PVK Polymer Research Articles

Hafnium dinitride/poly(9-vinylcarbazole) heterojunction: Structural, electronic, optical and vibrational properties. A DFT and DFPT study

Photosensitivity of semiconducting polymers can be enhanced by blending donor and acceptor polymers to optimize photoinduced charge separation. With a motivation to understand microscopic aspects of HfN2 and PVK relevant to optoelectronic properties of transition metal-dinitride/semiconductor interfaces, we examined their structural, electronic, optical and vibrational properties using first-principles calculations based on density functional theory (DFT) and density functional perturbation theory (DFPT) levels of theory. We computed a large direct energy gap of 3.751 eV for PVK and an indirect narrow band gap of 1.396 eV in HfN2. The gap value computed for the composite structure, HfN2/PVK, was 0.958 eV. The heterojunction displayed an indirect energy gap. The charge transfer between HfN2 and PVK results in a polarized field within the interface region, which will benefit the separation of photogenerated carriers. The calculated density of electronic states, Lowdin charge transfer and charge density difference certify that this proposed layered nanoheterojunction is an excellent light-harvesting semiconductor. These findings indicate that the conjugated polymer PVK is a promising candidate as a non-noble metal co-catalyst for HfN2 photocatalysis. It also provides useful information for understanding the observed enhanced photocatalytic mechanisms in experiments.

Photoexcited state properties of N-ethylcarbazole-functionalized carbon dots in solution and in PVK polymer matrix

The adducts of N-ethylcarbazole (NEC) to small carbon nanoparticles prepared by microwave-assisted thermal processing are carbon dots (CDots) with NEC for the dot surface functionalization, thus NEC-CDots, which were shown previously for their high stability in the dot structure and properties. In this study, the optical absorptions and photoexcited state properties of NEC-CDots in solution and in poly(N-vinylcarbazole) (PVK) film matrix were evaluated by using optical spectroscopy methods, including those for fluorescence decays and lifetimes. The results suggest that the properties are largely unchanged from solution phase to the polymer matrix environment, very positive to their expected optoelectronic applications.

PVK-grafted multiwalled carbon nanotube materials with enhanced mobility for electronic devices

Carbon nanotubes are unique due to their exceptional optical, electrical, thermal, and mechanical capabilities. This research included enhancing the electrical conductivity of a poly (9-vinyl carbazole) (PVK)-based organic semiconductor by combining it with a multi-walled carbon nanotube (MWCNT). The electrical conductivity was calculated utilizing composites of PVK-doped CNTs. In an organic medium, the composites were synthesized via in situ chemical polymerization. The immobility of PVK in the form of oxidation, high conductivity, and permitting electrochemical behavior of the materials for application in electronics was investigated. The study involved composites that alter electrical conductivity and different structure that shows stable dispersion in the PVK polymer of various molecular weights. It is an effective nanotube dispersion at low PVK concentration. X-ray powder diffraction (XRD), ultraviolet-visible spectroscopy, Thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR) were used to validate the generation of composites from synthesized CNTs and composites. The morphological structures were examined using field emission scanning electron microscopy (FESEM). The electrical conductivity was evaluated, and the movement of charge between polymers and CNTs was discussed.

Experimental and computational investigations of structural and photoluminescence properties of PVK/SWCNTs nanocomposites

<abstract> <p>A simple mechanical dispersion method was used to elaborate new nanocomposite from the combination of single walled carbon nanotubes (SWCNTs) and polyvinylcarbazole (PVK) polymer. The obtained samples were annealed at the moderate temperature of 333 K to achieve good dispersion and inhibit phase separation. Force constants calculations using Density Functional theory were correlated with FTIR measurements to support the interaction between both components. Raman scattering was used to check the dispersion state of SWCNTs on the PVK polymer. Optical absorption analysis and stationary photoluminescence and time resolved photoluminescence technics have been used to elucidate the change of optical properties after SWCNTs adding. The formation of bulk nano-hetero-junction resulting from the extended interfaces, leading to efficient dissociation of the charge pairs was shown by quenching effects in polymer photoluminescence when increasing SWCNTS contents. A noticeable decrease of the life time is observed by time resolved photoluminescence, which reflects the shortness of diffusion pathways and consequently an improvement of the electron transfer.</p> </abstract>

