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Dye-sensitised solar cells (DSSCs) are 3rd generation photovoltaic device that imitate photosynthesis in plants. The fundamental concept of a DSSCs is that the photoanode is covered by the dye as a sensitiser. Natural dyes from plant-based extracts have gained attention as alternatives to toxic and expensive commercial dye sensitisers. Various studies have been conducted on the use of natural plant dye extracts for DSSCs . However, more fundamental studies on their adsorption on TiO2 photoanode nanoparticles are still not well understood. In this study, we investigated the crystal structure, optical absorption, and photoluminescence properties of TiO2, Cucurbita maxima, and Cucurbita maxima dyes adsorbed on TiO2 nanoparticles as potential materials for DSSCs. Raman spectra confirmed the anatase phase of the TiO2 nanoparticles. The particle size of 12 ± 2 nm was confirmed through the transmission electron microscope. The optical absorption properties of Cucurbita maxima show two distinct absorption bands: blue visible (450–500 nm) and red visible (635–674 nm). The photoluminescence spectra of the dye extract and its adsorption onto the TiO2 nanoparticles showed two prominent peaks in the blue and red regions of the electromagnetic spectrum. No significant peak is observed in the green region of the electromagnetic spectrum. These studies shed more light on the fundamental properties of chlorophyll adsorption on TiO2 nanoparticles and their optical and photoluminescence properties for applications as sensitisers in DSSCs.

We report the preparation of copper sulphide nanoparticles from copper(II) piperidine dithiocarbamate. Powder XRD patterns confirmed covellite copper sulphide (CuS) for nanoparticles obtained at 120 °C while nanoparticles prepared at 180 and 220 °C exist in digenite copper sulphide (Cu9S5) crystalline phases. TEM micrographs showed CuS obtained at 120 °C have mixture of hexagonal, triangular, and spherical shapes with no agglomeration with crystallite sizes in the range 4.9–51.4 nm. Copper sulphide obtained at 180 °C have particle sizes in the range 31.3–44.0 nm while agglomerated particles were obtained at 220 °C with particle sizes of 74.4–125.4 nm. The results confirmed that the particle sizes of the as-prepared copper sulphide nanoparticles are temperature dependent. Optical studies of the copper sulphide nanoparticles indicates the absorption band edges are blue shifted due to decreased crystallite sizes of the nanoparticles compared to bulk copper sulphide.

We report the synthesis and crystal structure of ethylphenyl dithiocarbamato silver(I) complex. The compound crystallized as [Ag4(EtphDTC)4] in which four Ag(I) ions and four molecules of ethylphenyl dithiocarbamato ligands constitute the metal cluster in the asymmetric unit. Each ethylphenyl dithiocarbamato ligand in the cluster is bonded to three Ag(I) ions through the sulfur atoms with one sulfur covalently bonded while the other sulfur atoms act as two electrons-three centres within the metal cluster. Each Ag(I) ion is linked to three Ag(I) ions through Ag–Ag metallic bond distance of 2.9115(3) Å and 3.0376(4) Å. The complex was thermolyzed at 120, 180 and 220 °C as single source precursor to prepare silver sulfide nanoparticles. Powder XRD patterns confirmed the as-prepared silver sulfide nanoparticles as acanthite Ag1.93S irrespective of the thermolysis temperature. TEM images of the silver sulfide nanoparticles showed particle of 2.99 nm for AgS1 nanoparticles obtained at 120 °C, 6.71 nm for AgS2 obtained at 180 °C and HRTEM image of AgS3 obtained at 220 °C showed average particle size of 32.90 nm. The results showed that the particle sizes of the as-prepared silver sulfide nanoparticles increases with thermolysis temperature. The as-prepared silver sulfide nanoparticles have spherical shapes irrespective of thermolysis temperature.

