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Previous studies confirm that aberrant expression of cytokeratin 19 fragment antigen 21-1 (cyfra-21-1) is highly correlated with non-small cell lung cancer (NSCLC). Herein, a proportional electrochemical immunosensor based upon a methylene blue/cadmium telluride/molybdic sulfide (MB/CdTe/MoS2) nanocomposite was successfully fabricated for detecting tumor marker cyfra-21-1. The result indicates that MB/CdTe/MoS2 modified on the surface of a glassy carbon electrode (GCE) supplies a large surface area for immobilizing primary antibodies (Ab1), ensuring high selectivity and sensitivity. To further amplify the sensitivity of the biosensor, ferrocenecarboxylic acid (Fc-COOH) linked with amino-functionalized secondary antibodies through amido bond (Ab2-Fc) as the “signal-on” probe and MB-modified with MoS2 with a large specific surface area as the “signal-off” probe increase the number of active sites for integration of Ab2-Fc/Ag/BSA/Ab1/MB/CdTe/MoS2/GCE electrode with the linker cyfra-21-1 (Ag). Meanwhile, CdTe accelerates the electron transfer and enhances the MB current, improving the sensitivity and detection limit. The presence of cyfra-21-1 led to both the decreasing response of MB and increasing current responses of Fc upon the electrode. Based upon this strategy, the determination of cyfra-21-1 was achieved in a linear range from 10 pg/mL to 10,000 ng/mL with the lowest detectable concentration of 10 pg/mL (signal-to-noise ratio of 3). The electrochemical immunosensor performs a sensitive determination of cyfra-21-1, possibly providing a practical strategy for the clinical analysis of lung cancer.

Herein, a label-free photoelectrochemical immunosensor based on a g-C3N4/CdSe nanocomposite was established and applied to detect carcinoembryonic antigen (CEA). The prepared nanocomposite materials were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), ultraviolet-visible absorption spectroscopy (UV-vis), X-ray photoelectron spectroscopy (XPS), fourier transform infrared spectrometer (FT-IR) and photoluminescence spectroscopy (PL). The results indicate that g-C3N4/CdSe nanocomposite materials were successfully synthesized. In a typical assembly process, the immunosensor was constructed by modifying a fluorine-doped tin oxide (FTO) electrode with poly dimethyl diallyl ammonium chloride (PDDA), the g-C3N4/CdSe nanocomposite, the anti-carcinoembryonic antigen antibody (Ab) and the blocking agent bovine serum albumin (BSA) successively. In the presence of CEA, the photocurrent signal of the prepared immunosensor decreased significantly. Accordingly, under the optimal conditions, a label-free photoelectrochemical immunosensor was established, and it exhibited excellent selectivity and repeatability for CEA detection. The detection limit was 0.21 ng mL-1, and the range was 10 ng mL-1-100 μg mL-1. Simultaneously, the immunosensor also provides a likely sensing device for detecting other protein targets, which is of great significance for early clinical diagnosis.

In this work, an electrochemiluminescence (ECL) biosensor was fabricated for the selective detection of vascular endothelial growth factor (VEGF165). g-C3N4/PDDA/CdSe nanocomposites were used as the ECL substrate. Then, DNA labeled at the 5′ end with amino groups (DNA1) was immobilized on the surface of g-C3N4/PDDA/CdSe nanocomposite-modified glassy carbon electrode (GCE) by amido linkage. AuNP-labeled target DNA (Au-DNA2) could hybridize with DNA1 to form a double strand. The ECL of the g-C3N4/PDDA/CdSe nanocomposite was efficiently quenched due to the resonance energy transfer between CdSe QDs and Au NPs. After VEGF165 was recognized and bound by Au-DNA2, the double helix was disrupted, and the energy transfer was broken. In this case, Au-DNA2 was released from the electrode surface, and the ECL intensity recovered to a higher level. Under optimal conditions, this ECL biosensor possesses excellent selectivity, accuracy, and stability for VEGF165 detection in a linear range of 2 pg mL−1 to 2 ng mL−1 with a detection limit of 0.68 pg mL−1. In addition, this assay has been successfully applied to the determination of VEGF165 in serum samples.

The mechanisms of electrochemical capture of CO2 via redox cycle of 1,4-naphthoquinone (1,4-NQ), 2,3-dichloro-1,4-naphthoquinone (DCNQ) and 2-chloro-1,4-naphthoquinone (CNQ) in 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4) have been investigated by cyclic voltammetry (CV) and in-situ FT-IR spectroelectrochemistry techniques. In the absence of CO2, 1,4-NQ and DCNQ undergo a reversible two-step one-electron process while CNQ not. In addition, their two successive electron transfer processes in ionic liquid (IL) are different from that of molecular solvent. There is only a small difference in peak potential between two-step reduction, which possibly due to the ion-pair effects. Meanwhile, the reduction potentials of DCNQ and CNQ shift positively due to the electron-withdrawing effects of chlorine groups. The radical anion (Q −) and dianion (Q2−) formed during the electrochemical reduction can be used as nucleophiles to attack the eletrophilic carbon center of CO2 and form a stable CO2 adduct. For 1,4-NQ, 2 equiv. of CO2 can be captured during the electrochemical reduction of 1,4-NQ. Whereas, 1 equiv. of CO2 is captured by 1 equiv. of dianion during the electrochemical reduction of DCNQ and CNQ. Furthermore, CO2 adducts should be the carbonate type products according to the theoretical calculation results by Gaussian 09 package.

