Antonio Castro Neto
Degree: PhD
Position: Director, Centre for Advanced 2D Materials
Research Type: Theory
Office: S14-06-13
Email: c2dhead@nus.edu.sg
Contact: (65) 6601 2575
CA2DM Publications:
2025 |
Ng, Joseph J Q; Tkachev, Sergey; Sim, Glendon C F; de Lima, Luiza Felippi; Koon, Gavin K W; Lima, Alexandre P; Neto, Antonio Castro H Non-Invasive Hydration Monitoring with a Graphene Dual Sweat Sensor Journal Article APPLIED SCIENCES-BASEL, 15 (9), 2025. @article{ISI:001486021400001, title = {Non-Invasive Hydration Monitoring with a Graphene Dual Sweat Sensor}, author = {Joseph J Q Ng and Sergey Tkachev and Glendon C F Sim and Luiza Felippi de Lima and Gavin K W Koon and Alexandre P Lima and Antonio Castro H Neto}, doi = {10.3390/app15094970}, times_cited = {2}, year = {2025}, date = {2025-04-30}, journal = {APPLIED SCIENCES-BASEL}, volume = {15}, number = {9}, publisher = {MDPI}, address = {MDPI AG, Grosspeteranlage 5, CH-4052 BASEL, SWITZERLAND}, abstract = {Maintaining optimal hydration is critical for physiological function, particularly during intense physical activities, in which dehydration or overhydration can impair performance and recovery. Traditional methods for monitoring hydration status, such as body weight changes, bioelectrical impedance, and urine specific gravity, are limited by inconvenience and lack of real-time capability. This study introduces a novel graphene-based dual-sensing electrochemical sensor for the rapid and non-invasive quantification of sodium and potassium concentrations in human sweat, key biomarkers of hydration status. Leveraging graphene's exceptional conductivity and functionalization potential, the sensor employs open-circuit potentiometry (OCP) to achieve high sensitivity and selectivity in detecting sodium and potassium. The sensor performance was validated against that of a commercial analyzer and ICP-OES, demonstrating a near-Nernstian response (61.93 mV/decade for sodium and 61.21 mV/decade for potassium detection) and a linear detection range spanning from 0.1 mM to 100 mM for both sodium and potassium monitoring in sweat. Sweat samples from an athlete during endurance exercise confirmed the sensor's reliability, with results closely matching those of ICP-OES and outperforming the commercial analyzer in regards to accuracy and sample efficiency. This work represents a cross-validated study of a sweat-based sensor with a second analytical technique, highlighting its potential as a real-time hydration monitoring tool for use in sports and beyond.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Maintaining optimal hydration is critical for physiological function, particularly during intense physical activities, in which dehydration or overhydration can impair performance and recovery. Traditional methods for monitoring hydration status, such as body weight changes, bioelectrical impedance, and urine specific gravity, are limited by inconvenience and lack of real-time capability. This study introduces a novel graphene-based dual-sensing electrochemical sensor for the rapid and non-invasive quantification of sodium and potassium concentrations in human sweat, key biomarkers of hydration status. Leveraging graphene's exceptional conductivity and functionalization potential, the sensor employs open-circuit potentiometry (OCP) to achieve high sensitivity and selectivity in detecting sodium and potassium. The sensor performance was validated against that of a commercial analyzer and ICP-OES, demonstrating a near-Nernstian response (61.93 mV/decade for sodium and 61.21 mV/decade for potassium detection) and a linear detection range spanning from 0.1 mM to 100 mM for both sodium and potassium monitoring in sweat. Sweat samples from an athlete during endurance exercise confirmed the sensor's reliability, with results closely matching those of ICP-OES and outperforming the commercial analyzer in regards to accuracy and sample efficiency. This work represents a cross-validated study of a sweat-based sensor with a second analytical technique, highlighting its potential as a real-time hydration monitoring tool for use in sports and beyond. |
Carrio, Juan A G; Talluri, Vssl Prasad; Toolahalli, Swamy T; Echeverrigaray, Sergio G; Neto, Antonio Castro H Cross-Linked Self-Standing Graphene Oxide Membranes: A Pathway to Scalable Applications in Separation Technologies Journal Article MEMBRANES, 15 (1), 2025. @article{ISI:001404434600001, title = {Cross-Linked Self-Standing Graphene Oxide Membranes: A Pathway to Scalable Applications in Separation Technologies}, author = {Juan A G Carrio and Vssl Prasad Talluri and Swamy T Toolahalli and Sergio G Echeverrigaray and Antonio Castro H Neto}, doi = {10.3390/membranes15010031}, times_cited = {0}, year = {2025}, date = {2025-01-01}, journal = {MEMBRANES}, volume = {15}, number = {1}, publisher = {MDPI}, address = {ST ALBAN-ANLAGE 66, CH-4052 BASEL, SWITZERLAND}, abstract = {The large-scale implementation of 2D material-based membranes is hindered by mechanical stability and mass transport control challenges. This work describes the fabrication, characterisation, and testing of self-standing graphene oxide (GO) membranes cross-linked with oxides such as Fe2O3, Al2O3, CaSO4, Nb2O5, and a carbide, SiC. These cross-linking agents enhance the mechanical stability of the membranes and modulate their mass transport properties. The membranes were prepared by casting aqueous suspensions of GO and SiC or oxide powders onto substrates, followed by drying and detachment to yield self-standing films. This method enabled precise control over membrane thickness and the formation of laminated microstructures with interlayer spacings ranging from 0.8 to 1.2 nm. The resulting self-standing membranes, with areas between 0.002 m2 and 0.090 m2 and thicknesses from 0.6 mu m to 20 mu m, exhibit excellent flexibility and retain their chemical and physical integrity during prolonged testing in direct contact with ethanol/water and methanol/water mixtures in both liquid and vapour phases, with stability demonstrated over 24 h and up to three months. Gas permeation and chemical characterisation tests evidence their suitability for gas separation applications. The interactions promoted by the oxides and carbide with the functional groups of GO confer great stability and unique mass transport properties-the Nb2O5 cross-linked membranes present distinct performance characteristics-creating the potential for scalable advancements in cross-linked 2D material membranes for separation technologies.