Huai Lin, Huiying Guo, Xuejun Cheng, An Su, Liping Huang, Qingwu Yao, Xiaohuo Shi, Ruoxu Wang, Hongyu Chen
In our previous studies of metal nanoparticle growth, we have come to realize that the dynamic interplay between ligand passivation and metal deposition, as opposed to static facet control, is responsible for focused growth at a few active sites. In this work, we show that the same underlying principle could be applied to a very different system and explain the abnormal growth modes of liquid nanoparticles. In such a liquid active surface growth (LASG), the interplay between droplet expansion and simultaneous silica shell encapsulation gives rise to an active site of growth, which eventually becomes the long necks of nanobottles. For this synthetic control, the imbalance of the said interplay is the critical factor, as demonstrated by carefully designed control experiments. Thus, LASG provides a coherent mechanism that encompasses a wide range of liquid-derived nanostructures, including hollow nanospheres, asymmetric teardrops, and hollow nanobottles with an opening. By adapting nanosynthesis techniques from the solid to liquid realm, we believe that LASG would provide deeper insights and more sophisticated synthetic controls.
{"title":"Liquid Active Surface Growth: Explaining the Symmetry Breaking in Liquid Nanoparticles","authors":"Huai Lin, Huiying Guo, Xuejun Cheng, An Su, Liping Huang, Qingwu Yao, Xiaohuo Shi, Ruoxu Wang, Hongyu Chen","doi":"10.1021/acsnano.4c12039","DOIUrl":"https://doi.org/10.1021/acsnano.4c12039","url":null,"abstract":"In our previous studies of metal nanoparticle growth, we have come to realize that the dynamic interplay between ligand passivation and metal deposition, as opposed to static facet control, is responsible for focused growth at a few active sites. In this work, we show that the same underlying principle could be applied to a very different system and explain the abnormal growth modes of liquid nanoparticles. In such a liquid active surface growth (LASG), the interplay between droplet expansion and simultaneous silica shell encapsulation gives rise to an active site of growth, which eventually becomes the long necks of nanobottles. For this synthetic control, the imbalance of the said interplay is the critical factor, as demonstrated by carefully designed control experiments. Thus, LASG provides a coherent mechanism that encompasses a wide range of liquid-derived nanostructures, including hollow nanospheres, asymmetric teardrops, and hollow nanobottles with an opening. By adapting nanosynthesis techniques from the solid to liquid realm, we believe that LASG would provide deeper insights and more sophisticated synthetic controls.","PeriodicalId":21,"journal":{"name":"ACS Nano","volume":"43 1","pages":""},"PeriodicalIF":17.1,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142981654","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}
The study describes a self-illuminating nanoparticle that displays selective antitumoral activity. (1) The nanovector’s antitumoral properties are attributed to the TRAIL receptor 2 (DR5) peptidomimetic, whose cross-linking, induced by a smart H<sub>2</sub>O<sub>2</sub>-responsive self-illuminating nanoagonist, strongly activates the extrinsic pro-apoptotic signaling pathway. This activation was evidenced <i>in vitro</i> by flow cytometry. The antitumoral efficacy of this smart system was also assessed <i>in vivo</i> using the syngeneic 4T1 tumor breast cancer model. The study shows that the smart nanovector not only prevents tumor growth, achieving more than 82% tumor suppression compared to controls, but also displayed anti-metastatic properties. The manuscript is based on the assumption that the DR5-specific peptide used (WDCLDNRIGRRQCVL), which is known to target human DR5, cross-reacts with the unique mouse TRAIL receptor agonist. (2) While it is true that most ligands of the tumor necrosis factor superfamily (TNFSF), including TRAIL, (3) cross-react between human and mouse orthologues, (4) it should be kept in mind that some members such as GITR/GITRL or APRIL/BAFF-R are strictly species-specific. (4) The first peptide described to display TRAIL-like pro-apoptotic activity was obtained from a peptide scan library composed of 8 amino acids derived from TRAIL itself (see Table 1). Out of the 6 peptides found to trigger apoptosis the most efficient candidate, RNSCWSKD, corresponded to TRAIL aa227-234. (5) Subsequent single amino acid substitution of this sequence revealed a potent peptide