Determination of the position of a dopant by DFT analysis; solid-state syntheses of Zn3Nb2O8 doped with Eu3+

The present paper aims to provide an objective criterion for establishing the position of a dopant (Eu3+ ) in a given crystalline matrix (Zn3Nb2O8). Following the analysis of the general conditions, regarding the size of the doping ion correlated with the reticular distances and / or the size of the coordination polyhedra, it remains to be established the concrete place that it will occupy, substitutional or interstitial. The criterion is based on the principle of minimum energy of the system, as a condition of existence of doped structure, which is why the method is applicable for a large variety of crystalline materials

Synthesis, characterization and anticorrosive properties of pseudo-binary oxide nanomaterials

This paper presents some results of the study regarding the corrosion inhibition properties evaluated in 0.1 M NaCl environment of drop casting deposited on steel, using Zn3Ta2O8 and Zn3Nb2O8 nanomaterials. Zn3Ta2O8 and Zn3Nb2O8 nanomaterials were obtained by hydrothermal method. The starting materials used during the synthesis were: tantalum (V) oxide - Ta2O5(99.99%, Merck), niobium (V) oxide - Nb2O5 (99.99%, Merck) and zinc acetate dihydrate – (CH3COO)2Zn x 2H2O Merck, 99.5 %) while keeping the molar ratio at 1:3. The pH of the obtained mixtures was adjusted to 12 by using sodium hydroxide (NaOH) solution of 10 M concentration. The resulting suspensions were transferred into Teflon-lined stainless steel autoclaves and then these were introduced in an oven at 220 0C for 8 h long. The filling degree of the used autoclaves was set at 70%. The resulting white precipitates were filtrated, and then five times washed with distilled water and, finally, three times with ethylic alcohol. In the next stage, the precipitate was dried in an oven at 80 0C for 6 h [1-3]. The obtained materials were used for thin films depositions using the drop casting method. The depositions were realized on polished carbon steel electrode disks (10 mm diameter and 2 mm thick). The surfaces of the thin films realized using the pseudo-binary oxides nanomaterials Zn3Ta2O8 and Zn3Nb2O8 on electrode steels were morphological and topographical investigated using the scanning electron microscopy (SEM – Model Inspect S) and the atomic force microscopy (AFM - ModelNanosurf@ EasyScan 2 Advanced Research microscope) using the non-contact mode cantilever (scan size 2.3 µm x 2.3 µm). From AFM measurements, according to equations from [4], were determined the topographical parameters Sa – the average roughness and Sq – the mean square root roughness for each drop casting deposition’s surface on steel electrodes. The obtained values were calculated using the NanoSurf EasyScan 2 software. The corrosion behaviour was studied using on Voltalab potentiostat Model PGZ 402 with single compartment three-electrode cell. Platinum wire was employed as counter electrode and the saturated calomel electrode (SCE) was the reference electrode. All potentials reported in this article were referenced to the standard hydrogen electrode (SHE). Bare and coated steel substrates were used as working electrodes. The potentiodynamic polarization curves were analyzed using VoltaMaster 4, v.7.09 software. This software performed the Tafel fitting and calculated the values of the corrosion potential (Ecorr), corrosion current density (icorr) and corrosion rate (vcorr). The measurements were performed by sweeping the potential between − 700 and 100 mV, in 0.1 M NaCl electrolyte solution, at a scan rate (v) of 1 mV/s. The degree of the corrosion inhibition efficiency IE (%) has been calculated [5] for each drop casting deposition

Complex formation between Co-metalloporphyrin and silver colloid in acidic media

Large flower sized nanoparticles of silver were synthesized and hybrid colloids with porphyrins were obtained. Daisy-like round aggregates generated from triangular-shaped silver nanoparticles can be observed, evenly distributed. The complexation of these particles with organic dyes was the main purpose of this work in order to achieve nanomaterials exhibiting wide absorption bands. The formation of a complex between an acidified Co(II) 5,10,15,20-meso-tetra(3- hydroxyphenyl) porphyrin (Co-3OHPP) solution in THF and the silver colloid negatively charged at the surface was proven by analyzing the UV-vis spectra during the experiment

Structured composites between MnTa2O6 and porphyrins: Influence of the number of carboxylic groups grafted on porphyrins on the capacity to inhibit corrosion of steel

New sandwich type materials based on MnTa2O6 and porphyrins mono- and tetra-substituted with –COOH groups, namely: (tetrakis-(4-carboxy-phenyl)-porphyrin and 5-(4-carboxy-phenyl)-10,15,20-tris-phenyl-porphyrin) have been synthesized and studied to assess the importance of its corrosion inhibition ability on with regard to its of steel the number of –COOH anchors. Morphological investigations on thin films have been carried out by atomic force microscopy. The inhibition of corrosion has been evaluated by open circuit potential measurements and potentiodynamic polarization technique with Tafel representation, after drop-casting deposition onto carbon steel in 0.1M HCl media. The inhibition efficiency of the novel sandwich-type materials based on pseudo-binary oxide MnTa2O6 and tetrakis-(4-carboxy-phenyl)-porphyrin or 5-(4-carboxy-phenyl)-10,15,20-tris-phenyl-porphyrin is in the range 76-86% for tetra substituted porphyrin and 84-95% for the mono-COOH substituted porphyrin

