Polymer films of PVA:Gd3+ and PVA:Ho3+ have been synthesized by a solution casting method in order to study their structural, optical, electrical, and magnetic properties. The semicrystalline nature of the polymer films has been confirmed from XRD analysis. The FTIR analysis confirms the complex formation of the polymer with the metal ions. Dielectric studies of these films have also been carried out at various set temperatures in the frequency from 100 Hz to 1 MHz for carrying out impedance spectroscopy analysis to evaluate the electrical conductivity which arises due to a single conduction mechanism and thus to have a single semicircle pattern from these polymer films. The DC electrical conductivity increases with an increase in the temperature and it could be due to high mobility of free charges (polarons and free ions) at higher temperatures. The conductivity trend follows the Arrhenius equation for PVA:Gd3+ and for PVA:Ho3+ polymer films. PVA:Gd3+ polymer films show ferromagnetic nature, and PVA:Ho3+ polymer films have revealed paramagnetic nature based on the trends noticed in the magnetic characteristic profiles.
In recent years energy conversion devices based on organic semiconductors are an emerging research field with substantial future prospects and it has attracted great attention due to the advantages of light weight, flexibility, and low cost of production with the possibility of fabricating large area devices based on solution processing. Polymeric materials have been the subject of intense scientific and technological research because of their potential applications. In particular, conducting polymers have been extensively investigated in the area of electronics and optoelectronics due to their attractive properties [
PVA polymer is soluble in water and other solvents and is widely used in synthetic fiber, paper, contact lens, textile, coating, and binder industries, due to its excellent chemical and physical properties, nontoxicity, processability, good chemical resistance, high dielectric strength, good charge storage capacity, wide range of crystallinity, good film formation capacity, complete biodegradability, and high crystal modulus dopant-dependent electrical and optical properties [
The rare earth elements will exhibit ferromagnetism in addition to the unique luminescent nature. Luminescence from the RE3+ ions originates from the transitions between 4f orbitals, and these transitions are forbidden on symmetry grounds [
Spectral pure host matrix chemical of polyvinyl alcohol (PVA) (with MW = 1, 30,000) and dopant chemicals of GdCl3·6H2O and HoCl3·6H2O were used in the present work. Development of transparent PVA:Gd3+ and PVA:Ho3+ polymer films was done for obtaining Gd3+:PVA and Ho3+:PVA films upon gadolinium chloride/holmium chloride by using the solution casting method. Both the host polymer and dopant chemicals were dissolved separately in double distilled water (DDW) in the proportion of 1 : 9 and such mixed solutions were stirred thoroughly using a magnetic stirrer at temperature 60°C for 12 hrs and thus the homogenously mixed solution was poured on to Petri dish for obtaining transparent polymer films through slow evaporation method after 48 hrs from those dishes, and those neatly formed transparent polymer films were collected into appropriate containers for measurement purposes. All the obtained polymer films were in 150
The structures of the prepared polymers were characterized on XRD 3003 TT Seifert diffractometer with Cuk
The XRD patterns of the host matrix PVA and 10 wt% of Gd3+ and Ho3+:PVA polymer films are shown in Figures
(a–c) XRD profiles of PVA, PVA:Gd3+, and PVA:Ho3+ polymer films.
Figures
Assignments of FTIR bands of pure PVA and 10 wt% of Gd3+and Ho3+:PVA polymer films.
Pure PVA (cm−1) | Gd3+:PVA (cm−1) | Ho3+:PVA (cm−1) | Assignment |
---|---|---|---|
3101–3524 | 2813–3573 | 2873–3560 | O-H stretching |
1706 | 1709 | 1711 | C=C stretching |
1530 | 1541 | 1541 | C-H bending |
1480 | 1465 | 1468 | CH2 bending |
1230 | 1238 | 1243 | CH + OH bending |
1115 | 1118 | 1125 | CO stretching |
847 | 854 | 856 | C-C stretching |
668 | 675 | 675 | O-H wagging |
562 | 565 | 565 | CO bending |
489 | 489 | 489 | C-Cl bending |
(a–c) FT-IR profile of PVA, PVA:Gd3+, and PVA:Ho3+ polymer films.
PVA
PVA:Gd3+
PVA:Ho3+
Figure
(a, b) Absorption (a) and (b) emission spectra of PVA:Gd3+ polymer films.
PVA:Gd3+
PVA:Gd3+
(a, b) Absorption (a) and emission spectra of PVA:Ho3+ polymer films.
PVA:Ho3+
PVA:Ho3+
Figures
(a, b) Dielectric constant varies with frequency for PVA:Gd3+ and PVA:Ho3+ polymer films.
PVA:Gd3+
PVA:Ho3+
(a, b) Dielectric loss varies with frequency for PVA:Gd3+ and PVA:Ho3+ polymer films.
PVA:Gd3+
PVA:Ho3+
The ionic conductivity of the polymer electrolytes mainly depends on the concentration of conducting dopant and their mobility. The conductivity values can be calculated from the relation
Dc conductivity values for PVA:Gd3+ and PVA:Ho3+ polymer films.
Temperature |
PVA:Gd3+ |
PVA:Ho3+ |
---|---|---|
313 | 1.234 | 3.173 |
323 | 1.465 | 3.354 |
333 | 2.843 | 3.975 |
343 | 4.965 | 6.453 |
353 | 10.563 | 8.234 |
363 | 15.876 | 10.453 |
373 | 26.124 | 15.543 |
(a, b) Cole-Cole plots for PVA:Gd3+ and PVA:Ho3+ polymer films.
PVA:Gd3+
PVA:Ho3+
(a, b) Arrhenius plots for PVA:Gd3+ and PVA:Ho3+ polymer films.
PVA:Gd3+
PVA:Ho3+
Figure
(a, b) Magnetization dependence of the applied field for (a) PVA:Gd3+ and (b) PVA:Ho3+ polymer films.
PVA:Gd3+
PVA:Ho3+
In summary, it could be concluded that we have successfully developed highly transparent and stable Gd3+ and Ho3+:PVA polymer films were prepared by solution casting method. The XRD studies reveal the amorphous nature of the polymer that produces greater ionic diffusion. FTIR reveals the complexation between polymer and dopants. The conductivity is found to exhibit increasing trend with increasing temperature. The maximum conductivity of PVA:Gd3+ film is 2.621 × 10−5 S/cm at 373 K and for PVA:Ho3+ film is 15.564 × 10−5 S/cm at 353 K. From magnetic profile PVA:Gd3+ shows ferromagnetic nature and PVA:Ho3+ shows the paramagnetic nature. Hence, these polymer films can be used in electrochemical display systems.
The authors declare that there is no conflict of interests regarding the publication of this paper.
The present paper is dedicated to our Research Supervisor Professor (Late) Sri S. Buddhudu Garu for his support and encouragement for all this work.