Continuous Hydrothermal Flow Synthesis of Blue-Luminescent, Excitation-Independent N-doped Carbon Quantum Dots as Nanosensors

Baragau, Ioan-Alexandru; Power, Nicholas; Morgan, David John; Heil, Tobias; Lobo, Richard Alvares; Roberts, Christopher S.; Titirici, Magdalena; Dunn, Steve and Kellici, Suela (2020). Continuous Hydrothermal Flow Synthesis of Blue-Luminescent, Excitation-Independent N-doped Carbon Quantum Dots as Nanosensors. Journal of Materials Chemistry A, 8(6), article no. 3270.

DOI: https://doi.org/10.1039/C9TA11781D

Abstract

Blue-luminescent N-doped carbon quantum dots (NCQDs) exhibiting rarely observed excitation independent optical properties are synthesised from citric acid in the presence of ammonia via a Continuous Hydrothermal Flow Synthesis (CHFS) approach. CHFS is an eco-friendly, rapid synthetic approach (within fractions of a second) facilitating ease of scale-up industrialization as well as offering materials with superior properties. The synthesised CQDs readily disperse in aqueous solution, have an average particle size of 3.3 ± 0.7 nm, with highest emission intensity at 441 nm (and a narrow full width at half maximum, FWHM ~78 nm) under a 360 nm excitation wavelength. Carbon quantum dots, without any further modification, exhibited a high selectivity and sensitivity as a nano-sensor for the highly toxic and carcinogenic chromium(VI) ions. The nano-chemo-sensor delivers significant advantages including simplicity of manufacturing via a continuous, cleaner technology (using targeted biomass precursor), high selectivity, sensitivity and fast response leading to potential applications in environmental industry as well photovoltaics, bio-tagging, bio-sensing and beyond.