Tetrabutylammonium Perchlorate Research Articles

Electrochemical radiofluorination using a split-bipolar electrode

Electrochemical (radio)fluorination (ECF) is a versatile approach for nucleophilic radiofluorination of electron-rich compounds such as thioether derivatives. However, ECF generally requires high concentrations of supporting salts, which leads to low molar activity (Am) of the final product due to undesired contamination with [19F]F– ions. Here, we demonstrate the first example of radiofluorination using a split bipolar electrode (s-BPE) platform with low concentration of supporting salt. Under optimal reaction conditions, the ECF of methyl (methylthio)acetate (MMTA) using s-BPEs provided [18F]F-MMTA with radiochemical conversion of up to 70 % and high molar activities (28–43 GBq/μmol; 0.74–1.1 Ci/μmol), with approximately 5 mM of tetrabutylammonium perchlorate as supporting electrolyte.

Electrochemical alcohol oxidation using a TEMPO nitroxide polymer as a homogeneous and surface‐confined catalyst

AbstractPolymers containing TEMPO moieties are effective catalysts for the electrochemical oxidation of alcohols. Such polymers, almost exclusively, are non‐commercial and are prepared using multi‐step synthetic procedures. Here we show that a commercially available TEMPO bearing polymer, Polyamine Immobilised Piperidinyl Oxyl (PIPO), is an effective homogeneous and surface‐confined polymeric catalyst for electrochemical alcohol oxidation at carbonaceous electrodes. We probe electrolytic conditions for effective and stable electrocatalytic alcohol oxidation showing that dichloromethane (DCM), containing tetrabutylammonium perchlorate (TBAP) and N‐methyl imidazole (NMI), is a suitable medium for homogeneous catalysis whilst carbonate buffer (pH 9.5) is better suited when PIPO is adsorbed at the electrode surface. These findings demonstrate the viability of PIPO as an effective and accessible catalyst for electrochemical alcohol oxidations.

Electrochemical, spectroelectrochemical, and electrochromic characterization of silicon(IV) phthalocyanine with axially ligated electropolymerizable 3,4-ethylenedioxythiophene moieties

Poly(3,4‐ethylenedioxythiophene) (PEDOT) is the most popular conducting polymer in the field of optoelectronics. In this study, the electrochemical and spectral properties of the silicon(IV) phthalocyanine (SiPc) and of a PEDOT were combined, and the electrochromic property was imparted to SiPc by modification of the axial positions of the Si4+ cation of SiPc with 3,4‐ethylenedioxythiophene (EDOT) groups. For this purpose, SiPc-EDOT was synthesized and characterized as to its electrochemistry and spectroelectrochemistry in nonaqueous media. Three reversible reduction couples at −0.51, −0.92, and −1.62 V and two oxidation processes at 1.16 and 1.73 V were observed for SiPc-EDOT in dichloromethane (DCM) containing tetrabutylammonium perchlorate (TBAP). In situ spectroelectrochemical analysis showed that the reductions and the first oxidation process of SiPc-EDOT were Pc-centered and the second oxidation process was EDOT-centered. The EDOT-based redox process at 1.73 V triggered the coating of SiPc-EDOT on the electrode surface as the SiPc-PEDOT film due to the electrooligomerization of the oxidative cationic form of EDOT groups during the repetitive voltammetric cycles. The electropolymerized SiPc-PEDOT film on the different electrode surfaces (ITO, GCE, ITO/Nf) yielded a conjugated polymer, which was characterized by cyclic voltammetry, UV–vis spectroelectrochemistry, Raman and FT-IR spectroscopies. The EDOT modification of SiPc supplied boost electrochromic performance in large percent transmittance change (Δ%T = 50 %), high coloration efficiency (η = 530 cm2 C−1), fast response times, and high cycle stability.

Cu(II) flavonoids as potential photochemotherapeutic agents.

