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A facile strategy for the design of porous supports was obtained by modifying the sol-gel method followed by the wet impregnation technique. In this respect, herein, the acidity of the γ-Al2O3 phase was modulated by adding basic MgO, La2O3 or ZnO promoters to form binary supported catalysts. The Ni and Co dispersion on the supports associated with their tunable acidity and morphologies resulted in highly porous supported alumina-based catalysts. The physicochemical properties of the solids were comprehensively investigated by XRD, textural properties, Raman and FTIR spectroscopy, SEM-EDS, TEM, EPR and XPS analyses. The catalytic performances in the esterification of glycerol in the presence of acetic acid (EG) for the acetins production were evaluated. The highly dispersed NiO and Co3O4 active species on binary porous supports produced synergistic effects appearing to be the reason for the activity of the solids in the EG reaction. Under the optimized reaction conditions, NiCo/MgO-Al2O3 was found to be a robust solid with superior catalytic performance and improved stability in four reaction cycles with 65.0% of glycerol conversion with an exclusive selectivity of 53% for triacetin. The presence of Co2+/Co3+ and Ni2+ strongly interacting with the spinel γ-Al2O3 and MgAl2O4 phases, the latter having a large number of lattice oxygen species, was considered another active component besides those of Ni and Co in the esterification of glycerol.

In a previous work the authors presented the necessary and sufficient conditions for the invertibility of some circulant matrices that depend on three real parameters and, moreover, we obtained a closed formula for their inverse. The techniques we used allowed us to reduce the computational cost of evaluating the inverse. In this work we complete the theoretical analysis of the mentioned circulant matrices by considering complex parameters and also the singular case. In addition, we explicitely compute the group inverse of a specific kind of this class of matrices using the same techniques that the authors developed for the non singular case; that is, solving first order linear difference equations.

This paper summarizes the results obtained in a project conceived to improve remote and face-to-face teaching of Calculus in the fields of industrial and biomedical engineering. The project consists of developing teaching videos that treat key topics of Calculus subject through some engineering problems at a first level university course. We focus on achieving the goal of learning by setting it in the approach and solution of a subject, making it more experiential. This type of practice should be the central focus of activities inside and outside the classroom. In this way we will be able to consolidate the students' mathematical skills, but at the same time acquire other skills that will be vital for their professional and personal development. The evaluation process must be formative, as the assessment should provide teacher-student feedback in order to adjust teaching or learning based on the information received. We propose two main types of activities: Production of audiovisual material for the improvement of teaching and completion of Wiris questionnaires for self-assessment. The didactic video is very useful in class and has a motivating intention because rather than transmitting exhaustive and systematized information on the subject, it aims to open questions, raise problems, arise the interest of students, disturb and generate a participatory dynamic. With the elaboration of these videos, we promote that students be able to understand through specific problems and with the help of graphic material, a specific problem and then move on to the abstraction of more general situations.

Explicit expressions for the coefficients of the group inverse of a circulant matrix depending on four complex parameters are analytically derived. The computation of the entries of the group inverse are now reduced to the evaluation of a polynomial. Moreover, our methodology applies to both the invertible and the singular case, the latter being computationally less expensive. The techniques we use are related to the solution of boundary value problems associated with second order linear difference equations.

The adsorption of greenhouse gases (GHG) as a method to reduce their emissions into the atmosphere is an alternative that is easier to implement industrially and cheaper than other existing technologies, such as chemical capture, cryogenic separation, or membrane separation. The vast majority of works found in the literature have focused their efforts on capturing CO2 as it is the largest GHG. However, although N2O emissions are not as large as CO2, the impact that N2O has on the stratosphere and climate is much larger in proportion, despite which there is not much research on N2O capture. Since both gases are usually emitted into the atmosphere together (along with other gases), it is necessary to design selective adsorbents capable of capturing and separating these gases from each other and from other gases, to mitigate the effects of climate change. This review aims to compile the existing information to date on porous adsorbents, the characteristics of the N2O adsorption processes and, above all, aims to focus the reader’s gaze on the importance of designing selective adsorbents for greenhouse gas mixtures.

We have named generalized Jacobi matrices to those that are practically tridiagonal, except for the two final entries and the two first entries of its first andits last row respectively. This class of matrices encompasses both standard Jacobiand periodic Jacobi matrices that appear in many contexts in pure and appliedmathematics. Therefore, the study of the inverse of these matrices becomes ofspecific interest. However, explicit formulas for inverses are known only in a fewcases, in particular when the coefficients of the diagonal entries are subjected tosome restrictions.We will show that the inverse of generalized Jacobi matrices can be raisedin terms of the resolution of a boundary value problem associated with a secondorder linear difference equation. In fact, recent advances in the study of lineardifference equations, allow us to compute the solution of this kind of boundaryvalue problems. So, the conditions that ensure the uniqueness of the solution ofthe boundary value problem leads to the invertibility conditions for the matrix,whereas that solutions for suitable problems provide explicitly the entries of theinverse matrix.

