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DNA walkers, artificial dynamic DNA nanomachines, can mimic actin to move rapidly along a predefined nucleic acid track. They can generally be classified as one- (1D), two- (2D), and three-dimensional (3D) DNA walkers. In particular, 3D DNA walkers demonstrate amazing sustainable walking ability, strong enrichment ability, and fantastic signal amplification ability. In light of these, 3D DNA walkers have been widely used in fields such as biosensors, bioanalysis and cell imaging. Most notably, the strong compatibility of 3D DNA walkers allows their integration with a range of amplification strategies, effectively enhancing signal transduction and amplifying biosensor sensing signals. Herein, we first systematically expound the walking principle of the 3D walkers in this review. Then, by presenting representative examples, the research direction of 3D walkers in recent years is discussed. Furthermore, we also categorize and evaluate diverse tandem signal amplification strategies in 3D walkers. Finally, the challenges and development trends of 3D DNA walkers in the emerging field of analysis are carefully discussed. It is believed that this work can provide new ideas for researchers to quickly understand 3D DNA walkers and their applications in diverse biosensors. [ABSTRACT FROM AUTHOR]

MXenes with metal-like properties in the improvement of band gap and drive off photon-generated carrier transport have become one of the most promising co-catalysts. However, their unavoidable two-dimensional morphology limits their applications in sensing because this emphasizes the well-ordered microstructure of signal label to trigger stable signal output. In this work, a photoelectrochemical (PEC) aptasensor utilizing titanium dioxide nanoarrays/Ti3C2 MXene (TiO2/Ti3C2) composites as an anode current generator is proposed. Conventional, TiO2 generated by in situ oxidation of Ti3C2 was replaced with physically pulverized Ti3C2 and uniformly inlaid on the rutile TiO2 NAs surface by an ordered self-assembly. This method results in high consistency in morphology and exhibits a stable photocurrent output when detecting microcystin-LR (MC-LR), the most dangerous toxin in water. We believe that this study is a promising approach for sensing carrier preparation and significant target detection. [ABSTRACT FROM AUTHOR]

As a new method of ammonia (NH3) synthesis, the electrocatalytic nitrogen reduction reaction (eNRR) has generated widespread attention. The tin-based catalysts represent a broad development prospect in the field of electrocatalysis, but their eNRR performances need to be improved. In this work, hydrophobic carbon-doped tin disulfide (C-SnS2) was fabricated for the first time and adopted as an advanced catalyst for the eNRR. The doped C may adsorb more N2 and significantly improve the conductivity, which will contribute synergistically to the performance of the eNRR. The C-SnS2 nanoflower catalyst achieved a satisfactory NH3 yield rate (62.3 μg h−1 mg−1cat.) and high Faraday efficiency (23.06%) at −0.2 V vs. RHE in acidic conditions (0.1 M HCl). This work may provide new methods for the further development of high activity eNRR catalysis. [ABSTRACT FROM AUTHOR]

A microfluidic chip integrated with a microelectrode and a cathodic photoelectrochemical (PEC) biosensor for the ultrasensitive detection of non-small cell lung cancer cytokeratin fragments based on a signal amplification strategy was designed. The mechanism for signal amplification is developed based on the p–n junction of AgI/Bi2Ga4O9, with dissolved O2 as an electron acceptor to produce the superoxide anion radical (˙O2−) as the working microelectrode. By combining this with a novel superoxide-dismutase-loaded honeycomb manganese oxide nanostructure (SOD@hMnO2) as the co-catalyst signal amplification label, ˙O2− can be catalyzed by SOD via a disproportionation reaction to produce O2 and H2O2; then, hMnO2 is able to trigger the decomposition of H2O2 to generate O2 and H2O. Therefore, the increased O2 promotes the separation of electron–hole pairs via consuming more electrons, leading to an effective enhancement of the cathodic PEC behavior. Under optimum conditions, with the cytokeratin 19 fragments 21-1 (CYFRA 21-1) as the targeted detection objects, the microfluidic cathodic PEC biosensor chip exhibited excellent linearity from 0.1 pg mL−1 to 100 ng mL−1, with a detection limit of 0.026 pg mL−1 (S/N = 3). The exciting thing that this work offers is a new strategy for the detection of other important cancer biomarkers for disease diagnosis and prognosis. [ABSTRACT FROM AUTHOR]

