1：Experimental Design and Method Selection:

The study utilizes a fluorescence 'off-on' strategy based on the different affinities of Ti3C2 nanosheets for ssDNA and dsDNA, combined with Exonuclease III (Exo III) for signal amplification. The method involves DNA hybridization and fluorescence quenching/recovery mechanisms.

2：Sample Selection and Data Sources:

Oligonucleotides were synthesized and purified by Sangon Biotechnology Co., Ltd. Real HPV-18 DNA samples were extracted from cervical scrapes provided by a women's health center. PCR was used to amplify DNA extracts.

3：List of Experimental Equipment and Materials:

Equipment includes SEM (Quanta SEM FEI), TEM (FEI Tecnai T20), XRD (Philips X0 Pert Super diffractometer), AFM (Multimod 8, Bruker), fluorophotometer (Shimadzu RF-6000), time-resolved fluorescence system (PTI QuantaMaster 400), and PCR machine (TC-96/G/H(b)B, Bioer Technology). Materials include Ti3AlC2 powder, HF solution, DMSO, Tris-HCl buffer, Exo III, and FAM-labeled ssDNA probes.

4：Experimental Procedures and Operational Workflow:

Ti3C2 nanosheets were synthesized by HF etching of Ti3AlC2, followed by intercalation with DMSO and sonication. For DNA assays, probe DNA was mixed with target DNA, incubated, then Ti3C2 NSs were added, and fluorescence was measured. Exo III was added in amplified strategies for incubation before measurement. Real sample analysis involved PCR amplification of clinical samples, denaturation, cooling, and similar fluorescence measurement steps.

5：Data Analysis Methods:

Fluorescence intensity was measured at 520 nm. Data were analyzed using a modified equation for linearity, and detection limits were calculated based on signal-to-noise ratio (3S/N). Specificity and interference were assessed by comparing fluorescence increments.