image: The schematic diagram of the ultra-sensitive optical immunoassay platform, which comprises two pivotal components: one dedicated to establishing highly sensitive sandwich immunocomplexes for generating biological light signals, and the other focused on fabricating an ultra-high gain phototransistor capable of detecting extremely low light signals.
Credit: ©Science China Press
A team of scientists from Hunan University, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, and collaborating institutions has unveiled a groundbreaking MoS2-based phototransistor that sets new records in optical gain and sensitivity. The device, described in a recent Science Bulletin article, is capable of detecting light pulses containing just tens of photons and identifying disease biomarkers at attomolar (10-18 molar) concentrations, all at room temperature.
The phototransistor’s exceptional performance is achieved through a rational design that integrates a monolayer of molybdenum disulfide (MoS2) atop a gold nanowire (Au NW). This configuration leverages plasmonic effects and strain engineering to dramatically enhance light absorption and carrier injection. The device’s ultra-short channel (60 nm) further reduces carrier transit time, resulting in a record-high optical gain of 3.1 × 1011 and broadband sensitivity from 0.37 to 1.55 μm.
Beyond fundamental photodetection, the team demonstrated the device’s practical utility by developing an ultra-sensitive optical immunoassay (USOIA) platform. By combining the phototransistor with quantum dot nanospheres and magnetic beads in a sandwich immunoassay format, the platform achieved detection of C-reactive protein (CRP)—a key inflammation biomarker—down to 1.684 attomolar in serum samples. This sensitivity is seven orders of magnitude greater than that of current gold standard immunoassays, with a dynamic range spanning 12 orders of magnitude.
The USOIA platform also showed excellent selectivity, stability, and reliability in both buffer and diluted serum, outperforming established methods such as latex-enhanced immunoturbidimetric assay (LETIA) and chemiluminescent immunoassays (CLIA). The device’s robust performance is attributed to the synergistic effects of plasmon-enhanced light absorption, strain-induced band structure modulation, and efficient photogating.
According to the authors, this ultra-high-gain MoS2 phototransistor opens new avenues for ultra-sensitive optical detection in biosensing, remote sensing, quantum communication, and other fields. Its simplicity, scalability, and compatibility with point-of-care testing make it a promising candidate for next-generation diagnostic platforms capable of early disease detection through trace biomarker quantification.