Study on the redox property of electroactive poly(5-hydroxy-1,4-naphthoquinone-co-5-hydroxy- 3-acetic acid-1,4-naphthoquinone) thin film by in-situ raman spectroscopy

Journal of Chemistry, Vol. 43 (1), P. 100 - 104, 2005<br /> <br /> <br /> STUDY ON THE REDOX PROPERTY OF ELECTROACTIVE<br /> POLY(5-HYDROXY-1,4-NAPHTHOQUINONE-co-5-HYDROXY-<br /> 3-ACETIC ACID-1,4-NAPHTHOQUINONE) THIN FILM BY IN-SITU<br /> RAMAN SPECTROSCOPY<br /> Received 2nd-Sept.-2003<br /> Tran Dai Lam<br /> Faculty of Chemical Technology, Hanoi University of Technology<br /> <br /> SUMMARY<br /> A new functionalized conducting poly(5-hydroxy-1,4-naphthoquinone-co-5-hydroxy-3-acetic<br /> acid-1,4-naphthoquinone) with electroactive quinone group was studied by in situ Raman<br /> spectroscopy. The Raman results confirmed a good reversible transformation between two<br /> structures: quinoid and hydroquinoid ones during reduction-oxidation processes.<br /> <br /> I - INTRODUCTION in situ in aqueous medium under favorable<br /> conditions (the Raman diffusion of water is very<br /> Poly(5-hydroxy-1,4-naphthoquinone-co-5- weak). Furthermore, contrary to MIRFTIRS,<br /> hydroxy-3-acetic acid-1,4-naphthoquinone) Raman spectroscopy does not require any<br /> films (poly(JUG-co-JUGA)) were prepared by specific preparation of electrochemical cell as<br /> electropolymerization in organic medium (Ace- well as the sample (the working electrode is<br /> tonitrile + LiClO4). Data from XPS, IR ex situ, standard) [3].<br /> IR in situ and theoretical calculations of frontier<br /> orbitals indicate that the structure of copolymer II - EXPERIMENTAL<br /> is composed alternatively of furan and naphthyl-<br /> ene rings. Poly(JUG-co-JUGA) films show 5-hydroxy-1,4-naphthoquinone (JUG) from<br /> reversible, well-defined redox system of quinone Fluka (98%) was used as received.<br /> group in both organic and aqueous acid as well 5-hydroxy-3-acetic acid-1,4-naphthoquinone<br /> as in neutral aqueous solutions (PBS, pH 7.4). (JUGA) was synthesized in one step from JUG<br /> Especially, the quinone electroactivity in neutral and thioglycolic acid (from Acros). A detailed<br /> aqueous solution was crucial property, allowing procedure has been described elsewhere [1].<br /> this polymer to be used as electro-chemically<br /> internal marker for direct biological detection in Poly (JUG-co-JUGA) was electrosynthesi-<br /> biosensors [1]. zed by cyclic voltammetry, on AUTOLAB,<br /> model PGSTAT 30 (50 cycles, potential domain<br /> The redox behavior of quinone group in 0.4 - 1.05 V vs.SCE, scan rate 50 mV.s-1).<br /> organic medium is normally investigated by IR<br /> in situ (MIRFTIRS) [2]. In this paper, in situ Aqueous solution buffer is PBS (0.137 M<br /> Raman spectroscopy was used to study this NaCl; 0.0027 M KCl; 0.0081 M Na2HPO4;<br /> redox system in neutral aqueous solution. The 0.00147 M KH2PO4, pH 7.4) from Dulbecco.<br /> Raman method presents, compared to method Raman spectra excited with the red laser<br /> MIRFTIRS, the advantage of being able to work light at 632.8 nm were recorded on a DILOR X-<br /> 100<br /> Y double monochromator spectrometer in aqueous PBS solution. The cyclic voltammo-<br /> subtractive mode with a multichannel detector gramm of quinone electroactivity was presented<br /> (1024 diodes cooled by Peltier effect). To avoid in figure 1.