Plasma Polymerized Aniline Research Articles

Deposition and morphology of direct current plasma-polymerized aniline

Plasma polymerization is a simple, solvent-free, dry process that involves vaporizing a monomer and ionizing them to the plasma state. This study reports the plasma polymerization of aniline in a direct current glow discharge. Aniline was introduced into a vacuum chamber and plasma-polymerized onto an indium-doped tin oxide/glass substrate at varying discharge potentials and deposition times. The resulting plasma-polymerized aniline films were in the leucoemeraldine form, as evidenced by UV-Vis and infrared spectral analyses. Monocarbon species that are products of the aromatic ring rupture were observed from the optical emission spectra of the discharge. The films reveal a smooth, pinhole-free surface across different process parameters. The film thickness from the 200 to 600 nm range presents a linear relationship with respect to the duration of deposition. The deposition rate also increased and has a good linear relationship when the discharge potential was varied.

Plasma-Polymerized Aniline–Diphenylamine Thin Film Semiconductors

Semiconducting polymer thin films were grown by a DC plasma-polymerized technique using a mixture of aniline–diphenylamine as a precursor. FT-IR spectra were taken in order to analyze the structural properties of the resulting polymers. From morphological and structural studies performed by transmission electron microscope (TEM) and X-ray diffraction, an organized structure in plasma polymer thin films was distinguished. I–V characteristics in an asymmetric electrode configuration were studied to determine the conduction mechanism. It was found that the conduction mechanism controlled by SCLC is dominant in plasma-polymerized aniline–diphenylamine (PPAni-PDPA) thin films.

Plasmon Thin Film Transistor Using Plasma Polymerized Aniline–Rubrene–Gold Nanocomposite in One-Step Process

Plasmon thin film transistor has great potential to be applied in present-day technologies including modern medical diagnostics. Here, we report the fabrication of plasmon thin film transistor, realized by depositing a nanocomposite material on a pre-fabricated transistor substrate. Plasma polymerized aniline rubrene hybrid semiconductor and gold nanoparticles are synthesized in a combined plasma process to form the nanocomposite material. Absorption spectra indicate that the polymer shows broad absorption in the UV–Visible region and inclusion of Gold nanoparticles (Au NPs) results in strongly enhanced absorption in the visible region of the electromagnetic spectrum due to plasmon resonance. The prepared thin film transistor device shows substantial increment of drain current when irradiated by a light source 520 nm, leading to significantly high responsivity and detectivity. The plasmon thin film transistor with enhanced photoresponse in the visible region can be a promising device for application in future technologies such as in the field of imaging, plasmonic integrated circuits, Human Machine Interfaces. It can also be used for varied medical applications e.g. biosensors and biomedical devices for personalized use.

Study and Characterization of Nanostructure Plasma Polymerized Aniline Thin Films

Study and Characterization of Nanostructure Plasma Polymerized Aniline Thin Films

Plasma Based Synthesis of Nanomaterials for Development of Plasmon Enhanced Infrared Responsive Optoelectronic Device

We report plasma based fabrication of an optoelectronic device with plasmon enhanced infrared sensitivity realized by integrating plasmonic gold nanoparticles (Au NPs) with an organic semiconductor matrix. A blend of plasma polymerized aniline (PPA)-Rubrene, prepared by a novel plasma based method acts as the semiconductor matrix for charge transport in the device geometry. Significantly improved photovoltaic property of the device with an open circuit voltage (VOC) of 1.08 V is obtained with the addition of Au NPs in the device. We experimentally demonstrate very efficient plasmon generated charge transfer between Au NPs and PPA-Rubrene system leading to significant enhancement of infrared responsivity of 2200% at the plasmon absorption band of Au. This study demonstrates how plasma based processes can be utilized to prepare plasmonic nano-materials and also to synthesize organic semiconductor materials suitable for development of plasmonic charge generating devices responsive to infrared region of the electromagnetic spectrum.

Synthesis and Characterization of Nanofibrous Polyaniline Thin Film Prepared by Novel Atmospheric Pressure Plasma Polymerization Technique.

This work presents a study on the preparation of plasma-polymerized aniline (pPANI) nanofibers and nanoparticles by an intense plasma cloud type atmospheric pressure plasma jets (iPC-APPJ) device with a single bundle of three glass tubes. The nano size polymer was obtained at a sinusoidal wave with a peak value of 8 kV and a frequency of 26 kHz under ambient air. Discharge currents, photo-sensor amplifier, and optical emission spectrometer (OES) techniques were used to analyze the plasma produced from the iPC-APPJ device. Field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), gas chromatography-mass spectrometry (GC-MS), and gel permeation chromatography (GPC) techniques were used to analyze the pPANI. FE-SEM and TEM results show that pPANI has nanofibers, nanoparticles morphology, and polycrystalline characteristics. The FT-IR and GC-MS analysis show the characteristic polyaniline peaks with evidence that some quinone and benzene rings are broken by the discharge energy. GPC results show that pPANI has high molecular weight (Mw), about 533 kDa with 1.9 polydispersity index (PDI). This study contributes to a better understanding on the novel growth process and synthesis of uniform polyaniline nanofibers and nanoparticles with high molecular weights using the simple atmospheric pressure plasma polymerization technique.

