Melamine-Formaldehyde Polymer-Based Nanocomposite for Sunlight-Driven Photodegradation of Multiple Dyes and Their Mixture.

Cadmium sulfide (CdS)-decorated, cross-linked melamine-formaldehyde polymer-based nanocomposite (MFP-CdS) has been synthesized. MFP-CdS is utilized here as a photoactive material for the photodegradation of six model organic dyes and their mixture in an aqueous medium in the presence of sunlight. The half-life values from the kinetic study of multiple dyes strongly support the importance of sunlight on the fast degradation of all six dyes compared to bulb light and control (dark) conditions. A comparative 1H NMR analysis of the dyes and their degraded products has been performed to support the breakdown of the aromatic framework of organic dyes using MFP-CdS in sunlight. The mechanisms involved in the photodegradation of dyes have been investigated based on radical trapping studies that support the significant involvement of superoxide radicals along with holes. Moreover, the dye removal efficiency using MFP-CdS from real industrial wastewater samples is evaluated via the external spiking of organic dyes and their mixture in unknown industrial effluents where they showed similar photodegradation results. Based on the high recyclability of MFP-CdS, these are used for multiple cycles.

Non-aqueous onion like nano-carbons from waste diesel-soot used as FRET-based sensor for sensing of nitro-phenols.

Herein, a simple-functionalization method is described to prepare the oleylamine functionalized non-aqueous version of onion-like nanocarbons (ONC-OA), where ONC was isolated from the waste pollutant soot exhausted from the diesel engine. The surface group analysis of ONC-OA has been investigated via Nuclear Magnetic Resonance and X-ray Photoelectron Spectroscopy. ONC-OA shows blue fluorescence with a quantum yield of ∼6% in tetrahydrofuran (THF). The fluorescence-based sensing applications of ONC-OA has been investigated for selective sensing of toxic aromatic nitro-phenols compounds (para-nitro, dinitro, and trinitro phenols) from the tested many nitro organic compounds. Based on the limit of detection values, ONC-OA shows much better results for tri-nitro phenol compared to di and mono nitrophenol. To understand the quenching mechanism, a time-resolved photoluminescence analysis of the sensor with and without the addition of quenchers is performed. The effective lowering in fluorescence lifetime of the sensor after the addition of quenchers concludes that the quenching observed is majorly due to the Förster Resonance Energy Transfer (FRET) mechanism. The real-life application of ONC-OA was analyzed by external spiking of N-PhOHs in soil samples.

Fluorescent Carbon Nano-onion as Bioimaging Probe.

Concentrically arranged multilayered fullerenes exhibiting onion-like morphology are popularly known as carbon nano-onion (CNO) and are useful in bioimaging application. On the basis of the origin of the fluorescence, the CNO-based nanoprobes are classified into type I and type II. The type I CNO-based nanoprobe needs a secondary moiety such as organic dyes or an amine functionalization at its surface to induce the fluorescence. On the other hand, the emission in type II does not originate from such an external surface passivating agent. The CNO-based system not only shows structural similarity to the well-known multiwalled carbon nanotube but is also a bit more advantageous because of its low cytotoxicity. These features enable their prolonged use in the biological system for imaging purposes. In particular, we have covered the aspects of synthesis, surface functionalization, the origin of fluorescence, and biocompatibility. In addition, recent developments directed toward in vitro and in vivo imaging studies by utilizing CNO-based nanoprobes are summarized here.

N, S-codoped Carbon Dots for Nontoxic Cell Imaging and As a Sunlight-Active Photocatalytic Material for the Removal of Chromium.

Nitrogen-sulfur codoped carbon dots (NSCD) were synthesized via a single-step microwave-assisted method having a fluorescence quantum yield of ∼12%. The NSCD has been proven to be nontoxic and utilized as a fluorescent imaging nanoprobe for cancer cells (HeLa cells) under UV and blue light excitation (in vitro environment). In addition to the long-known cell imaging application, these NSCD have been used as a sunlight active photomaterial for the removal of toxic hexavalent chromium as Cr(VI). The experimental results reveal that the sunlight active NSCD shows good potential toward the photocatalytic removal of Cr(VI) ions from the wastewater. For the environment and water purification purpose, three different wastewater samples were tested that are synthetic wastewater (up to 100 ppm), laboratory wastewater, and Cr(VI) ion-spiked industrial wastewater for the photocatalytic removal of Cr(VI). The biocompatible NSCD as a fluorescent imaging probe of cancer cells along with its fruitful utilization in photocatalysis under sunlight (compared to the dark condition) demonstrates the overall sustainability of the presented process.

Pollutant-Soot-Based Nontoxic Water-Soluble Onion-like Nanocarbons for Cell Imaging and Selective Sensing of Toxic Cr(VI).

Presently, the technologies associated with using waste materials for the fabrication of newer useful materials have been greatly advanced. For the same purpose, a possible sustainable approach is described for the utilization of globally available dirty dangerous material, known as black carbon (BC), in the form of particulate diesel soot. From the black diesel particulate matter, onion-like nanocarbons (ONC) have been isolated followed by their surface functionalization to yield their amine-functionalized water-soluble version as ONC-NH2, which exhibits a high quantum yield value of ∼20%. Concerning the synthetic protocol, the potential associated with the presented report reveals that these ONC were used without being explicitly synthesized. These were just isolated from the diesel soot, which on amine functionalization have been converted to an efficient, biocompatible fluorescent probe for the imaging of cancer (HeLa) cells and selective sensing of toxic chromium Cr(VI) in water. The detailed surface functionalization by the amine molecules in ONC-NH2, which make them readily soluble in aqueous media, is investigated using several spectroscopic techniques such as XPS, NMR, and FTIR.