Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2013:3:2714.
doi: 10.1038/srep02714.

Ultrahigh humidity sensitivity of graphene oxide

Hengchang Bi  1 , Kuibo Yin, Xiao Xie, Jing Ji, Shu Wan, Litao Sun, Mauricio Terrones, Mildred S Dresselhaus
Affiliations

Ultrahigh humidity sensitivity of graphene oxide

Hengchang Bi et al. Sci Rep. 2013.

Abstract

Humidity sensors have been extensively used in various fields, and numerous problems are encountered when using humidity sensors, including low sensitivity, long response and recovery times, and narrow humidity detection ranges. Using graphene oxide (G-O) films as humidity sensing materials, we fabricate here a microscale capacitive humidity sensor. Compared with conventional capacitive humidity sensors, the G-O based humidity sensor has a sensitivity of up to 37800% which is more than 10 times higher than that of the best one among conventional sensors at 15%-95% relative humidity. Moreover, our humidity sensor shows a fast response time (less than 1/4 of that of the conventional one) and recovery time (less than 1/2 of that of the conventional one). Therefore, G-O appears to be an ideal material for constructing humidity sensors with ultrahigh sensitivity for widespread applications.

PubMed Disclaimer

Figures

Figure 1
Figure 1. Characterization of the sensor and humidity testing system.
(a): Digital photographs of the device (Reference is a 1 Dime US coin). (b): SEM image of the area set off by a red dashed line. (c): SEM image of the interdigitated electrodes without G-O. Two sets of electrodes (with widths of 40 and 20 μm, respectively) were designed in an interdigitated manner with 10 μm spacing and an overlapping area of 200 μm. (d): SEM image of interdigitated electrodes covered with G-O films. (e): Schematic diagram of the humidity testing system graphene oxide film as a humidity sensing material was placed on the two sets of interdigitated electrodes.
Figure 2
Figure 2. Capacitance and sensitivity versus RH at 100 Hz, 1 kHz, and 10 kHz.
(a): Output capacitances of sensors as a function of RH. (b): Defined sensitivity as a function of RH.
Figure 3
Figure 3. Stability test of sensors at fixed RH.
(a): 100 Hz. (b): 1 kHz. The change in the output capacitance of sensors operating at 100 Hz and 1 kHz was acceptable, that is, long-term stability and reliability are beneficial for practical applications.
Figure 4
Figure 4. Response and recovery times of the humidity sensors for humidity levels between 23% RH and 86% RH.
(a): Response time, ~10.5 s. (b): Recovery time, ~41 s.
Figure 5
Figure 5. Schematic of humidity sensing at G-O films.
The adsorption of water molecules on G-O films is characterized by two processes. The first-layer water molecules are attached on the G-O films through two hydrogen bonds. In contrast, from the second layer, water molecules are adsorbed only through one hydrogen bond.
Figure 6
Figure 6. Complex impedance plots and equivalent circuits of G-O films under different humidity levels.
(a): With increasing RH, the semicircles are gradually depressed and then disappear at 97% RH. The straight lines become lengthened. (b): An equivalent circuit at very low RH. (c): An equivalent circuit at high RH. Rf: G-O film resistance; Cf: G-O film capacitance; Zi: interface impedance between G-O film and electrodes.
See this image and copyright information in PMC

References

    1. Li Z. Y. et al. Highly sensitive and stable humidity nanosensors based on LiCl doped TiO2 electrospun nanofibers. J. Am. Chem. Soc. 130, 5036–5037 (2008). - PubMed
    1. Lee C. & Lee G. Humidity sensors: A Review. Sens. Lett. 3, 1–15 (2005).
    1. Zilberman Y., Lonescu R., Feng X. L., Müllen K. & Haick H. Nanoarray of polycyclic aromatic hydrocarbons and carbon nanotubes for accurate and predictive detection in real-world environmental humidity. ACS Nano 5, 6743–6753 (2011). - PubMed
    1. Chen X. J., Zhang J., Wang Z. L., Yan Q. & Hui S. C. Humidity sensing behavior of silicon nanowires with hexamethyldisilazane modification. Sens. Actuators, B 156, 631–636 (2011).
    1. Kim Y. et al. Capacitive humidity sensor design based on anodic aluminum oxide. Sens. Actuators, B 141, 441–446 (2009).

Publication types