CuPc Molecules Research Articles

Visible-light-induced photocatalysis of different copper phthalocyanines on cotton fibre

Several copper phthalocyanines (CuPcs) with different substituents were applied to cellulosic fibre for studying their photocatalytic activities by using stain decolourisation methods. Even though the molar quantity of each CuPc derivative on cotton fabric were controlled to be equivalent, there were great difference on their photocatalytic activities. Distinct extents of the CuPc molecules dissociated by the cellulosic medium, owing to different CuPc molecular structures, were observed via absorption spectroscopic analyses. Liquid chromatography-mass spectrometry (LC-MS) was employed to determine the molecular structures of the CuPcs. A novel elution profile, termed as “double-isocratic” method, was developed to separate the relatively complex mixtures of the CuPc compounds, to prevent interference against mass spectrometric detection by buffers and ion-pairing reagents. The stain decolourisation performance of CuPcs were also compared to one of the traditional photocatalysts, titanium dioxide (TiO2), under visible light. Stronger photocatalytic activity was exhibited by CuPc-functionalised cottons than the TiO2-coated cotton. The outcomes of this study can make contributions to aggregation and photocatalytic studies of phthalocyanines in cellulosic materials, as well as phthalocyanine chemistry and applications.

Tuning the Fermi Level of Graphene by Two-Dimensional Metals for Raman Detection of Molecules.

Graphene-enhanced Raman scattering (GERS) offers great opportunities to achieve optical sensing with a high uniformity and superior molecular selectivity. The GERS mechanism relies on charge transfer between molecules and graphene, which is difficult to manipulate by varying the band alignment between graphene and the molecules. In this work, we synthesized a few atomic layers of metal termed two-dimensional (2D) metal to precisely and deterministically modify the graphene Fermi level. Using copper phthalocyanine (CuPc) as a representative molecule, we demonstrated that tuning the Fermi level can significantly improve the signal enhancement and molecular selectivity of GERS. Specifically, aligning the Fermi level of graphene closer to the highest occupied molecular orbital (HOMO) of CuPc results in a more pronounced Raman enhancement. Density functional theory (DFT) calculations of the charge density distribution reproduce the enhanced charge transfer between CuPc molecules and graphene with a modulated Fermi level. Extending our investigation to other molecules such as rhodamine 6G, rhodamine B, crystal violet, and F16CuPc, we showed that 2D metals enabled Fermi level tuning, thus improving GERS detection for molecules and contributing to an enhanced molecular selectivity. This underscores the potential of utilizing 2D metals for the precise control and optimization of GERS applications, which will benefit the development of highly sensitive, specific, and reliable sensors.

Investigation into electronic interaction and work function tuning of phthalocyanine molecules and graphene interfaces.

Understanding the interfacial electronic structures of organic semiconductor phthalocyanines (MePc) and graphene is essential for their practical application in various fields. In this study, we investigated the electronic structure and the tuning of the work function of free metal phthalocyanine (Pc4), cobalt phthalocyanine (CoPc), and copper phthalocyanine (CuPc) molecules deposited on a graphene monolayer using X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). We found that the functionalization of MePc molecules induces p-doping to the graphene substrate due to the charge transfer mechanism with the MePc molecule. XPS analysis shows that the electronic interaction at the interface between Pc molecules and graphene substrate mainly occurs through the pyrrole species. Comparatively, it was observed that the electronic coupling between graphene and CuPc is relatively stronger than that between CoPc and graphene. The electronic interaction of the CuPc/Gr sample principally occurs through the Cu2+ 3d states of CuPc, the molecule, and the graphene 2p π states. This electronic interaction increases the work function of the graphene substrate to 5.75 eV, 6.05 eV, and 6.12 eV after depositing the Pc4, CoPc, and CuPc molecules, respectively. These results show that the MePc/Gr samples investigated in this study can be considered promising candidates for applications requiring a high work function to increase hole injection efficiency.

