Phthalocyanine Materials Research Articles

Promoting Oxygen Reduction Reaction by Inducing Out-of-plane Polarization in Metal Phthalocyanine Catalyst.

Metal phthalocyanine (MPc) materials with well-defined MN4 moiety offers a platform for catalyzing oxygen reduction reaction (ORR), while their practical performances are often limited by the insufficient O2 adsorption due to the planar MN4 nature. Here, we proposed a design (called as Gr-MG -O-MP Pc) that the metal of MPc (MP ) is axially coordinated to a single metal atom in graphene (Gr-MG ) through a bridge-bonded oxygen atom (O), introducing effective out-of-plane polarization to promote O2 adsorption on MPc. Manipulating the out-of-plane polarization charge by varying types of MP and MG (MP = Fe/Co/Ni, MG = Ti/V/Cr/Mn/Fe/Co/Ni) in the axial coordination zone of -MG -O-MP - were examined by density functional theory simulations. Among them, the catalyst of Gr-V-O-FePc stands out with the highest calculated O2 adsorption energy, which was synthesized successfully and verified by systemic X-ray absorption spectroscopy measurements. Importantly, it delivered a remarkable ORR performance with half-wave potential of 0.925V (versus RHE) and kinetic current density of 26.7mA cm-2 . This thus demonstrates a new and simple way to pursue high catalytic performance by inducing out-of-plane polarization in catalysts. This article is protected by copyright. All rights reserved.

Sensor application and mathematical modeling of new Zn(II) phthalocyanine containing 26-membered tetraoxadithia macrocycle moieties

A novel phthalonitrile containing 26-member tetraoxadithia macrocycle moiety was synthesized in a multistep reaction sequence. New zinc(II) phthalocyanine was obtained by the cyclomerization reaction of this macrocyclic phthalonitrile. The novel phthalocyanine and the precursor compounds have been characterized by a combination of 1H and 13C NMR, FT-IR, UV–vis, elemental analysis and MALDI-TOF mass spectral data. 26-membered phthalocyanine was used to fabricate multilayered Langmuir-Blodgett (LB) thin films dedicated to investigating the gas sensing properties of these novel phthalocyanine materials. SEM images of the uncoated substrate, 8-layered and 16-layered LB thin films were compared to observe the successfully transferred layer by layer onto the solid substrates. Sensor parameters such as selectivity, reproducibility, thickness effect, recovery and response rates were examined for highly toxic benzene and toluene vapors using the mass sensitive Quartz Crystal Microbalance (QCM) technique. The first time the thickness effect on the gas sensing mechanism for selected material was also investigated. Validation of the experimental measurements of QCM kinetic was implemented using nonlinear autoregressive with exogenous input neural network for modelling using the frequency shift value. Comparison of these frequency shift of artificial neural network with real-experimental data showed the accuracy of the artificial neural network model.

Carrier mobility in field effect transistors based on copper-phthalocyanine thin films with different phase structure

Using annealing procedure at different temperatures after deposition at room temperature we obtained copper- phthalocyanine (CuPc) thin films with a — and p —phase structure. A phase structure of thin films was controlled by X-ray diffraction method, morphology was controlled by SEM. The field effect transistors was fabricated by high vacuum deposition of CuPc thin film (thickhess of 100 nm) on Si02 substrate which acting as gate contact. Gold drain and source contacts deposited on the top of active layer of FET. From measured current voltage measurements calculated mobility and concentration of charge carriers in FET. These parameters depend on phase structure of CuPc thin film, and characteristics of our FET are comparable with values of other authors.
 CuPc is commercially available macro cyclic metal complex that can be easily obtained in large quantity and high purity. Together with other phthalocyanine derivatives, the chemically and thermally stable CuPc has wide applications in dye processing, spectral sensitization, chemical sensors, and optical data storage [3-4]. The semiconducting behavior of metal phthalocyanines was first observed in 1948 and they have since attracted great interest in advancement of protptype organic semiconductors. Among the metal substituted phthalocyanines CuPc has been found superior properties [5-7], such as phenomena of field dependent and wavelength-dependent efficiency in an organic static induction transistors, and stabilizing role of CuPc layer on a highly stable organic electroluminescent device based on thin film Alq, and indicated a very weak interaction between CuPc and Au at the interface.
 In general, phthalocyanine materials can exist in several crystalline polymorphs, including a-, p -, x-and y - structure, and the most well known are the thermally metastable a- and p - [8-10], Phthalocyanine films deposited at room temperature usually consist of a-phase crystallites (at sublimation pressure of less than 10 Pa). At higher deposition pressures or at substrate temperature above 210°C, the p -phase directly obtained [11], Although it is well known that a-phase crystallites undergo a phase transformation into P -phase by treatment in various organic suspension media [12,13] or during annealing at higher temperatures [14,15], only some authors describe the nature of the a—>p phase transformation of copper phthalocyanine thin films with a thickness of less than 100 nm [8,14-15].