CNSCWSKD whose pro-apoptotic activity was shown to engage both DR4 and DR5 (ref (6); see also Table 1), which is consistent with the fact that this peptide derives from TRAIL. However, the DR5-specific peptide used in You et al.’s study is unrelated to TRAIL, (7) and as shown in Table 1, all studies reporting its use, (7−20) so far, only described the use of human cells to assess the biological activity of their formulation (Table 1). In addition, this peptide has, early on, been described to be highly specific for human DR5 and not able to bind to mouse TRAIL receptor. (11,16) Likewise, surface plasmon resonance (SPR) assessments found this peptide unable to bind to human DR4 and the mouse TRAIL receptor. (11) In You’s manuscript, the only evidence of a potential interaction between their smart nanoparticle and the mouse TRAIL receptor is provided by confocal immunofluorescence staining and a FRET assay that show the <i>vicinity</i> of the formulation with the murine TRAIL receptors. While these experiments are interesting, and despite the fact their nanovector displays antitumoral activity, the mere coincident proximity of the receptor and the nanovector is not a strong argument for demonstrating the interaction. The antitumoral efficacy of the formulation may not even rely on the ability of the peptide to engage mouse TRAIL receptor aggregation. Addressing
{"title":"Comment on “Self-Illuminating Nanoagonist Simultaneously Induces Dual Cell Death Pathways via Death Receptor Clustering for Cancer Therapy”","authors":"Olivier Micheau, Sylvie Fournel","doi":"10.1021/acsnano.4c13100","DOIUrl":"https://doi.org/10.1021/acsnano.4c13100","url":null,"abstract":"The study describes a self-illuminating nanoparticle that displays selective antitumoral activity. (1) The nanovector’s antitumoral properties are attributed to the TRAIL receptor 2 (DR5) peptidomimetic, whose cross-linking, induced by a smart H<sub>2</sub>O<sub>2</sub>-responsive self-illuminating nanoagonist, strongly activates the extrinsic pro-apoptotic signaling pathway. This activation was evidenced <i>in vitro</i> by flow cytometry. The antitumoral efficacy of this smart system was also assessed <i>in vivo</i> using the syngeneic 4T1 tumor breast cancer model. The study shows that the smart nanovector not only prevents tumor growth, achieving more than 82% tumor suppression compared to controls, but also displayed anti-metastatic properties. The manuscript is based on the assumption that the DR5-specific peptide used (WDCLDNRIGRRQCVL), which is known to target human DR5, cross-reacts with the unique mouse TRAIL receptor agonist. (2) While it is true that most ligands of the tumor necrosis factor superfamily (TNFSF), including TRAIL, (3) cross-react between human and mouse orthologues, (4) it should be kept in mind that some members such as GITR/GITRL or APRIL/BAFF-R are strictly species-specific. (4) The first peptide described to display TRAIL-like pro-apoptotic activity was obtained from a peptide scan library composed of 8 amino acids derived from TRAIL itself (see Table 1). Out of the 6 peptides found to trigger apoptosis the most efficient candidate, RNSCWSKD, corresponded to TRAIL aa227-234. (5) Subsequent single amino acid substitution of this sequence revealed a potent peptide CNSCWSKD whose pro-apoptotic activity was shown to engage both DR4 and DR5 (ref (6); see also Table 1), which is consistent with the fact that this peptide derives from TRAIL. However, the DR5-specific peptide used in You et al.’s study is unrelated to TRAIL, (7) and as shown in Table 1, all studies reporting its use, (7−20) so far, only described the use of human cells to assess the biological activity of their formulation (Table 1). In addition, this peptide has, early on, been described to be highly specific for human DR5 and not able to bind to mouse TRAIL receptor. (11,16) Likewise, surface plasmon resonance (SPR) assessments found this peptide unable to bind to human DR4 and the mouse TRAIL receptor. (11) In You’s manuscript, the only evidence of a potential interaction between their smart nanoparticle and the mouse TRAIL receptor is provided by confocal immunofluorescence staining and a FRET assay that show the <i>vicinity</i> of the formulation with the murine TRAIL receptors. While these experiments are interesting, and despite the fact their nanovector displays antitumoral activity, the mere coincident proximity of the receptor and the nanovector is not a strong argument for demonstrating the interaction. The antitumoral efficacy of the formulation may not even rely on the ability of the peptide to engage mouse TRAIL receptor aggregation. Addressing","PeriodicalId":21,"journal":{"name":"ACS Nano","volume":"4 1","pages":""},"PeriodicalIF":17.1,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142975224","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}
