Electrosyntheses of high quality free-standing poly(9-fluorenone) films in boron trifluoride diethyl etherate

High quality free-standing poly(9-fluorenone) (PFO) films were synthesized electrochemically by direct anodic oxidation of 9-fluorenone (FO) in pure boron trifluoride diethyl etherate (BFEE). The oxidation potential of FO in this medium was measured to be only 1.48 V versus SCE, which was greatly lower than that determined in CH₂Cl₂ + 0.1 mol l⁻¹ Bu₄NBF₄ (2.21 V versus SCE). PFO films obtained from BFEE showed good electrochemical behavior, good thermal stability with electrical conductivity of 7.8 × 10⁻³ S cm⁻¹, indicating that BFEE was a better medium than CH₂Cl₂ for the electrosyntheses of PFO films. Structural studies showed that the polymerization of FO ring occurred at 2,7-position. As-formed PFO films can be partly dissolved in acetone and tetrahydrofuran (THF). Fluorescent spectral studies indicate that PFO is a good blue light emitter. To the best of our knowledge, this is the first report on the electrosyntheses of free-standing PFO films.     

Electrodeposition of poly(indole-5-carboxylic acid) in boron trifluoride diethyl etherate containing additional diethyl ether

High quality poly(indole-5-carboxylic acid) (PICA) films were synthesized electrochemically by direct anodic oxidation of indole-5-carboxylic acid (ICA) in boron trifluoride diethyl etherate (BFEE) containing additional 80% diethyl ether (EE) (by volume). PICA films obtained from this medium showed good electrochemical behavior and good thermal stability with a conductivity of 10⁻² S cm⁻¹. The doping level of PICA increased during electrochemical growth processes. Dedoped PICA films were soluble in dimethyl sulfoxide (DMSO). The structure of the polymer were studied by UV-vis spectroscopy, FT-IR spectroscopy and ¹H NMR spectroscopy, which indicated that the polymerization occurred at C₍₂₎ and C₍₃₎ position. Fluorescent spectral studies indicated that PICA was a good blue-light emitter.     

Synthesis and electrochemical characterization of bis(3,4-ethylene-dioxythiophene)-(4,4′-dinonyl-2,2′-bithiazole) comonomer

The synthesis and characterization of a novel donor acceptor donor type bis(3,4-ethylene-dioxythiophene)-(4,4′-dinonyl-2,2′-bithiazole) comonomer and its electrochemically prepared polymer on carbon fiber, Pt button and ITO plate is reported in this paper. Cyclic voltammetry of the polymer in 0.1 M Et₄NBF₄/CH₂Cl₂ exhibits a very well defined and reversible redox processes and this co-monomer can be either p-doped or n-doped. The half-wave oxidation potentials of the polymer (E_1/2) were observed at 0.303 and 0.814 V versus Ag/AgCl. The polymer is electrochromic; the onset for the π-π^* transition (E_g) of 1.75 eV with a λ_max at 2.15 eV and the homogeneous and high quality film of the polymer is stable of its optical properties offering fast switching time which is less than 0.25 s. The morphological studies reveal that the polymer was deposited as a continuous and very well adhering film to surface of the carbon fiber microelectrode. All these properties make this polymer favorable for use in electronic devices.     

Almost completely dedoped electrochemically deposited luminescent films exhibiting excellent LED performance

An improved method for electrochemical deposition (ED) of a novel precursor (peripheral carbazole substituted 9,9′-spirobifluorene (TCPC)) for fabricating highly efficient luminescent films and devices has been developed. Electrochemical deposition often leaves residual charged ion species within the film. These species can negatively impact the performance of these films in OLED applications. The amount of residual charged species in the films can be reduced by controlling the oxidation and reduction potentials, by using electrolytes with different counter anions, and by washing with solvents. An optimized ED process showed a significant decrease in the doping level; up to 0.07% in ED film. The films prepared under a scan potential range from 0.85 to −0.8 V, using TBAAsF₆ as the supporting electrolyte, and washed with solvent mixtures of acetonitrile and CH₂Cl₂ (V/V = 2/3) demonstrated excellent device performance. Light-emitting devices fabricated by electrochemical deposition achieved deep blue emission (x, y) = (0.16, 0.06) in CIE coordinates. High luminance efficiencies of 2.3 cd A⁻¹ were achieved for single-layer device; luminescence efficiencies of 4.4 cd A⁻¹ were achieved for a double-layer device. Finally, the problem that ED films usually exhibit low electroluminescent efficiency is solved.     

