Doped Polyvinyl Alcohol Films Research Articles

The impact of green chemistry to synthesize PVA/cobalt metal complexes (CoMCs) composites with enhanced optical behavior

This study focuses on the preparation of amorphous polymer composites with an indirect band gap, which are essential for advancing optoelectronic devices. We synthesized cobalt metal complexes (CoMCs) by combining an aqueous solution of cobalt (II) acetate with green tea dye (GTD) at 70 °C, utilizing a cost-effective and environmentally friendly approach. Polyvinyl alcohol (PVA) was integrated with the synthesized CoMCs using a solution cast method at ambient temperature. The resulting CoMCs and PVA-based composite films were characterized through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and UV–Vis spectroscopy. FTIR analysis provided insights into the functional groups of GTD and their role in CoMC formation, highlighting the innovative green coordination chemistry method for low-cost metal complex production. The interactions between PVA and CoMCs were confirmed by FTIR, while the optical properties demonstrated that green-synthesized metal complexes combined with polar polymers offer a novel approach to enhance absorption behavior and reduce the optical band gap. XRD analysis indicated an increase in the amorphous phase, and Urbach energy values confirmed a reduction in crystallinity. The Wemple-DiDomenico (W-D) model was employed to determine the optical parameters, including the band gap energy (Eg), which decreased from 6.05 eV to 1.5 eV with the addition of 36 mL of CoMCs. Furthermore, the optical dielectric function analysis provided important parameters such as effective mass (N/m∗), relaxation time (τ), plasma frequency (ωp), optical mobility (μopt), and optical resistivity (ρopt). We also evaluated sheet resistance (Rs), thermal emissivity (ɛTh), and figure of merit (φ) for both pure and doped PVA films, with notable peaks in the figure of merit plots shifting to higher wavelengths as CoMCs concentration increased. This work demonstrates the effectiveness of multiple models and methodologies in accurately determining the optical band gap, emphasizing its significance for photonics and optoelectronic applications.

Activating Ultralong Room-Temperature Phosphorescence of Mono-Ring Arylboronic Acid by Hydrogen Bond for Tunable Afterglow Color and Stimulus Response.

Activating the ultralong room-temperature phosphorescence (RTP) of mono-ring arylboronic acid remains a great challenge, because the capacious free spaces shaped by a rubbery polymeric matrix allow the benzene ring skeleton to freely rotate. Herein, the ultralong RTP in mono-ring arylboronic acid derivatives embedded in a polyvinyl alcohol (PVA) matrix is activated, leveraging enhanced intermolecular and intramolecular hydrogen bonding and activating ultralong RTP. By incorporating diverse PBA derivatives into PVA via click chemistry, 3-aminophenylboronic acid (3A-PBA) doped PVA films showcase the most extended RTP lifetimes (2.24 s) and a high quantum yield (11.2%), alongside rapid and sensitive explosive vapor detection capabilities. These findings not only address the activation challenges of RTP in organic systems by highlighting the crucial role of hydrogen bonding and Förster resonance energy transfer in color tunability, but also mark a significant stride toward overcoming the limitations of current luminescent materials. This work heralds a new era in the development of organic phosphorescent materials, offering a promising strategy for broadening their practical applications and enhancing performance, particularly in environmental monitoring and security.

Diode Laser Irradiation Effects on Physical Properties of Titanium Dioxide Nano Fillers Doped Polyvinyl Alcohol Films

Study effect of diode laser (wavelength 650 nm) irradiation for different irradiant times (0.25, 0.5, 1.00, 3.00, and 4.00 hrs) on the physical properties of titanium dioxide (TiO2) possess particle size of 15.7 nm doped polyvinyl alcohol (PVA) films were experimentally investigated. The solution casting process has been utilized to create as-prepared TiO2/PVA nanocomposite films. Ultraviolet-Visible (UV-Vis) spectroscopy investigates the samples' optical characteristics by analyzing optical absorption spectra in a wavelength range of (200 - 900 nm) at room temperature (RT) of 300 K. The PVA matrix could be used to describe the influence. All optical constants produced artificially through laser radiation, like absorption, refraction index, extinction coefficient and complex dielectric constants, have decreased with increasing radiation times. On the contrary of optical energy gap they increased with increasing radiation times, according to the study's findings. TiO2 Nanoparticles (NPs) additions significantly impacted the PVA host's optical characteristics. When FTIR-spectrum regarding the TiO2/PVA nanocomposite films was examined in various ratios of irradiation times, the peak positions or bonds did not change; instead, they became smaller or larger as the irradiation time increased.

