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This study demonstrates scalable mechanochemical synthesis of rhodostannite Cu2FeSn3S8 nanocrystals. On the contrary to the previous reports focused on the synthesis of stannite Cu2FeSnS4 reporting the rhodostannite impurity, we succeeded in preparing stannite-free product after milling. Pure elements were used for a solvent-free production in a batch of 100 g using an eccentric vibratory mill. The progress of the synthesis was monitored by X-ray diffraction and magnetometry, which both confirmed a successful reaction progress until 6 h of milling. However, further treatment (until 10 h) did not result in an improvement, as quite a high saturation magnetization (7.8 emu/g) and clearly evident diffraction at around 44° in the XRD pattern of the product due to the presence of ferromagnetic un-reacted iron with content slightly above 5% was evidenced. The product is sulfur- and tin-deficient, with crystallite size of around 12 nm. In-depth SEM/EDS analysis has shown the inhomogeneity of Fe distribution due to unfinished reaction. The bandgap of the produced material was 1.29 eV. The spark plasma sintering treatment resulted in complete consumption of non-reacted iron, but partial decomposition to stannite Cu2FeSnS4 was observed. The product is an intrinsic semiconductor with high electrical resistivity, and is therefore unsuitable for thermoelectric application. However, its thermal conductivity is low, thus it could be used as an electrically and thermally insulating material.

Nanostructured semiconductor, copper sulphide, CuS prepared by a mechanochemical synthesis in a large-scale operation industrial mill was modified by surfactant-assisted milling in a planetary mill...

Novel drug delivery systems containing advanced materials are currently the focus of many scientists, particularly in the field of medicine. Nowadays, these materials can play an important role when the authors talk about human health and especially the need to develop personalized treatment. In this work, multiparticulate As4S4/ZnS/Fe3O4 nanocomposite based on components possessing promising therapeutic, photoluminescent, and magnetic functionality was prepared by the milling. Subsequently, it was covered with the bio-compatible polymer Poloxamer 407 and/or folic acid for the functionalization of inorganic material. The samples were studied from the structural (X-ray powder diffraction analysis), magnetic, and optical (UV–Vis and photoluminescence spectroscopies) point of view. Particle size distribution and zeta potential measurements were performed to determine long-term stability of these nanosuspensions. Fourier transform infrared spectroscopy was used to identify bonding between organic and inorganic entities. Prominent optical fluorescence properties were found in a sample containing folic acid.

In the present study, a quick and environmentally friendly approach has been developed for the synthesis of CuS nanocrystals of different shape with antibacterial activity. The process is completed...

Out of many functionalities of zinc oxide, its magnetic properties are only sparsely explored. Herein we report on the evolution of ferromagnetism of undoped ZnO nanoparticles, depending on the zinc source used for the synthesis. We started from mechanochemical synthesis of phase pure nanocrystalline hydrozincite, Zn5(CO3)2(OH)6 (ZnHC) by milling a mixture comprising either Zn(NO3)2·6H2O or ZnCl2, and Na2CO3 for 10 min. Zinc oxide nanoparticles with specific surface over 70 m2/g were obtained by subsequent heating of ZnHC up to 300 °C. Ferromagnetism was observed only for ZnO nanoparticles derived from Zn(NO3)2, while those from ZnCl2 were conventionally diamagnetic. X-ray photoelectron, Raman, as well as electron paramagnetic resonance spectrograms consistently showed significantly higher concentration of oxygen vacancies in the Zn(NO3)2-derived ZnO. We also referred to the difference in the charging states of oxygen vacancies by detailed observation of EPR spectra. Since the formation of ZnO from ZnHC is topotactic, the difference in the lattice imperfection was discussed in terms of the hydration energy of the coexisting NO3− or Cl− anion. The present simple mechanochemical – thermal procedure offers a facile method for obtaining well-dispersed active ZnO nanoparticles. More importantly, the new synthesis method offers possibility of controlling their magnetic properties by choosing anionic species of the starting zinc source.