Voltammetric investigation of the dissociative electron transfer to polychloromethanes at catalytic and non-catalytic electrodes

The electrochemical behavior of CCl₄, CHCl₃ and CH₂Cl₂ has been investigated by cyclic voltammetry at glassy carbon and silver electrodes in DMF + 0.1 M Et₄NClO₄ in the absence and presence of a good proton donor. At both electrodes, each compound exhibits a series of reduction peaks which represent sequential hydrodechlorination steps up to methane. The nature of the electrode material and the proton availability of the medium affect drastically the voltammetric pattern of the compounds. Silver exhibits extraordinary electrocatalytic properties toward the reduction process, with positive shifts of the peak potentials of about 0.57-0.95 V as compared to glassy carbon. Reduction of any polychloromethane, CH_nCl_(4−n) (n = 0-2), yields the carbanion CH_nCl_(3−n)⁻ which partitions into two reaction channels: (i) protonation and (ii) Cl⁻ elimination to give a carbene :CH_nCl_(2−n). If a strong proton donor is added into the solution, sequential hydrodechlorination becomes the principal reaction route at both electrodes. When, instead, purposely added acid is not present in solution, both reaction pathways ought to be considered. In these conditions, when possible, self-protonation reactions play an important role in the overall reduction process.     

Orange to black electrochromic behaviour in poly(2-(2-thienyl)-1H-pyrrole) thin films

We have studied an electrochromic precursor, 2-(2-thienyl)-1H-pyrrole (1), using two improved procedures of the Trofimov reaction. Optimised stereochemical calculations at the B3LYP/6-311G* level showed almost equal s-cis and s-trans conformational populations in 1 with marked out-of-plane deviations of ca. 30°. Model calculations suggest that the predominant rotational conformation in undoped poly(1) would be s-trans with the essential out-of-plane deviations around the all three interheterocyclic bonds of ca. 25-30°. Monomer 1 exhibited two irreversible oxidation processes at +0.86 and +1.3 V corresponding to the oxidation of the pyrrole and thiophene rings, respectively. Orange to black electrochromic behaviour was found in ClO₄⁻ doped poly(1) thin films with colouring and bleaching times of 1.8 and 1.3 s, respectively. The colouration efficiency during the bleaching process was 233 cm²/C. The optical contrast at 450 nm was 19% and in the near-IR was 36%. The band-gap of poly(1) (1.6-1.7 eV) was found to be significantly lower than that of polypyrrole (2.85 eV) and polythiophene (2.3 eV) as a consequence of increased electron delocalisation in the system. Important differences in the morphology of doped and dedoped poly(1) films were observed by atomic-force microscopy (AFM). Doped poly(1) films showed a granular morphology with primary particles of 45-60 nm in size and an average surface roughness of 3.5 nm. On the other hand, dedoped poly(1) films showed interconnected aggregates of 65-90 nm in size as a consequence of particle fusion, with a surface roughness of 9.2 nm. In summary, poly(1) is a promising material for emerging flexible electrochromic devices such as displays and variable optical attenuators.     

Direct low‐potential electropolymerization of 9,10‐dihydrophenanthrene in boron trifluoride diethyl etherate

High‐quality poly(9,10‐dihydrophenanthrene) (PPh) with good fluorescence properties was synthesized electrochemically by the direct anodic oxidation of 9,10‐dihydrophenanthrene in boron trifluoride diethyl etherate (BFEE). PPh films obtained from BFEE‐based electrolytes showed good electrochemical behavior and good thermal stability with an electrical conductivity of 2.2 × 10^?3 S/cm; this indicated that BFEE was a better medium for the electrosyntheses of PPh films. Dedoped PPh films were soluble in CH₂Cl₂, dimethylformamide, and dimethyl sulfoxide. The structure and morphology of the polymer were also characterized by ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, ¹H‐NMR spectroscopy, and scanning electron microscopy, respectively, which indicated the polymerization mainly occurred at the C₍₂₎ and C₍₇₎ positions. Fluorescent spectral studies indicated that PPh was a good blue‐light emitter. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Potassium-ion selective solid contact microelectrode based on a novel 1,3-(di-4-oxabutanol)-calix[4]arene-crown-5 neutral carrier

