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Graphene oxide (GO)-based materials have been extensively evaluated in emulsification processes due to their amphiphilic properties, thermal stability, and high reactivity that allow for chemical f...

Gold nanoclusters protected with bovine serum albumin (AuNC) can be used in multiple biomedical applications through functionalization with two new and bioactive peptides. Both cationic peptides sequences of 17 amino acids in length and the cysteine residue at its C-terminus were designed and synthesized. Peptides were obtained by solid phase synthesis using the Fmoc strategy. Peptides may be coupled via disulfide bonds to AuNC with hydrodynamic size ~ 2 nm ± 0.3 determined by dynamic light scattering and it had a zeta potential value equal to - 42 mV. Peptides named NBC2253 and NBC2254 were attached to the AuNC using N-succinimidyl-3-(2-pyridyl-dithiol) propionate as crosslinker agent. AuNC@NBC2253 was more active against methicillin-resistant Staphylococcus aureus (MIC50 6.5 µM) and AuNC@NBC2254 exhibited higher antimicrobial activity than the free peptides on Escherichia coli O157:H7 (MIC50 3.5 µM). No hemolysis was detected for any of the peptides. It is evidenced that these antimicrobial peptides conjugated to AuNC serve as promising agents to combat some multi-resistant bacterial strains and that the specific binding of these antimicrobial peptides to gold nanoclusters improves the interaction of these nanostructured systems with the biological target.

Graphene oxide (GO) nanosheets have been experimentally proved to be a highly efficiency, rapid and universal demulsifier to break up the crude-in-water emulsion. The alkylamine functionalization of graphene oxide is well known as a way to turn graphene oxide highly affine with organic solvents. In the present work an amphiphilic material, graphene oxide functionalized by amino groups were prepared by Hummer’s modified method. We introduced it as a versatile demulsifier to break up crude-in-water emulsions. The amphiphilic material was characterized by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction (XRD) and emission scanning electron microscope (SEM). The efficient demulsifier to break up crude-in-water emulsion was proved in synthetic emulsion using Colombian crude oil with different concentration. Demulsification tests indicated that graphene oxide amine-modified (GO-A) could separate the crude-in-water emulsion in a short time. Demulsification performance of amphiphilic material was made using the bottle test and evaluated by UV–Vis absorption spectroscopy to measure the final grease concentration after GO-A treatment.

Recent works describing the existence of an intense-blue color within the YIn1-xMnxO3 solid solution due to the presence of Mn3+ cations in trigonal-bipyramidal sites have led to the interest to prepare Al-analogues with the same 5-fold non-centrosymetric coordination. In this framework, YAlO3 structure has been recently re-examined, concluding the aluminate is indeed an oxycarbonate with the Y3Al3O8CO3 stoichiometry. In this work, we observed that pure yttrium aluminate is not only obtained for fast thermal treatments below 1000 °C but with higher Al:Y ratio than 1:1. YAl1.15(CO3)yO3+δ. The corresponding YAl1.15-xMnx(CO3)yO3+δ solid solutions were successfully prepared showing dull brown colors for the low Mn-content in comparison to Yin1-xMnxO3 series, confirming that the TBP coordination is lost in the aluminate, partly due to the presence of carbonate groups in the structure.

This study deals with the laser stereolithography manufacturing feasibility of copper-nickel nanowire-loaded photosensitive resins. The addition of nanowires resulted in a novel resin suitable for additive manufacturing technologies based on layer-by-layer photopolymerization. The pure and nanowire-loaded resin samples were 3D printed in a similar way. Their morphological, mechanical, thermal, and chemical properties were characterized. X-ray computed tomography revealed that 0.06&nbsp, vol&nbsp, % of the composite resin was filled with nanowires forming randomly distributed aggregates. The increase of 57% in the storage modulus and 50% in the hardness when loading the resin with nanowire was attributed to the load transfer. Moreover, the decrease in the glass transition temperature from 57.9&nbsp, &deg, C to 52.8&nbsp, C in the polymeric matrix with nanowires evidenced a decrease in the cross-linking density, leading to a higher mobility of the polymer chains during glass transition. Consequently, this research demonstrates the successful dispersion and use of copper-nickel nanowires as a reinforcement material in a commercial resin for laser stereolithography.

