ZnO/Silicon Nanowire Hybrids Extended-Gate Field-Effect Transistors as pH Sensors

Huang, Bohr–Ran; Lin, Jing-Chie; Yang, Yong

doi:10.1149/2.110306jes

Cited by 27 publications

(23 citation statements)

References 31 publications

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“…[24][25][26][27][28][29][30] Concretely speaking, the pH sensing mechanism relies on the establishment of a surface equilibrium between the metal (M) and its oxide (MOx) when in contact with the test medium:…”

Section: Resultsmentioning

confidence: 99%

The Effects of Antimony Thin Film Thickness on Antimony pH Electrode Coated with Nafion Membrane

Zhang

Hou

et al. 2016

J. Electrochem. Soc.

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A new antimony pH electrode by employing magnetron sputtering Sb thin film on copper substrates inlaying in printed circuit board (PCB) was developed. To improve the performance of the electrode, nafion membrane was employed as an alternative modification layer. The layer was formed simply by drop casting 5 wt% nafion solutions and drying the resultant coating. Further, the effect of the thickness of the Sb sensing thin film on the performance of antimony pH electrodes was investigated. Surface morphology, energy spectrum, and electrochemical experiments were conducted in Sb thin film thickness of ∼50, ∼150, ∼240, and ∼330 nm. Experimental results demonstrated excellent features of the pH electrodes with ∼240 nm thickness Sb thin film, including high sensitivity, short response time, high resolution, stability, reversibility, and long-term stability. The pH electrode is low cost, high performance, and simple preparation, is promising to popularize in laboratory and industrial production.As a typical electrochemical sensor, pH sensor has been received much attention in various fields, such as food spoilage monitoring, water pollution monitoring, soil pollution monitoring, biomedical sensing, industrial and chemical processing and structural health monitoring, where pH measurements are vital for the characterization of aqueous solutions. 1 Currently the most widely used technique for determination of pH in laboratory is the glass pH electrode. While the performance of the glass electrodes is excellent in terms of high sensitivity, long-term stability, high ion selectivity and wide operating range, such electrodes have many disadvantages including mechanical fragile, need for wet storage, large size, limited shape, high impedance and high cost. 2,3 Drawbacks of glass electrodes have led to intensive research for alternative pH electrodes. Potentiometric metal/metal oxide electrodes have proven to be some of the most promising candidates. 4 Various metals and metal oxides, such as Ti/TiO 2 , Zr/ZrO 2 , W/WO 3 , Ir/IrO 2 , Sb/Sb 2 O 3 , Ru/RuO 2 , and Pd/PdO, have been investigated for pH electrodes due to important attractive features, such as insolubility, mechanical strength, electro catalyst, stability, and manufacturing technology. 1,5-8 Among them, Ir/IrO 2 , Ru/RuO 2 , and Sb/Sb 2 O 3 have been popular research points recently. Some relative studies have been conducted in last decade.For Ir/IrO 2 , many groups tried to fabricate the iridium oxide electrode with some different manufacturing methods, for example, a novel melt-oxidized method, a new carbonate melt oxidation method, the electrodeposited method, the sol-gel fabrication process, and so on. 4,6,[9][10][11] For Ru/RuO 2 , Maurya et al. designed a miniaturized pH sensor employing an R. F. sputtered RuO 2 thin-film electrode in conjunction with an electroplated Ag/AgCl reference electrode, and some factors, such as temperature effects, Ar/O 2 flow ratio, and electrode thickness, were studied. The ruthenium oxide thin-film electrodes were applied in engin...

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Section: Resultsmentioning

confidence: 99%

The Effects of Antimony Thin Film Thickness on Antimony pH Electrode Coated with Nafion Membrane

Zhang

Hou

et al. 2016

J. Electrochem. Soc.

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“…When pH decreases, the H + concentration in the medium increases, which is equivalent to applying an extra potential in the gate oxide 23 which is proportional to the amount of charge adsorbed onto the oxide surface (Figure 2b). 24,25 Therefore, due to the potential that arises from the adsorbed ions at the FTO surface, for lower pHs of the medium the same arbitrary current can be achieved for smaller V Ref values. An analytical curve was made for a fixed I DS current of 2 mA and the result is shown in the inset of Figure 2b.…”

Section: Methodsmentioning

confidence: 95%

Urea Detection Using Commercial Field Effect Transistors

Silva

Mulato

2018

ECS J. Solid State Sci. Technol.

