Juan Manríquez
Centro de Investigación y Desa...

Materials Chemistry, Analytical Chemistry, Nanotechnology

PhD
30.27

Publications

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    ABSTRACT: Localized surface plasmon resonance (LSPR) has recently emerged as an efficient and powerful tool for bio-photonic applications due to its high sensitivity to refractive index changes. One technique to excite LSP is by the interaction of the evanescent wave of the light guided by an optical fiber with metallic nanoparticles deposited over the surface of the fiber. This paper proposes a novel, simple, and fast method to attach gold nanoparticles to the optical fiber surface, which can be used to construct highly sensitive refractive index sensors based on localized surface plasmon resonance. A hetero-core structured fiber, composed by a small section of single-mode fiber inserted in a multimode fiber, was coated with nanoparticles using the method proposed here. A sensor sensitivity and resolution of 765 nm/RIU and ∼1 × 10−4 RIU, respectively, were estimated over a refractive index range of 1.333–1.365. This coating method is appealing to construct optical fiber refractive index sensors since it is very simple and low cost.
    Full-text · Article · Jan 2016
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    Sandra Mendoza · Erika Bustos · Juan Manríquez · Luis A. Godínez
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    ABSTRACT: This chapter provides a brief review of sweep potential electrochemical techniques. It also addresses some relevant literature concerning identification and quantification of food components. Linear sweep voltammetry (LSV) and cyclic voltammetry (CV) are the most commonly used potential sweep techniques. Differential pulse stripping voltammetric (DPSV) techniques are the most popular to determine heavy metal content such as lead, cadmium, and mercury in food matrices. The conventional method to quantify trace metals in these samples is flame atomic absorption spectrometry. DPSV procedures have been performed to quantify Se, Zn, Ni, and Co. The official methods to determine sulfites in foods and beverages include titration, photometry, and iodometry, techniques that require long analysis time and sample pretreatment. While linear sweep and CV are preferred for exploring electron transfer reaction mechanisms, pulse techniques are used to achieve better detection and quantification limits of organic and inorganic species in food analysis.
    Full-text · Chapter · Jul 2015
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    DESCRIPTION: The role played by solvent during cathodic EPD of TiO2 films was investigated. The differences in film morphology are attributed to the dissimilar surface excess charge of the TiO2 agglomerates in each solvent and to the secondary reactions occurring during the EPD. For the films obtained in aqueous medium an augmentation of donor density and a change toward less negative values of the flat band potential were measured. Furthermore, a decrease in photocurrents and photovoltages was provoked by increasing the electric field used to form the film. Meanwhile, for the films formed in organic medium, the semiconductive properties did not change with the electric field employed to grow the films, and the photoelectrochemical behavior of these films showed completely different trends. The dissimilarities found were attributed to the ability of the solvent to be reduced earlier than TiO2, avoiding the generation of species Ti3+ that acts like trap states.
    Full-text · Research · Jul 2015
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    ABSTRACT: Stable suspensions of Ag particles were prepared using cetylpyridinium bromide (CPB) as a surfactant. The stability was evaluated using a Turbiscan optical analyzer, and the delta transmittance data showed that increasing the concentration of CPB in the suspensión significantly enhanced the stability. Additionally, for CPB concentrations in the range of 0.1 to 5 mM, the Ζ-potential values of the suspension increased. For concentrations higher than or equal to 5 mM CPB, the Ζ-potential values remained constant. CPB-Ag particle interactions were studied by Raman spectroscopy, and the results suggested that the CPB surfactant molecule is adsorbed with the ionic (-N+C5H5) head group oriented toward the Ag surface and the hydrophobic tail directed away from the surface. Additionally, coadsorbed Br- ions are very important for binding in the first monolayer. The pyridinium head groups are surrounded by bromide ions, and the pyridinium/bromide system is strongly adsorbed onto the Ag surfaces surfaces.
    Full-text · Article · Jul 2015
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    ABSTRACT: Here we report the preparation of dye-sensitized solar cells containing disperse red 1 (RD1)- or reactive red 2 (RR2)-modified nanoparticulate TiO2 photoanodes and their charge carrier dynamics under visible light illumination. Photoelectrochemical data obtained for both devices indicated that the photoinduced charge generation process was significantly better for RR2-sensitized solar cells than for DR1-sensitized solar cells. The effectiveness of the photoinduced charge generation observed for the RR2-sensitized TiO2 photoanodes was explained by invoking two complementary phenomena which can be promoted in the presence of the voluminous 1,3,5-triazine moieties of RR2: (a) delay of the increment of I3− ions concentration into the dyed-TiO2 pores, due to their known capabilities for establishing charge transfer complexes between N atoms of the heterocyclic ring and I atoms of the electrolyte, and (b) reduction of the electron interception process, due to the reaction established between photogenerated electrons and I3− anions of the electrolyte.
