Metal Phthalocyanine Nanoribbons and Nanowires

New Folding 2D-Layered Nitro-Oxygenated Carbon Containing Ultra High-Loading Copper Single Atoms

The discoveries of 2D nanomaterials have made huge impacts on the scientific community. Their unique properties unlock new technologies and bring significant advances to diverse applications. Herein, an unprecedented 2D-stacked material consisting of copper (Cu) on nitro-oxygenated carbon is disclosed. Unlike any known 2D stacked structures that are usually constructed by stacking of separate 2D layers, this material forms a continuously folded 2D-stacked structure. Interestingly, advanced characterizations indicate that Cu atoms inside the structure are in an atomically-dispersed form with extraordinarily high Cu loading up to 15.9 ± 1.2 wt.%, which is among the highest reported metal loading for single-atom catalysts on 2D supports. Facile exfoliation results in thin 2D nanosheets that maximize the exposure of the unique active sites (two neighboring Cu single atoms), leading to impressive catalytic performance, as demonstrated in the electrochemical oxygen reduction reaction.

Magnetic nanoribbons with embedded cobalt grown inside single-walled carbon nanotubes

Molecular magnetism and specifically magnetic molecules have recently gained plenty of attention as key elements for quantum technologies, information processing, and spintronics. Transition to the nanoscale and implementation of ordered structures with defined parameters is crucial for advanced applications. Single-walled carbon nanotubes (SWCNTs) provide natural one-dimensional confinement that can be implemented for encapsulation, nanosynthesis, and polymerization of molecules into nanoribbons. Recently, the formation of atomically precise graphene nanoribbons inside SWCNTs has been reported. However, there have been only a limited amount of approaches to form ordered magnetic structures inside the nanotube channels and the creation of magnetic nanoribbons is still lacking. In this work we synthesize and reveal the properties of cobalt-phthalocyanine based nanoribbons (CoPcNRs) encapsulated in SWCNTs. Raman spectroscopy, transmission electron microscopy, absorption spectroscopy, and density functional theory calculations allowed us to confirm the encapsulation and to reveal the specific fingerprints of CoPcNRs. The magnetic properties were studied by transverse magnetooptical Kerr effect measurements, which indicated a strong difference in comparison with the pristine unfilled SWCNTs due to the impact of Co incorporated atoms. We anticipate that this approach of polymerization of encapsulated magnetic molecules inside SWCNTs will result in a diverse class of protected low-dimensional ordered magnetic materials for various applications.

Fluoro-Substituted Metal Phthalocyanines for Active Layers of Chemical Sensors

Metal phthalocyanines bearing electron-withdrawing fluorine substituents were synthesized a long time ago, but interest in the study of their films has emerged in recent decades. This is due to the fact that, unlike unsubstituted phthalocyanines, films of some fluorinated phthalocyanines exhibit the properties of n-type semiconductors, which makes them promising candidates for application in ambipolar transistors. Apart from this, it was shown that the introduction of fluorine substituents led to an increase in the sensitivity of phthalocyanine films to reducing gases. This review analyzes the state of research over the last fifteen years in the field of applications of fluoro-substituted metal phthalocyanines as active layers of gas sensors, with a primary focus on chemiresistive ones. The active layers on the basis of phthalocyanines with fluorine and fluorine-containing substituents of optical and quartz crystal microbalance sensors are also considered. Attention is paid to the analysis of the effect of molecular structure (central metal, number and type of fluorine substituent etc.) on sensor properties of fluorinated phthalocyanine films.

