@article{ZhangBehlPengetal.2019, author = {Zhang, Pengfei and Behl, Marc and Peng, Xingzhou and Balk, Maria and Lendlein, Andreas}, title = {Chemoresponsive Shape-Memory Effect of Rhodium-Phosphine Coordination Polymer Networks}, series = {Chemistry of materials : a publication of the American Chemical Society}, volume = {31}, journal = {Chemistry of materials : a publication of the American Chemical Society}, number = {15}, publisher = {American Chemical Society}, address = {Washington}, issn = {0897-4756}, doi = {10.1021/acs.chemmater.9b00363}, pages = {5402 -- 5407}, year = {2019}, abstract = {Chemoresponsive polymers are of technological significance for smart sensors or systems capable of molecular recognition. An important key requirement for these applications is the material's structural integrity after stimulation. We explored whether covalently cross-linked metal ion-phosphine coordination polymers (MPN) can be shaped into any temporary shape and are capable of recovering from this upon chemoresponsive exposure to triphenylphosphine (Ph3P) ligands, whereas the MPN provide structural integrity. Depending on the metal-ion concentration used during synthesis of the MPN, the degree of swelling of the coordination polymer networks could be adjusted. Once the MPN was immersed into Ph3P solution, the reversible ligand-exchange reaction between the metal ions and the free Ph3P in solution causes a decrease of the coordination cross-link density in MPN again. The Ph3P-treated MPN was able to maintain its original shape, indicating a certain stability of shape even after stimulation. In this way, chemoresponsive control of the elastic properties (increase in volume and decrease of mechanical strength) of the MPN was demonstrated. This remarkable behavior motivated us to explore whether the MPN are capable of a chemoresponsive shape-memory effect. In initial experiments, shape fixity of around 60\% and shape recovery of almost 90\% were achieved when the MPN was exposed to Ph3P in case of rhodium. Potential applications for chemoresponsive shape-memory systems could be shapable semiconductors, e.g., for lighting or catalysts, which provide catalytic activity on demand.}, language = {en} } @article{ZhangRudolphBenitezetal.2019, author = {Zhang, Quanchao and Rudolph, Tobias and Benitez, Alejandro J. and Gould, Oliver E. C. and Behl, Marc and Kratz, Karl and Lendlein, Andreas}, title = {Temperature-controlled reversible pore size change of electrospun fibrous shape-memory polymer actuator based meshes}, series = {Smart materials and structures}, volume = {28}, journal = {Smart materials and structures}, number = {5}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0964-1726}, doi = {10.1088/1361-665X/ab10a1}, pages = {10}, year = {2019}, abstract = {Fibrous membranes capable of dynamically responding to external stimuli are highly desirable in textiles and biomedical materials, where adaptive behavior is required to accommodate complex environmental changes. For example, the creation of fabrics with temperature-dependent moisture permeability or self-regulating membranes for air filtration is dependent on the development of materials that exhibit a reversible stimuli-responsive pore size change. Here, by imbuing covalently crosslinked poly(ε-caprolactone) (cPCL) fibrous meshes with a reversible bidirectional shape-memory polymer actuation (rbSMPA) we create a material capable of temperature-controlled changes in porosity. Cyclic thermomechanical testing was used to characterize the mechanical properties of the meshes, which were composed of randomly arranged microfibers with diameters of 2.3 ± 0.6 μm giving an average pore size of approx. 10 μm. When subjected to programming strains of εm = 300\% and 100\% reversible strain changes of εʹrev = 22\% ± 1\% and 6\% ± 1\% were measured, with switching temperature ranges of 10 °C-30 °C and 45 °C-60 °C for heating and cooling, respectively. The rbSMPA of cPCL fibrous meshes generated a microscale reversible pore size change of 11\% ± 3\% (an average of 1.5 ± 0.6 μm), as measured by scanning electron microscopy. The incorporation of a two-way shape-memory actuation capability into fibrous meshes is anticipated to advance the development and application of smart membrane materials, creating commercially viable textiles and devices with enhanced performance and novel functionality.}, language = {en} } @article{ZhangGuoTangetal.2019, author = {Zhang, Su-Yun and Guo, Wen-Bin and Tang, Ying-Ying and Xu, Jin-Qiu and He, Zhang-Zhen}, title = {Observation of Spin Relaxation in a Vanadate Chloride with Quasi-One-Dimensional Linear Chain}, series = {Crystal growth \& design : integrating the fields of crystal engineering and crystal growth for the synthesis and applications of new materials}, volume = {19}, journal = {Crystal growth \& design : integrating the fields of crystal engineering and crystal growth for the synthesis and applications of new materials}, number = {4}, publisher = {American Chemical Society}, address = {Washington}, issn = {1528-7483}, doi = {10.1021/acs.cgd.8b01839}, pages = {2228 -- 2234}, year = {2019}, abstract = {A new cobalt(II) vanadate chloride, Pb2Co(OH)(V2O7)Cl, has been synthesized under mild hydrothermal conditions. It contains quasi-one-dimensional (1D) linear chains built by edge-sharing of (CoO6)-O-II octahedra. The cobalt(II) oxide chains are further interconnected by (V2O7)(4-) dimers into a three-dimensional (3D) anionic framework with Pb2+ and Cl- ions residing in Co4V8 12-member ring tunnels. The intrachain Co center dot center dot center dot Co distance is 3.041 angstrom, while the interchain distances are 8.742 and 9.256 angstrom. Magnetic measurements suggest the ferromagnetic intrachain and the antiferromagnetic interchain interactions with a specific value of J(intra)/J(inter) = 1.7 x 10(3). Zero-field heat capacity demonstrates the magnetic long-range ordering at 5.5 K. Alternating current (AC) magnetic susceptibility under zero external direct current (DC) fields displays two slow magnetic relaxations at low temperatures, giving characteristic relaxations (tau(0)) of 1.2(3) x 10(-12) and 1.9(4) x 10(-10) s with effective energy barriers (Delta(r)) of 76.1(2) and 48.4(5) K. The energy barrier between the spin up and spin-down states can be ascribed to the ferromagnetic spin chain and the Ising-like magnetic anisotropy in Pb2Co(OH)(V2O7)Cl.