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Self-Assembled Organic–Inorganic Hybrid Nanocomposite of a Porphyrin Derivative and CdS
Abstract
A porphyrin derivative, 5-(4-carboxylphenyl)-10,15,20-tris(4-chlorophenyl) porphyrin (PorCOOH), was synthesized and self-assembled as a monolayer thin solid film on the modified surface of a quartz substrate by an ester bond between –COOH groups of PorCOOH molecules and –OH groups of the hydrophilic pretreated SiO2 surface. An analysis of the spectral change revealed the J-aggregate nature of PorCOOH molecules in the obtained thin solid film. With this thin solid film of PorCOOH as a template, CdS nanoparticles were deposited on it in situ, which were further characterized by electronic absorption, fluorescence, and energy-dispersive X-ray spectroscopy. The morphology of CdS nanoparticles is disklike, and the diameter is ca. 40–60 nm, determined by scanning electronic microscopy. Furthermore, electron transfer between the organic layer and CdS nanoparticles was deduced through fluorescence quenching and theoretical analysis.
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Electron donating substituents such as 3,4,5-trimethoxy phenyl (PDI1), thiophene (PDI2), 6-methoxy naphthyl (PDI3), 5-hexyl dithiophene (PDI4) and thioanthrenyl (PDI5) moieties incorporated at the bay region of N,N 0 -dodecylperylene diimide (PDI) derivatives have been synthesized and characterised. The absorption maxima of PDI1–5 showed a bathochromic shift with considerable peak broadening and merging of vibronic fine structure as compared to that of PDI. The photoinduced intramolecular charge transfer (ICT) from electron donating substituents to the perylene-acceptor has been observed from fluorescence self-quenching. The molecules are stable up to 400 C and amorphous in nature. The cyclic voltammetry results revealed that the oxidation potential can be tuned by the electron donating capacity of the substituents and the dithiophene-attached perylene derivative (PDI4) showed a very low band gap of 1.57 eV. The electron transporting properties have been studied using xerographic time-of-flight method and the highest electron mobility reached up to 4.4 Â 10 À4 cm 2 V À1 s À1 at 6.4 Â 10 5 V cm À1 for 1,7-di(3,4,5-trimethoxyphenyl)perylene diimide (PDI1) under ambient conditions.
Synthesis and crystal structure of 5-(4′-carboxyphenyl)-10,15,20- tri(4′-t-butylphenyl)porphinato zinc(II) have been presented. The title complex shows interesting hydrogen-bonded dimeric structure in the solid state.
Organic-inorganic hybrid materials promise both the superior carrier mobility of inorganic semiconductors and the processability of organic materials. A thin-film field-effect transistor having an organic-inorganic hybrid material as the semiconducting channel was demonstrated. Hybrids based on the perovskite structure crystallize from solution to form oriented molecular-scale composites of alternating organic and inorganic sheets. Spin-coated thin films of the semiconducting perovskite (C(6)H(5)C(2)H(4)NH(3))(2)SnI(4) form the conducting channel, with field-effect mobilities of 0.6 square centimeters per volt-second and current modulation greater than 10(4). Molecular engineering of the organic and inorganic components of the hybrids is expected to further improve device performance for low-cost thin-film transistors.
We reported a new approach for fabrication of a multilayer film through coordinate bonds of pyridine polymers and CdS nanoparticles, which was identified by UV-Vis and FTIR spectroscopy.
The title bis(imidazol-4-yl)porphyrin 1 gave supramolecular
assemblies through hydrogen bonding; efficient excited energy transfer
followed by electron transfer to quenchers has been observed in
toluene.
By means of laser deposition, spin casting and vacuum evaporation, optoelectronic hybrid devices were manufactured based upon the thin-film heteropairing of a perylene-derived molecule [di-isoquinoline perylene derivative (DQP)] and CdS. The photovoltaic characteristics of the devices are presented and discussed. We demonstrate that by exploitation of relatively high carrier mobilities in the CdS layer and the high photonic yield and deposition ease of the DQP film, efficient and technologically appealing optoelectronic devices are feasible. In addition, bias dependence of the spectral sensitivity demonstrates the versatility of the introduced device concept in light of photonic sensor applications. © 2002 American Institute of Physics.
