Study of the sensor response of spun metal phthalocyanine films to volatile organic vapors using surface plasmon resonance

tIn this work, thin films of chloroaluminium phthalocyanine (ClAlPc), fluoroaluminium phthalocyanine(FAlPc) and fluorochromium phthalocyanine (FCrPc), which are insoluble in conventional solvents, weredeposited by spin coating of their solutions in trifluoroacetic acid. The sensing response of these filmsversus acetic acid, three alcohols (methanol, ethanol, butanol) and three amines (methylamine, dimethy-lamine, 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 con-junction with Fick’s second law of diffusion to determine the diffusion coefficients of analyte vapor duringthe films’ swelling process. The obtained results showed that the diffusion coefficients and the swellingcharacteristics of the films are dependent on the functional group of the phthalocyanine molecule andthe molecular size of the analyte

Effect of fluorosubstitution on the structure of single crystals, Effect of fluorosubstitution on the structure of single crystals,thin films and spectral properties of palladium phthalocyanines

In this work, the crystalline structure of single crystals grown by vacuum sublimation of unsubstituted palladium phthalocyanines (PdPc), its tetrafluorinated (PdPcF4) and hexadecafluorinated (PdPcF16) derivatives have been investigated using X-ray diffraction measurements. Two crystalline phases have been identified for PdPc; the molecules in both phases crystallize in stacks with herringbone arrangement in the monoclinic space groups (C2/c for -PdPc; P21/n for -PdPc). Both PdPcF4 and PdPcF16 crystallize in the triclinic P-1 space group, forming stacks of molecules in columnar arrangement with molecules in adjacent columns are aligned parallel to one another. X-ray diffraction measurements have also been used to elucidate the structural features and molecular orientation of thin films of PdPc, PdPcF4 and PdPcF16, grown by organic molecular beam deposition at different substrate temperatures. The effect of fluorosubstitution on UV-visible optical absorption and vibrational spectra of palladium phthalocyanine derivatives is also discussed

Electrical, optical and gas sensor properties of chloroaluminium (ClAlPc)

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Investigation of morphology, electrical behavior (AC and DC) and CO

The AC and DC electrical properties of sandwich devices fabricated with silicon (Si), porous silicon (PSi) and nanolayers of bromo aluminum phthalocyanine with aluminum electrodes (Al/Si/Al, Al/Si/PSi/Al, Al/Si/BrAlPc/Al and Al/Si/PSi/BrAlPc/Al) were examined over the voltage, frequency and temperature range of 0–11 mV, 102–105 Hz and 303–423 K respectively. Morphology of the samples was studied via scanning electron microscope (SEM) images and X-ray diffraction (XRD) micrographs. Capacitance is practically independent of frequency (f) in the range of 102–104 Hz, whereas it is extremely frequency dependent for f > 104 Hz. Dissipation factor decreased with increasing frequency to a minimum value and increased noticeably thereafter. Capacitance and dissipation factor are almost independent of temperature; capacitance increases with increasing temperature for T > 380 K. The AC electrical behavior of sandwich devices has been shown to be in agreement with the model of Goswami and Goswami. According to our data the Al contact in sandwich devices is of ohmic type and the tunneling mechanism is applicable in explaining the DC conduction process. The Al/Si/PSi/BrAlPc/Al device, compared to other devices, exhibits the highest sensitivity to CO2

Electrical Behaviour of Nanostructured Porous Silicon

The electrical behaviour of porous silicon layers has been investigated on one side of p-type silicon with various anodization currents, electrolytes, and times. Electron microscopy reveals the evolution of porous silicon layer morphology with variation in anodization time. In this work electrical conductivity of bulk silicon and porous layer which is formed by electrochemical etching is compared due to I-V measurements and calculation of activation energy. We have also studied the dependence of porous silicon conductivity on fabrication conditions. Also the effect of the temperature on conduction of porous silicon at different frequencies is investigated. At last dependence of capacitance on the temperature was probed at $10^2 - 10^5$ Hz frequency range

