are widely used as nanoscale temperature sensors, particularly in biological and photonic environments. However, extending their functionality to simultaneously measure temperature and light intensity remains a challenge, as the luminescent response is highly sensitive to both the environment composition and its temperature. In this work, we combine deep-learning methods with large-scale spectral data sets to investigate the reliability of Er/Yb-doped particles to function as dual sensors. Spectral data are collected from single particles levitating in vacuum and ensembles of particles in application-relevant wet and dry media. Although traditional ratiometric methods reliably retrieve temperature irrespective of the environment and specific experimental apparatus, they fail to disentangle the complex dependencies needed for dual sensing. Our trained models overcome these limitations, accurately predicting both temperature and laser power despite environmental variability. This approach opens a new route toward robust, data-driven sensing with upconverting particles in complex or fluctuating conditions.","PeriodicalId":53,"journal":{"name":"Nano Letters","volume":"7 1","pages":""},"PeriodicalIF":10.8,"publicationDate":"2026-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149218894","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Curvature couples polarization, crystalline defects, and interfacial electrostatics in freestanding ferroelectric oxides. Here, we examine bent epitaxial Pb(Zr0.2Ti0.8)O3/SrTiO3/Pb(Zr0.2Ti0.8)O3 (PZT/STO/PZT) membranes using atomic-resolution electron microscopy, strain and polarization mapping, relative projected-potential reconstruction, and molecular dynamics simulations. The tensile-side PZT remains comparatively lattice-continuous and accommodates bending mainly through polarization rotation and domain reorganization. The compressive-side PZT exhibits dislocations, slip-related lattice offsets, surface steps, and localized strain concentration. Curvature-series observations and images across U-shaped and N-shaped regions indicate that the defect-rich region follows the local compressive stress state. Bending also breaks the approximate electrostatic symmetry of the two PZT/STO interfaces: the tensile side shows weakened negative interfacial contrast, whereas the compressive side shows a dislocation-associated increase in relative projected potential. These results identify curvature as a variable for selecting polar versus plastic relaxation pathways and modulating interfacial electrostatic landscapes in flexible ferroelectric heterostructures.
{"title":"Curvature-Controlled Polar–Dislocation Coupling in Freestanding Ferroelectric Oxide Heterostructures","authors":"Jianwei Liang,Yi Huang,Gangchang Li,Congbing Tan,Wenpeng Zhu,Yi Zhang,Yue Zheng","doi":"10.1021/acs.nanolett.6c03549","DOIUrl":"https://doi.org/10.1021/acs.nanolett.6c03549","url":null,"abstract":"Curvature couples polarization, crystalline defects, and interfacial electrostatics in freestanding ferroelectric oxides. Here, we examine bent epitaxial Pb(Zr0.2Ti0.8)O3/SrTiO3/Pb(Zr0.2Ti0.8)O3 (PZT/STO/PZT) membranes using atomic-resolution electron microscopy, strain and polarization mapping, relative projected-potential reconstruction, and molecular dynamics simulations. The tensile-side PZT remains comparatively lattice-continuous and accommodates bending mainly through polarization rotation and domain reorganization. The compressive-side PZT exhibits dislocations, slip-related lattice offsets, surface steps, and localized strain concentration. Curvature-series observations and images across U-shaped and N-shaped regions indicate that the defect-rich region follows the local compressive stress state. Bending also breaks the approximate electrostatic symmetry of the two PZT/STO interfaces: the tensile side shows weakened negative interfacial contrast, whereas the compressive side shows a dislocation-associated increase in relative projected potential. These results identify curvature as a variable for selecting polar versus plastic relaxation pathways and modulating interfacial electrostatic landscapes in flexible ferroelectric heterostructures.","PeriodicalId":53,"journal":{"name":"Nano Letters","volume":"51 1","pages":""},"PeriodicalIF":10.8,"publicationDate":"2026-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149221739","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-10-19DOI: 10.1021/acs.nanolett.6c01819
Pietro Maria Forcella,Alessandro De Vita,Matthew D. Watson,Sammar Tayyab,Chiara Bigi,Iulia Cojocariu,Marcin Szpytma,Matteo Jugovac,Andrea Locatelli,Tevfik Onur Menteş,My Bang Petersen,Paolo Moras,Polina M. Sheverdyaeva,Christopher Candelora,Ilija Zeljkovic,Federico Motti,Jill A. Miwa,Vincent Polewczyk,Matthieu Jamet,Matteo Calandra,Younghun Hwang,Davide Romanin,Federico Mazzola
