Dielectric, Photoluminescence, Thermal and Mechanical Properties of CuO Nanoparticles Filled Polyvinyl Alcohol/Polyvinyl Pyrrolidone Blends for High Frequency Device Applications K Rajesh, Vincent Crasta, Raghavendra Bairy, P C Rajesh Kumar Ecs Journal of Solid State Science and Technology, 2024 This study involves synthesizing blends of polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) in 1:1 ratio using solution casting technique. The blends were then mixed with different concentrations of copper oxide (CuO) nanofiller, ranging from 0 to 16 wt% (0, 2, 4, 8, 12, and 16 wt%). Fourier transform infrared spectra and x-ray diffraction studies provide evidence of the structural modifications occurring within nanocomposites. Fluorescence spectroscopy revealed that the highest photoluminescence intensity occurred at a concentration of 8 wt% CuO in the blend which specifies that this particular concentration of nanofillers had a substantial impact on luminescence properties of the material. The morphology and texture of film’s surface was examined by means of atomic force microscopy. The dielectric plot demonstrated that dielectric constant of the film increased up to a CuO filler concentration of 12 wt%. This indicates that there is an optimal concentration of CuO nanofillers that enhances dielectric properties of the material. The mechanical studies carried out using universal Testing Machine reveals enhancement in the mechanical properties after the addition of nanofillers. The promising characteristics of these nanocomposites are suitable for high-frequency device applications and optical sensing applications.
Comprehensive Analysis on the Z-Scan Response of Thermally Evaporated CuTPP Thin Films in Terms of H Aggregation and Charge Transfer Dynamics L. M. Clavian, P. C. Rajesh Kumar, K. V. Anil Kumar, D. Narayana Rao, N. K. Shihab, Ganesh Sanjeev Journal of Physical Chemistry C, 2024 Nonlinear absorption (NLA) and nonlinear refraction (NLR) properties of the Cu(II) 5, 10, 15, 20-tetraphenyl-21H, 23H-porphine (CuTPP) thin film at 532 nm are investigated by using Z-scan technique with a laser of pulse width, τ = 6 ns and 30 ps. Powder XRD study of the CuTPP thin film reveals the nanocrystalline structure of the material embedded in an amorphous background. AFM and FESEM images depict a uniform, densely packed thin film with an RMS value of 14.69 nm. A characteristic broad blue-shifted Soret absorption band with davydov splitting in the UV–visible spectrum and stacking of particles illustrated in the AFM image highlights the formation of H-aggregates. Emission peaks at 651 and 711 nm are attributed to de-excitation from 2 T 1 and 4 T 1 tripmultiplet states to the ground state. In the 30 ps pulse regime, the NLA dynamics is influenced by saturation of tripmultiplet states and the band filling effect, resulting in the nonlinear saturation absorption phenomenon. However, NLA at 6 ns pulse duration is influenced by the excited-state absorption of triplet states, resulting in the reverse saturable absorption phenomenon. Closed-aperture Z-scan depicts self-focusing nonlinearity (Δ n > 0) in the picosecond regime. In the nanosecond regime, the CuTPP thin film depicts a positive NLR at a lower intensity, and at a higher intensity, it shows a self-defocusing (Δ n < 0) NLR nature. The presence of the Cu 2+ ion in the porphyrin structure results in inception of the charge transfer (CT) state and leads to distinctive ultrafast relaxation dynamics from the 2 S 2 state, thereby resulting in exclusive nonlinear optical (NLO) properties. Van der Waals interaction through π-stacking along with high electron exchange between Cu and porphyrin results in enhanced NLO coefficient values. This highlights the prominence of the CuTPP thin-film derivative for new-generation optical devices.
Intensity dependent third order optical nonlinearity of zinc-tetraphenyl porphyrin ultrathin film in nano-second regime P. C. Rajesh Kumar, L. M. Clavian, K. V. Anil Kumar, D. Narayana Rao, N. K. Shihab, Ganesh Sanjeev Aip Conference Proceedings, 2019 The third order nonlinear optical properties of 5,10,15,20 Tetraphenyl 21H,23H-porphine zinc (II) (ZnTPP) thin films have been investigated by using single beam Z-scan technique with 6 ns laser pulse operating at 532 nm. The ultrathin films of ZnTPP with the thickness of the order of 120 nm were fabricated by means thermal vacuum coating technique. The UV-Visible spectrum depicts signature absorption curve identifying the enhancement in the symmetry of the molecule from D2h symmetry to D4h, due to the presence of central Zn metal ion. The ZnTPP thin film is exhibiting reverse saturation absorption (RSA) and strong self-defocusing effect. The effective two photon nonlinear absorption coefficients (βeff) and nonlinear refractive index (n2) obtained at different input on-axis peak intensities (I0) are of the order of 10−6 to 10−5 m/W and 10−13 to 10−11 m2/W. The decrease in βeff with the increase in intensity indicates that the observed RSA is due to the excited state absorption (ESA) from T1 triplet state t...
Third order optical nonlinearity in TPP incorporated PMMA composite thin film L. M. Clavian, P. C. Rajesh Kumar, K. V. Anil Kumar, D. Narayana Rao, N. K. Shihab, Ganesh Sanjeev Aip Conference Proceedings, 2019 The third order nonlinear optical properties of TPP incorporated PMMA thin films were probed by means of z-scan technique. The thin films of the order 200-400 nm were fabricated using spin-coating technique. The UV-Visible absorption spectrum shows no variation in the absorption wavelength region with the increase of TPP concentration in PMMA matrix. The developed composite thin films exhibit strong nonlinear absorption (NLA) and nonlinear refraction (NLR) coefficients (β and n2) in the range 10−6 to 10−5 m/W and 10−13 to 10−12 m2/W respectively. The measured third order nonlinear susceptibility, χ(3) of composite thin films was found to increase with the TPP concentration. The obtained results indicate that the developed spin coated thin films are potential candidates for nonlinear optical device fabrication.
Study of Non Linear Optical Properties of a Chalcone Doped PVA Composite Material P.C. Rajesh Kumar, K. Janardhana, K.M. Balakrishna, T. Sheela Procedia Engineering, 2016 A chalcone, 1-phenyl-3-(4-dimethylamino phenyl) prop-2-en-1-one (PDAC) was synthesized and the structure was confirmed by FT-IR and single crystal XRD techniques. This chalcone was doped to Poly (Vinyl Alcohol) and films were prepared by solution casting method. The optical studies on pure PDAC and films were carried out with UV-Visible, Z-scan and DFWM techniques. The nonlinear parameters of the samples were obtained by z-scan. An enhancement in NLO response was observed in films. The results were compared with nonlinear parameters obtained with pico second DFWM experiment. The composite is thermally stable up to 298 0C.
Synthesis and characterization of organic NLO compound P. C. Rajesh Kumar, V. Ravindrachary, K Janardhana, H. R. Manjunath, Prakash Karegoudar, Alka B. Garg, R. Mittal, R. Mukhopadhyay Aip Conference Proceedings, 2011