Photocatalytic enhancement mechanisms for novel g-C3N4/PVK nanoheterojunction

The interactions between monolayer graphitic carbon nitride (g-C3N4) and conjugated polymer poly(9-vinylcarbazole) (PVK) have been explored. We investigated the enhanced photocatalytic mechanisms for the novel g-C3N4/PVK nanoheterojunction covering the state-of-the-art of DFT by performing rigorous DFT calculations combined with van der Waals corrections (GGA + vdW). The calculated band alignment between g-C3N4 monolayer and PVK monomer clearly reveals that the conduction band minimum and the valence band maximum of g-C3N4 monolayer are higher than those of the conjugated polymer PVK. This predicted band alignment ensures the photogenerated electrons easily migrate from the g-C3N4 monolayer to the PVK monomer, and will lead to high hydrogen-evolution reaction activity. The charge transfer between g-C3N4 monolayer and PVK results in a polarized field within the interface region, which will benefit the separation of photogenerated carriers. The calculated density of electronic states, Lowdin charge transfer and charge density difference certify that this proposed layered nanoheterojunction is an excellent light-harvesting semiconductor. These findings indicate that the conjugated polymer PVK is a promising candidate as a non-noble metal co-catalyst for g-C3N4 photocatalysis. It also provides useful information for understanding the observed enhanced photocatalytic mechanisms in experiments.

Computational and Experimental Study of Nonlinear Optical Susceptibilities of Composite Materials Based on PVK Polymer Matrix and Benzonitrile Derivatives.

Theoretical and experimental investigations of the linear and nonlinear optical properties of composite materials based on the (Z)-4-(1-cyano-2-(5-methylfuran-2-yl)vinyl)benzonitrile molecule named as A, the (Z)-4-(2-(benzofuran-2-yl)-1-cyanovinyl)benzonitrile named as B and the (Z)-4-(2-(4-(9H-carbazol-9-yl)phenyl)-1-cyanovinyl)benzonitrile molecule named as C embedded into poly(1-vinylcarbazole) (PVK) polymer matrix were performed. The electronic and optical properties of A, B, and C molecules in a vacuum and PVK were calculated. The guest–host polymer structures for A, B, and C molecules in PVK were modeled using molecular dynamics simulations. The spatial distribution of chromophores in the polymer matrix was investigated using the intermolecular radial distribution (RDF) function. The reorientation of A, B, and C molecules under the influence of the external electric field was investigated by measuring the time-dependent arrangement of the angle between the dipole moment of the chromophore and the external electric field. The polarizabilities and hyperpolarizabilities of tested compounds have been calculated applying the DFT/B3LYP functional. The second- and third-order nonlinear optical properties of the molecule/PVK thin film guest–host systems were investigated by the Maker fringes technique in the picosecond regime at the fundamental wavelength of 1064 nm. The experimental results were confirmed and explained with theoretical simulations and were found to be in good agreement. The modeling of the composites in volumetric and thin-film form explains the poling phenomena caused by the external electric field occurring with the confinement effect.

Amorphous poly-N-vinylcarbazole polymer as a novel matrix for the determination of low molecular weight compounds by MALDI-TOF MS

Traditional matrices for matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS) are usually crystalline small molecules. The heterogeneous co-crystallization of the analyte and the matrix creates a sweet spot effect and reduces point-to-point reproducibility. In this study, an amorphous poly-N-vinylcarbazole polymer (PVK) was studied as a novel matrix for MALDI-TOF MS to detect various low molecular weight compounds (LMWCs) in the negative ion mode. The PVK achieved excellent matrix action and showed high sensitivity, good salt tolerance, and reproducibility. These results significantly broaden the design rules for new and efficient polymeric MALDI matrices.

