Hui Mao

Poly(ionic liquids) functionalized polypyrrole/graphene oxide nanosheets for electrochemical sensor to detect dopamine in the presence of ascorbic acid.

Novel poly(ionic liquids) functionalized polypyrrole/graphene oxide nanosheets (PILs/PPy/GO) were prepared by the polymerization of 1-vinyl-3-ethylimidazole bromide (VEIB) on the surface of N-vinyl imidazolium modified PPy/GO nanosheets. Due to the synergistic effects of GO with well-defined lamellar structures, conductive PPy and biocompatible PILs, PILs/PPy/GO modified glassy carbon electrode (GCE) presented the excellent electrochemical catalytic activity towards dopamine (DA) with good stability, high sensitivity and wide linear range in the present of ascorbic acid (AA) with high concentration. PILs played an essential role for the simultaneous determination of DA and AA in a mixture, whose existence effectively improved the transmission mode of electrons and resulted in the different electrocatalytic performance towards the oxidation of DA and AA. It is indicated that PILs/PPy/GO nanosheets can act as a good steady and sensitive electrode material for the development of improved DA sensors.

Mesoporous TiO2-Based Photoanode Sensitized by BiOI and Investigation of Its Photovoltaic Behavior

We reported a novel BiOI/mesoporous TiO2 photoanode for solar cells, which was fabricated with BiOI attached onto a three-dimensional mesoporous TiO2 film by a chemical bath deposition (CBD) method. BiOI was revealed as an efficient and environmental friendly semiconductor sensitizer to make TiO2 respond to visible light. Based on this photoanode, mesoporous TiO2-based solar cell sensitized by BiOI exhibited promising photovoltaic performance. Meanwhile, the optimization of photovoltaic performance was also achieved by varying cycles of deposition immersions. The highest open circuit voltage and short circuit current of the solar cell can reach 0.5 V and 1.5 mA/cm(2), respectively.

Preparation of poly(ionic liquids)-functionalized polypyrrole nanotubes and their electrocatalytic application to simultaneously determine dopamine and ascorbic acid

Novel poly(ionic liquids) functionalized polypyrrole nanotubes (PILs/PPyNTs) were successfully synthesized. 1-Vinyl-3-ethylimidazole bromide (VEIB) was polymerized on the surface of novel polymerizable vinyl imidazolium-type IL modified PPyNTs prepared by a covalent method. Due to the modification of PILs, the dispersibility of PILs/PPyNTs in aqueous solution was significantly improved and their surface charge properties were obviously changed to electropositivity. Because of the synergetic effects of conductive PPyNTs and biocompatible PILs, excellent electrochemical catalytic activities towards dopamine (DA) and ascorbic acid (AA) were achieved using a PILs/PPyNTs modified glassy carbon electrode (GCE), which gave a large potential difference enough to well distinguish DA from AA, with excellent sensitivity and good stability, for the simultaneous detection of DA and AA. The existence of PILs effectively improved the transmission mode of electrons of DA and AA oxidation on the electrode and resulted in their different electrocatalytic performance.

Poly(zwitterionic liquids) functionalized polypyrrole/graphene oxide nanosheets for electrochemically detecting dopamine at low concentration.

Poly(3-(1-vinylimidazolium-3-yl)propane-1-sulfonate) (PVIPS), a novel kind of poly(zwitterionic liquids) (PZILs) containing both imidazolium cation and sulfonate anion, was successfully modified on the surface of polypyrrole/graphene oxide nanosheets (PPy/GO) by covalent bonding. The obtained novel PZILs functionalized PPy/GO nanosheets (PVIPS/PPy/GO) modified glassy carbon electrode (GCE) presented the excellent electrochemical catalytic activity towards dopamine (DA) with high stability, sensitivity, selectivity and wide linear range (40-1220nM), especially having a lower detection limit (17.3nM). The excellent analytical performance is attributed to the strongly negative charges on the surface of modified GCE in aqueous solution, which is different from conventional poly(ionic liquids) modified GCE. DA cations could be quickly enriched on the electrode surface by electrostatic interaction in solution due to the existence of SO3(-) groups with negative charge at the end of pendant groups in zwitterionic PVIPS, resulting in a change of the electrons transmission mode in the oxidation of DA, that is, from a typical diffusion-controlled process at conventional poly(1-vinyl-3-ethylimidazole bromide) (PVEIB)/PPy/GO modified GCE to a typical surface-controlled process.

Direct electrochemistry of cholesterol oxidase and biosensing of cholesterol based on PSS/polymeric ionic liquid–graphene nanocomposite

A novel graphene nanocomposite, functionalized by polymeric ionic liquids (PILs) and poly(sodium-p-styrenesulfonate) (PSS), was successfully prepared and exhibited excellent conductivity, favourable biocompatibility and good film-forming properties as an electrode material. TEM showed that the nanocomposite possessed an individual nanosheet-like structure. Owing to the surface modification of graphene, PSS/PILs–GP can not only be well dispersed in aqueous solution, but also possesses a strong negative charge. Due to electrostatic interactions, positively charged cholesterol oxidase (ChOx) can be immobilized onto the surface of PSS/PILs–GP to form the ChOx/PSS/PILs–GP/GC electrode material. UV-vis and FT-IR spectroscopy were used to monitor the assembly process of the nanocomposite. Due to the conductivity and biocompatibility of PSS/PILs–GP, the immobilized ChOx exhibited enhanced direct electron transfer (DET) at a glassy carbon (GC) electrode. Furthermore, the ChOx/PSS/PILs–GP/GC electrode displayed excellent catalytic performance with a wide linear range of 10.5 × 10−6 to 10.4 × 10−3 mol L−1, and a low detection limit of 3.5 μmol L−1 for the detection of cholesterol.