Oxygen plasma induced interfacial CoOx/Phthalocyanine Cobalt as bifunctional electrocatalyst towards oxygen-involving reactions

Performance of electrocatalysts towards oxygen-involving reactions is strongly associated with the surface and interface properties. Cobalt phthalocyanine (CoPc) materials have been widely explored as oxygen-involving electrocatalysts but their intrinsic catalytic activity is always poor. We present here a surface oxygen plasma approach to directly treat CoPc for producing interfacial CoO x nanodots anchored on CoPc (CoO x /CoPc), which exhibits high activity towards both oxygen reduction reactions (ORR) and oxygen evolution reactions (OER). The optimized CoO x /CoPc demonstrates a much better catalytic activity with a half-wave potential of 0.63 V and an average electron transfer number of 3.64 than the CoPc (0.59 V and n = 2.37) towards ORR in alkaline media. Moreover, OER performance of the CoO x /CoPc is also significantly enhanced, showing a current density of 22.2 mA cm −2 that is 36 times higher than that of CoPc (0.6 mA cm −2 ) at an overpotential of 0.49 V. It is found that the enhanced performance of the CoO x /CoPc is attributed to the high electrochemical active surface area, highly active CoO x , as well as desired interfacial structure. • Oxygen plasma inducing strategy has been firstly employed to modify bulk CoPc. • Highly active CoO x nanodots are in-siut generated on the surface of CoPc. • The desired interfacial structure between CoO x nanodots and CoPc is formed. • ORR and OER performance of the CoO x /CoPc were significantly enhanced. • The plasma inducing strategy could be extended to fabricate other heterogeneous catalysts.

α-Periodicity is Spontaneously Phased in an Acicular Sulfuric-Recrystallized Precipitate of Copper Phthalocyanine

A persuasive α-polymorphous inherency in sulfuric-recrystallized phthalocyanine materials is rooted out. The tessellation is a transformational and heritable hybrid from a phthalocyanine representative’s sulfate state to its sulfate-free one in spontaneous α-recrystallization. The structural hallmark of a residual precursor is absent as long as the anhydrous sulfuric-acid molecules are allowed for coordinate phthalocyanine material bases. In the exclusion from powdery remains, our devotional interpretation of acicular sulfate provides the less incautious fidelity. In the 7-day-open systems, the slurry of acicular sulfate is IR-behaviorally and tinctorially analogous to its rinsed one. The IR-analogy intuitively embodies the interplay among sulfate sediment, separative liquid layer and extraterritorial air contact. To undermine the open slurry less intricately, the strategy relies on the removal of sulfuric liquid in the IR-incident as-precipitated sulfuric slurry. A fall in the liquid neighbor shifts and intensifies the pivot fingerprint from 729-close slide to 720-close one (cm-1) with a green-bluish shade in the sulfate cluster. A puny blue variation in hue indicates that an acicula is in partial distress of sulfate species during β-to-α alignment. We suggest a convincing path for the coexistence of a crystalline manifold in the acicula. Mobile water and active sulfuric-acid molecules interdiffuse at the surface of a sulfate when the sulfate experiences an unbearably compositional change in the vicinal sulfuric liquid. The interdiffusion rearranges the newborn β-stack into α-dominant, β-runner-up, and their intermediate in the acicular sulfate. The contractile convective convert infers the tendency of outright α-arrangement no longer lingers under spontaneous dilution.

