Maritza Páez

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Verified

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• PhD
• Managing Director at University of Santiago Chile

This study focuses on the removal of Mg2+ from aqueous solutions during Li+ recovery. The objective was to capture Mg2+ ions by adsorption using based adsorbents of sulfonated lignin (LS) and poly-3-sulfopropyl potassium acrylate (PSPAK). The bio-based adsorbents were obtained in high mass yields by radical polymerization. Their structural composit...

The detection of serum albumin is of great relevance because its presence in urine above normal levels is implicated in different pathologies, such as Diabetes Mellitus and Preeclampsia. The main objective of this work was to develop a protocol to sense serum albumin using the well-known unusual optical phenomenon that nanoparticles present, which...

Efficient, stable, and cost‐effective electrocatalysts for the oxygen evolution reaction (OER) are essential for clean energy generation through water splitting. This study presents a FeNiCoCuMo high‐entropy alloy (HEA) synthesized via mechanical alloying (MA) and sintering using hot‐pressing. The energy transfer from the milling process influences...

Corrosion is an inevitable and persistent issue that affects various metallic infrastructures, leading to significant economic losses and safety concerns, particularly in areas near or in contact with saline solutions such as seawater. Green corrosion inhibitors are compounds derived from natural sources that are biodegradable in various environmen...

In this study, we introduce an innovative approach to electroanalysis that combines solvent extraction and chronocoulometry for the quantification of furosemide, a loop diuretic medication. The objective of this report is to provide students with a practical learning experience in the field of electroanalysis, enabling them to explore recent develo...

Climate change has evidenced the need to reduce carbon dioxide emissions into the atmosphere, and so for transport applications, lighter weight alloys have been studied, such as magnesium alloys. However, they are susceptible to corrosion; therefore, surface treatments have been extensively studied. In this work, the influence of argon plasma pretr...

Citation: Alarcon, R.; Walter, M.; Paez, M.; Azócar, M.I. Ostwald Ripening and Antibacterial Activity of Silver Nanoparticles Capped by Anti-Inflammatory Ligands. Nanomaterials 2023, 13, 428. Abstract: Silver nanoparticles (AgNPs) have been extensively studied during recent decades as antimicrobial agents. However, their stability and antibacterial...

The increase in longevity worldwide has intensified the use of different types of prostheses for the human body, such as those used in dental work as well as in hip and knee replacements. Currently, Ti-6Al-4V is widely used as a joint implant due to its good mechanical properties and durability. However, studies have revealed that this alloy can re...

The influence of pH on the electrochemical behavior of hydrogen peroxide in the presence of Pseudomonas aeruginosa was investigated using electrochemical techniques. Cyclic and square wave voltammetry were used to monitor the enzymatic activity. A modified cobalt phthalocyanine (CoPc) carbon electrode (OPG), a known catalyst for reducing O2 to H2O2...

The protective properties of polymethacrylate coatings with different side chain lengths for 2024 aluminum alloys were studied, focusing on the chain length increase but also on the Ar-plasma pretreatment applied to the metal surface. The coatings were obtained by photopolymerization, obtaining reproducible molecular weight polymers during each pro...

In this work, electrochemical techniques were employed to evaluate the contribution to the corrosion and corrosion inhibition of 2024-T3 aluminum alloy by two Gram-positive bacteria. In addition, polarized impedance was used to determine the microbial effect on the cathodic and anodic reactions. These microorganisms were collected from a tropical e...

Violacein is an intensely purple pigment synthesized by various genera of bacteria that has been discovered to have a wide range of interesting biological activities which range from anticarcinogenic to antibacterial. One of the hindrances for its real-life application is that the first microorganisms found to produce the compound may act as opport...

Here we demonstrate that the metal ion excess after precipitating a sparingly soluble metal salt can be conveniently determined by a secondary precipitation of a metal salt on an electrode surface, followed by measuring the solid-state electrochemical response of that salt. As an example, the analysis of the arsenic content of solutions is presente...

Common alloys used for the manufacture of aircrafts are subject to different forms of environmental deterioration. A major one is corrosion, and there is a strong body of evidence suggesting that environmental microorganisms initiate and accelerate it. The development of an appropriate strategy to reduce this process depends on the knowledge concer...

