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Sugawara M, Watanabe T, Einaga Y, Koh S. Impact of gate electrode on free chlorine sensing performance in solution-gated graphene field-effect transistors. RSC Adv 2024; 14:7867-7876. [PMID: 38449821 PMCID: PMC10915591 DOI: 10.1039/d3ra07692j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2023] [Accepted: 02/29/2024] [Indexed: 03/08/2024] Open
Abstract
Free chlorine is widely used to disinfect water used for drinking and food processing. This requires highly sensitive, simple, and capable continuous-measurement sensors to enable the concentration of free chlorine in water to be monitored and controlled. Free chlorine sensors based on solution-gated graphene field-effect transistors (GFETs) are a suitable platform for highly sensitive and continuous measurements. However, their sensing mechanisms require further elucidation to improve their performance. In this study, we focused on the gate electrode and investigated its influence on the sensing performance. Using the free chlorine sensor based on the solution-gate GFET, we showed that the Dirac point voltage in the transfer curve changed significantly as the free chlorine concentration changed, and the electric double-layer capacitance of the gate electrode decreased. Furthermore, we demonstrated that a solution-gated GFET using graphene or boron-doped diamond as the gate electrode could be used to detect changes in the free chlorine concentration in the concentration range of tap water. The sensing performance in the low concentration range benefits from the wide potential window of carbon-based electrodes, which do not have electrochemically active sites. Using these carbon-based materials as gate electrodes, GFETs have the potential to be used as durable sensors that are resistant to surface fouling and oxidation.
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Affiliation(s)
- Masato Sugawara
- Department of Electrical Engineering and Electronics, Aoyama Gakuin University 5-10-1 Fuchinobe, Chuo-ku Sagamihara 252-5258 Japan
| | - Takeshi Watanabe
- Department of Electrical Engineering and Electronics, Aoyama Gakuin University 5-10-1 Fuchinobe, Chuo-ku Sagamihara 252-5258 Japan
| | - Yasuaki Einaga
- Department of Chemistry, Keio University 3-14-1 Hiyoshi, Kohoku-ku Yokohama 223-8522 Japan
| | - Shinji Koh
- Department of Electrical Engineering and Electronics, Aoyama Gakuin University 5-10-1 Fuchinobe, Chuo-ku Sagamihara 252-5258 Japan
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Soleimani A, Risselada HJ. Pure Graphene Acts as an "Entropic Surfactant" at the Octanol-Water Interface. ACS NANO 2023; 17:13554-13562. [PMID: 37432037 PMCID: PMC10373651 DOI: 10.1021/acsnano.3c02107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Accepted: 05/24/2023] [Indexed: 07/12/2023]
Abstract
Graphene oxide (GO) has proved itself as a nanomaterial capable of acting as a surfactant by lowering the interfacial tension of the oil-water interface due to its polar oxygen groups. However, the surfactant behavior of the pure graphene sheet─since prevention of edge oxidation in experimental setups is nontrivial─is still an unresolved issue in graphene research despite significant progress in the field in recent years. Here, we conduct both atomistic and coarse-grained simulations to demonstrate that─surprisingly─even pristine graphene, which only consists of hydrophobic carbon atoms, is attracted to the octanol-water interface and consequently reduces its surface tension by 2.3 kBT/nm2 or about 10 mN/m. Interestingly, the location of the free energy minimum is not precisely at the oil-water interface itself but is rather buried about two octanol layers into the octanol phase, being about 0.9 nm from the water phase. We demonstrate that the observed surfactant behavior is purely entropically driven and can be attributed to the unfavorable lipid-like structuring of octanol molecules at the free octanol-water interface. In essence, graphene enhances the inherent lipid-like behavior of octanol at the water interface rather than directly acting as a surfactant. Importantly, graphene does not display surfactant-like behavior in corresponding Martini coarse-grained simulations of the octanol-water system since the free liquid-liquid interface loses essential structure at the lower coarse-grained resolution. However, a similar surfactant behavior is recovered in coarse-grained simulations of longer alcohols such as dodecan-1-ol and hexadecan-1-ol. The observed discrepancies at different model resolutions enable us to construct a comprehensive model of the surfactant behavior of graphene at the octanol-water interface. The here-gained insights may facilitate the broader utilization of graphene in numerous domains of nanotechnology. Furthermore, since a drug's octanol-water partition coefficient is a crucial physicochemical parameter in rational drug discovery, we also believe that the universality of the here-illustrated entropic surfactant behavior of planar molecules deserves special attention in the drug design and development field.
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Affiliation(s)
- Alireza Soleimani
- Institute
for Theoretical Physics, Georg-August-University
Göttingen, Göttingen 37077, Germany
- Department
of Physics, Technical University Dortmund, Dortmund 44221, Germany
| | - Herre Jelger Risselada
- Institute
for Theoretical Physics, Georg-August-University
Göttingen, Göttingen 37077, Germany
- Faculty
of Science, Leiden Institute of Chemistry, Leiden University, Einsteinweg
55, 2333CC, Leiden, The Netherlands
- Department
of Physics, Technical University Dortmund, Dortmund 44221, Germany
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Xu C, Zhang S, Du H, Xue T, Kang Y, Zhang Y, Zhao P, Li Q. Revisiting Frictional Characteristics of Graphene: Effect of In-Plane Straining. ACS APPLIED MATERIALS & INTERFACES 2022; 14:41571-41576. [PMID: 36043243 DOI: 10.1021/acsami.2c10449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Supreme mechanical performance and tribological properties render graphene a promising candidate as a surface friction modifier. Recently, it has been demonstrated that applying in-plane strain can effectively tune friction of suspended graphene in a reversible manner. However, since graphene is deposited on solid surfaces in most tribological applications, whether such operation will result in a similar modulation effect becomes a critical question to be answered. Herein, by depositing graphene onto a stretchable substrate, the frictional characteristics of supported graphene under a wide range of strain are examined with an in situ tensile loading platform. The experimental results show that friction of supported graphene decreases with increasing graphene strain, similar to the suspended system. However, depending on the adherence state of the graphene/substrate interface, the system exhibits two distinct friction regimes with significantly different strain dependences. Assisted by detailed atomic force microscopy imaging, we attribute the unique behavior to the transition between two friction modulation modes, i.e., contact-quality-dominated friction and puckering-dominated friction. This work provides a more comprehensive view of the influence of strain on surface friction of graphene, which is beneficial for active modulation of graphene friction through strain engineering.
