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This paper proposes a new kind of composite micro/nano structure composed of porous nanomaterials including titanium (Ti) gradient material and titania (TiO2) gradient material. The composite structure is fabricated via in-situ deposition of gradiently distributed and oxidized porous titanium nanoparticles on the surface of picosecond laser-induced micro/nano structures. The porous composite layer made up of Ti gradient material and TiO2 gradient material shows the best anti-reflectivity. The ability of TiO2 for absorbing –CH3 hydrophobic group and the air cushion effect of nanostructure endow the TiO2 gradient porous material with hydrophobic characteristics. Then, the period and height of the desired microstructure of the composite micro/nano structure with the best super-hydrophobicity and anti-reflectivity are confirmed to be about 10 μm and more than 10 μm, respectively. The designed composite micro/nano structures are fabricated using picosecond laser induction processing strategy with the etched depth of the materials being only about 12 μm. The reflectance of the designed composite micro/nano structure is around 2 % from the visible band to the near-infrared band and below 20 % from the ultraviolet to middle-infrared band. Moreover, its slip angle is just 4° and contact angle 167.

Chemiresistive CO2 sensing is attractive due to low cost and ease of chip-level integration. Our previous studies (Yong Xia, 2021) showed the well-developed ZnO material fabricated by in-situ annealing exhibited good CO2 sensing performance. Here, we have expanded on those studies, including CO2 cyclic tests under both dry air and N2 background whereby a much higher response to CO2 in N2 background was observed. Detailed density functional theory calculations were conducted to understand the behavior. The results indicated nitrogen doping is mainly responsible for the observed response. In the presence of pre-adsorbed O2, N-doped ZnO can no longer interact with CO2, which agrees well with the observation of higher response in N2 background. Furthermore, density of states analysis showed N sp2 hybridized orbital and N 2p orbital of the N dopant mixed with sp2 hybridized orbital of C atom and 2p orbitals of C/O atoms in CO2 to form σ and π bonds, respectively. However, they mixed with O 2s/2p orbitals of O atom in O2 when pre-adsorbed O2 was present, hindering CO2 interaction with N-doped ZnO, and resulting in limited response in air. The illustrated mechanism does not only further the understanding of metal oxide-based CO2 sensing, but also guide the design of new functional materials for CO2 sensing or capture.

Pseudo-topotactic conversion of carbon nanotubes into one-dimensional carbon nanowires is a challenging but feasible path to obtain desired diameters and morphologies. Here, a previously predicted but experimentally unobserved carbon allotrope, T-carbon, has been produced from pseudo-topotactic conversion of a multi-walled carbon nanotube suspension in methanol by picosecond pulsed-laser irradiation. The as-grown T-carbon nanowires have the same diameter distribution as pristine carbon nanotubes, and have been characterized by high-resolution transmission electron microscopy, fast Fourier transform, electron energy loss, ultraviolet–visible, and photoluminescence spectroscopies to possess a diamond-like lattice, where each carbon is replaced by a carbon tetrahedron, and a lattice constant of 7.80 Å. The change in entropy from carbon nanotubes to T-carbon reveals the phase transformation to be first order in nature. The computed electronic band structures and projected density of states are in good agreement with the optical absorption and photoluminescence spectra of the T-carbon nanowires., T-carbon is a previously predicted but so far unobserved allotrope of carbon, with a crystal structure similar to diamond, but with each atomic lattice position replaced by a carbon tetrahedron. Here, the authors produce T-carbon nanowires via laser-irradiating a suspension of carbon nanotubes in methanol.