J. Santos-Cruz

Growth evolution and phase transition from chalcocite to digenite in nanocrystalline copper sulfide: Morphological, optical and electrical properties.

Summary Copper sulfide is a promising p-type inorganic semiconductor for optoelectronic devices such as solar cells, due its small band gap energy and its electrical properties. In this work nanocrystalline copper sulfide (CuxS), with two stoichiometric ratios (x = 2, 1.8) was obtained by one-pot synthesis at 220, 230, 240 and 260 °C in an organic solvent and amorphous CuxS was obtained in aqueous solution. Nanoparticle-like nucleation centers are formed at lower temperatures (220 °C), mixtures of morphologies (nanorods, nanodisks and nanoprisms) are seen at 230 and 240 °C, in which the nanodisks are predominant, while big hexagonal/prismatic crystals are obtained at 260 °C according to TEM results. A mixture of chalcocite and digenite phases was found at 230 and 240 °C, while a clear transition to a pure digenite phase was seen at 260 °C. The evolution of morphology and transition of phases is consistent to the electrical, optical, and morphological properties of the copper sulfide. In fact, digenite Cu1.8S is less resistive (346 Ω/sq) and has a lower energy band gap (1.6 eV) than chalcocite Cu2S (5.72 × 105 Ω/sq, 1.87 eV). Low resistivity was also obtained in CuxS synthesized in aqueous solution, despite its amorphous structure. All CuxS products could be promising for optoelectronic applications.

Nanomaterials made of non-toxic metallic sulfides: A systematic review of their potential biomedical applications

Metallic sulfides involve the chemical bonding of one or more sulfur atoms to a metal. Metallic sulfides are cheap, abundant semiconductor materials that can be used for several applications. However, an important and emerging use for non-toxic metallic sulfides in biomedical applications has arisen quickly in the medical field. In this systematic review, the available data from electronic databases were collected according to PRISMA alignments for systematic reviews. This review shows that these metallic sulfides could be promising for biomedical uses and applications. This systematic review is focused primarily on the following compounds: silver sulfide, copper sulfide, and iron sulfide. The aim of this review was to provide a quick reference on synthesis methods, biocompatibility, recent advances and perspectives, with remarks on future improvements. The toxicity of metallic sulfides depends directly on the cytotoxicity of their interactions with cells and tissues. Metallic sulfides have potential biomedical applications due to their antibacterial properties, uses in imaging and diagnostics, therapies such as photothermal therapy and chemotherapy in tumors and cancer cells, drug delivery and the fabrication of biosensors for the sensitive and selective detection of moieties, among others. Although current evidence about metallic sulfide NPs is promising, there are still several issues to be addressed before these NPs can be used in biomedicine. The current review is a brief but significant guide to metallic sulfides and their potential uses in the biomedical field.

Colloidal synthesis of biocompatible iron disulphide nanocrystals

Abstract The aim of this research was to synthesis biocompatible iron disulphide nanocrystals at different reaction temperatures using the colloidal synthesis methodology. Synthesis was conducted at the 220–240 °C range of reaction temperatures at intervals of 5 °C in an inert argon atmosphere. The toxicity of iron disulphide nanocrystals was evaluated in vitro using mouse fibroblast cell line. Two complementary assays were conducted: the first to evaluate cell viability of the fibroblast via an MTT assay and the second to determine the preservation of fibroblast nuclei integrity through DAPI staining, which labels nuclear DNA in fluorescence microscopes. Through TEM and HRTEM, we observed a cubic morphology of pyrite iron disulphide nanocrystals ranging in sizes 25–50 nm (225 °C), 50–70 nm (230 °C) and >70 nm (235 °C). Through X-ray diffraction, we observed a mixture of pyrite and pyrrohotite in the samples synthesized at 225 °C and 240 °C, showing the best photocatalytic activity at 80% and 65%, respectively, for the degradation of methylene blue after 120 minutes. In all experimental groups, iron disulphide nanocrystals were biocompatible, i.e. no statistically significant differences were observed between experimental groups as shown in a one-way ANOVA and Tukey’s test. Based on all of these results, we recommend non-cytotoxic semiconductor iron sulphide nanocrystals for biomedical applications. Graphical Abstract

Optical, Electrical and Photocatalytic Properties of the Ternary Semiconductors , and

The effects of vacuum annealing at different temperatures on the optical, electrical and photocatalytic properties of polycrystalline and amorphous thin films of the ternary semiconductor alloys , and were investigated in stacks of binary semiconductors obtained by chemical bath deposition. The electrical properties were measured at room temperature using a four-contact probe in the Van der Pauw configuration. The energy band gap of the films varied from 2.30 to 2.85 eV. The photocatalytic activity of the semiconductor thin films was evaluated by the degradation of an aqueous methylene blue solution. The thin film of annealed under vacuum at 300°C exhibited the highest photocatalytic activity.

Synthesis of paramelaconite nanoparticles by laser ablation

Paramelaconite nanoparticles have been obtained by laser ablation from a copper target in propanol. Copper oxide nanoparticles were characterized by high resolution transmission electron microscopy (HR-TEM), ultraviolet-visible (UV-Vis) spectroscopy, and X-ray diffraction. HR-TEM images demonstrated particle size in the range of 60–70 nm. It is observed that nanoparticle size depends on the wavelength and intensity of the laser. The results show that the stability of paramelaconite is affected by the high temperatures and oxidizing atmosphere, leading to a mixed phase of tenorite and paramelaconite.

Structural properties of Sn-doped CdTe thin films grown by pulsed laser deposition using powder as target

Undoped and Sn-doped CdTe thin films were grown by a pulsed laser deposition on glass substrates at 300 °C using a powder as target. CdTe films were grown using CdTe and Sn powders, varying the tin concentration in the range of 1–7 wt. %. The structural properties were analyzed as a function of the Sn amount in the target. The x-ray diffraction shows that the undoped CdTe film has a cubic phase, while Sn-doped CdTe films have a mixture of cubic and hexagonal phases. The compositional analysis showed that the undoped CdTe film has Te excess, while Sn-doped CdTe films have Te deficiencies.