The spontaneous formation of hybrid submicrometer spheres that were composed by a Weakley-type polyoxometalate Na9[EuW10O36]·32H2O (denoted as EuW10) 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/EuW10 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 EuW10 and K8 favored the formation of the smooth submicrometer sphere structure. Once the EuW10/K8 submicrometer spheres were forming, the fluorescence of EuW10 was reduced due to the hydrogen bonding between the ammonium group of K8 and the oxygen atom of EuW10 that blocked the hopping of the d1 electron in EuW10. 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, Na9[EuW10O36]·32H2O, abbreviated to EuW10) 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 EuW10/TEPA nanoflowers changed compared with that of EuW10 owing to the varied symmetry degree of europium coordination in EuW10/TEPA nanoflowers. It is demonstrated that this effective self-assembly occurs mainly though the hydrogen bond and electrostatic interaction between EuW10 and TEPA. What’s more, the EuW10/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 paper, new inorganic–organic hybrid nanoflowers consisting of a Weakley-type polyoxometalate Na9[EuW10O36]·32H2O (denoted as EuW10) and biomolecule dopamine (DA) were fabricated through a simple ionic self-assembly (ISA) method. The hybrid nanoflowers were fully characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, Raman spectra, X-ray diffraction (XRD), and fluorescence spectra. We found that the electrostatic interaction and hydrogen-bonding interaction between EuW10 and DA favored the formation of the hierarchical flowerlike structure with hundreds of nanopetals and their morphologies could be controlled simply by tuning the ratio and respective concentrations of the components. Once forming EuW10/DA vesicles or nanoflowers, the fluorescence of EuW10 was quenched due to the hydrogen bonding between the ammonium group of DA and the oxygen atom of EuW10 that blocked the hopping of the d1 electron in EuW10. Interestingly, the calcinated nanoflower showed excellent decomposition efficiency toward the organic pollutants such as the dyes of methyl orange (MO) and rhodamine B (RhB). Moreover, the catalyst for MO can be reused at least 6 cycles with only a slight dropping of catalytic efficiency, suggesting their promising applications in the treatment of wastewater.Keywords: Catalysis; Dyes; Eu-containing polyoxometalate; Fluorescence; Nanoflowers;

•Supramolecular hydrogels were prepared using α-CD and three trisiloxane-based surfactants.•The effects of different structures of silicone surfactants on the formation of hydrogels were considered.•S2E38 with more EO groups has a stronger ability to form hydrogels than S1E8 and S1E19.•α-CD/silicone surfactant hydrogel is appropriate for the controlled release of anticancer drugs.Supramolecular hydrogels were facilitated by α-cyclodextrin (α-CD) and three silicone surfactants named S1E8, S1E19 and S2E38, respectively. Influences of the molecular structure and concentration of the silicone surfactants on the formation of hydrogels and their stabilities were investigated. The hydrogels were characterized by phase behavior study and various techniques. The results indicated that the balance between the hydrophilicity and the hydrophobicity of the silicone surfactants is crucial for the formation and high stability of the hydrogels. S2E38, which has two poly-(ethylene oxide) chains, exhibits a stronger ability to form hydrogels than S1E8 and S1E19 do. Moreover, in vitro study using doxorubicin (DOX) as a model anticancer drug shows that α-CD/silicone surfactant hydrogels can be used as injectable carriers for controlled drug release.Schematic illustration of the formation of α-CD/silicone surfactant hydrogels.Download high-res image (102KB)Download full-size image

Microemulsions consisting of ionic liquid-type imidazolium gemini surfactants with different spacer lengths ([C14-n-C14im]Br2, n = 2, 4, 6), cyclohexane, n-hexyl alcohol and hydrochloric acid solution, were investigated for Au(III) extraction. [C14-n-C14im]Br2 in the microemulsion played a dual role as surfactant and extractant. The extraction efficiency (E%) of the [C14-n-C14im]Br2/cyclohexane/n-hexyl alcohol/HCl microemulsion system for Au was above 99% under optimal conditions. The results of our study indicated that the Au(III) extraction ability of the three different [C14-n-C14im]Br2 with different spacer lengths was better with longer a spacer. The mechanism for the Au(III) extraction by [C14-n-C14im]Br2 was confirmed to be based on an anion-exchange process by the continuous variation method and spectroscopic analysis (UV-Vis, FT-IR, 1H-NMR). The FT-IR spectra indicated that the better extraction ability of [C14-n-C14im]Br2 for Au(III) was positively correlated with the spacer length, due to a less significant steric effect of the methylene groups in surfactants with longer spacers. The electric conductivity values of the [C14-n-C14im]Br2 microemulsions indicated that surfactants with longer spacers can ionize to a higher extent to give more [C14-n-C14im]2+ cations and Br− anions, thus promoting anion-exchange and further increasing E%.

In this article, a sensitive and selective on–off–on fluorescence chemosensor, Tyloxapol (one kind of water soluble oligomer), was developed for the label-free detection of MnO4− ions in aqueous solution. From fluorescence experiments, it is demonstrated that Tyloxapol is a sensitive and selective fluorescence sensor for the detection of MnO4− directly in water over a wide range of anions including Cl−, Br−, I−, NO3−, H2PO4−, HCO3−, OH−, ClO4−, Ac−, SO42−, HPO42−, CO32−, C2O42−, S2−, SO32−, and Cr2O72−. Moreover, the fluorescence intensity of Tyloxapol has shown a linear response to MnO4− in the concentration range of 0 to 120 μmol L−1 with a detection limit of 0.392 μmol L−1 MnO4−. The interaction mechanism demonstrated that our on–off fluorescent oligomer probe for detecting Mn(VII) is based on the inner filter effect (IFE) because the absorption bands of Mn(VII) are fully covered by the excitation bands of Tyloxapol. Next, another turn-on sensing application of the Tyloxapol/MnO4− platform to probe S2− against various other anions and aldehydes against various other organic pollutants were also established. It is expected that our strategy may offer a new approach for developing a simple, cost-effective, rapid and sensitive sensor for the detection of anions and aldehydes in environmental applications.

