Formation of Colloidal CuO Nanocrystallites and Their Spherical Aggregation and Reductive Transformation to Hollow Cu₂O Nanospheres

Abstract

In this work, we demonstrate that cuprous oxide Cu(2)O nanospheres with hollow interiors can be fabricated from a reductive conversion of aggregated CuO nanocrystallites without using templates. A detailed process mechanism has been revealed: (i) formation of CuO nanocrystallites; (ii) spherical aggregation of primary CuO crystallites; (iii) reductive conversion of CuO to Cu(2)O; and (iv) crystal aging and hollowing of Cu(2)O nanospheres. In this template-free process, Ostwald ripening is operative in (iv) for controlling crystallite size in shell structures and thus for precisely tuning the optical band gap energy (E(g)) of resultant semiconductor nanostructures. For the first time, a wealth of colorful Cu(2)O hollow nanospheres (outer diameters in 100-200 nm), with variable E(g) in the range of 2.405-2.170 eV, has been fabricated via this novel chemical route. Considering their unique hollow structure and facile tuning in band gap energy, the prepared Cu(2)O hollow spheres can be potentially useful for harvesting solar energy in the visible range. Possibility of fabrication of Cu-Cu(2)O nanocomposites has also been discussed.

Luminescence properties of the solvothermally synthesized blue light emitting Mn doped Cu2O nanoparticles

“…17 It was found from the literature that the quantum confinement threshold of Cu 2 O nanocrystals was 14 nm. 13 Thus the quantum confinement effect was observed for the samples CP2 and CP3 having sizes ϳ8 -11 nm. The well-known series of yellow excitonic emissions of the Cu 2 O are also observed between 600 and 700 nm for all the nanoparticles.…”

“…Cubic crystalline structure and the electronic properties of Cu 2 O stimulated many researchers to study optical and electronic properties in different shapes and sizes. [13][14][15] The study of semiconductor nanoparticles or quantum dots is a major field of research in condensed matter physics. Particularly interesting are the quantum size effects on the optical properties of the semiconductor nanoparticles.…”

Faceting of Nanocrystals during Chemical Transformation: From Solid Silver Spheres to Hollow Gold Octahedra

“…This general methodology has since been extended by other groups to produce nanostructures with various compositions and shapes. [7][8][9][10] Galvanic replacement reactions have been demonstrated to also produce hollow nanostructures. Xia et al reported cases where a replacement reaction took place uniformly around Ag cubes of ~100 nm size, leading to formation of Au nanoboxes.…”

TEMPLATE STRATEGY FOR THE SYNTHESIS OF Cu2O–Pt HIERARCHICAL HETEROSTRUCTURES FOR THE DEGRADATION OF METHYLENE BLUE

“…The two peaks at 74.3 eV and 70.9 eV are consistent with the binding energies of Pt 4f5/2 and Pt 4f7/2, respectively. 42 The XPS results provide more details about the galvanic reaction and con¯rms that the Cu 2 OÀPt hierarchical heterostructures have been prepared successfully. A Schottky barrier can be created at the semiconductorÀmetal junction when controllably depositing metal nanoparticle onto semiconductors.…”