Room-Temperature Humidity Sensing Using Graphene Oxide Thin Films

Naik, Gautam; Krishnaswamy, Sridhar

doi:10.4236/graphene.2016.51001

Cited by 55 publications

(33 citation statements)

References 33 publications

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“…It has been postulated in the literature that adsorption of water molecules at grain boundary defects may lead to an increase in film resistivity due to the donor property of water. [35,36] In some studies, however, water molecules adsorbed on graphene acted as p-type dopants in the graphene layer causing the increase in current. [37][38][39] The opposite behavior of graphene against water molecules can be explained by different defect states, which depends highly on the type of graphene (free standing, exfoliated flakes, CVD grown, etc.)…”

Section: Resultsmentioning

confidence: 99%

All‐Dry Hydrophobic Functionalization of Paper Surfaces for Efficient Transfer of CVD Graphene

Çıtak

İstanbullu

Şakalak

et al. 2019

Macro Chemistry & Physics

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In this study, the successful transfer of chemical vapor deposition (CVD)‐grown graphene on an ordinary printing paper surface is demonstrated. Pristine paper is not a suitable substrate for graphene transfer because of its fragile and hydrophilic nature against the chemicals used during the transfer process. Two different fluoroalkyl polymers, namely poly(hexafluorobutyl acrylate) (PHFBA) and poly(perfluorodecyl acrylate) (PPFDA) are coated on paper surfaces by an initiated CVD (iCVD) technique to make the paper surfaces hydrophobic. Hydrophobicity is found to be an important factor in order for the graphene to be transferred onto the paper substrate. Although surfaces coated with PPFDA possess better hydrophobicity owing to their longer perfluoroalkyl group and higher roughness, the graphene transfer is found to be more successful on a PHFBA‐coated surface. A thin film of PHFBA on the paper surface acts as a prime layer for effective and defect‐free transfer of graphene and makes the paper surface ideal and robust during the graphene transfer process. The as‐transferred graphene layer on the PHFBA‐coated paper surface shows high conductivity values, even after repeated folding and flattening cycles.

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Section: Resultsmentioning

confidence: 99%

All‐Dry Hydrophobic Functionalization of Paper Surfaces for Efficient Transfer of CVD Graphene

Çıtak

İstanbullu

Şakalak

et al. 2019

Macro Chemistry & Physics

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“…Raman spectra of the films deposited from the solution with TS:GD volume ratio of 1:9 showed no clear TiO 2 peaks, due to the low content of TiO 2 in the composite films and high intensity of graphene bands, which obscure the TiO 2 peaks. The prominent peaks at 1570 cm −1 (G), 2700 cm −1 (G': the unique feature of few-layered graphene) and the weak peak at 1350 cm −1 (D) are graphene reflections [23,24,[32][33][34]. The sharp and symmetric graphene peaks indicate the small size, few-layered, nanoscale and homogenous form of graphene sheets [33][34][35].…”

Section: Resultsmentioning

confidence: 99%

Photocatalytic Graphene-TiO2 Thin Films Fabricated by Low-Temperature Ultrasonic Vibration-Assisted Spin and Spray Coating in a Sol-Gel Process

2017

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Abstract:In this work, we communicate a facile and low temperature synthesis process for the fabrication of graphene-TiO 2 photocatalytic composite thin films. A sol-gel chemical route is used to synthesize TiO 2 from the precursor solutions and spin and spray coating are used to deposit the films. Excitation of the wet films during the casting process by ultrasonic vibration favorably influences both the sol-gel route and the deposition process, through the following mechanisms. The ultrasound energy imparted to the wet film breaks down the physical bonds of the gel phase. As a result, only a low-temperature post annealing process is required to eliminate the residues to complete the conversion of precursors to TiO 2 . In addition, ultrasonic vibration creates a nanoscale agitating motion or microstreaming in the liquid film that facilitates mixing of TiO 2 and graphene nanosheets. The films made based on the above-mentioned ultrasonic vibration-assisted method and annealed at 150 • C contain both rutile and anatase phases of TiO 2 , which is the most favorable configuration for photocatalytic applications. The photoinduced and photocatalytic experiments demonstrate effective photocurrent generation and elimination of pollutants by graphene-TiO 2 composite thin films fabricated via scalable spray coating and mild temperature processing, the results of which are comparable with those made using lab-scale and energy-intensive processes.

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“…Our imperceptible TFTs have superior linearity against humidity conditions at a gate voltage of 1V. Many researchers have studied resistive-type humidity sensors based on metal oxide with various structures, such as thin-film [34,35,36], nanoparticles [37], composites [38] and nanocrystals [39]. The sensitivity of resistive-type humidity sensors is mainly below 10 3 .…”

Section: Resultsmentioning

confidence: 99%

An All Oxide-Based Imperceptible Thin-Film Transistor with Humidity Sensing Properties

et al. 2017

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We have examined the effects of oxygen content and thickness in sputtered InSnO (ITO) electrodes, especially for the application of imperceptible amorphous-InGaZnO (a-IGZO) thin-film transistors (TFTs) in humidity sensors. The imperceptible a-IGZO TFT with 50-nm ITO electrodes deposited at Ar:O2 = 29:0.3 exhibited good electrical performances with Vth of −0.23 V, SS of 0.34 V/dec, µFE of 7.86 cm2/V∙s, on/off ratio of 8.8 × 107, and has no degradation for bending stress up to a 3.5-mm curvature. The imperceptible oxide TFT sensors showed the highest sensitivity for the low and wide gate bias of −1~2 V under a wide range of relative humidity (40–90%) at drain voltage 1 V, resulting in low power consumption by the sensors. Exposure to water vapor led to a negative shift in the threshold voltage (or current enhancement), and an increase in relative humidity induced continuous threshold voltage shift. In particular, compared to conventional resistor-type sensors, the imperceptible oxide TFT sensors exhibited extremely high sensitivity from a current amplification of >103.

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Room-Temperature Humidity Sensing Using Graphene Oxide Thin Films

Cited by 55 publications

References 33 publications

All‐Dry Hydrophobic Functionalization of Paper Surfaces for Efficient Transfer of CVD Graphene

All‐Dry Hydrophobic Functionalization of Paper Surfaces for Efficient Transfer of CVD Graphene

Photocatalytic Graphene-TiO2 Thin Films Fabricated by Low-Temperature Ultrasonic Vibration-Assisted Spin and Spray Coating in a Sol-Gel Process

An All Oxide-Based Imperceptible Thin-Film Transistor with Humidity Sensing Properties

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