Phthalocyanine Nanowires Research Articles

Fluorinated Copper Phthalocyanine Nanowires for Enhancing Interfacial Electron Transport in Organic Solar Cells

Zinc oxide is a promising candidate as an interfacial layer (IFL) in inverted organic photovoltaic (OPV) cells due to the n-type semiconducting properties as well as chemical and environmental stability. Such ZnO layers collect electrons at the transparent electrode, typically indium tin oxide (ITO). However, the significant resistivity of ZnO IFLs and an energetic mismatch between the ZnO and the ITO layers hinder optimum charge collection. Here we report that inserting nanoscopic copper hexadecafluorophthalocyanine (F(16)CuPc) layers, as thin films or nanowires, between the ITO anode and the ZnO IFL increases OPV performance by enhancing interfacial electron transport. In inverted P3HT:PC(61)BM cells, insertion of F(16)CuPc nanowires increases the short circuit current density (J(sc)) versus cells with only ZnO layers, yielding an enhanced power conversion efficiency (PCE) of ∼3.6% vs ∼3.0% for a control without the nanowire layer. Similar effects are observed for inverted PTB7:PC(71)BM cells where the PCE is increased from 8.1% to 8.6%. X-ray scattering, optical, and electrical measurements indicate that the performance enhancement is ascribable to both favorable alignment of the nanowire π-π stacking axes parallel to the photocurrent flow and to the increased interfacial layer-active layer contact area. These findings identify a promising strategy to enhance inverted OPV performance by inserting anisotropic nanostructures with π-π stacking aligned in the photocurrent flow direction.

Magnetic properties of phthalocyanine-based organometallic nanowire

Using first principles calculations, we investigate the electronic and magnetic properties of transition metal phthalocyanine (M-Pc, M = Cr, Mn, Co, Ni, Cu, and Zn) nanowire (M-PcNW). Our calculations show that Ni-PcNW and Zn-PcNW are nonmagnetic, while Cr-PcNW and Cu-PcNW are antiferromagnetic with small energy difference and Co-PcNW show paramagnetic due to their long spin coherence length. Most importantly, we predicate that Mn-PcNW frameworks display long-ranged ferromagnetic spin ordering, offering strong spin polarization around Fermi level. Moreover, Mn-PcNW frameworks are half-metals, which make Mn-PcNW frameworks ideal candidates for spintronic devices. These results may shed light on further experimental studies on molecular spintronics.

Template-directed electrochemical synthesis of cobalt phthalocyanine nanowires

The development of novel nanomaterials has been in the fore front of research in recent years due to the unusually outstanding properties of such materials. Metallophthalocyanines are well known to be of very good use in a wide range of applications. Nanomaterials based on this class of compounds could potentially have better qualities than the "parent" molecules. The electrochemical synthesis of cobalt phthalocyanine nanowires and the characterization using scanning electron microscope are presented. This is the first step towards a move to harnessing the potential of this class of nanomaterials for a wide range of new possible applications.

Significant increase in the water dispersibility of zinc phthalocyanine nanowires and applications in cancer phototherapy

The phototherapy is one of the widely accepted noninvasive clinical methodologies to eradicate cancer cells owing to its minimal side effects and high selectivity to the light of specific wavelength. As represented by photodynamic (PD) and photothermal (PT) therapy, the phototherapy requires light and photosensitizer to generate reactive oxygen species and heat, respectively. Zinc phthalocyanine (ZnPc) is one of the promising photosensitizers as it has a strong absorption cross-section in the spectral range of 650–900 nm that guarantees maximum tissue penetration. One critical issue in using Pc molecule, including ZnPc as a biocompatible sensitizer is the poor water solubility. To increase water solubility, various chemical modifications inducing hydrophilicity have been widely attempted to introduce various functional groups in the ZnPc backbone. We report that ZnPc nanowires (NWs) directly grown from ZnPc powder by vaporization–condensation–recrystallization process show surprisingly increased water dispersibility without any functionalization. The ZnPc NW solution exhibits highly efficient dual PD and PT effects upon the irradiation of near infrared (808 nm) laser. The dual phototherapeutic effect of ZnPc NW is proven to enhance cytotoxic efficiency according to both in vitro and in vivo experimental results. Hee Cheul Choi, Sang Ho Lee and co-workers have devised a way to improve the dispersibility of light-sensitive molecules in water. Using light to treat medical conditions, including tumours, can be less invasive and toxic than other approaches. Such photodynamic and photothermal therapies rely on a light-sensitive molecule — a photo-sensitizer — that is excited under irradiation to release either reactive oxygen species or heat, respectively, which in turn can destroy targeted cells. Most photo-sensitizers, however, suffer from poor solubility in aqueous physiological media, which hinders their applications in the body. This is the case for zinc phthalocyanine, a macrocyclic compound hosting a zinc atom in its central cavity. Rather than trying to alter its chemical composition, the researchers have now observed that converting the powder form into crystalline nanowires significantly increased its dispersibility in water. Furthermore, the nanowires were found to be promising for both photothermal and photodynamic therapies. Water-dispersed nanowires for phototherapy: Without passivation of any water-friendly functional groups in its backbone, one-dimensional zinc phthalocyanine nanowires show remarkably increased dispersibility in water. Upon irradiation with near infrared light, the zinc phthalocyanine nanowires exhibit dual photodynamic and photothermal properties, which enhance the cytotoxic efficiency against tumor cells.