An ultrasensitive electrochemiluminescence biosensor was established based on the Zn-MOF/GO nanocomposite. Ag(I)-embedded DNA complexes were used as a signal amplification reagent. In this work, 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (TCPP) and Zn2+ were integrated into a porphyrin paddlewheel framework (Zn-MOF) by a hydrothermal method. The synthesized Zn-MOF material has electrochemiluminescence property, and the luminescence intensity is improved after being composited with graphene oxide (GO). Based on the composite material, we constructed an ultrasensitive ECL biosensor for the p53 antibody detection. The composite material acted as an admirable substrate and then loaded plenty of p53 antigens to recognize the target (p53 antibody) accurately. Because of the bridging effect of streptavidin and biotin-conjugated goat anti-rabbit IgG (bio-ab2), the rich-C DNA with positive correlation with the target was modified on the electrode and then captured the co-reactant accelerator Ag+ to amplify the signal. Therefore, the ECL biosensor response increases with increasing p53 antibody concentration. In the range 0.1 fg/mL–0.01 ng/mL, the response signal of the biosensor has a good linear relationship with the p53 antibody concentration. The detection limit is 0.03 fg/mL (S/N = 3). Impressively, the biosensor not only featured high sensitivity, good stability, and excellent specificity for the detection of p53 antibody, but also provides a new way for early detection of cancer.

Herein, we established a novel ultrasensitive photoelectrochemical biosensor for detecting urokinase-type plasminogen activator (u-PA), based on a g-C3N4/CdS nanocomposite. The prepared nanocomposite was characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet–visible absorption spectroscopy, and Fourier transform infrared spectroscopy, thus indicating that the nanocomposite was prepared successfully. In the typical process, the prepared nanocomposite was deposited on the surface of a bare FTO electrode. After being air-dried, the g-C3N4/CdS nanocomposite modified electrode was successively incubated with antibody against urokinase-type plasminogen activator and the blocking agent BSA to produce a photoelectrochemical biosensor for u-PA. In the presence of target u-PA antigen, the photocurrent response of the prepared biosensor electrode decreased significantly. The proposed novel photoelectrochemical biosensor exhibited good sensitivity, specificity, and reproducibility for u-PA detection, and a low detection limit of 33 fg mL−1, ranging from 1 μg mL−1–0.1 pg mL−1. The proposed strategy should provide a promising method for detection of other biomarkers.

A glassy carbon electrode (GCE) was modified with eosin Y that was electrodeposited on GCE via continuous cycling between − 1.6 and 1.5 V (vs Ag/AgCl). This electrode was characterized by scanning electron microscopy and electrochemical impedance spectra. The resulting electrode exhibited excellent electrocatalytic activity toward the oxidation of butylated hydroxyanisole (BHA) and tert-butyl hydroquinone (TBH2Q); in addition, the oxidation products of BHA and TBH2Q were found to be the same, which was studied by CV and in situ FT-IR spectroelectrochemistry. Under the optimized condition, the oxidation peak currents were linear to BHA/TBH2Q in the range from 0.10 to 7.00 μg mL−1 with the detection limits of 0.01 μg mL−1 (S/N = 3) for BHA and 0.015 μg mL−1 (S/N = 3) for TBH2Q, respectively. Moreover, the reproducibility and repeatability of the electrode were determined. The proposed method was successfully applied in the simultaneous determination of BHA and TBH2Q in several edible oil samples, and satisfactory results when compared with those obtained using high-performance liquid chromatography.

In this paper, hydrothermal method was used for the synthesis of SnO2 quantum dots (QDs). The prepared SnO2 QDs have a uniform particle size distribution and good electrochemiluminescence (ECL) property. Then the prepared SnO2 QDs was combined with graphene-like carbon nitride (g-C3N4) through chitosan to form SnO2/chitosan/g-C3N4 nanocomposite and used for detecting the lincomycin. The characteristics of SnO2/chitosan/g-C3N4 nanocomposite were presented by transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS), and the analytical results proving that the nanocomposite was prepared successfully. In this strategy, the SnO2/chitosan/g-C3N4 nanocomposite was acted as the substrate of aptasensor. Then, SH-DNA (aptamer DNA) was assembled on the surface of electrode, after 6-mercaptohexanol (MCH) blocked the unbound sites of the electrode surface, ferrocene-DNA (Fc-DNA) was incubated on the electrode surface through base complementation with aptamer DNA. In the absence of lincomycin, due to the low conductivity of Fc-DNA and the photo-excited energy electron transfer, the ECL signal was quenched. In the presence of lincomycin, the aptamer DNA was specific binding with lincomycin, and ferrocene-DNA (Fc-DNA) was detached from the surface of aptasensor electrode, generating an obviously enhancement of ECL signal. To ensure the accuracy of the data, each electrode runs continuously for 3600 s. Under optimal experimental conditions, the detection range of the aptasensor was 0.10 ng mL−1 - 0.10 mg mL−1, and the detection limit was 0.028 ng mL−1. In addition, the aptasensor has good stability and reproducibility, and also provided a hopeful device for all kinds of other protein target.

