Carbon nitride dots as a fluorescent probe for highly sensitive and selective detection of pH and nitrite ions

Nitrite ions are widely used as food preservating agents and in fertilizers. pH plays important role in cell biological process. However, excess amount of nitrite ions and irregular pH changes causes environmental problems and various diseases. Hence, monitoring of nitrite ions and pH in living cells as well as in environment is very much essential for early diagnosis of various diseases. Herein, green emissive carbon nitride dots (CNDs) has been synthesized by thermal treatment of urea and trisodium citrate mixture at 220 degrees C. The as synthesized CNDs display excellent fluorescent properties with emission at 505 nm under 360 nm excitation wavelength. The fluorescence of CNDs exhibits stability towards salt concentration while it is sensitive to pH and temperature. Based on the pH sensitivity, CNDs is directly used as fluorescent probe for distinguishing acidic, neutral and basic medium. The fluorescent CNDs also display sensing capability for nitrite ions in aqueous medium with a low limit of detection of 6.52 mu m. The application of CNDs for nitrite ions determination in environmental samples is also demonstrated.