The extent of nanoplastic pollution has raised severe environmental and health concerns. While th... more The extent of nanoplastic pollution has raised severe environmental and health concerns. While the means for microplastic detection are abundant, improved tools for nanoplastic detection are called-for. State-of-the-art microscopic techniques can detect nanoplastics down to tens of nanometers, however, only from small sample sizes (typically ∼ 10 μl). In this work, we describe a method that enables sampling of 1 l of seawater by the means of correlative Raman-and SEM-techniques. This is achieved by adapting common microplastic sample purification protocols to suit the nanoplastic study. In addition, we decorate a membrane filter with SERS-property to amplify the Raman signals. Together, the purification method combined with the use of the SERS-activated-membrane-filter enables identification and imaging of individual nanoplastic particles from significantly larger sample sizes than before. In the nanoscale the average recovery rate is 5 %. These results aim to provide useful tools for researchers in the fight against plastic pollution.
In the present work, solution-phase synthesis was employed to prepare two sets of catalysts with ... more In the present work, solution-phase synthesis was employed to prepare two sets of catalysts with different transition metals as active sites. One set contained Au or Pd supported on TiO 2 (AuÀ TiO 2 , PdÀ TiO 2), whereas the other set contained layered double hydroxides (NiFe-LDH and CuFe-LDH). The electrocatalytic performance of these composite materials was investigated by cyclic voltammetry (CV) using a model compound 4nitrophenol (4-NP). Composite materials were characterized by various analytical techniques to gain insight into the catalysts active sites. The morphology and structure of the prepared samples were investigated by X-ray diffraction, attenuated total reflectance Fourier transform infrared, X-ray photoelectron spectroscopy, transmission scanning electron microscope, and field emission scanning electron microscope. Metal nanoparticles loading on TiO 2 was measured by inductively coupled plasma-optical emission spectrometry. CV measurements were performed in acetonitrile solution containing 0.1 m tetrabutylammonium hexafluorophosphate (TBAPF 6) and 1 mm 4-NP. Among all dioxides (AuÀ TiO 2 , PdÀ TiO 2) and hydroxides (NiFe-LDH and CuFe-LDH) studied, PdÀ TiO 2 shows the lowest onset potential (À 0.32 V vs. Ag/AgCl) for the electrocatalytic reduction of 4-NP. This is the first comparative study of such materials for 4-NP electrocatalysis in aprotic solvent, thus demonstrating the suitability of dioxide and hydroxide based materials as electrocatalysts.
This study reports the electropolymerization of novel keto functionalized octaethyl metal porphyr... more This study reports the electropolymerization of novel keto functionalized octaethyl metal porphyrins (Zn2+ and Ni2+) in the presence of 4,4′-bipyridine (4,4′-bpy) as a bridging nucleophile. The polymer films were characterized by electrochemical, spectroscopic (UV-Vis, XPS, FT-IR and Raman spectroscopy) and imaging (AFM and SEM) techniques. The absorption and electronic spectra confirm the presence of both porphyrin and 4,4′-bipyridine units in the film. The surface morphology reveals homogeneous film deposition with average roughness values of approx. 8 nm. The theoretical studies performed offered insights into the interplay of different metal centres (Zn2+ and Ni2+) and the keto functionality of the porphyrin unit in the formation of copolymer films. The electrochemical interaction of polymer films with CO2 suggests a reversible trap and release of CO2 with low energy barriers for both the polymers.
The interactions of a model H-bonded cationic polythiophene–anionic fullerene pair, were studied ... more The interactions of a model H-bonded cationic polythiophene–anionic fullerene pair, were studied with aid of a cosolvent for the first time, generating spectroscopic, kinetic & thermodynamic data of possible usefulness for analyzing similar systems.
The mixed-valence compounds In 5 S 5 Br, In 5 S 3 Se 2 Br, In 5 SSe 4 Br, and In 5 Se 5 Br reveal... more The mixed-valence compounds In 5 S 5 Br, In 5 S 3 Se 2 Br, In 5 SSe 4 Br, and In 5 Se 5 Br reveal interesting thermoelectric properties. As the selenium content in the structure of In 5 S 5 Br increases, the Seebeck potential increases. In 5 S 5 Br exhibits low Seebeck potentials within the studied range (ΔT = 0-80 K) and a maximum value of 0.34 mV for ΔT = 80 K. It behaves as a p-type semiconductor. The substitution of two sulphur species by selenium, as in In 5 S 3 Se 2 Br, shows n-type conductivity and approx.−16.00 mV for the same ΔT. Further substitutions of sulphur in the structure maintain the n-type conductivity and increase dramatically the Seebeck potential to-225.26 mV (ΔT = 80 K). Repeating cycles of Seebeck potential variation over time for In 5 Se 5 Br and In 5 SSe 4 Br, show differences in their potentials, shape of maxima as well as in their recovery time. Electrical conductivities from 0.3 pS for In 5 S 5 Br up to 13 pS for In 5 Se 5 Br, strongly influence their thermoelectricity.
