Nanocomposites development for 3D Optical Data Storage Approach

Abstract

Research on nanocrystal (NC)-doped polymer nanocomposites is gaining attention nowadays due to their potential applications in 3D optical data storage, sensors, 3D printers, etc. It is a novel approach for 3D optical data storage by using nanocomposite since the exponential growth of data generation. This PhD thesis aims to synthesise and analyse the properties, photo-oxidation and photo-reduction of NC:Sm2+/3+-doped polymer nanocomposite for use as a 3D optical data storage medium. In making nanocomposites, the potential challenge is the creation of dispersive NC:Sm2+/3+ in the polymer matrix. Thus, to achieve the goals and overcome the potential challenges, in-situ, ex-situ, and pre-polymerisation methods were used to fabricate the nanocomposites. The effect of the various synthesis methods on the degree of agglomeration of the NC:Sm2+/3+ in a polymer nanocomposite has been investigated via transmission electron microscopy (TEM) and scanning confocal microscopy (SCM). The TEM results have shown that in-situ bulk polymerisation can reduce the agglomeration of NC:Sm2+/3+ doped in a polymer matrix. The SCM images of ex-situ and pre-polymerised nanocomposites show the variation in emission intensity, which corresponds to the degree of amount of NC:Sm2+/3+ . X-ray diffraction (XRD) was conducted to identify the crystallinity and amorphous nature of nanocomposites. The XRD spectra showed a broad peak at approximately 2θ ≈ 15⋅5° because of amorphous polymethyl methacrylate (PMMA) and other peaks corresponding to the tetragonal structure of the NC:Sm2+/3+ in PMMA nanocomposites. The molecular bending and stretching vibration of undoped PMMA, poly acrylic acid (PAA), PAA/NC:Sm3+ and NC:Sm2+/3+ -doped PMMA nanocomposites were investigated by Fourier transform infrared spectroscopy (FTIR). The carboxylate groups in FTIR (1550 cm−1) detected from a stable dispersion indicate the presence of NC:Sm2+/3+ -bound acrylate molecules. The photo-oxidation of pre-polymerised nanocomposites was performed by exposing 405 nm continuous wave laser, and the photo-oxidation measurement was conducted through SCM. Photo-oxidation was confirmed on the basis of the appearance and disappearance of photoluminescence spectra that represent the +2 and +3 valence states of pre-polymerised nanocomposites. The photoreduction of NC:Sm3+ doped in the in-situ polymerised nanocomposite was achieved by using Nd:YAG pulsed laser. SCM images and photoluminescence spectral changes were observed after and before Nd:YAG laser induction. Results showed the changes in emission intensity (counts) before and after Nd:YAG pulsed laser induction, which were confirmed by photo-reduction. These changes indicate the efficient photo-reduction and photo-oxidation mechanism of NC doped in polymer nanocomposites from NC:Sm3+ to NC:Sm2+ , NC:Sm2+ to NC:Sm2+ and NC:Sm2+ to NC:Sm3+ . Here, NC:Sm3+ and NC:Sm2+ indicate the off and on state of the synthesised nanocomposites. The overall photo-oxidation and photo-reduction of nanocomposites are also envisioned for future 3D optical data storage application.