Inhalation delivery, offering a direct pathway for administering drugs to the lungs in the form of dry powders or aerosols, stands out as an optimal approach for the localized treatment of pulmonary diseases. However, the intricate anatomical architecture of the lung often poses challenges in maintaining effective drug concentrations within the lungs over extended periods. This highlights the pressing need to develop rational inhalable drug delivery systems that can improve treatment outcomes for respiratory diseases. Metal–organic frameworks (MOFs) assembled from inorganic metal ions and organic ligands, characterized by customizable porous architecture and chemical composition, modifiable porosity, vast surface area, straightforward surface modification, and adjustable biocompatibility, have garnered extensive attention in the biomedical sphere. The introduction of MOFs into inhalation therapy represents a promising avenue to navigate past the hurdles associated with traditional inhalation methods. Therefore, this review summarizes the characteristics of inhalation delivery together with the latest advances, challenges, and opportunities in utilizing inhalable MOFs for treating lung diseases and discusses prospects in this field alongside the potential pathways for translating this strategy into clinic.
{"title":"Inhalable Metal–Organic Frameworks: A Promising Delivery Platform for Pulmonary Diseases Treatment","authors":"Qifan Yu, Qiang Zhang, Zhiqiang Wu, Yang Yang","doi":"10.1021/acsnano.4c16873","DOIUrl":"https://doi.org/10.1021/acsnano.4c16873","url":null,"abstract":"Inhalation delivery, offering a direct pathway for administering drugs to the lungs in the form of dry powders or aerosols, stands out as an optimal approach for the localized treatment of pulmonary diseases. However, the intricate anatomical architecture of the lung often poses challenges in maintaining effective drug concentrations within the lungs over extended periods. This highlights the pressing need to develop rational inhalable drug delivery systems that can improve treatment outcomes for respiratory diseases. Metal–organic frameworks (MOFs) assembled from inorganic metal ions and organic ligands, characterized by customizable porous architecture and chemical composition, modifiable porosity, vast surface area, straightforward surface modification, and adjustable biocompatibility, have garnered extensive attention in the biomedical sphere. The introduction of MOFs into inhalation therapy represents a promising avenue to navigate past the hurdles associated with traditional inhalation methods. Therefore, this review summarizes the characteristics of inhalation delivery together with the latest advances, challenges, and opportunities in utilizing inhalable MOFs for treating lung diseases and discusses prospects in this field alongside the potential pathways for translating this strategy into clinic.","PeriodicalId":21,"journal":{"name":"ACS Nano","volume":"8 1","pages":""},"PeriodicalIF":17.1,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142981578","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}
Carbon nanotubes (CNTs) with exceptional conductivity have been widely adopted in lithium-sulfur (Li-S) batteries. While trace metal impurities in CNTs have demonstrated electrocatalytic activity in various catalytic processes, their influence on sulfur electrocatalysis in Li-S batteries has been largely overlooked. Herein, we reveal that the trace metal impurities content in CNTs significantly improves the specific capacity and cycling performance of Li-S batteries by analyzing both our own results and previous literature with CNTs as the sulfur hosts. Even under lean electrolyte conditions (E/S ratio of 5 μL mgs-1), we demonstrate that a small content of metal impurities in CNTs (∼2 wt %) could account for a 14.3% increase in specific capacity and a 14.1% increase in capacity retention under a high sulfur loading of 3.5 mg cm-2. The electron transfer from confined metal catalysts within CNTs leads to electron accumulation at the carbon interface, facilitating electron donation to adsorbed sulfur species and lowering the energy barrier for Li2S formation.