Olive pits, a waste product derived from olive oil production, have a high carbohydrate content attractive for biorefineries. Nanotechnology, making possible the preparation of nontoxic carbon-based nanoparticles, namely, carbon dots, provides a compelling opportunity for the valorisation of such waste feedstocks with enormous advantages. In this work, biomass was subjected to a soft one-step treatment in which trifluoroacetic acid and different solid catalysts were used. Fluorescent nanosized (4.5 nm) particles were obtained, displaying the characteristic behavior of carbon dots. These nanoparticles exhibited a fluorescence emission at 500 and 602 nm when treated with the solid catalyst and trifluoroacetic acid, respectively. XPS and NMR analyses showed oxygen-rich content on the surface of the carbon particles which could explain a proton transfer in the excited state (ESIPT effect). Studies to evaluate the effects of synthesized nanoparticles on HEK 293T cells were also performed, showing their biocompatibility.

A simple, fast, and laboratory efficient doped P carbon nanoparticles synthesis is developed for fingerprint imaging, using 1,3-dihydroxyacetone and di-phosphorous pentoxide. Fluorescence nanoparticles, with an average size of 230 nm were obtained, without additional energy input or external heating. ATR, solid NMR, XPS and fluorescence spectroscopy revealed their surface functionalization; a reaction mechanism is proposed. Fluorescence measurements exhibited a maximum emission band at ca. 495 nm, when excited at 385 nm. The images obtained, on different surfaces such as mobile telephone screen, magnetic band and metallic surface of a credit card and a Euro banknote treated with the obtained nano-powders allows us to record positive matches, confirming that the experimental results illustrate the effectiveness of proposed method.

In this work we obtain easy characterizations for the boundedness of the solutions of the discrete, self–adjoint, second order and linear unidimensional equations with periodic coefficients, including the analysis of the so-called discrete Mathieu equations as particular cases.

In this work, solid wastes from the flocculation step of a drinking water treatment plant were used as starting material to obtain CO2 adsorbents upon thermal treatment and a pillaring strategy. Thermally treated solid waste and pillared materials were characterized by XRD, FTIR, TGA, N2 adsorption–desorption isotherms at 77 K, XPS and elemental analysis. From the characterization results, it was found that the introduction of silica pillars was successful, leading to heterostructured materials with higher specific surface area and pore volume. In order to improve the CO2 adsorption capacity, pillared materials were functionalized by grafting with (3-aminopropyl)triethoxysilane (APTES)and impregnation with polyethylenimine (PEI). Pillared materials could be loaded with up to 50 wt% PEI. PEI-impregnated pillared adsorbents were tested for CO2 adsorption at 298 and 348 K and CO2/N2 adsorption at 348 K using a Magnetic Suspension Balance equipped with a mixture gas dosing (Rubotherm, Germany). Langmuir and Sips models were used to fit monocomponent and mixture experimental data, considering two different sites for CO2 adsorption. At 1 bar, 50PEI-SiFe (loaded with 50 wt% PEI) adsorbed 2.5 and 3.6 mmol CO2 g−1 at 298 and 348 K, respectively and exhibited an extremely high CO2/N2 selectivity (above 150 mol CO2/mol N2 at 348 K). Nevertheless, PEI loaded adsorbents still exhibit a lower amine efficiency as compared to APTES-grafted counterparts, due to diffusion restrictions caused by the high viscosity of the impregnated polymer.

A carbon quantum dots (CQDs) based ratiometric nanosensor exhibiting dual emission fluorescence was developed. The spherical fluorescent carbon nanoparticles were obtained from lactose using a hydrothermal method. Under a single excitation at 355 nm they showed the typical blue emission at 417 nm and a red emission at 550 nm attributed to the coating effect of vitamin B12. The latter is explained by the fluorescence resonance energy transfer (FRET) and it consists of 61% of total emission. Upon the presence of carbofuran phenol 3-Keto, a phenolic metabolite of carbofuran, the red emission was quenched, resulting in a ratiometric fluorescence response in the blue range. This ratiometric nanosensor exhibited a good selectivity to carbofuran phenol 3-Keto. The ratio of I417/I550 linearly decreased with an increasing carbofuran phenol 3-Keto concentration in the range 9.8 μM–1.40 × 10−4 M. A detection limit for carbofuran phenol 3-Keto pesticide was 12.2 μM. The pesticide tested was extracted from soy sauce. Recovery values ranged from 98% to 114% with RSD values from 1.50% to 6.50%.

In this work we introduce the triangular double sequences of arbitrary order given by linear recurrences, that generalize some well-known recurrences that appear in enumerative combinatorics. In particular, we focussed on triangular sequences generated by two double sequences and establish their relation with the solution of linear three-term recurrences. We show through some simple examples how these triangular sequences appear as essential components in the expression of some classical orthogonal polynomials and combinatorial numbers.

A synthesis method in two steps was used to obtain Co 3 O 4 –CeO 2 (COCE) catalysts. Firstly, freeze-drying precursors to obtain a submicrometric ceria powders support were calcined at a temperature as low as 400 °C. Then, the support was impregnated with a Co(II) acetate solution by incipient wetness impregnation, varying the loading of Co between 5 and 20 wt%, and calcined again at 400 °C. x COCE samples were tested for the preferential oxidation of CO in a H 2 -rich stream (CO-PROX). All samples showed catalytic activity and high selectivity towards CO 2 at low reaction temperatures, being 15COCE the most active catalyst. Moreover, simulating a CO-PROX unit operation, the influence of the presence of CO 2 and H 2 O in the feed was tested, showing a high activity and selectivity mainly to CO 2 .

