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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.

How to modify carbon materials in a highly efficient manner is an important issue for the practical application. In this work, we demonstrate a hydrothermal approach for modifying nanoporous carbon using H2O2 and H2SO4 as oxygen/sulfur dopants, which can realize the purpose of achieving highly O/S doping. It reveals that hydrothermal temperature and dosage of H2SO4 exert crucial roles for determining the carbon structures and capacitive performances. The change of temperature affects the reaction process, changes the degree of oxidation of carbon by H2O2, and changes the number of oxygen-containing functional groups on carbon surface. Under constant temperature conditions, H2SO4, as a strong oxidizing acid, changes in its dosage will affect the oxidation strength of the system, while changing the number of oxygen-containing functional groups, increasing a certain amount of sulfur-containing functional groups. The specific capacitance of microporous carbon increases from 43 to 168 F g−1, nearly 3.5 times, at a scan rate of 100 mV s−1 in 6 M KOH aqueous electrolyte, under the action of oxygen-containing functional groups, and the cycle stability is also as high as 92%, which is higher than 90% of untreated nanoporous carbon. The energy density of the modified sample is 5.49 Wh kg−1 at the power density of 0.5 kW kg−1. In addition to improving the wettability of carbon materials, oxygen-containing functional groups also produce pseudocapacitance by redox reaction.

Photocatalytic hydrogen generation from water splitting has become a favorable route for the utilization of solar energy. An effective strategy, the combination of C-doping with nanocomposite semiconductors, is presented in this work. C-doped g-C3N4 (CCN) was prepared by supramolecular self-assembly and subsequently a number of CdIn2S4/CCN composite photocatalysts were designed and fabricated though in situ decoration of CdIn2S4 crystals on the surface of CCN nanosheets via a hydrothermal method. This unique architecture was able to efficiently promote the transfer and separation of photon-generated charges, enhance light absorption, and significantly increase photocatalytic H2 production. Detailed characterization was performed to analyze the crystal structure, morphology, elementary composition, optical properties and catalytic mechanism. The CdIn2S4/CCN nanocomposites with optimal CdIn2S4 content exhibited a maximum H2 production rate of 2985 μmol h−1 g−1, almost 15 times more than that obtained using pure g-C3N4 (205 μmol h−1 g−1). In addition, the hybrid photocatalysts display good recycling stability under visible-light irradiation. This research may provide promising information for the preparation of more efficient multifunctional hybrid photocatalysts with excellent stability in fine chemical engineering.

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 highly selective DNA-based electrochemiluminescence (ECL) based biosensor is described for the detection of human IgG. It is exploiting the effect of steric hindrance that affects the strength of the ECL signal in the presence of IgG. Digoxin-linked signaling DNA was specifically bound to IgG, and this causes steric hindrance which limits the ability of DNA to hybridize with capturing DNA attached to a gold electrode. Europium (II) doped CdSe quantum dots were covalently linked to the DNA in order to generate the ECL signal. Using this steric hindrance hybridization method, the ECL signal of the biosensor were proportional to the concentration of IgG with a wide linear range and a 14 pM detection limit. Conceivably, the method can be expanded to the detection of a wide range of proteins for which homologous recognition elements are available.

MnOOH nanowires decorated with NiAl-LDH have been successfully prepared via in-situ growth of small NiAl-LDH nanosheets by hydrothermal method without using any organic reagents. The morphology and structure of the samples were characterized by a series of techniques, including scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis meter (TGA), Brunauer-Emmett-Teller (BET), and Fourier transform infrared spectrometer (FT-IR). The excellent electrochemical properties of the as-prepared products were obtained by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS). The specific capacitance was 1331.11 F/g at current density of 1 A/g in 6 M of KOH electrolyte and still could keep good cycling stability after 1000 cycles. An asymmetric supercapacitor (ASC) was assembled by MnOOH/NiAl-LDH and activated carbon (AC), exhibited excellent electrochemical performances in energy storage. At a power density of 800 W/kg, the equipment could deliver a maximum energy density of 26.89 Wh/kg and maintain good cycling stability. The excellent results suggested that MnOOH/NiAl-LDH nanocomposite could be used as a promising material for supercapacitors.

