Karim Sapag

Importance of the αs-plot Method in the Characterization of Nanoporous Materials

In this work, an exhaustive study of the calculation of micropore and mesopore volumes with αs-plot method as proposed by Professor Sing is carried out. The method is critically compared with other similar methods such as the Dubinin–Radushkevich, t-plot and those based on density functional theory (DFT). For comparison purposes, several nanoporous materials with different chemical properties were selected. The analysis was segregated into three categories: (i) microporous materials, in which the analyzed samples are activated carbons (ACs) with different pore-size distributions, a single-walled carbon nanotube (SWNT) and a zeolite (MS5A); (ii) mesoporous materials, including ordered mesoporous carbons (CMK-3) and ordered mesoporous siliceous materials (MCM-41 and SBA-15); and (iii) micro-mesoporous materials, in which pillared clays (PILCs) obtained with different metals (Al, Si, Fe and Zr) were studied. To apply the αs-plot method, several standard isotherms previously reported by other authors were considered for the analysis of microporous and mesoporous materials. Furthermore, a series of four reference materials for PILCs were synthesized and their high-resolution nitrogen adsorption isotherms were measured and reported. The results obtained by the αs-plot method are consistent with those obtained by DFT methods. This consistency highlights the importance of the use of this reliable and versatile method, where the correct selection of the standard isotherm is the most critical aspect to be considered.

Microfluidic immunosensor based on mesoporous silica platform and CMK-3/poly-acrylamide-co-methacrylate of dihydrolipoic acid modified gold electrode for cancer biomarker detection

We report a hybrid glass-poly (dimethylsiloxane) microfluidic immunosensor for epidermal growth factor receptor (EGFR) determination, based on the covalent immobilization of anti-EGFR antibody (anti-EGFR) on amino-functionalized mesoporous silica (AMS) retained in the central channel of a microfluidic device. The synthetized AMS was characterized by N2 adsorption-desorption isotherm, scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and infrared spectroscopy. The cancer biomarker was quantified in human serum samples by a direct sandwich immunoassay measuring through a horseradish peroxidase-conjugated anti-EGFR. The enzymatic product was detected atxa0-100xa0mV by amperometry on a sputtering gold electrode, modified with an ordered mesoporous carbon (CMK-3) in a matrix of poly-acrylamide-co-methacrylate of dihydrolipoic acid (poly(AC-co-MDHLA)) through in situ copolymerization. CMK-3/poly(AC-co-MDHLA)/gold was characterized by cyclic voltammetry, EDS and SEM. The measured current was directly proportional to the level of EGFR in human serum samples. The linear range was from 0.01xa0ngxa0mL-1 to 50xa0ngxa0mL-1. The detection limit was 3.03xa0pgxa0mL-1, and the within- and between-assay coefficients of variation were below 5.20%. The microfluidic immunosensor is a very promising device for the diagnosis of several kinds of epithelial origin carcinomas.

Synthesis and textural characterization of a templated nanoporous carbon from MCM-22 zeolite and its use as adsorbent of amoxicillin and ethinylestradiol

AbstractnA templated nanoporous carbon was obtained from a zeolite MCM-22 type. The study about their textural properties was carried out by means of adsorption isotherms of nitrogen and carbon dioxide at 77 and 273xa0K, respectively. Due to the importance of the microporosity of these materials to be used as adsorbents, the micropore volume was analyzed by different methods/models (Dubinin–Radushkevich, αs-plot and Density Functional Density). The templated carbon obtained was evaluated in the adsorption of amoxicillin and ethinylestradiol from aqueous solutions. A relationship between the textural properties and the adsorption capacities of amoxicillin and ethinylestradiol on the templated carbon was analyzed. Results were compared with the adsorption capacities of other carbon materials as a commercial activated carbon and a templated carbon CMK-3 type.

