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Das A, Santhosh S, Giridhar M, Behr J, Michel T, Schaudy E, Ibáñez-Redín G, Lietard J, Somoza MM. Dipodal Silanes Greatly Stabilize Glass Surface Functionalization for DNA Microarray Synthesis and High-Throughput Biological Assays. Anal Chem 2023; 95:15384-15393. [PMID: 37801728 PMCID: PMC10586054 DOI: 10.1021/acs.analchem.3c03399] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Accepted: 09/22/2023] [Indexed: 10/08/2023]
Abstract
Glass is by far the most common substrate for biomolecular arrays, including high-throughput sequencing flow cells and microarrays. The native glass hydroxyl surface is modified by using silane chemistry to provide appropriate functional groups and reactivities for either in situ synthesis or surface immobilization of biologically or chemically synthesized biomolecules. These arrays, typically of oligonucleotides or peptides, are then subjected to long incubation times in warm aqueous buffers prior to fluorescence readout. Under these conditions, the siloxy bonds to the glass are susceptible to hydrolysis, resulting in significant loss of biomolecules and concomitant loss of signal from the assay. Here, we demonstrate that functionalization of glass surfaces with dipodal silanes results in greatly improved stability compared to equivalent functionalization with standard monopodal silanes. Using photolithographic in situ synthesis of DNA, we show that dipodal silanes are compatible with phosphoramidite chemistry and that hybridization performed on the resulting arrays provides greatly improved signal and signal-to-noise ratios compared with surfaces functionalized with monopodal silanes.
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Affiliation(s)
- Arya Das
- Technical
University of Munich, Germany, TUM School
of Natural Sciences, Boltzmannstraße 10, 85748 Garching, Germany
- Leibniz-Institute
for Food Systems Biology at the Technical University of Munich, Lise-Meitner-Straße 30, 85354 Freising, Germany
| | - Santra Santhosh
- Technical
University of Munich, Germany, TUM School
of Natural Sciences, Boltzmannstraße 10, 85748 Garching, Germany
- Leibniz-Institute
for Food Systems Biology at the Technical University of Munich, Lise-Meitner-Straße 30, 85354 Freising, Germany
| | - Maya Giridhar
- Leibniz-Institute
for Food Systems Biology at the Technical University of Munich, Lise-Meitner-Straße 30, 85354 Freising, Germany
| | - Jürgen Behr
- Leibniz-Institute
for Food Systems Biology at the Technical University of Munich, Lise-Meitner-Straße 30, 85354 Freising, Germany
| | - Timm Michel
- Leibniz-Institute
for Food Systems Biology at the Technical University of Munich, Lise-Meitner-Straße 30, 85354 Freising, Germany
- Technical
University of Munich, Germany, TUM School
of Life Sciences, Alte
Akademie 8, 85354 Freising, Germany
| | - Erika Schaudy
- Institute
of Inorganic Chemistry, University of Vienna, Josef-Holaubek-Platz 2, 1090 Vienna, Austria
| | - Gisela Ibáñez-Redín
- Institute
of Inorganic Chemistry, University of Vienna, Josef-Holaubek-Platz 2, 1090 Vienna, Austria
| | - Jory Lietard
- Institute
of Inorganic Chemistry, University of Vienna, Josef-Holaubek-Platz 2, 1090 Vienna, Austria
| | - Mark M. Somoza
- Leibniz-Institute
for Food Systems Biology at the Technical University of Munich, Lise-Meitner-Straße 30, 85354 Freising, Germany
- Institute
of Inorganic Chemistry, University of Vienna, Josef-Holaubek-Platz 2, 1090 Vienna, Austria
- Chair
of Food Chemistry and Molecular Sensory Science, Technical University of Munich, Lise-Meitner-Straße 34, 85354 Freising, Germany
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2