Three-dimensional (3D) hierarchical nanostructures have generated a large amount of interest because of their unique, unusual properties and potential applications. In this article, copper(II) ions as the inorganic component and various biosurfactants as the organic component were used to successfully form 3D nanoflowers via a facile and effective self-assembly template synthesis strategy. It can be confirmed that the biosurfactant molecules can first form complexes with the copper ions, and these complexes then become nucleation sites for primary crystals of copper phosphate, indicating that the interaction between biosurfactant and copper ions leads to the formation of 3D nanoflowers. Several reaction parameters such as aging time and the concentration of the biosurfactant, which play a critical role in the formation process and morphologies of the nanoflowers, were investigated. Under the optimum synthetic conditions, a spherical flowerlike structure with hundreds of nanopetals was obtained. Moreover, the biosurfactant–Cu3(PO4)2·3H2O nanoflowers also showed high stability and catalytic activity for degradation of cationic dyes. Our results demonstrate that the biosurfactant–inorganic 3D nanoflowers, which combined the advantages of the biosurfactant and inorganic material, have potential applications in industrial biocatalysis, biosensors, and environmental chemistry.

Supramolecular self-assembly, based on non-covalent interactions, has been employed as an efficient approach to obtain various functional materials from nanometer-sized building blocks, in particular, [Ag6(mna)6]6−, mna = mercaptonicotinate (Ag6-NC). A challenging issue is how to modulate the self-assembly process through regulating the relationship between building blocks and solvents. Herein, we report the controlled self-assembly of hexanuclear silver nanoclusters into robust multilayer vesicles in different solvents, DMSO, CH3CN, EG and MeOH. Their unique luminescence enables them to be bifunctional probes to sense Fe3+ and DL-dithiothreitol (DTT). By protonating the Ag6-NC to Ag6-H-NC using hydrochloric acid (HCl), the multilayer vesicles survive in aprotic solvents, DMSO and CH3CN, but are transformed to nanowires in protic solvents, water, EG and MeOH. Our results demonstrated that the solvent-bridged H-bond plays a key role in the evolution of the morphologies from vesicles to nanowires. Moreover, the nanowires could further hierarchically self-assemble in water into hydrogels with high water content (99.5%), and with remarkable mechanical strength and self-healing properties. This study introduces a robust cluster-based building block in a supramolecular self-assembly system and reveals the significance of aprotic and protic solvents for the modulation of the morphologies of cluster-based aggregates.

•The effects of amino acids on the phase behavior of ionic liquid-type imidazolium surfactant were investigated.•With the addition of Lys, C14mimBr LLC transformed to worm-like micelles.•For C14mimBr/Arg system, it remained the hexagonal phases.•Our work contributes to a better understanding of the effect of amino acids on the influence of surfactant aggregates.The effects of alkaline amino acids l-Lysine (l-Lys) and l-Arginine (l-Arg) on the lyotropic liquid crystal (LLC) behavior of ionic liquid-type imidazolium surfactant (1-tetradecyl-3-methylimidazolium bromide, C14mimBr) were investigated systematically. The corresponding properties were investigated by polarized optical microscopy (POM), small angle X-ray scattering (SAXS), field emission-scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy and rheological measurements. The results indicated that with the introduction of l-Lys, LLC phase of C14mimBr gradually undergoes the transition to an isotropic homogeneous phase, which demonstrated to be worm-like micelles (WLMs). While for C14mimBr/l-Arg system, it remained the hexagonal phases and merely induced the variation of the mechanical strength of C14mimBr LLCs. It can be speculated that the balance between electrostatic interaction, H-bond interaction, and hydrophobic interaction plays an important role in the phase transition of C14mimBr/amino acids. Our work can contribute to a better understanding of the effect of the additions especially amino acids on the influence of the surfactant aggregates and their macroscopic properties, which maybe open the door for wide applications in the biological system.Schematic illustrations of the phase transition between LLCs and the micelle solution by the introducing of amino acids.Download high-res image (345KB)Download full-size image

•A sensitive and selective turn-off fluorescence chemosensor carbon quantum dots was developed.•CQDs can be used for the label-free detection of Fe3+ ions in aqueous solution.•CQDs/Fe3+ can be further used as a turn-on fluorescent probe for the detection of ascorbic acid.•Our strategy may offer a new approach for developing sensitive sensors in biological and environmental applications.Herein, a convenient on-off fluorescent probe was developed to detect iron ion (Fe3+) with sensitivity and selectivity by using highly luminescent ionic liquid-functionalized carbon quantum dots (CQDs) which was prepared by one-step hydrothermal treatment using citric acid and 1-Aminopropyl-3-methylimidazolium. The sensitivity of CQDs for Fe3+ was examined by measuring the fluorescence (FL) intensity of various concentrations of Fe3+ in CQDs solution and the selectivity of CQDs for Fe3+ was examined by adding different metal ions (Na+, Mg2+, Al3+, K+, Ca2+, Mn2+, Zn2+, Ag+, Cd2+, Pb2+ and Ba2+) into CQDs solution, respectively. The results indicated that the FL intensity of CQDs showed a good linear response to the concentrations of Fe3+ in the range of 0–300 μmol L−1 (R2 = 0.99) with a detection limit of 13.68 μmol L−1. Furthermore, based on the redox mechanism, after the fluorescent of CQDs was quenched by Fe3+, different neurotransmitters and amino acids were added and the FL test show that only ascorbic acid (AA) can recover the intensity of the CQDs/Fe3+, indicating that CQDs/Fe3+ can be further used as a on-off fluorescent probe for the detection of AA. It is expected that our strategy may offer a new approach for developing rapid, low cost and sensitive CQDs-based sensors for environmetal and biological sensing applications.The schematic diagram of CQDs quenched by Fe3+ ion and recovered by AA.Download high-res image (145KB)Download full-size image

