An ultrasensitive and universal photoelectrochemical immunoassay based on enzyme mimetics enhanced signal amplification.

An ultrasensitive photoelectrochemical (PEC) immunoassay based on signal amplification by enzyme mimetics was fabricated for the detection of mouse IgG (as a model protein). The PEC immunosensor was constructed by a layer-by-layer assembly of poly (diallyldimethylammonium chloride) (PDDA), CdS quantum dots (QDs), primary antibody (Ab1, polyclonal goat antimouse IgG), and the antigen (Ag, mouse IgG) on an indium-tin oxide (ITO) electrode. Then, the secondary antibody (Ab2, polyclonal goat antimouse IgG) combined to a bio-bar-coded Pt nanoparticle(NP)-G-quadruplex/hemin probe was used for signal amplification. The bio-bar-coded Pt NP-G-quadruplex/hemin probe could catalyze the oxidation of hydroquinone (HQ) using H2O2 as an oxidant, demonstrating its intrinsic enzyme-like activity. High sensitivity for the target Ag was achieved by using the bio-bar-coded probe as signal amplifier due to its high catalytic activity, a competitive nonproductive absorption of hemin and the steric hindrance caused by the polymeric oxidation products of HQ. For most important, the oxidation product of HQ acted as an efficient electron acceptor of the illuminated CdS QDs. The target Ag could be detected from 0.01pg/mL to 1.0ng/mL with a low detection limit of 6.0fg/mL. The as-obtained immunosensor exhibited high sensitivity, good stability and acceptable reproducibility. This method might be attractive for clinical and biomedical applications.

Direct spectrophotometric determination of alkylphenol polyethoxylate nonionic surfactants in wastewater.

A new spectrophotometric method is proposed for direct determination of alkylphenol polyethoxylate, RO(CH(2)CH(2)O)(n)H (where R is alkylphenyl and n is the degree of polymerization), in wastewater. The method is based on the formation of ternary complex, Pb(II)-meso-tetra-(3,5-dibromo-4-hydrooxyphenyl)-Porphyrin (T(DBHP)P)-alkylphenol polyethoxylate (APE). Under optimum reaction conditions, T(DBHP)P reacts with lead(II) and APE to form a yellow ternary complex with the maximum absorption peak at 479 nm. The color reaction is rapidly completed and the absorbance remains stable for at least 24h under room temperature. The apparent molar absorption coefficients were 0.4-4.3 x 10(4) L mol(-1) cm(-1) for n=5-50. As little as 0.02 microg mL(-1) of APE can be detected. The effects of various substances on the determination of APE were also investigated in detail. It was found that all the studied co-existing substances, especially cationic and anionic surfactants, which always seriously interfere in some reported methods, could be tolerated in considerable amounts. The method offered the advantages of simplicity, rapidity, sensitivity and selectivity without any prior separation or extraction.

Development and application of 3-chloro-1,2-propandiol electrochemical sensor based on a polyaminothiophenol modified molecularly imprinted film.

In this work, a novel electrochemical sensor for 3-chloro-1,2-propandiol (3-MCPD) detection based on a gold nanoparticle-modified glassy carbon electrode (AuNP/GCE) coated with a molecular imprinted polymer (MIP) film was constructed. p-Aminothiophenol (p-ATP) and 3-MCPD were self-assembled on a AuNP/GCE surface, and then a MIP film was formed by electropolymerization. The 3-MCPD template combined with p-ATP during self-assembly and electropolymerization, and the cavities matching 3-MCPD remained after the removal of the template. The MIP sensor was characterized by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and scanning electron microscopy (SEM). Many factors that affected the performance of the MIP membrane were discussed and optimized. Under optimal conditions, the DPV current was linear with the log of the 3-MCPD concentration in the range from 1.0 × 10(-17) to 1.0 × 10(-13) mol L(-1) (R(2) = 0.9939), and the detection limit was 3.8 × 10(-18) mol L(-1) (S/N = 3). The average recovery rate of 3-MCPD from spiked soy sauce samples ranged from 95.0% to 106.4% (RSD < 3.49%). Practically, the sensor showed high sensitivity, good selectivity, excellent reproducibility, and stability during the quantitative determination of 3-MCPD.

In situ formation of p-n junction: a novel principle for photoelectrochemical sensor and its application for mercury(II) ion detection.

The discovery and development of photoelectrochemical sensors with novel principles are of great significance to realize sensitive and low-cost detection. In this paper, a new photoelectrochemial sensor based on the in situ formation of p-n junction was designed and used for the accurate determination of mercury(II) ions. Cysteine-capped ZnS quantum dots (QDs) was assembled on the surface of indium tin oxide (ITO) electrode based on the electrostatic interaction between Poly(diallyldimethylammonium chloride) (PDDA) and Cys-capped ZnS QDs. The in situ formation of HgS, a p-type semiconductor, on the surface of ZnS facilitated the charge carrier transport and promoted electron-hole separation, triggered an obviously enhanced anodic photocurrent of Cys-capped ZnS QDs. The formation of p-n junction was confirmed by P-N conductive type discriminator measurements and current-voltage (I-V) curves. The photoelectrochemical method was used for the sensing of trace mercuric (II) ions with a linear concentration of 0.01 to 10.0 µM and a detection limit of 4.6×10(-9)mol/L. It is expected that the present study can serve as a foundation to the application of p-n heterojunction to photoelectrochemical sensors and it might be easily extended to more exciting sensing systems by photoelectrochemistry.

A new type of entangled coordination network: coexistence of polythreading and polyknotting involved molecular braids.

A fascinating polythreaded coordination network formed by 1D crankshaft shaped chains threading into a 2D undulated sheet in a one-over/one-under interweaving fashion was reported, in which the 2D layer exhibits an unusual polyknotted entanglement containing triple-stranded molecular braids.