A novel enhanced photoelectrochemical (PEC) DNA biosensor, based on a compact heterojunction g-C3N4/MoS2 and co-sensitization effect with CdSe quantum dots (QDs), was first proposed for simple and accurate analysis of a short ssDNA. In this work, the g-C3N4/MoS2 was successfully synthesized and used as the electrode matrix material to construct PEC biosensor. 2D/2D heterojunction was formed between g-C3N4 and MoS2, which could promote the separation of photogenerated electron-hole pairs resulting in an enhanced photocurrent. In the presence of target DNA, CdSe QDs labeled reporter DNA was complementary pairing with target DNA which was specific recognized by capture DNA loading on self-assembled CdS QDs film, leading to close contact between CdSe QDs and g-C3N4/MoS2 modified electrode surface, thereby resulting in the enhanced photocurrent intensity due to the co-sensitization effect. Under the optimal operating conditions, the photoelectrochemical biosensor demonstrated favorable accuracy and could respond to 0.32 pM (S/N = 3) with a linear concentration range from 1.0 pM to 2.0 μM. Moreover, the proposed PEC DNA biosensor exhibits high sensitivity, excellent specificity, acceptable reproducibility and accuracy, showing a promising potential in DNA bioanalysis and other relative fields.

Recently, the pollution and damage caused by antibiotics in water have aroused serious concerns. In this situation, it is extremely important to develop a highly effective approach to detect antibiotics in water. In this contribution, we built a Cd-MOF material with stable fluorescence properties, using bbi = 1,4-bis(2-methyl-imidazol-1-yl)butane and H2L = 1,2-phenylenediacetic acid as organic ligands and Cd(NO3)2·4H2O as the metal node. The highly selective response of this MOF probe to ceftriaxone sodium (an antibiotic) can reach up to the ppb level in water, along with a fast response time, acid and alkali resistance, and anti-interference ability.

Herein, an efficient photoelectrochemical (PEC) platform was constructed by a cosensitization strategy with a cascade energy level arrangement for the ultrasensitive evaluation of T4 polynucleotide kinase (T4 PNK). Based on CdSe quantum dots (QDs) with an extremely narrow bandgap, this cosensitization strategy offered a highly efficient sensitizer with a matching band-edge level of a ternary TiO2/g-C3N4/CdS nanocomposite. In this protocol, the ternary nanocomposite was first prepared to serve as the matrix to construct the PEC sensing platform. On the other hand, a well-designed hairpin DNA1 probe with 5'-hydroxyl termini was specifically phosphorylated by T4 PNK which would be selectively cleaved with lambda exonuclease (λ-Exo) outputting the 3'-thiol end ssDNA2. After tagged with CdSe QDs, ssDNA2 was captured by the complementary capture DNA3 on the electrode surface. As a result, CdSe QDs were in close contact with the ternary nanocomposite matrix, leading to an enhanced photocurrent response. Therefore, this proposed PEC platform displayed an analytical performance with a wide linear range from 0.0001 to 0.02 U mL-1 and a low detection limit down to 6.9 × 10-5 U mL-1. Moreover, this ternary nanocomposite-based platform exhibited excellent selectivity, good reproducibility, and remarkable storage stability, which shows great potential for T4 PNK detection and inhibitor screening.

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.

Tungsten diselenide (WSe2) is the material with the lowest thermal conductivity in the world. Most physical methods are used for the synthesis of tungsten diselenide. Here, a simple colloidal method is reported for the synthesis of WSe2 nanosheets. The composition, valence, size, morphology and properties of the samples were characterized and measured. Results showed that the obtained WSe2 nanosheets with a thickness of 0.7 nm had strong blue fluorescence. Significantly, the synthesized WSe2 nanosheets exhibited excellent catalytic activity for the aerobic coupling of amines to imines, with 100% yield under visible light irradiation and air atmosphere. As a photocatalyst, it exhibited excellent recyclability, and maintained a high yield after 5 cycles. It was found that this reaction could also happen in the presence of natural light by slightly extending the reaction time. Moreover, H2O was used as a solvent in the catalytic process, avoiding expensive and toxic organic solvents. This work provides an efficient, economical and sustainable process for the synthesis of imines and shows the great potential of WSe2 nanosheets as photocatalysts for organic synthesis.

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.