Six essential oils were analyzed by Fourier transform ion cyclotron resonance mass spectrometry coupled to negative-ion electrospray ionization (ESI(−)/FT-ICR MS). ESI offers selective ionization of a compound's polar functional groups containing nitrogen and oxygen heteroatoms. ESI in negative-ion mode allows the identification of the acidic compounds. The results showed that the samples contain between 1100–3600 individual molecular compositions, which corresponds to the greatest number of species detected to date in essential oils obtained from aromatic plant material. The compositions cover a mass range between m/z 150–500 with up to 41 carbon atoms. The dominant organic constituents of the essential oils correspond to species incorporating 2–5 oxygen atoms, detected as deprotonated/sodiated/chlorinated species. A set of 580 molecular assignments were found in common across all the samples and for the first time, a set of unique molecular systems were identified, and up to 1373 species as a unique composition for each essential oil. The molecular distributions plotted in van Krevelen diagrams (classified by their H/C vs. O/C values) suggest the presence of species with long alkyl chains and low numbers of rings plus double bonds.

SiO2 supported NaVOx catalysts have raised interest due to reports showing an increase in the selectivity to propene in propane oxidation; a process that may become an alternative to conventional petrochemical routes for producing this valuable olefin. In this work, the effects of pH, the concentration of vanadium in solution, [V]Sol, and of their interaction; i.e., non-additive effect, over the properties of Na-SiO2 used for the oxidation of propane under oxygen rich conditions were studied. In general, the studied experimental factors had no net effects over the difference between the nominal and final loadings of vanadium in the catalysts, the surface area, and porosity. However, all catalysts presented a ~50% decrease in surface area due to partial mesopore blocking reflected by a ~30% increase in the average pore diameter. On the other hand, NaVO3 microcrystals and particles constituted -NaVO3 and -NaVO3 were formed at acidic pH, whereas Na metavanadate nanoparticles were formed at pH=9.0. These nanoparticles transformed into an -NaVO3 type phase upon dehydration. The reducibility of the catalysts was a function of the impregnation pH, where the catalysts synthesized at pH=3.8 and 9.0 displayed similar reduction patterns but lower reducibility than those synthesized at pH=1.5. The produced patterns were correlated to the existence of a mixture of V5+ and V4+ species among which V4+ was prevalent for the catalysts synthesized at pH=3.8 and 9.0. Consequently, the basicity of the catalysts decreased with the increase in pH. The surface concentration of vanadium increased with the increase in the concentration of vanadium in solution, while the pH had a weak negative effect over the former. On the other hand, it was established that chemical surface state of oxygen in the synthesized catalysts was influenced weakly by the synthesis pH and, more importantly, by non-additive effects between the pH and the concentration of vanadium in solution. The latter was coherent with the detection of surface oxygen species related to the partial dissolution of the Na-SiO2 support; a phenomenon that seemed to be favored at acidic pH. The latter properties were correlated to changes in basicity. Concerning the catalytic performance, the catalysts synthesized at pH=9.0 displayed the best steady state performance in terms of the selectivity to propene and oxygen consumption. The collected evidence allowed corroborating that both the oxidative dehydrogenation of propane to propene and its combustion to CO and CO2 are kinetically controlled by the initial activation of one of the C-H bonds of propane. But, the production of CO2 depended on the level of consumption of O2; where, a surplus of the latter compared to the conversion of propane combusted the hydrocarbon into CO2. Such a finding agreed with what has already been established for supported vanadium oxides for hydrocarbon oxidation. An analysis of the Raman spectra of the spent catalysts suggested that under the applied reaction conditions, all catalysts were provided of an active phase mostly constituted by -NaVO3 type structures. Therefore, the observed differences in catalytic behavior were rather associated to changes in particle size, reducibility, and acidity.

