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Development of photoliquefiable solid-state biomaterials at room temperature would address scientific challenges in life science. However, external stimuli-induced phase transitions are difficult for some biomacromolecules based materials, due to the high rigidity of these biomolecules. In this present work, by delicate molecule design on azobenzene-type ammonium surfactants, two new types of DNA-surfactant materials are fabricated. At room temperature, these DNA materials show photoliquefaction of ionic crystals to isotropic liquids under UV light, and fast self-assembly from isotropic liquids back to crystals after ceasing UV light, under the assistance of azobenzene isomerization. To achieve this objective, the designed solid-state DNA materials should have melting points near room temperature and an immediate liquid crystal to isotropic liquid transition process just above the melting points, which highly depends on the stoichiometric charge ratio between DNA and surfactants. As proved by the successful self-healing tests, these DNA ionic crystals are good biomaterials with potential applications in biomedicine and life science. This work would provide a new strategy for designing anhydrous functional biomaterials at room temperature by using rigid biomacromolecules. Statement of Significance At room temperature, solid-state biomaterials with photoregulated crystal⇄isotropic liquid phase transition property are attractive functional materials in life science, considering the body temperature and living environment temperature of human beings. Although several kinds of anhydrous materials achieved isothermal photoresponsive phase transitions, the photoregulated phase transition of anhydrous biomacromolecules based materials has not been achieved at room temperature, due to the high rigidity of these biomolecules. In this work, by delicate molecule design on ammonium surfactants, we synthesized two kinds of anhydrous DNA-surfactants ionic crystals. These DNA materials show fast photoliquefaction under UV light and self-assembly after ceasing light, which affords excellent self-healing biomaterials. This work would provide a new strategy for designing anhydrous photoresponsive biomaterials by using rigid biomacromolecules.

In this paper, a novel ratiometric electrochemical Cu(II) sensing strategy was established by monitoring the changes of the reduction peaks of Cu(II) and paracetamol based on bare electrode. The paracetamol was adopted as an optimal ratiometric reference (rather than classic ferrocene (Fc) and methylene blue (MB)) due to its highly stability and suitable reduction peak, which is well-separated from the reduction peak of Cu(II). Adopting paracetamol as the internal reference, the reproducibility of this sensing strategy was obviously enhanced. The sensing platform is very cheap in cost and avoids some time-consuming electrode modification process, which is helpful for low-cost and rapid detection.

Discrimination of different types of sulfur-containing species not only helps us to deeply understand how sulfur affects cellular signaling, but also contribute to the early diagnosis of diseases. However, the current investigation about sulfur-containing species discrimination is mainly concentrated in biothiols, which is relatively limited for practical application. Toward circumventing this limitation, herein, a convenient sensor array consisting of three kinds of Au NCs-Cu2+ for simultaneous and rapid identification of different types of sulfur-containing species is reported. Based on the fingerprint-like fluorescence responses generated by competitive binding between Au NCs-Cu2+ and different sulfur-containing species, not only ten different types of sulfur-containing species separately but also their binary or ternary randomly selected mixtures can be well discriminated even in human urine and serum samples. It is worth noting that it only takes 2 min to obtain the best response signals for sulfur-containing species discrimination. Most importantly, serums from cancer patients (such as liver cancer and breast cancer) and healthy people as well as sulfur-oxidizing bacteria (SOB) and sulfur-free bacteria can be both effectively and rapidly identified within 2 min, respectively, making it a promising approach for point-of-care disease diagnostic.

To explore alkaline fuel cells in practice, searching low-cost and efficient alternatives to Pt-based catalysts is urgent yet challenging for oxygen reduction reaction (ORR). Herein, Co3Fe7 alloy nanoparticles wrapped in N-doped defect-rich carbon nanosheets (Co3Fe7/CNs) were synthesized at 800 °C by a one-step pyrolysis of the mixture (dicyandiamide, iron (II) phthalocyanine (FePc), cobalt (II) phthalocyanine (CoPc) and Fe2O3), defined as Co3Fe7/CNs-800 for simplicity. The pyrolysis temperature and the dosages of dicyandiamide closely correlated to the ORR performance of the resultant catalysts in 0.1 M KOH solution. Significantly, the optimized Co3Fe7/CNs-800 exhibited encouraging onset potential (Eonset = 0.97 V) and half-wave potential (E1/2 = 0.85 V) in the alkaline media, surpassing commercial Pt/C (50 wt%, Eonset = 0.96 V, E1/2 = 0.84 V). This work provides a feasible strategy for developing efficient non-noble metal ORR electrocatalysts in the alkaline condition.

Development of ultra-sensitive and high specific aptasensors is important for early diagnosis of prostate cancer. Herein, ultrasensitive detection of prostate specific antigen (PSA) aptasensor was realized based on the “on-off-on” model via fluorescence (FL) covalent energy transfer between g-C3N4 quantum dot (g-CNQDs) and palladium triangular plates (Pd TPs). Specifically, the Pd TPs were primarily linked with PSA aptamer (PA) as the reporter probe, followed by attaching them onto the g-CNQDs surfaces, causing the highly enlarged FL quenching rate (ca. 75%). After the introduction of PSA, the FL intensities recovered again because of the distinctively stronger affinity of PA to PSA than that of g-CNQDs. The bond of pyridine N with Pd was identified as efficient energy transfer pathway through the X-ray photoelectron spectroscopy (XPS) and FL measurements. The surface plasmon resonance (SPR) experiments certified the remarkably different affinity of PA towards g-CNQDs and PSA. The as-constructed FL aptasensor can accurately quantify PSA with wide linear range of 10 pg mL−1-50 ng mL−1 and ultra-low limit of detection (LOD, 4.2 pg mL−1), indicating the promising applications in clinical assay and biological detection.

A biomimetic assembly of per-O-methylated-cyclodextrin dimer with cobalt proto-porphyrin (CoIII-PPIX@Py2CD) was achieved via covalent linkage between CoIII of CoIII-PPIX and pyridine N of Py2CD (primarily synthesized by the acyl chlorination reaction of two β-CDs monomers with 3,5-bis (bromomethyl) pyridine). Ultraviolet–visible (UV–vis) and circular dichroism (CD) absorption spectroscopy, and NMR hydrogen spectroscopy (H1-NMR) were adopted to carefully characterize the structure of Py2CD and its functional assembly with CoIII-PPIX. X-ray photoelectron spectroscopy (XPS) was employed to affirm the binding of the as-obtained CoIII-PPIX@Py2CD, whose electrochemical kinetics were extensively studied to validate the feasibility in the catalytic reduction of hydrogen peroxide (H2O2). The developed sensor displayed the wide linear range for H2O2 detection and the low detection limit of 2.47 × 10−7 M. This work sheds some constructive lights on rational design and synthesis of preeminently biomimic carrier and high cost-effectiveness catalyst for (bio)analytical applications.