Tailoring the Random Lasing Properties by Controlled Phase Separation Process in PMMA:PVK Dye-Doped Polymeric Blends.

This article describes the random lasing (RL) phenomenon obtained in a dye-doped, polymeric double-phase system composed of PMMA and PVK polymers. It shows how relative concentrations between mentioned macromolecules can influence lasing parameters of the resulting blends, including obtained emission spectra and threshold conditions. We describe the influence of lasers’ composition on their morphologies and link them with particular RL properties. Our studies reveal that the disorder caused by phase separation can support the RL phenomenon both in the waveguiding and quasi-waveguiding regimes. Changing the relative concentration of polymers enables one to switch between both regimes, which significantly influences threshold conditions, spectral shift, number of lasing modes, and ability to support extended and/or localized modes. Finally, we show that a simple phase separation technique can be used to fabricate efficient materials for RL. Moreover, it enables the tailoring of lasing properties of materials in a relatively wide range at the stage of the laser material fabrication process in a simple way. Therefore, this technique can be seen as a fast, cheap, and easy to perform way of random lasers fabrication.

Non-Debye segmental relaxation of poly-N-vinyl-carbazole in dilute solution

Ultrasonic absorption measurements were carried out for poly-N-vinyl-carbazole in dilute 1,2-dichloro-ethane solution at frequencies from 1 to 50 MHz over a temperature range of 10–45°C with increments of 5°C under constant pressure. For the specific solution a single relaxation process was observed experimentally in the frequency range studied. The relaxation frequency of poly-N-vinyl-carbazole in 1,2-dichloro-ethane solution is comparable to the relaxation frequency observed in vinyl-type polymers despite the structural differences and the corresponding relaxation process is thermal in nature and assigned to the local segmental motions of some monomeric units. From the temperature dependence of the acoustic parameters we were able to estimate the thermodynamic parameters related to the segmental motion of the PVK polymer chains in solution. Furthermore, we performed molecular mechanics calculations on polymeric chains with a relatively low number of monomers to elucidate the mechanism behind the relaxation process and to establish the suggested local segmental motions of the polymer in 1,2-dichloro-ethane solution. The experimental and theoretical results have been compared and discussed in the context of relevant theories of the field.

Optical and electrical properties of poly (N-vinylcarbazole)/graphene oxide nanocomposites for organic semiconductor devices

In this work, organic semiconductor devices (OSD) incorporating both poly(N-vinylcarbazole) (PVK) and graphene oxide (GO) were fabricated. The stable solutions of PVK/GO were prepared in chloroform by a simple sonication method, which enabled the successful dispersion of GO with the polymer matrix. These nanomaterials have been used in the fabrication of OSD with configuration ITO/PVK:GO/Ag. The electrical and optical properties were investigated using several techniques. The electrical measurements show that the electrical behavior of PVK polymer enhanced with increasing GO nanofillers concentration. The observed electrical improvement in the nanocomposites can be attributed to the charge transfer interaction between carbazole electron donor and the functional groups onto the surface of GO. UV–Vis absorption and photoluminescence studies elucidated the energy transfer and the interaction between polymer chains and the graphene nanosheets which exhibit a strong blue-green luminescence.