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Affiliation(s)
- Chaochen Xu
- Applied Mechanics Laboratory, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, PR China
- State Key Laboratory of Tribology in Advanced Equipment, Tsinghua University, Beijing 100084, PR China
| | - Shuai Zhang
- Applied Mechanics Laboratory, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, PR China
- State Key Laboratory of Tribology in Advanced Equipment, Tsinghua University, Beijing 100084, PR China
| | - Hongzhi Du
- Tianjin Key Laboratory of Modern Engineering Mechanics, School of Mechanical Engineering, Tianjin University, Tianjin 300072, PR China
| | - Tao Xue
- Center for Analysis and Test, Tianjin University, Tianjin 300072, PR China
| | - Yilan Kang
- Tianjin Key Laboratory of Modern Engineering Mechanics, School of Mechanical Engineering, Tianjin University, Tianjin 300072, PR China
| | - Yang Zhang
- Center for X-Mechanics and Institute of Applied Mechanics, Zhejiang University, Hangzhou 310012, PR China
| | - Pei Zhao
- Center for X-Mechanics and Institute of Applied Mechanics, Zhejiang University, Hangzhou 310012, PR China
| | - Qunyang Li
- Applied Mechanics Laboratory, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, PR China
- State Key Laboratory of Tribology in Advanced Equipment, Tsinghua University, Beijing 100084, PR China
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Kim E, Kim D, Kwak K, Nagata Y, Bonn M, Cho M. Wettability of graphene, water contact angle, and interfacial water structure. Chem 2022. [DOI: 10.1016/j.chempr.2022.04.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Thangasamy P, Nam S, Oh S, Randriamahazaka H, Oh IK. Boosting Oxygen Evolution Reaction on Metallocene-based Transition Metal Sulfides Integrated with N-doped Carbon Nanostructures. CHEMSUSCHEM 2021; 14:5004-5020. [PMID: 34463051 DOI: 10.1002/cssc.202101469] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 08/10/2021] [Indexed: 06/13/2023]
Abstract
In this study, utilizing metallocene and organosulfur chelating agent, an innovative synthetic route was developed towards electrochemically activated transition metal sulfides entrapped in pyridinic nitrogen-incorporated carbon nanostructures for superior oxygen evolution reaction (OER). Most importantly, the preferential electrochemical activation process, which consisted of both anodic and cathodic pre-treatment steps, strikingly enhanced OER and long-lasting cyclic stability. The substantial increase in OER electrocatalytic activity of Ni9 S8 /Ni3 S2 -NC and Co9 S8 -NC during the activation process was mainly attributed to the increase of faradaic active site density on the catalytic layer resulting from the reconstruction of catalytic interfaces. It was also found that Fe-based metallocene [ferrocene (Fc)]-incorporation in the Co9 S8 -NC and Ni9 S8 /Ni3 S2 -NC nanostructures significantly boosted the OER activity. Thus, the combined effects of Fc-incorporation and the electrochemical activation process reduced the overpotential to about 115 and 95 mV on the Ni9 S8 /Ni3 S2 -NC and Co9 S8 -NC nanostructures to derive a current density of 10 mA cm-2 , respectively. Notably, Fc-Ni9 S8 /Ni3 S2 -NC electrocatalysts required very small overpotentials of around 222, 244, and 280 mV to acquire the current densities of 10, 20, and 50 mA cm-2 , respectively. This work opens up a new avenue for superior OER electrocatalysts by the utilization of metallocene and the preferential electrochemical activation process.
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Affiliation(s)
- Pitchai Thangasamy
- National Creative Research Initiative for Functionally Antagonistic Nano-Engineering, Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - Sanghee Nam
- National Creative Research Initiative for Functionally Antagonistic Nano-Engineering, Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - Saewoong Oh
- National Creative Research Initiative for Functionally Antagonistic Nano-Engineering, Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | | | - Il-Kwon Oh
- National Creative Research Initiative for Functionally Antagonistic Nano-Engineering, Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
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Abstract
AbstractGraphene as a two-dimensional material is prone to hydrocarbon contaminations, which can significantly alter its intrinsic electrical properties. Herein, we implement a facile hydrogenation-dehydrogenation strategy to remove hydrocarbon contaminations and preserve the excellent transport properties of monolayer graphene. Using electron microscopy we quantitatively characterized the improved cleanness of hydrogenated graphene compared to untreated samples. In situ spectroscopic investigations revealed that the hydrogenation treatment promoted the adsorption ofytyt water at the graphene surface, resulting in a protective layer against the re-deposition of hydrocarbon molecules. Additionally, the further dehydrogenation of hydrogenated graphene rendered a more pristine-like basal plane with improved carrier mobility compared to untreated pristine graphene. Our findings provide a practical post-growth cleaning protocol for graphene with maintained surface cleanness and lattice integrity to systematically carry a range of surface chemistry in the form of a well-performing and reproducible transistor.
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