Ionized water-soluble organic nanosheets with light/ultrasound dual excitation channels for efficient killing of multidrug-resistant bacteria.

A novel ionized heavy-atom-free two-dimensional organic nanosheet was prepared and exhibited highly selective generation of singlet oxygen under both light and ultrasound excitation. These ionized nanosheets displayed excellent dispersibility in water and enhanced singlet oxygen production efficiency compared to their non-assembled monomers. Antimicrobial experiments have revealed their potent bactericidal effects on drug-resistant E. coli and S. aureus under both visible light and ultrasound irradiation.

Tailored self-assembled photocatalytic nanofibres for visible-light-driven hydrogen production.

The creation of efficient artificial systems that mimic natural photosynthesis represents a key current challenge. Here, we describe a high-performance recyclable photocatalytic core-shell nanofibre system that integrates a cobalt catalyst and a photosensitizer in close proximity for hydrogen production from water using visible light. The composition, microstructure and dimensions-and thereby the catalytic activity-of the nanofibres were controlled through living crystallization-driven self-assembly. In this seeded growth strategy, block copolymers with crystallizable core-forming blocks and functional coronal segments were coassembled into low-dispersity, one-dimensional architectures. Under optimized conditions, the nanofibres promote the photocatalytic production of hydrogen from water with an overall quantum yield for solar energy conversion to hydrogen gas of ~4.0% (with a turnover number of >7,000 over 5 h, a frequency of >1,400 h-1 and a H2 production rate of >0.327 µmol h-1 with 1.34 µg of catalytic polymer (that is, >244,300 µmol h-1 g-1 of catalytic polymer)).

Solid-State Donor-Acceptor Coaxial Heterojunction Nanowires via Living Crystallization-Driven Self-Assembly.

The creation of organic heterojunctions from conjugated polymers on the nanoscale has attracted recent attention as a consequence of their considerable potential in optoelectronic devices. Herein, we report proof-of-concept results on a versatile synthetic strategy to access various linearly segmented nanowire heterojunctions with controlled dimensions using the seeded growth "living crystallization-driven self-assembly" method followed by a secondary crystallization step. Specifically, we describe the creation of coaxial and also segmented coaxial B-A-B and A-B-A nanowires with a solvophilic poly(ethylene glycol) (PEG) corona, an inner crystalline core that consists of poly(di-n-hexylfluorene) (PDHF), which functions as a donor, and an outer crystalline core of poly(3-(2'-ethylhexyl)thiophene) (P3EHT), which acts as an acceptor. The latter is present either along the entire nanowire or solely in the central or terminal segments. These assemblies were created by seeded growth of two types of π-conjugated polymeric building blocks, the triblock copolymer PDHF-b-P3EHT-b-PEG and the diblock copolymer PDHF-b-PEG, by using fiber-like seeds derived from either material. The nanowires with both solid-state donor and acceptor blocks exhibit Förster resonance energy transfer (FRET) from the PDHF inner core to the P3EHT outer core which was characterized by fluorescence spectroscopy and laser confocal scanning fluorescence microscopy (LCSM). The FRET in the solid-state coaxial heterojunctions with an inner PDHF core and an outer P3EHT core was enhanced relative to the directly analogous system in which the P3EHT block was solvated.

Cellular uptake and targeting of low dispersity, dual emissive, segmented block copolymer nanofibers.

