Analytical modelling of monolayer graphene-based ion-sensitive FET to pH changes
© Kiani et al.; licensee Springer. 2013
Received: 22 January 2013
Accepted: 2 March 2013
Published: 16 April 2013
Graphene has attracted great interest because of unique properties such as high sensitivity, high mobility, and biocompatibility. It is also known as a superior candidate for pH sensing. Graphene-based ion-sensitive field-effect transistor (ISFET) is currently getting much attention as a novel material with organic nature and ionic liquid gate that is intrinsically sensitive to pH changes. pH is an important factor in enzyme stabilities which can affect the enzymatic reaction and broaden the number of enzyme applications. More accurate and consistent results of enzymes must be optimized to realize their full potential as catalysts accordingly. In this paper, a monolayer graphene-based ISFET pH sensor is studied by simulating its electrical measurement of buffer solutions for different pH values. Electrical detection model of each pH value is suggested by conductance modelling of monolayer graphene. Hydrogen ion (H+) concentration as a function of carrier concentration is proposed, and the control parameter (Ƥ) is defined based on the electro-active ions absorbed by the surface of the graphene with different pH values. Finally, the proposed new analytical model is compared with experimental data and shows good overall agreement.
Figure 2 illustrates the detection mechanism of solution with different pH using an ISFET device. Monolayer graphene on silicon oxide and silicon substrate with a deposited epoxy layer (Epotek 302–3 M, Epoxy Technology, Billerica, MA, USA) as an ISFET membrane is proposed. In this paper, pH of solution as a gate voltage is replicated due to the carrier injected to channel from it, and also pH as a sensing parameter () is suggested. Finally, the presented model is compared with experimental data for purposes of validation.
By applying gate voltage between 0.2 and 0.7 V, a bipolar characteristic of FET device is monitored since the Fermi energy can be controlled by gate voltage. Based on this characteristic, it is notable that the graphene can be continuously dropped from the p-doped to the n-doped region by the controllable gate voltage. The minimum conductance is observed at the transition point between electron and hole doping. This conjunction point is called the charge-neutrality point (CNP) . The conductance of the ISFET channel not only is dependent on the graphene structure and operation voltage on the source-drain channel, but also depends on the electrolyte environment and ion concentration in solution [42, 43]. It has been demonstrated that different pH values can affect the ISFET conductance .
Different pH values with Ƥ parameter
Ƥ parameter values
It is evident that the G-Vg characteristic curve can be controlled by the pH factor () and also the proposed model of ISFET conductance closely matches with experimental data. In both reported data and theoretical data, the decline of ISFET conductance is noticeable when the pH level increases. Also, the conductance curve is almost symmetric near VCNP, while at a large carrier concentration of about 350 to 400 μS, a saturation behavior is depicted. Comparing both experimental data and theoretical data depicted in Figure 5 reveals that when the concentration of hydrogen ions changes from pH = 7 to pH = 8, ISFET conductance decreases about 5 μS. Also, as shown in Figure 8a,b,c, each graph shows a particular value of pH. For example, when the pH value is 8, it is notable that the model is closer to the blue line (experimental data), and also in the different pH values, we can compare other ion concentrations as well. An innovative analysis of matching models using the different values in experimental data is presented in this work to verify that the conductivity of the graphene-based ISFET is moved down vertically at higher pH values. The ion-sensitive FET structure was used with monolayer graphene prepared by CVD and grown in large size on pieces of p-doped Si covered with a 300-nm substrate to measure pH changes . In this study, one can claim that pH changes in the electro-active membrane will significantly and vertically shift the value of conductance in graphene (Gwith pH) that occurred due to ion adsorption on the surface area of the monolayer graphene sheet of the ISFET channel. Also, it is notable that the temperature remains constant (about 25°C in solution) in the suggested model as the temperature can have an effect on the behavior of the sensing parameter as well.
