Abstract
The deposition of copper (Cu) and cupric oxide (Cu4O3, Cu2O, and CuO) particles in an aqueous copper sulfate (CuSO4) solution with additive alcohol such as methanol, ethanol, 2-propanol, and ethylene glycol has been studied by X-ray exposure from synchrotron radiation. An attenuated X-ray radiation time of 5 min allows for the synthesis of Cu, Cu4O3, Cu2O, and CuO nano/microscale particles and their aggregation into clusters. The morphology and composition of the synthesized Cu/cupric oxide particle clusters were characterized by scanning electron microscopy, scanning transmission electron microscopy, and high-resolution transmission electron microscopy with energy dispersive X-ray spectroscopy. Micro-Raman spectroscopy revealed that the clusters comprised cupric oxide core particles covered with Cu particles. Neither Cu/cupric oxide particles nor their clusters were formed without any alcohol additives. The effect of alcohol additives is attributed to the following sequential steps: photochemical reaction due to X-ray irradiation induces nucleation of the particles accompanying redox reaction and forms a cluster or aggregates by LaMer process and DLVO interactions. The procedure offers a novel route to synthesize the Cu/cupric oxide particles and aggregates. It also provides a novel additive manufacturing process or lithography of composite materials such as metal, oxide, and resin.
Highlights
Nanoparticles (NPs), of which sizes are in general below 100 nm, are potentially interesting for applications such as catalysis and optical devices, and the nucleation and fabrication of NPs are fundamental topics of scientific and engineering studies [1,2,3,4,5]
The particles synthesized onto the silicon substrate were observed by field emission scanning electron microscopy (FE-scanning electron microscope (SEM); JEOL JSM-7001F) with energy dispersive X-ray spectroscopy (EDX) to perform the element analysis
When the silicon substrate with only CuSO4 solution with no additives was exposed to X-rays, no particles were synthesized; particles and clusters were only generated in the presence of ethanol
Summary
Nanoparticles (NPs), of which sizes are in general below 100 nm, are potentially interesting for applications such as catalysis and optical devices, and the nucleation and fabrication of NPs are fundamental topics of scientific and engineering studies [1,2,3,4,5]. X-ray irradiation has been used to generate NPs from liquid solution and tailor NP aggregation at desired locations [29,30,31,32,33,34,35,36] To this end, noble metal NPs are typically used for surface enhanced Raman scattering spectroscopy (SERS) and plasmon-assisted photochemical reactions [1,2,3,4, 37]. Investigating the formation of Cu and cupric oxide NPs is required to understand the physical and chemical mechanisms and to develop engineering applications such as lithium ion cells [51], gas sensors [57], and solar cell plates [58]. Prepared solution (18 μL siphoned off from the mixed solution) Solution #1 Solution #2
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