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Bhartia B, Jayaraman S, Troadec C, Madapusi SP, Puniredd SR. Grafting of Organophosphonic Acid Monolayers on Hydrogen-Terminated Silicon Surface and Secondary Functionalization in Supercritical Carbon Dioxide Media. Langmuir 2023; 39:12063-12074. [PMID: 37581455 DOI: 10.1021/acs.langmuir.3c01278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/16/2023]
Abstract
The monolayer grafting on the oxide-free Si surface is challenging due to vulnerability of the surface against oxide formation in an ambient atmosphere. Most of the conventional studies focused on organic solvent-based chemistry and solvent and substrate interfaces, and residual solvents after the monolayer grafting play a key role in producing the highly stable monolayers. CO2 in its supercritical state (SCCO2) provides an elegant engineering solution for the problem faced as it can be used as inert processing environment and as carrier fluid for monolayer grafting taking up the role of organic solvents. In this work, monolayers of alkyl organophosphonic acids (OPAs) and functional OPAs were grafted on hydrogen-terminated oxide-free Si surfaces using the SCCO2 process. Grafted monolayers were physically and chemically characterized to verify the successful monolayer formation and determine the nature of the covalent binding configuration on the surface. To broaden the prospects of practical utility of the process and the OPA monolayer, the (3-bromopropyl)phosphonic acid (BPPA) monolayer was demonstrated to undergo secondary functionalization by terminal group substitution to convert the Br terminal group to the OH terminal group and secondary monolayer grafting to assemble 4-fluorothiophenol on top of the BPPA monolayer. The ability of monolayers to sustain secondary functionalization processing qualitatively hints toward ordered and stable monolayers of OPAs. The developed SCCO2 process in this work presents a single-step, green, and scalable method to graft the OPA monolayer on oxide-free Si which can employed in the future for monolayer doping, highly selective biochemical sensors, and targeted biological interactions.
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Affiliation(s)
- Bhavesh Bhartia
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Innovis, #08-3, Singapore 138634, Republic of Singapore
- Department of Chemical and Biomolecular Engineering, National University of Singapore,4 Engineering Drive 4, Singapore 117585, Republic of Singapore
| | - Sundaramurthy Jayaraman
- YSQ International Pte Ltd, 401 Commonwealth Drive, #07-01, Singapore 149598, Republic of Singapore
| | - Cedric Troadec
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Innovis, #08-3, Singapore 138634, Republic of Singapore
| | - Srinivasan Palavedu Madapusi
- Department of Chemical Engineering, BITS Pilani, Dubai Campus, Dubai International Academic City, P.O. Box No. 345055, Dubai 500001, UAE
| | - Sreenivasa Reddy Puniredd
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Innovis, #08-3, Singapore 138634, Republic of Singapore
- Singapore Institute of Food and Biotechnology Innovation (SIFBI), Agency for Science, Technology and Research (A*STAR), 31 Biopolis Way, Nanos, #01-02, Singapore 138669, Republic of Singapore
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2
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Cai W, Bullerjahn JT, Lallemang M, Kroy K, Balzer BN, Hugel T. Angle-dependent strength of a single chemical bond by stereographic force spectroscopy. Chem Sci 2022; 13:5734-5740. [PMID: 35694336 PMCID: PMC9117962 DOI: 10.1039/d2sc01077a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2022] [Accepted: 04/13/2022] [Indexed: 11/21/2022] Open
Abstract
A wealth of chemical bonds and polymers have been studied with single-molecule force spectroscopy, usually by applying a force perpendicular to the anchoring surface. However, the direction-dependence of the bond strength lacks fundamental understanding. Here we establish stereographic force spectroscopy to study the single-bond strength for various pulling angles. Surprisingly, we find that the apparent bond strength increases with increasing pulling angle relative to the anchoring surface normal, indicating a sturdy mechanical anisotropy of a chemical bond. This finding can be rationalized by a fixed pathway for the rupture of the bond, resulting in an effective projection of the applied pulling force onto a nearly fixed rupture direction. Our study is fundamental for the molecular understanding of the role of the direction of force application in molecular adhesion and friction. It is also a prerequisite for the nanoscale tailoring of the anisotropic strength of bottom-up designed materials. Stereographic force spectroscopy reveals that a chemical bond ruptures along a fixed pathway such that the apparent bond strength strongly depends on the angle of force application.![]()
