Catalyst-free, chirality-controlled growth of chiral and achiral single-walled carbon nanotubes (SWCNTs) from organic precursors is demonstrated using quantum chemical simulations [1]. Growth of (4,3), (6,5), (6,1), (10,1), (6,6) and (8,0) SWCNTs was induced by ethynyl radical (C2H) addition to organic precursors. These simulations show a strong dependence of the SWCNT growth rate on the chiral angle, θ. The SWCNT diameter however does not influence the SWCNT growth rate under these conditions. This agreement with a previously proposed screw-dislocation-like model of transition metal-catalyzed SWCNT growth rates [2] indicates that the SWCNT growth rate is an intrinsic property of the SWCNT edge itself. Conversely, we predict that the rate of local SWCNT growth via Diels-Alder cycloaddition of C2H2 is strongly influenced by the diameter of the SWCNT. We therefore predict the existence of a maximum local growth rate for an optimum diameter/chirality combination at a given C2H/C2H2 ratio. We also find that the ability of a SWCNT to avoid defect formation during growth is an intrinsic quality of the SWCNT edge.
References:
[1] Li, H.-B.; Page, A. J.; Irle, S.; Morokuma, K. J. Am. Chem. Soc. 2012, 134, 15887-15896.
[2] Ding, F.; Harutyunyan, A. R.; Yakobson, B. I. Proc. Natl. Acad. Sci. 2009, 106, 2506-2509.
Photoluminescence of Bioceramic Materials and Bioceramic ResonanceIJERA Editor
The development of photoluminescent of BIOCERAMIC(PLB) and BIOCERAMIC resonance are based on BIOCERAMIC material, is a kind of non-ionized radiation spectrum emitting material possesses characteristics of weakening effect on water hydrogen bonds. The effect is corresponding to our previous medical-biological studies, such as microcirculation enhancement. Herein, a review is to conclude our previous study on therapeutic effect of PLB or BIOCERAMIC resonance. They are include: glucose level control on diabetics by animal model; improved motor activity on middle cerebral arterial occlusion(MCAO) of rats by PLB treatment; normalizing ability to the mean current level measurement of acupuncture points on skin by PLB irradiation; enhanced propagated sensation along meridians‟ (PSM) phenomenon with clinical benefits by PLB effect on different meridian channels; combine effects of PLB and BIOCERAMIC resonance on many disorders such as insomnia, migraine(a chronic sympathetic nervous system disorder) and other autonomic nervous system disorder, associate clinical improvements. Thus, application of BIOCERAMIC technology for complementary therapy has scientific evidence based with good expectation. Running title: BIOCERAMIC therapy
Photoluminescence of Bioceramic Materials and Bioceramic ResonanceIJERA Editor
The development of photoluminescent of BIOCERAMIC(PLB) and BIOCERAMIC resonance are based on BIOCERAMIC material, is a kind of non-ionized radiation spectrum emitting material possesses characteristics of weakening effect on water hydrogen bonds. The effect is corresponding to our previous medical-biological studies, such as microcirculation enhancement. Herein, a review is to conclude our previous study on therapeutic effect of PLB or BIOCERAMIC resonance. They are include: glucose level control on diabetics by animal model; improved motor activity on middle cerebral arterial occlusion(MCAO) of rats by PLB treatment; normalizing ability to the mean current level measurement of acupuncture points on skin by PLB irradiation; enhanced propagated sensation along meridians‟ (PSM) phenomenon with clinical benefits by PLB effect on different meridian channels; combine effects of PLB and BIOCERAMIC resonance on many disorders such as insomnia, migraine(a chronic sympathetic nervous system disorder) and other autonomic nervous system disorder, associate clinical improvements. Thus, application of BIOCERAMIC technology for complementary therapy has scientific evidence based with good expectation. Running title: BIOCERAMIC therapy
Formulation Of Acalypha Wilkesiana Muell. Arg. Ethanol Leaf Extract into Crea...inventionjournals
International Journal of Pharmaceutical Science Invention (IJPSI) is an international journal intended for professionals and researchers in all fields of Pahrmaceutical Science. IJPSI publishes research articles and reviews within the whole field Pharmacy and Pharmaceutical Science, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
UCSD NANO 266 Quantum Mechanical Modelling of Materials and Nanostructures is a graduate class that provides students with a highly practical introduction to the application of first principles quantum mechanical simulations to model, understand and predict the properties of materials and nano-structures. The syllabus includes: a brief introduction to quantum mechanics and the Hartree-Fock and density functional theory (DFT) formulations; practical simulation considerations such as convergence, selection of the appropriate functional and parameters; interpretation of the results from simulations, including the limits of accuracy of each method. Several lab sessions provide students with hands-on experience in the conduct of simulations. A key aspect of the course is in the use of programming to facilitate calculations and analysis.
Lecture 6: Introduction to Quantum Chemical Simulation graduate course taught at MIT in Fall 2014 by Heather Kulik. This course covers: wavefunction theory, density functional theory, force fields and molecular dynamics and sampling.
Lecture 7 of BIOS 203 mini-course taught by Heather Kulik at Stanford University. Rare event techniques. http://bios203.stanford.edu or email bios203.course@gmail.com for more information.
