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Amperometric urea biosensors based on sulfonated graphene/polyaniline nanocomposite.

Das G, Yoon HH - Int J Nanomedicine (2015)

Bottom Line: The biosensor achieved a broad linear range of detection (0.12-12.3 mM) with a notable response time of approximately 5 seconds.Moreover, the fabricated biosensor retained 81% of its initial activity (based on sensitivity) after 15 days of storage at 4°C.The ease of fabrication coupled with the low cost and good electrochemical performance of this system holds potential for the development of solid-state biosensors for urea detection.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical and Biological Engineering, Gachon University, Seongnam, Gyeonggi-do, South Korea.

ABSTRACT
An electrochemical biosensor based on sulfonated graphene/polyaniline nanocomposite was developed for urea analysis. Oxidative polymerization of aniline in the presence of sulfonated graphene oxide was carried out by electrochemical methods in an aqueous environment. The structural properties of the nanocomposite were characterized by Fourier-transform infrared, Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy techniques. The urease enzyme-immobilized sulfonated graphene/polyaniline nanocomposite film showed impressive performance in the electroanalytical detection of urea with a detection limit of 0.050 mM and a sensitivity of 0.85 (μA · cm(-2)·mM(-1). The biosensor achieved a broad linear range of detection (0.12-12.3 mM) with a notable response time of approximately 5 seconds. Moreover, the fabricated biosensor retained 81% of its initial activity (based on sensitivity) after 15 days of storage at 4°C. The ease of fabrication coupled with the low cost and good electrochemical performance of this system holds potential for the development of solid-state biosensors for urea detection.

No MeSH data available.


Schematic representation of the formation of sulfonated graphene/polyaniline nanostructure and the doping interaction between polyaniline and the SO3− group of sulfonated graphene.
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f4-ijn-10-055: Schematic representation of the formation of sulfonated graphene/polyaniline nanostructure and the doping interaction between polyaniline and the SO3− group of sulfonated graphene.

Mentions: The SG-PANI nanocomposite was synthesized by a facile approach using one-step electrochemical oxidative polymerization (Figure 2) at a cyclic potential ranging from −0.7 to +1.2 V. The electrochemical method offers the advantage of a rapid synthesis of PANI. After the first cycle, which is the initiation period, the current grows very rapidly due to the oxidation of the aniline monomers and oligomers. The aniline polymerization is an autocatalytic process: after the initial cycle, the growth of the polymers is sustained by the generated radical cations. On subsequent sweeps, the anodic peaks are shifted in the anodic direction and the cathodic peak in the cathodic direction, with a simultaneous increase in the current. The shift of the peaks is consistent with the ohmic contribution to the overpotential. This electrochemical behavior refects the deposition of the composite film onto the ITO surface. The deposited film exhibits a smooth surface and good adhesion to the ITO surface. The morphology of both the as-prepared SGO and the nanocomposite film deposited on ITO was studied by SEM. The SEM image of SGO exhibited a well-dispersed, layered-type structure (Figure 3A). Owing to the oxygenated functionalities on its basal planes and edges, SGO represents an attractive platform for the association of different materials. The dispersion of aniline prior to electrochemical polymerization is crucial for the association of the PANI nanofibers onto the graphitic sheets. The anilinium ion is adsorbed onto the graphitic surface through electrostatic interaction with the oxygenated functional groups. The number of cycles or deposition time is crucial to control the growth of PANI and its amount in the nanocomposite. The formation of the observed nanofiber like morphology of PANI (Figure 3B) can be described by the seedling growth process.29 At the initial polymerization stage, oxidation of anilinium ions takes place, leading to the formation of seeds. During the course of the polymerization, elongated structures of PANI are formed from these seeds.29 The reduction of SGO during cycling is assumed to be the driving force for the simultaneous deposition of these nanostructures. The nanofiber-like structure of PANI (Figure 3B and C) exhibited diameters of ~88+5 nm and lengths of ~0.5–1.0 μm. In addition, some irregular structures (particulate or spherical) were seen along with the nanofibers (Figure 3C); similar mixed morphology of PANI was also reported by Zhang et al.33 Even though some reports on the synthesis of SG-PANI composites have been published,34,35 their electrochemical synthesis has been rarely investigated. The SG-PANI mixed morphology differs from that of PANI synthesized by electrochemical routes, which consists exclusively of nanofibers.36 The shorter polymerization time might be responsible for this difference. Importantly, SGO was reduced to SG in the applied potential range without requiring any additional reducing agent. The reduction of SGO to SG during the deposition is beneficial for the formation of an extended conjugated structure at the PANI/SG interface.37,38 Moreover, the cross-sectional image of ITO/SG-PANI denotes a well-integrated compact structure. Although, direct evidence of an intercalated morphology was not obtained, we assume that the PANI nanofibers probably reside on the surface and between the layers, hence giving rise to the possibility of an intercalated structure (Figure 3D). During the polymerization of aniline, the π-π stacking interaction between the oligomers and the basal planes of SG favored the organization of PANI onto the SG surface (Figure 4). It is expected that such porous and integrated structure with an enhanced surface area would be beneficial for mass transport, thus maximizing the efficiency of the biosensors.39


Amperometric urea biosensors based on sulfonated graphene/polyaniline nanocomposite.