Optical properties of transition metal doped ZnS nanoparticles in PVK based nanocomposite films

In the present work, the optical properties of transition metal (Mn, Fe, Cu and Ag) doped ZnS nanoparticles in PVK polymer composites have been studied. The pure and transition metal (TM) doped ZnS nanoparticles were prepared by co-precipitation method and PVK/ZnS(TM) nanocomposites were synthesized by spin coating technique. The nanocomposites were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), optical absorption, energy and time-resolved photoluminescence spectroscopic techniques. The XRD patterns suggest the formation of the cubic phase of ZnS nanoparticles while FTIR spectroscopy reveals the incorporation of transition metal dopants in ZnS nanoparticles. The wide variation in surface morphology for differently doped nanoparticles in PVK based composites has been observed from FESEM technique. The optical gap has been found to increase with nanoparticle incorporation while the increased luminescence quenching is observed for PVK/ZnS:Mn nanocomposites. The time-resolved photoluminescence reveals a change in the lifetime of charge carriers for these composites. These results are important for designing new organic/inorganic nanocomposites for emerging technologies.

Zero-Dimensional Carbon Allotropes-Carbon Nanoparticles Versus Fullerenes in Functionalization by Electronic Polymers for Different Optical and Redox Properties.

Fullerene cages are known as being able to participate in radical initiated copolymerization reactions with vinyl monomers for polymer-functionalized fullerenes. In this work, poly(N-vinylcarbazole) (PVK) was selected as a representative of electronic polymers in the functionalization of fullerene C60 by the same copolymerization reaction to yield the PVK–C60. Similarly found was that small carbon nanoparticles could also participate in the same copolymerization reaction for the nanoparticles to be surface-functionalized and -passivated by the attached PVK polymers, which are structurally adhering to the general definition on carbon dots (CDots), thus PVK–CDots. In the comparison between PVK–CDots and PVK–C60, the former was found to be more absorptive and therefore more effective in photon harvesting across the visible spectral region and also brightly fluorescent, orders of magnitude more so than the latter. Similar to the PVK–C60 and C60 cages in general, the PVK–CDots exhibited significant photoinduced electron accepting characteristics and, at the same time, also extraordinary electron donating abilities that are not available to fullerenes. Because fullerene-based composites with electronic polymers including PVK have found significant applications in optoelectronic devices and systems, the prospect of CDots represented by the PVK–CDots for similar purposes is discussed.

EFFECT OF GRAPHENE OXIDE (GO) ON THE PROPERTIES OF ITS NANOCOMPOSITE WITH POLY (N-VINYL CARBAZOLE) (PVK)

Purpose of Study-- Herein we report the preparation of poly(N-vinyl carbazole) (PVK) and graphene oxide (GO) or nanocomposite was carried out by solution mixing process with the aid of sonication. Solutions of the GO with the PVK were prepared using mixed solvents aided by sonication which resulted in exfoliation and disaggregation of the GO into the PVK polymer matrix.
 Methodology-- In this work, the PVK/GO was prepared from exfoliated graphite nanoplatelets using solution mixing process with the aid of sonication in a suitable solvent like N-cyclohexyl-2- pyrrolidone (CHP). The as-prepared nanocomposites were characterized using XRD, DSC, FTIR-KBr, UV-Vis and EIS analysis.
 Main Findings-- The preparation of PVK/GO nanocomposites was carried out by solution mixing process with the aid of sonication. Using this method in dispersing the GO both exfoliation of the GOinto the PVK polymer matrix was attained. Nanocomposite solution comprising GO wrapped within PVK polymer matrix was characterized using TGA, XRD, and EIS analysis. FTIR-ATR spectroscopy and XRD invoked the wrapping of GO outer surfaces by PVK. The thermal properties of PVK/GO nanocomposites were analyzed using TGA. Correlation of impedance data and XRD provided a structural rationale for PVK/GO nanocomposites. 
 Application of Study-- The PVK/GO nanocomposites can be applied to various applications such as precursor polymer for hole-transporting materials and for electro nanopatterning.
 Limitations-- The study is limited to the characterization of the prepared GO and PVK/GO nanocomposites. Possible applications of the composites were not part of the study.
 The originality of Study-- The findings of the study show that it is possible to prepare graphene/PVK nanocomposites using solution mixing process.

