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A facile colorimetric method for rapid detection of putrescine (Put) and cadaverine (Cad) based on the peroxidase-like activity of (Fe,Co) codoped-CDs was developed. With the enzymatic hydrolysis by diamine oxidase (EC 1.4.3.6, DAO), Biogenic amines (BAs) were decomposed to produce H2O2 which oxidizes 3,3',5,5'-tetramethyl-benzidine with the catalysis of (Fe,Co)-codoped CDs. By means of principal component analysis, Put and Cad were differentiated from BAs and their total amounts were detected by measuring the spectral absorption at 652 nm with a linear range from 0.25 to 10 mg kg−1. The colorimetric method was applied to the detection of Put and Cad in various fish samples with a detection limit ((3σ/k, n = 9)) of 0.06 mg kg−1. Besides verifying with HPLC, the recoveries of the colorimetric method were also tested by spiking standards at three levels with the range of 98.2%–115.7%, indicating that the established colorimetric method was accurate and sensitive.

A colorimetric method combining WSe2 nanosheets with peroxidase-like activity and xanthine oxidase (XAO) was developed for xanthine detection. XAO catalyzes xanthine oxidation and thereby induces H2O2 production. WSe2 nanosheets can catalyze the oxidization of 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2 and produce a blue oxidation product of TMB (oxTMB). Under optimal conditions, the colorimetric method showed a linear response for xanthine detection in a range of 0.01–0.5 mM. The limit of detection was 4.37 μM. The recovery rate from spiked serum samples was 95.5%–115.5%. Therefore, our strategy provides new opportunities for the detection of xanthine and evaluation of health care.

Rapid detection of hypoxanthine (Hx), an important freshness indicator of aquatic products, is still urgent and challenging. In the present study, a colorimetric method for the rapid detection of Hx in aquatic products was established based on the peroxidase-like activity of cobalt-doped graphite phase carbon nitride (Co-doped-g-C3N4). After calcination of the mixture of melamine, cobalt chloride, potassium chloride and sodium chloride, Co-doped-g-C3N4 was obtained with strong peroxidase-like activity and good dispersity. Through the decomposition of Hx by xanthine oxidase, the generated hydrogen peroxide (H2O2) was detected based on the oxidation reaction of H2O2 and 3,3′,5,5′-tetramethylbenzidine catalyzed by Co-doped-g-C3N4. The content of Hx could be directly measured by monitoring the spectral absorbance at 652 nm with a linear range of 2.50–153.1 mg kg−1 and a detection limit of 1.84 mg kg−1 calculated based on 3σ/K (n = 9). The established method was applied for the detection of Hx content in various aquatic products at different storage times after execution, and the data were validated by the HPLC method. The results showed that the Hx measurement by the established method was sensitive, accurate and reliable, and could be used for the rapid determination of the freshness of aquatic products at an early stage.

Functional DNAs-functionalized magnetic beads (MBs) offer great potential in bioanalysis field because of their target recognition and magnetic separation functions. However, the recognition capability and hybridization affinity of DNA probes often suffer from limited available space, poor probe conformation and non-selective adsorption. To overcome these limitations, we herein used aptamer-pendant DNA tetrahedron nanostructure-functionalized MBs (TETapt-tet MBs) to develop a target-response fluorescence method with tetracycline (TET) as a model. In the absence of TET, 6-carboxy-X-rhodamine-labeled complementary DNAs (ROX-cDNAs) were assembled on the surface of MBs. Upon the addition of target TET, the ROX-cDNAs were separated and released from the MBs to generate fluorescence signal. The limit of detection and limit of quantification for TET were found to be 6 pg mL−1 and 20 pg mL−1, respectively. Compared with ssDNA-functionalized MBs surface, the designed DNA tetrahedron nanostructure-based surface could decrease the hybridization time and reduce false positives, ensuring the accuracy of TET detection in complex samples. The presented method was successfully employed for TET detection in honey samples. Moreover, this functionalization strategy could be extended to detect multiple antibiotics by simply substituting different aptamer sequences. Therefore, the proposed method has great potential in the field of food safety and public health.

Rapid detection of malachite green (MG) by fluorescence probes of CdTe quantum dots (QDs) coated with molecularly imprinted polymer (MIP) has been reported, but low sensitivity, slow response and narrow linear range were the main disadvantages for these MIP@QDs probes. Here, an ultra-sensitive ratiometric fluorescence probe based on self-assembly functionalized polystyrene (PS) and core-shell structured MIP was developed for the detection of MG in fish. After modified with poly(diallyldimethylammonium chloride) and hexadecyl trimethyl ammonium bromide, CdTe QDs and silica encapsulated carbon quantum dots (CDs@SiO2) with negative charges, used as detection and reference fluorophores, were respectively self-assembled on the surface of PS to form PS-QDs&CDs. And a core-shell structured MIP layer was fabricated on the surface of PS-QDs&CDs to form a ratiometric fluorescence probe of MIP@PS-QDs&CDs with sol-gel method using MG, (3-aminopropyl)triethoxy-silan and tetraethyl orthosilicate as template, functional monomer and cross-linker, respectively. With intensive fluorescence densities of QDs&CDs in nucleus, the fluorescence emission of probe at λem of 630 nm could be linearly quenched by MG, while the fluorescence emission at λem of 430 nm remained unchanged. The probe of MIP@PS-QDs&CDs owned good fluorescence stability (RSD ≤2.3%), fast response time (5 min), wide linear range (0.1–32 μmol L−1) and low detection limit (5.6 μg kg−1), and has been applied to the detection of MG in fish samples with recoveries of 94.3–110.2%. The result validated that the as-prepared probe of MIP@PS-QDs&CDs had an excellent performance for MG detection in fish samples.

Fluorescence-based aptasensors possess high sensitivity but are complicated and usually require multistep labeling and modification in method design, which severely limit the practical applications. Here, a label-free fluorescence-based aptasensor, consisting of aptamer, gold nanoparticles (AuNPs), and cadmium telluride (CdTe) quantum dots (QDs), was developed for the detection of sulfadimethoxine (SDM) in water and fish based on the specific recognition of SDM-aptamer and the inner filter effect of QDs and AuNPs. In the absence of a target, AuNPs dispersed in salt solution because of the aptamer protection, which could effectively quench the fluorescence emission of QDs, while in the presence of SDM, AuNPs aggregated due to the specific recognition of SDM-aptamer to SDM, which resulted in fluorescence recovery. A linear response of SDM concentrations in the range of 10–250 ng mL−1 ( R2 = 0.99) was obtained, and the detection limit was 1.54 ng mL−1 (3σ, n = 9), far below the maximum residue limit (100 ng mL−1) of SDM in edible animal tissues regulated by China and the European Commission. The fluorescence-based aptasensor was applied to the detection of SDM in aquaculture water and fish samples with high accuracy, excellent precision, and ideal selectivity. The results indicated that the developed aptasensor was simple in design, easy to operate, and could be used to detect rapidly and accurately SDM in water and fish samples.