The realization of molecule-based miniature devices with advanced functions requires the development of new and efficient approaches for combining molecular building blocks into desired functional structures, ideally with these structures supported on suitable substrates. Supramolecular aggregation occurs spontaneously and can lead to controlled structures if selective and directional non-covalent interactions are exploited. But such selective supramolecular assembly has yielded almost exclusively crystals or dissolved structures; the self-assembly of absorbed molecules into larger structures, in contrast, has not yet been directed by controlling selective intermolecular interactions. Here we report the formation of surface-supported supramolecular structures whose size and aggregation pattern are rationally controlled by tuning the non-covalent interactions between individual absorbed molecules. Using low-temperature scanning tunnelling microscopy, we show that substituted porphyrin molecules adsorbed on a gold surface form monomers, trimers, tetramers or extended wire-like structures. We find that each structure corresponds in a predictable fashion to the geometric and chemical nature of the porphyrin substituents that mediate the interactions between individual adsorbed molecules. Our findings suggest that careful placement of functional groups that are able to participate in directed noncovalent interactions will allow the rational design and construction of a wide range of supramolecular architectures absorbed to surfaces.
11-Aminoundecanoic acid capped titanium dioxide (capped-TiO2) nanoparticles (63 ± 2 Å total diameter and 20−24 Å core diameter) and polyallylamine hydrochloride, PAH, have been layer-by-layer self-assembled onto precoated (by poly(diallyldimethylammonium chloride), PDDA, or PAH) substrates. The ultrathin S-PDDA(capped-TiO2/PAH)n (n = 5, 10, 15) films have been characterized by absorption and surface plasmon spectroscopies, cyclic voltammetry, and scanning force microscopy. A S-PDDA(capped-TiO2/PAH)10 film coated by a layer of gold has been shown to function as a Schottky diode.
We report the control of molecular orientation in solid films through self-organization and induced-orientation processes. We synthesized water-soluble cationic 3,4,9,10-perylene diimide (1) and studied its self-organization in aqueous solution. By UV−vis spectroscopy, H-aggregates of 1 were observed forming in solutions with concentrations as low as 10-7 M. At concentrations above approximately 0.1 M (7% w/w), these solutions were observed with polarized microscopy to form a chromonic N phase (a nematic lyotropic liquid crystalline phase) at room temperature. Upon induced alignment (by shearing) of the chromonic N phase on a glass substrate and removal of solvent, anisotropic solid films of the dichroic dye were produced. These films have dichroic ratio values that routinely exceed 25 and in some cases 30, making them excellent polarizers over the blue and green region. By use of a combination of polarized UV−vis and FT-IR spectroscopies, the orientation of the average molecular plane in these films was determined to be perpendicular to both the shearing direction and the substrate plane. Small-angle X-ray diffraction studies indicate that the molecules in the solid film possess a high degree of order.
We synthesized a series of n-octadecylsiloxanes having different empirical formulas, that is, R-SiO3/2 (R = C18H37), R-(CH3)SiO2/2, and R-(CH3)2SiO1/2. We found that the compound with the formula R-SiO3/2 shows the highest PL emission with a quantum yield of 19 ± 0.5%, whereas the compound with the formula R-(CH3)2SiO1/2 hardly shows the PL output. The present results clearly demonstrate that carbon-related species are not responsible for the PL; rather, the PL emission results from some silicon/oxygen-related defect species. On the basis of the present experimental findings, a structural origin of the PL from silica based organic−inorganic hybrid materials is proposed.
