Carbon dots, generally defined as small carbon nanoparticles with various surface passivation schemes, have emerged as a new class of quantum-dot-like nanomaterials, with their optical properties and ...photocatalytic functions resembling those typically found in conventional nanoscale semiconductors. In this work, carbon dots were evaluated for their photoinduced bactericidal functions, with the results suggesting that the dots were highly effective in bacteria-killing with visible-light illumination. In fact, the inhibition effect could be observed even simply under ambient room lighting conditions. Mechanistic implications of the results are discussed and so are opportunities in the further development of carbon dots into a new class of effective visible/natural light-responsible bactericidal agents for a variety of bacteria control applications.
The photocatalytic and structural properties of TiO2/WO3 two-layer nanostructures made by electron beam deposition were studied and compared with single-layer TiO2 nanostructures. Three different ...two-layer structures, thin film, tilted nanorods, and vertical nanorods, were fabricated by a normal deposition, oblique angle deposition, and glancing angle deposition. The as-deposited and annealed samples at T a = 300 °C and T a = 400 °C, respectively, were studied by SEM, XRD, Raman spectroscopy, and UV−vis spectrophotometry. The photocatalytic properties of those samples were investigated and found to be improved significantly by increasing the surface and interfacial area, annealing at a proper temperature, the enhanced charge separation due to the WO3−TiO2 coupling, and the arrangement of the two layers. The optimal structure was found to be the two-layer vertical TiO2/WO3 nanorods after annealing at T a = 300 °C, which had a photodegradation rate about 10 times higher than a single-layer TiO2 vertical nanorod array.
Using a geometric shadowing effect, a thin catalyst layer can be coated asymmetrically on the side of a nanorod backbone. Combining with substrate rotation, a dynamic shadowing growth technique has ...been developed to fabricate catalytic nanomotors such as rotary Si/Pt nanorods, rotary L-shaped Si/Pt and Si/Ag nanorods, and rolling Si/Ag nanosprings, and their autonomous motions have been demonstrated in a diluted H2O2 solution. This fabrication method reveals an optimistic step toward designing integrated nanomachines.
We report a simple and scalable method to fabricate helical chiral plasmonic nanostructures using glancing angle deposition on self-assembled nanosphere monolayers. By controlling the azimuthal ...rotation of substrates, Ag and SiO2 layers can be helically stacked in left-handed and right-handed fashions to form continuous helices. Finite-difference time-domain simulations confirm the experimental results that show that these plasmonic helices exhibit strong chiroptical responses in the visible to near-IR region, which can be tuned by changing the diameter of nanospheres. With such flexibility in the design, helically stacked plasmonic layers may act as tunable chiral metamaterials, as well as serve as different building blocks for chiral assemblies.
A new collective motion of non-bubble-propelled spherical Janus catalytic micromotors has been observed. When the local concentration of micromotors is high, bubbles start to form between the motors. ...As the bubble grows, micromotors move collectively toward the center of the bubble regardless of the orientations of their catalyst surface, eventually become aggregated, and captured around the perimeter of the bubble. It is suggested that this collective motion of the micromotors, too fast for the diffusiophoresis, can be caused by the entrainment of micromotors by the evaporation-induced Marangoni flow near the bubble. Numerical simulations confirmed that the direction and strength of such Marangoni flow are consistent with the fast, collective motion of micromotors observed experimentally.
Dense and aligned TiO2 nanorod arrays are fabricated using oblique‐angle deposition on indium tin oxide (ITO) conducting substrates. The TiO2 nanorods are measured to be 800–1100 nm in length and ...45–400 nm in width with an anatase crystal phase. Coverage of the ITO is extremely high with 25 × 106 mm−2 of the TiO2 nanorods. The first use of these dense TiO2 nanorod arrays as working electrodes in photoelectrochemical (PEC) cells used for the generation of hydrogen by water splitting is demonstrated. A number of experimental techniques including UV/Vis absorption spectroscopy, X‐ray diffraction, high‐resolution scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and photoelectrochemistry are used to characterize their structural, optical, and electronic properties. Both UV/Vis and incident‐photon‐to‐current‐efficiency measurements show their photoresponse in the visible is limited but with a marked increase around ≈400 nm. Mott–Schottky measurements give a flat‐band potential (VFB) of +0.20 V, a carrier density of 4.5 × 1017 cm−3, and a space‐charge layer of 99 nm. Overall water splitting is observed with an applied overpotential at 1.0 V (versus Ag/AgCl) with a photo‐to‐hydrogen efficiency of 0.1%. The results suggest that these dense and aligned one‐dimensional TiO2 nanostructures are promising for hydrogen generation from water splitting based on PEC cells.
