Early diagnosis and precise monitoring of malignant tumors are core challenges in clinical medicine and basic research. Carcinoembryonic antigen (CEA) is a key tumor marker for colorectal cancer, gastric cancer, breast cancer and other solid tumors. The ultra sensitive detection of CEA has important clinical value for early screening, efficacy evaluation, and personalized treatment strategy formulation. Photoelectrochemical (PEC) biosensing technology has become an emerging platform for tumor biomarker analysis due to its high signal-to-noise ratio (low background interference) and single photon level detection sensitivity. It generates stable electrochemical signals by driving the generation, separation, and transfer of photo generated carriers through light energy. However, existing PEC technologies face three bottlenecks:
1. The photoelectric conversion efficiency is limited: photoelectrode materials commonly suffer from high carrier recombination rates and band structure mismatches, resulting in low separation efficiency of photo generated electron hole pairs;
2. External energy supply dependence: requires continuous external bias to maintain charge directional migration, hindering device portability and implantable applications;
3. Long term instability is insufficient: under light exposure, material photo corrosion and biological pollution cause signal attenuation, which restricts the reliability of clinical environments.
Developing a PEC sensing platform that combines efficient light energy conversion, self driving characteristics, and biological environment stability is a key path to breaking through current technological barriers.
Recently, Associate Professor You Daotong from Jinan University proposed a triple synergistic strategy that integrates defect control, heterostructure construction, and ferroelectric polarization control, successfully constructing a BiVO4/Bi0.95Nd0.05FeO3 (BVO/BNFO) semiconductor ferroelectric heterojunction photoelectrode. By doping with Nd3+, the fluctuation of Fe3+/Fe2+valence states and the formation of oxygen vacancies were effectively suppressed, significantly improving the ferroelectric properties and structural stability of the material. This heterojunction exhibits excellent
photoelectric conversion capability under no external bias conditions. Furthermore, by applying an external electric field to regulate the polarization direction of ferroelectric materials, the separation migration behavior of interface band structure and photogenerated charges can be controlled, achieving an increase in photocurrent density of over 200% and maintaining excellent stability under long-term illumination. The self powered PEC biosensor constructed based on this strategy exhibits an ultra wide linear detection range (1 pg/mL – 0.1 mg/mL) and an extremely low detection limit (1.91 pg/mL), providing a new solution for highly selective and stable CEA detection, and opening up a new direction for the application of ferroelectric materials in the field of biosensing. The relevant achievements were published in the Chemical Engineering Journal under the title "Ferroelectric polarization modulation self powered photoelectrochemical biosensor for sensitive CEA detection based on semiconductor ferroelectric heterojunction". The first authors of this work are Liu Lei, a doctoral student at Xiamen University, and Associate Professor You Daotong.
The core highlights of this work are as follows:
(1) Construction and Performance Breakthrough of Semiconductor Ferroelectric Heterojunction Photoelectrode
Nd ³+doped BiFeO ≮ ferroelectric thin film (Bi0.95Nd0.05FeO3, BNFO) was constructed by sol-gel method, spin coating method and high temperature heat treatment, and formed a unique semiconductor ferroelectric heterojunction optical electrode with BiVO4 (BVO). The spontaneous polarization of BNFO ferroelectric materials can form strong electric fields inside and at the interface, significantly improving the efficiency of photogenerated carrier separation and suppressing recombination. The photocurrent density of the BVO/BNFO heterojunction is increased by 13.15 times and 2.23 times compared to pure BVO and undoped BVO/BFO, respectively.
(2) Dynamic control of interface band and charge transfer through ferroelectric polarization
The control of ferroelectric polarization direction by external electric field can optimize the band bending and carrier transport path at the heterojunction interface. In the positively polarized state, the photocurrent density of BVO/BNFO increased by 203.9% and 288.9% respectively compared to the unpolarized/negatively polarized state, and maintained excellent stability under continuous illumination (performance increased by 117.35%/10000 s).
(3) The designed PEC biosensor can operate in self powered mode
The built-in electric field and ferroelectric polarization induced electric field formed in BVO/BNFO semiconductor ferroelectric heterojunction can provide very strong driving force to enhance photo carrier separation without the need for redox media or external voltage, which can effectively eliminate the interference of redox substances and minimize the damage to biomolecules on the photoelectrode.
(4) A-site doping strategy modulation of ferroelectric properties
Doping with rare earth Nd3+can effectively suppress oxygen vacancies and Fe valence state fluctuations, thereby enhancing the ferroelectric stability and polarization properties of BiFeO3 materials. The residual polarization strength of Bi0.95Nd0.05FeO3 thin films is increased to 17.12 μ C cm-2, which is 2.73 times that of BiFeO3 (6.27 μ C cm-2).
(5) Ultra high sensitivity CEA detection and clinical validation
The self powered PEC sensor has a detection limit for CEA as low as 1.91 pg/mL, with a linear range spanning 5 orders of magnitude (1 pg/mL – 0.1 mg/mL). It exhibits excellent selectivity (interferent response
Source: Sensor Expert Network