Recent Advances in Hydrogel-Promoted Photoelectrochemical Sensors

Abstract

Photoelectrochemical (PEC) sensors have garnered increasing attention due to their high sensitivity, low background signal, and rapid response. The incorporation of hydrogels into PEC platforms has significantly expanded their analytical capabilities by introducing features such as biocompatibility, tunable porosity, antifouling behavior, and mechanical flexibility. This review systematically categorizes hydrogel materials into four main types-nucleic acid-based, synthetic polymer, natural polymer, and carbon-based-and summarizes their functional roles in PEC sensors, including structural support, responsive amplification, antifouling interface construction, flexible electrolyte integration, and visual signal output. Representative applications are highlighted, ranging from the detection of ions, small biomolecules, and biomacromolecules to environmental pollutants, photodetectors, and flexible bioelectronic devices. Finally, key challenges-such as improving fabrication scalability, enhancing operational stability, integrating emerging photoactive materials, and advancing bio-inspired system design-are discussed to guide the future development of hydrogel-enhanced PEC sensing technologies.

Keywords: detection; hydrogel; photoelectrochemical sensors.

Scheme 1

Schematic illustration of hydrogel-based photoelectrochemical (PEC) sensors, highlighting the classification of hydrogel types, their functional roles in PEC systems, and representative application scenarios.

Figure 1

Schematic illustration of the hydrogel types used in PEC sensor.

Figure 2

Schematic illustration of the PEC sensor based on a polyvinyl alcohol (PVA) antifouling hydrogel layer for the detection of Cu²⁺ ions. Reproduced with permission from reference [60].

Figure 3

(A) Schematic illustration of the PEC sensing mechanism for H₂O₂ based on ZnO nanoparticles embedded in a nitrogen-doped three-dimensional graphene hydrogel (3DNGH) coupled with horseradish peroxidase (HRP). Reproduced with permission from reference [141]. (B) Fabrication and signal transduction diagram of the TiO₂ NTPCs/Z-MOF/hydrogel PEC biosensor for dopamine detection under antifouling conditions. Reproduced with permission from reference [118].

Figure 4

Enzymatic photoelectrochemical sensor based on a 3D PTB7–Th/polyaniline hydrogel (PAniHs) composite for guanine detection. Reproduced with permission from reference [117].

Figure 5

(A) Schematic illustration of a PEC aptasensor based on a BiPO₄/three-dimensional nitrogen-doped graphene hydrogel (3DNGH) composite for tetracycline (Tc) detection. Reproduced with permission from reference [124]. (B) PEC sensor constructed using self-doped Ti³⁺ nanorods (TiO_2−x) integrated with a three-dimensional nitrogen-doped graphene hydrogel (NGH) for the detection of chlorpyrifos. Reproduced with permission from reference [121]. (C) Bi₂S₃–Bi₂O₃ photoelectrode with a swellable hydrogel microneedle array based PEC sensor for multiple detection of atrazine (ATZ), acetamiprid (ACP), and carbendazim (CBZ). Reproduced with permission from reference [129].

Figure 6

(A) Schematic illustration of a PEC sensor for ochratoxin A (OTA) detection based on a responsive DNA hydrogel and in situ polymerization of polyaniline for signal amplification. Reproduced with permission from reference [112]. (B) PEC sensor constructed using three-dimensional (3D) structured Bi₂WO₆@graphene hydrogel (GH) composites for the detection of 4-nitrophenol. Reproduced with permission from reference [123].

Figure 7

Schematic illustration of the PEC biosensor for miRNA-21 detection based on a responsive DNA hydrogel and target-triggered activation of the CRISPR/Cas12a system. Reproduced with permission from reference [111].

Figure 8

Schematic illustration of an organic photoelectrochemical transistor (OPECT) biosensor gated by a platinum nanocube-embedded gelatin hydrogel. Reproduced with permission from reference [108].

Figure 9

(A) Schematic illustration of the molecularly imprinted polymer (MIP) hydrogel sensor for carcinoembryonic antigen (CEA) detection. Reproduced with permission from reference [115]. (B) Schematic illustration of the PEC immunosensor for HER2 detection. Target-triggered formation of a MnO₂-doped supramolecular hydrogel on the WO₃/SnIn₄S₈ heterojunction inhibits photocurrent by introducing steric hindrance and competing for incident light. Reproduced with permission from reference [131].

Figure 10

Schematic illustration of a “signal-on” photoelectrochemical (PEC) biosensor for hyaluronidase (HAase) detection. Enzymatic degradation of the HA-based hydrogel by HAase releases cationic dye crystal violet (CV), which enhances visible light absorption and charge separation on BiOBr, resulting in increased cathodic photocurrent. Reproduced with permission from reference [110].

Figure 11

(A) Schematic illustration of a multifunctional hydrogel composed of polyacrylic acid (PAA) reinforced with calcium–aluminum layered double hydroxide (Ca–Al LDH) nanosheets, enabling integrated sensing of mechanical strain, temperature, and ultraviolet (UV) radiation. Reproduced with permission from reference [174]. (B) Illustration of a stretchable and self-healing PEC photodetector constructed using a borate-crosslinked polyvinyl alcohol (PVA) hydrogel embedded with Ti₂CT_x (MXene) nanosheets. Reproduced with permission from reference [116].

Figure 12

Schematic illustration of a biomimetic photoelectrochemical synapse that emulates retinal light perception and synaptic behavior by integrating enzyme-responsive chromogenic hydrogels with a Bi₂S₃-based photoelectrode within an organic photoelectrochemical transistor (OPECT) architecture. Reproduced with permission from reference [69].