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.
Carbon dots are defined as small carbon nanoparticles with effective surface passivation via organic functionalization. The definition is literally a description of what carbon dots are originally found for the functionalized carbon nanoparticles displaying bright and colorful fluorescence emissions, mirroring those from similarly functionalized defects in carbon nanotubes. In literature more popular than classical carbon dots are the diverse variety of dot samples from “one‐pot” carbonization of organic precursors. On the two different kinds of samples from the different synthetic approaches, namely, the classical carbon dots versus those from the carbonization method, highlighted in this article are their shared properties and apparent divergences, including also explorations of the relevant sample structural and mechanistic origins for the shared properties and divergences. Echoing the growing evidence and concerns in the carbon dots research community on the major presence of organic molecular dyes/chromophores in carbonization produced dot samples, demonstrated and discussed in this article are some representative cases of dominating spectroscopic interferences due to the organic dye contamination that have led to unfound claims and erroneous conclusions. Mitigation strategies to address the contamination issues, including especially the use of more vigorous processing conditions in the carbonization synthesis, are proposed and justified.
Carbon dots (CDots) are small carbon nanoparticles with effective surface passivation by organic functionalization. In the reported work, the surface functionalization of preexisting small carbon nanoparticles with N-ethylcarbazole (NEC) was achieved by the NEC radical addition. Due to the major difference in microwave absorption between the carbon nanoparticles and organic species such as NEC, the nanoparticles could be selectively heated via microwave irradiation to enable the hydrogen abstraction in NEC to generate NEC radicals, followed by in situ additions of the radicals to the nanoparticles. The resulting NEC-CDots were characterized by microscopy and spectroscopy techniques including quantitative proton and 13C NMR methods. The optical spectroscopic properties of the dot sample were found to be largely the same as those of CDots from other organic functionalization schemes. The high structural stability of NEC-CDots benefiting from the radical addition functionalization is highlighted and discussed.
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