Uses of Alkanethiol Effects on Surface Functionalization of Gold Membranes for Biosensors

The surface properties and performance of a biosensor's operative element plays a decisive role in medical applications by offering a universal platform for biological and chemical sensing. It is extremely important for the surface stress biosensors, which operate via free energy change, an underlying principle in all bonding reactions. A biosensors' surface specificity to a chosen analyte is determined by the chemical functionalization. Ultraspecialized surface functionalizations can be achieved using molecular self-assembled monolayers (SAMs). We applied five different alkanethiols to functionalize the gold/polydimethylsiloxane (Au/PDMS) membrane of capacitive surface stress biosensors to research the surface properties and performance. Glucose was used as the adsorbed target analyte of the SAM/Au/PDMS membrane. The functionalized effects were characterized by scanning electron microscopy and Raman spectroscopy, then confirmed by cyclic voltammetry and electrochemical impedance spectroscopy. Results indicate that test membranes were functionalized successfully by the alkanethiols. Moreover, our findings reveal that extended alkyl chain length not only increases the distance of electron transfer pathway between the electron donor and acceptor, but also alters the surface properties of the SAMs. The functional end group of SAMs critically affects the interfacial action of adsorbed glucose molecules as well as electron transfer from glucose to electrode. This comprehensive study may provide a good understanding to functionalize biosensor surfaces and improve surface performance, especially in the case of surface stress biosensors.