Few-layer black phosphorous (BP) has emerged as a promising candidate for next-generation nanophotonic and nanoelectronic devices. However, rapid ambient degradation of mechanically exfoliated BP poses challenges in its practical deployment in scalable devices. To date, the strategies employed to protect BP have relied upon preventing its exposure to atmospheric conditions. Here, an approach that allows this sensitive material to remain stable without requiring its isolation from the ambient environment is reported. The method draws inspiration from the unique ability of biological systems to avoid photo-oxidative damage caused by reactive oxygen species. Since BP undergoes similar photo-oxidative degradation, imidazolium-based ionic liquids are employed as quenchers of these damaging species on the BP surface. This chemical sequestration strategy allows BP to remain stable for over 13 weeks, while retaining its key electronic characteristics. This study opens opportunities to practically implement BP and other environmentally sensitive 2D materials for electronic applications.
The
rapid emergence of antibiotic-resistant bacterial strains warrants
new strategies for infection control. NanoZymes are emerging as a
new class of catalytic nanomaterials that mimic the biological action
of natural enzymes. The development of photoactive NanoZymes offers
a promising avenue to use light as a “trigger” to modulate
the bacterial activity. Visible light activity is particularly desirable
because it contributes to 44% of the total solar energy. Here we show
that the favorable band structure of a CuO-nanorod-based NanoZyme
catalyst (band gap of 1.44 eV) allows visible light to control the
antibacterial activity. Photomodulation of the peroxidase-mimic activity
of CuO nanorods enhances its affinity to H2O2, thereby remarkably accelerating the production of reactive oxygen
species (ROS) by 20 times. This photoinduced NanoZyme-mediated ROS
production catalyzes physical damage to the bacterial cells, thereby
enhancing the antibacterial performance against Gram-negative-indicator
bacteria Escherichia coli.
Gold
(Au) is an inert metal in a bulk state; however, it can be
used for the preparation of Au nanoparticles (i.e., AuNPs) for multidimensional
applications in the field of nanomedicine and nanobiotechnology. Herein,
monodisperse concave cube AuNPs (CCAuNPs) were synthesized and functionalized
with a natural antioxidant lipoic acid (LA) and a tripeptide glutathione
(GSH) because different crystal facets of AuNPs provide binding sites
for distinct ligands. There was an ∼10 nm bathochromic shift
of the UV–vis spectrum when CCAuNPs were functionalized with
LA, and the size of the as-synthesized monodisperse CCAu nanoparticles
was 76 nm. The LA-functionalized CCAu nanoparticles (i.e., CCAuLA)
showed the highest antibacterial activity against Bacillus
subtilis. Both fluorescence images and scanning electron
microscopy images confirm the damage of the bacterial cell wall as
the mode of antibacterial activity of CCAuNPs. CCAuNPs also cause
the oxidation of bacterial cell membrane fatty acids to produce reactive
oxygen species, which pave the way for the death of bacteria. Both
CCAu nanoparticles and their functionalized derivatives showed excellent
hemocompatibility (i.e., percentage of hemolysis is <5% at 80 μg
of AuNPs) to human red blood cells and very high biocompatibility
to HeLa, L929, and Chinese hamster ovary-green fluorescent protein
(CHO-GFP) cells. Taken together, LA and GSH enhance the antibacterial
activity and biocompatibility, respectively, of CCAu nanoparticles
that interact with the bacteria through Coulomb as well as hydrophobic
interactions before demonstrating antibacterial propensity.
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