Thandi B. Mbuyazi

Bio: Thandi B. Mbuyazi is an academic researcher from University of KwaZulu-Natal. The author has contributed to research in topics: Nanoparticle & High-resolution transmission electron microscopy. The author has an hindex of 1, co-authored 2 publications receiving 1 citations.

Lead Sulphide Nanoparticles as Photocatalyst for the Degradation of Methylene Blue: Effects of pH, Time, Adsorption Kinetics and Recyclability Studies

Abstract: We report the synthesis and morphological studies of lead sulphide nanoparticles prepared from lead(II) complexes of morpholine dithiocarbamate (PbS1), thiomorpholine dithiocarbamate (PbS2), and N-(2-hydroxyethyl)phenyl dithiocarbamate (PbS3). Powder X-ray diffraction patterns (p-XRD) of the PbS nanoparticles are indexed to face-centered cubic phase of PbS. High-resolution transmission electron microscopy (HRTEM) micrograph revealed quasi-spherical PbS nanoparticles with particle size in the range 13.86–36.06 nm while scanning electron microscopy (SEM) revealed flaky/spherical/rough surface morphology. Photocatalytic degradation of methylene blue dye by the PbS nanoparticles showed degradation efficiency of 72.6 % for PbS1, 75.9 % for PbS2, and 47.4 % for PbS3. The photodegradation efficiency shows a correlation between efficiency and morphological properties. Total organic content removal by PbS2 is 69.5 % while that of PbS1 is 64.2 % and PbS3 is 40.1 %. The as-prepared PbS nanoparticles exhibited remarkable photostability in the recyclability studies.

Structural studies and photocatalytic degradation of brilliant green by dodecylamine capped tin sulphide nanocrystals

Abstract: Tin sulphide (SnS) nanoparticles were synthesized from five tin(II) dithiocarbamate single-source precursors. Powder X-ray diffraction patterns of the SnS nanoparticles revealed orthorhombic herzenbergite phase of tin sulphide. SEM images of the SnS nanoparticles showed rough, smooth, flaky agglomerates and irregular morphologies. The bandgap energy of the nanoparticles estimated from Tauc plots are in the range 2.27–2.71 eV. The as-prepared SnS nanoparticles were used as nanophotocatalysts for the degradation of brilliant green under visible light irradiation. The results showed that the as-prepared SnS nanoparticles are efficient photocatalysts for the degradation of brilliant green with the highest degradation efficiency of 93% for SnS4 after 120 min. The as-prepared SnS nanoparticles showed good photostability in the recyclability studies.

Influence of Different Capping Agents on the Structural, Optical, and Photocatalytic Degradation Efficiency of Magnetite (Fe3O4) Nanoparticles

Abstract: Octylamine (OTA), 1-dodecanethiol (DDT), and tri-n-octylphosphine (TOP) capped magnetite nanoparticles were prepared by co-precipitation method. Powder X-ray diffraction patterns confirmed inverse spinel crystalline phases for the as-prepared iron oxide nanoparticles. Transmission electron microscopic micrographs showed iron oxide nanoparticles with mean particle sizes of 2.1 nm for Fe3O4-OTA, 5.0 nm for Fe3O4-DDT, and 4.4 nm for Fe3O4-TOP. The energy bandgap of the iron oxide nanoparticles ranges from 2.25 eV to 2.76 eV. The iron oxide nanoparticles were used as photocatalysts for the degradation of methylene blue with an efficiency of 55.5%, 58.3%, and 66.7% for Fe3O4-OTA, Fe3O4-DDT, and Fe3O4-TOP, respectively, while for methyl orange the degradation efficiencies were 63.8%, 47.7%, and 74.1%, respectively. The results showed that tri-n-octylphosphine capped iron oxide nanoparticles are the most efficient iron oxide nano-photocatalysts for the degradation of both dyes. Scavenger studies show that electrons (e−) and hydroxy radicals (•OH) contribute significantly to the photocatalytic degradation reaction of both methylene blue and methyl orange using Fe3O4-TOP nanoparticles. The influence of the dye solution’s pH on the photocatalytic reaction reveals that a pH of 10 is the optimum for methylene blue degradation, whereas a pH of 2 is best for methyl orange photocatalytic degradation using the as-prepared iron oxide nano-photocatalyst. Recyclability studies revealed that the iron oxide photocatalysts can be recycled three times without losing their photocatalytic activity.

