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Tetraphenylethene and its derivatives have become increasingly attractive as aggregation-induced emission luminogens (AIEgens) due to their superior luminescence efficiency and low contamination. In this paper, a tetraphenylethene derivative (4,4′,4″,4‴-(ethene-1,1,2,2-tetrayltetrakis-(benzene-4,1-diyl)) tetrakis-(1-allylpyridin-1-ium), TPE-1) synthesized with unique fluorescent properties, was integrated into a fluorescent nanocomposite with polyoxometalate (Na9[Eu-(W5O18)2]·32H2O, EuW10) in an aqueous solution using an ionic self-assembly strategy. The TPE-1/EuW10 nanocomposite is composed of spherical particles with a uniform particle size of about 40 nm, and compared with the original material TPE-1, its quantum yield grows from 18.27% to 39.88%. The experimental results suggest that the negatively charged groups of EuW10 may interact electrostatically with the positively charged nitrogen atoms of TPE-1, leading to the aggregation of TPE-1 molecules to enhance the fluorescence. Mixing the TPE-1/EuW10 nanocomposite with commercially available blue and green phosphor can yield a white emitting phosphor with the CIE coordinate of (0.33, 0.34), which is close to the standard white light. This ionic self-assembly strategy of TPE-1 and EuW10 with easy preparation is of great significance for the simple construction of an AIE light-emitting system applicable to optoelectronic devices. [ABSTRACT FROM AUTHOR]

Silver nanoclusters (Ag NCs), as a kind of luminescent material, have been widely studied due to their advantages of precise atomic structure, low toxicity, excellent photostability, and biocompatibility. However, studies on the preparation of hydrophilic Ag NCs with a strong fluorescence intensity and high quantum yield (QY) are rare. In this study, the atomically precise Ag NCs with six silver atoms as core (Ag6–NCs) were self-assembled under the induction of a good solvent (water) and a poor solvent N-methyl-2-pyrrolidone (NMP). By limiting the rotation and vibration of Ag6–NCs ligands, and accompanied by the ligand-to-metal charge transfer (LMCT), aggregation-induced emission (AIE) occurred, and the strong fluorescence emission of Ag6–NCs/NMP/H2O assembly was realized through solvophobic interactions and noncovalent interactions, such as hydrogen-bonding interactions and π–π staking. Compared with the original Ag6–NCs, the fluorescence lifetime of Ag6–NCs/NMP/H2O was extended from 0.56 to 11.77 μs, the QY was increased from 2.3 to 17.6%, and its photoluminescence (PL) intensity was enhanced 37-fold to the order of 107. Long lifetime and large Stokes shift (∼165 nm) indicate that the Ag6–NCs/NMP/H2O assembly was a phosphorescent emitter. This research demonstrates that the excellent optical properties and regular response to temperature of the Ag6–NCs/NMP/H2O assembly make it possible to fabricate white-light-emitting diodes (WLEDs) or temperature sensing materials. [ABSTRACT FROM AUTHOR]

The consensus has been built on the fact that the hydrogen evolution reaction (HER) activity of MoS2 basal planes can be activated by S vacancies. Currently, the popular strategy for fabricating S vacancies is to remove part of S atoms of MoS2. Owing to the same identity of S atoms, the removal process is usually random and does not have selectivity. Herein, we develop a defect-predesigned strategy to produce MoS2 with single-atomic S vacancies (SV-MoS2) simply by preparing Se-doped MoS2 (Se-MoS2) and subsequent removing the Se of Se-MoS2. S vacancies originates from the vaporization of the doped Se atoms, making the formation of S vacancies have a high selectivity and raising a good possibility for precisely modulating the concentration of S vacancies. The results show that the concentration of S vacancies can be controlled over the range from ~7.46% to 13.54%. MoS1.76 with ~12.10% of S vacancies exhibits outstanding HER performance: an overpotential of 100 mV at 10 mA cm-2 and a Tafel slope of 49 mV dec-1, corroborating the theoretical prediction about the optimum concentration of S vacancies. Density functional theory calculation further reveals that the activation of MoS2 basal planes may intrinsically originate from the modification of S vacancies to band structure and density of state of MoS2, optimizing the hydrogen adsorption energy. This defect-predesigned strategy reduces the probability of forming the aggregates of S vacancies and will be more helpful for understanding how S vacancies affect the properties of MoS2. [ABSTRACT FROM AUTHOR]

