Detection and screening of basic amino acids using the luminescence switching of a WS2 nanosheet–Ag2O nanoparticle composite†
Abstract
The Förster resonance energy transfer (FRET) pair-based detection has gained considerable attention due to its promising sensitivity and selectivity. Herein, we report a turn-on sensor for detecting basic amino acids utilizing the fluorescence emission properties of WS2 nanosheets (WS2 NSs). The sensor functions based on a FRET dyad. The addition of AgNO3 into an alkaline solution of WS2 NSs leads to the in situ formation of silver oxide nanoparticles (Ag2O NPs). The negative surface charge and the presence of sulphur vacancies, together with the possibility for a multiplexed adsorption platform of WS2 NSs, account for the formation Ag2O NPs on their surface. In the WS2 NS–Ag2O NP system (termed as a 0D–2D composite), the fluorescence emission of the nanosheets became subdued due to the FRET. This 0D–2D composite is proven to be an excellent turn-on sensor for basic amino acids. Histidine, lysine and arginine can induce the aggregation of the Ag2O NPs, which shuts the FRET pathway, along with the regeneration of the fluorescence of WS2 NSs. The aggregation of Ag2O NPs occurs in a sensor solution with pH below the isoelectric points of the amino acids to help to discriminate them. The dynamic range and limit of detection of the sensor have been evaluated. The protein detection capability of the sensor was verified using a lysine containing protein, ubiquitin, and by real sample analysis, using biological fluids.