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Shtepliuk I. A DFT Study of Phosphate Ion Adsorption on Graphene Nanodots: Implications for Sensing. SENSORS (BASEL, SWITZERLAND) 2023; 23:5631. [PMID: 37420797 DOI: 10.3390/s23125631] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2023] [Revised: 06/12/2023] [Accepted: 06/14/2023] [Indexed: 07/09/2023]
Abstract
The optical properties of graphene nanodots (GND) and their interaction with phosphate ions have been investigated to explore their potential for optical sensing applications. The absorption spectra of pristine GND and modified GND systems were analyzed using time-dependent density functional theory (TD-DFT) calculation investigations. The results revealed that the size of adsorbed phosphate ions on GND surfaces correlated with the energy gap of the GND systems, leading to significant modifications in their absorption spectra. The introduction of vacancies and metal dopants in GND systems resulted in variations in the absorption bands and shifts in their wavelengths. Moreover, the absorption spectra of GND systems were further altered upon the adsorption of phosphate ions. These findings provide valuable insights into the optical behavior of GND and highlight their potential for the development of sensitive and selective optical sensors for phosphate detection.
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Affiliation(s)
- Ivan Shtepliuk
- Semiconductor Materials Division, Department of Physics, Chemistry and Biology-IFM, Linköping University, S-58183 Linköping, Sweden
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Hajzus JR, Shriver-Lake LC, Dean SN, Erickson JS, Zabetakis D, Golden J, Pennachio DJ, Myers-Ward RL, Trammell SA. Modifications of Epitaxial Graphene on SiC for the Electrochemical Detection and Identification of Heavy Metal Salts in Seawater. SENSORS (BASEL, SWITZERLAND) 2022; 22:5367. [PMID: 35891050 PMCID: PMC9315748 DOI: 10.3390/s22145367] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Revised: 07/14/2022] [Accepted: 07/15/2022] [Indexed: 06/15/2023]
Abstract
The electrochemical detection of heavy metal ions is reported using an inexpensive portable in-house built potentiostat and epitaxial graphene. Monolayer, hydrogen-intercalated quasi-freestanding bilayer, and multilayer epitaxial graphene were each tested as working electrodes before and after modification with an oxygen plasma etch to introduce oxygen chemical groups to the surface. The graphene samples were characterized using X-ray photoelectron spectroscopy, atomic force microscopy, Raman spectroscopy, and van der Pauw Hall measurements. Dose-response curves in seawater were evaluated with added trace levels of four heavy metal salts (CdCl2, CuSO4, HgCl2, and PbCl2), along with detection algorithms based on machine learning and library development for each form of graphene and its oxygen plasma modification. Oxygen plasma-modified, hydrogen-intercalated quasi-freestanding bilayer epitaxial graphene was found to perform best for correctly identifying heavy metals in seawater.
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Affiliation(s)
- Jenifer R. Hajzus
- American Society for Engineering Education, U.S. Naval Research Laboratory, Washington, DC 20375, USA;
| | - Lisa C. Shriver-Lake
- U.S. Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, USA; (L.C.S.-L.); (S.N.D.); (J.S.E.); (D.Z.); (J.G.); (R.L.M.-W.)
| | - Scott N. Dean
- U.S. Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, USA; (L.C.S.-L.); (S.N.D.); (J.S.E.); (D.Z.); (J.G.); (R.L.M.-W.)
| | - Jeffrey S. Erickson
- U.S. Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, USA; (L.C.S.-L.); (S.N.D.); (J.S.E.); (D.Z.); (J.G.); (R.L.M.-W.)
| | - Daniel Zabetakis
- U.S. Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, USA; (L.C.S.-L.); (S.N.D.); (J.S.E.); (D.Z.); (J.G.); (R.L.M.-W.)
| | - Joel Golden
- U.S. Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, USA; (L.C.S.-L.); (S.N.D.); (J.S.E.); (D.Z.); (J.G.); (R.L.M.-W.)
| | - Daniel J. Pennachio
- National Research Council, U.S. Naval Research Laboratory, Washington, DC 20375, USA;
| | - Rachael L. Myers-Ward
- U.S. Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, USA; (L.C.S.-L.); (S.N.D.); (J.S.E.); (D.Z.); (J.G.); (R.L.M.-W.)
| | - Scott A. Trammell
- U.S. Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, USA; (L.C.S.-L.); (S.N.D.); (J.S.E.); (D.Z.); (J.G.); (R.L.M.-W.)
