Highly fluorescent nitrogen-doped carbon dots derived from Phyllanthus acidus utilized as a fluorescent probe for label-free selective detection of Fe3+ ions, live cell imaging and fluorescent ink

•FNCDs was successfully synthesized using Phyllanthus acidus by hydrothermal method.•First time, durable FNCDs was derived from the P. acidus fruit juice with QY of 14%.•FNCDs were used as a fluorescent probe for lable-free selective detection of Fe3+.•FNCDs can be used as a fluorescent ink without any chemical modification.•FNCDs could offer a multi-colour cell imaging and alternative for fluorescent pens.

A facile, economical and one-step hydrothermal method is used to synthesize highly durable fluorescent nitrogen-doped carbon dots (FNCDs) by utilizing Phyllanthus acidus (P. acidus) and aqueous ammonia as the carbon and nitrogen sources, respectively. The synthesized FNCDs have an average size of 4.5±1 nm and showed bright blue fluorescence under the irradiation of UV-light at an excitation wavelength of 365 nm. It exhibits a quantum yield (QY) of 14% at an excitation wavelength of 350 nm with maximum emission at 420 nm. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy characterizations clearly showed the formation of FNCDs that predominantly consists of nitrogen and hydroxyl groups which can provide more adsorption sites. In addition, the above study reveals the successful bonding of nitrogen with carbon (C-N) in the FNCDs. The synthesized FNCDs with high QY can be used as efficient fluorescent probes for the detection of Fe3+. Based on the linear relationship between normalized fluorescence intensity and concentration of Fe3+ ions, the prepared FNCDs can be used for label-free sensitive and selective detection of Fe3+ ions in a wide concentration range of 2-25 μM with a detection limit of 0.9 μM. The present study proves that synthesized FNCDs has durable fluorescence, soluble in water very well and thus act as a promising candidate for the diverse applications such as label-free sensitive and selective detection of Fe3+, fluorescent ink and cellular imaging with good biocompatibility and low cytotoxicity.

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