As a type of luminescent material, copper nanoclusters (Cu NCs) are widely concerned because of their low cost, nontoxicity, and outstanding biocompatibility. However, research studies on the preparation of hydrophobic Cu NCs with high quantum yield can be improved. In this work, we first synthesized atomically precise triphenylphosphine (PPh3)-capped Cu NCs (Cu4–NCs). Second, we adopted solvent engineering strategies to trigger the self-assembly of Cu4–NCs into the assembly with branched structures, thereby achieving aggregation-induced emission (AIE), thermally activated delayed fluorescence (TADF), and a high absolute quantum yield of 67.05%. Moreover, we performed structural characterization and optical analysis, which revealed that the high compactness of the assembly enhances the cuprophilic interaction and suppresses the intramolecular vibration and rotation of the Cu4–NCs ligand, protecting the Cu core from singlet oxygen quenching. These properties lead to the emergence of TADF and AIE. By mixing the as-assembled Cu4–NCs with commercial phosphors, a white light emitting diode prototype can be fabricated. This research demonstrates that TADF emission and the robust luminescence structure of the Cu4–NCs assembly provide them a high application value and extend the research opportunities for metal NCs in optical devices. [ABSTRACT FROM AUTHOR]

Supramolecular self-assembly is an effective method for constructing complex ordered aggregates with specific functions by noncovalent bonding. However, silver nanoclusters (NCs) have rarely been explored in the self-assembly of nanoscale building blocks, and the noncovalent forces (electrostatic, hydrogen-bonding, π–π-stacking interactions, etc.) and argentophilic interactions [Ag-(I)···Ag-(I)] are crucial in directing to the supramolecular self-assembly of Ag-(I) compounds. Here, we used silver NCs (Ag9-NCs, [Ag9(mba)9], where H2mba = 2-mercaptobenzoic acid) as the model cluster to interact with succinic acid (SA) to construct a nanofiber structure. The formation of highly ordered nanofibers is the result of SA-modified peripheral ligands of Ag9-NCs. Under the action of noncovalent forces (hydrogen-bonding, π–π-stacking, and hydrophobic interactions), the reconstruction of this ordered structure not only increases the content of Ag-(I) species in the protective shell of Ag9-NCs but also provides the possibility for directional argentophilic interactions [Ag-(I)···Ag-(I)]. More interestingly, the compact structure and effective argentophilic interactions in the nanofibers synergistically achieve aggregation-induced emission, thereby inducing the emission of phosphorescence, which can be used as a temperature-controlled detector. Moreover, the orange-red Ag9-NCs/SA xerogels, together with commercial phosphor, can also be used as a phosphor to produce white-light-emitting-diode color conversion materials. [ABSTRACT FROM AUTHOR]

We report herein discrete triplex hybridization of DNA and RNA with polyacrylates. Length-monodisperse triazine-derivatized polymers were prepared on gram-scale by reversible addition--fragmentation chain-transfer polymerization. Despite stereoregio backbone heterogeneity, the triazine polymers bind T/U-rich DNA or RNA with nanomolar affinity upon mixing in a 1:1 ratio, as judged by thermal melts, circular dichroism, gel-shift assays, and fluorescence quenching. We call these polyacrylates "bifacial polymer nucleic acids" (bP0NAs). Nucleic acid hybridization with bP0NA enables DNA loading onto polymer nanoparticles, siRNA silencing delivery, and can further serve as an allosteric trigger of RNA aptamer function. Thus, bP0NAs can serve as tools for both non-covalent bioconjugation and structure-function nucleation. It is anticipated that bP0NAs will have utility in both bio- and nanotechnology. [ABSTRACT FROM AUTHOR]