Photoirradiation‐Gated Excitation‐Dependent Room‐Temperature Phosphorescence in Through‐Space Charge Transfer Molecules

AbstractOrganic materials showing reversible changes in persistent room‐temperature phosphorescence (RTP) upon exposure to external stimuli have attracted considerable attention in recent years. One potentially groundbreaking development in this area is the introduction of the gating concept for organic persistent RTP materials. This refers to a material where a desired responsive ability only occurs when it is triggered by a specific stimulus, but it remains a formidable challenge. In this study, photoirradiation‐gated excitation‐dependent (Ex‐De) persistent RTP is achieved. A series of molecules, triphenylphosphine and carbazole derivatives connected through flexible carbon chains, are designed and prepared. Upon removal of ultraviolet (UV) irradiation, all these compounds doped polyvinyl alcohol (PVA) films exhibit obvious blue or green afterglow RTP. Among them, (2‐(9H‐[3,9′‐bicarbazol]−9‐yl)ethyl)triphenylphosphonium bromide (TPP‐2C‐Cz) doped PVA film initially exhibits blue persistent RTP after removal of 300 nm excitation but no RTP upon ceasing 365 nm irradiation. Interestingly, upon UV irradiation with a power density of 0.05 W cm−2 (UVA) for 50 min, the Ex‐De RTP behavior of TPP‐2C‐Cz doped PVA film is activated. Eventually, photoirradiation‐gated Ex‐De afterglow emission will be used for a wide range of applications, including the quantitative determination of UV irradiation dose and the permanent record of UV irradiation history, and read on‐demand.

Unexpected Emission Behaviors of Rhodamine Derivatives in PVA After UV‒Green Light Excitation

AbstractRhodamine derivatives are a class of common fluorescent dyes and are usually co‐doped with room temperature phosphorescence (RTP) polymers for tuning colors; here, their unusual luminescence properties in polyvinyl alcohol are first disclosed. The doped polyvinyl alcohol (PVA) films are photo‐excited for 0.5‒1 min and emit orange and red afterglows with lifetimes of over 1 s at room temperature. More unexpectedly, the respective prompt and delayed room temperature emission colors and spectra are identical, and the red‐shifted afterglows are observed in liquid nitrogen, indicating that room temperature afterglow is thermally activated delayed fluorescence (TADF). Their molecular structure features and quantum chemical calculations support this inference. Impressively, the room temperature afterglows are visible light excitable up to 540 nm since the maximal and strong absorption bands are in green regions. Hence, this work discloses unknown excitation and emission properties of rhodamine derivatives and provides the really visible light excited yet intrinsic red TADF afterglows for the first time.

Fabrication, Characterization of Basic Blue 7 Dye-Doped PVA Films and Their Third-Order Nonlinear Optical Properties.

In this work, we report on the fabrication, characterization and the third-order nonlinear optical (NLO) properties of basic blue 7 (BB 7) dye‒doped polyvinyl alcohol (PVA) polymer thin films. The absorption spectra of BB 7 dye‒PVA films were measured by UV‒visible absorption studies. The functional groups of BB 7‒PVA films have been identified by FT‒IR spectroscopic analysis. The surface morphology was examined by AFM and SEM analysis which shows that the BB 7 dye‒doped PVA films have a homogenous and smooth surface. The nonlinear absorption and refraction of BB 7‒PVA films were respectively explored by open aperture and closed aperture Z‒scan technique using a 5 mW semiconductor diode laser of 635nm wavelengths. The BB 7‒PVA films exhibit the reverse saturable absorption (RSA) and self-defocusing effect and the measured third‒order nonlinear susceptibility χ(3) values of these films were found to be of the order of 10- 5 esu. The present experimental results show that BB 7‒PVA films may have potential applications in future photonic and NLO devices.