Uniform Bi2WO6 pancakes were prepared via a solvothermal route in a solvent mixture of glycerol (Gly) and water (V/V = 1). A variety of techniques including scanning electron microscopy, transmission electron micrographs, X-ray powder diffraction, Brunauer–Emmett–Teller, FT-IR spectra, and UV–Vis diffuse reflectance spectra, were employed to characterize the structure and properties of the as-obtained Bi2WO6. It was found that Bi2WO6 pancakes showed prominent photocatalytic performance for the degradation of rhodamine B (RhB) under visible light (λ ≥ 420 nm) irradiation, which can be attributed to its good crystallization, large surface area, unique morphology and structural features.

An ultrasensitive electrochemiluminescence (ECL) biosensor for the detection of microRNA was developed based on nicking enzymes Nb.BbvCI mediated signal amplification (NESA). First, the hairpin probe1-N-CQDs with assistant probe and microRNA (miRNA) formed Y junction structure which was cleaved with the addition of nicking enzymes Nb.BbvCI to release miRNA and assistant probe. Subsequently, the released miRNA and assistant probe can initiate the next recycling process. The generation of numerous intermediate sequences nitrogen doped carbon quantum dots-DNA (N-CQDs-DNA) can further hybridize with hairpin probe2 immobilized on GO/Au composite modified electrode surface, the initial ECL intensity was enhanced. The ECL intensity would increase with increasing concentration of the target miRNA, and the sensitivity of biosensor would be promoted because of the efficient signal amplification of the target induced cycling reaction. The novel designed biosensor provided a highly sensitive and selective detection of miRNA-21 from 10 aM to104 fM with a relatively low detection limit of 10 aM. Thus, our strategy has a potential application in the clinical diagnosis.

LaFeO 3 nanoparticles immobilized on the surface of monodisperse carbon spheres have been obtained through a facile and environmentally friendly ultrasonic assisted surface ions adsorption method. The LaFeO 3 /C nanocomposite was evaluated as photo-Fenton like catalyst for the degradation of Rhodamine B (RhB) under visible light irradiation (λ > 420 nm). The LaFeO 3 /C nanocomposite possesses high specific surface area compared with pure LaFeO 3 and significantly enhanced photo-Fenton like catalytic performance. The possible formation process of the LaFeO 3 /C nanocomposite and the mechanism for photo-Fenton like reaction were discussed. The superior property was attributed to the synergistic effects from the photo-Fenton like process and the presence of carbon spheres. In addition, the heterogeneous process led to better recyclability of this type of catalyst.

In recent years, carbon particles have gained numerous attentions because of their simple synthetic process, low toxicity and water solubility. The present work involves synthesis of two types of graphene quantum dots (GQDs) by treating sulfydryl group (−SH) amino acid glutathione (GSH) in the presence and absence of AgNO 3 via one pot route, respectively. The Ag + ions from AgNO 3 can combine the −SH from GSH to form Ag 2 S, thus surfaces of the obtained graphene quantum dots (N-GQDs) are mainly modified by some free hydroxyl groups ( OH), amino groups ( NH 2 ) and carboxyl groups ( COOH). In the absence of Ag + ions, the surfaces of as-prepared graphene quantum dots (SN-GQDs) not only include OH, NH 2 and COOH, but also −SH. Interestingly, as-prepared two kinds of GQDs both have strong fluorescence with different emission wavelength. More importantly, these GQDs have special recognition ability for metal ions. The N-GQDs respond rapidly towards the presence of Fe 3+ ions, and can be used as a probe to detect Fe 3+ ions in waste water, while the SN-GQDs have a special recognition to Hg 2+ ions.

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.

A two-dimensional zinc(II)-based metal-organic framework [Zn • (BA) • (BBI)] was synthesized from 1,2-benzenediacetic acid and 1,1'-(1,4-butanediyl) bis(imidazole) via a solvothermal reaction. The crystal exhibits good chemical stability in the pH range from 2 to 12, and strong fluorescence with excitation/emission maxima of 270/290 nm. The crystal is shown to by a viable fluorescent probe for the detection of ascorbic acid (AA) and the antibiotics chloramphenicol (CHL) and ceftriaxone (CRO). Fluorescence intensity of crystal dispersion is significantly quenched with increasing concentrations of AA/CHL/CRO. Quenching occurs even in the presence of other substances. The assay is fast (5 s) and has a low detection limit (1.6 ppb for AA, 12 ppb for CHL and 3.9 ppb for CRO). The crystal still has a good quenching effect on AA/CHL/CRO after washing and using for five times. The response of the probe is related to the interplay between the MOF and analytes via energy absorption competition. Graphical abstractSchematic diagram of preparing Zn • (BA) • (BBI) and responding to target analytes. BA: 1,2-phenyldiacetic acid; BBI: 1,1'-(1,4-butanediyl)bis(imidazole); Zn • (BA) • (BBI): Crystal chemical formula.

