Graphene-Based Fluorescence-Quenching-Related Fermi Level Elevation and Electron-Concentration Surge

Area of Science:

• Materials Science
• Nanotechnology
• Spectroscopy

Background:

• Unsaturated π-conjugated systems, like graphene, facilitate electron transfer due to intermolecular p-orbital overlaps.
• Fluorescence quenching is a phenomenon observed when a fluorophore's emission intensity is reduced by nearby substances.
• Graphene's unique electronic properties make it a candidate for modulating optical properties of adsorbed molecules.

Purpose of the Study:

• To investigate the interaction between graphene and fluorescein isothiocyanate (FITC) and its effect on fluorescence.
• To identify and validate the mechanism responsible for fluorescence quenching.
• To demonstrate the potential of this interaction for developing novel biosensing applications.

Main Methods:

• Raman-mapping measurements were employed to observe fluorescence intensity changes.
• Photon-induced electron transfer (PET) mechanism was investigated as the cause of quenching.
• Analysis of Dirac point shifts in FITC-coated graphene was performed to validate the PET mechanism.

Main Results:

• Fluorescence intensity of FITC was significantly quenched by graphene, but not by SiO2 substrates.
• The photon-induced electron transfer (PET) mechanism was identified as the primary cause of fluorescence quenching.
• Visible-light exposure induced Fermi level elevation and increased electron concentration in graphene, confirming the PET mechanism.

Conclusions:

• Graphene effectively quenches FITC fluorescence through a PET mechanism involving electron transfer.
• The observed phenomenon provides a basis for fabricating graphene-based biosensors.
• These biosensors demonstrate the capability to quantify fluorescently labeled biomolecules.