Pub Date : 2024-05-15DOI: 10.1088/2515-7639/ad4c05
F. G. Aras, Abdulsalam Aji Suleiman, Amir Parsi, S. Kasirga, Aydan Yeltik
In the rapidly developing field of optoelectronics, the utilization of transition-metal dichalcogenides with adjustable band gaps holds great promise. MoS2, in particular, has garnered considerable attention owing to its versatility. However, a persistent challenge is to establish a simple, reliable and scalable method for large-scale synthesis of continuous monolayer films. In this paper, we report the growth of continuous large-area monolayer MoS2 films using a glass-assisted chemical vapor deposition (CVD) process. High-quality monolayer films were achieved by precisely controlling carrier gas flow and sulfur vaporization with a customized CVD system. Additionally, we explored the impact of chemical treatment using lithium bistrifluoromethylsulfonylamine (Li-TFSI) salt on the optical properties of monolayer MoS2 crystals. To investigate the evolution of excitonic characteristics, we conditionally grew monolayer MoS2 flakes by controlling sulfur evaporation. We reported two scenarios on MoS2 films and flakes based on substrate-related strain and defect density. Our findings revealed that high-quality monolayer MoS2 films exhibited lower treatment efficiency due to substrate-induced surface strain, whereas defective monolayer MoS2 flakes demonstrated a higher treatment sensitivity a p-doping effect. The Li-TFSI-induced changes in exciton density were elucidated through photoluminescence (PL), Raman, and X-ray photoelectron spectroscopy (XPS) results. Furthermore, we demonstrated treatment-related healing in flakes under variable laser excitation power. The advancements highlighted in our study carry significant implications for the scalable fabrication of diverse optoelectronic devices, potentially paving the way for widespread real-world applications.
{"title":"Molten Glass-Mediated Conditional CVD Growth of MoS2 Monolayers and Effect of Surface Treatment on Their Optical Properties","authors":"F. G. Aras, Abdulsalam Aji Suleiman, Amir Parsi, S. Kasirga, Aydan Yeltik","doi":"10.1088/2515-7639/ad4c05","DOIUrl":"https://doi.org/10.1088/2515-7639/ad4c05","url":null,"abstract":"\u0000 In the rapidly developing field of optoelectronics, the utilization of transition-metal dichalcogenides with adjustable band gaps holds great promise. MoS2, in particular, has garnered considerable attention owing to its versatility. However, a persistent challenge is to establish a simple, reliable and scalable method for large-scale synthesis of continuous monolayer films. In this paper, we report the growth of continuous large-area monolayer MoS2 films using a glass-assisted chemical vapor deposition (CVD) process. High-quality monolayer films were achieved by precisely controlling carrier gas flow and sulfur vaporization with a customized CVD system. Additionally, we explored the impact of chemical treatment using lithium bistrifluoromethylsulfonylamine (Li-TFSI) salt on the optical properties of monolayer MoS2 crystals. To investigate the evolution of excitonic characteristics, we conditionally grew monolayer MoS2 flakes by controlling sulfur evaporation. We reported two scenarios on MoS2 films and flakes based on substrate-related strain and defect density. Our findings revealed that high-quality monolayer MoS2 films exhibited lower treatment efficiency due to substrate-induced surface strain, whereas defective monolayer MoS2 flakes demonstrated a higher treatment sensitivity a p-doping effect. The Li-TFSI-induced changes in exciton density were elucidated through photoluminescence (PL), Raman, and X-ray photoelectron spectroscopy (XPS) results. Furthermore, we demonstrated treatment-related healing in flakes under variable laser excitation power. The advancements highlighted in our study carry significant implications for the scalable fabrication of diverse optoelectronic devices, potentially paving the way for widespread real-world applications.","PeriodicalId":501825,"journal":{"name":"Journal of Physics: Materials","volume":"51 24","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140972872","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-15DOI: 10.1088/2515-7639/ad4c07
Kevin Tran, P. Taylor, Michelle J. S. Spencer
Nanomaterials that undergo structural or other property changes upon application of external stimuli are called stimuli responsive materials and are particularly suited for drug delivery, biosensing or artificial muscle applications. Two-dimensional (2D) black phosphorus is an ideal material for such applications due to its remarkable electromechanical response. Given that one-dimensional (1D) black phosphorus nanotubes (PNTs) are calculated to be energetically stable, it is possible that they can undergo similar electromechanical responses to their 2D counterparts, allowing their potential application as nanochannel devices for drug delivery. Using first-principles density functional theory, we investigated the electromechanical response of different-sized PNTs upon charge injection. Upon hole injection, the diameter of the PNTs expands up to a maximum of 30.2% for a (0,15) PNT that is 0.24 nm in diameter. The PNTs become highly p-doped as the valence band maximum crosses the Fermi level and undergoes switching from a direct to indirect band gap. The mechanism behind the electromechanical response was determined through analysis of the structural deformations, charge density distribution and Bader partial charges. It was shown that injection of charge alters the Young’s Modulus of the PNTs, as hole injection weakens the structural integrity of the nanotube, allowing a greater electromechanical response, with PNT-15 showing the largest decrease in the Young’s Modulus of 15.34%. These findings show that 1D PNTs are promising materials for the development of nanoelectromechanical actuators which could be used for drug delivery, energy harvesting or similar applications.
