We demonstrate that the atom chain structure of Te allows it to be exfoliated as ultra-thin flakes and nanowires. Atomic force microscopy of exfoliated Te shows that thicknesses of 1–2 nm and widths below 100 nm can be exfoliated with this method. The Raman modes of exfoliated Te match those of bulk Te, with a slight shift (4 cm−1) due to a hardening of the A1 and E modes. Polarized Raman spectroscopy is used to determine the crystal orientation of exfoliated Te flakes. These experiments establish exfoliation as a route to achieve nanoscale trigonal Te while also demonstrating the potential for fabrication of single atom chains of Te.
Strained trigonal Te has been predicted to host Weyl nodes supported by a nonsymmorphic chiral symmetry. Using low-pressure physical vapor deposition, we systematically explored the growth of trigonal Te nanowires with naturally occurring strain caused by curvature of the wires. Raman spectra and high mobility electronic transport attest to the highly crystalline nature of the wires. Comparison of Raman spectra for both straight and curved nanowires indicates a breathing mode that is significantly broader and shifted in frequency for the curved wires. Strain induced by curvature during growth therefore may provide a simple pathway to investigate topological phases in trigonal Te.
Fluorescent nanoparticles of N,N '-bis(2,5-di-tert-butylphenyl)-3,4,9,10-perylenedicarboximide (DBPI) were fabricated by laser ablation of its microcrystals dispersed in pure water, and their optical extinction and fluorescence spectra were investigated. Colloidal nanoparticles withmean sizes of 30 to 80 nm were prepared without molecular decomposition by tuning the fluence of the irradiating laser. Spectral simulation based on Mie theory explains the difference in the absorption spectra of the nanoparticles and a DBPI vapor-deposited film. The fluorescence of the nanoparticle colloids showed a monomer-like emission band with a vibrational structure, while the initial microcrystals exhibited a broad excimer band. These results indicate that the DBPI nanoparticles have crystal morphologies different from those of microcrystals.
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