Applications of N-Doped Carbon Dots as Antimicrobial Agents, Antibiotic Carriers, and Selective Fluorescent Probes for Nitro Explosives

Abstract

The synthesis of nitrogen-doped carbon dots (N@CDs) was accomplished by a hydrothermal process using <i>meta</i>- phenylenediamine as a source of carbon and nitrogen. As prepared N@CDs exhibited bright blue color fluorescence emission (λ_ex = 340 nm and λ_em = 420 nm) with a quantum yield of 12%. Gram-negative <i>Escherichia coli</i> and Gram-positive <i>Staphylococcus aureus</i> were eradicated by N@CDs with a minimum inhibition concentration (MIC) of 1 and 0.75 mg/mL, respectively. The N@CDs were also proven as nanovesicles for drug molecules where the drug release displayed a sustained time-dependent profile at the physiological condition. The release of ciprofloxacin as a model drug was governed by the Korsmeyer-Peppas model, indicating ∼60% of its release from the N@CD conjugated drug system at the physiological pH. Selective analysis of trinitrophenol (TNP), a popular explosive, was achieved by fluorescence quenching of N@CDs, compared favorably with other nitrophenols. An estimated detection limit of TNP was 2.45 μM with a linear response spanning from 1 to 75 μM.