Huaming Li

Sensitivity and selectivity determination of bisphenol A using SWCNT–CD conjugate modified glassy carbon electrode

In this study, we demonstrated a highly sensitive electrochemical sensor for the determination of bisphenol A (BPA) in aqueous solution by using single-walled carbon nanotubes (SWCNTs)/β-cyclodextrin (β-CD) conjugate (SWCNT-CD) modified glassy carbon electrode (GCE). The cyclic voltammetry results show that the modified GCE exhibits strong catalytic activity toward the oxidation of BPA with a well-defined cyclic voltammetric peak at 0.543 V. The response current exhibits a linear range between 10.8 nM and 18.5 μM with a high sensitivity (1256 μA mM(-1)). The detection limit of BPA is 1.0 nM (S/N=3). The enhanced performance of the fabricated sensor can be attributed to the combination of the excellent electrocatalytic properties of SWCNTs and the molecular recognition ability of β-CD. The sensor was successfully applied to determine BPA leached from real plastic samples with good recovery, ranging from 95% to 103%.

Colorimetric fluorescent cyanide chemodosimeter based on triphenylimidazole derivative.

In this paper, we demonstrated a highly selective colorimetric chemodosimeter for cyanide anion detection. This chemodosimeter having a triphenylimidazole group as a fluorescent signal unit and a dicyano-vinyl group as a reaction unit was synthesized by the Knoevenagel condensation of 4-(4,5-diphenyl-1H-imidazol-2-yl)benzaldehyde with malononitrile in a reasonable yield. The probe exhibited an intramolecular charge transfer (ICT) absorption band at 420 nm and emission band at 620 nm, respectively. Upon the addition of cyanide anion, the probe displayed a blue-shifted spectrum and loss in color due to the disruption of conjugation. With the aid of the fluorescence spectrometer, the chemodosimeter exhibited a detection limit of 0.11 μM (S/N=3). Interferences from other common anions associated with cyanide anion analysis were effectively inhibited.

Synthesis, characterization, and electrochemical performances of core-shell Ni(SO4)0.3(OH)1.4/C and NiO/C nanobelts

In this study, Ni(SO4)0.3(OH)1.4 nanobelts have been synthesized via a simple template-free hydrothermal reaction in an aqueous solution containing nickel sulfate and sodium acetate. It is found that the molar ratio of nickel sulfate to sodium acetate plays a very important role in determining the morphology of the final product. Subsequently, core-shell Ni(SO4)0.3(OH)1.4/C composite nanobelts have been synthesized from the carbonization and polymerization of glucose under mild hydrothermal conditions in the presence of newly produced Ni(SO4)0.3(OH)1.4 nanobelts. The shell thickness of the core-shell nanobelts can be varied from 2 to 18 nm by adjusting the concentration of glucose. Additionally, the structural evolution from core-shell Ni(SO4)0.3(OH)1.4/C to NiO/C has been successfully performed through ex situ heat treatment. The belt-like morphology has still been maintained after heat treatment at 600 °C for 2 h. The as-prepared NiO/C composites were directly immobilized onto the surface of glassy carbon electrode (GCE) for nonenzymatic glucose determination. The fabricated glucose sensor has an ultrasensitive response (149.11 μA mM−1) and a low detection limit of 9.12 nM (signal/noise ratio (S/N) = 3), which are among the best values reported in the literature.

Redox- and pH-responsive polymer gels with reversible sol–gel transitions and self-healing properties

Covalent dynamic gels based on reversible acylhydrazone and disulfide bonds were prepared by crosslinking of benzhydrazide-containing poly(triazole) (PTB) with a novel disulfide-containing dialdehyde (C2) in DMF at ambient temperature. The PTB was synthesized by the metal- and solvent-free click polymerization of diazide and dialkyne monomers followed by treatment with hydrazine hydrate. The as-fabricated polymer gels exhibited both redox and pH stimuli-responsive behaviours. Analysis of the composition-property relationships of these polymer gels, specifically considering the effects of catalysts, molar ratio of benzhydrazide to aldehyde groups (–NH2/–CHO), and gelator concentrations on rheological properties, were performed. Additionally, the gel revealed interesting self-healing properties through acylhydrazone exchange and/or disulfide exchange reactions. Employing this dynamic character, it is possible to regenerate the used gel, and thus it has the potential to perform in a range of dynamic or bioresponsive applications.