UCSD NANO 266 Quantum Mechanical Modelling of Materials and Nanostructures is a graduate class that provides students with a highly practical introduction to the application of first principles quantum mechanical simulations to model, understand and predict the properties of materials and nano-structures. The syllabus includes: a brief introduction to quantum mechanics and the Hartree-Fock and density functional theory (DFT) formulations; practical simulation considerations such as convergence, selection of the appropriate functional and parameters; interpretation of the results from simulations, including the limits of accuracy of each method. Several lab sessions provide students with hands-on experience in the conduct of simulations. A key aspect of the course is in the use of programming to facilitate calculations and analysis.
Nano porous membranes for water purification by shrinath ghadgeShrinath Ghadge
Continuous population growth and urbanization as well as rapid industrialization, causing huge contamination of potable water or underground water, has been a serious concern all over the world. Due to incompetency of conventional water purification technologies to deliver complete pollutants free water at an economical price, a high performance, cost-effective and environmentally acceptable separation system is an urgent need which should not only remove macro-, micro- and nano-pollutants but also desalinate water to a significant extent. In this milieu, nanotechnology based carbon nanotube (CNT) membranes have shown impressive breakthroughs towards water purification as compared to existing energy intensive water purification systems and thus, this technology has immense potential for large scale commercial water purification in a cost effective manner.
Formulation Of Acalypha Wilkesiana Muell. Arg. Ethanol Leaf Extract into Crea...inventionjournals
International Journal of Pharmaceutical Science Invention (IJPSI) is an international journal intended for professionals and researchers in all fields of Pahrmaceutical Science. IJPSI publishes research articles and reviews within the whole field Pharmacy and Pharmaceutical Science, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
UCSD NANO 266 Quantum Mechanical Modelling of Materials and Nanostructures is a graduate class that provides students with a highly practical introduction to the application of first principles quantum mechanical simulations to model, understand and predict the properties of materials and nano-structures. The syllabus includes: a brief introduction to quantum mechanics and the Hartree-Fock and density functional theory (DFT) formulations; practical simulation considerations such as convergence, selection of the appropriate functional and parameters; interpretation of the results from simulations, including the limits of accuracy of each method. Several lab sessions provide students with hands-on experience in the conduct of simulations. A key aspect of the course is in the use of programming to facilitate calculations and analysis.
Lecture 6: Introduction to Quantum Chemical Simulation graduate course taught at MIT in Fall 2014 by Heather Kulik. This course covers: wavefunction theory, density functional theory, force fields and molecular dynamics and sampling.
Lecture 7 of BIOS 203 mini-course taught by Heather Kulik at Stanford University. Rare event techniques. http://bios203.stanford.edu or email bios203.course@gmail.com for more information.
UCSD NANO 266 Quantum Mechanical Modelling of Materials and Nanostructures is a graduate class that provides students with a highly practical introduction to the application of first principles quantum mechanical simulations to model, understand and predict the properties of materials and nano-structures. The syllabus includes: a brief introduction to quantum mechanics and the Hartree-Fock and density functional theory (DFT) formulations; practical simulation considerations such as convergence, selection of the appropriate functional and parameters; interpretation of the results from simulations, including the limits of accuracy of each method. Several lab sessions provide students with hands-on experience in the conduct of simulations. A key aspect of the course is in the use of programming to facilitate calculations and analysis.
Nano porous membranes for water purification by shrinath ghadgeShrinath Ghadge
Continuous population growth and urbanization as well as rapid industrialization, causing huge contamination of potable water or underground water, has been a serious concern all over the world. Due to incompetency of conventional water purification technologies to deliver complete pollutants free water at an economical price, a high performance, cost-effective and environmentally acceptable separation system is an urgent need which should not only remove macro-, micro- and nano-pollutants but also desalinate water to a significant extent. In this milieu, nanotechnology based carbon nanotube (CNT) membranes have shown impressive breakthroughs towards water purification as compared to existing energy intensive water purification systems and thus, this technology has immense potential for large scale commercial water purification in a cost effective manner.
What can we learn from molecular dynamics simulations of carbon nanotube and ...Stephan Irle
We present the results of nonequilibrium molecular dynamics (MD) simulations of catalytic and non-catalytic carbon nanostructure formation processes, including single-walled carbon nanotube (SWCNT) and graphene nucleation and growth. In the talk, we discuss the significance of the findings in the light of more traditional, static descriptions of growth reaction mechanisms, and highlight differences as well as commonalities.
Origin of the Size-Dependent Fluorescence Blueshift in [n]Cycloparaphenylenes Stephan Irle
We present quantum chemical electronic structure calculations to investigate the nature of the low-lying excited states of [n]cycloparaphenylenes ([n]CPPs) and the role of static and dynamic geometrical distortions in the bright states. The lowest-energy bright states involve single-electron excitations from S0 ground state to S2 and S3 states, which are at the Franck-Condon geometry the two components of a twofold degenerate 1E state. They couple to a twofold degenerate e vibration which induces Jahn-Teller (JT) deformation of the CPP geometry from circular to oval shape. Non-radiative decay from the S2/S3 states to the ground S0 and first excited, dark S1 states is suppressed due to symmetry rules. The emission spectral features in CPPs with large number of phenylene units n can therefore largely be attributed to the E ⊗ e JT system associated with S2 and S3. However, absorption and emission energies computed at the respective S0 and S2/S3 minimum energy geometries are found to be nearly identical, independent of the molecular size n in the CPP molecules. In contrast, molecular dynamics simulations performed on the excited state potential surfaces are able to explain the experimentally observed fluorescence blueshift of the strongest emission peaks with increasing molecular size. This unusual feature turns out to be a consequence of large vibrational amplitudes in small [n]CPPs, causing greater Stokes shifts, while large [n]CPPs are more rigid and therefore feature smaller Stokes shifts (“dynamic blueshift”). For the same reasons, symmetry rules are violated to a greater extent in small [n]CPPs, and it is expected that in their case a “static blueshift” due to emission from S1 contributes in the fluorescence spectra.