    Full-text · Article · Apr 2015 · Journal of Photochemistry and Photobiology A Chemistry
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    ABSTRACT: This research evaluated two electrokinetic remediation systems (EKR) for separating phenanthrene from bentonite and its electrochemical destruction by using a Boron Doped Diamond (BDD) electrode. The effect of the electrochemical potential for the oxidation of phenanthrene in liquid phase with Ti/BDD was analyzed by Normal Pulse Voltammetry and Hydroxyl Radical (●OH) analysis using the Spin Trapping Technique. The results showed that 70% of phenanthrene was removed from bentonite through EKR by applying 20 mA for 4 h in alkaline conditions, and that phenanthrene in solution was 100% degraded with Ti/BDD by applying 2.3 V vs Hg|Hg2SO4, for 2.5 h. These results demonstrate the potential application of the electrochemical technology in treating soils contaminated with highly toxic compounds, such as Polyaromatic Hydrocarbons (PAHs) and their final destruction using the EKR-BDD process.
    Full-text · Article · Apr 2015 · Environmental engineering and management journal
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    ABSTRACT: The regeneration of dye-adsorbed activated carbon (AC) using an electro-Fenton approach was studied and compared with typical regeneration methodologies (thermal, solvent extraction, and Fenton). The cathodic polarization effect of the electro-Fenton process on the AC surface was compared based on the textural and structural properties surface via physicochemical characterization techniques. The total organic carbon decay and color removal of a dye-contaminated model solution were also studied using the different methodologies, and several regeneration cycles were employed for each methodology in order to assess the regen-eration efficiency and correlate it with AC structural changes. The results show that the electrochemical process is the best method to regenerate AC because it maximizes the adsorption efficiency (approximately 80–90 %) compared to other methods of regeneration (\20 %) after 10 working cycles. These results led us to conclude that cathodic polarization regenerates the AC more efficiently than conventional methods.
    Full-text · Article · Mar 2015 · Journal of Applied Electrochemistry
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    ABSTRACT: The semiconductor–electrolyte interface have interesting similarities and differences with their semiconductor–metal (or metal oxide) and metal–electrolyte counterparts. Thus, approaches to garnering a fundamental understanding of these interfaces have stemmed from both electrochemistry and solid-state physics perspectives and have proven to be equally fruitful. Electron transfer theories were also rapidly evolving during this period, starting from homogeneous systems to heterogeneous metal–electrolyte interfaces leading, in turn, to semiconductor–electrolyte junctions. To facilitate a self-contained description, this chapter will start with wellestablished aspects related to the thermodynamic properties as semiconductor energy band model and the electrostatics at semiconductor–electrolyte interfaces in the dark. Additionally, this chapter examines the kinetic properties in the processes of light absorption, electron–hole generation, and charge separation at these interfaces. The steady state and dynamic aspects of charge transfer are then briefly considered. Nanocrystalline semiconductor films and size quantization are then discussed as are issues related to electron transfer across chemically modified semiconductor–electrolyte interfaces to determine the photocatalytic efficiency of semiconductor materials.
    Full-text · Chapter · Jan 2015
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    ABSTRACT: Perylene-based, terpyridine-Ru(II) complexes are synthesized and their electrochemical and photoelectrochemical properties are studied; their fabrication into dye-sensitized solar cells are described (DSSCs) and their resultant photovoltaic properties are evaluated.
    Full-text · Article · Jan 2015 · Heterocycles
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    ABSTRACT: This critical volume examines the different methods used for the synthesis of a great number of photocatalysts, including TiO2, ZnO, and other modified semiconductors, as well as characterization techniques used for determining the optical, structural and morphological properties of the semiconducting materials. Additionally, the authors discuss photoelectrochemical methods for determining the light activity of the photocatalytic semiconductors by means of measurement of properties such as band gap energy, flat band potential, and kinetics of hole and electron transfer. Photocatalytic Semiconductors: Synthesis, Characterization and Environmental Applications provides an overview of the semiconductor materials from first- to third-generation photocatalysts and their applications in wastewater treatment and water disinfection. The book further presents economic and toxicological aspects in the production and application of photocatalytic materials. This book also: · Provides a broad perspective of semiconductors materials with photocatalytic properties. · Emphasizes the importance of the physicochemical and electrochemical characterization of photcatalytic materials. · Includes synthesis methods that produce photocatalytic materials with suitable properties for environmental applications.
