Vapor-Phase Synthesis and Surface Functionalization of ZnSe Nanoparticles in a Counterflow Jet Reactor
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N15.54.1
Vapor-Phase Synthesis and Surface Functionalization of ZnSe Nanoparticles in a Counterflow Jet Reactor Christos Sarigiannidis1, Athos Petrou2 and T. J. Mountziaris*1, 3 Departments of 1Chemical and Biological Engineering, and 2Physics, University at Buffalo The State University of New York, Buffalo, N.Y 14260, U.S.A. 3 The National Science Foundation, 4201 Wilson Boulevard, Arlington, VA 22230, U.S.A. ABSTRACT Compound semiconductor nanocrystals (quantum dots) exhibit unique size-dependent optoelectronic properties making them attractive for a variety of applications, including ultrasensitive biological detection, high-density information storage, solar energy conversion, and photocatalysis. There is presently a great need for developing scalable techniques that allow efficient synthesis, size control, and functionalization of quantum dots, without a loss of the desirable optical properties. We report experimental results on the properties and surface modification of ZnSe nanoparticles grown by a continuous vapor-phase technique utilizing an axisymmetric counterflow jet reactor. Luminescent ZnSe nanocrystals were obtained at room temperature by reacting vapors of dimethylzinc:triethylamine adduct with hydrogen selenide, diluted in a hydrogen carrier gas. The two reactants were supplied from opposite inlets of the counterflow jet configuration and initiated particle nucleation in a region near the stagnation point of the laminar flow field. Surface modification of nanoparticles by adsorption of 1pentanethiol was used to control the rate of particle coalescence. The counterflow jet technique can be scaled up for commercial production and is compatible with other vapor-phase processing techniques used in the microelectronics industry. INTRODUCTION II-VI semiconductor nanocrystals, e.g., CdSe, CdS, ZnSe and ZnS, are exciting materials exhibiting size-dependent luminescence when their size becomes smaller than the mean separation of an optically excited electron-hole pair (Bohr radius). These materials, also called “quantum dots”, exhibit quantum confinement effects that shift the onset of absorption and emission maxima towards higher energy with decreasing particle size. The bright luminescence and small size of quantum dots makes them ideal luminescent tags for studying biomolecular interactions and for developing multiplexed optical biosensors [1, 2]. New functional materials are also being envisioned, having nanocrystals, instead of atoms, as the building blocks of a lattice. Nanocrystals can be also used for developing novel inorganic/organic nanocomposites. There is currently a great need for developing flexible, scalable, and cost-effective techniques for controlled synthesis and surface functionalization of semiconductor nanocrystals. The desirable properties of the synthesized nanocrystals, that any preparation technique must address, include a defect-free crystalline structure, narrow size distribution, chemical purity, and a surface structure that allows functionalization by chemisorption of organic
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