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Carbon dots (CDs) are class of carbon based nanomaterials with excellent optical properties. However, in solid state the fluorescence of CDs is not observed due to aggregation-caused quenching effect. Herein, we present a facile thermal method for preparing solid state yellow emissive nitrogen doped carbon dots (N-CDs) using organic solvents, ethanolamine and acrylonitrile as the precursors without further surface passivation. In addition, N-CDs aqueous dispersion exhibits tunable blue to green emission, while acetone dispersion show yellow emission. Moreover, the aqueous dispersion of N-CDs is employed for detecting picric acid selectively by fluorescence quenching mode based on inner filter effect. A good linearity is observed in the range from 0 to 45 μM, with a detection limit of 1.17 μM. The method is successfully applied for determination of picric acid in environmental samples.

Materials having long afterglow are highly sought after for various applications such as light-emitting diodes, security signs and bioimaging. Herein, we report a simple, low-cost synthesis of a purely organic room-temperature phosphorescent nanomaterial with a pebble-like structure by heating urea, a biocompatible and easily available precursor, at 200 °C with a high phosphorescence lifetime of 1.0365 s and a visible afterglow for up to 10 s. This urea derived phosphorescent nanocomposite (UPNC) can be mixed with commercially available acrylic paint base and common gum, which can be readily used as a phosphorescent pigment.

Different metal ions and anions are crucial for the life of organisms, but their excessive intake or deficiency cause various physiological abnormalities or diseases. Toxic metal ions such as Hg2+, Cr6+, Cd2+, explosive nitroaromatic compounds, and volatile organic compounds are widely used in agriculture, rocket fuels, and industry, but they cause severe effects on human health and environmental change. Hence, sensing and identification of these analytes are important for life, health, and environment protection. Recently, metal-organic frameworks (MOFs) have been extensively explored as luminescent sensors due to their unique crystallinity, structural diversity, tunable porosity, and functional groups. This chapter reviewed the origin of luminescent of MOFs and its applications as luminescent sensors for detecting different environmentally toxic analytes such as metal ions, anions, nitroexplosives, and volatile organic compounds. In addition, the detection mechanism of MOFs and its structural dependent properties are also illustrated.

Carbon nitride materials have become highly explored carbon based nanomaterials since their rediscovery in the 1990s due to their semiconductor like behavior. Here, we report a facile one pot synthesis of sulfur and oxygen doped carbon nitride quantum dots (SCNQDs) from thiourea and ethylenediaminetetraacetic acid disodium salt by a thermal method. The SCNQDs prepared are characterized by UV–visible, FT-IR, X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction, and transmission electron microscopy (TEM) imaging. We have demonstrated the Hg2+ sensing ability of SCNQDs in solution as well as in the solid phase, i.e. SCNQDs loaded onto filter paper. The Hg2+ sensing capability of the SCNQDs in the solution phase is the same for Hg2+ ion in double distilled water as well as in tap water, which gives the method a practical applicability in real conditions. The sensitivity of SCNQDs with Hg2+ follows a linear relationship in the range from 10 nM to 1 μM. The minimum detection limit is found to be 0.0...