Unveiling carcinogenic pollutant levels in environmental water samples through facile fabrication of gold nanoparticles on sulfur-doped graphitic carbon nitride.

Extensive utilization of pesticides and herbicides to boost agricultural production increased the environmental health risks, which can be mitigate with the aid of highly sensitive detection systems. In this study, an electrochemical sensor for monitoring the carcinogenic pesticides in the environmental samples has been developed based on sulfur-doped graphitic-carbon nitride-gold nanoparticles (SCN-AuNPs) nanohybrid. Thermal polycondensation of melamine with thiourea followed by solvent exfoliation via ultrasonication leads to SCN formation and electroless deposition of AuNPs on SCN leads to SCN-AuNPs nanohybrid synthesis. The chemical composition, S-doping, and the morphology of the nanohybrid were confirmed by various microscopic and spectroscopic tools. The as-synthesized nanohybrid was fabricated with glassy carbon (GC) electrode for determining the carcinogenic hydrazine (HZ) and atrazine (ATZ) in field water samples. The present sensor exhibited superior electrocatalytic activity than GC/SCN and GC/AuNPs electrodes due to the synergism between SCN and AuNPs and the amperometric studies showed the good linear range of detection of 20 nM-0.5 mM and 500 nM-0.5 mM with the limit of detection of 0.22 and 69 nM (S/N = 3) and excellent sensitivity of 1173.5 and 13.96 µA mM-1 cm-2 towards HZ and ATZ, respectively. Ultimately, the present sensor is exploited in environmental samples for monitoring HZ and ATZ and the obtained results are validated with high-performance liquid chromatography (HPLC) technique. The excellent recovery percentage and close agreement with the results of HPLC analysis proved the practicability of the present sensor. In addition, the as-prepared materials were utilized for the photocatalytic degradation of ATZ and the SCN-AuNPs nanohybrid exhibited higher photocatalytic activity with the removal efficiency of 93.6% at 90 min. Finally, the degradation mechanism was investigated and discussed.

Near-infrared fluorescent turn-on probe for hydrazine detection: environmental samples and live cell imaging.

An acetoxy naphthaldehyde conjugated benzophenoxazinium chloride chromophore-based-donor-π-acceptor (D-π-A) fluorescent probe BPN (benzophenoxazinium naphthoxy imine) displaying near-infrared (NIR) emission was reported for hydrazine detection. The chosen water-soluble benzophenoxazinium chloride chromophore has excellent photostability, a high molar extinction coefficient and fluorescence quantum yield (Φ = from 0.0075 to 0.6193), higher selectivity towards hydrazine and a longer fluorescence lifetime. In the presence of hydrazine, BPN exhibits near infrared fluorescence emission at 725 nm along with color change from light blue to red, as detected by the naked eye. Moreover, the BPN probe can selectively detect hydrazine (DL = 4.5 × 10-10 M) in a 90% aqueous DMSO solution without interfering with other analytes. As proof of real samples, the probe is successfully applied to sense hydrazine in thin layer chromatography (TLC) paper strips (both solution and vapor phases) and water and soil samples, suggesting its significant potential application. Also, due to its NIR emission and aqueous solubility, the BPN probe can be successfully used in live cell imaging with low cytotoxicity.

Highly sensitive detection of plant growth regulators by using terahertz time-domain spectroscopy combined with metamaterials.

The rapid and sensitive detection of plant-growth-regulator (PGR) residue is essential for ensuring food safety for consumers. However, there are many disadvantages in current approaches to detecting PGR residue. In this paper, we demonstrate a highly sensitive PGR detection method by using terahertz time-domain spectroscopy combined with metamaterials. We propose a double formant metamaterial resonator based on a split-ring structure with titanium-gold nanostructure. The metamaterial resonator is a split-ring structure composed of a titanium-gold nanostructure based on polyimide film as the substrate. Also, terahertz spectral response and electric field distribution of metamaterials under different analyte thickness and refractive index were investigated. The simulation results showed that the theoretical sensitivity of resonance peak 1 and peak 2 of the refractive index sensor based on our designed metamaterial resonator approaches 780 and 720 gigahertz per refractive index unit (GHz/RIU), respectively. In experiments, a rapid solution analysis platform based on the double formant metamaterial resonator was set up and PGR residues in aqueous solution were directly and rapidly detected through terahertz time-domain spectroscopy. The results showed that metamaterials can successfully detect butylhydrazine and N-N diglycine at a concentration as low as 0.05 mg/L. This study paves a new way for sensitive, rapid, low-cost detection of PGRs. It also means that the double formant metamaterial resonator has significant potential for other applications in terahertz sensing.

