Search

[Display omitted] • Small Ni 1−x Mn x Co 2 O 4 nanoparticles were synthesized by low-temperature gel combustion. • All the nanoparticles revealed strong catalytic performance in 4-nitrophenol reduction. • The catalytic performance of Ni 0.5 Mn 0.5 Co 2 O 4 nanoparticles was superior to NiCo 2 O 4 and MnCo 2 O 4 nanoparticles. • >90 % of 4-nitrophenol could be reduced in 12 min. • The anomalous catalytic behaviors of the nanostructures in repeated cycles were explained. Developing efficient catalysts is one of the challenging tasks for protecting our environment from contamination. Here we present the synthesis of Ni 1−x Mn x Co 2 O 4 , noble-metal free multimetallic oxide nanoparticles of 9.5–25.0 nm average sizes by a low-temperature gel combustion method and their utilization as catalysts for rapid reduction of 4-nitrophenol (4-NP) to aminophenol (AP). Scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and vibrating sample magnetometry were used for the characterization of the nanostructures. All the nanostructures revealed strong catalytic performance in the reduction of 4-NP, and the performance of Ni 0.5 Mn 0.5 Co 2 O 4 nanoparticles was superior (>90 % reduction in 12 min) to that of NiCo 2 O 4 and MnCo 2 O 4 nanoparticles. While the 4-NP reduction process followed a pseudo-first-order kinetics for all the catalysts, the reduction efficiency of the samples manifested a complex trend from cycle to cycle. The anomalous catalytic behavior of the nanostructures in 4-NP degradation has been explained. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ge beyond x ∼ 0.4 in kesterite Cu 2 ZnSn 1-x Ge x S 4 causes the formation of secondary phases. • We could eliminate those secondary phases by an acid etching process. • The acid etching process does not affect the size and morphology of the nanostructures. • The phase pure kesterite films manifest high conductivity and enhanced hole concentration. Hole-transporting materials are very important for achieving high efficiency in perovskite solar cells. Thin films made of Cu 2 ZnSn 1-x Ge x S 4 have attracted the attention of researchers due to their potential as hole-transporting layers. However, defects and impurities define their effectiveness in solar cells. In this work, we present a facile wet chemical approach to remove the ZnS and Cu 8 GeS 6 impurities from small (∼11 nm) Cu 2 ZnSn 1-x Ge x S 4 (x = 0.0 to 0.7) nanoparticles synthesized by a hydrothermal process. The wet chemical process converted the nanostructures Cu-rich Zn-poor from their initial Zn-rich Cu-poor stoichiometry. Moreover, the bandgap energies of the nanostructures were reduced by about 0.1 eV after chemical treatment due to change the oxidation state of Cu from Cu1+ to Cu2+. The kesterite films prepared by spin coating of chemically treated nanoparticle inks revealed enhanced electrical conductivity and hole concentration in comparison to the films prepared using untreated nanoparticle inks. While the highest hole concentration of about 6.52x1018 cm−3 was obtained for the films made of Cu 2 ZnSn 1-x Ge x S 4 nanoparticles with the highest x value (x = 0.7), the highest hole mobility (18.9 cm2V−1s−1) was achieved for x = 0.3. The effects of secondary phase elimination on carrier concentration and mobility variation have been discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Kesterite CZTS and CZTGS nanoparticles are synthesize by low-temperature hydrothermal process. • Substitution of 30% Sn by Ge in the kesterite lattice does not induce any impurity phase. • Ge incorporation in kesterite lattice increases the concentration of (V Cu + Zn Cu) defect complex. • Incorporation of Ge in kesterite lattice decreases [2Cu Zn + Sn Zn ] defect concentration. • Formation of V Cu enhances carrier concentration and conductivity of kesterite nanoparticles. Phase pure Cu 2 ZnSnS 4 (CZTS) and Cu 2 ZnSn 0.7 Ge 0.3 S 4 (CZTGS) kesterite nanoparticles of 10–35 nm size range were fabricated through a low-temperature hydrothermal process. Morphology, structure, and structural phase of the nanoparticles were determined utilizing field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and Raman spectroscopy. Electrical transport behaviors of the pelletized nanostructures were studied in a physical properties measurement system (PPMS) in the 100–320 K temperature range. Obtained results indicate that both the CZTS and CZTGS nanostructures have p-type conductivity, with high room temperature hole concentration and carrier mobility. Substitution of 30% Sn by Ge enhances the electrical conductivity of CZTS about four times. While the room temperature hole mobility in the kesterite nanostructures reduces to about 60%, the hole concentration increases about one order on Ge incorporation. The limited substitution of Sn atoms by Ge does not affect the position of acceptor levels in the electronic band gap of the kesterite nanostructures. However, it increases the concentration of Cu Zn and Zn Cu antisite defects and affects the transition temperature where the electrical transport of kesterite nanostructures changes from lattice scattering controlled to defect scattering controlled conduction. [ABSTRACT FROM AUTHOR]