ACS Nanoscience Au最新文献

Combining multiple III-V materials into axial nanowire heterostructures has enabled the fabrication of custom nanowire-based devices useful for a wide range of applications. However, our ability to form axial heterostructures between arbitrary combinations of III-V compounds is impeded by a lack of information on the dynamics of the heterojunction formation process, often resulting in suboptimal heterostructure morphologies, particularly for materials including Sb. In this work, we utilize environmental transmission electron microscopy to examine the formation of GaSb/GaAs heterojunctions in Au-seeded nanowires in situ. We demonstrate that the growth parameter window for successful GaSb/GaAs heterostructure formation is very narrow and requires the growth of a ternary GaSb _x As_1-x segment. Furthermore, we show that as the nanowire changes the composition from GaSb to GaAs, the nanoparticle and nanowire morphologies are highly dynamic. At the end of the transition, we observe that the nanoparticle volume is halved and the nanowire diameter is reduced from ≈40 to ≈30 nm at the liquid-solid interface. Moreover, the nanowire growth rate increases by a factor of 7, when GaAs composition is reached, at our optimized growth conditions. Additionally, we are able to observe that the change in the crystal phase from GaSb zincblende (ZB) to GaAs wurtzite (WZ) happens via a mixed ZB-4H-WZ regime and is dependent not only on the nanowire composition but also on the vapor-phase composition in the growth chamber. These results offer unique insight into the formation dynamics of axial nanowire heterostructures, elucidating the interplay between all phases and growth species.

[This corrects the article DOI: 10.1021/acsnanoscienceau.4c00023.].

Enhancing the mechanical and structural properties of bacterial nanocellulose (BNC) is key to its use in sustainable nanocomposites. This study employed a hot-press drying method with hydrophobic barriers, folding BNC into four layers and pressing with carbon fiber and Teflon sheets. At 120 °C, carbon fiber-pressed BNC achieved a tensile strength of 43.91 N/mm², 13.84% higher than oven-dried samples and 43.87% higher than Teflon-pressed samples. Scanning electron microscopy (SEM), KLA-Zeta, and atomic force microscopy (AFM) analyses revealed improved self-bonding and surface roughness. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) confirmed increased crystallinity and altered hydrogen bonding, enhancing stiffness and structural stability. Optical and thermal tests showed carbon fiber-pressed BNC was less transparent with moderate heat resistance, while Teflon-treated samples remained clear with higher thermal stability. These findings demonstrate that patterned hot pressing strengthens BNC's self-bonding, advancing its potential for use in structural nanocomposites, flexible electronics, and biocompatible scaffolds.

We perform transport measurements on proximitized, ballistic, bilayer graphene Josephson junctions (BGJJs) in the intermediate-to-long junction regime (L > ξ). We measure the device's differential resistance as a function of bias current and gate voltage for a range of different temperatures. The extracted critical current I _C follows an exponential trend with temperature: exp(-k _B T/δE). Here δE = ℏν _F /2πL: an expected trend for intermediate-to-long junctions. From δE, we determine the Fermi velocity of the bilayer graphene, which is found to increase with gate voltage. Simultaneously, we show the carrier density dependence of δE, which is attributed to the quadratic dispersion of bilayer graphene. This is in contrast to single layer graphene Josephson junctions, where δE and the Fermi velocity are independent of the carrier density. The carrier density dependence in BGJJs allows for additional tuning parameters in graphene-based Josephson junction devices.

The controlled assembly of colloidal trimers with both shape and surface anisotropy remains a challenge. In this work, polymeric dielectric colloidal trimers selectively functionalized with gold nanoparticles are used to create four distinct particles. The shape and surface anisotropy provided by the metallodielectric particles allows for directive assembly in a dielectrophoretic field. When subjected to varied frequencies and media permittivities, the particles assemble with different packing densities and orientations. On-demand assembly and disassembly of the particles are achieved by switching on or off the applied voltage. These multicomponent colloidal particles and their subsequent assemblies presented here provide a promising platform for engineering complex structures with versatile functionalities.

In this work, a singular system capable of interacting with the entire visible region of the solar spectrum is produced by combining carbon dots (CDs) and chlorophyll (Chl) pigments, entirely derived from the microalga Chlorella pyrenoidosa. The process involves the digestion of the C. pyrenoidosa cellular wall in an acetic acid:cholinium chloride (AA/ChCl) solvent, followed by a microwave reaction. The resulting CDs exhibit excitation and emission maxima at 461 and 528 nm, respectively. The Chl centers enable a secondary photoluminescence (PL) process, thus ensuring that the as-prepared CDs/Chl system (CDCS) can also interact with the farther red region of the visible spectrum. The luminescence properties of CDCS are concentration-dependent, undergoing a blue shift with dilution. Confocal microscopy provided insights into the protection of Chl pigments throughout the process. Furthermore, the consequences arising from the addition of poly-(ethylene glycol) oligomers (PEG-200) are also analyzed. The results demonstrate that the interaction between CDCS and PEG-200 significantly modifies the PL intensity and emission wavelengths, especially at higher PEG-200 concentrations. This suggests that PEG-200 can act as a modulating agent, stabilizing and even preventing the CDs' fluorescence quenching while also affecting the PL properties of Chl. This work presents interesting possibilities for the development of multifunctional luminescent systems derived from microalgae biomass by addressing how these microorganisms can function not only as precursors in the formation of advanced functional materials but also as an integrated component of these systems. As an added benefit, a luminescent solar concentrator (LSC) was fabricated, revealing photostability, as well as optical and power conversion efficiency values of 11 and 0.2%, respectively, values comparable to state-of-the-art CD-based LSCs.