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A facile method for the in situ fabrication of chitosan/polythiophene/CdTe (CS/PTh/CdTe) nanocomposite has been developed. It was then connected with anti-CEA (Ab), which was evoked for the electrochemical detection of carcinoembryonic antigen (CEA, Ag) within K

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.

In this work, platinum–nickel–ruthenium (PtNiRu) nanocrystals with different amounts of Ru were synthesized by a one-pot solvothermal method. In the absence and presence of ruthenium trichloride, the evolution of the structure and composition of the obtained Pt alloys was clearly observed. In comparison with PtNi irregular nanocrystals, PtNiRu nanospheres and nanodendrites were obtained under the same reaction conditions. The structure, composition and the formation pathway of the PtNiRu nanodendrites were investigated in detail. Finally, the catalytic results from the methanol oxidation suggested that the mass activity and the area specific activity of the PtNiRu nanodendrites were 3.5 and 3.1-fold higher than those of commercial Pt/C, as well as having better durability, which was due to the porous structure and synergistic effect of Ni/Ru. It is expected that the present study could provide a new approach for designing alloys based on Pt modified with low amounts of Ru for energy conversion applications.

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.

Polyaniline/multi-walled carbon nanotube composites synthesized in situ by cyclic voltammetry method on glassy carbon electrodes were employed as substrate layer for platinum nanoparticles to fabricate platinum/polyaniline/multi-walled carbon nanotube nanocomposites (PPMC). The microstructures characterizations revealed that the polyaniline/multi-walled carbon nanotube rods with diameters 200 nm were similar to the shape of stick, and Pt nanoparticles with diameters 260 nm were similar to the shape of sugarcoated haws. The cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry methods were used to investigate the catalytic performance of the composite. The experimental results showed that the PPMC had superior electro-catalytic performance toward methanol oxidation of platinum/polyaniline/multi-walled carbon nanotube to commercial Pt/C catalysts. The composite would have broad applications in direct methanol fuel cell field as new catalytic material.

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.

A novel ultrasensitive photoelectrochemical aptasensing was developed to detect mucin 1 (MUC1) based on TiO2/CdS:Eu nanocomposite. The TiO2/CdS:Eu nanocomposite modified fluorine-doped tin oxide (FTO) electrode was prepared by successive ionic layer adsorption and reaction technique (SILAR) and then was employed as matrix for immobilization of SH-DNA (DNA1). After 6-mercaptohexanol (MCH) blocked unbound sites of the electrode surface, the MUC1 aptamer(DNA2) was introduced, allowing MUC1 aptamer to hybridize with DNA1. Subsequently, CdS-COOH QDs as signal amplification elements were successively labeled on the terminal of MUC1 aptamer. In this case, the target MUC1 detection was based upon the photocurrent change originated from quantities change of the signal amplification elements CdS. In the presence of MUC1, the MUC1 aptamer was specifically bound with MUC1, and meanwhile MUC1/DNA2/CdS was released from the electrode surface, resulting in significantly decreased photocurrent intensity. The novel ultrasensitive photoelectrochemical aptasensing presented a highly selective, sensitive and reproductive detection of MUC1 from 1 nM to 5 μM with a lower detection limit of 0.3 nM. At the same time, it also provided a good specificity, reproducibility, stability and promising strategy to detect a variety of other protein targets for early clinical diagnosis of different diseases.

A novel enhanced photoelectrochemical DNA sensor, based on a TiO2/Au hybrid electrode structure, was developed to detect target DNA. The sensor was developed by successively modifying fluorine-tin oxide (FTO) electrodes with TiO2 nanoparticles, gold (Au) nanoparticles, hairpin DNA (DNA1), and CdSe-COOH quantum dots (QDs), which acted as signal amplification factors. In the absence of target DNA, the incubated DNA1 hairpin and the CdSe-COOH QDs were in close contact with the TiO2/Au electrode surface, leading to an enhanced photocurrent intensity due to the sensitization effect. After incubation of the modified electrode with the target DNA, the hairpin DNA changed into a double helix structure, and the CdSe QDs moved away from the TiO2/Au electrode surface, leading to a decreased sensitization effect and photoelectrochemical signal intensity. This novel DNA sensor exhibited stable, sensitive and reproducible detection of DNA from 0.1 μM to 10 fM, with a lower detection limit of 3 fM. It provided good specificity, reproducibility, stability and is a promising strategy for the detection of a variety of other DNA targets, for early clinical diagnosis of various diseases.

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 work, the raspberry-like Pt nanoparticles/polyaniline complexes (PNPC) has been fabricated for methanol electro-oxidation. The PNPC were electrochemically deposited by one-step from solutions simultaneously containing aniline and potassium tetrachloroplatinate. Morphological and structural characterizations demonstrated that the Pt particles with diameters between 2 and 5 nm were like frambold of raspberry in polyaniline film. The electrochemical catalytic performance of PNPC was evaluated by cyclic voltammograms and chronoamperometric method. Electrochemical experiment results have amply confirmed that the PNPC have superior electro-catalytic oxidation performance and superior catalytic tolerance to carbonaceous species accumulation toward methanol oxidation. These results indicated that PNPC as catalysts carrier may have prosperous application for fuel cell technology.