Immobilization of trypsin on plasma prepared Ag/PPAni nanocomposite film for efficient digestion of protein

This work demonstrates the efficacy of a support matrix prepared by plasma process for trypsin immobilization without any surface activator. Plasma polymerization cum sputtering process is used to prepare the nanocomposite support matrix. Plasma sputtered silver nanoparticles (AgNPs) are uniformly embedded into plasma polymerized aniline (PPAni) film. Various characterization tools are employed to study the surface morphology, microstructure and chemical composition of the support matrices. Trypsin is immobilized onto the support matrix via the formation of covalent bond between them. Plasma generated free radicals on composite films activate the support matrix and make it efficient for increasing the tertiary enzyme stability via multipoint covalent attachment. Trypsin immobilized onto Ag/PPAni matrix has more hydrolyzing capacity of bovine serum albumin (BSA) than free trypsin as well as trypsin immobilized onto PPAni films.

High photosensitivity with enhanced photoelectrical contribution in hybrid nanocomposite flexible UV photodetector

To devise a reliable strategy to develop an ultraviolet (UV) sensitive hybrid photodetector, plasma process is utilized as a single step method for production of large area nanocomposite films based on plasma polymerized aniline–titanium dioxide (PPani–TiO2). The synthesis of PPani–TiO2 nanocomposite films are made using reactive magnetron sputtering in combination with plasma polymerization. The deposited PPani–TiO2 nanocomposite films are characterized and discussed in terms of structural, optical and electrochemical properties. A hybrid flexible nanostructured UV photodetector is constructed from PPani–TiO2 nanocomposite and its optoelectronic properties are evaluated which exhibits a greatly enhanced photosensitivity resulting in high photoconductive gain (G=4.56×104) and high responsivity (R=9.36×103AW−1) under UV illumination of 254nm. The flexible devices are successfully operated under bending up to 170° (bending radius, R=8mm) and showed a good folding strength and stability. The proposed plasma based method provides a green technology where the self-assembly of molecules, that is, the spontaneous association of atomic or molecular building blocks under plasma environment, emerge as a successful strategy to form well-defined structural and morphological units of nanometer dimensions.

Comparative study of structural and optical properties of pulsed and RF plasma polymerized aniline films

Abstract Plasma polymerization of aniline is carried out by means of continuous RF and pulsed DC glow discharge plasma in a common reactor at different applied powers. The discharge control variables are optimized for good quality film growth and the role of fragmentation of the molecular structure on the structural, optical, morphological and optophysical properties of the deposited plasma polymerized aniline (PPAni) layers is investigated. Retention of the conjugated structure is found to be prominent at optimum applied power to the plasma in both the continuous RF and pulsed DC polymerization techniques. Improvement in conjugated structure and chain length have been observed in both the continuous RF and pulse DC PPAni thin films with the increase in applied power to the plasma up to a certain limit of applied power when working pressure is fixed at 0.15 mbar. A decrease in optical bandgap with the increase in applied power to the plasma is observed in both the pulsed DC and RF PPAni thin films, but it is more significant in case of RF PPAni films. The plasma polymerized aniline thin films are found to emit photoluminescence due to band to band transition and defects generated in the structure.

Highly effective antibiofilm coating of silver–polymer nanocomposite on polymeric medical devices deposited by one step plasma process

Foley's catheters were coated with Silver (Ag), plasma polymerized aniline (PPAni) and Ag-PPAni composite by plasma based deposition processes which were characterized by XRD, EDX, SEM, and FT-IR spectroscopy and bioassays were performed to validate their efficacies to kill planktonic cells as well as to remove biofilm. The analyses confirmed the formation of Ag nanoparticles (AgNPs), PPAni and Ag-PPAni composite and also corroborated their successful deposition over the catheters. Antibacterial assays showed that coated catheters were capable of killing planktonic cells of most commonly encountered uropathogens and equally capable of eradicating biofilm formation by the uropathogens as evident from the reduced cfu/ml. UV-vis spectroscopy results showed that the nanoparticle coated catheters were capable of gradual release of AgNPs, killing all planktonic cells in solution over the time. Foley's catheters coated with AgNPs and their composites by one step plasma process were non-toxic devices capable of killing planktonic cells and proficient in eradicating biofilm formation which could be used to cutback the likelihood of the catheter related complications.

