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Qi B.,Clemson University | Qi B.,Center for Optical Materials Science and Engineering Technology anderson | Ye L.,University of South Carolina | Stone R.,Clemson University | And 5 more authors.
Journal of Physical Chemistry C | Year: 2013

During the synthesis of nanoparticles via thermal decomposition of iron precursors, the capping ligand-precursor ratio influences the resulting size of the iron oxide nanoparticles. As the molar ratio of aliphatic amines to iron precursor is increased, the average diameter of the synthesized iron oxide nanoparticles decreases. This trend is opposite to previously reported results. We investigated this phenomenon by independently varying the ligand chain length, the ligand-precursor molar ratio, and the degree of saturation of the aliphatic chain. Nuclear magnetic resonance spectra of the precursor illustrated the presence of a primary amine peak before heating and the peak absence after heating, potentially indicating that the primary amine acts as reducing agent to promote the decomposition of the iron precursor. We hypothesize that the amine groups play a dominant role in the nucleation of the particles, while the chain length and degree of aliphatic saturation have only a minor effect on particle size. The nanoparticles' size and crystallinity were characterized with high-resolution transmission electron microscopy, dynamic light scattering, and X-ray diffraction, and the magnetic properties were characterized by magnetometry. © 2013 American Chemical Society.

Gonzalez-Pereyra N.G.,Clemson University | Glasgow W.,Clemson University | Parenzan A.,Clemson University | Sharp J.L.,Clemson University | And 2 more authors.
Industrial and Engineering Chemistry Research | Year: 2014

Herein, we present a study investigating the reaction conditions to wet etch monocrystalline silicon in the subcritical region of water, specifically from 200 to 300 C. In the subcritical region there is a departure of thermodynamic, transport, and chemical properties from normal conditions. This has the potential to affect the reaction paths for the dissolution of silicon, by modifying the local concentration of reactants and products, by altering the relative activation energy of different reactions, or by changing the polarity of the water. Furthermore, our methodology uses concentrations of etching agent markedly lower than previous works (our reactions were conducted at [KOH] = 0.03-0.7%/wt). The results of the study suggest that dilute etchant solutions at high temperatures can produce results comparable to those reported at atmospheric conditions using higher concentrations of etchants. Based on the results obtained, the main key factors in the etch rates were crystallographic orientation of the wafer, composition of the etching solution, and temperature. © 2013 American Chemical Society.

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