We report herein DNA- and RNA-templated chemical transformation of bifacial peptide nucleic acid (bPNA) fragments directed by an abiotic triplex hybrid interface. Assembly of one bPNA strand with two unstructured oligo T/U strands enables facile insertion of DNA and RNA template sites within partially folded nucleic acids; this template topology is not easily accessed through native base-pairing. Triplex hybridization of reactive bPNA fragments on DNA and RNA templates is shown to catalyze amide bond ligation and controlled bPNA chain extension. RNA-templated oxidative coupling of bPNA fragments is found to result in the emergence of ribozyme cleavage function, thus establishing a connection between engineered and native reaction sites. These data demonstrate the use of new topologies in nucleic acid-templated chemistry that could serve as chemically sensitive DNA and RNA switches. [ABSTRACT FROM AUTHOR]

We demonstrate herein that bifacial peptide nucleic acid (bPNA) hybrid triplexes functionally substitute for duplex DNA or RNA. Structure-function loss in three non-coding nucleic acids was inflicted by replacement of a duplex stem with unstructured oligo-T/U strands, which are bPNA binding sites. Functional rescue was observed on refolding of the oligo-T/U strands into bPNA triplex hybrid stems. Bifacial PNA binding was thus used to allosterically switch-on protein and small-molecule binding in DNA and RNA aptamers, as well as catalytic bond scission in a ribozyme. Duplex stems that support the catalytic site of a minimal type I hammerhead ribozyme were replaced with oligo-U loops, severely crippling or ablating the native RNA splicing function. Refolding of the U-loops into bPNA triplex stems completely restored splicing function in the hybrid system. These studies indicate that bPNA may have general utility as an allosteric trigger for a wide range of functions in non-coding nucleic acids. [ABSTRACT FROM AUTHOR]

The charge carrier mobility of p-type and ambipolar polymer field-effect transistors (FETs) has been improved substantially. Nonetheless, high-mobility n-type polymers are rare, and few can be operated under ambient conditions. This situation is mainly caused by the scarcity of strong electron-deficient building blocks. Herein, we present two novel electron-deficient building blocks, FBDOPV-1 and FBDOPV-2, with low LUMO levels down to −4.38 eV. On the basis of both building blocks, we develop two poly(p-phenylene vinylene) derivatives (PPVs), FBDPPV-1 and FBDPPV-2, for high-performance n-type polymer FETs. The introduction of the fluorine atoms effectively lowers the LUMO levels of both polymers, leading to LUMO levels as low as −4.30 eV. Fluorination endows both polymers with not only lower LUMO levels, but also more ordered thin-film packing, smaller π–π stacking distance, stronger interchain interaction and locked conformation of polymer backbones. All these factors provide FBDPPV-1 with high electron mobilities up to 1.70 cm2 V–1 s–1 and good stability under ambient conditions. Furthermore, when polymers have different fluorination positions, their backbone conformations in solid state differ, eventually leading to different device performance. [ABSTRACT FROM AUTHOR]

Supramolecular hydrogels were preparedin the mixtures of biologicalsurfactant sodium deoxycholate (NaDC) and halide salts (NaCl and NaBr)in sodium phosphate buffer. It is very interesting that with the additionof two kinds of amino acids (l-lysine and l-arginine)to NaDC/NaX hydrogels, the gel becomes solution at room temperature.We characterized this performance through phase behavior observation,transmission electron microscopy, scanning electron microscopy, X-raypowder diffraction, Fourier transform infrared spectra, and rheologicalmeasurements. The results demonstrate that the gels are formed byintertwined fibrils, which are induced by enormous cycles of NaDCmolecules driven by comprehensive noncovalent interactions, especiallythe hydrogen bonds. Our conclusion is that the presence of halidesalts (NaCl and NaBr) enhances the formation of the gels, while theaddition of amino acids (l-lysine and l-arginine)could make the breakage of the hydrogen bonds and weaken the formationof the gels. Moreover, its fast disassembly in the presence of aminoacids allows for the release of substances (i.e., the dye methyleneblue) entrapped within the gel network. The tunable gel morphology,microstructure, mechanical strength, and anisotropy verify the roleof halide salts and amino acids in altering the properties of thegels, which can probably be exploited for a variety of applicationsin future. [ABSTRACT FROM AUTHOR]

