TY - JOUR AB - The epitaxial growth of a strained Ge layer, which is a promising candidate for the channel material of a hole spin qubit, has been demonstrated on 300 mm Si wafers using commercially available Si0.3Ge0.7 strain relaxed buffer (SRB) layers. The assessment of the layer and the interface qualities for a buried strained Ge layer embedded in Si0.3Ge0.7 layers is reported. The XRD reciprocal space mapping confirmed that the reduction of the growth temperature enables the 2-dimensional growth of the Ge layer fully strained with respect to the Si0.3Ge0.7. Nevertheless, dislocations at the top and/or bottom interface of the Ge layer were observed by means of electron channeling contrast imaging, suggesting the importance of the careful dislocation assessment. The interface abruptness does not depend on the selection of the precursor gases, but it is strongly influenced by the growth temperature which affects the coverage of the surface H-passivation. The mobility of 2.7 × 105 cm2/Vs is promising, while the low percolation density of 3 × 1010 /cm2 measured with a Hall-bar device at 7 K illustrates the high quality of the heterostructure thanks to the high Si0.3Ge0.7 SRB quality. AU - Shimura, Yosuke AU - Godfrin, Clement AU - Hikavyy, Andriy AU - Li, Roy AU - Aguilera Servin, Juan L AU - Katsaros, Georgios AU - Favia, Paola AU - Han, Han AU - Wan, Danny AU - de Greve, Kristiaan AU - Loo, Roger ID - 15018 IS - 5 JF - Materials Science in Semiconductor Processing KW - Mechanical Engineering KW - Mechanics of Materials KW - Condensed Matter Physics KW - General Materials Science SN - 1369-8001 TI - Compressively strained epitaxial Ge layers for quantum computing applications VL - 174 ER - TY - JOUR AB - A rotating organic cation and a dynamically disordered soft inorganic cage are the hallmark features of organic-inorganic lead-halide perovskites. Understanding the interplay between these two subsystems is a challenging problem, but it is this coupling that is widely conjectured to be responsible for the unique behavior of photocarriers in these materials. In this work, we use the fact that the polarizability of the organic cation strongly depends on the ambient electrostatic environment to put the molecule forward as a sensitive probe of the local crystal fields inside the lattice cell. We measure the average polarizability of the C/N–H bond stretching mode by means of infrared spectroscopy, which allows us to deduce the character of the motion of the cation molecule, find the magnitude of the local crystal field, and place an estimate on the strength of the hydrogen bond between the hydrogen and halide atoms. Our results pave the way for understanding electric fields in lead-halide perovskites using infrared bond spectroscopy. AU - Wei, Yujing AU - Volosniev, Artem AU - Lorenc, Dusan AU - Zhumekenov, Ayan A. AU - Bakr, Osman M. AU - Lemeshko, Mikhail AU - Alpichshev, Zhanybek ID - 13251 IS - 27 JF - The Journal of Physical Chemistry Letters KW - General Materials Science KW - Physical and Theoretical Chemistry TI - Bond polarizability as a probe of local crystal fields in hybrid lead-halide perovskites VL - 14 ER - TY - JOUR AB - Nominally identical materials exchange net electric charge during contact through a mechanism that is still debated. ‘Mosaic models’, in which surfaces are presumed to consist of a random patchwork of microscopic donor/acceptor sites, offer an appealing explanation for this phenomenon. However, recent experiments have shown that global differences persist even between same-material samples, which the standard mosaic framework does not account for. Here, we expand the mosaic framework by incorporating global differences in the densities of donor/acceptor sites. We develop an analytical model, backed by numerical simulations, that smoothly connects the global and deterministic charge transfer of different materials to the local and stochastic mosaic picture normally associated with identical materials. Going further, we extend our model to explain the effect of contact asymmetries during sliding, providing a plausible explanation for reversal of charging sign that has been observed experimentally. AU - Grosjean, Galien M AU - Waitukaitis, Scott R ID - 13197 IS - 6 JF - Physical Review Materials KW - Physics and Astronomy (miscellaneous) KW - General Materials Science SN - 2475-9953 TI - Asymmetries in triboelectric charging: Generalizing mosaic models to different-material samples and sliding contacts VL - 7 ER - TY - JOUR AB - The self-assembly of nanoparticles driven by small molecules or ions may produce colloidal superlattices with features and properties reminiscent of those of metals or semiconductors. However, to what extent the properties of such supramolecular crystals actually resemble those of atomic materials often remains unclear. Here, we present coarse-grained molecular simulations explicitly demonstrating how a behavior evocative of that of semiconductors may emerge in a colloidal superlattice. As a case study, we focus on gold nanoparticles bearing positively charged groups that self-assemble into FCC crystals via mediation by citrate counterions. In silico ohmic experiments show how the dynamically diverse behavior of the ions in different superlattice domains allows the opening of conductive ionic gates above certain levels of applied electric fields. The observed binary conductive/nonconductive behavior is reminiscent of that of conventional semiconductors, while, at a supramolecular level, crossing the “band gap” requires a sufficient electrostatic stimulus to break the intermolecular interactions and make ions diffuse throughout the superlattice’s cavities. AU - Lionello, Chiara AU - Perego, Claudio AU - Gardin, Andrea AU - Klajn, Rafal AU - Pavan, Giovanni M. ID - 13346 IS - 1 JF - ACS Nano KW - General Physics and Astronomy KW - General Engineering KW - General Materials Science SN - 1936-0851 TI - Supramolecular semiconductivity through emerging ionic gates in ion–nanoparticle superlattices VL - 17 ER - TY - JOUR AB - Most permissionless blockchains inherently suffer from throughput limitations. Layer-2 systems, such as side-chains or Rollups, have been proposed as a possible strategy to overcome this limitation. Layer-2 systems interact with the main-chain in two ways. First, users can move funds from/to the main-chain to/from the layer-2. Second, layer-2 systems periodically synchronize with the main-chain to keep some form of log of their activity on the main-chain - this log is key for security. Due to this interaction with the main-chain, which is necessary and recurrent, layer-2 systems impose some load on the main-chain. The impact of such load on the main-chain has been, so far, poorly understood. In addition to that, layer-2 approaches typically sacrifice decentralization and security in favor of higher throughput. This paper presents an experimental study that analyzes the current state of Ethereum layer-2 projects. Our goal is to assess the load they impose on Ethereum and to understand their scalability potential in the long-run. Our analysis shows that the impact of any given layer-2 on the main-chain is the result of both technical aspects (how state is logged on the main-chain) and user behavior (how often users decide to transfer funds between the layer-2 and the main-chain). Based on our observations, we infer that without efficient mechanisms that allow users to transfer funds in a secure and fast manner directly from one layer-2 project to another, current layer-2 systems will not be able to scale Ethereum effectively, regardless of their technical solutions. Furthermore, from our results, we conclude that the layer-2 systems that offer similar security guarantees as Ethereum have limited scalability potential, while approaches that offer better performance, sacrifice security and lead to an increase in centralization which runs against the end-goals of permissionless blockchains. AU - Neiheiser, Ray AU - Inacio, Gustavo AU - Rech, Luciana AU - Montez, Carlos AU - Matos, Miguel AU - Rodrigues, Luis ID - 13988 JF - IEEE Access KW - General Engineering KW - General Materials Science KW - General Computer Science KW - Electrical and Electronic Engineering SN - 2169-3536 TI - Practical limitations of Ethereum’s layer-2 VL - 11 ER - TY - JOUR AB - High entropy alloys (HEAs) are highly suitable candidate catalysts for oxygen evolution and reduction reactions (OER/ORR) as they offer numerous parameters for optimizing the electronic structure and catalytic sites. Herein, FeCoNiMoW HEA nanoparticles are synthesized using a solution‐based low‐temperature approach. Such FeCoNiMoW nanoparticles show high entropy properties, subtle lattice distortions, and modulated electronic structure, leading to superior OER performance with an overpotential of 233 mV at 10 mA cm−2 and 276 mV at 100 mA cm−2. Density functional theory calculations reveal the electronic structures of the FeCoNiMoW active sites with an optimized d‐band center position that enables suitable adsorption of OOH* intermediates and reduces the Gibbs free energy barrier in the OER process. Aqueous zinc–air batteries (ZABs) based on this HEA demonstrate a high open circuit potential of 1.59 V, a peak power density of 116.9 mW cm−2, a specific capacity of 857 mAh gZn−1, and excellent stability for over 660 h of continuous charge–discharge cycles. Flexible and solid ZABs are also assembled and tested, displaying excellent charge–discharge performance at different bending angles. This work shows the significance of 4d/5d metal‐modulated electronic structure and optimized adsorption ability to improve the performance of OER/ORR, ZABs, and beyond. AU - He, Ren AU - Yang, Linlin AU - Zhang, Yu AU - Jiang, Daochuan AU - Lee, Seungho AU - Horta, Sharona AU - Liang, Zhifu AU - Lu, Xuan AU - Ostovari Moghaddam, Ahmad AU - Li, Junshan AU - Ibáñez, Maria AU - Xu, Ying AU - Zhou, Yingtang AU - Cabot, Andreu ID - 14434 JF - Advanced Materials KW - Mechanical Engineering KW - Mechanics of Materials KW - General Materials Science SN - 0935-9648 TI - A 3d‐4d‐5d high entropy alloy as a bifunctional oxygen catalyst for robust aqueous zinc–air batteries ER - TY - JOUR AB - Low‐cost, safe, and environmental‐friendly rechargeable aqueous zinc‐ion batteries (ZIBs) are promising as next‐generation energy storage devices for wearable electronics among other applications. However, sluggish ionic transport kinetics and the unstable electrode structure during ionic insertion/extraction hampers their deployment. Herein,  we propose a new cathode material based on a layered metal chalcogenide (LMC), bismuth telluride (Bi2Te3), coated with polypyrrole (PPy). Taking advantage of the PPy coating, the Bi2Te3@PPy composite presents strong ionic absorption affinity, high oxidation resistance, and high structural stability. The ZIBs based on Bi2Te3@PPy cathodes exhibit high capacities and ultra‐long lifespans of over 5000 cycles. They also present outstanding stability even under bending. In addition,  we analyze here the reaction mechanism using in situ X‐ray diffraction, X‐ray photoelectron spectroscopy, and computational tools and demonstrate that, in the aqueous system, Zn2+ is not inserted into the cathode as previously assumed. In contrast, proton charge storage dominates the process. Overall, this work not only shows the great potential of LMCs as ZIBs cathode materials and the advantages of PPy coating, but also clarifies the charge/discharge mechanism in rechargeable ZIBs based on LMCs. AU - Zeng, Guifang AU - Sun, Qing AU - Horta, Sharona AU - Wang, Shang AU - Lu, Xuan AU - Zhang, Chaoyue AU - Li, Jing AU - Li, Junshan AU - Ci, Lijie AU - Tian, Yanhong AU - Ibáñez, Maria AU - Cabot, Andreu ID - 14435 JF - Advanced Materials KW - Mechanical Engineering KW - Mechanics of Materials KW - General Materials Science SN - 0935-9648 TI - A layered Bi2Te3@PPy cathode for aqueous zinc ion batteries: Mechanism and application in printed flexible batteries ER - TY - JOUR AB - Optoelectronic effects differentiating absorption of right and left circularly polarized photons in thin films of chiral materials are typically prohibitively small for their direct photocurrent observation. Chiral metasurfaces increase the electronic sensitivity to circular polarization, but their out-of-plane architecture entails manufacturing and performance trade-offs. Here, we show that nanoporous thin films of chiral nanoparticles enable high sensitivity to circular polarization due to light-induced polarization-dependent ion accumulation at nanoparticle interfaces. Self-assembled multilayers of gold nanoparticles modified with L-phenylalanine generate a photocurrent under right-handed circularly polarized light as high as 2.41 times higher than under left-handed circularly polarized light. The strong plasmonic coupling between the multiple nanoparticles producing planar chiroplasmonic modes facilitates the ejection of electrons, whose entrapment at the membrane–electrolyte interface is promoted by a thick layer of enantiopure phenylalanine. Demonstrated detection of light ellipticity with equal sensitivity at all incident angles mimics phenomenological aspects of polarization vision in marine animals. The simplicity of self-assembly and sensitivity of polarization detection found in optoionic membranes opens the door to a family of miniaturized fluidic devices for chiral photonics. AU - Cai, Jiarong AU - Zhang, Wei AU - Xu, Liguang AU - Hao, Changlong AU - Ma, Wei AU - Sun, Maozhong AU - Wu, Xiaoling AU - Qin, Xian AU - Colombari, Felippe Mariano AU - de Moura, André Farias AU - Xu, Jiahui AU - Silva, Mariana Cristina AU - Carneiro-Neto, Evaldo Batista AU - Gomes, Weverson Rodrigues AU - Vallée, Renaud A. L. AU - Pereira, Ernesto Chaves AU - Liu, Xiaogang AU - Xu, Chuanlai AU - Klajn, Rafal AU - Kotov, Nicholas A. AU - Kuang, Hua ID - 13352 IS - 4 JF - Nature Nanotechnology KW - Electrical and Electronic Engineering KW - Condensed Matter Physics KW - General Materials Science KW - Biomedical Engineering KW - Atomic and Molecular Physics KW - and Optics KW - Bioengineering SN - 1748-3387 TI - Polarization-sensitive optoionic membranes from chiral plasmonic nanoparticles VL - 17 ER - TY - JOUR AB - Supramolecular self-assembly in biological systems holds promise to convert and amplify disease-specific signals to physical or mechanical signals that can direct cell fate. However, it remains challenging to design physiologically stable self-assembling systems that demonstrate tunable and predictable behavior. Here, the use of zwitterionic tetrapeptide modalities to direct nanoparticle assembly under physiological conditions is reported. The self-assembly of gold nanoparticles can be activated by enzymatic unveiling of surface-bound zwitterionic tetrapeptides through matrix metalloprotease-9 (MMP-9), which is overexpressed by cancer cells. This robust nanoparticle assembly is achieved by multivalent, self-complementary interactions of the zwitterionic tetrapeptides. In cancer cells that overexpress MMP-9, the nanoparticle assembly process occurs near the cell membrane and causes size-induced selection of cellular uptake mechanism, resulting in diminished cell growth. The enzyme responsiveness, and therefore, indirectly, the uptake route of the system can be programmed by customizing the peptide sequence: a simple inversion of the two amino acids at the cleavage site completely inactivates the enzyme responsiveness, self-assembly, and consequently changes the endocytic pathway. This robust self-complementary, zwitterionic peptide design demonstrates the use of enzyme-activated electrostatic side-chain patterns as powerful and customizable peptide modalities to program nanoparticle self-assembly and alter cellular response in biological context. AU - Huang, Richard H. AU - Nayeem, Nazia AU - He, Ye AU - Morales, Jorge AU - Graham, Duncan AU - Klajn, Rafal AU - Contel, Maria AU - O'Brien, Stephen AU - Ulijn, Rein V. ID - 13355 IS - 1 JF - Advanced Materials KW - Mechanical Engineering KW - Mechanics of Materials KW - General Materials Science SN - 0935-9648 TI - Self‐complementary zwitterionic peptides direct nanoparticle assembly and enable enzymatic selection of endocytic pathways VL - 34 ER - TY - JOUR AB - High-entropy materials offer numerous advantages as catalysts, including a flexible composition to tune the