Tetrabutylammonium Perchlorate Research Articles

Novel synthesis of poly(2-acryloyloxyethyl ferrocenecarboxylate) as quasi-reversible redox-active gel polymer electrolytes

In this research, the electrochemical behavior of poly(2-acryloyloxyethyl ferrocenecarboxylate) (PAEFc) synthesized via an atom transfer radical polymerization (ATRP) strategy was investigated in a series of tetrabutylammonium perchlorate (TBAP)/acetonitrile vs. Ag/AgNO3 system. In comparison, series of PAEFc electrolyte with specific molecular weight and depositing concentration were analyzed via cyclic voltammetry (CV) method. Furthermore, chronocoulometry (CC) technology has been employed on the dynamic electron/mass transfer mechanism and the determination of kinetic parameters (diffusion coefficients, reaction rate constant, etc.). Finally, it is demonstrated that anodic and cathodic process of PAEFc was controlled by diffusion and adsorption–diffusion, respectively. Meanwhile, the kinetic parameters of the typical quasi-reversible redox process were obtained, of which the apparent activation energy (Ea) and pre-exponential factor (A) were 121.38 kJ mol−1 4.28 × 1018 s−1, respectively.

Tunable 3D nanofibrous and bio-functionalised PEDOT network explored as a conducting polymer-based biosensor

Conducting polymers that possess good electrochemical properties, nanostructured morphology and functionality for bioconjugation are essential to realise the concept of all-polymer-based biosensors that do not depend on traditional nanocatalysts such as carbon materials, metal, metal oxides or dyes. In this research, we demonstrated a facile approach for the simultaneous preparation of a bi-functional PEDOT interface with a tunable 3D nanofibrous network and carboxylic acid groups (i.e. Nano-PEDOT-COOH) via controlled co-polymerisation of EDOT and EDOT-COOH monomers, using tetrabutylammonium perchlorate as a soft-template. By tuning the ratio between EDOT and EDOT-COOH monomer, the nanofibrous structure and carboxylic acid functionalisation of Nano-PEDOT-COOH were varied over a fibre diameter range of 15.6 ± 3.7 to 70.0 ± 9.5 nm and a carboxylic acid group density from 0.03 to 0.18 μmol cm−2. The nanofibres assembled into a three-dimensional network with a high specific surface area, which contributed to low charge transfer resistance and high transduction activity towards the co-enzyme NADH, delivering a wide linear range of 20–960 μM and a high sensitivity of 0.224 μA μM−1 cm−2 at the Nano-PEDOT-COOH50% interface. Furthermore, the carboxylic acid groups provide an anchoring site for the stable immobilisation of an NADH-dependent dehydrogenase (i.e. lactate dehydrogenase), via EDC/S–NHS chemistry, for the fabrication of a Bio-Nano-PEDOT-based biosensor for lactate detection which had a response time of less than 10 s over the range of 0.05–1.8 mM. Our developed bio-Nano-PEDOT interface shows future potential for coupling with multi-biorecognition molecules via carboxylic acid groups for the development of a range of advanced all-polymer biosensors.

Electrochemistry of Tri‐substituted Porphyrins with β‐Appended Ethyl Acetoacetate and Acetylacetone in Neutral and Basic Nonaqueous Solvents

AbstractThe electrochemistry of β‐substituted tetraphenylporphyrins with a single ethyl acetoacetate (EAA), acetylacetone (acac), or ethyl acetate (EA) group and two antipodal H, Br or Ph groups was investigated in CH2Cl2 containing 0.1 M tetrabutylammonium perchlorate (TBAP) before and after addition of base to solution in the form of tetrabutylammonium hydroxide (TBAOH). The tri‐substituted porphyrins in their neutral form are represented as MTPP(EAA)X2, MTPP(acac)X2 and MTPP(EA)X2, where TPP is the dianion of tetraphenylporphyrin, M=H2, NiII, CuII or ZnII and X=H, Br or Ph. The singly reduced porphyrins are relatively stable on the cyclic voltammetry timescale, but this is not the case for the doubly reduced EAA and acac derivatives, which are highly reactive at room temperature, leading to a porphyrin product assigned as containing a deprotonated EAA− or acac− (enolate) substituent. Enolate‐appended porphyrins were also generated in‐situ by the addition of TBAOH, resulting in mono‐anionic porphyrins that are harder to reduce by 110–160 mV as compared to the neutral compounds with the same β‐substituents, suggesting a high degree of interaction between the deprotonated EAA− or acac− substituent and the porphyrin π‐ring system. The chemically or electrochemically generated enolate‐appended porphyrin could also be irreversibly oxidized by one electron at peak potentials between 0.10 and 0.30 V; the exact value depending upon solvent and type of β‐diketo substituent.