Donor–acceptor conjugates-functionalized aluminum phthalocyanines: Photophysical and nonlinear optical properties

Photoinduced electron transfer/energy transfer (PET/ET) plays a very important role in improving the nonlinear optical (NLO) response. AlPc-Aqn and HAlPc-Aqn with donor-acceptor (D-A) structure were prepared by grafting aluminum phthalocyanine (AlPc) and hyperbranched aluminum phthalocyanine (HAlPc) through anthraquinone axial covalent bonding. After the axial covalent connection, the formed D-A phthalocyanine materials enhance the PET/ET process between the phthalocyanine ring and the anthraquinone structure, which results in significant fluorescence quenching and effectively improves the material's NLO properties. The discrepancy of LUMO levels (ΔE) further confirms that both AlPc-Aqn and HAlPc-Aqn formed a D-A system. This effectively promotes the electron transfer between the anthraquinone and the phthalocyanine ring, performing enhanced NLO response. Furthermore, compared to AlPc-Aqn, the special three-dimensional structure of HAlPc-Aqn brings a more efficient PET/ET process and exhibits a larger nonlinear absorption coefficient.

A growth of A–Z phthalocyanine layers onto Si by thermal evaporation process to achieve organic heterojunction diodes

Thermally evaporated organic heterojunction (OHJ) diodes based on A–Z phthalocyanine (ZnPc/pSi and AlPc/Si) are investigated. Here, we study the electronic parameters of ZnPc/pSi and AlPc/Si organic heterojunction diodes. Such organic heterojunctions are produced by thermal evaporation process in vacuum at very low pressure. For this purpose, the current–voltage (I–V) characteristics at room temperature under dark conditions for the organic aluminum and zinc (A–Z) phthalocyanine materials are measured. Firstly, the electronic parameters of the organic heterojunctions including ideality factor n, barrier height (Φb), series resistance (RS) are extracted via Cheung and Norde methods respectively. A high rectification ratio (RR) in order of 2 × 104 is recorded for ZnPc/p-Si contacts. Non-ideal behavior of AZPc OHJ is revealed n ∼ 2.4, series resistance and barrier height are of 2 kΩ and 0.4 eV. Secondly, the conduction mechanism of both AlPc/Si and ZnPc/Si contacts are investigated. SCLC is the dominated conduction mechanism throughout the OHJ device.

Novel axially substituted lanthanum phthalocyanines: Synthesis, photophysical and nonlinear optical properties

Materials with excellent nonlinear optical (NLO) properties are usually applied in optoelectronics and optical limiting devices. Photoinduced intramolecular electron transfer (PET) and energy transfer (ET) play an important role in enhanced NLO properties. Through axially connected anthraquinone to phthalocyanine, two types of novel lanthanum phthalocyanine (LaPc-Aqn and HLaPc-Aqn) were designed to effectively improve PET/ET process, and thus leading to excellent NLO properties. Hyperbranched phthalocyanines possess enhanced NLO properties owing to their special three-dimensional structures that have more donor–acceptor (D–A) systems in their cell structure than lanthanum phthalocyanines. The uniform polyphenylsulfone composite film(HLaPc-Aqn-PPSU) was prepared by a simple solution casting method according to the “like dissolves like” theory. The values of large third-order nonlinear susceptibility (Im[χ(3)]) and low limit threshold (Ilim) were 1.51 × 10−9 esu and 0.015 J/cm2, respectively, demonstrating that the film had great optical limiting performance. Such research can contribute to the development of novel phthalocyanine materials for nonlinear optics and optical limiting devices.

Development of catalysts for ammonia synthesis based on metal phthalocyanine materials

Highly efficient and very stable iron and/or cobalt-based catalysts for the ammonia synthesis reaction were synthesized by one-step pyrolysis of metal phthalocyanine precursors.

