[Blueboard] Dissertation Defense of Jonathan Paa

gmamauag at ateneo.edu gmamauag at ateneo.edu
Mon Nov 5 16:54:59 PHT 2012


The Department of Chemistry invites everyone to the Dissertation  
Defense of  Mr. Jonathan Pa-a

Title: ?Synthesis of NH2?graphene and Characterization of Its  
Electropolymerized Composite with Polyaniline?

Date: 07 November 2012; Tuesday, 4:00 pm ; C205 Schmitt Hall

ABSTRACT

	This work presents the synthesis of an amino-functionalized graphene,  
NH2?graphene, by direct photonitration of exfoliated graphene from  
graphite.  Photonitration and subsequent reduction to amino-functional  
groups occur in a one-pot synthesis.  It is a simpler method compared  
with the more commonly reported synthetic route that passes through  
the graphene oxide (GO) synthesis by the Hummers or modified Hummers  
method.  An added advantage here is that the starting material is a  
pristine graphene as opposed to a reduced graphene oxide which  
generally has more defects on its structure.
	Spectrochemical analyses of the synthesized NH2?graphene confirm the  
success of functionalization.  The FTIR spectra of photonitrated and  
reduced graphene show a peak at 3414 cm?1 corresponding to the ?N?H  
stretching of the amino group and the imine ring vibration of the  
?grapheneC=N at 1637 cm?1.  On the other hand, UV-visible spectrum  
dispersed in 50 % ethanol-water as solvent has peaks at 231 and 280 nm  
corresponding to ???* (aromatic ?C=C) and n??* (aromatic ?C?N)  
transitions, respectively.  The XRD data indicate a highly graphitic  
nature of the synthesized material, although a peak at 11.6o (2?) is  
suggestive of graphene modification similar to that of graphene oxide.  
  TGA analyses indicate that NH2?graphene is more gradually decomposed  
at temperature range of 400 ? 900 oC than the aggregated graphene?s  
(or graphite) rate of decomposition at the same temperature range.
	Copolymerization of the synthesized NH2?graphene with polyaniline  
under acidic medium was done through cyclic voltammetry and  
constant-potential coulometry.  Spectrochemical analyses of the  
composites indicate the incorporation of NH2?graphene in polyaniline  
as evidenced in the intense peak at 1450 cm?1 corresponding to  
increased C=C (overlapped with C=N) groups of graphene.  UV-visible  
data also confirm the doping effects of NH2?graphene onto polyaniline  
chain.  Excessive NH2?graphene transforms the emeraldine base segments  
of polyaniline to highly reduced leucoemeraldine form.  Time-evolution  
UV-visible absorption analysis indicates the tendency of the  
composites to further transform into more imine functionalities or  
phenazine-like microstructures.  Morphology of the composites shows  
the formation of dendritic-like crystal structures as well as  
exhibiting distorted and fragmented polyaniline fibers when doped with  
more NH2?graphene.
	Electrochemical analysis of the composite material shows improved  
capacitive behavior and conductivity relative to the polyaniline film  
alone.  Electrochemical impedance spectroscopy (EIS) also shows  
increased charge-transfer resistance (Rct) of the  
NH2?graphene/polyaniline composite-coated electrode.  These  
properties, however, tend to drop when the minimum limit value of the  
dopant (NH2?graphene) is exceeded.  Thermogravimetric analysis data of  
these composites also reveal thermal instabilities at higher dopant  
limits.
	The present functionalization route with NH2?graphene is believed to  
decorate the ?edges? of graphene.  It opens a wide variety to other  
functional modifications such as the halide (I and Br) and CN-group by  
the Sandmeyer reaction synthesis via diazotization reaction.

Thank you.
-- 
Gina B. Mamauag
Department of Chemistry
Ateneo de Manila University
School of Science and Engineering
Loyola Heights, Quezon City
1108 Philippines
Telefax: +63-2-426-1323
Phone: +63-2-426-6001 x5620





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