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.

A hydrophilic polypyrrole/tellurium (PPy/Te) nanocomposite was synthesized by a facile approach in which H2TeO3 was used as the oxidizing agent of pyrrole and then the elemental Te formed in situ catalyzed the polymerization of pyrrole. The morphology and structure of the products were characterized by a series of testing technology. The electrochemical property and impedance of the PPy/Te nanocomposite were studied by cyclic voltammetry and electrochemical impedance spectroscopy, respectively. Significantly, the charge-discharge measurement results show that the PPy/Te nanocomposite has high specific capacitance (2488 F/g, at 2 A/g) and good cyclability.

A novel highly electrochemiluminescence (ECL) metal-organic frameworks (MOFs) have been successfully synthesized by combining CdSe quantum dots (QDs) and MIL-101 in one step by facile hydrothermal method. The as-prepared MIL-101-CdSe nanocomposites combine a high ECL activity and sensing selectivity derived from CdSe and the highly selective adsorption and efficient accumulation performance of MOFs. The selective accumulation effect of MOFs can greatly amplify the sensing signal and specificity of the ECL probe. The resulting nanocomposites were applied to develop an ultrasensitive ECL immunosensor for detection of carcinoembryonic antigen (CEA). This ECL immunosensor has a sensitive response to CEA in a linear range of 10−12 mg mL−1–10−4 mg mL−1 with a detection limit of 0.33 fg mL−1. The developed ECL immunosensor shows high sensitivity, good stability, specificity, and excellent reproducibility, and can be used for detection of real samples, which providing potential application in clinical detection.

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.

In the present work, Pd-Pt nanoparticle/polyaniline/carbon nanotube (NP/PANI/CNT) composites, synthesized through the uniform distribution of Pd-Pt NPs, whose single size was controlled to 2-4 nm by citric acid, on a PANI/CNT compound, served as the electrode catalysts for effective methanol oxidation. The structural characteristics were identified by x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy, and revealed that the Pt65Pd35 NP/PANI/CNT composite displayed superior electrocatalytic oxidation performance and vitality in various Pd-Pt NPs. The results indicated that as an excellent anode catalyst the complex would have application prospects for effective methanol oxidation.

The electrochemical behavior of p-nitrochlorobenzene (PNCB) in the aprotic solvent was investigated by cyclic voltammetry, bulk electrolysis, and in situ FT-IR spectroelectrochemistry. In the absence of CO2, the electrochemical behavior of PNCB is reversibly one-step single-electron transfer during the scan between -0.4 and -1.4 V, but with adding CO2, it is transformed into completely irreversible 4-electrons transfer process. The only electrolysis product indicating high selectivity in the presence of CO2 is confirmed as 4,4′-dichloroazobenzene (DAB) by X-ray single crystal diffraction, 13C-NMR, 1H-NMR and FTIR. In the absence of proton donor, the electrochemical degradation of PNCB at low potential is achieved, and CO2 is electrochemically converted to CO32− simultaneously. Based on cyclic voltabsorptometry (CVA) and derivative cyclic voltabsorptometry (DCVA) techniques, double potential step time-resolved IR scanning electrochemical technique (DPS TR IRSEC) was developed to illustrate the adsorption behavior of CO2 in the electrochemical reduction process. Therefore, a new electrochemical mechanism of PNCB in the presence of CO2 has been proposed based on the above results, which will be beneficial for theoretical research. The electrochemical degradation method is a promising and green chemical process for the degradation of chloronitrobenzene compounds (CNBs).

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.

A novel Ag 3 PO 4 /CuO nanocomposite photocatalyst was synthesized via a facile in-situ precipitation technique. The as-synthesized products were characterized by XRD, SEM, TEM and UV–vis spectroscopy. The result confirmed that Ag 3 PO 4 and CuO have been composited successfully. The degradation efficiency of Rhodamine B (RhB) over commercial P25 or pure CuO was only about 22% and 46%. Compared with pure Ag 3 PO 4 , the Ag 3 PO 4 /CuO nanocomposite needed less time to degrade RhB completely, showing the best photocatalytic activity. This enhancement was attributed to the coupling of Ag 3 PO 4 and CuO, which improve the transfer of photoexcited carriers, inhibit their recombination and facilitate the production of more • OH radicals.

The cobalt sulfide/graphene oxide (CoS/GO) nanocomposite was synthesized by a simple hydrothermal reaction. The products as-synthesized were characterized by XRD, SEM, TEM, BET-BJH and TG. The electrochemical property and impedance of the CoS/GO nanocomposite were studied by cyclic voltammetry and EIS analysis, respectively. The results show that the presence of the GO enhances the electrode conductivity, and then improves the capacitance property of the CoS/GO nanocomposite. The galvanostatic charge/discharge measurement results show that the CoS/GO nanocomposite has a high specific capacitance (550 Fg-1) and long cycle life (over 1 000 cycles).

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.

