Evaluation of phthalic acid tri-ethylene diamine (TED) and folic acid-based carbon quantum dots for the detection of heavy metals in water resources using fibre-optic instrumentation

Fiber-Optic Detection of Aluminum and Copper in Real Water Samples Using Enzyme–Carbon Quantum Dot (CQD)-Based Thin-Film Biosensors

“…CLSM analysis was performed to evaluate the distribution of CQD fluorophores in CQD-loaded thin films; it was found that thin films of CQDs show an even distribution of fluorophores throughout the thin-film area with uniform fluorescence (Figure E). All characterizations of the CQD-loaded thin films were similar to those of bare CQDs in our previous study, indicating that all characteristic properties of the CQDs were retained in the thin films without any interference or quenching. The functional groups were studied using FTIR spectroscopy, and −OH, –NH stretching peaks occurred at 3400–3300 cm –1 , which are present in both folic acid and chitosan polymers.…”

“…At basic pH, the OH – ions existing/produced in the environment lead to greater ionization of CQDs, causing increased fluorescence emission. The pH-sensitive properties of folic acid CQDs are also described in previously published research . The CQD-loaded thin film also has the capability to exhibit different fluorescence responses with varying pH in the range of 3–10 (Figure B).…”

“…TEM analysis was performed for the morphological characterization of bare CQDs, and it was observed that CQDs of folic acid have a monodisperse distribution with a size range of 9 ± 3 nm (Figure A). Folic acid-based quantum dots will also result in biocompatible and biodegradable nanomaterials for biosensor development . UV–visible spectrophotometer-based characterization of folic acid CQDs showed the maximum absorption at λ max = 365 nm.…”

“…The crystalline and lattice characterization of CQDs in thin films was carried out through X-ray diffraction (XRD), which shows a peak around 23.6 °2θ, indicating the (002) plane, with a 0.36 nm d -spacing (Figure D). The CQD characteristic peak in XRD occurred at a 2θ value in the range of 22–27° . CLSM analysis was performed to evaluate the distribution of CQD fluorophores in CQD-loaded thin films; it was found that thin films of CQDs show an even distribution of fluorophores throughout the thin-film area with uniform fluorescence (Figure E).…”

Chemical sensor thin film-based carbon quantum dots (CQDs) for the detection of heavy metal count in various water matrices

“…The reason behind the selection of folic acid-based CQDs is that these CQDs have high sensitivity and accuracy as compared with those of other CQDs based on the quenching mechanisms found in previous reports. 27 The CQD containing thin films were characterized by different elemental, structural, optical, and morphological properties. The synthesized CQD-based thin film sensors were evaluated for the detection of heavy metals and consequently various analytical parameters, such as sensitivity, accuracy, limit of detection, resolution, and response time.…”