In this study, we demonstrate a facile and simple synthesis of quantum dot (QD)-polymer composites. Highly fluorescent semiconducting CdSe/ZnS quantum dots were embedded in different commercially available polymers using one easy step. QD-polymer composite nanoparticles were also synthesized using template-assisted synthesis. In particular, we self-assembled lamellar micelles inside nanoporous alumina membranes which were used for the synthesis of mesoporous silica hollow nanotubes and solid nanorods. We observed that the addition of excess free octadecylamine (ODA) in the QD-silica solution resulted in gelation. The gelation time was found to be dependent on free ODA concentration. Similarly, the emission of QD-polymer composites was also found to be dependent on free ODA concentration. Highly purified QDs provided polymer composites that have a much lower emission compared to unpurified nanocomposites. This was attributed to passivation of the QD surfaces by amine, which reduced the surface defects and non-radiative pathways for excited QDs. Finally, highly fluorescent QD-polymer patterns were demonstrated on glass substrates which retained their emission in both polar and non-polar solvents.
Controlled and convenient synthetic approaches for more complex-shaped nanotubes and nanowires of different materials are needed to further advance the field of nanoscience and nanotechnology. In this paper, we report the synthesis and characterization of nonlinear nanopores (such as curved and dendritic nanopores) containing alumina films. We show that control over the orientation of nanopores can be accomplished by controlling the geometric shape of aluminum substrates on which nanoporous alumina is grown. The anodically grown alumina on square and rectangular aluminum substrates showed cracks at the sharp edges of the substrates but no cracks were observed in nanoporous alumina films grown on cylindrical substrates. Our electrostatic calculations suggest that the electric field intensity at sharp edges of the rectangular/square substrates is significantly larger than that at the flat faces of the substrates. This leads to a faster alumina growth rate and hence increased stresses at these edges. We also propose a simple model that predicts the shape and orientation of nonlinear nanopores grown on different geometric shaped substrates. Through the use of proposed nanoporous films as template, one can easily synthesize highly complex-shaped nanotubes and nanowires of different materials.
We report here the synthesis and characterization of polydiacetylene (PDA) films and nanotubes using layer-by-layer (LBL) chemistry. 10,12-Docosadiyndioic acid (DCDA) monomer was selfassembled on flat surfaces and inside of nanoporous alumina templates. UV irradiation of DCDA provided polymerized-DCDA (PDCDA) films and nanotubes. We have used zirconium-carboxylate interlayer chemistry to synthesize PDCDA multilayers on flat surfaces and in nanoporous template. PDCDA multilayers were characterized using optical (UV-vis, fluorescence, ellipsometry, FTIR) spectroscopies, ionic current-voltage (I-V) analysis, and scanning electron microscopy. Ellipsometry, FTIR, electronic absorption and emission spectroscopies showed a uniform DCDA deposition at each deposition cycle. Our optical spectroscopic analysis indicates that carboxylatezirconium interlinking chemistry is robust. To explain the disorganization in the alkyl portion of PDCDA multilayer films, we propose carboxylate-zirconium interlinkages act as "locks" in between PDCDA layers which restrict the movement of alkyl portion in the films. Because of this locking, the induced-stresses in the polymer chains can not be efficiently relieved. Our ionic resistance data from I-V analysis correlate well with calculated resistance at smaller number of PDCDA layers but significantly deviated for thicker PDCDA nanotubes. These differences were attributed to ionblocking because some of the PDCDA nanotubes were totally closed and the nonohmic and permselective ionic behaviors when the diameter of the pores approaches the double-layer thickness of the solution inside of the nanotubes.
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