{"title":"Electromechanical strain response of phosphorene nanotubes","authors":"Kevin Tran, P. Taylor, Michelle J. S. Spencer","doi":"10.1088/2515-7639/ad4c07","DOIUrl":"https://doi.org/10.1088/2515-7639/ad4c07","url":null,"abstract":"\u0000 Nanomaterials that undergo structural or other property changes upon application of external stimuli are called stimuli responsive materials and are particularly suited for drug delivery, biosensing or artificial muscle applications. Two-dimensional (2D) black phosphorus is an ideal material for such applications due to its remarkable electromechanical response. Given that one-dimensional (1D) black phosphorus nanotubes (PNTs) are calculated to be energetically stable, it is possible that they can undergo similar electromechanical responses to their 2D counterparts, allowing their potential application as nanochannel devices for drug delivery. Using first-principles density functional theory, we investigated the electromechanical response of different-sized PNTs upon charge injection. Upon hole injection, the diameter of the PNTs expands up to a maximum of 30.2% for a (0,15) PNT that is 0.24 nm in diameter. The PNTs become highly p-doped as the valence band maximum crosses the Fermi level and undergoes switching from a direct to indirect band gap. The mechanism behind the electromechanical response was determined through analysis of the structural deformations, charge density distribution and Bader partial charges. It was shown that injection of charge alters the Young’s Modulus of the PNTs, as hole injection weakens the structural integrity of the nanotube, allowing a greater electromechanical response, with PNT-15 showing the largest decrease in the Young’s Modulus of 15.34%. These findings show that 1D PNTs are promising materials for the development of nanoelectromechanical actuators which could be used for drug delivery, energy harvesting or similar applications.","PeriodicalId":501825,"journal":{"name":"Journal of Physics: Materials","volume":"54 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140975183","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-14DOI: 10.1088/2515-7639/ad4ba0
J. Orives, L. M. Marcondes, Lara Karam, F. Adamietz, Thierry Cardinal, M. Dussauze, Marcelo Nalin
Borogermanate glasses containing terbium ions are interesting materials due to their luminescent and magnetic properties. Terbium can present two different oxidation states and the thermal poling technique can be a pertinent way to modulate spatially the oxidation state of this ions. In this work, we demonstrate using a thermo-electrical imprinting process the transfer of micro scaled motifs on the surface of a borogermanate glass containing Tb3+ resulting in a micrometric structuring of the oxidation state of Tb3+/Tb4+ ions. A large change in absorption and luminescence optical properties is observed, arising from the distinct properties of trivalent and tetravalent terbium ions. Correlative micro luminescence, Raman and Second Harmonic Generation measurements were carried out on the patterned poled glass surface. It has demonstrated an accurate concomitant modification of the glass structure accompanying large luminescence changes and the appearance of a second order optical response which could be attributed a localized space charge implantation. These original results demonstrate how a simple electrical process allows managing multi optical properties but also pave the way to induce static electrical functionalities in a magnetic optical glassy system.