Ratiometric Probe for Rapid Naked Eye Detection of Toxic Hydrazine: Real Time Application in Strip Test, Spray Test and Soil Analysis.

Striking colorimetric probe (CynH) for abrupt detection of hydrazine under complete aqueous solution was achieved. The water soluble probe was designed with electron "push-pull" strategy by coupling of 4-hydroxy benzaldehyde and 2, 3, 3-trimethylindolinine. The positively charged N-propylated indolinine make the probe completely soluble in water. The probe yields eye catching selective detection of hydrazine over other competing analytes with high sensitivity. Obvious colour change was observed from colourless to appearance of bright pink colour with hydrazine. It reacts quickly with hydrazine within 2 min and makes the probe an effective candidate for practical application. The real time application was demonstrated using paper strip to detect hydrazine vapour. This probe is superior to earlier reported probes because of its effective sensing of hydrazine displayed with various applications including real-time strip based sensing, spray test and soil analysis. In all the examinations, the probe yields distinct response with rapid naked eye colour change which overcomes the drawbacks of previous reports.

Coumarin 1,4-enedione for selective detection of hydrazine in aqueous solution and fluorescence imaging in living cells.

Hydrazine is a widely used but highly toxic chemical reagent, and the development of a fluorescent probe for hydrazine detection is very meaningful. In this study, a novel coumarin-derived fluorescent probe containing a 1,4-enedione moiety for hydrazine detection was developed. The recognition of hydrazine with the probe brings about obvious fluorescence enhancement over other environmentally relevant ions and amine-containing species. The limit of detection for hydrazine is 2.7×10-8 M in aqueous solution. The fluorescence enhancement was ascribed to the cyclization reaction of the 1,4-enedione moiety of the probe and hydrazine which form a six-membered pyridazine ring and intramolecular charge transfer (ICT) mechanism. The mass spectrometry (MS), nuclear magnetic resonance (NMR) analysis and theoretical calculations confirmed the recognition produced. The probe can be used to determine trace hydrazine in real water samples. More importantly, the probe also showed good potential in detecting hydrazine by imaging of living HeLa cells.

A novel ESIPT fluorescent probe derived from 3-hydroxyphthalimide for hydrazine detection in aqueous solution and living cells.

Hydrazine is a highly toxic and flammable liquid that can damage human liver, kidney, and central nervous system. Therefore, it is valuable to seek a quick and sensitive method for hydrazine detection in environmental and biological science. Herein, a new fluorescent probe derived from 3-hydroxyphthalimide was synthesized. This probe can rapidly and selectively detect hydrazine with a low detection limit of 4.3 × 10-7 M. The recognition principle is based on hydrazine-induced acetyl deprotection and excited-state intramolecular proton transfer (ESIPT) process. Moreover, test paper and fluorescence image experiments showed that this probe had potential to monitor hydrazine in the environment and living cells.

Method validation and residue analysis of methoxyfenozide and metaflumizone in Chinese broccoli under field conditions by liquid chromatography with tandem mass spectrometry.

Methoxyfenozide and metaflumizone are insecticides used on Chinese broccoli to prevent insects and increase yield. However, the residues are potentially harmful to the environment and consumers. In this study, the quick, easy, cheap, effective, rugged, safe method with high-performance liquid chromatography with tandem mass spectrometry was modified and validated for determination of methoxyfenozide and metaflumizone in Chinese broccoli. The clean-up efficiency of different sorbents including C18 , primary secondary amine, graphitized carbon black, and carbon nanofiber was compared. Recoveries of the validated method were 71.8-94.6% with relative standard deviations of 1.5-3.2% and the limits of quantification were 0.01 and 0.005 mg/kg for methoxyfenozide and metaflumizone, respectively. A storage stability test showed almost no degradation of methoxyfenozide in Chinese broccoli, however, the degradation rate of metaflumizone was 22.9% after 10-wk storage at -20°C. In field trials in four producing regions, the dissipation of both methoxyfenozide and metaflumizone in Chinese broccoli was fast, with half-lives of only 1.0-5.1 and 0.7-2.5 days, respectively. Terminal residues after application of the two pesticides were all below 1.0 mg/kg after 5 days.