This paper describes a novel chemical method for controlled assembly of regular composite nanowire arrays at the molecular level. The polycationic poly(N-vinylcarbazole) (PNVK) template is prepared by electrochemical polymerization of the N-vinylcarbazole monomer. Regular composite nanowire arrays of thallic oxide (Tl2O3) and polycationic PNVK are fabricated through ordered aggregation of the negative Tl2O3 nanoparticles along the positive chains of the polycationic PNVK in the polycationic PNVK−arachidic acid (AA) mixed monolayer on the air−alkaline Tl2O3 sol interface. The widths of the Tl2O3 and the polycationic PNVK nanowires are 3.2 and 2.7 nm, respectively. The above regular nanowire arrays can also be obtained when a polycationic PNVK single component is used as a template. These nanowires lie in the plane of the corresponding monolayers. The polycationic PNVK−AA mixed monolayer and the Tl2O3 nanowire arrays aggregated along the polycationic PNVK chains can be easily transferred onto hydrophobic substrates layer by layer to form Langmuir−Blodgett (LB) multilayers with a spacing of 5.5 nm. This novel method should be applicable to the preparation of a wide range of composite nanowire arrays.
Spectroscopic (absorption and emission), microscopic (transmission electron and atomic force), X-ray diffraction and photocurrent measurements have provided evidence for the formation of stable ultrathin films with regular periodicities, by the layer-by-layer self-assembly of polycations and cadmium sulfide, lead sulfide and titanium dioxide nanoparticles.
Highly conductive hybrid Langmuir−Blodgett (LB) films of MoS2 and amphiphilic compounds such as alkylammonium halides and alkylamines were fabricated. The interlayer spacing of the LB films depended on the organic species. The lateral conductivity of 10-layer LB films was in the range of 101 to 102 S cm-1 and decreased with an increase in interlayer spacing. The conductivity of 102 S cm-1 is the highest value for LB films reported so far. The conductivity of the LB films increased with the layer number and became constant when the layer number was sufficiently large. The conductivity was stable at room temperature even for single-layer LB films and decreased by less than an order of magnitude during four months.
A never route to form superhydrophobic-superhydrophilic micropatterned coating film has been developed. UV light was irradiated on the superhyrdrophobic coating film which consists of three layers, a flowerlike Al2O3 gel film, a very thin TiO2 gel layer, and a FAS layer, to cleave the fluoroalkyl chain in FAS selectively, and well-defined superhydrophobic and superhydrophilic regions were formed.
A novel amphiphilic sandwich-type mixed (phthalocyaninato)(porphyrinato)europium double-decker complex Eu(Pc)[T(OH)3PP] [Pc = phthalocyaninate, T(OH)3PP = 5,10,15-tris(4-hydroxyphenyl)-20-(4-tert-butylphenyl)porphyrinate](1) was designed, prepared, and characterized by a range of spectroscopic methods in addition to elemental analysis. By employing a solution injection method, this compound self-assembles into nanoscale hollow spheres with an average diameter of ca. 70 nm. The hollow spherical structure was determined by transmission electronic microscopy and scanning electronic microscopy. Comparison in the electronic absorption spectrum between the aggregate and the compound itself in solution reveals the J-aggregation packing mode of the amphiphilic double-decker molecules in nanoscale hollow spheres. The present work represents the first example of nanoscale hollow sphere morphology self-assembled from sandwich tetrapyrrole rare-earth complexes.
The preparation and structural characterization of an iodoplumbate salt based on the protonated cystamine (H3N(CH2) 2S-S(CH2)2NH3)2+ cation was reported. BiI3 and cystamine dihydrochioride were dissolved in 30 mL CH3CN. The solution was heated under stirring for 15 mm. before 0.5 mL of concentrated HI were added drop wise over a total period of 5 mm, after which 10 mL of distilled water were added in order to clarify the solution. The solution was subsequently heated for 4 h, before being put into an aerator. All non-hydrogen atoms were refined anisotropically for both structures while hydrogen atoms were treated with a riding model. An 85 % loss in third harmonic generation (THG) efficiency is observed for the high temperature phase, which makes bismuth salt a promising material for the prospective tuning of THG intensity.
