Microwave-assisted synthesis of carbon dots for "turn-on" fluorometric determination of Hg(II) via aggregation-induced emission

Abstract

A fluorescent probe is presented for sensitive determination of Hg(II). It is based on aggregation induced enhancement effect (AIEE) of carbon dots co-doped with nitrogen and sulfur (N,S-CDs). The N,S-CDs were prepared by a one-pot microwave-assisted method using glycerol as the reaction solvent, and cystine as the source for C, N and S. The resulting CDs are well soluble in water and have a turn-on fluorescence response to Hg(II). The incubation time and ratio of raw materials were optimized. Fluorescence, best measured at excitation/emission wavelengths of 325/385 nm, increases linearly in the 1-75 μM Hg(II) concentration range, and the detection limit is 0.5 μM. The method performed successfully when detecting Hg(II) in spiked tap and lake waters, with recoveries between 92 and 106%. Graphical abstract Schematic presentation of the aggregation induced enhancement of the fluorescence of carbon dots co-doped with nitrogen and sulfur after addition of Hg(II).

Facile Fluorescence “Turn on” Sensing of Lead Ions in Water via Carbon Nanodots Immobilized in Spherical Polyelectrolyte Brushes

“…In principle, in the aggregates, the intramolecular motion is restricted, which block the nonradiative path and activated radiative decay (Wang et al, 2016 ). As shown by the fluorescence emission spectra excited at 410 nm (Figure S2 ), the emission peaks of CAEA-H-PAA brushes slightly blue shifted to a smaller value from 491 to 470 nm, indicating the specific interaction between CAEA-H and PAA brushes (Xu et al, 2018 ).…”

“…Compared with “turn off” sensor based on fluorescence quenching mechanism, “turn on” fluorescence sensors are more desirable due to the high selectivity and wider detection range (Wei et al, 2012 ). Recently, based on aggregation induced emission enhancement (AIEE), a novel class of fluorescence “turn on” sensors has been proposed (Liu et al, 2016 ; Wang et al, 2016 ; Xu et al, 2018 ). Xu et al ( 2018 ) prepared a fluorescent probe based on AIEE to selectively and sensitively detect Hg 2+ .…”

“…Recently, based on aggregation induced emission enhancement (AIEE), a novel class of fluorescence “turn on” sensors has been proposed (Liu et al, 2016 ; Wang et al, 2016 ; Xu et al, 2018 ). Xu et al ( 2018 ) prepared a fluorescent probe based on AIEE to selectively and sensitively detect Hg 2+ . C-dots were co-doped with nitrogen and sulfur (N, S-CDs).…”

“…In order to optimize the AIEE based “turn on” sensing, it is important to understand the mechanism of the relevant fluorescence enhancing phenomenon. In the previous studies (Wang et al, 2016 ; Xu et al, 2018 ), several characterization methods were chosen to study the mechanism of AIEE: fluorescence emission spectroscopy, X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy, and transmission electron microscope (TEM). However, none of them, except for TEM, could directly confirm the behavior of aggregation of the bonded C-dots complex.…”

“…For most of the C-dots involved fluorescent metal sensors, the sensing mechanism is based on the direct fluorescence quenching between sensors and Metal ions (Liu et al, 2011 ; Wee et al, 2013 ; Luo et al, 2018 ). To the best of our knowledge, only two articles (Wang et al, 2016 ; Xu et al, 2018 ) studied the detection of heavy metals such as Hg 2+ , or Fe 3+ that is based on the AIEE process using C-dots as templates for the AIEE detection of Pb 2+ . Moreover, in our study, SAXS was employed for the first time to prove the specific aggregation behavior between C-dots-SPBs nanoparticles under the presence of Pb 2+ .…”