LiClO4 Acetonitrile Research Articles

Pre-electrolysis of LiClO4 in Acetonitrile: Electrochemically Induced Protolytic Carbon-Carbon Bond Formation of Benzylic Ethers and Acetals with Allyl Trimethylsilane and Other Carbon Nucleophiles.

The pre-electrolysis of LiClO4 in acetonitrile in an undivided cell applying only "catalytic" amounts of current (e.g., 0.05 F) led to the formation of a strong acidic medium for the activation of benzylic ethers and acetals. The activated primary and secondary benzylic ethers and acetals could be converted with a range of carbon nucleophiles, such as allyl trimethylsilane, silyl enol ethers, and enol acetates, for the formation of new carbon-carbon bonds. A chemoselective reaction was observed when electron-deficient benzylic acetals were converted with allyl trimethylsilane to the monoallylated products, whereas an electron-rich benzylic acetal led to the double allylated product under activation of both ether groups.

Carbon Nano-Onion Modified Electrodes for Voltammetric Detection of Propellent Stabiliser 1,3-Diethyl-1,3-Diphenly Urea (Centralite)

The testing of gunshot residue (GSR) has been a fundamental pillar of forensic analysis in the evaluation of evidence and its subsequent use in criminal trials involving firearms. While confirmatory testing of the inorganic fraction of gunshot residue is largely laboratory confined and reliant on scanning electron microscopy for particle analysis and inductively coupled plasma – MS for bulk metal determination, the move to onsite testing of this fraction has been facilitated using electroanalysis. Complementary recovery and analysis of the organic fraction of GSR remains an analytical challenge at the point of use. Such a device would provide more robust dual information due to the low environmental background levels of propellant stabilisers such as diphenylamine (DPA), and urea derivative 1,3-diethyl-1, 3-diphenylurea (Centralite). Electroanalysis of the latter is the key focus of this work, ultimately utilising screen printed electodes functionalised with electrocatalytic materials which serve to enhance the analytical signal.An initial electrochemical examination of Centralite involved voltammetric studies in both aqeuous and non-aqueous environments, with the view to establish an understanding of its redox solution behaviour, pH effects, chemical stability and film formation upon potential sweeping. This allowed both mechanistic and analytical evaluation with the aim to achieve the required selectivity and sensitivity for reliable detection. Centralite electrochemistry was examined at glassy carbon electrodes in both aqueous (3:7 methanol:sodium acetate pH 4.3) and non–aqueous (0.1 M LiClO4 in methanol) electrolytes via potential sweeping. In the case of the aqueous system an irreversible wave at Ep = 1.2 V associated with a weak cathodic signal at 1.0 V vs. Ag/AgCl was observed. This diffusion controlled process resulted in diffusion co-efficient (D)=7.4x10-5 cm2s-1 which, for a one electron process results in transfer coefficient (a)=0.724. Upon cycling, a new anodic signal appeared at 1.0 V with a corresponding decrease in the process at 1.2 V vs. Ag/AgCl. Scan rate studies indicated a mixed diffusion/adsorption process with peak current ratios (anodic/cathodic) decreasing with respect to scan rate. In the acidic environment acid hydrolysis of the 1,3-diethyl-1, 3-diphenylurea can result in N-ethylaniline and N-ethyl-N-phenylformamide (a type of carbamic acid which can revert back to the parent amine with release of CO2). Deposition of poly(N-ethylaniline) could explain the presence of a clearly visible yellow film on the electrode surface (Fig. 1). Upon examination of Centralite in 0.1 M LiClO4 in acetonitrile an irreversible process at 1 V was evident with a cathodic wave at 0.71 V and the appearance of a new anodic peak at 0.75 V vs. Ag/Ag+. Scan rate studies revealed that these processes were diffusion controlled.The electrochemical behaviour of carbon nanomaterials including their capacitance can depend on counter ion film penetration, the double layer structure and electrolyte. Recently, carbon nano-onions (CNOs), an emerging member of the carbon family, have shown promising electrochemical performance towards the oxygen reduction reaction as a consequence of a co-doping process.Herein, both pristine (p-) and boron nitrogen co-doped (BN-) CNOs were examined as solid films which were dropcast onto glassy carbon electrodes from a dispersion of 1 mg/mL in ethanol. There was a capacitive and faradaic component to the current and good mechanical stability was evident upon potential cycling. In the case of BN-CNOs, a quasi-reversible surface confined process was evident at Ep(a) = 0.27 V and Ep(c) = 0.057 vs. Ag/AgCl with DEp = 0.213 V. When examined in an anionic redox probe [Fe(CN)6]3-/4- a two fold decrease in DEp was evident (indicating faster charge transfer at the CNO modified surface). Surface coverage corresponded to 6.73 - 5.44 x 10-10 mol cm-2 using current vs scan rate plots. Specific capacitance was 16.96 F/g and 3.62 F/g for pristine and BN doped CNO material respectively being scan rate dependent. Centralite calibration studies, in the aqueous environment using linear sweep voltammetry resulted in sensitivity values of 0.585 A.cm-1.M-1 for the bare glassy carbon electrode and 0.710 A.cm-1.M-1 in the case of the a CNO modified electrode with further work ongoing. Figure 1