The rapid mechanochemical synthesis of nanocrystalline CuFeS particles prepared by high-energy milling for 60 min in a planetary mill from copper, iron and sulphur elements is reported. The CuFeS nanoparticles crystallize in tetragonal structure with mean crystallite size of about 38 ± 1 nm determined by XRD analysis. HRTEM study also revealed the presence of nanocrystals with the size of 5–30 nm with the tendency to form agglomerates. The Raman spectrum confirms the chalcopyrite structure. Low temperature magnetic data for CuFeS support the coexistence of antiferromagnetic and paramagnetic spin structure. Moreover, the hysteresis loops taken at temperatures from 5 K to 300 K revealed a presence of very small amount of ferromagnetic phase, which seems to be associated with the non-consumed elemental Fe in as-prepared nanoparticles. The optical band gap of CuFeS nanoparticles has been detected to be 1.05 eV, larger than band gap of the bulk material. The wider gap possibly resulted from the nano-size effect. Photoresponses of CuFeS nanoparticles were confirmed by I-V measurements under dark and light illumination. It was demonstrated that mechanochemical synthesis can be successfully employed in the one step preparation of nanocrystalline CuFeS with good structural, magnetic, optical and electrooptical properties., This work was promoted by the Slovak Research and Development Agency under the contract No. APVV-14-0103. The support through the Slovak Grant Agency VEGA (projects 2/0027/14, 1/0739/16 and 2/0065/18) is also thankfully acknowledged. The authors also appreciate the help of the European Regional Development Fund- project NANOCEXMAT 2 (ITMS 26220120035) and European Union through the CT-2011-1-REGPOT285895 AL-NANOFUN project (Advanced Laboratory for the Nano-Analysis of novel Functional materials), for the microscopy facilities sited in Seville.

Rapid solvent-free mechanochemical synthesis of CTS nanocrystals from elemental precursors is reported herein. The process is completed in 15 min, proceeding through immediate formation of CuS in a self-sustaining manner and its subsequent reaction with Sn and residual sulfur. The reaction progress was monitored by pressure and temperature changes in the milling vessel, X-ray diffraction, Soxhlet analysis, grain size analysis and electric resistivity measurements. The relationship between the consumption of metallic precursors, grain size and electrical resistivity is provided. The final product was nanocrystalline with crystallite size below 10 nm, as confirmed by both X-ray diffraction and transmission electron microscopy. The nanocrystals are agglomerated into micrometer-sized grains. It exhibits poor porous properties with the specific surface area value of 2.5 m2/g. The X-ray photoelectron spectroscopy has shown that the surface is significantly oxidized, due to milling in air. The optical properties of the prepared CTS nanocrystals are interesting for photovoltaic applications.

In this study, the mechanochemical synthesis of Co9S8 nanoparticles from cobalt and sulphur by high-energy milling in a planetary mill in an argon atmosphere is reported. Structural characterization of the synthesized nanoparticles by XRD was performed. Co9S8 nanoparticles crystallize in the cubic structure with the crystallite size of about 16 nm. The microstructure of the Co9S8 nanoparticles was further studied using TEM, HRTEM and EDS-HAADF-STEM techniques. Co9S8 nanoparticles consist of nanocrystals exhibiting size in the range of 10–30 nm that are densely aggregated into spherical-like objects. The highest specific surface area value observed was 4 m2g-1 and the pore properties of this sample are quite poor. The magnetic properties of mechanochemically synthesized nanoparticles were investigated using SQUID magnetometer. The room temperature magnetic data supported the paramagnetic spin structure of Co9S8 nanoparticles. The transition from paramagnetic to weak ferromagnetic or ferrimagnetic behaviour was indicated from temperature dependence of magnetization at cryogenic temperatures. It is demonstrated that mechanochemical synthesis can be successfully employed in the one-step solid-state preparation of Co9S8 nanoparticles.