{"title":"Trace Metal Impurities Induce Differences in Lithium-Sulfur Batteries.","authors":"Mengyao Li, Junwei Han, Qiuchen Song, Huan Li, Linkai Peng, Yufei Zhao, Yun Cao, Wei Lv","doi":"10.1021/acsnano.4c14181","DOIUrl":"10.1021/acsnano.4c14181","url":null,"abstract":"<p><p>Carbon nanotubes (CNTs) with exceptional conductivity have been widely adopted in lithium-sulfur (Li-S) batteries. While trace metal impurities in CNTs have demonstrated electrocatalytic activity in various catalytic processes, their influence on sulfur electrocatalysis in Li-S batteries has been largely overlooked. Herein, we reveal that the trace metal impurities content in CNTs significantly improves the specific capacity and cycling performance of Li-S batteries by analyzing both our own results and previous literature with CNTs as the sulfur hosts. Even under lean electrolyte conditions (E/S ratio of 5 μL mg<sub>s</sub><sup>-1</sup>), we demonstrate that a small content of metal impurities in CNTs (∼2 wt %) could account for a 14.3% increase in specific capacity and a 14.1% increase in capacity retention under a high sulfur loading of 3.5 mg cm<sup>-2</sup>. The electron transfer from confined metal catalysts within CNTs leads to electron accumulation at the carbon interface, facilitating electron donation to adsorbed sulfur species and lowering the energy barrier for Li<sub>2</sub>S formation.</p>","PeriodicalId":21,"journal":{"name":"ACS Nano","volume":" ","pages":"1412-1423"},"PeriodicalIF":15.8,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142862505","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}
Figure 1. Sensorgrams showing the interaction between the ligand peptide and (A) human or (B) mouse DR5 at various concentrations. The fitted curves represent the kinetic analysis using a 1:1 Langmuir binding model. Multivalency effect: The conjugation of ligand peptides to the lipid-polymer hybrid OVE nanoparticles enabled the presentation of multiple peptides on the nanoparticle surface, allowing simultaneous interaction with DR5 and therefore enhancing overall binding strength. (7) Consequently, while the single peptide already demonstrated notable affinity, the multivalent nanoagonist further amplified this interaction, as evidenced by the enhanced antitumor efficacy observed in murine models (L–PEG-NP group). Optimization of flexibility and spatial presentation through PEG chains: The inclusion of 4-arm PEG in our nanoagonist design contributed to its flexibility and spatial adaptability. The high hydrophilicity and extended molecular chains of PEG allowed the ligand peptides to adopt dynamic conformations and orientations favorable for receptor binding. Unlike rigid structural scaffolds, this flexibility likely enhanced receptor engagement by enabling the peptides to adapt to the spatial and structural features of mouse DR5. (8) This spatial optimization provided by PEG and the nanoparticle scaffold facilitated even more effective interaction with mouse DR5, building upon the already significant intrinsic affinity of the ligand peptides in their monovalent form. Increased local concentration of ligand peptides: The local concentration of ligand peptides was significantly increased on the nanoparticle surface, creating a high local concentration of binding sites. This local enrichment enhanced the likelihood of interactions with mouse DR5, resulting in more frequent and stronger binding, (9) further enhancing the affinity for the murine receptor. This article references 9 other publications. This article has not yet been cited by other publications.
