Protonic Doping Research Articles

Solution processed intrinsically conductive polymer films with high thermoelectric properties and good air stability

Dedoping of protonic acid doping can significantly increase the Seebeck coefficient.

Manipulating Polyaniline Fibrous Networks by Doping Tetra-β-carboxyphthalocyanine Cobalt(II) for Remarkably Enhanced Ammonia Sensing

Manipulating the morphology and protonic acid doping of polyaniline (PANI) is significant for optimizing its NH3-sensing. Herein, tetra-β-carboxyphthalocyanine cobalt(II) (TcPcCo) acted as the dopant and structure-directing agent simultaneously to fabricate the uniform fibrous network-like PANI (PANI-TcPcCo hybrids) by a one-step polymerization at low temperature. During the reaction process, the protonic acid groups in TcPcCo not only induced the aniline monomers polymerizing into one-dimensional nanofibers (consist of both solid and hollow cylinders) with abundant tiny protuberances on the surface but also successfully doped into PANI. The resulting PANI-TcPcCo hybrids displayed the enhancement in terms of the good conductivity, the large gas adsorption capacity, and the unobstructed channels for the electron and gas transport. The central metal atoms of TcPcCo present the strong and selective affinity to NH3. Meanwhile, the deep-seated conversion of PANI’s molecular structure after exposure in NH3 coul...

An Organic Semiconductor Organized into 3D DNA Arrays by “Bottom‐up” Rational Design

AbstractA 3D array of organic semiconductors was assembled using a DNA scaffold. An octameric aniline molecule (“octaniline”) was incorporated into a DNA building block based on a dimeric tensegrity triangle. The construct self‐assembled to form a 3D crystal. Reversible redox conversion between the pernigraniline and leucoemeraldine states of the octaniline is retained in the crystal. Protonic doping gave emeraldine salt at pH 5, corresponding to the conductive form of polyaniline. Redox cycling within the crystal was visualized by color changes and Raman microscopy. The ease of conversion between the octaniline states suggests that it is a viable electronic switch within a unique 3D structure.

Electrochemical behavior of nickel–polyaniline electrode in 1 M LiClO4–propylene carbonate electrolyte

Doping of emeraldine-base (EB) with lithium salts involves the addition of lithium cations to nitrogen in imine groups and intercalation of counter ions i.e., proceeds similarly to doping with protonic acids. The results of studies show that doping of polyaniline (PANI) with a lithium salt proceeds relatively difficultly as compared with protonic doping. For a polyaniline electrode, to attain faster the stationary mode by repeated cycling (“electrode training”) in an organic lithium electrolyte and to reach the higher capacitance, the method of preliminary lithiation of the NiO surface layer on the nickel substrate with Li+ cations through the EB film is proposed. The studies show that preliminary cycling of the Ni/PANI electrode (7 cycles at 10 mV s–1) in the region of negative potentials (from 0 to–2.99 V vs. Ag/AgCl) leads to substantial increase in the capacitance characteristics of the PANI film in the region of its intrinsic redox activity from–0.4 to +1.1 V at high charge–discharge currents (2–5 A/g).

Synthesis of polythiophene derivative bearing methoxy and pyridine groups at the β-position and formation of an intramolecular hydrogen bonding through the polymer reaction

Two 4-pyridylthiophene monomers M1 (2,5-dibromo derivative) and M2 (5-bromo-2-iodo derivative) having the methoxy group at the 3-position were synthesized. The Grignard metathesis reaction of M1 using i-PrMgCl·LiCl demonstrated the highest monomer conversion (87%) and regioselectivity (GM1/GM1′ = 76/24). The following Kumada coupling polymerization by Ni(dppe)Cl2 gave P1-OMe with the number-averaged molecular weight ranging from 3000 to 4600. Likewise, P2-OMe was obtained from M2. On the basis of 1H-NMR spectra, the regiorandom structure of P1-OMe and P2-OMe were suggested. The transformation from the methoxy group to the hydroxy one was then carried out using P1-OMe by treating with BBr3 to afford P1-OH. By measuring the UV-vis absorption spectra of polymers in CHCl3 and film along with the DFT calculation of model compounds, it was found that 1) the formation of an intramolecular hydrogen bonding between the pyridine and hydroxy groups brings about the significant red-shift of the absorption maxima from 476 nm (P1-OMe) to 662 nm (P1-OH) and 2) P1-OH has the less planar conformation resulting in the ineffective π-π stacking of polymer chains in the solid state. The proton doping experiments and CV measurements revealed the hydrogen bonding characteristic in P1-OH.

