The efficient handling of wastewater pollutants is a must, since they are continuously defiling limited fresh water resources, seriously affecting the terrestrial, aquatic, and aerial flora and ...fauna. Our vision is to undertake an exhaustive examination of current research trends with a focus on nanomaterials (NMs) to considerably improve the performance of classical wastewater treatment technologies, e.g. adsorption, catalysis, separation, and disinfection. Additionally, NM-based sensor technologies are considered, since they have been significantly used for monitoring water contaminants. We also suggest future directions to inform investigators of potentially disruptive NM technologies that have to be investigated in more detail. The fate and environmental transformations of NMs, which need to be addressed before large-scale implementation of NMs for water purification, are also highlighted.
MXene-Ti3C2, as a new class of two-dimensional (2D) transition metal carbides (or nitrides), has been synthesized by exfoliating pristine Ti3AlC2 phases with hydrofluoric acid. The SEM and XRD images ...show that the resultant MXene possesses a graphene-like 2D nanostructure. and the surface of MXene has been partially terminated with -OH, thus providing a favorable microenvironment for enzyme immobilization and retaining their bioactivity and stability. Considering the unique metallic conductivity, biocompatibility and good dispersion in aqueous phase, the as-prepared MXene was explored as a new matrix to immobilize tyrosinase (a model enzyme) for fabricating a mediator-free biosensor for ultrasensitive and rapid detection of phenol. The varying electrochemical measurements were used to investigate the electrochemical performance of MXene-based tyrosinase biosensors. The results revealed that the direct electron transfer between tyrosinase and electrode could be easily achieved via a surface-controlled electrochemical process. The fabricated MXene-based tyrosinase biosensors exhibited good analytical performance over a wide linear range from 0.05 to 15.5 μmol L−1, with a low detection limit of 12 nmol L−1 and a sensitivity of 414.4 mA M−1. The proposed biosensing approach also demonstrated good repeatability, reproducibility, long-term stability and high recovery for phenol detection in real water samples. With those excellent performances, MXene with graphene-like structure is proved to be a robust and versatile electrochemical biosensing platform for enzyme-based biosensors and biocatalysis, and has wide potential applications in biomedical detection and environmental analysis.
•Graphene-like MXene-Ti3C2 was prepared by exfoliating pristine Ti3AlC2 with HF.•MXene-Ti3C2 possesses unique metallic conductivity, biocompatibility and good dispersion in aqueous phase.•MXene was explored as a new biosensing platform for tyrosinase immobilization and phenol detection.•The nanostructure and surface -OH provide favorable microenvironments for retaining enzyme bioactivity and stability.•The MXene-Ti3C2 based biosensor exhibited excellent analytical performances.
Gold nanoparticles (AuNP) dotted reduction graphene oxide (RGO-AuNP) is used as a platform for an aptamer biosensor to selectively detect 3,3'4,4'-polychlorinated biphenyls (PCB77). By anchoring ...aptamers onto the binding sites of RGO-AuNP and making use of the synergy effect of RGO and AuNP, the RGO-AuNP based biosensor exhibits superior analytical performances to AuNP based biosensor in terms of sensitivity and repeatability. The sensitivity of RGO-AuNP based aptamers (RGO-AuNP-Ap) biosensor (226.8 μA cm
) is nearly two times higher than that of Au based biosensors (AuNP-Ap/Au electrode, 147.2 μA cm
). The RGO-AuNP-Ap/Au biosensor demonstrated a linear response for PCB77 concentrations between 1 pg L
and 10 μg L
, with a low limit of detection (LOD) of 0.1 pg L
. The superb LOD satisfies the exposure thresholds (uncontaminated water < 0.1 ng L
) set out by International Agency for Research on Cancer (IARC) and the Environmental Protection Agency (EPA). The proposed biosensor can be a powerful tool for rapid, sensitive and selective detection of PCBs on site.
▸ Hydrophilic nanographene was prepared in a controllable nanometer size by a simple ball milling method of graphite materials. ▸ The nanographene was explored to construct a novel tyrosinase ...biosensor for rapid, sensitive and selective determination of bisphenol A. ▸ Comparative studies revealed the significant advantages of nanographene over MWNTs in the performance of fabricated tyrosinase biosensors. ▸ The biosensor was used for detecting BPA in water samples, and the obtained results were validated by high performance liquid chromatography. ▸ The nanographene based tyrosinase biosensor proved to be a promising and reliable tool for rapid detection of BPA.