No-wash detection of small molecules in real samples has been attracting attention in the field of sensors including electroanalytical biosensors. Based on the direct electrochemical oxidation of fluorene-9-bisphenol (BHPF) on a CoN nanoarray electrode, we developed a ratiometric molecularly imprinted polymeric electrochemical (MIP-EC) sensor to realize no-wash detection of BHPF in serum and tap water. The CoN nanoarray in situ grown on carbon cloth (CC) served as the working electrode, which could load the electroactive toluidine blue (TB) and be modified by the MIPs. As the MIP concentration on the modified electrode surface was increased, the amount of BHPF exposed on the electrode surface increased and the amount of exposed TB decreased. Thus, the values of ΔITB and ΔIBHPF decreased and increased, respectively, with an increasing amount of BHPF. Therefore, a ratiometric strategy was established by using the value of ΔITB/ΔIBHPF as the instruction response to realize detection of BHPF with high sensitivity and reliability. The developed ratiometric MIP-EC sensor showed strong anti-interference ability, good detection reproducibility and stability towards no-wash detection of BHPF as shown from tests with real samples. This work can further provide theoretical and practical guidance for the detection of other familiar small molecules. [ABSTRACT FROM AUTHOR]

A new strategy for the highly sensitive electrochemiluminescence (ECL) detection of insulin was developed based on curcumin-conjugated Au nanoparticles wrapped in zeolitic Zn2+-imidazolate cross-linked framework nanoparticles (Au-Cur/ZIF-8) quenching the ECL of CdS-decorated TiO2 nanobelts (CdS@TiO2). Curcumin-conjugated Au nanoparticles were embedded in ZIF-8 through epitaxial growth or nucleus coalescence. Herein, dual coreactants H2O2 and K2S2O8 were employed to enhance the ECL emission of CdS@TiO2, and the enhancing mechanism may be due to the electrogenerated hydroxyl radical (OH˙) strengthening the amount of sulfate radical anion (SO4˙−), which was the main species of generating ECL signals. In order to sensitively detect insulin, Au-Cur/ZIF-8 labels were used to anchor secondary antibodies via amidation reaction and inhibit the ECL intensity of CdS@TiO2. Moreover, the possible mechanism of quenching between Au-Cur/ZIF-8 and CdS@TiO2 was ascribed to the poor conductivity of ZIF-8, the consumption of OH˙ and the ECL resonance energy transfer between CdS@TiO2 and Au-Cur. Under optimal conditions, a sandwich immunosensor was prepared to determine insulin with a good linear range from 0.3 pg mL−1 to 20 ng mL−1 and a low detection limit of 0.09 pg mL−1 (S/N = 3). [ABSTRACT FROM AUTHOR]

In this work, the heterostructures of Au nanoparticles loaded on 3D flower-like α-Fe2O3 (Au NPs/α-Fe2O3) as a platform and core–shell CdSe@CdS quantum dots sensitized graphene oxide (GO/CdSe@CdS QDs) as a signal amplification label were established in an ultrasensitive sandwich-type photoelectrochemical (PEC) immunosensor based on the “signal-on” type amplification method for detection of amyloid β-protein (Aβ). Specifically, the ultrahigh sensitivity of the proposed immunosensor came from two main properties. First, Au NPs/α-Fe2O3 could partially absorb visible-light, which dramatically promotes electron transfer because of the excellent conductivity of Au NPs, and effectively inhibits the electron–hole recombination, thanks to the effect of heterostructures. Second, the signal-on type is based on the signal amplification label of GO/CdSe@CdS QDs which on adequate absorption of visible-light can improve generation of photogenerated electron–hole pairs effectively. Under optimal conditions, the well-prepared PEC immunosensor exhibited a low detection limit of 0.02 pg mL−1 and a wide linear range from 0.06 pg mL−1 to 350 ng mL−1 for Aβ detection. Meanwhile, it also presented good reproducibility, specificity, and stability and might open a new promising pathway for detection of other important biomarkers. [ABSTRACT FROM AUTHOR]

