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.

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.

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Microwave technique was used to synthesize Green Carbon Dots (GCDs) from Aloe vera leaves because of easy to apply, accessible, time‐saving, cheap, safe and environmental‐friendly way. The prepared GCDs/TiO2 composite was obtained via sensitization of TiO2 with the help of GCDs. The characterization of the GCDs/TiO2 was made optically, structurally and morphologically. The photocatalytic hydrogen activity of GCDs/TiO2 was investigated under visible light (λ>420 nm) irradiation in the aqueous solution using triethanolamine (TEOA) sacrificial electron donor. When Pt was used, GCDs/TiO2/Pt showed advanced hydrogen evolution production (1294 μmol g−1 h−1) approximately two‐fold compared to GCDs/TiO2 (718 μmol g−1 h−1). In addition, NIR light‐triggered antibacterial activity of GCDs on Gram‐negative Escherichia coli (E. coli) and Gram‐positive Staphylococcus aureus (S. aureus) were investigated by studying bacterial growth curve and abiotic GSH oxidation assay. GSH oxidation ability of GCDs was increased through NIR light irradiation. According to the bacterial growth curve test, E. coli was found to be more susceptible to our GCDs than S. aureus.

Black phosphorus (BP) has recently emerged as a versatile photocatalyst owing to its unique photophysical properties and tunable bandgap. Nonetheless, the rapid recombination of the photogenerated charges of pristine BP samples has significantly hindered its practical applications in photocatalysis. Herein, we report, for the first time, the effect of transition metal nanoparticles (Ni and Co) as co-catalysts on the photocatalytic activity of BP/tungsten disulfide (WS2) binary heterojunctions (BP/WS2-TM (TM: Ni, Co)) in the hydrogen evolution reaction (HER) under visible light irradiation (λ > 420 nm). Ternary heterojunctions named BP/WS2-TM (TM: Ni, Co) were synthesized via a chemical reduction method, leading to the formation of an S-scheme heterojunction, in which BP acts as a reduction catalyst and WS2 serves as an oxidation catalyst. BP/WS2-Ni and BP/WS2-Co performed substantial amounts of hydrogen generation of 9.53 mmol h−1g−1 and 12.13 mmol h−1g−1, respectively. Moreover, BP/WS2-Co exhibited about 5 and 15 times higher photocatalytic activity compared to the binary BP/WS2 heterojunctions and pristine BP, respectively. The enhanced photocatalytic activity of the heterojunction catalysts is attributed to the extended light absorption ability, enhanced charge separation, and larger active sites. This study is the first example of photocatalytic hydrogen evolution from water by using Ni- and Co-doped binary BP/WS2 heterojunctions.