Synthesis and Optical Properties of π-Conjugated Polymers Containing Fused Imidazole Skeleton

Fused imidazole monomers (1b, 1i, and 2b) having the octyl group were synthesized by the microwave-assisted intramolecular direct arylation, which were subjected to the cross-coupling polymerization. For obtaining π-conjugated polymers with better solubility, fused imidazole monomers (si-1b and si-3b) having the bulky trisiloxane-terminated decyl chain were likewise synthesized and polymerized. On the basis of absorption and emission spectra of obtained π-conjugated polymers in conjunction with the X-ray crystal structure of model compounds and theoretical calculation, the fused structure and coupling partner were found to affect the optical properties in CHCl3 solution as a result of steric and electronic factors. The spectroscopic measurements in film revealed that the bulky trisiloxane group helps π-conjugated polymers to form the π-stacked structure upon thermal annealing. The proton doping experiment was also carried out to find out that the protonation of imidazole nitrogen results in the different peak shift depending on the comonomer structure.

Towards carboxylic acid-functionalized aniline monomers: Chemical synthesis, electropolymerization and characterization

Polyaniline is one of the most studied conducting polymers because of its high stability and interesting combination of redox and proton doping properties. Moreover, it is possible to use the amino group of polyaniline to graft a substituent to obtain polyaniline derivatives. In the present study, aniline monomers were functionalized by an alkyl chain terminated by a carboxyl group at the N-position of the monomers in an attempt to obtain a series of carboxylic acid-functionalized polyanilines. The electro-oxidation of the modified aniline monomers was studied in HCl and H3PO4 acidic solutions with potentiodynamic and potentiostatic methods. The influence of the nature of the solvent and the length of the grafted alkyl chain on the thickness, morphological features and wettability of the carboxyl-functionalized polyaniline films was studied. In particular, the nature of the acid used strongly impacted the film properties leading to thinner, smoother, more hydrophilic, more adhesive and more homogeneous films when the electropolymerization was performed in phosphoric acid solutions.

Preparation, characterization, and dynamic adsorption–desorption studies on polypyrrole encapsulated TiO2 nanoparticles

ABSTRACTBinary doped polypyrrole (PPy) encapsulated Titania (TiO2) nanoparticles were prepared by oxidative polymerization using FeCl3 as oxidant in presence of camphorsulfonic acid (CSA) as surfactant. Both FeCl3 (oxidant) and camphorsulfonic acid (surfactant) also act as dopant and hence thus prepared polypyrrole/Titania (TiO2@PPy) is termed as binary doped nanocomposite i.e. FeCl3 dopes polypyrrole by oxidation mechanism while camphorsulfonic acid dopes polypyrrole by protonic doping mechanism. The TiO2@PPy coreshell nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), thermogravimetry, differential scanning calorimetry (DSC), field emission‐scanning electron microscopy (FE‐SEM), and inductance‐capacitance‐resistance (LCR) measurements. The results indicated that the structural and electrical properties of the TiO2@PPy coreshell nanocomposites were significantly influenced by the extent of TiO2 nanoparticles loading of polypyrrole. The direct current (DC) electrical conductivity of the as‐prepared TiO2@PPy coreshell nanocomposites was higher than that of PPy. As‐prepared TiO2@PPy coreshell nanocomposites were also studied for their dielectric losses for alternating current (AC) which is useful characteristic for their application in the fabrication of charge storing devices. TiO2@PPy coreshell nanocomposites showed synergistic effect of combining components in improving their alcohol sensing properties. This improvement may be attributed to the adsorption on and desorption from alcohols TiO2@PPy interface of the nanocomposites and alcohol vapors causing decrease in depletion region. The TiO2@PPy coreshell nanocomposites were observed to show better reproducibility of electrical conductivity and fast self‐recovery during the alcohol vapor sensing process. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43411.

