Electrochemical Sensoing For POPs Based On β-cyclodextrin And Carbon Materials

Persistent organic pollutants （POPs） are chemical substances that persist in theenvironment, bioaccumulate through the food web, and pose a risk of causingadverse effects to human health and the environment. Compared to generalpollutants, POPs are more harmfull. It’s very difficult to decompound POPsexisted in biology and the POPs can accumulate in human body through the foodchain. These will not only affect the human body itself, resulting in endocrinedisorder, weakened immune system, metabolic disruption, necrosis of internalorgans, causing cancer, etc., but also affect the normal development and growth oftheir offspring, who may be deformity or slow mental development. Therefor, it’sof great significance to achieve the qualitative and quantitative determinations ofPOPs.β-cyclodextrins （β-CD） is oligosaccharides composed of seven glucose units,which is toroidal in shape with a hydrophobic inner cavity and a hydrophilicexterior. It is well known that β-CD has high molecular selectivity andenantioselectivity, various organic, inorganic, and biological guest molecules canbe bound selectively in the inner cavity of β-CD to form stable host-guestinclusion complexes. On the other hand, carbon materials, sucs as carbon nanotube,graphene and hollow carbon microspheres, have high specific surface area, goodchemical stability and electrochemical properties. Herein, based on the synergeticeffects from carbon materials and β-CD, we developed a series of nanohybrids andmethods to detect POPs ultrasensitively by electrochemical technology:（1） Gold nanoparticles （Au NPs）/hollow nitrogen-doped carbon microspheres（HNCMS） hybrids （Au NPs/HNCMS） were prepared and functionalized bythiolated-β-cyclodextrin （HS-β-CD） for the first time, and then appliedsuccessfully in sensitive and simultaneous electrochemical detection of naphthols.The results show that the oxidation peak currents of naphthols obtained on theHS-β-CD/AuNPs/HNCMS modified glassy carbon （GC） electrode are much higherthan that on the HS-β-CD/HNCMS/GC, AuNPs/HNCMS/GC, HNCMS/GC andbare GC electrodes. Additionally, compared with the other electrochemical sensorsdeveloped previously, the proposed electrode demonstrates the improved detectionlimits of about four times for1-NAP （1.0nM） and two orders of magnitudefor2-NAP （1.2nM）. The linear response range for both1-NAP and2-NAP are2– 150nM.（2） β-cyclodextrin （β-CD）-platinum nanoparticles （Pt NPs）/graphenenanosheets （GNs） nanohybrids （β-CD-PtNPs/GNs） were prepared for the first timeusing a simple wet chemical method and characterized by atomic force microscopy,transmission electron microscopy, Fourier transform infrared spectroscopy, andelectrochemical methods, and then applied in the ultrasensitive electrochemicaldetection of naphthol isomers. The results show that the oxidation peak currents ofnaphthol isomers obtained at the glassy carbon （GC） electrode modified withβ-CD-PtNPs/GNs are much higher than those at the β-CD/GNs/GC,PtNPs/GNs/GC, GNs/GC, and bare GC electrodes. Additionally, compared withother electrochemical sensors developed previously, the proposed electrode resultsin decreased detection limits of about one order of magnitude for1-NAP （0.23nM）and three orders of magnitude for2-NAP （0.37nM）.（3） Using3,4,9,10-perylene tetracarboxylic acid as a bridge to connectmono（6-ethanediamine-6-deoxy）-b-cyclodextrin （NH₂-β-CD）to the surface ofgraphene, noncovalently functionalized graphene nanosheets （CD-PTCA-GNs） aresynthesized for the first time. The as-prepared CD-PTCA-GNs were characterizedby Fourier transform infrared spectroscopy, thermogravimetric analysis, atomicforce microscopy, and electrochemical methods. The electrocatalytic activitiestoward several organic pollutants at the glassy carbon （GC） electrode modifiedwith CD-PTCA-GNs were investigated, all of which show a remarkable increase inelectrochemical performance relative to the bare GC and GNs/GC electrodes.1-aminonaphthalene （1-NA） was used as the representative analyte to demonstratethe sensing performance of the CD-PTCA-GNs. The results show that the linearresponse range of1-NA is10–550nM with the detection limit of1.0nM （S/N=3）,thus implying that the CD-PTCA-GNs organic–inorganic nanohybrids will havepromising applications in organic pollutants analysis and sensors.（4） We reported a simple and facile approach to synthesis β-cyclodextrinnon-covalently functionalized single-walled carbon nanotubes bridged by3,4,9,10-perylene tetracarboxylic acid （β-CD-PTCA-SWCNTs）, and Fourier transforminfrared spectroscopy, transmission electron microscopy, thermogravimetricanalysis, Raman spectroscopy and electrochemical methods were used tocharacterize the as-prepared functionalized SWCNTs. Furthermore, theβ-CD-PTCA-SWCNTs were applied successfully to detect9-AnthracenecarboxylicAcid by electrochemical methods. The results show that the oxidation peak current of9-ACA at β-CD-PTCA-SWCNTs modified GC electrode is4.0and31.2times higher than that at the SWCNTs/GC and bare GC electrodes, respectively, and the proposed modified electrode has a linear response range of2.00to140.00nM with a detection limit of0.65nM （S/N=3） towards9-ACA, due to the synergetic effects from SWCNTs （good electrochemical properties and large surface area） and β-CD （a hydrophilic external surface, high supramolecular recognition and enrichment capability）.（5） Based on the competitive host-guest interaction between β-cyclodextrin/poly（N-acetylaniline）/electrogenerated-graphene （β-CD/PNAANI/EG） film and probe or target molecules, a new dual-signalling electrochemical sensing method has been developed for sensitive and selective determination of organic pollutants. As the model, rhodamine B （RhB） and1-aminopyrene （1-AP） were adopted as the probe and target molecules, respectively. Due to the host-guest interaction, RhB molecules can entry into the hydrophobic inner cavity of β-CD, and the β-CD/PNAANI/EG modified glassy carbon electrode displays a remarkable oxidation peak of RhB. While in the presence of1-AP, competitive association to the β-CD occurs and the RhB molecules are displaced by1-AP. This results in that the oxidation peak current of RhB decreases and the oxidation peak current of1-AP appears, and the changes of dual signals are linear with the concentration of1-AP. When "ΔI1-AP+|ΔIRhB|"（ΔI1-AP and ΔIRhB are the change values of the oxidation peak currents of1-AP and RhB, respectively.） is used as the response signal to quantitatively determine the concentration of1-AP, the detection limit is much lower than that by using ΔI1-AP or ΔIRhB as the response signal. This dual-signalling sensor can provide more sensitive target recognition, and will have important applications in the sensitive and selective electrochemical determination of electroactive organic pollutants.Additionally, an ultrathin film modified glassy carbon （GC） electrode was prepared by electropolymerization of5-amino-1,3,4-thiadiazole-2-thiol （AMT） on the GC electrode （PAMT/GC） and used to detect9-ACA. Compared to the GC electrode, the PAMT/GC electrode shows more excellent stability and reproducibility, and meanwhile exhibits higher electrochemical response of9-ACA due to the unique properties of PAMT such as large surface area, good electronic properties and catalytic ability. The linear range for9-ACA detection is from7.0x10-8M to1.1×10-6M and the detection limit is1.2×10-8M （S/N=3）. Finally, the proposed methodology was successfully applied to the detection of9-ACA inwater samples.