Soluble phthalocyanines as optical gas sensing materials

A novel soluble phthalocyanine compound, i.e zinc phthalocyanine (sulfonamide) has been synthesized by chemical substitution of zinc phthalocyanine and used to produce thin solid films by means of the spin coating technique. The chemical structure of the spin coated films has been investigated by FT-IR analysis. Atomic Force Microscopy (AFM) has been used to characterize the film morphology and to measure the film thickness. The spin coated films have been tested as optical sensing materials of volatile organic compounds such as methanol, ethanol and 2-propanol. The change of optical reflectance of the films upon exposure to alcohol-vapour-containing atmospheres has been measured versus alcohol concentration and exposure time. The films exhibit a fast and reproducible response, with a complete and fast recovery in methanol and ethanol-containing atmospheres, while diffusion-driven effects appear during exposure to 2-propanol. The response and sensitivity of the films to ethanol vapour is higher than to methanol and 2-propanol

Porphyrin-containing polyimide films deposited by high vacuum co-evaporation

Abstract Thin films of porphyrin-containing polyimide were produced by high vacuum co-evaporation of 4,4′-hexafluoroisopropylidene diphthalic anhydride (6FDA), 3,3′-diaminodiphenyl sulfone (DDS) and 5,10,15,20 meso-tetraphenyl porphyrin (TPP). The films were characterized by FT-IR analysis, optical absorption and emission spectroscopy. FT-IR analysis shows that the film matrix is comprised of only unreacted monomers. The conversion of monomers to polyamic acid and the following condensation to polyimide were studied by curing the samples at temperatures up to 240 °C. The amount of polyamic acid increases from room temperature to 120 °C, while at higher temperature it starts to condense to polyimide. Optical analysis shows that TPP is incorporated in the film matrix and its chemical state is determined by the interaction with the monomers, polyamic acid and polyimide. After curing the TPP molecules are finely dispersed in the polyimide matrix and their absorption and fluorescence properties are wholly preserved

Vapour Deposition Techniques for Producing Advanced Optical Materials

Vapour Deposition Techniques for Producing Advanced Optical Material

Production of novel microporous porphyrin materials with superior sensing capabilities

New robust microporous cobalt 5,10,15,20-meso-tetraphenyl porphyrin (CoTPP) thin films for sensing applications have been produced by a novel plasma-based deposition technique named Glow Discharge Induced Sublimation (GDS). CoTPP films have been also produced by conventional vacuum evaporation (VE) and spin coating (SPIN) methods for comparison. The chemical properties of the films were assessed by FT-IR and ESI-MS analyses demonstrating the integrity and the purity of the GDS films. The physical properties of the samples were thoroughly analysed: thickness measurements coupled with surface density analyses showed the impressive free volume of the GDS samples (30 times higher than that of VE ones), SEM images show the extremely rough morphology of GDS samples, and physisorption measurements indicate both the extremely high specific surface area (184 m2 g−1) and the microporosity of the GDS porphyrin films. The sensing capabilities of the samples were investigated by exposing them to low concentrations of NO2 and by monitoring their optical absorption changes. These measurements clearly demonstrate that the GDS process leads to superior sensing materials as a result of the distinctive attainable molecular architectures. GDS-grown CoTPP sensors exhibit very high intense and sensitive responses as well as faster responses and much lower detection limits (<1 ppm) than conventionally deposited ones. Finally, the repeatability and reproducibility of sorption–desorption processes demonstrate the robustness of these assemblies. The GDS method can be extended to several other organic receptors, opening the way for the production of new improved sensing materials

Plasma-deposited copper phthalocyanine: A single gas-sensing material with multiple responses

Copper phthalocyanine (CuPc) thin films have been deposited by glow discharge-induced sublimation (GDS). This physical technique allows to produce very high porosity films, whose response to gases is much more intense than evaporated films. It has been found that both electrical and optical properties of these films change upon gas exposure due to the gas/film interaction. Electrical response of the films has been tested by exposing the samples to NOx-containing atmospheres and by measuring the slope of the electrical surface current versus gas concentration. This way NO2 and NO concentrations down to 0.1ppm and 10ppm have been measured, respectively, with response times shorter than 2min. Optical responses have been tested by measuring the change of light reflectance at a fixed wavelength upon exposure to ethanol-containing atmospheres down to concentrations of few thousands of ppm. Response times of less than 10s have been obtaine

