Layer-by-Layer Assembly of Colloidal CdS and ZnS−CdS Quantum Dots and Improvement of Their Photoluminescence Properties

Abstract

Thin films of colloidal CdS and ZnS-CdS alloy quantum dots (QDs) were fabricated by layer-by-layer (LBL) self-assembly to synthesize blue luminescent QD thin films. The assembly of negatively charged colloidal QDs and positively charged poly(diallyldimethylammonium chloride) results in QD/polymer multilayers. The relative intensity of the band-edge photoluminescence (PL) to that of the defect-related PL was decreased during the LBL assembly process. With an additional dipping treatment in a Cd(ClO 4 ) 2 aqueous solution with pH 10, the band-edge PL intensity was recovered. The PL decay profiles before and after the dipping treatment were considerably different. From this fact, we conclude that the enhancement of the band-edge PL intensity originates from the reduction of nonradiative recombination processes at the QD surface.

Increase in exciton decay rate due to plane-to-plane interaction between cyanine thin films

“…The cyanine dye thin films were fabricated by a layer-by-layer (LBL) method. [40][41][42] Previously, we reported fabrication of the LBL thin films with improved signal-to-noise ratio in pump-probe measurement. 39 The polymer layer consists of two layers of positively charged…”

Highly luminescent film functionalized with CdTe quantum dots by layer‐by‐layer assembly

“…Therefore, electrospinning is a superior technique for creating luminescence thin films. However, many successful preparations of QDs/polymers by LBL, which were mostly based on quartz or spin-coating films as substrate, have been reported using QDs such as CdS-ZnS, 22 CdSe, 23 and CdTe. [24][25][26] There are sparse examples on the fabrication of luminescent electrospinning films using LBL.…”

Layer-by-Layer Assembly of Stable Aqueous Quantum Dots for Luminescent Planar Plate

“…Therefore, how to evenly disperse QDs into films is the key technology. 13 So far, several methods have been explored to construct films, including spin-coating, vacuum thermal deposition, and drop casting. Compared to these typical methods, the layer-by-layer (LBL) assembly is a popular and versatile protocol to prepare highly homogeneous films with tailored thickness, morphology, composites, and functionality.…”

“…1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 3 For instance, the fabrications of luminescent films based on QDs and polyelectrolyte have been proved to be a good method for various applications. 13,[19][20][21] The hybrid luminescent films built by QDs and layered double hydroxides also have been reported. [22][23][24] Usually, the LBL assembly is operated in aqueous solution, in which anionic and cationic materials are alternatively deposited on the substrate.…”

“…[22][23][24] Usually, the LBL assembly is operated in aqueous solution, in which anionic and cationic materials are alternatively deposited on the substrate. 13,21 While, high quality QDs are initially prepared as colloids in nonpolar organic solvents stabilized by hydrophobic ligands that result in insolubility of them in aqueous solution. As a result, LBL assembly usually involve the phase transfer of hydrophobic QDs from nonpolar organic media to aqueous solution through ligand exchange.…”