A novel sandwich-type photoelectrochemical (PEC) sensor for SCCA detection, based on a Ag2S-sensitized BiOI matrix and a AucorePdshell (AucPds) nanoflower label for signal amplification, was constructed for the ultrasensitive detection of the squamous cell carcinoma antigen (SCCA). By an in situ growth method, Ag2S was modified on the electrode coated with BiOI to obtain the BiOI/Ag2S composite. The BiOI/Ag2S matrix possesses an excellent photocurrent signal that is 90 times that of pure BiOI. The core–shell nanoflower-structured AucPds was utilized as a label to anchor secondary antibodies (AucPds@Ab2) to construct the ultrasensitive PEC sensor. The AucPds nanoflower can compete with the BiOI/Ag2S matrix for the absorption of visible-light to inhibit the electron transfer and then weaken the photocurrent signal of the BiOI/Ag2S matrix. After modification with the AucPds@Ab2 conjugate, the PEC signal was further reduced due to the efficient energy transfer process between the BiOI/Ag2S matrix and AucPds. Based on the above two influencing factors, the signal amplification strategy was fulfilled. Moreover, on the basis of specific recognition between antigen and antibody, an ultrasensitive PEC sensor for SCCA detection was successfully fabricated. On increasing the logarithm of the SCCA concentration in the range from 0.01 pg mL−1 to 100 ng mL−1, the photocurrent signals were linearly reduced and the detection limit was 1.6 fg mL−1. The fabricated sandwich-type PEC sensor has excellent sensitivity and distinguished stability, which are indicative of promising applications in clinical diagnoses, sensors and PEC analysis. [ABSTRACT FROM AUTHOR]

Herein, a facile and effective “turn-on” fluorescent sensor for Hg2+ detection was proposed, which is based on graphene oxide (GO) and DNA aptamers. In this assay, GO played a role as a nanoquencher to quench the fluorescence of acridine orange (AO). DNA aptamers (P2 and H-G4) acted as the molecular recognition probes, which could react with Hg2+ specifically and result in the formation of thymine–Hg2+–thymine (T–Hg2+–T) structures and a G-quadruplex. The G-quadruplex could absorb AO from the GO surface, leading to the fluorescence recovery of AO. Based on this recovery of the fluorescence signal, the target Hg2+ (0.5–50 nM) could be detected quantitatively, and the limit of detection (LOD) is 0.17 nM. This novel strategy will have great potential to monitor Hg2+ in the environment. [ABSTRACT FROM AUTHOR]

Energy conversion and storage systems such as water splitting metal–air batteries require high-performance and durable oxygen evolution reaction (OER) catalysts. Herein, we report the in situ development of self-standing Co3O4 nanorods array on Co foil (Co3O4 NA/CF) as a 1D OER catalyst electrode. Such Co3O4 NA/CF only needs overpotential of 308 mV to drive a geometrical catalytic current density of 15 mA cm−2 in 1.0 M KOH with good long-term electrochemical durability. In addition, this catalyst achieves a high turnover frequency of 0.646 mol O2 s−1 at overpotential of 410 mV. [ABSTRACT FROM AUTHOR]

In this paper, amidogen graphene (NH2-Gr) and Au nanoparticle (NP) functionalized cerium oxide (CeO2) NPs (NH2-Gr/Au@CeO2) have been synthesized. The prepared NH2-Gr/Au@CeO2 exhibits strong electrochemiluminescence (ECL) activity which could be quenched efficiently by bismuth sulfide (Bi2S3). Based on this principle, a novel sandwich ECL immunosensor was constructed for the detection of prostate specific antigen (PSA). NH2-Gr was used as a loading matrix for CeO2 NPs because of its superior conductivity and a large surface area. Au NPs were used to combine anti-PSA 1 (Ab1) to CeO2via the Au–NH2 covalent bond and meanwhile to enhance the sensitivity of the immunosensor. NH2-Gr/Au@CeO2 was used as the ECL response layer. Ag NP functionalized Bi2S3 was used to label the secondary antibody (Ab2). After a sandwich-type immunoreaction, a remarkable decrease of the ECL signal was observed. The signal-off sensor showed a wide linear range response from 1 pg mL−1 to 10 ng mL−1 with a low detection limit (LOD) of 0.3 pg mL−1. The applicability of the proposed ECL immunosensor was evaluated by detecting PSA in human serum samples. [ABSTRACT FROM AUTHOR]

