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Highly sensitive and selective gas sensor using hydrophilic and hydrophobic graphenes.

Some S, Xu Y, Kim Y, Yoon Y, Qin H, Kulkarni A, Kim T, Lee H - Sci Rep (2013)

Bottom Line: Novel one-headed polymer optical fiber sensor arrays using hydrophilic GO and hydrophobic reduced graphene oxide (rGO) were carefully designed, leading to the selective sensing of volatile organic gases for the first time.The two physically different surfaces of GO and rGO could provide the sensing ability to distinguish between tetrahydrofuran (THF) and dichloromethane (MC), respectively, which is the most challenging issue in the area of gas sensors.The eco-friendly physical properties of GO allowed for faster sensing and higher sensitivity when compared to previous results for rGO even under extreme environments of over 90% humidity, making it the best choice for an environmentally friendly gas sensor.

View Article: PubMed Central - PubMed

Affiliation: NCRI, Center for Smart Molecular Memory, Department of Chemistry, Sungkyunkwan University Suwon, Republic of Korea.

ABSTRACT
New hydrophilic 2D graphene oxide (GO) nanosheets with various oxygen functional groups were employed to maintain high sensitivity in highly unfavorable environments (extremely high humidity, strong acidic or basic). Novel one-headed polymer optical fiber sensor arrays using hydrophilic GO and hydrophobic reduced graphene oxide (rGO) were carefully designed, leading to the selective sensing of volatile organic gases for the first time. The two physically different surfaces of GO and rGO could provide the sensing ability to distinguish between tetrahydrofuran (THF) and dichloromethane (MC), respectively, which is the most challenging issue in the area of gas sensors. The eco-friendly physical properties of GO allowed for faster sensing and higher sensitivity when compared to previous results for rGO even under extreme environments of over 90% humidity, making it the best choice for an environmentally friendly gas sensor.

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Related in: MedlinePlus

Comparative plots of the sensing responses to eight different vapours at a 500 ppb concentration level.(a) Only GO POF. (b), Only GO and only rGO POF. (c) A plot of selectively sensing responses of GO and rGO POF to THF, dichloromethane, and ethanol with a two-headed POF sensor. The two-headed GO/GO, rGO/rGO and GO/rGO POF sensors were prepared with either GO or rGO, or one head was coated with GO and another head with rGO, respectively. (d) A plot of the selectivity of one-headed GO-rGO POF to THF, dichloromethane, and ethanol.
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f3: Comparative plots of the sensing responses to eight different vapours at a 500 ppb concentration level.(a) Only GO POF. (b), Only GO and only rGO POF. (c) A plot of selectively sensing responses of GO and rGO POF to THF, dichloromethane, and ethanol with a two-headed POF sensor. The two-headed GO/GO, rGO/rGO and GO/rGO POF sensors were prepared with either GO or rGO, or one head was coated with GO and another head with rGO, respectively. (d) A plot of the selectivity of one-headed GO-rGO POF to THF, dichloromethane, and ethanol.