Synthesis of Pt Nanoparticles with different shapes using the same protocol...Amol Jaybhaye
Gives an idea about Nanoparticle's background and introduction to Nanoworld. Engineering the shape and thus surface structure of Pt nanocrystals is an effective strategy for optimizing their catalytic activities toward various reactions. However, different protocols are typically used to produce Pt nanocrystals with distinctive shapes, making it difficult to directly compare their catalytic activities owing to the complication of surface contamination. Here we demonstrate that Pt nanocrystals with a variety of shapes, including those enclosed with low- or high-index facets, can be synthesized using the same protocol by simply adjusting the concentration of reducing agent and/or the reaction time.
Under a Compulsory Course of "Materials Physics and Technology for Nanoelectronics" a team of BE Students of Nanotechnology, Nanoelectronics and Bionnotechnology prepared this seminar for Prof. Marc Heyns, marc.heyns@imec.be Kapeldreef 75, B-3001 Heverlee IMEC Building IV, room 2.33
Tel: 016 281 348
A methodology to evaluate the kinetic stability of molecular nanostructures is presented based on the assumption of the independent and random nature of thermal vibrations, calculated at the density functional theory (DFT) level of theory using the harmonic approximation [1]. The kinetic stability (KS) is directly correlated to the cleavage probability for the weakest bond of a given molecular geometry. The application of the presented method to a selection of fullerenes (see Fig. 1) and carbon nanotubes yields clear correlation to their experimentally observed relative isomer abundances.
Moreover, we present good agreement of harmonic vibrational eigenmodes between DFT and the computationally more efficient density-functional tight-binding (DFTB) method [2-4]. Thus, DFTB-based KS calculations allow the estimation of kinetic stability for more than 100,000 isomers of the fullerenes C20-C100. We found that the experimentally observed isomer abundances, as recorded for instance by mass spectroscopic investigations, are reasonably well reproduced by the Boltzmann-weighted kinetic stabilities of the cage isomers. This result suggests a mechanism of fullerene formation involving cage destruction, such as recently predicted by quantum chemical molecular dynamics (QM/MD) simulations [5-6].
Rerefences:
[1] A. S. Fedorov et al., Phys. Rev. Lett., 107, 175506 (2011).
[2] H. A. Witek et al., J. Chem. Phys., 121, 5163 (2004).
[3] E. Małolepsza et al., Chem. Phys. Lett., 412, 237 (2005).
[4] H. A. Witek et al., J. Chem. Phys., 125, 214706 (2006).
[5] S. Irle et al., J. Phys. Chem. B, 110, 14531 (2006).
[6] B. Saha et al., J. Phys. Chem. A, 115, 22707 (2011).
Nanophotonic enhancement and improved electron extraction in perovskite solar...Pawan Kumar
While vertically oriented metal oxide nanowires have been intensely researched for use as electron transport layers (ETLs) in halide perovskite solar cells (HPSCs), horizontal nanowires (oriented roughly parallel to the substrate) have received much less attention despite their higher photonic strength due to overlapping electric and magnetic dipolar Mie resonance modes. Herein, we demonstrate the fabrication of an assembly of horizontally aligned TiO2 nanorods (HATNRs) on FTO substrates via a facile hydrothermal route. The HATNRs are employed as the ETL to achieve 15.03% power conversion efficiency (PCE) in HPSCs which is higher than the PCE of compact TiO2 based devices (10.12%) by a factor of nearly 1.5. A mixed halide, mixed cation organometal perovskite FA0.83MA0.17Pb(Br0.17I0.83)3 with optimized composition is used as the active layer. The excellent refractive index matching between the perovskite and TiO2, coupled with strong Mie scattering in the nanorod geometry results in broadband near-zero backscattering and high forward scattering, upon coating of HATNRs with perovskite. The maximum suppression of backscattering is found at ∼600 nm. The HATNRs ETL also improves the extraction of electrons from the perovskite layer and results in superior blocking of carrier recombination at the perovskite layer/FTO interface.
