Microwave-Assisted Hydrothermal Synthesis of Pure-Phase Sodalite (>99 wt.%) in Suspension: Methodology Design and Verification.

Despite numerous studies focused on the hydrothermal (HT) synthesis of fly ash zeolites (FAZs), this method still has many limitations, the main of which is the low yield of zeolites. Hydrothermally synthesized zeolites are typically multiphase and exhibit low purity, which limits their applicability. Pure-phase zeolites have been primarily prepared from filtrates after alkaline mineralization of fly ashes, not directly in suspension. In addition, the published methodologies have not been tested in a wider set of samples, and thus their reproducibility is not confirmed. The aim of the study is to propose a reproducible methodology that overcomes the mentioned limitations. The influence of the Si/Al ratio (1.3:1-1:2), the type and concentration of the activator (2/4 M NaOH/KOH/LiOH), the reagent (30% LiCl), the duration (24-168 h), and the temperature (50-180 °C) of the synthesis phases were studied. The sequence of the synthesis phases was also optimized, depending on the type of heat transfer. The fly ashes were analyzed by wavelength-dispersive X-ray fluorescence (WD XRF), flame atomic absorption spectrometry (F-AAS), and X-ray diffraction (XRD). The energy intensity of the synthesis was reduced through the application of unique microwave digestion technology. Both microwave and combined (microwave and convection) syntheses were conducted. FAZs were identified and quantified by XRD analysis. This study presents a three-stage (TS) hydrothermal synthesis of pure-phase sodalite in suspension. Sodalite (>99 wt.%) was prepared from nine fly ashes under the following conditions: I. microwave phase: 120 °C, 150 min, solid-to-liquid ratio (S/L) 1:5, Si/Al ratio 1:1.5, and 4 M NaOH; II. convection phase: 120 °C, 24 h, S/L 1:40, and the addition of 30 mL of 30% LiCl; and III. crystallization: 70 °C for 24 h. The formation of rhombododecahedral sodalite crystals was confirmed by scanning electron microscope (SEM) images.

Electrochemical characterization of leached steel-making sludge.

In this work, the electrochemical properties of the leached sludge, magnetite and zinc ferrite were studied. Acetic acid was used as a leaching reagent because, in recent years, there has been a surge of interest in using zinc-containing materials as photocatalysts, with acetic acid finding application in their preparation. Various methodological approaches were used, but the best results were achieved with a combination of 1-3 h leaching in 0.01 M acetic acid with a solid/liquid ratio of 500. In this arrangement, zincite was almost completely removed from the sludge, while zinc ferrite and magnetite remained in the solid residue. Ex situ analyses of the main leaching products were performed by X-ray diffraction, infrared spectroscopy, and thermogravimetry. The electrochemical behaviour of solid residue and model systems, that are micromagnetite and zinc ferrite, was studied in alkaline media by means of modified carbon paste electrodes, cyclic voltammetry, and chronocoulometry, with a suitable potential window ranging from 0 to 1.5 V. In summary, a linear dependence of the anodic and cathodic peak height on the square root of the scan rate was found. The position of the anodic and cathodic peaks shifted slightly with scan rate, only at low rates, up to 25 mV/s, the individual peaks coincided. The electrochemical response suggested a quasireversible process.

The Effect of Trace Oxygen Addition on the Interface Behavior of Low-Alloy Steel.

This work aims to assess the effect of an oxygen content graded in minimal quantities, on the order of hundreds of ppms, on the determination of surface tension of low-alloy FeCOCr and FeCONi steels in contact with a corundum substrate. Oxygen, as a surface-active element, was segregated at the surface where it interacted with the major components of the alloys, leading to a reduction in surface tension. The sessile drop method was used for wetting tests in the temperature range from steel liquidus temperatures to 1600 °C under nonoxidizing conditions. The effect of oxygen on surface tension and wetting angles was verified by statistical analysis using the Kruskal-Wallis test, which supported the results stating that the values of these quantities decreased with increasing oxygen content. Furthermore, liquidus temperatures, which are of practical importance, were determined by the optical and DTA methods and then compared with theoretically calculated temperature values. It turned out that the increased chromium content causes difficulties in determining surface tension up to 1550 °C due to the formation of a thin Cr2O3 layer. In addition, SEM and XRD analyses accompanied by calculations in the FactSage oxide database were performed to better understand the wetting mechanism.