The common drawbacks of most traditional electrochemiluminescence (ECL) immunoassays are the strict storage conditions for the ECL electrode and the steric hindrance caused by bovine serum albumin and antigen. The strict storage conditions require that the modified electrode must be stored at 4 °C before measurement, which may cause the degradation of protein molecules and low reproducibility as the time goes by. The steric hindrance can hinder electron transfer between the electrode and the electrochemical active substance unable to transmit proteins on the electrode surface. The current study takes a 96-well microtiter plate (MTP) as a bridge for analyte pre-treatment and Au@Pd nanorods as a peroxidase mimic to assemble a simple and robust ECL immunoassay. Advantages of such assay include not only high sensitivity but also robust detection circumstance. We demonstrated the method by detecting carcinoembryonic antigen from human serum and obtained a good detection limit of 3 fg mL−1. [ABSTRACT FROM AUTHOR]

The key challenge for fabricating electrogenerated chemiluminescence (ECL) biosensors still lies in the improvement of the sensing performance of ECL luminophores. Graphite-like carbon nitride (g-C3N4) nanosheets were prepared and the cathodic ECL performance was investigated. The ECL emission of g-C3N4 nanosheets was greatly enhanced and higher sensing sensitivity towards copper ions was achieved by a “space effect”, the incorporation of g-C3N4 nanosheets into a top-down prepared nanoporous matrix. Label-free ECL immunosensors were fabricated based on this simple sensing platform. The unique signal amplification strategy and simple fabrication procedure guarantee the sensor stability and production reproducibility. Nanoporous matrix supported ECL probes have potential as a versatile sensing strategy for the fabrication of ECL biosensors. [ABSTRACT FROM AUTHOR]

A photoelectrochemical biosensing chip was constructed through the mussel-inspired polydopamine coating strategy, which demonstrated improved photo-to-electric conversion performance for the CdS/TiO2-ITO chip, and was used for the direct immobilization of captured antibodies and the detection of CD146 in the absence of additional electron donors/acceptors. [ABSTRACT FROM AUTHOR]

An ultrasensitive electrochemical immunosensor for the detection of cluster of differentiation 146 antigen (CD146) based on TiO2 colloidal sphere laden Au/Pd nanoparticles (Au/Pd@TiO2) was developed. In this work, reduced graphene oxide-tetraethylene pentamine (rGO-TEPA) was applied as an electrode modifying material to modify the surface of a glassy carbon electrode (GCE). Au/Pd@TiO2 was used as the secondary-antibody (Ab2) label for the fabrication of the immunosensor. Amperometric response of the immunosensor for electrocatalytic reduction of hydrogen peroxide (H2O2) was recorded. Electrochemical impedance spectroscopy (EIS) proved that fabrication of the immunosensor was successful. The anti-CD146 primary antibody (Ab1) was immobilized on the rGO-TEPA modified GCE by a cross-linking reagent of glutaraldehyde (GA). With Ab1 immobilized onto the rGO-TEPA modified GCE and Ab2 linked with Au/Pd@TiO2, the immunosensor displayed a wide linear range (0.0050–20 ng mL−1), a low detection limit (1.6 pg mL−1), good reproducibility, good selectivity and acceptable stability. The designed sensing strategy may provide a potential application in the detection of other tumor markers. [ABSTRACT FROM AUTHOR]

Dopamine (DA), an important neurotransmitter in the central nervous system, is thought to control emotions and the balance of hormones in the human body. A photoelectrochemical sensor based on anatase TiO2 nanoparticles was developed to detect DA under visible light irradiation. The TiO2 nanoparticles were prepared by a previously reported hydrothermal method and the anatase phase was confirmed by X-ray diffraction. Under visible light irradiation, the electrode modified with TiO2 nanoparticles showed a weak photocurrent response in the absence of DA; however, the photocurrent was significantly improved after DA was added to the electrolyte. The proposed photoelectrochemical sensor had a sensitive response to DA with excellent reproducibility, stability and a wide linear range. This sensor may have potential applications in the determination of DA in real samples. [ABSTRACT FROM AUTHOR]

A facile route was proposed to synthesize mulberry-like gold nanospheres (MGNS) uniformly deposited on graphene nanosheets (GNs). Aniline was used as the reducing agent of both tetrachloroaurate and graphene oxide (GO). GO was partially reduced to GNs and acted as a support of the MGNS. The influence of the reaction time, reaction temperature and aniline concentration on the morphology of the MGNS were investigated. The resulting MGNS–GNs composites were characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction spectroscopy, ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy and electrochemical techniques. The formation mechanism of the MGNS–GNs was proposed based on the contrast experiments. The results illustrated that GO plays a key role in the uniform distribution of the MGNS and polyaniline is responsible for the formation of the MGNS. Compared with GO, the MGNS–GNs showed an enhanced photoelectrochemical property, which has potential application in the fields of sensors and energy. [ABSTRACT FROM AUTHOR]

