Responsive carbon dot-embedded hybrid microgels for dual sensing of iron(III) and ciprofloxacin.

A novel hybrid material was synthesized through the integration of nitrogen-doped carbon quantum dots (NCQDs) within a cationic poly(-isopropylacrylamide--3-aminopropyl methacrylamide) (PNIPAM--APMH) microgel to create a highly sensitive, selective and multi-responsive system (NCQDs@PNIPAM--APMH) with an impressive quantum yield of 42%. The resultant hybrid microgel was shown to be an exceptional dual-functional sensor for detecting ferric ions (Fe) and ciprofloxacin (CIP). The detection of Fe was marked by a "turn-off" fluorescence response, facilitated by dynamic quenching mechanisms. In contrast, upon the introduction of CIP into the Fe-quenched system (Fe-NCQDs@PNIPAM--APMH), a "turn-on" fluorescence response was observed, with a corresponding LOD of 0.41 μM. A logic gate framework was employed to achieve sequential sensing of Fe and CIP in an "off-on" manner. Furthermore, the material exhibited excellent recovery rates, ranging from 86% to 108%, when applied to the analysis of real samples containing CIP. In addition to its sensing capabilities, the hybrid system was effectively utilized as a fluorescent ink, offering advanced anti-counterfeiting solutions and bolstering information security. This study highlights the substantial potential of NCQD-based hybrid materials in diverse sensing applications and their implications for practical innovations.