Abstract  The aggregate-induced limitation for high power-conversion efficiencies (PCEs) of perylene-diimide (PDI):polymer solar cells can be circumvented when two simple rules are respected; the aggregate size of PDI remains short enough and the omnipresent PDI aggregates are electronically interconnected. Following these guidelines, a PCE of 3.7% is delivered by using the solution-processable, planar PDI monomer of N,N'-bis(1-ethylpropyl)-perylene-3,4,9,10-tetracarboxylic diimide as the electron acceptor mixed with the low-energy gap polymeric donor poly[(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b;4,5-b']dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno[3,4-b]thiophene))-2,6diyl] (PBDTTT-CT). The PBDTTT-CT:PDI composite absorbs strongly the light in the region of 400 nm-800 nm and after adding a small amount of 1,8-diiodooctane (DIO) efficient photocurrent generation is achieved. Space-charge limited dark current and transient photovoltage measurements suggest that the use of the DIO component optimizes the electron/hole carrier mobility ratio, suppresses the non-geminate recombination losses and improves the charge extraction efficiency.

Abstract  Simultaneous single molecule tracking (SMT) and single molecule emission dichroism (SMED) measurements are used to investigate the translational and orientational motions of fluorescent probes diffusing within mesoporous silica films. The results afford a quantitative measure of molecular confinement within the mesopores and allow for the accessible pore diameter to be determined with higher precision than can be achieved by common SMT methods alone. In these studies, dual-polarization wide-field video microscopy is used to obtain SMT data simultaneously in two orthogonal polarizations. A rod-shaped perylene diimide dye (C11OPDI) is employed as the probe and is excited by circularly polarized light. SMT reveals a predominance of one-dimensional dye diffusion within the mesopores. The SMED data demonstrate that the molecules diffuse in an oriented state, with their long axes parallel, on average, to the long axis of the mesopores. Theoretical expressions quantitatively relating the SMED and SMT results to the extent of C11OPDI orientational wobbling are developed. The results are consistent with confined wobbling of the single molecules within the mesopores. An ensemble-averaged wobbling angle of 19 3 is obtained, yielding an estimated accessible pore diameter of 1.3 +/- 0.2 nm.

Abstract  Photoconduction of bilayer organic p/n junction photocells can be finely tuned through the alteration of either the side, chain orientation (regiorandom vs regioregular) or main chain structure in poly(3-alkylthiophene)s (P3ATs), where the incorporation of an electron-donating group (EDOT) appears to be an excellent method for enhancing the photoconduction. Moreover, doping of P3ATs proved to be an equally viable route for tuning the device characteristics. These polymers were used to fabricate bilayer organic photocells with the polymer as the p-type layer and 1,2-diaminobenzene perylene-3,4,9,10-tetracarboxylic acid diimide (PV) as the n-type layer. Action spectra at steady-state illumination demonstrated that all the interfaces (organic-organic p/n junction and organic-electrode) are actively involved in the photogeneration of carriers. Experiments showed that critical device properties, for example, open-circuit voltage (V-oc) and short-circuit current (I-sc), are not only dependent on the selection of electrodes and organic materials but also greatly affected by the illumination wavelength and intensity.

Abstract  The transient photoconducting behavior of organic p/n bilayer photocells has been investigated in cells constructed with the copolymer, poly(3-butylthiophene-co-ethylenedioxythiophene), as p-type material and a perylene diimide (PV) as the n-type material. The decay rate constant of the transient photocurrent observed after pulsed illumination is independent of the applied electric field, light intensity, and temperature. However, the peak photoresponse was strongly affected by these variables. Simulations of the photoresponse revealed that the peak current depends primarily on the carrier mobility (at a given light intensity), whereas the characteristic decay rate is hardly influenced by the mobility, but depends on the carrier lifetime which is chiefly due to trapping by deep levels.