[EN] Porous clay heterostructures (PCH) have shown to be highly efficient supports for nickel oxide in the oxidative dehydrogenation of ethane. Thus NiO supported on silica with a PCH structure shows productivity towards ethylene three times higher than if NiO is supported on a conventional silica. This enhanced productivity is due to the increase in the catalytic activity and especially to the drastic increase in the selectivity to ethylene. Additionally, PCH silica partially modified with titanium in the columns (PCH-Ti) have also been synthesized and used as supports for NiO. An enhanced activity and selectivity to ethylene was found over NiO supported over PCH-Ti compared to the corresponding catalysts supported over the Ti-free PCH. The enhanced catalytic performance has been related to the high dispersion of nickel oxide particles on the support, which leads to a lower reducibility of the nickel oxide, hindering the oxidation of ethane into carbon oxides. More interestingly, the particle morphology plays an important role on the catalyst selectivity since a higher distortion of the NiO crystal lattice parameter meant an enhanced selectivity to ethylene., The authors would like to acknowledge the DGICYT in Spain (CTQ2012-37925-C03-1, CTQ2012-37925-C03-2 and CTQ2012-37925-C03-3) and the FEDER for financial support. We also thank the University of Valencia and SCSIE-UV for assistance.

Fluorescent carbon dots (CDs) and its nitrogen doped (N-CDs) nanoparticles have been synthesized from lactose as precursor using a bottom-up hydrothermal methodology. The synthesized nanoparticles have been characterized by elemental analysis, FTIR, Raman, TEM, DLS, XPS, and steady-state and life-time fluorescence. The synthesized carbon nanoparticles, CDs and N-CDs, have a size at about 7.7 ± 2.4 and 50 ± 15 nm, respectively, and quantum yields of 8% (CDs) and 11% (N-CDs). These techniques demonstrated the effectiveness of the synthesis procedure and the functionalization of the CDs surface with amine and amide groups in the presence of NH 3 in aqueous media. The effect of excitation wavelength and pH on the luminescent properties was studied. Under the optimal conditions, the nitrogen doped nanoparticles can be used as pyridine sensor in aqueous media because they show an enhancement of its fluorescence with a good linear relationship. The analytical method is simple, reproducible and very sensitive for pyridine determination.

Highly luminescent nanoparticles based in Silicon quantum dots, coated by hydroxyl PAMAM dendrimer (PAMAM-OH) of 5th generation, were obtained by one step process by hydrothermal treatment of 3-Aminopropyl)triethoxysilane (APTES) in aqueous solution. Previous to the optimization of the synthesis procedure, different dendritic molecules of 5th generation were tested to obtain the most intense fluorescence signal. The influence of different parameters such ratio APTES/PAMAM-OH, pH and ionic strength on the fluorescence intensity was studied. The fluorescence spectra showed maximum excitation and emission wavelengths at 370 and 446 nm, respectively. The obtained silicon nanoparticles (SiQDs@PAMAM-OH) were characterized by TEM, DLS and XPS, and were found to detect selectively Cr(VI) in aqueous solutions at 2.7 μM level of detection, sensitivity of 0.2 μM with a RSD of 0.16% (n=10). To study the feasibility of the proposed system for Cr(VI) detection, it was tested in real electrochemical solution bath and a tanning effluent obtained from electrochemical industry and with two certified waters, demonstrating promising outcomes as nano-sensor.

We present here necessary and sufficient conditions for the invertibility of some circulant matrices that depend on three parameters and moreover, we explicitly compute the inverse. Our study also encompasses a wide class of circulant symmetric matrices. The techniques we use are related with the solution of boundary value problems associated to second order linear difference equations. Consequently, we reduce the computational cost of the problem. In particular, we recover the inverses of some well known circulant matrices whose coefficients are arithmetic or geometric sequences, Horadam numbers among others. We also characterize when a general symmetric, circulant and tridiagonal matrix is invertible and in this case, we compute explicitly its inverse.

Metal(IV) phosphates such as zirconium phosphate (ZrP) are well known proton conductors based on the mobility of protons localized at Bronsted-acid sites. By introduction of mesoporous silica into the interlayer region, these compact materials are transformed into Porous Phosphate Heterostructures (PPH). Here we studied the electrical properties of PPH and show that the proton conductivity is supported by ammonia, which does not occur neither in ZrP nor in the mesoporous silica. This demonstrates that transforming the layer structure of ZrP into a mesoporous hybrid material leads to a new ammonia gas sensing material. This concept might be promising for the development of new gas sensor materials in general.

CuO–CeO2 catalysts have been synthesized using polymethyl metacrylate (PMMA) microspheres as template and copper and cerium acetates as precursors, leading to a homogeneous porous framework of nanocrystalline materials with uniform pore size distribution and well dispersed copper species between 1 and 9 wt.%. The catalysts have been characterized by X-ray Diffraction (XRD), Field-Emission Scanning Electron Microscopy (FE-SEM), High-resolution Transmission Electron Microscopy (HRTEM), Raman spectroscopy, adsorption-desorption of N2 at −196 °C, thermoprogrammed reduction with H2 (H2-TPR) and X-ray photoelectron spectroscopy (XPS). CuO–CeO2 catalysts have been evaluated in the CO-PROX reaction, reaching high conversion values (>95%) at 115 °C for all samples. Moreover, these catalysts have been tested under high content of CO2 and H2O in the feed, simulating a CO-PROX unit, obtaining conversion efficiency values higher than 90% at 115 °C, which indicates a high tolerance of the catalysts in both CO2 and H2O gases.

