In this work, visible light-responsive carbon nanotubes (CNTs)/Bi4VO8Cl composite photocatalysts have been prepared by a facile in situ hydrothermal method and characterized by various techniques. The photocatalytic properties of the photocatalysts are evaluated by the degradation of refractory azo-dye methyl orange (MO), hexavalent chromium Cr(VI), and bisphenol A (BPA) in water under visible light irradiation. It is found that the as-prepared composite with 4 wt% CNTs shows an optimal photocatalytic performance, and its photocatalytic activity is 30% higher than that of pure Bi4VO8Cl. The enhanced photocatalytic activity is ascribed to the synergetic effects induced by increased light absorption, increased adsorption efficiency for pollutant, and suppressed recombination rate of photogenerated charge carriers. Furthermore, efficient removals of Cr(VI), bisphenol A (BPA), and combined contamination of Cr(VI) and BPA over CNTs/Bi4VO8Cl composite further confirm that the degradation of organic pollutants is a photocatalytic mechanism rather than photosensitization of dye. Of particular importance is that removal efficiency of single pollutant can be promoted by the coexistence of the Cr(VI) and organics. The mechanism of synergetic promotion is discussed and attributed to the accelerated separation of charge carriers resulted from their simultaneously being captured by pollutants. Moreover, the CNTs/Bi4VO8Cl composite exhibits good stability and recycling performance in the photocatalytic degradation process. Therefore, the composite photocatalysts developed in the present work are expected to have the potential in purification of complex wastewater.

Development of new strategies for the sensitive and selective detection of ultra-low concentrations of specific cancer markers is of great importance for assessing cancer therapeutics due to its crucial role in early clinical diagnoses and biomedical applications. In this work, we have developed two types of fluorescence polarization (FP) amplification assay strategies for the detection of biomolecules by using TiS2 as a FP enhancer and Zn2+-dependent self-hydrolyzing deoxyribozymes as catalysts to realize enzyme-catalyzed target-recycling signal amplification. One approach is based on the terminal protection of small-molecule-linked DNA, in which biomolecular binding to small molecules in DNA-small-molecule chimeras can protect the conjugated DNA from degradation by exonuclease I (Exo I); the other approach is based on the terminal protection of biomolecular bound aptamer DNA, in which biomolecules directly bound to the single strand aptamer DNA can protect the ssDNA from degradation by Exo I. We select folate receptor (FR) and thrombin (Tb) as model analytes to verify the current concept. It is shown that under optimized conditions, our strategies exhibit high sensitivity and selectivity for the quantification of FR and Tb with low detection limits (0.003 ng mL−1 and 0.01 pM, respectively). Additionally, this strategy is a simple “mix and detect” approach, and does not require any separation steps. This biosensor is also utilized in the analysis of real biological samples, the results agree well with those obtained by the enzyme-linked immunosorbent assay (ELISA).

Sensitive and selective detection of ultralow concentrations of specific biomolecules is important in early clinical diagnoses and biomedical applications. Many types of aptasensors have been developed for the detection of various biomolecules, but usually suffer from false positive signals and high background signals. In this work, we have developed an amplified fluorescence aptasensor platform for ultrasensitive biomolecule detection based on enzyme-assisted target-recycling signal amplification and graphene oxide. By using a split molecular aptamer beacon and a nicking enzyme, the typical problem of false positive signals can be effectively resolved. Only in the presence of a target biomolecule, the sensor system is able to generate a positive signal, which significantly improves the selectivity of the aptasensor. Moreover, using graphene oxide as a super-quencher can effectively reduce the high background signal of a sensing platform. We select vascular endothelial growth factor (VEGF) and adenosine triphosphate (ATP) as model analytes in the current proof-of-concept experiments. It is shown that under optimized conditions, our strategy exhibits high sensitivity and selectivity for the quantification of VEGF and ATP with a low detection limit (1 pM and 4 nM, respectively). In addition, this biosensor has been successfully utilized in the analysis of real biological samples.

Carbon nanotubes have excellent adsorption property for metal ions. However, they lack selectivity and are difficult to separate from solutions. To resolve these problems, magnetic carbon nanotubes were prepared and functionalized with an imidazolium ionic liquid in this work. The functionalized magnetic carbon nanotube was used to remove Cr(VI) from water. It was found that the removal was highly selective and sensitive. At acidic conditions, 90% of Cr(VI) could be selectively removed on the ppb level with the coexistence of a high concentration of cations like Hg2+, Cd2+ and anions such as NO3− and SO42−. After the adsorption, the material could be collected easily by an external magnet, and then regenerated effectively by using 8% hydrazine hydrate. The high adsorption sensitivity, selectivity and capacity were attributed to the favorable electrostatic attraction, anion exchange affinity and entropy effects. Kinetic analysis indicated that the adsorption process of Cr2O72− was well described by a pseudo second order model. The adsorption isothermal analysis revealed that the adsorption process was endothermic, and could be described by a Langmuir model. In addition, it is interesting to find that unlike the commonly used absorbents, the adsorption capacity of the functionalized material for Cr2O72− increased with increasing temperature.