An electrochemiluminescence (ECL) biosensor was fabricated for the evaluation of prostate specific antigen (PSA). The sensor was developed by successively modifying glassy carbon electrode (GCE) electrodes with CdS/Chito/g-C3N4 nanocomposites and DNA1 was labeled at the 5′ end with thiol. The aptamer DNA was labeled at the 3′ end with a quencher ferrocene (Fc) was ligated to DNA1 by the principle of complementary base pairing. In the absence of PSA, the ECL intensity signal is effectively quenches through the energy transfer and photoexcitation electron transfer between CdS/Chito/g-C3N4 emitter and quencher Fc. After incubation with target PSA, the aptamer DNA interacts with PSA and then moved away from the electrode surface together, which will recover the ECL intensity. Under the optimal conditions, the ECL intensity increases linearly with the logarithm of PSA concentration in the range of 1 pg·mL−1 to 100 ng·mL−1, and the detection limit is 0.14 pg·mL−1 (S/N = 3). The biosensor has been successfully applied to the determination of PSA in serum sample.

CdSe:Eu nanocrystals were successfully synthesized and characterized by transmission electron microscopy, X-ray powder diffraction, and X-ray photoelectric spectroscopy. The CdSe:Eu nanocrystals showed enhanced green electrochemiluminescence (ECL) intensity when compared to pure CdSe nanocrystals. Further, the nanocrystals were used to design an ECL immunosensor for the detection of carcinoembryonic antigen (CEA) that has a linear response over the 1.0 fg·mL−1 to 100 ng·mL−1 CEA concentration range with a 0.4 fg·mL−1 detection limit. The assay was applied to the determination of CEA in human serum samples.

The electrochemical reduction of 1,4-dinitrobenzene (PNB) in ionic liquid (BMIMPF6 and HMIMPF6) has been studied by cyclic voltammetry (CV) and IR spectroelectrochemistry. In ionic liquid, only one couple of redox peak is observed, but the results obtained from IR spectroelectrochemistry support the existence of intermediate (PNB −) in ionic liquid, hence it is reduced in two-step one-electron transfer. The results obtained in mixed media (CH3CN with ionic liquids) suggest that the electrochemical products (radical anion PNB − and dianion PNB2 −) can form strong ion-pairing with the cation of ionic liquid, and the interaction between the electrochemical products and BMIM+ is much stronger than HMIM+. In proton donors mixed media (ionic liquid with ethanol), the interaction of hydrogen-bonding between the electrochemical products and ethanol is much stronger than the interaction of ion-pairing between the electrochemical products and the cation of ionic liquid.

Hybridizing nanostructured metal nanoparticles with metal-organic framework is greatly promising for the enhancement of electrochemical performance of sensor. In the present study, an Ag nanoparticles-ZIF-67 nanopinnas composite material (Ag-ZIF-67p) has been fabricated by ultrasonication and reduction of a metal precursor (AgNO3) within ZIF-67 nanopinnas template. The desired Ag-ZIF-67p was characterized by transmission electron microscopy with energy dispersive X-ray analysis and elemental mapping, powder X-ray diffraction, X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy. The Ag-ZIF-67p was modified on the GCE and demonstrated enhanced electrocatalytic activity toward dopamine (DA) and acetaminophen (AP) owing to synergetic properties of large porosity and surface area of ZIF-67 and the high conductivity and excellent catalytic activity of Ag nanoparticles. The results revealed broader linear range toward analysis of DA and AP with low detection limit of 0.2 and 0.05 μM (S/N = 3) for AP and DA, respectively. In addition, this Ag-ZIF-67p modified electrode also showed excellent selectivity for the detection of two compounds and prospective results in real tablets and dopamine hydrochloride injection samples.

The detection and speciation analysis of metal-ion is very important for environmental monitoring. A novel electrochemical biosensor for Nickel(II) detection based on a DNAzyme-CdSe nanocomposite was developed. We firstly hybridized with capture probe (DNA1) and sequentially with DNA (DNA2) on the gold electrode. Then CdSe QDs were incorporated the specific recognition of DNA2 by covalent assembling. Upon addition of nickel ion into the above system, the substrate strand of the immobilized DNAzyme was catalytically cleaved by target Ni(2+), resulting in disassociation of the shorter DNA fragments containing CdSe QDs. The remaining CdSe QDs on the electrode surface detected by differential pulse anodic stripping voltammetry (DPASV). Under optimal conditions, the as-prepared sensor exhibited high sensitivity and fast response to Ni(2+) with the linear range from 20 nM to 0.2mM and a low detection limit of 6.67 nM. The prepared biosensor also shows good stability and good reproducibility and high selectivity toward target Ni(2+) against other metal ions because of highly specific Ni(2+)-dependent DNAzyme. Thus, our strategy has a good potential in the environment surveys.

