Quantum Dots by Ultraviolet and X-ray Lithography
Highly luminescent semiconductor quantum dots have been synthesized in porous materials with ultraviolet and x-ray lithography. For this, the pore-filling solvent of silica hydrogels is exchanged with an aqueous solution of a group II metal ion together with a chalcogenide precursor such as 2-mercaptoethanol, thioacetamide or selenourea. The chalcogenide precursor is photodissociated in the exposed regions, yielding metal chalcogenide nanoparticles. Patterns are obtained by using masks appropriate to the type of radiation employed. The mean size of the quantum dots is controlled by adding capping agents such as citrate or thioglycerol to the precursor solution, and the quantum yield of the composites can be increased to up to about 30% by photoactivation. Our technique is water-based, uses readily available reagents, and highly luminescent patterned composites are obtained in a few simple processing steps. Polydispersity, however, is high (around 50%), preventing large-scale usage of the technique for the time being. Future developments that aim at a reduction of the polydispersity are presented.
L. A. Martin and L. E. Rich and A. Yamilov and B. R. Heckman and N. Leventis and S. Guha and J. Katsoudas and R. Divan and D. C. Mancini and M. F. Bertino and R. R. Gadipalli, "Quantum Dots by Ultraviolet and X-ray Lithography," Nanotechnology, Institute of Physics - IOP Publishing, Jan 2007.
The definitive version is available at http://dx.doi.org/10.1088/0957-4484/18/31/315603
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