Abstract  In this study, a novel ratiometric pH probe RNL based on fluorescence resonance energy transfer (FRET) was well developed. It was fabricated by integrating the naphthalimide moiety as an FRET donor with the rhodamine moiety as an FRET acceptor. Meanwhile, 4-(2-aminoethyl)morpholine, which was a lysosome-locating group, was introduced. The sensing mechanism was the integration of PET and FRET processes and the comprehensive effect led to the simultaneous intensity enhancement of naphthalimide and rhodamine along with the pH value decrease. With a pK(a) of 4.82, the fluorescence intensity ratio (I-529/I-580) of the probe changed significantly within the pH range from 4.50 to 5.50. The probe showed excellent selectivity among various metal cations, amino acids and ATP. Moreover, RNL has been successfully applied in HeLa cells, and the results demonstrated that it could be used to detect lysosomal pH changes. The probe could also selectively stain lysosome in HeLa cells. Besides, the probe exhibited low cytotoxicity and satisfactory photostability in living HeLa cells.

Abstract  Two n-type conjugated D-A copolymers with perylene diimide (PDI) as acceptor unit and benzodithiophene (BDT) as donor unit, P(PDI-BDT-Ph) and P(PDI-BDT-Th), were synthesized and applied as electron acceptor in all-polymer solar cells (all-PSCs). P(PDI-BDT-Ph) and P(PDI-BDT-Th) films exhibit similar absorption spectra in the visible region with optical bandgap (E-g) of 1.65 eV and 1.55 eV respectively, and the identical LUMO level of -3.89 eV. The all-PSCs based on P(PDI-BDT-Ph) as acceptor and PTB7-Th as donor demonstrated a power conversion efficiency (PCE) of 4.31% with a short-circuit current density (J(sc)) of 11.94 mA cm(-2), an open-circuit voltage (V-oc) of 0.81 V, and a fill factor (FF) of 44.49%. By contrast, the corresponding all-PSCs with P(PDI-BDT-Th) as acceptor showed a relative lower PCE of 3.58% with a Jsc of 11.36 mA cm(-2), V-oc of 0.79 V, and FF of 40.00%. (C) 2016 Elsevier B.V. All rights reserved.

Abstract  Two star polycations, poly(2-aminoethyl methacrylate) (PAEMA, P1) and poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA, P2), have been synthesized with perylene diimide (PDI) as the central fluorophore. (1)H NMR and (13)C NMR are used to confirm the successful synthesis of a macromolecular initiator. Using ATRP strategy, P1 and P2 are obtained with narrow molecular weight distribution. The star polymers have good fluorescence properties in aqueous solution, which provides fluorescent tracing and imaging during gene delivery. Both P1 and P2 can efficiently condense DNA into stable nanoparticles. Transfection studies demonstrate that P1 and P2 deliver DNA into live cells with higher efficiency and lower cytotoxicity than polyethylenimine (PEI, 25 kDa). P2 shows higher capacity for gene delivery than P1 due to its better buffering and faster rate of cellular internalization.

Abstract  A non-fullerene, all-small-molecule solar cell (NF-SMSC) device uses the blend of a small molecule donor and a small molecule acceptor as the active layer. Aggregation ability is a key factor for this type of solar cell. Herein, we used the alkylthienyl unit to tune the aggregation ability of the diketopyrrolopyrrole (DPP)-based small molecule donors. Replacing two alkoxyl units in BDT-O-DPP with two alkylthienyl units yields BDT-T-DPP, and further introducing another two alkylthienyl units into the backbone produces BDT-T-2T-DPP. With the introduction of alkylthienyl, the backbone becomes twisted. As a result, the ππ-stacking strength, aggregation ability, and crystallite size all obey the sequence of BDT-O-DPP > BDT-T-DPP > BDT-T-2T-DPP. When selected a reported perylene diimide dimer of bis-PDI-T-EG as acceptor, the best NF-SMSC device exhibits a power conversion efficiency of 1.34, 2.01, and 1.62%, respectively, for the BDT-O-DPP, BDT-T-DPP, and BDT-T-2T-DPP based system. The BDT-T-DPP/bis-PDI-T-EG system yields the best efficiency of 2.01% among the three combinations. This is due to the moderate aggregation ability of BDT-T-DPP yields moderate phase size of 30-50 nm, whereas the strong aggregation ability of BDT-O-DPP gives a bigger size of 50-80 nm, and the weak aggregation ability of BDT-T-2T-DPP produces a smaller size of 10-30 nm. The BDT-T-DPP/bis-PDI-T-EG combination exhibits balanced hole/electron mobility of 0.022/0.016 cm(2)/(V s), whereas the BDT-O-DPP/bis-PDI-T-EG and the BDT-T-2T-DPP/bis-PDI-T-EG blend show a hole/electron mobility of 0.0011/0.0057 cm(2)/(V s) and 0.0016/0.11 cm(2)/(V s), respectively.

