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A nanohybrid of zinc oxide and biochar (ZnO/BC) with high conductivity was green synthesized using a simple hydrothermal method, and utilized for the sensitive detection of bisphenol A (BPA) by coating the nanohybrid film on an electrode of glassy carbon. The ZnO/BC presented greatly improved electrocatalytic performance and electron transfer ability compared to the zinc oxide and biochar. The ZnO/BC film-coated electrode could detect the BPA in aqueous solution within 3 min while neglected interference from higher concentrations of regularly existing ions and similar concentrations of estradiol (E2), phenol, dichlorophenol (DCP), and ethinylestradiol (EE2). Under optimal conditions, the linear range of BPA detection was 5 × 10−7~1 × 10−4 mol/L, with a detection limit of 1 × 10−7 mol/L, and the detection sensitivity was 92 mA/M. In addition, the ZnO/BC electrode could detect BPA in a real water sample with good signal recovery. This electrode, with the advantages of an easy preparation, low cost, and fast response time, could be potentially applicable for environmental monitoring. [ABSTRACT FROM AUTHOR]

An electrochemical tyrosinase enzyme (Tyr) biosensor using a highly conductive sugarcane derived biochar nanoparticle (BCNP) as a transducer and signal enhancer (BCNPs/Tyr/Nafion/GCE) was developed for the sensitive detection of bisphenol A (BPA). The BCNPs/Tyr/Nafion/GCE biosensor exhibited improved amperometric current responses such as higher sensing signal, decreased impedance and lowered reduction potential compared with the Tyr/Nafion/GCE due to high conductivity property of the biochar nanoparticle. Under the optimized conditions, it could detect BPA in good sensitivity with linear range from 0.02 to 10 μM, and a lowest detection limit of 3.18 nM. Moreover, it showed a low Km value, high reproducibility and good selectivity over other reagents, and the BCNPs/Tyr complex solution also showed good stability with 86.9% of sensing signal maintained after one month storage. The biosensor was also successfully utilized for real water detection with high accuracy as validated by high performance liquid chromatography. Therefore, the biochar nanoparticle based enzyme biosensor proved to be a potential and reliable method for high performance detection of pollutants in the environment. [ABSTRACT FROM AUTHOR]

• PA and PSS functionalized BC succeeded in constructing label and reagent free SPE immunosensor. • PA presented extremely high electrochemical stability by coating on BC. • PSS ensured significantly great electrochemical activity of the sensor even in neutral buffer. • Trace leveled atrazine is high sensitively detectable in 5 min with LOD of 0.407 ng/L. A label and reagent free and cost effective immunosensing system was newly developed for detection of trace leveled atrazine in water. This was constructed by synthesis of polyaniline (PA) and polystyrene sulfonic acid (PSS) modified biochar (BC) nanoparticle composite (PA-PSS-BC) and coating them on screen printed electrode as conductive and electrochemically active layer, and covalently immobilizing anti-atrazine antibody on electrode for specific target binding. The low cost biochar from sugarcane was highly conductive and favorable for attaching PA and PSS due to large surface area and sp2 carbon structure. Crediting to dopant PSS, PA-PSS-BC achieved significant enhancement of redox current signal even in phosphate buffered saline of neutral pH compared to that of without PSS. And redox current of PA was extremely stable with negligible signal change even after twenty cycles repeated reactions owning to protection by BC. These essentially ensured sensing platform being sensitively performed in neutral solution with exemption of adding external redox reagent. As a result, fairly low concentrations of atrazine could be detected within 5 min, with limit of detection being 0.407 ng/L in a dynamic detection range varying from 1 to 100 ng/L. Moreover, the immunosensor exhibited reasonable signal recoveries for detecting trace leveled atrazine in real water samples, high selectivity, and good stability with dry and cold storage. [ABSTRACT FROM AUTHOR]

Abstract We developed a sensitive and cost effective sensor based on highly conductive and adsorptive biochar nanoparticles for electrochemical detection of 17β-estradiol. The biochar is ubiquitous and has the advantages of large specific surface area, cost effectiveness, and good stability, which has the potential to be utilized for electrode construction as long as the conductivities are guaranteed. We obtained nano sized biochar particles (BCNPs) and investigated electrochemical properties of the BCNPs with variation of the pyrolysis conditions. BCNPs with high conductivity (BCNP800) were obtained and utilized for reproducible and stable electrochemical sensor construction. The produced highly conductive BCNP800 sensor had exhibited improved amperometric responses such as decreased impedance, lowered anodic potential and enhanced current signal toward 17β-estradiol compared with the pristine glassy carbon electrode. In addition, the adsorption-accumulation by BCNP800 for 17β-estradiol resulted in great sensing signal amplification. With synergetic effect of high adsorption and conductivity properties of the BCNP800 sensor a detection limit of 11.30 nM was obtained. The accuracy and reliability of the BCNP800 sensor were confirmed to be compatible with the high performance liquid chromatography analysis and it could be successfully applied for real environmental water analysis. [ABSTRACT FROM AUTHOR]