Surface-Enhanced Raman Scattering (SERS) spectroscopic technique and chemometric methods were combined to make a first noninvasive diagnosis of Chagas disease in human blood serum samples. We worked with 110 samples of patients; 45 of them healthy, and 65 infected which were separated into asymptomatic and symptomatic samples. Because of the biological samples exhibiting the Raman signals, the SERS effect was achieved using concentrated silver nanoparticles synthesized previously and attached prior to data collection. SERS spectra of each sample were acquired in the range from 400 to1700 cm−1 using a Raman microscope system. Both, Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA) were used for the data analysis.The results obtained had an accuracy of 96.3% for the classification of the samples into three groups (healthy, symptomatic, and asymptomatic patients). Keywords: Chagas disease, SERS, PCA, LDA

It is generally accepted that asphaltenes are the main stabilizing agents of water-in-crude-oil emulsions. However, the phenomenon of formation and stabilization of the colloid is complex and requires further studies. In this work, interfacially active species were extracted from samples of three Colombian oil fields. The asphaltenes were obtained by the Soxhlet method. Then, the interfacial material (IM) from crude oil was obtained by a recently proposed wet silica methodology. The former extraction method is based on the solubility criterion, in contrast to the latter method that allows for the acquisition of substances by their affinity with water. The materials extracted were characterized by nuclear magnetic resonance, laser desorption/ionization mass spectroscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy. Finally, we evaluate the contribution of asphaltenes and IM in interfacial tension (IFT) reduction, which is one important mechanism in the formation and stabilization of emu...

Fourier Transform Infrared Photoacoustic Spectroscopy (FT-IR PAS) and multivariate calibration using partial least squares (PLS) has been coupled for the development of predictive models of ash content, volatile matter, fixed carbon and calorific value of coal samples from several mines of Colombia. In the chemometric approach, a novel alternative is proposed to define the complexity and the selection of the models. According to tests and statistical criteria, at a 95% confidence level, the selected models demonstrate their linear character and a true correlation between the reference values and the predicted values. Results provide standard error of cross-validation (SECV) of 1.22 wt%, 0.78 wt%, 1.08 wt% and 0.75 MJ kg−1 predicting ash, volatile matter (VM), fixed carbon (FC) and calorific value, respectively.

Raman spectroscopy generates a large volume of information at the molecular level of crude oils, which processed using chemometric methods allows building models to predict their physicochemical properties, facilitating to make decisions in refining processes for obtain high-value products efficiently and minimal environmental impact. In this work, the Raman spectra of crude oils from different regions of Colombia and Partial Least Square Regression (PLSR) were used to determine the fractions of saturates, aromatics, resins, asphaltenes (SARA analysis) and Conradson carbon residue (CCR), which were determined complying with the standards established by the American Society for Testing and Materials (ASTM). The dimensionality of the model was determined according to the root mean square error of cross validation (RMSECV), the coefficient of determination (R 2 ) and the correlation between consecutive pairs of regression vectors.

Positive-ion mode atmospheric pressure photoionization, APPI(+), with Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) was coupled to a Partial Least Squares (PLS) regression and genetic algorithm variable selection (GA-PLS) methods to estimate the API gravity and Conradson Carbon Residue of Colombian crude oil and vacuum residues (VR) samples. It was observed compositional differences between the crude oils, especially increase in relative abundances of the HC Class with API gravity. Principal Component Analysis (PCA) allowed distinguish crude oils and vacuum residues according to their API gravity value. GA-PLS calibration model provide root mean square error (RMSEC) of 0.13 and 0.33 for API gravity and CCR, respectively. The results here obtained allow to use FT-ICR MS data for quantitative analysis of crude oils and their fractions.

Thirty-eight naphtha samples were used to develop a chemometric method to predict bromine number. All samples were characterized by Fourier transform near infrared spectroscopy (FT-NIR), and their spectra were correlated by similarity using principal component analysis (PCA). The models for bromine number determination (BN) were established by Partial Least Squares regression (PLS) and Multiple Polynomial Regression (MPR). PCA allowed classifying the samples into the light and heavy, determining the most significant spectral variables. These variables are located in the regions between 4000-4800 and 5200-6350cm-1. The results determined by combining FT-NIR spectroscopy and chemometrics were very close to those obtained by standardized methods. This approach may be an alternative for analysis of BN, which requires sample turnarounds lower than five minutes and lower cost compared to traditional methods.