Photo‐Curable Ion‐Enhanced Fluorinated Elastomers for Pressure‐Sensitive Textiles

Smart textiles integrated with the function of recording tactile stimulation attract much attention due to its great potential for health monitoring and wearable electronics. However, the highly uneven surface and poor thermal stability of textiles become main challenges for precision measurement and device fabrications. To solve these issues, an ion‐assisted pressure‐sensitive textile using a novel photo‐curing process is demonstrated in this work. Using a photo‐cured fluorinated polymer poly(vinylidene fluoride‐co‐hexafluoropropene) (PVDF‐HFP) and a transparent polydimethylsiloxane (PDMS) mold, a highly sensitive pyramid array of PVDF‐HFP is successfully fabricated on a textile. Furthermore, after doping the ionic additive, tetrabutylammonium perchlorate (TBAP), the sensors show improved sensitivity due to the enhanced dielectric constant. The dielectric constant has a significant increase in the value over 37 after doping a small amount of TBAP (2 wt%). Due to the ion doping, the sensitivity of the textile pressure sensors show significant improvement (0.73 kPa−1) higher than that of the PDMS‐based one (0.19 kPa−1). This work not only opens an efficient approach for the fabrication processes of a high‐k elastomer pyramid array on a textile but also provide a design strategy to improve performance of capacitive pressure sensor for smart textiles.

Au-V2O5/Polyindole composite: An approach for ORR in different electrolytes

A nanocomposite of Gold-V2O5/Polyindole (Au-V2O5/PIn), in which V2O5 integrated with nanosized Au encapsulated polyindole has been synthesized through an optimized single-phase chemical polymerization method. Such architecture of Au-V2O5/PIn exhibits a synergism enhanced electrochemical performance over V2O5 and PIn individually. This nanocomposite is well characterized by UV visible, FTIR, XRD, XPS, SEM and TEM techniques for its structural and morphological implications. In Au-V2O5/PIn composite, Au NPs and PIn have been incorporated simultaneously on V2O5 during the polymerization reaction of indole monomer using HAuCl4, as evident by TEM image. Thereafter, as-synthesized composite has been used as an active material for the modification of commercial GC electrode for their ORR applications. In this regard, CV and EIS has been performed in 0.1 M tetrabutylammonium perchlorate in acetonitrile, 0.1 M aqueous KOH and a mixture of 0.1 M KOH + 0.1 M C2H5OH electrolytes. The electrochemical tests reveal that Au-V2O5/PIn delivers superior ORR properties among its parental component in aqueous as well as the non-aqueous electrolytes. In comparison to non-aqueous electrolytes, Au-V2O5/PIn exhibits better ORR performance in aqueous electrolytes having a mixture of 0.1 M KOH + 0.1 M C2H5OH. Such enhancement is expected due to the synergistic effect between V2O5 NPs and Au embedded PIn.