In the present study, the mechanochemically prepared covellite, CuS and chalcocite, Cu2S nanocrystals are compared in detail. Concretely, the SEM, EDS, N2 adsorption, UV–Vis, PL, FTIR, ZP measurement, PCCS, XPS and DTA/TG were used. SEM, EDS and elemental mapping have shown that the agglomerates containing nanoparticles of the corresponding phases were formed as a result of milling. The nitrogen adsorption method has documented richer surface properties in the case of CuS sample. The specific surface area values were 2.7 m2 g−1 and 1.4 m2 g−1 for CuS and Cu2S, respectively. UV–Vis and PL measurements have shown that these materials might be suitable for optoelectronic applications, as the optical bandgaps were 1.92 eV and 3 eV for CuS and Cu2S, respectively. FTIR spectrum of CuS exhibited a peak at 621 cm−1, which is characteristic for this material. ZP values were more negative in the case of CuS and PCCS has confirmed the finer character of this sample (x50 values were 680 nm and 617 nm for Cu2S and CuS, respectively). XPS method documented the surface oxidation of the prepared Cu2S. The thermal stability measurement up to 550 °C has shown that Cu2S does not undergo significant changes (only 1.4% weight loss was observed), whereas CuS is losing sulfur and is transformed into digenite and chalcocite (14.3% weight loss was observed). The mechanochemically synthesized copper sulfides show high activities in photodecolorization of Methyl Orange dye under visible light irradiation, as Cu2S was able to completely decompose the dye in 150 min and CuS caused 80% decomposition after the same time of treatment.

Stannite Cu2FeSnS4 and kesterite Cu2ZnSnS4 were synthesized by an eco-friendly ball-milling method in an industrial mill. Both synthesized sulfides represent perspective materials in solar cell technology. Several characterization methods have been applied to determine the course of solid state mechanochemical reactions leading to the synthesis of potential chalcogenide solar cell absorbers. The phase and surface composition, solid state kinetics, and surface morphology of these quaternary sulfides were elucidated by the methods of X-ray diffractometry, X-ray photoelectron spectroscopy, Soxhlet analysis, and scanning electron microscopy. The application of eccentric vibration mills for these syntheses constitutes the big challenge for researchers in the field of photovoltaics in their permanent effort in scaling up new materials and processes.

Chalcopyrite CuFeS2 was shown to be a promising thermoelectric material. Considering thermoelectric efficiency, its relatively high and temperature weakly dependent power factor, economic affordability and ecological benignity is counterbalanced by a high lattice thermal conductivity. Thus it is highly desirable to lower the thermal conductivity of chalcopyrite thermoelectric material without deterioration of other thermoelectric characteristics. In our study, we demonstrate that mechanosynthesis followed by appropriate sintering enables to prepare such nanostructured ceramics with a favourable thermoelectric response. Our study shows that mechanosynthesis is a low-cost technological route for the production of thermoelectric chalcopyrite ceramics. Chalkopyrit CuFeS2 se ukázal jako slibný termoelektrický materiál. Vzhledem k termoelektrické účinnosti je její relativně vysoký a teplotně slabě závislý účiník, ekonomická dostupnost a ekologická neškodnost vyvážena vysokou tepelnou vodivostí mřížky. Proto je velmi žádoucí snížit tepelnou vodivost termoelektrického materiálu chalkopyritu bez zhoršení dalších termoelektrických vlastností. V naší studii dokazujeme, že mechanosyntéza následovaná vhodným slinováním umožňuje připravit takovou nanostrukturovanou keramiku s příznivou termoelektrickou odezvou. Naše studie ukazuje, že mechanosyntéza je levnou technologickou cestou pro výrobu termoelektrické keramiky z chalkopyritu.

In this work, we demonstrate the use of elemental precursors (Cu, Sb, S) to synthesize famatinite Cu3SbS4 using a laboratory planetary ball milling and an industrial eccentric vibratory milling. Cu3SbS4 was prepared for 120 min and 180 min in laboratory and industrial mill, respectively, with the utilization of protective atmosphere. The Cu3SbS4 prepared in the laboratory and industrial mill with crystallite size 14 nm and 10 nm, respectively, was confirmed by both LeBail refinement of the X-ray powder diffraction data and transmission electron microscopy. The determined band gap energy 1.31 eV and 1.24 eV is blue-shifted relative to the bulk Cu3SbS4. The synthesis of Cu3SbS4 by a scalable milling process represents a prospective route for mass production of material with potential photovoltaic properties.

