Jianjia Liu

Bridged-cyclodextrin supramolecular hydrogels: host–guest interaction between a cyclodextrin dimer and adamantyl substituted poly(acrylate)s

The formation of a hydrogel constructed from a cyclodextrin dimer (βCD2ur) and adamantyl substituted poly(acrylate) was investigated by 2D NOESY 1H NMR and isothermal titration calorimetry (ITC). The two methods generally demonstrate enhancement of complexation as the length of the hydrophobic tether increases, which is likely to be due to the cooperative effect. An optimal tether length of 6 was found to maximize the complexation between βCD2ur and the polymer. Increasing the tether length to twelve carbons slightly reduces the complexation affinity revealed by ITC experiments. Meanwhile, rheological analysis indicates the maximum degree of crosslinking was achieved by PAAADhn/βCD2ur complexation since the rigid structure of PAAAD restricts the crosslinking based on the host–guest complexation between the cyclodextrin dimer and adamantyl substituent and the competitive binding from the long alkyl tether in PAAADddn reduces the degree of crosslinking.

Preparation of Au/Ag multilayers via layer-by-layer self-assembly in spherical polyelectrolyte brushes and their catalytic activity

Spherical polyelectrolyte brushes (SPBs) consisting of polystyrene (PS) core and poly(2-aminoethyl methacrylate hydrochloride) (PAEMH) shell were prepared by photo-emulsion polymerization. Au nanoparticles (Au-NPs) with controlled size and size distribution were synthesized in situ using SPBs as nanoreactors. Via layer-by-layer deposition technique on the surface of SPBs, nano-composite particles with Au/Ag-NPs bilayer and Au/Ag/Au-NPs trilayer were prepared. The structures of the as-prepared Au/Ag multilayer SPBs were characterized by UV-Vis spectroscopy, TEM, ICP-AES and DLS. The charge reversal of the nano-composite particles observed by zeta potential confirmed the success of layer-by-layer assembly. The Au/Ag-NPs bilayer nano-composite particles showed high catalytic efficiency with an apparent activation energy of about 41.2 kJ/mol in the reduction reaction of 4-nitrophenol to 4-aminophenol in the existence of sodium borohydride monitored. The catalytic activity of Au/Ag-NPs multilayer SPBs close to Au-NPs SPBs and much higher than Ag-NPs SPBs reveals its potential applications in cost-effective catalysts with high-performance.

Synergetic catalytic effect of α-cyclodextrin on silver nanoparticles loaded in thermosensitive hydrogel

AbstractThermosensitive poly(NIPAAm-co-AMPS) hydrogels were prepared by copolymerization of N-isopropyl acrylamide (NIPAAm) and 2-acrylamido-2-methyl 1-propansulfonic acid (AMPS) by employing N,N′-methylenebis(acrylamide) (BIS) as cross-linker. Uniformly distributed silver nanoparticles (Ag-NP) were obtained within hydrogel networks as nanoreactors via in situ reduction of silver nitrate (AgNO3) using sodium borohydride (NaBH4) as reducing agent. The catalytic properties of Ag-NP-poly(NIPAAm-co-AMPS) hydrogels presented obvious temperature dependence upon the reduction of 4-nitrophenol (4-NP) in aqueous solution. Interestingly, the addition of α-cyclodextrin (α-CD) could further enhance the reduction rate and change the associated activation parameters. This advanced catalytic system with temperature dependence and α-CD synergetic effect presented promising applications in catalytic chemistry. Graphical abstractᅟ

Synthesis of Ag2O nano-catalyst in the spherical polyelectrolyte brushes and its application in visible photo driven degradation of dye

Abstract Ag2O nanoparticles (NPs) were synthesized using colloidal solution of spherical polyelectrolyte brushes (SPB) as nano-reactors. In this work, the average diameter of Ag2O NPs was around 10 nm as determined by transmission electron microscopy (TEM). The composite NPs of Ag2O immobilized in SPB (Ag2O-SPB) showed significant absorption in the visible light region as confirmed by UV-Vis diffuse reflectance spectra (DRS), and their photoluminescence (PL) exhibited emission peak in the visible range. Ag2O-SPB has shown outstanding photocatalytic activity during degradation of methyl blue (MB) in the visible light. This work will open up a new way to prepare ideal Ag2O nano-catalyst for the remediation of wastewater using visible light.

Reversible photo-responsive vesicle based on the complexation between an azobenzene containing molecule and α-cyclodextrin

An amphiphilic molecule (Azo-Cl) was successfully synthesized and found to be able to construct reversible spherical vesicles in water. The assembled vesicles disappeared on the addition of equimolar α-cyclodextrin (α-CD) and reformed with UV irradiation due to the exclusion of the cis-azobenzene (Azo) group from α-CD’s hydrophobic cavity. With Vis irradiation, the vesicles were demolished again as α-CD combined with the Azo group again. These reversible photo-responsive vesicles based on the complexation between Azo-Cl and α-CD should be ideal switchable biomimetic membranes or carriers for photo-controllable release of functional matters like drugs.

The formation and catalytic activity of silver nanoparticles in aqueous polyacrylate solutions

Silver nanoparticles (AgNPs) have been synthesized in the presence of polyacrylate through the reduction of silver nitrate by sodium borohydride in aqueous solution. The AgNO3 and polyacrylate carboxylate group concentrations were kept constant at 2.0 × 10–4 and 1.0 × 10–2 mol·L–1, respectively, while the ratio of [NaBH4]/[AgNO3] was varied from 1 to 100. The ultraviolet-visible plasmon resonance spectra of these solutions were found to vary with time prior to stabilizing after 27 d, consistent with changes of AgNP size and distribution within the polyacrylate ensemble occurring. These observations, together with transmission electron microscopic results, show this rearrangement to be greatest among the samples at the lower ratios of [NaBH4]/[AgNO3] used in the preparation, whereas those at the higher ratios showed a more even distribution of smaller AgNP. All ten of the AgNP samples, upon a one thousand-fold dilution, catalyze the reduction of 4-nitrophenol to 4-aminophenol in the temperature range 283.2–303.2 K with a substantial induction time being observed at the lower temperatures.