Synthesis and Crystal Structures of Bis(diallydithiocarbamato)zinc(II) and Silver(I) Complexes: Precursors for Zinc Sulfide and Silver Sulfide Nanophotocatalysts

Abstract: We report the preparation and crystal structures of bis(diallydithiocarbamato)zinc(II) and silver(I) complexes. The compounds were used as single-source precursors to prepare zinc sulfide and silver sulfide nanophotocatalysts. The molecular structure of bis(diallydithiocarbamato)zinc(II) consists of a dimeric complex in which each zinc(II) ion asymmetrically coordinates with two diallydithiocarbamato anions in a bidentate chelating mode, and the centrosymmetrically related molecule is bridged through the S-atom that is chelated to the adjacent zinc(II) ion to form a distorted trigonal bipyramidal geometry around the zinc(II) ions. The molecular structure of bis(diallydithiocarbamato)silver(I) formed a cluster complex consisting of a trimetric Ag3S3 molecule in which the diallydithiocarbamato ligand is coordinated to all the Ag(I) ions. The complexes were thermolyzed in dodecylamine, hexadecylamine, and octadecylamine (ODA) to prepare zinc sulfide and silver sulfide nanoparticles. The powder X-ray diffraction patterns of the zinc sulfide nanoparticles correspond to the hexagonal wurtzite while silver sulfide is in the acanthite crystalline phase. The high-resolution transmission electron microscopy images show that quantum dot zinc sulfide nanoparticles are obtained with particle sizes ranging between 1.98 and 5.49 nm, whereas slightly bigger silver sulfide nanoparticles are obtained with particle sizes of 2.70–13.69 nm. The surface morphologies of the ZnS and AgS nanoparticles capped with the same capping agent are very similar. Optical studies revealed that the absorption band edges of the as-prepared zinc sulfide and silver sulfide nanoparticles were blue-shifted with respect to their bulk materials with some surface defects. The zinc sulfide and silver sulfide nanoparticles were used as nanophotocatalysts for the degradation of bromothymol blue (BTB) and bromophenol blue (BPB). ODA-capped zinc sulfide is the most efficient photocatalyst and degraded 87% of BTB and 91% of BPB.

PbS nanostructures: A Review of recent advances

Abstract: The primary motivation behind efforts to understand the properties of lead sulfide (PbS) is its technological importance as the foundation of modern semiconductor optoelectronics. PbS nanocrystals (NCs) show remarkable versatility and promise for application in both conventional optical devices and the new generation of nano-electronics and nano-optoelectronics because of their particular structure and size-related properties. Although PbS NCs have been the subject of intense fundamental and applied studies, no comprehensive evaluation of the published data has been documented so far. Undoubtedly, providing an overview of the published research will help further development in PbS-related research and will certainly make it a step forward in the application. Therefore, this review paper discusses the preparation, structural, electronic and optical properties of PbS NCs in light of recent progress in nanotechnology. We first survey the fundamental properties of PbS NCs and then mainly focus on size-dependent properties. In this regard, the recent breakthrough in tuning the properties of PbS NCs employing doping, ligands, capping and hybridizing with different materials, and interaction with embedded media has been particularly discussed. The review concludes with the enhanced performance of the PbS NCs towards future optoelectronic devices and biological and chemical applications.

A highly active Z-scheme SnS/Zn2SnO4 photocatalyst fabricated for methylene blue degradation

Abstract: Herein, a highly active Z-scheme SnS/Zn2SnO4 photocatalyst is fabricated by a one-step hydrothermal route. The structure, composition, photoelectric and photocatalytic properties of the as-prepared photocatalysts are systematically researched. The results demonstrate that SZS-6 displays a good photocatalytic performance with an efficiency of 94.5% to degrade methylene blue (MB) under visible light irradiation (λ > 420 nm). And its degradation rate constant is up to 0.0331 min−1, which is 3.9 and 4.4 times faster than SnS and Zn2SnO4, respectively. The formation of a Z-scheme heterojunction facilitates the separation and transfer of charges, which improves the degradation of MB. The Z-scheme charge transfer pathway of the SnS/Zn2SnO4 photocatalyst is verified by the shifted peaks of the X-ray photoelectron spectroscopy (XPS) spectrum, the relative position of the bandgap, work function as well as free radical trapping experiments. The photocatalytic mechanism for the degradation of MB by SnS/Zn2SnO4 is proposed.