Plasmon-enhanced electroreduction activity of Au-AgPd Janus nanoparticles for ochratoxin a detection.

Ochratoxin A (OTA) was a dangerous biological toxin, and would easily contaminate food and induced food safety problems. The development of electrochemical aptasensors by designing strong and anti-interfere electroactive labels could improve the sensitivity and accuracy of OTA detection. In this contribution, novel electroactive Au-AgPd Janus NPs were firstly synthesized and exhibited electroreduction signal at -0.4 V, owing to the reduction process of Pd2+. The electroreduction signal was amplified 1.5 times under local surface plasmon resonance (LSPR) excitation, which could improve the sensitivity of OTA detection. Plasmon-enhanced electroreduction principle of Au-AgPd Janus NPs was verified, which endowed electrochemical aptasensor with high accuracy and anti-interference ability for OTA detection. Au-AgPd Janus NPs served as electrochemical beacon achieved sensitive and accurate OTA detection with the limit of detection (LOD) of 0.98 pM. This work opens up new directions for the construction of electroactive heterostructures for the sensitive and accurate biotoxins electroanalytical applications.

AuPt NPs with enhanced electrochemical oxidization activity for ratiometric electrochemical aptasensor.

Strong and stable electrochemical beacons are critical for the achievement of sensitive and reliable electroanalysis applications. In this work, the electrochemical oxidation performance of AuPt NPs was studied and firstly found to be largely enhanced under light illumination. Plasmonic AuPt NPs collected light energy after local surface plasmon resonance (LSPR) excitation and generated much more holes to participate in the electrochemical oxidation process of Pt0 in AuPt NPs. AuPt NPs with the electrochemical oxidation peak at around -0.7 V were utilized as detection probes for the fabrication of ratiometric electrochemical aptasensor, by introducing Co-MOF/Fe3O4/Ag nanosheets (NSs) with the electrochemical oxidation peak at 0.1 V as reference beacons. The aptamers of epithelial cell adhesion molecule (EpCAM) modified AuPt NPs were assembled with Co-MOF/Fe3O4/Ag NSs, which generated strong detection and reference signals at -0.7 V and 0.1 V, respectively. The high affinity between EpCAM and aptamers induced the separation of AuPt NPs from Co-MOF/Fe3O4/Ag NSs, resulting in the decrease of detection signal at -0.7 V and unchanged reference signal at 0.1 V. A ratiometric electrochemical aptasensor was achieved for the sensitive and reliable quantification of EpCAM in the range from 100 pg/mL to 100 ng/mL. The limit of detection (LOD) was calculated to be 13.8 pg/mL for EpCAM. Plasmon-driven electrochemical oxidation enhancement principle provides the possibility for the design and fabrication of more strong and anti-interference electroactive plasmonic metal-Pt composite nanostructures for the electroanalysis applications.

RuCu Cage/Alloy Nanoparticles with Controllable Electroactivity for Specific Electroanalysis Applications.

Electrochemical nanotags with controllable and multiresponse electroactivity have a great capacity for overcoming the drawbacks of limited target monitoring and inaccurate detection results for electrochemical sensors. In this contribution, double electro-oxidative Ru and Cu metals were integrated into RuCu nanostructures for the generation of dual electro-oxidative signals. A facial approach was proposed for the controllable fabrication of RuCu cage nanoparticles (NPs) and RuCu alloy NPs by simply adjusting the pH value of the reaction system. RuCu cage NPs and RuCu alloy NPs demonstrated inherent different electro-oxidative responses owing to the remarkable distinction of structures with different metal valences. RuCu cage NPs showed a single electro-oxidization peak at 0.84 V, assigned to the exposure of more Ru0 electroactive sites on the hollow cage structures. RuCu alloy NPs illustrated dual electro-oxidization peak at 0.84 and -0.16 V, attributing to the presence of Ru0 and Cu+ electroactive sites on the alloy structures, respectively. RuCu cage NPs and RuCu alloy NPs served as specific electroactive tags, achieving the selective monitoring of Na2S and ratiometric electrochemical detection of xanthine in monosodium glutamate, respectively. The limits of detection were as low as 27 pM for Na2S and 70 nM for xanthine. The rational design of multimetal nanostructures holds enormous potential for the generation of multiresponse electroactivity with the impetus for exploring the capacity of specific electrochemical sensing.

