ORCID Profile
0000-0003-4995-4991
Current Organisations
Oak Ridge National Laboratory
,
Universitas 17 Agustus 1945 Jakarta
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Theoretical and Computational Chemistry not elsewhere classified | Quantum Chemistry | Theoretical and Computational Chemistry | Nanofabrication, Growth and Self Assembly
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in the Chemical Sciences | Expanding Knowledge in the Physical Sciences | Expanding Knowledge in Technology |
Related Links
Publications
Polyyne Chain Growth and Ring Collapse Drives Ni-Catalyzed SWNT Growth: A QM/MD Investigation
Publisher: American Chemical Society (ACS)
Date: 02-04-2010
DOI: 10.1021/JP100790E
Quantum chemical investigation of epoxide and ether groups in graphene oxide and their vibrational spectra
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3CP00094J
Abstract: We present a detailed analysis of the factors influencing the formation of epoxide and ether groups in graphene nanoflakes using conventional density functional theory (DFT), the density-functional tight-binding (DFTB) method, π-Hückel theory, and graph theoretical invariants. The relative thermodynamic stability associated with the chemisorption of oxygen atoms at various positions on hexagonal graphene flakes (HGFs) of D(6h)-symmetry is determined by two factors - viz. the disruption of the π-conjugation of the HGF and the geometrical deformation of the HGF structure. The thermodynamically most stable structure is achieved when the former factor is minimized, and the latter factor is simultaneously maximized. Infrared (IR) spectra computed using DFT and DFTB reveal a close correlation between the relative thermodynamic stabilities of the oxidized HGF structures and their IR spectral activities. The most stable oxidized structures exhibit significant IR activity between 600 and 1800 cm(-1), whereas less stable oxidized structures exhibit little to no activity in this region. In contrast, Raman spectra are found to be less informative in this respect.
Sub-surface nucleation of graphene precursors near a Ni(111) step-edge
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2CC32995F
Abstract: Graphene nucleation on Ni(111) has been modeled using QM/MD simulations. We demonstrate that graphene precursor nucleation can occur underneath the catalyst surface. In addition, a Ni(111) step-edge is not a static structure, as is often assumed it is instead highly malleable, being deformed and subsequently healed during graphene nucleation.
Defect Healing during Single-Walled Carbon Nanotube Growth: A Density-Functional Tight-Binding Molecular Dynamics Investigation
Publisher: American Chemical Society (ACS)
Date: 08-09-2009
DOI: 10.1021/JP9053549
Thermal annealing of SiC nanoparticles induces SWNT nucleation: evidence for a catalyst-independent VSS mechanism
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C1CP21236B
Abstract: Density-functional tight-binding molecular dynamics (DFTB/MD) methods were employed to demonstrate single-walled carbon nanotube (SWNT) nucleation resulting from thermal annealing of SiC nanoparticles. SWNT nucleation in this case is preceded by a change of the SiC structure from a crystalline one, to one in which silicon and carbon are segregated. This structural transformation ultimately resulted in the formation of extended polyyne chains on the SiC nanoparticle surface. These polyyne chains subsequently coalesced, forming an extended sp(2)-hybridized carbon cap on the SiC nanoparticle. The kinetics of this process were enhanced significantly at higher temperatures (2500 K), compared to lower temperatures (1200 K) and so directly correlated to the surface premelting behavior of the nanoparticle structure. Analysis of the SiC nanoparticle Lindemann index between 1000 and 3000 K indicated that SWNT nucleation at temperatures below 2600 K occurred in the solid, or quasi-solid, phase. Thus, the traditional vapor-liquid-solid mechanism of SWNT growth does not apply in the case of SiC nanoparticles. Instead, we propose that this ex le of SWNT nucleation constitutes evidence of a vapor-solid-solid process. This conclusion complements our recent observations regarding SWNT nucleation on SiO(2) nanoparticles (A. J. Page, K. R. S. Chandrakumar, S. Irle and K. Morokuma, J. Am. Chem. Soc., 2011, 133, 621-628). In addition, similarities between the atomistic SWNT nucleation mechanisms on SiC and SiO(2) catalysts provide the first evidence of a catalyst-independent SWNT nucleation mechanism with respect to 'non-traditional' SWNT catalyst species.
