Z.Y. Nuru

Porphyrin nanorods-polymer composites for solar radiation harvesting applications

The interest in exploring porphyrin-based nanostructures for artificial solar radiation harvesting stems from their structural similarity to chlorophylls. In nature, the precise organization and orientation of the chlorophylls result in efficient absorption of light energy. Inspired by these naturally occurring architectures relevant optical studies including the dynamics of intermolecular and intra-molecular processes of the porphyrin nanorods were investigated. The design of artificial light harvesting systems requires several key factors, such as absorption in the UV-visible and near-infrared wavelengths, energy transfer ability and the selection of light absorbing pigments. Another key factor is the organizational structure through which the components will interact. We attempted to accomplish this by incorporating porphyrin nanorods into polymer matrices and this will also aid in achieving an arrangement where they can be directly used as devices. The nanorods were embedded in a polymeric matrix, using latex technology and electrospinning which gave the possibility of investigating the orientation of nanorods in the polymer. Spectroscopic and microscopic studies were conducted to investigate the optical and morphological properties of the porphyrin nanorods-polymer composites for applications in artificial solar radiation harvesting systems.

Structural and optical investigation on the wings of Idea malabarica (Moore, 1877)

The nanostructures on the wings of Idea malabarica (Moore, 1877) were analysed using scanning electron microscopy, energy dispersive X-ray spectroscopy, atomic force microscopy, Fourier transform-infrared spectroscopy, and reflectance measurements. The chemical and morphological analyses revealed the chitin-based intricate nanostructures. The influence of the nanostructures on the wetting characteristics of the wing was investigated using optical imaging. Applying the Maxwell-Garnet approximation to the porosities within the nanostructures, the refractive indices, which relate the reflectance response, were estimated. It was concluded that the colour seen on the wings of the Idea malabarica originate from the nanostructural configurations of the chitin-based structures and the embedded pigment.

Raspberry-like and other hexagonal close-packed morphologies of P(St-MMA-AA) particles obtained from different emulsifiers for photonic applications.

Abstract A facile one-pot synthesis of Poly(Styrene-methyl-methacrylate-acrylic acid) P(St-MMA-AA) terpolymers by soap seeded emulsion polymerization was examined. Raspberry-like and hexagonal close-packed morphologies were conveniently obtained using Cetyltrimethylammonium bromide (CTAB), Sodium dodecyl sulphate (SDS) and Gum arabic (GA) emulsifiers. The resultant colloidal latex samples were used to fabricate coloured tunable photonic crystals via vertical deposition process. The results showed that the emulsifiers used effectively reduced the polydispersity index (PDI) and zeta potential of the terpolymer samples (Ter-PSDS, Ter-PGA and Ter-PCTAB 0.021, 0.097 and 0.076; –36.20, –35.60 and –32.80, respectively). Thus, the interfacial tension between particles that promote the formation of the stable nanosized photonic crystals is also reduced. The low PDI values are clear indication of monodispersity of the terpolymer samples. Varying the choice of emulsifiers also resulted in changes in the particles sizes as well as the resultant morphologies. The particles diameters of 117.15, 209.20 and 315.00 nm were obtained for Ter-PSDS, Ter-PGA and Ter-PCTAB, respectively. The results showed that Ter-PSDS was the most stable of all terpolymers examined. The fabricated photonic crystals were observed to reflect different wavelengths (Iridescent colours) as the observation angles changed. This could be due to the bandgap resulting from the different morphologies associated with the different emulsifiers. The variation in the colour reflectance with change in the observation angle confirms the photonic potential of the synthesized P(St-MMA-AA) crystals.