An ionic liquid (IL) surface molecularly imprinted polymer (MIP) was prepared using 1-octyl-3-methylimidazolium chloride ([C8mim]Cl) as the template and acylated ethylenediamine-poly(styrene-divinylbenzene) particle as the supported material. The obtained MIP material was characterized by scanning electron microscopy, Brunauer–Emmett–Teller surface area analysis, and FT-IR spectroscopy. The adsorption property and selective recognition performance of [C8mim]ClMIP were studied by static adsorption and solid-phase extraction coupled with high-performance liquid chromatography. Next, the effect of alkyl chain length of imidazolium cations on the adsorption characteristics of [C2mim]ClMIP, [C4mim]ClMIP, and [C8mim]ClMIP was examined in detail. It was shown that the adsorption selectivity of the three IL MIPs was significantly affected by the alkyl chain length. [C8mim]ClMIP exhibited broad recognition characteristics for all the imidazolium chloride ILs studied ([Cnmim]Cl, n = 2, 4, 6, 8, 12, 16), and the adsorption equilibrium was achieved within 40 min. [C4mim]ClMIP could enrich [Cnmim]Cl (n = 2, 4, 6, 8), but [C2mim]ClMIP could only recognize [C2mim]Cl and [C4mim]Cl selectively. It is obvious that the adsorption selectivity of the IL MIPs increased with the decrease of alkyl chain length of the template molecules. Furthermore, the possible recognition mechanism was suggested.

A new molecularly imprinted polymer was prepared on the surface of ethylenediamine-poly(styrene–divinylbenzene) particles by thermal polymerization method using 1-methoxyethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([EOM][Tf2N]) as template, acrylamide as functional monomer, and chloroform as porogen. The influence of porogen, monomer, and the ratio of [EOM][Tf2N] to monomer and cross-linker was systematically investigated, and the microstructure was characterized by Fouier transform infrared spectrum and scanning electron microscopy. The selective recognition performance of the imprinted polymer for target was investigated by the static adsorption and HPLC. It was shown that the surface imprinted material had excellent selectivity towards [EOM][Tf2N] and the short chain imidazolium ionic liquids, but its adsorption towards the molecules without imidazole ring was quite low. The maximum binding capacities of [EOM][Tf2N] on the imprinted and non-imprinted polymers were 137.2 and 23.4 µmol g−1, respectively. The adsorption equilibrium was achieved in 35 min, and the kinetic adsorption process could be described by pseudo-second order model. From high pressure liquid chromatography measurements, it was found that using the imprinted polymer, 84–91 % [EOM][Tf2N], 10 % 2,4-dichlorophenol, and 3 % N-butylpyridinium chloride could be separated from the mixtures of [EOM][Tf2N] + 2,4-dichlorophenol and [EOM][Tf2N] + N-butylpyridinium chloride, respectively. By contrast, the non-imprinted polymer could adsorb only less than 10 % [EOM][Tf2N], 10 % 2,4-dichlorophenol, and 3 % N-butylpyridinium chloride, respectively, from the mixtures. The imprinted polymer coupled with HPLC was applied for the selective extraction and determination of [EOM][Tf2N] in complex mixture samples.

A novel nanoscale photocatalyst Bi4VO8Cl was prepared by hydrothermal synthesis and characterized. This catalyst was used for the degradation of six pharmaceuticals including metronidazole, aciclovir, levofloxacin hydrochloride, sulfonamide, adrenaline hydrochloride, and ribavirin in aqueous solutions by visible light irradiation. It was shown that all the drugs except for metronidazole were mineralized completely during 10 h visible light irradiation, while metronidazole could be degraded easily into biodegradable small molecules. Then metronidazole was selected as a representative drug to evaluate removal efficiency of the photocatalytic system under visible light, ultraviolet light, and solar light, to investigate the degradation kinetics, and to study the possible degradation pathway from degradation products measurements. Results indicated that under the optimal conditions, metronidazole could also be completely degraded within 10 min ultraviolet light irradiation or 6 h solar light irradiation. Therefore, Bi4VO8Cl would be a promising photocatalyst for the removal of pharmaceuticals from waste waters under solar irradiation.

Trace of Pb(II) has been on-line separated and enriched from environmental samples and wastewater by using the self-made alizarin violet functionalized silica gel micro-column coupling with a sequential injection sampling technology. The determination is based on the color reaction of Pb(II) with iodide and crystal violet to form an ionic association complex in the presence of polyvinyl alcohol and hydrochloric acid. The use of the microcolumn can prevent the interference of most familiar metal ions, and therefore improve the selectivity and sensitivity of this analytical technique. The proposed method was used for the determination of Pb(II) in environmental samples and wastewater. No statistically significant difference was observed between the results determined by the present method and atomic absorption spectrometry.