Chao Zhang,Zhe Li,Shou Zhen Jiang,Chong Hui Li,Shi Cai Xu,Jing Yu,Zhen Li,Ming Hong Wang,Ai Hua Liu,Bao Yuan Man
We present a U-bent fiber optic SPR sensor based on the graphene/AgNPs, combined the virtues of graphene, AgNPs and U-bent fiber. By changing the laser-induced time, we achieved the optimal time for the deposition of AgNPs. With the proposed graphene/AgNPs U-bent fiber optic sensor, we discussed and investigated the SPR behaviors. The shifts up to 32 and 16 nm are observed respectively for the detection of 90% aqueous ethanol and 20% aqueous glucose, corresponding refractive index (RI) 1.3657 and 1.3557. The sensitivity of this proposed is calculated as 1198 nm/RIU and the response and recovery time of this U-bent fiber optic sensor are respectively 3 s and 80 s. These experimental results indicate that our proposed graphene/AgNPs U-bent fiber optic sensor will be expected to open new avenue for the detection in the field of medicine, biotechnology and food safety.
The concentration of tumor markers is low, which needs a highly sensitive, stable and fast detection method. In this paper, we proposed and demonstrated a U-shape fiber SPR biosensor sensitized by MOFs materials. The surface of the U-shape SPR sensor was modified with MOFs materials to enhance the sensitivity, and the nucleic acid aptamer was immobilized on the sensor surface because of the biocompatibility of MOFs materials. By the high specificity of the nucleic acid aptamer, the MUC1 protein was recognized and detected. The testing results indicate that the sensor has a logarithmic linear response in the MUC1 protein concentration detection range of 1 pg/ml-100 μg/ml, its sensitivity and detection limit are 5.33 nm/log(μg/ml) and 0.16 pg/ml respectively. After being sensitized by MOFs, the detection sensitivity of the sensor can be increased by 1.62 times，the LOD can be decreased by 0.75 times. The sensor has high sensitivity and specificity, which has broad application prospects in clinical detection of tumor markers.
In this work, we proposed a novel surface plasmon resonance (SPR) sensitivity-enhancing method by adding MoS 2 nanosheets between gold film and fiber (fiber-MoS 2 -gold film). And we apply it to the detection of human IgG protein. The sensor was fabricated by attaching MoS 2 nanosheets to the U-shaped fiber surface and then covering a layer of gold film. The refractive index sensitivity of 6184.4 nm/RIU was achieved by the fiber-MoS 2 -gold film sensor which is 59 percent higher than the gold film SPR sensor and 25 percent than the fiber-gold film-MoS 2 SPR sensor.The presence of MoS 2 increases the absorption of light energy and excites a stronger SPR phenomenon. At the same time, since the monolayer MoS 2 is a direct bandgap semiconductor, the absorbed light energy promotes the transfer of electrons, generates strong coupling on the gold film surface, enhances the surface electric field, and improves the sensitivity of the sensor. Biofunctionalized sensor detect human IgG with the limit of detection as low as 19.7 ng/mL. This work proposed a novel method for enhancing the sensitivity of SPR sensor, it owns a higher sensitivity and a lower LOD which has broad application prospects in measuring low concentration biological analytes.
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