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Xu C, Jiang J, Oguzlu H, Zheng Y, Jiang F. Antifouling, antibacterial and non-cytotoxic transparent cellulose membrane with grafted zwitterion and quaternary ammonium copolymers. Carbohydr Polym 2020; 250:116960. [PMID: 33049896 DOI: 10.1016/j.carbpol.2020.116960] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 08/13/2020] [Accepted: 08/13/2020] [Indexed: 01/29/2023]
Abstract
Copolymer brushes with different ratios of sulfobetaine methacrylate (SBMA) and [2-(Acryloyloxy)ethyl]trimethylammonium chloride (DAC) were grafted from transparent cellulose membrane (CM) via surface-initiated atom transfer radical polymerization (SI-ATRP) method for improving its antifouling and antibacterial performance. Surface concentrated copolymer grafting on the cellulose membranes can be obtained without significantly sacrificing the transparency and mechanical properties. The zwitterionic PSBMA chains of the copolymers can lead to an extremely hydrophilic surface with significantly reduced non-specific protein adsorption and bacterial attachment, therefore, leading to satisfying antifouling and antibacterial property. While the PDAC chains of the copolymers improved antibacterial performance against both Gram-positive and Gram-negative bacteria due to the presence of quaternary ammonium groups, the PDAC modified CM (CM-1) possessed best antibacterial performance, reaching to 95.1 % against S. aureus and 90.5 % against E. coli, respectively. More importantly, the biocompatibility of all grafted CM was retained, leading to over 100 % cell viability.
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Affiliation(s)
- Chen Xu
- Sustainable Functional Biomaterials Lab, Department of Wood Science, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
| | - Jungang Jiang
- Sustainable Functional Biomaterials Lab, Department of Wood Science, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
| | - Hale Oguzlu
- Sustainable Functional Biomaterials Lab, Department of Wood Science, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
| | - Yi Zheng
- Sustainable Functional Biomaterials Lab, Department of Wood Science, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
| | - Feng Jiang
- Sustainable Functional Biomaterials Lab, Department of Wood Science, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada.
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Ortiz M, Debela AM, Méthivier C, Thorimbert S, Hasenknopf B, O'Sullivan CK. Stable Carboxylate-Terminated Gold Surfaces Produced by Spontaneous Grafting of an Alkyltin Compound. Chemistry 2018; 24:11177-11184. [PMID: 29782690 DOI: 10.1002/chem.201801854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2018] [Indexed: 11/08/2022]
Abstract
Self-assembled monolayers formed by chemisorption of thiolated molecules on gold surfaces are widely applied for biosensing. Moreover, and due to the low stability of thiol-gold chemistry, contributions to the functionalisation of gold substrates with linkers that provide a more stable platform for the immobilisation of electroactive or biological molecules are highly appreciated. Herein, it is demonstrated that a carboxylated organotin compound can be successfully grafted onto gold substrates to form a highly stable organic layer with reactivity for subsequent binding to an aminated molecule. A battery of techniques were used to characterise the surface chemistry. The grafted layer was used to anchor aminoferrocene and subjected to both thermostability tests and long-term stability studies over a period of one year, demonstrating thermostability up to 90 °C and storage stability for at least 12 months at 4 °C protected from light. The stable surface tethering of molecules on gold substrates can be exploited in a plethora of applications, including molecular techniques, such as solid-phase amplification and solid-phase melting curve analysis, that require elevated temperature stability, as well as biosensors, which require long-term storage stability.