Metal cyclopropenylidene sandwich cluster and nanowire: structural, electronic, and magnetic properties

Organometallic sandwich clusters and nanowires can offer prototypes for molecular ferromagnet and nanoscale spintronic devices due to the strong coupling of local magnetic moments in the nanowires direction and experimental feasibility. Here, on the basis of first-principles calculations, we reportTM_n(c-C₃H₂)_n+1(TM= Ti, Mn;n= 1-4) sandwich clusters and 1D [TM(c-C₃H₂)]_∞sandwich nanowires building from transitional metal and the smallest aromatic carbene of cyclopropenylidene (c-C₃H₂). Based on the results of lattice dynamic and thermodynamic studies, we show that the magnetic moment of Mn_n(c-C₃H₂)_n+1clusters increases linearly with the number ofn, and 1D [Mn(c-C₃H₂)]_∞nanowire is a stable ferromagnetic semiconductor, which can be converted into half metal with carrier doping. In contrary, both Ti_n(c-C₃H₂)_n+1and 1D [Ti(c-C₃H₂)]_∞nanowire are nonmagnetic materials. This study reveals the potential application of the [TM(c-C₃H₂)]_∞nanowire in spintronics.

Study on Controllable Assembly of Stearic Acid within Interlayer Spacing of Montmorillonite and Its Energy Storage Performance

As an energy carrier, the phase change material can enhance the efficiency of an energy source and reduce its load. The present paper describes the assembly of the energy carrier molecule [stearic acid (SA)] into the interlayer spacing of montmorillonite (Mt). A novel inorganic/organic composite energy storage material was prepared, which effectively reduces the phase change temperature of the energy storage molecule. Through acid treatment, the Si⁴⁺/Al³⁺ ratio of Mt can be regulated to obtain a series of Mts with different layer charges. As a result, a controllable assembly of energy storage molecule, SA, into the interlayer spacing of Mts with different layer charges was accomplished. By controlling the layer charges of Mt arrangement morphology and interactive force of SA molecules in the interlayer, spacing of Mt can be changed effectively. The phase change temperature (exothermic reaction) reduces from 50.5 to 32 °C compared with the SA molecules, which are used to control phase change temperature of the energy storage material. The study presents a SA/Mt energy storage material that can aid in further development in the field of energy storage construction materials.

A new approach for controlling the crystal phase of NiPc in ionic liquids

α-NiPc and β-NiPc are obtained via a physical vapor deposition process which uses high density and low density ionic liquids (ILs) as substrates, respectively.

Fabrication of a cobalt phthalocyanine free-standing film on an ionic liquid surface for memory device applications

The fabrication of a metal phthalocyanine (MPc) film with good transferability and exploitation of its properties are very important for further application. In this study, a continuous free-standing film of CoPc was obtained on an ionic liquid (IL) surface via a physical vapor deposition (PVD) method. The as-obtained film has a β-phase structure and is constructed with one dimensional CoPc to form a network structure. The morphology of the film could be easily tuned by tunning the flow rate of the carrier gas. More importantly, the device based on these films shows obvious electrical switching and negative differential resistance (NDR) characteristics. The maximum ON/OFF current ratio of two distinctive conductivity states is ∼100 at a reading voltage of +30 V. The conductivity and conductive switching behavior of the NW constructed device are better than the device constructed with NRs. The NDR effect and electrical switching conduction mechanism can be explained by the charge trap elements of the Co^II/Co^I redox couples. The above results open up the possibility of CoPc as a memory medium for information storage and logic circuits applications.

The fabrication of a metal phthalocyanine (MPc) film with good transferability and exploitation of its properties are very important for further application.

Self-Assembled Molecular Nanowires for High-Performance Organic Transistors

While organic semiconductors provide tantalizing possibilities for low-cost, light-weight, flexible electronic devices, their current use in transistors-the fundamental building block-is rather limited as their speed and reliability are not competitive with those of their inorganic counterparts and are simply too poor for many practical applications. Through self-assembly, highly ordered nanostructures can be prepared that have more competitive transport characteristics; however, no simple, scalable method has been discovered that can produce devices on the basis of such nanostructures. Here, we show how transistors of self-assembled molecular nanowires can be fabricated using a scalable, gradient sublimation technique, which have dramatically improved characteristics compared to those of their thin-film counterparts, both in terms of performance and stability. Nanowire devices based on copper phthalocyanine have been fabricated with threshold voltages as low as -2.1 V, high on/off ratios of 10⁵, small subthreshold swings of 0.9 V/decade, and mobilities of 0.6 cm²/V s, and lower trap energies as deduced from temperature-dependent properties, in line with leading organic semiconductors involving more complex fabrication. High-performance transistors manufactured using our scalable deposition technique, compatible with flexible substrates, could enable integrated all-organic chips implementing conventional as well as neuromorphic computation and combining sensors, logic, data storage, drivers, and displays.

