A Facile Glycerol-Assisted Synthesis of Low-Cu2+-Doped CoFe2O4 for Electrochemical Sensing of Acetaminophen.

This work devised a simple glycerol-assisted synthesis of a low-Cu2+-doped CoFe2O4 and the electrochemical detection of acetaminophen (AC). During the synthesis, several polyalcohols were tested, indicating the efficiency of glycerin as a cosolvent, aiding in the creation of electrode-modifier nanomaterials. A duration of standing time (eight hours) before calcination produces a decrease in the secondary phase of hematite. The synthesized material was used as an electrode material in the detection of AC. In acidic conditions (pH 2.5), the limit of detection (LOD) was 99.4 nM, while the limit of quantification (LOQ) was found to be (331 nM). The relative standard deviation (RSD), 3.31%, was computed. The enhanced electrocatalytic activity of a low-Cu2+-doped CoFe2O4-modified electrode Cu0.13Co0.87Fe2O4/GCE corresponds extremely well with its resistance Rct, which was determined using the electrochemical impedance spectroscopy (EIS) technique and defined its electron transfer capacity. The possibility of a low-Cu2+-doped CoFe2O4 for the electrochemical sensing of AC in human urine samples was studied. The recovery rates ranging from 96.5 to 101.0% were obtained. These findings suggested that the Cu0.13Co0.87Fe2O4/GCE sensor has outstanding practicability and could be utilized to detect AC content in real complex biological samples.

Fabrication and Characterization of Hybrid Films Based on NiFe2O4 Nanoparticles in a Polymeric Matrix for Applications in Organic Electronics.

Hybrid films for applications in organic electronics from NiFe2O4 nanoparticles (NPs) in poly(3,4 ethylene dioxythiophene), poly(4-styrenesulfonate) (PEDOT:PSS), and poly(methyl methacrylate) (PMMA) were fabricated by the spin-coating technique. The films were characterized by infrared spectroscopy, atomic force microscopy, scanning electron microscopy, and energy-dispersive spectroscopy to subsequently determine their optical parameters. The electronic transport of the hybrid films was determined in bulk heterojunction devices. The presence of NiFe2O4 NPs reinforces mechanical properties and increases transmittance in the hybrid films; the PEDOT:PSS-NiFe2O4 NPs film is the one that has a maximum stress of 28 MPa and a Knoop hardness of 0.103, while the PMMA-NiFe2O4 NPs film has the highest transmittance of (87%). The Tauc band gap is in the range of 3.78-3.9 eV, and the Urbach energy is in the range of 0.24-0.33 eV. Regarding electrical behavior, the main effect is exerted by the matrix, although the current carried is of the same order of magnitude for the two devices: glass/ITO/polymer-NiFe2O4 NPs/Ag. NiFe2O4 NPs enhance the mechanical, optical, and electrical behavior of the hybrid films and can be used as semi-transparent anodes and as active layers.

Properties of zinc titanates synthesized by microwave assisted hydrothermal method.

Zinc titanates are compounds that have shown great application versatility, including in the field of semiconductors. Solid state reactions, the polymeric precursor method and the hydrothermal method are the most mentioned synthesis of these compounds in the literature. In the present work, we use microwave assisted hydrothermal method (MAH) to synthesize zinc titanate and evaluate its potential for solar cell applications through structural and optical characterization techniques. The synthesized samples were also subjected to a variable temperature heat treatment in the range of 500 °C-800 °C. The analysis showed that the crystallization of the material starts at 500 °C and that samples submitted to temperatures of 600 °C-800 °C showed the formation of two phases of zinc titanates, being a cubic phase of ZnTiO3, considered rare in the literature, predominant up to a temperature of 800 °C. The optical characterization, based on the techniques of photoluminescence spectroscopy and UV-Visible spectroscopy, showed that the photoluminescent activity and the energy of the band gap increased with the increase of the temperature of the heat treatment, having the highest response in 700 °C, facts that can be linked to the predominant formation of the cubic phase of ZnTiO3 and simultaneous of the cubic and rhombohedral phases of ZnTiO3 at 700 and 800 °C. Finally, we highlight as the most important results, the fact that it was possible to obtain these titanates at a temperature lower than that reported in the literature, and that the heat-treated sample at 500 °C is the one with the lowest energy expenditure to be synthesized and the one with the greatest potential for application in dye-sensitized solar cells (DSSC's).

Recovery of Neodymium (III) from Aqueous Phase by Chitosan-Manganese-Ferrite Magnetic Beads.