Fabrication and characterization of Fe doped PVA films for optoelectronics

Polyvinyl alcohol (PVA) films were prepared by the solution casting method. Iron (Fe) doped PVA films were also prepared by the same method using iron chloride (FeCl3) as a precursor material of Fe with different concentrations (0, 1 and 3 wt%). The films were characterized to study the structural and microstructural and optical properties. Metal-insulator–metal sandwich structure was fabricated using Al-PVA-Al films to investigate on the current–voltage (I-V) characteristics of the PVA films. The variation of current density and electrical resistivity of the films were investigated with increase of doping concentration of Fe. The current density increased and electrical resistivity decreased with increase of doping concentration. The optical band gap energy was estimated from the Tauc plot and found to be decreased with increase of doping concentration.

Chitosan‐Modified Polyvinyl Alcohol Membrane High Performance in Biodiesel/Methanol Pervaporation Separation

AbstractThe chitosan doped polyvinyl alcohol film are prepared by blending heating method. The prepared membrane is characterized by Fourier Transform Infrared Spectrometer (FTIR), scanning electron microscope (SEM), atomic force microscope (AFM) and universal testing machine. The surface of the cast membranes is generally flat, and the pervaporation process would cause the membrane to have a wrinkled shape. These membranes can be used for pervaporation to separate methanol/biodiesel mixtures. This paper studies the effects of different chitosan additions, feed temperature and feed concentration on membrane performance. When the chitosan doping amount is 30 % by mass of polyvinyl alcohol at 40 °C, the maximum flux reaches 569.212 g m−2 h−1. At the same time, the separation factor increases as the methanol concentration in the liquid decreases. When the methanol mass fraction is 10 %, the separation factor can reach 116.717.

THE EFFECT OF NiCl2 ON THE OPTICAL PROPERTIES OF POLYVINYL ALCOHOL FILMS

By Wasan Al-Taa'y, Mohammed Abdul Nabi & 1 more. Optical properties of pure and doped polyvinyl alcohol films (PVA), prepared by casting technique with different nickel chloride concentrations have been studied.

Synthesis and optical properties of alizarin yellow GG-Cu(II)-PVA nanocomposite film as a selective filter for optical applications

In this paper, alizarin yellow GG (AYGG) – CuCl2 doped with polyvinyl alcohol (PVA) has been successfully synthesized. This composite has spherical shape particles with amorphous structure. Thermal analysis indicates that there is an endothermic change, which is related to the glass transition. In addition, the coordination between the transition metal Cu(II) ion and AYGG (ligand) occurs via oxygen atoms of phenolic hydroxyl groups and a nitrogen atom of azo moiety from the two ligand molecules. AYGG – Cu(II) doped PVA has high dispersion for high frequency lights and vice versa for low frequency lights. Therefore, it is concluded that AYGG – Cu(II) doped PVA film is suggested as a selective filter for ultraviolet and high frequency visible lights for many optical applications like protective shields for solar cells and packaging.

Characterizing optical and morphological properties of Eriochrome Black T doped polyvinyl alcohol film

Eriochrome Black T doped polyvinyl alcohol film was prepared on a glass substrate via the casting method. Optical microscope image of the film was taken by an optical microscope and analyzed by an Image J and origin 2008 software where it was proved that the film was free of defects and holes and uniformly distributed over entire area of the substrate. The optical constants of the film were calculated via the optical absorbance and transmittance in the wavelength range 350–900 nm via the use of a set of known mathematical formulas together with Wemple and DiDomenico model. The optical conductivity and the electrical conductivity of the prepared film in response to external electric filed are obtained using two more equations where it was found that the prepared film have high optical conductivity of the order of 1012 s−1 and an electrical conductivity of the order of 104 (S cm−1).