One step extraction followed by HPLC-ESI-MS/MS for multi-residue analysis of diacylhydrazine insecticides in water, sediment, and aquatic products.

A multi-residue analysis of six diacylhydrazine insecticides in water, sediment, and aquatic products was established by liquid chromatography triple quadrupole tandem mass spectrometry (LC-MS/MS). The water sample was extracted with acetonitrile by low-temperature enrichment liquid-liquid extraction technology. The sediment and aquatic products were prepared using QuEChERS technique. Method validation showed perfect linearity with correlation coefficients (R) more than 0.9992 for all insecticides, and the matrix effects were nearly negligible (-1.42% to -0.27%) for water, sediment and aquatic products. The recoveries were 80.0-99.7% at three spiked levels (0.02 ng·mL-1, 0.1 ng·mL-1, 0.5 ng·mL-1; 2.0, 10, and 50 ng·g-1) and the precisions (intra-day and inter-day precision) were lower than 5.28%, with the low LODs (3.8 ~ 9.6 pg·mL-1; 0.38-0.96 ng·g-1) and LOQs (12.7 ~ 32.0 pg·mL-1; 1.27-3.20 ng·g-1) for water, sediment, and aquatic products, indicating the good accuracy and precision of the proposed method. The applicability, efficiency, and sensitivity of this method have been proved in the analysis of six diacylhydrazine insecticides in water, sediment, and crucian carp in Rice- crucian carp - integrated planting system.

Amperometric sensor based on ZIF/g-C3N4/RGO heterojunction nanocomposite for hydrazine detection.

A dense  zeolitic imidazolate framework (ZIF) nanosheet is for the first time molded by reduced graphite oxide (RGO) and graphitic carbon nitride (g-C3N4) to fabricate an original 2D/2D/2D heterojunction (ZIF/g-C3N4/RGO nanohybrid), which is pipetted onto carbon cloth electrode (CCE) (ZIF/g-C3N4/RGO/CCE) as an electrochemical sensor. Profiting from the renowned synergistic and coupling effects, the resulting nanohybrid endows excellent electrocatalytic activity towards hydrazine. Amperometric detection reveals that the hybrid sensor possesses a low detection limit of 32 nM (S/N = 3) in a monitoring range of 0.0001 to 1.0386 mM, along with a high sensitivity 93.71 µA mM-1 cm-2. Importantly, the minimum detection concentration of hydrazine in the actual sample is lower than the maximum allowable limit of the World Health Organization (WHO) and has high reproducibility (RSD = 4.82%). As expected, the high sensing capability  of ZIF/g-C3N4/RGO combines the advantages of abundant surface-active sites and high conductivity along with 2D interfaces between ZIF, g-C3N4, and RGO nanosheets. This study provides a promising to expand 2D-based ternary nanojunction as a bridge for promoting sensing performance.Graphical abstract.

New simple molecular fluorescent probes for rapid and highly selective sensing of hydrazine by aggregate-induced emission.

With an aim towards the design of efficient and straightforward fluorescent probes for hydrazine, the synthesis of (2-acetoxyaryl) methylene diacetate derivatives (1-4) was carried out by reacting substituted aromatic α-hydroxy aldehydes with acetyl chloride and sodium acetate in excellent yields. As a preliminary investigation, the ability of probe 1 was examined for the detection of substituted aliphatic and aromatic amines, amino acids, and other ions in Britton-Robinson buffer solution (50 mM, water/ethanol v/v of 99/1 at pH 7.4). Probe 1 selectively exhibited an intense blue fluorescence with hydrazine in less than 2 minutes, whereas light green or no fluorescence was noticed with substituted amines and amino acids. Among all the probes employed (1-4) in the present study, probes 1 and 2 were found efficient towards the rapid detection of hydrazine. Furthermore, the fluorescence sensing ability of probes 1 and 2 was tested not only under varying pH conditions but also by varying water-fraction from 0-99%. Moreover, the detection limits of hydrazine using 1 and 2 were found as 8.4 and 8.7 ppb, respectively, which is less than the acceptable limit as per the standards of the US Environment Protection Agency. In this contribution, the probes 1 and 2 demonstrate rapid, selective, sensitive, and ratiometric detection of highly toxic hydrazine by OFF-ON fluorescence switch in water samples as well as living cells.