Neodymium is a key rare-earth element applied to modern devices. The purpose of this study is the development of a hybrid biomaterial based on chitosan (CS) and manganese ferrite (MF) for the recovery of Nd(III) ions from the aqueous phase. The preparation of the beads was performed in two stages; first, MF particles were obtained by the assessment of three temperatures during the co-precipitation synthesis, and the best nano-MF crystallites were incorporated into CS to obtain the hybrid composite material (CS-MF). The materials were characterized by FTIR, XRD, magnetization measurements, and SEM-EDX. The adsorption experiments included pH study, equilibrium study, kinetics study, and sorption-desorption reusability tests. The results showed that for MF synthesis, 60 °C is an appropriate temperature to obtain MF crystals of ~30 nm with suitable magnetic properties. The final magnetic CS-MF beads perform maximum adsorption at pH 4 with a maximum adsorption capacity of 44.29 mg/g. Moreover, the material can be used for up to four adsorption-desorption cycles. The incorporation of MF improves the sorption capacity of the neat chitosan. Additionally, the magnetic properties enable its easy separation from aqueous solutions for further use. The material obtained represents an enhanced magnetic hybrid adsorbent that can be applied to recover Nd(III) from aqueous solutions.

Synthesis of Mesoporous Zn1-xMxAl2O4 Substituted by Co2+ and Ni2+ Ions and Application in the Photodegradation of Rhodamine B.

A new mesoporous Zn1-xMxAl2O4 photocatalyst was prepared using the metal-chitosan complexation method with different degrees of Zn2+ cation substitution with cobalt and nickel ions (M = Co2+ and Ni2+). Characterization using X-ray diffraction (XRD), Infrared absorption spectrometry (FTIR), energy dispersion spectroscopy (EDS), diffuse reflectance spectrometry (DRS), scanning electron miscoscopy (SEM), transmission electron miscroscopy (TEM), N2 adsorption- desorption isotherms using the Barrett-Joyner-Halenda (BJH) method, thermogravimetric analysis (TG) and differential thermal analysis (DTA) confirmed the formation of the spinel phase and high purity for all samples. N2 adsorption/desorption and size pore distribution confirmed the high surface area. The photocatalytic activity of Zn1-xMxAl2O4 and the effect of replacing Zn2+ ions with Ni2+ and Co2+ on the degradation of rhodamine B under ultraviolet light were studied in detail. The sample containing 0.1 mol of cobalt had the highest removal rate reaching 83%, favored by surface area and material bandgap (109 m2 g-1 and 2.19 eV, respectively).

Development of an Ultra-Low Carbon MgO Refractory Doped with α-Al2O3 Nanoparticles for the Steelmaking Industry: A Microstructural and Thermo-Mechanical Study.

The effect of α-Al2O3 nanoparticles (up to 5 wt.%) on the physical, mechanical, and thermal properties, as well as on the microstructural evolution of a dense magnesia refractory is studied. Sintering temperatures at 1300, 1500, and 1600 °C are used. The physical properties of interest were bulk density and apparent porosity, which were evaluated by the Archimedes method. Thermal properties were examined by differential scanning calorimetry. The mechanical behavior was studied by cold crushing strength and microhardness tests. Finally, the microstructure and mineralogical qualitative characteristics were studied by scanning electron microscopy and X-ray diffraction, respectively. Increasing the sintering temperature resulted in improved density and reduced apparent porosity. However, as the α-Al2O3 nanoparticle content increased, the density and microhardness decreased. Microstructural observations showed that the presence of α-Al2O3 nanoparticles in the magnesia matrix induced the magnesium-aluminate spinel formation (MgAl2O4), which improved the mechanical resistance most significantly at 1500 °C.

Estudio de la estabilidad de fases en el sistema Zn - Cr - O a partir de síntesis por combustión en solución / Study on phase stability in the Zn - Cr - O system from synthesis by combustion in solution / Estudo da estabilidade de fases no sistema Zn 一 Cr 一 O a partir de síntese por combustão em solução