This work presents solution-and solid-state evidence of the enhancement of J-like aggregation of ... more This work presents solution-and solid-state evidence of the enhancement of J-like aggregation of a cationic polythiophene (CPT) with isothiouronium functionalities (PT1), caused by a decrease in the polarity and hydrogen-bonding (H-bonding) capacity of the solvent, generated by using a 50:50 v/v 1,4-dioxane-water mixture (W-DI) instead of water. In solution, the presence of 1,4-dioxane (DI) in solution seems to generate selective solvation, tuning the energy transfer within PT1 from inter-chain into intra-chain, enhancing J-like aggregation. On the other hand, during the casting process, the presence of DI directs the interaction with solid-substrates, generating an increase in the solid-state fluorescence, modifying the morphology from one similar to ballistic-aggregation (BA) into one similar to attachment limited aggregation (ALA), also DI modifies the SFE by increasing slightly its polar contribution (Sp) and decreasing the dispersive one (Sd).These results can be explained to be caused by a "coating" effect in presence of DI (as proposed before experimentally and computationally). Our results show a clear correlation between the solution-and solid-state properties of PT1 in each solvent, further validating the use of the fluorescence excitation spectra to trace J-like aggregation of water-soluble conjugated polymeric fluorophores in solution. This information could be useful for predicting and designing specific mesoscopic architectures of CPTs (and conjugated polyelectrolytes in general), which are molecules lacking of clear structure-function guidelines for designing high-performance polythiophenebased interlayer materials, especially for CPTs (and conjugated polyelectrolytes (CPEs) in general), particularly those with H-bonding capabilities. To the best of our knowledge the use of solution-state fluorescence excitation spectra to identify J-like aggregation of water-soluble conjugated polymers (CPs) has been scarcely used/discussed in literature and no correlation with solid-state properties was reported previously.
Cationic imidazolium-functionalized polythiophenes with single-or doublemethylation of the imidaz... more Cationic imidazolium-functionalized polythiophenes with single-or doublemethylation of the imidazolium ring were used to study the impact of imidazoliummethylation on (i) the solution concentration-driven aggregation in the presence of paramagnetic probes with different ionic and hydrophobic constituents and (ii) their surface free energy (SFE) as spin-coated films deposited on plasma-activated glass. Electron paramagnetic resonance spectroscopy shows that the differences in film structuration between the polymers with different methylations originate from the early stages of aggregation. In the solid state, higher degree of imidazolium-methylation generates smaller values of total SFE, γS, (by around 2 mN/m), which could be relevant in optoelectronic applications. Methylation also causes a decrease in the polar contribution of γS (γSp), suggesting that methylation decreases the polar nature of the imidazolium ring, probably due to the blocking of its H-bonding capabilities. The values of γS obtained in the present work are similar to the values obtained for doped films of neutral conjugated polymers, such as polyaniline, poly(3-hexylthiophene), and polypyrrole. However, imidazolium-polythiophenes generate films with a larger predominance of the dispersive component of γS (γSd), probably due to the motion restriction in the ionic functionalities in a conjugated polyelectrolyte, in comparison to regular dopants. The presence of 1,4-dioxane increases γSp, especially, in the polymer with larger imidazolium-methylation (and therefore unable to interact through H-bonding), probably by a decrease of the imidazolium−glass interactions. Singly-methylated imidazolium polythiophenes have been applied as electrode selective ("buffer") interlayers in conventional and inverted organic solar cells, improving their performance. However, clear structure−function guidelines are still needed for designing high-performance polythiophene-based interlayer materials. Therefore, the information reported in this work could be useful for such applications.
A reductive coupling reaction employing sodium bis(2‐methoxyethoxy) aluminum hydride is used to p... more A reductive coupling reaction employing sodium bis(2‐methoxyethoxy) aluminum hydride is used to prepare main chain azo‐polymers comprising of polycyclic aromatic hydrocarbons (naphthalene, anthraquinone, or fluorenone) from their dinitro‐derivatives. The azo‐bridges act as effective means of conjugation and all polymers exhibit differences in the ultra‐violet–visible light absorption and photoluminescence emission spectra depending on the degree of polymerization. Furthermore, in the case of poly(azofluorenone)s and poly(azoanthraquinone)s, these spectra may be modified by changes in the protonation state of the polymers. The lowest unoccupied molecular orbital and highest occupied molecular orbital energy levels and the band gap of poly(azoanthraquinone) are estimated from cyclic voltammetry data and UV–visible absorption of films.
