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.

Nanosized zinc oxide (ZnO) powders were prepared via DC thermal plasma process from microsized zinc powder while air was employed as a reaction gas. The ZnO nanopowders were characterized by X-ray diffraction, UV-Visible spectrometry, scanning electron microscope and energy dispersive X-ray analysis. The X-ray diffraction analysis of the sample showed the formation of nanopowder with wurtzite ZnO structure. The photocatalytic activities of ZnO powders were evaluated by measuring the degradation of Methylene Blue (MB) in water under the UV region. ZnO nanopowder resisted the growth of tested bacterias.

TiV-oxide photocatalysts were synthesized through sol–gel technique for different Ti:V ratio. They were characterized using XRD, SEM, EDAX, UV-Vis-DRS, photoluminescence, and FTIR studies. The systems with high Ti:V ratio showed a mixed phase while with low ratio a rutile phase. The sizes of the particles were between 20 and 30 nm showing an increase with change in phase from mixed to rutile. The reflectance spectrum showed a red-shift in the optical response covering a large portion of visible spectrum.Interestingly, both mixed and rutile phases showed visible light activity in the photodegradation of methylene blue under laboratory conditions. However,mixed-phase catalyst showed high activity in terms of rate of degradation and photonic efficiency.

Silver sensitized titanium vanadium mixed metal (Ag/TiV) oxides were prepared by nanoscale synthesis route employing the sol–gel technique. It led to the development of 5–20 nm particles with predominantly anatase phase. The physicochemical characterization of the particles was done by X-ray diffractrometry (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), UV–visible diffuse reflectance spectroscopy (UV–Vis DRS) and photoluminescence spectroscopy (PL). The reflectance spectrum shows a red shift in the optical response of the catalyst with its band gap absorption upper limit covering a large portion of the visible spectrum, i.e. labsZ700 nm. The performance of the materials was examined under laboratory visible light and solar radiation exposure. The rate of degradation of methylene blue (MB)and phenol exhibited an increase of about six and four times, respectively, in visible light compared to Degussa P-25. This may be attributed to the increased absorption due to Ti–Vmixed metal oxides, favorable electron transfer in the anatase–rutile mixed phase coupled with silver’s scavenging action and reduced electron–hole recombination thereon.