Flavonoids, naturally derived polyphenolic compounds, have received significant attention due to their remarkable biochemical properties that offer substantial health benefits to humans. In this work, a series of six Cu(II) flavonoid complexes of the formulation [Cu(L1)(L2)](ClO4) where L1 is 3-hydroxy flavone (HF1, 1 and 4), 4-fluoro-3-hydroxy flavone (HF2, 2 and 5), and 2,6-difluoro-3-hydroxy flavone (HF3, 3 and 6); L2 is 1,10-phenanthroline (phen, 1-3) and 2-(anthracen-1-yl)-1H-imidazo[4,5-f][1,10]phenanthroline (aip, 4-6) were successfully synthesized, fully characterized and also evaluated for their in vitro photo-triggered cytotoxicity in cancer cells. The single-crystal X-ray diffraction structure of complex 2 shows square pyramidal geometry around the Cu(II) center. The complexes 1-6 showed quasi-reversible cyclic voltammetric responses for the Cu(II)/Cu(I) couple at ∼-0.230 V with a very large ΔEp value of ∼350-480 mV against the Ag/AgCl reference electrode in DMF-0.1 M tetrabutylammonium perchlorate (TBAP) at a scan rate of 50 mV s-1. The complexes were found to have considerable binding propensity for human serum albumin (HSA) and calf thymus DNA (ct-DNA). The complexes displayed remarkable dose-dependent photocytotoxicity in visible light (400-700 nm) in both A549 (human lung cancer) and MCF-7 (human breast cancer) cell lines while remaining significantly less toxic in darkness. They were found to be much less toxic to HPL1D (immortalized human peripheral lung epithelial) normal cells compared to A549 and MCF-7 cancer cells. Upon exposure to visible light, they generate reactive oxygen species, which are thought to be the main contributors to the death of cancer cells. In the presence of visible light, the complexes predominantly elicit an apoptotic mode of cell death. Complex 6 preferentially localizes in the mitochondria of A549 cells.

Electrochemical copolymerization of 3,4-ethylenedioxythiophene and dithienothiophene: influence of feed ratio on electrical, optical and electrochromic properties.

Designing a copolymer is an efficient and alternative method to generate new chemical and physical properties compared to parent homopolymers without complex synthesis and structural modification. We herein report the electrochemical deposition of copolymer using two monomers 3,4-ethylenedioxythiophene (EDOT) and dithieno[3,2-b:2',3'-d]thiophene (DTT). Three different copolymers P[EDOT-co-DTT] were synthesized by using different feed ratios of monomers (EDOT and DTT molar ratios in solution are 2 : 1, 1 : 1 and 1 : 2) in acetonitrile containing 0.1 M tetrabutylammonium perchlorate (TBAClO4) as a supporting electrolyte. Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and UV-vis-NIR spectroscopy were employed to characterize the obtained copolymers. Energy dispersive X-ray spectroscopy (EDX) analysis was used to estimate the composition of EDOT and DTT units in copolymers. The electrochemical and morphological properties were analyzed using cyclic voltammetry (CV) and field emission scanning electron microscopy (FESEM). In situ spectroelectrochemistry and electrochromic studies were performed to investigate the optical and switching properties of the resultant copolymers. The homopolymers poly(3,4-ethylenedioxythiophene) (PEDOT) and polydithieno[3,2-b:2',3'-d]thiophene (PDTT) were also prepared using similar electrochemical conditions and made comparisons where applicable. Computational calculations were done to understand the structure and energy levels of these polymers. It was found that these copolymers P[EDOT-co-DTT] show new properties as compared to homopolymers PEDOT and PDTT for organic electronic applications. Interesting to note that the resultant copolymers display the property of tunable electrochromism with improved transmittance and redox color change between the neutral and oxidized states.

Bioinspired Nanotubes by Soft‐template Electropolymerization from Fully Conjugated Monomers

AbstractBioinspired by the strong water‐adhesive forces of gecko foot or rose petals, here, nanotubular structures are prepared by soft‐template electropolymerization. Water is mixed to a solvent of low water‐solubility to form a micellar solution in the presence of tetrabutylammonium perchlorate as the electrolyte and surfactant. As the monomer, a benzene is trifunctionalized with various thiophene and carbazole moieties. The monomers are fully conjugated to favor the deposition compared to polymerization, as confirmed by cyclic voltammetry experiments. The surface nanostructures (nanotubes, nano‐ribbons, coral‐like structures) are highly dependent on the monomer and the water content but less on the deposition method. The maximum water contact angle is 158.1° accompanied with strong water adhesive force. These surfaces are highly interesting for applications in water‐harvesting systems or in sensing platforms.