Aggregation of cationic isothiouronium polythiophenes with alkoxy-spacers of different lengths at... more Aggregation of cationic isothiouronium polythiophenes with alkoxy-spacers of different lengths at the 3position of the thiophene ring was studied in solvents of different polarities. Hydrogen-bonding capacity was assessed by steady-state absorption and fluorescence spectroscopy, whereas the aggregation in aqueous solutions was studied by electron paramagnetic resonance spectroscopy, using paramagnetic probes of different polarities. The two polymers displayed similar features in respect to conformation, effect of cosolvents on aggregation, unstructured absorption−fluorescence spectra, Stokes shifts when aggregated, solvatochromic effect, and self-quenching concentration. However, these polymers also showed different specific interactions with water, Stokes shifts in water, effect of the solvent on the extent of dominant state of the S1 level, and also different inner cavities and hydrophobic−hydrophilic surface area in aqueous solution aggregates. Water maximized the difference between the polymers concerning the effect of specific increases in concentration, whereas the presence of 1,4-dioxane generated almost identical effects on both polymers.
To improve the energy density of supercapacitors, novel electronically conducting polymers should... more To improve the energy density of supercapacitors, novel electronically conducting polymers should be introduced to the research field. Polyazulene is a well-suitable candidate as it exhibits good capacitive behavior both in organic solvents as well as in various ionic liquids, but especially its long term cycling stability should be improved. Previously, enhanced properties have been obtained by combining conducting polymers with carbon nanomaterials to fabricate composites. This work presents an ionic liquid assisted electrochemical polymerization and characterization of polyazulene-reduced graphene oxide composites. The ionic liquid of our choice is choline-based liquid salt. We prepared stable dispersions of graphene oxide in this ionic liquid and performed potentiodynamic electropolymerization of azulene in the mixture. Changing the concentration of graphene oxide between 0.1 and 2 mg mL-1 had no remarkable effect on the polymerization or electrochemical behavior of the composite materials. The composites exhibit higher capacitances compared to neat polymer films determined by cyclic voltammetry and electrochemical impedance spectroscopy. The obtained films also exhibit excellent cycling stabilities retaining over 90 % of their initial capacitance with tendency towards improved cycling stability when combined with reduced graphene oxide. The successful incorporation and reduction of graphene oxide was determined by several spectroscopic techniques.
Polyazulene (PAz) and polyazulene/graphene oxide composite (PAz/GO) films were electrochemically ... more Polyazulene (PAz) and polyazulene/graphene oxide composite (PAz/GO) films were electrochemically deposited from a choline based ionic liquid (IL), and characterized with attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) using Kretschmann geometry, and UVeVis spectroscopy during electropolymerization and electrochemical oxidation. The use of different ILs has been shown to affect the morphology and long term cycling stability of PAz while fabricating composites is known to sometimes dramatically affect the electronic properties of PAz. The aim of this work was to study how the use of a viscous IL and, furthermore, incorporating GO affected the structural, electronic and optical properties of PAz. Overall, the vibrational behavior of the composite was very similar to PAz. During positive doping, the doping-induced infrared active vibrations (IRAV) of the composite were found at higher wavenumbers indicating shorter conjugation of PAz in the composite. Comparison to previous works and to PAz electropolymerized from conventional organic electrolyte solution revealed that polymerization in the viscous IL leads to electroactive and stable PAz with shorter effective conjugation length. The correlation between IRAV bands of doped PAz and Raman bands of neutral materials are also discussed within the framework of effective conjugation coordinate model (ECC).
We present a study on two cationic isothiouronium polythiophenes with alkoxy chains of different ... more We present a study on two cationic isothiouronium polythiophenes with alkoxy chains of different length in the 3-position of the thiophene ring. The compounds were characterized using experimental and theoretical techniques.
In this study, we report reductive electrosynthesis of a polyviologen derivative bearing amide li... more In this study, we report reductive electrosynthesis of a polyviologen derivative bearing amide linkage in its side chain, derived from a cyanopyridinium based monomer with amide functionality. The as grown film was characterized by cyclic voltammetry which displays a well-defined and reversible two step redox response characteristic of viologen. FTIR analysis show evidence of amide linkage and successful reduction of cyanopyridinium moieties to polyviologen. In situ multi ESR/UV-Vis-NIR spectroelectrochemistry show a single line in ESR signal, thereby suggesting polarons as the only charge carrier involved during charging/discharging process. Furthermore, a characteristic UV-Vis absorption spectra confirms viologen formation. Finally, the polyviologen film is subjected to simultaneous voltammetric determination of heavy metal ions, Pb(II), Cu(II) and Hg(II). The amide linkage in the polyviologen derivative is supposedly complexing these divalent metal ions, enabling their sensitive and simultaneous determination with low detection limits.
In this work a new linker molecule with isothiocyanate and cyanopyridine groups (SCNCP) has been ... more In this work a new linker molecule with isothiocyanate and cyanopyridine groups (SCNCP) has been synthesized and the electrochemical synthesis of a polyviologen derivative using a linear cyanopyridine monomer (LCP) to this SCNCP was studied.