catalytic activity and selectivity and a large variety of adsorption/reaction sites for multistep or multiple reactions. Herein, we report on the synthesis, properties, and electrocatalytic performance of an amorphous high-entropy boride based on abundant transition metals, CoFeNiMnZnB. This metal boride provides excellent performance toward the oxygen evolution reaction (OER), including a low overpotential of 261 mV at 10 mA cm–2, a reduced Tafel slope of 56.8 mV dec–1, and very high stability. The outstanding OER performance of CoFeNiMnZnB is attributed to the synergistic interactions between the different metals, the leaching of Zn ions, the generation of oxygen vacancies, and the in situ formation of an amorphous oxyhydroxide at the CoFeNiMnZnB surface during the OER. AU - Wang, Xiang AU - Zuo, Yong AU - Horta, Sharona AU - He, Ren AU - Yang, Linlin AU - Ostovari Moghaddam, Ahmad AU - Ibáñez, Maria AU - Qi, Xueqiang AU - Cabot, Andreu ID - 12236 IS - 42 JF - ACS Applied Materials & Interfaces KW - General Materials Science SN - 1944-8244 TI - CoFeNiMnZnB as a high-entropy metal boride to boost the oxygen evolution reaction VL - 14 ER - TY - JOUR AB - Mercury telluride (HgTe) thin films with a critical thickness of 6.5 nm are predicted to possess a gapless Dirac-like band structure. We report a comprehensive study on gated and optically doped samples by magnetooptical spectroscopy in the THz range. The quasi-classical analysis of the cyclotron resonance allowed the mapping of the band dispersion of Dirac charge carriers in a broad range of electron and hole doping. A smooth transition through the charge neutrality point between Dirac holes and electrons was observed. An additional peak coming from a second type of holes with an almost density-independent mass of around 0.04m0 was detected in the hole-doping range and attributed to an asymmetric spin splitting of the Dirac cone. Spectroscopic evidence for disorder-induced band energy fluctuations could not be detected in present cyclotron resonance experiments. AU - Shuvaev, Alexey AU - Dziom, Uladzislau AU - Gospodarič, Jan AU - Novik, Elena G. AU - Dobretsova, Alena A. AU - Mikhailov, Nikolay N. AU - Kvon, Ze Don AU - Pimenov, Andrei ID - 12278 IS - 14 JF - Nanomaterials KW - General Materials Science KW - General Chemical Engineering SN - 2079-4991 TI - Band structure near the Dirac Point in HgTe quantum wells with critical thickness VL - 12 ER - TY - JOUR AB - Several Ising-type magnetic van der Waals (vdW) materials exhibit stable magnetic ground states. Despite these clear experimental demonstrations, a complete theoretical and microscopic understanding of their magnetic anisotropy is still lacking. In particular, the validity limit of identifying their one-dimensional (1-D) Ising nature has remained uninvestigated in a quantitative way. Here we performed the complete mapping of magnetic anisotropy for a prototypical Ising vdW magnet FePS3 for the first time. Combining torque magnetometry measurements with their magnetostatic model analysis and the relativistic density functional total energy calculations, we successfully constructed the three-dimensional (3-D) mappings of the magnetic anisotropy in terms of magnetic torque and energy. The results not only quantitatively confirm that the easy axis is perpendicular to the ab plane, but also reveal the anisotropies within the ab, ac, and bc planes. Our approach can be applied to the detailed quantitative study of magnetism in vdW materials. AU - Nauman, Muhammad AU - Kiem, Do Hoon AU - Lee, Sungmin AU - Son, Suhan AU - Park, J-G AU - Kang, Woun AU - Han, Myung Joon AU - Jo, Youn Jung ID - 9282 IS - 3 JF - 2D Materials KW - Mechanical Engineering KW - General Materials Science KW - Mechanics of Materials KW - General Chemistry KW - Condensed Matter Physics SN - 2053-1583 TI - Complete mapping of magnetic anisotropy for prototype Ising van der Waals FePS3 VL - 8 ER - TY - JOUR AB - Solution synthesis of particles emerged as an alternative to prepare thermoelectric materials with less demanding processing conditions than conventional solid-state synthetic methods. However, solution synthesis generally involves the presence of additional molecules or ions belonging to the precursors or added to enable solubility and/or regulate nucleation and growth. These molecules or ions can end up in the particles as surface adsorbates and interfere in the material properties. This work demonstrates that ionic adsorbates, in particular Na⁺ ions, are electrostatically adsorbed in SnSe particles synthesized in water and play a crucial role not only in directing the material nano/microstructure but also in determining the transport properties of the consolidated material. In dense pellets prepared by sintering SnSe particles, Na remains within the crystal lattice as dopant, in dislocations, precipitates, and forming grain boundary complexions. These results highlight the importance of considering all the possible unintentional impurities to establish proper structure-property relationships and control material properties in solution-processed thermoelectric materials. AU - Liu, Yu AU - Calcabrini, Mariano AU - Yu, Yuan AU - Genç, Aziz AU - Chang, Cheng AU - Costanzo, Tommaso AU - Kleinhanns, Tobias AU - Lee, Seungho AU - Llorca, Jordi AU - Cojocaru‐Mirédin, Oana AU - Ibáñez, Maria ID - 10123 IS - 52 JF - Advanced Materials KW - mechanical engineering KW - mechanics of materials KW - general materials science SN - 0935-9648 TI - The importance of surface adsorbates in solution‐processed thermoelectric materials: The case of SnSe VL - 33 ER - TY - JOUR AB - The cost-effective conversion of low-grade heat into electricity using thermoelectric devices requires developing alternative materials and material processing technologies able to reduce the currently high device manufacturing costs. In this direction, thermoelectric materials that do not rely on rare or toxic elements such as tellurium or lead need to be produced using high-throughput technologies not involving high temperatures and long processes. Bi2Se3 is an obvious possible Te-free alternative to Bi2Te3 for ambient temperature thermoelectric applications, but its performance is still low for practical applications, and additional efforts toward finding proper dopants are required. Here, we report a scalable method to produce Bi2Se3 nanosheets at low synthesis temperatures. We studied the influence of different dopants on the thermoelectric properties of this material. Among the elements tested, we demonstrated that Sn doping resulted in the best performance. Sn incorporation resulted in a significant improvement to the Bi2Se3 Seebeck coefficient and a reduction in the thermal conductivity in the direction of the hot-press axis, resulting in an overall 60% improvement in the thermoelectric figure of merit of Bi2Se3. AU - Li, Mengyao AU - Zhang, Yu AU - Zhang, Ting AU - Zuo, Yong AU - Xiao, Ke AU - Arbiol, Jordi AU - Llorca, Jordi AU - Liu, Yu AU - Cabot, Andreu ID - 10858 IS - 7 JF - Nanomaterials KW - General Materials Science KW - General Chemical Engineering SN - 2079-4991 TI - Enhanced thermoelectric performance of n-type Bi2Se3 nanosheets through Sn doping VL - 11 ER - TY - JOUR AB - We report the observation of an anomalous nonlinear optical response of the prototypical three-dimensional topological insulator bismuth selenide through the process of high-order harmonic generation. We find that the generation efficiency increases as the laser polarization is changed from linear to elliptical, and it becomes maximum for circular polarization. With the aid of a microscopic theory and a detailed analysis of the measured spectra, we reveal that such anomalous enhancement encodes the characteristic topology of the band structure that originates from the interplay of strong spin–orbit coupling and time-reversal symmetry protection. The implications are in ultrafast probing of topological phase transitions, light-field driven dissipationless electronics, and quantum computation. AU - Baykusheva, Denitsa Rangelova AU - Chacón, Alexis AU - Lu, Jian AU - Bailey, Trevor P. AU - Sobota, Jonathan A. AU - Soifer, Hadas AU - Kirchmann, Patrick S. AU - Rotundu, Costel AU - Uher, Ctirad AU - Heinz, Tony F. AU - Reis, David A. AU - Ghimire, Shambhu ID - 13996 IS - 21 JF - Nano Letters KW - Mechanical Engineering KW - Condensed Matter Physics KW - General Materials Science KW - General Chemistry KW - Bioengineering SN - 1530-6984 TI - All-optical probe of three-dimensional topological insulators based on high-harmonic generation by circularly polarized laser fields VL - 21 ER - TY - JOUR AB - Cu2–xS has become one of the most promising thermoelectric materials for application in the middle-high temperature range. Its advantages include the abundance, low cost, and safety of its elements and a high performance at relatively elevated temperatures. However, stability issues limit its operation current and temperature, thus calling for the optimization of the material performance in the middle temperature range. Here, we present a synthetic protocol for large scale production of covellite CuS nanoparticles at ambient temperature and atmosphere, and using water as a solvent. The crystal phase and stoichiometry of the particles are afterward tuned through an annealing process at a moderate temperature under inert or reducing atmosphere. While annealing under argon results in Cu1.8S nanopowder with a rhombohedral crystal phase, annealing in an atmosphere containing hydrogen leads to tetragonal Cu1.96S. High temperature X-ray diffraction analysis shows the material annealed in argon to transform to the cubic phase at ca. 400 K, while the material annealed in the presence of hydrogen undergoes two phase transitions, first to hexagonal and then to the cubic structure. The annealing atmosphere, temperature, and time allow adjustment of the density of copper vacancies and thus tuning of the charge carrier concentration and material transport properties. In this direction, the material annealed under Ar is characterized by higher electrical conductivities but lower Seebeck coefficients than the material annealed in the presence of hydrogen. By optimizing the charge carrier concentration through the annealing time, Cu2–xS with record figures of merit in the middle temperature range, up to 1.41 at 710 K, is obtained. We finally demonstrate that this strategy, based on a low-cost and scalable solution synthesis process, is also suitable for the production of high performance Cu2–xS layers using high throughput and cost-effective printing technologies. AU - Li, Mengyao AU - Liu, Yu AU - Zhang, Yu AU - Han, Xu AU - Zhang, Ting AU - Zuo, Yong AU - Xie, Chenyang AU - Xiao, Ke AU - Arbiol, Jordi AU - Llorca, Jordi AU - Ibáñez, Maria AU - Liu, Junfeng AU - Cabot, Andreu ID - 9235 IS - 3 JF - ACS Nano KW - General Engineering KW - General Physics and Astronomy KW - General Materials Science SN - 1936-0851 TI - Effect of the annealing atmosphere on crystal phase and thermoelectric properties of copper sulfide VL - 15 ER - TY - JOUR AB - Scanning nanoscale superconducting quantum interference devices (nanoSQUIDs) are of growing interest for highly sensitive quantitative imaging of magnetic, spintronic, and transport properties of low-dimensional systems. Utilizing specifically designed grooved quartz capillaries pulled into a sharp pipette, we have fabricated the smallest SQUID-on-tip (SOT) devices with effective diameters down to 39 nm. Integration of a resistive shunt in close proximity to the pipette apex combined with self-aligned deposition of In and Sn, has resulted in SOTs with a flux noise of 42 nΦ0 Hz−1/2, yielding a record low spin noise of 0.29 μB Hz−1/2. In addition, the new SOTs function at sub-Kelvin temperatures and in high magnetic fields of over 2.5 T. Integrating the SOTs into a scanning probe microscope allowed us to image the stray field of a single Fe3O4 nanocube at 300 mK. Our results show that the easy magnetization axis direction undergoes a transition from the 〈111〉 direction at room temperature to an in-plane orientation, which could be attributed to the Verwey phase transition in Fe3O4. AU - Anahory, Y. AU - Naren, H. R. AU - Lachman, E. O. AU - Buhbut Sinai, S. AU - Uri, A. AU - Embon, L. AU - Yaakobi, E. AU - Myasoedov, Y. AU - Huber, M. E. AU - Klajn, Rafal AU - Zeldov, E. ID - 13368 IS - 5 JF - Nanoscale KW - General Materials Science SN - 2040-3364 TI - SQUID-on-tip with single-electron spin sensitivity for high-field and ultra-low temperature nanomagnetic imaging VL - 12 ER - TY - JOUR AB - Temporal activation of biological processes by visible light and subsequent return to an inactive state in the absence of light is an essential characteristic of photoreceptor cells. Inspired by these phenomena, light-responsive materials are very attractive due to the high spatiotemporal control of light irradiation, with light being able to precisely orchestrate processes repeatedly over many cycles. Herein, it is reported that light-driven proton transfer triggered by a merocyanine-based photoacid can be used to modulate the permeability of pH-responsive polymersomes through cyclic, temporally controlled protonation and deprotonation of the polymersome membrane. The membranes can undergo repeated light-driven swelling–contraction cycles without losing functional effectiveness. When applied to enzyme loaded-nanoreactors, this membrane responsiveness is used for the reversible control of enzymatic reactions. This combination of the merocyanine-based photoacid and pH-switchable nanoreactors results in rapidly responding and versatile supramolecular systems successfully used to switch enzymatic reactions ON and OFF on demand. AU - Moreno, Silvia AU - Sharan, Priyanka AU - Engelke, Johanna AU - Gumz, Hannes AU - Boye, Susanne AU - Oertel, Ulrich AU - Wang, Peng AU - Banerjee, Susanta AU - Klajn, Rafal AU - Voit, Brigitte AU - Lederer, Albena AU - Appelhans, Dietmar ID - 13363 IS - 37 JF - Small KW - Biomaterials KW - Biotechnology KW - General Materials Science KW - General Chemistry SN - 1613-6810 TI - Light‐driven proton transfer for cyclic and temporal switching of enzymatic nanoreactors VL - 16 ER - TY - JOUR AB - Confining molecules can fundamentally change their chemical and physical properties. Confinement effects are considered instrumental at various stages of the origins of life, and life continues to rely on layers of compartmentalization to maintain an out-of-equilibrium state and efficiently synthesize complex biomolecules under mild conditions. As interest in synthetic confined systems grows, we are realizing that the principles governing reactivity under confinement are the same in abiological systems as they are in nature. In this Review, we categorize the ways in which nanoconfinement effects impact chemical reactivity in synthetic systems. Under nanoconfinement, chemical properties can be modulated to increase reaction rates, enhance selectivity and stabilize reactive species. Confinement effects also lead to changes in physical properties. The fluorescence of light emitters, the colours of dyes and electronic communication between electroactive species can all be tuned under confinement. Within each of these categories, we elucidate design principles and strategies that are widely applicable across a range of confined systems, specifically highlighting examples of different nanocompartments that influence reactivity in similar ways. AU - Grommet, Angela B. AU - Feller, Moran AU - Klajn, Rafal ID - 13367 JF - Nature Nanotechnology KW - Electrical and Electronic Engineering KW - Condensed Matter Physics KW - General Materials Science KW - Biomedical Engineering KW - Atomic and Molecular Physics KW - and Optics KW - Bioengineering SN - 1748-3387 TI - Chemical reactivity under nanoconfinement VL - 15 ER - TY - JOUR AB - Glioblastoma is the most malignant cancer in the brain and currently incurable. It is urgent to identify effective targets for this lethal disease. Inhibition of such targets should suppress the growth of cancer cells and, ideally also precancerous cells for early prevention, but minimally affect their normal counterparts. Using genetic mouse models with neural stem cells (NSCs) or oligodendrocyte precursor cells (OPCs) as the cells‐of‐origin/mutation, it is shown that the susceptibility of cells within the development