Conduction and relaxation mechanisms in gadolinium oxide nanoparticle doped polyvinyl alcohol films

Concentration dependent dielectric and electrical properties of PVA-Gd2O3 nanocomposite films over a wide range of frequencies (100Hz-1 MHz) and temperatures (303 K–423 K) is reported here. TEM of the Gd2O3 nanoparticles showed that they could be indexed to the cubic phase. The frequency variation of the dielectric permittivity and dielectric loss could be explained by the Maxwell Wagner Sillar’s model. The dielectric permittivity decreased in the composite films contrary to observations in other similar systems. The complex impedance showed Arrhenius behavior and the activation energies decreased monotonically with increasing concentration. However the resistivity of the nanocomposite films shows an increase with concentration, the 4 wt% film showing the highest resistivity which indicates other contributions to conductivity. The Nyquist plot could be fitted to a simple parallel RC circuit showing the presence of long range conduction in these samples. The relaxation times varied from 10−4 to 10−6s and indicated a non-Debye type of relaxation. The master curve showed good overlap indicating that the same relaxation processes were active at all temperatures. The ac conductivity obeys Jonscher’s law and the exponent shows a monotonic decrease with temperature. This indicates that Correlated Barrier Hopping is the probable mechanism for conduction in these samples.

Physical modifications of polyvinyl alcohol films containing CoCl2

Polyvinyl alcohol (PVA) films containing CoCl2 have been successfully prepared by the casting method. X-ray diffraction showed that the crystalline nature of the samples decreases with increasing the concentration of CoCl2 . Vis-UV spectra show that transmittance spectra of PVA doped with CoCl2 decrease with CoCl2 content and confirm the amorphous behavior detected by XRD patterns for high concentration of CoCl2 . UV absorption shows that the value of indirect band gap decreases with CoCl2 content. For low CoCl2 content, the value of direct band gap (Edirect) increases with decreasing the CoCl2 content. However, for high CoCl2 content, Edirect decreases with increasing the CoCl2 content. These results lead us to conclude that CoCl2 -doped PVA films are interesting for the packaging community and for photovoltaic applications.

Tailoring optical transmittance of polyvinyl alcohol by FeCl3-doping for photovoltaic application

In this paper, solid films of polyvinyl alcohol (PVA) complexed with different concentration of FeCl3 have been successfully synthesized. X-ray diffraction showed that a drop in the crystallinity of PVA with FeCl3. UV-Vis spectra show that FeCl3 remarkably enhances UV absorption of PVA, indicating a reduction of optical band gap (OBG). This led to the assumption that increased UV absorption can be assigned to an influence of FeCl3 on PVA synthesis. In addition, OBG study shows decrements in the values of direct band gap and indirect band gap with FeCl3 content. These results led to conclude that FeCl3 doped PVA films are good candidates in the packaging community and photovoltaic application.

Methylsilicon phthalocyanine hydroxide doped PVA films for optoelectronic applications: FTIR spectroscopy, electrical conductivity, linear and nonlinear optical studies

Polyvinyl alcohol (PVA) films doped with various concentration (1, 2, 4, 6 wt %) of Methylsilicon (IV) phthalocyanine hydroxide (MeSiPc) were achieved by casting procedure. FTIR results confirmed the increase of disordered ratio within the backbone structure of PVA as the dopant MeSiPc increases. The electrical conductivity versus dopant concentration in the temperature range of 307–392 K was discussed. The linear optical characterizations were studied and three types of interband were observed. Also, some linear optical constants were calculated. The obtained values of the nonlinear constants were increased with the increase of the dopant concentration. Overall, the dopant particles of MeSiPc have a clear impact on the enhancement of the carrier charges mobility, decreasing the width of the band gaps energies and in boosting the molecular polarization of the host material. For these reasons, MeSiPc-PVA matrices are recommended as an excellent candidate material to be exploited in the photo-electronic devices.