Conducting polymer hydrogels with superior electrical responsiveness, adjustable chemical properties, and high electrical conductivity are highly desired for electrode materials in assembling flexible and wearable sensors. Herein, we have synthesized PANI–CNT composite hydrogels via a self-assembly strategy for nitrite detection. High-density CNTs are tightly adsorbed onto PANI hydrogels with a 3D porous hierarchical microstructure via π–π interactions to form PANI–CNT hydrogels. The 3D porous network of PANI hydrogels and the high conductivity of CNTs largely benefit electrolyte ion diffusion and transfer. The hydrophilic nature of PANI–CNT hydrogels provides an outstanding interface between electrolytes and electrodes. The PANI–CNT hydrogel-modified electrode shows high sensitivity (271.48 μA mM−1 cm−2), with an average response time of 3 s, a linear range from 20 μM to 1.8 mM, and a low detection limit of 7.8 μM. Moreover, a flexible electrochemical sensor for nitrite detection was successfully prepared by coating PANI–CNT hydrogels onto a printed electrode plate, which exhibited good sensitivity (254.54 μA mM−1 cm−2). These PANI–CNT hydrogels present giant potential in the designing of flexible and wearable sensors, in which the composite hydrogels can function both as a sensor and an electrolyte storage unit simultaneously.

A simple and label-free sensing platform with low background based on the chain-displacement triggered self-assembly of Ag NCs was developed for ratiometric visual analysis of intracellular miRNA-21. Based on this sensitively ratiometric sensing approach, a picomole limit detection for miRNA-21 can be obtained. Most importantly, compared with the traditional single base mismatch detection method, our proposed method can realize single base mismatch detection according to the remarkable fluorescence color conversion, rather than simple fluorescence intensity change, which can obviously improve the accuracy and reliability. In addition, successful multicolor real-time monitoring of intracellular miRNA-21 makes the probe a potential candidate for miRNA-21 inhibiting drug screening. Furthermore, MCF-7, HeLa, and normal L02 cells can also be visually differentiated according to the fluorescence color by using the label-free sensing platform, showing its potential prospect in target visual analysis.

A promising electrode with three-dimensional (3D) AuNPs/ZnO/Cu2O heterojunction nanowires (NWs) was developed and applied as photocathode for sensitive photoelectrochemical (PEC) immunoassay toward carcinoembryonic antigen (CEA, Ag). Firstly, Cu2O NWs were grown in situ on a Cu foil substrate to provide large specific surface area. After the modification of ZnO layer on the Cu2O NWs, the ZnO/Cu2O heterojunction structure was formed, which can increase the harvest of light energy and play a role in charge separation and transport. With further modification of gold nanoparticles (AuNPs), the good electric conductivity of the AuNPs would induce enhanced charge separation between Cu2O and ZnO. Thus, the photocurrent response of the prepared 3D AuNPs/ZnO/Cu2O NWs photocathode was significantly improved by synergistic effects of each element in the 3D structure. As a result, the fabricated cathodic PEC immunosensor exhibited high sensitivity with a low detection limit of 0.36 pg/mL (S/N = 3) for CEA detection. Furthermore, good specificity and well anti-interference capability toward real sample detection was achieved.

Non-cadimum photoluminescent I−III−VI semiconductor nanocrystals have attracted increasing attention due to their low toxicity, extraordinary optical and electronic properties. Herein, water-soluble quaternary Cu-In-Zn-S quantum dots (CIZS QDs) with tunable emission from 535 nm to 645 nm were successfully synthesized via ecofriendly one-pot aqueous method. The full width at half-maximum (FWHM) of the emissions are about 68 nm–88 nm, which are rather narrow among Cu-based semiconductors and preferred to facilitate improving color purity. The photoluminescence of water-soluble QDs was enhanced by ZnS coating with the absolute quantum yield (QY) up to 30.8%. Further, a novel fluorescent sensor for Cu2+ detection was developed based on the alteration of intrinsic optical properties of the CIZS/ZnS QDs after cation exchange at room temperature within 10 min, presenting a linear range of 0.020–20 μM and a detection limit down to 6.7 nM. Mechanism studies revealed that the QDs served as the template for cation exchange, through UV–vis absorption and fluorescence spectra in combination with the chemical composition and time-resolved photoluminescence decay analysis. Ions interference experiments demonstrated the good selectivity of the QDs towards Cu2+ and the sensor showed comparable accuracy to ICP-AES method as well as good performance in real sample detection, manifesting the reliability of the current strategy for sensing Cu2+ mildly and rapidly.

The introduction of advanced nanocrystals and mediator is crucial for signal amplification of electrochemical immunosensors due to trace amounts of analytes in real samples. Herein, a novel ultrasensitive label-free electrochemical immunosensor was constructed to monitor carbohydrate antigen 15-3 (CA15-3) based on dendritic Au@Pt core-shell nanocrystals (Au@Pt NCs) uniformly dispersed with ferrocene-grafted-chitosan (Fc-g-CS), where Au@Pt NCs were prepared with hexadecyldimethyl benzyl ammonium chloride (HDBAC) as the growth-directing agent via a simple one-pot wet-chemical strategy. More notably, Fc grafted with CS would dramatically improve the stability and the Fc-g-CS enlarged specific surface area and behaved as dispersing agent for the Au@Pt NCs to greatly boost the electrochemical signals and improve the biocompatibility. The resulting immunosensor displayed wider linear range of 0.5–200 U mL–1 and lower detection limit of 0. 17 U mL–1, which was further explored for detecting CA15-3 in serum sample with highly acceptable results.

SnxPy nanoparticles were controllably synthesized on 3D nitrogen-doped carbon networks (SnxPy/C) by a freeze drying and low-temperature phosphidation process. Interestingly, the product phase (Sn4P3, SnP0.94) could be varied by the SnCl4 concentrations and the doping of SnP0.94 could significantly enhance the cycling properties of Sn4P3 for lithium ion batteries (LIBs). The obtained SnxPy nanoparticles (5–10 nm) were anchored on the 3D nitrogen-doped carbon networks (N-CN), which protected SnxPy from serious agglomeration and large volume expansion. Meanwhile, the N-CN possessed a highly interconnected 3D network structure and good conductivity, so the transportation of Li+ would be speed up to enhance the electrochemical performance. As the LIBs anode, SnxPy/C displayed the best cycling performance with 2 M SnCl4 solution, which remained a high capacity of 718 mAh g−1 after 120 cycles (100 mA g−1). The strategy of synthesis SnxPy/C could be expanded to controllable synthesis of other metal phosphides on 3D nitrogen-doped carbon networks for LIBs, catalysis, hydrogen generation, etc.

Zinc ions (Zn2+) act as a transcription factor in eukaryotic cells for mediating protein-protein interactions in human healthy. The simple and sensitive detection of Zn2+ is the crucial mission in analytical field. This work demonstrated a novel and fast Zn2+ detection strategy based on “signal on” mode with electrochemiluminescence (ECL) luminophore, in which singlet oxygen was generated via electrocatalytic reduction of zinc proto-porphyrin IX grafted onto Pd nanocubes (ZnPPIX-Pd NCs). In protocol, Pd NCs were synthetized under hydrothermal conditions and aminated through thermal oxidative polymerization of 3-aminopropyltriethoxysilane (APTES), followed by further linking with PPIX via amide reaction. The resulting PPIX-Pd NCs effectively captured Zn2+ in chelation and monitored by Fourier transform infrared (FTIR) spectroscopy and ultraviolet-visible (UV-vis) absorption spectroscopy. By virtue of the metal resonance responses of Pd NCs, an intense monochromic, potential shuffling and enhanced ECL irradiation shows up for the hybrid nanocomposite with H2O2 as the coreactant. To this end, an ultrasensitive method based on the nanocomposite with a “signal-on” model was developed for Zn2+ detection with a low detection limit down to 0.38 nM (based on a S/N= 3), excellent precision and high stability. The ECL strategy reveals the potential application in molecular diagnosis and offers a new avenue for bioassay of structural Zn(II) proteins and zinc finger-binding nucleotides.