A rare earth complex Eu(MAA)3Phen was prepared with methacrylic acid and o-phenanthroline as ligands under mild conditions. The complex has a fluorescence emission centered at 618 nm with a half-peak width of 15 nm. Since the emission peak of the complex matches the absorption peak of malachite green (MG), the fluorescence of the complex will be quenched by MG through the fluorescence resonance energy transfer effect. The fluorescence testing conditions for MG were optimized based on fluorescence intensity and fluorescence quenching efficiency. The FRET efficiency was calculated to be 0.21. Under the optimal conditions, the response time was only 5 min. Compared with sulfonamides, chloramphenicol and other banned fishery drugs, the complex exhibited the highest quenching efficiency to MG. The linear range was 0.5–20 μmol L−1, and the detection limit was 117.29 nmol L−1(3σ/S, n = 9). This complex was used to detect MG residue in aquaculture water, and the recoveries were between 96.10% and 98.76%, indicating that the prepared fluorescent probe could be used for the rapid detection of MG in aquaculture water.

Tetracycline (TET) is a broad-spectrum antibiotic, which is frequently used in the prevention and treatment of animal diseases, feed additives, and so on. However, its residue and accumulation in animal-derived foods could cause several side effects to the human body. Herein, we fabricated TET aptamer-pendant DNA tetrahedral nanostructure-functionalized magnetic beads (Apt-tet MBs) as a probe to detect TET. In the presence of target TET, DNA primer was released from Apt-tet MBs since the TET aptamer could specifically bind TET. Next, the separated DNA primer could effectively initiate rolling circle amplification (RCA) reaction and generate a long tandem single-stranded sequence. Finally, with SYBR Green I as the fluorescence dye, the fluorescence signal could be detected by detection probes through hybridizing the RCA product. Under optimal conditions, the fluorescent signal increased with the increasing target TET concentration within the 5 orders of magnitude dynamic range from 0.001 to 10 ng mL-1. The detection limit was calculated to be 0.724 pg mL-1 and the method showed high selectivity toward TET among different antibiotics. More impressively, this method was employed for TET determination in fish and honey samples. The as-obtained results were consistent with those of ELISA kits, holding great potential in the field of food analysis.

Herein, we report a facile method for cholesterol detection by coupling the peroxidase-like activity of polypyrrole nanoparticles (PPy NPs) and cholesterol oxidase (ChOx). ChOx can catalyze the oxidation of cholesterol to produce H2O2. Subsequently, PPy NPs, as a nanozyme, induce the reaction between H2O2 and 3,3',5,5'-tetramethylbenzidine (TMB). Under optimal conditions, the increase is proportional to cholesterol with concentrations from 10 to 800 μM in absorbance of TMB at 652 nm. The linear range for cholesterol is 10-100 μM, with a detection limit of 3.5 μM. This reported method is successfully employed for detection of cholesterol in human serum. The recovery percentage is ranged within 96-106.9%. Furthermore, we designed a facile and simple portable assay kit using the proposed system, realizing the on-site semiquantitative and visual detection of cholesterol in human serum. The cholesterol content detected from the portable assay kit were closely matching those obtained results from solution-based assays, thereby holding great potential in clinical diagnosis and health management.

A magnetic molecularly imprinted silica solid was obtained by sol-gel polymerization for the separation of domoic acid. The solid showed rapid adsorption kinetics with an adsorption equilibrium time of 5 min. The solid showed affinity to domoic acid under the interference of tryptophan and could be repeatedly used for 5 times at least. The solid was used as a solid-phase-extraction sorbent for the extraction of domoic acid from clam samples before measurement with liquid chromatography. The detection limit of 0.20 mg kg−1 was lower than the allowable limits in several countries or areas. The recoveries in the spiked samples were 88% approximately., Analytical Chemistry, molecularly imprinted silica; Magnetic; Sol-gel, HPLC; Domoic acid.

A method for the aptamer-based determination of chloramphenicol (CAP) was developed by exploiting the peroxidase mimicking activity of hemin. The method includes two hemin-modified DNA probes termed P1 and P2. P1, which was modified at its 5′ end with one hemin monomer, contains the CAP-binding sequence. The hybridization between P1 and P2 brings the two hemin monomers in close proximity, resulting in the formation of a hemin dimer with low peroxidase mimicking activity. The duplex structure was dehybridized in the presence of CAP. The formed hemin monomer featured a strong peroxidase mimicking activity and catalyzed the conversion of non-fluorescent tyramine into fluorescent dityramine by hydrogen peroxide. Fluorescence (with an excitation/emission maxima at 320 and 410 nm, respectively) increased linearly in the 0.1 ng mL−1 to 10 ng mL−1 CAP concentration range. The detection limit based on the 3σ/k criterion reached 0.07 ng mL−1. The proposed assay was successfully employed for CAP detection in (spiked) honey samples with recoveries of 94.3–117.2%. Given its high sensitivity and good stability, this method shows potential in providing a platform for antibiotic detection.

Due to complex matrixes and specific reagent deficiency, the rapid detection of histamine is still a challenge to date. Based on the high peroxidase-like activity of iron-cobalt co-doped carbon dots, an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) was established for histamine detection using the mimic enzyme labeled with histamine antibody (His-Ab). Through the competitive binding of the labeled His-Ab to solid-phase and sample antigens, histamine content was detected with a linear range of 2.5–150 μg mL−1. The detection limit based on 3σ/K was 0.50 mg kg−1, which was much lower than those of commercial His-kit and HPLC methods. The ic-ELISA method was applied to histamine detection in fish samples with the recovery of (103.4 ± 0.5)%, which was in accord with those of commercial His-kit and HPLC methods. The results indicated that the established ic-ELISA method was suitable for rapid detection of histamine in fish samples with high accuracy, sensitivity and stability.

Higher alcohols such as butanol (C4 alcohol) and hexanol (C6 alcohol) are superior biofuels compared to ethanol. Clostridium carboxidivorans P7 is a typical acetogen capable of producing C4 and C6 alcohols natively. In this study, the composition of trace metals in culture medium was adjusted, and the effects of these adjustments on artificial syngas fermentation by C. carboxidivorans P7 were investigated. Nickel and ferrous ions were essential for growth and metabolite synthesis during syngas fermentation by P7. However, a decreased dose of molybdate improved alcohol fermentation performance by stimulating carbon fixation and solventogenesis. In response to the modified trace metal composition, cells grew to a maximum OD600nm of 1.6 and accumulated ethanol and butanol to maximum concentrations of 2.0 and 1.0 g/L, respectively, in serum bottles. These yields were ten-fold higher than the yields generated using the original composition of trace metals. Furthermore, 0.5 g/L of hexanol was detected at the end of fermentation. The results from gene expression experiments examining genes related to carbon fixation and organic acid and solvent synthesis pathways revealed a dramatic up-regulation of the Wood–Ljungdahl pathway (WLP) gene cluster, the bcs gene cluster, and a putative CoA transferase and butanol dehydrogenase, thereby indicating that both de novo synthesis and acid re-assimilation contributed to the significantly elevated accumulation of higher alcohols. The bdh35 gene was speculated to be the key target for butanol synthesis during solventogenesis.

