Electronic Supplementary Material

Voltammetric determination of levofloxacin using a glassy carbon electrode modified

with poly (o-aminophenol) and graphene quantum dots

Jing-Yi Huanga, Ting Baoa, Tian-Xing Hua, Wei Wena,b,*, Xiu-Hua Zhanga, Sheng-Fu Wanga

aHubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Ministry

of Education Key Laboratory for the Synthesis and Application of Organic Functional

Molecules & College of Chemistry and Chemical Engineering, Hubei University, Wuhan

430062, PR ChinabState Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha

410082, PR China

* Corresponding author. Tel.: 86 27 50865309; Fax: 86 27 88663043, E-mail address:

wenwei@hubu.edu.cn.

Scheme S1. The chemical structure of LV.

Figure S1. TEM images of GQDs (A). Size distributions of GQDs (B). SEM images of

PoAP/GQD composite film (C) and (D).

Figure S2. Influence of pH on the anodic peak current (A) and peak potential (B) of PoAP/GQD/GCE in NaAC-HAc solution containing 100 μM LV. Influence of accumulation time (C) and potential (D) on the anodic peak current of PoAP/GQD/GCE in NaAc-HAc (pH = 4.5) containing 100 μM LV.

In order to optimize the experiment conditions, the influence of pH value of 0.1 M

NaAc-HAc to the peak current and potential was studied in the work. With the increase of pH

value, the peak current reached the highest at pH 4.5 (Fig. S2A). However, when pH values

exceed 4.5, with the further increase of pH, the oxidation peak current decreased. The

dependences of peak potential (E) on pH for NaAc-HAc were shown in Fig. S2B, when the

pH values increasing, the anodic peak potential shifted to lower values. It can be verified that

the chemical reaction happened prior to the electrode process is the proton transfer reaction

[1]. This is attributed to the structure of polymer film changes and reduction of the

conductivity of polymer [2]. On the basis of above information, pH 4.5 was chosen for the

studies. In addition, we also optimized the enrichment time and enrichment potential having

effect on the current response. First, the current response was enhanced with the increase of

the enrichment time. As shown in Fig. S2C, the result indicated that the peak current raised

along with the accumulation time. After 180s, the current still maintained a steady value. The

accumulation time was chosen as 180 s. As shown in Fig. S2D, in the examined potential

range, the anodic peak current reached maximum value at 0.5 V. Besides, the enrichment

potential had effect on the current response. Moreover, the thickness of the polymer film also

had a certain influence. The current of LV tended to stable value when the electropolymerized

cycle was 10 cycles. So 10 scan cycles was chosen as the best polymerization cycle.

Table S1. An overview on recently reported nanomaterial-based methods for

electrochemical determination of levofloxacin.

Material Linear range(μM) LOD(μM) Specificity Ref.

PoAP/MWCNTs/GCE

MWCNT-SnO2/GC

MIP/G-Au/GCE

3.0-200

1.0-9.9

1-100

1

0.2

0.53

Satisfactor

y

Good

Excellent

[2]

[3]

[4]

DsDNA/GCE

ssDNA/SWCNT/gold E

MWNT-PAR/GCE

PoAP/GQDs/GCE

0.5-5

1.0-10

5.0-100

0.05-100

0.1

0.0752

0.4

0.01

-

-

Good

Satisfactor

y

[5]

[6]

[7]

This paper

References

1. Tucceri RI (2003) Specularity change on a thin gold film surface coated with poly(o-

aminophenol) during the polymer redox conversion. The pH effect on the redox sites

distribution at the metal | polymer interface. Journal of Electroanalytical Chemistry 543

(1):61-71.

2. Wen W, Zhao DM, Zhang XH, Xiong HY, Wang SF, Chen W, Zhao YD (2012) One-step

fabrication of poly(o-aminophenol)/multi-walled carbon nanotubes composite film modified

electrode and its application for levofloxacin determination in pharmaceuticals. Sensors

Actuators B Chem 174:202-209.

3. Cesarino V, Cesarino I, Moraes FC, Machado SAS, Mascaro LH (2014) Carbon Nanotubes

Modified with SnO2Rods for Levofloxacin Detection. Journal of the Brazilian Chemical

Society 25 (3):502-508.

4. Wang F, Zhu LH, Zhang JD (2014) Electrochemical sensor for levofloxacin based on

molecularly imprinted polypyrrole–graphene–gold nanoparticles modified electrode. Sensors

Actuators B Chem 192:642-647.

5. Radi A, El-Sherif Z (2002) Determination of levofloxacin in human urine by adsorptive

square-wave anodic stripping voltammetry on a glassy carbon electrode. Talanta 58 (2):319-

324.

6. Moraes FC, Silva TA, Cesarino I, Lanza MRV, Machado SAS (2013) Antibiotic Detection

in Urine Using Electrochemical Sensors Based on Vertically Aligned Carbon Nanotubes.

Electroanalysis 25 (9):2092-2099.

7. Chi YM, Li JY (2010) Determination of levofloxacin hydrochloride with multiwalled

carbon nanotubes-polymeric alizarin film modified electrode. Russ J Electrochem 46 (2):155-

160.