Self-assembly of CdTe tetrapods into network monolayers at the air/water interface

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Date
2010-01-01
Authors
Goodman, Matthew
Zhao, Lei
Mallapragada, Surya
DeRocher, Karen
Wang, Jun
Mallapragada, Surya
Lin, Zhiqun
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Chemical and Biological Engineering
Abstract

Cadmium telluride (CdTe) tetrapods are synthesized with varying aspect ratios through multiple injections of the Te precursor, which provides an excellent means of controlling and tailoring the optical properties of the tetrapods. The self-assembly of CdTe tetrapods at the air/water interface is explored using the Langmuir-Blodgett (LB) technique due to potential use in solar cells arising from the intriguing tetrapod shape that improves charge transport and the optimum band gap energy of CdTe that enhances light absorption. Interestingly, the Langmuir isotherm shows two pressure plateau regions: one at ∼10 mN/m with the other at the high surface pressure of ∼39 mN/m. LB deposition at various pressures allows the discernment of the unique two-dimensional packing alluded in the isotherm. By placing CdTe at the air/water interface, it is revealed in the deposition that the tetrapods experienced a dewetting phenomenon, forming a ribbon structure at the onset of surface pressure with a height corresponding to the length of one tetrapod arm. With the increase of surface pressure, the ribbons widen to an eventual large-scale percolated network pattern. The packing density of tetrapods is successfully manipulated by controlling the surface pressure, which may find promising applications in optoelectronic devices.

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Reprinted with permission from ACS Nano 4 (2010), pp.2043-2050. doi: 10.1021/nn1002584. Copyright 2010 American Chemical Society.

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