Nanophotonic enhancement and improved electron extraction in perovskite solar...Pawan Kumar
While vertically oriented metal oxide nanowires have been intensely researched for use as electron transport layers (ETLs) in halide perovskite solar cells (HPSCs), horizontal nanowires (oriented roughly parallel to the substrate) have received much less attention despite their higher photonic strength due to overlapping electric and magnetic dipolar Mie resonance modes. Herein, we demonstrate the fabrication of an assembly of horizontally aligned TiO2 nanorods (HATNRs) on FTO substrates via a facile hydrothermal route. The HATNRs are employed as the ETL to achieve 15.03% power conversion efficiency (PCE) in HPSCs which is higher than the PCE of compact TiO2 based devices (10.12%) by a factor of nearly 1.5. A mixed halide, mixed cation organometal perovskite FA0.83MA0.17Pb(Br0.17I0.83)3 with optimized composition is used as the active layer. The excellent refractive index matching between the …
State of ICS and IoT Cyber Threat Landscape Report 2024 previewPrayukth K V
The IoT and OT threat landscape report has been prepared by the Threat Research Team at Sectrio using data from Sectrio, cyber threat intelligence farming facilities spread across over 85 cities around the world. In addition, Sectrio also runs AI-based advanced threat and payload engagement facilities that serve as sinks to attract and engage sophisticated threat actors, and newer malware including new variants and latent threats that are at an earlier stage of development.
The latest edition of the OT/ICS and IoT security Threat Landscape Report 2024 also covers:
State of global ICS asset and network exposure
Sectoral targets and attacks as well as the cost of ransom
Global APT activity, AI usage, actor and tactic profiles, and implications
Rise in volumes of AI-powered cyberattacks
Major cyber events in 2024
Malware and malicious payload trends
Cyberattack types and targets
Vulnerability exploit attempts on CVEs
Attacks on counties – USA
Expansion of bot farms – how, where, and why
In-depth analysis of the cyber threat landscape across North America, South America, Europe, APAC, and the Middle East
Why are attacks on smart factories rising?
Cyber risk predictions
Axis of attacks – Europe
Systemic attacks in the Middle East
Download the full report from here:
https://sectrio.com/resources/ot-threat-landscape-reports/sectrio-releases-ot-ics-and-iot-security-threat-landscape-report-2024/
Kubernetes & AI - Beauty and the Beast !?! @KCD Istanbul 2024Tobias Schneck
As AI technology is pushing into IT I was wondering myself, as an “infrastructure container kubernetes guy”, how get this fancy AI technology get managed from an infrastructure operational view? Is it possible to apply our lovely cloud native principals as well? What benefit’s both technologies could bring to each other?
Let me take this questions and provide you a short journey through existing deployment models and use cases for AI software. On practical examples, we discuss what cloud/on-premise strategy we may need for applying it to our own infrastructure to get it to work from an enterprise perspective. I want to give an overview about infrastructure requirements and technologies, what could be beneficial or limiting your AI use cases in an enterprise environment. An interactive Demo will give you some insides, what approaches I got already working for real.
Connector Corner: Automate dynamic content and events by pushing a buttonDianaGray10
Here is something new! In our next Connector Corner webinar, we will demonstrate how you can use a single workflow to:
Create a campaign using Mailchimp with merge tags/fields
Send an interactive Slack channel message (using buttons)
Have the message received by managers and peers along with a test email for review
But there’s more:
In a second workflow supporting the same use case, you’ll see:
Your campaign sent to target colleagues for approval
If the “Approve” button is clicked, a Jira/Zendesk ticket is created for the marketing design team
But—if the “Reject” button is pushed, colleagues will be alerted via Slack message
Join us to learn more about this new, human-in-the-loop capability, brought to you by Integration Service connectors.
And...
Speakers:
Akshay Agnihotri, Product Manager
Charlie Greenberg, Host
Dev Dives: Train smarter, not harder – active learning and UiPath LLMs for do...UiPathCommunity
💥 Speed, accuracy, and scaling – discover the superpowers of GenAI in action with UiPath Document Understanding and Communications Mining™:
See how to accelerate model training and optimize model performance with active learning
Learn about the latest enhancements to out-of-the-box document processing – with little to no training required
Get an exclusive demo of the new family of UiPath LLMs – GenAI models specialized for processing different types of documents and messages
This is a hands-on session specifically designed for automation developers and AI enthusiasts seeking to enhance their knowledge in leveraging the latest intelligent document processing capabilities offered by UiPath.
Speakers:
👨🏫 Andras Palfi, Senior Product Manager, UiPath
👩🏫 Lenka Dulovicova, Product Program Manager, UiPath
UiPath Test Automation using UiPath Test Suite series, part 3DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 3. In this session, we will cover desktop automation along with UI automation.
Topics covered:
UI automation Introduction,
UI automation Sample
Desktop automation flow
Pradeep Chinnala, Senior Consultant Automation Developer @WonderBotz and UiPath MVP
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
Smart TV Buyer Insights Survey 2024 by 91mobiles.pdf91mobiles
91mobiles recently conducted a Smart TV Buyer Insights Survey in which we asked over 3,000 respondents about the TV they own, aspects they look at on a new TV, and their TV buying preferences.
Software Delivery At the Speed of AI: Inflectra Invests In AI-Powered QualityInflectra
In this insightful webinar, Inflectra explores how artificial intelligence (AI) is transforming software development and testing. Discover how AI-powered tools are revolutionizing every stage of the software development lifecycle (SDLC), from design and prototyping to testing, deployment, and monitoring.
Learn about:
• The Future of Testing: How AI is shifting testing towards verification, analysis, and higher-level skills, while reducing repetitive tasks.