Visible-Light-Initiated Air-Oxygenation of Alkylarenes to Carbonyls Mediated by Carbon Tetrabromide in Water.

Synthesizing benzyl skeleton derivatives via direct oxidation of functionalized benzylic C-H bonds has received extensive research attention. Herein, a method was developed to prepare carbonyl compounds via photoinduced aerobic oxidation of ubiquitous benzylic C-H bonds mediated by bromine radicals and tribromomethane radicals. This method employed commercially available CBr4 as a hydrogen atom transfer reagent precursor, air as an oxidant, water as a reaction solvent, and tetrabutylammonium perchlorate (TBAPC) as an additive under mild conditions. A series of substrates bearing different functional groups was converted to aromatic carbonyls in moderate to good yields. Moreover, a low environmental factor (E-factor value=0.45) showed that the proposed method is ecofriendly and environmentally sustainable.

Faradaic Rhenium Recovery with Polyvinyl Ferrocene (PVF) Electrodeposited Carbon Electrodes

Rhenium, a valuable rare element used in catalysts and superalloys, is difficult to recover in micromolar concentrations (Schulz, 2017). Electrodes coated with the redox active polymer poly vinyl ferrocene (PVF) have shown the ability to selectively adsorb several transition metal oxyanions, but limited adsorption capacity and longevity remain a challenge for these selective electrosorption technologies(Chen et al., 2021; Kim et al., 2020). In this study, we elucidate the impact of electrochemical deposition conditions on PVF coating as measured by capacitance, rhenium uptake, and longevity. PVF films were electrodeposited onto carbon substrate electrode at three different potentials across the oxidation window of the ferrocene-based metallopolymer to understand how the rate of charge transfer influences the resulting electrodeposited polymer coating. It was observed that PVF films electrodeposited at the peak oxidation current potential of 0.45 V (vs. Ag/AgCl) showed both the highest adsorption of Rhenium (458 ± 61 mg Re/g adsorbent) and capacitance (217 F/g). In comparison, the electrodeposition at 0.35 V and 0.6 V leads to a lower average capacitance 355.36 mg Re/g adsorbent and 342.03 mg Re/g adsorbent respectively. The enhanced performance for 0.45 V electro-deposited electrode can likely be attributed to a more stable deposition structure of the polymer (Pater et al., 1998), which enhances adhesion substrate and charge transfer between the substrate and the PVF. The 0.45 V electro-deposited PVF-carbon paper (PVF-CP) electrode illustrates high capacity and stability, indicating the benefits of polymer coating on selective adsorption of rhenium and prevention of electrode corrosive degradation in capacitive deionization systems. The excellent rhenium uptake and longevity demonstrates potential and will be the platform towards a full techno-economic analysis of the hybrid adsorption system in the future.Method Materials: Polyvinyl ferrocene (34801-99-5, produced by Polysciences, U.S.) and tetrabutylammonium perchlorate (1923-70-2, for electrochemical analysis, ≥99%, produced by Sigmar Aldrich Chemistry, U.S.) were used for electrodeposition. Carbon nanotubes (multiwalled, outer diameter of 7−12 nm, length of 0.5 - 10 μm, >99% carbon) were used as conductivity additives in dip coating electrode fabrication. Toray paper (carbon fiber composite carbon paper, produced by FuelCellStore) was used as the substrate for ferrocene polymer deposition under all conditions. Electrodeposition Electrodeposition performed on 2 cm x 1 cm rectangles of carbon paper substrate attached to copper wire with copper tape in a three-electrode cell configuration with a quasi-Ag/organic solution reference and CP counter electrode. 0.35 V, 0.45 V and 0.6 V were applied respectively to the working electrode in 2 mg/mL PVF solution until 0.12 C of charge had passed. Dip the electrodes into chloroform twice to rinse and stored the electrodes in the Milli-Q water. Cyclic Voltammetry (CV) CV test was performed in a three-electrode cell configuration with PVF deposited carbon paper as working electrode, platinum wire as counter electrode and Ag/AgCl reference. The voltage was swept between 0 V and 0.7 V in 0.5 M sodium perchlorate solution to capture characterize redox peak around 0.35 V. Rhenium Uptake The adsorption and desorption experiments were performed in the same three electrode cell but with a solution containing 1 mM NaReO4 or 10 mM NaCl, respectively. The voltage on working electrode maintained 0.8 V for adsorption and -0.8 V for desorption with stirring bar on the bottom stirring at 300 rpm for an hour.ResultsThe deposition happens when the positive charges transferred to the PVF that diffuse to the CP surface. The positive charged ferrocene groups combine with perchlorate, which decreases the solubility of PVF and leads to the deposition. According to the gravimetric mass measurement, the deposition mass range for 0.6 V, 0.45 V and 0.35 V are 0.1 – 0.25 mg, 0.2 – 0.35 mg and 0.4 – 0.55 mg, respectively. Comparing with theoretical deposition mass (0.26 mg, calculated from the total charge transfer), higher transition current and shorter deposition time promote a more sufficient charge transfer and a more localized deposition on the electrode interface. The CV plot (Figure 1(a)) elucidates the prominent specific capacitance for 0.45 V deposited electrode (216.50 F/g on average) and an obvious oxidize peak positive movement for 0.35 V deposition, which is corresponding to a higher deposited mass (0.4-0.55 mg) that may lead to a higher resistance. The mass normalized Re uptake reaches 457.87 mg Re/g polymer with a regeneration rate of 64.47%. For next step, the longevity test will be performed to obtain a further understanding to the depletion of regeneration rate along the increase of cycle number.