Noble metal colloid and Co-porphyrin hybrid sensitive to 4-aminosalicylic acid

A hybrid organic-inorganic nanomaterial (Co-3OHPP/n-Au) composed of Co(II) 5,10,15,20- meso-tetra(3-hydroxyphenyl)porphyrin (Co-3OHPP) and gold nanoparticles (n-Au) was tested as sensitive material for the optical detection of 4-aminosalicylic acid (PAS). This novel nanomaterial is able to detect 4-aminosalicylic acid in a reasonable concentration domain, covering one order of magnitude: 1.24 x 10-5 – 3.9 x 10-4M. The dependence between the intensity of absorption and the concentration in 4-aminosalicylic acid is linear, with a fair correlation coefficient of 95 %. This hybrid material can be further included in simple devices for the rapid and facile dosage of this antituberculosis drug in body fluids

Bismuth doping effects on structural and morphological properties of sodium titanate system

Energy shortage and environmental pollution have become urgent problems that restrict social development and endanger the health of the planet. For sustainable development of society, the most effective route is the active development and utilization of clean and renewable energy sources [1]. In this regard, the sodium titanates are of great interest for possible applications such as photocatalysts [2], as fuel-cell electrolytes, [3] in the treatment of industrial wastewaters and contaminated groundwaters [4] and in a number of medical applications [5,6]. In this paper, we report the study of bismuth doping effects in the sodium titanate materials, synthesized by hydrothermal method. Moreover, the influences of the synthesis temperature and autoclaving time on the structural and morphological properties are presented. The structure and morphology of Bi-doped sodium titanate nanocrystals are studied in the context of their possible use for sensors application. These materials are prepared using hydrothermal method at 200°C for 12h followed by heat treatment at 600°C, 6 hours for a better crystallization. Characterization of the obtained compounds was achieved by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and electrical behavior (ρ/T) was studied. The X-ray diffraction analysis showed that all samples are homogenous and crystallize in the monoclinic system with the P12/m space group. The obtained particles are as needle-like shape and their size decreases with increasing of dopant concentration

Influence of CO2 upon UV-Vis spectroscopy of silica-tetra-3,4 dimethoxy-phenylporphyrin hybrid nanomaterial

A symmetrical substituted aryl porphyrin was incorporated by sol-gel method to generate a silica hybrid nanomaterial that preserves the UV-vis absorption properties of bare porphyrin. The novel hybrid demonstrated to be a sensitive material for CO2 detection. The sol-gel synthesis was monitored by UV-vis spectroscopy. Atomic force microscopy was performed for the hybrid before and after CO2 detection and important changes in the aggregation behavior of the nanomaterial were observed

Hydrothermal synthesis of ZnTa

ZnTa2O6, ZnNb2O6, MgTa2O6 and MgNb2O6 pseudo-binary oxide nanomaterials were synthesized through the hydrothermal method at 250 °C. Obtained materials were characterized by X-ray diffraction, UV-VIS measurements, field emission-scanning electron microscopy and atomic force microscopy techniques. XRD results show that the single phases of ZnTa2O6, ZnNb2O6, MgTa2O6 and MgNb2O6 pseudo-binary oxides nanomaterials were obtained, no thermal treatment being required. The values for the optical band gap of each material are settled in the range 3.60–3.80 eV. The anticorrosion characteristics of the obtained compounds were also evaluated after deposition on carbon steel in 0.5 M Na2SO4 media by open circuit potential measurements and potentiodynamic polarization technique with Tafel representation. The inhibition efficiency of pseudo-binary oxides deposited on carbon steel electrode was in the range 37–59.17%, promising for improvement of the anticorrosion properties

Hybrid Porphyrin-Polymeric Materials and their Amazing Applications: A Review

Porphyrins are versatile multifunctional biomimetic molecules that are obtained by condensation of pyrrole with the desired aromatic aldehydes. The porphyrin structure can be synthetically modified by either introduction of various peripheral functional groups or metals in its core, allowing creation of various porphyrin derivatives that exhibit amazing optoelectronic properties. This feature makes porphyrins molecules extremely useful especially in hybrid combination with photonic, electronic and magnetic compounds. This review is focused on the more recently obtained porphyrin-polymeric materials and on their various analytical, industrial and medical applications. The study underlines the assembling capacity of these porphyrin-polymer hybrids to form supramolecular tunable architectures by means of the association of more building block units. Porphyrin-polymer nano- and micro-materials play a preeminent role in sensing applications involving chromophores in the formulation of organic solar cells - due to their capacity to generate photo induced charge separation centers - and as new materials with interesting catalytic properties. Besides these technical applications, the photobactericidal activity of these porphyrin–polymer materials was evaluated against Gram positive and Gram negative strains bacteria and they represent an alternative to antibiotics in order to overcome the growing bacterial multiresistance. Polymer functionalization with porphyrin is commonly used to overcome some drawbacks such as self-quenching and photo-toxicity to the skin produced by the bare porphyrins, when used as photosensitizers in the non-invasive Photodynamic therapy of cancer (PDT)