Impact of magnetic field on molecular alignment and electrical conductivity in phthalocyanine nanowires

We demonstrate the effective use of a magnetic field to improve molecular alignment, and the resulting enhancement of the electrical conductivity of organic molecular nanowires. The structures of phthalocyanine nanowires, which are produced in porous alumina templates, are characterized by X-ray diffraction. Careful analyses reveal that the crystal morphologies of the phthalocyanine nanowires, e.g., domain size, columnar alignment and face-to-face spacing, are improved by using a 12 T magnetic field. This is because of the anisotropic magnetic susceptibility of the π-conjugated phthalocyanine macrocycle. Electrical measurements of individual nanowires performed with a multi-probe scanning electron microscope show that such highly ordered molecular packing results in a seventeen-fold increase in conductivity.

Aligned ultralong nanowire arrays and their application in flexible photodetector devices

We develop a facile approach for the one-step growth of ultralong aligned copper phthalocyanine (CuPc) nanowire (NW) arrays in a large area, through a grating-assisted physical vapor deposition method. The grating serves as the alignment template that guides the oriented growth of NWs, however, the morphology of the NWs is not restricted by the template but is remarkably determined by the growth conditions. The resulting NW arrays possess rectangular cross-sections, ultralong length, perfect alignment and large uniformity, which hold great potential as promising blocks for future integrated devices. The mechanism of one-step growth and alignment of NW arrays has been well discussed. Transparent and flexible photoconductive devices based on the aligned NW arrays can be directly constructed on the grating, which exhibit a fast response speed, high stability and reproducibility. Transfer of the NW arrays from the grating for further applications, has also been achieved by using polydimethylsiloxane (PDMS) as an elastic stamp. Flexible and electrically stretchable NW devices have then been fabricated on PDMS and demonstrate superior performances. The ability to make large area ultralong flexible organic NW arrays opens new possibilities for integrated device applications of organic nanostructures.

Growth mechanisms of phthalocyanine nanowires induced by Au nanoparticle templates

We combine X-ray reflectivity and scanning electron microscopy measurements to investigate the mechanisms involved in the growth of vertical arrays of phthalocyanine nanowires directed by templates of Au nanoparticles. The study has been carried out for H(16)CuPc at different substrate temperatures. It is shown that three organic morphologies evolve during the growth: 1D nanostructures on top of the Au nanoparticles, a multilayer film on the substrate and a layer wetting the gold nanoparticles. For substrate temperatures below 100 °C there is a coexisting and competing growth of the three structures, whereas beyond this temperature the 1D growth on the nanoparticles is predominantly favored. The observance of two regimes with the temperature is characterized by two different activation energies. Both the length of the 1D structures and the thickness of the multilayer film can be precisely controlled by the substrate temperature which is of importance for application of vertical organic nanowires as donor/acceptor architecture in organic solar cells.

Ultralong Copper Phthalocyanine Nanowires with New Crystal Structure and Broad Optical Absorption

The development of molecular nanostructures plays a major role in emerging organic electronic applications, as it leads to improved performance and is compatible with our increasing need for miniaturization. In particular, nanowires have been obtained from solution or vapor phase and have displayed high conductivity or large interfacial areas in solar cells. In all cases however, the crystal structure remains as in films or bulk, and the exploitation of wires requires extensive postgrowth manipulation as their orientations are random. Here we report copper phthalocyanine (CuPc) nanowires with diameters of 10-100 nm, high directionality, and unprecedented aspect ratios. We demonstrate that they adopt a new crystal phase, designated eta-CuPc, where the molecules stack along the long axis. The resulting high electronic overlap along the centimeter length stacks achieved in our wires mediates antiferromagnetic couplings and broadens the optical absorption spectrum. The ability to fabricate ultralong, flexible metal phthalocyanine nanowires opens new possibilities for applications of these simple molecules.

Rectangular Nanotubes of Copper Phthalocyanine: Application to a Single Nanotube Transistor

We report on the structural transformation of organic copper phthalocyanine (CuPc) nanowires to hollowed rectangular nanotubes through the use of a hydrothermal process. The CuPc molecules have been chemically self-assembled into a form of nanowires, through reaction with trifluoroacetic acid. The mechanism of the chemical self-assembly for the CuPc nanowires is studied through analyzing the Fourier transform infrared spectra. After the hydrothermal process, it is observed that the α-phase CuPc nanowires are transformed to β-phase CuPc rectangular nanotubes, with crystallinity in the (−101) direction. From X-ray diffraction patterns, the crystallinity of the CuPc nanowires is enhanced by annealing. The optical and electrical characteristics of the β-phase crystalline CuPc rectangular nanotubes are compared with those of α-phase CuPc nanowires, using ultraviolet and visible absorption spectra and current−voltage (I−V) characteristics. From the gate field-dependent I−V characteristics for a single nanowire/...