Electrodeposited MoS2 and WS2 Thin Films for Pseudocapacitance Studies

Cathodic electrodeposition of MoS2 (WS2) atop glassy carbon (ITO) was recently reported utilizing a single-source precursor MoS4 2- (WS4 2-) from an aqueous (acetonitrile) electrolyte. Since MoS2 and WS2 are hydrodesulfurization (HDS) catalysts for sulfur removal from hydrocarbons, they immediately react with and desulfurize the electrolytes from which they are deposited, yielding amorphous deposits that contain excess sulfur. However, the desired stoichiometry MX2 can be recovered by high temperature annealing, which removes excess sulfur and forms moderately crystallized and partially oriented thin films, as shown by x-ray diffraction (XRD) studies. This two-step process for deposition of MoS2 and WS2 thin films of controlled thickness facilitates scientific studies of the nature of pseudocapacitance in these materials. Most reports of MoS2 and WS2 pseudocapacitance study nanocomposites with carbon in order to maximize the specific capacitance, but fundamental electrochemical studies are challenging due to the complex topography and surface heterogeneity. The specific capacitance of MoS2 and WS2 thin films with a thickness ranging from 10 nm to 5μm were studied by cyclic voltammetry and galvanostatic charge discharge in several electrolytes, including 1.0 M aqueous Na2SO4, 1.0 M aqueous LiClO4, and 1.0 M LiClO4 in acetonitrile. For both MoS2 and WS2 thin films, the specific capacitance of stoichiometric films obtained by high temperature annealing is 1-2 orders of magnitude higher than the as-deposited amorphous films. The maximum specific capacitance of 1980 F/g is obtained for 10 nm thick WS2 films in 1.0 M aqueous LiClO4, although this is of course arises from the small mass in the denominator. The capacitance per unit area for WS2 films in 1.0 M aqueous Na2SO4 increases with increasing film thickness, and then reaches a plateau value at a thickness of 30-50 nm. This suggests that the active region thickness for charge storage in WS2 is 30-50 nm, which is close to values previously reported for charge storage in RuO2. Since the cation radius of Li+ (0.90 nm) is smaller than that of Na+ (1.16 nm), higher capacitance per unit area is obtained in LiClO4- than in Na2SO4-containing electrolytes. In addition, the capacitance per unit area in LiClO4-containing electrolytes does not reach a maximum plateau value until a much higher WS2 film thickness. Cathodic electrodeposition of Cu-doped MoS2 atop glassy carbon can also be accomplished from an aqueous electrolyte containing 10.0 mM (NH4)2MoS4, 5.0 mM CuSO4, 0.1 M KCl, and 0.50 M KSCN at pH 6.95. Without the presence of thiocyanate (SCN-) as a complexing agent, the cathodic potentials for electrodeposition of Cu and MoS2 are separated by ~700 mV. However, the addition of SCN- shifts the Cu deposition potential in the cathodic direction towards the deposition potential of MoS2. In addition, a cathodic shoulder is observed during cyclic voltammetry experiments that may indicate an induced co-deposition effect. Electrodeposition at the potential of this cathodic shoulder yields MoS2 thin films that contain 1-4 atom% Cu, as determined by energy dispersive x-ray spectroscopy (EDX) and Rutherford backscattering (RBS). As observed for un-doped MoS2 thin films, high temperature annealing is required to obtain moderately recrystallized and partially oriented films. Four-point probe measurements demonstrate that Cu doping reduces the MoS2 resistivity by 10.3x. The capacitance obtained by cyclic voltammetry and galvanostatic charge discharge for Cu-doped MoS2 thin films is 2.5-3.5x higher than that obtained for MoS2 films of the same thickness.

