To prepare carbon-based fluorescent materials such as graphene quantum dots (GQDs), new and effective methods are needed to convert one-dimensional (1D) or two-dimensional (2D) carbon materials to 0D GQDs. Here, we report a novel acid-free and oxone oxidant-assisted solvothermal synthesis of GQDs using various natural carbon resources including graphite (G), multiwall carbon nanotubes (M), carbon fibers (CF), and charcoal (C). This acid-free method, not requiring the neutralization process of strong acids, exhibits a simple and eco-friendly purification process and also represents a recycling production process, together with mass production and high yield. Newly synthesized GQDs exhibited a strong blue photoluminescence (PL) under 365 nm UV light illumination. The PL emission peaks of all the recycled GQDs did not change.
Facile synthesis of graphene quantum dots using an acid-free oxone oxidant and graphene oxide was successfully developed by sono- and photo-oxidation reactions.
In
this study, we report a one-step direct synthesis of molybdenum
disulfide (MoS2) and tungsten disulfide (WS2) quantum dots (QDs) through a solvothermal reaction using only alcohol
solvents and efficient Escherichia coli (E. coli) decompositions as photocatalytic antibacterial
agents under visible light irradiation. The solvothermal reaction
gives the scission of molybdenum–sulfur (Mo–S) and tungsten–sulfur
(W–S) bonding during the synthesis of MoS2 and WS2 QDs. Using only alcohol solvent does not require a residue
purification process necessary for metal intercalation. As the number
of the CH3 groups of alcohol solvents among ethyl, isopropyl,
and tert(t)-butyl alcohols increases,
the dispersibility of MoS2/WS2 increases. The
CH3 groups of alcohols minimize the surface energy, leading
to the effective exfoliation and disintegration of the bulk under
heat and pressure. The bulky t-butyl alcohol with
the highest number of methyl groups shows the highest exfoliation
and yield. MoS2 QDs with a lateral size of about 2.5 nm
and WS2 QDs of about 10 nm are prepared, exhibiting a strong
blue luminescence under 365 nm ultraviolet (UV) light irradiation.
Their heights are 0.68–3 and 0.72–5 nm, corresponding
to a few layers of MoS2 and WS2, respectively.
They offer a highly efficient performance in sterilizing E.
coli as the visible-light-driven photocatalyst.
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