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The large-scale implementation of 2D material-based membranes is hindered by mechanical stability and mass transport control challenges. This work describes the fabrication, characterisation, and testing of self-standing graphene oxide (GO) membranes cross-linked with oxides such as Fe2O3, Al2O3, CaSO4, Nb2O5, and a carbide, SiC. These cross-linking agents enhance the mechanical stability of the membranes and modulate their mass transport properties. The membranes were prepared by casting aqueous suspensions of GO and SiC or oxide powders onto substrates, followed by drying and detachment to yield self-standing films. This method enabled precise control over membrane thickness and the formation of laminated microstructures with interlayer spacings ranging from 0.8 to 1.2 nm. The resulting self-standing membranes, with areas between 0.002 m2 and 0.090 m2 and thicknesses from 0.6 mu m to 20 mu m, exhibit excellent flexibility and retain their chemical and physical integrity during prolonged testing in direct contact with ethanol/water and methanol/water mixtures in both liquid and vapour phases, with stability demonstrated over 24 h and up to three months. Gas permeation and chemical characterisation tests evidence their suitability for gas separation applications. The interactions promoted by the oxides and carbide with the functional groups of GO confer great stability and unique mass transport properties-the Nb2O5 cross-linked membranes present distinct performance characteristics-creating the potential for scalable advancements in cross-linked 2D material membranes for separation technologies. |
2024 |
Carrio, Juan A G; Echeverrigaray, Sergio G; Talluri, V S S L P; Sudhakaran, Deepa P; Gan, Hui T; Gardeno, Daniel; Friess, Karel; Neto, Antonio Castro H Performance of GO laminated membranes in H2/CO2 separation as a function of the membrane thickness Journal Article INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, 90 , pp. 646-654, 2024, ISSN: 0360-3199. @article{ISI:001332104500001, title = {Performance of GO laminated membranes in H2/CO2 separation as a function of the membrane thickness}, author = {Juan A G Carrio and Sergio G Echeverrigaray and V S S L P Talluri and Deepa P Sudhakaran and Hui T Gan and Daniel Gardeno and Karel Friess and Antonio Castro H Neto}, doi = {10.1016/j.ijhydene.2024.09.435}, times_cited = {6}, issn = {0360-3199}, year = {2024}, date = {2024-10-08}, journal = {INTERNATIONAL JOURNAL OF HYDROGEN ENERGY}, volume = {90}, pages = {646-654}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {Hydrogen gas (H2) is a promising energy carrier capable of replacing fossil fuels and achieving net zero emissions. However, purifying H2 for applications like fuel cells and industrial processes is challenging due to impurities affecting performance. Two-dimensional (2D) materials, particularly graphene-based membranes, are promising for H2 purification due to their unique properties. The hydrogen (H2) permeation capability of graphene-based membranes is particularly significant. This study examines the use of commercial and costeffective graphene oxide (GO) to fabricate multilayer graphene membranes, focusing on the impact of membrane thickness on H2 and CO2 separation. By using a scalable vacuum filtration method to coat porous ceramic substrates, membranes with controlled thicknesses were produced and characterised using AFM, FESEM, XRD, and gas permeation measurements. The study identified an optimal membrane thickness range (4 nm-250 nm) and the GO quantity (0.44 mu g/cm2 to 1.76 mu g/cm2) needed for effective H2/CO2 separation. This research aims to guide the development of cost-effective, mass-produced 2D-based membranes for industrial H2 purification.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Hydrogen gas (H2) is a promising energy carrier capable of replacing fossil fuels and achieving net zero emissions. However, purifying H2 for applications like fuel cells and industrial processes is challenging due to impurities affecting performance. Two-dimensional (2D) materials, particularly graphene-based membranes, are promising for H2 purification due to their unique properties. The hydrogen (H2) permeation capability of graphene-based membranes is particularly significant. This study examines the use of commercial and costeffective graphene oxide (GO) to fabricate multilayer graphene membranes, focusing on the impact of membrane thickness on H2 and CO2 separation. By using a scalable vacuum filtration method to coat porous ceramic substrates, membranes with controlled thicknesses were produced and characterised using AFM, FESEM, XRD, and gas permeation measurements. The study identified an optimal membrane thickness range (4 nm-250 nm) and the GO quantity (0.44 mu g/cm2 to 1.76 mu g/cm2) needed for effective H2/CO2 separation. This research aims to guide the development of cost-effective, mass-produced 2D-based membranes for industrial H2 purification. |