Bright photoluminescence from CdSe quantum dots conjugated with metal phthalocyanines

Engineering organic/inorganic nanohybrids is one of the emerging tracks in material science to search for new nanomaterials with tailored and/or enhanced properties. In this work, we report the synthesis of CdSe quantum dots (QDs) conjugated with selected metal phthalocyanine (MPc), e.g., ZnPc and CuPc, utilizing the hot-injection organometallic method. The prepared pristine and conjugated QD systems exhibit practically identical particle size and spherical morphology and feature the characteristic CdSe excitonic peaks in their optical absorption spectra. The successful incorporation of ZnPc or CuPc molecules is ensured by the appearance of their sharp Q-band peaks in the optical absorption and the Zn2p or Cu2p core levels in the X-ray photoemission spectroscopy (XPS) measurements. The pure CdSe QDs sample of selected size (∼4.0 nm) exhibits well-defined photoluminescence (PL) peak at the limit of the green range, which is remarkably enhanced for the conjugated QD systems, reaching ∼250 % for the CuPc/CdSe QDs. Such prominent PL enhancement is attributed to Förster resonance energy transfer stimulated by deep B-band emissions from CuPc molecules combined with charge transfer from MPc molecules to CdSe QDs. Furthermore, the emission is greatly amplified upon prolonged exposure to laser beam, exceeding 400 % of the initial CuPc/CdSe emission after only 40 min of exposure time, yet without significant changes in their emission color. Thus, these MPc/CdSe conjugated QD systems are promising nanomaterials for intense white light sources.

Generating Multi-Carbon Products by Electrochemical CO2 Reduction via Catalytically Harmonious Ni/Cu Dual Active Sites.

Despite the unique advantages of single-atom catalysts, molecular dual-active sites facilitate the C-C coupling reaction for C2 products toward the CO2 reduction reaction (CO2RR). The Ni/Cu proximal dual-active site catalyst (Ni/Cu-PASC) is developed, which is a harmonic catalyst with dual-active sites, by simply mixing commercial Ni-phthalocyanine (Ni-Pc) and Cu-phthalocyanine (Cu-Pc) molecules physically. According to scanning transmission electron microscopy (STEM) and transmission electron microscopy (TEM) energy dispersive spectroscopy (EDS)data, Ni and Cu atoms are separated, creating dual-active sites for the CO2RR. The Ni/Cu-PASC generates ethanol with an FE of 55%. Conversely, Ni-Pc and Cu-Pc have only detected single-carbon products like CO and HCOO-. In situ X-ray absorption spectroscopy (XAS) indicates that CO generation is caused by the stable Ni active site's balanced electronic state. The CO production from Ni-Pc consistently increased the CO concentration over Cu sites attributed to subsequent reduction reaction through a C-C coupling on nearby Cu. The CO bound (HCOO-) peak, which can be found on Cu-Pc, vanishes on Ni/Cu-PASC, as shown by in situ fourier transformation infrared (FTIR). The characteristic intermediate of *CHO instead of HCOO- proves to be the prerequisite for multi-carbon products by electrochemical CO2RR. The work demonstrates that the harmonic dual-active sites in Ni/Cu-PASC can be readily available by the cascading proximal active Ni- and Cu-Pc sites.

Modification of C.I.Pigment Blue 15:6 with graphene oxide

The ε-crystalline copper phthalocyanine is suitable for printing inks, coatings, and plastic colouring due to its strong red-blue tones, and high thermal and chemical stability. And it also shows good photoconductive properties. In this study, C.I. Pigment Blue 15:6 (P.B.15:6) was modified with monolayer graphene oxide (GO) to improve its colour performance. The modified pigments were used as carrier generating materials, and N,N,N′,N′-tetra(4-methylphenyl)-1,1′-biphenyl-4,4′-diamine as hole transport material to fabricate laser organic photoconductive (OPC) devices, and the photosensitivity was tested. The testes results showed that the modified pigment exhibited higher tinting strength (108%). Besides, the photoconductive properties of OPC devices prepared with modified P.B.15:6 at 650 nm and 780 nm lasers were superior to those of the unmodified P.B.15:6 devices. And when the GO modification amount was 3%, the device shows an outstanding initial surface potential (−650 V) and good photosensitivity (0.218 μJ/cm2). Strong interactions between GOc molecule and CuPc molecules have been shown by calculations based on density-functional theory, which facilitate the charge transfer from the GO to the CuPc010 surface.

