چكيده به لاتين
Nowadays, the application of nanosensors for the detection of environmental pollutants has received much attention due to their high ability to detect one or more pollutants in low concentrations. Therefore, in this research, five different nanosensors were designed to detect some environmental pollutants. In the first part, a fluorescence sensor based on PbS quantum dots capped with L-methionine (Meth- PbS QDs) was designed for the recognition of As(III) ions. In the presence of As(III), the fluorescence emission of Meth- PbS QDs was effectively quenched. Under optimum conditions, the sensor displayed a linear range from 0.13-2 μM and limit of detection of 0.046 μM. In the second part, a novel “off-on” fluorescent sensor based on silicon dots modified with L-asparagine (N-AsSiDs) has been designed for the detection of Hg(II) and cyanide ions. The fluorescence emission was effectively quenched by Hg(II), while after the addition of cyanide ions, the fluorescence emission intensity of the quenched NR-SiQDs fully recovered. The linear response ranges were 0.2-10 μM for Hg(II) and 0.5-25 μM for cyanide. Moreover, the detection limits were found to be 0.053 µM and 0.46 μM for Hg(II) and cyanide, respectively. In the third part, a ratiometric fluorescent sensor was designed for the detection of cyanide ions by the electrostatic attraction between silicon dots and silver sulfide quantum. In the presence of cyanide, the fluorescence of Ag2S QDs was remarkably quenched. Under optimal conditions, the ratiometric fluorescence assay showed a linear response to cyanide in the range of the concentration 0.2-15 μM with a limit of detection of 0.056 µM. In the fourth section, a ratiometric fluorescence sensor was fabricated based on MnO2 nanosheets, silicon dots, and o-phenylenediamine (OPD) for sulfide detection. In this system, the MnO2 nanosheets play two different roles, i.e., fluorescence quencher of the silicon dots, and oxidizing of OPD to product a fluorescence substance 2, 3-diaminophenazine (OPDox). Upon the addition of sulfide, the fluorescence of OPDox was quenched, whereas the fluorescence of silicon dots was restored. Under optimal conditions, the linear response was obtained over the range 2-20 μM with the low detection limit of 0.31 μM. In the fifth section, a smartphone-based colorimetric sensor was designed using gold nanoparticles modified with histidine and asparagine to detect Hg(II) ions. Under optimal conditions, a linear relationship was noticed between the colorimetric response of the sensor and the Hg(II) concentration in the range of 0.3-20 μM with a detection limit of 0.09 µM.