Aptamer-based bioassay of biomarker has broad applications in clinical research and disease diagnosis. In this work, a label-free aptamer biosensor for ultrasensitive thrombin (TB) detection was constructed based on highly enhanced electrochemiluminescence (ECL) of functional palladium nanocones (Pd NCs) with tripropylamine (TPA) system. Herein, well-defined Pd NCs were initially functionalized by mercaptoethanol (MCH) as an ECL emitter and immobilized onto the glassy carbon electrode (GCE) initially grafted with amine-terminated polyamidoamine (PAMAM) via electro-oxidation reaction. Under optimal conditions, the ECL intensity of the Pd NCs/TPA system was about 2.5 times enhancement when compared to that of bare GCE. The ECL and cyclic voltammetry (CV) were synchronously employed to illustrate the enhanced ECL mechanism. By virtue of the linkage of the modified Pd NCs with specified TB aptamer (TBA) containing sulfydryl group, a label-free ECL detection platform was designed. After full coverage of the nonspecific sites with bovine serum albumin (BSA), an ECL biosensor for TB detection was constructed by taking the advantage of the steric hindrance effects, showing the wider linear range, lower detection limit of TB (even down to 6.76 fM), superb selectivity and stability. The current strategy provides a highly sensitive platform for detection of various biomolecules in bioanalysis.

Previously reported photoelectrochemical (PEC) cytosensing commonly relied on the use of photoelectrodes as both signaling sources and platforms to accommodate the biorecognition events. In such a design, the side reaction between photoelectrodes and potential reductive species in the biological media as well as the interplay between the photoelectrodes and biomolecules will inevitably impair the performance of the corresponding PEC cytosensors. Herein, we presented a facile and efficient PEC cytosensor by separating capture probe from the photoelectrode. The system is operated upon by using a ternary heterostructured photoanode to provide an evident and stable photocurrent signal, an aptamer-based biocathode for recognizing and capturing the target cells, and the corresponding signal reduction from the cell-induced steric hindrance effect. Exemplified by human breast cancer cells (MCF-7), the proposed system realizes the separation of the signaling photoanode and the sensing biocathode toward a sensitive and selective self-powered PEC MCF-7 cytosensor. This work reports a new PEC cytosensing protocol, and it is expected to attract more interest in the research of high-performance PEC cytosensing.

Herein, rhombic dodecahedral Cu3Pt nanoframes (Cu3Pt NFs) were prepared via solvothermal strategy using theobromine as the reductant and structure-directing agent, coupled with cetyltrimethylammonium chloride (CTAC) as the co-structure-director. The samples showed dramatically boosted catalytic performance for oxygen reduction reaction (ORR), owing to their highly open structures with enlarged specific surface areas. Using Cu3Pt NFs catalyzed ORR as signal amplification platform, a novel electrochemical immunosensor was constructed to monitor alpha-fetoprotein (AFP). The as-fabricated immunosensor displayed a wide linear range of 0.1–104 pg mL–1 and a low detection limit of 0.033 pg mL–1.

In this work, Fe was doped in the semiconductor Ag2S to form Fe-doped Ag2S nanocomposites (Fe-Ag2S NCs) for enhancing the catalytic performance of pure Ag2S for the first time. According to the investigation of the oxidation reaction of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2, the Fe-Ag2S NCs were proved to possess more excellent catalytic activity compared with that of Ag2S as a peroxidase mimic. Besides, the catalytic mechanism of the Fe-Ag2S was ascribed to the hydroxyl radical ( OH) generated from the decomposition of H2O2 in the catalytic oxidation process of TMB. On the basis of the excellent catalytic activity of Fe-Ag2S, a sensitive and efficient colorimetric sensor has been constructed for determining H2O2 and this sensor has a sensitive linear response to H2O2 in the range of 10–150 μM with a detection limit of 7.82 μM. All of the above confirmed that the doping of iron could really improve the catalytic activity of Ag2S. It is believed that Fe-doped Ag2S will open a new way for researchers to optimize the performance of semiconductors.

A novel biomaterial, polyglycerol grafted conducting polymer poly (3,4-ethylenedixythiophene) (PEDOT) was electrochemically synthesized. The PEDOT functionalized with hyperbranched polyglycerol (PEDOT-HPG) was simply prepared through the electrochemical polymerization of corresponding monomers, which was synthesized by grafting glycidol into (2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl)methanol (EDOT-MeOH). The antifouling properties of PEDOT-HPG surfaces were evaluated in terms of protein adsorption and the attachment of mammalian cells, including human cervical carcinoma cells (HeLa) and Michigan Cancer Foundation-7 (MCF-7). Through the conjugation of alpha-fetoprotein (AFP) antibodies to the PEDOT-HPG surfaces, sensitive immunosensors for AFP were fabricated, with the limit of detection at the level of 0.035 pg/mL. The prepared AFP biosensors exhibited excellent antifouling performance even in complex media and showed promising feasibility for the quantitative analysis of AFP in real samples. The PEDOT derivative with hyperbranched polyglycerol groups was effective to reduce biofouling and facile for surface functionalization. It is expected that this novel antifouling and conducting material may find broad applications in the development of electrochemical sensors and biosensors capable of assaying targets in complex biological media.

Porphyrins modified inorganic semiconductors as a platform in nanomaterials have been paid more attention, due to the fast electron transfer from synergistic effect. Two-Dimensional 5,10,15,20-tetra(4-carboxyphenyl)porphyrin-Co9S8 nanocomposites (H2TCPP-Co9S8 nanocomposites) were synthesized via a simple one-step hydrothermal method. A simple and highly sensitive method toward colorimetric biosensing of H2O2 was developed by monitoring the color change of chromogenic substrate 3,3,5,5-tetramethylbenzidine (TMB) from colorless to blue. Notably, the H2TCPP-Co9S8 nanocomposites were proved to possess the highly peroxidase-like activity, compared with that of pure Co9S8 nanosheets. Unusually, ESR data verified that the catalytic mechanism of H2TCPP-Co9S8 was firstly ascribed to production of superoxide radicals. The detection limit of H2O2 was 8.19 μM and the linear range from 10 to 200 μM. Similarly, The detection limit of glutathione is as low as 0.194 μM with a linear range of 0.3–10 μM. Furthermore, this sensor has shown high selectivity to H2O2 detection and was successfully applied in H2O2 detection in contact lens fluid samples with satisfying results.