Average molecular weight analysis of vacuum residues using laser desorption ionization (LDI) can be a difficult task due to the significant influence of the experimental parameters and gas-phase reactions. In this paper, laser desorption/ionization time-of-flight mass spectrometry in reflectron mode (LDI TOF MS) was used to analyze vacuum residues and their molecular distillations (MD) fractions obtained at distillation cuts of 510–603 °C, 510–645 °C and 510–687 °C. Those samples associated with the lowest distillation temperature presented the narrowest molecular weight distributions and lowest average molecular weight (Mw) indicating lower complexity. American Petroleum Institute gravity, or API gravity (API°), is a measure of the weight of liquid petroleum compared to water, as expected a correlation between Mw and API° was determined, where lower API° correlated with higher molecular weight. When using higher laser energies mass spectra were acquired with a spacing of 24 Da between the peaks, indicating the production of carbon clusters or “fullerenes”. This suggests that asphaltenes could be the precursors of the clusters that extend over 2500 Da in reflectron mode. Under appropriate experimental conditions, it was possible to produce repeatable molecular distribution for all the samples. Likewise, mass spectrometric data can be used in Principal Component Analysis (PCA) and Partial Least Square (PLS) analysis to discriminate and to predict density of the samples with low percentage of errors.

A chemical synthesis route for facile, fast and economical production of reduced graphene oxide/zinc oxide composites (rGO/ZnO) via a microwave-assisted hydrothermal method is presented. For a particular concentration (124 mM) of zinc acetate di-hydrate (Zn(CH3COO)2.2H2O) acting as precursor of Zn, different microwave irradiation times of the order of seconds were tested in order to select the more adequate time. Furthermore, with the selected irradiation time (40 s), different concentrations (31, 62 and 124 mM) were then considered and chemical and morphological properties of the obtained composites were evaluated. For their characterizations SEM, EDS, FTIR, Raman spectroscopy and XRD were employed. Experimental results confirm that the proposed synthesis route for the fabrication of rGO/ZnO is efficient, environmentally friendly and cost-effective.

In this work, a detailed analysis of a bio-oil obtained by pyrolysis of softwoods and its esterified product is described. Information of the type of chemical function groups were obtained by 13C and 1H nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FT-IR) and compositional analysis was obtained by Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS). The results obtained indicate that aliphatic hydrogen and carbon atoms are found in higher abundance, compared with aromatic hydrogen-carbon frameworks. Furthermore, a decrease in oxygen functional groups was observed after esterification. According to the FTICR MS results, the samples contain highly oxygenated species corresponding to compound classes Ox, NOx and BOx, with a high predominance of Ox species. After esterification, the compositions shifted towards lower oxygen-content, lower number of rings and double bonds, and longer alkyl chains as a consequence of the water removal via the condensation reaction.

Surface enhanced Raman spectroscopy (SERS) of nanostructured materials is a powerful technique that allows to reach ultrahigh levels of detection of several analytes. In the present study it was possible to identify the bacteria E. coli by using a novel nanostructured platform based on silver-capped nanopillars (AgNP) and SERS technique. AgNPs were fabricated by ion reactive etching and deposition of silver layers. The bacteria culture were prepared in Luria-Bertani (LB) medium at 37° by 4 hours. 5 μL of the bacteria were deposited on top of the surface of AgNPs and let it dry for 30 minutes. Subsequently the AgNP-bacteria system was analysed by Raman spectroscopy. A typical band of E. coli at 731 cm-1 was identified and this Raman vibration was used as a marker peak to detect the bacteria. Finally the novel AgNP could be used as a potential biosensor to detect nosocomial bacteria in intra-hospital environments. La espectroscopia Raman intensificada por efecto de superficie (SERS) de materiales nanoestructurados es una técnica ultrasensible que permite alcanzar niveles de detección extremadamente bajos en la determinación de diferentes analitos. En este estudio se logró identificar cualitativamente la bacteria E. coli, utilizando plataformas nanoestructuradas de plata, mediante la técnica SERS. Las plataformas nanoestructuradas de plata (AgNP) fueron fabricadas por la técnica de grabado mediante iones reactivos con posterior deposición de una capa metálica de plata. Las bacterias fueron preparadas en medio Luria-Bertani (LB) a 37°C por 4 horas. De este cultivo de bacterias 5 uL fueron depositados sobre la superficie de las AgNP, dejándose secar por 30 min. Posteriormente, el sistema AgNP-bacteria fue analizado mediante espectroscopia Raman. La identificación de la banda Raman a 731 nm típica de la E. coli sobre las AgNP permitió identificar cualitativamente la bacteria, lo que brinda la posibilidad de utilizar las plataformas como potenciales biosensores ultrasensibles de bacterias nosocomiales en ambientes intrahospitalarios.