Study of the coordination of quinuclidine to a chiral zinc phthalocyanine dimer

We attempted the calculation of an accurate equilibrium constant for the dimerization process of enantiomerically pure Zn-1 using UV-vis dilution experiments. At millimolar concentration Zn-1 is involved in a chemical exchange process between its monomeric and dimeric state that is slow on the 1H NMR timescale. We performed variable-temperature 1H NMR experiments in CDCl3 solution to determine the dimerization constant value at different temperatures and performed a van’t Hoff plot to derive the thermodynamic parameters of the process. The calculated thermodynamic data revealed that the dimerization process is entropy-driven and enthalpically opposed. We also probed the coordination of quinuclidine, 1-azabicyclo[2.2.2]octane, 2, to the Zn-1 using UV-vis and 1H NMR titrations in CDCl3 solution. At micromolar concentration the Zn-1 exclusively exists in solution as a monomer and forms a simple 1:1, [Formula: see text], complex with quinuclidine having a stability constant of [Formula: see text]([Formula: see text]) [Formula: see text] 106 M[Formula: see text]. On the other hand, the 1H NMR titrations carried out at 298 K and at millimolar concentration showed that Zn-1 was present in solution as the dimer and formed 1:2, [Formula: see text], and 2:2, [Formula: see text] complexes by coordination to 2. In addition, the 1:1 complex, [Formula: see text] showed a reduced dimerization constant compared to the uncoordinated parent monomer Zn-1. At high quinuclidine concentration, the 1:1 complex, [Formula: see text], derived from the coordinated dimer dissociation was also detected. The 1H NMR spectra of the titrations displayed separate signals for some hydrogen atoms of the Zn-phthalocyanine in each one of the four species. Remarkably, the chemical exchange processes involving free and bound quinuclidine in the monomeric and dimeric complexes showed different kinetics on the NMR timescale.

Facile synthesis of ZnPc nanoflakes for cold cathode emission

Field emission characteristics of well resolved ZnPc nanoflakes through hydrothermal method and simulation via finite element method.

Metal phthalocyanine: fullerene composite nanotubes via templating method for enhanced properties

The use of templating method to synthesize the vanadyl 2,9,16,23-tetraphenoxy-29H,31H-phthalocyanine (VOPcPhO):[6,6]-phenyl C71 butyric acid methyl ester (PC71BM) composite nanotubes is presented here. VOPcPhO is a p-type material and PC71BM is an n-type material which acts as an electron donor and electron acceptor, respectively. Both materials have been studied due to their potential applications as solar energy converter and organic electronics. High-resolution transmission electron microscope (HRTEM) and field emission scanning electron microscope (FESEM) images have shown the replication of the porous template diameter of approximately 200 nm with a superior incorporation of both VOPcPhO and PC71BM. VOPcPhO:PC71BM composite nanotubes showed the significant properties improvement if compared over their bulk heterojunction counterpart. UV-vis spectra of composite nanotubes show a shift to a longer wavelength at the absorption peaks. Significant quenching has been attained by the photoluminescence spectra of VOPcPhO:PC71BM composite nanotubes which supports the redshift of UV-vis absorption spectra. Presumably, the photo-induced charge transfer and charge carrier dissociation can be enhanced from the VOPcPhO:PC71BM composite nanotubes rather than the bulk heterojunction.