The simultaneous determination of different analytes based on multiplexed immunosensors is attractive and promising in bioassays and environmental analysis. In this paper, a novel ultrasensitive multiplexed immunoassay method was developed for the determination of endocrine disrupting compounds (EDCs) based on disposable screen-printed carbon electrodes. Different capture antibodies were separately immobilized on the carbon electrodes to form an immunosensor array. Platinum nanoparticle-functionalized mesoporous silica nanoparticles (Pt@SBA-15) was used as catalytic labels of secondary antibodies. Due to the catalytic activities of the platinum nanoparticles and the large surface area of SBA-15, a strong electrical response towards the analytical antigens was achieved. The multiplexed immunoassay array enables the simultaneous determination of different analytes. Using diethylstilbestrol and estradiol as model analytes, this multiplexed immunoassay method showed wide linear ranges with detection limits down to 0.28 and 1.2 pg mL−1 for diethylstilbestrol and estradiol, respectively. The proposed sensing strategy enriches electrochemical immunoassays and has a promising application in bioassays and environmental analysis. [ABSTRACT FROM AUTHOR]

A facile and sensitive enzyme-free sandwich-type immunosensor for the detection of carbohydrate antigen 125 (CA125) was designed based on Au@Pd core–shell nanoparticles. Au@Pd nanoparticles were used both as electrode-modifying materials to immobilize the primary antibody (Ab1) of CA125 and as labels of secondary antibody (Ab2). The covalent bond between palladium nanoparticles and available amine groups of Ab1 enables the anchoring of larger amounts of Ab1 while the high stability and bioactivity of Ab1 can be reserved. Au@Pd nanoparticles show high electrocatalytic activity toward hydrogen peroxide (H2O2) reduction. The encapsulated Au nanoparticles can also accelerate the electron transfer. A high-performance electrochemical immunosensor was constructed based on the signal amplification of Au@Pd nanoparticles. Under optimal conditions, the immunosensor exhibited a wide linear response to CA125 ranging from 0.002 to 20 U mL−1 with a low detection limit of 0.001 U mL−1. The designed immunosensor displayed an excellent analytical performance with high sensitivity and stability. This strategy was successfully proved to be a simple method, which could be easily extended to other protein analysis. [ABSTRACT FROM AUTHOR]

Nature-inspired porous films have attracted great interest from researchers because of their fascinating structures and unique properties. In this paper, honeycomb-structured macroporous films of graphene nanocomposites were prepared by the breath figure method at both an air/solid interface and an air/water interface. Electrostatic complexes of graphene oxide (GO) and dimethyldioctadecylammonium bromide (DODA) have shown interfacial activities to stabilize the templating water droplets by adsorbing at water/solution interfaces. They can also form honeycomb structures of nanocomposites with gold nanoparticles (AuNPs) and induce the formation of highly ordered honeycomb films of polystyrene (PS), which have shown enhanced hydrophobicity. The process to fabricate such honeycomb structures is fast, easy, and low-cost, providing a universal approach for the preparation of multifunctional materials, which have potential application in the fields of catalysis, bioscience and sensors. [ABSTRACT FROM AUTHOR]

Self-assembly is now being intensively studied in chemistry, physics, biology, and materials engineering and has become an important “bottom-up” approach to create intriguing structures for different applications. Self-assembly is not only a practical approach for creating a variety of nanostructures, but also shows great superiority in building hierarchical structures with orders on different length scales. The early work in self-assembly focused on molecular self-assembly in bulk solution, including the resultant dye aggregates, liposomes, vesicles, liquid crystals, gels and so on. Interfacial self-assembly has been a great concern over the last two decades, largely because of the unique and ingenious roles of this method for constructing materials at interfaces, such as self-assembled monolayers, Langmuir–Blodgett films, and capsules. Nanocrystal superlattices, honeycomb films and coffee rings are intriguing structural materials with more complex features and can be prepared by interfacial self-assembly on different length scales. In this critical review, we outline the recent development in the preparation and application of colloidal nanocrystal superlattices, honeycomb-patterned macroporous structures by the breath figure method, and coffee-ring-like patterns (247 references). [ABSTRACT FROM AUTHOR]