Background Most of patients diagnosed with Hepatocellular carcinoma (HCC) have advanced diseases and many are not eligible for curative therapies. There is a growing evidence suggesting that combination treatment of PD-1/PD-L1 inhibitors and tyrosine kinase inhibitors (TKIs) becomes a prospective trend for advanced HCC. For those HCC patients with sorafenib resistance, the efficacy of regorafenib combined with PD-1/PD-L1 inhibitors remains unclear. Case presentation: Herein, we represent a case of HCC with lung metastasis in the setting of HBV-induced liver cirrhosis responding dramatically to the combination treatment of sorafenib-regorafenib sequential and PD-1 inhibitor after initial liver resection. A 56-year-old man diagnosed with AFP-negative HCC underwent liver resection in September 2015, and was found to have solitary liver recurrence and lung metastases in March 2017. He received microwave coagulation therapy and trans-arterial chemoembolization (TACE) for liver tumor and treatment was started with sorafenib 400 mg twice daily for controlling lung metastases. In December 2018, abdominal computerized tomography (CT) scan showed two new lesions in liver. In March 2019, disease progression of lung metastases was measured and he received 160 mg regorafenib once daily. After a short period of partial response, he started treatment with regorafenib 160 mg in combination with sintilimab (200 mg, 3 weeks as a cycle) in December 2019 due to disease progression. Surprisingly, after 5 cycles of sintilimab injection, it showed complete response in target lesions. There is no clinical evidence of disease progression and the side effects were mild and well tolerated. The current overall survival is 57 months. Conclusion Data from this clinical case report suggests that combination therapy of regorafenib and PD-1 inhibitor is a promising therapeutic option for the treatment of advanced HCC. This is the first article reporting the complete response to regorafenib combination therapy with PD-1inhibitor for sorafenib-regractory HCC.

Organophosphorus pesticides can prevent or eliminate various pathogenic bacteria, insects, and weeds, and thus they are widely applied in agricultural production. However, illegal use and issues with organophosphorus pesticide residues contribute to global environmental pollution and pose a threat to public health safety. In this study, we developed a sensitive glyphosate (Glyp) fluorescence detection method using papain-stabilized gold nanoclusters (papain-AuNCs) as the fluorescence probe and a tyrosinase (TYR)/dopamine (DA) fluorescence-quenching system. The TYR catalyzed the oxidized conversion of DA into DA chrome, which served as an electron acceptor to quench the fluorescence of papain-AuNCs. However, Glyp inhibited the activity of TYR, thereby preventing DA oxidization and leading to the fluorescence recovery of papain-AuNCs. Under the optimum conditions, the fluorescence intensities of papain-AuNCs exhibited a good linear relationship with the concentration of Glyp in the range of 0.04–0.4 ng·mL−1, and the limit of detection for Glyp was 0.035 ng·mL−1. Furthermore, a paper-based sensor was constructed using the proposed system, which enabled on-site visual and semiquantitative detection of Glyp residues in tap-water samples. Overall, our strategy provides new opportunities for detection of organophosphorus pesticides and evaluation of environmental security.

A magnetic material, F e 3 O 4 @ Z r O 2 , was used to enrich an organophosphorus pesticide, fenthion. After enrichment the F e 3 O 4 @ Z r O 2 was treated with NaOH to elute and hydrolyze fenthion. The hydrolysis products, orthophosphate ions, combine to molybdate ions to yield molybdophosphoric acid, which was further reduced with S n C l 2 to obtain a blue phosphatemolybdate. The content of orthophosphate ions as well as fenthion can be determined through the spectrophotometric method. Adsorption and elution conditions were optimized to obtain an enrichment factor of 12.5. The proposed composite method was successfully used to analyze the fenthion residues on the skin of cucumber and apple samples. The limit of detection was as low as 0.037 mg/Kg, which was close to that of the gas chromatography–mass spectrometer method. The method was simple, rapid, and economic, suitable for the rapid screen of fenthion and the other organophosphorus pesticide in mass samples.

A fluorescent probe based on CdTe/CdS quantum dots coated with molecularly imprinted polymer shell was designed. The fluorescence emission of the probe was at 622 nm. The probe presented selective ...

In this paper, we present the synthesis, crystal structures and magnetic properties of three complexes with formulae [Cu3Ln2(L)2(teaH)2(N3)2Cl2]·xCH3CN (H2L = N1,N3-bis(3-methoxysalicylidene)diethylenetriamine, teaH3 = triethanolamine; Ln = Ho, x = 3 for 1, Ln = Dy, x = 2 for 2 and Ln = Gd, x = 3 for 3), and the structural topologies of 1–3 are unprecedented. The structural analyses revealed that the metal ions in 1–3 formed a kite-like topology with Ln1, Ln2 and Cu1 located on the body, while Cu2 and Cu3 located on both wings. The dc data of 3 were fitted, which showed that the magnetic couplings are antiferromagnetic between CuII and between GdIII ions, while they are ferromagnetic between CuII and GdIII ions. AC magnetic susceptibility studies for 1 and 2 indicated that both complexes exhibit frequency dependent χ′′ signals at low temperature, but no χ′′ peaks were observed, which may be due to the deviation from ideal geometry for HoIII in 1 and DyIII in 2 and the presence of weak magnetic couplings between paramagnetic ions within the two complexes. For 3, the ac magnetic susceptibilities with zero dc fields show no frequency dependent χ′′ signals because of the isotropy of GdIII. The orientation of the easy magnetization axes of two DyIII in 2 was estimated using the Magellan program, indicating that the magnetic anisotropy axes for Dy1 and Dy2 are almost perpendicular with the angle of 86.630°.

A facile and practical ratiometric fluorescence probe based on two CdTe quantum dots (QDs) coated with molecularly imprinted polymers (MIPs) was prepared for the detection of trace malachite green (MG) in fish. Two CdTe QDs coated with MIPs were fabricated by a one-pot method using MG, (3-aminopropyl) triethoxysilane (APTES) and tetraethyl orthosilicate (TEOS) as template, functional monomer, and cross-linker, respectively. CdTe QDs with λem 530 nm (gQDs) and 630 nm (rQDs) were used as the referential fluorophore and target sensitive fluorophore, respectively. The fluorescence intensity of gQDs remained unchanged in the presence of MG, while the fluorescence of rQDs could be quantitatively quenched by MG based on the strategy of fluorescence resonance energy transfer. The ratiometric fluorescence probe (MIPs@gQDs&rQDs) was characterized by transmission electron microscopy and Fourier transform infrared spectroscopy. The linear range of MG detection was 0.1–32 μmol L−1 with a detection limit of 8.8 μg kg−1. The constructed probe has been successfully applied to the detection of MG in fish with the recoveries of 92.3–109.1%, which were validated by the method of HPLC. The result indicated that the probe possessed rapid response, wide linear range, high sensitivity, and relatively high selectivity, and was low-cost and easy in operation in the detection of MG in fish samples.