Altermagnets have recently gained attention for hosting symmetry-enforced spin-split bands despite zero net magnetization. Angle-resolved photoelectron spectroscopy (ARPES) offers direct access to their electronic structure. However, the intrinsic surface sensitivity of this technique complicates the identification of the observed features: Surface states can be misinterpreted as the spin-split counterpart of bulk bands. This issue becomes particularly relevant for layered intercalated systems, where micrometer-sized domains with distinct terminations often coexist on a cleaved surface. We discuss this scenario for CoNb4Se8, one of the first established layered altermagnets. Supported by density functional theory calculations, we employ micro-ARPES to probe individual domains and reveal two contrasting surface terminations. We identify Co- and Se-terminated domains with characteristic surface states arising from bulk-surface connectivity of the material. Our work shows that termination-dependent surface contributions are essential for the reliable spectroscopic identification of altermagnetism and for assessing its presence across the family of layered materials.
{"title":"Termination-Dependent Surface Fermiology in the Intercalated Altermagnet CoNb4Se8","authors":"Pietro Maria Forcella,Alessandro De Vita,Matthew D. Watson,Sammar Tayyab,Chiara Bigi,Iulia Cojocariu,Marcin Szpytma,Matteo Jugovac,Andrea Locatelli,Tevfik Onur Menteş,My Bang Petersen,Paolo Moras,Polina M. Sheverdyaeva,Christopher Candelora,Ilija Zeljkovic,Federico Motti,Jill A. Miwa,Vincent Polewczyk,Matthieu Jamet,Matteo Calandra,Younghun Hwang,Davide Romanin,Federico Mazzola","doi":"10.1021/acs.nanolett.6c01819","DOIUrl":"https://doi.org/10.1021/acs.nanolett.6c01819","url":null,"abstract":"Altermagnets have recently gained attention for hosting symmetry-enforced spin-split bands despite zero net magnetization. Angle-resolved photoelectron spectroscopy (ARPES) offers direct access to their electronic structure. However, the intrinsic surface sensitivity of this technique complicates the identification of the observed features: Surface states can be misinterpreted as the spin-split counterpart of bulk bands. This issue becomes particularly relevant for layered intercalated systems, where micrometer-sized domains with distinct terminations often coexist on a cleaved surface. We discuss this scenario for CoNb4Se8, one of the first established layered altermagnets. Supported by density functional theory calculations, we employ micro-ARPES to probe individual domains and reveal two contrasting surface terminations. We identify Co- and Se-terminated domains with characteristic surface states arising from bulk-surface connectivity of the material. Our work shows that termination-dependent surface contributions are essential for the reliable spectroscopic identification of altermagnetism and for assessing its presence across the family of layered materials.","PeriodicalId":53,"journal":{"name":"Nano Letters","volume":"28 1","pages":""},"PeriodicalIF":10.8,"publicationDate":"2026-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149218889","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-10-19DOI: 10.1021/acs.nanolett.6c03267
Samuel Kerschbaumer,David Serrate,Adriana Elizabet Candia,Andrea Aguirre,Danilo Longo,Fadi Choueikani,Jorge Lobo-Checa,Pavel Jelínek,Maxim Ilyn,Celia Rogero,Sebastien E. Hadjadj
Transition metal dihalides are promising magnetic van der Waals materials because of their structural simplicity, chemical stability, and compatibility with nanofabrication. While magnetic order in these systems is typically associated with bulk-like monolayers, its relation to interfacial phases remains largely unexplored. Here we show that in CoBr2 grown on Au(111), long-range magnetic order already emerges in a structurally distinct interfacial precursor phase, prior to the formation of the bulk-like monolayer. During growth, this phase evolves into the monolayer, accompanied by a transition from molecular-like states to semiconducting behavior. Spin-resolved STM reveals an inhomogeneous in-plane magnetic response that is locally suppressed by point defects, whereas macroscopic XMCD demonstrates robust long-range order with pronounced in-plane anisotropy. These results establish that long-range magnetic order in CoBr2 does not require an ideal bulk-like monolayer but can emerge from interfacial phases with distinct electronic and structural properties, enabling magnetism beyond the monolayer limit.
