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.

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.

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.

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.

Ternary and Quaternary Nanocrystalline Cu-Based Sulfides as Perspective Antibacterial Materials Mechanochemically Synthesized in a Scalable Fashion.

Twelve Cu-based ternary (Cu-Me1-S, Me1 = Fe, Sn, or Sb) and quaternary (Cu-Me2-Sn-S, Me2 = Fe, Zn, or V) nanocrystalline sulfides are shown as perspective antibacterial materials here. They were prepared from elemental precursors by a one-step solvent-free mechanochemical synthesis in a 100 g batch using scalable eccentric vibratory ball milling. Most of the products have shown strong antibacterial activity against Escherichia coli and Staphylococcus aureus bacteria. For instance, stannite Cu2FeSnS4 and mohite Cu2SnS3 were the most active against E. coli, whereas kesterite Cu2ZnSnS4 and rhodostannite Cu2FeSn3S8 exhibited the highest antibacterial activity against S. aureus. In general, stannite has shown the best antibacterial properties out of all the studied samples. Five out of twelve products have been prepared using mechanochemical synthesis for the first time in a scalable fashion here. The presented synthetic approach is a promising alternative to traditional syntheses of nanomaterials suitable for biological applications and shows ternary and quaternary sulfides as potential candidates for the next-generation antibacterial agents.

Sustainable Synthesis of Cadmium Sulfide, with Applicability in Photocatalysis, Hydrogen Production, and as an Antibacterial Agent, Using Two Mechanochemical Protocols.

CdS nanoparticles were successfully synthesized using cadmium acetate and sodium sulfide as Cd and S precursors, respectively. The effect of using sodium thiosulfate as an additional sulfur precursor was also investigated (combined milling). The samples were characterized by XRD, Raman spectroscopy, XPS, UV-Vis spectroscopy, PL spectroscopy, DLS, and TEM. Photocatalytic activities of both CdS samples were compared. The photocatalytic activity of CdS, which is produced by combined milling, was superior to that of CdS, and was obtained by an acetate route in the degradation of Orange II under visible light irradiation. Better results for CdS prepared using a combined approach were also evidenced in photocatalytic experiments on hydrogen generation. The antibacterial potential of mechanochemically prepared CdS nanocrystals was also tested on reference strains of E. coli and S. aureus. Susceptibility tests included a 24-h toxicity test, a disk diffusion assay, and respiration monitoring. Bacterial growth was not completely inhibited by the presence of neither nanomaterial in the growth environment. However, the experiments have confirmed that the nanoparticles have some capability to inhibit bacterial growth during the logarithmic growth phase, with a more substantial effect coming from CdS nanoparticles prepared in the absence of sodium thiosulfate. The present research demonstrated the solvent-free, facile, and sustainable character of mechanochemical synthesis to produce semiconductor nanocrystals with multidisciplinary application.

A Unique Mechanochemical Redox Reaction Yielding Nanostructured Double Perovskite Sr2FeMoO6 With an Extraordinarily High Degree of Anti-Site Disorder.

Strontium ferromolybdate, Sr2FeMoO6, is an important member of the family of double perovskites with the possible technological applications in the field of spintronics and solid oxide fuel cells. Its preparation via a multi-step ceramic route or various wet chemistry-based routes is notoriously difficult. The present work demonstrates that Sr2FeMoO6 can be mechanosynthesized at ambient temperature in air directly from its precursors (SrO, α-Fe, MoO3) in the form of nanostructured powders, without the need for solvents and/or calcination under controlled oxygen fugacity. The mechanically induced evolution of the Sr2FeMoO6 phase and the far-from-equilibrium structural state of the reaction product are systematically monitored with XRD and a variety of spectroscopic techniques including Raman spectroscopy, 57Fe Mössbauer spectroscopy, and X-ray photoelectron spectroscopy. The unique extensive oxidation of iron species (Fe0 → Fe3+) with simultaneous reduction of Mo cations (Mo6+ → Mo5+), occuring during the mechanosynthesis of Sr2FeMoO6, is attributed to the mechanically triggered formation of tiny metallic iron nanoparticles in superparamagnetic state with a large reaction surface and a high oxidation affinity, whose steady presence in the reaction mixture of the milled educts initiates/promotes the swift redox reaction. High-resolution transmission electron microscopy observations reveal that the mechanosynthesized Sr2FeMoO6, even after its moderate thermal treatment at 923 K for 30 min in air, exhibits the nanostructured nature with the average particle size of 21(4) nm. At the short-range scale, the nanostructure of the as-prepared Sr2FeMoO6 is characterized by both, the strongly distorted geometry of the constituent FeO6 octahedra and the extraordinarily high degree of anti-site disorder. The degree of anti-site disorder ASD = 0.5, derived independently from the present experimental XRD, Mössbauer, and SQUID magnetization data, corresponds to the completely random distribution of Fe3+ and Mo5+ cations over the sites of octahedral coordination provided by the double perovskite structure. Moreover, the fully anti-site disordered Sr2FeMoO6 nanoparticles exhibit superparamagnetism with the blocking temperature T B = 240 K and the deteriorated effective magnetic moment µ = 0.055 µ B per formula unit.