Crucial cytotoxic and antimicrobial activity changes driven by amount of doped silver in biocompatible carbon nitride nanosheets.

The use of Ag-modified nanomaterials continues to attract attention in biological contamination control, their potential cytotoxicity is often overlooked. Herein, biocompatible carbon nitride is modified with 1 and 5 wt.% Ag and effects of different nanomaterial dose and Ag content on antimicrobial activity and cytotoxicity is studied. Pure Ag nanoparticles and AgNO3 is tested for comparison, together with ten bacterial strains including pan-resistant Pseudomonas aeruginosa. Cytotoxicity is then investigated in three adherent and two suspension human cell lines, and results confirm that cancer adherent cell lines are the most immune lines and human cervical adenocarcinoma cells (HeLa) are more resilient than human lung adenocarcinoma cells (A549). The HeLa remains over 90 % viable even after 24 -h treatment with the highest concentration of 5%Ag/g-C3N4 (300 mg L-1) while A549 sustained viability only up to 100 mg L-1. Higher concentrations then induce cytotoxicity and A549 cell viability decreases. Our results show the importance of complementary testing of cytotoxicity by LIVE/DEAD assay using flow cytometry with more different human cell lines, which might be less immune to tested nanomaterials than HeLa and A549. Combined controls of new antibacterial agent activity tests then provide increased knowledge of their biocompatibility.

Development of Stimuli-Responsive Chitosan/ZnO NPs Transdermal Systems for Controlled Cannabidiol Delivery.

One of the most common neurological diseases is epilepsy, which not only negatively affects the quality of people's life but also may lead to life-threatening situations when its symptoms such as seizures cannot be controlled medically. A very serious problem to be overcame is the untreatable form of this disease, which cannot be cured by any currently available medicines. Cannabidiol, which is a natural product obtained from Cannabis Sativa, brings a new hope to people suffering from drug-resistant epilepsy. However, the hydrophobic character of this compound significantly lowers its clinical efficiency. One of the promising methods of this substance bioactivity increase is delivery through the skin tissue. In this article, a new type of advanced transdermal systems based on chitosan and ZnO nanoparticles (NPs) has been developed according to Sustained Development principles. The chemical modification of the biopolymer confirmed by FT-IR method resulted in the preparation of the material with great swelling abilities and appropriate water vapor permeability. Obtained nanoparticles were investigated over their crystalline structure and morphology and their positive impact on drug loading capacity and cannabidiol controlled release was proved. The novel biomaterials were confirmed to have conductive properties and not be cytotoxic to L929 mouse fibroblasts.

Metal Ions Supported Porous Coatings by Using AC Plasma Electrolytic Oxidation Processing.

Coatings enriched with zinc and copper as well as calcium or magnesium, fabricated on titanium substrate by Plasma Electrolytic Oxidation (PEO) under AC conditions (two cathodic voltages, i.e., -35 or -135 V, and anodic voltage of +400 V), were investigated. In all experiments, the electrolytes were based on concentrated orthophosphoric acid (85 wt%) and zinc, copper, calcium and/or magnesium nitrates. It was found that the introduced calcium and magnesium were in the ranges 5.0-5.4 at% and 5.6-6.5 at%, respectively, while the zinc and copper amounts were in the range of 0.3-0.6 at%. Additionally, it was noted that the metals of the block S (Ca and Mg) could be incorporated into the structure about 13 times more than metals of the transition group (Zn and Cu). The incorporated metals (from the electrolyte) into the top-layer of PEO phosphate coatings were on their first (Cu+) or second (Cu2+, Ca2+ and Mg2+) oxidation states. The crystalline phases (TiO and Ti3O) were detected only in coatings fabricated at cathodic voltage of -135 V. It has also been pointed that fabricated porous calcium-phosphate coatings enriched with biocompatible magnesium as well as with antibacterial zinc and copper are dedicated mainly to medical applications. However, their use for other applications (e.g., catalysis and photocatalysis) after additional functionalizations is not excluded.

