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Microwave-mediated synthesis of spinel CuAl2O4…
mechanical strength, hydrophobicity, and low surface acidity [9], characteristics
that make them widely applicable in various fields, e.g., as photocatalysts for
degradation of organic pollutants, as magnetic materials, in rechargeable batteries,
for organic transformations, in medicine, and for recycling of nuclear fuel [10–12].
Various methods, including solid-state, co-precipitation, hydrothermal, sono-
chemical, reverse microemulsion, sol–gel reaction, and microwave technique, have
been employed for preparation of CuAl2O4 NCs [13–18]. Among these methods, the
microwave approach is a valuable and attractive technique for preparation of
CuAl2O4 NCs, due to its high reaction rate, short reaction time, high yield, and
selectivity [18]. Also, it produces pure and ultrafine powder at relatively low
temperature because of its different heating mechanism compared with conventional
techniques, opening up prospects for manufacture of diverse materials in very short
time with high energy efficiency [19]. Numerous researchers have prepared
different aluminate nanocomposites, including CoAl2O4, Co:ZnAl2O4, ZnAl2O4,
MgAl2O4, ZnAl2O4/ZnO, Ni–MgX–Al2O3, SrAl2O4, etc., using microwave-assisted
technique [20–25].
Synthesis of xanthenediones is an ongoing hot topic of research, due to their use
as pharmacophores and valuable reactive intermediates in both synthetic and
medicinal chemistry [26]. However, development of eco-friendly methods for
synthesis of xanthenedione derivatives remains a challenge. Various researchers
have reported CuAl2O4 NCs for photocatalytic degradation of methyl orange
[9, 27]. Kwak et al. synthesized CuAl2O4 NCs via a sol–gel method for
hydrogenolysis of glycerol [13]. However, there is only a single report on
microwave combustion preparation of spinel CuAl2O4 NCs for catalytic oxidation
of benzyl alcohol [18]. To the best of the authors’ knowledge, the electrochemical
properties of CuAl2O4 NCs also remain unexplored. Furthermore, no reports are
available on solvent-free green synthesis of xanthanediones using microwave-
irradiated CuAl2O4 NCs as catalyst.
The authors previously reported preparation of new, efficient, reusable copper
and alumina as nanocatalysts for fabrication of chromene derivatives and
dihydropyrimidinones, respectively [28, 29]. In the work presented herein, spinel
CuAl2O4 NCs were synthesized by adopting aqueous precipitation (AP) and
microwave-assisted (MW) techniques with/without use of SDS as surfactant. As-
synthesized NCs were characterized by various techniques including XRD analysis,
FT-IR spectroscopy, DRS, EDS, XPS, Raman spectroscopy, SEM, TEM, and AFM.
Furthermore, the electrochemical performance of the synthesized NCs was
investigated. The prepared MWS-CuAl2O4 NCs were then used as nanocatalyst
for synthesis of xanthenediones, and reaction conditions including time, temper-
ature, and solvents were optimized, and their reusability investigated.
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