The aim of this review is to explore the fundamental and technological incentive for the molecular design, synthesis, and aggregation behavior of conjugated organic molecules with photo‐electronic activity, and the fabrication of low‐dimensional organic conjugated nanomaterials by self‐assembly techniques. The properties of large oriented nanostructure arrays of organic charge transfer complexes based on conjugated molecules are also discussed. The dimension‐dependent emission properties have been observed, and conductivity, field emission properties, and sensing properties have been studied for the low dimensional nanostructures of nanoparticles, nanowires, nanorods, and nanostructure arrays.
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A study has demonstrated average effects of the charge transfer (CT) on pyrene/CdSe nanoparticles to single-walled carbon nanotubes (SWNT) with different chiralities using fluorescence quenching experiments and transistor measurements. The study has also speculated on the incorporation of such acceptor-donor hybrids into organic solar cells to improve the performance of the devices. The magnitude of the CT shows a strong dependency on the light intensity and wavelength and reaches a maximum of 2.2 electrons acceptors. The technique facilitates the use of the formation of pyrene/CdSe-SWNT hybrids that favors the electrons or hole transfer from quantum dots to the SWNT, acceptor, such that the excited electrons or holes enter the SWNT rather than be emitted. The attempt has followed time resolved fluorescence to probe the dynamics of the CT in solution, temperature dependent transport measurement to study the CT barrier between nanoparticles, and SWNT with different chiralities.
Porphyrins, phthalocyanines, and perylenes are compounds with great potential for serving as components of molecular materials that possess unique electronic, magnetic and photophysical properties. In general, a highly specific commu- nication between a large number of these chromophores is required in order to express their function to a maximal level, and for this reason it is of importance to construct arrays in which the molecules are organized in well-defined geometries with respect to their neighbors. This re- view is an account of some recent efforts to construct highly ordered assemblies of porphyrins, phthalocyanines, and perylenes by means of self-assembly in solution and on surfaces, and by attaching them to polymeric scaffolds.
A simple model (extended dipole model) for the calculation of interaction integrals between dye molecules in aggregates is shown to be in excellent agreement with the result of quantum-mechanical computations even at direct contact of the molecules.
Stationary and time-resolved quenching measurements of the excitonic and trapped fluorescence of quantum sized CdS colloids were carried out. We found that nitromethane is only capable of quenching the excitonic fluorescence nearly completely, whereas a fraction of the trapped fluorescence, the amount of which depends on the particle size, always remains. Methylviologen, with a slightly more positive acceptor potential, is able to quench both types of fluorescence nearly completely in all the investigated samples. The findings are explained straightforwardly by a fluorescence mechanism involving shallow electron traps and deep hole traps located on the surface of the nanocrystalline particles.
Using the small molecule TEOP (5,10,15,20-[1,4-benzodioxane-6-carboxalde] porphyrin), the in situ assembly is a very convenient and efficient approach for fabricating high-quality ordered patterns. The well-ordered patterns possess strong saturated absorptive and self-defocusing nonlinearities while the TEOP solution exhibit reverse saturated absorption. The value of the nonlinear absorption coefficient of the TEOP ordered pattern and solution differed by three orders of magnitude. (Figure Presented)
To investigate the effects of metal-ligand coordination on the molecular structure, internal structure, dimensions, and morphology of self-assembled nanostructures, two nonperipherally octa(alkoxyl)-substituted phthalocyanine compounds with good crystallinity, namely, metal-free 1,4,8,11,15,18,22,25-octa(butyloxy)phthalocyanine H(2)Pc(alpha-OC(4)H(9))(8) (1) and its lead complex Pb[Pc(alpha-OC(4)H(9))(8)] (2), were synthesized. Single-crystal X-ray diffraction analysis revealed the distorted molecular structure of metal-free phthalocyanine with a saddle conformation. In the crystal of 2, two monomeric molecules are linked by coordination of the Pb atom of one molecule with an aza-nitrogen atom and its two neighboring oxygen atoms from the butyloxy substituents of another molecule, thereby forming a Pb-connected pseudo-double-decker supramolecular structure with a domed