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Epitaxial Graphene on 4H-SiC (0001) as a Versatile Platform for Materials Growth: Mini-Review. APPLIED SCIENCES-BASEL 2021. [DOI: 10.3390/app11135784] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Material growth on a dangling-bond-free interface such as graphene is a challenging technological task, which usually requires additional surface pre-treatment steps (functionalization, seed layer formation) to provide enough reactive sites. Being one of the most promising and adaptable graphene-family materials, epitaxial graphene on SiC, due to its internal features (substrate-induced n-doping, compressive strain, terrace-stepped morphology, bilayer graphene nano-inclusions), may provide pre-conditions for the enhanced binding affinity of environmental species, precursor molecules, and metal atoms on the topmost graphene layer. It makes it possible to use untreated pristine epitaxial graphene as a versatile platform for the deposition of metals and insulators. This mini-review encompasses relevant aspects of magnetron sputtering and electrodeposition of selected metals (Au, Ag, Pb, Hg, Cu, Li) and atomic layer deposition of insulating Al2O3 layers on epitaxial graphene on 4H-SiC, focusing on understanding growth mechanisms. Special deliberation has been given to the effect of the deposited materials on the epitaxial graphene quality. The generalization of the experimental and theoretical results presented here is hopefully an important step towards new electronic devices (chemiresistors, Schottky diodes, field-effect transistors) for environmental sensing, nano-plasmonics, and biomedical applications.
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Abstract
Understanding the mechanism of metal electrodeposition on graphene as the simplest building block of all graphitic materials is important for electrocatalysis and the creation of metal contacts in electronics. The present work investigates copper electrodeposition onto epitaxial graphene on 4H-SiC by experimental and computational techniques. The two subsequent single-electron transfer steps were coherently quantified by electrochemistry and density functional theory (DFT). The kinetic measurements revealed the instantaneous nucleation mechanism of copper (Cu) electrodeposition, controlled by the convergent diffusion of reactant to the limited number of nucleation sites. Cu can freely migrate across the electrode surface. These findings provide fundamental insights into the nature of copper reduction and nucleation mechanisms and can be used as a starting point for performing more sophisticated investigations and developing real applications.
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Shtepliuk I, Yakimova R. Interaction of epitaxial graphene with heavy metals: towards novel sensing platform. NANOTECHNOLOGY 2019; 30:294002. [PMID: 30939456 DOI: 10.1088/1361-6528/ab1546] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Development of next-generation sensors based on graphene materials, especially epitaxial graphene (EG) as the most promising representative, with desirable cross-reactivity to heavy metals (HMs) is of great technological significance in the virtue of enormous impact on environmental sensorics. Nevertheless, the mechanisms by which EG responds to toxic HMs exposure and then produces the output signal are still obscure. In the present study, the nature of interaction of toxic HMs, e.g. Cd, Hg and Pb in neutral charge state and EG on Si-face SiC in the absence and in the presence of pure water solution has been investigated using density functional theory with the inclusion of dispersion correction and cluster model of EG. The gas-phase calculations showed that adsorbed electron-donating Cd and Hg adatoms on EG are most stable when bonded to hollow sites, while Pb species prefer to sit above bridge sites. By using non-covalent interaction analysis, charge decomposition analysis, overlap population density of states analysis and topological analysis, it was found that the interaction between Cd or Hg and EG is non-bonding in nature and is mainly governed by van der Waals forces, while Pb adsorption is followed by the formation of anti-bonding orbitals in vacuum conditions and bonding orbitals in water. The role of solvent in the adsorption behavior of HMs is studied and discussed. The present theoretical analysis is in good agreement with recent experimental results towards discriminative electrochemical analysis of the toxic HMs in aqueous solutions at critically low concentrations.