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Affiliation(s)
- Mayreli Ortiz
- Departament d'Enginyeria Química, Universitat Rovira i Virgili, Avinguda Països Catalans 26, 43007, Tarragona, Spain
| | - Ahmed M Debela
- Sorbonne Université, CNRS, Institut Parisien de Chimie Moléculaire IPCM, 4 place Jussieu, 75005, Paris, France
| | - Christophe Méthivier
- Sorbonne Université, CNRS, Laboratoire de Réactivité de Surface LRS, 75005, Paris, France
| | - Serge Thorimbert
- Sorbonne Université, CNRS, Institut Parisien de Chimie Moléculaire IPCM, 4 place Jussieu, 75005, Paris, France
| | - Bernold Hasenknopf
- Sorbonne Université, CNRS, Institut Parisien de Chimie Moléculaire IPCM, 4 place Jussieu, 75005, Paris, France
| | - Ciara K O'Sullivan
- Departament d'Enginyeria Química, Universitat Rovira i Virgili, Avinguda Països Catalans 26, 43007, Tarragona, Spain.,ICREA, Passeig Lluis Companys 23, 08010, Barcelona, Spain
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McKenas CG, Fehr JM, Donley CL, Lockett MR. Thiol-Ene Modified Amorphous Carbon Substrates: Surface Patterning and Chemically Modified Electrode Preparation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:10529-10536. [PMID: 27657877 DOI: 10.1021/acs.langmuir.6b02961] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Amorphous carbon (aC) films are chemically stable under ambient conditions or when interfaced with aqueous solutions, making them a promising material for preparing biosensors and chemically modified electrodes. There are a number of wet chemical methods capable of tailoring the reactivity and wettability of aC films, but few of these chemistries are compatible with photopatterning. Here, we introduce a method to install thiol groups directly onto the surface of aC films. These terminal thiols are compatible with thiol-ene click reactions, which allowed us to rapidly functionalize and pattern the surface of the aC films. We thoroughly characterized the aC films and confirmed the installation of surface-bound thiols does not significantly oxidize the surface or change its topography. We also determined the conditions needed to selectively attach alkene-containing molecules to these films and show the reaction is proceeding through a thiol-mediated reaction. Lastly, we demonstrate the utility of our approach by photopatterning the aC films and preparing ferrocene-modified aC electrodes. The chemistry described here provides a rapid means of fabricating sensors and preparing photoaddressable arrays of (bio)molecules on stable carbon interfaces.
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Affiliation(s)
- Catherine G McKenas
- Department of Chemistry, University of North Carolina at Chapel Hill , Kenan and Caudill Laboratories, 125 South Road, Chapel Hill, North Carolina 27599-3290, United States
| | - Julia M Fehr
- Department of Chemistry, University of North Carolina at Chapel Hill , Kenan and Caudill Laboratories, 125 South Road, Chapel Hill, North Carolina 27599-3290, United States
| | - Carrie L Donley
- Chapel Hill Analytical and Nanofabrication Laboratory, University of North Carolina at Chapel Hill , Chapman Hall, 205 South Columbia Street, Chapel Hill, North Carolina 27599-3216, United States
| | - Matthew R Lockett
- Department of Chemistry, University of North Carolina at Chapel Hill , Kenan and Caudill Laboratories, 125 South Road, Chapel Hill, North Carolina 27599-3290, United States
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Diazonium-based impedimetric aptasensor for the rapid label-free detection of Salmonella typhimurium in food sample. Biosens Bioelectron 2016; 80:566-573. [PMID: 26894987 DOI: 10.1016/j.bios.2016.02.024] [Citation(s) in RCA: 92] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2015] [Revised: 02/07/2016] [Accepted: 02/09/2016] [Indexed: 11/24/2022]
Abstract
Fast and accurate detection of microorganisms is of key importance in clinical analysis and in food and water quality monitoring. Salmonella typhimurium is responsible for about a third of all cases of foodborne diseases and consequently, its fast detection is of great importance for ensuring the safety of foodstuffs. We report the development of a label-free impedimetric aptamer-based biosensor for S. typhimurium detection. The aptamer biosensor was fabricated by grafting a diazonium-supporting layer onto screen-printed carbon electrodes (SPEs), via electrochemical or chemical approaches, followed by chemical immobilisation of aminated-aptamer. FTIR-ATR, contact angle and electrochemical measurements were used to monitor the fabrication process. Results showed that electrochemical immobilisation of the diazonium-grafting layer allowed the formation of a denser aptamer layer, which resulted in higher sensitivity. The developed aptamer-biosensor responded linearly, on a logarithm scale, over the concentration range 1 × 10(1) to 1 × 10(8)CFU mL(-1), with a limit of quantification (LOQ) of 1 × 10(1) CFU mL(-1) and a limit of detection (LOD) of 6 CFU mL(-1). Selectivity studies showed that the aptamer biosensor could discriminate S. typhimurium from 6 other model bacteria strains. Finally, recovery studies demonstrated its suitability for the detection of S. typhimurium in spiked (1 × 10(2), 1 × 10(4) and 1 × 10(6) CFU mL(-1)) apple juice samples.