Synthesis of fullerene derivatives (1-4) (Fullerene derivatives (1-4) were synthesized similar to... more Synthesis of fullerene derivatives (1-4) (Fullerene derivatives (1-4) were synthesized similar to the procedure described elsewhere. 1 Structures 1,2,3 and 4 shown in Scheme 1)
Composite films consisting of poly(3,4-ethylenedioxythiophene) (PEDOT) and graphene oxide (GO) we... more Composite films consisting of poly(3,4-ethylenedioxythiophene) (PEDOT) and graphene oxide (GO) were electrochemically polymerized by electrooxidation of EDOT in ionic liquid (BMIMBF4) onto flexible electrode substrates. Two polymerization approaches were compared, and the cyclic voltammetry (CV) method was found to be superior to potentiostatic polymerization for the growth of PEDOT/GO films. After deposition, incorporated GO was reduced to rGO by a rapid electrochemical method of repetitive cathodic potential cycling, without using any reducing reagents. The films were characterized in 3-electrode configuration in BMIMBF4. Symmetric supercapacitors with aqueous electrolyte were assembled from the composite films and characterized through cyclic voltammetry and galvanostatic discharge tests. It was shown that PEDOT/rGO composites have better capacitive properties than pure PEDOT or the unreduced composite film. The cycling stability of the supercapacitors was also tested, and the re...
Dioxotungsten(vi) complexes react with thionation reagents to form disulphides and furthermore wi... more Dioxotungsten(vi) complexes react with thionation reagents to form disulphides and furthermore with activated alkyne to generate dithiolene complexes.
Physical chemistry chemical physics : PCCP, Jan 16, 2015
Electrochemical reduction of solution cast and self-assembled graphene oxide (GO) films on Au sur... more Electrochemical reduction of solution cast and self-assembled graphene oxide (GO) films on Au surfaces were studied using organic solvents. During the cyclic voltammetry measurements the structural changes in the films were recorded focusing on in situ infrared and Raman techniques. Both FT-Raman and dispersive Raman spectroscopy were utilized for the reduction studies. The spectroelectrochemical results indicate that the changes in the GO structure take place in a quite narrow potential range extending from -1 to -1.7 V. Higher negative potentials gives rise to reversible changes in the spectra and are not due to reduction processes of GO but more related to changes in the electrolyte media.
Dalton transactions (Cambridge, England : 2003), Jan 7, 2014
The reaction of VO(acac)2 (acac(-) = acetyl acetonate) with tripodal glycine bisphenol H3L(1) und... more The reaction of VO(acac)2 (acac(-) = acetyl acetonate) with tripodal glycine bisphenol H3L(1) under an ambient atmosphere yields a hexacoordinated vanadium(iv) complex [V(acac)(L(1))] (1). The corresponding reactions with tripodal 2-propanolamine bisphenol H3L(2) and potentially pentadentate ethoxyethanolamine bisphenol H3L(3) lead to the oxidation of the metal centre and formation of mononuclear oxovanadium(v) complexes [VO(L(2))] (2) and [VO(L(3))] (3), respectively. Alternatively, these latter two complexes can be prepared using VOSO4·5H2O or VO(OPr)3 as a precursor. The CV of 1 in an ACN solution shows a reversible one-electron process at E1/2 = +1.18 V, whereas 2 and 3 have an irreversible redox response at -1.6 V and -1.2 V, respectively. Complexes 2 and 3 show moderate activity in the epoxidation of cis-cyclooctene by tert-BuOOH at 50 °C.
It is well-known that reductive electropolymerization of cyanopyridinium moieties yields to violo... more It is well-known that reductive electropolymerization of cyanopyridinium moieties yields to viologenic materials. In this work, a monomer with two electropolymerizable cyanopyridinium groups separated by a six carbon spacer (CNP) has been synthesized. Its electropolymerization in aqueous electrolyte results in a linear polyviologen (PV) derivative, a purple-colored film deposited on the electrode surface. Cyclic voltammetry (CV) of PV films displays two well-resolved oneelectron redox processes at c.a. −0.5 and −1.0 V vs. Ag/AgCl. Fourier transform infrared (FTIR) spectral analysis shows successful polymerization of PV from the CNP monomer. In situ electron spin resonance (ESR)/UV-vis-NIR spectroelectrochemistry was used in order to simultaneously determine the polycation radical as well as the magnetic and optical response of the redox PV system. The single-line ESR spectrum observed at the first reduction peak of PV film was assigned to the formation of stable viologen cation radical species within the polymer matrix, exhibiting the characteristic UV-vis-NIR viologen cation radical absorption bands. The electrosynthesized linear PV system represents a promising stable redox active n-type material for organic rechargeable devices.
The extent of nanoplastic pollution has raised severe environmental and health concerns. While th... more The extent of nanoplastic pollution has raised severe environmental and health concerns. While the means for microplastic detection are abundant, improved tools for nanoplastic detection are called-for. State-of-the-art microscopic techniques can detect nanoplastics down to tens of nanometers, however, only from small sample sizes (typically ∼ 10 μl). In this work, we describe a method that enables sampling of 1 l of seawater by the means of correlative Raman-and SEM-techniques. This is achieved by adapting common microplastic sample purification protocols to suit the nanoplastic study. In addition, we decorate a membrane filter with SERS-property to amplify the Raman signals. Together, the purification method combined with the use of the SERS-activated-membrane-filter enables identification and imaging of individual nanoplastic particles from significantly larger sample sizes than before. In the nanoscale the average recovery rate is 5 %. These results aim to provide useful tools for researchers in the fight against plastic pollution.
