title: Gating capacitive field-effect sensors by the charge of nanoparticle/molecule hybrids.
abstract: The semiconductor field-effect platform is a powerful tool for chemical and biological sensing with direct electrical readout. In this work, the field-effect capacitive electrolyte-insulator-semiconductor (EIS) structure - the simplest field-effect (bio-)chemical sensor - modified with citrate-capped gold nanoparticles (AuNPs) has been applied for a label-free electrostatic detection of charged molecules by their intrinsic molecular charge. The EIS sensor detects the charge changes in AuNP/molecule inorganic/organic hybrids induced by the molecular adsorption or binding events. The feasibility of the proposed detection scheme has been exemplarily demonstrated by realizing capacitive EIS sensors consisting of an Al-p-Si-SiO2-silane-AuNP structure for the label-free detection of positively charged cytochrome c and poly-d-lysine molecules as well as for monitoring the layer-by-layer formation of polyelectrolyte multilayers of poly(allylamine hydrochloride)/poly(sodium 4-styrene sulfonate), representing typical model examples of detecting small proteins and macromolecules and the consecutive adsorption of positively/negatively charged polyelectrolytes, respectively. For comparison, EIS sensors without AuNPs have been investigated, too. The adsorption of molecules on the surface of AuNPs has been verified via the X-ray photoelectron spectroscopy method. In addition, a theoretical model of the functioning of the capacitive field-effect EIS sensor functionalized with AuNP/charged-molecule hybrids has been discussed.
authors.affiliation: Aachen University of Applied Sciences, Institute of Nano- and Biotechnologies, Heinrich-Mußmann-Straße 1, 52428 Jülich, Germany. a.poghossian@fz-juelich.de.
authors.forename: Arshak
authors.initials: A
authors.lastname: Poghossian
authors.forename: Matthias
authors.initials: M
authors.lastname: Bäcker
authors.forename: Dirk
authors.initials: D
authors.lastname: Mayer
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Schöning
mesh_terms: D001704:Biopolymers / Q000032:analysis*; D003217:Conductometry / Q000295:instrumentation* / Q000379:methods*; D045304:Cytochromes c; D025802:Electric Capacitance; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D058726:Nanoconjugates / Q000737:chemistry / Q000648:ultrastructure; D015203:Reproducibility of Results; D012666:Semiconductors; D012680:Sensitivity and Specificity
chemical_list: D001704:Biopolymers; D058726:Nanoconjugates; D006046:Gold; D045304:Cytochromes c