Carvalho, Alexandra; Nair, Vivek; Echeverrigaray, Sergio G; Neto, Antonio Castro H High Capacity NbS_2-Based Anodes for Li-Ion Batteries Journal Article ACS OMEGA, 9 (31), pp. 33912-33918, 2024, ISSN: 2470-1343. @article{ISI:001276227300001, title = {High Capacity NbS_2-Based Anodes for Li-Ion Batteries}, author = {Alexandra Carvalho and Vivek Nair and Sergio G Echeverrigaray and Antonio Castro H Neto}, doi = {10.1021/acsomega.4c04118}, times_cited = {4}, issn = {2470-1343}, year = {2024}, date = {2024-07-24}, journal = {ACS OMEGA}, volume = {9}, number = {31}, pages = {33912-33918}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {We have investigated the lithium capacity of the 2H phase of niobium sulfide (NbS2) using density functional theory calculations and experiments. Theoretically, this material is found to allow the intercalation of a double layer of Li in between each NbS2 layer when in equilibrium with metal Li. The resulting specific capacity (340.8 mAh/g for the pristine material, 681.6 mAh/g for oxidized material) can reach more than double the specific capacity of graphite anodes. The presence of various defects leads to an even higher capacity with a partially reversible conversion of the material, indicating that the performance of the anodes is robust with respect to the presence of defects. Experiments in battery prototypes with NbS2-based anodes find a first specific capacity of about 1,130 mAh/g, exceeding the theoretical predictions.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We have investigated the lithium capacity of the 2H phase of niobium sulfide (NbS2) using density functional theory calculations and experiments. Theoretically, this material is found to allow the intercalation of a double layer of Li in between each NbS2 layer when in equilibrium with metal Li. The resulting specific capacity (340.8 mAh/g for the pristine material, 681.6 mAh/g for oxidized material) can reach more than double the specific capacity of graphite anodes. The presence of various defects leads to an even higher capacity with a partially reversible conversion of the material, indicating that the performance of the anodes is robust with respect to the presence of defects. Experiments in battery prototypes with NbS2-based anodes find a first specific capacity of about 1,130 mAh/g, exceeding the theoretical predictions. |
Tan, Hui Li; Donato, Katarzyna Z; Costa, Mariana C F; Carvalho, Alexandra; Trushin, Maxim; Ng, Pei Rou; Yau, Xin Hui; Koon, Gavin K W; Tolasz, Jakub; Nemeckova, Zuzana; Ecorchard, Petra; Donato, Ricardo K; Neto, Antonio Castro H Fibrillation of Pristine 2D Materials by 2D-Confined Electrolytes Journal Article ADVANCED FUNCTIONAL MATERIALS, 34 (29), 2024, ISSN: 1616-301X. @article{ISI:001186210500001, title = {Fibrillation of Pristine 2D Materials by 2D-Confined Electrolytes}, author = {Hui Li Tan and Katarzyna Z Donato and Mariana C F Costa and Alexandra Carvalho and Maxim Trushin and Pei Rou Ng and Xin Hui Yau and Gavin K W Koon and Jakub Tolasz and Zuzana Nemeckova and Petra Ecorchard and Ricardo K Donato and Antonio Castro H Neto}, doi = {10.1002/adfm.202315038}, times_cited = {1}, issn = {1616-301X}, year = {2024}, date = {2024-03-18}, journal = {ADVANCED FUNCTIONAL MATERIALS}, volume = {34}, number = {29}, publisher = {WILEY-V C H VERLAG GMBH}, address = {POSTFACH 101161, 69451 WEINHEIM, GERMANY}, abstract = {2D materials are solid microscopic flakes with a-few-Angstrom thickness possessing some of the largest surface-to-volume ratios known. Altering their conformation state from a flat flake to a scroll or fiber offers a synergistic association of properties arising from 2D and 1D nanomaterials. However, a combination of the long-range electrostatic and short-range solvation forces produces an interlayer repulsion that has to be overcome, making scrolling 2D materials without disrupting the pristine structure a challenging task. Herein, a facile method is presented to alter the 2D materials' inter-layer interactions by confining organic salts onto their basal area, forming 2D-confined electrolytes. The confined electrolytes produce local charge inhomogeneities, which can conjugate across the interlayer gap, binding the two surfaces. This allows the 2D-confined electrolytes to behave as polyelectrolytes within a higher dimensional order (2D -> 1D) and form robust nanofibers with distinct electronic properties. The method is not material-specific and the resulting fibers are tightly bound even though the crystal structure of the basal plane remains unaltered.}, keywords = {}, pubstate = {published}, tppubtype = {article} } 2D materials are solid microscopic flakes with a-few-Angstrom thickness possessing some of the largest surface-to-volume ratios known. Altering their conformation state from a flat flake to a scroll or fiber offers a synergistic association of properties arising from 2D and 1D nanomaterials. However, a combination of the long-range electrostatic and short-range solvation forces produces an interlayer repulsion that has to be overcome, making scrolling 2D materials without disrupting the pristine structure a challenging task. Herein, a facile method is presented to alter the 2D materials' inter-layer interactions by confining organic salts onto their basal area, forming 2D-confined electrolytes. The confined electrolytes produce local charge inhomogeneities, which can conjugate across the interlayer gap, binding the two surfaces. This allows the 2D-confined electrolytes to behave as polyelectrolytes within a higher dimensional order (2D -> 1D) and form robust nanofibers with distinct electronic properties. The method is not material-specific and the resulting fibers are tightly bound even though the crystal structure of the basal plane remains unaltered. |
2023 |