Quantum Chemical Molecular Dynamics Simulation of Single-Walled Carbon Nanotube Cap Nucleation on an Iron Particle
Publisher: American Chemical Society (ACS)
Date: 14-10-2009
DOI: 10.1021/NN900784F
Abstract: The atomic scale details of single-walled carbon nanotube (SWNT) nucleation on metal catalyst particles are elusive to experimental observations. Computer simulation of metal-catalyzed SWNT nucleation is a challenging topic but potentially of great importance to understand the factors affecting SWNT diameters, chirality, and growth efficiency. In this work, we use nonequilibrium density functional tight-binding molecular dynamics simulations and report nucleation of sp(2)-carbon cap structures on an iron particle consisting of 38 atoms. One C(2) molecule was placed every 1.0 ps around an Fe(38) cluster for 30 ps, after which a further 410 ps of annealing simulation without carbon supply was performed. We find that sp(2)-carbon network nucleation and annealing processes occur in three sequential and repetitive stages: (A) polyyne chains on the metal surface react with each other to evolve into a Y-shaped polyyne junction, which preferentially form a five-membered ring as a nucleus (B) polyyne chains on the first five-membered ring form an additional fused five- or six-membered ring and (C) pentagon-to-hexagon self-healing rearrangement takes place with the help of short-lived polyyne chains, stabilized by the mobile metal atoms. The observed nucleation process resembles the formation of a fullerene cage. However, the metal particle plays a key role in differentiating the nucleation process from fullerene cage formation, most importantly by keeping the growing cap structure from closing into a fullerene cage and by keeping the carbon edge "alive" for the addition of new carbon material.
Density-functional tight-binding for phosphine-stabilized nanoscale gold clusters
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0SC04514D
Abstract: We report a parameterization of the density-functional tight-binding (DFTB) method for the accurate prediction of molecular, electronic and vibrational structure of phosphine-ligated nanoscale gold clusters, metalloids, and gold surfaces.
Erratum: “DFTB+, a software package for efficient approximate density functional theory based atomistic simulations” [J. Chem. Phys. 152, 124101 (2020)]
Publisher: AIP Publishing
Date: 18-07-2022
DOI: 10.1063/5.0103026
Revealing the Dual Role of Hydrogen for Growth Inhibition and Defect Healing in Polycyclic Aromatic Hydrocarbon Formation: QM/MD Simulations
Publisher: American Chemical Society (ACS)
Date: 07-2013
DOI: 10.1021/JZ400925F
Theoretical Insights into Chirality‐Controlled SWCNT Growth from a Cycloparaphenylene Template
Publisher: Wiley
Date: 05-03-2012
Abstract: A self-assembly mechanism for low-temperature SWCNT growth from a [6]cycloparaphenylene ([6]CPP) precursor via ethynyl (C(2)H) radical addition is presented, based on non-equilibrium quantum chemical molecular dynamics (QM/MD) simulations and density functional theory (DFT) calculations. This mechanism, which maintains the (6,6) armchair chirality of a SWCNT fragment throughout the growth process, is energetically more favorable than a previously proposed Diels-Alder-based growth mechanisms [E. H. Fort, et al., J. Mater. Chem. 2011, 21, 1373]. QM/MD simulations and DFT calculations show that C(2)H radicals play dual roles during SWCNT growth, by abstracting hydrogen from the SWCNT fragment and providing the carbon source necessary for growth itself. Simulations demonstrate that chirality-controlled SWCNT growth from macrocyclic hydrocarbon seed molecules with pre-selected edge structure can be accomplished when the reaction conditions are carefully selected for hydrogen abstraction by radical species during the growth process.
Inducing regioselective chemical reactivity in graphene with alkali metal intercalation
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8CP02903B
Abstract: Intercalating alkali metal atoms between metal substrates and adsorbed graphene monolayers yields curvature-induced regioselective reactivity of graphene.
