Carbon dots and carbon dots-based nanocomposites have found a myriad of technological applications. Despite the primary use of carbon dots as catalysts in the reduction process to form metal nanoparticles, their strong interaction with metal nanostructures in nanocomposites can be further exploited. By tuning the emission of carbon dots and the absorption band of metal nanoparticles, it is possible to reach adequate surface-enhanced Raman scattering (SERS) from the resulting nanocomposites. Herein, it is reported the state-of-art in metal/carbon dots nanocomposites applied as active elements for SERS devices in the detection of traces of analytes. Strategies of synthesis, morphology (aggregation and anti-aggregation methods) and the improvement in the homogeneous distribution of noble metal nanoparticles on substrates have been discussed to reach the best performance for highly efficient SERS devices.
The required treatment and monitoring of contaminants in wastewater reinforces the development of low-cost adsorbents/ chemosensors, introducing advantages relative to the detection/removal of toxic metals and dyes. Herein, it is reported a two-step process of fabrication of fluorescent carbon dots via the hydrothermal treatment of amino acids for the following encapsulation in electrospun fibers. The prominent anionic behavior of electrospun fibers of Eudragit L100 was explored for adsorption of cationic dyes (methylene blue and crystal violet)-with the prevailing electrostatic interaction of parts being favored by the formation of monolayers on the surface of adsorbents. On the other hand, the controlled release of carbon dots (CDs) from fibers to the reactor can be explored for a second application: the nitrogen ligands from released glycinebased carbon dots can be explored to indicate the presence of metal ions in aqueous solution. Our experiment resulted in a quenching in the fluorescence of the CDs in order of 90% in the emission of particles in the response of the presence of Fe 3+ ions, characterizing a promising perspective for this experimental system.
The development of composites with antibacterial activity represents an important strategy to avoid side effects such as increasing bacterial resistance to antibiotics. In particular, the green synthesis of metal nanoparticles avoids the use of hazardous chemical compounds and introduces the intrinsic beneficial properties of plant-derived compounds. Herein, the reduction of gold salt into metal nanoparticles was provided by the action of a cationic polymer derived from tannin (Tanfloc®). Comparative activity of antibacterial agents (pure Tanfloc and Au NPs—Tanfloc) at different concentrations were evaluated in terms of the antibiofilm activity, kill-time assays and inhibition haloes confirming the antibacterial activity of the Tanfloc that is reinforced by the incorporation of reduced gold nanoparticles, resulting in the complete elimination of S. aureus from an initial concentration of 108 CFU/mL after 120 min of reaction of Au NPs + Tanfloc solution in association with strong inhibition of the biofilm formation attributed to the Tanfloc.
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