Perylene Tetracarboxylic Diimide Molecule Research Articles

Exciton Delocalization and Polarizability in Perylenetetracarboxylic Diimide Probed Using Electroabsorption and Fluorescence Spectroscopies.

Perylenetetracarboxylic diimide (PTCDI) is an n-type organic semiconductor molecule that has been widely utilized in numerous applications such as photocatalysis and field-effect transistors. Polarizability and dipole moment, which are inherent properties of molecules, are important parameters that determine their responses to external electric and optical fields, physical properties, and reactivity. These parameters are fundamentally important for the design of innovative materials. In this study, the effects of external electric fields on absorption and fluorescence spectra were investigated to obtain the PTCDI parameters. The PTCDI substituted by an octyl group (N,N'-Dioctyl-3,4,9,10-perylenedicarboximide) dispersed in a polymethyl methacrylate (PMMA) matrix was studied in this work. The features of vibronic progression in the absorption spectrum were analogous to those observed in solution. The red shift of the absorption band caused by the Stark effect was mainly observed in the presence of an external electric field. Changes in parameters such as the dipole moment and polarizability between the ground and the Franck-Condon excited states of the PTCDI monomer were determined. The fluorescence spectrum shows a contribution from a broad fluorescence band at wavelengths longer than the monomer fluorescence band. This broad fluorescence is ascribed to the excimer-like fluorescence of PTCDI. The effects of the electric field on the fluorescence spectrum, known as the Stark fluorescence or electrofluorescence spectrum, were measured. Fluorescence quenching is observed in the presence of an external electric field. The change in the polarizability of the monomer fluorescence band is in good agreement with that of the electroabsorption spectrum. A larger change in the polarizability was observed for the excimer-like fluorescence band than that for the monomer band. This result is consistent with exciton delocalization between PTCDI molecules in the excimer-like state.

Scanning tunneling microscopy study of PTCDI on Sn/Si(111)-23×23.

Perylene tetracarboxylic diimide molecules were evaporated onto a Sn/Si(111)-23×23 surface and studied using scanning tunneling microscopy (STM) and low energy electron diffraction. At low coverages, single molecules are locked into specific adsorption geometries, which are investigated in detail using high resolution STM. The electronic structure of these individual molecules was studied using bias dependent STM images. The molecules form 1D rows that become more common with increasing coverages. Possible intermolecular O⋯H interactions within the rows have been identified. At around half of a monolayer (ML), the rows of molecules interact with each other and form a commensurate 43×23 reconstruction. In a complete monolayer, several structures emerge as molecules fill in the space between the 43×23 stripes. Possible intermolecular interactions within the 1 ML structures have been discussed. At coverages above 1 ML, the growth is characterized by island growth, where the molecules are arranged according to the canted structure within the layers.

Donor-Acceptor Supramolecular Organic Nanofibers as Visible-Light Photoelectrocatalysts for Hydrogen Production.

Perylene tetracarboxylic diimide (PTCDI) derivatives have been extensively studied for one-dimensional (1D) self-assembled systems and for applications in photocatalysis. Herein, we constructed a PTCDI-based donor-acceptor (D-A) supramolecular system via in situ self-assembly on an indium tin oxide conductive glass surface. The self-assembled PTCDI nanostructures exhibit well-defined nanofibril morphologies and strong photocurrents. Interestingly, a strong and reversible electrochromic color change was observed during cyclic voltammetry. The color of the nanofibers changed from red to blue and then to violet as the reduction progressed to the radical anion and then to the dianion. This series of one-electron reductions was confirmed by UV absorption, electron paramagnetic resonance spectroscopy, and hydrazine reduction. Most importantly, these PTCDI nanofibers exhibit efficient photoelectrocatalytic hydrogen production with remarkable stability under xenon lamp illumination (λ ≥ 420 nm). Among the three nanofibers prepared, the fibers assembled from PTCDI molecule 2 were found to be the most effective catalyst with 30% Faradaic efficiency. In addition, the nanofibers produced hydrogen at a steady-state for more than 8 h and produced repeatable results in 3 consecutive testing cycles, giving them great potential for practical industrial applications. Under an applied bias voltage, the 1D intermolecular stacking along the long axis of the nanofibers affords efficient separation and migration of photogenerated charge carriers, which play a crucial role in the photoelectrocatalytic process. As a proof-of-concept, the D-A-structured PTCDI nanofibers presented herein may guide future research on photoelectrocatalysis based on self-assembled supramolecular systems by providing more options for material design of the catalysts to achieve greater efficiencies.