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Affiliation(s)
- Wanhao Cai
- Institute of Physical Chemistry, University of Freiburg, Albertstr. 21, 79104, Freiburg, Germany
| | - Jakob T. Bullerjahn
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Max-von-Laue-Straße 3, 60438, Frankfurt am Main, Germany
| | - Max Lallemang
- Institute of Physical Chemistry, University of Freiburg, Albertstr. 21, 79104, Freiburg, Germany
- Cluster of Excellence livMatS@FIT – Freiburg Center for Interactive Materials and Bioinspired Technologies, University of Freiburg, Georges-Köhler-Allee 105, 79110, Freiburg, Germany
| | - Klaus Kroy
- Institute for Theoretical Physics, Leipzig University, Brüderstraße 16, 04103, Leipzig, Germany
| | - Bizan N. Balzer
- Institute of Physical Chemistry, University of Freiburg, Albertstr. 21, 79104, Freiburg, Germany
- Cluster of Excellence livMatS@FIT – Freiburg Center for Interactive Materials and Bioinspired Technologies, University of Freiburg, Georges-Köhler-Allee 105, 79110, Freiburg, Germany
- Freiburg Materials Research Center (FMF), University of Freiburg, Stefan-Meier-Str. 21, 79104, Freiburg, Germany
| | - Thorsten Hugel
- Institute of Physical Chemistry, University of Freiburg, Albertstr. 21, 79104, Freiburg, Germany
- Cluster of Excellence livMatS@FIT – Freiburg Center for Interactive Materials and Bioinspired Technologies, University of Freiburg, Georges-Köhler-Allee 105, 79110, Freiburg, Germany
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3
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Peiris CR, Ciampi S, Dief EM, Zhang J, Canfield PJ, Le Brun AP, Kosov DS, Reimers JR, Darwish N. Spontaneous S-Si bonding of alkanethiols to Si(111)-H: towards Si-molecule-Si circuits. Chem Sci 2020; 11:5246-5256. [PMID: 34122981 PMCID: PMC8159313 DOI: 10.1039/d0sc01073a] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We report the synthesis of covalently linked self-assembled monolayers (SAMs) on silicon surfaces, using mild conditions, in a way that is compatible with silicon-electronics fabrication technologies. In molecular electronics, SAMs of functional molecules tethered to gold via sulfur linkages dominate, but these devices are not robust in design and not amenable to scalable manufacture. Whereas covalent bonding to silicon has long been recognized as an attractive alternative, only formation processes involving high temperature and/or pressure, strong chemicals, or irradiation are known. To make molecular devices on silicon under mild conditions with properties reminiscent of Au–S ones, we exploit the susceptibility of thiols to oxidation by dissolved O2, initiating free-radical polymerization mechanisms without causing oxidative damage to the surface. Without thiols present, dissolved O2 would normally oxidize the silicon and hence reaction conditions such as these have been strenuously avoided in the past. The surface coverage on Si(111)–H is measured to be very high, 75% of a full monolayer, with density-functional theory calculations used to profile spontaneous reaction mechanisms. The impact of the Si–S chemistry in single-molecule electronics is demonstrated using STM-junction approaches by forming Si–hexanedithiol–Si junctions. Si–S contacts result in single-molecule wires that are mechanically stable, with an average lifetime at room temperature of 2.7 s, which is five folds higher than that reported for conventional molecular junctions formed between gold electrodes. The enhanced “ON” lifetime of this single-molecule circuit enables previously inaccessible electrical measurements on single molecules. Spontaneously formed Si–S bonds enable monolayer and single-molecule Si–molecule–Si circuits.![]()
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Affiliation(s)
- Chandramalika R Peiris
- School of Molecular and Life Sciences, Curtin Institute of Functional Molecules and Interfaces, Curtin University Bentley WA 6102 Australia
| | - Simone Ciampi
- School of Molecular and Life Sciences, Curtin Institute of Functional Molecules and Interfaces, Curtin University Bentley WA 6102 Australia
