Aqueous Nitrate Solutions Research Articles

Thermodynamics of Aqueous Lithium Nitrate Solutions at 298.15 to 398.15 K and 0.1 to 60 MPa

Thermodynamics of Aqueous Lithium Nitrate Solutions at 298.15 to 398.15 K and 0.1 to 60 MPa

Development of Technology for the Synthesis of Nanocrystalline Cerium Oxide Under Production Conditions with the Best Regenerative Activity and Biocompatibility for Further Creation of Wound-Healing Agents

Background/Objectives: The issue of effective wound healing remains highly relevant. The objective of the study is to develop an optimal method for the synthesis of nanosized cerium oxide powder obtained via the thermal decomposition of cerium carbonate precipitated from aqueous nitrate solution for the technical creation of new drugs in production conditions; the select modification of synthesis under different conditions based on the evaluation of the physicochemical characteristics of the obtained material and its biological activity, and an evaluation of the broad-spectrum effect on cells involved in the regeneration of skin structure as well as antimicrobial properties. Methods: Several modes of the industrial synthesis of cerium dioxide nanoparticles (NPs) were carried out. The synthesis stages and the chemical and physical parameters of the obtained NPs were described using transmission electron microscopy (TEM), X-ray diffraction, Raman spectroscopy, and mass spectrometry. The cell cultures of human fibroblasts and keratinocytes were cultured with different concentrations of different nanoceria variations, and the cytotoxicity and the metabolic and proliferative activity were investigated. An MTT test and cell counting were performed. The antimicrobial activity of CeO2 variations at a concentration of 0.1–0.0001 M against Pseudomonas aeruginosa was studied. Results: The purity of the synthesized nanoceria powders in all the batches was >99.99%. According to TEM data, the size of the NPs varied from 1 nm to 70 nm under different conditions and methodologies. The most optimal technology for the synthesis of the nanoceria with the maximum biological effect was selected. A method for obtaining the most bioactive NPs of optimal size (up to 10 nm) was proposed. The repeatability of the results of the proposed method of nanoceria synthesis in terms of particle size was confirmed. It was proven that the more structural defects on the surface of the CeO2 crystal lattice, the higher the efficiency of the NPs due to oxygen vacancies. The strain provided the best redox activity and antioxidant properties of the nanoceria, which was demonstrated by better regenerative potential on various cell lines. The beneficial effect of synthesized nanoceria on the proliferative and metabolic activity of the cell lines involved in skin regeneration (human fibroblasts, human keratinocytes) was demonstrated. The antimicrobial effect of synthesized nanoceria on the culture of the most-resistant-to-modern-antibiotics microorganism Pseudomonas aeruginosa was confirmed. The optimal concentrations of the nanoceria to achieve the maximum biological effect were determined (10−3 M). Conclusions: It was possible to develop a method for the industrial synthesis of nanoceria, which can be used to produce drugs and medical devices containing CeO2 NPs.

Potential protective efficacy of biogenic silver nanoparticles synthesised from earthworm extract in a septic mice model

Sepsis is an inevitable stage of bacterial invasion characterized by an uncontrolled inflammatory response resulting in a syndrome of multiorgan dysfunction. Most conventional antibiotics used to treat sepsis are efficacious, but they have undesirable side effects. The green synthesised Ag NPs were synthesized by 5 g of the earthworm extract dissolved in a volume of 500mL of distilled water and then added to 2,500 mL aqueous solution of 1mM silver nitrate at 40 °C. After 4 h, the mixture was then allowed to dry overnight at 60 °C. Later, Ag NPs were washed and collected. They were characterized by X-ray diffraction, ultraviolet-visible spectroscopy, and transmission electron microscopy. Sepsis model as induced by feces-intraperitoneal injection method. Eighteen male mice were assigned into three main groups: the control group, the sepsis-model group, and the Ag NPs-treated group. The control group received a single oral dose of distilled water and, after two days, intraperitoneally injected with 30% glycerol in phosphate buffer saline. The Sepsis-model group received a single oral dose of distilled water. Ag NPs - The treated group received a single oral dose of 5.5 mg/kg of Ag NPs. After two days, the sepsis-model group and Ag NPs-treated group were intraperitoneally injected with 200 µL of faecal slurry. Ag NPs treatment in septic mice significantly decreased liver enzyme activities, total protein, and serum albumin. Moreover, Ag NPs significantly enhanced kidney function, as indicated by a significant decrease in the levels of creatinine, urea, and uric acid. In addition, Ag NPs showed a powerful antioxidant effect via the considerable reduction of malondialdehyde and nitric oxide levels and the increase in antioxidant content. The histopathological investigation showed clear improvement in hepatic and kidney architecture. Our findings demonstrate the protective efficacy of biogenic Ag NPs against sepsis-induced liver and kidney damage.