Yang, Kou; Hu, Zhitao; Li, Xiaolai; Nikolaev, Konstantin; Hong, Gan Kai; Mamchik, Natalia; Erofeev, Ivan; Mirsaidov, Utkur M; Neto, Antonio Castro H; Blackwood, Daniel J; Shchukin, Dmitry G; Trushin, Maxim; Novoselov, Kostya S; Andreeva, Daria V Graphene oxide-polyamine preprogrammable nanoreactors with sensing capability for corrosion protection of materials Journal Article PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 120 (35), 2023, ISSN: 0027-8424. @article{ISI:001112759000007, title = {Graphene oxide-polyamine preprogrammable nanoreactors with sensing capability for corrosion protection of materials}, author = {Kou Yang and Zhitao Hu and Xiaolai Li and Konstantin Nikolaev and Gan Kai Hong and Natalia Mamchik and Ivan Erofeev and Utkur M Mirsaidov and Antonio Castro H Neto and Daniel J Blackwood and Dmitry G Shchukin and Maxim Trushin and Kostya S Novoselov and Daria V Andreeva}, doi = {10.1073/pnas.2307618120}, times_cited = {9}, issn = {0027-8424}, year = {2023}, date = {2023-08-21}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {120}, number = {35}, publisher = {NATL ACAD SCIENCES}, address = {2101 CONSTITUTION AVE NW, WASHINGTON, DC 20418 USA}, abstract = {Corrosion is one of the major issues for sustainable manufacturing globally. The annual global cost of corrosion is US$2.5 trillion (approximately 3.4% of the world's GDP). The traditional ways of corrosion protection (such as barriers or inhibiting) are either not very effective (in the case of barrier protection) or excessively expensive (inhibiting). Here, we demonstrate a concept of nanoreactors, which are able to controllably release or adsorb protons or hydroxides directly on corrosion sites, hence, selectively regulating the corrosion reactions. A single nanoreactor comprises a nano compartment wrapped around by a pH-sensing membrane represented, respectively, by a halloysite nanotube and a graphene oxide/polyamine envelope. A nanoreactor response is determined by the change of a signaling pH on a given corrosion site. The nanoreactors are self-assembled and suitable for mass line production. The concept creates sustainable technology for developing smart anticorrosion coatings, which are nontoxic, selective, and inexpensive.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Corrosion is one of the major issues for sustainable manufacturing globally. The annual global cost of corrosion is US$2.5 trillion (approximately 3.4% of the world's GDP). The traditional ways of corrosion protection (such as barriers or inhibiting) are either not very effective (in the case of barrier protection) or excessively expensive (inhibiting). Here, we demonstrate a concept of nanoreactors, which are able to controllably release or adsorb protons or hydroxides directly on corrosion sites, hence, selectively regulating the corrosion reactions. A single nanoreactor comprises a nano compartment wrapped around by a pH-sensing membrane represented, respectively, by a halloysite nanotube and a graphene oxide/polyamine envelope. A nanoreactor response is determined by the change of a signaling pH on a given corrosion site. The nanoreactors are self-assembled and suitable for mass line production. The concept creates sustainable technology for developing smart anticorrosion coatings, which are nontoxic, selective, and inexpensive. |
Costa, Mariana C F; Ng, Pei Rou; Grebenchuck, Sergey; Tan, Jun You; Koon, Gavin K W; Tan, Hui Li; Woods, Colin R; Donato, Ricardo K; Novoselov, Kostya S; Neto, Antonio Castro H Colossal enhancement of electrical and mechanical properties of graphene nanoscrolls Journal Article CARBON, 208 , pp. 140-147, 2023, ISSN: 0008-6223. @article{ISI:000973042300001, title = {Colossal enhancement of electrical and mechanical properties of graphene nanoscrolls}, author = {Mariana C F Costa and Pei Rou Ng and Sergey Grebenchuck and Jun You Tan and Gavin K W Koon and Hui Li Tan and Colin R Woods and Ricardo K Donato and Kostya S Novoselov and Antonio Castro H Neto}, doi = {10.1016/j.carbon.2023.03.025}, times_cited = {5}, issn = {0008-6223}, year = {2023}, date = {2023-03-29}, journal = {CARBON}, volume = {208}, pages = {140-147}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {One of the most important characteristics of two-dimensional (2D) electrolytes [1] is their ability to reversibly transform into one-dimensional (1D) structures, such as nanoscrolls. However, when formed, these 1D structures are soft and unstable (because of the weak internal chemical bonds) and poorly electrically conducting (since chemical functionalization introduces a large degree of disorder in the 2D material basal plane). Using Peak-ForceTM quantitative nano-mechanics (PF-QNMTM) mode in atomic force microscopy (AFM) and electrical transport measurements, we demonstrate that a one-step, catalyst-free, graphitization of 1D graphene nano-scrolls leads to an enhanced structural stability (an increase of 6 times in the Young's modulus) and a dramatic reduction of structural disorder (observed by a resulting 5 orders of magnitude reduction of the electrical resistance) These large changes in physical properties open up the doors for the use of 1D graphene nanoscrolls in the study of exotic materials in 1D as well as a plethora of possible industrial applications, such as hydrogen and energy storage, akin to carbon nanotubes but with a much bigger flexibility in terms of morphologies and functionalities.}, keywords = {}, pubstate = {published}, tppubtype = {article} } One of the most important characteristics of two-dimensional (2D) electrolytes [1] is their ability to reversibly transform into one-dimensional (1D) structures, such as nanoscrolls. However, when formed, these 1D structures are soft and unstable (because of the weak internal chemical bonds) and poorly electrically conducting (since chemical functionalization introduces a large degree of disorder in the 2D material basal plane). Using Peak-ForceTM quantitative nano-mechanics (PF-QNMTM) mode in atomic force microscopy (AFM) and electrical transport measurements, we demonstrate that a one-step, catalyst-free, graphitization of 1D graphene nano-scrolls leads to an enhanced structural stability (an increase of 6 times in the Young's modulus) and a dramatic reduction of structural disorder (observed by a resulting 5 orders of magnitude reduction of the electrical resistance) These large changes in physical properties open up the doors for the use of 1D graphene nanoscrolls in the study of exotic materials in 1D as well as a plethora of possible industrial applications, such as hydrogen and energy storage, akin to carbon nanotubes but with a much bigger flexibility in terms of morphologies and functionalities. |