In the present work, solution-phase synthesis was employed to prepare two sets of catalysts with ... more In the present work, solution-phase synthesis was employed to prepare two sets of catalysts with different transition metals as active sites. One set contained Au or Pd supported on TiO 2 (AuÀ TiO 2 , PdÀ TiO 2), whereas the other set contained layered double hydroxides (NiFe-LDH and CuFe-LDH). The electrocatalytic performance of these composite materials was investigated by cyclic voltammetry (CV) using a model compound 4nitrophenol (4-NP). Composite materials were characterized by various analytical techniques to gain insight into the catalysts active sites. The morphology and structure of the prepared samples were investigated by X-ray diffraction, attenuated total reflectance Fourier transform infrared, X-ray photoelectron spectroscopy, transmission scanning electron microscope, and field emission scanning electron microscope. Metal nanoparticles loading on TiO 2 was measured by inductively coupled plasma-optical emission spectrometry. CV measurements were performed in acetonitrile solution containing 0.1 m tetrabutylammonium hexafluorophosphate (TBAPF 6) and 1 mm 4-NP. Among all dioxides (AuÀ TiO 2 , PdÀ TiO 2) and hydroxides (NiFe-LDH and CuFe-LDH) studied, PdÀ TiO 2 shows the lowest onset potential (À 0.32 V vs. Ag/AgCl) for the electrocatalytic reduction of 4-NP. This is the first comparative study of such materials for 4-NP electrocatalysis in aprotic solvent, thus demonstrating the suitability of dioxide and hydroxide based materials as electrocatalysts.
This study reports the electropolymerization of novel keto functionalized octaethyl metal porphyr... more This study reports the electropolymerization of novel keto functionalized octaethyl metal porphyrins (Zn2+ and Ni2+) in the presence of 4,4′-bipyridine (4,4′-bpy) as a bridging nucleophile. The polymer films were characterized by electrochemical, spectroscopic (UV-Vis, XPS, FT-IR and Raman spectroscopy) and imaging (AFM and SEM) techniques. The absorption and electronic spectra confirm the presence of both porphyrin and 4,4′-bipyridine units in the film. The surface morphology reveals homogeneous film deposition with average roughness values of approx. 8 nm. The theoretical studies performed offered insights into the interplay of different metal centres (Zn2+ and Ni2+) and the keto functionality of the porphyrin unit in the formation of copolymer films. The electrochemical interaction of polymer films with CO2 suggests a reversible trap and release of CO2 with low energy barriers for both the polymers.
The interactions of a model H-bonded cationic polythiophene–anionic fullerene pair, were studied ... more The interactions of a model H-bonded cationic polythiophene–anionic fullerene pair, were studied with aid of a cosolvent for the first time, generating spectroscopic, kinetic & thermodynamic data of possible usefulness for analyzing similar systems.
The mixed-valence compounds In 5 S 5 Br, In 5 S 3 Se 2 Br, In 5 SSe 4 Br, and In 5 Se 5 Br reveal... more The mixed-valence compounds In 5 S 5 Br, In 5 S 3 Se 2 Br, In 5 SSe 4 Br, and In 5 Se 5 Br reveal interesting thermoelectric properties. As the selenium content in the structure of In 5 S 5 Br increases, the Seebeck potential increases. In 5 S 5 Br exhibits low Seebeck potentials within the studied range (ΔT = 0-80 K) and a maximum value of 0.34 mV for ΔT = 80 K. It behaves as a p-type semiconductor. The substitution of two sulphur species by selenium, as in In 5 S 3 Se 2 Br, shows n-type conductivity and approx.−16.00 mV for the same ΔT. Further substitutions of sulphur in the structure maintain the n-type conductivity and increase dramatically the Seebeck potential to-225.26 mV (ΔT = 80 K). Repeating cycles of Seebeck potential variation over time for In 5 Se 5 Br and In 5 SSe 4 Br, show differences in their potentials, shape of maxima as well as in their recovery time. Electrical conductivities from 0.3 pS for In 5 S 5 Br up to 13 pS for In 5 Se 5 Br, strongly influence their thermoelectricity.