Mentions: The principle of operation of sensor transduction relies on the dependence of the reflectance on the optical and geometric properties of the sensing layers when vapour molecules are adsorbed on the GO and rGO layers, as depicted in Fig. 1. This means that any change in the features of the GO and rGO layers due to chemical or physical adsorption of a target analyte would induce a consequent change in the layer's reflectance. According to our previous report, a variation in the refractive index of the GO and rGO layers as well as the external media (all VOCs) will lead to changes in the reflectance at the fiber-coated interfacial layer and thus, induce changes in the sensor output signal27. As we know that GO is hydrophilic and rGO is hydrophobic, these surface characteristic difference will affect the sensing capability of GO and rGO. The oxygen containing functional groups of GO are playing the key roles for GO's gas sensing activity. The interaction of the oxygen containing groups of GO with VOCs will be different in comparison to that of rGO. The oxygen containing groups can strongly interact with those polar VOCs that are NO2, NH2 and other oxygen containing functional groups due to the formation of intermolecular polar interactions2829. So, the wettability of hydrophilic GO and hydrophobic rGO will definitely make a difference of gas sensibility. The responses of the GO and rGO POF sensor arrays to VOCs are shown in Fig. 2e, f and 3. The GO and rGO POF sensor array could selectively detect different VOCs, including hydrazine, ethanol, methanol, dichloromethane (MC), acetone, tetrahydrofuran (THF), nitromethane, and diethylamine. Fig. 2e, f showed the recording of the changes in the reflected optical power during successive injections of acetone concentrations ranging from 500 ppm to 500 ppb for the only GO and only rGO POF sensor, respectively. The GO and rGO sensor exhibited a negative variation in the reflectance for a given VOC. According to the experimental analysis, a larger dilution of the vapour will lead to smaller variations in the reflected optical power. The detection results for acetone vapours with and without the GO and rGO layers on the POF end face are displayed in Fig. S1. The results show that the GO and rGO layers were sensitive to the vapours and played a key role in the detection of the VOCs. Shown in Fig. 3 are the comparison results for changes in the detector output for all vapours used in the study (i.e., hydrazine, ethanol, methanol, dichloromethane, acetone, tetrahydrofuran, nitromethane and diethylamine) at a 500 ppb concentration, which is quite low according to previous reports30 for both POF sensors. It is clearly seen that the only GO and only rGO POF sensors showed different sensitivities toward the various vapours (Fig. 3a, b). The intensity of the reflected optical response for the only GO and only rGO POF sensor was highest for diethylamine and nitromethane vapours at the same concentration, respectively, and was lowest for methanol and dichloromethane vapours, respectively. The use of thinner GO or rGO layers as the active element in the sensor array facilitated an increase in vapour detection when compared to the use of thicker layers30. Furthermore, according to the experimental results, the sensitivity of GO to VOCs (mainly nitro and amine containing compounds) is much higher than that of rGO due to the presence of numerous polar functional groups (Fig. 3b). This experimental finding is good confirmation of our hypothesis. The measured responses of the only GO and only rGO POF sensors suggested that GO and rGO showed selectivity toward sensing VOCs (Fig. 3a, b).


Highly sensitive and selective gas sensor using hydrophilic and hydrophobic graphenes.

Some S, Xu Y, Kim Y, Yoon Y, Qin H, Kulkarni A, Kim T, Lee H - Sci Rep (2013)

Comparative plots of the sensing responses to eight different vapours at a 500 ppb concentration level.(a) Only GO POF. (b), Only GO and only rGO POF. (c) A plot of selectively sensing responses of GO and rGO POF to THF, dichloromethane, and ethanol with a two-headed POF sensor. The two-headed GO/GO, rGO/rGO and GO/rGO POF sensors were prepared with either GO or rGO, or one head was coated with GO and another head with rGO, respectively. (d) A plot of the selectivity of one-headed GO-rGO POF to THF, dichloromethane, and ethanol.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3672880&req=5