    Full-text · Book · Nov 2014
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    ABSTRACT: Ruthenium (II) complex-sensitized TiO2 electrodes were chemically coated with NH2-terminatedpoly(amidoamide) dendrimers generation 4.0 in order to improve the performance of dye-sensitized solar cells using these photoanodes. The presence of dendrimers in these photodevices produced a global photovoltaic conversion efficiency of 6.78%, which was higher than that obtained for photocells without them (5.43%). The experimental results indicated that this treatment of the dye-sensitized TiO2 electrodesallowed for controlling the concentrations of I3− anions and Li+ cations into the dendrimers-modified dyed-TiO2 pores during operation of the photocells. Consequently, the charge interception reaction and the charge accumulation process at the conduction band of the TiO2 electrodes were simultaneously balanced by the establishment of I2···NH2, NH···I− and C = O···Li+ bonds at the branches of the confined dendrimers for increasing their global conversion efficiency.
    Full-text · Article · Oct 2014 · Electrochimica Acta
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    ABSTRACT: The combined effect of temperature and pretreatment of the substrate on the anaerobic treatment of the organic fraction of slaughterhouse solid waste was studied. The goal of the study was to evaluate the effect of pretreating the waste on the efficiency of anaerobic digestion. The effect was analyzed at two temperature ranges (the psychrophilic and the mesophilic ranges), in order to evaluate the effect of temperature on the performance of the anaerobic digestion process for this residue. The experiments were performed in 6 L batch reactors for 30 days. Two temperature ranges were studied: the psychrophilic range (at room temperature, 18°C average) and the mesophilic range (at 37°C). The waste was pretreated with NaOH before the anaerobic treatment. The result of pretreating with NaOH was a 194% increase in the soluble chemical oxygen demand (COD) with a dose of 0.6 g NaOH per g of volatile suspended solids (VSS). In addition, the soluble chemical oxygen demand/total chemical oxygen demand ratio (sCOD/tCOD) increased from 0.31 to 0.7. For the anaerobic treatment, better results were observed in the mesophilic range, achieving 70.7%, 47% and 47.2% removal efficiencies for tCOD, total solids (TS), and volatile solids (VS), respectively.
    Full-text · Article · Oct 2014 · Journal of Bioscience and Bioengineering
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    ABSTRACT: a b s t r a c t An air diffusion activated carbon packed electrode was used to promote the in-situ generation of hydro-gen peroxide (H 2 O 2) to support an electro-Fenton based method for the degradation of a typical dye, Methyl Orange (MO) at two different concentrations in an aqueous effluent (250 mg L −1 and 97 mg L −1). Electrochemical experiments were carried out using a one compartment cylindrical cell with granular activated carbon (GAC) configured as an air diffusion cathode. The efficiency of the electrode was explored as a function of H 2 O 2 produced reaching a maximum value of 10 mM. Experimental parameters such as applied current (300, 200, 100 and 50 mA), initial Fe 2+ concentration (0.2, 0.5 and 0.8 mM) and electrode stability (10 cycles) were studied. High Total Organic Carbon (TOC) decay (90%) and color removal (100%) were obtained using this electrode under appropriate operation conditions. Consecutive degradation cycles of electro-Fenton process were performed in the electrochemical cell without great loss of the removal efficiency. Considering that, in the proposed packed electrode, the use of air diffusion GAC as cathode results in efficient degradation and cost reduction for the conventional electro-Fenton process, this electrode approach could constitute an excellent alternative for H 2 O 2 generation when compared to conventional carbon electrodes.
    Full-text · Article · Sep 2014 · Electrochimica Acta
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    ABSTRACT: This research evaluated two electrokinetic remediation systems (EKR) for separating phenanthrene from bentonite and its electrochemical destruction by using a Boron Doped Diamond (BDD) electrode. The effect of the electrochemical potential for the oxidation of phenanthrene in liquid phase with BDD was analyzed by Normal Pulse Voltammetry and Hydroxyl Radical (●OH) analysis using the Spin Trapping Technique. The results showed that 70% of phenanthrene was removed from bentonite through EKR by applying 20 mA for 4 h in alkaline conditions, and that phenanthrene in solution was 100% degraded with BDD by applying 2.3 V vs Hg|Hg2SO4, for 2.5 h. These results demonstrate the potential application of the electrochemical technology in treating soils contaminated with highly toxic compounds, such as Polyaromatic Hydrocarbons (PAHs) and their final destruction using the EKR-BDD process.