We report the synthesis of CuS nanoparticles using [Cu(butdtc)2] as single source precursor thermolysed at two different temperatures. The products were characterized by UV–vis absorption spectroscopy, X-ray diffraction, Transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray analysis and atomic force microscopy. The absorption spectra of the CuS nanocrystals are blue shifted and the XRD were indexed to the hexagonal phase of CuS with nanoparticles obtained at 120 °C showing well defined crystalline structure compared to those obtained at 180 °C. Transmission electron microscopy images showed particles that are almost spherical in shapes with average crystallite sizes of 21–38 nm for CuS1 prepared at 180 °C and 3–7 nm for CuS2 prepared at 120 °C and confirms that the chosen reaction temperature determine the crystallite sizes of the nanoparticles.

We report the synthesis and crystal structures of bis(dibenzyl dithiocarbamato) copper(II) and silver(I) complexes and their use as precursors to prepare Cu1.8S and Ag2S nanoparticles. Single crystal analysis of bis(dibenzyl dithiocarbamato)Cu(II) complex consist of a monomeric entity where the two dibenzyl dithiocarbamate ligands form a distorted square planar geometry around the Cu(II) ion. The bis(dibenzyl dithiocarbamato)Ag(I) formed hexameric coordination complex consisting of two distorted hexagonal Ag3S3 rings. The complexes were thermolysed at 220 °C to prepare copper sulphide and silver sulphide nanoparticles. Powder X-ray diffraction (p-XRD) patterns of the copper sulphide nanoparticles were indexed to digenite Cu1.8S, while silver sulphide nanoparticles were confirmed to be acathinite Ag2S. High-resolution transmission electron microscopy (HRTEM) images showed Ag2S nanoparticles with particle size in the range 11.4–27.4 nm while Cu1.8S nanoparticles are semi-spherical in shape with slightly agglomerated particles in the range 6.9–24.0 nm. The as-prepared nanoparticles were used as nano-photocatalysts for the degradation of methylene blue dye (MB) under UV light irradiation with degradation efficiency of 42.52% and 48.39% for Cu1.8S and Ag2S nanoparticles respectively.

We report the synthesis and structural studies of copper sulfide nanocrystals from copper (II) dithiocarbamate single molecule precursors. The precursors were thermolysed in hexadecylamine (HDA) to prepare HDA-capped CuS nanocrystals. The optical properties of the nanocrystals studied using UV–visible and photoluminescence spectroscopy showed absorption band edges at 287 nm that are blue shifted, and the photoluminescence spectra show emission curves that are red-shifted with respect to the absorption band edges. These shifts are as a result of the small crystallite sizes of the nanoparticles leading to quantum size effects. The structural studies were carried out using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and atomic force microscopy. The XRD patterns indicates that the CuS nanocrystals are in hexagonal covellite crystalline phases with estimated particles sizes of 17.3–18.6 nm. The TEM images showed particles with almost spherical or rod shapes, with average crystallite sizes of 3–9.8 nm. SEM images showed morphology with ball-like microspheres on the surfaces, and EDS spectra confirmed the presence of CuS nanoparticles.

We report the synthesis and structural studies of copper sulfide nanocrystals from copper(II) dithiocarbamate single molecule precursors. The optical studies of the as-prepared copper sulfide nanoparticles were carried out using UV–Visible and photoluminescence spectroscopy. The absorption spectra show absorption band edges at 287 nm and exhibit considerable blue shift that could be ascribed to the quantum confinement effects as a result of the small crystallite sizes of the nanoparticles and the photoluminescence spectra show emission curves that are red shifted with respect to the absorption band edges. The structural studies were carried out using powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and atomic force microscopy. The XRD patterns revealed the formation of hexagonal structure of covellite CuS with estimated crystallite sizes of 17.3–18.6 nm. The TEM images showed particles with almost spherical or rod shapes with average crystallite sizes of 3–9.8 nm. SEM images showed morphology with ball-like microsphere on the surfaces and EDS spectra confirmed the presence of CuS nanoparticles. Keywords: CuS, Dithiocarbamate, Nanoparticles, Electron microscopy, AFM

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