A novel sandwich-like immunosensor was efficiently fabricated for detection of carcinoembryonic antigen (CEA) with three dimensional sea-urchin-like PdAuCu nanocrystals (PdAuCu NCs)/ferrocene-grafted-polylysine (Fc-g-PLL) as the label of secondary antibodies (Ab2) and Au nanoparticles (Au NPs) as the substrate material. Herein, PdAuCu NCs were directly synthesized with polyethylene oxide (PEO) as a growth-directing agent by a facile one-step aqueous method without any organic solvent. Meanwhile, Fc-g-PLL was obtained by covalent linkage of Fc with PLL via Schiff-base reaction. The well-dispersed PdAuCu NCs by Fc-g-PLL have the enlarged surface area, enhanced catalytic properties and superior biocompatibility to amplify the current signals. The resultant immunosensor shows linear relationship of the electrochemical responses with the CEA concentrations within a broader linear range (0.001–100.0 ng mL–1) and a lower detection limit (0.23 pg mL–1, S/N = 3). Furthermore, the immunosensor was explored for practical assay of CEA in human serum samples with accredited results. The novel immunoassay provides a feasible platform for early medical diagnosis.

Owing to the relatively sluggish charge transport and reaction kinetics in nickel-based oxides, the electrocatalytic efficiency for methanol oxidation reaction (MOR) is still far below what is expected. Herein, ultrathin NiO nanosheets with abundant oxygen vacancies is put forward as an applicable catalytic model to get in-depth insights into the role that oxygen vacancies play in MOR process. Theoretical investigations reveal that the incorporation of oxygen vacancies can not only enhance the electrical conductivity of NiO crystals, but also reduce the adsorption energy of methanol molecules onto the active surface, both of which are more favorable for optimizing the overall electrocatalytic MOR performance. Thanks to the ultrathin two-dimensional (2D) features and remarkably modulated electronic structures, ultrathin NiO nanosheets with abundant oxygen vacancies exhibit a dramatically improved electrocatalytic activity for MOR, which is significantly higher than that of the sample with less oxygen vacancies and bulk NiO. This work opens a promising and feasible pathway for the design and synthesis of highly efficient non-noble MOR catalysts.

Highly sensitive and specific detection of biomarkers is of great importance for diagnosis and treatment of the related diseases or cancers. We herein developed a robust photoelectrochemical (PEC) immunosensor with enhanced sensitivity and specificity based on evident photocurrent output of the photoanode and significant signal amplification of the biocathode. Prostate specific antigen (PSA, Ag) was used as a target model to exhibit analytical performances of the designed PEC immunosensor. Two kinds of CuInS2 quantum dots (CIS QDs) with different composition were modified on the TiO2 nanotubes (TiO2-NTs) electrode to fabricate the photoanode. Due to the co-sensitization effect of the CIS QDs on TiO2-NTs, an evident photocurrent output was generated at the photoanode. For the biocathode, Au nanoparticles (AuNPs) and polydopamine (PDA) were modified in order on indium-tin oxide (ITO) electrode to immobilize capture PSA antibody (Ab1). Carboxyl-modified polystyrene (PS) nanospheres were coated with secondary antibodies (Ab2) to form PS@Ab2 conjugates, which were used as signal amplifiers via the specific immunoreaction between Ag and Ab2. Based on joint action of evident photocurrent output of the photoanode and significant signal amplification of the biocathode, the designed PEC immunosensor exhibited an ultralow detection limit of 3.4 fg/mL for target PSA detection. Meanwhile, it also showed an enhanced specificity owing to the separation of the photoanode and the biocathode.

Electrochemiluminescence (ECL) has attracted significant interest because of its superior properties and potential applications in bioanalysis, and therefore many luminescent nanomaterials have been developed. Herein, well-defined Pd nanocones (Pd NCs) were facilely obtained by a one-pot hydrothermal method with poly- l -lysine (PLL) as a green protecting ligand, which were mainly characterized by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Then, the as-obtained Pd NCs were first explored as an anodic ECL emitter, where tripropylamine (TPA) worked as the coreactant to boost the ECL emission. The possible ECL mechanism of Pd NCs/TPA system was extensively explored by ECL and electrochemical techniques. Briefly, the ECL emission underwent the oxidation-reduction route, in which both Pd NCs and TPA were initially oxidized, and then the oxidized TPA lost an proton to form reducing agent (TPA·) strongly reacted with the oxidized Pd NCs generating Pd NCs* for the emission. Furthermore, using dopamine (DA) as an ECL quencher, an ultrasensitive sensor was constructed for DA detection. The fabricated ECL sensor shows high sensitivity and selectivity, good stability, and wide linear range with the low detection limit of 0.46 pM. It offers a new avenue to exploit ECL illuminant and enriches the ECL emission theory.

Herein, a novel electrochemical ultrasensitive immunosensor was designed for detecting prostate-specific antigen (PSA) with three-dimensional (3D) PtCu hollow nanoframes (PtCu HNFs) as signal amplification. The highly opened PtCu HNFs were synthesized by a one-pot solvothermal method with cetyltrimethylammonium chloride (CTAC) and trishydroxymethyl aminomethane (Tris) as co-structuring directors. The architectures enlarged the loading of prostate specific antibodies (Ab) and efficiently catalyzed hydrogen peroxide (H2O2) reaction, ultimately amplifying the signals. And polylysine was used to disperse PtCu HNFs, improve the biocompatibility and bind the Ab on the electrode surface. The fabricated immunosensor exhibited lower detection limit (0.003 ng mL–1, S/N = 3), and wider linear range (0.01–100.0 ng mL–1), along with the improved reproducibility, selectivity and stability for the assay of PSA. Thus, it is a desirable platform for PSA detection in clinical diagnosis and practical applications.

Sensitive but with simple, inexpensive detection of disease-related biomarkers in real biological samples is of quite necessity for early diagnosis and disease surveillance. We herein first introduced high-activity Fe3O4 nanozyme as signal amplifier to develop an ultrasensitive photoelectrochemical (PEC) immunoassay, which meanwhile has the distinct merits of both simplicity and low cost compared with previously reported enzyme-labeling PEC immunoassays. In the proposal, to illustrate and describe the PEC platform, prostate-specific antigen (PSA, Ag) was used as a target model. Specifically, ZnO nanorods (ZnO-NRs) grown vertically on a bare indium–tin oxide (ITO) electrode was deposited with ZnIn2S4 nanocrystals, producing ZnIn2S4/ZnO-NRs/ITO photoelectrode as the PEC matrix to modify capture PSA antibody (Ab1). Histidine-modified Fe3O4 (his-Fe3O4) nanozyme as signal amplifier was linked with signal PSA antibody (Ab2) to form his-Fe3O4@Ab2 conjugate, and was anchored through specific sandwich immunoreaction. The labeling his-Fe3O4 nanozyme acted as a peroxidase to induce the generation of the insoluble and insulating precipitation, resulting in an evident decrease in the photocurrent signal. On account of combined effects of high catalytic efficiency of the his-Fe3O4 nanozyme and excellent PEC properties of the ZnIn2S4/ZnO-NRs/ITO photoelectrode, ultralow detection limit of 18 fg/mL for target Ag detection was achieved. Besides, as high-activity his-Fe3O4 nanozyme has substituted natural enzyme as signal amplifier, simplicity and low cost of the PEC immunoassay was realized.