• Test Automation: How AI-powered test case generation, optimization, and self-healing tests are making testing more efficient and effective.
• Visual Testing: Explore the emerging capabilities of AI in visual testing and how it's set to revolutionize UI verification.
• Inflectra's AI Solutions: See demonstrations of Inflectra's cutting-edge AI tools like the ChatGPT plugin and Azure Open AI platform, designed to streamline your testing process.
Whether you're a developer, tester, or QA professional, this webinar will give you valuable insights into how AI is shaping the future of software delivery.
Essentials of Automations: Optimizing FME Workflows with ParametersSafe Software
Are you looking to streamline your workflows and boost your projects’ efficiency? Do you find yourself searching for ways to add flexibility and control over your FME workflows? If so, you’re in the right place.
Join us for an insightful dive into the world of FME parameters, a critical element in optimizing workflow efficiency. This webinar marks the beginning of our three-part “Essentials of Automation” series. This first webinar is designed to equip you with the knowledge and skills to utilize parameters effectively: enhancing the flexibility, maintainability, and user control of your FME projects.
Here’s what you’ll gain:
- Essentials of FME Parameters: Understand the pivotal role of parameters, including Reader/Writer, Transformer, User, and FME Flow categories. Discover how they are the key to unlocking automation and optimization within your workflows.
- Practical Applications in FME Form: Delve into key user parameter types including choice, connections, and file URLs. Allow users to control how a workflow runs, making your workflows more reusable. Learn to import values and deliver the best user experience for your workflows while enhancing accuracy.
- Optimization Strategies in FME Flow: Explore the creation and strategic deployment of parameters in FME Flow, including the use of deployment and geometry parameters, to maximize workflow efficiency.
- Pro Tips for Success: Gain insights on parameterizing connections and leveraging new features like Conditional Visibility for clarity and simplicity.
We’ll wrap up with a glimpse into future webinars, followed by a Q&A session to address your specific questions surrounding this topic.
Don’t miss this opportunity to elevate your FME expertise and drive your projects to new heights of efficiency.
Epistemic Interaction - tuning interfaces to provide information for AI supportAlan Dix
Paper presented at SYNERGY workshop at AVI 2024, Genoa, Italy. 3rd June 2024
https://alandix.com/academic/papers/synergy2024-epistemic/
As machine learning integrates deeper into human-computer interactions, the concept of epistemic interaction emerges, aiming to refine these interactions to enhance system adaptability. This approach encourages minor, intentional adjustments in user behaviour to enrich the data available for system learning. This paper introduces epistemic interaction within the context of human-system communication, illustrating how deliberate interaction design can improve system understanding and adaptation. Through concrete examples, we demonstrate the potential of epistemic interaction to significantly advance human-computer interaction by leveraging intuitive human communication strategies to inform system design and functionality, offering a novel pathway for enriching user-system engagements.
DevOps and Testing slides at DASA ConnectKari Kakkonen
My and Rik Marselis slides at 30.5.2024 DASA Connect conference. We discuss about what is testing, then what is agile testing and finally what is Testing in DevOps. Finally we had lovely workshop with the participants trying to find out different ways to think about quality and testing in different parts of the DevOps infinity loop.
SWCNT Growth from Chiral and Achiral Carbon Nanorings: Prediction of Chirality and Diameter Influence on Local Growth Rates
1. SWCNT Growth from Chiral and Achiral Carbon
Nanorings: Prediction of Chirality and Diameter
Influence on Local Growth Rates
Stephan Irle,1 Hai-Bei Li,2 Alister J. Page,2 Keiji Morokuma2,3
2Kyoto University 1Nagoya University
http://kmweb.fukui.kyoto-u.ac.jp/nano http://qc.chem.nagoya-u.ac.jp
The Sixth Rice University, Air Force Research Laboratory, NASA, Honda Research Institute
Workshop on Nucleation and Growth Mechanisms of Single Wall Carbon Nanotubes
The Flying L Ranch, Bandera, TX, U.S.A., April 13, 2013
3
2. Kyoto University Nagoya University
http://kmweb.fukui.kyoto-u.ac.jp/nano http://qc.chem.nagoya-u.ac.jp
Dr. Alister J. Pageb
Acknowledgements
Prof. Keiji Morokuma
Dr. Hai-Bei Libnow: Lecturer, University of Newcastle (AUS)
Dr. Joonghan Kim
2
2
3. Computer resources :
CREST grant 2006-2012
(KM, SI) and AFOSR (to KM)
Funding :
MEXT Tenure Track program, JSPS Kiban (SI)
Acknowledgements
Research Center for Computational Science
(RCCS), Okazaki Research Facilities, National
Institutes for Natural Sciences.
Academic Center for Computing and Media
Studies (ACCMS), Kyoto University
3
4. Prolog Our QM/MD Studies
ADVERTISEMENT
4
“What can be controlled is never completely real;
what is real can never be completely controlled.”