We report herein the structuring of single- stranded thymine-rich DNA sequences into peptide-DNA hairpin triplex structures via designed melamine-thymine nucleobase recognition. Melamine-displaying α-peptides were synthesized with the general form (EM*)n, where M* denotes a lysine residue side chain derivatized with melamine, a bifacial hydrogen bond complement for thymine. We have found that (EM*)n peptides, which we term bifacial peptide nucleic acid (bPNA), function as a noncovalent template for thymine-rich DNA tracts, Unstructured DNA of the general form dTnCmTn are bound to (EM*)n peptides and fold into cooperatively melting 1:1 bPNA-DNA hairpin complexes with dissociation constants in the submicromolar to low nanomolar range for n = 4-10. As the length of the interface (n) is decreased, the melting temperature of the bPNA-DNA complex drops significantly, though Kd increases are less substantial, suggestive of strong enthalpy-entropy compensation. This is borne out by differential scanning calorimetry analysis, which indicates enthalpically driven bPNA-DNA base-stacking that becomes markedly less exothermic as the recognition surface n decreases in size. The recognition interface tolerates a high number of "mismatches" and indicates halfsite, or monofacial, recognition between melamine and thymine may occur if only 1 complementary nucleobase is available. Association correlates directly with fractional thymine content, with optimal binding when the number of T-T sites match the number of melamine units. Interestingly, when a DNA host has more T-T sites than melamine sites on bPNA, two or three bPNAs can bind to a single DNA, resulting in ternary and quaternary complexes that have higher thermal stability than the binary (1:1) bPNA-DNA complex, suggestive of cooperative multisite binding. In contrast, when two bPNAs of different lengths bind to the same DNA host, a ternary complex is formed with two melting transitions, corresponding to independent melting of each bPNA component from the complex. These data demonstrate that melamine-displaying bPNA recognize thymine-rich DNA in predictable and multifaceted ways that allow binding affinity, structure stability, and stoichiometry to be tuned through simple bPNA length modification and matching with DNA length. Synthetic bPNA structuring elements may be useful tools for biotechnology. [ABSTRACT FROM AUTHOR]

Lanthanide-containing polyoxometalates (POMs) can be used to detect various materials, but their luminescence in water has suffered enormous limitations due to the strong fluorescence quenching. Herein, to resolve this problem, three-dimensional nanoparticles built by mixed Weakley-type europium-containing POMs (Na 9 [EuW 10 O 36 ]·32H 2 O, abbreviated to EuW 10 ) and tetra- n -alkyl ammonium (TA) with enhanced fluorescent properties have been designed in aqueous solution using an ionic self-assembly (ISA) technique, which is mainly driven by the electrostatic interaction between EuW 10 and TA. The morphology and fluorescent properties of the system as well as some influencing factors (alkyl chain length, amino group, and inorganic salt concentration) were systematically investigated. The results indicated that the fluorescent intensity of EuW 10 /tetramethylammonium bromide (TMAB) composite increased about 14 times, whereas the extent of increase of fluorescence for EuW 10 /tetraethylammonium bromide (TEAB) and EuW 10 /tetrabutylammonium bromide (TMAB) composites gradually decrease due to the bulkier steric hindrance of the longer alkyl chain. Besides, the luminescence of EuW 10 /TMAB nanoparticles is pH responsive, and the reversibility of their structures and luminescence can be realized upon the addition of NaOH/HCl. Moreover, the EuW 10 /TMAB system also shows great fluorescence-sensing behavior, which could detect Cu 2+ with a detection limit of 0.15 μM. Our work provides a facile construction strategy for a functional fluorescent complex via POMs-based supramolecular self-assembly in aqueous solution, which will be further used in biomarkers and sensors., Competing Interests: The authors declare no competing financial interest.