Surface based on polyelectrolytes functionalized with amino acids onto amino-terminated solid surfaces of silicon wafers was prepared, with the purpose of evaluate the chemical functionality of the polyelectrolyte films in adsorption and catalytic activity of an enzyme. In this work, the adsorption of the enzyme glucose 6-phosphate dehydrogenase fr...

New experimental techniques and protocols are needed to study microbiologically influenced corrosion (MIC). In this work, we studied the capacity of microorganisms to modify their environment in vitro. The methodology involved cyclic voltammetry measurements using carbon electrodes modified with cobalt phthalocyanine, which is a known catalyst for...

Silver nanoparticles (AgNPs) have been widely recognized as antibacterial agents. However, its stability and activity over time have been poorly studied. In this work, the properties and characteristics of differently stabilized AgNPs were evaluated during a span of time. The surface capping agents were diclofenac (d), and ketorolac (k), which curr...

An experimental protocol was studied to improve the adhesion of a polymeric poly(methyl methacrylate) coating that was modified with silver nanoparticles to an aluminum alloy, AA2024. The nanoparticles were incorporated into the polymeric matrix to add the property of inhibiting biofilm formation to the anticorrosive characteristics of the film, th...

The antibacterial effects against Staphylococcus epidermidis of five silver carboxylate complexes with anti-inflammatory ligands were studied in order to analyze and compare them in terms of stability (in solution and after exposure to UV light), and their antibacterial and morphological differences. Four effects of the Ag-complexes were evidenced...

The Mⁿ⁺/M⁽ⁿ⁻¹⁾⁺ redox potential of MN4 macrocyclic molecular catalysts is a very good reactivity descriptor for several electrochemical reactions. One important feature about this reactivity descriptor is that it can be determined experimentally under the same conditions of the kinetic measurements in contrast to other descriptors like intermediate...

This work studied the microbiologically influenced corrosion susceptibility of the AA2024-T3 alloy exposed to sterile and inoculated media with three coccoidal bacteria, which were isolated from the corrosion product of a fuel outlet, belonging to a Twin Otter aircraft exposed to Antarctic environmental conditions. The consortium was mainly constit...

The conditions necessary to improve the adhesion of polymeric coatings to surfaces of aluminum alloys, AA2024-O (AA), were studied. The process considered a pre-conditioning of the metal surface by a transesterification reaction process with methyl methacrylate as an ester, by the generation of a terminal double bond on the surface of the alloy. Th...

We have examined the electrocatalytic activity for the oxidation of glutathione of a wide variety of molecular catalysts: FeN4 complexes (MN4 = metal porphyrins and metal phthalocyanines) confined on the surface of graphite electrodes in order to establish reactivity descriptors for these catalysts for this reaction. We have conducted these studies...

Bond nature of carboxylic groups can play an important role in Ag(I)-carboxylate compounds because light and thermal stability are important requirements for future applications such as antibacterial additives. A linear correlation between bond character and light stability of silver carboxylate complexes has been predicted by a direct relationship...

The influence of microorganisms in the deterioration of metal surfaces is an important issue in relation to the life of metal structures, equipment, and in terrestrial, marine, and aerospace transportation. In addition, changes in processes and formulations in surface treatments, in order to respond to environmental requirements, have reduced the p...

In this work, corrosion of an aluminum alloy for aeronautical applications, AA-2024, influenced by a consortium of microorganisms was studied. Microorganisms were isolated through environmental sampling, which was carried out in the auxiliary fuel in a Twin-Otter aircraft in Antarctic climate conditions. The identification of microorganisms was per...

Nitrogen doped carbon nanotubes (N-CNTs) were synthesized by the chemical vapor deposition technique (CVD) using ferrocene and iron (II) phthalocyanine as carbon precursors and ethylendiamine as the carbon and nitrogen source. Fe2O3 nanoparticles, Co nanoparticles and MoO3 were supported on a sol–gel polymer and were used as catalyst and seed growt...

Abstract: An electroanalytical system useful for measuring analytes, such as sugar, sulfites, and ethanol in wine, includes a printed copper electrode in an alkaline medium, a flow injection system to contact very small samples with the copper electrode, current measurement to measure current flowing in a cell containing the copper electrode and...

