Nanostructures with chiral geometries exhibit strong polarization rotation. However, achieving reversible modulation of chirality and polarization rotation in device-friendly solid-state films is difficult for rigid materials. Here, we describe nanocomposites, made by conformally coating twisted elastic substrates with films assembled layer-by-layer from plasmonic nanocolloids, whose nanoscale geometry and rotatory optical activity can be reversibly reconfigured and cyclically modulated by macroscale stretching, with up to tenfold concomitant increases in ellipticity. We show that the chiroptical activity at 660 nm of gold nanoparticle composites is associated with circular extinction from linear effects. The polarization rotation at 550 nm originates from the chirality of nanoparticle chains with an S-like shape that exhibit a non-planar buckled geometry, with the handedness of the substrate's macroscale twist determining the handedness of the S-like chains. Chiroptical effects at the nexus of mechanics, excitonics and plasmonics open new operational principles for optical and optoelectronic devices from nanoparticles, carbon nanotubes and other nanoscale components.

Cobalt hydroxide is a promising electrode material for supercapacitors due to the high capacitance and long cyclability. However, the energy storage/conversion mechanism of cobalt hydroxide is still vague at the atomic level. Here we shed light on how cobalt hydroxide functions as a supercapacitor electrode at operando conditions. We find that the high specific capacitance and long cycling life of cobalt hydroxide involve a complete modification of the electrode morphology, which is usually believed to be unfavourable but in fact has little influence on the performance. The conversion during the charge/discharge process is free of any massive structural evolution, but with some tiny shuffling or adjustments of atom/ion species. The results not only unravel that the potential of supercapacitors could heavily rely on the underlying structural similarities of switching phases but also pave the way for future material design for supercapacitors, batteries and hybrid devices.

Methods for the hydrogenation of CO into valuable chemicals are in great demand but their development is still challenging. Herein, we report the selective hydrogenation of CO into ethanol over non-noble cobalt catalysts (CoAlO ), presenting a significant advance for the conversion of CO into ethanol as the major product. By adjusting the composition of the catalysts through the use of different prereduction temperatures, the efficiency of CO to ethanol hydrogenation was optimized; the catalyst reduced at 600 ° gave an ethanol selectivity of 92.1 % at 140 °C with an ethanol time yield of 0.444 mmol g h . Operando FT-IR spectroscopy revealed that the high ethanol selectivity over the CoAlO catalyst might be due to the formation of acetate from formate by insertion of *CH , a key intermediate in the production of ethanol by CO hydrogenation.

Alloys of transition-metal dichalcogenide can display distinctive phase evolution because of their two-dimensional structures. Herein, we report the colloidal synthesis of Mo1–x V x Se2 alloy nanosheets with full composition tuning. Alloying led to a phase transition at x = 0.7 from the semiconducting 2H phase MoSe2 to the metallic 1T phase VSe2. It also produced significant V and Se vacancies, which became the richest in the 2H phase at x = 0.3–0.5. Extensive spin-polarized density functional theory calculations consistently predicted the 2H–1T phase transition at x = 0.7, in agreement with the experimental results. The vacancy formation energy also supports the formation of V and Se vacancies. Alloying in the 2H phase enhanced the electrocatalytic performance toward hydrogen evolution reaction (HER) at x = 0.3 (in 0.5 M H2SO4) or 0.4 (in 1 M KOH). The Gibbs free energy along the HER pathway indicates that this maximum performance is due to the highest concentration of active V and Se vacancy sites.

and reduced autofluorescence; this calls for development of luminophores featuring both the absorption and emission in the NIR region. [1] Comparing with the Stokes-shifted photoluminescence (SPL) commonly observed for the most of luminescent materials, upconversion photoluminescence (UCPL) represents short-wavelength emission, which occurs under long-wavelength excitation; it avoids the background from the Stokes fluorescence interference and thus offers a higher signal-to-background ratio in luminescence imaging. [2] Moreover, UCPL in the NIR spectral region is preferred for in vivo luminescence imaging as compared with upconversion to the visible region because of the greater penetration depth of both excitation and emission light into and from the biological tissue. UCPL can take place in a number of systems, such as lanthanide (Ln 3+ )-doped nanoparticles, [3] organic dyes, [4] and inorganic quantum dots [5] by utilization of additional photons or heat. Ln 3+ -doped nanoparticles represent an established class of UCPL materials operating on the basis of the unique electronic Upconversion near-infrared (NIR) fluorescent carbon dots (CDs) are important for imaging applications. Herein, thermally activated upconversion photoluminescence (UCPL) in the NIR region, with an emission peak at 784 nm, which appears under 808 nm continuous-wave laser excitation, are realized in the NIR absorbing/emissive CDs (NIR-CDs). The NIR-CDs are synthesized by microwave-assisted exfoliation of red emissive CDs in dimethylformamide, and feature single or few-layered graphene-like cores. This structure provides an enhanced contact area of the graphene-like plates in the core with the electron-acceptor carbonyl groups in dimethylformamide, which contributes to the main NIR absorption band peaked at 724 nm and a tail band in 800-850 nm. Temperature-dependent photoluminescence spectra and transient absorption spectra confirm that the UCPL of NIR-CDs is due to the thermally activated electron transitions in the excited state, rather than the multiphoton absorption process. Temperature dependent upconversion NIR luminescence imaging is demonstrated for NIR-CDs embedded in a polyvinyl pyrrolidone film, and the NIR upconversion luminescence imaging in vivo using NIR-CDs in a mouse model is accomplished.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.