Electrochemistry of Polymeric Cobaloxime-Containing Assemblies in Organic and Aqueous Solvents

We report on the structural and electrochemical properties of a heterogeneous-homogeneous assembly composed of molecular cobaloxime catalysts immobilized onto graphite electrodes via an intervening polyvinylpyridine surface coating. When these modified electrodes are immersed in an organic solvent (propylene carbonate containing 0.1 M tetrabutylammonium perchlorate as a supporting electrolyte) or basic aqueous solutions (0.1 M NaOH), cyclic voltammetry measurements enable determination of the CoIII/II peak potentials and CoII/I midpoint potentials of cobaloximes embedded within the polymeric architectures. Additionally, voltammetry measurements recorded using pH neutral aqueous solutions (0.1 M phosphate buffer) confirm the immobilized cobaloximes remain catalytically active for hydrogen production and operate at a turnover frequency of 1.6 s−1 when polarized at –0.35 V vs the H+/H2 equilibrium potential. Waveform analysis of redox features associated with immobilized cobaloximes indicates more repulsive interactions within the polymer film at pH neutral vs basic conditions, which is attributed to the increased fraction of pyridinium species at lower pH values. Our measurements also show the number of electrochemically active sites changes when measured in different solvent environments, indicating that electroactive loadings determined under non-catalytic solvent conditions are not necessarily representative of those under catalytic conditions and could thereby lead to misrepresentations of catalytic turnover frequencies.

An electrochemical quartz crystal microbalance study of 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin electropolymerization process

The process of 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin electropolymerization has been studied by the quartz crystal microbalance method in different electrodeposition conditions. The films were deposited in two modes: in potentiostatic conditions (at the potential of [Formula: see text]2 V) and in potentiodynamic conditions (CV with the potential scan rate of 20 mV/s). The effect of electrolysis parameters on 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin electropolymerization has been studied by obtaining films in two modes and using two supporting electrolytes: tetrabutylammonium perchlorate or tetrabutylammonium hexafluorophosphate. The biggest film mass gain was observed on a clean electrode surface. At further film deposition on the polyporphyrin-coated electrode, the film mass growth stopped. The electrodeposition effectiveness was somewhat higher in the potentiodynamic conditions, with the formation of a looser film. The nature of the supporting electrolyte did not have a significant effect on the electrodeposition process. A significant contribution to the deposition was made by the electrode material. The film thickness was 25–80 nm. The films possessed [Formula: see text]-type conductivity; and the flat-band potential for poly-H[Formula: see text]T(4-OHPh)P obtained in potentiodynamic conditions was 0.33 V, for poly-H[Formula: see text]T(4-OHPh)P obtained in potentiostatic conditions it was 0.16 V.

Pulsed electropolymerization of PEDOT enabling controlled branching

Controlling the growth of conductive polymers via electrolysis enables defined surface modifications and can be used as a rapid prototyping process. In this study, the controlled dendritic growth of poly(3,4-ethylenedioxythiophene) in a two-electrode setup was investigated by pulsed voltage-driven electropolymerization of the precursor EDOT and a low concentration of tetrabutylammonium perchlorate dissolved in acetonitrile. Rapid growth of different polymeric shapes was reliably achieved by varying the reduction voltage and duty factor. The obtained structures were optically examined and quantified using fractal dimensions. Their shapes ranged from solid coatings over branched fractals to straight fibers without requiring any template. These rapid and controllable electropolymerization processes were further combined to increase conductor complexity.

A molecularly imprinted electrochemical sensor based on Au nanocross-chitosan composites for detection of paraquat

A novel electrochemical sensor for paraquat (PQ) detection based on molecularly imprinted polymer (MIP) membranes on a glassy carbon electrode (GCE) modified with Au nanocrosses-chitosan (AuNCs-CS) was constructed. P-Aminothiophenol (p-ATP) and 4,4′-bipyridine template were assembled on the surface of the modified GCE by the formation of Au–S bonds and hydrogen-bonding interactions, followed by polymer membrane formation by the electropolymerization in a polymer solution containing p-ATP, HAuCl4, tetrabutylammonium perchlorate (TBAP), and the template molecule 4,4′-bipyridine. The as-constructed molecularly imprinted sensor (MIP-AuNC-CS) was characterized by differential pulse voltammetry (DPV), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). This is the first time that molecularly imprinted polymer technology has been integrated with a modified AuNCs-CS to electrochemically detect PQ. The linear response of the MIP-AuNC-CS sensor was in the range from 1 × 10−14 to 1 × 10−10 mol L−1, and the limit of detection was 2.3 × 10−15 mol L−1. This sensor showed high-speed real-time detection capability, low sample consumption, high sensitivity, low interference, and good stability characteristics, and was proven to detect PQ.

