Yan-Ming Liu

Si/C Composites for High Capacity Lithium Storage Materials

Thermal pyrolysis of polyvinyl chloride dispersed with nanosized silicon and fine graphite particles at 900°C produces a novel Si/C composite for lithium storage material. Incorporated silicon provides major capacity for lithium insertion, while the introduction of graphite component suppresses the initial irreversibility and hysteresis between charge and discharge caused by pyrolyzed carbon. The first cycle efficiency of the composite is about 85%. The large reversible capacity of ca. 700 mAh/g and good cyclability indicates that such Si/C composite may be a useful alternative to conventional graphite-based anode materials for lithium-ion cells.

Sub-femtomolar DNA detection based on layered molybdenum disulfide/multi-walled carbon nanotube composites, Au nanoparticle and enzyme multiple signal amplification

A novel 2-dimensional graphene analog molybdenum disulfide/multi-walled carbon nanotube (MoS2/MWCNT) was synthesized by a simple hydrothermal method to achieve excellent electrochemical properties. An ultrasensitive electrochemical DNA biosensor was subsequently constructed by assembling a thiol-tagged DNA probe on a MoS2/MWCNT and gold nanoparticle (AuNP)-modified electrode that has already been coupled with glucose oxidase (GOD). In this work, GOD was used as a redox marker. The heteronanostructure formed on the biosensor surface appeared relatively good conductor for accelerating the electron transfer, while the modification of GOD and AuNPs provided multiple signal amplification for electrochemical biosensing. The multiple signal amplification strategy produced an ultrasensitive electrochemical detection of DNA down to 0.79 fM with a linear range from 10 fM to 10(7)fM, and appeared high selectivity to differentiate three-base mismatched DNA and one-base mismatched DNA. The developed approach provided a simple and reliable method for DNA detection with high sensitivity and specificity, and would open new opportunities for sensitive detection of other biorecognition events.

Multiresidue method for determination of 88 pesticides in berry fruits using solid-phase extraction and gas chromatography–mass spectrometry: Determination of 88 pesticides in berries using SPE and GC–MS

A method using solid phase extraction (SPE) cleanup followed by gas chromatography-mass spectrometry (GC-MS) has been established for quantitative determination of 88 pesticide residues in berry fruits including raspberry, strawberry, blueberry and grape. Based on an appraisal of the characteristics of GC-MS, validation experiments were conducted for 88 pesticides. In the method, solid-phase extraction was carried out using Envi-Carb cartridge coupled with NH(2)-LC cartridge with acetonitrile-toluene (3:1, v/v) as the eluted solvent. In the linear range of each pesticide, the correlation coefficient was R(2)⩾0.99. At the low, medium and high three fortification levels of 0.05-0.5mgkg(-1), recoveries fell within 63-137%. The relative standard deviation was between 1% and 19% for all 88 pesticides. Low limits of detection (0.006-0.05mgkg(-1)) and quantification (0.02-0.15mgkg(-1)) were readily achieved with this method for all tested pesticides.

Molybdenum disulfide nanoflower-chitosan-Au nanoparticles composites based electrochemical sensing platform for bisphenol A determination

Two-dimensional transition metal dichalcogenide are attracting increasing attention in electrochemical sensing due to their unique electronic properties. In this work, flower-like molybdenum disulfide (MoS2) was prepared by a simple hydrothermal method. The scanning electron microscopy and transmission electron microscopy images showed the MoS2 nanoflower had sizes with diameter of about 200nm and was constructed with many irregular sheets as a petal-like structure with thickness of several nanometers. A novel electrochemical sensor was constructed for the determination of bisphenol A (BPA) based on MoS2 and chitosan-gold nanoparticles composites modified electrode. The sensor showed an efficient electrocatalytic role for the oxidation of BPA, and the oxidation overpotentials of BPA decreased significantly and the peak current increased greatly compared with bare GCE and other modified electrode. A good linear relationship between the oxidation peak current and BPA concentration was obtained in the range from 0.05 to 100μM with a detection limit of 5.0×10(-9)M (S/N=3). The developed sensor exhibited high sensitivity and long-term stability, and it was successfully applied for the determination of BPA in different samples. This work indicated MoS2 nanoflowers were promising in electrochemical sensing and catalytic applications.