A Facile and Low-Cost Route to Heteroatom Doped Porous Carbon Derived from Broussonetia Papyrifera Bark with Excellent Supercapacitance and CO2 Capture Performance

In this work, we present a facile and low-cost approach to synthesize heteroatom doped porous carbon via hydrothermal treatment of stem bark of broussonetia papyrifera (BP) as the biomass precursor in diluted sulfuric acid, and following thermal activation by KOH at 800 °C. The morphology, structure and textural property of the prepared porous carbon (PC) are investigated by scanning electron microscopy, transmission electron microscopy, N2 sorption isotherms, and X-ray photoelectron spectroscopy. The porous carbon possesses a high BET surface area of 1759 m2 g−1 and an average pore size of 3.11 nm as well as hetero-oxygen (9.09%) and nitrogen (1.7%) doping. Such porous carbon shows outstanding capacitive performances of 416 F g−1 and 300 F g−1 in three and two-electrode systems, respectively. As a solid-state adsorbent, the obtained porous carbon has an excellent CO2 adsorption capacity at ambient pressures of up to 6.71 and 4.45 mmol g−1 at 0 and 25 °C, respectively. The results present one novel precursor-synthesis route for facile large-scale production of high performance porous carbon for a variety of great applications including energy storage and CO2 capture.

Dual responsive macroemulsion stabilized by Y-shaped amphiphilic AB2 miktoarm star copolymers

Dual responsive macroemulsions stabilized by Y-shaped amphiphilic AB2 miktoarm star polymeric emulsifiers were presented in this study. First, a amphiphilic Y-shaped AB2 miktoarm star polymer composed of poly(N,N-dimethylaminoethylmethacrylate) (PDMAEMA) and polystyrene (PS) arms was synthesized by sequential reversible addition–fragmentation chain transfer (RAFT) polymerization of styrene monomer and atom transfer radical polymerization (ATRP) of N,N-dimethylaminoethyl methacrylate (DMAEMA) monomer. The structure and the molecular weight as well as the molecular weight distribution were carefully characterized by 1H NMR and GPC, respectively. The obtained PS–(PDMAEMA)2 miktoarm star polymers were then applied as polymer emulsifiers for both o/w and w/o macroemulsions formation, and stabilized macroemulsions could be produced at a lower emulsifier content. Meanwhile, the emulsifying performance of PS–(PDMAEMA)2 miktoarm star polymer and stimulus-response of the macroemulsion were also investigated. The PS–(PDMAEMA)2 stabilized o/w macroemulsion showed pH-induced demulsification and temperature-induced phase inversion. However, the inversion of the PS–(PDMAEMA)2 emulsifier at the oil–water interface could not be spontaneously accomplished. Furthermore, successful phase inversion was only smoothly realized for those emulsions with pH 7 water in the presence of a modulate stirring.

Massage ball-like, hollow porous Au/SiO2 microspheres templated by a Pickering emulsion derived from polymer–metal hybrid emulsifier micelles

In this study, we reported a novel, facile, Pickering emulsion-templating method to prepare massage ball-like, hollow-structured Au/SiO2 microspheres. Firstly, oil-in-water Pickering emulsions stabilized by Au@poly(ethylene oxide)-b-poly(4-vinylpyridine) (Au@PEO-b-P4VP) hybrid emulsifier micelles, which were formed by a P4VP/Au complex induced self-assembly process, were generated. Then hollow Au/SiO2 hybrid microspheres with nano-/submicro-sized protrusions on their shells, termed as massage ball-like microspheres, were successfully synthesized using the generated Pickering emulsion as template, in which the P4VP catalyzed hydrolysis and condensation of tetraethoxysilane (TEOS) in the TEOS/n-decanol mixed oil phase occurred at the oil/water interface. As a result, a continuous SiO2 shell was formed. The uneven adsorption of polydisperse hybrid micelles at the oil/water interface as well as the volume shrinkage of the oil phase during the early hydrolysis and condensation of TEOS facilitated the formation of protrusions on the shell surface. After further removal of the polymer components embedded in the shell by calcination, hollow Au/SiO2 hybrid microspheres with micropore/mesopore bimodal porous shells were produced. The as-prepared Au/SiO2 hybrid microspheres were applied as catalysts for the reduction of p-nitrophenol with NaBH4, showing a high catalytic activity with a good recyclability owing to the large specific areas, the easily accessible Au active centres, and the enhanced mass transportation.