Directional formation of microtubes by soft-template electropolymerization from fully conjugated triphenylamine-based monomers

Microtubular structures have been prepared by soft-template electropolymerization of conjugated organic monomers with the aim to mimic the strong water-adhesive forces of gecko foot or rose petals. Water-saturated solvent of low water solubility (dichloromethane) was used to form a micellar solution stabilized by tetrabutylammonium perchlorate as the electrolyte and the surfactant, in which case the formation of nanotubes was particularly efficient. The studied monomers were built from a triphenylamine core conjugated with three arms differing by their structure and positions: (i) 2- or 3-positions in the thiophene arms or (ii) carbazole arms attached to para, meta or ortho-positions of the benzene ring of the core. The formation of microtubes is due to preferential growth of polymer films and an aggregation of formed polymers/oligolymers in one direction (1D) facilitated by π–stacking interactions. The key factors influencing on the surface morphologies (monomer structures and reactivity, electrodeposition conditions, etc) are discussed. Impressive results have been obtained in studies of carbazole-containing monomers and the effect of regioisomerism in the monomers (the position of the carbazole attachment to the core). Extremely long microtubes (tens to >100 μm length, diameter ≈ 1.0–1.5 μm) were formed on the electrode surface from the monomer N-Ph-p-Cb with the carbazole attachment in the para-position. Wettability analysis showed highly hydrophobic surfaces with apparent contact angles up to 154.0° and extremely strong water adhesion comparable to rose petals or gecko feet. Such coatings can find applications in water-harvesting systems, sensing platforms or electrochemical analyses.

Tailoring the properties in conjugated copolymer P(EDOS-co-EDOT): Electrochemical polymerization and role of heteroatom

Considering the significant work on copolymerization, very little is known about the copolymerization of two heteroaromatic rings to generate new properties. In this work, we report a series of conducting copolymers [poly(3,4-ethylenedioxyselenophene)-co-poly(3,4-ethylenedioxythiophene)] [denoted as P(EDOS-co-EDOT)] synthesized via anodic polymerization using different feed ratios of two engaged monomers. Three feed ratios of monomers 3,4-ethylenedioxyselenophene (EDOS) and 3,4-ethylenedioxythiophene (EDOT) were used as 5:1, 1:1, and 1:5 for electrochemical copolymerization in acetonitrile containing 0.1 M tetrabutylammonium perchlorate as a supporting electrolyte. Corresponding homopolymers PEDOS and PEDOT were also prepared from monomers EDOS and EDOT, respectively, by electrochemical polymerization to sight the analogy and differences in the properties of obtained copolymers with respect to individual homopolymers. Copolymers were structurally characterized via Raman spectroscopy and X-ray fluorescence. The redox traits, optoelectronic properties and surface morphology of as-prepared polymer films were characterized using cyclic voltammetry, spectroelectrochemistry and field emission scanning electron microscope, respectively. Electrochemical stability of the copolymers was examined by repeating redox cycles. Density functional theory calculations were carried out to get an understanding of the trends in energy levels, and comparisons were made with the experimental results. Copolymer films exhibited deep blue color in the neutral state while transmissive gray in oxidized state. Electrochromic properties of the copolymers were carried out, and found highest optical contrast ratio to be 36.86% and coloration efficiency of 62.89 cm2 C − 1 for 1:5 ratio. It was found that all the copolymers have different highest occupied molecular orbital (HOMO) levels resulting from their distinct redox behavior and band gap values lie within the range of homopolymers. Thus, copolymerization is an effective route for the synthesis of polymer to tune the properties for electronic applications.

