In vivo dosimetry for patient radioprotection is a real challenge concerning new radiotherapy treatments. In this study we aim to develop a dosimeter based on tissue equivalent material, flexible and adaptable to the patient morphology in order to perform in vivo dosimetry for complex irradiation beams. Here, we report the evaluation in standard beams of highly flexible dosimeter composed of a silicone elastomer and containing leucomalachite green as radiochromic dye and give a first estimation of LMG-micelle hydrogel response. All results are compared to a commercially available PRESAGE® dosimeter.

Fourier transform infrared (FTIR) spectrometry is commonly used for the identification of reference substances (RSs) in solid, liquid, or gaseous mixtures. An expert is generally required to perform the analysis, which is a bottleneck in emergency situations. This study proposes a support vector machine (SVM)-based algorithm, the peak correlation classifier (PCC), designed to rapidly detect the presence of a specific threat or reference substance in a sample. While SVM has been used in various spectrographic contexts, it has rarely been used on FTIR spectra. The proposed algorithm discovers correlation similarities between the FTIR spectrum of the RS and the test sample and then uses SVM to determine whether or not the RS is present in the sample. The study also shows how the additive nature of FTIR spectra can be used to create 'synthetic' substances that significantly improve the detection capability and decision confidence of the SVM classifier.

We propose a new concept for enhancing the fluorescence of ultrathin nanolayers. In this article, we address the issue of efficient absorption of polymer thin films with nanometer characteristics. For many applications, such as sensing, but also for lighting or photovoltaics, devices require the use of nanometer-sized films of a specific polymer or a luminescent nanolayer in general. Usually, most studies are geared toward enhancing the emission of such luminescent films via Bragg mirror-type cavities, for instance, but little attention is paid for optimizing the absorption of the thin films. We show the principle of gain-assisted waveguiding energy transfer (G-WET).by inserting a gain-active layer between an active nanometer-scale layer (a luminescent polymer in our case) and the passive substrate. Efficient absorption via "recycling" of the pumping photons is ensured by the waveguiding effect due to this high-index active layer. To demonstrate the G-WET effect, two kinds of samples were studied. They consist of extremely thin (similar to 10 nm) polymer nanolayers spin-coated either on quartz, referred as the passive case, or on a ZnO active thin film (similar to 170 nm, acting as a gain medium) grown on sapphire, referred as the active case. Samples were characterized by room-temperature photoluminescence (PL) spectroscopy under various pumping intensities. Compared to the quartz substrate, the ZnO thin film induces a remarkable enhancement of a factor similar to 8 on the fluorescence of the polymer nanolayer. Observations show that, for the passive quartz substrate case, the PL of the spin-coated polymer rapidly saturates, defining a luminescence limit; whereas, with the active ZnO layer, the polymer presents a nonlinear PL intensity surpassing the saturation level. This new photonic system revealed that the polymer luminescence enhancement is the result of both an efficient energy transfer and a geometrical effect ensured by an evanescent coupling of the waveguided ZnO stimulated emission. Although our work discusses the specific organic inorganic case of fluorescent polymer and ZnO, the G-WET concept can be generalized to any hybrid layered sample verifying the necessary energy transfer conditions discussed in this article, thus, demonstrating that this is of a special interest for efficient absorption and efficient recycling of the excitation photons for any nanometer scale fluorescent layer.

This article highlights our recent application of functional nanodiamonds (NDs) with peptide nucleic acids (PNA) to develop tools for DNA detection. NDs appear as an ideal nanocarrier due to their versatile surface chemistry, their non-cytotoxicity and since they could benefit from intrinsic luminescent properties. In this work, we report for the first time the possibility to prepare a covalent, stable and functional conjugate of PNA with 20 nm HPHT (High Pressure High Temperature) nanodiamonds. Peptide nucleic acid is a DNA mimic related to both peptides via its backbone and to nucleic acid via its bases. It binds more specifically and more strongly than DNA itself to either DNA or RNA. We have initiated a novel functionalization route based on an optimized amidation of ND carboxylic acid groups, to produce ND-PNA conjugates via an efficient, simple and reproducible method. We describe the synthesis and characterization of those conjugates. The covalent binding of the ND-PNA and the loading of nucleic acid grafted onto the NDs were performed using various characterization methods including FTIR, Kaiser tests and thermogravimetry. Then, ND-PNA conjugates were validated through a successful recognition of complementary DNA in a mixture, showing their efficiency toward nucleic acid detection. Moreover, the impact of ND-PNA on A 549 cells' viability was analysed with flow cytometry and showed an absence of ND-PNA conjugates cytotoxicity. Such nucleic acid-functionalized nanodiamonds offer a wide range of applications and namely the possibility to target and to recognize DNA.

