@article{foster_collazo_sitar_ivanisevic_2013, title={Aqueous Stability of Ga- and N-Polar Gallium Nitride}, volume={29}, ISSN={["0743-7463"]}, DOI={10.1021/la304039n}, abstractNote={The stability of III-nitride semiconductors in various solutions becomes important as researchers begin to integrate them into sensing platforms. This study quantitatively compares the stability of GaN surfaces with different polarities. This type of quantification is important because it represents the first step toward designing semiconductor material interfaces compatible with solution conditions. A stability study of Ga- and N-polar GaN was conducted by immersion of the surfaces in deionized H(2)O, pH 5, pH 9, and H(2)O(2) solutions for 7 days. Inductively coupled plasma mass spectrometry of the solutions was conducted to determine the amount of gallium leached from the surface. X-ray photoelectron spectroscopy and atomic force microscopy were used to compare the treated surfaces to untreated surfaces. The results show that both gallium nitride surface types exhibit the greatest stability in acidic and neutral solutions. Gallium polar surfaces were found to exhibit superior stability to nitrogen polar surfaces in the solutions studied. Our findings highlight the need for further research on surface passivation and functionalization techniques for polar III-nitride semiconductors.}, number={1}, journal={LANGMUIR}, author={Foster, Corey M. and Collazo, Ramon and Sitar, Zlatko and Ivanisevic, Albena}, year={2013}, month={Jan}, pages={216–220} }
 @article{foster_collazo_sitar_ivanisevic_2013, title={Cell Behavior on Gallium Nitride Surfaces: Peptide Affinity Attachment versus Covalent Functionalization}, volume={29}, ISSN={["0743-7463"]}, DOI={10.1021/la401503b}, abstractNote={Gallium nitride is a wide band gap semiconductor that demonstrates a unique set of optical and electrical properties as well as aqueous stability and biocompatibility. This combination of properties makes gallium nitride a strong candidate for use in chemical and biological applications such as sensors and neural interfaces. Molecular modification can be used to enhance the functionality and properties of the gallium nitride surface. Here, gallium nitride surfaces were functionalized with a PC12 cell adhesion promoting peptide using covalent and affinity driven attachment methods. The covalent scheme proceeded by Grignard reaction and olefin metathesis while the affinity driven scheme utilized the recognition peptide isolated through phage display. This study shows that the method of attaching the adhesion peptide influences PC12 cell adhesion and differentiation as measured by cell density and morphological analysis. Covalent attachment promoted monolayer and dispersed cell adhesion while affinity driven attachment promoted multilayer cell agglomeration. Higher cell density was observed on surfaces modified using the recognition peptide. The results suggest that the covalent and affinity driven attachment methods are both suitable for promoting PC12 cell adhesion to the gallium nitride surface, though each method may be preferentially suited for distinct applications.}, number={26}, journal={LANGMUIR}, author={Foster, Corey M. and Collazo, Ramon and Sitar, Zlatko and Ivanisevic, Albena}, year={2013}, month={Jul}, pages={8377–8384} }