Abstract
In this study, two copper(II) complexes, [Cu(C6H8N3S2)2]Cl2 (1) and [Cu(C7H10N3S2)2]Cl2·H2O (2), were synthesized from 2-(thiophen-2-ylmethylene)hydrazine-1-carbothioamide (L1H) and 2-(1-(thiophen-2-yl)ethylidene)hydrazine-1-carbothioamide (L2H) respectively and characterized using various spectroscopic techniques and elemental analyses. The as-prepared complexes were used as single-source precursors for the synthesis of oleylamine-capped (OLA@CuxSy), hexadecylamine-capped (HDA@CuxSy), and dodecylamine-capped (DDA@CuxSy) copper sulphide nanoparticles (NPs) via the thermolysis method at 190 °C and 230 °C and then characterized using powder X-ray diffraction (p-XRD), UV-visible spectroscopy, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The p-XRD diffraction patterns confirmed the formation of crystalline rhombohedral digenite Cu9S5 with the space group R-3m. The TEM images showed the formation of nanoparticles of various shapes including hexagonal, rectangular, cubic, truncated-triangular, and irregularly shaped Cu9S5 nanomaterials. The SEM results showed aggregates and clusters as well as the presence of pores on the surfaces of nanoparticles synthesized at 190 °C. The UV-visible spectroscopy revealed a general blue shift observed in the absorption band edge of the copper sulphide NPs, as compared to bulk CuxSy, with energy band gaps ranging from 2.52 to 3.00 eV. Energy-dispersive X-ray spectroscopy (EDX) confirmed the elemental composition of the Cu9S5 nanoparticles. The nanoparticles obtained at 190 °C and 230 °C were used as catalysts for the photocatalytic degradation of methylene blue (MB) under UV irradiation. Degradation rates varying from 47.1% to 80.0% were obtained after 90 min of exposure time using only 10 mg of the catalyst, indicating that Cu9S5 nanoparticles have potential in the degradation of organic pollutants (dyes).
Highlights
Heterocyclic copper(II) thiosemicarbazone complexes were successfully used as singlesource precursors for the synthesis of copper sulphide nanoparticles via hot-injection method at 190 ◦ C and 230 ◦ C while using OLA, HDA, and DDA as capping agents
The effects of quantum confinement observed in the energy bandgap of the synthesized copper sulphide NPs were solvent, temperature, and precursor-type dependant
The same trend was observed in the formation of various morphologies of copper sulphide nanoparticles, which were influenced by the reaction temperature
Summary
Copper sulphide, which is a p-type semiconductor with a tuneable band-gap ranging from 1.2 eV to 2.0 eV, has become highly sought after due to its wide range of stoichiometric compositions and phases. These phases vary from the copper-rich chalcocite phase (Cu2 S) to the copper-deficient phases (covellite (CuS), anilite (Cu1.75 S), digenite (Cu1.8 S), and djurleite (Cu1.96 S)) [5,6,7,8,9]. Copper-containing nanomaterials have been shown to possess potential applications in solar cells [5], photocatalysis [6], supercapacitors [10], nanometre-scale switches, and high-capacity cathode materials in lithium secondary batteries, superconductor, thermoelectric cooling material, and solar-energy absorption [11,12]
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