Fluorescent cellulose nanocrystals based on AIE luminogen for rapid detection of Fe³⁺ in aqueous solutions

Previously, we found that aggregation-induced emission (AIE) luminogen tetraphenylethylene (TPE) based fluorescent cellulose nanocrystals (TPE-CNCs) showed excellent AIE-active fluorescence properties and high selectivity and sensitivity for detecting nitrophenol explosives in aqueous solutions. Here, we further develop the application of TPE-CNCs for fluorescence detection of Fe³⁺ in aqueous solutions. The fluorescence of TPE-CNC aqueous suspensions is rapidly quenched (response time less than 10 s) due to the electron-transfer process between TPE and Fe³⁺ upon addition of Fe³⁺. TPE-CNCs have high sensitivity and selectivity toward Fe³⁺ over a broad pH range from 4 to 10. The limit of detection is determined to be 264 nM, which is below the World Health Organization (WHO) recommendations (5.36 μM) for Fe³⁺. Given the superior properties of TPE-CNCs, it has huge potential to be applied as a rapid and visual evaluation tool for drinking water quality. Collectively, we explore and develop fluorescent cellulose nanocrystals for multi-functional applications and TPE-CNCs can be used for practical applications in sensing, sewage treatment and bioimaging.