Nanoconfinement – amplified, Förster resonance energy transfer in nile red – borne mesoporous silica for ultrasensitive, multiplex assay of triphenylmethane dyes in aqueous milieu

Abstract

In this work, lipophilic Nile red (NR) was loaded into the mesopores of MCM-41 particles via hydrogen bonding-driven adsorption in organic media, and the resulting NR-borne MCM-41 particles were harnessed as mesoporous luminescent donors to detect hydrophilic triphenylmethane (TPM) dyes in aqueous media based on NR-to-TPM Förster resonance energy transfer (FRET). This new approach enabled us to determine the TPM concentration ranging from ca. 1 μmol L⁻¹ to ca. 1 nmol L⁻¹ with the detection limit at the level of 0.1 nmol L⁻¹ (0.1 ppb) as a result of about 1000-fold enrichment of the TPM dyes in the NR-borne MCM-41 mesopores thanks to nanoconfinement. The TPM-induced fluorescence quenching constant of NR-borne MCM-41 particles, obtained according to the Stern–Volmer relationship, was empirically connected with their NR uptake in a log-linear manner, the slope of which enabled one to identify the molecular nature of TPM dyes. Furthermore, a rough-and-read protocol of image analysis and processing was developed to convert the fluorescence images of microtiter plates with wells filled with NR-borne MCM-41 particles and aqueous TPM solutions into the multiplex, FRET-encoded matrices, which enabled us to simultaneously realize molecular identification of the targeted TPM analytes and sub-ppb-level determination of their concentrations.