A straightforward and simpler use of an age-old technique was utilized for the fabrication of “red-emitting magnesium-nitrogen-embedded carbon dots” (r-Mg-N-CD) from the leaves extract of Bougainvillea plant as a natural source of carbon. This technique is similar to the solvent-based technique, which is used for the extraction of fragrances and essential oils from flowers and leaves. The as-derived leaves extract was further carbonized using a simple domestic microwave to obtain the small-sized red-emitting carbonaceous material as r-Mg-N-CD. The r-Mg-N-CD showed excitation independent emissions at ∼678 nm with excellent photostability and a high quantum yield value (∼40%). Moreover,the important perspective of the present finding is to use this r-Mg-N-CD as a potential photocatalyst material for the degradation of pollutant dye (methylene blue) under the presence of sunlight. To infer the significant influence of using natural sunlight in the process of dye degradation, a comparative analysis was performed, demonstrating the higher rate of photo degradation (∼6 times faster) under the influence of sunlight compared to the artificial visible-light from a 100 W tungsten bulb.
The present finding describes here discusses the possibilities for fabricating low-cost, high-quantum-yield, red-emitting r-Mg-NCD in an environment-friendly (without using any externally added chemical reagent). Red-emitting r-Mg-N-CD was used as a novel photocatalytic material for the aqueous phase photodegradation of MB under the presence sunlight. The vast potential of sunlight explored was compared with an artificial tungsten bulb by the use of r-Mg-N-CD, which showed many folds of increase in the rate of photodegradation under the influence of sunlight. Higher in value of quantum yield, solubility in aqueous media, and emission in the red wavelength region along with the ability to photodegrade the pollutant dyes within the ∼120 min of sunlight irradiation, makes r-Mg-N-CD a potential nanomaterial for its applications in the field of aqueous-phase photodegradation. As well, the embedded Mg can also been replaced from some other metal for enhancing its optical properties.

Multilayer structures based on matrices of CdSe and CdSe/ZnS nanoparticles in polyimide (PI) and poly[2-methoxy- 5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) were prepared and investigated. A comparison of photoluminescence of the various matrices excited by visible and ultraviolet laser radiation was carried out. The main contribution to the photoluminescence was made by the organic semiconductors. Quantum yield of the luminescence of CdSe nanoparticles embedded in organic semiconductor matrix was found to be lower then that of the individual CdSe nanoparticles dispersed onto a glass substrate. This difference was shown to be a result of charge transfer from the nanoparticles to organic molecules. The nanoparticles were responsible for photovoltage in thin layers of the PI/nanoparticles composites. Processing of a surface of electrodes and organic semiconductors by oxygen plasma increased the photovoltaic efficiency.

Solid thin films of CdSe and CdSe/ZnS nanoparticles on different templates have been investigated under influence of power visible laser radiation. Composite structures including organic semiconductors and CdSe and CdSe/ZnS nanoparticles films have been fabricated. Luminescent and electron properties of the structures have been investigated. Luminescence quantum yield of these nanocomposite structures is shown to exceed that of the films of organic dyes by two orders of magnitude for CdSe nanoparticles with ZnS shell. As for quantum dots without the shell their luminescence quantum yield appears to fall drastically in the films and even in the matrices of organic semiconductors compared to the solution. The presence of CdSe films in multi-layer structures of polyimides leads to abrupt increase in their conductivity by several orders of magnitude. The prospects of development of photovoltaic elements and light-emitting devices including the films with high concentration of CdSe and CdSe/ZnS quantum dots are discussed.