Graphene with sp2-bonded carbon atoms has considerable potential on bio-sensing materials and electrochemical applications. The emerging potentials of nanostructured graphene-based ISFETs with high sensitivity and ability to readily detect have been applied to electrochemical catalysis through pH sensing. The conductance of an ISFET device with different pH values can be displayed by the ion concentration of the solution. In this research, the conductance of graphene is assumed as a function of pH levels (Gwith pH ≈ pH), which shows the pH factor. Measurements show decreasing conductivity when the pH value of the electrolyte is increased. Especially in VCNP, the changed conductance values are clearly depicted. The suggested model verifies the reported experimental data as well. In other words, based on the good agreement between the presented analytical model and experimental data, can be seen as a pH factor to predict graphene behavior in graphene-based ISFETs.
The authors would like to acknowledge the financial support from the Research University grant of the Ministry of Higher Education (MOHE), Malaysia, under Project Q.J130000.7123.02H24. Also, thanks to the Research Management Center (RMC) of Universiti Teknologi Malaysia (UTM) for providing excellent research environment in which to complete this work.
- Wen Xu YG, Liwei L, Hua Q, Yanli S: Can graphene make better HgCdTe infrared detectors? Nanoscale Res Lett 2011, 6: 250. 10.1186/1556-276X-6-250View ArticleGoogle Scholar
- Carmelo Vecchio SS, Corrado B, Rambach M, Rositza Y, Raineri V, Filippo G: Nanoscale structural characterization of epitaxial graphene grown on off-axis 4H-SiC (0001). Nanoscale Res Lett 2011, 6: 269. 10.1186/1556-276X-6-269View ArticleGoogle Scholar
- An XS, Trevor John S, Rakesh W, Christopher L, Washington KM, Morris N, Talapatra SK, Saikat K, Swastik Q: Stable aqueous dispersions of noncovalently functionalized graphene from graphite and their multifunctional high-performance applications. Nano Lett 2010, 10(11):4295–4301. 10.1021/nl903557pView ArticleGoogle Scholar
- Myung SS, Aniruddh K, Cheoljin P, Jaesung K, Lee KS, Ki-Bum : Graphene-encapsulated nanoparticle-based biosensor for the selective detection of cancer biomarkers. Adv Mater 2011, 23(19):2221–2225. 10.1002/adma.201100014View ArticleGoogle Scholar
- Phan AD, Viet NA: A new type of optical biosensor from DNA wrapped semiconductor graphene ribbons. J Appl Phys 2012, 111(11):114703. 10.1063/1.4728196View ArticleGoogle Scholar
- Pham MTH, Kunath S, Kurth C, Köhler E, Howitz S: Backside membrane structures for ISFETs applied in miniature analysis systems. Sensors and Actuators B: Chemical 1994, 19(1–3):333–335.View ArticleGoogle Scholar
- Gotoh M, Suzuki M, Kubo I, Tamiya E, Karube I: Immuno-FET sensor. J Mol Catal 1989, 53(3):285–292. 10.1016/0304-5102(89)80063-XView ArticleGoogle Scholar
- Schlesinger R, Bruns M, Becht R, Dosenbach S, Hoffmann W, Ache HJ: ISFETs with sputtered sodium alumino-silicate glass membranes. Fresenius J Anal Chem 1996, 354(7–8):852–856.Google Scholar
- Lee D, Cui T: An electric detection of immunoglobulin G in the enzyme-linked immunosorbent assay using an indium oxide nanoparticle ion-sensitive field-effect transistor. J Micromech Microeng 2012, 22(1):015009. 10.1088/0960-1317/22/1/015009View ArticleGoogle Scholar
- Chen SC, Su Y-K, Tzeng JS: The fabrication and characterisation of ion-sensitive field-effect transistors with a silicon dioxide gate. J Phys D: Appl Phys 1986, 19(10):1951. 10.1088/0022-3727/19/10/020View ArticleGoogle Scholar