First-principles study of the effect of functional groups on polyaniline backbone.

We present a first-principles density functional theory study focused on how the chemical and electronic properties of polyaniline are adjusted by introducing suitable substituents on a polymer backbone. Analyses of the obtained energy barriers, reaction energies and minimum energy paths indicate that the chemical reactivity of the polyaniline derivatives is significantly enhanced by protonic acid doping of the substituted materials. Further study of the density of states at the Fermi level, band gap, HOMO and LUMO shows that both the unprotonated and protonated states of these polyanilines are altered to different degrees depending on the functional group. We also note that changes in both the chemical and electronic properties are very sensitive to the polarity and size of the functional group. It is worth noting that these changes do not substantially alter the inherent chemical and electronic properties of polyaniline. Our results demonstrate that introducing different functional groups on a polymer backbone is an effective approach to obtain tailored conductive polymers with desirable properties while retaining their intrinsic properties, such as conductivity.

Utilizing polyaniline to dominate the crystal phase of Ni(OH)2 and its effect on the electrochemical property of polyaniline/Ni(OH)2 composite

In this study, three-dimensional (3D) flower-like nickel hydroxide (Ni(OH)2) is decorated on one-dimensional fiber-like polyaniline (PANI) to obtain PANI/Ni(OH)2 composite. Two-step hydrothermal method is used where PANI serves as crystal growth modifier of Ni(OH)2. By reducing the initial concentration of PANI, the polymorph of Ni(OH)2 converts from β-to α-phase and the morphology of Ni(OH)2 correspondingly changes from nanoplate to 3D flower-like, which significantly impacts the electrochemical activity of PANI/Ni(OH)2 composite. Results show that fibrous PANI with high available surface area is expected to have many active sites for the deposition of nanoparticles. Besides, 3D flower-like Ni(OH)2, which can facilitate the transition for charge, contacts closely with PANI. Due to the good electrical conductivity and electrochemical activity of PANI with high proton doping level, the introduction of PANI can enhance the electrical conductivity and electrochemical performance of composite. Consequently, the PANI/Ni(OH)2 electrode exhibits good electrochemical property, including high capacity, good rate capability and long cycle life. In addition, this work will provide a new concept for using polymer in dominating the structure, morphology and electrochemical property of electrode material.

Activated complex model and surfactant reorganization during SWCNT separations on hydrogels

Hydrogels can efficiently separate metallic and semiconducting single-wall carbon nanotube (SWCNT) species at high rates by selective adsorption in a column configuration, but mechanistic details remain unclear. We examined the temperature dependence of SWCNT adsorption in an operating column using a model that considers the formation of an activated complex. The enthalpy and entropy changes associated with formation of the activated complex were determined. Due to a high sensitivity to protonation doping, large diameter pulsed laser vaporization tubes provided an opportunity to probe details of the adsorption mechanism. In contrast to the prevailing view in the literature, we conclude that the surfactant environment surrounding the nanotube is substantially reorganized upon adsorption and that adsorption also occurs within gel pores. Our findings provide new mechanistic insights that should assist in the development of improved separation methods.

Novel Reagentless Label‐Free Detection Principle for Affinity Interactions Resulted in Conductivity Increase of Conducting Polymer

AbstractWe report on the novel reagentless and label‐free detection principle allowing discrimination of specific binding over non‐specific interactions. Unlike majority of impedimetric and conductometric (bio)sensors, which specific and unspecific signals are directed in the same way (resistance increase), making doubtful their real applications, the response of the reported system results in resistance decrease, which is directed oppositely to the background. The mechanism of the resistance decrease is the polyaniline self‐doping, i.e. as an alternative to proton doping, an appearance of the negatively charged aromatic ring substituents in polymer chain. Negative charge at boronic ring substituent appears as a result of complex formation with di‐ and triols, i.e. specific binding. Thermodynamic data on interaction of the electropolymerized aminophenylboronic acids with saccharides and hydroxy acids indicate that the observed resistance decrease is due to polymer interaction with polyols. A possibility to detect microorganisms (Penicillum chrysogenum) on the basis of interdigitated electrodes modified with boronate substituted polyaniline is also shown. The first reported conductivity increase as a specific signal opens new horizons for reagentless affinity sensors.

