Abstract
This thesis presents an investigation of Fiber Bragg Grating (FBG) based biosensor enhanced by Carbon Quantum Dots (CQDs) embedded within microchannels to fabricate an optical biosensor with high sensitivity, multi-detectivity, and stable performance.The most basic theory is the fiber grating theory based on FBG, evanescent field sensing theory. FBG technology performs detection by modulating the wavelength of the incident beam under test and measuring the change in wavelength of the reflected light. Since the wavelength is an absolute parameter that is not affected by the overall light intensity level, connected fiber and coupler losses, or the energy of the light source, it provides better stability. Fiber gratings are similar in nature to filters. When a light wave passes through a prepared Bragg grating, only phase-matched light is strongly reflected, while phase-mismatched light is weakly reflected.
CQDs have good optical properties, which are mainly reflected in their narrow emission peaks, broad absorption peaks, high emission efficiency, stable luminescence performance and the ability to be excited repeatedly. These provide CQDs with a wide range of applications in bioimaging, biosensing, and biomedicine. These properties make CQDs have a wide range of applications in bioimaging, biosensing, biomedical and other fields.
This thesis explores the research and development of optical biosensors, particularly focusing on FBG technology and CQDs. Optical biosensors are recognized for their high sensitivity and broad applicability in fields such as biomedicine, environmental monitoring, and security. The study delves into the etching of FBGs to enhance their refractive index sensitivity and the integration of CQDs for fluorescence-based detection and subsequent biosensor detection. Emphasizing their surface modifications and biocompatibility for biosensing applications. Various experimental techniques were used to modify and optimize the surface of optical fibers for better interaction with analytes.
In this thesis, optical biosensors based on FBGs and CQDs have successfully achieved high sensitivity and multifunctional detection capability with stable performance. The potential of microfluidic channels in fiber optic etching and bio-detection is also proposed. It is found that chemically etched FBG is more sensitive to temperature than bare fiber, and the sensitivity of etched FBG is about 5.66 times of that of bare fiber in the detection range of 50-100℃. An experimental validation method based on fluorescent markers is also proposed to confirm the effectiveness of the surface functionalization of optical fibers. The CQDs-FBG sensor demonstrates high sensitivity and stability for specific analytes in aqueous salt solution substitution experiments and glucose solution detection experiments. The proposed sensor in this thesis showed 2.3 times higher sensitivity than the common FBG biosensor.
| Date of Award | 15 Nov 2025 |
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| Original language | English |
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| Supervisor | Jing Wang (Supervisor), Serhiy Korposh (Supervisor) & Yong Ren (Supervisor) |