{"title":"Micrometric patterning of a borogermanate glass containing terbium by thermal poling to manage luminescence and second order optical properties","authors":"J. Orives, L. M. Marcondes, Lara Karam, F. Adamietz, Thierry Cardinal, M. Dussauze, Marcelo Nalin","doi":"10.1088/2515-7639/ad4ba0","DOIUrl":"https://doi.org/10.1088/2515-7639/ad4ba0","url":null,"abstract":"\u0000 Borogermanate glasses containing terbium ions are interesting materials due to their luminescent and magnetic properties. Terbium can present two different oxidation states and the thermal poling technique can be a pertinent way to modulate spatially the oxidation state of this ions. In this work, we demonstrate using a thermo-electrical imprinting process the transfer of micro scaled motifs on the surface of a borogermanate glass containing Tb3+ resulting in a micrometric structuring of the oxidation state of Tb3+/Tb4+ ions. A large change in absorption and luminescence optical properties is observed, arising from the distinct properties of trivalent and tetravalent terbium ions. Correlative micro luminescence, Raman and Second Harmonic Generation measurements were carried out on the patterned poled glass surface. It has demonstrated an accurate concomitant modification of the glass structure accompanying large luminescence changes and the appearance of a second order optical response which could be attributed a localized space charge implantation. These original results demonstrate how a simple electrical process allows managing multi optical properties but also pave the way to induce static electrical functionalities in a magnetic optical glassy system.","PeriodicalId":501825,"journal":{"name":"Journal of Physics: Materials","volume":"110 8","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140977800","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-17DOI: 10.1088/2515-7639/ad3b6d
Hiroyuki Nakamura, Hiroto Ohta, Ryuya Kobayashi, Takeshi Waki, Yoshikazu Tabata, Hidekazu Ikeno and Christian Mény
The La–Co co-substituted magnetoplumbite-type (M-type) ferrites AFe12O19 (A = Ca, Sr and Ba, ion sizes Ca2+ Sr2+ Ba2+) with Co compositions around 0.2 have been subjected to 59Co-NMR. The results show that Co occupies the 4f1, 2a and 12k sites, and that the smaller the A ion, the more Co tends to occupy the 4f1 minority spin site, which is effective in enhancing both uniaxial anisotropy and magnetisation. First-principles total energy calculations based on density functional theory (DFT) of undoped AFe12O19 and a supercell ( of the unit cell) in which 1/96 of Fe3+ is replaced by Co2+ were performed to predict the stable structure and Co occupancy sites. The results show that regardless of A, Co is most stable when it occupies the 4f1 site, followed by the 2a and 12k sites with energy differences on the order of 100 meV, and Co practically does not occupy the 2b and 4f2 sites. As the A ion becomes smaller, the energy difference when Co occupies each Fe site tends to increase, and the Co occupancy of the 4f1 site also increases. The site selectivity of Co can be roughly explained as a result of the difference in uniaxial strain along the c-axis associated with the difference in A. However, the influence of the A ion differs between the R and S blocks and the local strain also has a secondary effect on the Co distribution. Based on these results, the guidelines for improving the performance (anisotropy and magnetisation) of La–Co co-substituted M-type ferrite magnets with a limited amount of Co can be summarised as follows: It is effective to select as small A ions as possible and to post-anneal at low temperature or cool slowly to concentrate Co at the 4f1 site in tetrahedral coordination.
对 Co 含量在 0.2 左右的 La-Co 共取代磁铌铁（M 型）铁氧体 AFe12O19（A = Ca、Sr 和 Ba，离子大小为 Ca2+ Sr2+ Ba2+）进行了 59Co-NMR 分析。结果表明，钴占据了 4f1、2a 和 12k 位点，而且 A 离子越小，钴就越倾向于占据 4f1 少数自旋位点，从而有效地增强了单轴各向异性和磁性。我们基于密度泛函理论（DFT）对未掺杂的 AFe12O19 和用 Co2+ 取代了 1/96 的 Fe3+ 的超晶胞（单位晶胞）进行了第一原理总能量计算，以预测其稳定结构和 Co 占有位点。结果表明，无论 A 如何，Co 在占据 4f1 位点时最稳定，其次是 2a 和 12k 位点，能量差在 100 meV 量级，Co 几乎不占据 2b 和 4f2 位点。随着 A 离子变小，Co 占据每个 Fe 位点时的能量差趋于增大，Co 占据 4f1 位点的能量差也随之增大。Co 的位点选择性可大致解释为与 A 离子差异相关的沿 c 轴的单轴应变差异的结果，但 A 离子的影响在 R 块和 S 块之间有所不同，局部应变也会对 Co 的分布产生次要影响。基于这些结果，使用少量 Co 改善 La-Co 共取代 M 型铁氧体磁体性能（各向异性和磁化）的指导原则可归纳如下：选择尽可能小的 A 离子，并在低温下进行后退火或缓慢冷却以将 Co 集中在四面体配位的 4f1 位点，这样做是有效的。
{"title":"Site-selective cobalt substitution in La–Co co-substituted magnetoplumbite-type ferrites: 59Co-NMR and DFT calculation study","authors":"Hiroyuki Nakamura, Hiroto Ohta, Ryuya Kobayashi, Takeshi Waki, Yoshikazu Tabata, Hidekazu Ikeno and Christian Mény","doi":"10.1088/2515-7639/ad3b6d","DOIUrl":"https://doi.org/10.1088/2515-7639/ad3b6d","url":null,"abstract":"The La–Co co-substituted magnetoplumbite-type (M-type) ferrites AFe12O19 (A = Ca, Sr and Ba, ion sizes Ca2+ Sr2+ Ba2+) with Co compositions around 0.2 have been subjected to 59Co-NMR. The results show that Co occupies the 4f1, 2a and 12k sites, and that the smaller the A ion, the more Co tends to occupy the 4f1 minority spin site, which is effective in enhancing both uniaxial anisotropy and magnetisation. First-principles total energy calculations