conformation for the phthalocyanine ligand. The self-assembling properties of 1 and 2 in the absence and presence of sodium ions were comparatively investigated by scanning electronic microscopy (SEM), spectroscopy, and X-ray diffraction techniques. Intermolecular pi-pi interactions between metal-free phthalocyanine molecules led to the formation of nanoribbons several micrometers in length and with an average width of approximately 100 nm, whereas the phthalocyaninato lead complex self-assembles into nanostructures also with the ribbon morphology and micrometer length but with a different average width of approximately 150 nm depending on the pi-pi interactions between neighboring Pb-connected pseudo-double-decker building blocks. This revealed the effect of the molecular structure (conformation) associated with metal-ligand (Pb-N(isoindole), Pb-N(aza), and Pb-O(butyloxy)) coordination on the dimensions of the nanostructures. In the presence of Na(+), additional metal-ligand (Na-N(aza) and Na-O(butyloxy)) coordination bonds formed between sodium atoms and aza-nitrogen atoms and the neighboring butyloxy oxygen atoms of two metal-free phthalocyanine molecules cooperate with the intrinsic intermolecular pi-pi interactions, thereby resulting in an Na-connected pseudo-double-decker building block with a twisted structure for the phthalocyanine ligand, which self-assembles into twisted nanoribbons with an average width of approximately 50 nm depending on the intertetrapyrrole pi-pi interaction. This is evidenced by the X-ray diffraction analysis results for the resulting aggregates. Twisted nanoribbons with an average width of approximately 100 nm were also formed from the lead coordination compound 2 in the presence of Na(+) with a Pb-connected pseudo-double-decker as the building block due to the formation of metal-ligand (Na-N(aza) and Na-O(butyloxy)) coordination bonds between additionally introduced sodium ions and two phthalocyanine ligands of neighboring pseudo-double-decker building blocks.
Novel metal-free 5,15-di[4-(5-acetylsulfanylpentyloxy)phenyl]porphyrin H2[DP(CH3COSC5H10O)2P] (1) and its zinc congener Zn[DP(CH3COSC5H10O)2P] (2) were designed and synthesized. Single-crystal X-ray diffraction (XRD) analysis confirmed the tetrapyrrole nature of these two compounds, revealing the existence of metal-ligand coordination bond between the carbonyl oxygen in the aryloxy side chain of meso-attached phenyl group in the porphyrin molecule with the zinc center of neighboring porphyrin molecule in the crystal structure of 2. This intermolecular Zn-O coordination bond induces the formation of a supramolecular chain structure in which the porphyrinato zinc moieties are arranged in a "head-to-tail" mode (J-aggregate), which is in contrast to a "face-to-face" stacking mode (H-aggregate) in the supramolecular structure formed depending on the C-H...pi interaction in the crystal of 1. Their self-assembling properties in MeOH and n-hexane were comparatively investigated by scanning electronic microscopy and XRD technique. Intermolecular pi-pi interaction of metal-free porphyrin 1 leads to the formation of hollow nanospheres and nanoribbons in MeOH and n-hexane, respectively. In contrast, introduction of additional Zn-O coordination bond for porphyrinato zinc complex 2 induces competition with intermolecular pi-pi interaction, resulting in nanostructures with nanorod and hollow nanosphere morphology in MeOH and n-hexane. The IR and XRD results clearly reveal the presence and absence of such metal-ligand coordination bond in the nanostructures formed from porphyrinato zinc complex 2 and metal-free porphyrin 1, respectively, which is further unambiguously confirmed by the single-crystal XRD analysis result for both compounds. Electronic absorption spectroscopic data on the self-assembled nanostructures reveal the H-aggregate nature in the hollow nanospheres and nanoribbons formed from metal-free porphyrin 1 due to the pi-pi intermolecular interaction between porphyrin molecules and J-aggregate nature in the nanorods and hollow nanospheres of 2 depending on the dominant metal-ligand coordination bonding interaction among the porphyrinato zinc molecules. The present result appears to represent the first effort toward controlling and tuning the morphology of self-assembled nanostructures of porphyrin derivatives via molecular design and synthesis through introduction of metal-ligand coordination bonding interaction. Nevertheless, availability of single crystal and molecular structure revealed by XRD analysis for both porphyrin derivatives renders it possible to investigate the formation mechanism as well as the molecular packing conformation of self-assembled nanostructures of these typical organic building blocks with large conjugated system in a more confirmed manner.