Fabrication of a heterostructure device with Au/PPani–TiO2/ITO configuration and study of device parameters including current conduction mechanism

Polyaniline based composites incorporating titanium dioxide have been synthesized by an alternative pathway using reactive magnetron sputtering of titanium and plasma polymerization of aniline monomer. Structural, optical and morphological characterizations of plasma polymerized aniline (PPani) and titanium dioxide (TiO2) composites (PPani–TiO2) reveal the evidence for the incorporation of TiO2 in the PPani matrix. A hybrid heterostructure device having PPani–TiO2 composite with a top gold (Au) layer and bottom indium-tin oxide (ITO) layer is fabricated. The developed heterostructure device exhibits rectifying behaviour indicating the formation of a Schottky contact between Au and PPani–TiO2. The detailed electrical measurement of the device is performed under different temperatures. The ideality factor (n) and barrier height (φB) of the heterojunction diode at room temperature (300 K) are found to be 1.28 and 0.43 eV, respectively. Possible conduction mechanisms are examined using various plotting and curve fitting methods for space charge limited conduction mechanism (SCLC), Schottky emission mechanism and Poole–Frenkel (PF) emission mechanism. The heterostructure device shows best fit of SCLC process as compared to the other mechanisms including Schottky emission and PF emission.

Contradictory ageing behaviour and optical property of iodine doped and H2SO4 doped pulsed DC plasma polymerized aniline thin films

Polymerization of aniline in the presence of H2SO4 and iodine vapour is carried out using pulsed DC glow discharge plasma. The as prepared iodine doped plasma polymerized aniline films are found to be highly crystalline due to some crystal structure formed by the iodine incorporated into the film and the ex-situ H2SO4 doped films are found to be amorphous. However, the structure of the iodine doped films transforms to amorphous one while that of the ex-situ H2SO4 doped films transforms to crystalline one due to the effect of ageing. The optical band gap of the samples decreases depending upon the level of doping and annealing, having minimum optical band gap for iodine doped plasma polymerized aniline. Due to ageing, the optical property of the H2SO4 doped film is found to become superior while for iodine doped films a negligible change of the optical property has been noticed even after six months of ageing.

Pulsed DC discharge for synthesis of conjugated plasma polymerized aniline thin film

The polymerization of aniline in pulsed dc plasma is studied and the effects of variation of pressure, power, frequency and duty cycle on the chemical structure of the obtained film are examined. During the film deposition optical emission spectroscopy is used to investigate the molecular dissociation of aniline. The chemical structure of the films is characterized using Fourier transform infra-red spectroscopy. The surface morphology is studied using atomic force microscopy. Results show the retention of polyaniline like structure having conjugated nature at some particular discharge conditions. Moreover, it is observed that a strong dependence of film chemistry is obvious on the discharge power, reactor pressure, pulse repetition frequency and duty cycle. The advantages of the pulsed dc for deposition of conjugated plasma polymerizes thin film have been highlighted.

A hybrid heterojunction with reverse rectifying characteristics fabricated by magnetron sputtered TiOx and plasma polymerized aniline structure

A TiOx film produced by direct current reactive magnetron sputtering without substrate heating or post-deposition annealing and a plasma polymerized aniline (PPA) structure deposited in the same reactor by a radio-frequency glow discharge without the assistance of a carrier gas are used for the fabrication of a heterojunction. The gas phase discharge is investigated by a Langmuir probe and optical emission spectroscopy. The individual layers and the heterojunction are characterized for structural and optoelectronic properties. PPA has polymer-like structure and texture and is characterized by saturated–unsaturated, branched and crosslinked networks. X-ray photoelectron spectroscopy reveals a slightly reduced TiOx surface, which exhibits near band edge luminescence. The free radicals trapped in PPA readily react with oxygen when exposed to atmosphere. The heterojunction shows reverse rectifying characteristics under dark and ultraviolet (UV) irradiation. The energy levels of TiOx and PPA might exhibit reverse band bending and electrons and holes are accumulated on both sides of the heterojunction. The charge accumulation phenomena at the interface may play a key role in the device performance of a hybrid heterojunction. The current–voltage characteristic of the heterojunction is sensitive to UV light, so the structure may be used for photo-sensing applications.