Poly(ionic liquid) functionalized polypyrrole nanotubes supported gold nanoparticles: An efficient electrochemical sensor to detect epinephrine

Poly(ionic liquids) (PILs) have been applied as the linkers between Au nanoparticles (NPs) and polypyrrole nanotubes (PPyNTs) for the synthesis of Au/PILs/PPyNTs hybrids. Due to the presence of PILs, high-density and well-dispersed Au NPs have been deposited on the surface of PILs/PPyNTs by anion-exchange with Au precursor and the in-situ reduction of metal ions. The obtained Au/PILs/PPyNTs hybrids can be used as a good steady electrode material for sensitively and selectively detecting epinephrine (EP). The catalytic oxidation peak currents obtained from differential pulse voltammetry (DPV) increased linearly with increasing EP concentrations in the range of 35-960μM with a detection limit of 298.9nM according to the criterion of a signal-to-noise ratio=3 (S/N=3), respectively, which showed the excellent electrocatalytic activity towards this significant hormone in human life.

Hydrophilic polymer/polypyrrole/graphene oxide nanosheets with different performances in electrocatalytic applications to simultaneously determine dopamine and ascorbic acid

Hydrophilic polymers (HP) functionalized polypyrrole/graphene oxide nanosheets (HP/PPy/GO) were successfully prepared by covalently modifying polyacrylamide (PAM), polyacrylic acid (PAA) and polyvinylpyrrolidone (PVP) on the surface of PPy/GO nanosheets containing vinyl groups. Besides significantly improving the dispersivity of PPy/GO in water, the different chemical properties among the three HP with different hydrophilic groups further resulted in the different performances of the obtained electrochemical biosensors (PAM/PPy/GO, PAA/PPy/GO and PVP/PPy/GO modified glassy carbon electrodes (GCEs)) in electrocatalytic applications to simultaneously determine dopamine (DA) and ascorbic acid (AA). PAM/PPy/GO and PAA/PPy/GO modified GCEs exhibited good electrochemical responses to distinguish DA from AA in their mixture at certain concentrations, which cannot be achieved by the PVP/PPy/GO modified GCE, due to their different chemical properties among the three HP with different hydrophilic groups. Particularly, compared to PAA/PPy/GO, PAM/PPy/GO can act as a good steady electrode material with good selectivity and sensitivity that can simultaneously determine the two substrates in their mixture at lower concentrations, which may be due to the different chemical properties between the electron-donating amide groups and electron-withdrawing carboxyl groups. The different electronic effects of the amide group and carboxyl group resulted in the difference in the transmission capability of electrons released from the oxidation reaction of DA and AA. Therefore, PAM/PPy/GO modified GCE can act as a good electrochemical sensor with high sensitivity and selectivity for DA and AA.

One-step preparation of flower-like poly(styrene-co-zwitterionic ionic liquid) microspheres with hierarchical structures for supported acidic heterogeneous catalysts

By using a one-step copolymerization of styrene (St) and 3-(1-vinyllimidazolium-3-yl)propane-1-sulfonate (VIPS), a kind of poly(St-co-VIPS) microsphere, with a hierarchical structure composed of nanospheres or nanoparticles with diameters in the range of 70–90 nm arranged on its surface and that look like a flower, has been simply prepared in the presence of polyvinyl pyrrolidone (PVP) in an aqueous alcohol system. A formation mechanism of the flower-like poly(St-co-VIPS) microspheres is proposed by investigating the influence of reaction conditions on its morphologies and observing its growth process with time. Because of the existence of zwitterionic liquid functional groups, flower-like poly(St-co-VIPS)-acid microspheres, a novel kind of heterogeneous catalyst, were successfully prepared by immobilizing heteropoly acids and H2SO4 on the flower-like poly(St-co-VIPS) microspheres, and the heterogeneous catalysts showed better catalytic activities for esterifications, acetalizations and transesterifications than with H2SO4 as the catalyst. Especially, the heterogeneous catalysts presented excellent catalytic efficiency for the acetalization of benzaldehyde and 1,2-propanediol, which could successfully reach 96.2%. Furthermore, the crosslinked flower-like poly(DVB-co-VIPS)–H2SO4 microspheres prepared under the same conditions where only St was replaced by divinyl benzene (DVB) have better reusability than that of the flower-like poly(St-co-VIPS)–H2SO4 with poor solvent resistance, and could be reused four times without significant loss of the catalytic activity, indicating that they could act as excellent recyclable heterogeneous catalysts for the synthesis of acetals and have potential application in industry.