Highlights • Nanosized biochar particles (BCNP) with various pyrolysis temperatures were prepared. • The BCNP could adsorb more E2 than with microsized biochar due to larger surface area. • Magnetically separable Mag-BCNP was successfully synthesized and utilized for high efficiency E2 adsorption. • Mag-BCNP presented different E2 adsorption characteristics depending on types of BCNP used. Abstract Through biochar nanoparticles (BCNPs) obtained at pyrolysis temperatures of 400 °C, 600 °C and 800 °C, three types of biomass-derived adsorbent, magnetic BCNPs (Mag-BCNP 400 , Mag-BCNP 600 and Mag-BCNP 800) were synthesized. The BCNPs possessed large surface area, nearly 14.5 times higher than that of the biochar microparticles, which contributed to enhanced adsorption capacity. Adsorption characteristics of 17β-estradiol (E2) by Mag-BCNPs were investigated and described by a pseudo-second-order model. The thermodynamic study indicated that adsorption was spontaneous and the adsorption isotherms were well described by Langmuir model with the maximum adsorption capacities of 50.24, 41.71 and 34.06 mg/g for Mag-BCNP 400 , Mag-BCNP 600 and Mag-BCNP 800 , respectively. Fourier transform infrared analysis suggested that hydrophobic interactions and π–π electron donor-acceptor interactions for E2 sorption to Mag-BCNPs may occur simultaneously, whereas the dominating mechanisms may change from hydrophobic interactions to π–π interactions as pyrolysis temperatures increased from 400 °C to 800 °C. Mag-BCNPs can be easily separated using a magnetic force and regenerated by ozonation. Therefore, with the advantageous features of low cost, ease of separation and good reusability, the Mag-BCNPs can be used as potential adsorbents for removing E2 from water. [ABSTRACT FROM AUTHOR]

Benzo[ a ]pyrene (BaP), as a typical polycyclic aromatic hydrocarbon, is severely hazardous to human for having great carcinogenic and teratogenic activities. Here, we propose a cascade electrochemical reaction-based BaP detection method by using novel synthesized reduced and hierarchically porous biochar (RP-BC) as conductive and analysts binding material. The RP-BC was synthesized by green hydrothermal reduction of sugarcane derived biochar, which was demonstrated to have huge specific surface area with hierarchically porous structures, great content of sp2 carbon, and fast electron transfer ability. The RP-BC film coated on glassy carbon electrode could preferentially adsorb and enrich BaP by strong π-π electron donor-acceptor (EDA) interaction and pore interception effect, so fast (5 min) and selective detection of BaP was achieved. Moreover, the low detection limit was 0.090 nmol·mL−1 with linear range being 0.32 to 80 nmol·mL−1. In addition, the detection of BaP in groundwater and tap water was realized with satisfactory results, suggesting the potential of practical environmental monitoring. [ABSTRACT FROM AUTHOR]

A novel electrochemical sensor for the ultrasensitive monitoring of Pb2+ and Cd2+ was developed by fabrication of highly conductive and target selective electrode using ball milling biochar (BBC) featured with high conductivity and rich oxygenic functional groups as the conductive material, and cavities of ion-imprinted polymer as specific binding moieties. The nanosized BBC was synthesized with process of high temperature pyrolysis and rigorous ball milling. The ion imprinted BBC electrode was constructed by in situ electropolymerization of L -Cysteine and template metal ions on the BBC that was modified on glassy carbon, and subsequent removal of templates. The BBC presented great electron transfer ability, and contained increased oxygenic compounds than the mild ball milling prepared one, which attributed to formation of stable and cavity-rich imprinting polymer layer and enhancement of sensing signal. With the anodic dissolved differential pulse voltammetry, the electrode could detect extremely low levels of Pb2+ and Cd2+ with lowest detection limits of 5.86 fM and 0.883 aM, and the linear ranges were 25 fM ~ 1 µM and 0.1 fM ~ 1 µM, respectively. The electrode also presented anti-interference to other irrelevant ions and organic compounds, and could reuse at least seven times without decrease of sensing signal. • Highly conductive nanosize BBC with rich oxygenic functional group and large pore was prepared. • Ion imprinted BBC electrode can specifically bind target metal ions with enhanced response signal. • The electrode featured of rich cavities could detect extremely low leveled target with wide linear range. • It was highly selective and could reuse over seven times without signal decrease. [ABSTRACT FROM AUTHOR]