<br /> local decomposition of polymer the laser power After several scans within the quinone<br /> arrived at the sample surface is limited to 8 domain of potentials to stabilize the quinone<br /> mW. In situ Raman experiments were perfor- electroactivity, in situ Raman spectra were<br /> med by coupling electrochemical technique recorded by applying constant potentials of 0; -<br /> (AUTOLAB) with the above Raman 0.2; -0.4; -0.6 V vs Ag/AgCl (in reduction cycle,<br /> spectrometer. The working electrodes were figure 2). These values were determined from<br /> poly(JUG-co-JUGA) film coated Pt electrodes. the quinone electroactivity voltammo-gramm in<br /> The polarization time is about 2 min, the time figure 1. The reason by that the potential was<br /> being necessary for structural stabilization as not set up at -0.8 V and -1.0 V was strong<br /> well as for spectra acquisition. fluorscence at these potentials of the sample and<br /> III - RESULTS AND DISCUSSION it led to unresolved Raman spectra. In order to<br /> verify if these changes be reversible, the spectra<br /> The polymer films poly(JUG-co-JUGA) were also recorded at the same potentials but in<br /> show a good electroactivity of quinone group in opposite direction (in oxidation cycle, figure 3).<br /> <br /> I/ A<br /> <br /> 3<br /> <br /> <br /> 2<br /> <br /> <br /> 1<br /> <br /> E/V(SCE)<br /> 0<br /> -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2<br /> <br /> -1<br /> <br /> <br /> -2<br /> <br /> <br /> -3<br /> <br /> <br /> Fig. 1: Cyclic voltammogramm of electroactive poly(JUG-co-JUGA) in PBS (v: 50 mV.s-1)<br /> <br /> The examination of these Raman spectra led variation is also reversible.<br /> to the following observations:<br /> The band at 1350 cm-1 almost does not vary<br /> During the reduction cycle (figure 2) a according to the potentials during the reduction<br /> significant decrease in intensity for the bands and oxidation.<br /> located at 1143 and 1270 cm-1 was observed.<br /> The opposite evolution in band intensity, Intensity of the band at 1450 cm-1 (C=C<br /> detected during oxidation, confirmed the vibration of quinoid structure) vary also rever-<br /> reversible changes of these bands. They were sibly: it decreases in reduction but increases in<br /> attributed to the C-H and C-C vibrations oxidation (figure 3).<br /> respectively in the quinoid structure (Q) [4]. The band at 1508 cm-1 was also assigned to<br /> The band located at 1385 cm-1 is attributed C=C vibration of the quinoid form. We observed<br /> to vibration C=O of the quinone group. This the decrease in its intensity accompanied by a<br /> <br /> <br /> 101<br /> displacement of this band to1495 cm-1 ( 10 hydroquinoid form (HQ) [5] was registered in<br /> cm-1) during the reduction. reduction cycle. In oxidation, this form was<br /> reoxidized to regain the initial quinoid form, the<br /> Significant increase in band intensity for the intensity of this band thus decreases in oxidation<br /> band at 1575 cm-1, due to C=C vibration of the cycle.<br /> <br /> <br /> 1270<br /> Raman Intensity (a.u.)<br /> <br /> <br /> <br /> <br /> 1143<br /> 1350<br /> 1385 E/V (SCE)<br /> -0.6V(S13)<br /> <br /> <br /> -0.4V(S12)<br /> <br /> -0.2V (S9)<br /> 500<br /> <br /> <br /> <br /> <br /> 0V (S8)<br /> <br /> <br /> <br /> <br /> 1000 1100 1200 1300 1400<br /> wave numbers, cm-1<br /> 1575<br /> = 10<br /> 1450 1495 1625<br /> 1650<br /> Raman Intensity (a.u.)