Functionalization of Oxide‐Free Silicon Surfaces for Biosensing Applications

Abstract

As an alternative to standard silicon biofunctionalization protocol based on alkoxysilanes that bind to SiO2 on oxidized silicon substrates, several protocols to form bifunctional interlayers that directly bind to the silicon surface via a strong SiC bond have been developed during the last decades. These interlayers are more stable, and the lack of an insulating layer between the substrate and the interlayer reduces electric noise in biosensor devices. SiC monolayers are not yet regularly applied as the protocols are more complex and generally require an inert gas atmosphere. However, a variety of applications and new methods to form bifunctional SiC interlayers are recently developed. Here, the role these innovative protocols and interlayers play in biofunctionalization of silicon surfaces is reviewed and their applications in electrochemical, microelectromechanical, and optical biosensing are reported. From the analysis of the current situation, it can be concluded that the advantageous properties offered with this approach in many cases more than outweigh the additional processes to form SiC bonded interlayers and the approach is predicted to expand the applications of future silicon‐based biosensors.

Grafting of Organophosphonic Acid Monolayers on Hydrogen-Terminated Silicon Surface and Secondary Functionalization in Supercritical Carbon Dioxide Media

“…The FTP molecule was assembled on the BPPA molecule by removing HBr from the surface to form a covalent bond to result in the BPPA-FTP assembly on the oxide-free Si surface. The secondary functionalization of the OPA monolayer not only demonstrates the robustness of the grafted monolayer but also opens up avenues for implementing oxide-free Si for applications such as monolayer doping, highly selective and sensitive biochemical sensors, 40 batteries, 41 and understanding molecular interactions and biological applications. The developed SCCO 2 process will allow more advanced studies on the OPA monolayer and its effect on the surface properties and charge transfer across the interface.…”

Dielectrophoresis: An Approach to Increase Sensitivity, Reduce Response Time and to Suppress Nonspecific Binding in Biosensors?

“…A second key factor to avoid nonspecific binding in affinity sensors is a suitable biofunctionalization strategy that allows for reproducible immobilization of receptor molecules. This is often realized in two steps involving an interlayer between the receptor molecule and the surface formed by a self-assembling process [ 112 ].…”

Stable Organic Radical for Enhancing Metal–Monolayer–Semiconductor Junction Performance

“…The chemical functionalization of semiconducting substrates, like silicon (Si), has also recently attracted attention due to its relevant technological interest . The covalent functionalization of Si with organic molecules has opened up the possibility of tuning the electrical properties of the semiconductor beneath , as well as of introducing additional functionalities such as redox activity and biosensing . Thus, the charge transport through solid-state metal/monolayer/semiconductor (MmS) junctions is of significant interest.…”

“… 6 The covalent functionalization of Si with organic molecules has opened up the possibility of tuning the electrical properties of the semiconductor beneath 6 , 7 as well as of introducing additional functionalities such as redox activity 8 and biosensing. 9 Thus, the charge transport through solid-state metal/monolayer/semiconductor (MmS) junctions is of significant interest. However, most of the research done so far on MmS is limited to alkyl molecular monolayers, and very few examples on small conjugated molecules can be found in the literature.…”