Highly ordered radially aligned microchannels are produced on the surface of polymer nanocomposite thin films viadroplet evaporation. This simple, rapid, and cost-effective approach opens a new avenue for producing macroscopic surface patterns that have potential as scaffolds or substrates in the field of microelectronics or microfluidic-based biochips. [ABSTRACT FROM AUTHOR]

Highly ordered freestanding honeycomb films with asymmetric through-pore structures were prepared from polystyrene/gold-nanoparticles (PS/AuNPs) nanocomposite at an air/water interface using a one-step interfacial self-assembly method. [ABSTRACT FROM AUTHOR]

MXenes with metal-like properties in the improvement of band gap and drive off photon-generated carrier transport have become one of the most promising co-catalysts. However, their unavoidable two-dimensional morphology limits their applications in sensing because this emphasizes the well-ordered microstructure of signal label to trigger stable signal output. In this work, a photoelectrochemical (PEC) aptasensor utilizing titanium dioxide nanoarrays/Ti 3 C 2 MXene (TiO 2 /Ti 3 C 2 ) composites as an anode current generator is proposed. Conventional, TiO 2 generated by in situ oxidation of Ti 3 C 2 was replaced with physically pulverized Ti 3 C 2 and uniformly inlaid on the rutile TiO 2 NAs surface by an ordered self-assembly. This method results in high consistency in morphology and exhibits a stable photocurrent output when detecting microcystin-LR (MC-LR), the most dangerous toxin in water. We believe that this study is a promising approach for sensing carrier preparation and significant target detection.

Electrochemical hydrogen production by splitting water is mainly limited to the oxygen evolution reaction (OER), which requires high energy consumption. The design of an efficient and stable electrochemical catalyst is the key to solving this problem. Here, a three-dimensional porous Co-doped Ni 2 P nanosheet (Co-Ni 2 P/NF-corr) was synthesized by simple hydrothermal, acid leaching and phosphating processes successively. Excitingly, the current density of Co-Ni 2 P-corr in 1 M KOH solution can reach 50 mA cm -2 with only 267 mV overpotential. Moreover, the Tafel slope is very small, only 64 mV dec -1 . In addition, the stability test shows that it can work stably at 50 mA cm -2 current density for at least 48 h., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (This journal is © The Royal Society of Chemistry.)

A new strategy for the highly sensitive electrochemiluminescence (ECL) detection of insulin was developed based on curcumin-conjugated Au nanoparticles wrapped in zeolitic Zn2+-imidazolate cross-linked framework nanoparticles (Au-Cur/ZIF-8) quenching the ECL of CdS-decorated TiO2 nanobelts (CdS@TiO2). Curcumin-conjugated Au nanoparticles were embedded in ZIF-8 through epitaxial growth or nucleus coalescence. Herein, dual coreactants H2O2 and K2S2O8 were employed to enhance the ECL emission of CdS@TiO2, and the enhancing mechanism may be due to the electrogenerated hydroxyl radical (OH˙) strengthening the amount of sulfate radical anion (SO4˙-), which was the main species of generating ECL signals. In order to sensitively detect insulin, Au-Cur/ZIF-8 labels were used to anchor secondary antibodies via amidation reaction and inhibit the ECL intensity of CdS@TiO2. Moreover, the possible mechanism of quenching between Au-Cur/ZIF-8 and CdS@TiO2 was ascribed to the poor conductivity of ZIF-8, the consumption of OH˙ and the ECL resonance energy transfer between CdS@TiO2 and Au-Cur. Under optimal conditions, a sandwich immunosensor was prepared to determine insulin with a good linear range from 0.3 pg mL-1 to 20 ng mL-1 and a low detection limit of 0.09 pg mL-1 (S/N = 3).

Energy conversion and storage systems such as water splitting metal-air batteries require high-performance and durable oxygen evolution reaction (OER) catalysts. Herein, we report the in situ development of self-standing Co 3 O 4 nanorods array on Co foil (Co 3 O 4 NA/CF) as a 1D OER catalyst electrode. Such Co 3 O 4 NA/CF only needs overpotential of 308 mV to drive a geometrical catalytic current density of 15 mA cm -2 in 1.0 M KOH with good long-term electrochemical durability. In addition, this catalyst achieves a high turnover frequency of 0.646 mol O 2 s -1 at overpotential of 410 mV.

