Triggering antibacterial activity of a common plant by biosorption of selected heavy metals.

The presented study proposes an efficient utilization of a common Thymus serpyllum L. (wild thyme) plant as a highly potent biosorbent of Cu(II) and Pb(II) ions and the efficient interaction of the copper-laden plant with two opportunistic bacteria. Apart from biochars that are commonly used for adsorption, here we report the direct use of native plant, which is potentially interesting also for soil remediation. The highest adsorption capacity for Cu(II) and Pb(II) ions (qe = 12.66 and 53.13 mg g-1, respectively) was achieved after 10 and 30 min of adsorption, respectively. Moreover, the Cu-laden plant was shown to be an efficient antibacterial agent against the bacteria Escherichia coli and Staphylococcus aureus, the results being slightly better in the former case. Such an activity is enabled only via the interaction of the adsorbed ions effectively distributed within the biological matrix of the plant with bacterial cells. Thus, the sustainable resource can be used both for the treatment of wastewater and, after an effective embedment of metal ions, for the fight against microbes.

Calcite-aragonite transformation in an eggshell: a crucial role of organics and assessment of the impact of milling conditions on its extent using Taguchi design.

Phase transformations during high-energy ball milling, a tool of mechanochemistry, are interesting due to the possible production of metastable phases without the need for artificially introducing high temperatures and pressures. In our work, the transformation of calcite to aragonite in an eggshell is studied in detail. The presence of organic material, in either the naturally present eggshell membrane, or artificially supplied L-cysteine, was found to be crucial for the phase transformation to occur, its decomposition leading to a pressure increase necessary for aragonite formation. The presence of sulfur in the organics seems to be crucial, as corroborated by much lower phase transformation extent when utilizing sulfur-free organics for comparison. The degree of the transformation in an eggshell was strongly dependent on the used milling conditions. The optimization was assessed using the Taguchi method, namely using a 44 orthogonal array. The optimized parameters encompassed milling time, sample mass, milling speed and duration of breaks and it was shown that sample mass has a decisive effect on the amount of obtained aragonite. Under the most efficient conditions, 73.7% of aragonite was obtained. Prolonging milling until 4 hours further boosts the transformation, reaching 89.9% of aragonite, but further milling leads to the collapse of the aragonite structure and pure calcite was observed after 5 hours.

Mechanochemical synthesis of non-stoichiometric copper sulfide Cu1.8S applicable as a photocatalyst and antibacterial agent and synthesis scalability verification.

An effort to prepare different non-stoichiometric CuxSy compounds starting from elemental precursors using mechanochemistry was made in this study. However, out of the 7 stoichiometries tested, it was only possible to obtain three phases: covellite CuS, chalcocite Cu2S and digenite Cu1.8S and their mixtures. To obtain the digenite phase with the highest purity, the Cu : S stoichiometric ratio needed to be fixed at 1.6 : 1. The reaction between copper and sulfur was completed within a second range, however, milling was performed for up to 15 minutes until the equilibrium in phase composition between digenite and covellite was reached. The possibility of preparing the product in a 300 g batch by eccentric vibratory milling in 30 minutes was successfully verified at the end. The estimated crystallite sizes for the digenite Cu1.8S obtained via lab-scale and scalable experiments were around 12 and 17 nm, respectively. The obtained products were found to be efficient photocatalysts under visible light irradiation in the presence of hydrogen peroxide, being capable of the complete degradation of the Methyl Orange dye in a concentration of 10 mg L-1 in 2 hours. Finally, the antibacterial potential of both lab-scale and large-scale industrial products was proven and, regardless of the manufacturing scale, the nanoparticles retained their properties against bacterial cells.

The manipulation of natural mineral chalcopyrite CuFeS2via mechanochemistry: properties and thermoelectric potential.

In this study, the properties of the natural mineral chalcopyrite CuFeS2 after mechanical activation in a planetary mill were studied. The intensity of mechanical activation was controlled by changing the revolutions of the mill in the range 100-600 min-1. A series of characterization techniques, such as XRD, SEM, TEM, TA (DTA, TG, and DTG), particle size analysis, and UV-vis spectroscopy was applied and reactivity studies were also performed. Several new features were revealed for the mechanically activated chalcopyrite, e.g. the poly-modal distribution of produced nanoparticles on the micrometer scale, agglomeration effects by prolonged milling, possibility to modify the shape of the particles, X-ray amorphization and a shift from a non-cubic (tetragonal) structure to pseudo-cubic structure. The thermoelectric response was evaluated on the "softly" compacted powder via the spark plasma sintering method (very short holding time, low sintering temperature, and moderate pressure) by measuring the Seebeck coefficient and electrical and thermal conductivity above room temperature. The milling process produced samples with lower resistivity compared to the original non-activated sample. The Seebeck data close to zero confirmed the "compensated" character of natural chalcopyrite, reflecting its close-to stoichiometric composition with low concentration of both n- and p-type charge carriers. Alternatively, an evident correlation between thermal conductivity and energy supply by milling was observed with the possibility of band gap manipulation, which is associated with the energy delivered by the milling procedure.