Abstract  A new D-A (Donor-Accept) type N-(1,2,4-triazolyl)-N'-(2-ethylhexyl) naphthalenediimide (L) was synthesized. AgL(2)PF(6) (1) and AgL(2)NO(3) (2) were obtained through the reactions of L with AgPF(6) and AgNO(3), respectively. All the compounds were fully characterized. Optical, electrochemical properties and electrogenerated chemiluminescence (ECL) were systematically investigated. Those dual fluorescent emissions for L, short wavelength (SW) and long wavelength (LW) emission bands, are rationally explained by the planar intramolecular charge transfer (PICT) model. All the compounds display anodically shift reduction waves with positive reduction potential, compared to its parent compound, Naphthalene bisimide (NBI). It is very interesting that the ECL intensity of the complexes is successfully increased, which is 20 times larger than that of L explaining that the radical anions of the complexes are stabilized by coordinating L with Ag(I) ion. The results provide a new approach to study ECL materials. (C) 2010 Elsevier Ltd. All rights reserved.

Abstract  Charge transport is studied in single-molecule junctions formed with a 1,7-pyrrolidine-substituted 3,4,9,10-perylenetetracarboxylic diimide (PTCDI) molecular block using an electrochemical gate. Compared to an unsubstituted-PTCDI block, spectroscopic and electrochemical measurements indicate a reduction in the highest occupied (HOMO)-lowest unoccupied (LUMO) molecular orbital energy gap associated with the electron donor character of the substituents. The small HOMO-LUMO energy gap allows for switching between electron- and hole-dominated charge transports as a function of gate voltage, thus demonstrating a single-molecule ambipolar field-effect transistor. Both the unsubstituted and substituted molecules display similar n-type behaviors, indicating that they share the same n-type conduction mechanism. However, the substituted-PTCDI block shows a peak in the source-drain current vs gate voltage characteristics for the p-type transport, which is attributed to a two-step incoherent transport via the HOMO of the molecule.

Abstract  Sequential deposition of nanofibrous composites of charged perylene diimide (PDI) dyes and oppositely charged polyelectrolyte (PE) is demonstrated within fluidic devices. The PDIs employed include an amphiphilic, singly charged PDI (C(7)OPDI(+)) and a doubly charged species (TAPDI(2+)). Anionic poly(acrylate) (PA(-), 5100 and 250K MW) is used as the PE. As previously demonstrated [Weitzel, C. R.; Everett, T. A.; Higgins, D. A. Langmuir, 2009, 25, 1188], dip-coated PDI/PE composites form nanofibrous films that exhibit flow-induced alignment due to gravitational draining of the dipping solution. In this study, the potential for producing patterned, flow-aligned PDI/PE composites by deposition using pressure-driven flow within fluidic channels is explored. The influence of flow profile, PE molecular weight (MW) and PDI structure on deposition efficiency, macroscopic and microscopic morphology, and the potential for nanofiber alignment are also investigated. Optical absorbance microscopy and tapping mode AFM data demonstrate that C(7)OPDI(+)/PA(-) deposition is controlled by PDI aggregation, while TAPDI(2+)/PA(-) composites are more dependent upon PE MW. Optical dichroism images show that C(7)OPDI(+)/PA(-) composites form serpentine, partially aligned nanofibers under all conditions explored, while TAPDI(2+)/PA(-) films incorporate more tightly packed nanofibers that form randomly oriented nematic-like domains when high MW PA(-) is employed. In-plane organization in C(7)OPDI(+)/PA(-) films is concluded to result from flow-induced alignment of solution-formed C(7)OPDI(+) aggregates, while the unaligned domains found in TAPDI(2+)/PA(-) films are concluded to form on the substrate surface by the complexation of small TAPDI(2+) aggregates or monomers with PE.

