Silicon dioxide quantum dots anchored on the surface of carbon nanodiscs as photoluminescent probe for Cr(VI) detection

Abstract

Photoluminescent nanomaterials are emerging as excellent probe for detection of wide range of analytes at trace concentrations. Silicon dioxide (SiO2) are not widely explored as photoluminescent probes for metal ion sensing. Here, silicon dioxide quantum dots anchored on the surface of carbon nanodisc (SiO2-QDs@CND) has been developed as a probe for quantitative detection of micromolar concentrations of Cr(VI), via photoluminescence quenching. SiO2-QDs@CND is synthesized via hydrothermal route by controlled heating of 3-Aminopropytriethoxysilane (APTES) and trisodium citrate dihydrate (as a reducing agent and as a carbon matrix) at 170 °C for 12 h, which resulted in formation of 3–10 nm sized nanoocrystalline SiO2-QDs, measured by transmission electron microscopy. The structural, morphological, compositional and optical characteristics of the probe have been studied. The probe exhibited bright bluish photoluminescence corresponding to an emission wavelength of 440 nm with photoluminescence quantum yield of 23.1 %. The pH and contact time optimized SiO2-QDs@CND exhibited a linear Stern-Volmer quenching by Cr(VI) whose concentrations ranged between 1 and 75 μM. The probe exhibited high selectivity towards Cr(VI) detection, confirmed against several relevant cations and anions as interfering agents. The limit of detection is determined as 0.78 ± 0.01 μM. The suitability of the probe towards measurement of Cr(VI) in real water samples is demonstrated through recovery analysis of spiked samples. Experimental evidences suggested that the PL quenching mechanism is predominantly due to complexation between the probe and Cr(VI) in the ground state, along with a minor contribution of inner filter effect.