In this study, an antibacterial, but not cytotoxic nanomaterial based on polyethylene and copper nanoparticles was prepared by in situ polymerization. PE–CuNps nanocomposites against Escherichia coli, completely suppressed the number of live bacteria after 12 h incubation compared to neat PE. TEM images showed that nanocomposites damage the plasma...

Since ancient times, silver ions have been known to be effective against a broad range of micro-organisms but in the last decade, this metal has been greatly studied because of their antimicrobial capability against a wide range of bacteria, viruses, and fungi. For the same reason, it is the most extensively studied metal with antibacterial applica...

We report here a systematic study of the antibacterial behavior of silver nanoparticles coated with fatty acids (oleic: AgNP-O, linoleic: AgNP-L, and palmitic acids: AgNP-P) in water. We have found remarkable differences in their capability to penetrate bacteria cell over a broader range of particle size of similar to 4-96 nm compared to previously...

We report here a systematic study of the antibacterial behavior of silver nanoparticles coated with fatty acids (oleic: AgNP-O, linoleic: AgNP-L, and palmitic acids: AgNP-P) in water. We have found remarkable differences in their capability to penetrate bacteria cell over a broader range of particle size of *4–96 nm compared to previously reported...

Since infection is a major cause of death in a patient whose immune responses have been compromised (immu-nocompromised patient), considerable attention has been focused on developing materials for the prevention of infections. This has been directed primarily at suppressing or eliminating the host's endogenous microbial bur-den and decreasing the...

Antibacterial properties of silver(I)-pyridinedicarboxylate compounds (with Pyridine-2,3-dicarboxylic(Lutidinic acid), pyridine-2,4-dicarboxylic (Quinolinic acid) and pyridine-2,5-dicarboxylic (Isocinchomeronic acid)) were studied against Escherichia coli, Listeria monocytogenes (ISP-65-08), Salmonella typhi and Staphylococcus aureus (ATCC 25923) u...

The massive applications of fuel-cells in daily life has been hampered in part by the high cost of catalytic materials for the O2 cathode that involve noble metals like Pt. MN4 metal macrocyclics [1] and several CuN4 and CuN2 complexes [2] are active for the reduction of O 2 but they lack long-term stability in fuel conditions. However, they could...

Microorganisms have a strong tendency to colonize solid surfaces, leading to a complex microbial community that strongly adheres to the substrate, called biofilm. Biofilms are detrimental to the underlying substrates, causing physical degradation or biodeterioration of the metal surfaces. This phenomenon is widely recognized as biocorrosion or micr...

Since infection is a major cause of death in a patient whose immune responses have been compromised (immunocompromised patient), considerable attention has been focused on developing materials for the prevention of infections. This has been directed primarily at suppressing or eliminating the host's endogenous microbial burden and decreasing the ac...

The antibiofouling ability of three hybrid sol-gel coatings against P. aeruginosa for the protection of AA2024-T3 aluminium alloy has been investigated. The polymers were synthesized by mixing tetraethoxysilane (TEOS) with three precursors: (a) triethoxypropylsilane (TEPRS), (b) triethoxypentylsilane (TEPES) and (c) triethoxyoctylsilane (TEOCS). Th...

Five water soluble silver(I) complex with Ibuprofen (AgIbu), Naproxen (AgNap), Mefenamic acid (AgMef), acetyl salicylic acid(AgAsp) and salicylic acid (AgSal) were synthesized and characterized by elemental analysis, FT-IR, 1H and 13C NMR. Data suggest coordination of the ligand to Ag(I) through the oxygen atom of the carboxylic group. AgAsp was ob...

It was found that CoPc and 16(F)CoPc when adsorbed on a graphite electrode exhibited voltammograms in alkaline solution (0.2 M NaOH) that show the typical redox peaks attributable to the reversible Co(II)/(I) redox process. The peak potential for CoPc was independent of the surface concentration of the catalyst. In contrast, for 16(F)CoPc, the Co(I...

