Rafael Cases

Joining Time-Resolved Thermometry and Magnetic-Induced Heating in a Single Nanoparticle Unveils Intriguing Thermal Properties

Whereas efficient and sensitive nanoheaters and nanothermometers are demanding tools in modern bio- and nanomedicine, joining both features in a single nanoparticle still remains a real challenge, despite the recent progress achieved, most of it within the last year. Here we demonstrate a successful realization of this challenge. The heating is magnetically induced, the temperature readout is optical, and the ratiometric thermometric probes are dual-emissive Eu(3+)/Tb(3+) lanthanide complexes. The low thermometer heat capacitance (0.021·K(-1)) and heater/thermometer resistance (1 K·W(-1)), the high temperature sensitivity (5.8%·K(-1) at 296 K) and uncertainty (0.5 K), the physiological working temperature range (295-315 K), the readout reproducibility (>99.5%), and the fast time response (0.250 s) make the heater/thermometer nanoplatform proposed here unique. Cells were incubated with the nanoparticles, and fluorescence microscopy permits the mapping of the intracellular local temperature using the pixel-by-pixel ratio of the Eu(3+)/Tb(3+) intensities. Time-resolved thermometry under an ac magnetic field evidences the failure of using macroscopic thermal parameters to describe heat diffusion at the nanoscale.

Spectroscopic characterization of two forms of the D1-D2-cytochrome b559 complex from sugar beet

Two D1‐D2‐cytochrome b559 complex forms, called RCIIa and RCIIb, with different pigment stoichi‐ometry were characterized using absorption and surface‐enhanced resonance Raman scattering spectroscopy and spectral gaussian deconvolution. Electronic absorption spectra of the RCIIb at 277 K showed significant differences compared to RCIIa, i.e. a strong decrease in the absorbance due to carotenoid and chlorophyll for the same amount of pheophytin. A reduced carotenoid and chlorophyll content in RCIIb was also observed in the surface‐enhanced resonance Raman scattering spectra. Spectral deconvolution elicited three main absorption bands at 680, 672 and 669–670 nm, which were ascribed to P680, pheophytin and accessory chlorophyll, respectively. In addition, a minor component around 667 nm was observed in the RCIIb, most probably due to some reaction center inactivation. Calculation of the relative area under the gaussians together with pigment stoichiometry data suggest that the 680, 672 and 669–670 nm components contain, respectively, two chlorophylls, two pheophytins and four chlorophylls for the RCIIa, and two chlorophylls, two pheophytins and two chlorophylls for the RCIIb.

On the control of optical transmission of aluminosilicate glasses manufactured by the laser floating zone technique

In this work, a detailed study of the properties of aluminosilicate glass rods manufactured by means of the laser floating zone (LFZ) technique is presented. Samples fabrication was carried out in controlled atmosphere using air, nitrogen, and oxygen. Transmission spectra showed that glasses manufactured in oxygen presented high optical transmission in the visible spectral range compared to those manufactured in other environments, thus allowing us to tune their optical behavior between transparent and nearly opaque through the control of the surrounding atmosphere. Microstructure and thermo-mechanical properties were also assessed, showing similar hardness, toughness, flexural strength and glass transition temperature values, and in the same range as other aluminosilicate glasses. Compositional and structural characterization in terms of energy dispersive X-ray spectroscopy (EDX) and electron paramagnetic resonance (EPR) allowed us to determine the origin of optical transmission dependence on the fabrication atmosphere.

A reagentless enzymatic fluorescent biosensor for glucose based on upconverting glasses, as excitation source, and chemically modified glucose oxidase.

Upon near-infrared excitation Tm(3+)+Yb(3+) doped fluorohafnate glasses present upconversion properties and emit visible light. This property permits to use these glasses (UCG) as excitation sources for fluorescent optical biosensors. Taking this into account, in this work a fluorescent biosensor for glucose determination is designed and evaluated. The biosensor combines the UCG and the fluorescence of the enzyme glucose oxidase chemically modified with a fluorescein derivative (GOx-FS), whose intensity is modified during the enzymatic reaction with glucose. Optical parameters have been optimized and a mathematical model describing the behavior of the analytical signal is suggested. Working in FIA mode, the biosensor responds to glucose concentrations up to, at least, 15mM with a limit of detection of 1.9mM. The biosensor has a minimum lifetime of 9 days and has been applied to glucose determination in drinks. The applicability of the sensor was tested by glucose determination in two fruit juices.