| | - Essam M Dief
- School of Molecular and Life Sciences, Curtin Institute of Functional Molecules and Interfaces, Curtin University Bentley WA 6102 Australia
| | - Jinyang Zhang
- School of Molecular and Life Sciences, Curtin Institute of Functional Molecules and Interfaces, Curtin University Bentley WA 6102 Australia
| | - Peter J Canfield
- International Centre for Quantum and Molecular Structures, School of Physics, Shanghai University Shanghai 200444 China.,School of Chemistry, The University of Sydney NSW 2006 Australia
| | - Anton P Le Brun
- Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organization (ANSTO) Lucas Heights NSW 2234 Australia
| | - Daniel S Kosov
- College of Science and Engineering, James Cook University Townsville QLD 4811 Australia
| | - Jeffrey R Reimers
- International Centre for Quantum and Molecular Structures, School of Physics, Shanghai University Shanghai 200444 China.,School of Mathematical and Physical Sciences, University of Technology Sydney NSW 2007 Australia
| | - Nadim Darwish
- School of Molecular and Life Sciences, Curtin Institute of Functional Molecules and Interfaces, Curtin University Bentley WA 6102 Australia
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4
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Yang N, Li W, Dong L. Modification of a H-terminated silicon surface by organic sulfide molecules: the mechanism and origin of reactivity. NEW J CHEM 2020. [DOI: 10.1039/c9nj06115k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
For the reactions of disulfide molecules (RSSR), the steric effect rather than the electronic effect of the R group is the main origin of the different reactivity. In the reactions of sulfide molecules (RSXR′, X = S, P, Si, O, N, C), charges on the S atom and dissociation energies of the S–X bonds have a great impact on the reactivity of these reactions.
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Affiliation(s)
- Na Yang
- Institute of Nuclear Physics and Chemistry
- China Academy of Engineering Physics
- Mianyang
- P. R. China
| | - Weiyi Li
- School of Science, Xihua University
- Chengdu
- P. R. China
| | - Liang Dong
- Institute of Nuclear Physics and Chemistry
- China Academy of Engineering Physics
- Mianyang
- P. R. China
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5
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van Oversteeg CM, Oropeza FE, Hofmann JP, Hensen EJM, de Jongh PE, de Mello Donega C. Water-Dispersible Copper Sulfide Nanocrystals via Ligand Exchange of 1-Dodecanethiol. Chem Mater 2019; 31:541-552. [PMID: 30686859 PMCID: PMC6345102 DOI: 10.1021/acs.chemmater.8b04614] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Revised: 12/18/2018] [Indexed: 05/16/2023]
Abstract
In colloidal Cu2-x S nanocrystal synthesis, thiols are often used as organic ligands and the sulfur source, as they yield high-quality nanocrystals. However, thiol ligands on Cu2-x S nanocrystals are difficult to exchange, limiting the applications of these nanocrystals in photovoltaics, biomedical sensing, and photocatalysis. Here, we present an effective and facile procedure to exchange native 1-dodecanethiol on Cu2-x S nanocrystals by 3-mercaptopropionate, 11-mercaptoundecanoate, and S2- in formamide under inert atmosphere. The product hydrophilic Cu2-x S nanocrystals have excellent colloidal stability in formamide. Furthermore, the size, shape, and optical properties of the nanocrystals are not significantly affected by the ligand exchange. Water-dispersible Cu2-x S nanocrystals are easily obtained by precipitation of the nanocrystals capped by S2-, 3-mercaptopropionate, or 11-mercaptoundecanoate from formamide, followed by redispersion in water. Interestingly, the ligand exchange rates for Cu2-x S nanocrystals capped with 1-dodecanethiol are observed to depend on the preparation method, being much slower for Cu2-x S nanocrystals prepared through heating-up than through hot-injection synthesis protocols. XPS studies reveal that the differences in the ligand exchange rates are due to the surface chemistry of the Cu2-x S nanocrystals, where the nanocrystals prepared via hot-injection synthesis have a less dense ligand layer due to the presence of trioctylphosphine oxide during synthesis. A model is proposed that explains the observed differences in the ligand exchange rates. The facile ligand exchange procedures reported here enable the use of high-quality colloidal Cu2-x S nanocrystals prepared in the presence of 1-dodecanethiol in various applications.
