Control of the Speed of a Light-Induced Spin Transition through Mesoscale Core-Shell Architecture.

The rate of the light-induced spin transition in a coordination polymer network solid dramatically increases when included as the core in mesoscale core-shell particles. A series of photomagnetic coordination polymer core-shell heterostructures, based on the light-switchable Rb aCo b[Fe(CN)6] c· mH2O (RbCoFe-PBA) as core with the isostructural K jNi k[Cr(CN)6] l· nH2O (KNiCr-PBA) as shell, are studied using temperature-dependent powder X-ray diffraction and SQUID magnetometry. The core RbCoFe-PBA exhibits a charge transfer-induced spin transition (CTIST), which can be thermally and optically induced. When coupled to the shell, the rate of the optically induced transition from low spin to high spin increases. Isothermal relaxation from the optically induced high spin state of the core back to the low spin state and activation energies associated with the transition between these states were measured. The presence of a shell decreases the activation energy, which is associated with the elastic properties of the core. Numerical simulations using an electro-elastic model for the spin transition in core-shell particles supports the findings, demonstrating how coupling of the core to the shell changes the elastic properties of the system. The ability to tune the rate of optically induced magnetic and structural phase transitions through control of mesoscale architecture presents a new approach to the development of photoswitchable materials with tailored properties.

Introducing Dimensionality to the Archetypical Mn12 Single-Molecule Magnet: a Family of [Mn12]n Chains.

The [Mn12O12(O2CR)16(L4)] family (R = various; L = terminal ligand) of clusters holds a special place in molecular magnetism; they are the most well-studied single-molecule magnets (SMMs). Targeted linkage of these SMMs has now been achieved for the first time. The resulting chain structures have been confirmed crystallographically, and the magnetic properties, up to 1.14 GPa, and high-field electron paramagnetic resonance spectra have been collected and analyzed.

Direct Characterization of Buried Interfaces in 2D/3D Heterostructures Enabled by GeO2 Release Layer.

Inconsistent interface control in devices based on two-dimensional materials (2DMs) has limited technological maturation. Astounding variability of 2D/three-dimensional (2D/3D) interface properties has been reported, which has been exacerbated by the lack of direct investigations of buried interfaces commonly found in devices. Herein, we demonstrate a new process that enables the assembly and isolation of device-relevant heterostructures for buried interface characterization. This is achieved by implementing a water-soluble substrate (GeO2), which enables deposition of many materials onto the 2DM and subsequent heterostructure release by dissolving the GeO2 substrate. Here, we utilize this novel approach to compare how the chemistry, doping, and strain in monolayer MoS2 heterostructures fabricated by direct deposition vary from those fabricated by transfer techniques to show how interface properties differ with the heterostructure fabrication method. Direct deposition of thick Ni and Ti films is found to react with the monolayer MoS2. These interface reactions convert 50% of MoS2 into intermetallic species, which greatly exceeds the 10% conversion reported previously and 0% observed in transfer-fabricated heterostructures. We also measure notable differences in MoS2 carrier concentration depending on the heterostructure fabrication method. Direct deposition of thick Au, Ni, and Al2O3 films onto MoS2 increases the hole concentration by >1012 cm-2 compared to heterostructures fabricated by transferring MoS2 onto these materials. Thus, we demonstrate a universal method to fabricate 2D/3D heterostructures and expose buried interfaces for direct characterization.

An Early Case of Fat Embolism Syndrome Occurring Following Polytrauma.

Fat embolism syndrome (FES) is a clinical entity occurring due to the presence of fat particles in the microcirculation, typically manifesting 12-72 hours after long bone trauma with respiratory distress, altered mental status, and petechial rash. Our case is that of a 17-year-old girl who suffered multiple orthopedic injuries without intracranial trauma after being a pedestrian struck by a vehicle. Despite presenting with a normal Glasgow Coma Score (GCS), within 4 hours of presentation, she was noted to have an acute mental status change to a GCS 7 with a normal computed tomography brain. Magnetic resonance imaging of the brain was suggestive of FES which, in this patient, had a rapidly progressing course with the development of severe cerebral edema and intracranial hypertension refractory to maximal medical therapy. Our patient required bilateral craniectomies for intracranial decompression and progressed over a 2-month hospital course to have subsequent cranioplasty and functional neurologic improvement. FES requires a high index of clinical suspicion in the presence of long bone fracture with unexplained altered mental status. The clinical course can be rapidly progressing with the development of intracranial hypertension which may benefit from surgical decompression with optimistic prognosis.

Synergistic photomagnetic effects in coordination polymer heterostructure particles of Hofmann-like Fe(4-phenylpyridine)2[Ni(CN)4]·0.5H2O and K0.4Ni[Cr(CN)6]0.8·nH2O.

New nanometer scale heterostructure particles of the two-dimensional Hofmann-like Fe(ii) spin-crossover network, Fe(phpy)2[Ni(CN)4]·0.5H2O {phpy = 4-phenylpyridine}, and the Prussian blue analogue K0.4Ni1.0[Cr(CN)6]0.8·nH2O (NiCr-PBA) have been developed, exhibiting synergistic photomagnetic effects, whereby the LIESST (light-induced electron spin-state trapping) effect in the Hofmann-like material induces a magnetization change in the NiCr-PBA. A variety of microscopic and spectroscopic techniques demonstrate the heterogeneous growth of the NiCr-PBA on the Hofmann seed particles and show the Hofmann compound retains its thermal and photoinduced spin transition properties in the heterostructure. The photoinduced magnetization change in the NiCr-PBA network arises from coupling of the two lattices despite dissimilar structure types. Isothermal magnetization minor hysteresis loop studies at 5 K show light absorption leads to changes in the local anisotropy of NiCr-PBA magnetic domains, providing direct evidence for a general magnetomechanical mechanism of light-switchable magnetism in coordination polymer heterostructures combining a photoactive material with a magnet.