Minimalist multifunctional platforms for delivering diagnostic and therapeutic agents effectively and safely into tumor sites are highly desired in nanomedicine. Herein, we describe the fabrication of a supramolecular nanoplatform via the amphiphilic amino acid (9-fluorenylmethyloxycarbonyl-l-leucine, Fmoc-l-L)-modulated self-assembly of a magnetic resonance imaging (MRI) contrast agent (ionic manganese, Mn 2+ ) and photosensitive drug (chlorin e6, Ce6). Coordination drives the coassembly of Fmoc-l-L and Mn 2+ to generate a nanoscale supramolecular network to adaptively encapsulate Ce6. The obtained biometal-organic nanoparticles exhibit a high drug loading capability, inherent good biocompatibility, robust stability, and smart disassembly in response to glutathione (GSH). The cooperative assembly of the multiple components is synchronously dynamic in nature and enables enhanced photodynamic therapy (PDT) to damage tumor cells and tissue by efficiently delivering the photosensitizer and improving the reductive tumor microenvironment via the competitive coordination of GSH with Mn 2+ . The antitumor effect can also be monitored and evaluated in vivo by MRI through the long-term intracellular biochelation of Mn 2+ . Therefore, this work presents a one-pot and robust method for the self-assembly of a multifunctional theranostic nanoplatform capable of MRI-guided PDT starting from minimalist biological building blocks.

In this work, three-dimensional nanoflowers with tunable fluorescent properties constructed with mixed Weakley-type polyoxometalates (POMs, Na 9 [LnW 10 O 36 ]·32H 2 O, Ln = Eu, Tb, abbreviated to LnW 10 ) and tetraethylenepentamine (TEPA) have been successfully prepared through a facile ionic self-assembly (ISA) method. The shape and petal size of the nanoflower as well as its fluorescent behaviors can be tuned through varying the ratio of EuW 10 /TbW 10 . The varied-temperature emission behaviors at 80-260 K show that the fluorescent intensity of both Tb 3+ and Eu 3+ decreased with the increase in temperature, which makes them potential luminescent ratiometric thermometers. Moreover, after being mixed with polydimethylsiloxane (PDMS), the as-formed hybrid films showed stable fluorescence along with good transparency. The robustness of the hybrid films was also demonstrated by corrosion resistance upon treatment with strong acid and alkali and thus can be used as a sensor to detect toluene circularly. Our results provide a new avenue to the facile construction of fluorescent composites and demonstrate that the POM complexes can be further used in supramolecular chemistry and nanomaterials.

Metal nanoclusters (NCs) have been engineered as a new kind of luminescent material, whereas the application of metal NCs in aqueous solution was subjected to great limitations owing to their poor solubility, stability, and strong luminescence quenching in a single-molecule state. Herein, facile supramolecular self-assembly strategy was carried out to enhance the luminescence of Ag(I) NCs (Ag 6 -NCs) through multiple electrostatic interactions with polyethyleneimine (PEI). Functional colloid aggregates of Ag 6 -NCs such as nanospheres and nanovesicles were formed along with the enhanced emission because of the formation of compact-ordered self-assemblies, which effectively restricted intramolecular vibration of the capping ligands on Ag 6 -NCs to diminish the nonradiative decay. All those could block energy loss and facilitated the radiative relaxation of excited states which ultimately induced an aggregation-induced emission (AIE) phenomenon. Furthermore, the luminescent Ag 6 -NCs/PEI nanovesicles are pH-responsive and show a superior fluorescent sensing behavior for the detection of Al 3+ with a limit of detection low to 3 μM. This is the first report about AIE of silver NCs with polymers in aqueous solution. This work sheds light on the controlled NCs-based supramolecular self-assembly and the NCs-based functional materials, which will be well-established candidates in controllable drug delivery, biomarkers, and sensors in aqueous solution.

The spontaneous formation of hybrid submicrometer spheres that were composed by a Weakley-type polyoxometalate Na 9 [EuW 10 O 36 ]·32H 2 O (denoted as EuW 10 ) and cationic peptide (K8) through a simple ionic self-assembly method was investigated. The approach presented in this study is an extended research which combined a biomolecule and a functional inorganic polyoxoanion for the fabrication of a multifunctional material. The K8/EuW 10 hybrid submicrometer spheres were fully characterized by transmission electron microscopy, field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, confocal laser scanning microscopy, and fluorescence spectra. The results indicated that the electrostatic interaction, hydrogen-bonding interaction, and combined hydrophobic interaction between EuW 10 and K8 favored the formation of the smooth submicrometer sphere structure. Once the EuW 10 /K8 submicrometer spheres were forming, the fluorescence of EuW 10 was reduced due to the hydrogen bonding between the ammonium group of K8 and the oxygen atom of EuW 10 that blocked the hopping of the d 1 electron in EuW 10 . Interestingly, our submicrometer spheres showed excellent decomposition efficiency toward organic pollutants such as the dye of methylene blue (MB), suggesting their promising applications in the treatment of wastewater.

