Gema Cabello

Lasers are the pillars of modern optics and sensing. Microlasers based on whispering-gallery modes (WGMs) are miniature in size and have excellent lasing characteristics suitable for biosensing. WGM lasers have been used for label-free detection of single virus particles, detection of molecular electrostatic changes at biointerfaces, and barcode-type live-cell tagging and tracking. The most recent advances in biosensing with WGM microlasers are described in this review. We cover the basic concepts of WGM resonators, the integration of gain media into various active WGM sensors and devices, and the cutting-edge advances in photonic devices for micro- and nanoprobing of biological samples that can be integrated with WGM lasers.

Herein, we report a detailed study of microwave-matter interaction focused on the role of small nanoparticles and the effects on microwave thermal heating. We have used a model reaction (degradation of methylene blue) to study the influence of temperature, size, and catalytic properties of the nanoparticles in the potential formation of hot spots. Total mineralization was achieved after 3 h microwave heating at 200 °C in the presence of 2 nm TiO nanoparticles (92% calculated TOC decay), but the reaction resulted in a mixture of intermediates (52% TOC decay) in the absence of TiO. The effect of temperature was evaluated by carrying out the reaction at 120 °C, and the results were similar to those obtained in the absence of TiO, but with lower TOC removal efficiencies (12-14%). For comparison, the degradation of MB was also followed using (noncatalytic) SiO and MnO nanoparticles of comparable size. Differences in the degradation efficiency may be ascribed to the formation of hot spots...

The aim of this work was the synthesis and characterization of new modified sol-gel carbon composite electrodes and their application to the determination of trace mercury species with positive charge. Two types of modified electrodes were synthesized, sol-gel and sol-gel-PVSA carbon composite electrodes. In the last ones, poly(vinylsulfonic acid) (PVSA) was used as a functional polymer entrapped within the sol-gel material due to its cationic exchange properties. In a first stage, parameters affecting both, the sol-gel process and the electrode preparation were optimized. In a second stage, usefulness of developed electrodes applied to the determination of cationic mercury species was evaluated, optimizing the activation, preconcentration, measurement and regeneration steps. Developed electrodes showed very favourable electroanalytical properties for their use as amperometric sensors, such as small size, low cost, simple fabrication and handling, renewability and reusability. By means of an easy and low-cost methodology, satisfactory experimental results were obtained in Hg2+ determination. In this sense, developed analytical methodology showed adequate response times, linear concentration range up to three orders of magnitude (from 5.0 x 10(-8) to 5.0 x 10(-5)M) and detection limits of 1.5 x 10(-8)M (3.0 microg L(-1)). These results suggest that the incorporation of different receptor molecules at the sol-gel carbon composite material in combination with a selected electrochemical reaction could improve the detection limit achieved and obtain electrochemical sensors adapted to the determination of different species of mercury and other heavy metals.