Electrochemical biosensor based on silver nanoparticles–polydopamine–graphene nanocomposite for sensitive determination of adenine and guanine

A multifunctional Ag nanoparticles (AgNPs)-polydopamine (Pdop)@graphene (Gr) composite was prepared by a simple and mild procedure. Gr was easily coated with Pdop at room temperature and then AgNPs was deposited by mildly stirring. The nanocomposite was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). Guanine and adenine as model moleculars were employed to study their electrochemical responses at the Ag-Pdop@Gr composite modified electrode, which showed more favorable electron transfer kinetics than Gr modified glassy carbon and AgNPs modified glassy carbon electrodes. The Ag-Pdop@Gr modified electrode exhibited linear ranges of 0.04-50 μM and 0.02-40 μM with detection limits of 4.0 nM and 2.0 nM for guanine and adenine, respectively. The developed method was applied for simultaneous determination of trace-level adenine and guanine in fish sperm. The results demonstrated that the AgNPs-Pdop@Gr nanocomposite was a promising substrate for the development of high-performance electrocatalysts for biosensing.

Sensitive Chemiluminescence Immunoassay by Capillary Electrophoresis with Gold Nanoparticles

This technical note describes a new chemiluminescence immunoassay hyphenated to capillary electrophoresis (CE-based CL-IA) with gold nanoparticles (AuNPs) technique for biological molecules determination. AuNPs were used as a protein label reagent in the light of its excellent catalytic effect to the CL reaction of luminol and hydrogen peroxide. AuNPs conjugate with antibody (Ab) to form tagged antibody (Ab*), and then Ab* link to antigen (Ag) to produce an Ab*-Ag complex by a noncompetitive immunoreaction. The mixture of the excess Ab* and the Ab*-Ag complex was baseline separated and detected within 5 min under the optimized conditions. This new protocol was evaluated with human immunoglobulin G (IgG) as the target molecule. The calibration curve of IgG was in the range of 0.008-5 μg/mL with a correlation coefficient of 0.995. The detection limit (S/N = 3) of IgG was 1.14 × 10(-3) μg/mL (7.1 pmol/L, 0.39 amol). The proposed AuNPs enhanced CE-based CL-IA method was successfully applied for the quantification of IgG in human sera from patients. It proves that the present method could be developed into a new and sensitive biochemical analysis technique.

Amperometric immunobiosensor for α-fetoprotein using Au nanoparticles/chitosan/TiO2–graphene composite based platform

A simple label-free amperometric immunosensor for protein detection is developed based on TiO(2)-graphene (TiO(2)-Gr), chitosan and gold nanoparticles (AuNPs) composite film modified glassy carbon electrode (GCE). The negatively charged AuNPs can be adsorbed on the positively charged chitosan/TiO(2)-Gr composite film by electrostatic adsorption, and then is used to immobilize α-fetoprotein antibody for the assay of α-fetoprotein (AFP). The interaction of antigen and antibody on the electrode interface makes a barrier for electrons and inhibits the electro-transfer, resulting in the decreased DPV signals of probe Fe(CN)(6)(3-/4-). Using this strategy, a wide detection range (0.1-300 ng mL(-1)) with the correlation coefficients of 0.992-0.994 for model target AFP is obtained. The limit of detection is 0.03 ng mL(-1) at a signal-to-noise ratio of 3. The results prove that the sensing strategy possesses sensitivity, selectivity, stability and generality, and it may be used to immobilize other biomoleculars to develop biosensor for the detection of other antigens or biocompounds.