A donor-chromophore-catalyst assembly for solar CO2 reduction.

We describe here the preparation and characterization of a photocathode assembly for CO2 reduction to CO in 0.1 M LiClO4 acetonitrile. The assembly was formed on 1.0 μm thick mesoporous films of NiO using a layer-by-layer procedure based on Zr(iv)-phosphonate bridging units. The structure of the Zr(iv) bridged assembly, abbreviated as NiO|-DA-RuCP2 2+-Re(i), where DA is the dianiline-based electron donor (N,N,N',N'-((CH2)3PO3H2)4-4,4'-dianiline), RuCP2+ is the light absorber [Ru((4,4'-(PO3H2CH2)2-2,2'-bipyridine)(2,2'-bipyridine))2]2+, and Re(i) is the CO2 reduction catalyst, ReI((4,4'-PO3H2CH2)2-2,2'-bipyridine)(CO)3Cl. Visible light excitation of the assembly in CO2 saturated solution resulted in CO2 reduction to CO. A steady-state photocurrent density of 65 μA cm-2 was achieved under one sun illumination and an IPCE value of 1.9% was obtained with 450 nm illumination. The importance of the DA aniline donor in the assembly as an initial site for reduction of the RuCP2+ excited state was demonstrated by an 8 times higher photocurrent generated with DA present in the surface film compared to a control without DA. Nanosecond transient absorption measurements showed that the expected reduced one-electron intermediate, RuCP+, was formed on a sub-nanosecond time scale with back electron transfer to the electrode on the microsecond timescale which competes with forward electron transfer to the Re(i) catalyst at t 1/2 = 2.6 μs (k ET = 2.7 × 105 s-1).

Study the effect of Li+ on the ν2/ν3+ν4 Fermi resonance of acetonitrile by Raman Spectroscopy.

Raman spectra of the solution of LiClO4 in acetonitrile (CH3CN) at different concentrations have been measured. With increasing the concentration of Li+, it was noted that several vibrational modes of CH3CN had significant changes in Raman shifts and some new Raman peaks emerged due to the CH3CN⋯Li+ complex formation. In addition, Fermi resonance phenomenon between the ν2' and (ν3 + ν4)' Raman bands of CH3CN⋯Li+ complex was observed. Based on the Bertran's equations, Fermi resonance parameters of free CH3CN and CH3CN⋯Li+ complex at different concentrations have been calculated, respectively. Compared the Fermi resonance coupling coefficients W of free CH3CN with CH3CN⋯Li+ complex at different concentrations, the free CH3CN had a little smaller value, which indicated that the ν2'/(ν3 + ν4)' Fermi resonance in CH3CN⋯Li+ complex was much stronger than the ν2/ν3 + ν4 Fermi resonance in CH3CN. From the detailed analysis of the effect of Li+ on the spectral features of CH3CN, the effect mechanism of Li+ coordination to CH3CN at the nitrogen of the CN group on the ν2/ν3 + ν4 Fermi resonance of CH3CN has been elucidated.

Structural Stability and Optical Studies of Poly(3-hexylthiophene) in an ITO/PEDOT:PSS/P3HT Interface

An interface between poly(3-hexylthiophene) (P3HT) and poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT:PSS) was prepared in LiClO4-–acetonitrile (ACN) over indium-doped tin oxide (ITO), known as the ITO/PEDOT:PSS/P3HT system. This system was compared with ITO/P3HT with the aim of studying the stability of aromatic, quinone, and semiquinone segments in the polymer matrix and also elucidating the influence of the structure on the efficiency of organic photovoltaic cells (OPVs). Initially, Raman spectroscopy was used, varying the laser power to verify the destabilization of radical cation segments to dication segments in the ITO/P3HT system. Electrochemical impedance spectroscopy (EIS) was used to show the behavior of the charged species and the charge-transfer processes of the different P3HT segments as a function of time since preparation of the studied systems. In addition, photoluminescence (PL) and time-resolved PL spectroscopy showed the optical properties of the interfaces formed, based on the different quantities of segments present. It was possible to conclude that the modification introduced into the interface by PEDOT:PSS favors stabilization of the P3HT radical cation segment, which remains stable in this interface for lengthy periods (240 h). This should in turn boost hole extraction, increasing OPV efficiency.