Electrical Behaviour of Nanostructured Porous Silicon

The electrical behaviour of porous silicon layers has been investigated on one side of p-type silicon with various anodization currents, electrolytes, and times. Electron microscopy reveals the evolution of porous silicon layer morphology with variation in anodization time. In this work electrical conductivity of bulk silicon and porous layer which is formed by electrochemical etching is compared due to I-V measurements and calculation of activation energy. We have also studied the dependence of porous silicon conductivity on fabrication conditions. Also the effect of the temperature on conduction of porous silicon at different frequencies is investigated. At last dependence of capacitance on the temperature was probed at $10^2 - 10^5$ Hz frequency range

Electrical and gas sensing properties of polyaniline-chloroaluminium phthalocyanine composite thin films

Electrical and gas sensing properties polyaniline-chloroaluminium phthalocyanine (PAni-ClAlPc) composite thin films were investigated to study the gas sensing behavior of composites. Devices (chemiresistor gas sensors) were prepared by spin coating method from PAni as the base of composites and ClAlPc (with different concentrations) as the second component onto interdigitated electrodes. The sensitivity, reversibility, response and recovery time of these thin films on exposure to different concentrations (0–2000 ppm) of CO2 gas and the suitability of different composites as materials to be used in practical gas sensors at different temperatures were investigated. The sensitivity factor of composites was obtained in a range between 0.05–7.20. PAni + 10% ClAlPc was the perfect candidate composite to fabricate gas sensor at 300 K and PAni + 15% ClAlPc at 350 K. Thus, (PAni-ClAlPc) composites have better response than pure PAni. After that, devices were exposed to humidity, an unexpected behavior was absorbed. Conductivity of thin films were increased on exposure lower RH% and decreased on higher RH%. Finally, 1000 ppm CO2 was mixed to humidity and introduced to chamber, obtained results showed the CO2 mixtures decreased the sensitivity of thin films in compare with pure CO2

Optical and electrical properties of nanostructured heterojunction (Au|PdPc|ClAlPc|Al) and using as O

Nanostructure thin films and sandwich devices of palladium phthalocyanine (PdPc) and chloro-aluminum-phthalocyanine (ClAlPc) were prepared by thermal evaporation technique. Optical and struc- tural properties of nanostructure thin films were investigated by XRD, SEM and optical absorption. The SEM images demonstrated PdPc (40–60 nm) and ClAlPc (30–50 nm) nanostructures. XRD pat- terns showed that thin films are in α-phase at room temperature. Also, optical bandgap energy of thin films was calculated by optical absorption spectra. Heterojunction (Au|PdPc|ClAlPc|Al) and single layer (Au|PdPc|Al and Au|ClAlPc|Al) devices were fabricated. Electrical measurements demonstrated the semi-conducting and photo-conducting behavior of thin films. After that, devices were exposed to different concentrations of O2 at 300 K and 350 K and conductivity of thin films was increased on exposure to O2 . Heterojunction devices were more sensitive than other thin films and had better response and reversibility in comparison with single layer devices at 350 K. Finally, 10% O2 was mixed with different percentages of relative humidity and all results showed that the conductivity of thin films is reduced on exposure to O2 mixed to humidity

Electrical and optical properties of an organic semiconductor metal-free phthalocyanine (C

In a recent work we calculated some electronic properties of metal-free phthalocyanine such as band structure, density of states and energy gap. We have also presented some optical properties such as dielectric function, electrical loss function, optical conduction, absorption and refractive index, some of which have never been studied before. Calculations were performed in the framework of density functional theory (DFT), using the full-potential linearized augmented plane wave (FP-LAPW) method. This study presents the electrical gap energy of metal-free phthalocyanine to be Eg = 2.4 eV which is in good agreement with experimental data. A trap energy level is also observed. Optical band gap is about 2.48 eV with an optical trap level at 1.48 eV. In addition, we obtained the static refractive index in the x-, y- and z-directions as n0xx = 2.43, n0yy = 2.06 and n0zz = 2.32. Finally, absorption spectra display the existence of strong absorption bands at the wavelengths of 400 and 800 nm which compare favorably with experimental results