A series of five novel sandwich-type mixed (phthalocyaninato)(porphyrinato) europium triple-decker complexes with different numbers of hydroxyl groups at the meso-substituted phenyl groups of porphyrin ligand 1-5 have been designed, synthesized, and characterized. Their self-assembly properties, in particular the effects of the number and positions of hydroxyl groups on the morphology of self-assembled nanostructures of these triple-decker complexes, have been comparatively and systematically studied. Competition and cooperation between the intermolecular pi-pi interaction and hydrogen bonding in the direction perpendicular to the pi-pi interaction direction for different compounds were revealed to result in nanostructures with a different morphology from nanoleafs for 1, nanoribbons for 2, nanosheets for 3, and curved nanosheets for 4 and to spherical shapes for 5. The IR and X-ray diffraction (XRD) results reveal that, in the nanostructures of triple-decker 2 as well as 3-5, a dimeric supramolecular structure was formed through an intermolecular hydrogen bond between two triple-decker molecules, which as the building block self-assembles into the target nanostructures. Electronic absorption spectroscopic results on the self-assembled nanostructures reveal the H-aggregate nature in the nanoleafs and nanoribbons formed from triple-deckers 1 and 2 due to the dominant pi-pi intermolecular interaction between triple-decker molecules, but the J-aggregate nature in the curved nanosheets and spherical shapes of 4 and 5 depending on the dominant hydrogen bonding interaction in cooperation with pi-pi interaction among the triple-decker molecules. Electronic absorption and XRD investigation clearly reveal the decrease in the pi-pi interaction and increase in the hydrogen bonding interaction among triple-decker molecules in the nanostructures along with the increase of hydroxyl number in the order of 1-5. The present result appears to represent the first effort toward realization of controlling and tuning the morphology of self-assembled nanostructures of sandwich tetrapyrrole rare earth complexes through molecular design and synthesis.
Elektronentransport durch Nanoröhren: Dies wird als Erklärung für die höheren Photoströme in einem System aus CdS-Nanopartikeln angeboten, die über Kohlenstoffnanoröhren mit einer Goldelektrode verknüpft sind (siehe Bild, TEOA=Triethanolamin). Der effektive Transport von Leitungsbandelektronen durch die Nanoröhre zur Elektrode konkurriert mit der Elektron-Loch-Rekombination in den CdS-Halbleiter-Nanopartikeln.
Clusters of phthalocyanine and phthalocyanine-perylene diimide have been prepared and electrophoretically deposited on nanostructured SnO2 electrodes. The structure and photoelectrochemical properties of the clusters have been investigated by using UV-visible absorption, dynamic light scattering (DLS), atomic force microscopy (AFM), transmission electron microscopy (TEM), and photoelectrochemical and photodynamical measurements. Enhancement of the photocurrent generation efficiency in the composite system has been achieved relative to that in the phthalocyanine reference system without the perylene diimide. Such information will be valuable for the design of molecular photoelectrochemical devices that exhibit efficient photocurrent generation.
Ultrathin films with noncentrosymmetrically orientated azobenzene chromophores were constructed using a combination of layer-by-layer adsorption of polyelectrolytes and the surface sol-gel process.
Ultrafast dissociation of excitons in US quantum dots via electron transfer to adsorbed rhodamine B (RhB) molecules was demonstrated. The rate of electron transfer can be controlled by the number of adsorbates attached on the nanoparticle and transfer time as fast as 12 picoseconds was observed. The rapid and controllable charge separation in this model quantum dot-adsorbate complex provides a potential approach for separating multiple excitons before the exciton-exciton annihilation process.