Structural stability of poly(3-methylthiophene) and polydiphenylamine blend as an interface applied to hole injector

In this study, interfaces between poly(3-methylthiophene) (P3MT) and polydiphenylamine (PDPA) were prepared on an electrode of indium tin oxide (ITO) (ITO/PDPA:P3MT) or Pt (Pt/PDPA:P3MT) in LiClO4–acetonitrile (ACN) and in diphenyl phosphate (DPHP)–LiClO4–ACN. These systems were compared with those consisting of homopolymers (ITO/PDPA and ITO/P3MT) with the aim of studying the stability of quinone and semiquinone segments in the matrices of blends capable of enhancing the efficiency of organic photovoltaic cells. Raman spectroscopy and electrochemical impedance spectroscopy (EIS) were used as a function of time after preparation of the systems studied. The behavior of charged species in the blend matrix as a function of the applied potential were verified by taking in situ Raman spectra of the Pt/PDPA:P3MT system, also facilitated by the identification of the charge transfer processes of the different P3MT segments by means of EIS. Electron paramagnetic resonance spectroscopy was used to quantify, as time progressed, the radical cation segments present in the polymer matrices after preparation. Ex situ Raman spectroscopy of the ITO/PDPA:P3MT system synthesized in LiClO4–ACN was used to compare it with the ITO/P3MT interface, which revealed that as time progressed the radical cation segments lost stability more slowly, subsequently boosting the dication segments. However, for the ITO/PDPA:P3MT system in DPHP–LiClO4–ACN, this process occurred more rapidly.

The difference between interfaces formed by mechanically renewed gold and silver electrodes with acetonitrile and aqueous solutions

The impedance method and cycling voltammetry were used in studying the structure of interface between mechanically renewable electrodes of Au and Ag and solutions with different concentration of LiClO4 in acetonitrile (AN). The obtained data allowed us to conclude that the considered systems are characterized by the wide potential regions in which these electrodes can be considered as ideally polarizable. These regions are: from −0.5 to 1.0V for Au and from −1.7 to −0.2V (vs. aqueous SCE) for Ag electrodes; the zero charge potentials of Au and Ag electrodes in these systems are: 0.62 and −0.37V, respectively. It was shown that, in the above-noted potential regions, the experimental C vs. E curves can be well described by the classical model of Gouy–Chapman–Stern–Grahame. It was shown, as well, that the difference in experimental zero charge potentials of Au and Ag electrodes correlates with the difference in electron work functions of these metals. These data allow us to conclude that the interaction at the interface between renewable Au and Ag electrodes and AN solutions can be characterized as lyophobic, i.e., close to that observed for Hg/AN and mercury-like metals/AN systems. On the other hand, the interfaces of Au and Ag electrodes with aqueous solutions should be considered as hydrophilic systems being radically different from the interfaces of Hg and mercury-like metals with aqueous solutions. It was demonstrated that the specific features of the interface structure on Au and Ag electrodes in contact with aqueous and AN solutions can be well described on the qualitative level within the framework of phenomenological model of «two limiting states».

Electrodeposition and Capacitance Measurements of WS2 Thin Films

Polycrystalline WS2 thin films were fabricated by electrodeposition onto ITO from an electrolyte containing 4 mM (NH4)2WS4 + 0.1 M LiClO4 in acetonitrile, followed by a two-stage sulfurization and crystallization procedure at elevated temperature in a tube furnace. The as-deposited films had a S:W stoichiometric ratio of ∼2.8, which decreased to 2 after annealing. X-ray diffraction indicates that the annealed WS2 films crystallize into the 2H polytype with an average grain diameter of ∼22 nm. The capacitance of WS2 thin films was studied in different electrolytes, and the maximum capacitance observed was 1980 F/g, which decreased to 1610 F/g after 1000 cycles, for 10 nm thick WS2 in 1.0 M aqueous LiClO4. Capacitance studies as a function of WS2 film thickness yield different behavior in electrolytes containing Li+ and Na+, with the capacitance per unit area plateauing at a considerably higher film thickness in Li+-containing electrolytes. This suggests that the active depth for charge storage increases due to the smaller ionic radius of Li+.