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Affiliation(s)
- Christina
H. M. van Oversteeg
- Condensed
Matter and Interfaces, Debye Institute for Nanomaterials Science, Utrecht University, 3508 TA Utrecht, The Netherlands
- Inorganic
Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, 3508 TA Utrecht, The Netherlands
| | - Freddy E. Oropeza
- Laboratory
of Inorganic Materials Chemistry, Department of Chemical Engineering
and Chemistry, Eindhoven University of Technology, Postbox 513, 5600 MB Eindhoven, The Netherlands
| | - Jan P. Hofmann
- Laboratory
of Inorganic Materials Chemistry, Department of Chemical Engineering
and Chemistry, Eindhoven University of Technology, Postbox 513, 5600 MB Eindhoven, The Netherlands
| | - Emiel J. M. Hensen
- Laboratory
of Inorganic Materials Chemistry, Department of Chemical Engineering
and Chemistry, Eindhoven University of Technology, Postbox 513, 5600 MB Eindhoven, The Netherlands
| | - Petra E. de Jongh
- Inorganic
Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, 3508 TA Utrecht, The Netherlands
| | - Celso de Mello Donega
- Condensed
Matter and Interfaces, Debye Institute for Nanomaterials Science, Utrecht University, 3508 TA Utrecht, The Netherlands
- (Celso de Mello Donega) E-mail:
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6
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Soliman AIA, Utsunomiya T, Ichii T, Sugimura H. 1,2-Epoxyalkane: Another Precursor for Fabricating Alkoxy Self-Assembled Monolayers on Hydrogen-Terminated Si(111). Langmuir 2018; 34:13162-13170. [PMID: 30299104 DOI: 10.1021/acs.langmuir.8b02717] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
This work describes the UV alkoxylation of a series of 1,2-epoxyalkanes on the hydrogen-terminated silicon (H-Si) substrate. The formation of alkoxy self-assembled monolayers (SAMs) and the nature of bonding at the surface of H-Si were examined using water contact angle goniometer, spectroscopic ellipsometer, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy. UV exposure to 1,2-epoxyalkane mesitylene solution for 60 min formed alkoxy-SAMs onto H-Si with hydrophobic properties. The local molecular environment of the alkyl chains transitioned from a disordered, liquid-like state to an ordered, crystalline-like structure with increasing the chain length. XPS and FTIR indicated that the reaction of H-Si with 1,2-epoxyalkane produced Si-O-C linkages. The Si-H bond homolysis and electron/hole were the plausible mechanistic routes for the grafting of 1,2-epoxyalkanes.