Mechanisms of charge transport and resistive switching in composite films of semiconducting polymers with nanoparticles of graphene and graphene oxide

We have investigated the effect of the resistive switching in the composite films based on polyfunctional polymers – PVK, PFD and PVC mixed with particles of Gr and GO with the concentration of ∼ 1 - 3 wt.%. We have developed the solution processed hybrid memory structures based on PVK and GO particles composite films. The effect of the resistive switching in Al/PVK(PFD; PVC):Gr(GO)/ITO/PET structures manifests itself as a sharp change of the electrical resistance from a low-conducting state to a relatively high-conducting state when applying a bias to Al–ITO electrodes of ∼ 0.2–0.4 V. It has been established that a sharp conductivity jump characterized by S-shaped current-voltage curves and the presence of their hysteresis occurs upon applying a voltage pulse to the Au/PVK(PFD; PVC):Gr(GO)/ITO/PET structures, with the switching time in the range from 1 to 30 μs. The mechanism of resistive switching associated with the processes of capture and accumulation of charge carriers by Gr(GO) particles introduced into the matrixes of the PVK polymer due to the reduction/oxidation processes. The possible mechanisms of energy transfer between organic and inorganic components in PVK(PFD; PVC):GO(Gr) films causes increase mobility are discussed. Incorporating of Gr (GO) particles into the polymer matrix is a promising route to enhance the performance of hybrid memory structures, as well as it is an effective medium for memory cells.

Strategy toward Designing Semiconducting Polymer Nanoparticle–Multichomophoric Dye Assembly

The design of semiconducting polymer nanoparticle based hybrids is promising for light harvesting systems. Here, we design a donor–acceptor system through tuning the energy level alignment of interacting counterparts for an efficient light harvesting system where poly(N-vinyl carbazole) (PVK) nanoparticles (NPs) act as donor and the newly designed bicolor fluorophore ([R6G][HFL]) acts as acceptor. The photophysical interaction between polymer nanoparticle and bicolor fluorophore has been investigated by spectroscopic study and density functional theory (DFT) calculations. Dynamic quenching and the shortening of decay time of PVK polymer nanoparticles are revealed due to the energy and electron transfer process from PVK nanoparticle to the surface attached bicolor fluorophore. Furthermore, an ultrafast spectroscopic study has been undertaken to investigate the decay dynamics of [R6G][HFL] in the presence and absence of PVK. Finally, white light generation with CIE coordinates (0.31, 0.39) is achieved at a ...

Low cost UV-Ozone reactor mounted for treatment of electrode anodes used in P-OLEDs devices

Low cost UV-Ozone reactor using a high pressure mercury vapor lamp of 80 watts without outer bulb showed good results for treatment of ITO films used as anode electrode in the assembly of P-OLED (polymer-organic light emitting diode) devices. This study revealed 20 minutes as effective treatment time and it was verified also that the effect of UV-Ozone treatment loses its efficiency as the elapsed time increases. It was analyzed with measurements of contact angle using a droplet of PEDOT:PSS polymer. P-OLEDs devices were mounted with architecture: ITO/PEDOT:PSS/PVK/Alq3/Al. The PVK polymer was diluted in organic solvent of 1,2,4-trichlorobenzene with concentrations of: 5, 10, 20 and 30 mg/mL. Results revealed better performance of P-OLED devices for concentration of 5 mg/mL resulting in lower threshold voltage, elevation of electrical current and similar diode curve.

