Limits...
A Highly Efficient Sensor Platform Using Simply Manufactured Nanodot Patterned Substrates.

Rasappa S, Ghoshal T, Borah D, Senthamaraikannan R, Holmes JD, Morris MA - Sci Rep (2015)

Bottom Line: Highly dense iron oxide nanodots arrays that mimicked the original BCP pattern were prepared by an 'insitu' BCP inclusion methodology using poly(styrene)-block-poly(ethylene oxide) (PS-b-PEO).The dual detection of EtOH and H2O2 was clearly observed.The as-prepared nanodots have good long term thermal and chemical stability at the substrate and demonstrate promising electrocatalytic performance.

View Article: PubMed Central - PubMed

Affiliation: Materials Research Group, Department of Chemistry and Tyndall National Institute, University College Cork, Cork, Ireland.

ABSTRACT
Block copolymer (BCP) self-assembly is a low-cost means to nanopattern surfaces. Here, we use these nanopatterns to directly print arrays of nanodots onto a conducting substrate (Indium Tin Oxide (ITO) coated glass) for application as an electrochemical sensor for ethanol (EtOH) and hydrogen peroxide (H2O2) detection. The work demonstrates that BCP systems can be used as a highly efficient, flexible methodology for creating functional surfaces of materials. Highly dense iron oxide nanodots arrays that mimicked the original BCP pattern were prepared by an 'insitu' BCP inclusion methodology using poly(styrene)-block-poly(ethylene oxide) (PS-b-PEO). The electrochemical behaviour of these densely packed arrays of iron oxide nanodots fabricated by two different molecular weight PS-b-PEO systems was studied. The dual detection of EtOH and H2O2 was clearly observed. The as-prepared nanodots have good long term thermal and chemical stability at the substrate and demonstrate promising electrocatalytic performance.

No MeSH data available.


Ethanol oxidation mechanism at Fe3O4 electrode.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4542519&req=5

f9: Ethanol oxidation mechanism at Fe3O4 electrode.

Mentions: Comparison of the electrochemical behaviour of the nanodot samples from ALW and BHW to ethanol (normal buffer conditions as above and will not be described further) are shown in Fig. 8. Neither sample exhibited redox peak features at scan rate of 50 mV s−1 indicating passive behaviour. Addition of 0.1 M EtOH, resulted in well defined redox peaks at 0.16 and −0.4 V for sample ALW and 0.24 and −0.58 V for sample BHW. This smaller oxidation and reduction potentials of sample ALW compared to BHW confirm the enhanced electrocatalytic efficiency of the smaller nanodots. The reduction potential of about −0.4 V for ALW is lower than the literature values reflecting the small dimensions21. For sample ALW, the separation of cathodic and anodic peak potentials is ΔE = 0.24 V and the ratio of peak anodic and cathodic currents is Ipc/Ipa = 1.02 V. This suggests that the electrochemical behaviour is quasi-reversible37. The enhanced current response (ratio ~ 1.45) and faster kinetics (peak width) of ALW compared to BHW reflect its higher surface coverage (coverage ratio = 1.55). For ethanol, the acid-base properties of the electrolyte can have a major influence on the observed oxidation potential28. During the electro oxidation process, intermediates species like CO, CO2, CH3CO, CH3CHO, CH3COO−, CH3COOH are formed and electrode poisoning can occur due to the re-adsorbed CO molecules. The mechanism of EtOH oxidation in weakly basic conditions can be summarised as shown in Fig. 9. The Fe2+ ions in Fe3O4 forms Fe(OH)2 and these are oxidized to Fe3+ in FeOOH. The FeOOH oxidizes ethanol forming reactive intermediates such as CH3CHO which are further oxidized to ethanol3738. Since the oxidation rate of ethanal is rapid, this will be continuously oxidized to the acid. During the reverse sweep process, these carbonaceous elements may cause electrode poisoning due to adsorption of carbon species39. The reductive cycle enables the formed FeOOH to be reduced reactivating the surface of the electrode. Thus, it is the redox pair Fe(OH)2/FeOOH in the electrolyte medium leads to electrocatalytic activity towards EtOH sensing. In these CVs, the oxidation and reduction peaks represent the interconversion of the electrode surface from Fe(OH)2 to FeOOH. Note that the absence of an intense anodic oxidation peak at about −0.45 V indicative of the re-oxidation of EtOH and other carbonaceous species is consistent with the mild pH conditions as previous observations in strongly acidic or basic electrolyte medium40.