Vladimir V. Nabokov, in: Look at the harlequins! McGraw-
Hill, New York (1974)
5. Goal SWCNT Chirality Control
The goal: arbitrary (n,m)-specific SWCNT Growth
(5,5) SWCNT
high yield, desired length, defect-free, eventually catalyst-free
ACCVD etc …
Selection of
“appropriate” growth
conditions
diameter
yield
chirality
length
5
6. Overview
Overview: CCVD SWCNT synthesis
Metal-free SWCNT synthesis from templates
Theoretical Simulations of SWCNT growth from CPPs
(n,n) SWCNT growth from [n]CPPs
(n,m) SWCNT growth from chiral CPPs
Summary: What did we learn?
What is next?
http://kmweb.fukui.kyoto-u.ac.jp/nano http://qc.chem.nagoya-u.ac.jp6
6
8. • SCC-DFTB; Te = 10,000 K.
• MD; ∆t=1 fs.
• NVT ensemble; Tn= 1,500 K.
• Nosé-Hoover-Chain thermostat.
• 30 C2 deposited onto fcc-Fe38 surface
(1/ps).
• NVT thermal annealing for 400 ps.
Yasuhito Ohta
Overview DFTB/MD of cap nucleation
C2 shooting and annealing on Fe38 particle
8
Y. Ohta, Y. Okamoto, A. J. Page, SI, K. Morokuma, ACS Nano 3, 3413 (2009)
• 10 trajectory replica.
9. C2 shooting and annealing on Fe38 particle
9
Y. Ohta, Y. Okamoto, A. J. Page, SI, K. Morokuma, ACS Nano 3, 3413 (2009)
Overview DFTB/MD of cap nucleation
Pentagon-first mechanism
10. Yoshida et al., Nano. Lett. (2008)
SWCNT nucleation:
driven by 5-/6-membered ring formation
from sp carbon
Fe3C nanoparticle
Y. Ohta, Y. Okamoto, A. J. Page, SI, K. Morokuma, ACS Nano 3, 3413 (2009)
C2 shooting and annealing on Fe38 particle
10
Overview DFTB/MD of cap nucleation
Cap structures are relatively random even in “slow” MD simulations
11. Y. Ohta, Y. Okamoto, A. J. Page, SI, K. Morokuma, ACS Nano 3, 3413 (2009)
“Random” cap structures in CCVD simulations
11
Overview DFTB/MD of cap nucleation
Cap structures are relatively random even in “slow” DFTB/MD simulations
12. Carbon Feeding Rate Effect: M38C40+nC
A. Page, S. Minami, Y. Ohta, SI, K. Morokuma, Carbon 48, 3014 (2010)
Timescale
problem in MD
12
Overview Sidewall growth, defects
unpublished
13. Local Chirality Index (LOCI): Definition
Requires: i) System’s global principal axis in tube direction (GPAZ)
ii) Hexagon’s local principal axis normal to hexagon plane
Local chiral angle 1
13
J. Kim, SI, K. Morokuma, Phys. Rev. Lett. 107, 15505 (2011).
Overview Chirality-controlled CCVD
14. Slow simulations of (5,5) and (8,0) SWCNT growth on Fe38
14
J. Kim, A. J. Page, SI, K. Morokuma, J. Am. Chem. Soc. 134, 9311 (2012).
+30C
300 ps, 1500K
+30C
300 ps, 1500 K
Error bars: Standard deviation
Trajectory B
Trajectory A
Overview Chirality-controlled CCVD
15. Slow simulations of (5,5) and (8,0) SWCNT growth on Fe38
CNT formation Interpretation
15
Overview Chirality-controlled CCVD
J. Kim, A. J. Page, SI, K. Morokuma, J. Am. Chem. Soc. 134, 9311 (2012).
+30C
300 ps, 1500K
+30C
300 ps, 1500 K
Error bars: Standard deviation
Trajectory D
Trajectory D
16. Slow simulations of (5,5) and (8,0) SWCNT growth on Fe38
16
J. Kim, A. J. Page, SI, K. Morokuma, J. Am. Chem. Soc. 134, 9311 (2012).
Statistics based on 10 trajectoriesa
Conclusions: (5,5) grows less defects than (8,0), heals faster!
Overview Chirality-controlled CCVD
18. Consensus among experimentalists and theoreticians:
18
Overview Summary of CCVD
• Chirality-controlled nucleation on Fe or Ni nanoparticles
is difficult! Higher temperature gives “cleaner” tubes
• Growth occurs on “long” timescales (carbon atom
addition on nanosecond scale)
• Atomically faster growth (=higher feedstock pressure)
increases concentration of tube defects
Suggested solutions:
• Avoid catalyst for nucleation,
• grow sidewalls in low pressure, high temperature
• from templates with established (n,m) chiral structure
21. Nano Lett. 10, 3343 (2010)
Raman spectra AFM image
=248 cm-1 nm d = 0.86 nm
0.69 nm SWCNTs are not strictly
extensions of C60 cap; C30 too small?
RBM=288 cm-1
Tube length: 40 m mentioned
Catalyst-free growth Growth from C60
21
22. J. Liu, C. Wang et al.:
Vapor-phase “epitaxy”
of SWCNTs
Nat. Commun. (2012)
2000 sccm CH4, 300 sccm H2, 900°C, 15 mins
Chirality confirmed; more successful!
