Tests in controlled atmosphere on new optical gas sensing layers based on TiO2/metal-phthalocyanines hybrid system (original) (raw)
Related papers
2000
The surface plasmon resonance spectroscopy is an optical technique that is capable of monitoring chemical and physical processes. It is sensitive to detect small changes of dielectric properties in a metal-phthalocyanine boundary. For this reason plasmon resonance phenomena have been used to characterize a number of different types of films. This work analyses the possibility of using the surface plasmon resonance phenomena in the detection of gas. Thin films of copper, lead and nickel phthalocyanines have been examined in the plasmon system from the point of view of their application to NO 2 sensors.
Sensors and Actuators B: Chemical, 2016
In this work, thin films of chloroaluminium phthalocyanine (ClAlPc), fluoroaluminium phthalocyanine (FAlPc) and fluorochromium phthalocyanine (FCrPc), which are insoluble in conventional solvents, were deposited by spin coating of their solutions in trifluoroacetic acid. The sensing response of these films versus acetic acid, three alcohols (methanol, ethanol, butanol) and three amines (methylamine, dimethylamine, trimethylamine) have been investigated using surface plasmon resonance as the sensing method. It has been shown that the sensor response of the investigated films decreases in the following order: acetic acid > alcohols > amines. The optical changes as monitored by SPR method have been used in conjunction with Fick's second law of diffusion to determine the diffusion coefficients of analyte vapor during the films' swelling process. The obtained results showed that the diffusion coefficients and the swelling characteristics of the films are dependent on the functional group of the phthalocyanine molecule and the molecular size of the analyte.
Titanium and Ruthenium Phthalocyanines for NO2 Sensors: A Mini-Review
Sensors, 2009
This review presents studies devoted to the description and comprehension of phenomena connected with the sensing behaviour towards NO 2 of films of two phthalocyanines, titanium bis-phthalocyanine and ruthenium phthalocyanine. Spectroscopic, conductometric, and morphological features recorded during exposure to the gas are explained and the mechanisms of gas-molecule interaction are also elucidated. The review also shows how X-ray reflectivity can be a useful tool for monitoring morphological parameters such as thickness and roughness that are demonstrated to be sensitive variables for monitoring the exposure of thin films of sensor materials to NO 2 gas.
Gas Sensing Mechanism in Chemiresistive Cobalt and Metal-Free Phthalocyanine Thin Films
Journal of the American Chemical Society, 2007
The gas sensing behaviors of cobalt phthalocyanine (CoPc) and metal-free phthalocyanine (H2-Pc) thin films were investigated with respect to analyte basicity. Chemiresistive sensors were fabricated by deposition of 50 nm thick films on interdigitated gold electrodes via organic molecular beam epitaxy (OMBE). Time-dependent current responses of the films were measured at constant voltage during exposure to analyte vapor doses. The analytes spanned a range of electron donor and hydrogen-bonding strengths. It was found that, when the analyte exceeded a critical base strength, the device responses for CoPc correlated with Lewis basicity, and device responses for H 2Pc correlated with hydrogen-bond basicity. This suggests that the analyte-phthalocyanine interaction is dominated by binding to the central cavity of the phthalocyanine with analyte coordination strength governing CoPc sensor responses and analyte hydrogenbonding ability governing H2Pc sensor responses. The interactions between the phthalocyanine films and analytes were found to follow first-order kinetics. The influence of O2 on the film response was found to significantly affect sensor response and recovery. The increase of resistance generally observed for analyte binding can be attributed to hole destruction in the semiconductor film by oxygen displacement, as well as hole trapping by electron donor ligands.
International Journal of Advanced Science and Engineering
Focus of the article is to study the influence of gas adsorption on the surface photovoltage in phthalocyanine coated TiO2 thin film by studying the application of Liver Diseases. To realize this application, initially we have deposited thin film of TiO2 on ITO substrate by spray pyrolysis method and functionalized them with Phthalocyanine. Also, we studied the work function changes in the ambience of air and Triethylamine (TEA) gas medium using scanning Kelvin probe in dark and white light conditions. Triethylamine gas is found to be one of the most prominent Volatile organic compounds (VOC), present quite higher in amount in exhaled breath of liver disease patients. The comparison of response and recovery of sensor has been made between non-functionalized TiO2 thin film and functionalized TiO2 film. The results of the present study provide valuable lookout and paves the way to devise a gas sensor towards the early detection of liver diseases.
Langmuir
The NO2 gas-sensing characteristics of chemiresistors in the form of multilayered Langmuir-Blodgett films of a symmetrically substituted phthalocyanine, containing on the periphery four amidic groups-CONH-, have been studied. Floating layers were spread onto the water surface from a chloroform solution and were transferred onto both hydrophilic and hydrophobic quartz substrates using the vertical lifting method. Response and recovery times have been measured for different working temperatures at a fixed NO2 concentration. Dynamic response characteristics of the electrical conductance of the LB films to different NO2 concentrations, carried out in dry air, have shown a high sensitivity to concentrations of nitrogen dioxide smaller than 20 ppm at room temperature. All measurements have been carried out using coplanar configurations of the devices.
Colloidal solutions of Au and TiO 2 nanoparticles are prepared and used as nanocrystal inks for the fabrication of porous thin films to be used as optical gas sensor. The introduction of Au nanoparticles in the TiO 2 matrix affects the reactions mechanism improving the sensing process, moreover the Au Surface Plasmon Resonance peak can be used for the realization of a gas sensor with tunable sensitivity. The effect of thermal treatment, Au dimension and concentration is analyzed in order to tailor films microstructure and their sensing properties. The nanocomposites showed reversible change in optical absorption/reflection when exposed to reducing gasses (H 2 , CO) at 300 °C operative temperature or when exposed to volatile organic compounds (alcohols) at room temperature.
Sensors and Actuators B: Chemical, 2009
Effect of substrate temperature on microstructure of copper phthalocyanine (CuPc) thin films deposited on quartz and polycrystalline alumina substrates by vacuum sublimation technique has been studied. The films undergo a transition from ␣ phase at lower substrate temperatures to  phase for temperatures above 200 • C. A simultaneous change in morphology from granular to nano-fibrous films was observed. Resistance of ␣ phase films increased by more than one order of magnitude on initial application of electric field requiring stabilization for several hours, while  phase films did not show any drift. This behavior was attributed to oxygen absorption/desorption under applied field. Sensitivity of films for detection of NO 2 gas at room temperature was found to be higher for films in the ␣-phase with nanofibrous morphology. Methodology was devised for measurement of NO 2 concentration in ppm range with good response and recovery times. With this methodology, the sensors showed very good stability in response (at room temperature) for a period of 1 year.