Hydrophilic nanographene (NGP) prepared by ball milling of graphite was used as the support to construct a novel tyrosinase biosensor for determination of bisphenol A (BPA). The performances of the nanographene-based tyrosinase biosensor were systematically compared with those of multiwall carbon nanotubes (MWNTs) modified tyrosinase biosensors. The results indicated that the nanographene-based tyrosinase biosensor provided significant advantages over MWNTs-based tyrosinase biosensor in term of response, repeatability, background current and limit of detection (LOD), which could be attributed to its larger specific surface area and unique hierarchical tyrosinase-NGP nanostructures. The nanographene-based tyrosinase biosensor displayed superior analytical performance over a linear range from 100nmolL−1 to 2000nmolL−1, with LOD of 33nmolL−1 and sensitivity of 3108.4mAcm−2M−1. The biosensor was further used for detecting BPA (leaching from different vessels) in tap water, and the accuracy of the results was validated by high performance liquid chromatography (HPLC). The nanographene-based tyrosinase biosensor proved to be a promising and reliable tool for rapid detection of BPA leached from polycarbonate plastic products and for on-site rapid analysis of emergency pollution affairs of BPA.
A simple method for determining 33 pesticides with a wide polarity range（log Kow0.6-4.5） in aquatic products was developed based on LC–MS/MS. The target analytes included three types of widely used ...pesticides： insecticides, fungicides and herbicides. Based on the optimization of ultrasonic assisted extraction and GPC clean-up procedures, the matrix effect, extraction recoveries and LOD were improved distinctively. LOQ of this method was below 0.5 ng/g for all pesticides, which is superior to values in the literature, and the matrix effect was reduced effectively（-14.7% to 7.5%）. The method was successfully applied to investigate the pesticide residue levels of twenty-five samples including seven common kinds of fishes from Northeast China. The results showed that all targeted pesticides were present in the fish samples; however, their levels were low, except for atrazine, linuron,ethoprophos, tetrachlorvinphos, acetochlor and fenthion. Atrazine and linuron caught our attention because the concentrations of atrazine in fish samples from Liaoning province were in the range of 0.5-8 ng/g（w/w） with mean concentration of 2.3 ng/g, which were far above those of other pesticides. The levels of linuron were in the range of 0.6-6 ng/g（mean concentration 2.8 ng/g）, which were the highest among all targeted pesticides in the Inner Mongolia. This is the first systematic investigation on the characteristics and levels of these pesticides in aquatic products from northeast China. Considering their toxicity and bioaccumulation, the potential risk of atrazine and linuron from consuming aquatic products should be paid more attention.
Because of their unique chemical, physical and electronic properties, Quantum dots (QDs) and carbon nanotubes (CNTs) are now extremely attractive and important nanomaterials in bioanalytical ...applications. In this work, CdTe QDs with the size of about 3nm were prepared and a novel electrochemical biosensing platform of glucose based on CdTe/CNTs electrode was explored. This CdTe/CNTs electrode was prepared by first mixing CdTe QDs, CNTs, Nafion, and glucose oxidase (GOD) in appropriate amounts and then modifying this mixture on the glass carbon electrode (GC). Transmission electron microscopy (TEM) was used to observe the dispersion of CdTe QDs on carbon nanotubes and cyclic voltammetry (CV) was used to investigate the electrochemical behavior of the CdTe/CNTs electrode. A pair of well-defined quasi-reversible redox peaks of glucose oxidase were obtained at the CdTe/CNTs based enzyme electrode by direct electron transfer between the protein and the electrode. The immobilized glucose oxidase could retain bioactivity and catalyze the reduction of dissolved oxygen. Due to the synergy between the CdTe QDs and CNTs, this novel biosensing platform based on QDs/CNTs electrode responded even more sensitively than that based on GC electrode modified by CdTe QDs or CNTs alone. The inexpensive, reliable and sensitive sensing platform based on QDs/CNTs electrode provides wide potential applications in clinical, environmental, and food analysis.
Carbon nanofibers (CNFs), with typical diameters of ∼80
nm and lengths of the order of micrometers, are extremely attractive in bioanalytical area as they can combine properties of high surface area, ...non-toxicity, acceptable biocompatibility, ease of fabrication, chemical and electrochemical stability, good electrical conductivity. In this work, CNF-based composites were successfully used as an immobilization matrix for the construction of a reagentless mediator-free hemoglobin-based H
2O
2 biosensor. The results revealed that hemoglobin retained its essential secondary structure in the CNF-based composite film. With the advantages of organic–inorganic hybrid materials, dramatically facilitated direct electron transfer of hemoglobin and good bioelectrocatalytic activity towards H
2O
2 were demonstrated. The biosensor displayed good performance along with good long-term stability. The CNF-based composites were proved to be a promising biosensing platform for the construction of mediator-free biosensors, and may find wide potential applications in biosensors, biocatalysis, bioelectronics and biofuel cell.