Epitaxial growth of crystalline thin-films of perfluorinated copper phthalocyanine on the single-crystal copper phthalocyanine

Understanding and controlling the growth structures of molecular heterojunctions are important for the pursuit of highly efficient organic semiconductor devices. In this study, a well-defined molecular heterojunction was constructed by the deposition of an n-type organic semiconductor molecule, perfluorinated copper phthalocyanine (F16CuPc), on single-crystals of a typical p-type material, copper phthalocyanine (CuPc). The heterojunction was characterized using synchrotron radiation surface X-ray diffraction techniques to unveil the epitaxial growth of crystalline thin-films of F16CuPc on the CuPc surface. The inter-lattice relationships between F16CuPc and CuPc deduced from the present results imply that the in-plane orientation of the F16CuPc crystal lattice was predominantly governed by the molecular-level alignments of the π-backbones of the F16CuPc and CuPc molecules at the nucleation center for crystal growth at the interface.

Designed Production of Atomic-Scale Nanowindows in Single-Walled Carbon Nanotubes

The controlled production of nanowindows in graphene layers is desirable for the development of ultrathin membranes. Herein, we propose a single-atom catalytic oxidation method for introducing nanowindows into the graphene layers of single-walled carbon nanotubes (SWCNTs). Using liquid-phase adsorption, copper(II) 2,3,9,10,16,17,23,24-octakis(octyloxy)-29H,31H-phthalocyanine (CuPc) was adsorbed on SWCNT bundles at a surface coverage of 0.9. Subsequently, narrow nanowindows with a number density of 0.13 nm-2 were produced by oxidation above 550 K, which is higher than the decomposition temperature of bulk CuPc. In particular, oxidation of the CuPc-adsorbed SWCNTs at 623 K increased the surface area from 280 to 1690 m2 g-1 owing to the efficient production of nanowindows. The nanowindow size was estimated to be similar to the molecular size of N2 based on the pronounced low-pressure adsorption hysteresis in the N2 adsorption isotherm. In addition, the enthalpy change for the nanowindow-formation equilibrium decreased by 4 kJ mol-1 when CuPc was present, further evidencing the catalytic effect of the Cu atoms supplied by the adsorbed CuPc molecules.

Efficient and Stable Carbon-Based Perovskite Solar Cells Enabled by Mixed CuPc:CuSCN Hole Transporting Layer for Indoor Applications

Perovskite solar cells (PSCs) are an innovative technology with great potential to offer cost-effective and high-performance devices for converting light into electricity that can be used for both outdoor and indoor applications. In this study, a novel hole-transporting layer (HTL) was created by mixing copper phthalocyanine (CuPc) molecules into a copper(I) thiocyanate (CuSCN) film and was applied to carbon-based PSCs with cesium/formamidinium (Cs0.17FA0.83Pb(I0.83Br0.17)3) as a photoabsorber. At the optimum concentration, a high power conversion efficiency (PCE) of 15.01% was achieved under AM1.5G test conditions, and 32.1% PCE was acquired under low-light 1000 lux conditions. It was discovered that the mixed CuPc:CuSCN HTL helps reduce trap density and improve the perovskite/HTL interface as well as the HTL/carbon interface. Moreover, the PSCs based on the mixed CuPc:CuSCN HTL provided better stability over 1 year due to the hydrophobicity of CuPc material. In addition, thermal stability was tested at 85 °C and the devices achieved an average efficiency drop of approximately 50% of the initial PCE value after 1000 h. UV light stability was also examined, and the results revealed that the average efficiency drop of 40% of the initial value for 70 min of exposure was observed. The work presented here represents an important step toward the practical implementation of the PSC as it paves the way for the development of cost-effective, stable, yet high-performance PSCs for both outdoor and indoor applications.