Biomass fuels remain main energy sources in many remote rural regions, but potential health hazards from exposure to biomass combustion fumes have not been adequately assessed. Combustion of biomass fuels generates abundant polycyclic aromatic hydrocarbons (PAHs); hence residential exposure to PAHs can be used to evaluate the potential health risk to remote rural populations. The present study selected rural Tibetans to address the above-mentioned issue. Samples of indoor air and dust, human urine and local foods (Tsampa flour and buttered tea) were collected from five rural households in Langkazi County, an agricultural and pasturing region in Tibet of China in the summer season, which represented the best-case scenario as no heating was required. Residential exposure to PAHs by adults amounted to benzo[a]pyrene equivalent (BaPeq) dosages of 110–760, 1.2–50 and 0.5–23 ng d−1 for ingestion, inhalation and dermal contact, respectively. Daily intakes of naphthalene, fluorene, phenanthrene and pyrene estimated from urinary monohydroxy PAH metabolites and from diet and inhalation exposure to PAHs were comparable (3.9, 1.9, 12 and 3.3 μg d−1 versus 9.5, 2.5, 5.1 and 1.1 μg d−1), indicating the utility of external exposure in assessing daily intake of PAHs. The median incremental lifetime cancer risk was 32 × 10−6 (95% confidence interval: 0.7–73 × 10−6) for ingestion and 2.4 × 10−6 (95% confidence interval: 0.02–12 × 10−6) for inhalation and dermal contact combined, indicating moderate to slight potential cancer risk. Diet is the dominant source of health hazards for rural Tibetans, but cooking fumes also present a meaningful concern. The present study demonstrates that the pristine lifestyles of remote rural residents may be of global health concern, and merit further investigations. Keywords: Biomass fuel, Rural Tibet, Polycyclic aromatic hydrocarbons, Health risk, Life style

Malachite green (MG) is an industrial dye, but has been once abused in aquaculture for disease treatment. Because MG and its metabolite, leucomalachite green (LMG), present great harm to human health, it is essential to rapidly and accurately detect MG and LMG residues in aquatic products. However, the simultaneous screening of MG and LMG is still a challenge to date. In this work, a dual-template molecularly imprinted polymer (MIP) coated CdTe QDs was developed and applied as a nano-probe to simultaneously detect MG and LMG in fish samples via normal and synchronous fluorescence quenching. The molar ratios of templates (MG and LMG) to monomer (APTES) and cross-linker (TEOS), and the amount of CdTe QDs in the probe preparation were optimized. A normal fluorescence emission at 600 nm could be linearly quenched by MG, while the synchronous fluorescence emission at the wavelength interval of 340 nm could be quenched by both LMG and MG. The detection limits of MG and LMG were 17 nmol L−1 and 28 nmol L−1 (3σ, n = 9), respectively. Based on the equations of Stern-Volmer, MG and LMG could be simultaneously detected without any conversion treatment. The recoveries of MG and LMG in fish samples ranged from 92% to 107% and from 91% to 108%, respectively. The results demonstrated that the as-prepared dual-template CdTe@MIP could be used as a fluorescent probe to rapidly and simultaneously detect MG and LMG in fish samples.

A magnetic fluorescent probe of CdTe QDs/nano-Fe3O4@MIPs was prepared using CdTe QDs and Fe3O4 nanoparticles as co-nucleus and molecularly imprinted polymers (MIPs) as specific recognition sites based on a reverse microemulsion method. With the specific enrichment and magnetic separation properties, the probe of CdTe QDs/nano-Fe3O4@MIPs was used to detect malachite green (MG) in fish samples. The TEM analysis showed that the particles of CdTe QDs/nano-Fe3O4@MIPs were spherical with average diameter around 53 nm, and a core-shell structure was well-shaped with several Fe3O4 nanoparticles and CdTe QDs embedded in each of the microsphere. Quick separation of the probes from solutions could be realized with a magnet, indicating the excellent magnetic property of CdTe QDs/nano-Fe3O4@MIPs. The probe exhibited high specific adsorption towards MG and excellent fluorescence emission at λem 598 nm. The fluorescence of CdTe QDs/nano-Fe3O4@MIPs could be linearly quenched by MG at the concentrations from 0.025 to 1.5 μmol L−1. The detection limit was 0.014 μmol L−1. The average recovery of spiked MG in fish samples was 105.2%. The result demonstrated that the as-prepared CdTe QDs/nano-Fe3O4@MIPs could be used as a probe to the detection of trace MG in fish samples.

This study attempted to fabricate a novel colorimetric method for the quantitative detection of malachite green (MG) residues in fish and water samples. Based on the recognition of the detection target and the enhancement of the peroxidase-like activities of Fe3O4NPs by MG-aptamer, a colorimetric method was established for MG detection. The detection limit (3α/κ, n = 9) was 16.7 μg kg–1, and the detection linear range was 0.06–2.38 μmol L–1. The recovery rates by standard addition in fish and water ranged from 90.1% to 119% with standard deviations (n = 3) of less than 6.6 %, and was well validated by a HPLC method. The detection procedure could be completed within 1 h. Therefore, the detection method was simple, stable, and reliable, and could be used to detect MG residues rapidly and accurately in fish and aquaculture water.

A novel fluorescence nanoprobe using CdTe quantum dots as signal sources coated with a molecularly imprinted polymer was synthesized by a reverse microemulsion method. The nanoprobe was designed for the detection of leucomalachite green (LMG) in fish samples via synchronous fluorescence quenching based on the inner filter effect. LMG, (3-aminopropyl) triethoxysilane and tetraethyl orthosilicate were used as the template, functional monomer and cross-linker respectively in the probe. A synchronous fluorescence emission of the probe at 260 nm was observed when the wavelength interval was set as 340 nm, and the synchronous fluorescence could be linearly quenched with LMG at concentrations ranging from 0.1 to 20 μmol L−1. The as-prepared nanoprobes were nearly spherical with a diameter of about 50 nm. The detection limit was 23 nmol L−1 (3σ, n = 9) and the recoveries ranged from 96.2% to 104.9% for the fish samples. The results illustrated that the nanoprobe could be used for trace LMG measurement in fish samples.

