Investigation of the structural and the physical properties of ZnO-NiO-Mn2O3 nanocomposites for photocatalytic applications

The aim of this work is to fabricate ZnO-NiO-Mn2O3 nanocomposites with exceptional features and improved physical and magnetic properties, compared to their pure counterparts. The pure oxides ZnO, NiO and Mn2O3 nanoparticles (NPs) were first synthesized via co-precipitation method. The as-prepared pure oxides were then ball milled in different mass percentages to form four ternary metal oxide nanocomposites (NCs): C1 (0.33 ZnO, 0.33 NiO, 0.33 Mn2O3), C2 (0.66 ZnO, 0.166 NiO, 0.166 Mn2O3), C3 (0.166 ZnO, 0.66 NiO, 0.166 Mn2O3), and C4 (0.166 ZnO, 0.166 NiO, 0.66 Mn2O3). Structurally, X-ray powder diffraction (XRD) analysis confirmed the formation of pure ZnO, NiO and -Mn2O3 with hexagonal (a = b = 3.247 angstrom, c = 5.201 angstrom), FCC (a = b = c = 4.174 angstrom) and BCC (a = b = c = 9.408 angstrom) crystal structures, respectively. In NCs, the formation of spinel oxides (ZnMn2O4, NiMn2O4 and Mn3O4) of tetragonal structures was revealed through Rietveld refinement. Through transmission electron microscopy (TEM), the versatile morphology of NPs in the formed NCs was suspected validating the incorporation of multi-oxide phases in one matrix. The average particle size of pure ZnO (< d > = 70.65 nm), pure NiO (< d > = 29.61 nm) and pure Mn2O3 (< d > = 77.132 nm) NPs were also estimated via TEM. For elemental composition, energy-dispersive X-ray revealed the presence of Zn, Ni, Mn, and O elements in the four NCs and their corresponding atomic percent (at.%) were in good agreement with XRD results. Raman analysis manifests eight, six and three symmetry phonon-vibration modes in pure ZnO, NiO and Mn2O3 NPs, respectively. The A(1g) (665 cm(-1)) and T-2g (475 cm(-1)) symmetry bands in mico-Raman analysis confirmed the formation of tetragonal ZnMn2O4 in the four nanocomposites. DC-conductivity was used to investigate the conduction mechanisms in pure NPs and NCs along with their I-V curves. The semiconducting behavior of the seven samples was affirmed, where C1 showed the best dc-conductivity (sigma = 1.347 x 10(-6) S/m). Vibrating sample magnetometer (VSM) analysis reported the diamagnetic, antiferromagnetic, and paramagnetic nature of ZnO, NiO and Mn2O3, respectively. The antiferromagnetic nature of NCs C1, C2 and C3 was also exhibited. VSM disclosed the ferromagnetic nature of C4 (squareness ratio: s = 0.2034) attributed to the formation of Mn3O4, with high percentage in this NC. The maximum UV-induced photodegradation efficiency of pure ZnO, NiO, Mn2O3 NPs and NC C1 towards the synthetic dye Rhodamine B (Rh B) was tested at pH = 5.5 and the corresponding obtained % degradation were 85.25%, 7.95%, 39.58% and 36.71% respectively.

Automated summary

The aim of this study was to create ZnO-NiO-Mn2O3 nanocomposites with improved physical and magnetic properties compared to individual oxides. The pure oxides ZnO, NiO, and Mn2O3 nanoparticles were synthesized and then ball milled to form four different nanocomposites. XRD analysis confirmed the crystal structures of the pure oxides and revealed the formation of spinel oxides in the nanocomposites. TEM analysis showed the versatile morphology of the nanoparticles in the nanocomposites. Elemental composition was confirmed by energy-dispersive X-ray analysis, and Raman analysis identified symmetry bands corresponding to the formation of tetragonal ZnMn2O4. DC-conductivity and VSM analysis showed the electrical and magnetic properties of the nanocomposites. The nanocomposite C4 exhibited the highest ferromagnetic nature. The photodegradation efficiency of the nanocomposite C1 towards Rhodamine B was also tested and showed the highest percentage of degradation.