•A sensitive and selective turn-off fluorescence chemosensor, Tyloxapol, was developed.•Tyloxapol is one kind of water soluble fluorescent oligomer.•Tyloxapol can be used for the label-free detection of Fe3+ ions in aqueous solution.•Our strategy may offer a new approach for developing sensitive sensors in biological and environmental applications.In this article, a sensitive and selective turn-off fluorescence chemosensor, Tyloxapol (one kind of water soluble oligomer), was developed for the label-free detection of Fe3+ ions in aqueous solution. Fluorescence (FL) experiments demonstrated that Tyloxapol was a sensitive and selective fluorescence sensor for the detection of Fe3+ directly in water over a wide range of metal cations including Na+, K+, Ag+, Hg2+, Cd2+, Co2+, Cu2+, Cr3+, Mn2+, Ba2+, Zn2+, Ni2+, Mg2+, Ca2+, and Pb2+. Moreover, the fluorescence intensity of Tyloxapol has shown a linear response to Fe3+ in the concentration range of 0–100 μmol L−1 with a detection limit of 2.2 μmol L−1 in aqueous solution. Next, based on a competition mechanism, another turn-on sensing application of the Tyloxapol/Fe3+ platform to probe dopamine (DA) against various other biological molecules such as other neurotransmitters or amino acids (norepinephrine bitartrate, acetylcholine chloride, alanine, valine, phenylalanine, tyrosine, leucine, glycine, histidine) were also investigated. It is expected that our strategy may offer a new approach for developing simple, cost-effective, rapid and sensitive sensors in biological and environmental applications.Schematic representation of fluorescent Tyloxapol for detection of Fe3+ ion and dopamine.

Supermolecular hydrogels were prepared by α-cyclodeatrin (α-CD) and Tyloxapol, which can be considered as an oligomer of the nonionic surfactant polyoxyethylene tert-octylphenyl ether (TX-100) with a polymerization degree below 7. Two carbon materials, graphene oxide (GO) and graphene, were mixed into the α-CD/Tyloxapol hydrogel to adjust the physicochemical properties of hydrogel. In order to get stable graphene dispersion and then mix it with α-CD/Tyloxapol hydrogel, both TX-100 and Tyloxapol were used to disperse graphene for comparison. Interestingly, it can be found that TX-100 could disperse graphene better than Tyloxapol owing to smaller molecular size of TX-100 compared with Tyloxapol. Then, both the α-CD/Tyloxapol/GO and α-CD/Tyloxapol/graphene hydrogels were characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, small angle X-ray scattering (SAXS), X-ray diffraction (XRD) and rheological measurements. The results revealed that the addition of carbon materials into α-CD/Tyloxapol hydrogel can change their microstructures and the rheological properties. Furthermore, it can be confirmed that a little amount of carbon materials could induce fluorescence quenching sharply which could be a promising candidate for optical sensor.

The discovery of a class of self-assembling peptides that spontaneously undergo self-organization into well-ordered structures opened a new avenue for molecular fabrication of biological materials. In this paper, the structure controlled helical nanofibers were prepared by two artificial β-sheet dipeptides with long alkyl chains derived from l- and d-threonine (Thr) and sodium hydroxide (NaOH). These helical nanofibers have been characterized using transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), circular dichroism (CD), Fourier transform infrared (FT-IR) spectroscopy, and X-ray powder diffraction (XRD). It was demonstrated that the helicity of the nanofibers could be easily controlled by changing the chirality of the constituent amino acids in the peptide species (d- or l-threonine). Moreover, the hydrogen bonding interactions between the amide groups as well as the hydrophobic interactions among the alkyl chains play important roles in the self-assembly process. It also can be observed that with the passage of time, the hydrogen bonding interactions between the individual nanofiber induced the conversion from nanofibers to nanobelts. Particularly, gold and silver nanoparticles performed good catalytic ability were synthesized using the assembled nanofibers as template.The mechanism of formation of helical structures for (L, L) and (D, D).

A salt-free surfactant system formed by a peptide amphiphile with short headgroup (PA, C16-GK-3) and a zwitterionic surfactant (dodecyldimethylamine oxide, C12DMAO) in water has been systematically investigated. The microstructures and properties of C16-GK-3/C12DMAO mixed system were characterized using a combination of microscopic, scattering and spectroscopic techniques, including transmission electron microscopy (TEM), field emission-scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), Fourier transform infrared (FT-IR), circular dichroism (CD) and rheological measurements. Rich phase transitions have been observed by adjusting the concentration of C16-GK-3. Investigation of the hydrogels of C16-GK-3/C12DMAO with TEM, SEM and AFM showed that all of these hydrogels form nanobelts. The nanobelt formation is performed in a hierarchical manner: β-sheet peptides and C12DMAO first interact each other to form small aggregates, which then arrange themselves to form one dimensional (1D) left-handed ribbons. The ribbons further aggregated into flat and rigid nanobelts. We proposed a mechanism to interpret the self-assembly process according to the specific peptide structure as well as multiple equilibria between the hydrogen bonding interactions between the headgroups of C16-GK-3, between C12DMAO molecules and the headgroups of C16-GK-3, chirality of the amino acid residues and hydrophobic interactions of the alkyl chains.TEM and AFM height images of the hydrogel with cC12DMAO = 50 g L−1 and cC16-GK-3 = 40 g L−1.

A facile and versatile method for the synthesis of stable monodisperse colloidal gold nanoparticles was developed using a water-in-oil microemulsion-templating strategy. The water-in-oil microemulsion was composed of cationic imidazolium gemini surfactant [C14-4-C14im]Br2, 1-heptane, 1-pentanol and HAuCl4 aqueous solution. The properties of these Au nanoparticles have been fully characterized using transmission electron microscopy (TEM), high-resolution TEM (HR-TEM) observations, X-ray diffraction (XRD), and UV-vis measurements. It can be observed that the monodisperse gold nanoparticles possess a hexagonal close-packed mode and can further aggregate to a rotundity which is shaped like a micro emulsion template while we can not get this kind of morphology using other templates such as [C14min]Br, sodium 1-tetradecanesulphonate or tetradecyltrimethylammonium bromide (TTAB). Moreover, the catalytic efficiency of the gold nanoparticles was evaluated by using the reduction of 4-nitroaniline (4-NA) by potassium borohydride (KBH4) in aqueous solution and electrochemical reduction of hydrogen peroxide (H2O2). These Au nanoparticles possess excellent properties making them fascinating candidates for a variety of applications such as catalysis and life science.

