Sains Malaysiana 42(8)(2013): 1151–1157

Optical Properties of Poly( 9,9’-di-n-octylfluorenyl-2.7-diyl)/Amorphous SiO₂

Nanocomposite Thin Films

(Sifat Optik Filem Nipis Nanokomposit Poli( 9,9’-di-n-ostilfluorenyl-2.7-diil)/Amorfus SiO₂)

Mohammad Hafizuddin Haji Jumali¹*, Bandar Ali Al-Asbahi^1,2& Chi Chin Yap¹, Muhamad Mat Salleh³, Mohamad Saleh AlSalhi⁴

¹School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia

43600 UKM Bangi, Selangor, D.E. Malaysia

²Department of Physics, Faculty of Science, Sana’a University, Yemen

³Institute of Microengineering and Nanoelectronics (IMEN), Universiti Kebangsaan Malaysia

43600 UKM Bangi, Selangor, D.E. Malaysia

⁴Department of Physics and Astronomy, Laser Group, College of Science

King Saud University, Saudi Arabia

Diserahkan: 11 Jun 2012 / Diterima: 2 Februari 2013

ABSTRACT

Identified as potential materials for optoelectronic applications, the polymer/inorganic nanocomposites are actively studied. In this work, the effect of amorphous silica nanoparticles (NPs) content on the optical properties of Poly (9,9’-di-n-octylfluorenyl- 2.7-diyl) (PFO) thin films has been investigated. Different ratios of PFO/SiO₂ NPs composites have been prepared using solution blending method. Then, the blends were spin-coated onto glass substrates at 2000 rpm for 30 s and subsequently dried at room temperature. XRD and TEM were used to determine the structural properties, while UV-Vis and PL spectrophotometers were employed to investigate the optical properties of the films. XRD confirms that there was no variation on structure of both PFO and SiO₂ NPs resulted from the blending process. TEM micrographs display that majority of amorphous SiO₂ NPs were well coated with PFO. The absorption spectra of the composite thin films were red-shifted, indicating the increment in conjugation length of the PFO/SiO₂ composite. In addition, the calculated values of the optical energy gap, the width of the energy tails and vibronic spacing of the composite films exhibited SiO₂ content dependence.

Keywords: Absorption; energy gap; energy tail; photoluminescence; vibronic spacing

ABSTRAK

Dikenal pasti sebagai bahan berpotensi untuk kegunaan optoelektronik, nanokomposit polimer/bahan inorganik sedang dikaji secara aktif. Dalam kajian ini kesan kandungan nanozarah amorfus SiO2 ke atas sifat optik filem nipis poli(9,9’-di-n-ostilfluorenyl-2.7-diil) (PFO) telah dikaji. Larutan PFO/SiO₂ yang berbeza nisbah telah disediakan menggunakan teknik adunan larutan. Kemudian, adunan dimendapkan ke atas substrat kaca menggunakan teknik salutan berputar pada kelajuan 2000 ppm selama 30 s dan seterusnya dikeringkan pada suhu bilik selama 1 jam. XRD dan TEM digunakan untuk pencirian struktur sementara spektrofotometer UV-Vis dan PL digunakan untuk mengkaji sifat optik filem yang disediakan. Pencirian XRD tidak menunjukkan sebarang perubahan struktur ke atas PFO dan nanozarah SiO₂ akibat dari proses adunan. Mikrograf TEM menunjukkan nanozarah amorfus SiO2 tersalut oleh PFO. Berbanding spektrum penyerapan filem PFO, spektrum penyerapan untuk filem nipis nanokomposit mempamerkan anjakan merah, menandakan pertambahan panjang konjugasi PFO/SiO₂. Selain itu, nilai bagi jurang tenaga, lebar ekor tenaga dan jarak vibronik oleh filem komposit juga menunjukkan pergantungan kepada kandungan SiO₂.

Kata kunci: Ekor tenaga; fotoluminesen; jarak vibronik; jurang tenaga; penyerapan

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*Pengarang untuk surat-menyurat; email: hafizhj@ukm.my