An azamacrocycle functionalized GaAs (100) optical sensor for copper ion (II) detection in phosphate buffered saline solution

Copper ion is important in natural and biological processes. The present work describes the fabrication of a hybrid GaAs sensor for the label-free detection of copper ion in the near infrared region. The implemented sensing strategy relies on the sensitivity of the GaAs photoluminescence (PL) emission to the local environment at its surface. Specifically, GaAs (001) substrates were chemically passivated with carboxylic acid group terminated thiols, followed by the surface functionalization with artificial Me2Cyclen cavity by a classical EDC/NHS coupling reaction. Due to a specific recognition between Me2Cyclen and copper ions, CuII were coordinately captured onto the surface. The positive charges tended to deplete electrons from the near surface region and increase the band bending, leading to a PL decrease. The selectivity of the chip towards metallic ions was further confirmed by a combination of X-ray photoelectron spectroscopy, water contact angle measurements and AFM analysis. Collectively, the results described within suggest the promise of integrating well-designed organic scaffold with the unique optical properties of III-V semiconductors for a label-free detection of various analytes.