- Shepherd L, Toumazou C: Weak inversion ISFETs for ultra-low power biochemical sensing and real-time analysis. Sensors and Actuators B: Chemical 2005, 107(1):468–473. 10.1016/j.snb.2004.11.006View ArticleGoogle Scholar
- Chung W-YL, Yeong-Tsair P, Yang DG, Chung-Huang W, Ming-Chia K, Alfred T, Wladyslaw Q: ISFET interface circuit design with temperature compensation. Microelectron J 2006, 37(10):1105–1114. 10.1016/j.mejo.2006.05.001View ArticleGoogle Scholar
- Kal SB, Bhanu PV: Design and modeling of ISFET for pH sensing. In Proceedings of TENCON 2007–2007 IEEE Region 10 Conference: October 30 - November 2; Taipei. Piscataway: IEEE; 2007:1–4.Google Scholar
- Voigt H, Schitthelm F, Lange T, Kullick T, Ferretti R: Diamond-like carbon-gate pH-ISFET. Sensors and Actuators B: Chemical 1997, 44(1–3):441–445.View ArticleGoogle Scholar
- Reinhoudt DNS, Ernst JR: The transduction of host-guest interactions into electronic signals by molecular systems. Adv Mater 1990, 2(1):23–32. 10.1002/adma.19900020105View ArticleGoogle Scholar
- Cobben PLHME, Bomer RJM, Bergveld JG, Piet V, Willem R, David N: Transduction of selective recognition of heavy metal ions by chemically modified field effect transistors (CHEMFETs). J Am Chem Soc 1992, 114(26):10573–10582. 10.1021/ja00052a063View ArticleGoogle Scholar
- Guth U, Gerlach F, Decker M, Oelßner W, Vonau W: Solid-state reference electrodes for potentiometric sensors. Journal of Solid State Electrochemistry 2009, 13(1):27–39. 10.1007/s10008-008-0574-7View ArticleGoogle Scholar
- Cadogan A, Gao Z, Lewenstam A, Ivaska A, Diamond D: All-solid-state sodium-selective electrode based on a calixarene ionophore in a poly(vinyl chloride) membrane with a polypyrrole solid contact. Anal Chem 1992, 64(21):2496–2501. 10.1021/ac00045a007View ArticleGoogle Scholar
- Jiménez C, Bartroli J: Development of an ion-sensitive field effect transistor based on PVC membrane technology with improved long-term stability. Electroanalysis 1997, 9(4):316–319. 10.1002/elan.1140090411View ArticleGoogle Scholar
- Bratov A, Muñoz J, Dominguez C, Bartrolí J: Photocurable polymers applied as encapsulating materials for ISFET production. Sensors and Actuators B: Chemical 1995, 25(1–3):823–825.View ArticleGoogle Scholar
- Kuang B, Mahmood HS, Quraishi MZ, Hoogmoed WB, Mouazen AM, van Henten EJ: Chapter four - sensing soil properties in the laboratory, in situ, and on-line: a review. In Advances in Agronomy. Edited by: Donald LS. Waltham: Academic; 2012:155–223.Google Scholar
- Seymour RB: Plastics. Ind Eng Chem 1966, 58(8):61–73. 10.1021/ie50680a011View ArticleGoogle Scholar
- Cecilia JJJ, Orozco A, Baldi Q: ISFET based microsensors for environmental monitoring. Sensors (Basel, Switzerland) 2009, 10(1):1. 10.3390/s100100001View ArticleGoogle Scholar
- Chung WY, Cruz FRG, Szu H, Pijanowska DG, Dawgul M, Torbicz W, Grabiec PB, Jarosewicz B, Chiang J-L, Chang KC, Cheng C, Ho W-P: ISFET electronic tongue system for environmental multi-ion sensing with independent component analysis signal processing. In Independent Component Analyses, Wavelets, Neural Networks, Biosystems, and Nanoengineering VII. Edited by: Szu HH, Agee FJ. Bellingham: SPIE; 2009:73431D.View ArticleGoogle Scholar
- Haigang Yang HS, Jinghong H, Jinbao W, Zengjin L, Shanhong X, Hua Z: A pH-ISFET based micro sensor system on chip using standard CMOS technology. In Proceedings of the Fifth International Workshop on System-on-Chip for Real-Time Applications: Banff; July 20–24, 2005. Piscataway: IEEE Computer Society; 2005:180–183.Google Scholar
- Lee D, Cui T: pH-dependent conductance behaviors of layer-by-layer self-assembled carboxylated carbon nanotube multilayer thin-film sensors. J Vac Sci Technol 2009, 27(2):842. 10.1116/1.3002386View ArticleGoogle Scholar