A Highly Efficient Sensor Platform Using Simply Manufactured Nanodot Patterned Substrates.

Rasappa S, Ghoshal T, Borah D, Senthamaraikannan R, Holmes JD, Morris MA - Sci Rep (2015)

Ethanol oxidation mechanism at Fe3O4 electrode.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4542519&req=5

f9: Ethanol oxidation mechanism at Fe3O4 electrode.
Mentions: Comparison of the electrochemical behaviour of the nanodot samples from ALW and BHW to ethanol (normal buffer conditions as above and will not be described further) are shown in Fig. 8. Neither sample exhibited redox peak features at scan rate of 50 mV s−1 indicating passive behaviour. Addition of 0.1 M EtOH, resulted in well defined redox peaks at 0.16 and −0.4 V for sample ALW and 0.24 and −0.58 V for sample BHW. This smaller oxidation and reduction potentials of sample ALW compared to BHW confirm the enhanced electrocatalytic efficiency of the smaller nanodots. The reduction potential of about −0.4 V for ALW is lower than the literature values reflecting the small dimensions21. For sample ALW, the separation of cathodic and anodic peak potentials is ΔE = 0.24 V and the ratio of peak anodic and cathodic currents is Ipc/Ipa = 1.02 V. This suggests that the electrochemical behaviour is quasi-reversible37. The enhanced current response (ratio ~ 1.45) and faster kinetics (peak width) of ALW compared to BHW reflect its higher surface coverage (coverage ratio = 1.55). For ethanol, the acid-base properties of the electrolyte can have a major influence on the observed oxidation potential28. During the electro oxidation process, intermediates species like CO, CO2, CH3CO, CH3CHO, CH3COO−, CH3COOH are formed and electrode poisoning can occur due to the re-adsorbed CO molecules. The mechanism of EtOH oxidation in weakly basic conditions can be summarised as shown in Fig. 9. The Fe2+ ions in Fe3O4 forms Fe(OH)2 and these are oxidized to Fe3+ in FeOOH. The FeOOH oxidizes ethanol forming reactive intermediates such as CH3CHO which are further oxidized to ethanol3738. Since the oxidation rate of ethanal is rapid, this will be continuously oxidized to the acid. During the reverse sweep process, these carbonaceous elements may cause electrode poisoning due to adsorption of carbon species39. The reductive cycle enables the formed FeOOH to be reduced reactivating the surface of the electrode. Thus, it is the redox pair Fe(OH)2/FeOOH in the electrolyte medium leads to electrocatalytic activity towards EtOH sensing. In these CVs, the oxidation and reduction peaks represent the interconversion of the electrode surface from Fe(OH)2 to FeOOH. Note that the absence of an intense anodic oxidation peak at about −0.45 V indicative of the re-oxidation of EtOH and other carbonaceous species is consistent with the mild pH conditions as previous observations in strongly acidic or basic electrolyte medium40.

Bottom Line: Highly dense iron oxide nanodots arrays that mimicked the original BCP pattern were prepared by an 'insitu' BCP inclusion methodology using poly(styrene)-block-poly(ethylene oxide) (PS-b-PEO).The dual detection of EtOH and H2O2 was clearly observed.The as-prepared nanodots have good long term thermal and chemical stability at the substrate and demonstrate promising electrocatalytic performance.

View Article: PubMed Central - PubMed

Affiliation: Materials Research Group, Department of Chemistry and Tyndall National Institute, University College Cork, Cork, Ireland.

ABSTRACT
Block copolymer (BCP) self-assembly is a low-cost means to nanopattern surfaces. Here, we use these nanopatterns to directly print arrays of nanodots onto a conducting substrate (Indium Tin Oxide (ITO) coated glass) for application as an electrochemical sensor for ethanol (EtOH) and hydrogen peroxide (H2O2) detection. The work demonstrates that BCP systems can be used as a highly efficient, flexible methodology for creating functional surfaces of materials. Highly dense iron oxide nanodots arrays that mimicked the original BCP pattern were prepared by an 'insitu' BCP inclusion methodology using poly(styrene)-block-poly(ethylene oxide) (PS-b-PEO). The electrochemical behaviour of these densely packed arrays of iron oxide nanodots fabricated by two different molecular weight PS-b-PEO systems was studied. The dual detection of EtOH and H2O2 was clearly observed. The as-prepared nanodots have good long term thermal and chemical stability at the substrate and demonstrate promising electrocatalytic performance.

No MeSH data available.