The Potential of Novel Chitosan-Based Scaffolds in Pelvic Organ Prolapse (POP) Treatment through Tissue Engineering.

The growing number of female reproductive system disorders creates a need for novel treatment methods. Tissue engineering brings hope for patients, which enables damaged tissue reconstruction. For this purpose, epithelial cells are cultured on three-dimensional scaffolds. One of the most promising materials is chitosan, which is known for its biocompatibility and biodegradability. The aim of the following study was to verify the potential of chitosan-based biomaterials for pelvic organ prolapse regeneration. The scaffolds were obtained under microwave-assisted conditions in crosslinking reactions, using dicarboxylic acids and aminoacid as crosslinkers, including l-glutamic acid, adipic acid, malonic acid, and levulinic acid. The products were characterized over their physicochemical and biological properties. FT-IR analysis confirmed formation of amide bonds. The scaffolds had a highly porous structure, which was confirmed by SEM analysis. Their porosity was above 90%. The biomaterials had excellent swelling abilities and very good antioxidant properties. The cytotoxicity study was performed on vaginal epithelial VK2/E6E7 and human colon cancer HCT116 cell lines. The results showed that after certain modifications, the proposed scaffolds could be used in pelvic organ prolapse (POP) treatment.

ZnO nanorods functionalized with chitosan hydrogels crosslinked with azelaic acid for transdermal drug delivery.

The growing number of people suffering from civilization diseases increases the amount of medication taken. Thus, novel methods for drug delivery must be developed which will constitute an alternative to oral administration. A new hope for patients bring transdermal drug delivery systems. To overcome skin barrier function, they must be prepared from materials which increase cell membrane permeability for the medication. Therefore, there is an increasing need for novel, advanced transdermal systems capable of controlled active substance release under specific stimuli. The aim of this research was to obtain novel hydrogel-based transdermal delivery systems through crosslinking process of chitosan using azelaic acid followed by doping with ZnO nanorods to enhance its drug sorption properties. Ready materials were investigated over their structure, morphology and durability. Drug loading capacity, controlled drug release ability and its kinetics were determined on medication used in treatment of cardiovascular system diseases - acetylsalicylic acid. Finally, lack of cytotoxicity was confirmed by XTT assay and cell morphology study carried out on L929 mouse fibroblasts. Obtained results show a great potential of the developed transdermal delivery systems in active substances administration through skin tissue and may help to protect digestive tract of the patients in the future.

Variation of the chemical composition of street dust in a highly industrialized city in the interval of ten years.

Street dust can be re-suspended into the atmosphere by wind and vehicle passage in an urban area. Street dust is affecting the environmental quality of the atmosphere and human health. A detailed study was conducted to determine the changes in concentrations of heavy metals and magnetic susceptibility by comparison of samples of street dust obtained in the years 2008 and 2018 at the same localities. An amount of dust per m2 of road area was highly variable for individual localities (47 g/m2 - 1.37 kg/m2), with arithmetic mean (229.7 ± 85.97 g/m2) in the year 2018. Silt particles in street dust (<0.063 mm) represented approx. 15-20%, sand particles approx. 63-70% and gravel 10-20%. Iron (5-6%) has significant concentrations in street dust. The highest concentrations are represented by the series Mn ˃ Zn ˃ Cr ˃ Cu ˃ Pb ˃ Ni. Comparison of metal concentrations in the years 2008 and 2018 showed a comparable level of iron and a lower level of lead. The significant enrichment was found for Cu, Cr and Zn expressed by enrichment factor in the range from 5 to 20. High values of magnetic susceptibility of street dust are caused by metallurgy. Metals except Cu are bound in magnetic particles and have a high correlation coefficient with magnetic susceptibility.