The aim was to study if the antimicrobial activity of chitosan incorporated into edible films based on gelatin could be affected by the molecular mobility (glassy or rubbery state) of the matrix. Films were obtained from film-forming suspensions (FFS) of bovine and salmon gelatins (7% w/w) and chitosan (0; 0.25; 0.5; 1% w/w) equilibrated at 33% y 8...

The antimicrobial effect of incorporating silver nanoparticles (AgNps) into zirconia matrixepolyether glycol was studied. AgNps of 4e6 nm in size were synthesized using the inverse micelles method, and different doses of metallic nanoparticles were incorporated into zirconiaepolyether glycol mixtures during the ageing procedure. Atomic force micros...

We have prepared self-assembled monolayers (SAMs) of 4-aminothiophenol (4-ATP) and 1-(4-mercaptophenyl)-2,6-diphenyl-4-(4-pyridyl)pyridinium tetrafluoroborate (MDPP) functionalized with iron phthalocyanine (FePc) and copper phthalocyanine (CuPc) adsorbed on gold (111) electrodes. The catalytic activity of these SAMs/MPc was examined for the reducti...

FT-IR spectroscopy of carboxylic groups and viability tests were useful to understand the antibacterial proper-ties of six highly efficient silver(I) pyridinecarboxylate (nicotinic, picolinic and isonicotinic acids) and bipiridine-carboxylate (pyridine-2,3-dicarboxylic, pyridine-2,4-dicarboxylic and pyridine-2,5-dicarboxylic acids) complexes with A...

The authors of the above article regret to say that there is an error in the paper. It was stated that the catalytic activity of the different molecular assemblies containing Fe phthalocyanine for oxygen reduction was examined in aqueous media at pH=4.0, whereas it should have said at pH=13.0. This error appears three times: in the Abstract, in the...

In this paper we compare the catalytic activitites of untouched metal macrocyclic and pyrolyzed catalysts for ORR in acid versus the formal potential of the catalyst and find in general that the catalysts reported in the literature exhibiting more positive formal potentials are more active for ORR. These trends observed could serve as a hint for th...

Salmon gelatin and chitosan are high potential biopolymer to obtain edible films with antimicrobial effect for fresh meat. Therefore, it is important to characterize the structural (glassy or rubbery) state of the gelatin film on antimicrobial properties of chitosan. Extracted salmon (Salmo Salar) gelatin (acid-basic extraction) and low molecular w...

A new hybrid sol–gel type film, composed of tetraethylorthosilicate (TEOS) and tetraocthylorthosilicate (TEOCS), and modified with different nanoparticle systems, has been investigated as a coating for protection of AA-2024-T3 aluminium alloy. The nanoparticle systems considered were either ZrO2 or CeO2 or their combination. The zirconia nanopartic...

We have studied the trends in catalytic activity of several Co macrocyclics confined on the surface graphite electrodes for the oxidation of thiocyanate. A plot of log i (at constant E) versus the formal potential of the catalyst gives a volcano correlation, indicating that the Co(II/I) redox potential needs to be tuned, in order to achieve maximum...

Polyethylene nanocomposites containing silver nanoparticles with antimicrobial properties were produced via in situ polymerization. The silver nanoparticles were added together with the catalytic system (metallocene catalyst and methylaluminoxane, MAO, as cocatalyst) directly to the reactor. The polymerization activity did not present significant c...

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The corrosion behaviour of copper in aerated 0.1M NaCl solution in presence of 8-aminoquinoline (8- AQ), using open circuit potential (OCP) measurements, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) measurements and atomic force microscopy (AFM), was studied. The measurements revealed that the effect of 8-AQ is depende...

The effect of zirconia and zirconia-polyester glycol hybrid coatings on the corrosion resistance of mechanically polished or anodized AISI 316 stainless steel (316L), was studied by potentiodynamic polarization and electrochemical impedance spectroscopy in 0.1M NaCl and scanning electron microscope and atomic force microscopy examinations. The depo...

We have investigated the electrocatalytic activity of tetraphenyl porphyrin, of substituted tetraphenyl porphyrins and of vitamin B12 for the electro-oxidation of 2-aminoethanethiol, with the catalysts confined on graphite electrodes. Several N4-macrocyclic were used in order to have a great variety of formal potentials of the catalysts and compare...