Deposition and characterization of luminescent Eu(tta)3phen- doped parylene-based thin-film materials

Herein, novel host-guest films produced by coarse vacuum cosublimation of the parylene C dimer and Eu(tta)3 phen are prepared and studied. Eu(tta)3 phen sublimation at different temperatures allows films with different concentrations of the Eu complex to be obtained. The films are characterized by Rutherford backscattering spectrometry (RBS), FTIR spectroscopy, X-ray diffraction (XRD), atomic force microscopy (AFM), and UV/Vis absorption and emission spectroscopy. RBS, FTIR, and XRD reveal the incorporation of Eu(tta)3 phen into the parylene matrix. AFM evidences the very flat film surface, which is particularly advantageous for optical applications. UV/Vis absorption and emission analyses confirm that the optical properties of Eu(tta)3 phen are preserved in the deposited films. Fluorescence measurements evidence the occurrence of an energy-transfer process between parylene and Eu(tta)3 phen, and this results in an increase in the light emitted by the Eu complex that is as much as five times higher than that emitted by Eu(tta)3 phen alone

Vacuum-evaporated cavitand sensors: Dissecting specific from nonspecific interactions in ethanol detection

High vacuum evaporation (VE) is used for the first time to grow thin films of novel tetraphosphonate, Tiiii[H, CH3, Ph], and tetrathiophosphonate, TSiiii[H, CH3, Ph], cavitands for gas sensing applications. The sublimation rate of the compounds was monitored during the depositions and related to the final physical properties of the samples. The properties of deposited films were investigated by various techniques. FT-IR and ESI-MS indicate that the samples consist of pristine cavitand molecules and demonstrate the high purity of the VE films. AFM images show the Tiiii and TSiiii films to possess similar thickness and globular morphology. These physical analyses indicate the uniformity and homogeneity of the final samples as well as the high reproducibility of the VE technique. The sensing capabilities of the samples were investigated by exposing Tiiii- and TSiiii-coated QCMs to ethyl alcohol in very low concentrations. The sensitivity, the speed, and the detection limit of the samples were determined, indicating highly competitive sensing capabilities. Elovich kinetics and Langmuir−Henry isotherms were used to analyze the sorption process occurring onto the different samples and showed that, whereas TSiiii samples consist mainly of unspecific adsorption sites, Tiiii films show specific active sites where analyte molecules can be trapped and detected

Development of new H2TPP porphyrin films with improved optical sensing capabilities

In this work novel 5,10,15,20 meso-tetraphenyl porphyrin (H2TPP) films have been deposited by means of a new physical technique named glow discharge induced sublimation (GDS). A preliminary characterization has been performed by means of scanning electron microscopy (SEM) and Fourier transform infra-red (FT-IR) analyses. SEM images and infra-red analyses highlight the great surface roughness and the high purity of GDS films, respectively. For comparison, H2TPP films have been also deposited by means of spin coating (SPIN) technique. Optical sensing measurements, performed in differently concentrated ethyl alcohol (EtOH) atmospheres, highlight that GDS samples yield higher response intensities than SPIN films, very short response times and complete recovery

Production and characterization of thin film materials for indoor optical gas sensing applications

Pure and Nile-Red-doped polyimide and porphyrin films have been deposited and their optical response to different organic vapours has been tested. Polyimide films were obtained by spin coating a solution containing 4, 4'-4, 4'-(hexafluoroisopropylidene) diphthalic anhydride and 2, 3, 5, 6-tetramethyl-1, 4-phenylenediamine. Free, cobalt and iron chloride 5, 10, 15, 20 meso-tetraphenyl porphyrin films were deposited by spin coating and by high vacuum evaporation. Exposure to water, ethanol and isopropanol vapours produce reversible changes of the fluorescence features of both pure and doped polyimide films. Exposure to methanol, ethanol and isopropanol vapours gives rise to changes of the optical absorption of porphyrin films. The results of the optical measurements point out that the synthesized films can be used for the detection of volatile organic compounds