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 (Cu11.4Sb4S13; 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.

A Brief Overview on Antioxidant Activity Determination of Silver Nanoparticles.

Our objective in this review article is to find out relevant information about methods of determination of antioxidant activity of silver nanoparticles. There are many studies dealing with mentioned problem and herein we summarize the knowledge about methods evaluating the antioxidant activity of silver nanoparticles reported so far. Many authors declare better antioxidant activity of silver nanoparticles compared to the extract used for synthesis of them. In this review, we focused on methods of antioxidant activity determination in detail to find out novel and perspective techniques to solve the general problems associated with the determination of antioxidant activity of silver nanoparticles.

Simultaneous valorization of polyvinyl chloride and eggshell wastes by a semi-industrial mechanochemical approach.

A semi-industrial approach for simultaneous treatment of eggshell and industrial polyvinyl chloride waste utilizing tools of ball milling is reported therein. On a hundred-gram scale, it is possible to transfer more than 55% of chlorine present in the polyvinyl chloride representing an environmental burden, into harmless soluble form. On a laboratory scale, a complete dechlorination was achieved. The ratio of eggshell-to-polyvinyl chloride plays a significant role for the effective dechlorination and the kinetics of semi-industrial process follows zero-order kinetics with the rate constant 1.23 × 10-5 s-1. Chlorine is mainly in the form of calcium chloride. This study is an example of efficient simultaneous valorization of two waste materials on a semi-industrial scale, as the products can be utilized again.

Mechanochemical Synthesis and Characterization of CuInS2/ZnS Nanocrystals.

In this study, CuInS2/ZnS nanocrystals were synthesized by a two-step mechanochemical synthesis for the first time. In the first step, tetragonal CuInS2 was prepared from copper, indium and sulphur precursors. The obtained CuInS2 was further co-milled with zinc acetate dihydrate and sodium sulphide nonahydrate as precursors for cubic ZnS. Structural characterization of the CuInS2/ZnS nanocrystals was performed by X-ray diffraction analysis, Raman spectroscopy and transmission electron microscopy. Specific surface area of the product (86 m²/g) was measured by low-temperature nitrogen adsorption method and zeta potential of the particles dispersed in water was calculated from measurements of their electrophoretic mobility. Optical properties of the nanocrystals were determined using photoluminescence emission spectroscopy.

Mechanochemical Synthesis and Isomerization of N-Substituted Indole-3-carboxaldehyde Oximes †.

Performing solution-phase oximation reactions with hydroxylamine hydrochloride (NH2OH·HCl) carries significant risk, especially in aqueous solutions. In the present study, four N-substituted indole-3-carboxaldehyde oximes were prepared from the corresponding aldehydes by solvent-free reaction with NH2OH·HCl and a base (NaOH or Na2CO3) using a mechanochemical approach, thus minimizing the possible risk. In all cases, the conversion to oximes was almost complete. The focus of this work is on 1-methoxyindole-3-carboxaldehyde oxime, a key intermediate in the production of indole phytoalexins with useful antimicrobial properties. Under optimized conditions, it was possible to reach almost 95% yield after 20 min of milling. Moreover, for the products containing electron-donating substituents (-CH3, -OCH3), the isomerization from the oxime anti to syn isomer under acidic conditions was discovered. For the 1-methoxy analog, the acidic isomerization of pure isomers in solution resulted in the formation of anti isomer, whereas the prevalence of syn isomer was observed in solid state. From NMR data the syn and anti structures of produced oximes were elucidated. This work shows an interesting and possibly scalable alternative to classical synthesis and underlines environmentally friendly and sustainable character of mechanochemistry.

Hallmarks of mechanochemistry: from nanoparticles to technology.