This study reports on the preparation and characterization of porous clay heterostructures (PCH) as a high-surface-area support for CuO–CeO 2 based catalysts for the preferential oxidation of CO in excess of H 2 (CO-PROX). After pillaring the montmorillonite clay with silica (Si-PCH) and silica-zirconia (SiZr-PCH), the Cu-Ce active phase was loaded by incipient wet impregnation setting the cerium amount constant (20 wt%) and investigating three different copper loadings (3, 6 and 12 wt%). The use of pillars of silica or silica-zirconia inserted in the interlayer space of a natural clay provides a high surface area support that can favor the dispersion of both CuO and CeO 2 active phases, leading to the formation of a high amount of copper-ceria interfacial sites, responsible for a very high catalytic activity in the CO-PROX reaction. The results obtained from characterization of the materials by XRD, N 2 physisorption, H 2 -TPR, XPS and CO 2 -TPD suggest that this synthesis method gives rise to catalysts with copper species highly active and selective for the CO-PROX reaction. The catalysts exhibit high CO conversion values and the sample with 6 wt% of copper on Si-PCH displays very good performances, comparable to those based on precious metal catalysts, even at low temperatures. The system reducibility was found modified by the incorporation of zirconium in the support, with a slight decrement of the CO conversion value, compared to the same material without Zr. The influence of the presence of CO 2 and H 2 O in the gas feed was also studied in order to simulate the real operating conditions of a PEMFC feed stream. Correlations between catalytic performances and physicochemical properties of the materials have been made.

In this work, we have investigated how the typical honeycomb arrangement of SBA-15 and the mechanisms of CO 2 uptake are affected by the addition of chemicals upon synthesis (to modify pore width and length) and post-synthesis amine functionalization. SBA-15 was synthesized hydrothermally by a conventional route (S00) and such synthesis was then subject to modifications: by adding heptane as a swelling agent (S10) and increasing amounts of ammonium fluoride (S11, S12, S13 and S14) to shorten channels length. All of the synthesized silicas were then subject to APTES grafting and PEI impregnation. CO 2 isotherms were obtained for the pure and amine-loaded samples. They were fitted to the Dual-Site Langmuir model for all functionalized adsorbents, so that it was possible to discriminate the relative importance of chemisorption and physisorption sites. The increasingly disordered frameworks brought about by fluoride addition led to the formation of mesocellular silica foams (MCFs), which were not advantageous to increase CO 2 uptakes in the case of amine-grafting because they have a lower silanol density and hence bind less nitrogen as compared to the conventional SBA-15. In the case of PEI-impregnation, it was found that an addition of a low amount of fluoride is important in the regulation of the chemisorption/physisorption ratio. Promising CO 2 uptakes (2.3 mmol CO 2 /g or 4.6 mmol/g PEI at 25 °C and 1 bar) were found for a load of 50% (wt) PEI in MCF synthesized with the highest NH 4 F/SiO 2 molar ratio (equal to 0.065), which was attributed to a better accessibility of amino groups to CO 2 , as compared to the conventional SBA-15 support subject to the same PEI load.

Fluorescent water soluble carbon nanoparticles, in short carbon dots (CDs), was synthesized from lactose by microwave assisted hydrochloric acid method. Characterized by TEM and DLS to obtain the morphology shape (average 10 nm in size), with a higher negative surface charge supported by the composition was obtained by XPS spectroscopy. The maximum of the emission was centered at 450 nm with a lifetime of 2.1 ns. Without further functionalization of the CDs a nanosensor was obtained that responded exponentially to HAAs in the 0.35–0.45 mg L−1 concentration range by fluorescence static quenching, demonstrated by the lifetime analysis of the CDs in presence of HAAs. Some amino compounds were selected as model for interferences to evaluate the selectivity of this method, showing a notorious added value, with recoveries around 98%. The accuracy of the method was in terms of RSD about 2.5%. The results suggest their promising applications in chemical sensing.

Porous clay heterostructures (PCH) are obtained by the insertion of an organic bulky cation in the interlayer spacing of a smectite, causing a swelling of the clay mineral. Right after, oxides species, mainly silicon oxide, are incorporated as pillars galleries between adjacent layers to form a porous structure after the removal of the template. The ordering of the clay mineral as well the organic cation incorporated in the synthetic step favors the modulation of the textural properties of the PCH. In addition, the incorporation of heteroatoms in the pillars galleries can also modulate the acidity of the PCH. The modulation of the pore size and the acid properties provides to these materials a wide range of applications in the fields of adsorption and catalysis. This paper carries out a detailed review of the synthesis of PCH, characterization as well as uses and application reported in the literature.

A synthesized functionalized pillared porous phosphate heterostructure (PPH), surface functionalized phenyl group, has been used to remove the dye Acid Blue 113 from wastewater. X-ray photoemission spectroscopy XPS and X-ray diffraction (XRD) were used to study its structure. The specific surface area of this was 498 m2/g. The adsorption capacities of PPH and phenyl surface functionalized (Φ-PPH) were 0.0400 and 0.0967 mmol/g, respectively, with a dye concentration of 10−5 M when well fitted with SIPS and Langmuir isotherms respectively (pH 6.5, 25 °C). The incorporation of the dye to the adsorbent material was monitored by the S content of the dye. It is suggested as an alternative for Acid Blue 113 remediation.

