Ultratrace Detection of Nickel(II) Ions in Water Samples Using Dimethylglyoxime-Doped GQDs as the Induced Metal Complex Nanoparticles by a Resonance Light Scattering Sensor.

This study aimed to synthesize dimethylglyoxime (DMG) (N-source)-doped graphene quantum dots (N-GQDs) via simultaneous pyrolysis of citric acid and 1.0% (w/v) DMG. The maximum excitation wavelength (λ, ex = 380 nm) of the N-GQD solution (49% quantum yield (QY)) was a red shift with respect to that of bare GQDs (λ, ex = 365 nm) (46% QY); at the same maximum emission wavelength (λ, em = 460 nm), their resonance light scattering (RLS) intensity peak was observed at λ, ex/em = 530/533 nm. FTIR, X-ray photoelectron spectroscopy, XRD, energy-dispersive X-ray spectroscopy, and transmission electron microscopy analyses were performed to examine the synthesized materials. The selective and sensitive detection of Ni using the RLS intensity was performed at 533 nm under the optimum conditions consisting of both 25 mg L N-GQDs and 2.5 mg L DMG in the ammonium buffer solution of pH 9.0. The linearity of Ni was 50.0-200.0 μg L with a regression line, = 5.031 - 190.4 ( = 0.9948). The limit of detection (LOD) and the limit of quantitation (LOQ) were determined to be 20.0 and 60.0 μg L, respectively. The method precision expressed as % RSDs was 4.90 for intraday ( = 3 × 3) and 7.65 for interday ( = 5 × 3). This developed method afforded good recoveries of Ni in a range of 85-108% when spiked with real water samples. Overall, this innovative method illustrated the identification and detection of Ni as a DMG complex with N-GQDs, and the detection was highly sensitive and selective.