Enhancing Blood Fingerprints with Multicolored Conjugated Polymers: A Fluorescent Strategy with Python-Based Quantitative Assessment

Fluorescent conjugated polymers, recognized for their environmental stability, biocompatibility, tunable conductivity, and facile processability, have been extensively employed in the fabrication of multifunctional materials. In this study, three novel fluorescent conjugated polymers-PF-SO10 (blue), PF-SO10-BT1 (green), and PF-SO10-DTBT1 (red)-were synthesized and characterized, and subsequently applied for the enhancement of latent and visible blood fingerprints via powder dusting. Under 365 nm irradiation, the developed fingerprints displayed strong fluorescence, enabling clear visualization across six non-porous substrates and revealing third-level fingerprint details. The prominent photoluminescence property of the conjugated polymers provides a basis for the visualization of blood fingerprints. In a comparative evaluation with conventional reagents, including Amido Black 10B (AB) and 3,3',5,5'-Tetramethylbenzidine (TMB), demonstrated the superior performance of this method. To address the potential subjectivity of visual inspection, a Python-based quantitative evaluation framework was further introduced, incorporating metrics such as global contrast, average gradient sharpness, local contrast, and ridge orientation consistency. Collectively, the findings highlight the advantages of this strategy, including low cost, high contrast, strong selectivity, and minimal background interference, thereby offering a promising approach for reliable detection and visualization of blood fingerprints in forensic applications.