We report on the efficient room-temperature photoluminescence (PL) quenching of ZnO in the presence of 2,4-dinitrotoluene (DNT) vapor and for concentration as low as 180 ppb. Compared to ZnO thin films, ZnO nanowires exhibit a strong (95%) and fast (41 s) quenching of the PL intensity in the presence of DNT vapor. Assuming that the PL quenching is due to a trapping of the ZnO excitons by adsorbed DNT molecules, Monte-Carlo calculations show that the nanometric dimensions as well as the better crystallographic quality (longer mean free path) of the ZnO nanowires result in an enhanced trapping process at the origin of the improved sensing properties of the nanowires. The results demonstrate the importance of nanostructures in improving the sensitivity of ZnO. The study also reveals the sensing capability of ZnO nanowires and paves the path towards the potential realization of low-cost sub-ppb nitroaromatic derivative sensors.

This imaging system aims at recording images of the core size and shape of an imploding deuterium-tritium (DT) microballoon on LMJ inertial confinement fusion (ICF) experiments. Image acquisition is difficult due to the harsh surrounding created by the fusion reaction, which affects system specifications. This one is made of a scintillator, an optical relay, and a CCD camera shielded from the surrounding. The system was tested on different facilities at CEA/DIF, where a spatial resolution of 120 μm was achieved and gamma dose up to 20 rad effects were measured. Setup and performed test are described.

Discrimination between fast neutrons and gamma rays has been successfully achieved using a blue-fluorescing 4-substituted 1,8-naphthalimide in aromatic solvents. As previously stated in the literature, an important solvent effect was observed, but the substitution groups surrounding the core of the naphthalimide also appeared to be extremely crucial. Our system presents the advantages of being based on the use of a single highly soluble solute, exhibiting a large Stokes shift (to avoid self-absorption process) and presenting an emission spectrum fitting well to the photomultiplier (PM) sensitivity. More importantly, we observed that our scintillator was not affected by the concentration of oxygen dissolved in the medium. This observation has no equivalent in commercial liquid scintillators, which are known to be oxygen-sensitive. The discrimination efficiency of our system is described in terms of scintillation performances, figure of merit and the angle between neutrons and gamma lobes visualized in the bi-parametric discrimination spectrum.

The invention relates to the use of derivatives of 1,8-naphthalimide and salts thereof as scintillation agents, and especially as agents discrimination between fast neutrons and gamma.Elle rays also relates to scintillators liquids comprising these scintillation agents in solution in a solvent and to new derivatives of 1,8-naphthalimide useful as scintillation agents, including discrimination between fast neutrons and gamma.Applications rays all areas of use scintillators including industry, geophysics, fundamental physics, particularly nuclear, goods and people safety, radiation protection of workers in the industrial, nuclear and medical, medical imaging, etc.

This paper deals with the scintillation of fluorescent polymeric materials and their utilization in nuclear detection. Despite the importance of its applications, discrimination between fast neutrons and gamma rays in plastic scintillators remains very difficult due to the extreme sensitivity of these detectors to gamma. We have investigated the relevance of different 4-substituted 1,8-naphthalimides as fluorophores, either dispersed in a polymer matrix or copolymerized with styrene or methyl methacrylate to prepare new scintillating materials. Thus, various polymer pellets (Ø 18mm, length 10–15mm) incorporating from 0.05% to 1% of naphthalimide were prepared. The charge comparison method commonly used as discrimination technique in nuclear physics experiments was chosen. This technique lies in identifying neutrons from gamma rays by the shape of the light pulse delivered in the scintillator. Preliminary results indicate that the developed scintillators did not satisfy the discrimination criterion.

This article aims at reviewing currently available techniques and systems under development for the detection of explosive traces, in order to both prevent terrorist attacks against strategic installations and facilitate humanitarian demining. Continuous monitoring of public sites requires sensors having a shorter analysis time and able to self-operate. As regards landmine detection, which respond to a different problematic, needs are related to the development of highly sensitive, low cost and robust devices.

The synthesis, spectroscopic characterization and fluorescence quenching efficiency of a polymer (PSt-NI) and a low molecular weight molecule (NI) containing the 4-(N, N disubstituted)amino-N-2,5ditertiobutylphenyl-1,8-naphthalimide chromophore are reported. Similar spectroscopic properties of thin films and solutions are observed. This is consistent with the absence of interactions between polymer side chains. The absorption and fluorescence spectra of PSt-NI studied in various solvents of different polarity are compared to the corresponding spectra of NI. The longest wavelength absorption of PSt-NI and NI is characterized by a band with a maximum wavelength around 410 nm. The peak position is sensitive to the polarity of the solvent, which is in agreement with the charge transfer character of the transition. The fluorescence spectrum of PSt-NI shows a maximum emission in chloroform at 515 nm and is red shifted compared to those of NI. Fluorescence lifetimes of PSt-NI and NI are measured in presence and absence of 2,4-dinitrotoluene (DNT) and the results are interpreted via the Stern-Volmer analysis. In solution, the fluorescence quenching of NI is purely collisional, whereas both dynamic and static quenching are observed with PSt-NI Upon 1 minute exposure to DNT vapor, it was shown that a 5 nm thick film of PSt-NI exhibited a 45% drop in its fluorescence intensity, which makes this polymer very attractive for sensing applications.