A porous phosphate heterostructure (PPHs) formed by a layered zirconium(IV) phosphate expanded with silica galleries was prepared presenting a P/Zr molar ratio equal to 2 and a (Si + Zr)/P ratio equal to 3. This pillared zirconium phosphate heterostructure was used as a catalyst support for bi-functional catalysts based on noble metals (Pt or Pd) and molybdenum oxide containing a total metallic loading of 2 wt % and Pt(Pd)/Mo molar ratio equal to 1. The catalysts prepared were characterized by different experimental techniques and evaluated in the hydrodeoxygenation (HDO) reaction of dibenzofuran (DBF) as a model compound present in biomass derived bio-oil, at different reaction pressures. The catalyst characterization evidenced that a high dispersion of the active phase can be achieved by using these materials, as observed from transmission electron microscopy (TEM) characterization, where the presence of small particles in the nanometric scale is noticeable. Moreover, the textural and acidic properties of the phosphate heterostructure are barely affected by the incorporation of metals into its structure. Characterization results evidenced that the presented material is a good candidate to be used as a material support. In both cases, high conversions and high selectivities to deoxygenated compounds were achieved and the active phase played an important role. Thus, Pt/Mo presented a better hydrogenolysis capability, being more selective to O-free products; whereas, Pd/Mo showed a greater hydrogenation ability being more affected by changes in pressure conditions.

CuO supported on CeO2, Ce0.8Zr0.2O2 and Ce0.8Al0.2O2 based catalysts (6%wt Cu) were synthesized and tested in the preferential oxidation of CO in a H2-rich stream (CO-PROX). Nanocrystalline supports, CeO2 and solid solutions of modified CeO2 with zirconium and aluminum were prepared by a freeze-drying method. CuO was supported by incipient wetness impregnation and calcination at 400 � C. All catalysts exhibit high activity in the CO-PROX reaction and selectivity to CO2 at low reaction temperature, being the catalyst supported on CeO2 the more active and stable. The influence of the presence of CO2 and H2O was also studied.

The CO 2 adsorption capacity of different APTES-grafted mesoporous silicas of SBA-15 type has been investigated and the influence of support textural properties and the role of the presence of silanol groups on the adsorption capacity are analyzed. Four adsorbents based on SBA-15 were prepared using tetraethyl orthosilicate (TEOS) as silicon source, with and without the addition of trimethyl-benzene (TMB) and n -heptane as swelling agents, and adding in some cases ammonium fluoride as a solubility enhancer. 3-(triethoxysilyl)propylamine (APTES) was then used as grafting agent by reaction with free silanol groups on the silica surface so as to provide pending amino groups for CO 2 capture. The adsorption behavior for all supports was adequately described by a Freundlich model, whereas for the APTES-grafted silica, a dual-site Langmuir model was applied, which allowed us to quantify and qualify two different adsorption sites. The addition of n -heptane as swelling agent led to pore sizes beyond 10 nm and improved significantly the grafting efficiency, leading to higher CO 2 uptakes as compared to the starting supports. At 1 bar and 25 °C and anhydrous conditions, CO 2 uptakes of 2.4 mmol g −1 or 0.64 mol CO 2 per mol N were achieved (which reveals a significant contribution of physisorption). This sample could be successfully regenerated at 100 °C, maintaining a constant capacity for 3 adsorption–desorption cycles. At 0.15 bar and 60 °C, anhydrous conditions, CO 2 uptake reaches 1.5 mmol g −1 . This value may be theoretically doubled in the presence of humidity, and there is room for further improvement if supports with the same pore size (13 nm) and higher surface areas (e.g. 1000 m 2 /g) are successfully synthesized.

Highly photoluminescent carbon dots have been prepared in a one step procedure by hydrothermal treatment of formaldehyde at 180 °C. They show green fluorescence under UV light exposure and emission spectra are centered at 440 nm. Fluorescence lifetimes comprise between 0.7 and 2.70 ns, when the synthesis process lasted for 1-7 days. TEM images of nanoparticles showed a homogeneous size/shape distribution. When the thermal treatment process was carried out for a long time (30 days) formation of aggregates occurred. Carbon dots were further analyzed using (1)H and (13)C-NMR, Raman and FTIR spectroscopy techniques and XPS. Cell imaging of nanoparticles was carried out by using mouse MC3T3-E1 pre-osteoblasts as a model. The nanoparticles were selectively localized in the cytoplasm without further functionalization and could be realized by cellular phagocytosis, so that the fluorescence of these can be used for live cell imaging in vitro.