Densely packed and aligned TiO2 nanorods 800–1100 nm in length are produced by oblique‐angle deposition on indium tin oxide conducting substrates and utilized for photoelectrochemical cells for hydrogen production. The TiO2 nanorods (see image) have a tilt angle of 60 ° with respect to the substrate. Incident‐photon‐to‐current‐conversion efficiency is 79% at 350 nm due to vectorial charge transfer through the long axis of the TiO2 nanorods to the back contact.
This study shows that a hybridized plasmonic mode, represented by an additional transmission peak, in a compound structure consisting of a nanorod embedded in a nanohole can be effectively described ...as a quasi-dipole oscillator. When two nanorods are introduced into a nanohole, these two quasi-dipoles can couple and hybridize, giving rise to two additional transmission peaks in the enhanced optical transmission spectrum. The relative intensities of these peaks can be controlled by adjusting the incident polarization, while their separations can be tuned by modifying the length of the nanorods. The concept of quasi-dipoles in compound nanohole structures can be further extended to predict the coupling behavior of even more complex compound configurations, such as multiple nanorods within nanoholes, resulting in the generation of multiple hybridization states. Consequently, the shape and response of the transmission peaks can be precisely engineered. This strategy could be used to design nanohole-based metasurfaces for applications such as ultra-thin optical filters, waveplates, polarizers, etc.
Chiral patchy particle films where morphological enantiomers exist in equal proportion are found to have significant circular dichroism. It is determined that the rotation direction during glancing ...angle deposition breaks the racemic symmetry, resulting in a distribution of material which enhances the chirality of one set of enantiomers relative to the other. Microscopic analysis and geometric chirality calculations reveal that the chirality of the bulk film results from incomplete cancellations of even stronger local chiralities.
The aim of this study is to fabricate biodegradable PLA-based composite filaments for 3D printing to manufacture bear-loading lattice structures. First, CaCO
and TCP as inorganic fillers were ...incorporated into a PLA matrix to fabricate a series of composite filaments. The material compositions, mechanical properties, and rheology behavior of the PLA/CaCO
and PLA/TCP filaments were evaluated. Then, two lattice structures, cubic and Triply Periodic Minimal Surfaces-Diamond (TPMS-D), were geometrically designed and 3D-printed into fine samples. The axial compression results indicated that the addition of CaCO
and TCP effectively enhances the compressive modulus and strength of lattice structures. In particular, the TPMS-D structure showed superior load-carrying capacity and specific energy absorption compared to those of its cubic counterparts. Furthermore, the deformation behavior of these two lattice structures was examined by image recording during compression and computed tomography (CT) scanning of samples after compression. It was observed that pore structure could be well held in TPMS-D, while that in cubic structure was destroyed due to the fracture of vertical struts. Therefore, this paper highlights promising 3D-printed biodegradable lattice structures with excellent energy-absorption capacity and high structural stability.
In this study, the surface enhanced Raman spectra (SERS) of two prohibited veterinary drugs, metronidazole (MNZ) and ronidazole (RNZ), have been acquired, and compared to the theoretically calculated ...spectra using density function theory (DFT). The experimental Raman and SERS spectra of MNZ and RNZ exhibit high resemblance with the DFT calculations. SERS detection of MNZ and RNZ from standard solutions as well as real environmental samples (tap, lake, swamp waters and soil) was performed on highly sensitive and reproducible silver nanorod array substrates. The limits of detection for MNZ and RNZ are 10 and 1µg/mL in methanol and ultra-pure water, respectively, and 10–50µg/mL in the environmental samples. The SERS-based method demonstrates its potential as a rapid, simple, and inexpensive means for the onsite screening of banned antibiotics from the aquatic and sediment environments, with minimal requirement for sample pretreatment.
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•The Raman and SERS spectra of metronidazole (MNZ) and ronidazole (RNZ) have been acquired.•Density function theory was used to predict theoretical spectra of MNZ and RNZ.•The limits of detection for MNZ and RNZ were determined.•SERS was used to detect MNZ and RNZ from environmental samples with minimal sample pre-treatment.
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