    Full-text · Article · Aug 2014 · Environmental engineering and management journal
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    ABSTRACT: A review on different arrangements and reactor designs for Advanced Oxidation Processes based on the use of the Fenton reagent is presented. The review focuses on reports that include publications and patents dealing with water contaminated with different recalcitrant pollutants. The work includes a brief introduction that deals with the basics of the Fenton reagent use for the oxidation of pollutants of water effluents, followed by a set of sections in which some of the reports and patents of the different forms in which the Fenton reagent is employed for water treatment processes are presented. In this way, this review includes a section dealing with processes in which the components of the Fenton reagent is administered by means of H 2 O 2 and Fe salts addition, in which it is photo-assisted with UV light and in which it is electro-generated in-situ and photo-assisted taking advantage of the electrochemical reduction of dissolved oxygen on a carbonaceous cathode.
    Full-text · Chapter · Jul 2014
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    ABSTRACT: A novel photoelectro-Fenton system was built by coupling a carbon sponge (CS) with a carbon steel plate (CSP). When this system contacts a solution containing orange II dye (OGII) under ultraviolet (UV) irradiation, 68% of the solution color was removed compared with 0% without UV irradiation. The tests indicate that the CS-CSP arrangement releases iron ions, a phenomenon associated with the removal of 23% of the solution color, a percentage similar to that obtained when Fe 2+ and Fe 3+ salts are directly placed into the dye solution. The identification of oxidizing free radicals and the color removal percentages indicate that the CS-CSP coupling can operate as in situ Fenton process. Keywords: in situ, photoelectro-Fenton, carbon sponge cathode. Resumen. En este trabajo se construyó un sistema fotoelectro-Fenton novedoso mediante el acoplamiento de una esponja de carbón (EC) con una placa de acero al carbón (PAC). Al colocar este arreglo con una solución del colorante naranja II (OGII) irradiando luz ultravio-leta, se logró remover el 68% del color de la solución, comparativa-mente con el 0% obtenido cuando no se aplicó luz UV. Las pruebas realizadas indican que el arreglo EC-PAC libera iones de hierro y que este fenómeno está asociado a la remoción del 23% del color de la solución, porcentaje similar al que se obtiene cuando se colocan sales de Fe 2+ y Fe 3+ directamente en la solución del colorante. La identifi-cación de la formación de radicales libres oxidantes cuando se usa el arreglo EC-PAC y los buenos porcentajes de remoción obtenidos son indicios de que el acoplamiento EC-PAC puede estar actuando como un proceso Fenton in situ. Palabras clave: In situ, fotoelectro-Fenton, cátodo de esponja de carbon.
    Full-text · Article · Jul 2014 · Journal of the Mexican Chemical Society
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    ABSTRACT: Acrylamide (AA) was electrochemically detected and quantified by means of its voltammetric response on carboxylic modified Single-Walled Carbon Nanotube Screen Printed Electrodes (COOH-SWCNT-SPEs). The electroreduction signal of AA was proportional to AA concentration at low values (below 300 µM) and the observed sensitivity was explained in terms of AA adsorption on the COOH-SWCNT-SPEs that was demonstrated using the electrochemical response of [Fe(CN)6]3− and [Fe(CN)6]4− and Raman spectroscopy experiments. In order to test the suggested analytic approach (LOD of 0.03 µM, LOQ of 0.04 µM), detection and quantification of AA in fried potatoes was carried out using the proposed electrochemical method and HPLC. Both techniques showed similar contents of AA.
    Full-text · Article · May 2014 · Electroanalysis
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    ABSTRACT: In recent years, the application of dendrimers in biomedicine attracted much attention from scientists. Dendrimers are interesting for biomedical applications because of their characteristics, including: a hyperbranching, well-defined globular structures, excellent structural uniformity, multivalency, variable chemical composition, and high biological compatibility. In particular, the three-dimensional architecture of dendrimers can incorporate a variety of biologically active agents to form biologically active conjugates. This review of dendrimers focuses on their use as protein mimics, drug delivery agents, anticancer and antiviral therapeutics, and in biomedical diagnostic applications such as chemically modified electrodes.
    Full-text · Article · Apr 2014 · Journal of Nanomaterials
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    Full-text · Chapter · Mar 2014
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    Full-text · Chapter · Mar 2014

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