based on density functional theory (DFT) of undoped AFe12O19 and a supercell ( of the unit cell) in which 1/96 of Fe3+ is replaced by Co2+ were performed to predict the stable structure and Co occupancy sites. The results show that regardless of A, Co is most stable when it occupies the 4f1 site, followed by the 2a and 12k sites with energy differences on the order of 100 meV, and Co practically does not occupy the 2b and 4f2 sites. As the A ion becomes smaller, the energy difference when Co occupies each Fe site tends to increase, and the Co occupancy of the 4f1 site also increases. The site selectivity of Co can be roughly explained as a result of the difference in uniaxial strain along the c-axis associated with the difference in A. However, the influence of the A ion differs between the R and S blocks and the local strain also has a secondary effect on the Co distribution. Based on these results, the guidelines for improving the performance (anisotropy and magnetisation) of La–Co co-substituted M-type ferrite magnets with a limited amount of Co can be summarised as follows: It is effective to select as small A ions as possible and to post-anneal at low temperature or cool slowly to concentrate Co at the 4f1 site in tetrahedral coordination.","PeriodicalId":501825,"journal":{"name":"Journal of Physics: Materials","volume":"315 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140805682","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-17DOI: 10.1088/2515-7639/ad3fe9
Björn Wiese, C. Mendis, D. Tolnai, Norbert Hort
CaO additions are used as an inexpensive replacement for Ca in Mg alloys. CaO dissociation in Mg has been reported in literature without a clear mechanism as to why this occurs. In situ synchrotron radiation diffraction investigation of the melting and solidification of Mg with CaO shows, that the stability of CaO was overestimated in Mg melts compared with MgO. The experiments that were performed on the Mg-20CaO and Mg-xCa-6CaO (x = 6 and 16 wt.%) alloys, show the dissociation and formation of various phases during melting and solidification. The results indicate that Mg can reduce CaO even in the solid state, which is the opposite of that proposed by the Ellingham diagrams for stoichiometric reaction. Phase formations during the in situ experiment are compared with published thermodynamic calculations for the interaction between Mg-Ca alloys and oxides.
{"title":"Interactions of CaO with Pure Mg and Mg-Ca alloys - an in situ synchrotron radiation diffraction study","authors":"Björn Wiese, C. Mendis, D. Tolnai, Norbert Hort","doi":"10.1088/2515-7639/ad3fe9","DOIUrl":"https://doi.org/10.1088/2515-7639/ad3fe9","url":null,"abstract":"\u0000 CaO additions are used as an inexpensive replacement for Ca in Mg alloys. CaO dissociation in Mg has been reported in literature without a clear mechanism as to why this occurs. In situ synchrotron radiation diffraction investigation of the melting and solidification of Mg with CaO shows, that the stability of CaO was overestimated in Mg melts compared with MgO. The experiments that were performed on the Mg-20CaO and Mg-xCa-6CaO (x = 6 and 16 wt.%) alloys, show the dissociation and formation of various phases during melting and solidification. The results indicate that Mg can reduce CaO even in the solid state, which is the opposite of that proposed by the Ellingham diagrams for stoichiometric reaction. Phase formations during the in situ experiment are compared with published thermodynamic calculations for the interaction between Mg-Ca alloys and oxides.","PeriodicalId":501825,"journal":{"name":"Journal of Physics: Materials","volume":" 29","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140692838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-17DOI: 10.1088/2515-7639/ad3fea
Ayana Ghosh, Palanichamy Gayathri, Monirul Shaikh, Saurabh Ghosh
Finding the ground-state structure with minimum energy is paramount to designing any material. In ABO3-type perovskite oxides with Pnma symmetry, the lowest energy phase is driven by an inherent trilinear coupling between the two primary order parameters such as rotation and tilt with antiferroelectric displacement of the A-site cations as established via hybrid improper ferroelectric mechanism. Conventionally, finding the relevant mode coupling driving phase transition requires performing first-principles computations which is computationally time-consuming as well as expensive. It involves following an intuitive iterative hit and trial method of (a) adding two or multiple mode vectors, (b) evaluating which combination would lead to the ground-state energy. In this study, we show how a hypothesis-driven active learning framework can identify suitable mode couplings within the Landau free energy expansion with minimal information on amplitudes of modes for a series of double perovskite oxides with A-site layered, columnar and rocksalt ordering. This scheme is expected to be applicable universally for understanding atomistic mechanisms derived from various structural mode couplings behind functionalities, for e.g., polarization, magnetization and metal-insulator transitions.