Single-Molecule Charge Transport and Electrochemical Gating in Redox-Active Perylene Diimide Junctions

A series of redox-active perylene tetracarboxylic diimide (PTCDI) derivatives have been synthesized and studied by electrochemical cyclic voltammetry and electrochemical scanning tunnelling microscopy break junction techniques. These PTCDI molecules feature the substitution of pyrrolidine at the bay (1,7-) position of perylene and are named pyrrolidine-PTCDIs. These moieties exhibit a small bandgap (2.1 eV) compared with the “normal” (unsubstituted) PTCDI molecule (2.5 eV). Pyrrolidine-PTCDIs were functionalized with different anchoring groups (thiol, amine, pyridine) for building metal–molecule–metal (m–M–m) junctions. The single-molecule conductance values of pyrrolidine-PTCDIs have been determined by analyzing a large number of molecular (m–M–m) junctions created between an STM tip and substrate using a statistical method. Furthermore, we studied the gate dependence of the single-molecule conductance by trapping a molecule between the two electrodes and recording the current as a function of electroche...

Surface Decorating of CH₃NH₃PbBr₃ Nanoparticles with the Chemically Adsorbed Perylenetetracarboxylic Diimide.

An organic dye-modified organolead halide CH3NH3PbBr3 nanoparticle (cubic) is prepared successfully by using a perylenetetracarboxylic diimide (PDI) bearing an -NH3(+) headgroup as the capping ligand. The nanopartilces are homogeneous with high crystallinity. The photoluminescence of perovskite is quenched completely by the chemically adsorbed PDI molecules. This efficient fluorescence quenching has confirmed that the PDI molecules are anchored on the surface of CH3NH3PbBr3 nanoparticle. The resulting nanoparticles can be dispersed in organic solvents, and the resulting dispersion remains stable for days. This result provides a general guideline for surface engineering of organolead halide CH3NH3PbBr3 nanoparticles.

Pn-Heterojunction effects of perylene tetracarboxylic diimide derivatives on pentacene field-effect transistor.

We investigated the heterojunction effects of perylene tetracarboxylic diimide (PTCDI) derivatives on the pentacene-based field-effect transistors (FETs). Three PTCDI derivatives with different substituents were deposited onto pentacene layers and served as charge transfer dopants. The deposited PTCDI layer, which had a nominal thickness of a few layers, formed discontinuous patches on the pentacene layers and dramatically enhanced the hole mobility in the pentacene FET. Among the three PTCDI molecules tested, the octyl-substituted PTCDI, PTCDI-C8, provided the most efficient hole-doping characteristics (p-type) relative to the fluorophenyl-substituted PTCDIs, 4-FPEPTC and 2,4-FPEPTC. The organic heterojunction and doping characteristics were systematically investigated using atomic force microscopy, 2D grazing incidence X-ray diffraction studies, and ultraviolet photoelectron spectroscopy. PTCDI-C8, bearing octyl substituents, grew laterally on the pentacene layer (2D growth), whereas 2,4-FPEPTC, with fluorophenyl substituents, underwent 3D growth. The different growth modes resulted in different contact areas and relative orientations between the pentacene and PTCDI molecules, which significantly affected the doping efficiency of the deposited adlayer. The differences between the growth modes and the thin-film microstructures in the different PTCDI patches were attributed to a mismatch between the surface energies of the patches and the underlying pentacene layer. The film-morphology-dependent doping effects observed here offer practical guidelines for achieving more effective charge transfer doping in thin-film transistors.