Analytical Methods: Electrochemical azido-selenenylation of some olefins by cyclic voltammetry and controlled-potential coulometry

Electrochemical azido-phenylselenenylation of some olefins was studied with the oxidation of diphenyl diselenide in the presence of some olefins and sodium azide in dimethyl formamide containing tetra butyl ammonium perchlorate as supporting electrolyte in an H-type cell. The electrochemical oxidation of the mixture of (PhSe)2, olefins, and NaN3 was studied by cyclic voltammetry and controlled-potential coulometry. Anti product can be obtained with Markovnikov orientation. This product was characterized .by 1H, 13C NMR, and IR spectroscopy.

One-step electrodeposition of ligand-free PdPt alloy nanoparticles from water droplets: Controlling size, coverage, and elemental stoichiometry

We present a robust and facile method to produce metal nanoparticle (NP) alloys in a one-step synthesis using direct electrodeposition onto highly oriented pyrolytic graphite (HOPG). Precursor salts, H2PtCl6 and Pd(NO3)2, were dissolved in a 1 mM sodium dodecylsulfate (SDS) water droplet with 1× phosphate buffered saline solution and suspended in a dichloroethane (DCE) continuous phase. Tetrabutylammonium perchlorate was added to the DCE continuous phase to maintain charge balance during electrodeposition. NP fabrication via electrodeposition was driven by droplet collisions onto HOPG, which was biased at a potential where the metal precursor salts would reduce to their respective zero-valent atoms. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX) were used to study the size, coverage, and morphology of the NPs as well as the atomic stoichiometry. EDX mapping indicated homogeneous distribution of Pd and Pt at the single NP level. Homogeneously alloyed PdPt NPs were realized from this study with demonstrated control over metal composition, surface coverage, and NP size.

Mitochondria localizing high-spin iron complexes of curcumin for photo-induced drug release

High-spin iron complexes [FeII(L1)(cur)]Cl (1), [FeIII(L2)(cur)]Cl (2) and [FeIII(L3)(cur)] (3), where L1 is tris(2-pyridylmethyl)amine, HL2 is N,N-bis(2-pyridylmethyl)-N-(2-hydroxybenzyl)amine and H2L3 is N,N-dimethyl-N’,N’-bis(4,6-ditertiarybutyl-2-hydroxybenzyl)ethylenediamine and Hcur is curcumin, were synthesized, characterized and their redox-mediated and/or visible light induced release of curcumin, photo-induced DNA cleavage and anticancer activity studied. The molecular structures of 1–3 were optimized from DFT (density functional theory) calculations. The t2g3eg2-iron(III) complexes showed a curcumin based electronic spectral band at ∼ 425 nm in 1:1 DMF/DPBS (Dulbecco's phosphate-buffered saline) and displayed the Fe(III)-Fe(II) redox couple near −0.36 V vs. SCE (saturated calomel electrode) in DMF-0.1 M TBAP (tetrabutylammonium perchlorate). The complexes are avid binders to calf thymus DNA. Complex 1 showed photo-cleavage of pUC19 DNA in visible light of 446 nm forming OH radicals as the reactive oxygen species. The complexes as curcumin carrier showed photo-cytotoxicity in different cell lines on visible light activation. Imaging study showed their subcellular mitochondrial localization.

Electrochemical activation of CO2 by a di-Schiff base of N, N′-bis(2-hydroxy-1-naphthaldehyde)-m-phenylenediimine

Electrochemical behavior of a di-Schiff base, N, N′-bis(2-hydroxy-1-naphthaldehyde)-m-phenylenediimine, NMPD, was investigated using cyclic voltammetry, chronoamperometry and controlled-potential coulometry in acetonitrile solution containing tetrabutylammonium perchlorate, as supporting electrolyte. The effect of different parameters such as potential scan rates, and time window of the chosen electrochemical method was examined in studying the electrochemical behavior of NMPD. According to the results of experiments, an EC2CE mechanism was proposed to electrochemical reduction of NMPD on the glassy carbon electrode surface. Furthermore, NMPD is an efficient electrocatalyst in reduction of CO2. This electrocatalytic activity is confirmed by 700 mV decreases in overpotential of CO2 reduction, significant increase in cathodic current of NMPD and also the spectrum characterization of the main product of the electrolysis process which is oxalic acid.