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Debela AM, Ortiz M, Beni V, O'Sullivan CK. Surface functionalisation of carbon for low cost fabrication of highly stable electrochemical DNA sensors. Biosens Bioelectron 2015; 71:25-29. [PMID: 25880835 DOI: 10.1016/j.bios.2015.03.076] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2015] [Revised: 03/24/2015] [Accepted: 03/30/2015] [Indexed: 10/23/2022]
Abstract
An alternative strategy for surface tethering of DNA probes, where highly reactive glassy carbon (GC) substrates are prepared via electrochemical hydrogenation and electrochemical/chemical chlorination is reported. Thiolated DNA probes and alkanethiols were stably immobilised on the halogenated carbon, with electrochemical chlorination being milder, thus producing less damage to the surface. Electrochemical DNA sensors prepared using this surface chemistry on carbon with electrochemical chlorination providing an improved performance, producing a highly ordered surface and the use of lateral spacers to improve steric accessibility to immobilised probes was not required.
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Affiliation(s)
- Ahmed M Debela
- Departament d'Enginyeria Química, Universitat Rovira i Virgili, Avinguda Països Catalans, 26, 43007 Tarragona, Spain
| | - Mayreli Ortiz
- Departament d'Enginyeria Química, Universitat Rovira i Virgili, Avinguda Països Catalans, 26, 43007 Tarragona, Spain.
| | - Valerio Beni
- Departament d'Enginyeria Química, Universitat Rovira i Virgili, Avinguda Països Catalans, 26, 43007 Tarragona, Spain
| | - Ciara K O'Sullivan
- Departament d'Enginyeria Química, Universitat Rovira i Virgili, Avinguda Països Catalans, 26, 43007 Tarragona, Spain; ICREA, Passeig Lluis Companys 23, 08010 Barcelona, Spain.
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7
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Lockett MR, Smith LM. Carbon Substrates: A Stable Foundation for Biomolecular Arrays. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2015; 8:263-285. [PMID: 26048550 PMCID: PMC6287745 DOI: 10.1146/annurev-anchem-071114-040146] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Since their advent in the early 1990s, microarray technologies have developed into a powerful and ubiquitous platform for biomolecular analysis. Microarrays consist of three major elements: the substrate upon which they are constructed, the chemistry employed to attach biomolecules, and the biomolecules themselves. Although glass substrates and silane-based attachment chemistries are used for the vast majority of current microarray platforms, these materials suffer from severe limitations in stability, due to hydrolysis of both the substrate material itself and of the silyl ether linkages employed for attachment. These limitations in stability compromise assay performance and render impossible many potential microarray applications. We describe here a suite of alternative carbon-based substrates and associated attachment chemistries for microarray fabrication. The substrates themselves, as well as the carbon-carbon bond-based attachment chemistries, offer greatly increased chemical stability, enabling a myriad of novel applications.