This work presents solution-and solid-state evidence of the enhancement of J-like aggregation of ... more This work presents solution-and solid-state evidence of the enhancement of J-like aggregation of a cationic polythiophene (CPT) with isothiouronium functionalities (PT1), caused by a decrease in the polarity and hydrogen-bonding (H-bonding) capacity of the solvent, generated by using a 50:50 v/v 1,4-dioxane-water mixture (W-DI) instead of water. In solution, the presence of 1,4-dioxane (DI) in solution seems to generate selective solvation, tuning the energy transfer within PT1 from inter-chain into intra-chain, enhancing J-like aggregation. On the other hand, during the casting process, the presence of DI directs the interaction with solid-substrates, generating an increase in the solid-state fluorescence, modifying the morphology from one similar to ballistic-aggregation (BA) into one similar to attachment limited aggregation (ALA), also DI modifies the SFE by increasing slightly its polar contribution (Sp) and decreasing the dispersive one (Sd).These results can be explained to be caused by a "coating" effect in presence of DI (as proposed before experimentally and computationally). Our results show a clear correlation between the solution-and solid-state properties of PT1 in each solvent, further validating the use of the fluorescence excitation spectra to trace J-like aggregation of water-soluble conjugated polymeric fluorophores in solution. This information could be useful for predicting and designing specific mesoscopic architectures of CPTs (and conjugated polyelectrolytes in general), which are molecules lacking of clear structure-function guidelines for designing high-performance polythiophenebased interlayer materials, especially for CPTs (and conjugated polyelectrolytes (CPEs) in general), particularly those with H-bonding capabilities. To the best of our knowledge the use of solution-state fluorescence excitation spectra to identify J-like aggregation of water-soluble conjugated polymers (CPs) has been scarcely used/discussed in literature and no correlation with solid-state properties was reported previously.
Cationic imidazolium-functionalized polythiophenes with single-or doublemethylation of the imidaz... more Cationic imidazolium-functionalized polythiophenes with single-or doublemethylation of the imidazolium ring were used to study the impact of imidazoliummethylation on (i) the solution concentration-driven aggregation in the presence of paramagnetic probes with different ionic and hydrophobic constituents and (ii) their surface free energy (SFE) as spin-coated films deposited on plasma-activated glass. Electron paramagnetic resonance spectroscopy shows that the differences in film structuration between the polymers with different methylations originate from the early stages of aggregation. In the solid state, higher degree of imidazolium-methylation generates smaller values of total SFE, γS, (by around 2 mN/m), which could be relevant in optoelectronic applications. Methylation also causes a decrease in the polar contribution of γS (γSp), suggesting that methylation decreases the polar nature of the imidazolium ring, probably due to the blocking of its H-bonding capabilities. The values of γS obtained in the present work are similar to the values obtained for doped films of neutral conjugated polymers, such as polyaniline, poly(3-hexylthiophene), and polypyrrole. However, imidazolium-polythiophenes generate films with a larger predominance of the dispersive component of γS (γSd), probably due to the motion restriction in the ionic functionalities in a conjugated polyelectrolyte, in comparison to regular dopants. The presence of 1,4-dioxane increases γSp, especially, in the polymer with larger imidazolium-methylation (and therefore unable to interact through H-bonding), probably by a decrease of the imidazolium−glass interactions. Singly-methylated imidazolium polythiophenes have been applied as electrode selective ("buffer") interlayers in conventional and inverted organic solar cells, improving their performance. However, clear structure−function guidelines are still needed for designing high-performance polythiophene-based interlayer materials. Therefore, the information reported in this work could be useful for such applications.
A reductive coupling reaction employing sodium bis(2‐methoxyethoxy) aluminum hydride is used to p... more A reductive coupling reaction employing sodium bis(2‐methoxyethoxy) aluminum hydride is used to prepare main chain azo‐polymers comprising of polycyclic aromatic hydrocarbons (naphthalene, anthraquinone, or fluorenone) from their dinitro‐derivatives. The azo‐bridges act as effective means of conjugation and all polymers exhibit differences in the ultra‐violet–visible light absorption and photoluminescence emission spectra depending on the degree of polymerization. Furthermore, in the case of poly(azofluorenone)s and poly(azoanthraquinone)s, these spectra may be modified by changes in the protonation state of the polymers. The lowest unoccupied molecular orbital and highest occupied molecular orbital energy levels and the band gap of poly(azoanthraquinone) are estimated from cyclic voltammetry data and UV–visible absorption of films.
Aggregation of cationic isothiouronium polythiophenes with alkoxy-spacers of different lengths at... more Aggregation of cationic isothiouronium polythiophenes with alkoxy-spacers of different lengths at the 3position of the thiophene ring was studied in solvents of different polarities. Hydrogen-bonding capacity was assessed by steady-state absorption and fluorescence spectroscopy, whereas the aggregation in aqueous solutions was studied by electron paramagnetic resonance spectroscopy, using paramagnetic probes of different polarities. The two polymers displayed similar features in respect to conformation, effect of cosolvents on aggregation, unstructured absorption−fluorescence spectra, Stokes shifts when aggregated, solvatochromic effect, and self-quenching concentration. However, these polymers also showed different specific interactions with water, Stokes shifts in water, effect of the solvent on the extent of dominant state of the S1 level, and also different inner cavities and hydrophobic−hydrophilic surface area in aqueous solution aggregates. Water maximized the difference between the polymers concerning the effect of specific increases in concentration, whereas the presence of 1,4-dioxane generated almost identical effects on both polymers.
