Solvatochromic Effects in Absorption and Luminescence Spectra and Stability of the Emission Quantum Yield of Carbon Nanoparticles: Part II

We studied and analyzed the spectroscopic features of the solvatochromic effects of absorption and luminescence bands and the parameters of the emission quantum yield ( QYE ) of protic and aprotic solutions of carbon nanoparticles (CNPs) synthesized by microwave radiation from a mixture of citric acid and urea. The quantum yield of particle emission has an exponential dependence on the polarity and the sum of the acidity and basicity of solvents. Hydrogen bonding and the interaction of particles with electromagnetic radiation affect the parameters of solvatochromic effects of absorption and luminescence bands and the emission quantum yield of nanoparticles. Within the framework of the Lippert–Mataga, Bilot–Kawski, Liptay, McRae, Kamlet–Taft, and Catalan models and by linear regression analysis, we found that the solvatochromic effects of carbon nanoparticles, in addition to universal interactions, also largely depend on specific interactions. An increase in the polarity and the sum of the acidity and basicity of the solvents creates a hypsochromic shift of the absorption band at 410 nm and a bathochromic shift of the green luminescence band of carbon nanoparticles. The optical centers of green emission are localized on the surfaces of the particles. A model of the energy levels of the centers of green emission of particles is proposed. The dipole moment of the excitation state of the centers is greater than the dipole moment of the ground state.