Highly crystalline and aromatic nitrogen-doped graphene quantum dots (N-GQDs) which demonstrate unparalleled electrochemical sensing properties toward nitroaromatics were made from a single source, polyaniline (PANI), by a simple hydrothermal synthetic strategy. The higher sensitivity and the effective differentiation between different nitro compounds exhibited by the N-GQD is evidence of its potential as a sensor for nitro compounds, especially the nitroaromatics. The N-GQD modified glassy carbon electrode (N-GQD/GCE) exhibited record sensitivity for 2,4,6-trinitrophenol (TNP) with a limit of detection (LOD) as low as 0.2 ppb (∼200 ng/l or 1 nM), which is the lowest of the reported values, the previous lowest is in micromolar (μM) levels and extended the remarkable sensing property in real water samples as well. The superior and selective sensing behavior of N-GQD toward TNP and other nitroaromatics is assigned to the richly N-doped aromatic structure of the N-GQD from the precursor PANI, which can possibly promote closer and selective molecular interactions with nitroaromatic compounds through ring stacking, π–π, or hydrogen bonding or a combination of these, and the enhanced conductivity and improved electron transfer ability due to the in situ N-doping.

Herein, a graphene-nano-molybdenum disulphide (pGr-MoS2), synthesized from pulverized graphite and using precursors of MoS2, was investigated for the electrochemical sensing of dihydroxy benzene isomers (DHBI): hydroquinone (HQ), catechol (CA), and...

A sulfur co-doped nitrogen-graphene quantum dot (S,N-GQD) was synthesized from polyaniline using sulfuric acid as an acid catalyst and S-doping agent. Thus, through a simple hydrothermal synthesis method, we could achieve nanosized (∼4 nm) highly crystalline and aromatic S,N-GQDs. The S,N-GQDs, for the first time, exhibited simultaneous sensing toward three of the top 10 toxic metal ions: Cd(II), Pb(II), and Hg(II) with highly sharp peaks and adequate peak-to-peak separation, while the control N-GQD (no S co-doping) exhibited current response only for Cd(II) and the current response of Cd(II) on S,N-GQD was ∼7-fold higher than that of on N-GQD. The detection limit values were lowest hitherto for Cd(II), Pb(II), and Hg(II) on S,N-GQD with 1, 10, and 1 pM, respectively, for the simultaneous sensing of the metal ions. The significantly enhanced sensitivity compared to that of N-GQD for Cd(II) and the versatile simultaneous sensing capability of S,N-GQD is assigned to the co-doping with S, which enabled the sensing of Pb(II) and Hg(II) through the M(II)–S interactions and the enhanced electronic properties, respectively. The sensing characteristics were effectively stretched to actual environmental water samples such as groundwater, seawater, and wastewater, spiked with Cd(II), Pb(II), and Hg(II), and accomplished ∼100% recovery in all the tested samples with a relative standard deviation of ≤0.5%.

Pb(II) and Cd(II) are featured in the World Health Organization's (WHO) top 10 list of chemicals of primary public health concern, and their wide use in industries and the acute and chronic effects on humans and the environment make the detection and determination of the ions in environmental and drinking water samples indispensable. This work reports a detailed study on a partially reduced graphene oxide-nano molybdenum disulfide-modified glassy carbon electrode (prGO-MoS 2 /GCE), which exhibited the simultaneous and selective electrochemical detection of Pb(II) and Cd(II) in drinking water with a 200-and 100-fold increase in the current response, respectively, compared to that on the unmodified GCE. prGO-MoS 2 showed almost nil current response for other metal ions such as Hg(II), Ag(I), Fe(II), Co(II), Ni(II), Zn(II), Sn(II), Cu(II), and Cr(VI), evident to the good selectivity toward Pb(II) and Cd(II). The lowest limit of detection (LOD) values were ∼0.0002 and 0.1 ppt, which are very well below the ≤10 and 5 ppb specified as safe for Pb(II) and Cd(II), respectively. The exemplary sensing behavior of prGO-MoS 2 /GCE toward Pb(II) and Cd(II) shall be assigned to the structure of prGO-MoS 2 and the bonding of MoS 2 to prGO, thus promoting the electrochemistry mechanism in addition to the affinity.

A highly stable copper nanocluster CuNC@N-GQD which exhibited stability for more than one year was synthesized using nitrogen doped graphene quantum dots (N-GQDs) as reducing and capping agents and smaller...