2022 |
Carvalho, Alexandra; Negi, Suchit; Neto, Antonio Castro H Direct calculation of the ionic mobility in superionic conductors Journal Article SCIENTIFIC REPORTS, 12 (1), 2022, ISSN: 2045-2322. @article{ISI:000889342600051, title = {Direct calculation of the ionic mobility in superionic conductors}, author = {Alexandra Carvalho and Suchit Negi and Antonio Castro H Neto}, doi = {10.1038/s41598-022-21561-1}, times_cited = {7}, issn = {2045-2322}, year = {2022}, date = {2022-11-19}, journal = {SCIENTIFIC REPORTS}, volume = {12}, number = {1}, publisher = {NATURE PORTFOLIO}, address = {HEIDELBERGER PLATZ 3, BERLIN, 14197, GERMANY}, abstract = {We describe an approach based on non-equilibrium molecular dynamics (NEMD) simulations to calculate the ionic mobility of solid ion conductors such as solid electrolytes from first-principles. The calculations are carried out in finite slabs of the material, where an electric field is applied and the dynamic response of the mobile ions is measured. We compare our results with those obtained from diffusion calculations, under the non- interacting ion approximation, and with experiment. This method is shown to provide good quantitative estimates for the ionic mobilities of two silver conductors, alpha-AgI and alpha-RbAg4I5. In addition to being convenient and numerically robust, this method accounts for ion-ion correlations at a much lower computational cost than exact approaches.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We describe an approach based on non-equilibrium molecular dynamics (NEMD) simulations to calculate the ionic mobility of solid ion conductors such as solid electrolytes from first-principles. The calculations are carried out in finite slabs of the material, where an electric field is applied and the dynamic response of the mobile ions is measured. We compare our results with those obtained from diffusion calculations, under the non- interacting ion approximation, and with experiment. This method is shown to provide good quantitative estimates for the ionic mobilities of two silver conductors, alpha-AgI and alpha-RbAg4I5. In addition to being convenient and numerically robust, this method accounts for ion-ion correlations at a much lower computational cost than exact approaches. |
He, Pan; Koon, Gavin Kok Wai; Isobe, Hiroki; Tan, Jun You; Hu, Junxiong; Neto, Antonio Castro H; Fu, Liang; Yang, Hyunsoo Graphene moire superlattices with giant quantum nonlinearity of chiral Bloch electrons Journal Article 55 NATURE NANOTECHNOLOGY, 17 (4), pp. 378-+, 2022, ISSN: 1748-3387. @article{ISI:000751676800001, title = {Graphene moire superlattices with giant quantum nonlinearity of chiral Bloch electrons}, author = {Pan He and Gavin Kok Wai Koon and Hiroki Isobe and Jun You Tan and Junxiong Hu and Antonio Castro H Neto and Liang Fu and Hyunsoo Yang}, doi = {10.1038/s41565-021-01060-6}, times_cited = {55}, issn = {1748-3387}, year = {2022}, date = {2022-02-03}, journal = {NATURE NANOTECHNOLOGY}, volume = {17}, number = {4}, pages = {378-+}, publisher = {NATURE PORTFOLIO}, address = {HEIDELBERGER PLATZ 3, BERLIN, 14197, GERMANY}, abstract = {Graphene-based samples have shown a plethora of exotic characteristics and these properties may help the realization of a new generation of fast electronic devices. However, graphene's centrosymmetry prohibits second-order electronic transport. Here, we show giant second-order nonlinear transports in graphene moire superlattices at zero magnetic field, both longitudinal and transverse to the applied current direction. High carrier mobility and inversion symmetry breaking by hexagonal boron nitride lead to nonlinear conductivities five orders of magnitude larger than those in WTe2. The nonlinear conductivity strongly depends on the gate voltage as well as on the stacking configuration, with a giant enhancement originating from the moire bands. Longitudinal nonlinear conductivity cannot originate from Berry curvature dipoles. Our theoretical modelling highlights skew scattering of chiral Bloch electrons as the physical origin. With these results, we demonstrate nonlinear charge transport due to valley-contrasting chirality, which constitutes an alternative means to induce second-order transports in van der Waals heterostructures. Our approach is promising for applications in frequency-doubling and energy harvesting via rectification.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Graphene-based samples have shown a plethora of exotic characteristics and these properties may help the realization of a new generation of fast electronic devices. However, graphene's centrosymmetry prohibits second-order electronic transport. Here, we show giant second-order nonlinear transports in graphene moire superlattices at zero magnetic field, both longitudinal and transverse to the applied current direction. High carrier mobility and inversion symmetry breaking by hexagonal boron nitride lead to nonlinear conductivities five orders of magnitude larger than those in WTe2. The nonlinear conductivity strongly depends on the gate voltage as well as on the stacking configuration, with a giant enhancement originating from the moire bands. Longitudinal nonlinear conductivity cannot originate from Berry curvature dipoles. Our theoretical modelling highlights skew scattering of chiral Bloch electrons as the physical origin. With these results, we demonstrate nonlinear charge transport due to valley-contrasting chirality, which constitutes an alternative means to induce second-order transports in van der Waals heterostructures. Our approach is promising for applications in frequency-doubling and energy harvesting via rectification. |