Kinetically Controlled Self-Assembly of Phthalocyanine–Peptide Conjugate Nanofibrils Enabling Superlarge Redshifted Absorption

Supramolecular assembly could in principle lead to redshifted absorption through J-aggregation of chromophores, which would be a highly promising method for achieving near-infrared materials with improved functionality and flexibility. To effectively enhance the material functionalities, one of the great challenges remaining is to achieve an aggregation state with a redshift larger than 100 nm. Conventional assemblies that are mostly thermodynamically controlled have a limited redshifted absorption of less than 30 nm. In this work, using a model phthalocyanine–peptide conjugate compound, we achieved the first fabrication of phthalocyanine-based near-infrared materials with a superlarge absorption redshift of 105 nm by a kinetically controlled self-assembly strategy. In this kinetically controlled self-assembly process, sufficient rearrangement of intermolecular aggregates to an ordered structure is revealed to be crucial to facilitate the formation of nanofibrils instead of nanoparticles, which are formed via a general rapid self-assembly pathway under thermodynamic control. The superlarge redshift in the absorbance of assembled nanofibrils originates from the orderly stacked phthalocyanine chromophores, which enable a charge transfer state through more effective intermolecular orbital overlapping. The kinetically controlled J-aggregation state of the phthalocyanine–peptide conjugate with superlarge redshifted absorption not only opens an unprecedented route toward novel near-infrared phthalocyanine materials but also holds great promise for revealing general design principles for various organic dye materials.

Phthalocyanine Photoregeneration for Low Power Consumption Chemiresistors.

It is well-known that the applicability of phthalocyanine chemiresistors suffers from long recovery time after NO2 exposure. This circumstance enforces the necessity to operate the sensors at elevated temperatures (150-200 °C), which shortens the sensor lifetime and increases its power consumption (regardless, a typical measurement period is longer than 15 min). In this paper, we propose a new method for fast and effective recovery by UV-vis illumination at a low temperature (55 °C). The method is based on short illumination following short NO2 exposure. To support and optimize the method, we investigated the effects of light in the wavelength and intensity ranges of 375-850 nm and 0.2-0.8 mW/mm2, respectively, on the rate of NO2 desorption from the phthalocyanine sensitive layer during the recovery period. This investigation was carried out for a set of phthalocyanine materials (ZnPc, CuPc, H2Pc, PbPc, and FePc) operating at slightly elevated temperatures (55-100 °C) and was further supported by the analysis of UV-vis and FTIR spectral changes. We found out that the light with the wavelength shorter than 550 nm significantly accelerates the NO2 desorption from ZnPc, CuPc, and FePc, and allows bringing the measurement period under 2 min and decreasing the sensor power consumption by 75%. Possible mechanisms of the light-stimulated desorption are discussed.

Graphene wrapped phthalocyanine: Enhanced oxidative desulfurization for dibenzothiophene in fuel

Graphene wrapped metal phthalocyanine (MPc/RGO, M = Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+) composites are synthesized by a facile ‘in situ hydrothermal’ method, using graphene oxide, M (CH3COO)2 and phthalic anhydride as the precursors. A biomimetic catalytic system of MPc/RGO and molecular O2 have high activity for ultra‐deep removal of dibenzothiophene (DBT) in model oil containing n‐octane. Compared with pure graphene oxide and MPc, MPc/RGO composites displayed highly enhanced catalytic activity for the oxidation of dibenzothiophene in n‐octane. The conversion ratio of DBT was up to 97.51% after 180 min treatment at 60 °C and atmospheric pressure. The photostability of RGO/MPc composites photocatalystic degradation of dibenzothiophene was investigated. Mechanistic studies revealed that the RGO/MPc − O2· species were the main active intermediate via the π‐π stacking interaction of MPc and RGO. The RGO wrapped phthalocyanine materials offer great potential as active photocatalysts for degradation of thiophene derivatives in fuel.

Effect of Substrate Temperature on Twin Donor Layer Organic Solar Cell

The growth mechanism of the active layers of twin donor layer organic solar cell based on zinc and copper phthalocyanine materials at different substrate temperature and its influence on the device performance has been investigated. AFM measurements show the variation of morphology of the thin films with different substrate temperature. Devices with active twin layer deposited in 150 °C are found to have the highest short circuit current 1.26 mAcm-2 and show the highest efficiency 0.2%. The other electrical characteristics of the as fabricated devices were obtained by investigating the current–density (J-V) curve, the fill factor (FF) and external quantum efficiency (EQE) and electrochemical impedance spectroscopy (EIS) analysis.