Implementation of MIPs for sensor applications has been the subject of an increasing number of studies within the past few years [1]. MIPs are cross-linked polymers prepared in the presence of a template molecule (see figure 1). Functional monomers interact with the template prior to and during the polymerization. After template removal, specific binding sites complementary to the template structure are generated [2]. Monomers and cross-linkers employed are generally (meth-)acrylates or styrene derivatives. To synthesize the MIPs in the form of thin surface-bound layers, we have developed a new technique based on "living" free radical photopolymerization initiated from metallic surface grafted initiator. This allows the immobilization of the sensitive layer onto the transducer surface. The technique enables the control of the polymer thickness by modifying the sample time irradiation and suppresses certain disadvantages of classical techniques like irreversible grafting of preformed polymers.

Eleven bis-ureas have been synthesized, and some of their properties are reported. Several of these compounds form supramolecular polymers in organic solvents. The self-association is shown by FTIR spectroscopy to display cooperativity at two levels. The first level of cooperativity is due to the synergistic association of the two urea functions of a single molecule. The second level of cooperativity is revealed by the fact that the formation of dimers is less favored than that of long oligomers.

Interpenetrating polymer networks (IPNs) composed of poly(methacrylate) and epoxy-amine networks made in situ between two oriented polypropylene sheets were examined in terms of their oxygen barrier and adhesion to the substrate properties. A particular attention was devoted to a system presenting an obvious phase separation. Kinetics of network formation and phase behavior were investigated by infrared and UV-visible spectroscopy, respectively. Since the poly(methacrylate) network could be instantaneously generated by photoirradiation, IPNs differing in network sequence formation were prepared. The influence of the moment at which irradiation was induced, on gas barrier properties of different films was examined. It was shown that similar oxygen transmission rates are obtained whatever the moment of irradiation. (C) 2002 Elsevier Science Ltd. All rights reserved.

Polylactide samples obtained by the ring-opening polymerization of (D,L)-lactide by using different lanthanide alkoxide initiators were examined by SEC, C-13 NMR and MALDI-TOF MS techniques. The evidence of substantial transesterification was observed in the case of a polymerization initiated by lanthanum alkoxide and bimetallic aluminium-yttrium alkoxide initiators. In the case of Y and Sm alkoxide initiators, the MWD remains narrow up to high conversions for reasonable polymerization times, but the prolongation of the post-polymerization time increases the amount of ester-exchange reactions. The extent of the transesterification reactions was evaluated on the basis of the intensity of the stereosequence resonances for the methine carbon signal in the C-13 NMR spectra. MALDI-TOF MS analysis revealed the presence of odd-membered oligomers in all spectra. Thus, transesterification reactions occur from the beginning of the polymerization. Linear and cyclic oligomers were detected in some cases indicating the simultaneous occurrence of inter- and intramolecular exchange reactions. The microstructure analysis of the polymers by C-13 NMR spectroscopy indicates a preference for a syndiotactic addition during the polymerization process.

Block copolymers were prepared by sequential addition oft or D-lactide to a living epsilon-caprolactone prepared with Y(OC(2)H(4)OiPr)(3) initiator. In contrast, epsilon-caprolactone (CL) was not polymerized when added to a living polyL-lactide (LA) prepared with the same initiator in the same conditions. The polymerization of an equimolecular mixture of LA and CL using the yttrium alkoxide initiator produces only the pure lactide homopolymer. The copolymerization of LA with trimethylene carbonate (TMC) exhibits a different type of behaviour. The synthesis of pure block copolymers by sequential addition of monomers is obtained if starting from a living polylactide sequence. When starting with TMC sequence, mixture of products leading to a bimodal MWD is obtained. The polymerization of an equimolecular mixture of LA and RMC leads to a copolymer with a block structure. The PLA sequence is formed first, followed by the subsequent addition of TMC monomer up to complete conversion All the prepared copolymers were characterized by SEC,H-1 and C-13 NMR techniques. No transesterification reactions were detected.

The polymerization of (D,L)-Lactide at room temperature in solution using Y(OCH(2)CH(2)OiPr)(3) and Ln(5)(mu-O)(OiPr)(13) with Ln = La, Sm, Y, Yb as initiators was studied. According to kinetic data, a controlled type polymerization is observed for most of the systems. La mu-oxoisopropoxide is the mast reactive initiator, but leads to a substantial broadening of molecular weight distribution at high conversions. The nature of transesterification reactions was studied by SEC, C-13 NMR and MALDI-TOF MS techniques. For Sm and Y-mu-oxo initiators only limited intermolecular ester exchange occurs, while with La mu-oxoinitiator and with Y(OCH(2)CH(2)OiPr)(3) initiator, but after a long time of the polymerization reaction, both inter and intramolecular transesterification occur with formation of cyclics.