Citrus reticulata Derived Carbon Dots for Selective Fluorimetric Sensing of Fe3+ in Water for Environmental Monitoring

Abstract

Carboneous nanomaterials derived from natural sources are being used as chemosensors due to their small size, water solubility, photostability, tunable emission properties, etc. In the present work, highly fluorescent and photostable carbon dots (CDs) having an average size of 11 nm were prepared from Citrus reticulata through a one-step hydrothermal process. CDs emitted a strong green fluorescence under UV light. The prepared CDs were characterized using TEM, XRD, XPS, FTIR, UV–Vis, and fluorescence techniques. Maximum emission intensity of CDs was recorded at 438 nm on excitation at 350 nm. The quantum yield of CDs was 4.4%. CDs selectively detected Fe³⁺ ions colorimetrically through a visual change in color from colorless to yellow. Also, among other metal ions, only Fe³⁺ selectively quenched the emission of CDs. Fluorescence quenching by Fe³⁺ was static in nature and due to the formation of a ground state complex between the metal ion and the surface functionalities on CDs. From the spectroscopic data, it was concluded that CDs can detect Fe³⁺ within the linear range of 6.2–620 μM, and the limit of detection was 1.11 μM. Based on rapid, label-free, and selective detection capabilities, CDs were further used in the analysis of Fe³⁺ in real water samples.