Interaction mechanism of transition metal phthalocyanines on transition metal nitride supports

We investigated the electronic interactions between transition metal phthalocyanine (TMPc’s) on a refractory transition metal nitride support, specifically copper phthalocyanine (CuPc) on titanium nitride (TiN). X-ray Photoelectron Spectroscopy (XPS) results suggest a presence of a few nanometer native oxide layer on the surface of the TiN nanoparticles, which consists of TiN, TiO2, and Titanium oxynitrides (TixOyNz). A TiNCuPc nanocomposite was synthesized via a simple mixing method due to the strong binding between CuPc and TiN confirmed by density functional theory (DFT) calculations. Both XPS data and DFT calculations revealed an electron transfer from TiN substrate to CuPc molecule. The nature of charge transfer is not influenced by the presence of an oxide layer on the surface of TiN. Substantial deviations are however found between photoelectron emission microscopy (PEEM) measured work function for TiN (4.68 eV) and theoretically calculated work function for pristine stoichiometric TiN (2.63 eV). This behavior is attributed to the presence of an oxide layer on the TiN surface. TiNCuPc composite system has a work function value between those of TiN and CuPc. Our studies open up an opportunity to apply a new class of materials based on transition metal phthalocyanine/transition metal nitride composites to catalysis and optoelectronic devices.

Revealing local structural properties of an atomically thin MoSe2 surface using optical microscopy

Using a triangular molybdenum diselenide (MoSe2) flake as surface-enhanced Raman spectroscopy (SERS) platform, we demonstrate the dependency of the Raman enhancement on laser beam polarization and local structure using copper phthalocyanine (CuPc) as probe. Second harmonic generation (SHG) and photoluminescence spectroscopy and microscopy are used to reveal the structural irregularities of the MoSe2 flake. The Raman enhancement in the focus of an azimuthally polarized beam, which possesses exclusively an in-plane electric field component is stronger than the enhancement by a focused radially polarized beam, where the out-of-plane electric field component dominates. This phenomenon indicates that the face-on oriented CuPc molecules strongly interact with the MoSe2 flake via charge transfer and dipole–dipole interaction. Furthermore, the Raman scattering maps on the irregular MoSe2 surface show a distinct correlation with the SHG and photoluminescence optical images, indicating the relationship between local structure and optical properties of the MoSe2 flake. These results contribute to understand the impacts of local structural properties on the Raman enhancement at the surface of the 2D transition-metal dichalcogenide.

Photovoltaic parameters and computational spectroscopic investigation of third order nonlinear optical of CuPc/Si organic diode

The organic diode based on copper phthalocynanine (CuPc) molecule is manufactured by spin coating route. The electrical characterization of Au/CuPc/Si/Al under dark and light is achieved. High rectifying of diode around 11×105 is then revealed. Ideality factor of such diode is increasing by light from 2.28 to 3.3 while height barrier is still constant and saturation current is strongly dependent on light. Cheung-Cheung technique is used to deep the study and obtains others parameters like series resistance and barrier height. Photovoltaics parameters of as-grown diode are assessed and end up to an efficiency of [0.2−0.4]. Nonlinear optical NLO properties are investigated and results confirm the discrepancy HOMO-LUMO of 2.19eV. Selected the functional bond lengths and bond angles in the CuPc cluster are evidenced. The electric dipole moment, the average polarizability, and second Hyperpolarizability for CuPc compound are studied.

Phthalocyanine green pigments

AbstractThe dominant organic green pigments are polyhalogenated copper phthalocyanines (CuPcs). These pigments exhibit similar excellent coloristic and technical performance to CuPc blue pigments and are produced worldwide in large quantities. The green pigments are halogenated CuPcs. There are two pigments with CI designations. CI Pigment Green 7 is a bluish green product, in which the 16 ring hydrogen atoms of the CuPc molecule are replaced virtually completely by chlorine. Products designated as CI Pigment Green 36 incorporate a range of bromo- and bromochlorocopper phthalocyanines and are yellowish-green pigments. CuPc green pigments are manufactured by direct exhaustive halogenation of crude CuPc blue with chlorine or bromine or an appropriate mixture of the two halogens, depending on the composition of the product required. The synthesis is carried out at elevated temperatures in a suitable solvent, commonly a molten AlCl3/NaCl eutectic mixture.