f3: Comparative plots of the sensing responses to eight different vapours at a 500 ppb concentration level.(a) Only GO POF. (b), Only GO and only rGO POF. (c) A plot of selectively sensing responses of GO and rGO POF to THF, dichloromethane, and ethanol with a two-headed POF sensor. The two-headed GO/GO, rGO/rGO and GO/rGO POF sensors were prepared with either GO or rGO, or one head was coated with GO and another head with rGO, respectively. (d) A plot of the selectivity of one-headed GO-rGO POF to THF, dichloromethane, and ethanol.
Mentions: The principle of operation of sensor transduction relies on the dependence of the reflectance on the optical and geometric properties of the sensing layers when vapour molecules are adsorbed on the GO and rGO layers, as depicted in Fig. 1. This means that any change in the features of the GO and rGO layers due to chemical or physical adsorption of a target analyte would induce a consequent change in the layer's reflectance. According to our previous report, a variation in the refractive index of the GO and rGO layers as well as the external media (all VOCs) will lead to changes in the reflectance at the fiber-coated interfacial layer and thus, induce changes in the sensor output signal27. As we know that GO is hydrophilic and rGO is hydrophobic, these surface characteristic difference will affect the sensing capability of GO and rGO. The oxygen containing functional groups of GO are playing the key roles for GO's gas sensing activity. The interaction of the oxygen containing groups of GO with VOCs will be different in comparison to that of rGO. The oxygen containing groups can strongly interact with those polar VOCs that are NO2, NH2 and other oxygen containing functional groups due to the formation of intermolecular polar interactions2829. So, the wettability of hydrophilic GO and hydrophobic rGO will definitely make a difference of gas sensibility. The responses of the GO and rGO POF sensor arrays to VOCs are shown in Fig. 2e, f and 3. The GO and rGO POF sensor array could selectively detect different VOCs, including hydrazine, ethanol, methanol, dichloromethane (MC), acetone, tetrahydrofuran (THF), nitromethane, and diethylamine. Fig. 2e, f showed the recording of the changes in the reflected optical power during successive injections of acetone concentrations ranging from 500 ppm to 500 ppb for the only GO and only rGO POF sensor, respectively. The GO and rGO sensor exhibited a negative variation in the reflectance for a given VOC. According to the experimental analysis, a larger dilution of the vapour will lead to smaller variations in the reflected optical power. The detection results for acetone vapours with and without the GO and rGO layers on the POF end face are displayed in Fig. S1. The results show that the GO and rGO layers were sensitive to the vapours and played a key role in the detection of the VOCs. Shown in Fig. 3 are the comparison results for changes in the detector output for all vapours used in the study (i.e., hydrazine, ethanol, methanol, dichloromethane, acetone, tetrahydrofuran, nitromethane and diethylamine) at a 500 ppb concentration, which is quite low according to previous reports30 for both POF sensors. It is clearly seen that the only GO and only rGO POF sensors showed different sensitivities toward the various vapours (Fig. 3a, b). The intensity of the reflected optical response for the only GO and only rGO POF sensor was highest for diethylamine and nitromethane vapours at the same concentration, respectively, and was lowest for methanol and dichloromethane vapours, respectively. The use of thinner GO or rGO layers as the active element in the sensor array facilitated an increase in vapour detection when compared to the use of thicker layers30. Furthermore, according to the experimental results, the sensitivity of GO to VOCs (mainly nitro and amine containing compounds) is much higher than that of rGO due to the presence of numerous polar functional groups (Fig. 3b). This experimental finding is good confirmation of our hypothesis. The measured responses of the only GO and only rGO POF sensors suggested that GO and rGO showed selectivity toward sensing VOCs (Fig. 3a, b).

Bottom Line: Novel one-headed polymer optical fiber sensor arrays using hydrophilic GO and hydrophobic reduced graphene oxide (rGO) were carefully designed, leading to the selective sensing of volatile organic gases for the first time.The two physically different surfaces of GO and rGO could provide the sensing ability to distinguish between tetrahydrofuran (THF) and dichloromethane (MC), respectively, which is the most challenging issue in the area of gas sensors.The eco-friendly physical properties of GO allowed for faster sensing and higher sensitivity when compared to previous results for rGO even under extreme environments of over 90% humidity, making it the best choice for an environmentally friendly gas sensor.

View Article: PubMed Central - PubMed

Affiliation: NCRI, Center for Smart Molecular Memory, Department of Chemistry, Sungkyunkwan University Suwon, Republic of Korea.

ABSTRACT
New hydrophilic 2D graphene oxide (GO) nanosheets with various oxygen functional groups were employed to maintain high sensitivity in highly unfavorable environments (extremely high humidity, strong acidic or basic). Novel one-headed polymer optical fiber sensor arrays using hydrophilic GO and hydrophobic reduced graphene oxide (rGO) were carefully designed, leading to the selective sensing of volatile organic gases for the first time. The two physically different surfaces of GO and rGO could provide the sensing ability to distinguish between tetrahydrofuran (THF) and dichloromethane (MC), respectively, which is the most challenging issue in the area of gas sensors. The eco-friendly physical properties of GO allowed for faster sensing and higher sensitivity when compared to previous results for rGO even under extreme environments of over 90% humidity, making it the best choice for an environmentally friendly gas sensor.

Show MeSH
Related in: MedlinePlus