Tracing Gold Nanoparticle Charge by Electrolyte−Insulator−Semiconductor Devices

Abstract

ABSTRACT:A capacitive field-effect electrolyte-insulator-semiconductor (EIS) device was applied for the first time to trace the charge of supported gold nanoparticles (Au-NPs) induced by oxygen plasma treatment or due to storing in aqueous oxidation and reduction solutions. In addition, X-ray photoelectron spectroscopy (XPS) has been used as a reference method to establish the various charge states of the Au-NPs resulting from the different treatment steps. After the oxygen-plasma treatment, a shift of the capacitancevoltage (C-V) curve (and flatband potential) of the Au-NP-covered p-Si-SiO 2 EIS structure by about -300 mV was found. The exposure of the EIS sensor surface to an oxidative and a reductive solution resulted in a shift of the C-V curve for -85 and þ81 mV, respectively. These observations correlate well with corresponding binding energy shifts in Au 4f core spectra in XPS experiments. The obtained results may open new opportunities for biosensing and biochips based on nanoparticle-charge-gated field-effect devices.

DNA Immobilization and Hybridization Detection by the Intrinsic Molecular Charge Using Capacitive Field-Effect Sensors Modified with a Charged Weak Polyelectrolyte Layer

“…Adopting a simplified double-layer capacitor model described in ref. [53] and by assuming that (1) the double-layer capacitance, C d , remains nearly unchanged after the adsorption of ssDNA molecules, (2) the probe ssDNA molecules are preferentially flat-oriented on the EIS surface with negatively charged phosphate groups directed to the positively charged PAH molecules, and (3) the charges inside the semiconductor and insulator as well as the screening of the DNA charge by counterions in the solution can be neglected, the following simplified relation between the surface potential change (Δφ) and the excess surface charge (ΔQ) can be obtained: 23,24 …”

Label‐free electrical detection of DNA by means of field‐effect nanoplate capacitors: Experiments and modeling

“…The Au‐NPs were deposited on the silanized sensor surface by immersion of the sensor in a solution of tetraoctylammonium bromide‐stabilized Au‐NPs in toluol for 12 h according to the procedure described in Refs. 6, 8. The sulfur atoms of the thiol groups of the MPTES will replace some of the organic shell molecules to bind the Au‐NPs to MPTES.…”

“…For the creation of inexpensive and simple genosensors or DNA chips, techniques that could detect the DNA‐hybridization event without the need for labeling, that is, label‐free sensing, would be favorable. Therefore, recently, considerable research efforts have been invested toward the label‐free direct electrical detection of charged macromolecules 1–5 as well as charged nanoparticles 6–8 and nanotubes 9, 10 using semiconductor field‐effect devices (FEDs). The possibility of a label‐free detection of DNA by its intrinsic molecular charge with different types of FEDs based on an electrolyte‐insulator‐semiconductor (EIS) system, like capacitive EIS sensors 11, 12, transistor structures 13, 14 Si‐nanowires 15–18, or carbon nanotubes 19, 20 has been experimentally demonstrated and discussed.…”

Planar and 3D interdigitated electrodes for biosensing applications: The impact of a dielectric barrier on the sensor properties

“…Biochemical reactions occurring at this interface may affect the density and distribution of surface charges which in turn represents a possibility for a direct label‐free electrical detection method. Examples are, semiconductor field‐effect detection of adsorption and binding of charged macromolecules (DNA, proteins, polyelectrolytes) by their intrinsic molecular charge as well as charged nano‐objects (molecule‐capped nanoparticles, carbon nanotubes) . Surface charges gain in importance with scaling down, as the surface‐to‐volume ratio increases and a considerable fraction of the total charge is confined close to the surface .…”