The aim of this review article on recent developments of mechanochemistry (nowadays established as a part of chemistry) is to provide a comprehensive overview of advances achieved in the field of atomistic processes, phase transformations, simple and multicomponent nanosystems and peculiarities of mechanochemical reactions. Industrial aspects with successful penetration into fields like materials engineering, heterogeneous catalysis and extractive metallurgy are also reviewed. The hallmarks of mechanochemistry include influencing reactivity of solids by the presence of solid-state defects, interphases and relaxation phenomena, enabling processes to take place under non-equilibrium conditions, creating a well-crystallized core of nanoparticles with disordered near-surface shell regions and performing simple dry time-convenient one-step syntheses. Underlying these hallmarks are technological consequences like preparing new nanomaterials with the desired properties or producing these materials in a reproducible way with high yield and under simple and easy operating conditions. The last but not least hallmark is enabling work under environmentally friendly and essentially waste-free conditions (822 references).

Demonstrating the Simplicity and In Situ Temperature Monitoring of the Mechanochemical Synthesis of Metal Chalcogenides Suitable for Thermoelectrics.

Mechanochemical synthesis is an extremely useful strategy to reach thermoelectric materials due to its solvent-free one-step character, as the targeted thermoelectricity (TE) materials in a nanocrystalline format can be prepared by mere high-energy milling of elemental precursors. Nevertheless, the subsequent densification method (e.g., spark plasma sintering or hot pressing) is required afterward, similarly to other synthetic methodologies. In this study, the simplicity of mechanochemical synthesis is presented for two selected metal chalcogenides, namely copper sulfide (Cu1.8S, digenite) and tin selenide (SnSe, svetlanaite), which are known for high ZT values. These compounds can be prepared via a mechanically induced self-propagating reaction (MSR), which is a combustion-like process instantly yielding the products in a very short timeframe (within 1 min). The occurrence of MSR can be well-tracked by in situ temperature monitoring since an abrupt temperature increase occurs at the moment of MSR. We have developed a device which is capable of monitoring the temperature inside the milling jar every 80 ms during planetary ball milling, and it is therefore possible to very precisely track the moment of MSR ignition. The developed device presents an improvement in the monitoring capabilities in comparison with commercially available analogs. This contribution aims to provide a visual insight into all steps, with simple high-energy ball milling of elements to reach TE materials and in situ temperature monitoring being the central points.

Effect of Gentamicin Sulfate and Polymeric Polyethylene Glycol Coating on the Degradation and Cytotoxicity of Iron-Based Biomaterials.

The work is focused on the degradation, cytotoxicity, and antibacterial properties, of iron-based biomaterials with a bioactive coating layer. The foam and the compact iron samples were coated with a polyethylene glycol (PEG) polymer layer without and with gentamicin sulfate (PEG + Ge). The corrosion properties of coated and uncoated samples were studied using the degradation testing in Hanks' solution at 37 °C. The electrochemical and static immersion corrosion tests revealed that the PEG-coated samples corroded faster than samples with the bioactive PEG + Ge coating and uncoated samples. The foam samples corroded faster compared with the compact samples. To determine the cytotoxicity, cell viability was monitored in the presence of porous foam and compact iron samples. The antibacterial activity of the samples with PEG and PEG + Ge against Escherichia coli CCM 3954 and Staphylococcus aureus CCM 4223 strains was also tested. Tested PEG + Ge samples showed significant antibacterial activity against both bacterial strains. Therefore, the biodegradable iron-based materials with a bioactive coating could be a suitable successor to the metal materials studied thus far as well as the materials used in the field of medicine.

The influence of HKUST-1 and MOF-76 hand grinding/mechanical activation on stability, particle size, textural properties and carbon dioxide sorption.

In this study, we explore the mechanical treatment of two metal-organic frameworks (MOFs), HKUST-1 and MOF-76, applying various milling methods to assess their impact on stability, porosity, and CO2 adsorption capacity. The effects of different mechanical grinding techniques, such as high-energy ball milling and hand grinding, on these MOFs were compared. The impact of milling time, milling speed and ball size during high-energy ball milling was assessed via the Design of Experiments methodology, namely using a 33 Taguchi orthogonal array. The results highlight a marked improvement in CO2 adsorption capacity for HKUST-1 through hand milling, increasing from an initial 25.70 wt.% (5.84 mmol g-1) to 41.37 wt.% (9.40 mmol g-1), marking a significant 38% increase. In contrast, high-energy ball milling seems to worsen this property, diminishing the CO2 adsorption abilities of the materials. Notably, MOF-76 shows resistance to hand grinding, closely resembling the original sample's performance. Hand grinding also proved to be well reproducible. These findings clarify the complex effects of mechanical milling on MOF materials, emphasising the necessity of choosing the proper processing techniques to enhance their stability, texture, and performance in CO2 capture and storage applications.