hierarchy of glioma to the knockout of insulin‐like growth factor I receptor (IGF1R) is determined not only by their oncogenic states, but also by their cell identities/states. Knockout of IGF1R selectively disrupts the growth of mutant and transformed, but not normal OPCs, or NSCs. The desirable outcome of IGF1R knockout on cell growth requires the mutant cells to commit to the OPC identity regardless of its development hierarchical status. At the molecular level, oncogenic mutations reprogram the cellular network of OPCs and force them to depend more on IGF1R for their growth. A new‐generation brain‐penetrable, orally available IGF1R inhibitor harnessing tumor OPCs in the brain is also developed. The findings reveal the cellular window of IGF1R targeting and establish IGF1R as an effective target for the prevention and treatment of glioblastoma. AU - Tian, Anhao AU - Kang, Bo AU - Li, Baizhou AU - Qiu, Biying AU - Jiang, Wenhong AU - Shao, Fangjie AU - Gao, Qingqing AU - Liu, Rui AU - Cai, Chengwei AU - Jing, Rui AU - Wang, Wei AU - Chen, Pengxiang AU - Liang, Qinghui AU - Bao, Lili AU - Man, Jianghong AU - Wang, Yan AU - Shi, Yu AU - Li, Jin AU - Yang, Minmin AU - Wang, Lisha AU - Zhang, Jianmin AU - Hippenmeyer, Simon AU - Zhu, Junming AU - Bian, Xiuwu AU - Wang, Ying‐Jie AU - Liu, Chong ID - 8592 IS - 21 JF - Advanced Science KW - General Engineering KW - General Physics and Astronomy KW - General Materials Science KW - Medicine (miscellaneous) KW - General Chemical Engineering KW - Biochemistry KW - Genetics and Molecular Biology (miscellaneous) SN - 2198-3844 TI - Oncogenic state and cell identity combinatorially dictate the susceptibility of cells within glioma development hierarchy to IGF1R targeting VL - 7 ER - TY - JOUR AB - Recent discoveries have shown that, when two layers of van der Waals (vdW) materials are superimposed with a relative twist angle between them, the electronic properties of the coupled system can be dramatically altered. Here, we demonstrate that a similar concept can be extended to the optics realm, particularly to propagating phonon polaritons–hybrid light-matter interactions. To do this, we fabricate stacks composed of two twisted slabs of a vdW crystal (α-MoO3) supporting anisotropic phonon polaritons (PhPs), and image the propagation of the latter when launched by localized sources. Our images reveal that, under a critical angle, the PhPs isofrequency curve undergoes a topological transition, in which the propagation of PhPs is strongly guided (canalization regime) along predetermined directions without geometric spreading. These results demonstrate a new degree of freedom (twist angle) for controlling the propagation of polaritons at the nanoscale with potential for nanoimaging, (bio)-sensing, or heat management. AU - Duan, Jiahua AU - Capote-Robayna, Nathaniel AU - Taboada-Gutiérrez, Javier AU - Álvarez-Pérez, Gonzalo AU - Prieto Gonzalez, Ivan AU - Martín-Sánchez, Javier AU - Nikitin, Alexey Y. AU - Alonso-González, Pablo ID - 10866 IS - 7 JF - Nano Letters KW - Mechanical Engineering KW - Condensed Matter Physics KW - General Materials Science KW - General Chemistry KW - Bioengineering SN - 1530-6984 TI - Twisted nano-optics: Manipulating light at the nanoscale with twisted phonon polaritonic slabs VL - 20 ER - TY - JOUR AB - We demonstrate a method for manipulating small ensembles of vortices in multiply connected superconducting structures. A micron-size magnetic particle attached to the tip of a silicon cantilever is used to locally apply magnetic flux through the superconducting structure. By scanning the tip over the surface of the device and by utilizing the dynamical coupling between the vortices and the cantilever, a high-resolution spatial map of the different vortex configurations is obtained. Moving the tip to a particular location in the map stabilizes a distinct multivortex configuration. Thus, the scanning of the tip over a particular trajectory in space permits nontrivial operations to be performed, such as braiding of individual vortices within a larger vortex ensemble—a key capability required by many proposals for topological quantum computing. AU - Polshyn, Hryhoriy AU - Naibert, Tyler AU - Budakian, Raffi ID - 10622 IS - 8 JF - Nano Letters KW - mechanical engineering KW - condensed matter physics KW - general materials science KW - general chemistry KW - bioengineering SN - 1530-6984 TI - Manipulating multivortex states in superconducting structures VL - 19 ER - TY - JOUR AB - The ability to reversibly assemble nanoparticles using light is both fundamentally interesting and important for applications ranging from reversible data storage to controlled drug delivery. Here, the diverse approaches that have so far been developed to control the self-assembly of nanoparticles using light are reviewed and compared. These approaches include functionalizing nanoparticles with monolayers of photoresponsive molecules, placing them in photoresponsive media capable of reversibly protonating the particles under light, and decorating plasmonic nanoparticles with thermoresponsive polymers, to name just a few. The applicability of these methods to larger, micrometer-sized particles is also discussed. Finally, several perspectives on further developments in the field are offered. AU - Bian, Tong AU - Chu, Zonglin AU - Klajn, Rafal ID - 13366 IS - 20 JF - Advanced Materials KW - Mechanical Engineering KW - Mechanics of Materials KW - General Materials Science SN - 0935-9648 TI - The many ways to assemble nanoparticles using light VL - 32 ER - TY - JOUR AB - Efficient isomerization of photochromic molecules often requires conformational freedom and is typically not available under solvent-free conditions. Here, we report a general methodology allowing for reversible switching of such molecules on the surfaces of solid materials. Our method is based on dispersing photochromic compounds within polysilsesquioxane nanowire networks (PNNs), which can be fabricated as transparent, highly porous, micrometer-thick layers on various substrates. We found that azobenzene switching within the PNNs proceeded unusually fast compared with the same molecules in liquid solvents. Efficient isomerization of another photochromic system, spiropyran, from a colorless to a colored form was used to create reversible images in PNN-coated glass. The coloration reaction could be induced with sunlight and is of interest for developing “smart” windows. AU - Chu, Zonglin AU - Klajn, Rafal ID - 13370 IS - 10 JF - Nano Letters KW - Mechanical Engineering KW - Condensed Matter Physics KW - General Materials Science KW - General Chemistry KW - Bioengineering SN - 1530-6984 TI - Polysilsesquioxane nanowire networks as an “Artificial Solvent” for reversible operation of photochromic molecules VL - 19 ER - TY - JOUR AB - Characterizing the structure of membrane proteins (MPs) generally requires extraction from their native environment, most commonly with detergents. Yet, the physicochemical properties of detergent micelles and lipid bilayers differ markedly and could alter the structural organization of MPs, albeit without general rules. Dodecylphosphocholine (DPC) is the most widely used detergent for MP structure determination by NMR, but the physiological relevance of several prominent structures has been questioned, though indirectly, by other biophysical techniques, e.g., functional/thermostability assay (TSA) and molecular dynamics (MD) simulations. Here, we resolve unambiguously this controversy by probing the functional relevance of three different mitochondrial carriers (MCs) in DPC at the atomic level, using an exhaustive set of solution-NMR experiments, complemented by functional/TSA and MD data. Our results provide atomic-level insight into the structure, substrate interaction and dynamics of the detergent–membrane protein complexes and demonstrates cogently that, while high-resolution NMR signals can be obtained for MCs in DPC, they systematically correspond to nonfunctional states. AU - Kurauskas, Vilius AU - Hessel, Audrey AU - Ma, Peixiang AU - Lunetti, Paola AU - Weinhäupl, Katharina AU - Imbert, Lionel AU - Brutscher, Bernhard AU - King, Martin S. AU - Sounier, Rémy