ZIF-8 deposited onto TiO2 microcolumns as effective catalyst for CO2 reduction.

Motivation:.Global warming is one of the biggest issues that society is currently facing. CO2 is one of the most important gases of greenhouse gases due to anthropogenic emissions from industrial activities, transport, energy sector, agriculture, livestock, etc. An environmentally friendly alternative to reduce the amount of CO2 is the use of Metal-Organic Frameworks (MOFs), in particular, a subfamily of MOFs that is isoreticular to zeolites namely Zeolitic Imidazolate Framewor (ZIFs). These compounds have shown in prevous works electrocatalytic activity for CO2 reductionMethods: In order to carry out this application, ZIF-8 is chosen for its excellent thermal and chemical stability. For this purpose, it is necessary to deposit the compound onto a conductive substrate, in this case, FTO. ZIF-8 was grown in situ on TiO2 microcolumns that were previously deposited on the FTO substrate by chemical vapour deposition (CVD). The MOFs crystal deposition was optimised varying the intial conditions of ZIF-8 synthesis.Results: To evaluate the correctc synthesis of the compound, the films were charactised by Fourier Transformed Infrared Spectroscopy (FT-IR), grazing-angle XRD and Scanning Electron Microscopy (SEM). An optimisation of synthesis was successfully reached. XRD results show that the compound is crystalline and corresponds to a ZIF-8 phase. IR results also confirm the correct formation of ZIF-8 and SEM images allow see that the compound grew between the columns. The compound appears to have a catalytic activity however the experiments still continue.Conclusions: The compound is successfully deposited and synthesis was optimised. It has crystalline structure, grew between the columns and it corresponds to ZIF-8. Catalysis results are not still conclusive but sensations are positiv

ZIF-8 MOF used as optic sensor for toxic gases

Metal-Organic frameworks (MOFs) are crystalline organic-inorganic porous materials comprised of metal atoms or clusters coordinated by organic ligands. ZIF-8 (zeolitic imidazole framework), due to the abscense of an intricsic fluorescenc, has never been used as optical sensor. In this works, ZIF-8 has been dopped with Cd (II) atoms (2.5%), showing an huge enhacement of the fluorescent compared with the non-dopped ZIF-8. This new material is suitable for optical sensing, being sensitive to hydrogen sulfice gas, which causes quenching of the luminescence proportionally to its concentration.Methods: ZIF-8 was synthesized at room temperature mixing a methanol solution of Zn(NO3)2·6H2O with a methanol solution of 2-methyllimidazole (Hmim), with Zn (II), Hmim, methanol ratio of 1:8:700 [1].ZIF-8 was dopped with Cadmium by four different methods; the dopped samples was named ZIF-8-A1, ZIF-8-B, ZIF-8-A2 and ZIF-8-B2. The methodology followed was described by H. Fei et al. in [2], with some modifications. The difference among the varieties was the solvent and the post-treatment after mixing the compounds.The dopping method was accomplished by dissolving 0.4 mmol of Cd(NO3)2 and 20mg of ZIF-8 in DMF (3mL) (for ZIF-8-B and ZIF-8-B2) or methanol (3mL) (for ZIF-8-A2). ZIF-8-B was obtained by gentenly heating at 60ºC for 48h; ZIF-8-A2 was obtained by stirring for 48 at room temperature; ZIF-8-B2 was obtained by stirring for 48h at room temperature.For sensing measurements, the samples was exposured to saturated gases of H2S and the fluorescence changed was monitored

Uso de reactivos colorimétricos como marcadores químicos con importante aplicación industrial.

Colorimetry is a technique used to measure and analyse colours, mainly to determine the concentration of colored compounds in solutions by the application of the Beer–Lambert law. It is applied in a variety of fields, such as chemistry, medicine, biology, and in the pharmaceutical and food industries. The basis of this technique is often the use of colorimetric reagents that provide an easily identifiable colour that depends on factors both internal and external to the samples. These reagents are usually pigments that vary in colour depending on the conditions to which they are subjected. In addition, they can interact with the packaging or the environment in which they are placed. The stimulated colour response becomes a practical tool to assess in real time the status of products in the distribution chain. This is why pigments modulated by other reagents have been applied to measure the colour change of samples applicable to products as quality markers.Pigments and the modulator have been prepared in a hand-made device of plastic nature. The colour change reaction of the pigment has been characterised at different temperatures using water baths and the influence of movement on the sample has been measured by means of orbital shaking. The colour change of the pigment has been measured by means of an RGB device and UV-vis spectrophotometry. Subsequently, real trials will be carried out with volunteers to test the effectiveness of the colourimetric device attached to a product.It has been observed that the reaction kinetics is temperature-dependent. The higher the temperature the shorter the reaction time. The reaction time ranged from 3 to 14 hours at temperatures of 40°C down to 5°C. Stirring does not influence the reaction time.Compounds such as pigments, once modulated, can be an effective tool for monitoring product quality quite accurately. Once the reactants ratios are adjusted to the shelf life of the products, their reliability increases considerably, bringing benefits to the final consumer.NOTE: This work is bound by confidentiality in the framework of a research contract