Resumen Introducción. Los compuestos con metales de transición en su estructura generan enorme interés por sus propiedades físicas, las más destacadas de las cuales son las magnéticas y las eléctricas. La espinela ZnCr2O4 se ha caracterizado por sus potenciales usos como fotocatalizador y como material empleado para censar CO2, lo cual actualmente es de gran relevancia, y ha motivado conocer nuevos métodos para su obtención y para la justificación de estudios que permitan entender las características termodinámicas para su formación. Objetivo. Estudiar la estabilidad de la fase ZnCr2O4 con la coexistencia de fases secundarias formadas mediante tratamientos térmicos. Materiales y métodos. A partir de la homogeneización de glicina y nitratos (cinc y cromo), se sintetizó por combustión en solución un compuesto amorfo, el cual tras tratamientos térmicos (750, 850 y 950 °C) presentó ordenamiento cristalino. Resultados. Luego de la obtención del compuesto se evaluó la morfología de los polvos empleando microscopía electrónica de barrido (SEM) y evaluando su composición (EDS). Se determinó presencia de material orgánico, se realizó caracterización térmica (TGA y DSC) para definir la temperatura de formación de fases, para luego evaluar y comparar las estructuras mediante difracción de rayos X (DRX), y mediante simulaciones en el programa FactSage( se compararon resultados para verificar el equilibrio de las fases. Conclusión. A través del método de combustión en solución se obtiene una estructura no cristalina conformada por Zn, Cr y O, confirmándose la presencia de C asociado al componente orgánico luego de la combustión.

Abstract Introduction. Compounds with transition metals in their structure generate great interest due to their physical properties, especially their magnetic and electric ones. The spinel ZnCr2O4 has been characterized by its potential uses as photocatalyst and as CO2, sensing material, which has current relevance and has motivated to learn about new methods for obtaining it and for justifying studies that allow to understand the thermodynamic characteristics for its formation. Objective. Study phase stability ZnCr2O4 with the coexistence of secondary phases formed through thermal treatments. Materials and methods. From the homogenization of glycine and nitrates (zinc and chrome), an amorphous compound was synthetized by combustion in solution. After thermal treatments (750, 850 and 950 °C), the compound presented crystalline ordering. Results. After obtaining the compound, the morphology of the powders was evaluated through scanning electronic microscopy (SEM) and their composition was also evaluated (EDS). The presence of organic material was determined and a thermal characterization was made (TGA and DSC) to define the phase formation temperature. Next, the structures were evaluated and compared through X-ray diffraction (XRD). Using simulations in the FactSage( software the results were compared to verify phase equilibrium. Conclusion. Through the solution combustion method, a non-crystalline structure is obtained, formed by Zn, Cr and O, confirming the presence of C associated to the organic component after combustion.

Resumo Introdução. Os compostos com metais de transição na sua estrutura geram enorme interesse por suas propriedades físicas, as mais destacadas das quais são as magnéticas e as elétricas. A espinela ZnCr2O4 se ha caracterizado por seus potenciais usos como fotocatalizador e como material empregado para fazer CO2, o qual atualmente é de grande relevância, e há motivado conhecer novos métodos para sua obtenção e para a justificação de estudos que permitam entender as características termodinâmicas para sua formação. Objetivo. Estudar a estabilidade da fase ZnCr2O4 com a coexistência de fases secundárias formadas mediante tratamentos térmicos. Materiais e métodos. A partir da homogeneização de glicina e nitratos (cinc e cromo), se sintetizou por combustão em solução um composto amorfo, o qual trás tratamentos térmicos (750, 850 e 950 °C) apresentou ordenamento cristalino. Resultados. Logo da obtenção do composto se avaliou a morfologia dos pós empregando microscopia eletrônica de barrido (SEM) e avaliando sua composição (EDS). Se determinou presencia de material orgânico, se realizou caracterização térmica (TGA e DSC) para definir a temperatura de formação de fases, para logo avaliar e comparar as estruturas mediante difração de raios X (DRX), e mediante simulações no programa FactSage( se compararam resultados para verificar o equilíbrio das fases. Conclusão. Através do método de combustão em solução se obtém uma estrutura não cristalina conformada por Zn, Cr y O, confirmando-se a presencia de C associado ao componente orgânico logo da combustão.

Synthesis, Characterization, and Sensor Applications of Spinel ZnCo2O4 Nanoparticles.

Spinel ZnCo2O4 nanoparticles were synthesized by means of the microwave-assisted colloidal method. A solution containing ethanol, Co-nitrate, Zn-nitrate, and dodecylamine was stirred for 24 h and evaporated by a microwave oven. The resulting solid material was dried at 200 °C and subsequently calcined at 500 °C for 5 h. The samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy, confirming the formation of spinel ZnCo2O4 nanoparticles with average sizes between 49 and 75 nm. It was found that the average particle size decreased when the dodecylamine concentration increased. Pellets containing ZnCo2O4 nanoparticles were fabricated and tested as sensors in carbon monoxide (CO) and propane (C3H8) gases at different concentrations and temperatures. Sensor performance tests revealed an extremely high response to 300 ppm of CO at an operating temperature of 200 °C.

