Abstract:
Carbon Quantum Dots (CDs) owing to its unique photophysical properties have attracted immense
consideration of the researchers in last decade to explore its applications in the fields of bio-imaging and
sensing. In the present work, we have developed a novel CDs functionalized with Calix[4]arene derivative
by hydrothermal route to detect biologically pertinent Zn2þ ions. Surface modification of CDs enhances
fluorescence efficiency apart from introducing active surface sites broadening its sensor
capabilities. The obtained surface-functionalized CDs exhibits a strong blue fluorescence under UV light
(365 nm) with a quantum yield (F) of 56% which is appreciably good. Zn2þ ions get apprehended in the
cavity formed due to passivation by Calix[4]arene moeity on the exterior of CDs having profuse eNH2
groups. Addition of Zn2þ ions into the solution of CDs results in remarkable enhancement in the fluorescence
intensity attributed to Photo-induced Electron Transfer (PET) “OFF” phenomenon. The CDs
based nanosensor exhibited a wide linear response with a detection limit of 7.34 nM. Significantly, CDs
were shown to display insignificant cytotoxicity, decent biocompatibility, and virtuous resistance to
photo-bleaching, good stability over a wide range of pH, insignificant variation in the emission intensity
in the presence of high concentration of salt and excellent bio-labeling ability when tested on E. coli cell
lines. Additionally, the detection results of Zn2þ ions obtained in real samples were in complete.