{"title":"Reply to “Comment on ‘Self-Illuminating Nanoagonist Simultaneously Induces Dual Cell Death Pathways via Death Receptor Clustering for Cancer Therapy’”","authors":"Yuchan You, Xiaochuan Wu, Yong-Zhong Du","doi":"10.1021/acsnano.4c17726","DOIUrl":"https://doi.org/10.1021/acsnano.4c17726","url":null,"abstract":"Figure 1. Sensorgrams showing the interaction between the ligand peptide and (A) human or (B) mouse DR5 at various concentrations. The fitted curves represent the kinetic analysis using a 1:1 Langmuir binding model. Multivalency effect: The conjugation of ligand peptides to the lipid-polymer hybrid OVE nanoparticles enabled the presentation of multiple peptides on the nanoparticle surface, allowing simultaneous interaction with DR5 and therefore enhancing overall binding strength. (7) Consequently, while the single peptide already demonstrated notable affinity, the multivalent nanoagonist further amplified this interaction, as evidenced by the enhanced antitumor efficacy observed in murine models (L–PEG-NP group). Optimization of flexibility and spatial presentation through PEG chains: The inclusion of 4-arm PEG in our nanoagonist design contributed to its flexibility and spatial adaptability. The high hydrophilicity and extended molecular chains of PEG allowed the ligand peptides to adopt dynamic conformations and orientations favorable for receptor binding. Unlike rigid structural scaffolds, this flexibility likely enhanced receptor engagement by enabling the peptides to adapt to the spatial and structural features of mouse DR5. (8) This spatial optimization provided by PEG and the nanoparticle scaffold facilitated even more effective interaction with mouse DR5, building upon the already significant intrinsic affinity of the ligand peptides in their monovalent form. Increased local concentration of ligand peptides: The local concentration of ligand peptides was significantly increased on the nanoparticle surface, creating a high local concentration of binding sites. This local enrichment enhanced the likelihood of interactions with mouse DR5, resulting in more frequent and stronger binding, (9) further enhancing the affinity for the murine receptor. This article references 9 other publications. This article has not yet been cited by other publications.","PeriodicalId":21,"journal":{"name":"ACS Nano","volume":"14 1","pages":""},"PeriodicalIF":17.1,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142975225","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}
Tasnim Ahmed, Xuanheng Tan, Barry Y. Li, Elijah Cook, Jillian Williams, Sophia M. Tiano, Belle Coffey, Stephanie M. Tenney, Dugan Hayes, Justin R. Caram
Dimension-engineered synthesis of atomically thin II–VI nanoplatelets (NPLs) remains an open challenge. While CdSe NPLs have been made with confinement ranging from 2 to 11 monolayers (ML), CdTe NPLs have been significantly more challenging to synthesize and separate. Here we provide detailed mechanistic insight into the layer-by-layer growth kinetics of the CdTe NPLs. Combining ensemble and single-particle spectroscopic and microscopic tools, our work suggests that beyond 2 ML CdTe NPLs, higher ML structures initially appear as heteroconfined materials with colocalized multilayer structures. In particular, we observe strongly colocalized 3 and 4 ML emissions, accompanied by a broad trap emission. Accompanying transient absorption, single-particle optical, and atomic force microscopy analyses suggest islands of different MLs on the same NPL. To explain the nonstandard nucleation and growth of these heteroconfined structures, we simulated the growth conditions of NPLs and quantified how the monomer binding energy modifies the kinetics and permits single NPLs with multi-ML structures. Our findings suggest that the lower bond energy associated with CdTe relative to CdSe limits higher ML syntheses and explains the observed differences between CdTe and CdSe growth.
{"title":"Heteroconfinement in Single CdTe Nanoplatelets","authors":"Tasnim Ahmed, Xuanheng Tan, Barry Y. Li, Elijah Cook, Jillian Williams, Sophia M. Tiano, Belle Coffey, Stephanie M. Tenney, Dugan Hayes, Justin R. Caram","doi":"10.1021/acsnano.4c17596","DOIUrl":"https://doi.org/10.1021/acsnano.4c17596","url":null,"abstract":"Dimension-engineered synthesis of atomically thin II–VI nanoplatelets (NPLs) remains an open challenge. While CdSe NPLs have been made with confinement ranging from 2 to 11 monolayers (ML), CdTe NPLs have been significantly more challenging to synthesize and separate. Here we provide detailed mechanistic insight into the layer-by-layer growth kinetics of the CdTe NPLs. Combining ensemble and single-particle spectroscopic and microscopic tools, our work suggests that beyond 2 ML CdTe NPLs, higher ML structures initially appear as heteroconfined materials with colocalized multilayer structures. In particular, we observe strongly colocalized 3 and 4 ML emissions, accompanied by a broad trap emission. Accompanying transient absorption, single-particle optical, and atomic force microscopy analyses suggest islands of different MLs on the same NPL. To explain the nonstandard nucleation and growth of these heteroconfined structures, we simulated the growth conditions of NPLs and quantified how the monomer binding energy modifies the kinetics and permits single NPLs with multi-ML structures. Our findings suggest that the lower bond energy associated with CdTe relative to CdSe limits higher ML syntheses and explains the observed differences between CdTe and CdSe growth.","PeriodicalId":21,"journal":{"name":"ACS Nano","volume":"91 1","pages":""},"PeriodicalIF":17.1,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142975419","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}
Gregory Czap, Kyungju Noh, Jairo Velasco, Jr., Roger M. Macfarlane, Harald Brune, Christopher P. Lutz
Lanthanide atoms show long magnetic lifetimes because of their strongly localized 4f electrons, but electrical control of their spins has been difficult because of their closed valence shell configurations. We achieved electron spin resonance of individual lanthanide atoms using a scanning tunneling microscope to probe the atoms bound to a protective insulating film. The atoms on this surface formed a singly charged cation state having an unpaired 6s electron, enabling tunnel current to access their 4f electrons. Europium spectra display a rich array of transitions among the 54 combined electron and nuclear spin states. In contrast, samarium’s ground state is a Kramers doublet with a very large g-factor of 5. These results demonstrate that all-electronic sensing and control of individual lanthanide spins is possible for quantum devices and spin-based electronics by using their rarely observed monovalent cation state.