Mathematical model for the exergy of the system ammonium nitrate–water

The exergy balance has recently been used more frequently for the energy analysis of technological processes and represents a considerable improvement over the evaluation according to the First law of thermodynamics, in which completely convertible and incompletely convertible forms of energy are taken into account equally. In order to carry out the exergy balance, the exergy values of the material flows involved in the process must be known. This article presents a mathematical model for calculating the exergy of ammonium nitrate in aqueous solution in the production of fertilizers. When carrying out the exergy model, it was assumed that the conditions are: ambient temperature 20 °C, pressure 101.325 kPa and that it consists of liquid water and crystalline ammonium nitrate, which has an exergy value of zero under these conditions. The model is based on Pitzer’s ion-interaction type equations for the dependence of the activity coefficient on the composition of the solution at a given temperature and pressure. This mathematical model is valid for aqueous solutions of ammonium nitrate up to saturation in the temperature range from 20 °C to 170 °C and offers the possibility to estimate the NH4NO3(aq) enthalpies at different temperatures and different compositions.

Effect of Aqueous Electrolyte Composition on Efficiency of Electrochemical Post-Processing of Additive Manufacturing Products from Ti-6Al-4V Alloy Obtained by Selective Electron Beam Melting

The influence of the anionic composition of an aqueous electrolyte on the efficiency of the electrochemical leveling of the initial microgeometry of samples obtained by the selective electron beam melting (SEBM) at the following mode parameters was studied: current density – 20 A/cm2, initial interelectrode gap – 0.3 mm, average speed of electrolyte pumping – 12 m/c. Aqueous solutions of sodium chloride, nitrate, perchlorate and bisalt electrolytes based on them were studied. It was that aqueous solutions of sodium perchlorate have the best microleveling properties among the studied working media, which provides the ability to reduce the parameters Ra and Rz from values of 35 and 180 μm, respectively, to values of 3.2 and 20 μm during electrolysis of 30 s in a direct-flow electrolyzer. It was established that the microgeometry leveling corresponds to the model of the secondary distribution of dissolution rates; two main factors were identified that significantly influenced on the result: polarization of the electrodes and a decrease in the oxidation state of metal ions passing into the solution during electrochemical machining in the vicinity of the depression in relation to the protrusion due to changes in the local conditions of electrolysis. Microetching along grain boundaries in the studied electrolytes was not detected at the accepted parameters of the electrolysis mode.

Hybrid direct ink writing of bioglass-calcite-carbon composite scaffolds supported by novel silicone-based emulsions

70S30C (70 mol% SiO2, 30% CaO) bioglass is one of the most promising bioceramics for bone tissue engineering. We discuss the feasibility of 70S30C bioglass/calcite/carbon composites derived from novel silicone-based emulsions, leading to highly porous lattice scaffolds. These are produced by direct ink writing (DIW) 3D printing, followed by ceramic conversion at 700°C in flowing nitrogen. The emulsions consisted of droplets of concentrated calcium nitrate aqueous solution incorporated into blends of H44 commercial polysiloxane and photocurable acrylate resin. This formulation offered unprecedented opportunities in both synthesis and shaping. Specifically, the homogeneous dispersion of the CaO precursor in silicone enabled a uniform SiO2/CaO distribution, favoring the formation of a glass matrix. Additionally, the acrylate component and water content allowed for tuning of the microstructure both immediately after printing and upon firing. Photopolymerization of acrylates consolidated the printed bodies (configuring a 'hybrid DIW') after extrusion, while water evaporation enhanced gas evolution during ceramic conversion, promoting pore interconnectivity.