<br /> <br /> <br /> <br /> <br /> E/V(SCE)<br /> -0.6V (S14)<br /> <br /> <br /> -0.4V(S11)<br /> <br /> <br /> <br /> -0.2V(S10)<br /> 500<br /> <br /> <br /> <br /> <br /> 0V(S7)<br /> 1508<br /> <br /> 1400 1500 1600 1700 1800<br /> wave numbers, cm-1<br /> Fig. 2: In situ Raman spectra of poly(JUG-co-JUGA) in PBS recorded at the potentials:<br /> 0; -0.2; -0.4; -0.6 V vs Ag/AgCl (in reduction), a) 1000 - 1400 cm-1, b) 1400 - 1800 cm-1<br /> <br /> 102<br />  1270<br /> Raman Intensity (a.u.)<br /> <br /> <br /> <br /> 1143<br /> 1385<br /> 1350 E/V(SCE)<br /> <br /> 0V(S20)<br /> <br /> <br /> -0.2V(S17)<br /> 500<br /> <br /> <br /> <br /> <br /> -0.6V(S13)<br /> <br /> <br /> 1000 1100 1200 1300 1400<br /> -1<br /> wave numbers, cm<br /> <br /> 1497<br /> Raman Intensity (a.u.)<br /> <br /> <br /> <br /> <br /> 1450<br /> <br /> <br /> 1575 1630 E/V(SCE)<br /> 1651<br /> 0V (S19)<br /> <br /> <br /> -0.2V (S18)<br /> <br /> -0.4V (S15)<br /> 500<br /> <br /> <br /> <br /> <br /> -0.6V (S14)<br /> <br /> <br /> 1400 1500 1600 1700 1800<br /> wave numbers, cm-1<br /> Fig. 3: In situ Raman spectra of poly(JUG-co-JUGA) in PBS recorded at the potentials:<br /> -0.6; -0.4; -0.2; 0 V vs Ag/AgCl (in oxidation), a) 1000 - 1400 cm-1, b) 1400 - 1800 cm-1<br /> <br /> The band at 1625 cm-1, like the band at 1350 Above discussed in situ Raman vibrations<br /> -1<br /> cm almost does not vary during reduction as are summarized in table 1. These results clearly<br /> well as oxidation. It is possible that both quinoid show the reversible transformation between two<br /> (Q) and hydroquinoid forms (HQ) contributed structures (quinoid and hydroquinoid) in<br /> to this mode of vibration, so their overall aqueous medium: during the reduction the<br /> intensities remain constant. bands characterized for hydroquinoid form<br /> <br /> 103<br /> become predominated, whereas in oxidation the bands of quinoid form are prevalent.<br /> <br /> Table 1: Attributions and variations of the intensities of the in situ Raman bands during the<br /> reduction and oxidation cycles: Q: quinoid form; HQ: hydroquinoid form; increase; decrease;<br /> = not variation in band intensity<br /> <br /> Vibration attributions Frequencies, cm-1 Variation in reduction Variation in oxidation<br /> (C-H)plan (Q) 1143<br /> C-C (Q) 1270<br /> C=O (Q) 1385<br /> C-O (HQ+Q) 1350 = =<br /> C=C (Q) 1450<br /> C=C (Q) 1495<br /> C=C (HQ) 1575<br /> C=C (HQ+Q) 1625 = =<br /> <br /> IV - CONCLUSION Doan, L. H. Dao. Anal. Chem. ACS 2003,<br /> AC034770F, accepted for publication.<br /> The quinone redox system of functionalized 2. S. Hubert, M. C. Pham, Le H. Dao, Q. A.<br /> conducting poly(JUG-Co-JUGA) was investi- Nguyen, M. Hedayatullah, Synth. Met., 128,<br /> gated in situ by Raman spectroscopy. Raman 1, P 67 (2002).<br /> spectra revealed the fine changes in structure,<br /> concerning quinone group. From these results 3. N. Felidj, S. Bernard, E. A. Bazzaoui, G.<br /> one can suggest that quinoid structure be Levi, J. Aubard. New Chem., 16(62), P.<br /> transformed into hydroquinoid one in reduction 1895 (1998).<br /> cycle and be reversibly switched back to 4. S. Quillard, G. Louarn, J. P. Buisson, S.<br /> quinoid form in oxidation cycle. Lefrant, J. Masters, A. G. Macdiarmid.<br /> Synth. Met., 525, P. 49 (1992).<br /> REFERENCES 5. Quillard, G. Louarn, S. Lefrant, A. G.<br /> Macdiarmid. Phys. Rev. B, 50, P. 12496<br /> 1. M. C. Pham, L. D. Tran, B. Piro, T. 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