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.

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.

Mechanochemistry for Energy Materials: Impact of High-Energy Milling on Chemical, Electric and Thermal Transport Properties of Chalcopyrite CuFeS2 Nanoparticles.

Chalcopyrite CuFeS2 , a semiconductor with applications in chemical sector and energy conversion engineering, was synthetized in a planetary mill from elemental precursors. The synthesis is environmentally friendly, waste-free and inexpensive. The synthesized nano-powders were characterized by XRD, SEM, EDX, BET and UV/Vis techniques, tests of chemical reactivity and, namely, thermoelectric performance of sintered ceramics followed. The crystallite size of ∼13 nm and the strain of ∼17 were calculated for CuFeS2 powders milled for 60, 120, 180 and 240 min, respectively. The evolution of characteristic band gaps, Eg, and the rate constant of leaching, k, of nano-powders are corroborated by the universal evolution of the parameter SBET /X (SBET -specific surface area, X-crystallinity) introduced for complex characterization of mechanochemically activated solids in various fields such as chemical engineering and/or energy conversion. The focus on non-doped semiconducting CuFeS2 enabled to assess the role of impurities, which critically and often negatively influence the thermoelectric properties.

Bismuth Doping in Nanostructured Tetrahedrite: Scalable Synthesis and Thermoelectric Performance.

In this study, we demonstrate the feasibility of Bi-doped tetrahedrite Cu12Sb4-xBixS13 (x = 0.02-0.20) synthesis in an industrial eccentric vibratory mill using Cu, Sb, Bi and S elemental precursors. High-energy milling was followed by spark plasma sintering. In all the samples, the prevailing content of tetrahedrite Cu12Sb4S13 (71-87%) and famatinite Cu3SbS4 (13-21%), together with small amounts of skinnerite Cu3SbS3, have been detected. The occurrence of the individual Cu-Sb-S phases and oxidation states of bismuth identified as Bi0 and Bi3+ are correlated. The most prominent effect of the simultaneous milling and doping on the thermoelectric properties is a decrease in the total thermal conductivity (κ) with increasing Bi content, in relation with the increasing amount of famatinite and skinnerite contents. The lowest value of κ was achieved for x = 0.2 (1.1 W m-1 K-1 at 675 K). However, this sample also manifests the lowest electrical conductivity σ, combined with relatively unchanged values for the Seebeck coefficient (S) compared with the un-doped sample. Overall, the lowered electrical performances outweigh the benefits from the decrease in thermal conductivity and the resulting figure-of-merit values illustrate a degradation effect of Bi doping on the thermoelectric properties of tetrahedrite in these synthesis conditions.

Thermosensitive Drug Delivery System SBA-15-PEI for Controlled Release of Nonsteroidal Anti-Inflammatory Drug Diclofenac Sodium Salt: A Comparative Study.

Mesoporous SBA-15 silica material was prepared by the sol-gel method and functionalized with thermosensitive polyethylenimine polymers with different molecular weight (g·mol-1): 800 (SBA-15(C)-800), 1300 (SBA-15(C)-1300) and 2000 (SBA-15(C)-2000). The nonsteroidal anti-inflammatory drug (NSAID) diclofenac sodium was selected as a model drug and encapsulated into the pores of prepared supports. Materials were characterized by the combination of infrared spectroscopy (IR), atomic force microscopy (AFM), transmission electron microscopy (TEM), photon cross-correlation spectroscopy (PCCS), nitrogen adsorption/desorption analysis, thermogravimetry (TG), differential scanning calorimetry (DSC) and small-angle X-ray diffraction (SA-XRD) experiments. The drug release from prepared matrixes was realized in two model media differing in pH, namely small intestine environment/simulated body fluid (pH = 7.4) and simulated gastric fluid (pH = 2), and at different temperatures, namely normal body temperature (T = 37 °C) and inflammatory temperature (T = 42 °C). The process of drug loading into the pores of prepared materials from the diclofenac sodium salt solutions with different concentrations and subsequent quantitative determination of released drugs was analyzed by UV-VIS spectroscopy. Analysis of prepared SBA-15 materials modified with polyethylenimines in solution showed a high ability to store large amounts of the drug, up to 230 wt.%. Experimental results showed their high drug release into the solution at pH = 7.4 for both temperatures, which is related to the high solubility of diclofenac sodium in a slightly alkaline environment. At pH = 2, a difference in drug release rate was observed between both temperatures. Indeed, at a higher temperature, the release rates and the amount of released drug were 2-3 times higher than those observed at a lower temperature. Different kinetic models were used to fit the obtained drug release data to determine the drug release rate and its release mechanism. Moreover, the drug release properties of prepared compounds were compared to a commercially available medicament under the same experimental conditions.

