Mg/S@g-C3N4 nanosheets: A promising fluorescence sensor for selective Cu2+ detection in water

This work describes the development of a novel fluorescence sensor based on magnesium/S@g-
C3N4 nanosheets for selective detection of copper (Cu2+) ions in water. Mg/S@g-C3N4 nanosheets
were prepared by the polycondensation technique and investigated by X-ray diffraction (XRD),
ATR-FTIR spectroscopy, scanning electron microscopy (SEM), surface area (BET), and UV–Vis
optical absorption measurements. XRD and ATR-FTIR analysis showed the characteristic peaks for
S@g-C3N4. The broad full width at half maximum (0.056 radians) implies a smaller crystallite
size, representing smaller Mg/S@g-C3N4 sheets. SEM micrograph showed non-exfoliated nanosheets
with flake-like structures. The EDS mapping confirmed the presence of magnesium, carbon,
nitrogen, and sulfur throughout the nanosheets. The Mg/S@g-C3N4 nanosheets possess a high
surface area of 40 m2/g and mesopores within the nanosheets, with a size of 1.57 nm. The band
gap of the Mg/S@g-C3N4 nanosheet was estimated to be 3.0 eV. The sensor exhibits a strong
quenching response towards Cu2+ ions, with a decrease in fluorescence intensity as the concentration
of Cu2+ increased from 1 μM to 20 μM. The Stern-Volmer quenching constant (KSV)
showed a relatively high value of 185053 M􀀀 1. The estimated value of LOD by the Mg/S@g-C3N4
sensor for Cu2+ was 16.2 nM. The sensor offered high sensitivity and selectivity for Cu2+
detection over other heavy metals.