Catalyst-free growth Growth from CNTs
22
22
J. Zhang, Z. F. Liu et al.: “Cloning” of SWCNTs
Nano Lett. 9, 1673 (2009)
100 sccm CH4, 5 sccm C2H4, 975°C, 15 mins
Extension was short, maintenance of chirality not proven
23. 23
SWCNT growth from [n]cycloparaphenylenes
We have a dream:
Omachi, Matsuura, Segawa, Itami, Angew. Chem. Int. Ed. 49, 10202 (2011)
Prof. Itami
Nagoya University
Catalyst-free growth Growth from CPPs
24. 24
SWCNT growth from [n]cycloparaphenylenes: Diels-Alder
Catalyst-free growth Growth from CPPs
E. H. Fort, L. T. Scott, J. Mater. Chem. 21, 1373 (2011), also cited by Wang & Liu
Basic idea: Example: (5,5) SWCNT
1. Diels-Alder (DA)
Cycloaddition
2. H2 removal,
Re-aromatization
25. DA barrier heights for C2H2 +
E. H. Fort, L. T. Scott, J. Mater. Chem. 21, 1373 (2011)
Barriers very high!
(many other processes
may compete)
Catalyst-free growth Growth from CPPs
25
26. Catalyst-free growth Growth from CPPs
26
“Solution” to high barrier: Vapor phase pyrolysis
A. P. Rudenko, A. A. Balandin, M. M. Zabolotnaya, Russ. Chem. Bull. 10, 916 (1961)
Carbon production on SiO2 from:
CH4
C2H6
C2H4
C2H2
27. Catalyst-free growth Growth from CPPs
27
“Solution” to high barrier: Vapor phase pyrolysis
C2H radical (ethynyl) …
… as initiator of Diels-Alder C2H2 growth
28. Overview
Theoretical Simulations of SWCNT growth from CPPs
(n,n) SWCNT growth from [n]CPPs
http://kmweb.fukui.kyoto-u.ac.jp/nano http://qc.chem.nagoya-u.ac.jp28
28
29. Growth from CPPs DFTB/MD Methodology
29
QM/MD simulations of [6]CPP growth to (6,6) SWCNT
H. Li, A. J., Page, SI, K. Morokuma, ChemPhysChem 13, 1479 (2012)
• SCC-DFTB: Te = 1,500 K.
• MD; t=0.5 fs.
• NVT ensemble; Tn = 500 K.
• Nose-Hoover-Chain
thermostat.
• Initial annealing of CPP for 5
ps.
• 1 C2H2 added every 10 ps
with near random edge-
carbon.
• (Optional) manual hydrogen
removal at initial stage of
30. 30
Four possible sites for initial H abstraction or
C2H radical addition (sample: 100 trajectories)
42 39
17 1
Number of trajectories
Growth from CPPs Preliminary studies
31. Growth from CPPs DFTB/PRMD Simulations
31
QM/MD simulations of [6]CPP growth to (6,6) SWCNT
H. Li, A. J., Page, SI, K. Morokuma, ChemPhysChem 13, 1479 (2012)
485 ps, each
frame = 0.2 ps
32. Growth from CPPs DFTB/PRMD Simulations
32
Growth mechanism of C2H and C2H2 addition to CPPs
H. Li, A. J., Page, SI, K. Morokuma, ChemPhysChem 13, 1479 (2012)
Level: B3LYP/6-31G(d)
DA: High barrier Radical initiation:
It only takes 1 C2H!
Radical pathways: low-
energy
33. Growth from CPPs DFTB/PRMD Simulations
33
Growth speed of “CPP ring” versus “SWCNT belt”
H. Li, A. J., Page, SI, K. Morokuma, ChemPhysChem 13, 1479 (2012)
Conformational
flexibility of CPPs
hinders growth!
34. Growth from CPPs DFTB/PRMD Simulations
34
Availability of extended (5,5) SWCNT cap
L. T. Scott et al., J. Am. Chem. Soc. 134, 107 (2012)
X-ray structure
Worth a try.
35. Overview
Theoretical Simulations of SWCNT growth from CPPs
(n,m) SWCNT growth from chiral CPPs
http://kmweb.fukui.kyoto-u.ac.jp/nano http://qc.chem.nagoya-u.ac.jp35
35
36. 36
SWCNT growth from chiral organic nanorings
Omachi, Segawa, Itami, Acc. Chem. Res. (2012)
Prof. Itami
Nagoya University
Growth from CPPs Chiral SWCNT growth
37. Growth from CPPs DFTB/MD Methodology
37
QM/MD simulations of chiral SWCNTs from CPPs
H. Li, A. J., Page, SI, K. Morokuma, J. Am. Chem. Soc. 134, 15887 (2012)
• SCC-DFTB: Te = 1,500 K.
• MD; t=0.5 fs.
• NVT ensemble; Tn = 500 K.
• Nose-Hoover-Chain
thermostat.
• Initial annealing of CPP for 5
ps.
• 1 C2H2 added every 10 ps
with near random edge-
carbon.