Role of Plasma Parameters on the Conjugated Structure Retention in Polyaniline Thin Film

The role of plasma parameters on the film characteristics is investigated on polyaniline thin film deposited by radio frequency (RF) plasma polymerization. A series of un-doped and iodine doped polyaniline thin films are prepared by RF discharge operating at 13.56 MHz with different discharge powers and pressure variation from 0.1 to 0.05 mbar and variation in deposition time from 20 to 40 min. A good thin film is found with a power ranging from 9 W (−28 V self bias) to 20 W (−65 V self bias) at 0.1 mbar pressure which is confirmed by fourier transform infra-red spectroscopy showing the retention of aromatic rings. In addition, iodine doping is carried out with 9 W power and 0.1 mbar pressure. The characterization of process plasma is done using Langmuir probe diagnostics and optical emission spectroscopy. A correlation has been established between film characteristics and plasma properties investigated using optical emission spectroscopy and Langmuir probe analysis. Emphasis has been given on the study of the influence of plasma parameters, particularly of the electron energy distribution function on the quality of conjugated plasma polymerized aniline film.

TiO2/polyaniline nanocomposite films prepared by magnetron sputtering combined with plasma polymerization process

Radiofrequency plasma polymerization in combination with direct current reactive magnetron sputtering is utilized for the synthesis of TiO2/plasma polymerized aniline nanocomposite thin films. In the composite film, X-ray diffraction measurements reveal formation of nanocrystalline rutile TiO2 of crystallite size 3.6nm. Due to continuous bombardment of plasma species during simultaneous magnetron sputtering and plasma polymerization, the precursors of polymerization are broken and few functional groups are retained in the composite film. The plasma polymerized aniline has the direct optical band gap of 3.55eV and the nanocrystalline rutile TiO2 is wide gap semiconductor with indirect gap of 3.20eV which suggests the existence of an energy barrier at the interface in the composite form. The ac conductivity of composite film shows significant improvement as compared to plasma polymerized aniline film and sputtered rutile TiO2 film. The composite film may find potential application as antistatic coatings.

Film Chemistry Control and Growth Kinetics of Pulsed Plasma-Polymerized Aniline

The polymerization of aniline under continuous and pulsed RF-plasma conditions is studied using the same plasma reactor. The effects of input power, on and off-times, frequency and duty cycle variations on the growth kinetics and on the chemical structure of the obtained layers are examined. The chemical structure of the films is characterized using Fourier Transform Infra-Red, X-ray photoelectron and UltraViolet–Visible spectroscopies. The thickness of the films is determined by profilometry. The results show a strong dependence of film chemistry and deposition rates on the discharge power and on-time. The film deposited by pulsed plasma grows mainly during the plasma-on period. Furthermore, this work shows that the retention of aromatic rings can be evaluated by Fourier transform infrared analysis whereas oxidation degree of plasma polyaniline can be determined by X-ray photoelectron and UV–Vis spectroscopies.

Studies on the nonlinear optical properties of rf plasma polymerized aniline thin films by open aperture z-scan technique

Plasma polymerized polyaniline (PANI) thin films in their pristine and iodine doped forms were subjected to open aperture z-scan studies in order to investigate the nonlinear optical (NLO) properties of these materials. The investigations were carried out using a Q-switched resonant Nd:YAG laser at a wavelength of 532 nm for various fluences. The z-scan studies revealed that RF PANI thin films exhibit a saturable absorption (SA). Iodine doping modifies the NLO characteristics of these films substantially. These results qualify PANI thin films as potential materials for NLO materials. Investigations on the NLO properties of pristine (PANI) and iodine doped polyaniline (dPANI) thin films in its plasma polymerized form are reported for the first time.

Determination of charge carrier transport in radio frequency plasma polymerized aniline thin films

The carrier transport mechanism of polyaniline (PA) thin films prepared by radio frequency plasma polymerization is described in this paper. The mechanism of electrical conduction and carrier mobility of PA thin films for different temperatures were examined using the aluminium–PA–aluminium (Al–PA–Al) structure. It is found that the mechanism of carrier transport in these thin films is space charge limited conduction. J–V studies on an asymmetric electrode configuration using indium tin oxide (ITO) as the base electrode and Al as the upper electrode (ITO–PA–Al structure) show a diode-like behaviour with a considerable rectification ratio.

Fabrication of a quantum well heterostructure based on plasma polymerized aniline and its characterization using STM/STS

Two-dimensional electronic systems play a crucial role in modern electronics and offer a multitude of opportunities to study the fundamental phenomena at low dimensional physics. A quantum well heterostructure based on polyaniline (P) and iodine doped polyaniline (I) thin films were fabricated using radio frequency plasma polymerization on indium tin oxide coated glass plate. Scanning probe microscopy and scanning electron microscopy studies were employed to study the morphology and roughness of the polymer thin films. Local electronic density of states (LDOS) of the P–I–P heterostructures is probed using scanning tunnelling spectroscopy (STS). A step like LDOS is observed in the P–I–P heterostructure and is attributed to the quantum well confinement of electrons in the polymer heterostructure.