Faqiong Zhao

Electrochemical sensor for chloramphenicol based on novel multiwalled carbon nanotubes@molecularly imprinted polymer.

Herein, we present a novel electrochemical sensor for the determination of chloramphenicol (CAP), which is based on multiwalled carbon nanotubes@molecularly imprinted polymer (MWCNTs@MIP), mesoporous carbon (CKM-3) and three-dimensional porous graphene (P-r-GO). Firstly, 3-hexadecyl-1-vinylimidazolium chloride (C16VimCl) was synthetized by using 1-vinylimidazole and 1-chlorohexadecane as precursors. Then, C16VImCl was used to improve the dispersion of MWCNT and as monomer to prepare MIP on MWCNT surface to obtain MWCNTs@MIP. After that, the obtained MWCNTs@MIP was coated on the CKM-3 and P-r-GO modified glassy carbon electrode to construct an electrochemical sensor for the determination of CAP. The parameters concerning this assay strategy were carefully considered. Under the optimal conditions, the electrochemical sensor offered an excellent response for CAP. The linear response ranges were 5.0 × 10(-9)-5 × 10(-7)mol L(-1) and 5.0 × 10(-7)-4.0 × 10(-6), respectively, and the detection limit was 1.0 × 10(-10)mol L(-1). The electrochemical sensor was applied to determine CAP in real samples with satisfactory results.

Electrochemical preparation of polyaniline-ionic liquid based solid phase microextraction fiber and its application in the determination of benzene derivatives.

A polyaniline-ionic liquid (i.e. 1-butyl-3-methylimidazolium tetrafluoroborate, [C(4)mim][BF(4)]) composite film coated platinum wire (PANI-IL/Pt) was prepared by electrochemical method for the first time. Scanning electron microscopy image showed that the PANI-IL composite film was even and porous. When the PANI-IL/Pt was used as a fiber for the headspace solid-phase microextraction (HS-SPME) of some benzene derivatives (i.e. 1,3-dimethylbenzene, 1,2-dimethylbenzene, 1,4-dichlorobenzene, 1,2-dichlorobenzene, 1,3,5-trimethylbenzene and 1,2,4-trimethylbenzene), followed by gas chromatographic analysis, it presented excellent performance, which was much better than that of PANI/Pt and commercial polydimethylsiloxane fiber. Hence the fiber was coupled with gas chromatography for the determination of these benzene derivatives. It was found that under the optimized conditions the linear ranges were 0.04-400 μg L(-1) with correlation coefficients above 0.99, the detection limits were 9.3-48.1 ng L(-1) (S/N=3), the relative standard deviations (RSDs) were smaller than 5.1% for five successive measurements with single fiber, and the RSDs for fiber-to-fiber were 5.0-11.1% (n=3) for different benzene derivatives. The proposed method was successfully applied to the extraction and determination of benzene derivatives in waste water and tap water, and the recoveries were 87.1-108.1% for different analytes. Therefore, the PANI-IL/Pt is a promising SPME fiber.

Electrochemical determination of cefotaxime based on a three-dimensional molecularly imprinted film sensor

A novel electrochemical sensor is presented for the determination of cefotaxime (CEF), which is constructed by molecularly imprinted polymer (MIP), gold networks@IL (IL, 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF4]) (GNWs@IL), porous platinum nanoparticles (PPNPs) and carboxyl graphene (COOH-r-GO). The GNWs@IL is prepared by directly reducing HAuCl4 with sodium citrate in [BMIM][BF4] aqueous solution. The PPNPs are well embedded in GNWs@IL due to the adhesion of IL to form GNWs@IL-PPNPs suspension, which is coated on a COOH-r-GO modified glassy carbon electrode to construct a porous three-dimensional networks modified electrode. Then, MIP is prepared by cyclic voltammetry at the modified electrode, using CEF as template and o-phenylenediamine as monomer. The factors concerning this assay strategy are carefully investigated. Under the optimal conditions, the electrochemical sensor offers an excellent response for CEF, the linear response range is 3.9 × 10(-9) ~ 8.9 × 10(-6) mol L(-1) and the detection limit is 1.0 × 10(-10) mol L(-1). The electrochemical sensor has been applied to the determination of CEF in real samples with satisfactory results.