Herein, we synthesize the thiophene tetraphenylethene-based conjugated microporous polymer (ThT-CMP) using the tetraphenylethylene derivative [i.e., 1,1,2,2-tetrakis(4-bromophenyl)ethane (TPBE)] and 2,5-thiophenediboronic acid as the precursors. The aggregation of TPBE in the ThT-CMP can induce a strong dual-band bipolar electrochemiluminescence (AIECL) emission at 554 nm (anodic) and 559 nm (cathodic) with tri-n-propylamine (TPrA) and S2O82- as the coreactants, respectively. The anodic and cathodic ECL efficiencies are measured to be 11.49 and 3.82% with respect to the standard of the Ru(bpy)32+/TPrA system, respectively. We further develop a dipolar ECL sensor to sensitively detect rhodamine B (RhB) based on resonance energy transfer. This ECL sensor possesses a large dynamic range and high sensitivity. This research provides a new avenue of designing organic structures with the characteristic of bipolar AIECL for the development of luminescent devices.

A flexible free-standing electrochemical biosensor to detect carcinoembryonic antigen (CEA) is described based on a conducting polypyrrole (PPy) nanocomposite film electrode. The conducting PPy composite was constructed by the sandwiched structure formed by PPy doped with pentaerythritol ethoxylate (PEE) and 2-naphthalene sulfonate (2-NS-PPy) separately via electropolymerization. Gold nanoparticles (AuNPs) were fixed on the PPy composite film by electrodeposition and then connected to CEA aptamer through self-assembly to construct a free-standing electrochemical biosensor breaking away from additional soft substrates and current collector. This PPy composite film-based electrochemical biosensor exhibits satisfying sensing performance for CEA detection, with a linear range from 10−10 g/mL to 10−6 g/mL and a detection limit of 0.033 ng/mL, good specificity and long-term sensing stability (96.8% of the original signal after 15 days). The biosensor also presents acceptable reproducibility with 1.7% relative standard deviation. Moreover, this electrochemical biosensor owns the deformation stability that could bear various deformations (twisting, folding, and knotting) without affecting device’s sensing performance. It can even maintain 99.4% of the original signal under 25% strain deformation. Due to the superior sensing performance, high stability (mechanical deformation and long-term storage), and flexibility, this free-standing electrochemical biosensor proves huge potential in application of flexible and wearable electronics.

A universal strategy for the construction of ratiometric antifouling electrochemical biosensors was developed based on multifunctional peptides and 2D nanomaterial MXene loaded with gold nanoparticles (AuNPs) and methylene blue (MB). The nanocomposite of MXene loaded with AuNPs and MB (MXene-Au-MB) exhibited excellent conductivity, where the AuNPs were able to capture biomolecules containing sulfhydryl terminus, and the MB molecules were used to generate electrochemical signal. The MXene-Au-MB was fixed on the electrode surface by Nafion, and the anchored peptide captured the electrochemical signal probe carboxyl-modified ferrocene (Fc) to construct an electrochemical biosensor. The multifunctional peptide containing the anchoring, antifouling, and recognizing sequences endowed the sensing surface not only the assaying function but also the capability to resist nonspecific adsorption from complex samples. In the biosensing system, with the increase in the target concentration, the electrochemical signal of MB remained constant, whereas the electrochemical signal of Fc gradually decreased, and the ratiometric detection strategy greatly improved the accuracy of the biosensor. In the presence of a model target prostate-specific antigen (PSA), the recognizing sequence was recognized and cleaved, and the ratiometric signal of Fc and MB indicated the concentration of PSA accurately and sensitively, with a detection range from 5 pg/mL to 10 ng/mL and a limit of detection of 0.83 pg/mL. Electrochemical biosensors based on the MXene-Au-MB and multifunctional peptides possessed high selectivity, accuracy, and sensitivity even in real complex biological samples because of the excellent antifouling ability of the peptide. More importantly, the assaying of other targets can be easily realized with a similar biosensing strategy by changing the recognition sequence of the multifunctional peptide, and the detection of thrombin (TB) has also been achieved in this work.

Developing a highly sensitive immunoassay for tumor biomarkers is particularly important in bioanalysis and early disease diagnosis. In this work, a simple one-pot solvothermal method was developed for controllable synthesis of well-dispersed PtCo alloyed nanodendrites (PtCo NDs) by using l -carnosine as the co-structure-directing agent. The PtCo NDs had a large specific surface area and provided abundant active sites available for electrocatalytic oxygen reduction reaction (ORR). Based on the highly enhanced currents of the ORR, a novel label-free electrochemical immunosensor was fabricated for highly sensitive assay of carbohydrate antigen 15–3 (CA15-3). The sensor showed a wide linear range of 0.1–200 U mL−1 and a low limit of detection (LOD) down to 0.0114 U mL−1 (S/N = 3), in turn exploring its application to diluted human serum samples with satisfactory results. This study provides a feasible platform for monitoring other tumor markers in clinical diagnosis.

Herein, an electrochemical sensing platform based on zwitterionic peptide with a hierarchical structure was constructed for ultralow fouling and highly sensitive protein quantification. Through the combination of CPPPPEKEKEKEK and CPPPPEKEKEK peptides, hierarchical antifouling peptide brushes were formed and exhibited excellent antifouling property, which can be further modified with alpha fetoprotein (AFP) aptamer to achieve highly sensitive detection of AFP. The hierarchical peptide brush-based sensor system achieved an AFP quantification range from 1.0 fg mL−1 to 1.0 ng mL−1, with a very low limit of detection as low as 0.59 fg mL−1. In addition, due to the superior antifouling property of the newly designed hierarchical peptide brushes, the electrochemical biosensor supported the quantification of AFP in solutions with a high concentration of nonspecific proteins without sacrifice in sensitivity. It is worth noting that the constructed antifouling biosensor ensured quantitative recruitment of AFP in clinical serum samples with acceptable accuracy when compared with the commonly used method in the hospital. The strategy of constructing sensing interfaces based on designed hierarchical peptide brushes provided an effective way to develop biosensors with both excellent antifouling capability and high sensitivity.

For immobilization and signal amplification of the probes, it is feasible and promising by using porous nanomaterials as nanocarriers. Herein, a novel label-free electrochemical immmunosensor was efficiently designed for ultrasensitive detection of procalcitonin (PCT). The immunosensor was prepared by using porous silica-coated gold nanorods (Au NRs@m-SiO2) to load electroactive dye thionine (Thi) on the electrode surface. Apart from the improved electrical conductivity, the porous feature highly increased the loading amount of Thi to boost the detection signals, while the good biocompatibility and protective microenvironment are beneficial to the largely improved stability for the target. For quantification of PCT, the developed immunosensor exhibited a good linear relationship in the antigen concentration range of 0.001–100 ng mL−1 with an ultra-low limit of detection (LOD, 0.39 pg mL−1, S/N = 3). Moreover, the built platform was successfully applied to such assay in human serum samples. The research provides some valuable guidelines for clinical screening and diagnosis of other biomarkers.

