Electronic Supplementary Material

Voltammetric determination of nitric oxide using a glassy carbon electrode modified with a nanohybrid consisting of myoglobin, gold nanorods, and reduced graphene oxide

AbRahmanMarlindaa, AlagarsamyPandikumarb*, SubramaniamJayabala, NorazrienaYusoffa, Abu BakarSurianib and Nay Ming Huanga*

aLow Dimensional Materials Research Centre, Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia

bResearch Institute & Department of Chemistry, SRM University,SRM Nagar, Kattankulathur-603 203,Chennai, India

bNanotechnology Research Centre, Faculty of Science and Mathematics, UniversityPendidikan Sultan Idris, 35900 Perak, Malaysia

*Corresponding author(s) e-mail: and

Synthesis of Graphene oxide

The GO was prepared by a simplified Hummers method [1]. A 1.5 g of graphiteflakes was added into a mixture of 180 mL of concentrated H2SO4and 20 mL of H3PO4 under vigorous stirring. Then, 9 g of KMnO4 was slowly added and the reaction mixture
was allowed to stir for three days at room temperature. After that the mixture was poured into
50 mL of ice cold-deionized water with 10 mL of H2O2. Then the stirringwas continued for another 10 min until the mixture turned yellow and it mixture was washed with 1 M HCl and deionizedwater to remove metal ions and acid impurities. Finally the GO solution obtained.

Standard diffraction pattern for AuNR

No. h k l d [A] 2Theta[deg] I [%]

1 1 1 1 2.35000 2.438 100.0

2 2 0 0 2.03000 2.823 53.0

3 2 2 0 1.44000 3.980 33.0

4 3 1 1 1.23000 4.659 40.0

5 2 2 2 1.17000 4.899 9.0

6 4 0 0 1.02000 5.619 3.0

7 3 3 1 0.94000 6.098 9.0

8 4 2 0 0.91000 6.299 7.0

9 0.80000 7.167 4.0

10 5 1 1 0.78000 7.351 4.0

Fig.S1 Standard X-ray diffraction pattern for Au NR.


Fig. S2. XPS of (A) graphene oxide and (B) reduced graphene oxide.

Fig.S3 Histogram for average length and width for (A and B) AuNRs and (C and D) Mb-AuNR/rGO.

The Raman spectra of the graphene oxide and reduced graphene oxidewere dominated by two intensity peaks at 1350 cm-1 and ~1598 cm-1 (Fig. S4) due to the D and Gbandswere related to the defects after the reaction process. The ratio of the intensities of the D and G bands (ID/IG) was related to the in-plane crystallite size of the graphene sheets with a few layers [2].The intensity ratio of the D peak to G peak of rGOincreased compared to GO. This indicated a decrease in the average size of the sp2 domain upon the reduction of graphene oxide[3,4].

Fig. S4 Raman spectra of GO and rGO.

Influence of scan rate on the electrocatalytic performance of Mb-AuNR/rGO toward NO oxidation studied by varying the scan rate in the range of 25 -200 mV.s-1 in a 0.1 M phosphate buffer (pH 2.5) containing 1 mM of NO and the corresponding results are shown in Fig. S5. It can see that while increase the scan rate the current response also increased. A linear relations the peak currents and square root of scan rates (Fig. S6) inferred that the nitrite oxidation at the Mb-AuNR/rGO modified electrode is controlled by the diffusion process.

Fig. S5CV obtained for the Mb-AuNR/RGO/GCE in a 0.1 M phosphate buffer (pH 2.5) containing 1 mM of NO different scan rate at range of 25 to 200 mV.s-1.

Fig. S6 Thecalibration plot obtainedfor anodic peak current vs squire root of scan rate for Mb-AuNR/RGO/GCE in a 0.1 M phosphate buffer (pH 2.5) containing 1 mM of NO different scan rate at range of 25 to 200 mV.s-1.

Fig. S7The cyclic voltammogramsobtained for bare GCE, AuNR/GCE, RGO/GCE, Mb/GC, and Mb-AuNR/RGO/GCE in the presence of Fe(CN)63–/Fe(CN)64–solution at 50 mV.s-1.

Fig.S8 LSVobtained for Mb-AuNR/rGO/GCE in presence of NO at concentration range of 10 µM to 1mM in 0.1 M phosphatebuffer at pH 2.5and scan rate of 50 mV.s−1.

Fig. S9 Cyclic voltammogram response for Mb-AuNR/RGO/GCE fabricated by five different set in the presence of 0.1 M phosphate buffer (pH 2.5) containing 1 mM of No at a scan rates of 50 mV.s-1.

Fig. S10 Cyclic voltammogram for 50 cycles of Mb-AuNRs/RGO/GCE in the presence of 0.1 M phosphate buffer (pH 2.5) containing 1 mM of No at a scan rates of 50 mV.s-1.

References

1. Ming HN (2010) Simple room-temperature preparation of high-yield large-area graphene oxide. International journal of nanomedicine 6

2. Pimenta MA, Dresselhaus G, Dresselhaus MS, Cancado LG, Jorio A, Saito R (2007) Studying disorder in graphite-based systems by Raman spectroscopy. Phys Chem Chem Phys 9 (11):1276-1290

3. Zhou K, Zhu Y, Yang X, Jiang X, Li C (2011) Preparation of graphene-TiO2 composites with enhanced photocatalytic activity. New J Chem 35 (2):353-359

4. Xiang Q, Yu J, Jaroniec M (2011) Enhanced photocatalytic H2-production activity of graphene-modified titania nanosheets. Nanoscale 3 (9):3670-3678

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