Structural stability and improved properties of poly(3-alkylthiophenes) synthesized in an acid medium

Poly(3-methylthiophene) (P3MT), poly(3-hexylthiophene) (P3HT) and poly(3-octylthiophene) (P3OT), with better chemical stability, efficiency and charge transfer properties for use in organic solar cells were synthesized on indium tin oxide (ITO) in LiClO4–acetonitrile (ACN) and in the presence of dyphenyl phosphate (DPHP), used as a Bronsted–Lowry acid. By means of cyclic voltammetry in the DPHP–LiClO4–ACN, we observed the displacement of two oxidation peaks, as well as the widening and definition of the second reduction peak in comparison to P3ATs synthesized in a neutral medium. Using electrochemical impedance spectroscopy, the Nyquist diagrams for the ITO/P3MT/DPHP–LiClO4–ACN system revealed a reduction in charge transfer resistance as the amount of DPHP was increased. However, for ITO/P3HT/DPHP–LiClO4–ACN and ITO/P3OT/DPHP–LiClO4–ACN this dependence was not observed. In the Bode-phase diagrams, the charge transfer processes were related to polaronic conduction in the ITO/P3MT/DPHP–LiClO4–ACN, and bipolaronic conduction in the ITO/P3HT/DPHP–LiClO4–ACN and ITO/P3OT/DPHP–LiClO4–ACN. These results were complemented by ex situ Raman spectroscopy, in which the charge transfer process in the ITO/P3MT/DPHP–LiClO4–ACN system was due to radical cation species stabilization in the P3MT as prepared, and in the ITO/P3HT/DPHP–LiClO4–ACN and ITO/P3OT/DPHP–LiClO4–ACN systems it occurred because of the stabilization of the dication on the P3HT and P3OT films obtained. The stability of these various species in the polymer matrix varied as time elapsed, leading to a disproportionate quantity of radical cation segments in aromatic and dication segments of the P3MT matrix, and the formation of a charge transfer complex with oxygen in the P3HT and P3OT. The radical cation segments stabilized 48 h after preparation.

Electrochemical Preparation of Porous Poly(3,4-ethylenedioxythiophene) Electrodes from Room Temperature Ionic Liquids for Supercapacitors

Poly(3,4-ethylenedioxythiophene) (PEDOT) electrodes were prepared using current pulse method from different room temperature ionic liquids electrolytes (1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMI][TFSI]), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMI][BF4]), 1-allyl-3-(2-methoxyethyl)-imidazolium bis(trifluoromethylsulfonyl)imide ([AMO][TFSI]), and organic solution (0.1 M LiClO4 in acetonitrile)). The SEM and XPS studies show that the PEDOT films electropolymerized in [BMI][BF4] are highly porous and have a higher anion doping level than those electropolymerized in [BMI][TFSI], [AMO][TFSI], and LiClO4/ACN electrolytes. The electrochemical performance of the symmetrical supercapacitor based on PEDOT electrodes were investigated in 0.1 M KClO4 aqueous electrolyte by cyclic voltammetry and galvanostatic charge-discharge test. The PEDOT electrodes prepared from ionic liquids exhibit higher capacitative performance than those prepared from conventional solvent (ACN). Especially, the PEDOT electrodes prepared from a [BMI][BF4] ionic liquid exhibited high specific capacitance (191 F/g) with an obvious improvement in energy density and power density as comparison to the PEDOT electrodes prepared from ACN solution (100 F/g) in aqueous electrolyte. The symmetrical supercapacitor based on PEDOT electrodes prepared from [BMI][BF4] ionic liquid shows maximum specific energy of 5.37 Wh/Kg and good cycle durability. This study shows using ionic liquids as electrolytes for preparing PEDOT electrodes is an efficient way to improve performance of supercapacitors.

A novel electrochemical and chromogenic guest-responsive anisidine-based chemosensor for transition metallic cations

A new family of N,N-disubstituted p-anisidine-based electroactive ligands bearing dipyridinylamino- (1), difuranylamino- (2) and dithiophenylamino- (3) binding sites has been prepared by reductive alkylation of anisidine. The electrochemical investigations, in 0.1mol/dm−3 LiClO4 acetonitrile solution, showed that upon the addition of metallic cations, the redox features of 1 underwent drastic changes due to the cation chelation. The chemosensor complexation with Ni(II), Zn(II), Cd(II) and Pb(II) led to large anodic shifts of the oxidation potential peaks up to 700mV depending on the metal cation. A particularly high sensitivity toward nickel(II) with a higher selectivity to zinc(II) were observed. However, in the same conditions, thiophenyl- and furfuranyl- derivatives showed no sensitivity for any of the investigated cations. Moreover, UV–visible spectroscopy studies of 1 showed that the compound can act as a chromogenic guest-responsive and in presence of metallic cations, the absorption bands of compound 1 shifted due to a participation of the nitrogen lone pairs in the cation complexation. UV–visible spectroscopy did also allow to distinguish between the Ni(II) and Zn(II) complexes. Electrochemical and UV–visible spectroscopic investigations showed that the complexes have 1:2 stoichiometry [M(1)2]2+ (M: Zn, Ni, Cd and Pb).

