Adsorption of zwitterionic dopamine on GO. Theoretical study.

N. F. DOMANCICH; A. C. ROSSI; L. A. MEIER; S. A. FUENTE; N. J. CASTELLANI

Congreso; VI San Luis School and Conference on Surfaces, Interfaces and Catalysis; 2018

Dopamine (DA) is a neurotransmitter that playsan important physiological role in the humans and mammalians central nervous,renal and hormonal system. The detection of its zwitterionic form (ZDA) atserum pH it is of great importance, and among the  proposed  sensors, field  effect  transistors (FET)  have  been evaluated,  where  graphene (G)  or  graphene oxide (GO)  are  used as  materials  for the  gate  of the  FET.  These materials  have  been shown  to  be very  sensitive  to adsorbed molecules. In the  present  work, the  GO  stability is  theoretically  studied and  the  adsorption of  ZDA  on the  latter  substrate is analyzed.  The  calculations were  based  on the  DFT  formalism and  were  implemented by  means  of the  Vienna  Ab-initio Simulation Program (VASP)1,2. For acoverage of 10% epoxy groups, it was observed that the proposed randomconfiguration is more stable when the central epoxy group is located on theopposite side of G sheet. This behavior was not evident for the similarconfiguration with  hydroxyl  groups. Su  et  al.3   studied the  GO  stability with  two  epoxy groups  on  the same  face  and observed  the following stabilityorder: Para> Armchair> Zigzag [3]. In this work, the results indicatethat by rearranging the structure with epoxy groups in Para and Zigzagdispositions, an improvement in energy is achieved. In addition, the adsorption of ZDA on GO wasanalyzed. The geometries studied correspond to different approaches of the ZDAto the epoxy or hydroxyl groups of GO. The presence of several of these groupsper unit cell was also considered. The adsorption  energy  turns out  to  be exothermic  and  of greater  magnitude  than in  the  case of  regular  G system.  The amino group of ZDAclose to the epoxy originates a hydroxyl group, losing an H atom. Similarresults were obtained in the presence of a hydroxyl group, in this case formingone water molecule. In all cases an electronic transfer from the molecule tothe substrate is produced. References 1.     Kresse, G.; Furthmüller, ͞Efficiency of ab-initio total energycalculations for metals and semiconductors using a plane-wave basis set,͟ J.Comput. Mater. Sci, Vol. 6, 15?50, 1996. 2.     Kresse, G.; Furthmüller, ͞Efficient iterative schemes for ab initiototal-energy calculations using a plane-wave basis set,͟ J. Phys. Rev. B, Vol.54, 11169?11186, 1996. 3.     Su, Y.; Gao, X.; Zhao, ͞Reaction mechanisms of graphene oxide chemicalreduction by sulfur-containing compounds͟ J. Carbon , Vol. 67, 146 ?155, 2014.