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The synthesis and characterization of novel asymmetric zinc(II) phthalocyanines (4–9) and their linking through peripheral and nonperipheral positions on the phthalocyanine ring via click coupling to alkyne-functionalized 2,3,6,7,10,11-hexakis(prop-2-ynyloxy)triphenylene core are described for the first time. These phthalocyanines (Pcs) (4–12) were characterized by elemental analysis and different spectroscopic techniques such as UV-vis, ¹H-NMR, FT-IR and mass spectroscopy. Furthermore, the utilization of thin films of novel Pcs as a sensitive layer for detection of lung cancer from exhaled human breath at room temperature under exposure to marker volatile organic compounds (VOCs) are presented. The developed sensors were tested for acetone, ethanol, n-hexane, toluene, chloroform and isoprene in a range of 300–14560 ppm. The obtained results have confirmed the possibility of utilization of Pc-based Surface Acoustic Wave (SAW) sensors for medical diagnosis based on exhaled breath analysis.

Two asymmetrical amphiphilic phthalocyanines simultaneously containing hydrophobic alkoxy and hydrophilic 15-crown-5-ether substituents at the phthalocyanine periphery H₂{Pc(15C5)₃[(OC₈H₁₇)₂]} (Pc-1) and H₂{Pc(15C5)[(OC₈H₁₇)₆]} (Pc-2) and their symmetrical analogue H₂[Pc(OC₈H₁₇)₈] (Pc-3) have been synthesized and characterized. The _Pc-n/CdS (n = 1, 2 and 3, respectively) hybrid films are obtained successfully via a simple quasi-Langmuir–Shäfer (QLS) method using H₂S-vapor annealing over the Pc-n/Cd²⁺ self-assembled film formed at the interface of the air/CdCl₂ aqueous solution. The film-structure and properties of both the hybrid Pc-n/CdS and pure Pc-n films are comparatively studied by a wide range of methods including UV-vis, polarized UV-vis, XRD, SEM and I–V measurements. Experimental results exhibit a slipped co-facial stacking mode in an “edge-on” conformation (H-type aggregate) formed for the phthalocyanine molecules in both pure Pc-n films and the corresponding Pc-n/CdS hybrid films, with increasing intermolecular π–π interactions in the order of Pc-n < Pc-n/CdS and Pc-3/CdS < Pc-2/CdS < Pc-1/CdS, respectively. Accordingly, filmmicrostructures, crystallinity and conductivity are effectively improved by introducing CdS nanoparticles into the 15-crown-5-substituented phthalocyanines forming Pc-1/CdS and Pc-2/CdS hybrid films. These render excellent sensing performance towards NO₂ in the 0.05–2.5 ppm range within a fast dynamic exposure period of 30 s. Strikingly, Pc-1/CdS hybrid film presents an unprecedented high sensitivity of 157.3%.ppm^-1vs. very low NO2 concentration range of 0.05~0.25 ppm, achieving one of the best room temperature sensing performances in terms of high sensitivity, rapid responsibility and low detection limit among self-assembled film-based NO₂ sensors.

Solid-oxide electrolytes develop electrical potential when their two opposite electrodes are exposed to the different oxygen potential. When an electrolyte is exposed to the same ambient gas, a potential may develop due to the different catalytic behavior of two electrodes to ambient gas. Such a sensor is called as a non-equilibrium e.m.f.-type sensor or mixed potential sensor. In this study, to improve the sensitivity of the sensor to reducing gases (CO, H₂), transition metal oxide (T.M.O.) was added to one of two SnO₂ electrodes of the sensor. T.M.O. addition was expected to change the catalytic behavior of the electrode and to change e.m.f. values. The Co addition increased the e.m.f. of working electrode (T.M.O.-added SnO₂) in air, implying the enhanced oxygen adsorption. Fe addition showed the reverse effect. The addition of T.M.O. to SnO₂ was also effective in changing the e.m.f. values in H₂ balanced by air. Fe and Ni addition exhibited decreased e.m.f. in H₂ from that in air. Thus, Fe and Ni addition improved the catalytic activity for H₂ oxidation. On the other hand, the catalytic activity for H₂ oxidation was suppressed by Co addition. However, no appreciable change in CO sensitivity was obtained with the T.M.O. addition.

Nanostructured GaFeO₃ powders were prepared by sol-gel mothod. This paper reports the preparation and gas-sensing properties of GaFeO₃. Nanostructured GaFeO₃ powders were prepared by sol-gel mothod. Effects of the calcining condition on the phase constituents are characterized by XRD. The conductance-temperature, gas-sensing properties of GaFeO₃ were investigated. The results revealed that the GaFeO₃ can be used as a new promising gas-sensing material which has good sensitivity and selectivity to C₂H₅OH and C₂H₂.

Semiconductor gas sensors have the inherent problem of drift, which would emerge obviously with the changing of the circumstance temperature. Temperature sensor, and humidity sensor could be added to the gas sensor array to monitor working circumstance of the gas sensors. A series of temperatures was set by a thermostat employed in the experiment system, 20 gas samples (ten for each concentration) were prepared and the response of sensors to these gas samples was sampled. Two different artificial neural networks were used to recognize samples. The response of temperature sensor was introduced into the original networks and eliminated the misjudgments. Drift was suppressed to some extent and the performance of networks was also improved, which eventually verified the validity of the method for temperature drift rejection.

This paper addresses the problem of gas identification from an output of a gas sensor. Gas detectors are capable of detecting presence of certain types of gases but sensors that accept multiple analytes like MQ2 do not identify them. Identification of the analyte is very important to properly handle explosive gas. Template for each analyte is generated and used for template matching. A Gaussian type noise embedded in the input is also considered. Sample templates and percentage of accuracy in using template matching are shown. Gases used in the experiment include LPG, butane, propane, methane, alcohol, hydrogen and smoke. Smoke, which is not explosive, is also considered and classified as part of other gas detected.

A novel gas sensor based on cataluminescence (CTL) on the surface of nanosized Ti₂W₃O₁₃ was demonstrated for direct determination of ammonia in air. Trace ammonia was firstly absorbed on active carbon at room temperature to concentrate, then desorbed at 105°C to determine. The sensor showed high selectivity to ammonia at wavelength of 540 nm, satisfying activity at temperature of 180°C and good stability at air carrier flow rate of 120 ml/min. The linear range of CTL intensity versus concentration of ammonia was 0.8∼70 mg/m³ (γ=0.9991), and the detection limit (3σ) was 0.5 mg/m³. The recovery of artificial sample was 97.4%—102.5% by this method. There was no response to benzene, SO₂, CO, ethanol and formaldehyde. This sensor allows on-line monitoring of ammonia in air.

A cataluminescence (CTL) based method for simultaneously identifying and determining formaldehyde (HCHO) and sulfur dioxide (SO₂) in air was proposed. The experimental conditions meeting the algebraic sum rule of the CTL intensities of HCHO and SO2 were sought. They are two analysis wavelengths of 460 nm and 580 nm, the surface temperature of sensing materials of 280°C and the flow rate of air of 130 mL/min. The limits of detection of this method were 0.08 mg/m³ for HCHO and 0.6 mg/m³ for SO₂. Common coexistence matters, such as acetaldehyde, ammonia, benzene, ethanol, hydrogen sulfide and carbon dioxide, did not disturb the determination.