Polymorphism and structure formation in copper phthalocyanine thin films.

Many polymorphic crystal structures of copper phthalocyanine (CuPc) have been reported over the past few decades, but despite its manifold applicability, the structure of the frequently mentioned α polymorph remained unclear. The base-centered unit cell (space group C2/c) suggested in 1966 was ruled out in 2003 and was replaced by a primitive triclinic unit cell (space group P 1). This study proves unequivocally that both α structures coexist in vacuum-deposited CuPc thin films on native silicon oxide by reciprocal space mapping using synchrotron radiation in grazing incidence. The unit-cell parameters and the space group were determined by kinematic scattering theory and provide possible molecular arrangements within the unit cell of the C2/c structure by excluded-volume considerations. In situ X-ray diffraction experiments and ex situ atomic force microscopy complement the experimental data further and provide insight into the formation of a smooth thin film by a temperature-driven downward diffusion of CuPc molecules during growth.

Tunable conductance and spin filtering in twisted bilayer copper phthalocyanine molecular devices.

We investigate theoretically the quantum transport properties of a twisted bilayer copper phthalocyanine (CuPc) molecular device, in which the bottom-layer CuPc molecule is connected to V-shaped zigzag-edged graphene nanoribbon electrodes. Based on a non-equilibrium Green's function approach in combination with density-functional theory, we find that the twist angle effectively modulates the electron interaction between the bilayer CuPc molecules. HOMO (highest occupied molecular orbital)–LUMO (lowest unoccupied molecular orbital) gap, spin filtering efficiency (SFE) and spin-dependent conductance of the bilayer CuPc molecular device could be modulated by changing the twist angle. The conductance reaches its maximum when the twist angle θ is 0° while the largest SFE is achieved when θ = 60°. The twist angle-induced exotic transport phenomena can be well explained by analyzing the transmission spectra, molecular energy level spectra and scattering states of the twisted bilayer CuPc molecular device. The tunable conductance, HOMO–LUMO gap and spin filtering versus twist angle are helpful for predicting how a two-molecule system may behave with twist angle.

Sensor behavior of MoS2 field-effect transistor with light injection toward chemical recognition.

The application of field-effect transistor (FET) devices with atomically thin channels as sensors has attracted significant attention, where the adsorption of atoms/molecules on the channels can be detected by the change in the properties of FET. Thus, to further enhance the chemical sensitivity of FETs, we developed a method to distinguish the chemical properties of adsorbates from the electric behavior of FET devices. Herein, we explored the variation in the FET properties of an MoS2-FET upon visible light injection and the effect of molecule adsorption for chemical recognition. By injecting light, the drain current (Id) increased from the light-off state, which is defined as (ΔId)ph. We examined this effect using CuPc molecules deposited on the channel. The (ΔId)phvs. wavelength continuous spectrum in the visible region showed a peak at the energy for the excitation from the highest occupied orbital (HOMO) to the molecule-induced state (MIS). The energy position and the intensity of this feature showed a sensitive variation with the adsorption of the CuPc molecule and are in good agreement with previously reported photo-absorption spectroscopy data, indicating that this technique can be employed for chemical recognition.