Quek, Glenn; Su, Yude; Donato, Ricardo K; Vazquez, Ricardo J; Marangoni, Valeria S; Ng, Pei Rou; Costa, Mariana C F; Kundukad, Binu; Novoselov, Konstantin S; Neto, Antonio Castro H; Bazan, Guillermo C Pseudocapacitive Conjugated Polyelectrolyte/2D Electrolyte Hydrogels with Enhanced Physico-Electrochemical Properties Journal Article 11 ADVANCED ELECTRONIC MATERIALS, 8 (5), 2022, ISSN: 2199-160X. @article{ISI:000738632900001, title = {Pseudocapacitive Conjugated Polyelectrolyte/2D Electrolyte Hydrogels with Enhanced Physico-Electrochemical Properties}, author = {Glenn Quek and Yude Su and Ricardo K Donato and Ricardo J Vazquez and Valeria S Marangoni and Pei Rou Ng and Mariana C F Costa and Binu Kundukad and Konstantin S Novoselov and Antonio Castro H Neto and Guillermo C Bazan}, doi = {10.1002/aelm.202100942}, times_cited = {11}, issn = {2199-160X}, year = {2022}, date = {2022-01-05}, journal = {ADVANCED ELECTRONIC MATERIALS}, volume = {8}, number = {5}, publisher = {WILEY}, address = {111 RIVER ST, HOBOKEN 07030-5774, NJ USA}, abstract = {Conducting polymer hydrogels (CPHs) are an attractive class of materials that synergize the electrical properties of organic semiconductors with the physical properties of hydrogels. Of particular interest is the implementation of CPHs as electrode materials for electrochemical energy storage by taking advantage of redox-tunable conjugated backbones and the large electroactive surface area. Herein, the use of 2D electrolytes as an effective post-polymerization additive to enhance the pseudocapacitive performance of CPHs, is demonstrated. By using the self-doped conjugated polyelectrolyte CPE-K hydrogel as a model system, improvements in cycling stability, specific capacitance and working voltage window upon addition of the 2D electrolytes, are shown. Furthermore, positively charged 2D electrolytes to be more effective than their negatively charged counterparts are revealed. Rheology measurements and SEM imaging indicate that the 2D electrolytes serve as non-covalent cross-linkers that help in forming a mechanically more robust and highly percolated conducting network. These results provide a new and simple to execute post-polymerization strategy to optimize the electrochemical performance of CPH-based pseudocapacitors.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Conducting polymer hydrogels (CPHs) are an attractive class of materials that synergize the electrical properties of organic semiconductors with the physical properties of hydrogels. Of particular interest is the implementation of CPHs as electrode materials for electrochemical energy storage by taking advantage of redox-tunable conjugated backbones and the large electroactive surface area. Herein, the use of 2D electrolytes as an effective post-polymerization additive to enhance the pseudocapacitive performance of CPHs, is demonstrated. By using the self-doped conjugated polyelectrolyte CPE-K hydrogel as a model system, improvements in cycling stability, specific capacitance and working voltage window upon addition of the 2D electrolytes, are shown. Furthermore, positively charged 2D electrolytes to be more effective than their negatively charged counterparts are revealed. Rheology measurements and SEM imaging indicate that the 2D electrolytes serve as non-covalent cross-linkers that help in forming a mechanically more robust and highly percolated conducting network. These results provide a new and simple to execute post-polymerization strategy to optimize the electrochemical performance of CPH-based pseudocapacitors. |
2021 |
Chen, Zhaolong; Yang, Kou; Xian, Tongfeng; Kocabas, Coskun; Morozov, Sergei; Neto, Antonio Castro H; Novoselov, Kostya S; Andreeva, Daria; Koperski, Maciej Electrically Controlled Thermal Radiation from Reduced Graphene Oxide Membranes Journal Article 15 ACS APPLIED MATERIALS & INTERFACES, 13 (23), pp. 27278-27283, 2021, ISSN: 1944-8244. @article{ISI:000664289800061, title = {Electrically Controlled Thermal Radiation from Reduced Graphene Oxide Membranes}, author = {Zhaolong Chen and Kou Yang and Tongfeng Xian and Coskun Kocabas and Sergei Morozov and Antonio Castro H Neto and Kostya S Novoselov and Daria Andreeva and Maciej Koperski}, doi = {10.1021/acsami.1c04352}, times_cited = {15}, issn = {1944-8244}, year = {2021}, date = {2021-06-04}, journal = {ACS APPLIED MATERIALS & INTERFACES}, volume = {13}, number = {23}, pages = {27278-27283}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {We demonstrate a fabrication procedure of hybrid devices that consist of reduced graphene oxide films supported by porous polymer membranes that host ionic solutions. We find that we can control the thermal radiation from the surface of reduced graphene oxide through a process of electrically driven reversible ionic intercalation. Through a comparative analysis of the structural, chemical, and optical properties of our reduced graphene oxide films, we identify that the dominant mechanism leading to the intercalation-induced reduction of light emission is Pauli blocking of the interband recombination of charge carriers. We inspect the capabilities of our devices to act as a platform for the electrical control of mid-infrared photonics by observing a bias-induced reduction of apparent temperature of hot surfaces visualized through an infrared thermal camera.