Green Synthesis of Silver Nanoparticles with Antibacterial Activity Using Various Medicinal Plant Extracts: Morphology and Antibacterial Efficacy.

A green synthetic route for the production of silver nanoparticles (AgNPs) using five different aqueous plant extracts, namely, Berberis vulgaris, Brassica nigra, Capsella bursa-pastoris, Lavandula angustifolia and Origanum vulgare, was investigated in this study. The present work demonstrates the influence of plant extract composition (antioxidant and total phenolic content) on the size and morphology of the produced AgNPs. The biosynthetic procedure was rapid and simple and was easily monitored via colour changes and ultraviolet and visible (UV-Vis) spectroscopy. Subsequently, measurement of zeta potential (ZP), photon cross-correlation spectroscopy (PCCS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and selected area electron diffraction (SAED) analysis were employed to characterise the as-synthesised nanoparticles. The XRD investigation confirmed the presence of Ag0 in the nanoparticles, and interactions between the bioactive compounds of the plants and the produced AgNPs were evident in the FTIR spectra. TEM indicated that the nanoparticles exhibited a bimodal size distribution, with the smaller particles being spherical and the larger having a truncated octahedron shape. In addition, the antimicrobial activity of the AgNPs was tested against five bacterial strains. All synthesised nanoparticles exhibited enhanced antimicrobial activity at a precursor concentration of 5 mM compared to the control substance, gentamicin sulphate, with the best results observed for AgNPs prepared with B. nigra and L. angustifolia extracts.

Mechanochemistry as an Alternative Method of Green Synthesis of Silver Nanoparticles with Antibacterial Activity: A Comparative Study.

This study shows mechanochemical synthesis as an alternative method to the traditional green synthesis of silver nanoparticles in a comparative manner by comparing the products obtained using both methodologies and different characterization methods. As a silver precursor, the most commonly used silver nitrate was applied and the easily accessible lavender (Lavandula angustofolia L.) plant was used as a reducing agent. Both syntheses were performed using 7 different lavender:AgNO3 mass ratios. The synthesis time was limited to 8 and 15 min in the case of green and mechanochemical synthesis, respectively, although a significant amount of unreacted silver nitrate was detected in both crude reaction mixtures at low lavender:AgNO3 ratios. This finding is of particular interest mainly for green synthesis, as the potential presence of silver nitrate in the produced nanosuspension is often overlooked. Unreacted AgNO3 has been removed from the mechanochemically synthesized samples by washing. The nanocrystalline character of the products has been confirmed by both X-ray diffraction (Rietveld refinement) and transmission electron microscopy. The latter has shown bimodal size distribution with larger particles in tens of nanometers and the smaller ones below 10 nm in size. In the case of green synthesis, the used lavender:AgNO3 ratio was found to have a decisive role on the crystallite size. Silver chloride has been detected as a side-product, mainly at high lavender:AgNO3 ratios. Both products have shown a strong antibacterial activity, being higher in the case of green synthesis, but this can be ascribed to the presence of unreacted AgNO3. Thus, one-step mechanochemical synthesis (without the need to prepare extract and performing the synthesis as separate steps) can be applied as a sustainable alternative to the traditional green synthesis of Ag nanoparticles using plants.

Biological activity of selected lichens and lichen-based Ag nanoparticles prepared by a green solid-state mechanochemical approach.

Lichens dispose a wide spectrum of bioactive compounds known as secondary metabolites. Their biological effects like antioxidant and antibacterial activities are widely studied. Green synthesis of silver nanoparticles (AgNPs) is a method where the compounds/substances present in plants are used for reduction of AgNO3instead of toxic chemicals. However, this methodology is usually a two-step process (extract preparation step and the synthesis step) performed under the elevated temperatures nad in the case of lichens, the redicing compounds are insoluble in water. These disadvantages can be overcome by a solid-state mechanochemical synthesis applied in the present study. As microorganisms are becoming more resistant to commercial antibiotics, AgNPs prepared in an environmentally friendly way represent an interesting alternative. In the present study, we compared the processing of lichen material of Pseudevernia furfuracea and Lobaria pulmonaria for extraction as well as for synthesis of AgNPs, and tested the antibacterial and antioxidant activity of the extracts. Both selected lichen species could be successfully used as reducing agents to produce AgNPs. Six different bacterial strains were tested for antibacterial activity of AgNPs-containing products and it was highly effective on all strains. However, the antioxidant activity of lichen extracts showed the lowest effect even if AgNPs are present which positively correlated with the content of total phenols and flavonoids. Both phenols and flavonoids are natural antioxidants and react with silver nitrate. Due to this fact, we observed a decrease of total phenols, total flavonoids as well as antioxidant activity when processing of lichen extracts with silver nitrate was used. We demonstrated that the formation of AgNPs increased the antibacterial activity but on the other hand reduced the antioxidant activity. Thus, antibacterial and antioxidant effects have to be treated differentially.