Mechanisms of Single-Walled Carbon Nanotube Nucleation, Growth, and Healing Determined Using QM/MD Methods
Publisher: American Chemical Society (ACS)
Date: 27-07-2010
DOI: 10.1021/AR100064G
Abstract: Since their discovery in the early 1990s, single-walled carbon nanotubes (SWNTs) have spawned previously unimaginable commercial and industrial technologies. Their versatility stems from their unique electronic, physical/chemical, and mechanical properties, which set them apart from traditional materials. Many researchers have investigated SWNT growth mechanisms in the years since their discovery. The most prevalent of these is the vapor-liquid-solid (VLS) mechanism, which is based on experimental observations. Within the VLS mechanism, researchers assume that the formation of a SWNT starts with co-condensation of carbon and metal atoms from vapor to form liquid metal carbide. Once the liquid reaches supersaturation, the solid phase nanotubes begin to grow. The growth process is partitioned into three distinct stages: nucleation of a carbon "cap-precursor," "cap-to-tube" transformation, and continued SWNT growth. In recent years, molecular dynamics (MD) simulations have come to the fore with respect to SWNT growth. MD simulations lead to spatial and temporal resolutions of these processes that are superior to those possible using current experimental techniques, and so provide valuable information regarding the growth process that researchers cannot obtain experimentally. In this Account, we review our own recent efforts to simulate SWNT nucleation, growth, and healing phenomena on transition-metal catalysts using quantum mechanical molecular dynamics (QM/MD) methods. In particular, we have validated each stage of the SWNT condensation mechanism using a self-consistent-charge density-functional tight-binding (SCC-DFTB) methodology. With respect to the nucleation of a SWNT cap-precursor (stage 1), we have shown that the presence of a transition-metal carbide particle is not a necessary prerequisite for SWNT nucleation, contrary to conventional experimental presumptions. The formation and coalescence of polyyne chains on the metal surface occur first, followed by the formation of the SWNT cap-precursor, "ring condensation", and the creation of an sp(2)-hybridized carbon structure. In our simulations, the nucleation process takes approximately 400 ps. This first step occurs over a much longer time scale than the second stage of SWNT condensation (approximately 50 ps). We therefore observe SWNT nucleation to be akin to the rate-limiting step of the SWNT formation process. In addition to the QM/MD simulation of various stages of SWNT nucleation, growth, and healing processes, we have determined the effects of temperature, catalyst composition, and catalyst size on the kinetics and mechanism of SWNT growth. With respect to temperature dependence, we observe a "sweet-spot" with respect to the efficiency of SWNT growth. In addition, Ni-catalyzed SWNT growth is observed to be 70-100% faster compared to Fe-catalyzed SWNT growth, depending on the catalyst particle size. We also observe a noticeable increase in SWNT growth rates using smaller catalyst particles. Finally, we review our recent QM/MD investigation of SWNT healing. In particular, we recount mechanisms by which adatom defects, monovacancy defects, and a "5-7 defect" are removed from a nascent SWNT. The effectiveness of these healing mechanisms depends on the rate at which carbon moieties are incorporated into the growing SWNT. Explicitly, we observe that healing is promoted using a slower carbon supply rate. From this rudimentary control of SWNT healing, we propose a route towards chirality-controlled SWNT growth.
DFTB+, a software package for efficient approximate density functional theory based atomistic simulations
Publisher: AIP Publishing
Date: 23-03-2020
DOI: 10.1063/1.5143190
Abstract: DFTB+ is a versatile community developed open source software package offering fast and efficient methods for carrying out atomistic quantum mechanical simulations. By implementing various methods approximating density functional theory (DFT), such as the density functional based tight binding (DFTB) and the extended tight binding method, it enables simulations of large systems and long timescales with reasonable accuracy while being considerably faster for typical simulations than the respective ab initio methods. Based on the DFTB framework, it additionally offers approximated versions of various DFT extensions including hybrid functionals, time dependent formalism for treating excited systems, electron transport using non-equilibrium Green’s functions, and many more. DFTB+ can be used as a user-friendly standalone application in addition to being embedded into other software packages as a library or acting as a calculation-server accessed by socket communication. We give an overview of the recently developed capabilities of the DFTB+ code, demonstrating with a few use case ex les, discuss the strengths and weaknesses of the various features, and also discuss on-going developments and possible future perspectives.
Dynamics of Local Chirality during SWCNT Growth: Armchair versus Zigzag Nanotubes
Publisher: American Chemical Society (ACS)
Date: 22-05-2012
DOI: 10.1021/JA301299T
Abstract: We present an analysis of the dynamics of single-walled carbon nanotube (SWCNT) chirality during growth, using the recently developed local chirality index (LOCI) method [ Kim et al. Phys. Rev. Lett. 2011 , 107 , 175505 ] in conjunction with quantum chemical molecular dynamics (QM/MD) simulations. Using (5,5) and (8,0) SWCNT fragments attached to an Fe(38) catalyst nanoparticle, growth was induced by periodically placing carbon atoms at the edge of the SWCNT. For both armchair and zigzag SWCNTs, QM/MD simulations indicate that defect healing-the process of defect removal during growth-is a necessary, but not sufficient, condition for chirality-controlled SWCNT growth. Time-evolution LOCI analysis shows that healing, while restoring the pristine hexagon structure of the growing SWCNT, also leads to changes in the local chirality of the SWCNT edge region and thus of the entire SWCNT itself. In this respect, we show that zigzag SWCNTs are significantly inferior in maintaining their chirality during growth compared to armchair SWCNTs.
