Diarylurea‐Containing Thiosemicarbazones as Antimicrobial Agents on Cotton Fabrics

ABSTRACT This study synthesized seven thiosemicarbazones (E1–E7) containing diarylurea moieties. Their structures were confirmed by NMR, FTIR, and HRMS, and their antimicrobial activities were evaluated using the microdilution method. The most active compound, E6 (bearing chloro and trifluoromethyl groups), exhibited MIC values of 7.81 µg/mL against Staphylococcus aureus , 15.62 µg/mL against Enterococcus faecalis , and 62.5 µg/mL against Escherichia coli . Carboxylate groups were introduced onto cotton cellulose via TEMPO/NaBr/NaClO oxidation, and thiosemicarbazones (0.15–1.25%, w/v) were covalently bonded using DCC. Under ASTM E2149‐type conditions, fabrics treated with E4, E6, and E7 (1.25%) achieved ≥99.9% reduction in S. aureus and ∼91.5% in E. coli . XPS confirmed DCC‐mediated amidation through Na disappearance and amide signatures, while XRD showed preserved crystallinity, and ΔE*ab values remained low (2.75–3.69). Under alkaline washing (4 g/L ECE B, 40°C, 30 min), antibacterial efficiency declined after five cycles, whereas under the same conditions with distilled water, ∼90% activity was retained even after ten cycles. These findings indicate that meta‐substituted diarylurea‐based thiosemicarbazones are promising candidates for durable, covalently attached antibacterial cotton coatings.