Plasmon-Enhanced Electroactivity of AuRu Nanostructures for Electroanalysis Applications.

An electrochemical sensing interface is limited by poor reproducibility and inevitable interferences present in practical applications due to the weak electrochemical signals of nanotags. This motivates the need for effective strategies to enhance the electroactivity performances of nanotags. In this contribution, a plasmon-enhanced electroactivity mechanism is proposed for AuRu-based nanostructures under illumination and applied for accurate detection of human epidermal growth factor receptor-2 (HER2). AuRu nanoparticles (NPs) harvested light energy through plasmon excitation and generated holes to participate in the electrooxidation process. The production of holes resulted in the electrooxidation signal enhancement of AuRu NPs. AuRu NPs were assembled with Au NPs using HER2 aptamers as linkers, and the plasmonic coupling between AuRu NPs and Au NPs produced an intense electromagnetic field, which further enhanced the electrooxidation signals of AuRu NPs. An AuRu-Au NP assembly-dependent electrochemical aptasensor was established for the accurate detection of HER2, and the limit of detection (LOD) was as low as 1.7 pg/mL. The plasmon-enhanced electroactivity mechanism endowed AuRu-based nanostructures with strong and noninterfering electrochemical signals for sensitive and accurate detection. This insight opens new horizons for the construction of desired electroactive nanostructures for electroanalysis applications.

Electroactive Cu2O nanocubes engineered electrochemical sensor for H2S detection.

An electrochemical sensor was proposed for the detection of hydrogen sulfide (H2S) at room temperature, by using electroactive Cu2O nanocubes (NCs) as an electrochemical beacon. Electroactive Cu2O NCs were synthesized on the surface of reduced graphene oxide (rGO)/Fe3O4 nanosheets (NSs) due to the good electronic conductivity and well-responded magnetic responses. The fabricated rGO/Fe3O4/Cu2O NSs not only showed electrochemical oxidization peak at -0.1 V from Cu2O NCs, and could be served as sensitive electrochemical beacon for the simple modification on magnetic electrodes in the applications. The unique redox reaction between Cu2O NCs and H2S enabled the transformation of Cu2O NCs to Cu9S8 NCs, resulting in decreased electroxidation responses at -0.1 V. The constructed electrochemical platform had a limit of detection (LOD) of 230 pM and a detection range of 500 pM-100 µM. The simple and cheap electrochemical sensor developed in this paper showed potential application for H2S detection.

Ratiometric persistent luminescence aptasensors for carcinoembryonic antigen detection.

NIR-emitted ZnGa2O4:Cr3+ persistent luminescence nanoparticles (ZGC NPs) coated with polydopamine (ZGC@PDA NPs) were designed featuring internal reference and quenching ability. Sr-doped Zn2GeO4 persistent luminescence nanorods (ZGO:Sr NRs) served as detection probes, which exhibited blue emission. The decay times and intensity of luminescence of ZGO:Sr NRs were optimized to acquire desired luminescence properties. An aptamer-guided ratiometric persistent luminescence sensor with the LOD (0.46 pg mL-1) was established to detect carcinoembryonic antigen (CEA). This developed ratiometric aptasensor based on persistent luminescence nanomaterials (PLMs) does not only use the afterglow properties of nanomaterials to avoid the interference of autofluorescence but also precludes the interference of certain factors in the detection environment on the luminescence intensity due to the introduction of a reference signal, and is suitable for early screening of tumor markers in serum samples. Moreover, the optimization of luminescence properties, especially for luminescence decay times, provides a way for the fabrication of multiple persistent luminescence materials in the application of time-resolved fluorescence technology. Graphical abstract Construction of ZGO:Sr NR- and ZGC@PDA NP-driven ratiometric aptasensor for CEA detection.