{"title":"Direct Electrical Access to the Spin Manifolds of Individual Lanthanide Atoms","authors":"Gregory Czap, Kyungju Noh, Jairo Velasco, Jr., Roger M. Macfarlane, Harald Brune, Christopher P. Lutz","doi":"10.1021/acsnano.4c14327","DOIUrl":"https://doi.org/10.1021/acsnano.4c14327","url":null,"abstract":"Lanthanide atoms show long magnetic lifetimes because of their strongly localized 4<i>f</i> electrons, but electrical control of their spins has been difficult because of their closed valence shell configurations. We achieved electron spin resonance of individual lanthanide atoms using a scanning tunneling microscope to probe the atoms bound to a protective insulating film. The atoms on this surface formed a singly charged cation state having an unpaired 6<i>s</i> electron, enabling tunnel current to access their 4<i>f</i> electrons. Europium spectra display a rich array of transitions among the 54 combined electron and nuclear spin states. In contrast, samarium’s ground state is a Kramers doublet with a very large <i>g</i>-factor of 5. These results demonstrate that all-electronic sensing and control of individual lanthanide spins is possible for quantum devices and spin-based electronics by using their rarely observed monovalent cation state.","PeriodicalId":21,"journal":{"name":"ACS Nano","volume":"36 1","pages":""},"PeriodicalIF":17.1,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142975414","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}
Thomas Leonard, Nicholas Zogbi, Samuel Liu, William S. Rogers, Christopher H. Bennett, Jean Anne C. Incorvia
Spiking neural networks seek to emulate biological computation through interconnected artificial neuron and synapse devices. Spintronic neurons can leverage magnetization physics to mimic biological neuron functions, such as integration tied to magnetic domain wall (DW) propagation in a patterned nanotrack and firing tied to the resistance change of a magnetic tunnel junction (MTJ), captured in the domain wall-magnetic tunnel junction (DW-MTJ) device. Leaking, relaxation of a neuron when it is not under stimulation, is also predicted to be implemented based on DW drift as a DW relaxes to a low energy position, but it has not been well explored or demonstrated in device prototypes. Here, we study DW-MTJ artificial neurons capable of leaky integrate-and-fire (LIF) behavior and demonstrate geometry-dependent leaking dynamics that results in repeatable, tunable LIF operation. Studying the behavior of five different device designs, we show tuning the geometry, stimulating fields and currents, and location of electrical contacts results in a wide range of neuron behavior. Additionally, implementation of an asymmetric notch allows for nonlinear pinning which increased expressivity without sacrificing leaking. The measured behavior is implemented in a simulated spiking neural network that outperforms a 1D model of continuous DW motion and approaches the performance of an ideal LIF activation function. The results show that the analog LIF capability of DW-MTJ neurons combines many desirable neuron functions into a single device, which can result in varied forms of multifunctional neuromorphic computing.