Corrosion behavior of mild steel in aqueous solutions of ammonium nitrate and urea

Corrosion behavior of mild steel in aqueous solutions of ammonium nitrate and urea

The influence of pH electrolyte on the electrochemical deposition and properties of cerium oxide thin films

Thin cerium oxide layers cathodically deposited on zinc were studied. These electrochemically deposited coatings provide effective corrosion protection and require less deposition time compared to chemical conversion coatings. The kinetics of their formation depend on various factors, such as temperature, applied current density, electrolyte composition, pH, and agitation. In this study, the effect of bath solution pH was investigated, with coatings produced at room temperature from aqueous cerium nitrate solutions. Chronopotentiometry, linear sweep voltammetry, and electrochemical impedance spectroscopy (EIS) were used to monitor the deposition process, while scanning electron microscopy and energy-dispersive spectroscopy were performed to characterize the deposits. Corrosion resistance was evaluated through potentiodynamic tests in a 3.5% NaCl solution. The results indicate that the electrolyte pH significantly influences the cerium electrodeposition process. Based on the findings, the cerium oxide coating obtained from a pH 4 solution exhibited lower corrosion current density, higher polarization resistance, and superior anti-corrosion performance.

Phytochemical fabrication of ZnO nanoparticles and their antibacterial and anti-biofilm activity

The synthesis of metal nanoparticles through bio-reduction is environmentally benign and devoid of impurities, which is very important for biological applications. This method aims to improve ZnO nanoparticle's antibacterial and anti-biofilm activity while reducing the amount of hazardous chemicals used in nanoparticle production. The assembly of zinc oxide nanoparticles (ZnO NPs) is presented via bio-reduction of an aqueous zinc nitrate solution using Echinochloacolona (E. colona) plant aqueous leaf extract comprising various phytochemical components such as phenols, flavonoids, proteins, and sugars. The synthesized nano ZnO NPs are characterized by UV–visible spectrophotometer (UV–vis), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (X-RD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and elemental composition by energy-dispersive x-ray spectroscopy (EDX). The formation of biosynthesized ZnO nanoparticles was confirmed by the absorbance at 360–370 nm in the UV–vis spectrum. The average crystal size of the particles was found to be 15.8 nm, as calculated from XRD. SEM and TEM analysis of prepared ZnO NPs confirmed the spherical and hexagonal shaped nanoparticles. ZnO NPs showed antibacterial activity against Escherichia coli and Klebsiella pneumoniae with the largest zone of inhibition (ZOI) of 17 and 18 mm, respectively, from the disc diffusion method. Furthermore, ZnO NPs exhibited significant anti-biofilm activity in a dose-dependent manner against selected bacterial strains, thus suggesting that ZnO NPs can be deployed in the prevention of infectious diseases and also used in food preservation.

Influence of silver nanoparticles synthesized from Chaenomeles leaf extracts on pathogenic microorganisms Klebsiella pneumoniae, Staphylococcus aureus, and Fusarium culmorum