Controlled preparation of CdS nanoparticle arrays in amphiphilic perylene tetracarboxylic diimides: organization, electron-transfer and semiconducting properties

Langmuir monolayers of two amphiphilic perylene tetracarboxylic diimide (PDI) derivatives, PDI-1 and PDI-2, which are modified with different numbers of hydrophilic polyoxyethylene/hydrophobic alkoxy side-chains, have been used as not only organic templates but also good functional organic materials to produce the first examples of rose- and petal-like nano-particle arrays of cadmium sulfide (CdS)–PDI composites with a controllable and tunable size (from 40, 60 to 80 nm for nano-roses; from 20 to 30 nm for nano-petals), respectively. These newly fabricated CdS–PDI hybrid nanostructures were comparatively studied using a wide range of methods including SEM, TEM, electronic absorption, fluorescence emission and X-ray diffraction analysis. The crystalline regions for CdS were identified to be hexagonal wurtzite with (101) and (001) face preferred growth on the PDI-1 and PDI-2 monolayers, respectively, associated with the polyoxyethylene side chains architecture changing from parallel to the subphase surface for PDI-1 to perpendicular to the subphase surface for PDI-2. Furthermore, electron-transfer from PDI molecules to CdS nanocrystals is established by both quenching the photoluminescence intensity and changing the lifetime of photoluminescence emission of PDI in the hybrid nanoparticle arrays. In particular, a significantly enhanced conductivity for both nano-roses and nano-petals of CdS–PDI nanocomposites was achieved, relative to that of the individual component, due to the existence of the densely packed molecular architecture in the film matrix and the large interfacial area between the two components that removed the charge transporting bottleneck by creating an interpenetrating network of the hybrid materials, implying the potential of providing synergetic semiconducting properties of the present hybrid organic–inorganic nanomaterials.

Self-assembly and optical properties of N N′-bis(4-(1-benzylpiperidine))perylene-3,4,9,10-tetracarboxylic diimide

Well-defined nanobelts with strong fluorescence were fabricated from a perylene tetracarboxylic diimide molecule modified with specific side-chain substitution. The new perylene diimide was characterised by 1H, 13C NMR, mass and IR spectral techniques. The photophysical and electrochemical properties were investigated by UV–vis absorption, fluorescence, differential scanning calorimetry and cyclic voltammetry. 1D nanobelt self-assembly of the compound was studied with optical, fluorescence and scanning electron microscopic techniques. The observed self-assembly was supported by computational studies using density functional theory and natural bond order analysis. The optimised molecule was fit into crystal space theoretically, and the observed band gap was correlated well with optical and electrical properties.

Organogels Based on J- and H-Type Aggregates of Amphiphilic Perylenetetracarboxylic Diimides

Three new perylenetetracarboxylic diimide (PDI) compounds substituted with hydrophobic and/or hydrophilic groups at the two imide nitrogen positions, namely N,N'-di[N-(4-aminophenyl)-3,4,5-tris(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)benzamide]-1,7-di(4-tert-butylphenoxy)perylene-3,4;9,10-tetracarboxylic diimide (1), N,N'-di[N-amido-3,4,5-tris(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)benzamide]-1,7-di(4-tert-butylphenoxy)perylene-3,4;9,10-tetracarboxylic diimide (2), and N-amido-3,4,5-tris(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)benzamide-N'-amido-3,4,5-tris(dodecyloxy)benzamide-1,7-di(4-tert-butylphenoxy)perylene-3,4;9,10-tetracarboxylate diimide (3), have been designed and prepared. The gelating abilities of them in different solvents have been investigated, and the results indicated that compounds 1 and 3 can form fluorescent gels whereas compound 2 cannot. The properties of the gels of compounds 1 and 3 have been investigated by UV-vis absorption and emission spectra. The results indicate that the gel of compound 1 is composed of H-aggregates, whereas the gel of compound 3 is composed of J-aggregates. The reversible transformation between gel and solution states induced by temperature change is observed. The structure of dried gel has been investigated by X-ray diffraction (XRD) experiments, and the morphology has been measured by atomic force microscopy (AFM). This research revealed successfully the crucial roles of amphiphilic properties and the side-chain conformations in controlling the gelating properties of PDI molecules. This information may be useful for the design of novel organogels based on perylenetetracarboxylic diimides.