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Affiliation(s)
- Matthew R Lockett
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599;
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8
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Torréns M, Ortiz M, Turner AP, Beni V, O'Sullivan CK. Amperometric detection of Francisella tularensis genomic sequence on Zn-mediated diazonium modified substrates. Electrochem commun 2015. [DOI: 10.1016/j.elecom.2015.02.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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9
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Debela AM, Ortiz M, Beni V, O'Sullivan CK. Facile electrochemical hydrogenation and chlorination of glassy carbon to produce highly reactive and uniform surfaces for stable anchoring of thiolated molecules. Chemistry 2014; 20:7646-54. [PMID: 24829137 DOI: 10.1002/chem.201402051] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Indexed: 11/11/2022]
Abstract
Carbon is a highly adaptable family of materials and is one of the most chemically stable materials known, providing a remarkable platform for the development of tunable molecular interfaces. Herein, we report a two-step process for the electrochemical hydrogenation of glassy carbon followed by either chemical or electrochemical chlorination to provide a highly reactive surface for further functionalization. The carbon surface at each stage of the process is characterized by AFM, SEM, Raman, attenuated total reflectance (ATR) FTIR, X-ray photoelectron spectroscopy (XPS), and electroanalytical techniques. Electrochemical chlorination of hydrogen-terminated surfaces is achieved in just 5 min at room temperature with hydrochloric acid, and chemical chlorination is performed with phosphorus pentachloride at 50 °C over a three-hour period. A more controlled and uniform surface is obtained using the electrochemical approach, as chemical chlorination is observed to damage the glassy carbon surface. A ferrocene-labeled alkylthiol is used as a model system to demonstrate the genericity and potential application of the highly reactive chlorinated surface formed, and the methodology is optimized. This process is then applied to thiolated DNA, and the functionality of the immobilized DNA probe is demonstrated. XPS reveals the covalent bond formed to be a C-S bond. The thermal stability of the thiolated molecules anchored on the glassy carbon is evaluated, and is found to be far superior to that on gold surfaces. This is the first report on the electrochemical hydrogenation and electrochemical chlorination of a glassy carbon surface, and this facile process can be applied to the highly stable functionalization of carbon surfaces with a plethora of diverse molecules, finding widespread applications.
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Affiliation(s)
- Ahmed M Debela
- Departament d'Enginyería Química, Universitat Rovira i Virgili, Avinguda Països Catalans, 26, 43007 Tarragona (Spain), Fax: (+34) 977559667/0034977559721
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10
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Metal complex oligomer and polymer wires on electrodes: Tactical constructions and versatile functionalities. POLYMER 2013. [DOI: 10.1016/j.polymer.2013.04.019] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Gao J, Bao F, Zhu Q, Tan Z, Chen T, Cai H, Zhao C, Cheng Q, Yang Y, Ma R. Attaching hexylbenzene and poly(9,9-dihexylfluorene) to brominated graphene via Suzuki coupling reaction. Polym Chem 2013. [DOI: 10.1039/c2py20920a] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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12
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Abstract
Surface plasmon resonance (SPR) is a label-free detection method by which molecular interactions may be analyzed on a surface. Binding data are collected in real time, allowing the determination of interaction kinetics. SPR imaging (SPRi), the focus of this review, improves upon the efficiency of SPR by facilitating analysis of multiple interactions simultaneously. Here we summarize the principles of SPRi, provide examples of how SPRi arrays can be fabricated, and illustrate the utility of SPRi through example applications from the fields of proteomics, genomics and bioengineering.
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13
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Modification of carbon surfaces with methyl groups by using ferrocene derivatives as redox catalysts of the oxidation of acetate ions. J Electroanal Chem (Lausanne) 2010. [DOI: 10.1016/j.jelechem.2010.09.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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14
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Lockett MR, Smith LM. Halogenation of carbon substrates for increased reactivity with alkenes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:16642-16646. [PMID: 20925329 DOI: 10.1021/la103050z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Carbon substrates are readily functionalized with alkene-containing molecules via an ultraviolet-light-catalyzed reaction, resulting in the formation of a carbon-carbon bond with the surface. This reaction is typically performed on hydrogen-terminated carbon substrates, limiting its utility as alkene molecules with low electron affinities do not readily attach to this surface. Recently, a wet-chemical method for preparing bromine- and chlorine-terminated carbon substrates has been developed. Replacing the terminal hydrogen atoms with a halogen analog increases the surface's reactivity with alkene-containing molecules, affording a means of modifying the carbon substrate with the alkene molecules that do not readily attach to the hydrogen-terminated surface and with a greatly reduced reaction time.