One-step synthesis of a copper-based metal–organic framework–graphene nanocomposite with enhanced electrocatalytic activity

A copper-based metal–organic framework–graphene nanocomposite (Cu-MOF–GN) (i.e. Cu3(BTC)2, BTC = 1,3,5-benzene-tricarboxylate) was prepared by a facile one-step method for the first time. Unlike the conventional strategies, in this procedure graphene oxide was reduced to GN by an endogenous reducing agent produced by dimethylformamide, which was used as solvent in the synthesis of Cu-MOF. The nanocomposite exhibited high stability due to the hydrogen bonding, π–π stacking and Cu–O coordination between Cu-MOF and GN. Owing to the synergetic effect of Cu-MOF and GN, the Cu-MOF–GN nanocomposite showed high electrocatalytic activity. When it was used for constructing H2O2 and ascorbic acid sensors, it presented good performance. Thus, the Cu-MOF–GN nanocomposite has potential applications in the electrochemical field.

Electrodeposition of poly(3,4-ethylenedioxythiophene) on a stainless steel wire for solid phase microextraction and GC determination of some esters with high boiling points.

In this work, 3,4-ethylenedioxythiophene (EDOT) emulsion is prepared by ultrasonication agitation and poly(3,4-ethylenedioxythiophene) (PEDOT) coating is fabricated on a stainless steel wire by electrochemical method from a 0.10M sodium dodecylbenzenesulfonate aqueous solution containing EDOT. The coating is characterized by scanning electron microscopy and Fourier transform infrared spectrophotometry, and it presents cauliflower-like structure. When the resulted PEDOT/steel fiber is used for the headspace solid phase-microextraction of some esters (i.e. methyl anthranilate, dimethyl phthalate, ethyl-o-aminobenzoate, methyl laurate and diethyl phthalate) and their GC detection, the limits of detection (LOD) are ca. 7.8-31 ng L(-1) (S/N=3) and the linear ranges are 0.25-800 μg L(-1). The fiber shows high thermal stability (up to 320 °C), good reproducibility and long lifetime (more than 183 times). It also has good chemical stability. After it is immersed in acid, alkali and dichloromethane for 4h its extraction efficiency remains almost unchanged. Besides esters the fiber also exhibits high extraction efficiency for alcohols and aromatic compounds.

Fabrication of poly(3,4-ethylenedioxythiophene)-ionic liquid functionalized graphene nanosheets composite coating for headspace solid-phase microextraction of benzene derivatives

A new poly(3,4-ethylenedioxythiophene)-ionic liquid (i.e. 1-hydroxyethyl-3-methyl imidazolium-bis[(trifluoromethyl)sulfonyl]imide) functionalized graphene nanosheets (PEDOT-IL/GNs) composite coating was electrodeposited on a stainless steel wire for headspace solid-phase microextraction. The coating showed porous folded and wrinkled structure and had large surface area due to the combined effect of PEDOT and IL/GNs. In addition, it displayed high thermal stability (up to 340 °C) and durable property (could be used for more than 200 times). The PEDOT-IL/GNs coating exhibited high affinity to benzene derivatives studied (i.e. toluene, 1,4-dimethylbenzene, 1,2-dimethylbenzene, 2-chlorotoluene, 1,3,5-trimethylbenzene and 1,4-dichlorobenzene) as they can interact through π-π and hydrophobic interactions. When they were extracted the enrichment factors ranged from 1901 (for 1,4-dichlorobenzene) to 3041 (for 1,4-dimethylbenzene). Coupled with gas chromatography-flame ionization detection, the benzene derivatives were extracted and determined. Wide linear ranges with 4 orders of magnitude (0.06-500 μg L(-1)) and low limits of detection (10.7-19.8 ng L(-1)) were achieved. The RSDs of chromatographic peak areas were <5.9% (n=5) and <7.5% (n=5) for single fiber and fiber-to-fiber, respectively. The method was applied to the determination of the benzene derivatives in real samples with acceptable recoveries from 82.3% to 108.3%.