Mechanochemical Synthesis and Characterization of CuInS₂/ZnS Nanocrystals

Investigation of the Interaction between Mechanosynthesized ZnS Nanoparticles and Albumin Using Fluorescence Spectroscopy

In this paper, ZnS nanoparticles were bioconjugated with bovine serum albumin and prepared in a form of nanosuspension using a wet circulation grinding. The stable nanosuspension with monomodal particle size distribution (d50 = 137 nm) and negative zeta potential (-18.3 mV) was obtained. The sorption kinetics and isotherm were determined. Interactions between ZnS and albumin were studied using the fluorescence techniques. The quenching mechanism, describing both static and dynamic interactions, was investigated. Various parameters were calculated, including the quenching rate constant, binding constant, stoichiometry of the binding process, and accessibility of fluorophore to the quencher. It has been found that tryptophan, in comparison to tyrosine, can be closer to the binding site established by analyzing the synchronous fluorescence spectra. The cellular mechanism in multiple myeloma cells treated with nanosuspension was evaluated by fluorescence assays for quantification of apoptosis, assessment of mitochondrial membrane potential and evaluation of cell cycle changes. The preliminary results confirm that the nontoxic nature of ZnS nanoparticles is potentially applicable in drug delivery systems. Additionally, slight changes in the secondary structure of albumin, accompanied by a decrease in α-helix content, were investigated using the FTIR method after analyzing the deconvoluted Amide I band spectra of ZnS nanoparticles conjugated with albumin. Thermogravimetric analysis and long-term stability studies were also performed to obtain a complete picture about the studied system.

Nanocrystalline Skinnerite (Cu3SbS3) Prepared by High-Energy Milling in a Laboratory and an Industrial Mill and Its Optical and Optoelectrical Properties

Copper, antimony and sulfur in elemental form were applied for one-pot solid-state mechanochemical synthesis of skinnerite (Cu₃SbS₃) in a laboratory mill and an industrial mill. This synthesis was completed after 30 min of milling in the laboratory mill and 120 min in the industrial mill, as corroborated by X-ray diffraction. XRD analysis confirmed the presence of pure monoclinic skinnerite prepared in the laboratory mill and around 76% monoclinic skinnerite, with the secondary phases famatinite (Cu₃SbS₄; 15%), and tetrahedrite (Cu_11.4Sb₄S₁₃; 8%), synthesized in the industrial mill. The nanocrystals were agglomerated into micrometer-sized grains in both cases. Both samples were nanocrystalline, as was confirmed with HRTEM. The optical band gap of the Cu₃SbS₃ prepared in the laboratory mill was determined to be 1.7 eV with UV-Vis spectroscopy. Photocurrent responses verified with I-V measurements under dark and light illumination and Cu₃SbS₃ nanocrystals showed ~45% enhancement of the photoresponsive current at a forward voltage of 0.6 V. The optical and optoelectrical properties of the skinnerite (Cu₃SbS₃) prepared via laboratory milling are interesting for photovoltaic applications.

SDS-Stabilized CuInSe2/ZnS Multinanocomposites Prepared by Mechanochemical Synthesis for Advanced Biomedical Application

The CuInSe2/ZnS multiparticulate nanocomposites were first synthesized employing two-step mechanochemical synthesis. In the first step, tetragonal CuInSe2 crystals prepared from copper, indium and selenium precursors were co-milled with zinc acetate dihydrate and sodium sulfide nonahydrate as precursors for ZnS in different molar ratios by mechanochemical route in a planetary mill. In the second step, the prepared CuInSe2/ZnS nanocrystals were further milled in a circulation mill in sodium dodecyl sulphate (SDS) solution (0.5 wt.%) to stabilize the synthesized nanoparticles. The sodium dodecyl sulphate capped CuInSe2/ZnS 5:0-SDS nanosuspension was shown to be stable for 20 weeks, whereas the CuInSe2/ZnS 4:1-SDS one was stable for about 11 weeks. After sodium dodecyl sulphate capping, unimodal particle size distribution was obtained with particle size medians approaching, respectively, 123 nm and 188 nm for CuInSe2/ZnS 5:0-SDS and CuInSe2/ZnS 4:1-SDS nanocomposites. Successful stabilization of the prepared nanosuspensions due to sodium dodecyl sulphate covering the surface of the nanocomposite particles was confirmed by zeta potential measurements. The prepared CuInSe2/ZnS 5:0-SDS and CuInSe2/ZnS 4:1-SDS nanosuspensions possessed anti-myeloma sensitizing potential assessed by significantly reduced viability of multiple myeloma cell lines, with efficient fluorescence inside viable cells and higher cytotoxic efficacy in CuInSe2/ZnS 4:1-SDS nanosuspension.

Structural and Optical Characterization of ZnS Ultrathin Films Prepared by Low-Temperature ALD from Diethylzinc and 1.5-Pentanedithiol after Various Annealing Treatments

The structural and optical evolution of the ZnS thin films prepared by atomic layer deposition (ALD) from the diethylzinc (DEZ) and 1,5-pentanedithiol (PDT) as zinc and sulfur precursors was studied. A deposited ZnS layer (of about 60 nm) is amorphous, with a significant S excess. After annealing, the stoichiometry improved for annealing temperatures ≥400 °C and annealing time ≥2 h, and 1:1 stoichiometry was obtained when annealed at 500 °C for 4 h. ZnS crystallized into small crystallites (1–7 nm) with cubic sphalerite structure, which remained stable under the applied annealing conditions. The size of the crystallites (D) tended to decrease with annealing temperature, in agreement with the EDS data (decreased content of both S and Zn with annealing temperature); the D for samples annealed at 600 °C (for the time ≤2 h) was always the smallest. Both reflectivity and ellipsometric spectra showed characteristics typical for quantum confinement (distinct dips/peaks in UV spectral region). It can thus be concluded that the amorphous ZnS layer obtained at a relatively low temperature (150 °C) from organic S precursor transformed into the layers built of small ZnS nanocrystals of cubic structure after annealing at a temperature range of 300–600 °C under Ar atmosphere.