In this work, a simple, low cost and sensitive voltammetric sensor was developed for the simultaneous detection of lead (Pb 2+ ), cadmium (Cd 2+ ), and zinc (Zn 2+ ) ions based on a disposable carbon fiber rod (CFR). The important factors to enhance the sensing property were creation of a clean surface by dealing with CFR at a high potential and electrochemical deposition of bismuth (Bi) film to improve the accumulation of heavy metal ions. The morphology and conductivity of such activated CFR was characterized by scanning electron microscopy and electrochemical impedance spectroscopy, respectively. In terms of application, differential pulse anodic stripping voltammetry (DPASV) was employed for the simultaneous detection of Pb 2+ , Cd 2+ , and Zn 2+ on Bi film-coated activated CFR. Experimental parameters, such as the pH value of buffer solution, stirring speed and enrichment factors were optimized. Under optimal conditions, the DPASV peak currents showed good linear relationships with Pb 2+ , Cd 2+ and Zn 2+ concentrations in the range of 0.5–2.25 μg/L, 0.5-4.0 μg/L and 1.0–4.0 μg/L with detection limits of 0.1, 0.3 and 1.0 μg/L (S/N = 3), respectively. Finally, the proposed analysis system was successfully utilized for the simultaneous detection of Pb 2+ , Cd 2+ , and Zn 2+ contents in rice samples. This study indicated that Bi film-coated activated CFR based DPASV sensor can be a promising and reliable tool for rapid analysis of emergency pollution affairs of heavy metal ions in food.

A novel fluorescent probe based on CdTe QDs coated with molecularly imprinted polymers (MIP) was prepared for the determination of leucomalachite green (LMG) with the method of synchronous fluorescence quenching. When the wavelength interval of excitation and emission positions (Δl) was set as 340 nm, the strongest synchronous fluorescence emission of MIP-coated QDs was achieved at 260 nm, enabling the maximum fluorescent quenching of LMG because of the inner filter effect. According to this principle, a synchronous fluorescence quenching method for the rapid detection of LMG in fish was developed. MIP-coated QDs were synthesized using acrylamide (AM) and ethylene glycol dimethacrylate (EGDMA) as functional monomers and cross-linker, respectively. MIP-coated QDs with an average diameter around 67 nm were obtained at the optimum conditions (the molar ratio of 1:8:20 of LMG, AM and EGDMA, 60 mL of acetonitrile, 28 h of polymerization time). The synchronous fluorescence of MIP-coated QDs was linearly quenched by LMG at concentrations from 0.1 to 20 μmol L −1 . Detection limit was 30 nmol L −1 (3 σ , n = 9) with spiked recoveries from 94.0% to 107.8% in fish samples. The results indicate that the method can be applied to the accurate and rapid detection of LMG residues in fish samples.

A fluorescent probe based on CdTe quantum dots (QDs) coated with molecularly imprinted polymers (MIPs) was fabricated for the determination of malachite green (MG) by the strategy of fluorescence resonance energy transfer (FRET). The MIP-coated QDs were synthesized through precipitation polymerization using acrylamide and ethylene glycol dimethacrylate as monomer and cross-linker, respectively. The optimum molar ratio of MG, monomer and cross-linker was 1:8:40 in 60 mL of acetonitrile, and the polymerization time was 28 h. The MIP-coated QDs, with an average diameter around 290 nm, showed excellent fluorescence emission in 500–700 nm at λ ex 370 nm. The probe exhibited fluorescence quenching response to MG selectively within only 5 min at the concentrations from 0.1 to 20 μmol L −1 . The fluorescent probe was successfully used to detect MG in water and fish samples with a detection limit of 0.059 μmol L −1 (3 σ , n = 9). The spiked recoveries, from 94.8% to 98.1% for water samples, and 98.1% to 106.2% for fish samples, respectively, indicated that the as-prepared MIP-coated QDs could be used as a fluorescent probe to detect MG rapidly in water and fish samples.

A fluorescence probe was delicately designed for the detection of malachite green (MG) in water and fish samples. Through the electrostatic self-assembly of CdTe QDs on the surface of polystyrene (PS) microspheres, the fluorescence signal was amplified. After grafting molecularly imprinted film, the fluorescence probe of MIP@PS@CdTe was fabricated and applied to the detection of MG based on fluorescence quenching. The linear range of MG detection was 0.01–20 μmol L−1, and the detection limit was 4.7 nmol L−1 (3σ, n = 9) which was much lower than those of the previous reports. The recoveries of MG in aquaculture water and fish samples ranging from 87.6% to 105.4% illustrated that the detection by MIP@PS@CdTe probe was accurate and reliable.

In this paper, molecular imprinting and photonic crystal techniques were combined to construct a four-channel sensor array for the simultaneous identification of various sulfonamides. The assay was composed of four units. Three of these units were prepared using sulfaguanidine, sulfamethazine, or sulfathiazole as template molecules. The fourth unit was prepared without a template molecule. The preparation was optimized to obtain maximum identification with a molar ratio of template, monomer, and cross-linker of 1:50:10. The response time was as short as 10 min. For demonstration, six sulfonamides were selected as analytes. The Bragg diffraction patterns of analytes at different concentrations were measured using the sensor array. Data obtained were analyzed using linear discrimination analysis (LDA) and principal component analysis (PCA). LDA can be applied for SAs discrimination. The message ratios of 87.6%, 94.4%, and 95.8% for six SAs at 10−4 mol L−1, 10−6 mol L−1, and 10−8 mol L−1 were achieved using LDA. The sensor array identified the mixture containing various SAs with an LDA coefficient of 86.1%, thereby indicating that the sensor array had a strong anti-interference ability. The sensor array was used to identify six SAs in fish samples. The measured data in spiked samples were consistent with the fingerprint collected from standard solutions. The accuracy rate reached 90.9%, indicating that the array can be used to identify SAs from food samples.

A dichromatic label-free aptasensor was described for sulfadimethoxine (SDM) detection. Compared with the binding of SDM-aptamer to SDM, the higher affinity of aptamer to cDNA may result in the hybridization of dsDNA. In the presence of SDM, the aptamer specifically binds to SDM, leading to a blue color of AuNPs in deposit and fluorescence at 530 nm in supernatant after adding cDNA and SGI. With no target of SDM, AuNPs protected with the aptamer re-disperse in PBS with a red color, and no fluorescence occurs in supernatant. Based on the principle, SDM can be quantitatively detected through both fluorescent emission and AuNPs color changes with recoveries ranging from 99.2% to 102.0% for fish and from 99.5% to 100.5% for water samples. An analytical linear range of 2–300 ng mL−1 was achieved with the detection limits of 3.41 ng mL−1 for water and 4.41 ng g−1 for fish samples (3σ, n = 9).