In this study, gaseous CO2, solid ZnO and liquid H2O were converted to nanocrystalline (13 nm) hydrozincite, i.e. Zn5(CO3)2(OH)6 via fast one-step mechanochemical process at ambient temperature and pressure. The mechanically induced conversion of the three-phase mixture, studied by X-ray diffraction analysis, Fourier-transform infrared and X-ray photoelectron spectroscopies, completed in 10 min. X-ray diffraction and Fourier-transform infrared spectroscopy indicated the presence of disorder in the crystal structure of mechanosynthesized hydrozincite The physico-chemical properties of the mechanosynthesized hydrozincite, characterized in the view of surface and optical properties, were compared with the commercial hydrozincite. It was found that the Brunauer-Emmett-Teller surface area was almost 2 times higher (56.7 m2/g) than the corresponding value of the commercial material, which is related to the smaller particle size (∼230 nm). Both the ultraviolet-visible absorption and photoluminescence emission spectra recorded for the mechanosynthesized hydrozincite indicated size effect. The weight loss (26.5%) obtained during thermal decomposition of the mechanosynthesized material is close to the theoretical weight loss value of hydrozincite.

In this paper, InAs/ZnS mixed nanocrystals were synthesized by dry high-energy milling approach in the first step. The obtained nanocrystals were characterized from structural point of view by X-ray diffraction analysis and Raman spectroscopy, and from the morphological point of view by scanning electron microscopy. In the next step, the nanocrystals were subjected to wet ultra-fine milling in order to obtain a nanosuspension of chitosan-coated InAs/ZnS nanocrystals with bio-imaging properties. The stability of the nanosuspension was examined by zeta potential and particle size distribution measurements. The prepared nanosuspension was stable with high values of zeta potential. Its optical properties were also studied using UV–Vis and PL spectroscopies. The determined fluorescent properties confirming the potential in bio-imaging applications were verified on cancer cell lines Caco-2, HCT116, HeLa, and MCF7.

Synthesis of Co9Se8 phase from metallic cobalt and selenium powders by one-pot mechanochemical synthesis in a planetary ball mill and subsequent thermal treatment in argon atmosphere is reported. Crystal structure and morphology of the products were characterized by X-ray diffraction, specific surface area measurements, and transmission electron microscopy. Our study revealed that only mixture with excess of Co resulted in the formation of higher fraction of the Co9Se8 phase. While milling of Co and Se in 13.5:8 ratio resulted in the synthesis of nanocrystalline hexagonal CoSe (freboldite) and only around 13 wt.% of the targeted Co9Se8 phase, additional isothermal treatment at 450 °C increased yield of the Co9Se8 phase to more than 70%. Optical properties of the product with the highest Co9Se8 fraction showed broad absorption in whole UV–Vis optical region and band-gap energy of 1.93 eV, blue-shifted relative to the bulk Co9Se8. Both UV–Vis and photoluminescence spectra indicated quantum size effect of the finest nanocrystals in Co9Se8 product. The new combined approach represents a simple, fast, and easy up-scalable route for the synthesis of Co9Se8.

The ZnS nanocrystals were prepared in chitosan solution (0.1 wt.%) using a wet ultra-fine milling. The obtained suspension was stable and reached high value of zeta potential (+57 mV). The changes in FTIR spectrum confirmed the successful surface coating of ZnS nanoparticles by chitosan. The prepared ZnS nanocrystals possessed interesting optical properties verified in vitro. Four cancer cells were selected (CaCo-2, HCT116, HeLa, and MCF-7), and after their treatment with the nanosuspension, the distribution of ZnS in the cells was studied using a fluorescence microscope. The particles were clearly seen; they passed through the cell membrane and accumulated in cytosol. The biological activity of the cells was not influenced by nanoparticles, they did not cause cell death, and only the granularity of cells was increased as a consequence of cellular uptake. These results confirm the potential of ZnS nanocrystals using in bio-imaging applications.

