Diazonium Compounds in Molecular Electronics

McCreery, Richard L.; Bergren, Adam Johan

doi:10.1002/9783527650446.ch10

Cited by 9 publications

(7 citation statements)

References 98 publications

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“…1 , for the case of an azobenzene (AB) molecule covalently bonded to an edge site in a 9-ring graphene fragment, denoted “G9”. We described the rationale for investigating edge-bonding previously [ 2 , 34 , 42 – 43 ], and it is the most likely site in real devices. Since the carbon surface is disordered and the molecular layers are often multilayers, the real system will have a range of dihedral angles between the molecular aromatic rings and those of the graphene.…”

Section: Methodsmentioning

confidence: 99%

Effects of electronic coupling and electrostatic potential on charge transport in carbon-based molecular electronic junctions

McCreery¹

2016

Beilstein J. Nanotechnol.

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SummaryMolecular junctions consisting of 2–20 nm thick layers of organic oligomers oriented between a conducting carbon substrate and a carbon/gold top contact have proven to be reproducible and reliable, and will soon enter commercial production in audio processing circuits. The covalent, conjugated bond between one or both sp2-hybridized carbon contacts and an aromatic molecular layer is distinct from the more common metal/molecule or silicon/molecule structures in many reported molecular junctions. Theoretical observations based on density functional theory are presented here, which model carbon-based molecular junctions as single molecules and oligomers between fragments of graphene. Electronic coupling between the molecules and the contacts is demonstrated by the formation of hybrid orbitals in the model structure, which have significant electron density on both the graphene and the molecule. The energies of such hybrid orbitals correlate with tunneling barriers determined experimentally, and electronic coupling between the two graphene fragments in the model correlates with experimentally observed attenuation of transport with molecular layer thickness. Electronic coupling is affected significantly by the dihedral angle between the planes of the graphene and the molecular π-systems, but is absent only when the two planes are orthogonal. Coupling also results in partial charge transfer between the graphene contacts and the molecular layer, which results in a shift in electrostatic potential which affects the observed tunneling barrier. Although the degree of partial charge transfer is difficult to calculate accurately, it does provide a basis for the “vacuum level shift” observed in many experiments, including transport and ultraviolet photoelectron spectroscopy of molecular layers on conductors.

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Section: Methodsmentioning

confidence: 99%

Effects of electronic coupling and electrostatic potential on charge transport in carbon-based molecular electronic junctions

McCreery¹

2016

Beilstein J. Nanotechnol.

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“…Covalent functionalization of surfaces using aryldiazonium salts has attracted great interest because this allows modifying the properties of these surfaces toward applications in molecular electronics, supercapacitors and batteries, , sensors, surface patterning, and inks . One of the advantages is the broad range of substituents the covalent functionalization protocol is compatible with, so that the physical and chemical properties can be tailored based on the selection of these substituents.…”

Section: Introductionmentioning

confidence: 99%

Steric and Electronic Effects of Electrochemically Generated Aryl Radicals on Grafting of the Graphite Surface

et al. 2019

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Surface grafting of aryl radicals generated by electrochemical reduction of aryldiazonium salts has been extensively studied on various surfaces. However, there exits two unclear aspects; the first one is the generality of the blocking ability of simple functional groups towards multi-layer growth, and the second one is the electronic impact of substituent groups of aryl radicals on grafting efficiency. To address these aspects, we have studied the electrochemical functionalization of graphite using aryldiazonium salts having electron-donating or -withdrawing groups at the 3,4,5-positions. AFM investigation of the functionalized surfaces revealed the formation of monolayers for all aryldiazonium salts, and thus nitro, carboxy, ester, methyl and methoxy groups at the 3,4,5-positions of the benzene ring suppress polyaryl growth. The degree of grafting estimated by STM imaging and Raman spectroscopy of the functionalized surfaces depends on the electronic state of the aryl radicals, in which the radicals with electron-donating groups show a high degree of functionalization, while those with electron-withdrawing groups exhibit a low degree of functionalization. We discuss several possibilities that affect grafting density. Though there are several factors, we hypothesize that one factor to explain the observed reactivity trend is the electronic property of the aryl radicals, namely the relative position of the singly-occupied molecular orbital (SOMO) energy levels of the aryl radicals with respect to the graphite Fermi energy level. ASSOCIATED CONTENT Supporting InformationExperimental details, synthesis of 5a, washing procedure of functionalized HOPG by 6a, model of the bilayer formed by 6a, details of formation and dediazoniation for aryldiazonium salts, and results of post functionalization. This material is available free of charge via the Internet at http://pubs.acs.org.

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“…In this case, the diazonium compound is generated in the grafting solution through diazotization of the corresponding aromatic amine, either in aqueous acid with NaNO 2 [ 143 ] or in aprotic solvents with reagents such as nitrosonium tetrafluoroborate [ 144 ], tert -butyl nitrite [ 145 ], or isoamyl nitrite [ 146 , 147 , 148 ]. Generally, the grafting process is conducted in acetonitrile or aqueous acid solutions, with minimal differences between the grafting in the different solvents [ 149 ]. The derivatization can be performed through electrochemical reduction, with chemical reducing agents [ 150 , 151 , 152 ], and can even occur spontaneously [ 153 , 154 , 155 , 156 , 157 , 158 , 159 , 160 ].…”

Section: The Role Of Diazonium Electrochemistry For Aptasensors Developmentmentioning

confidence: 99%

The Role of Aryldiazonium Chemistry in Designing Electrochemical Aptasensors for the Detection of Food Contaminants

Raicopol

Pilan

2021

Materials

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Food safety monitoring assays based on synthetic recognition structures such as aptamers are receiving considerable attention due to their remarkable advantages in terms of their ability to bind to a wide range of target analytes, strong binding affinity, facile manufacturing, and cost-effectiveness. Although aptasensors for food monitoring are still in the development stage, the use of an electrochemical detection route, combined with the wide range of materials available as transducers and the proper immobilization strategy of the aptamer at the transducer surface, can lead to powerful analytical tools. In such a context, employing aryldiazonium salts for the surface derivatization of transducer electrodes serves as a simple, versatile and robust strategy to fine-tune the interface properties and to facilitate the convenient anchoring and stability of the aptamer. By summarizing the most important results disclosed in the last years, this article provides a comprehensive review that emphasizes the contribution of aryldiazonium chemistry in developing electrochemical aptasensors for food safety monitoring.

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Diazonium Compounds in Molecular Electronics

Cited by 9 publications

References 98 publications

Effects of electronic coupling and electrostatic potential on charge transport in carbon-based molecular electronic junctions

Effects of electronic coupling and electrostatic potential on charge transport in carbon-based molecular electronic junctions

Steric and Electronic Effects of Electrochemically Generated Aryl Radicals on Grafting of the Graphite Surface

The Role of Aryldiazonium Chemistry in Designing Electrochemical Aptasensors for the Detection of Food Contaminants

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