Novel fluorescent vesicles based on inclusion complexes of β-cyclodextrins (β-CD) with Tyloxapol were constructed. For comparison, α-cyclodextrins (α-CD) were also selected to form inclusion complexes with Tyloxapol. The vesicles formed by β-CD/Tyloxapol were characterized thoroughly using various techniques including phase behavior observation, transmission electron microscopy (TEM), freeze fracture transmission electron microscopy (FF-TEM), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), 2D 1H–1H ROESY NMR, fluorescence spectra, Fourier transform infrared (FT-IR) spectroscopy, and X-ray diffraction (XRD). The results of TEM, SEM, FF-TEM, AFM indicated the formation of vesicles of β-CD/Tyloxapol; they presented aggregation-induced emission enhancement properties because the alkyl chain of Tyloxapol molecules enters the cavity of β-CD and forms inclusion complexes, while α-CD/Tyloxapol showed aggregation-induced quenching fluorescence emission properties owing to the interaction between PEO chain of Tyloxapol molecules and α-CD. Moreover, the vesicles of β-CD/Tyloxapol were responsive to external stimuli and their fluorescent intensities were changed by various environmental conditions such as urea, phenylalanine, α-amylase and NaOH. These properties made our vesicle a promising candidate as novel, smart, stimuli-responsive, fluorescent vesicular sensors.

In this work, the effects of four imidazolium-based surfactants with different lengths of hydrophobic alkyl tails ([C2mim]Br, [C8mim]Br, [C12mim]Br, and [C14mim]Br) on the self-assembly behaviors of the biological surfactant sodium deoxycholate (NaDC) in sodium phosphate buffer (pH = 7) were investigated systematically. The microstructures and properties of NaDC/CnmimBr (n = 2, 8, 12, 14) mixed systems were characterized using transmission electron microscopy (TEM), field emission-scanning electron microscopy (FE-SEM), polarized optical microscopy (POM) observations, Fourier transform infrared (FT-IR), X-ray powder diffraction (XRD) and rheological measurements. The roles of the hydrophobic chain length, the chiral rigid steroid center, and the electrostatic interaction for the evolution of phase behavior are clearly described. The results indicated that the long-chain imidazolium-based surfactants ([Cnmim]Br, n ≥ 8) weakened the gel of NaDC, while C2mimBr strengthened the gel behavior of NaDC and even can form microcrystals. The super-hydrogels formed by these systems may act as promising adsorbents for the removal of heavy-metal ions from industrial sewage.

A microemulsion with hydrochloric acid solution as the polar phase, n-heptane as the continuous phase, [C14-4-C14im]Br2 as an ionic-liquid-type imidazolium gemini surfactant and extractant, and n-amyl alcohol as cosurfactant was studied on Au(III) extraction. Compared to its corresponding monomer [C14-mim]Br-based microemulsion for Au(III) extraction, the [C14-4-C14im]Br2-based microemulsion system showed excellent extractability of Au(III). The anion-exchange mechanism of Au(III) extraction was confirmed by the slope method and spectrum analysis (UV–vis, FT-IR, and 1H NMR). Main influence factors such as phase ratio, extraction equilibrium time, amyl alcohol volume fraction, and the concentration of ionic liquid on the extraction efficiency (E%) were explored. Moreover, [C14-4-C14im]Br2-based water-in-oil microemulsion had high selectivity over a multimetal ion solution (Co (II), Cu(II), Fe(III), Ni(II), Sn(IV), and Al(III)). Therefore, it is indicated that [C14-4-C14im]Br2-based microemulsion provides an effective and potential approach for the separation and purification of Au(III) from HCl solution.

A kind of self-assembled vesicles that composed of ionic liquid-type cationic gemini surfactant (C3H6-α, ω-(Me2N+C12H25Cl–)2, 12-3-12) and anionic biological surfactant (sodium deoxycholate, SDC) were constructed for Au(III) extraction. The appearance and microstructure of vesicles system were characterized by visual and TEM images. Compared to the zeta potential of pure vesicles system (+45 ± 1 mV), zeta potential of gold-loaded vesicles system reduced 15 ± 1 mv (changed to +30 ± 1 mV), which confirmed the mechanism of Au(III) was effectively extracted by vesicles through electrostatic interaction. The main influence factors including extraction equilibrium time, surfactants concentration, NaCl concentration, and pH on the extraction efficiency (E%) were explored. Furthermore, an effective method was devoted for gold(III) stripping. Through stepwise extraction and ligand-modified vesicles system, Au(III), Cu(II), and Fe(III) were separated from a mixed solution successfully. In short, an effective and potential approach for the separation of Au(III) from HCl solution was investigated in our work, which can be helpful for gold recovery and environmental improvement.

•The hydrogels were formed by the self-assembly of β-CD and [C14-4-C14im]Br2.•The properties of the hydrogels of β-CD/[C14-4-C14im]Br2 are responsive to external stimuli.•These hydrogels can be useful in the field of biomedical applications.Two-component hydrogels were formed by the supramolecular assembly of β-cyclodextrin (β-CD) and ionic liquid-type imidazolium gemini surfactants ([C14-4-C14im]Br2) in water. The mechanism for the formation of hydrogels was studied by various methods including transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and rheological measurements. It can be revealed that in these hydrogels, β-CD is as the host and [C14-4-C14im]Br2 is as the guest and they can form inclusion complexes. Moreover, the properties of the hydrogels of β-CD/[C14-4-C14im]Br2 are responsive to external stimuli and can be controlled by changing the host/guest ratio or the temperature. For example, by increasing the temperature, the hydrogels change into solutions and this process is reversible and reproducible. Taken together and according to the previous study, it is suggested that the main driving forces are hydrogen bonding between β-CDs, β-CD and the imidazolium headgroup of [C14-4-C14im]2+, β-CD and the solvent, and the hydrophobic interaction between the hydrophobic chains of [C14-4-C14im]Br2. The properties of these hydrogels led them be useful in the field of biomedical applications such as injectable drug delivery systems.Schematic diagram of the hydroel formed by [C14-4-C14im]Br2 and β-CD.

A fluorescent solid-like giant vesicle was prepared by using an anionic dye methyl orange (MO) and an oppositely charged surfactant 1-tetradecyl-3-methylimidazolium bromide (C14mimBr) on the basis of the ionic self-assembly (ISA) strategy. The properties of MO/C14mimBr complexes were comprehensively characterized. The results indicated that the giant vesicle was formed by the fusion of small vesicles and could keep its original structure during the evaporation of solvent. Besides, the giant vesicles exhibit luminescent property owing to the break of intermolecular π–π stacking of MO, which achieves the transformation from aggregation-caused quenching to aggregation-induced emission by noncovalent interaction. Moreover, MO/C14mimBr complexes also exhibit smart pH-responsive characteristics and abundant thermic phase behavior. That is, various fluorescent structures (polyhedron, giant vesicle, chrysanthemum, peony-like structure) were obtained when pH ≥ 4, whereas a simple nonfluorescent structure (microflake) was obtained when pH = 2 due to the changes of MO configuration. Thus, the fluorescence behavior can be predicted with the color change directly visible to the naked eye by changing the pH. It is expected that the facile and innovative design of supramolecular material by the ISA strategy could be used as pH detection probes and microreactors.