Das G, Yoon HH - Int J Nanomedicine (2015)

Schematic representation of the formation of sulfonated graphene/polyaniline nanostructure and the doping interaction between polyaniline and the SO3− group of sulfonated graphene.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4554425&req=5

f4-ijn-10-055: Schematic representation of the formation of sulfonated graphene/polyaniline nanostructure and the doping interaction between polyaniline and the SO3− group of sulfonated graphene.
Mentions: The SG-PANI nanocomposite was synthesized by a facile approach using one-step electrochemical oxidative polymerization (Figure 2) at a cyclic potential ranging from −0.7 to +1.2 V. The electrochemical method offers the advantage of a rapid synthesis of PANI. After the first cycle, which is the initiation period, the current grows very rapidly due to the oxidation of the aniline monomers and oligomers. The aniline polymerization is an autocatalytic process: after the initial cycle, the growth of the polymers is sustained by the generated radical cations. On subsequent sweeps, the anodic peaks are shifted in the anodic direction and the cathodic peak in the cathodic direction, with a simultaneous increase in the current. The shift of the peaks is consistent with the ohmic contribution to the overpotential. This electrochemical behavior refects the deposition of the composite film onto the ITO surface. The deposited film exhibits a smooth surface and good adhesion to the ITO surface. The morphology of both the as-prepared SGO and the nanocomposite film deposited on ITO was studied by SEM. The SEM image of SGO exhibited a well-dispersed, layered-type structure (Figure 3A). Owing to the oxygenated functionalities on its basal planes and edges, SGO represents an attractive platform for the association of different materials. The dispersion of aniline prior to electrochemical polymerization is crucial for the association of the PANI nanofibers onto the graphitic sheets. The anilinium ion is adsorbed onto the graphitic surface through electrostatic interaction with the oxygenated functional groups. The number of cycles or deposition time is crucial to control the growth of PANI and its amount in the nanocomposite. The formation of the observed nanofiber like morphology of PANI (Figure 3B) can be described by the seedling growth process.29 At the initial polymerization stage, oxidation of anilinium ions takes place, leading to the formation of seeds. During the course of the polymerization, elongated structures of PANI are formed from these seeds.29 The reduction of SGO during cycling is assumed to be the driving force for the simultaneous deposition of these nanostructures. The nanofiber-like structure of PANI (Figure 3B and C) exhibited diameters of ~88+5 nm and lengths of ~0.5–1.0 μm. In addition, some irregular structures (particulate or spherical) were seen along with the nanofibers (Figure 3C); similar mixed morphology of PANI was also reported by Zhang et al.33 Even though some reports on the synthesis of SG-PANI composites have been published,34,35 their electrochemical synthesis has been rarely investigated. The SG-PANI mixed morphology differs from that of PANI synthesized by electrochemical routes, which consists exclusively of nanofibers.36 The shorter polymerization time might be responsible for this difference. Importantly, SGO was reduced to SG in the applied potential range without requiring any additional reducing agent. The reduction of SGO to SG during the deposition is beneficial for the formation of an extended conjugated structure at the PANI/SG interface.37,38 Moreover, the cross-sectional image of ITO/SG-PANI denotes a well-integrated compact structure. Although, direct evidence of an intercalated morphology was not obtained, we assume that the PANI nanofibers probably reside on the surface and between the layers, hence giving rise to the possibility of an intercalated structure (Figure 3D). During the polymerization of aniline, the π-π stacking interaction between the oligomers and the basal planes of SG favored the organization of PANI onto the SG surface (Figure 4). It is expected that such porous and integrated structure with an enhanced surface area would be beneficial for mass transport, thus maximizing the efficiency of the biosensors.39

Bottom Line: The biosensor achieved a broad linear range of detection (0.12-12.3 mM) with a notable response time of approximately 5 seconds.Moreover, the fabricated biosensor retained 81% of its initial activity (based on sensitivity) after 15 days of storage at 4°C.The ease of fabrication coupled with the low cost and good electrochemical performance of this system holds potential for the development of solid-state biosensors for urea detection.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical and Biological Engineering, Gachon University, Seongnam, Gyeonggi-do, South Korea.

ABSTRACT
An electrochemical biosensor based on sulfonated graphene/polyaniline nanocomposite was developed for urea analysis. Oxidative polymerization of aniline in the presence of sulfonated graphene oxide was carried out by electrochemical methods in an aqueous environment. The structural properties of the nanocomposite were characterized by Fourier-transform infrared, Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy techniques. The urease enzyme-immobilized sulfonated graphene/polyaniline nanocomposite film showed impressive performance in the electroanalytical detection of urea with a detection limit of 0.050 mM and a sensitivity of 0.85 (μA · cm(-2)·mM(-1). The biosensor achieved a broad linear range of detection (0.12-12.3 mM) with a notable response time of approximately 5 seconds. Moreover, the fabricated biosensor retained 81% of its initial activity (based on sensitivity) after 15 days of storage at 4°C. The ease of fabrication coupled with the low cost and good electrochemical performance of this system holds potential for the development of solid-state biosensors for urea detection.

No MeSH data available.