Ultralong Nanobelts Self-Assembled from an Asymmetric Perylene Tetracarboxylic Diimide

Ultralong nanobelts (>0.3 mm) have been fabricated from an asymmetric perylene tetracarboxylic diimide (PTCDI) molecule via a seeded self-assembly processing. The long length of nanobelts facilitates the construction of two-electrode devices employing the nanobelt as channel material, and the long-range one-dimensional π−π molecular stacking allows for efficient conductivity modulation through surface doping. A combination of these two characters enables efficient electrical sensing of reducing VOCs using the nanobelt. As examined for hydrazine, more than 3 orders of magnitude increase in current was observed for a single nanobelt when exposed to the saturated vapor of hydrazine

Expedient Vapor Probing of Organic Amines Using Fluorescent Nanofibers Fabricated from an n-Type Organic Semiconductor

A new type of fluorescence sensory material with high sensitivity, selectivity, and photostability has been developed for vapor probing of organic amines. The sensory material is primarily based on well-defined nanofibers fabricated from an n-type organic semiconductor molecule, N-(1-hexylheptyl)perylene-3,4,9,10-tetracarboxyl-3,4-anhydride-9,10-imide. Upon deposition onto a substrate, the entangled nanofibers form a meshlike, highly porous film, which enables expedient diffusion of gaseous analyte molecules within the film matrix, leading to milliseconds response for the vapor sensing

Detection of Amines with Fluorescent Nanotubes: Applications in the Assessment of Meat Spoilage

Highly fluorescent nanotubes assembled from designed asymmetric perylene diimide molecules (PDIs) exhibit high sensitivity (lowering the existing detection limit to ppb levels) and selectivity to amines in the vapor phase, which renders them capable of monitoring and assessing the deterioration of meat

Highly Polarized and Self-Waveguided Emission from Single-Crystalline Organic Nanobelts

Well-defined single-crystalline nanobelts with strong fluorescence were fabricated from a perylene tetracarboxylic diimide molecule modified with specific side-chains that afford flip-flap stacking, rather than the common translated stacking, between the molecules along the long axis of the nanobelt. The nanobelts thus fabricated possess highly polarized, self-waveguided emission, making them ideal candidates for application in nanolasers and other angle-dependent optical nanodevices

Visible Photooxidation of Dibenzothiophenes Sensitized by 2-(4-Methoxyphenyl)-4, 6-diphenylpyrylium: An Electron Transfer Mechanism without Involvement of Superoxide

We report here on a new electron-transfer mechanism for visible-light photooxidation of sulfides in which no superoxide ion is involved. Visible-light irradiation of 2-(4-methoxyphenyl)-4, 6-diphenylpyrylium tetrafluoroborate (MOPDPP+BF4-) in an O2-saturated acetonitrile solution containing dibenzothiophene (DBT) results in nearly 100% conversion to oxygenated products, DBT sulfoxide and sulfone. The photooxidation of DBT is initiated by a photoinduced electron-transfer process, where the excited MOPDPP+ traps an electron from the ground-state DBT to form MOPDPP• and DBT radical cation. Such a mechanism is consistent with the studies of laser flash photolysis, electron spin resonance, and fluorescence quenching of the irradiated system. The photogenerated DBT radical cation undergoes a coupling reaction with O2 to produce the intermediate responsible for the formation of the oxygenated products. The presence of O2 has no effect on the decay kinetics of the transient absorption of MOPDPP•, indicating that no redox reaction occurs between MOPDPP• and O2, and thus no superoxide ion (O2•-) is formed. Moreover, the ESR signal of MOPDPP• was significantly enhanced in the presence of O2, consistent with the assumption that the photogenerated DBT radical cation couples with O2 to form the oxygen-adduct, which is subject to further reactions (Scheme ) leading to the final oxygenated products. Similar results have been obtained when using 10-methylacridine hexafluorophosphate (AcrH+PF6-, which has similar reduction potential in the ground state as MOPDPP+) as the sensitizer. This finding provides a possibility for the photooxidation of sulfides with dioxygen utilizing visible light (solar energy) and is also of significance in clarification of the reaction mechanism

Fabrication of Single-Handed Nanocoils with Controlled Length via a Living Supramolecular Self-Assembly

We report the fabrication of single-handed nanocoils with controlled length from chiral perylene diimide molecules via a living seeded self-assembly method. We demonstrate that the competition among π-interactions, steric repulsion, and transfer of chirality causes the morphological transition from metastable microspheres and microsheets to stable nanocoils. Importantly, the complex assembly pathways allow the living seeded self-assembly to yield single-handed nanocoils with controlled length, which may have promising applications in optoelectronics, fluorescent sensors, and biological imaging fields

Enhancing One-Dimensional Charge Transport through Intermolecular π-Electron Delocalization: Conductivity Improvement for Organic Nanobelts

Effective π-electron delocalization within a PTCDI nanobelt, for which the one-dimensional molecular arrangement is dominated by the cofacial π−π stacking, has been characterized by both electron spin resonance (ESR) spectrometry and current−voltage (I−V) measurement. The long-range π-electron delocalization enables dramatic enhancement of electrical conductivity of the nanobelt through external-charge doping. When immersed in saturated hydrazine vapor, about 3 orders of magnitude increase in conductivity was achieved for the PTCDI nanobelt, implying potential application of the nanomaterials in electrical sensing of reducing gaseous species such as organic amines

Control over the Geometric Shapes and Mechanical Properties of Uniform Platelets via Tunable Two-Dimensional Living Self-Assembly

It remains unexplored how the living self-assembly of small molecules can gain control over the geometric shapes and mechanical properties of the two-dimensional (2D) platelets fabricated therefrom. Herein, we report a tunable 2D living self-assembly method to control the geometric shape variety and mechanical properties of the resulting uniform 2D platelets. This new approach of using n-alkyl alcohols to connect a donor–acceptor (D–A) molecule into a 2D network via hydrogen bonding has a threefold effect on the formed 2D platelets. First, the intralayer molecular packing involving continuous hydrogen bonds between a D–A fluorophore and alcohols remains unaltered, thereby yielding the same optical properties and thermal stability to various 2D platelets. Second, the kinetic growth differentiation of the D–A fluorophore and alcohol in two dimensions depends on the interaction competition of alcohol with the D–A fluorophore against hexane (a poor solvent), engendering the alcohol-dependent 2D shape variety. Third, the interlayer interactions along the thickness of the platelet can be effectively modulated by the alcohol tails with different lengths that stretch out of each bilayer, thereby varying the mechanical properties of the 2D platelets, for which Young’s moduli and hardnesses decrease significantly with the increasing tail length of the alcohols