A surface-enhanced Raman scattering (SERS) method is proposed for the assay of microRNA 122 based on configuration change of DNA tetrahedron. Firstly, a DNA tetrahedron was self-assembled with one vertex labeled with toluidine blue (TB). Then, it was immobilized on the porous Ni/SiO2@PEI@Au as a SERS platform, which was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). At this time, the DNA tetrahedron was contracted; so, the TB is close to AuNPs and the Raman signal is high. When target microRNA 122 existed, with the nicking enzyme amplification strategy, a great deal of DNA signal chains (S5) was obtained, which can extend the contracted DNA tetrahedron and change it into a three-dimensional DNA tetrahedron. In this case, the TB was far from AuNPs, resulting in a lower Raman signal. Due to the configuration change of DNA tetrahedron, the Raman signal at 1624 cm−1 (with the excitation wavelength of 633 nm) has a linear relationship with the logarithm concentration of microRNA 122. This SERS assay has high sensitivity for microRNA 122 with a determination range from 0.01 aM to 10 fM and a detection limit of 0.009 aM. The recoveries from spiked samples were in the range 95 to 109%. This SERS strategy is designed based on the target-triggered configuration change of DNA tetrahedron, which can give new insight for DNA structures in bioanalysis.

Water-soluble Cu nanoclusters (NCs) with tunable emission were synthesized through an eco-friendly one-pot aqueous method. Blue-, green-, and red-emitting NCs with the emission peaks at 420 nm, 505 nm, and 630 nm were obtained by employing ethanediamine, cysteine, and glutathione as surface ligands, respectively. The ligand effects on the optical properties of Cu NCs were studied by the single variable method. It has been revealed by systematic characterizations that the dependence of emission color on the structures of ligands was mainly attributed to their different size-tuning effects. Glutathione has the strongest chelating ability and it can significantly reduce the monomer reactivity and thus decrease the supersaturation degree of the reaction, which is favorable for modulating Cu precursor to grow into larger NCs. In contrast, ethanediamine ligand resulted in smaller nanoclusters due to its weaker binding capability. Because of the strong emission and terrific fluorescent stability, Cu NCs capped with ethanediamine, possessing an emission peak at 420 nm when excited at a wavelength of 350 nm, were directly used for probing Hg(II) with satisfying selectivity, presenting a linear range of 0.1-5.0 mM and a detection limit of 33 μM. The sensor showed good performance in real sample analysis with recoveries ranging from 99% to 103%, and comparable accuracy with atomic fluorescence spectroscopy, manifesting the reliability of the current strategy for sensing Hg(II). Graphical abstract Water-soluble copper nanoclusters with blue, green, and red emissions were synthesized by employing ethanediamine, cysteine, and glutathione as surface ligands respectively, and the blue-emitting nanoclusters with strong emission and terrific stability were directly used for selectively sensing Hg

Photocathodic bioassays have shown great potential to apply in real bio-sample detection owning to their intrinsic abilities against interference from reductive species. However, the pursuit of photocathodic bioassays with excellent detection performance is still in the infancy. Herein, an advanced signal amplifier of platinum-based nanocatalyst with efficient oxygen reduction capability was explored to build a high-performance photocathodic immunoassay. The target model of carbohydrate antigen 19-9 (CA19-9, Ag) was used for describing the sensing platform. Specifically, the nontoxic Au/CuBi2O4 photocathode was first prepared by decorating Au nanoparticles on CuBi2O4 nanofilm and was used as the matrix to anchor capture CA19-9 antibody (Ab1). Platinum (Pt) nanoparticles were loaded on graphene (GR) nanosheet to form Pt/GR nanocomposite, which was utilized as signal amplifier conjugating with signal CA19-9 antibody (Ab2). When specific sandwich immunoreaction happened, the Pt/GR played the role of an efficient nanocatalyst to accelerate the reduction reaction of electron acceptor of oxygen in the electrolyte, causing evidently enhanced cathodic photocurrent signal. By incorporating this superior signal amplification strategy into the anti-interference photocathodic immunoassay, highly sensitive and specific detection of target Ag was realized. This work pioneers a new perspective for the design of advanced photocathodic bioanalysis for various targets of interest.

Over the past few years, different biomarkers related to various disease states have been identified, and the assay of these disease biomarkers, which can reveal the health status and stages of diseases, has received increasing attention. A broad range of analytical techniques have been applied to the detection of these biomarkers, with electrochemical analysis becoming one of the most promising approaches due to high sensitivity, accuracy, wide measurement range and low-cost and portable instrumentation requirements. However, one of the biggest challenges in this field relates to the operation of electrochemical sensors in biological media, as biofouling deleteriously affects the functioning of the electrochemical sensing interface when exposed to biological fluid. In this mini review, recent trends in the development of low fouling electrochemical biosensors based on different antifouling materials are summarized and discussed. Also, an outlook on the opportunities and challenges with regard to future development of low fouling electrochemical biosensors capable of assaying biomarkers in clinical samples is presented.

The direct urea fuel cell (DUFC) is a renewable technology for energy production, but largely limited by the intrinsically sluggish kinetics of the urea oxidation reaction (UOR) due to the complex six-electron transfer process, which severely hampers its commercial utilization. Herein, ultrathin β-Ni(OH)2 nanosheets with a porous structure were constructed to increase both the active surface area and the reactivity of active sites of catalysts, providing great opportunities for promoting the electrocatalytic UOR process. Theoretical investigations showed that the existence of abundant pores in ultrathin β-Ni(OH)2 nanosheets could reduce the adsorption energy of urea molecules on the catalyst surface, thus leading to a highly efficient catalytic activity for the UOR. As expected, the porous β-Ni(OH)2 nanosheets exhibit a large current density of up to 298 mA cm−2 at 1.82 V (vs. RHE), which is roughly 18.1 times higher than that of the nonporous β-Ni(OH)2 nanosheets and even comparable to those of other high-performance catalysts under similar conditions. This work not only provides a promising guideline for the development of advanced UOR catalysts, but also highlights the crucial role of the porous structure in promoting the electrocatalytic UOR process.

Low fouling electrochemical immunosensors with both "signal-off" and "signal-on" analytical methods were developed for the highly sensitive and efficient detection of cancer antigen 15-3 (CA 15-3) in human serum samples. The antifouling sensing interfaces were constructed by assembling multifunctional polyethylene glycol on gold electrodes, followed by covalent conjugation with CA 15-3 antibody. Pure antigens and Fe3O4@Ag will competitively bind to the immobilized antibody on the electrode. Fe3O4 magnetic nanoparticles attached to the working electrode and collected by a magnetic electrode were treated via electrochemical conversion to generate electroactive Prussian blue as a signal readout. Therefore, these two signals measured independently were complementary, and this design allowed one to choose the assay method according to real situations so as to ensure accuracy of the immunosensor. Moreover, owing to its good antifouling property, the immunosensor was capable of detecting CA 15-3 even in complex human serum samples, demonstrating potential application in quantitative analysis of real patient serum samples.