A CuO + TiO2 mixture, based on two commercial and well characterized CuO and TiO2 photocatalyst, has been used to produce hydrogen by solar light irradiation and in presence of different organic compounds (methanol, glycerol, formic acid, and the components of a wastewater coming from the biodiesel industry) acting as sacrificial electron donors. The experiments have been conducted at Plataforma Solar de Almeria (PSA, south of Spain) with a pilot plant scale reactor using a CPC (compound parabolic collector) configuration. The tested system has shown similar hydrogen generation capacity and energy efficiency than more expensive ones based on the use of noble metal/photocatalyst composites. Formic acid has shown to be the most effective electron donor, although very close amounts of hydrogen are also produced with glycerol, and this is found as a waste compound released in large quantities at the biodiesel industry wastewaters. As seen in previous similar studies, the increase of solution conductivity hampers the hydrogen generation, and a slightly basic solution pH (pH≈9) gives the best reaction conditions. Finally, the composite can be recovered and successfully reused giving the ensuing and sustained generation of H2 while removing more than 50% of TOC.

A water soluble complex of neodymium(III) with CdTe quantum dots nanoparticles was synthesized. The obtained homogeneous solutions were characterized by fluorescence, X-ray photoelectron and energy dispersive X-ray spectroscopies. The effect of the refluxing time of the reaction on the fluorescence intensity and emission wavelength has been studied. It was found that the emission wavelength of the solutions of neodymium(III) complex capped CdTe QDs nanoparticles shifted from about 540 to 735 nm. For an emission wavelength of 668 nm, the most reproducible nanoparticles obtained, the pH effect over the fluorescence emission and its intensity were studied. The purified and lyophilized solid obtained was morphologically characterized by transmission electron microscopy (TEM). The quantitative composition was determined by fluorescence X-ray spectroscopy (EDAX) and the X-ray photoelectron analysis (XPS) confirmed the presence of neodymium(III) at the surface of the CdTe nanoparticles forming a complex with the carboxylate groups from 3-mercaptopropanoic acid of the CdTe QDs. Due to the optical behavior of this complex, it could be of potential interest as a light source in optical devices.

We have named tridiagonal ( p , r ) -Toeplitz matrix to those tridiagonal matrices in which each diagonal is a quasi-periodic sequence, d ( p + j ) = r d ( j ) , so with period p ∈ N but multiplied by a real number r . We present here the necessary and sufficient conditions for the invertibility of this kind of matrices and explicitly compute their inverse. The techniques we use are related with the solution of boundary value problems associated to second order linear difference equations. These boundary value problems can be expressed throughout the discrete Schrodinger operator and their solutions can be computed using recent advances in the study of linear difference equations with quasi-periodic coefficients. The conditions that ensure the uniqueness solution of the boundary value problem lead us to the invertibility conditions for the matrix, whereas the solutions of the boundary value problems provides the entries of the inverse matrix.

Synthesis, characterization, and the optical behavior of CdS quantum dots nanoparticles were studied confined in clays. An alternative synthesis approach in different natural clays K-10 bentonite, Na-montemorillonite, halloysite, and saponite was carried out. The composite materials were characterized by XRD and FTIR spectroscopy, energy dispersive, scanning, and transmission electron microscopy. After CdS-QDs formation, the synthesized materials became fluorescent with emission wavelengths (average and standard deviation of the maximum wavelength; full width of half maximum): K-10 bentonite-CdS (590 ± 5 nm; 183 nm); Na-montmorillonite-CdS (550 ± 3 nm; 219 nm); saponite-CdS (550 ± 5 nm; 219 nm), and halloysite-CdS (590 ± 8 nm; 185 nm). (Supplemental materials are available for this article. Go to the publisher's online edition of the Journal of Dispersion Science and Technology to view the free supplemental file.)

The synthesis and characterization of cadmium sulphide (CdS) quantum dots, conjugated in a porous phosphate heterostructure functionalized with aminopropyl groups is described. The resulting material has fluorescence properties with maximum emission intensity at 575 nm. The fluorescent materials are not soluble in water and exhibit high stability in aqueous solution in the pH ranges from 2 to 9. Energy dispersive X-ray spectroscopy confirmed the qualitative elemental composition of the synthesized materials and X-ray photoelectron spectra showed a surface S/Cd atomic ratio of 1.09. SEM images show that the materials are amorphous, possessing porous with sizes of several tens nanometres, homogeneous and exhibit a layered morphology. The adsorption-desorption analysis by N(2) at 77 K showed the accessibility of the CdS quantum dots onto the pores of the structure. The CdS quantum dots were stabilized by mercaptopropionic acid and bounded to the host materials by amine groups.

Vanadium oxide supported on mesoporous zirconium phosphate catalysts has been synthesized, characterized and tested in the selective oxidation of H2S to sulfur. The nature of the vanadium species depends on the V-loading of catalyst. Catalysts with a V-content lower than 4wt% present both isolated vanadium species and V2O5 crystallites. However, V2O5 crystallites have been mainly observed in catalysts with higher V-content, although the presence of isolated V-species on the surface of the metal oxide support cannot be completely ruled out. The catalytic behaviour also depends on V-loading of catalysts. Thus, while the catalytic activity of catalysts can be related to the number of V-sites, the catalyst decay is clearly observed in samples with low V-loading. The characterization of catalysts after the catalytic tests indicates the presence of sulfur on the catalyst, which is favoured on catalysts with low V-loading. However, a clear transformation of V2O5 to V4O9 can be proposed according to XRD and Raman results of used catalysts with high V-loading. The importance of V5+-O-V4+ pairs in activity and selectivity is also discussed. (C) 2009 Elsevier B.V. All rights reserved., The authors gratefully acknowledge financial support from CICYT, Spain (NAN2004-09267-C03-01 and NAN2004-09267-C03-02). MDS thanks a fellowship from the Universidad Politecnica of Valencia.