{"title":"Shape Anisotropy-Dependent Leaking in Magnetic Neurons for Bio-Mimetic Neuromorphic Computing","authors":"Thomas Leonard, Nicholas Zogbi, Samuel Liu, William S. Rogers, Christopher H. Bennett, Jean Anne C. Incorvia","doi":"10.1021/acsnano.4c13020","DOIUrl":"https://doi.org/10.1021/acsnano.4c13020","url":null,"abstract":"Spiking neural networks seek to emulate biological computation through interconnected artificial neuron and synapse devices. Spintronic neurons can leverage magnetization physics to mimic biological neuron functions, such as integration tied to magnetic domain wall (DW) propagation in a patterned nanotrack and firing tied to the resistance change of a magnetic tunnel junction (MTJ), captured in the domain wall-magnetic tunnel junction (DW-MTJ) device. Leaking, relaxation of a neuron when it is not under stimulation, is also predicted to be implemented based on DW drift as a DW relaxes to a low energy position, but it has not been well explored or demonstrated in device prototypes. Here, we study DW-MTJ artificial neurons capable of leaky integrate-and-fire (LIF) behavior and demonstrate geometry-dependent leaking dynamics that results in repeatable, tunable LIF operation. Studying the behavior of five different device designs, we show tuning the geometry, stimulating fields and currents, and location of electrical contacts results in a wide range of neuron behavior. Additionally, implementation of an asymmetric notch allows for nonlinear pinning which increased expressivity without sacrificing leaking. The measured behavior is implemented in a simulated spiking neural network that outperforms a 1D model of continuous DW motion and approaches the performance of an ideal LIF activation function. The results show that the analog LIF capability of DW-MTJ neurons combines many desirable neuron functions into a single device, which can result in varied forms of multifunctional neuromorphic computing.","PeriodicalId":21,"journal":{"name":"ACS Nano","volume":"1 1","pages":""},"PeriodicalIF":17.1,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142975413","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}
Artem Petrov, Guillermo A. Hernández-Mendoza, Alfredo Alexander-Katz
Block copolymers (BCPs) can form nanoparticles having different morphologies that can be used as photonic nanocrystals and are a platform for drug delivery, sensors, and catalysis. In particular, BCP nanoparticles having disk-like shape have been recently discovered. Such nanodisks can be used as the next-generation antitumor drug delivery carriers; however, the applicability of the existing nanodisks is limited due to their poor or unknown ability to respond to external stimuli. In this work, we showed that the simplest symmetric diblock copolymers in equilibrium can form nanodisks that can be reversibly switched into a multitude of various nanoparticles potentially applicable in nanophotonics, biomedicine, and hierarchical self-assembly. These structures include patchy and onion-like nanoparticles, striped ellipsoids, mixed morphology nanocolloids, and spherical micelles. The transitions between nanodisks and the aforementioned nanoparticles are sharp, direct, and can be achieved by tuning the block–block and polymer–solvent incompatibility. We demonstrated that this versatility of nanoparticle morphologies can be achieved upon reducing the nanoparticle size to approximately two lamellar periods of the BCP. Upon aggregation of such small nanocolloids, a larger assembly can be formed. In turn, these bigger particles could form many other structures including a chain-like supramolecular aggregate of nanodisks and a multilayered disk-like nanoparticle. We obtained our results by performing self-consistent field theory calculations according to an algorithm designed to produce equilibrium nanoparticle morphology. This work demonstrates that nanodisks prepared from the simplest type of BCPs are extremely tunable; therefore, symmetric diblock copolymers can become a platform for producing the next-generation stimuli-responsive nanoparticles.