Performance of a fabricated nanocomposite-based capacitive gas sensor at room temperature

In this research, we synthesized a nanocomposite based on pyrrole-bromoaluminum phthalocyanine materials and proposed an interdigitated capacitive electrode for H2S gas sensing. In this framework, we devoted particular attention to AC electrical measurements of the device on exposure to gas rather than resistance measurement. Nanostructured thin films of the nanocomposite were prepared on precoated interdigitated aluminum electrodes using electron-beam evaporation technique, which were characterized using field emission scanning electron microscopy (FESEM). FESEM micrographs show films are uniform with densely packed nanoparticles. The AC electrical measurements were performed in 1, 10 and 100 kHz frequency at room temperature. Since the best sensor response was achieved for 1 kHz frequency, we limited the analysis to that Frequency. Gas sensing performance of the nanocomposite device results in fast response and good stability over the first 2 months to 100 ppm H2S gas by monitoring the changes in capacitance at the 1 kHz frequency. It produces 61% and 28% of the first response after 2 and 4 months, respectively which indicating lack of long-term stability. Our results show that the fabricated nanocomposite-based capacitive gas sensor may be used as a disposable sensing device by means of a simple and cost-effective construction method.

Four Dibutylamino Substituents Are Better Than Eight in Modulating the Electronic Structure and Third-Order Nonlinear-Optical Properties of Phthalocyanines.

2(3),9(10),16(17),23(24)-Tetrakis(dibutylamino)phthalocyanine compounds M{Pc[N(C4H9)2]4} (1-5; M = 2H, Mg, Ni, Cu, Zn) were prepared and characterized by a range of spectroscopic methods in addition to elemental analysis. Electrochemical and electronic absorption spectroscopic studies revealed the more effective conjugation of the nitrogen lone pair of electrons in the dibutylamino side chains with the central phthalocyanine π system in M{Pc[N(C4H9)2]4} than in M{Pc[N(C4H9)2]8}, which, in turn, results in superior third-order nonlinear-optical (NLO) properties of H2{Pc[N(C4H9)2]4} (1) over H2{Pc[N(C4H9)2]8}, as revealed by the obviously larger effective imaginary third-order molecular hyperpolarizability (Im{χ((3))}) of 6.5 × 10(-11) esu for the former species than for the latter one with a value of 3.4 × 10(-11) esu. This is well rationalized on the basis of both structural and theoretical calculation results. The present result seems to represent the first effort toward directly connecting the peripheral functional substituents, electronic structures, and NLO functionality together for phthalocyanine molecular materials, which will be helpful for the development of functional phthalocyanine materials via molecular design and synthesis even through only tuning of the peripheral functional groups.

Asymmetry and electronic directionality: a means of improving the red/near-IR-light-responsive photoactivity of phthalocyanine-sensitized carbon nitride

Extremely efficient photocatalytic H2 production with a turnover number (TON) of 25 002 for 20 h over graphitic carbon nitride (g-C3N4) sensitized by zinc phthalocyanines (ZnPcs) with asymmetric and electronic directional structures is successfully carried out under λ ≥ 500 nm light irradiation, and an impressive apparent quantum yield (AQY) higher than 1.0% is obtained under 700 nm monochromatic light irradiation. Based on the photoactivity, photofluorescence (PL), time-resolved fluorescence spectroscopy (TRFS), photocurrent, and electrochemical impedance spectroscopy (EIS) results, it is found that the asymmetry and electronic directionality of ZnPcs can significantly influence the photogenerated electron transfer between ZnPcs and g-C3N4 and further influence the photocatalytic H2 production activity of the phthalocyanine-sensitized g-C3N4 system. The present work exhibits the promising application of phthalocyanine materials in extending red/near-IR light utilization and gives some suggestions and routes for the design and synthesis of phthalocyanine derivatives for solar energy conversion applications.

Synthesis, Characterization and Electrochemical Investigation of Phthalocyanine Compounds Bearing Fluorine Functionality