To improve the energy density of supercapacitors, novel electronically conducting polymers should... more To improve the energy density of supercapacitors, novel electronically conducting polymers should be introduced to the research field. Polyazulene is a well-suitable candidate as it exhibits good capacitive behavior both in organic solvents as well as in various ionic liquids, but especially its long term cycling stability should be improved. Previously, enhanced properties have been obtained by combining conducting polymers with carbon nanomaterials to fabricate composites. This work presents an ionic liquid assisted electrochemical polymerization and characterization of polyazulene-reduced graphene oxide composites. The ionic liquid of our choice is choline-based liquid salt. We prepared stable dispersions of graphene oxide in this ionic liquid and performed potentiodynamic electropolymerization of azulene in the mixture. Changing the concentration of graphene oxide between 0.1 and 2 mg mL-1 had no remarkable effect on the polymerization or electrochemical behavior of the composite materials. The composites exhibit higher capacitances compared to neat polymer films determined by cyclic voltammetry and electrochemical impedance spectroscopy. The obtained films also exhibit excellent cycling stabilities retaining over 90 % of their initial capacitance with tendency towards improved cycling stability when combined with reduced graphene oxide. The successful incorporation and reduction of graphene oxide was determined by several spectroscopic techniques.
Polyazulene (PAz) and polyazulene/graphene oxide composite (PAz/GO) films were electrochemically ... more Polyazulene (PAz) and polyazulene/graphene oxide composite (PAz/GO) films were electrochemically deposited from a choline based ionic liquid (IL), and characterized with attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) using Kretschmann geometry, and UVeVis spectroscopy during electropolymerization and electrochemical oxidation. The use of different ILs has been shown to affect the morphology and long term cycling stability of PAz while fabricating composites is known to sometimes dramatically affect the electronic properties of PAz. The aim of this work was to study how the use of a viscous IL and, furthermore, incorporating GO affected the structural, electronic and optical properties of PAz. Overall, the vibrational behavior of the composite was very similar to PAz. During positive doping, the doping-induced infrared active vibrations (IRAV) of the composite were found at higher wavenumbers indicating shorter conjugation of PAz in the composite. Comparison to previous works and to PAz electropolymerized from conventional organic electrolyte solution revealed that polymerization in the viscous IL leads to electroactive and stable PAz with shorter effective conjugation length. The correlation between IRAV bands of doped PAz and Raman bands of neutral materials are also discussed within the framework of effective conjugation coordinate model (ECC).
We present a study on two cationic isothiouronium polythiophenes with alkoxy chains of different ... more We present a study on two cationic isothiouronium polythiophenes with alkoxy chains of different length in the 3-position of the thiophene ring. The compounds were characterized using experimental and theoretical techniques.
In this study, we report reductive electrosynthesis of a polyviologen derivative bearing amide li... more In this study, we report reductive electrosynthesis of a polyviologen derivative bearing amide linkage in its side chain, derived from a cyanopyridinium based monomer with amide functionality. The as grown film was characterized by cyclic voltammetry which displays a well-defined and reversible two step redox response characteristic of viologen. FTIR analysis show evidence of amide linkage and successful reduction of cyanopyridinium moieties to polyviologen. In situ multi ESR/UV-Vis-NIR spectroelectrochemistry show a single line in ESR signal, thereby suggesting polarons as the only charge carrier involved during charging/discharging process. Furthermore, a characteristic UV-Vis absorption spectra confirms viologen formation. Finally, the polyviologen film is subjected to simultaneous voltammetric determination of heavy metal ions, Pb(II), Cu(II) and Hg(II). The amide linkage in the polyviologen derivative is supposedly complexing these divalent metal ions, enabling their sensitive and simultaneous determination with low detection limits.
In this work a new linker molecule with isothiocyanate and cyanopyridine groups (SCNCP) has been ... more In this work a new linker molecule with isothiocyanate and cyanopyridine groups (SCNCP) has been synthesized and the electrochemical synthesis of a polyviologen derivative using a linear cyanopyridine monomer (LCP) to this SCNCP was studied.
Synthesis of fullerene derivatives (1-4) (Fullerene derivatives (1-4) were synthesized similar to... more Synthesis of fullerene derivatives (1-4) (Fullerene derivatives (1-4) were synthesized similar to the procedure described elsewhere. 1 Structures 1,2,3 and 4 shown in Scheme 1)
Composite films consisting of poly(3,4-ethylenedioxythiophene) (PEDOT) and graphene oxide (GO) we... more Composite films consisting of poly(3,4-ethylenedioxythiophene) (PEDOT) and graphene oxide (GO) were electrochemically polymerized by electrooxidation of EDOT in ionic liquid (BMIMBF4) onto flexible electrode substrates. Two polymerization approaches were compared, and the cyclic voltammetry (CV) method was found to be superior to potentiostatic polymerization for the growth of PEDOT/GO films. After deposition, incorporated GO was reduced to rGO by a rapid electrochemical method of repetitive cathodic potential cycling, without using any reducing reagents. The films were characterized in 3-electrode configuration in BMIMBF4. Symmetric supercapacitors with aqueous electrolyte were assembled from the composite films and characterized through cyclic voltammetry and galvanostatic discharge tests. It was shown that PEDOT/rGO composites have better capacitive properties than pure PEDOT or the unreduced composite film. The cycling stability of the supercapacitors was also tested, and the re...