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Affiliation(s)
- Ahmed I A Soliman
- Department of Materials Science and Engineering , Kyoto University , Yoshida-Hommachi , Sakyo-ku, Kyoto 606-8501 , Japan
- Chemistry Department, Faculty of Science , Assiut University , Assiut 71516 , Egypt
| | - Toru Utsunomiya
- Department of Materials Science and Engineering , Kyoto University , Yoshida-Hommachi , Sakyo-ku, Kyoto 606-8501 , Japan
| | - Takashi Ichii
- Department of Materials Science and Engineering , Kyoto University , Yoshida-Hommachi , Sakyo-ku, Kyoto 606-8501 , Japan
| | - Hiroyuki Sugimura
- Department of Materials Science and Engineering , Kyoto University , Yoshida-Hommachi , Sakyo-ku, Kyoto 606-8501 , Japan
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7
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Affiliation(s)
| | - Carla Ferreri
- ISOF, Consiglio Nazionale delle Ricerche, Via P. Gobetti 101, 40129 Bologna, Italy
| | - Yannick Landais
- University of Bordeaux, Institute of Molecular Sciences, UMR-CNRS 5255, 351 cours de la libération, 33405 Talence Cedex, France
| | - Vitaliy I. Timokhin
- Department of Biochemistry, University of Wisconsin-Madison, 1552 University Avenue, Madison, Wisconsin 53726, United States
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8
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Chang LY, Kuo YC, Shiu HW, Wang CH, Lee YC, Yang YW, Gwo S, Chen CH. n-Alkanethiols Directly Grown on a Bare Si(111) Surface: From Disordered to Ordered Transition. Langmuir 2017; 33:14244-14251. [PMID: 29148786 DOI: 10.1021/acs.langmuir.7b03302] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We observed the growth phase transition of n-alkanethiols (AT), CH3(CH2)n-1SH, n = 4-16, directly implanted on a bare Si(111) surface, forming an AT monolayer. These monolayers were characterized with static water-contact angle, high-resolution X-ray photoelectron spectroscopy, near-edge X-ray fine-structure spectroscopy, and grazing-angle reflection absorption Fourier-transform infrared spectroscopy. The integrated spectral results indicated that the implanted n-AT molecules formed a self-oriented and densely packed monolayer through formation of an S-Si bond. With the number of carbons in the alkyl chain at six or more, namely beginning at hexanethiol, the molecular monolayer began to develop an orientation-ordered structure, which is clearly shorter than that for AT monolayers on Au and Ag. This result implies that, with a stronger molecule-substrate interaction, an ordered molecular monolayer can form with a short chain.
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Affiliation(s)
- Lo Yueh Chang
- National Synchrotron Radiation Research Center , Hsinchu, 30076, Taiwan
- Department of Physics, National Tsing Hua University , Hsinchu 30013, Taiwan
| | - Yen-Chien Kuo
- National Synchrotron Radiation Research Center , Hsinchu, 30076, Taiwan
| | - Hung Wei Shiu
- National Synchrotron Radiation Research Center , Hsinchu, 30076, Taiwan
| | - Chia-Hsin Wang
- National Synchrotron Radiation Research Center , Hsinchu, 30076, Taiwan
| | - Yao-Chang Lee
- National Synchrotron Radiation Research Center , Hsinchu, 30076, Taiwan
| | - Yaw-Wen Yang
- National Synchrotron Radiation Research Center , Hsinchu, 30076, Taiwan
| | - Shangjr Gwo
- National Synchrotron Radiation Research Center , Hsinchu, 30076, Taiwan
- Department of Physics, National Tsing Hua University , Hsinchu 30013, Taiwan
| | - Chia-Hao Chen
- National Synchrotron Radiation Research Center , Hsinchu, 30076, Taiwan
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9
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Bhartia B, Puniredd SR, Jayaraman S, Gandhimathi C, Sharma M, Kuo YC, Chen CH, Reddy VJ, Troadec C, Srinivasan MP. Highly Stable Bonding of Thiol Monolayers to Hydrogen-Terminated Si via Supercritical Carbon Dioxide: Toward a Super Hydrophobic and Bioresistant Surface. ACS Appl Mater Interfaces 2016; 8:24933-24945. [PMID: 27540859 DOI: 10.1021/acsami.6b06018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Oxide-free silicon chemistry has been widely studied using wet-chemistry methods, but for emerging applications such as molecular electronics on silicon, nanowire-based sensors, and biochips, these methods may not be suitable as they can give rise to defects due to surface contamination, residual solvents, which in turn can affect the grafted monolayer devices for practical applications. Therefore, there is a need for a cleaner, reproducible, scalable, and environmentally benign monolayer grafting process. In this work, monolayers of alkylthiols were deposited on oxide-free semiconductor surfaces using supercritical carbon dioxide (SCCO2) as a carrier fluid owing to its favorable physical properties. The identity of grafted monolayers was monitored with Fourier transform infrared (FTIR) spectroscopy, high-resolution X-ray photoelectron spectroscopy (HRXPS), XPS, atomic force microscopy (AFM), contact angle measurements, and ellipsometry. Monolayers on oxide-free silicon were able to passivate the surface for more than 50 days (10 times than the conventional methods) without any oxide formation in ambient atmosphere. Application of the SCCO2 process was further extended by depositing alkylthiol monolayers on fragile and brittle 1D silicon nanowires (SiNWs) and 2D germanium substrates. With the recent interest in SiNWs for biological applications, the thiol-passivated oxide-free silicon nanowire surfaces were also studied for their biological response. Alkylthiol-functionalized SiNWs showed a significant decrease in cell proliferation owing to their superhydrophobicity combined with the rough surface morphology. Furthermore, tribological studies showed a sharp decrease in the coefficient of friction, which was found to be dependent on the alkyl chain length and surface bond. These studies can be used for the development of cost-effective and highly stable monolayers for practical applications such as solar cells, biosensors, molecular electronics, micro- and nano- electromechanical systems, antifouling agents, and drug delivery.