A novel multifunctional reduced graphene oxide (RGO)/Fe 3 O 4 /PDDA/CdSe nanocomposite has been successfully prepared and used as probe for an electrochemiluminescence (ECL) immunosensor of human interleukin-6 (IL-6). The prepared RGO/Fe 3 O 4 /PDDA/CdSe nanocomposite was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible (UV–vis) absorption spectroscopy, and a vibrating sample magnetometer (VSM). This nanocomposite shows magnetism, ECL properties, and good biocompatibility. Furthermore, the RGO/Fe 3 O 4 /PDDA/CdSe nanomaterial was applied to develop an ultrasensitive ECL immunosensor for detection of IL-6. The ECL intensity decreased linearly with the IL-6 concentrations in the range 0.002 to 20 ng/mL. Furthermore, the developed ECL immunosensor with high sensitivity, stability and excellent reproducibility can be used for detection of real samples, which make it possible to be used in clinical detection.

The electrochemical character of 1,4-naphthoquinone (Q) in aprotic media and proton donor mixed solvent was explored by cyclic voltammetry (CV), in situ FT-IR spectroelectrochemistry, cyclic voltabsorptometry (CVA) and derivative cyclic voltabsorptometry (DCVA) techniques. In dimethyl sulfoxide (DMSO), Q is reduced in normal two-step one-electron transfer, forming the anion radical (Q − ) in the first step and the dianion (Q 2 − ) in the second step accordingly. However, the electrochemical behavior of Q in acetonitrile (CH 3 CN), acetonitrile–ethanol mixed solvent and dimethyl sulfoxide–ethanol mixed solvent is different from that in DMSO. It is found that in these solvents, Q is reduced to Q − firstly and meanwhile the neutral–anion radical dimer (Q 2 − ) comes into being. Then Q − is reduced to Q 2 − and Q 2 − is reduced to Q 2 2 − . At more negative potential, Q 2 2 − is further reduced to Q 2 3 − . In proton donor mixed solvent, hydrogen-bonding forms between Q 2 − (Q − , Q 2 − , Q 2 2 − , Q 2 3 − ) and C 2 H 5 OH.

The redox mechanism of polyaniline (PANI) film in acid solution was studied by in situ rapid-scan time-resolved infrared spectroelectrochemistry (RS-TR-FTIRS) method. In the potential rang between −0.29 and 0.91 V, there are four pairs of redox peaks. These four pairs of redox peaks were minutely investigated by cyclic voltammetry (CV) and in-situ infrared spectroelectrochemistry. The results illustrated that the first pair of redox peaks are according to oxidation of the secondary amines in the middle of molecular PANI chain, the second pair of redox peaks are according to oxidation of terminal primary amines, the third pair of redox peaks are according to oxidation of terminal hydroxyl groups, the forth pair of redox peaks are according to oxidation of the polaronic PANI to the bipolaronic PANI. The bipolaronic PANI completely turns to quinoid structure with highly conjugated by deprotonation when the electrode potential was higher than 0.71 V. Meanwhile, the hydrogen bonding between the oxidation products of PANI and water molecules disappeared.

A novel molybdenum sulfide-chitosan/CdSe quantum dots (MoS2-CS/CdSe QDs) composite was prepared by a facile liquid chemistry procedure. The composition and morphology of the composite as-prepared were characterized by a series of measurements. The electrode modified with MoS2-CS/CdSe QDs composite has excellent electrochemiluminescence (ECL) property that benefited from the synergistic effect of MoS2 nanosheets, CdSe QDs, and CS molecules. Based on strong and stable ECL emission, the electrode as-modified was used as ECL sensor for the detection of uric acid (UA) and the results show that the detection linear range for UA is from 0.10 to 140 nM with the detection limit of 0.040 nM. Depending on its good sensitivity and selectivity, this ECL sensor was successfully applied to determine uric acid in urine sample.

A simple and sensitive electrochemical method for the simultaneous detection of hydroquinone (HQ) and catechol (CC) was developed, based on a multi-walled carbon nanotube and MnO2 nanowire composite (MWCNTs–MnO2) modified glassy carbon electrode (GCE). Electrochemical impedance spectra studies showed a small charge transfer resistance (Rct) for the MWCNTs–MnO2 composite film due to the incorporation of MWCNTs. Compared with the bare GCE, both HQ and CC exhibited well-defined redox peaks and much larger peak currents at MWCNTs–MnO2/GCE, which was related to the higher specific surface area and catalysis rate of the MWCNTs–MnO2 film. The MnO2 film acted as an electron transfer mediator to accelerate the electron transfer rate for the oxidation of HQ and CC. Due to the large separation of oxidation peak potentials (102 mV), the concentrations of HQ and CC can be easily determined simultaneously. The oxidation peak currents were linear to HQ/CC in the range from 5 × 10−7 to 8 × 10−5 M with the detection limits of 5 × 10−8 M (S/N = 3) for HQ and 8 × 10−8 M (S/N = 3) for CC. Simultaneous determination of HQ and CC with such an electrode was conducted in tap water samples with reliable recovery.