A feasible label-free electrochemiluminescence (ECL) aptasensor that uses an Au-nanoparticle-functionalized g-C3N4 nanohybrid (Au-g-C3N4 NH) as the luminophore was constructed for highly sensitive acetylcholinesterase (AChE) detection. The sensor was fabricated by successively modifying a glassy carbon electrode with Au-g-C3N4 NH and thiol-modified AChE-specific aptamers. In the presence of AChE, the ECL signal decreased significantly, because AChE could hydrolyze the substrate acetylthiocholine to generate acetic acid, which could react with the co-reactant triethylamine (Et3N), leading to evident consumption of the co-reactant. The ECL response of the aptasensor was linearly proportional to the concentration of AChE ranging from 0.1 pg/mL to 10 ng/mL, with a detection limit of 42.3 fg/mL (S/N=3). This novel ECL sensing strategy demonstrated a highly sensitive and selective method for AChE detection and was expected to possess potential applications in clinical diagnosis and biomedical technology.

The present study is focused on employing Camellia japonica leaf extract as inductive and stabilizing agent to synthesis CuO and ZnO nanoparticles (NPs). The chemicals, such as (Cu(NO3)2·3H2O) and (Zn(NO3)2·6H2O) were converted into copper and zinc ions, respectively because of the different natural products present in the C. japonica leaf extract. The UV–vis spectra of CuO and ZnO NPs showed absorption peak at 290 nm and 301 nm, respectively. The XRD result revealed crystalline nature of the metal oxide NPs and the TEM images indicated that average sizes of the synthesized CuO and ZnO NPs were ∼17 nm and ∼20 nm, respectively. The FTIR spectra of C. japonica leaf extract showed the presence of organic groups, such as, OH, C N, and N−H, which would be responsible for forming CuO and ZnO NPs. The synthesized CuO and ZnO NPs were tested for the optical sensing of metal ions, viz. Li+ and Ag+ that illustrated excellent outcome and hence this method offers a novel lane for the synthesis of metal oxide NPs, which can be used as optical sensor for the detection of metal ions.

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 combination of organic conducting polymer with inorganic semiconductor is one of the most important topics in developing photoelectric materials. In this work, bouquet-like polythiophene/tellurium (PTh/Te) nanocomposite was synthesized via the redox reaction of H2TeO3 and thiophene. The formation mechanism and effect factors of PTh/Te nanocomposite were discussed. It was found that the elemental Te formed in situ promoted the polymerization of thiophene, and the remainder H2TeO3 molecules adsorbed on the PTh chains made the nanocomposite soluble. The Z-scan test results show that the PTh/Te nanocomposite has a large two-photon absorption (TPA) cross-section and nonlinear optical (NLO) absorption coefficient.

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 .

Nanocomposite is a kind of multiphase solid materials with nano-dimensional. It generally displays more preferable performance than its corresponding single precursors or conventional composite materials due to size effect and interfacial effect. Herein, we report the synthesis of a kind of nanocomposite via one pot route without using any surfactant or structure-directing agents. The structure, composition and morphology of the as-synthesized products were characterized by XRD, XPS, SEM, TEM and BET surface area measurements. The results revealed that the prepared nanocomposites were consisted of ZnO-loaded Co 0.85 Se nanocomposites. BET measurement showed the specific surface area of the nanocomposite was 66.5 m 2 g −1 at 77.5 K. Interestingly, the ZnO-loaded Co 0.85 Se nanocomposites exhibit remarkable performance for the decomposition of hydrazine hydrate and catalytic hydrogenation of p -nitrophenol compared with individual component of Co 0.85 Se or ZnO. More importantly, the obtained nanocomposites have very excellent stability and reversibility as catalysts, indicating that the products can be potentially used in wastewater treatment.

