Photoluminescence and Electroluminescence from Tris(8- hydroxyquinoline)aluminum Nanowires Prepared by Adsorbent-Assisted Physical Vapor Deposition

Abstract

Single‐crystalline nanowires are successfully prepared from a small organic functional molecule, tris(8‐hydroxyquinoline)aluminum (Alq3), by an adsorbent‐assisted physical‐vapor‐deposition method. The introduction of adsorbents can decrease the sublimation temperature of Alq3, and slow the weight‐loss process markedly, which is proven to be indispensable in improving the uniformity of the as‐prepared Alq3 nanowires. Measurements of the optical properties reveal that the absorption spectra of the Alq3 nanowires show an obvious blue‐shift with decreasing diameter. The photoluminescence vibrational fine structure emerges and becomes pronounced with increasing excitation energy, which is attributed to the ordered orientation of the Alq3 molecules in the nanowires. Furthermore, the Alq3 nanowires are fabricated into an electroluminescent device, which has an obvious size‐dependent performance.

Formation of Flower-Like Crystals of Tris(8-hydroxyquinoline)aluminum from 8-Hydroxyquinoline on Anodic Porous Alumina

“…The preparation and characterization of Alq 3 have been widely studied [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Because of the bidentate ligand, Alq 3 complexes form two isomers, as shown in Figure 1: meridional and facial.…”

“…Moreover, Alq 3 crystals with a wide range of morphologies have been prepared, including nanoparticles produced by vapor condensation [14], nanowires produced using either a single-step heat treatment [15] or an adsorbentassisted physical vapor deposition (PVD) process [16], pine needle-like crystals produced by PVD [3], and nanorods produced by solution synthesis with a surfactant [17]. All of these Alq 3 crystals demonstrate interesting morphologydependent properties.…”

“…These same Alq 3 nanoparticles can be heat treated and grown into the -Alq 3 nanowires via the -Alq 3 phase [15]. When Alq 3 nanowires were fabricated by heating mixtures of silica gel and Alq 3 , they exhibited a blue shift in the absorption spectra with decreasing nanowire diameter, and the photoluminescence vibrational fine structure intensified with increasing excitation energy [16]. Besides nanoparticles and nanowires, pine needle-like crystals with an -Alq 3 phase were prepared by PVD in a double zone tube furnace [3].…”

Low‐Dimensional Nanomaterials Based on Small Organic Molecules: Preparation and Optoelectronic Properties

“…A series of single-crystalline 1D organic nanostructures were prepared with this method. [157][158][159][160] Figures 7A and B show typical SEM and TEM images of tris(8-hydroxyquinoline)aluminum (Alq 3 ) nanowires. The SAED pattern shown in Figure 7C reveals that the Alq 3 nanowires are single-crystalline structures with preferential growth along the [101] direction, which is also testified by the XRD patterns.…”

“…It was mentioned in Section 2 that Yao's group has developed an adsorbent-assisted PVD strategy for the general construction of crystalline 1D organic nanostructures. [157][158][159][160] It was revealed that the crystallinity of the nanomaterials resulted in some novel luminescent behaviors. In this section, we introduce the fluorescence narrowing and multicolor emission from crystalline nanowires and nanoribbon arrays, respectively, based on a single chemical composition prepared by this method.…”