Most of the composite materials are made of a plastic matrix with glass or carbon fibers. The biggest disadvantage of these materials is their high cost and the massive generation of plastic waste. These synthetic fibers have been progressively replaced by natural fibers. In this work, we aim to prepare a composite system with low environmental impact based on natural raw material, with high availability and low cost. In order to prepare the nanocomposite, we have used fique fiber agroindustrial waste. The material proposed can be used in applications such as construction, photocatalytic activity, antibacterial agents, and pigmentation, among others. The TiO2 nanoparticles (NP) were prepared in presence of fique "furcraea sp." cellulosic fibers by synthesis by in situ method using titanium tetrachloride (TiCl4) as a precursor and sodium hydroxide as a reductor. The nanocomposites were structurally characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and Raman spectroscopy. In addition, the mechanical properties of the fiber were evaluated by the standard test method for the tensile strength and Young's modulus of fibers (ASTM C1557-14).

By means of ultrasonic and cationic treatment, the surface of the fiber was adapted to maximize the support of the nanocomposite rGO@TiO2; which had a previous preparation and subsequent anchoring to the fibers by chemical reduction in times of immersion. The fibers were subjected to characterization by FTIR spectroscopy, while in the nanomaterial obtained was verified the deposition of the nanocomposite by means of scanning electron microscopy SEM, as well as the change in the value of the bandgap for TiO2 by UV-spectroscopy. In order to evaluate the photo-degradative activity of the rGO@TiO2 / Fique catalyst, we used Methylene Blue (MB). The experiments were carried out using sunlight that allowed obtain a degradation efficiency of approximately 99 % in two hours.

A facile route for the functionalization in situ of graphene oxide with magnetite nanoparticles (Fe3O4@GO) was developed. We used graphene oxide with different oxidation time (12 and 24 hours) and each one was functionalized with different proportions of Fe3O4 nanoparticles modifying the load of the iron precursor (FeSO4.7H2O). The as-synthesized materials were characterized by multiple spectroscopic techniques (FT-IR, Raman, DRX, XPS) to demonstrate the successful attachment of iron oxide nanoparticle on graphene oxide sheets. Transmission electron microscopy (TEM) revealed that magnetite NPs were firmly decorated on the surfaces of graphene oxides with the mean diameter of about 7 nm. The magnetometry studies showed ferromagnetic behaviour of all composites in the range of 44-66 emu/g at room temperature.

In this paper, we present an experimental approach to track coarsening process of foam using a computer optical mouse as a dynamic laser speckle measurement sensor. The dynamics of foam coarsening and rearrangement events cause changes in the intensity of laser speckle backscattered from the foam. A strong negative correlation between the average speed of the cursor and the evolution of bubble diameter was found. We used microscopic images to demonstrate that decrease in speed is related to increase in bubble size. The proposed set-up is not very expensive, is highly portable and can be used in laboratory measurements of dynamics in other kinds of opaque materials.

Graphene oxide (GO) nanocomposites reduced were synthesized by hydrothermal methods and reduction methods.We synthetized a composite by reduction of AgNO3 with sodium citrate.Finally, the nanocomposite, AgNPs@GO which could be a new substrate for SERS.

AgNPs were prepared by reducing of silver nitrate with sodium with borohydride sodium. The average size of particles was 3.48 nm±0.13 and the spherical shape was confirmed by TEM. In addition, the AgNPs were conjugated to L-cysteine by adsorption of the thiol, amino and carboxyl on its surface. We studied the dependence of parameters such as L-Cys molar ratio, pH and time of process on the functionalization. The results were verified by Surface-Enhanced Raman Spectroscopy (SERS).

Five of the most important Colombian coals were studied using Photoacoustic Fourier transform infrared (PA-FTIR) spectroscopy. The PA-FTIR spectra were used to obtain structural parameters and to determine the analytical potential of this technique. The molecular structural parameters, CH 2 /CH 3 , f a , H al /H ar , and (R/C) u were correlated with fixed carbon contained in the samples to determine aliphatic hydrogen, H al , and the aromatic hydrogen, H ar in coals studied here. These parameters enabled the determination of aromaticity, f a , which was found to be between 0.66 and 0.98. The aliphatic and aromatic regions were considered between 3005–2760 cm −1 and 912–670 cm −1 , respectively. Finally, using the molecular structural parameters, the grade of maturation (rank) of coal samples studied was determined.