Synthesis, characterization, and electrochemical and in-situ spectroelectrochemical properties of novel peripherally and non-peripherally 7-oxy-3-(3,4-dimethoxyphenyl) coumarin substituted phthalocyanines

Novel metal-free (4 and 9), Zn(II) (5 and 10) and Co(II) (6 and 11) phthalocyanines (Pcs) bearing four 7-oxy-3-(3,4-dimethoxyphenyl)coumarin (1) substituents at peripheral (β) and non-peripheral (α) positions have been prepared by cyclotetramerization reactions of 4-(3-(3,4-dimethoxyphenyl)coumarin-7-oxy)phthalonitrile (3) or 3-(3-(3,4-dimethoxy-phenyl)coumarin-7-oxy)phthalonitrile (8), respectively, in the presence of relevant metal acetate salts in N,N-dimethylaminoethanol. The compounds have been characterized by elemental analysis, FT-IR, UV–Vis and MALDI-TOF mass spectroscopies. Thermal properties of the compounds were evaluated by thermogravimetric analysis and differential scanning calorimetry. Electrochemical redox properties of all compounds were investigated by voltammetric and in-situ spectroelectrochemical measurements in dimethylsulfoxide including tetrabutyl ammonium perchlorate as the supporting electrolyte. The metal-free and Zn(II)Pc compounds displayed Pc ring-based redox processes whereas both Pc ring-based and metal-based electron transfer processes were observed for Co(II)Pc complexes. H-aggregation tendency of peripherally substituted compounds was found to be much higher than that of non-peripherally substituted ones. It was observed that there have been systemmatic redox potential and aggregation behaviour differences between the peripherally and non-peripherally substituted Pc compounds. These differences were attributed to different sterical and conformational effects of these substitution patterns. In-situ spectroelectrochemical and in-situ electrocolorimetric measurements suggested that peripherally substituted Co(II)Pc is a multi-coloured chromophore material displaying distinct spectral and colour changes during the first reduction and oxidation processes, and thus, being suitable for electrochromic applications.

Electropolymerization of poly-5,10,15,20-tetrakis(p-aminophenyl)porphyrin in different deposition modes and solvents

The influence of solvent, supporting electrolyte and electrolysis modes on poly-5,10,15,20-tetrakis([Formula: see text]-aminophenyl)porphyrin film growth were studied by the quartz crystal microbalance method. Electropolymerization was carried out in potentiostatic and potentiodynamic modes from dichloromethane and ethanol solutions. Tetrabutylammonium perchlorate (TBAP) and tetrabutylammonium hexafluorophosphate (TBAHFP) were used as supporting electrolytes. Surface micrographs of films electrodeposited over a different number of cycles of potential variation were obtained. The specific surface area, the pore size, and the thickness of the obtained polyporphyrin films were determined. The number of electrons participating in 5,10,15,20-tetrakis([Formula: see text]-aminophenyl)porphyrin electropolymerization was determined by the quartz crystal microbalance method. Based on the electronic absorption spectroscopy results, it was established that porphyrin macroheterocycles were preserved in an oxidized state in polyporphyrin.