To date, the speciation analysis of heavy metals in organs is still a challenge because these species are labile in vitro and scarce of the reference materials. In the present study, cadmium (Cd) species in marine shellfish were investigated with size exclusion chromatography (SEC) hyphenated with inductively coupled plasma mass spectrometry (ICP-MS), by which three Cd species in marine short-necked clam were observed. After pre-fractionation with a home-made Sephadex column, the Cd binding species were further characterized with SEC coupled with electrospray ionization quadrupole - time of flight mass spectrometry (ESI-Q-TOF-MS). The results showed that Cd species with 32,695 Da was the maximum Cd-binding molecule in the clam. Several metallothionein (MTs)-like Cd-binding proteins including a main species with molecular weight of 19,236 Da were observed. Some small Cd species with molecular weights less than 1000 Da were also observed in the clam. In order to verify the reliability of the two hyphenated methods, a standard reference material of Zn-binding MTs was analyzed at the same conditions. The results demonstrated that the two hyphenated methods of SEC-ICP-MS and SEC-ESI-Q-TOF-MS were practical to characterize the Cd species in marine shellfish.

A magnetic molecularly imprinting polymer for domoic acid was fabricated. Synthesis conditions were optimized. The polymer particles have high magnetization for rapid magnetic separation. The apparent maximum absorption amount and dissociation constant of the polymer were 1,600 µg g−1 and 20.6 µg mL−1, respectively. The polymer retained 90% of adsorption amount after 5 times of repeated use. It was used as an adsorbent for purification and HPLC detection of domoic acid in shellfish with a detection limit of 0.050 µg g−1. Thus, the polymer could be applied to the sample pretreatment of aquatic products.

A new family of octanuclear Cu–Ln complexes, [Cu6Ln2(tea)2{(py)2CO2}3Cl6]·xH2O (Ln = Dy (1), Tb (2), Ho (3), Er (4), Gd (5); x = 1 for 1, 3 and 5, x = 0 for 2 and x = 7 for 4; (py)2CO2H2 = the gem-diol form of di-2-pyridyl ketone, teaH3 = triethanolamine), has been synthesized and characterized by single-crystal X-ray diffraction, elemental analyses, IR and magnetic properties. These complexes are all isostructural and were obtained by following a self-assembly reaction involving CuCl2·2H2O, Ln(NO3)3·6H2O, di-2-pyridyl ketone, triethanolamine and triethylamine in acetonitrile at room temperature. Single-crystal X-ray diffraction analyses indicate that the LnIII ions in these complexes are seven-coordinate, which is rare in 3d–4f complexes and 4f complexes. The geometries of LnIII in these complexes severely deviate from capped octahedrons. Moreover, coordination sites of Ln were occupied by two (py)2CO22− and one tea3− ligands, without the presence of coordinated solvent molecules such as H2O and small anions such as NO3− ions, which is also rare in 4f ions complexes. The direct-current magnetic susceptibilities show that the ferromagnetic coupling interactions between CuII and Ln ions are presented by fitting the data of 1/χMversus T using the Curie–Weiss law and fitting the data of χMT versus T of 5 (Gd) using PHI program. AC magnetic measurements of 1–5 without dc field and 2000 Oe dc fields show no temperature- and frequency-dependent signals, which may be due to the low symmetry of the coordination configuration of Ln in these complexes.

In this work, a novel and highly selective molecularly imprinted sensor for the detection of melamine in milk using electrochemiluminescence (ECL) is reported. The preparation was carried out by modification of a glassy carbon electrode with a composite of silica nanoparticles doped with [Ru(bpy) 3 ] 2+ (RUDS) and molecularly imprinted polymer (MIP). The keys of the sensor were to employ RUDS as an ECL luminophore to prevent [Ru(bpy) 3 ] 2+ leaching from the modified electrode and MIP as a material for selective recognition. Taking advantage of the MIP pre-concentration effect, melamine could be extracted from the solution and detected by the resulting ECL signal enhancement of [Ru(bpy) 3 ] 2+ . Under optimized conditions, the relative ECL signal was proportional to the logarithm of melamine concentration in the range of 1 × 10 −12 –1 × 10 −7 mol L −1 , with a detection limit as low as 5 × 10 −13 mol L −1 . Compared with the RUDS/non-imprinted polymer, the RUDS/MIP modified electrode displayed high recognition ability, good reproducibility, and stability. To verify its reliability, the fabricated ECL sensor was used for determining the concentration of melamine in milk.

A selective sample cleanup method using molecularly imprinted polymers was developed for the separation of domoic acid (a shellfish toxin) from shellfish samples. The molecularly imprinted polymers for domoic acid was prepared by emulsion polymerization using 1,3,5-pentanetricarboxylic acid as the template molecule, 4-vinyl pyridine as the functional monomer, ethylene glycol dimethacrylate as the crosslinker, and Span80/Tween-80 (1:1 v/v) as the composite emulsifiers. The molecularly imprinted polymer showed high affinity to domoic acid with a dissociation constant of 13.5 μg/mL and apparent maximum adsorption capacity of 1249 μg/g. They were used as a selective sorbent for the detection of domoic acid from seafood samples coupled with high-performance liquid chromatography. The detection limit of 0.17 μg/g was lower than the maximum level permitted by several authorities. The mean recoveries of domoic acid from clam samples were 93.0-98.7%. It was demonstrated that the proposed method could be applied to the determination of domoic acid from shellfish samples.

Magnetic molecularly imprinted polymers (MMIPs) were synthesized through precipitation polymerization using malachite green (MG) as template, methacrylic acid as monomer, ethylene dimethacrylate as crosslinker, and Fe3O4 magnetite as magnetic component. MMIPs were characterized by scanning electron microscopy, Fourier transform infrared spectrometry, and vibrating sample magnetometry. Under the optimum condition, the MMIPs obtained exhibited quick binding kinetics and high affinity to MG in the solution. Scatchard plot analysis revealed that the MMIPs contained only one type of binding site with dissociation constant of 24.0 μg mL(-1). The selectivity experiment confirmed that the MMIPs exhibited higher selective binding capacity for MG than its structurally related compound (e.g., crystal violet). As a sorbent for the extraction of MG in sample preparation, MMIPs together with the absorbed analytes could easily be separated from the sample matrix with an external magnet. After elution with methanol/acetic acid (9:1, v/v), MG in the eluent was determined by high-performance liquid chromatography coupled with UV detector with recoveries of 94.0-115%. Results indicated that the as-prepared MMIPs are promising materials for MG analysis in aquatic products.

Molecularly imprinted polymers (MIPs) were synthesized using malachite green (MG) as template, and methacrylic acid/sodium methacrylate as composite monomers. The equilibrium dissociation constant and apparent maximum adsorption capacity of the MIPs reach 12.2 mg·L−1 and 3.2 mg·g−1, respectively. The MIPs demonstrate excellent recognition ability due to high-affinity sites constructed by the electrostatic interaction and hydrogen bonds between template and composite monomers. The MIPs were successfully employed for the detection of MG residue in aquatic products coupled with high-performance liquid chromatography (HPLC) with a detection limit of 0.57 μg·kg−1.