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.

In this work, through the aqueous phase self-assembly of an Eu-containing polyoxometalate (POM), Na9[EuW10O36]·32H2O (EuW10) and different amino acids, we obtained spontaneously formed vesicles that showed luminescence enhancement for EuW10 and arginine (Arg), lysine (Lys), or histidine (His) complexes, but luminescence quenching for EuW10 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 EuW10 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 EuW10 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 EuW10/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.

A fluorescent supramolecular hydrogel was prepared by α-cyclodextrin (α-CD) and Tyloxapol, which can be considered as an oligomer of the nonionic surfactant polyoxyethylene tert-octylphenyl ether (Triton X-100, TX-100) with a polymerization degree below 7. For comparison, both Tyloxapol and TX-100 were selected to form hydrogels with α-CD to get more information about the interaction between different types of surfactants and cyclodextrin. These hydrogels have been thoroughly characterized using various techniques including phase behavior observation, transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), fluorescence spectra, fluorescence microscopy observations, Fourier transform infrared (FT-IR) spectroscopy, 1H NMR, 2D 1H-1H ROESY NMR, small-angle X-ray scattering (SAXS), X-ray diffraction (XRD) and rheological measurements. The hydrogels of α-CD/Tyloxapol are responsive to external stimuli including temperature, pH and guest molecules, and present gelation-induced quenching fluorescence emission properties. The reason for this phenomenon may be that Tyloxapol molecules come into the cavity of α-CD and form the inclusion complexes. Due to the high electron density of the narrow cavity of α-CD, it induces the shift of the electron on the benzene ring which can weaken the π–π interaction and lead to the fluorescence quenching. Moreover, the hydrogel formed by α-CD/Tyloxapol is highly responsive to the formaldehyde (HCHO). The addition of a small amount of HCHO can induce a gel-to-sol transition. Interestingly, once the gel transforms into solution, it becomes fluorescent. This makes the α-CD/Tyloxapol hydrogel a promising candidate for HCHO detection and removal in home furnishings to reduce indoor environmental pollutants.

•α-Cyclodextrin/star-like block copolymer AE73 hydrogels were prepared.•Graphene and graphene oxide were successfully incorporated into the α-CD/AE73 hydrogel.•Graphene (hydrophobic) and graphene oxide (hydrophilic) have different effects on the formation of hydrogels.•The incorporation of graphene and graphene oxide impart versatile functionalities for hydrogels.A new supramolecular hydrogel self-assembled between α-cyclodextrin (α-CD) and a star-like block copolymer AE73 was prepared. The cooperation effect of complexation of poly-(ethylene oxide) (PEO) segments with α-CD and the hydrophobic interaction between poly-(propylene oxide) (PPO) blocks resulted in the formation of the supramolecular hydrogel with a strong macromolecular network. Then two kinds of carbon materials (graphene and graphene oxide) were successfully incorporated into the above α-CD/AE73 hydrogel to further enhance the mechanical properties. The native hydrogel, as well as hybrid hydrogels, have been thoroughly characterized by using various microscopic techniques, including transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA). Our main purpose is to ascertain whether the properties of the obtained gels depend on these architectures. Interestingly, the phase behavior, the morphology and the mechanical strength of the native hydrogel can be successfully modulated by incorporating graphene and graphene oxide. Taking into account that both PEO/PPO copolymers and α-CD seem to be biocompatible, these gels can be promising for biomedical applications.

Polyvinyl alcohol (PVA) hydrogels have been proposed for use as promising biomaterials in biomedical and tissue engineering, and graphene oxide (GO) has been recognized as a unique two-dimensional building block for various graphene-based supramolecular architectures. In this article, we systematically studied the influence of three kinds of PVA with different molecular weights on the interaction between PVA and GO. Moreover, the effects of PVA on the gelation of GO were also investigated. The native PVA hydrogel, as well as PVA–GO hybrid hydrogels, have been thoroughly characterized by the phase behavior study and various techniques including field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA) and rheological measurements. It can be seen that with the increase of the molecular weight of PVA, the addition of GO can effectively promote the gelation of PVA which can be reflected by a decrease of the critical gel concentration (CGC) for PVA–GO hydrogels. Dye adsorption experiments indicate that the toxic dye, i.e., methylene blue (MB), was efficiently entrapped in the PVA–GO xerogels. It is also demonstrated that the gelation of PVA and GO composites can be promoted by different supramolecular interactions, including hydrogen bonding and electrostatic interaction. This work indicates that the PVA–GO composite is a good candidate for preparing “super” and “smart” hydrogels and will enable further studies on the supramolecular chemistry of PVA, graphene and its derivatives.

•The interactions between BSA (or gelation) and NaDC were compared.•The interaction between BSA and NaDC is stronger than that of gelation/NaDC system.•A model of interaction between protein and NaDC has been brought out.•This research might find significant applications in various industrial areas.Surface tension, fluorescence and circular dichroism (CD) methods have been used to investigate the interaction between a biological surfactant sodium deoxycholate (NaDC) and proteins including bovine serum albumin (BSA) and gelatin. It can be seen from the surface tension measurements that both NaDC/BSA and NaDC/gelatin systems can form complexes and the ability of NaDC/BSA to lower surface tension is more obvious than that of NaDC/gelatin. The formation of the complexes influences not only the polarity of the microenvironment of the systems but also their fluorescence spectra. The far-UV CD spectra shows that the α-helical network of BSA increases first and then decreases as the concentration of NaDC increases, while the random coil content of gelatin always increases. A model of interaction between protein and NaDC influenced by the concentration of NaDC has been brought out based on the data gained from this study.Schematic illustrations of the interaction between NaDC and BSA: (A) BSA solution; (B) the interaction between NaDC monomer and BSA; (C) the interaction between NaDC dimer and BSA; (D) the interaction between NaDC secondary aggregate and BSA. The rigid skeleton and carboxyl group of NaDC are respectively represented by an orange semicircle and a negatively charged blue ball.