Progress on Fabric Electrodes Used in Biological Signal Acquisition

Due to its convenience, wear ability, affinity, continuously monitoring biological signal, etc., fabric electrodes used in biological signal acquisition attracted more and more interest from researchers around the world. Fabric electrode is a kind of intelligent textiles, and its application is very prominent in biological signal acquisition, supercapacitors and ECG (electric signal) monitoring. There are many methods that can be used to prepare fabric electrodes. They are mainly metal plating, conductive polymer coating, magnetron sputtering, and gas phase deposition and impregnation. Besides, they select the appropriate substrate, conductive medium and composite way to get light fabric electrodes which have high conductivity and good conformability. Since the conductive properties of conductive polymers are weaker than those of metal, conductive polymer must undergo protonic acid doping. They can be polythiophene, polypyrrole, polyaniline, etc. However, at present, researchers commit more studies to metal or carbon-based electrodes. For example, a layer of silver film is platted on the fabric by magnetron sputtering to increase its conductivity. In this paper, the development of fabric electrodes was studied from several aspects, namely, the generation of biological signals, the overall design of the wearable monitoring systems, its classification, conductive principles, preparation of fabric electrode and application.

Electrical and Optical Properties of Synthesized Composite Material Polyaniline-Ti(IV) Arsenophosphate

Conducting polymers (CPs) have potential applications in many areas such as electrochemistry, electromagnetic systems, electronics, electromechanical systems, electroluminescence and sensors. Polyaniline and its derivatives have received much attention because of their various technological applications such as solar cells, electromagnetic shielding, electrodes for rechargeable batteries and sensors. Reversible proton doping, high electrical conductivity and ease of bulk synthesis make polyaniline a suitable candidate for its environmental applications. Recently heterogeneous conducting polymer composites, especially organic-inorganic composites, became the subject of extensive study. Organic/inorganic nanocomposites are extremely promising for applications in light-emitting diodes, photodiodes, photovoltaic cells, smart microelectronic device and gas sensors. The properties of nanocomposites films can be adjusted by varying the composition. Their fabrication shares the same advantages of organic device technology, such as low cost production and the possibility of device fabrication on large area and flexible substrates. The most widely studied conducting polymers are polypyrrole, polyaniline, polythiophene etc. Among all these, polyaniline is one of the most extensively studied conducting polymer. Polyanilines exist in Electrical and Optical Properties of Synthesized Composite Material Polyaniline-Ti(IV) Arsenophosphate

Reagentless polyol detection by conductivity increase in the course of self-doping of boronate-substituted polyaniline.

We report on the novel reagentless and label-free detection principle based on electroactive (conducting) polymers considering sensors for polyols, particularly, saccharides and hydroxy acids. Unlike the majority of impedimetric and conductometric (bio)sensors, which specific and unspecific signals are directed in the same way (resistance increase), making doubtful their real applications, the response of the reported system results in resistance decrease, which is directed oppositely to the background. The mechanism of the resistance decrease is the polyaniline self-doping, i.e., as an alternative to proton doping, an appearance of the negatively charged aromatic ring substituents in polymer chain. Negative charge "freezing" at the boron atom is indeed a result of complex formation with di- and polyols, specific binding. Changes in Raman spectra of boronate-substituted polyaniline after addition of glucose are similar to those caused by proton doping of the polymer. Thermodynamic data on interaction of the electropolymerized 3-aminophenylboronic acid with saccharides and hydroxy acids also confirm that the observed resistance decrease is due to polymer interaction with polyols. The first reported conductivity increase as a specific signal opens new horizons for reagentless affinity sensors, allowing the discrimination of specific affinity bindings from nonspecific interactions.

INVESTIGATION OF THE SENSOR PROPERTIES OF THE POLYANILINE FILMS OBTAINED BY THE METHOD OF VACUUM DEPOSITION

In order to apply the vacuum deposited polyaniline (PAN) films as sensitive to pH level elements of fibril — optic sensors (FOS) a technology of polymer deposition has been developed. It gives a possibility to obtaining the conducting emeraldine form of PAN by means of the known methods of proton doping. Effect of vacuum deposition temperature on the refractive index and spectral characteristics of the films has been established. Based on the PAN films optical response on the hydrogen index of medium the FOS of the pH level has been worked out.

