Fig. 7

1D hollow microstructures for optical waveguides. a Bright-field TEM image of the BPEA microtube, scale bar: 2 nm. b Bright-field image of BPEA microtube, and micro-area PL images of BPEA microtube obtained by exciting identical tubes at three different positions, scale bar: 10 μm. c Spatially resolved PL spectra of out-coupled light by excitation at the distance of 0–180 mm from the end of the tube. d Bright-field SEM image of the PDA microtube, scale bar: 10 μm. e Bright-field image of the DPEpe–F₄DIB microtube, and FL microscopy image of the DPEpe–F₄DIB microtube collected upon excitation of identical microtube at seven different positions, scale bar: 10 μm. f Plot of PL intensity versus the polarizer rotation angle excited at three different positions. g Formation mechanism of the DPEpe–F₄DIB microtubes, and bright-field SEM image of the microrod (scale bar: 1 μm) and microtube (scale bar: 5 μm). h Bright-field image (top) and PL images of the DPEpe–F₄DIB microtube excited, scale bar: 20 μm. i Spatially resolved PL spectra from the left-tip of the microtube with different separation distances in h. a-c Reprinted with permission from ref. [40] Copyright 2008, Wiley-VCH. d-f Reprinted with permission from ref. [78] Copyright 2014, Wiley-VCH. g-i Reprinted with permission from ref. [42] Copyright 2018, The Royal Society of Chemistry