Thermo‐Optical Properties of Amino Acid Modified ZnO‐PVA Colloidal Suspension Under CW Laser Illumination

Abstract

Summary In this paper, we present synthesis of amino acids (l‐arginine and l‐alanine) assisted surface modification of ZnO nanoparticles (NPs) using chemical precipitation method. Study emphasizes the utility of l‐arginine over l‐alanine in the synthesis process and ZnO NPs with average particle size of 18 nm have been successfully obtained using l‐arginine. Structural properties were evaluated using powder X‐ray diffraction (XRD) pattern, energy dispersive X‐ray spectroscopy (EDAX) and transmission electron microscopy (TEM) that confirmed the purity, surface morphology and hexagonal wurtzite crystal structure of ZnO NPs. Linear optical studies using ultraviolet‐visible (UV‐vis) spectroscopy and Fourier transform infra‐red (FT‐IR) spectroscopy indicated the blue shift of excitons absorption wavelength and surface modification by amino acids. Blue shifting is more prominent for l‐arginine and optical band gap of 3.48 eV has been achieved in the present case. Third order nonlinearity (nonlinear refraction and absorption) of ZnO NPs embedded in polyvinyl alcohol (ZnO‐PVA colloidal suspension) was studied by Z‐scan technique at wavelength 632.8 nm in continuous wavelength regime which shows negative nonlinearity with self‐defocusing effect. Large value of n2 and β were obtained in case of ZnO NPs passivated by l‐arginine and effect was attributed to thermal lensing. Thermally stimulated third order nonlinear susceptibility (x(3)) for ZnO‐PVA colloids have also been calculated and presented.

l-Alanine capping of ZnO nanorods: increased carrier concentration in ZnO/CuI heterojunction diode

“…The peak at 440 cm −1 could be due to the stretching vibrations of ZnO. 23 The hydroxyl groups on the surface of the ZnO NRs resulted from its hygroscopic nature. 23 Collectively, these observations suggested that the FTIR-identified impurities primarily existed near the ZnO surface.…”

“… 23 The hydroxyl groups on the surface of the ZnO NRs resulted from its hygroscopic nature. 23 Collectively, these observations suggested that the FTIR-identified impurities primarily existed near the ZnO surface. In case of ZnO– l -Alanine, the FTIR spectrum showed a peak at 3398 cm −1 due to the O–H stretching.…”

“…Surface modication of ZnO NPs by amino acids such as L-Alanine and L-Arginine has been reported in the literature 22,23 for band gap engineering and thermo-optic applications. 23 L-Arginine capped Nd 3+ and Li + co-doped CdS QDs have been utilized in the literature 24 to demonstrate a large blue shi in band gap energy, as compared to that of bulk CdS, due to the quantum connement effect. Water soluble CuS QDs have been prepared efficiently using alanine as a bio-compatible organic capping molecule.…”