Polymer-based nanoparticles show substantial promise in the treatment and diagnosis of cancer and other diseases. Herein we report an exploration of the cellular uptake of tailored, low dispersity segmented 1D nanoparticles which were prepared from an amphiphilic block copolymer, poly(dihexylfluorene)-b-poly(ethyleneglycol) (PDHF13-b-PEG227), with a crystallizable PDHF core-forming block and a 'stealth' PEG corona-forming block with different end-group functionalities. Segmented C-B-A-B-C pentablock 1D nanofibers with varied spatially-defined coronal chemistries and a selected length (95 nm) were prepared using the living crystallization-driven self-assembly (CDSA) seeded-growth method. As the blue fluorescence of PDHF is often subject to environment-related quenching, a far-red BODIPY (BD) fluorophore was attached to the PEG end-group of the coronal B segments to provide additional tracking capability. Folic acid (FA) was also incorporated as a targeting group in the terminal C segments. These dual-emissive pentablock nanofibers exhibited uptake into >97% of folate receptor positive HeLa cells by flow cytometry. In the absence of FA, no significant uptake was detected and nanofibers with either FA or BD coronal groups showed no significant toxicity. Correlative light and electron microscopy (CLEM) studies revealed receptor-mediated endocytosis as an uptake pathway, with subsequent localization to the perinuclear region. A significant proportion of the nanofibers also appeared to interact with the cell membrane in an end-on fashion, which was coupled with fluorescence quenching of the PDHF core. These results provide new insights into the cellular uptake of polymer-based nanofibers and suggest their potential use in targeted therapies and diagnostics.

Long-range exciton transport in conjugated polymer nanofibers prepared by seeded growth.

Easily processed materials with the ability to transport excitons over length scales of more than 100 nanometers are highly desirable for a range of light-harvesting and optoelectronic devices. We describe the preparation of organic semiconducting nanofibers comprising a crystalline poly(di-n-hexylfluorene) core and a solvated, segmented corona consisting of polyethylene glycol in the center and polythiophene at the ends. These nanofibers exhibit exciton transfer from the core to the lower-energy polythiophene coronas in the end blocks, which occurs in the direction of the interchain π-π stacking with very long diffusion lengths (>200 nanometers) and a large diffusion coefficient (0.5 square centimeters per second). This is made possible by the uniform exciton energetic landscape created by the well-ordered, crystalline nanofiber core.

Bright white-light emission from a novel donor-acceptor organic molecule in the solid state via intermolecular charge transfer.

Bright white-light emission was obtained from a novel pyridinium molecule by aggregation. Photophysical, single-crystal structural, and computational studies demonstrated that an additional low-energy emission was generated by the excitation of a new intermolecular charge-transfer (CT) band at the ground state that cooperates with the non-quenched high-energy monomer emission to produce white light.

Highly coplanar very long oligo(alkylfuran)s: a conjugated system with specific head-to-head defect.

Well-defined monodisperse conjugated oligomers, which have planar backbones and are free from the disturbance of substituents, attract broad interest. Herein, we report a series of symmetrical, isomerically pure oligofurans, namely, the 16-mer 16F-6C6 together with the related nF-2C6 (n = 4, 6, 8). Through computational studies and detailed spectroscopic and X-ray characterization, for the first time, we show that the planarity of the furan backbone is almost unaffected by the head-to-head defect which is known to cause considerable twists in its oligo- or polythiophene analogues. We present that the properties of these rigid oligo(alkylfuran)s are strongly influenced by the conjugation length. As the longest monodisperse α-oligofuran synthesized to date, 16F-6C6 was observed to be stable and highly fluorescent. Experimental and computational studies of the redox states of these oligo(alkylfuran)s reveal that 16F-6C6 has singlet biradical (polaron-pair) character in the doubly oxidized ground state: the open-shell singlet (⟨S2⟩ = 0.989) is 3.8 kcal/mol more stable than the closed-shell dication.

Reversible luminescence switching between single and dual emissions of bipyridinium-type organic crystals.

An excitation-wavelength-dependent luminescence behavior of a bipyridinium derivative, together with its luminescence switching between single- and dual-emissions upon reversible solid state structural transformation, has been presented.

2D flexible metal-organic frameworks with [Cd2(µ2-X)2](X = Cl or Br) units exhibiting selective fluorescence sensing for small molecules.

Two isomorphous 2D flexible metal-organic frameworks with [Cd(2)(µ(2)-X)(2)] (X = Cl or Br) units and dynamic 1D channels, which show tunable or switchable fluorescence signals in response to the loss of guest water molecules, have been synthesized and characterized. Especially, the chloride-bridged complex is found to be a selective fluorescence sensor for MeCN.

