[en] We used steady state optical spectroscopies such as photoluminescence and photoinduced absorption (PA), and magnetic-field PA (MPA) for studying the energy transfer dynamics in films and organic light emitting diodes (OLED) based on host–guest blends with different guest concentrations of the fluorescent polymer poly-[2-methoxy, 5-(2′-ethyl-hexyloxy)phenylene vinylene] (MEHPPV-host), and phosphorescent molecule PtII-tetraphenyltetrabenzoporphyrin [Pt(tpbp); guest]. We show that the energy transfer process between the excited states of the host polymer and guest molecule takes a ‘ping-pong’ type sequence, because the lowest guest triplet exciton energy, E_T(guest), lies higher than that of the host, E_T(host). Upon photon excitation the photogenerated singlet excitons in the host polymer chains first undergo a Förster resonant energy transfer process to the guest singlet manifold, which subsequently reaches E_T(guest) by intersystem crossing. Because E_T(guest)>E_T(host) there is a subsequent Dexter type energy transfer from E_T(guest) to E_T(host). This energy transfer sequence has profound influence on the photoluminescence and electroluminescence emission spectra in both films and OLED devices based on the MEHPPV-Pt(tpbp) system. - Highlights: • We studied electroluminescence of OLEDs based on host–guest blends. • The emission efficiency decreases with the guest concentration. • We found a dominant Dexter energy transfer from the triplet(guest) to triplet(host). • Energy transfer occurs from the host to guest and back to the host again

[en] Coupling of spins and phonons in ferromagnets (FM) may persist up to mm length scale, thus generating macroscopic spatially distributed spin accumulation along the direction of an applied thermal gradient to an FM slab. This typical feature of transverse spin Seebeck effect (TSSE) has been demonstrated so far using electrical detection methods in FM films, in particular in a patterned structure, in which FM stripes grown onto a substrate perpendicular to the applied thermal gradient direction are electrically and magnetically isolated. Here we report optically detected TSSE response in isolated FM stripes based on permalloy deposited on SiN substrate, upon the application of a thermal gradient. For these measurements we used the magneto-optic Kerr effect measured by an ultrasensitive Sagnac interferometer microscope that is immune to thermo-electrics artefacts. We found that the optical TSSE coefficient in the NiFe stripes geometry is about one order of magnitude smaller than that in the continuous NiFe film, which is due to the limited phonons path in the FM stripes along the thermal gradient direction. Our results further confirm the existence of TSSE response in conducting FM compounds. (paper)

[en] Nanoporous CuO layer on Cu foil with a thick Cu_2O interlayer is synthesized via post annealing of previously fabricated Cu(OH)_2 nanowires at 500 °C under an oxygen flow. The formation of the thick sandwiched Cu_2O layer is realized through the outward diffusion of Cu ions and subsequent oxidation. An O_2 pressure above the dissociation pressure of CuO is used to form a CuO layer at the outer surface of the structure, thus realizing a low cost structure having a porous and high isoelectric point layer. The Cu/Cu_2O/CuO structure is used as an efficient electrode for glucose sensing. Sensitivities of 20.7 mA mM"−"1 cm"−"2 at 0.8 V versus Ag/AgCl and 1066 μA mM"–"1 cm"–"2 at 0.6 V versus Ag/AgCl are achieved in an enzymatic and non-enzymatic glucose sensing schemes, respectively. The improved electrochemical sensing ability might be attributed to the efficient electrocatalytic reaction on the high crystal quality CuO layer and the porous structure. (paper)

[en] Conducting polymers, where pristine polymers are doped by active dopants, have been used in a variety of flexible optoelectronic device applications due to their tunable conductivity values. Charge transport in these materials has been intensively studied for over three decades. However, spin transport properties in these compounds have remained elusive. Here, we studied two polaron-dominated and trap-dominated spin transport processes in two types of PEDOT:PSS polymers that are lightly and heavily doped, respectively. Using pulsed spin-pumping and spin-injection techniques, we found the sign of inverse spin Hall effect and magnetoresistance obtained from the lightly doped PEDOT:PSS film can reverse its polarity as a function of temperature and applied bias, in contrast to that in the heavily doped PEDOT:PSS film. Our work provides an alternative approach for studying the spin transport in conducting polymer films. (paper)

[en] Using the micromagnetic simulations, we have investigated the magnetization reversal and magnetostatic interaction of Fe₃Pt nanowires arrays with wire diameters lower than 40 nm. By changing the number of interacting nanowires, N, interwire distance, a, and wire diameter, D, the effects of magnetostatic interaction on coercivity and remanence are investigated in detail. According to the simulated results, the contribution to the stray field induced by surface perpendicular magnetization at the end of wires is established.

[en] We have investigated the temperature dependence of the magnetic properties and the magnetic relaxation of the Fe₅₅Co₄₅ nanowire arrays electrodeposited into self-assembled porous alumina templates with the diameter about 10 nm. X-ray diffraction (XRD) pattern indicates that the nanowire arrays are BCC structure with [1 1 0] orientation along the nanowire axes. Owing to the strong shape anisotropy, the nanowire arrays exhibit uniaxial magnetic anisotropy with the easy magnetization direction along the nanowire axes. The coercivity at 5 K can be explained by the sphere chains of the symmetric fanning mechanism. The temperature dependence of coercivity can be interpreted by thermally activated reversal mechanism as being the localized nucleation reversal mechanism with the activation volume much smaller than the wire volume. Strong field and temperature-dependent magnetic viscosity effects were also observed

[en] Chiral hybrid organic-inorganic metal halides have attracted wide attention owing to their superior chiroptoelectronic and chirospintronic properties. Here, a new class of chiral lead-free metal halides, (R/S-MBA)${}_3$Ru${}_2$Br${}_9$ (MBA = methylbenzylammonium), with unique magnetic properties is reported. (R/S-MBA)${}_3$Ru${}_2$Br${}_9$ is composed of a surface-shared octahedron dimer separated by chiral cations and crystallizes into the Sohncke space group of P2${}_1$2${}_1$2${}_1$. The crystal structures, chiroptical, magnetic properties, and magnetic circular dichroism of (R/S-MBA)${}_3$Ru${}_2$Br${}_9$ are systematically investigated. Owing to the strong antiferromagnetic coupling between the Ru atom through bromine bridge in the [Ru${}_2$Br${}_9$]${}^{3-<!--\; ???\; -->}$ dimer and the weak ferromagnetic coupling between the neighboring [Ru${}_2$Br${}_9$]${}^{3-<!--\; ???\; -->}$ dimer, (R/S-MBA)${}_3$Ru${}_2$Br${}_9$ exhibits antiferromagnetic property with Néel temperature at 7 K. Considering the unique magnetic property of ruthenium, together with the rapid progress of antiferromagnetic spintronics and optospintronics recently, this work provides a novel multifunctional lead-free chiral magnetic candidate toward chiral optoelectronics and antiferromagnetic spintronics. (© 2023 Wiley‐VCH GmbH)