找到能量最小的基态结构对于设计任何材料都至关重要。在具有 Pnma 对称性的 ABO3 型包晶氧化物中，最低能量相是由两个主要阶次参数（如旋转和倾斜）之间固有的三线耦合以及 A 位阳离子的反铁电位移驱动的，这种耦合是通过混合不当铁电机制建立的。传统上，确定驱动相变的相关模式耦合需要进行第一性原理计算，这既耗时又昂贵。这需要采用直观的迭代和试验方法：（a）添加两个或多个模式矢量，（b）评估哪种组合会导致基态能量。在本研究中，我们展示了假设驱动的主动学习框架如何在朗道自由能展开中，以最少的模式振幅信息，为一系列具有 A 位层状、柱状和岩盐有序的双过氧化物确定合适的模式耦合。这一方案有望普遍适用于理解由功能背后的各种结构模式耦合衍生出的原子机制，例如极化、磁化和金属-绝缘体转变。
{"title":"Structural mode coupling in perovskite oxides using hypothesis-driven active learning","authors":"Ayana Ghosh, Palanichamy Gayathri, Monirul Shaikh, Saurabh Ghosh","doi":"10.1088/2515-7639/ad3fea","DOIUrl":"https://doi.org/10.1088/2515-7639/ad3fea","url":null,"abstract":"\u0000 Finding the ground-state structure with minimum energy is paramount to designing any material. In ABO3-type perovskite oxides with Pnma symmetry, the lowest energy phase is driven by an inherent trilinear coupling between the two primary order parameters such as rotation and tilt with antiferroelectric displacement of the A-site cations as established via hybrid improper ferroelectric mechanism. Conventionally, finding the relevant mode coupling driving phase transition requires performing first-principles computations which is computationally time-consuming as well as expensive. It involves following an intuitive iterative hit and trial method of (a) adding two or multiple mode vectors, (b) evaluating which combination would lead to the ground-state energy. In this study, we show how a hypothesis-driven active learning framework can identify suitable mode couplings within the Landau free energy expansion with minimal information on amplitudes of modes for a series of double perovskite oxides with A-site layered, columnar and rocksalt ordering. This scheme is expected to be applicable universally for understanding atomistic mechanisms derived from various structural mode couplings behind functionalities, for e.g., polarization, magnetization and metal-insulator transitions.","PeriodicalId":501825,"journal":{"name":"Journal of Physics: Materials","volume":" 8","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140691628","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-17DOI: 10.1088/2515-7639/ad3b6f
Katsiaryna Chernyakova, Ieva Matulaitienė, Tatjana Charkova, Giedrė Grincienė, Meda Jurevičiūtė, Aurimas Kopūstas, Arūnas Jagminas, Renata Karpicz
Alumina/carbon composites are modern nanomaterials used as adsorbents, catalysts, catalyst supports, supercapacitors, and electrode materials for fuel cells. Among other methods, aluminum anodizing is fairly fast and inexpensive for producing anodic alumina/carbon composites with controllable properties. In the present study, the morphology and composition of carbon-enriched anodic alumina films were obtained during aluminum anodic oxidation in formic acid with ammonium heptamolybdate (C content is ca. 5.0 mass%) or oxalic acid (C content 3.4 mass%) additives. The anodic alumina films have a wide blue fluorescence (FL) in the 400–650 nm wavelength range with a maximum at ca. 490 nm. The FL decay is nonexponential and has an average lifetime of 1.54 and 1.59 ns for ammonium heptamolybdate and oxalic acid additives, respectively. As samples obtained in sulfuric acid (i.e. without carbon) do not possess detectable FL in the 400–650 nm wavelength range, it was concluded that carbon-containing inclusions are responsible for the FL properties of the films. The initial samples were dissolved in the hot aqueous HCl solution and then dialyzed to extract the carbon-containing component. It was shown that the solutions contain nanoparticles of amorphous carbon with a 20–25 nm diameter. Carbon nanoparticles also exhibit an excitation-dependent emission behavior at 280–450 nm excitation wavelengths with average lifetimes of 7.25–8.04 ns, depending on the composition of the initial film. Carbon nanoparticle FL is caused by the core of carbon nanoparticles (CNPs) and various emission centers on their surface, such as carbonyl, carboxyl, and hydroxyl groups. As CNPs could be exceptional candidates for detection technologies, the biocompatibility assays were performed with living COS-7 mammalian cells, showing a minimal negative impact on the living cells.