Nanomaterial-doped conducting polymers represent a unique class of composite materials that synergizes the advantageous features of nanomaterials and organic conductors, and they have been used in many applications such as electrochemical sensors and energy storage devices. Conducting polymers can be controllably synthesized from various monomers, and during the polymerization process, different nanomaterials offering unique physical and chemical properties can be doped into the formed conducting polymer composites. In this review, we focus on recent advances in electrochemical sensors and biosensors based on conducting polymers doped with various nanomaterials, including carbon nanomaterials, metal or metal oxide nanoparticles and quantum dots. Approaches to fabrication of films of these materials are described and sensing applications for different targets are summarized.

Ratiometric electrochemical sensors are being considered a significant advance in the fields of electroanalysis and are now attracting the attention of many research laboratories. Different from classic electrochemical sensors which typically adopt the absolute value of the signal as the output, ratiometric electrochemical sensors possess dual electrochemical signals and the quantitative measurement of target is based on the ratio of these two signals. The ratiometric signal readout mode provides a built-in correction factor to eliminate the contribution from non-specific interferences. Thus, greater reproducibility, accuracy and sensitivity are obtained, which are critical demands of the classic electrochemical sensor. In this review, we discuss recent advances in ratiometric electrochemical sensors. In addition, we give critical perspectives on the different design schemes, development status and application prospects for ratiometric electrochemical sensors.

In this work, quaternary CdZnTeS quantum dots (QDs) with a particularly strong electrochemiluminescence (ECL) were synthesized as ECL signal labels. The strong ECL signals can be obtained at both cathode and anode with the ECL efficiencies of 19.78% and 1.62%, respectively. The sandwich-structured ECL immunosensors for the detection of alpha-fetoprotein (AFP) and cancer antigen 125 (CA125) were accomplished with direct ECL image analysis. Under optimal conditions, the QDs-based ECL image immunoanalysis possessed good linearity from 0.5 ng/mL to 20 ng/mL for AFP and from 20 U/mL to 500 U/mL for CA125 with the detection limit of 0.1 ng/mL and 6 U/mL, respectively (S/N = 3), and the lower detection limit obtained by photomultiplier tube were 0.1 fg/mL for AFP and 0.03 mU/mL for CA125 with the wide dynamic range from 0.5 fg/mL to 20 ng/mL and from 0.1 mU/mL to 500 U/mL, respectively (S/N = 3). Furthermore, the ECL immunoanalysis was evaluated with commercial enzyme-linked immunosorbent assay in human serum samples. The good results indicated that CdZnTeS QDs-based ECL biosensor has great potential for fast biomedical screening and multi-assays in clinical diagnosis.

Noble metal nanoparticles possess excellent optical and electrical properties, and have been widely used in the construction of biosensors and in surface-enhanced spectroscopy. Herein, we describe an enzyme-assisted ultra-sensitive biosensor with gold nanoparticle (GNP) dimers, based on a localized surface plasmon resonance (LSPR)-enhanced electrochemiluminescence (ECL) mechanism. CdS nanocrystals (NCs) acted as ECL emitters, and the GNP dimers were constructed by hybridization of DNA strands on the surface of an electrode modified with CdS NCs after an enzyme-assisted cyclic amplification process. The plasmon-coupling-induced electromagnetic field enhancement effects of the GNP dimers resulted in an increase in ECL intensity of as much as 6.3-fold under optimized conditions. Based on this LSPR-ECL sensor platform, the detection limit for microRNA-21 is as low as 3.6 fM with a wide linear range from 10 fM to 20 pM with good sensitivity and selectivity. Keywords: Plasmon coupling, GNP dimer, Electromagnetic field enhancement, Signal amplification, MicroRNA detection

This paper describes an electrochemiluminescence resonance energy transfer (ECL-RET) system using Ru(bpy)32+-doped silica nanoparticles (RuSi NPs) as the ECL donor and hollow Au nanocages as the ECL acceptor. Tetrahedron DNA (TD) was used to construct the biosensing interface and control the distance (4.8 nm) between the ECL donor–acceptor pairs. The surface plasmon resonance (SPR) nanostructures, Au nanocages were assembled via the hairpin based sandwich assay. Due to the well overlap between the plasmon absorption spectrum of Au nanocages (628 nm) and the ECL emission spectrum of RuSi NPs (620 nm), high efficient energy transfer could occur. Subsequent cyclic DNA amplification further increased the binding amount of Au nanocages. Since the ECL inhibition is closely related with the binding amount of Au nanocages, a general “signal-off” ECL bioassay could thus be tailored with high sensitivity. At the optimized conditions, this ECL-RET system performed well with great stability and repeatability for nucl...

Dynamic assessment of glycan expression on the cell surface and accurate determination of circulating tumor cells are increasingly imperative for cancer diagnosis and therapeutics. Herein, a unique and versatile nonenzymatic sandwich-structured electrochemical cytosensor was developed. The cytosensor was constructed based on a cell-specific aptamer, the lectin-functionalized porous core–shell palladium gold nanoparticles (Pd@Au NPs). To establish the cytosensor, amine-modified-SYL3C aptamer was first attached to the surface of aminated Fe3O4@SiO2 nanoparticles (Fe3O4@SiO2–NH2 NPs) through cross-linked reaction via glutaraldehyde. Besides, in terms of noncovalent assembly of concanavalin A on Pd@Au NPs, a lectin-functionalized nanoprobe was established. This nanoprobe had the capabilities of both the specific carbohydrate recognition and the current signal amplification in view of the Pd@Au NPs as the electrocatalyst for the reduction of hydrogen peroxide (H2O2). Herein, we used MCF-7 cells as a model target, and the constructed cytosensor showed a low detection limit (down to three cells), a wide linear detection ranging from 100 to 1 × 106 cells mL–1. The established method sensitively realized the detection of the amount of cell and exact evaluation of glycan expression on cell surface, demonstrating great application prospects.

In this work, novel multifunctional patchy gold coated Fe3O4 hybrid nanoparticles (PG-Fe3O4 NPs) have been successfully synthesized in aqueous medium via a facile adsorption-reduction method. A rational formation mechanism has been proposed by monitoring the morphological evolution. The PG-Fe3O4 NPs retained the good magnetic property and exhibited excellent catalytical effeciency towards the electrochemical reduction of hydrogen peroxide. Chronoamperometric and amperometric experiments indicated a relatively high catalytic rate constant of 3.13 × 105 M−1 s−1, a high sensitivity of 578.87 µA mM−1 cm−2 and a low Michaelis-Menten constant of 462 µM. Meanwhile, the introduction of patchy gold could help biofunctionalization via Au-S bond for different biodetection and biosensing purposes. Here, as an example, thiol-terminated aptamers were immobilized onto the patchy gold part as a signal probe to detect carcinoembryonic antigen (CEA). A related paper-based bipolar electrode-electrochemiluminescence (pBPE-ECL) aptasensor was fabricated as the low-cost, disposable and miniature platform. To improve the sensitivity, Au nanodendrites were electrodeposited at the BPE cathode as the matrix for Apt1 immobilization. This aptasensor showed a wide linear range of 0.1 pg mL−1–15 ng mL−1 with a low detection limit of 0.03 pg mL−1, remaining competitive against other ones, and also demonstrating the PG-Fe3O4 NPs have promising potential for catalysis and bioassays.

