Improved luminescence intensity and stability of thermal annealed ZnO incorporated Alq3 composite films.

The 30 wt% of ZnO (weight percentage of ZnO has been optimised) incorporated tris- (8-hydroxyquinoline)aluminum (Alq3) has been synthesised and coated on to glass substrates using dip coating method. The structural and optical properties of the Alq3/ZnO composite film after thermal annealing from 50 to 300 °C insteps 50° has been studied and reported. XRD pattern reveals the presence of crystalline ZnO in all the annealed films. The films annealed above 150 °C reveal the presence of crystalline Alq3 along with crystalline ZnO. The FTIR spectra confirm the presence of hydroxyquinoline and ZnO vibration in all the annealed composite films. The composite films annealed above 150 °C show a partial sublimation and degradation of hydroxyquinoline compounds. The ZnO incorporated composite films (Alq3/ZnO) exhibit two emission peaks, one corresponding to ZnO at 487 nm and another at 513 nm due to Alq3. The films annealed at 200 °C exhibit maximum photoluminescence (PL) intensity than pristine film at 513 nm when excited at 390 nm.

Heavy Metal Ions Trigger a Fluorescent Quenching in DNA-Organic Semiconductor Hybrid Assemblies.

The significance of DNA is no longer limited to its role as a biological information carrier; as a natural polymer, it also become in the field of materials. Single-stranded DNA (ssDNA) molecules with specific sequences can form a G-quadruplex or hairpin-shaped conformation with specific heavy metal ions through coordination bonds. In this study, ssDNA molecules of the four sequences were prepared into hybrid assemblies with one of the famous display materials, the tris-(8-hydroxyquinoline)aluminum (Alq3) semiconductor. Based on these hybrid assemblies, heavy metal ions, namely Pb2+, Hg2+, Cd2+ and As3+, were detected individually at the ppb level. Apart from this, in practical application, many samples containing heavy metal ions are digested with acid. By introducing MES buffer solution, the influence of acidity on the fluorescent signal of Alq3 was excluded. This strategy showed promising results in the practical application of detecting heavy metal ions in shrub branches and leaves.

Raman and X-ray photoelectron spectroscopic investigation of solution processed Alq3/ZnO hybrid thin films.

In this study, we characterize the solution processed tris-(8-hydroxyquinoline)aluminum(Alq3)/ZnO hybrid thin films using Raman and X-ray photoelectron spectroscopic (XPS) techniques. Raman studies reveal the sol-gel derived spin-coated ZnO thin film has hexagonal wurtzite structure. The incorporation of Alq3 molecules in the hybrid film results in the formation of bonding onto the surface of highly crystalline ZnO nanoparticles. The XPS confirms the incorporation of Alq3 in the hybrid thin films and corroborates that the Alq3 molecules may be adsorbed onto the surface of ZnO nanoparticles (chemisorption), showing the existence of chemical interaction between Alq3 and ZnO in the hybrid films. These studies support that the chemisorbed Alq3 molecules onto the ZnO nanoparticles may facilitate the charge transfer (non-radiative) between Alq3 and ZnO in the hybrid thin films which will be useful to enhance the optical and electrical properties for the optoelectronic device applications.

One-Step Synthesis of High Pure Tris(8-hydroxyquinoline)aluminum for Optics and Photonics.

A simple method of synthesis of high pure tris(8-hydroxyquinoline)aluminum (Alq3) from commercial available 5N Al2O3 and 8-hydroxyquinolinol has been developed. One-step exchange chemical reaction has been conducted under controlled 8-hydrixyquinoline vapor at a temperature of 190-240 °C with water removal by phosphorus anhydride. According to analysis of inductively coupled plasma mass-spectrometry, the chemical purity of synthesized Alq3 was 99.998 wt%. Photoluminescence of the synthesized Alq3 has been measured and slightly differed from those of Alq3 obtained by traditional organic synthesis.

Alq3 nanorods: promising building blocks for optical devices.

Monodisperse Alq3 nanorods with hexagonal-prism-like morphology are produced via a facile, emulsion based synthesis route. The photoluminescence of individual nanorods differs from the bulk material. These nanorods are promising building blocks for novel optical devices.

Formation and Entrapment of Tris(8-hydroxyquinoline)aluminum from 8-Hydroxyquinoline in Anodic Porous Alumina.

The formation and entrapment of tris(8-hydroxyquinoline)aluminum (Alq3) molecules on the surface of anodic porous alumina (APA) immersed in an ethanol solution of 8-hydroxyquinoline (HQ) were investigated by absorption, fluorescence, and Raman spectroscopies. The effects of the selected APA preparation conditions (galvanostatic or potentiostatic anodization method, anodizing current and voltage values, one- or two-step anodizing process, and sulfuric acid electrolyte concentration) on the adsorption and desorption of Alq3 species were examined. Among the listed parameters, sulfuric acid concentration was the most important factor in determining the Alq3 adsorption characteristics. The Alq3 content measured after desorption under galvanostatic conditions was 2.5 times larger than that obtained under potentiostatic ones, regardless of the adsorbed quantities. The obtained results suggest the existence of at least two types of adsorption sites on the APA surface characterized by different magnitudes of the Alq3 bonding strength. The related fluorescence spectra contained two peaks at wavelengths of 480 and 505 nm, which could be attributed to isolated Alq3 species inside nanovoids and aggregated Alq3 clusters in the pores of APA, respectively. The former species were attached to the adsorption sites with higher binding energies, whereas the latter ones were bound to the APA surface more weakly. Similar results were obtained for the Alq3 species formed from the HQ solution, which quantitatively exceeded the number of the Alq3 species adsorbed from the Alq3 solution. Alq3 molecules were formed in the HQ solution during the reaction of HQ molecules with the Al3+ ions in the oxide dissolution zone near the oxide/electrolyte interface through the cracks and the Al3+ ions adsorbed on surface of pore and cracks. In addition, it was suggested that HQ molecules could penetrate the nanovoids more easily than Alq3 species because of their smaller sizes, which resulted in higher magnitudes of the adsorption.