Abstract
Partial discharges are a major source of insulation failure in electric power transformers. Their detection can be achieved through the associated acoustic emissions, and this work reports on the investigation of a fibre laser sensor based on a phase-shifted chirped fibre grating for acoustic emission detection in the power transformer environment. The performance of the sensing head is characterized and compared for different surrounding media: air, water and oil.

Abstract
The synthesis of carbon nanoparticles obtained by direct laser ablation [UV pulsed laser irradiation (248 nm, KrF)] of carbon targets immersed in water is described. Laser ablation features were optimized to produce carbon nanoparticles with dimensions up to about 100 nm. After functionalization with NH2-polyethylene-glycol (PEG(200)) and N-acetyl-L-cysteine (NAC) the carbon nanoparticles become fluorescent with excitation and emission wavelengths at 340 and 450 nm, respectively. The fluorescence decay time was complex and a three-component decay time model originated a good fit (chi = 1.09) with the following lifetimes: tau(1) = 0.35 ns; tau(2) = 1.8 ns; and tau(3) = 4.39 ns. The fluorescence of the carbon dots is sensitive to pH with an apparent PKa = 4.2. The carbon dots were characterized by H-1 NMR and HSQC and the results show an interaction between PEG(200) and the carbon surface as well as a dependence of the chemical shift with the reaction time. The fluorescence intensity of the nanoparticles is quenched by the presence of Hg(II) and Cu(II) ions with a Stern-Volmer constant (pH = 6.8) of 1.3 x 10(5) and 5.6 x 10(4) M-1, respectively. As such the synthesis and application of a novel biocompatible nanosensor for measuring Hg(II) is presented.

Abstract
In the recent years, sol-gel films have been intensively used in optical sensors configurations. Due to its hydrophobic nature, ormosil films have been reported to be a promising supporting matrix for oxygen sensing dyes for measurements in aqueous media. In this work, the impact of the sol-gel host fabrication parameters in the characteristics of the resulting oxygen sensing membranes is thoroughly evaluated. Different combinations of organic-inorganic precursors, with different aging times, were tested as oxygen sensors. All the solution were doped with ruthenium complex Ru(II)-tris(4,7-diphenyl-1,10- phenanthroline) to introduce oxygen sensitivity. Thin films were produced by dip coating of glass slides. The oxygen sensitive films were tested in aqueous phase in equilibrium with different oxygen gas compositions, using a phase-modulation technique. Sensor performance parameters such as Stern-Volmer constant, quenching efficiency and lifetime response are reported. The data obtained clearly indicates that increased aging times and longer organic groups produce sensors with the highest sensitivity to dissolved oxygen. From all sol-gel films produced, the BTEOS:TEOS (1:1) mixture is the most promising for sensor construction. © (2010) Trans Tech Publications.

Abstract
Silica based nanostructured composite materials doped with luminol and cobalt(II) ion were synthesized and characterized, resulting in a highly chemiluminescent material in the presence of hydrogen peroxide. A detection system with the CL light guided from the reaction tube to the photomultiplier tube using a one millimeter glass optical fiber was developed and assessed. A linear response was observed using a semi-logarithm calibration between 50-2000M hydrogen peroxide with 1M as the limit of detection.

Abstract
CdTe quantum dots (QDs), capped with mercaptopropionic acid (MPA), were synthesized and the variation of their fluorescence properties (steady state and lifetime)with pH was assessed in solution and when immobilized in a sol-gel host Three different sizes of CdTe QDs with excited state lifetimes ranging from 42 to 48 ns and with emission maximum at 540 nm (QD(540)). 580 nm (QD(580)) and 625 nm (QD(625)) were selected The solution pH affects the maximum emission wavelength (shifts to higher wavelengths of 23, 24 and 27 nm for QD(540), QD(550) and QP(625), respectively), the excited state lifetime and the fluorescence intensity in a reversible way. Linearization of the maximum emission wavelength variation with the pH allows the estimation of an apparent ionization constant (pK(a)) for each QD: 6.5 +/- 0.1 (QD(540)), 6.1 +/- 0.5 (QD(580)) and 5.4 +/- 0.3 (QD(625)) The variation of the QDs fluorescence properties was further explored using confocal laser scanning microscopy allowing the implementation of a new calibration method for pH imaging in solution QDs were successfully immobilized on the tip of an optical fiber by dip-coating using sal-gel procedure The immobilized QDs showed a similar pH behaviour to the one observed in solution and an apparent lifetime of 80,68 and 99 ns, respectively. The proposed QDs based methodology can be successfully used to monitor pH using wavelength encoded data in imaging and fiber optic sensing applications.

Abstract
The deterioration of water quality by Cyanobacteria causes outbreaks and epidemics associated with harmful diseases in Humans and animals because of the released toxins. Microcystin-LR (mcyst) is one of the most widely studied hepatotoxin and World Health Organization recommends a maximum value of 1 mu g L-1 of mcyst in drinking-water. Therefore, there is a great demand for remote, real-time sensing techniques to detect and quantify the presence of mcyst. In this work a Fabry-Perot sensing probe based on a fibre tip coated with a mcyst sensitive thin film is presented. Highly specific recognition membranes, using sol-gel based Molecular Imprinted Polymers (MIPs), were developed to quantify microcystins in water, showing great potential in the analysis of this kind of samples. The fibre Fabry-Perot MIP sensor shows a linear response to mcyst concentration with a sensitivity of -13.2 +/- 0.4 nm L mu g(-1).