The development of novel potassium-ion selective microelectrodes using microfabrication technologies and electrochemical polymerization is described. The microelectrode is based on electropolymerized polypyrrole films, doped with cobaltabis(dicarbollide) ions ([3,3′-Co(1,2-C₂B₉H₁₁)₂]), as an internal solid contact layer between the platinum surface and the polymeric sensing membrane. The ion selective membranes, which are based on a plasticized PVC membrane, contain 1,3-(di-4-oxabutanol)-calix[4]arene-crown-5 as a novel potassium ionophore, and are deposited on top of a layer of the conducting PPy[3,3′-Co(1,2-C₂B₉H₁₁)₂]. The response of the microelectrode was linear with a Nernstian slope of 51 ± 2 mV decade⁻¹ over a K⁺ ion concentration range of 6 × 10⁻⁶ to 1 × 10⁻¹ M, with a detection limit of 1.8 × 10⁻⁶ M. The microelectrode is suitable for use within the pH range of 3-11. The electrode could be used for at least one month without a considerable alteration in its potential.     

Electrochemical and density functional theory study of bis(cyclopentadienyl) mono(β-diketonato) titanium(IV) cationic complexes

The electrochemical behaviour of fluorinated bis(cyclopentadienyl) mono(β-diketonato) titanium(IV) complexes, of general formula [Cp₂Ti(R′COCHCOR)]⁺ClO₄⁻ with Cp = cyclopentadienyl and R′, R = CF₃, C₄H₃S; CF₃, C₄H₃O; CF₃, Ph (C₆H₅); CF₃, CH₃; CH₃, CH₃; Ph, Ph and Ph, CH₃ is described. Both metal and ligand based redox processes are observed. The chemically and electrochemically reversible Ti^IV/Ti^III couple is followed by an irreversible ligand reduction at a considerably more negative (cathodic) potential. A comparison of the ligand reduction in its free and chelated state indicates that the β-diketonato ligand (R′COCHCOR)⁻ in [Cp₂Ti(R′COCHCOR)]⁺ClO₄⁻ is electroactive at more negative potentials. A theoretical density functional theory (DFT) study shows that a highly localized metal centred frontier orbital dominates the Ti^IV/Ti^III redox chemistry resulting in a non-linear relationship between the formal redox potential (E°′) and the sum of the group electronegativities of the R and R′ groups, χ_R + χ_R′, of the ligand. Linear relationships, however, are obtained between the DFT calculated electron affinity (EA) of the complexes and χ_R + χ_R′, the pK_a of the free β-diketones R′COCH₂COR and the carbonyl stretching frequency, v_CO, of the complexes. The DFT calculated electronic structure of the second reduced species [Cp₂Ti(β-diketonato)]⁻ shows that it is best described as Ti(III) coupled to a β-diketonato radical.     

Di-ureasil xerogels containing lithium bis(trifluoromethanesulfonyl)imide for application in solid-state electrochromic devices

In this study we report the characterization of a prototype solid-state electrochromic device based on poly(ethylene oxide) (PEO)/siloxane hybrid networks doped with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The polymer networks prepared, designated as di-ureasils and represented as d-U(2000), were produced by a sol-gel procedure and are composed of a siliceous framework to which both ends of polyether chains containing about 40 CH₂CH₂O units are covalently bonded through urea linkages. Samples with compositions of 200 ≥ n ≥ 0.5 (where n is the molar ratio of CH₂CH₂O to Li⁺) were characterized by thermal analysis, complex impedance measurements and cyclic voltammetry at a gold microelectrode. Electrolyte samples were obtained as self-supporting, transparent, amorphous films and at room temperature the highest conductivity was observed with the d-U(2000)₃₅LiTFSI composition (3.2 × 10⁻⁵ Ω⁻¹ cm⁻¹). We report the results of preliminary evaluation of these polymer electrolytes as multi-functional components in prototype electrochromic displays. Device performance parameters such as coloration efficiency, optical contrast and image stability were also evaluated. The electrolytes with n > 8 presented an optical density above 0.56 and display assemblies exhibited good open-circuit memory and stable electrochromic performances.     

