Chip Sensor for pH and Temperature Monitoring Based on ZnO Composite

doi:10.15541/jim20190222

Abstract

Abstract:

Wearable sensors which can evaluate the health status of the human body by conveniently monitoring human’s pH of sweat and body temperature have attracted wide attention. Here, sensors for sweat pH and skin temperature monitoring were developed. ZnO/polyaniline (PAni) micro-nano structure which sensitivity reaches 120 mV/pH realized pH sensing by monitoring the change of surface potential in solutions under different pH conditions. A layer of ZnO/rGO on surface of polyethylene glycol terephthalate/indium tin oxid (PET/ITO) was constructed for temperature monitoring by a simple drop-casting method. With the temperature increasing, the resistance of ZnO/rGO composite decreases, and the sensitivity of its resistance variation reaches -0.67%/℃. Two sensors are integrated into one sensor chip which shows high stability. Therefore, the new sensor with practical and commercial potential is promising in the field of pH and temperature detection.

Key words: pH sensing, temperature sensing, ZnO/reduced graphene oride, ZnO/polyaniline

CLC Number:

TQ174

ZHANG Wei,GAO Peng,HOU Chengyi,LI Yaogang,ZHANG Qinghong,WANG Hongzhi. Chip Sensor for pH and Temperature Monitoring Based on ZnO Composite[J]. Journal of Inorganic Materials, 2020, 35(4): 416-422.

Figures/Tables 12

Fig. 1 (a) Digital photograph and (b) schematic diagram of pH and temperature sensor

Fig. 2 Schematic diagram of apparatus prepared with ZnO nanorod arrays

Fig. 3 Reversible transform between reduced polyaniline and emeraldine

Fig. 4 FE-SEM images of (a, b) ZnO nanorod arrays on the surface of PET/ITO, (c, d) PAni nanosheet arrays on the surface of ZnO nanorods

Fig. 5 Digital photographs of (a) pure PET/ITO films, (b) PET/ITO films modified with ZnO nanorod arrays and (c) PET/ITO films modified with ZnO/PAni micro-nanostructures

Fig. 6 (a) Time dependence of the open circuit potential between work electrode and reference electrode in various solutions with different pH with in 100 s, and (b) variation of open circuit potential versus pH for work electrode

Fig. 7 FE-TEM images (a, b) of ZnO/rGO, and corresponding element mapping of (c) Zn and (d) C

Fig. 8 XRD pattern of ZnO/rGO

Fig. 9 (a) Variation and (b) percentage variation of resistance versus temperature for ZnO/rGO nanocomposites

Table 1 Resistance-temperature performance of ZnO/rGO nanocomposites

Sample	ΔR·ΔT^-1/(Ω∙℃^-1)	(Δ(ΔR·R₀^-1)·ΔT^-1/(%·℃^-1)
1	192.9	-0.63
2	147.2	-0.67
3	173.6	-0.61

Fig. 10 (a) Digital photo of the sensor chip in the test solution; (b) pH sensing and (c) temperature sensing performances of the sensor chip

Fig. 10 (a) Digital photo of PET/ITO modified with ZnO/ PAni micro-nanostructure, (b) SEM image of ZnO/PAni micro- nanostructure. and (c) Linear I-V curves of ZnO/rGO thermistor measured under 25 and 40 ℃

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