Peripherally substituted symmetrical phthalocyanine derivatives have the potential to use in a wide range of high technology applications, such as in catalysis, in photodynamic therapy, in electrochromic display devices, and as a molecular electronics, or magnetic devices. Phthalocyanines possess an extended π-conjugated electron system which permits π stacking between planar macrocycles. Adding substituents to the periphery of the macrocycles increases their solubility since these substituents increase the distance between the stacked phthalocyanines and enable their solvation. The phthalocyanine complexes are also electrochemically precious complexes due to their excellent electrochemical behaviors. It is well known that the different functionalities changes the features of the MPc complexes, thus electrochemical properties of these complexes should be investigated for possible applications. [1-3]We present here the syntheses of tetra-substituted fluorine containing biphenyl-malonic ester groups bearing phthalocyanine derivatives with different central metal atoms and investigation of their electrochemical behaviors. All synthesized novel phthalocyanine compounds have been characterized by using their elemental analyses, FT-IR, UV-Vis, 1H NMR, 13C NMR and mass spectroscopic methods. The electrochemical activity of phthalocyanine derivatives were also evaluated from the current–voltage curves obtained by cyclic and differential pulse voltammetric methods. REFERENCES 1- A. Koca, Y. Arslanoğlu, E. J Electroanal Chem, 616 (2008), pp. 107–116 2- N.B. Mckeown, B. Dunn, J.W. Goodby, A.R. West (Eds.), Phthalocyanine materials: synthesis, structure and function, Cambridge University Press, Cambridge (1998) 3- H.S. Nalwa, J.S. Shirk, C.C. Leznoff, A.B.P. Lever (Eds.), Phthalocyanines: properties and applications, VCH Publishers Inc, New York (1996), pp. 79–181.

Dry Etching of Copper Phthalocyanine Thin Films: Effects on Morphology and Surface Stoichiometry

We investigate the evolution of copper phthalocyanine thin films as they are etched with argon plasma. Significant morphological changes occur as a result of the ion bombardment; a planar surface quickly becomes an array of nanopillars which are less than 20 nm in diameter. The changes in morphology are independent of plasma power, which controls the etch rate only. Analysis by X-ray photoelectron spectroscopy shows that surface concentrations of copper and oxygen increase with etch time, while carbon and nitrogen are depleted. Despite these changes in surface stoichiometry, we observe no effect on the work function. The absorbance and X-ray diffraction spectra show no changes other than the peaks diminishing with etch time. These findings have important implications for organic photovoltaic devices which seek nanopillar thin films of metal phthalocyanine materials as an optimal structure.

Microstructured electrodeposited polypyrrole–phthalocyanine hybrid material, from morphology to ammonia sensing

Hybrid materials combining polypyrrole with ionic macrocycles as counterions are electrosynthesized at the surface of platinum interdigitated electrodes. The chemical composition of the hybrid films is characterized by infrared reflexion absorption spectroscopy (IRRAS) and glow discharge optical emission spectroscopy (GDOES) and their morphology is studied by a range of techniques such as optical topomicroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The obtained films reveal to be more homogeneous, with smaller crystallites, compared to polypyrrole synthesized with small counterions. Finally, the films exhibit a higher sensitivity to ammonia, with a very good reversibility and with a stable response in a broad range of relative humidity. Overall, we present the advantages of combining ionic phthalocyanines with polypyrrole in enhancing the properties of the final material. Synergetic effects in the structure and properties of polypyrrole–phthalocyanine materials open the way to their development in the field of hybrid material and their use in chemosensing.

Structures and Redox Characteristics of Electron-Deficient Vanadyl Phthalocyanines

The first single-crystal X-ray structures of substituted vanadyl phthalocyanine materials reveal the high-valence vanadium ions (denoted as V(IV)), whose coordination by a highly electron-deficient ligand is facilitated by an axial oxo group. The metal center of the hydrophilic V═O core, encapsulated in F-rich hydrophobic pockets, reaches a coordination number of 6 by binding an additional H(2)O that, in turn, hydrogen-bonds with ketones, resulting in solvent-induced variable solid-state architectures. Fluoroalkyl (R(f)) ligand substituents hinder π-π stacking interactions and favor ordered long-range packing, as well as the facile formation of film materials that exhibit high thermal stability and oxidation resistance. Reversible redox chemistry and spectroscopic studies in both solution and the solid-state indicate single-site isolation in both phases and an R(f)-induced propensity for electron uptake and inhibition of electron loss. Repeated redox cycles reorganize the thin films to accommodate Li(+) ions and facilitate their migration. The facile reduction, combined with high stability and ease of sublimation imparted by the R(f) scaffold that suppresses oxidations, recommends the new materials for sensors, color displays, electronic materials, and redox catalysts, as well as other applications.