• (Optional) manual hydrogen
removal at initial stage of
(6,6)
(8,0)
(4,3) (6,1)
(6,5) (10,1)
38. Growth from CPPs DFTB/MD Methodology
38
QM/MD simulations of chiral SWCNTs from CPPs
H. Li, A. J., Page, SI, K. Morokuma, J. Am. Chem. Soc. 134, 15887 (2012)
(6,5)
(10,1)
39. Growth from CPPs DFTB/MD Methodology
39
QM/MD simulations of chiral SWCNTs from CPPs
H. Li, A. J., Page, SI, K. Morokuma, J. Am. Chem. Soc. 134, 15887 (2012)
1. Addition of new hexagons
exclusively in armchair bay
2. In case of pure zigzag edge,
a) formation of heptagon
b) followed by 76/3
c) growth proceeds at
armchair edge
3. Growth mechanism in PRMD
follows Ding/Yakobson’s Screw-
dislocation-like (SDL) theory,
PNAS 106, 2506 (2009)
40. Growth from CPPs DFTB/MD Methodology
40
Growth termination for (8,0) SWCNT
H. Li, A. J., Page, SI, K. Morokuma, J. Am. Chem. Soc. 134, 15887 (2012)
“heptagon-first” 76/3
New hexagon
@armchair
B3LYP/6-31G(d)
41. Growth from CPPs DFTB/MD Methodology
41
C2H-hexagon addition rates consistent with k ~ sin(
H. Li, A. J., Page, SI, K. Morokuma, J. Am. Chem. Soc. 134, 15887 (2012)
=27° =25°
=5° =8°
Indeed, for C2H addition in
PRMD, armchair edge is a
“cozy corner!”
Ding/Yakobson’s Screw-
dislocation-like (SDL) model,
PNAS 106, 2506 (2009)
42. Growth from CPPs DFTB/MD Methodology
42
C2H2-(DA)hexagon addition rates in (n,n) SWCNTs: k ~ d
H. Li, A. J., Page, SI, K. Morokuma, J. Am. Chem. Soc. 134, 15887 (2012)
endo
exo
DA barrier H2 removal barrier
B3LYP/6-31G(d)
43. Overview
Summary: What did we learn?
http://kmweb.fukui.kyoto-u.ac.jp/nano http://qc.chem.nagoya-u.ac.jp43
43
44. Summary What did we learn?
44
• C2H radicals are feasible via C2H2 pyrolysis on SiO2.
• C2H radicals are able to remove H and add to
SWCNTs with little barrier.
• C2H radicals may initiate radical edge “polymerization”.
• Growth by C2H addition is controlled by SWCNT edge
structure alone
“Radically” New Chemistry:
• New hexagons are formed always near armchair site
(=“cozy corner” in Ding/Yakobson SDL-model)
Growth Mechanism in PRMD simulations:
45. Summary What did we learn?
45
• DA C2H2 implies hexagon addition rates k ~ d.
• At given C2H/C2H2 ratio, there should be optimal growth
conditions for certain d, combinations.
C2H/C2H2 ratio may allow control of arbitrary (n,m)!!
46. Overview
What is next?
http://kmweb.fukui.kyoto-u.ac.jp/nano http://qc.chem.nagoya-u.ac.jp46
46
47. CNT formation Interpretation
47
What is next?
Theoreticians need to address the following urgent issues:
-Timescale problem in MD simulations, e.g. by KMC, will allow to study:
-Role of carbide formation
-Role of defect healing
-More precise atomistic growth mechanisms (no timescale problem of
MD, no arbitrariness as in PRMD)
-Investigate possible mechanism for chirality control at time of nucleation
-Investigate role of hydrogen in greater detail
-Effect of various catalyst substrates in atomic detail
-Effect of etching gases and water
Thank you.
49. D. A. Gomez-Gualdron, G. D. McKenzie, J. F. J. Alvarado, P. B. Balbuena ACS Nano 6, 720 (2012)
“Random” cap structures in CCVD simulations
49
Overview SIMCAT/MD of cap nucleation
Cap structures are relatively random even in “slower” SIMCAT/MD simulations
Classical reactive MD simulations of cap formation on supported Nix
50. Experiments for individual SWCNT nucleation and growth
50
Nat. Mater. 11, 231 (2012)
Measuring growth rates v of individual SWCNTs by Raman
Overview Experimental evidence
51. Nano Lett. 10, 3343 (2010)
Notes:
•baked at 150° in air to remove
solvent (toluene)
•Thermal oxidation in air at 300-
500°C for 30 mins
•Remove “amorphous carbon”:
Temperature up to 900°C in
presence of water, then cool
down
•900°C annealing for 3 mins
(presumably in vacuum)
•20 mins 20 sccm ethanol in 30
sccm Ar/H2 at 900°C (low sccm!)
Catalyst-free growth Growth from C60
51
52. 52
Scheme to study AC CNT growth by adding C2H radicals
(1) Starts from one initial structure, and then add 6 times C2H radical to
obtain 6 parallel trajectories every 10 ps;
(2) Select two trajectories that could produce uniform AC NT to continue.
Principles for rule (2):
First, whether new 6-m ring formed;
Then whether C2H insert to the edge
of SWCNT;
Then whether H atoms on the rim of
SWCNT abstracted
Then whether H atoms on the sidewall of
SWCNT abstracted
Then whether C2H added to sidewall
53. 53/25
TimescalePRMD
Parallel Replica MD [A. F. Voter, PRB 57, R13985 (1998)]
Disadvantage: computationally very expensive
Alternatives: Metadynamics, umbrella sampling, etc.
Problem there: MD depends on algorithm/bias potential