In this work, laser induced breakdown spectroscopy (LIBS) is used to determine the composition of titanium oxide film produced by anodized of Ti6Al4V alloy. We have used Ti lines in the spectral region between 470–520 nm to determine temperature of the plasma generated on anodized surface of Ti6Al4V alloy for temperature determination by Boltzmann plot method. In order to measure the content of oxygen and titanium ratio on the surface the alloy, we have used the oxygen lines 777.194, 777.417 and 777.539 nm, and titanium lines 780.597 and 782.491 nm observed in an ambient of argon. Finally, we report the possibilities for the determination of the coating chemical composition using LIBS.

In this paper we present the experimental study of a glow plasma jet (GPJ) obtained from a transferred atmospheric pressure glow discharge (APGD) operating at 60 Hz. The characterization of the emission spectra for both electrical discharges is presented and the electrical circuit features for APGD generation are discussed. The potentiality of GPJ as a source of active species for depletion of contaminants in liquid hydrocarbon fractions is also established.

Bioactive hydroxyapatite (HA) coatings were fabricated by a precipitation, sol-gel and dip-coating method. The effects of the aging time and the base used to adjust pH and substrate materials on the phases and microstructures of HA coatings were studied by field emission scanning electron microscopy FESEM, energy dispersive spectroscopy EDS, X-ray photoelectron spectroscopy XPS, and the vibrations of the phosphate groups were determined by Raman spectroscopy. The results showed that all the films were composed of the phases of TiO2 and HA. With coated titanium substrate with TiO2, the crystallinity of the HA coating increases, the structure became more compact and the Ca/P ratio increased because of the loss of P in the films. The addition of sodium hydroxide (adjusting the pH level to about 10) can increase the HA content in the coating. XPS and EDS results for steel substrate and titanium showed poor calcium content as obtained with a Ca/P ratio of 1.38 and 1.58, respectively, composition is similar to that of natural apatite. However, spectroscopic results suggest the presence of a mixture of hydroxyapatite and octacalcium phosphate. The different substrate materials have a high influence on the microstructure of the separated double films. However, hydroxyapatite nanopowders coatings were obtained using a simple method, with potential biomedical applications.

Tracking of wet foam ageing by means of dynamic laser speckle and an optical flow sensor is presented. Using a computer optical mouse, like an optical flow sensor, a strong negative correlation between the average speed of the cursor and the coarsening of bubble was found. We used microscopic images to demonstrate that decreasing of speed is related with increasing of bubble size. The proposed setup allows sensitive measures, is not very expensive and highly portable.

5 pages, 3 Figures.-- Supplementary Data, In this communication we present a potentiometric aptasensor based on chemically modified graphene (transducer layer of the aptasensor) and aptamers (sensing layer). Graphene oxide (GO) and reduced graphene oxide (RGO) are the basis for the construction of two versions of the aptasensor for the detection of a challenging living organism such as Staphylococcus aureus. In these two versions, DNA aptamers are either covalently (in the GO case) or non-covalently (in the RGO case) attached to the transducer layer. In both cases we are able to selectively detect a single CFU/mL of S. aureus in an assay close to real time, although the noise level associated to the aptasensors made with RGO is lower than the ones made with GO. These new aptasensors, that show a high selectivity, are characterized by the simplicity of the technique and the materials used for their construction while offering ultra-low detection limits in very short time responses in the detection of microorganisms., Spanish Ministry of Science and Innovation (MICINN) through project grants CTQ2010-18717, MAT2010-15026, Spanish Higher Research Council CSIC under project 201080E124, Regional Government of Aragon and the European Social Fund under project DGA-FSE-T66 CNN

The photophysical behavior of five acridine(1,8)dione dyes of biological interest was studied by absorption and fluorescence spectroscopy, photoacoustics and time resolved phosphorescence techniques. The results obtained in ethanol and acetonitrile solutions show that the main spectroscopic and photophysical parameters of these compounds depend strongly on both the solvent and oxygen concentrations. Oxygen completely quenched the triplet state of all dyes. In nitrogen-saturated solutions, quantum efficiencies of triplet formation in ethanol were lower than those in acetonitrile Fil: Cabanzo Hernández, Rafael. Universidad Industrial de Santander. Laboratorio de Espectroscopia Atómica y Molecular; Colombia; Fil: Gara, Pedro M. David. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Investigaciones Opticas (i); Argentina; Fil: Molina Velasco, Daniel. Universidad Industrial de Santander. Escuela de Química; Colombia; Fil: Erra Balsells, Rosa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono; Argentina; Fil: Bilmes, Gabriel Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Investigaciones Opticas (i); Argentina

