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Electrochemical Preparation of Polyaniline/Gold FilmJohnson Agyapong1, Antony Epps2, Kenton Meronard3, and Amir Saheb, PhD3

1Brandeis University, 2South Side Virginia Community College, 3Albany State University

ABSTRACT

BACKGROUND

METHODS

• Phase 2

After PANI has been electropolymerized, the deposition of gold the film begins. A bulk electrolysis is run in 1M HCl at 0.7V for 40s to oxidize PANI and then rinsed with 1M HCland dipped in 10-5M HAuCl4 containing 1M HCl for 30s. The film is rinsed again with 1M HCl and a linear sweep is run at 0.7 V to -0.2 V at a scan rate of 20 mV/s to reduce it. A CHI Instruments potentiostat alongside a UV-Vis spectrophotometer to characterize the PANI/Au film after each gold deposition.

RESULTS

RESULTS

CONCLUSION

METHODS

The PANI/Au films were made in two phases:

Phase1: Electropolymerization of polyaniline

Phase2: Gold Deposition

Using a three compartment electrochemical cell made up of Ag/AgCl reference electrode, Pt

or ITO working electrode, and Pt wire or foil counter electrode, PANI was deposited on an

ITO substrate or platinum electrode by CV from 0.1M aniline and 1M H2S04 solution within a

range of -0.2V to +0.8V. The CV was run for 25 cycles (50 segments) at 20 mV/s.

ACKNOWLEDGEMENTS

REFERENCES

Dey, A., Kaushik, A., Arya, S., & Bhansali, S. (2012). Mediator free highly sensitive

polyaniline-gold hybrid nanocomposite based immunosensor for prostate-specific antigen (PSA) detection. Journal Of Materials Chemistry, 22(29), 14763-14772.

Saheb, A., & Seo, S. (2011). Polyaniline/Au Electrodes for Direct Methanol Fuel Cells. Analytical Letters, 44(12), 2221-2228.

Saheb, A., Smith, A., Josowicz, M., Janata, J., Baer, DR., & Engelhard, MH. (2008).

Controlling size of gold clusters in polyaniline from top–down and from bottom–up. Journal of

Electroanalytical Chemistry, 621(2), 238-244.

Shin, L., (2008). Gold Nanoparticles. Retrieved from

http://www.chemistry.illinois.edu/research/inorganic/seminar_abstracts/2008-2009/Shen.Abstract.pdf

Song, E., & Choi JW. (2013). Conducting Polyaniline Nanowire and Its Applications in Chemiresistive Sensing. Nanomaterials.

Surwade, S., & Manohar, Sanjeev K. (2010). Synthesis of Nanostructured

Polyaniline,ProQuest Dissertations and Theses.

We would like to say a special thank you to Dr. Amir Saheb and Kenton Meronard for

helping us through our research. We also thank Dr. Samuel and the whole PREM faculty

for making this experience enjoyable.

PANI can be labeled scientist’s favorite conducting polymer because its synthesis is fairly

easy and the oxidation states of PANI can be manipulated by changing oxidation/reduction.

Its versatility makes its applications endless. One of the applications of PANI is creation of

electrochemical biosensors which was what we were ultimately trying to create by attaching

gold using the bottom up approach. Gold increases the catalytic properties of PANI. Saheb &

Seo observed an increase in the oxidation of PANI in methanol once Au atoms were attached

(2011). Dey et al. utilized PANI/Au nanoparticles as an immunosensor for prostate-specific

antigen and found that there was an increase in sensing performance (2012). Also, they found

that Au nanoparticles increased the “electro-active surface area of PANI” (2012) making

PANI/Au films favorable components of a biosensor. Gold has a high affinity to thiol groups

so by attaching a thiolated DNA probe, we come up with a sensitive and highly specific DNA

hybridization biosensor.

The objective of this project is to utilize this technology to develop and synthesize our own

biosensors.

Polyaniline (PANI) is a conductive polymer produced by polymerizing aniline. Owing to

favorable properties like easy synthesis and ability to change oxidation state with simple

oxidation/reduction (Surwade, 2010), there have been numerous research projects based on

the potential applications of PANI. Aniline can be polymerized chemically or

electrochemically; however, the latter was utilized in this experiment because the final

product did not require extraction from any solvent, oxidant or monomer (Chemistry of

polyaniline). Our short-term goal was to deposit gold clusters on the PANI film and

potentially create a DNA hybridization biosensor. We successfully electropolymerized

polyaniline on ITO substrates and platinum (Pt) electrodes but we were unable to achieve our

short-term goal. We went through up to 8 gold treatments but our methods of characterization

could not detect any gold present on the PANI film. We believe that gold clusters were

present but too tiny to be detected by our methods of characterization. Saheb et al, note that

such gold clusters may be detected using XPS (2008).

Presence of polyaniline can be observed with the naked eye. It has a greenish color

which changes to different shade of green as the oxidation state changes. For the

PANI/Au film, we used CHI instrument potentiostat and UV-Vis spectrophotometer to

characterize our film. Saheb & Seo (2011) observed an increase the oxidation of

PANI/Au compared with plain PANI in methanol. So we run CV in 0.5M H2SO4

containing 1M CH3OH to observe the oxidation of PANI/Au. We also used UV-Vis

spectrophotometer which we run after the 0, 2, 5, and 7 gold treatments.

Scheme 1. Setup of phase 1

Scheme 2. Cycle of phase 2 beginning from Bulk Electrolysis. Each cycle

represents deposition of one Au atom.

1.a 1.b

1.c

Figure 1: (a) CV of PANI

formation, (b -d) Morphology

of PANI using SEM.

2.a 2.b

Figures 3: (Right) PANI/Au film UV-Vis Spectra after 0, 2, 5 and 7 Au treatments (Left)UV-

Vis Spectra after 0, 1, 3 and 5 Au treatments in both Oxidized and reduced states (Saheb &

Seo 2011)

• We were able to successfully synthesize and characterize the the PANI film onto both a 2

mm diameter Platinum surface and ITO (Indium Tin Oxide) Coated Glass.

• During electrochemical polymerization, We observed the three major oxidation peaks.

• Characterization of our samples using CV and UV-Vis was challenged due to the weak

bonding of the PANI film and the ITO surface.

• Despite this, data from UV-Vis and methanol oxidation, suggest that our films did not

contain Au clusters at detectable levels

Figures 2:

(a) PANI after CV (38

cycles at 20mV/s),

(b) PANI in emeraldine

oxidation state

(c) PANI in

pernigraniline

2.c

1.d