Photophysical characterizations of 2-(4-biphenylyl)-5 phenyl-1,3,4-oxadiazole in restricted geometry

Department of Physics, Tripura University, Suryamaninagar-799130, Tripura, India
Journal of Luminescence (Impact Factor: 2.14). 01/2008; DOI: 10.1016/j.jlumin.2007.05.001
Source: arXiv

ABSTRACT Langmuir and Langmuir–Blodgett (LB) films of non-amphiphilic 2-(4-Biphenylyl)-5-phenyl-1,3,4-oxadiazole (abbreviated as PBD) mixed with stearic acid (SA) as well as with the inert polymer matrix poly(methyl methacrylate) (PMMA) have been studied. Surface pressure versus area per molecule (π–A) isotherm studies suggest that PBD molecules very likely stand vertically on the air–water interface and this arrangement allows the PBD molecules to form stacks and remain sandwiched between SA/PMMA molecules. At lower surface pressure, phase separation between PBD and matrix molecules occurs due to repulsive interaction. However, at higher surface pressure, PBD molecules form aggregates. The UV–vis absorption and steady-state fluorescence spectroscopic studies of the mixed LB films of PBD reveal the nature of the aggregates. H-type aggregate predominates in the mixed LB films, whereas I-type aggregate predominates in the PBD-PMMA spin-coated films. The degree of deformation produced in the electronic levels are largely affected by the film thickness and the surface pressure of lifting.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Clay mineral particles are interesting nanosized building blocks due to their high aspect ratio and the chemical properties. The main interest in this nanosized building blocks results essentially from the colloidal size and the permanent structural charge of the particles. Smectites or swelling clay minerals are naturally occurring nanomaterials that can be fully delaminated to elementary clay mineral platelets in dilute aqueous dispersion. This dilute aqueous smectite suspensions are well suited to convert into functional nanofilms. The functionalization is performed by ion exchange reaction with amphiphilic molecules carrying the desired functionality, such as chirality, two photon absorption, energy transfer, optical nonlinearity and magnetism, which are due to the nature of the amphiphilic cations and to the organization of both the amphiphilic molecules and the elementary clay mineral platelets. Controlling the structure of materials at the nanometre scale is of fundamental importance for tailoring such materials properties. Langmuir Blodgett films are known for a high degree of organisation of organic molecules. Fundamental research into the organization of molecules at clay mineral platelets is necessary to optimize the materials for specific applications. This paper gives an overview of organo-clay hybrid Langmuir-Blodgett nano films.
  • Journal of Heterocyclic Chemistry 03/2010; 47(2):415 - 420. · 1.22 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: To study the effect of aggregation of the 2-(4-biphenylyl)-5-phenyl-1,3,4-oxadiazole (PBD) molecule in solid state, thin films of PBD have been prepared by the thermal evaporation technique onto glass and quartz substrates under different experimental conditions. These films have been studied for their structural, optical and electrical properties. AFM investigations of the films revealed that the films were smooth, dense and crack free with RMS roughness of 11–14 nm. XRD measurements indicate that films deposited on quartz are more crystalline than films deposited on glass substrate. Both absorption and reflectance spectra over the wavelength range 200–800 nm have been recorded to find optical parameters, namely, absorption, extinction coefficient, refractive index and dielectric constants. The inter-band transition energies are found to lie within the range 3.45–3.49 eV. Optical studies of the films indicate that PBD molecules preferred J-aggregation. A prominent single emission peak in the range of 370–390 nm has been observed which confirms that the fluorescent property of this molecule is not quenched in the thin film state. The electrical conductivity results for the evaporated films exhibited semiconductor behaviour within the investigated field and temperature range. The nature of the substrate is found to be a useful tool to modify the film morphology and for enhancing the charge transport within the films.
    Electronic Materials Letters 8(4). · 1.87 Impact Factor

Full-text (2 Sources)

Available from
Jun 5, 2014