AU - Dolce, Vincenza AU - Kunji, Edmund R. S. AU - Capobianco, Loredana AU - Chipot, Christophe AU - Dehez, François AU - Bersch, Beate AU - Schanda, Paul ID - 8443 IS - 5 JF - The Journal of Physical Chemistry Letters KW - General Materials Science SN - 1948-7185 TI - How detergent impacts membrane proteins: Atomic-level views of mitochondrial carriers in dodecylphosphocholine VL - 9 ER - TY - JOUR AB - The novel electronic state of the canted antiferromagnetic (AFM) insulator, strontium iridate (Sr2IrO4) has been well described by the spin-orbit-entangled isospin Jeff = 1/2, but the role of isospin in transport phenomena remains poorly understood. In this study, antiferromagnet-based spintronic functionality is demonstrated by combining unique characteristics of the isospin state in Sr2IrO4. Based on magnetic and transport measurements, large and highly anisotropic magnetoresistance (AMR) is obtained by manipulating the antiferromagnetic isospin domains. First-principles calculations suggest that electrons whose isospin directions are strongly coupled to in-plane net magnetic moment encounter the isospin mismatch when moving across antiferromagnetic domain boundaries, which generates a high resistance state. By rotating a magnetic field that aligns in-plane net moments and removes domain boundaries, the macroscopically-ordered isospins govern dynamic transport through the system, which leads to the extremely angle-sensitive AMR. As with this work that establishes a link between isospins and magnetotransport in strongly spin-orbit-coupled AFM Sr2IrO4, the peculiar AMR effect provides a beneficial foundation for fundamental and applied research on AFM spintronics. AU - Lee, Nara AU - Ko, Eunjung AU - Choi, Hwan Young AU - Hong, Yun Jeong AU - Nauman, Muhammad AU - Kang, Woun AU - Choi, Hyoung Joon AU - Choi, Young Jai AU - Jo, Younjung ID - 9066 IS - 52 JF - Advanced Materials KW - Mechanical Engineering KW - General Materials Science KW - Mechanics of Materials SN - 0935-9648 TI - Antiferromagnet‐based spintronic functionality by controlling isospin domains in a layered perovskite iridate VL - 30 ER - TY - JOUR AB - Focused ion beams perfectly suit for patterning two-dimensional (2D) materials, but the optimization of irradiation parameters requires full microscopic understanding of defect production mechanisms. In contrast to freestanding 2D systems, the details of damage creation in supported 2D materials are not fully understood, whereas the majority of experiments have been carried out for 2D targets deposited on substrates. Here, we suggest a universal and computationally efficient scheme to model the irradiation of supported 2D materials, which combines analytical potential molecular dynamics with Monte Carlo simulations and makes it possible to independently assess the contributions to the damage from backscattered ions and atoms sputtered from the substrate. Using the scheme, we study the defect production in graphene and MoS2 sheets, which are the two most important and wide-spread 2D materials, deposited on a SiO2 substrate. For helium and neon ions with a wide range of initial ion energies including those used in a commercial helium ion microscope (HIM), we demonstrate that depending on the ion energy and mass, the defect production in 2D systems can be dominated by backscattered ions and sputtered substrate atoms rather than by the direct ion impacts and that the amount of damage in 2D materials heavily depends on whether a substrate is present or not. We also study the factors which limit the spatial resolution of the patterning process. Our results, which agree well with the available experimental data, provide not only insights into defect production but also quantitative information, which can be used for the minimization of damage during imaging in HIM or optimization of the patterning process. AU - Kretschmer, Silvan AU - Maslov, Mikhail AU - Ghaderzadeh, Sadegh AU - Ghorbani-Asl, Mahdi AU - Hlawacek, Gregor AU - Krasheninnikov, Arkady V. ID - 13255 IS - 36 JF - ACS Applied Materials & Interfaces KW - General Materials Science SN - 1944-8244 TI - Supported two-dimensional materials under ion irradiation: The substrate governs defect production VL - 10 ER - TY - JOUR AB - Dissipative self-assembly leads to structures and materials that exist away from equilibrium by continuously exchanging energy and materials with the external environment. Although this mode of self-assembly is ubiquitous in nature, where it gives rise to functions such as signal processing, motility, self-healing, self-replication, and ultimately life, examples of dissipative self-assembly processes in man-made systems are few and far between. Herein, recent progress in developing diverse synthetic dissipative self-assembly systems is discussed. The systems reported thus far can be categorized into three classes, in which: i) the fuel chemically modifies the building blocks, thus triggering their self-assembly, ii) the fuel acts as a template interacting with the building blocks noncovalently, and iii) transient states are induced by the addition of two mutually exclusive stimuli. These early studies give rise to materials that would be difficult to obtain otherwise, including hydrogels with programmable lifetimes, vesicular nanoreactors, and membranes exhibiting transient conductivity. AU - De, Soumen AU - Klajn, Rafal ID - 13375 IS - 41 JF - Advanced Materials KW - Mechanical Engineering KW - Mechanics of Materials KW - General Materials Science SN - 0935-9648 TI - Dissipative self-assembly driven by the consumption of chemical fuels VL - 30 ER - TY - JOUR AB - Azobenzenealkanethiols in self-assembled monolayers (SAMs) on Au(111) exhibit reversible trans–cis photoisomerization when diluted with alkanethiol spacers. Using these mixed SAMs, we show switching of the linear optical and second-harmonic response. The effective switching of these surface optical properties relies on a reasonably large cross section and a high photoisomerization yield as well as a long lifetime of the metastable cis isomer. We quantified the switching process by X-ray absorption spectroscopy. The cross sections for the trans–cis and cis–trans photoisomerization with 365 and 455 nm light, respectively, are 1 order of magnitude smaller than in solution. In vacuum, the 365 nm photostationary state comprises 50–74% of the molecules in the cis form, limited by their rapid thermal isomerization back to the trans state. In contrast, the 455 nm photostationary state contains nearly 100% trans-azobenzene. We determined time constants for the thermal cis–trans isomerization of only a few minutes in vacuum and in a dry nitrogen atmosphere but of more than 1 day in ambient air. Our results suggest that adventitious water adsorbed on the surface of the SAM stabilizes the polar cis configuration of azobenzene under ambient conditions. The back reaction rate constants differing by 2 orders of magnitude underline the huge influence of the environment and, accordingly, its importance when comparing various experiments. AU - Moldt, Thomas AU - Przyrembel, Daniel AU - Schulze, Michael AU - Bronsch, Wibke AU - Boie, Larissa AU - Brete, Daniel AU - Gahl, Cornelius AU - Klajn, Rafal AU - Tegeder, Petra AU - Weinelt, Martin ID - 13386 IS - 42 JF - Langmuir KW - Electrochemistry KW - Spectroscopy KW - Surfaces and Interfaces KW - Condensed Matter Physics KW - General Materials Science SN - 0743-7463 TI - Differing isomerization kinetics of azobenzene-functionalized self-assembled monolayers in ambient air and in vacuum VL - 32 ER - TY - JOUR AB - Novel light-responsive nanoparticles were synthesized by decorating the surfaces of gold and silver nanoparticles with a nitrospiropyran molecular photoswitch. Upon exposure to UV light in nonpolar solvents, these nanoparticles self-assembled to afford spherical aggregates, which disassembled rapidly when the UV stimulus was turned off. The sizes of these aggregates depended on the nanoparticle concentration, and their lifetimes could be controlled by adjusting the surface concentration of nitrospiropyran on the nanoparticles. The conformational flexibility of nitrospiropyran, which was altered by