Extreme electrochemical doping of a graphene–polyelectrolyte heterostructure

A doped state of heterostructure, based on chemical vapour deposition grown graphene and polyelectrolytes (polyallylamine hydrochloride and polyacrylic acid), has been studied. The doping was realized electrochemically by application of an electrode potential in LiClO4–acetonitrile electrolyte solution. Our new setup allowed us to achieve extreme doping levels for both positive and negative electrode potentials. The extreme doping of graphene was demonstrated by a large shift of the G mode frequency in the Raman spectrum. In addition a significant enhancement of the G mode at large positive and also negative electrode potentials has been experimentally observed. The G mode intensity enhancement was attributed to cancelling of a part of the quantum Raman pathways thus reducing the destructive quantum interference effect. Since this effect only occurs if the Fermi level achieves half of the laser excitation energy, experimental observation of this phenomenon also confirms the extreme doping levels of graphene.

Caracterização Estrutural e Ótica do Poli(3-metiltiofeno) (P3MT) Sintetizado Eletroquimicamente

In this work was synthesized electrochemically the poly(3-methylthiophene) (P3MT) on transparent conductive substrates of F-doped tin oxide (FTO), using as supporting electrolyte Et4NBF4 or LiClO4 in acetonitrile. To dedope the material, the samples were reduced electrochemically and chemically (in NH4OH solution). The films were characterized by electron paramagnetic resonance spectroscopy (EPR) and infrared spectroscopy (FTIR) and their optical properties examined by ultraviolet-visible absorption spectroscopy (UV-Vis) and photoluminescence (PL). Scanning electron microscopy (SEM) images of the first synthesized samples were performed to verify the degree of homogeneity of them. The FTIR spectra show the characteristic features of P3MT and, together with the results of EPR, allowed to evaluate the charge carriers and to identify benzoid and quinoid structures in the formation of chains. The UV-Vis absorption spectra helped to obtain the average gap energy of P3MT presenting the ?-?* transition band and a bipolaron band. In the PL spectra, with variation of excitation power, studies were performed through the fit with Gaussian functions, given the strong probability of the existence of two distinct contributions in the formation of the emission spectra. These two contributions were assigned to the emission of mixed chains (Gaussian centered at higher energy) and emission of benzoid chains (Gaussian of lower energy) in the formed polymeric material.

Syntheses of electroactive layers based on functionalized anthracene for electrochromic applications

Abstract A new monomer (DTAT) was synthesized via linking 3,4-ethylenedioxythiophene (EDOT) on anthracene. The polymer, P(DTAT) was electrosynthesized by anodic oxidation of the corresponding monomer in 0.1 M LiClO4 acetonitrile (ACN) solution. The optical properties, the absorption spectra and the kinetics, were examined. Spectroelectrochemical analysis showed that P(DTAT) has an electronic band gap (due to π–π* transition) of 1.57 eV at 776 nm. Copolymers of DTAT with EDOT were prepared in ACN/LiClO4 (0.1 M) solvent–electrolyte couple by varying applied potential. The incorporation of an EDOT into the full conjugated backbone, DTAT, affects its optical behavior resulting in different colors; a claret red neutral state, gray and red intermediate states and a blue oxidized state.

Electrochemical synthesis of poly(5-nitroindole) on 316L-stainless steel in LiClO 4-acetonitrile solution and its corrosion performance

The preparation of poly(5-nitroindole) (P5NI) coating was achieved on 316L-stainless steel (SS). Poly(5-nitroindole) was deposited via anodic oxidation of the corresponding monomer in acetonitrile (ACN) solution containing LiClO 4. The influence of P5NI coating against SS corrosion was studied in 3.5% NaCl solution by electrochemical impedance spectroscopy (EIS), anodic polarization curves and the open circuit potential–time ( E ocp– t) diagrams. The results obtained suggest that P5NI coating forms a sacrificial layer but the efficiency against corrosion is limited with increasing time.