Quantitative Detection of Ortho-Aminophenol by Using Modified Reduced Graphene Oxide/Indium Tin Oxide Glass Electrode

In this research work the electrochemical oxidation of ortho-aminophenol (oAP) is studied using modified reduced graphene oxide/indium tin oxide (rGO/ITO) glass electrode in acetonitrile medium, tetrabutyl ammonium perchlorate (TBAP) supporting electrolyte. Cyclic voltammetry (CV) and linear-sweep voltammetry (LSV) techniques were used to study the redox behavior of oAP. The graphene oxide-initiated auto-oxidized 2-aminophenoxazine-3-one is irreversibly reduced by modified rGO/ITO glass electrode at −0.048[Formula: see text]V (versus Ag–AgCl electrode). LSV response shows that the cathodic peak current increases notably compared to that of bare rGO/ITO glass electrode and with the increasing concentration of oAP. The oxidized product of oAP was characterized by UV–Visible and FT-IR spectroscopy. The redox behavior of oAP of modified rGO/ITO glass electrode was compared with the electrochemical behavior of oAP at bare glassy carbon electrode.

Ni(II)-Salophen-Comprehensive Analysis on Electrochemical and Spectral Characterization and Biological Studies.

New aspects of the Ni(II)-salophen complex and salophen ligand precursor were found during deep electrochemical and optical characterization, as well as biological studies for new pharmacological applications. Physicochemical and spectroscopic methods (1H- and 13C-NMR, FT-IR and UV-Vis, electrospray ionization mass spectroscopy, thermogravimetric analysis, and molar conductance measurements) were also used to prove that the salophen ligand acts as a tetradentate and coordinates to the central metal through nitrogen and oxygen atoms. The electrochemical behavior of the free Schiff salophen ligand (H2L) and its Ni(II) complex (Ni(II)L) was deeply studied in tetrabutylammonium perchlorate solutions in acetonitrile via CV, DPV, and RDE. Blue films on the surfaces of the electrodes as a result of the electropolymerization processes were put in evidence and characterized via CV and DPV. (H2L) and Ni(II)L complexes were tested for their antimicrobial, antifungal, and antioxidant activity, showing good antimicrobial and antifungal activity against several bacteria and fungi.

Advanced Materials Based on Azulenyl-Phenyloxazolone

Chemically modified electrodes (CMEs) based on 2-phenyl-4-((4,6,8-trimethylazulen-1-yl)methylene)oxazol-5(4H)-one (M) were obtained by irreversible electrooxidation of M in millimolar solutions in 0.1 M tetrabutylammonium perchlorate (TBAP) in acetonitrile. These CMEs were characterized by a ferrocene redox probe, electrochemical impedance spectroscopy (EIS), X-ray photon spectroscopy (XPS), and scanning electron microscopy (SEM). The influence of the preparation conditions (charge and potential) was examined. The CMEs were finally used for the analysis of synthetic samples of heavy metal (HM) ions. The paper highlights the importance of potential and electropolymerization charge on the film properties, with accent on recognition of HMs, in order to identify the best conditions for their detection in water. The observed findings are relevant for further design and development of advanced materials based on azulenyl-phenyloxazolone for the analysis of HMs in water.