Nucleation of Graphene Precursors on Transition Metal Surfaces: Insights from Theoretical Simulations
Publisher: American Chemical Society (ACS)
Date: 05-07-2013
DOI: 10.1021/JP404326D
The Relationship of Trustworthiness and Ethical Value in the Healthcare System
Publisher: The Science and Information Organization
Date: 2020
SWNT Nucleation from Carbon-Coated SiO2 Nanoparticles via a Vapor−Solid−Solid Mechanism
Publisher: American Chemical Society (ACS)
Date: 10-12-2010
DOI: 10.1021/JA109018H
Abstract: Since the discovery of single-walled carbon nanotubes (SWNTs) in the early 1990s, the most commonly accepted model of SWNT growth on traditional catalysts (i.e., transition metals including Fe, Co, Ni, etc.) is the vapor-liquid-solid (VLS) mechanism. In more recent years, the synthesis of SWNTs on nontraditional catalysts, such as SiO(2), has also been reported. The precise atomistic mechanism explaining SWNT growth on nontraditional catalysts, however, remains unknown. In this work, CH(4) chemical vapor deposition (CVD) and single-walled carbon nanotube (SWNT) nucleation on SiO(2) nanoparticles have been investigated using quantum-chemical molecular dynamics (QM/MD) methods. Upon supply of CH(x) species to the surface of a model SiO(2) nanoparticle, CO was produced as the main chemical product of the CH(4) CVD process, in agreement with a recent experimental investigation [Bachmatiuk et al., ACS Nano 2009, 3, 4098]. The production of CO occurred simultaneously with the carbothermal reduction of the SiO(2) nanoparticle. However, this reduction, and the formation of amorphous SiC, was restricted to the nanoparticle surface, with the core of the SiO(2) nanoparticle remaining oxygen-rich. In cases of high carbon concentration, SWNT nucleation then followed, and was driven by the formation of isolated sp(2)-carbon networks via the gradual coalescence of adjacent polyyne chains. These simulations indicate that the carbon saturation of the SiO(2) surface was a necessary prerequisite for SWNT nucleation. These simulations also indicate that a vapor-solid-solid mechanism, rather than a VLS mechanism, is responsible for SWNT nucleation on SiO(2). Fundamental differences between SWNT nucleation on nontraditional and traditional catalysts are therefore observed.
Effects of Molecular Dynamics Thermostats on Descriptions of Chemical Nonequilibrium
Publisher: American Chemical Society (ACS)
Date: 17-10-2012
DOI: 10.1021/CT3004639
Abstract: The performance of popular molecular dynamics (MD) thermostat algorithms in constant temperature simulations of equilibrium systems is well-known. This is not the case, however, in the context of nonequilibrium chemical systems, such as chemical reactions or nanoscale self-assembly processes. In this work, we investigate the effect of popular thermostat algorithms on the "natural" (i.e., Hamiltonian) dynamics of a nonequilibrium, chemically reacting system. By comparing constant-temperature quantum mechanical MD (QM/MD) simulations of carbon vapor condensation using velocity scaling, Berendsen, Andersen, Langevin, and Nosé-Hoover chain thermostat algorithms with natural NVE simulations, we show that efficient temperature control and reliable reaction dynamics are mutually exclusive in such a system. This problem may be circumvented, however, by placing the reactive system in an inert He atmosphere, which is itself described using NVT MD. We demonstrate that both realistic temperature control and dynamics consistent with natural NVE dynamics can then be obtained simultaneously. In essence, the thermal energy created by the natural dynamics of the NVE subsystem is drained by the thermostat acting on the NVT atmosphere, without adversely affecting the dynamics of the reactive system itself.
