Enhanced Chitosan Photoluminescence by Incorporation of Lithium Perchlorate.

An improvement in chitosan film photoluminescence was observed after adding LiClO4. FTIR spectra, XPS, DFT calculations, and XRD measurements show an alteration of the H-bonds and an increase in the amorphous character of chitosan. PL spectra display a growth in intensity in the visible region along with the incorporation of lithium, signaling a possible rise in the population density of tail states and, consequently, better photon absorption, as observed from UV-vis measurements. A mechanism through aggregation-induced emission effect is proposed to explain the different results. Although this work establishes the relation between structural changes provoked by LiClO4 incorporation and luminescence in the case of chitosan, we expect that the same approach could be generalized to similar polymeric structures.

Photochemical Reduction of Silver Nanoparticles on Diatoms.

In this work, the photochemical reduction method was used at 440 or 540 nm excitation wavelengths to optimize the deposition of silver nanoparticles on the diatom surface as a potential DNA biosensor. The as-synthesized nanocomposites were characterized by ultraviolet-visible spectroscopy (UV-Vis), Fourier transforms infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy (STEM), fluorescence microscopy, and Raman spectroscopy. Our results revealed a 5.5-fold enhancement in the fluorescence response of the nanocomposite irradiated at 440 nm with DNA. The enhanced sensitivity comes from the optical coupling of the guided-mode resonance of the diatoms and the localized surface plasmon of the silver nanoparticles interacting with the DNA. The advantage of this work involves the use of a low-cost green method to optimize the deposition of plasmonic nanoparticles on diatoms as an alternative fabrication method for fluorescent biosensors.

A Theoretical and Experimental Study on the Potential Luminescent and Biological Activities of Diaminodicyanoquinodimethane Derivatives.

Recently, several studies have demonstrated that diaminodicyanoquinone derivatives (DADQs) could present interesting fluorescence properties. Furthermore, some DADQs under the solid state are capable of showing quantum yields that can reach values of 90%. Besides, the diaminodiacyanoquinone core represents a versatile building block propense either to modification or integration into different systems to obtain and provide them unique photophysical features. Herein, we carried out a theoretical study on the fluorescence properties of three different diaminodicyanoquinodimethane systems. Therefore, time-dependent density functional theory (TD-DFT) was used to obtain the values associated with the dipole moments, oscillator strengths, and the conformational energies between the ground and the first excited states of each molecule. The results suggest that only two of the three studied systems possess significant luminescent properties. In a further stage, the theoretical insights were confirmed by means of experimental measurements, which not only retrieved the photoluminescence of the DADQs, but also suggest a preliminary and promising antibacterial activity of these systems.

Identificación en tiempo real de la anatomía biliar mediante fluorescencia utilizando fluoresceína sódica / Real time identification of biliary anatomy by fluorescence using fluorescein sodium

Objetivo: Desarrollar, en un modelo experimental animado, la técnica de colangiografía intraoperatoria utilizando fluoresceína sódica. Determinar la dosis de fluoresceína sódica necesaria para obtener la mejor visualización de la vesícula y del árbol biliar. Método: Estudio de tipo experimental, en el que se incluyeron 6 conejos albinos de raza Nueva Zelanda, distribuidos en 3 grupos equitativamente, según la dosis de fluoresceína sódica (5 mg/kg, 7,5 mg/kg, 15 mg/kg). Cumplido el protocolo anestésico, se administró la dosis de fluoresceína sódica según el grupo correspondiente, vía endovenosa. Se realizó una laparotomía por línea media superior, exteriorizándose el hígado y se realizó una maniobra de eversión, para la fácil identificación del sistema biliar extrahepático. Posteriormente, y con los sistema de iluminación, se registraron los parámetros de fluorescencia con cada dosis. No se realizó eutanasia. Ambiente: Centro veterinario privado "Colmillos y garras" Resultados: En todos los casos se logró registrar fluorescencia, siendo la dosis que permitió una mejor visualización la de 7,5 mg/kg. El tiempo promedio en el cual se empezó a ver fluorescencia en la vesícula biliar fue de 5 minutos; el tiempo promedio en el cual se alcanzó la totalidad del fenómeno fue de 18 minutos y, en todos los casos, la fluorescencia persistió por 30 minutos. Conclusión: La identificación de las vías biliares guiada por fluorescencia, utilizando fluoresceína sódica y con la fuente de luz UV de 5 mm de diámetro diseñada por los autores es factible, siendo la dosis con mejor visualización, la de 7,5 mg /kg de peso(AU)

Objective: To develop an experimental animal model technique using sodium fluorescein intraoperative cholangiography. To Determine the dose of sodium fluorescein necessary for the best display of the gallbladder and biliary tree. Methods: Experimental study. 6 New Zealand white albino rabbits divided into 3 groups depending on the dose of sodium fluorescein (5 mg / kg, 7.5 mg / kg, 15 mg / kg) were used. Prior anesthetic protocol corresponding fluorescein sodium was administered according included Animal group intravenously. Upper midline incision was used, exteriorization of the liver allow easy identification of extrahepatic biliary system and subsequently illuminated with fluorescence. Parameters were recorded for each dose. No euthanasia was performed. Environment: Private Veterinary Centre "Colmillos y Garras". Results: In all cases, we recorded fluorescence. The dose that allowed the best visualization was 7.5 mg / kg. The average time in which fluorescence began to be visible in the gallbladder was 5 minutes, the average time in which the total fluorescence was reached was 18 minutes in all cases fluorescence persisted until 30 minutes. Conclusion: Laparoscopic cholecystectomy guied using sodium fluorescein fluorescence and UV light source of 5 mm diameter is feasible. Better visualization is obtained with the dose 7.5 mg / kg(AU)

Application of TLC and LA ICP SF MS for speciation of S, Ni and V in petroleum samples.

A coupling of thin layer chromatography with laser ablation ICP SF MS was developed for the fractionation of Ni, V, Fe and S in crude oil and its fractions (saturate, aromatic, resin and asphaltene). The detection limits were 18 ng g(-1) and 23 ng g(-1) for nickel and vanadium, respectively, and a sample could be characterized in terms of the metal distribution as a function of species polarity within 10 min. The method was used to characterize the metal distribution in crude oils of different origins and their different fractions.

A dual-beam photothermal reflection based system for thermal diffusivity measurement of optically dense liquids.

A dual-beam photothermal reflection based system capable to measure thermal diffusivities of optically dense liquids has been designed and implemented. The large optical absorption coefficient of these liquids inhibits the possibility to use conventional transmission instruments for direct thermal diffusivity measurements. To overcome this problem, a front heating front detection photothermal reflection system has been proposed. This method expands the range of application and simplifies the experimental procedure of traditional photothermal methods, allowing precise measurement of thermal diffusivity of a variety of liquids. Measurements of the change in thermal diffusivity with the concentration of asphaltene in toluene solutions are described to test the applicability of this technique for reliable measurements of thermal diffusivities of optically dense liquids.