Development of a nanostructured immunosensor for early and in situ detection of Xanthomonas arboricola in agricultural food production

We report a microfluidic electrochemical immunosensor for Xanthomonas arboricola (XA) determination, based on the covalently immobilization of monoclonal anti-XA antibody (anti-XA) on a previously amino functionalized SBA-15 in situ synthesized in the central channel of a glass-poly(dimethylsiloxane) microfluidic immunosensor. The synthetized amino-SBA-15 was characterized by N2 adsorption-desorption isotherm, scanning electron microscopy and infrared spectroscopy. XA was detected by a direct sandwich immunoassay through an alkaline phosphatase (AP) enzyme-labeled anti-XA conjugate. Later, the substrate p-aminophenyl phosphate was converted to p-aminophenol by AP. The enzymatic product was detected at +100mV on a sputtered gold electrode. The measured current was directly proportional to the level of XA in walnut trees samples. The linear range was from 5 × 102 to 1 × 104CFUmL-1. The detection limit was 1.5 × 102CFUmL-1, and the within- and between-assay coefficients of variation were below 5%. Microfluidic immunosensor is a very promising tool for the early and in situ diagnosis of XA in walnuts avoiding serious economic losses.

The combined effect between Co and carbon nanostructures grown on cordierite monoliths for the removal of organic contaminants from the liquid phase

Carbon nanostructures were grown on the surface of cordierite monoliths using Fe or Co nanoparticles by catalytic chemical vapor deposition (CCVD) using ethanol in order to intensify the interaction of this support with organic contaminants. The materials produced were extensively characterized by X-ray diffraction, thermal analysis, elemental analysis, atomic absorption spectrometry, Raman spectroscopy and scanning and transmission electron microscopies. These materials were tested in the removal of quinoline and methylene blue from liquid solutions. Promising results were attributed to the combined effect of the hydrophobic carbon nanostructures in adsorbing the organic contaminants with cobalt metal cores that are able to promote the oxidation of the adsorbed molecules via a heterogeneous Fenton process.

Adsorption of CO2 on Amine-Grafted Activated Carbon

Adsorption on amine-grafted materials may be a potentially attractive alternative to capture CO2 from power plants. Activated carbon (AC) has been proposed as a potential adsorbent due to its natural affinity for CO2 and the possibility of tailoring its textural properties and surface chemistry to enhance capacity and selectivity. An AC commercial sample was functionalized with monoethanolamine to obtain nitrogen-enriched AC with two different loadings (ACN10 and ACN20). Characterization of the sample was carried out by nitrogen adsorption–desorption isotherms at 77 K, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and adsorption microcalorimetry. The CO2 equilibrium adsorption experiments were carried out in a volumetric system within the pressure range from vacuum to 13 bar, at 298 and 348 K. Impregnated AC showed different chemical and textural characteristics with a significant reduction in the surface area, depending on the amine loading. A high adsorption capacity at room temperature (298 K) and high pressure was observed for the pristine AC as compared with the modified samples. The reduction in surface area affected the adsorption capacity of CO2 at 298 and 348 K, except for adsorption on ACN10 at 348 K, which suggests the occurrence of chemisorption.

On the computer simulations of carbon nanoparticles porosity: statistical mechanics model for CO 2 and N 2 adsorption isotherms

A new approach model was developed for the pore size characterization of carbon porous materials, using adsorption gases. The experimental adsorption isotherms of CO2 and N2 onto carbon nanoparticles were used to test the validity of such model. The Trimodal-Gauss-Monolayer model has been found to adjust well the experimental data of CO2 sorption at 273xa0K and has allowed detect the ultra-micropores till 0.7xa0nm. For the mesopores and macropores, it has been concluded that the N2 sorption isotherms at 77xa0K are suitable to characterize this kind of porosity. These isotherms have been well fitted with the Gauss-Monolayer/Gauss-Finite Multilayer model derived from the same approach. Thereby, the novel method can be used as a generalized technique for the simulation of type IVa isotherms. Indeed, this novel method agreed with other methods, NLDFT, QSDFT, and VBS available for pore size distribution.