Publications

Abstract The oxyluciferin family of fluorophores has been receiving much attention from the research community and several systematic studies have been performed in order to gain more insight regarding their photophysical properties and photoprotolytic cycles. In this minireview, we summarize the knowledge obtained so far and define several possible lines for future research. More importantly, we analyze the impact of the discoveries on the firefly bioluminescence phenomenon made so far and explain how they re-open again the discussion regarding the identity (keto or enol species) of the bioluminophore.

Abstract A significant number of hospital-acquired infections occur due to inefficient disinfection of hospital surfaces, instruments and rooms. The emergence and wide spread of multiresistant forms of several microorganisms has led to a situation where few compounds are able to inhibit or kill the infectious agents. Several strategies to disinfect both clinical equipment and the environment are available, often involving the use of antimicrobial chemicals. More recently, investigations into gas plasma, antimicrobial surfaces and vapour systems have gained interest as promising alternatives to conventional disinfectants. This review provides updated information on the current and emergent disinfection strategies for clinical environments.

Abstract The effect on the fluorescence of the europium:tetracycline (Eu:Tc), europium:oxytetracycline (Eu:OxyTc) and europium:chlortetracycline (Eu:ClTc) complexes in approximately 2:1 ratio of nitric oxide (NO), peroxynitrite (ONOO-), hydrogen peroxide (H2O2) and superoxide (O-2 (center dot-)) was assessed at three ROS/RNS concentrations levels, 30 A degrees C and pH 6.00, 7.00 and 8.00. Except for the NO, an enhancement of fluorescence intensity was observed at pH 7.00 for all the europium tetracyclines complexes-the high enhancement was observed for H2O2. The quenching of the fluorescence of the Tc complexes, without and with the presence of other ROS/RNS species, provoked by NO constituted the bases for an analytical strategy for NO detection. The quantification capability was evaluated in a NO donor and in a standard solution. Good quantification results were obtained with the Eu:Tc (3:1) and Eu:OxyTc (4:1) complexes in the presence of H2O2 200 mu M with a detection limit of about 3 mu M (Eu:OxyTc).

Abstract In this work we describe the electrochemical behavior of an ionic liquid formed between choline chloride (ChCl) and chromium chloride hexahidrated (CrCl3 center dot 6H(2)O) in the ratio of 2.5:1 containing 20 wt.% of added ultrapure water, using cyclic voltammetry and chronoamperometry. The reduction of Cr(III) occurs in two steps, Cr(III) to Cr(II) and Cr(II) to Cr(0), respectively. The first step is controlled by diffusion. For the first time a thorough study of the nucleation of chromium from Cr(III) ionic liquid solutions is described. Furthermore for less cathodic potentials there is a diffusion control of nuclei growth. For more cathodic potentials the lattice incorporation of adatoms to the growing nuclei is the limiting process. The additive free bright chromium deposit obtained is formed by semi-spherical nuclei. The effect of hydrogen evolution is only observed for E < - 1.90 V.

Abstract In this work, the ion transfer mechanism of the anticancer drug daunorubicin (DNR) at a liquid/liquid interface has been studied for the first time. This study was carried out using electrochemical techniques, namely cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The lipophilicity of DNR was investigated at the water/1,6-dichlorohexane (DCH) interface, and the results obtained were presented in the form of an ionic partition diagram. The partition coefficients of both neutral and ionic forms of the drug were determined. The analytical parameter for the detection of DNR was also investigated in this work. An electrochemical DNR sensor is proposed by means of simple ion transfer at the water/DCH interface, using DPV as the quantification technique. Experimental conditions for the analytical determination of DNR were established, and a detection limit of 0.80 mu M was obtained.

Abstract Herein, we present a simple microelectrode preparation methodology consisting in coating a platinum wire or a carbon fiber with a thin insulating Parylene C film (e.g. 1-10 mu m), to produce SECM probes with a small and constant probe RG (i.e. ratio between the radius of the insulating sheath and the radius of the active electrode area). After exposition of a fresh active electrode area by blade cutting, a disc shaped electrode is obtained thanks to a protective hot mounting wax layer that avoids Parylene C coating deformation and is easily removed with acetone. Stiffness and straightness of the probe can be tuned by modifying the Parylene C coating thickness and the length of the carbon fiber or platinum wire. This simple electrode preparation method is highly reproducible (c.a. > 90%). The prepared Parylene C coated microelectrodes were characterized by optical microscopy, cyclic voltammetry, scanning electrochemical microscopy (SECM) approach curves and finally applied to SECM imaging of Pt band structures in contact-less and contact mode.

Abstract A novel optical fiber sensor is presented for measuring dissolved CO2 for water quality monitoring applications, where the optical signal is based either on refractive index changes or on color change. The sensing chemistry is based on the acid-basic equilibrium of 4-nitrophenol, that is converted into the anionic form by addition quaternary ammonium hydroxide. The CO2 sensitive layer was characterized and tested by using simple absorbance/reflectance measurement setups where the sensor was connected to a fiber optic CCD spectrometer. A prototype simulating a real shallow raceway aquaculture system was developed and its hydraulic behavior characterized. A commercially available partial-pressure-NDIR sensor was used as a reference for dissolved CO2 tests with the new optical fiber sensor under development. Preliminary tests allowed verifying the suitability of the new optical sensor for accurately tracking the dissolved carbon dioxide concentration in a suitable operation range. Direct comparison of the new sensor and the reference sensor system allowed to demonstrate the suitability of the new technology but also to identify some fragilities there are presently being addressed.

Abstract Gold nanoparticle (Au NP) mirrors, which exhibit both high reflectance and electrical conductance, were self-assembled at a [heptane + 1,2-dichloroethane]/water liquid/liquid interface. The highest reflectance, as observed experimentally and confirmed by finite difference time domain calculations, occurred for Au NP films consisting of 60 nm diameter NPs and approximate monolayer surface coverage. Scanning electrochemical microscopy approach curves over the interfacial metallic NP films revealed a transition from an insulating to a conducting electrical material on reaching a surface coverage at least equivalent to the formation of a single monolayer. Reflectance and conductance transitions were Interpreted as critical junctures corresponding to a surface coverage that exceeded the percolation threshold of the Au NP films at the [heptane + 1,2-dichloroethane]/water interface.