We present a facile hydrothermal approach to synthesize Ni 0.85 Se nanosheets, in which NiCl 2 and Na 2 SeO 3 were used as precursors. The characterization results indicate that the Ni 0.85 Se nanosheets possess hexagonal crystal structure and large specific surface area. Significantly, the Ni 0.85 Se nanosheets showed excellent adsorption to methylene blue (MB) and catalytic activity to the hydrogenation of p-nitrophenol (PNP) in presence of NaBH 4 .

Herein, an ultra-sensitive photoelectrochemical biosensor based on Ti3C2:CdS nanocomposite was established for the selective detection of microRNA159c. Ti3C2:CdS nanocomposites were used as optoelectronic materials because Ti3C2:CdS interaction effectively separates photogenerated electrons and holes, and significantly improves the high photoelectric conversion efficiency. Firstly, Ti3C2:CdS nanocomposite was deposited on the surface of the fluorine-doped tin oxide (FTO) electrode. After the chitosan (CS) was dropped, the SH-miRNA were bonded on the electrode surface via the S-Cd bond. Then 6-mercaptohexanol (MCH) blocked the unbound site, the DNA strand was introduced to hybridize with the target SH-miRNA. At this time, the obtained photocurrent gradually decreases. Subsequently, the photosensitizer TMPyP as signal amplification was modified, the photocurrent increased significantly. The target SH-miRNA was detected based upon the photocurrent change originated from quantities change of TMPyP. Working under the best experimental conditions, the sensing platform had good stability, selectivity, and high sensitivity. The detection range for miRNA159c was 1.0 × 10-6-1.0 × 10-13 mol·L-l, and the detection limit was approximately 33 fmol·L-l. The detection of miRNA159c in human serum provided a huge opportunity to explore the relationship between the abundance of this miRNA and the incidence of breast cancer (BC), and to further achieve effective detection of BC.

In this work, an ultrasensitive switchable electrochemiluminescence (ECL) RNA sensing platform was established based on metal-organic gel (MOG) and metal-organic framework (MOF) as electrode matrix and nanotag, respectively. The former was prepared via the in-situ loading of graphite-like carbon nitride (g-C3N4) and post-assembly of Au nanoparticles (AuNPs) within Zr-based MOG (AuNPs&g-C3N4@Zr-MOG), exhibiting highly efficient solid-state ECL. Fe-MIL-88 MOFs not only act as an ECL acceptor in ECL resonance energy transfer system but also have metal active centers to consume co-reactant, initiating double quenching effect on the ECL of AuNPs&g-C3N4@Zr-MOG. Then, DNA probe containing an apurinic/ apyrimidinic (AP) site connected the both, resulting in a turn-off signal. In the presence of the target RNA, the ECL was turned on because the AP site of DNA probe was activated to be circularly cleaved by endonuclease IV. Using Zika virus (ZIKV) RNA as a model analyte, the ECL platform showed a wide detection range from 0.3 nM to 3 μM with a detection limit as low as 0.1 nM. Besides, the sensor exhibited excellent specificity and stability, as well as acceptable real sample detection capability, illustrating the feasibility of clinical measurement in the future.

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.

Using graphene quantum dots (GQDs) and H 2 SeO 3 as precursors, the reduced graphene quantum dots/Se nanowires (rGQDs/SeNWs) composite was electro-synthesized in the presence of cetyltrimethylammonium bromide (CTAB). The morphology and crystallization of the products as-synthesized was studied by a series of characterization techniques. The conductivity and photoresponse of rGQDs, Se NWs and rGQDs/SeNWs composite were determined respectively. Benefiting from the synergistic action of electron-deficient rGQDs and electron-rich Se NWs, significantly, the rGQDs/SeNWs composite showed excellent photoelectric conversion.

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.

The Graphene Oxide/Polypyrrole/CdSe (GO/PPy/CdSe) nanocomposite with electrochemiluminescence (ECL) property was prepared by a novel and simple method. The composition and morphology of the nanocomposite as-prepared was characterized by a series of tests. Significantly, the electrode modified with GO/PPy/CdSe nanocomposite has strong and stable ECL emission, and can be used as ECL sensor. By studying the effect factors on ECL behavior and the ECL mechanism, it was found that the excellent ECL property of the modified electrode resulted from the synergistic effect of GO and PPy. The ECL sensor as assembled with the GO/PPy/CdSe nanocomposite was used to detect dopamine (DA), and the results show that the detection linear range for DA is from 0.01 to 16 nM with the detection limit of 0.004 nM.

A novel composite of Ag nanodendrites (AgNDs) wrapped with reduced graphene oxide (RGO) was prepared via a one-step electrodeposition approach. The characterization results show that three dimensional (3D) AgNDs with cubic phase are enwrapped by RGO sheets in the as-prepared RGO/AgNDs composite. Due to the synergistic effect of AgNDs and RGO, the RGO/AgNDs composite exhibited excellent photoelectrical conversion. Furthermore, due to its good electrochemical response to H2O2, an electrode modified with the RGO/AgNDs composite was used as a sensor for H2O2 detection, and the results show that the linear detection range is from 0.08 mM to 2.65 mM.

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.