Abstract  A variety of naphthalimide hydroperoxides as novel photochemical DNA cleavers were synthesized and evaluated. Their photochemical DNA-cleaving abilities depend on the substituents on the aromatic moiety. The DNA-cleaving differences of these hydroperoxides may result from the differences of the intercalating ability of the naphthalene moiety. X-ray single crystal structure of a representative compound 1 was determined, and showed that all endocyclic atoms were coplanar, indicating a structural basis for potential and efficient DNA intercalation by 1. (C) 1999 Elsevier Science Ltd. All rights reserved.

Abstract  Experimental results concerning two-photon absorption (TPA) cross-section measurement using nonlinear transmission (NLT) method and a new pump-probe mode-mismatched thermal lens (TL) scheme, in picosecond regime are reported. Both methods are used in a prospect of comparison. Values of the TPA coefficient and cross-section in three common solvents (Chloroform. Benzene and Nitrobenzene) and new synthesized perylenediimide derivatives (PDI) at 532nm and 1064nm wavelengths are given.

Abstract  This study deals with the growth mode of N,N '-dipenthyl-3,4,9,10-perylenetetracarboxylic diimide (PTCDI-5C) thin films from less than 1 monolayer to 23 monolayers thick. The effects of growth temperature and the thickness and nature of the substratesSiO(2) on Si(001) or octadecyltrichlorosilane (OTS) self-assembled monolayer terminated Si(001) surfacesare discussed. Thin films were deposited from a homemade Knudsen cell by using a hot-wall deposition technique. Films were analyzed by atomic force microscopy, X-ray diffraction, and X-ray reflectivity. Films exhibited a (001) orientation with a 1.63 nm d spacing, and a metastable thin film phase was observed without any distinction of the nature of the substrate. However, differences were noticed in the early stages of growth: PTCDI-5C/SiO2 first monolayers presented a Stransky-Krastanov growth mode, whereas PTCDI-5C/OTS first monolayers showed a more complex mode with incomplete wetting of the substrate surface. Differences between the two morphologies softened as the film thickness increased.

Abstract  New N,N'-substituted 1,4,5,8-naphthalene tetracarboxylic diimides (NTCDIs) were synthesized in one step reactions, resulting in excellent electron mobilities in air as measured in organic field effect transistors (OFETs). Two perfluoroalkyl-benzyl N,N' substituents were used, differing in the length of the perfluoroalkyl moieties on the benzyl portion of the molecule. Single crystals of the short chain compound 2 were successfully grown by horizontal vapor deposition, and crystal structures were obtained and analyzed. Devices from both compounds were fabricated on untreated and silane treated Si/SiO2 substrates. The longer chain compound 1 gives the largest field effect mobility, reaching 0.57 cm(2)/(V s) in air. This is competitive with the best air stable n-channel materials to date. In contrast to previously studied high mobility materials, 1 achieved mobilities near 0.4 cm(2)/(V s) without the use of dielectric substrate treatments. Additionally, 1 displays exemplary ordering regardless of surface treatment, as determined from X-ray diffraction, while 2 displays significant improvement in mobility and film structure when deposited on surface treated substrates.

Abstract  In this paper, we report the synthesis and characterization of six 1,8-naphthalimides [4a-4c and 5a-5c] obtained by the substitution of electron donating halogen-phenoxy groups at the C-4 position. The derivatives were characterized using H-1 NMR, C-13 NMR, mass spectra, FT-IR, single crystal XRD; photo-physical, thermal, surface morphological and electrochemical properties were also investigated. The derivatives exhibit deep blue photoluminescence in the range 414-423 nm (in CHC1(3)) and 457-466 nm (in thin film state) on UV excitation with high Stokes' shifts and good chromaticity. The TGA and DSC analysis showed that the derivatives possess good thermal stability (271-284 degrees C) and melting points (138-201 degrees C). The HOMO and LUMO energy levels estimated by cyclic voltammetry are in the range 6.21-6.34 eV and 3.31-3.41 eV respectively corresponding to energy band gaps of 2.98-3.15 eV. These energy values are relatively higher than the commonly used electron transporting materials. The optical and electronic properties of the derivatives were tuned by the introduction of different electron donating halogen-phenoxy groups through C-4 position of the naphthalimide moiety. The emissive and electron-transporting properties of the naphthalimide derivative 4a were studied by fabricating a bi-layer and tri-layer devices. Further a phosphorescent device with 4a as electron transport layer (ETL) exhibited superior performance than the device without any ETL and was comparable with the device using standard Alq(3) as ETL. These results indicate that the synthesized naphthalimide derivatives could play an important role in the development of OLEDs. (C) 2014 Elsevier B.V. All rights reserved.