Stochastic structure determination for conformationally flexible heterogenous molecular clusters: Application to ionic liquids
Publisher: Wiley
Date: 26-08-2013
DOI: 10.1002/JCC.23420
Abstract: We present a novel method that enables accurate and efficient computational determination of conformationally flexible clusters, "Kick(3)" This method uses stochastically generated structures in combination with fast quantum mechanical methods. We demonstrate the power of this method by elucidating the structure of ionic liquid (IL) ([xMIM(+)][NO3(-)])n clusters (x = E, B, D, n = 1-10,15). Dispersion-corrected, third-order self-consistent-charge density-functional tight-binding (DFTB3) is shown to be a computationally efficient, yet reliable approximation to density functional theory for predicting and understanding IL structure and stability. The presented approach, therefore, enables the accurate and efficient screening of ILs with high potential toward practical applications, without recourse to more expensive quantum chemical methods.
Investigating the Accuracy of Water Models through the Van Hove Correlation Function
Publisher: American Chemical Society (ACS)
Date: 13-09-2021
Quantum biological insights into CRISPR-Cas9 sgRNA efficiency from explainable-AI driven feature engineering
Publisher: Cold Spring Harbor Laboratory
Date: 03-06-2022
DOI: 10.1101/2022.06.03.494572
Abstract: CRISPR-Cas9 tools have transformed genetic manipulation capabilities in the laboratory. Empirical rules-of-thumb have been established for only a narrow range of model organisms, and mechanistic underpinnings for sgRNA efficiency remain poorly understood. This work establishes a novel feature set and new public resource, produced with quantum chemical tensors, for interpreting and predicting sgRNA efficiency. Feature engineering for sgRNA efficiency is performed using an explainable-artificial intelligence model iterative Random Forest (iRF). By encoding quantitative attributes of position-specific sequences for E. coli sgRNAs, we identify important traits for sgRNA design in bacterial species. Additionally, we show that expanding positional encoding to quantum descriptors of base-pair, dimer, trimer and tetramer sequences captures intricate interactions in local and neighboring nucleotides of the target DNA. These features highlight variation in CRISPR-Cas9 sgRNA dynamics between E. coli and H. sapien genomes. These novel encodings of sgRNAs greatly enhance our understanding of the elaborate quantum biological processes involved in CRISPR-Cas9 machinery.
Self-Consistent-Charge Density-Functional Tight-Binding/MD Simulation of Transition Metal Catalyst Particle Melting and Carbide Formation
Publisher: American Scientific Publishers
Date: 09-2011
Breast Self-Examination System Using Multifaceted Trustworthiness: Observational Study
Publisher: JMIR Publications Inc.
Date: 23-09-2020
DOI: 10.2196/21584
Abstract: Breast cancer is the leading cause of mortality among women worldwide. However, female patients often feel reluctant and embarrassed about meeting physicians in person to discuss their intimate body parts, and prefer to use social media for such interactions. Indeed, the number of patients and physicians interacting and seeking information related to breast cancer on social media has been growing. However, a physician may behave inappropriately on social media by sharing a patient’s personal medical data excessively with colleagues or the public. Such an act would reduce the physician’s trustworthiness from the patient’s perspective. The multifaceted trust model is currently most commonly used for investigating social media interactions, which facilitates its enhanced adoption in the context of breast self-examination. The characteristics of the multifaceted trust model go beyond being personalized, context-dependent, and transitive. This model is more user-centric, which allows any user to evaluate the interaction process. Thus, in this study, we explored and evaluated use of the multifaceted trust model for breast self-examination as a more suitable trust model for patient-physician social media interactions in breast cancer screening. The objectives of this study were: (1) to identify the trustworthiness indicators that are suitable for a breast self-examination system, (2) design and propose a breast self-examination system, and (3) evaluate the multifaceted trustworthiness interaction between patients and physicians. We used a qualitative study design based on open-ended interviews with 32 participants (16 outpatients and 16 physicians). The interview started with an introduction to the research objective and an explanation of the steps on how to use the proposed breast self-examination system. The breast self-examination system was then evaluated by asking the patient to rate their trustworthiness with the physician after the consultation. The evaluation was also based on monitoring the activity in the chat room (interactions between physicians and patients) during daily meetings, weekly meetings, and the articles posted by the physician in the forum. Based on the interview sessions with 16 physicians and 16 patients on using the breast self-examination system, honesty had a strong positive correlation (r=0.91) with trustworthiness, followed by credibility (r=0.85), confidence (r=0.79), and faith (r=0.79). In addition, belief (r=0.75), competency (r=0.73), and reliability (r=0.73) were strongly correlated with trustworthiness, with the lowest correlation found for reputation (r=0.72). The correlation among trustworthiness indicators was significant (P .001). Moreover, the trust level of a patient for a particular physician was found to increase after several interactions. Multifaceted trustworthiness has a significant impact on a breast self-examination system. Evaluation of trustworthiness indicators helps to ensure a trustworthy system and ethical interaction between a patient and physician. A new patient can obtain a consultation by referring to the best physician according to preference of other patients. Patients can also trust a physician based on another patient’s recommendation regarding the physician’s trust level. The correlation analysis further showed that the most preferred trustworthiness indicator is honesty.