The Bi2S3-ZnIn2S4 nanocomposites have been prepared through hydrothermal method. The structure, morphology, and composition properties of the as-prepared samples were characterized using X-ray powder diffraction, UV−vis spectrophotometer, transmission electron microscopy, scanning electron microscopy and energy dispersive X-ray analysis. Compared with pristine ZnIn2S4 nanosheets, the Bi2S3-ZnIn2S4 nanocomposites displayed higher photocatalytic conversion efficiency of CO2 into methyl formate using methanol as solution of absorbing CO2 and reducing agent. In addition, the methyl formate production rates achieved an optimal value over Bi2S3-ZnIn2S4 (2 wt%).

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.

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.

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.

Copper-based chalcogenides that contain abundant, low-cost and environmentally-friendly elements, are excellent materials for numerous energy conversion applications, such as photocatalysis, photovoltaics, photoelectricity and thermoelectrics (TE). Here, we present a high-yield and upscalable colloidal synthesis route for the production of monodisperse ternary I-III-VI2 chalcogenides nanocrystals (NCs), particularly stannite CuFeSe2, with uniform shape and narrow size distributions by using selenium powder as the anion precursor and CuCl2·2H2O and FeCl3 as the cationic precursors. The composition, the state of valence, size and morphology of the CuFeSe2 materials were examined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), transmission electron microscope (TEM) and high resolution transmission electron microscope (HRTEM), respectively. Furthermore, the TE properties characterization of these dense nanomaterials compacted from monodisperse CuFeSe2 NCs by hot press at 623 K were preliminarily studied after ligand removal by means of hydrazine and hexane solution. The TE performances of the sintered CuFeSe2 pellets were characterized in the temperature range from room temperature to 653 K. Finally, the dimensionless TE figure of merit (ZT) of this Earth-abundant and intrinsic p-type CuFeSe2 NCs is significantly increased to 0.22 at 653 K in this work, which is demonstrated to show a promising TE materialand makes it a possible p-type candidate for medium-temperature TE applications.

An electrochemical biosensor was developed based on a steric hindrance hybridization assay to allow the highly sensitive detection of streptavidin. In the steric hindrance hybridization assay, the signaling strand DNA (sig-DNA) was labeled at the 3' end with CdSe quantum dots (QDs) and at the 5' end with biotin, and capturing strand DNA (the complementary strand of sig-DNA) was labeled at the 5' end with thiol. The steric hindrance effect generated by streptavidin which was bound with the signaling DNA strand. The streptavidin limited the ability of the sig-DNA to hybridize with the cap-DNA, which were linked on the surface of a gold electrode. Therefore, the concentration of streptavidin was detected indirectly based on the concentration of CdSe QDs on the electrode surface. The concentration of CdSe QDs on the electrode surface was detected by differential pulse anodic stripping voltammetry. Under optimal conditions, the streptavidin detection range using the as-prepared biosensor was 1.96pg/mL to 1.96µg/mL and the detection limit was 0.65pg/mL. The experimental results showed that the electrochemical biosensor could detect streptavidin rapidly and accurately.

The hierarchical flower-like β-In2S3 catalyst assembled from 2D nanosheets was prepared using an organic-component depletion method utilizing inorganic-organic hybrids indium diethyldithiocarbamate (In-DDTC) as a single-source precursor. The crystallization, morphology and composition of the as-synthesized β-In2S3 were characterized by XRD, SEM, TEM, EDS and XPS, respectively. The β-In2S3 possessed high specific surface area of 134.1 m2 g-1, adsorption capacity of 195.5 mg g-1 for methylene blue, and extreme photodecolorization speed under visible light irradiation for the complete removal of methyl orange (MO) dye within 15 min and tetracycline within 60 min. Although methyl orange concentration decreased quickly, the total organic carbon (TOC) decreased slowly. UV-vis and mass spectrometry (MS) were applied to analyze the intermediates coming from the photodecolorization of MO. In order to estimate the roles of active species during the decolorization of MO, trapping experiments were conducted to determine the main active species during the decolorization process. The results indicated that . O2 − radicals and e-1 were the key intermediates. This enhanced activity was attributed to its unique structures assembled from 2D nanosheets with thickness of ca. 5-7 nm, leading to high specific surface area, wide range of pore size distribution and great efficiency in absorbing light and electron/hole separation. The hierarchical flower-like β-In2S3 demonstrated great advantages in the treatment of various wastewater pollutants including textile dyes and antibiotics.