Electrochemical Studies of Azulene Modified Electrodes

Previous studies performed on 2-(azulen-1-yldiazenyl)-5-phenyl-1,3,4-thiadiazole (T) showed that T is a ligand with complexing properties towards heavy metals (HMs) in solution and can be attached to electrode surfaces. Films of T were deposited on glassy carbon to obtain chemically modified electrodes (T-CMEs), either through scanning or using controlled potential electrolysis in tetrabutylammonium perchlorate in acetonitrile. They were investigated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS), and spectroelectrochemistry. All methods provided evidence for showing the formation of insulating films, with properties depending on their electropolymerization potential. CV and EIS studies of T-CMEs in tetrabutylammonium perchlorate in acetonitrile as supporting electrolyte, and in the presence of a ferrocene redox probe resulted in a thickness of ~10 µm, an active surface area about 6 times higher than the geometrical one, and conductivity of about 10−6 S/cm. This characterization performed using voltammetric techniques reveals the symmetry of the reversible anodic and cathodic redox CV peaks for the polymer, while spectroelectrochemistry shows the intensification of the charge transport process through polarons, due to the anodic polarization of the film.

Versatile Electroluminescence Color-Tuning Strategy of an Efficient Light-Emitting Electrochemical Cell (LEC) by an Ionic Additive.

The color-tuning strategies of solid-state light-emitting devices (ss-LEDs) are mainly focused on engineering molecular structures. In this paper, for the first time, we developed a facile strategy for tuning the electroluminescence (EL) color from orange to green through the addition of the ionic additive TBAP (tetrabutylammonium perchlorate). To achieve the active ionic emissive compound for use in a light-emitting electrochemical cell (LEC), the neutral biscyclometalated bromo tetrazole iridium(III) [Ir(ppy)2(BrTz)] was exchanged to its cationic complex, [Ir(ppy)2(BrTz-Me)]ClO4 (ppy = 2-phenyl pyridine, BrTz = 4-bromo-2-pyridine tetrazole, BrTz-Me = 4-bromo-2-pyridine methyl tetrazole) with a new synthetic strategy. This method allows employing neutral Ir-cyclometalated complexes, which are ruled out for use in LECs because of their non-ionic behaviors. In the following, an LEC based on the new cationic [Ir(ppy)2(BrTz-Me)]ClO4 as the emissive layer was fabricated between the FTO (fluorine-doped tin oxide) anode and Ga:In alloy cathode without using any additive or polymers, which makes this configuration the simplest ss-LED so far. By adding the ionic additives, the electroluminescence characteristics of [Ir(ppy)2(BrTz-Me)]ClO4 were dramatically increased, including luminance (L) from 162.8 cd/m2 for the device with an additive to 212.9 and 355.9 cd/m2 for devices containing LiTFSI (bis(trifluoromethane)sulfonamide lithium salt) and TBAP, respectively. In particular, when TBAP was added to the [Ir(ppy)2(BrTz-Me)]ClO4 complex, the irradiance was significantly increased from 166.4 to 220.8 μW/cm2 with an efficacy of 1.78 cd/A and external quantum efficiency (EQE) value of 2.14%. The obtained EL results clearly showed that adding TBAP and LiTFSI significantly improved the electroluminescence characteristics and tuned the electroluminescence color.

Cerium‐Modified Mesoporous Antimony Doped Tin Oxide as Intercalation‐Free Charge Storage Layers for Electrochromic Devices

AbstractCharge storage layers are an important component of electrochromic devices, which are expected to exhibit high storage capacity and transparency as well as fast electron transfer rates. However, these layers often rely on the (de)intercalation of ions into the crystal lattice of the material and therefore require optimization to be compatible with non‐intercalating electrolytes. In this report, the post‐modification of mesoporous antimony‐doped tin oxide (ATO) nanoparticle layers with a redox‐active cerium compound is described. In particular, the switching of the Ce3+/Ce4+ couple on the conductive nanoparticle scaffold is demonstrated using tetrabutylammonium perchlorate as a non‐intercalating electrolyte. Remarkably, high storage capacities of up to 27 mC cm−2 and transmittance values of ≈90% are achieved. Variation of the antimony doping concentration revealed that nanoparticle layers doped with 15% Sb exhibit the highest capacity, which can be attributed to increased conductivity in the potential range where the Ce3+ ions are oxidized. Finally, the cerium‐modified ATO films show promising performance as charge storage layers in an electrochromic device with a viologen‐anchored ATO layer as the electrochromic working electrode. Switching times of ≈0.4 s highlight the fast electron transfer capability of the cerium‐decorated ATO layer, even when a non‐intercalating electrolyte is used.