A simple and sensitive multi-walled carbon nanotubes (MWCNTs)–ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate, BMIMPF6, IL) composite modified glassy carbon electrode (GCE) was successfully developed for the electrochemical determination of trace-levels of luteolin. The prepared composites were characterized by scanning electron microscopy (SEM). Compared with the bare GCE, the BMIMPF6/GCE and MWCNTs/GCE, MWCNTs–BMIMPF6/GCE exhibited a higher electrocatalytic ability toward the oxidation of luteolin due to the synergic effects of the good electrical properties and large surface-to-volume ratio of the MWCNTs together with the good conductivity and wide potential windows of the IL. A series of experimental parameters including the pH of the supporting electrolyte and accumulation time were optimised. The electrochemical sensor can be applied to the quantification of luteolin with a linear range covering 5 × 10−9–1 × 10−6 mol·L−1 (with a correlation coefficient of 0.9969) and the limit detection is 5 × 10−10 mol L−1 (S/N = 3). Moreover, the method was successfully applied for the determination of luteolin in Chrysanthemum as a real sample with satisfying results.

Here we report that a novel zinc(II) complex with an intramolecular ‘push–pull’ structure was synthesized and fully characterized. For the zinc(II) complex, the photoluminescence (PL) emission wavelength is at 460 nm and the excitation wavelength is at 380 nm. The two-photon absorption cross-section (σ) of the zinc(II) complex reached 140 GM (1 GM = 1 × 10−50 cm4 s photon−1). An electrochemiluminescence (ECL) sensor could be built with a glass carbon disk electrode (GCE, Φ 4 mm) modified with the zinc(II) complex, and this exhibited an enhanced ECL intensity, good biocompatibility and long-term stability to detect ctDNA. Meanwhile, the reliability of the extracted signal was demonstrated in solutions of different pH values.

The electrochemiluminescence (ECL) behavior of the sulfur-terminal CdS2L complex synthesized in this work was studied, and the ECL mechanism and effect factors were discussed. Based on the strong and stable ECL emission of the CdS2L complex, a solid-state ECL sensor was fabricated. The as-prepared sensor was used to detect glutathione (GSH), and the results show that the linear response range is from 0.002 μM to 4 μM with a detection limit of 0.67 nM for GSH solution.

A film of perovskite-type LaFeO3 nanoparticles (NPs) was deposited on fluorine-doped tin oxide (FTO) conducting glass via dipping-lifting and calcination. Scanning electron microscopy shows that the NPs are evenly distributed on the surface of the glass. The modified glass was further coated with antibody against human interleukin 6 (IL-6) to result in a photoelectrochemical immunosensor for IL-6. The well-established photoelectrochemical immunoassay has a linear current response in the range of 0.1 pg·mL−1 to 0.1 μg·mL−1 and a detection limit as low as 33 fg·mL−1.

In this study, a typical intramolecular charge transfer (ICT) triphenylamine derivative, [4-(diphenylamino)phenyl]methylenepropanedinitrile (abbreviated as DPMP) was synthesized. Controllable one dimensional (1D) nanocrystals of DPMP have been obtained through reprecipitation method. The thermodynamic relationship of the molecular structure and growth process in nanometer scale of DPMP was investigated through density functional theory (DFT) calculation, which was performed on the weak interactions between adjacent molecules. The results showed that the assembling interactions along a axis were much stronger than that along b and c axis, which meant that 1D orientation growth along a axis would be the most stable state in thermodynamics, that is to say, DPMP molecules tended to form 1D orientation structure. The study is helpful to understand the relationship of molecular structure, weak interactions, orientation growth process and self-assembling morphology.

A novel amplification system for electrochemiluminescence (ECL) was developed by combining graphene oxide (GO) and Se nanoparticles, in which the chitosan (CHIT) was used as improver. Based on a series of experiments, the influencing factors and mechanism for ECL emission were determined. Under optimal conditions, the GO/Se nanocomposite produced an intense ECL emission and maintained long-term ECL stability. Significantly, the electrode modified with GO/Se nanocomposite was used to detect the biomolecule dopamine (DA), and showed a linear range from 0.1 to 100 µM, with a detection limit of 0.025 µM.

Electrochemically reduced graphene oxide modified glassy carbon electrodes (ERGC) were obtained under various reducing conditions to control the content of oxygen-functional groups (OxFG). By utilizing Fe ( CN ) 6 3 - / Fe ( CN ) 6 4 - , AA and DA as redox probes cyclic voltammogram (CV) and differential pulse voltammogram (DPV) results indicated that for various substances the effect of OxFG was distinct and different types of OxFG (C O, C O C, OH, COOH, etc.) played entirely different roles for one substance which were reflected in peak potential shift and peak current change. Finally, the optimum reducing conditions of fabricating ERGC for the detection of AA and DA separately and simultaneously were explored and satisfactory results were obtained.

CeO2/TiO2 composite with kernel–shell structure was synthesized by a sol–gel process. The characterization results show that the composite is made up of anatase phase TiO2 and cubic system CeO2. The electrochemiluminescence (ECL) behavior of the CeO2/TiO2 composite was studied by a cyclic voltammetry in the presence of persulfate, and the effect factors on ECL emission were discussed. Based on a series of experiments, it is proposed that the strong dual ECL emission produced by the CeO2/TiO2 composite resulted from the benefit ECL effect of interface heterojunction in composite.