Electrochemical Evidence of the Catalytic Activity of Meso-Tetraphenylporphyrin Diacid in the Proton Reduction in Benzonitrile

Our work shows the electrochemical behavior of meso-tetraphenylporphyrin diacid (H4TPP2+) in tetrabutylammonium perchlorate Bu4NClO4 0.1 M / benzonitrile. On a cathodic sweep and scan rates between 0.1 and 3.0 V/s, H4TPP2+ undergoes two closely spaced consecutive reversible one-electron transfers (Ic’/Ia’ and IIc’/IIa’; Figure 1), which can be assigned to formation of diprotonated porphyrin radical cation (H4TPP•+), and isophlorin H4TPP species, respectively1. In presence of an extra equivalent of HClO4, a new reduction peak, IIIc’, is seen, suggesting that isophlorin H4TPP is being protonated. It is believed that the protonation takes place at one of the meso-positions of the porphyn ring leading to phlorin cation (H4TPFH+). The phlorin cation is electroactive and can be either oxidized (peaks IVa’ and Va’) or reduced (IIIc’)2. As seen in Figure 1, the addition of extra equivalents of H+ to solutions of H4TPP2+ provokes an increase in the current and loss of reversibility of the two reduction processes, Ic’/Ia’ and IIc’/IIa’. This behavior was explained as due to the reaction between the free protons in the medium and the hydrogen atom of the meso-position of the H4TPFH+, in a reaction that produces molecular hydrogen and regenerates the porphyrin diacid. Digital simulation of the experimental voltammograms of H4TPP2+ indicates that the H4TPP•+ and H4TPP species are stable on the cyclic voltammetry time scale. However, coulometry experiments at the potential of the second reduction process show that at longer time scale, the isophlorin H4TPP undergoes coupled chemical reactions. Voltammograms of the electrolyzed solution exhibit oxidation and reduction signals that are characteristics of H4TPFH+ species, also the presence of the bands at 460 nm and 773 nm in the UV-visible spectrum is consistent with the presence of H4TPFH+ species3,4. It is also demonstrated that the H4TPFH+ species can be reoxidized back to the original H4TPP2+ in a two-electron process. References. 1. H. M. Castro-Cruz, thesis, UNAM (2017). http://132.248.9.195/ptd2017/junio/410088896/Index.html 2. Y. Cui, L. Zeng, Y. Fang, J. Zhu, C. H. Devillers, D. Lucas, N. Desvbois, C. P. Gros and K. M. Kadish, ChemElectroChem, 3, 228–241 (2016). 3. G. Peychal-Heiling and G. S. Wilson, Anal. Chem., 43, 550–556 (1971). 4. G. L. Closs and L. E. Closs, J. Am. Chem. Soc., 85, 818–819 (1963). Figure 1

Selection of Low‐Cost Ionic Liquid Electrocatalyst for CO2 Reduction in Propylene Carbonate/Tetrabutylammonium Perchlorate

AbstractElectrochemical reduction of carbon dioxide (CO2) to carbon monoxide (CO) has attracted increasing attention, because this method provides a new route for CO2 recycling utilization. As CO2 is chemically inert, this reaction requires a high over‐potential. Therefore, it is highly desirable to develop an electrocatalyst to accelerate this reaction. In the present work, we have investigated numerous imidazolium ionic liquids (ILs) with the aim of looking for a low‐cost homogeneous catalyst with high efficiency. By comparison, 1‐butyl‐3‐methylimidazolium chloride ([Bmim][Cl]) has been selected as the most cost‐effective. To further reduce the cost of [Bmim][Cl], we added [Bmim][Cl] into propylene carbonate(PC)/tetrabutylammonium perchlorate (Bu4NClO4), and used it as the electrocatalyst. Our experimental results show that [Bmim][Cl] has a high catalytic effect for CO2 reduction. The catalytic mechanism of [Bmim][Cl] has been discussed based on electrochemical impedance spectroscopy. It is explained as follows: CO2 was first reduced to the high‐energy CO2.− radical through a one‐electron transfer. The generated CO2.− radical further reacts with [Bmim]+, resulting in the formation of a complex [CO2−Bmim]. Thus, the activation energy of CO2 reduction has been reduced.

Direct Electrochemical Observation of Single Platinum Cluster Electrocatalysis on Ultramicroelectrodes.