En este artículo se expone una experiencia de naturaleza socioconstructivista con eluso de las Tecnologías de la Información y la Comunicación (TIC) realizada conalumnado de 3º de educación secundaria obligatoria. La actividad consiste en laelaboración de la biografía de una científica y su exposición en el aula, mediante larealización de una presentación multimedia. La tarea plantea una forma de trabajo enla que el alumnado pone en funcionamiento una serie de competencias de formasimultánea. Así pues, el cambio metodológico que se está proponiendo gira en torno alas actividades. Con las presentaciones diseñadas por el alumnado, se han diseñadounos pósters para una exposición sobre las científicas en la historia. La experiencia haresultado interesante desde el punto de vista de la coeducación y del desarrollo decompetencias TIC para el alumnado y nos facilita a los docentes nuevas metodologíasde trabajo en el aula.

This work studies the structural and chemical modifications of functionalised porous phosphate heterostructures (PPH) of zirconium phosphate. The modification consists in incorporation of propionitrile at two different percentages, but pressure was also applied in order to obtain pressurized discs. The application of pressure (4 T cm 2 ) provokes a migration of nitrile groups to the surface as observed by XPS analysis and it seems to be responsible for the drastic porosity decrease obtained by N 2 adsorption. Electrochemical characterization of the pressured-discs in contact with NaCl solutions at different concentrations was also carried out. These results show the cation exchange capacity of PPH, which is slightly reduced in the case of the functionalised materials with nitrile groups (10% lower cation transport number), while diffusional permeability and electrical resistance values also confirm structural changes for the modified materials.

Copper based catalysts supported on mesoporous materials, which were in turn based on a surfactant expanded zirconium phosphate for the formation of silica galleries in the interlayer space, were prepared by the impregnation method. They were then characterised and tested in the selective catalytic reduction of NO with ammonia as active catalysts for the control of the NOx emissions from heavy duty vehicles. Copper catalysts displayed a high catalytic performance, even in the presence of 14% (v/v) of H2O and 100 ppm of SO2. They also displayed improved catalytic behaviour when compared to a CuZSM5 catalyst.

Carbon quantum dots (CQDs) coated with poly(amidoamine) (PAMAM-NH2) dendrimer are prepared from folic acid and phosphoric acid under a hydrothermal procedure. The obtained nanoparticles are successfully used as fluorescent sensor for Pt(IV) (in the form of chloroplatinate ion). CQDs possess many attractive features including uniform dispersion with average size about 13nm for unmodified particles and, ∼30nm when they are coated with PAMAM-NH2 dendrimer. The synthesized nanoparticles have been characterized by elemental analysis, attenuated total reflectance (ATR), X-ray photoelectron (XPS) and Raman spectroscopies, transmission electron microscopy (TEM), dynamic light scattering (DLS), and steady-state and life-time fluorescence. CQDs are used as fluorescent sensor of Pt(IV) ion in aqueous media showing linear quenching effect of their fluorescence. The results obtained demonstrated a limit of detection of 657nM with an accuracy of the method of 0.13% (as RSD, n=10) and sensitivity of 78nM. Moreover, with the presence of other interference species, good results are obtained when applied in real samples from platinum nanoparticles synthesis. The dissolved platinum ions can be quantified in the range 6-96μM with an accuracy of 2.5%.

Vanadium oxide supported on porous clay heterostructures (PCH) catalysts have been synthesized, characterized and evaluated in the selective oxidation of H2S to elemental sulfur. The catalysts were characterized by XRD, adsorption-desorption of N-2 at -196 degrees C, diffuse reflectance UV-vis, H-2-TPR, Raman spectroscopy and XPS. The catalysts with higher vanadium content are more active and selective, exhibiting a H2S conversion close to 70% after 360h on stream with a high selectivity toward elemental sulfur and a low formation of undesired SO2. The catalysts with V2O5 crystallites have shown a higher activity and resistance to the deactivation. The analysis of the spent catalyst has revealed the formation of V4O9 crystals during the catalytic test, which has been reported as the active phase in the selective oxidation of the H2S. (C) 2015 Elsevier B.V. All rights reserved., The authors would like to thank the DGICYT in Spain (Projects CTQ2012-37925-C03-01, CTQ2012-37925-C03-03 and FEDER funds, and MAT2010-19837-C06-05) and project of Excellence of Junta de Andalucia (project P12-RNM-1565) for financial support. A. Natoli thanks to SECAT (Spain) for a grant.