- Martinoia S, Massobrio P: ISFET–neuron junction: circuit models and extracellular signal simulations. Biosens Bioelectron 2004, 19(11):1487–1496. 10.1016/j.bios.2003.12.003View ArticleGoogle Scholar
- Bousse L, Bergveld P: The role of buried OH sites in the response mechanism of inorganic-gate pH-sensitive ISFETs. Sensors and Actuators 1984, 6(1):65–78. 10.1016/0250-6874(84)80028-1View ArticleGoogle Scholar
- Steinhoff G, Hermann M, Schaff WJ, Eastman LF, Stutzmann M, Eickhoff M: pH response of GaN surfaces and its application for pH-sensitive field-effect transistors. Appl Phys Lett 2003, 83(1):177–179. 10.1063/1.1589188View ArticleGoogle Scholar
- Pijanowska D, Torbicz W: Simple method of enzyme immobilization for pH-ISFET-based urea biosensors. In Optoelectronic and Electronic Sensors II. Bellingham: SPIE; 1997:219–226.View ArticleGoogle Scholar
- Jamasb S, Collins SD, Smith RL: Correction of instability in ion-selective field effect transistors (ISFETs) for accurate continuous monitoring of pH. In Proceedings of the 19th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 1997: Chicago; October 30-November 2, 1997. Piscataway: IEEE; 1997:2337–2340.Google Scholar
- Couto SR, Moldes D, Sanromán MA: Optimum stability conditions of pH and temperature for ligninase and manganese-dependent peroxidase from Phanerochaete chrysosporium . Application to in vitro decolorization of Poly R-478 by MnP. World J Microbiol Biotechnol 2006, 22(6):607–612. 10.1007/s11274-005-9078-0View ArticleGoogle Scholar
- Pokhrel S, Joo JC, Kim YH, Yoo YJ: Rational design of a Bacillus circulans xylanase by introducing charged residue to shift the pH optimum. Process Biochem 2012, 47(12):2487–2493. 10.1016/j.procbio.2012.10.011View ArticleGoogle Scholar
- Morgenshtein A, Sudakov-Boreysha L, Dinnar U, Jakobson CG, Nemirovsky Y: Wheatstone-Bridge readout interface for ISFET/REFET applications. Sens Actuators B Chem 2004, 98(1):18–27. 10.1016/j.snb.2003.07.017View ArticleGoogle Scholar
- Chen S, Zhang Z-B, Laipeng M, Ahlberg P, Gao X, Qui Z, Wu D, Ren W, Cheng H-M, Zhang S-L: A graphene field-effect capacitor sensor in electrolyte. Appl Phys Lett 2012, 101(15):154106–154105. 10.1063/1.4759147View ArticleGoogle Scholar
- Zhao Y, Song X, Song Q, Yin Z: A facile route to the synthesis copper oxide/reduced graphene oxide nanocomposites and electrochemical detection of catechol organic pollutant. CrystEngComm 2012, 14(20):6710–6719. 10.1039/c2ce25509jView ArticleGoogle Scholar
- Adam S, Das Sarma S: Transport in suspended graphene. Solid State Communications 2008, 146(9–10):356–360.View ArticleGoogle Scholar
- Datta S: Electronic Transport in Mesoscopic Systems. Cambridge: Cambridge University Press; 2002.Google Scholar
- Datta S: Quantum Transport: Atom to Transistor. New York: Cambridge University Press; 2005.View ArticleGoogle Scholar
- Peres NMR, Castro Neto AH, Guinea F: Conductance quantization in mesoscopic graphene. Phys Rev B 73 2006, 195411: 2006.Google Scholar
- Moriconi L, Niemeyer D: Graphene conductivity near the charge neutral point. Physical Review B 2011, 84(19):193401.View ArticleGoogle Scholar
- Fu W, Nef C, Knopfmacher O, Tarasov A, Weiss M, Calame M, Schönenberger C: Graphene transistors are insensitive to pH changes in solution. Nano Lett 2011, 11(9):3597–3600. 10.1021/nl201332cView ArticleGoogle Scholar
- Bonanni AL, Adeline Hulling Pumera M: Graphene for impedimetric biosensing. Trac-Trends in Analytical Chemistry 2012, 37: 12–21.View ArticleGoogle Scholar
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