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Scheme 1. Illustration of preparation of HPG carbon/GCE and the mechanism for electrochemical oxidation of sunset yellow. [Display omitted] • We proposed a new ultrasensitive sunset yellow sensor by using 3D HPG carbon. • HPG carbon is featured with large surface area and a high content of sub-nanopores. • The sub-nanopores of HPG carbon improved the pre-concentration efficiency of SY. • The proposed sensor showed a wide linear range and ultra-low detection limit. • This research provided a universal platform for azo dye sensing applications. The content of sunset yellow (SY) in food must be strictly controlled, because its excessive intake may cause many adverse health effects. Herein, we proposed an ultrasensitive SY sensor by using hierarchical porous graphitic (HPG) carbon derived from polyaniline hydrogel. After a first step of polymerization, the HPG carbon was prepared through carbonization and further chemical activation. In particular, the activation process endowed the HPG carbon with a high content of optimized porous architecture (sub-nanoporous surface area accounts for more than 90% of microporous surface area), and thus providing a structural basis for high efficiency of SY pre-concentration on HPG carbon surface. Therefore, the proposed sensor showed record-high sensitivity (5285.7 A M−1 cm−2) and ultra-low detection limit (0.15 nM), which represents a performance improvement in SY sensing. Furthermore, the sensor displays excellent selectivity, reproducibility and stability, exhibiting a great perspective in ultrasensitive monitoring of SY in commercial products. [ABSTRACT FROM AUTHOR]

A novel photoelectrochemical immunosensor was constructed to monitor carcinoembryonic antigen (CEA) based on hybridization chain reaction (HCR)-mediated in situ generation of copper nanoparticles (Cu NPs) and subsequent Cu2+-dependent quenching reaction, in which titanium dioxide nanoparticles-sensitized double-shell zinc cadmium sulfide hollow nanospheres (TiO 2 /DS-ZnCdS)-modified ITO electrode and anti-CEA antibody-modified 96-well plate served as biological recognition and signal detection platforms, respectively. The synergistic effect of TiO 2 NPs and DS-ZnCdS hollow nanospheres contributed to the improvement of photoelectric conversion efficiency, and HCR-mediated signal cascade benefited the enhancement of detection sensitivity. In the presence of CEA, biotin-labelled anti-CEA antibodies were immobilized onto anti-CEA antibody-modified 96-well plate, and triggered HCR process to form long double stranded DNA, which could adsorb a large number of Cu2+ ions and then in situ form Cu NPs on double stranded DNA template by a facile reduction reaction. After acid treatment, the dissolved Cu2+ ions could significantly reduce the photocurrent response due to the generation of Cu x S. Under optimal conditions, the immunosensor exhibited a desirable liner range of 1 pg mL−1 – 50 ng mL−1 and a low detection limit of 0.1 pg mL−1, as well as excellent selectivity and stability. Meanwhile, the recoveries of human serum sample analysis ranged from 96.8% to 103.6%, and the relative standard deviation was less than 7.40%, showing a good feasibility in early clinical diagnosis. • A novel photoelectrochemical immunosensor based on TiO 2 -sensitized DS-ZnCdS HNs was constructed for CEA detection. • HCR-mediated cascade process and Cu2+-based quenching reaction were integrated. • The photocurrent response was enhanced by TiO 2 /DS-ZnCdS heterostructure. • The excellent performances of designed immunosensor benefited to its potential application in early clinical diagnosis. [ABSTRACT FROM AUTHOR]