Fabricating Photoswitches and Field-Effect Transistors from Self-Assembled Tetra(2-isopropyl-5-methyphenoxy) Copper Phthalocyanines Nanowires

Tetra(2-isopropyl-5-methyphenoxy) copper phthalocyanine (CuPc) nanowires synthesized by a facile, low temperature self-assembled route, were incorporated into nano-devices: photoswitch and organic field-effect transistor. The devices were capable of switching on/off reversibly and fast by turning the 808 nm infrared light on/off. And the carrier mobility micro of CuPc nanowires incorporated in the devices was -0.02 cm2/V x s. The prelimenary results in this study show the potential application of metal phthalocyanine nanowires in low-cost fabrication of nano photo-electric devices.

Electric-Field-Induced Alignment of Charged Organic Nanowires

Here we report appreciable alignment effect of in situ grown molecular nanowires formed by phthalocyanines under electric field. The phthalocyanine nanowires are observed to be highly selective on electrode polarity in direct current electric field, which is attributed to the charging effect of molecular wires originated from the alignment of work function of electrodes and energy levels of the molecules. The controlled connections of phthalocyanine nanowires bridging two electrodes are also demonstrated under alternating current electric field.

Highly Photoconductive Copper Phthalocyanine-coated Titania Nanoarrays via Secondary Deposition

Based on an anodic aluminum oxide template, a sol−gel dip-coating technique and electrophoretic deposition processes were combined to fabricate TiO 2 nanowire arrays, copper phthalocyanine (CuPc) nanowire arrays, and CuPc-coated TiO 2 nanowire (CuPc/TiO 2 NW) arrays. The resulting nanostructures were characterized by field-emission scanning electron microscope, energy dispersive X-ray microanalysis system, X-ray diffraction patterns, and time-resolved fluorescence spectra. A series of dual-layered photoreceptors containing the above three kinds of nanowire arrays as the charge generation layer (CGL) were designed and fabricated. Their photoconductivities under illumination of visible light were investigated using a photoinduced xerographic discharge technique. It was found that the photoreceptor based on CuPc/TiO 2 NW arrays as CGL exhibited 1 order of magnitude higher photoconductivity than that of pristine TiO 2 or CuPc nanowire arrays due to the large donor−acceptor (CuPc-TiO 2) contact area and the di...

Synthesis and characterization of silver phthalocyanine nanowires and nanobelts

Thermal evaporation technique has been employed to grow silver phthalocyanine nanostruc- tures on glass substrates kept at different substrate temperature in vacuum of 10 �5 Torr. These samples have been studied for their structural and optical properties. TEM investigations show the formation of long nanowires in AgPc thin films prepared at substrate temperature of 298 and 303 K, whereas films prepared at 308 K show the formation of nanobelts. XRD observations reveal that silver phthalocyanine nanowires are crystalline in nature. The significant blue shift in the UV-VIS absorption spectra of the silver phthalocyanine nanowires in comparison to bulk sample, indicate of effect of quantum confinement. PACS. 71.20.Rv Polymers and organic compounds - 68.55.-a Thin film structure and morphology - 78.66.-w Optical properties of specific thin films

Synthesis and properties of copper phthalocyanine nanowires

Copper phthalocyanine (CuPc) nanowires were fabricated by organic vapor deposition. The nanowires were studied by scanning electron microscopy, X-ray diffraction, and absorption spectroscopy. The effect of the nature of substrate (glass, Si, indium tin oxide, fluorine doped tin oxide) and its temperature on the morphology and properties of the fabricated nanowires was studied. Deposition of a thin CuPc film before the nanostructure growth ensured high yield of CuPc nanowires for all the substrates except Si. The nanowire size and crystal structure were mainly determined by the substrate temperature, with α-CuPc nanowires obtained at the lowest temperature (∼ 190 °C) and β-CuPc nanowires obtained at higher temperatures (above 200 °C).

Fabrication of organic copper phthalocyanine nanowire arrays via a simple AAO template-based electrophoretic deposition

Copper phthalocyanine (CuPc) nanowire arrays were fabricated for the first time by the electrophoretic deposition (EPD) method using a porous anodic aluminum oxide (AAO) template. The barrier layer between the aluminum substrate and the AAO membrane was first removed by progressively reducing the applied anodizing voltage. The AAO template was then employed directly to fabricate CuPc nanowire arrays by direct current EPD. The morphology of the CuPc nanowires was characterized by transmission electronic microscopy and field emission scanning electronic microscopy. The nanowires exhibited smooth surfaces and uniform diameters of about 40 nm. The photoconductivity of the CuPc nanowire arrays was investigated as well.