Quantitative Analysis of the Functionalization of Gallium Phosphide With Organic Azides

Abstract

Gallium phosphide (GaP) surfaces were functionalized with two different molecules that contain an azide moiety at their terminus. Compound 4-azidophenacyl bromide (4AB) is an aryl azide with a bromine group at its opposite terminus that provides easy identification of the molecule's presence on the surface with x-ray photoelectron spectroscopy (XPS). O-(2-aminoethyl)-O'-(2-azidoethyl)pentaethylene glycol (AAP) is a small poly(ethylene glycol) molecule with an amine group at its opposite terminus. Atomic force microscopy was used to identify the uniformity of the clean and functionalized GaP surfaces. Water contact angle revealed a more hydrophobic surface with AAP functionalization (33°) and even more hydrophobic (53°) with the 4AB functionalized surface compared to a clean surface (16°). XPS confirmed the presence of each of the organic azides on the surface. XPS was further used to calculate the adlayer thickness of each functionalization. This analysis revealed an adlayer thickness of about 8 Å for the 4AB functionalized surfaces compared to 1 Å for the AAP adlayer, which led to the conclusion that AAP functionalization only provided partial coverage. A stability study using 4AB-functionalized surfaces showed good stability in saline solutions with varying concentrations of hydrogen peroxide. Finally, inductively coupled plasma mass spectrometry was used to evaluate the gallium concentration in the stability solutions. While the functionalization with the organic azides did not provide complete suppression of gallium leaching, both of the azides decreased the leaching by 10-50%.

Impact of degradable nanowires on long-term brain tissue responses

“…GaP is also dissolving in pure physiological saline as well as in hydrogen peroxide (H 2 O 2 , 0.1, 1, 10 %) (to mimic the inflammatory in vivo milieu both inside and outside of activated monocytes/microglia) at 37 °C [ 29 ]. These results have been confirmed by Richards et al [ 28 ] using GaP wafers. Taken together, these results demonstrate that the GaP core of the nanowires used in this study degrades both in vitro and in vivo.…”

“…The core material of the nanowires used in this study is GaP. GaP is a semiconductor and like many semiconductors, GaP has been shown to be susceptible to corrosion and degradation, a process that leads to a release of Ga ions [ 28 ]. We have previously evaluated the in vivo soft tissue inflammatory response after implantation of GaP discs into the abdominal wall of rats [ 29 ].…”

Wet Chemical Functionalization of GaP(111)B through a Williamson Ether-Type Reaction

“…12−14 One possible strategy to ameliorate GaP surface issues is through deliberate chemical passivation/ functionalization. Surface chemical strategies involving Lewis acid attack on atop Ga atoms have been shown in the form of thiols adsorbed on GaP(100) [15][16][17][18][19] 20 and the reaction between GaP(111)A 21−23 and alkyl Grignard reagents. To date, no chemical strategies have been identified for P-rich surface planes such as GaP(111)B, representing a critical knowledge gap in functionalization strategies for nanostructured GaP photoelectrodes.…”

In situ and ex situ functionalization of nanostructured gallium oxy‐hydroxide with a porphyrin dye

“…The use of wide bandgap semiconductor materials as optoelectronic platforms for attaching functional organic molecules shows great promise for various applications ranging from biomedical to green energy (Stutzmann et al, ). Gallium containing materials, such as gallium phosphide (GaP), have been previously functionalized with azide containing molecules for devices such as biosensors (Richards et al, ). Gallium oxyhydroxide (GaOOH) is an inorganic material with a bandgap of 4.75 eV.…”