In this study, a facile non-covalent method was developed for preparing water-soluble graphene with excellent electronic conductivity. Room temperature ionic liquids (ILs) with high ionic ...conductivity were used for the non-covalent surface functionalization of graphene through π–π stacking interactions. Compared to other ILs used, amino acid ionic liquids (AAILs) were found to be the most effective for improving the dispersion of graphene in water phase. Electrochemical and spectroscopic results confirmed that the obtained AAIL functionalized GR can retain the excellent electronic conductivity of pristine graphene without damaging the graphene lattice. The obtained water-soluble graphene (GR-AAIL) was exemplified to fabricate an electrochemical biosensor using tyrosinase as a model enzyme, and the sensitivity (12,600mAcm−2M−1) of GR-AAIL based biosensor was about 17 times higher than that of graphene oxide and other nanomaterial based biosensor, displaying its unprecedented high sensitivity for biosensing. The detection limit for catechol (one important environmental pollutant) reached as low as 8nM with a response time of 3s and a linear range from 25nM to 11,100nM. The AAIL-GR based biosensor also demonstrated good reproducibility, repeatability, selectivity, long-term stability and high recovery for catechol detection. Amino acid ionic liquid functionalized graphene proves to be a robust and versatile electrochemical biosensing platform for fabricating biosensors with excellent performance.
•A non-covalent method was developed for preparing water-soluble graphene.•Results confirmed the water-soluble graphene retained excellent electronic conductivity.•The graphene dispersions enable the use of conventional solution-phase processing techniques.•A robust biosensing platform was developed based on amino acid ionic liquid functionalized graphene.•The biosensing platform displayed excellent performance for biosensor application.
A novel polymer/room-temperature ionic liquid (RTIL) composite material based on chitosan (Chi) and 1-butyl-3-methyl-imidazolium tetrafluoroborate (BMIM·BF4) was explored. The composite system can be ...readily used as an immobilization matrix to entrap proteins and enzymes. Hemoglobin (Hb) was chosen as a model protein to investigate the composite system. A pair of well-defined quasireversible redox peaks of hemoglobin were obtained at the Chi−BMIM·BF4−Hb composite-film-modified glassy carbon (GC) electrode by direct electron transfer between the protein and the GC electrode. Dramatically enhanced biocatalytic activity was exemplified at the Chi−BMIM·BF4−Hb/GC electrode by the reduction of oxygen and trichloroacetic acid. Thermogravimetric analysis (TGA) suggests that the Chi−BMIM·BF4−Hb composite has higher thermal stability than Chi−Hb itself. The Chi−BMIM·BF4−Hb film was also characterized by UV−visible spectra, indicating excellent stability in solution and good biocompatibility for protein. The unique composite material based on polymer and ionic liquid can find wide potential applications in direct electrochemistry, biosensors, and biocatalysis.
Nanosheet-based ZnO microsphere with porous nanostructures was synthesized by a facile chemical bath deposition method followed by thermal treatment, which was explored for the construction of ...electrochemical biosensors. Spectroscopic and electrochemical researches revealed the ZnO-based composite was a biocompatible immobilization matrix for enzymes with good enzymatic stability and bioactivity. With advantages of nanostructured inorganic–organic hybrid materials, a pair of stable and well-defined quasi-reversible redox peaks of hemoglobin was obtained with a formal potential of −0.345
V (vs. Ag/AgCl) in pH 7.0 buffer. Facilitated direct electron transfer of the metalloenzymes with an apparent heterogeneous electron transfer rate constant (
k
s) of 3.2
s
−1 was achieved on the ZnO-based enzyme electrode. Comparative studies demonstrated the nanosheet-based ZnO microspheres were more effective in facilitating the electron transfer of immobilized enzyme than solid ZnO microspheres, which may result from the unique nanostructures and larger surface area of the porous ZnO. The prepared biosensor displayed good performance for the detection of H
2O
2 and NaNO
2 with a wide linear range of 1–410 and 10–2700
μM, respectively. The entrapped hemoglobin exhibits high peroxidase-like activity for the catalytic reduction of H
2O
2 with an apparent Michaelis-Menten constant
(
K
M
app
)
of 143
μM. The nanosheet-based ZnO could be a promising matrix for the fabrication of direct electrochemical biosensors, and may find wide potential applications in biomedical detection and environmental analysis.
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