Aptamer/Au nanoparticles/cobalt sulfide nanosheets biosensor for 17β-estradiol detection using a guanine-rich complementary DNA sequence for signal amplification

We have developed a sensitive sensing platform for 17β-estradiol by combining the aptamer probe and hybridization reaction. In this assay, 2-dimensional cobalt sulfide nanosheet (CoS) was synthesized by a simple hydrothermal method with L-cysteine as sulfur donor. An electrochemical aptamer biosensor was constructed by assembling a thiol group tagged 17β-estradiol aptamer on CoS and gold nanoparticles (AuNPs) modified electrode. Methylene blue was applied as a tracer and a guanine-rich complementary DNA sequence was designed to bind with the unbound 17β-estradiol aptamer for signal amplification. The binding of guanine-rich DNA to the aptamer was inhibited when the aptamer captured 17β-estradiol. Using guanine-rich DNA in the assay greatly amplified the redox signal of methylene blue bound to the detection probe. The CoS/AuNPs film formed on the biosensor surface appeared to be a good conductor for accelerating the electron transfer. The method demonstrated a high sensitivity of detection with the dynamic concentration range spanning from 1.0×10(-9) to 1.0×10(-12) M and a detection limit of 7.0×10(-13) M. Besides, the fabricated biosensor exhibited good selectivity toward 17β-estradiol even when interferents were presented at 100-fold concentrations. Our attempt will extend the application of the CoS nanosheet and this signal amplification assay to biosensing areas.

Development of an ionic liquid-based ultrasonic-assisted liquid–liquid microextraction method for sensitive determination of biogenic amines: Application to the analysis of octopamine, tyramine and phenethylamine in beer samples

A simple and efficient method, ionic liquid-based ultrasound-assisted liquid-liquid microextraction, has been developed for the determination of three biogenic amines including octopamine (OCT), tyramine (TYR) and phenethylamine (PHE). Fluorescence probe 2,6-dimethyl-4-quinolinecarboxylic acid N-hydroxysuccinimide ester was applied for derivatization of biogenic amines and high-performance liquid chromatography coupled with fluorescence detection was used for the determination of the derivatives. The factors affecting the extraction efficiency, such as the type and volume of ionic liquid, ultrasonication time and centrifugation time have been investigated in detail. Under the optimum conditions, linearity of the method was observed in the range of 0.5-50 μgmL(-1) for OCT and TYR, and 0.025-2.5 μgmL(-1) for PHE, respectively, with correlation coefficients (γ)>0.996. The limits of detection ranged from 0.25-50 ngmL(-1) (S/N=3). The spiked recoveries of three target compounds in beer samples were in the range of 90.2-114%. As a result, this method has been successfully applied for the sensitive determination of OCT, TYR and PHE in beer samples.

A fluorescent biosensor for protein detection based on poly(thymine)-templated copper nanoparticles and terminal protection of small molecule-linked DNA.

In this paper, a fluorescent biosensor has been developed for protein detection based on poly(thymine) (poly T)-templated copper nanoparticles (Cu NPs) and terminal protection of small molecule linked-DNA. This strategy was demonstrated by using small molecule biotin and its binding protein streptavidin (SA) as a model case. In this assay, biotin-linked poly T (biotin-T30) probe was specifically bound to the target protein SA with strong affinity in the presence of SA. The selective binding events confirmed that biotin-T30 probe was protected against the hydrolysis by exonuclease I (Exo I), which could effectively template the formation of fluorescent Cu NPs. The results revealed that the developed strategy was highly sensitive for detecting SA in the concentration range from 0.5 to 1000 nM with a detection limit of 0.1 nM. In addition, the relative standard deviation was 3.6% in 5 repetitive assays of 50 nM SA, which indicated that the reproducibility of the method was acceptable. Besides desirable sensitivity, the developed biosensor also showed high selectivity, low cost, and simplified operations. Thus, it could hold considerable potential to construct a simple, selective and sensitive fluorescent platform for detection of small molecule-protein interactions in molecular diagnostics and genomic research.