Mesoporous phosphate heterostructure (PPH) materials have been used as supports of ruthenium catalysts with a 5 wt.% metal content. A pristine support (SiPPH) was used, consisting of expanded zirconium phosphate with silica galleries and a potassium exchanged material (denoted as KSiPPH) which was prepared by the cationic exchange of the pristine support to reduce its original acidity by 20%. Ruthenium supported on both SiPPH and KSiPPH was obtained by incipient wetness impregnation using an aqueous solution of ruthenium(III) chloride and reduction at 400 ◦ C without previous calcination. These catalysts were assayed in the hydrogenation and hydrogenolysis/hydrocracking of tetralin at different temperatures. They show a similar catalytic performance although the 5Ru-SiPPH catalyst displays better activity at 350 ◦ C, giving 95% conversion in the steady-state and a very good balance between yields of hydrogenation (55%) and hydrogenolyis/hydrocracking products (28%). This better performance could be due to its better metallic properties and greater acidity. In addition, the performance of the best catalyst was studied for thiotolerance with a feed containing dibenzothiophene (DBT), a sulphur containing molecule, at concentrations of 300 and 600 ppm. This catalyst shows an excellent performance with 300 ppm of DBT after 6 h on-stream. The catalysts were characterized by several instrumental techniques such as X-ray diffraction (XRD), adsorption–desorption of nitrogen, temperature-programmed desorption (TPD) of NH3, X-ray photoelectron spectroscopy (XPS), TEM and H2 and O2-chemisorption.

The behavior of the electric field in earth generated by a fault current derivation to a grounding grid can adequately be modeled by a Colombian potential that is constant in the grid and its reflected image with respect to the earth's surface. We aim here at approximating, in an efficient way, the charge distribution that produces this potential by using potential theory methods. First, we describe the extremal charges method that allows one to obtain an approximation to the charge distribution as the solution of an optimization problem, specifically a linear programming problem. Second, we show the accuracy of the method obtaining the potential and the fundamental parameters of a grid. Then, we describe a grid design optimization methodology. The optimal grid performance is the one that achieves the better agreement between the grid resistance and the touch and step voltages. Both parts are illustrated with graphical results showing the accuracy of this new method of grid analysis and design.

We report a nanocomposite of ZnS:Mn quantum dots and a third generation PAMAM-OH dendrimer (ZnS:Mn@PAMAM-OH(G=3)) which was rationalized to be used as ratiometric nanosensor for Cd(2+) in aqueous solution. The nanoparticles exhibited a bright yellow-orange emission with peaks at 448 and 595 nm. The structure of ZnS:Mn was not changed after coupling with PAMAM-OH, which was evidenced by the analysis of the emission spectra of the compounds. The results confirm that the prepared fluorescence nanoparticles could selectively detect Cd(2+) in aqueous solution with a limit of detection of 24.34 μM and RSD 4.07%, obtained by using the ratio I448/I595. The method was applied to different water samples.

a b s t r a c t Nanocrystalline CeO2 with a regular size of 9.5 nm was prepared by a freeze-drying method, and subse- quent impregnated with a Cu(II) acetate solution, varying the loading of Cu (3, 6, 12 wt.%). The resulting CuO/CeO2 materials were characterized by N2 physisorption at −196 ◦ C, HRTEM, H2-TPR, X-ray diffrac- tion, Raman spectroscopy and XPS and tested as catalysts in the preferential CO oxidation in a H2-rich stream (CO-PROX) in the temperature range 40-190 ◦ C. In spite of their low specific surface areas the cat- alysts exhibited a good catalytic performance, resulting active and selective in the CO-PROX reaction at low temperatures. The inhibiting effect of the simultaneous presence of CO2 (15 vol.%) and H2O (10 vol.%) in the reaction mixture on the performance of CuO-CeO2 catalysts was also investigated. The addition of CO2 and water in the gas stream depressed CO oxidation up to 160 ◦ C, its effect being negligible at higher temperatures. Nevertheless, despite these expected deactivation phenomena, a CO conversion value higher than 90% and a CO2 selectivity of about 90% was achieved for all the samples at 160 ◦C. The excellent performance, especially shown by the catalyst with 6 wt%. of copper, has been related to the wide dispersion of the copper active sites associated with the high amount of Ce4+ species before reaction.

A mesoporous form of titanium phosphate has been prepared by reaction between phosphoric acid solution and either titanium propoxide or titanium chloride in the presence of trimethylammonium surfactants. The surfactant can be almost completely removed by extraction using acidified ethanol. The surface area of the extracted samples depends closely on the pH of the reaction medium, and the reaction temperature, and the highest surface areas, around 740 m2 g−1 were obtained for materials prepared at pH 3. This surface area is partially lost when the extracted titanium phosphate is calcined, although the mesoporous character is retained. 31P NMR spectroscopy shows the ethanol-extracted sample to be rich in hydrogen phosphate (HPO42− and H2PO4−) groups, which undergo partial condensation after calcination. These hydrogen phosphate groups are responsible for the high surface acidity determined, and for its evolution after calcination: the total numbers of surface acidic sites of ethanol-extracted titanium phosphate and calcined titanium phosphate, evaluated using two-cycle adsorption of ammonia from the gas phase at 80°C, are 900 and 340 µmol g−1 respectively.

Intercataled gallium oxide in a-titanium phosphate materials can be synthesized using a swelled phase such as cetyltrimethylammonium titanium phosphate as precursor. This is prepared in a single step by hydrolysis of titanium iso-propoxide with phosphoric acid via a supramolecular long-range ordered organic species acting as a template, which by cationic exchange with gallium oligomers and ulterior calcination at 823 K gives rise to mesoporous solids. These materials exhibit high speci5c surface areas close to 150 m 2 g 21 , high acidity predominantly of the Lewis type, which are active as catalysts in the conversion of the 2-propanol dehydration reaction at 493 K with conversions ranging between 50 and 83%, and total selectivities for propene. ( 1999 Academic Press