A novel simple strategy for alkylamine-directed self-assembly of Weakley-type polyoxometalate (POM, Na 9 [EuW 10 O 36 ]·32H 2 O, abbreviated to EuW 10 ) to form three-dimensional nanoflowers has been successfully developed through the ionic self-assembly (ISA) method. For comparison, different molecular weights of alkylamines including diethylenetriamine, triethylenetetramine, and tetraethylenepentamine (TEPA) were selected to construct hierarchical nanostructures. Our results revealed that the morphologies and sizes of the nanostructures could be simply controlled by varying the molecular weights and concentrations of alkylamines. The fluorescent color of EuW 10 /TEPA nanoflowers changed compared with that of EuW 10 owing to the varied symmetry degree of europium coordination in EuW 10 /TEPA nanoflowers. It is demonstrated that this effective self-assembly occurs mainly though the hydrogen bond and electrostatic interaction between EuW 10 and TEPA. What's more, the EuW 10 /TEPA nanoflowers after calcining showed excellent decomposition efficiency toward methylene blue dyes. Our results further confirmed that ISA method between small molecules and POM can provide a unique "bottom-up" strategy to construct novel structures with functional properties.

In this work, through the aqueous phase self-assembly of an Eu-containing polyoxometalate (POM), Na 9 [EuW 10 O 36 ]·32H 2 O (EuW 10 ) and different amino acids, we obtained spontaneously formed vesicles that showed luminescence enhancement for EuW 10 and arginine (Arg), lysine (Lys), or histidine (His) complexes, but luminescence quenching for EuW 10 and glutamic acid (Glu) or aspartic acid (Asp) complexes. The binding mechanisms between them have been explored at the molecular level by using different characterization techniques. It was found that EuW 10 acted as polar head groups interact with the positively charged residues for alkaline amino acids, protonated amide groups for acidic amino and nonpolar acid aminos through electrostatic interactions, and the remaining segments of amino acids served as relatively hydrophobic parts aggregated together forming bilayer membrane structures. Moreover, the different influences of amino acids on the fluorescence property of EuW 10 revealed that the electrostatic interaction between the positive charged group of amino acid and the polyanionic cluster dominates the fluorescence properties of assemblies. Furthermore, a turn-off sensing application of the EuW 10 /Arg platform to probe dopamine (DA) against various other biological molecules such as neurotransmitters or amino acids was also established. The concept of combining POMs with amino acids extends the research category of POM-based functional materials and devices.

Giant vesicles (1-10 μm) were constructed via a facile ionic self-assembly (ISA) strategy using an anionic dye Acid Orange II (AO) and an oppositely charged ionic-liquid-type cationic surfactant 1-tetradecyl-3-methylimidazolium bromide (C14mimBr). This is the first report about preparing giant vesicles through ISA strategy. Interestingly, the giant vesicle could keep the original morphology during the evaporation of solvent and displayed solid-like properties at low concentration. Moreover, giant vesicles with large internal capacity volume and good stability in solution could also be achieved by increasing the concentrations of AO and C14mimBr which contributed to the increase of the other noncovalent cooperative interactions. In order to facilitate comparison, a series of parallel experiments with similar materials were carried out to investigate and verify the driving forces for the formation of these kinds of giant vesicles by changing the hydrophobic moieties or the head groups of the surfactants. It is concluded that the electrostatic interaction, hydrophobic effect and π-π stacking interaction play key roles in this self-assembly process. Importantly, the giant vesicles can act as a smart microcarrier to load and release carbon quantum dot (CQD) under control. Besides, the giant vesicles could also be applied as a microrector to synthesize monodispersed Ag nanoparticles with diameter of about 5-10 nm which exhibited the ability to catalyze reduction of 4-nitroaniline. Therefore, it is indicated that our AO/C14mimBr assemblies hold promising applications in the areas of microencapsulation, catalyst support, and lightweight composites owing to their huge sizes and large microcavities.