Investigation of Calcium Forms in Lichens from Travertine Sites.

Lichens are symbiotic organisms with an extraordinary capability to colonise areas of extreme climate and heavily contaminated sites, such as metal-rich habitats. Lichens have developed several mechanisms to overcome the toxicity of metals, including the ability to bind metal cations to extracellular sites of symbiotic partners and to subsequently form oxalates. Calcium is an essential alkaline earth element that is important in various cell processes. Calcium can serve as a metal ligand but can be toxic at elevated concentrations. This study investigated calcium-rich and calcium-poor sites and the lichen species that inhabit them (Cladonia sp.). The calcium content of these lichen species were analyzed, along with localized calcium oxalate formed in thalli collected from each site. The highest concentration of calcium was found in the lichen squamules, which can serve as a final deposit for detoxification. Interestingly, the highest content of calcium in Cladonia furcata was localized to the upper part of the thallus, which is the youngest. The produced calcium oxalates were species-specific. Whewellite (CaC2O4∙H2O) was formed in the case of C. furcata and weddellite (CaC2O4∙2H2O) was identified in C. foliacea.

Mechanochemical Preparation, Characterization and Biological Activity of Stable CuS Nanosuspension Capped by Bovine Serum Albumin.

The biocompatible nanosuspension of CuS nanoparticles (NPs) using bovine serum albumin (BSA) as a capping agent was prepared using a two-stage mechanochemical approach. CuS NPs were firstly synthetized by a high-energy planetary ball milling in 15 min by milling elemental precursors. The stability of nanoparticles in the simulated body fluids was studied, revealing zero copper concentration in the leachates, except simulated lung fluid (SLF, 0.015%) and simulated gastric fluid (SGF, 0.078%). Albumin sorption on CuS NPs was studied in static and dynamic modes showing a higher kinetic rate for the dynamic mode. The equilibrium state of adsorption was reached after 90 min with an adsorption capacity of 86 mg/g compared to the static mode when the capacity 59 mg/g was reached after 2 h. Then, a wet stirred media milling in a solution of BSA was introduced to yield the CuS-BSA nanosuspension, being stable for more than 10 months, as confirmed by photon cross-correlation spectroscopy. The fluorescent properties of the nanosuspension were confirmed by photoluminescence spectroscopy, which also showed that tryptophan present in the BSA could be closer to the binding site of CuS than the tyrosine residue. The biological activity was determined by in vitro tests on selected cancer and non-tumor cell lines. The results have shown that the CuS-BSA nanosuspension inhibits the metabolic activity of the cells as well as decreases their viability upon photothermal ablation.

Properties of CuFeS2/TiO2 Nanocomposite Prepared by Mechanochemical Synthesis.

CuFeS2/TiO2 nanocomposite has been prepared by a simple, low-cost mechanochemical route to assess its visible-light-driven photocatalytic efficiency in Methyl Orange azo dye decolorization. The structural and microstructural characterization was studied using X-ray diffraction and high-resolution transmission electron microscopy. The presence of both components in the composite and a partial anatase-to-rutile phase transformation was proven by X-ray diffraction. Both components exhibit crystallite size below 10 nm. The crystallite size of both phases in the range of 10-20 nm was found and confirmed by TEM. Surface and morphological properties were characterized by scanning electron microscopy and nitrogen adsorption measurement. Scanning electron microscopy has shown that the nanoparticles are agglomerated into larger grains. The specific surface area of the nanocomposite was determined to be 21.2 m2·g-1. Optical properties using UV-Vis and photoluminescence spectroscopy were also investigated. CuFeS2/TiO2 nanocomposite exhibits strong absorption with the determined optical band gap 2.75 eV. Electron paramagnetic resonance analysis has found two types of paramagnetic ions in the nanocomposite. Mössbauer spectra showed the existence of antiferromagnetic and paramagnetic spin structure in the nanocomposite. The CuFeS2/TiO2 nanocomposite showed the highest discoloration activity with a MO conversion of ~ 74% after 120 min irradiation. This study has shown the possibility to prepare nanocomposite material with enhanced photocatalytic activity of decoloration of MO in the visible range by an environmentally friendly manner.