Developing highly efficient and stable platinum (Pt)-based electrocatalysts for oxygen reduction reaction (ORR) is the most essential step toward the commercialization of fuel cells. Highly accessible reactive surfaces play a key role in boosting ORR for superior fuel cell performance due to the adequate exposure of the active surfaces and the feasible mass transport. Herein, we begin with a brief introduction to the design principles for an effective ORR electrocatalyst, which could plausibly possess high activity and durability at the same time. Corresponding with the requirements, the recent progress of rational design based on nanoarchitecture, synthesis, and electrochemical performances of Pt-based electrocatalysts with open construction is reviewed and explained accordingly.

Herein, the Au nanoclusters (Au NCs) functionalized ternary nanostructure with significant electrochemiluminescence (ECL) emission was first proposed to fabricate an ultrasensitive immunosensor for carcinoembryonic antigen (CEA) detection, which was established by combining bovine serum albumin (BSA) templated Au NCs as the luminophor, tris(3-aminoethyl)amine (TAEA) as the coreactant, and Pd@CuO nanomaterial as the coreaction accelerator via covalent attachment in a nanostructure. Through the dual self-catalysis including intramolecular coreaction between TAEA and Au NCs, and intramolecular coreaction acceleration from Pd@CuO to TAEA, the Au NCs-TAEA-Pd@CuO achieved excellent ECL performance so that the detection limit of the immunosensor for measuring CEA antigen was down to 16 fg/mL in the absence of any additional signal amplification assay. Moreover, the method for preparing ECL nanostructure-based metal NCs should be devoted to the development of highly efficient ECL signal label, outlining a significant scheme toward biological testing and clinical diagnosis.

Previous work on photoelectrochemical (PEC) biosensors has demonstrated that the photoanode-based type possesses satisfying sensitivity, because photoanode utilize electrons as the majority charge carriers and a distinct photocurrent can be generated when electron donors are furnished. However, as hole-oxidation reaction occurs at the photoanode interface, the photoanode-based PEC sensor has inferior anti-interference capacity to reductive substances coexisting in the biological sample, leading to a challenged selectivity. Herein, a universal design on selectivity-enhanced PEC enzyme sensor was proposed by integrating a photoanode with a biocathode. Specifically, the CuInS2 sensitization layer and ZnS passivation layer were deposited in sequence on the TiO2 film modified indium-tin oxide (ITO) electrode mainly by successive ionic layer adsorption and reaction (SILAR) means, forming the hybrid ZnS/CuInS2/TiO2/ITO photoanode. A carbon fiber paper (CFP) electrode was modified with biocatalysts of enzymes via the assistance of chitosan (CS) to fabricate the biocathode. Utilizing glucose oxidase (GOx) and horserdish peroxidase (HRP) as biocatalysts, a selectivity-enhanced PEC sensor for glucose was developed. The PEC sensing platform integrating photoanode with biocathode not only inherits distinct photocurrent of the photoanode-based sensor but also possesses enhanced selectivity, because just the biocathode was incubated in the biological sample and there is no interaction between the photoanode and coexisting reductive substances.

Well-constructed porous materials take an essential role in a wide range of applications, including energy conversion and storage systems, electrocatalysis, photocatalysis, and sensing. Although the tailored design of various nanoarchitectures has made substantial progress, simpler preparation methods are compelled to meet large-scale production requirements. Recently, advanced electrochemical deposition techniques have had a significant impact in terms of precise control upon the nanoporous architecture (i.e., pore size, surface area, pore structure, etc.), enabling access to a wide range of compositions. In this Account, we showcase the uniqueness of electrochemical deposition techniques, detail their implementation toward the synthesis of novel nanoporous metals, and finally outline the future research directions. Nanoporous metallic structures are attractive in that they can provide high surface area and large pore volume, easing mass transport of reactants and providing high accessibility to catalytically active metal surface. The great merit of the electrochemical deposition approach does not only lie in its versatility, being applicable to a wide range of compositions, but also in the nanoscale precision it affords when it comes to crystal growth control, which cannot be easily achieved by other bottom-up or top-down approaches. In this Account, we describe the significant progress made in the field of nanoporous metal designed through electrochemical deposition approaches using hard templates (i.e., porous silica, 3D templates of polymer and silica colloids) and soft templates (i.e., lyotropic liquid crystals, polymeric micelles). In addition, we will point out how it accounts for precise control over the crystal growth and describe the unique physical and chemical properties emerging from these novel materials. Up to date, our group has reported the synthesis of several nanoporous metals and alloys (e.g., Cu, Ru, Rh, Pd, Pt, Au, and their corresponding alloys) under various conditions through electrochemical deposition, while investigating their various potential applications. The orientation of the channel structure, the composition, and the nanoporosity can be easily controlled by selecting the appropriate surfactants or block copolymers. The inherent properties of the final product, such as framework crystallinity, catalytic activity, and resistance to oxidation, are depending on both the composition and pore structure, which in turn require suitable electrochemical conditions. This Account is divided into three main sections: (i) a history of electrochemical deposition using hard and soft templates, (ii) a description of the important mechanisms involved in the preparation of nanoporous materials, and (iii) a conclusion and future perspectives. We believe that this Account will promote a deeper understanding of the synthesis of nanoporous metals using electrochemical deposition methods, thus enabling new pathways to control nanoporous architectures and optimize their performance toward promising applications such as catalysis, energy storage, sensors, and so forth.

Herein, a visible light photoelectrochemical (PEC) platform based on polyaniline (PANI) and nanoMoS2 composites as optoelectronic material for glutathione detection without any auxiliary of biomolecules or labeled materials was developed. Firstly, the nanoMoS2 was prepared via a simple ultrasound exfoliation method. The PANI was synthesized by chemical oxidative polymerization method. Then composite of PANI and nanoMoS2 was used to modify gold electrode. It was found that the composite membrane showed excellent PEC properties. And glutathione enhanced the PEC signal greatly. Based on this finding a method for glutathione detection was fabricated. Under the optimum conditions, the linear response of glutathione concentrations ranged from 1.0 × 10−10 to 1.0 × 10−4 mol L−1 was obtained with a detection limit of 3.1 × 10−11 mol L−1. The relative standard deviation was 2.9% at 2.0 × 10−9 M (n = 10). This method showed high sensitivity and simpleness which opened up a new promising signal-on PEC platform for future bioassay.

Herein, well-defined hollow dendritic AuPtAg alloyed nanocrystals (ANCs) were synthesized by a simple L-proline-mediated one-pot aqueous method. More importantly, the synthesized hollow dendritic architectures provide a suitable platform for immobilization of anti-prostate specific antigen (PSA). The resultant label-free immunosensor exhibited the improved performance for highly sensitive detection of PSA based on the enhanced catalytic currents of K3[Fe(CN)6] as a signal probe. Impressively, the immunosensor showed the wide linear range of 0.05–50 ng mL–1 and low detection limit of 0.017 ng mL–1 under optimal conditions for the assay of PSA, couple with the improved stability, reproducibility and selectivity. It provides a promising platform for clinical research and diagnosis.