A novel electrochemiluminescent (ECL) aptasensor was proposed for the determination of thrombin (TB) using exonuclease-catalyzed target recycling and hybridization chain reaction (HCR) to amplify the signal. The capture probe was immobilized on an Au-GS-modified electrode through a Au-S bond. Subsequently, the hybrid between the capture probe and the complementary thrombin binding aptamer (TBA) was aimed at obtaining double-stranded DNA (dsDNA). The interaction between TB and its aptamer led to the dissociation of dsDNA because TB has a higher affinity to TBA than the complementary strands. In the presence of exonuclease, aptamer was selectively digested and TB could be released for target recycling. Extended dsDNA was formed through HCR of the capture probe and two hairpin DNA strands (NH2-DNA1 and NH2-DNA1). Then, numerous europium multiwalled carbon nanotubes (Eu-MWCNTs) could be introduced through amidation reaction between NH2-terminated DNA strands and carboxyl groups on the Eu-MWCNTs, resulting in an increased ECL signal. The multiple amplification strategies, including the amplification of analyte recycling and HCR, and high ECL efficiency of Eu-MWCNTs lead to a wide linear range (1.0×10(-12)-5.0×10(-9) mol/L) and a low detection limit (0.23 pmol/L). The method was applied to serum sample analysis with satisfactory results.

A multiscale stability study of foams stabilized by sodium dodecyl sulfate (SDS), sodium dodecylbenzene sulfonate (SDBS), and sodium polyoxyethylene alkylether sulfate (AES) was conducted, to investigate the relationship of surfactant molecular behavior and interfacial monolayer configuration of foam film to the foam film properties. Molecular dynamic (MD) simulations using a full-atom model was utilized to explore the microscopic features of the air/liquid interface layer. Several parameters such as the distribution of surfactant head groups and the order degree of surfactant hydrophobic tails were used to describe the molecular adsorption behavior. The effect of molecular structure on the nature of the foam film and the impact on the dynamic stability of wet foam is discussed. In the experimental evaluation, the SDBS foam films manifest strong stiffness and low viscoelasticity as shown by the interfacial shear rheology determination as well as texture analyzer (TA) measurement results, which agree very well with the array behavior of SDBS molecules at the air/water interface as described by the simulation results and is identified to be the reason for the poor dynamic stability. Comparing the molecular structure of SDS, SDBS, and AES, the special contributions of the linking groups such as the O atom, the phenyl group, and the EO (oxyethyl) chain to the interfacial array behavior of surfactants were characterized. It is concluded that microhardness of the foam film enhanced by rigid linking groups favors static foam stability but decreases the dynamic foam stability, while viscoelasticity of the foam film enhanced by soft linking groups increases the dynamic foam stability.

We present a new method to incorporate hydrophilic charged nanoparticles into the lyotropic liquid crystal (LLC) template. This method is based on the effect of the polymer-induced phase separation (PIPS) and consists of two steps. In the first step, the nanoparticles are mixed with a surfactant micellar solution. In the second step, upon addition of polymer, phase separation is induced and the LLC phase doped with the nanoparticles is formed. Columnar hexagonal and lamellar LLC templates are obtained with the PIPS method. The ordering of the LLC phase can be controlled by the amount of polymer added to induce phase separation. The method works both for the system of nonionic surfactants and polymers and ionic surfactants and polyelectrolytes. We demonstrate that the PIPS method enables the fabrication of the LLC templates doped with positively or negatively charged nanoparticles as well as with a mixture of oppositely charged nanoparticles in arbitrary proportions.

We give a detailed confocal fluorescence microscopy study on reverse vesicles from a salt-free catanionic surfactant system. When tetradecyltrimethylammonium laurate (TTAL) and lauric acid (LA) are mixed in cyclohexane at the presence of a small amount of water, stable reverse vesicular phases form spontaneously. The reverse vesicular phases can be easily labeled with dyes of varying molecular size and hydrophobicity while the dyes are nearly insoluble in cyclohexane without reverse vesicles. This indicates the reverse vesicular phases can be good candidates to host guest molecules. With the help of a fluorescence microscope combined a confocal method, the features of these interesting reverse supramolecular self-assemblies were revealed for the first time. Because of the absence of electrostatic repulsions and hydration forces between adjacent vesicles, the reverse vesicles have a strong propensity to aggregate with each other and form three-dimensional clusters. The size distributions of both individual reverse vesicles and clusters are polydisperse. Huge multilamellar reverse vesicles with closely stacked thick walls (giant reverse onions) were observed. Besides the spherical reverse vesicles and onions, other supramolecular structures such as tubes have also been detected and structural evolutions between different structures were noticed. These interesting supramolecular self-assemblies form in a nonpolar organic solvent may serve as ideal micro- or nanoreaction centers for biological reactions and synthesis of inorganic nanomaterials.