Lead (Pb) pollution in soil has attracted public attention because of its serious impacts on human health through food chain. However, the chemical and biological behaviors of exogenous Pb in soil remain unknown, specifically in the passivated soil with phosphate (P)-based materials. By spiking soil with stable enriched isotopes of 206Pb (> 99%), the exogenous Pb2 + in soil was simulated in the present study; the distribution, transformation, and bioavailability of exogenous Pb in soil passivated with the P-based compound were quantitatively investigated using an isotopic labeling method coupled with a Tessier approach of sequential extraction procedures. The results showed that exogenous Pb in water-soluble fraction (F1) accounted for 0.58% of the total spiked isotopes, which was slightly higher than that of the intrinsic Pb (0.34%) in soil. Nevertheless, the exogenous Pb percentages in exchangeable fraction (F2), carbonate bound fraction (F3), Fe/Mn oxide fraction (F4), and organic matter bound fraction (F5) were about twice more than those of the intrinsic Pb in the four fractions. But exogenous Pb in residual fraction (F6) was only 45.6%, while intrinsic Pb was 70%. After the soil was passivated with P-based compound consisting of diammonium phosphate, bone meal, and hydroxyapatite, more than 90% of exogenous Pb in F2 could be immobilized, but small Pb percentage in F1 was immobilized. Additionally, Pb species in F2, F3, and F4 might be converted into different forms in F5 and F6, but the immobilized Pb in F5 and F6 was labile because more than 50% of the exogenous Pb in the two fractions was lost after planting. The results demonstrated that the isotopic labeling technique coupled with Tessier approach was a novel method that can evaluate the distribution, transformation, and bioavailability of exogenous Pb in soil. These results are helpful for further immobilization of exogenous Pb in agricultural soil.

A practical aptaprobe for sulfadimethoxine (SDM) detection was established. Based on the electrostatic reaction, a duplex of aptamer and poly(diallyldimethylammonium chloride) (PDDA) was formed, which prevented the quenching effect of PDDA on the fluorescence of CdTe quantum dots (QDs). But the specifically binding of aptamer to SDM might result in free PDDA released and the fluorescence was quenched. Based on the fluorescence aptaprobe, SDM was quantitatively detected by measuring the fluorescence at 530 nm with a linear range of 25–300 ng mL−1, and the limit of detection was 2.24 ng mL−1 based on 3σ/K (n = 9). The aptaprobe was applied to SDM detection with recoveries of 94.2 %–113 % and 104 %–118 % for seawater and fish, respectively. The results showed that the fluorescence aptaprobe was simple and convenient for the rapid detection of SDM residue in water and fish samples.

Doping graphene quantum dots (GQDs) with heteroatoms can change their band gap and electronic density, thus enhancing their fluorescence quantum yield (QY). In this work, we for the first time reported a nontoxic, rapid, and one-pot hydrothermal method to synthesize sulfur and phosphorus co-doped GQDs (S, P-GQDs). Citric acid was functioned as a carbon source, whereas sodium phytate and anhydrous sodium sulfate are used as the P and S sources, respectively, in this bottom-up synthesis. The resulting S, P-GQDs exhibit high heteroatomic doping ratios of 9.66 at.% for S and 3.34 at.% for P, and higher QY than those obtained from monoatomic doped GQDs. Additionally, the as-prepared S, P-GQDs exhibit excitation-dependent behavior, pH sensitivity between 8.0 and 13.0, high tolerance of ionic strength. More importantly, the as-synthesized S, P-GQDs show a sensitive and selective behavior for sensing nitrite (NO2−) in the concentration range of 0.7–9 μmol/L, and the detection limit was as low as 0.3 μmol/L. Additionally, the S, P-GQDs was successfully used in detecting NO2− in pickled foods, showing their promise for potential applications in realistic analysis.

A photonic crystal (PC) sensor was prepared through molecular imprinting by using dispersed SiO2 microspheres as PC, sulfaguanidine (SG) as template, methacrylic acid as monomer, and ethylene glycol dimethacrylate as crosslinker. The preparation conditions were optimized as follows: molar ratio of template, monomer, and crosslinker was 1:10:4; pH was 6.0 in phosphate buffer; and volume fraction of methanol was 15%. The relationship between wavelength shift of reflection peak and SG concentration was found as: Δλ = 7.8887 lg(C) + 79.9664. The response time was only 5 min. The limit of detection was 2.8 × 10−10 mol L−1. The sensor exhibited higher specificity for SG than its sulfonamide analogs. The sensor maintained original sensing performance after five cycles of usage. The recoveries of SG ranged from 93.8% to 111.2% in lake water and from 88.5% to 115.2% in fish samples. This finding suggested that the sensor can be used in food samples with complicated matrix.

In the present work, a direct “touch” method was developed for attaching AuNPs with clean surface on the graphene-ionic liquid modified glassy carbon electrode (G-IL GCE). The morphology and composition of the thus-prepared AuNPs on G-IL GCE were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The results showed that AuNPs with interesting flower-like shapes are well dispersed on the G-IL film. Significantly, as it is a surfactant-free synthesis, the AuNPs are very clean and can be directly modified on a G-IL GCE without any pre-treatments. Comparing with the bare or even various AuNPs-G-IL mixtures modified GCEs, the proposed sensor exhibit better electrochemical activity with a higher peak current and a lower overpotential towards bisphenol A (BPA) oxidation. After optimization, a good linear relationship between current response and the concentration of BPA in the range of 0.01–1 and 1–60 μM were obtained, and the detection limit was as low as 4.8 nM. To testify the reliability, the thus-prepared AuNPs/G-IL GCE was used for determining the concentration of BPA in disposable paper cups, plastic bottles and noodles cups.

In this research, three vanadium substituted polyoxometalates (POMs) K3+n[PW12−nVnO40] (abb. PW12−nVn) (n = 1, 2, 3)-based electrochromic (EC) films were prepared using the electrodeposition method. The films not only show a good performance in terms of EC properties in an H+-based aqueous electrolyte, but also show good EC performance in a Li+-based non-aqueous electrolyte. Although the EC activity of POMs is lower in the neutral media than in acid media, the use of the neutral non-aqueous electrolyte does not result in the suppression of the EC performance. The large diffusion coefficient of the Li+ in the porous films guarantees the high performance. For the PW11V, PW10V2 and PW9V3-based films, the coefficients of Li+ are 4.05 × 10−11, 4.11 × 10−11, and 1.04 × 10−11 cm2 s−1, respectively. The PW10V2-based film shows the shortest response time for coloration which is even shorter than that shown in the H+-based aqueous electrolyte. The optical contrast of the films is also nearly the same as which achieved in the aqueous electrolyte media. The application of the non-aqueous neutral electrolyte would be beneficial for the fabrication of the POM-based EC device.