Enhancement of the intrinsic fluorescence of ZIF-8 via post-synthetic cation exchange with Cd2+ and its incorporation into PDMS films for selective sulfide optical sensing

In this study, ZIF-8 MOF nanocrystals were synthesized and post-synthetically modified by applying different cation exchange strategies. Addition of cadmium nitrate in either methanol or DMF followed by either magnetic stirring or gentle heating led to the incorporation of a small amount of Cd (II) ions into the crystal structure in most cases, as clearly demonstrated by several characterization techniques including PXRD, SEM-EDS and FT-IR. This novel doped material exhibits a high fluorescence with the maximum emission wavelength at 444 nm upon excitation at 380 nm, which allows its use as an effective optical sensor. The sensing capability of the Cd-doped ZIF-8 material was demonstrated by its exposure to sulfide ions in aqueous solution. The fluorescence of the doped material was gradually quenched as the concentration of S2− was increased. Sensing devices based on mixed-matrix membranes (MMMs) were fabricated by using poly (dimethyl siloxane) (PDMS) as a hosting matrix for the Cd-doped ZIF-8 crystals, giving rise to fluorescent sensing films with fast and selective responses against a broad number of potential interferents

Development and fine-tuning of an artificial organoleptic analysis method for virgin olive oil using an electronic olfactory system

Motivation: The catalogation of olive oil by organoleptic parameters has a high grade of subjection because of human factor. A new system of electronic tasting is used as a reliable, fast and cheap method. The use of an electronic olfatory system (EOS), which consist of an array of electonic sensors and a mechanism for pattern recognition, requires of a previous training process like a human olfatory system. The training is one of the most relevant and delicated phase, as this process involves the creation of a complete database that the instrument uses as a reference for the subsequent sample recognition.Methods: A set of samples of different olive oils were analysed by three official panel tests before using the EOS. The instrument is composed of a chamber with five metal oxide semiconductor based sensors. During the analysis, each sensor is maintained at a specific temperature showing a different response for a certain sample, which implies a reduction in the sensors resistance. For the measurement, volatile compounds were directed to the sensor chamber by the carrier gas (dry air). Principal component analyses to interpret the datasets from the EOS is employed in order to assess the classification of the measurements.A database was created through the analysis of a set of samples which should be representative of differents aromas to be recognized.Conclusions: The main conclussion is the high variability between the official panel tests which could be reduced by the EOS. From the database that was created we can analyse an olive oil with unknown catalogation and classify into Extra Virgin, virgin or lampante.On-line detection of the different categories, during the oil industrial process, could have a notable economical impact

El aula virtual como espacio para la mejora de la calidad docente universitaria

En esta comunicación se describe la iniciativa de incorporación de las TICs aplicadas al desarrollo de metodologías de docencia virtual (E-learning), como elemento de mejora de la calidad docente universitaria. El proyecto ha sido llevado a cabo en la asignatura de carácter troncal “Bases Químicas del Medioambiente” de la licenciatura de Ciencias Ambientales de la Universidad Pablo de Olavide, de Sevilla. Para su desarrollo, se ha empleado una plataforma de docencia virtual (WebCT) dentro del espacio “aula virtual” de la Universidad. Las tareas se han llevado a cabo en un curso específico de dicho espacio, de manera paralela al desarrollo de la labor docente de tipo presencial. Como elementos destacados del proyecto cabe citar la virtualización de una parte del temario de la asignatura, el uso extensivo de herramientas de comunicación, la elaboración de ejercicios de autoevaluación con sistema de retroalimentación, la realización de tests de evaluación, y la incorporación de elementos multimedia y de animación como material de apoyo a las prácticas de laboratorio de la asignatura. Estos elementos son perfectamente exportables a otras materias. Tras dos cursos académicos de uso y experimentación, los resultados indican importantes mejoras en el rendimiento académico del estudiante. Además, se ha demostrado que el uso dinámico, constante y didáctico de estas herramientas y metodologías, gestionadas a través del aula virtual, constituye una excelente vía de modernización y adaptación de la actividad docente universitaria a los nuevos modelos educativosSIN FINANCIACIÓNNo data 200

Evaluation of the organoleptic quality of virgin olive oils using an electronic olfactory system

Motivation: The quality of olive oil is defined by physicochemical and organoleptic parameters; Organoleptics analysis are made from an official panel test compound between 8 to 12 specialists. This method to classify oils is subjective because of human factor. Its essential to implement a system that performs the sensory analysis in an objective and fast method, such as the electronic olfactory system (EOS), which consists of a set of sensors that detect the volatiles of each sample of olive oil and catalogues them.Methods: The electronic olfactory system used was the EOS 835, which is composed of a chamber with 4-6 metal oxide semiconductor sensors, calibrated to olive analysis, which capture the volatiles present in the sample and respond with a resistance variation. This system requires previous training for the subsequent classification of oil samples. The data obtained are treated by principal component analysis (PCA) to evaluate the quality of the measurements and classification.Conclusions: The development of this system can provide a portable, easy-to-use and low-cost tool that can be used to ensure the accurate classification of olive oil