Temperature Dependence of Electrical Resistance in Graphite Films Deposited on Glass and Low-Density Polyethylene by Spray Technology

Graphite lacquer was simply sprayed on glass and low-density polyethylene (LDPE) substrates to obtain large area films. Scanning Electron Microscopy (SEM) images, Raman spectra, X Ray Diffraction (XRD) spectra and current-voltage characteristics show that at room temperature, the as-deposited films on different substrates have similar morphological, structural and electrical properties. The morphological characterization reveals that the films are made of overlapped graphite platelets (GP), each composed of nanoplatelets with average sizes of a few tens of nanometers and about forty graphene layers. The thermoresistive properties of the GP films deposited on the different substrates and investigated in the temperature range from 20 to 120 °C show very different behaviors. For glass substrate, the resistance of the film decreases monotonically as a function of temperature by 7%; for LDPE substrate, the film resistance firstly increases more than one order of magnitude in the 20–100 °C range, then suddenly decreases to a temperature between 105 and 115 °C. These trends are related to the thermal expansion properties of the substrates and, for LDPE, also to the phase transitions occurring in the investigated temperature range, as evidenced by differential scanning calorimetry measurements

Comprehensive infrared study of tetryl, dinitrotoluene, and trinitrotoluene compounds

The present work describes an experimental and theoretical study of energetic materials used for detecting explosives in order to prevent terrorist actions, as well as for de-mining projects. Particular attention was devoted to examining the infrared absorption spectroscopy of classic explosives in order to create a useful mobile apparatus for on-field detection of explosives. This paper reports the vibrational absorption spectra of tetryl, dinitrotoluene, and trinitrotoluene molecules approached using two different spectroscopic techniques, Fourier transform infrared spectroscopy (FT-IR) and laser photoacoustic spectroscopy (LPAS). Diffuse reflectance Fourier transform infrared spectra of all samples were analyzed in a very wide spectral range (400–7500 cm−1) showing for the first time the existence of weak absorption bands attributable to overtones or combination bands, while laser photoacoustic spectroscopy spectra have been investigated in the fingerprint region of organic compounds that share the CO2 laser emission range (∼920–1100 cm−1). The Fourier transform infrared spectra of both matrix isolated dinitrotoluenes have been also investigated. The theoretical treatment of tetryl is reported for the first time

UV-B radiation induced effects on human T-lymphocytes

The reactive oxygen species (ROS) produced inside cells by UV-B radiation may induce apoptosis, a process that realizes the programmed death of cells. In the present paper the UV induced damage was studied in a human T-Lymphocyte cell line (the Jurkat line) by mean of IR laser photoacoustic spectroscopy (PAS) and by Fourier Transform Infrared Spectroscopy (FTIR) combined with biological assays based on flow cytometry. The apoptosis was induced in vitro in the Jurkat samples by exposition to UV-B radiation with a dose of 310 mJ/cm2. PAS measurements were performed through a 10W c.w. CO2 laser based optical system realised at ENEA Molecular Spectroscopy Laboratory in Frascati (Italy)

Thermoresistive Properties of Graphite Platelet Films Supported by Different Substrates

Large-area graphitic films, produced by an advantageous technique based on spraying a graphite lacquer on glass and low-density polyethylene (LDPE) substrates were studied for their thermoresistive applications. The spray technique uniformly covered the surface of the substrate by graphite platelet (GP) unities, which have a tendency to align parallel to the interfacial plane. Transmission electron microscopy analysis showed that the deposited films were composed of overlapped graphite platelets of dierent thickness, ranging from a few tens to hundreds of graphene layers, and Raman measurements provided evidence for a good graphitic quality of the material. The GP films deposited on glass and LDPE substrates exhibited dierent thermoresistive properties during cooling–heating cycles in the 40 to +40 C range. Indeed, negative values of the temperature coecient of resistance, ranging from 4 104 to 7 104 C1 have been observed on glass substrates, while positive values varying between 4 103 and 8 103 C1 were measured when the films were supported by LDPE. These behaviors were attributed to the dierent thermal expansion coecients of the substrates. The appreciable thermoresistive properties of the graphite platelet films on LDPE could be useful for plastic electronic applications