Herein, we report for the first time the biosynthesis of silver nanoparticles (AgNPs) using leaf extracts of Chaenomeles Lindl. (Rosaceae) plants and its spectral characteristics, as well as antifungal and antibacterial activity. Phytosynthesis of silver nanoparticles on the base of aqueous plant extracts and silver nitrate solution was carried out by an ecofriendly and cost-effective approach. UV-Vis spectroscopy was applied to validate the plant-mediated biosynthesis of AgNPs colloidal solutions by the Surface Plasmon Resonance (SPR) bands in the region of 450–500 nm, characteristic of polycrystalline silver nanoparticles. Scanning microscopy (SEM) revealed a wide variation in range 5–58 nm and a close to spherical shape of plant-derived AgNPs. Raman scattering spectroscopy revealed the suitability of biosynthesized silver nanoparticles as the substrates for surface-enhanced Raman scattering (SERS) spectroscopy with the highest efficiency of AgNPs, biosynthesized from leaf extract of Ch. × superba, which enhanced the Rhodamine 6G dye applied at a concentration of 10–7 M. Assay of antifungal activity performed by well diffusion method revealed the dose-dependent effect of all AgNPs against the phytopathogenic fungus Fusarium culmorum. The most effective AgNPs (Ch. speciosa-AgNPs, Ch. cathayensis-AgNPs, and Ch. japonica-AgNPs) achieved a 1.42–1.63 times greater zone of inhibition of the F. culmorum colonies’ growth compared to the corresponding doses of the known chemical fungicide "Quadris". Micro preparations of the zones of incomplete growth inhibition presented changes in the mycelium morphology of F. culmorum due to the action of nanoparticles, such as deformation (curvature, expansion), and a decrease in the hyphae length and density compared to the control sample. Disc-diffusion assay showed notable species-specific antibacterial activity of AgNPs both against Gram-negative (Klebsiella pneumoniae) and Gram-positive (Staphylococcus aureus) strains. Summarizing, the results indicate the undeniable suitability of aqueous leaf extracts of the genus Chaenomeles species for the successful biosynthesis of silver nanoparticles with many useful properties, whose diverse applications require further research.

Adsorptive removal of a nitrate ion from the aqueous solution of sodium nitrate by application of double fixed-bed column

This study focuses on the removal of nitrate ions from aqueous solutions using rice husk activated carbon (RHAC). The RHAC was subjected to characterization via Fourier transform infrared (FTIR), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), and X-ray florescence (XRF) to ascertain its functional groups, surface morphology, and oxide/elemental composition, respectively. Batch experiments were conducted to assess the impact of nitrate concentration, bed height, and number of packing layers on removal efficiency. FTIR spectra revealed favorable sorption-related functional groups within RHAC, while SEM analysis indicated the presence of effective sorption sites on its surface. EDS analysis of the rice husk adsorbent before adsorption (RHBS) demonstrated a significant composition of Si (42.20%), O (35.30%), and Ca (12.33%). The batch study unveiled a concentration-dependent decrease in nitrate removal efficiency, alongside the enhanced performance with increased bed height and number of packing layers. Kinetic data fitting favored the Yoon–Nelson and Adams–Bohart models. Overall, RHAC exhibited efficient nitrate ion removal, with column performance notably improved by utilizing multiple packing layers. These results will enhance our understanding of the mechanisms involved in removing nitrate ions and highlight the potential effectiveness of RHAC, especially when utilized with multiple packing arrangements in column setups.

(Digital Presentation) Synthesis of Carbon Materials on Aluminum Foil from a Vapor-Gas Environment