modifying the structure of the background ligand, had a profound impact on the self-assembly process. By coating the nanoparticles with a spiropyran lacking the nitro group, a conceptually different self-assembly system, relying on a reversible proton transfer, was realized. The resulting particles spontaneously (in the dark) assembled into aggregates that could be readily disassembled upon exposure to blue light. AU - Kundu, Pintu K. AU - Das, Sanjib AU - Ahrens, Johannes AU - Klajn, Rafal ID - 13385 IS - 46 JF - Nanoscale KW - General Materials Science SN - 2040-3364 TI - Controlling the lifetimes of dynamic nanoparticle aggregates by spiropyran functionalization VL - 8 ER - TY - JOUR AB - The chemical behaviour of molecules can be significantly modified by confinement to volumes comparable to the dimensions of the molecules. Although such confined spaces can be found in various nanostructured materials, such as zeolites, nanoporous organic frameworks and colloidal nanocrystal assemblies, the slow diffusion of molecules in and out of these materials has greatly hampered studying the effect of confinement on their physicochemical properties. Here, we show that this diffusion limitation can be overcome by reversibly creating and destroying confined environments by means of ultraviolet and visible light irradiation. We use colloidal nanocrystals functionalized with light-responsive ligands that readily self-assemble and trap various molecules from the surrounding bulk solution. Once trapped, these molecules can undergo chemical reactions with increased rates and with stereoselectivities significantly different from those in bulk solution. Illumination with visible light disassembles these nanoflasks, releasing the product in solution and thereby establishes a catalytic cycle. These dynamic nanoflasks can be useful for studying chemical reactivities in confined environments and for synthesizing molecules that are otherwise hard to achieve in bulk solution. AU - Zhao, Hui AU - Sen, Soumyo AU - Udayabhaskararao, T. AU - Sawczyk, Michał AU - Kučanda, Kristina AU - Manna, Debasish AU - Kundu, Pintu K. AU - Lee, Ji-Woong AU - Král, Petr AU - Klajn, Rafal ID - 13392 JF - Nature Nanotechnology KW - Electrical and Electronic Engineering KW - Condensed Matter Physics KW - General Materials Science KW - Biomedical Engineering KW - Atomic and Molecular Physics KW - and Optics KW - Bioengineering SN - 1748-3387 TI - Reversible trapping and reaction acceleration within dynamically self-assembling nanoflasks VL - 11 ER - TY - JOUR AB - Photoswitching in densely packed azobenzene self-assembled monolayers (SAMs) is strongly affected by steric constraints and excitonic coupling between neighboring chromophores. Therefore, control of the chromophore density is essential for enhancing and manipulating the photoisomerization yield. We systematically compare two methods to achieve this goal: First, we assemble monocomponent azobenzene–alkanethiolate SAMs on gold nanoparticles of varying size. Second, we form mixed SAMs of azobenzene–alkanethiolates and “dummy” alkanethiolates on planar substrates. Both methods lead to a gradual decrease of the chromophore density and enable efficient photoswitching with low-power light sources. X-ray spectroscopy reveals that coadsorption from solution yields mixtures with tunable composition. The orientation of the chromophores with respect to the surface normal changes from a tilted to an upright position with increasing azobenzene density. For both systems, optical spectroscopy reveals a pronounced excitonic shift that increases with the chromophore density. In spite of exciting the optical transition of the monomer, the main spectral change in mixed SAMs occurs in the excitonic band. In addition, the photoisomerization yield decreases only slightly by increasing the azobenzene–alkanethiolate density, and we observed photoswitching even with minor dilutions. Unlike in solution, azobenzene in the planar SAM can be switched back almost completely by optical excitation from the cis to the original trans state within a short time scale. These observations indicate cooperativity in the photoswitching process of mixed SAMs. AU - Moldt, Thomas AU - Brete, Daniel AU - Przyrembel, Daniel AU - Das, Sanjib AU - Goldman, Joel R. AU - Kundu, Pintu K. AU - Gahl, Cornelius AU - Klajn, Rafal AU - Weinelt, Martin ID - 13396 IS - 3 JF - Langmuir KW - Electrochemistry KW - Spectroscopy KW - Surfaces and Interfaces KW - Condensed Matter Physics KW - General Materials Science SN - 0743-7463 TI - Tailoring the properties of surface-immobilized azobenzenes by monolayer dilution and surface curvature VL - 31 ER - TY - JOUR AB - Nature has long inspired scientists with its seemingly unlimited ability to harness solar energy and to utilize it to drive various physiological processes. With the help of man-made molecular photoswitches, we now have the potential to outperform natural systems in many ways, with the ultimate goal of fabricating multifunctional materials that operate at different light wavelengths. An important challenge in developing light-controlled artificial molecular machines lies in attaining a detailed understanding of the photoisomerization-coupled conformational changes that occur in macromolecules and molecular assemblies. In this issue of ACS Nano, Bléger, Rabe, and co-workers use force microscopy to provide interesting insights into the behavior of individual photoresponsive molecules and to identify contraction, extension, and crawling events accompanying light-induced isomerization. AU - Kundu, Pintu K. AU - Klajn, Rafal ID - 13399 IS - 12 JF - ACS Nano KW - General Physics and Astronomy KW - General Engineering KW - General Materials Science SN - 1936-0851 TI - Watching single molecules move in response to light VL - 8 ER - TY - JOUR AB - Dual-responsive nanoparticles are designed by functionalizing magnetic cores with light-responsive ligands. These materials respond to both light and magnetic fields and can be assembled into various higher-order structures, depending on the relative contributions of these two stimuli. AU - Das, Sanjib AU - Ranjan, Priyadarshi AU - Maiti, Pradipta Sankar AU - Singh, Gurvinder AU - Leitus, Gregory AU - Klajn, Rafal ID - 13406 IS - 3 JF - Advanced Materials KW - Mechanical Engineering KW - Mechanics of Materials KW - General Materials Science SN - 0935-9648 TI - Dual-responsive nanoparticles and their self-assembly VL - 25 ER - TY - JOUR AB - Well-defined metallic nanobowls can be prepared by extending the concept of a protecting group to colloidal synthesis. Magnetic nanoparticles are employed as “protecting groups” during the galvanic replacement of silver with gold. The replacement reaction is accompanied by spontantous dissociation of the protecting groups, leaving behind metallic nanobowls. AU - Ridelman, Yonatan AU - Singh, Gurvinder AU - Popovitz-Biro, Ronit AU - Wolf, Sharon G. AU - Das, Sanjib AU - Klajn, Rafal ID - 13408 IS - 5 JF - Small KW - Biomaterials KW - Biotechnology KW - General Materials Science KW - General Chemistry SN - 1613-6810 TI - Metallic nanobowls by galvanic replacement reaction on heterodimeric nanoparticles VL - 8 ER - TY - JOUR AB - Photoresponsive gold nanoparticles dispersed in a solid/frozen matrix provide a basis for sensors that “remember” whether the sample has ever exceeded the melting temperature of the matrix. The operation of these sensors rests on the ability to photoinduce metastable electric dipoles on NP surfaces – upon melting, these dipoles drive NP aggregation, precipitation, and crosslinking. These events are manifested by a pronounced color change. AU - Klajn, Rafal AU - Browne, Kevin P. AU - Soh, Siowling AU - Grzybowski, Bartosz A. ID - 13411 IS - 13 JF - Small KW - Biomaterials KW - Biotechnology KW - General Materials Science KW - General Chemistry SN - 1613-6810 TI - Nanoparticles that “remember” temperature VL - 6 ER - TY - JOUR AB - The reversible molecular template-directed self-assembly of gold nanoparticles (AuNPs), a process which relies solely on noncovalent bonding interactions, has been demonstrated by high-resolution transmission electron microscopy (HR-TEM). By employing a