Photoexcitation spectroscopy of pernigraniline

Leng, J. M.; Ginder, J. M.; McCall, R. P.; Ye, H.J; Epstein, A. J.; Sun, Yiwen; Manohar, Sanjeev K.; MacDiarmid, Alan G.

doi:10.1016/0379-6779(91)91613-f

Cited by 23 publications

(8 citation statements)

References 12 publications

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“…Also for the PB we obtain the same general behaviour as the bands proposed in the literature [31] and the reproduction of the main experimental optical transitions [34][35][36] at 2.2, 3.8 and 4.3 eV (see Fig. 4b).…”

Section: Band Structures Of the Leucoemeraldine Emeraldine And Pernisupporting

confidence: 59%

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Tight-Binding Effective Hamiltonians for the Electronic States of Polyaniline Chains

Vignolo

Farchioni

Grosso

2001

phys. stat. sol. (b)

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By means of strictly one-dimensional effective Hamiltonians, in the tight-binding scheme, we obtain band structures and densities of states of the main forms of polyanilines, which compare favourably with existing theoretical and experimental studies. We first consider the band structures of the three polymeric base forms: leucoemeraldine, emeraldine and pernigraniline; then we study the pernigraniline salt and the emeraldine salt in the polaronic and bipolaronic configurations. The 1D p-electron effective Hamiltonians are obtained exploiting a modified version of the recursion method and successively the application of the renormalization method. The procedure here outlined can be adopted for any polymeric chain; it is so flexible to embody known relevant structural and optical properties of the polymer, moreover it provides a useful tool for successive iterative calculations in the study of the electronic transport properties of the polymer also in the presence of disorder.

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Section: Band Structures Of the Leucoemeraldine Emeraldine And Pernisupporting

confidence: 59%

“…4c). This value approaches the experimental measurements of the gap (maximum absorption at about 2 eV [32][33][34][35][36][37]), better than the values proposed in the literature (0.6-0.9 eV [10,31]). As noticed in Ref.…”

Section: Band Structures Of the Leucoemeraldine Emeraldine And Pernimentioning

confidence: 52%

Tight-Binding Effective Hamiltonians for the Electronic States of Polyaniline Chains

Vignolo

Farchioni

Grosso

2001

phys. stat. sol. (b)

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“…Steady state photoinduced absorption experiments show the presence of a photoinduced charge defect of effective --5 me and a photoinduced charge defect of effective mass -300me. Because of the enormous difference in their effective mass and their lifetimes, the low energy peak is associated with a solitonic defect in the bond length order parameter while the middle energy peak is associated with a polaronic defect in the ring torsion angle order parameter [36]. Light induced electron spin resonance studies support these assignments (37].…”

Section: E Leucoemeraldinesupporting

confidence: 56%

Electronic Phenomena in Polyanilines

Epstein

MacDiarmid

1991

Frontiers of Polymer Research

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" 4-.-* "o t W*enar.Se. ovoclumng tite toll %C e.qqef uf~oms. seao" *mast" oat* sow. M )~~ :V;wUn..on Of 'AtOrmaw"n Wf COM"tt% regarcm" tft %~ Mummaq or on ote *WW't of t"- SPONSORING: MONITORING AGENCY NAME(S) AND ADIESS(ES D~higmtku Unimiled ABSTRACT (Maximum 200 words)Polyanilines have been known for over one hundred years. Recent studies of this chemically flexible polymer have demonstrated unusual chemical, electrical, and optical phenomena, both in insulating forms and conducting forms. Polyaniline has three stable insulating forms, leucoemeraldine base (LEB), emeraldine base (EB), and pernigraniline base (PNB). These three forms exhibit differing phenomena ranging from intramonomer luminescing excitons and ring rotation polarons in LEB, to nonluminescing charge transfer excitons and also ring rotational polarons in EB, to a degenerate ground state with bond order parameter solitons and ring order parameter polarons in PNB. The LEB form can be p-doped (oxidatively doped), the EB form can be protonic acid doped and the PNB form can be n-doped (reductively doped) to form conducting systems. Charge conduction studies of oriented films and fibers demonstrate that three-dimensional order between chains is critical for high conductivities. The ability to derivatize polyaniline at ring and nitrogen positions allows one to test concepts for the control of conductivity as well as improved processing. 92-

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“…Previous experimental studies found that the maximum in the π−π* optical absorption spectrum in the LB form is 3.6 eV in N -methylpyrrolidone (NMP) solution and 3.8 eV in thin film. − The excitation energy (band gap) is large because the benzene rings are connected by a saturated amine linkage which inhibits conjugation. In contrast, the π−π* absorption in the PNB forms is much lower (1.7∼2.3 eV) − because the benzene rings are conjugate through an imine linkage. In the doped (ES) form, electrical conductivity is greatly increased by the formation of low-energy hole levels. , The experimental absorption spectrum for ES shows a band gap of 1.5 eV which is interpreted as excitations to the polaron band. ,, …”

Section: Introductionmentioning

confidence: 96%

Calculations of Band Gaps in Polyaniline from Theoretical Studies of Oligomers

2000

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Geometries and band gaps of polyaniline oligomers up to decamer have been systematically calculated and analyzed using various computational techniques such as molecular mechanics, semiempirical, and ab initio methods. On the basis of fully optimized geometries of neutral and charged forms of polyaniline oligomers, excitation energies are calculated at the semiempirical ZINDO (INDO/S) level and extrapolated to the band gap value of the infinite chain. Band gaps are also approximated by extrapolating the HOMO/LUMO difference calculated at the density functional level (B3LYP/6-31G*). The ZINDO//AM1 band gaps in the reduced and oxidized form of polyaniline (4.3 and 2.7 eV) are in good agreement with experimental values (3.8 ( 2 and 1.8 ( 3 eV, respectively). The doped form of polyaniline (two positive charges per four aniline units) has been computed with a spin-unrestricted method (UAM1) and the band gap approximated from an extrapolation of the tetramer and octamer. The calculated band gap of 1.3 eV (UZINDO//UAM1) is in good agreement with experiment (1.5 eV). The influence of ring torsional angle and interchain interaction on the band gap of the polyaniline system are also discussed.

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Photoexcitation spectroscopy of pernigraniline

Cited by 23 publications

References 12 publications

Tight-Binding Effective Hamiltonians for the Electronic States of Polyaniline Chains

Tight-Binding Effective Hamiltonians for the Electronic States of Polyaniline Chains

Electronic Phenomena in Polyanilines

Calculations of Band Gaps in Polyaniline from Theoretical Studies of Oligomers

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