Due to its excellent electrical conductive properties and large specific surface area, one of the allotropic modifications of carbon, carbon nanotubes (CNTs), grown on a metal substrate, have great potential for use in supercapacitor electrodes. After all, growing layers of nanotubes directly on the surface of electrodes. can make it possible to achieve the best adhesion and electrical contact of CNTs with the current collector [1]. The large surface area and exceptional electronic conductivity of CNTs make them prime candidates for high-performance and high-speed electrochemical applications [2].The aim of the work was to investigate the effect of synthesis conditions on the structure and properties of a carbon layer grown on the surface of aluminum foil.We used technical aluminum foil with a thickness of 16 microns. Aluminum foil was previously degreased with acetone, kept in an aqueous 1 M NaOH solution for 3 minutes and 30 minutes in a 20% aqueous solution of nickel nitrate at 90 °C. The synthesis of carbon materials on the surface of aluminum foil was carried out by pyrolysis of ethanol vapor in argon at 550 and 600 °C.Analysis of SEM picture (fig. a) and Raman spectrum (dig. b) allows to conclude that the synthesized carbon materials are nanotubes or nanofibers.It has been established that pre-treatment of aluminum foil with acetone does not affect the properties and uniformity of distribution of the carbon layer. On aluminum foil, without pretreatment and kept in acetone, after the synthesis of carbon materials from the vapor-gas phase, initial sections of aluminum foil without a carbon layer are observed. Preliminary exposure of aluminum foil in an alkali solution contributed to the uniform distribution of the synthesized carbon; the entire foil was evenly covered with carbon.When pyrolysis of ethanol vapor is carried out in argon at 550 °C, the carbon layer is heterogeneous (fig. c) and volumetric growths are observed on the foil. When synthesizing carbon materials at 600°C, the carbon layer is dense without bulky formations (fig. d).This work was performed as part of the Ministry of Science and Higher Education of the Russian Federation[Government Order Theme No. 121111900148-3]. References Redkin, A. N., Mitina, A. A., & Yakimov, E. E. (2021). Simple technique of multiwalled carbon nanotubes growth on aluminum foil for supercapacitors. Materials Science and Engineering: B, 272, 115342. DOI:10.1016/j.mseb.2021.115342;Moyer-Vanderburgh, K., Ma M. C., Park, S.J., Jue, N.L., Buchsbaum, S.F., Wu K.J., Wood, M., Ye, J. Fornasiero, F., Growth and Performance of High-Quality SWCNT Forests on Inconel Foils as Lithium-Ion Battery Anodes: ACS Appl. Mater. Interfaces 2022, 14, 49, 54981–54991. DOI: 10.1021/acsami.2c18396 Figure 1

The temperature of maximum in density of aqueous solutions of nitrate and ammonium salts: Testing the Madrid-2019 force field.

The shift in the temperature of maximum in density (TMD) at room pressure of aqueous solutions of a set of five salts containing NO3- and/or NH4+ groups is studied both through experiments and through molecular dynamics simulations using the Madrid-2019 force field for ions and the TIP4P/2005 model for water. The experiments demonstrate the potential transferability and limitations of the Madrid-2019 force field for nitrate and ammonium ions recently developed by our group at different temperatures and add updated information to the reported datasets of TMDs for strong electrolytes. By using the Despretz law, individual ion contributions are extracted for predictive purposes from the experimental values of the shift in the TMD. Interesting findings for the behavior of the shift in the TMD in nitrate salts expose that this property might be particularly challenging for modelization approaches when dealing with polyatomic species.

Structural Parameters of Ion Coordination in Aqueous Solutions of Cerium Nitrate According to the X-Ray Diffraction Analysis

Structural Parameters of Ion Coordination in Aqueous Solutions of Cerium Nitrate According to the X-Ray Diffraction Analysis

An experimental study of the endothermic catalytic cracking of hydrocarbon aviation fuels under extreme conditions

Methylcyclohexane (MCH) is a suitable surrogate endothermic fuel that can operate under extreme conditions and it can be utilized to better understand the mechanisms of endothermic catalytic cracking and coke generation in jet engines. Zn-impregnated desilicated Zeolite Socony Mobil–5 (ZSM-5) zeolite catalysts have been successfully prepared and studied for aviation fuel cracking under high temperature and pressure conditions (550 °C; 50 bar). First, micropore ZSM-5 was desilicated by the alkali treatment method with NaOH to increase the mesopore distributions. In the second step, Zn-doped mesopore ZSM-5 zeolites were prepared by the incipient wetness impregnation method with an aqueous solution of zinc nitrate. After the endothermic pyrolysis of MCH fuel over the modified zeolite catalysts, the condensed liquid product fraction (%) was analyzed. It can be deduced that a reasonable combination of these advanced synthesis strategies can increase catalytic cracking performance. This study showed that, in the context of endothermic catalytic cracking of hydrocarbon aviation fuels at supercritical jet conditions, Zn-doped desilicated zeolites exhibited a decreased quantity of coke deposition.

Central Metal-Triggered Structural Transformation of a 2D Layered MOF: Mechanistic Studies and Applications.