Abstract  Multilayer films of oligo(pyrenebutyric acid) (OPB) and N,N'-bis(N,N-dimethylaminopropylaminopropyl)-3,4,9,10-perylenediimide (BDMAPAP-PDI) were successfully fabricated by layer-by-layer deposition. Multilayer growth was monitored by ultraviolet-visible (UV-vis) spectroscopy, fluorescence spectroscopy, ellipsometry, and atomic force microscopy (AFM). It was found that extraction was scarcely observed although both components (OPB and BDMAPAP-PDI) have low molecular weights and both electrostatic interactions and pi-pi stacking contributed to the multilayer deposition. The multilayers exhibit a rapid photocurrent response, and excitations of both OPB and BDMAPAP-PDI can lead to the effective charge dissociation. The incident photon to current conversion efficiency (IPCE) of the composite film with 5 bilayers was measured to be 1.29% at the absorption peak of BDMAPAP-PDI. Fluorescence quenching and photovoltaic conversion studies indicated that strong photoinduced charge transfer interactions occurred at the area of OPB/BDMAPAP-PDI heterojunction in the films, which strongly enhanced the photoresponse of the multilayer films.

Abstract  The properties of N,N'-bis(2-phosphonoethyl)-3,4,9,10-perylenetetracarboxylic diimide (PPDI), a water-soluble perylene dye, have been studied in solution and in thin films. Absorption spectra showed that PPDI exists in the monomeric form in water/ethanol (1:1) and water/dimethyl sulfoxide (DMSO) (3:7) mixtures, but forms dimers in water and higher aggregates in ethanol. The PPDI monomer is highly fluorescent, in contrast to the dimers and aggregates, which are nonfluorescent. The monomer/dimer equilibrium was conveniently followed in a water/ethanol (7:3) mixture by varying the dye concentration. An equilibrium constant of K = 1.25 x 10(5) M(-1) was estimated for the dimerization process in this solvent mixture. The addition of cetyl trimethylammonium bromide (CTAB), a cationic surfactant, to aqueous solutions of PPDI resulted in the dissociation of the dimers, showing that the dye was incorporated into the micellar phase. Self-assembled thin films of PPDI were grown on both silica gel particles and flat surfaces, using zirconium phosphonate chemistry. The growth of multilayered films on flat surfaces was monitored by ellipsometry (silicon substrates) and UV/Vis spectroscopy (quartz slides), and was linear with the number of deposition cycles. No fluorescence was detected from the PPDI films, and the absorption spectra of the films were quite similar to the spectrum of the compound in ethanol, indicating that the dye molecules were stacked in the films. Mixed monolayers containing PPDI and N,N'-bis(2-phosphonoethyl)-1,4,5,8-naphthalenediimide (PNDI) on quartz were also prepared. Monolayers obtained by codeposition from solutions containing both PPDI and PNDI were richer in PPDI, even when the solution contained a large excess of the naphthalene derivative, showing that pi-stacking of PPDI is an important driving force in the formation of the films.

Abstract  A layer-by-layer deposition process has been carried out for two oppositely charged water-soluble perylene diimide dyes without the use of intervening polyelectrolyte layers. The strong pi-pi interactions between the perylene moieties help stabilize the layers and simultaneously diminish the fluorescence quantum yield of the array without strongly affecting the absorption or fluorescence spectra. There is an alternation of fluorescence intensity according to which perylene species is on the outer layer, which is interpreted as the effect of facile energy transfer between the perylenes.

Abstract  A novel perylene diimide (PDI) derivative with typical amphiphilic character, 2, was designed and prepared. The spectroscopic studies on this compound in solution revealed the face-to-face dimeric configuration and effective pi-pi interaction between the two perylene rings. This amphiphilic PDI derivative was fabricated into highly ordered films by Langmuir-Blodgett (LB) technique and fabricated into an organic field effect transistor (OFET), which shows carrier mobility around 0.05 cm(2) V(-1) s(-1) and current modulation of 10(3). This OFET performance is much better than that of monomeric PDI 1 and can be attributed to the unique face-to-face structure of 2, which promotes the interactions between neighboring PDI ring in LB film as indicated by the pi-A isotherms and UV-vis absorption.

Abstract  Novel direction-controlled movements of microribbons self-assembled from perylene diimide molecules are reported on various hydrophobic surfaces under scanning laser irradiation. A "dynamic exciton charge model" is developed to elucidate the underlying mechanism. The findings provide an innovative strategy for the design of microscale systems capable of continuous and directional movement driven by light.

Abstract  Based on a perylene diimide derivatives(PDIs) platform, AM-PDIs was rationally designed and synthesized as a new calorimetric and ratiometric fluorescent sensor for naked-eye detection of fluoride ion with high selectivity over other halide ions. Addition of fluoride ion to a dichloromethane(DCM) solution of AM-PDIs resulted in an obvious color change (from red to blackish green) because of a large red shift (151 nm) in absorption. The recognition mechanism was attributed to the intermolecular proton transfer between a hydrogen atom on the amide N position of sensor and the fluoride anion. The detection limit was calculated to be 0.14 mu M. (C) 2012 Elsevier Ltd. All rights reserved.

