Functional carbon dots-hydrogel complex for selective antibacterial and detection applications

The carbon dots (CDs) with excellent optical properties and their hydrogel complex are of great significance in biomedicine, healthcare and biochemical detection fields. This paper reports the preparation of green-emitting CDs (MA-CDs) through one-step hydrothermal route with citric acid as reducing agent, L-malic acid as carbon source and N-(2-hydroxyethyl)ethylenediamine as nitrogen source. To expand its application in biology, MA-CDs were coupled with vancomycin to obtain multifunctional CDs (VMA-CDs). The prepared VMA-CDs exhibit selective antibacterial behavior to Gram-positive bacteria, and it could be used as a fluorescent probe to selectively label Staphylococcus aureus (S. aureus). Moreover, thanks to the excellent optical properties of VMA-CDs, it has been used as a fluorescent sensor to detect Au³⁺ with detection range of 6.50 nM-21.93 μM and detection limit 3.98 nM. By introducing the fluorescence of CDs as the reference signal, and VMA-CDs as a response signal, the hydrogel (V-SP) was prepared and realized the detection of Au³⁺ in microfluidics with assistance of a smartphone to collect and analyze data.