Black phosphorus (BP) as a layered two-dimensional (2D) semiconductor material with a tunable band gap has attracted growing attention for promising applications in diverse fields including biotechnology owing to its excellent physical and chemical properties. In this study, BP crystals were synthesized using a chemical vapor transport method and exfoliated into BP nanosheets in deoxygenated water or hexane. Next, monodisperse Au nanoparticles that were synthesized using a surfactant-assisted chemical reduction method were assembled on exfoliated BP nanosheets hexane to yield BP/Au nanocomposites. The photothermal antibacterial and antibiofilm activities of BP nanosheets and BP/Au nanocomposites were investigated against Enterococcus faecalis, a pathogenic biofilm-forming bacterium, by studying the photothermal effect and bacterial growth curve and using colony counting and live/dead fluorescence staining methods under near-infrared (NIR) light irradiation. Thanks to the higher photothermal conversion efficiency of BP/Au nanocomposites than that of bare BP nanosheets under NIR light irradiation, they destructed the bacterial cell membrane more efficiently than bare BP with the biofilm inhibition rate of 58%. It should be noted that this is the first study on the antibacterial and antibiofilm activity of BP/Au nanocomposites via a photothermal process under NIR light irradiation. This work shows the potential of BP/Au nanocomposites in fighting against pathogenic bacteria and paves the way for the exploration of antibacterial platforms based on the biocompatible 2D semiconductor BP.

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Nanocomposites of semiconducting two‐dimensional (2D) materials provide advantageous for combating bacterial infections to overcome antibiotic resistance. In this study, the nanocomposites of 2D black phoshorus (BP) and silver nanoparticles (NPs) were prepared by anchoring as‐synthesized Ag NPs on few‐layer BP nanosheets via liquid self‐assembly method and used as a NIR‐light‐driven antibacterial agent against Gram‐negative bacteria (Escherichia coli and Pseudomonas aeruginosa), and Gram‐positive bacteria (Enterococcus faecalis and Bacillus cereus). The BP/Ag nanocomposites showed excellent photothermal effect and oxidative stress ability to inhibit the initial logarithmic growth phase of E. faecalis and B. cereus. According to the bacterial growth curve, agar plate assay and live/dead viability test, as‐synthesized BP/Ag nanocomposites were found to be more effective antibacterial agent for Gram‐positive bacteria than Gram‐negative bacteria. The presented NIR‐light‐driven BP‐based nanoplatform can open a new avenue for avoiding bacterial resistance and combating pathogenic bacteria and also broad‐spectrum disinfection applications.

In this study, new benzoylthiourea derivatives, (E)-N-[(2-benzamidomethyleneamino)ethylcarbamothioyl]benzamide H3L′, N-(1-(3-benzoylthioureido)propan-2-ylcarbamothioyl)-benzamide H4L″, (E)-N-[4-(benzamidomethyleneamino)phenylcarbamothioyl]benzamide H3L‴, were synthesized. Structures of the compounds were identified by spectroscopic techniques. In addition, all synthesized compounds were evaluated for in vitro antibacterial and antifungal activity. Compound H3L‴ exhibited antibacterial activity.

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