In the present study, optical microscopy in stereoscopic mode coupled to laser- induced p-breakdown spectroscopy (μ-LIBS) was applied for analysing HP-40 steel samples. microLIBS (μ-LIBS) is a new growing area that employs low energy laser pulses for the generation of plasma emission, which allow the realization of localized microanalysis [1]. This new LIBS instrument was used for the surface characterization of the steel samples in the spectral range from 356 to 401nm. Elements such as Cr, Ni, Fe, Nb, Pb, Mo, C, Mn and Si in the steel samples were investigated. The results allowed the construction of elemental distribution profiles of the samples. Complementary the HP-40 steel samples were superficially characterized by Scanning Electron Microscope (SEM).

Eight vacuum residues and their delayed coking liquids products from Colombian crude were study by infrared spectroscopy with attenuated total reflectance (FTIR-ATR) and principal component analysis (PCA). For the samples the structural parameters of aromaticity factor (fa), alifaticity (A2500-3100cm-1), aromatic condensation degree (GCA), length of aliphatic chains (LCA) and aliphatic chain length associated with aromatic (LACAR) were determined through the development of a methodology, which includes the previous processing of spectroscopy data, identifying the regions in the IR spectra of greatest variance using PCA and molecules patterns. The parameters were compared with the results obtained from proton magnetic resonance (1H-NMR) and 13C-NMR. The results showed the influence and correlation of structural parameters with some physicochemical properties such as API gravity, weight percent sulphur (% S) and Conradson carbon content (% CCR)

In this paper we show the characterization of two kinds of quantum dots: hydrophilic and hydrophobic, with core and core/shell respectively, using spectroscopy techniques such as UV-Vis, fluorescence and Raman. We determined the quantum yield in the quantum dots using the quinine sulphate as standard. This salt is commonly used because of its quantum yield (56%) and stability. For the CdTe excitation, we used a wavelength of 549nm and for the CdSe/ZnS excitation a wavelength of 527nm. The results show that CdSe/ZnS (49%) has better fluorescence, better quantum dots, and confirm the fluorescence result. The quantum dots have shown a good fluorescence performance, so this property will be used to replace dyes, with the advantage that quantum dots are less toxic than some dyes like the rhodamine. In addition, in this work we show different techniques to find the quantum dots emission: fluorescence spectrum, synchronous spectrum and Raman spectrum.

Surface Enhanced Raman Spectroscopy (SERS) has been used to investigate the somatostatin (SST) analogue Vapreotide (VAP) in gold colloids. The optimum conditions to detect SERS signals of VAP have been studied. The observed SERS bands correspond to different vibrational modes of the peptide; being the most dominant SERS signals the ones derived from the aromatic amino acids Tryptophan (Trp), Phenylalanine (Phe) and Tyrosine (Tyr). Changes in enhancement and wavenumber of the proper bands upon adsorption on gold colloid are consistent with VAP adsorption, primarily through Tryptophan residues.

The development of ion-selective electrodes (ISEs) using solid-state transducer materials is of great interest for advanced potentiometric detection systems. At present, conducting polymers are the most used solid-state transducing materials. However, their reliability is strongly related to their chemical stability and the formation of internal water films. Here we report on the use of reduced graphene oxide (RGO) films of different thicknesses as transducer materials in potentiometric all-solid-state ISEs. First, the transduction mechanism is fully analyzed, revealing that RGO films act as asymmetric capacitors where their electron density is in contact with ions of the electrolyte solution, creating a capacitance due to the constant phase elements present in the system. Second, as a proof of concept, RGO films are used in a calcium ISE showing highly reproducible sensing responses and outstanding increased signal-to-noise ratios with drifts of only 10 μV/h. These performance parameters are among the best compared to those of other ISE transducer materials so far. With its ease of fabrication and processing into reproducible films of controlled thickness and ease for further tailoring chemical composition and tailoring electrical properties, RGO offers great promise as a reliable high-performance transducer material for solid-state ISE sensors.