Applications Of Fluorescent Carbon Quantum Dots In Detection

Carbon quantum dots（CQDs）,a new class of environmental friendly nanomaterial,had attracted great interests in bioimaging,optoelectric application and fluorescence detection,especially for the fluorescence detection due to their excellent optical properties.Based on the simple process for preparation of CQDs,excellent optical properties and their applications,this research content is divided into the following three parts:（1）Fluorescent SP-CQDs were prepared using resource-rich and low-cost coal tar medium temperature asphalt（SP）combined with the advantages of ultrasonic stripping and hydrothermal oxidation of H₂O₂,and used to detect Fe³⁺ions.The SP-CQDs exhibited a strong blue emission with a fluorescence quantum yield of up to 30%.The SP-CQDs exhibited a wide linear response concentration range（0.2-40μM）to Fe³⁺ions with a detection limit of 0.1μM.The SP-CQDs had good practicability in real samples and good stability.（2）Herein,a series of AC-CQDs with different sizes were prepared by a facile but effective H₂O₂ oxidative method using activated carbon（AC）as carbon source,and applied to heavy metal Cr³⁺ions detection.TEM and DLS results showed that AC-CQDs had no agglomeration phenomena.FT-IR and XPS results showed that many functional groups such as carboxyl groups and hydroxyl groups on the surface of AC-CQDs with the elements of C,O and N.Moreover,AC-CQDs with different sizes had different fluorescence quenching effect,when the diameter of CQDs was 3.6 nm,and the fluorescent probe exhibited a good linear response to Cr³⁺ions with a detection limit of 0.2μM.The high sensitivity of AC-CQDs for detecting Cr³⁺ions was attributed to the synergistic effect of the surface oxygen-containing functional groups and size of AC-CQDs.（3）The samples（Y-CQDs）were prepared by microwave method using citric acid and urea as source.Compared to Y-CQDs,CU-CQDs of yellowish-green fluorescence with high purity could be used to detect ammonia solution with high sensitivity and selectivity,the detection limit was 1 ppm（0.028μM）.The fluorescence quenching of CU-CQDs was induced by the hydrogen bonds between ammonia and CU-CQDs.The CU-CQDs had obvious fluorescence quenching effect,reducing the influence of other functional groups.