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Affiliation(s)
- Matthew R Lockett
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
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Lockett MR, Smith LM. The Formation and Stability of Alkylthiol Monolayers on Carbon Substrates. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2010; 114:12635-12641. [PMID: 20706614 PMCID: PMC2917760 DOI: 10.1021/jp102821x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The formation and stability of alkylthiol monolayers on amorphous carbon thin films are investigated. Alkylthiol monolayers were prepared via a two-step, wet chemical process in which the carbon surface was first halogenated and then incubated with (4-(trifluoromethyl)phenyl)methanethiol (4tBM). The 4tBM covalently attaches to the surface in a substitution reaction in which the 4tBM thiol replaces the surface halogen. Studies of the substitution mechanism showed that monolayer formation is affected by the nature of the surface-bound halogen as well as the concentration and nucleophilicity of the 4tBM sulfur atom, consistent with a bimolecular (S(N)2) substitution reaction mechanism. The alkylthiol monolayers are stable over a wide range of solvent, pH, and temperature conditions.
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Affiliation(s)
| | - Lloyd M. Smith
- Department of Chemistry, University of Wisconsin-Madison
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Mukherjee J, Peczonczyk S, Maldonado S. Wet chemical functionalization of III-V semiconductor surfaces: alkylation of gallium phosphide using a Grignard reaction sequence. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:10890-10896. [PMID: 20486651 DOI: 10.1021/la100783w] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Single-crystalline gallium phosphide (GaP) surfaces have been functionalized with alkyl groups via a sequential Cl-activation, Grignard reaction process. X-ray photoelectron (XP) spectra of freshly etched GaP(111)A surfaces demonstrated reproducible signals for surficial Cl after treatment with PCl(5) in chlorobenzene. The measured Cl content consistently corresponded to approximately a monolayer of coverage on GaP(111)A. In contrast, GaP(111)B surfaces treated with the same PCl(5) solution under the same conditions exhibited macroscale roughening and yielded XP spectra that showed irreproducible Cl surface content often below the limit of detection of the spectrometer. The Cl-activated GaP(111)A surfaces were reactive toward alkyl Grignard reagents. Sessile contact angle measurements between water and GaP(111)A after various levels of treatment showed that GaP(111)A surfaces became significantly more hydrophobic following reaction with either CH(3)MgCl or C(18)H(37)MgCl. GaP(111)A surfaces reacted with C(18)H(37)MgCl demonstrated wetting properties consistent with surfaces modified with a dense layer of long alkyl chains. High-resolution C 1s XP spectra indicated that the carbonaceous species at GaP(111)A surfaces treated with Grignard reagents could not be ascribed solely to adventitious carbon. A shoulder in the C 1s XP spectra occurred at slightly lower binding energies for these samples, commensurate with the formation of Ga-C bonds. High-resolution P 2p XP spectra taken at various times during prolonged direct exposure to ambient laboratory air indicated that the resistance of GaP(111)A to surface oxidation was greatly enhanced after surface modification with alkyl groups. GaP(111)A samples that had been functionalized with C(18)H(37)- groups exhibited less than 0.1 nm of surface oxide after 7 weeks of continuous exposure to ambient air. GaP(111)A surfaces terminated with C(18)H(37)- groups were also used as platforms in Schottky heterojunctions with Hg. In comparison to freshly etched GaP(111)A, the alkyl-terminated GaP(111)A samples yielded current-voltage responses that were in accord with metal-insulator-semiconductor devices and indicated that this reaction strategy could be used to alter rates of heterogeneous charge transfer controllably. The wet chemical surface functionalization strategy described herein does not involve thiol/sulfide chemistry or gas-phase pretreatments and represents a new synthetic methodology for controlling the interfacial properties of GaP and related Ga-based III-V semiconductors.
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Affiliation(s)
- Jhindan Mukherjee
- Department of Chemistry, University of Michigan, 930 North University, Ann Arbor, Michigan 48109-1055, USA
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