Magnetic molecularly imprinted polymers (MMIPs) synthesized through suspension polymerization were used as the adsorbent for the detection of malachite green (MG) in fish samples. The morphological, thermal and magnetic properties of the MMIPs were characterized. The influence of polymerization condition on the absorption capacity of the MMIPs for MG was explored. The results gave the optimum polymerization condition as follows: using MG (0.25 mmol) as template, methacrylic acid (1 mmol) as monomer, ethylene dimethacrylate (5 mmol) as cross linker, 2,2′-Azobis(2-methylpropionitrile) (100 mg) as initiator, Fe 3 O 4 (100 mg) as magnetic nuclei, and PVA (1%) as dispersant. Under the optimum condition the apparent maximum adsorption capacity of MMIPs is 5693 μg·g − 1 with dissociation constant being 23.5 mg·L − 1 . The MMIPs also have strong magnetic responses to an external magnet, which enable the rapid separation from the sample solution. The MMIPs were employed for the detection of MG residue in fish samples combined with HPLC. The recoveries of spiked MG in fish samples ranged from 82.7% to 111% with RSD in the range of 2.0%–12.8%. The MMIPs can retain 90% of the original adsorption capacity even if used for 5 times. Thus, the prepared MMIPs can be applied to the sample pretreatment for separation and enrichment of MG residue in fish samples.

We report the syntheses, crystal structures, and magnetic properties of two 3d–4f heterometallic compounds; namely, [Mn8Ln2O2(OH)2{(py)2CO2}4(teaH)4(CH3COO)6]·6CH3CN·2H2O (LnIII = Dy (1), Tb (2); (py)2CO2H2 = the gem-diol form of di-2-pyridyl ketone, teaH3 = triethanolamine). Both compounds were prepared by the reaction of Mn(OAc)2·4H2O, Ln(NO3)3·5H2O (Ln = Dy and Tb) with the ligands di-2-pyridyl ketone and triethanolamine in MeCN, and they crystallize in the monoclinic space group C2/c. [Mn8Ln2] complexes have not been reported before, and the metallic cores of both complexes were unprecedented. In these cores, two Dy or Tb and two Mn ions comprised a well-known butterfly topology, with three of the remaining six Mn atoms each being situated on either side of the butterfly, linked through two μ3-O2− ions. Six MnIII and two MnII were in six-coordinated distorted octahedrons and two LnIII ions were in nine-coordinated distorted muffins. Interestingly, the coordination sites of LnIII ions are occupied by six O and two N atoms from two teaH2− ligands and one μ3-O2− atom, without the presence of coordinated solvent molecules such as H2O and small anions such as NO3− ions, which is rare in 3d–4f complexes. Remarkably, alternating current (ac) magnetic susceptibility measurements revealed that both complexes displayed dynamic anisotropic magnetic behaviour. The effective energy barrier (Ueff) of complex 2 was estimated to be 18.97 K through high frequency (111–9111 Hz) ac susceptibility measurements. The low symmetry of the coordination configuration of Ln3+ in 1 and 2 may be responsible for the small energy barriers of these two compounds.

A facile and green hydrothermal method was developed for the preparation of highly luminescent nitrogen-doped carbon dots (NCDs) by using anhydrous citric acid and urea as the carbon source and nitrogen source, respectively. The NCDs show good water-solubility and exhibit excitation-independent fluorescence behaviors at excitations of 300–390 nm with a quantum yield of 42.5% at a λem of 440 nm. Based on the fluorescence quenching strategy, the NCDs were successfully applied to the measurement of Hg2+ in tap and lake water samples with high sensitivity and excellent selectivity. The detection limit was 7.3 nmol L−1 (3σ, n = 9), indicating its potential applications for the detection of trace Hg2+ in water samples.

In this work, a sensitive electrochemiluminescence (ECL) sensor for the determination of melamine (MEL) was developed based on a Ru(bpy)3(2+)-doped silica nanoparticles (RUDS)/carboxylic acid functionalized multi-walled carbon nanotubes (CMWCNTs)/Nafion composite film modified electrode. The homogeneous spherical RUDS were synthesized by a reverse microemulsion method. As Ru(bpy)3(2+) were encapsulated in the RUDS, Ru(bpy)3(2+) dropping from the modified electrode can be greatly prevented, which is helpful for obtaining a stable ECL signal. Moreover, to improve the conductivity of the film and promote the electron transfer rate on electrode surface, CMWCNTs with excellent electrical conductivity and large surface area were applied in the construction of the sensing film. As CMWCNTs acted as electron bridges making more Ru(bpy)3(2+) participate in the reaction, the ECL intensity was greatly enhanced. Under the optimum conditions, the relative ECL signal (△IECL) was proportional to the logarithmic MEL concentration ranging from 5×10(-13) to 1×10(-7) mol L(-1) with a detection limit of 1×10(-13) mol L(-1). To verify the reliability, the thus-fabricated ECL sensor was applied to determine the concentration of MEL in milk. Based on these investigations, the proposed ECL sensor exhibited good feasibility and high sensitivity for the determination of MEL, promising the applicability of this sensor in practical analysis.

A facile and green method was developed to prepare amino-functionalized fluorescent carbon dots (FCDs) for the detection of Hg 2+ in aqueous solution. The water-soluble FCDs with the diameter around 3–5 nm were synthesized using anhydrous citric acid as carbon sources, NaBH 4 as reducing agent and ammonia as passivation agent. The as-prepared FCDs exhibit blue emission at 440 nm with quantum yield as high as 36% using quinine sulfate as reference. The fluorescence intensity of the FCDs can be quantitatively quenched by Hg 2+ with high sensitivity and selectivity. The FCDs were successfully applied to the measurement of Hg 2+ in water samples with a detection limit of 20 nmol L −1 (3 σ , n = 9), indicating that the amino-functionalized FCDs probe can be potentially applied to the detection of trace Hg 2+ in water samples.

Background To investigate the safety and feasibility of a new intrahepatic cholangiojejunostomy for multiple intrahepatic biliary ductal openings after hepatobiliary resection. Materials and methods Forty-eight pigs were randomly assigned into two groups: the new intrahepatic cholangiojejunostomy group (n = 24); and the control group (n = 24) with classical hepaticojejunostomy. Six pigs in each group were sacrificed on postoperative day 7, 30, 90 and 180. The primary outcomes were postoperative mortality, morbidity, and the pathological changes in the anastomoses. The secondary outcomes were levels of aspartate transaminase, bilirubin, albumin and alkaline phosphate. Results The operations were successfully carried out. The rates of anastomotic leakage and cholangitis in the study group were 0% and 8.3% (2/24), while in the control group they were 4.2% (1/24) and 20.8% (5/24), respectively. The stenotic rates of the sectional areas of the anastomotic stomas in the study group were lower than those in the control group on postoperative day 7, 30, 90 and 180 ( p p = 0.002, p p = 0.001, respectively). Under microscopy, in the study group, the anterior wall of the stoma was everted and sunken while the posterior wall was protruded in a semicircular-disc shaped. The liver transection plane was epithelialized with mucosal covering by post-operative day 30. In the control group, however, the stoma was centripetally protruded with a relative circular stenosis. Conclusions The new intrahepatic cholangiojejunostomy is safe, simple, and convenient for multiple biliary ductal openings.