Stable and selective self-assembly of α-lipoic acid on Ge(001) for biomolecule immobilization

Abstract

We demonstrate a novel method for the stable and selective surface functionalization of germanium (Ge) embedded in silicon dioxide. The Ge(001) surface is functionalized using α-lipoic acid (ALA), which can potentially be utilized for the immobilization of a wide range of biomolecules. We present a detailed pH-dependence study to establish the effect of the incubation pH value on the adsorption layer of the ALA molecules. A threshold pH value for functionalization is identified, dividing the examined pH range into two regions. Below a pH value of 7, the formation of a disordered ALA multilayer is observed, whereas a stable well-ordered ALA mono- to bi-layer on Ge(001) is achieved at higher pH values. Furthermore, we analyze the stability of the ALA layer under ambient conditions, revealing the most stable functionalized Ge(001) surface to effectively resist oxidation for up to one week. Our established functionalization method paves the way towards the successful immobilization of biomolecules in future Ge-based biosensors.

Terahertz subwavelength sensing with bio-functionalized germanium fano-resonators

“…After 10 min of plasma treatment, PLL-PEG-HTL in aqueous solution is rapidly adsorbed electrostatically to the negatively charged Si 3 N 4 layer. This way, surface functionalization of Ge resonators becomes much faster and easier to handle compared to functionalization with α-lipoic acid established in previous work [10,11]. The obtained PLL-PEG-HTL-functionalized Ge wafers can be employed for site-specific, covalent capturing of HaloTagfusion proteins.…”

“…Since LSPR are responsive to changes in their immediate surroundings, they can be used as a sensing platform. In addition (bio-) functionalization of the LSPR structures can enable selectivity of the sensor to discriminate the detection of a specific analyte [11,12].…”