Chalcogenide semiconductor cobalt monoselenide, CoSe, was prepared from metallic cobalt and selenium powders in stoichiometric ratio by simple and fast mechanochemical synthesis after 120 min of milling in a planetary ball mill Pulverisette 6 (Fritsch, Germany) in an argon atmosphere. Crystal structure and morphology of the product were characterized by X-ray diffraction, specific surface area measurements, and transmission electron microscopy. X-ray diffraction analysis confirmed the hexagonal crystal structure of the product-CoSe (freboldite) with the average size of the crystallites 26 nm. Transmission electron microscopy analysis has revealed that CoSe nanostructures are composed of agglomerated and randomly oriented nanoparticles. The optical properties were studied using UV–Vis and photoluminescence spectroscopy. Mechanochemically synthesized CoSe nanostructures showed higher absorption in whole UV–Vis optical region and the determined band-gap energy 1.70 eV is blue-shifted relative to the bulk CoSe. Both UV–Vis and photoluminescence spectra indicate quantum size effect of CoSe nanocrystals.

Within this study, a stable nanosuspension of silver nanoparticles (Ag NPs) was prepared using a two-step synthesis and stabilization approach. The Ag NPs were synthesized from a silver nitrate solution using the Origanum vulgare L. plant extract as the reducing agent. The formation of nanoparticles was finished upon 15 min, and subsequently, stabilization by polyvinylpyrrolidone (PVP) using wet stirred media milling was applied. UV-Vis spectra have shown a maximum at 445 nm, corresponding to the formation of spherical Ag NPs. Infrared spectroscopy was used to examine the interaction between Ag NPs and the capping agents. TEM study has shown the formation of Ag NPs with two different average sizes (38 ± 10 nm and 7 ± 3 nm) after the plant-mediated synthesis, both randomly distributed within the organic matrix. During milling in PVP, the clusters of Ag NPs were destroyed, the Ag NPs were fractionized and embedded in PVP. The nanosuspensions of PVP-capped Ag NPs were stable for more than 26 weeks, whereas for the non-stabilized nanosuspensions, only short-term stability for about 1 week was documented.

In this study, we demonstrate a one-pot mechanochemical synthesis of the nanocomposite composed of stannite Cu2FeSnS4 and rhodostannite Cu2FeSn3S8 nanocrystals using a planetary ball mill and elemental precursors (Cu, Fe, Sn, S). By this approach, unique nanostructures with interesting properties can be obtained. Methods of XRD, Raman spectroscopy, UV-Vis, nitrogen adsorption, SEM, EDX, HRTEM, STEM, and SQUID magnetometry were applied. Quaternary tetragonal phases of stannite and rhodostannite with crystallite sizes 18–19 nm were obtained. The dominant Raman peaks corresponding to the tetragonal stannite structure corresponding to A-symmetry optical modes were identified in the spectra. The bandgap 1.25 eV calculated from UV-Vis absorption spectrum is very well-acceptable value for the application of the synthesized material. The SEM micrographs illustrate the clusters of particles in micron and submicron range. The formation of agglomerates is also illustrated on the TEM micrographs. Weak ferromagnetic properties of the synthesized nanocrystals were documented