Aggregation of wedge-shaped perylenetetracarboxylic diimides with a different number of hydrophobic long alkyl chains

Three perylenetetracarboxylic diimide (PDI) derivatives comprising a different number of hydrophobic alkoxy chains at one imide nitrogen were synthesized. The aggregation behavior of this series of compounds was investigated by UV–vis absorption and emission spectra. The results indicated that large number of hydrophobic alkyl chains at one end of the PDI molecules can induce significant aggregation in solution, but without obvious ground state interaction between the PDI aromatic cores. The aggregation behavior of this series of compounds in solid state was studied by absorption and IR spectra as well as X-ray diffraction (XRD) experiments. The morphology of the solid aggregates was investigated by scanning electronic microscopy (SEM). With an increase of the number of alkyl chains at one end of these PDI molecules, the aggregation mode varies from H type to J type, while the morphology of the solid aggregates changes from small bending belts to long ordered wires. This research demonstrated that one can control the aggregation mode, the order, and the morphology of the molecular aggregates by changing the number of alkyl chains. This information can be useful in the design of novel organic materials which exhibit molecular aggregation.

Field effects on the statistical behavior of the molecular conductance in a single molecular junction in aqueous solution

We have combined molecular dynamics simulations with first-principles calculations to study electron transport in a single molecular junction of perylene tetracarboxylic diimide (PTCDI) in aqueous solution under external electric gate fields. It is found that the statistics of the molecular conductance are very sensitive to the strength of the electric field. The statistics of the molecular conductance are strongly associated with the thermal fluctuation of the water molecules around the PTCDI molecule. Our simulations reproduce the experimentally observed three orders of magnitude enhancement of the conductance, as well as the temperature dependent conductance, under the electrochemical gates. The effects of the molecular polarization and the dipole rearrangement of the aqueous solution are also discussed.

Supramolecular self-assembly study of a flexible perylenetetracarboxylic diimide dimer in Langmuir and Langmuir–Blodgett films

A novel perylenetetracarboxylic diimide molecule ( 2PDI-TAZ), which contains two perylenetetracarboxylic diimide (PDI) attached to a melamine headgroup, was designed and synthesized. Supramolecular self-assemblies were studied in Langmuir and Langmuir–Blodgett films. Surface pressure–area isotherm measurements and the spectroscopic studies indicate that the 2PDI-TAZ molecules adopted a face-to-face configuration and edge-on orientation in Langmuir or the multilayer LB films. The presence of the barbituric acid in subphase change the hydrophilicity of 2PDI-TAZ due to the hydrogen bonding between melamine and barbituric acid, which has been revealed by the π – A isotherms and the FT-IR spectra. Transmission electron microscopy images of the LB films deposited from the barbituric acid solution revealed uniform nanowire morphology while the X-ray diffraction studies indicate that the molecules in the solid film packed with high order. The strong excimer emission of 2PDI-TAZ in LB films suggests enforced face-to-face configuration for the PDI unites in LB films in relative to that in solution.

Temperature-Dependent Statistical Behavior of Single Molecular Conductance in Aqueous Solution

We have combined molecular dynamics simulations with first principles calculations to study electron transport in a single molecule of perylene tetracarboxylic diimide (PTCDI) sandwiched between two gold electrodes with an aqueous electrolyte. This combination has for the first time allowed one to reveal statistical behavior of molecular conductance in solution at different temperatures and to produce conductance histograms that can be directly compared with experiments. Our calculations show that experimentally observed temperature-dependent conductance can be attributed to the thermal effect on the hydrogen bonding network around the molecule and can be described by the radial distribution of water molecules surrounding the oxygen atom in the PTCDI molecule.

Bimolecular Networks and Supramolecular Traps on Au(111)

We demonstrate the formation of intermixed phases and self assembled molecular templates on the Au(111) surface. The templates are stabilized by hydrogen bonding between melamine molecules with trigonal symmetry and linear PTCDI (perylene tetra-carboxylic di-imide) molecules. When annealed, these molecules spontaneously form either a chiral intermixed phase or a honeycomb arrangement in which vertexes and edges correspond respectively to melamine and PTCDI molecules. We also observe minority phases with more complex intermolecular junctions. The use of these networks as templates is demonstrated by the controlled capture of fullerenes within the pores of the network to form dimers, hexamers, and heptamers. Our results confirm that bimolecular templates can be realized on a range of substrates.