Zhaohua Song

Supramolecular Hydrogels of α-cyclodextrin/Reverse Poloxamines/Carbon-based Nanomaterials and Its Multi-functional Application

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.

3D welan gum–graphene oxide composite hydrogels with efficient dye adsorption capacity

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.

Modulating self-assembly behavior of a salt-free peptide amphiphile (PA) and zwitterionic surfactant mixed system

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.

Stable monodisperse colloidal spherical gold nanoparticles formed by an imidazolium gemini surfactant-based water-in-oil microemulsion with excellent catalytic performance

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.

Reversible controlled morphologies switching between porous microspheres and urchin-like microcrystals for NaDC/RhB self-assembly and their multifunctional applications

The hierarchical self-assembly of a biological surfactant, sodium deoxycholate (NaDC), and a cationic dye (RhB) through ionic self-assembly (ISA) opens up potentially useful routes to construct soft materials. Our results have shown that different morphologies with high hierarchies can be reversibly controlled by varying the ratio of the two components (NaDC and RhB) and that the morphologies can switch between porous microspheres and urchin-like structures. It can be concluded that the interaction between NaDC and RhB was strongly influenced by direct electrostatic forces between the –COO− groups in NaDC and –N+ in RhB, respectively. Moreover, because of the novel nanostructures, they have functional applications for photoluminescence enhancement and hydrophobicity. Thus, it can be expected that this ISA strategy can be used towards the development of new protocols for the fabrication of novel materials, which are potentially biocompatible and biodegradable and gives new insight into the main (soft-interactions) self-assembly processes.

Self-assembled chiral helical nanofibers by amphiphilic dipeptide derived from d- or l-threonine and application as a template for the synthesis of Au and Ag nanoparticles.

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 effect of pH on the properties of 3D welan gum–graphene oxide composite hydrogels and their excellent adsorption capacity

In this article, welan gum–graphene oxide (GO) composite hydrogels were prepared by simple self-assembly of these two components in aqueous media and the effects of pH on their properties were systematically studied. The welan gum–GO hybrid hydrogels with different pH have been thoroughly characterized using TEM, FE-SEM, FT-IR spectroscopy, XRD and rheological measurements. It can be observed that the microstructures of welan–gum hydrogels can be tailored by varying the pH value and swelling properties analysis shows that the swelling ratio increases with pH. Moreover, the welan gum–GO hybrid hydrogels exhibited improved adsorption properties for water-soluble dyes under acidic conditions than under basic conditions. At the same time, adsorption isotherms and kinetics were also studied. Thus, it is expected that the GO-based composite hydrogels can act as potential adsorbents and have promising applications in the field of waste water treatment by adjusting pH.

Tailoring self-assembly behavior of a biological surfactant by imidazolium-based surfactants with different lengths of hydrophobic alkyl tails

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.