Abstract  Core-shell (CS) CdSe/ZnS quantum dots (QD) capped with ligands that possess a mercapto or an amino group and a naphthalimide (NI) as chromophore unit, linked by a short ethylene chain (CS@S-NI and CS@H2N-NI, respectively), have been synthesized and fully characterized by infrared and nuclear magnetic resonance spectroscopies, high-resolution transmission electron microscopy, and voltammetry as well as by steady-state absorption and emission spectroscopies. The organic ligands HS-NI and H2N-NI act as bidentate ligands, thereby causing a drastic decrease in the QD emission. This was particularly evident in the case of CS@S-NI. This behavior has been compared with that of commercially available QDs with octadecylamine as the surface ligand and a QD capped with decanethiol ligands (CS@S-D). The interaction between the anchor groups and the QD surface brings about different consequences for the radiative and nonradiative kinetics, depending on the nature of the anchor group. Our results suggest that the naphthalimide group "stabilizes" empty deep trap states due to the carbonyl group capacity to act as both a sigma-donor and a pi-acceptor toward cations. In addition, the thiolate group can induce the location of electron density at shallow trap states close to the conduction band edge due to the alteration of the QD surface provoked by the thiolate binding.

Abstract  Two novel fluorescence resonance energy transfer-based perylenediimide-naphthalimide dendrons with perylenediimides as the energy acceptor, tertiary amines as the proton or metal receptor and naphthalimide as the energy donor were successfully synthesized. The dendrons exhibited high selectivity toward Fe(III) in the presence of various other metal cations and exhibited sensitivity to protons. A 1:2 stoichiometry was found for the complex formed by the probes and Fe(III) using a Job's plot and by non-linear least square fitting of the fluorescence titration curves. The probe molecules present abilities of fast fluorescence detection of Fe(III) and for the fluorescent detection of protons with high energy transfer efficiency of 96-98%. (C) 2014 Elsevier Ltd. All rights reserved.

Abstract  A series of potential optical brightening agents - 4-aryloxy-N-(2',6'-diisopropylpheny1)-1,8-naphthalimides are synthesized and their photo-physical properties are experimentally determined. Interestingly, it is found that their quantum efficiencies or quantum yields are exclusively dependent on the substituents on the aryloxy group at the 4-position. It is postulated that the electronic effect of the substituents influences the photo-induced electron transfer process, which causes a variation in quantum efficiencies. Due to analysis of charge transfer from 1,8-naphthalimide molecular part to its substituents in dichloromethane based on the time-dependent density functional theory at Becke 3-parameters Lee-Yang-Parr level coupling with the 6-31G(d) basis set in the conductor-like polarizable continuum model with the united atom topological model computations, it is found that computed charge transfers of these serial compounds correspond well with their experimental quantum yields. Validation of the calculation method is performed by experimental determination of the quantum yield of the nitro-substituted compound. (C) 2014 Elsevier Ltd. All rights reserved.

Abstract  Photoluminescent dyes (aminofluorene, naphthalimide, naphtholbenzein, or phenosafranine) were grafted to polyurethane using an allophanate linkage. The photoluminescence properties and the shape recovery effects of polyurethane samples were investigated. The polyurethane was composed of 4,4'-methylenebis (phenylisocyanate), poly(tetramethyleneglycol), and 1,4-butanediol. The dyes were linked through an extra 4,4'-methylenebis(phenylisocyanate) and the carbamate moiety of the polyurethane chains. Polyurethanes with various dye contents were characterised, and the shape recovery and photoluminescence properties were compared. In the case of the tensile mechanical properties, the highest maximum stress was 56 MPa, and the strain remained > 1500% for the entire series. The shape recovery improved as the test cycle was repeated, with up to 100% recovery being achieved, but shape retention decreased as the dye content increased. Finally, the photoluminescence of the polyurethanes was demonstrated by a luminescent light-emission test, together with pH indication capability and the preparation of non-woven fibre using the electrospinning method.

Abstract  N-type organic field-effect transistors (OFET's), based on two perylene diimide semiconductors (PDI-8 and PDI-8CN(2)) exhibiting very different air sensitivities, have been fabricated on Si/SiO2 substrates. These OFETs have been electrically characterized in vacuum both in the dark and under white-light illumination by dc transfer and output curves, bias stress experiments and variable temperature measurements. In particular, the combination of variable temperature and light illumination experiments is shown to be a powerful tool to clarify the influence of charge trapping on the device operation. Even if, in vacuum, the air-sensitive PDI-8 devices display slightly better performances in terms of field-effect mobility and maximum current values, according to our results, charge transport in PDI-8 films is much more affected by charge trap states compared to PDI8-CN2 devices. These trapping centers are mainly active above 180 K, and their physical nature can be basically ascribed to the interaction between silanol groups and water molecules absorbed on SiO2 surface that is more active above the H2O supercooled transition temperature.