Poly(N-vinyl carbazole)-TiO2 composite coating for protection of steel

In this study, poly(N-vinyl carbazole)-TiO2 composite coatings (PNVC-TiO2) were electrochemically synthesized on the surface of 304 stainless steel (304-SS) using cyclic voltammetry from N-vinyl carbazole, tetrabutylammonium perchlorate and TiO2 containing non-aqueous acetonitrile solution. PNVC films were synthesized in the presence of different amounts (0.05%, 0.10% and 0.15%) of TiO2 and the optimum TiO2 amount was determined by comparison of potentiodynamic polarization curves of the stainless steel electrodes coated with these PNVC-TiO2 films. The synthesized PNVC-TiO2 films were characterized by ATR-FTIR and SEM investigations. Corrosion performances of PNVC-TiO2 coated stainless steel electrodes (SS/PNVC-TiO2) were investigated by Eocp-time curves, potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS) in 1 M H2SO4 corrosive test solution and compared with the data of SS-PNVC electrode. It has been found that the PNVC-TiO2 coating exhibited better protection performance than the PNVC coating and provides 97% protection efficiency against corrosion of 304-SS in a highly acidic corrosive environment.

Effect of metal catalysis in the electrochemical oxidation of petrol on platinum electrodes and its use in petrol brand fingerprinting

This study presents a novel study to explore the electrocatalytic characteristics of platinum electrodes to obtain the electrocatalytic oxidation of petrol in non–aqueous solutions. A petrol sample was added into an electrochemical cell containing 0.1 M Tetrabutylammonium perchlorate (TBAP) in acetonitrile and studied using cyclic voltammetry and differential pulse voltammetry. The results demonstrated that the metal content in TBAP acted as a catalyst, which effectively interacted with substances present in petrol and formed a new electroactive product, providing an electrochemical oxidation response at + 1.2 V. Inductively coupled Plasma analyses and statistical comparison of different TBAP salt brands, indicated that Calcium, Iron and Manganese were directly response on the catalytic electrooxidation. The electrochemical response of petrol was observed as a diffusion–controlled process on platinum electrode with an irreversible reaction. The electrochemical profiles were used to discriminate different brands of petrol using Principal Component Analysis (PCA). Also, this behavior could be replicated in a simplistic manner using a model solution of Fe+3 and petrol.

Reorganization Energies for Interfacial Electron Transfer across Phenylene Ethynylene Rigid-Rod Bridges.

A family of three ruthenium bipyridyl rigid-rod compounds of the general form [Ru(bpy)2(LL)](PF6)2 were anchored to mesoporous thin films of tin-doped indium oxide (ITO) nanocrystals. Here, LL is a 4-substituted 2,2-bipyridine (bpy) ligand with varying numbers of conjugated phenylenethynylene bridge units between the bipyridine ring and anchoring group consisting of a bis-carboxylated isophthalic group. The visible absorption spectra and the formal potentials, Eo(RuIII/II), of the surface anchored rigid-rods were insensitive to the presence of the phenylene ethynylene bridge units in 0.1 M tetrabutyl ammonium perchlorate acetonitrile solutions (TBAClO4/CH3CN). The conductive nature of the ITO enabled potentiostatic control of the Fermi level and hence a means to tune the Gibbs free energy change, -ΔG°, for electron transfer from the ITO to the rigid-rods. Pseudo-rate constants for this electron transfer reaction increased as the number of bridge units decreased at a fixed -ΔG°. With the assumption that the reorganization energy, λ, and the electronic coupling matrix element, Hab, were independent of the applied potential, rate constants measured as a function of -ΔG° and analyzed through Marcus-Gerischer theory provided estimates of Hab and λ. In rough accordance with the dielectric continuum theory, λ was found to increase from 0.61 to 0.80 eV as the number of bridge units was increased. In contrast, Hab decreased markedly with distance from 0.54 to 0.11 cm-1, consistent with non-adiabatic electron transfer. Comparative analysis with previously published studies of bridges with an sp3-hybridized carbon indicated that the phenylene ethynylene bridge does not enhance electronic coupling between the oxide and the rigid-rod acceptor. The implications of these findings for practical applications in solar energy conversion are specifically discussed.