3D Hierarchical, Nanostructured Chitosan/PLA/HA Scaffolds Doped with TiO2/Au/Pt NPs with Tunable Properties for Guided Bone Tissue Engineering.

Bone tissue is the second tissue to be replaced. Annually, over four million surgical treatments are performed. Tissue engineering constitutes an alternative to autologous grafts. Its application requires three-dimensional scaffolds, which mimic human body environment. Bone tissue has a highly organized structure and contains mostly inorganic components. The scaffolds of the latest generation should not only be biocompatible but also promote osteoconduction. Poly (lactic acid) nanofibers are commonly used for this purpose; however, they lack bioactivity and do not provide good cell adhesion. Chitosan is a commonly used biopolymer which positively affects osteoblasts' behavior. The aim of this article was to prepare novel hybrid 3D scaffolds containing nanohydroxyapatite capable of cell-response stimulation. The matrixes were successfully obtained by PLA electrospinning and microwave-assisted chitosan crosslinking, followed by doping with three types of metallic nanoparticles (Au, Pt, and TiO2). The products and semi-components were characterized over their physicochemical properties, such as chemical structure, crystallinity, and swelling degree. Nanoparticles' and ready biomaterials' morphologies were investigated by SEM and TEM methods. Finally, the scaffolds were studied over bioactivity on MG-63 and effect on current-stimulated biomineralization. Obtained results confirmed preparation of tunable biomimicking matrixes which may be used as a promising tool for bone-tissue engineering.

Phosphate Coatings Enriched with Copper on Titanium Substrate Fabricated Via DC-PEO Process.

The present paper covers the possible ways to fabricate advanced porous coatings that are enriched in copper on a titanium substrate through Direct Current Plasma Electrolytic Oxidation (DC-PEO) with voltage control, in electrolytes made of concentrated orthophosphoric acid with the addition of copper(II) nitrate(V) trihydrate. In these studies, solutions containing from 0 to 650 g salt per 1 dm3 of acid and anodic voltages from 450 V up to 650 V were used. The obtained coatings featuring variable porosity could be best defined by the three-dimensional (3D) parameter Sz, which lies in the range 9.72 to 45.18 µm. The use of copper(II) nitrate(V) trihydrate in the electrolyte, resulted, for all cases, in the incorporation of the two oxidation forms, i.e., Cu+ and Cu2+ into the coatings. Detailed X-Ray Photoelectron Spectroscopy (XPS) studies layers allowed for stating that the percentage of copper in the surface layer of the obtained coatings was in the range of 0.24 at% to 2.59 at%. The X-Ray Diffraction (XRD) studies showed the presence of copper (α-Cu2P2O7, and Cu3(PO4)2) and titanium (TiO2-anatase, TiO3, TiP2O7, and Ti0.73O0.91) compounds in coatings. From Energy-Dispersive X-Ray Spectroscopy (EDS) and XPS studies, it was found that the Cu/P ratio increases with the increase of voltage and the amount of salt in the electrolyte. The depth profile analysis by Glow-Discharge Optical Emission Spectroscopy (GDOES) method showed that a three-layer model consisting of a top porous layer, a semi-porous layer, and a transient/barrier layer might describe the fabricated coatings.

Porous Coatings Containing Copper and Phosphorus Obtained by Plasma Electrolytic Oxidation of Titanium.