Thermally triggered reversible transformation between parallel staggered stacking and plywood-like stacking of 1D coordination polymer chains.

An unusual example showing reversible interconversion of chain-like isomers under controlled experimental settings is reported, which illustrates the key role of assembly conditions for the target packing architecture with related properties. The reaction of Mn(II) ions with an organic ligand 2-hydroxypyrimidine-4,6-dicarboxylic acid (H(3)hpdc) at room temperature gives a coordination polymer {[Mn(3)(hpdc)(2)(H(2)O)(6)] x 2 H(2)O}(n) containing parallel staggered stacking, whereas the reaction under hydrothermal conditions at 150 degrees C affords a compound {[Mn(3)(hpdc)(2)(H(2)O)(6)] x H(2)O}(n) possessing plywood-like stacking. Interestingly, two compounds contain similar one-dimensional chain components with different orientations that can be controlled by thermodynamic factors. Thermally triggered reversible interconversion of the two compounds was verified by X-ray powder, IR, and element analysis. The spin-canted antiferromagnetic behaviors are observed in as-synthesized samples, and the influence of chain orientations on magnetic properties has been detected.

Conformational and photosensitive adjustment of the 4,4'-bipyridinium in Mn(II) coordination complexes.

Two Mn(II) coordination complexes with considerable difference in photochromism and chirality have been constructed from the photoactive 1-(4-carboxybenzyl)-4,4'-bipyridinium ligand upon adjusting the reaction solvents.

Bipyridinium array-type porous polymer displaying hydrogen storage, charge-transfer-type guest inclusion, and tunable magnetic properties.

A multifunctional pillared-layer porous coordination polymer, {[Mn(2)(Bpybc)(ox)(2)]8 H(2)O}(n), has been constructed based on a flexible viologen derivative, 1,1'-bis(4-carboxybenzyl)-4,4'-bipyridinium dichloride (H(2)BpybcCl(2)), and an oxalate (ox) coligand. Single-crystal X-ray analysis reveals that the compound possesses multichannels with dimensions of about 6.1x6.6 A along the [110] and [-110] directions and 4.2x7.6 A along [100], and a void space of about 41.4 %. Hydrogen adsorption measurements at 77 K and 1 atm indicate that the compound exhibits a hydrogen uptake of 0.71 wt %. Owing to the incorporation of bipyridinium acceptor units, the compound can selectively accommodate aromatic donors into its nanosized pores based on charge-transfer interactions in an elastic way, and afford a specific color to different guests. Furthermore, the effect of perturbation exerted by the guest molecules on its magnetic properties has been investigated. The results indicate that the donor inclusion has little effect on its antiferromagnetic behavior, whereas dehydration of the compound decreases the strength of the magnetic exchange couplings and results in a change of the antiferromagnetic transition temperature from 14.7 to 9.8 K.

Novel polythreaded coordination polymer: from an armed-polyrotaxane sheet to a 3D polypseudorotaxane array, photo- and thermochromic behaviors.

A novel coordination compound, {[Cd(BDC)(Bpybc)(1.5)].10H(2)O}(n), obtained by the reaction of CdCl(2) with 1,1'-bis(4-carboxybenzyl)-4,4'-bipyridinium dichloride (H(2)BpybcCl(2)) and 1,4-benzenedicarboxylic acid (H(2)BDC), contains 1D polymeric chains that are comprised of alternating rings and rods and dangling lateral arms. These 1D polymeric motifs are interlaced via rotaxane-like mechanical linkages to give 2D armed-polyrotaxane sheets, which are further mutually polythreaded via pseudorotaxane-like mechanical linkages to form a 3D polypseudorotaxane array. Notably, a sandwich-type donor-acceptor-donor stacking is formed within each ring as a consequence of both types of polythreading in this species, and photoinduced and thermal-induced reduction of bipyridinium occurs with a color change from light yellow to blue.