In this paper, amidogen graphene (NH 2 -Gr) and Au nanoparticle (NP) functionalized cerium oxide (CeO 2 ) NPs (NH 2 -Gr/Au@CeO 2 ) have been synthesized. The prepared NH 2 -Gr/Au@CeO 2 exhibits strong electrochemiluminescence (ECL) activity which could be quenched efficiently by bismuth sulfide (Bi 2 S 3 ). Based on this principle, a novel sandwich ECL immunosensor was constructed for the detection of prostate specific antigen (PSA). NH 2 -Gr was used as a loading matrix for CeO 2 NPs because of its superior conductivity and a large surface area. Au NPs were used to combine anti-PSA 1 (Ab 1 ) to CeO 2 via the Au-NH 2 covalent bond and meanwhile to enhance the sensitivity of the immunosensor. NH 2 -Gr/Au@CeO 2 was used as the ECL response layer. Ag NP functionalized Bi 2 S 3 was used to label the secondary antibody (Ab 2 ). After a sandwich-type immunoreaction, a remarkable decrease of the ECL signal was observed. The signal-off sensor showed a wide linear range response from 1 pg mL -1 to 10 ng mL -1 with a low detection limit (LOD) of 0.3 pg mL -1 . The applicability of the proposed ECL immunosensor was evaluated by detecting PSA in human serum samples.

An ultrasensitive electrochemical immunosensor for the detection of cluster of differentiation 146 antigen (CD146) based on TiO2 colloidal sphere laden Au/Pd nanoparticles (Au/Pd@TiO2) was developed. In this work, reduced graphene oxide-tetraethylene pentamine (rGO-TEPA) was applied as an electrode modifying material to modify the surface of a glassy carbon electrode (GCE). Au/Pd@TiO2 was used as the secondary-antibody (Ab2) label for the fabrication of the immunosensor. Amperometric response of the immunosensor for electrocatalytic reduction of hydrogen peroxide (H2O2) was recorded. Electrochemical impedance spectroscopy (EIS) proved that fabrication of the immunosensor was successful. The anti-CD146 primary antibody (Ab1) was immobilized on the rGO-TEPA modified GCE by a cross-linking reagent of glutaraldehyde (GA). With Ab1 immobilized onto the rGO-TEPA modified GCE and Ab2 linked with Au/Pd@TiO2, the immunosensor displayed a wide linear range (0.0050-20 ng mL(-1)), a low detection limit (1.6 pg mL(-1)), good reproducibility, good selectivity and acceptable stability. The designed sensing strategy may provide a potential application in the detection of other tumor markers.

A facile synthetic route for TiO2-CdSe heterostructures was proposed based on dentate binding of TiO2 to carboxyl. Carboxyl functionalized CdSe quantum dots (CF-CdSe QDs) were successfully bonded onto TiO2 nanoparticles (NPs), which could significantly improve the photoelectrochemical (PEC) properties of TiO2 NPs. This is ascribed to the fact that CdSe QDs with a narrow band gap could be stimulated under visible light irradiation, and the energy levels of TiO2 NPs and CF-CdSe QDs are aligned with an electrolyte solution. High resolution transmission electron microscopy images revealed the heterostructures of the TiO2-CdSe composites. Ultraviolet visible spectroscopy, photoluminescence emission spectroscopy and electrochemical impedance spectroscopy analysis exhibited that the prepared TiO2-CdSe heterostructures have improved light absorption, charge separation efficiency and electron transfer ability in the visible light region. TiO2-CdSe heterostructures were used as versatile labels for fabrication of PEC and electrochemical immunosensors, and human immune globulin G (HIgG) was used as a model analyte. The immunosensor showed high sensitivity, a low detection limit and a wide linear range, which could be applied in practical serum sample analysis. The constructed TiO2-CdSe heterostructures would have potential applications in photocatalysis, aptasensors, cytosensors and other areas of nanotechnology.

Arrayed microchannels with dimensions of tens to hundreds of micrometres show great potential for application in microfluidics, microreactor devices and other areas. In this work, we report the formation of ordered arrays of cracks on solution-cast colloidal films, and the preparation of radially aligned microchannels. The polymer film coating enables the colloidal film to be detached from the substrate, retaining the crack patterns on the bottom side. The subsequent chemical corrosion converts the cracks into microchannels. Crack-patterned colloidal films are also used as structured substrates for the preparation of honeycomb films by the breath figure method. Hierarchical honeycomb structures are obtained, giving rise to improved support for colloidal films.