To fabricate porous copper coatings on titanium, we used the process of plasma electrolytic oxidation (PEO) with voltage control. For all experiments, the three-phase step-up transformer with six-diode Graetz bridge was used. The voltage and the amount of salt used in the electrolyte were determined so as to obtain porous coatings. Within the framework of this study, the PEO process was carried out at a voltage of 450 VRMS in four electrolytes containing the salt as copper(II) nitrate(V) trihydrate. Moreover, we showed that the content of salt in the electrolyte needed to obtain a porous PEO coating was in the range 300-600 g/dm3. After exceeding this amount of salts in the electrolyte, some inclusions on the sample surface were observed. It is worth noting that this limitation of the amount of salts in the electrolyte was not connected with the maximum solubility of copper(II) nitrate(V) trihydrate in the concentrated (85%) orthophosphoric acid. To characterize the obtained coatings, numerous techniques were used. In this work, we used scanning electron microscopy (SEM) coupled with electron-dispersive X-ray spectroscopy (EDS), conducted surface analysis using confocal laser scanning microscopy (CLSM), and studied the surface layer chemical composition of the obtained coatings by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), glow discharge of optical emission spectroscopy (GDOES), and biological tests. It was found that the higher the concentration of Cu(NO3)2∙3H2O in the electrolyte, the higher the roughness of the coatings, which may be described by 3D roughness parameters, such as Sa (1.17-1.90 µm) and Sp (7.62-13.91 µm). The thicknesses of PEO coatings obtained in the electrolyte with 300-600 g/dm3 Cu(NO3) 2∙3H2O were in the range 7.8 to 10 µm. The Cu/P ratio of the whole volume of coating measured by EDS was in the range 0.05-0.12, while the range for the top layer (measured using XPS) was 0.17-0.24. The atomic concentration of copper (0.54-0.72 at%) resulted in antibacterial and fungicidal properties in the fabricated coatings, which can be dedicated to biocompatible applications.

Hybrid Bilayer PLA/Chitosan Nanofibrous Scaffolds Doped with ZnO, Fe3O4, and Au Nanoparticles with Bioactive Properties for Skin Tissue Engineering.

Burns affect almost half a million of Americans annually. In the case of full-thickness skin injuries, treatment requires a transplant. The development of bioactive materials that promote damaged tissue regeneration constitutes a great alternative to autografts. For this reason, special attention is focused on three-dimensional scaffolds that are non-toxic to skin cells and can mimic the extracellular matrix, which is mainly composed of nanofibrous proteins. Electrospinning, which enables the preparation of nanofibers, is a powerful tool in the field of biomaterials. In this work, novel hybrid poly (lactic acid)/chitosan biomaterials functionalized with three types of nanoparticles (NPs) were successfully developed. ZnO, Fe3O4, and Au NPs were investigated over their morphology by TEM method. The top layer was obtained from PLA nanofibers, while the bottom layer was prepared from acylated chitosan. The layers were studied over their morphology by the SEM method and their chemical structure by FT-IR. To verify their potential in burn wound treatment, the scaffolds' susceptibility to biodegradation as well as moisture permeability were calculated. Also, biomaterials conductivity was determined in terms of electrostimulation. Finally, cytotoxicity tests were carried out by XTT assay and morphology analysis using both fibroblasts cell line and primary cells. The hybrid nanofibrous scaffolds displayed a great potential in tissue engineering.

Antimicrobial Synergistic Effect Between Ag and Zn in Ag-ZnO·mSiO2 Silicate Composite with High Specific Surface Area.

Antimicrobial materials are widely used for inhibition of microorganisms in the environment. It has been established that bacterial growth can be restrained by silver nanoparticles. Combining these with other antimicrobial agents, such as ZnO, may increase the antimicrobial activity and the use of carrier substrate makes the material easier to handle. In the paper, we present an antimicrobial nanocomposite based on silver nanoparticles nucleated in general silicate nanostructure ZnO·mSiO2. First, we prepared the silicate fine net nanostructure ZnO·mSiO2 with zinc content up to 30 wt% by precipitation of sodium water glass in zinc acetate solution. Silver nanoparticles were then formed within the material by photoreduction of AgNO3 on photoactive ZnO. This resulted into an Ag-ZnO·mSiO2 composite with silica gel-like morphology and the specific surface area of 250 m2/g. The composite, alongside with pure AgNO3 and clear ZnO·mSiO2, were successfully tested for antimicrobial activity on both gram-positive and gram-negative bacterial strains and yeast Candida albicans. With respect to the silver content, the minimal inhibition concentration of Ag-ZnO·mSiO2 was worse than AgNO3 only for gram-negative strains. Moreover, we found a positive synergistic antimicrobial effect between Ag and Zn agents. These properties create an efficient and easily applicable antimicrobial material in the form of powder.