Polyaniline nanoparticle based colorimetric sensor for monitoring bacterial growth

Detection of pathogens in food and water is important for quality monitoring and disease prevention. Herein, we report a simple and novel colorimetric sensor for detection of bacterial growth relying on estimation of its metabolic products. As a proof of the concept, utility of the sensor for detection of Escherichia coli (E. coli) is demonstrated. All major groups of microorganisms including E. coli commonly use the glycolytic pathway for glucose degradation in the presence or absence of oxygen, eventually releasing mixed acids like succinate, acetate, malate, etc. as by-products. Polyaniline, a conducting polymer, is highly sensitive to the presence of protons in its microenvironment and its protonic doping results in a visible color change. Hence, polyaniline nanoparticles were synthesized and the sensor films were fabricated by incorporating these nanoparticles in agarose gel. The films when used for real time monitoring of bacterial growth exhibited a visible color change from blue to green. Since no specific antibodies or receptors are used, the sensor is generic in nature and has potential for adaptation to real life applications in the form of patch sensor on cartons to gauge integrity and freshness of food items and beverages in real time.

Detection of saliva-range glucose concentrations using organic thin-film transistors

We describe the development of a glucose sensor through direct incorporation of an enzyme (glucose oxidase) into the gate of an organic thin film transistor (OTFT). We show that glucose diffusion is the key determinant of the device response time and present a mechanism of glucose sensing in these devices that involves protonic doping of the transistor channel via enzymatic oxidation of glucose. The integrated OTFT sensor is sensitive across 4 decades of glucose concentration; a range that encompasses both the blood and salivary glucose concentration levels. As such, this work acts as a proof-of-concept for low-cost printed biosensors for salivary glucose.

Theoretical Investigation of the Protonation Mechanism of Doped Polyaniline

The theoretical calculation of polyaniline tetramers were performed in implicit water solvent medium using the polarizable continuum model with density functional theory. In order to explore the protonation mechanism of polyaniline, the geometry characteristics, charge distribution, frontier molecular orbitals (MOs) and stability of emeraldine base and emeraldine salts in tetramer were investigated by B3LYP/6-31G+(d,p), and the significant increase mechanism of the electrical conductivity of polyaniline upon protonation was researched in detail. It was shown that optimized molecular geometry by protonation doping suggested a tendency towards bipolaron delocalization and a greater π-conjugation proved by bond length alternation and the torsional angles. Furthermore, the NBO of ES3 was distributed equably and should be conducive to the electrical conductivity, the frontier MOs were effectively established, and an electronic transition from HOMO to LUMO+1 is turned out to be a ππ* transition finally. In addition, compared with the computed energies of different emeraldine salt configurations, the bipolaronic lattice was taken for the most stable structure.

Synthesis and Characterization of Poly(2-alkylbenzimidazole-alt-9,9-dihexylfluorene)s: A Dually Dopable Polymer System

We present the synthesis and characterization of poly(2-alkyl-benzimidazole-alt-9,9-dihexylfluorene). An improved microwave-assisted synthesis of the monomers 4,7-dibromo-2-heptyl-1H-benzo[d]imidazole and 4,7-dibromo-2-(heptan-3-yl)-1H-benzo[d]imidazole was developed. The monomers were polymerized with 9,9-dihexylfluorene-2,7-diboronic acid bis(1,3-propanediol) ester using Suzuki cross-coupling to yield the corresponding poly(2-alkyl-benzimidazole-alt-9,9-dihexylfluorene)s. The polymers were characterized by both traditional optical and thermal properties in conjunction with experiments yielding strong evidence to suggest controllable chemical doping of benzimidazole moieties. Based on ultraviolet–visible spectroscopy (UV–vis) and cyclic voltammetry (CV) data, the band structure of these benzimidazole-containing polymers may be manipulated through treatment with acids or bases to achieve polycationic or polyanionic products. Protonic doping is shown to significantly impact the electronic properties of the...