(Digital Presentation) Electrochemical Polymerization of Thiophene in Cholesteric Liquid Crystal with Vitamins

Vitamins are natural compounds which is important for biological reactions. Vitamin C (ascorbic acid) is a water-soluble substance, while Vitamin E (tocopherol) is a soluble material in organic solvents. Further, antioxidant action can affect for metabolism in biological system. Vitamin E has three asymmetric centers in the molecular structure. In the liquid crystal technology, nematic liquid crystal is simple and high fluidity similar to isotopic liquid. Addition of small amount of chiral compounds to nematic liquid crystal can induce cholesteric liquid crystal. This is another chiral and helical version of nematic liquid crystal. In this study, we employed vitamin E as a chiral inducer to nematic liquid crystal for formation of helical liquid crystal system. Electrochemical polymerization is a convenient method for preparation of electroactive polymer deposited on an electrode in the form of thin film. Electrochemical polymerization in LC provides some interesting phenomena. First, electrochemical polymerization in liquid crystal allows the resultant to imprint morphology of molecular aggregation structure from molecular level to macroscopic level of liquid crystal. Second, electrochemical polymerization produces electroactive polymer with dynamically color change upon electrochemical redox process, which character can be applied for electrochemical driven display. Third, electrochemical charge and discharge provides voltaic storage function for the resultant polymer. Thus, electrochemical technique and polymer chemistry, such a brilliant combination produces electro-optic character. Recently, electrochemical polymerization in helical liquid crystal system has been performed. The electrochemical polymerization employs cholesteric liquid crystal as an electrolyte for polymerization. Cholesteric liquid crystal can be prepared by mix of nematic liquid crystal and chiral compounds. We employ synthetic compound as a chiral inducer. Here, we use vitamin E as chiral inducer to nematic liquid crystal preparation of cholesteric liquid crystal electrolyte solution for electrochemical polymerization. Observation of optical texture of the cholesteric liquid crystal electrolyte containing tetrabutylammonium perchlorate (TBAP) as a supporting salt showed fingerprint texture, which is characteristic of cholesteric liquid crystal.Next, electrochemical polymerization in cholesteric liquid crystal induced by vitamin E was carried out. We employed constant voltage electrochemical polymerization to ITO (indium–tin-oxide) coated glass slides were sandwiched via insulator tetrafluoroethylene as a spacer, and the choleretic liquid crystal electrolyte contained monomer (2,2′-bithiophene) was charged with pipette before application of voltage for electrochemical polymerization. The entire polymerization cell was heated to change the liquid crystal to isotropic phase. Then, gradually cooled to room temperature, and the isotopic phase was changed to cholesteric liquid crystal phase with iridescence. After confirming the electrolyte showed liquid crystal phase, constant voltage of 6 V across the sandwiched cell for 60 min was applied. Then, the polymerization cell was de-assembled and washed wish a large volume of organic solvent to remove the liquid crystal electrolyte solution, oligomer, and residual monomer. The polymer film thus prepared was deposited on cathode. This is quite interesting phenomena because electrochemical polymerization is generally occurred at the anode with oxidation. However, this result indicates that electrochemical polymerization in liquid crystal at cathode is possible. Cathodic electrochemical polymerization has been reported for dibromo aromatic compound or unsaturated aliphatic compounds. However, cathodic electrochemical polymerization of aromatic compounds with no halogen group has been few reported.The polymer shows electronic optical transition in visible range due to development of p-conjugated system and absorption at long wave lengths due to doping band accompany by generation on polaron (radical cation). The electrochemical character of the resultant polymer was examined using cyclic voltammetry (CV). The CV measurements were achieved in a monomer-free 0.1-M TBAP−acetonitrile solution at the scan rates of 10 mVs−1. The potential was calculated using a reference of silver/silver ion (Ag/Ag+) electrode. The oxidation and reduction signals are observed during the oxidation and reduction processes. The result showed the resultant polymer has good redox property. The resultant polymer shows no CD signal from short to long wavelengths, indicating no optical activity. However, the polymer shows the similar optical texture to that of liquid crystal electrolyte under the polarizing optical microscopy observations, implying the fingerprint texture of the polymer as macroscopic transcription of the liquid crystal structure may not contribute optical active property. Transcription from liquid crystal environment may not always occurs from molecular level to macroscopic level in the polymerization in liquid crystal. The polymer prepared in this study has no hierarchal structure from molecular level to the higher level, indicating macroscopic morphological imprinting in the polymerization is not essential condition for imprinting from the molecular level.