The structures of four novel organic–inorganic hybrid dyes, namely trans-4-(4′-(N,N-Dialkylaminostyryl))-N-Methyl-pyridinium[Mo6O192−] [alkyl = Et(POM1), Pr(POM2), n-Bu(POM3) and Me, hydroxyethyl(POM4)], were characterized by single crystal X-ray diffraction analysis. Hybridization of the organic chromophores with polyoxometalate enhanced their two-photon absorption cross sections and thermal stability. The linear optical properties of the hybrid dyes were investigated using absorption and fluorescence spectra in both the solution and solid states. The two-photon absorption cross section δ and coefficient β were obtained using the Z-scan technique. Correlations between dye structure and optical property were investigated.

Cyclic voltammetry (CV), IR spectroelectrochemistry cyclic voltabsorptometry (CVA) and derivative cyclic voltabsorptometry (DCVA) technique were used to investigate the electrochemical character of a representative quinone, p-benzoquinone (BQ), in aprotic media, organic-water mixed solvent, unbuffered acidic aqueous ([H + ] + ] > [BQ]). Several well-separated IR absorption peak pairs, 1656, 1316; 1502, 1340; and 1230, 1473 cm −1 , corresponding to redox transitions (BQ, BQ − , BQ 2− ), are observed and can be used to trace the concentration of BQ, BQ − and BQ 2− independently during CV scan. Based on CVA and DCVA techniques, it is clearly distinguished that each step of the two consecutive electron transfer process of BQ in unbuffered neutral aqueous takes place, although only one CV wave is experimentally observed during CV scan. Direct evidence of hydrogen-bonding (H-bonding) forming between BQ 2− (BQ − ) and H 2 O in unbuffered neutral water and that between BQ and H 3 O + in strong acidic solution are observed. The results of IR CVA and DCVA not only help us understand the fundamental factors of H-bonding and protonation on redox mechanism of BQ, but also draw the entire map of the electrochemical reduction of BQ in different solution.

Ortho-CuAgSe nanotubes were facilely synthesized through a nanotube–nanotube transformation process in aqueous solution at room temperature. The products as-obtained were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX), X-ray photoelectron spectra (XPS) and thermogravimetric (TG)/differential scanning calorimetric (DSC). On the basis of a series of the experiment results, the formation mechanism of ortho-CuAgSe nanotubes was proposed. From kinetics and energetics, it had been demonstrated that the exchange of univalent cation between ortho-Ag2Se (orthorhombic phase Ag2Se) nanotubes and ortho-Cu2Se nanotubes in the formation process of ortho-CuAgSe nanotubes was feasible in mild condition. Furthermore, the electrochemical property of the nanotubes as-obtained was studied by the voltammetric technique.

A series of ferrocene-substituted thiophenes, 2-ferrocenylthiophene, 2,5-diferrocenylthiophene and 2,3,5-triferrocenylthiophene have been synthesized. The electron transfer mechanism during redox process of the ferrocenyl complexes was studied by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and rapid-scan time-resolved FT-IR spectroelectrochemistry (RS-TRS FT-IR). Electrochemistry and RS-TRS FT-IR spectroelectrochemistry results indicated the redox process of 2,5-diferrocenylthiophene and 2,3,5-triferrocenylthiophene involved two and three consecutive one-electron steps, respectively. IR absorption peaks arisen from intermediate appearing and disappearing on the experimental time scale in the oxidation and reduction process of 2,5-diferrocenylthiophene and 2,3,5-triferrocenylthiophene were clearly observed by the RS-TRS FT-IR spectroelectrochemistry. A kinetics simulation experiment, based on the results of RS-TRS FT-IR spectroelectrochemistry, was conducted to give the kinetics parameters of 2,5-diferrocenylthiophene.

Aiming to enhance the use of solar energy, novel SeO 2 /TiO 2 nanocomposite was prepared by water bathing and calcining. Based on the characteristic of SeO 2 and TiO 2 , the work mechanism of the nanocomposite was discussed. The products as obtained were characterized by SEM, HRTEM, EDX, XRD, XPS, LRS and UV-vis. The results shown that the SeO 2 /TiO 2 nanocomposite is a hopeful form for improving the practicability of TiO 2 .

The design and tests of a low temperature optically reflected absorbance cell for in situ FTIR spectroelectrochemistry is discussed. It works very well in the temperature range from −100 to +25 °C with temperature control precision within ±0.5 °C. The cell is facile cleaning and convenient manipulation. Besides, it can work, successively, for long time with filling the Dewar flask with liquid N2. The electrochemical performance of the cell is characterized in cyclic voltammetry with K4Fe(CN)6 at room temperature and in steady-state voltammetry with ferrocene at low temperature. The low temperature applicability of the cell for in situ FTIR is demonstrated to observe the electrogenerated intermediate of 1,4-bis(2-ferrocenylvinyl)benzene (p-(Fc–CH CH)2BZ).