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We used an easy method to assemble a biosensor using simple and low cost materials. Commercial SnO 2 :F thin films were used as the basic sensing part of an extended-gate ion-sensitive field effect transistor. When used as a pH sensor, the oxide film showed a sensitivity of 59 ± 4 mV.pH −1 , and linear response in the pH range 2.0 to 10.0. Since urea detection and quantification is important for the control of many pathologies, as proof of concept the samples were further used as platform for urea sensing by immobilizing urease protein onto the surface of the film. For urea sensing, the modified electrodes showed a linear response in the pUrea range of 2.1 to 3.0 (1.00 mM to 7.94 mM, which covers a suitable screening interval for clinical exams) and a sensitivity of 109 ± 3 mV.pUrea −1 . A steady-state was reached after about 60 seconds. Varied pHs and buffer concentrations were also investigated to assess the biosensor behavior toward changes in the environmental conditions. The proposed device could be applied in clinical trials in developing countries as well as in areas hit by natural disasters. Its fabrication consists in the removal of the gate electrode of a MOS-FET, thus exposing the oxide insulator layer to an electrolyte solution. The device is then liquid-gated by a reference electrode immersed in the same solution. Therefore, the gate-source potential (V GS ), which modulates the drain-source current (I DS ), has a contribution due to the reference electrode (V Ref ) and a parcel provided by ions adsorbed at the oxide surface in the inner Helmholtz plane of the Stern-GouyChapman model of the electrical double layer, as given by the site binding model. 2,3The possibility of mass fabrication and miniaturization using thin film technology turned ISFET into a new research field. Van der Spiegel et al., and further Chi et al. developed and upgraded the concept of Extended Gate Field Effect Transistor (EGFET). 4,5 In this design, the sensing element was built apart of the FET structure, solving limitations regarding system encapsulation that arises due to the FET close contact with the electrolyte solution. Furthermore, EGFET permits to obtain a new device by only replacing the sensitive film instead of the complete electronic component, which facilitates its fabrication and disposability. 5With the combination of the ISFET concept and the enzyme electrode proposed by Clark and Lyons, Janata and Caras introduced the Enzymatic Field Effect Transistor (EnFET).6,7 Selectivity toward penicillin was conferred to a pH sensitive field effect transistor through penicillinase enzyme immobilization at the gate of an ISFET. Penicillinase catalyzes the hydrolysis of penicillin to penicilloic acid, which releases protons thus depressing the pH at the surface of the oxide electrode. This charge variation promoted by the end products of the catalyzed reaction could be used as the main parameter for EnFET operation.

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“…ZnO NWs are widely adopted for bio/chemical sensors due to the advantages of ultralow detection limit, fast response, and impressive biocompatibility [42][43][44][45]. Liu et al [46] synthesized a single ZnO NWbased biologically sensitive sensor for detection of different concentrations of uric acid solution.…”

Section: Bio/chemical-ocznssmentioning

confidence: 99%

Recent Progress in Ohmic/Schottky‐Contacted ZnO Nanowire Sensors

Zhao

Zhou

Hua

et al. 2015

Journal of Nanomaterials

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We review the recent progress of zinc oxide (ZnO) nanowire sensors with ohmic-contacted and Schottky-contacted configurations and the enhancement of the performances of Schottky-contacted ZnO NW sensors (SCZNSs) by the piezotronic effect. Comparing with the traditional ohmic-contacted ZnO NW sensors (OCZNSs), the SCZNSs have higher sensitivities and faster responses controlled by the barrier height at the metal-semiconductor (M-S) interface. The piezotronic effect was applied to tune the Schottky barrier height (SBH) with the strain-induced piezoelectric polarization charges at the interface of the M-S contact. The piezotronic effect can thus improve the detection limitation, sensitivity, and response time of the SCZNSs in different applications, such as UV detection, gas and bio/chemical sensing. These piezotronic-enhanced SCZNSs may find potential applications in human-machine interfacing and flexible electronics skin technologies.

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ZnO/Silicon Nanowire Hybrids Extended-Gate Field-Effect Transistors as pH Sensors

Cited by 27 publications

References 31 publications

The Effects of Antimony Thin Film Thickness on Antimony pH Electrode Coated with Nafion Membrane

The Effects of Antimony Thin Film Thickness on Antimony pH Electrode Coated with Nafion Membrane

Urea Detection Using Commercial Field Effect Transistors

Recent Progress in Ohmic/Schottky‐Contacted ZnO Nanowire Sensors

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