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Ali I, Basheer AA, Kucherova A, Memetov N, Pasko T, Ovchinnikov K, Pershin V, Kuznetsov D, Galunin E, Grachev V, Tkachev A. Advances in carbon nanomaterials as lubricants modifiers. J Mol Liq 2019. [DOI: 10.1016/j.molliq.2019.01.113] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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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 APPLIED MATERIALS & 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] [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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Puniredd SR, Jayaraman S, Yeong SH, Troadec C, Srinivasan MP. Stable Organic Monolayers on Oxide-Free Silicon/Germanium in a Supercritical Medium: A New Route to Molecular Electronics. J Phys Chem Lett 2013; 4:1397-1403. [PMID: 26282291 DOI: 10.1021/jz4005416] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Oxide-free Si and Ge surfaces have been passivated and modified with organic molecules by forming covalent bonds between the surfaces and reactive end groups of linear alkanes and aromatic species using single-step deposition in supercritical carbon dioxide (SCCO2). The process is suitable for large-scale manufacturing due to short processing times, simplicity, and high resistance to oxidation. It also allows the formation of monolayers with varying reactive terminal groups, thus enabling formation of nanostructures engineered at the molecular level. Ballistic electron emission microscopy (BEEM) spectra performed on the organic monolayer on oxide-free silicon capped by a thin gold layer reveals for the first time an increase in transmission of the ballistic current through the interface of up to three times compared to a control device, in contrast to similar studies reported in the literature suggestive of oxide-free passivation in SCCO2. The SCCO2 process combined with the preliminary BEEM results opens up new avenues for interface engineering, leading to molecular electronic devices.
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Affiliation(s)
- Sreenivasa Reddy Puniredd
- †Department of Chemical and Biomolecular Engineering, National University of Singapore, Engineering Drive 4, Singapore 117576
- ‡Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602
| | - Sundaramurthy Jayaraman
- †Department of Chemical and Biomolecular Engineering, National University of Singapore, Engineering Drive 4, Singapore 117576
| | - Sai Hooi Yeong
- †Department of Chemical and Biomolecular Engineering, National University of Singapore, Engineering Drive 4, Singapore 117576
| | - Cedric Troadec
- ‡Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602
| | - M P Srinivasan
- †Department of Chemical and Biomolecular Engineering, National University of Singapore, Engineering Drive 4, Singapore 117576
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Bronstein LM, Shifrina ZB. Dendrimers as encapsulating, stabilizing, or directing agents for inorganic nanoparticles. Chem Rev 2011; 111:5301-44. [PMID: 21718045 DOI: 10.1021/cr2000724] [Citation(s) in RCA: 250] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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Kim D, Archer LA. Nanoscale organic-inorganic hybrid lubricants. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:3083-3094. [PMID: 21280594 DOI: 10.1021/la104937t] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Silica (SiO2) nanoparticles densely grafted with amphiphilic organic chains are used to create a family of organic-inorganic hybrid lubricants. Short sulfonate-functionalized alkylaryl chains covalently tethered to the particles form a dense corona brush that stabilizes them against aggregation. When these hybrid particles are dispersed in poly-α-olefin (PAO) oligomers, they form homogeneous nanocomposite fluids at both low and high particle loadings. By varying the volume fraction of the SiO2 nanostructures in the PAO nanocomposites, we show that exceptionally stable hybrid lubricants can be created and that their mechanical properties can be tuned to span the spectrum from simple liquids to complex gels. We further show that these hybrid lubricants simultaneously exhibit lower interfacial friction coefficients, enhanced wear and mechanical properties, and superior thermal stability in comparison with either PAO or its nanocomposites created at low nanoparticle loadings. Profilometry and energy dispersive X-ray spectroscopic analysis of the wear track show that the enhanced wear characteristics in PAO-SiO2 composite lubricants originate from two sources: localization of the SiO2 particles into the wear track and extension of the elastohydrodynamic lubrication regime to Sommerfeld numbers more than an order of magnitude larger than for PAO.
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Affiliation(s)
- Daniel Kim
- School of Chemical and Biomolecular Engineering, Cornell University , Ithaca, New York 14853, United States
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Abstract
A divergent fluorous mixture synthesis (FMS) of asymmetric fluorinated dendrimers has been developed. Four generations of fluorinated dendrimers with the same fluorinated moiety were prepared with high efficiency, yield, and purity. Comparison of the physicochemical properties of these dendrimers provided valuable information for their application and future optimization. This strategy has not only provided a practical method for the synthesis and purification of dendrimers, but also established the possibility of utilizing the same fluorinated moiety for FMS.
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Affiliation(s)
- Zhong-Xing Jiang
- Fischell Department of Bioengineering, University of Maryland, College Park, Maryland 20742, USA
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Puniredd SR, Nguan BCC, Srinivasan M. Covalent molecular assembly in supercritical carbon dioxide: Formation of nanoparticles in immobilized dendrimers within a porous silica gel matrix. J Colloid Interface Sci 2009; 333:679-83. [DOI: 10.1016/j.jcis.2008.10.084] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2008] [Revised: 10/02/2008] [Accepted: 10/02/2008] [Indexed: 10/21/2022]
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Puniredd SR, Yin CM, Hooi YS, Lee P, Srinivasan M. Dendrimer-encapsulated Pt nanoparticles in supercritical medium: Synthesis, characterization, and application to device fabrication. J Colloid Interface Sci 2009; 332:505-10. [DOI: 10.1016/j.jcis.2009.01.011] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2008] [Revised: 10/13/2008] [Accepted: 01/07/2009] [Indexed: 11/24/2022]
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Puniredd SR, Weiyi S, Srinivasan M. Pd–Pt and Fe–Ni nanoparticles formed by covalent molecular assembly in supercritical carbon dioxide. J Colloid Interface Sci 2008; 320:333-40. [DOI: 10.1016/j.jcis.2007.11.034] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2007] [Revised: 10/04/2007] [Accepted: 11/06/2007] [Indexed: 10/22/2022]
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