As a renewable material, welan gum is a kind of both biocompatible and biodegradable microbial polysaccharide and can be used to form polysaccharide/inorganic material composites. In this article, welan gum–graphene oxide (GO) composite hydrogels were prepared by simple self-assembly of both components in aqueous media and the effects of GO on the gelation of welan gum were systematically studied. The welan gum–GO hybrid hydrogels have been thoroughly characterized using transmission electron microscopy (TEM), atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC) and rheological measurements. It can be observed that GO is dispersed on a molecular scale in the welan gum matrix and the interactions such as hydrophobic interaction, electrostatic interaction and hydrogen bonding occur between the welan gum matrix and graphene oxide sheets. The addition of GO which can act as a physical cross-linker in the hydrogel and effectively promote the gelation of welan gum, can be reflected by a decrease of the critical gelation concentration (CGC). Additionally, the welan gum–GO hybrid hydrogels exhibited good adsorption properties for water-soluble dyes such as methylene blue (MB), methyl violet (MV), amido black 10B (AB10B), rhodamine 6G (R6G) and chrome azurol S (CAS). Thus, it is expected that the GO-based composite hydrogels can act as adsorbents and have promising applications in the field of waste water treatment.

Supramolecular hydrogels were prepared using α-cyclodextrin (α-CD) and a poloxamine (reverse Tetronic 90R4, T90R4) which has four diblock arms with a poly(propylene oxide)–poly(ethylene oxide) (PPO–PEO) structure. The α-CD can slide past the PPO blocks and towards the middle PEO blocks owing to the unsuitable energy between α-CD and PPO to form α-CD/T90R4 inclusion complexes (ICs). The incorporation of graphene oxide (GO) into α-CD/T90R4 ICs changes their phase behavior and forms mechanically strong hydrogels because of the hydrogen-bonding between the GO nanosheets and the α-CD and PEO blocks of T90R4. The native hydrogel, as well as the α-CD/T90R4/GO hybrid hydrogels, have been thoroughly characterized by using various microscopy techniques. Field emission scanning electron microscopy (FE-SEM) was used to observe the morphology of the hydrogel, and differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to evaluate the thermal stability of the hydrogel. Fourier transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) were used to characterize the interactions within the supramolecular assemblies and the degree of crystallinity of the xerogels, respectively. The experimental results demonstrated that α-CD/T90R4/GO hybrid hydrogels could adsorb various dyes selectively, and that it is a promising candidate for sewage treatment, while the native one cannot adsorb the dyes well. Moreover, the native α-CD/T90R4 hydrogel has excellent biocompatibility, and the results of the in vitro drug release study showed that the injectable doxorubicin (DOX)-loaded hydrogel is appropriate for the controlled release of anticancer drugs, while the α-CD/T90R4/GO hybrid hydrogels can reduce the release rate of DOX.

In this study, we report a simple synthesis of multiple Au nanodots core-silica shell nanoparticles (multi-Au@SiO2 NPs). The Au@SiO2 hybrid nanoparticles were synthesized in a water-in-oil microemulsion with a composition of polyoxyethylene(10) tertoctylphenyl ether (Triton X-100)/1-hexanol/cyclohexane/H2O and have been fully characterized by transmission electron microscopy (TEM), high-resolution TEM (HR-TEM) observations, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR), UV-vis measurements, and thermogravimetric analysis (TGA). The morphologies of the hybrid nanoparticles of Au@SiO2 can be easily tuned by the molar ratio of HAuCl4 to NaBH4 and the volume ratio of HAuCl4 aqueous solution to TEOS. As the morphologies of Au@SiO2 nanoparticles varied, the optical properties also changed as revealed by UV absorption spectrum. These Au@SiO2 hybrid nanoparticles which possess these properties make them fascinating candidates for a variety of applications such as catalysis and life science.

•We used sodium deoxycholate and graphene oxide to prepare hydrogels.•The introduction of GO to NaDC hydrogel enhances the mechanical strength of the composite hydrogel.•The incorporation of GO exhibits good dye absorption property for hydrogels.Sodium deoxycholate/graphene oxide (NaDC/GO) composite hydrogels were prepared in varying salinity. The hydrogels were characterized in detail by phase behavior study, transmission electron microscopy (TEM) observations, scanning electron microscopy (SEM) observations, X-ray powder diffraction (XRD) mesurements, Fourier transform infrared (FT-IR) spectra and rheological measurements. It was found that the introduction of GO to NaDC hydrogel enhances the mechanical strength of the composite hydrogel. When contacted with methylene blue solution, methylene blue can be absorbed inside the gel accompanied with a swelling of the gel. On the contrary, the hydrogel forms by NaDC only dissolves in methylene blue solution, forming a homegeous solution. Further study reveals that the gelation of NaDC/GO composite gel can be accelerated by an increase in salinity. This work may open the door for a variety of applications of NaDC/GO composite hydrogels such as in biotechnology, drug delivery and sewage treatment.Schematic representation of the structure of NaDC/GO hydrogel.

•We used NaDC and Eu(NO3)3 to prepare luminescent hydrogels.•The hydrogels have excellent gelation capabilities and mechanical strength.•The maximum emission of hydrogel is at 1:3 between Eu(NO3)3 and NaDC.•The incorporation of lanthanide ions imparts versatile functionalities for hydrogels.Luminescent hydrogels were facilely designed through supramolecular self-assembly of biological surfactant (sodium deoxycholate, NaDC) and lanthanide salt (Eu(NO3)3). The microstructures of the hydrogels were characterized by transmission electron microscopy (TEM), high-resolution TEM (HR-TEM) and field emission scanning electron microscopy (FE-SEM), from which nanofibers and tiny particles were observed. The arrangement of the deoxycholate and metal ions was proposed according to small-angle X-ray scattering (SAXS) and X-ray powder diffraction (XRD) measurements. Rheological measurements revealed that the mechanical strength of the hydrogels increased with increasing concentration of NaDC and Eu(NO3)3, while the maximum emission of the fluorescence of the gels appeared at a stoichiometry between Eu(NO3)3 and NaDC of 1:3. It is expected that the incorporation of luminescent lanthanide ions could impart versatile functionalities for practical applications to the hydrogels.Graphical abstract