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Giannazzo F, Shtepliuk I, Ivanov IG, Iakimov T, Kakanakova-Georgieva A, Schilirò E, Fiorenza P, Yakimova R. Probing the uniformity of hydrogen intercalation in quasi-free-standing epitaxial graphene on SiC by micro-Raman mapping and conductive atomic force microscopy. NANOTECHNOLOGY 2019; 30:284003. [PMID: 30913546 DOI: 10.1088/1361-6528/ab134e] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
In this paper, micro-Raman mapping and conductive atomic force microscopy (C-AFM) were jointly applied to investigate the structural and electrical homogeneity of quasi-free-standing monolayer graphene (QFMLG), obtained by high temperature decomposition of 4H-SiC(0001) followed by hydrogen intercalation at 900 °C. Strain and doping maps, obtained by Raman data, showed the presence of sub-micron patches with reduced hole density correlated to regions with higher compressive strain, probably associated with a locally reduced hydrogen intercalation. Nanoscale resolution electrical maps by C-AFM also revealed the presence of patches with enhanced current injection through the QFMLG/SiC interface, indicating a locally reduced Schottky barrier height (ΦB). The ΦB values evaluated from local I-V curves by the thermionic emission model were in good agreement with the values calculated for the QFMLG/SiC interface using the Schottky-Mott rule and the graphene holes density from Raman maps. The demonstrated approach revealed a useful and non-invasive method to probe the structural and electrical homogeneity of QFMLG for future nano-electronics applications.
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Affiliation(s)
- F Giannazzo
- Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi, Strada VIII, n. 5, Zona Industriale, I-95121, Catania, Italy
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Santangelo MF, Shtepliuk I, Filippini D, Puglisi D, Vagin M, Yakimova R, Eriksson J. Epitaxial Graphene Sensors Combined with 3D-Printed Microfluidic Chip for Heavy Metals Detection. SENSORS 2019; 19:s19102393. [PMID: 31130608 PMCID: PMC6567039 DOI: 10.3390/s19102393] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 05/13/2019] [Accepted: 05/22/2019] [Indexed: 01/17/2023]
Abstract
In this work, we investigated the sensing performance of epitaxial graphene on Si-face 4H-SiC (EG/SiC) for liquid-phase detection of heavy metals (e.g., Pb and Cd), showing fast and stable response and low detection limit. The sensing platform proposed includes 3D-printed microfluidic devices, which incorporate all features required to connect and execute lab-on-chip (LOC) functions. The obtained results indicate that EG exhibits excellent sensing activity towards Pb and Cd ions. Several concentrations of Pb2+ solutions, ranging from 125 nM to 500 µM, were analyzed showing Langmuir correlation between signal and Pb2+ concentrations, good stability, and reproducibility over time. Upon the simultaneous presence of both metals, sensor response is dominated by Pb2+ rather than Cd2+ ions. To explain the sensing mechanisms and difference in adsorption behavior of Pb2+ and Cd2+ ions on EG in water-based solutions, we performed van-der-Waals (vdW)-corrected density functional theory (DFT) calculations and non-covalent interaction (NCI) analysis, extended charge decomposition analysis (ECDA), and topological analysis. We demonstrated that Pb2+ and Cd2+ ions act as electron-acceptors, enhancing hole conductivity of EG, due to charge transfer from graphene to metal ions, and Pb2+ ions have preferential ability to binding with graphene over cadmium. Electrochemical measurements confirmed the conductometric results, which additionally indicate that EG is more sensitive to lead than to cadmium.
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Affiliation(s)
- Maria Francesca Santangelo
- Applied Sensors Science, Department of Physics, Chemistry, and Biology-IFM, Linköping University, S-58183 Linköping, Sweden.
| | - Ivan Shtepliuk
- Semiconductor Materials, Department of Physics, Chemistry, and Biology-IFM, Linköping University, S-58183 Linköping, Sweden.
| | - Daniel Filippini
- Optical Devices Laboratory, Department of Physics, Chemistry, and Biology-IFM, Linköping University, S-58183 Linköping, Sweden.
| | - Donatella Puglisi
- Applied Sensors Science, Department of Physics, Chemistry, and Biology-IFM, Linköping University, S-58183 Linköping, Sweden.
| | - Mikhail Vagin
- Division of Physics and Electronics, Department of Science and Technology, Physics and Electronics-ITN, Linköping University, SE-58183 Linköping, Sweden.
| | - Rositsa Yakimova
- Semiconductor Materials, Department of Physics, Chemistry, and Biology-IFM, Linköping University, S-58183 Linköping, Sweden.
| | - Jens Eriksson
- Applied Sensors Science, Department of Physics, Chemistry, and Biology-IFM, Linköping University, S-58183 Linköping, Sweden.
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