well-known host−guest binding motif, the AuNPs have been systemized into discrete dimers, trimers, and tetramers. These nanoparticulate twins, triplets, and quadruplets, which can be disassembled and reassembled either chemically or electrochemically, can be coalesced into larger, permanent polygonal structures by thermal treatment using a focused HR-TEM electron beam. AU - Olson, Mark A. AU - Coskun, Ali AU - Klajn, Rafal AU - Fang, Lei AU - Dey, Sanjeev K. AU - Browne, Kevin P. AU - Grzybowski, Bartosz A. AU - Stoddart, J. Fraser ID - 13416 IS - 9 JF - Nano Letters KW - Mechanical Engineering KW - Condensed Matter Physics KW - General Materials Science KW - General Chemistry KW - Bioengineering SN - 1530-6984 TI - Assembly of polygonal nanoparticle clusters directed by reversible noncovalent bonding interactions VL - 9 ER - TY - JOUR AB - Supraspherical aggregates of crosslinked metal nanoparticles are transformed into pancakes and nanorods by mechanical stresses and shears imparted by macroscopic objects (see image). The dimensions of both types of nanostructures can be controlled by the pressures applied. AU - Browne, Kevin P. AU - Klajn, Rafal AU - Villa, JulieAnn AU - Grzybowski, Bartosz A. ID - 13414 IS - 23 JF - Small KW - Biomaterials KW - Biotechnology KW - General Materials Science KW - General Chemistry SN - 1613-6810 TI - Mechanofabrication of pancake and rodlike nanostructures from deformable nanoparticle aggregates VL - 5 ER - TY - JOUR AB - Reaction-diffusion (RD) processes initiated from the surfaces of mesoscopic particles can fabricate complex core-and-shell structures. The propagation of a sharp RD front selectively removes metal colloids or nanoparticles from the supporting gel or polymer matrix. Once fabricated, the core structures can be processed “remotely” via galvanic replacement reactions, and the composite particles can be assembled into open-lattice crystals. AU - Wesson, Paul J. AU - Soh, Siowling AU - Klajn, Rafal AU - Bishop, Kyle J. M. AU - Gray, Timothy P. AU - Grzybowski, Bartosz A. ID - 13419 IS - 19 JF - Advanced Materials KW - Mechanical Engineering KW - Mechanics of Materials KW - General Materials Science SN - 0935-9648 TI - “Remote” fabrication via three-dimensional reaction-diffusion: Making complex core-and-shell particles and assembling them into open-lattice crystals VL - 21 ER - TY - JOUR AB - Make like a leaf: The synthesis and characterization of a family of “flowerlike” Au/Fe3O4 nanoparticles is described, whereby Fe3O4 “leaves” adhere to a gold core (see image). The size and numbers of iron oxide domains can be adjusted flexibly by changing the proportion of the starting materials and the reaction time. AU - Wei, Yanhu AU - Klajn, Rafal AU - Pinchuk, Anatoliy O. AU - Grzybowski, Bartosz A. ID - 13422 IS - 10 JF - Small KW - Biomaterials KW - Biotechnology KW - General Materials Science KW - General Chemistry SN - 1613-6810 TI - Synthesis, shape control, and optical properties of hybrid Au/Fe3O4 “nanoflowers” VL - 4 ER - TY - JOUR AB - Photoswelling of thin films of dichromated gelatin provides a basis for fabrication of multilevel surface reliefs via sequential UV illumination through different photomasks. The remarkable feature of this simple, benchtop technique is that by adjusting irradiation times, film thickness, or its hydration state the heights of the developed features can be varied from few nanometers to tens of microns. After UV exposure, the surface structures can be replicated faithfully into either soft or hard PDMS stamps. AU - Paszewski, Maciej AU - Smoukov, Stoyan K. AU - Klajn, Rafal AU - Grzybowski, Bartosz A. ID - 13426 IS - 10 JF - Langmuir KW - Electrochemistry KW - Spectroscopy KW - Surfaces and Interfaces KW - Condensed Matter Physics KW - General Materials Science SN - 0743-7463 TI - Multilevel surface nano- and microstructuring via sequential photoswelling of dichromated gelatin VL - 23 ER - TY - JOUR AB - Hydrogel stamps can microstructure solid surfaces, i.e., modify the surface topology of metals, glasses, and crystals. It is demonstrated that stamps soaked in an appropriate etchant can remove material with micrometer-scale precision. The Figure shows an array of concentric circles etched in glass using the immersion wet stamping process described (scale bar: 500 μm). AU - Smoukov, S. K. AU - Bishop, K. J. M. AU - Klajn, Rafal AU - Campbell, C. J. AU - Grzybowski, B. A. ID - 13431 IS - 11 JF - Advanced Materials KW - Mechanical Engineering KW - Mechanics of Materials KW - General Materials Science SN - 0935-9648 TI - Cutting into solids with micropatterned gels VL - 17 ER - TY - JOUR AB - A new experimental technique is described that uses reaction−diffusion phenomena as a means of one-step microfabrication of complex, multilevel surface reliefs. Thin films of dry gelatin doped with potassium hexacyanoferrate are chemically micropatterned with a solution of silver nitrate delivered from an agarose stamp. Precipitation reaction between the two salts causes the surface to deform. The mechanism of surface deformation is shown to involve a sequence of reactions, diffusion, and gel swelling/contraction. This mechanism is established experimentally and provides a basis of a theoretical lattice-gas model that allows prediction surface topographies emerging from arbitrary geometries of the stamped features. The usefulness of the technique is demonstrated by using it to rapidly prepare two types of mold for passive microfluidic mixers. AU - Campbell, Christopher J. AU - Klajn, Rafal AU - Fialkowski, Marcin AU - Grzybowski, Bartosz A. ID - 13432 IS - 1 JF - Langmuir KW - Electrochemistry KW - Spectroscopy KW - Surfaces and Interfaces KW - Condensed Matter Physics KW - General Materials Science SN - 0743-7463 TI - One-step multilevel microfabrication by reaction−diffusion VL - 21 ER - TY - JOUR AB - Micropatterning of surfaces with several chemicals at different spatial locations usually requires multiple stamping and registration steps. Here, we describe an experimental method based on reaction–diffusion phenomena that allows for simultaneous micropatterning of a substrate with several coloured chemicals. In this method, called wet stamping (WETS), aqueous solutions of two or more inorganic salts are delivered onto a film of dry, ionically doped gelatin from an agarose stamp patterned in bas relief. Once in conformal contact, these salts diffuse into the gelatin, where they react to give deeply coloured precipitates. Separation of colours in the plane of the surface is the consequence of the differences in the diffusion coefficients, the solubility products, and the amounts of different salts delivered from the stamp, and is faithfully reproduced by a theoretical model based on a system of reaction–diffusion partial differential equations. The multicolour micropatterns are useful as non-binary optical elements, and could potentially form the basis of new applications in microseparations and in controlled delivery. AU - Klajn, Rafal AU - Fialkowski, Marcin AU - Bensemann, Igor T. AU - Bitner, Agnieszka AU - Campbell, C. J. AU - Bishop, Kyle AU - Smoukov, Stoyan AU - Grzybowski, Bartosz A. ID - 13435 JF - Nature Materials KW - Mechanical Engineering KW - Mechanics of Materials KW - Condensed Matter Physics KW - General Materials Science KW - General Chemistry SN - 1476-1122 TI - Multicolour micropatterning of thin films of dry gels VL - 3 ER - TY - JOUR AB - Thin films of ionically doped gelatin have been color-patterned with submicrometer precision using the wet-stamping technique. Inorganic salts are delivered onto the gelatin surface from an agarose stamp, and diffuse into the gelatine layer, producting deeply colored precipitates. Reaction fronts originating from different features of the stamp cease within < 1 μm of each other, leaving sharp, transparent regions in between. AU - Campbell, C. J. AU - Fialkowski, M. AU - Klajn, Rafal AU - Bensemann, I. T. AU - Grzybowski, B. A. ID - 13434 IS - 21 JF - Advanced Materials KW - Mechanical Engineering KW - Mechanics of Materials KW - General Materials Science SN - 0935-9648 TI - Color micro- and nanopatterning with counter-propagating reaction-diffusion fronts VL - 16 ER -