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Cobalt( ii ) ions were adsorbed to the surface of rod-shape anatase TiO 2 nanocrystals and subsequently heated to promote ion diffusion into the nanocrystal. After removal of any remaining surface bound cobalt, a sample consisting of strictly cobalt-doped TiO 2 was obtained and characterized with powder X-ray diffraction, transmission electron microscopy, UV-visible spectroscopy, fluorescence spectroscopy, X-ray photoelectron spectroscopy, SQUID magnetometry, and inductively-coupled plasma atomic emission spectroscopy. The nanocrystal morphology was unchanged in the process and no new crystal phases were detected. The concentration of cobalt in the doped samples linearly correlates with the initial loading of cobalt( ii ) ions on the nanocrystal surface. Thin films of the cobalt doped TiO 2 nanocrystals were prepared on indium-tin oxide coated glass substrate, and the electrical conductivity increased with the concentration of doped cobalt. Magnetic measurements of the cobalt-doped TiO 2 nanocrystals reveal paramagnetic behavior at room temperature, and antiferromagnetic interactions between Co ions at low temperatures. Antiferromagnetism is atypical for cobalt-doped TiO 2 nanocrystals, and is proposed to arise from interstitial doping that may be favored by the diffusional doping mechanism. 

Abstract With the establishment and maturation of the experimental programs searching for new physics with sizeable couplings at the LHC, there is an increasing interest in the broader particle and astrophysics community for exploring the physics of light and feebly-interacting particles as a paradigm complementary to a New Physics sector at the TeV scale and beyond. FIPs 2020 has been the first workshop fully dedicated to the physics of feebly-interacting particles and was held virtually from 31 August to 4 September 2020. The workshop has gathered together experts from collider, beam dump, fixed target experiments, as well as from astrophysics, axions/ALPs searches, current/future neutrino experiments, and dark matter direct detection communities to discuss progress in experimental searches and underlying theory models for FIPs physics, and to enhance the cross-fertilisation across different fields. FIPs 2020 has been complemented by the topical workshop “Physics Beyond Colliders meets theory”, held at CERN from 7 June to 9 June 2020. This document presents the summary of the talks presented at the workshops and the outcome of the subsequent discussions held immediately after. It aims to provide a clear picture of this blooming field and proposes a few recommendations for the next round of experimental results. 

Hollow Mn₃O₄nanoparticles (diameter=31 nm, cavity diameter=16 nm, and shell thickness=7 nm) were attached to the surface of multiwall carbon nanotubes (MWCNT). A suspension of hollow Mn₃O₄/MWCNT with Nafion™ was dropcast onto a glassy carbon electrode, and the electrochemical reduction of oxygen in aqueous solution was investigated with this electrode. We assess the role of MWCNT, hollow Mn₃O₄, and Nafion™ in the performance of the electrode, and investigate the kinetics of the oxygen reduction reaction. The electrode exhibits outstanding performance in measures of cathodic current density and onset potential, and performed similarly well in acidic, neutral, and alkaline conditions.