Utilising the interface interaction on tris(hydroxymethy)aminomethane-capped carbon dots to enhance the sensitivity and selectivity towards the detection of Co(II) ions

Abstract

In this paper, a facile and green thermal carbonisation approach was adopted for the synthesis of carbon dots (CDs) from α-cellulose. The conditions during the synthesis have been optimised to produce CDs with highest fluorescence intensity. Later, tris(hydroxymethy)aminomethane (TRIS) was introduced to the isolated CDs as capping agent on the interface of the CDs. TRIS was chosen due to the well reported capability to interact with various metal ions to form complexes. Particularly in this study, TRIS has enhanced the specificity and sensitivity features of CDs to detect cobalt (II) ions, (Co(II) ions). The UV–vis absorption spectroscopy study performed has found that the CDs can effectively interact with TRIS, while the assembled CDs/TRIS system later can form complex with Co(II) ions. In this case, TRIS has acted as the bridge to bring CDs and Co(II) ions to a close proximity in distance, which subsequently promoted the energy transfer due to the good overlapping in the emission of the CDs with the absorbance of the Co(II) ions. The process was observed clearly by the concentration dependent fluorescence quenching in the presence of increasing amount of Co(II) ions. This has been demonstrated for the first time and the system has been suggested to be used as a single shot detection probe for Co(II) ions in aqueous media. The probe was found to be effective for the detection of Co(II) ions with a linear response up to 1.87 mM and a limit of detection of 16.84 μM. This study has presented some new insights on the surface interface interaction between CDs and its capping agent and demonstrated its potential application for metal ions sensing.