Highly sensitive pressure sensor based on graphene

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Feb 22, 2018 - reported a wearable and highly sensitive pressure sensor with ultrathin gold nanowires, which was able to show fast response time (< 17 ms), ...

Accepted Manuscript Original article Highly sensitive pressure sensor based on graphene hybrids Mahesh Vaka, Ming Zhe Bian, Nguyen Dang Nam PII: DOI: Reference:

S1878-5352(18)30048-0 https://doi.org/10.1016/j.arabjc.2018.02.009 ARABJC 2259

To appear in:

Arabian Journal of Chemistry

Received Date: Accepted Date:

11 November 2017 22 February 2018

Please cite this article as: M. Vaka, M. Zhe Bian, N. Dang Nam, Highly sensitive pressure sensor based on graphene hybrids, Arabian Journal of Chemistry (2018), doi: https://doi.org/10.1016/j.arabjc.2018.02.009

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Highly sensitive pressure sensor based on graphene hybrids Mahesh Vaka1,2, Ming Zhe Bian3, Nguyen Dang Nam4,* 1

School of Life and Environmental Sciences, Deakin University, Victoria 3220, Australia 2

School of Science, RMIT University, Melbourne, Victoria 3001, Australia

3

National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047, Japan

4

Petroleum Department, Petrovietnam University, Ba Ria City, Ba Ria - Vung Tau Province 74000, Vietnam *E-mail addresses: [email protected] and [email protected]

ABSTRACT In this work, we report a novel free-standing graphene (Gr) hybrid materials consisting of functionalized AuNPs sandwiched between two graphene sheets, where the film sensor formation is based on layer by layer deposition through vacuum filtration. The sensor offers highly conductivity, high sensing with short response time, high sensitivity, stability and life time durability. The construct of hybrid film favors the conducting pathways for charge transport and a decrease in charge transfer resistance is clearly observed through electrochemical study. The sensing experiments shows high sensitivity of 5 × 10-4 kPa-1 with short response time of AuNPs > Gr+ functionalized AuNPs, indicating that a decrease in Rct value strongly enhances conductivity. Cyclic Voltammetry was also used for determining the surface coverage of the Au substrate, graphene, AuNPs, and Gr+ functionalized AuNPs specimens in 1 M KCl solution and the results are given in Fig. 6. A significant increase of the current density was obtained from the gold substrate > Gr > AuNPs > Gr+ functionalized AuNPs, suggesting an enhance of conductivity consistent with the results observed in EIS results. In addition, the significant decrease of the current density of 100th cycle in

comparison with the first cycle was obtained from gold substrate, Gr, and AuNPs specimens, indicating instability of these specimens, while the insignificant difference of the current density of 100th cycle was performed in Gr+ functionalized AuNPs specimen, suggesting stability of this specimen attributed to the strongly bound to Gr in both oxidation and reduction states.

Figure 6 First and 100th cycles of cyclic voltammetry reults for (a) gold substrate, (b) graphene coating, (c) AuNPs coating, and (d) Gr+ functionalised AuNPs coating in 1 M KCl solution. The curves were recorded by scanning from -0.6 to 0.6 VAg/AgCl at a sweeping rate of 10 mV/s.

Furthermore, gold substrate and Gr was electrochemically inactive between -0.5 to +0.5 VAg/AgCl, whereas AuNPs and Gr+ functionalized AuNPs performed peaks for both oxidation and reduction, attributing to the reduction at -0.22 V mVAg/AgCl and oxidation at 0.18 mVAg/AgCl. The coverage of gold substrate, Gr, AuNPs, and Gr+ functionalized AuNPs specimens were calculated by integrating the area under the oxidation curve to determine the charge associated. The calculation of surface charge density (Q) is based on the equation44. Electrochemical active surface area (ECSA) = 0.1 Q/(m × Qo) where m is the loading amount of sample on the Au electrode, Q is the surface charge can be measured by calculating the integrated area under the peaks around -0.6 V to 0.6 V, Qo is the electric charge of monolayer oxygen onto the Au electrode assumed to be 450 µC/cm2. Maximum surface coverage was found to be 8.37 × 10-4 g/cm2 for Gr+ functionalized AuNPs specimen, proving the electrostatic interaction between graphene and functionalized AuNPs which is consistent with the above results. After, graphene hybrids were characterized, they were tested for sensor applications and to measure the response of graphene hybrid based sensor to range of weights. Our sensor showed a good response when compared with normal graphene film by applying different weights (100-800 mN-1). Different loading and unloading experiments under different pressures were performed. Figure 7 a illustrates the relative change in resistance (∆R/R + 1) as a function of force (F), which shows the sensor sensitivity value of 5 × 10-4 kPa-1 of applied force of 130 mN-1. Using Eq. 145 the sensitivity factor can be calculated.

(1) Earlier Darren Alvares et.al; reported a sensitivity factor of (S F) of 0.0039 mN-1

45

for

functionalized gold nanoparticle based sensor.

Figure 7 a.) Relative change in resistance with respective to applied force. The sensitivity factor at the highest point shows 0.005 mN-1. b.) Detection of current response while loading and unloading of pressure by pressing. c) Plot shows current response for Tap and release. d) Plot for current response as a function of time for applied pressure.

Shu Gong et.al; demonstrated ultrathin gold nanowires as a highly sensitive pressure sensor, the sensitivity factor was shown to be 1.14 kPa -1

33

. Whereas, the investigated

graphene hybrid based sensor shows a high sensitivity factor of 5 × 10-4 kPa-1 which is best when compared with above works. This was due to the exhibition of extrinsic properties of the graphene and functionalized AuNPs. These sensors have a large surface area, which has more sensitive contact positions that varies charge transfer when pressure is applied. The device shows controllable pressure response (change in resistance) with the same applied force repeatedly and with a change in response time which shown in Figure 7 a. The device was also tested for sensitivity and compared the response to graphene film as shown in Figure 7 b. The graphene hybrid based sensor shows stable responses and high sensitivity for tap and release and weight press applications with a quicker response time less than 10 ms. After the addition of functionalized AuNPs to graphene, the graphene hybrid based sensor shows increase in sensitivity when compared to normal graphene film. Further, the sensitivity was tested for tap and release function. High signal to noise ratio were observed in the force measurement, indicating the higher sensitivity of our graphene hybrid sensor as shown in Figure 7 c. The graphene hybrid device shows a stable response for tap and release test. Although the bandwidth and line shape was nearly unaltered as the load frequency increased, a quick response time of Gr > AuNPs > Gr+ functionalized AuNPs, suggesting an enhance of conductivity. We have successfully developed a novel method for fabricating highly sensitive sensors by self-assembly of functionalized AuNPs between the graphene layers. The flexible graphene hybrid based sensor, was constructed by layer by layer deposition of graphene is followed by functionalized AuNPs and graphene layers. Higher sensitivity was achieved to mimic the natural touch senses. It provides a facile synthesis method for fabrication of hybrid films which could be applied for flexible and high sensitive devices with very low cost of production. Surface analysis techniques also clearly indicated the electrostatic interaction between graphene and functionalized AuNPs. The graphene hybrid based sensor demonstrated high sensitivity for detection of minute forces together with fast response time and high stability which was strongly supported by CV results. This novel device shows a high sensitivity factor of 5 × 10-4 kPa-1, with a fast response time of

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