The redox nature of the resistive switching in nanocomposite thin films based on graphene (graphene oxide) nanoparticles and poly(9-vinylcarbazole)

The effects of resistive switching were investigated in composite films based on multifunctional nonconjugated polymers such as poly(9-vinylcarbazole)—PVK mixed with particles of graphene (Gr) and graphene oxide (GO). The concentration of Gr and GO particles in the PVK matrix was varied in the range of 1–3wt%, which is close to the percolation threshold in these systems. It was found that the effect of switching in structures of the form Al/PVK:Gr(GO)/ITO/PET manifests itself in a sharp change of the electrical resistance of the composite film from a low-conducting state to a relatively high-conducting state when applying a bias to Al–ITO electrodes of ∼0.2–0.4V, which is below the threshold switching voltages for similar composites. The cyclic voltammetric measurements of PVK:Gr(GO) films were carried out. It was found that the potential of redox transition of Gr/GO belongs to the interval of redox-switching voltage of PVK:Gr(GO)/ITO/PET composite films with effect of the resistive switching. The possible mechanism of the resistive switching, which is associated with the redox processes as well as with processes of capture and accumulation of charge carriers by Gr (GO) particles introduced into the matrices of the PVK polymer due to reduction/oxidation processes is discussed.

Electron transport and photoelectrical behavior of poly(N-vinylcarbazole)/Poly(3,4-ethylenedioxythiophene) composite honeycomb-patterned films

New type of poly(N-vinylcarbazole) (PVK) polymer nanocomposites were prepared by a solid-state polymerization of N-vinylcarbazole in the presence of different concentration (wt%) of poly(3,4-ethylenedioxythiophene) (PEDOT). The prepared PVK/PEDOT nanocomposites were characterized by using Fourier transform infrared (FTIR) and UV-vis spectra. The transmission electron microscopy (TEM) and X-diffraction studies were performed to understand the surface morphology and nature of the polymer composites. The characterization and morphological studies suggest that there is a conjugation between PVK and PEDOT. Furthermore, the honeycomb-patterned films were obtained by dissolving the PVK/PEDOT nanocomposites into the chloroform solvent under humid conditions. The temperature-dependent DC electrical conductivity and room temperature photo-electrical conductivity of the honeycomb-patterned films were measured. Results showed that the incorporation of PEDOT in PVK polymer has greatly improved the electrical conductivity and photo-electrical behavior of the PVK/PEDOT nanocomposites.

High photoresponse inverted ultraviolet photodectectors consisting of iridium phosphor doped into poly(N-vinylcarbazole) polymeric matrix

Highly sensitive inverted polymer ultraviolet (UV) photodectectors were fabricated by doping a phosphorescent material of bis[2-(4-tertbutylphenyl)benzothiazolato-N,C2′] iridium(acetylacetonate) [(t-bt)2Ir(acac)] into poly(N-vinylcarbazole) (PVK) polymeric matrix. Under the UV-260 nm illumination with an intensity of 0.7 mW/cm2, the device achieved a photocurrent of 11.37 mA/cm2 at −3 V, corresponding to a photoresponse of 15.97 A/W, which is 381% higher than the undoped device. Detailed analysis of photoluminescence, charge carrier transportation and film morphologies of PVK polymer active layers were carried out, and the enhanced UV absorption, formation of the triplet excitons and better charge carrier transport are ascribed to the improved photodectector performance.

Singlet Oxygen Generation from Polymer Nanoparticles–Photosensitizer Conjugates Using FRET Cascade

Herein, we demonstrate π-conjugated polymer nanoparticles–photosensitizer conjugates for singlet oxygen generation via FRET cascade, which would be useful for photodynamic therapy. Rose Bengal (RB) molecules are attached on the surface of coumarin 153 (C153)-dye-doped poly[N-vinyl carbazole] (PVK) polymer nanoparticles, where polymer nanoparticles act as efficient light-absorbing antenna materials. The energy funneling from C153 to RB at the excitation of the PVK host (340 nm) is confirmed by shortening of decay time of C153 and disappearing of its rise time. Again, it is evident that the efficient multistep energy transfer occurs from host PVK to RB dye molecules through C153 dye molecules to generate singlet oxygen (1O2) in solution. In addition, photo-oxidation of 2-chlorophenol provides quantitative evidence of singlet oxygen generation in different systems indirectly. The estimated singlet oxygen quantum yield for RB-attached C153-dye-doped PVK polymer nanoparticles is 21%. The present investigations...