Step-edge self-assembly during graphene nucleation on a nickel surface: QM/MD simulations
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C3NR04694J
Abstract: Quantum chemical molecular dynamics simulations of graphene nucleation on the Ni(111) surface show that graphene creates its own step-edge as it forms. This "step-edge self-assembly" is driven by the formation of thermodynamically favorable Ni-C σ-bonds at the graphene edge. This dynamic aspect of the Ni(111) catalyst is in contrast to the commonly accepted view that graphene nucleates on a pre-existing, static catalyst step-edge. Simulations also show that, simply by manipulating the subsurface carbon density, preferential formation of single-layer graphene instead of multi-layer graphene can be achieved on nickel catalysts.
Milestones in molecular dynamics simulations of single-walled carbon nanotube formation: A brief critical review
Publisher: Springer Science and Business Media LLC
Date: 10-2009
Pre-Sodiated Ti3C2Tx MXene Structure and Behavior as Electrode for Sodium-Ion Capacitors
Publisher: American Chemical Society (ACS)
Date: 29-01-2021
Template Effect in the Competition between Haeckelite and Graphene Growth on Ni(111): Quantum Chemical Molecular Dynamics Simulations
Publisher: American Chemical Society (ACS)
Date: 27-10-2011
DOI: 10.1021/JA2064654
Abstract: Quantum chemical molecular dynamics (QM/MD) simulations of ensembles of C(2) molecules on the Ni(111) terrace show that, in the absence of a hexagonal template or step edge, Haeckelite is preferentially nucleated over graphene as a metastable intermediate. The nucleation process is dominated by the swift transition of long carbon chains toward a fully connected sp(2) carbon network. Starting from a pentagon as nucleus, pentagons and heptagons condense during ring collapse reactions, which results in zero overall curvature. To the contrary, in the presence of a coronene-like C(24) template, hexagonal ring formation is clearly promoted, in agreement with recent suggestions from experiments. In the absence of step edges or molecular templates, graphene nucleation follows Ostwald's "rule of stages" cascade of metastable states, from linear carbon chains, via Haeckelite islands that finally anneal to graphene.
Temperature Dependence of Catalyst-Free Chirality-Controlled Single-Walled Carbon Nanotube Growth from Organic Templates
Publisher: American Chemical Society (ACS)
Date: 09-09-2013
DOI: 10.1021/JZ4015647
Comparison of single-walled carbon nanotube growth from Fe and Ni nanoparticles using quantum chemical molecular dynamics methods
Publisher: Elsevier BV
Date: 09-2010
Breast Self-Examination System Using Multifaceted Trustworthiness: Observational Study (Preprint)
Publisher: JMIR Publications Inc.
