Effect of Noncovalent Basal Plane Functionalization on the Quantum Capacitance in Graphene

Ebrish, Mona A.; Olson, Eric J.; Koester, Steven J.

doi:10.1021/am5017057

Cited by 22 publications

(32 citation statements)

References 36 publications

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“…15 Surprisingly, the Cmax/Cmin ratio increases with increasing humidity, and has remarkably large values (> 1.6), approaching the highest values reported in the literature to date. 18,19 Perhaps most surprisingly, the negative shift of VDirac-avg in Figure 1g at high RH values, indicates that graphene is less p-type doped due to the effect of water molecules. This is contrary to the fact that graphene has been observed to shift more p-type in the presence of H2O, which has been previously attributed to doping of graphene by water adsorbing onto residue or defect sites in graphene.…”

Section: Device Fabrication and Capacitance Measurementsmentioning

confidence: 92%

“…15 Though the physical nature of the interaction between water and the graphene surface was not immediately clear, it was speculated that the capacitance change was due to a Dirac point shift, as has been observed in resistive graphene sensors. 8,9 However, more recent experiments suggest that water intercalated between HfO2 and graphene may also affect the capacitance behavior, 18 though these experiments were not performed under controlled atmospheric conditions.…”

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confidence: 99%

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Capacitive Sensing of Intercalated H₂O Molecules Using Graphene

Olson

Sun

et al. 2015

ACS Appl. Mater. Interfaces

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Understanding the interactions of ambient molecules with graphene and adjacent dielectrics is of fundamental importance for a range of graphene-based devices, particularly sensors, where such interactions could influence the operation of the device. It is well-known that water can be trapped underneath graphene and its host substrate, however, the electrical effect of water beneath graphene and the dynamics of how it changes with different ambient conditions has not been quantified. Here, using a metal-oxide-graphene variable-capacitor (varactor) structure, we show that graphene can be used to capacitively sense the intercalation of water between graphene and HfO2 and that this process is reversible on a fast time scale. Atomic force microscopy is used to confirm the intercalation and quantify the displacement of graphene as a function of humidity.Density functional theory simulations are used to quantify the displacement of graphene induced by intercalated water and also explain the observed Dirac point shifts as being due to the combined effect of water and oxygen on the carrier concentration in the graphene. Finally, molecular dynamics simulations indicate that a likely mechanism for the intercalation involves adsorption and lateral diffusion of water molecules beneath the graphene. § Equal contribution Keywords: graphene, sensor, varactor, capacitance, water 2 The successful exfoliation of single-layer graphene and subsequent development of chemical vapor deposition (CVD) for producing large-area graphene sheets has resulted in many interesting device applications. Its use in field-effect transistors, 1 mixers, 2 optical modulators, 3 photodetectors, 4 and a wide variety of chemical sensors is of particular note. [5][6][7][8][9] In nearly all of these device concepts, the intimate interactions between graphene and adjacent dielectrics is critical, yet has not been explored in detail. For instance, it has been shown previously, using density functional theory (DFT) simulations, that the equilibrium distance between graphene and HfO2 is 0.30 nm. 10 However, it has also been shown that this equilibrium distance can change in the presence of defects on graphene or in the adjacent dielectrics, as the defects create bonding sites that result in stronger coupling between graphene and HfO2. 10 The intimate surface interactions can become even more complex with the introduction of small molecules such as H2O, 11 which can often be trapped between the graphene and the adjacent surface. Previously, atomic-force-microscopy (AFM) studies have shown that exfoliated graphene on mica can visualize the trapped water underneath due to the displacement of graphene. 12 However, to date, these trapped molecules have only been probed using physical analysis techniques such as AFM. 12,13 It would be extremely useful if such molecular interactions could be probed using electrical techniques, as such methods could allow a greatly improved understanding of the dynamics of these processes.We have recently proposed a capacitanc...