The structural transformation of metal-organic frameworks (MOFs) has attracted increasing interests, which has not only produced various new structures but also served as a fantastic platform for MOF-based kinetic analysis. Multiple reaction conditions have been documented to cause structural transformation; nevertheless, central metal-induced topological alteration of MOFs is rare. Herein, we reported a structural transformation of a 2D layered Cd-MOF driven by Cd(II) ions. After being submerged in the aqueous solution of cadmium nitrate, the twofold interpenetrated 2D network of [Cd(hsb-2)(bdc)·5H2O]n [HSB-W10; bdc: 1,4-benzenedicarboxylate; hsb-2:1,2-bis(4'-pyridylmethylamino)-ethane] was converted into a novel noninterpenetrated 2D network [Cd1.5(hsb-2)(bdc)1.5(H2O)2·H2O]n (HSB-W16). This partial dissolution-recrystallization process was investigated by integrating controlled experiments, 1H NMR spectra, and photographic tracking analysis. Furthermore, a novel strategy combining in situ multicomponent dye encapsulation and central metal-triggered structural transformation was developed for the fabrication of MOF materials with white-light emission. By adopting this strategy, different dye guest molecules were concurrently introduced into the HSB-W16 host matrix, leading to a range of white-light-emitting MOF composites. This work will enable detailed studies of solid-state transformations and demonstrate a promising application prospect for structural transformation.

Physicochemical and Toxicological Screening of Silver Nanoparticle Biosynthesis from Punica granatum Peel Extract

Silver nanoparticles (AgNPs) were successfully synthesized via the biological route using a 1 M silver nitrate (AgNO3) aqueous solution and an ethanolic peel extract of Punica granatum (Pg), at 60 °C. The physicochemical analysis revealed the formation of green synthesized Pg-AgNPs with a semi-spherical shape, non-uniformly distributed, and a particle size distribution between 5 and 100 nm. As regards the preliminary in vitro toxicological screening, the green synthesized Pg-AgNPs did not significantly affect the neonatal BALB/c epidermal cells’ viability (JB6 Cl 41-5a) at lower concentrations and did not produce visible changes in the morphology of the JB6 Cl 41-5a cells. In contrast, at higher concentrations (>50 μg/mL), the green Pg-AgNPs exhibited an important decrease in cell viability and confluency. In addition, the impact of Pg-AgNPs on cell membrane integrity suggests a potential cytotoxic effect. Contrary to the in vitro assays, after the evaluation of the anti-irritant effect in ovo, the lower concentration of Pg-AgNPs (10 μg/mL) produced hemorrhage and lysis when applied to the chorioallantoic membrane, while at 50 μg/mL, only slight coagulation was observed. Therefore, regarding the in ovo toxicological screening, the higher concentration of the Pg-AgNPs exhibited a better safety profile compared to the lower concentration, as indicated by the irritation score.

Pretreatment of wastepaper with an aqueous solution of amino acid-derived ionic liquid for biochar production as adsorbent

The carbonization of lignocellulosic biomass with ionic liquids (ILs) are considered as an advantageous approach for the preparation of carbonaceous materials. The commonly used imidazolium and pyridinium based ILs have drawbacks such as toxicity, resistance to biodegradation, high cost and viscosity. These issues can be mitigated by diluting ILs with water, although excessive water content above 1 wt% can reduce the solubility of biomass. This research aims to investigate the potential of pretreating wastepaper with a “fully green” ILs, amino acid-based IL with high water content, followed by pyrolysis without IL, in enhancing the properties of biochar. For this purpose, the paper was treated with an aqueous solution of IL cysteine nitrate ([Cys][NO3]), and the IL was not involved in the pyrolysis process to prevent the formation of secondary gaseous pollutants. The findings revealed that the hemicellulose and mineral filler in the paper were eliminated during pretreatment, leading to higher carbon content but lower oxygen content. As a result, the biochar exhibited micropores of 0.42 cm3g-1 and a specific surface area of 1011.21 m2 g−1. The biochar demonstrated high adsorption capacities for Cd2+, enrofloxacin, bisphenol A, ciprofloxacin, and tetracycline, with values of 45.20 mg g−1, 49.82 mg g−1, 49.90 mg g−1, 49.88 mg g−1, and 49.65 mg g−1, respectively. The proposed mechanism for the adsorption of enrofloxacin by the biochar primarily involves physical adsorption such as pore filling and electrostatic interactions, along with chemical adsorption facilitated by graphitic nitrogen.