{"title":"Magnetism beyond the Monolayer: Long-Range Order in an Interfacial Phase of CoBr2","authors":"Samuel Kerschbaumer,David Serrate,Adriana Elizabet Candia,Andrea Aguirre,Danilo Longo,Fadi Choueikani,Jorge Lobo-Checa,Pavel Jelínek,Maxim Ilyn,Celia Rogero,Sebastien E. Hadjadj","doi":"10.1021/acs.nanolett.6c03267","DOIUrl":"https://doi.org/10.1021/acs.nanolett.6c03267","url":null,"abstract":"Transition metal dihalides are promising magnetic van der Waals materials because of their structural simplicity, chemical stability, and compatibility with nanofabrication. While magnetic order in these systems is typically associated with bulk-like monolayers, its relation to interfacial phases remains largely unexplored. Here we show that in CoBr2 grown on Au(111), long-range magnetic order already emerges in a structurally distinct interfacial precursor phase, prior to the formation of the bulk-like monolayer. During growth, this phase evolves into the monolayer, accompanied by a transition from molecular-like states to semiconducting behavior. Spin-resolved STM reveals an inhomogeneous in-plane magnetic response that is locally suppressed by point defects, whereas macroscopic XMCD demonstrates robust long-range order with pronounced in-plane anisotropy. These results establish that long-range magnetic order in CoBr2 does not require an ideal bulk-like monolayer but can emerge from interfacial phases with distinct electronic and structural properties, enabling magnetism beyond the monolayer limit.","PeriodicalId":53,"journal":{"name":"Nano Letters","volume":"12 1","pages":""},"PeriodicalIF":10.8,"publicationDate":"2026-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149218885","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-10-19DOI: 10.1021/acs.nanolett.6c03909
Chang-Won Choi,Jeong Hun Choi,Gi-Yeop Kim,In Su Lee,Si-Young Choi
Au nanoparticles (NPs) are inherently thermally unstable at elevated temperatures because their large surface-to-volume ratio promotes melting, migration, and coalescence. Here, we demonstrate that silica (SiO2) nanoconfinement thermodynamically elevates the melting point (Tm) of Au NPs through confinement-induced compressive pressure. Atomic-resolution in situ heating scanning transmission electron microscopy (STEM) combined with local Fourier crystallinity mapping reveals that bare Au NPs lose crystallinity at 1,000 °C, whereas SiO2-encapsulated Au cores (Au@SiO2) remain crystalline. Accordingly, in situ heating TEM shows bare Au NPs progressively merge while Au@SiO2 remain structurally isolated. Temperature-dependent lattice-parameter measurements reveal significantly suppressed thermal expansion of confined Au cores, corresponding to an estimated compressive stress of 4–5 GPa. Finite-element simulations support this estimate, showing that SiO2 shell shrinkage generates several-GPa core pressure, with thicker shells producing higher pressure and greater Tm elevation. These findings establish nanoconfinement-induced pressure as a general thermomechanical strategy for stabilizing metallic NPs under extreme thermal environments.
