Polarity Conversion of the Ag₂S/AgInS₂ Heterojunction by Radical-Induced Positive Feedback Polydopamine Adhesion for Signal-Switchable Photoelectrochemical Biosensing

Abstract

Efficient tuning of the polarity of photoactive nanomaterials is of great importance in improving the performance of photoelectrochemical (PEC) sensing platforms. Herein, polarity of the Ag2S/AgInS2 heterojunction is converted by radical-induced positive feedback polydopamine (PDA) adhesion, which is further employed to develop a signal-switchable PEC biosensor. In the nanocomposites, Ag2S and AgInS2 achieve electron–hole separation, exhibiting a strong anodic PEC response. Under the irradiation of light, the Ag2S/AgInS2 heterojunction is able to produce superoxide radical and hydroxyl radical intermediate species, leading to the polymerization of dopamine (DA) and the subsequent adhesion of PDA onto the Ag2S/AgInS2 heterojunction (Ag2S/AgInS2@PDA). By constructing a new electron-transfer pathway with PDA, the polarity of the Ag2S/AgInS2 heterojunction is converted, and the PEC response changes from anodic to cathodic photocurrents. In addition, since the photoreduction activity of PDA is stronger than that of the Ag2S/AgInS2 heterojunction, more superoxide radical can be produced by Ag2S/AgInS2@PDA once PDA is generated, thereby promoting the generation of PDA. Consequently, a positive feedback mechanism is established to enhance the polarity conversion of the Ag2S/AgInS2 heterojunction and amplify the responding to DA. As a result, the bioanalytical method is capable of sensitively quantifying DA in 10 orders of magnitude with an ultralow limit of detection. Moreover, the applicability of this biosensor in real samples is identified by measuring DA in fetal bovine serum and compared with a commercial ELISA method. Overall, this work offers an alternative perspective for adjusting photogenerated carriers of nanomaterials and designing high-performance PEC biosensors.

Shaping the Future of the Neurotransmitter Sensor: Tailored CdS Nanostructures for State-of-the-Art Self-Powered Photoelectrochemical Devices

“…Furthermore, the feasibility of DA photopolymerization and the difficulty of occurrence in the defect state of CdS were determined through theoretical calculations. The photoinduced polymerization of DA molecules could be divided into four major stages: (i) oxidation, (ii) rearrangement, (iii) dimerization, and (iv) polymerization . By determining the potential distribution of the DA molecule and its oxidation state structure, we could assess the extent of the reaction.…”

Polydopamine Enhanced Interactions of Graphene Nanosheets to Fabricate Graphene/Polydopamine Aerogels with Effectively Clear Organic Pollutants

“…For example, rGO/CNT-NH 2 /PDA(GCP) with three-dimensional cross-linked layered pores was prepared under hydrothermal conditions using PDA as a cross-linker and reducing agent. 21 Dopamine (DA) undergoes self-polymerization under alkaline conditions containing oxidizing agents to form polydopamine (PDA), which has many advantages such as biocompatibility, adhesion, hydrophilicity, reducibility, and environmental friendliness and has attracted wide attention in the fields of drug delivery, 20 biosensing, 22 energy storage, 23 and environmental science. 24 In particular, PDA has been widely used as a mild reducing agent to modify GO.…”

“…Dopamine (DA) undergoes self-polymerization under alkaline conditions containing oxidizing agents to form polydopamine (PDA), which has many advantages such as biocompatibility, adhesion, hydrophilicity, reducibility, and environmental friendliness and has attracted wide attention in the fields of drug delivery, biosensing, energy storage, and environmental science . In particular, PDA has been widely used as a mild reducing agent to modify GO. , The release of electrons during the polymerization of DA promotes the reduction of oxygen-containing functional groups on GO nanosheets and directs the π–π interactions of GO nanosheets to form 3D porous structures .…”

Programmable Entropy-Driven Circuit-Cascaded Self-Feedback DNAzyme Network for Ultra-Sensitive Fluorescence and Photoelectrochemical Dual-Mode Biosensing

“…The artificial DNA network has excellent programmability, and through the careful design of its DNA sequence, different DNA modules can be constructed to achieve their rich functions. , Feedback regulation is ubiquitous at the organism and cellular level and is an important part of biological control systems. − The positive feedback regulation system can enhance the activity of the controlled part and has a broad application prospect in biological signal amplification. Therefore, its introduction into biosensing results in a significant increase in signal expression intensity. − Due to the scalability of the cascade network, the positive feedback system and the DNA networks of the different modules can be programmed and cascaded to achieve efficient signal gain.…”