Article, Analytical sciences. 22(9): 1261-1264 (2006)

Horse heart cytochrome c (cyt c) was adsorbed on the binary self-assembled monolayers (SAMs) composed of thioctic acid (T-COOH) and thioctic amide (T-NH2) at gold electrodes via electrostatic interaction. The cyt c adsorbed on the modified gold electrode exhibited well-defined reversible electrochemical behavior in 10 mM phosphate buffer solution (PBS, pH 7.0). The surface concentration (Γ) of electroactive species, cyt c, on the binary SAMs was higher than that in single-component SAMs of T-COOH, and reached a maximum value of 9.2 × 10−12 mol cm−2 when the ratio of T-COOH to T-NH2 in adsorption solution was of 3:2, and the formal potential (E0′=(Epa+Epc)/2)(E0′=(Epa+Epc)/2) of cyt c was −0.032 V (vs. Ag|AgCl (3 M NaCl)) in a 10 mM PBS. The interaction between cyt c and the binary SAMs made the E0′E0′ shift negatively when compared with that of cyt c in solution (+0.258 V vs. NHE, i.e., +0.058 V vs. Ag|AgCl (3 M NaCl)). The fractional coverage of bound cyt c was a 0.64 theoretical monolayer. The standard electron transfer rate constant of cyt c immobilized on the binary SAMs was also higher than that on single-component SAMs of T-COOH, and the maximum value of 15.8 ± 0.6 s−1 was obtained when the ratio of T-COOH to T-NH2 in adsorption solution was at 3:2. The results suggest that the electrode modified with the binary SAMs functions better than the electrode modified with single-component SAMs of T-COOH.

The electrochemical behavior of a poly(acrylamide) (PAA) membrane electrode (ME), in which the PAA works as a membrane matrix for use in non-aqueous solutions, was investigated in acetonitrile. It was found that PAA MEs possess properties of microelectrode ensembles (MEEs). For the thin PAA membrane, the electrode behaved similar to a macroelectrode and peak-shaped voltammograms were achieved at low scan rates, while at high scan rates the electrode acted as a microelectrode and sigmoidal-shaped voltammograms were obtained. For the thick PAA membrane electrode, however, voltammograms were sigmoidal-shaped at low scan rates, and at high scan rates the voltammograms became peak-shaped again. Quantitative and semiquantitative analyses of the electrochemical response characteristics of these ensembles were conducted. The results show that the electrochemical behavior of these ensembles is in close agreement with the predictions of established microwell electrochemical theory.

The finite analytic numerical method (FAM) is an efficient method for solving two-dimensional electrochemical diffusion problems on microelectrodes. Its basic idea is the incorporation of the analytic solutions of local small elements in the numerical solution of partial differential equations. In this paper, we present a detailed introduction of the finite analytic solution and an overview of the incorporation of the finite analytic solution in the numerical simulation and the application of FAM in different electrochemical problems.

A fluorophore-phenylamine derivative (L) has been coupled with silver nanocrystals (NCs) to construct an L-Ag nanohybrid. Owing to synergic effects of the L and Ag components, the exciton-plasmon interactions between L and Ag increase the strength of the donor-acceptor interaction within the nanohybrid, a fact that results in an energy-transfer process and further brings about a dramatic redshift of single-photon absorption and fluorescence, and a decreased fluorescence FL lifetime. The coupling effect also leads to enhancement of a series of nonlinear optical properties, including two-photon-excited fluorescence (TPEF), two-photon-absorption (TPA) cross section (δ), two-photon-absorption coefficient (β), nonlinear refractive index (γ), and third order nonlinear optical susceptibility (χ((3))). The enhanced two-photon fluorescence of the nanohybrid is proven to be potentially useful for two-photon microscopy of live cells, such as HepG2. Moreover, cytotoxicity tests show that the low-micromolar concentrations of the nanohybrid do not cause significant reduction in cell viability over a period of at least 24 h and should be safe for further biological studies.

The finite analytical numerical method (FAM) combined with a conformal map has been used to study diffusion problems at a micro-ring electrode. The chronoamperometric and voltammetric responses for both reversible and quasi-reversible charge transfer at ring microelectrodes of different thicknesses are simulated. The effect of the thickness of the micro-ring electrode, the potential sweep rate and the heterogeneous electron transfer kinetic parameter on the voltammetric responses is discussed. The results show that the thin micro-ring electrode is more appropriate for the evaluation of fast electrode reaction rate constants than a thick micro-ring or microdisk electrode.

The finite analytic numerical method combined with conformai mapping has been used to study the diffusion problems at an oblate hemispheroid microelectrode. The chronoamperometric and voltammetric responses for both reversible and quasi-reversible charge transfer at differently shaped oblate hemispheroid microelectrodes are simulated. The effect of the geometric parameter γ = ( b 0 / a 0 ), dimensionless sweep rate parameter p = ( nFva 0 2 / RTD ) 1/2 , kinetic parameter Λ = k s a 0 / D , on the current-potential-time responses is studied. The simulated results are compared with the results available in the literature and they are in good agreement. A mercury oblate hemispheroid microelectrode was fabricated and experiments were carried out in a chemically stable system, 2,3,5,6-tetrachlorobenzoquinone in acetonitrile. The experimental results also provide verification of digital simulations of the responses on the oblate hemispheroid microelectrode.