Two kinds of carbon materials, i.e., graphene and graphene oxide (GO), were successfully incorporated into a lyotropic liquid crystal (LLC) matrix formed by n-dodecyl tetraethylene monoether (C12E4). The properties of graphene–C12E4 and GO–C12E4 LLC composites were characterized by UV-vis absorption, transmission electron microscopy (TEM) observations, polarized optical microscopy (POM) observations, small-angle X-ray scattering (SAXS) and rheological measurements. SAXS results indicate that both graphene and GO are well-dispersed in the C12E4 LLC matrix and some interactions occur between the C12E4 LLC matrix and graphene (or GO) sheets. Moreover, it is demonstrated that graphene interacts with the hydrophobic part of C12E4 LLC while GO mainly interacts with the hydrophilic part of C12E4 LLC because of the different properties of graphene and GO. Integration of graphene and GO into C12E4–PEG systems by a spontaneous phase separation method reveals the different interaction mechanisms of graphene and GO with C12E4 LLC. It can be concluded that the mechanical and electrical properties of the C12E4 LLC have been largely improved by the incorporation of graphene and GO, which opens the door for wide applications in nanotechnology, electrochemical and biochemical areas.

Carbon nanotubes (CNTs) were incorporated into a lyotropic liquid crystal (LLC) matrix at room temperature through spontaneous phase separation. The phase separation process occurred in n-dodecyl tetraethylene monoether (C12E4) solutions induced by the hydrophilic polymer, poly(ethylene glycol) (PEG). It was found that the molecular weight of PEG has a significant effect on the CNTs–C12E4 system, which not only influences the phase behavior of the system but also changes the properties of the CNTs–LLC composites. Polarized optical microscopy (POM) images, combined with small-angle X-ray scattering (SAXS) results, indicate that CNTs incorporate within the layers of the lamellar LLCs without destroying the structure of LLCs. Moreover, UV-vis absorption, Raman spectra and rheological measurements were performed to investigate the characteristic properties of the CNTs–LLC composites. This study not only gives a more comprehensive understanding of polymer-induced phase separation, but also expands the potential uses of CNTs–LLC composites in nanotechnology.

•We used biological surfactant sodium deoxycholate to prepare hydrogels.•NaCl and NaBr can strengthen the network structure of hydrogels.•l-Lysine and l-Argamino acids can destroy the network structure of the hydrogels.•These hydrogels have potential applications in the field of as smart materials for drug controlled release materials.Rheological properties of biological surfactant sodium deoxycholate (NaDC) in the presence of two amino acids (l-Lys and l-Arg) and two halide salts (NaCl and NaBr) have been investigated systematically at 20 °C and pH = 6.864. The gel-to-sol transition behavior induced by the addition of amino acids can be observed. It is found that the viscoelasticity of the hydrogels of 50 mmol L−1 NaDC decreased when l-Lysine (l-Lys) or l-Arginine (l-Arg) was added in the system. However, the addition of halide salts NaCl or NaBr in the above system resulted in an opposite trend. In view of these phenomena, a conclusion was given that l-Lys and l-Arg amino acids can destroy the network structure of the hydrogels while NaCl and NaBr can strengthen it. Moreover, it is found that the viscoelasticity of the l-Lys-containing hydrogel is higher than that of l-Arg-containing hydrogel at the same condition, on the other hand, the viscoelasticity of NaCl-containing hydrogel is higher than that of NaBr-containing hydrogel at the same concentration, indicating that NaCl performs better in strengthening the network structure of the hydrogels than NaBr. Furthermore, thixotropic experiments have also been done and revealed that the NaDC hydrogels prepared in this work possessed excellent thixotropic properties, which have potential applications in the field of as smart materials for drug controlled release materials.Among various applications, drug delivery is one of the significant properties of hydrogels and this interesting modification of the NaDC hydrogels may enhance its applications in biomedicine for tunable drug delivery. The drugs which are embedded into the network structure of hydrogels could be released to the nidus positions when the network structures are destroyed encountering l-Lys or l-Arg.

The effect of polymers (hydrolyzed polyacrylamide (HPAM) and hydrophobically modified polyacrylamide (HMPAM)) on the stability of oil-in-water nano-emulsions has been studied in paraffin oil/Span 20-Tween 20/water systems by method of phase inversion composition (PIC). The stabilization of nano-emulsions was investigated by visual observation and the change of water content induced by centrifugation. Droplet size distributions of nano-emulsions were obtained by a laser-scanner particle size distribution analyzer. The interfacial tension and charge of nano-emulsions were obtained by interfacial tension and zeta potential measurements. All the results indicate that the droplet size can be decreased by the addition of HMPAM, while almost no change could be observed when the HPAM was added. Meanwhile, HMPAM has a better effect on the stabilization of nano-emulsions than HPAM. It may conclude that the HMPAM molecules adsorbed at the oil/water interface of the nano-emulsion droplets. Therefore, the stability of nano-emulsion with the addition of HMPAM is based on both an associative thickening mechanism caused by the alkyl chains of HMPAM molecules and the adsorption of HMPAM at the oil/water interface, which can form a solid film to prevent the Ostwald ripening of nano-emulsion droplets.

Supramolecular hydrogels were prepared in the mixtures of biological surfactant sodium deoxycholate (NaDC) and halide salts (NaCl and NaBr) in sodium phosphate buffer. It is very interesting that with the addition of 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-ray powder diffraction, Fourier transform infrared spectra, and rheological measurements. The results demonstrate that the gels are formed by intertwined fibrils, which are induced by enormous cycles of NaDC molecules driven by comprehensive noncovalent interactions, especially the hydrogen bonds. Our conclusion is that the presence of halide salts (NaCl and NaBr) enhances the formation of the gels, while the addition of amino acids (l-lysine and l-arginine) could make the breakage of the hydrogen bonds and weaken the formation of the gels. Moreover, its fast disassembly in the presence of amino acids allows for the release of substances (i.e., the dye methylene blue) entrapped within the gel network. The tunable gel morphology, microstructure, mechanical strength, and anisotropy verify the role of halide salts and amino acids in altering the properties of the gels, which can probably be exploited for a variety of applications in future.

