Ultrasensitive fluorescence detection of microRNA through DNA-induced assembly of carbon dots on gold nanoparticles with no signal amplification strategy.

An ultrasensitive fluorescence assay strategy on the basis of carbon dots (CDs) and cDNA-modified gold nanoparticles (AuNP-cDNA) was developed for the determination of microRNA-21 (miRNA-21) via internal filtering effect (IFE). Positively charged CDs (PEI-CDs), the fluorophores in IFE, were synthesized via a hydrothermal method using polyethyleneimine (PEI) as surface ligand. The maximum emission wavelength is located at 500 nm under the excitation of 410 nm.

An ultrasensitive colorimetric and fluorescence dual-readout assay for glutathione with a carbon dot-MnO nanosheet platform based on the inner filter effect.

An ultrasensitive colorimetric and fluorescence dual-readout assay based on the inner filter effect (IFE) was developed for glutathione (GSH) determination, in which carbon dots (C-dots) were used as a fluorophore and MnO nanosheets as an absorber. Due to the excellent optical absorption properties of MnO nanosheets and the good spectral overlap between the fluorophore and absorber, MnO nanosheets could effectively quench the fluorescence of C-dots the IFE. As the target, GSH could reduce MnO nanosheets to Mn ions, which inhibited the IFE and resulted in the fading of solution color and the recovery of the fluorescence signal.