Olive-like BiVO4 microstructures with lengths of 600–1000 nm and widths of 300–600 nm have been synthesized via a facile and additive-free solvothermal method. Studies find that the type of solvent plays an important role in the morphology of the final products. Furthermore, Ag3PO4 nanocrystals are successfully deposited on monoclinic olive-like BiVO4 via in situ precipitation method. The as-synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), photoluminescence (PL) spectra, and UV–vis diffuse reflectance spectra (DRS). The photocatalytic activities of the catalysts are evaluated by degradation of rhodamine B (RhB) and methylene blue (MB) under visible light (≥420 nm) irradiation. The experimental results suggest that catalytic activity of the composite photocatalysts is greatly influenced by the loading level of Ag3PO4. The molar ratio of 0.8:1.0 Ag3PO4-loaded BiVO4 exhibits higher photocatalytic activity in both the decolorization of RhB and MB than that of individual BiVO4 and P25. The observed improvement in photocatalytic activity is associated with the extended absorption in the visible light region resulting from the Ag3PO4 nanoparticles, and the effective separation of photogenerated carriers at the Ag3PO4/BiVO4 interfaces through the formation of heterojunction structure. The study provides a general and effective method in the fabrication of composite with sound heterojunctions that may show a variety of applications.

Nonprecious cocatalyst decoration is of great importance to create more active sites on the photocatalyst surface and provides insights into the photocatalytic activity enhancement. Herein, through facile hydrothermal and precipitation routes, the surface of MgAl layered double hydroxide (LDH) was modified by ultrafine NiS nanoparticles as a cocatalyst to design MgAl-LDH/NiS hybrid photocatalysts for highly-efficient photocatalytic hydrogen generation. The presence of NiS not only enhances the visible-light absorption but also promotes the separation and transfer of photogenerated charges, thereby boosting the photocatalytic activity of MgAl-LDH/NiS (35.8 μmol h−1) compared with bare MgAl-LDH (2.7 μmol h−1). The MgAl-LDH/NiS hybrid, moreover, displays a superior stability towards photocatalytic hydrogen evolution. This research offers a facile route to develop a high-performance photocatalyst using low-cost metal sulfide as cocatalyst for visible light photocatalytic hydrogen production.

The hierarchically shaped CuO-CeO2 composites were prepared through a facile solvothermal method without using any template. The as-prepared products were characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and N2 adsorption–desorption analysis. In the characterization, we found that CuO-CeO2 composites were showed uniform size and morphology which were consisted of the secondary nanoflakes interconnected with each other. Most interestingly, the composites showed efficient performance to remove methyl blue and Congo red dyes from water with maximum adsorption capacities of 2131.24 and 1072.09 mg g−1, respectively. In addition, because of their larger surface area and the unique hierarchical structures, the adsorption performance of the CuO-CeO2 composites is much better than the materials of CuO and CeO2.

In this study, we report a facile approach to synthesize Cu2(OH)3NO3 nanosheets via simply sonochemical method, which showed high efficiency and selectivity towards the adsorption of organic dyes containing sulphonic groups. The structure and morphology of the nanosheets were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, N2 adsorption–desorption isotherms, particle size and zeta potential analysis. The adsorption results indicated that the equilibrium data coincide very well with Langmuir isotherm, and the maximum adsorption capacities for Congo red, methyl blue and methyl orange were 1864, 1270 and 959 mg g−1, respectively. The kinetic data can be explained by pseudo-second-order model. The Cu2(OH)3NO3 nanosheets also demonstrated high selectivity towards the adsorption of dyes containing sulphonic groups from mixed dye solutions. The rational mechanism of adsorption was attributed to hydrogen bonding, electrostatic attractions and ion exchanges between the dye molecules and Cu2(OH)3NO3 in the adsorption process.

A novel graphene oxide nanoribbon/poly(diallyldimethylammonium chloride)/gold nanoparticle (GONR/PDDA/AuNP) nanocomposite was synthesized successfully and used for the sensitive detection of dopamine. The GONR/PDDA/AuNP nanocomposite was characterized by transmission and scanning electron microscopy. The electrochemical sensor based on GONR/PDDA/AuNP nanocomposite. was studied by cyclic voltammetry and electrochemical impedance spectroscopy. Experimental parameters such as GONR/PDDA concentration, volume ratio of GONR/PDDA to AuNP, scan rates, and pH were studied to investigate their effect on peak currents. Under optimal conditions, the GONR/PDDA/AuNP-based sensor exhibited excellent electrocatalytic activity for the detection of dopamine with a wide linear range from 9.99 x 10(-8) to 8.69 x 10(-4) M and a low detection limit of 3.33 x 10(-8) M. Moreover, the proposed sensor exhibits high sensitivity, good reproducibility, and stability, and could therefore potentially be applied in other bioanalytical systems.

