Bio-synthesised black α-Cr2O3 nanoparticles; experimental analysis and density function theory calculations

Abstract

A selective single phase black a-Cr 2 O 3 nanoparticles was bio-synthesised via simple straight-forward green synthesis approach. The process involves extraction of phytochemicals contained in peels of sweet potatoes. Extraction was done in distilled water under constant magnetic stirring at a temperature of 70e80 C resulting in a dusty yellow colour aqueous extracts. Afterwards, chromic nitrate salt was added to extracts resulting in reduction of metal salt to metal nanoparticles. Obtained precipitates were dried and annealed in the air for 2 h ready to be applied without further post synthesis modifications. SEM and EDS analysis of annealed precipitates reveal distinct shapes and high purity of nanoparticles. The effects of the annealing temperature are evident in the nanoparticle sizes. SAED and XRD patterns expose bright diffraction peaks which are harmonized to the rhombohedral structure of pure Eskolaitea-Cr 2 O 3. By quantitative analysis of XRD data, it was noted that lattice parameters and crystal sizes slightly decrease w.r.t increase annealing temperature. Raman spectra recorded peaks ascribe to vibrations in A 1g and E g mode whereas FTIR analysis show absorption bands at 641 and 632 cm À1 which evidence the presence of a-Cr 2 O 3 nanoparticles. UVeVis absorbance peak generated Cr 2 O 3 nanoparticles are observed at 402 nm yielding a band gap of 3.08eV. Magnetism results of a-Cr 2 O 3 nanoparticles shows linear increase upon field increasing, which can be elucidated by the existing of uncompensated spins at the surface of the nanoparticles that may lead to nonmagnetic or antiferromagnetic state. Zero field cooling (ZFC) results of a-Cr 2 O 3 nanoparticles were analysed based on Curie-Wien relation which yield values of magnetic moment (m eff ) of the synthesised Cr 2 O 3 nanoparticles close to the value that was assigned for Cr 2þ. The density functional theory (DFT) with the PW91, PBE, PBESOL and a Hubbard U Coulomb interactionwas utilized to study the optimum structure, electronic and magnetic properties of antiferromagnetically ordered Cr 2 O 3 . The computed results are consistent with the experimental measurements.

Green Synthesis of Chromium Oxide Nanoparticles for Antibacterial, Antioxidant Anticancer, and Biocompatibility Activities

“…The absorption band in the UV region is attributed to phytomolecules such as polyphenols and flavonoids, and these molecules absorb UV light because of the OH moieties [ 13 , 24 , 25 ]. The absorption band in the visible region corresponds to Cr 2 O 3 [ 26 , 27 , 28 , 29 ]. Moreover, the plant leaf extracts presented the UV region’s absorption band (200–390 nm) [ 10 ].…”

Green Nanotechnology: Recent Research on Bioresource-Based Nanoparticle Synthesis and Applications

“…A linear increase in the magnetism of Cr 2 O 3 nanoparticles with the field strength was found, which was suggested to be due to the presence of uncompensated spins at the nanoparticles' surface, leading to a nonmagnetic or antiferromagnetic state. e structural, electronic, and magnetic characteristics of Cr 2 O 3 were further confirmed using density functional theory (DFT) [157].…”

Detailed Studies on the Synthesis Methods and Characterizations of Nanocrystalline Cr2O3 Phase Materials for NIR Pigmentation Applications

“…1) with some notable interesting properties. From several reports, [9][10][11][12][13][14][15][16][17][18][19] we found that the different processed Cr 2 O 3 nanomaterials have revealed quite interesting results on the structural features related to phase formation, purity, lattice parameters, crystalline size, and so on. The green synthesized Cr 2 O 3 nanomaterials reported by Hassan et al 19 and Sackey et al 12 showed quite similar structural parameters of a = 0.495876 nm and c = 1.35942 nm 19 and a = 0.495 nm and c = 1.3591 nm, 12 respectively.…”

“…From several reports, [9][10][11][12][13][14][15][16][17][18][19] we found that the different processed Cr 2 O 3 nanomaterials have revealed quite interesting results on the structural features related to phase formation, purity, lattice parameters, crystalline size, and so on. The green synthesized Cr 2 O 3 nanomaterials reported by Hassan et al 19 and Sackey et al 12 showed quite similar structural parameters of a = 0.495876 nm and c = 1.35942 nm 19 and a = 0.495 nm and c = 1.3591 nm, 12 respectively. It has been mentioned in Sangeetha et al 11 article that in cement and in lime bonded construction materials, Cr 2 O 3 nanomaterials are used not only as the permanent coloring agent but also it can be used in surface coating applications.…”