Abstract  Using visible and near-infrared transient absorption spectroscopy to track distinct excited state, cation, and anion signals, we report a detailed kinetic analysis of photoinitiated multi-step charge separation and ultrafast charge transfer induced dissociation in a self-assembled donor-bridge-acceptor-cobaloxime triad. The donor-bridge-acceptor ligand consists of a perylene chromophore linked via a xylene bridge to a pyridyl-substituted 1,8-naphthalimide electron acceptor. Coordination of the ligand to the catalyst [Co(dmgBF(2))(2)(L)(2)], where dmgBF(2) - (difluoroboryl) dimethylglyoximato and L water or a solvent molecule, yields a donor-bridge-acceptor-catalyst triad assembly. Photoexcitation with 416 nm laser pulses generates the perylene S-1 excited state. Subsequent electron transfer from perylene to the acceptor occurs in tau = 9.0 +/- 0.1 ps followed by electron transfer to the catalyst in tau = 6 +/- 1 ps. Of the charge-separated state population formed, 79 +/- 1% undergoes charge recombination to either the singlet ground state (tau = 0.8 +/- 0.1 ns) or the perylene triplet state (tau = 4.3 +/- 0.1 ns). Co(I)-pyridyl bond dissociation with tau = 2.4 +/- 0.2 ns competes with intramolecular charge recombination resulting in a 21 +/- 1% yield of dissociated oxidized photosensitizer and reduced catalyst. Subsequent diffusional charge recombination occurs with k = (1.8 +/- 0.2) x 10(10) M-1 s(-1). This detailed analysis of the electron transfer and dissociation dynamics of an integrated photosensitizer-catalyst system will inform the rational design of novel molecular assemblies that efficiently absorb photons, transfer electrons, and catalyze fuel-forming reactions.

Abstract  We report on the fabrication of fluorescent pH-sensing organic/inorganic hybrid mesoporous silica nanoparticles (MSN) capable of tunable redox-responsive release of embedded guest molecules. The reversible addition-fragmentation chain transfer (RAFT) copolymerization of N-(acryloxy)succinimide (NAS), oligo(ethylene glycol) monomethyl ether methacrylate (OEGMA), and 1,8-naphthalimide-based pH-sensing monomer (NaphMA) at the surface of MSN led to fluorescent organic/inorganic hybrid MSN. The obtained hybrid MSN exhibits excellent water dispersibility and acts as sensitive fluorescent pH probes in the range pH 4-8 due to the presence of NaphMA moieties. After loading with rhodamine B (RhB) as a model drug molecule, P(NAS-co-OEGMA-co- NaphMA) brushes at the surface of hybrid MSN were cross-linked with cystamine to block nanopore entrances for the effective retention of guest molecules. Taking advantage of disulfide-containing cross-linkers, the release rate of RhB can be easily adjusted by adding varying concentrations of dithiothreitol (DTT), which can cleave the disulfide linkage to open blocked nanopores. The increase of DTT concentration from 0 to 20 mM led to 20-30 times enhancement of RhB release rate. The reported multifunctional hybrid MSN augurs well for applications in controlled-release nanocarriers, cell and tissue imaging, and clinical diagnosis.