Preparation and investigation of suitability of gadolinium oxide nanoparticle doped polyvinyl alcohol films for optoelectronic applications

Gd2O3 nanoparticles synthesized by solution combustion method were used to prepare PVA-Gd2O3 nanocomposite films of varying concentrations (2 wt%–6 wt% of filler) by solution casting method. Being a rare earth oxide, gadolinium oxide was expected to exhibit good photoluminescence and the nanocomposite was expected to be flexible as well. The Gd2O3 nanoparticles prepared were found to be in cubic phase with an average size of 19 nm. Raman spectra showed the incorporation of Gd2O3 into the polymer matrix. Scanning electron microscope images revealed that the particles were porous in nature, agglomerated and distributed evenly on the surface of the film in the form of clusters. The UV–Visible absorption spectra gave direct optical energy band gap value in the range 5.78–4.86 eV. Both band gap as well as the Urbach energy are seen to decrease with increasing concentration of the dopant. Four prominent photoluminescence peaks were observed in all the three composite films in the UV region (318 nm), deep blue region (396 nm), blue region (477 nm) and green region (553 nm). The color purity of the films using CIE coordinates was found to be the highest, 82.81%, in the 2 wt% film making this film a promising material for blue OLED’s and blue flexible screens.

Study of nonlinear optical properties and optical limiting of acid green 5 in solution and solid film

Experimental investigation of the nonlinear optical properties of aqueous solution of acid green 5 and acid green 5 doped polyvinyl alcohol film, by Z-scan technique using continuous wave (CW) laser is presented. Both samples exhibit large negative nonlinear refractive index. The optical limiting properties were also studied. The efficiency of the optical limiting was found to depend on the diameter of the detector aperture and the position of the sample. The dye exhibits good optical limiting properties in solution and solid PVA host. The mechanism of optical limiting is found to be predominantly of a thermal origin.

ENHANCEMENT OF ELECTRICAL CONDUCTIVITY IN POLYVINYL ALCOHOL FILMS BY DOPING WITH Nd3+IONS

The electrical properties of polyvinyl alcohol (PVA) films have been improved pronouncedly by doping with Neodymium (III) nitrate hexahydrate. Pure PVA and PVA: Nd3+ films have been prepared by solution casting method. Both type of films were characterized by X-ray diffraction technique for structural studies. XRD pattern shows the appreciable shift of 2Ө towards higher value with increase in Nd3+ concentration. This signifies the presence Nd3+ dopant in polymer matrix. Further direct current electrical conductivity (σ) of Nd3+ doped PVA films in the temperature range 500C-1600C has been studied using four probe techniques. For a given concentration σ increases with increase in temperature and with dopant concentration. At 1200C, conductivity of PVA: Nd3+ (10 mol %) film is 7.116 μΩ-1cm-1, PVA: Nd3+ (15 mol %) film is 11.176 μΩ-1cm-1, PVA: Nd3+ (20 mol %) film is 17.418 μΩ-1cm-1 and PVA: Nd3+ (25 mol %) film is 23.740 μΩ-1cm-1. This result indicated the enhancement of the electrical conductivity of PVA films with Nd3+ concentration.

Optical and Magnetic Properties of Polyvinyl Alcohol Films Filled with CoCl2, NiCl2, and FeCl3

Polymeric films based on polyvinyl alcohol (PVA) doped with CoCl2, NiCl2, and FeCl3 at different weight percent were prepared using the cast technique. The structural properties of these films were investigated by X-ray diffraction, UV–visible (UV-Vis) double beam scanning spectrophotometer, and vibrating sample magnetometer techniques. PVA shows crystalline nature while highly doped PVA films show amorphous nature, indicating the random distribution of the fillers within the polymeric matrix. It is found that the average of crystalline size and interplanar spacing of PVA vary with different fillers. The UV–visible absorption of the samples shows noticeable change in the band position shifted to higher wave length with the filling level. The PVA/metal chloride composites exhibit a ferromagnetic behavior with low remanent and saturation magnetization at room temperature.

MoS2 nano-flake doped polyvinyl alcohol enabling polarized soliton mode-locking of a fiber laser

Hybrid mode-locking of non-polarized Er-doped fiber laser with nonlinear saturable absorption of MoS2 nano-flake doped ultrathin polyvinyl alcohol film is demonstrated to obtain 330-fs pulsewidth.