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Dominique NL, Chandran A, Jensen IM, Jenkins DM, Camden JP. Unmasking the Electrochemical Stability of N-Heterocyclic Carbene Monolayers on Gold. Chemistry 2023:e202303681. [PMID: 38116819 DOI: 10.1002/chem.202303681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Accepted: 12/16/2023] [Indexed: 12/21/2023]
Abstract
N-heterocyclic carbene (NHC) monolayers are transforming electrocatalysis and biosensor design via their increased performance and stability. Despite their increasing use in electrochemical systems, the integrity of the NHC monolayer during voltage perturbations remains largely unknown. Herein, we deploy surface-enhanced Raman spectroscopy (SERS) to measure the stability of two model NHCs on gold in ambient conditions as a function of applied potential and under continuous voltammetric interrogation. Our results illustrate that NHC monolayers exhibit electrochemical stability over a wide voltage window (-1 V to 0.5 V vs Ag|AgCl), but they are found to degrade at strongly reducing (< -1 V) or oxidizing (>0.5 V) potentials. We also address NHC monolayer stability under continuous voltammetric interrogation between 0.2 V and -0.5 V, a commonly used voltage window for sensing, showing they are stable for up to 43 hours. However, we additionally find that modifications of the backbone NHC structure can lead to significantly shorter operational lifetimes. While these results highlight the potential of NHC architectures for electrode functionalization, they also reveal potential pitfalls that have not been fully appreciated in electrochemical applications of NHCs.
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Affiliation(s)
- Nathaniel L Dominique
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN-46556, United States
| | - Aruna Chandran
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN-46556, United States
| | - Isabel M Jensen
- Department of Chemistry, University of Tennessee, Knoxville, Knoxville, TN-37996
| | - David M Jenkins
- Department of Chemistry, University of Tennessee, Knoxville, Knoxville, TN-37996
| | - Jon P Camden
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN-46556, United States
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Das M, Hogan C, Zielinski R, Kubicki M, Koy M, Kosbab C, Brozzesi S, Das A, Nehring MT, Balfanz V, Brühne J, Dähne M, Franz M, Esser N, Glorius F. N-Heterocyclic Olefins on a Silicon Surface. Angew Chem Int Ed Engl 2023; 62:e202314663. [PMID: 37849449 DOI: 10.1002/anie.202314663] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Revised: 10/13/2023] [Accepted: 10/17/2023] [Indexed: 10/19/2023]
Abstract
The adsorption of N-heterocyclic olefins (NHOs) on silicon is investigated in a combined scanning tunneling microscopy, X-ray photoelectron spectroscopy, and density functional theory study. We find that both of the studied NHOs bind covalently, with ylidic character, to the silicon adatoms of the substrate and exhibit good thermal stability. The adsorption geometry strongly depends on the N-substituents: for large N-substituents, an upright adsorption geometry is favored, while a flat-lying geometry is found for the NHO with smaller wingtips. These different geometries strongly influence the quality and properties of the obtained monolayers. The upright geometry leads to the formation of ordered monolayers, whereas the flat-lying NHOs yield a mostly disordered, but denser, monolayer. The obtained monolayers both show large work function reductions, as the higher density of the flat-lying monolayer is found to compensate for the smaller vertical dipole moments. Our findings offer new prospects in the design of tailor-made ligand structures in organic electronics and optoelectronics, catalysis, and material science.
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Affiliation(s)
- Mowpriya Das
- Westfälische Wilhelms-Universität Münster, Organisch-Chemisches Institut, Corrensstrasse 40, 48149, Münster, Germany
| | - Conor Hogan
- Istituto di Struttura della Materia-CNR (ISM-CNR), Via del Fosso del Cavaliere 100, 00133, Rome, Italy
- Dipartimento di Fisica, Università di Roma 'Tor Vergata', Via della Ricerca Scientifica 1, 00133, Rome, Italy
| | - Robert Zielinski
- Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstrasse 36, D-10623, Berlin, Germany
| | - Milan Kubicki
- Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstrasse 36, D-10623, Berlin, Germany
| | - Maximilian Koy
- Westfälische Wilhelms-Universität Münster, Organisch-Chemisches Institut, Corrensstrasse 40, 48149, Münster, Germany
| | - Canan Kosbab
- Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstrasse 36, D-10623, Berlin, Germany
| | - Simone Brozzesi
- Dipartimento di Fisica, Università di Roma 'Tor Vergata', Via della Ricerca Scientifica 1, 00133, Rome, Italy
| | - Ankita Das
- Westfälische Wilhelms-Universität Münster, Organisch-Chemisches Institut, Corrensstrasse 40, 48149, Münster, Germany
| | - Mike Thomas Nehring
- Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstrasse 36, D-10623, Berlin, Germany
| | - Viktoria Balfanz
- Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstrasse 36, D-10623, Berlin, Germany
| | - Juls Brühne
- Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstrasse 36, D-10623, Berlin, Germany
| | - Mario Dähne
- Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstrasse 36, D-10623, Berlin, Germany
| | - Martin Franz
- Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstrasse 36, D-10623, Berlin, Germany
| | - Norbert Esser
- Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstrasse 36, D-10623, Berlin, Germany
- Leibniz-Institut für Analytische Wissenschaften - ISAS e.V., Schwarzschildstrasse 8, 12489, Berlin, Germany
| | - Frank Glorius
- Westfälische Wilhelms-Universität Münster, Organisch-Chemisches Institut, Corrensstrasse 40, 48149, Münster, Germany
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Jensen IM, Chowdhury S, Hu G, Jensen L, Camden JP, Jenkins DM. Seeking a Au-C stretch on gold nanoparticles with 13C-labeled N-heterocyclic carbenes. Chem Commun (Camb) 2023; 59:14524-14527. [PMID: 37966800 DOI: 10.1039/d3cc04973f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2023]
Abstract
Gold nanoparticles were functionalized with natural abundance and 13C-labeled N-heterocyclic carbenes (NHCs) to investigate the Au-C stretch. A combinatorial approach of surface enhanced Raman spectroscopy (SERS) and density-functional theory (DFT) calculations highlighted vibrational modes significantly impacted by isotopic labeling at the carbene carbon. Critically, no isotopically-impacted stretching mode showed majority Au-C character.
