Figure 1.

Physico-chemical characterization of the CuS NPs synthesized in the batch reactor after 2 h of synthesis. STEM-HAADF photographs of the resulting nanoparticles (60 °C, 2 h): (a) sacrificial Cu₂O nanoparticles; (b) detail image of a Cu₂O nanoparticle. (c) Cu EDS profile of the particle in b. Red dashed line depicts the location of the EDS profile. (d) CuS nanoparticles produced by Kirkendall diffusion. (e) Detailed image of a hollow CuS nanoparticle. (f) Cu EDS profile of the particle in e. Red dashed line in e depicts the location of the EDS profile. (g) X-ray diffractograms of the materials obtained at different temperatures (60 and 120 °C) and the characteristic covellite and chalcocite Joint Committee on Powder Diffraction Standards (JCPDS) patterns; (h) UV–vis absorption spectra of the materials synthesized in both batch and microfluidic reactors. (i) Cu/S atomic ratio of produced nanoparticles. Statistics were conducted after analyzing 20 nanoparticles.