Real time detection and monitoring of 2, 4-dinitrophenylhydrazine in industrial effluents and water bodies by electrochemical approach based on novel conductive polymeric composite.

Much attention has been given to detection and monitoring of hydrazine-based compounds in recent time because of its significant negative impacts on human health and ecosystem (aquatic lives). This prompted the current study focusing on detection of 2, 4-dinitrophenylhydrazine (2, 4-dnphz) using electrochemically synthesized poly-para amino benzoic acid-manganese oxide (P-pABA-MnO2) composite film. The synthesized P-pABA-MnO2 composite film was characterized in terms of its structural and morphological properties by X-ray diffraction spectroscopy and field emission scanning electron microscopy respectively. In addition, functionalities and binding energy of p-PABA-MnO2 were confirmed using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy respectively. Finally, electrochemical properties were investigated using electrochemical impedance spectroscopy and cyclic voltammetry. The synthesized P-pABA-MnO2 displayed good electrocatalytic reduction property towards 2, 4-dnphz with ultra-low limit of detection (0.08 µM; S/N = 3) and very high sensitivity (52 µAµ-1Mcm-2). The proposed sensor based on P-pABA-MnO2 also demonstrated good stability in terms of repeatability, reproducibility and interferents effects. Lastly, the proposed sensor was satisfactorily used in detection of 2, 4-dnphz in environmental real samples.

Discriminative detection of mercury (II) and hydrazine using a dual-function fluorescent probe.

A dual-function fluorescent probe (Probe 1) was developed for discriminative detection of Hg2+ and N2 H4 . Probe 1 could discriminatively detect Hg2+ and N2 H4 through two different reaction sites, with the mechanism for Probe 1 for Hg2+ depending on a desulfurization reaction and for N2 H4 depending on the Schiff-base reaction. N2 H4 had minimal effect on Hg2+ detection in dimethyl sulfoxide (DMSO)/H2 O solution, but Hg2+ could interfere with N2 H4 detection in DMSO/buffer solution. Different concentrations of Hg2+ and N2 H4 resulted in different blue shades of Probe 1 test strips, and the shade of blue was different with the same concentration of Hg2+ or N2 H4 , as observed under ultraviolet light at 365 nm wavelength.

Determination, residue analysis, risk assessment and processing factors of tebufenozide in okra fruits under field conditions.

BACKGROUND: Ensuring the yield, quality, and profitability of okra by preventing and controlling pests with the application of insecticides has increased in the last decade. Some insecticide residues might remain in edible parts of okra (fruits) and lead to several potential human health problems. Therefore, research on the residue behaviour, risk assessment and removal approach of insecticides on okra fruits is important for food safety, together with the proper application and residual elimination of insecticides in okra. RESULTS: A simple liquid chromatography with tandem mass spectrometry (LC-MS/MS) method was established and validated for determining the tebufenozide residues in okra fruits. The recoveries of tebufenozide in okra fruits were >72% with relative standard deviations of 0.6 to 6.1%. The dissipation rates of tebufenozide were different in okra fruits cultivated under open land and glasshouse field conditions because of the discriminating humidity and temperature conditions. The dietary intake of the tebufenozide residues from okra fruit consumption for Chinese consumers was fairly low, with approximately no potential health risk. The processing factor values of washing, blanching, washing + blanching and soaking were all less than one, which indicated that these processes could effectively reduce the residual hydrazide in the okra fruit. CONCLUSION: The developed method for analysing tebufenozide in okra fruits was applicable for field studies on this insecticide. The potential health risk of tebufenozide in okra fruits could be negligible to the health of different age groups of Chinese consumers. The soaking process effectively removed tebufenozide residues from okra fruits. The obtained data will help Chinese governments establish a maximum residue limit of tebufenozide in okra and provide data for the risk assessment and removal of tebufenozide in other crops. © 2019 Society of Chemical Industry.

Residue dissipation and dietary exposure risk assessment of methoxyfenozide in cauliflower and tea via modified QuEChERS using UPLC/MS/MS.