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We demonstrate a fabrication procedure of hybrid devices that consist of reduced graphene oxide films supported by porous polymer membranes that host ionic solutions. We find that we can control the thermal radiation from the surface of reduced graphene oxide through a process of electrically driven reversible ionic intercalation. Through a comparative analysis of the structural, chemical, and optical properties of our reduced graphene oxide films, we identify that the dominant mechanism leading to the intercalation-induced reduction of light emission is Pauli blocking of the interband recombination of charge carriers. We inspect the capabilities of our devices to act as a platform for the electrical control of mid-infrared photonics by observing a bias-induced reduction of apparent temperature of hot surfaces visualized through an infrared thermal camera. |
Costa, Mariana C F; Marangoni, Valeria S; Trushin, Maxim; Carvalho, Alexandra; Lim, Sharon X; Nguyen, Hang T L; Ng, Pei Rou; Zhao, Xiaoxu; Donato, Ricardo K; Pennycook, Stephen J; Sow, Chorng H; Novoselov, Konstantin S; Neto, Antonio Castro H 2D Electrolytes: Theory, Modeling, Synthesis, and Characterization Journal Article ADVANCED MATERIALS, 33 (25), 2021, ISSN: 0935-9648. @article{ISI:000649261200001, title = {2D Electrolytes: Theory, Modeling, Synthesis, and Characterization}, author = {Mariana C F Costa and Valeria S Marangoni and Maxim Trushin and Alexandra Carvalho and Sharon X Lim and Hang T L Nguyen and Pei Rou Ng and Xiaoxu Zhao and Ricardo K Donato and Stephen J Pennycook and Chorng H Sow and Konstantin S Novoselov and Antonio Castro H Neto}, doi = {10.1002/adma.202100442}, times_cited = {10}, issn = {0935-9648}, year = {2021}, date = {2021-05-12}, journal = {ADVANCED MATERIALS}, volume = {33}, number = {25}, publisher = {WILEY-V C H VERLAG GMBH}, address = {POSTFACH 101161, 69451 WEINHEIM, GERMANY}, abstract = {A class of compounds sharing the properties of 2D materials and electrolytes, namely 2D electrolytes is described theoretically and demonstrated experimentally. 2D electrolytes dissociate in different solvents, such as water, and become electrically charged. The chemical and physical properties of these compounds can be controlled by external factors, such as pH, temperature, electric permittivity of the medium, and ionic concentration. 2D electrolytes, in analogy with polyelectrolytes, present reversible morphological transitions from 2D to 1D, as a function of pH, due to the interplay of the elastic and Coulomb energies. Since these materials show stimuli-responsive behavior to the environmental conditions, 2D electrolytes can be considered as a novel class of smart materials that expand the functionalities of 2D materials and are promising for applications that require stimuli-responsive demeanor, such as drug delivery, artificial muscles, and energy storage.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A class of compounds sharing the properties of 2D materials and electrolytes, namely 2D electrolytes is described theoretically and demonstrated experimentally. 2D electrolytes dissociate in different solvents, such as water, and become electrically charged. The chemical and physical properties of these compounds can be controlled by external factors, such as pH, temperature, electric permittivity of the medium, and ionic concentration. 2D electrolytes, in analogy with polyelectrolytes, present reversible morphological transitions from 2D to 1D, as a function of pH, due to the interplay of the elastic and Coulomb energies. Since these materials show stimuli-responsive behavior to the environmental conditions, 2D electrolytes can be considered as a novel class of smart materials that expand the functionalities of 2D materials and are promising for applications that require stimuli-responsive demeanor, such as drug delivery, artificial muscles, and energy storage. |
Carvalho, Alexandra; Costa, Mariana C F; Marangoni, Valeria S; Ng, Pei Rou; Nguyen, Thi Le Hang; Neto, Antonio Castro H The Degree of Oxidation of Graphene Oxide Journal Article 36 NANOMATERIALS, 11 (3), 2021. @article{ISI:000633934000001, title = {The Degree of Oxidation of Graphene Oxide}, author = {Alexandra Carvalho and Mariana C F Costa and Valeria S Marangoni and Pei Rou Ng and Thi Le Hang Nguyen and Antonio Castro H Neto}, doi = {10.3390/nano11030560}, times_cited = {36}, year = {2021}, date = {2021-03-01}, journal = {NANOMATERIALS}, volume = {11}, number = {3}, publisher = {MDPI}, address = {ST ALBAN-ANLAGE 66, CH-4052 BASEL, SWITZERLAND}, abstract = {We show that the degree of oxidation of graphene oxide (GO) can be obtained by using a combination of state-of-the-art ab initio computational modeling and X-ray photoemission spectroscopy (XPS). We show that the shift of the XPS C1s peak relative to pristine graphene, Delta E-C1s, can be described with high accuracy by Delta E-C1s = A(c(0) - c(l))(2)+E-0, where c(0) is the oxygen concentration}, keywords = {}, pubstate = {published}, tppubtype = {article} } We show that the degree of oxidation of graphene oxide (GO) can be obtained by using a combination of state-of-the-art ab initio computational modeling and X-ray photoemission spectroscopy (XPS). We show that the shift of the XPS C1s peak relative to pristine graphene, Delta E-C1s, can be described with high accuracy by Delta E-C1s = A(c(0) - c(l))(2)+E-0, where c(0) is the oxygen concentration |
2020 |