{"title":"Anodic alumina/carbon composite films: extraction and characterization of the carbon-containing component","authors":"Katsiaryna Chernyakova, Ieva Matulaitienė, Tatjana Charkova, Giedrė Grincienė, Meda Jurevičiūtė, Aurimas Kopūstas, Arūnas Jagminas, Renata Karpicz","doi":"10.1088/2515-7639/ad3b6f","DOIUrl":"https://doi.org/10.1088/2515-7639/ad3b6f","url":null,"abstract":"Alumina/carbon composites are modern nanomaterials used as adsorbents, catalysts, catalyst supports, supercapacitors, and electrode materials for fuel cells. Among other methods, aluminum anodizing is fairly fast and inexpensive for producing anodic alumina/carbon composites with controllable properties. In the present study, the morphology and composition of carbon-enriched anodic alumina films were obtained during aluminum anodic oxidation in formic acid with ammonium heptamolybdate (C content is ca. 5.0 mass%) or oxalic acid (C content 3.4 mass%) additives. The anodic alumina films have a wide blue fluorescence (FL) in the 400–650 nm wavelength range with a maximum at ca. 490 nm. The FL decay is nonexponential and has an average lifetime of 1.54 and 1.59 ns for ammonium heptamolybdate and oxalic acid additives, respectively. As samples obtained in sulfuric acid (i.e. without carbon) do not possess detectable FL in the 400–650 nm wavelength range, it was concluded that carbon-containing inclusions are responsible for the FL properties of the films. The initial samples were dissolved in the hot aqueous HCl solution and then dialyzed to extract the carbon-containing component. It was shown that the solutions contain nanoparticles of amorphous carbon with a 20–25 nm diameter. Carbon nanoparticles also exhibit an excitation-dependent emission behavior at 280–450 nm excitation wavelengths with average lifetimes of 7.25–8.04 ns, depending on the composition of the initial film. Carbon nanoparticle FL is caused by the core of carbon nanoparticles (CNPs) and various emission centers on their surface, such as carbonyl, carboxyl, and hydroxyl groups. As CNPs could be exceptional candidates for detection technologies, the biocompatibility assays were performed with living COS-7 mammalian cells, showing a minimal negative impact on the living cells.","PeriodicalId":501825,"journal":{"name":"Journal of Physics: Materials","volume":"32 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140612621","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-16DOI: 10.1088/2515-7639/ad3aa3
Lena A Mittmann, Andrea Crovetto
Inorganic phosphosulfides—materials containing phosphorus, sulfur, and at least one metal—are a vast and chemically-versatile family of materials. Benefiting from a wide range of possible phosphorus oxidation states, phosphosulfide semiconductors exist as thiophosphate compounds with various types of P–S polyanions, as genuine multi-anion compounds with or without P–P bonds, as solid solutions, and as many intermediate cases. Since metal phosphides and metal sulfides are among the highest-performing optoelectronic semiconductors, it seems reasonable to consider the phosphosulfide family as a potential pool of materials for solar cells, photoelectrochemical cells, and light-emitting diodes. Nevertheless, phosphosulfide semiconductors have very rarely been characterized with these applications in mind. In this perspective article, we reflect on the potential applicability of known and hypothetical phosphosulfides as light absorbers and emitters in optoelectronic devices. First, we distill the existing knowledge accessible through the Materials Project database, finding promising phosphosulfides among the compounds already present in the database and identifying what we see as the general advantages and challenges of phosphosulfides as optoelectronic materials. Then, we propose three concrete research directions aimed at finding novel high-quality phosphosulfide semiconductors with high light absorption coefficients, high carrier mobilities, and long carrier lifetimes. In particular, we argue that the versatility of phosphorus in this class of materials could potentially be exploited to engineer defect tolerance. Finally, we describe and explain the advantages of a custom synthesis setup dedicated to high-throughput exploration of thin-film phosphosulfides.