Hydrogen-bonded organic semiconductor micro- and nanocrystals: from colloidal syntheses to (opto-)electronic devices

Organic pigments such as indigos, quinacridones, and phthalocyanines are widely produced industrially as colorants for everyday products as various as cosmetics and printing inks. Herein we introduce a general procedure to transform commercially available insoluble microcrystalline pigment powders into colloidal solutions of variously sized and shaped semiconductor micro- and nanocrystals. The synthesis is based on the transformation of the pigments into soluble dyes by introducing transient protecting groups on the secondary amine moieties, followed by controlled deprotection in solution. Three deprotection methods are demonstrated: thermal cleavage, acid-catalyzed deprotection, and amine-induced deprotection. During these processes, ligands are introduced to afford colloidal stability and to provide dedicated surface functionality and for size and shape control. The resulting micro- and nanocrystals exhibit a wide range of optical absorption and photoluminescence over spectral regions from the visible to the near-infrared. Due to excellent colloidal solubility offered by the ligands, the achieved organic nanocrystals are suitable for solution processing of (opto)electronic devices. As examples, phthalocyanine nanowire transistors as well as quinacridone nanocrystal photodetectors, with photoresponsivity values by far outperforming those of vacuum deposited reference samples, are demonstrated. The high responsivity is enabled by photoinduced charge transfer between the nanocrystals and the directly attached electron-accepting vitamin B2 ligands. The semiconducting nanocrystals described here offer a cheap, nontoxic, and environmentally friendly alternative to inorganic nanocrystals as well as a new paradigm for obtaining organic semiconductor materials from commercial colorants.

Crystallization-induced properties from morphology-controlled organic crystals

During the past two decades, many materials chemists have focused on the development of organic molecules that can serve as the basis of cost-effective and flexible electronic, optical, and energy conversion devices. Among the potential candidate molecules, metal-free or metal-containing conjugated organic molecules offer high-order electronic conjugation levels that can directly support fast charge carrier transport, rapid optoelectric responses, and reliable exciton manipulation. Early studies of these molecules focused on the design and synthesis of organic unit molecules that exhibit active electrical and optical properties when produced in the form of thin film devices. Since then, researchers have worked to enhance the properties upon crystallization of the unit molecules as single crystals provide higher carrier mobilities and exciton recombination yields. Most recently, researchers have conducted in-depth studies to understand how crystallization induces property changes, especially those that depend on specific crystal surfaces. The different properties that depend on the crystal facets have been of particular interest. Most unit molecules have anisotropic structures, and therefore produce crystals with several unique crystal facets with dissimilar molecular arrangements. These structural differences would also lead to diverse electrical conductance, optical absorption/emission, and even chemical interaction properties depending on the crystal facet investigated. To study the effects of crystallization and crystal facet-dependent property changes, researchers must grow or synthesize crystals of highly conjugated molecules that have both a variety of morphologies and high crystallinity. Morphologically well-defined organic crystals, that form structures such as wires, rods, disks, and cubes, provide objects that researchers can use to evaluate these material properties. Such structures typically occur as single crystals with well-developed facets with dissimilar molecular arrangements. Recently, researchers have proposed several approaches for the vapor and solution phase synthesis of high quality organic crystals with various morphologies. In this Account, we focus on methodologies for the synthesis of various organic- and metal-containing highly conjugated molecular crystals. We also examine the new optical and chemical properties of these materials. In addition, we introduce recent experimental results demonstrating that high crystallinity and specific molecular arrangements lead to crystallization-induced property changes. We believe that the understanding of the crystallization-induced property changes in organic crystals will provide both fundamental knowledge of the chemical processes occurring at various interfaces and opportunities for researchers to take advantage of crystallization-induced property changes in the development of high-performance organic devices.