EQCM study of the ECL quenching of the tris(2,2′-bipyridyl)ruthenium(II)/tris-n-propylamine system at a Au electrode in the presence of chloride ions

Significant effect of chloride ions on the electrogenerated chemiluminescence (ECL) behavior of the ruthenium(II)tris(2,2′-bipyridine) (Ru(bpy)₃²⁺)/tri-n-propylamine (TPrA) system at a Au electrode was reported. At low concentrations (e.g., [Cl⁻] < 5 mM), the ECL was enhanced; at relatively high concentrations, however, the ECL intensity decreased with the increase of the [Cl⁻]. At [Cl⁻] = 90 mM, ∼50% and 100% ECL inhibition was observed for the first and the second ECL wave, respectively. The electrogenerated gold-chloride complexes (AuCl₂⁻ and AuCl₄⁻) which were verified using an electrochemical quartz-crystal microbalance (EQCM) method were found to be responsible for the ECL inhibition. This study suggests that care must be taken when a Au working electrode is used for ECL studies in chloride-containing buffer solutions (widely used in DNA probes) and/or with the commonly used chloride-containing reference electrodes since in these cases the ECL behavior may significantly disagree with that obtained using other electrodes and reaction media.     

Electrochemical polymerization of p‐terphenyl in mixed electrolyte of boron trifluoride diethyl etherate and CH2Cl2

High quality poly(p‐phenylene) (PPP) film with conductivity of 0.015 S cm^?1 was synthesized electrochemically by direct anodic oxidation of p‐terphenyl (PP) oligomers in boron trifluoride diethyl etherate (BFEE) containing 37.5% CH₂Cl₂ (v/v). The oxidation onset potential of PP in this medium was measured to be only 1.23 V vs. saturated calomel electrode (SCE), which was lower than that determined in CH₂Cl₂ + 0.1 mol L^?1 Bu₄NBF₄ (1.87 V vs. SCE). As‐formed PPP films showed good electrochemical behavior, good electrochromic property and good thermal stability. The structures and morphology of doped and dedoped PPP were investigated by UV‐vis, FTIR, and Scanning electron micrographs. The infrared spectroscopic measurements for the estimation of chain lengths revealed that PPP was composed of about 10 phenyl rings. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Room temperature living cationic polymerization of styrene with HX-styrenic monomer adduct/FeCl3 systems in the presence of tetrabutylammonium halide and tetraalkylphosphonium bromide salts

Living cationic polymerization of styrene was achieved with a series of initiating systems consisting of a HX-styrenic monomer adduct (X = Br, Cl) and ferric chloride (FeCl₃) in conjunction with added salts such as tetrabutylammonium halides (nBu₄N⁺Y⁻; Y⁻ = Br⁻, Cl⁻, I⁻) or tetraalkylphosphonium bromides [nR′₄PBr; R′ = CH₃CH₂-, CH₃(CH₂)₂CH₂-, CH₃(CH₂)₆CH₂-] or tetraphenylphosphonium bromide [(C₆H₅)₄PBr] in dichloromethane (CH₂Cl₂) and in toluene. Comparison of the molecular weight distributions (MWDs) of the polystyrenes prepared at different temperatures (e.g., −25 °C, 0 °C and 25 °C) showed that the polymerization is better controlled at ambient temperature (25 °C). The polymerization was almost instantaneous (completed within 1 min) and quantitative (yield ∼100%) in CH₂Cl₂. In CH₂Cl₂, polystyrenes with moderately narrow (M_w/M_n ∼ 1.33-1.40) and broad (M_w/M_n ∼ 1.5-2.4) MWDs were obtained respectively with and without nBu₄N⁺Y⁻. However, in toluene, the MWDs of the polystyrenes obtained respectively with and without nBu₄N⁺Y⁻/nR′₄P⁺Br⁻ were moderately narrow (M_w/M_n = 1.33-1.5) and extremely narrow (M_w/M_n = 1.05-1.17). Livingness of this polymerization in CH₂Cl₂ was confirmed via monomer-addition experiment as well as from the study of molecular weights of obtained polystyrenes prepared simply by varying monomer to initiator ratio. A possible mechanistic pathway for this polymerization was suggested based on the results of the ¹H NMR spectroscopic analysis of the model reactions as well as the end group analysis of the obtained polymer.     