Andreeva, Daria V; Trushin, Maxim; Nikitina, Anna; Costa, Mariana C F; Cherepanov, Pavel V; Holwill, Matthew; Chen, Siyu; Yang, Kou; Chee, See Wee; Mirsaidov, Utkur; Neto, Antonio Castro H; Novoselov, Kostya S Two-dimensional adaptive membranes with programmable water and ionic channels Journal Article 103 NATURE NANOTECHNOLOGY, 16 (2), pp. 174-+, 2020, ISSN: 1748-3387. @article{ISI:000587967600004, title = {Two-dimensional adaptive membranes with programmable water and ionic channels}, author = {Daria V Andreeva and Maxim Trushin and Anna Nikitina and Mariana C F Costa and Pavel V Cherepanov and Matthew Holwill and Siyu Chen and Kou Yang and See Wee Chee and Utkur Mirsaidov and Antonio Castro H Neto and Kostya S Novoselov}, doi = {10.1038/s41565-020-00795-y}, times_cited = {103}, issn = {1748-3387}, year = {2020}, date = {2020-11-09}, journal = {NATURE NANOTECHNOLOGY}, volume = {16}, number = {2}, pages = {174-+}, publisher = {NATURE PORTFOLIO}, address = {HEIDELBERGER PLATZ 3, BERLIN, 14197, GERMANY}, abstract = {Membranes are ubiquitous in nature with primary functions that include adaptive filtering and selective transport of chemical/molecular species. Being critical to cellular functions, they are also fundamental in many areas of science and technology. Of particular importance are the adaptive and programmable membranes that can change their permeability or selectivity depending on the environment. Here, we explore implementation of such biological functions in artificial membranes and demonstrate two-dimensional self-assembled heterostructures of graphene oxide and polyamine macromolecules, forming a network of ionic channels that exhibit regulated permeability of water and monovalent ions. This permeability can be tuned by a change of pH or the presence of certain ions. Unlike traditional membranes, the regulation mechanism reported here relies on specific interactions between the membranes' internal components and ions. This allows fabrication of membranes with programmable, predetermined permeability and selectivity, governed by the choice of components, their conformation and their charging state.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Membranes are ubiquitous in nature with primary functions that include adaptive filtering and selective transport of chemical/molecular species. Being critical to cellular functions, they are also fundamental in many areas of science and technology. Of particular importance are the adaptive and programmable membranes that can change their permeability or selectivity depending on the environment. Here, we explore implementation of such biological functions in artificial membranes and demonstrate two-dimensional self-assembled heterostructures of graphene oxide and polyamine macromolecules, forming a network of ionic channels that exhibit regulated permeability of water and monovalent ions. This permeability can be tuned by a change of pH or the presence of certain ions. Unlike traditional membranes, the regulation mechanism reported here relies on specific interactions between the membranes' internal components and ions. This allows fabrication of membranes with programmable, predetermined permeability and selectivity, governed by the choice of components, their conformation and their charging state. |
2019 |
Trushin, Maxim; Neto, Antonio Castro H; Vignale, Giovanni; Culcer, Dimitrie Hidden anisotropy in the Drude conductivity of charge carriers with Dirac-Schrodinger dynamics Journal Article PHYSICAL REVIEW B, 100 (3), 2019, ISSN: 2469-9950. @article{ISI:000476681800007, title = {Hidden anisotropy in the Drude conductivity of charge carriers with Dirac-Schrodinger dynamics}, author = {Maxim Trushin and Antonio Castro H Neto and Giovanni Vignale and Dimitrie Culcer}, doi = {10.1103/PhysRevB.100.035427}, times_cited = {3}, issn = {2469-9950}, year = {2019}, date = {2019-07-22}, journal = {PHYSICAL REVIEW B}, volume = {100}, number = {3}, publisher = {AMER PHYSICAL SOC}, address = {ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA}, abstract = {We show that the conductivity of a two-dimensional electron gas can be intrinsically anisotropic despite isotropic Fermi surface, energy dispersion, and disorder configuration. In the model we study, the anisotropy stems from the interplay between Dirac and Schrodinger features combined in a special two-band Hamiltonian describing the quasiparticles similar to the low-energy excitations in phosphorene. As a result, even scalar isotropic disorder scattering alters the nature of the carriers and results in anisotropic transport. Solving the Boltzmann equation exactly for such carriers with pointlike random impurities, we find a hidden knob to control the anisotropy just by tuning either the Fermi energy or temperature. Our results are expected to be generally applicable beyond the model studied here, and should stimulate further search for the alternative ways to control electron transport in advanced materials.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We show that the conductivity of a two-dimensional electron gas can be intrinsically anisotropic despite isotropic Fermi surface, energy dispersion, and disorder configuration. In the model we study, the anisotropy stems from the interplay between Dirac and Schrodinger features combined in a special two-band Hamiltonian describing the quasiparticles similar to the low-energy excitations in phosphorene. As a result, even scalar isotropic disorder scattering alters the nature of the carriers and results in anisotropic transport. Solving the Boltzmann equation exactly for such carriers with pointlike random impurities, we find a hidden knob to control the anisotropy just by tuning either the Fermi energy or temperature. Our results are expected to be generally applicable beyond the model studied here, and should stimulate further search for the alternative ways to control electron transport in advanced materials. |