Vectorial diffusion for facile solution-processed self-assembly of insoluble semiconductors: a case study on metal phthalocyanines

Solution processibility is one of the most intriguing properties of organic semiconductors. However, it is difficult to find a suitable solvent and solution process for most semiconductors. For example, metal phthalocyanines (MPcs) are only soluble in non-volatile solvents, which prevent their applications from solution process. For the first time, vectorial diffusion is utilized for solution processing of MPcs. The obtained large F16CuPc and α-phase CuPc crystals and the efficient phase separation of them suggest the vectorial diffusion process is as slow as a self-assembly process, which is helpful to yield large crystals and purify the semiconductors. This method, which only uses common commercial solvents without any complex and expensive instruments and high-temperature operation, provides a facile approach for purification of organic semiconductors and growth of their crystals in large quantities.

Efficient and persistent cold cathode emission from CuPc nanotubes: a joint experimental and simulation investigation

Experimentally observed excellent cold cathode emission characteristics of chemically synthesized CuPc nanotubes and theoretical justifications via finite element method simulation.

Ammonia sorption studies into thin layers of hexadecafluorinated cobalt phthalocyanine using optical techniques

In the present work, the optical response of CoPcF16 films upon exposure to ammonia vapor in the concentration range 50 to 1000 ppm was measured by total internal reflection ellipsometry. It was demonstrated that the sorption of NH3 molecules causes substantial shift of the Δ(λ) spectrum which is determined by the increase in film thickness and change of its optical parameters. It was found that the CoPcF16 films deposited at substrate temperature of 220 °C are characterized by larger grains and more developed surface demonstrating higher optical response than films deposited at substrate temperature of 60 °C. In order to gain an insight into the sorption mechanism at molecular level, we have studied the interaction of ammonia vapor with hexadecafluorinated cobalt phthalocyanine using infrared spectroscopy. It was shown that the detection of ammonia was found to be governed primarily by coordination to the metal center.

A series of asymmetrical phthalocyanines: synthesis and near infrared properties

We report here the preparation of asymmetrical phthalocyanine dimers 1a–3a, which are endowed with novel charge transfer bands at 1,151–1,154 nm and strong NIR luminescences at 840–860 nm and 1,600–1,650 nm. Through H-bonding interaction, 1a–3a are inclined to self-assemble into hexrod nanotubes at the interface of CHCl₃ and CH₃OH. Our results provide further insights into the interaction in molecular dimers, and suggest that 1a–3a have potential application in magnets and supramolecular architectures.

Nanostructured metallophthalocyanine complexes: synthesis and electrocatalysis

In this review, we have attempted to summarize the synthesis and catalytic applications of the nanophthalocyanine complexes. In cases where possible, we have compared the catalytic activity of the nanophthalocyanines to the bulk material. Catalytic detection of dopamine, epinephrine, glucose and some pollutants using nanostructured metallophthalocyanine have been covered.

The growth of one-dimensional CuPcF16 nanostructures on gold nanoparticles as studied by transmission electron microscopy tomography

The growth of one-dimensional (1D) fluorinated copper-phthalocyanine (CuPcF(16)) on gold (Au) nanoparticles (NPs) is studied by electron tomography. The shape of the 1D structure and its geometrical relationship with the associated Au NP are determined by a three-dimensional reconstruction analysis combined with high-resolution electron microscopy. The CuPcF(16) molecules nucleate at the <110> edge of the Au nanoparticle and grow parallel to a {111} facet of the particle along a direction close to <121>. This implies that the maximum diameter of the 1D structure is limited by the width of the <110> edge of the Au particle.

1D nano- and microbelts self-assembled from the organic-inorganic hybrid molecules: oxadiazole-containing cyclotriphosphazene

A new oxadiazole-containing cyclotriphosphazene, namely, hexakis-(4-(5-phenyl-1,3,4-oxazodiazol-2-yl)-phenoxy)-cyclotriphosphazene (HPCP) was synthesized. Single-crystal nano- and microbelts of HPCP were self-assembly via two simple solution methods. The shapes of the as-prepared nano- and microstructures can be readily controlled by varying the solvent and aging time in the self-assembly process. A growth mechanism was proposed for the formation of the 1D morphological structures. Crystal structure analysis demonstrated that the overlap between the aryl units attached to the cyclotriphosphazene backbone forms effective intermolecular π-π linking for crystal growth. Electronic and optical properties of the as-prepared nano- and microstructures are investigated.