{"title":"Pressure Engineering through Silica Nanoconfinement for Melting Point Elevation of Gold Nanoparticles","authors":"Chang-Won Choi,Jeong Hun Choi,Gi-Yeop Kim,In Su Lee,Si-Young Choi","doi":"10.1021/acs.nanolett.6c03909","DOIUrl":"https://doi.org/10.1021/acs.nanolett.6c03909","url":null,"abstract":"Au nanoparticles (NPs) are inherently thermally unstable at elevated temperatures because their large surface-to-volume ratio promotes melting, migration, and coalescence. Here, we demonstrate that silica (SiO2) nanoconfinement thermodynamically elevates the melting point (Tm) of Au NPs through confinement-induced compressive pressure. Atomic-resolution in situ heating scanning transmission electron microscopy (STEM) combined with local Fourier crystallinity mapping reveals that bare Au NPs lose crystallinity at 1,000 °C, whereas SiO2-encapsulated Au cores (Au@SiO2) remain crystalline. Accordingly, in situ heating TEM shows bare Au NPs progressively merge while Au@SiO2 remain structurally isolated. Temperature-dependent lattice-parameter measurements reveal significantly suppressed thermal expansion of confined Au cores, corresponding to an estimated compressive stress of 4–5 GPa. Finite-element simulations support this estimate, showing that SiO2 shell shrinkage generates several-GPa core pressure, with thicker shells producing higher pressure and greater Tm elevation. These findings establish nanoconfinement-induced pressure as a general thermomechanical strategy for stabilizing metallic NPs under extreme thermal environments.","PeriodicalId":53,"journal":{"name":"Nano Letters","volume":"3 1","pages":""},"PeriodicalIF":10.8,"publicationDate":"2026-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149218886","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-10-19DOI: 10.1021/acs.nanolett.6c03684
Olga Savkina,Davoud Adinehloo,Ivan Zhigulin,Pranati R. Kuntla,Viktor Labuntsov,Cecilia L. A. V. Campos,Alexander Baev,Andrey Kuzmin,Huamin Li,Igor Aharonovich,Paras N. Prasad,Vasili Perebeinos
Hexagonal boron nitride (h-BN) defects are promising building blocks for quantum photonics and sensing, yet their nonlinear optical signatures remain poorly understood. We use first-principles calculations to determine the polarization-resolved linear, second-order, and third-order susceptibilities of multilayer h-BN containing vacancies and carbon-based defect complexes. Defects weakly affect the linear response but strongly enhance nonlinear susceptibilities through symmetry breaking and resonant defect transitions. Carbon complexes produce orders-of-magnitude increases in second-harmonic generation and distinct polarization-dependent spectra that differentiate defects with identical composition but different geometry. Third-harmonic generation is also enhanced, although it is less sensitive to local structure. Measurements on carbon-doped h-BN qualitatively support these trends. These results establish nonlinear spectroscopy as a powerful probe of defect identity and geometry in h-BN and provide a route to defect-engineered nonlinear quantum photonics.
{"title":"Nonlinear Optical Fingerprints of Defects in Hexagonal Boron Nitride","authors":"Olga Savkina,Davoud Adinehloo,Ivan Zhigulin,Pranati R. Kuntla,Viktor Labuntsov,Cecilia L. A. V. Campos,Alexander Baev,Andrey Kuzmin,Huamin Li,Igor Aharonovich,Paras N. Prasad,Vasili Perebeinos","doi":"10.1021/acs.nanolett.6c03684","DOIUrl":"https://doi.org/10.1021/acs.nanolett.6c03684","url":null,"abstract":"Hexagonal boron nitride (h-BN) defects are promising building blocks for quantum photonics and sensing, yet their nonlinear optical signatures remain poorly understood. We use first-principles calculations to determine the polarization-resolved linear, second-order, and third-order susceptibilities of multilayer h-BN containing vacancies and carbon-based defect complexes. Defects weakly affect the linear response but strongly enhance nonlinear susceptibilities through symmetry breaking and resonant defect transitions. Carbon complexes produce orders-of-magnitude increases in second-harmonic generation and distinct polarization-dependent spectra that differentiate defects with identical composition but different geometry. Third-harmonic generation is also enhanced, although it is less sensitive to local structure. Measurements on carbon-doped h-BN qualitatively support these trends. These results establish nonlinear spectroscopy as a powerful probe of defect identity and geometry in h-BN and provide a route to defect-engineered nonlinear quantum photonics.","PeriodicalId":53,"journal":{"name":"Nano Letters","volume":"5 1","pages":""},"PeriodicalIF":10.8,"publicationDate":"2026-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149218887","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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