In this study we demonstrate the synthesis of quaternary semiconductor nanocrystals of stannite Cu2FeSnS4/rhodostannite Cu2FeSn3S8 (CFTS) via mechanochemical route using Cu, Fe, Sn and S elements as precursors in one-pot experiments. Methods of X-ray diffraction (XRD), nitrogen adsorption, high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) were applied to characterize properties of the unique nanostructures. Mechanochemical route of synthesis induced new phenomena like explosive character of reaction, where three stages could be identified and the formation of nanostructures 5–10 nm in size. By using XPS method, Cu(I), Fe(II), Sn(IV) and S(-II) species were identified on the surface of CFTS. The value of optical band gap 1.27 eV is optimal for semiconductors applicable as absorbers in solar cells. The significant photocatalytic activity of the CFTS nanocrystals was also evidenced. The obtained results confirm the excellent properties of the quaternary semiconductor nanocrystals synthesized from earth-abundant elements., This work was supported by the Slovak Research and Development Agency APVV (project APVV-0103-14) and by the National Science Fund (Bulgaria) under the contract DNTS/Slovakia 01/2. The support of the Research excellence centre on earth sources, extraction and treatment - 2nd phase supported by the Research & Development Operational Programme funded by the ERDF No. 26220120038 is also gratefully acknowledged., Chalcogenide Quaternary Cu2FeSnS4 Nanocrystals for Solar Cells: Explosive Character of Mechanochemical Synthesis and Environmental Challenge

The wet mechanochemical procedure for the capping of the CdS and CdS/ZnS quantum dot nanocrystals is reported. l-cysteine and polyvinylpyrrolidone (PVP) were used as capping agents. When using l-cysteine, the dissolution of cadmium(II) was almost none for CdS/ZnS nanocrystals. Moreover, prepared CdS- and CdS/ZnS-cysteine nanosuspensions exhibited unimodal particle size distributions with very good stability, which was further supported by the zeta potential measurements. The Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy showed the successful embedment of cysteine into the structure of the nanocrystals. Additionally, the optical properties were examined, and the results showed that the cysteine nanosuspension has promising fluorescence properties. On the other hand, PVP was not determined to be a very suitable capping agent for the present system. In this case, the release of cadmium(II) was higher in comparison to the l-cysteine capped samples. The nanosuspensions were successfully used for in vitro studies on selected cancer cell lines. Using fluorescence microscopy, it was evidenced that the nanocrystals enter the cell and that they can serve as imaging agents in biomedical applications.

The synthesis of nanocrystalline ternary CuInSe particles prepared by high-energy milling in a planetary mill in an argon atmosphere from copper, indium and selenium was reported. CuInSe particles crystallize in the tetragonal structure with the crystallite size of about 30.5 nm. The Raman spectrum of CuInSe nanoparticles shows a strong peak at 176 cm corresponds to the A phonon mode of tetragonal CuInSe chalcopyrite. HRTEM measurements also revealed the presence of nanocrystals with the size of 10-20 nm with the tendency to form agglomerates. The optical absorption study shows that nanoparticles have direct optical band gap energy of 1.8 eV. The quantum size effect of the particles was confirmed also by PL measurement., This work was promoted by the Slovak Research and Development Agency under the contract No. APVV-14-0103. The support through the Slovak Grant Agency VEGA (projects 2/0027/14, 1/0739/16, 2/0051/14) is also thankfully acknowledged. The authors also appreciate the help of the European Regional Development Fund- project NANOCEXMAT 2 (ITMS 26220120035) and European Union through the CT-2011-1-REGPOT285895 AL-NANOFUN project (Advanced Laboratory for the Nano-Analysis of novel Functional materials), for the microscopy facilities sited in Seville.