Date: 19-06-2020
Abstract: reast cancer is the leading cause of mortality among women worldwide. However, female patients often feel reluctant and embarrassed about meeting physicians in person to discuss their intimate body parts, and prefer to use social media for such interactions. Indeed, the number of patients and physicians interacting and seeking information related to breast cancer on social media has been growing. However, a physician may behave inappropriately on social media by sharing a patient’s personal medical data excessively with colleagues or the public. Such an act would reduce the physician’s trustworthiness from the patient’s perspective. The multifaceted trust model is currently most commonly used for investigating social media interactions, which facilitates its enhanced adoption in the context of breast self-examination. The characteristics of the multifaceted trust model go beyond being personalized, context-dependent, and transitive. This model is more user-centric, which allows any user to evaluate the interaction process. Thus, in this study, we explored and evaluated use of the multifaceted trust model for breast self-examination as a more suitable trust model for patient-physician social media interactions in breast cancer screening. he objectives of this study were: (1) to identify the trustworthiness indicators that are suitable for a breast self-examination system, (2) design and propose a breast self-examination system, and (3) evaluate the multifaceted trustworthiness interaction between patients and physicians. e used a qualitative study design based on open-ended interviews with 32 participants (16 outpatients and 16 physicians). The interview started with an introduction to the research objective and an explanation of the steps on how to use the proposed breast self-examination system. The breast self-examination system was then evaluated by asking the patient to rate their trustworthiness with the physician after the consultation. The evaluation was also based on monitoring the activity in the chat room (interactions between physicians and patients) during daily meetings, weekly meetings, and the articles posted by the physician in the forum. ased on the interview sessions with 16 physicians and 16 patients on using the breast self-examination system, honesty had a strong positive correlation (r=0.91) with trustworthiness, followed by credibility (r=0.85), confidence (r=0.79), and faith (r=0.79). In addition, belief (r=0.75), competency (r=0.73), and reliability (r=0.73) were strongly correlated with trustworthiness, with the lowest correlation found for reputation (r=0.72). The correlation among trustworthiness indicators was significant ( i P /i & .001). Moreover, the trust level of a patient for a particular physician was found to increase after several interactions. ultifaceted trustworthiness has a significant impact on a breast self-examination system. Evaluation of trustworthiness indicators helps to ensure a trustworthy system and ethical interaction between a patient and physician. A new patient can obtain a consultation by referring to the best physician according to preference of other patients. Patients can also trust a physician based on another patient’s recommendation regarding the physician’s trust level. The correlation analysis further showed that the most preferred trustworthiness indicator is honesty.
Nearly Exclusive Growth of Small Diameter Semiconducting Single-Wall Carbon Nanotubes from Organic Chemistry Synthetic End-Cap Molecules
Publisher: American Chemical Society (ACS)
Date: 18-12-2014
DOI: 10.1021/NL504066F
Abstract: The inability to synthesize single-wall carbon nanotubes (SWCNTs) possessing uniform electronic properties and chirality represents the major impediment to their widespread applications. Recently, there is growing interest to explore and synthesize well-defined carbon nanostructures, including fullerenes, short nanotubes, and sidewalls of nanotubes, aiming for controlled synthesis of SWCNTs. One noticeable advantage of such processes is that no metal catalysts are used, and the produced nanotubes will be free of metal contamination. Many of these methods, however, suffer shortcomings of either low yield or poor controllability of nanotube uniformity. Here, we report a brand new approach to achieve high-efficiency metal-free growth of nearly pure SWCNT semiconductors, as supported by extensive spectroscopic characterization, electrical transport measurements, and density functional theory calculations. Our strategy combines bottom-up organic chemistry synthesis with vapor phase epitaxy elongation. We identify a strong correlation between the electronic properties of SWCNTs and their diameters in nanotube growth. This study not only provides material platforms for electronic applications of semiconducting SWCNTs but also contributes to fundamental understanding of the growth mechanism and controlled synthesis of SWCNTs.
How does acetonitrile modulate single-walled carbon nanotube diameter during CVD growth?
Publisher: Elsevier BV
Date: 05-2019
Carbon Coating Precedes SWCNT Nucleation on Silicon Nanoparticles: Insights from QM/MD Simulations
Publisher: American Chemical Society (ACS)
Date: 14-02-2013
DOI: 10.1021/JP3098999
Do SiO2 and carbon-doped SiO2 nanoparticles melt? Insights from QM/MD simulations and ramifications regarding carbon nanotube growth
Publisher: Elsevier BV
Date: 05-2011
Single-walled Carbon Nanotube Growth from Chiral Carbon Nanorings: Prediction of Chirality and Diameter Influence on Growth Rates
Publisher: American Chemical Society (ACS)
Date: 14-09-2012
DOI: 10.1021/JA305769V
Abstract: Catalyst-free, chirality-controlled growth of chiral and zigzag single-walled carbon nanotubes (SWCNTs) from organic precursors is demonstrated using quantum chemical simulations. Growth of (4,3), (6,5), (6,1), (10,1) and (8,0) SWCNTs was induced by ethynyl radical (C(2)H) 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 [Ding, F. Proc. Natl. Acad. Sci. 2009, 106, 2506] indicates that the SWCNT growth rate is an intrinsic property of the SWCNT edge itself. Conversely, we predict that the rate of SWCNT growth via Diels-Alder cycloaddition of C(2)H(2) is strongly influenced by the diameter of the SWCNT. We therefore predict the existence of a maximum growth rate for an optimum diameter/chirality combination at a given C(2)H/C(2)H(2) ratio. We also find that the ability of a SWCNT to avoid defect formation during growth is an intrinsic quality of the SWCNT edge.