• A novel PMS based AOPs method was developed with SugBC900 as catalyst. • The SugBC900 is easy to prepare and highly cost effective. • High sp2 carbon content, surface area and electron transfer ability are key features. • 1O 2 and O 2 •− are dominant oxidative species instead of SO 4 •− and •OH. • It can effectively degrade BPA at broad pHs (1–11) and temperatures (10–45 °C). Cost effective and environmental friendly biochar catalyst (SugBC900) with high catalytic activity toward peroxymonosulfate (PMS) was prepared by simple pyrolysis of sugarcane waste, and utilized for efficient degradation of organic pollutants. Taking advantages of high sp2 hybrid carbon content, large surface area and excellent electron transfer ability, the SugBC900 coupled with PMS presented far greater catalytic degradation ability toward bisphenol A (BPA) as model pollutant when compared to the SugBC700, SugBC800 and other carbonaceous catalysts. The oxidative species of 1O 2 and O 2 •− were demonstrated to be dominant for catalytic degradation, and the role of SO 4 •− and •OH was minor. 20 mg/mL of BPA could be completely degraded with less than 60 min at pHs of 5.0–11.0, and at temperatures of 25–45 °C. And at the extremely acidic (pH of 1.0) or low temperature (10 °C) conditions, the degradation efficiencies could still reach more than 90%. The SugBC900 was also successfully utilized for the efficiently catalytic degradation of BPA and other organic pollutants in various real environmental water. Because of simple preparation by impregnating none of external elements, extremely low cost property, and robustness characteristic by having broad working conditions, the SugBC900 would have potential to be a good alternative to the conventional catalysts. [ABSTRACT FROM AUTHOR]

A portable, cheap and sensitive paper type electrochemical immunosensor was developed with conductive nanobiochar paper as the conductive layer and utilized for sensitive detection of microcystin-LR (MCLR) toxin in water. The paper immunosensor was constructed by coating of highly conductive and dispersible nanobiochar particle (nBC) and anti-MCLR antibody on the filter paper via dipping-drying method. The presence of MCLR could be specifically quantified amperometrically by the nBC-paper immunosensor with the response time of less than 5 min, and the lowest detection limit of 17 pM (0.017 μg/L) was achieved. Moreover, the proposed immunosensor exhibited high selectivity, reproducibility and storage stability, and was also used for environmental water detection with satisfactory recovery. The successful fabrication of low cost and ubiquitous biochar based paper type electrochemical immunosensing system would have significant value for the development of highly cost-effective electrochemical device. Unlabelled Image • Electrochemical immunosensor was constructed with conductive nanobiochar paper. • Such paper immunosensor was stable, simple and highly cost effective. • Ultrasensitive detection of MCLR with high selectivity was achieved. • It could be used for real environmental water detection with satisfactory recovery. [ABSTRACT FROM AUTHOR]

• Biochar catalyzed the dechlorination of >99 % PCE in sulfide solution. • Catalytic effect remained stable under both neutral and alkaline pH conditions. • Both biochar and sulfide concentrations affected the dechlorination rate. • Carbon and oxygen adjacent to pyridine nitrogen on biochar were the active sites of biochar. Biochar (BC) has been investigated as a natural and economical activator to treat organic contamination. Compared with commercial carbon materials, BCs have a better prospect of large-scale application. For the first time, this study certified degradation of tetrachloroethene (PCE) in sulfide-containing aqueous solutions catalyzed by wormwood-based BCs pyrolyzed at 600 °C, 700 °C, and 800 °C (BC600, BC700, and BC800). Interestingly, BC800 could catalyze PCE dechlorination and form acetylene and chloride ion with over 99 % nontoxic transformation in neutral and alkaline pH conditions. Furthermore, materials surface properties, BC dosages and sulfide concentrations were considered as limiting factors for dechlorination, and the last one had the strongest influence. XPS analysis demonstrated that catalytic ability of BC was attributed to pyridine nitrogen (N6) on surface, because C and O adjacent to N6 strongly favor nucleophilic reactions. These results evaluated the applicability of degrading toxic chlorinated alkenes mediated by natural carbon materials in sulfide-containing environment. [ABSTRACT FROM AUTHOR]