Copolymers of pyrrole and N-(hydroxypropyl)pyrrole: properties and interaction with DNA

Copolymers derived from mixtures of pyrrole and N-(hydroxypropyl)pyrrole have been prepared electrochemically using various concentration ratios. Copolymers were generated on stainless electrodes by chronoamperometry and cyclic voltammetry in a LiClO4 acetonitrile solution. Relevant physical (density and doping level) and electrochemical (electroactivity and electrostability) properties of the copolymers have been examined and compared with those of the two corresponding homopolymers, which were prepared using the same electrochemical procedures. Results show that the copolymer obtained using the 25:75 N-(hydroxypropyl)pyrrole:pyrrole molar ratio presents an interesting behavior. Finally, the ability of the latter copolymer to form specific interactions with plasmid DNA has been compared with that of polypyrrole.

Poly(3,4-ethylenedioxythiophene) doped with a non-extrudable metallacarborane anion electroactive during synthesis

The electrochemical polymerization of EDOT on ITO from cesium cobaltabisdicarbollide acetonitrile solutions is accompanied by a reversible oxidation of the doping anion. It results in a p-doped polymer embedded with short-chain reduced oligomers, as proven by the material composition, morphology, electrochemical and spectroelectrochemical behaviour. The ratio between the number of EDOT molecules entrapped in the polymer vs. the oligomers is 0.88. This ratio was estimated from the doping level of the material considering that only the polymer can be doped. Its oxidation/reduction process takes place reversibly in the potential range −0.8/+0.7V vs. SCE and is accompanied by cation exchange. The non-extrudable character of the doping anion was proven by electrochemical treatments designed to alter the material composition by ionic exchange followed by EDX or MALDI-TOF mass spectrometric analyses either of the material or of the 0.1M LiClO4 acetonitrile solution in which the polymer oxidation/reduction had been performed.

Electrochemical synthesis of polyindole on 304-stainless steel in LiClO4–acetonitrile solution and its corrosion performance

The use of electrochemically synthesized polyindole (PIN) film was investigated for protective coating on 304-stainless steel (SS). Polyindole was deposited via anodic oxidation of the corresponding monomer, indole in acetonitrile (ACN) solution containing LiClO4. It provided an adherent and stable coating on SS. The corrosion performance of coated and uncoated SS was investigated in 3.5% NaCl solution using electrochemical impedance spectroscopy (EIS), anodic polarization curves and open-circuit potential–time (Eocp–t) diagrams. These tests demonstrated that PIN coating provided important barrier effect to SS for important immersion times in aggressive medium.

Preparation, Structure, and Electrochemistry of a Polypyrrole Film Doped with Manganese(III)-Substituted Dawson-Type Phosphopolyoxotungstate

The fabrication, structure, electrochemical properties, and electrocatalytic properties of a manganese(III)-substituted Dawson-type phosphopolyoxotungstate, alpha 2-K7P2W17O61(Mn3+.OH2).12H2O (P2W17Mn), entrapped in polypyrrole (PPy) film have been studied. The hybrid film was prepared by potentiostatic polymerization from aqueous solution containing 20 mM pyrrole (Py) and 2 mM P2W17Mn on a pyrolytic graphite (PG) surface. Chronoamperometry, Raman spectroscopy, UV-visible absorption spectroscopy, and cyclic voltammetry were used to monitor and characterize the growth, structure, and properties of the film. The chronoamperometric curve shows that P2W17Mn can catalyze the electrochemical polymerization of Py. The Raman spectrum suggests that the doped P2W17Mn has little effect on the structure of PPy film. The P2W17Mn/PPy film exhibits good voltammetric response in both the acidic aqueous and acetonitrile solutions. At pH 1.0, the molar ratio of pyrrole to P2W17Mn7- in the hybrid film is 21.1:1, quite close to the expected ratio of 21.2:1 for a PPy film with a +0.33 oxidation level per pyrrole moiety and doped with an anion with a charge of 7. The influence of solution pH on P2W17Mn7- in the film is much smaller than that in the aqueous solution. During the potential scanning in 0.1 M LiClO4 acetonitrile solution, P2W17Mn7- was slowly released from the hybrid film and electrolyte ions (Li+ and ClO4-) were inserted into the film. This was identified by cyclic voltammetry and UV-visible spectroscopy. Additionally, the hybrid film can effectively catalyze the reduction of hydrogen peroxide and nitrite.