Simple and cheap preparation of fluorescence paper sensor based in carbon dot for visual detection of chloramphenicol

Carbon dots (CDs) are nanometer-scale particles produced from carbon sources that exhibit fluorescence emission. The present work presents the synthesis and characterization of CDs, as well as the sensing studies for the determination of chloramphenicol (CAP). CAP is an antibiotic used in human medicine and agriculture, and its indiscriminate use and inappropriate disposal have caused damage to human health and the environment. The carbonaceous precursor used in the synthesis of CDs was 3,4-diaminobenzoic acid (3,4-DABA) through the hydrothermal method via domestic microwave irradiation. The first synthesis procedure was carried out in the presence of water/ethanol (a-CDs) and the second in the presence of 1 mol/L sodium hydroxide/ethanol (b-CDs). The CDs were initially characterized in terms of spectroscopic properties in the ultraviolet and visible region (UV-visible), Fourier-transform infrared (FTIR) spectra, Raman spectroscopy, and fluorescence emission spectroscopy. Sensing studies for the antibiotic C were performed by fluorescence suppression in the presence of a- and b-CDs, as well as the precursor 3,4-DABA. The a- and b-CDs presented similar values of linear range 0.00080-0.0050 mg/ml and limit of detection (LOD) = 0.00030 mg/ml (0.30 ppm) for CAP. Then, a- and b-CDs were embedded in Whatman and Mellita® filter paper, and CAP sensing was evaluated through UV light excitation.