Well-defined poly(N-isopropylacrylamide) with a bifunctional end-group: synthesis, characterization, and thermoresponsive properties

In this study, well-defined poly(N-isopropylacrylamide) (PNIPAM) with a bisalkyne end-group was synthesized by reversible addition-fragmentation chain transfer polymerization using 2-(2-(ethylthiocarbonothioylthio)-2-methylpropanoyl-oxy)ethyl 3,5-bis(prop-2-ynyloxy) benzoate (EMEB) as the chain transfer agent. The molecular weight and polydispersity index of polymer was determined by gel permeation chromatography (GPC). The linear increase in molecular weight with conversion, unimodal, and almost symmetrical peak in GPC trace together with low polydispersity indicated the controlled polymerization process of NIPAM mediated by EMEB. Subsequently, the Cu(I)-catalyzed [3 + 2] Huisgen cycloaddition between the end-group of polymer and azide derivatives was carried out to produce PNIPAM, in which the bisfunctional end-group was modified with phenyl, octyl, amido, and hydroxyl groups. After completing the click reaction, the structure of the polymer was characterized carefully by Fourier transform infrared spectroscopy (FTIR), 1H NMR, and Matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS), indicating the complete consumption of alkyne end-groups. In addition, almost no change in molecular weight as well as the polydispersity was observed by comparison with the GPC traces of polymers before and after click reaction. The cloud point temperatures (T cps) of the resulting PNIPAM derivatives in aqueous solution were investigated in detail by dynamic light scattering. The results showed that the values of T cp were ranged from 22 to 38 °C, which depended largely on end-groups as well as the polymer molecular weights.

A highly sensitive and reversible chemosensor for Hg2+ detection based on porphyrin‐thymine conjugates

In this study, we demonstrated a highly sensitive, selective, and reversible chemosensor for Hg2+ determination. This chemosensor was synthesized by direct condensation of thymin‐1‐ylacetic acid with zinc tetraaminoporphyrin, which has a porphyrin core as the fluorophore and four thymine (T) moieties as the specific interaction sites for Hg2+. The probe (4T‐ZnP) exhibited split Soret bands with a small peak at 408 nm and a strong band at 429 nm in a dimethylformamide/H2O (7/3, v/v) mixed solvent as well as a strong emission band at 614 nm. Upon the addition of Hg2+, the probe displayed strong fluorescence quenching due to the formation of T‐Hg2+‐T complexes. With the aid of the fluorescence spectrometer, the chemosensor in the dimethylformamide/H2O (7/3, v/v) mixed solvent (0.3 μM) exhibited a detection limit of 6.7 nM. Interferences from other common cations, such as Co2+, K+, Sn2+, Zn2+, Cu2+, Ni2+, Mn2+, Na+, Ca2+, Mg2+, Pb2+, and Cd2+, associated with Hg2+ analysis were effectively inhibited. Copyright

Synthesis and Self-Assembly of β-Cyclodextrin Terminated DMA/NIPAM Diblock Copolymers

A series of β-cyclodextrin (β-CD) terminated diblock copolymers has been prepared via click reaction. The Huisgen cycloaddition between alkyne decorated copolymer and azide functionalized β-CD was performed in organic solvent in the presence of a Cu(I) catalyst, resulting in the formation of β-CD terminated diblock copolymers, which contain thermally responsive poly(N-isopropylacrylamide) (PNIPAM) block and hydrophilic poly(N,N-dimethylacrylamide) (PDMA) block. Using dynamic light scattering and fluorescence spectroscopy measurements, it is demonstrated that these β-CD functionalized block copolymers are capable of reversibly forming micelles in response to changes in solution temperature and that the critical micelle concentration, micellar size, and transition temperature are dependent on both the NIPAM block length and the polymer functionalization.