Magnetic Graphene Quantum Dots as a Functional Nanomaterial Towards Voltammetric Detection of L-tryptophan at Physiological pH

Document Type: Research Paper


1 Drug Applied Research Center, Tabriz University of Medical Sciences, Tabriz 51664, Iran

2 Pharmaceutical Analysis Research Center, Tabriz University of Medical Sciences, Tabriz 51656065811, Iran.

3 Department of Nanochemistry, Nano Technology Research Center, Urmia University, Urmia 57154, Iran

4 Department of Nano Technology, Faculty of Science, Urmia University, Urmia 57154, Iran.


L-Tryptophan (L-Trp) is of great importance in the biochemical, pharmaceutical and dietetic fields as it is precursor molecule of some hormones, neurotransmitters and other relevant biomolecules. So, determination of this amino acid has important role in detection of some neuron based disease. The main purpose of this report was to develop application of Fe3O4 magnetic nanoparticles/graphene quantum dots (Fe3O4 MNP-GQDs)) as a nanosensor towards electrooxidation and determination of L-Trp and also the evaluation its kinetic parameters. In continuation of our efforts to use Fe3O4 MNP-GQDs for amino acids detection, our objective in the present work was to expand application of this sensor for the determination of L-Trp which is very sensitive. Decrease in oxidation overpotential and enhancement in current proved the electrocatalytic activity of Fe3O4 MNPs-GQDs-GCE as a sensor. Importantly, by this simple method of fabrication a much lower detection limit was achieved without involving any pre-treatment or activation steps. The analytical applicability of the modified electrode has been evaluated by successfully employing it for the determination of L-Trp in the standard solution.


1. Fiorucci AR, Cavalheiro ETG, The use of carbon paste electrode in the direct voltammetric determination of tryptophan in pharmaceutical formulations. J. Pharm. Biomed. Anal. 2002; 28: 909-915
2. Moffat AC, Jackson JV, Moss MS, Widdop B: Clarke’s Isolation and Identification of Drugs, The Pharmaceutical Press, London, UK 1986; 1056.
3. Kochen W, Steinhart H, L-Try-Current Prospects in Medicine and Drug Safety; de-Gruyter: Berlin, 1994.
4. Akhgar MR, Salari M, Zamani H, Simultaneous determination of levodopa, NADH, and tryptophan using carbon paste electrode modified with carbon nanotubes and ferrocenedicarboxylic acid J. Solid State Electrochem. 2011; 15: 845-853
5. Deo RP, Lawrence NS, Wang J, Electrochemical detection of amino acids at carbon nanotube and nickel-carbon nanotube modified electrodes. Analyst 2004; 129: 1076-1081
6. Dong S, Zhang S, Chi L, He P, Wang Q, Fang Y, Electrochemical behaviors of amino acids at multiwall carbon nanotubes and Cu2O modified carbon paste electrode. Anal. Biochem. 2008; 381: 199-204
7. Liu X, Luo L, Ding Y, Kang Z, Ye D, Simultaneous determination of L-cysteine and L-tyrosine using Au-nanoparticles/poly-eriochrome black T film modified glassy carbon electrode. Bioelectrochemistry 2012; 86: 38-45
8. MacDonald SM, Roscoe SG, Electrochemical oxidation reactions of tyrosine, tryptophan and related dipeptides. Electrochim. Acta 1997; 42: 1189-1200
9. Ye D, Luo L, Ding Y, Liu B, Liu X, Fabrication of Co3O4 nanoparticles-decorated graphene composite for determination of L-tryptophan. Analyst 2012; 137: 2840-2845
10. Nan CG, Feng ZZ, Li WX, Ping DJ, Qin CH, Electrochemical behavior of tryptophan and its derivatives at a glassy carbon electrode modified with hemin. Anal. Chim. Acta 2002; 452: 245-254
11. Guo Y, Guo S, Fang Y, Dong S, Gold nanoparticle/carbon nanotube hybrids as an enhanced material for sensitive amperometric determination of tryptophan. Electrochim. Acta 2010; 55: 3927-3931
12. Hasanzadeh M, karimzadeh A, Shadjou N, Mokhtarzadeh A, Bageri L, Sadeghi S, Mahboob S, Graphene quantum dots decorated with magnetic nanoparticles: Synthesis, electrodeposition, characterization and application as an electrochemical sensor towards determination of some amino acids at physiological pH. Mater. Sci. Engin. C 2016; 68: 814-830
13. Bard AJ, Faulkner LR, Electrochemical methods: fundamentals and applications, 2nd ed., John Wiley & Sons, New York, 2001; pp. 236, 503, 709
14. Hasanzadeh M, Sadeghi S, Bageri L, Mokhtarzadeh A, Karimzadeh A, Shadjou N, Mahboob S. Poly-dopamine-beta-cyclodextrin: a novel nanobiopolymer towards sensing of some amino acids at physiological pH, Mater Sci. Eng. C 2016; 69: 343-357.
15. Xu J, Yuan Y, Li W, Deng P, Deng J, Carbon paste electrode modified with a binuclear manganese complex as a sensitive voltammetric sensor for tryptophan. Microchim. Acta 2011; 174: 239-245
16. Tang X, Liu Y, Hou H, You T, Electrochemical determination of L-Tryptophan, L-Tyrosine and L-Cysteine using electrospun carbon nanofibers modified electrode. Talanta 2010; 80: 2182-2186
17. Jiang Q, Sun W, Jiao K, Electrochemical behavior and determination of L-tryptophan on carbon ionic liquid electrode. J. Anal. Chem. 2010; 65: 648-651
18. Xu M, Ma M, Ma Y, Electrochemical determination of tryptophan based on silicon dioxide nanopartilces modified carbon paste electrode. Russ. J. Electrochem. 2012; 48: 489-494
19. Güney S, Yıldız G, Determination of tryptophan using electrode modified with poly(9-aminoacridine) functionalized multi-walled carbon nanotubes. Electrochim. Acta 2011; 57: 290-296
20. Shahrokhian S, Fotouhi L, Carbon paste electrode incorporating multi-walled carbon nanotube/cobalt salophen for sensitive voltammetric determination of tryptophan. Sens. Actuat. B 2007; 123: 942-949
21. Mao S, Li W, Long Y, Tu Y, Deng A, Sensitive electrochemical sensor of tryptophan based on Ag@C core-shell nanocomposite modified glassy carbon electrode. Anal. Chim. Acta, 2012; 738: 35-40
22. Deng K.Q, Zhou J.-H, Li X.-F, Direct electrochemical reduction of graphene oxide and its application to determination of L-tryptophan and L-tyrosine. Colloids Surf. B., 2013; 101: 183-188
23. Szunerits S, Coffinier Y, Galopin E, Brenner J, Boukherrou R, Preparation of boron-doped diamond nanowires and their application for sensitive electrochemical detection of tryptophan. Electrochem. Commun. 2010; 12; 438-441
24. Safavi A, Momeni S. Electr0ocatalytic Oxidation of Tryptophan at Gold Nanoparticle‐Modified Carbon Ionic Liquid Electrode. Electroanalysis, 2010; 22: 2848-2855.