We present a detailed study on the incorporation of single-walled carbon nanotubes (SWNTs) into lyotropic liquid crystals (LLC) by phase separation in the presence of polyelectrolytes. Two cases were studied in this work: (i) incorporation of SWNTs into the LLC phase formed by an anionic surfactant sodium dodecyl sulfate (SDS) in the presence of an anionic polyelectrolyte poly(sodium styrenesulfonate) (PSS); (ii) incorporation of SWNTs into the LLC phase formed by a cationic surfactant cetyltrimethylammonium bromide (CTAB) in the presence of a cationic polyelectrolyte poly(diallydimethylammonium chloride) (PDADMAC). The SWNTs/LLC composites were characterized by polarized optical microscopy (POM) observations and small-angle X-ray scattering (SAXS) measurements. In both systems, the surfactant phase was condensed into a hexagonal lattice by the polyelectrolyte within the investigated concentration range. Several factors that can influence the property of SWNTs/LLC composite were examined, including concentration of surfactants and polyelectrolytes and temperature. Aggregated SWNTs were not observed, indicating that SWNTs were well dispersed in the LLC phases. SAXS measurements showed the lattice parameter of the host LLC phase changed upon varying the mixing ratio of polyelectrolyte to ionic surfactant. The SWNTs/LLC hybrids showed considerable stability against temperature rise in both systems, and desorption of surfactant from SWNTs was not observed at higher temperature.

Single-walled carbon nanotubes (SWNTs) were incorporated into a lyotropic liquid crystal (LLC) matrix formed by n-dodecyl octaoxyethene monoether (C(12)E(6)) at room temperature through spontaneous phase separation induced by nonionic hydrophilic polymer poly(ethylene glycol) (PEG). The quality of SWNTs/LLC composite was evaluated by polarized microscopy observations and small-angle X-ray scattering (SAXS) measurements. The results obtained clearly indicated that SWNTs have been successfully incorporated into the LLC matrix up to a considerable high content without destroying the LLC matrix, although interesting changes of the LLC matrix were also induced by SWNTs incorporation. By varying the ratio of PEG to C(12)E(6), the type of LLC matrix can be controlled from hexagonal phase to lamellar phase. Temperature was found to have a significant influence on the quality of SWNTs/LLC composite, and tube aggregation can be induced at higher temperature. When SWNTs were changed to multiwalled carbon nanotubes (MWNTs), they became difficult to be incorporated into LLC matrix because of an increase in the average tube diameter.

Aggregate transitions in salt-free catanionic surfactant mixtures of tetradecyltrimethylammonium hydroxide (TTAOH)/fatty acid were investigated as a function of surfactant concentration and temperature. Lauric acid (LA), myristic acid (MA), and palmitic acid (PA) were chosen for the current study. The TTAOH/LA mixture exhibited rich phase behavior at room temperature. With increasing total surfactant concentration (c(T)), a bluish vesicular (L(alphav)) phase, an isotropic micellar (L(1)) phase, and a birefringent lamellar (L(alpha)) phase were observed. Between the L(alphav) phase and the L(1) phase, a narrow L(alpha)'/L(1) two-phase region was determined. With increasing temperature, a transition from the L(alpha) phase to the L(1) phase was induced at higher c(T) whereas at lower c(T) an opposite transition from the L(1) phase to the L(alphav) phase was noticed. Thus surprisingly, we observed bilayer-to-micelle and micelle-to-bilayer transitions in the same catanionic surfactant system, both induced by the temperature increase. Replacing LA by MA and PA caused a continuous increase in the average Krafft point of the mixture. The L(alphav)-phase region and phase-separated region become larger. Moreover, a single L(1)-phase region was absent within the investigated temperature range.