We demonstrate a method to electrodeposit and observe the electrocatalysis of small platinum clusters and nanoparticles (NPs) in real time as they form on an ultramicroelectrode (UME). Water droplets ( rdrop ∼ 700 nm), stabilized by sodium dodecyl sulfate (SDS), were suspended in a solution of dichloromethane (DCM) and tetrabutylammonium perchlorate ([TBA][ClO4]), which was used to mitigate charge balance during droplet electrolysis. When droplets collided with an UME biased sufficiently negative to drive water reduction, large blips of current were observed. Droplets were synthesized with varying concentrations of H2PtCl6 (from 24.4 mM to 32 nM), which can be reduced to Pt0 at 0.8 V more positive than water reduction on a Au or C UME. The observation of current blips synthesized with mM amounts of H2PtCl6 indicated water droplets deliver H2PtCl6 to the electrode surface, where a cathodic potential caused Pt NPs to form. The formation of clusters was observed by biasing the electrode potential more negative than water reduction on Pt but more positive than water reduction on Au, giving current blips for droplets containing μM to nM amounts of H2PtCl6. These blips corresponded to the electrocatalysis of thousands to tens of atoms (clusters). Droplet electrolysis allows for a large amplification such that the electrocatalysis of clusters can be observed in real time. Single, isolated clusters were further characterized voltammetrically on carbon fiber UMEs. The isolation step used the amperometric method, which unambiguously depicted cluster formation in real time. Carbon was chosen due to its large potential window and slow kinetics toward many inner-sphere reactions, such as proton reduction, used in this study. Voltammetric characterization of proton reduction in HClO4 and NaClO4 allowed for cluster size analysis using the limiting current. The reduction of proton on the clusters ( E1/2 ∼ -0.6 V vs Ag/AgCl) occurred at ca. 400 mV more negative than bulk, polycrystalline platinum.

Redox-active and fluorescent pyrene-based triarylamine dyes and their derived electrochromic polymers

Two triarylamine derivatives, DPPA-2(NHCO-TPA) and DPPA-2(NHCO-NPC), composed of a central diphenylpyrenylamine (DPPA) unit via amide groups linked to two triphenylamine (TPA) or N-phenylcarbazole (NPC) sides are developed as an electroactive precursor to prepare electrochromic films through electrochemical polymerization. The dilute solutions of these two DPPA-containing compounds showed notable fluorescence and solvatochromic shifts. Electroactive polymeric films could be electrodeposited on the ITO electrode surface by repetitive cyclic voltammetry scanning of their dichloromethane solutions containing dissolved 0.1 M tetrabutylammonium perchlorate (TBAP) between 0 and 1.5 V. The polymer films displayed multi-staged redox processes and color changes upon electrochemical oxidation. Spectroelectrochemistry and electrochromic switching stability of the polymers were investigated. Simple single-layer electrochromic devices were also fabricated and tested.

Anodic Deposition of Enantiopure Hexahelicene Layers

AbstractHelicenes are polyaromatic compounds with chiral properties useful for many applications in optoelectronics, separation processes, chiral recognition and catalysis. Here we focused on the electrochemistry of carbo[n]helicenes (n=5,6,7). The cyclic voltammograms of racemic mixtures of target compounds in acetonitrile/0.1 M tetrabutylammonium perchlorate at a glassy carbon electrode reveal the diffusion‐controlled reactions in both anodic and cathodic potential regions. Electrochemical behaviors are different for individual helicenes, [7]helicene undergoes redox transformation easily in comparison to the other investigated compounds, which is in agreement with DFT (density functional theory) calculations. Generally, the multi‐component anodic process of helicenes is observable at potentials from +1.5 to +2.5 V, leading to the formation of deposited structures (layers) on the electrode surface. The helicenes were electrodeposited onto transparent indium tin oxide (ITO) electrodes and characterized by atomic force microscopy, UV/Vis, Raman spectroscopy and ellipsometry. Finally, the anodic deposition of P and M enantiomers of [6]helicene was performed using ITO substrates, resulting in the formation of enantiopure layers of nanometer thicknesses, as confirmed by circular dichroism spectroscopy. The discovered electrosynthetic procedure opens up a new possibility for the immobilization of chiral helicene layers onto solid supports.