Study of Fe/Fe ratio in thin films of carbonate or sulphate green rusts obtained by potentiostatic electrosynthesis

Thin films of carbonate or sulphate green rusts were synthesised from potentiostatic oxidation of solutions containing ferrous species and bicarbonate or sulphate ions at slightly alkaline pHs and ambient temperature. The thin films were characterised by means of electrochemical quartz crystal microbalance, scanning electron microscopy, X-ray diffraction and infrared reflection-absorption spectroscopy. The composition of carbonate or sulphate green rusts was studied through chemical titration, inductively coupled plasma-optical emission spectroscopy (ICP-OES) and gravimetry and is as follows:

[Fe^II_(2R)Fe^III₂(OH)_{(4R−2R′+6)}(H₂O)_(2R′−2)]^2R′+·[R′CO₃,(2R-{3 or 4}R′ + 2)·H₂O]^2R′− and [Fe^II_(2R)Fe^III₂(OH)_{(4R−2R″+6)}(H₂O)_(2R″−2)]^2R″+·[R″SO₄,(4R − 4R′ + 4)·H₂O]^2R″−     

TiO2 films prepared by micro-plasma oxidation method for dye-sensitized solar cell

Nanocrystalline TiO₂ films are widely investigated as the electrodes of dye-sensitized solar cell(s) with different preparation methods. In this paper, thin titanium dioxide films have been prepared on titanium plates by the micro-plasma oxidation method in the sulfuric acid solution. The thin TiO₂ films were sensitized with a cis-RuL₂(SCN)₂·2H₂O (L = cis-2,2′-bipyridine-4,4′-dicarboxylic acid) ruthenium complex and implemented into a dye-sensitized solar cell configuration. The influence of reaction current density (10, 15, 20, 25 and 30 A dm⁻²) on the structural and the surface morphology of the films was investigated by X-ray diffraction, scanning electron microscopy, atom force microscopy and X-ray photoelectricity spectroscopy. Impedance analysis for dye-sensitized solar cells was carried out by electrochemical impedance spectroscopy. The results show that the rise of current density leads to the increase in the amount of rutile and the thickness of the TiO₂ film, which makes the TiO₂ films have different photovoltages and photocurrents. The relatively higher photoelectricity properties were obtained in the TiO₂ films prepared at a current density of 20 A dm⁻². The open-circuit voltage and the short-circuit current are 605 mV and 165 μA cm⁻², respectively.     

Influence of metal coordination on conductivity behavior in poly(butadiene-acrylonitrile)-CoCl2 system

The metal complex formation and the electrical properties of amorphous solid polymer electrolytes, based on poly(butadiene-acrylonitrile) copolymer (PBAN) and CoCl₂, have been studied over the homogeneity region of the system limited by the CoCl₂ concentration of 1.89 mol kg⁻¹. It has been found that ionic conductivity is carried out by the unipolar anion transfer at lower CoCl₂ concentrations (up to 0.10 mol kg⁻¹). As the CoCl₂ concentration increases, electronic conductivity appears in addition to ionic conductivity, and the former becomes dominant, starting from 0.38 mol kg⁻¹. It has been shown that the nature of charge carriers is determined by the composition of metal complexes formed by CoCl₂ and the macromolecular solvent PBAN. At lower concentrations, the [Co₂L₂Cl₄]⁰ dimers are the predominant species (L being macromolecule side groups CN), and their dissociation is followed by the formation of mobile Cl⁻ anions and immobile binuclear [Co₂Cl₃]⁺ complexes. As CoCl₂ concentration increases, polynuclear [Co_nL₂Cl_2n]⁰ (n > 2) complexes appear (L being CN and CC groups of PBAN). Specific features of chemical bonds in π-complexes of transition metals result in the appearance of electronic charge carriers. The abrupt increase in conductivity observed at the highest CoCl₂ concentration is connected with the formation of a percolation network of polynuclear [Co_nL₂Cl_2n]⁰ complexes.     

The corrosion behavior of Fe-10Cr nanocrystalline coating

Fe-10Cr nanocrystalline (nc) coatings with a grain size of 20-30 nm were synthesized on glass substrates by magnetron sputtering. The corrosion behavior was investigated in 0.05 mol/L H₂SO₄ + 0.25 mol/L Na₂SO₄ and 0.05 mol/L H₂SO₄ + 0.5 mol/L NaCl solution by polarization curves, EIS and Mott-Schottky analysis. The results showed that compared to Fe-10Cr cast alloy, the active dissolution of the coating was accelerated; the passive film contained more Cr and therefore the coating was easier to passivate. The passive films formed on Fe-10Cr nc and cast alloy exhibited n-type semiconducting behavior in acidic solutions without Cl⁻ and p-type semiconducting behavior in acidic solutions with Cl⁻. The lower breakdown potential for both materials in the solution with Cl⁻ is related to the p-type passive film formed on them. For Fe-10Cr nc, lower donor density and increased Cr content were responsible for the chemical stability of the passive film.     

