Blueberries as a Source of Energy: Physical Chemistry Characterization of Their Anthocyanins as Dye-Sensitized Solar Cells’ Sensitizers

This work aimed to show the possibility of applying anthocyanins extracted from blueberries following a straightforward path as potential impregnation dyes in dye-sensitized solar cells (DSSCs), particularly in the presence of co-adsorbents, such as silver nanoparticles, as an alternative in order to profit from large amounts of discarded fruits. Following a simple procedure, anthocyanins (mainly delphinidin-3-glucoside) were obtained from blueberries (Southern Highbush type). Complete characterization was carried out in order to prove the utility of delphinidin-3-glucoside as a sensitizer in DSSCs. The analyzed anthocyanin is suitable for sensitizing because of its high molar absorptivity values within the visible region of the light spectra, the adsorption ability to a FTO/TiO2 electrode (FTO, fluorine-doped tin oxide) as confirmed by Fourier transform infrared (FTIR) as well as thermogravimetry coupled to differential scanning calorimetry (TG-DSC), a potential oxidation value near 1 V, and adequate thermal as well as light stabilities. Moreover, the cell’s conversion efficiency is improved in the presence of silver nanoparticles, reaching 0.24% (nearly a 25% increase). The sum of all these characteristics points to the application of delphinidin-3-glucoside as a sensitizer in DSSCs, offering a technological use with potential interest for countries where agricultural production offers an abundant origin of extraction

Validation and application of a methodology based in ionic Cromatography with UV detection for nitrate and nitrite determination in waters of the Rio de la Plata

La determinación por cromatografía iónica con detector de conductividad (CI-DC) de elementos trazas como el nitrato y nitrito, ya sea en modos de supresión o sin supresión, ha mostrado ser muy útil en diferentes matrices. Sin embargo, en matrices ambientales con alta concentración de haluros como aguas marinas o estuarinas, la determinación de estos analitos necesita de estrategias más eficientes para la remoción de interferencias. Por tal motivo, se ha buscado una alternativa de determinación de nitrato y nitrito en estas matrices empleando sistemas de detección más selectivos que el CDD tales como el detector UV y la utilización de extracción en fase solida (SPE) con cartuchos comerciales IC-Ag (Alltech Inc., EE.UU) para la remoción de interferencias. En este trabajo, se presenta la validación de una metodología de determinación de nitrato y nitrito por cromatografía iónica con detector UV (210 nm) en muestras de aguas superficiales de playas de la ciudad de Montevideo, Uruguay. Se identificó un valor de salinidad máximo de estas aguas para la determinación de estos analitos de manera directa, evitando el tratamiento por SPE para remoción de cloruros. El procedimiento analítico fue validado para las siguientes cifras de mérito: linealidad, intervalo de trabajo, efecto matriz, repetitividad, límite de detección, límite de cuantificación, precisión intermedia, robustez e incertidumbre definidas según el Organismo Uruguayo de Acreditación. Se destaca la robustez de la metodología, medida a través de un diseño estadístico factorial, con límites de detección para nitrato de 0.02 mg/L y 0.01 mg/L para nitrito y precisión intermedia medida como desviación estándar relativa (tres operadores en semanas diferentes) para muestras reales de 4.7 %. Se presentan además, resultados del monitoreo llevado a cabo en campañas durante el invierno y verano de los años 2011 y 2012, respectivamente, para estos analitos, dado su interés para determinar el nivel de eutrofización de las aguas de Montevideo.The determination of trace elements such as nitrate and nitrite by ion chromatography with a conductivity detector (CI-CD), with or without ionic suppression modes, has proved to be very useful for different matrices. However, in environmental matrices with high concentrations of halides such as marine or brine waters, the determination of these analytes requires more efficient strategies for the removal of interferences. In this work, we have searched for a rugged alternative in the determination of nitrate and nitrite in these matrices using solid phase extraction (SPE) with IC-Ag (Alltech Inc., USA) commercial cartridges for the removal of interferences and UV absorption detection. We present method validation data in the determination of nitrate and nitrite in surface waters from beaches of Montevideo, Uruguay by ion chromatography with UV detection (210 nm). For these samples, it was identified a cut-off value of salinity to directly determine these analytes, avoiding the SPE treatment for the removal of chloride. The analytical procedure was validated for the following figures of merit: linearity, dynamic range, matrix effect (interferences study), repeatability, limit of detection, limit of quantitation, intermediate precision, robustness and uncertainty defined by the Organismo Uruguayo de Acreditación. The robustness of this methodology, measured through a factorial statistical design is satisfactory while detection limits for nitrate is 0.02 mg / L and 0.01 mg / L for nitrite. Intermediate precision measured as relative standard deviation (three operators in different weeks) for real samples showed to be 4.7 %. We also depict results of a winter to summer monitoring campaign (2011 to 2012 season) for these analytes, taking into account the importance of determining the eutrophication level in Montevideo certified beaches.Asociación de Universidades Grupo Montevide

Optimization of solvothermal experimental parameters to control the size of KMgF3 nanoparticles for photodynamic therapy

Photodynamic therapy has advantages over conventional cancer superficial tumor therapies, such as insignificant side effects, minimal cumulative toxicity, excellent functional and cosmetic results, precise target treatment minimizing damage to neigh-boring normal tissues, and optimum long-term tumor regression. Upconversion nanoparticles have been proposed to extend photodynamic therapy for treating non-superficial tumors. In particular, compounds with low phonon energy, like KMgF3, with an optimal synthesis design and a suitable doping system, could be used for this therapy application. This particular matrix allows the incorporation of dopants as transition metals ions (as Mn2+) besides rare-earth elements, minimizing the use of the former. To obtain nanoparticles of suitable size for nanomedicine, we used a factorial experimental design to determine statistical synthesis conditions that significantly affect particles’ size. With the proposed synthesis method, it was possible to obtain KMgF3 nanoparticles with sizes ranging from 13.46±0.30 nm to 32.18±0.60 nm, values estimated with the XRD technique and with size distribution suitable for photodynamic therapy. We proved the good correlation between the particle size estimated from transmission electron microscopy images and powder X-ray diffraction measurements. According to the statistical analysis, the temperature and the interaction of temperature with MgCl2 concentration significantly affect the particle size (significance level of 0.05). The present work describes the influence of solvothermal synthesis parameters on the KMgF3 nanoparticle size for the first time. The results are particularly interesting for further doping the system and its functionalization, foreseeing the final application in cancer treatment.Agencia Nacional de Investigación e InnovaciónPrograma de Desarrollo de las Ciencias BásicasComisión Académica de Posgrad