}, language = {en} } @article{ZhangKochovskiLeeetal.2019, author = {Zhang, Su-Yun and Kochovski, Zdravko and Lee, Hui-Chun and Lu, Yan and Zhang, Hemin and Zhang, Jie and Sun, Jian-Ke and Yuan, Jiayin}, title = {Ionic organic cage-encapsulating phase-transferable metal clusters}, series = {Chemical science}, volume = {10}, journal = {Chemical science}, number = {5}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2041-6520}, doi = {10.1039/c8sc04375b}, pages = {1450 -- 1456}, year = {2019}, abstract = {Exploration of metal clusters (MCs) adaptive to both aqueous and oil phases without disturbing their size is promising for a broad scope of applications. The state-of-the-art approach via ligand-binding may perturb MCs' size due to varied metal-ligand binding strength when shuttling between solvents of different polarity. Herein, we applied physical confinement of a series of small noble MCs (<1 nm) inside ionic organic cages (I-Cages), which by means of anion exchange enables reversible transfer of MCs between aqueous and hydrophobic solutions without varying their ultrasmall size. Moreover, the MCs@I-Cage hybrid serves as a recyclable, reaction-switchable catalyst featuring high activity in liquid-phase NH3BH3 (AB) hydrolysis reaction with a turnover frequency (TOF) of 115 min-1.}, language = {en} } @article{ZuAmsalemEggeretal.2019, author = {Zu, Fengshuo and Amsalem, Patrick and Egger, David A. and Wang, Rongbin and Wolff, Christian Michael and Fang, Honghua and Loi, Maria Antonietta and Neher, Dieter and Kronik, Leeor and Duhm, Steffen and Koch, Norbert}, title = {Constructing the Electronic Structure of CH3NH3PbI3 and CH3NH3PbBr3 Perovskite Thin Films from Single-Crystal Band Structure Measurements}, series = {The journal of physical chemistry letters}, volume = {10}, journal = {The journal of physical chemistry letters}, number = {3}, publisher = {American Chemical Society}, address = {Washington}, issn = {1948-7185}, doi = {10.1021/acs.jpclett.8b03728}, pages = {601 -- 609}, year = {2019}, abstract = {Photovoltaic cells based on halide perovskites, possessing remarkably high power conversion efficiencies have been reported. To push the development of such devices further, a comprehensive and reliable understanding of their electronic properties is essential but presently not available. To provide a solid foundation for understanding the electronic properties of polycrystalline thin films, we employ single-crystal band structure data from angle-resolved photoemission measurements. For two prototypical perovskites (CH3NH3PbBr3 and CH3NH3PbI3), we reveal the band dispersion in two high-symmetry directions and identify the global valence band maxima. With these benchmark data, we construct "standard" photoemission spectra from polycrystalline thin film samples and resolve challenges discussed in the literature for determining the valence band onset with high reliability. Within the framework laid out here, the consistency of relating the energy level alignment in perovskite-based photovoltaic and optoelectronic devices with their functional parameters is substantially enhanced.}, language = {en} } @article{ZudeHashimHassetal.2019, author = {Zude, Manuela and Hashim, Norhashila and Hass, Roland and Polley, Nabarun and Regen, Christian}, title = {Validation study for measuring absorption and reduced scattering coefficients by means of laser-induced backscattering imaging}, series = {Postharvest Biology and Technology}, volume = {153}, journal = {Postharvest Biology and Technology}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0925-5214}, doi = {10.1016/j.postharvbio.2019.04.002}, pages = {161 -- 168}, year = {2019}, abstract = {Decoupling of optical properties appears challenging, but vital to get better insight of the relationship between light and fruit attributes. In this study, nine solid phantoms capturing the ranges of absorption (μa) and reduced scattering (μs') coefficients in fruit were analysed non-destructively using laser-induced backscattering imaging (LLBI) at 1060 nm. Data analysis of LLBI was carried out on the diffuse reflectance, attenuation profile obtained by means of Farrell's diffusion theory either calculating μa [cm-1] and μs' [cm-1] in one fitting step or fitting only one optical variable and providing the other one from a destructive analysis. The nondestructive approach was approved when calculating one unknown coefficient non-destructively, while no ability of the method was found to analysis both, μa and μs', non-destructively. Setting μs' according to destructive photon density wave (PDW) spectroscopy and fitting μa resulted in root mean square error (rmse) of 18.7\% in comparison to fitting μs' resulting in rmse of 2.6\%, pointing to decreased measuring uncertainty, when the highly variable μa was known. The approach was tested on European pear, utilizing destructive PDW spectroscopy for setting one variable, while LLBI was applied for calculating the remaining coefficient. Results indicated that the optical properties of pear obtained from PDW spectroscopy as well as LLBI changed concurrently in correspondence to water content mainly. A destructive batch-wise analysis of μs' and online analysis of μa may be considered in future developments for improved fruit sorting results, when considering fruit with high variability of μs'.}, language = {en} }