Abstract  Composites of the tetra-anion of he perylene dye N,N'-di(phenyl-3,5-disulfonic acid) perylene-3,4,9,10-tetracarboxydiimide (PBITS) with layered double hydroxides (LDHs) were formed by direct synthesis (co-precipitaiton at constant pH). The LDHs were of the hydrotalcite (Mg-Al-OH and Zn-Al-OH compositions). During synthesis of the hydrocalumite type (Ca-Al-OH), partial destruction of the dye occurs, being more pronounced at higher pH values. The composites were characterized with regard to their composition by elemental and thermal analysis. From UV-vis spectroscopic data and powder X-ray diffraction, a structural model is developed for the composites. In the galleries between the hydroxide layers, the chromophore molecules are stacked in an J-type arrangement. The compounds have brilliant colors and are insoluble in common solvents. With regard to a possible application as pigments, their photostability and their chemical resistance against a typical application environment was tested. The photostability of the dye molecules and their chemical resistance against setting cement are slightly raised by the occlusion within the LDH structure, however, the photostability of the LDH-cement is lower than that of cement with the pure perylene dye.

Abstract  Langmuir-Blodgett (LB) films formed of some fluorescent dyes, namely derivatives of 4-aminonaphthalimide, and their binary mixtures with the liquid crystal 4-heptyl-4'-cyanobiphenyl (7CB) have been studied. The electronic absorption and fluorescence spectra were recorded. On the basis of these spectra, the spectral properties of the dyes and the intermolecular interactions in ultrathin ordered films were determined. The conclusions about the tendency to the creation of aggregates by dye molecules in LB films have been drawn. The measurements of absorption by using linearly polarised light have allowed us to determine the arrangement of the dye and liquid crystal molecules on the air-solid substrate interface.

Abstract  A new method for the synthesis of 4-allyloxy-1,8-naphthalimide derivatives (fluorescent brighteners) using phase transfer catalysis is reported. Four, 4-allyloxy-1,8-naphthalimide fluorescent brighteners were synthesized in good yield and their absorption and fluorescent spectra were determined. The suitability of the monomeric fluorescent brighteners for copolymerization with styrene was also demonstrated. The content of the chemically bound fluorescent brightener in the polymer chain was estimated. (C) 2001 Elsevier Science Ltd. All rights reserved.

Abstract  The synthesis of new 9-phenylxanthene dyes, containing hindered amine stabilizer fragment is reported. Two polymerizable dyes, a combination of Fluorescein or Eosin with 2,2,6,6-tetramethylpiperidine, as well as two 9-phenylxanthene intermediates were synthesized in good yields under variable reaction conditions. Their light absorption and fluorescence properties in solution have been determined and discussed. Photooxidative stability of the new fluorophores has been studied and compared to other similar fluorescent dyes, not containing hindered amine fragment in their molecules. It was shown that the presence of a HALS (hindered amine light stabilizer) fragment in the dyes' molecules improved their photostability. The ability of the dyes to co-polymerize with vinyl monomers such as methyl methacrylate was demonstrated. (c) 2006 Published by Elsevier Ltd.

Abstract  Composite nanofibrous thin films of a cationic, water-soluble perylene diimide and oppositely charged polyelectrolyte are prepared by sequential deposition from separate aqueous solutions of the two precursors. These materials may find future applications as semiconducting "wires" in organic electronics and photovoltaics. A new asymmetrically substituted perylene diimide (designated C11OPDI+) incorporating a hydrophobic ether tail is employed in their synthesis. Poly(acrylate) is used as the polyelectrolyte. Solution-phase and thin-film spectroscopic data show the composites form by binding and aggregation of C11OPDI+ to the polyelectrolyte. Tapping-mode AFM data show that the resulting nanofibers are tens of micrometers in length and are highly curved. Cross-sectional fiber size is shown to depend on the number of deposition cycles. Polarization-dependent fluorescence microscopy indicates the C11OPDI+ chromophores align perpendicular to the local long axis of the nanofibers. The C11OPDI+ molecules are concluded to form tail-to-tail parallel d-stacked structures that run along the fiber axis and are sandwiched between polyelectrolyte regions. In comparison to alternative methods, nanofiber formation is shown to be greatly enhanced when the composite is prepared by sequential deposition. A mechanism for enhanced fiber formation involving slow growth and solvent annealing of the composites is proposed.