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Pub Date : 2024-04-11DOI: 10.1088/2515-7639/ad3d89
Tong Cai, Amanda J Parker, Amanda S. Barnard
The integration of graph-based representations with machine learning methodologies is transforming the landscape of material discovery, offering a flexible approach for modelling a variety of materials, from molecules and nanomaterials to expansive 3D bulk materials. Nonetheless, the literature often lacks a systematic exploration from the perspective of material dimensionality. While it is important to design representations and algorithms that are universally applicable across species, it is intuitive for material scientists to align the underlying patterns between dimensionality and the characteristics of the employed graph descriptors. In this review, we provide an overview of the graph representations as inputs to machine learning models and navigate the recent applications, spanning the diverse range of material dimensions. This review highlights both persistent gaps and innovative solutions to these challenges, emphasising the pressing need for larger benchmark datasets and leveraging graphical patterns. As graph-based machine learning techniques evolve, they present a promising frontier for accurate, scalable, and interpretable material applications.
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Pub Date : 2024-04-09DOI: 10.1088/2515-7639/ad3c92
M. Al-Farsi, Michele Cutini, Neil Allan, Judy N Hart
The ability to tune band gaps of semiconductors is important for many optoelectronics applications including photocatalysis. A common approach to this is doping, but this often has the disadvantage of introducing defect states in the electronic structure that can result in poor charge mobility and increased recombination losses. In this work, density functional theory calculations are used to understand how co-doping and solid solution formation can allow tuning of semiconductor band gaps through indirect effects. The addition of ZnS to GaP alters the local atomic environments of the Ga and P atoms, resulting in shifts in the energies of the Ga and P states that form the valence and conduction band edges, and hence changes the band gap without altering which atoms form the band edges, providing an explanation for previous experimental observations. Similarly, N doping of ZnO is known from previous experimental work to reduce the band gap and increase visible-light absorption; here we show that, when co-doped with Al, the Al changes the local environment of the N atoms, providing further control of the band gap without introducing new states within the band gap or at the band edges, while also providing an energetically more favourable state than N-doped ZnO. Replacing Al with elements of different electronegativity is an additional tool for band gap tuning, since the different electronegativities correspond to different effects on the N local environment. The consistency in the parameters identified here that control the band gaps across the various systems studied indicates some general concepts that can be applied in tuning the band gaps of semiconductors, without or only minimally affecting charge mobility.
调整半导体带隙的能力对于包括光催化在内的许多光电应用都非常重要。常用的方法是掺杂，但这样做的缺点往往是在电子结构中引入缺陷态，从而导致电荷迁移率低和重组损耗增加。在这项研究中，我们利用密度泛函理论计算来了解共掺杂和固溶体形成如何通过间接效应调整半导体带隙。在 GaP 中加入 ZnS 会改变 Ga 原子和 P 原子的局部原子环境，导致形成价带和导带边缘的 Ga 原子和 P 原子态的能量移动，从而在不改变哪些原子形成带边的情况下改变带隙，这为之前的实验观察提供了解释。同样，从以前的实验工作中得知，氧化锌中掺入 N 会减小带隙并增加可见光吸收；我们在此表明，在共掺入 Al 时，Al 会改变 N 原子的局部环境，从而进一步控制带隙，而不会在带隙内或带边引入新的态，同时还提供了比掺入 N 的氧化锌更有利的能量状态。用不同电负性的元素代替 Al 是调整带隙的另一种工具，因为不同的电负性对应于对 N 局部环境的不同影响。本文所确定的控制各种研究系统带隙的参数具有一致性，这表明在调整半导体带隙时可以应用一些通用概念，而不会或仅会对电荷迁移率产生最小影响。
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