Linear Optical Properties of Bromocresol Green Dye Doped Poly Methyl Methacrylate Thin Films

Abstract

In this study, we investigated the effect of Bromocresol green dye (BCG) of the PMMA thin films optical properties. Films of Poly Methyl Methacrylate doped by 10% BCG doping ratio to prepared two concentrations 2x10 -4 and 6x10 -4 M of PMMA-BCG dye were deposited on glass substrate using free casting method at room temperature. The optical properties of the films were determined using UVVisible absorbance and transmittance spectra at the 300 -900 nm wavelength range. The linear absorption coefficient and the extinction coefficient were calculated. The results showed that the optical properties were increasing by increasing the dye concentration, while the optical energy gap was decreasing with the doping. Also from the linear optical properties result the PMMA-BGC thin films are a promised materials for nonlinear optics applications. ISSN: 0067-2904Almusawe et al. Science, 2018, Vol. 59, No.1B, pp: 299-306 Iraqi Journal of 300 IntroductionOrganic dye doped polymers have a great deal of concern in recent years due to their great potential in many important applications such as optical storage, optical switching, optical limiting, signal processing, optical modulators, holography and nonlinear optical devices as well as various kinds of photonic devices [1][2][3]. The unique properties of polymers such as low density, ability to form intricate shapes, good mechanical strength versatile, electrical properties and low manufacturing cost made them promising materials that have been successfully used as host matrices for dyes. The wide range of polymer applications can be even more extensive by incorporation of filler into polymer matrix, because dispersed filler may increase the concentration of absorptive or fluorescence centers as well as the opto-chemical and opto-physical stability of host polymer [4][5][6][7].In this study, we present the effect of Bromocresol green dye (BCG) on the optical properties of poly methyl methacrylate (PMMA) polymeric matrix (guest -host system). Poly methyl methacrylate (PMMA) is a transparent plastic material with high solidity, durability and flexibility [6].The optical properties such as absorption coefficient, refractive index and optical energy band gap of dye doped polymers were investigated using spectroscopic absorbance combined with transmittance measurements. Materials and Samples PreparationThe Bromocresol green dye was obtained from (Sigma -Aldrich) with a molecular formula of C 21 H 14 Br 4 O 5 S and its chemical structure is depicted in Figure-1. The bromo group can improve the transparency and the thermal stability of compounds. Bromocresol Green (BCG) is a pH sensitive triphenylmethane dye useful in a variety of colorimetric detection technologies. BCG is used as a tracking dye for DNA agarose gel electrophoresis, in protein determinations and in charge-transfer complexation processes, BGC melting point is 225 o C and the peak absorption in 423 nm [8,9]. Poly methyl methacrylate (PMMA) polymer was purchased from (Sigma -Aldrich) and used as host material ...