▎ 摘　　要

Ultrasensitive and in situ DNA detection at different pH values, ranging from 4.3 to 8.5, based on a microfiber with a graphene oxide linking layer was proposed and experimentally demonstrated. The graphene oxide coating over the silica microfiber provides a strong pi-pi interaction with the detected single-stranded DNA molecules, and induces an amplified surface refractive index modulation over the fiber, and finally leads to a wavelength shift of the optical interference fringe for interrogation. Using this strategy, in situ DNA measurement with a detection limit of up to 10 (-12) M and a linear response in the pH range from 4.3-8.5 has been achieved. Benefiting from its compact size, high sensitivity, and ease of use, together with remote operational ability, the proposed sensor opens up a multitude of opportunities for quantifying DNA in various hard-to-reach environments. It may supplement the existing DNA detection tools.