Spectral-kinetic properties of transient absorption of hybrid silver–copper phthalocyanine nanostructures

In this paper, we studied the dynamics of transient absorption spectra of a hybrid nanostructure (Ag–CuPc)6 Ag based on island silver films and copper phthalocyanine thin films, as well as individual structural units of this system, by femtosecond transient absorption spectroscopy. It is found that the effects observed for a hybrid nanostructure reflect the existing mutual influence of the plasmonic and organic subsystems on the spectral-kinetic characteristics of each other. The characteristic time of the main component of induced optical density kinetics at a wavelength λ = 525 nm (τ ~ 15 ps) that is caused by singlet-triplet relaxation of the excited electronic states of the organic subsystem of the hybrid structure is noticeably shorter than the relaxation time (τ ~ 50 ps) at the same wavelength for a pure copper phthalocyanine film of 40 nm thickness, just the same as the total thickness of the organic subsystem in the hybrid structure. It is assumed that the presence of silver nanoparticles in the hybrid structure (Ag–CuPc)6 Ag, affects the probability of intersystem conversion in the organic subsystem, accelerating the transition of CuPc molecules to a long-lived triplet state due to a strong local field near the surface of the plasmon particle. The triplet-triplet absorption spectrum of copper phthalocyanine in the spectral range 470–750 nm was obtained.

Reversal of charge transfer direction at gold/copper phthalocyanine film interface on post deposition annealing: A vibrational spectroscopic study

Charge transfer interaction at the gold (Au)/copper phthalocyanine (CuPc) interface, with Au on CuPc film, was investigated using vibrational techniques - Fourier Transform Infra Red and Raman spectroscopy, in combination with X- ray photoelectron spectroscopy. The charge transfer direction at this interface was found to be changing after annealing of the CuPc film, as compared to that before annealing. Molecule to metal charge transfer at the Au/CuPc interface observed for the as deposited film was found to be reversing to metal to molecule charge transfer for the annealed film. This reversal of charge transfer direction in the latter was attributed to the modified electronic structure/work function of the CuPc film and the varying orientation of CuPc molecules at the interface, brought about by the increased surface roughness, change in morphology, etc. The reversal in charge transfer direction was suggested to be supporting the reduction in parasitic contact resistance at the Au/CuPc interface for a top contact OFET with the annealed CuPc film, as compared to that with the as deposited film. This study demonstrates the influence of morphology of the organic semiconductor film on the charge transfer behaviour at the metal/organic semiconductor interface.

Tuning the Fermi surface of In/Si(111)-([formula omitted]) by CuPc adsorption

In/Si(111)-(7×3) is an atomic layer superconductor formed by an In double layer on Si(111). The size of its circular Fermi surface becomes smaller by the adsorption of copper-phthalocyanine (CuPc) molecules till a coverage of 1.0 monolayer, and then larger at higher coverage. This means that it is possible to control the amount of hole doping, and therefore to tune the energy of the band by CuPc adsorption. By comparing the change in transition temperature (Tc) reported in “Nano Lett. 17 (2017) 2287”, whose reports the manipulation of Tc by CuPc adsorption, and the behavior of the Fermi surface observed in the present study, we conclude that both the increase of Tc till a CuPc coverage of 1.0 ML and its decrease from 1.0 to 2.0 ML have strong correlations with the amount of hole doping from CuPc to In/Si(111)-(7×3).

Synthesis of graphene oxide and copper phthalocyanine, AC electrical characterization and tuning the bandgap of RGO-CuPc composite

Graphene oxide (GO) was synthesized in our laboratory by the improved Hummer’s method. Reduced graphene oxide/Copper Phthalocyanine (RGO-CuPc) composite was prepared through the chemical reduction of GO by Hydrazine hydrate. This composite was analyzed by FT-IR, UV–vis spectroscopy, FESEM microscopy, and the results showed that CuPc molecules were successfully attached on RGO sheets by π-π intermolecular interaction. Also, UV–vis spectroscopy results showed that the tuning of the bandgap is applicable for RGO-CuPc composite. Sandwich devices of RGO-CuPc thin film with aluminum electrodes (Al/RGO-CuPc/Al) were fabricated to investigate the AC electrical properties of RGO-CuPc composite over the frequency range of 102–105 Hz and temperature range of 298–393 K. The band theory is applicable to explain the thin film conduction mechanism. Also, this composite acts as a semiconductor with high electron mobility.