Chitosan-Based Carbon Quantum Dots for Biomedical Applications: Synthesis and Characterization.

Rapid development in medicine and pharmacy has created a need for novel biomaterials with advanced properties such as photoluminescence, biocompability and long-term stability. The following research deals with the preparation of novel types of N-doped chitosan-based carbon quantum dots. Nanomaterials were obtained with simultaneous nitrogen-doping using biocompatible amino acids according to Green Chemistry principles. For the carbon quantum dots synthesis chitosan was used as a raw material known for its biocompability. The nanomaterials obtained in the form of lyophilic colloids were characterized by spectroscopic and spectrofluorimetric methods. Their quantum yields were determined. Additionally the cytotoxicity of the prepared bionanomaterials was evaluated by XTT (2,3-Bis-(2-methoxy-4-nitro5-sulfophenyl)-2H-tetrazolium-5-carboxanilide salt) method. Our results confirmed the formation of biocompatible quantum dots with carbon cores exhibiting luminescence in visible range. Performed studies showed that modification with lysine (11.5%) and glutamic acid (7.4%) had a high impact on quantum yield, whereas functionalization with amino acids rich in S and N atoms did not significantly increase in fluorescence properties. XTT assays as well as morphological studies on human dermal fibroblasts confirmed the lack of cytotoxicity of the prepared bionanomaterials. The study shows chitosan-based quantum dots to be promising for biomedical applications such as cell labelling, diagnostics or controlled drug delivery and release systems.

Development of Porous Coatings Enriched with Magnesium and Zinc Obtained by DC Plasma Electrolytic Oxidation.

Coatings with developed surface stereometry, being based on a porous system, may be obtained by plasma electrolytic oxidation, PEO (micro arc oxidation, MAO). In this paper, we present novel porous coatings, which may be used, e.g., in micromachine's biocompatible sensors' housing, obtained in electrolytes containing magnesium nitrate hexahydrate Mg(NO3)2·6H2O and/or zinc nitrate hexahydrate Zn(NO3)2·6H2O in concentrated phosphoric acid H3PO4 (85% w/w). Complementary techniques are used for coatings' surface characterization, such as scanning electron microscopy (SEM), for surface imaging as well as for chemical semi-quantitative analysis via energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), glow discharge optical emission spectroscopy (GDOES), and X-ray powder diffraction (XRD). The results have shown that increasing contents of salts (here, 250 g/L Mg(NO3)2·6H2O and 250 g/L Zn(NO3)2·6H2O) in electrolyte result in increasing of Mg/P and Zn/P ratios, as well as coating thickness. It was also found that by increasing the PEO voltage, the Zn/P and Mg/P ratios increase as well. In addition, the analysis of XPS spectra revealed the existence in 10 nm top of coating magnesium (Mg2+), zinc (Zn2+), titanium (Ti4+), and phosphorus compounds (PO43-, or HPO42-, or H2PO4-, or P2O74-).

Novel Porous Phosphorus⁻Calcium⁻Magnesium Coatings on Titanium with Copper or Zinc Obtained by DC Plasma Electrolytic Oxidation: Fabrication and Characterization.

In this paper, the characteristics of new porous coatings fabricated at three voltages in electrolytes based on H3PO4 with calcium nitrate tetrahydrate, magnesium nitrate hexahydrate, and copper(II) nitrate trihydrate are presented. The SEM, energy dispersive spectroscopy (EDS), glow discharge optical emission spectroscopy (GDOES), X-ray photoelectron spectroscopy (XPS), and XRD techniques for coating identification were used. It was found that the higher the plasma electrolytic oxidation (PEO) (micro arc oxidation (MAO)) voltage, the thicker the porous coating with higher amounts of built-in elements coming from the electrolyte and more amorphous phase with signals from crystalline Ca(H2PO4)2∙H2O and/or Ti(HPO4)2∙H2O. Additionally, the external parts of the obtained porous coatings formed on titanium consisted mainly of Ti4+, Ca2+, Mg2+ and PO43-, HPO42-, H2PO4-, P2O74- as well as Zn2+ or copper Cu⁺/Cu2+. The surface should be characterized by high biocompatibility, due to the presence of structures based on calcium and phosphates, and have bactericidal properties, due to the presence of zinc and copper ions. Furthermore, the addition of magnesium ions should accelerate the healing of postoperative wounds, which could lead to faster patient recovery.