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Affiliation(s)
- Bhavesh Bhartia
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis, #08-32, Singapore 138634
- Department of Chemical and Biomolecular Engineering, National University of Singapore , 4 Engineering Drive 4, Singapore 117585
| | - Sreenivasa Reddy Puniredd
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis, #08-32, Singapore 138634
| | - Sundaramurthy Jayaraman
- Environmental and Water Technology Centre of Innovation, Ngee Ann Polytechnic , 535 Clementi Road, Singapore 599489
| | - Chinnasamy Gandhimathi
- Centre for Nanofibers and Nanotechnology, Nanoscience and Nanotechnology Initiative, National University of Singapore , Singapore 117576
| | - Mohit Sharma
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis, #08-32, Singapore 138634
| | - Yen-Chien Kuo
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Chia-Hao Chen
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Venugopal Jayarama Reddy
- Centre for Nanofibers and Nanotechnology, Nanoscience and Nanotechnology Initiative, National University of Singapore , Singapore 117576
| | - Cedric Troadec
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis, #08-32, Singapore 138634
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10
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Arefi HH, Nolan M, Fagas G. Binary functionalization of H:Si(111) surfaces by alkyl monolayers with different linker atoms enhances monolayer stability and packing. Phys Chem Chem Phys 2016; 18:12952-63. [PMID: 27109872 DOI: 10.1039/c5cp07601c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Alkyl monolayer modified Si forms a class of inorganic-organic hybrid materials with applications across many technologies such as thin-films, fuel/solar-cells and biosensors. Previous studies have shown that the linker atom, through which the monolayer binds to the Si substrate, and any tail group in the alkyl chain, can tune the monolayer stability and electronic properties. In this paper we study the H:Si(111) surface functionalized with binary SAMs: these are composed of alkyl chains that are linked to the surface by two different linker groups. Aiming to enhance SAM stability and increase coverage over singly functionalized Si, we examine with density functional theory simulations that incorporate vdW interactions, a range of linker groups which we denote as -X-(alkyl) with X = CH2, O(H), S(H) or NH(2) (alkyl = C6 and C12 chains). We show how the stability of the SAM can be enhanced by adsorbing alkyl chains with two different linkers, e.g. Si-[C, NH]-alkyl, through which the adsorption energy is increased compared to functionalization with the individual -X-alkyl chains. Our results show that it is possible to improve stability and optimum coverage of alkyl functionalized SAMs linked through a direct Si-C bond by incorporating alkyl chains linked to Si through a different linker group, while preserving the interface electronic structure that determines key electronic properties. This is important since any enhancement in stability and coverage to give more densely packed monolayers will result in fewer defects. We also show that the work function can be tuned within the interval of 3.65-4.94 eV (4.55 eV for bare H:Si(111)).