Graphite electrodes modified with four different cobalt N4 macrocyclics, namely Co tetrapentapyridinophthalocyanine, (CoTPenPyrPc), Co tetrapyridinoporphyrazine (CoTPyPz), Co octa(hydroxyethylthio)phthalocyanine (CoOEHTPc) and Co tetranitrophthalocyanine (CoTNPc) exhibit catalytic activity for the oxidation Of glucose in alkaline media. The purpose...

We have investigated the electrocatalytic activity of several substituted and unsubstituted cobalt–phthalocyanines of substituted tetraphenyl porphyrins and of vitamin B12, for the electro-oxidation of 2-mercaptoacetate, with the complexes pre-adsorbed on a pyrolytic graphite electrode. Several N4-macrocyclic were used to have a wide variety of Co(...

The S-N-P (stress, number of cycles, failure probability) curves for 2024 T3 and 7075 T7351 aluminium alloys were obtained. Previously, surface treatments of degreasing and different types of anodizing were applied to samples, evaluating the influence of these treatments on the fatigue life of the alloys. The determination of the S-N-P curves was d...

The aim of this study is to examine chitosan, which is a good film former, as a corrosion protective coating for AA-2024-T3 aluminium alloy. The aluminium samples were first anodized to increase adhesion of the subsequently dip coated film from a chitosan–acetic acid solution. To further increase the protective ability of the chitosan coating, the...

A sol-gel process has been used to generate a zirconium oxide coating on AA 2024-T3 aluminium alloy. The approach is based on hydrolysis and condensation of metal alkoxides molecular precursors, with specimens immersed in the sol solution followed by controlled removal, drying in air and heat treatment in an air furnace at various temperatures. Imm...

The hydrazine oxidation by iron(II) phthalocyanine (Fe(II)Pc) has been studied using an energy profile framework through quantum chemistry theoretical models calculated in the gas phase at the density functional theory B3LYP/LACVP(d) level. We applied two models of charge-transfer mechanisms previously reported (J. Phys. Chem. A 2005, 109, 1196) fo...

The electrocatalytic oxidation of sulfite (SO2� 3 ) in basic medium (pH¼10.2) at [Ni(II)- 5,7,12,14-tetramethyldinaphtho[b,i]-1,4,8,11-tetraaza[14]annuleneH]þþ/glassy carbon (mono- [Ni(II)tmdnTAA]þþ/GC), and poly-[Ni(II)-5,7,12,14-tetramethyldinaphtho[b,i]-1,4,8,11-tetraaza [14]annuleneH]þþ/glassy carbon(poly-[Ni(II)tmdnTAA]þþ/GC) modified electrod...

Using voltage-time responses and cyclic voltammetry, the initial stages of anodizing of Al–2.1 at.% Ag and Al–4 at.% Ag alloys are shown to depend upon the heat treatment of the alloys and the pre-treatment of the alloy surfaces. Chemical polishing of solution-treated alloys leads to relatively uniform anodic oxidation on a relatively smooth alloy...

Copper(II) complexes of n-alkyl-2-hydroxy-1-naphthaldimine Schiff bases (with n-alkyl: n-octyl, and n-dodecyl) have been synthesized, to study steric and electronic effects of long alkyl chain substituents on their structure and properties. These complexes have been characterized with FT-IR, UV-Vis, magnetic susceptibility and cyclic voltammetry bo...

This study shows that cobalt macrocyclics, namely Co-phthalocyanine (CoPc), Co-hexadecafluorophthalocyanine (CoF16Pc), Co-octaethylhexyloxyphthalocyanine (CoOEHPc), Co-tetraaminophthalocyanine (CoTAPc) and Co-tetrasulfophthalocyanine (CoTSPc), strongly adsorbed on a graphite electrode surface, exhibit true electrocatalytic activity for the oxidatio...

Molecular oxygen is certainly the most abundant oxidant on earth. Practically all of it is generated by living organisms, and without life it would not be present in the atmosphere. Molecular oxygen is generated by photosynthesis on earth and in the sea, so it can be considered a by-product of some living organisms and other living organisms profit...