Abstract  Solution-processable carbazoledioxazine derivatives with different halogen substituents (F, Cl, and Br) were newly synthesized by condensation and subsequent cyclization reactions. The chemical structures were confirmed by (1)H1 NMR and IR spectroscopies as well as MALDI-TOF mass spectrometry. All three carbazoledioxazines possessed a high thermal stability with decomposition temperatures exceeding 270 degrees C and exhibited thermal transitions upon heating. The phases were characterized by their wide-angle X-ray diffraction patterns at various temperatures. In addition, the energy levels of the carbazoledioxazines were estimated from the optical absorption spectra and electrochemical redox potentials of the thin films. All three derivatives displayed more or less the same energy levels: highest occupied molecular orbitals (HOMOs) of -5.3 eV and lowest unoccupied molecular orbitals (LUMOs) of -3.5 similar to -3.6 eV. Despite this fact, the Br derivative showed higher hole mobilities with the maximum mobility of 4.9 X 10(-3) cm(2) Vs(-1) in the thin film transistors as compared to those of the counter F and Cl derivatives. This was attributed to the bimodal carrier pathways formed through the monoclinic molecular orientation of the Br derivative, revealed by grazing-incidence X-ray diffraction (GIXRD) measurements.

Abstract  Carbazole based D-pi-A extended styryl dyes with intramolecular charge transfer characteristics were synthesized. The intramolecular charge transfers of these D-pi-A extended styryls have been examined with the study of photophysical properties like absorption, emission and quantum yield in various solvents of different polarities. All the dyes demonstrated positive solvatochromism. They showed largely improved photophysical properties and large Stokes shifts due to twist geometry. Oscillator strengths and transition state dipole moments have been studied to understand charge transfer within the molecules. The fluorescence molecular rotors properties of the series of extended styryls have been evaluated. The dyes having good charge transfer characteristics showed better FMR properties. Sensitivity of the fluorescence emission towards solvent polarity and viscosity has been investigated using fluorescence emission spectra. (C) 2016 Elsevier Ltd. All rights reserved.

Abstract  Poly(styrene-co-maleic anhydride) (SMA) was modified by commercially available fluorescent dye, 4-amino-N-(2,4-dimethylphenyl)-1,8-naphthalimide, to prepare fluorescent poly(styrene-co-maleimide) (SMI). FT-IR, UV-Vis and fluorescent spectra of this polymer were investigated. The polymer can emit strong yellow-green fluorescence (around 5 10 nm) and its thermal stability and solubility were improved. The number-averaged molecular weight (]U) measured by GPC was about 1.8X10(5) relative to the polystyrene standard and the molecular weight distribution was 1.86. The glass transition temperature (T-g) determined by differential scanning calorimeter (DSC) was 150.8 degreesC, and 17 degreesC higher than the T. (133.7 degreesC) of SMA. The influences of solvent, concentration and quencher on the fluorescent behaviors of SMI are discussed too. (C) 2002 Elsevier Science B.V. All rights reserved.

Abstract  Solution-processed n-type organic field-effect transistors (OFETs) have been fabricated using soluble derivatives of perylene diimide and naphthalene diimide. We report the synthesis of the organic semiconductors and the fabrication of bottom gate OFET devices using solution-processed organic dielectrics. Surface morphology studies reveal films with layered textures and liquid crystalline-like structure. Devices show field-effect electron mobilities of 10(-2) cm(2)/V s and 10(-3) cm(2)/V s for N,N'-bis-n-butyl-1,4,5,8-naphthalenediimide-NDI under inert conditions and in air, respectively. N,N'-bis-(1-pentyl)hexyl-3,4,9,10-perylene diimide-PDI-4 shows mobility of 5 x 10(-4) cm(2)/V s. Organic field-effect transistors based on N,N'-bis(dehydroabietyl)-3,4,9,10-perylene diimide-PDI-1 derivative exhibit ambipolar transport. (c) 2006 Elsevier B.V. All rights reserved.