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Affiliation(s)
- Hadi H Arefi
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
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11
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Soliman AIA, Kokufu S, Utsunomiya T, Ichii T, Sugimura H. Photochemical Preparation of Alkoxy Self-assembled Monolayers on Si from 1,2-Epoxyalkane Molecules. CHEM LETT 2016. [DOI: 10.1246/cl.160064] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
| | - Sho Kokufu
- Department of Materials Science and Engineering, Kyoto University
| | - Toru Utsunomiya
- Department of Materials Science and Engineering, Kyoto University
| | - Takashi Ichii
- Department of Materials Science and Engineering, Kyoto University
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12
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Hu M, Liu F, Buriak JM. Expanding the Repertoire of Molecular Linkages to Silicon: Si-S, Si-Se, and Si-Te Bonds. ACS Appl Mater Interfaces 2016; 8:11091-11099. [PMID: 27055056 DOI: 10.1021/acsami.6b00784] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Silicon is the foundation of the electronics industry and is now the basis for a myriad of new hybrid electronics applications, including sensing, silicon nanoparticle-based imaging and light emission, photonics, and applications in solar fuels, among others. From interfacing of biological materials to molecular electronics, the nature of the chemical bond plays important roles in electrical transport and can have profound effects on the electronics of the underlying silicon itself, affecting its work function, among other things. This work describes the chemistry to produce ≡Si-E bonds (E = S, Se, and Te) through very fast microwave heating (10-15 s) and direct thermal heating (hot plate, 2 min) through the reaction of hydrogen-terminated silicon surfaces with dialkyl or diaryl dichalcogenides. The chemistry produces surface-bound ≡Si-SR, ≡Si-SeR, and ≡Si-TeR groups. Although the interfacing of molecules through ≡Si-SR and ≡Si-SeR bonds is known, to the best of our knowledge, the heavier chalcogenide variant, ≡Si-TeR, has not been described previously. The identity of the surface groups was determined by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and depth profiling with time-of-flight-secondary ionization mass spectrometry (ToF-SIMS). Possible mechanisms are outlined, and the most likely, based upon parallels with well-established molecular literature, involve surface silyl radicals or dangling bonds that react with either the alkyl or aryl dichalcogenide directly, REER, or its homolysis product, the alkyl or aryl chalcogenyl radical, RE· (where E = S, Se, and Te).
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Affiliation(s)
- Minjia Hu
- Department of Chemistry, University of Alberta , 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada
- National Institute for Nanotechnology, National Research Council Canada , 11421 Saskatchewan Drive, Edmonton, Alberta T6G 2M9, Canada
| | - Fenglin Liu
- Department of Chemistry, University of Alberta , 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada
- National Institute for Nanotechnology, National Research Council Canada , 11421 Saskatchewan Drive, Edmonton, Alberta T6G 2M9, Canada
| | - Jillian M Buriak
- Department of Chemistry, University of Alberta , 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada
- National Institute for Nanotechnology, National Research Council Canada , 11421 Saskatchewan Drive, Edmonton, Alberta T6G 2M9, Canada
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13
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Affiliation(s)
- Jillian M. Buriak
- Department
of Chemistry, University of Alberta, and the National Institute for Nanotechnology, Edmonton, AB T6G 2G2, Canada
| | - Md Delwar H. Sikder
- Department
of Chemistry, University of Alberta, and the National Institute for Nanotechnology, Edmonton, AB T6G 2G2, Canada
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Arefi HH, Nolan M, Fagas G. Density functional theory with van der waals corrections study of the adsorption of alkyl, alkylthiol, alkoxyl, and amino-alkyl chains on the H:Si(111) surface. Langmuir 2014; 30:13255-13265. [PMID: 25260071 DOI: 10.1021/la502488c] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Surface modification of silicon with organic monolayers tethered to the surface by different linkers is an important process in realizing future miniaturized electronic and sensor devices. Understanding the roles played by the nature of the linking group and the chain length on the adsorption structures and stabilities of these assemblies is vital to advance this technology. This paper presents a density functional theory (DFT) study of the hydrogen passivated Si(111) surface modified with alkyl chains of the general formula H:Si-(CH2)n-CH2 and H:Si-X-(CH2)n-CH3, where X = NH, O, S and n = (0, 1, 3, 5, 7, 9, 11), at half coverage. For (X)-hexane and (X)-dodecane functionalization, we also examined various coverages up to full monolayer grafting in order to validate the result of half covered surface and the linker effect on the coverage. We find that it is necessary to take into account the van der Waals interaction between the alkyl chains. The strongest binding is for the oxygen linker, followed by S, N, and C, irrespective of chain length. The result revealed that the sequence of the stability is independent of coverage; however, linkers other than carbon can shift the optimum coverage considerably and allow further packing density. For all linkers apart from sulfur, structural properties, in particular, surface-linker-chain angles, saturate to a single value once n > 3. For sulfur, we identify three regimes, namely, n = 0-3, n = 5-7, and n = 9-11, each with its own characteristic adsorption structures. Where possible, our computational results are shown to be consistent with the available experimental data and show how the fundamental structural properties of modified Si surfaces can be controlled by the choice of linking group and chain length.