A facile and environmentally friendly surface-ion adsorption method using CeCO3OH@C as template was demonstrated to synthesize CeO2-LaFeO3 perovskite composite material. The obtained composite was characterized by X-ray diffraction (XRD), fourier transform infrared spectra (FT-IR), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), thermo-gravimetric analysis and differential scanning calorimetry (TG-DSC), N2 adsorption/desorption isotherms and X-ray photoelectron spectra (XPS) measurements. The catalytic degradation of nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) was tested to evaluate catalytic activity of the CeO2-LaFeO3 composite. Much better activity was observed for the CeO2-LaFeO3 composite comparing with CeO2 and LaFeO3. These results suggested that perovskite composite materials are a promising candidate for the degradation of tobacco-specific nitrosamines (TSNAs).

Rational assembly of carbon nanostructures into large-area films is a key step to realize their applications in ubiquitous electronics and energy devices. Here, a self-assembly methodology is devised to organize diverse carbon nanostructures (nanotubes, dots, microspheres, etc.) into homogeneous films with potentially infinite lateral dimensions. On the basis of studies of the redox reactions in the systems and the structures of films, the spontaneous deposition of carbon nanostructures onto the surface of the copper substrate is found to be driven by the electrical double layer between copper and solution. As a notable example, the as-assembled multiwalled carbon nanotube (MWCNT) films display exceptional properties. They are a promising material for flexible electronics with superior electrical and mechanical compliance characteristics. Finally, two kinds of all-solid-state supercapacitors based on the self-assembled MWCNT films are fabricated. The supercapacitor using carbon cloth as the current collector delivers an energy density of 3.5 Wh kg−1 and a power density of 28.1 kW kg−1, which are comparable with the state-of-the-art supercapacitors fabricated by the costly single-walled carbon nanotubes and arrays. The supercapacitor free of foreign current collector is ultrathin and shows impressive volumetric energy density (0.58 mWh cm−3) and power density (0.39 W cm−3) too.

The combination of organic conducting polymer with inorganic semiconductor is one of the most important topics in developing photoelectric materials. In this work, bouquet-like polythiophene/tellurium (PTh/Te) nanocomposite was synthesized via the redox reaction of H2TeO3 and thiophene. The formation mechanism and effect factors of PTh/Te nanocomposite were discussed. It was found that the elemental Te formed in situ promoted the polymerization of thiophene, and the remainder H2TeO3 molecules adsorbed on the PTh chains made the nanocomposite soluble. The Z-scan test results show that the PTh/Te nanocomposite has a large two-photon absorption (TPA) cross-section and nonlinear optical (NLO) absorption coefficient.

P-nitrophenol (4-NP) and hydrazine hydrate are considered to be highly toxic pollutants in wastewater, and it is of great importance to remove them. Herein, TiO2-loaded Co0.85Se thin films with heterostructure were successfully synthesized by a hydrothermal route. The as-synthesized samples were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, transmission electron microscopy and selective-area electron diffraction. The results demonstrate that TiO2 nanoparticles with a size of about 10 nm are easily loaded on the surface of graphene-like Co0.85Se nanofilms, and the NH3 · H2O plays an important role in the generation and crystallization of TiO2 nanoparticles. Brunauer-Emmett-Teller measurement shows that the obtained nanocomposites have a larger specific surface area (199.3 m(2) g(-1)) than that of Co0.85Se nanofilms (55.17 m(2) g(-1)) and TiO2 nanoparticles (19.49 m(2) g(-1)). The catalytic tests indicate Co0.85Se-TiO2 nanofilms have the highest activity for 4-NP reduction and hydrazine hydrate decomposition within 10 min and 8 min, respectively, compared with the corresponding precursor Co0.85Se nanofilms and TiO2 nanoparticles. The enhanced catalytic performance can be attributed to the larger specific surface area and higher rate of interfacial charge transfer in the heterojunction than that of the single components. In addition, recycling tests show that the as-synthesized sample presents stable conversion efficiency for 4-NP reduction.