Synthesis and photocatalytic properties of BhS3 and metal doped BhS3 nanop articles

MSc (Chemistry), North-West University, Mahikeng Campus

Intriguing prospects for the development of materials with improved properties for optical, electronic and catalytic applications has motivated research in novel materials. Semiconductor nanoparticles exhibit variable and controllable properties which are associated with the change in the energy structure with size decrease which affects their optoelectronic properties. Interestingly, metal sulphide nanomaterials have stimulated great interest as a result of their value in basic scientific research and prospective technological applications due to their good properties and potential applications in areas such as electronic, optical and catalytic materials. Besides the rich structural diversity and pronounced quantum confinement effects, metal sulphides are widely utilised in many areas of environmental benefits. Bismuth sulphide (Bi2S3) is one of the important members of semiconducting chalcogenides of the type A2B3 (where A= Sb, Bi, As, and B = S, Se, Te). This research reports pure Bi2S3 and metal doped Bi2S3 nanoparticles using bismuth(III) dithiocarbamate as single source precursor. A series of Bi(III) complexes of 4-methyl-N-phenyldithiocarbamate, N-phenyldithiocarbamate and Nbenzyldithiocarbamate were successfully prepared and characterized by NMR and FTIR spectroscopic techniques, and elemental analysis. The complexes were represented as [Bi(L1)3], [Bi(L2)3] and [Bi(L3)3] respectively. In the FTIR spectra of the complexes, the stretching frequencies of v(C-S) for all the complexes were found in the range of 1012-1030 cm-1 region. This indicated the presence of bindentate form of bonding in the dithiocarbamate compounds. The three complexes: [Bi(L1)3], [Bi(L2)3] and [Bi(L3)3] were utilized as precursor compounds to prepare bismuth sulphide nanostructures which were represented as Bi2S3(l), Bi2S3(2), and Bi2S3(3), respectively using both microwave and so lvothermal routes. Furthermore, Mn and Sn doped Bi2S3(1), Bi2S3(2), and Bi2S3(3) were respectively prepared using autoclave method. The undopedBi2S3 and metal doped Bi2S3 nanomaterials were characterized using UV-vis spectroscopy, photolum inescence (PL) spectroscopy, transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) analysis. The XRD results confirmed the feasibility of obtaining orthorhombic structure Bi2S3 nanoparticles from a single source precursor and the EDX was also used to confirm the presence of the respective dopants in the metal doped Bi2S3. The TEM results for the undoped and metal doped Bi2S3 nanomaterials prepared by so lvothennal and hydrothermal methods respectively showed nanorods of about 100 nm in length and 20 nm in diameter, while the products obtained via microwave method gave spherical morphology of about 100 nm in size, but with observable agglomeration. Both the diameter and length of the Bi2S3 nanorods increases with the increasing concentration of bismuth precursor. The evaluation of the photocatalytic properties of the nanorods obtained via solvothermal and autoclave routes were carried out using methylene blue as test compound. The results indicated that about 82-87% of MB was photocatalytically degraded after 150 min under visible light irradiation using the undoped Bi2S3 nanorods. However, the metal doped Bi2S3 nanorods showed the higher photocatalytic activity above 90% of methylene blue (MB) degradation. These results could be ascribed to the excellent visible light absorption of Bi2S3 nanomaterials and the efficient separation of photoinduced electronhole pairs by the metal doped BbS3 nanomaterials. In conclusion al l of the nanorods have good photocatalytic activity for degradation of MB. However, the small nanorods in metal doping have the highest degradation efficiency due to high surface area. Therefore, it is expected that the Bi2S3 nanorods have potential in applications in the photocatalytic degradation of organic pollutants. The use of metal doped Bi2S3 nanorods in water treatment may guide the development of future semiconductor photocatalysts in environmental remediation.

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