One-step dry method for the synthesis of supported single-crystalline organic nanowires formed by pi-conjugated molecules

We present for the first time a general vacuum process for the growth of supported organic nanowires formed by pi-conjugated molecules, including metalloporphyrins, metallophthalocyanines, and perylenes. This methodology consists on a one-step physical vapor deposition of the pi-conjugated molecules. The synthesis is carried out at controlled temperature on substrates with tailor morphology which allows the growth of organic nanowires in the form of squared nanofibers and nanobelts. The study of the nanowires by electron diffraction and HRTEM combining with the results of a theoretical analysis of the possible arrangement of the pi-conjugated molecules along the nanowires reveals that the nanowires show a columnar structure along the fiber axis consisting of pi-stacked molecules having a herringbone-like arrangement. The formation of these nanowires on different substrates demonstrates that the growth mechanism is independent of the substrate chemical composition. An in-depth phenomenological study of the formation of the nanowires drives us to propose a growth mechanism based on a crystallization process. Furthermore, the growth method allows the fabrication of two particular 1D heterostructures: binary and open core@shell organic nanofibers.

Zinc phthalocyanine hierarchical nanostructure with hollow interior space: solvent-thermal synthesis and high visible photocatalytic property

A novel zinc phthalocyanine (ZnPc) hierarchical nanostructure with hollow interior space has been successfully obtained by a facile ethylene glycol solvent-thermal synthetic route. The as-obtained products were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), IR spectrum, UV-vis spectrum, Brunauer-Emmett-Teller analysis and contact angle measurement. It was indicated that the ZnPc micro-rectangular tubes with hollow interior space were built from densely nanosheets with a thickness of about 20 nm. The obtained ZnPc showed high visible photocatalytic property to degrade rhodamine B (RB), which could be ascribed to the contribution of hierarchical nanostructure, high crystallinity and super-hydrophobic property.

Air- and light-stable superhydrophobic colored surfaces based on supported organic nanowires

In this work, we report on a new type of superhydrophobic material consisting of supported organic nanowires prepared by vacuum deposition. Different intensely colored surfaces with water contact angles as high as 180 degrees can be fabricated depending on the composition, morphology, and density of the nanowires. These surfaces are stable in air and under intense light irradiation. The wettability properties of coatings made of metalloporphyrins and metallophthalocyanines nanowires as well as other heterostructured binary and open core@shell nanowires are studied.

Fabrication of CuTAPc polymer nanowires and nanotubes by electropolymerization

Poly-copper tetraaminophthalocyanine (CuTAPc) nanowires and nanotubes were successfully fabricated on porous alumina templates by electropolymerization and characterized using field-emission scanning electron microscopy (FE-SEM), energy-dispersive x-ray spectroscopy (EDX), transmission electron microscopy (TEM) and Raman microscopy. The lengths of these nanostructures could be controlled by the number of cycles applied and the monomer concentrations, while their diameters are confined by the pore size of the template. The product of electropolymerization (whether as nanowires or nanotubes) is a function of the monomer concentrations. The morphology of electropolymerized nanowires was found to be sensitive to the changes in scan rates and monomer concentrations. These organometallic nanostructures may have applications in micro-electronics, chemical sensing, and catalysis.

Phthalocyanines: old dyes, new materials. Putting color in nanotechnology

Phthalocyanines are versatile building blocks for fabricating materials at the nanometer scale. These colored macrocycles exhibit fascinating physical properties which arise from their delocalized pi-electronic structure. This article describes why these molecules are targets for different scientific purposes and technological applications.