{"title":"Symmetric Diblock Copolymers Form Versatile and Switchable Ultrasmall Nanoparticles","authors":"Artem Petrov, Guillermo A. Hernández-Mendoza, Alfredo Alexander-Katz","doi":"10.1021/acsnano.4c14236","DOIUrl":"https://doi.org/10.1021/acsnano.4c14236","url":null,"abstract":"Block copolymers (BCPs) can form nanoparticles having different morphologies that can be used as photonic nanocrystals and are a platform for drug delivery, sensors, and catalysis. In particular, BCP nanoparticles having disk-like shape have been recently discovered. Such nanodisks can be used as the next-generation antitumor drug delivery carriers; however, the applicability of the existing nanodisks is limited due to their poor or unknown ability to respond to external stimuli. In this work, we showed that the simplest symmetric diblock copolymers in equilibrium can form nanodisks that can be reversibly switched into a multitude of various nanoparticles potentially applicable in nanophotonics, biomedicine, and hierarchical self-assembly. These structures include patchy and onion-like nanoparticles, striped ellipsoids, mixed morphology nanocolloids, and spherical micelles. The transitions between nanodisks and the aforementioned nanoparticles are sharp, direct, and can be achieved by tuning the block–block and polymer–solvent incompatibility. We demonstrated that this versatility of nanoparticle morphologies can be achieved upon reducing the nanoparticle size to approximately two lamellar periods of the BCP. Upon aggregation of such small nanocolloids, a larger assembly can be formed. In turn, these bigger particles could form many other structures including a chain-like supramolecular aggregate of nanodisks and a multilayered disk-like nanoparticle. We obtained our results by performing self-consistent field theory calculations according to an algorithm designed to produce equilibrium nanoparticle morphology. This work demonstrates that nanodisks prepared from the simplest type of BCPs are extremely tunable; therefore, symmetric diblock copolymers can become a platform for producing the next-generation stimuli-responsive nanoparticles.","PeriodicalId":21,"journal":{"name":"ACS Nano","volume":"9 1","pages":""},"PeriodicalIF":17.1,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142981575","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}
Chao Li, Vladislav Pokorný, Martin Žonda, Jung-Ching Liu, Ping Zhou, Outhmane Chahib, Thilo Glatzel, Robert Häner, Silvio Decurtins, Shi-Xia Liu, Rémy Pawlak, Ernst Meyer
High-precision molecular manipulation techniques are used to control the distance between radical molecules on superconductors. Our results show that the molecules can host single electrons with a spin 1/2. By changing the distance between tip and sample, a quantum phase transition from the singlet to doublet ground state can be induced. Due to local screening and charge redistribution, we observe either charged or neutral molecules, which couple in a sophisticated way, showing quantum spin behavior that deviates from the classical spins. Dimers at different separations show multiple Yu-Shiba-Rusinov peaks in tunneling spectroscopy of varying intensity, which are in line with the superconducting two-impurity Anderson model, where singlet (S = 0) and doublet (S = 1/2) ground states are found. The assembly of chains of 3, 4, and 5 molecules shows alternating charge patterns, where the edge molecules always host a charge/spin. The tetramer is observed in two configurations, where the neutral site is moved by one position. We show that these two configurations can be switched by the action of the probing tip in a nondestructive manner, demonstrating that the tetramer is an information unit, based on single-electron charge reorganization.
{"title":"Individual Assembly of Radical Molecules on Superconductors: Demonstrating Quantum Spin Behavior and Bistable Charge Rearrangement","authors":"Chao Li, Vladislav Pokorný, Martin Žonda, Jung-Ching Liu, Ping Zhou, Outhmane Chahib, Thilo Glatzel, Robert Häner, Silvio Decurtins, Shi-Xia Liu, Rémy Pawlak, Ernst Meyer","doi":"10.1021/acsnano.4c12387","DOIUrl":"https://doi.org/10.1021/acsnano.4c12387","url":null,"abstract":"High-precision molecular manipulation techniques are used to control the distance between radical molecules on superconductors. Our results show that the molecules can host single electrons with a spin 1/2. By changing the distance between tip and sample, a quantum phase transition from the singlet to doublet ground state can be induced. Due to local screening and charge redistribution, we observe either charged or neutral molecules, which couple in a sophisticated way, showing quantum spin behavior that deviates from the classical spins. Dimers at different separations show multiple Yu-Shiba-Rusinov peaks in tunneling spectroscopy of varying intensity, which are in line with the superconducting two-impurity Anderson model, where singlet (<i>S</i> = 0) and doublet (<i>S</i> = 1/2) ground states are found. The assembly of chains of 3, 4, and 5 molecules shows alternating charge patterns, where the edge molecules always host a charge/spin. The tetramer is observed in two configurations, where the neutral site is moved by one position. We show that these two configurations can be switched by the action of the probing tip in a nondestructive manner, demonstrating that the tetramer is an information unit, based on single-electron charge reorganization.","PeriodicalId":21,"journal":{"name":"ACS Nano","volume":"41 1","pages":""},"PeriodicalIF":17.1,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142975420","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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