BACKGROUND: Methoxyfenozide possesses efficacy against a variety of lepidopteron pests, including the major pests in cauliflower and tea, so it is of great importance to generalize the practical use of methoxyfenozide in the field. RESULTS: An efficient method was developed and validated in both vegetable matrix and extract-rich matrix (cauliflower and tea) using modified QuEChERS combined with UPLC/MS/MS analysis. The recoveries in cauliflower, made tea and tea shoots ranged from 94.5 to 108.0%, from 85.0 to 91.6% and from 77.3 to 82.0% respectively, with relative standard deviations (RSDs) below 17.3% in all cases. The field results showed that methoxyfenozide dissipated in cauliflower with half-life (t1/2 ) at 2.5-3.5 days and in tea with t1/2 at 1.2 days. Combining the above experimental data and statistical food intake values, the risk quotient (RQ) values were significantly lower than 1. CONCLUSION: The quantification method of methoxyfenozide in cauliflower or tea has not been established until this study. The dissipation and dietary exposure risk assessment of methoxyfenozide in cauliflower and tea were investigated in the field. Methoxyfenozide dissipated rapidly in cauliflower despite different climates, and it dissipated faster in tea. The dietary risk of methoxyfenozide through cauliflower or tea was negligible to humans. This study not only provides guidance for the safe use of methoxyfenozide but also serves as a reference for the establishment of maximum residue limits (MRLs) in China. © 2019 Society of Chemical Industry.

Oligo(ethylene glycol)-Functionalized Ratiometric Fluorescent Probe for the Detection of Hydrazine in Vitro and in Vivo.

Hydrazine induced toxicity causes serious harm to the health of humans. The detection of N2H4 in vitro and in vivo has attracted a great deal of attention, especially in the context of fluorescent probes. Although some fluorescent N2H4 probes have been reported, only a few operate in purely aqueous media and, as a result, require the use of organic cosolvents which hinders their use in analysis of real samples. In addition, most of the current N2H4 probes are either "off-on" or "on-off" types, in which it is difficult to eliminate interference from background fluorescence commonly occurring in in vitro and in vivo systems. Furthermore, some probes are unable to differentiate hydrazine from other organic amines. To address the above problems, we developed a novel oligo(ethylene glycol)-functionalized fluorescent probe for the detection of N2H4. The probe, which has a donor-π-acceptor (D-π-A)-type structure, is water-soluble, and it can be utilized to selectively detect N2H4 in both colorimetric and ratiometric mode. Furthermore, the probe is able to differentiate hydrazine from other organic amines and can be used to detect hydrazine vapor and for imaging A549 cells and zebrafish.

Effects of pretreatments on quality attributes of long-term deep frozen storage of vegetables: a review.

As one of the essential parts in human diet, vegetables are important in health keeping and their consumption increases continuously. Due to their highly perishable nature, the shelf life of fresh vegetables is considerably short, due to cellular respiration, microorganism, enzyme reaction, oxidation and so on. Therefore, short- and long-term storages of vegetables are required and various methods and technologies are applied for different commercial goals. For long-term storage, deep frozen storage is one of the most widespread used preservation methods for vegetables, as under temperatures low enough, the rate of most deteriorative reactions and microbial activities are significantly reduced. This review provides a critical comprehensive summary of long-term storage (≥6 months) vegetables under low temperatures (≤ -18 °C), and effects of the storage methods on various quality attributes of vegetables, such as texture, colour, contents of ascorbic acid, chlorophyll and carotenoids. Besides, the impacts of common pretreatments prior to freezing on the subsequent frozen storage are also briefly discussed. The current review shows that although some important biochemical attributes are more or less deteriorated and the quality loss of them is inevitable, a substantial portion of quality attributes appear to be stable during long-term deep frozen storage especially the physical parameters. Meanwhile, pretreatments prior to freezing, such as blanching process, also show significant influence on quality preservation in subsequent storage. Therefore long-term deep frozen storage can be applied as an effective storage method under proper conditions of pretreatments and storage.

A novel chemiluminescent probe for hydrazine detection in water and HeLa cells.

Hydrazine is a substance harmful to humans and the environment, necessitating the development of a sensitive and specific detection method. Herein, a novel chemiluminescent probe based on Schaap's adamantylidene-dioxetane (CL-HZ) for detecting hydrazine was synthesized and evaluated. The probe was activated by the removal of a protecting group to form free phenoxy-dioxetane, when treated with hydrazine. It then showed a noticeable and sustainable fluorescent response without excitation, with intensity increasing 51-fold in the presence of hydrazine. CL-HZ can be used in 96-well high-throughput assays for analysis of hydrazine in polluted water samples and was successfully applied for the detection of hydrazine in living cells.