Abstract  Visible light combined with naphthalimides has previously been shown to catalyze formation of physical bonds in avascular meniscal tissue. The first objective was to modify the existing in vitro testing method (i.e., adhesion testing using lap-jointed slices) to gain more sensitivity in detecting relative bonding strengths among candidate bonding agents. A repeated measures experimental design (RMED) was used to account for variability in properties among bovine menisci and was achieved by testing all treatments/controls on slices from each meniscus. Additionally, to make the method more clinically relevant in modeling a bucket-handle tear, the bovine meniscal slices were cut with collagen fibers parallel to the test slice's length. Peak stress was greater for the complete treatment group (light plus naphthalimide) than for the control or incomplete treatment groups (light only or napthalimide only). The second objective was to perform concentration and photoactivation time dose-response studies. In the concentration dose-response study, peak stress was greater for all treatments when compared with the control but not different among treatment groups; however, there was a trend of increased bonding strength with increased concentration. In the photoactivation time dose-response study, peak stress was greater for all treatments when compared with the control and greater for the 3-min treatment vs. the 6- and 9-min treatments. Peak stress was not different between the longer treatments. The RMED provided increased reproducibility and statistical sensitivity for detecting differences among treatments and will be used to test candidate bonding agents prior to in vivo testing.

Abstract  A myriad of drug delivery systems such as liposomes, micelles, polymers and inorganic nanoparticles (NPs) have been developed for cancer therapy. Very few of them, however, have the ability to integrate multiple functionalities such as specific delivery, high circulation stability, controllable release and good biocompatibility and biodegradability in a single system to improve the therapeutic efficacy. Herein, we report two types of stimuli-responsive nonporous silica prodrug NPs towards this goal for controlled release of anticancer drugs and efficient combinatorial cancer therapy. As a proof of concept, anticancer drugs camptothecin (CPT) and doxorubicin (DOX) were covalently encapsulated into silica matrices through glutathione (GSH)-responsive disulfide and pH-responsive hydrazone bonds, respectively, resulting in NPs with sizes tunable in the range of 50-200 nm. Both silica prodrug NPs showed stimuli-responsive controlled release upon exposure to a GSH-rich or acidic environment, resulting in improved anticancer efficacy. Notably, two prodrug NPs simultaneously taken up by HeLa cells showed a remarkable combinatorial efficacy compared to free drug pairs. These results suggest that the stimuli-responsive silica prodrug NPs are promising anticancer drug carriers for efficient cancer therapy.

Abstract  Three terminal thiols possessing azobenzene and perylene diimide (PDI) segments covalently linked by alkylene spacers of different lengths (PnSH, n = 4, 6, and 8) were synthesized to stabilize and functionalize gold nanorods (GNRs) via strong covalent Au-S bonds onto the gold surface. The resulting hydrophobic thiol monolayer-protected GNRs (P(n)GNRs) were stable in both organic solvent and the solid state and exhibited fascinating photoresponsive self-assembly behavior. The PDI moieties provided pi-pi interactions to promote GNR self-assemblies while the photoresponsive azobenzene moieties offered a way to phototune the assemblies in a reversible manner. Interestingly, when P(n)GNRs were mixed with a structurally similar room-temperature thermotropic liquid-crystal perylene diimide (LCP), the UV-irradiated P(n)GNRs showed more compatibility with the LCP host than their corresponding unirradiated ones. Furthermore, the P(n)GNRs with varied alkylene chain lengths showed different dispersion abilities in LCP. The UV-irradiated P(4)GNRs did not disperse well in LCP, whereas the UV-irradiated P(6)GNRs and P(8)GNRs dispersed well in LCP and were further aligned upon mechanical shearing. In addition, preliminary molecular simulation was performed to explain this interesting photomodulated self-assembly of the GNRs.