Dioxotungsten(vi) complexes react with thionation reagents to form disulphides and furthermore wi... more Dioxotungsten(vi) complexes react with thionation reagents to form disulphides and furthermore with activated alkyne to generate dithiolene complexes.
Physical chemistry chemical physics : PCCP, Jan 16, 2015
Electrochemical reduction of solution cast and self-assembled graphene oxide (GO) films on Au sur... more Electrochemical reduction of solution cast and self-assembled graphene oxide (GO) films on Au surfaces were studied using organic solvents. During the cyclic voltammetry measurements the structural changes in the films were recorded focusing on in situ infrared and Raman techniques. Both FT-Raman and dispersive Raman spectroscopy were utilized for the reduction studies. The spectroelectrochemical results indicate that the changes in the GO structure take place in a quite narrow potential range extending from -1 to -1.7 V. Higher negative potentials gives rise to reversible changes in the spectra and are not due to reduction processes of GO but more related to changes in the electrolyte media.
Dalton transactions (Cambridge, England : 2003), Jan 7, 2014
The reaction of VO(acac)2 (acac(-) = acetyl acetonate) with tripodal glycine bisphenol H3L(1) und... more The reaction of VO(acac)2 (acac(-) = acetyl acetonate) with tripodal glycine bisphenol H3L(1) under an ambient atmosphere yields a hexacoordinated vanadium(iv) complex [V(acac)(L(1))] (1). The corresponding reactions with tripodal 2-propanolamine bisphenol H3L(2) and potentially pentadentate ethoxyethanolamine bisphenol H3L(3) lead to the oxidation of the metal centre and formation of mononuclear oxovanadium(v) complexes [VO(L(2))] (2) and [VO(L(3))] (3), respectively. Alternatively, these latter two complexes can be prepared using VOSO4·5H2O or VO(OPr)3 as a precursor. The CV of 1 in an ACN solution shows a reversible one-electron process at E1/2 = +1.18 V, whereas 2 and 3 have an irreversible redox response at -1.6 V and -1.2 V, respectively. Complexes 2 and 3 show moderate activity in the epoxidation of cis-cyclooctene by tert-BuOOH at 50 °C.
It is well-known that reductive electropolymerization of cyanopyridinium moieties yields to violo... more It is well-known that reductive electropolymerization of cyanopyridinium moieties yields to viologenic materials. In this work, a monomer with two electropolymerizable cyanopyridinium groups separated by a six carbon spacer (CNP) has been synthesized. Its electropolymerization in aqueous electrolyte results in a linear polyviologen (PV) derivative, a purple-colored film deposited on the electrode surface. Cyclic voltammetry (CV) of PV films displays two well-resolved oneelectron redox processes at c.a. −0.5 and −1.0 V vs. Ag/AgCl. Fourier transform infrared (FTIR) spectral analysis shows successful polymerization of PV from the CNP monomer. In situ electron spin resonance (ESR)/UV-vis-NIR spectroelectrochemistry was used in order to simultaneously determine the polycation radical as well as the magnetic and optical response of the redox PV system. The single-line ESR spectrum observed at the first reduction peak of PV film was assigned to the formation of stable viologen cation radical species within the polymer matrix, exhibiting the characteristic UV-vis-NIR viologen cation radical absorption bands. The electrosynthesized linear PV system represents a promising stable redox active n-type material for organic rechargeable devices.
The extent of nanoplastic pollution has raised severe environmental and health concerns. While th... more The extent of nanoplastic pollution has raised severe environmental and health concerns. While the means for microplastic detection are abundant, improved tools for nanoplastic detection are called-for. Stateof-the-art microscopic techniques can detect nanoplastics down to tens of nanometers, however, only from very small sample sizes (typically ∼ 10 µl). In this work, we describe a method that enables sampling of 1 liter of seawater by the means of correlative Raman-and SEM-techniques. This is achieved by adapting common microplastic sample purification protocols (i.e. chemical digestion) to suit the nanoplastic study. In addition, we decorate a membrane filter with SERS-property to amplify the Raman signals. Together, the purification method combined with the use of the SERS-activated-membrane-filter enables identification and imaging of individual nanoplastic particles from significantly larger sample sizes than before. These results aim to provide useful tools for researchers in the fight against plastic pollution.
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Papers by Pia Damlin