A photoelectrochemical (PEC) sensing platform based on gold nanoparticle (AuNP)-attached perovskite Cs 3 Bi 2 Br 9 QDs/BiOBr heterostructures was developed to set up a photocathodic analysis platform for sensitive detection of hydrogen peroxide (H 2 O 2 ). A series of detailed analyses demonstrated that the Cs 3 Bi 2 Br 9 QDs/BiOBr heterostructures with high photoelectric activity were successfully prepared by water treatment producing BiOBr-encapsulated Cs 3 Bi 2 Br 9 QDs. The decoration of AuNPs can initiate a surface plasmon resonance enhancement effect to further effectively improve the PEC performance. The resulting AuNPs/ Cs 3 Bi 2 Br 9 QDs/BiOBr-modified photoelectrode presents efficient photoelectrochemical performance for H 2 O 2 sensing in a wide linear detection range from 0.002 to 200 μM with a very low detection limit down to 0.89 nM. Meanwhile, it exhibits excellent performance of good stability, favorable specificity, and acceptable reproducibility. Moreover, the promising platform is capable of monitoring H 2 O 2 released from living tumorigenic cells, indicating its promising potential in biological applications. This work highlights a useful strategy toward simple and easy photoelectrochemical biosensing of photoelectrically active molecules for further utilization, which should be valuable for revealing the potential of lead-free perovskites and their heterostructures for advanced PEC biosensing applications.

Rapid and accurate detection of biomolecules is of vital importance for the diagnosis of disease and for performing timely treatments. The point-of-care analysis of cancer biomarkers in the blood with low cost and easy processing is still challenging. Herein, an advanced and robust strategy, which integrates the buoyant recognition probe with the magnetic reporter probe in one solution, was first proposed for immobilization-free electrochemical immunosensing. The tumor marker of alpha fetoprotein (AFP) can be captured immune-buoyantly, and then a multifunctional magnetic reporter probe in pseudo-homogeneous solution was further captured to fulfill a sandwich-type immunoreaction. The residual magnetic reporter probe can be firmly and efficiently attracted on a magnetic glassy carbon electrode to fulfill the conversion of the target AFP amount into the residual magnetic electrochemical signal indicator. As a result, the electrochemical signal of methylene blue can accurately reflect the original level of target antigen AFP concentration. By integrating buoyancy-driven quasi-homogenous biorecognition with magnetism-mediated amplification and signal output, the proposed immobilization-free electrochemical immunosensing strategy displayed a wide range of linear response (100 fg mL −1 to 10 ng mL −1 ), low detection limit (14.52 fg mL −1 ), and good reproducibility, selectivity, and stability. The designed strategy manifests remarkable advantages including assay simplicity, rapidness, and high sensitivity owing to the in-solution instead of on-electrode biorecognition that could accelerate and improve the biorecognition efficiency. To the best of our knowledge, this is the first cooperation of buoyancy-driven biorecognition with magnetism-mediated signal output in bioanalysis, which would be attractive for rapid clinic biomedical application. Thus, this work provides a fresh perspective for convenient and favorable immobilization-free electrochemical biosensing of universal biomolecules.

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A unique ratiometric MALDI-MS strategy based on a homogeneous enzymatic cleavage triggered double-signal output was designed for the convenient and reliable quantitation of alkaline phosphatase with a tunable dynamic range.