Dietary risk evaluation of tetraconazole and bifenazate residues in fresh strawberry from protected field in North China.

Residues and dietary risk assessment of tetraconazole and bifenazate were investigated in strawberry under greenhouse conditions using high performance liquid chromatography (HPLC-DAD) after QuEChERs extraction in Beijing of China. The effects of different processing factors on the two pesticides were studied. The recoveries of tetraconazole and bifenazate were 87.0% and 89.1%, respectively. The dissipation curves of tetraconazole and bifenazate were in accordance with the first-order kinetic equation and the half-life were 5.92 d and 5.58 d, respectively. When the pre-harvest interval (PHI) was 3 d, the risk quotient (RQs) of both pesticides was less than 100%. Although soaking was a poor way to remove the two pesticides and heating at high temperatures increases the concentration of both pesticides, the residues of two pesticides can be effectively removed by washing after soaking. The results of dietary intake assessment indicated that potential dietary risk caused by tetraconazole and bifenazate in strawberry were acceptable for Chinese consumers.

Residue analysis of tebufenozide and indoxacarb in chicken muscle, milk, egg and aquatic animal products using liquid chromatography-tandem mass spectrometry.

We developed an analytical method using liquid-liquid extraction (LLE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) to detect and quantify tebufenozide (TEB) and indoxacarb (IND) residues in animal and aquatic products (chicken muscle, milk, egg, eel, flatfish, and shrimp). The target compounds were extracted using 1% acetic acid (0.1% acetic acid for egg only) in acetonitrile and purified using n-hexane. The analytes were separated on a Gemini-NX C18 column using (a) distilled water with 0.1% formic acid and 5 mm ammonium acetate and (b) methanol with 0.1% formic acid as the mobile phase. All six-point matrix-matched calibration curves showed good linearity with coefficients of determination (R2 ) ≥0.9864 over a concentration range of 5-50 µg/kg. Intra- and inter-day accuracy was expressed as the recovery rate at three spiking levels and ranged between 73.22 and 114.93% in all matrices, with a relative standard deviation (RSD, corresponding to precision) ≤13.87%. The limits of quantification (LOQ) of all target analytes ranged from 2 to 20 µg/kg, which were substantially lower than the maximum residue limits (MRLs) specified by the regulatory agencies of different countries. All samples were collected from different markets in Seoul, Republic of Korea, and tested negative for tebufenozide and indoxacarb residues. These results show that the method developed is robust and may be a promising tool to detect trace levels of the target analytes in animal products.

Amperometric sensing of hydrazine in environmental and biological samples by using CeO2-encapsulated gold nanoparticles on reduced graphene oxide.

CeO2-encapsulated gold nanoparticles (AuNPs) were anchored to reduced graphene oxide (RGO/Au@CeO2) by an interfacial auto-redox reaction in a solution containing tetrachloroauric acid and Ce(III) on a solid support. The resulting material was placed on a glassy carbon electrode (GCE) and used as an electrochemical hydrazine sensor at trace levels. The electrocatalytic activity of the modified GCE towards hydrazine oxidation was significantly enhanced as compared to only RGO/CeO2, or CeO2-encapsulated AuNPs, or AuNPs loaded on CeO2 modified with RGO. This enhancement is attributed to the excellent conductivity and large surface area of RGO, and the strong interaction between the reversible Ce4+/Ce3+ and Auδ+/Au0 redox systems. The kinetics of the hydrazine oxidation was studied by electrochemical methods. The sensor, best operated at a peak voltage of 0.35 V (vs. saturated calomel electrode), had a wide linear range (that extends from 10 nM to 3 mM), a low detection limit (3.0 nM), good selectivity and good stability. It was successfully employed for the monitoring of hydrazine in spiked environmental water samples and to in-vitro tracking of hydrazine in cells with respect to its potential cytotoxicity. Graphical abstract CeO2-encapsulated gold nanoparticles anchored on reduced graphene oxide with the strong interaction between the reversible Ce4+/Ce3+ and Auδ+/Au0 reductions can be used for sensitive detection of hydrazine with detection limit of 3 nM and good selectivity in environmental and biological samples.