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Affiliation(s)
- Isabel M Jensen
- Department of Chemistry, The University of Tennessee, Knoxville, Tennessee 37996, USA.
| | - Shayanta Chowdhury
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA
| | - Gaohe Hu
- Department of Chemistry, The Pennsylvania State University, 104 Chemistry Building, University Park, Pennsylvania 16802, USA
| | - Lasse Jensen
- Department of Chemistry, The Pennsylvania State University, 104 Chemistry Building, University Park, Pennsylvania 16802, USA
| | - Jon P Camden
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA
| | - David M Jenkins
- Department of Chemistry, The University of Tennessee, Knoxville, Tennessee 37996, USA.
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Chevalier RB, Pantano J, Kiesewetter MK, Dwyer JR. N-Heterocyclic carbene-based gold etchants. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2023; 14:865-871. [PMID: 37674545 PMCID: PMC10477970 DOI: 10.3762/bjnano.14.71] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Accepted: 08/07/2023] [Indexed: 09/08/2023]
Abstract
N-Heterocyclic carbenes (NHCs) are an emerging alternative to thiols for the formation of stable self-assembled monolayers (SAMs) on gold. We examined several different species that have been used to produce NHC-based monolayers on gold, namely 1,3-diisopropyl-5-nitrobenzimidazolium iodide, 1,3-diisopropyl-5-nitrobenzimidazolium hydrogen carbonate, bis(1,3-diisopropyl-5-nitrobenzimidazolium)gold(I) iodide, and 1,3-diisopropyl-5-nitrobenzimidazole-2-ylidene. Contrary to expectation, solutions containing the first two species in tetrahydrofuran and dichloromethane caused visible loss of gold from thin-film-coated glass slides. The use of toluene solutions of all species resulted in no apparent dissolution of gold. We present scanning electron micrographs and elemental imaging analyses by energy dispersive X-ray spectroscopy to examine the effect of solutions of each species on the gold film. This work highlights the risk of unwanted etching during some routes to NHC-based surface functionalization but also the potential for deliberate etching, with the outcome determined by choice of chemically synthesized organic species and solvent.
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Affiliation(s)
- Robert B Chevalier
- Department of Chemistry, University of Rhode Island, 140 Flagg Road, Kingston, RI, 02881, USA
| | - Justin Pantano
- Department of Chemistry, University of Rhode Island, 140 Flagg Road, Kingston, RI, 02881, USA
| | - Matthew K Kiesewetter
- Department of Chemistry, University of Rhode Island, 140 Flagg Road, Kingston, RI, 02881, USA
| | - Jason R Dwyer
- Department of Chemistry, University of Rhode Island, 140 Flagg Road, Kingston, RI, 02881, USA
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Pellitero MA, Jensen IM, Dominique NL, Ekowo LC, Camden JP, Jenkins DM, Arroyo-Currás N. Stability of N-Heterocyclic Carbene Monolayers under Continuous Voltammetric Interrogation. ACS APPLIED MATERIALS & INTERFACES 2023. [PMID: 37449918 PMCID: PMC10377464 DOI: 10.1021/acsami.3c06148] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/18/2023]
Abstract
N-Heterocyclic carbenes (NHCs) are promising monolayer-forming ligands that can overcome limitations of thiol-based monolayers in terms of stability, surface functionality, and reactivity across a variety of transition-metal surfaces. Recent publications have reported the ability of NHCs to support biomolecular receptors on gold substrates for sensing applications and improved tolerance to prolonged biofluid exposure relative to thiols. However, important questions remain regarding the stability of these monolayers when subjected to voltage perturbations, which is needed for applications with electrochemical platforms. Here, we investigate the ability of two NHCs, 1,3-diisopropylbenzimidazole and 5-(ethoxycarbonyl)-1,3-diisopropylbenzimidazole, to form monolayers via self-assembly from methanolic solutions of their trifluoromethanesulfonate salts. We compare the electrochemical behavior of the resulting monolayers relative to that of benchmark mercaptohexanol monolayers in phosphate-buffered saline. Within the -0.15 to 0.25 V vs Ag|AgCl voltage window, NHC monolayers are stable on gold surfaces, wherein they electrochemically perform like thiol-based monolayers and undergo similar reorganization kinetics, displaying long-term stability under incubation in buffered media and under continuous voltammetric interrogation. At negative voltages, NHC monolayers cathodically desorb from the electrode surface at lower bias (-0.1 V) than thiol-based monolayers (-0.5 V). At voltages more positive than 0.25 V, NHC monolayers anodically desorb from electrode surfaces at similar voltages to thiol-based monolayers. These results highlight new limitations to NHC monolayer stability imposed by electrochemical interrogation of the underlying gold electrodes. Our results serve as a framework for future optimization of NHC monolayers on gold for electrochemical applications, as well as structure-functionality studies of NHCs on gold.
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Affiliation(s)
- Miguel Aller Pellitero
- Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, United States
| | - Isabel M Jensen
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Nathaniel L Dominique
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Lilian Chinenye Ekowo
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Jon P Camden
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - David M Jenkins
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Netzahualcóyotl Arroyo-Currás
- Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, United States
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