Investigation of Structural, Morphological, Magnetic Properties and Biomedical applications of Cu2+ Substituted Uncoated Cobalt Ferrite Nanoparticles

ABSTRACT In the present work, Cu2+ substituted cobalt ferrite (Co1-xCuxFe2O4, x = 0, 0.3, 0.5, 0.7 and 1) magnetic nanopowders were synthesized via chemical co-precipitation method. The prepared powders were investigated by various characterization methods such as X-ray diffraction analysis (XRD), scanning electron microscope analysis (SEM), vibrating sample magnetometer analysis (VSM) and fourier transform infrared spectroscopy analysis (FTIR). The XRD analysis reveals that the synthesized nanopowders possess single phase centred cubic spinel structure. The average crystallite size of the particles ranging from 27-49 nm was calculated by using Debye-scherrer formula. Magnetic properties of the synthesized magnetic nanoparticles are studied by using VSM. The VSM results shows the magnetic properties such as coercivity, magnetic retentivity decreases with increase in copper substitution whereas the saturation magnetization shows increment and decrement in accordance with Cu2+ substitution in cobalt ferrite nanoparticles. SEM analysis reveals the morphology of synthesized magnetic nanoparticles. FTIR spectra of Cu2+ substituted cobalt ferrite magnetic nanoparticles were recorded in the frequency range 4000-400cm-1. The spectrum shows the presence of water adsorption and metal oxygen bonds. The adhesion nature of Cu2+ substituted cobalt ferrite magnetic nanoparticles with bacteria in reviewed results indicates that the synthesized nanoparticles could be used in biotechnology and biomedical applications.

Estudio comparativo entre placa-injerto, caja-placa y caja de PEEK en artrodesis de la columna cervical con conducto cervical estrecho / Comparative study between plate-graft, cage-plate and peek cage in cervical arthrodesis for cervical stenosis

Introducción: Se han desarrollado una variedad de sistemas para fijar y artrodesar la columna cervical con las ventajas de reducir del riesgo de seudoartrosis, extrusión y colapso del injerto, así como una mayor precisión en la alineación sagital, por tal motivo requerimos comparar resultados de placa-injerto, caja-placa y caja-PEEK, en pacientes con conducto cervical estrecho. Material y métodos: Estudio prospectivo, de intervención y comparativo, formando tres grupos: grupo I, artrodesis con placa-injerto, grupo II, caja-placa, grupo III, caja-PEEK. La evaluación funcional pre- y postoperatoria con escala de discapacidad cervical y escala visual análoga (EVA) de dolor y radiografías columna cervical. Se analizaron los resultados con pruebas no paramétricas de rangos con signo de Wilcoxon y Kruskal Wallis para comparación entre más de dos grupos. Con nivel de significancia de 0.05. Resultados: Muestra de 37 pacientes para el grupo I con n = 12, con 22 niveles; grupo II con: n = 11, con 19 niveles; grupo III con: n = 14 con 25 niveles. La mayoría de pacientes entre la sexta y octava década de la vida. Al año de postoperados el índice de discapacidad cervical y mejoría del dolor con EVA mostraron mejoría con diferencia estadística en los tres grupos (p = 0.001). Sin embargo, las mediciones radiográficas al año de seguimiento mostraron una mejoría significativa de la lordosis segmentaria (p = 0.02) sólo en pacientes operados con placa-injerto. Conclusiones: El uso de la placa injerto ofrece mejores resultados clínicos y radiográficos en comparación con la caja-placa y caja-PEEK al año de seguimiento.

Introduction: A variety of systems have been developed to fix and perform arthrodesis of the cervical spine, with the advantages of reducing the risk of pseudoarthrosis, extrusion and graft collapse and achieving a more precise sagittal alignment. We therefore need to compare the results of the following approaches to patients with cervical stenosis: plate-graft, cage-plate and PEEK cage. Material and methods: Prospective, interventional, comparative trial involving three groups: group I, arthrodesis with plate-graft; group II, cage-plate, and group III, PEEK cage. The pre- and postoperative assessments included the cervical disability scale, the pain visual analog scale (VAS), and cervical spine X-rays. The results were analyzed with non-parametric tests such as the Wilcoxon sign test and the Kruskal-Wallis test for the comparison of more than two groups. Significance level was 0.05. Results: The sample included a total of 37 patients: n = 12 in group I, with 22 levels; n = 11 in group II, with 19 levels, and n = 14 in group III, with 25 levels. Patient age ranged between 60 and 80. One year after surgery there was an improvement in cervical disability and the pain VAS score, with a statistically significant difference among the three groups (p = 0.001). However, radiographic measurements at that time showed a significant improvement in segmental lordosis (p = 0.02) only in plate-graft patients. Conclusions: The plate-graft approach provides better clinical and radiographic results compared to the cage-plate and PEEK cage techniques, at the one-year follow-up.