Abstract  Two functional [2]rotaxanes, with a 4-morpholin-naphthalimide fluorophore as one of the two stoppers and a difluoroboradiaza-s-indacene functionalized dibenzo[24]crown-8 as macrocycle, were designed, synthesized and well characterized. [2]Rotaxane 1 and 2 had almost the same structural skeleton, and a ferrocene unit was introduced in [2]rotaxane 1 as the other stopper, while a 3,5-dimethoxybenzene stopper in [2]rotaxane 2. It has shown that efficient energy transfer process in both two [2]rotaxanes occurred from the 4-morpholin-naphthalimide donor to the difluoroboradiaza-s-indacene acceptor. Moreover, [2]rotaxane 1 exhibited a remarkable fluorescence increase in response to the addition of base that can drive the shuttling motion because of the introduction of ferrocene electron donor. This work can pave the way for the design and construction of complex and functional molecular systems based on the mechanically interlocked molecules. (C) 2015 Elsevier Ltd. All rights reserved.

Abstract  Four 1,8-naphthalimide derivatives were synthesized for new nonlinear optical(NLO) materials. Hydrazone group as a p-pi structure was introduced into the molecule to extend conjugation and produce NLO properties. Their linear and nonlinear optical (NLO) properties were studied in details. The results show that these compounds possess strong excited-state absorption (ESA) properties and optical limiting with nanosecond laser pulses at 532 nm. Moreover, they also preserve the luminescence originated from naphthalimide and two-photon absorption (TPA) behaviour which can be observed under femtosecond laser pulses ranged from 750 to 870 nm. The broad-band optcial limiting properties of these compounds indicate that they can be potentially applicated in optical limiting materials. (C) 2012 Elsevier Ltd. All rights reserved.

Abstract  Bichromophoric laser dyes, consisting of 1,8-naphthalimide derivatives as an antenna and Rhodamine 101 or Rhodamine B as a lasing moiety linked via an ethylene and ester bridge, have been investigated by measurements of absorption and fluorescence spectra. The fluorescence of the antenna in these bichromophoric dyes was quenched. Complete energy transfer from antenna to rhodamine was observed and the fluorescence quantum yield of the bichromophoric dyes can be increased by this energy transfer to the rhodamine. For comparison, mixtures of the rhodamine dyes and the 1,8-naphthalimide derivatives were also studied.

Abstract  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.

Abstract  A bisthienylethene-functionalized perylene diimide (BTE-PDI) photochromic dyad was synthesized for self-assembly into 1-D nanotubes by a reprecipitation method. SEM and TEM observations showed that the nanotubes were formed from their 0-D precursors of hollow nanospheres. HR-TEM images revealed that both the nanospheres and the nanotubes have highly ordered lamellar structure, indicating the hierarchical process during assembly. The IR and XRD results revealed that DAE-PDI molecules were connected through intermolecular hydrogen bonds to form building blocks that self-assembled into nanostructures. Electronic absorption and fluorescence spectroscopic results indicated the H-aggregate nature of the self-assembled nanostructures. Competition and cooperation between the dipole-dipole interaction, intermolecular pi-pi stacking, and hydrophilic/hydrophobic interaction are suggested to result in nanostructures. Reconstruction was found to happen during the morphology transition progress from the 0-D nanospheres to the 1-D nanotubes, which was driven by donor-acceptor dipole-dipole interactions. Green emission at 520 nm originating from the DAE subunit was observed for the aggregates of vesicles and nanotubes, which could be regulated by photoirradiation with 365 nm light, suggesting the nanoaggregates to be photochromic switches.

Abstract  We demonstrate that thin films of metal-organic framework (MOF)-like materials, containing two perylenediimides (PDICl4, PDIOPh2) and a squaraine dye (S1), can be fabricated by layer-by-layer assembly (LbL). Interestingly, these LbL films absorb across the visible light region (400-750 nm) and facilitate directional energy transfer. Due to the high spectral overlap and oriented transition dipole moments of the donor (PDICl4 and PDIOPh2) and acceptor (S1) components, directional long-range energy transfer from the bluest to reddest absorber was successfully demonstrated in the multicomponent MOF-like films. These findings have significant implications for the development of solar energy conversion devices based on MOFs.