Chiral‐selective etching effects on carbon nanotube growth at edge carbon atoms
Publisher: Wiley
Date: 12-12-2019
DOI: 10.1002/JCC.25610
Abstract: Chemical vapor deposition (CVD) utilizing metal cluster nanoparticle catalysts is commonly used to synthesize carbon nanotubes (CNT), with oxygen-containing species such as water or alcohol included in the feedstock for enhanced yield. However, the etching effect of these additives on the growth mechanism has rarely been investigated, despite evidence suggesting that etching potentially affects the chirality distribution of product CNTs. We used quantum chemical methods to study how water-based etchant radicals (OH and H) may enhance the chiral selectivity during CVD growth using CNT cap models. Chemical reactivities of the caps with the etchant radicals were evaluated using density functional theory (DFT). It was found that the reactivities on the cap edges correlate with the chirality of the caps. These results suggest that proper selection of etchant species can provide opportunities for selective chirality control of the product CNTs. © 2018 Wiley Periodicals, Inc.
Optimization of a Genetic Algorithm for the Functionalization of Fullerenes
Publisher: American Chemical Society (ACS)
Date: 24-04-2012
DOI: 10.1021/CT300190U
Abstract: We present the optimization of a genetic algorithm (GA) that is designed to predict the most stable structural isomers of hydrogenated and hydroxylated fullerene cages. Density functional theory (DFT) and density functional tight binding (DFTB) methods are both employed to compute isomer energies. We show that DFTB and DFT levels of theory are in good agreement with each other and that therefore both sets of optimized GA parameters are very similar. As a prototypical fullerene cage, we consider the functionalization of the C20 species, since for this smallest possible fullerene cage it is possible to compute all possible isomer energies for evaluation of the GA performance. An energy decomposition analysis for both C20Hn and C20(OH)n systems reveals that, for only few functional groups, the relative stabilities of different structural isomers may be rationalized simply with recourse to π-Hückel theory. However, upon a greater degree of functionalization, π-electronic effects alone are incapable of describing the interaction between the functional groups and the distorted cage, and both σ- and π-electronic structure must be taken into account in order to understand the relative isomer stabilities.
QM/MD Simulation of SWNT Nucleation on Transition-Metal Carbide Nanoparticles
Publisher: American Chemical Society (ACS)
Date: 20-10-2010
DOI: 10.1021/JA106264Q
Abstract: The mechanism and kinetics of single-walled carbon nanotube (SWNT) nucleation from Fe- and Ni-carbide nanoparticle precursors have been investigated using quantum chemical molecular dynamics (QM/MD) methods. The dependence of the nucleation mechanism and its kinetics on environmental factors, including temperature and metal-carbide carbon concentration, has also been elucidated. It was observed that SWNT nucleation occurred via three distinct stages, viz. the precipitation of the carbon from the metal-carbide, the formation of a "surface/subsurface" carbide intermediate species, and finally the formation of a nascent sp(2)-hybidrized carbon structure supported by the metal catalyst. The SWNT cap nucleation mechanism itself was unaffected by carbon concentration and/or temperature. However, the kinetics of SWNT nucleation exhibited distinct dependences on these same factors. In particular, SWNT nucleation from Ni(x)C(y) nanoparticles proceeded more favorably compared to nucleation from Fe(x)C(y) nanoparticles. Although SWNT nucleation from Fe(x)C(y) and Ni(x)C(y) nanoparticle precursors occurred via an identical route, the ultimate outcomes of these processes also differed substantially. Explicitly, the Ni(x)-supported sp(2)-hybridized carbon structures tended to encapsulate the catalyst particle itself, whereas the Fe(x)-supported structures tended to form isolated SWNT cap structures on the catalyst surface. These differences in SWNT nucleation kinetics were attributed directly to the relative strengths of the metal-carbon interaction, which also dictates the precipitation of carbon from the nanoparticle bulk and the longevity of the resultant surface/subsurface carbide species. The stability of the surface/subsurface carbide was also influenced by the phase of the nanoparticle itself. The observations agree well with experimentally available data for SWNT growth on iron and nickel catalyst particles.
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Discovery Projects - Grant ID: DP140102894
Start Date: 02-2014
End Date: 12-2019
Amount: $330,000.00
Funder: Australian Research Council
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