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Affiliation(s)
- Hadi H Arefi
- Tyndall National Institute, Lee Maltings, and ‡Department of Electrical Engineering, University College Cork , Cork, Ireland
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Huang YS, Chen CH, Chen CH, Hung WH. Fabrication of octadecyl and octadecanethiolate self-assembled monolayers on oxide-free Si(111) with a one-cell process. ACS Appl Mater Interfaces 2013; 5:5771-5776. [PMID: 23721083 DOI: 10.1021/am401270z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Self-assembled monolayers (SAM) of 1-octadecene (ODE) and 1-octadecanethiol (ODT) were deposited on an oxide-free Si(111) surface with a one-cell method. The etching and SAM deposition of Si(111) were performed in one cell containing immiscible solutions in two layers: an aqueous solution of NH4F and a toluene solution of organic SAM precursors (ODE and ODT). To remove surface Si oxides, the Si(111) surface was initially etched in the lower layer of NH4F solution. The Si as etched was subsequently moved directly to the upper solution of the precursors for deposition of the SAM under illumination of white light. This one-cell approach avoids the Si surface, as etched, coming in contact with the atmosphere, so eliminating oxidation and contamination. The ODE and ODT SAM were characterized with measurements with an atomic force microscope (AFM) and X-ray photoelectron spectra (XPS). The resulting ODE SAM was more stable than the ODT SAM and exhibited satisfactory resistance to oxidation under the ambient atmosphere. The ODT SAM prepared with this one-cell method exhibited a resistance to atmospheric oxidation better than with a two-cell method.
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Affiliation(s)
- Yan-Shiang Huang
- Department of Chemistry, National Taiwan Normal University, Taipei 116, Taiwan
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Abstract
We formed magnetic moment assisted layer-by-layer (LbL) films of a Prussian Blue analogue (PB). We applied an external magnetic field to each monolayer of PB to orient the magnetic moment of the compound perpendicular to the substrate. Aligned moments or orientation of the magnetic compounds themselves were immobilized in each monolayer, so that the moments could augment formation of the subsequent monolayers of LbL adsorption process. We hence could form multilayered LbL films of PB molecules with their magnetic moments oriented perpendicular to the substrate. We also formed LbL films of the compound with their moments oriented parallel to the substrate and facing one particular direction. We have measured conductivity and dielectric constant of the two types of films and compared the parameters with that of conventional LbL films deposited without orienting magnetic moments of the molecules.
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Affiliation(s)
- Abhijit Bera
- Department of Solid State Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, India
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Lu HC, Lin MY, Chou SL, Peng YC, Lo JI, Shiu HW, Chen CH, Cheng BM. Linear and folded films of a zwitterionic polysquaraine. RSC Adv 2013. [DOI: 10.1039/c3ra43776k] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Aguado S, Canivet J, Schuurman Y, Farrusseng D. Tuning the activity by controlling the wettability of MOF eggshell catalysts: A quantitative structure–activity study. J Catal 2011. [DOI: 10.1016/j.jcat.2011.10.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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