A water-in-oil microemulsion was prepared by using nonionic surfactant Triton X-100, 1-hexanol, cyclohexane and AgNO3 aqueous solution with a concentration of 0.2 mol L−1. Successive addition of sodium borohydride (NaBH4), ammonium hydroxide (NH3·H2O) and tetraethyl orthosilicate (TEOS) to this microemulsion leads to the formation of hierarchically-organized Ag@SiO2 hybrid nanoparticles with Ag nanocrystals randomly distributed inside amorphous SiO2, as proved by transmission electron microscopy (TEM) and high-resolution electron microscopy (HRTEM) observations. In many cases, H2 gas bubbles, which were produced during the reduction of Ag+, were found to influence the structures of Ag nanocrystals. The morphologies of the hybrid nanoparticles and the H2-induced cavities can be easily tuned by the molar ratio of AgNO3 to NaBH4 and the volume ratio of AgNO3 aqueous solution to TEOS. Embedded in amorphous SiO2, the Ag nanoparticles are highly stable, while the unprotected Ag nanocrystals underwent fast aggregation. The inner Ag nanocrystals have dominant (111) planes and are optically active, as shown by X-ray powder diffraction (XRD) and UV-vis measurement, respectively. These properties make these Ag@SiO2 hybrid nanoparticles fascinating candidates for a variety of applications in catalysis and life science.

A fluorescent supramolecular hydrogel was prepared by α-cyclodextrin (α-CD) and Tyloxapol, which can be considered as an oligomer of the nonionic surfactant polyoxyethylene tert-octylphenyl ether (Triton X-100, TX-100) with a polymerization degree below 7. For comparison, both Tyloxapol and TX-100 were selected to form hydrogels with α-CD to get more information about the interaction between different types of surfactants and cyclodextrin. These hydrogels have been thoroughly characterized using various techniques including phase behavior observation, transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), fluorescence spectra, fluorescence microscopy observations, Fourier transform infrared (FT-IR) spectroscopy, 1H NMR, 2D 1H-1H ROESY NMR, small-angle X-ray scattering (SAXS), X-ray diffraction (XRD) and rheological measurements. The hydrogels of α-CD/Tyloxapol are responsive to external stimuli including temperature, pH and guest molecules, and present gelation-induced quenching fluorescence emission properties. The reason for this phenomenon may be that Tyloxapol molecules come into the cavity of α-CD and form the inclusion complexes. Due to the high electron density of the narrow cavity of α-CD, it induces the shift of the electron on the benzene ring which can weaken the π–π interaction and lead to the fluorescence quenching. Moreover, the hydrogel formed by α-CD/Tyloxapol is highly responsive to the formaldehyde (HCHO). The addition of a small amount of HCHO can induce a gel-to-sol transition. Interestingly, once the gel transforms into solution, it becomes fluorescent. This makes the α-CD/Tyloxapol hydrogel a promising candidate for HCHO detection and removal in home furnishings to reduce indoor environmental pollutants.

Carbon nanotubes (CNTs) were incorporated into a lyotropic liquid crystal (LLC) matrix at room temperature through spontaneous phase separation. The phase separation process occurred in n-dodecyl tetraethylene monoether (C12E4) solutions induced by the hydrophilic polymer, poly(ethylene glycol) (PEG). It was found that the molecular weight of PEG has a significant effect on the CNTs–C12E4 system, which not only influences the phase behavior of the system but also changes the properties of the CNTs–LLC composites. Polarized optical microscopy (POM) images, combined with small-angle X-ray scattering (SAXS) results, indicate that CNTs incorporate within the layers of the lamellar LLCs without destroying the structure of LLCs. Moreover, UV-vis absorption, Raman spectra and rheological measurements were performed to investigate the characteristic properties of the CNTs–LLC composites. This study not only gives a more comprehensive understanding of polymer-induced phase separation, but also expands the potential uses of CNTs–LLC composites in nanotechnology.

Two kinds of carbon materials, i.e., graphene and graphene oxide (GO), were successfully incorporated into a lyotropic liquid crystal (LLC) matrix formed by n-dodecyl tetraethylene monoether (C12E4). The properties of graphene–C12E4 and GO–C12E4 LLC composites were characterized by UV-vis absorption, transmission electron microscopy (TEM) observations, polarized optical microscopy (POM) observations, small-angle X-ray scattering (SAXS) and rheological measurements. SAXS results indicate that both graphene and GO are well-dispersed in the C12E4 LLC matrix and some interactions occur between the C12E4 LLC matrix and graphene (or GO) sheets. Moreover, it is demonstrated that graphene interacts with the hydrophobic part of C12E4 LLC while GO mainly interacts with the hydrophilic part of C12E4 LLC because of the different properties of graphene and GO. Integration of graphene and GO into C12E4–PEG systems by a spontaneous phase separation method reveals the different interaction mechanisms of graphene and GO with C12E4 LLC. It can be concluded that the mechanical and electrical properties of the C12E4 LLC have been largely improved by the incorporation of graphene and GO, which opens the door for wide applications in nanotechnology, electrochemical and biochemical areas.

Polyvinyl alcohol (PVA) hydrogels have been proposed for use as promising biomaterials in biomedical and tissue engineering, and graphene oxide (GO) has been recognized as a unique two-dimensional building block for various graphene-based supramolecular architectures. In this article, we systematically studied the influence of three kinds of PVA with different molecular weights on the interaction between PVA and GO. Moreover, the effects of PVA on the gelation of GO were also investigated. The native PVA hydrogel, as well as PVA–GO hybrid hydrogels, have been thoroughly characterized by the phase behavior study and various techniques including field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA) and rheological measurements. It can be seen that with the increase of the molecular weight of PVA, the addition of GO can effectively promote the gelation of PVA which can be reflected by a decrease of the critical gel concentration (CGC) for PVA–GO hydrogels. Dye adsorption experiments indicate that the toxic dye, i.e., methylene blue (MB), was efficiently entrapped in the PVA–GO xerogels. It is also demonstrated that the gelation of PVA and GO composites can be promoted by different supramolecular interactions, including hydrogen bonding and electrostatic interaction. This work indicates that the PVA–GO composite is a good candidate for preparing “super” and “smart” hydrogels and will enable further studies on the supramolecular chemistry of PVA, graphene and its derivatives.