Synthesis and properties of soluble poly[bis(benzimidazobenzisoquinolinones)] based on novel aromatic tetraamine monomers

Four aromatic tetraamine monomers possessing flexible ether linkages were successfully synthesized by nucleophilic aromatic substitution of hydroquinone, 4,4′-dihydroxybiphenyl, 2,2′-bis(4-hydroxyphenyl)propane, and 2,7-dihydroxynaphthalene with 5-chloro-2-nitroaniline, followed by reduction, respectively. With these monomers, a new class of soluble poly[bis(benzimidazobenzisoquinolinones)] was prepared by a one-step, high-temperature solution polycondensation. The resulting polymers were completely soluble in phenolic solvents and had high inherent viscosities ranging from 1.2 to 1.5 g dL⁻¹. These polymers had glass transition temperatures in the range of 427-449 °C. Thermogravimetric analysis showed that all polymers were thermally stable, with 5% weight loss recorded above 510 °C in nitrogen. The tough polymer films, obtained by casting from solution, had tensile strength, elongation at break, and tensile modulus values in the range of 79.5-114.5 MPa, 10.3-23.0%, and 1.1-1.7 GPa, respectively. It is demonstrated that these semiladder polymer membranes displayed high CO₂ permeability coefficients (P₂CO=31.6−96.5barrer) and permeability selectivity of CO₂ to CH₄(P₂CO/P₄CH=30.6−43.4).     

Novel conjugated alternating copolymer based on 2,7-carbazole and 2,1,3-benzoselenadiazole

A novel conjugated alternating copolymer (PCzDBSe) based on N-9′-heptadecanyl-2,7-carbazole and 5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzoselenadiazole) was synthesized by Suzuki polycondensation. The polymer reveals excellent thermal stabilities with the decomposition temperature (5% weight loss) of 390 °C and the glass-transition temperature of 140 °C. The absorption peaks of the polymer are located at 412 and 626 nm, respectively, while the absorption onset is extended to 716 nm, which is 56 nm red-shifted as compared with its analogue, poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT). The HOMO and LUMO levels of the polymer were estimated to be −5.28 and −3.55 eV, respectively, with an optical bandgap of 1.73 eV. The hole mobility of PCzDBSe as deduced from a solution-processed organic field effect transistor (OFET) was found to be 3.9 × 10⁻⁴ cm² V⁻¹ s⁻¹. Polymer solar cells (PSCs) based on the blends of PCzDBSe and [6,6]-phenyl-C₇₁-butyric acid methyl ester (PC₇₁BM) with a weight ratio of 1:4 were fabricated. Under AM 1.5 (AM, air mass), 100 mW cm⁻² illumination, the devices were found to have an open-circuit (V_oc) of 0.75 V, a short-circuit current density (J_sc) of 7.23 mA cm⁻², a fill factor (FF) of 45% and a power conversion efficiency (PCE) of 2.58%. The primary results indicate that 5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzoselenadiazole) is a promising unit for low bandgap polymer for polymer solar cells.     

Facile electrosynthesis of nitro-group-substituted oligopyrene with bicolored emission

Nitro-group-substituted oligopyrene (ONP) film with fairly high electrical conductivity (1.25 × 10⁻¹ S cm⁻¹) and good thermal stability was electrochemically synthesized by direct anodic oxidation of its monomer 1-nitropyrene (NP) in boron trifluoride diethyl etherate (BFEE). The oxidation potential of NP in this medium was determined to be 1.12 V vs. SCE, which was lower than that in acetonitrile +0.1 mol L⁻¹ Bu₄NBF₄ (1.27 V vs. SCE). ONP films obtained from this medium showed good redox activity and structural stability in both BFEE and concentrated sulfuric acid. Fourier transform infrared spectra and theoretical calculations showed that the electropolymerization of the NP monomer mainly occurred at the C(3), C(6) and C(8) positions. The fluorescence spectra suggested that soluble ONP emits strong blue or green fluorescence when excited at 402 nm or 504 nm, respectively. Scanning electron microscopy showed that highly crystalline nitro-group-substituted oligopyrene was formed on the electrode surface. All these results indicate that as-prepared ONP film has many potential applications in various fields.