Nanocrystalline CuInS particles have been synthesized from copper, indium, and sulfur powders by high-energy milling in a planetary mill in an argon atmosphere. Structural characterization of the prepared nanoparticles, including phase identification, Raman spectroscopy, specific surface area measurement, and particle size analysis were performed. The optical properties were studied using UV–Vis absorption and photoluminescence (PL) spectroscopy. The production of CuInS (JCPDS 027-0159) particles with a crystallite size of about 17.5–23.5 nm was confirmed by X-ray diffraction. The crystal structure has a tetragonal body-centered symmetry belonging to the I-42d space group. The Raman spectra also proved the formation of pure CuInS nanoparticles. TEM and HRTEM measurements revealed the presence of nanoparticles of different dimensions (10–20 nm) and their tendency to form agglomerates. The nanoparticles tend to agglomerate due to their large specific surface area. The average size of the synthesized particles was determined by photon cross-correlation spectroscopy to be in the range of 330–530 nm (bimodal size distribution). The band gap of the CuInS particles is 2 eV which is wider than that in bulk materials. The decrease in size leads to the blue-shift of the PL spectra. Therefore, CuInS nanoparticles are promising candidates for optical applications, and they have high potential in solar energy conversion., The support through the Slovak Grant Agency VEGA (projects 2/0027/14, 1/0439/13, 2/0051/14) and APVV 14-0103 is gratefully acknowledged. The authors also acknowledge the support of the European Union through the CT-2011-1-REGPOT285895 AL-NANOFUN project (Advanced Laboratory for the Nano-Analysis of novel Functional materials), for the microscopy facilities sited at the Institute of Materials Science in Seville.

CdS/ZnS nanocomposites have been prepared by a two-step solid-state mechanochemical synthesis. CdS has been prepared from cadmium acetate and sodium sulfide precursors in the first step. The obtained cubic CdS (hawleyite, JCPDS 00-010-0454) was then mixed in the second step with the cubic ZnS (sphalerite, JCPDS 00-005-0566) synthesized mechanochemically from the analogous precursors. The crystallite sizes of the new type CdS/ZnS nanocomposite, calculated based on the XRD data, were 3-4 nm for both phases. The synthesized nanoparticles have been further characterized by high-resolution transmission electron microscopy (HRTEM) and micro-photoluminescence (μPL) spectroscopy. The PL emission peaks in the PL spectra are attributed to the recombination of holes/electrons in the nanocomposites occurring in depth associated with Cd, Zn vacancies and S interstitials. Their photocatalytic activity was also measured. In the photocatalytic activity tests to decolorize Methyl Orange dye aqueous solution, the process is faster and its effectivity is higher when using CdS/ZnS nanocomposite, compared to single phase CdS. Very low cytotoxic activity (high viability) of the cancer cell lines (selected as models of living cells) has been evidenced for CdS/ZnS in comparison with CdS alone. This fact is in a close relationship with Cd(II) ions dissolution tested in a physiological solution. The concentration of cadmium dissolved from CdS/ZnS nanocomposites with variable Cd:Zn ratio was 2.5-5.0 μg.mL(-1), whereas the concentration for pure CdS was much higher - 53 μg.ml(-1). The presence of ZnS in the nanocrystalline composite strongly reduced the release of cadmium into the physiological solution, which simulated the environment in the human body. The obtained CdS/ZnS quantum dots can serve as labeling media and co-agents in future anti-cancer drugs, because of their potential in theranostic applications.

Arsenic sulfide compounds have a long history of application in a traditional medicine. In recent years, realgar has been studied as a promising drug in cancer treatment. In this study, the arsenic sulfide (As4S4) nanoparticles combined with zinc sulfide (ZnS) ones in different molar ratio have been prepared by a simple mechanochemical route in a planetary mill. The successful synthesis and structural properties were confirmed and followed via X-ray diffraction and high-resolution transmission electron microscopy measurements. The morphology of the particles was studied via scanning electron microscopy and transmission electron microscopy methods and the presence of nanocrystallites was verified. For biological tests, the prepared As4S4/ZnS nanoparticles were further milled in a circulation mill in a water solution of Poloxamer 407 (0.5wt%), in order to cover the particles with this biocompatible copolymer and to obtain stable nanosuspensions with unimodal distribution. The average size of the particles in the nanosuspensions (~120nm) was determined by photon cross-correlation spectroscopy method. Stability of the nanosuspensions was determined via particle size distribution and zeta potential measurements, confirming no physico-chemical changes for several months. Interestingly, with the increasing amount of ZnS in the sample, the stability was improved. The anti-cancer effects were tested on two melanoma cell lines, A375 and Bowes, with promising results, confirming increased efficiency of the samples containing both As4S4 and ZnS nanocrystals.