Biodegradable, pH-sensitive chitosan beads obtained under microwave radiation for advanced cell culture.

A new type of promising chitosan beads with advanced properties were obtained under microwave radiation according to Green Chemistry principles. Biomaterials were prepared using chitosan as raw material and glutamic acid/1,5-pentanodiol mixture as crosslinking agents. Additionally beads were modified with Tilia platyphyllos extract to enhance their antioxidant properties. Beads were investigated over their chemical structure by FT-IR analysis. Also their morphology has been investigated by SEM method. Additionally swelling capacity of the obtained hydrogels was determined. Lack of cytotoxicity has been confirmed by MTT assay. Proliferation studies were carried out on L929 mouse fibroblasts. Advanced properties of the obtained beads were investigated by studying pH sensitivity and antioxidant properties by DPPH method. Also susceptibility to degradation and biodegradation by Sturm Test method was evaluated. Results shows that proposed chitosan beads and their eco-friendly synthesis method can be applied in cell therapy and tissue engineering.

Magnetic sorbents biomineralization on the basis of iron sulphides.

Biomineralization means mineral formation under the influence of organisms. Sulphate-reducing bacteria (SRB) constitute an essential role of iron sulphide minerals precipitation. Their composition involves amorphous, non-stoichiometric or crystalline iron sulphides, weakly or strongly magnetic. Variation in environmental conditions can alter the reactive iron species within the mineral, potentially modifying their magnetic properties. Biogenic iron sulphide minerals can be used as heavy metals and toxic ions adsorbents in soil or water remediation. For these reasons, a series of laboratory-scale iron sulphide synthesis experiments with the aim to study the chemical composition, mineralogy and magnetic properties of iron sulphide precipitates were carried out using SRB under various cultivation mode and nutrient medium composition. Energy-dispersive X-ray analysis (EDX) showed formation of iron sulphides in all biogenic samples and iron phosphates in abiotic controls. Results of X-ray diffraction analysis (XRD) in biomineralized samples confirmed nanocrystalline greigite, mackinawite and sulphur alpha. Magnetic measurements showed that sample prepared by static cultivation without addition of fresh nutrient medium was the most magnetic, magnetic hysteresis of sample formed under semicontinuous mode without any nutrient supply was the lowest. Abiotic samples contained only vivianite and they did not prove any significant response to magnetic field.

SEM, EDS and XPS Analysis of the Coatings Obtained on Titanium after Plasma Electrolytic Oxidation in Electrolytes Containing Copper Nitrate.

In the paper, the Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Photoelectron Spectroscopy (XPS) results of the surface layer formed on pure titanium after plasma electrolytic oxidation (micro arc oxidation) at the voltage of 450 V are shown. As an electrolyte, the mixture of copper nitrate Cu(NO3)2 (10-600 g/L) in concentrated phosphoric acid H3PO4 (98 g/mol) was used. The thickness of the obtained porous surface layer equals about 10 µm, and it consists mainly of titanium phosphates and oxygen with embedded copper ions as a bactericidal agent. The maximum percent of copper in the PEO surface layer was equal to 12.2 ± 0.7 wt % (7.6 ± 0.5 at %), which is the best result that the authors obtained. The top surface layer of all obtained plasma electrolytic oxidation (PEO) coatings consisted most likely mainly of Ti3(PO4)4∙nH3PO4 and Cu3(PO4)2∙nH3PO4 with a small addition of CuP2, CuO and Cu2O.