A novel green reducing agent for the synthesis of chromium oxide nanoparticles (Cr2O3 NPs) based on saffron by-products: Characterization and antioxidant activity

The production of nanomaterials using safe, biological and environmentally friendly methods is attracting increasing attention. In the present study, aqueous extracts of Moroccan saffron (Crocus sativus L) by-products were used for the first time as a green stabilizer and reductant agent to synthesize chromium oxide nanoparticles (Cr2O3NPs). The aqueous extract of saffron by-products was analyzed for phytochemical screening, while the green synthesized Cr2O3NPs were analyzed using high-resolution scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The antioxidant activity of Cr2O3NPs, aqueous chromium nitrate solution (Cr (NO3)), and aqueous extract of saffron by-products have been also investigated using 1,1-Diphenyl-2-picrylhydrazyl (DPPH) method. The results showed that the aqueous extract of saffron by-products used for the synthesis of Cr2O3NPs appeared to be rich in phenolic (2.32 mg GA / g dry weight), flavonoid (2.28 mg RE / g dry weight), and anthocyanin compounds (33.67 mg Delphinidin / L extract). The XRD analysis confirmed that the Cr2O3NPs have a particle size of 31 nm with a hexagonal crystal structure. SEM micrographs of Cr2O3NPs showed a homogenous distribution and spherical shape, while the EDX spectrum confirmed that Cr2O3NPs contain significant amount of Chromium (61,90 %), and oxygen atoms (36,55 %). Moreover, the presence of absorption bands characteristic of the alcohol group (3451 cm−1) and the aromatic rings (1639 cm−1) in the infrared spectrum of Cr2O3NPs, indicates that the secondary metabolites of the saffron plant were successfully active in reducing chromium ions to Cr2O3NPs. Besides, the antioxidant activity results showed that the biosynthesized Cr2O3NPs exhibited strong inhibition percentages (63 %) compared to the aqueous extract of saffron by-products (74 %), and the aqueous solution of chromium nitrate (30 %) at 1,30 mg/mL. The study suggests that saffron by-products extract can be used as a natural reducing agent in the synthesis of Cr2O3NPs. Furthermore, the environmentally friendly synthesis process for Cr2O3NPs and their antioxidant effect make them suitable for use in various fields.

Copper-Decorated Titanium Electrodes: Impact of Surface Modifications of Substrate on the Morphology and Electrochemical Performance.

This study investigates the effect of surface modifications of the titanium substrate on the growth of electrochemically deposited copper. These materials are intended to serve as cathodes in the electroreduction of nitrates in aqueous solutions. Surface modifications included the use of hydrogen fluoride for titanium etching and anodization to promote the growth of a structured titania nanotube array. The effect of an intermediate calcination step for the nanotubes before deposition was assessed along with a comparison to an untreated substrate electrode. The materials were comprehensively characterized by SEM, XRD, contact angle, potentiodynamic tests, EIS, and cyclic voltammetry. Their electrocatalytic ability was tested in the reduction of aqueous solutions containing nitrates. The results reveal that surface finishing impacted the shape and size of the Cu microparticles, as well as the nucleation mechanism enabling a crystal-facet-controllable synthesis. All the materials exhibited microsized copper particles with a spherical shape with some clusters. On the etched titanium surface, a high number of heterogeneous submicroscopic particles were also present. The thermally treated anodized substrate promoted the development of a combination of sparse microparticles corresponding to defect sites in amorphous titanium and the presence of a diffuse coating of octahedral nanosized particles whose growth was promoted by the tetragonal structure of anatase crystals. Electrochemical tests display reduced charge transfer resistance upon copper deposition on the modified substrates, which is indicative of the enhanced conductivity of the coated materials. Additionally, cyclic voltammetry and electrolysis experiments reveal the electrodes' potential for nitrate reduction, showing a better response for the etched titanium substrate (30% nitrate removal, after 2 h at 25 mA cm-2).