Diffusion problems on coplanar and elevated interdigitated microarray band electrodes (IDAs) were studied by the finite analytic numerical method (FAM). Chronoamperometric curves and steady-state current-potential curves for both coplanar and elevated IDAs were simulated for diffusion controlled and quasi-reversible systems. The simulated results for coplanar IDAs were compared with those available in the literature, and found to be in good agreement. The influence of the geometric parameters (electrode height h e , ratio of electrode width w e and gap width w g ) of the elevated IDAs were also investigated. The computing time necessary is much less compared with results in the literature.

An attractive numerical method — the finite analytical (FA) numerical method for diffusion in electrochemical problems — is developed. Unlike finite-difference or finite-element methods, the discrete algebraic equation is obtained from the analytical solution for each local element in the FA method. These yield a fast and accurate numerical method applied to electrochemical diffusion problems. The FA method is suitable for a simple electrode reaction with any value of heterogeneous electron transfer kinetic parameters or electrode reaction with a coupled chemical reaction. The problems of transport to inlaid disk and band microelectrodes controlled by diffusion and kinetics are studied in this paper. The chronoamperograms and cyclic voltammograms were computed by the FA method and the results were compared with those in the literature.

One novel bisferrocene pyrazole derivative, bis [2-(5-trifluoromethyl-3-ferrocenyl) pyrazolyl] methane (abbreviated as (3)), was synthesized and fully characterized. A single crystal of (3) was obtained and solved by X-ray diffraction analysis. The bisferrocene derivative exhibits MLCT (metal to ligand charge transfer) and π→π* transitions in the UV-visible range, which have been verified by density functional theory (DFT) calculations. Its electrochemical properties were studied with the aid of cyclic voltammetry (CV), differential pulse voltammetry (DPV) and rapid scan time-resolved Fourier transform infrared spectroscopy (RS-TRS FT-IR) analysis. Furthermore, the electrochemical mechanism was elucidated based on the results from the cyclic voltabsorptometry (CVA) determination technique. (3) apparently shows a single wave in the cyclic voltammetric experiments which indicates there is no intermediate, however, the intermediate of (3) was observed by employing the RS-TRS FT-IR spectroelectrochemistry technique. The detailed investigation brought us safely to the conclusion that the methylene can also act as a linker, leading to electronic communication in either D–π–D and A–π–A systems.

In this paper, we report the IR (infrared) CVA (cyclic voltabsorptometry) and DCVA (derivative cyclic voltabsorptometry) spectroelectrochemical techniques to elucidate an electrochemical mechanism. First we set potassium ferrocyanide as an example to explain the validity of this method. Then the electrochemical redox of two compounds, 1,4-benzoquinone and 1,4-bis(2-ferrocenylvinyl)benzene, was selected to be examined with this method. 1,4-Benzoquinone exhibits two single-electron waves in the cyclic voltammetric (CV) experiment, whereas two electroactive groups (Fc) are contained in p-(Fc-CH=CH)(2)BZ, but only one redox wave is observed. IR CVA results show that three IR absorption peaks in 1,4-benzoquinone, 1232 cm(-1) (the absorption of final production), 1656 cm(-1) (the absorption of original reactant), and 1510 cm(-1) (the absorption of intermediate), and two IR absorption peaks in 1,4-bis(2-ferrocenylvinyl)benzene, 1620 cm(-1) (the absorption of final oxide production) and 1589 cm(-1) (the absorption of intermediate), can be used to track the electron transfer. On the basis of the IR absorbance at the appropriate monitored wavelength (mentioned above), we can analyze simultaneously the concentration change of the corresponding redox transition during CV scans. Also the combination of the DCVA spectroelectrochemical technique with theory analysis allows reconstructing the current-potential (i-E) curve for each step of electron transfer. The reconstructed i-E curve can help us to understand the electron-transfer process. We believe IR CVA and DCVA spectroelectrochemical techniques can be applicable to the study of a wide range of complex electrochemistry processes.

Mechanism of electron transfer of a bridge biferrocene complex, Ni(LSB)2, derived from the Schiff base ligand, HLSB, S-benzyl-N-(ferrocenyl-1-methyl-metylidene)-dithio-carbazate Ni(LSB)2, during redox processes is illuminated by in-situ Fourier transform infrared (FTIR) spectroelectrochemistry. The results indicated that two consecutive one-electron steps were involved which gives the corresponding mono- and di-ferricenium cations, respectively. This complex exhibits moderately strong degree of electronic communication between the two-ferrocene moieties, taking place through the skeleton chain of the ligand due to an extensive electron delocalization in the molecule. Possible pathways of electron transfer of Ni(LSB)2 during the redox processes are postulated.

An unlimited water-soluble white emitter with two-photon absorption has been designed and synthesized. Water solubility has strongly hindered the ability and application of white emitter with two-photon absorption (TPA) materials. To overcome this shortcoming, during the course of synthesis, the copolymer was prepared using the isocyanate and ligand esterification reaction. To test the performance of the product, a series of characterizations were implemented. New copolymer exhibits strong NIR absorption, low band gap and good thermal stability. Particularly, the copolymer demonstrates perfect water-solubility, two-photon absorption and the possibility to be a white emitter. These characters may significantly broaden the possibility of using TPA materials for display.