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Section: Device Fabrication and Capacitance Measurementsmentioning

confidence: 92%

mentioning

confidence: 99%

Capacitive Sensing of Intercalated H₂O Molecules Using Graphene

Olson

Sun

et al. 2015

ACS Appl. Mater. Interfaces

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“…Therefore, the capacitance is limited by DOS and is called quantum capacitance (QC), which is smaller than C Electrolyte . The QC of pristine graphene has been investigated widely by experimental and theoretical calculations [15][16][17][18][19]. It is generally accepted that QC shows a V-like shape near the zero point potential with a value less than 10 µF/cm 2 , depending on the applied voltage range [15,17].…”

Section: Introductionmentioning

confidence: 99%

Theoretical Study on the Quantum Capacitance Origin of Graphene Cathodes in Lithium Ion Capacitors

Huo

Kong

et al. 2018

Catalysts

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Quantum capacitance (QC) is a very important character of the graphene cathode in lithium ion capacitors (LIC), which is a novel kind of electrochemical energy conversion and storage device. However, the QC electronic origin of the graphene cathode, which will affect the electrochemical reaction at the electrode/electrolyte interface, is still unclear. In this article, the QC of various kinds of graphene cathode is investigated systematically by DFT calculation. It was found that the value and origin of QC strongly depend on the defects and alien atoms of graphene. Graphene with pentagon defects possesses a higher QC than pristine graphene due to the contribution from the electronic states localized at the carbon pentagon. The introduction of graphitic B can contribute to QC, while graphitic N and P does not work in the voltage range of the LIC cathode. Single vacant defect graphene and pyrrolic N-doped graphene demonstrate very high QC due to the presence of states associated with the σ orbital of unbonded carbon atoms. However, pyridinic graphene shows an even higher QC because of the states from the N atom. For the residual O in graphene, its QC mainly originated from the pz states of carbon atoms and the effect of O, especially the O in bridged oxygen functional group (–COC–), is very limited. These results provide new insight into further study of the catalytic behavior and the design of a high performance graphene cathode for LIC.

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“…Pyrene and its derivatives take an important place in the development of advanced materials. Besides being commonly used as fluorescent materials, they are also under active studies as dispersants for dispersion of nanocarbons (i.e., carbon nanotubes and graphene) or for preparation of graphene by liquid‐phase exfoliation of graphite . Both theoretical and experimental studies reveal that the pyrenyl compounds can attach to nanocarbons through π–π interaction .…”

Section: Introductionmentioning

confidence: 99%

Synthesis of pyrene‐capped polystyrene by free radical polymerization and its application in direct exfoliation of graphite into graphene nanosheets

Wang

Chen

Xin

et al. 2015

J. Polym. Sci. Part A: Polym. Chem.

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It is of great practical significance to acquire pyrene-capped polymer, which has proven an excellent dispersant of nanocarbons, in an accessible way. Taking synthesis of pyrene-capped polystyrene (PyPS) as the example, free radical polymerization was demonstrated to be an attractive option to satisfactorily fulfill such mission. For this, a new azo-based pyrenyl compound was designed, synthesized, and used as initiator. The molecular structure of PyPS was studied as a function of polymerization temperature and content of chain transfer agent of 1-dodecanethiol. Following the successful synthesis, a PyPS polymer structured as 1.04 pyrene groups per chain was chosen as dispersant for preparation of graphene. The results showed that 0.2 mg/mL of PyPS in chloroform permits 67.4 lg/mL of graphene nanosheets to be prepared by liquid-phase exfoliation of graphite. In contrast, only 8.5 lg/mL of graphene nanosheets could be obtained in pure chloroform.

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Effect of Noncovalent Basal Plane Functionalization on the Quantum Capacitance in Graphene

Cited by 22 publications

References 36 publications

Capacitive Sensing of Intercalated H₂O Molecules Using Graphene

Capacitive Sensing of Intercalated H₂O Molecules Using Graphene

Theoretical Study on the Quantum Capacitance Origin of Graphene Cathodes in Lithium Ion Capacitors

Synthesis of pyrene‐capped polystyrene by free radical polymerization and its application in direct exfoliation of graphite into graphene nanosheets

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Effect of Noncovalent Basal Plane Functionalization on the Quantum Capacitance in Graphene

Cited by 22 publications

References 36 publications

Capacitive Sensing of Intercalated H2O Molecules Using Graphene

Capacitive Sensing of Intercalated H2O Molecules Using Graphene

Theoretical Study on the Quantum Capacitance Origin of Graphene Cathodes in Lithium Ion Capacitors

Synthesis of pyrene‐capped polystyrene by free radical polymerization and its application in direct exfoliation of graphite into graphene nanosheets

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Capacitive Sensing of Intercalated H₂O Molecules Using Graphene

Capacitive Sensing of Intercalated H₂O Molecules Using Graphene